Aiming at the characteristics of multi-stage and(extremely)small samples of the identification problem of key effectiveness indexes of weapon equipment system-of-systems(WESoS),a Bayesian intelligent identification an...Aiming at the characteristics of multi-stage and(extremely)small samples of the identification problem of key effectiveness indexes of weapon equipment system-of-systems(WESoS),a Bayesian intelligent identification and inference model for system effectiveness assessment indexes based on dynamic grey incidence is proposed.The method uses multi-layer Bayesian techniques,makes full use of historical statistics and empirical information,and determines the Bayesian estima-tion of the incidence degree of indexes,which effectively solves the difficulties of small sample size of effectiveness indexes and difficulty in obtaining incidence rules between indexes.Sec-ondly,The method quantifies the incidence relationship between evaluation indexes and combat effectiveness based on Bayesian posterior grey incidence,and then identifies key system effec-tiveness evaluation indexes.Finally,the proposed method is applied to a case of screening key effectiveness indexes of a missile defensive system,and the analysis results show that the proposed method can fuse multi-moment information and extract multi-stage key indexes,and has good data extraction capability in the case of small samples.展开更多
Failure mode and effect analysis(FMEA)is a preven-tative risk evaluation method used to evaluate and eliminate fail-ure modes within a system.However,the traditional FMEA method exhibits many deficiencies that pose ch...Failure mode and effect analysis(FMEA)is a preven-tative risk evaluation method used to evaluate and eliminate fail-ure modes within a system.However,the traditional FMEA method exhibits many deficiencies that pose challenges in prac-tical applications.To improve the conventional FMEA,many modified FMEA models have been suggested.However,the majority of them inadequately address consensus issues and focus on achieving a complete ranking of failure modes.In this research,we propose a new FMEA approach that integrates a two-stage consensus reaching model and a density peak clus-tering algorithm for the assessment and clustering of failure modes.Firstly,we employ the interval 2-tuple linguistic vari-ables(I2TLVs)to express the uncertain risk evaluations provided by FMEA experts.Then,a two-stage consensus reaching model is adopted to enable FMEA experts to reach a consensus.Next,failure modes are categorized into several risk clusters using a density peak clustering algorithm.Finally,the proposed FMEA is illustrated by a case study of load-bearing guidance devices of subway systems.The results show that the proposed FMEA model can more easily to describe the uncertain risk information of failure modes by using the I2TLVs;the introduction of an endogenous feedback mechanism and an exogenous feedback mechanism can accelerate the process of consensus reaching;and the density peak clustering of failure modes successfully improves the practical applicability of FMEA.展开更多
Random dynamic responses caused by the uncertainty of structural parameters of the coupled train-ballasted track-subgrade system under train loading can pose safety concerns to the train operation.This paper introduce...Random dynamic responses caused by the uncertainty of structural parameters of the coupled train-ballasted track-subgrade system under train loading can pose safety concerns to the train operation.This paper introduced a computational model for analyzing probabilistic dynamic responses of three-dimensional(3D)coupled train-ballasted track-subgrade system(TBTSS),where the coupling effects of uncertain rail irregularities,stiffness and damping properties of ballast and subgrade layers were simultaneously considered.The number theoretical method(NTM)was employed to design discrete points for the multi-dimensional stochastic parameters.The time-histories of stochastic dynamic vibrations of the TBSS with systematically uncertain structural parameters were calculated accurately and efficiently by employing the probability density evolution method(PDEM).The model-predicted results were consistent with those by the Monte Carlo simulation method.A sensitivity study was performed to assess the relative importance of those uncertain structural parameters,based on which a case study was presented to explore the stochastic probability evolution mechanism of such train-ballasted track-subgrade system.展开更多
The microscopic response characteristics of nuclear magnetic resonance(NMR) are widely used for characterizing complex pore structures of rocks. Due to the prohibitive NMR experiment cost, numerical simulation was emp...The microscopic response characteristics of nuclear magnetic resonance(NMR) are widely used for characterizing complex pore structures of rocks. Due to the prohibitive NMR experiment cost, numerical simulation was employed as an alternative approach to verify some theoretical aspects of NMR responses. Firstly, the basic principles of pore-scale NMR simulation based on random-walk method(RWM) were introduced. The RWM-simulated results were benchmarked with the analytical results for an ideal spherical pore model. Then, the effects of two numerical parameters, namely diffusion radius and walk numbers, were studied on the simulation accuracy. The simulation method is then applied to various pore models with different pore sizes and pore shapes filled with different fluids to study the microscopic NMR response characteristics. The numerical experiments are useful for understanding and interpreting NMR measurements and the simulation code provides a numerical tool to perform pixel-based digital rock analysis.展开更多
Depending on the numerical test approach on a computer, the relationships among relevant parameters, eg branch number, node number, mesh number, computation accuracy, preliminary value of airflow rate, iteration numbe...Depending on the numerical test approach on a computer, the relationships among relevant parameters, eg branch number, node number, mesh number, computation accuracy, preliminary value of airflow rate, iteration number, computation time and convergence in a mine ventilation network analysis, were investigated based on 5 mine ventilation systems. The results show that a higher computation accuracy greatly influences the iteration number. When the accuracy reaches 10-6m3·s-1 for solving a complicated mine ventilation network, the running time is too long though a high-speed computer is used. The preliminary value of airflow rate in the range of 1100m3·s-1 has little effects the iteration number. The structure of network also has some effect on the iteration number.展开更多
To evaluate the effectiveness of weapon systems, the advantages and disadvantages of grey relational analysis and TOPSIS for multiattribute decision-making is pointed out, and an effectiveness evaluation model of weap...To evaluate the effectiveness of weapon systems, the advantages and disadvantages of grey relational analysis and TOPSIS for multiattribute decision-making is pointed out, and an effectiveness evaluation model of weapon systems by combining grey relational analysis and TOPSIS is proposed. The model aggregates the grey relational grade and the distance to a new integrated closeness and reflects not only the trend but also the situation of the alternative. The example illuminates that the model is effective for the effectiveness evaluation of weapon systems.展开更多
Higher-order shear and normal deformation theory is used in this paper to account thickness stretching effect for free vibration analysis of the cylindrical micro/nano shell subjected to an applied voltage and uniform...Higher-order shear and normal deformation theory is used in this paper to account thickness stretching effect for free vibration analysis of the cylindrical micro/nano shell subjected to an applied voltage and uniform temperature rising.Size dependency is included in governing equations based on the modified couple stress theory.Hamilton’s principle is used to derive governing equations of the cylindrical micro/nano shell.Solution procedure is developed using Navier technique for simply-supported boundary conditions.The numerical results are presented to investigate the effect of significant parameters such as some dimensionless geometric parameters,material properties,applied voltages and temperature rising on the free vibration responses.展开更多
The parameter sensitivities affecting the flutter speed of the NREL （National Renewable Energy Laboratory） 5-MW baseline HAWT （horizontal axis wind turbine） blades are analyzed. An aeroelastic model, which compris...The parameter sensitivities affecting the flutter speed of the NREL （National Renewable Energy Laboratory） 5-MW baseline HAWT （horizontal axis wind turbine） blades are analyzed. An aeroelastic model, which comprises an aerodynamic part to calculate the aerodynamic loads and a structural part to determine the structural dynamic responses, is established to describe the classical flutter of the blades. For the aerodynamic part, Theodorsen unsteady aerodynamics model is used. For the structural part, Lagrange’s equation is employed. The flutter speed is determined by introducing “V–g” method to the aeroelastic model, which converts the issue of classical flutter speed determination into an eigenvalue problem. Furthermore, the time domain aeroelastic response of the wind turbine blade section is obtained with employing Runge-Kutta method. The results show that four cases （i.e., reducing the blade torsional stiffness, moving the center of gravity or the elastic axis towards the trailing edge of the section, and placing the turbine in high air density area） will decrease the flutter speed. Therefore, the judicious selection of the four parameters （the torsional stiffness, the chordwise position of the center of gravity, the elastic axis position and air density） can increase the relative inflow speed at the blade section associated with the onset of flutter.展开更多
When the tunnel underpasses through the building,it will cause deformation and even damage to the buildings above,and the deformation of building foundation is the key to building safety.Based on the engineering case,...When the tunnel underpasses through the building,it will cause deformation and even damage to the buildings above,and the deformation of building foundation is the key to building safety.Based on the engineering case,the theoretical analysis was employed to evaluate the influence of shield tunnel underpass construction on the stability of the building,and the optimal tunneling parameters in the field construction have been obtained through the verified theoretical model and parameter analysis.First,the strip foundation of the building was simplified to the Timoshenko beam,which was taken into account the shear effect,and then the deformation displacement of the soil at the same place of strip foundation was applied to the simplified Timoshenko beam.Finally,the numerical solution of the displacement of the strip foundation was obtained by using the finite element method and verified its reliability using Euler-Bernoulli beam theoretical model,field monitoring data,and numerical simulation.Parameters analysis for the deformation and internal force of strip foundation under different types of shield machine tunneling parameters showed that the influence of the pressure of shield excavation chamber,thrust of shield,and driving speed played an important role in the deformation of the building’s strip foundation and internal force.展开更多
When a penetrator with enhanced lateral effect(PELE) impacts on a reinforced concrete(RC) target,the target is damaged with a large opening.An understanding of how PELE projectile parameters affect the opening dimensi...When a penetrator with enhanced lateral effect(PELE) impacts on a reinforced concrete(RC) target,the target is damaged with a large opening.An understanding of how PELE projectile parameters affect the opening dimension,is essential for effective design of the PELE projectile.In this study,under the condition that the impact velocity and target parameters(strength and thickness) were fixed values,the important influence factors of the PELE(jacket wall thickness B,jacket material strength Y1,filling material strength Y2 and angle of monolithic jacket θ) were determined by a dimensional analysis.Tests and simulations of the PELE penetrating the RC target were conducted to analyze the influence of these factors on opening diameter(D,an equivalent diameter under relative kinetic energy).Based on the test and simulation results,it is found that the influence of these factors B,Y1 and θ on the deformation mode of the jacket shows a similar trend:as values of the three factors decrease,the jacket deforms from small bending deformation to large one,and then to curling deformation.This causes the opening diameter to first increase with the decrease of these three factors,and then decreases.It is well known that the bending resistance of the jacket is related to these factors B,Y1 and θ.Therefore,a plastic limit bending moment(M0) of the jacket was quoted to characterize the influence of these factors on the bending deformation of the jacket and the opening diameter of the target.The influence factor Y2 causes D to first increase with the increase of Y2,and then decreases.A formula was developed to predict the opening diameter,whose influence parameters were considered in a dimensionless way.It has been shown that the dimensionless opening diameter D/d1 is dependent on two dimensionless parameters■ and■,where d1 and fc are the outer diameter of the projectile and the compressive strength of the target,respectively.展开更多
Based on the explicit finite element(FE) method and platform of ABAQUS,considering both the inhomogeneity of soils and concave-convex fluctuation of topography,a large-scale refined two-dimensional(2D) FE nonlinear an...Based on the explicit finite element(FE) method and platform of ABAQUS,considering both the inhomogeneity of soils and concave-convex fluctuation of topography,a large-scale refined two-dimensional(2D) FE nonlinear analytical model for Fuzhou Basin was established.The peak ground motion acceleration(PGA) and focusing effect with depth were analyzed.Meanwhile,the results by wave propagation of one-dimensional(1D) layered medium equivalent linearization method were added for contrast.The results show that:1) PGA at different depths are obviously amplified compared to the input ground motion,amplification effect of both funnel-shaped depression and upheaval areas(based on the shape of bedrock surface) present especially remarkable.The 2D results indicate that the PGA displays a non-monotonic decreasing with depth and a greater focusing effect of some particular layers,while the 1D results turn out that the PGA decreases with depth,except that PGA at few particular depth increases abruptly; 2) To the funnel-shaped depression areas,PGA amplification effect above 8 m depth shows relatively larger,to the upheaval areas,PGA amplification effect from 15 m to 25 m depth seems more significant.However,the regularities of the PGA amplification effect could hardly be found in the rest areas; 3) It appears a higher regression rate of PGA amplification coefficient with depth when under a smaller input motion; 4) The frequency spectral characteristic of input motion has noticeable effects on PGA amplification tendency.展开更多
Based on the analysis method for tailings dam in upstream raising method presently used in metallurgy and nonferrous metals tailings depository in the world, an effective stress analysis method of seismic response for...Based on the analysis method for tailings dam in upstream raising method presently used in metallurgy and nonferrous metals tailings depository in the world, an effective stress analysis method of seismic response for high tailings dam was developed according to the results of engineering geological exploration, static and dynamic test and stability analysis on Baizhishan tailing dam 113.5 m high. The law of generation, diffusion and dissipation of seismic pore water pressure during and after earthquake was investigated, and the results of tailings dam’s acceleration, seismic dynamic stress and pore water pressure were obtained. The results show that the seismic stability and liquefaction resistance of high tailings dam are strengthened remarkably, and the scope and depth of liquefaction area at the top of dam are reduced greatly. The interior stress is compressive stress, the stress level of every element is less than 1.0 and the safety coefficient of every element is greater than 1.0. The safety coefficient against liquefaction of every element of tailing dam is greater than 1.5 according to the effective stress analysis of seismic response by finite element method. The calculated results prove that liquefaction is the main reason of seismic failure of high tailing dams, and the effect of seismic inertia forces on high tailing dams’ stability during earthquake is secondary reason.展开更多
In order to obtain better quality cookies, food 3D printing technology was employed to prepare cookies. The texture, color, deformation, moisture content, and temperature of the cookie as evaluation indicators, the in...In order to obtain better quality cookies, food 3D printing technology was employed to prepare cookies. The texture, color, deformation, moisture content, and temperature of the cookie as evaluation indicators, the influences of baking process parameters, such as baking time, surface heating temperature and bottom heating temperature, on the quality of the cookie were studied to optimize the baking process parameters. The results showed that the baking process parameters had obvious effects on the texture, color, deformation, moisture content, and temperature of the cookie. All of the roasting surface heating temperature, bottom heating temperature and baking time had positive influences on the hardness, crunchiness, crispiness, and the total color difference(ΔE) of the cookie. When the heating temperatures of the surfac and bottom increased, the diameter and thickness deformation rate of the cookie increased. However,with the extension of baking time, the diameter and thickness deformation rate of the cookie first increased and then decreased. With the surface heating temperature of 180 ℃, the bottom heating temperature of 150 ℃, and baking time of 15 min, the cookie was crisp and moderate with moderate deformation and uniform color. There was no burnt phenomenon with the desired quality. Research results provided a theoretical basis for cookie manufactory based on food 3D printing technology.展开更多
In order to solve the problem that the ripple-effect analy- sis for the operational architecture of air defense systems （OAADS） is hardly described in quantity with previous modeling approaches, a supernetwork model...In order to solve the problem that the ripple-effect analy- sis for the operational architecture of air defense systems （OAADS） is hardly described in quantity with previous modeling approaches, a supernetwork modeling approach for the OAADS is put for- ward by extending granular computing. Based on that operational units and links are equal to different information granularities, the supernetwork framework of the OAADS is constructed as a “four- network within two-layer” structure by forming dynamic operating coalitions, and measuring indexes of the ripple-effect analysis for the OAADS are given combining with Laplace spectral radius. In this framework, via analyzing multidimensional attributes which inherit relations between operational units in different granular scales, an extended granular computing is put forward integrating with a topological structure. Then the operation process within the supernetwork framework, including transformation relations be- tween two layers in the vertical view and mapping relations among functional networks in the horizontal view, is studied in quantity. As the application case shows, comparing with previous modeling approaches, the supernetwork model can validate and analyze the operation mechanism in the air defense architecture, and the ripple-effect analysis can be used to confirm the key operational unit with micro and macro viewpoints.展开更多
In existing studies, most slope stability analyses concentrate on conditions with constant temperature, assuming the slope is intact, and employ the Mohr-Coulomb (M-C) failure criterion for saturated soil to character...In existing studies, most slope stability analyses concentrate on conditions with constant temperature, assuming the slope is intact, and employ the Mohr-Coulomb (M-C) failure criterion for saturated soil to characterize the strength of the backfill. However, the actual working temperature of slopes varies, and natural phenomena such as rainfall and groundwater infiltration commonly result in unsaturated soil conditions, with cracks typically present in cohesive slopes. This study introduces a novel approach for assessing the stability of unsaturated soil stepped slopes under varying temperatures, incorporating the effects of open and vertical cracks. Utilizing the kinematic approach and gravity increase method, we developed a three-dimensional (3D) rotational wedge failure mechanism to simulate slope collapse, enhancing the traditional two-dimensional analyses. We integrated temperature-dependent functions and nonlinear shear strength equations to evaluate the impact of temperature on four typical unsaturated soil types. A particle swarm optimization algorithm was employed to calculate the safety factor, ensuring our method’s accuracy by comparing it with existing studies. The results indicate that considering 3D effects yields a higher safety factor, while cracks reduce slope stability. Each unsaturated soil exhibits a distinctive temperature response curve, highlighting the importance of understanding soil types in the design phase.展开更多
Surface Preparation is very important in adhesive b on ding of spray coatings to the surface of a work piece. The common practice is gr it-blasting of the surface before subjecting it to the spray coating process. In ...Surface Preparation is very important in adhesive b on ding of spray coatings to the surface of a work piece. The common practice is gr it-blasting of the surface before subjecting it to the spray coating process. In this study, grit-blasting of an AISI 4130 steel (of different heat treatmen ts) with Al 2O 3 particles was studied. Various grit-blasting parameters such as blasting particle size, the distance between blasting nozzle and the work pi ece (25, 30 and 40 cm.), blasting pressure (3,4,5,6 and 7 bars), blasting time ( 3, 6 and 10 seconds), and the blasting angle (45° and 90°) were examined in or der to find the optimum roughness. The mean roughness (Ra) of the grit-blasted surfaces were measured and the vari ations of the roughness with respect to the above mentioned variables were studi ed. The results show that by increasing blasting time, surface roughness increas es up to a maximum and then slightly decreases it with further duration of t he process. On the other hand a lengthy blasting causes some undesirable results such as an increase in residual particles between surface irregularities. There fore an optimum blasting time is of great importance. Increasing the blasting pr essure also provides a rougher surface, but in grit blasting of harder specimens the surface roughness decreases when the pressure reaches a certain limit. About the blasting angle, it was noticed that an angle of 45° results in less r esidual particles between the surface irregularities, in comparison to the angle of 90°. After grit-blasting, the specimens were plasma spray coated with 80% ZrO 2-20 % Y 2O 3 powder. The adhesive strength of the coating to the substrate was the n measured according to the DIN 50160 standard. The results show that for a certain base metal, the adhesive strength is directl y related to the surface roughness of the base material. Residual particles afte r grit-blasting the surface of the specimens can also have a strong deteriorati ng effect on adhesive strength. Finally, it was shown that the hardness of the b ase material had a direct effect on the adhesive strength of the sprayed coating s.展开更多
It is important but difficult to analyze the electromagnetic environment effect(E3) in the designing of modern airborne,sea,space,and ground systems.Thus a hybrid algorithm of time domain integral equation,finite diff...It is important but difficult to analyze the electromagnetic environment effect(E3) in the designing of modern airborne,sea,space,and ground systems.Thus a hybrid algorithm of time domain integral equation,finite difference time domain and modified nodal analysis(TDIE-FDTD-MNA) is developed to analyze the E3 of complex systems with cables and nonlinear circuit structures.The plane wave time domain(PWTD) enhanced TDIE method is adopted to solve field problems.The higher order FDTD(2,4) is adopted to solve cable problems.The MNA is adopted to obtain the response of complex circuits(with nonlinear structures).Numerical examples demonstrate the effectiveness of the proposed algorithm.展开更多
基金supported by the National Natural Science Foundation of China(72271124,72071111).
文摘Aiming at the characteristics of multi-stage and(extremely)small samples of the identification problem of key effectiveness indexes of weapon equipment system-of-systems(WESoS),a Bayesian intelligent identification and inference model for system effectiveness assessment indexes based on dynamic grey incidence is proposed.The method uses multi-layer Bayesian techniques,makes full use of historical statistics and empirical information,and determines the Bayesian estima-tion of the incidence degree of indexes,which effectively solves the difficulties of small sample size of effectiveness indexes and difficulty in obtaining incidence rules between indexes.Sec-ondly,The method quantifies the incidence relationship between evaluation indexes and combat effectiveness based on Bayesian posterior grey incidence,and then identifies key system effec-tiveness evaluation indexes.Finally,the proposed method is applied to a case of screening key effectiveness indexes of a missile defensive system,and the analysis results show that the proposed method can fuse multi-moment information and extract multi-stage key indexes,and has good data extraction capability in the case of small samples.
基金supported by the Fundamental Research Funds for the Central Universities(22120240094)Humanities and Social Science Fund of Ministry of Education China(22YJA630082).
文摘Failure mode and effect analysis(FMEA)is a preven-tative risk evaluation method used to evaluate and eliminate fail-ure modes within a system.However,the traditional FMEA method exhibits many deficiencies that pose challenges in prac-tical applications.To improve the conventional FMEA,many modified FMEA models have been suggested.However,the majority of them inadequately address consensus issues and focus on achieving a complete ranking of failure modes.In this research,we propose a new FMEA approach that integrates a two-stage consensus reaching model and a density peak clus-tering algorithm for the assessment and clustering of failure modes.Firstly,we employ the interval 2-tuple linguistic vari-ables(I2TLVs)to express the uncertain risk evaluations provided by FMEA experts.Then,a two-stage consensus reaching model is adopted to enable FMEA experts to reach a consensus.Next,failure modes are categorized into several risk clusters using a density peak clustering algorithm.Finally,the proposed FMEA is illustrated by a case study of load-bearing guidance devices of subway systems.The results show that the proposed FMEA model can more easily to describe the uncertain risk information of failure modes by using the I2TLVs;the introduction of an endogenous feedback mechanism and an exogenous feedback mechanism can accelerate the process of consensus reaching;and the density peak clustering of failure modes successfully improves the practical applicability of FMEA.
基金Projects(51708558,51878673,U1734208,52078485,U1934217,U1934209)supported by the National Natural Science Foundation of ChinaProject(2020JJ5740)supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(KF2020-03)supported by the Key Open Fund of State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures,ChinaProject(2020-Special-02)supported by the Science and Technology Research and Development Program of China Railway Group Limited。
文摘Random dynamic responses caused by the uncertainty of structural parameters of the coupled train-ballasted track-subgrade system under train loading can pose safety concerns to the train operation.This paper introduced a computational model for analyzing probabilistic dynamic responses of three-dimensional(3D)coupled train-ballasted track-subgrade system(TBTSS),where the coupling effects of uncertain rail irregularities,stiffness and damping properties of ballast and subgrade layers were simultaneously considered.The number theoretical method(NTM)was employed to design discrete points for the multi-dimensional stochastic parameters.The time-histories of stochastic dynamic vibrations of the TBSS with systematically uncertain structural parameters were calculated accurately and efficiently by employing the probability density evolution method(PDEM).The model-predicted results were consistent with those by the Monte Carlo simulation method.A sensitivity study was performed to assess the relative importance of those uncertain structural parameters,based on which a case study was presented to explore the stochastic probability evolution mechanism of such train-ballasted track-subgrade system.
基金Project(265201248) supported by the Fundamental Research Funds for the Central Universities,ChinaProject(41172130) supported by the National Natural Science Foundation of China+2 种基金Project(2011ZX05014-001) supported by the Major State S&T Special Fund,ChinaProject(201205002) supported by the China Scholarship CouncilProject(2011D-5006-0305) supported by the China National Petroleum Co.Innovation Foundation,China
文摘The microscopic response characteristics of nuclear magnetic resonance(NMR) are widely used for characterizing complex pore structures of rocks. Due to the prohibitive NMR experiment cost, numerical simulation was employed as an alternative approach to verify some theoretical aspects of NMR responses. Firstly, the basic principles of pore-scale NMR simulation based on random-walk method(RWM) were introduced. The RWM-simulated results were benchmarked with the analytical results for an ideal spherical pore model. Then, the effects of two numerical parameters, namely diffusion radius and walk numbers, were studied on the simulation accuracy. The simulation method is then applied to various pore models with different pore sizes and pore shapes filled with different fluids to study the microscopic NMR response characteristics. The numerical experiments are useful for understanding and interpreting NMR measurements and the simulation code provides a numerical tool to perform pixel-based digital rock analysis.
基金Project (50474050) supported by the National Natural Science Foundation of China
文摘Depending on the numerical test approach on a computer, the relationships among relevant parameters, eg branch number, node number, mesh number, computation accuracy, preliminary value of airflow rate, iteration number, computation time and convergence in a mine ventilation network analysis, were investigated based on 5 mine ventilation systems. The results show that a higher computation accuracy greatly influences the iteration number. When the accuracy reaches 10-6m3·s-1 for solving a complicated mine ventilation network, the running time is too long though a high-speed computer is used. The preliminary value of airflow rate in the range of 1100m3·s-1 has little effects the iteration number. The structure of network also has some effect on the iteration number.
文摘To evaluate the effectiveness of weapon systems, the advantages and disadvantages of grey relational analysis and TOPSIS for multiattribute decision-making is pointed out, and an effectiveness evaluation model of weapon systems by combining grey relational analysis and TOPSIS is proposed. The model aggregates the grey relational grade and the distance to a new integrated closeness and reflects not only the trend but also the situation of the alternative. The example illuminates that the model is effective for the effectiveness evaluation of weapon systems.
基金The authors would like to thank the Iranian Nanotechnology Development Committee for their financial support.
文摘Higher-order shear and normal deformation theory is used in this paper to account thickness stretching effect for free vibration analysis of the cylindrical micro/nano shell subjected to an applied voltage and uniform temperature rising.Size dependency is included in governing equations based on the modified couple stress theory.Hamilton’s principle is used to derive governing equations of the cylindrical micro/nano shell.Solution procedure is developed using Navier technique for simply-supported boundary conditions.The numerical results are presented to investigate the effect of significant parameters such as some dimensionless geometric parameters,material properties,applied voltages and temperature rising on the free vibration responses.
基金Project(2015B37714)supported by the Fundamental Research Funds for the Central Universities of ChinaProject(51605005)supported by the National Natural Science Foundation of China+1 种基金Project(ZK16-03-03)supported by the Open Foundation of Jiangsu Wind Technology Center,ChinaProject([2013]56)supported by the First Group of 2011 Plan of Jiangsu Province,China
文摘The parameter sensitivities affecting the flutter speed of the NREL （National Renewable Energy Laboratory） 5-MW baseline HAWT （horizontal axis wind turbine） blades are analyzed. An aeroelastic model, which comprises an aerodynamic part to calculate the aerodynamic loads and a structural part to determine the structural dynamic responses, is established to describe the classical flutter of the blades. For the aerodynamic part, Theodorsen unsteady aerodynamics model is used. For the structural part, Lagrange’s equation is employed. The flutter speed is determined by introducing “V–g” method to the aeroelastic model, which converts the issue of classical flutter speed determination into an eigenvalue problem. Furthermore, the time domain aeroelastic response of the wind turbine blade section is obtained with employing Runge-Kutta method. The results show that four cases （i.e., reducing the blade torsional stiffness, moving the center of gravity or the elastic axis towards the trailing edge of the section, and placing the turbine in high air density area） will decrease the flutter speed. Therefore, the judicious selection of the four parameters （the torsional stiffness, the chordwise position of the center of gravity, the elastic axis position and air density） can increase the relative inflow speed at the blade section associated with the onset of flutter.
基金Projects(41807265,41972286,42072309)supported by the National Natural Science Foundation of ChinaProjects(HKLBEF202001,HKLBEF202002)supported by the Hubei Key Laboratory of Blasting Engineering Foundation,China。
文摘When the tunnel underpasses through the building,it will cause deformation and even damage to the buildings above,and the deformation of building foundation is the key to building safety.Based on the engineering case,the theoretical analysis was employed to evaluate the influence of shield tunnel underpass construction on the stability of the building,and the optimal tunneling parameters in the field construction have been obtained through the verified theoretical model and parameter analysis.First,the strip foundation of the building was simplified to the Timoshenko beam,which was taken into account the shear effect,and then the deformation displacement of the soil at the same place of strip foundation was applied to the simplified Timoshenko beam.Finally,the numerical solution of the displacement of the strip foundation was obtained by using the finite element method and verified its reliability using Euler-Bernoulli beam theoretical model,field monitoring data,and numerical simulation.Parameters analysis for the deformation and internal force of strip foundation under different types of shield machine tunneling parameters showed that the influence of the pressure of shield excavation chamber,thrust of shield,and driving speed played an important role in the deformation of the building’s strip foundation and internal force.
基金supported by the National Natural Science Foundation of China (Grant No: 11472008, 11772160, 11802141)the Opening Project of State Key Laboratory of Explosion Science and Technology (KFJJ18-01M), Beijing Institute of Technology。
文摘When a penetrator with enhanced lateral effect(PELE) impacts on a reinforced concrete(RC) target,the target is damaged with a large opening.An understanding of how PELE projectile parameters affect the opening dimension,is essential for effective design of the PELE projectile.In this study,under the condition that the impact velocity and target parameters(strength and thickness) were fixed values,the important influence factors of the PELE(jacket wall thickness B,jacket material strength Y1,filling material strength Y2 and angle of monolithic jacket θ) were determined by a dimensional analysis.Tests and simulations of the PELE penetrating the RC target were conducted to analyze the influence of these factors on opening diameter(D,an equivalent diameter under relative kinetic energy).Based on the test and simulation results,it is found that the influence of these factors B,Y1 and θ on the deformation mode of the jacket shows a similar trend:as values of the three factors decrease,the jacket deforms from small bending deformation to large one,and then to curling deformation.This causes the opening diameter to first increase with the decrease of these three factors,and then decreases.It is well known that the bending resistance of the jacket is related to these factors B,Y1 and θ.Therefore,a plastic limit bending moment(M0) of the jacket was quoted to characterize the influence of these factors on the bending deformation of the jacket and the opening diameter of the target.The influence factor Y2 causes D to first increase with the increase of Y2,and then decreases.A formula was developed to predict the opening diameter,whose influence parameters were considered in a dimensionless way.It has been shown that the dimensionless opening diameter D/d1 is dependent on two dimensionless parameters■ and■,where d1 and fc are the outer diameter of the projectile and the compressive strength of the target,respectively.
基金Project(2011CB013601) supported by the National Basic Research Program of ChinaProject(51378258) supported by the National Natural Science Foundation of China
文摘Based on the explicit finite element(FE) method and platform of ABAQUS,considering both the inhomogeneity of soils and concave-convex fluctuation of topography,a large-scale refined two-dimensional(2D) FE nonlinear analytical model for Fuzhou Basin was established.The peak ground motion acceleration(PGA) and focusing effect with depth were analyzed.Meanwhile,the results by wave propagation of one-dimensional(1D) layered medium equivalent linearization method were added for contrast.The results show that:1) PGA at different depths are obviously amplified compared to the input ground motion,amplification effect of both funnel-shaped depression and upheaval areas(based on the shape of bedrock surface) present especially remarkable.The 2D results indicate that the PGA displays a non-monotonic decreasing with depth and a greater focusing effect of some particular layers,while the 1D results turn out that the PGA decreases with depth,except that PGA at few particular depth increases abruptly; 2) To the funnel-shaped depression areas,PGA amplification effect above 8 m depth shows relatively larger,to the upheaval areas,PGA amplification effect from 15 m to 25 m depth seems more significant.However,the regularities of the PGA amplification effect could hardly be found in the rest areas; 3) It appears a higher regression rate of PGA amplification coefficient with depth when under a smaller input motion; 4) The frequency spectral characteristic of input motion has noticeable effects on PGA amplification tendency.
基金Projects(03JJY3078, 04JJ40032) supported by the Natural Science Foundation of Hunan Province, China project(03A006) supported by Scientific Research Fund of Hunan Provincial Education Department, China
文摘Based on the analysis method for tailings dam in upstream raising method presently used in metallurgy and nonferrous metals tailings depository in the world, an effective stress analysis method of seismic response for high tailings dam was developed according to the results of engineering geological exploration, static and dynamic test and stability analysis on Baizhishan tailing dam 113.5 m high. The law of generation, diffusion and dissipation of seismic pore water pressure during and after earthquake was investigated, and the results of tailings dam’s acceleration, seismic dynamic stress and pore water pressure were obtained. The results show that the seismic stability and liquefaction resistance of high tailings dam are strengthened remarkably, and the scope and depth of liquefaction area at the top of dam are reduced greatly. The interior stress is compressive stress, the stress level of every element is less than 1.0 and the safety coefficient of every element is greater than 1.0. The safety coefficient against liquefaction of every element of tailing dam is greater than 1.5 according to the effective stress analysis of seismic response by finite element method. The calculated results prove that liquefaction is the main reason of seismic failure of high tailing dams, and the effect of seismic inertia forces on high tailing dams’ stability during earthquake is secondary reason.
基金Supported by Heilongjiang Provincial Fruit Tree Modernization Agro-industrial Technology Collaborative Innovation and Promotion System Project(2019-13)。
文摘In order to obtain better quality cookies, food 3D printing technology was employed to prepare cookies. The texture, color, deformation, moisture content, and temperature of the cookie as evaluation indicators, the influences of baking process parameters, such as baking time, surface heating temperature and bottom heating temperature, on the quality of the cookie were studied to optimize the baking process parameters. The results showed that the baking process parameters had obvious effects on the texture, color, deformation, moisture content, and temperature of the cookie. All of the roasting surface heating temperature, bottom heating temperature and baking time had positive influences on the hardness, crunchiness, crispiness, and the total color difference(ΔE) of the cookie. When the heating temperatures of the surfac and bottom increased, the diameter and thickness deformation rate of the cookie increased. However,with the extension of baking time, the diameter and thickness deformation rate of the cookie first increased and then decreased. With the surface heating temperature of 180 ℃, the bottom heating temperature of 150 ℃, and baking time of 15 min, the cookie was crisp and moderate with moderate deformation and uniform color. There was no burnt phenomenon with the desired quality. Research results provided a theoretical basis for cookie manufactory based on food 3D printing technology.
基金supported by the National Natural Science Foundation of China(61272011)
文摘In order to solve the problem that the ripple-effect analy- sis for the operational architecture of air defense systems （OAADS） is hardly described in quantity with previous modeling approaches, a supernetwork modeling approach for the OAADS is put for- ward by extending granular computing. Based on that operational units and links are equal to different information granularities, the supernetwork framework of the OAADS is constructed as a “four- network within two-layer” structure by forming dynamic operating coalitions, and measuring indexes of the ripple-effect analysis for the OAADS are given combining with Laplace spectral radius. In this framework, via analyzing multidimensional attributes which inherit relations between operational units in different granular scales, an extended granular computing is put forward integrating with a topological structure. Then the operation process within the supernetwork framework, including transformation relations be- tween two layers in the vertical view and mapping relations among functional networks in the horizontal view, is studied in quantity. As the application case shows, comparing with previous modeling approaches, the supernetwork model can validate and analyze the operation mechanism in the air defense architecture, and the ripple-effect analysis can be used to confirm the key operational unit with micro and macro viewpoints.
基金Project(51378510) supported by the National Natural Science Foundation of China。
文摘In existing studies, most slope stability analyses concentrate on conditions with constant temperature, assuming the slope is intact, and employ the Mohr-Coulomb (M-C) failure criterion for saturated soil to characterize the strength of the backfill. However, the actual working temperature of slopes varies, and natural phenomena such as rainfall and groundwater infiltration commonly result in unsaturated soil conditions, with cracks typically present in cohesive slopes. This study introduces a novel approach for assessing the stability of unsaturated soil stepped slopes under varying temperatures, incorporating the effects of open and vertical cracks. Utilizing the kinematic approach and gravity increase method, we developed a three-dimensional (3D) rotational wedge failure mechanism to simulate slope collapse, enhancing the traditional two-dimensional analyses. We integrated temperature-dependent functions and nonlinear shear strength equations to evaluate the impact of temperature on four typical unsaturated soil types. A particle swarm optimization algorithm was employed to calculate the safety factor, ensuring our method’s accuracy by comparing it with existing studies. The results indicate that considering 3D effects yields a higher safety factor, while cracks reduce slope stability. Each unsaturated soil exhibits a distinctive temperature response curve, highlighting the importance of understanding soil types in the design phase.
文摘Surface Preparation is very important in adhesive b on ding of spray coatings to the surface of a work piece. The common practice is gr it-blasting of the surface before subjecting it to the spray coating process. In this study, grit-blasting of an AISI 4130 steel (of different heat treatmen ts) with Al 2O 3 particles was studied. Various grit-blasting parameters such as blasting particle size, the distance between blasting nozzle and the work pi ece (25, 30 and 40 cm.), blasting pressure (3,4,5,6 and 7 bars), blasting time ( 3, 6 and 10 seconds), and the blasting angle (45° and 90°) were examined in or der to find the optimum roughness. The mean roughness (Ra) of the grit-blasted surfaces were measured and the vari ations of the roughness with respect to the above mentioned variables were studi ed. The results show that by increasing blasting time, surface roughness increas es up to a maximum and then slightly decreases it with further duration of t he process. On the other hand a lengthy blasting causes some undesirable results such as an increase in residual particles between surface irregularities. There fore an optimum blasting time is of great importance. Increasing the blasting pr essure also provides a rougher surface, but in grit blasting of harder specimens the surface roughness decreases when the pressure reaches a certain limit. About the blasting angle, it was noticed that an angle of 45° results in less r esidual particles between the surface irregularities, in comparison to the angle of 90°. After grit-blasting, the specimens were plasma spray coated with 80% ZrO 2-20 % Y 2O 3 powder. The adhesive strength of the coating to the substrate was the n measured according to the DIN 50160 standard. The results show that for a certain base metal, the adhesive strength is directl y related to the surface roughness of the base material. Residual particles afte r grit-blasting the surface of the specimens can also have a strong deteriorati ng effect on adhesive strength. Finally, it was shown that the hardness of the b ase material had a direct effect on the adhesive strength of the sprayed coating s.
基金supported by National Basic Research Program of China(973 Program)
文摘It is important but difficult to analyze the electromagnetic environment effect(E3) in the designing of modern airborne,sea,space,and ground systems.Thus a hybrid algorithm of time domain integral equation,finite difference time domain and modified nodal analysis(TDIE-FDTD-MNA) is developed to analyze the E3 of complex systems with cables and nonlinear circuit structures.The plane wave time domain(PWTD) enhanced TDIE method is adopted to solve field problems.The higher order FDTD(2,4) is adopted to solve cable problems.The MNA is adopted to obtain the response of complex circuits(with nonlinear structures).Numerical examples demonstrate the effectiveness of the proposed algorithm.
