The evaluation system of aircraft noise and environment noise should be integrated, because aircraft noise belongs to environment noise. At the same time, there should be some difference in the evaluation system of ai...The evaluation system of aircraft noise and environment noise should be integrated, because aircraft noise belongs to environment noise. At the same time, there should be some difference in the evaluation system of aircraft noise. For solving this contradiction, this article puts forward a new evaluation system of aircraft noise. This new system unifies the evaluation of aircraft noise and other environment noise effectively, and adds a new evaluation index single event noise exposure level. The system not only considers the characteristics of aircraft noise, which is different from other traffic noise, but also adds aircraft noise to other traffic noise, which can reflect sound environment around airport really. This system has practical worthiness and theory significance.展开更多
Comfort levels on modern superyachts have recently been the object of specific attention of the most important Classification Societies, which issued new rules and regulations for evaluating noise and vibration maximu...Comfort levels on modern superyachts have recently been the object of specific attention of the most important Classification Societies, which issued new rules and regulations for evaluating noise and vibration maximum levels. These rules are named "Comfort Class Rules" and set the general criteria for noise and vibration measurements in different vessels' areas, as well as the maximum noise and vibration limit values. As far as the vibration assessment is concerned, the Comfort Class Rules follow either the ISO 6954:1984 standard or the ISO 6954:2000. After an introduction to these relevant standards, the authors herein present a procedure developed to predict the vibration levels on ships. This procedure builds on finite element linear dynamic analysis and is applied to predict the vibration levels on a 60 m superyacht considered as a case study. The results of the numerical simulations are then benchmarked against experimental data acquired during the sea trial of the vessel. This analysis also allows the authors to evaluate the global damping ratio to be used by designers in the vibration analysis of superyachts.展开更多
The safety and the fatigue comfort were compared between a domestic and a Japanese postal bicycle. Firstly, the fatigue comfort of these two kinds of bicycles was evaluated by surface electromyographic signal (sEMG) e...The safety and the fatigue comfort were compared between a domestic and a Japanese postal bicycle. Firstly, the fatigue comfort of these two kinds of bicycles was evaluated by surface electromyographic signal (sEMG) experiment, in which human lower limb muscle groups were research objects, and the average EMG (AEMG) index and median frequency (MF) were chosen as the evaluation indexes. Secondly, the safety of these two kinds of bicycle frames was analyzed and compared by using the finite element analysis. The results show that the riding fatigue comfort of the Japanese postal bicycle is better, and the Japanese postal bicycle frame is more safe and reasonable although both the postal bicycles meet the requirement for strength. Finally, based on the above analysis, the frame structure and related parameters of the domestic postal bicycle were improved with reference to the Japanese postal bicycle and biomechanics theory.展开更多
This paper presents an analytical scheme for predicting the collapse strength of a flexible pipe, which considers the structural interaction between relevant layers. The analytical results were compared with a FEA mod...This paper presents an analytical scheme for predicting the collapse strength of a flexible pipe, which considers the structural interaction between relevant layers. The analytical results were compared with a FEA model and a number of test data, and showed reasonably good agreement. The theoretical analysis showed that the pressure armor layer enhanced the strength of the carcass against buckling, though the barrier weakened this effect. The collapse strength of pipe was influenced by many factors such as the inner radius of the pipe, the thickness of the layers and the mechanical properties of the materials. For example, an increase in the thickness of the barrier will increase contact pressure and in turn reduce the critical pressure.展开更多
Based on the upper bound of limit analysis, the plane-strain analysis of the slopes reinforced with a row of piles to the 3D case was extended. A 3D rotational failure mechanism was adopted to yield the upper bound of...Based on the upper bound of limit analysis, the plane-strain analysis of the slopes reinforced with a row of piles to the 3D case was extended. A 3D rotational failure mechanism was adopted to yield the upper bound of the factor of safety. Parametric studies were carried out to explore the end effects of the slope failures and the effects of the pile location and diameter on the safety of the reinforced slopes. The results demonstrate that the end effects nearly have no effects on the most suitable location of the installed piles but have significant influence on the safety of the slopes. For a slope constrained to a narrow width, the slope becomes more stable owing to the contribution of the end effects. When the slope is reinforced with a row of piles in small space between piles, the effects of group piles are significant for evaluating the safety of slopes. The presented method is more appropriate for assessing the stability of slopes reinforced with piles and can be also utilized in the design of plies stabilizing the unstable slopes.展开更多
The reinforcement effect of a reconstruction scheme for a steel factory building was investigated using finite element method and dynamic performance test. The workshop concerned is a portal frame structure with four ...The reinforcement effect of a reconstruction scheme for a steel factory building was investigated using finite element method and dynamic performance test. The workshop concerned is a portal frame structure with four spans and two slope roofs, of which ten columns need cutting for expanding span. The design and reconstruction project of column-cut supported by joist were introduced, which includes column reinforcement, connection rebuilding between brackets and crane beams, and the changing of rigid joint into hinge joint. The construction scheme was put forward in the light of the characteristics of the reinforcement and reconstruction. Spot test of dynamic performance on the workshop and comparison with theoretical analysis results show that the column-cut supported by joist design is effective and the reconstruction project is successful.展开更多
The financial comprehensive evaluation of listed company is a grey problem. In this paper, a grey relational analysis method is used to evaluate the financial situation of listed companies. A grey relational evaluatio...The financial comprehensive evaluation of listed company is a grey problem. In this paper, a grey relational analysis method is used to evaluate the financial situation of listed companies. A grey relational evaluation model is set up and studied practically, and then a conclusion about the order of the comprehensive financial situation of these six listed companies is drawn. This analysis method is flexible and can avoid the disadvantages of evaluating financial situation from only one aspect in the past.展开更多
The purpose of this paper is to present and evaluate a method of free gait generation for HITCRI,a hexapod walking robot.The HITCR-I is designed as a modularized structure of legs that is based upon a four-bar linkage...The purpose of this paper is to present and evaluate a method of free gait generation for HITCRI,a hexapod walking robot.The HITCR-I is designed as a modularized structure of legs that is based upon a four-bar linkage mechanism and with force sensors in the tip of legs,distributed hardware structure and a modular software structure of the control system.Based on a set of local rules between adjacent legs,finite state machine(FSM) model is built to control the coordination of legs.An automatic smooth transition of gait pattern is achieved through deriving the mathematical relation between gait pattern and locomotion parameters.The disordered inter-leg phase sequence is adjusted to a regular state smoothly and quickly by the local rules based FSM,and the gait pattern can transform automatically adapting to irregular terrain.The experiment on HITCR-I has demonstrated that it can walk through irregular terrain reliably and expeditiously with the free gait controller designed in this paper.展开更多
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
Extended finite element method (XFEM) implementation of the interaction integral methodology for evaluating the stress intensity factors (SIF) of the mixed-mode crack problem is presented. A discontinuous function...Extended finite element method (XFEM) implementation of the interaction integral methodology for evaluating the stress intensity factors (SIF) of the mixed-mode crack problem is presented. A discontinuous function and the near-tip asymptotic function are added to the classic finite element approximation to model the crack behavior. Two-state integral by the superposition of actual and auxiliary fields is derived to calculate the SIFs. Applications of the proposed technique to the inclined centre crack plate with inclined angle from 0° to 90° and slant edge crack plate with slant angle 45°, 67.5° and 90° are presented, and comparisons are made with closed form solutions. The results show that the proposed method is convenient, accurate and computationallv efficient.展开更多
In this work we show the influence of the edge-effect on the electric field distribution and, hence, on the inner and outer capacitance in an inclined-plate capacitor system surrounded by an insulating medium taking i...In this work we show the influence of the edge-effect on the electric field distribution and, hence, on the inner and outer capacitance in an inclined-plate capacitor system surrounded by an insulating medium taking into account the thickness of the conducting plates for a complete set of dimensions and insulating characteristics. Where available, we compare our results with previously published works. Finally, using statistical tools, we obtain approximate expression for computing the relationship between capacitance and insulation material characteristics, insulation gap, plate dimensions and angle.展开更多
The analysis used simple finite elements is performed to simulate the tensile behavior of corroded reinforcing bars extracted from three actual concrete structures. The cross-sectional area of the elements is set to h...The analysis used simple finite elements is performed to simulate the tensile behavior of corroded reinforcing bars extracted from three actual concrete structures. The cross-sectional area of the elements is set to have the actual distribution measured by 3D laser scanner system. The variable factor in the analysis is the length of the elements. The analysis results show that the length of the elements has a major influence on the deformation capacity after yielding. The calculated stress-strain curves, obtained using the elements with a length that is 2 times the bar diameter, are in good agreement with the tensile test results. The calculated stress-strain curves are modeled using a bi-linear model to facilitate the FEA (finite element analysis) of an overall concrete structure. From the analysis results, both the tensile and yield strengths decrease in proportion to the reduction of the minimum cross-sectional area of corroded bars. The ultimate strain has a remarkable decrement as the reduction of the minimum cross-sectional area. Formulas for determining these values are proposed as a function of the decrement ratio of the minimum cross-sectional area of a corroded bar.展开更多
Abstract: In a test-fixture that the authors were using, steel tabs adhesively bonded to an aluminum panel debonded before the design load on the real test panel was fully applied. Therefore, studying behavior of adh...Abstract: In a test-fixture that the authors were using, steel tabs adhesively bonded to an aluminum panel debonded before the design load on the real test panel was fully applied. Therefore, studying behavior of adhesive joints for joining dissimilar materials was deemed to be necessary. To determine the failure load responsible for debonding of adhesive joints of two dissimilar materials, stress distributions in adhesive joints as obtained by a nonlinear finite element model of the test-fixture were studied under a gradually increasing compression-shear load. It was observed that in-plane stresses were responsible for the debonding of the steel tabs. To achieve a better understanding of adhesive joints of dissimilar materials, finite element models of adhesive lap joints and ADCB (asymmetric double cantilever beam) were studied, under loadings similar to the loading faced by the test-fixture. The analysis was performed using ABAQUS, a commercially available software, and the cohesive zone modeling was used to study the debonding growth.展开更多
The seismic behavior of the bedrock foundation during earthquakes concerns the stability and safety of nuclear power plants. Discontinuities like joints and faults existing in rock masses affect significantly the dyna...The seismic behavior of the bedrock foundation during earthquakes concerns the stability and safety of nuclear power plants. Discontinuities like joints and faults existing in rock masses affect significantly the dynamic behavior of bedrock. The dynamic FEM (finite element method) has been commonly utilized to analyze the seismic responses of bedrock, however, it cannot well represent the large deformation behavior of discontinuities. The DEM (distinct element method) has a better capability of simulating the sliding and separation of discontinuities existing in the bedrock, which influence the propagation of seismic waves. In this study, the dynamic FEM and DEM simulations were carried out to investigate the seismic behavior of the bedrock foundation under a nuclear power plant, and the differences between those two methods were illuminated. Numerical simulation results indicate that the FEM underestimates the attenuation effect of faults on the propagation of seismic waves. With the capability of simulating large deformation behavior of discontinuities, the DEM can be regarded as a better method for studying the seismic responses of bedrock foundation which contains discontinuities.展开更多
文摘The evaluation system of aircraft noise and environment noise should be integrated, because aircraft noise belongs to environment noise. At the same time, there should be some difference in the evaluation system of aircraft noise. For solving this contradiction, this article puts forward a new evaluation system of aircraft noise. This new system unifies the evaluation of aircraft noise and other environment noise effectively, and adds a new evaluation index single event noise exposure level. The system not only considers the characteristics of aircraft noise, which is different from other traffic noise, but also adds aircraft noise to other traffic noise, which can reflect sound environment around airport really. This system has practical worthiness and theory significance.
文摘Comfort levels on modern superyachts have recently been the object of specific attention of the most important Classification Societies, which issued new rules and regulations for evaluating noise and vibration maximum levels. These rules are named "Comfort Class Rules" and set the general criteria for noise and vibration measurements in different vessels' areas, as well as the maximum noise and vibration limit values. As far as the vibration assessment is concerned, the Comfort Class Rules follow either the ISO 6954:1984 standard or the ISO 6954:2000. After an introduction to these relevant standards, the authors herein present a procedure developed to predict the vibration levels on ships. This procedure builds on finite element linear dynamic analysis and is applied to predict the vibration levels on a 60 m superyacht considered as a case study. The results of the numerical simulations are then benchmarked against experimental data acquired during the sea trial of the vessel. This analysis also allows the authors to evaluate the global damping ratio to be used by designers in the vibration analysis of superyachts.
基金Supported by Special Fund Project for Technology Innovation of Tianjin (No.10FDZDGX00500)Tianjin Product Quality Inspection Technology Research Institute
文摘The safety and the fatigue comfort were compared between a domestic and a Japanese postal bicycle. Firstly, the fatigue comfort of these two kinds of bicycles was evaluated by surface electromyographic signal (sEMG) experiment, in which human lower limb muscle groups were research objects, and the average EMG (AEMG) index and median frequency (MF) were chosen as the evaluation indexes. Secondly, the safety of these two kinds of bicycle frames was analyzed and compared by using the finite element analysis. The results show that the riding fatigue comfort of the Japanese postal bicycle is better, and the Japanese postal bicycle frame is more safe and reasonable although both the postal bicycles meet the requirement for strength. Finally, based on the above analysis, the frame structure and related parameters of the domestic postal bicycle were improved with reference to the Japanese postal bicycle and biomechanics theory.
文摘This paper presents an analytical scheme for predicting the collapse strength of a flexible pipe, which considers the structural interaction between relevant layers. The analytical results were compared with a FEA model and a number of test data, and showed reasonably good agreement. The theoretical analysis showed that the pressure armor layer enhanced the strength of the carcass against buckling, though the barrier weakened this effect. The collapse strength of pipe was influenced by many factors such as the inner radius of the pipe, the thickness of the layers and the mechanical properties of the materials. For example, an increase in the thickness of the barrier will increase contact pressure and in turn reduce the critical pressure.
基金Projects(51278382,51479050)supported by the National Natural Science Foundation of ChinaProject(2015CB057901)supported by the National Key Basic Research Program of China+3 种基金Project(201501035-03)supported by the Public Service Sector R&D Project of Ministry of Water Resource of ChinaProject(2014B06814)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(B13024)supported by the"111"ProjectProject(YK913004)supported by the Open Foundation of Key Laboratory of Failure Mechanism and Safety Control Techniques of Earthrock Dam of the Ministry of Water Resources,China
文摘Based on the upper bound of limit analysis, the plane-strain analysis of the slopes reinforced with a row of piles to the 3D case was extended. A 3D rotational failure mechanism was adopted to yield the upper bound of the factor of safety. Parametric studies were carried out to explore the end effects of the slope failures and the effects of the pile location and diameter on the safety of the reinforced slopes. The results demonstrate that the end effects nearly have no effects on the most suitable location of the installed piles but have significant influence on the safety of the slopes. For a slope constrained to a narrow width, the slope becomes more stable owing to the contribution of the end effects. When the slope is reinforced with a row of piles in small space between piles, the effects of group piles are significant for evaluating the safety of slopes. The presented method is more appropriate for assessing the stability of slopes reinforced with piles and can be also utilized in the design of plies stabilizing the unstable slopes.
基金Supported by Program for New Century Excellent Talents in University (No. NCET-06-0228)
文摘The reinforcement effect of a reconstruction scheme for a steel factory building was investigated using finite element method and dynamic performance test. The workshop concerned is a portal frame structure with four spans and two slope roofs, of which ten columns need cutting for expanding span. The design and reconstruction project of column-cut supported by joist were introduced, which includes column reinforcement, connection rebuilding between brackets and crane beams, and the changing of rigid joint into hinge joint. The construction scheme was put forward in the light of the characteristics of the reinforcement and reconstruction. Spot test of dynamic performance on the workshop and comparison with theoretical analysis results show that the column-cut supported by joist design is effective and the reconstruction project is successful.
文摘The financial comprehensive evaluation of listed company is a grey problem. In this paper, a grey relational analysis method is used to evaluate the financial situation of listed companies. A grey relational evaluation model is set up and studied practically, and then a conclusion about the order of the comprehensive financial situation of these six listed companies is drawn. This analysis method is flexible and can avoid the disadvantages of evaluating financial situation from only one aspect in the past.
基金Supported by the National High Technology Research and Development Programme of China(No.2007AA041550)the National NaturalScience Foundation of China(No.51105101)
文摘The purpose of this paper is to present and evaluate a method of free gait generation for HITCRI,a hexapod walking robot.The HITCR-I is designed as a modularized structure of legs that is based upon a four-bar linkage mechanism and with force sensors in the tip of legs,distributed hardware structure and a modular software structure of the control system.Based on a set of local rules between adjacent legs,finite state machine(FSM) model is built to control the coordination of legs.An automatic smooth transition of gait pattern is achieved through deriving the mathematical relation between gait pattern and locomotion parameters.The disordered inter-leg phase sequence is adjusted to a regular state smoothly and quickly by the local rules based FSM,and the gait pattern can transform automatically adapting to irregular terrain.The experiment on HITCR-I has demonstrated that it can walk through irregular terrain reliably and expeditiously with the free gait controller designed in this paper.
基金Supported by the Ministry of Education, Science, Sports, and Culture, Grant-in-aid for Scientific Research (A), (23246150), 2011
文摘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.
基金Projects(41172244,41072224) supported by the National Natural Science Foundation of ChinaProject(2009GGJS-037) supported by the Foundation of Youths Key Teacher by the Henan Educational Committee,China
文摘Extended finite element method (XFEM) implementation of the interaction integral methodology for evaluating the stress intensity factors (SIF) of the mixed-mode crack problem is presented. A discontinuous function and the near-tip asymptotic function are added to the classic finite element approximation to model the crack behavior. Two-state integral by the superposition of actual and auxiliary fields is derived to calculate the SIFs. Applications of the proposed technique to the inclined centre crack plate with inclined angle from 0° to 90° and slant edge crack plate with slant angle 45°, 67.5° and 90° are presented, and comparisons are made with closed form solutions. The results show that the proposed method is convenient, accurate and computationallv efficient.
文摘In this work we show the influence of the edge-effect on the electric field distribution and, hence, on the inner and outer capacitance in an inclined-plate capacitor system surrounded by an insulating medium taking into account the thickness of the conducting plates for a complete set of dimensions and insulating characteristics. Where available, we compare our results with previously published works. Finally, using statistical tools, we obtain approximate expression for computing the relationship between capacitance and insulation material characteristics, insulation gap, plate dimensions and angle.
文摘The analysis used simple finite elements is performed to simulate the tensile behavior of corroded reinforcing bars extracted from three actual concrete structures. The cross-sectional area of the elements is set to have the actual distribution measured by 3D laser scanner system. The variable factor in the analysis is the length of the elements. The analysis results show that the length of the elements has a major influence on the deformation capacity after yielding. The calculated stress-strain curves, obtained using the elements with a length that is 2 times the bar diameter, are in good agreement with the tensile test results. The calculated stress-strain curves are modeled using a bi-linear model to facilitate the FEA (finite element analysis) of an overall concrete structure. From the analysis results, both the tensile and yield strengths decrease in proportion to the reduction of the minimum cross-sectional area of corroded bars. The ultimate strain has a remarkable decrement as the reduction of the minimum cross-sectional area. Formulas for determining these values are proposed as a function of the decrement ratio of the minimum cross-sectional area of a corroded bar.
文摘Abstract: In a test-fixture that the authors were using, steel tabs adhesively bonded to an aluminum panel debonded before the design load on the real test panel was fully applied. Therefore, studying behavior of adhesive joints for joining dissimilar materials was deemed to be necessary. To determine the failure load responsible for debonding of adhesive joints of two dissimilar materials, stress distributions in adhesive joints as obtained by a nonlinear finite element model of the test-fixture were studied under a gradually increasing compression-shear load. It was observed that in-plane stresses were responsible for the debonding of the steel tabs. To achieve a better understanding of adhesive joints of dissimilar materials, finite element models of adhesive lap joints and ADCB (asymmetric double cantilever beam) were studied, under loadings similar to the loading faced by the test-fixture. The analysis was performed using ABAQUS, a commercially available software, and the cohesive zone modeling was used to study the debonding growth.
文摘The seismic behavior of the bedrock foundation during earthquakes concerns the stability and safety of nuclear power plants. Discontinuities like joints and faults existing in rock masses affect significantly the dynamic behavior of bedrock. The dynamic FEM (finite element method) has been commonly utilized to analyze the seismic responses of bedrock, however, it cannot well represent the large deformation behavior of discontinuities. The DEM (distinct element method) has a better capability of simulating the sliding and separation of discontinuities existing in the bedrock, which influence the propagation of seismic waves. In this study, the dynamic FEM and DEM simulations were carried out to investigate the seismic behavior of the bedrock foundation under a nuclear power plant, and the differences between those two methods were illuminated. Numerical simulation results indicate that the FEM underestimates the attenuation effect of faults on the propagation of seismic waves. With the capability of simulating large deformation behavior of discontinuities, the DEM can be regarded as a better method for studying the seismic responses of bedrock foundation which contains discontinuities.