Electrocoagulation For The Treatment Of Polluted Water Using Electricity



2.1 General

Electrocoagulation is a technology for the treatment of polluted water using electricity. Electrocoagulation process is effective in treating soluble or colloidal pollutants in various effluents including municipal, laundry, food industry, tanneries, textile, and agro-based industry wastewaters. Electrocoagulation process includes coagulation and precipitation of contaminants by applying direct current. It consists of an electrolytic cell and electrodes. A direct current is applied to the electrodes to induce the reaction needed to achieve the coagulation.

In recent years, smaller scale electrocoagulation processes have advanced to the point where they are seen as a reliable and effective technology. A wide range of reactors has been tried, with individual designs being largely determined by the volumetric scale and nature of the pollutant being treated. This diversity in reactors has resulted in isolated advances being made in electrocoagulation technology. (Naje and Abbas, 2013, Malaysia).

2.2 Theory of Electrocoagulation

The basic principle of electrocoagulation process depends on the cations produced electrolytically from anode and coagulation of contaminants are increased in the aqueous solution. Electrophoretic motion tends to concentrate negatively charged particle in the region of the anode and positively charged particles in the region of the cathode. The consumable metal anodes are used to continuously produce polyvalent metal cations in the region of the anode. These cations neutralize the negative charge of the particles and move towards the anodes by production of polyvalent cations from the oxidation of the sacrificial anode and the electrolysis gases like hydrogen evolved at the anode and oxygen evolved at the cathode.

The three successive stages of electrocoagulation process involve:

‘ Electrolytic oxidation of the sacrificial electrode for the formation of coagulants.

‘ Suspension of contaminant particulate and emulsion breakage are due to the destabilization.

‘ Flocs formation due to the aggregation of the destabilizes phase

The mechanism involved in destabilization of contaminants and particulate suspension are as follows:

i. Generation and interaction of ions are possible due to the oxidayion of the sacrificial anode. Compression of the diffuse double layer is seen possible around the charged ions.

ii. Counter ions are produced from the electrochemical dissolution of the sacrificial anode. Neutralization of ionic species in the wastewater is because of these counter ions. The reduction of the electrostatic interparticle repulsion is due to these counter ions, Vander Walls attraction predominates and coagulation occurs and approaches zero net charge.

iii. In the aqueous medium, coagulation causes formation of flocs and also creates a blanket of sludge.

iv. Adsorption of contaminated contents is due to the negative surfaces of the hydroxides, oxyhydroxides and solid oxides.

v. Metal ions are generated due to the dissolution of the elelctrodes from the anode. Polymeric ions or metal hydroxides are hydrolyzed immediately after the generation of metal ions.

The main function of sacrificial anode is to generate polymeric hydroxides nearby the anode. These polymeric hydroxides are act as excellent coagulating agents. Due to electrophoresis action, negative ions which are produced from the cathode moves towards anode Small bubble of oxygen at anode and small bubbles of hydrogen at cathode are generated and are responsible for electrolysis of water. These bubbles attract the flocculated particles. Due to the natural buoyancy towards the surface the flocculated particle floats.

The physicochemical reactions that occur in the electrocoagulation cell is described as follows:

i. Metal ions reduction takes place at the cathode.

ii. Impurities are responsible for cathodic reduction in the wastewater.

iii. Due to the electrode erosion, colloidal particles are generated.

iv. Coagulation and discharge of colloidal particles are because of electroflotation or sedimentation and filtration.

v. Electrophoresis in the solution causes ions migration.

vi. At anode and cathode oxygen and hydrogen bubbles are produced.

vii. Other chemical and electrochemical process also occurs and an external power supply is used for the electrocoagulation process.

Deposition and dissolution of metal ions at the electrodes are due to the quantity of electricity that has been passed. A relationship between current density (Acm-2) and the quantity of the metal (M) dissolved (g of Mcm-2) can be found out by using Faraday’s law.

Where, W is the electrode dissolution (g of Mcm-2), I is the current density (Acm-2), t is the time in second, M is the electrode’s relative molar mass, n is the no. of electrodes, F is the Faraday’s constant, 96,500 Cmol-1.

The operating condition of electrocoagulation mainly depends on the chemistry of the aqueous medium, conductivity and pH. Particle size, electrode material, electrode distance and chemical constituent concentration are other important characteristics. Electrophoresis motion tends to concentrate positively charged ions in the regions of the cathode and negatively charged particles in the region of the anode. Polyvalent metal cations are continuously produced in the vicinity of the anode. The negative charge of the particle is neutralized by the produced cations by the motion of electrophoresis.

2.3 Reaction mechanism in Electrocoagulation process

The processes and reactions that occur during electrocoagulation are explained as follows. When current is passed through electrochemical reactor, it just overcomes the equilibrium potential difference, anode over potential, cathode over potential and potential drop of the solution. The anode over potential includes the activation over potential and concentration potential, as well as the possible passive over potential resulted from the passive film at the anode surface, while the cathode over potential is principally composed of the activation over potential and concentration over potential. Reaction occurs at electrode surfaces and forms coagulants in aqueous phase, adsorption of soluble or colloidal pollutants occurs on coagulants. The chemical reactions generally taking place at the anode and cathode are given as follows:

At the anode:

M (s) M (aq)

n+ + ne-

2H2O 4H+ + O2 + 4e-

At the cathode:

M (aq)

n+ + ne- M (s)

2H2O + 2e- H2 (g) + 2OH-

M represents the material used as electrode and n is the number of electrodes.

Generally, aluminum and iron electrodes are used as electrode materials in the electrocoagulation process. In the iron electrode, following two mechanisms are expected to occur.

Mechanism 1:


4Fe(s) 4Fe2+ (aq) + 8e-

4Fe2+ (aq) + 10H2O (I) + O2 (g) 4Fe (OH)3 (s) + 8H+ (aq)


8H+ (aq) + 8e- 4H2 (g)

Overall: 4Fe(s) + 10H2O (I) + O2 (g) 4Fe (OH)3 (s) + 4H2 (g)

Mechanism 2:

Anode: Fe (s) Fe2+ (aq) + 2e-

Fe2+ (aq) + 2OH- (aq) Fe (OH)2 (s)


2H2O (I) +2e- H2 (g) + 2OH- (aq)

Overall: Fe (s) + 2H2O (I) Fe (OH)2 (s) + H2 (g)

Due to oxidation in an electrolyte system, iron produces form of monomeric ions. Fe(OH)3 and polymeric hydroxyl complex such as: Fe(H2O)63+ , Fe(H2O)52+, Fe(H2O)4(OH)2+, Fe(H2O)8(OH)24+ and Fe(H2O)6(OH)44+ depending upon the pH of the aqueous medium.

In the case of aluminum electrodes, reactions are as follows:

Anode: Al (s) Al3+ (aq) + 3e-

Cathode: 3H2O (I) + 3e- 3/2 H2 + 3H+

For the aluminum electrodes, Al3+ (aq) ions will immediately undergo further spontaneous reaction to generate corresponding hydroxides and polyhydroxides. Due to hydrolysis of Al3+: Al (H2O)63+, Al(H2O)5OH2+, Al(H2O)5OH2+, Al(H2O)OH2+ are generated. This hydrolysis products produced may be monomeric and polymeric substance such as, Al(OH)2+, Al2(OH)24+, Al6(OH)153+, Al7 (OH)174+, Al8(OH)204+, Al13O4(OH)247+, Al13(OH)345+ (Chaturvedi, 2013, India).

2.4 Factors influencing electrochemical coagulation

The removal efficiency of the pollutants from wastewater is affected by the various parameters. The parameters influencing the process of electrocoagulation are:

‘ Electrode material: The material of the electrodes can be iron, aluminum or inert material (cathode). Optimal material selection depends on the pollutants to be removed and the chemical properties of the electrolyte. Aluminum seems to be superior compared to iron in most cases, when only the efficiency of the treatment is considered. However, it should be noted that aluminum is more expensive compared to iron. Inert electrodes, such as metal oxides coated titanium, are used in some cases. When water has significant amounts of calcium and magnesium ions, the inert cathode materials can be used. For COD and phenol removal, iron is good and for color and turbidity removal aluminum gives better results. If electrochemically inert materials like stainless steel as cathode are used, gets protection from corrosion. Besides, stainless steel produces smaller bubbles which posses larger surface and can remove more impurities through floatation.

‘ pH: pH of the wastewater has an effect on the speciation of metal hydroxides in the solution. During electrocoagulation pH increases due to the contribution of OH- ions into the solution and it enhances the efficiency of the system. Initial pH between 7-9 gives better results and if pH raises beyond 9 the efficiency decreases because of the formation of soluble Fe(OH)4 and Al(OH)4. Only insoluble metal hydroxides of iron can remove pollutants by electrostatic attraction. The kinetics of conversion of Fe2+ to Fe3+ is strongly affected by bulk solution pH.

‘ Current density: Current density is proportional to the amount of electrochemical reactions taking place on the electrode surface. When current density increases, the reaction rate also increases by the more metal ions in solution. But the rapid contribution of metal ions in the system cost more and further increases the results in restabilization of metal particles in the solution.

‘ Electrolysis time: Treatment time added per volume is proportional to the amount of coagulants produced in the electrocoagulation system and other reactions taking place in the system. Efficiency increases with increase in electrolysis time. But if we increase the electrolysis time beyond some extend the removal efficiency decreases because of the free metal ions in the solution.

‘ Temperature: Temperature affects floc formation, reaction rates and conductivity. Depending on the pollutants, the increasing temperature can have a negative or a positive effect on the removal efficiency. Normally, better results are obtained at low temperature, while at higher temperature results in dissolution of metal ions into the solution.

‘ Inter electrode distance: The distance between the electrodes has greater importance in elctrocoagulation. Very less electrode distance may cause short circuit and very high distance results in lesser contribution of metal ions into the solution which minimizes the efficiency of the system. So it is better to keep this in medium according to the characteristics of the wastewater (Shreesadh et al, 2014).

2.5 Investigation of ECC for domestic wastewater and greywater

Barisci and Turkay, 2016, Turkey conducted experiments on ‘Domestic greywater treatment by electrocoagulation using hybrid electrode combinations’. Electrochemical coagulation experiments were carried out with different electrode combination for the treatment of domestic greywater. The different electrode combinations were Al-Al-Al-Al, Fe-Fe-Fe-Fe, Fe-Al-Al-Fe, Al-Fe-Fe-Al, Fe-Al-Fe-Al, Al-Fe-Al-Fe, Fe-Al-Al-Al, Al-Fe-Fe-Fe. The operating parameters they considered were current density, initial pH and supporting electrolyte concentration. They have conducted the experiments for the current densities 0.5, 1.0 and 1.5 mA cm-2. The supporting electrolyte they have used is sodium sulfate. They have also carried out experiments to see the effect of initial pH in all the range i.e., original pH (7.62), acidic (3) and basic (9.5). The electrolyte concentrations were 0, 50 and 100 mgL-1. The maximum COD removal efficiency was 98% at the current density of 1.5 mA cm-2 while using Al-Fe-Fe-Al electrode combination.

Hussien et al, 2015, Egypt carried out ‘Sewage water treatment via electrocoagulation using iron anode’. The operating parameters considered in this research were current density, electrolysis time, electrolyte concentration, electrode distance. The reactor used was of 1.25 liter capacity. Iron electrodes of 2 x 2 cm were used. Different grade emery washed with distilled water was used to polish the electrodes mechanically and rinsed with acetone, and dried in a stream of air. The electrode distance was 3 cm. One liter sewage used in each experiment. Digital multimeter was used to measure both voltage and current. The Sodium chloride was used as supporting electrolyte. The electrocoagulation experiments were carried out at ambient temperature 250C. Supporting electrolyte was added in the desired amount to raise the conductivity of the solution and then the pH adjusted to the desired value. The sludge was separated by filtration with Whatman filter paper. Then supernatant was analyzed, and the weight of the dissolved iron was calculated from the change in weights of the electrode before and after electrocoagulation. The anodic dissolution percentage was calculated from the equation,

, where, ECE is the electrochemical equivalent of iron. The effective removal of S.S, COD, and BOD were obtained under the optimum operating parameters: pH 7.6, 65 mA cm-2 of current density was applied, ET 30 min, and sodium chloride as supporting electrolyte concentration of 1gL-1 and electrode gap distance of 3 cm. The suspended solids, COD, and BOD decreased from 507, 670, and 446 to 5, 98, and 77mgL-1 respectively.

‘Domestic Wastewater Treatment by Electrocoagulation using copper and aluminum electrodes’ was carried out by Impa et al, 2015, India. Borosil glass beaker of 5 liter capacity was used as reactor to hold the sample. Aluminum and copper electrodes of dimension 150”50”3 mm were used. Electrode spacing was 3 cm. The cell was equipped with the magnetic stirrer. The efficiency was studied for different voltages and electrolysis time. For every 10, 20, 30 min the sample were drawn from the reactor and parameter like COD and nitrates was measured. Before every run the electrodes were washed with 15% HCl and then rinsed with distilled water. After the experiment, the sample is transferred to another beaker and kept undisturbed for 20 min to allow the flocs formed to settle. Under the operating parameters such as electrolysis time: 30 min, pH: 7-8 and voltage: 20V, the 63.2% and 62% of COD and nitrate removal was obtained respectively. After conducting the experiments, they have concluded that the applied potential increases the rate of dissolution of electrodes. They have also stated that COD and nitrate removal efficiency is directly proportional to the input voltage and contact duration. Finally the results of study showed that the electrochemical coagulation could be applied for the cost effective treatment of domestic wastewater.

Santhosh et al, 2015, India worked on ‘Treatment of sullage wastewater by electrocoagulation using stainless steel electrodes’. This study was carried out for the treatment of sullage wastewater using electroagulation with stainless steel electrodes as sacrificial anode in bipolar arrangement. pH, cell voltage and electrolysis time were the operating parameters they have considered. The experiments were carried out in a batch reactor of 500 mL beaker. Electrode used was stainless steel with dimensions 70 x 50 x 3 mm. The electrode distance was maintained at 40 mm. The experiments were carried out at different voltages such as 4, 6 and 8V. Before every experiment the electrodes were washed with 1M H2SO4 and then rinsed with deionised water. After the experiment, the treated sample is kept undisturbed for 20 min to allow the flocs to settle, and then the supernatant was analyzed for suspended solids, COD and BOD. 92.71%, 88.76% and 93.1% reduction of COD, BOD and SS was obtained at 8V, 30min respectively.

Kanawade, 2015, India worked on ‘The Wastewater Treatment and its Reuse’. The circular cell having 20cm internal diameter and 50cm height with the effective volume of 5L and two iron electrodes of 32cm2 surface area was used for experiments. The distance between the electrodes was 3cm. The temperature was maintained between 25-300C. The agitation speed was 100rpm. The operating parameters were electrolysis time, electrode spacing and applied current. To examine the influence of current density, 0.03, 0.2, 0.4, 0.79 and 1.0A current was applied for the electrolysis time of 30min, with the corresponding current densities of 0.94, 6.25, 12.5, 24.7 and 31.25 mA cm-2 respectively. The maximum removal of turbidity, COD and TSS was 91.8%, 77.2% and 68.5% at of 24.7 mA cm-2 current density with an inter-electrode distance of 5cm within the electrolysis time of 30min.

Alex and Paul, 2015, India worked on ‘Municipal Wastewater Treatment by Electrocoagulation’. The process of electrocoagulation was examined with the laboratory setup with aluminum anode and stainless steel cathode for the removal of COD and TS. The electrolytic cell reactor was made up of acrylic sheet with internal dimensions of 12.5x 8x 9 (L x B x H) cm. The wetted surface area of the electrodes was 90cm2. For each run 500mL sample was taken. After each run 1min of rapid mixing and 4min of slow mixing was done using magnetic stirrer for getting completely settled sludge. 90min of settling time was allowed after each run. The operating parameters were cell voltage, electrode distance and electrolysis time. The different applied cell voltages were 8, 10, 12, 14 and 16V. The inter electrode distance was varied from 1-4 cm. The electrolysis time was from 10-30 min. The maximum removal of COD and TS was obtained at 10V with 2cm electrode spacing at 25min. At the optimal conditions, the Cod got reduced from 332mgL-1 to 64mgL-1 and TS got reduced from 984mgL-1 to 380mgL-1. Therefore, the removal efficiency of COD and TS were 80.70% and 61.38% respectively. It was inferred that with the increase in cell voltage and electrolysis time, the removal efficiency increases. Also, smaller electrode distance produces more anions which increase the treatment efficiency.

In 2014, Kruna and Pandya, India, carried out ‘Electrocoagulation – A Promising Technology for Sewage Treatment’. The batch reactor of dimension 380 x 235 x 255mm was used for the experiment. Electrodes (4 Aluminum as cathode and 3 Mild Steel as anode) were used. The electrode spacing was 10 and 15mm. 10A and 24V are fixed in power supply unit. Sampling was done at time interval of 15min, 20min, 25min, and 30min. After the experiment, the sample is kept undisturbed for 60min in order to allow the flocs to settle. After settling, the supernatant is collected and analyzed for suspended solids, COD and TDS. The operating parameters were electrolysis time, electrode distance, and current density. Suspended solids, COD and TDS removal efficiency was 95%, 86% and 70% respectively at 42 Am-2 current density, 10mm electrode distance in 30min at the optimum pH of 8.3.

Dayananda et al, 2014, India carried out the experiment for ‘Domestic wastewater using Fe-Al electrodes’. The glass reactor of 1.3L capacity of dimension 250”70”100 mm was used and sample volume was maintained 1L for every experiment. Iron electrodes were used as anode while aluminum as cathode. The dimension of the electrodes was 90”40”2 mm. The spacing between the electrodes was 50mm. Different set of experiments was conducted used 2 electrodes and 4 electrodes for various voltages such as 5, 10, 15V for electrolysis time of 30min. While using 2 electrodes the removal efficiency of phosphate, nitrate and COD was less than 30% for 15V at 30min but BOD removal efficiency was 80%. Phosphate, nitrate, COD and BOD removal efficiency was 92.98%, 95%, 90% and 95% with 4 electrodes at 30min for 15V.

Nguyen et al, 2014, Korea worked on ‘Enhanced phosphorus and COD removals for retrofit of existing sewage treatment by electrocoagulation process with cylindrical aluminum electrodes’. A series of experiments were conducted to investigate the retrofit ability of removing total phosphorus and COD from wastewater using cylindrical aluminum electrodes in batch and continuous operating modes. The operating parameters were pH, electrolyte concentration, HRT, initial phosphorus concentration and temperature. The applied cell voltages were 3, 4 and 5V with the current densities 7.04 to 16.08 Am-2 in batch mode and from 7.48 to 21.69 Am-2 in continuous mode. The electrolyte used was NaCl. The electrolysis time in the limits of 1- 20min were tired for different wastewater including synthetic wastewater and municipal wastewater. The maximum removal efficiency of TP and COD is 99% and 75% for the above operating conditions.

‘Optimization of electrocoagulation process to treat grey wastewater in batch mode using response surface methodology’ was studied by Karichappan et al, 2014, India. To treat the greywater, the electrocoagulation process was carried out under the different operating conditions such as initial pH, current density, electrode distance and electrolysis time by using stainless steel electrodes. Electrolytic cell was made up of acrylic material of 3L volume but 1.6L of wastewater was used for the all the experiments. The dimensions of the electrodes were 33cm x 6mm. The distance between the electrodes was varied from 4-6cm. The active surface area of the electrodes was 108cm2. The agitation speed was kept constant at 250rpm. NaCl and HCl were used as the supporting electrolyte. After the treatment, wastewater was centrifuged at 6500rpm for 15min and the supernatant was analyzed for TS, COD and FC. Box-Behnken response surface experimental design (BBD) with four factors at five levels was used to optimize and investigate the influence of process variables such as initial pH (4’8), current density (10-30 mA cm-2), electrode distance (4-6 cm) and electrolysis time (5’25 min) on the TS, COD and FC removal. The optimal conditions were found to be: initial pH of 7, current density of 20 mA cm-2, electrode distance of 5cm and electrolysis time of 20min. Under these optimal operating conditions, the experimental removal efficiencies (98.45, 94.75 and 96.34%) were closely agreed with the predicted values (99.87, 95.47 and 97.15%).

Sharma and Chopra, 2013, India worked on ‘Removal of COD and BOD from biologically treated municipal wastewater by electrochemical treatment’. Here, they investigated the effect of current density (CD), operating time (OT), inter electrode distance (IED), electrode area (EA), initial pH and settling time (ST) using Fe-Fe electrode combination on the removal of chemical oxygen demand (COD) and biochemical oxygen demand (BOD) from biologically treated municipal wastewater (BTMW) of Sewage Treatment Plant (STP). The maximum removal of COD (92.35%) from BTMW was found with the optimum operating conditions of CD (2.82 Am-2), OT (40 min), IED (0.5 cm), EA (160 cm2), initial pH (7.5) and ST (60min), while the maximum removal of BOD (84.88%) was found with the ST (30 min) at the same operating conditions. There was no need of pH adjustment of the BTMW during ET as the optimal removal efficiency was close to the pH of 7.5. Under optimal operating conditions, the operating cost was found to be 54.29 Rs.m-3 / 1.08 US$ m-3 in terms of the electrode consumption (78.48 x 10-5 kg Al m-3) and energy consumption (108.48 Kwh m-3).

Iswanto et al, 2013, Indonesia conducted the experiments for ‘Domestic Waste Water Treatment by Electrocoagulation’. In this study, the wastewater treatment reactor consists of electrocoagulation and flocculation unit. The dimension of the electrocoagulation unit was 20cm length, 10cm width, 15cm height. Aluminum plates were used as anode and iron plates as cathode. Each plate has a dimension of 10x10x14cm. The distance between each plate was 0.5cm. The total number of plates used was 34. Flocculation unit have the capacity of 480L with rapid stirring of 150rpm and slow stirring of 60rpm during 20min. Wastewater was collected from settlement and restaurant area. Retention time for each treatment consisted of 5s to discharge 24 L min-1, 10s to discharge 12 Lmin-1 and 20s at the rate 6 Lmin-1. The parameters considered in this study were TSS, COD, BOD5 and NO3. For the settlement wastewater with the retention time of 20s, the removal efficiency of TSS (80.50%), COD (82.10%), BOD5 (85.72%) and NO3 (57.06%) was observed. For the restaurant wastewater, the removal efficiency of TSS (77.26%), COD (55.93%), BOD5 (58.10%) and NO3 (59.70%) was achieved.

In 2012, Sarala, India reported ‘Domestic Wastewater Treatment by Electrocoagulation with Fe-Fe Electrodes’. The electrolytic cell was of 1.2L capacity. In this experiment iron electrodes are used and the sampling is made at the different interval of time i.e., 5, 10, 15 and 20min. Experiments were conducted at different current 0.12, 0.25, 0.36A.The combination effects of current, pH and time to the efficiency of the electrocoagulation process for the removal of COD, TDS, pH, color, chlorides etc. from the domestic wastewater showed that only current and time have correlation with each other. In this process, sludge formed after the electrocoagulation process was removed by filtration. COD was reduced to 90% with increase of contact time for different current. Maximum COD reduction of COD was observed at 20min for 0.25A and 0.36A. It was observed that the experiment conducted at 0.25A for 20min has maximum removal efficiency of COD, TDS, chlorides and suspended solids of 76.9%, 91%, 38.3% and 87.5% respectively.

Yadav et al, 2012, India conducted ‘Removal of various pollutants from wastewater by electrocoagulation using iron and aluminum electrode’. This study dealt with removal of various pollutants from the industrial wastewater by electrocoagulation treatment. Wastewater was collected and treated by electrocoagulation process using iron and aluminum electrodes. The removal of Cr, Zn, Ni and Cu were achieved up to 100, 98.71, 69.22 and 48.08% respectively using aluminum electrode while Cr, Cu, Zn and Ni were removed up to 100, 78.57, 75.48 and 58.68% respectively using iron electrode electrocoagulation. COD, TDS and sulfate were removed up to 83.94%, 46.92%, 74.16% and 83.66%, respectively in aluminum electrode electrocoagulation while the same were removed up to 54.83, 77.39, 52.85 and 60.74% respectively in iron electrode electrocoagulation.

‘Treatment of laundry wastewater by electrocoagulation’ was studied by Janpoor et al, 2011, Iran. Using an undivided plastic electrocoagulation cell of dimension (20cm”10cm”15cm) and aluminum sheets of dimension 20×7.5×2 mm was used as electrodes. The operating parameters were pH, voltage, HRT and number of electrodes. The electrodes spacing was varied 15 and 30 mm. Magnetic stirring of speed 400 rpm was applied for homogenous mixing of the sample. A DC stabilized power source was used to supply constant current (0’2 A) at variable voltage 10, 20 and 30V. The maximum removal efficiency of COD and phosphorus was 89.9% and 90.0 % at 30V, 90min and 1.5cm electrode spacing.

Wang et al, 2009, Taiwan worked on ‘Removal of COD from laundry wastewater by electrocoagulation/electroflotation’. The electrocoagulation unit consists of the electrochemical reactor of 1 dm3 with 3 Al anodes and 3 Al cathodes. The dimension the electrodes was 40mmx30mm. The total surface area of the cathode and anode was 72cm2. The electrode distance was maintained 10mm. The agitation speed was 200rpm. The operating parameters were cell voltage and initial pH. The initial pH of the wastewater was 7.5. To investigate the effect of initial pH for the removal of COD, the pH of the wastewater was adjusted to the desired value, ranging from 2.5-9.5. The COD removal of 66% was observed when the pH of the wastewater is 5.1. To examine the effect of cell voltage on the removal of COD, the experiments were carried out with the different voltages: 1, 3, 5 and 7V. The maximum COD removal was 65% for 7V for 40min ET.

Bukhari, 2008, Saudi Arabia, conducted experiments on ‘Investigation of the electrocoagulation treatment process for the removal of total suspended solids and turbidity from municipal wastewater’. In this study, wastewater samples of 1.2L was collected in an electrochemical cell with the stainless steel electrodes dipped into the sample solution up to an active surface area of 88cm2. The operating parameters were current density and contact time. The different applied currents were 0.05, 0.1, 0.2, 0.4 and 0.8A. The maximum TSS and BOD removal efficiency of 95.4% and 99% respectively was observed at the current of 0.8A at the ET of 5min.


Race, class, and gender – importance in sport: writing essay help

A good place to start with a discussion about race, class, and gender and its importance in sport is to talk about the way that sociologists or social theorists broadly talk about these issues. There seems to be a recurring theme with anyone who writes theoretically about these issues. Social theorists are regularly critiqued for not including enough of one social inequality or the other, lacking nuance in gender, race, class, ability, sexuality, and so on. It is possible, in fact probable, that all theories on these subjects could be critiqued in this way. The field of social inequalities is simply too broad. It covers such vast distances of experiences, ideologies, cultures, institutions, and structures that some argue it is impossible to have singular “grand theories” (not necessarily in the historical sense, but simply ones that attempt to holistically cover things) that can accomplish such a task.

The way I hope to accomplish this task throughout this section, as well as other sections in this area, is by doing what Patricia Hill Collins calls a strategy of “dynamic centering”. This strategy of studying social inequalities involves “foregrounding selected themes and ideas while moving others to the background” (2008:68). In her case, this means emphasizing different aspects of oppression and resistance in different ways, at different times. The benefit to dynamic centering of ideas is that it allows the author, as well as the reader, to more closely examine particular types of social inequality. Patricia Hill Collins is best known for her work on intersectional research, and readily acknowledges that it, too, is generally “partial”. The comparative nature of looking at race and class, or race and gender allow us to understand the similarities and differences in those works (Collins 2008).

As a final thought, Collins calms criticism so eloquently by exclaiming:

“There is a rush to tidy up the messiness of always having to say race and class and gender and sexuality and ethnicity and age and nationality and ability by searching for overarching terms that will capture this complexity. The term “difference” tries to do this kind of heavy lifting, typically unsuccessfully. If we are not careful, the term “intersectionality” runs the same risk of trying to explain everything yet ending up saying nothing.” (Collins 2008)

This section begins by discussing the relevant race, class, and gender theories separately are pertinent to sport. But throughout there is an attempt to interject the intersectional ideas of what is missing in those theories, or how they relate. This is not to say that it will be able to address every form of intersecting or overlapping oppression. That, knowing limitations, is not possible and probably not a fruitful endeavor.

This essay will, however, address the major theories as well as related works to understanding sport through race, class, and gender. For the purposes of clarity, I will split those “theoretical camps” along those lines. After the discussion of each separately, there will be a section to address intersectional research and its fit into sport. Finally, the conclusion will address insights from the sociology of sport and how those are more useful to broader understandings of race, class, and gender.

In general, there is a theoretical consistency with studying race, class, and gender in sport. As a major cultural and economic institution, sport is generally one of the most widely understood and simultaneously one of the most theoretically underdeveloped areas of sociology (Carrington 2013). Cases have been made by sociologists of sport (whether they derive from different backgrounds is another case) as well as journalists that sports indeed do matter (Carrington 2012). One needs to look no further than our own university to see recent examples of why sport can be an important cultural institution.

In February 2014 Michael Sam, an All-American defensive lineman for the Tigers came out as gay, and was the first openly gay man drafted into the major American sports: Football, Baseball, Basketball and Hockey (Connelly 2014; Wagoner 2014). A year later, Missouri football players joined in on campus protests by the group Concerned Student 1950 over the “racist, sexist, homophobic, etc., incidents that have dynamically disrupted the learning experience” of students on campus (Tracy and Southall 2015). It also dovetailed the protests that had happened over racial injustices that had happened two hours west, in Ferguson where another unarmed black man was shot by police. The protest by the players appeared to be the tipping point of the protest, as it resulted in the firing of the Chancellor as well as the President. The players wielded the most power available to them as they threatened to boycott the next football game against BYU, a move that would have cost the University one million dollars.

The events over the past few years at the University are just one of many microcosms where sport is increasingly relevant and political. With the current protests of the police brutality and racial injustice by NFL players, started by Colin Kaepernick, sport has come into the limelight for its focus on inequality. All of this is to say that sport is an key aspect of society, and worth investigating further. Overall, sport can be better understood by using the breadth of literature and theory that exists outside of itself. But there is also a reciprocal nature to this question, as the literature on inequalities could greatly benefit by studying sport, and adopting understandings from the studies located there.

Theories and Studies of Race, Class and Gender that are important to sport.

A field as wide as “social inequalities” could be a large enough umbrella to fit nearly any sociological study. Therefore, it is a somewhat difficult task to pick out just a small number of sociological theories that would directly benefit the subfield of sport. Some studies that I think are worth exploring and investigating with more space and time would include critical race theories (CRT) that can be very important in understanding racial dynamics. Here, I will focus on a few “branches” of the larger social inequalities “tree”, that would be worth adopting further into sport.


Race may be the most theoretically developed area of sport. As the first Sport Sociologist, Dr. Harry Edwards wrote what is considered to be one of the first Sport studies, The Revolt of the Black Athlete (1969) as well as the first Sociology of Sport textbook (1973). Edwards was also directly linked to helping create the idea for the 1968 Olympic protest by John Carlos and Tommy Smith, who’s picture is now known worldwide. Dr. Edwards writings on race were truly transformative and ahead of their time, changing understandings about race and structural inequalities facing African Americans. Although the term was not yet created, his work would likely now be considered intersectional based on its ideas centered around masculinity, race, and class.

As far as race theories (or theorists) that help us understand the Sociology of Sport, a good place to start with Michael Omi and Howard Winant’s Racial Formation theory. Omi and Winant have written multiple updates to their 1994 text, helping clarify the theory and including more relevant examples. They define racial formation as “the sociohistorical process by which racial identities are created, lived out, transformed, and destroyed” (Omi and Winant 2014:109). Historically, the black/white binary has dominated the way people think and talk about race (Bonilla-Silva 2014). Racial formation complicates this idea by understanding race as a process.

One of Omi and Winant’s key concepts of their theory is what they call “racial projects”. Racial projects are a space in which social structures and cultural representations clash. Many theoretical paradigms in race (but also class and gender) are primarily focus on either a) structural phenomena that are unable to account for cultural patterns, meanings, and identities or b) systems of culture, identity and signification. Frequently, theorists are uncomfortable with the ambiguity and murky nature of operating within those two boundaries (the implications of this will be discussed further in a later essay). It is in this space where racial projects exist.

The authors define racial project as “simultaneously an interpretation, representation, or explanation of racial identities and meanings, and an effort to organize and distribute resources (economic, political, cultural)”(Omi and Winant 2014:125). Racial projects can occur on both the large scale as well as the small scale, and can be carried out by anyone regardless of their social position.

Included in these ideas of racial projects are things as small as the decision to wear dreadlocks and as large as voting rights laws or civil rights movements (Omi and Winant 2014:125). Using this definition, we should consider the actions and discourse over social media between Jeremy Lin and Kenyon Martin. Lin is the first American NBA player of Taiwanese descent to play in the NBA. His story as a whole has been widely studied in sociology. Kenyon Martin is a retired African American NBA player. To summarize the recent issue, Lin decided to premiere in the most recent NBA season with dreadlocks, and was criticized by Martin for wanting to “be black” saying “Do I need to remind this damn boy that his last name Lin?” to which Lin responded with:

“At the end of the day, I appreciate that I have dreads and you have Chinese tattoos [because] I think its a sign of respect. And I think as minorities, the more that we appreciate each other’s cultures, the more we influence mainstream society” (Begley 2017)

Both the initial act of having dreadlocks, as well as both responses could be different types of racial projects. Lin challenged the system and well as the cultural signification and history that is deeply embedded in dreadlocks. Martin had a racial project of his own, that sought to reaffirm the structures and cultural significance of hair choice. Lin’s response was yet another, one that sought to subvert the system to reclassify the understanding of cultural appropriation and its ties to race.

Although the Lin/Martin example is a micro-instance, it is reflective of how sport can recapitulate our ideas about race through racial projects. Similarly, one could argue that Jack Johnson beating “great white hope”, Joe Louis fighting Italian Primo Carnera in 1935, and certainly Jesse Owens in the 1936 Olympics would be termed “sporting racial projects”.

This idea of “sporting racial projects”. This idea is scarcely developed. Carrington discusses the invention of the natural black athlete as a “global sporting racial project” that was an attempt to “other” blackness into sub-humanized category (2010). In Carrington’s own words “Sports help to make race make sense and sport then works to reshape race” (2010:66). Although he provides the basic definition and connection to the idea of sport, he merely scratches the surface of the possibilities and importance of racial projects to sport.

All of the above previously discussed University of Missouri examples are sporting racial projects. Many of them have pushed unconscious ideas about race to the foreground of discourse. Michael Sam and the implications for race and sexuality. He is simultaneously subverting ideas about sexuality and masculinity, while reaffirming ideas about blackness and athletics. The football team protesting is a racial project challenging the power structure of white dominated and white centered institutions (both sport and the university). Simultaneously, the backlash by white boosters, administration, and fans, run “counter” projects that overlap and compete. Their emphasis on colorblindness operates between the structural and cultural level.

Racial formation theory in general and racial projects specifically are a useful theoretical tool to understand the dynamics of sport and how it intersects with race. But there has been critiques from many different areas of how “useful” a theory it actually is. Feagin and Elias (2013) critique racial formation theory for not being explicit enough with their critique of the racial framework as they see it. Feagin has especially built his career on what he coins “systemic racism theory” (Feagin 2013, 2014). It directly confronts the hierarchical nature of racial oppression in the United States, and implicates whites in the process. The theory includes more grounded ideas than that of racial formation, by discussing the different levels on inequality and how whites use power to oppress racial minorities (although many times Feagin is using a black/white essentialism). To Feagin and Elias, there is not enough critical theory for racial formation to “work” as a theory. Ironically enough, Feagin and Elias’ systemic racism theory is also critiqued, as it privileges race and does not include enough theory of gender and sexuality as a component for oppression (Harvey Wingfield 2013)

The arguments that have been levied against racial formation theory are valid. There is a substantial lack of critical theory implied in racial formation theory. Omi and Winant (2013) have argued that their theory still works, as its goal is not to attempt to pin down the racial classification system as it currently exists. It’s much more ambitious goal is to be able to speak to race as it operates across time and space. Still, it is debatable that it succeeds in doing so.

It would be particularly helpful to revisit the idea regularly with current events that weren’t discussed. Colin Kaepernick, Jemele Hill, Trump, NFL Owners, and the recent World Series racism have all happened in the last couple weeks. Racial formation can help us better historically place these ideas and what they mean, as well as understanding social movements that occur within and around the “field” of sport (in a Bourdieusian sense).

Other contemporary theories of race that are useful in understanding sport include the aforementioned Feagin theory on systemic racism, and Bonilla Silva’s theory of racialized social systems and its implications for colorblind ideologies (Bonilla-Silva 1997, 2014).


With class and stratification being a core tenant of sociology, it would be impossible to list every theory and branch, or even every school of thought here. So I will not address, even though there is most definitely a pertinence, Marx or conflict approaches to class. Although their contributions to the general field of sociology are numerous and critical, I am of the opinion that for the study of sport there are more important theories.

Bourdieu (2011) says there are three guises of capital: economic, cultural, and social. Economic is directly convertible into money, or institutionalized as property. Cultural is convertible into economic capital, or institutionalized as education credentials. Social is connections, convertible into economic, institutionalized as title or nobility.

He goes on to argue that there are three forms of cultural capital. The embodied state which are long lasting dispositions of the mind and body. Parts of the embodied state include external wealth converted into part of the person (habitus). It can be obtained unconsciously like an accent. It is in some ways linked to biological capacity, its often misrepresented a legitimate competence rather than as capital. Finally, it derives a scarcity value from its position of cultural capital. The profits of this form of cultural capital is distinction. According to Bourdieu transmission of cultural capital through families is:

is “no doubt the best hidden form of hereditary transmission of capital, and it therefore receives proportionately greater weight in the system of reproduction strategies…” (p.245)

The second form of cultural capital is the objectified state. These can be appropriated materially (economic capital) or symbolically (cultural capital). It is defined in the relationship with cultural capital in its embodied form, and can be yielded as a weapon and a stake in the struggles which go on in the fields of cultural production.

Finally, the institutionalized state (education) is the final form of cultural capital. Bourdieu states that academic ability itself is a product of time and cultural capital. Viewing education as cultural capital helps us se educations role in the social structure. We could view education as a “certificate in cultural competence” (p.248). This finally makes it possible to compare “conversion rates” for cultural and economic capital.

As we have seen in earlier discussions and sections, cultural capital is key to understanding what a society values (distinction) as well as the different ways that culture operates with class. Building off of this, a couple theorists adopt Bourdieusian ideas and employ them in interesting ways.

Annette Lareau’s (2011) book Unequal Childhoods, describes two differences in the logic in childrearing. The first is centered on what the author calls “concerted cultivation,” which is characterized by viewing children as a project to be cultivated. Parents who subscribe to this method of child rearing seek opportunities for growth and take an active approach in the formation and development of their child. They “invite” and encourage the child to interact within the adult world and often treat them as “equals.”

The second logic in childrearing is centered on the “accomplishment of natural growth,” which views childhood as a somewhat natural and organic process that requires little adult intervention. Parents who subscribe to this logic are less “hands on” and maintain a separation between the adult world and the child world. While Lareau is quick to point out that the dominant social institutions that children come in contact with (namely school), value “concerted cultivation” and stress opportunities for parents to further this plight, there is a clear class distinction on the use of each method.

Concerted cultivation was by and large something that middle class parents subscribed to more frequently that lower and working class parents. Arguably, the access to resources that lend themselves well to the concept of “concerted cultivation” are more easily accessed for the middle class families in the study than the lower and working class families. To be clear, the opportunities for concerted cultivation were more readily available, not necessarily the actual event itself (often the events themselves take an enormous amount of time on the behalf of the family even going so far as being the center of the families social calendars). The interactions have many benefits for the child as children learn: ease in interacting with adults, viewing themselves as equals, developing their voice, larger vocabularies, negotiation skills, and time management skills. However, because their time is constantly regulated by adults, children often have trouble managing “unmanaged time,” are often disconnected from family members, lack interactions with children of different age groups, often feel “bored” and/or exhausted, and develop a sense of entitlement. The skill sets that are developed for children with regard to the “accomplishment of natural growth,” are quite different.

Parents who are committed to the “accomplishment of natural growth,” view their roles quite differently. Often from working class and poor backgrounds families’ concern for children is being able to meet their basic needs. Navigating children throughout the day and providing them their basic needs often takes an enormous amount of time and effort. These families often rely on a vast network of friend and kin relationships for resources (cars, bus passes, phone calls, clothing, etc.). As a result of the effort to provide for children (navigating the bus system, public aid, etc.), children often have close relationships to kin, are resourceful, create ties with children of different age groups, manage their own time, engage in creative activities and have quite a bit of autonomy. Therefore, these children have an emerging sense of restraint, yield to adult authority, and often have difficulty interacting within some social institutions (medical, school, etc.). While there is merit in the development of both skill sets, they are not equally valued by the dominant social institutions in society. Lareau, notes that the skills learned by “natural growth” while important are rendered somewhat “invisible” and these skills (creativity, respect for authority) are rarely valued/praised to the degree that skills (negotiation, language, time management) learned under concerted cultivation receive.

These ideas of concerted cultivation and natural growth are especially useful when trying to understand how class operates in relation to sport. In some cases, the parents are making huge personal sacrifices to give their children “values” (or cultural capital). Sport, commonly viewed as a positive area for socialization and growth, is just one of these cultural arenas that has to be “cultivated”.

Bourdieu combined with Lareau and Prudence Carter’s ideas on the “culture of power” in school (Discussed in another essay) all can be important to understand the field of sport. They are important in understanding the forms of culture that are privileged, and the importance of different types of capital other than economic forms.


Of the many areas of sociology that touch sport, none may be as developed or shaped by the subfield as much as the study of gender. Sport, as a physical activity, have traditionally been spaces where men can prove their physical superiority over each other. To this day, sport continue to be male dominated, male identified, and male centric (Coakley and Pike 2009)spaces that shape our ideas about masculinity and femininity. But much like race and class, it is also a place where ideologies are contested in a much grander form.

The first theory that comes to mind as central to studying sport and gender is hegemonic masculinity. Hegemonic masculinity is a theoretical concept first proposed from a field study of social inequality in Australia, which provided data of interwoven hierarchies of gender (and class) that were active projects in gender construction (Connell 1982; Kessler et al. 1982). The most widely cited, however, came from Connell(1987). According to that work, hegemonic masculinity is “understood as the pattern of practice that allowed men’s dominance over women to continue.” (Connell and Messerschmidt 2005:832).

This meant that there were multiple forms of masculinities that existed in the hierarchy. Some were hegemonic, others subordinated. This wasn’t an exercise in statistics. It’s not as if the form of hegemonic masculinity that they were studying was practiced by the most people. In fact, it may be a minority of people. What was significant was that other man had to position themselves in relation to this form of masculinity.

Sport may be the pinnacle of hegemonic masculine practice. Hegemonic masculinity, according to Connell and Messerschmidt (2005) could be achieved through culture, institutions, and persuasion. Some of the earliest adopters of this hegemonic masculinity framework were sociologists of sport. Michael Messner became renowned for his use of the topics on media representation of masculinity, and its connection to violence and homophobia (Messner 1992; Messner and Sabo 1990). Messner (1993) argues that forms of softer or sensitive masculinity are developing but don’t necessarily contribute to the emancipation of women. (Messner 1993: 725) Linked to this is Messner’s (2007) analysis of the changes in the public image of Arnold Schwarzenegger, e.g., illustrates what he calls an “ascendant hybrid masculinity” combining toughness with tenderness in ways that work to obscure – rather than challenge – systems of power and inequality.


The amalgamation of the above points leads logically leads us to theories of intersectionality. At different points reference has been made to intersections of race, class, and gender. But it truly may be a facile endeavor to try and discuss the relevance of any of those theories separately. Much of the research in the area of intersectionality tells us as much.

Davis (2008) argues that intersectionality has been a ‘buzzword’ of feminist theory ever since its inception. As Crenshaw (1991) writes, this is because an intersectional approach is crucial to addressing the experiences of ethnic minority women for two reasons; the first is ethnic minority women’s experiences and political struggles have been largely neglected by mainstream feminist movements and second, because anti-racism discourses have focused too heavily on the experiences of men, rendering invisible the experiences of women.

An example which demonstrates the impact of structural intersectionality is found in domestic violence cases where race and class formations make women of color’s experiences of rape, violence and remediation ‘qualitatively different from [those] of white women’ (Crenshaw 1991: 1245). Intersectional ideas are also linked closely to Patricia Hill Collins’ (1990)matrices of domination which is a paradigm that different forms of oppression are interconnected. Intersectional ideas can be inclusive of all of the above forms of inequality (race, class, and gender), and although it is considered a “buzzword” that risks losing meaning, it is important for my research especially in understanding race, masculinity, and class.

Sociology of Sport and Its Influence

Hopefully I have illuminated many of the important works on race, class, and gender. In many of the instances, I included the connections to sport, already. I would like to mention some of the other main works in sociology of sport that are critical to understanding inequality.

Much of Messner’s work on gender is essential. He has arguably done more than anyone in the area. For race, Dr. Harry Edwards classic studies are important to set up sport as an area to study inequalities. Of course, there are many race studies such as CLR James Beyond a Boundary that looks at colonialism and sport (cricket). Hartmann has written on Midnight Basketball and its implications for neoliberal society. Brooks and May both looked at race and basketball, and would be considered important contemporary contributions.

All of these readings have in common a challenging of ideas in race, class, and gender. Sport, as one of the largest cultural institutions in the US, will continue to be “contested terrain” for these intersecting and overlapping subject areas, and will continue to challenge and recapitulate our understandings of social theory and global inequality.


Portable pneumatic drill – project report


In work shops and automotive shops, there are frequent needs of tightening and smoothening of screws, drilling, boring, grinding machines.

Huge and complicated parts can not be well machined with the help of ordinary machine. In electrical drilling machine power consumption is too high whereas accuracy is not good. Drilling the hole in particular workpiece becomes a time consuming process and human effort is also large.

Hence by application of pneumatics human effort becomes less, accuracy becomes more precise and time is saved. In this project the pneumatic cylinder with piston which is operated by an air compressor will give the successive action to operate this drilling operation.

Design and fabrication of portable pneumatic drilling machine will be done using basic principles of pneumatics.

Chapter 1 Introduction

1.1 Introduction

Power tools must be fitted with guards and safety switches; they are extremely hazardous when used improperly. The types of power tools are determined by their power source: electric, pneumatic, liquid fuel, hydraulic, and powder-actuated.

Figure 1.1 Different type of drilling machine

1.2 Pneumatic System

Figure 1.2 Pneumatic system

There is an constant supply of air in atmosphere to produce compressed air. This compressed air can be generated by various sources such as compressor, air cylinder, etc. Moreover, the compressed air is not affected by distance, as it can easily be transmitted through pipes. After that with the help of pressure relief valve it can be directly supplied to the compressor.

A pneumatic system is a system that uses compressed air to transmit and control energy. Pneumatic systems are used in controlling train doors, automatic production lines, mechanical clamps, etc.

1.3 Drilling Machine

Figure 1.3 Drilling Machine

Drilling machines are mainly used to originate through or blind straight cylindrical holes in solid rigid bodies and/or enlarge pre-machining holes of different diameter.

Ranging from about 1 mm to 40 mm of varying length depending upon the requirement.

The diameter of the drill in different materials excepting very hard or very soft materials like rubber, polythene, rock etc.

1.4 The different types of drilling machines

1. Portable drilling machine (or) Hand drilling machine

2. Sensitive drilling machine (or) Bench drilling machine

3. Upright drilling machine

4. Radial drilling machine

5. Gang drilling machine

6. Multiple spindle drilling machine

7. Deep hole drilling machine

1.4.1Pneumatic Drilling Machine System

Pneumatic Drilling Machine is portable drill with features of explosive-proof, large torque, high rotate speed, light weight, suitable dimension, high efficiency, stable structure and convenient maintenance. Mainly used for drilling holes for exploring and discharging water and gas, also used for bolting tunnel side and drilling explosive holes on soft rock, coal and half-coal layer.

Chapter-2 Literature Review

2.1 Literature Review

A.Karthik, R.Krishnaraj, Nunnakarthik, R.Kumaresan, S.Karthik, R.Murali, ‘Single Axis Semi Automatic Drilling Machine with PLC Control”, 10.15680/IJIRSET.2015.0403009 [1] had represented hydraulic cylinder which is used to the drill the workpiece of the given size. In this model the solenoid valve is used which is used to control the the flow of the fluid. Limit switch is used which is used in adjusting the height of the workpiece to be drilled. And programmable logic controller is used to control the whole drilling operation hence accuracy and time is saved by this model.

Manish Kale, Prof. D. A. Mahajan, Prof. (Dr.) S. Y. Gajjal, ‘A Review Paper on Development of SPM for Drilling and Riveting Operation”, International Journal of Emerging Technology and Advanced Engineering, Volume 5, Issue 4, April 2015 [2] had represented the paper discuss the case study and comparison of productivity of component using conventional radial drilling machine and special purpose machine(SPM) for drilling and tapping operation. In this case study, the SPM used for 8 multi drilling operation (7 of ”6.75 and ”12), linear tapping operation of ”12 and angular tapping operation of ”5.1 of TATA cylinder block. In this paper the following studies are carried out 1. Time saved by component handling (loading and unloading), using hydraulic clamping, 2. Increase in productivity both qualitative and quantitative, 3. Less human intervention, indirectly reduction in operator fatigue, 4. Less rejection due to automatic controls, and 5. Increase the profit of company.

Mohammad Javad Rahimdel, Seyed Hadi Hosienie, ‘The Reliability and Maintainability Analysis of Pneumatic System of Rotary Drilling Machines”, Springer, 07 November 2013 [3] had Trend and serial correlation tests shown that the TBF data are iid, therefore, RP technique can be used for reliability modeling. The reliability of pneumatic system was calculated by the use of best-‘tted distribution. Data analysis and ‘nding the best-‘t distributions were done using Easy Fit 5.5 software. The Kolmogorov’Smirnov (K’S) test has been used for selecting the best distributions for reliability analysis. The results of data analysis with top six ‘tted and the best-‘tted distributions.

Prof. P.R. Sawant, Mr. R. A.Barawade, ‘Design and Development of Spm-A Case Study in Multi Drilling and Tapping Machine’, International Journal of Advanced Engineering Research and Studies, Vol. I, Issue II, January-March, 2012/55-57 [4] had represented the case study and comparison of productivity of component using conventional radial drilling machine and special purpose machine(SPM) for drilling and tapping operation. In this case study, the SPM used for 8 multi drilling operation (7 of ”6.75 and ”12), linear tapping operation of ”12 and angular tapping operation of ”5.1 of TATA cylinder block. In this paper the following studies are carried out

Time saved by component handling (loading and unloading), using hydraulic clamping,
Increase in productivity both qualitative and quantitative,
Less human intervention, indirectly reduction in operator fatigue,
Less rejection due to automatic controls, and
Increase the profit of company.

A.Sivasubramaniam, ‘Design of Pneumatic Operated Drill Jig for Cylindrical Component”, IJSR-International Journal of Scientific Research, Volume 3, Issue 3, March 2014 [5] had represented the growth of Manufacturing industry and its need for increased productivity is greatly enhanced by the nature of the industry, their possible work culture and most important thing is the use of improvised techniques and systems. The concept of increased productivity, reduced lead time, high quality and precision can be achieved by making some improvisation in available systems and techniques. In this paper we would deal with a design of pneumatic operated drill jig which can be universally used for a specific drill size. We have designed the jig especially for cylindrical components which involves drilling of hole of size 6mm and 12mm diameter. This design would greatly help in increased productivity of jobs in mass production.

Ogundele, O. J.,Osiyoku, D. A. Braimoh, J., and Yusuf, I., ‘Maintenance of an Air Compressor Used in Quarries”, Scholars Journal of Engineering and Technology (SJET), 2014; 2(4C):621-627 [6] had represented how the aie is mainted in all the system during its operating condition . Main moto of this model is the maintenance of drilling machine on which the drilling operations are carried out.

2.2 Problem Definition

The research survey was reflected different drilling system such as Single Axis Semi Automatic Drilling Machine, SPM for Drilling, Pneumatic System of Rotary Drilling Machines, Multi Drilling and Tapping Machine, pneumatic Operated Drill Jig for Cylindrical Component etc.
Some research paper indicated about design and analysis different type drilling machine system.
There was proposed work done on pneumatic drilling machine for human comfort.

2.3 Objectives

1. To after Study details of pneumatic drill machine operate it as simpler.

2. To maintain it easy by worker.

3. To operate as faster with higher torque.

4. To used by compressed air so low power consumption.

5. Operating cost as lowest as possible to maintain.

6. To reduce the disadvantages of electrical drill.

Chapter 3 Analysis of Mechanical Component of Pneumatic Drilling Machine

3.1 Pneumatic Control Component

3.1.1 Pneumatic cylinder

An pneumatic cylinder is a device which operates on the air and has input of compressed air i.e. pneumatic power is converted in to mechanical output power, by reducing the pressure of the air to that of the atmosphere.

a) Single acting cylinder

Single acting cylinder is the cylinder in which the piston acts on the single side of the cylinder.

b) Double acting cylinders:

Double acting cylinder acts on the both side of the cylinder. In this piston acts on the both side. Direction and flow control valves are used in the double acting cylinder.

3.2 Generally Used Materials

Table 3.1 Cylinder Tube Material

Light Duty Medium Duty Heavy Duty

Plastic brass tube brass tube

Hard drawn Aluminum tube Aluminum Casting steel tube

Hard drawn Brass tube Brass, Bronze, Iron or Casting, welded steel tube

Table 3.2 End Cover Material

Light Duty Medium Duty Heavy Duty

Aluminum stock (Fabricated) Aluminum stock (Fabricated) Casting

Brass stock (Fabricated) Brass stock (Fabricated)

Aluminum Casting Aluminum, Brass, iron or steel casting

Table 3.3 Piston Material

Light Duty Medium Duty Heavy Duty

Aluminum Casting Brass Aluminum Forgings,

Aluminum Casting

Bronze (Fabricated) Bronze

Iron Casting Brass, Bronze, Iron or

Steel Casting

Table 3.4 Mount Material

Light Duty Medium Duty Heavy Duty

Aluminum Casting Aluminum, Brass and steel casting High tensile

Steel Casting

Light Alloy (Fabricated) High tensile

Steel Fabrication

Table 3.5 Piston Rod Material

Light Duty Medium Duty Heavy Duty

Mild Steel ground and polished Generally preferred chrome plated

Stainless Steel Ground and Polished Less scratch resistant

3.3 Valves

3.3.1 Solenoid Valve

The directional valve is one of the irrefutable parts of a pneumatic system. Commonly known as DCV, this valve is used to control the direction of air flow in the pneumatic system. The directional valve does this by changing the position of its internal movable part.

A solenoid is a device that converts electrical energy into line motion and force. These are also used to operate a mechanical operation which in turn operated the valve mechanism. Solenoid valves can be push type or pull type. The push type solenoid valves are one in which the plunger is pushed when the solenoid is energized electrically. The pull type solenoid valves are one is which the plunger is pulled when the solenoid is energized.

3.3.2 Parts of a Solenoid Valve.

1. Coil:

The solenoid coil is made of copper. The layers of wire are separated by layers which are insulated. The coil is covered with a varnish which is best material that is not affected by solvents, moisture, etc.

2. Frame:

Solenoid frame is made of laminated sheets, it is magnetized when the current passes through the coil. Then coil attracts the plunger which is made of metal to move. The frame has provisions for attaching the mounting. They are usually bolted or welded to the frame.

3. Solenoid Plunger:

The solenoid plunger is formation of steel laminations which are riveted together under high pressure, so that there will be no movement of the lamination with respect to one another. At the top of the plunger a pin hole is placed for making a connection to some device. The plunger is moved by a which is magnetize in nature and in one direction and is usually returned by spring action.. In many applications it is necessary to use explosion proof solenoids.

3.4 Solenoid Valve (or) Cut Off Valve

It is used to control the direction of flow of liquid in case of hydraulics and air in case of pneumatics.

3.4.1 Flow control valve

In any fluid power circuit, flow control valve is used to control the speed of the actuator. The flow control can be achieved by varying the area of flow through which the air in passing. When area is increased, more quantity of air will be sent to actuator as a result its speed will increase. If the quantity of air entering into the actuator is reduced, the speed of the actuatoris reduced.

3.4.2 Pressure Control Valve

The main function of the pressure control valve is to limit (or) control the pressure required in a pneumatic circuit. Depending upon the method of controlling they are classified as

Pressure relief Valve2.

Pressure reducing Valve

3.5 Drilling Head

3.5.1 Barrel

It contains hollow cylinder and it is the part of the frilling head.

3.5.2 Shaft

It’s made up of mild steel. It is a straight rod having a step. It is supported by two bearings in the cylinder. The diameter of rod is 15 mm for a length of 180 mm and 13.5 mmdiameter for 22 mm length. The fan is fitted on the shaft through flanges. The fan is fixed to flanges and the flanges are fixed to the shaft through drilled holes.

3.5.3 Couplings

It is used to fasten the shaft with flanges and also transmit the motion.

3.5.4 Flanges

Its arrangement is made in such a way that the drilling hole and tool coincide with each other.

3.5.5 Vane

Due to rotation of vane motion is transmitted to the shaft..

3.6 Hoses

Hoses used in this pneumatic system. These hoses can withstand at a maximum pressure level of 10 N/m”. it is used to transmit air flow from compressor to the system.

3.6.1. Connectors

There are 3 connectors in our system. It is used to connect various valves such as flow , direction control valves , etc.

Chapter 4 CAD Modeling and Calculation of Pneumatic Drilling Machine

4.1 Pneumatic components and its specification

The pneumatic auto feed drilling machine consists of the following components:

1. Double acting pneumatic cylinder

2. Solenoid Valve

3. Flow control Valve

4. Connectors

5. Hoses

1. Double acting pneumatic cylinder

Technical Data

Stroke length : Cylinder stoker length = 80 mm

Piston diameter: 40 mm

Piston rod: 25 mm

Quantity: 2

Seals: Nitride material

End cones: Grey cast iron

Piston: 10 bar

Media: Atmospheric Air

Temperature: 0-95 ” C

Pressure : 5 N/m”

2. Solenoid Valve

Technical data

Size: 0.6355 x 10-2 m

Part size: G 0.6355x 10-2 m

Max pressure: 0-12 bar

Quantity: 1

3. Flow control Valve

Technical Data

Port size : 20 mm

Pressure: 0-8 bar

Media : Atmospheric Air

Quantity : 4

4. Connectors

Technical data

Max working pressure: 10 bar

Temperature: 0-115 ” C

Fluid media: Air

Material: Brass

5. Hose Pipes

Technical data

Max pressure: 9 bar

Outer diameter: 10mm

Inner diameter: 5 mm

4.2 General machine Specifications

Drill unit

Short capacity: 0.6355 x 10-2 m

Barrel diameter (ID): 50 mm = 50 x 10-3m

Clamping unit

Clamping: Auto clamping

Max Clamping Size: 110 mm = 0.11m

Pneumatic unit

Type of cylinder: Double acting cylinder

Type of valve: Flow control valve & solenoid valve & Direction control valve

Max air pressure: 9 bar

General unit

Size of machine (L x H) : 0.7100 m x 0.7100 m Weight : 15 kg

4.3 Design Calculations

Max pressure applied in the cylinder (p) : 10 bar

Area of cylinder (A) : (3.14 D”) / 4

: 1256 mm2

Force exerted in the piston (F) : Pressure x area of cylinder.

= 1000000 x 1.256

= 1256 kN

( for maximum pressure, not working pressure)

4.4 CAD Tool-Solid Work 2015

Solid Works 2015 is 3D mechanical design system built with adaptive technology and solid modeling capabilities.

The Solid Works 2015 software includes features for 3D modeling, information management, collaboration, and technical support that you can:

Create 3D models and 2D drawings.
Create features, parts, and subassemblies.
Manage thousands of parts and huge assemblies.
Use third-party applications, with an (API).
Collaborate with multiple designers in the modeling process.
Link to web tools to access resources, share data, and communicate with colleagues.
Use the integrated (DSS) for help as you work.
Better accuracy with appropriate analysis and design.

4.5 Working with assemblies

Turn off visibility of components. Access the parts we need and update graphics faster.
Use design representations.
Turn off adaptivity of parts and vice versa.
Assign different colors to components. Select colors from the Color list on the Standard toolbar.
Use the browser to find components.

Fig.4.1 Detail view drawing of base of pneumatic drilling machine

The structures of pneumatic drilling machine is divided in to two part one for X-axis which axis for work piece like rectangle block and another for Y-axis for movement of Z-axis which having a tool for 2 D hole cutting.

Fig.4.2 Detail view drawing of pneumatic drilling machine Structure

Fig.4.1 and 4.2 are reflected detail drawing of both structure of base and detailed view respectively.

Using part features creates all components of structure. All assemblies are created using various components (part) by constrained there relative motion.

Using part modeling environment to create structure.

First to make geometry of standard section pipe with respect their practical data to measure thickness of plate and amount of extruded part by using extrude command in feature operation.

Further using new sketch on base extruded component and draw sketch on existing extruded feature to identifying model width.

As shown in Figure 4.3 to 4.6, there are different orientations of Pneumatic Drilling Mahcine Structure such as isometric view, front view, top view and side view.

Fig.4.3 Isometric view of Pneumatic Drilling Machine Structure

Fig.4.4 Front view of Pneumatic Drilling Machine Structure

Fig.4.5 Top view of Pneumatic Drilling Machine Structure

Fig.4.6 Side view of Pneumatic Drilling Machine Structure

The compressed air from the air compressor is used as the basic force zone for this operation. One Single acting and double acting cylinder is used in this machine .The air from the compressor enters into the flow control Valve and then it comes in contact with direction control valve. Air enters in to the cask through one way and the two way of air enters to the solenoid valve. When air enters to the cylinder 1, due to pressure difference work is done on the cylinder and it is pressed and when air enters to the other cylinder due to pressure difference drilling operation takes place as the drilling head comes down and drills the work piece. After this operation the cylinder releases the head with the help of arm and drilling head comes to its original position.

4.7 Factors Determining the Choice Of Materials

The various factors which determine the choice of material are discussed below.

1. Properties:

The material selected must posses the necessary properties for the proposed application. The various requirements to be satisfied can be weight, surface finish, rigidity, ability to withstand effect from chemicals, service life, reliability, maintainability etc. The following three types of properties of materials affect their selection

a. Physical

b. Mechanical


The various physical properties concerned are melting point, Thermal Conductivity, Specific heat, coefficient of thermal expansion, specific gravity, electrical Conductivity, Magnetic purposes etc.The various Mechanical properties are strength in tensile,shear, bending, torsional and buckling load, fatigue resistance, impact resistance, elastic limit,endurance limit. The various properties concerned from the manufacturing point of view are.

Ability of cast
Ability of weld,
Ability of forging,
surface properties,

2. Manufacturing Case:

Sometimes the demand for lowest possible manufacturing cost or surface qualities obtainable by the application of suitable coating substances may demand the use of special materials.

3. Quality Required:

The quality required for the market selling point of view should be accurate and good enough to be sold. So, according the advanced technologies in the field of drilling, forging, casting the quality of raw material as well as finished product should be such that to take tough competition in the market.

4.Availability of Material:

Some materials may have shortage or in short supply. It then becomes mandatory for the designer to use some other material which may not be a perfect element for the material designed.The delivery of materials and the delivery date of product should also be set such that the deal can be made in time without obstacles.

5. Space Consideration:

Sometimes high strength materials have to be selected because the forces involved arehigh and the space limitations are there.

6. Cost:

As in any other problem, in selection of material the cost of material plays an important part and should not be ignored. Some times factors like scrap utilization, appearance, and non-maintenance of the designed part are involved in the selection of proper materials. The cost should be optimum so it wull be helpful to customer as well as manufacturer.

Table 4.1 List of Materials

Sr. No. Description Qty Material

1 Double acting pneumatic cylinder 1 Aluminum

2 Solenoid valve 2 Aluminum

3 Flow control valve 1 Aluminum

4 Drill head 1 C.I.

5 Control unit 1 Electronic

6 Pneumatic driller 1 M.S.

7 PU Tubes 5 meter Polureethene

8 Hose Collar 8 Brass

9 Reducer 8 Brass

10 Frame stand 1 M.S.

11 Fixed Plate 1 M.S.

12 Moving Plate 1 M.S.

13 Column Support 1 M.S.

Chapter 5 Detailed description of all components

5.1 Cylinder

It is used to generate linear motion in the whole equipment. It is used to generate the linear motion for holding the workpiece and it is used to generate the workpiece for drilling the workpiece. Following is the detailed drawing.

Fig. 5.1 Cylinder

5.2 L- Frame

It is used to clamp the wokpiece as well as it is used to hold the cylinders and entire drilling mechanism. The detailed drawing is shown in the figure.

Fig. 5.2 L-Frame

5.3 Connector

It is used to connect the pneumatic cylinder with the drill mechanism. Hence it compells drill to follow rotating mechanism. Following is the drawing of the connector:

Fig. 5.3 Connector

5.4 Piston Rod

It is used to do linear motion hence it is used to generate force inside the cylinder which is eventually used to generate linear motion. Following is the drawing of piston rod.

Fig. 5.4 piston Rod

5.5 Drill Bit

It is most important part of drilling machine as it is used to drill the workpiece. The drawing of the drill bit is as shown below:

Fig. 5.5 Drill Bit

Chapter 6 Project Management

6.1 Project Planning and Scheduling

As the design fulfills the drawbacks and limitations faced by electric drilling machine as a heavy weight. That heavy weight and human efforts lead us to the development of the project. With the principles of the pneumatics it helped us to create something innovative. As we had developed conceptual design in the 7th semester. We have developed the working model prototype in the 8th semester. At the beginning of the semester 8th we started collecting the components of drill. It took approximately 3 weeks to find components with proper specifications. After 3 weeks we started planning of fabrication of drilling machine. For proper fabrication we needed industry. Hence we started finding industry for the support of manufacturing the model. After that we started fabrication of drill.

6.2 Project development Approach

Project development approach consists of the limitations of electric drill. As per the drawbacks of electric drill we started to first find out the feasibility of hydralic drill. But it was carrying tremendous amount of weight. Hence we enlarged our planning to develop drill based on the pneumatic drill which consists of light weight. Hence it led us to develop the approach of project.

6.3 Project Scheduling and planning

1 Design Approach

2 Enlargement Of Design

3 Feasibility Of Design

4 Analysis Of Design

5 Optimization Of Design

6 Selection Of Materials

7 Optimization Of Materials

8 Searching Industry For Fabrication

9 Implimentation Of Manufacturing the Project

10 Final Preparation Of Report

11 Final Shape to Model

6.4 Risk Management

Risk is very significant parameter to be considered for making any project.There are certain amount of risks are involved as the project contains various factors such as Electricity, Human touch involvement and other unaccounted economic risks.The main aim of risk management is to reduce the risk to such extent the project touches the profit.

6.5 Risk Identification Analysis And Planning

Risk Identification is termed as the identification all the risks which are involved prior to make the project, during making the project and after making the project.As per the title of the Project the main risk involved is leackage of air as we came to know regarding this risk during fabrication of project.

To reduce the risk analysis was carried out by our team.This risk analysis was done on certain calculations which were done by hand calculations and on softwares.The reason behind the problem was foundnout and successfully soved.

To reduce the risk proper planning was carried out in order to check it for the Quality and Safety Purpose.

Chapter 7 Cost Analysis

Table 4.1 Cost of Components

Sr. No. Description Qty Material Cost ( Rs.)

1 Double acting pneumatic cylinder 2 Aluminum 3040

2 Solenoid valve 1 Aluminum 600

3 Flow control valve 4 Aluminum 1000

4 Drill head 1 C.I. 800

5 Control unit 1 Electronic 200

6 Pneumatic driller 1 M.S. 50

7 Hose Pipes 2 Polureethene 250

8 Hose Collar 2 Brass 250

9 Reducer 4 Brass 100

10 Frame stand 1 M.S. 600

11 Fixed Plate 1 M.S. 110

12 Moving Plate 1 M.S. 250

13 Column Support 1 M.S. 250

Total Cost 7500

Chapter 8 Feasibility Analysis

Feasibility analysis is termed as the feasibility of the whole project as it will be practically feasible in the industry as well as beneficial in long term and short term future.As our project was started in 7th semester we made only conceptual design but after studying all the prospects of the project we applied the principles of Pneumatics and with redesign and proper analysis we made the feasible design which will be helpful for industry as well as further modifications in the further project.Given below are the real model pictures which are practically feasible hence we include it under feasibility analysis.

Fig. 8.1 Top View

Fig 8.2 Isometric View

Fig 8.3 Side View

Fig. 8.4 Control Mechanism

Fig. 8.5 Switch Mechanism

Fig. 8.6 Front View

Chapter 9 Limitations

As every projects have the limitations our project has also one limitation of air leackage as well as the depth of the drill is limited to 10 mm because of the design considerations of the Cylinder and Drill head.

Chapter 10 Conclusion

The project carried out by us made an impressing task in the field of small scale industries and automobile maintenance shops. It is very usefully for the workers to carry out a number of operations in a single machine. This project has also reduced the cost involved in the concern

Bibliography &References


[1] A.Karthik, R.Krishnaraj, Nunnakarthik, R.Kumaresan, S.Karthik, R.Murali, ‘Single Axis Semi Automatic Drilling Machine with PLC Control”, 10.15680/IJIRSET.2015.0403009.

[2] Manish Kale, Prof. D. A. Mahajan, Prof. (Dr.) S. Y. Gajjal, ‘A Review Paper on Development of SPM for Drilling and Riveting Operation”, International Journal of Emerging Technology and Advanced Engineering, Volume 5, Issue 4, April 2015.

[3] Mohammad Javad Rahimdel, Seyed Hadi Hosienie, ‘The Reliability and Maintainability Analysis of Pneumatic System of Rotary Drilling Machines”, Springer, 07 November 2013.

[4] Prof. P.R. Sawant, Mr. R. A.Barawade, ‘Design and Development of Spm-A Case Study in Multi Drilling and Tapping Machine’, International Journal of Advanced Engineering Research and Studies, Vol. I, Issue II, January-March, 2012/55-57.

[5] A.Sivasubramaniam, ‘Design of Pneumatic Operated Drill Jig for Cylindrical Component”, IJSR-International Journal of Scientific Research, Volume 3, Issue 3, March 2014.

[6] Ogundele, O. J.,Osiyoku, D. A. Braimoh, J., and Yusuf, I., ‘Maintenance of an Air Compressor Used in Quarries”, Scholars Journal of Engineering and Technology (SJET), 2014; 2(4C):621-627.


Business accelerators and incubators: essay help free

Executive Summary

As an entrepreneur candidate and a recently established startup employee, I was always interested in how a startup survives the initial grow, perhaps the most risky phase of a startup’s life cycle. I face with business issues everyday. Unfortunately, we are not working with an accelerator. Since we are a small, in fact a micro company, I work as an accountant, HR manager and the sales manager. We face the lack of mentoring and the financial support everyday. Even though, there are lots of grants and scholarships for startups, especially for those that promote innovative products or services, the selection process is quite difficult than the one in accelerators, in my experience.

Over the past decades a wide variety of incubation mechanisms have been introduced by policy makers, private investors, corporates, universities, research institutes etc. to support and accelerate the creation of successful entrepreneurial companies (Pauwels et al., 2014). The subject I want to discuss is relatively different from the incubation mechanisms. Most common names for this mechanisms are startup accelerators or seed accelerators. A relatively new incubation model, seed accelerators, emerged out mid 2000-s as a response to the shortcomings of previous generation incubation models, which are primarily focused on providing office space and in-house business support services (Bruneel et al., 2012). I wanted to see and learn what key performance indicators for these accelerators are. The accelerator phenomenon has been cited across the globe as a key contributor to the rate of business startup success (Dempwolf, et al., 2016).

While the number of accelerators has been increasing rapidly, the roles and effectiveness of these programs are not very vivid. Nonetheless, local governments and founders of such programs often cite the motivation for their establishment and funding as the desire to transform their local economies through the establishment of a startup technology cluster in their region (Fehder & Hochberg, 2014). In this study, I will provide a review of the research literature on the definition and characteristics of start up accelerators; how they differ from other incubation models; their benefits for the overall startup ecosystem. While accelerators appear to be proliferating quickly, little is known regarding the value of these programs; how to define accelerator programs; the difference between accelerators, incubators, angel investors and co-working environments; and the importance of the various aspects of these programs to the ultimate success of their graduates, the local entrepreneurship ecosystems and the broader economy (Cohen & Hochberg, 2014).

In 2014 I had the chance to work as an intern in one of these Startup Accelerators, called Eleven. Eleven is based in Sofia, Bulgaria. At the end of my dissertation, I will try to explain some of the knowledge I gained from my internship experience in addition to the interview I conducted with Belizar …, business developer of Eleven.

Evolution of Incubators

Words “accelerators” and “incubators” are sometimes used similarly, creating confusion about the differences between the two. Both concepts were created in the US. An incubator can be thought as a beginning office for startups. They support entrepreneurs survive during the most fragile phases of their startups’ life cycle, the start and the growth. Incubators usually accept teams that have just started converting their ideas into a business model. Incubators, on this evolution, usually help these teams to achieve their primary goals by providing co-working space and mentorship. Even though it’s not mandatory, in some rare cases, they also provide seed investments in exchange of equity.

In its generic sense, the term incubator is broadly used for collaborative programmes which help people solve problems associated with launching a startup by providing a variety of organizations and initiatives, which strive to help entrepreneurs in developing business ideas from the start, to commercialization and eventually the launch and independent operation of new business ventures. According to a paper by Almubartaki & Al-Karaghouli & Busler (2010), the business incubation is a term describing business development process that is used to grow successful, and to create sustainable entrepreneurial ventures that will contribute to the economic developments of a healthy economy. The paper notes that successful incubation process is about supportive environment in which new ventures can develop and fulfil their potential growths as well as giving them access to a wide range of business development resources and tailored services. Business incubators play significant roles in seeding and developing new ventures and technology transfer with potential growth in most areas and sectors of the economy (Almubartaki, Al-Karaghouli & Busler, 2010).

Many agree on that the first business incubator was established by Joseph Mancuso in Batavia, New York, in 1959. Since the establishment of first incubators the incubation model has evolved and in 2006 there were approximately seven thousand incubators worldwide (Lewis et al 2001). Incubators typically provide their companies with programs, services and space for different amounts of times based on the company needs and their incubator graduation policies (Carvalho, 2016). The main purpose of a business incubator, is to create a favourable business environment for startup firms to compensate for the lack of financial, knowledge and networking resources they generally have (Commission, 2002). The startup firms in an incubator are in general provided with office space, shared equipment, administrative services and other business related services (bollingtoft, 2012). With changing business needs, the organizational structure, the operational sector and value added elements of business incubators have significantly changed.

Business incubators have proven to be an economic development tool for the communities they serve. According to the European Commission Enterprise Directorate-General’s Final Report on Benchmarking on Business Incubators in February, 2002, business incubators have two main functions:

1. The provision of physical space is central to the incubator model. Standard good practices now exist with regard to the most appropriate configuration of incubator space.

2. The value added of incubator operations lies increasingly in the type and quality of business support services provided to clients and developing this aspect of European incubator operations should be a key priority in the future.

Birth of Accelerators

With the increasing tendency towards technology and the support to SMEs(Small Medium Enterprise), there was a new window of opportunities for investors. With exponentially increasing number of new players joining to the startup ecosystem, venture capitalists needed to find a way to support, fund and invest in those companies.

There is no denial about how small businesses play a massive role in any country’s economy. They have a very large impact on the national GDP and they create countless jobs for people. They are the backbone of a country’s economy. With the technology available at our hands, everyday hundreds of new companies are set up. People are eager to create, to provide for others. Innovative ideas are being turned into businesses everyday. New sectors, new products and new services emerging out of nothing, making people’s life easier and contributing to a nation’s economy. However, there are also ideas that can’t be turned into a business or businesses that have to shut down because of insufficient funds. This is why local enterprise funds, grants, non-profit support groups for SMEs started to grow recently. Whether they are non-profit or not, we cannot deny that this is an excellent way to increase the wellbeing of overall society. One phenomena, called seed accelerators or startup accelerators, aimed at helping startups at the very early stage of their business.

According to the research Accelerating Startups: The Seed Accelerator Phenomenon by Susan G. Cohen and Yael V. Hochberg, published in March 2014, the first accelerator, Y Combinator, was founded by Paul Graham in 2005 in Cambridge, Massachusetts, and soon moved and established itself in Silicon Valley. The research states that in 2007, David Cohen and Brad Feld, two startup investors, set up set up Techstars in Boulder, Colorado, hoping to transform its startup ecosystem through the accelerator model. Since 2005 YC has funded 1,430 companies and almost 3,500 founders and the total market cap of all YC companies is over $85B (Mañalac, 2017). Y Combinator was the first accelerator to provide a small amount of seed investment money in exchange for a minor equity stake in startups participating in a three-month program with networking and advice from experienced entrepreneurs (Kohler, 2016).

Accelerator TechStars Y Combinator

Location Boulder, Boston, New York, Seattle Silicon Valley

Launched 2006 2005

Length of Program 3 months 3 months

Batch Size 9-12 teams 65 teams

Seed Funding per Team $6k -$18k $11K-$20K

Equity Stake Required 6% 2-­‐10%

Acceptance Rate 1% 3%

Table 1. Techstars and Y Combinator Source: Accelerating Success: A Study of Seed Accelerators and their Defining Characteristics by Barrehag, Fornell, Larrson, Mardstrom, Westergard & Wrackefeldt published in 2011.

After the birth of startup accelerator phenomena, the number of existing accelerators rapidly increased. Today, estimates of the number of accelerators range from 300+ to over 2000, spanning six continents (Cohen & Hochberg, 2014). Even though they have some similarity with their ancestors, incubators; the lack of mentoring and financial support in the incubation system makes startups loose money and time, which they could invest in building and improving their business instead of trying to raise funds and find the right way to take certain steps.

Launched in 2007, Seedcamp is considered by many to be the first “Y-Combinator Style” European accelerator (Brunet, Grof, & Izquierdo, The European Accelerator Report 2015, 2015).

Researchers I mentioned above, Susan G. Cohen, Daniel Fehder and Yael V. Hochberg are three of the lead researchers when it comes to the seed accelerators. Together and seperately they have published several papers on accelerator concept. Due to fast increasing numbers, naturally, it attracted the media and researchers. Discussions still go on about how to measure the performance of an accelerator.

Characteristics Of Accelerators

The definition for accelerators is continuously evolving. The change in the industry and the fast-paced evolution makes it quite difficult to find a stable definition. With the new models emerging, the term accelerator changes, as well. Recent years have seen the emergence of a new institutional form in the entrepreneurial ecosystem: thee seed accelerator (Fehder & Hochberg, 2014). These fixed-term, cohort-based, “boot camps” for startups that offer educational and mentorship programs for startup founders, exposing them to wide variety of mentors, including former entrepreneurs, venture capitalists, angel investors, and corporate executives, and culminate in a public pitch event, or “demo day,” during which the graduating cohort of startup companies pitch their businesses to a large group of potential investors (Fehder & Hochberg, 2014).

“ Certainly, much of this sound familiar. After all, incubators and angel investors, which are more established phenomena, also help and fund nascent firms. Accelerators certainly bear certain similarities to incubators and angel investors. Like the former, accelerators aim to help nascent ventures during the formation stage. We therefore might expect that many of the activities provided by incubators and angels would also be provided by accelerators. But accelerators differ in several ways. Perhaps the most fundamental difference is the limited duration of accelerator programs compared to continuous nature of incubators and angels investments.” (Cohen & Hochberg, 2014).

Before the definition of Fehder and Hochberg (2014), I noticed that most of the definitions were uncertain, or in other words, unofficial. Paul Miller and Kirsten Bound defined accelerators in their discussion paper “Startup Factories” in 2011 as:

• An application process that is open yet highly competitive (Miller & Bound, 2011).

The paper states that the application process usually consists of filling out an online application as the first step. Many of the programs have a very high application rate, the most well known accept less than 1% of the applicants (Miller & Bound, 2011).

• Provision of pre-seed investment, usually in exchange for equity (Miller & Bound, 2011).

The paper indicates that the investment provided by accelerator programmes varies but is usually based on assumption about how much it costs per co-founder to live during the period of the programme and for a short period afterwards. Miller and Bound stated that programmes usually provide a minimum of £10,000 and a maximum of £50,000 investment during the first three months. This can be in the form of a convertible note or an equity investment (Miller & Bound, 2011).

• A focus on small teams not individuals (Miller & Bound, 2011).

• Time-limited support comprising programmed events and intensive mentoring (Miller & Bound, 2011).

Miller and Bound state that accelerator programmes provide support for a set of period of time – usually between three and six months. Furthermore, the paper inidicates that this time frame is partly linked to the decreasing length of time it takes to launch a web startup, but it’s also about creating a high pressure environment that will drive rapid progress.

Frequent direct contact with experienced founders, investors and other relevant professionals is a core aspect of an accelerator programme (Miller & Bound, 2011).

The paper states that it’s essential for an accelerator programme to develop an extensive network of high quality mentors. Attracting high quality mentors requires high quality mentors (Miller & Bound, 2011).

• Startups supported in cohort batches or ‘classes’. (Miller & Bound, 2011)

While many accelerators are generalists across industries, others are vertically-focused(healthcare, energy, digital-media) (Fehder & Hochberg, 2014). The focus of accelerators is to help startups grow. This happens usually through mentorship and educational programme for a fixed period of time. After the programme, startups are prepared for a funding by private or public investors. Basically, in my opinion, accelerators try to do in a few months what would normally a startup aim to do in several years. Accelerators are for-profit organizations, publicly or privately funded. Depending on the accelerator programme, they generally provide a small seed investment in exchange for a small amount of equity.

Table 2 below gives us a summary of the characteristics of both Incubators and Accelerators. As you can see, the accelerators are more eager to include web- or software based startups, who promote innovation in their value proposition, in their portfolio in comparison to incubators, who follow a more tolerating path when it comes to accepting companies. Accelerators follow a distinct elimination process: “firms that do not require significant immediate investment or proof of concept”.

One of primary goals of incubators is to help firms from the local community. Accelerators’ selection process, on the other hand, can include firms within local to regional or nationwide borders.

Typical “boot camp” programme varies from 1 to 6 months in accelerators. As mentioned earlier, during this bootcamp, startups go through intense education, mentorship and consulting practices. After this period, startups have the chance to pitch to investors for further funding.

Another, maybe the most important distinction between accelerators and incubators is the investment to startups in exchange of equity. Table 3 below shows us several accelerators in Europe and their length of programme, investment size (in £) and equity-stake taken in exchange. The equity stake taken is mostly between 3-10%. This is mostly related to the investment size, naturally.

Table 2. Characteristics of incubators and accelerators

Characteri-stics Incubators Accelerators

All kinds, including science-based

Businesses (biotech, medical devices, nanotechnology, clean energy, etc.) and nontechnology; all ages and genders; includes those with previous experience in an industry or sector. Web-based, mobile apps, social networking, gaming, cloud-based, software, etc.; firms that do not require significant immediate investment or proof of concept; primarily youthful, often male technology enthusiasts gamers, and hackers.


Selection Competitive selection, mostly from the local community. Competitive selection of firms from wide regions or even nationally (or globally).


Terms of 1 to 5 or more years (33 months on average) Generally 1- to 3-month boot camps


Offers access to management and other consulting, specialized intellectual property and networks of experienced entrepreneurs; helps businesses mature to self-sustaining or high-growth stage; helps entrepreneurs round out skills, develop a management team, and, often, obtain external financing. “Fast-test” validation of ideas; opportunities to create a functioning beta and find initial customers; linkage of entrepreneurs to business consulting and experienced entrepreneurs in the Web or mobile apps space; assistance in preparing pitches to try to obtain follow-up investment.


Investment Usually does not have funds to invest directly in the company; more frequently than not, does not take equity. Invests $18,000 to $25,000 in teams of co-founders; takes equity in every investee (usually 4 to 8 percent).

Source: Excepts from Atkins, D. 2011. What are the new seed or venture accelerators? (cited in Innovation Accelerators: Defining Characteristics Among Startup Assistance Organizations by Dempwolf, Auer and D’Ippolito published in October, 2014)

Accelerator Location Date Length of Investment Equity Output (# active

created programme size9 stake companies/follow–

taken on funding)

Techstars UK, London 2013 3 months £ 12,500 + 6% 22/~£10,4M

London option

conv. loan

Healthbox UK, London 2012 4 months £50,000 10% 7/undisclosed


Fintech UK, London 2012 3 months / / 14/undisclosed

Innovation Lab

Bethnal Green UK, London 2011 3 months £ 15,000 6% 34/~£9,3M


Climate–KIC Europe 2010 12–18 Max. of / 45/~£46,5M

Europe months £75,500

Microsoft Germany, 2013 4 months / / 16/undisclosed

Ventures Acc. Berlin

Axel Springer Germany 2013 3 months £ 19,900 5% 46~£6M

Plug & Play Berlin


ProSiebenSat.1 Germany, 2013 3 months £ 19,900 5% 26/undisclosed

Accelerator Münich/


Startupboot– Germany, 2012 3 months £ 11,900 8% 16~£4,9M

camp Berlin Berlin

Le Camping France, Paris 2010 6 months £ 3600 3% 72~£14,8M

TheFamily France, Paris 2013 Indefinite / 3% undisclosed

L’Accélérateur France, Paris 2012 4 months £ 7,900 + 7–10% 49/undisclosed

option for


Scientipôle France, Paris 2002 6 months £ 15,900 – / undisclosed

Croissance £ 71,500

Table 3 Accelerators in Europe Source: A look Inside the Accelerators by (Clarysse, Mike, & Van Hove, 2015)

Business Model of an Accelerator

The business model describes how the accelerator is structured to obtain its goals, how it prices its products and services, and how it generates income and, in some cases, profit (Dempwolf, Auer, & D’Ippolito, 2014). Furthermore, Dempwolf et al. states that most of the existing accelerators to date have operated in the software or mobile applications arena, an industry characterized by relatively low capital requirements and short prototyping durations. The accelerator’s revenue assumptions are then built around rapid growth and large-scale markets (Dempwolf, Auer, & D’Ippolito, 2014).

Miller and Bound in their paper “Startup Factories, 2011” state that there are a number of variations, but the core business model of accelerators is simple: investors invest in the accelerator programme which acts as a small fund. Some part of the fund goes on the costs of running the programme while some of the fund is invested into startups that are accepted onto the programme (Miller & Bound, 2011). The paper continues: The accelerator programmes take equity in the startups and hope to make a return on those shares. Some programmes take ordinary shares, others prefer what’s called a ‘convertible note’ which offers a discount on stock should the company raise further funding, others have a clause that makes the investment into a soft loan to be returned if certain conditions are met (Miller & Bound, 2011).

Table 4 below gives us the statistics the main source of revenue of accelerators in Europe in 2016. The European Accelerators Report published in 2016 by (Brunet, Miklos, & Izquierido, European Accelerator Report 2016, 2016) states that the relationship between accelerators and corporations have grown stronger and more numerous. Corporate revenue generated by accelerators came from two main sources in 2016: 23% was a result of corporate partnership, generally in the form of white labeled or jointly run acceleration program created by the accelerator on behalf of the corporation, and 32% came from corporate sponsorship packages sold by accelerators.

Interestingly, (Brunet, Miklos, & Izquierido, European Accelerator Report 2016, 2016) found that the traditional “cash-for-equity” model is becoming rare as accelerators reconsider in their general outlook. The report states that 50.5% of accelerators do not invest cash in startups. Accelerators that do not invest cash generally focus on providing services and resources such as workshops, mentorship, co-working spaces and connections (Brunet, Miklos, & Izquierido, European Accelerator Report 2016, 2016). The report continues: Most likely, the small number of exits -52 reported in 2016- has proven insufficient in funding their operations. Only 6% of accelerators operating in the region reported exits as a main source of revenue (Brunet, Miklos, & Izquierido, European Accelerator Report 2016, 2016).

Table 4. Main source of Revenue of Accelerators

Table 4 Main source of revenue of accelerators in 2016. Source: European Accelerators Report in 2016 available at http://gust.com/accelerator_reports/2016/europe/ (Brunet, Miklos, & Izquierido, European Accelerator Report 2016, 2016)

According to the European Accelerators Report 2016 by (Brunet, Miklos, & Izquierido, European Accelerator Report 2016, 2016), there were total of €47,575,976 investment in 3.701 startups by 193 accelerator programmes. The report states that the United Kingdom had both the highest amount of money invest in startups, €15,566,629 as well as the highest number of startups accelerated, 992 startups. Furthermore, the report indicates that 66.3% of the accelerators in the region claim to be for profit ventures. “Typically for-profit accelerators are funded with private capital from investors aiming to generate long-term profit. This is primarily accomplished by the appreciation of their equity in startups, but also by providing business support services and by offering acceleration as-a-service to large corporations” (Brunet, Miklos, & Izquierido, European Accelerator Report 2016, 2016).

Non-profit accelerators support industries that provide a specific public benefit, such as Healthtech and Edtech (Brunet, Miklos, & Izquierido, European Accelerator Report 2016, 2016).

The strategic focus of an accelerator can be strongly shaped by the types of funders or stakeholders supporting the programme (Clarysse, Mike, & Van Hove, 2015). There are two important elements to the funding of structure of an accelerator: the funding of the accelerator itself and the funding of available to startups (Clarysse, Mike, & Van Hove, 2015). The paper A Look Inside the Accelerators by (Clarysse, Mike, & Van Hove, 2015) found that most programmes received the major part of their working capital from shareholders, such as investors, corporates and public authorities.

The strategic focus concerns the accelerator’s strategic choices regarding industry, sector and geoghrapical focus (Pauwels, Clarysse, Wright, & Van Hove, 2015). The industry and sector focus ranges from being very generic (no vertical focus at all) to very specific (specialized in a specific industry, sector or technology domain) (Pauwels, Clarysse, Wright, & Van Hove, 2015). When it comes the geographical focus, the accelerators choose between being localized or international.

Types of Accelerators

Innovation Accelerators

Innovation accelerators are the main focus of this paper. Innovation accelerators are stand-alone, for-profit ventures that look forward to identifying classes of promising startup companies with fast, high-growth potential, making seed-stage investments in those companies usually in exchange for equity, being part of innovation-acceleration activities with such companies to help them get next-stage funding and cashing out for a profit when these companies are acquired or have successful IPOs (Dempwolf, Auer, & D’Ippolito, 2014). The immediate goal of the accelerator is to help ventures get next-stage funding, but their primary goal in the long-term scenario is to make substantial profit when those companies are acquired or have successful IPOs (Dempwolf, Auer, & D’Ippolito, 2014).

Examples for this type of accelerators are Y-Combinator and Techstars. Its objective is to bridge the equity gap between very early stage projects and investible businesses (Clarysse, Mike, & Van Hove, 2015). Often we see that these accelerators begin to focus on startups that are in later stages of development; they tend to select ventures which already have some proven track record, and in some cases have already pre-seed finance (Clarysse, Mike, & Van Hove, 2015).

Corporate accelerators

“These accelerators engage in provision of seed capital and various combinations of mentoring, technical assistance, networking, and facilities to entrepreneurs, investors, and startup teams to advance certain goals of the corporate or institutional parent. Corporate accelerators grow and manage portfolios of complementary startups to accelerate innovation and gain a competitive advantage.” (Dempwolf, Auer, & D’Ippolito, 2014). They are a promising way for established companies to explore new ideas for their corporate innovation efforts (Kohler, 2016). The corporate accelerator trend extends well beyond high technology and has gained transaction across the globe and across the industries, from healthcare (Bayer), to insurance (Allianz) to entertainment (Disney) to consumer packaged goods (Kohler, 2016). Effective corporate accelerators combine the best of two worlds: the scale and scope of large, established corporations and the entrepreneurial spirit of small startup firms (Kohler, 2016).

One of the main trends in the acceleration world is that the increasing collaboration between accelerators and corporations (Brunet, Miklos, & Izquierido, European Accelerator Report 2016, 2016). There is a growing trend for corporations to outsource their acceleration programs due to the their limited skills in accelerating programs (Brunet, Miklos, & Izquierido, European Accelerator Report 2016, 2016).

The European Accelerators Report in 2016 by (Brunet, Miklos, & Izquierido, European Accelerator Report 2016, 2016) describes the 5 different ways in which corporations can benefit from startup accelerators:

1. Launching a program quickly and cost-effectively: by partnering with accelerators, corporations can quickly enter the acceleration business and adopt best practices developed by accelerators over years of operation.

2. Enhancing deal flow: by accessing the accelerator’s immense marketing power and network.

3. Staying up to date: by having access to an accelerator’s deal flow, they receive insight into the innovation pipeline in their market. Corporations have learned that competitors now often come from the startup world.

4. Building an innovative corporate culture: by placing their corporate executives as mentors in the accelerator or by enabling their own corporate executives to innovate. In the latter case, the new product could be placed into a separate company that is then accelerated by the accelerator.

5. Building a more innovative brand: by aligning with accelerators and their startups which have become symbols of innovation in the eyes of the public.

University Accelerators

University accelerators are educational nonprofits that accelerate the development of student entrepreneurs and innovation at universities throughout the United States (Dempwolf, Auer, & D’Ippolito, 2014). Universities seem to recognize the importance of fostering the local entrepreneurial ecosystem and some of them have decided to launch their own accelerator programs (Carvalho, 2016). University accelerators typically provide seed grants to support students through the early stages of development (Dempwolf, Auer, & D’Ippolito, 2014). Unlike for profit accelerators, university accelerators do not take equity stakes in student-founded companies and they are typically agnostic when it comes to technology focus (Dempwolf, Auer, & D’Ippolito, 2014).

Case Study: Eleven

As I mentioned in my Executive Summary, I had the chance to do an internship there in August-October, 2016. Eleven is one of the major startup accelerators in Europe. It is a seed accelerator based in Sofia, Bulgaria (Eleven Ventures). “Eleven is one of the pioneers in early-stage investments in Eastern Europe, comprising a team of entrepreneurs and investment professionals passionate about the world of technology and innovation. With 150 collective investments of our partners over 5 years, we have gained the unfair advantage of how to transform a startup into a scaleup in a capital efficient way. Eleven started in 2012 with an EUR 12 million acceleration and seed fund, which was fully invested in 115 startups over three years.” (Eleven Ventures).

“We initially invest pre-seed tickets of EUR 100 000 for 10-12%. The fund itself has the ability to follow with up to EUR 200 000 more. Together with the investors in the Founders Fund, comprising some of the most active angel and seed investors in the region, we can fully subscribe funding rounds of EUR 500 000+, thus allowing our portfolio companies to focus on building their business and not waste too much time on fundraising.” (Eleven Ventures)

On-demand support mechanisms provided by Eleven as described in their website:

• Business knowledge and deep industry know-how brought by our mentors and investors.

• Global Network of partners, friends, and like-minded business organizations.

• The #OneOf11 community – our biggest asset and backbone of Eleven. The family, you can always rely on, learn and inspire from.

• One Roof to unite us as a home and become our base camp on the way to the summit.

I had the chance to interview Belizar Marinov, the Business Developer in Eleven. Belizar has been working in Eleven for 4,5 years.

Table 5. Top Vertical Industry Startups Invested by Eleven

Table 6. Business types invested by Eleven

Belizar mentioned that 39% of 116 startups that they have invested in were international. These countries included Serbia(15%), Croatia(7%), Romania (4%) and Slovenia(3%).

Belizar describes Eleven’s 3 pillars based formula as following:

1. Quantitative Investment Approach: We receive more than 1000 applications per annum and invest in about 30-40 startups, effectively 10x more than a standard VC.

2. Community-Driven Peer Network: We engage our 300+ startup founders through peer groups, founder weekends, selection days, ambassador events, etc. The #oneof11 community is one of our biggest strength.

3. Product and Operations Support: Dedicated accelerator and post-accelerator program, design thinking workshops, entrepreneurs in residence. This is the are we could improve most.

Table 7. Eleven’s Investment thesis

Source: Belizar Marinov, Eleven’s Business Developer


(n.d.). Retrieved 03 15, 2018, from Eleven Ventures: https://www.11.me

Barrehag, L., Fornell, A., Larrson, G., Mardstrom, V., Westergard, V., & Wrackefeldt, S. (2012). Accelerating Success: A Study of Seed Accelerators and Their Defining Characteristics.

Brunet, S., Grof, M., & Izquierdo, D. (2015). The European Accelerator Report 2015. Retrieved 03 15, 2018, from Gust: http://gust.com/european-accelerator-report-2015/

Brunet, S., Miklos, G., & Izquierido, D. (2016). European Accelerator Report 2016. Retrieved 03 15, 2018, from gust.com: http://gust.com/accelerator_reports/2016/europe/?utm_content=bufferf582c&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

Carvalho, A. C. (2016). Digital Startups Accelerators: Characteristics and Evolution Trends .

Clarysse, B., Mike, W., & Van Hove, J. (2015). A Look Inside the Accelerators. Nesta.

Cohen, S., & Hochberg, Y. (2014, March). Accelerating Startups: The Seed Accelerator Phenomenon. http://ssrn.com/abstract=2418000 .

Dempwolf, S., Auer, J., & D’Ippolito, M. (2014, 10). Innovation Accelerators: Defining Characteristics Among Startup Assistance Organizations . Small Business Administration, Office of Advocacy .

Fehder, D., & Hochberg, Y. (2014, 09 19). Accelerators and the Regional Supply of Venture Capital Investment. http://ssrn.com/abstract=2518668 .

Kohler, T. (2016, May). Corporate accelerators: Building bridges between corporations and startups . ScienceDirect .

Mañalac, K. (2017, 08 21). YC Summer 2017 Stats. Retrieved 03 14, 2018, from Y Combinator Blog: blog.ycombinator.com

Miller, P., & Bound, K. (2011, June). The Startup Factories. NESTA .

Pauwels, C., Clarysse, B., Wright, M., & Van Hove, J. (2015). Understanding a new generation incubation model: The accelerator. Elsevier .


Memory systems present in the mammalian brain

The historical unraveling of the memory systems present in the mammalian brain has been an extensive journey of scientific discovery. Through the work of countless individuals, major hypotheses have been proposed which have led to the current view of how memory is stored and retrieved. Though many uncertainties and controversies still exist, the general mode of memory persists, with substantive research corroborating the principal findings. Research thus far has concluded that there are two major forms of memory: declarative (explicit) and nondeclarative (implicit). These forms of memory are defined by the nature of what is remembered, but memory can also be categorized based on the time in which it remains effective. These classes of memory can be divided into ‘immediate’ memory, ‘working’ or ‘short-term’ memory, and ‘long-term’ memory. A further analysis of how these separate forms of memory exist in the mammalian brain, which neuroanatomical substrates are important in their actions, as well as the general characteristics of each type of system will be conducted. But first, it is important to examine the historical events and characters that have led to the present understanding of these distinct memory systems.

The first discipline to examine memory and question how learning occurs and how memories are stored was philosophy. As far back as the B.C. time of Socrates, philosophers were questioning how humans learn new information and how they store it as memories. Using methods of conscious introspection, logical analysis, and argument, they sought to explain how memory worked. However, these non-experimental methods did not lead to agreeable conclusions. Later, a French philosopher named Maine de Biran was the first to have the idea that memory could be separated into different systems. His notion was that memory could be distinguished into three distinct forms based on habits: representative memory, mechanical memory, and sensitive memory. Representative memory was characterized as the recollection of ideas, mechanical memory dealt with the habitual repetition of a movement, and sensitive memory referred to the habitual generation of a feeling without recalling the ideas behind it.1 De Biran remarkably theorized these three distinct forms without any actual experimentation or consideration of the anatomy of the brain. His theories, although not exactly correct, highly resemble the modern day accepted forms of memory systems. Albeit, his theories were not well accepted until much more recently, when the idea of separate memory systems was found to be strongly supported by modern cognitive neuroscience. Others, like Franz Joseph Gall, also had ideas that there were different types of memory systems. Gall was the founder of phrenology, the idea that you could feel the bumps on the head of a person and get an accurate idea about their personality and other characteristics, and theorized that there were different types of memory localized in certain spots of the cortex. He was wrong mostly, but correct about different types of memories localized in different areas.

By the nineteenth century, trying to explain the complex workings of memory through philosophical methods was replaced by the empirical methodology of the newly-founded discipline of psychology. Experimental psychologists like Hermann Ebbinghaus showed that memories have different life spans, while William James further explained the fundamental difference between short-term and long-term memories, as well as drew the distinction between declarative memory and procedural memories. At the same time, psychiatrist Sergei Korsakoff was the first to document a memory disorder that resulted in human amnesia. In the twentieth century, another prominent psychologist figure named Karl Lashley sought to ‘localize the engram’, or find the one, or couple, localized regions of memory. He did this by testing the maze-running ability of mice when different sections of cortex were surgically removed. He found that mice were still able to complete the maze no matter the lesion, which led him to conclude that memory was not localized to a single region and was widely distributed throughout the entire brain. This ‘mass action view’ of memory stuck with psychologists and was the major theory of memory for many decades. With hindsight, the choosing of a maze-running task to examine memory was not ideal, as maze-running involves many brain systems, from vision and olfaction to spatial sense and others, and cannot be pinned to just general root memory. As it is now known, Lashley’s influential theory on ‘whole brain’ memory was partially correct in the aspect that memory is widely distributed. However, he assumed that memory was comprised of one unitary system that was widespread and stored all over the brain. The view by Lashley that memory was not localized held sway up until the 1950’s, when a new style of memory research came into play. Interestingly, Lashley influenced psychologists to believe that with brain injury other areas of brain tissue would be able to substitute for the function of the affected region.2 This view by Lashley will come to be challenged by the work that was soon begun by researchers with patients who have amnesia or other memory disorders.

Recent researchers circled back to the work of Korsakoff and began investigating disorders causing memory impairment, often brought on by lesions in certain regions of the brain. It wasn’t until researchers realized that persons with memory disorders could elucidate the structure and organization of normal memory that huge leaps in the understanding of memory systems occurred. Psychologists and researchers began looking extensively at the cause and function of amnesic patients to help explain how memory worked in the brain.

Canadian psychologist Brenda Milner’s study of the amnesic patient H.M. led to many revolutionary findings that formed some of today’s understandings of the memory systems. Brain injury as a young boy plagued H.M with frequent seizures, which led to him receiving an experimental treatment. The treatment included the bilateral removal of the inner surface of the temporal lobe, including the hippocampus. This treated his epilepsy, but left him with large-scale memory loss that compromised his ability to form new long-term memories. From this led to a comprehensive 50-year study of his memory condition. H.M.’s most drastic deficit was that he appeared to forget events as soon as they happened. Although he could retain new information as long as his attention was not diverted from it, but as soon as a new task was begun, that previous information was forgotten. Milner was able to extract four novel principles on memory from her study of H.M.. First, she alleged that the ability to acquire new memories is a distinct cerebral function, localized to the medial portion of the temporal lobes of the brain, and separable from other perceptual and cognitive abilities. This was evident as H.M. was without the medial part of his temporal lobe and could not form new long-term memories. Second, she hypothesized that the medial temporal lobes are not required for immediate memory. H.M. could still retain information for a short time after learning, and carry on a brief conversation. Third, she said that the medial temporal lobe and the hippocampus cannot be the ultimate storage sites of long-term memories, since H.M. still had complete recollection of events from his childhood and time before his experimental treatment. Lastly, Milner found that H.M. could still learn a type of knowledge allowing for perception and intellectual functions. In an experiment, it was discovered that H.M. could learn to trace the outline of a star in a mirror, and with each day of practice there was improvement, even without remembering previously completely the task. It seemed as if there was a separate type of memory that did not originate in the medial temporal lobes.3

In a critical evaluation of Milner’s conclusions, it would be important to note that H.M. had such an extensive lesion of the medial temporal lobe that it makes it difficult to attribute these theoretical functions to the region as a whole. It could be very likely that only small regions of the medial temporal lobe (MTL) play a role in each of H.M.’s memory impairments, and it was hasty of Milner to attribute the acquiring of new memories to the entire region. Also, in evaluating the findings now, it could be possible that formation of new episodic memories could follow a neural pathway involving more than one region of the brain, with the MTL acting as intermediate location in the pathway of formation of new episodic memories from short-term ones. Disrupting the function of these substrates could in essence ‘cut the cord’ in the pathway, disrupting the pathway for coding the episodic and semantic information. With this in mind, it could elucidate that the substrates composing the MTL are important for the formation of new episodic memories, but not the main center for this memory system. Further evaluation of other subjects with varying degrees of memory impairments caused by different lesions could reveal more information about the memory system proposed by Milner.

Finding subjects with amnesia to study for multiple years, as well as being able to examine their brains post-mortem for damage makes this realm of memory study difficult. Over the years, there have been several more amnesiac patients that have been well-studied and can offer clues into the brain’s systems of memory along with H.M. Two other well-studied amnesiacs, R.B. and G.D., developed amnesia following ischemic episodes involving a loss of the blood supply to the brain. Like H.M., their general intelligence and cognitive abilities were unimpaired, but both experienced trouble forming new memories. A post-mortem evaluation of their brains showed extensive bilateral damage to the CA1 field of the hippocampus, with no sign of damage elsewhere, fortifying the theory that the hippocampus is important in the acquisition of new episodic memories. It also highlighted the idea that damage to small subregions of the hippocampus can cause extensive memory impairment. R.B. and G.D.’s impairment was only moderate in comparison to H.M. though, which could signify that other regions of the hippocampus play roles in memory.

Two other subjects, L.M. and W.H. displayed more severe impairment than R.B. and G.D. in terms of anterograde amnesia, and also exhibited extensive retrograde amnesia. After post-mortem evaluations, it was shown that both had extensive damage to the CA1 field of the hippocampus, as well as the CA2 and CA3 fields, the related area called the dentate gyrus, the outer edge of the hippocampus called the subiculum, and a neighboring area called the entorhinal cortex. Altogether, it seems conclusive that the hippocampus and MTL play a large role in memory, as more damage to the hippocampus and the surrounding MTL substrates elicited increasing memory impairment. It was evident that one or all of the additional regions affecting R.B. and G.D. (CA2, CA3, dentate gyrus, subiculum) played a role in causing retrograde amnesia, posing the idea that one of these regions is responsible for the housing of past declarative memories, or at least a major substrate in the pathway responsible for storage and/or retrieval of past declarative memories. However, even with the data presented by these cases, it is unclear the specificities of memory that each individual region of the MTL plays in the declarative memory system. And again, it could still be possible that the MTL acts as a sort of the ‘hub’ or the main location along the episodic memory formation or retrieval pathway, but still could have other brain regions operating in this memory system. Clearly, it is evident that another form of research needs to be conducted where the individual structures and connections of the MTL and other regions can be examined to determine the complexity of the declarative memory system.5

With the theories provided by the study of these amnesic patients, it is clear now that memory does in fact have highly localized regions that come into play with certain types of memory. Now that the basic human model of declarative memory was understood from amnestic patients, these specific regions that played a role in declarative memory could be examined in more detail using animal models. An animal model was constructed with the nonhuman primate; one of humans’ closely related species in terms of brain function and structure. With the animal model, the specific structures of the MTL that are essential to declarative memory came to light. Although it’s evident that animals cannot express declarative memories in the form of conscious remembering the same way that humans can, researchers have managed to determine ways in which to test declarative memory in these animals. They look at declarative memory’s other operating characteristics by examining the kind of information that is processed in certain tasks given to the monkeys. The first task is the ‘delayed nonmatching-to-sample’ task and entails the animal to simply recognize an object as familiar when first being presented with the object as a sample, and then after a delay, spanning from seconds to minutes, presenting the same object along with a new, novel object in which they’ve never been exposed to. If the animal subject chooses the new object, signifying that they recognize that the other object is familiar, they get rewarded with food. In the second task, the subject is presented with two simple, easily distinguishable objects. One of the two objects is designated the ‘correct’ object, and if the animal chooses the correct object they received food as reward. A normal monkey took between ten and twenty trials to learn the correct object.

Using animal models provided the unique opportunity to surgically induce lesions at specific chosen regions of the brain and run them on the same tasks, giving remarkable insight to the physiological function of certain regions of the brain. As you might imagine, this is not possible, for ethical and other reasons, in human subjects. The only memory impaired human subject available to obtain information regarding memory systems either has lesions resulting from accidental events, conditions like cerebral anoxia, or simple genetics resulting in atypical brain conditions. Memory impairment diseases like alzheimers have become the subject of much research lately in terms of its effects on memory in regard to the declination of healthy brain tissue.

It took a while for these views on memory systems provided by the study of amnesic patients to gain ground, as many at the time thought amnesia was merely caused by a retrieval deficit. Additional experiments on amnesiacs were conducted to broadly examine the information that could be gathered on different memory systems of the brain. In well-structured experiments where three-letter word stems were presented with instructions that told the subject to use this word stem to form the first word that comes to mind, amnesiacs were able to perform just as well as the control group. Tasks using this sort of instruction became known as ‘priming’, and showed that it was a distinct form of memory that was unimpaired when MTL regions were damaged. It can therefore be deduced that procedural tasks involving priming involve brain regions outside of the main memory MTL region, possibly in the cortex. If the task instructions were phrased in such a way to mimic conventional memory, like telling the subject to use the word stem as a cue to retrieve a word that was previously presented, the amnesiacs performed much worse. This was significant, as amnesiacs often experienced the inability to encode and store previously presented words. Furthermore, similar to H.M.’s mirror star-drawing task, other tasks of the sort (mirror reading, resolving stereoscopic images, cognitive skill learning, artificial grammar learning, and category learning) were conducted with other amnesiacs. Although they had poor memory of the tasks they had just completed, over time they experienced improvement in the specific task. These tasks elucidated a different form of memory using skill-like abilities that was also unimpaired in amnesic subjects with various MTL lesions. Data from these experiments showed a distinction between declarative and nondeclarative procedural knowledge memory systems. However, the broad division of memory between those two systems were challenged, as influential experiments showed many more types of memory present in the brain.6

Experiments examining associative learning used the method of eyeblink conditioning, in which a simple associative task using a conditioned stimulus like a light or a tone, paired with an unconditioned stimulus like a peri-orbital shock, elicited a reflexive eyeblink. Using variants of trace and delay conditioning, the unconditioned shock stimulus became paired with the conditioned light or tone, and after several trials, a reflexive eyeblink was observed even when the light or tone was presented on its own without the shock. Researchers tested this method with animals in which all brain tissue above the thalamus or midbrain was removed and the effect was still present.7 It was concluded that the cerebellum was essential to this type of conditioned learning. The effect was also shown to still be present in amnesiac patients, eliciting that again there was another form of memory centered outside the standard declarative hippocampal area regions.8

The data compounded from all these experiments could be shown as memory systems distinguishable by the figure below (Figure 1). The broad division of memory remained distinguishable between declarative and nondeclarative systems, but further evaluation led to the umbrella of individual systems that contributed to the two broad divisions. Overall, it has been shown with forms of evidence that the hippocampus and the MTL substrates are responsible for forming new declarative memories, although the storage of those memories happens in the frontal lobe and elsewhere in the cortex. The nondeclarative memory systems have a wider array of inputs into the generalized broad system, as many parts are seen to contribute to the overall encoding, storage, and retrieval of nondeclarative memories, all outside of the general MTL localization. If anything is to be realized from the experiments conducted thus far on amnesiacs and animal models, it is that memory as a whole is not localized to a single region of the brain as some early philosophers reasoned, but rather followed a combination of Lashley’s view of ‘whole-brain’ memory in combination with Gall’s theory that different forms of memory were localized in different regions. As a conclusive interpretation of memory in the brain, it can be stated that memory systems are localized to different parts of the brain, but interconnect in ways to form memory pathways that still remain not fully understood.

Do non-human animals even have episodic memory? It is even possible that while humans learn some tasks, like with visual pattern discrimination, in a declarative manner, other non-human animals learn the same tasks nondeclaratively. If animal models are not learning and using their memory systems in the same way as humans, how can they be considered representative as to how humans process memory? Humans often approach tasks as simple problems of memorization, while monkeys and other animals gradually learn the visual pattern discrimination over lots of trials in a way that resembles skill learning.


Frontal cortex has the function of holding information for impending action

The view stemming from Milner’s study of H.M. suggested that regions outside of the MTL are critical for the long-term storage of declarative memories.

Direct damage to these surrounding MTL areas impairs memory even more severely than damage to the hippocampus proper. Important for path integration between working memory and long-term memory, includes the proposal that the path integrator is located in these structures.

Amnesic patients were used in a task where they were lead on a path, blindfolded, of no longer than 15 meters and included up to three turns. At the end of the path, the subjects were asked to point in the direction of their starting location. If the subjects were told to actively keep the path in their mind, they were as accurate as the control group. However, when the researchers increased the demand of long-term memory by waiting a few minutes, the amnesiac subjects performed significantly worse. Two patients with the most severe damage (E.P. and G.P.) were unable to remember anything of what they had been doing several minutes after the task. Further proves that MTL regions are imperative for long-term memory. Immediate memory and working memory are still intact with damaged MTL substrates.

Flexibility of declarative memory and relative inflexibility of nondeclarative memory, shown in a study of spatial learning and memory in a rat (page 109)

Now biology is coming into play, as molecular components are being combined with psychology to explain the inner-workings of the brain and its complex memory systems

There are many forms of memory, different brain structures carry out specific jobs, memory is encoded in individual nerve cells and depends on the strength of their interconnections