1,720,987 research outputs found
Phenotypic comparison of C57BL/6J mice fed the chow, AHF, AHF + EPA, and AHF + DHA diet for 4 weeks.
No full textPhenotypic comparison of C57BL/6J mice fed the chow, AHF, AHF + EPA, and AHF + DHA diet for 4 weeks.</p
System optimal traffic assignment with departure time choice
No full textThis thesis investigates analytical dynamic system optimal assignment with departure time
choice in a rigorous and original way. Dynamic system optimal assignment is formulated here
as a state-dependent optimal control problem. A fixed volume of traffic is assigned to
departure times and routes such that the total system travel cost is minimized. Although the
system optimal assignment is not a realistic representation of traffic, it provides a bound on
performance and shows how the transport planner or engineer can make the best use of the
road system, and as such it is a useful benchmark for evaluating various transport policy
measures. The analysis shows that to operate the transport system optimally, each traveller in
the system should consider the dynamic externality that he or she imposes on the system from
the time of his or her entry. To capture this dynamic externality, we develop a novel
sensitivity analysis of travel cost. Solution algorithms are developed to calculate the dynamic
externality and traffic assignments based on the analyses. We also investigate alternative
solution strategies and the effect of time discretization on the quality of calculated
assignments. Numerical examples are given and the characteristics of the results are discussed.
Calculating dynamic system optimal assignment and the associated optimal toll could be too
difficult for practical implementation. We therefore consider some practical tolling strategies
for dynamic management of network traffic. The tolling strategies considered in this thesis
include both uniform and congestion-based tolling strategies, which are compared with the
dynamic system optimal toll so that their performance can be evaluated. In deriving the
tolling strategies, it is assumed that we have an exact model for the underlying traffic
behaviour. In reality, we do not have such information so that the robustness of a toll
calculation method is an important issue to be investigated in practice. It is found that the
tolls calculated by using divided linear traffic models can perform well over a wide range of
scenarios. The divided linear travel time models thus should receive more attention in the
future research on robust dynamic traffic control strategies design. In conclusion, this thesis
contributes to the literature on dynamic traffic modelling and management, and to support
further analysis and model development in this area
Cost functions for railway operations and their application to timetable optimisation
Get PDFThis thesis investigates cost functions for evaluating and optimising the performance of a timetable with mixed train services. Specifically, the performance considered herein includes crowdedness, journey time, punctuality and waiting time. To examine the implications of optimising using these cost functions, a multi-objective optimisation algorithm is developed to derive an optimised timetable for mixed train services. The optimisation algorithm consists of three stages: a Genetic Algorithm (GA) is used to determine the optimal sequence of train runs, followed by Dijkstras shortest path algorithm for determining the optimal schedule based on the sequence determined by GA, and finally an iterative Hill-Climbing procedure for determining the optimal number of train runs in the system. Experiments were carried out on the Brighton Main Line and examined the effect of different timetabling parameters. The first series of experiments showed that the cost of the timetable can be driven down simply through resequencing the trains such that trains exiting the network quickly are more evenly distributed through the time period examined. This occurs since trains exiting early create a buffer which can absorb delays, preventing their propagation. The experiments have also shown that different demand levels influence the number of trains to be scheduled. The optimal number of trains to schedule though relies on the equilibrium between the crowdedness and punctuality cost function. Scheduling additional trains leads to a non-linear reduction in the marginal gains in terms of the crowdedness function while, on the other hand, the cost of punctuality increase exponentially. Finally, we derive the Pareto Frontiers for different combinations of cost functions. This research contributes to the state-of-art of railway system analysis and optimisation
Adaptive traffic control system: a study of strategy, computation speed, and prediction errors
No full textHeterogeneous urban traffic data and their integration through kernel-based interpolation
Get PDFThis paper presents collection and analysis of heterogeneous urban traffic data, and integration of them through a kernel-based approach. The recent development in sensing and information technology opens up opportunities for researching the use of this vast amount of new urban traffic data. In this paper, the data fusion algorithm is developed by using a kernel based interpolation approach. Our objective is to reconstruct the underlying urban traffic pattern with fine spatial and temporal granularity through processing and integrating data from different sources. The fusion algorithm can work with data collected in different space time resolution, with different level of accuracy, and from different kinds of sensors. The properties and performance of the fusion algorithm is evaluated by using a virtual test-bed produced by VISSIM microscopic simulation. The methodology is demonstrated through a real-world application in Central London. This paper contributes to analysis and management of urban transport facilities
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
Effects of high-speed rail megalopolis on regional economic growth
Get PDFThis paper quantifies the multifold economic impacts of high-speed railway (HSR) in China. Firstly, the effect of introducing HSR on the prefecture-level gross regional product (GRP) is investigated using the difference-in-differences method. Results show that HSR inauguration has positive effects on economic development. Secondly, the effect of proximate HSR station density is examined. We find that when taking into account the density of HSR stations near a city, the existence of a HSR station in its own realm is insignificant; instead, the station density plays a significant role in the regional economic growth. This indicates that as long as the city is located in an area with high density of HSR stations, whether it possesses HSR is less important. Thirdly, the heterogeneity of economic impact is studied by categorizing cities by 2017 GRP, which demonstrates that HSR has larger positive impacts on the wealthier regions
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