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熵最大化方法被广泛应用于交通规划,为交通需求预测模型提供了理论依据.本文使用信息论中的熵概念描述居民出行分布,并根据最大信息熵理论提出了基于原点矩典型特征量约束条件下的出行分布模型,详细阐述了模型中各个参数的实际含义,该模型是一个普适性模型,其具体形式决定于最高阶原点矩阶数的取值,此值对模型精度及参数标定难易程度有重要影响.为确定模型参数,提出了实用的参数标定方法.由于模型中原点矩的最高阶数对模型精度有较大影响,为找到两者之间的关系,利用长春市出行调查数据研究了四种出行方式分别时应于五种原点矩最高阶数的模型拟合情况.因文中所建立的模型是一系列模型,为比较其描述问题的优劣差异,按照最大信息熵原理给出了确定系统分布的熵方法,并运用该方法对前述模型进行了比较.调查数据的验证结果表明,出行分布的信息熵模型可以正确地描述出行分布规律,熵方法可以简单有效地评价不同模型对同一问题描述的优劣差异.本文提出的熵模型和熵方法对城市交通规划具有指导意义.     

耐压壳非圆度偏差检测研究

耐压壳是水下航行器的主要构件,其热膨胀系数大,刚度大,厚度大,易造成焊接变形.文章利用工程数学分析推导了耐压壳非圆度偏差计算、换算及简化方法,编制了偏差计算程序.研究结果为降低制造误差提供了依据.     

偶极子源与力激励作用下截顶锥形壳振动与声辐射研究

螺旋桨噪声是舰船辐射噪声的主要组成部分,采用有限长截顶锥形壳模拟潜艇艉部,根据螺旋桨噪声产生机理,对比分析了集中力激励与偶极子源激励下锥形壳产生的辐射噪声,并讨论了激励作用位置对壳体振动与辐射噪声的影响。结论显示力激励作用引起的壳体的振动与声辐射要大于偶极子源作用下的情况;当激励施加在锥形壳体截面的中心位置时,壳体在低频时的振动与声辐射要小于激励施加在截面非对称位置处的情况。     

Conflict in the US maritime industry: An account of historical cycles

Historically there have been only two groups involved in the conflict that has engulfed the US maritime industry for the past fifty years maritime labour unions and shipping companies. The configuration of these groups at different times in this struggle, has led to distinct periods of conflict in the industry. This paper analyses the basis and continuation of the problem.     

MANTO — a research project of telecommunication applications for the future information society

The impact of new technologies has been mostly under-estimated in the past and, as a result, the transitions from one era to another have occurred more or less by chance. The MANTO research project is intended to avoid mischances. So it indicates potential developments in the telecommunications sector and, in particular, investigates their effects upon transport and settlement and also upon society, the economy and the environment. Nevertheless, MANTO does not merely take a look at the future, like the Greek oracle from whom it takes its name; by means of concrete recommendations, MANTO is intended to provide persons in responsible positions with a tool with which they can consciously organise that future. Risky developments are to be precluded in advance while desirable consequences are to be promoted. Explanation of the used term: MANTO was the daughter of the famous prophet Teiresios of Theben and a seer herself too. As a (German) abbreviation MANTO also stands for: human being (Mensch), offer (Angebot) and needs (Nachfrage) for transportation and telecommunication (Transport und Telekommunikation), considering economy and ecology (Oekonomie und Oekologie).     

Estimation of capacity utilization in world shipping

The surplus of tonnage which has characterized the shipping industry for over a decade has severely affected profitability and investment opportunities in the industry. This has prompted various schemes to reduce the surplus. A proper assessment of the size of the surplus is an essential requirement for sound policy measures. This paper, which focuses on the tanker sector, examines selected methods used to compute surplus tanker tonnage and proposes other methods. It observes that methods currently used give estimates of surplus tonnage which are basically identical to those obtained by using alternative methods. It concludes that while from 1984 the surplus tanker tonnage has been declining, from 1986 the decline has been rather small and the volume of the surplus is likely to stabilize in the next few years at more or less current levels. However, the paper points out conceptual and practical problems of determining the appropriate base periods or base operating conditions upon which surplus tonnage may be computed.     

The Bathside Bay story

In this article the author considers whether an opportunity to develop harbour facilities at a strategically located site in Harwich Harbour on the east coast of England may have been missed in the 1960s and 1970s. The complications of divided ownership and powers to develop the site are explained; and successive attempts to obtain Government approval for harbour development under section 9 of the Harbours Act 1964 (since repealed) are described. The effective operation of that control in this case, influenced at one stage by political considerations, is questioned.     

基于波叠加原理的辐射声场的计算研究

描述了用波叠加原理来计算任意形状的辐射体的辐射声场的方法。即用叠加来代替Kirchhoff-Helmholtz积分的方法．给定辐射体表面的振动速度就可求解辐射源的强度。进而求解辐射体表面的声压和辐射的声功率．文中对刚性球面上振动活塞源和脉动球源的辐射问题进行了求解。并将之与分析(解析)解进行了对比，结果表明用该方法进行计算时，可以用简单的数字方法产生矩阵元素，从而提高计算速度。结果的精度高。并能克服边界元法声场计算内在的奇异性问题．