• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1038-1040
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• 1992

Booster is used widely as one of the step-up DC/DC power converter in power conversion process for fuel cell power plant which have the electrical characteristic of the high current density and low cell voltage. In view of control system, booster can be unstable when it is operated in broad operation range because the transfer function of booster has zero in right half plane of s-domain. So for reliable operation, controller must make the system stable in whole working range. In this paper, the two control method such as digital PID control and fuzzy control is studied for booster output voltage regulation in fuel cell plant. The design procedure of PID control and fuzzy control is described. And the experiment of designed controller action is performed in various operation points for controller performance test.

• Journal of Hydrogen and New Energy
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• v.25 no.4
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• pp.378-385
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• 2014

In this research, we investigate electrical performance and electrochemical properties of graphene supported Pt (Pt/G) and PtM (M = Ni and Y) alloy catalysts (PtM/Gs) that are synthesized by modified polyol method. With the PtM/Gs that are adopted for oxygen reduction reaction (ORR) as cathode of proton exchange membrane fuel cells (PEMFCs), their catalytic activity and ORR performance and electrical performance are estimated and compared with one another. Their particle size, particle distribution and electrochemically active surface (EAS) area are measured by TEM and cyclic voltammetry (CV), respectively. On the other hand, regarding ORR activity and electrical performance of the catalysts, (i) linear sweeping voltammetry by rotating disk electrode and rotating ring-disk electrode and (ii) PEMFC single cell tests are used. The TEM and CV measurements demonstrate particle size and EAS of PtM/Gs are compatible with those of Pt/G. In case of PtNi/G, its half-wave potential, kinetic current density, transferred electron number per oxygen molecule and $H_2O_2$ production % are excellent. Based on data obtained by half-cell test, when PEMFC singlecell tests are carried out, current density measured at 0.6V and maximum power density of the PEMFC single cell employing PtNi/G are better than those employing Pt/G. Conclusively, PtNi/Gs synthesized by modified polyol shows better ORR catalytic activity and PEMFC performance than other catalysts.

• Journal of the Korean Society of Safety
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• v.29 no.6
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• pp.87-93
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• 2014

In this study, the reinforced concrete rahmen bridge damaged by the chloride attack was investigated. According to the investigation, the degraded concretes on cantilever kerb and end part were intensively observed. Thus, the chloride content test and half-cell method were performed to evaluate the degraded parts. As a result, the contents of chloride on degraded parts were C and D grade. On the other hand, the half-cell potential values of rebar in degraded concrete were measured with the minor corrosion. This rebar corrosion is expected to progressing. Chloride content D grade is due to expansion pressure by corrosion of rebar and freeze-thaw by permeate water, could see progresses rapidly degradation. In order to prevent chloride attack to concrete deck caused by deicing salts, corresponding to the chloride critical concentration must maintain grade b or at least grade c. Chloride condition evaluation standard apply to evaluation of marine structure chloride attack with chloride attack by deicing salts.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.179-180
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• 2010

The literature of present study was performed with content of chloride by total 6 level. After casting, and then, to measure the results of corrosion in a quick time used accelerated method of corrosion during 20 weeks. Both Galvanic and Half-cell for 20 weeks was used to model the initial time to corrosion, and then current of corrosion was measured by using Linear polarization at the end of cycling. The processing of steel used in concrete is same way as the case of mortar and also the initial time of corrosion was measured.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1C
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• pp.29-38
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• 2011

The smaller diameter cone penetrometer has been widely used to estimate the characteristics of local area due to high vertical resolution. The half-bridge cirucits have been adopted to measure the mechnical strength of soil through the smaller diameter cone penetrometer due to the limitation of the areas for configuring the full-bridge circuit. The half-bridge circuit, however, is known as being easily affected to the temperature variation. The objective of this study suggests the temperature-compensated method in mini-cones. The diameter and length of the mini-cone is designed to 15mm and 56mm. The load cell of the mini-cone is extended about 54mm on the behind of the mini-cone to reflect the only temperature variation. The full-bridge circuit is installed to measure the temperature-compensated values in the mini-cone and the half-bridge circuit is also organized to compare the temperature compensated values with uncompensated values. The seasonal variation tests are performed to define the effect of temperature variation under summer and winter temperature condition. The densification tests are also carried out to investigate temperature effects during penetration. The measured mechanical resistances with temperature-compensated method show more reliable and reasonable values than those measured by thermal uncompensated system. This study suggests that the temperature-compensated method of the mini-cone may be a useful technique to obtain the more reliable resistances with minimizing the temperature effect.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3145-3150
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• 2010

Ruthenium catalysts modified by selenium have been introduced as alternative materials to Pt in Direct methanol fuel cells (DMFCs). RuSe nano-particles were synthesized on the Vulcan XC72R carbon supports via polyol method. The prepared catalysts were electrochemically and physically characterized by cyclic voltammetry (CV,) linear sweep voltammetry, methanol tolerance test, X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energydispersive Spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). Increasing the Se concentration up to 20 at % increased the electro-catalytic activity for the oxygen reduction. By increasing Se amount, Ru metallic form on the surface was increased. The $Ru_{80}Se_{20}$/C catalysts showed the highest oxygen reduction reaction (ORR) activity and outstanding methanol tolerant property in half cell tests as well as single cell test.

• Journal of Soil and Groundwater Environment
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• v.8 no.2
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• pp.70-77
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• 2003

Theoretical estimation of overall stoichiometry for the microbial degradation of hazardous organic compounds is described. Half-reaction method based on microbial energetics was used in the theoretical estimation. In addition to the half-reaction method, other theoretical methods such as intermediate formation, oxygenation reaction, and estimation of the standard free energy of formation by group contribution theory were also applied. As a case study, the application of these methods was demonstrated for the estimation of microbial kinetics in the biodegradation of phenanthrene which was chosen as a model hazardous organic compound along with glucose and hexadecane. The cell yield, oxygen requirement, nitrogen requirement, and mineralization ratio could be estimated from the overall stoichiometry. It is believed that these theoretical estimation methods are useful tools for practical design and assessment of bioremediation of soil and groundwater contaminated with hazardous organic compounds.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.2
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• pp.113-120
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• 2017

HCP(Half Cell Potential) method has been widely used since it is recognized as a efficient NDT(Non Destructive Technique) for corrosion detection. This work is for an evaluation of relation between corrosion amount and measured HCP in dried condition through ICM(Impressed Current Method) for accelerating corrosion. For the work, cement mortar specimens with three w/c ratios and four cover depths are prepared, and corrosion test based on ICM is performed for 6 hours, 18 hour, and 42 hours with constant 20V of electrical charge, respectively. From the test, corrosion amount increases with reduced cover depth, increasing w/c ratio, and extended corrosion period, where corrosion amount is evaluated to linearly increases with measured HCP in dried condition. In order to evaluate corrosion amount through measured HCP, the measured HCP level is firstly determined and then corrosion amount is to be compared with measured HCP, which is evaluated to be more reasonable with higher C.O.V.

• Journal of the Korean Electrochemical Society
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• v.2 no.2
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• pp.75-80
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• 1999

Li-ion cells employ lithium transtion metal oxide as the cathode material and carbon as anode material. To manufacture Li-ion cell with higher capacity and better cycle life, the utilization of electrode materials should be as high as possible without lithium deposition onto the carbon surface during charging. A careful design of cell balance between cathode and anode materials as well as a proper charge method is a key factor to design Li-ion cell with long cycle life. In this study, we investigated the effect of cathode/anode weight ratio on the performance of $LiCoO_2/MPCF$ cell. First we evaluated the charge-discharge behaviours of half-cells. And cylindrical Li-ion cells were fabricated using graphitized MPCF anode and $LiCoO_2$ cathode. The voltage profiles for each half-cell in $LiCoO_2/MPCF$ cell were measured by using lithium metal as a reference electrode. Also, we evaluated the cyclic performance of $LiCoO_2/MPCF$ cells according to weight ratio. From the result of experiment $LiCoO_2$ cathode utilization was independent of weight ratio, but MPCF anode utilization was dependant on weight ratio. Also, the optimal weight ratio of $LiCoO_2/MPCF$ cell was found to be $2.0\~2.2$.

• YAKHAK HOEJI
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• v.47 no.4
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• pp.224-229
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• 2003

We have investigated the transport characteristics of synthetic antioxidant and free radical scavenger, $\alpha$-phenyl-n-tert-butyl nitrone (PBN) at the blood-brain barrier (BBB) by in vitro uptake study in conditionally immortalized rat brain capillary endothelial cell line (TR-BBB). Also, the efflux of PBN from brain to blood is estimated using the brain efflux index (BEI) method. Choline is a charged organic cation, including nitrogen-methyl group and shows the carrier-mediated distribution to the brain. [$^3$H]Choline uptake by TR-BBB cells was significantly inhibited by PBN with $IC_{50}$/ of 1.2 mM, which appears to be due to similar structures between choline and PBN. And, PBN was microinjected into Par2 of the rat brain by BEI method, and was eliminated from the brain with an apparent elimination half-life of about 2 min. Also, [$^3$H]choline efflux was significantly inhibited by PBN using BEI method. In conclusion, the efflux transport of PBN takes place across the BBB and PBN may be transported into the brain and eliminated from the brain by BBB choline transporter.