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A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication problems

null

《机械工程前沿（英文）》 2014年 第9卷 第2期   页码 156-167 doi: 10.1007/s11465-014-0297-7

摘要：

A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication (EHL) problems is presented. First, by introducing a special matrix splitting iteration method into the traditional compound direct iterative method, the full matrices for the linear systems of equations are transformed into sparse banded ones with any half-bandwidth; then, an extended Thomas method which can solve banded linear systems with any half-bandwidth is derived to accelerate the computing speed. Through the above two steps, the computational complexity of each iteration is reduced approximately from O(N3/3) to O(β2N), where N is the total number of nodes, and β is the half-bandwidth. Two kinds of numerical results of transient EHL line contact problems under sinusoidal excitation or pure normal approach process are obtained. The results demonstrate that the new algorithm increases computing speed several times more than the traditional compound direct iterative method with the same numerical precision. Also the results show that the new algorithm can get the best computing speed and robustness when the ratio, half-bandwidth to total number of nodes, is about 7.5%–10.0% in moderate load cases.

关键词： elastohydrodynamic lubrication     transient     line contact     matrix splitting iteration method     the Thomas method    

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numerical framework for underground structures in layered ground under inclined P-SV waves using stiffness matrix

《结构与土木工程前沿（英文）》 2023年 第17卷 第1期   页码 10-24 doi: 10.1007/s11709-022-0904-3

摘要： A numerical framework was proposed for the seismic analysis of underground structures in layered ground under inclined P-SV waves. The free-field responses are first obtained using the stiffness matrix method based on plane-wave assumptions. Then, the domain reduction method was employed to reproduce the wavefield in the numerical model of the soil–structure system. The proposed numerical framework was verified by providing comparisons with analytical solutions for cases involving free-field responses of homogeneous ground, layered ground, and pressure-dependent heterogeneous ground, as well as for an example of a soil–structure interaction simulation. Compared with the viscous and viscous-spring boundary methods adopted in previous studies, the proposed framework exhibits the advantage of incorporating oblique incident waves in a nonlinear heterogeneous ground. Numerical results show that SV-waves are more destructive to underground structures than P-waves, and the responses of underground structures are significantly affected by the incident angles.

关键词： underground structures     seismic response     stiffness matrix method     domain reduction method     P-SV waves    

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Rotation errors in numerical manifold method and a correction based on large deformation theory

Ning ZHANG, Xu LI, Qinghui JIANG, Xingchao LIN

《结构与土木工程前沿（英文）》 2019年 第13卷 第5期   页码 1036-1053 doi: 10.1007/s11709-019-0535-5

摘要： Numerical manifold method (NMM) is an effective method for simulating block system, however, significant errors are found in its simulation of rotation problems. Three kinds of errors, as volume expansion, stress vibration, and attenuation of angular velocity, were observed in the original NMM. The first two kind errors are owing to the small deformation assumption and the last one is due to the numerical damping. A large deformation NMM is proposed based on large deformation theory. In this method, the governing equation is derived using Green strain, the large deformation iteration and the open-close iteration are combined, and an updating strategy is proposed. The proposed method is used to analyze block rotation, beam bending, and rock falling problems and the results prove that all three kinds of errors are eliminated in this method.

关键词： numerical manifold method     rotation     large deformation     Green strain     open-close iteration    

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A dynamic model of mobile concrete pump boom based on discrete time transfer matrix method

Wu REN, Yunxin WU, Zhaowei ZHANG

《机械工程前沿（英文）》 2013年 第8卷 第4期   页码 360-366 doi: 10.1007/s11465-013-0280-8

摘要：

Mobile concrete pump boom is typical multi-body large-scale motion manipulator. Due to posture constantly change in working process, kinematic rule and dynamic characteristic are difficult to solve. A dynamics model of a mobile concrete pump boom is established based on discrete time transfer matrix method (DTTMM). The boom system is divided into sub-structure A and sub-structure B. Sub-structure A is composed by the 1st boom and hydraulic actuator as well as the support. And sub-structure B is consists of the other three booms and corresponding hydraulic actuators. In the model, the booms and links are regarded as rigid elements and the hydraulic cylinders are equivalent to spring-damper. The booms are driven by the controllable hydraulic actuators. The overall dynamic equation and transfer matrix of the model can be assembled by sub-structures A and B. To get a precise result, step size and integration parameters are studied then. Next the tip displacement is calculated and compared with the result of ADAMS software. The displacement and rotation angle curves of the proposed method fit well with the ADAMS model. Besides it is convenient in modeling and saves time. So it is suitable for mobile concrete pump boom real-time monitoring and dynamic analysis. All of these provide reference to boom optimize and engineering application of such mechanisms.

关键词： multi-body     mobile concrete pump boom     discrete time transfer matrix method (DTTMM)     kinematic     dynamic     tip displacement    

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Identification of dynamic stiffness matrix of bearing joint region

Feng HU, Bo WU, Youmin HU, Tielin SHI

《机械工程前沿（英文）》 2009年 第4卷 第3期   页码 289-299 doi: 10.1007/s11465-009-0064-3

摘要： The paper proposes an identification method of the dynamic stiffness matrix of a bearing joint region on the basis of theoretical analysis and experiments. The author deduces an identification model of the dynamic stiffness matrix from the synthetic substructure method. The dynamic stiffness matrix of the bearing joint region can be identified by measuring the matrix of frequency response function (FRFs) of the substructure (axle) and whole structure (assembly of the axle, bearing, and bearing housing) in different positions. Considering difficulty in measuring angular displacement, applying moment, and directly measuring relevant FRFs of rotational degree of freedom, the author employs an accurately calibrated finite element model of the unconstrained structure for indirect estimation. With experiments and simulation analysis, FRFs related with translational degree of freedom, which is estimated through the finite element model, agrees with experimental results, and there is very high reliability in the identified dynamic stiffness matrix of the bearing joint region.

关键词： frequency response function (FRFs)     dynamic stiffness     finite element     synthetic substructure method     joint region    

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Research and practice on system engineering management of a mobile payment project

Yongkai ZHOU, Hongfeng CHAI

《工程管理前沿（英文）》 2017年 第4卷 第2期   页码 127-137 doi: 10.15302/J-FEM-2017011

摘要： The popularization of the mobile internet has given rise to demand for flexible and convenient payment methods. For China, it is necessary to keep pace with or even lead the trend of innovation and development in the age of mobile payment. From the perspective of systems engineering, this paper introduces research and implementation of China UnionPay’s mobile payment project. The general requirements and core engineering problems of the mobile payment project are summarized based on analyses of the characteristics and engineering difficulties of this project. Integration of innovative technologies is introduced to resolve the contradiction between ease-of-use and security. A rapid iterative development process is adopted to improve the product release efficiency as well as the users' experience. The launch of the mobile payment project also opens the window to coordinating and upgrading the whole payment industry chains.

关键词： systems engineering     mobile payment     engineering management method     Mobile QuickPass     national information security     rapid iteration process     financial security     coordination and cooperation    

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风险矩阵方法与应用述评

朱启超,匡兴华,沈永平

《中国工程科学》 2003年 第5卷 第1期   页码 89-94

摘要：

技术项目的风险管理一直深受美国国防部的重视。介绍了在美国国防采办风险管理中广泛应用的风险矩阵方法，并对其优缺点和适用性进行分析，结合我国国防预研技术项目管理的特点，提出我国开展技术性项目风险管理的思路。

关键词： 风险矩阵     风险管理     项目管理    

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Generation of enhanced stability of SnO/In(OH)/InP for photocatalytic water splitting by SnO protection

《能源前沿（英文）》 2021年 第15卷 第3期   页码 710-720 doi: 10.1007/s11708-021-0764-x

摘要： InP shows a very high efficiency for solar light to electricity conversion in solar cell and may present an expectation property in photocatalytic hydrogen evolution. However, it suffers serious corrosion in water dispersion. In this paper, it is demonstrated that the stability and activity of the InP-based catalyst are effectively enhanced by applying an anti-corrosion SnO layer and In(OH)3 transition layer, which reduces the crystal mismatch between SnO and InP and increases charge transfer. The obtained Pt/SnO/In(OH)3/InP exhibits a hydrogen production rate of 144.42 µmol/g in 3 h under visible light illumination in multi-cycle tests without remarkable decay, 123 times higher than that of naked In(OH)3/InP without any electron donor under visible irradiation.

关键词： SnO/In(OH)3/InP photocatalyst     enhanced activity and stability for water splitting     corrosion inhibition     enhancing charge transfer and decreasing crystal mismatch    

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Approaching the commercial threshold of solar water splitting toward hydrogen by III-nitrides nanowires

《能源前沿（英文）》 doi: 10.1007/s11708-023-0870-z

摘要： Approaching the commercial threshold of solar water splitting toward hydrogen by III-nitrides nanowires

关键词： threshold solar water     splitting hydrogen III    

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An overview and recent advances in electrocatalysts for direct seawater splitting

《化学科学与工程前沿（英文）》 2021年 第15卷 第6期   页码 1408-1426 doi: 10.1007/s11705-021-2102-6

摘要： In comparison to pure water, seawater is widely accepted as an unlimited resource. The direct seawater splitting is economical and eco-friendly, but the key challenges in seawater, especially the chlorine-related competing reactions at the anode, seriously hamper its practical application. The development of earth-abundant electrocatalysts toward direct seawater splitting has emerged as a promising strategy. Highly efficient electrocatalysts with improved selectivity and stability are of significance in preventing the interference of side reactions and resisting various impurities. This review first discusses the macroscopic understanding of direct seawater electrolysis and then focuses on the strategies for rational design of electrocatalysts toward direct seawater splitting. The perspectives of improved electrocatalysts to solve emerging challenges and further development of direct seawater splitting are also provided.

关键词： seawater splitting     electrocatalysts     oxygen evolution reaction     hydrogen evolution reaction     chlorine chemistry    

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a novel perforated ultrasonic vibration platform in the grinding of particulate-reinforced titanium matrix

《机械工程前沿（英文）》 2023年 第18卷 第1期 doi: 10.1007/s11465-022-0730-2

摘要： Ultrasonic vibration-assisted grinding (UVAG) is an advanced hybrid process for the precision machining of difficult-to-cut materials. The resonator is a critical part of the UVAG system. Its performance considerably influences the vibration amplitude and resonant frequency. In this work, a novel perforated ultrasonic vibration platform resonator was developed for UVAG. The holes were evenly arranged at the top and side surfaces of the vibration platform to improve the vibration characteristics. A modified apparent elasticity method (AEM) was proposed to reveal the influence of holes on the vibration mode. The performance of the vibration platform was evaluated by the vibration tests and UVAG experiments of particulate-reinforced titanium matrix composites. Results indicate that the reasonable distribution of holes helps improve the resonant frequency and vibration mode. The modified AEM, the finite element method, and the vibration tests show a high degree of consistency for developing the perforated ultrasonic vibration platform with a maximum frequency error of 3%. The employment of ultrasonic vibration reduces the grinding force by 36% at most, thereby decreasing the machined surface defects, such as voids, cracks, and burnout.

关键词： ultrasonic vibration-assisted grinding     perforated ultrasonic vibration platform     vibration characteristics     apparent elasticity method     grinding force     surface integrity    

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Acoustic emissions evaluation of the dynamic splitting tensile properties of steel fiber reinforced concrete

《结构与土木工程前沿（英文）》   页码 1341-1356 doi: 10.1007/s11709-023-0988-4

摘要： This study empirically investigated the influence of freeze–thaw cycling on the dynamic splitting tensile properties of steel fiber reinforced concrete (SFRC). Brazilian disc splitting tests were conducted using four loading rates (0.002, 0.02, 0.2, and 2 mm/s) on specimens with four steel fiber contents (0%, 0.6%, 1.2%, and 1.8%) subjected to 0 and 50 freeze–thaw cycles. The dynamic splitting tensile damage characteristics were evaluated using acoustic emission (AE) parameter analysis and Fourier transform spectral analysis. The results quantified using the freeze–thaw damage factor defined in this paper indicate that the degree of damage to SFRC caused by freeze–thaw cycling was aggravated with increasing loading rate but mitigated by increasing fiber content. The percentage of low-frequency AE signals produced by the SFRC specimens during loading decreased with increasing loading rate, whereas that of high-frequency AE signals increased. Freeze–thaw action had little effect on the crack types observed during the early and middle stages of the loading process; however, the primary crack type observed during the later stage of loading changed from shear to tensile after the SFRC specimens were subjected to freeze–thaw cycling. Notably, the results of this study indicate that the freeze–thaw damage to SFRC reduces AE signal activity at low frequencies.

关键词： steel fiber reinforced concrete     freeze–thaw cycling     Brazilian disc splitting test     acoustic emission technique     dynamic splitting tensile acoustic emission properties    

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复杂并流多效蒸发系统的数学模型与矩阵解法

阮奇,陈文波,黄诗煌,叶长燊

《中国工程科学》 2001年 第3卷 第4期   页码 36-41

摘要：

建立了有冷凝水闪蒸和额外蒸汽引出的复杂并流多效蒸发系统的数学模型, 常规并流多效蒸发模型只是该模型的一个特例。提出一种新算法--迭代法结合矩阵法求解模型并给出算法框图。算例表明新算法比常用的牛顿迭代法和Broyden法效率更高，具有对初值要求不高、收敛稳定性好、收敛速度快等优点。对三效并流蒸发蔗糖水溶液系统，采用冷凝水闪蒸和引出额外蒸汽将原料液从26.7 ℃预热至90 ℃，约可节省16%的加热生蒸汽，节能效果显著。

关键词： 冷凝水闪蒸     额外蒸汽引出     并流流程     多效蒸发     数学模型     矩阵解法    

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Excitation-emission matrix (EEM) fluorescence spectroscopy for characterization of organic matter in

Jinlan Yu, Kang Xiao, Wenchao Xue, Yue-xiao Shen, Jihua Tan, Shuai Liang, Yanfen Wang, Xia Huang

《环境科学与工程前沿（英文）》 2020年 第14卷 第2期 doi: 10.1007/s11783-019-1210-8

摘要： • Principles and methods for fluorescence EEM are systematically outlined. • Fluorophore peak/region/component and energy information can be extracted from EEM. • EEM can fingerprint the physical/chemical/biological properties of DOM in MBRs. • EEM is useful for tracking pollutant transformation and membrane retention/fouling. • Improvements are still needed to overcome limitations for further studies. The membrane bioreactor (MBR) technology is a rising star for wastewater treatment. The pollutant elimination and membrane fouling performances of MBRs are essentially related to the dissolved organic matter (DOM) in the system. Three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy, a powerful tool for the rapid and sensitive characterization of DOM, has been extensively applied in MBR studies; however, only a limited portion of the EEM fingerprinting information was utilized. This paper revisits the principles and methods of fluorescence EEM, and reviews the recent progress in applying EEM to characterize DOM in MBR studies. We systematically introduced the information extracted from EEM by considering the fluorescence peak location/intensity, wavelength regional distribution, and spectral deconvolution (giving fluorescent component loadings/scores), and discussed how to use the information to interpret the chemical compositions, physiochemical properties, biological activities, membrane retention/fouling behaviors, and migration/transformation fates of DOM in MBR systems. In addition to conventional EEM indicators, novel fluorescent parameters are summarized for potential use, including quantum yield, Stokes shift, excited energy state, and fluorescence lifetime. The current limitations of EEM-based DOM characterization are also discussed, with possible measures proposed to improve applications in MBR monitoring.

关键词： excitation-emission matrix (EEM)     dissolved organic matter (DOM)     membrane bioreactor (MBR)     fluorescence indicator     characterization method    

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带约束的矩阵值分布式随机优化

夏子聪,刘洋,卢文联,桂卫华

《信息与电子工程前沿（英文）》 2023年 第24卷 第9期   页码 1239-1252 doi: 10.1631/FITEE.2200381

摘要： 本文研究带有不等式约束和等式约束的矩阵值分布随机优化问题。其中，问题的目标函数是具有随机变量的多个矩阵值函数的和，并以分布式方式解决了该问题。本文推导了处理约束的惩罚方法，并提出选择可行惩罚函数和惩罚增益的原则。针对随机优化问题，提出一种基于gossip模型的分布式优化算法，并对其收敛性进行证明和分析。最后，为验证所提算法的可行性，本文提供了两个数值示例。

关键词： 分布式优化     矩阵值优化     随机优化     罚函数法     Gossip模型    

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标题 作者 时间 类型 操作

A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication problems

null

期刊论文

numerical framework for underground structures in layered ground under inclined P-SV waves using stiffness matrix

期刊论文

Rotation errors in numerical manifold method and a correction based on large deformation theory

Ning ZHANG, Xu LI, Qinghui JIANG, Xingchao LIN

期刊论文

A dynamic model of mobile concrete pump boom based on discrete time transfer matrix method

Wu REN, Yunxin WU, Zhaowei ZHANG

期刊论文

Identification of dynamic stiffness matrix of bearing joint region

Feng HU, Bo WU, Youmin HU, Tielin SHI

期刊论文

Research and practice on system engineering management of a mobile payment project

Yongkai ZHOU, Hongfeng CHAI

期刊论文

风险矩阵方法与应用述评

朱启超,匡兴华,沈永平

期刊论文

Generation of enhanced stability of SnO/In(OH)/InP for photocatalytic water splitting by SnO protection

期刊论文

Approaching the commercial threshold of solar water splitting toward hydrogen by III-nitrides nanowires

期刊论文

An overview and recent advances in electrocatalysts for direct seawater splitting

期刊论文

a novel perforated ultrasonic vibration platform in the grinding of particulate-reinforced titanium matrix

期刊论文

Acoustic emissions evaluation of the dynamic splitting tensile properties of steel fiber reinforced concrete

期刊论文

复杂并流多效蒸发系统的数学模型与矩阵解法

阮奇,陈文波,黄诗煌,叶长燊

期刊论文

Excitation-emission matrix (EEM) fluorescence spectroscopy for characterization of organic matter in

Jinlan Yu, Kang Xiao, Wenchao Xue, Yue-xiao Shen, Jihua Tan, Shuai Liang, Yanfen Wang, Xia Huang

期刊论文

带约束的矩阵值分布式随机优化

夏子聪,刘洋,卢文联,桂卫华

期刊论文