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无氢渗碳 2

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MOF基催化剂 1

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Static and dynamic analysis of functionally graded fluid-infiltrated porous skew and elliptical nanoplates using an isogeometric approach

《结构与土木工程前沿（英文）》 2023年第17卷第3期页码 477-502 doi: 10.1007/s11709-023-0918-5

摘要： The analysis of static bending and free and forced vibration responses of functionally graded fluid-infiltrated porous (FGFP) skew and elliptical nanoplates placed on Pasternak’s two-parameter elastic foundation is performed for the first time using isogeometric analysis (IGA) based on the non-uniform rational B-splines (NURBSs) basis function. Three types of porosity distributions affect the mechanical characteristics of materials: symmetric distribution, upper asymmetric distribution, and lower asymmetric distribution. The stress–strain relationship for Biot porous materials was determined using the elastic theory. The general equations of motion of the nanoplates were established using the four-unknown shear deformation plate theory in conjunction with the nonlocal elastic theory and Hamilton’s principle. A computer program that uses IGA to determine the static bending and free and forced vibration of a nanoplate was developed on MATLAB software platform. The accuracy of the computational program was validated via numerical comparison with confidence assertions. This set of programs presents the influence of the following parameters on the static bending and free and forced vibrations of nanoplates: porosity distribution law, porosity coefficient and geometrical parameters, elastic foundation, deviation angle, nonlocal coefficient, different boundary conditions, and Skempton coefficients. The numerical findings demonstrated the uniqueness of the FGFP plate’s behavior when the porosities are saturated with liquid compared with the case without liquid. The findings of this study have significant implications for engineers involved in the design and fabrication of the aforementioned type of structures. Furthermore, this can form the basis for future research on the mechanical responses of the structures.

关键词： static bending free and forced vibrations nonlocal theory isogeometric analysis fluid-infiltrated porous nanoplates

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Experimental and theoretical investigations of the lateral vibrations of an unbalanced Jeffcott rotor

Ali ALSALEH, Hamid M. SEDIGHI, Hassen M. OUAKAD

《结构与土木工程前沿（英文）》 2020年第14卷第4期页码 1024-1032 doi: 10.1007/s11709-020-0647-y

摘要： The current work experimentally explores and then theoretically examines the lateral vibrations of an unbalanced Jeffcott rotor-system working at several unbalance conditions. To this end, three conditions of eccentric masses are considered by using a Bently Nevada RK-4 rotor kit. Measurements of the steady-state as well as the startup data at rigid and flexible rotor states are captured by conducting a setup that mimics the vibration monitoring industrial practices. The linear governing equation of the considered rotor is extracted by adopting the Lagrange method on the basis of rigid rotor assumptions to theoretically predict the lateral vibrations. The dynamic features of the rotor system such as the linearized bearing induced stiffness are exclusively acquired from startup data. It is demonstrated that, with an error of less than 5%, the proposed two-degrees-of-freedom model can predict the flexural vibrations at rigid condition. While at flexible condition, it fails to accurately predict the dynamic response. In contrast to the other works where nonlinear mathematical models with some complexities are proposed to mathematically model the real systems, the present study illustrates the applicability of employing simple models to predict the dynamic response of a real rotor-system with an acceptable accuracy.

关键词： rotor-dynamics Jeffcott rotor lateral vibrations Lagrange method system-equivalent stiffness sleeve bearings oil film induced stiffness

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Torsional vibrations of a cylindrical foundation embedded in a saturated poroelastic half-space

Dazhi WU,Lu YU

《结构与土木工程前沿（英文）》 2015年第9卷第2期页码 194-202 doi: 10.1007/s11709-015-0292-z

摘要： Considering the interactions between an embedded foundation and saturated soil, the torsional vibrations of a cylindrical foundation embedded in a saturated poroelastic medium are analyzed in this paper. Both a rigid foundation and an elastic foundation are considered. Assuming both the side surface and the bottom surface of the foundation are perfectly bonded to soil, the reaction torques that the side soil and bottom soil acting on the foundation can be gained from basic dynamic equations of the poroelastic medium. According to the dynamic equilibrium equations of a foundation under harmonic torque, the torsional vibrations of an embedded cylindrical foundation are presented. Besides, the angular amplitude of the foundation, the equivalent stiffness and damping coefficients of the soil are expressed explicitly. Selected examples are presented to investigate the influence of relevant parameters on the torsional vibrations.

关键词： embedded foundation saturated soil rigid foundation elastic foundation torsional vibration

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Multi-harmonic forced vibration and resonance of simple beams to moving vehicles

《结构与土木工程前沿（英文）》页码 981-993 doi: 10.1007/s11709-023-0979-5

摘要： This study modeled the moving-vehicle-induced forcing excitation on a single-span prismatic bridge as a multiple frequency-multiplication harmonic load on the modal coordinates of a linear elastic simple Euler–Bernoulli beam, and investigated the forced modal oscillation and resonance behavior of this type of dynamic system. The forced modal responses consist of multiple frequency-multiplication steady-state harmonics and one damped mono-frequency complementary harmonic. The analysis revealed that a moving load induces high-harmonic forced resonance amplification when the moving speed is low. To verify the occurrence of high-harmonic forced resonance, numerical tests were conducted on single-span simple beams based on structural modeling using the finite element method (FEM) and a moving sprung-mass oscillator vehicle model. The forced resonance amplification characteristics of the fundamental mode for beam response estimation are presented with consideration to different end restraint conditions. The results reveal that the high-harmonic forced resonance may be significant for the investigated beams subjected to vehicle loads moving at specific low speeds. For the investigated single-span simple beams, the moving vehicle carriage heaving oscillation modulates the beam modal frequency, but does not induce notable variation of the modal oscillation harmonic structure for the cases that vehicle of small mass moves in low speed.

关键词： forced vibration linear Euler beam moving load harmonic structure frequency modulation end restraints

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Environmental problems of vibrations induced by railway traffic

XIA He, CAO Yanmei, De Roeck Guido, Degrande Geert

《结构与土木工程前沿（英文）》 2007年第1卷第2期页码 142-152 doi: 10.1007/s11709-007-0015-1

摘要： In this paper, a general review is made on the problems of vibrations of the ground and nearby buildings induced by railway traffic, and on the researches on this subject in theoretical analyses, numerical simulations, and field experiments. The characteristics of ground vibrations induced by railway traffic and their propagation, from the aspects of duration, intensity distribution, vehicle load and speed, are summarized. The vibration influences on the daily life of people, the operation of high-tech devices and the safety of buildings, and the vibration properties of subsoil and buildings adjacent to the underground, ground and elevated railway systems are introduced.

关键词： underground vibration numerical subsoil propagation

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Study on forced air convection cooling for electronic assemblies

LI Bin, TAO Wenquan, HE Yaling

《能源前沿（英文）》 2008年第2卷第2期页码 158-163 doi: 10.1007/s11708-008-0009-2

摘要： The slotted fin concept was employed to improve the air cooling performance of plate-fin in heat sinks. Numerical simulations of laminar heat transfer and flow pressure drop were conducted for the integral plate fin, discrete plate fin and discrete slotted fin heat sinks. It is found that the performance of the discrete plate fin is better than that of the integral continuum plate fin and the performance of slotted fin is better than that of the discrete plate fin at the same pumping power of the fan. A new type of heat sink characterized by discrete and slotted fin surfaces with thinner fins and smaller spaces between fins is then proposed. Preliminary computation shows that this type of heat sink may be useful for the next generation of higher thermal load CPUs. The limit of cooling capacity for air-cooling techniques was also addressed.

关键词： concept slotted air-cooling Preliminary computation generation

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Thermally developing forced convection and the corresponding thermal stresses in a porous plate channel

YANG Xiao, LIU Xuemei

《机械工程前沿（英文）》 2007年第2卷第1期页码 57-61 doi: 10.1007/s11465-007-0009-7

摘要： Based on the Darcy fluid model, by considering the effects of viscous dissipation due to the interaction between solid skeleton and pore fluid flow and thermal conduction in the direction of the fluid flow, the thermally developing forced convection of the local thermal equilibrium and the corresponding thermal stresses in a semi-infinite saturated porous plate channel are investigated in this paper. The expressions of temperature, local Nusselt number and corresponding thermal stresses are obtained by means of the Fourier series, and the distributions of the same are also shown. Furthermore, influences of the P晱let number () and Brinkman number () on temperature, Nusselt number () and thermal stress are revealed numerically.

关键词： semi-infinite saturated direction interaction skeleton thermal equilibrium

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Soybean drying characteristics in microwave rotary dryer with forced convection

Ruifang WANG, Zhanyong LI, Yanhua LI, Jingsheng YE

《化学科学与工程前沿（英文）》 2009年第3卷第3期页码 289-292 doi: 10.1007/s11705-009-0022-y

摘要： A new hybrid drying technique by combining microwave and forced convection drying within a rotary drum, i.e., microwave rotary drying, was developed with the purpose to improve the uniformity of microwave drying. In a laboratory microwave rotary dryer, rewetted soybean was utilized as experimental material to study the effects of drum rotating speed, ventilation flow rate, and specific microwave power on the drying kinetics and cracking ratio of soybean. It was found that, with rotation, the cracking ratio can be lowered but without distinct improvement in the drying rate. Increasing ventilation flow rate and specific microwave power can improve the drying rate, but the cracking ratio also increases as a negative result. The cracking ratio lower than 10% can be attained for ventilation flow rate lower than 2.0 m ·h or specific microwave energy lower than 0.4 kW·kg in the present experiments.

关键词： cracking microwave rotary drying soybean

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An invariant descriptor for conjugate forced convection-conduction cooling of 3D protruding heaters in

Thiago ANTONINI ALVES,Paulo H. D. SANTOS,Murilo A. BARBUR

《机械工程前沿（英文）》 2015年第10卷第3期页码 263-276 doi: 10.1007/s11465-015-0345-y

摘要：

In this research, the temperatures of three-dimensional (3D) protruding heaters mounted on a conductive substrate in a horizontal rectangular channel with laminar airflow are related to the independent power dissipation in each heater by using a matrix G⁺ with invariant coefficients, which are dimensionless. These coefficients are defined in this study as the conjugate influence coefficients (g⁺) caused by the forced convection-conduction nature of the heaters’ cooling process. The temperature increase of each heater in the channel is quantified to clearly identify the contributions attributed to the self-heating and power dissipation in the other heaters (both upstream and downstream). The conjugate coefficients are invariant with the heat generation rate in the array of heaters when assuming a defined geometry, invariable fluid and flow rate, and constant substrate and heater conductivities. The results are numerically obtained by considering three 3D protruding heaters on a two-dimensional (2D) array by ANSYS/Fluent^TM 15.0 software. The conservation equations are solved by a coupled procedure within a single calculation domain comprising of solid and fluid regions and by considering a steady state laminar airflow with constant properties. Some examples are shown, indicating the effects of substrate thermal conductivity and Reynolds number on conjugate influence coefficients.

关键词： channel flow conjugate forced convection-conduction cooling conjugate influence coefficients discrete heating invariant descriptor thermal management

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Running train induced vibrations and noises of elevated railway structures and their influences on environment

He XIA, Fei GAO, Xuan WU, Nan ZHANG, Guido DE ROECK, Geert DEGRANDE

《结构与土木工程前沿（英文）》 2009年第3卷第1期页码 9-17 doi: 10.1007/s11709-009-0010-9

摘要： The vibrations and noises of elevated railway structures have been cause for concern due to their effects on the environment and the people living near elevated lines. In this paper, the main structural features of some new elevated bridges and station hall were introduced. The generation mechanism of vibrations and noise of elevated structures induced by trains were investigated. The noise induced by different types of elevated bridges, their influences on the environment and the theoretical method for the analysis of structure borne noise was analyzed. Finally, several field measurements on train induced noises at the platforms of elevated subway stations and bridges were presented.

关键词： railway elevated structure bridge station vibration noise environment

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efficiency optimization and Sobol’s sensitivity indices of MTMDs design parameters for buffeting and flutter vibrations

Nazim Abdul NARIMAN

《结构与土木工程前沿（英文）》 2017年第11卷第1期页码 66-89 doi: 10.1007/s11709-016-0356-8

摘要： This paper studies optimization of three design parameters (mass ratio, frequency ratio and damping ratio) of multiple tuned mass dampers MTMDs that are applied in a cable stayed bridge excited by a strong wind using minimax optimization technique. ABAQUS finite element program is utilized to run numerical simulations with the support of MATLAB codes and Fast Fourier Transform FFT technique. The optimum values of these three parameters are validated with two benchmarks from the literature, first with Wang and coauthors and then with Lin and coauthors. The validation procedure detected a good agreement between the results. Box-Behnken experimental method is dedicated to formulate the surrogate models to represent the control efficiency of the vertical and torsional vibrations. Sobol’s sensitivity indices are calculated for the design parameters in addition to their interaction orders. The optimization results revealed better performance of the MTMDs in controlling the vertical and the torsional vibrations for higher mode shapes. Furthermore, the calculated rational effects of each design parameter facilitate to increase the control efficiency of the MTMDs in conjunction with the support of the surrogate models.

关键词： MTMDs power spectral density fast Fourier transform minimax optimization technique Sobol’s sensitivity indices Box-Behnken method

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Aerodynamic interference effects and mitigation measures on vortex-induced vibrations of two adjacent

Xiaoliang MENG, Ledong ZHU, Zhenshan GUO

《结构与土木工程前沿（英文）》 2011年第5卷第4期页码 510-517 doi: 10.1007/s11709-011-0129-3

摘要： By examining the two neighboring Haihe Bridges with semi- and full-closed bridge decks, the aerodynamic interference between the two decks on the vortex-induced vibration (VIV) and the corresponding aerodynamic mitigation measures are investigated via a series of wind tunnel tests with a spring-suspended sectional model aided with computational fluid dynamics (CFD) method. The results show that the VIV responses of both bridges can be significantly affected by the aerodynamic interference and that the extent of the influence varies with the shapes of the windward and leeward decks. The VIV amplitudes of the windward bridge are often fairly close to those of the single bridge. However, those of the leeward bridge are magnified substantially by aerodynamic interference if the same structural and aerodynamic configurations are adopted for the two bridges. Otherwise, the VIV responses are not significantly increased and may even be reduced by the aerodynamic interference if different configurations are employed for the two bridges. Furthermore, an effective combined measure of adding wind barriers and sharpening the wind fairing noses of the two box decks is presented for mitigating both the vertical and torsional VIV responses of the windward and leeward bridges.

关键词： separated parallel decks vortex-induced vibration aerodynamic interference aerodynamic mitigation measure semi-closed box deck full-closed box deck

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Vehicle-bridge coupled vibrations in different types of cable stayed bridges

Lingbo WANG,Peiwen JIANG,Zhentao HUI,Yinping MA,Kai LIU,Xin KANG

《结构与土木工程前沿（英文）》 2016年第10卷第1期页码 81-92 doi: 10.1007/s11709-015-0306-x

摘要： Numerical analyses of the coupled vibrations of vehicle-bridge system and the effects of different types of cable stayed bridges on the coupled vibration responses have been presented in this paper using ANSYS. The bridge model and vehicle model were independently built which have no internal relationship in the ANSYS. The vehicle-bridge coupled vibration relationship was obtained by using the APDL program which subsequently imposed on the vehicle and bridge models during the numerical analysis. The proposed model was validated through a field measurements and literature data. The judging method, possibility, and criterion of the vehicle-bridge resonance (coupled vibrations) of cable stayed bridges (both the floating system and half floating system) under traffic flows were presented. The results indicated that the interval time between vehicles is the main influence factor on the resonance excitation frequency under the condition of equally spaced traffic flows. Compared to other types of cable stayed bridges, the floating bridge system has relatively high possibility to cause vehicle-bridge resonance.

关键词： vehicle-bridge coupled vibration cable stayed bridge resonances of vehicle-bridge system

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地铁火灾中强制通风烟控系统作用的模拟

蔡波,李辉亮,廖光煊

《中国工程科学》 2005年第7卷第8期页码 80-83

摘要：

地铁火灾比地面火灾具有更大的危险性。通过对地铁火灾的模拟可以重现火灾过程，研究火灾现象，分析火灾原因。通过FDS模拟，对比大邱市地铁火灾在有无强制通风烟控系统条件下，火灾现场的温度场和烟尘分布，研究讨论其对控制地铁火灾的重要作用。

关键词：地铁火灾 FDS数值模拟强制通风烟控系统

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移动荷载作用下三塔悬索桥的强迫振动研究

冯兆祥,陈亮,缪长青

《中国工程科学》 2012年第14卷第5期页码 80-84

摘要：

针对泰州大桥开展结构动力特性计算，分析了不同移动速度以及不同移动荷载大小对于三塔两跨悬索桥结构动力响应的影响。结果表明，三塔两跨悬索桥的一阶竖弯振动基频约为0.08 Hz,远低于载重汽车的固有频率，不会形成共振条件。简单的移动荷载作用下三塔两跨连续支承悬索桥的内力、位移响应与同等静力荷载作用效果比较接近。移动荷载的质量越大、速度越大，结构的内力、位移响应就越大，并与车重呈近似正比例关系。结构内力、位移的荷载放大系数不随移动荷载质量的大小而改变。

关键词：动力特性强迫振动响应荷载放大系数