1,720,958 research outputs found
General methods for synchromodal planning of freight containers and transports
No full textSynchromodal freight transport is introduced as intermodal transport, so container transport that uses several transportation vehicles, with an increased focus on a-modal booking, cooperation and real-time flexibility.It is confirmed that general synchromodal network planning methods are rare or non-existent at the operational level. An extensive framework is developed that describes characteristics of different mathematical synchromodal optimisation problems on the tactical-operational levels.Three different problems are defined using this framework. Solution methods for these three problems are developed in this thesis, with a focus on low computation times so as to facilitate decision-support and real-time flexibility, and a focus on generality so as to make the methods applicable throughout different organisation structures.In the first problem, it is assumed that the transportation vehicles have fixed time tables and one only has to decide on a container-to-mode assignment, so by what modality-paths all containers reach their destination against minimal total cost. The containers have release times and deadlines. A model that also allows soft due dates is developed. Moreover, the option of using trucks or other ‘infinite resources’ to help fulfil requests is added. With appropriate graph reductions, this problem can be solved to optimality in little time by solvingthe minimum cost multi-commodity flow problem on an appropriate space-time network.In the second problem, the goal is the same but almost any element can be stochastic: for instance, travel times and container release times could be given a discrete probability distribution rather than a fixed value. Rigorous definitions are formulated to capture the generalities in this stochasticity. Multistage stochastic optimisation and Markov Decision Processes are illustrated, but advised against for their computing time: instead, Expected Future Iterationand 70%-Pessimistic Future Iteration are developed and shown to yield near-optimal results in a small amount of time in the simulated environment.In the final problem, there are no stochastic elements, but the decision-maker is given control over the vehicle time tables in addition to the control over container-to-mode assignments. This problem is argued to be a departure from classical optimisation problems, but shown to still be strongly NP-hard. An integer linear program is developed to solve the problem, butthe results show that it scales too poorly to solve problems of ‘real life size’ in an appropriate amount of time for decision support. The Greedy Gain heuristic and Compatibility Clustering heuristic are developed: they solve much more limited sub-problems with the ILP, but unfortunately, even these sub-problems require too much computational effort at the wished instance size.A number of topics for future research are formulated, giving concrete advice on how to solve the second problem more robustly and how to solve the third problem more quickly.Applied Mathematic
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Median Routing Problems:Integrated optimisation of network maintenance and emergency response
Get PDFThis thesis studies the shift planning of emergency response organisations and how to include plannable, preventive tasks into the schedules of the responders, such that they remain well spread in case of emergencies. Both halves of this planning have individually received significant attention throughout the past decades: that is, much is known about either positioning responders to minimise emergency response times (e.g. the k-Median Problem) or about efficiently visiting plannable jobs with a fleet of agents (e.g. the Vehicle Routing Problem). However, when trying to do both simultaneously, the literature appears to still be in its infancy. Such a simultaneous planning seems promising: more preventive work can get done, and if tasks are chosen that are spread well, then the spread of agents can be better than if they are bunched together at the same response station. In Chapter 2, the Median Routing Problem is introduced as a model to compute how to visit plannable jobs in a graph in a fixed-length time horizon using a fleet of emergency response agents, while minimising the expected response time to the next emergency in the graph. Aside from an exponential-time algorithm that can compute the optimal solution, heuristics are developed that can be used in practice. Most notably, the MDSA-algorithm is found to be an effective heuristic: on benchmark instances, including case study data, it finds a solution in 2.4 seconds on average, which is on average only 3.2% away from optimal. Because it is NP-complete to decide for the Median Routing Problem whether a feasible solution exists, it makes no sense to develop a polynomial-time approximation algorithm for the general problem. Instead, in Chapter 3, a special version is studied in the form of the (Uniform) Travelling k-Median Problem. A constant-factor approximation is given for specific graph metrics: namely, those graphs on which we can solve the problem in polynomial time if the agents are allowed to move ‘continuously’ over the graph instead of ‘discretely’. Using a rounding theorem, it is shown that these ‘continuous solutions’ can be rounded back with bounded loss. For all other metrics, we provide a polynomial-time algorithm with an approximation factor that depends linearly on the graph diameter and sublinearly on the length of the time horizon. In Chapter 5, the Enriched Median Routing Problem is posed as an extension of the Median Routing Problem with fifteen additional features. In the same spirit of MDSA, a more flexible algorithm is developed that still decomposes some of the decisions into smaller problems. In order to have this simpler problem again act on a small decision space, a subroutine is developed in Chapter 4 that can take an input graph and ‘sparsify’ it into a graph with much fewer nodes and edges that can still reasonably ‘represent’ the original graph. In Chapter 4, not only is it demonstrated that this sparsification works well in a sample of practical Median Routing Problem use cases, but a proven upper bound is also given on how much quality loss can occur through sparsification, by introducing and using the Mixed Integer Jester Game framework for explicit worst-case computation. Finally, in the second half of Chapter 5, the Enriched Median Routing Problem and its MDSA-inspired heuristic are compared to the current practice of a case study organisation. It is concluded that, indeed, the results of this thesis can help the case study organisation to simultaneously perform 31.0% more plannable work and decrease emergency response times by 14.2%. A solver based on this heuristic has been taken into use, and the further implementation of this solver and other outlooks are discussed in Chapter 6
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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