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Chinese Physics B 2014年第8期23卷 389-395页

作者： Vahid Esfahanian Esmaeil Dehdashti Amir Mehdi Dehrouye-Semnani Department of mechanical engineering University of Tehran

Fluid-structure interaction （FSI） problems in microchannels play a prominent role in many engineering applications. The present study is an effort toward the simulation of flow in microchannel considering FSI. The bottom boundary of the microchannel is simulated by size-dependent beam elements for the finite element method （FEM） based on a modified cou- ple stress theory. The lattice Boltzmann method （LBM） using the D2Q13 LB model is coupled to the FEM in order to solve the fluid part of the FSI problem. Because of the fact that the LBM generally needs only nearest neighbor information, the algorithm is an ideal candidate for parallel computing. The simulations are carried out on graphics processing units （GPUs） using computed unified device architecture （CUDA）. In the present study, the governing equations are non-dimensionalized and the set of dimensionless groups is exhibited to show their effects on micro-beam displacement. The numerical results show that the displacements of the micro-beam predicted by the size-dependent beam element are smaller than those by the classical beam element.

关键词： fluid-structure interaction graphics processing unit lattice Boltzmann method size-dependentbeam element

Stability in Probability and Inverse Optimal Control of Evolution Systems Driven by Levy Processes

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IEEE/CAA Journal of Automatica Sinica 2020年第2期7卷 405-419页

作者： Khac Duc Do School of Civil and mechanical engineering CurtinUniversity

This paper first develops a Lyapunov-type theorem to study global well-posedness(existence and uniqueness of the strong variational solution)and asymptotic stability in probability of nonlinear stochastic evolution systems(SESs)driven by a special class of Levy processes,which consist of Wiener and compensated Poisson *** theorem is then utilized to develop an approach to solve an inverse optimal stabilization problem for SESs driven by Levy *** inverse optimal control design achieves global well-posedness and global asymptotic stability of the closed-loop system,and minimizes a meaningful cost functional that penalizes both states and *** approach does not require to solve a Hamilton-Jacobi-Bellman equation(HJBE).An optimal stabilization of the evolution of the frequency of a certain genetic character from the population is included to illustrate the theoretical developments.

关键词： Evolution system inverse optimal control Levy processes stability in probability well-posedness

Running Accuracy Analysis of a 3-RRR Parallel Kinematic Machine Considering the Deformations of the Links

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Chinese Journal of mechanical engineering 2014年第5期27卷 890-899页

作者： WANG Liping JIANG Yao LI Tiemin Department of mechanical engineering Tsinghua University

Parallel kinematic machines have drawn considerable attention and have been widely used in some special ***,high precision is still one of the challenges when they are used for advanced machine *** of the main reasons is that the kinematic chains of parallel kinematic machines are composed of elongated links that can easily suffer deformations,especially at high speeds and under heavy loads.A 3-RRR parallel kinematic machine is taken as a study object for investigating its accuracy with the consideration of the deformations of its links during the motion *** on the dynamic model constructed by the Newton-Euler method,all the inertia loads and constraint forces of the links are computed and their deformations are *** the kinematic errors of the machine are derived with the consideration of the deformations of the *** further derivation,the accuracy of the machine is given in a simple explicit expression,which will be helpful to increase the calculating *** accuracy of this machine when following a selected circle path is *** influences of magnitude of the maximum acceleration and external loads on the running accuracy of the machine are *** results show that the external loads will deteriorate the accuracy of the machine tremendously when their direction coincides with the direction of the worst stiffness of the *** proposed method provides a solution for predicting the running accuracy of the parallel kinematic machines and can also be used in their design optimization as well as selection of suitable running parameters.

关键词： parallel kinematic machine dynamic model accuracy deformations

Modeling the effects of rainfall on vehicular traffic

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Journal of Modern Transportation 2018年第2期26卷 133-146页

作者： Etikaf Hussain Syed Imran Ahmed Mir Shabbar Ali Civil engineering Department NED University of Engineering & Technology faculty of Civil engineering and architecture NED University of Engineering & Technology

Traffic management and drainage system are two vital issues for any metropolitan city. Like other big cities, Karachi is also facing problems due to lack of traffic management and poor drainage system. The main objective of the study is to model the interdisciplinary issues of storm water and its effect on the traffic of Karachi. The specific objectives are （1） to calibrate and validate urban hydraulic and traffic micro-simulation models and （2） to model storm water and traffic for future conditions. This study is carried out on a 3-km section of arterial road. In this study, loose coupling of two models is done. For urban drainage, PCSWMM, and for traffic, VISSIM is used. Both models are calibrated for an existing situation on rainfall event of August 3, 2013, and then used for prediction of future scenario based on 50-year and 100-year return periods of rainfall. Sensitivity analysis of VISSIM is performed. Locations and lengths of road sections, where ponding happens for the future scenario, are identified using PCSWMM. These lengths axe then marked in VISSIM as low-speed areas, and delays are measured. Analysis of PCSWMM shows that for 100-year return period, there is maximum 0.318 ha-m （3180 cubic meters） water stored in the depressions of the road after 10 h of rainfall. Analysis of VISSIM shows that for a 100-year return period, there is a maximum delay of 35 min on NIPA to Hasan Square section of University Road.

关键词： Traffic micro-simulation Hydraulic modeling Rainfall Delays Ponding

Computational Analysis of Airflow in Upper Airway under Light and Heavy Breathing Conditions for a Realistic Patient Having Obstructive Sleep Apnea

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Computer Modeling in engineering & Sciences 2021年第8期128卷 583-604页

作者： W.M.Faizal N.N.N.Ghazali C.Y.Khor M.Z.Zainon Irfan Anjum Badruddin Sarfaraz Kamangar Norliza Binti Ibrahim Roziana Mohd Razi faculty of mechanical engineering Technology University Malaysia PerlisPerlisMalaysia Department of mechanical engineering Faculty of EngineeringUniversity of MalayaKuala Lumpur50603Malaysia Research Center for Advanced Materials Science King Khalid UniversityAbha61413Saudi Arabia Department of mechanical engineering College of EngineeringKing Khalid UniversityAbha61421Saudi Arabia Department of Oral&Maxillofacial Clinical Science Faculty of DentistryUniversity of MalayaKuala Lumpur50603Malaysia Department of Paediatric Dentistry and Orthodontics Faculty of DentistryUniversity of MalayaKuala Lumpur50603Malaysia

Background:Obstructive sleep apnea is a sleeping disorder that has troubled a sizeable *** is an active area of research on obstructive sleep apnea that intends to better understand airflow behaviors and therefore treat patients more *** paper aims to investigate the airflow characteristics of the upper airway in an obstructive sleep apnea(OSA)patient under light and heavy breathing conditions by using Turbulent Kinetic Energy(TKE),an accurate method in expressing the flow concentration mechanisms of sleeping *** is important to visualize the concentration of flow in the upper airway in order to identify the severity level of the obstruction during ***:Computational fluid dynamic(CFD)analysis was used as a solution tool to evaluate the airflow during light and heavy breathing conditions.A medical imaging technique was used to extract the 3D model from the CT scan ***,mesh generation and simulation were carried out via CFD software to evaluate the light and heavy breathing characteristics related to obstructive sleep *** state Reynold’s averaged Navier-Stoke(RANS)with the k-ωshear stress transport(SST)turbulence model was *** airflow characteristics were quantified using parameters such as pressure distribution,skin friction coefficient,velocity profile,Reynolds number,turbulent Reynolds number and turbulence kinetic ***:Contour plots at different planes were used to visualize the airflow distribution as it passed through different cross-sectional areas of the *** results revealed that the presence of a smaller cross-sectional area of the airway caused an increase in airflow parameters,especially during heavy ***,turbulent airflow conditions along the airway were noticed during heavy *** severity of OSA could be measured by the turbulent kinetic energy which is able to show the behavior and concentration of mean *** study is expected to p

关键词： Human upper airway computational fluid dynamics obstructive sleep apnea turbulent kinetic energy

Over-Constraints and a Unified Mobility Method for General Spatial Mechanisms Part 2:Application of the Principle

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Chinese Journal of mechanical engineering 2016年第1期29卷 1-10页

作者： LU Wenjuan ZENG Daxing HUANG Zhen School of mechanical engineering Yanshan University

The pre-research on mobility analysis presented a unified-mobility formula and a methodology based on reciprocal screw theory by HUANG, which focused on classical and modem parallel mechanisms. However its range of application needs to further extend to general multi-loop spatial mechanism. This kind of mechanism is not only more complex in structure but also with strong motion coupling among loops, making the mobility analysis even more complicated, and the relevant research has long been ignored. It is focused on how to apply the new principle for general spatial mechanism to those various multi-loop spatial mechanisms, and some new meaningful knowledge is further found. Several typical examples of the genera/multi-loop spatial mechanisms with motion couple even strong motion couple are considered. These spatial mechanisms include different closing way： over-constraint appearing in rigid closure, in movable closure, and in dynamic closure as well; these examples also include two different new methods to solve this kind of issue： the way to recognize over-constraints by analyzing relative movement between two connected links and by constructing a virtual loop to recognize over-constraints. In addition, over-constraint determination tabulation is brought to analyze the motion couple. The researches above are all based upon the screw theory. All these multi-loop spatial mechanisms with different kinds of structures can completely be solved by following the directions and examples, and the new mobility theory based on the screw theory is also proved to be valid. This study not only enriches and develops the theory and makes the theory more universal, but also has a special meaning for innovation in mechanical engineering.

关键词： mobility analysis over-constraint multi-loop spatial mechanism motion coupling screw theory

A semi-analytical approach for calculating the equilibrium structure and radial breathing mode frequency of single-walled carbon nanotubes

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Acta Mechanica Sinica 2016年第6期32卷 1075-1087页

作者： J.Gong L.Thompson G.Li Department of mechanical engineering Clemson University

A semi-analytical model for determining the equilibrium configuration and the radial breathing mode (RBM) frequency of single-wall carbon nanotubes (CNTs) is presented. By taking advantage of the symmetry characteristics, a CNT structure is represented by five independent variables. A line search optimization procedure is employed to determine the equilibrium values of these variables by minimizing the potential energy. With the equilibrium configuration obtained, the semi-analytical model enables an efficient calculation of the RBM frequency of the CNTs. The radius and radial breathing mode frequency results obtained from the semi-analytical approach are compared with those from molecular dynamics (MD) and ab initio calculations. The results demonstrate that the semi-analytical approach offers an efficient and accurate way to determine the equilibrium structure and radial breathing mode frequency of CNTs.

关键词： Carbon nanotubes Equilibrium structure Radial breathing mode frequency

Quantitative Prediction of Reduction in Large Pipe Setting Round Process

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Chinese Journal of mechanical engineering 2013年第4期26卷 722-729页

作者： ZHAO Jun ZHAN Peipei MA Rui ZHAI Ruixue College of mechanical engineering Yanshan University

The control manner during the process to ensure the quality of pipe products mainly relies on the operator’s experience, so it is very necessary to study the setting round process and obtain its spring-back law. The setting round process is shaping an oval section pipe into circular section, so it is difficult to provide a quantificational analysis for its spring-back process because of the curvature inequality of pipe section neutral layer. However, the spring-back law of the circle-oval process can be easily predicted. The experimental method is firstly used to establish the equivalent effect between the setting round process and the circle-oval process. The setting round process can be converted into the circle-oval process. There are two difficulties in the theoretical analysis for the circle-oval process: elastic-plastic bending problem of curved beam; statically indeterminate problem. A quantitative analytic method for the circle-oval process is presented on the basis of combination of the spring-back law of plane curved beam with the element dividing idea in finite element method. The ovality after unloading versus the relative reduction is plotted with analytical and experimental results respectively, which shows a fair agreement. Finally, the method of quantitative prediction of reduction for large pipe setting round is given based on the equivalent effect and the analytical results. Five pipes, which are needed to be set round, are used to carry out experiment so as to verify this method. The results of verification experiment indicates that, in the experimental range, the residual ovality are all under 0.35% after the once only setting round with the theoretical prediction reductions. It is much less than the 1% requirement of pipe standard. Applying the established theoretical analysis is able to correct the pipe ovality with sufficient accuracy, which provides theoretical direction to plant use.

关键词： large pipes setting round circle-oval process spring-back analysis

Design,fabrication and kinematics of a bio-inspired robotic bat wing

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Science China(Technological Sciences) 2016年第12期59卷 1921-1930页

作者： YIN Dong Fu ZHANG Zhi Sheng School of mechanical engineering Southeast University

The current work is oriented toward the development of a novel biologically inspired bat aerial robot with morphing wings. Based on the flight characteristics data of natural bats(Eptesicus fuscus), a novel four degrees of freedom robotic bat wing was developed to emulate the movements of bat wing. The design, fabrication, programing and wind tunnel experiments of the robot bat wing are described in this paper. Based on this robotic wing, the influence of flap amplitude, wind speed, flight frequency, downstroke ratio and stroke plane angle as well as the contributions of flap, elbow, sweep and wrist motions on the aerodynamic force and mechanical power were studied and analyzed. Results of wind tunnel experiments validated that higher lift would bring greater power consumption, and the flap motion would generate the most force and need more energy expenditure compared with other motions of bat. The experimental results suggest that the flap and fold motions are indispensable to make a robotic bat wing that has a better flight performance. This study provides some implications and a better understanding for the future robotic bat.

关键词： bio-inspiration wing robotic bat flight kinematics wrist motion

基于石墨烯和回收金制备便携式、可清洗太阳能蒸发器及其高效即时水净化研究（英文）

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Science China Materials 2024年第11期67卷 3700-3709页

作者：李飞黄炯鹏胥丁心王程锦赵亮龚新渝李航张灿阳宋清华苏阳成会明 Tsinghua-Berkeley Shenzhen Institute & Institute of Materials Research & Institute of Biopharmaceutical and Health engineering Tsinghua Shenzhen International Graduate SchoolTsinghua University Shenzhen Key Laboratory of Energy Materials for Carbon Neutrality Institute of Technology for Carbon NeutralityShenzhen Institute of Advanced TechnologyChinese Academy of Sciences faculty of Materials Science and Energy engineering Shenzhen University of Advanced Technology Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences

太阳能蒸发器为应对全球淡水短缺问题,提供了一种可持续且高效的水净化解决方案.尽管此前的研究在最大化水蒸发速率方面取得了显著进展,但尚无单一蒸发器具备实际应用所需的所有特性,如生成饮用水的高效性、用于现场水净化的优异便携性... 详细信息

太阳能蒸发器为应对全球淡水短缺问题,提供了一种可持续且高效的水净化解决方案.尽管此前的研究在最大化水蒸发速率方面取得了显著进展,但尚无单一蒸发器具备实际应用所需的所有特性,如生成饮用水的高效性、用于现场水净化的优异便携性、减少蒸发器结垢的良好可清洗性,以及良好的可重复使用性.本文提出了一种用于即时水净化的高性能光热材料制备策略.通过在具有优异机械性能的海绵中同时引入石墨烯和从电子垃圾中提取的金颗粒,实现了高效水净化.在一个太阳光强度照射下水蒸发速率达到3.55 kg/m2/h,这得益于对石墨烯原子结构的控制以及金纳米颗粒尺寸依赖性表面等离子体共振效应.此外,该材料便携性强,可折叠、可真空压缩、干燥、再使用而不影响性能,且可以通过反复清洗去除污染物结垢,从而实现重复使用.研究表明该蒸发器可以将多种类型的污染水转化为可饮用的清洁水,并且可以任意角度安装,便于追踪太阳入射角,实现太阳光的高效利用.所组装的蒸发器在户外阳光下的水蒸发速率高达9.36 kg/m2/h,所产出的净化水符合世界卫生组织的饮用水标准.

关键词： graphene gold resources recovery and reuse solar steam evaporator sustainable development