Volumetric hydrogen sorption measurements – Uncertainty error analysis and the importance of thermal equilibration time

The design of a volumetric measurement apparatus is studied by means of an uncertainty analysis to provide guidelines for optimum hydrogen sorption measurements. The reservoir volume should be as small as possible (i.e., 10 cc) to minimize the uncertainty. In addition, the sample mass loading has a profound effect on the uncertainty and the optimum loading is a function of the sample's intrinsic storage capacity. In general, the higher the sample mass loading the lower the uncertainty, regardless of any other parameter. In cases where the material to be tested is not available in gram quantities, the use of high accuracy pressure and temperature transducers significantly mitigates the uncertainty in the sample's hydrogen uptake. Above all, the thermal equilibration time is an important parameter for high accuracy measurements and needs to be taken into consideration at the start of the measurements. Based on a computational analysis, a 5 min wait time is required for achieving thermal equilibrium when the instrument enclosure temperature is different than the ambient temperature.     

基于COMSOL4.2的波导模式特性仿真

本文介绍了使用电磁场仿真工具COMSOL 4.2进行仿真的一般步骤,以及使用COMSOL 4.2对基本类型光波导模式特性进行仿真的实例,并介绍了在此基础上进行光波导模式特性仿真实验设计中的几个教学重点,遵循由简单到复杂、由理论到实践、由演示到设计的思维训练过程。基于COMSOL 4.2的光波导模式特性仿真实验主要应用于"光纤通信"课程的实践化教学中,COMSOL 4.2的使用也可引入到其他场类课程的教学中。     

二元复合微波增强沥青混凝土加热效率仿真与试验研究

微波加热是沥青混凝土路面的一种新型绿色养护技术,但目前微波吸收效率低下与沥青混凝土导热能力差是阻碍其推广应用的关键。基于阻抗匹配理论,考虑到掺加单一微波增强剂的局限性,提出一种改进的二元电磁复合型微波增强剂;将SiC和_^Fe3O₄二元复合作为微波增强剂,采用矢量网络分析仪对微波增强剂样品的电磁参数进行测量。考虑到实验室缺少测量沥青混凝土内部温度的有效方法,采用COMSOL Multiphysics软件对微波加热沥青混凝土的温升速率和热量分布进行数值模拟,同时对其路用性能进行试验研究。研究结果表明：当SiC和Fe₃O₄的质量比是1∶2时(S₁F₂),S₁F₂的反射损耗达到了-22.12dB,比纯SiC的反射损耗低13.97dB。掺S1F2的沥青混凝土的平均升温速率为0.322℃/s,是对照组的1.87倍,并且高于单掺SiC (0.212℃/s)和Fe₃O₄ (0.231℃/s)的沥青混凝土,且热量分布最均匀;相较于单相微波增强剂,掺二元复合材料的沥青混凝土微波吸收能力更强;同时,掺S₁F₂的沥青混凝土的抗水损害性能有一定程度的提高。     

井筒变质量流与油藏渗流耦合参数研究

为进一步研究水平井筒变质量流与油藏渗流的耦合流动,本文将复杂的油藏—井筒区域流体动力学问题转化为油藏渗流、井筒附近Brinkman渗流和井筒管流3种流动形式的耦合问题,建立了油藏—井筒耦合流体动力学有限元数值模型,采用多物理场耦合软件COMSOL对所建模型进行求解。定量描述了油藏—井筒区域流动形态,并分析了储层渗透率、原油动力粘度、井径、井长等因素对井筒内压力损失和井筒入流剖面的影响规律。     

采动影响下地表移动变形监测及模拟研究

掌握矿山重大风险灾害总体情况,明确其发展动态,并进行监测分析、预警及预报,对矿山安全监管与减少事故有着重要的现实意义.以某铁矿开采为工程背景,对地表及河床的移动和变形进行了分析研究,通过建立COMSOL数值模型,分析不同开采进度下地表与河床的位移变化,结合无人机和无人船监测系统的实测数据,在验证模型准确性的同时,分析了...     

基于COMSOL的电解加工炮管膛线加工间隙的研究

为了缩短阴极研制周期,按照无源导电媒质中的电场建立间隙电场的数学模型,按照气液两相流建立流场的数学模型,根据膛线电解加工工艺参数设置边界条件,采用COMSOL Multiphysics3.4多物理场耦合软件对加工间隙进行数值模拟,结合工艺试验的数据,分析加工间隙电场分布对实际加工精度的影响。结果表明,当阴极工作齿向内收一定角度,有利于减小膛线槽壁倾角和槽底圆角,计算机模拟与工艺试验结果一致。     

Rapid synthesis of silver nanowires during the polyol-microwave method and COMSOL multiphysics simulation of electromagnetic heating

To date, various methods have been used to synthesize silver nanowires, but some require long reaction times. In this work, we synthesized widely used silver nanowires with high efficiency and with the least time and energy during the polyol-microwave method. Also, the effects of microwave irradiation time, silver nitrate concentration, and type of etching agent on the shape and size of nanostructures were investigated experimentally. In fact, the shape and production efficiency of silver nanowires were controlled and the optimal conditions were obtained at the microwave irradiation time of 210 s. The characterization of the silver nanowires showed that silver nanowires with an average diameter of 80 nm and an average length of 20 µm can be produced with high efficiency under optimal conditions. Finally, for the first time, in the microwave-based synthesis method, electromagnetic heating was studied and simulated with the help of the “finite element” method implemented by the COMSOL Multiphysics software. The results showed that with increasing time, the temperature increases, and as a result, the number density of glycolaldehyde reducing agents increases. This could also explain the fast growth of silver nanowires during this method.     

超声振动辅助激光烧蚀铝表面形貌仿真分析

为研究超声复合激光蚀除机理,本文使用COMSOL软件对超声振动辅助激光烧蚀金属铝表面烧蚀过程进行仿真,对比研究了超声振动对激光蚀除机理和过程的影响。研究发现,激光烧蚀的开始阶段主要以高温汽化来去除材料。随着烧蚀时间的增加,蚀除方式主要转变为熔融物飞溅蚀除,这对烧蚀凹坑的形成起主要作用。并研究了不同频率下激光蚀除材料的速度,研究发现,引入超声振动后,蚀除速度降低了26.2%-39.43%。     

阵列细胞微培养腔的设计与制造

采用光刻成型技术、"多次光刻、一次显影"工艺以及热键合工艺制备了基于三层、具有阀控开关和浓度梯度的PDMS微阵列细胞微培养腔,重点研究了浓度梯度、细胞培养腔结构的设计.研究表明浓度梯度的形成主要受芯片管道结构影响;在低雷诺数、被动混合方式情况下,采用简单结构进行混合的效率会很低;在本课题中,将瓦片状结构与管道复合起来提高混合效率,实验结果表明:即使在高流速情况下,也能得很高的混合效率并使各管道间浓度呈很好的线性分布;同时,对细胞培养腔的结构进行了设计;此外,将有限元分析软件COMSOL应用到混合管道及培养腔内流体、流态进行了分析,进一步利用分析结果优化了结构设计.     

Optimization and Aerodynamic Characteristics of New Air-Cushion Nozzle of Floating Furnace for Automobile Body Sheet

It is very important to develop new air-cushion nozzles so as to raise the heat treatment property of aluminum alloy automobile body sheet(ABS). A geometric model of air-cushion furnace equipment of ABS was built up and flow field was simulated by using k-ε turbulence equations of COMSOL Multi-physics. The influence and regularity of number(n),diameter(d) and arrangement of middle hole,and main control parameters of new air-cushion nozzle on aerodynamic characteristics and flow field were studied. The results show that:1) with n increases,airflow vortexes in air-cushion area increase in multiple; d decreases or n increases,air cushion pressure(p_c) becomes uniform; 2) average of p_c is proportional to pressure in nozzle box(p_t),when n increases,ratio of average of p_c to p_t increases,and when n ≤ 3 and d b / 2,they have little effect on ratio of p_c average to p_t; 3) when n is an even number,n ≥4,and d ≤ b/2,p_c shows good uniformity; when n is an odd number,the center hole affects p_c uniformity greatly,and,when diameter of center hole is less than b / 4 and diameter of non-center is between b / 4 and b / 2,p_c has good uniformity. A new air-cushion jet model was presented,and the deviation of this new model with simulation data and experimental measured data are less than 7.75% and 7.76%,respectively. The present research is valuable for improving air-cushion stability,Al strip temperature homogeneity,and temperature control precision.