Block Iterative Methods for a Finite Family of Generalized Nonexpansive Mappings in Banach Spaces

In this paper, we study an operator generated by a finite family of generalized nonexpansive mappings in a Banach space. We first prove that the set of fixed points of this operator is identical to the set of all common fixed points of the mappings. Next, using this operator, we construct an iterative sequence to approximate a common fixed point of the family of generalized nonexpansive mappings. We finally apply our results to solve the feasibility problem in Banach spaces.     

A simulation optimization approach for a two-echelon inventory system with service level constraints

In this paper, we present a simulation optimization algorithm for solving the two-echelon constrained inventory problem. The goal is to determine the optimal setting of stocking levels to minimize the total inventory investment costs while satisfying the expected response time targets for each field depot. The proposed algorithm is more adaptive than ordinary optimization algorithms, and can be applied to any multi-item multi-echelon inventory system, where the cost structure and service level function resemble what we assume. Empirical studies are performed to compare the efficiency of the proposed algorithms with other existing simulation algorithms.     

国防工程除甲醛技术研究

简单叙述了室内和国防工程空气中甲醛的来源,以及甲醛的性质和对人体的危害。介绍了近年来国内外除甲醛技术的研究现状,结合国防工程的特点,对除甲醛技术的可行性进行了分析。     

Feasibility of motion planning on acyclic and strongly connected directed graphs

Motion planning is a fundamental problem of robotics with applications in many areas of computer science and beyond. Its restriction to graphs has been investigated in the literature, for it allows one to concentrate on the combinatorial problem abstracting from geometric considerations. In this paper, we consider motion planning over directed graphs, which are of interest for asymmetric communication networks. Directed graphs generalize undirected graphs, while introducing a new source of complexity to the motion planning problem: moves are not reversible. We first consider the class of acyclic directed graphs and show that the feasibility can be solved in time linear in the product of the number of vertices and the number of arcs. We then turn to strongly connected directed graphs. We first prove a structural theorem for decomposing strongly connected directed graphs into strongly biconnected components. Based on the structural decomposition, we show that the feasibility of motion planning on strongly connected directed graphs can be decided in linear time.     

一种准确滴定判别的统一方法

提出一种基于滴定突跃的准确滴定判别方法,以统一方式完成不同滴定类型的判别。该方法具有原理明确、步骤简单、记忆负担轻和计算效率高的优点;当目测不确定性或者允许误差等参数发生改变时,计算效率不受影响。对于多组分复杂滴定体系,该方法同样高效,只是涉及的数值计算稍显繁复,然而通过软件也能够快速完成。该方法为准确滴定判别提供了一种不同于传统判别式的解决途径。     

基于二维相关红外光谱的鱼糜品质检测可行性分析

对二维相关光谱在鱼糜品质检测中的可行性进行了分析。利用二维相关技术结合中红外光谱技术对冻融处理后白鲢鱼糜蛋白二级结构变化进行了分析。在冻融次数和温度双重外扰的作用下对样品进行了分析。以冻融次数为外扰的二维相关光谱分析结果揭示了鱼糜蛋白二级结构的变化顺序： α-螺旋结构、分子内聚集的β-折叠结构→反平行的β-折叠结构→羰基结构;基于温度外扰的二维相关光谱分析结果表明： 冻融处理1次和2次后鱼糜蛋白二级结构变化轻微。而冻融处理3次之后鱼糜蛋白二级结构已遭到严重破坏。结果分析还发现： 外扰温度为45℃时,温度对羰基的影响比大大小于冻融循环对鱼糜蛋白二级结构的影响。以上结果说明二维相关光谱技术可以探测并直观的反应出鱼糜蛋白二级结构变化程度。如果能将这种变化程度量化,则可以利用该技术对鱼糜新鲜度等品质进行快速检测。     

Cyclic subgradient projections

A cyclically controlled method of subgradient projections (CSP) for the convex feasibility problem of solving convex inequalities is presented. The features of this method make it an efficient tool in handling huge and sparse problems. A particular application to an image reconstruction problem of emission computerized tomography is mentioned.Research supported by National Institute of Health Grant HL 28438-01.     

A constraints-aware Reweighted Feasibility Pump approach

We extend the Reweighted Feasibility Pump (RFP) approach of De Santis et al. (2014) [9], De Santis et al. (2013) [8], which is based on the interpretation of the (main step of the) Feasibility Pump as the Frank-Wolfe method applied to an appropriate penalty function that drives the search towards integer solutions. We modify the function that is minimized by incorporating barrier terms that provide information about how much changing a variable is possible due to it being involved in (almost) active constraints. The corresponding Constraints-Aware RWP is experimentally tested on two sets of hard pure binary feasibility problems, and the results show that, all other things being equal, the modification leads to a more effective and robust method w.r.t. the original RFP one.     

Global and local convergence of a class of penalty-free-type methods for nonlinear programming

We present a class of trust region algorithms without using a penalty function or a filter for nonlinear inequality constrained optimization and analyze their global and local convergence. In each iteration, the algorithms reduce the value of objective function or the measure of constraints violation according to the relationship between optimality and feasibility. A sequence of steps focused on improving optimality is referred to as an f-loop, while some restoration phase focuses on improving feasibility and is called an h-loop. In an f-loop, the algorithms compute trial step by solving a classic QP subproblem rather than using composite-step strategy. Global convergence is ensured by requiring the constraints violation of each iteration not to exceed an progressively tighter bound on constraints violation. By using a second order correction strategy based on active set identification technique, Marato’s effect is avoided and fast local convergence is shown. The preliminary numerical results are encouraging.