检索结果-南通市图书馆

Frequency domain fundamental solutions for a poroelastic half-space

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2014年第2期30卷 206-213页

作者： Pei Zheng Bo-Yang Ding She-Xu Zhao School of Mechanical engineering University of Shanghai for Science and Technology College of Civil engineering and Architecture Zhejiang University of Technology Department of engineering Mechanics Shanghai Jiaotong University

In frequency domain, the fundamental solutions for a poroelastic half-space are re-derived in the context of Biot＇s theory. Based on Biot＇s theory, the governing field equations for the dynamic poroelasicity are established in terms of solid displacement and pore pressure. A method of potentials in cylindrical coordinate system is proposed to decouple the homogeneous Biot＇s wave equations into four scalar Helmholtz equations, and the general solutions to these scalar wave equations are obtained. After that, spectral Green＇s functions for a poroelastic full-space are found through a decomposition of solid displacement, pore pressure, and body force fields. Mirror-image technique is then applied to construct the half-space fundamental ***, transient responses of the half-space to buried point forces are examined.

关键词： Poroelastic Fundamental solutions Wave prop-agation Half-space

Oxidation behavior of niobized TiAl by plasma surface alloying

在线全文

学校读者我要写书评

暂无评论

Journal of university of Science and Technology Beijing 2008年第5期15卷 590-593页

作者： Dongdong Chen Wenhuai Tian Jian Wang Xiaoping Liu School of Materials Science and engineering University of Science and Technology Beijing Beijing 100083 China Research institute of Surface engineering Taiyuan University of Technology Taiyuan 030024 China

Plasma surface alloying of element Nb in TiAl-based alloys and the oxidation behavior were studied. The composition and microstructure of the surface alloyed layers were investigated by means of scanning electron microscopy （SEM）,energy dispersive X-ray analysis （EDX）,and X-ray diffraction （XRD）. The experimental results indicate that the diffusion layers are formed on the TiAl substrate during the plasma niobizing process. The result from oxidation resistance investigation shows that plasma niobizing greatly improves the oxidation resistance of TiAl compared with the untreated TiAl. The role of element Nb for improving the oxidation resistance is considered to be achieved by strengthening the activity of Al,which is induced by the plasma niobizing process.

关键词： TiAl alloys plasma niobizing oxidation resistance surface alloying

Enhanced mechanical properties in die-upset Nd-Fe-B magnets via die-upsetting process

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2012年第11期30卷 1112-1115页

作者：胡志华瞿海锦赵佳奇罗成李军刘颖 Department of Materials engineering Hubei University of Automotive Technology Material&Technology institute Dongfeng Motor Company Limited College of Materials Science and engineering Sichuan University

The mechanical properties of die-upset Nd-Fe-B magnets produced at different die-upset processes were investigated. The results showed that the optimum comprehensive mechanical properties of die-upset Nd-Fe-B magnets were obtained at the deformation temperature of 680 ℃. The anisotropy of Vickers hardness was more obvious at the die-upset level of 55%, and the Vickers hardness measured parallel to the c-axis was significantly lower than that perpendicular to the c-axis. The fracture toughness measured parallel to the c-axis first increased, and then decreased with increase in die-upset level. The maximum fracture toughness of Nd-Fe-B magnets was obtained at the die-upset level of 60%. The microstmcture showed that the width of defect layers and the average size of large grains increased, and the layered structure of die-upset Nd-Fe-B magnets was obviously different with increase in the die-upset level.

关键词： Nd-Fe-B magnets mechanical properties die-upset level fracture toughness Vickers hardness rare earths

Modified origin-based algorithm for traffic equilibrium assignment problems

在线全文

学校读者我要写书评

暂无评论

Journal of Central South university 2011年第5期18卷 1765-1772页

作者：张天然杨超陈冬栋 Shanghai City Comprehensive Transportation Planning institute School of Transportation engineering Tongji University Shanghai Municipal engineering Design institute (Group) Co. Ltd.

Key tactics of origin-based user equilibrium (OUE) algorithm was studied,which involved the algorithm procedure and several implementation *** speed up the convergence,update policies of flows,costs and bushes were *** methods of step-size searching and bush construction are proved to be *** modified OUE algorithm procedure was also optimized to take the advantage of multi-thread *** performances were compared with those of other algorithms by different sizes of urban transportation *** result shows this modified OUE algorithm is more efficient and consumes less time to achieve the reasonable relative gap in practical applications.

关键词： traffic assignment origin-based user equilibrium algorithm acyclic network

Three-Dimensional Bursting Phenomena in Meander Channel

在线全文

学校读者我要写书评

暂无评论

Transactions of Tianjin university 2013年第1期19卷 17-24页

作者：刘小谢白玉川 State Key Laboratory of Hydraulic engineering Simulation and Safety Tianjin University institute for Sedimentation on River and Coastal engineering Tianjin University

Experiments were conducted in a U-shaped open-channel flume with the intention of investigating the bursting phenomena in the meander channel. The experimental results of the secondary flow fields and the Reynolds shear stress distributions show that the velocity and velocity fluctuation in the transverse direction are not negligible. Moreover, the bursting process is investigated using the three-dimensional quadrant analysis, which is more accurate than using the traditional two-dimensional quadrant analysis for the meandering channel. It is obtained from the experimental results that the internal group of events occurs more frequently than the external group, particularly the internal ejection and internal sweep events. In addition, the transition probabilities of the movements, which are defined as the changes of events from the current situation to the next situation in a time series, show that the stable organizations of events are the most possible movements, whereas the cross organizations of events have the least possible movements.

关键词： meander channel bursting phenomena turbulent characteristics three-dimension

Dynamical modeling and non-planar coupled behavior of inclined CFRP cables under simultaneous internal and external resonances

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2019年第5期40卷 649-678页

作者： Houjun KANG Tieding GUO Weidong ZHU Junyi SU Bingyu ZHAO Hunan Provincial Key Lab on Damage Diagnosis for engineering Structures Hunan University Department of Mechanical engineering University of Maryland College of Civil engineering Hunan University

A dynamic model for an inclined carbon ?ber reinforced polymer(CFRP)cable is established, and the linear and nonlinear dynamic behaviors are investigated in detail. The partial differential equations for both the in-plane and out-of-plane dynamics of the inclined CFRP cable are obtained by Hamilton's principle. The linear eigenvalues are explored theoretically. Then, the ordinary differential equations for analyzing the dynamic behaviors are obtained by the Galerkin integral and dimensionless *** steady-state solutions of the nonlinear equations are obtained by the multiple scale method(MSM) and the Newton-Raphson method. The frequency-and force-response curves are used to investigate the dynamic behaviors of the inclined CFRP cable under simultaneous internal(between the lowest in-plane and out-of-plane modes) and external resonances, i.e., the primary resonances induced by the excitations of the in-plane mode,the out-of-plane mode, and both the in-plane mode and the out-of-plane mode, respectively. The effects of the key parameters, e.g., Young's modulus, the excitation amplitude,and the frequency on the dynamic behaviors, are discussed in detail. Some interesting phenomena and results are observed and concluded.

关键词： inclined carbon fiber reinforced polymer(CFRP)cable bifurcation nonlinear dynamics internal resonance external resonance

Convective heat transfer of nanofluids with correlations

在线全文

学校读者我要写书评

暂无评论

Particuology 2011年第6期9卷 626-631页

作者： Lazarus Godson Asirvatham Balakrishnan Raja Dhasan Mohan Lal Somchai Wongwises R&AC Division Department of Mechanical Engineering College of Engineering Guindy Anna University Indian institute of Information Technology Design and Manufacturing (IIITD&M)-Kancheepuram Fluid Mechanics Thermal Engineering and Multiphase Flow Research Lab (FUTURE) Department of Mechanical Engineering King Mongkut's University of Technology Thonburi The Academy of Science The Royal Institute of Thailand

To investigate the convective heat transfer of nanofluids, experiments were performed using silver-water nanofluids under laminar, transition and turbulent flow regimes in a horizontal 4.3 mm inner-diameter tube-in-tube counter-current heat transfer test section. The volume concentration of the nanoparticles varied from 0.3% to 0.9% in steps of 0.3%, and the effects of thermo-physical properties, inlet temperature, volume concentration, and mass flow rate on heat transfer coefficient were investigated. Experiments showed that the suspended nanoparticles remarkably increased the convective heat transfer coefficient, by as much as 28.7% and 69.3% for 0.3% and 0.9% of silver content, respectively. Based on the experimental results a correlation was developed to predict the Nusselt number of the silver-water nanofluid, with ＋10% agreement between experiments and prediction.

关键词： Convective heat transfer Silver Nanofluid Correlation Laminar Turbulent Transition

Synthesis,Structure,and Magnetic Property of One Novel Entangled Cobalt~Ⅱ-organic Compound

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Structural Chemistry 2011年第7期30卷 995-1000页

作者：张梁栋范黎明刘光增魏培海李斌张修堂 Advanced Material institute of Research Department of ChemistryQilu Normal University College of Chemistry and Chemical engineering Jinan University College of Chemistry and Chemical engineering Liaocheng University

One novel entangled cobalt compound, {[Co3（nbta）2（4,4＇-bpy）2（H2O）2]（H2O）2}n （1, H3nbta = 5-nitro-1,2,3-benzenetricarboxylic acid, 4,4＇-bpy = 4,4＇-bipyridyl）, was prepared and characterized by X-my diffraction, magnetism, elemental analysis, XPS, TGA and IR spectroscopy. The crystal of 1 crystallizes in monoclinic, space group Pc with a = 13.0717（16）, b = 11.4167（14）, c = 15.9342（19） A, β = 90.5190（10）°, V= 2377.9（5） A3, Z= 2, C48H36Co3N8O20, Mr = 1221.64, Dc = 1.706 g/cm3, F（000） = 1242 and μ（MoKa） = 1.128 mm^-1. The final R = 0.0497 and wR = 0.1461 for 4185 observed reflections with I 〉 20（0 and R = 0.0721 and wR = 0.1619 for all data. X-ray diffraction analyses revealed that Co（l） is linked by the nbta3- ligands to form the ladder shape along the c axis, which is further extended into two-dimensional networks via the joint of Co（2） along the a axis. Moreover, these two dimensional motifs are interconnected by the 4,4＇-bpy bridges to form a complicated 3-D polymeric framework. Magnetic measurements revealed that compound 1 shows strong antiferromagnetic property.

关键词： 5-nitro-1,2,3-benzenetricarboxylic acid 4,4-bipyridyl cobalt(Ⅱ) XPS antiferromagnetic

Efficient Nanosecond Dual-Signal Optical Parametric Generator with a Periodically Phase Reversed PPMgLN

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2007年第11期24卷 3157-3159页

作者：纪峰李喜福张百钢张铁犁徐德刚姚建铨 College of Precision Instrument and Opto-Electronics engineering Institute of Laser and Optoelectronics Tianjin University Tianjin 300072 School of Electrical engineering and Automation Tianjin University Tianjin 300072

We report an efficient nanosecond optical parametric generator （OPG） with a periodically-phase-reversed periodically poled MgO：LINbO3 （ppr-PPMgLN）, which produces two pairs of signal and idler waves. The OPG is pumped by a 1.064μm Q-switched Nd：YVO4 laser. When the repetition rate is set at 10kHz, the maximum average total output power of 570mW is achieved, including 410mW of dual-signal radiations and 160mW of dual-idler radiations. The total conversion efficiency is 32.5%. The tunable dual-signal wavelengths in the range of 1.474-1.518μm and 1.490-1.539μm and the dual-idler of 3.826-3.558 μm and 3. 726-3.451 μm are obtained by changing the crystal temperature from 30℃ to 200℃.

关键词： coated conductor buffer layer self-epitaxy CeO2