基于SMT的局部无嫉妒资源分配问题求解

公平分配问题在经济学、政治学和计算机科学等多个领域都受到了关注。针对不可分物品的局部无嫉妒资源分配问题,通过把问题转化为SMT(Satisfiability Modulo Theories)问题进行求解。实验结果表明,SMT求解这类NP难问题是可能的,有关资源分配问题的相关研究主要集中于理论上的分析和有关复杂度的证明。     

以太无源光网络带宽分配算法研究

以太无源光网络综合了PON技术和以太网技术的优点,成为目前先接入网的优选方案。本文通过分析现有以太无源光网络带宽分配算法存在的问题．提出DBA的两个发展方向：自适应上行带宽的DBA算法,有流量预测功能的DBA算法。     

近空间无尾飞行器解耦与控制分配方法研究

关于飞行器稳定性优化控制问题,由于近空间无尾飞行器具有典型的通道间强耦合且多个操纵面介入单个通道控制,执行机构的复杂化和非线性导致控制系统设计实时性和响应性差,精度达不到要求。为提高姿态控制器控制精度,减小力矩分配误差,提出通过解耦控制系统和控制分配逻辑来分别解决对象的耦合和多操纵面的力矩分配问题。通过将动态逆设计方法与变结构控制理论相结合,设计了一种强鲁棒性的解耦控制律,并在加权伪逆算法的基础上,提出采用舵面偏角修正操纵面的效率矩阵,从而实现了强耦合非线性对象的高精度控制。仿真结果表明,控制器解耦效果良好且具有较强鲁棒性,控制分配算法减小了80%力矩分配误差,满足了飞行器的控制需求。     

近似公平带宽分配的无状态队列管理

本文提出了一种基于速率和RED的公平排队算法RRFQ，算法能够达到近似公平的带宽分配，较好地区分短暂拥塞和持续拥塞，改善总体吞吐量，对参数设置的敏感度低。     

基于TDMA的无冲突动态时隙分配算法

针对分簇Ad Hoc网络中固定时隙分配算法信道资源浪费和竞争时隙分配算法传输延迟不固定的问题,提出一种基于时分多址接入的无冲突动态时隙分配算法。该算法根据网络负载动态调整帧长,即当网络负载增大时,增加帧长,提高信道利用率;当网络负载减小时,减少帧长,降低信道申请时延。仿真结果表明,与NEBS算法和时隙ALOHA算法相比,该算法可根据网络负载动态调整资源分配,从而提高系统的吞吐量。     

多极数无刷双馈电机分数槽绕组分配规律研究

多极数无刷双馈电机（BDFM）具有无刷可靠、低变频器容量、省去变速箱等优点,在交流调速和直驱风力发电系统中有着广阔的应用前景。论文全面分析研究定子不同极数下绕组排列和槽电动势星形图,得到了每极每相槽数取不同数值时绕组的嵌线规律,这些规律为多极数BDFM进一步设计和推广应用具有重要意义。     

基于效用函数的无源光网络动态带宽分配算法

为解决无源光网络由于传播距离较远而导致传播时延较长、信道利用率较低的问题,提出一种基于效用函数的无源光网络动态带宽分配算法。在无源光网络上行数据传输方向上,凭借光线路终端规律性地轮询各光分配网,获取上行带宽的请求信息。在无源光网络下行数据传输方向上,光线路终端把光网络的下行业务分组装入帧,并以广播的形式进行数据传输,结合此特点,利用带宽分配与微观经济学之间的相似度。以传输功率和传输信号增益,建立基于效用函数的分配问题优化模型,并通过路由器矩阵及其逆矩阵对该问题模型进行求解,得出各链路的最优传输速率,实现无源光网络动态带宽分配。实验结果表明,所提算法的信道利用率较高且时延抖动较低,能够有效提升网络动态实时性。     

基于路由器的公平带宽分配算法研究

本文介绍了目前在路由器上存在的几种带宽分配的不公平性问题,阐述了在路由器上如何避免这种不公平性,并对核心无状态公平队列调度(CSFQ)算法进行详尽分析,指出了CSFQ算法的问题并总结了目前的解决方法以达到带宽分配的尽可能公平.     

一种以太网无源光网络（EPON）动态带宽分配算法

对EPON系统的上行信道复用技术进行了深入的研究。在EPON系统上行信道复用技术中,带宽分配算法是一个热点和难点。文章基于DifrerServ模型探讨了一种支持多业务的、保证QoS的混合动态带宽分配算法（HBA）,并与静态、动态带宽分配算法进行了仿真比较。结果表明HBA算法在时延、时延抖动和信道利用率等方面优于其它算法。     

A note on envy-free cake cutting with polynomial valuations

The cake cutting problem models the fair allocation of a heterogeneous divisible resource among multiple players. The central fairness criterion is envy-freeness and a major open question in this domain is the design of a bounded protocol that can compute an envy-free allocation of the cake for any number of players. The only existing finite envy-free cake cutting protocol for any number of players, designed by Brams and Taylor [4], has the property that its runtime can be made arbitrarily large by setting up the valuation functions of the players appropriately. Moreover, there is no closed formula that relates the valuation functions to the number of queries required by the protocol.     

正交切削加工过程仿真

为优化正交切削加工参数,采用弹-塑热耦合有限元方法,建立正交切削加工有限元模型.应用DEFORM软件,模拟出45号钢件切削过程中变形区内温度、应力、应变以及切削力的分布,采用自适应网格重划技术避免大塑性变形引起的网格畸变.该仿真结果能对切削加工参数的选择及实际的切削加工提供指导.     

一种有效的求解一维下料问题的启发式算法

使用了一种改进的顺序启发式算法,在排样方式的生成过程中不断修正当前排入毛坯的价值,使之趋于合理,依次选取求解背包函数获得的最大单位价值的排样方式组成当前排样方案,迭代调用该过程多次,最终选取最优的排样方案。在保证较高材料利用率的同时考虑减少排样方式,增加最后一根材料余料长度等多个优化目标。通过多组实验结果比较,证实了算法的有效性。     

Sequential optimization approach for nesting and cutting sequence in laser cutting

The economy of the laser cutting process depends on two productivity issues: (i) nesting, a classic problem of finding the most efficient layout for cutting parts with minimum material waste; (ii) cutting sequence, which targets the optimal sequence of edges of the parts to be cut for minimum cycle time. This paper presents a two stage sequential optimization procedure for nesting and cutting sequence for the objectives of maximizing material utilization and minimization of ideal (non-cut) travel distance of laser cut tool. However, the focus of this paper is the development of solution technique for optimal cutting sequence to any given layout. Simulated annealing algorithm (SAA) is considered to evolve the optimal cutting sequence. The proposed SAA is illustrated with the optimal material utilization layout obtained using sheet cutting suite software, a professional rectangular nesting software package. The robust test carried out with five typical problems shows that the SAA proposed for cutting sequence is capable of providing near optimal solutions. The performance comparison with two literature problems reveals that the proposed SAA is able to give improved result than GA and ACO algorithms.     

Algorithms for 3D guillotine cutting problems: Unbounded knapsack, cutting stock and strip packing

We present algorithms for the following three-dimensional (3D) guillotine cutting problems: unbounded knapsack, cutting stock and strip packing. We consider the case where the items have fixed orientation and the case where orthogonal rotations around all axes are allowed. For the unbounded 3D knapsack problem, we extend the recurrence formula proposed by [1] for the rectangular knapsack problem and present a dynamic programming algorithm that uses reduced raster points. We also consider a variant of the unbounded knapsack problem in which the cuts must be staged. For the 3D cutting stock problem and its variants in which the bins have different sizes (and the cuts must be staged), we present column generation-based algorithms. Modified versions of the algorithms for the 3D cutting stock problems with stages are then used to build algorithms for the 3D strip packing problem and its variants. The computational tests performed with the algorithms described in this paper indicate that they are useful to solve instances of moderate size.     

Hybrid heuristic algorithm for two-dimensional steel coil cutting problem

This paper is concerned with the problem of two-dimensional cutting of small rectangular items, each of which has its own deadline and size, from a large rectangular plate, whose length are more than one thousand times its width, so as to minimize the trim loss and the reduction of the times of clamping and changing speed are also concerned. This problem is different with the classical two-dimensional cutting problem. In view of the distinguishing features of the problem proposed, we put forward the definition of non-classical cutting, that is to say, put a series of items on the rectangular plates in their best layout, so as to enhance utility and efficiency at the same time. These objectives may be conflicting and a balance should be necessary, so we present a Hybrid Heuristic Algorithm (HHA), consisting of clustering, ordering, striping and integer programming etc. We demonstrate the efficiency of the proposed algorithm through the comparison with the algorithm we studied before.     

A heuristic for the skiving and cutting stock problem in paper and plastic film industries

This paper investigates the skiving and cutting stock problem (SCSP) encountered in the paper and plastic film industries, in which a set of nonstandard reels generated from previous cutting processes are used to produce finished rolls through the skiving and cutting process. First, reels are skived together lengthwise to form a reel‐pyramid (a polygon), and then the reel‐pyramid is cut into finished rolls of small widths. Depending on if a reel can be divided lengthwise into subreels to form the reel‐pyramid, the problem can be classified into divisible SCSP (DSCSP) and indivisible SCSP (ISCSP). In this paper, two integer programming (IP) models are proposed for DSCSP and ISCSP, respectively. A sequential value correction procedure combined with the two IP models (SVCTIP) is developed to solve the two SCSPs. The effectiveness of the SVCTIP is demonstrated through extensive computational tests.     

Heuristic for the two-dimensional arbitrary stock-size cutting stock problem

A heuristic is presented for the two-dimensional arbitrary stock-size cutting stock problem, where a set of rectangular items with specified demand are cut from plates of arbitrary sizes that confirm to the supplier’s provisions, such that the plate cost is minimized. The supplier’s provisions include: the lengths and widths of the plates must be in the specified ranges; the total area of the plates with the same size must reach the area threshold. The proposed algorithm uses a pattern-generation procedure with all-capacity property to obtain the patterns, and combines it with a sequential heuristic procedure to obtain the cutting plan, from which the purchasing decision can be made. Practical and random instances are used to compare the algorithm with a published approach. The results indicate that the trim loss can be reduced by more than half if the algorithm is used in the purchasing decision of the plates.     

基于VTK的三维模型切割研究*

为提高模型切割的效率与自然性,利用VTK提供的接口,采用射线拾取方法实现了对表面模型的标记点方式切割,结合四元数的方法实现了对体模型的平面切割。实验表明,通过扩展VTK来实现对三维模型的任意切割是可行的,并可达到较为理想的切割效果。     

CO_2激光器加工晶圆切缝控制工艺研究

晶体硅是当前最重要的半导体材料,主要用于微电子技术。随着微电子技术的发展,对晶圆的切割技术要求越来越高,而在实际切割中,对晶圆的切割十分注重于晶圆的切割宽度,以降低晶圆损耗。研究CO2激光切割机的脉宽、频率以及切割速度对晶圆切割宽度的影响,从而达到高效率、小宽度、高标准的激光切割加工。