面向对象的数据建模方法及系统仿真中的应用

建模与仿真已成功地应用于军事、社会、经济等各个领域。文章以作战仿真系统中的部分数据为例,描述了利用面向对象的方法,建立基于UML和XML的作战数据模型的过程。     

海洋力学环境建模及其分布式仿真应用

海洋力学环境建模是飞行器分布式仿真研究中的重要一环,它为飞行器控制系统仿真提供扰动环境,其模拟精度直接关系到仿真结果的置信度。文章首先简要介绍了环境仿真节点在分布式仿真系统中作用和数据传递关系,然后基于时空离散的思想提出了一种海洋力学环境建模方案并简要描述了环境参数的初始化、可视化设置、快速检索和插值方法。该方案及其算法已成功应用于某分布式仿真系统。     

水润滑橡胶轴承结构形式对接触状况影响研究

应用有限元软件ANSYS分别对3种板条结构形式的水润滑橡胶轴承进行静态接触仿真分析,研究板条接触变形后形成的楔角、水囊以及接触压力对润滑性能的影响规律。结果表明:在相同载荷下,凸面型轴承垂向位移最大,平面型次之,凹面型最小;平面型橡胶轴承比凹面型橡胶轴承具有更好的润滑性能,更适合实际应用。     

某综合调查船声学换能器安装工艺

针对某综合调查船的换能器安装于船底部、其尺寸大、技术要求高、安装工艺复杂等技术问题,采用高精度测量、焊接变形控制、电缆管隧以及优化施工工艺等措施,提高声学设备的安装精度和工作效率。     

复合材料层合板螺栓连接强度实验研究

通过对不同预紧力下舰船复合材料层合板单剪连接和双剪连接两种结构形式的静拉伸强度实验,考核了复合材料层板螺栓连接处的强度特性。实验结果表明:双剪连接结构强度随着预紧力的增大而增大。而在单剪连接结构中,一定范围内的预紧力可以增加连接结构的强度,过大的预紧力会使其连接强度减小。通过对以上实验现象的分析,认为预紧力对板的侧向约束限制并延缓了局部开裂和分层是预紧力增加螺栓连接结构强度的主要原因。     

Income-contingent user preferences in policy evaluation: application and discussion based on multi-agent transport simulations

Standard economic policy evaluation allows the realization of projects if the aggregated economic benefit outweighs their costs. The use of one single aggregated welfare measure for evaluating and ranking projects has often been criticized for many reasons. A major issue is that differentiated effects on individuals or subgroups of the population are not taken into consideration. This leads to the need for transport planning tools that provide additional information for politicians and decision makers. The microscopic multi-agent simulation approach presented in this paper is capable of helping to design better solutions in such situations. In particular, it is shown that the inclusion of individual income in utility calculations allows a better understanding of problems linked to public acceptance. First, individual income-contingent utility functions are estimated based on survey data in order to describe human mobility behavior. Subsequently, using the MATSim framework, the implementation is tested in a test scenario. Furthermore, and going beyond Franklin (2006), it is shown that the approach works in a large-scale real world example. Based on a hypothetical speed increase of public transit, effects on the welfare distribution of the population are discussed. It is shown that the identification of winners and losers seems to be quite robust. However, results indicate that a conversion or aggregation of individual utility changes for welfare analysis is highly dependent on the functional form of the utility functions as well as on the choice of the aggregation procedure.     

A random utility maximization (RUM) based dynamic activity scheduling model: Application in weekend activity scheduling

The paper presents a modeling framework for dynamic activity scheduling. The modeling framework considers random utility maximization (RUM) assumption for its components in order to capture the joint activity type, location and continuous time expenditure choice tradeoffs over the course of the day. The dynamics of activity scheduling process are modeled by considering the history of activity participation as well as changes in time budget availability over the day. For empirical application, the model is estimated for weekend activity scheduling using a dataset (CHASE) collected in Toronto in 2002–2003. The data set classifies activities into nine general categories. For the empirical model of a 24-h weekend activity scheduling, only activity type and time expenditure choices are considered. The estimated empirical model captures many behavioral details and gives a high degree of fit to the observed weekend scheduling patterns. Some examples of such behavioral details are the effects of time of the day on activity type choice for scheduling and on the corresponding time expenditure; the effects of travel time requirements on activity type choice for scheduling and on the corresponding time expenditure, etc. Among many other findings, the empirical model reveals that on the weekend the utility of scheduling Recreational activities for later in the day and over a longer duration of time is high. It also reveals that on the weekend, Social activity scheduling is not affected by travel time requirements, but longer travel time requirements typically lead to longer-duration social activities.     

Analyzing the time frame for the transition from leisure-cyclist to commuter-cyclist

A recent survey reported that many commuter-cyclists had enjoyed leisure bicycling on a regular basis prior to becoming a commuter-cyclist. While bicycling for leisure, it is assumed that they considered various factors that led them to consider becoming commuter-cyclists. This study began with the question of how long it would take for a leisure-cyclist to become a commuter-cyclist, and it focused on the time that elapsed between leisure-cyclists transitioning to commuter-cycling. In order to analyze the time frame, it was hypothesized that the probability that a leisure-cyclist would become a commuter-cyclist at a certain time would be conditional on the duration that elapsed from the onset of leisure cycling till that time, which represents the “snowballing” or “inertial” dynamics of duration. A robust methodology, which is known as the “hazard model,” was adopted to accommodate such characteristics of a time period. In addition, various external covariates such as individual-specific characteristics, variables associated with the current or previous commuting mode, supply variables regarding bicycle facilities, and individual latent propensities were adopted to account for the duration of changes that would be generally applicable. As a result, many useful results were derived that could be used in fomenting policies to promote cycling to work. It was found that government should invest in establishing segregated lanes for leisure- and commuter-cyclists. It also turned out that a long distance to work hinders a leisure-cyclist from progressing to commuter-cycling. According to the results, young white-collar workers who live in high-rise apartments and enjoy intensive leisure-cycling in groups, are a good target toward whom promotions for commuter-cycling should be focused. However, an unfortunate development was that, when compared with car-commuters, it was found that transit-commuters are more likely to become commuter-cyclists.