This paper presents an approximation method to display realistic pictures of numerical control (NC) machining simulation very quickly. T he tool movement envelope is divided into many small regions and the normal to...This paper presents an approximation method to display realistic pictures of numerical control (NC) machining simulation very quickly. T he tool movement envelope is divided into many small regions and the normal to t hese small regions is calculated. The system saves the calculated result in a fi le before starting animation display. When the system starts displaying machinin g animation, it does not need to calculate small triangular facets normal to the workpiece surface. It only needs to find out what part of the cutter cuts the w orkpiece surface and to read the normal from the file. A highly efficient NC cod e verification method is also presented in this paper. The method first detects the error in z direction. If some points are reported to be out of the tolerance , the system divides neighborhood of these points into smaller grids and calcula tes the normal surface at each grid intersection and the error in the normal ve ctor direction.展开更多
This paper presents the design and ground verification for vision-based relative navigation systems of microsatellites,which offers a comprehensive hardware design solution and a robust experimental verification metho...This paper presents the design and ground verification for vision-based relative navigation systems of microsatellites,which offers a comprehensive hardware design solution and a robust experimental verification methodology for practical implementation of vision-based navigation technology on the microsatellite platform.Firstly,a low power consumption,light weight,and high performance vision-based relative navigation optical sensor is designed.Subsequently,a set of ground verification system is designed for the hardware-in-the-loop testing of the vision-based relative navigation systems.Finally,the designed vision-based relative navigation optical sensor and the proposed angles-only navigation algorithms are tested on the ground verification system.The results verify that the optical simulator after geometrical calibration can meet the requirements of the hardware-in-the-loop testing of vision-based relative navigation systems.Based on experimental results,the relative position accuracy of the angles-only navigation filter at terminal time is increased by 25.5%,and the relative speed accuracy is increased by 31.3% compared with those of optical simulator before geometrical calibration.展开更多
A mathematical hydraulic support self-tracking model for three-machine cooperative mining is proposed to address low efficiency and difficulties in strategy evaluation of a fully mechanized coal face.The proposed mode...A mathematical hydraulic support self-tracking model for three-machine cooperative mining is proposed to address low efficiency and difficulties in strategy evaluation of a fully mechanized coal face.The proposed model uses the coordinates and traction speed of the shearer to calculate the frequency of the circular hydraulic support and realize the coordinated operation of the three-machine mining technology.A unity3d hardware-in-the-loop simulation experimental hearer and hydraulic support platform was used to validate the model of autonomous follow-up.The results indicate that collaborative control of coal mining allowed for an efficiency 3.76%higher than under automatic operation mode and 46.03%higher than under manual control;thus,The mathematical model provided an improved production efficiency of the fully mechanized mining face.The mathematical model also provides a more intelligent and reliable security support,and improves the intelligent level of hydraulic support follow-up control.展开更多
S surface controllers have been proven to provide effective motion control for an autonomous underwater vehicle (AUV).However, it is difficult to adjust their control parameters manually.Choosing the optimum parameter...S surface controllers have been proven to provide effective motion control for an autonomous underwater vehicle (AUV).However, it is difficult to adjust their control parameters manually.Choosing the optimum parameters for the controller of a particular AUV is a significant challenge.To automate the process, a modified particle swarm optimization (MPSO) algorithm was proposed.It was based on immune theory, and used a nonlinear regression strategy for inertia weight to optimize AUV control parameters.A semi-physical simulation system for the AUV was developed as a platform to verify the proposed control method, and its structure was considered.The simulation results indicated that the semi-physical simulation platform was helpful, the optimization algorithm has good local and global searching abilities, and the method can be reliably used for an AUV.展开更多
Before the task of autonomous underwater vehicle(AUV) was implemented actually,its semi-physical simulation system of pipeline tracking had been designed.This semi-physical simulation system was used to test the softw...Before the task of autonomous underwater vehicle(AUV) was implemented actually,its semi-physical simulation system of pipeline tracking had been designed.This semi-physical simulation system was used to test the software logic,hardware architecture,data interface and reliability of the control system.To implement this system,the whole system plan,including interface computer and the methods of pipeline tracking,was described.Compared to numerical simulation,the semi-physical simulation was used to test the real software and hardware more veritably.In the semi-physical simulation system,tracking experiments of both straight lines and polygonal lines were carried out,considering the influence of ocean current and the situation of buried pipeline.The experimental results indicate that the AUV can do pipeline tracking task,when angles of pipeline are 15°,30°,45° and 60°.In the ocean current of 2 knots,AUV could track buried pipeline.展开更多
The plasma optical boundary reconstruction technique based on Hommen's theory is promising for future tokamaks with high parameters. In this work, we conduct detailed analysis and simulation verification to estima...The plasma optical boundary reconstruction technique based on Hommen's theory is promising for future tokamaks with high parameters. In this work, we conduct detailed analysis and simulation verification to estimate the ‘logic loophole' of this technique. The finite-width effect and unpredictable errors reduce the technique's reliability, which leads to this loophole. Based on imaging theory, the photos of a virtual camera are simulated by integrating the assumed luminous intensity of plasma. Based on Hommen's theory, the plasma optical boundary is reconstructed from the photos. Comparing the reconstructed boundary with the one assumed, the logic loophole and its two effects are quantitatively estimated. The finite-width effect is related to the equivalent thickness of the luminous layer, which is generally about 2-4 cm but sometimes larger. The level of unpredictable errors is around 0.65 cm. The technique based on Hommen's theory is generally reliable, but finite-width effect and unpredictable errors have to be taken into consideration in some scenarios. The parameters of HL-2M are applied in this work.展开更多
The restraint intensity （RI） of the pipeline girth welding joint was investigated using finite element method and experimental method to predict the cold cracking susceptibility of pipeline steel. The distribution o...The restraint intensity （RI） of the pipeline girth welding joint was investigated using finite element method and experimental method to predict the cold cracking susceptibility of pipeline steel. The distribution of RI along the girth weld was investigated to study the influence of welding position on the RL Subsequently, the effects of outer diameter （OD） and wall thickness of pipeline on the RI were studied with ABAQUS software. The results show that the RI is almost independent of welding position. The RI increased with the increasing wall thickness but decreased with the increasing OD. A prediction model of Rl was developed based on the effects of the OD and the wall thickness. It has been found that the predicted RIs were in good agreement with the experimental values. The maximum fractional error between the predicted RI and the experimental values was just about 10%. h was indicated that the errors were mainly caused by the heterogeneous of the weld bead.展开更多
In order to improve the overall resilience of the urban infrastructures, it is required to conduct blast resistant design for important building structures in the city. For complex terrain in the city, it is recommend...In order to improve the overall resilience of the urban infrastructures, it is required to conduct blast resistant design for important building structures in the city. For complex terrain in the city, it is recommended to determine the blast load on the structures via numerical simulation. Since the mesh size of the numerical model highly depends on the explosion scenario, there is no generally applicable approach for the mesh size selection. An efficient method to determine the mesh size of the numerical model of near-ground detonation based on explosion scenarios is proposed in this study. The effect of mesh size on the propagation of blast wave under different explosive weights was studied, and the correlations between the mesh size effect and the charge weight or the scaled distance was described. Based on the principle of the finite element method and Hopkinson-Cranz scaling law, a mesh size measurement unit related to the explosive weight was proposed as the criterion for determining the mesh size in the numerical simulation. Finally, the applicability of the method proposed in this paper was verified by comparing the results from numerical simulation and the explosion tests and was verified in AUTODYN.展开更多
This paper presents a formal verification method based on logic simulation. In our method, using symbolic values even circuits which include data paths can be verified without abstraction of data paths. Our verifier e...This paper presents a formal verification method based on logic simulation. In our method, using symbolic values even circuits which include data paths can be verified without abstraction of data paths. Our verifier extracts a transition relation from the state graph (given as a specification) which is expressed using symbolic values, and verifies based on simulation using those symbolic values if the circuit behaves correctly with respect to each transition of the specification. If the verifier terminates with "correct", then we can guarantee that for any applicable input vector sequences, the circuit and the specification behaves identically. We have implemented the proposed method on a Unix workstation and verified some FIFO and LIFO circuits by using it.展开更多
This paper reviews some aspects of evaluation of climate simulation, including the ITCZ, the surface air temperature （SAT）, and the monsoon. A brief introduction of some recently proposed approaches in weather forec...This paper reviews some aspects of evaluation of climate simulation, including the ITCZ, the surface air temperature （SAT）, and the monsoon. A brief introduction of some recently proposed approaches in weather forecast verification is followed by a discussion on their possible application to evaluation of climate simulation. The authors suggest five strategies to extend the forecast verification methods to climate simulation evaluation regardless significant differences between the forecasts and climate simulations. It is argued that resolution, convection scheme, stratocumulus cloud cover, among other processes in the atmospheric general circulation model （AGCM） and the ocean-atmosphere feedback are the potential causes for the double ITCZ problem in coupled models and AGCM simulations, based on the system- and component-level evaluations as well as the downscaling strategies in some recent research. Evaluations of simulated SAT and monsoons suggest that both coupled models and AGCMs show good performance in representing the SAT evolution and its variability over the past century in terms of correlation and wavelet analysis but poor at reproducing rainfall, and in addition, the AGCM alone is not suitable for monsoon regions due to the lack of air-sea interactions.展开更多
In terms of controlling groundwater in deep foundation pit projects, the usual methods include increasing the curtain depth, reducing the amount of pumped groundwater, and implementing integrated control, in order to ...In terms of controlling groundwater in deep foundation pit projects, the usual methods include increasing the curtain depth, reducing the amount of pumped groundwater, and implementing integrated control, in order to reduce the drawdown and land subsidence outside pits. In dewatering design for confined water, factors including drawdown requirements, the thickness of aquifers, the depth of dewatering wells and the depth of cutoff curtains have to be considered comprehensively and numerical simulations are generally conducted for calculation and analysis. Longyang Road Station on Shanghai Metro Line 18 is taken as the case study subject in this paper, a groundwater seepage model is developed according to the on-site engineering geological conditions and hydrogeological conditions, the excavation depth of the foundation pit as well as the design depth of the enclosure, hydrogeological parameters are determined via the pumping test, and the foundation pit dewatering is simulated by means of the three-dimensional finite difference method, which produces numerical results that consistent with real monitoring data as to the groundwater table. Besides, the drawdown and the land subsidence both inside and outside the pit caused by foundation pit dewatering are calculated and analyzed for various curtain depths. This study reveals that the drawdown and the land subsidence change faster near the curtain with the increase in the curtain depth, and the gradient of drawdown and land subsidence changes dwindles beyond certain depths. In this project, the curtain depth of 47/49 m is adopted, and a drawdown-land subsidence verification test is completed given hanging curtains before the excavation. The result turns out that the real measurements basically match the calculation results from the numerical simulation, and by increasing the depth of curtains, the land subsidence resulting from dewatering is effectively controlled.展开更多
The bionic structure drip irrigation emitter(BSDE)is a new-type emitter,by which better hydraulic performances can be obtained.In the present work,twenty-five sets of orthogonal test schemes were implemented to analyz...The bionic structure drip irrigation emitter(BSDE)is a new-type emitter,by which better hydraulic performances can be obtained.In the present work,twenty-five sets of orthogonal test schemes were implemented to analyze the influence of the geometric parameters of the flow channel on the hydraulic characteristics and energy dissipation efficiency of this emitter.Through numerical simulations and verification tests,the flow index and energy dissipation coefficient were obtained.According to the results,the flow index of the BSDE is 0.4757-0.5067.The energy dissipation coefficient under the pressure head of 5-15 m is 584-1701.The verification test has shown that the relative errors among measured values,simulated values and estimated values are less than 3%,which indicates that the flow index can be estimated reliably.展开更多
From the viewpoints of environmental conservation and energy efficiency,seawater-source heat pump system(SWHP) to provide district cooling and heating is applied in coastal areas.Based on the system,a heat transfer mo...From the viewpoints of environmental conservation and energy efficiency,seawater-source heat pump system(SWHP) to provide district cooling and heating is applied in coastal areas.Based on the system,a heat transfer model was established for cast heat exchanger(CHE) adopted by SWHP systems.The CHE consists of pipes immersed in the seawater and used for transferring heat between the seawater and the heat exchanger pipes of SWHP system.An experimental study was carried out to test the validity of the model.A program was developed in VB language and the effects of inlet temperature,flow rate of the secondary refrigerant and length of CHE on the results were investigated.The results of the numerical simulation are in consistence with the experiments in both winter and summer conditions.As a result,application of SWHP systems with CHE in coastal areas in China is feasible due to the favorable geographical conditions and environment.展开更多
Japanese IMS-VHT project on the Virtual Heat Treatment tool for monitoring and optimising HT process in relation with the international cooperative programs is briefly introduced. This project motivates to develop vir...Japanese IMS-VHT project on the Virtual Heat Treatment tool for monitoring and optimising HT process in relation with the international cooperative programs is briefly introduced. This project motivates to develop virtual tools for computer to optimize the heat treatment condition and to support decision for HT operation by knowledge based database in addition to process simulation. As one of the activities with the cooperation of the Society of Materials Science, Japan and the Japan Society for Heat Treatment, a benchmark project is undergoing. This includes simulation of carburized quenching process of a cylinder, disc, and ring as well as a helical gear by use of common data of materials properties and cooling characteristics by several available simulation programs. A part of the newly obtained results is presented as an interim report.展开更多
In order to solve the problems of rolling forming accuracy and fillet thinning of alloy steel rim, a three-dimensional model of three pass rolling process was established, and the influence of different process parame...In order to solve the problems of rolling forming accuracy and fillet thinning of alloy steel rim, a three-dimensional model of three pass rolling process was established, and the influence of different process parameters on forming quality was analyzed by using the finite element software, and the optimal process parameter combination was obtained. On this basis, the simulation results of wheel rim stress and strain for each pass rolling are analyzed, and the particle tracking technology is introduced to analyze the variation rule of stress in each incremental step. Finally, the simulation and experimental results show that the simulation thickness is basically consistent with the actual thickness, which improves the accuracy of rim rolling forming, and further verifies the correctness of rolling process simulation.展开更多
In view of problems on the traditional education for marine hydrodynamic course, such as obsolete course content and methods of instruction, disjointed theory and experiment, and obscure effects, this paper explores a...In view of problems on the traditional education for marine hydrodynamic course, such as obsolete course content and methods of instruction, disjointed theory and experiment, and obscure effects, this paper explores and proposes a new reform and practice strategy for the marine hydrodynamic course using numerical simulation and experiment verification. The reform in education based on experiment verification focuses on the high-level theory, the experiment research and the professional skills. The results show that innovative potential and independent learning ability of students are aroused and cultivated, which satisfy the teaching requirements in the new era.展开更多
Valve train dynamic behaviors need to be considered at the beginning of the engine mechanical design,especially during choosing valve spring parameters.From parameter definition to simulation,the valve train parameter...Valve train dynamic behaviors need to be considered at the beginning of the engine mechanical design,especially during choosing valve spring parameters.From parameter definition to simulation,the valve train parameters around dynamic performance are determined step by step.The valve train dynamic test is done finally to verify the design result since it is a such important facet for valve train design.And reliability from mass production and product life view must be considered during whole design process too.展开更多
文摘This paper presents an approximation method to display realistic pictures of numerical control (NC) machining simulation very quickly. T he tool movement envelope is divided into many small regions and the normal to t hese small regions is calculated. The system saves the calculated result in a fi le before starting animation display. When the system starts displaying machinin g animation, it does not need to calculate small triangular facets normal to the workpiece surface. It only needs to find out what part of the cutter cuts the w orkpiece surface and to read the normal from the file. A highly efficient NC cod e verification method is also presented in this paper. The method first detects the error in z direction. If some points are reported to be out of the tolerance , the system divides neighborhood of these points into smaller grids and calcula tes the normal surface at each grid intersection and the error in the normal ve ctor direction.
基金supported in part by the Doctoral Initiation Fund of Nanchang Hangkong University(No.EA202403107)Jiangxi Province Early Career Youth Science and Technology Talent Training Project(No.CK202403509).
文摘This paper presents the design and ground verification for vision-based relative navigation systems of microsatellites,which offers a comprehensive hardware design solution and a robust experimental verification methodology for practical implementation of vision-based navigation technology on the microsatellite platform.Firstly,a low power consumption,light weight,and high performance vision-based relative navigation optical sensor is designed.Subsequently,a set of ground verification system is designed for the hardware-in-the-loop testing of the vision-based relative navigation systems.Finally,the designed vision-based relative navigation optical sensor and the proposed angles-only navigation algorithms are tested on the ground verification system.The results verify that the optical simulator after geometrical calibration can meet the requirements of the hardware-in-the-loop testing of vision-based relative navigation systems.Based on experimental results,the relative position accuracy of the angles-only navigation filter at terminal time is increased by 25.5%,and the relative speed accuracy is increased by 31.3% compared with those of optical simulator before geometrical calibration.
基金This work was supported by the Project funded by China Postdoctoral Science Foundation under Grant 2019M651081the Merit Funding for the Returned Overseas Personnel Sci-Tech Activities of Shanxi Province under Grant 2016 and Key Research and Development Program of Shanxi(2019)and Innovation Programs of Higher Education Institutions in Shanxi(2019L0305).
文摘A mathematical hydraulic support self-tracking model for three-machine cooperative mining is proposed to address low efficiency and difficulties in strategy evaluation of a fully mechanized coal face.The proposed model uses the coordinates and traction speed of the shearer to calculate the frequency of the circular hydraulic support and realize the coordinated operation of the three-machine mining technology.A unity3d hardware-in-the-loop simulation experimental hearer and hydraulic support platform was used to validate the model of autonomous follow-up.The results indicate that collaborative control of coal mining allowed for an efficiency 3.76%higher than under automatic operation mode and 46.03%higher than under manual control;thus,The mathematical model provided an improved production efficiency of the fully mechanized mining face.The mathematical model also provides a more intelligent and reliable security support,and improves the intelligent level of hydraulic support follow-up control.
基金Supported by the 863 Project under Grant No.2008AA092301the Fundamental Research Foundation of Harbin Engineering University under Grant No.2007001
文摘S surface controllers have been proven to provide effective motion control for an autonomous underwater vehicle (AUV).However, it is difficult to adjust their control parameters manually.Choosing the optimum parameters for the controller of a particular AUV is a significant challenge.To automate the process, a modified particle swarm optimization (MPSO) algorithm was proposed.It was based on immune theory, and used a nonlinear regression strategy for inertia weight to optimize AUV control parameters.A semi-physical simulation system for the AUV was developed as a platform to verify the proposed control method, and its structure was considered.The simulation results indicated that the semi-physical simulation platform was helpful, the optimization algorithm has good local and global searching abilities, and the method can be reliably used for an AUV.
基金Projects(50909025,51179035) supported by the National Natural Science Foundation of ChinaProject(HEUCFZ1003) supported by the Fundamental Research Funds for Central Universities of China
文摘Before the task of autonomous underwater vehicle(AUV) was implemented actually,its semi-physical simulation system of pipeline tracking had been designed.This semi-physical simulation system was used to test the software logic,hardware architecture,data interface and reliability of the control system.To implement this system,the whole system plan,including interface computer and the methods of pipeline tracking,was described.Compared to numerical simulation,the semi-physical simulation was used to test the real software and hardware more veritably.In the semi-physical simulation system,tracking experiments of both straight lines and polygonal lines were carried out,considering the influence of ocean current and the situation of buried pipeline.The experimental results indicate that the AUV can do pipeline tracking task,when angles of pipeline are 15°,30°,45° and 60°.In the ocean current of 2 knots,AUV could track buried pipeline.
基金supported by the Tsinghua University 2021 Doctoral Summer Projectsupported by the National Key R&D Program of China (No. 2018YFE0301102)National Natural Science Foundation of China (Nos. 11875020 and 11875023)。
文摘The plasma optical boundary reconstruction technique based on Hommen's theory is promising for future tokamaks with high parameters. In this work, we conduct detailed analysis and simulation verification to estimate the ‘logic loophole' of this technique. The finite-width effect and unpredictable errors reduce the technique's reliability, which leads to this loophole. Based on imaging theory, the photos of a virtual camera are simulated by integrating the assumed luminous intensity of plasma. Based on Hommen's theory, the plasma optical boundary is reconstructed from the photos. Comparing the reconstructed boundary with the one assumed, the logic loophole and its two effects are quantitatively estimated. The finite-width effect is related to the equivalent thickness of the luminous layer, which is generally about 2-4 cm but sometimes larger. The level of unpredictable errors is around 0.65 cm. The technique based on Hommen's theory is generally reliable, but finite-width effect and unpredictable errors have to be taken into consideration in some scenarios. The parameters of HL-2M are applied in this work.
基金financially supported by the Tianjin Natural Science Foundation(No.11JCYBJC06000)the Key Project of Tianjin Municipal Science and Technology Support Program(No.11ZCGYSF00100)the Gansu Province Science and Technology Support Program(No.1204GKCA007)
文摘The restraint intensity （RI） of the pipeline girth welding joint was investigated using finite element method and experimental method to predict the cold cracking susceptibility of pipeline steel. The distribution of RI along the girth weld was investigated to study the influence of welding position on the RL Subsequently, the effects of outer diameter （OD） and wall thickness of pipeline on the RI were studied with ABAQUS software. The results show that the RI is almost independent of welding position. The RI increased with the increasing wall thickness but decreased with the increasing OD. A prediction model of Rl was developed based on the effects of the OD and the wall thickness. It has been found that the predicted RIs were in good agreement with the experimental values. The maximum fractional error between the predicted RI and the experimental values was just about 10%. h was indicated that the errors were mainly caused by the heterogeneous of the weld bead.
基金the funding supports of the National Key Research and Development Plan,China(Grant No.2022YFC3801800)National Natural Science Foundation of China(Grant Nos.52038010 and 52078368)。
文摘In order to improve the overall resilience of the urban infrastructures, it is required to conduct blast resistant design for important building structures in the city. For complex terrain in the city, it is recommended to determine the blast load on the structures via numerical simulation. Since the mesh size of the numerical model highly depends on the explosion scenario, there is no generally applicable approach for the mesh size selection. An efficient method to determine the mesh size of the numerical model of near-ground detonation based on explosion scenarios is proposed in this study. The effect of mesh size on the propagation of blast wave under different explosive weights was studied, and the correlations between the mesh size effect and the charge weight or the scaled distance was described. Based on the principle of the finite element method and Hopkinson-Cranz scaling law, a mesh size measurement unit related to the explosive weight was proposed as the criterion for determining the mesh size in the numerical simulation. Finally, the applicability of the method proposed in this paper was verified by comparing the results from numerical simulation and the explosion tests and was verified in AUTODYN.
文摘This paper presents a formal verification method based on logic simulation. In our method, using symbolic values even circuits which include data paths can be verified without abstraction of data paths. Our verifier extracts a transition relation from the state graph (given as a specification) which is expressed using symbolic values, and verifies based on simulation using those symbolic values if the circuit behaves correctly with respect to each transition of the specification. If the verifier terminates with "correct", then we can guarantee that for any applicable input vector sequences, the circuit and the specification behaves identically. We have implemented the proposed method on a Unix workstation and verified some FIFO and LIFO circuits by using it.
基金supported by the National Basic Research Program of China (973 Program, Grant No 2005CB321703) the National Natural Science Foundation of China (NSFC) Innovation Research Group Fund (Grant No 40821092)
文摘This paper reviews some aspects of evaluation of climate simulation, including the ITCZ, the surface air temperature （SAT）, and the monsoon. A brief introduction of some recently proposed approaches in weather forecast verification is followed by a discussion on their possible application to evaluation of climate simulation. The authors suggest five strategies to extend the forecast verification methods to climate simulation evaluation regardless significant differences between the forecasts and climate simulations. It is argued that resolution, convection scheme, stratocumulus cloud cover, among other processes in the atmospheric general circulation model （AGCM） and the ocean-atmosphere feedback are the potential causes for the double ITCZ problem in coupled models and AGCM simulations, based on the system- and component-level evaluations as well as the downscaling strategies in some recent research. Evaluations of simulated SAT and monsoons suggest that both coupled models and AGCMs show good performance in representing the SAT evolution and its variability over the past century in terms of correlation and wavelet analysis but poor at reproducing rainfall, and in addition, the AGCM alone is not suitable for monsoon regions due to the lack of air-sea interactions.
基金supported by the Researches on the Control of Confined Water Drawdown and Subsidence in Foundation Pit Projects (Project No. JS-KY16R009-1)this project is funded by Shanghai Metro Line 18 Development Co., Ltd.
文摘In terms of controlling groundwater in deep foundation pit projects, the usual methods include increasing the curtain depth, reducing the amount of pumped groundwater, and implementing integrated control, in order to reduce the drawdown and land subsidence outside pits. In dewatering design for confined water, factors including drawdown requirements, the thickness of aquifers, the depth of dewatering wells and the depth of cutoff curtains have to be considered comprehensively and numerical simulations are generally conducted for calculation and analysis. Longyang Road Station on Shanghai Metro Line 18 is taken as the case study subject in this paper, a groundwater seepage model is developed according to the on-site engineering geological conditions and hydrogeological conditions, the excavation depth of the foundation pit as well as the design depth of the enclosure, hydrogeological parameters are determined via the pumping test, and the foundation pit dewatering is simulated by means of the three-dimensional finite difference method, which produces numerical results that consistent with real monitoring data as to the groundwater table. Besides, the drawdown and the land subsidence both inside and outside the pit caused by foundation pit dewatering are calculated and analyzed for various curtain depths. This study reveals that the drawdown and the land subsidence change faster near the curtain with the increase in the curtain depth, and the gradient of drawdown and land subsidence changes dwindles beyond certain depths. In this project, the curtain depth of 47/49 m is adopted, and a drawdown-land subsidence verification test is completed given hanging curtains before the excavation. The result turns out that the real measurements basically match the calculation results from the numerical simulation, and by increasing the depth of curtains, the land subsidence resulting from dewatering is effectively controlled.
基金This work was supported by the Basic Scientific Research Fund of Heilongjiang Provincial Universities(2020-KYYWF-1042).
文摘The bionic structure drip irrigation emitter(BSDE)is a new-type emitter,by which better hydraulic performances can be obtained.In the present work,twenty-five sets of orthogonal test schemes were implemented to analyze the influence of the geometric parameters of the flow channel on the hydraulic characteristics and energy dissipation efficiency of this emitter.Through numerical simulations and verification tests,the flow index and energy dissipation coefficient were obtained.According to the results,the flow index of the BSDE is 0.4757-0.5067.The energy dissipation coefficient under the pressure head of 5-15 m is 584-1701.The verification test has shown that the relative errors among measured values,simulated values and estimated values are less than 3%,which indicates that the flow index can be estimated reliably.
基金Project(2006BAJ04A15-03) supported by the National Science and Technology Pillar Program during the Eleventh Five-year Plan Period
文摘From the viewpoints of environmental conservation and energy efficiency,seawater-source heat pump system(SWHP) to provide district cooling and heating is applied in coastal areas.Based on the system,a heat transfer model was established for cast heat exchanger(CHE) adopted by SWHP systems.The CHE consists of pipes immersed in the seawater and used for transferring heat between the seawater and the heat exchanger pipes of SWHP system.An experimental study was carried out to test the validity of the model.A program was developed in VB language and the effects of inlet temperature,flow rate of the secondary refrigerant and length of CHE on the results were investigated.The results of the numerical simulation are in consistence with the experiments in both winter and summer conditions.As a result,application of SWHP systems with CHE in coastal areas in China is feasible due to the favorable geographical conditions and environment.
文摘Japanese IMS-VHT project on the Virtual Heat Treatment tool for monitoring and optimising HT process in relation with the international cooperative programs is briefly introduced. This project motivates to develop virtual tools for computer to optimize the heat treatment condition and to support decision for HT operation by knowledge based database in addition to process simulation. As one of the activities with the cooperation of the Society of Materials Science, Japan and the Japan Society for Heat Treatment, a benchmark project is undergoing. This includes simulation of carburized quenching process of a cylinder, disc, and ring as well as a helical gear by use of common data of materials properties and cooling characteristics by several available simulation programs. A part of the newly obtained results is presented as an interim report.
文摘In order to solve the problems of rolling forming accuracy and fillet thinning of alloy steel rim, a three-dimensional model of three pass rolling process was established, and the influence of different process parameters on forming quality was analyzed by using the finite element software, and the optimal process parameter combination was obtained. On this basis, the simulation results of wheel rim stress and strain for each pass rolling are analyzed, and the particle tracking technology is introduced to analyze the variation rule of stress in each incremental step. Finally, the simulation and experimental results show that the simulation thickness is basically consistent with the actual thickness, which improves the accuracy of rim rolling forming, and further verifies the correctness of rolling process simulation.
文摘In view of problems on the traditional education for marine hydrodynamic course, such as obsolete course content and methods of instruction, disjointed theory and experiment, and obscure effects, this paper explores and proposes a new reform and practice strategy for the marine hydrodynamic course using numerical simulation and experiment verification. The reform in education based on experiment verification focuses on the high-level theory, the experiment research and the professional skills. The results show that innovative potential and independent learning ability of students are aroused and cultivated, which satisfy the teaching requirements in the new era.
文摘Valve train dynamic behaviors need to be considered at the beginning of the engine mechanical design,especially during choosing valve spring parameters.From parameter definition to simulation,the valve train parameters around dynamic performance are determined step by step.The valve train dynamic test is done finally to verify the design result since it is a such important facet for valve train design.And reliability from mass production and product life view must be considered during whole design process too.
