Wire rod coating process of gas diffusion layers fabrication for proton exchange membrane fuel cells

Gas diffusion layers (GDLs) were fabricated using non-woven carbon paper as a macro-porous layer substrate developed by Hollingsworth & Vose Company. A commercially viable coating process was developed using wire rod for coating micro-porous layer by a single pass. The thickness as well as carbon loading in the micro-porous layer was controlled by selecting appropriate wire thickness of the wire rod. Slurry compositions with solid loading as high as 10 wt.% using nano-chain and nano-fiber type carbons were developed using dispersion agents to provide cohesive and homogenous micro-porous layer without any mud-cracking. The surface morphology, wetting characteristics and pore size distribution of the wire rod coated GDLs were examined using FESEM, Goniometer and Hg porosimetry, respectively. The GDLs were evaluated in single cell PEMFC under various operating conditions (temperature and RH) using hydrogen and air as reactants. It was observed that the wire rod coated micro-porous layer with 10 wt.% nano-fibrous carbon based GDLs showed the highest fuel cell performance at 85 °C using H₂ and air at 50% RH, compared to all other compositions.     

Simulation of the fluid-structure-interaction of steam generator tubes and bluff bodies

The accuracy of computational fluid dynamics in simulating the cross-flow around a steam generator and the feasibility of a full scale coupled CFD/FEA fluid-structure-interaction (FSI) analysis is examined through successive validations.The study begins with a comparison between experiment and computation of flow within a stationary tube bank. Results from the simulation of an individual tube experiencing two-degree-of-freedom flow-induced vibration (at a Reynolds number of 3800) are then shown to compare favorably to experimental results. Finally, free vibration of a single cantilevered hydrofoil is simulated with comparison of mean square acceleration at resonant and non-resonant velocities, respectively. The magnitudes and frequencies of vibration are shown to be accurately captured.     

Defect characterization in boron implanted silicon after flash annealing

Flash-assisted rapid thermal processing (fRTP) has gained considerable interests for fabrication of ultra-shallow junction in silicon. fRTP can significantly reduce boron diffusion, while attaining boron activation at levels beyond the limits of traditional rapid thermal annealing. The efficiency of fRTP for defect annealing, however, needs to be systematically explored. In this study, a (1 0 0) silicon wafer was implanted with 500 eV boron ions to a fluence of 1 × 10¹⁵ cm⁻². fRTP was performed with peak temperatures ranging from 1100 °C to 1300 °C for approximately one milli-second. High resolution transmission electron microscopy and secondary ion mass spectrometry were performed to characterize as-implanted and annealed samples. The study shows that fRTP at 1250 °C can effectively anneal defects without causing boron tail diffusion.     

铝合金激光深熔焊气孔形成机理与控制技术

观察了铝合金激光深熔焊气孔的分布特征和形貌特征,深入分析了气孔的形成机理,研究了双光点能量分布的激光对铝合金激光深熔焊气孔的控制效果.结果表明,铝合金激光深熔焊焊缝中存在分布特征和形貌特征不同的两类气孔,即冶金类气孔和工艺类气孔.冶金类气孔的形成与氢在熔池中的析出、聚集与合并有关,而工艺类气孔产生的根本原因是焊接过程中匙孔的瞬间失稳.采用双光点能量分布的激光焊接铝合金可以扩大匙孔张口和根部直径,改善匙孔壁的波动状态,增强匙孔的稳定性,从而减少工艺类气孔的产生,但对冶金类气孔没有明显影响.     

Measurement and characterization of HEMT dynamics

The variation of high electron-mobility transistor (HEMT) large-signal behavior with a change in operating condition is examined with a view to understanding the dynamics involved and developing a modeling strategy. The observed variation exhibits the dynamics of thermal, impact ionization, and trapping effects. A novel measurement of drain characteristic transients gives time-evolution information that clearly shows these as separate quantifiable phenomena with significant dependence on initial operating conditions. A drain-current model that describes high-frequency characteristics with pinchoff, gain, and drain feedback parameters is adapted to describe the variation of the characteristics with changing operating conditions. The results reported give insight and grounding for simulation of HEMT circuits     

Social and environmental factors influence the suppression of pup-directed aggression and development of paternal behavior in captive meadow voles (Microtus pennsylvanicus).

During summer, female meadow voles (Microtus pennsylvanicus) maintain territories and males do not engage in paternal care. As day length shortens, territories dissolve and males nest with females and young. Because paternal behavior has never been studied in free-living meadow voles during colder months or in the laboratory under short photoperiods, the authors examined whether males housed in short day (SD) lengths exhibited more frequent or better quality paternal behavior than males housed in long day (LD) lengths. Sexually and parentally inexperienced (naive) SD males exhibited proportionally more and qualitatively better paternal care than naive LD males. SD males were more responsive than LD males to classic social cues associated with preparturn aggression inhibition and paternal onset. SD sires also displayed qualitatively better paternal behavior than LD sires. These data suggest that meadow vole paternal state is regulated by specific social and environmental cues that may contain reliable information about ecological conditions that favor paternal care. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The impact of self-efficacy on stressor–strain relations: Coping style as an explanatory mechanism.

The present study was designed to examine whether coping style influences the impact of self-efficacy on stressor–strain relations. It was hypothesized that high self-efficacy would weaken stressor–strain relations when accompanied by frequent use of active coping and infrequent use of avoidance coping. Data collected from 2,293 members of the U.S. Army revealed 3-way interactions among self-efficacy, role clarity, and active coping and among self-efficacy, work overload, and avoidance coping. As predicted, self-efficacy mitigated the effects of low role clarity on strain only when active coping was high. Also as expected, strain levels were lower for participants with high self-efficacy than for participants with lower self-efficacy when work overload was low but avoidance coping was high. Implications of these findings for occupational stress research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive constraints on multimedia learning: When presenting more material results in less understanding.

In 4 experiments, college students viewed an animation and listened to concurrent narration explaining the formation of lightning. When students also received concurrent on-screen text that summarized (Experiment 1) or duplicated (Experiment 2) the narration, they performed worse on tests of retention and transfer than did students who received no on-screen text. This redundancy effect is consistent with a dual-channel theory of multimedia learning in which adding on-screen text can overload the visual information-processing channel, causing learners to split their visual attention between 2 sources. Lower transfer performance also occurred when the authors added interesting but irrelevant details to the narration (Experiment 1) or inserted interesting but conceptually irrelevant video clips within (Experiment 3) or before the presentation (Experiment 4). This coherence effect is consistent with a seductive details hypothesis in which the inserted video and narration prime the activation of inappropriate prior knowledge as the organizing schema for the lesson. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

需求预测合同和订货系统

提出了一种需求预测驱动的合同和订货系统。计算机仿真真证明该新能产生合理,固定的订货,及减少库存。     

Combined BS and MS Degree Program in Architectural Engineering

This paper describes the implementation of a combined bachelor of science and master of science degree program in architectural engineering at Kansas State University (KSU). The BS degree in architectural engineering at KSU is a five-year, 162-credit program. Students accepted into the combined BS∕MS program have the potential to reduce their undergraduate program by 15 complementary and free electives and then complete a 30-credit MS program. Availability of the program has contributed to a significant increase in the number and quality of graduate students with the potential to make a significant contribution in the building industry.