装备维修宏观调控指标体系研究

在对大量历史数据的统计分析基础上 ,科学确定了全军装备维修宏观管理所需的调控指标 ,并建立了计量经济学模型和回归模型 ,为装备维修宏观调控提供了基本依据。     

Discrete‐time analysis of MAP/PH/1 multiclass general preemptive priority queue

We use the matrix‐geometric method to study the MAP/PH/1 general preemptive priority queue with a multiple class of jobs. A procedure for obtaining the block matrices representing the transition matrix P is presented. We show that the special upper triangular structure of the matrix R obtained by Miller [Computation of steady‐state probabilities for M/M/1 priority queues, Oper Res 29(5) (1981), 945–958] can be extended to an upper triangular block structure. Moreover, the subblock matrices of matrix R also have such a structure. With this special structure, we develop a procedure to compute the matrix R. After obtaining the stationary distribution of the system, we study two primary performance indices, namely, the distributions of the number of jobs of each type in the system and their waiting times. Although most of our analysis is carried out for the case of K = 3, the developed approach is general enough to study the other cases (K ≥ 4). © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 662–682, 2003.     

Reliability of a two-dimensional demand-based networked system with multistate components

Existing research on multistate system reliability has mainly focused on one-dimensional systems such as parallel systems, linear sliding window systems, and linearly consecutively connected systems. However, two-dimensional networked systems widely exist in real-world applications such as lighting systems, monitoring systems, and computer network systems. This research considers a two-dimensional networked system consisting of multistate components. The system fails if the cumulative performance of any row or any column cannot meet a predetermined demand. A novel reliability evaluation algorithm is proposed for the considered two-dimensional networked system by extending the universal generating function technique. Furthermore, the proposed model and reliability evaluation algorithm are extended to a two-dimensional networked system with phased missions. The proposed models and algorithms are illustrated by a matrix heating system in a thermoforming machine.     

螺栓法兰连接结构有限元模型参数确定方法

螺栓法兰连接广泛用于各种工业结构中,为准确预测该连接在实际工作中发挥的作用,需要建立准确高效的有限元模型。针对有限元建模过程中模型各种参数的确定问题,综合使用数值仿真手段和试验手段分别对模型网格参数和接触参数的确定开展研究。参数确定后的螺栓法兰连接结构有限元模型在保证计算精度的前提下,计算效率得到显著提高。     

基于云贝叶斯网络的毁伤效果评估方法

目标毁伤效果评估是为指挥员提供决策的量化的依据,是现代信息化战争中必不可少的一环。基于图像的毁伤评估技术更是现代信息化战争必不可少的评估手段,通过对毁伤图像进行特征量提取,基于贝叶斯网络的概率推理和云模型强大的知识表示,进行毁伤评估值和毁伤等级的计算。仿真结果表明,该方法充分考虑到了不确定信息的模糊性和随机性,具有有效性和可行性。     

基于神经网络的复杂导弹系统可靠性预测

介绍了如何利用神经网络对复杂导弹系统可靠性进行预测。对利用导弹地面测试数据和可靠性数据预测未来导弹可靠性问题进行了描述。给出了建模思路和方法框架。探讨了基于因子分析的可靠性数据特征选择方法、循环神经网络(RNN)、长短时记忆网络(LSTM)、门循环网络(GRU)以及输出数据融合方法。在实例中利用该方法对其飞行可靠性进行了预测,验证了方法的可行性与有效性。该方法可以充分利用复杂系统地面测试数据、可靠性数据中隐含的信息以及多种神经网络的优点,具有一定的通用性与实用性。     

石墨烯作为水基半合成切削液添加剂的硬质合金-钢材料摩擦学特性分析

改善加工过程润滑条件是延缓刀具磨损的重要途径。将石墨烯作为3034水基半合成切削液的添加剂,研究石墨烯悬浮切削液的硬质合金-钢材料摩擦学性能,研究对象是由硬质合金YG8制备的金属球和由45#钢制备的圆盘形试件;采用球-盘摩擦副接触方式在摩擦磨损试验机上进行试验,测定了质量分数为0. 1%~0. 9%的石墨烯悬浮切削液的平均摩擦特性和摩擦系数;采用激光共聚焦显微镜对磨痕轮廓进行提取,并得出磨损定量评价指数,并用扫描电镜和拉曼光谱仪对磨痕进行磨损机理分析;进行切削实验来分析石墨烯悬浮切削液对切削性能指标的改善情况。实验分析结果表明:石墨烯悬浮切削液能明显改善硬质合金-45#钢之间的润滑条件,摩擦系数和磨损率显著下降,采用不同质量分数石墨烯悬浮切削液的平均摩擦系数较原半合成切削液下降12. 9%~57. 3%,磨损率下降33. 82%,同时切削合力较原半合成切削液下降18. 58%,加工后工件表面粗糙度下降7. 5%。     

几何约束的改进弹性体网格变形方法研究及应用

针对现有弹性体网格变形方法无法有效抑制网格单元出现"负体积"和过度畸变等问题,引入体积弹性模量约束和挤压弹性模量约束,提出一种基于几何约束的改进弹性体法。借助Patrick网格质量参数,选取三维长方体边界在旋转、平移和伸展变形三种方式下的大幅度运动,对比研究引入几何约束后的改进效果。仿真计算二维NACA0012翼型的俯仰振荡和三维伸缩翼变形过程的气动特性,结果表明:基于几何约束的改进弹性体法显著提高了变形网格的鲁棒性,尤其在大变形时能够有效约束较差网格单元,改善经典方法存在的问题,可为非定常流场问题的求解提供有力支撑。