Effect of water distribution in gas diffusion layer on proton exchange membrane fuel cell performance

Water management of proton exchange membrane fuel cells remains a prominent issue in research concerning fuel cells. In this study, the gas diffusion layer (GDL) of a fuel cell is partially treated with a hydrophobic agent, and the effect of GDL hydrophobicity on the water distribution in the fuel cell is examined. First, the effect of the position of the cathode GDL hydrophobic area relative to the channel on the fuel cell performance is investigated. Then, the water distribution in the fuel cell cathode GDL is observed using X-ray imaging. The experimental results indicate that when the hybrid GDL's hydrophobic area lies on the channel, water tends to accumulate under the rib, and the water content in the channel is low; this improves the fuel cell performance. When the hydrophobic area is under the rib, the water distribution is more uniform, but the performance deteriorates.     

An experimental study on moisture transport through a porous plate with micro pores

An experiment was carried out to examine heat and mass transfer between constant-temperature water and dry air through a porous plate having extremely small pores. The effects of the thermal conductivity in the porous plate on moisture transport were investigated. The controlling factor for moisture transport was found to be the thermal resistance inside the porous plate having a low-thermal-conductivity and the heat transfer at the surface of the porous plate having a high-thermal-conductivity.     

Differences in startle reactivity during the perception of angry and fearful faces.

Emotion researchers often categorize angry and fearful face stimuli as "negative" or "threatening". Perception of fear and anger, however, appears to be mediated by dissociable neural circuitries and often elicit distinguishable behavioral responses. The authors sought to elucidate whether viewing anger and fear expressions produce dissociable psychophysiological responses (i.e., the startle reflex). The results of two experiments using different facial stimulus sets (representing anger, fear, neutral, and happy) indicated that viewing anger was associated with a significantly heightened startle response (p     

Asymmetric λ/4-shifted InGaAsP/InP DFB lasers

1.5 μm asymmetriclambda/4-shifted InGaAsP/InP DFB lasers, in which thelambda/4-shift position was moved from the center of the DFB region toward the front side, were made in order to obtain higher output power with high single-longitudinal-mode (SLM) yield. Statistical measurements revealed that it was effective for the increase of the differential quantum efficiency from the front facet without a remarkable decrease of the SLM yield to move thelambda/4-shift position to the front facet by 10-15 percent of the total DFB length. The output efficiencies of the diodes with AR coatings on the window structure were almost coincident to those expected from theoretical calculations. The main to submode ratioP_{0}/P_{1}in the rear spectra of the asymmetric devices noticeably decreased with increasing asymmetry. From an experimental point of view, a criterion for stable SLM operation, for example,P_{0}/P_{1} gsim 1.5in the rear spectrum atI = 0.9 Ithfor thelambda/4-shift positionl_{f} : l_{r} = 35 : 65, is presented.     

Behaviors of micro‐layer in micro‐channel boiling system applying laser extinction method

To elucidate the mechanism and characteristics of boiling heat transfer in a micro‐channel vaporizer, the experimental investigation of the micro‐layer thickness that formed between the heating surface and vapor generated was important. The micro‐layer thickness was measured applying the laser extinction method for channel gap sizes of 0.5, 0.3, and 0.15 mm. It was clarified that the gap size, the rate of bubble growth, and the distance from the incipient bubble site have an effect on the micro‐layer thickness in a micro‐channel boiling system. The initial micro‐layer thickness grew with an increase of the velocity of bubble forefront to moderate the value of the velocity. In the region of greater velocity, the thickness was constant for each gap. The distributions of the initial thickness of micro‐layer on the heat transfer surface were shown. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(1): 35–46, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20096     

1.5-µm λ/4-shifted InGaAsP/InP DFB lasers

A single wavelength light source in 1.5-μm range was developed using InGaAsP/InPlambda/4-shifted distributed feedback (DFB) semiconductor heterostructures. Superiority of thelambda/4-shifted DFB structure in terms of stability of the main mode at the Bragg wavelength was shown theoretically, in which the threshold, the output, and the polarization characteristics were taken into account. Alambda/4-shifted corrugated grating was made by a newly developed negative and positive photoresists technique. Buried heterostructure (BH) diode lasers with nonreflective window ends were fabricated and highly stable single-mode operation with a low threshold was obtained reproducibly. Direct modulation properties and life-tests results indicated that thelambda/4-shifted DFB lasers could be a reliable single-mode light source in a long span lightwave transmission system in 1.5-μm range.     

Single-wavelength operation of 1.53 ?m GaInAsP/InP buried-heterostructure integrated twin-guide laser with distributed Bragg reflector under direct modulation up to 1 GHz

1.53 ?m GaInAsP/InP buried-heterostructure integrated twin-guide laser with distributed Bragg reflector (BH-DBR-ITG laser) was directly modulated with microwave modulation current superimposed on a DC bias which was fixed at 1.1 times the threshold current, and single-wavelength operation was experimentally confirmed with a modulation frequency up to 1 GHz and a modulation depth of 100%.     

Room-temperature CW operation of distributed-feedback buried-heterostructure InGaAsP/InP lasers emitting at 1.57 ?m

Room temperature CW operation of distributed-feedback buried-heterostructure InGaAsP/InP lasers emitting at 1.57 ?m was achieved. A DC threshold of about 250 mA at 25°C and a temperature coefficient of the lasing wavelength of 1.0 ?/°C were obtained. Some of these lasers manifested single longitudinal mode operation both in DC condition and in deeply modulated condition at 500 Mbit/s.     

1.5?1.6 ?m GaInAsP/InP Integrated twin-guide lasers with first-order distributed Bragg reflectors

The room-temperature operation of 1.5?1.6 ?m GaInAsP/InP integrated twin-guide lasers with first-order distributed Bragg reflectors is reported. Single-longitudinal-mode oscillation was observed up to 1.4 times the threshold current. The temperature dependence of lasing wavelength was only 0.8 ?/degree.     

用电子束曝光方法在优化设计的绝缘体上硅脊状波导上实现布拉格光栅的制作和评价

报道了一种用电子束曝光的方法在绝缘体上硅的脊状光波导上制做布拉格光栅的技术.考虑到实际的光子学集成的应用,讨论了这个带有布拉格光栅的脊状光波导的优化设计,给出了该布拉格光栅的测试和理论模拟结果.通过薄化绝缘体上硅的波导层的厚度和光栅的深腐蚀加工,获得了高达30cm-1的光栅耦合系数.