In order to reflect the stochastic characteristics of structures more comprehensively and accurately, a theory and method for modeling of structures with stochastic parameters is presented by using probability finite ...In order to reflect the stochastic characteristics of structures more comprehensively and accurately, a theory and method for modeling of structures with stochastic parameters is presented by using probability finite element method and stochastic experiment data of structures based on the modeling of structures with deterministic parameters. Double-decker space frame is taken as an example to validate this theory and method, good results are gained.展开更多
Influence of multiple structural parameters on the performance of a gun launch system driven by highpressure reactive gases is important for structural design and performance adjustment.A coupled lumped parameter mode...Influence of multiple structural parameters on the performance of a gun launch system driven by highpressure reactive gases is important for structural design and performance adjustment.A coupled lumped parameter model was utilized to predict the propellant combustion,and a dynamic finite element method was applied to approximate the mechanical interactions between the projectile and the barrel.The combustion and the mechanical interactions were coupled through a user subroutine interface in ABAQUS.The correctness and the capability of the finite element approximations in capturing small structural changes were validated by comparing predicted resistance with experiments.Based on the coupled model,the influence of structural parameters of a medium-caliber gun on the system performance was investigated.In order to reduce the research costs,orthogonal tests were designed to investigate the comprehensive effects of the parameters.According to statistical analysis,the important order of the structural parameters on the launching process was obtained.The results indicate that the influence of the width of the rotating band stands out among the studied parameters in the gun.The work provides a method to investigate the influence of multiple parameters on system performance and gives guidance for controlling the system performance.展开更多
Eccentric decoupling blasting is commonly used in underground excavation.Determination of perimeter hole parameters(such as the blasthole diameter,spacing,and burden)based on an eccentric charge structure is vital for...Eccentric decoupling blasting is commonly used in underground excavation.Determination of perimeter hole parameters(such as the blasthole diameter,spacing,and burden)based on an eccentric charge structure is vital for achieving an excellent smooth blasting effect.In this paper,the Riedel-Hiermaier-Thoma(RHT)model was employed to study rock mass damage under smooth blasting.Firstly,the parameters of the RHT model were calibrated by using the existing SHPB experiment,which were then verified by the existing blasting experiment results.Secondly,the influence of different charge structures on the blasting effect was investigated using the RHT model.The simulation results indicated that eccentric charge blasting has an obvious pressure eccentricity effect.Finally,to improve the blasting effect,the smooth blasting parameters were optimized based on an eccentric charge structure.The overbreak and underbreak phenomena were effectively controlled,and a good blasting effect was achieved with the optimized blasting parameters.展开更多
Input-output data fitting methods are often used for unknown-structure nonlinear system modeling. Based on model-on-demand tactics, a multiple model approach to modeling for nonlinear systems is presented. The basic i...Input-output data fitting methods are often used for unknown-structure nonlinear system modeling. Based on model-on-demand tactics, a multiple model approach to modeling for nonlinear systems is presented. The basic idea is to find out, from vast historical system input-output data sets, some data sets matching with the current working point, then to develop a local model using Local Polynomial Fitting (LPF) algorithm. With the change of working points, multiple local models are built, which realize the exact modeling for the global system. By comparing to other methods, the simulation results show good performance for its simple, effective and reliable estimation.展开更多
Model-set is utilized in state estimation for maneuver- ing target tracking. Two minimal symmetric model-subsets are designed and investigated by moment matching method, which include hypersphere-symmetric model-subse...Model-set is utilized in state estimation for maneuver- ing target tracking. Two minimal symmetric model-subsets are designed and investigated by moment matching method, which include hypersphere-symmetric model-subset and axis-symmetric model-subset, if system mode is a random variable and obeys certain probability distribution. They can be used as the fun- damental model-subset for multiple models estimation with fixed structure, variable structure and moving bank. The model-groups constructed by above designed subsets are given, which give the practical guidance for use of model-set in multiple models ap- proach with a variable structure. Simulation results show that the performances of two minimal model-set significantly outperform the corresponding model-sets with fixed spacing.展开更多
现有的基于失效物理(physics of failure,PoF)模型的可靠性预计只能计算电子产品在寿命周期内经历单一典型任务剖面的失效时间。本文提出了一种基于失效物理模型,并利用蒙特卡罗仿真定量分析电子产品在寿命周期内实际经历多任务剖面的...现有的基于失效物理(physics of failure,PoF)模型的可靠性预计只能计算电子产品在寿命周期内经历单一典型任务剖面的失效时间。本文提出了一种基于失效物理模型,并利用蒙特卡罗仿真定量分析电子产品在寿命周期内实际经历多任务剖面的可靠性水平的新方法。将该方法应用于某机载电子设备的平均失效前时间(mean time to failure,MTTF)的计算,建立失效率和可靠度的时间函数,与目前国内工程实践中常用的失效率经验模型法以及设备可靠性强化试验的结果进行了对比分析。结果表明,该方法不仅可以计算可靠性参数,而且通过分析与计算过程可发现设计薄弱环节与可靠性参数的定量关系,有效指导设计改进。展开更多
在气候变化背景下,模拟土壤侵蚀的时空演变特征并探讨其与气候因子之间的响应,对于应对气候变化和防灾减灾具有重要意义。现有研究主要聚焦于气候变化、坡度及植被恢复等因素对黄土高原土壤侵蚀的影响,但较少同时考虑各驱动因子之间的...在气候变化背景下,模拟土壤侵蚀的时空演变特征并探讨其与气候因子之间的响应,对于应对气候变化和防灾减灾具有重要意义。现有研究主要聚焦于气候变化、坡度及植被恢复等因素对黄土高原土壤侵蚀的影响,但较少同时考虑各驱动因子之间的相互作用及其对土壤侵蚀的直接与间接影响。基于气象站点、土地利用/土地覆被和土壤质地等数据,采用Theil⁃Sen Median趋势和Mann⁃Kendal检验对气候因子的时空变化特征进行了分析,利用InVEST(Integrated Valuation of Ecosystem Services and Tradeoffs)模型模拟了1990年、2000年、2010年和2020年黄土高原土壤侵蚀的时空分布,并通过最优参数地理探测器和偏最小二乘结构方程模型在考虑自然因子和植被因子的基础上,重点对气候因子对土壤侵蚀的影响强度和路径进行分析。结果表明:气候因子时空变化具有阶段性和区域性,降水量在1990—2000年以-55.96 mm/10a的速率下降,而2000—2020年以53.99 mm/10a的速率上升;研究期内年降水量、降水强度指数、大雨日数、强降水量、平均气温和最低气温的增长率分别为26.15 mm/10a、0.26 mm d^(-1)10a^(-1)、0.56 d/10a、15.21 mm/10a、0.32℃/10a和0.40℃/10a。从空间上看,1990—2000年降水量减少区域为86.36%,而2000年以后增加区域达97.42%;2000—2020年,极端降水指标在整个研究区基本为增加;气温上升区域主要分布在东、西部,气候变化呈现明显的暖湿化趋势且降水的极端性增强。1990—2020年,黄土高原土壤侵蚀模数呈现先减少再增加趋势,2020年土壤侵蚀量为2.19亿t。最优参数地理探测器分析显示,坡度、降水和植被覆盖是土壤侵蚀的主要驱动因素,其中降水量对土壤侵蚀的解释力从1990年的0.11在2020年增至0.18。结合偏最小二乘结构方程模型分析结果,温度主要通过影响降水间接影响土壤侵蚀,降水和自然因子对土壤侵蚀有直接正贡献,而植被因子对土壤侵蚀有直接负贡献,但2020年比2010年降低0.02。因此,在气候暖湿化和降水极端化趋势下,其对土壤侵蚀的影响不可忽视,在未来的土壤侵蚀防控和可持续发展中,需将气候适应和区域发展相结合,以应对未来气候变化的挑战。展开更多
基金the National Natural Science Foundation of China (5963140) Doctor Point Fund of National Education Committee Parent Company Fund of Aviation Industry
文摘In order to reflect the stochastic characteristics of structures more comprehensively and accurately, a theory and method for modeling of structures with stochastic parameters is presented by using probability finite element method and stochastic experiment data of structures based on the modeling of structures with deterministic parameters. Double-decker space frame is taken as an example to validate this theory and method, good results are gained.
基金the financial support from the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYLX_0399)
文摘Influence of multiple structural parameters on the performance of a gun launch system driven by highpressure reactive gases is important for structural design and performance adjustment.A coupled lumped parameter model was utilized to predict the propellant combustion,and a dynamic finite element method was applied to approximate the mechanical interactions between the projectile and the barrel.The combustion and the mechanical interactions were coupled through a user subroutine interface in ABAQUS.The correctness and the capability of the finite element approximations in capturing small structural changes were validated by comparing predicted resistance with experiments.Based on the coupled model,the influence of structural parameters of a medium-caliber gun on the system performance was investigated.In order to reduce the research costs,orthogonal tests were designed to investigate the comprehensive effects of the parameters.According to statistical analysis,the important order of the structural parameters on the launching process was obtained.The results indicate that the influence of the width of the rotating band stands out among the studied parameters in the gun.The work provides a method to investigate the influence of multiple parameters on system performance and gives guidance for controlling the system performance.
基金Projects(11802058,52074262)supported by the National Natural Science Foundation of ChinaProjects(BK20170670,BK20180651)supported by the Jiangsu Youth Foundation,China+2 种基金Project(2020QN06)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(SKLGDUEK1803)supported by the State Key Laboratory for Geomechanics and Deep Underground Engineering,ChinaProject supported by the Mass Entrepreneurship and Innovation Project of Jiangsu,China。
文摘Eccentric decoupling blasting is commonly used in underground excavation.Determination of perimeter hole parameters(such as the blasthole diameter,spacing,and burden)based on an eccentric charge structure is vital for achieving an excellent smooth blasting effect.In this paper,the Riedel-Hiermaier-Thoma(RHT)model was employed to study rock mass damage under smooth blasting.Firstly,the parameters of the RHT model were calibrated by using the existing SHPB experiment,which were then verified by the existing blasting experiment results.Secondly,the influence of different charge structures on the blasting effect was investigated using the RHT model.The simulation results indicated that eccentric charge blasting has an obvious pressure eccentricity effect.Finally,to improve the blasting effect,the smooth blasting parameters were optimized based on an eccentric charge structure.The overbreak and underbreak phenomena were effectively controlled,and a good blasting effect was achieved with the optimized blasting parameters.
基金This project was supported by National Natural Science Foundation (No. 69934020).
文摘Input-output data fitting methods are often used for unknown-structure nonlinear system modeling. Based on model-on-demand tactics, a multiple model approach to modeling for nonlinear systems is presented. The basic idea is to find out, from vast historical system input-output data sets, some data sets matching with the current working point, then to develop a local model using Local Polynomial Fitting (LPF) algorithm. With the change of working points, multiple local models are built, which realize the exact modeling for the global system. By comparing to other methods, the simulation results show good performance for its simple, effective and reliable estimation.
基金supported by Liaoning Province Innovative Team of Higher Education(2008T090)
文摘Model-set is utilized in state estimation for maneuver- ing target tracking. Two minimal symmetric model-subsets are designed and investigated by moment matching method, which include hypersphere-symmetric model-subset and axis-symmetric model-subset, if system mode is a random variable and obeys certain probability distribution. They can be used as the fun- damental model-subset for multiple models estimation with fixed structure, variable structure and moving bank. The model-groups constructed by above designed subsets are given, which give the practical guidance for use of model-set in multiple models ap- proach with a variable structure. Simulation results show that the performances of two minimal model-set significantly outperform the corresponding model-sets with fixed spacing.
文摘现有的基于失效物理(physics of failure,PoF)模型的可靠性预计只能计算电子产品在寿命周期内经历单一典型任务剖面的失效时间。本文提出了一种基于失效物理模型,并利用蒙特卡罗仿真定量分析电子产品在寿命周期内实际经历多任务剖面的可靠性水平的新方法。将该方法应用于某机载电子设备的平均失效前时间(mean time to failure,MTTF)的计算,建立失效率和可靠度的时间函数,与目前国内工程实践中常用的失效率经验模型法以及设备可靠性强化试验的结果进行了对比分析。结果表明,该方法不仅可以计算可靠性参数,而且通过分析与计算过程可发现设计薄弱环节与可靠性参数的定量关系,有效指导设计改进。
文摘在气候变化背景下,模拟土壤侵蚀的时空演变特征并探讨其与气候因子之间的响应,对于应对气候变化和防灾减灾具有重要意义。现有研究主要聚焦于气候变化、坡度及植被恢复等因素对黄土高原土壤侵蚀的影响,但较少同时考虑各驱动因子之间的相互作用及其对土壤侵蚀的直接与间接影响。基于气象站点、土地利用/土地覆被和土壤质地等数据,采用Theil⁃Sen Median趋势和Mann⁃Kendal检验对气候因子的时空变化特征进行了分析,利用InVEST(Integrated Valuation of Ecosystem Services and Tradeoffs)模型模拟了1990年、2000年、2010年和2020年黄土高原土壤侵蚀的时空分布,并通过最优参数地理探测器和偏最小二乘结构方程模型在考虑自然因子和植被因子的基础上,重点对气候因子对土壤侵蚀的影响强度和路径进行分析。结果表明:气候因子时空变化具有阶段性和区域性,降水量在1990—2000年以-55.96 mm/10a的速率下降,而2000—2020年以53.99 mm/10a的速率上升;研究期内年降水量、降水强度指数、大雨日数、强降水量、平均气温和最低气温的增长率分别为26.15 mm/10a、0.26 mm d^(-1)10a^(-1)、0.56 d/10a、15.21 mm/10a、0.32℃/10a和0.40℃/10a。从空间上看,1990—2000年降水量减少区域为86.36%,而2000年以后增加区域达97.42%;2000—2020年,极端降水指标在整个研究区基本为增加;气温上升区域主要分布在东、西部,气候变化呈现明显的暖湿化趋势且降水的极端性增强。1990—2020年,黄土高原土壤侵蚀模数呈现先减少再增加趋势,2020年土壤侵蚀量为2.19亿t。最优参数地理探测器分析显示,坡度、降水和植被覆盖是土壤侵蚀的主要驱动因素,其中降水量对土壤侵蚀的解释力从1990年的0.11在2020年增至0.18。结合偏最小二乘结构方程模型分析结果,温度主要通过影响降水间接影响土壤侵蚀,降水和自然因子对土壤侵蚀有直接正贡献,而植被因子对土壤侵蚀有直接负贡献,但2020年比2010年降低0.02。因此,在气候暖湿化和降水极端化趋势下,其对土壤侵蚀的影响不可忽视,在未来的土壤侵蚀防控和可持续发展中,需将气候适应和区域发展相结合,以应对未来气候变化的挑战。
