水下机器人结构形式及其发展趋势分析

水下机器人的结构是影响其运动性能的重要因素。按框架式、刚性外壳仿生式、柔性外壳仿生式、球形、滑翔式和链式6类结构,对水下机器人结构形式的发展现状和存在的关键技术问题进行分析。重点分析各类结构的驱动速度、加装载重和运动灵活性,以及在水下环境中的运动性和适应性。研究结果表明,水下机器人的结构形式正朝着高度柔性化、整体与局部结构之间高度变形化和多体结构可分离化的方向发展。     

出租车超速行为道路因素随机系数空间模型构建

为准确揭示道路因素与路段出租车超速行为特征的关联关系，本文以成都市中心城区主 干道路段为研究单元，通过车载GPS设备获取大范围出租车超速行为样本。在筛选出10类典型城市道路特征的基础上，选择路段超速线密度和不同百分位数超速严重度作为研究对象；为减少空间效应对估计的干扰，本文验证了超速特征的空间相关性，并分别构建基于对数-高斯分布的标准线性模型和空间条件自回归模型、空间误差模型及空间滞后模型这3类空间模型，探究不同空间模型与出租车超速行为特征的拟合情况；同时，考虑道路组间异质性，进一步构建随机系数空间模型。结果表明：出租车路段超速线密度和超速严重度均存在显著空间自相关性，空间模型 对其拟合效果普遍优于传统模型；不同超速行为特征适用不同的空间模型，随机系数空间条件自回归模型对超速线密度拟合效果最优，而不同百分位数超速严重度适用的最佳拟合模型差异较大；路段限速、一块板横断面及非机动车车道这3类因素表现出对出租车超速行为特征的组间影响异质性；因素解释方面，路段限速、一块板横断面、非机动车车道、路段施工区与超速线密度显著相关；路段限速、非机动车车道、上下坡匝道、路段施工区及路段长度与超速严重度显著相关。     

Stochastic averaging for estimating a ship roll in random longitudinal or oblique waves

In this work, the C11 container ship is taken as an example to analyze its rolling performances in random longitudinal or oblique waves. Firstly, a dynamic model of C11 roll in random waves is improved, and it is verified by the model test and numerical simulation. Mathematically, this dynamic model is a one-dimensional stochastic differential equation with random parametric (and external) excitation. Secondly, an enhanced stochastic averaging method is proposed to solve this stochastic differential equation. The validity of the solutions was verified by Monte Carlo simulation. At last, the probabilistic characteristics of the extreme rolling response were investigated based on the calculated results using enhanced stochastic averaging method. According to the analysis, some advices for ship's manoeuvring can be put forward when ships are navigating in random waves.     

“新永安”号客滚船整体舱室空调系统设计

随着人们生活水平的提高,市场对高端客滚船的需求越来越多,对于客滚船舒适度的关注也不断提升,尤其随着整体舱室技术的使用,其对空调系统设计提出了更高要求。以“新永安”号客滚船为例,从整体舱室、变风量系统、结构、噪声等方面着重介绍了空调系统的设计要点。通过设计要点的研究总结,既能够为未来整体舱室的运用可行性评估提供一个重要的评估指标,保证前期方案的准确性,也为客滚船空调系统的设计提供了一个较为全面的参考。     

Applications of Random-Utility-based Multi-region Input–Output Models of Transport and the Spatial Economy

Abstract

An introduction to random-utility-based multiregional input–output models used for the purpose of spatial economic and transport interaction modelling is provided. The main methodological developments and important results of a dozen applications from the years 1996–2013 are described. This is followed by an outlook of potential future directions. Further research is mainly needed in five areas: (a) overall validation of the method, perhaps through back-casting applications on infrastructure plans with observed trade impacts; (b) extensions of trade coefficient models to add realism and improve accuracy; (c) the use of multi-scale modelling to capture interdependencies between geographical scales and to improve the representation of exports and imports; (d) improvements in the representation of price effects, as well as innovation and technological progress, by way of variable technical coefficients; and (e) a deeper investigation of the algorithm used to include elastic selling prices.     

Random regret minimization or random utility maximization: an exploratory analysis in the context of automobile fuel choice

Interest in alternative behavioural paradigms to random utility maximization (RUM) has existed ever since the dominance of the RUM formulation. One alternative is known as random regret minimization (RRM), which suggests that when choosing between alternatives, decision makers aim to minimize anticipated regret. Although the idea of regret is not new, its incorporation into the same discrete choice framework of RUM is very recent. This paper is the first to apply the RRM‐model framework to model choice amongst durable goods. Specifically, we estimate and compare the RRM and RUM models in a stated choice context of choosing amongst vehicles fuelled with petrol, diesel and hybrid (associated with specific levels of fuel efficiency and engine capacity). The RRM model is found to achieve a marginally better fit (using a non‐nested test of differences) than its equally parsimonious RUM counterpart. As a second contribution, we derive a formulation for regret‐based elasticities and compare utility‐based and regret‐based elasticities in the context of stated vehicle type choices. We find that in the context of our choice data, mean estimates of elasticities are different for many of the attributes and alternatives. Copyright © 2011 John Wiley & Sons, Ltd.     

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高速公路投资风险评估对高速公路可持续发展具有重要作用.首先,本文针对传统的准三层BP神经网络评价模型运算精度和运算效率之间的矛盾,从其结构优化的角度出发,提出并设计了输入层神经元到隐含层神经元、隐含层神经元到输出层神经元的随机重连过程的变结构神经网络模型;其次,针对中国高速公路的投资特点,建立了高速公路项目投资风险的评价指标体系,设计了基于随机重连过程的变结构神经网络的高速公路项目投资风险评价模型,运用中国10条高速公路项目对模型进行了训练并对4条高速公路投资风险进行评估.研究结果表明,该模型预测的平均相对误差为1.91%,最大相对误差为2.63%,具有良好的预测效果.     

Oracle变异表错误解决方案选择

Oracle行级触发器应用中常遇到变异表错误,急需一个高性能的解决方案。概述Oracle DML触发器的特点,给出变异表错误出现的场景,分析出现错误的原因,提出分别基于包变量、临时表或复合触发器的3种解决方案,大规模数据测试表明:基于复合触发器的解决方案性能最好。     

双重不确定环境下的闭环供应链网络优化模型

分析闭环供应链系统各种不确定性的基础上,综合考虑需求量、回收量的随机性以及逆向处理费用的模糊性,构建以成本和环境污染最小化为双目标的闭环供应链系统网络优化模型,采用随机机会约束和模糊期望值方法对将不确定模型转变为等价确定型模型进行优化求解;最后通过求解实例验证模型的优化效果,构建的评价指标定量分析了成本投入对环境影响的提升效果,为企业决策者对2个目标的权衡提供相应指导.     

山区高墩桥梁的多点激励随机响应

为了研究山区高墩桥梁在地震动作用下的特殊抗震性能,基于随机振动理论,研究了场地效应、相干效应及行波效应对高墩桥梁在强地震多点激励下的随机响应规律,及墩高变化对高墩桥梁地震响应规律的影响.研究表明:场地效应对高墩桥梁地震响应影响明显,软场地墩的位移值约为硬场地的12倍,行波效应的影响次之,相干效应的影响最小.场地效应对桥梁的影响大小取决于场地卓越频率是否接近于桥梁自振频率;行波效应是不可忽略的一个重要因素,中场地时桥墩最小的位移值约为最大值的30％,软场地时最小值约为最大值的60％;与场地效应和行波效应相比,部分相干效应对桥墩顺桥向位移影响较小.对于山区高墩桥梁随机地震响应分析,考虑地震动空间效应的多点激励分析是必要的.应对有可能的桥型(不同墩高和墩高差)进行分析,以确定地震力最小的桥型并注意桥梁截面抗力的提升和附加减震措施.