Büeckner Rice weight function method was used to analyse mixed mode fracture of center cracked circular disk subjected to uniaxial compression. Based on Wu Carlsson procedure semi analytical modes Ⅰ and Ⅱ weigh...Büeckner Rice weight function method was used to analyse mixed mode fracture of center cracked circular disk subjected to uniaxial compression. Based on Wu Carlsson procedure semi analytical modes Ⅰ and Ⅱ weight functions were derived from corresponding reference displacement fields and stress intensity factors calculated by finite element method. Normalized mode Ⅰ and mode Ⅱ stress intensity factors, f Ⅰ, f Ⅱ , were derived from the obtained semi analytical weight functions. The results were then fitted into polynomials, the precision is within 0.5%. It is interesting to note that when the inclined angle θ of a crack is less than 15°, the f Ⅰvalues are positive. when θ =15°, the f Ⅰ values are positive for the crack length a varying from 0.1 to 0.7, but when a =0.8, the f Ⅰ takes the negative value -0.51. When θ >15°, all the f Ⅰ values become negative, which denotes that the compression shear mode is achieved at crack tips. These results are very useful in the investigation of mixed mode fracture of brittle materials.展开更多
The clustering evaluation can be used to scientifically classify the objects to be evaluated according to the information aggregation of various evaluation rules. In grey weighted clustering evaluation, the index clus...The clustering evaluation can be used to scientifically classify the objects to be evaluated according to the information aggregation of various evaluation rules. In grey weighted clustering evaluation, the index clustering rule relies on the construction of the whitenization weight function, while the existing construction method of the linear function lacks the construction mechanism analysis and validity explanation. A normative construction principle is put forward by analyzing the construction mechanism of the function. Through proving the normative principle of the function,the basic modal function(BMF) is proposed and characterized by different function forms. Then, a new type of the whitenization weight function and its grey clustering evaluation model algorithm are given by studying the mechanism and nature of the construction of different forms of the function. Finally, the comparative study for self-innovation capability of defense science and technology industry(DSTI) is taken as an example. The results show that the different construction ways of the function have an effect on the clustering result. The proposed construction mechanism can better explain the index clustering rules and evaluation effectiveness,which will perfect the theoretical system of grey clustering evaluation and be applied to practice effectively.展开更多
It follows from the analysis of artillery fire errors that approximately two-thirds of the inaccuracy of indirect artillery fire is caused by inaccuracies in the determination of the meteo parameters included in fire ...It follows from the analysis of artillery fire errors that approximately two-thirds of the inaccuracy of indirect artillery fire is caused by inaccuracies in the determination of the meteo parameters included in fire error budget model.Trajectories calculated under non-standard conditions are considered to be perturbed.The tools utilized for the analysis of perturbed trajectories are weighting factor functions(WFFs)which are a special kind of sensitivity functions.WFFs are used for calculation of meteo ballistic elements B(ballistic wind w B,densityρB,virtual temperatureτB,pressure p B)as well.We have found that the existing theory of WFF calculation has several significant shortcomings.The aim of the article is to present a new,improved theory of generalized WFFs that eliminates the deficiencies found.Using this theory will improve methods for designing firing tables,fire control systems algorithms,and meteo message generation algorithms.展开更多
A new kind of combining forecasting model based on the generalized weighted functional proportional mean is proposed and the parameter estimation method of its weighting coefficients by means of the algorithm of quadr...A new kind of combining forecasting model based on the generalized weighted functional proportional mean is proposed and the parameter estimation method of its weighting coefficients by means of the algorithm of quadratic programming is given. This model has extensive representation. It is a new kind of aggregative method of group forecasting. By taking the suitable combining form of the forecasting models and seeking the optimal parameter, the optimal combining form can be obtained and the forecasting accuracy can be improved. The effectiveness of this model is demonstrated by an example.展开更多
在连续且密集奖励的任务中,离线强化学习取得了显著的效果.然而由于其训练过程不与环境交互,泛化能力降低,在离散且稀疏奖赏的环境下性能难以得到保证.扩散模型通过加噪结合样本数据邻域的信息,生成贴近样本数据分布的动作,强化智能体...在连续且密集奖励的任务中,离线强化学习取得了显著的效果.然而由于其训练过程不与环境交互,泛化能力降低,在离散且稀疏奖赏的环境下性能难以得到保证.扩散模型通过加噪结合样本数据邻域的信息,生成贴近样本数据分布的动作,强化智能体的学习和泛化能力.针对以上问题,提出一种扩散模型期望最大化的离线强化学习方法(offline reinforcement learning with diffusion models and expectation maximization,DMEM).该方法通过极大似然对数期望最大化更新目标函数,使策略具有更强的泛化性.将扩散模型引入策略网络中,利用扩散的特征,增强策略学习数据样本的能力.同时从高维空间的角度看期望回归更新价值函数,引入一个惩戒项使价值函数评估更准确.将DMEM应用于一系列离散且稀疏奖励的任务中,实验表明,与其他经典的离线强化学习方法相比,DMEM性能上具有较大的优势.展开更多
为了解决传统硬阈值方法在处理异常测站时难以应对模糊边界的问题,提出一种新方法,将构造运动和观测误差引起的测站异常均视为粗差,并利用隶属度函数构建IGGⅢ等价权函数,以减小异常测站的影响。新方法引入模糊集理论,是一种基于标准化...为了解决传统硬阈值方法在处理异常测站时难以应对模糊边界的问题,提出一种新方法,将构造运动和观测误差引起的测站异常均视为粗差,并利用隶属度函数构建IGGⅢ等价权函数,以减小异常测站的影响。新方法引入模糊集理论,是一种基于标准化残差属于粗差的模糊子集隶属度函数改进的IGGⅢ抗差估计方法(membership function IGGⅢ,MF-IGGⅢ)。首先,通过模糊统计确定标准化残差受粗差污染程度最大的模糊子集的隶属度函数;然后,依据这些隶属度函数值构建等价权函数,并进行选权迭代。模拟实验和对环渤海区域GNSS速度场的拟合分析结果表明,该方法在异常测站检测方面的表现优于假设检验法、均值漂移法和IGGⅢ法,显示出较强的异常测站识别能力。展开更多
文摘Büeckner Rice weight function method was used to analyse mixed mode fracture of center cracked circular disk subjected to uniaxial compression. Based on Wu Carlsson procedure semi analytical modes Ⅰ and Ⅱ weight functions were derived from corresponding reference displacement fields and stress intensity factors calculated by finite element method. Normalized mode Ⅰ and mode Ⅱ stress intensity factors, f Ⅰ, f Ⅱ , were derived from the obtained semi analytical weight functions. The results were then fitted into polynomials, the precision is within 0.5%. It is interesting to note that when the inclined angle θ of a crack is less than 15°, the f Ⅰvalues are positive. when θ =15°, the f Ⅰ values are positive for the crack length a varying from 0.1 to 0.7, but when a =0.8, the f Ⅰ takes the negative value -0.51. When θ >15°, all the f Ⅰ values become negative, which denotes that the compression shear mode is achieved at crack tips. These results are very useful in the investigation of mixed mode fracture of brittle materials.
基金supported by the National Natural Science Foundation of China(71671090)the Aeronautical Science Foundation of China(2016ZG52068)+1 种基金the Liberal Arts and Social Sciences Foundation of the Ministry of Education(MOE)in China(15YJCZH189)the Qinglan Project for Excellent Youth or Middle-aged Academic Leaders in Jiangsu Province
文摘The clustering evaluation can be used to scientifically classify the objects to be evaluated according to the information aggregation of various evaluation rules. In grey weighted clustering evaluation, the index clustering rule relies on the construction of the whitenization weight function, while the existing construction method of the linear function lacks the construction mechanism analysis and validity explanation. A normative construction principle is put forward by analyzing the construction mechanism of the function. Through proving the normative principle of the function,the basic modal function(BMF) is proposed and characterized by different function forms. Then, a new type of the whitenization weight function and its grey clustering evaluation model algorithm are given by studying the mechanism and nature of the construction of different forms of the function. Finally, the comparative study for self-innovation capability of defense science and technology industry(DSTI) is taken as an example. The results show that the different construction ways of the function have an effect on the clustering result. The proposed construction mechanism can better explain the index clustering rules and evaluation effectiveness,which will perfect the theoretical system of grey clustering evaluation and be applied to practice effectively.
基金support of financing from the Research Project for the Development of the Department of Weapons and Ammunition, Faculty of Military Technology, University of Defence, Brno, DZRO K–201
文摘It follows from the analysis of artillery fire errors that approximately two-thirds of the inaccuracy of indirect artillery fire is caused by inaccuracies in the determination of the meteo parameters included in fire error budget model.Trajectories calculated under non-standard conditions are considered to be perturbed.The tools utilized for the analysis of perturbed trajectories are weighting factor functions(WFFs)which are a special kind of sensitivity functions.WFFs are used for calculation of meteo ballistic elements B(ballistic wind w B,densityρB,virtual temperatureτB,pressure p B)as well.We have found that the existing theory of WFF calculation has several significant shortcomings.The aim of the article is to present a new,improved theory of generalized WFFs that eliminates the deficiencies found.Using this theory will improve methods for designing firing tables,fire control systems algorithms,and meteo message generation algorithms.
文摘A new kind of combining forecasting model based on the generalized weighted functional proportional mean is proposed and the parameter estimation method of its weighting coefficients by means of the algorithm of quadratic programming is given. This model has extensive representation. It is a new kind of aggregative method of group forecasting. By taking the suitable combining form of the forecasting models and seeking the optimal parameter, the optimal combining form can be obtained and the forecasting accuracy can be improved. The effectiveness of this model is demonstrated by an example.
文摘在连续且密集奖励的任务中,离线强化学习取得了显著的效果.然而由于其训练过程不与环境交互,泛化能力降低,在离散且稀疏奖赏的环境下性能难以得到保证.扩散模型通过加噪结合样本数据邻域的信息,生成贴近样本数据分布的动作,强化智能体的学习和泛化能力.针对以上问题,提出一种扩散模型期望最大化的离线强化学习方法(offline reinforcement learning with diffusion models and expectation maximization,DMEM).该方法通过极大似然对数期望最大化更新目标函数,使策略具有更强的泛化性.将扩散模型引入策略网络中,利用扩散的特征,增强策略学习数据样本的能力.同时从高维空间的角度看期望回归更新价值函数,引入一个惩戒项使价值函数评估更准确.将DMEM应用于一系列离散且稀疏奖励的任务中,实验表明,与其他经典的离线强化学习方法相比,DMEM性能上具有较大的优势.
文摘为了解决传统硬阈值方法在处理异常测站时难以应对模糊边界的问题,提出一种新方法,将构造运动和观测误差引起的测站异常均视为粗差,并利用隶属度函数构建IGGⅢ等价权函数,以减小异常测站的影响。新方法引入模糊集理论,是一种基于标准化残差属于粗差的模糊子集隶属度函数改进的IGGⅢ抗差估计方法(membership function IGGⅢ,MF-IGGⅢ)。首先,通过模糊统计确定标准化残差受粗差污染程度最大的模糊子集的隶属度函数;然后,依据这些隶属度函数值构建等价权函数,并进行选权迭代。模拟实验和对环渤海区域GNSS速度场的拟合分析结果表明,该方法在异常测站检测方面的表现优于假设检验法、均值漂移法和IGGⅢ法,显示出较强的异常测站识别能力。
