浅析中国造船业未来的发展战略

2003年世界经济复苏推动了航运市场的迅速发展。随着订船量的高涨,世界造船业开始空前规模的扩张。对世界造船业的现状和发展进行了分析,对中国造船业如何能够扬长避短抓住机遇迎接挑战,实现快速成长,进行了战略性思考。     

一种基于Dijkstra算法的动态进路规划方法

为解决调车作业计划自动转化为联锁进路问题,介绍一种动态进路规划方法.把站场抽象为一个无向联通图,使用Dijkstra算法,求解出计划中的起点轨道到终点轨道的一条顺序包含无岔区段和道岔的最短路径.使用模糊匹配算法,对联锁表基本进路中的设备与最短路径中的设备,按照顺序以及设备实时状态进行匹配,获取到正确的进路组合,实现动态...     

基于完全信息条件下的港口竞争合作静态博弈分析

在激烈的竞争中,港口采取不同的策略不仅关系到自身的利润获得,同时也对其他港口的利润产生一定程度上的影响.在完全信息条件下构建了港口竞争合作静态博弈模型,寻求该博弈模型的Nash均衡,并且分析了不同参数的变化对该模型结果的影响.研究表明,港口服务替代率是影响港口竞争合作决策的主要因素.     

基于因子分析与Kohonen网络的公路运输枢纽分类方法

采用因子分析将公路运输枢纽载体城市的14项统计指标简化为3类综合因子,构建Koho-nen网络模型并输入综合因子变量得到公路运输枢纽的初步分类方案,通过F-统计量检验分类效果发现将所选44个公路运输枢纽分为4类最佳.结果表明,因子分析与Kohonen网络结合是一种有效的公路运输枢纽分类方法,公路运输枢纽具有较明显的4个层级结构.     

A simulation study of service differentiation for the bandwidth request scheme in fixed IEEE 802.16 network

Various flexible mechanisms related to quality of service (QoS) provisioning have been specified for uplink traffic at the medium access control (MAC) layer in the IEEE 802.16 standards. Among the mechanisms, contention based bandwidth request scheme can be used to indicate bandwidth demands to the base station for the non-real-time polling and best-effort services. These two services are used for most applications with unknown traffic characteristics. Due to the diverse QoS requirements of those applications, service differentiation (SD) is anticipated over the contention based bandwidth request scheme. In this paper we investigate the SD with the bandwidth request scheme by means of assigning different channel access parameters and bandwidth allocation priorities at different packets arrival probability. The effectiveness of the differentiation schemes is evaluated by simulations. It is observed that the initial backoff window can be efficient in SD, and if combined with the bandwidth allocation priority, the SD performances will be better. Foundation item: the National Basic Research Program (973) of China (No. 2005C13321804)     

Batch RSA signature scheme

We describe a batch RSA digital signature scheme in which a signer can sign messages for multiple recipients simultaneously. The construction is quite efficient due to the batch signing method. This is useful to improve the performance of a high-loaded signing server, for example a secure electronic transaction (SET) gateway. Theoretical calculations and experimental results show that the proposed scheme can improve the performance of the signing server significantly. Foundation item: the National Basic Research Program (973) of China (No. 2005CB321804)     

Mechanical response of steel wire wound reinforced rubber flexible pipe under internal pressure

Steel wire wound reinforced flexible pipe in this study mainly consists of multiple anisotropic steel wire wound reinforcement layers and multiple isotropic rubber layers. Based on 3D anisotropic elastic theory, the analytic solutions of stresses and elastic deformations of steel wire wound reinforced rubber flexible pipe under internal pressure are presented. As the adjacent reinforcement layers with wound angle have different radii, the single reinforcement layer shows the effect of tensile-shear coupling. Moreover, the static loading test results of steel wire wound reinforced rubber flexible pipe under internal pressure are basically coincided with the calculated values by present method.     

An range-free localization scheme for large scale underwater wireless sensor networks

In this paper, we study an area localization problem in large scale underwater wireless sensor networks (UWSNs). The limited bandwidth, the severely impaired channel and the cost of underwater equipment all make the underwater localization problem very challenging. Exact localization is very difficult for UWSNs in deep underwater environment. We propose a range free method based on mobile detachable elevator transceiver (DET) and 3D multi-power area localization scheme (3D-MALS) to address the challenging problem. In the proposed scheme, the ideas of 2D multi-power area localization scheme (2D-ALS) and utilizing DET are used to achieve the simplicity, location accuracy, scalability and low cost performances. The DET can rise and get down to broadcast its position. And it is assumed that all the underwater nodes underwater have pressure sensors and know their z coordinates. We evaluate the performances of 2D-ALS and our proposed 3D-MALS schemes under both ideal and non-ideal channel propagation conditions, in terms of localization error and localization ratio. The simulation results show that our proposed scheme is much more efficient than the 2D-ALS.     

Facility Layout Based on Sequence Analysis： Design of Flowshops

A computer-aided method to design a hybrid layout—tree-shape planar flowlines is presented. In newtype flowshop layout, the common machines shared by several flowlines could be located together in functional sections. The approach combines traditional cell formation techniques with sequence alignment algorithms. Firstly, a sequence analysis based cell formation procedure is adopted; then the operation sequences for parts are aligned to maximize machines adjacency in hyperedge representations; finally a tree-shape planar flowline will be obtained for each part family. With the help of a sample of operation sequences obtained from industry, this algorithm is illustrated.     

Voxelizating 3D mesh models with gray levels

A novel algorithm to voxelize 3D mesh models with gray levels is presented in this paper. The key innovation of our method is to decide the gray level of a voxel according to the total area of all surfaces contained by it. During the preprocessing stage, a set of voxels in the extended bounding box of each triangle is established. Then we travel each triangle and compute the areas between it and its set of voxels one by one. Finally, each voxel is arranged a discrete gray level from 0 to 255. Experiments show that our algorithm gets a comparatively perfect result compared with the prevenient ones and approaches the original models in a more accurate way.