The effect of Co-Co3O4 coating on the electrochemical properties of Si as an anode material for Li ion battery

In order to improve the electrochemical performance of Si as an anode material for Li ion secondary batteries, a biphasic layer composed of Co and Co₃O₄ was coated on Si particles by sol-gel method. Compared to Si, Co-Co₃O₄ coated Si showed the drastic improvement in several electrochemical properties, such as initial coulombic efficiency (55% → 88%), cyclic efficiency and cycle life. The comparison between Co-Co₃O₄ coated Si and heat-treated Si without the coating let us know that the improvement of electrochemical properties only results from Co-Co₃O₄ coating layer. Little changed cyclic properties (cyclic efficiency and cycle life) of Co-Co₃O₄ coated Si even at a higher charge-discharge rate insinuated that Co-Co₃O₄ coating layer plays a crucial role in maintaining the electronic contacts between particles and conducting parts. When trying to measure a thickness variation of the electrodes each containing Si and Co-Co₃O₄ coated Si as active materials, it was notified that Co-Co₃O₄ coating layer can accommodate the volume expansion of Si during Li⁺ insertion, which has its original thickness almost recovered after Li⁺ extraction.     

VAV变风量系统控制的研究和探索（二）

本文主要对VAV变风量系统中出现的高大空间场所控制问题、回风系统风量平衡问题、系统噪声问题、新风量控制问题、风量测量单元（FMS）的优势、控制策略的选择和比较进行了分析、探讨,并提出了相应的解决方法。     

下泄调节阀开度对下泄流影响的数值分析

对某压水堆核电站化学和容积控制系统(RCV)的下泄管路,采用Flowmaster程序作为计算平台进行了正常工况下的热工水力计算.分析了下泄调节阀RCV013VP的开度对下泄流量以及下泄管路中的一些物理参数的影响.计算结果表明,RCV013VP的阀门开度小于60%时,阀门开度对下泄流量影响显著;阀门开度大于60%时,下泄流量不再随阀门开度增加而明显变化.正常工况下即使RCV013VP全开,下泄流冷却剂也不会发生气化现象,但随着RCV013VP开度的增加,下泄管路冷却剂压力会越来越接近其对应温度下的饱和压力.     

集聚纺车间地沟均匀吸风设计方法探讨

探讨集聚纺车间地沟均匀吸风设计方法。介绍了地沟均匀吸风的设计原理和实现均匀吸风的措施;分析了变风量系统对均匀吸风性能的影响;介绍了变风量均匀吸风系统的设计;计算分析表明:回风沟道应采用变截面分段设计法,吸风口采用条缝型形高速自适应风口,吸风口面积之和与沟道截面积之比不大于0.4,前后吸口的吸风不均匀程度可以控制在15%以内。认为:采用支沟道变截面分段设计能较好地控制吸风的均匀性,可以保证集聚纺车间气流均匀稳定。     

基于连续拟稳定法的页岩气体积压裂水平井产量计算

水平井体积压裂是开发页岩气藏的关键技术。体积压裂后,未改造区域的流动为受微纳米孔隙介质控制的非线性渗流,而改造区域的流动则是由微米级裂缝网络控制的达西渗流。综合考虑页岩气藏体积压裂后的多尺度流动、页岩气解吸附、扩散等特点,建立了耦合未改造区域和改造区域流动的稳态产量计算模型;在此基础上,首次运用连续拟稳定法,考虑压力波不稳定扩散,结合物质平衡方程建立了页岩储层体积压裂水平井非稳态产量计算方法,并对页岩气体积压裂水平井非稳态产量的影响因素进行了分析。结果表明：基于连续拟稳定法建立的产量预测模型具有求解过程简单、计算速度快,与数值模拟结果吻合程度高的特点;页岩气的解吸效应主要影响生产中后期的产量;随着体积压裂区半径、压裂区渗透率、扩散系数、朗格缪尔体积的增大,页岩气井产能增大,且增加幅度逐渐减小;朗格缪尔压力对产量的影响较小。该方法为页岩气体积压裂水平井非稳态产量的计算提供了理论依据。     

Three dimensional flow simulation over a sharp-crested V-Notch weir

Thin-plate weirs are widely used to monitor the flow rate in open channels. Thereby, three dimensional (3D) modeling of the flow over a weir in an open channel can be considered as one of the main topics in hydraulic science. In this study, the flow over a sharp-crested v-notch weir (SCVW) is simulated by a 3D numerical model. Laboratory experiments were conducted to monitor and measure the behavior of the SCVW in practice. Finally, the simulated velocity distributions, water surface profiles, and hydraulic jump were compared with those of the experimental data. Due to the turbulent nature of the flow over the SCVW, a Reynolds stress model (RSM) and three types of the k–ϵ turbulence models with the fractional volume of fluid technique (VOF) were used in the analysis. In this respect, the two-phase solution method and dense mesh were used in generating the simulation domain. Results indicated that the RSM exhibited higher accuracy in defining the velocity distribution, complex flow pattern, and predicting the hydraulic jump formation downstream of the SCVW.     

高精度高比容独石电容器用瓷料研究及其介电常数的计算

首先利用蒙特卡罗有限元法在分析陶瓷材料内电场分布的基础上 ,对微粒混合陶瓷材料的介电常数与各成分含量及其介电常数之间的关系进行了探讨。研究表明 ,由于介质极化的原因 ,在陶瓷材料内部 ,等势线的分布将主要集中于低介电常数成分所占的区域 ,并且 ,微粒混合陶瓷材料各成分的含量及其介电常数都会对陶瓷材料内电场的分布产生重要影响 ,并使陶瓷材料的宏观介电常数发生变化。当陶瓷材料中含有与其他成分介电常数差别相当大的成分时 ,利用蒙特卡罗有限元法可获得较其他传统方法更为准确的结果系统地研究了钡钛钕系统陶瓷的介电性能。研究结果表明 ,Ba Ti O3中掺入极少量的 Nd2 O3(例如摩尔分数 x为 0 .1% )时 ,材料呈半导性 ,电阻率呈明显的 PTCR效应。Ba Ti O3中掺入少量的 Nd2 O3(x≥ 0 .2 % )时 ,材料呈绝缘性 ,且随着 Nd2 O3掺入量的增加 ,材料的平均晶粒尺寸不断减小 ,居里峰向负温方向移动 ,居里峰不断降低。Ba Ti O3中掺入少量 Nd2 O3· 2 Ti O2时 ,随着掺入量的增加 ,居里峰向负温方向移动 ,晶粒尺寸不断增大 ;Ba Ti O3中掺入较多的 Nd2 O3· 2 Ti O2 时 ,随着掺入量的增加 ,介电常数不断减小 ,介电常数的温度特性曲线的非线性程度不断减小 ,并且 ,当 Ba Ti O3与 Nd2 O3· 2 Ti O2 的摩尔比?     

NUMERICAL SIMULATION OF EXTREME WAVE GENERATION USING VOF METHOD

Numerical simulations of extreme wave generation are carried out by using the Volume Of Fluid (VOF) method. Extreme waves are generated based on wave focusing in a 2-D numerical model. To validate the capability of the VOF-based model described in this article, the propagation of regular waves is computed and compared with the theoretical results. By adjusting the phases of wave components, extreme waves are formed at given time and given position in the computation. The numerical results are compared with theoretical solutions and experimental data. It is concluded that the present model based on the VOF technique can provide acceptably accurate numerical results to serve practical purposes.     

基于非圆齿轮的非等速比、多作用传动装置的应用研究

根据回转式泵、压缩机等容积式机械工作时转子要有相对运动以实现容腔容积变化的特点,设计了整周期内速度连续变化和整周期内只有高、低两种转速的非等速比、多作用的两种传动装置,为回转式容积机械的研究提供了一条新思路.     

IDEAS based synthesis of minimum volume reactor networks featuring residence time density/distribution models

This work addresses for the first time, the synthesis of globally minimum volume reactor networks, featuring segregated flow reactors (SFR) and/or maximum mixedness reactors (MMR), with the same normalized residence time density (NRTd) function. Global optimality is ascertained by demonstrating that the input–output information maps of SFR and MMR with general RTd/RTD models satisfy all properties required for the application of the infinite dimensional state-space (IDEAS) approach to the RTd/RTD reactor network synthesis problem. The resulting IDEAS formulation is shown to possess a number of novel properties, which can be used to facilitate its solution. The power of the proposed methodology is demonstrated on three case studies featuring segregated laminar flow reactors (SLFR) in which the Trambouze reaction scheme is carried out. In one of the case studies, the identified reactor network is shown to have volume that is as low as half the volume of a single reactor.