结构方程模型参数估计的GME方法

提出应用广义最大熵的方法对结构方程模型的参数进行估计,该方法能够处理有限的或者不完全数据。为了验证广义最大熵方法在估计结构方程模型参数时的性能,采用了一个应用于美国顾客满意指数(ACSI)的结构方程模型生成仿真数据,仿真结果表明,与PLS相比,GME方法具有更高的拟合精度和较低的预测误差,在样本数据较少时,表现更为明显。     

基于数值模拟的拔伸成形工艺分析与优化

变薄拔伸是厚壁深筒件生产的关键工序,成形难度大.针对现行的拔伸成形工艺,为改善成形稳定性、提高成形质量、延长模具寿命,通过采用刚粘塑性有限元法,根据不同参数和条件,在计算机上对拔伸工艺进行数值模拟分析,分别讨论了拔伸模圈道数、变形量分配、模圈间距及入模角等因素对拔伸成形过程的影响,进而提出了"多模短距长拔"、变形量依次递减和较小入模角等优化措施.这样既减少了大量现场试验,又达到了工艺优化的目的.     

SEAD场景异构无人机配置与任务规划联合优化方法

对敌防空压制(suppression of enemy air defenses, SEAD)场景是多无人机协同的典型应用,针对该场景特点,在任务规划问题基础上将各类型无人机数量也作为决策变量,充分表征目标、任务和无人机的多种约束,建立异构无人机编队路径问题模型。设计了双层联合优化方法求解该模型：上层设计了任务衔接参数指标,精确评估各类型无人机需求,指导无人机配置调整;下层设计了改进遗传算法,高效处理多类型约束并能结合无人机数量变化对任务方案进行精细调整;双层相互协调获得满足需求的无人机配置和执行方案。仿真结果表明,该方法可以在避免遍历无人机配置组合的前提下获得合理的无人机配置方案和高效可行的执行方案。     

面向NCW的C2参考模型研究

对C2系统仿真及评价而言,在网络中心战背景下构建一个良好的参考模型是目前C2领域研究中的瓶颈问题.以过程模型及MOM框架为核心构建了面向复杂网络的C2系统概念性模型框架.在构筑抽象的C2过程模型框架基础上,借鉴认知决策(RPD)模型的概念,从感知分析及参数估计、态势评估、模式匹配、行为确定四个方面对C2过程模型进行了形式化描述,同时从个体信息能力度量、个体态势感知能力度量、个体决策能力度量、个体指挥引导能力度量、信息共享能力度量、态势共享能力度量、协同决策能力度量、作战意图共享能力度量、作战意图同步能力度量9个方面对C2 MOM框架进行了分析.     

Institutional parameters that condition farmer–herder conflicts in Tivland of Benue State,Nigeria

ABSTRACT

This conceptual review examines institutional parameters that underpin farmer–herder conflicts in Tivland of Benue State, Nigeria. Anchored on the theory of New Institutionalism, it argues that tensions and conflicts between Tiv-farmers and the Fulani-herdsmen is occasioned largely by the disarticulation of the traditional institutional norms/rules of interaction by formal political institutions expressed in land use laws, West African sub-regional protocol, human rights provision of the Nigerian constitution and the Benue State law on anti-grazing. In these contrasting institutional forms, the formal political institution is prioritised by the state while farmers and herders are divided about the institutional basis of their coexistence. Farmers who host the herdsmen demonstrate preference for traditional norms of land ownership and control while the herdsmen incline towards new political/legal instruments which they interpret, purports to give them access to grazing lands and hence an alibi for rejecting institutions that contradict their claim to access spaces for pastoralism. Thus, persisting claims to the exercise of rights to freedom of movement and access to grazing land as opposed to claims to traditional rights of ownership and control of ancestral lands explain the origin and continuity of the farmer–herder conflicts in Benue state, Nigeria.     

Level product form QSF processes and an analysis of queues with Coxian interarrival distribution

In this article, we study a class of Quasi‐Skipfree (QSF) processes where the transition rate submatrices in the skipfree direction have a column times row structure. Under homogeneity and irreducibility assumptions we show that the stationary distributions of these processes have a product form as a function of the level. For an application, we will discuss the ‐queue that can be modeled as a QSF process on a two‐dimensional state space. In addition, we study the properties of the stationary distribution and derive monotonicity of the mean number of the customers in the queue, their mean sojourn time and the variance as a function of for fixed mean arrival rate. © 2016 Wiley Periodicals, Inc. Naval Research Logisticsxs 66:57–72, 2019