齐北线K34+296中桥沉井施工病害及处理措施

结合齐北线K34+296铁路中桥施工,分析了沉井施工中常见的下沉过慢、下沉过快、倾斜、偏移或扭转、遭遇流沙和施工引起邻近建筑物下沉等施工问题,提出了预防措施和治理办法,供类似工程参考.     

南京地铁二号线信号系统多级后备控制模式

后备控制模式是提高信号系统可靠性,保证其正常运营的重要手段之一。南京地铁二号线在西门子Trainguard MTA TC系统原有后备控制模式的基础上,又引入了中国电子科技集团公司第十四研究所研发的后备控制模式,使整个系统的可靠性得以提高。通过对多级后备控制模式的设计及原理进行分析,为今后进一步完善后备系统提供参考。     

Estimation of link performance functions from incomplete flow data

Despite the pivotal importance of link performance functions to models of transport systems, relatively little work has been done on practical aspects of estimating these functions from observed data. Furthermore it is difficult to find any examples in the literature of estimated urban link performance functions faithfully reproducing theoretical travel time-flow relationships. One reason for the paucity of research in this area is the difficulty and expense of obtaining the requisite data. The increase in automatic collection of traffic flow data goes part way to resolving this problem, but matching such flows to manually recorded travel times can present considerable statistical difficulties in the estimation procedure. This paper considers the estimation of link performance functions from a combination of automatically recorded traffic counts and travel collected by hand, using a non-standard statistical methodology. The study is motivated by a set of data of precisely this type, from the UK city of Leicester.     

Energy use in passenger transport in OECD countries: Changes since 1970

This paper analyzes some of the changes that took place in the structure of energy use for passenger travel in industrialized countries. Data is presented on energy use and travel activity for the four major modes of travel — automobile, bus, rail and air — for eight OECD countries: the United States, Japan, the United Kingdom, West Germany, France, Italy, Sweden, and Norway. We use the Laspeyres and Divisia indices to analyze the causes of the change in energy use between 1970 and 1987. The total change in energy use for travel is explained by changes in domestic passenger transport volumes, the mix of modes of travel, and the energy intensities of each mode. We have found two important effects that have a fundamental impact on energy use for travel since 1970. First, shifts among modes of transport towards more energy-intensive ones and large increases in volumes of travel (measured in passenger-kilometers) increased energy use for travel in many OECD countries, often more rapidly than the overall growth in GDP. Second, energy intensities, measured in mJ/passenger-kilometer, of passenger transport fell only in a few countries between 1970 and 1987. Even though individual automobiles have become more energy-efficient, greater size, power, and weight, worsening traffic conditions in Japan and Europe, and fewer people in cars restrained or even offset efficiency improvements. Particularly notable are the increases in intensities in Japan and Germany. The most important exception to this trend was the United States, but the intensities of land-based travel remain higher there than in most other countries. These findings lead to a pessimistic outlook for future energy use for travel. After all, if little or no energy was saved during the decades of high fuel prices, what can be expected in the 1990s?     

A Model for Determining Rider Induced Energy Losses in Bicycle Suspension Systems

The energy dissipated by the suspension systems used for off-road bicycles is a major concern due to the limited power source in cycling. Rider induced energy losses are those that arise from the muscular action of the rider. The purpose of this study was to develop and verify a dynamic model of a seated cyclist riding an off-road bicycle up a smooth road. With the absence of terrain irregularities, all suspension motion was rider induced. Knowing the stiffness and dissipative characteristics of the suspension elements, the power dissipated by the suspensions was calculated.

Simulation results were compared to suspension deflections that were experimentally measured for a cyclist riding a commercially available dual suspension bicycle up a 6% grade at 6.5m/s. For this particular case, no fork motion was observed in the experiments which was consistent with the simulation results. For the rear suspension, the mean and amplitude of the largest harmonic were experimentally determined to be 6.6 and ±2.7 mm respectively. Simulation results were within 0.7mm of the mean and within 0.3mm of the amplitude. The only major discrepancy between the experiments and the simulations was the presence of a phase lag in the simulation results which was attributed to inter-subject variability. The power dissipated by the rear suspension was calculated to be 6.9 Watts or 1.3% of the total power input by the rider. Given the grade and forward velocity, this translated into an equivalent mass of 1.8 kg. Thus, the bicycle appeared to be roughly 12% heavier than it actually was.     

铌磷半钢在中磷铸铁闸瓦中应用的研究

本文通过对用铌磷半钢配制的中磷闸瓦的金相组织、力学性能、物理性能和摩擦-磨损特性的研究及其实际运行,证明:其质量指标和使用性能完全满足 TB1159-76标准,并超过普通中磷闸瓦的技术水平;可使中磷铸铁闸瓦的原材料成本降低10%左右.     

Use of the box and Jenkins time series technique in traffic forecasting

This paper explores the use of recently developed time series techniques for short term traffic volume forecasts. A data set containing monthly volumes on a freeway segment for the years 1968 through 1976 is used to fit a time series model. The resulting model is used to forecast volumes for the year 1977. The forecast volumes are then compared to actual volumes in 1977. The results of this study indicate that time series techniques can be used to develop highly accurate and inexpensive short term forecasts. A discussion of the ways in which such models can be used to evaluate the effects of policy changes or other outside impacts is included.     

Reconsidering the multinomial probit model

Recently developed computational methods have greatly reduced the difficulty of estimating multinomial probit models and may soon make multinomial probit a computationally feasible option in applied travel demand modeling. This paper discusses some of the benefits and costs that are associated with the use of multinomial probit in demand modeling. It is argued that although there are situations in which multinomial probit is essential for achieving a satisfactory model, most problems with existing demand models are unlikely to be mitigated by the use of multinomial probit.     

胆石中游离和结合胆汁酸定量分析研究(薄层扫描色谱法)

在付立叶变换红外光谱(FT-IR)定性分类胆石的基础上,用薄层扫描色谱法进行胆石中游离和结合胆汁酸的定量分析研究。60例胆石经FT-IR 分为7种类型:胆固醇结石,胆固醇混合石、胆色素混合石、色素新型石、类色素型石、黑石磷酸盐型和黑石蛋白型。本文将从不同类型胆石游离和结合胆汁酸含量的差异,探讨胆汁酸在胆石成因中的作用.