客车车身计算机辅助造型与动画演示设计

以一个轻型客车为例,介绍客车车身造型中计算机辅助概念设计、三维建模、车身主图板制作以及造型动画演示设计的方法和过程。     

基于UML的舰艇综合通信监控系统的设计与实现

新型舰艇综合通信系统以SDH光环网构成的宽带传输交换平台为交换承载媒体、设备控制单元为外通设备控制节点,实现了各种用户设备、终端设备和信道设备的接入、控制、交换、传输和管理的统一,达到内通和外通业务融合,满足了海军对现代战争新型综合指挥通信平台的需求。基于面向对象方法的舰艇综合通信监控系统充分运用了UML的开发思想,实现了对舰艇综合通信系统功能的需求。随着舰艇通信设备的陆续更新、通信体制的不断发展,通信监控软件经过不断升级,软件的可靠性和可重用性得到了检验。     

An analysis of bicycle route choice preferences in Texas,US

In the US, the rise in motorized vehicle travel has contributed to serious societal, environmental, economic, and public health problems. These problems have increased the interest in encouraging non-motorized modes of travel (walking and bicycling). The current study contributes toward this objective by identifying and evaluating the importance of attributes influencing bicyclists’ route choice preferences. Specifically, the paper examines a comprehensive set of attributes that influence bicycle route choice, including: (1) bicyclists’ characteristics, (2) on-street parking, (3) bicycle facility type and amenities, (4) roadway physical characteristics, (5) roadway functional characteristics, and (6) roadway operational characteristics. The data used in the analysis is drawn from a web-based stated preference survey of Texas bicyclists. The results of the study emphasize the importance of a comprehensive evaluation of both route-related attributes and bicyclists’ demographics in bicycle route choice decisions. The empirical results indicate that travel time (for commuters) and motorized traffic volume are the most important attributes in bicycle route choice. Other route attributes with a high impact include number of stop signs, red light, and cross-streets, speed limits, on-street parking characteristics, and whether there exists a continuous bicycle facility on the route.

A copula-based joint multinomial discrete–continuous model of vehicle type choice and miles of travel

In this paper, a joint model of vehicle type choice and utilization is formulated and estimated on a data set of vehicles drawn from the 2000 San Francisco Bay Area Travel Survey. The joint discrete–continuous model system formulated in this study explicitly accounts for common unobserved factors that may affect the choice and utilization of a certain vehicle type (i.e., self-selection effects). A new copula-based methodology is adopted to facilitate model estimation without imposing restrictive distribution assumptions on the dependency structures between the errors in the discrete and continuous choice components. The copula-based methodology is found to provide statistically superior goodness-of-fit when compared with previous estimation approaches for joint discrete–continuous model systems. The model system, when applied to simulate the impacts of a doubling in fuel price, shows that individuals are more likely to shift vehicle type choices than vehicle usage patterns.

A Bayesian approach for modeling origin-destination matrices

The majority of origin destination (OD) matrix estimation methods focus on situations where weak or partial information, derived from sample travel surveys, is available. Information derived from travel census studies, in contrast, covers the entire population of a specific study area of interest. In such cases where reliable historical data exist, statistical methodology may serve as a flexible alternative to traditional travel demand models by incorporating estimation of trip-generation, trip-attraction and trip-distribution in one model. In this research, a statistical Bayesian approach on OD matrix estimation is presented, where modeling of OD flows derived from census data, is related only to a set of general explanatory variables. A Poisson and a negative binomial model are formulated in detail, while emphasis is placed on the hierarchical Poisson-gamma structure of the latter. Problems related to the absence of closed-form expressions are bypassed with the use of a Markov Chain Monte Carlo method known as the Metropolis-Hastings algorithm. The methodology is tested on a realistic application area concerning the Belgian region of Flanders on the level of municipalities. Model comparison indicates that negative binomial likelihood is a more suitable distributional assumption than Poisson likelihood, due to the great degree of overdispersion present in OD flows. Finally, several predictive goodness-of-fit tests on the negative binomial model suggest a good overall fit to the data. In general, Bayesian methodology reduces the overall uncertainty of the estimates by delivering posterior distributions for the parameters of scientific interest as well as predictive distributions for future OD flows.     

大型船闸金属结构BIM技术的应用

针对大型船闸金属结构的特点和发展瓶颈,结合京杭运河、赣江、湘江、西江等近20个大型船闸金属结构设计的应用,采用BIM技术进行了船闸金属结构的辅助设计、结构计算和优化、工程表达方式、工程数据提取、运维资料、推动专业发展和建设等方面的探索和论述。研究结果表明:BIM技术对于掌握船闸全寿命周期核心技术、提高船闸金属结构的通用性和互换性、推进船闸金属结构的标准化和系列化、推动行业发展和完善专业理论体系具有非常重要的意义。     

某型船用柴油发电机系统的建模与仿真

针对目前船舶柴油发电机系统监控软件测试难度大、周期长、成本高等问题,提出利用仿真模型在软件与硬件搭接联调之前先行测试,以减少软件的开发周期和成本。基于模块化建模的思想,分析柴油发电机系统中的热功转换、能量转换和质量迁移等多种能量作用。在SimuWorks仿真平台上根据基本物理学规律将柴油发电机系统分为进气系统、燃油供应系统、PID调节器、气缸、曲轴连杆、轴系转子和发电机七个模块,按照能量传递和转移的方向,搭建起柴油发电机系统的整体模型。利用建立的柴油发电机系统进行仿真研究,通过对稳态和动态仿真实验值的分析,证明了模型的准确性,为柴油发电机系统监控软件的测试奠定基础。     

舰船电子综合化系统总线网络DSPN建模与分析

周期性消息和非周期性消息对舰船电子综合化系统总线网络性能的影响是舰船电子综合化电子系统总线网络设计过程的难点之一.针对该问题,提出采用以确定与随机Petri网(Deterministic and Stochastic Petri Net,DSPN)建立周期性消息的总线网络DSPN模型和考虑非周期性消息的总线网络DSPN模型,有效模拟了周期性消息和非周期性消息在舰船电子综合化系统总线网络传输的动态行为.以TimeNET4.2软件为仿真平台,分别实现了周期性消息的总线网络DSPN模型和考虑非周期性消息的总线网络DSPN模型,研究分析周期性消息和非周期性消息对舰船电子综合化系统总线网络性能的影响.该成果可以为设计满足特定性能要求的舰船电子综合化电子系统总线网络提供理论依据.     

固体氧化物燃料电池与微型燃气轮机联合发电建模仿真研究

设计一种固体氧化物燃料电池与微型燃气轮机的联合发电系统,并对其进行建模仿真及性能研究.基于Matlab/Simulink仿真软件,采用模块化建模方法,再以拓扑结构连接各个子系统模型,搭建SOFC-MGT联合发电系统模型.仿真结果表明:模型满足仿真要求,系统具有较高的发电效率.在变工况,尤其是高背压条件下,该系统不能稳定工作,必须附加水处理系统才能保证该系统良好运行.     

加筋圆柱壳开孔结构强度分析

加筋圆柱壳开孔结构是潜艇典型耐压船体的主要结构形式之一,如何避免在开孔周围造成应力集中,即开孔结构补强是工程中特别关心的问题。在设计过程中,因为要多次建模分析,会导致设计分析效率变低,所以开发了加筋圆柱壳开孔结构的参数化建模分析程序。基于参数化建模分析程序,讨论了多参数对于开孔周围应力集中的影响。