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Free vibration analysis of laminated FG-CNT reinforced composite beams using finite element method

T. VO-DUY, V. HO-HUU, T. NGUYEN-THOI

《结构与土木工程前沿（英文）》 2019年 第13卷 第2期   页码 324-336 doi: 10.1007/s11709-018-0466-6

摘要： In the present study, the free vibration of laminated functionally graded carbon nanotube reinforced composite beams is analyzed. The laminated beam is made of perfectly bonded carbon nanotubes reinforced composite (CNTRC) layers. In each layer, single-walled carbon nanotubes are assumed to be uniformly distributed (UD) or functionally graded (FG) distributed along the thickness direction. Effective material properties of the two-phase composites, a mixture of carbon nanotubes (CNTs) and an isotropic polymer, are calculated using the extended rule of mixture. The first-order shear deformation theory is used to formulate a governing equation for predicting free vibration of laminated functionally graded carbon nanotubes reinforced composite (FG-CNTRC) beams. The governing equation is solved by the finite element method with various boundary conditions. Several numerical tests are performed to investigate the influence of the CNTs volume fractions, CNTs distributions, CNTs orientation angles, boundary conditions, length-to-thickness ratios and the numbers of layers on the frequencies of the laminated FG-CNTRC beams. Moreover, a laminated composite beam combined by various distribution types of CNTs is also studied.

关键词： free vibration analysis     laminated FG-CNTRC beam     finite element method     first-order shear deformation theory     composite material    

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Modified landfill gas generation rate model of first-order kinetics and two-stage reaction

Jiajun CHEN , Hao WANG , Na ZHANG ,

《环境科学与工程前沿（英文）》 2009年 第3卷 第3期   页码 313-319 doi: 10.1007/s11783-009-0025-4

摘要： This investigation was carried out to establish a new domestic landfill gas (LFG) generation rate model that takes into account the impact of leachate recirculation. The first-order kinetics and two-stage reaction (FKTSR) model of the LFG generation rate includes mechanisms of the nutrient balance for biochemical reaction in two main stages. In this study, the FKTSR model was modified by the introduction of the outflow function and the organic acid conversion coefficient in order to represent the in-situ condition of nutrient loss through leachate. Laboratory experiments were carried out to simulate the impact of leachate recirculation and verify the modified FKTSR model. The model calibration was then calculated by using the experimental data. The results suggested that the new model was in line with the experimental data. The main parameters of the modified FKTSR model, including the LFG production potential (), the reaction rate constant in the first stage (), and the reaction rate constant in the second stage () of 64.746 L, 0.202 d, and 0.338 d, respectively, were comparable to the old ones of 42.069 L, 0.231 d, and 0.231 d. The new model is better able to explain the mechanisms involved in LFG generation.

关键词： landfill gas (LFG)     generation rate model     first-order kinetics     two-stage reaction     outflow function    

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Dynamic analysis of composite beam subjected to harmonic moving load based on the third-order shear deformationtheory

Mohammad Javad REZVANIL, Mohammad Hossein KARGARNOVIN, Davood YOUNESIAN

《机械工程前沿（英文）》 2011年 第6卷 第4期   页码 409-418 doi: 10.1007/s11465-011-0245-8

摘要：

The response of an infinite Timoshenko beam subjected to a harmonic moving load based on the third-order shear deformation theory (TSDT) is studied. The beam is made of laminated composite, and located on a Pasternak viscoelastic foundation. By using the principle of total minimum potential energy, the governing partial differential equations of motion are obtained. The solution is directed to compute the deflection and bending moment distribution along the length of the beam. Also, the effects of two types of composite materials, stiffness and shear layer viscosity coefficients of foundation, velocity and frequency of the moving load over the beam response are studied. In order to demonstrate the accuracy of the present method, the results TSDT are compared with the previously obtained results based on first-order shear deformation theory, with which good agreements are observed.

关键词： timoshenko composite beam     pasternak viscoelastic foundation     third-order shear deformation theory (TSDT)     harmonic moving load    

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Flow behavior of liquid-solid coupled system of piezoelectric micropump

LU Lijun, WU Jiankang

《机械工程前沿（英文）》 2008年 第3卷 第1期   页码 50-54 doi: 10.1007/s11465-008-0003-8

摘要： This paper employs a shallow water model and the finite element method to approximate periodical flows of a micropump to a two-dimensional thickness-averaged flow. A liquid-solid coupled system equation of the micropump is presented. Through the mode analysis of the liquid-solid coupled system, the first-order natural frequency, diaphragm vibration shape and amplitude-frequency relationship are obtained. The vibration response of the diaphragm is calculated when an external electric field is applied. Based on the thickness-averaged flow equation, the periodical flow of the micropump is studied using the finite volume method to investigate the flow behavior and flow rate-frequency characteristics. Numerical results indicate that an optimal working frequency can be obtained, at which the flow rate of the micropump achieves the maximum when the external electric voltage is fixed.

关键词： amplitude-frequency relationship     first-order     micropump     diaphragm vibration     electric    

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Simultaneous removal of trihalomethanes by bimetallic Ag/Zn: kinetics study

Ahmed H A DABWAN, Satoshi KANECO, Hideyuki KATSUMATA, Kiyoyuki EGUSA, Tohru SUZUKI, Kiyohisa OHTA,

《化学科学与工程前沿（英文）》 2010年 第4卷 第3期   页码 322-327 doi: 10.1007/s11705-009-0261-y

摘要： In the present work, bimetallic silver/zinc was applied into the degradation of trihalomethanes, THMs: CHCl, CHBrCl, CHBrCl, and CHBr. The kinetics reaction rates and removal efficiencies of the THM compound mixtures, in the aqueous solutions, were investigated. Batch experiments were conducted under mild conditions, ambient temperature, and pressure. The primary degradation reaction followed a pseudo-first-order kinetic law. The first-order rate constants and the degradation efficiencies followed the decreasing order of CHBr>CHBrCl>CHBrCl>CHCl. The bond dissociation energy and hydrophilic/hydrophobic characteristics of the THM compounds may become the most important parameters affecting the degradation kinetics and efficiency by bimetallic Ag/Zn.

关键词： reaction     first-order     dissociation     degradation reaction     aqueous    

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Comparison between linear and non-linear forms of pseudo-first-order and pseudo-second-order adsorption

Junxiong LIN , Lan WANG ,

《环境科学与工程前沿（英文）》 2009年 第3卷 第3期   页码 320-324 doi: 10.1007/s11783-009-0030-7

摘要： The best-fit equations of linear and non-linear forms of the two widely used kinetic models, namely pseudo-first-order and pseudo-second-order equations, were compared in this study. The experimental kinetics of methylene blue adsorption on activated carbon was used for this research. Both the correlation coefficient () and the normalized standard deviation Δ(%) were employed as error analysis methods to determine the best-fitting equations. The results show that the non-linear forms of pseudo-first-order and pseudo-second-order models were more suitable than the linear forms for fitting the experimental data. The experimental kinetics may have been distorted by linearization of the linear kinetic equations, and thus, the non-linear forms of kinetic equations should be primarily used to obtain the adsorption parameters. In addition, the Δ(%) method for error analysis may be better to determine the best-fitting model in this case.

关键词： adsorption     pseudo-first order     pseudo-second order     kinetic model     linear method     non-linear method    

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solid-state thermoelectric energy conversion via inorganic metal halide perovskites under tailored mechanical deformation

Lifu YAN, Lingling ZHAO, Guiting YANG, Shichao LIU, Yang LIU, Shangchao LIN

《能源前沿（英文）》 2022年 第16卷 第4期   页码 581-594 doi: 10.1007/s11708-022-0831-y

摘要： Solid-state thermoelectric energy conversion devices attract broad research interests because of their great promises in waste heat recycling, space power generation, deep water power generation, and temperature control, but the search for essential thermoelectric materials with high performance still remains a great challenge. As an emerging low cost, solution-processed thermoelectric material, inorganic metal halide perovskites CsPb(I1–xBrx)3 under mechanical deformation is systematically investigated using the first-principle calculations and the Boltzmann transport theory. It is demonstrated that halogen mixing and mechanical deformation are efficient methods to tailor electronic structures and charge transport properties in CsPb(I1–xBrx)3 synergistically. Halogen mixing leads to band splitting and anisotropic charge transport due to symmetry-breaking-induced intrinsic strains. Such band splitting reconstructs the band edge and can decrease the charge carrier effective mass, leading to excellent charge transport properties. Mechanical deformation can further push the orbital energies apart from each other in a more controllable manner, surpassing the impact from intrinsic strains. Both anisotropic charge transport properties andZT values are sensitive to the direction and magnitude of strain, showing a wide range of variation from 20% to 400% (with a ZT value of up to 1.85) compared with unstrained cases. The power generation efficiency of the thermoelectric device can reach as high as approximately 12% using mixed halide perovskites under tailored mechanical deformation when the heat-source is at 500 K and the cold side is maintained at 300 K, surpassing the performance of many existing bulk thermoelectric materials.

关键词： inorganic metal halide perovskites     mechanical deformation     thermoelectrics     first-principle calculations     Boltzmann transport theory    

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具有区域约束的一阶多智能体系统的有限时间编队控制 Research Articles

杨正全1,潘小芳1,张青1,陈增强2

《信息与电子工程前沿（英文）》 2021年 第22卷 第1期   页码 1-140 doi: 10.1631/FITEE.2000177

摘要： 研究具有区域约束的多智能体系统的有限时间编队控制问题。多智能体具有一阶动力学和一个共同目标区域。提出一种利用局部信息和交互作用的控制算法。如果通信图是无向连通的以及所设计框架是刚性的，证明该控制器可用于解决具有目标区域的编队问题。该控制算法可控制所有智能体在有限时间内进入所需区域，同时达到并保持所需队形。最后，给出一个数值例子说明算法的有效性。

关键词： 有限时间编队；多智能体系统；渐进收敛；约束集；李雅普诺夫定理    

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Electrocoagulation process for the treatment of metal-plating wastewater: Kinetic modeling and energy consumption

Fatih Ilhan, Kubra Ulucan-Altuntas, Yasar Avsar, Ugur Kurt, Arslan Saral

《环境科学与工程前沿（英文）》 2019年 第13卷 第5期 doi: 10.1007/s11783-019-1152-1

摘要： The wastewater from industrial area was treated by EC via Fe and Al electrodes. Cu, Ni, Cr and Zn were highly removed at the first minutes, simultaneously. Pseudo-2nd-order was found to be more suitable for kinetics. Adsorption capacities based on kinetic modeling were observed as Cr>Cu>Ni>Zn. The chemical cost in the case of pH adjustment after EC was less as 3.83 $/m3. It is known that wastewater produced by the metal-plating industry contains several heavy metals, which are acidic in nature and therefore toxic for the environment and for living creatures. In particular, heavy metals enter the food chain and accumulate in vital organs and cause serious illness. The precipitation of these metals is mostly achieved by pH adjustment, but as an alternative to this method, the electrocoagulation process has investigated in this study using iron and aluminum electrodes. The effects of the pH adjustment on removal before and after the electrocoagulation process were investigated, and cost analyses were also compared. It was observed that a high proportion of removal was obtained during the first minutes of the electrocoagulation process; thus, the current density did not have a great effect. In addition, the pH adjustment after the electrocoagulation process using iron electrodes, which are 10% more effective than aluminum electrodes, was found to be much more efficient than before the electrocoagulation process. In the process where kinetic modeling was applied, it was observed that the heavy metal removal mechanism was not solely due to the collapse of heavy metals at high pH values, and with this modeling, it was seen that this mechanism involved adsorption by iron and aluminum hydroxides formed during the electrocoagulation process. When comparing the ability of heavy metals to be adsorbed, the sequence was observed to be Cr>Cu>Ni>Zn, respectively.

关键词： Electrochemical treatment     Heavy metals     Kinetic modeling     Pseudo first order kinetic     Pseudo second order kinetic    

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Shallow foundation response variability due to soil and model parameter uncertainty

Prishati RAYCHOWDHURY,Sumit JINDAL

《结构与土木工程前沿（英文）》 2014年 第8卷 第3期   页码 237-251 doi: 10.1007/s11709-014-0242-1

摘要： Geotechnical uncertainties may play crucial role in response prediction of a structure with substantial soil-foundation-structure-interaction (SFSI) effects. Since the behavior of a soil-foundation system may significantly alter the response of the structure supported by it, and consequently several design decisions, it is extremely important to identify and characterize the relevant parameters. Moreover, the modeling approach and the parameters required for the modeling are also critically important for the response prediction. The present work intends to investigate the effect of soil and model parameter uncertainty on the response of shallow foundation-structure systems resting on dry dense sand. The SFSI is modeled using a beam-on-nonlinear-winkler-foundation (BNWF) concept, where soil beneath the foundation is assumed to be an assembly of discrete, nonlinear elements composed of springs, dashpots and gap elements. The sensitivity of both soil and model input parameters on shallow foundation responses are investigated using first-order second-moment (FOSM) analysis and Monte Carlo simulation through Latin hypercube sampling technique. It has been observed that the degree of accuracy in predicting the responses of the shallow foundation is highly sensitive soil parameters, such as friction angle, Poisson’s ratio and shear modulus, rather than model parameters, such as stiffness intensity ratio and spring spacing; indicating the importance of proper characterization of soil parameters for reliable soil-foundation response analysis.

关键词： shallow foun dation     sensitivity analysis     centrifuge data     first-order-second-moment (FOSM) method     parameter uncertainty    

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Mechanism of methanol decomposition on the Pd/WC(0001) surface unveiled by first-principles calculations

Jinhua Zhang, Yuanbin She

《化学科学与工程前沿（英文）》 2020年 第14卷 第6期   页码 1052-1064 doi: 10.1007/s11705-019-1908-y

摘要： In this study, the decomposition of methanol into the CO and H species on the Pd/tungsten carbide (WC)(0001) surface is systematically investigated using periodic density functional theory (DFT) calculations. The possible reaction pathways and intermediates are determined. The results reveal that saturated molecules, i.e., methanol and formaldehyde, adsorb weakly on the Pd/WC(0001) surface. Both CO and H prefer three-fold sites, with adsorption energies of ‒1.51 and ‒2.67 eV, respectively. On the other hand, CH O stably binds at three-fold and bridge sites, with an adsorption energy of ‒2.58 eV. However, most of the other intermediates tend to adsorb to the surface with the carbon and oxygen atoms in their sp and hydroxyl-like configurations, respectively. Hence, the C atom of CH OH preferentially attaches to the top sites, CHOH and CH O adsorb at the bridge sites, while COH and CHO occupy the three-fold sites. The DFT calculations indicate that the rupture of the initial C–H bond promotes the decomposition of CH OH and CH OH, whereas in the case of CHOH, O–H bond scission is favored over the C–H bond rupture. Thus, the most probable methanol decomposition pathway on the Pd/WC(0001) surface is CH OH → CH OH → -CHOH → CHO → CO. The present study demonstrates that the synergistic effect of WC (as carrier) and Pd (as catalyst) alters the CH OH decomposition pathway and reduces the noble metal utilization.

关键词： density functional theory     methanol     direct methanol fuel cells     WC(0001)-supported Pd monolayer     decomposition mechanism    

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thin-walled box continuous girder with variable cross-sections in considering effect of large deflection and shear

Yuji CHEN, Qizhi LUO,

《结构与土木工程前沿（英文）》 2009年 第3卷 第4期   页码 352-356 doi: 10.1007/s11709-009-0057-7

摘要： In order to study the mechanics behavior of a thin-walled box continuous girder with variable cross-sections, using potential variation theories, considering the effect of shear lag of flange’s stress and the nonlinear geometry of vertical displacement, and evolving five generalized displacements with the spline function, the large deflection problem of the thin-walled box continuous girder with variable cross-section was transformed to a nonlinear algebraic equation, which was solved using the Newton-Raphon iterative method. The results of the calculation show that different shear lag warp functions to the cantilever, top and bottom plate should be taken to analyze the mechanics behavior of the thin-walled box continuous girder reliably. The thin-walled box continuous girder with variable cross-sections has more reasonable stress state and is more adaptable for the longitudinal change of internal forces than that with equal cross-sections. The effect of large deflection on the stress and displacement of the thin-walled box continuous girder with variable cross-sections depends on the values of the load.

关键词： thin-walled box girder with variable cross-sections     potential variational theory     shear lag     large deflection problem    

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Boundary conditions for axisymmetric piezoelectric cylinder

Baosheng ZHAO, Di WU, Xi CHEN

《机械工程前沿（英文）》 2013年 第8卷 第4期   页码 401-408 doi: 10.1007/s11465-013-0272-8

摘要：

For axisymmetric piezoelectric cylinder, the reciprocal theorem and the axisymmetric general solution of piezoelasticity are applied in a novel way to obtain the appropriate stress and mixed boundary conditions accurate to all orders for the cylinder of general edge geometry and loadings. A decay analysis technique developed by Gregory and Wan is converted into necessary conditions on the end-data of axisymmetric piezoelectric circular cylinder, and the rapidly decaying solution is established. The prescribed end-data of the circle cylinder must satisfy these conditions in order that they could generate a decaying state within the cylinder. When stress and mixed conditions are imposed on the end of cylinder, these decaying state conditions for the case of axisymmetric deformation of piezoelectric cylinder are derived explicitly. They are then used for the correct formulation of boundary conditions for the theory solution (or the interior solution) of axisymmetric piezoelectric cylinder. The results of the present paper enable us to establish a set of correct boundary conditions, most of which are obtained for the first time.

关键词： solid and structures     the axisymmetric deformation     the piezoelectric circular cylinder     the refined theory     Bessel’s Function    

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基于熵模型的大型建筑企业组织结构研究

王兴,詹伟,王国庆

《中国工程科学》 2014年 第16卷 第10期   页码 84-88

摘要：

分析了组织结构对企业管理的重要意义以及组织结构设计与信息传递的关系，基于国内外大型建筑企业组织结构的对比，发现国内外大型建筑企业组织结构的共性与差异。提出运用信息熵模型从时效和质量两个方面评价组织结构的有序度，为考查组织信息传递有效性提供了定量方法，据此对日本鹿岛建设集团和中国铁建股份有限公司进行了评价。

关键词： 组织结构     大型建筑企业     信息熵     有序度    

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Effect of metal ion-doping on characteristics and photocatalytic activity of TiO

Rongfang YUAN,Beihai ZHOU,Duo HUA,Chunhong SHI

《环境科学与工程前沿（英文）》 2015年 第9卷 第5期   页码 850-860 doi: 10.1007/s11783-014-0737-y

摘要： The effect of ion-doping on TiO nanotubes were investigated to obtain the optimal TiO nanotubes for the effective decomposition of humic acids (HA) through O /UV/ion-doped TiO process. The experimental results show that changing the calcination temperature, which changed the weight fractions of the anatase phase, the average crystallite sizes, the Brunauer-Emmett-Teller surface area, and the energy band gap of the catalyst, affected the photocatalytic activity of the catalyst. The ionic radius, valence state, and configuration of the dopant also affected the photocatalytic activity. The photocatalytic activities of the catalysts on HA removal increased when Ag , Al , Cu , Fe , V , and Zn were doped into the TiO nanotubes, whereas such activities decreased as a result of Mn - and Ni -doping. In the presence of 1.0 at.% Fe -doped TiO nanotubes calcined at 550°C, the removal efficiency of HA was 80% with a pseudo-first-order rate constant of 0.158 min . Fe in TiO could increase the generation of ·OH, which could remove HA. However, Fe in water cannot function as a shallow trapping site for electrons or holes.

关键词： TiO2 nanotubes     ion-doping     humic acids     pseudo-first-order     mechanism    

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标题 作者 时间 类型 操作

Free vibration analysis of laminated FG-CNT reinforced composite beams using finite element method

T. VO-DUY, V. HO-HUU, T. NGUYEN-THOI

期刊论文

Modified landfill gas generation rate model of first-order kinetics and two-stage reaction

Jiajun CHEN , Hao WANG , Na ZHANG ,

期刊论文

Dynamic analysis of composite beam subjected to harmonic moving load based on the third-order shear deformationtheory

Mohammad Javad REZVANIL, Mohammad Hossein KARGARNOVIN, Davood YOUNESIAN

期刊论文

Flow behavior of liquid-solid coupled system of piezoelectric micropump

LU Lijun, WU Jiankang

期刊论文

Simultaneous removal of trihalomethanes by bimetallic Ag/Zn: kinetics study

Ahmed H A DABWAN, Satoshi KANECO, Hideyuki KATSUMATA, Kiyoyuki EGUSA, Tohru SUZUKI, Kiyohisa OHTA,

期刊论文

Comparison between linear and non-linear forms of pseudo-first-order and pseudo-second-order adsorption

Junxiong LIN , Lan WANG ,

期刊论文

solid-state thermoelectric energy conversion via inorganic metal halide perovskites under tailored mechanical deformation

Lifu YAN, Lingling ZHAO, Guiting YANG, Shichao LIU, Yang LIU, Shangchao LIN

期刊论文

具有区域约束的一阶多智能体系统的有限时间编队控制

杨正全1,潘小芳1,张青1,陈增强2

期刊论文

Electrocoagulation process for the treatment of metal-plating wastewater: Kinetic modeling and energy consumption

Fatih Ilhan, Kubra Ulucan-Altuntas, Yasar Avsar, Ugur Kurt, Arslan Saral

期刊论文

Shallow foundation response variability due to soil and model parameter uncertainty

Prishati RAYCHOWDHURY,Sumit JINDAL

期刊论文

Mechanism of methanol decomposition on the Pd/WC(0001) surface unveiled by first-principles calculations

Jinhua Zhang, Yuanbin She

期刊论文

thin-walled box continuous girder with variable cross-sections in considering effect of large deflection and shear

Yuji CHEN, Qizhi LUO,

期刊论文

Boundary conditions for axisymmetric piezoelectric cylinder

Baosheng ZHAO, Di WU, Xi CHEN

期刊论文

基于熵模型的大型建筑企业组织结构研究

王兴,詹伟,王国庆

期刊论文

Effect of metal ion-doping on characteristics and photocatalytic activity of TiO

Rongfang YUAN,Beihai ZHOU,Duo HUA,Chunhong SHI

期刊论文