Taehun Ha

Deficits of Organizational Strategy and Visual Memory in Obsessive-Compulsive Disorder

This study was conducted to investigate the deficits of organizational strategy and visual memory in obsessive-compulsive disorder (OCD). Thirty OCD patients and 30 healthy controls aged 20-35 years participated. The Maudsley Obsessive-Compulsive Inventory, Beck Anxiety Inventory, Wechsler Adult Intelligence Scale, and Rey-Osterrieth Complex Figure (ROCF) test were administered to participants. The authors scored ROCF performances using the Boston Qualitative Scoring System. The OCD patients showed poorer planning ability and higher fragmentation than did healthy controls when copying the ROCF, and they showed even poorer performances in the immediate and delayed recall conditions. The authors found that the Organization score in the copy condition mediated the difference between the OCD group and the healthy group in immediate recall. The direct effect of diagnosis (OCD or healthy) on the immediate recall condition of the ROCF was also significant. This study indicates that people with OCD have poor memory function and organizational deficits.

Visualization Study of Cathode Flooding With Different Operating Conditions in a PEM Unit Fuel Cell

Visualization technique was used to better understand the water build-up phenomena on the cathode side of a proton exchange membrane (PEM) unit fuel cell. In this study, a transparent PEM unit fuel cell with an active area of 25 cm2 was designed and fabricated to allow for the visualization of cathode channel with fuel cell performance characteristics. Two-phase flow due to the electrochemical reaction of fuel cell was experimentally investigated. The images photographed by CCD camera with various cell temperatures (30–50°C) and different inlet humidification levels were presented in this study. Results indicated that the flooding on the cathode side first occurs near the exit of cathode flow channel. As the fuel cell operating temperature increases, it was found that water droplets tend to evaporate easily because of increased saturation vapor pressure and it can have an influence on lowering the flooding level. The approaches of this study can effectively contribute to the detailed researches on water transport phenomena including modeling water transport of an operating PEM fuel cell.Copyright

Numerical Analysis of the Gas Flow Distribution Characteristics in the Anode Flow Channel of Molten Carbonate Fuel Cell (MCFC)

조준현 * 하태훈 · * 김한상 · ** 민경덕 · 박종훈 · *** 장인갑 · *** 이태원 · *** Abstract A three-dimensional computational fluid dynamics (CFD) analysis is performed to investigate flow characteristics in the anode channels and manifold of the internal reforming type molten carbonate fuel cell (MCFC). Considering the computational difficulties associated with the size and geometric complexity of the MCFC system, the polyhedral meshes that can reduce mesh connectivity problems at the intersection of the channel and the manifold are adopted and chemical reactions inside the MCFC system are not included. Through this study, the gas flow rate uniformity of the anode channels is mainly analyzed to provide basic insights into improved design parameters for anode flow channel design. Results indicate that the uniformity in flow-rate is in the range of ±1% between the anode channels. Also, the mal-distributed inlet flow-rate conditions and the change in the size of the manifold depth have no significant effect on the flow-rate uniformity of the anode channels.

A Study of Water and Oxygen Distributions in the Cathode Flow Channels of a PEM Fuel Cell

Water management is a critical operation issue for achieving the highest possible performance of proton exchange membrane (PEM) fuel cells. Quantitative determination of water and species distribution is needed to understand the water management and reactant distribution effects. In this study, the measurement of water and oxygen distributions along cathode flow channels was carried out using gas chromatography (GC). Generally, it is difficult to measure water distribution where water concentration is too high. Here, the measurement of high levels of water saturation in cathode channels was performed according to fuel cell operating conditions. GC measurement was also carried out for flooding and non-flooding conditions. To compare the experimental results with computational results, the three-dimensional CFD simulation of a unit fuel cell was performed using es-pemfc, which is the PEM fuel cell module of commercial CFD code STAR-CD. For the entrance of flow channel that has relatively lower level of water content, the calculated results showed good agreement with measured results. However, some discrepancy between calculated and experimental results was still found for the flow channels near the cathode outlet. The study provides the necessity of the development and adoption of a comprehensive multidimensional PEM fuel cell models including two-phase flow and cathode flooding phenomena for the optimization of fuel cell performance.Copyright