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Research and Development of Growth Design System for Mechanical Products

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武汉理工大学学报 2006年第S1期28卷 90-95页

作者： YANG Bo1,ZE Xiangbo1,YANG Tao2,CUI Weihua1,LIU Luning1 (1.College of Mechanical Engineering,Jinan University,Jinan 250022,China 2.singapore Technologies Dynamics Pte ltd.singapore) College of Mechanical Engineering Jinan UniversityJinan 250022China singapore Technologies Dynamics Pte ltd Singapore

By applying genetic engineering methodology into the incremental product growth design,a generic structural design approach is put forward,as well as an intelligent evolution strategy of the product units growth,which is based on the multilevel Decomposition and Reconstruction of product gene. To guarantee a successful transformation from functional requirement to geometry constraints between parts in the incremental growth design of mechanical product,the integrated design method incorporates the design requirements and assembly perspective into product genetic information. The mathematical model of state transition during incremental design process are given at first,based on which product can grow step by step from functional requirement to the final geometrical product structure automatically. And then,to quantify the measurement of assembly efficiency,a mathematical model as well as a technology to quantify assembly constraints was developed by application of some fuzzy logic algorithms. Finally,examples have been proved that the approach is promising.

关键词： growth design automatic design functional decomposition assemblability

Effect of grain structure on the mechanical properties of a Monel alloy fabricated by laser-based directed energy deposition

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Journal of Materials Science & Technology 2023年第33期164卷 129-139页

作者： Ze Chen Wei Fan Shubo Gao Yang Qi Sastry Yagnanna Kandukuri Kun Zhou singapore Centre for 3D Printing School of Mechanical and Aerospace EngineeringNanyang Technological University50 Nanyang AvenueSingapore 639798Singapore DNV AS HøvikOslo 1363Norway

Monel K-500 is a Ni–Cu alloy widely used in the marine and offshore industry due to their superior resistance to corrosion in seawater and hence easily *** address this problem,laser-based directed energy deposition(LDED)is used to repair or refabricate these high-value worn *** optimize the mechanical properties of repaired parts,the commonly applied solution and aging is not ideal because it also changes the properties of the base ***,in situ control of the grain structures during the LDED process becomes an effective approach for high-performance *** this study,we fabricated a duplex grain structure with small grain size and low texture intensity using low laser power and scanning *** duplex microstructure consists of short columnar grains and zigzag-distributed fine equiaxed *** formation of this grain structure is dependent on both the solidification and recrystallization *** strength of this grain structure is improved to 523.5 MPa without the sacrifice of ductility,which is instead 20%higher than that of the counterpart consisting of typical columnar grains due to the grain refinement and crack *** mechanical properties of the alloy with the duplex grain structure are even comparable to heat-treated Monel K-500 fabricated by wire arc additive *** work provides valuable insights into the in situ optimization of the microstructure and mechanical properties of LDED-fabricated parts.

关键词： Additive manufacturing Directed energy deposition Monel alloy Grain structure Mechanical properties

Dynamic model of normal behavior of rock fractures

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Journal of Coal Science & Engineering(China) 2005年第2期11卷 24-28页

作者：杨文义孔广亚蔡军刚 Tiandi Jincaotian(Beijing) Science and Technology Co. ltd Beijing 100013China Tritech Consultants Pte ltd.416180 Singapore

Based on laboratory tests of artificial fractures in mortar material, established the dynamic constitutive model of normal behaviour of rock fracture,. The tests were systematically conducted under quasi-static and dynamic monotonic loading conditions. The fractures were of different numbers of asperities in contact and were subsequently of different initial contact areas, which imitated the natural rock fractures. The rate of compressive load applied normal to the fractures covers a wide range from 10–1 MPa/s (quasi-static) up to 103 MPa/s (highly dynamic). The normal stress-closure responses of fractures were measured for different loading rates. Based on the stress-closure relation curves measured, a nonlinear (hyperbolic) dynamic model of fracture, normal behaviour, termed as dynamic BB model, was proposed, which was modified from the existing BB model of static normal behaviour of fractures by taking into account the effect of loading rate.

关键词： rock fracture dynamic constitutive model dynamic loading loading rate

A new carbon phase with direct bandgap and high carrier mobility as electron transport material for perovskite solar cells

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npj Computational Materials 2019年第1期5卷 1063-1069页

作者： Ping-Ping Sun Lichun Bai Devesh R.Kripalani Kun Zhou School of Mechanical and Aerospace Engineering Nanyang Technological University50 Nanyang AvenueSingapore 639798Singapore SMRT-NTU Smart Urban Rail Corporate Laboratory Nanyang Technological University50 Nanyang AvenueSingapore 639798Singapore

Rapid development of perovskite solar cells is challenged by the fact that current semiconductors hardly act as efficient electron transport materials that can feature both high electron mobility and a well-matched energy level to that of the *** we show that T-carbon,a newly emerging carbon allotrope,could be an ideal candidate to meet this *** using first-principles calculations and deformation potential theory,it is found that T-carbon is a semiconductor with a direct bandgap of 2.273 eV,and the energy level in the conduction band is lower than that of perovskite by 0.5 eV,showing a larger force of electron ***,the calculated electron mobility can reach up to 2.36×10^(3) cm^(2) s^(–1) V^(–1),superior to conventional electron transport materials such as TiO2,ZnO and SnO2,which will facilitate more efficient electron separation and more rapid diffusion away from their locus of generation within the perovskite ***,the bandgap of T-carbon is highly sensitive to strain,thus providing a convenient method to tune the carrier transport ***,T-carbon satisfies the requirements for a potential efficient electron transport material and could therefore be capable of accelerating the development of perovskite solar cells.

关键词： perovskite absorber satis

Improved Hybrid Reactive Power Compensation System Based on FC and STATCOM and Its Control Method

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Chinese Journal of Electrical Engineering 2022年第2期8卷 29-41页

作者： Xiheng Liang Fei Jiang Xing Peng Liansong Xiong Yongbin Jiang Samir Gautam Zhichang Li School of Electrical and Information Engineering Changsha University of Science&TechnologyChangsha 410076China School of Electrical Engineering Xi’an Jiaotong UniversityXi’an 710049China School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore 639798Singapore School of Electrical Engineering The University of SydneySydney NSW 2006Australia Beijing Sgitg-Accenture Information Technology Co. Ltd.Beijing 100080China

The purpose of this study is to solve the main problems in distribution networks,including increased line loss and reduced power supply quality caused by insufficient capacitive reactive *** reduce the capacity,voltage,and current stress of an active module of a compensation device and improve the cost performance of the device,an improved hybrid reactive power compensation system based on a fixed capacitor(FC)and a static synchronous compensator(STATCOM)is *** topological structure and basic operating principle of the proposed reactive power compensation system are *** addition,from the perspectives of output voltage,current,power,loss of the active part,and system compensation cost,the performances of the proposed reactive compensator and the inductively coupled STATCOM(L-STATCOM)are compared and ***,the key parameters of the proposed system are designed,and the joint optimization control strategy of the FC and STATCOM is *** correctness and effectiveness of the proposed topology structure and control method are verified by simulations.

关键词： Static synchronous compensator hybrid topology reactive power compensation fixed capacitor

A three-dimensional gas-kinetic flux solver for simulation of viscous flows with explicit formulations of conservative variables and numerical flux

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Advances in Aerodynamics 2020年第1期2卷 250-277页

作者： Y.Sun L.M.Yang C.Shu C.J.Teo Huawei Technologies Co. LtdBantianLonggang DistrictShenzhen 518129China Department of Mechanical Engineering National University of Singapore10 Kent Ridge CrescentSingapore 119260Singapore

A truly three-dimensional(3D)gas-kinetic flux solver for simulation of incompressible and compressible viscous flows is presented in this *** local reconstruction of continuous Boltzmann equation,the inviscid and viscous fluxes across the cell interface are evaluated simultaneously in the *** from conventional gaskinetic scheme,in the present work,the distribution function at cell interface is computed in a straightforward *** an extension of our previous work(Sun et al.,Journal of Computational Physics,300(2015)492–519),the non-equilibrium distribution function is calculated by the difference of equilibrium distribution functions between the cell interface and its surrounding *** a result,the distribution function at cell interface can be simply calculated and the formulations for computing the conservative flow variables and fluxes can be given *** validate the proposed flux solver,several incompressible and compressible viscous flows are *** results show that the current scheme can provide accurate numerical results for three-dimensional incompressible and compressible viscous flows.

关键词： 3D flux solver Gas-kinetic scheme Viscous flow Navier-Stokes equations 1 Introduction

Adam revisited:a weighted past gradients perspective

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Frontiers of Computer Science 2020年第5期14卷 61-76页

作者： Hui Zhong Zaiyi Chen Chuan Qin Zai Huang Vincent W.Zheng Tong Xu Enhong Chen Anhui Province Key Laboratory of Big Data Analysis and Application University of Science and Technology of ChinaHefei230027China Zhejiang Cainiao Supply Chain Management Co.ltd Hangzhou311122China Advanced Digital Sciences Center Singapore138602Singapore

Adaptive learning rate methods have been successfully applied in many fields,especially in training deep neural *** results have shown that adaptive methods with exponential increasing weights on squared past gradients(i.e.,ADAM,RMSPROP)may fail to converge to the optimal *** many algorithms,such as AMSGRAD and ADAMNC,have been proposed to fix the non-convergence issues,achieving a data-dependent regret bound similar to or better than ADAGRAD is still a challenge to these *** this paper,we propose a novel adaptive method weighted adaptive algorithm(WADA)to tackle the non-convergence *** AMSGRAD and ADAMNC,we consider using a milder growing weighting strategy on squared past gradient,in which weights grow *** on this idea,we propose weighted adaptive gradient method framework(WAGMF)and implement WADA algorithm on this ***,we prove that WADA can achieve a weighted data-dependent regret bound,which could be better than the original regret bound of ADAGRAD when the gradients decrease *** bound may partially explain the good performance of ADAM in ***,extensive experiments demonstrate the effectiveness of WADA and its variants in comparison with several variants of ADAM on training convex problems and deep neural networks.

关键词： adaptive learning rate methods stochastic gradient descent online learning

Study on relationships of electromagnetic band gap structures and left/right handed structures

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Science in China(Series F) 2007年第2期50卷 251-260页

作者： GAO Chu CHEN ZhiNing WANG YunYi YANG Ning State Key Lab of Millimeter Waves Southeast University Nanjing 210096 China Institute for I nfocomm Research Science Park 117674 Singapore Motorola Electronics Co. ltd 569088 Singapore

Two types of dual periodic circuits are introduced. The distributions of passbands and stopbands are generated from their dispersion relationships. Based on the study, Brillouin diagrams of three representative special cases are drawn; S parameters of these three cases are simulated by Aglient ADS; the S parameters of one of the three cases are verified by an experiment. The phase characteristics are compared with those generated from the dispersion relationship. The theoretical analysis and the experimental verification show that both types of the periodic structures can behave as electromagnetic band gap （EBG） structures, right-handed structures （RHS）, and left-handed structures （LHS）, when they operate at different frequency ranges. Thus, the possibility of a physical structure showing these three different characteristics at different frequency ranges is proven.

关键词： electromagnetic band gap structure right-handed structure left-handed structure Brillouin diagram

Towards Cost-Effective Cloud Downloading with Tencent Big Data

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Journal of Computer Science & Technology 2015年第6期30卷 1163-1174页

作者：李振华刘刚嵇智源 Roger Zimmermann School of Software Tsinghua University Beijing 100084 China Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China QQXuanfeng System Group Tencent Co. Ltd Shanghai 200233 China High Technology Research and Development Center Ministry of Science and Technology Beijing 10004 China Department of Computer Science National University of Singapore Singapore 117417 Singapore

The cloud downloading scheme, first proposed by us in 2011, has effectively optimized hundreds of millions of users＇ downloading experiences. Also, people start to build a variety of useful Internet services on top of cloud downloading. In brief, by using cloud facilities to download （and cache） the requested file from the ＂best-effort＂ Internet on behalf of the user, cloud downloading ensures the data availability and remarkably enhances the data delivery speed. Although this scheme seems simple and straightforward, designing a real-world cloud downloading system involves complicated and subtle trade-offs （between deployment cost and user experience） when serving a large number of users： 1） how to plan the cloud cache capacity to achieve a high and affordable cache hit ratio, 2） how to accelerate the data delivery from the cloud to numerous users, 3） how to handle the dense user requests for highly popular files, and 4） how to judge a potential downloading failure of the cloud. This paper addresses these design trade-offs from a practical perspective, based on big data from a nationwide commercial cloud downloading system, i.e., Tencent QQXuanfeng. Its running traces help us find reasonable design strategies and parameters, and its real performances confirm the efficacy of our design. Our study provides solid experiences and valuable heuristics for the developers of similar and relevant systems.

关键词： cloud downloading cost-effective design trade-off big data