资源类型

期刊论文 117

会议视频 2

年份

2023 13

2022 8

2021 11

2020 7

2019 6

2018 7

2017 9

2016 6

2015 2

2014 3

2013 3

2012 3

2011 9

2010 7

2009 6

2008 4

2007 2

2006 6

2004 1

2003 1

展开 ︾

关键词

原子层沉积 2

地震预测 2

汶川地震 2

湍流边界层 2

直接数值模拟 2

相干结构 2

(GaxIn1−x)2O3薄膜；带隙可调谐；磁控溅射 1

3D支架平台 1

4D打印 1

5G 1

n-Si 1

三维 1

下穿 1

临震信号 1

亚分级 1

信息中心网络；拥塞控制；跨层优化；多跳无线网络 1

先进制造 1

光伏/光电化学器件 1

光阳极 1

展开 ︾

检索范围：

排序： 展示方式：

Chemically reactive solute transfer in a boundary layer slip flow along a stretching cylinder

Swati Mukhopadhyay

《化学科学与工程前沿（英文）》 2011年 第5卷 第3期   页码 385-391 doi: 10.1007/s11705-011-1101-4

摘要： This paper presents the distribution of a solute undergoing a first order chemical reaction in an axisymmetric laminar boundary layer flow along a stretching cylinder. Velocity slip condition at the boundary is used instead of no-slip condition. Similarity transformations are used to convert the partial differential equations corresponding to momentum and concentration into highly nonlinear ordinary differential equations. Numerical solutions of these equations are obtained by the shooting method. The velocity decreases with increasing slip parameter. The skin friction as well as the mass transfer rate at the surface is larger for a cylinder than for a flat plate.

关键词： boundary layer     stretching cylinder     partial slip     mass transfer     similarity solution    

HTML PDF 收藏

Modeling nanostructured catalyst layer in PEMFC and catalyst utilization

Jiejing ZHANG, Pengzhen CAO, Li XU, Yuxin WANG

《化学科学与工程前沿（英文）》 2011年 第5卷 第3期   页码 297-302 doi: 10.1007/s11705-011-1201-1

摘要： A lattice model of the nanoscaled catalyst layer structure in proton exchange membrane fuel cells (PEMFC) was established by Monte Carlo method. The model takes into account all the four components in a typical PEMFC catalyst layer: platinum (Pt), carbon, ionomer and pore. The elemental voxels in the lattice were set fine enough so that each average sized Pt particulate in Pt/C catalyst can be represented. Catalyst utilization in the modeled catalyst layer was calculated by counting up the number of facets of Pt voxels where “three phase contact” are met. The effects of some factors, including porosity, ionomer content, Pt/C particle size and Pt weight percentage in the Pt/C catalyst, on catalyst utilization were investigated and discussed.

关键词： catalyst layer     PEM fuel cell     lattice model     Monte Carlo method     catalyst utilization    

HTML PDF 收藏

Crystallographic orientation effect on cutting-based single atomic layer removal

Wenkun XIE, Fengzhou FANG

《机械工程前沿（英文）》 2020年 第15卷 第4期   页码 631-644 doi: 10.1007/s11465-020-0599-x

摘要： The ever-increasing requirements for the scalable manufacturing of atomic-scale devices emphasize the significance of developing atomic-scale manufacturing technology. The mechanism of a single atomic layer removal in cutting is the key basic theoretical foundation for atomic-scale mechanical cutting. Material anisotropy is among the key decisive factors that could not be neglected in cutting at such a scale. In the present study, the crystallographic orientation effect on the cutting-based single atomic layer removal of monocrystalline copper is investigated by molecular dynamics simulation. When undeformed chip thickness is in the atomic scale, two kinds of single atomic layer removal mechanisms exist in cutting-based single atomic layer removal, namely, dislocation motion and extrusion, due to the differing atomic structures on different crystallographic planes. On close-packed crystallographic plane, the material removal is dominated by the shear stress-driven dislocation motion, whereas on non-close packed crystallographic planes, extrusion-dominated material removal dominates. To obtain an atomic, defect-free processed surface, the cutting needs to be conducted on the close-packed crystallographic planes of monocrystalline copper.

关键词： ACSM     single atomic layer removal mechanism     crystallographic orientation effect     mechanical cutting     Manufacturing III    

HTML PDF 收藏

Effect of a less permeable stronger soil layer on the stability of non-homogeneous unsaturated slopes

Nabarun DEY, Aniruddha SENGUPTA

《结构与土木工程前沿（英文）》 2020年 第14卷 第6期   页码 1462-1475 doi: 10.1007/s11709-020-0674-8

摘要： Slope failure occurs due to an increase in the saturation level and a subsequent decrease in matric suction in unsaturated soil. This paper presents the results of a series of centrifuge experiments and numerical analyses on a 55° inclined unsaturated sandy slope with less permeable, stronger silty sand layer inclusion within it. It is observed that a less permeable, stronger silty sand layer in an otherwise homogeneous sandy soil slope hinders the infiltration of water. The water content of the slope just above the stronger layer increases significantly, compared to elsewhere. No shear band is found to initiate in a homogeneous sandy soil slope, whereas for a non-homogeneous slope, they initiate just above the less pervious, stronger layer. A discontinuity of the shear zone is also observed for the case of a non-homogeneous soil slope. The factor of safety of a non-homogeneous, unsaturated soil slope decreases because of the less permeable, stronger layer. It decreases significantly if this less permeable, stronger soil layer is located near the toe of the slope.

关键词： non-homogeneous slope     stronger soil layer     factor of safety     centrifuge model test     unsaturated soils    

HTML PDF 收藏

Numerical investigation of the effectiveness of effusion cooling for plane multi-layer systems with different

Dieter BOHN, Robert KREWINKEL

《能源前沿（英文）》 2009年 第3卷 第4期   页码 406-413 doi: 10.1007/s11708-009-0041-x

摘要： Within Collaborative Research Center (SFB) 561 “Thermally Highly Loaded, Porous and Cooled Multi-Layer Systems for Combined Cycle Power Plants” at RWTH Aachen University, an effusion-cooled multi-layer plate configuration is investigated numerically by the application of a three-dimensional in-house fluid flow and heat transfer solver, CHTflow. CHTflow is a conjugate code, which yields information on the temperature distribution in the solid body. This enables a detailed discussion of the effects of a change in materials. The geometrical set-up and the fluid flow conditions derive from modern gas turbine combustion chambers and bladings. Within the SFB, two different multi-layer systems, one consisting of substrate made of CMSX-4 (a single-crystal super-alloy), an MCrAlY-bondoat and a ZrO thermal barrier coating (TBC), and the other consisting of a NiAl-alloy and a graded bondcoat/TBC, have been investigated. The grading will increase the life-span of the TBC as it can better compensate the different thermal expansion coefficients of different materials. The main focus in this study is on the different substrate materials, because the thermal conductivity of the NiAl is considerably higher than that of CMSX-4, which leads to different temperature profiles in the components. The numerical grid for the simulations contains the coolant supply (plenum), the solid body for the conjugate calculations, and the main flow area on the plate. The effusion-cooling is realized by finest drilled shaped holes with a diameter of 0.2mm. The investigation is concentrated on a cooling hole geometry with a laterally widened fan-shaped outlet, contoured throughout, and one without lateral widening that is only shaped in the TBC-region of the system. Two blowing ratios, =0.28 and =0.48, are investigated, both for a hot gas Mach number of 0.25. The results for the lower blowing ratio and the fully contoured hole are discussed as well as those of the higher blowing ratio and the non-laterally widened hole. These represent two characteristic cases.

关键词： conjugate calculation     effectiveness of effusion cooling     multi-layer systems     CMSX-4     NiAl-FG75    

HTML PDF 收藏

The influence of manufacturing parameters and adding support layer on the properties of Zirfon

Li XU,Yue YU,Wei LI,Yan YOU,Wei XU,Shaoxing ZHANG

《化学科学与工程前沿（英文）》 2014年 第8卷 第3期   页码 295-305 doi: 10.1007/s11705-014-1433-y

摘要： The composite separator comprising of polysulfone and zirconia was prepared by phase inversion precipitation technique. The influence of manufacturing parameters on its properties was investigated, and the results show that the manufacturing parameters affect the ionic resistance and maximum pore size significantly. A modified composite separator with a support layer was prepared to enhance the tensile strength of separator. By adding support layer, the tensile strength of the separator increases from 1.85 MPa to 13.66 MPa. In order to evaluate the practical applicability of the composite separator, a small-scale industrial electrolytic experiment was conducted to investigate the changes of cell voltage, gas purity and separator stability. The results show that the modified composite separator has a smaller cell voltage and a higher H purity than the asbestos separator, and are promising material for industrial hydrogen production.

关键词： separator     alkaline water electrolysis     manufacturing parameters     support layer    

HTML PDF 收藏

MHD effect on the critical temperature differences of oscillatory thermocapillary convection in two-layer

Hulin HUANG, Xiaoming ZHOU,

《能源前沿（英文）》 2010年 第4卷 第2期   页码 155-160 doi: 10.1007/s11708-009-0063-4

摘要： The effect of different directional magnetic fields on critical temperature differences of oscillatory thermocapillary convection in a rectangular cavity with differentially heated side walls filled with two viscous, immiscible, incompressible fluids is simulated in the absence of gravity. In this two-layer fluid system, the upper layer fluid is the electrically non-conducting encapsulant boron oxide (BO), while the lower one is the electrically conducting molten indium phosphide (InP). The interface between the two fluids is assumed to be flat and non-deformable. The computational results show that all the magnetic fields along the , and directions can delay the transition from steady convection to oscillatory convection, and critical temperature differences increase with an increasing Hartmann number. Furthermore, the effect of a magnetic field along the direction is strongest, followed by that along the direction, and that along the direction is the weakest for the same intensity of the magnetic field.

关键词： magnetohydrodynamic     magnetic fields     thermocapillary convection     critical temperature difference     oscillatory convection     two-layer fluid system    

HTML PDF 收藏

Dynamic characteristics analysis of active constrained layer damping plate with various boundary conditions

Jing LU, Yu XIANG, Qiao NI

《机械工程前沿（英文）》 2011年 第6卷 第4期   页码 449-455 doi: 10.1007/s11465-011-0240-0

摘要：

Considering the direct and converse piezoelectric effect, expressions of piezoelectric membrane internal forces in the piezoelectric constrained layer were given. The control equations of the piezoelectric constrained layer and host plate were obtained in according with the thin plate theory. Based on the layer wised principle, the integrated first order differential equation of an active constrained layer damping (ACLD) plate was derived for the simply supported boundary condition. Then, this method was expanded to the ACLD plate with cantilever boundary condition by virtue of geometric analogy method. Employing the extended homogeneous capacity precision integration approach, a high precision semi-analytical method was proposed to analyze the dynamic characteristics of the ACLD plate with various boundary conditions. The comparison with the literature results has verified the accuracy and effectiveness of the present method.

关键词： active constrained layer damping (ACLD) plate     dynamic characteristics     semi-analytical method     extended homogeneous capacity precision integration approach    

HTML PDF 收藏

Review of characterization and modeling of polymer electrolyte fuel cell catalyst layer: The blessing

Jun HUANG, Zhe LI, Jianbo ZHANG

《能源前沿（英文）》 2017年 第11卷 第3期   页码 334-364 doi: 10.1007/s11708-017-0490-6

摘要： Ionomer impregnation represents a milestone in the evolution of polymer electrolyte fuel cell (PEFC) catalyst layers. Ionomer acts as the binder, facilitates proton transport, and thereby drastically improves catalyst utilization and effectiveness. However, advanced morphological and functional characterizations have revealed that up to 60% of Pt nanoparticles can be trapped in the micropores of carbon support particles. Ionomer clusters and oxygen molecules can hardly enter into micropores, leading to low Pt utilization and effectiveness. Moreover, the ionomer thin-films covering Pt nanoparticles can cause significant mass transport loss especially at high current densities. Ionomer-free ultra-thin catalyst layers (UTCLs) emerge as a promising alternative to reduce Pt loading by improving catalyst utilization and effectiveness, while theoretical issues such as the proton conduction mechanism remain puzzling and practical issues such as the rather narrow operation window remain unsettled. At present, the development of PEFC catalyst layer has come to a crossroads: staying ionomer-impregnated or going ionomer-free. It is always beneficial to look back into the past when coming to a crossroads. This paper addresses the characterization and modeling of both the conventional ionomer-impregnated catalyst layer and the emerging ionomer-free UTCLs, featuring advances in characterizing microscale distributions of Pt particles, ionomer, support particles and unraveling their interactions; advances in fundamental understandings of proton conduction and flooding behaviors in ionomer-free UTCLs; advances in modeling of conventional catalyst layers and especially UTCLs; and discussions on high-impact research topics in characterizing and modeling of catalyst layers.

关键词： polymer electrolyte fuel cell     ultra-thin catalyst layer     electrostatic interactions     characterization and modeling     structure-property-performance relation     water management    

HTML PDF 收藏

Bridging the gap between laboratory and field moduli of asphalt layer for pavement design and assessment

Huailei CHENG; Liping LIU; Lijun SUN

《结构与土木工程前沿（英文）》 2022年 第16卷 第3期   页码 267-280 doi: 10.1007/s11709-022-0811-7

摘要： Asphalt pavement is a key component of highway infrastructures in China and worldwide. In asphalt pavement design and condition assessment, the modulus of the asphalt mixture layer is a crucial parameter. However, this parameter varies between the laboratory and field loading modes (i.e., loading frequency, compressive or tensile loading pattern), due to the viscoelastic property and composite structure of the asphalt mixture. The present study proposes a comprehensive frequency-based approach to correlate the asphalt layer moduli obtained under two field and three laboratory loading modes. The field modes are vehicular and falling weight deflectometer (FWD) loading modes, and the laboratory ones are uniaxial compressive (UC), indirect tensile (IDT), and four-point bending (4PB) loading modes. The loading frequency is used as an intermediary parameter for correlating the asphalt layer moduli under different loading modes. The observations made at two field large-scale experimental pavements facilitate the correlation analysis. It is found that the moduli obtained via laboratory 4PB tests are pretty close to those of vehicular loading schemes, in contrast to those derived in UC, IDT, and FWD modes, which need to be adjusted. The corresponding adjustment factors are experimentally assessed. The applications of those adjustment factors are expected to ensure that the moduli measured under different loading modes are appropriately used in asphalt mixture pavement design and assessment.

关键词： asphalt mixture layer     stiffness modulus     loading mode     UC/4PB/IDT     FWD     frequency    

HTML PDF 收藏

NiCo2O4@quinone-rich N–C core–shell nanowires as composite electrode for electric double layer capacitor

《化学科学与工程前沿（英文）》 2023年 第17卷 第4期   页码 373-386 doi: 10.1007/s11705-022-2223-6

摘要： The bind-free carbon cloth-supported electrodes hold the promises for high-performance electrochemical capacitors with high specific capacitance and good cyclic stability. Considering the close connection between their performance and the amount of carbon material loaded on the electrodes, in this work, NiCo2O4 nanowires were firstly grown on the substrate of active carbon cloth to provide the necessary surface area in the longitudinal direction. Then, the quinone-rich nitrogen-doped carbon shell structure was formed around NiCo2O4 nanowires, and the obtained composite was used as electrode for electric double layer capacitor. The results showed that the composite electrode displayed an area-specific capacitance of 1794 mF∙cm–2 at the current density of 1 mA∙cm–2. The assembled symmetric electric double layer capacitor achieved a high energy density of 6.55 mW∙h∙cm–3 at a power density of 180 mW∙cm–3. The assembled symmetric capacitor exhibited a capacitance retention of 88.96% after 10000 charge/discharge cycles at the current density of 20 mA∙cm–2. These results indicated the potentials in the preparation of the carbon electrode materials with high energy density and good cycling stability.

关键词： carbon cloth     NiCo2O4 nanowires     core−shell structure     quinone-rich     electric double layer capacitor    

HTML PDF 收藏

Effects of radiation and heat source/sink on unsteady MHD boundary layer flow and heat transfer over

Krishnendu Bhattacharyya

《化学科学与工程前沿（英文）》 2011年 第5卷 第3期   页码 376-384 doi: 10.1007/s11705-011-1121-0

摘要： In this paper, an investigation is made to study the effects of radiation and heat source/sink on the unsteady boundary layer flow and heat transfer past a shrinking sheet with suction/injection. The flow is permeated by an externally applied magnetic field normal to the plane of flow. The self-similar equations corresponding to the velocity and temperature fields are obtained, and then solved numerically by finite difference method using quasilinearization technique. The study reveals that the momentum boundary layer thickness increases with increasing unsteadiness and decreases with magnetic field. The thermal boundary layer thickness decreases with Prandtl number, radiation parameter and heat sink parameter, but it increases with heat source parameter. Moreover, increasing unsteadiness, magnetic field strength, radiation and heat sink strength boost the heat transfer.

关键词： MHD boundary layer     unsteady flow     heat transfer     thermal radiation     heat source/sink     shrinking sheet     suction/injection    

HTML PDF 收藏

Effective diffusivity of oxygen in the ash layer of Huadian oil shale semicoke

Yiqun HUANG, Yiran LI, Man ZHANG, Boyu DENG, Hao KONG, Junfeng WANG, Junfu LYU, Hairui YANG, Lingmei WANG

《能源前沿（英文）》 2021年 第15卷 第2期   页码 320-327 doi: 10.1007/s11708-020-0674-3

摘要： Diffusion of oxygen in the ash layer usually dominated the combustion of oil shale semicoke particles due to the high ash content. Thus, effective diffusivity of oxygen in the ash layer was a crucial parameter worthy of careful investigation. In this paper, the effective diffusivity of oxygen in the ash layer of Huadian oil shale semicoke was measured directly using an improved Wicke-Kallenbach diffusion apparatus. The experimental results showed that higher temperature would lead to a higher effective diffusivity and a thicker ash layer had the negative effect. Especially, the effective diffusivity along the direction perpendicular to bedding planes was much lower than that along the direction parallel to bedding planes. In addition, an effective diffusivity model was developed, which could be used to describe the mass transfer of oxygen in the ash layer of oil shale semicoke.

关键词： oil shale semicoke     diffusivity     pore structure     ash layer    

HTML PDF 收藏

Two-dimensional modeling of sintering of a powder layer on top of nonporous substrate

Tiebing CHEN, Yuwen ZHANG,

《机械工程前沿（英文）》 2010年 第5卷 第2期   页码 143-148 doi: 10.1007/s11465-010-0006-0

摘要： Selective laser sintering (SLS) of a two-component metal powder layer on the top of multiple sintered layers by a moving Gaussian laser beam is modeled. The loose metal powder layer is composed of a powder mixture with significantly different melting points. The physical model that accounts the shrinkage induced by melting is described by using a temperature-transforming model. The effects of the porosity and the thickness of the atop loose powder layer with different numbers of the existing sintered metal powder layers below on the sintering process are numerically investigated. The present work will provide a better understanding to simulate much more complicated three-dimensional SLS process.

关键词： laser     sintering     melting     solidification     heat transfer    

HTML PDF 收藏

Molecular dynamics investigation of mechanical properties of single-layer phagraphene

Ali Hossein Nezhad SHIRAZI

《结构与土木工程前沿（英文）》 2019年 第13卷 第2期   页码 495-503 doi: 10.1007/s11709-018-0492-4

摘要： Phagraphene is a very attractive two-dimensional (2D) full carbon allotrope with very interesting mechanical, electronic, optical, and thermal properties. The objective of this study is to investigate the mechanical properties of this new graphene like 2D material. In this work, mechanical properties of phagraphene have been studied not only in the defect-free form, but also with the critical defect of line cracks, using the classical molecular dynamics simulations. Our study shows that the pristine phagraphene in zigzag direction experience a ductile behavior under uniaxial tensile loading and the nanosheet in this direction are less sensitive to temperature changes as compared to the armchair direction. We studied different crack lengths to explore the influence of defects on the mechanical properties of phagraphene. We also investigated the temperature effect on the mechanical properties of pristine and defective phagraphene. Our classical atomistic simulation results confirm that larger cracks can reduce the strength of the phagraphene. Moreover, it was shown the temperature has a considerable weakening effect on the tensile strength of phagraphene. The results of this study may be useful for the design of nano-devices using the phagraphene.

关键词： phaqraphene     mechanical properties     crack propaqation     molecular dynamics     thermal effects    

HTML PDF 收藏

标题 作者 时间 类型 操作

Chemically reactive solute transfer in a boundary layer slip flow along a stretching cylinder

Swati Mukhopadhyay

期刊论文

Modeling nanostructured catalyst layer in PEMFC and catalyst utilization

Jiejing ZHANG, Pengzhen CAO, Li XU, Yuxin WANG

期刊论文

Crystallographic orientation effect on cutting-based single atomic layer removal

Wenkun XIE, Fengzhou FANG

期刊论文

Effect of a less permeable stronger soil layer on the stability of non-homogeneous unsaturated slopes

Nabarun DEY, Aniruddha SENGUPTA

期刊论文

Numerical investigation of the effectiveness of effusion cooling for plane multi-layer systems with different

Dieter BOHN, Robert KREWINKEL

期刊论文

The influence of manufacturing parameters and adding support layer on the properties of Zirfon

Li XU,Yue YU,Wei LI,Yan YOU,Wei XU,Shaoxing ZHANG

期刊论文

MHD effect on the critical temperature differences of oscillatory thermocapillary convection in two-layer

Hulin HUANG, Xiaoming ZHOU,

期刊论文

Dynamic characteristics analysis of active constrained layer damping plate with various boundary conditions

Jing LU, Yu XIANG, Qiao NI

期刊论文

Review of characterization and modeling of polymer electrolyte fuel cell catalyst layer: The blessing

Jun HUANG, Zhe LI, Jianbo ZHANG

期刊论文

Bridging the gap between laboratory and field moduli of asphalt layer for pavement design and assessment

Huailei CHENG; Liping LIU; Lijun SUN

期刊论文

NiCo2O4@quinone-rich N–C core–shell nanowires as composite electrode for electric double layer capacitor

期刊论文

Effects of radiation and heat source/sink on unsteady MHD boundary layer flow and heat transfer over

Krishnendu Bhattacharyya

期刊论文

Effective diffusivity of oxygen in the ash layer of Huadian oil shale semicoke

Yiqun HUANG, Yiran LI, Man ZHANG, Boyu DENG, Hao KONG, Junfeng WANG, Junfu LYU, Hairui YANG, Lingmei WANG

期刊论文

Two-dimensional modeling of sintering of a powder layer on top of nonporous substrate

Tiebing CHEN, Yuwen ZHANG,

期刊论文

Molecular dynamics investigation of mechanical properties of single-layer phagraphene

Ali Hossein Nezhad SHIRAZI

期刊论文