肥大型船舶伴流分数的估算方法研究

基于肥大型船的快速性试验数据,通过对传统估算公式结果的分析及船舶伴流成因的研究,选定部分船型参数及无因次量作为影响因子,建立线性数学模型,采用逐步回归法得到一种新的、更加精确的肥大型船伴流分数估算方法,通过实例验证其精确性和正确性。     

基于多元线性回归分析的水位短期预测方法

为了给长江电子航道图终端用户提供更为准确的水深预测信息,以统计学为基础,通过回归分析的方法,以预测长江监利站水位为例,探讨基于多元线性回归分析的水位短期预测方法实施步骤和实际应用,取得了很好的效果。     

Exploring vessel-price dynamics: the case of the dry bulk market

We investigate second-hand vessel price heterogeneity. Based on a sample of 5,591 purchase and sale transactions in the dry bulk sector over the period 1998–2016, we deploy a nonparametric regression technique to assess the determinants of vessel price and vessel price variability. Next, we use quantile regression to estimate the effect of regressors (sources of heterogeneity) at different parts of the vessel price distribution. We find evidence that main sources of vessel price heterogeneity are the age of the ship (the older the vessel the higher its maintenance cost), the 3-month LIBOR (reflecting the cost of financing) and the annual charter rate (revenues from operation). Their influence is stronger at all higher quantiles (periods of expansion) and the median of the vessel price distribution.     

远洋船舶空调系统的动态负荷仿真分析

采用黑箱模型理论建立了船舶多功能舱室动态负荷数学模型,经分析求解,获得了某典型欧亚远洋航线上的船舶动态负荷变化规律.结果表明:船舶空调负荷随航区、航行时刻发生显著变化,通风负荷占总负荷的51.92%,而舱壁导热、辐射负荷仅分别占总负荷的7.47%,6.68%;同一航区同一时刻,各功能舱室负荷最大值是最小值的2.684倍;此外,运用回归分析知,可变舱室负荷的91.72%受室外温度变化的影响.     

灾后公路交通基础设施功能快速恢复研究

灾后交通基础设施功能快速恢复，对于提高多样化军事任务军交运输保障能力有着重要意义。从加强抢修抢建的技术保障、计划组织和应急交通保障中新技术、新材料的研制与应用三个方面，阐述了提高灾后公路交通基础设施功能快速恢复的措施，有助于提高灾后公路交通基础设施功能恢复的时效性。     

The relationship among highway geometrics,traffic-related elements and motor-vehicle accident frequencies

This research provides a demonstration of a statistical model of accident frequency that can eventually be used as part of a proactive program to allocate safety-related highway improvement funds. Negative binomial regressions of annual accident frequency on sections of principal arterials in Washington State were estimated using data from two years (1992 and 1993). In all, 31306 observations were used in model estimation (annual accident frequencies on specific sections of highway). Our estimation results isolated the effects of various highway geometric and traffic characteristics on annual accident frequency. Subsequent elasticity computations identified the relative importance of the variables included in our specifications. The findings show that the negative binomial regression used in this paper is a powerful predictive tool and one that should be increasingly applied in future accident frequency studies.     

支持向量机在单桩竖向极限承载力预测中的应用

单桩竖向极限承载力是桩基础设计中一项重要的内容,本文应用V-支持向量回归机算法,对单桩竖向极限承载力进行了预测。结果表明这种方法可以作为单桩竖向极限承载力计算的一种参考。     

The Influences of the Built Environment and Residential Self-Selection on Pedestrian Behavior: Evidence from Austin, TX

Pedestrian travel offers a wide range of benefits to both individuals and society. Planners and public health officials alike have been promoting policies that improve the quality of the built environment for pedestrians: mixed land uses, interconnected street networks, sidewalks and other facilities. Whether such policies will prove effective remains open to debate. Two issues in particular need further attention. First, the impact of the built environment on pedestrian behavior may depend on the purpose of the trip, whether for utilitarian or recreational purposes. Second, the connection between the built environment and pedestrian behavior may be more a matter of residential location choice than of travel choice. This study aims to provide new evidence on both questions. Using 1368 respondents to a 1995 survey conducted in six neighborhoods in Austin, TX, two separate negative binomial models were estimated for the frequencies of strolling trips and pedestrian shopping trips within neighborhoods. We found that although residential self-selection impacts both types of trips, it is the most important factor explaining walking to a destination (i.e. for shopping). After accounting for self-selection, neighborhood characteristics (especially perceptions of these characteristics) impact strolling frequency, while characteristics of local commercial areas are important in facilitating shopping trips.     

基于支持向量机的物流量预测——以成都市为例

考虑到支持向量机强大的泛化能力,运用支持向量机技术预测了成都市近期和中期物流量.研究表明,随着样本数据的增加,支持向量机的预测值与实际值间的相对误差总体呈下降趋势,并且与多元线性回归方法相比,支持向量机具有较高的预测精度,证明了支持向量机用于物流量预测的有效性.     

Pedestrian gap acceptance for mid-block street crossing

Abstract

This paper investigates pedestrians' traffic gap acceptance for mid-block street crossing in urban areas. A field survey was carried out at an uncontrolled mid-block location in Athens, Greece. Pedestrians' decisions and traffic conditions were videotaped in terms of the size of traffic gaps rejected or accepted, waiting times and crossing attempts and vehicle speeds. A lognormal regression model was developed to examine pedestrian gap acceptance. It was found that gap acceptance was better explained by the distance from the incoming vehicle, rather than its speed. Other significant effects included illegal parking, presence of other pedestrians and incoming vehicles’ size. A binary logistic regression model was developed to examine the effect of traffic gaps and other parameters on pedestrians' decisions to cross the street or not. The results reveal that this decision is affected by the distance from the incoming vehicles and the waiting times of pedestrians.