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Experimental verification of the interface wave method to detect interlaminar damage of a metal multilayerstructure

Bing LI,Xu GENG,Tong LU,Lei QIANG,Minghang LI

《机械工程前沿(英文)》 2015年 第10卷 第4期   页码 380-391 doi: 10.1007/s11465-015-0365-7

摘要:

The interface wave traveling along the boundary of two materials has been studied for nearly a century. However, experiments, engineering applications, and interface wave applications to the non-destructive inspection of interlaminar composite have developed slowly. In this research, an experiment that applies Stoneley waves (a type of interfacial wave between two solid half-spaces) is implemented to detect the damage in a multilayer structure. The feasibility of this method is also verified. First, the wave velocity and wave structure of Stoneley waves at a perfectly bonded aluminum-steel interface are obtained by solving the Stoneley wave dispersion equation of two elastic half-spaces. Thereafter, an experiment is conducted to measure the Stoneley wave velocity of an aluminum-steel laminated beam and to locate interlaminar cracks by referring to the Stoneley wave velocity and echo wave time. Results indicate that the location error is less than 2%. Therefore, Stoneley waves show great potential as a non-destructive inspection method of a multilayer structure.

关键词: crack localization     interface waves     Stoneley waves     interlaminar damage     multilayer structure    

Experimental research on the multilayer compartmental particle damper and its application methods on

Zhenyuan LUO, Weiming YAN, Weibing XU, Qinfei ZHENG, Baoshun WANG

《结构与土木工程前沿(英文)》 2019年 第13卷 第4期   页码 751-766 doi: 10.1007/s11709-018-0509-z

摘要: Particle damping technology has attracted extensive research and engineering application interest in the field of vibration control due to its prominent advantages, including wide working frequency bands, ease of installation, longer durability and insensitivity to extreme temperatures. To introduce particle damping technology to long-period structure seismic control, a novel multilayer compartmental particle damper (MCPD) was proposed, and a 1/20 scale test model of a typical long-period self-anchored suspension bridge with a single tower was designed and fabricated. The model was subjected to a series of shaking table tests with and without the MCPD. The results showed that the seismic responses of the flexible or semi-flexible bridge towers of long-period bridges influence the seismic responses of the main beam. The MCPD can be conveniently installed on the main beam and bridge tower and can effectively reduce the longitudinal peak displacement and the root mean square acceleration of the main beam and tower. In addition, no particle accumulation was observed during the tests. A well-designed MCPD can achieve significant damping for long-period structures under seismic excitations of different intensities. These results indicate that the application of MCPDs for seismic control of single-tower self-anchored suspension bridges and other long-period structures is viable.

关键词: energy dissipation devices     multilayer compartmental particle damper     self-anchored suspension bridges     shaking tables test     long-period structure     seismic control    

FEM-based strain analysis study for multilayer sheet forming process

Rongjing ZHANG,Lihui LANG,Rizwan ZAFAR

《机械工程前沿(英文)》 2015年 第10卷 第4期   页码 373-379 doi: 10.1007/s11465-015-0371-9

摘要:

Fiber metal laminates have many advantages over traditional laminates (e.g., any type of fiber and resin material can be placed anywhere between the metallic layers without risk of failure of the composite fabric sheets). Furthermore, the process requirements to strictly control the temperature and punch force in fiber metal laminates are also less stringent than those in traditional laminates. To further explore the novel method, this study conducts a finite element method-based (FEM-based) strain analysis on multilayer blanks by using the 3A method. Different forming modes such as wrinkling and fracture are discussed by using experimental and numerical studies. Hydroforming is used for multilayer forming. The Barlat 2000 yield criteria and DYNAFORM/LS-DYNA are used for the simulations. Optimal process parameters are determined on the basis of fixed die-binder gap and variable cavity pressure. The results of this study will enhance the knowledge on the mechanics of multilayer structures formed by using the 3A method and expand its commercial applications.

关键词: finite element method (FEM)     strain analysis     multilayer sheet forming    

A spectrally selective surface structure for combined photothermic conversion and radiative sky cooling

Bin ZHAO, Xianze AO, Nuo CHEN, Qingdong XUAN, Mingke HU, Gang PEI

《能源前沿(英文)》 2020年 第14卷 第4期   页码 882-888 doi: 10.1007/s11708-020-0694-z

摘要: The sun and outer space are the ultimate heat and cold sources for the earth, respectively. They have significant potential for renewable energy harvesting. In this paper, a spectrally selective surface structure that has a planar polydimethylsiloxane layer covering a solar absorber is conceptually proposed and optically designed for the combination of photothermic conversion (PT) and nighttime radiative sky cooling (RC). An optical simulation is conducted whose result shows that the designed surface structure (i.e., PT-RC surface structure) has a strong solar absorption coefficient of 0.92 and simultaneously emits as a mid-infrared spectral-selective emitter with an average emissivity of 0.84 within the atmospheric window. A thermal analysis prediction reveals that the designed PT-RC surface structure can be heated to 79.1°C higher than the ambient temperature in the daytime and passively cooled below the ambient temperature of approximately 10°C in the nighttime, indicating that the designed PT-RC surface structure has the potential for integrated PT conversion and nighttime RC utilization.

关键词: solar energy     photothermic conversion     radiative sky cooling     spectral selectivity     multilayer film    

Mechanical properties and microstructure of multilayer graphene oxide cement mortar

《结构与土木工程前沿(英文)》 2021年 第15卷 第4期   页码 1058-1070 doi: 10.1007/s11709-021-0747-3

摘要: This study reports on the effects of multilayer graphene oxide (MGO) on compressive strength, flexural strength, and microstructure of cement mortar. The cement mortar was prepared with type P. II. 52.5 Portland cement, standard sand, and MGO. Four mixes were prepared with inclusion of MGO (0%, 0.02%, 0.04%, and 0.06% by weight of cement). The testing result shows that the compressive of GO-cement mortar increased by 4.84%–13.42%, and the flexural strength increased by 4.37%–8.28% at 3 d. GO-cement mortar’s compressive strength and flexural strength at 7 d increased by 3.84%–12.08% and 2.54%–13.43%, respectively. MGO made little contribution to the increases of compressive strength and flexural strength of cement mortar at 28 d. The results of X-ray diffraction (XRD), scanning electron microscope (SEM), and nitrogen (N2) adsorption/desorption tests show that the types of hydration products and crystal grain size did not change after adding MGO. Still, it can help to improve the microstructure of the cement mortar via regulating hydration products and can provide more condensed cores to accelerate hydration. Furthermore, the regulating action of MGO for the microstructure of cement mortar at an early age was better than that at 28 d.

关键词: graphene oxide     cement     mortar     mechanical properties     microstructure    

Eddy current measurement of the thickness of top Cu film of the multilayer interconnects in the integrated

Zilian QU,Yonggang MENG,Qian ZHAO

《机械工程前沿(英文)》 2015年 第10卷 第1期   页码 1-6 doi: 10.1007/s11465-015-0325-2

摘要:

This paper proposes a new eddy current method, named equivalent unit method (EUM), for the thickness measurement of the top copper film of multilayer interconnects in the chemical mechanical polishing (CMP) process, which is an important step in the integrated circuit (IC) manufacturing. The influence of the underneath circuit layers on the eddy current is modeled and treated as an equivalent film thickness. By subtracting this equivalent film component, the accuracy of the thickness measurement of the top copper layer with an eddy current sensor is improved and the absolute error is 3 nm for sampler measurement.

关键词: CMP     eddy current     multilayer wafer     Cu interconnects     equivalent unit    

Modeling of coal swelling induced by water vapor adsorption

Zhejun PAN

《化学科学与工程前沿(英文)》 2012年 第6卷 第1期   页码 94-103 doi: 10.1007/s11705-011-1172-2

摘要: Gas adsorption-induced coal swelling is a well-know phenomenon. Coal swelling or shrinkage by adsorption or desorption of water vapor has not been well understood but has significant implications on gas drainage process for underground coal mining and for primary and enhanced coalbed methane production. Decreased matrix moisture content leads to coal shrinkage and thus the change of cleat porosity and permeability under reservoir conditions. Unlike gas adsorption in coal which usually forms a single layer of adsorbed molecules, water vapor adsorption in the coal micropores forms multilayer of adsorbed molecules. In this work, a model has been developed to describe the coal swelling strain with respect to the amount of moisture intake by the coal matrix. The model extended an energy balance approach for gas adsorption-induced coal swelling to water vapor adsorption-induced coal swelling, assuming that only the first layer of adsorbed molecules of the multilayer adsorption changes the surface energy, which thus causes coal to swell. The model is applied to describe the experimental swelling strain data measured on an Australian coal. The results show good agreement between the model and the experimental data.

关键词: multilayer adsorption     vapour pressure     coal shrinkage     relative humidity     permeability    

Ion conduction path in composite solid electrolytes for lithium metal batteries: from polymer rich to ceramic rich

Zhouyu ZHANG, Hao CHEN, Zhenglin HU, Shoubin ZHOU, Lan ZHANG, Jiayan LUO

《能源前沿(英文)》 2022年 第16卷 第5期   页码 706-733 doi: 10.1007/s11708-022-0833-9

摘要: Solid-state electrolytes (SSEs) can address the safety issue of organic electrolyte in rechargeable lithium batteries. Unfortunately, neither polymer nor ceramic SSEs used alone can meet the demand although great progress has been made in the past few years. Composite solid electrolytes (CSEs) composed of flexible polymers and brittle but more conducting ceramics can take advantage of the individual system for solid-state lithium metal batteries (SSLMBs). CSEs can be largely divided into two categories by the mass fraction of the components: “polymer rich” (PR) and “ceramic rich” (CR) systems with different internal structures and electrochemical properties. This review provides a comprehensive and in-depth understanding of recent advances and limitations of both PR and CR electrolytes, with a special focus on the ion conduction path based on polymer-ceramic interaction mechanisms and structural designs of ceramic fillers/frameworks. In addition, it highlights the PR and CR which bring the leverage between the electrochemical property and the mechanical property. Moreover, it further prospects the possible route for future development of CSEs according to their rational design, which is expected to accelerate the practical application of SSLMBs.

关键词: composite solid electrolytes     active filler/framework     ion conduction path     interphase compatibility     multilayer design    

Influence of pore structure on biologically activated carbon performance and biofilm microbial characteristics

《环境科学与工程前沿(英文)》 2021年 第15卷 第6期 doi: 10.1007/s11783-021-1419-1

摘要:

• Pore structure affects biologically activated carbon performance.

关键词: Granular activated carbon     Biologically activated carbon filter     Bacterial community structure     Pore structure    

Hierarchical fractal structure of perfect single-layer graphene

T. Zhang, K. Ding

《机械工程前沿(英文)》 2013年 第8卷 第4期   页码 371-382 doi: 10.1007/s11465-013-0279-1

摘要:

The atomic lattice structure of perfect single-layer graphene that can actually be regarded as a kind of hierarchical fractal structure from the perspective of fractal geometry was studied for the first time. Three novel and special discoveries on hierarchical fractal structure and sets were unveiled upon examination of the regular crystal lattices of the single-layer graphene. The interior fractal-type structure was discovered to be the fifth space-filling curve from physical realm. Two efficient methods for calculating the fractal dimension of this fresh member was also provided. The outer boundary curve had a fractal dimension equal to one, and a multi-fractal structure from a naturally existing material was found for the first time. A series of strict self-similar hexagons comprised a rotating fractal set. These hexagons slewed at a constant counterclockwise angle of 19.1° when observed from one level to the next higher level. From the perspective of fractal geometry, these pioneering discoveries added three new members to the existing regular fractal structures and sets. A fundamental example of a multi-fractal structure was also presented.

关键词: hierarchical fractal structure     fractal dimension     the fifth space-filling curve     multi-fractal structure    

Floating forest: A novel breakwater-windbreak structure against wind and wave hazards

《结构与土木工程前沿(英文)》 2021年 第15卷 第5期   页码 1111-1127 doi: 10.1007/s11709-021-0757-1

摘要: A novel floating breakwater-windbreak structure (floating forest) has been designed for the protection of vulnerable coastal areas from extreme wind and wave loadings during storm conditions. The modular arch-shaped concrete structure is positioned perpendicularly to the direction of the prevailing wave and wind. The structure below the water surface acts as a porous breakwater with wave scattering capability. An array of tubular columns on the sloping deck of the breakwater act as an artificial forest-type windbreak. A feasibility study involving hydrodynamic and aerodynamic analyses has been performed, focusing on its capability in reducing wave heights and wind speeds in the lee side. The study shows that the proposed 1 km long floating forest is able to shelter a lee area that stretches up to 600 m, with 40%–60% wave energy reduction and 10%–80% peak wind speed reduction.

关键词: floating structure     breakwater     windbreak     hydrodynamic     CFD    

多点协同传输机制下的多层无人机—地面异构网络覆盖性能分析 Research Article

王维昊,蒋逸凡,费泽松,郭婧

《信息与电子工程前沿(英文)》 2022年 第23卷 第1期   页码 61-72 doi: 10.1631/FITEE.2100310

摘要: 为满足第六代移动通信的泛在连接需求,无人机作为未来通信网络主要组成部分发挥着关键作用。频谱共享和视距链路传输造成的干扰是无人机通信的一个主要问题。近年来,为减少无人机—地面异构网络干扰,提出多点协同传输技术。本文提出一个三维多层无人机—地面异构网络,其中无人机作为空中基站部署于不同高度。利用随机几何理论,提出一个易于处理的数学框架评估这个异构网络的干扰统计特性和覆盖概率。数值结果表明多点协同传输机制能有效缓解网络中的干扰,尤其当基站密度较大时。此外,部署在更高的空中基站的系统参数是影响所提三维异构网络覆盖性能的主要因素。

关键词: 无人机;泊松点过程;多点协同;干扰统计特性;覆盖性能    

Bicontinuous porous membranes with micro-nano composite structure using a facile atomization-assisted

《化学科学与工程前沿(英文)》 2022年 第16卷 第8期   页码 1268-1280 doi: 10.1007/s11705-022-2143-5

摘要: The micro-nano composite structure can endow separation membranes with special surface properties, but it often has the problems of inefficient preparation process and poor structural stability. In this work, a novel atomization-assisted nonsolvent induced phase separation method, which is also highly efficient and very simple, has been developed. By using this method, a bicontinuous porous microfiltration membrane with robust micro-nano composite structure was obtained via commercially available polymers of polyacrylonitrile and polyvinylpyrrolidone. The formation mechanism of the micro-nano composite structure was proposed. The microphase separation of polyacrylonitrile and polyvinylpyrrolidone components during the atomization pretreatment process and the hydrogen bonding between polyacrylonitrile and polyvinylpyrrolidone molecules should have resulted in the nano-protrusions on the membrane skeleton. The membrane exhibits superhydrophilicity in air and superoleophobicity underwater. The membrane can separate both surfactant-free and surfactant-stabilized oil-in-water emulsions with high separation efficiency and permeation flux. With excellent antifouling property and robust microstructure, the membrane can easily be recycled for long-term separation. Furthermore, the scale-up verification from laboratory preparation to continuous production has been achieved. The simple, efficient, cost-effective preparation method and excellent membrane properties indicate the great potential of the developed membranes in practical applications.

关键词: atomization     nonsolvent induced phase separation     bicontinuous porous structure     micro-nano composite structure     oil-water separation    

Smart optical-fiber structure monitoring based on granular computing

Guan LU, Dakai LIANG,

《机械工程前沿(英文)》 2009年 第4卷 第4期   页码 462-465 doi: 10.1007/s11465-009-0073-2

摘要: Using an optic fiber self-diagnosing system in health monitoring has become an important direction of smart materials and structure research. The buried optic fiber sensor can be used to test the parameters of the composite material. The granular computing method can reach the requirement of damage detection by analyzing digital signals and character signals of the smart structure at the same time. The paper investigates an optic fiber smart layer and presents a method for realizing optic fiber smart structure monitoring and damage detection by using granular computing. After the analysis, it is presumed that optic fiber smart structure monitoring based on granular computation can identify the damage from complex signals.

关键词: smart material and structure     GrC     optical fiber sensor     rough set     clustering algorithm    

Automated classification of civil structure defects based on convolutional neural network

Pierclaudio SAVINO, Francesco TONDOLO

《结构与土木工程前沿(英文)》 2021年 第15卷 第2期   页码 305-317 doi: 10.1007/s11709-021-0725-9

摘要: Today, the most commonly used civil infrastructure inspection method is based on a visual assessment conducted by certified inspectors following prescribed protocols. However, the increase in aggressive environmental and load conditions, coupled with the achievement of many structures of the life-cycle end, has highlighted the need to automate damage identification and satisfy the number of structures that need to be inspected. To overcome this challenge, this paper presents a method for automating concrete damage classification using a deep convolutional neural network. The convolutional neural network was designed after an experimental investigation of a wide number of pretrained networks, applying the transfer-learning technique. Training and validation were conducted using a database built with 1352 images balanced between “undamaged”, “cracked”, and “delaminated” concrete surfaces. To increase the network robustness compared to images in real-world situations, different image configurations have been collected from the Internet and on-field bridge inspections. The GoogLeNet model, with the highest validation accuracy of approximately 94%, was selected as the most suitable network for concrete damage classification. The results confirm that the proposed model can correctly classify images from real concrete surfaces of bridges, tunnels, and pavement, resulting in an effective alternative to the current visual inspection techniques.

关键词: concrete structure     infrastructures     visual inspection     convolutional neural network     artificial intelligence    

标题 作者 时间 类型 操作

Experimental verification of the interface wave method to detect interlaminar damage of a metal multilayerstructure

Bing LI,Xu GENG,Tong LU,Lei QIANG,Minghang LI

期刊论文

Experimental research on the multilayer compartmental particle damper and its application methods on

Zhenyuan LUO, Weiming YAN, Weibing XU, Qinfei ZHENG, Baoshun WANG

期刊论文

FEM-based strain analysis study for multilayer sheet forming process

Rongjing ZHANG,Lihui LANG,Rizwan ZAFAR

期刊论文

A spectrally selective surface structure for combined photothermic conversion and radiative sky cooling

Bin ZHAO, Xianze AO, Nuo CHEN, Qingdong XUAN, Mingke HU, Gang PEI

期刊论文

Mechanical properties and microstructure of multilayer graphene oxide cement mortar

期刊论文

Eddy current measurement of the thickness of top Cu film of the multilayer interconnects in the integrated

Zilian QU,Yonggang MENG,Qian ZHAO

期刊论文

Modeling of coal swelling induced by water vapor adsorption

Zhejun PAN

期刊论文

Ion conduction path in composite solid electrolytes for lithium metal batteries: from polymer rich to ceramic rich

Zhouyu ZHANG, Hao CHEN, Zhenglin HU, Shoubin ZHOU, Lan ZHANG, Jiayan LUO

期刊论文

Influence of pore structure on biologically activated carbon performance and biofilm microbial characteristics

期刊论文

Hierarchical fractal structure of perfect single-layer graphene

T. Zhang, K. Ding

期刊论文

Floating forest: A novel breakwater-windbreak structure against wind and wave hazards

期刊论文

多点协同传输机制下的多层无人机—地面异构网络覆盖性能分析

王维昊,蒋逸凡,费泽松,郭婧

期刊论文

Bicontinuous porous membranes with micro-nano composite structure using a facile atomization-assisted

期刊论文

Smart optical-fiber structure monitoring based on granular computing

Guan LU, Dakai LIANG,

期刊论文

Automated classification of civil structure defects based on convolutional neural network

Pierclaudio SAVINO, Francesco TONDOLO

期刊论文