Influence of repeated and delayed excitations in combined subspace identification

The application of combined subspace identification methods to land vehicles would allow the modal parameters of the vehicle to be obtained, while it is in operation, thus improving the vehicle modal characterisation. However, when a land vehicle is circulating through a straight line, the excitations applied to the different axles are identical among them but with a certain time delay. The presence of repeated excitations with different time delays implies that the past and future subspaces include common vectors that may lead to problems in the application of the method. To analyse its influence, an index called the reduction coefficient resulting from excitations (RCE) has been defined. RCE evaluates the amount of information eliminated in the oblique projection due to the effect of repeated excitations. The use of RCE enables the selection of analysis parameters, particularly the sampling frequency, the signals grouping and some specific parameters of the subspace identification methods.     

A dynamic approach to road freight flows modeling in Spain

This paper presents an innovative approach to analyzing road vehicle freight traffic that uses a dynamic panel data specification derived from a gravity model. This dynamic approach, which has recently been employed in international goods trade models in lieu of the traditional static specification, is applied to the case of Spain using data for the countrys 15 NUTS-3 regions between 1999 and 2009. Using the system general method of moments approach, we obtained significant evidence that the flow of vehicles carrying commodities by road has a strong persistence effect when controlling for unobserved heterogeneity. We also found that the quality of road transport infrastructure has a significant impact on vehicle trips. According to our findings, we suggest that this type of specification be employed in distribution models in which fixed effects and lags of the dependent variable are included to account for unobserved heterogeneity and persistence effects, respectively.     

Efficiency sensitivity analysis of a hydrostatic transmission for an off-road multiple axle vehicle

There is a large variety of multiple driven axle vehicles. Some of the most common are the 3-axle rigid vehicles and the 4-axle articulated vehicles, which can in some cases have different steering mechanisms, adaptive suspension, etc. This last kind of vehicles usually have very complex transmission configurations. Moreover, the required torques in each of the wheels can be very different, especially when the vehicle is working in rough terrains. The aim of this work is to study and model the driveline of this kind of vehicles, when using a hydrostatic transmission, from the performance and efficiency point of view, by analysing the influence of the operating conditions in the transmission efficiency. A global model is used to quantify the power flow in each of the transmission elements and the overall performance of the entire vehicle driveline, given the operating conditions thereof. A sensitivity analysis has also been done showing the influence of vehicle speed, rolling resistance, terrain slope and hydraulic motors displacement in the overall transmission efficiency. The interest of this work is also to make a contribution to the literature in the field of global modelling of drivelines under variable operating conditions and its application to ATVs. One important aspect is the influence of different actuation requirements that occur in different wheels at the same time. The results show that the overall performance of the transmission is highly dependent on operating conditions, on the selected transmission configuration and on the used components.     

The econometric estimation of airports’ cost function

The econometric estimation of cost functions has been proposed in the literature as a suitable approach in order to obtain estimations of marginal costs, efficiency levels and scale elasticities for transport industries. However, regarding the airport industry, no significant attention has been paid in developing an airport-specific estimation methodology rather than adapting the procedures applied to other industries. The lack of comparable airport data is one of the causes which could explain the scarcity of this literature in the past, as well as the use of very limited approaches to explain airport technology. This paper tries to overcome these limitations by developing an airport-specific methodology to estimate a multi-output long-run cost function using an unbalanced pooled database on 161 airports worldwide. The specification of hedonically-adjusted aircraft operations, domestic and international passengers, cargo and commercial revenues in the output vector, as well as the calculation of input prices are discussed. Both technical and allocative inefficiencies are specified in the model using a Stochastic Frontier method that has been estimated through Bayesian Inference and Markov Chain Monte Carlo methods.     

Telemetric system for monitoring and automation of railroad networks

This paper describes a new method of real-time train monitoring based on the ZigBee/IEEE 802.15.4 protocol. The system consists of a mobile device embedded in the moving train which transmits parameter signals that are being measured by a base unit with the help of routers. When applied, the technique monitors and controls vehicles operating on permanent routes, making a real-time evaluation of their performance and location, and allowing an effective planning of trains. It consists of a low cost, low power consumption and safe modular technology capable of monitoring many different variables simultaneously.     

The political economy of ports in the United States and Great Britain

Abstract

This is an exploration of the political economy of ports in the United States and Great Britain. A number of technical, economic, and political issues concerning ports are examined. Particular attention is paid to the institutional evolution of ports from private to public ownership, and its consequences for port efficiency. The paper concludes with a set of recommendations designed to reverse the trend toward port nationalization in both countries.     

Marketing management at the world's major ports

Recent technological developments in maritime transport, particularly in container shipping and larger vessels, are having major repercussions at ports the world over. The latest wave of innovations has increased the level of competition in maritime transport, in particular in port activities. Shippers have many more alternatives available, something that tends to increase the hinterland of each port, precisely by reducing captive hinterlands. Ports are now generally moving towards formulas in which private initiative has a bigger role to play. Increases in competition combined with growth in private initiatives highlight the usefulness of marketing tools in two ways. Externally, because they help to achieve throughputs from remote points of origin and destination, and internally, by aiding the proper coordination of business and organizational activity at a commercial port. The present paper is a transversal study of the current situation of marketing and quality tools at major ports, including the opinions of a range of port commercial and marketing managers. We have also tried to describe the differentiated groups to be found at ports, as a useful methodology for identifying the nearest competition or ports with similar characteristics.     

What determines university student’s willingness to pay for bikeways?

Transportation - Inadequate infrastructure is recognized as an important barrier to cycling; therefore, improvements in the provision of bicycle facilities, such as bikeways, are frequently...     

The Brazilian National Plan for Coastal Management (PNGC)

The article is divided into three clearly defined sections. The first outlines the Brazilian National Coastal Zone Management Plan. The second offers a critical assessment of its introduction. To conclude, some general considerations are made. In this way, the author aims to achieve two objectives: to disseminate the aforementioned plan and offer a critical opinion of it.