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51.
《International Journal of Hydrogen Energy》2019,44(17):8904-8913
Hydrogen, producing electricity in fuel cells, is a versatile energy source, but with risks associated with flammability. Fuel cells use enclosures for protection which need ventilating to remove hydrogen emitted during normal operation or from supply system leaks. Passive ventilation, using buoyancy driven flow is preferred to mechanical systems. Performance depends upon vent design, size, shape, position and number. Vents are usually plain rectangular openings, but environmentally situated enclosures use louvres for protection. The effect of louvres on passive ventilation is not clear and has therefore been examined in this paper. Comparison ‘same opening area’ louvre and plain vent tests were undertaken using a 0.144 m3 enclosure with opposing upper and lower vents and helium leaking from a 4 mm nozzle on the base at rates from 1 to 10 lpm, simulating a hydrogen leak. Louvres increased stratified level helium concentrations by typically in excess of 15%. The empirical data obtained was also used in a validation exercise with a SolidWorks: Flow Simulation CFD model, which provided a good qualitative representation of flow behaviour and close empirical data correlations. 相似文献
52.
Chunyan Xie Lu Zhao Bin Jiang Jiashan Mao Yan Lin Peng Wang Xiantao Wei Min Yin Yonghu Chen 《Journal of the American Ceramic Society》2019,102(12):7500-7508
Mn4+ and Tb3+ singly doped and Mn4+/Tb3+ codoped lutetium aluminum garnet (Lu3Al5O12, or simply LuAG) phosphors were synthesized and investigated for the application of optical thermometry. X-ray powder diffraction and luminescence spectroscopy measurements were performed on all samples to analyze their crystal phases and optical properties. In particular, temperature-dependent luminescence of the LuAG:Mn4+/Tb3+ sample was measured at the temperature range of 270–420 K. The results showed that the luminescence intensity of Mn4+ has gone through a remarkable decline while the luminescence of Tb3+ has an only insignificant change with the rise of temperature which leads to a dramatic decrease in the fluorescence intensity ratio (FIR) between the two activator Mn4+ and Tb3+. Further analysis showed that the LuAG:Mn4+/Tb3+ sample used for temperature sensing has a high relative sensitivity with maximum value of 4.3% K−1 at 333 K. Our research indicated that this LuAG:Mn4+/Tb3+ material is a promising candidate for FIR-type optical temperature sensing. 相似文献
53.
Shuai Wang Yangyang Deng Shuaibo Gao Mingsheng Yang Pengfei Xing 《International Journal of Applied Ceramic Technology》2020,17(6):2569-2579
B4C-TiB2-SiC composites toughened by (TiB2-SiC) agglomerates were prepared via reactive hot pressing with B4C and TiSi2 as raw materials. Phase composition, microstructure, and mechanical properties of the fabricated composites were investigated. The function of (TiB2-SiC) agglomerates was analyzed, and the strengthening and toughening mechanism were also discussed. Results indicated that some of the in situ formed TiB2 and SiC were interlocked to form special (TiB2-SiC) agglomerates in the matrix. The good comprehensive performances of 510 MPa flexural strength, 5.84 MPa·m1/2 fracture toughness, and 31.93 GPa hardness were obtained in the composites fabricated with 30 wt% TiSi2. The in situ introduced fine TiB2 and SiC grains refined the grains of B4C due to the pinning effect, which enhanced the strength. The special (TiB2-SiC) agglomerates and the existing toughening phenomena such as crack deflection, branching, and microcrack regions induced by the mismatch of thermal expansion coefficients, had cumulative effects on improving the fracture toughness. 相似文献
54.
Tomoko Okuyama Jun Shirakawa Kazuki Tajima Yoko Ino Heidrun Vethe Yu Togashi Mayu Kyohara Ryota Inoue Daisuke Miyashita Jinghe Li Nozomi Goto Taiga Ichikawa Shingo Yamasaki Haruka Ohnuma Rie Takayanagi Yayoi Kimura Hisashi Hirano Yasuo Terauchi 《International journal of molecular sciences》2020,21(21)
55.
Loadbearing capacity of infill masonry walls considering the deformation‐based membrane effect 下载免费PDF全文
《Mauerwerk》2018,22(3):151-161
According to currently valid codes, it is not possible to determine the loadbearing capacity of unreinforced infill walls considering the deformation‐based membrane effect by incorporating the exact support conditions. One reason for this is the lack of a validated calculation procedure, which in addition to the equilibrium conditions also realistically represents the compatibility conditions of these systems. In the present paper, therefore, a new non‐linear analytical calculation procedure is presented. The main focus of the analysis of walls subject to area loading is the incorporation of the support conditions and thus the consideration of the deformation‐based membrane compressive force. Through generalised formulation and a standardised notation of the determination equations, different material behaviours and various support conditions can be taken into account with few parameters. On the action side, both lighter loading like wind loads and heavier loading like explosion loads can be considered. Through the implementation of the partial factor concept, it is possible to comply with the requirements of European codes and thus ensure the applicability of the analysis model. 相似文献
56.
Liang Feng Jiandong Pang Ping She Jia-Luo Li Jun-Sheng Qin Dong-Ying Du Hong-Cai Zhou 《Advanced materials (Deerfield Beach, Fla.)》2020,32(44):2004414
Metal–organic frameworks (MOFs) based on group 3 and 4 metals are considered as the most promising MOFs for varying practical applications including water adsorption, carbon conversion, and biomedical applications. The relatively strong coordination bonds and versatile coordination modes within these MOFs endow the framework with high chemical stability, diverse structures and topologies, and interesting properties and functions. Herein, the significant progress made on this series of MOFs since 2018 is summarized and an update on the current status and future trends on the structural design of robust MOFs with high connectivity is provided. Cluster chemistry involving Y, lanthanides (Ln, from La to Lu), actinides (An, from Ac to Lr), Ti, and Zr is initially introduced. This is followed by a review of recently developed MOFs based on group 3 and 4 metals with their structures discussed based on the types of inorganic or organic building blocks. The novel properties and arising applications of these MOFs in catalysis, adsorption and separation, delivery, and sensing are highlighted. Overall, this review is expected to provide a timely summary on MOFs based on group 3 and 4 metals, which shall guide the future discovery and development of stable and functional MOFs for practical applications. 相似文献
57.
58.
分析了国内外露天矿山用卡车无人驾驶技术发展现状,详细介绍了露天矿山卡车无人驾驶关键技术;通过分析对比前装线控和后装线控两种技术路线的优缺点以及超声波雷达、毫米波雷达、激光雷达、4D光场智能感知系统、红外传感器、视觉传感器等环境感知技术的优缺点;提出多传感器高度融合将是露天矿山卡车实现全天候环境感知的发展方向。通过分析对比惯性导航系统、GNSS差分定位技术、车联网定位技术、电子地图定位技术、视觉传感器等定位导航技术的差异,指出多定位技术融合是露天矿山无人驾驶卡车定位方式的必然选择。结合露天煤矿的生产实际,提出将现有的无人驾驶各种技术算法与露天矿山标准作业流程有机融合是实现卡车无人驾驶的必由之路。最后指出无人驾驶卡车应用5G技术是露天矿山安全生产的关键和核心,是无人驾驶的必备技术。 相似文献
59.
自2008年起,我国地勘行业投资规模迅速增长,随后快速回落,近年来市场规模趋于稳定,预计2020年我国的岩心钻机相关市场规模约为100亿元左右,从业人员也将超过5万人。为了使我国岩心钻机操作人员能够掌握在“高精尖”设备转型下的自动化全液压岩心钻机的操作技能,本研究利用虚拟现实技术,还原岩心钻机的实际现场工作状态;采用SolidWorks,3ds Max,Cinema 4D等软件对钻机进行三维建模、坐标更改和纹理着色;以C#语言为脚本,研究关键帧动画设定、摄像机视角控制、刚体碰撞模块、射线检测等技术,提出基于Unity 3D的岩心钻机模拟操作系统设计方案并最终实现。该模拟操作系统具有多视角展示、钻进控制、参数显示和语音指导等功能,呈现了能够身临其境的钻机操作体验。 相似文献
60.
K. Balamurugan S. Sankar U. S. Hareesh K. G. K. Warrier 《Materials and Manufacturing Processes》2018,33(4):405-413
In this work, lanthanum phosphate with a 20% yttria (LaPO4/Y2O3) composite prepared by an Aqueous Sol–Gel process is machined using an Abrasive Water Jet Machine (AWJM). The machinability of this composite is studied by varying the input parameters namely Jet Pressure (JP), Stand-Off Distance (SOD), and Traverse Speed (TS) on Surface finish. Garnet of 80 mesh size is used as an abrasive with a flow rate of 85?g/min. The microstructural characterization study reveals the presence of new element YPO4. This element enhances the machinability and reduced porosity in the composite. Microscopy examinations on the machined surface reveals that partial overlapping at low JP, poor surface finish at high JP and SOD, forged deficiency at maximum SOD and TS. The minimum levels of all input parameters are influenced to obtain acceptable Ra. Atomic Force Microscopy (AFM) on the kerf surface shows micro wear track and peaks. The Multiple Regression Analysis (MRA) is developed for Ra to check the adequacy. From the Analysis of Variance (ANOVA), SOD has a significant effect on Ra with a contribution of 53%. The influence of JP and TS on Ra is found to be 31% and 15%, respectively. 相似文献