管道惯性测绘系统研制及应用

针对管道中心线地理坐标信息的测量需求,基于惯性导航原理,研制了以管道内检测器为载体的管道中心线测绘内检测设备,并将其与漏磁内检测器结合进行工程应用。选取了5处已知点对测绘结果进行了验证,测绘结果和实际验证结果表明:研制的惯性导航内检测器能够准确测绘管道中心线轨迹坐标,在校验点间距约为2 km时,5个距校验点约1 km的已知点的平均测绘误差约为1.8 m;通过将惯性导航检测器与漏磁检测器的组合使用,可有效获取管道缺陷的地理坐标信息,提高了管道内检测缺陷检测定位的精度。     

基于电磁传感器的转速测量装置在船用直流电机控制系统的应用

本文介绍了一种基于磁电式传感器和旋转式信号盘的电机转速信号采集系统,将转速信号转换为等频率的脉冲信号,通过F/V电路实现脉冲频率到电压的线性转换,并作为转速反馈电压信号应用于某船用直流电机控制系统中,具有可靠性高、实时性好、维修调试便捷的特点.     

Visualisation of uncertainty in probabilistic traffic models for policy and operations

This study investigates different methods to visualise uncertainty in static representations of probabilistic traffic models predictions on road-networks. Although various graphical cues may be used to represent uncertainty it is not a priori clear which of them are most suited for this purpose, since their legibility, intelligibility and the degree to which they interfere with other graphical elements in a representation differ widely. Several graphical uncertainty representations were therefore developed and analysed in expert sessions. A selection of the initial set of uncertainty visualisations was further evaluated in a cognitive alternative task-switching experiment. The results show that graphical representations are able to convey uncertainty information relatively accurately, while some uncertainty visualisations outperform others. It depends on the model and scenario which representation is most suited for a given application. This paper presents an overview of possible graphic uncertainty representations and the considerations involved when applying them to uncertainty in traffic model visualisations.     

汽油发动机的尾气分析与应用

汽油发动机尾气中主要成份为HC、CO、CO2、NOX、O2等。本文分析了尾气的形成、特征和超标排放原因,以及尾气检测原理和标准,通过几例本人在工作中的实例,说明尾气检测在维修实践中所起到的重要作用,可供维修单位检测参考。     

Correlates of bicycling trip flows in Hamilton,Ontario: fastest,quietest, or balanced routes?

Transportation - Bicycling is an increasingly popular mode of travel in Canadian urban areas, like the Greater Toronto and Hamilton Area (GTHA). While trip origins and destinations can be inferred...     

Impacts of urban built environment on empty taxi trips using limited geolocation data

This study identifies the determinants of the empty taxi trip duration (ETTD) by combining three high-resolution databases—geolocation data in New York City, geodatabase of urban planning data, and transportation facilities data. Considering the nature of duration data, hazard-based duration model is proposed to explore the relationships between causal factors and ETTD, coupling with three variations of baseline hazard distribution, i.e., Weibull distribution with heterogeneity, Weibull distribution, and log-logistic. Furthermore, the likelihood ratio test is presented to implement comparisons of three baseline hazard distributions, as well as spatial and temporal transferability of causal factors. The results show significant complementary effects by subway system and competitive effects by city bus and bicycling system, as well as significant impacts of trip length, airport trip, average annual income, and employment rate. Urban built environment, for instance, density of road, public facilities, and recreational sites and ratio of green space, has various impacts on ETTD. The elasticity estimations confirm significant spatial and temporal heterogeneity in impacts on ETTD. In addition, the analysis on elasticity also reveals the considerable impacts of severe traffic congestion on ETTD within Manhattan. The modeling can assist stakeholders in understanding empty taxi movements and measuring taxi system efficiency in urban areas.     

The continental shelf and the exclusive economic zone: the problem of delimitation at UNCLOS III

If the Third United Nations Conference on the Law of the Sea succeeds in adopting a new Caracas Convention on the Law of the Sea, it is likely to embody detailed provisions on the delimitation of both the continental shelf and the new zone, the exclusive economic zone. In this paper, the most recent draft of these rules—contained in the Revised Single Negotiating Text—is subjected to a detailed and critical scrutiny which leads to the conclusion that the Sixth Session of the Conference still has a great deal of work to do before agreement can be reached on a satisfactory set of rules.     

Estimation of delay variability at signalized intersections for urban arterial performance evaluation

Urban arterial performance evaluation has been broadly studied, with the major focus on average travel time estimation. However, in view of the stochastic nature of interrupted flow, the ability to capture the characteristics of travel time variability has become a critical step in determining arterial level of service (LOS). This article first presents a stochastic approach that integrates classic cumulative curves and probability theories in order to investigate delay variability at signalized intersections, as a dominant part of the link travel time variability. This serves as a basis for arterial travel time estimation, which can be obtained through a convolution of individual link travel time distributions. The proposed approach is then applied in the estimation of travel time along one arterial in Shanghai, China, with abundant automatic vehicle identification (AVI) data sources. The travel time variability is evaluated thoroughly at 30-min intervals, with promising results achieved in comparison to the field measurements. In addition, the estimated travel time distributions are utilized to illustrate the probability of multiple LOS ranges, namely, reliability LOS. The results provide insights into how we might achieve a more reliable and informative understanding of arterial performance.