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Guizhong XIE,Dehai ZHANG,Jianming ZHANG,Fannian MENG,Wenliao DU,Xiaoyu WEN
《机械工程前沿（英文）》 2016年 第11卷 第4期 页码 412-422 doi: 10.1007/s11465-016-0396-8
As a widely used numerical method, boundary element method (BEM) is efficient for computer aided engineering (CAE). However, boundary integrals with near singularity need to be calculated accurately and efficiently to implement BEM for CAE analysis on thin bodies successfully. In this paper, the distance in the denominator of the fundamental solution is first designed as an equivalent form using approximate expansion and the original sinh method can be revised into a new form considering the minimum distance and the approximate expansion. Second, the acquisition of the projection point by Newton-Raphson method is introduced. We acquire the nearest point between the source point and element edge by solving a cubic equation if the location of the projection point is outside the element, where boundary integrals with near singularity appear. Finally, the subtriangles of the local coordinate space are mapped into the integration space and the sinh method is applied in the integration space. The revised sinh method can be directly performed in the integration element. A verification test of our method is proposed. Results demonstrate that our method is effective for regularizing the boundary integrals with near singularity.
关键词： computer aided engineering (CAE) boundary element method (BEM) near singularity sinh method coordinate transformation integration space
Singularity loci of an orthogonal spherical two-degree-of-freedom parallel mechanism
Jialun YANG, Feng GAO,
《机械工程前沿（英文）》 2009年 第4卷 第4期 页码 379-385 doi: 10.1007/s11465-009-0075-0
关键词： 2-DOF orthogonal spherical parallel mechanism singularity loci self-motions
Influence of kinematic redundancy on the singularity-free workspace of parallel kinematic machines
Jens KOTLARSKI, Bodo HEIMANN, Tobias ORTMAIER
《机械工程前沿（英文）》 2012年 第7卷 第2期 页码 120-134 doi: 10.1007/s11465-012-0321-8
In this paper the effect of kinematic redundancy in order to reduce the singularity loci of the direct kinematics and to increase the operational, i.e., singularity-free, workspace is demonstrated. The proposed approach consists of additional prismatic actuators allowing one or more base joints to move linearly. As a result, a selective reconfiguration can be performed in order to avoid singular configurations. Exemplarily, kinematically redundant schemes of four structures, the 3RRR, the 3RPR, the 6UPS, and the 6RUS, are considered. The relationship between the redundancy and the operational workspace is studied and several analysis examples demonstrate the effectiveness of the proposed concept. Furthermore, the additional benefit of an increasing number of redundant actuators is discussed.
关键词： parallel robots kinematic redundancy singularity avoidance operational workspace
Study on the Path of “Near-zero Emission” Coal-based Clean Energy Ecosystem Development
Zhang Yu-zhuo
《工程管理前沿（英文）》 2014年 第1卷 第1期 页码 37-41 doi: 10.15302/J-FEM-2014007
关键词： near-zero emission clean energy ecosystem study on the path
Research and industrialization of near-net rolling technology used in shaft parts
Zhenghuan HU, Baoyu WANG, Zhenhua ZHENG
《机械工程前沿（英文）》 2018年 第13卷 第1期 页码 17-24 doi: 10.1007/s11465-018-0480-3
Shaft part rolling is an efficient and green near-net shaping technology offering many advantages, including high production efficiency, high material utilization rate, high product quality, and excellent production environment. In this paper, the features of shaft part rolling are introduced along with the working principles of two main shaft part rolling technologies, namely, cross wedge rolling (CWR) and skew rolling (SR). In relation to this technology, some R&D achievements gained by the University of Science and Technology Beijing are summarized. Finally, the latest developments in shaft part rolling are presented, including SR steel balls, precise forming of camshaft blank by CWR, SR phosphorous copper balls at room temperature, and CWR hollow axle sleeve. Although the shaft part rolling technology has been widely used in China, it only accounts for about 15% of applicable parts at present. Nevertheless, this technology has broad application prospects.
关键词： cross wedge rolling skew rolling near-net rolling shaft part
Special issue: Near-net shaping technology
Dequn LI, Dongming GUO, Qingxue HUANG, Yanchun LOU
《机械工程前沿（英文）》 2018年 第13卷 第1期 页码 1-2 doi: 10.1007/s11465-018-0497-7
Determining casting defects in near-net shape casting aluminum parts by computed tomography
Jiehua LI, Bernd OBERDORFER, Daniel HABE, Peter SCHUMACHER
《机械工程前沿（英文）》 2018年 第13卷 第1期 页码 48-52 doi: 10.1007/s11465-018-0493-y
Three types of near-net shape casting aluminum parts were investigated by computed tomography to determine casting defects and evaluate quality. The first, second, and third parts were produced by low-pressure die casting (Al-12Si-0.8Cu-0.5Fe-0.9Mg-0.7Ni-0.2Zn alloy), die casting (A356, Al-7Si-0.3Mg), and semi-solid casting (A356, Al-7Si-0.3Mg), respectively. Unlike die casting (second part), low-pressure die casting (first part) significantly reduced the formation of casting defects (i.e., porosity) due to its smooth filling and solidification under pressure. No significant casting defect was observed in the third part, and this absence of defects indicates that semi-solid casting could produce high-quality near-net shape casting aluminum parts. Moreover, casting defects were mostly distributed along the eutectic grain boundaries. This finding reveals that refinement of eutectic grains is necessary to optimize the distribution of casting defects and reduce their size. This investigation demonstrated that computed tomography is an efficient method to determine casting defects in near-net shape casting aluminum parts.
关键词： near-net shape casting aluminum parts casting defects low pressure die casting die casting semi-solid casting computed tomography
Chemisorption solid materials for hydrogen storage near ambient temperature: a review
Yiheng ZHANG, Shaofei WU, Liwei WANG, Xuefeng ZHANG
《能源前沿（英文）》 2023年 第17卷 第1期 页码 72-101 doi: 10.1007/s11708-022-0835-7
关键词： hydrogen storage capacity chemisorption near-ambient-temperature modification methods alloy hydrides
Factors influencing near infrared spectroscopy analysis of agro-products: a review
Xiao XU, Lijuan XIE, Yibin YING
《农业科学与工程前沿（英文）》 2019年 第6卷 第2期 页码 105-115 doi: 10.15302/J-FASE-2019255
The near infrared (NIR) spectroscopy technique has wide applications in agriculture with the advantages of being nondestructive, sensitive, safe and rapid. However, there are still more than 40 error sources influencing the robustness and accuracy of its calibration and operation. Environmental, sample and instrument factors that influence the analysis are discussed in this review, including temperature, humidity and other factors that introduce uncertainty. Error sources from livestock products, fruit and vegetables, which are the most common objects in the field of NIR analysis, are also emphasized in the second part. In addition, studies utilizing different instruments, spectral pretreatments, variable selection methods, wavelength ranges, detection modes and calibration methods are tabulated to illustrate the complications they introduce and how they influence NIR analysis. It is suggested that large scale of data with abundant varieties can be used to build a more robust calibration model, in order to improve the robustness and accuracy of the NIR analytical model, and overcome problems caused by confining analysis to too many uniform samples.
关键词： agro-product error source influence factor near infrared spectroscopy
马景兰,王伟,万京生,张永丽
《中国工程科学》 2009年 第11卷 第8期 页码 93-96
低频振荡是影响电力系统稳定运行的一个重要方面。阐述了低频振荡产生的机理和分析方法，利用Hopf分歧理论，针对一个四阶模型的单机无穷大系统，分析了在临界点附近时可能出现的非线性奇异现象。研究表明：由于分歧的存在，导致系统稳定性在临界点附近出现奇异，从而影响了电力系统的稳定域。
Modeling of oil near-infrared spectroscopy based on similarity and transfer learning algorithm
Yifei Wang, Kai Wang, Zhao Zhou, Wenli Du
《化学科学与工程前沿（英文）》 2019年 第13卷 第3期 页码 599-607 doi: 10.1007/s11705-019-1807-2
关键词： near-infrared spectroscopy transfer learning similarity modeling
Alin STOICA, Doina PISLA, Szilaghyi ANDRAS, Bogdan GHERMAN, Bela-Zoltan GYURKA, Nicolae PLITEA
《机械工程前沿（英文）》 2013年 第8卷 第1期 页码 70-79 doi: 10.1007/s11465-013-0365-4
In the last ten years, due to development in robotic assisted surgery, the minimally invasive surgery has greatly changed. Until now, the vast majority of robots used in surgery, have serial structures. Due to the orientation parallel module, the structure is able to reduce the pressure exerted on the entrance point in the patient’s abdominal wall. The parallel robot can also handle both a laparoscope as well an active instrument for different surgical procedures. The advantage of this parallel structure is that the geometric model has been obtained through an analytical approach. The kinematic modelling of a new parallel architecture, the inverse and direct geometric model and the inverse and direct kinematic models for velocities and accelerations are being determined. The paper will demonstrate that with this parallel structure, one can obtain the necessary workspace required for a minimally invasive operation. The robot workspace was generated using the inverse geometric model. An in-depth study of different types of singularity is performed, allowing the development of safe control algorithms of the experimental model. Some kinematic simulation results and the experimental model of the robot are presented in the paper.
关键词： parallel robot minimally invasive surgery kinematics simulation
Po-Chih LEE, Jyh-Jone LEE
《机械工程前沿（英文）》 2012年 第7卷 第2期 页码 163-187 doi: 10.1007/s11465-012-0324-5
This paper presents the analysis of three parallel manipulators with Schoenflies-motion. Each parallel manipulator possesses two limbs in structure and the end-effector has three DOFs (degree of freedom) in the translational motion and one DOF in rotational motion about a given direction axis with respect to the world coordinate system. The three isoconstrained parallel manipulators have the structures denoted as CuuUwHw-//-CvvUwHw, CuRuuUhw-//-CvRvvUhwand CuPuUhw-//- CvPvUhw. The kinematic equations are first introduced for each manipulator. Then, Jacobian matrix, singularity, workspace, and performance index for each mechanism are subsequently derived and analysed for the first time. The results can be helpful for the engineers to evaluate such kind of parallel robots for possible application in industry where pick-and-place motion is required.
关键词： parallel manipulator schoenflies motion kinematics singularity workspace performance index
Stress field near circular-arc interface crack tip based on electric saturation concept
Longchao DAI, Xinwei WANG
《机械工程前沿（英文）》 2009年 第4卷 第3期 页码 320-325 doi: 10.1007/s11465-009-0042-9
关键词： piezoelectric material arc crack strip saturation stress intensity factor
null
《机械工程前沿（英文）》 2014年 第9卷 第3期 页码 281-294 doi: 10.1007/s11465-014-0307-9
In this study, the stress concentration factors (SCF) in cross-and-angle-ply laminated composite plates as well as in isotropic plates with single circular holes subjected to uniaxial loading is studied. A quadrilateral finite element of four-node with 32 degrees of freedom at each node, previously developed for the bending and mechanical buckling of laminated composite plates, is used to evaluate the stress distribution in laminated composite plates with central circular holes. Based up on the classical plate theory, the present finite element is a combination of a linear isoparametric membrane element and a high precision rectangular Hermitian element. The numerical results obtained by the present element compare favorably with those obtained by the analytic approaches published in literature. It is observed that the obtained results are very close to the reference results, which demonstrates the accuracy of the present element. Additionally, to determine the first ply failure (FPF) of laminated plate, several failure criterions are employed. Finally, to show the effect of ratio on the failure of plates, a number of figures are given for different fiber orientation angles.
关键词： laminated composite plates stress concentration geometric singularity anisotropic effect
标题 作者 时间 类型 操作
Implementation of sinh method in integration space for boundary integrals with near singularity in potential
Guizhong XIE,Dehai ZHANG,Jianming ZHANG,Fannian MENG,Wenliao DU,Xiaoyu WEN
期刊论文
Singularity loci of an orthogonal spherical two-degree-of-freedom parallel mechanism
Jialun YANG, Feng GAO,
期刊论文
Influence of kinematic redundancy on the singularity-free workspace of parallel kinematic machines
Jens KOTLARSKI, Bodo HEIMANN, Tobias ORTMAIER
期刊论文
Study on the Path of “Near-zero Emission” Coal-based Clean Energy Ecosystem Development
Zhang Yu-zhuo
期刊论文
Research and industrialization of near-net rolling technology used in shaft parts
Zhenghuan HU, Baoyu WANG, Zhenhua ZHENG
期刊论文
Determining casting defects in near-net shape casting aluminum parts by computed tomography
Jiehua LI, Bernd OBERDORFER, Daniel HABE, Peter SCHUMACHER
期刊论文
Chemisorption solid materials for hydrogen storage near ambient temperature: a review
Yiheng ZHANG, Shaofei WU, Liwei WANG, Xuefeng ZHANG
期刊论文
Factors influencing near infrared spectroscopy analysis of agro-products: a review
Xiao XU, Lijuan XIE, Yibin YING
期刊论文
Modeling of oil near-infrared spectroscopy based on similarity and transfer learning algorithm
Yifei Wang, Kai Wang, Zhao Zhou, Wenli Du
期刊论文
Kinematic, workspace and singularity analysis of a new parallel robot used in minimally invasive surgery
Alin STOICA, Doina PISLA, Szilaghyi ANDRAS, Bogdan GHERMAN, Bela-Zoltan GYURKA, Nicolae PLITEA
期刊论文
Singularity and workspace analysis of three isoconstrained parallel manipulators with schoenflies motion
Po-Chih LEE, Jyh-Jone LEE
期刊论文
Stress field near circular-arc interface crack tip based on electric saturation concept
Longchao DAI, Xinwei WANG
期刊论文
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