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Benchmark Model: Natural Convection of Water-Aluminum Oxide Nanofluids in a Square Cavity

M. Z. Saghir [1], A. Ahadi [1], A. A. Mohamad [2],
[1] Department of Mechanical Engineering, Ryerson University, Toronto, ON, Canada
[2] Department of Mechanical Engineering, University of Calgary, Calgary, AB, Canada

Nanofluids is a new class of fluid consisting of particles in a liquid. Different base liquid has been proposed and the most common one is water. The concentration of these particles can range from 0.1% to 5% or greater. Different numerical models have been proposed to solve this interesting problem. Some scheme assumed the fluid as a single fluid and other assumed as a two phase system ...

Statistical Modeling and Contact Analysis of RF MEMS Surface

J. Liu [1], V. B. Chalivendra [1], C. Goldsmith [2], W. Huang [1],
[1] Department of Mechanical Engineering, University of Massachusetts - Dartmouth, Dartmouth, MA, USA
[2] MEMtronics Corporation, Richardson, TX, USA

Radio frequency (RF) micro-electro mechanical system(MEMS) switch works in on/off modes controlled by electrostatic forces. In off mode, rough surfaces of electrodes come into a contact to shunt the RF signal. Surface contact area has been recognized as a key factor in RF MEMS performance and reliability. Multi scale regular-fractal structure is observed on MEMS surface. Nonlinear Structural ...

FEM Modeling in Robust Design for Graphene-Based Electromagnetic Shielding

S. Elia [1], G. Granata [1], P. Lamberti [1], V. Tucci [1],
[1] University Of Salerno, Italy

Electromagnetic shielding design is usually approached referring to nominal values of the main parameters. This could lead to malfunctioning devices and its performance differ widely from what was really aimed at or, worse, the final design product could even be physically unrealizable. This work presents a robust approach to the design of EM Shielding based on Graphene (Gph) layers. It is a two ...

基于 ALE 方法的脉冲磁体不可逆电感变化计算

蒋帆 [1], 孙衢骎 [1],
[1] 武汉脉冲强磁场中心,武汉,湖北,中国

目前,脉冲磁体广泛采用导体绕组和加固材料分层交替绕制的工艺(内部层间加固),以提高磁体的整体结构强度。磁体在长期的放电工作过程中,反复经历强电磁力的作用,导体材料(一般为纯铜、铜基合金以及铜基复合材料)在重复的加卸载过程中存在着塑性应变的累积效应,即棘轮效应。导体材料塑性应变的逐渐累积,导致了磁体不可逆电感值的不断增加。因此,磁体的不可逆电感变化可表征磁体内部的整体变形情况,可用于脉冲磁体的疲劳失效预测。 本文基于 COMSOL Multiphysics® 5.1 软件,对脉冲磁体的放电过程建立了电路、电磁场、温度场及结构场的二维轴对称全耦合模型。考虑了放电过程中集肤效应对磁体电阻、电感的影响;在结构场中引入了接触对,采用罚函数法对磁体内部的层间分离机制进行了有效的模拟;利用耦合变量,基于 ALE 方法计算了脉冲磁体在服役过程中 ...

基于声学超材料的近场点声源亚波长分辨率显微成像模拟

韩建宁 [1],
[1] 中北大学,太原,山西,中国

所谓近场声学,是相对于远场声学而言。传统的声学理论,通常只研究远离光源或者远离物体的声场分布,一般统称为远场声学。远场声学在原理上存在着一个远场衍射极限,限制了利用远场光学原理进行显微和其它光学应用时的最小分辨尺寸和最小标记尺寸。而近场声学则研究距离光源或物体一个波长范围内的光场分布。在近场声学研究领域,远场衍射极限被打破,分辨率极限在原理上不再受到任何限制,可以无限地小,从而基于近场声学原理可以提高显微成像与其它光学应用时的光学分辨率。 声学超材料自问世之日起就受到了国内外科学家们的广泛追捧,在很多领域都可以看到其踪迹,以声子晶体为代表的声超材料具有很多天然材料所不具备的声学特性,为声学信号处理带来了很多创新的思路和途径。 声超材料的突出特点在于采用尺寸远小于入射波长的人工结构构建出等效参数,利用等效参数实现“小尺寸结构调控大尺寸波长”的目的。 ...

Modeling and Simulation of Flat Sheet Membrane with Physical and Chemical Absorption

N. Ghasem [1], M. Al-Marzouqi [2],
[1] UAE University, Al-Ain, UAE
[2] UAE University, Al-Ain, UAE

Greenhouse gases trap heat and make the planet warmer. The main greenhouse gases emitted by human activities are: Carbon dioxide (CO2). The use of fossil fuel is the primary source of CO2 [1, 2]. Accordingly, there is a need for an efficient and novel separation processes for removal of carbon dioxide from gas streams [3, 4]. Here, a flat sheet membrane contactor is used to remove carbon ...

Frequency Response Analysis of a Printed Circuit Board

S. Mathmann[1]
[1]University of Applied Sciences Bielefeld, Department of Engineering Sciences and Mathematics, Bielefeld, Germany

During a practical course the students compare the measured frequency response of an assembled PCB (Printed Circuit Board) with the simulated data out of COMSOL Multiphysics® software. For this the whole PCB with all components are feed in the simulator and afterwards an eigenfrequency-analysis is carried out. To simplify the effort to do this, a COMSOL® app was created. As result the user ...

Multiple-Mode Polymeric-Silicon Dual-Channel Gas Sensors

K. Liang [1], A. Dodabalapur [1], D. Sharma [1],
[1] Microelectronics Research Center, University of Texas, Austin, TX, USA

An organic-inorganic dual-channel sensor makes a strong chemical gas sensor because this device design combines the high chemical sensitivities and selectivity of organic semiconductors [1-4] with the superior electrical performance and convenient integration of silicon semiconductors. As shown in the device schematic in Figure 1, the organic channel is the chemically-active material and is ...

The Effect of Eccentricity in Fully Developed Annular Pipe Flow on Convection Heat Transfer and the Darcy Friction Factor

S. Rabbani [1], A. Elzawawy [1], J. D'Arrigo [1], J. D. Freels [2]
[1] Vaughn College of Aeronautics and Technology, New York, NY, USA
[2] Oak Ridge National Laboratory, Oak Ridge, TN, USA

Eccentricity in annular channels contributes to changes in fluid flow characteristics which in turn, affects the performance and integrity of the configuration. This research investigates a model of an annular channel with a diameter ratio of 0.762, an aspect ratio of 68.9:1 and heating of the internal surface of the inner cylinder with a 1.105MW/m2 heat flux. The Reynolds number ranges from 5 ...

Modeling of Radial Source Flow in Porous Media: Miscible Viscous Fingering Patterns

V. Sharma [1], S. Pramanik [2], M. Mishra [1],
[1] Indian Institute of Technology Ropar, Rupnagar, India
[2] Indian Institute of Technology Ropar, Rupnagar, India; Nordita, SE-10691 Stockholm, Sweden.

COMSOL Multiphysics® software was used to model radial source flow in two dimensional homogeneous porous media. Two-Phase Darcy's Law (tpdl) is used to model miscible viscous fingering. Fingering patterns obtained on using different mesh are discussed. Evolution from 'flowers' to 'branches' is observed in the fingering patterns. Stable displacement is generated even in the presence of unstable ...