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346 results on '"Karlaftis, Matthew G."'

132. An improved harmony search algorithm for emergency inspection scheduling.

Author

Kallioras, Nikos A., Lagaros, Nikos D., and Karlaftis, Matthew G.

Subjects
SEARCH algorithms, COMPUTER scheduling, PROBLEM solving, ROUTING (Computer network management), PARAMETER estimation
Abstract

The ability of nature-inspired search algorithms to efficiently handle combinatorial problems, and their successful implementation in many fields of engineering and applied sciences, have led to the development of new, improved algorithms. In this work, an improved harmony search (IHS) algorithm is presented, while a holistic approach for solving the problem of post-disaster infrastructure management is also proposed. The efficiency of IHS is compared with that of the algorithms of particle swarm optimization, differential evolution, basic harmony search and the pure random search procedure, when solving the districting problem that is the first part of post-disaster infrastructure management. The ant colony optimization algorithm is employed for solving the associated routing problem that constitutes the second part. The comparison is based on the quality of the results obtained, the computational demands and the sensitivity on the algorithmic parameters. [ABSTRACT FROM AUTHOR]

Published
2014
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149. An analysis of air traffic controller-pilot miscommunication in the NextGen environment.

Author

Skaltsas, Gerasimos, Rakas, Jasenka, and Karlaftis, Matthew G.

Subjects
AIR traffic controllers, AIR pilots, MISCOMMUNICATION, STATISTICAL models, RADIO frequency, COMMUNICATIONS industries
Abstract

Abstract: This paper extends research on miscommunication between air traffic controllers and pilots by developing statistical models that predict the outcome of communications within the scope of controller-pilot data communications in the Next Generation Air Transportation environment. A database of controller-pilot voice messages from high and super-high altitude en-route sectors of US airspace is investigated. Emphasis is given to parameters that can be utilized in the voice-only communication, as well as in the mixed media, environment. This allows formulation of reasonable assumptions about the impact of data communications on controller and pilot behavior. The models indicate that the most important factors affecting communications are length and context of the message, entering of an aircraft into a sector, transfer of communication, and radio frequency congestion. The results also suggest that the transmission of non-time critical routine messages via data communications could reduce the number of communication errors and alleviate radio frequency congestion. [Copyright &y& Elsevier]

Published
2013
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150. Efficiency measurement in public transport: Are findings specification sensitive?

Author

Karlaftis, Matthew G. and Tsamboulas, Dimitrios

Subjects
*TRANSPORTATION, *METHODOLOGY, *POLITICAL planning, *CIVIL engineering, *TRANSPORTATION engineering, *TIME management
Abstract

Abstract: The need to measure transit system performance along with its various dimensions such as efficiency and effectiveness has led to the development of a wide array of approaches and vast literature. However, depending upon the specific approach used to examine performance, different conclusions are oftentimes reached. Using data from 15 European transit systems for a ten year time period (1990–2000), this paper discusses three important transit performance questions; (i) Do different efficiency assessment methodologies produce similar results? (ii) How are the two basic dimensions of transit performance, namely efficiency and effectiveness, related? and (iii) Are findings regarding organizational regimes (public operations, contracting and so on) sensitive to the methodological specifications employed? Results clearly indicate that efficiency scores and associated recommendations are sensitive to the models used, while efficiency and effectiveness are – albeit weakly – negatively related; these two findings can have far reaching policy implications. [Copyright &y& Elsevier]

Published
2012
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