信任管理在电子商务中的实现

在电子商务中，信任已经成为谈判策略中的一个重要因素，信任管理也成为安全服务的重要组成部分。本文给出了信任管理在电子商务中的实现。     

等距离圆线阵波达方向的估计

文章简述了智能天线的基本原理，并对智能天线的工作基础：波达方向估计进行了讨论，通过建模与仿真，用波达方向估计的3种方法：延迟相加、最小方差无畸变响应(Capon)，多重信号分类(Music)，分别对来自不同方向的4个信号利5个信号进入8个阵元的等距离圆天线阵列进行试验，得出了仿真结果和最大分辨率。     

医用线阵换能器声场指向性曲线的计算机模拟

本文介绍了基于Visual Basic语言的线阵换能器声场指向性曲线的计算机模拟.     

Direction relations and two-dimensional range queries: optimisation techniques

This paper defines direction relations (e.g., north, northeast) between two-dimensional objects and shows how they can be efficiently retrieved using B-, KDB- and R- tree-based data structures. Essentially, our work studies optimisation techniques for 2D range queries that arise during the processing of direction relations. We test the efficiency of alternative indexing methods through extensive experimentation and present analytical models that estimate their performance. The analytical estimates are shown to be very close to the actual results and can be used by spatial query optimizers in order to predict the retrieval cost. In addition, we implement modifications of the existing structures that yield better performance for certain queries. We conclude the paper by discussing the most suitable method depending on the type of the range and the properties of the data.     

比幅和差式单脉冲雷达微波和差器建模

在定向雷达中，微波和差器的不理想性，对单脉冲雷达定向特性构成了一定的影响，这种不理想性主要由组成和差器的微波桥各端口的小失配形成。为了模拟这种影响，对三通道单脉冲定向雷达微波和差器进行了分析，建立了微波和差器仿真用模型，应用这一模型可以模拟构成和差器的微波桥端口小失配对单脉冲雷达定向特性的影响。这在分析单脉冲雷达定向性能、时域仿真研究单脉冲雷达抗干扰性能等应用中是有意义的。     

Multi-scale qualitative location: A direction-based model

Qualitative locations describe the locations of spatial objects by relating them to a reference frame with qualitative relations. Existing models concerned with regional partitions are mainly topology-based and do not consider the effects of scale changes on locations. This study develops a direction-based multi-scale qualitative location (DMQL) model to fill this gap. First, a cell partition is defined by extending the borders of the minimum bounding rectangles of the regions in a regional partition. Relating spatial objects to all regions by a set of directions is equal to representing the objects as a set of cells in a cell partition. Second, due to the multiple cell representations of spatial objects and the changes in direction relations across scales, some approaches are presented to derive the direction changes between regions in different frames, between spatial objects and regions, and between spatial objects at different scales. Third, the location and relation consistencies of qualitative locations are evaluated based on the cell representations of spatial objects at multiple scales through a case study. The results indicate that the DMQL model can locate objects more precisely than the topology-based models.     

Force direction and physical load in dynamic pushing and pulling

In pushing and pulling wheeled carts, the direction of force exertion may, beside the force magnitude, considerably affect musculoskeletal loading. This paper describes how force direction changes as handle height and force level change, and the effects this has on the loads on the shoulder and low back. Eight subjects pushed against or pulled on a stationary bar or movable cart at various handle heights and horizontal force levels while walking on a treadmill. The forces at the hands in the vertical and horizontal direction were measured by a forcetransducer. The forces, body movements and anthropometric data were used to calculate the net joint torques in the sagittal plane in the shoulder and the lumbosacral joint. The magnitudes and directions of forces did not differ between the cart and the bar pushing and pulling. Force direction was affected by the horizontal force level and handle height. As handle height and horizontal force level increased, the pushing force direction changed from 45° (SD 3.3°) downward to near horizontal, while the pulling force direction changed from pulling upward by 14° (SD 15.3°) to near horizontal. As a result, it was found that across conditions the changes in force exertion were frequently reflected in changes in shoulder torque and low back torque although of a much smaller magnitude. Therefore, an accurate evaluation of musculoskeletal loads in pushing and pulling requires, besides a knowledge of the force magnitude, knowledge of the direction of force exertion with respect to the body.     

基于天线分集和空-时编码的抗舰载卫星天线指向损耗方法研究

本文针对舰载卫星天线指向损耗问题,将接收分集和空-时编码技术应用于舰艇卫星通信中。构建了舰船卫星通信信道模型,分析了舰载天线随机指向损耗特点,研究了接收分集和空-时编码技术,进行了舰船卫星MIMO通信性能仿真。研究结果表明,将MIMO技术应用于舰艇卫星通信可以有效改善舰载卫星天线指向损耗的不良影响。     

基于空间行为的数字几何空间建造 上海卜石艺术馆改造设计

文章通过介绍卜石艺术馆的改造,探讨了空间行为塑形在建筑设计方法上的应用。指出建筑师在对人的行为过程进行推演和模拟时,形成了几何折叠的空间界面,这种反向生形手法,是一个自下而上的过程,也是在数字性能化设计中所用到的设计逻辑,这种逻辑同时又作为建造方式的指导,给予建筑师实现多维空间创造的可能。     

Efficient Euclidean projections via Piecewise Root Finding and its application in gradient projection

Recently, the gradient (subgradient) projection method, especially by incorporating the idea of Nesterov's method, has aroused more and more attention and achieved great successes on constrained optimization problems arising in the field of machine learning, data mining and signal processing. In the gradient projection method, a critical step is how to efficiently project a vector onto a constraint set. In this paper, we propose a unified method called Piecewise Root Finding (PRF) to efficiently calculate Euclidean projections onto three typical constraint sets: ?₁-ball, Elastic Net (EN) and the Intersection of a Hyperplane and a Halfspace (IHH). In our PRF method, we first formulate a Euclidean projection problem as a root finding problem. Then, a Piecewise Root Finding algorithm is applied to find the root and global convergence is guaranteed. Finally, the Euclidean projection result is obtained as a function of the found root in a closed form. Moreover, the sparsity of the projected vector is considered, leading to reduced computational cost for projection onto the ?₁-ball and EN. Empirical studies demonstrate that our PRF algorithm is efficient by comparing it with several state of the art algorithms for Euclidean projections onto the three typical constraint sets mentioned above. Besides, we apply our efficient Euclidean projection algorithm (PRF) to the Gradient Projection with Nesterov's Method (GPNM), which efficiently solves the popular logistic regression problem with the ?₁-ball/EN/IHH constraint. Experimental results on real-world data sets indicate that GPNM has a fast convergence speed.