Making mode detection transferable: extracting activity and travel episodes from GPS data using the multinomial logit model and Python

The increasing popularity of global positioning systems (GPSs) has prompted transportation researchers to develop methods that can automatically extract and classify episodes from GPS data. This paper presents a transferable and efficient method of extracting and classifying activity episodes from GPS data, without additional information. The proposed method, developed using Python®, introduces the use of the multinomial logit (MNL) model in classifying extracted episodes into different types: stop, car, walk, bus, and other (travel) episodes. The proposed method is demonstrated using a GPS dataset from the Space-Time Activity Research project in Halifax, Canada. The GPS data consisted of 5127 person-days (about 47 million points). With input requirements directly derived from GPS data and the efficiency provided by the MNL model, the proposed method looks promising as a transferable and efficient method of extracting activity and travel episodes from GPS data.     

中远集运船舶全球动态监控系统的技术特点

为实现全球航行船舶的有效监控,公司自主开发的“中远集运船舶全球动态监控系统”解决了岸端主控的难题,实现了对船舶航行状态进行准确、实时跟踪,并将船舶动态、静态、人员、工况、载货、自动识别系统（AIS）、保安报警系统（SSAS）与气象等多态异构数据整合在同一信息平台,是具有实际应用价值的全球船舶动态监控系统。该系统获2008年度“中国航海学会科学技术一等奖”。     

浅析GPS及其抗干扰技术

随着全球定位系统在民用和军事领域的迅速推广,其易受干扰的问题日益显现出来．通过对GPS的脆弱性进行阐述,并对其干扰方式进行分析,在此基础上探讨了GPS的抗干扰措施．     

国际金融危机对广西-东盟物流业的影响及对策

文章基于对东盟的贸易结构、运输方式和广西-东盟的物流业发展现状的分析,以广西物流基础设施发展举措为重点,对国际金融危机下广西-东盟的物流业发展对策进行了探讨。     

Coarse mesh finite element model for cruise ship global and local vibration analysis

This paper presents a practical procedure for creating finite element (FE) model for vibration analysis of cruise ships. The most preferable FE modelling approaches are studied and discussed through case studies of common ship structures, which cover the range from low to high frequencies. The application of homogenized equivalent single layer (ESL) theory based equivalent element for stiffened panel is extended to local forced vibration analysis, where inertia induced interaction between plate and stiffener occurs. Modal method is used with an energy-based correction for accounting the plate-stiffener interaction into modal properties. Case study results reveal that mesh density of one 4-node element per web frame spacing is suitable for global FE-model when vibration analysis is limited to global hull girder modes. For such modes it is sufficient to only include the membrane stiffness of stiffened panels. For investigating the response at higher frequencies, bending properties of stiffened panel should be included and mesh density should be at least two elements per web frame spacing. Then forced vibration analysis can be performed with an excellent accuracy up to frequencies about one third of the local plate natural frequencies between the stiffeners. Beyond that, the influence of the local plate vibration becomes more significant in panel vibration, making the ESL-theory based element limited. With the applied correction method, the validity of the ESL-model can be extended to approximately two thirds of the local plate natural frequency.     

Dynamic responses analysis of a 5 MW spar-type floating wind turbine under accidental ship-impact scenario

Ship impact against offshore floating wind turbine (OFWT) has been identified as one of the major hazards with the development of OFWTs. The dynamic responses of OFWTs under ship impact should be taken into consideration during the design phase. This paper addresses a study on the dynamic responses of an OFWT in ship collision scenarios. Firstly, a mathematical model for external mechanism of ship-OFWT collision scenario is developed. Secondly, this model is combined with an in-house programme, DARwind, which can be used to predict nonlinear dynamic responses of whole OFWT system in time-domain. With the newly combined analysis tool, simulation cases for different scenarios are conducted to investigate the nonlinear dynamic responses of OFWT system, including the cases of still water condition, wave-only condition and wind-wave condition. It is shown that in still water condition, the ship impact will more obviously change the responses of motions and mooring system, compared with those in wave and wave-wind conditions. In the wave-only condition, these motions responses of platform are suppressed by wave effect, but the tower vibration and tower top deformation are sensitive to ship collision. For the wave-wind combined condition, the motions increment in surge and pitch due to ship collision becomes smaller than that of wave-only condition, but yaw motion has a considerable variation compared with those of the other two conditions. Additionally, the blade tip deformation increment due to ship collision are analyzed and it is found that the edgewise tip deformation got more obvious increment than that of flapwise. To further asses the safety of OFWT, the acceleration at nacelle are analyzed because some equipment might be sensitive to acceleration. The analysis results indicate that even though the OFWT structure doesn't get critical damage by ship impact, the equipment inside may still fail to work due to the high value of acceleration induced by ship impact. The research outcomes can benefit the safety design of OFWT in the engineering practice.     

An aircraft performance model implementation for the estimation of global and regional commercial aviation fuel burn and emissions

Estimates of global aviation fuel burn and emissions are currently nearly 10 years out of date. Here, the development of the Aircraft Performance Model Implementation (APMI) software which is used to update global commercial aviation fuel burn and emissions estimates is described. The results from APMI are compared with published estimates obtained using the US Federal Aviation Administration’s System for Assessing Aviation’s Global Emissions (SAGE) for the year 2006. The number of global departures modelled with the APMI software is 8% lower compared with SAGE and reflects the difference between their commercial air traffic statistics data sources. The mission fuel burn, CO₂ and H₂O estimates from APMI are approximately 20% lower than those predicted by SAGE for 2006 while the estimate for the total global aircraft SO_x emissions is approximately 40% lower. The estimates for the emissions of CO, HC and NO_x are 10%, 140% and 30% higher than those predicted by SAGE respectively. The reasons for these differences are discussed in detail.     

Experimental and theoretical studies on lateral buckling of submarine pipelines

Global buckling of a submarine pipeline during high pressure/high temperature (HP/HT) operation results in a loss of pipeline stability that is similar to a bar in compression; this phenomenon constitutes one of the key factors affecting pipeline integrity and design. To intuitively study the buckling response, a test system was designed that can account for thermal loading and pipe-soil interactions, and this system was used to perform a series of small-scale model tests on the lateral buckling of submarine pipelines with different initial imperfections. Based on the hat-shaped buckling profiles of the test pipelines, a new buckling mode called "hat-shaped buckling" was proposed. In an attempt to study the conditions under which the pipeline exhibits this hat-shaped buckling mode, the changing law of the buckling mode was investigated through finite element analyses of pipelines with different parameters, including the length of the pipeline and the amplitude and wavelength of the initial imperfection. Subsequently, an analytical solution for calculating the buckling amplitude of a pipeline with a hat-shaped buckling profile was proposed. The theoretical solution was compared to the experimental data, which verified the feasibility of the model in calculating pipeline buckling deformation. The experimental data, the buckling mode based on these data and the corresponding analytical model discussed herein may provide a reference for future experimental studies of pipeline buckling.     

气温升高对多年冻土地区路基稳定性影响

为了分析在气温升高的状况下冻土退化对东北多年冻土地区路基稳定性的影响,假设气温年增长率为0.05℃,通过ANSYS有限元软件计算了不同地表状况和不同含冰量情况下,多年冻土最大季节融化深度变化,根据不同土质、不同含冰量的融沉系数,计算得到不同含冰量冻土的沉降量.结果表明:在气温逐年升高的状况下,含冰量大的土层沉降量大于含...     

Naturalistic driving data collection to investigate into the effects of road geometrics on track behaviour

Road designers assume that drivers will follow the road alignment with trajectories centred in the lane, and move at the design speed parallel to the road centreline (i.e., the horizontal alignment). Therefore, they assume that if the horizontal alignment indicates the “designed trajectory”, the driving path indicates the “operating trajectory”. However, at present, they do not have the necessary tools to measure the relationship between the designed alignment and possible vehicle trajectories.The paper has two objectives: (a) to develop an understanding of the root causes of differences between road alignment and vehicle trajectories; and (b) to define and calibrate a model that estimates the local curvature of trajectories on the basis of the designed horizontal alignment.The two objectives were pursued by carrying out a naturalistic survey using vehicles equipped with high precision GPS in real-time kinematics (RTK) mode driven by test drivers on road sections of known geometric characteristics. The results provide an insight into the effects of road geometrics on driver behaviour, thus anticipating possible driving errors or unexpected/undesired behaviours, information which can then be used to correct possible inconsistencies when making decisions at the design stage.