YZ20D超重型振动压路机

从主要技术参数、技术特点及工业造型设计应用三个方面对YZ20D新型超重型振动压路机作了全面介绍，以供参考。     

Questioning the need for full amortization in PPP contracts for transport Infrastructure

PPP contracts most often have durations of between 20 and 35 years, but in some cases even longer. The main reason for this is the wish of the Public side to minimize its financial contribution, by including in the contract many years of revenue generation by the project to help cover the investment contribution of the private partner. Implicit however is the need to fully amortize the initial investment, which in many countries is even included in the relevant legislation.PPP contracts are normally framed around the delivery of a range of services during the lifetime of the contract, those services requiring the initial construction or recovery of an expensive infrastructure. The specification of the financial clauses of the contract requires the estimation of demand for those services over the period of the contract and this is usually taken as the major incidence of uncertainty in the contract. Indeed, experience shows that demand forecasts often fail substantially, in many cases by more than 20%, mostly by excess, as State side project promoters (and the bidding private partners) tend to be excessively optimistic about the development of such demand.But when we consider the nature of these contracts we should recognize the existence of at least two other very important types of uncertainty: first, the socially desirable scope and specification of the services to be offered as technology and social preferences evolve; and second, the policy guidelines relative to the total quantity and the social distribution of those services, as that quantity may be causing congestion in other parts of the system, or it may become important to (positively or negatively) discriminate some user segments.In both cases, it is almost impossible to foresee at the time of writing the initial contract if, when and in what direction such types of socially beneficial changes in the provision of the services would intervene, but this rigidness may bear a great loss of social welfare in relation to a more adjustable framework. This criticism affects not only PPPs but all kinds of concession contracts with long duration, so it is not the “partnership” element that must be questioned but rather the duration of the contract.An alternative way is relatively straightforward: abandon the assumption that these contracts must provide full amortization of the infrastructure, which allows adoption of contracts with a shorter life, and the use of multiple such contracts over the lifecycle of the infrastructure.The first generation contract would still have to face the full cost of the construction, but the private partner would receive the unamortized part at the end of that contract, to be paid by the State, directly from the public budget if no more private participation is wanted, or indirectly through the acquisition fee for the contract to be paid by the partner to the second life segment. But, crucially, the State recovers the right to re-specify the terms of the service to be provided without the need for any indemnity, and also the uncertainty associated with the evolution of demand in that period will be much smaller, as this will be my then a mature system in operation.This may seem to increase the transaction costs for the State as more contracts (although of a similar type, especially from the second onwards) may have to be negotiated and signed. But if we take into consideration the difficulties of the frequently needed renegotiations of long duration contracts and the conditions of asymmetry of information in which the State normally finds itself in such cases, we will conclude that, besides avoiding the loss of welfare due to the poor fit of the contract after 20 years or so, this solution after all may also reduce the transaction costs associated with negotiations over the duration of the traditional contracts.     

Are we doing it wrong or do we expect too much? Forces that push authorities to become public transport designers

This paper presents a number of reasons that are responsible for the disappointment of authorities in their operators’ efforts to develop public transport (PT) to the advantage of their travellers. The lessons drawn in this paper are based upon the competitive tendering experience of the authors and upon the results of meetings organised with parties involved in competitive tendering and aimed at exchanging lessons. There appears to be three main causes: (1) there is freedom for the operator, but the contract is bad; (2) there is freedom for the operator, there is a good contract, but there is no market; and (3) there is freedom for the operator, but the operator is not able to use it. The paper concludes with a few perspectives for improvement.     

A comprehensive analysis of household transportation expenditures relative to other goods and services: an application to United States consumer expenditure data

This paper proposes a multiple discrete continuous nested extreme value (MDCNEV) model to analyze household expenditures for transportation-related items in relation to a host of other consumption categories. The model system presented in this paper is capable of providing a comprehensive assessment of how household consumption patterns (including savings) would be impacted by increases in fuel prices or any other household expense. The MDCNEV model presented in this paper is estimated on disaggregate consumption data from the 2002 Consumer Expenditure Survey data of the United States. Model estimation results show that a host of household and personal socio-economic, demographic, and location variables affect the proportion of monetary resources that households allocate to various consumption categories. Sensitivity analysis conducted using the model demonstrates the applicability of the model for quantifying consumption adjustment patterns in response to rising fuel prices. It is found that households adjust their food consumption, vehicular purchases, and savings rates in the short run. In the long term, adjustments are also made to housing choices (expenses), calling for the need to ensure that fuel price effects are adequately reflected in integrated microsimulation models of land use and travel.     

State-of-the art of freight forecast modeling: lessons learned and the road ahead

In this paper we review freight forecasting models and current advances and needs with respect to data and model development. We then present a case study to suggest which models should be developed for the State of California in the US. We suggest several alternatives including an aggregate commodity flow model, a disaggregate regional logistics model and a hybrid regional logistics model with a truck touring model. We point out however, that the data requirements for the latter model would be extensive. In addition, the development of hybrid models, for example progress in the integration of regional logistics models with urban truck touring models, will introduce new problems such as reconciling the outputs of multiple models for consistency.     

Measuring the completeness of complete streets

A tool for measuring the “completeness” of a complete street has applications in developing policy, prioritising areas for infrastructure investment for a network, and solving the right-of-way allocation problem for individual streets. A literature review was conducted on the state-of-art in the assessment complete street designs. Complete streets assessment requires a context-sensitive approach, thus context-sensitive standards of “completeness” must first be established by combining a street classification system with sets of priorities and target performance levels for the different types of streets. Performance standards should address a street’s fulfilment of the movement, environmental, and place functions, and be flexible enough to account for the many ways that these functions of a street can be fulfilled. Most frameworks reviewed are unsuitable for evaluating complete streets because, with few exceptions, they guide street design by specifying the design elements for inclusion on the street. Secondly, the performance of a street can be assessed according to transportation, environmental, and place criteria, and compared to the target performance levels specified by the street’s classification. As there are many different impacts to consider on a street, additional work is required to define the priorities and performance objectives for different types of streets.     

Impact of biometric and anthropometric characteristics of passengers on aircraft safety and performance

Demand for commercial air travel has been increasing over the years and recent forecasts indicate similar future trends. New aircraft with enhanced design features are being built and entering the airline service globally. These enhancements aim to ensure continued safety, efficiency, performance and prolonged life serviceability. However, these new enhancements often neglect the impact of the changing anthropometric characteristics of the passenger. Past studies have identified increasing trends in the average weight, height and other anthropometrical and biometrical measures of people at a global scale. However, many are limited to only exploring the ramifications primarily from the perspective of passenger experience. This paper highlights the importance of considering passengers’ anthropometric characteristics from a holistic perspective and identifies gaps for future research.     

Mechanical Behaviors and Design Parameters of Segmental Tunnel Linings with New Type of Joints北大核心CSCD

Segmental linings in shield tunnelling are composed of segments and joints. Mechanical behaviors of the joints govern overall behaviors of tunnel linings. Two new types of joints are adopted in Shanghai Metro Line 18, including the fast-insertion joints for adjacent rings, and the fast-slide joints for adjacent segments. In order to explore the overall behavior of segmental linings with these new types of joints, the full-scale tests are carried out for new lining structure with aligned and staggered longitudinal joints. The mechanical behaviors of the tunnel linings under different loading conditions are obtained. Furthermore, the calculation models of the tunnel linings are discussed, and regarding the modified routine method, the structural design parameters under different loading conditions are calculated, which provides a reference for the design and the comparison of the assembly method of the tunnel linings with new types of joints. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Application of Chinese Characters in the Design and Construction of the Badaling Great Wall Station of the Beijing-Zhangjiakou High-Speed Railway北大核心CSCD

The new Badaling tunnel is the longest tunnel on the under-construction Beijing-Zhangjiakou highspeedrailway, with the Badaling Great Wall station to be built in the tunnel. This station, which is under the Badaling Great Wall historic site, is the world’s largest underground high-speed railway station with the most complicated structure and the largest overburden and excavation area. It is therefore a representative project for China’s highspeed railway development strategy, supporting infrastructure facilities for the Beijing Horticultural Expo 2019 and the 2022 Winter Olympics in Beijing, and it is important that it be of high quality and completed safely. In the de-sign and construction of the station, the glyphs of the Chinese characters of "中",”国”,”人”and”品”are used, re-spectively, along the station route, in the rescue and evacuation mode, auxiliary adit and partial excavation, which is a way to successfully integrate the art of Chinese characters into tunnel engineering. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Application of Rock Fissure Grouting in a Deep Foundation Pit in the Kuala Lumpur Karst Region北大核心CSCD

For the bed rock of the foundation pit of the Bandar Malaysia North Station (BMNS) in Kuala Lumpur,the karst, fissure and cave are very developed, and curtain grouting, spud grouting and compaction grouting were conducted to achieve waterproofing and reinforcement. A Lugeon test and pumping test were carried out to test the grouting performance. The results show that the waterproofing effect of the Bandar Malaysia North Station (BMNS) is significant, meeting the basic requirements for waterproofing. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.