激光切割排样系统在硅钢板材加工中的应用

激光切割技术是当前世界上最先进的切割工艺之一，加之排样软件的应用，使板材的利用率得到了很大提高。为了填补扇片零件研究的不足，借鉴传统多边形顶点射线算法的基本原理，提出扇片零件顶点射线算法，解决了任意包角以及任意半径的扇片零件在硅钢板材上的优化排样问题。同时，以该算法为基础，利用VC++6.0开发了一套激光切割排样系统，进行了大量实际排样优化计算。实验结果表明，该算法既满足了实际生产中激光切割的工艺要求，又能够有效地提高硅钢板材的利用率。     

少无废料激光板材切割技术

采用少无废料激光板材切割技术,可以大幅度地提高材料利用率,缩短切割时间,提高生产效率。激光切割路径优化算法和板材的无搭边排样技术是少无废料激光板材切割的关键技术问题。文章研究了少无废料激光切割路径优化原则,在此基础上,研究了少无废料激光切割编程技巧,并结合纺机板材的激光切割实践,进行了少无废料激光板材切割技术研究,结果表明,采用少无废料激光切割技术,材料利用率可10%~30%,切割长度可减少5%~10%。     

导销支架线切割工艺图排样的改进

本文介绍了线切割工艺图排样中,材料利用率和加工时间的目标函数,对导销支架零件工艺图排样方式进行了改进。     

分层实体制造激光头切割路径的建模与优化

分层实体制造(LOM)技术中分层制造时间是由该层的切割速度与切割路径确定的，当切割工艺参数(如：切割功率、切割速度)确定之后，每一层制造的时间是由该层切割(扫描)路径确定的。因此优化切割(扫描)路径对提高成型效率有重要意义，而分层实体制造技术中激光切割路径优化的实质是空行程路径的优化。建立了切割路径空行程路径优化的数学模型。由于求解该模型的复杂性，采用了分级规划的两个分步算法：首先用改进的最近邻域算法求解轮廓边界线上的切割起点，然后当切割点确定后把路径优化问题归结为旅行售货员问题(TSP)，采用了高效的智能仿生算法一蚁群系统算法来求解。运行结果表明，该算法显著缩短了分层制造中的空行程，提高了快速原型制造的效率。     

激光切割板材的工艺处理

本文在现有的激光切割工艺研究的基础上对激光切割板材的工艺处理进行了进一步的探讨 ,其中包括引入线、引出线的设置 ,辅助切割路径的合理安排 ,路径优化和优化排样以及加工参数的优选等等 ,结合计算机的应用 ,实现计算机辅助工艺设计 (CAPP)。     

计算机辅助激光切割布局系统的研发

针对激光切割机切割板材的特点,开发了计算机辅助激光切割布局系统。论文介绍了计算机辅助优化布局的相关基本知识,阐述了计算机辅助系统的优化算法,描述了系统的界面,输入方式,使用方法;并利用开发的系统做了8组随机仿真布局试验,给出了两组布局方案图。试验结果表明:利用开发的系统可以快速生成材料利用率高的优化布局图。按照布局图对板材进行布局设计,可以大大提高材料的利用率,降低生产成本,提高企业利润。     

填充启发式算法的二维矩形排样问题

针对小矩形切割的二维排样问题,尤其是对玻璃或厚钢板等材料,在切割时定向一次性切割到头的排布.结合综合蚂蚁算法和模拟退火算法思想,提出了一种最低水平线与填充式算法相结合的启发式排样算法.通过对计算机上随机产生的实验数据进行模拟,实现了自动排样.实验表明,该算法提高了单次切割的材料利用率,得到较好的排样效果.     

矩形毛坯四块排样方式及其算法

提出矩形毛坯四块排样方式的生成算法,并将该算法与线形规划相结合形成矩形毛坯四块排样方案生成算法,用于求解大规模矩形毛坯排样问题.该算法采用三条剪切线将板材分成四个矩形区域,每个区域中包含一个由同尺寸毛坯组成的规范块.利用文献中报道的例题进行实验计算,与二阶段、T形、两段、三阶段排样算法相比,该算法生成的排样方案在保证利用率的前提下,能够在一定程度上简化切割工艺.     

基于机器视觉的变焦激光切割路径优化研究

针对目前变焦激光切割路径优化方法存在优化时间长、空程行程大以及优化性能低的问题,对基于机器视觉的变焦激光切割路径优化进行了研究。该方法依据机器视觉原理获取激光切割路径相关参数;通过计算机技术对相关路径进行了遍历处理,根据路径约束条件与目标优化函数,建立路径优化模型。进而基于改进后的蚁群算法完成模型的求解,获取最佳的变焦激光切割路径,实现路径的优化。试验结果表明,运用该方法进行变焦激光切割路径优化时,优化准确率高于95%,优化时间随着试验次数的增加也保持在3.5 s左右。因此,该方法优化时长低、空程行程小以及优化性能高。     

新型打印机精密结构装置左／右墙板工艺设计

根据新型打印机精密结构装置左／右墙板的技术要求，提出了一系列工艺措施：通过合理分配工序内容，把加工应力所引起的零件变形控制在最小范围，确保了零件的平面度要求；采用复合引苞、组合成形等复合工序，提高了生产效率；合理排样，提高了材料利用率。并给出了具体的工艺流程和工艺内容。     

An efficient pursuit automata approach for estimating stable all‐pairs shortest paths in stochastic network environments

This paper presents a new solution to the dynamic all‐pairs shortest‐path routing problem using a fast‐converging pursuit automata learning approach. The particular instance of the problem that we have investigated concerns finding the all‐pairs shortest paths in a stochastic graph, where there are continuous probabilistically based updates in edge‐weights. We present the details of the algorithm with an illustrative example. The algorithm can be used to find the all‐pairs shortest paths for the ‘statistical’ average graph, and the solution converges irrespective of whether there are new changes in edge‐weights or not. On the other hand, the existing popular algorithms will fail to exhibit such a behavior and would recalculate the affected all‐pairs shortest paths after each edge‐weight update. There are two important contributions of the proposed algorithm. The first contribution is that not all the edges in a stochastic graph are probed and, even if they are, they are not all probed equally often. Indeed, the algorithm attempts to almost always probe only those edges that will be included in the final list involving all pairs of nodes in the graph, while probing the other edges minimally. This increases the performance of the proposed algorithm. The second contribution is designing a data structure, the elements of which represent the probability that a particular edge in the graph lies in the shortest path between a pair of nodes in the graph. All the algorithms were tested in environments where edge‐weights change stochastically, and where the graph topologies undergo multiple simultaneous edge‐weight updates. Its superiority in terms of the average number of processed nodes, scanned edges and the time per update operation, when compared with the existing algorithms, was experimentally established. Copyright © 2008 John Wiley & Sons, Ltd.     

Unsupervised contour closure algorithm for range image edge-based segmentation.

This paper presents an efficient technique for extracting closed contours from range images' edge points. Edge points are assumed to be given as input to the algorithm (i.e., previously computed by an edge-based range image segmentation technique). The proposed approach consists of three steps. Initially, a partially connected graph is generated from those input points. Then, the minimum spanning tree of that graph is computed. Finally, a postprocessing technique generates a single path through the regions' boundaries by removing noisy links and closing open contours. The novelty of the proposed approach lies in the fact that, by representing edge points as nodes of a partially connected graph, it reduces the contour closure problem to a minimum spanning tree partitioning problem plus a cost function minimization stage to generate closed contours. Experimental results with synthetic and real range images, together with comparisons with a previous technique, are presented.     

Cost Effective Shared Path Protection for WDM Optical Mesh Networks with Partial Wavelength Conversion

In this paper, we study routing and wavelength assignment of connection requests in survivable WDM optical mesh networks employing shared path protection with partial wavelength conversion while 100% restorability is guaranteed against any single failures. We formulate the problem as a linear integer program under a static traffic model. The objective is to minimize the total cost of wavelength-links and wavelength converters used by working paths and protection paths of all connections. A weight factor is used which is defined as the cost ratio of a wavelength converter and a wavelength-link. Depending on the relative cost of bandwidth and wavelength conversion, the optimization objective allows a proper tradeoff between the two. The proposed algorithm, the shortest-widest-path-first (SWPF) algorithm, uses a modified Dijkstra's algorithm to find a working path and a protection path for each connection request in the wavelength graph transformed from the original network topology. When there are multiple candidate paths that have the same minimum total cost, the path along which the maximum number of converters used at each node is minimized is chosen by the SWPF algorithm. We have evaluated the effectiveness of the proposed algorithm via extensive simulation. The results indicate that the performance of the proposed algorithm is very close to that of the optimal solutions obtained by solving the ILP formulation and outperforms existing heuristic algorithms in terms of total number of converters used and the maximum number of converters required at each node in the network. The proposed algorithm also achieves slightly better performance in terms of total cost of wavelength-links and converters used by all connections. We also investigated shared path protection employing converter sharing. The results show that the technique can reduce not only the total number of converters used in the network but also the maximum number of converters required at each node, especially when a large number of converters are needed in the network. In this study, although the ILP formulation is based on static traffic, the proposed algorithm is also applicable to routing dynamic connection requests.     

Minimum delay algorithm based on time aggregated graph in DTN network

The DTN network has the characteristics of dynamic topology change,thus the routing algorithm of static network can not solve the routing problem of time-varying network,and can not support fast transmission of given tasks.The existing time-variant routing algorithm CGR (contact graph routing) uses the earliest contact to obtain the shortest path,but because of the influence of the order of the connectivity period,the CGR algorithm has low link utilization.To solve this problem,the method of finding the shortest path was proposed.Besides,in order to characterize the relation between the different connect periods of the same link,the time series of node cache was added to the time aggregated graph.Based on this,the end-to-end multi-path shortest delay routing algorithm for the known task requirements was proposed.Finally,the feasibility of the algorithm was proved by an example.     

Implementation Method of Cutting Simulation Based on Transient Display and Delay Adjustment Strategy

In the light of the problems that exist in the current cutting algorithms: first, the number of tetrahedron elements increases as the cutting goes on, which leads to the decrease of the algorithm efficiency. Second, the topology structure is constantly updated during the cutting process, which leads to the stutter phenomenon in cutting display. In this paper, a cutting simulation implementation method based on transient display and delay adjustment strategy is proposed. Firstly, the feature points in the original path are screened by the feature criterion function, and the feature path is established. Then, by using the concept of minimum sum of square defined in this paper, the optimal path of the separation is found with the help of feature path points, and the pseudo effect of cutting is directly displayed by designing the transient display module. The delay adjustment is carried out in the cutting gap, and the topology separation in the delay adjustment is implemented by the node offset spread algorithm and the duplicate removal process with timeliness. Finally, the advantages and feasibility of the cutting algorithm proposed in this paper are verified by practical tests. The test results show that the transient display algorithm proposed in this paper takes about 20 ms. With the number of triangular patches increasing, the growth rate of transient display time remains low. The cutting simulation is implemented by using transient display and delay adjustment strategy, which greatly improves the simulation efficiency.     

无线传感器网络中新的最小暴露路径问题及其求解算法

无线传感器网络中原始的最小暴露路径问题没有考虑对路径的实际限制条件,提出一种要求经过某一特别保护区域部分边界的最小暴露路径问题。由于无法建立相应的图模型,原有求解最小暴露路径问题的经典方法（网格法和维诺图法）对提出的新问题不再起效。先将该问题转化成带约束条件的优化问题,然后针对转化后的数学模型高度非线性、高维度而不好用确定性优化方法的特点,结合问题实际背景设计出混合人工蜂群求解算法。通过在多种情况下的仿真实验发现,设计的带约束条件优化模型和混合人工蜂群求解算法能有效解决提出的最小暴露路径问题。     

激光切割超音速喷嘴设计

分析了传统喷嘴工作在较高的供气压力下进行激光切割时产生激波的原因及激波对切割工艺的不良影响.为了解决这一问题,提出了一种设计超音速拉瓦尔喷嘴的新方法.这种新型超音速喷嘴包括四部分:稳定段、收缩段、喉部、扩张段.每一部分都是严格按照空气动力学理论进行设计的.这种喷嘴喷射出的气流动量高,流速均匀,边界整齐.利用这种喷嘴进行激光切割,可有效地提高切割质量和切割速度.     

一种基于图割的全变差图像去噪算法

本文提出一种基于图割的全变差(TV)图像去噪算法.该算法将全变差去噪模型的能量函数最小化问题转化为图的最小割问题,然后采用图割技术(最大流/最小割算法)求得能量函数的全局最优解.并给出了去噪模型中,均衡系数的自适应设定方案.实验结果及分析表明,该算法能有效抑制以往最小化方法产生的阶梯效应,具有较优的复原效果.     

Performance enhancement for impairment-aware SRLG failure protection in wavelength-routed optical networks

With the increase of size and number of shared risk link groups (SRLGs) in WDM networks, path protection tends to have longer working paths and backup paths due to SRLG-disjoint constraints, which makes physical impairment a major concern in working path and backup path provisioning, particularly in large-sized all optical networks. As a simple and efficient algorithm, the working path first algorithm is often used for path protection against SRLG failures, where the working path is calculated first by using the shortest-path algorithm on the graph, followed by using the SRLG-disjoint shortest path as backup path. Compared with the working path, the backup path calculated after the working path in the working path first algorithm is more vulnerable to physical impairment, since it may be much longer than the working path. As a result, if we reject those connections that cannot meet the physical impairment requirement, with SRLGs the blocking probability of path protection will be much higher. We argue that impairment must be taken into account together with capacity efficiency in a comprehensive way during SRLG-disjoint working path and backup path selection. To solve this problem, we motivate the needs to study physical impairment-aware shared-path protection by considering two policies. Policy I uses two SRLG-disjoint least impairment paths as working path and backup path, respectively, and Policy II tries to benefit from both the shortest path and the least impairment path by choosing them intelligently. Analytical and simulation results show: (1) compared with impairment-unawareness, impairment-aware SRLG failure protection performs much better in terms of blocking probability especially with strong physical impairment constraints; (2) impairment-aware SRLG failure protection can significantly reduce physical-layer blocking probability; and (3) the algorithm based on Policy II achieves a good balance between capacity efficiency and physical impairment requirement.