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372篇 您的检索式:关键字=parallel
    题名 作者 年代 出处 被引量
1Toward New-Generation Intelligent Manufacturing显示文摘Zhou Ji Li Peigen Zhou Yanhong Wang Baicun Zang Jiyuan Meng Liu 2018Engineering2018,4,1:224
2基于撬棒并联动态电阻的自适应双馈风力发电机低电压穿越显示文摘当电网故障引起电压跌落时,为防止大装机容量风电场的风机脱网,双馈风力发电机(DFIG)多采用Crowbar电路来实现低电压穿越(LVRT)。传统Crowbar电路采用固定阻值的电阻,很难兼顾对转子电流和直流母线电压的抑制以及对Crowbar的投入工作时间的控制。针对传统Crowbar的不足提出了一种基于Crowbar并联动态电阻的双馈风力发电机低电压穿越方案,制定了该方案的自适应控制策略以及其阻值的整定方法。仿真分析不同跌落深度下所提方案的LVRT特性,并与改变IGBT的导通脉宽的变电阻Crowbar方案进行了比较,结果表明带并联动态电阻Crowbar方案的LVRT效果较好,不仅兼顾了对转子过电流和直流母线过电压的抑制,而且在电压深度跌落时可缩短Crowbar的投入时间,有利于系统电压的恢复。张曼 姜惠兰 2014电工技术学报2014,29,2:37
3Classification of hypersurfaces with parallel Mobius second fundamental form in S^(n+1)显示文摘Let Mn(n≥2) be an immersed umbilic-free hypersurface in the(n+1)-dimensional unit sphere Sn+1. Then Mn is associated witha so-called M(o)bius metric g, and a M(o)bius second fundamental form Bwhich are invariants of Mn under the M(o)bius transformation groupof Sn+1.In this paper, we classify all umbilic-free hypersurfaces withparallel M(o)bius second fundamental form.HU Zejun LI Haizhong Department of Mathematics, Zhengzhou University Zhengzhou 450052, China Department of Mathematical Sciences, Tsinghua University, Beijing 100084, China 2004Science China Mathematics2004,47,3:33
4A general methodology for mobility analysis of mechanisms based on constraint screw theory显示文摘It is well known that the traditional Grübler-Kutzbach formula fails to calculate the mobility of some classical mechanisms or many modern parallel robots,and this situation seriously hampers mechani-cal innovation.To seek an efficient and universal method for mobility calculation has been a heated topic in the sphere of mechanism.The modified Grübler-Kutzbach criterion proposed by us achieved success in calculating the mobility of a lot of highly complicated mechanisms,especially the mobility of all recent parallel mechanisms listed by Gogu,and the Bennett mechanism known for its particular difficulty.With wide applications of the criterion,a systematic methodology has recently formed.This paper systematically presents the methodology based on the screw theory for the first time and ana-lyzes six representative puzzling mechanisms.In addition,the methodology is convenient for judgment of the instantaneous or full-cycle mobility,and has become an effective and general method of great scientific value and practical significance.In the first half,this paper introduces the basic screw theory,then it presents the effective methodology formed within this decade.The second half of this paper presents how to apply the methodology by analyzing the mobility of several puzzling mechanisms.Finally,this paper contrasts and analyzes some different methods and interprets the essential reason for validity of our methodology.Zhen Huang JingFang Liu DaXing Zeng 2009Science China(Technological Sciences)2009,52,5:30
5OpenRS-Cloud:A remote sensing image processing platform based on cloud computing environment显示文摘This paper explores the use of cloud computing for remote sensing image processing.The main contribution of our work is to develop a remote sensing image processing platform based on cloud computing technology(OpenRS-Cloud).This paper focuses on enabling methodical investigations into the development pattern,computational model,data management and service model exploring this novel distributed computing model.The experimental INSAR processing flow is implemented to verify the efficiency and feasibility of OpenRS-Cloud platform.The results show that cloud computing is well suited for computationally-intensive and data-intensive remote sensing services.GUO Wei,GONG JianYa,JIANG WanShou,LIU Yi & SHE Bing State Key Laboratory for Information Engineering in Surveying,Mapping and Remote Sensing,Wuhan University,Wuhan 430074,China 2010Science China(Technological Sciences)2010,53,S1:24
6转录组平台技术及其在代谢工程中的应用显示文摘组学技术在系统水平上对细胞代谢进行全面的分析,极大地促进了代谢工程的发展和应用。全基因组水平的转录分析可以使研究者更加精确地评估细胞表型,加深对细胞代谢的理解。而且转录组分析也有助于研究者鉴定菌种改良的目标基因,加速对微生物细胞工厂的合理设计及构建。文中介绍了3种主要转录组平台技术的原理,并总结了转录组学在代谢工程领域中应用的最新进展和未来发展趋势。史硕博 陈涛 赵学明 2010生物工程学报2010,26,9:23
7基于Fluent的绕流问题的数值模拟与并行计算显示文摘使用商用软件Fluent对二维不可压流问题进行了两次实验,两次实验的网格数相差很多,发现当网格数少的时候,并行计算反而不如单机的效果好;而当网格数足够大的时候,并行计算就显示出其优越性来,目的在于考察Fluent软件的并行计算能力,为进行大规模工程应用计算提供技术参照。辛晓华 张武 周华 2005计算机工程与设计2005,26,8:15
8An approach to determining the local boundaries of voltage stability region with wind farms in power injection space显示文摘A new approach to determining the local boundaries of voltage stability region in power injection space (IVSR) for power system with wind farms is presented. It can be used for power system voltage stability analysis and on-line security assessment with considering the output uncertainty of the wind farms. Firstly, power flow tracing and double dispatching are used to determine the generators that are closely related to the wind farms, in order to balance the power fluctuations caused by the wind speed variation. Then, modal analysis is used to get the key generators to achieve an effective dimension reduction for IVSR. Finally, the forecasting output power (or wind speed) of wind farms is divided into several intervals. For each interval, the corresponding local IVSR boundaries can be calculated by the method based on small disturbance. Moreover, parallel process is used to accelerate the computing speed. The presented approach is validated by several power systems. It can be revealed that the approach can give the local IVSR boundaries at different wind speeds and has a good engineering application prospect.MU YunFei & JIA HongJie Key Laboratory of Power System Simulation and Control of Ministry of Education, Tianjin University, Tianjin 300072, China 2010Science China(Technological Sciences)2010,53,12:13
9Kinematics and Dynamics Analysis of a Quadruped Walking Robot with Parallel Leg Mechanism显示文摘It is desired to require a walking robot for the elderly and the disabled to have large capacity,high stiffness,stability,etc.However,the existing walking robots cannot achieve these requirements because of the weight-payload ratio and simple function.Therefore,Improvement of enhancing capacity and functions of the walking robot is an important research issue.According to walking requirements and combining modularization and reconfigurable ideas,a quadruped/biped reconfigurable walking robot with parallel leg mechanism is proposed.The proposed robot can be used for both a biped and a quadruped walking robot.The kinematics and performance analysis of a 3-UPU parallel mechanism which is the basic leg mechanism of a quadruped walking robot are conducted and the structural parameters are optimized.The results show that performance of the walking robot is optimal when the circumradius R,r of the upper and lower platform of leg mechanism are 161.7 mm,57.7 mm,respectively.Based on the optimal results,the kinematics and dynamics of the quadruped walking robot in the static walking mode are derived with the application of parallel mechanism and influence coefficient theory,and the optimal coordination distribution of the dynamic load for the quadruped walking robot with over-determinate inputs is analyzed,which solves dynamic load coupling caused by the branches' constraint of the robot in the walk process.Besides laying a theoretical foundation for development of the prototype,the kinematics and dynamics studies on the quadruped walking robot also boost the theoretical research of the quadruped walking and the practical applications of parallel mechanism.WANG Hongbo SANG Lingfeng HU Xing ZHANG Dianfan YU Hongnian 2013Chinese Journal of Mechanical Engineering2013,26,5:12
10Crank conditions and rotatability of 3-RRR planar parallel mechanisms显示文摘This paper investigates the rotatability of planar parallel mechanisms by revealing the crank conditions that relate to link parameters.The paper extends the theorem of assemblability and the rotatability criterion and applies these criteria to parallel mechanisms in investigating the crank conditions of a parallel mechanism,leading to classification of three types of crank existing conditions including three-crank’s,six-crank’s and nine-crank’s of 3-RRR planar parallel mechanisms.The results are summarized as constraint conditions in relation with link parameters with a concluding table and case studies.LI RuiQin 1 &DAI Jian S 2 1 College of Mechanical Engineering and Automation,North University of China,Taiyuan 030051,China 2 Department of Mechanical Engineering,King’s College London,University of London,WC2R 2LS,UK 2009Science China(Technological Sciences)2009,52,12:12
11Type synthesis principle of minor-mobility parallel manipulators显示文摘This paper originally presents a systematic general type synthesis principle of minor-mobility parallel manipulators. Based on the properties and geometrical conditions of structure constraint of minor-mobility parallel manipulators, this principle will be a cornerstone in solving the problem of type synthesis of minor-mobility parallel manipulators. Many mechanisms have been synthesized by this principle, which illustrated the validity and universality of this principle.黄真 李秦川 2002Science China(Technological Sciences)2002,45,3:12
12Optimal design of a new spatial 3-DOF parallel robot with respect to a frame-free index显示文摘Optimal design is one of the most important issues in robots. Since the very beginning, the concepts of the Jacobian matrix, manipulability and condition number, which are used successfully in the field of serial robots, have been applied to parallel robots. Unlike serial robots, parallel robots are good for motion/force transmission. Their performance evaluation and design should be correspondingly dif- ferent. This paper is an attempt to optimally design a novel spatial three-degree-of-freedom (3-DOF) parallel robot by using the concept of motion/force transmission. Accordingly, three indices are defined. The suggested indices are independent of any coordinate frame and could be applied to the analysis and design of a parallel robot whose singularities can be identified wholly by using the relative angle between the output and adjacent links, and by using the relative angle between the input and adjacent links.JinSong Wang XinJun Liu Chao Wu 2009Science China(Technological Sciences)2009,52,4:12
13基于Parallel_CORDIC的高精度高速度直接数字频率合成器的FPGA实现显示文摘本文提出了一种直接数字频率合成器(DDFS)的设计,以Parallel_CORDIC(COrdinate Rotation Digital Computer)算法模块替代传统的查找表方式,实现了相位与幅度的一一对应,输出相位完全正交的正余弦波形;同时应用旋转角度预测及4:2的进位保存加法器(CSA)技术,将速度比传统CORDIC算法提高41.7%,精度提高到10-4.最后以Xilinx的FPGA硬件实现整个设计.祁艳杰 刘章发 2014电子学报2014,42,7:12
14Parallel Building: A Complex System Approach for Smart Building Energy Management显示文摘These days' smart buildings have high intensive information and massive operational parameters, not only extensive power consumption. With the development of computation capability and future 5 G, the ACP theory(i.e., artificial systems,computational experiments, and parallel computing) will play a much more crucial role in modeling and control of complex systems like commercial and academic buildings. The necessity of making accurate predictions of energy consumption out of a large number of operational parameters has become a crucial problem in smart buildings. Previous attempts have been made to seek energy consumption predictions based on historical data in buildings. However, there are still questions about parallel building consumption prediction mechanism using a large number of operational parameters. This article proposes a novel hybrid deep learning prediction approach that utilizes long short-term memory as an encoder and gated recurrent unit as a decoder in conjunction with ACP theory. The proposed approach is tested and validated by real-world dataset, and the results outperformed traditional predictive models compared in this paper.Abdulaziz Almalaq Jun Hao Jun Jason Zhang Fei-Yue Wang 2019IEEE/CAA Journal of Automatica Sinica2019,6,6:10
15Error modeling, sensitivity analysis and assembly process of a class of 3-DOF parallel kinematic machines with parallelogram struts显示文摘This paper presents an error modeling methodology that enables the tolerance design, assembly and kinematic calibration of a class of 3-DOF parallel kinematic machines with parallelogram struts to be integrated into a unified framework. The error mapping function is formulated to identify the source errors affecting the uncompensable pose error. The sensitivity analysis in the sense of statistics is also carried out to investigate the influences of source errors on the pose accuracy. An assembly process that can effectively minimize the uncompensable pose error is proposed as one of the results of this investigation.黄田 李亚 唐国宝 李思维 赵兴玉 David.J.Whitehouse Derek G.Chetewyn Xianping Liu 2002Science China(Technological Sciences)2002,45,5:10
16Parallel Planning:A New Motion Planning Framework for Autonomous Driving显示文摘Motion planning is one of the most significant technologies for autonomous driving. To make motion planning models able to learn from the environment and to deal with emergency situations, a new motion planning framework called as'parallel planning' is proposed in this paper. In order to generate sufficient and various training samples, artificial traffic scenes are firstly constructed based on the knowledge from the reality.A deep planning model which combines a convolutional neural network(CNN) with the Long Short-Term Memory module(LSTM) is developed to make planning decisions in an end-toend mode. This model can learn from both real and artificial traffic scenes and imitate the driving style of human drivers.Moreover, a parallel deep reinforcement learning approach is also presented to improve the robustness of planning model and reduce the error rate. To handle emergency situations, a hybrid generative model including a variational auto-encoder(VAE) and a generative adversarial network(GAN) is utilized to learn from virtual emergencies generated in artificial traffic scenes. While an autonomous vehicle is moving, the hybrid generative model generates multiple video clips in parallel, which correspond to different potential emergency scenarios. Simultaneously, the deep planning model makes planning decisions for both virtual and current real scenes. The final planning decision is determined by analysis of real observations. Leveraging the parallel planning approach, the planner is able to make rational decisions without heavy calculation burden when an emergency occurs.Long Chen Xuemin Hu Wei Tian Hong Wang Dongpu Cao Fei-Yue Wang 2019IEEE/CAA Journal of Automatica Sinica2019,6,1:9
17Spectral element analysis on the characteristics of seismic wave propagation triggered by Wenchuan M_s8.0 earthquake显示文摘The 2008 Wenchuan earthquake occurred in an active earthquake zone, i.e., Longmenshan tectonic zone. Seismic waves triggered by this earthquake can be used to explore the characteristics of the fault rupture process and the hierarchical structure of the Earth's interior. We employ spectral element method incorporated with large-scale parallel computing technology, to investigate the characteristics of seismic wave propagation excited by Wenchuan earthquake. We calculate synthetic seismograms with one-point source model and three-point source model respectively. The AK135 model is employed as a prototype of our numerical global Earth model. The Earth's ellipticity, Earth’s medium attenuation, and topography data are taken into consideration. These wave propagation processes are simulated by solving three-dimensional elastic wave governing equations. Three-dimensional visualization of our numerical results displays the profile of the seismic wave propagation. The three-point source, which is proposed from the latest investigations through field observation and reverse estimation, can better demonstrate the spatial and temporal characteristics of the source rupture process than the one-point source. We take comparison of synthetic seismograms with observational data recorded at 16 observatory stations. Primary results show that the synthetic seismograms calculated from three-point source agree well with the observations. This can further reveal that the source rupture process of Wenchuan earthquake is a multi-rupture process, which is composed by at least three or more stages of rupture processes.YAN ZhenZhen ZHANG Huai YANG ChangChun SHI YaoLin 2009Science China Earth Sciences2009,52,6:9
18The molecular and evolutionary basis of reproductive isolation in plants显示文摘Reproductive isolation is defined as processes that prevent individuals of different populations from mating, survival or producing fertile offspring. Reproductive isolation is critical for driving speciation and maintaining species identity, which has been a fundamental concern in evolutionary biology. In plants,reproductive isolation can be divided into prezygotic and postzygotic reproductive barriers, according to its occurrence at different developmental stages. Postzygotic reproductive isolation caused by reduced fitness in hybrids is frequently observed in plants, which hinders gene flow between divergent populations and has substantial effects on genetic differentiation and speciation, and thus is a major obstacle for utilization of heterosis in hybrid crops. During the past decade, China has made tremendous progress in molecular and evolutionary basis of prezygotic and postzygotic reproductive barriers in plants. Present understandings in reproductive isolation especially with new data in the last several years well support three evolutionary genetic models, which represent a general mechanism underlying genomic differentiation and speciation. The updated understanding will offer new approaches for the development of wide-compatibility or neutral varieties, which facilitate breeding of hybrid rice as well as other hybrid crops.Yidan Ouyang Qifa Zhang 2018Journal of Genetics and Genomics2018,45,11:9
19Molecular dynamics simulation of complex multiphase flow on a computer cluster with GPUs显示文摘Compute Unified Device Architecture (CUDA) was used to design and implement molecular dynamics (MD) simulations on graphics processing units (GPU). With an NVIDIA Tesla C870, a 20-60 fold speedup over that of one core of the Intel Xeon 5430 CPU was achieved, reaching up to 150 Gflops. MD simulation of cavity flow and particle-bubble interaction in liquid was implemented on multiple GPUs using a message passing interface (MPI). Up to 200 GPUs were tested on a special network topology, which achieves good scalability. The capability of GPU clusters for large-scale molecular dynamics simulation of meso-scale flow behavior was, therefore, uncovered.CHEN FeiGuo GE Wei LI JingHai 2009Science China Chemistry2009,52,3:9
20Type Synthesis of 1T2R Parallel Mechanisms Using Structure Coupling-Reducing Method显示文摘Direct kinematics with analytic solutions is critical to the real-time control of parallel mechanisms.Therefore,the type synthesis of a mechanism having explicit form of forward kinematics has become a topic of interest.Based on this purpose,this paper deals with the type synthesis of 1T2R parallel mechanisms by investigating the topological structure coupling-reducing of the 3UPS&UP parallel mechanism.With the aid of the theory of mechanism topology,the analysis of the topological characteristics of the 3UPS&UP parallel mechanism is presented,which shows that there are highly coupled motions and constraints amongst the limbs of the mechanism.Three methods for structure coupling-reducing of the 3UPS&UP parallel mechanism are proposed,resulting in eight new types of 1T2R parallel mechanisms with one or zero coupling degree.One obtained parallel mechanism is taken as an example to demonstrate that a mechanism with zero coupling degree has an explicit form for forward kinematics.The process of type synthesis is in the order of permutation and combination;therefore,there are no omissions.This method is also appli cable to other configurations,and novel topological structures having simple forward kinematics can be obtained from an original mechanism via this method.Haitao Liu Ke Xu Huiping Shen Xianlei Shan Tingli Yang 2019Chinese Journal of Mechanical Engineering2019,32,5:9
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