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961.
《International Journal of Hydrogen Energy》2022,47(24):12119-12134
For Pd thin films, microstructural changes involved during hydrogen cycling provide the information needed to predict and optimize the film's mechanical strength. In this paper, a systematic study of the morphology, microstructure, texture, and stress has been performed on Pd thin films during hydrogen loading and deloading cycles at room temperature. Pd thin films of similar morphology were prepared by magnetron sputtering on substrates of different compliances, i.e., Si-oxide, Titanium (Ti) and Polyimide (PI). The evolution of the morphology, grain-orientation distribution (texture), state of stress, and dislocation densities are analyzed for each of the film substrate types for 20 hydrogen loading/deloading cycles. The lattice expansion and contraction caused by the transition from Pd to Pd-hydride and back result in a strong stress increase. This stress increase stabilizes after a few cycles by grain boundary motion that leads to a gradual enhancement of the (111) texture and changes in the dislocation density for Pd films that are strongly clamped on to an oxidized Si(100) wafer substrate with an intermediate layer (Ti or PI). For Pd on PI, the stress is also partly released by a crack-based (crack widening/growth/propagation) pathway. Pd films on Ti and PI do not buckle or blister after 20 hydrogen cycles. By providing a sufficiently compliant substrate the traditional problems of buckle-delamination of a film on a stiff substrate are mitigated. 相似文献
962.
为研究SBS改性沥青混合料在饱水过程中的力学强度演化过程,提出了一种基于圆孔孔边应力集中效应的力学模型,分别计算了非饱水和饱水孔隙的孔边应力.对不同沥青含量的SBS改性沥青混合料试件进行水敏感性试验(MIST)和恒温浸水试验,采用间接拉伸强度(ITS)和拉伸强度比(TSR)来表征沥青混合料的强度演化过程,分析孔隙水压循环次数、水浴时间、孔隙水压力和温度对沥青混合料强度的影响.结果表明:在劈裂荷载作用下,孔隙水压抗力消散了薄弱孔隙的应力集中;随着孔隙水压循环次数或恒温水浴时间的增加,试件的ITS先减小后增大,TSR持续增大;沥青混合料在饱水过程中的强度增加,实际上采集到的是沥青混合料自身强度与孔隙水压力的加和;温度对沥青混合料强度的影响比孔隙水压力的影响更加显著. 相似文献
963.
为实现WaSSI-C(Water Supply Stress Index-C)模型地理信息系统(GIS)可视化模拟系统,为区域水碳资源分析和模拟决策提供模型工具,在解析WaSSI-C模型理论框架和运行机理的基础上,对模型计算过程进行模块化分解和结构化设计;采用C/S模式构建软件体系架构,基于时空数据模型设计E-R模型图,并应用Geodatabase空间数据库与SQLite关系型数据库联合管理模型参数和时空数据;在.Net开发环境下,基于ArcGIS Engine二次开发组件,使用C#语言进行混合编程,实现WaSSI-C模型GIS可视化模拟系统的功能,进而以焉耆盆地为试验对象进行应用验证。结果表明:系统同时支持文本和空间数据格式输入,能够在GIS可视化环境下自动化输出研究区月尺度蒸散、径流和总生态系统生产力等水碳耦合过程变量的模拟地图,系统模拟结果率定期R2和NS均值分别为0.83和0.81,验证期两指标均值分别为0.8和0.76,总体上显示出良好的模拟效果。系统具有简单易用、运算效率高、普适性强等特点,可为相关领域研究提供有力工具支撑,也可为生态学、水文学等专业领域模型可视化研究提供借鉴思路。 相似文献
964.
《Ceramics International》2022,48(5):6443-6452
Two types of Y2O3 partially stabilized ZrO2(YSZ)-based agglomerated powders with and without SiC whiskers were prepared by spray granulation, and the flow ability, apparent density and particle size distribution of them were investigated. The thermal cycling performance and failure mechanism of conventional high temperature sealing coating and modified one with additional layer with whiskers, which were sprayed by air plasma spraying (APS), were comparatively analyzed. The results showed that, compared to the powder without whiskers, the flow ability of that with whiskers reduced by 2.32%, and the apparent density and the proportion of 45–150 μm agglomerated powder increased by 1.53% and 2.29%, respectively. The thermal cycling failure mode of conventional high temperature sealing coating was the overall spalling of ceramic coating, and the spalling position originated from the interface of thermally grown oxide (TGO)/ceramic coating. Microstructure observation indicated that the structure integrity of SiC whiskers in the additional layer sprayed by APS was still retained. The whiskers were uniformly distributed and theinterface between bonding coating and ceramic coating exhibited excellent bonding. With the additional layer containing whiskers, the thermal cycling life of the coating was increased by 102.53%. In the thermal cycling process, the “bridging” and “pulling-out” effects of whiskers located at the additional layer consumed considerable energy, which could reduce the driving force of crack growth. Besides, a porous structure of the additional layer after thermal cycling was formed due to “bridging” and “pulling-out” of whiskers, further improving the thermal cycling life of coating with the additional layer. 相似文献
965.
《Microelectronics Reliability》2015,55(6):912-918
A typical emitter contact of an IGBT consists of a front metallization and bond wires. In this study, the power cycling performance of a special emitter contact design is experimentally verified. The emitter contact includes a metal plate, which is Ag-sintered to the metallization and wire bonded on the top surface. Either Cu or Al bond wires were implemented. Power cycling tests were performed to investigate the performance of such IGBT modules. The results were very promising and a cycling lifetime was achieved, which is about 20 times higher than the lifetime of typical IGBT modules. For a better understanding of the experimental results, the electrical and thermal response of the IGBT modules were simulated by FEM. The results of this study, provide a key for high-reliability designs of the emitter contact of IGBT modules with superior power cycling capability. 相似文献
966.
Bike sharing nowadays is a must-have element of the urban transport system that is changing mobility patterns in cities worldwide. BiciMAD, a fleet of bicycles with electric pedal-assistance (pedelecs)—introduced in the center of Madrid (Spain) in 2014—is an example of the latest generation. In this article, Innovation Diffusion Theory (IDT) is adapted and applied as a framework to study data from a series of surveys among BiciMAD subscribers to describe adopter profiles and analyze attributes that influence the time of adoption, including an additional one: cycling familiarity. Empirical results are presented to show how an innovation (in terms of technology and service configuration on the level of a city) is dispersed. Conclusions show that smart bike sharing is an innovation vector in urban mobility, an attractive new travel mode for the identified adopter categories, namely (1) lifestyle cyclists, the venturesome and technology enthusiast Earliest Adopters, (2) dedicated cyclists, the rational and deliberate Early Majority, (3) leisure cyclists, the skeptical and peer-dependent Late Majority, and (4) fair-weather cyclists, the prudent Laggards. 相似文献
967.
《Journal of the European Ceramic Society》2019,39(7):2397-2408
Forsterite-type Mg2SiO4 was investigated systematically for thermal barrier coating (TBC) applications. Results showed that Mg2SiO4 synthesized by solid-state reaction possessed the good phase stability up to 1573 K. The thermal conductivity of Mg2SiO4 at 1273 K was lower ˜20% than that of yttria stabilized zirconia (8YSZ). Mg2SiO4 also presented moderate thermal expansion coefficients, which increased from 8.6 × 10−6 K−1 to 11.3 × 10−6 K−1 (473˜1623 K). Mechanical properties including hardness, fracture toughness, and Young’s modulus of Mg2SiO4 were comparable to those of 8YSZ. The sintering results indicated a promising low-sintering activity of Mg2SiO4. Mg2SiO4 samples were subjected to water quenching test at 1573 K and showed a superior thermal shock resistance compared to 8YSZ. Mg2SiO4 coating with stoichiometric composition was produced by atmospheric plasma spraying. The thermal cycling test result showed that Mg2SiO4 coating had a lifetime more than 830 cycles at 1273 K, which is desirable for TBC applications. 相似文献
968.
Shaleph O’Neill 《Digital Creativity》2019,30(2):127-140
This paper develops ideas around cycling as art practice. The questions at the heart of it revolve around how new data technologies enable us to represent such experiences as artworks. Recent research in neuroscience has begun to establish the ways in which modes of perception are processed in the brain. Related research suggests that Synaesthesia may be caused by a genetic mutation that results in a ‘cross wiring’ of these modes of perception. Within the arts there is a long history of exploration around synaesthesia, ideas that are becoming relevant again particularly in relation to the growth in personal data. Representing sensations and transferring them from one mode to another offers a way to handle some of this data and potentially say new things about our experiences. The author explores these ideas through artworks made using data from cycling to investigate the visualization of this experience. 相似文献
969.
通过Sonogashira Hagihara偶联聚合制备了一系列具有多孔结构的网状交联聚卟啉光催化剂,设计了双溴双炔卟啉和四溴卟啉两种结构的卟啉单体,通过双溴双炔卟啉自聚得到多孔有机聚卟啉(PPOP-1),通过四溴卟啉与含双炔基的单体(1,7-辛二炔、对苯二炔、联苯二炔)共聚得到聚卟啉PPOP-2、PPOP-3和PPOP-4.通过SEM和物理吸附仪观测聚合物的表面形貌和表征孔结构.结果显示,4种聚合物均具有均匀的颗粒形态和微孔结构,孔径约1 nm,比表面积分别为38.484、12.494、10.880和19.858 m2/g.以聚卟啉为异相光催化剂,通过可见光诱导二苄胺、缩硫酮、二苄基硫醚的有氧氧化证实了其对C—N和C—S键的氧化均具有优于单体催化剂的催化活性.PPOP-1(0.01 mmol)在可见光下催化二苄胺(0.1 mmol)的氧化反应,8 h后体系原料转化率和选择性均可达99%.经过4次循环催化后,PPOP-1仍保持较高的催化活性,原料转化率仍能达到99%. 相似文献
970.
Yanzhou Qin Suhui Ma Yafei Chang Yuwen Liu Yan Yin Junfeng Zhang Zhi Liu Kui Jiao Qing Du 《International Journal of Hydrogen Energy》2021,46(12):8722-8735
Relative humidity (RH) cycling during the frequent startup/shutdown (SUSD) process may lead to the generation and propagation of mechanical defects in the polymer electrolyte membrane (PEM) fuel cell. In this study, a 2D finite element model for the evolution of internal defects in PEM fuel cell is established, and the interfacial behavior of the membrane/catalyst layer (CL) is simulated based on the cohesive zone model (CZM), focusing on the RH cycling effect on the membrane/CL delamination evolution. Emphasis is placed on the evolution of membrane/CL delamination when cracks have been generated in the CL. The results show that the existence of the CL crack aggravates the membrane/CL delamination, and the more the position of the CL crack is off-center, the more serious the delamination propagation is. The initial delamination length (IDL) and interface length synergistically affect the interface behavior of membrane/CL. Higher frequency (or shorter period) and greater amplitude of the RH cycle intensify the membrane/CL delamination. 相似文献