1,720,957 research outputs found
Modelling Freight Modal Energy Use
No full textThis paper discusses the development of a model to compare corridor energy consumption of road and rail options. The key parameters influencing the energy estimation and comparison procedure are identified and a methodology to compare door to door freight movement is provided
Modelling road and rail freight energy consumption: A comparative study
No full textAfter reviewing land based freight growth trends nationally and internationally, this
thesis discusses the main parameters governing fuel consumption, as well as past
approaches in modelling road and rail energy consumption. Past work on comparing
these two main modes is also reviewed here. The review included ways of estimating
energy consumption of a complete freight task i.e., from origin to destination.
Mathematical models estimating modal energy consumption are presented in this thesis.
Modal energy consumption is a complex function to be approximated in practice due to numerous variables affecting their outcome. Energy demands are particularly sensitive to changes in vehicle characteristics such as mass and size; route parameters such as grade and curvature; traffic conditions such as level of congestion; and less sensitive to
ambient conditions, such as temperature and altitude.
There is a large set of energy estimation models available to transportation planners.
Unfortunately, unless simple relationships are established for energy estimation and
modal comparison, their application in freight movement planning and corridor
development becomes computationally prohibitive.
This thesis describes the development of a modal freight energy comparison tool to
quantify the energy advantage from mode choice, corridor development and vehicle
types and loading improvements. The thesis also describes the used modelling processes
and the trade-offs between model complexity and data quality.
The tool developed in this thesis is based on well established relationships between
energy consumption and traffic flow, route and vehicle operating characteristics for road freight movement. The rail freight component was developed from equations of motion together with parameters obtained from past studies. The relationships have been enhanced to fit the purpose of corridor level comparative analysis. The comparison tool has been implemented using a spreadsheet based approach developed specifically to calculate the total door to door energy consumption for given task options. A series of linked sheets enable the user to: specify all necessary inputs; estimate road and rail energy by trip segment. The outputs consist of trip segment energy demand and total energy efficiency of each option.
A case study approach, for aiding in model development and testing, is presented.
Toowoomba second range crossing in Southern Queensland, Australia (section between
below Postman's Ridge and Gowrie Junction) was selected. Four options considered
include existing and proposed road and rail corridors. The existing rail and road
corridors could be taken as a typical poor case, with very high grades and sharp
curvatures. The proposed new road section has a relaxed curvature and gradient. The
section of proposed rail corridor, under consideration here, still contains a high grade section. However, the proposed track length is considerably shorter than the base-case.
The new proposed train alignment was found as the most efficient mode and the existing
trains as the least efficient mode when measured based on absolute expected fuel gain (litres/tonnage of freight moved). This could be attributed to the improvement in
curvature and load carrying capacity. However, when the options are compared in terms of litres/1000 NTK, the new train option did not show a significant advantage.
Furthermore, the developed model was applied on some simulated cases to test the
functionality of other aspects of the model. The total door-to-door energy consumption
and the efficiency were compared for all the simulated cases. It showed that the energy
efficiency of scenarios varies exponentially with the variation in the ratio of road pickup and delivery legs to the rail line-haul length. In general, energy efficiency of the intermodal options was found to be better unless the best case of the road and the worst case of intermodal option was compared.
The modelling approaches presented in the thesis and the comparison model developed
in this study could be used for several purposes namely: to assess the energy (and hence greenhouse gas) implications of specific modal freight movements; to aid in the economic and environmental evaluation of transport options; and to assess the potential for energy efficiency gains from vehicle and infrastructure improvements. A number of suggested improvements to the model are also discussed
Examining lateral positions of cars and heavy vehicles on a two lane, two way motorway
No full textWhile most motorways in Queensland are divided with at least two lanes in each direction, a few motorways have been constructed as two lane, two way roads. These "half motorways" have been designed and constructed with the intent of eventual duplication to divided carriageways. This type of roadway is similar to a two lane, two way highway constructed to a high standard. Motorways are critical elements of urban freight networks. There is a growing need from the freight industry to allow multi-combination vehicles to use a larger network of urban roads. This raises concerns regarding the psychological impacts on drivers of surrounding vehicles, and their behaviour around the MCVs. \ud
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Lennie and Bunker (2004) studied some behavioural characteristics of passenger car drivers surrounding MCVs on a four lane, divided motorway. However, drivers are expected to behave differently while opposing each other on an undivided two lane, two way motorway or highway. That study was extended here to examine driver behaviour on the Port of Brisbane Motorway, which is a "half motorway". Specifically, the following were examined: Lateral position distribution for passenger cars, semi-trailers and B-doubles (23m or longer); and lateral separation distribution of passenger cars from heavy vehicles and other passenger cars. \ud
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The study showed that a maximum 7s time gap between opposing vehicles influenced drivers’ positioning of their vehicles. It was shown that the lateral positions of cars, utility vehicles, and semi-trailers are statistically different when opposed than when unopposed; whereas, the lateral positions of B-doubles were not. This indicates that B-double drivers did not tend to move laterally when opposed by oncoming traffic.\ud
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On average, passenger car drivers did not position their vehicles appreciably differently when opposed by semi-trailers and B-doubles than other passenger cars, and there was no appreciable difference in passenger car drivers’ positions when faced by oncoming semi-trailers than B-doubles.\ud
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Average and 95th percentile envelopes were provided to indicate position in the lane of unopposed and opposed vehicles on this type of roadway section. The off-side edge of the 95th percentile passenger car straddled the edge line, while both the 95th percentile semi-trailer and B-double occupied part of the wide, sealed shoulder. The semi-trailer wandered further onto the shoulder. The vehicle envelopes are useful to understand the impacts of heavy vehicles on driver behaviour, and can also inform road design and pavement asset management
Freight modal energy efficiency: A comparison model
No full textThis paper describes the findings of a state-of-the-art literature review on the energy consumption of land based freight transport modes and outlines the development of a model to compare corridor energy consumption of road and rail options. The key parameters influencing the energy estimation and comparison procedure are identified and a methodology to compare door to door freight movement is provided
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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