A Concurrent Fuzzy-Neural Network Approach for Decision Support Systems

Decision-making is a process of choosing among alternative courses of action for solving complicated problems where multi-criteria objectives are involved. The past few years have witnessed a growing recognition of Soft Computing technologies that underlie the conception, design and utilization of intelligent systems. Several works have been done where engineers and scientists have applied intelligent techniques and heuristics to obtain optimal decisions from imprecise information. In this paper, we present a concurrent fuzzy-neural network approach combining unsupervised and supervised learning techniques to develop the Tactical Air Combat Decision Support System (TACDSS). Experiment results clearly demonstrate the efficiency of the proposed technique

A web spatial decision support system for vehicle routing using Google Maps

This article presents a user-friendly web-based Spatial Decision Support System (wSDSS) aimed at generating optimized vehicle routes for multiple vehicle routing problems that involve serving the demand located along arcs of a transportation network. The wSDSS incorporates Google Maps™ (cartography and network data), a database, a heuristic and an ant-colony meta-heuristic developed by the authors to generate routes and detailed individual vehicle route maps. It accommodates realistic system specifics, such as vehicle capacity and shift time constraints, as well as network constraints such as one-way streets and prohibited turns. The wSDSS can be used for “what-if” analysis related to possible changes to input parameters such as vehicle capacity, maximum driving shift time, seasonal variations of demand, network modifications, imposed arc orientations, etc. Since just a web browser is needed, it can be easily adapted to be widely used in many real-world situations. The system was tested for urban trash collection in Coimbra, Portugal

Air traffic flow management slot allocation to minimize propagated delay and improve airport slot adherence

In Europe, one of the instruments at the Network Manager’s (NM) disposal to tackle demand-capacity imbalance is to impose ground, i.e. Air Traffic Flow Management (ATFM), delays to flights. To compensate for anticipated delays and improve on-time performance, Aircraft Operators usually embed a buffer time in their schedules. The current practice for allocating ATFM delays does not take into account if flights have any remaining schedule buffer to absorb ATFM delay and reduce delay propagation to subsequent flights. Furthermore, the policy presently employed is to minimize ATFM delays, an order of magnitude of half a minute per flight, while propagated delays are approximately ten times higher. In this paper, we explore the possibility to control ATFM delay distribution in a way so as to minimize delay propagated to subsequent flights, but also to increase flights’ adherence to airport slots at coordinated airports. To this aim, we propose a two-level mixed-integer optimization model to solve en-route demand-capacity imbalance problem and further improve airport slot adherence. The rationales behind the research are drawn from practical experience, while the model proposed is compatible with the one currently being used by the NM, making it easy to implement. We test the model on two real-world case studies and conduct ex post analysis to test the effects of violation of model assumptions on results. The results show that it is possible to use the proposed methodology to lower delay propagated to subsequent flights and at the same time to improve airport slot adherence. In addition, they suggest that the current regulatory settings aiming to minimize ATFM delay minutes, as well as operational implementation thereof, are neither necessarily fully aligned with the desires and operating goals of Aircraft Operators, nor they improve the predictability of operations in the network

A multi-scale risk assessment for tephra fallout and airborne concentration from multiple Icelandic volcanoes – Part 2: Vulnerability and impact

This is the final version of the article. Available from EGU via the DOI in this record.We perform a multi-scale impact assessment of tephra fallout and dispersal from explosive volcanic activity in Iceland. A companion paper (Biass et al., 2014; "A multi-scale risk assessment of tephra fallout and airborne concentration from multiple Icelandic volcanoes – Part I: hazard assessment") introduces a multi-scale probabilistic assessment of tephra hazard based on selected eruptive scenarios at four Icelandic volcanoes (Hekla, Askja, Eyjafjallajökull and Katla) and presents probabilistic hazard maps for tephra accumulation in Iceland and tephra dispersal across Europe. Here, we present the associated vulnerability and impact assessment that describes the importance of single features at national and European levels and considers several vulnerability indicators for tephra dispersal and deposition. At the national scale, we focus on physical, systemic and economic vulnerability of Iceland to tephra fallout, whereas at the European scale we focus on the systemic vulnerability of the air traffic system to tephra dispersal. This is the first vulnerability and impact assessment analysis of this type and, although it does not include all the aspects of physical and systemic vulnerability, it allows for identifying areas on which further specific analysis should be performed. Results include vulnerability maps for Iceland and European airspace and allow for the qualitative identification of the impacts at both scales in the case of an eruption occurring. Maps produced at the national scale show that tephra accumulation associated with all eruptive scenarios considered can disrupt the main electricity network, in particular in relation to an eruption of Askja. Results also show that several power plants would be affected if an eruption occurred at Hekla, Askja or Katla, causing a substantial systemic impact due to their importance for the Icelandic economy. Moreover, the Askja and Katla eruptive scenarios considered could have substantial impacts on agricultural activities (crops and pastures). At the European scale, eruptive scenarios at Askja and Katla are likely to affect European airspace, having substantial impacts, in particular, in the Keflavík and London flight information regions (FIRs), but also at FIRs above France, Germany and Scandinavia. Impacts would be particularly intense in the case of long-lasting activity at Katla. The occurrence of eruptive scenarios at Hekla is likely to produce high impacts at Keflavík FIR and London FIRs, and, in the case of higher magnitude, can also impact France's FIRs. Results could support land use and emergency planning at the national level and risk management strategies of the European air traffic system. Although we focus on Iceland, the proposed methodology could be applied to other active volcanic areas, enhancing the long-term tephra risk management. Moreover, the outcomes of this work pose the basis for quantitative analyses of expected impacts and their integration in a multi-risk framework.This work has been funded by the Spanish research project “Atmospheric transport models and massive parallelism: applications to volcanic ash clouds and dispersion of pollutants at an urban micro-scale” (ATMOST, CGL2009-10244) and the Fonds National Suisse project “Volcanic-Ash Dispersal from Selected Icelandic Volcanoes: Risk Assessment for the European Region” (IZK0Z2_142343). S. Biass is supported by SNF (#200021-129997) and ESF/MemoVolc (#5193) subsidies

Mixed-Integer Programming Solution to Zone-Based Air Traffic Management Problem

The study presented in this research discusses the Air Traffic Flow Management Problem by introducing alternative routing options for aircrafts in a constrained 3-dimensional capacitated airspace. The airspace is divided into a set of capacitated 3-dimensional sectors in order to depict the concept of a free flight situation in which the pilots have more autonomy. This study aims to minimize the total arrival time of all aircrafts to their final destinations while upholding timing and routing constraints and most importantly regarding the capacity constraints through which mid-air collision is avoided and safety is ensured. In order to achieve such a goal, a non-time indexed mixed integer programming model has been developed. Solving the model provides us with a comprehensive flight schedule consisting of the sequence of sectors each flight has to take and the exact departure and arrival times from/to each sector while the capacity constraints defined for all sectors ensure flight safety and collision avoidance at all times. This model takes multiple airports into consideration and despite the complexity of the problem and its NP-hard nature, is able to be solved for a number of flights on a personal computer using CPLEX. Furthermore, three different solution strategies are introduced in this research in order to tackle real-life size instances. First, we investigated the computational complexity of the problem by considering all flights in the system. Next, a sequential solution methodology is proposed. In the sequential solution method, first the problem is solved for a subset of flights. Next, new set of flights from remaining flight list according to their departure time are added to the airspace by considering the en-route flight plans of previously solved flight sets. The addition of new flights continued until an en-route flight plan for all flights is determined. Obviously the sequential solution method cannot guarantee optimality, yet the problem for large instance can be solved. Finally, an iterative conflict resolution methodology is proposed. In this method, first we relax some of the constraints so large instances can be solved. Next, flights that conflict with the actual constraint are identified and problem is solved to satisfy only these flights. The iteration is continued until no unresolved conflict is left. Performance of each solution methodology is demonstrated through various case studies

Modeling strategies for volcanic ash dispersal and management of impacts on civil aviation

During April-May 2010, the eruption of Eyjafjallajokull volcano in Iceland caused the larger breakdown of civil aviation after World War II. Although the eruption was weak in intensity, the dispersal of volcanic ash clouds over northern and central Europe resulted in more than 100.000 flights canceled and caused over USD 1.7 billion economical losses. This event and its unexpected effects raised many questions amongst the affected communities and stakeholders. How could volcanic eruptions cause severe disruptions at continental scales? Were these impacts totally unexpected? What could have been done to improve preparedness of aviation sector and reduce societal impacts of disruptions? The harmful effects of volcanic ash on aircraft's components have long been recognized, and volcanic ash dispersal patterns can be forecasted thanks to sophisticated numerical models. However, the procedures to be implemented in case of ash-contaminated airspace where applied only in few occasions, due to the relatively low frequency of explosive eruptions events. The 2010 Eyjafjallajokull crisis revealed a low preparedness of society to direct and indirect impacts of volcanic eruptions, and pointed out some flaws to be improved for mitigating impacts of explosive eruptions on aviation operations. The issues pointed out by the 2010 crisis are the starting point of this PhD research, which aims at offering new methods for improving aviation management during explosive volcanic eruptions. This manuscript describes the novel contributions developed during a 4-year period of research. The adoption of new techniques is proposed in order to improve current tephra dispersal modeling strategies and produce results focused on aviation needs. This research develops the first methodology to assess vulnerability of air traffic system and its elements to volcanic tephra dispersal. In addition, an impact assessment methodology has been designed to estimate expected impacts of explosive volcanic eruptions on the air traffic network and its elements. The impact assessment methodology has been implemented into a map-based tool to automatically assess expected impacts of volcanic eruptions based on real ash dispersal and air traffic data. Results of the vulnerability and impact assessment can support the stakeholders involved in the definition of risk-management strategies. Contributions of this research have been applied to case-studies and specific results have been published in a collection of journal papers. Main outcomes of the research are discussed identifying further work to be done in this rapidly evolving field. This research provides useful insights to reduce impacts of volcanic eruptions on civil aviation and, eventually, on the whole society.En Abril 2010, la erupción del volcán Islandés Eyjafjallajokull causó la interrupción mas grande del tráfico aéreo en Europa desde la segunda guerra mundial. A pesar de su baja intensidad, esta erupción produjo una nube de ceniza que cubrió Europa central causando la cancelación de mas de 100.000 vuelos y perdidas económicas de más de 1.700 millones de USD. Este evento generó muchas preguntas en la opinión publica y las comunidades impactadas. ¿Pero cómo pudo una erupción volcánica provocar impactos tan fuertes a escala continental? ¿Fueron estos impactos realmente inesperados? ¿Qué se habría podido hacer para mejorar la preparación de la aviación civil? Los daños que la ceniza volcánica puede provocar en los componentes de los aviones se han documentado desde los años ochenta. También, gracias a sofisticados modelos numéricos desarrollados en las ultimas décadas, los patrones de dispersión de ceniza volcánica se pueden pronosticar. Aun así, la erupción de Eyjafjallajokull en 2010 evidenció que la sociedad no estaba preparad a lidiar con este tipo de eventos y sus impactos directos e indirectos. En Europa los procedimientos a seguir en caso de ceniza volcánica en el espacio aéreo se habían aplicado en pocas ocasiones, debido a la frecuencia relativamente baja de erupciones volcánicas explosivas. Las dificultades sufridas por los gestores del trafico aéreo en 2010 subrayan algunos aspectos a mejorar para mitigar impactos similares en el futuro. Estos aspectos son el punto de partida de esta investigación, que tiene como objetivo ofrecer nuevos métodos para mejorar la gestión del tráfico aéreo durante erupciones volcánicas explosivas. Este documento describe las contribuciones desarrolladas durante los 4 años de investigación pre-doctoral. Esta investigación propone algunas mejoras en las estrategias de modelado utilizadas actualmente para dispersión de ceniza en la atmósfera, y generar resultados que satisfagan las necesidades de la aviación civil. Se presenta la primera metodología que permite estimar la vulnerabilidad del trafico aéreo en caso de erupciones volcánicas y los impactos de la ceniza volcánica sobre sus elementos. También se ha creado una herramienta informática que permite automatizar el análisis de impactos y producir resultados utilizando datos reales de dispersión de ceniza y de trafico aéreo. Este documento discute los resultados principales de la investigación y propone directrices para su desarrollo futuro. Las contribuciones de esta investigación se han aplicado a varios casos de estudio para producir resultados específicos, y se pueden potencialmente aplicar a otras zonas. Los resultados se han presentado y discutido en un compendio de artículos científicos, publicados en revistas internacionales. Los análisis de vulnerabilidad e impacto pueden dar soporte a los actores involucrados en la gestión de trafico aéreo y la definición de estrategias para la gestión de riesgo. Sus resultados son significativos para dar soporte y definir estrategias para la gestión de riesgo. Los desarrollos futuros de esta investigación podrían utilizarse para reducir el impacto de erupciones volcánicas sobre la aviación civil, que afectan indirectamente a toda la socieda