铁路防振轨道的现状与理论解析法

介绍日本地铁为改善铁路沿线的居住环境而采用的防振轨道,对防振轨道的特征及防振轨道建设时所需要的设计计算方法进行详细说明。     

加筋土结构可靠度分析中两个重要参数的分布规律探讨

在进行加筋土结构可靠度分析计算中,加筋土结构作用和抗力的统计参数及其分布形式对其可靠指标有显著的影响.笔者针对加筋土结构本身的特点,结合试验结果,采用数理统计的方法,对加筋土填料(主要为砂卵石填料)的重度γ、加筋材料的拉力进行统计分析,并将其应用于工程可靠度验算,其结果表明是合理的,可为加筋土结构设计规范修订提供一定的参考.     

A new statistical method of assigning vehicles to delivery areas for CO2 emissions reduction

Transportation CO₂ emissions are expected to increase in the following decades, and thus, new and better alternatives to reduce emissions are needed. Road transport emissions are explained by different factors, such as the type of vehicle, delivery operation and driving style. Because different cities may have conditions that are characterized by diversity in landforms, congestion, driving styles, etc., the importance of assigning the proper vehicle to serve a particular region within the city provides alternatives to reduce CO₂ emissions. In this article, we propose a new methodology that results in assigning trucks to deliver in areas such that the CO₂ emissions are minimized. Our methodology clusters the delivery areas based on the performance of the vehicle fleet by using the k-means algorithm and Tukey’s method. The output is then used to define the optimal CO₂ truck-area assignment. We illustrate the proposed approach for a parcel company that operates in Mexico City and demonstrate that it is a practical alternative to reduce transportation CO₂ emissions by matching vehicle type with delivery areas.     

A new functional optimization method applied to the pitch distribution of a marine propeller

Based on Hilbert space theory, an infinite-dimensional optimization method to find the optimal pitch distribution of marine propellers was developed. Thereby, the three-dimensional effect of induced velocity could effectively be controlled in an optimal way; i.e., an investigation was carried out to learn whether the present method is applicable to the design of marine propellers, especially pitch distributions, by maximizing the propeller efficiency functional. In addition, with the help of Hilbert space theory, it was successfully shown that the optimization method developed has a unique mathematical solution. In this work, only the pitch distribution was optimized, while other parameters such as the camber and thickness of the trial propeller remained as in the original. With a numerical study, it is shown that the present optimization method gives an optimal pitch distribution, the open-water characteristic curve being superior to the original curve. Received: August 24, 2000 / Accepted: July 16, 2001     

规则波中船舶运动六自由度数学模型

为了提高船舶操纵模拟器的精度,应用船舶操纵性分离建模理论,基于傅汝德-克雷诺夫假设,将船舶近似为箱型船,估算波浪对船舶六自由度运动的干扰力与力矩,并将波浪的干扰力与力矩作为外力与力矩的一部分,叠加到分离型船舶运动数学模型中,建立了船舶在规则波作用下六自由度船舶运动的数学模型,给出5级海况下船舶全速旋回运动响应的时间历程仿真曲线.仿真结果显示:仿真结果与相关文献结果相近,运动趋势一致,能够满足大型船舶操纵模拟器对船舶运动数学模型仿真的精度要求,同时船舶运动数学模型由3自由度增至6自由度,提高了模拟的逼真度.     

滨州港大堡泊位扩建工程潮流分析

建立了套尔河15 km河段二维潮流数学模型。计算中首先采用天然实测资料对模型进行率定与验证,通过有关参数调整,使模型数值计算成果与天然实测资料达到精度要求。然后通过对河段自然条件下实测潮位、潮流过程进行的模拟,分析了工程区潮流变化特点。随后对泊位扩建工程措施的不同工况条件与潮流的相互影响进行了模拟,分析了各方案的潮流情况,对不同规划方案成果的优劣进行了比较。方案三在新老码头区潮流流向平顺、流速增加、无回流,利于港池稳定;河道宽阔利于船舶进出码头;岸上施工便利,是扩建工程泊位规划的优选方案。为规划设计提供了科学依据。     

长江下游安庆水道航道条件与整治方案

近期安庆水道的河床演变表明,安庆水道进出口狭窄、中间开阔,河心洲滩发育,进口主流居中。目前的河势有利于新中汊的发展,左汊航道条件有向不利方向发展的趋势。因此,需要对安庆水道实施航道整治工程,确保航道达到6.0 m×200 m×1 050 m的标准。采用二维水沙数学模型,首先,进行了控制守护方案的计算,计算结果分析表明护底带和潜坝能够较好地限制新中汊分流;其次,进行了各整治方案的计算,经过对比分析和综合考虑,提出了航道整治控制守护推荐方案;再次,对推荐方案实施的航道条件变化进行了系列年计算、分析,研究结果可供工程建设参考。     

局部模型在工程潮流数值模拟中的应用

根据局部模型的形式和特点对其进行了归类分析 ;通过两个工程实例对局部模型在海岸河口工程潮流数值模拟中的应用进行了探讨和介绍。计算实例的结果表明 ,局部模型的使用既可以减少计算时间从而提高数学模型的效率 ,又可以提高局部海区潮流模拟的计算精度。局部模型在用数学模型手段研究工程潮流问题中起着重要作用     

潮流泥沙数学模型在码头平面布置和码头等级确定中的应用

为保证国家宝贵的岸线资源能得以充分利用,确定合理的码头平面布置方案和码头等级是码头工程设计的重点。采用平面二维潮流泥沙数学模型对拟建码头的不同前沿线位置和码头等级进行多方案计算,模拟得出各方案实施后的流速流向、疏浚区域冲淤变化情况,以及码头水域和航道的泥沙回淤量,通过计算分析并结合经济效益、港口发展、周边影响等因素提出推荐方案。     

潜艇应急上浮操纵与控制研究评述

在调研和查阅大量文献资料的基础上,综述了国内外潜艇应急上浮运动分析、操纵与控制研究的发展概况,着重对潜艇应急上浮运动数学模型、分析方法及控制策略等方面存在的问题进行了分析讨论,指出了有待深入研究的重点问题及关键技术.