5 research outputs found
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Shortest path algorithms for dynamic transportation networks
Over the last decade, many interesting route planning problems can be solved by finding the shortest path in a weighted graph that represents a transportation network. Such networks are private transport networks or timetabled public transportation networks. In the shortest path problem, every network type requires different algorithms to compute one or more than one shortest path. However, routing in a public transportation network is completely different and is much more complex than routing in a private transport network, and therefore different algorithms are required.
For large networks, the standard shortest path algorithms - Dijkstra's algorithm (1959) and Bellman's algorithm (1958)- are too slow. Consequently, faster algorithms have been designed to speed up the search. However, these algorithms often consider only the simplest scenario of finding an optimal route on a graph with static real edge costs. But real map routing problems are often not that simple – it is often necessary to consider time-dependent edge costs. For example, in public transportation routing, consideration of the time-dependent model of these networks is mandatory.
However, there are a number of transportation applications that use informed search algorithms (where the algorithm uses heuristics that guide the search toward the destination), rather than one of the standard static shortest path algorithms. This is primarily due to shortest paths needing to be rapidly identified either because an immediate response is required. For example, the A* algorithm (Nilsson, 1971) is widely used in artificial intelligence. Heuristic information (in the form of estimated distance to the destination) is used to focus the search towards the destination node. This results in finding the shortest path faster than the standard static search algorithms.
Road traffic congestion has become an increasingly significant problem in a modern society. In a dynamic traffic environment, traffic conditions are time-dependent. For instance, when travelling from home to the work, although an optimal route can be planned prior to departure based on the traffic conditions at that time, it may be necessary to adjust the route while en route because traffic conditions change all the time. In some cases, it is necessary to modify the travelling route from time to time and re-plan a new route from the current location to the destination, based on the real-time traffic information. The challenge lies in the fact that any modification to the optimal route to adapt to the dynamic environment necessitates speeding up of the search efforts. Among the algorithms suggested for the dynamic shortest path problem is the algorithm of Lifelong Planning A* algorithm (LPA*) (Koenig, Likhachev and Furcy, 2004). This algorithm has been given this name because of its ability to reuse information from previous searches. It is used to adjust a shortest path to adapt to the dynamic transportation network.
Search space and fast shortest path queries can be used for finding fastest updated route on road and bus networks. Consequently, the efficient processing of both types of queries is of first-rate significance. However, most search methods focus only on one type of query and do not efficiently support the other. To address this challenge, this research presents the first novel approach; an Optimised Lifelong Planning A* (OLPA*) algorithm. The OLPA* used an appropriate data structure to improve the efficiency of the dynamic algorithms implementation making it capable of improving the search performance of the algorithm to solve the dynamic shortest path problem, which is where the traveller may have to re-compute the shortest path while travelling in a dynamic transportation environment.
This research has also proposed bi-directional LPA* (BLPA*) algorithm. The proposed algorithm BLPA* used bi-directional search strategy and the main idea in this strategy is to divide the search problem into two separate problems. One search proceeds forwards from the start node, while the other search proceeds backwards from the end node. The solution requires the two search problems to meet at one middle node. The BLPA* algorithm has the same overall structure as the LPA* algorithm search, with some differences that the BLPA* contains a priority queue for each direction.
This research presented another algorithm that designed to adaptively derive the shortest path to the desired destination by making use of previous search results and reducing the total execution time by using the benefits of a bi-directional search strategy . This novel algorithm has been called the bi-directional optimised Lifelong A* algorithm (BiOLPA*). It was originally proposed for road transport networks and later also applied to public transportation networks. For the road transport network, the experimental results demonstrate that the proposed incremental search approach considerably outperforms the original approach method, which recomputed the shortest path from scratch each time without utilization of the previous search results. However, for public transportation, the significant problem is that it is not possible to apply a bi-directional search backwards using estimated arrival time. This has been further investigated and a better understanding of why this technique fails has been documented. While the OLPA* algorithms give an impressive result when applied on bus network compared with original A* algorithms, and our experimental results demonstrate that the BiOLPA* algorithm on road network is significantly faster than the LPA*, OLPA* and the A* algorithms, not only in terms of number of expansion nodes but also in terms of computation time
Proceedings of the International Congress on Interdisciplinarity in Social and Human Sciences
Interdisciplinarity is the main topic and the main goal of this conference.
Since the sixteen century with the creation of the first Academy of Sciences, in Napoles (Italy) (1568), and before
that with the creation of the Fine Arts Academies, the world of science and arts began to work independently, on
the contrary of the Academy of Plato, in Classical Antiquity, where science, art and sport went interconnected. Over
time, specific sciences began to be independent, and the specificity of sciences caused an increased difficulty in mutual
understanding.
The same trend has affected the Human and Social Sciences. Each of the specific sciences gave rise to a wide
range of particular fields. This has the advantage of allowing the deepening of specialised knowledge, but it means
that there is often only a piecemeal approach of the research object, not taking into account the its overall complexity.
So, it is important to work for a better understanding of the scientific phenomena with the complementarity of the different sciences, in an interdisciplinary perspective.
With this growing specialisation of sciences, Interdisciplinarity acquired more relevance for scientists to find moreencompassing and useful answers for their research questions.info:eu-repo/semantics/publishedVersio
Formaciones imaginarias del diseñador gráfico en el discurso del campo académico.
En este trabajo se describe un proyecto de tesis doctoral en el que se analiza el discurso sobre el diseñador gráfico. Se parte del supuesto de que existe una tricotomÃa de su perfil: 1) el campo profesional, 2) el campo educativo y, 3) el campo académico. Proponemos que dicha tricotomÃa permite la identificación de imaginarios sobre el tema, y no solo eso, sino que también aporta elementos que conforman la identidad (Bauman, 2002) de un diseñador gráfico. La pregunta de investigación es ¿Cuál
es la identidad discursiva del diseñador gráfico en el campo académico? La investigación descrita es de tipo cualitativo y deductivo; para la construcción la identidad discursiva (Van Dijk, T; 2008) del diseñador gráfico, se toman en cuenta diversas publicaciones: principalmente investigaciones y breves artÃculos difundidos en comunidades/foros de reflexión y debate en torno a la temática, además de memorias de congresos y libros. En apoyo al desarrollo del proyecto se ha diseñado un Laboratorio de Intervención en el Diseño, cuyos objetivos son impulsar el desarrollo social y cultural de los diseñadores gráficos por medio de la investigación, educación continua, producción y vinculación. En un primer acercamiento a las formaciones imaginarias (Pêcheux, 1978) sobre la identidad del diseñador gráfico se centran en el grado de erudición para la ejecución de su trabajo, en la cultura que demuestran y en la autonomÃa con la que producen
Proceedings of the International Congress on Interdisciplinarity in Social and Human Sciences
Interdisciplinarity is the main topic and the main goal of this conference.
Since the sixteen century with the creation of the first Academy of Sciences, in Napoles (Italy) (1568), and before
that with the creation of the Fine Arts Academies, the world of science and arts began to work independently, on
the contrary of the Academy of Plato, in Classical Antiquity, where science, art and sport went interconnected. Over
time, specific sciences began to be independent, and the specificity of sciences caused an increased difficulty in mutual
understanding.
The same trend has affected the Human and Social Sciences. Each of the specific sciences gave rise to a wide
range of particular fields. This has the advantage of allowing the deepening of specialised knowledge, but it means
that there is often only a piecemeal approach of the research object, not taking into account the its overall complexity.
So, it is important to work for a better understanding of the scientific phenomena with the complementarity of the different sciences, in an interdisciplinary perspective.
With this growing specialisation of sciences, Interdisciplinarity acquired more relevance for scientists to find moreencompassing and useful answers for their research questions.info:eu-repo/semantics/publishedVersio
UML consistency rules: a systematic mapping study
Context: The Unified Modeling Language (UML), with its 14
different diagram types, is the de-facto standard tool for objectoriented
modeling and documentation. Since the various UML
diagrams describe different aspects of one, and only one, software
under development, they are not independent but strongly depend
on each other in many ways. In other words, the UML diagrams
describing a software must be consistent. Inconsistencies between
these diagrams may be a source of the considerable increase of
faults in software systems. It is therefore paramount that these
inconsistencies be detected, ana