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Tensile ratcheting behaviors of bronze powder filled polytetrafluoroethylene

Wenjuan XU, Hong GAO, LiLan GAO, Xu CHEN, Yong WANG

《化学科学与工程前沿(英文)》 2013年 第7卷 第1期   页码 103-109 doi: 10.1007/s11705-013-1315-8

摘要: A series of tensile and ratcheting experiments for compacted polytetrafluoroethylene (PTFE) and bronze filled PTFE (PTFE/bronze) were conducted on dynamic mechanical analyzer (DMA-Q800). The effects of mean stress, stress amplitude and temperature on the ratcheting behaviors of PTFE and PTFE/bronze were investigated. It is found that the stress-strain response of PTFE/bronze is nonlinear and its elastic modulus is higher than that of pure PTFE. For uniaxial ratcheting test, the dissipation strain energy density (DSED) decreases rapidly in the first 10 cycles and approaches a constant after 20 cycles. The ratcheting strain and the DSED corresponding to 100 cycles increase with increasing mean stress, stress amplitude and temperature. Additionally, the DSED and ratcheting strain of PTFE/bronze are much lower than those of pure PTFE under the same experimental conditions. It is also found that both pure PTFE and PTFE/bronze present cyclic hardening characteristics. Above all, the addition of bronze can improve both the uniaxial tensile property and the cyclic property of PTFE.

关键词: bronze filled polytetrafluoroethylene (PTFE/bronze)     uniaxial tensile behavior     ratcheting behavior     dissipation strain energy density (DSED)    

Determination of energy dissipation of a spider silk structure under impulsive loading

Jorge ALENCASTRE,Carlos MAGO,Richard RIVERA

《机械工程前沿(英文)》 2015年 第10卷 第3期   页码 306-310 doi: 10.1007/s11465-015-0349-7

摘要:

Various researches and studies have demonstrated that spider silk is much stronger and more deformable than a steel string of the same diameter from a mechanical approach. These excellent properties have caused many scientific disciplines to get involved, such as bio-mechanics, bio-materials and bio-mimetics, in order to create a material of similar properties and characteristics. It should be noted that the researches and studies have been oriented mainly as a quasi-static model. For this research, the analysis has taken a dynamic approach and determined the dissipation energy of a structure which is made of spider silk “Dragline” and produced by the Argiope-Argentata spider, through an analytical-experimental way, when being subjected to impulsive loading. Both experimental and analytical results, the latter obtained by using adjusted models, have given high levels of dissipation energy during the first cycle of vibration, which are consistent with the values suggested by other authors.

关键词: dissipation energy     impact     visco-elastic material     spider silk    

A model for creep life prediction of thin tube using strain energy density as a function of stress triaxiality

Tahir MAHMOOD, Sangarapillai KANAPATHIPILLAI, Mahiuddin CHOWDHURY

《机械工程前沿(英文)》 2013年 第8卷 第2期   页码 181-186 doi: 10.1007/s11465-013-0257-7

摘要:

This paper demonstrates the application of a new multiaxial creep damage model developed by authors using stress traixiality to predict the failure time of a component made of 0.5%Cr-0.5%Mo-0.25%V low alloy steel. The model employs strain energy density and assumes that the uniaxial strain energy density of a component can be easily calculated and can be converted to multi-axial strain energy density by multiplying it to a function of stress trixiality which is a ratio of mean stress to equivalent stress. For comparison, an elastic-creep and elastic-plastic-creep finite element analysis (FEA) is performed to get multi-axial strain energy density of the component which is compared with the calculated strain energy density for both cases. The verification and application of the model are demonstrated by applying it to thin tube for which the experimental data are available. The predicted failure times by the model are compared with the experimental results. The results show that the proposed model is capable of predicting failure times of the component made of the above-mentioned material with an accuracy of 4.0%.

关键词: elastic-creep     elastic-plastic-creep     stress triaxiality     life prediction     pressure vessels     finite element analysis (FEA)    

Aseismic smart building isolation systems under multi-level earthquake excitations: Part II, energy-dissipation

Min-Ho CHEY,J. Geoffrey CHASE,John B. MANDER,Athol J. CARR

《结构与土木工程前沿(英文)》 2015年 第9卷 第3期   页码 297-306 doi: 10.1007/s11709-015-0308-8

摘要: Based on the performance results of the previously suggested smart building isolation systems (1st companion paper), this following study verifies the control effects of the systems from the view point of energy dissipation and damage level metrics. Several different model cases of the strategically isolated multi-story building structures utilizing passive dampers and semi-active resettable devices are analyzed and the energy-based target indices are compared. Performance comparisons are conducted on statistically calculated story/structural hysteretic energy and story/structural damage demands over realistic suites of earthquake ground motion records, representing seismic excitations of specific return period probability. Again, the semi-active solutions show significant promise for applications of resettable device, offering advantages over passive systems in the consistent damage reductions. The specific results of this study include the identification of differences in the mechanisms by which smart building isolation systems remove energy, based on the differences in the devices used. Less variability is also seen for the semi-active isolation systems, indicating an increased robustness.

关键词: smart building isolation     story and structural     energy-dissipation     damage assessment    

Experimental investigations of internal energy dissipation during fracture of fiber-reinforced ultra-high-performance

Eric N. LANDIS, Roman KRAVCHUK, Dmitry LOSHKOV

《结构与土木工程前沿(英文)》 2019年 第13卷 第1期   页码 190-200 doi: 10.1007/s11709-018-0487-1

摘要: Split-cylinder fracture of fiber-reinforced ultra-high-performance concrete (UHPC) was examined using two complementary techniques: X-ray computed tomography (CT) and acoustic emission (AE). Fifty-mm-diameter specimens of two different fiber types were scanned both before and after load testing. From the CT images, fiber orientation was evaluated to establish optimum and pessimum specimen orientations, at which fibers would have maximum and minimum effect, respectively. As expected, fiber orientation affected both the peak load and the toughness of the specimen, with the optimum toughness being between 20% and 30% higher than the pessimum. Cumulative AE energy was also affected commensurately. Posttest CT scans of the specimens were used to measure internal damage. Damage was quantified in terms of internal energy dissipation due to both matrix cracking and fiber pullout by using calibration measurements for each. The results showed that fiber pullout was the dominant energy dissipation mechanism; however, the sum of the internal energy dissipation measured amounted to only 60% of the total energy dissipated by the specimens as measured by the net work of load. It is postulated that localized compaction of the UHPC matrix as well as internal friction between fractured fragments makes up the balance of internal energy dissipation.

关键词: ultra-high-performance concrete     concrete fracture     X-ray computed tomography     acoustic emission    

Multiple damage detection in complex bridges based on strain energy extracted from single point measurement

Alireza ARABHA NAJAFABADI, Farhad DANESHJOO, Hamid Reza AHMADI

《结构与土木工程前沿(英文)》 2020年 第14卷 第3期   页码 722-730 doi: 10.1007/s11709-020-0624-5

摘要: Strain Energy of the structure can be changed with the damage at the damage location. The accurate detection of the damage location using this index in a force system is dependent on the degree of accuracy in determining the structure deformation function before and after damage. The use of modal-based methods to identify damage in complex bridges is always associated with problems due to the need to consider the effects of higher modes and the adverse effect of operational conditions on the extraction of structural modal parameters. In this paper, the deformation of the structure was determined by the concept of influence line using the Betti-Maxwell theory. Then two damage detection indicators were developed based on strain energy variations. These indices were presented separately for bending and torsion changes. Finite element analysis of a five-span concrete curved bridge was done to validate the stated methods. Damage was simulated by decreasing stiffness at different sections of the deck. The response regarding displacement of a point on the deck was measured along each span by passing a moving load on the bridge at very low speeds. Indicators of the strain energy extracted from displacement influence line and the strain energy extracted from the rotational displacement influence line (SERIL) were calculated for the studied bridge. The results show that the proposed methods have well identified the location of the damage by significantly reducing the number of sensors required to record the response. Also, the location of symmetric damages is detected with high resolution using SERIL.

关键词: damage detection     strain energy     influence line     complex bridges     rotation displacement    

Effect of current density on groundwater arsenite removal performance using air cathode electrocoagulation

《环境科学与工程前沿(英文)》 2021年 第15卷 第6期 doi: 10.1007/s11783-021-1399-1

摘要:

• With the same charge, current density had little effect on As(III) removal in ACEC.

关键词: Electrocoagulation     Air cathode     Arsenic     Current density     Energy consumption    

Synthesis of aluminum nanoparticles as additive to enhance ignition and combustion of high energy density

Xiu-Tian-Feng E, Lei Zhang, Fang Wang, Xiangwen Zhang, Ji-Jun Zou

《化学科学与工程前沿(英文)》 2018年 第12卷 第3期   页码 358-366 doi: 10.1007/s11705-018-1702-2

摘要:

High energy density fuels are critical for hypersonic aerospace propulsion but suffer from difficulties of ignition delay and incomplete combustion. This research reports aluminum nanoparticles (Al NPs) assisted ignition and combustion of high energy density JP-10 fuel. Al NPs with a size of 16 nm were fabricated through a mild and simple method by decomposing AlH3·Et2O with the addition of a surfactant ligand. The uniform size distribution, nanoscaled size and surface ligand make Al NPs stably suspend in JP-10, with 80% NPs being dispersed in the liquid fuel after six months. A shock tube test shows that the presence of 1 wt-% Al NPs can significantly shorten ignition delay time at temperature of 1500 to 1750 K, promote the combustion, and enhance energy release of JP-10. This work demonstrates the potential of Al NPs as ignition and combustion additive for high energy density fuel in hypersonic applications.

关键词: aluminum nanoparticles     combustion     ignition     shock tube test     high energy density fuel    

Evaluation of a developed bypass viscous damper performance

Mahrad FAHIMINIA, Aydin SHISHEGARAN

《结构与土木工程前沿(英文)》 2020年 第14卷 第3期   页码 773-791 doi: 10.1007/s11709-020-0627-2

摘要: In this study, the dynamic behavior of a developed bypass viscous damper is evaluated. Bypass viscous damper has a flexible hose as an external orifice through which the inside fluid transfer from one side to the other side of the inner piston. Accordingly, the viscosity coefficient of the damper can be adjusted using geometrical dimensions of the hose. Moreover, the external orifice acts as a thermal compensator and alleviates viscous heating of the damper. According to experimental results, Computational Fluid Dynamic (CFD) model, a numerical formula and the simplified Maxwell model are found and assessed; therefore, the verification of numerical and computational models are evaluated for simulating. Also, a simplified procedure is proposed to design structures with bypass viscous dampers. The design procedure is applied to design an 8-story hospital structure with bypass viscous dampers, and it is compared with the same structure, which is designed with concentric braces and without dampers. Nonlinear time history analyses revealed that the hospital with viscous damper experiences less structural inelastic demands and fewer story accelerations which mean fewer demands on nonstructural elements. Moreover, seismic behaviors of nonstructural masonry claddings are also compared in the cases of hospital structure with and without dampers.

关键词: developed viscous damper     external orifice     energy dissipation     seismic behavior     CFD model of viscous damper     a simplified model    

Damage detection in beam-like structures using static shear energy redistribution

《结构与土木工程前沿(英文)》 2022年 第16卷 第12期   页码 1552-1564 doi: 10.1007/s11709-022-0903-4

摘要: In this study, a static shear energy algorithm is presented for the damage assessment of beam-like structures. According to the energy release principle, the strain energy of a damaged element suddenly changes when structural damage occurs. Therefore, the change in the static shear energy is employed to determine the damage locations in beam-like structures. The static shear energy is derived from the spectral factorization of the elementary stiffness matrix and structural deflection variation. The advantage of using shear energy as opposed to total energy is that only a few deflection data points of the beam structure are required during the process of damage identification. Another advantage of the proposed approach is that damage detection can be performed without establishing a structural finite-element model in advance. The proposed technique is first validated using a numerical example with single, multiple, and adjacent damage scenarios. A channel steel beam and rectangular concrete beam are employed as experimental cases to further verify the proposed approach. The results of the simulation and experiment examples indicate that the proposed algorithm provides a simple and effective method for defect localization in beam-like structures.

关键词: damage detection     beam structure     strain energy     static displacement variation     energy damage index    

Effect of strata restraint on seismic performance of prefabricated sidewall joints in fabricated subway stations

《结构与土木工程前沿(英文)》 2023年 第17卷 第5期   页码 763-779 doi: 10.1007/s11709-023-0917-6

摘要: A disadvantage of the conventional quasi-static test method is that it does not consider the soil restraint effect. A new method to test the seismic performance of prefabricated specimens for underground assembled structures is proposed, which can realistically reflect the strata restraint effect on the underground structure. Laboratory work combined with finite element (FE) analysis is performed in this study. Three full-scale sidewall specimens with different joint forms are designed and fabricated. Indices related to the seismic performance and damage modes are analyzed comprehensively to reveal the mechanism of the strata restraint effect on the prefabricated sidewall components. Test results show that the strata restraint effect effectively improves the energy dissipation capacity, load-bearing capacity, and the recoverability of the internal deformation of the precast sidewall components. However, the strata restraint effect reduces the ductility of the precast sidewall components and aggravates the shear and bending deformations in the core region of the connection joints. Additionally, the strata restraint effect significantly affects the seismic performance and damage mode of the prefabricated sidewall components. An FE model that can be used to conduct a seismic performance study of prefabricated specimens for underground assembled structures is proposed, and its feasibility is verified via comparison with test data.

关键词: underground structures     precast sidewall specimen     seismic test method     bearing capacity     energy dissipation capacity     plastic deformation    

Review on cellulose paper-based electrodes for sustainable batteries with high energy densities

《化学科学与工程前沿(英文)》 2023年 第17卷 第8期   页码 1010-1027 doi: 10.1007/s11705-023-2307-y

摘要: Powering the future, while maintaining strong socioeconomic growth and a cleaner environment, is going to be one of the biggest challenges faced by mankind nowadays. Thus, there is a transition from the use of fossil fuels to renewable energy sources. Cellulose, the main component of paper, represents a unique type of bio-based building blocks featuring exciting properties: low-cost, hierarchical fibrous structures, hydrophilicity, biocompatible, mechanical flexibility, and renewability, which make it perfect for use in paper-based sustainable energy storage devices. This review focuses on lithium-ion battery application of celluloses with cellulose at different scales, i.e., cellulose microfibers, and nanocellulose, and highlights the new trends in the field. Recent advances and approaches to construct high mass loading paper electrodes toward high energy density batteries are evaluated and the limitations of paper-based cathodes are discussed. This will stimulate the use of natural resources and thereby the development of renewable electric energy systems based on sustainable technologies with low environmental impacts and carbon footprints.

关键词: cellulose     paper electrodes     Li-ion batteries     high energy density    

Tripotassium citrate monohydrate derived carbon nanosheets as a competent assistant to manganese dioxide with remarkable performance in the supercapacitor

《化学科学与工程前沿(英文)》 2022年 第16卷 第3期   页码 420-432 doi: 10.1007/s11705-021-2065-7

摘要: Production cost, capacitance, and electrode materials safety are the key factors to be concerned about for supercapacitors. In this work, a type of carbon nanosheets was produced through the carbonization of tripotassium citrate monohydrate and nitric acidification. Subsequently, a well-designed manganese dioxide/carbon nanosheets composite was synthesized through hydrothermal treating. The carbon nanosheets served as the substrate for growing the manganese dioxide, regulating its distribution, and preventing it from inhomogeneous dimensions and severe agglomeration. Many manganese dioxide nanosheets grew vertically on the numerous functional groups generated on the surface of the carbon nanosheets during acidification. The synergistic combination of carbon nanosheets and manganese dioxide tailors the electrochemical performance of the composite, which benefits from the excellent conductivity and stability of carbon nanosheets. The carbon nanosheets derived from tripotassium citrate monohydrate are conducive to the remarkable performance of manganese dioxide/carbon nanosheets electrode. Finally, an asymmetric supercapacitor with active carbon as the cathode and manganese dioxide/carbon nanosheets as the anode was assembled, achieving an outstanding energy density of 54.68 Wh·kg–1 and remarkable power density of 6399.2 W·kg–1 superior to conventional lead-acid batteries. After 10000 charge-discharge cycles, the device retained 75.3% of the initial capacitance, showing good cycle stability. Two assembled asymmetric supercapacitors in series charged for 3 min could power a yellow light emitting diode with an operating voltage of 2 V for 2 min. This study may provide valuable insights for applying carbon materials and manganese dioxide in the energy storage field.

关键词: carbon nanosheets     manganese dioxide     asymmetric supercapacitors     energy density     power density    

高能量密度爆炸与化学爆炸的物理特征及爆炸次生洪水波效应探讨

周丰峻

《中国工程科学》 2000年 第2卷 第12期   页码 45-51

摘要:

文章根据高能量密度爆炸的辐射流体动力学计算与TNT装药爆炸计算的结果,对二类爆炸波系的形成发展,爆炸近区、远区的物理特征和爆炸作用物理模拟问题进行了研究,得出了对防护工程比较重要的几点结论。同时对于同两类爆炸引起的次生洪水波灾害进行了探讨,阐明了系统开展洪水波防护研究的重要意义。

关键词: 高能量密度爆炸     化学焊炸     冲击波     洪水波    

Behaviour of self-centring shear walls——A state of the art review

《结构与土木工程前沿(英文)》 2023年 第17卷 第1期   页码 53-77 doi: 10.1007/s11709-022-0850-0

摘要: The application of unbonded post-tensioning (PT) in structural walls has led to the development of advanced self-centring (rocking) shear wall systems that has significant advantages, including accelerated construction due to the incorporation of prefabricated elements and segmental construction for different materials (e.g., concrete, masonry, and timber), reduced residual drifts, and little damage upon extreme seismic and wind loads. Concrete, masonry, and timber are often used for the construction of unbonded PT structural wall systems. Despite extensive research since the 1980s, there are no well-established design guidelines available on the shear wall configuration with the required energy dissipation system, joint’s locations and acceptance criteria for shear sliding, confinement, seismic performance factors, PT loss, PT force range and residual drifts of shear walls subjected to lateral loads. In this research a comprehensive state-of-the-art literature review was performed on self-centring shear wall system. An extensive study was carried out to collect a database of 100 concrete, masonry, and self-centring shear wall tests from the literature. The established database was then used to review shear walls’ configurations, material, and components to benchmark requirements applicable for design purposes. The behaviour of concrete, masonry and timber shear walls were compared and critically analysed. The general behaviour, force-displacement performance of the walls, ductility, and seismic response factors, were critically reviewed and analysed for different self-centring wall systems to understand the effect of different parameters including configurations of the walls, material used for construction of the wall (concrete, masonry, timber) and axial stress ratio. The outcome of this research can be used to better understand the behaviour of self-centring wall system in order to develop design guidelines for such walls.

关键词: self-centring shear walls     rocking walls     energy dissipation     seismic performance factors     PT loss     residual drift    

标题 作者 时间 类型 操作

Tensile ratcheting behaviors of bronze powder filled polytetrafluoroethylene

Wenjuan XU, Hong GAO, LiLan GAO, Xu CHEN, Yong WANG

期刊论文

Determination of energy dissipation of a spider silk structure under impulsive loading

Jorge ALENCASTRE,Carlos MAGO,Richard RIVERA

期刊论文

A model for creep life prediction of thin tube using strain energy density as a function of stress triaxiality

Tahir MAHMOOD, Sangarapillai KANAPATHIPILLAI, Mahiuddin CHOWDHURY

期刊论文

Aseismic smart building isolation systems under multi-level earthquake excitations: Part II, energy-dissipation

Min-Ho CHEY,J. Geoffrey CHASE,John B. MANDER,Athol J. CARR

期刊论文

Experimental investigations of internal energy dissipation during fracture of fiber-reinforced ultra-high-performance

Eric N. LANDIS, Roman KRAVCHUK, Dmitry LOSHKOV

期刊论文

Multiple damage detection in complex bridges based on strain energy extracted from single point measurement

Alireza ARABHA NAJAFABADI, Farhad DANESHJOO, Hamid Reza AHMADI

期刊论文

Effect of current density on groundwater arsenite removal performance using air cathode electrocoagulation

期刊论文

Synthesis of aluminum nanoparticles as additive to enhance ignition and combustion of high energy density

Xiu-Tian-Feng E, Lei Zhang, Fang Wang, Xiangwen Zhang, Ji-Jun Zou

期刊论文

Evaluation of a developed bypass viscous damper performance

Mahrad FAHIMINIA, Aydin SHISHEGARAN

期刊论文

Damage detection in beam-like structures using static shear energy redistribution

期刊论文

Effect of strata restraint on seismic performance of prefabricated sidewall joints in fabricated subway stations

期刊论文

Review on cellulose paper-based electrodes for sustainable batteries with high energy densities

期刊论文

Tripotassium citrate monohydrate derived carbon nanosheets as a competent assistant to manganese dioxide with remarkable performance in the supercapacitor

期刊论文

高能量密度爆炸与化学爆炸的物理特征及爆炸次生洪水波效应探讨

周丰峻

期刊论文

Behaviour of self-centring shear walls——A state of the art review

期刊论文