一种螺旋桨参数化建模方法

对螺旋桨进行优化时,需要建立起优化计算的样本空间,即要实现初始桨的参数化建模。本文基于贝塞尔曲线拟合原理编程实现了螺旋桨的参数化建模,对螺旋桨的径向参数分布分别用一条贝塞尔曲线进行拟合,曲线的控制点通过遗传算法寻优求得。文中以4382桨为例,对其进行参数化建模,讨论了三、四、五、六阶贝塞尔曲线的拟合效果,发现三阶贝塞尔曲线拟合光顺性最好、拟合平均误差可以控制在0.3%以内,而且控制点个数较少,最适合拟合螺旋桨径向参数分布。最后通过调整三次贝塞尔曲线控制点的位置调整了原桨叶的几何形状,得到光顺性较好的新桨叶模型,表明该参数化建模方法合理。     

Within day rescheduling microsimulation combined with macrosimulated traffic

The concept of rescheduling is essential to activity-based modeling in order to calculate effects of both unexpected incidents and adaptation of individuals to traffic demand management measures. When collaboration between individuals is involved or timetable based public transportation modes are chosen, rescheduling becomes complex. This paper describes a new framework to investigate algorithms for rescheduling at a large scale. The framework allows to explicitly model the information flow between traffic information services and travelers. It combines macroscopic traffic assignment with microscopic simulation of agents adapting their schedules. Perception filtering is introduced to allow for traveler specific interpretation of perceived macroscopic data and for information going unnoticed; perception filters feed person specific short term predictions about the environment required for schedule adaptation. Individuals are assumed to maximize schedule utility. Initial agendas are created by the FEATHERS activity-based schedule generator for mutually independent individuals using an undisturbed loaded transportation network. The new framework allows both actor behavior and external phenomena to influence the transportation network state; individuals interpret the state changes via perception filtering and start adapting their schedules, again affecting the network via updated traffic demand. The first rescheduling mechanism that has been investigated uses marginal utility that monotonically decreases with activity duration and a monotonically converging relaxation algorithm to efficiently determine the new activity timing. The current framework implementation is aimed to support re-timing, re-location and activity re-sequencing; re-routing at the level of the individual however, requires microscopic travel simulation.     

基于相关性模型的舰船系统测试性建模与分析

本文提出一种基于相关性模型的舰船系统级产品的测试性建模与分析方法.该方法通过建立产品任务模型、相关性图示模型等,利用一阶相关性列矢量法求解产品的相关性数学模型,进而建立产品诊断树和进行测试性预计,并为优化产品诊断策略提供建议.同时,根据舰用燃气轮机滑油系统组成和任务特征,建立其典型任务模型并进行精简,并在此基础上进行测试性建模、诊断树建立、测试性预计以及诊断策略优化等工作,为舰船系统级产品的测试性建模、分析和诊断策略研究提供新思路和手段.     

(Unintended) Transport impacts of an energy-environment policy: The case of CNG conversion of vehicles in Dhaka

Motor vehicles are one of the major sources of air pollution in Dhaka, the capital of Bangladesh. The government took various policies to convert the petroleum vehicles on road to run on compressed natural gas (CNG), which allows both air quality improvements and energy security benefits. One of the market friendly policies to encourage the fuel switch was to increase the price differential between CNG and petrol and diesel. This has allowed a wide-scale adoption of CNG as the fuel of choice. However, several years into the policy, there is now a widespread belief among the policymakers that the CNG conversion may have increased car ownership and car travel due to their lower running costs, resulting in more congestion and a reversal of the strategy is on the cards. It is therefore important to test the hypothesis whether CNG conversion had genuinely increased car ownership and car travel in Dhaka city. This paper presents the results of a questionnaire survey and an econometric intervention analysis to understand the impact of CNG conversion on car ownership and car travel in Dhaka. Attention is also given to disentangle the self-selection and price-induced travel effects of CNG conversion. Results show that ownership did not increase, but travel of on-road vehicles increased due to the CNG policy. However, additional congestion costs are still around one half of the health benefits brought about by the policy.     

The Bid-rent Land Use Model of the simple,efficient, elegant,and effective model of land use and transportation

Integrated land use/transportation forecasting models add significant policy and infrastructure alternatives analysis capabilities to the urban planning process. The financial, time, and staff requirements to develop these models has put them beyond the reach of most small to medium sized urban areas. This paper presents the land use allocation submodel of the Simple, Efficient, Elegant, and Effective model of land use and transportation (SE³M), an integrated land use and transportation forecasting model founded upon Economic Base Theory and Bid-rent Theory. The Bid-rent Land Use Model (BLUM) is an agent based, spatial competition model utilizing unique utility curves for willingness to pay and incomes for budget constrained abilities to pay for each agent. The model structure, estimation, calibration, implementation, and validation are presented. With a single year of land use data available, the validation approach used the Kappa Index of Agreement to spatially check model outputs against base year control data while controlling for agreement by chance. The U.S. territory of Guam is used as the case study/proof of concept implementation for this model framework. Once calibrated, BLUM could solve the spatial competition problem on Guam in less than two minutes of processing time with over 90% accuracy.     

Privacy protection method for fine-grained urban traffic modeling using mobile sensors

With the ubiquitous nature of mobile sensing technologies, privacy issues are becoming increasingly important, and need to be carefully addressed. Data needs for transportation modeling and privacy protection should be deliberately balanced for different applications. This paper focuses on developing privacy mechanisms that would simultaneously satisfy privacy protection and data needs for fine-grained urban traffic modeling applications using mobile sensors. To accomplish this, a virtual trip lines (VTLs) zone-based system and related filtering approaches are developed. Traffic-knowledge-based adversary models are proposed and tested to evaluate the effectiveness of such a privacy protection system by making privacy attacks. The results show that in addition to ensuring an acceptable level of privacy, the released datasets from the privacy-enhancing system can also be applied to urban traffic modeling with satisfactory results. Albeit application-specific, such a “Privacy-by-Design” approach would hopefully shed some light on other transportation applications using mobile sensors.     

装载机连杆机构优化设计

结合传统设计方法和现代优化方法有效地解决了原设计中装载机不能满足平移性和自动放平性的问题;在用作图法确定铰接点大致位置的基础上,建立了连杆机构参数化模型,并对模型进行了优化研究。结果表明:新机构能满足平移性和自动放平性要求。该方法对类似的机构优化问题有一定的参考价值。     

薄壁高墩大跨连续刚构桥地震时程反应参数研究

运用大质量法,建立并推导了长大跨度桥梁考虑行波效应的分析模型及解析方程。以内蒙古小沙湾黄河特大桥为工程背景,选取墩身刚度、地震波视波波速、地震波激励方向等主要参数,建立动力计算模型,对该桥上述各种参数工况下地震时程反应作了参数对比分析研究。利用分析结果,探讨了同类桥梁在各种参数变化情况下墩顶位移和墩底内力的变化规律。     

无粘结预应力混凝土梁的强度与变形特性研究

给出了无粘结预应力混凝土梁强度和受力性能的分析结果。建立了适用于无粘结预应力混凝土梁非线性全过程分析的有限元简化模型,利用该模型探讨了跨高比、有效预应力和加载方式这3种参数对无粘结预应力混凝土梁弯曲性能以及无粘结预应力筋极限应力的影响。分析结果表明,跨高比对无粘结预应力筋极限应力无明显影响,增大无粘结预应力筋的有效预应力能显著提高梁的开裂和极限荷载,加载方式对梁的受力性能有着非常重要的影响。     

基于浑沌神经网络的动态交通量预测方法研究

介绍了目前国内外道路交通量预测的方法、特点及实际的预测效果.由于城市道路交通的复杂性,使得一些现有交通量预测方法的预测精度不高.针对这些问题,应用混沌神经网络,建立了城市道路交叉口出口交通量的浑沌神经网络预测模型,并与传统的BP神经网络预测结果对比,表明此模型具有较好的预测效果.