Identifying optimal data aggregation interval sizes for link and corridor travel time estimation and forecasting

With the recent increase in the deployment of ITS technologies in urban areas throughout the world, traffic management centers have the ability to obtain and archive large amounts of data on the traffic system. These data can be used to estimate current conditions and predict future conditions on the roadway network. A general solution methodology for identifying the optimal aggregation interval sizes for four scenarios is proposed in this article: (1) link travel time estimation, (2) corridor/route travel time estimation, (3) link travel time forecasting, and (4) corridor/route travel time forecasting. The methodology explicitly considers traffic dynamics and frequency of observations. A formulation based on mean square error (MSE) is developed for each of the scenarios and interpreted from a traffic flow perspective. The methodology for estimating the optimal aggregation size is based on (1) the tradeoff between the estimated mean square error of prediction and the variance of the predictor, (2) the differences between estimation and forecasting, and (3) the direct consideration of the correlation between link travel time for corridor/route estimation and forecasting. The proposed methods are demonstrated using travel time data from Houston, Texas, that were collected as part of the automatic vehicle identification (AVI) system of the Houston Transtar system. It was found that the optimal aggregation size is a function of the application and traffic condition.

Regulation of the informal transport sector in Rio de Janeiro,Brazil: welfare impacts and policy analysis

In Brazil, the explosion of informal transport activity during the past decade has had profound effects on formal public transport systems and is a source of great controversy in the urban transportation sector. A variety of policies have been proposed to manage the growth of the sector. This study seeks to understand how proposed policies will impact the users of these systems. A corridor in Rio de Janeiro with substantial informal activity was used as a case study. Measures of welfare changes in a discrete choice framework were used to estimate proposed policies’ impacts on users. Eleven candidate policies were evaluated, ranging from the eradication of the informal modes and investment in formal modes, to the legalization of the informal modes. Benefits were compared with costs and the distribution of benefits across income classes was explored. Net benefits from some policies were found to be substantial. Legalizing the informal sector was found to benefit users slightly but further investments in the sector are probably inefficient. Users benefited most from improvements in formal mass transit modes, at roughly 100–200 dollars per commuter per year. Finally, policies to foster a competitive environment for the delivery of both informal and formal services were shown to benefit users about 100 dollars per commuter per year. Together, the regulation of the informal sector and investments in the formal sector serve to reinforce the movement towards competitive concessions for services and help reduce the impacts of cartelization and costly in-road competition.

概述地铁工程中的人防设计

地铁作为城市人防总体规划的重要组成部分,战备效益显著,但目前国家尚无一个针对地铁人防的设计规范。结合北京、上海、深圳的地铁人防设计,论述人防设防标准的同异内容,探讨制订统一规范的必要性;提出在确保战备效益的前提下,人防设计要立足兼顾经济效益和社会效益最大化的原则。     

基于改进蚁群算法的物流配送路径优化问题研究

物流配送在国民经济中发挥着越来越重要的作用,先进的物流配送系统是企业增强竞争力的重要手段.而进行物流配送系统的优化,主要就是配送路径的选择.虽然蚁群算法已广泛应用于解决路径优化问题,但此算法所固有的收敛速度缺陷一直制约着物流系统配送路径优化问题的解决.本文在系统分析蚁群算法的基础上,结合遗传算法,提出了一种新型的改进蚁群算法,并通过算例对改进蚁群算法的有效性进行了验证.     

Tool for Predicting the Ultimate Bending Moment of Ship and Ship-Shaped Hull Girders

The present paper presents a historical review associated with the research works on hull girder strength of ship and ship-shaped structures. Then, a new program is developed to determine the ultimate vertical bending moment of hull girder by applying direct method, stress distribution method, and progressive collapse analysis method. Six ships and ship-shaped structures used in the benchmark study of International Ship and Offshore Structures Congress (ISSC) in 2012 are adopted as examples. The calculation results by applying the developed program are analyzed and compared with the existing results. Finally, the roles of the developed program and its further development are discussed.     

Real-Time Fault Diagnosis for Gas Turbine Blade Based on Output-Hidden Feedback Elman Neural Network

In order to remotely monitor and maintain large-scale complex equipment in real time, China Telecom plans to create a total solution that integrates remote data collection, transmission, storage, analysis and prediction. This solution can provide manufacturers with proactive, systematic, integrated operation and maintenance service, and the data analysis and health forecasting are the most important part. This paper conducts health management for the turbine blades. Elman neural network, and improved Elman neural network, i.e., outputhidden feedback (OHF) Elman neural network are studied as the main research methods. The results verify the applicability of OHF Elman neural network.     

Review of Secure Communication Approaches for In-Vehicle Network

In the connected vehicles, connecting interfaces bring threats to the vehicles and they can be hacked to impact the vehicles and drivers. Compared with traditional vehicles, connected vehicles require more information transfer. Sensor signals and critical data must be protected to ensure the cyber security of connected vehicles. The communications among ECUs, sensors, and gateways are connected by in-vehicle networks. This paper discussed the state-of-art techniques about secure communication for in-vehicle networks. First, the related concepts in automotive secure communication have been provided. Then we have compared and contrasted existing approaches for secure communication. We have analyzed the advantages/disadvantages of MAC and digital signatures for message authentication and compared the performance and limitations of different cryptographic algorithms. Firewall and intrusion detection system are introduced to protect the networks. The constraints and features of different intrusion detection approaches are presented. After that, the technical requirements for cryptographic mechanism and intrusion detection policy are concluded. Based on the review of current researches, the future development directions of the automotive network security have been discussed. The purpose of this paper is to review current techniques on automotive secure communication and suggest suitable secure approaches to implement on the in-vehicle networks.     

Creep Life Prediction of Alloy 718 for Automotive Engine Materials

This study was carried out to investigate the creep life at the high temperature of the Alloy 718 for automotive engine components using the initial strain parameter method (ISPM). Creep tests have performed at elevated temperatures in the range of 550 oC to 700 oC in this work. We also carried out constant stress creep tests. The initial strains were measured during 1 minute after loading. Both the creep stress and rupture time depend on the initial strain. We calculated the creep life of Alloy 718 by using the creep life prediction equations obtained from the ISPM. Then, we compared the creep life predicted by the ISPM to the Larson-Miller parameter (LMP). The experimental rupture time and the calculated rupture time by using the ISPM agreed with a confidence level of 95 %. The creep life predicted by using the ISPM was in very good agreement with the creep life predicted using the LMP method.     

Fast Ferry Smoothing Motion via Intelligent PD Controller

A novel type of control law was adopted to reduce the vertical acceleration of a fast ferry as well as the motion sickness incidence suffered by the passengers onboard by means of a submerged T-foil. Considering the system changing characteristics under high disturbances, a model-free approach was adopted. In addition, an upgraded proportional-derivative (PD) controller with correction terms resulting from a fast-online estimation of the system dynamics was designed. The overall controller, known as intelligent PD (i-PD) controller, was tested, and the obtained results were compared with those of a classic PD controller. The controllers were also tested in a changing environment and at different operating velocities. The results confirmed the effectiveness of the i-PD controller to smooth the motions with low computational cost control schemes. Furthermore, thanks to ability of the i-PD controller to continually update the estimated dynamics of the system, it showed a better reduction in both vertical motions and the seasickness level of the passengers with the needed robustness under external disturbances and system changing parameters.