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排序方式: 共有169条查询结果,搜索用时 15 毫秒
1.
Automotive proton exchange membrane fuel cell stacks need to meet manufacturer specified rated beginning-of-life (BOL) performance before being assembled into vehicles and shipped off to customers. The process of “breaking-in” of a freshly assembled stack is often referred to as “conditioning.” It has become an intensely researched area especially in automotive companies, where imminent commercialization of fuel cell electric vehicles (FCEVs) demands a short, energy- and cost-efficient, and practical conditioning protocol. Significant advances in reducing the conditioning time from 1 to 2 days to as low as 4h or less, in some cases without the use of additional inert gases such as nitrogen, and with minimal use of hydrogen, and specialized test stations will be discussed. 相似文献
2.
Military training commonly results in land degradation, but protocols for assessing and predicting long-term environmental impact are lacking. An ability to assess the impact of repeated disturbance and subsequent recovery is needed to balance training requirements against environmental quality. To develop methodology for assessing soil quality, a study evaluating disturbance resulting from tank maneuvers was initiated on Fort Riley Military Installation, Kansas. The objectives were to identify and quantify soil-quality indicators on two soil types exposed to controlled tank traffic. We examined physical, chemical, and biotic indicators after treatments were applied during wet and dry soil conditions. A randomized complete-block design, with three blocks per soil type and three treatments per block, was used. Treatments consisted of disturbance created by a 63-ton M1A1 tank making five passes in a figure-8 pattern during either dry or wet soil conditions. The M1A1 was operated at a speed of approximately 8 km/h. Control plots received no tank traffic. Soil-quality indicators evaluated were soil compaction, soil penetration resistance, rut depth, soil bulk density, soil texture, soil chemical composition, plant biomass, soil microbial diversity, and nematode and earthworm taxa. Soil-quality indicators were sampled within one week after tank disturbance. Preliminary data indicate soil-texture-dependent treatment effects (p 0.05) for bulk density and porosity. Bulk density increased and porosity decreased on trafficked areas, in the silt loam soil, but showed no change in the silty clay loam soil. Disturbance during wet soil conditions raised penetrometer resistance and gravimetric water content more than disturbance during dry soil conditions (p 0.05). A significant difference in disturbance was measured between the outside and inside portion of the same track (p 0.01 and 0.001, respectively). The outside track caused the greatest amount of disturbance, as measured by the height of the disturbed soil ridge above the track bed. Tank disturbance significantly reduced total vegetative biomass (p 0.05) compared with that of un-trafficked areas. Disturbance under wet soil conditions significantly reduced grass biomass (p = 0.040), whereas disturbance under dry soil conditions significantly reduced forb biomass (p = 0.0247) compared to un-trafficked areas. Total earthworm abundance (p = 0.011) was reduced by 82% when disturbance occurred during wet soil conditions regardless of soil type. 相似文献
3.
K. C. Le 《Continuum Mechanics and Thermodynamics》2007,18(6):335-342
An initiation criterion and a kinetic relation describing hysteresis in shape memory alloys consistent with non-equilibrium
thermodynamics are proposed. The initiation of phase transition begins always at zero driving force, defined as the negative
derivative of free energy with respect to the volume fraction of high strain phase. The kinetic relation is obtained from
the dissipation potential which is proportional to the magnitude of the volume fraction rate times the newly formed volume
fraction. The proposed theory turns out to be rate-independent, but history dependent, and can describe all features of hysteresis
loops observed in experiments.
相似文献
4.
An emulsion interface materialization method was used to obtain amphiphilic silica Janus nanoparticles. Reducing the photosynthesis of aquatic organisms after water pollution. PW12O403− was introduced onto Janus particles by ion exchange, and an amphiphilic particle emulsion catalyst (PWO-J) was prepared. Hydrogen peroxide was used as the oxygen source, and the amphiphilicty of the catalyst was used to assemble the catalyst at the Pickering emulsion interface. The PWO-J catalyst was found to exhibit very high catalytic activity toward the oxidation of oleic acid in water-in-oil systems. The results showed that PWO-J catalysis of oxidation had similar results as CTAB and phosphotungstic acid (control system) under the same conditions. The azelaic acid recovery rate was 86.7%, and PWO-J could be reused 4 times. A reaction mechanism was proposed, and the constructed model was used to calculate a reaction rate constant of 15.32 × 10−5L•mol−1•s−1 for the PWO-J system. The PWO-J system had a lower activation energy than the control system, showing that the catalytic oxidation of oleic acid into azelaic acid was more likely to occur in the PWO-J system. 相似文献
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In this study, we define a class of non-self-adjoint boundary value problems on finite networks associated with Schrödinger operators. The novel feature of this study is that no data are prescribed on part of the boundary, whereas both the values of the function and of its normal derivative are given on another part of the boundary. We show that overdetermined partial boundary value problems are crucial for solving inverse boundary value problems on finite networks since they provide the theoretical foundations for the recovery algorithm. We analyze the uniqueness and the existence of solution for overdetermined partial boundary value problems based on the nonsingularity of partial Dirichlet-to-Neumann maps. These maps allow us to determine the value of the solution in the part of the boundary where no data was prescribed. We also execute full conductance recovery for spider networks. 相似文献
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8.
With the reduction of crude oil throughout the world, enhance oil recovery technology has become a major oil research topics, which can greatly increase the recovery ratio of the crude oil before the dawning of renewable energy era. Near-well ultrasonic processing technology, as one new method, has attracted more attention for Enhanced Oil Recovery due to its low cost, good applicability and no environmental pollution in recent rears. There are two important relevant aspects about Near-well ultrasonic processing technology: (a) how to enhance the oil flow through the rocks into the pumping pool and (b) how to reduce the oil viscosity so that it can be easier to pump. Therefore, how to design a high-power ultrasonic equipment with excellent performance is crucial for Near-well ultrasonic processing technology. In this paper, recent new high-power ultrasonic transducers for Near-well ultrasonic processing technology are summarized. Each field application of them are also given. The purpose of this paper is to provide reference for the further development of Near-well ultrasonic processing technology.With the reduction of crude oil throughout the world, enhance oil recovery technology has become a major oil research topics, which can greatly increase the recovery ratio of the crude oil before the dawning of renewable energy era. Near-well ultrasonic processing technology, as one new method, has attracted more attention for Enhanced Oil Recovery due to its low cost, good applicability and no environmental pollution in recent rears. There are two important relevant aspects about Near-well ultrasonic processing technology: (a) how to enhance the oil flow through the rocks into the pumping pool and (b) how to reduce the oil viscosity so that it can be easier to pump. Therefore, how to design a high-power ultrasonic equipment with excellent performance is crucial for Near-well ultrasonic processing technology. In this paper, recent new high-power ultrasonic transducers for Near-well ultrasonic processing technology are summarized. Each field application of them are also given. The purpose of this paper is to provide reference for the further development of Near-well ultrasonic processing technology 相似文献
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10.
WANG Yu-tian BIAN Xu SHANG Feng-kai WANG Jun-zhu WANG Shu-tao YANG Zhe ZHANG Li-juan 《光谱学与光谱分析》2018,38(12):3780-3784
三维荧光光谱技术与自加权交替三线性分解(SWATLD)算法相结合,对三类农药混合溶液进行检测。在乙腈溶剂中配制西维因、速灭威和三唑磷不同浓度比的混合溶液为测量样品(西维因、速灭威及三唑磷的最佳激发波长/发射波长分别为285/325,305/345和265/305 nm),利用荧光光谱仪获取样品的三维荧光光谱,经过空白扣除以及激发与发射校正,有效地去除仪器误差以及散射产生的影响,得到样品的真实光谱。采用基于自加权交替三线性分解算法对测得的光谱数据进行分析,得到的三种农药的平均回收率为96.9%±1.9%,99.8%±1.0%和100.8%±3.2%。根据SWATLD算法预测结果,计算三类农药的预测均方根误差(RMSEP)值为0.616×10-2,0.539×10-2和0.374×10-2 μg·mL-1,低于平行因子(PARAFAC)分析法预测结果的RMSEP值,且最低检测限均在0.005~0.022 μg·mL-1范围内。和PARAFAC算法相比较,突出了SWATLD算法的优势,表明该算法对光谱重叠严重的三类农药混合物有较好的分解能力。 相似文献