含时间参量的传感器网络修正感知模型

目标与传感器之间的距离对传感器感知能力具有重要影响,但现有研究仅考虑以距离作为参量建立量化传感器感知能力的模型,而忽略了时间因素的影响。为此,引入时间参量建立修正的传感器感知模型。实验结果表明,与已有的感知模型相比,该模型能更真实地模拟传感器对目标的感知行为,量化传感器对运动目标的感知能力。     

基于CB+-tree的时态XML索引

针对时态查询与时间属性紧密相关的特点,利用时间区间作为改进后B+-tree的索引关键字建立索引,改进后的B+-tree命名为Changing B+-tree(CB+-tree)。实验证明,在CB+-tree上进行时态查询比B+-tree及基于DOM的XML文档的查询效率有所提高。     

行为时态逻辑TLA定理系统证明及公平性研究

行为时态逻辑TLA(temporal logic of actions)能够在一种语言中同时表达模型程序与逻辑规则,是目前模型检测技术中一个较新的研究方向.为了理解行为时态逻辑与传统时态逻辑之间的理论联系,研究了时态逻辑的语义和定理系统,并根据行为时态逻辑TLA的自身特征指出了TLA中的行为属于时态逻辑T4系统.在此基础上严格的证明了TIA的定理系统及TLA中强公平性蕴涵弱公平性的重要性质,讨论了强公平性与弱公平性等价的条件.最后以实例说明了如何确定动作的强弱公平性,进而建立系统的TLA模型.     

Annotation Based Query Answer over Inconsistent Database

In this paper, we introduce a concept of Annotation Based Query Answer, and a method for its computation, which can answer queries on relational databases that may violate a set of functional dependencies. In this approach, inconsistency is viewed as a property of data and described with annotations. To be more precise, every piece of data in a relation can have zero or more annotations with it and annotations are propagated along with queries from the source to the output. With annotations, inconsistent da...     

欠驱动刚性航天器时间最优轨迹规划设计

应用伪谱法解决欠驱动刚性航天器的时间最优轨迹规划问题.首先建立欠驱动刚性航天器的动力学和运动学模型,对于给定的初末姿态,选取机动时间最短为待优化的性能指标,并考虑到实际控制输入受限,将其转化为优化过程中的不等式约束条件;然后应用Legendre伪谱法,将优化问题离散化为非线性规划问题进行求解.仿真结果表明,应用伪谱法规划得到的欠驱动航天器最优轨迹,能够较好地满足各种约束条件,而且计算精度高、速度快,具有良好的实时性.     

Heuristics for the multi-period orienteering problem with multiple time windows

We present the multi-period orienteering problem with multiple time windows (MuPOPTW), a new routing problem combining objective and constraints of the orienteering problem (OP) and team orienteering problem (TOP), constraints from standard vehicle routing problems, and original constraints from a real-world application. The problem itself comes from a real industrial case. Specific route duration constraints result in a route feasibility subproblem. We propose an exact algorithm for this subproblem, and we embed it in a variable neighborhood search method to solve the whole routing problem. We then provide experimental results for this method. We compare them to a commercial solver. We also adapt our method to standard benchmark OP and TOP instances, and provide comparative tables with state-of-the-art algorithms.     

Min-degree constrained minimum spanning tree problem: New formulation via Miller–Tucker–Zemlin constraints

Given an undirected network with positive edge costs and a positive integer $d>2$, the minimum-degree constrained minimum spanning tree problem is the problem of finding a spanning tree with minimum total cost such that each non-leaf node in the tree has a degree of at least $d$. This problem is new to the literature while the related problem with upper bound constraints on degrees is well studied. Mixed-integer programs proposed for either type of problem is composed, in general, of a tree-defining part and a degree-enforcing part. In our formulation of the minimum-degree constrained minimum spanning tree problem, the tree-defining part is based on the Miller–Tucker–Zemlin constraints while the only earlier paper available in the literature on this problem uses single and multi-commodity flow-based formulations that are well studied for the case of upper degree constraints. We propose a new set of constraints for the degree-enforcing part that lead to significantly better solution times than earlier approaches when used in conjunction with Miller–Tucker–Zemlin constraints.     

An effective heuristic for flexible job-shop scheduling problem with maintenance activities

Most production scheduling problems, including the standard flexible job-shop scheduling problem (FJSP), assume that machines are continuously available. However, in most realistic situations, machines may become unavailable during certain periods due to preventive maintenance (PM). In this paper, a flexible job-shop scheduling problem with machine availability constraints is considered. Each machine is subject to preventive maintenance during the planning period and the starting times of maintenance activities are either flexible in a time window or fixed beforehand. Moreover, two cases of maintenance resource constraint are considered: sufficient maintenance resource available or only one maintenance resource available. To deal with this variant FJSP problem with maintenance activities, a filtered beam search (FBS) based heuristic algorithm is proposed. With a modified branching scheme, the machine availability constraint and maintenance resource constraint can be easily incorporated into the proposed algorithm. Simulation experiments are conducted on some representative problems. The results demonstrate that the proposed filtered beam search based heuristic algorithm is a viable and effective approach for the FJSP with maintenance activities.     

有时态本体模型及其管理原型系统

为使本体能够方便地表达、处理与时间相关的信息,将有效时间概念引入本体模型,介绍有时态本体模型定义及相关定理,在此基础上,实现有时态本体管理原型系统,并将该原型系统应用于存在时态冲突的信息集成系统中进行实验。实验结果证明了将本体用有效时间进行扩展,从而形成有时态本体模型,并对其进行存储管理的必要性,同时也显示了该原型系统对时态查询的支持能力。     

Semi‐global stabilization of discrete‐time systems subject to non‐right invertible constraints

This paper investigates time‐invariant linear systems subject to input and state constraints. We study discrete‐time systems with full or partial constraints on both input and state. It has been shown earlier that the solvability conditions of stabilization problems are closely related to important concepts such as the right invertibility or non‐right invertibility of the constraints, the location of constraint invariant zeros, and the order of constraint infinite zeros. In this paper, for general time‐invariant linear systems with non‐right invertible constraints, necessary and sufficient conditions are developed under which semi‐global stabilization in the admissible set can be achieved by state feedback. Sufficient conditions are also developed for such a stabilization in the case where measurement feedback is used. Such sufficient conditions are almost necessary. Controllers for both state feedback and measurement feedback are constructed as well. Copyright © 2009 John Wiley & Sons, Ltd.