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静态球对称引力场对钟和尺的影响
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作者 杨青勇 《广西师范学院学报(自然科学版)》 2003年第2期105-109,共5页
从爱因斯坦引力场方程的严格解———史瓦西解的物理解释出发 ,讨论了引力场中“钟慢”、“尺缩”效应与弯曲时空几何结构的对应关系 ,指出真实引力场对钟和尺的影响与表观引力场中的“钟慢”、“尺缩”效应有本质上的区别 .
关键词 史瓦西几何 引力效应 “钟慢” “尺缩”
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闵氏时空图在相对论教学中的应用 被引量:2
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作者 杨志万 《大学物理》 北大核心 2016年第2期27-29,59,共4页
将闵科夫斯基二维时空图应用于大学物理课程中的相对论教学,直观地揭示了狭义相对论时空观以及"尺缩钟慢"效应与"同时的相对性"的内在联系.
关键词 相对论教学 二维时空图 同时的相对性 “尺钟慢”效应 内在联系
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关于狭义相对论两种不同的长度测量方式 被引量:1
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作者 文兴吾 《物理通报》 2012年第10期101-103,共3页
分析了“尺缩效应”的导出过程及其可能引起的误解,阐述了狭义相对论关于不同惯性系对同一物体.长度测量的另一种观点,并对两种不同长度测量方式进行了比较.
关键词 狭义相对论 “尺效应” 洛伦兹变换 长度测量
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Size effects on plastic deformation behavior in micro radial compression of pure copper 被引量:4
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作者 程利东 王传杰 +2 位作者 王春举 郭斌 王振龙 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2013年第9期2686-2691,共6页
Micro radial compression tests were carried out on cylindrical specimens of pure copper polycrystals with different grain sizes. Experimental results indicated that phenomena of decreasing forming force, increasing sc... Micro radial compression tests were carried out on cylindrical specimens of pure copper polycrystals with different grain sizes. Experimental results indicated that phenomena of decreasing forming force, increasing scatter of forming force and more irregular surface topography occurred with the increase of grain size. A modified surface model based on dislocations pile-up in surface layer grains, and a flow stress scattering formulation based on standard deviation and grain size distribution were proposed to analyze size effects on forming force in micro compression. The inhomogeneous deformation of surface layer grains was discussed by the main deformation manner of rotation. A good agreement with the experimental results was achieved. 展开更多
关键词 MICRO-FORMING size effects radial compression inhomogeneous deformation scatter of forming force
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Parameter optimization for improved aerodynamic performance of louver-type wind barrier for train-bridge system 被引量:16
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作者 HE Xu-hui FANG Dong-xu +1 位作者 LI Huan SHI Kang 《Journal of Central South University》 SCIE EI CAS CSCD 2019年第1期229-240,共12页
To improve the safety of trains running in an undesirable wind environment,a novel louver-type wind barrier is proposed and further studied in this research using a scaled wind tunnel simulation with 1:40 scale models... To improve the safety of trains running in an undesirable wind environment,a novel louver-type wind barrier is proposed and further studied in this research using a scaled wind tunnel simulation with 1:40 scale models.Based on the aerodynamic performance of the train-bridge system,the parameters of the louver-type wind barrier are optimized.Compared to the case without a wind barrier,it is apparent that the wind barrier improves the running safety of trains,since the maximum reduction of the moment coefficient of the train reaches 58%using the louver-type wind barrier,larger than that achieved with conventional wind barriers(fence-type and grid-type).A louver-type wind barrier has more blade layers,and the rotation angle of the adjustable blade of the louver-type wind barrier is 90–180°(which induces the flow towards the deck surface),which is more favorable for the aerodynamic performance of the train.Comparing the 60°,90°and 120°wind fairings of the louver-type wind barrier blade,the blunt fairing is disadvantageous to the operational safety of the train. 展开更多
关键词 wind barrier aerodynamic force train-bridge system scaled wind tunnel simulation parameter optimization
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Settlement characteristics of bridge approach embankment based on scale model test 被引量:3
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作者 ZHANG Jiu-peng LIU Tao +3 位作者 PEI Jian-zhong LI Rui ZOU Dao-guang ZHANG Yu-qing 《Journal of Central South University》 SCIE EI CAS CSCD 2020年第7期1956-1964,共9页
In order to analyze the effects of backfill materials, geometries and slab setting on the settlement of bridge approach embankment, scale model was built based on the structural characteristics of bridge approach emba... In order to analyze the effects of backfill materials, geometries and slab setting on the settlement of bridge approach embankment, scale model was built based on the structural characteristics of bridge approach embankment, and scale model tests were carried out under different conditions. The results show that when graded gravels were selected as the backfill materials, the effect of setting approach slab to reduce the differential settlement is more prominent. When lime soils were selected as the backfill material, approach slab can moderate the longitudinal settlement slope. When using different backfill materials, the ultimate settlement of the positive trapezoidal backfill geometries is less than that of the inverted trapezoid, and the backfill geometries have little effect on the settlement slope. 展开更多
关键词 bridge approach EMBANKMENT scale model SETTLEMENT BACKFILL
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Experimental study on a pre-damaged scaled tunnel model strengthened with CFRP grids
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作者 李文胜 吴刚 +1 位作者 董志强 王淑莹 《Journal of Southeast University(English Edition)》 EI CAS 2017年第2期196-202,共7页
The effectiveness of carbon fiber reinforced polymer(CFRP) grids as the strengthening materials for a pre-damaged scaled tunnel model is experimentally investigated. First, the bond performances between the CFRP gri... The effectiveness of carbon fiber reinforced polymer(CFRP) grids as the strengthening materials for a pre-damaged scaled tunnel model is experimentally investigated. First, the bond performances between the CFRP grid and the concrete under different types of adhesive and surface treatment were tested. The most efficient anchoring system was adopted for the subsequent scaled tunnel strengthening. Test results show that when the epoxy structural adhesive was used as the bonding material, the failure mode was CFRP grids rupturing,and the anchorage performance was optimal. When the polymer mortar was used as the adhesive, the surface treatments with anchored bolts and grooves can improve the bond performance, and the failure mode was sliding failure with the polymer mortar peeled off. After strengthening with CFRP grids, both the stiffness and the load capacity of the pre-damaged scaled tunnel model were improved. Additionally,the results obtained by fiber bragg grating(FBG) sensors indicate that the strains across tunnel segments were reduced,and the overall performance of the tunnel was improved. 展开更多
关键词 carbon fiber reinforced polymer(CFRP) grid double-shear bond test surface treatment scaled tunnel model relative displacement
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Experimental Study on Uniaxial Compressive Strength of Reservoir Ice 被引量:4
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作者 张丽敏 李志军 +1 位作者 贾青 黄文峰 《Transactions of Tianjin University》 EI CAS 2012年第2期112-116,共5页
Uniaxial compression experiments on horizontal and ervoir were conducted at different temperatures and strain rates vertical samples of first-year freshwater ice in a res- with an electronic universal machine equipped... Uniaxial compression experiments on horizontal and ervoir were conducted at different temperatures and strain rates vertical samples of first-year freshwater ice in a res- with an electronic universal machine equipped with low temperature cabinet. The results show that there is no difference between the strengths of two horizontal samples with grain sizes ranging from 1 to 4 mm and 4 to 14 mm, while the strength of the 1--4 mm vertical samples is 1.4 times higher than that of the 4--14 mm vertical samples because of the change of crystal structure. For different load- ing directions, the strengths of the horizontal samples do not differ from those of the vertical samples with the same grain sizes. The relation among the uniaxial compressive strength, strain rate and temperature was established through data analysis in both the ductile and brittle regions. 展开更多
关键词 freshwater ice compressive strength strain rate TEMPERATURE grain size
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Experimental Evaluation of the Post-ultimate Strength Behavior of a Ship's Hull Girder in Waves 被引量:7
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作者 Kazuhiro Iijima Ryota Wada Masahiko Fujikubo 《Journal of Marine Science and Application》 2012年第1期34-43,共10页
Experimental investigations into the collapse behavior of a box-shape hull girder subjected to extreme wave-induced loads are presented.The experiment was performed using a scaled model in a tank.In the middle of the ... Experimental investigations into the collapse behavior of a box-shape hull girder subjected to extreme wave-induced loads are presented.The experiment was performed using a scaled model in a tank.In the middle of the scaled model,sacrificial specimens with circular pillar and trough shapes which respectively show different bending moment-displacement characteristics were mounted to compare the dynamic collapse characteristics of the hull girder in waves.The specimens were designed by using finite element(FE)-analysis.Prior to the tank tests,static four-point-bending tests were conducted to detect the load-carrying capacity of the hull girder.It was shown that the load-carrying capacity of a ship including reduction of the capacity after the ultimate strength can be reproduced experimentally by employing the trough type specimens.Tank tests using these specimens were performed under a focused wave in which the hull girder collapses under once and repetitive focused waves.It was shown from the multiple collapse tests that the increase rate of collapse becomes higher once the load-carrying capacity enters the reduction path while the increase rate is lower before reaching the ultimate strength. 展开更多
关键词 post-ultimate strength collapse behavior experimental evaluation load-carrying capacity hull girder
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Gravity compression forward modeling and multiscale inversion based on wavelet transform 被引量:4
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作者 Sun Si-Yuan Yin Chang-Chun +2 位作者 Gao Xiu-He Liu Yun-He Ren Xiu-Yan 《Applied Geophysics》 SCIE CSCD 2018年第2期342-352,365,共12页
The main problems in three-dimensional gravity inversion are the non-uniqueness of the solutions and the high computational cost of large data sets. To minimize the high computational cost, we propose a new sorting me... The main problems in three-dimensional gravity inversion are the non-uniqueness of the solutions and the high computational cost of large data sets. To minimize the high computational cost, we propose a new sorting method to reduce fluctuations and the high frequency of the sensitivity matrix prior to applying the wavelet transform. Consequently, the sparsity and compression ratio of the sensitivity matrix are improved as well as the accuracy of the forward modeling. Furthermore, memory storage requirements are reduced and the forward modeling is accelerated compared with uncompressed forward modeling. The forward modeling results suggest that the compression ratio of the sensitivity matrix can be more than 300. Furthermore, multiscale inversion based on the wavelet transform is applied to gravity inversion. By decomposing the gravity inversion into subproblems of different scales, the non-uniqueness and stability of the gravity inversion are improved as multiscale data are considered. Finally, we applied conventional focusing inversion and multiscale inversion on simulated and measured data to demonstrate the effectiveness of the proposed gravity inversion method. 展开更多
关键词 Wavelet transform matrix compression multiscale inversion gravity forwardmodeling
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Size effect on compressive strength of reactive powder concrete 被引量:18
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作者 AN Ming-zhe ZHANG Li-jun YI Quan-xin 《Journal of China University of Mining and Technology》 EI 2008年第2期279-282,共4页
In this paper the coefficient and law of the size effect of RPC were studied through experiments and theoretical analysis. The size-effect coefficients for the compressive strength of RPC are deduced through experimen... In this paper the coefficient and law of the size effect of RPC were studied through experiments and theoretical analysis. The size-effect coefficients for the compressive strength of RPC are deduced through experiments.They indicate that RPC without fiber behaves quite the same as normal or high strength concrete.The size effect on compressive strength is more prominent in RPC containing fiber.Bazant's size effect formula of compressive strength applies to RPC.A formula is given to predict the compressive strength of cubic RPC specimens 100 mm on a side where the fiber dosage ranges from 0-2%. 展开更多
关键词 reactive powder concrete (RPC) compressive strength size effect influence factor forecast formula
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Numerical analysis and geotechnical assessment of mine scale model 被引量:2
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作者 Khanal Manoj Adhikary Deepak Balusu Rao 《International Journal of Mining Science and Technology》 SCIE EI 2012年第5期693-698,共6页
Various numerical methods are available to model,simulate,analyse and interpret the results;however a major task is to select a reliable and intended tool to perform a realistic assessment of any problem.For a model t... Various numerical methods are available to model,simulate,analyse and interpret the results;however a major task is to select a reliable and intended tool to perform a realistic assessment of any problem.For a model to be a representative of the realistic mining scenario,a verified tool must be chosen to perform an assessment of mine roof support requirement and address the geotechnical risks associated with longwall mining.The dependable tools provide a safe working environment,increased production,efficient management of resources and reduce environmental impacts of mining.Although various methods,for example,analytical,experimental and empirical are being adopted in mining,in recent days numerical tools are becoming popular due to the advancement in computer hardware and numerical methods.Empirical rules based on past experiences do provide a general guide,however due to the heterogeneous nature of mine geology(i.e.,none of the mine sites are identical),numerical simulations of mine site specific conditions would lend better insights into some underlying issues.The paper highlights the use of a continuum mechanics based tool in coal mining with a mine scale model.The continuum modelling can provide close to accurate stress fields and deformation.The paper describes the use of existing mine data to calibrate and validate the model parameters,which then are used to assess geotechnical issues related with installing a new high capacity longwall mine at the mine site.A variety of parameters,for example,chock convergences,caveability of overlying sandstones,abutment and vertical stresses have been estimated. 展开更多
关键词 Mining Coal Chock Abutment
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A new adaptive bending method using closed loop feedback control 被引量:4
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作者 T.WELO B.GRANLY 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2010年第11期2111-2117,共7页
As the competition from companies in low cost countries increases,the need for more automated production which reduces labour cost while improving product quality is required.A new rotary compression bending set-up wi... As the competition from companies in low cost countries increases,the need for more automated production which reduces labour cost while improving product quality is required.A new rotary compression bending set-up with automated closed-loop feedback control is thus being developed.By transferring in-process measurement data into an algorithm for predicting springback and bend angle prior to the unloading sequence,the dimensional accuracy is improved.This work focuses on the development of this steering model.Since the method used does not increase cycle time,it is attractive for high-volume industrial applications.More than 150 bending tests of AA6060 extrusions were conducted to determine the capability of the technology.The results show that by activating the automated closed-loop feedback system,the dimensional accuracy of the bent parts is more than three times better than that obtained by traditional compression bending.Since the steering model permits the direct use of additional process data,such as instant wall thickness and cross sectional distortions,it is believed that extension of the measurement capabilities would improve the accuracy of the methodology even further. 展开更多
关键词 adaptive bending closed-loop feedback dimensional accuracy SPRINGBACK aluminium EXTRUSION
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Modeling investigation of geometric size effect on pervaporation dehydration through scaled-up hollow fiber NaA zeolite membranes 被引量:4
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作者 Jiacheng Wang Peng Ye +2 位作者 Xuechao Gao Yuting Zhang Xuehong Gu 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2018年第7期1477-1484,共8页
A mass transfer model in consideration of multi-layer resistances through NaA zeolite membrane and lumen pressure drop in the permeate side was developed to describe pervaporation dehydration through scaled-up hollow ... A mass transfer model in consideration of multi-layer resistances through NaA zeolite membrane and lumen pressure drop in the permeate side was developed to describe pervaporation dehydration through scaled-up hollow fiber supported NaA zeolite membrane. It was found that the transfer resistance in the lumen of the permeate side is strongly related with geometric size of hollow fiber zeolite membrane, which could not he neglected. The effect of geometric size on pervaporation dehydration could be more significant under higher vacuum pressure in the permeate side. The transfer resistance in the lumen increases with the hollow fiber length but decreases with lumen diameter. The geometric structure could be optimized in terms of the ratio of lumen diameter to membrane length. A critical value of d1/L (Rc) to achieve high permeation flux was empirically correlated with extraction pressure in the permeate side. Typically, for a hollow fiber supported NaA zeolite membrane with length of 0.40 m, the lumen diameter should be larger than 2.0 mm under the extraction pressure of 1500 Pa. 展开更多
关键词 PERVAPORATION NaA zeolite membrane Hollow fiber Lumen pressure drop Geometric parameters
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Influence of Maximum Aggregate Size on Dynamic Size Effect of Concrete Under Low Strain Rates:Meso-scale Simulations 被引量:1
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作者 JIN Liu YANG Wangxian +1 位作者 YU Wenxuan DU Xiuli 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2020年第1期27-39,共13页
This study is to explore the influence of maximum aggregate size(MAS)on the failure and corresponding size effect of concrete materials under low strain rates.The failure process of concrete was simulated by the mesos... This study is to explore the influence of maximum aggregate size(MAS)on the failure and corresponding size effect of concrete materials under low strain rates.The failure process of concrete was simulated by the mesoscale numerical method considering the internal heterogeneity of concrete and strain rate effect.Based on the mesoscale method,the failure behavior of concrete specimens with different structural sizes and MAS was investigated.Also,the influence of MAS on the failure modes,nominal strength and corresponding size effect of concrete were studied at the meso-scale.The simulation results indicated that MAS has an obvious influence on the failure modes of concrete subjected to axial compressive and tensile loads.The nominal tensile strength increased as the MAS increased,while the nominal compressive strength increased first and then decreased as the MAS increases under quasi-static load.In addition,it was found that the size effect on nominal strength of concrete would be weakened with the increase of strain rate.When the applied strain rate reached 1 s^-1,the size effect on nominal strength of concrete disappeard.Moreover,the MAS has an ignorable influence on the dynamic size effect of concrete under uniaxial compression and tension. 展开更多
关键词 CONCRETE maximum aggregate size size effect dynamic compression dynamic tension strain rate
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On Implementing a Simulated Moment of Inertia in a Reduced Scale Brake Dynamometer
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作者 Georg-Peter Ostermeyer Stephan Raczek 《Journal of Mechanics Engineering and Automation》 2017年第4期180-185,共6页
This paper describes the implementation of brake procedures with simulated inertia on a reduced scale brake dynamometer For this purpose, the theoretical foundations are first explained, and test measurements are carr... This paper describes the implementation of brake procedures with simulated inertia on a reduced scale brake dynamometer For this purpose, the theoretical foundations are first explained, and test measurements are carried out. The results show good agreement between calculated and measured accelerations during brake applications. Furthermore, braking processes with various driver models were carried out using associated normal force functions, and examined with regard to their coefficients of friction. A clear difference between these models can be observed. This introduces the possibility for new measurement methods for the analysis of NVH-behavior in brake systems. This work is the first step towards identifying a transfer function between full- and reduced-scale brake dynamometers. In a second step, the temperature scaling must be taken into account. Based on these results, it is possible to isolate the influences of the braking system components from those of the dynamics of the friction coefficient in the boundary layer. 展开更多
关键词 BRAKE simulated inertia friction tribometer.
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Compressibility induced bubble size variation in bubble column reactors:Simulations by the CFD–PBE
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作者 Dongyue Li Zhipeng Li Zhengming Gao 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2018年第10期2009-2013,共5页
Bubble column reactors can be simulated by the two fluid model(TFM) coupled with the population balance equation(PBE). For the large industrial bubble columns, the compressibility due to the pressure difference may in... Bubble column reactors can be simulated by the two fluid model(TFM) coupled with the population balance equation(PBE). For the large industrial bubble columns, the compressibility due to the pressure difference may introduce notable bubble size variation. In order to address the compressibility effect, the PBE should be reformulated and coupled with the compressible TFM. In this work, the PBE with a compressibility term was formulated from single bubble dynamics, the mean Sauter diameters predicted by the compressible TFM coupled with the PBE were compared with the analytical solutions obtained by the ideal gas law. It was proven that the mesoscale formulations presented in this work were physically consistent with the macroscale modeling. It can be used to simulate large industrial plants when the compressibility induced bubble size variation is important. 展开更多
关键词 Bubble column reactors Computational fluid dynamics Population balance equation COMPRESSIBILITY
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Size effect of confined concrete subjected to axial compression 被引量:4
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作者 李振宝 宋佳 +1 位作者 杜修力 杨修广 《Journal of Central South University》 SCIE EI CAS 2014年第3期1217-1226,共10页
In order to investigate the size effect and other effects on the stress-strain relationship of confined concrete, 42 specimens with different sizes and section shapes were placed under axial compression loading. Effec... In order to investigate the size effect and other effects on the stress-strain relationship of confined concrete, 42 specimens with different sizes and section shapes were placed under axial compression loading. Effects of key parameters such as size of specimens, tie configuration, transverse reinforcement ratio, and concrete cover were studied. The results show that for specimens with the same configuration and the same volumetric ratio of the transverse reinforcement, along with the increasing specimen size, the peak stress, peak strain and deformation of the post-peak show a down trend, however, the volumetric ratio of the transverse reinforcement is lowered, the decreasing of the peak stress is accelerated, but the decreasing of the deformation is slow down. For specimens with the same volumetric ratio but different configurations of transverse reinforcement, though the transverse reinforcement configuration becomes more complicated, the peak stress of the large size specimen does not improve more than that of the small size. However, the deformation occurs before the stress declines to 85% of peak stress, and the improvement with the grid pattern tie configuration is much greater due to size effect. 展开更多
关键词 confined concrete mechanical property size effect configuration type of transverse reinforcement volumetric ratio oftransverse reinforcement concrete cover
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Modeling on dynamic recrystallization of aluminium alloy 7050 during hot compression based on cellular automaton 被引量:6
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作者 李军超 谢志远 +1 位作者 李松蒲 臧艳艳 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第3期497-507,共11页
The dynamic recrystallization(DRX) process of hot compressed aluminium alloy 7050 was predicted using cellular automaton(CA) combined with topology deformation. The hot deformatation characteristics of aluminium alloy... The dynamic recrystallization(DRX) process of hot compressed aluminium alloy 7050 was predicted using cellular automaton(CA) combined with topology deformation. The hot deformatation characteristics of aluminium alloy 7050 were investigated by hot uniaxial compression tests in order to obtain the material parameters used in the CA model. The influences of process parameters(strain, strain rate and temperature) on the fraction of DRX and the average recrystallization grain(R-grain) size were investigated and discussed. It is found that larger stain, higher temperature and lower strain rate(less than 0.1 s^(–1)) are beneficial to the increasing fraction of DRX. And the deformation temperature affects the mean R-grain size much more greatly than other parameters. It is also noted that there is a critical strain for the occurrence of DRX which is related to strain rate and temperature. In addition, it is shown that the CA model with topology deformation is able to simulate the microstructural evolution and the flow behavior of aluminium alloy 7050 material under various deformation conditions. 展开更多
关键词 cellular automaton dynamic recrystallization aluminium alloy 7050 flow stress
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Miniature Actuators and Scaling Effect
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作者 Tatiana Kelemenova Michal Kelemen 《Journal of Mechanics Engineering and Automation》 2013年第6期393-396,共4页
The paper deals with miniature actuators and scaling effect, which occurs in using of these actuators. Scaling effect describes how much decreased performance in miniaturized actuator is. Scaling effect law helps to m... The paper deals with miniature actuators and scaling effect, which occurs in using of these actuators. Scaling effect describes how much decreased performance in miniaturized actuator is. Scaling effect law helps to make perfect decision for right type of actuator. This analysis should be as the first strategic step for actuator selection. Research in area of in-pipe machine shows that scaling effect in both used actuator types (electromagnetic and piezoelectric) is the same. Passive forces cannot be neglected, because of their values, which are comparable with active forces in system. There is a potential risk, that designed system will have bigger passive forces than active forces and system cannot fulfill requirements. Energy sources selection has also important role in system design with respecting the energy requirements of selected actuator. Consequently, energy balance is also important viewpoint for actuator selection. 展开更多
关键词 ACTUATOR MECHATRONICS scale effect.
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