一种在矢量基础上进行图形识别的通用方法

本文描述了一种在矢量基础上进行图形识别的通用方法．该方法包括２个步骤：第１步，寻找组成该图形的第１个关键图素；第２步，根据该图形的构造模式，从第１个关键图素出发，不断在其周围区域寻找组成该图形的其它图素．本文还提出了一种新的平面空间数据结构——位置索引．这种数据结构把平面图上的图形及图素用它们的平面位置索引组织起来，从而提高了按区域位置查找的效率．本文还介绍了该方法的２个应用实例：虚线识别和剖面线识别.     

Incremental arc segmentation algorithm and its evaluation

We present an incremental arc segmentation algorithm, which recovers the vectorized arc fragments obtained by the vectorization of a piece of arc image in a stepwise fashion. Due to proper threshold selection and consistent checking of cocircularity of the assumed arc pieces, the algorithm accurately constructs arcs from the vector input. Nearly 200 synthetic arcs, ranging in radius from five to 50 pixels, in open angle from 1/8π to 2π, and in thickness from one to nine pixels, are used in the experiments and evaluation. Parts of six real drawings, containing about 200 arcs, are also processed. The algorithm works well for arc segments greater than 10 pixels in radius, π/4 in angle, and one pixel in width     

Analysis of back-to-back mechanically stabilized earth walls

Back-to-back Mechanically Stabilized Earth (MSE) walls are commonly used for embankments approaching bridges. However, available design guidelines for this wall system are limited. The distance between two opposing walls is a key parameter used for determining the analysis methods in FHWA Guidelines. Two extreme cases are identified: (1) reinforcements from both sides meet in the middle or overlap, and (2) the walls are far apart, independent of each other. However, existing design methodologies do not provide a clear and justified answer how the required tensile strength of reinforcement and the external stability change with respect to the distance of the back-to-back walls. The focus of this paper is to investigate the effect of the wall width to height ratio on internal and external stability of MSE walls under static conditions. Finite difference method incorporated in the FLAC software and limit equilibrium method (i.e., the Bishop simplified method) in the ReSSA software were used for this analysis. Parametric studies were carried out by varying two important parameters, i.e., the wall width to height ratio and the quality of backfill material, to investigate their effects on the critical failure surface, the required tensile strength of reinforcement, and the lateral earth pressure behind the reinforced zone. The effect of the connection of reinforcements in the middle, when back-to-back walls are close, was also investigated.     

Stress wave propagation when the elastic coefficients vary with depth

Of concern is the propagation of distortionless surface waves in a medium that may be nonuniform relative to depth. Distortionless wave propagation in inhomogeneous media was discussed by V. Burke, R. J. Duffin and D. Hazony, inQuart. Appl. Math., 183–194 (1976). Accordingly, the media could be modeled by a distributed electrical ladder network, nonuniform along the axis. We give a two-dimensional development based on Hooke's law and Newton's law which leads to the well-known case of Rayleigh waves in homogeneous media. It will be seen that the available pool of propagation modes greatly increases when high-pass propagation is included. The emphasis is on media where the elastic coefficients track one another as a function of depth. Special cases are studied in detail showing that as a disturbance travels along the surface, it may assume a broadband phase change, which translates into a shape distortion in the time domain, which is periodic with distance. Applications may be found in acousto-optics, in situ monitoring of elongated bodies, high-frequency SAW filters, microstrips, and any situations where surface waves are used in an environment of high precision or relatively large distances. Work supported, in part, by the ONR, C. K. Vasudevan contract monitor.     

Dynamic non-Bayesian decision making in multi-agent systems

We consider a group of several non-Bayesian agents that can fully coordinate their activities and share their past experience in order to obtain a joint goal in face of uncertainty. The reward obtained by each agent is a function of the environment state but not of the action taken by other agents in the group. The environment state (controlled by Nature) may change arbitrarily, and the reward function is initially unknown. Two basic feedback structures are considered. In one of them — the perfect monitoring case — the agents are able to observe the previous environment state as part of their feedback, while in the other — the imperfect monitoring case — all that is available to the agents are the rewards obtained. Both of these settings refer to partially observable processes, where the current environment state is unknown. Our study refers to the competitive ratio criterion. It is shown that, for the imperfect monitoring case, there exists an efficient stochastic policy that ensures that the competitive ratio is obtained for all agents at almost all stages with an arbitrarily high probability, where efficiency is measured in terms of rate of convergence. It is also shown that if the agents are restricted only to deterministic policies then such a policy does not exist, even in the perfect monitoring case. This revised version was published online in June 2006 with corrections to the Cover Date.     

Patterns of individualism and collectivism across the United States.

Although the individualism–collectivism dimension is usually examined in a U.S. versus Asian context, there is variation within the United States. The authors created an eight-item index ranking states in terms of collectivist versus individualist tendencies. As predicted, collectivist tendencies were strongest in the Deep South, and individualist tendencies were strongest in the Mountain West and Great Plains. In Part 2, convergent validity for the index was obtained by showing that state collectivism scores predicted variation in individual attitudes, as measured by a national survey. In Part 3, the index was used to explore the relationship between individualism–collectivism and a variety of demographic, economic, cultural, and health-related variables. The index may be used to complement traditional measures of collectivism and individualism and may be of use to scholars seeking a construct to account for unique U.S. regional variation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effectiveness of an Internet-based program for reducing risk factors for eating disorders.

This study evaluated an Internet-delivered computer-assisted health education (CAHE) program designed to improve body satisfaction and reduce weight/shape concerns—concerns that have been shown to be risk factors for the development of eating disorders in young women. Participants were 60 women at a public university randomly assigned to either an intervention or control condition. Intervention participants completed the CAHE program Student Bodies. Measures of body image and disordered eating attitudes were assessed at baseline, postintervention, and 3-month follow-up. At follow-up, intervention participants, compared with controls, reported a significant improvement in body image and a decrease in drive for thinness. This program provides evidence for the feasibility and effectiveness of providing health education by means of the Internet. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reducing risk factors for eating disorders: Comparison of an Internet- and a classroom-delivered psychoeducational program.

This controlled trial compared Internet- (Student Bodies [SB]) and classroom-delivered (Body Traps [BT]) psychoeducational interventions for the reduction of body dissatisfaction and disordered eating behaviors/attitudes with a control condition. Participants were 76 women at a private university who were randomly assigned to SB, BT, or a wait-list control (WLC) condition. Measures of body image and eating attitudes and behaviors were measured at baseline, posttreatment, and 4-month follow-up. At posttreatment, participants in SB had significant reductions in weight/shape concerns and disordered eating attitudes compared with those in the WLC condition. At follow-up, disordered behaviors were also reduced. No significant effects were found between the BT and WLC conditions. An Internet-delivered intervention had a significant impact on reducing risk factors for eating disorders. (PsycINFO Database Record (c) 2010 APA, all rights reserved)