Sloshing experiment is crucial to determine the reaction performance of regeneration columns on an offshore floating platform.A novel type of column motion simulating device and a Marine Predator Algorithm-based Slidi...Sloshing experiment is crucial to determine the reaction performance of regeneration columns on an offshore floating platform.A novel type of column motion simulating device and a Marine Predator Algorithm-based Sliding Mode Controller(MPA-SMC)are proposed for such sloshing experiments.The simulator consists of a Stewart platform and a steel framework.The Stewart platform is located at the column's center of gravity(CoG)and supported by the steel framework.The platform's hydraulic servo system is controlled by a sliding mode controller with parameters optimized by MPA to improve robustness and precision.A numerical sloshing experiment is conducted using the proposed device and controller.The results show that the novel motion simulator has lower torque during the column sloshes,and the proposed controller performs better than a well-tuned PID controller in terms of target tracking precision and anti-interference capability.展开更多
Most of the existing studies on tunnel blast wave are based on spherical or grouped charges, however,conventional weapons are mostly cylindrical rather than spherical. In order to analyze the impact of cylindrical cha...Most of the existing studies on tunnel blast wave are based on spherical or grouped charges, however,conventional weapons are mostly cylindrical rather than spherical. In order to analyze the impact of cylindrical charges on the tunnel blast wave loads and to develop a quantitative calculation method, this study carried out experimental and numerical research. Initially, external explosion experiments were conducted using both 35 kg spherical charges and cylindrical charges with aspect ratio of 4.8 at two different distances from the tunnel entrance. Comparative analysis of the blast wave parameters in the tunnel revealed that the explosive equivalent of the cylindrical charges was significantly higher than that of the spherical charges. To address this, an equivalent coefficient κ based on the spherical charges was proposed for the cylindrical charges. Subsequently, numerical simulations were conducted for the experimental conditions, and the numerical simulation results match the experiments well. Through numerical calculations, the reliability of the equivalent coefficient κ under the experimental conditions was verified, and comparison analysis indicated that the explosion energy of cylindrical charges spreads more radially, resulting in more explosion energy entering the tunnel, which is the fundamental reason for the increase in tunnel blast wave loads. Additionally, analyzing the explosion energy ratio entering the tunnel is an effective method for calculating the equivalent coefficient κ. Finally, through more than one hundred sets of numerical calculation results, the impact of the proportional distance λ and the ratio of charge mass to the tunnel cross-section dimension φ on the equivalence coefficients κ was investigated. An empirical formula for the equivalence coefficient κ was derived through fitting, and the accuracy of the formula was validated through literature experimental results. The research findings of this paper will provide valuable guidance for the calculation of blast wave loads in tunnel.展开更多
A mobile robot developed by Wuhan University for full-path hotline inspection on 220 kV transmission lines was presented. With 4 rotating joints and 2 translational ones, such robot is capable of traveling along non- ...A mobile robot developed by Wuhan University for full-path hotline inspection on 220 kV transmission lines was presented. With 4 rotating joints and 2 translational ones, such robot is capable of traveling along non- obstaclestraight-line segment and surmounting straight-line segment obstacles as well as transferring between two spans automatically. Lagrange’s equations were utilized to derive dynamic equations of all the links, including items of inertia, coupling inertia, Coriolis acceleration, centripetal acceleration and gravity. And a dynamic response experiment on elemental motions of robot prototype’s travelling along non-obstacle straight-line segment and surmounting obstacles was performed on 220 kV 1∶1 simulative overhanging transmission-line in laboratory. In addition, dynamic numerical simulation was conducted in the corresponding condition. Comparison and analysis on results of experiment and numerical simulation have validated theoretical model and simulation resolution. Therefore, the dynamic model formed hereunder can be used for the study of robot control.展开更多
Vegetation plays a key role in improving wind environment of residential districts,and is helpful for creating a comfortable and beautiful living environment.The optimal design of vegetation for wind environment impro...Vegetation plays a key role in improving wind environment of residential districts,and is helpful for creating a comfortable and beautiful living environment.The optimal design of vegetation for wind environment improvement in winter was investigated by carrying out field experiments in Heqingyuan residential area in Beijing,and after that,numerical simulation with SPOTE(simulation platform for outdoor thermal environment) experiments for outdoor thermal environment of vegetation was adopted for comparison.The conclusions were summarized as follows:1) By comparing the experimental data with simulation results,it could be concluded that the wind field simulated was consistent with the actual wind field,and the flow distribution impacted by vegetation could be accurately reflected;2) The wind velocity with vegetation was lower than that without vegetation,and the wind velocity was reduced by 46%;3) By adjusting arrangement and types of vegetation in the regions with excessively large wind velocity,the pedestrian-level wind velocity could be obviously improved through the simulation and comparison.展开更多
In the process of thin-wall parts assembly for an antenna,the parts assembly deformation deviation is occurring due to the riveting assembly.In view of the riveting assembly deformation problems,it can be analyzed thr...In the process of thin-wall parts assembly for an antenna,the parts assembly deformation deviation is occurring due to the riveting assembly.In view of the riveting assembly deformation problems,it can be analyzed through transient and static simulation.In this work,the theoretical deformation model for riveting assembly is established with round head rivet.The simulation analysis for riveting deformation is carried out with the riveting assembly piece including four rivets,which comparing with the measuring points experiment results of riveting test piece through dealing with the experimental data using the point coordinate transform method and the space line fitting method.Simultaneously,the deformation deviation of the overall thin-wall parts assembly structure is analyzed through finite element simulation;and its results are verified by the measuring experiment for riveting assembly with the deformation deviation of some key points on the thin-wall parts.Through the comparison analysis,it is shown that the simulation results agree well with the experimental results,which proves the correctness and effectiveness of the theoretical analysis,simulation results and the given experiment data processing method.Through the study on the riveting assembly for thin-wall parts,it will provide a theoretical foundation for improving thin-wall parts assembly quality of large antenna in future.展开更多
In order to research spread law and distribution law of temperature nearby fire sources on roadway in mine, according to combustion theory and other basic, the theory model of temperature attenuation was determined un...In order to research spread law and distribution law of temperature nearby fire sources on roadway in mine, according to combustion theory and other basic, the theory model of temperature attenuation was determined under unsteady heat-exchange between wind and roadway wall. The full-size roadway fire simulation experiments were carried out in Chongqing Research Institute of China Coal Technology & Engineering Group Corporation. The development processes of mine fire and flow pattern of high temperature gas were analyzed. Experimental roadway is seen as physical model, and through using CFD software, the processes of mine fire have been simulated on computer. The results show that, after fire occurs, if the wind speed is less than the minimum speed which can prevent smoke from rolling back, then the smaller wind speed can cause smoke to roll back easily. Hot plume will lead to secondary disasters in upwind side. Because of roadway wall, hot plume released from roadway fire zone has caused the occurrence of the ceiling jet, and the hot plume has been forced down. Whereas, owing to the higher temperature, buoyancy effect is more obvious. Therefore, smoke rises gradually along the roadway in the flow process, and the hierarchical interface appears wavy.Oxygen-enriched combustion and fuel-enriched combustion are the two kinds of combustion states of fire. The oxygen content of downwind side of fire is maintained at around 15% for oxygen-enriched combustion, and the oxygen content of downwind side of fire is maintained at around 2% for fuel-enriched combustion. Furthermore, fuel-enriched combustion can lead to secondary disasters easily.展开更多
Ongoing research is described that is focused upon modelling the space base information network and simulating its behaviours： simulation of spaced based communications and networking project. Its objective is to dem...Ongoing research is described that is focused upon modelling the space base information network and simulating its behaviours： simulation of spaced based communications and networking project. Its objective is to demonstrate the feasibility of producing a tool that can provide a performance evaluation of various eonstellation access techniques and routing policies. The architecture and design of the simulation system are explored. The algorithm of data routing and instrument scheduling in this project is described. Besides these, the key methodologies of simulating the inter-satellite link features in the data transmissions are also discussed. The performance of both instrument scheduling algorithm and routing schemes is evaluated and analyzed through extensive simulations under a typical scenario.展开更多
The frequent occurrence of safety accidents during the calendering process is caused by the flammable and explosive properties of composite modified double-base(CMDB)propellant.Optimization of process parameters with ...The frequent occurrence of safety accidents during the calendering process is caused by the flammable and explosive properties of composite modified double-base(CMDB)propellant.Optimization of process parameters with the aid of fluid simulation technology could effectively ensure the safety of the calendering process.To improve the accuracy of the simulation results,material parameters and model structure were corrected based on actual conditions,and adaptive grid technology was applied in the local mesh refinement.In addition,the rheological behavior,motion trajectories and heat transfer mechanisms of CMDB propellant slurry were studied with different gaps,rotational rates and temperatures of two rollers.The results indicated that the refined mesh could significantly improve the contour clarity of boundaries and simulate the characteristics of CMDB propellant slurry reflux movement caused by the convergent flow near the outlet.Compared with the gap,the increased rotational rate of roller could promote the reflux movement and intensify the shear flow of slurry inside the flow region by viscous shear dragging.Meanwhile,under the synergistic effect of contact heat transfer as well as convective heat exchange,heat accumulated near the outlet and diffused along the reflux movement,which led to the countercurrent heat dissipation behavior of CMDB propellant slurry.The plasticizing mechanism of slurry and the safety of calendering under different conditions were explored,which provided theoretical guidance and reference data for the optimization of calendering process conditions.Based on the simulation results,the safety of the CMDB propellant calendering process could be significantly improved with a few tests conducted during a short research and development cycle.展开更多
The Ailaoshan aquamarine-bearing pegmatites are associated with Proterozoic metamorphic rocks in the southern portion of the Ailaoshan fault-folded complex.The gem-bearing pegmatite mineralization zones of the region ...The Ailaoshan aquamarine-bearing pegmatites are associated with Proterozoic metamorphic rocks in the southern portion of the Ailaoshan fault-folded complex.The gem-bearing pegmatite mineralization zones of the region occur in areas generally consistent with the regional tectonic trend.The pegmatites are found in metamorphic rocks,migmatites and in the inner/outer contact zones of gneissoid granites. The Rb-Sr isochron drawn for the pegmatites is 26～31 Ma,(i.e.in Himalayan).The homogenization temperatures of melt and liquid inclusions in minerals vary from 185 to 920℃,which are comparable to the inclusions observed in banded migmatites and ptygmatic quartz veins in the surrounding metamorphic rocks. The mineralization fluids of the pegmatite were rich in HCO_3 and CO_2,and their compositional assemblages are comparable to metamorphic fluids.Results of H,O,C,Si etc.isotopic analyses and REE,and Be analyses indicates that the sources of mineralization components that formed the pegmatites are closely associated with metamorphic fluids and the enclosing metamorphic rocks. A pegmatite structure simulation experiment was conducted at high temperature and pressure(840℃and 1,500×105Pa.),with various metamorphic rock samples in a water-rich and volatile-rich environment.When the liquidus was reached,the temperature was gradually decreased at the rate of 5～10℃/day over a time period of three months.SEM energy-dispersive spectrum analyses were performed on the experimental products.A series of pegmatoid textures were observed including zonal texture,megacryst texture,drusy cavities,crystal druses,and vesicular texture along with more than ten types of minerals including plagioclase,microcline,quartz and biotite.Different metamorphic rock melts generated different mineral assemblages.Experiment results revealed that the partial melting of metamorphic rocks could form melts similar to pegmatite magmas. Based upon the geological characteristics,geochemistry,and pegmatite texture simulation experimental results,it is concluded that the mineralization components of Ailaoshan aquamarine-bearing pegmatites came from metamorphic rocks.The petrogenetic model for the origin of pegmatites is related to ultrametamorphism and metamorphic anatexis.展开更多
This paper reports an aspiration-directed, model-based decision support system (AMDSS) integrated with a knowledge-based simulation system. The system is designed to study China's mid-range economic development st...This paper reports an aspiration-directed, model-based decision support system (AMDSS) integrated with a knowledge-based simulation system. The system is designed to study China's mid-range economic development strategy. The capacity of the system is enhanced by the knowledge-based component which provides a knowledge-based simulation environment for model management. Currently the system has passed the stage of prototype and achieves its implementation capacity. The paper first presents the mathematical aspects of decision making including aspiration-directed decision making, then discusses the architecture of the system. The purpose of the paper is to provide insights into how such an integrated system could provide decision support for complex decision analysis.展开更多
The kinetics of the thermal decomposition for a naturally ageing ammonium perchlorate(AP) and hydroxyl-terminated-polybutadiene(HTPB) base bleed composite propellant were investigated using a differential scanning cal...The kinetics of the thermal decomposition for a naturally ageing ammonium perchlorate(AP) and hydroxyl-terminated-polybutadiene(HTPB) base bleed composite propellant were investigated using a differential scanning calorimetry(DSC). The naturally ageing AP/HTPB base bleed propellant samples have been stored in a sealed plastic bag at room temperature(5-25 ℃) for more than 20 years. The experimental DSC results were obtained by placing samples(each about 1.5 mg) in a sealed pan under non-isothermal condition under different heating rates, 5.0, 10.0, 15.0, 20.0 and 30.0 ℃·min^(-1). The activation energy and pre-exponential factor were estimated based on the relationship between the exothermic peak temperature and the heating rate by Ozawa and Kissinger methods, respectively. The decomposition kinetic parameters is lower the values under laboratorial aging condition.展开更多
In order to improve the benefits of base bleed in base flow field,the base flow with hot base bleed for two jet models is studied.Twodimensional axisymmetric Navier-Stokes equations are computed by using a finite volu...In order to improve the benefits of base bleed in base flow field,the base flow with hot base bleed for two jet models is studied.Twodimensional axisymmetric Navier-Stokes equations are computed by using a finite volume scheme.The base flow of a cylinder afterbody with base bleed is simulated.The simulation results are validated with the experimental data,and the experimental results are well reproduced.On this basis,the base flow fields with base bleed for a circular jet model and an annulus jet model are investigated by selecting the injection temperature from 830 K to 2200 K.The results show that the base pressure of the annular jet model is higher than that of the circular jet model with the changes of the injection parameter and the injection temperature.For the circular jet model,the hot gases are concentrated in the vicinity of the base.For the annular jet model,the bleed gases flow into the shear layer directly so that the hot gases are concentrated in the shear layer.The latter temperature distribution is better for the increase of base pressure.展开更多
Train traffic rescheduling is a complicated and large-scaled combinatorial problem. According to the characteristics of China railway system and from the point of practical use, this paper introduces a rule-based trai...Train traffic rescheduling is a complicated and large-scaled combinatorial problem. According to the characteristics of China railway system and from the point of practical use, this paper introduces a rule-based train traffic reschedule interactive simulator. It can be used as a powerful training tool to train the dispatcher and to carry out experimental analysis. The production rules are used as the basic for describing the processes to be simulated. With the increase of rule, users can easily upgrade the simulator by adding their own rules.展开更多
Equipment systems-of-systems （SOS） effectiveness evaluation can provide important reference for construction and optimization of the equipment SoS. After discussing the basic theory and methods of parallel experimen...Equipment systems-of-systems （SOS） effectiveness evaluation can provide important reference for construction and optimization of the equipment SoS. After discussing the basic theory and methods of parallel experiments, we depict an SoS effectiveness analysis and evaluation method using parallel expe- riments theory in detail. A case study is carried out which takes the missile defense system as an example. An artificial system of the missile defense system is constructed with the multi-agent modeling method. Then, single factor, multiple factors and defense position deployment computational experiments are carried out and evaluated with the statistical analysis method. Experiment re- sults show that the altitude of the secondary interception missile is not the key factor which affects SoS effectiveness and putting the defense position ahead will increase defense effectiveness. The case study demonstrates the feasibility of the proposed method.展开更多
During the compaction of a road subgrade, the mechanical parameters of the soil mass change in real time, but current research assumes that these parameters remain unchanged. In order to address this discrepancy, this...During the compaction of a road subgrade, the mechanical parameters of the soil mass change in real time, but current research assumes that these parameters remain unchanged. In order to address this discrepancy, this paper establishes a relationship between the degree of compaction K and strain ε. The relationship between the compaction degree K and the shear strength of soil(cohesion c and frictional angle φ) was clearly established through indoor experiments. The subroutine UMAT in ABAQUS finite element numerical software was developed to realize an accurate calculation of the subgrade soil compaction quality. This value was compared and analyzed against the assumed compaction value of the model, thereby verifying the accuracy of the intelligent compaction calculation results for subgrade soil. On this basis, orthogonal tests of the influential factors(frequency, amplitude, and quality) for the degree of compaction and sensitivity analysis were carried out. Finally, the ‘acceleration intelligent compaction value’, which is based on the acceleration signal, is proposed for a compaction meter value that indicates poor accuracy. The research results can provide guidance and basis for further research into the accurate control of compaction quality for roadbeds and pavements.展开更多
This paper reviews the current status of investigation on snow accumulation on the bogies of high-speed trains(HSTs) running in snowy region. First, the background of the snow issue occurring to the HST and the contra...This paper reviews the current status of investigation on snow accumulation on the bogies of high-speed trains(HSTs) running in snowy region. First, the background of the snow issue occurring to the HST and the contra-measures for the snow issue proposed in the past decades are provided by reviewing previous studies. Next, the methodology for investigating the snow issue developed by High-Speed Train Research Center of Central South University is introduced, including the numerical simulation research platform and the experimental devices for two-phase flow wind tunnel tests. Then, effective anti-snow flow control schemes for guiding the underbody airflow and their impact on the motion and accretion of snow in the installation region of the bogies are presented. Finally, the remaining investigating challenge for the snow issue of HST and the future research with respect to the challenge are provided from an engineering application viewpoint.展开更多
Aiming at the position and attitude tracking of coaxial rotor aircraft(CRA),this paper proposes a combinatorial control method of sliding mode control(SMC)coupled with proportional-integralderivative control(PIDC).Con...Aiming at the position and attitude tracking of coaxial rotor aircraft(CRA),this paper proposes a combinatorial control method of sliding mode control(SMC)coupled with proportional-integralderivative control(PIDC).Considering the complete description of flight dynamics,aerodynamics and airflow interference,the dynamical model of CRA is established.The dynamical model is simplified according to the actual flight,then the simplified dynamical model is divided into two subsystems:a fully-actuated subsystem and an under-actuated subsystem.The controller of the fully-actuated subsystem consists of a SMC controller coupled with a rate bounded PIDC controller,while the controller of the under-actuated subsystem is composed of a SMC controller.The sliding manifold is defined by combining the position and velocity tracking errors of the state variables for each subsystem.Lyapunov stability theory is used to verify the stability of the sliding mode controller,which ensures that all state trajectories of the system can reach and stay on the sliding mode surface,the uncertainty and external interference of the model are compensated.Simulation and experiment compared with the conventional PIDC are carried out,the results demonstrate the effectiveness and the robustness of the proposed control method of this paper.展开更多
To improve the productivity of cluster tools in semiconductor fabrications,on the basis of stating scheduling problems,a try and error-based scheduling algorithm was proposed with residency time constraints and an obj...To improve the productivity of cluster tools in semiconductor fabrications,on the basis of stating scheduling problems,a try and error-based scheduling algorithm was proposed with residency time constraints and an objective of minimizing Makespan for the wafer jobs in cluster tools.Firstly,mathematical formulations of scheduling problems were presented by using assumptions and definitions of a scheduling domain.Resource conflicts were analyzed in the built scheduling model,and policies to solve resource conflicts were built.A scheduling algorithm was developed.Finally,the performances of the proposed algorithm were evaluated and compared with those of other methods by simulations.Experiment results indicate that the proposed algorithm is effective and practical in solving the scheduling problem of the cluster tools.展开更多
文摘Sloshing experiment is crucial to determine the reaction performance of regeneration columns on an offshore floating platform.A novel type of column motion simulating device and a Marine Predator Algorithm-based Sliding Mode Controller(MPA-SMC)are proposed for such sloshing experiments.The simulator consists of a Stewart platform and a steel framework.The Stewart platform is located at the column's center of gravity(CoG)and supported by the steel framework.The platform's hydraulic servo system is controlled by a sliding mode controller with parameters optimized by MPA to improve robustness and precision.A numerical sloshing experiment is conducted using the proposed device and controller.The results show that the novel motion simulator has lower torque during the column sloshes,and the proposed controller performs better than a well-tuned PID controller in terms of target tracking precision and anti-interference capability.
文摘Most of the existing studies on tunnel blast wave are based on spherical or grouped charges, however,conventional weapons are mostly cylindrical rather than spherical. In order to analyze the impact of cylindrical charges on the tunnel blast wave loads and to develop a quantitative calculation method, this study carried out experimental and numerical research. Initially, external explosion experiments were conducted using both 35 kg spherical charges and cylindrical charges with aspect ratio of 4.8 at two different distances from the tunnel entrance. Comparative analysis of the blast wave parameters in the tunnel revealed that the explosive equivalent of the cylindrical charges was significantly higher than that of the spherical charges. To address this, an equivalent coefficient κ based on the spherical charges was proposed for the cylindrical charges. Subsequently, numerical simulations were conducted for the experimental conditions, and the numerical simulation results match the experiments well. Through numerical calculations, the reliability of the equivalent coefficient κ under the experimental conditions was verified, and comparison analysis indicated that the explosion energy of cylindrical charges spreads more radially, resulting in more explosion energy entering the tunnel, which is the fundamental reason for the increase in tunnel blast wave loads. Additionally, analyzing the explosion energy ratio entering the tunnel is an effective method for calculating the equivalent coefficient κ. Finally, through more than one hundred sets of numerical calculation results, the impact of the proportional distance λ and the ratio of charge mass to the tunnel cross-section dimension φ on the equivalence coefficients κ was investigated. An empirical formula for the equivalence coefficient κ was derived through fitting, and the accuracy of the formula was validated through literature experimental results. The research findings of this paper will provide valuable guidance for the calculation of blast wave loads in tunnel.
文摘A mobile robot developed by Wuhan University for full-path hotline inspection on 220 kV transmission lines was presented. With 4 rotating joints and 2 translational ones, such robot is capable of traveling along non- obstaclestraight-line segment and surmounting straight-line segment obstacles as well as transferring between two spans automatically. Lagrange’s equations were utilized to derive dynamic equations of all the links, including items of inertia, coupling inertia, Coriolis acceleration, centripetal acceleration and gravity. And a dynamic response experiment on elemental motions of robot prototype’s travelling along non-obstacle straight-line segment and surmounting obstacles was performed on 220 kV 1∶1 simulative overhanging transmission-line in laboratory. In addition, dynamic numerical simulation was conducted in the corresponding condition. Comparison and analysis on results of experiment and numerical simulation have validated theoretical model and simulation resolution. Therefore, the dynamic model formed hereunder can be used for the study of robot control.
基金Project(50878111) supported by the National Natural Science Foundation of China
文摘Vegetation plays a key role in improving wind environment of residential districts,and is helpful for creating a comfortable and beautiful living environment.The optimal design of vegetation for wind environment improvement in winter was investigated by carrying out field experiments in Heqingyuan residential area in Beijing,and after that,numerical simulation with SPOTE(simulation platform for outdoor thermal environment) experiments for outdoor thermal environment of vegetation was adopted for comparison.The conclusions were summarized as follows:1) By comparing the experimental data with simulation results,it could be concluded that the wind field simulated was consistent with the actual wind field,and the flow distribution impacted by vegetation could be accurately reflected;2) The wind velocity with vegetation was lower than that without vegetation,and the wind velocity was reduced by 46%;3) By adjusting arrangement and types of vegetation in the regions with excessively large wind velocity,the pedestrian-level wind velocity could be obviously improved through the simulation and comparison.
基金Project(51675100)supported by the National Natural Science Foundation of ChinaProject(2016ZX04004008)supported by the National Numerical Control Equipment Major Project of ChinaProject(6902002116)supported by the Foundation of Certain Ministry of China
文摘In the process of thin-wall parts assembly for an antenna,the parts assembly deformation deviation is occurring due to the riveting assembly.In view of the riveting assembly deformation problems,it can be analyzed through transient and static simulation.In this work,the theoretical deformation model for riveting assembly is established with round head rivet.The simulation analysis for riveting deformation is carried out with the riveting assembly piece including four rivets,which comparing with the measuring points experiment results of riveting test piece through dealing with the experimental data using the point coordinate transform method and the space line fitting method.Simultaneously,the deformation deviation of the overall thin-wall parts assembly structure is analyzed through finite element simulation;and its results are verified by the measuring experiment for riveting assembly with the deformation deviation of some key points on the thin-wall parts.Through the comparison analysis,it is shown that the simulation results agree well with the experimental results,which proves the correctness and effectiveness of the theoretical analysis,simulation results and the given experiment data processing method.Through the study on the riveting assembly for thin-wall parts,it will provide a theoretical foundation for improving thin-wall parts assembly quality of large antenna in future.
基金Projects(51274099,51474106)supported by the National Natural Science Foundation of ChinaProject(10C0660)supported by the Scientific Research Fund of Hunan Provincial Education Department,China
文摘In order to research spread law and distribution law of temperature nearby fire sources on roadway in mine, according to combustion theory and other basic, the theory model of temperature attenuation was determined under unsteady heat-exchange between wind and roadway wall. The full-size roadway fire simulation experiments were carried out in Chongqing Research Institute of China Coal Technology & Engineering Group Corporation. The development processes of mine fire and flow pattern of high temperature gas were analyzed. Experimental roadway is seen as physical model, and through using CFD software, the processes of mine fire have been simulated on computer. The results show that, after fire occurs, if the wind speed is less than the minimum speed which can prevent smoke from rolling back, then the smaller wind speed can cause smoke to roll back easily. Hot plume will lead to secondary disasters in upwind side. Because of roadway wall, hot plume released from roadway fire zone has caused the occurrence of the ceiling jet, and the hot plume has been forced down. Whereas, owing to the higher temperature, buoyancy effect is more obvious. Therefore, smoke rises gradually along the roadway in the flow process, and the hierarchical interface appears wavy.Oxygen-enriched combustion and fuel-enriched combustion are the two kinds of combustion states of fire. The oxygen content of downwind side of fire is maintained at around 15% for oxygen-enriched combustion, and the oxygen content of downwind side of fire is maintained at around 2% for fuel-enriched combustion. Furthermore, fuel-enriched combustion can lead to secondary disasters easily.
基金This project was supported by the National "863" High-Tech Research and Development Program of China(2002AA7170)
文摘Ongoing research is described that is focused upon modelling the space base information network and simulating its behaviours： simulation of spaced based communications and networking project. Its objective is to demonstrate the feasibility of producing a tool that can provide a performance evaluation of various eonstellation access techniques and routing policies. The architecture and design of the simulation system are explored. The algorithm of data routing and instrument scheduling in this project is described. Besides these, the key methodologies of simulating the inter-satellite link features in the data transmissions are also discussed. The performance of both instrument scheduling algorithm and routing schemes is evaluated and analyzed through extensive simulations under a typical scenario.
文摘The frequent occurrence of safety accidents during the calendering process is caused by the flammable and explosive properties of composite modified double-base(CMDB)propellant.Optimization of process parameters with the aid of fluid simulation technology could effectively ensure the safety of the calendering process.To improve the accuracy of the simulation results,material parameters and model structure were corrected based on actual conditions,and adaptive grid technology was applied in the local mesh refinement.In addition,the rheological behavior,motion trajectories and heat transfer mechanisms of CMDB propellant slurry were studied with different gaps,rotational rates and temperatures of two rollers.The results indicated that the refined mesh could significantly improve the contour clarity of boundaries and simulate the characteristics of CMDB propellant slurry reflux movement caused by the convergent flow near the outlet.Compared with the gap,the increased rotational rate of roller could promote the reflux movement and intensify the shear flow of slurry inside the flow region by viscous shear dragging.Meanwhile,under the synergistic effect of contact heat transfer as well as convective heat exchange,heat accumulated near the outlet and diffused along the reflux movement,which led to the countercurrent heat dissipation behavior of CMDB propellant slurry.The plasticizing mechanism of slurry and the safety of calendering under different conditions were explored,which provided theoretical guidance and reference data for the optimization of calendering process conditions.Based on the simulation results,the safety of the CMDB propellant calendering process could be significantly improved with a few tests conducted during a short research and development cycle.
基金the National Natural Science Foundation of Ghina （Funds Nos.49673189 , 49873018 ） the Doctoral Scientific Program Special Fund of the Education Department （Fund No.98055807） The State Key Laboratory for Mineral Deposits. ...Research, Nanjing University.
文摘The Ailaoshan aquamarine-bearing pegmatites are associated with Proterozoic metamorphic rocks in the southern portion of the Ailaoshan fault-folded complex.The gem-bearing pegmatite mineralization zones of the region occur in areas generally consistent with the regional tectonic trend.The pegmatites are found in metamorphic rocks,migmatites and in the inner/outer contact zones of gneissoid granites. The Rb-Sr isochron drawn for the pegmatites is 26～31 Ma,(i.e.in Himalayan).The homogenization temperatures of melt and liquid inclusions in minerals vary from 185 to 920℃,which are comparable to the inclusions observed in banded migmatites and ptygmatic quartz veins in the surrounding metamorphic rocks. The mineralization fluids of the pegmatite were rich in HCO_3 and CO_2,and their compositional assemblages are comparable to metamorphic fluids.Results of H,O,C,Si etc.isotopic analyses and REE,and Be analyses indicates that the sources of mineralization components that formed the pegmatites are closely associated with metamorphic fluids and the enclosing metamorphic rocks. A pegmatite structure simulation experiment was conducted at high temperature and pressure(840℃and 1,500×105Pa.),with various metamorphic rock samples in a water-rich and volatile-rich environment.When the liquidus was reached,the temperature was gradually decreased at the rate of 5～10℃/day over a time period of three months.SEM energy-dispersive spectrum analyses were performed on the experimental products.A series of pegmatoid textures were observed including zonal texture,megacryst texture,drusy cavities,crystal druses,and vesicular texture along with more than ten types of minerals including plagioclase,microcline,quartz and biotite.Different metamorphic rock melts generated different mineral assemblages.Experiment results revealed that the partial melting of metamorphic rocks could form melts similar to pegmatite magmas. Based upon the geological characteristics,geochemistry,and pegmatite texture simulation experimental results,it is concluded that the mineralization components of Ailaoshan aquamarine-bearing pegmatites came from metamorphic rocks.The petrogenetic model for the origin of pegmatites is related to ultrametamorphism and metamorphic anatexis.
文摘This paper reports an aspiration-directed, model-based decision support system (AMDSS) integrated with a knowledge-based simulation system. The system is designed to study China's mid-range economic development strategy. The capacity of the system is enhanced by the knowledge-based component which provides a knowledge-based simulation environment for model management. Currently the system has passed the stage of prototype and achieves its implementation capacity. The paper first presents the mathematical aspects of decision making including aspiration-directed decision making, then discusses the architecture of the system. The purpose of the paper is to provide insights into how such an integrated system could provide decision support for complex decision analysis.
文摘The kinetics of the thermal decomposition for a naturally ageing ammonium perchlorate(AP) and hydroxyl-terminated-polybutadiene(HTPB) base bleed composite propellant were investigated using a differential scanning calorimetry(DSC). The naturally ageing AP/HTPB base bleed propellant samples have been stored in a sealed plastic bag at room temperature(5-25 ℃) for more than 20 years. The experimental DSC results were obtained by placing samples(each about 1.5 mg) in a sealed pan under non-isothermal condition under different heating rates, 5.0, 10.0, 15.0, 20.0 and 30.0 ℃·min^(-1). The activation energy and pre-exponential factor were estimated based on the relationship between the exothermic peak temperature and the heating rate by Ozawa and Kissinger methods, respectively. The decomposition kinetic parameters is lower the values under laboratorial aging condition.
基金supported by National Nature Science Foundation of China(Grant No.51176076)
文摘In order to improve the benefits of base bleed in base flow field,the base flow with hot base bleed for two jet models is studied.Twodimensional axisymmetric Navier-Stokes equations are computed by using a finite volume scheme.The base flow of a cylinder afterbody with base bleed is simulated.The simulation results are validated with the experimental data,and the experimental results are well reproduced.On this basis,the base flow fields with base bleed for a circular jet model and an annulus jet model are investigated by selecting the injection temperature from 830 K to 2200 K.The results show that the base pressure of the annular jet model is higher than that of the circular jet model with the changes of the injection parameter and the injection temperature.For the circular jet model,the hot gases are concentrated in the vicinity of the base.For the annular jet model,the bleed gases flow into the shear layer directly so that the hot gases are concentrated in the shear layer.The latter temperature distribution is better for the increase of base pressure.
文摘Train traffic rescheduling is a complicated and large-scaled combinatorial problem. According to the characteristics of China railway system and from the point of practical use, this paper introduces a rule-based train traffic reschedule interactive simulator. It can be used as a powerful training tool to train the dispatcher and to carry out experimental analysis. The production rules are used as the basic for describing the processes to be simulated. With the increase of rule, users can easily upgrade the simulator by adding their own rules.
文摘Equipment systems-of-systems （SOS） effectiveness evaluation can provide important reference for construction and optimization of the equipment SoS. After discussing the basic theory and methods of parallel experiments, we depict an SoS effectiveness analysis and evaluation method using parallel expe- riments theory in detail. A case study is carried out which takes the missile defense system as an example. An artificial system of the missile defense system is constructed with the multi-agent modeling method. Then, single factor, multiple factors and defense position deployment computational experiments are carried out and evaluated with the statistical analysis method. Experiment re- sults show that the altitude of the secondary interception missile is not the key factor which affects SoS effectiveness and putting the defense position ahead will increase defense effectiveness. The case study demonstrates the feasibility of the proposed method.
基金Project(51878164) supported by the National Natural Science Foundation of ChinaProjects(BK20161421, BK20140109) supported by the Natural Science Foundation of Jiangsu Province, China+4 种基金Project(141076) supported by the Huoyingdong Foundation of the Ministry of Education of ChinaProject(BZ2017011) supported by the Science and Technology Support Project of Jiangsu Province, ChinaProject(2242015R30027) supported by the Fundamental Research Funds for the Central Universities, ChinaProject(grant number KFJ170106) supported by the Changsha University of Science & Technology via Open Fund of National Engineering Laboratory of Highway Maintenance Technology, ChinaProject(2018B51) supported by the Science and Technology Support Project of Qilu Transportation Development Group, China。
文摘During the compaction of a road subgrade, the mechanical parameters of the soil mass change in real time, but current research assumes that these parameters remain unchanged. In order to address this discrepancy, this paper establishes a relationship between the degree of compaction K and strain ε. The relationship between the compaction degree K and the shear strength of soil(cohesion c and frictional angle φ) was clearly established through indoor experiments. The subroutine UMAT in ABAQUS finite element numerical software was developed to realize an accurate calculation of the subgrade soil compaction quality. This value was compared and analyzed against the assumed compaction value of the model, thereby verifying the accuracy of the intelligent compaction calculation results for subgrade soil. On this basis, orthogonal tests of the influential factors(frequency, amplitude, and quality) for the degree of compaction and sensitivity analysis were carried out. Finally, the ‘acceleration intelligent compaction value’, which is based on the acceleration signal, is proposed for a compaction meter value that indicates poor accuracy. The research results can provide guidance and basis for further research into the accurate control of compaction quality for roadbeds and pavements.
基金Project(2016YFB1200404)supported by the National Key Research and Development Program of ChinaProjects(51605044,U1534210)supported by the National Science Foundation of China。
文摘This paper reviews the current status of investigation on snow accumulation on the bogies of high-speed trains(HSTs) running in snowy region. First, the background of the snow issue occurring to the HST and the contra-measures for the snow issue proposed in the past decades are provided by reviewing previous studies. Next, the methodology for investigating the snow issue developed by High-Speed Train Research Center of Central South University is introduced, including the numerical simulation research platform and the experimental devices for two-phase flow wind tunnel tests. Then, effective anti-snow flow control schemes for guiding the underbody airflow and their impact on the motion and accretion of snow in the installation region of the bogies are presented. Finally, the remaining investigating challenge for the snow issue of HST and the future research with respect to the challenge are provided from an engineering application viewpoint.
基金supported by National Natural Science Founda-tion of china(Grant No.51774042).
文摘Aiming at the position and attitude tracking of coaxial rotor aircraft(CRA),this paper proposes a combinatorial control method of sliding mode control(SMC)coupled with proportional-integralderivative control(PIDC).Considering the complete description of flight dynamics,aerodynamics and airflow interference,the dynamical model of CRA is established.The dynamical model is simplified according to the actual flight,then the simplified dynamical model is divided into two subsystems:a fully-actuated subsystem and an under-actuated subsystem.The controller of the fully-actuated subsystem consists of a SMC controller coupled with a rate bounded PIDC controller,while the controller of the under-actuated subsystem is composed of a SMC controller.The sliding manifold is defined by combining the position and velocity tracking errors of the state variables for each subsystem.Lyapunov stability theory is used to verify the stability of the sliding mode controller,which ensures that all state trajectories of the system can reach and stay on the sliding mode surface,the uncertainty and external interference of the model are compensated.Simulation and experiment compared with the conventional PIDC are carried out,the results demonstrate the effectiveness and the robustness of the proposed control method of this paper.
基金Projects(71071115,60574054) supported by the National Natural Science Foundation of China
文摘To improve the productivity of cluster tools in semiconductor fabrications,on the basis of stating scheduling problems,a try and error-based scheduling algorithm was proposed with residency time constraints and an objective of minimizing Makespan for the wafer jobs in cluster tools.Firstly,mathematical formulations of scheduling problems were presented by using assumptions and definitions of a scheduling domain.Resource conflicts were analyzed in the built scheduling model,and policies to solve resource conflicts were built.A scheduling algorithm was developed.Finally,the performances of the proposed algorithm were evaluated and compared with those of other methods by simulations.Experiment results indicate that the proposed algorithm is effective and practical in solving the scheduling problem of the cluster tools.
