Modelling,simulation and evaluation of ground vibration caused by rail vehicles*

ABSTRACT

There is a great need to develop rail networks over long distances and within cities as more sustainable transport options. However, noise and vibration are seen as a negative environmental consequence. Compared with airborne noise, the related problem of ground vibration is much more complex. The properties of the ground vary significantly from one location to another. There is no common assessment criterion or measurement quantity and no equivalent to the noise maps. Ground-borne vibration is transmitted into buildings and perceived either as feelable whole-body vibration or as low frequency noise; it can also affect sensitive equipment but it is generally at a level that is too low to cause structural or cosmetic damage to buildings. A review is given of evaluation criteria for both feelable vibration and ground-borne noise, empirical and numerical prediction methods, the main vehicle and track parameters that can affect the vibration levels and a range of possible mitigation methods.     

Container port systems in China and the USA: a comparative study

This study compares the evolution of container port systems in China and the USA in terms of port throughput, number of container ports and the concentration level in the container port system, based on the time-series data on these three features over the period 1979–2009 for China and 1970–2009 for the USA. The results show that the densities of container ports in the two countries are similar, and their evolutionary processes are alike, which has led to a comparable market structure in the port industries of the two countries. In addition, the disparities between container ports closely represent the unevenness in the regional economic development. We further compare the port management regimes of the two countries in terms of the administrative processes for port development and expansion, the ownership structure and the providers of port functions, which offer some explanation on the dynamics of port evolution in the two countries. In conclusion, it can be seen that the evolution of the container port system and the management regime in the USA can be a de facto reference for the future development of the Chinese container port system.     

A combined science and management framework for developing regional monitoring objectives

Abstract

Designing environmental monitoring programs to deal with widespread, subtle, and/or cumulative impacts on a regional basis is challenging. It requires a shift away from focusing primarily on individual point sources to a more regional perspective. It also necessitates involving scientists and managers together in a cooperative effort to establish priorities and articulate clear objectives. In our view, this objective‐setting task is neither a strictly scientific nor a strictly management activity. It depends on effective communication between scientists and managers but is confounded by differing perspectives, value systems, and behaviors. We present a conceptual framework to assist managers and scientists in this process. This is intended to structure such communication by helping to create a context that permits fruitful give‐and‐take between the two groups. We then describe a six‐part model for specifying the key elements of regional monitoring objectives.     

Evolution and research trends of container shipping

The shipping industry was transformed by the expansion of international trade and technological innovation, notably containerization, since the 1960s. Accordingly, this was followed by a significant increase in research addressing different aspects of container shipping. Despite such availability, important questions have remained unanswered: what are the major contributions that the research community has made to the container shipping industry, global and regional economies? Have their contributions been skewed towards particular themes, directions, and geographical areas? What can the shipping research community learn from the evolution and trends of container shipping research so that they can continue to contribute to the well-being of the global and regional economies? To address these questions, the paper undertakes a critical review and analysis on the evolution and trends of research in container shipping in the past four decades, based on a collection of 282 papers investigating different topics in container shipping featuring in major scholarly journals between 1967 and 2012. The study enables the shipping research community to enhance self-understandings and identifies major gaps for further research.     

Optimal Linear Active Suspensions with Derivative Constraints and Output Feedback Control

In optimally controlled active suspensions with either full or incomplete state feedback there is tradeoff between system performance and overall stiffness. It is sought to remove this limitation by incorporating integral action which results in a system with infinite stiffness towards static loading, but which is soft with respect to road inputs. The system is also able to eliminate the steady state deflections due to step and (potentially) ramp type inputs at the wheel. Optimality is retained at the cost only of a derivative constraint and the system can be physically realised using output feedback control.     

The utility analysis of risk attitudes in shipping

Many methodologies have been developed in order to optimize business decision making. By definition, optimization is only possible when an objective, or set of objectives, has been specified. However, the presence of risk obscures the potential payoffs of a particular decision. How different decision makers react to this phenomenon is reflected in the different objectives which they adopt. One corollary of this diversity of objectives is that any generally applicable optimization method must explicitly take into account the influence of risk attitude on decision choice. Because of the magnitude of the risks involved, virtually nowhere is this requirement more relevant than in relation to shipping decisions. This paper presents and justifies a method for assessing and measuring attitudes towards market risk. The method is applied to a sample of shipowners in Britain, Norway, Hong Kong and Greece and the risk profiles that are developed have some surprising, and important, implications for decision making in shipping.     

橡胶沥青的输送和计量

橡胶沥青作为道路工程中的高温、高粘度介质,想要成功地将其泵送可能并不容易,而进行橡胶沥青的计量则更具挑战性。由于胶粉的磨蚀性,使用机械式的齿轮流量计已被证明是不可靠的。因为随着时间的推移,胶粉对齿轮的磨损会造成啮合齿轮打滑,由此造成的测量误差会超过精度许可范围。     

Spillover effects and dynamic correlations between spot and forward tanker freight markets

Monitoring and analysing information transmission across different shipping markets is an important tool for participants to predict shipping freight rates, design portfolio investments and manage freight rate risks. The purpose of this article is to investigate spillover effects and dynamic correlations between shipping spot and derivatives markets (tanker forward freight agreement, FFA) under the multivariate generalized autoregressive conditional heteroscedasticity framework. Empirical results show that spillovers in returns are unilateral from one-month FFA to spot markets, while they are bilateral between one-month and two-month FFA markets. However, insignificant mean spillovers between spot and two-month FFA markets are found. Volatility spillover effects among one-month FFA, two-month FFA and spot freight markets are bilateral. By analysing the correlation between different markets, highly persistent and significantly volatile correlations are found. Moreover, time-varying correlations between one-month and two-month FFA markets are much higher than those of between spot and each FFA market. Results from this article will be helpful to improve participants’ predictions of return, volatility and correlation, which are significant for determining hedge strategies. In addition, the management of freight rate risk and portfolio investment can also benefit from the empirical results obtained in this article.     

IAME 2011 – contemporary studies on maritime transport in Latin America

Latin America and the Caribbean have evolved as a region of increased interest for the maritime and port industry as well as for academic research. Maritime transport activity in the region has experienced sustained growth rates over the last decades, resulting in ever-increasing demand for maritime services and port infrastructure. At the 2011 Annual Conference of the International Association of Maritime Economists (IAME), Latin America received significant attention. This editorial responds to growing research by giving a brief overview of the current situation and contemporary issues in maritime transport within the region. It also introduces the six selected papers for this Special Issue.