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81.
《珠江三角洲地区改革发展规划纲要》的颁布实施,对珠三角地区经济社会的发展具有重要战略意义,为珠三角地区船舶工业和航运业的发展提供了历史机遇。本文以珠江三角洲地区相关的船检分支机构[主要以广州海事局(广东省船舶检验局广州分局)为例]如何把握这一历史时期,更好地履行船舶检验职责和体现公共服务职能,发挥专业优势为船舶工业和航运业发展服务,在服务地方经济建设的同时实现自身科学发展为课题进行思考,提出了相应的对策建议。 相似文献
82.
Pacejka's Magic Formula Tyre Model is widely used to represent force and moment characteristics in vehicle simulation studies meant to improve handling behaviour during steady-state cornering. The experimental technique required to determine this tyre model parameters is fairly involved and highly sophisticated. Also, total test facilities are not available in most countries. As force and moment characteristics are affected by tyre design attributes and tread patterns, manufacturing of separate tyres for each design alternative affects tyre development cycle time and economics significantly. The objective of this work is to identify the interactions among various tyre design attributes-cum-operating conditions and the Magic Formula coefficients. This objective is achieved by eliminating actual prototyping of tyres for various design alternatives as well as total experimentation on each tyre through simulation using finite element analysis. Mixed Lagrangian–Eulerian finite element technique, a specialized technique in ABAQUS, is used to simulate the steady-state cornering behaviour; it is also efficient and cost-effective. Predicted force and moment characteristics are represented as Magic Formula Tyre Model parameters through non-linear least-squares fit using MATLAB. Issues involved in the Magic Formula Tyre Model representation are also discussed. A detailed analysis is made to understand the influence of various design attributes and operating conditions on the Magic Formula parameters. Tread pattern, tread material properties, belt angle, inflation pressure, frictional behaviour at the tyre–road contact interface and their interactions are found to significantly influence vehicle-handling characteristics. 相似文献
83.
This paper investigates punctuality at bus stops. Although it is typically evaluated from the point of view of bus operators, it must also account for users, as required in recent service quality norms. Therefore, evaluating punctuality at bus stops is highly important, but may also be a complex task, because data on both bus arrivals (or departures) and users must be taken into account and processed. Data on buses can be collected by Automatic Vehicle Location (AVL) systems, but several challenges must be addressed in order to use them effectively. Passengers data at bus stops cannot be derived from AVL, but they can be used to derive passenger patterns and need to be integrated into processed AVL data. This paper proposes a new punctuality measure defined as the fraction of passengers who will be served within an acceptably short interval after they arrive. A method is proposed to determine this measure: it provides (i) several rules to handle AVL collected data, (ii) a procedure integrating processed AVL data and potential passengers’ patterns and (iii) a hierarchical process to perform the punctuality measure on each bus route direction of a transit network, as well as for every bus stop and time period. The paper illustrates the experimentation of this method on more than 4,000,000 data of a real bus operator and represents outcomes by easy-to-read control dashboards. 相似文献
84.
It is commonly accepted that the modal choice of a shipper is influenced not only by the pure economic attributes of transportation – time and cost – but also by more qualitative factors. These quality attributes relate to frequency, reliability, flexibility, transport duration and risk of loss or damage; they are usually difficult to quantify in monetary terms. Different techniques exist that help to understand better how these different quality attributes of freight transportation influence modal choice. In this paper we apply a stated preference design. Using real business data, the aim is then to derive partial utility functions that allow us to calculate monetary values for these different quality attributes. 相似文献
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During 10 years experience with competitive tendering of regional and local public transport in the Netherlands, national average trip satisfaction of passengers increased from 6.84 to 7.25 (+0.41). This is a remarkable improvement, but a closer look at the data reveals that also in regions without competitive tendering the improvement in satisfaction was substantial. The difference in the improvement for regions with and without tendering is only +0.06. Tendering led in the majority of concession areas to an improvement of average trip satisfaction, but in some 40% of the cases a deterioration was observed. A change of operator in general has a negative impact on satisfaction. We also find that the effect on satisfaction of early tendering is larger than of later tendering. This may well be the consequence of a shift in emphasis of authorities and operators from quality improvement to efficiency improvements. The model building and analysis is based on the comparison per year-pair of regions tendered versus regions non-tendered (in that specific year-pair). So we compare the effects on satisfaction of tendered regions relative to non-tendered regions.An analysis concerning the weighted satisfaction judgments of 15 underlying service attributes revealed that ‘service frequency, on-time performance, travel speed, and vehicle tidiness’ contribute the most to the effect on satisfaction in the tendered regions. We found that new vehicles impact highly on satisfaction with travel speed and vehicle tidiness. The emphasis in the tenders with increasing service frequency, led to an increase in satisfaction but, may have a deteriorating effect on (the satisfaction with) on-time performance. 相似文献
88.
铁路货运服务质量关系到铁路企业形象和效益。采取定性和定量相结合的研究方法,建立功能质量测评体系,根据货运部门自身的特点建立相应的技术质量量化测评体系,最终将指标数量值转化成评定的等级。并通过实例验证了该评价方法的现实性和可操作性。 相似文献
89.
Public transport in towns - Inevitably on the decline? 总被引:1,自引:0,他引:1
Bus transport in Linköping, a town of 140?000 people, was strongly on the increase up to the beginning of the 1980s, when a negative trend-break occurred. A demand model is developed which explains both the ongoing decline and the preceding increase. Based on this model, it is examined whether a change of the current bus transport policy towards an optimal pricing and investment policy from a social point of view could evoke a new and positive trend-break. Taking current trends in the exogenous factors into account it would. However, this could depend on a possible revival of bicycling in towns. 相似文献
90.
根据汽车制动器的工作条件和磨损性质,采用理论计算的方法预测汽车制动器的使用寿命。通过理论计算,认为制动器制动衬片宽,制动鼓直径大,均能延长制动器工作期限;在使用中,汽车载货质量大,行驶速度高均将加速制动器间隙的增长,缩短其工作期限。 相似文献