• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.172-176
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• 2019

A benthic microbial fuel cells(BMFC) is fuel cell using electricity produced by decomposing organic matter in a sea or a lake. In this study, we used a gas diffusion layer (GDL) of a polymer electrolyte fuel cell (PEMFC) as a BMFC electrode to find out the operation conditions with high performance. The performance of BMFC was increased as resistance of external resistor increased. It was possible to maintain the performance by avoiding the increase of the contact resistance with the electrode due to corrosion of the lead wire in seawater. The bubble generator was able to increase the maximum power density by more than 2 times and the optimum operating temperature was $40^{\circ}C$.

• Journal of the Korean Chemical Society
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• v.31 no.5
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• pp.444-451
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• 1987

The dependence of polarographic parameters on the pressure for the reduction of copper(II), cadmium(II), and zinc(II) complex ions with ethylenediamine, propylenediamine, and diethylenetriamine has been studied. In this study the dropping mercury electrode, the mercury pool electrode, and helix type of platinum wire were used as the working, the reference, and the auxilary electrode, respectively. With increasing the pressure from 1 atmosphere to 1,500 atmospheres, the reduction half-wave potentials of metal complex ions are shifted to the negative values and the diffusion currents become considerably larger, in keeping with the theory on the change of the physical properties of the electrolytic solution such as the density, the viscosity, the dielectric constant, and the electrical conductance, etc. The slope values of the logarithmic plot are increased with increasing the pressure, which indicates the more irreversible reduction. The temperature coefficients of diffusion current observed over the range of the temperature from 25$^{\circ}$C to 35$^{\circ}$C are about two percentage with increasing the pressure, therefore the polarographic reduction under the high pressure is controlled by diffusion. The linear relationships between diffusion current and concentration of metal complex ions are established over all pressure range.

• Journal of the Korean Chemical Society
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• v.33 no.4
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• pp.399-405
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• 1989

The dependence of voltammetric parameters on the pressure for the reduction of Cu(II) in 0.5M KCl aqueous solution has been studied. In this system micro platinum electrode, standard calomel electrode and a helix type of platinum wire were used as the working, the reference and the auxilary electrode, respectively. With increasing the pressure from 1 to 1,800 bars, the half wave potentials of first reduction wave are shifted to the more negative potentials. And the diffusion currents of first and second reduction wave become considerably larger with increase in pressure from 1 to about 1,000 bars but are getting smaller beyond 1,000 bars. The good linear relationships between diffusion current and the concentrations of Cu(II) are established over all pressure range($1{\sim}1,800$ bars). The reversibility of the each reduction step is not changed with increasing pressure.

• Applied Science and Convergence Technology
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• v.23 no.1
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• pp.14-26
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• 2014

Copper is an important component from coin metal to electronic wire, integrated circuit, and to lithium battery. Copper oxides, mainly including $Cu_2O$ and CuO, are important semiconductors for the wide applications in solar cell, catalysis, lithium-ion battery, and sensor. Due to their low cost, low toxicity, and easy synthesis, copper oxides have received much research interest in recent year. Herein, we review the crystallization of copper oxides by designing various chemical reaction routes, for example, the synthesis of $Cu_2O$ by reduction route, the oxidation of copper to $Cu_2O$ or CuO, the chemical transformation of $Cu_2O$ to CuO, the chemical precipitation of CuO. In the designed reaction system, ligands, pH, inorganic ions, temperature were used to control both chemical reactions and the crystallization processes, which finally determined the phases, morphologies and sizes of copper oxides. Furthermore, copper oxides with different structures as electrode materials for lithium-ion batteries were also reviewed. This review presents a simple route to study the reaction-crystallization-performance relationship of Cu-based materials, which can be extended to other inorganic oxides.

• The korean journal of orthodontics
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• v.20 no.1
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• pp.47-59
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• 1990

Respiration is one of the most important functions which are carried out in stomatognathic system. When nasal orifice is obstructed or the resistance of upper airway is increased mouth breathing is initiated. Mouth breathing is regarded as an important etiologic factor of dentofacial anomalies. This experiment was performed to observe the influences of metabolic acidosis, tracheal resistance and vagotomy on mouth breathing. After rabbits were anesthetized with sodium pentobarbital, a pair of wire electrode was inserted into mylohyoid muscle, anterior belly of digastric muscle and dilator naris muscle to record EMG activity. Femoral vein and artery were cannulated for infusion of 0.3N HCl and collection of blood sample to determine the blood pH, and tracheal intubation was done to control airway resistance. Mouth breathing was induced by metabolic acidosis. Increase of the airway resistance through tracheal cannula intensified the activity of dilator naris, mylohyoid and digastric muscle. The higher the resistance, the larger the EMG amplitude. After bilateral vagotomy, respiratory volume and inspiatory time were increased and the activities of dilator naris, mylohyoid and digastric muscle were strengthened. It was concluded that the muscle activity related to mouth breathing was induced by metabolic acidosis and increase of tracheal tube resistance.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.87-95
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• 1998

The use of flux cored arc welding(FCAW) process has grown dramatically since it has been developed because of the remarkable operating characteristics and the resulting weld properties. The feature that distinguishes the FCAW process from other arc welding processes is the enclosure of fluxing ingredients within a continuously fed tubular electrode. The benefits of FCAW process are the increased productivity due to continuous wire feeding, the metallurgical effects derived from the reactions with flux, and the shapes of weld bead formed by slag. However, FCAW process causes the problem in working environment because it generates much more fume than other welding processes. Recently, the welding fume became a hot issue in the field after some welders were diagnosed as manganese toxcosis and siderosis. This study was started to investigate the characteristics of welding fume and utilize the results from the investigation to protect the welders from welding fume. As a first step, the effect of welding conditions on the fume generation rate(FGR) were investigated during FCAW process with $CO_2$ shielding. The considered welding conditions were welding current, arc voltage, travel speed, contact tube to work distance, and torch angle. The results showed that FGR was affected by all of these factors.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.5
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• pp.745-752
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• 2016

The parameters of Debye's equation were applied to analyze the frequency-dependent ground impedance of horizontally-buried wires. We present a new method, based on Debye's equation, of analyzing the effect of polarization on frequency-dependent ground impedance. The frequency-dependent ground impedances of a horizontally-buried wire are directly measured and calculated by applying sinusoidal current in the frequency range of 100 Hz to 10 MHz. Also, the results obtained in this work were compared with the data calculated from empirical equations and commercial programs. A new methodology using the delta-gap source model is proposed in order to calculate frequency-dependent ground impedance when the ground current is injected at the middle-point of the horizontal ground electrode. The high frequency ground impedance of horizontal electrodes longer than 30 m is larger or equal to its low frequency ground resistance. Consequently, the frequency-dependent ground impedance simulated with the proposed method is in agreement with the experimental data, and the validity of the computational simulation approach is confirmed.

• Journal of Welding and Joining
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• v.14 no.6
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• pp.131-139
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• 1996

The response of the arc sensor using the welding current and/or welding voltage as its outputs has been obtained by the analysis and/or experiments of the static characteristics of arc sensor. But in order to improve the reliability of arc sensor, it is necessary to know its dynamic characteristics. So in this paper, it is presented the dynamic model of arc sensor including the power source, arc voltage, electrode burnoff rate, and wire feed rate. A numerical simulation of the dynamic model of arc sensor was implemented, computing the welding current with input of CTWD. The results of computer simulations and experiments of $CO_2$arc welding showed that a linear relationship between weaving center - weld line distance and current area difference was established. Additionally, a real-time weld seam tracking system interfaced with industrial welding robot was constructed, the result of the weld seam tracking experiment for weld line with an initial offset error of 5$^{\circ}$was good.

• International Journal of Automotive Technology
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• v.5 no.3
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• pp.181-188
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• 2004

A cylindrical constant-volume combustion chamber was used to investigate the flow characteristics at the spark electrode gap and the combustion characteristics of an inhomogeneous charge methane-air mixture under several parameters such as stratified pattern, initial charge pressure, ignition time and the excess air ratio of the initial charge mixture. Flow characteristics including mean velocity and turbulence intensity were analyzed by a hot-wire anemometer. The combustion pressure development, measured by a piezo-electric pressure transducer, was used to investigate the effect of initial charge pressure, excess air ratio and ignition times on combustion pressure and combustion duration. It was found that the mean velocity and turbulence intensity had the maximum value around 200-300 ms and then decreased gradually to near-zero value at 3000 ms. For the stratified patterns, the combustion rate under the rich injection (RI) condition was the fastest. Under the initial charge conditions, the second mixture was accompanied by an increase in the combustion rate, and that the higher the mass which is added in the second stage injection, the faster the combustion rate.

• Journal of Korean Society for Atmospheric Environment
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• v.28 no.6
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• pp.675-687
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• 2012

Applying an external electric field across air filter media is one of methods to improve the filtration performance. Metal wire meshes have been commonly used as electrodes situated on both sides of a thick filter pad. For a thin filter medium a short circuit, known as the biggest drawback for applying an external electric field to air filter, can occur at the closest point between electrodes. In this study several types of insulated meshes were prepared by coating #50 meshes with a dielectric material, Nylon 66, and the filtration property of air filter was evaluated at the presence of external electric field using those insulated meshes as electrodes and compared with that of filters using bared meshes. The collection efficiency of tested filter was increased from 78% to 95% for singly charged 100 nm particles by application of external electric field. As a result, there was no significant difference in collection efficiency between filters with insulated and bared electrodes. Similar results could be also seen from the tests using polydisperse particles. Finally, through this study, we found that the insulation of mesh electrodes doesn't affect the filtration performance of fibrous air filter under external electric field.