Exploring ride-hailing fares: an empirical analysis of the case of Madrid

Transportation - Ride-hailing is an emerging service that is transforming door to door mobility in urban areas. Users can easily request a ride through a smartphone app that informs them of the...     

C2H2作燃料的DF化学激光器燃烧室反应的数值分析

本文选用C2H2作为DF化学激光器燃烧室燃料,采用最小自由能法计算了C2H2-NF3体系不同配比下的燃烧温度和平衡组分,为进行这方面的实验提供了参考。     

风积沙填筑路基施工质量控制

如何利用风积沙填筑路堤(含填高大于10m的路堤)，既达到设计要求．又保证路基稳定，并满足各项技术指标，是工程建设中的一个难题。目前国内尚无成熟的沙漠区路基施工技术规范、施工工艺和方法。文章结合工程实际，阐述了风积沙作为路基填料，其施工质量控制办法。     

Urban walkability considering pedestrians’ perceptions of the built environment: a 10-year review and a case study in a medium-sized city in Latin America

ABSTRACT

Numerous methodologies measuring walkability have been developed over the last years. This paper reviews the Walkability Index (WI) literature of the last decade (2009–2018) and highlights some limitations in the current approaches. Only a few studies have evaluated walkability in Latin America, mainly in big cities but not in medium and small-sized cities in the region, which present their own urbanisation dynamics, security issues, sidewalk invasion problems, and poor planning. Furthermore, most WIs in the literature use objective mesoscale variables to assess walkability in a given area. This paper contributes to filling these gaps by generating new evidence from a medium-sized city in Latin America to question if characteristics of the built environment encourage walking trips, as found in the literature, are transferable among regions. The study also proposes a novel index comprised of microscale and mesoscale built environment variables to assess walkability using virtual tools and considering users’ perceptions. The WI estimation relies on ranking probability models. The results of the case study suggest that subjective Security and Traffic Safety are the most crucial factors influencing walkability in these kind of cities, which is different from what is found in the literature from cities in developed countries where Sidewalk Condition and Attractiveness are the most important factors. Security appeared to be strongly associated with a subjective dimension, represented by the fear of crime or perceived risk for crime, instead of the actual occurrence of crimes. This result evidences the importance of the physical attributes of the real world and how they are captured, judged, and processed by pedestrians. Then, regional transferability of WIs needs to be done carefully. Finally, results in this paper highlight the importance of microscale built environment characteristics in the WI formulation in these cities. Results are in line with other research in some cities of the region, which found that microscale variables such as pavement quality and presence of obstacles on the sidewalks are relevant components to promote walkability.     

Towards improving resilience of cities: an optimisation approach to minimising vulnerability to disruption due to natural disasters under budgetary constraints

Transportation - In recent years, climate change emerged as a dominant concern to many parts of the world bringing in huge economic losses disturbing normal business/life. In particular cities are...     

Economic efficiency in Spanish ports: some empirical evidence

In this study, a stochastic frontier cost function is used to estimate the econmic efficiency of Spanish ports through panel data. The sample covers annual data of 27 Spanish ports from 1985–1989. By comparing a Cobb-Douglas function with a translog, it is found that the latter best represents the technology according to the data. Analysing the efficiency indices obtained, it is found that the relatively larger ports are more economically inefficient. Moreover, the presence of large scale economies has been detected, as well as a lack of technical progress for the period considered.     

A model for forecasting future supply of shipping services at Australian ports

This paper aims to develop an integrated model for forecasting both the number of ship visits and their characteristics in the medium and long term. Knowledge of future shipping trends for any port is no doubt important, as the future number of ship visits and their characteristics may have implications for the physical facilities of a port. In addition, more reliance on tonnages as a revenue source has made this knowledge more valuable. The proposed model identifies such major economic determinants as the expected trade throughput, world shipping trends, standards of facilities and future plans of shipping companies/agents. The model examines three possible scenarios for the Port of Melbourne and produces a range of shipping forecasts based on certain assumptions. From the model the major findings were:

world trends in shipping did not have any immediate impact on the shipping trends at the Port of Melbourne;

Future shipping services at the Port of Melbourne in the next 11 years are most likely to be determined by trade demand rather than by technological developments overseas;

there has been no evidence to indicate that the Port of Melbourne has been excluded from the schedule of general cargo ships due to the Port's physical constraints.     

光化学蚀刻在增益发生器加工中的应用前景

增益发生器是化学激光器的关键部件之一。为了提高激光光束的质量和激光器的工作性能,本文从增益发生器的加工工艺出发,简单的介绍了传统工艺及其优势与劣势,在此基础上提出了光化学蚀刻与扩散焊结合的新工艺及其优势。重点总结了光蚀刻工艺效果的影响因素及其解决方案。