Investigation of the Potential Impacts of the Entry of Very Light Jets in the National Airspace System

Very Light Jets (VLJs) constitute a class of three to eight passenger turbofan-powered aircraft that will enter service in 2006 and will need to be integrated into the National Airspace System. An aircraft performance analysis showed similarities between the predicted performance and capability of Very Light Jets and the performance of existing Light Jets. Based on this an analysis of operating patterns of existing Light Jets was used to predict how Very Light Jets will be operated. Using 396 days of traffic data from the FAA Enhanced Traffic Management System (ETMS), the operating patterns of existing Light Jets were analyzed. It was found that 64% of all the flights flown by Light Jets had their origin, destination or both within the top 23 regional airport systems in the continental United States. This concentration of LJ traffic was found in areas of the air transportation system that are currently exhibiting dense traffic and capacity constraints. The structure of the network of routes flown by existing Light Jets was also studied and a model of network growth was developed. It is anticipated that this concentration will persist with emerging Very Light Jet traffic. This concentration of traffic at key areas in the system will have implications for air traffic control management and airport activity. For regional airport systems, core airports are expected to saturate and, reliever airports will become critical for accommodating traffic demand. The entry of Very Light Jets will significantly increase the traffic load at the terminal airspace; Terminal Radar Approach Control (TRACON). These impacts need to be taken into account to allow a successful integration of these aircraft in the National Airspace System

Emergence of Secondary Airports and Dynamics of Regional Airport Systems in the United States

With the growing demand for air transportation and limited capacity at major airports, there is a need to increase the capacity of airport systems at the metropolitan area level. The increased use of secondary airports has been and is expected to be one of the key mechanisms by which future demand is met in congested metropolitan areas. This thesis provides an analysis of the factors influencing the emergence of secondary airports and the dynamics of multi-airport systems. The congestion of the core airport, the distribution of population at the regional level, the existence and the proximity of a secondary basin of population close to secondary airports were identified as major factors. Ground access and airport infrastructure, the low level of connecting passengers at the core airport were also identified as a contributing factors. The entry of an air carrier –generally a low-cost carrier- was determined to be an essential stimulus in the emergence phenomenon impacting fares and airport competition levels resulting in market stimulation. But the emergence of secondary airports imposes new constraints that need to be taken into account in the national air transportation system improvements. By providing an identification of the factors that influence the emergence of secondary airports and an understanding of the dynamics of regional airport systems this research provides useful support for the planning and the future development of multi-airport systems.NASA Langley, NAG-1-203

Emergence of secondary airports and dynamics of regional airport systems in the United States

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005.Includes bibliographical references (p. 95-100).With the growing demand for air transportation and limited capacity at major airports, there is a need to increase the capacity of airport systems at the metropolitan area level. The increased use of secondary airports has been and is expected to be one of the key mechanisms by which future demand is met in congested metropolitan areas. This thesis provides an analysis of the factors influencing the emergence of secondary airports and the dynamics of multi-airport systems. The congestion of the core airport, the distribution of population at the regional level, the existence and the proximity of a secondary basin of population close to secondary airports were identified as major factors. Ground access and airport infrastructure, the low level of connecting passengers at the core airport were also identified as a contributing factors. The entry of an air carrier -generally a low-cost carrier- was determined to be an essential stimulus in the emergence phenomenon impacting fares and airport competition levels resulting in market stimulation. But the emergence of secondary airports imposes new constraints that need to be taken into account in the national air transportation system improvements. By providing an identification of the factors that influence the emergence of secondary airports and an understanding of the dynamics of regional airport systems this research provides useful support for the planning and the future development of multi-airport systems.by Philippe A. Bonnefoy.S.M

Application d'un modèle de viscosité à la coulée d'explosifs : Modélisation du temps de coulée.

14 pagesLa rhéologie des coulées d'explosifs est décrite par la dynamique des écoulements diphasiques de suspensions concentrées. Afin d'améliorer la manipulation de produits présentant par nature un risque vis-à-vis des agressions mécaniques et thermiques, des avancées issues des travaux de recherche menés depuis de nombreuses années dans le secteur du génie civil permettent de développer de nouveaux procédés pyrotechniques. L'objectif de ces travaux est de proposer un modèle prédictif des temps d'écoulement des suspensions concentrées en matériaux énergétiques dans une configuration similaire au procédé de mise en oeuvre développé en production. Les résultats expérimentaux sont comparés à trois modèles (Quémada, Krieger-Dougherty, Mooney) représentant la viscosité dynamique comme étant fonction de la fraction volumique solide , de l'empilement compact maximal et de la viscosité du fluide interstitiel . Le modèle de De Larrard est utilisé pour le calcul de . Les hypothèses d'un fluide parfait et incompressible, pour le calcul du temps de coulée du fluide interstitiel , aboutissent à la relation de Bernoulli et satisfont à l'expérience. Nous montrons que le modèle de Quémada conduit à des valeurs théoriques du temps de coulée de la suspension en bon accord avec les valeurs expérimentales

Incorporation of a Horizontally Transferred Gene into an Operon during Cnidarian Evolution

Genome sequencing has revealed examples of horizontally transferred genes, but we still know little about how such genes are incorporated into their host genomes. We have previously reported the identification of a gene (flp) that appears to have entered the Hydra genome through horizontal transfer. Here we provide additional evidence in support of our original hypothesis that the transfer was from a unicellular organism, and we show that the transfer occurred in an ancestor of two medusozoan cnidarian species. In addition we show that the gene is part of a bicistronic operon in the Hydra genome. These findings identify a new animal phylum in which trans-spliced leader addition has led to the formation of operons, and define the requirements for evolution of an operon in Hydra. The identification of operons in Hydra also provides a tool that can be exploited in the construction of transgenic Hydra strains

Structure, Function, and Evolution of the Thiomonas spp. Genome

Bacteria of the Thiomonas genus are ubiquitous in extreme environments, such as arsenic-rich acid mine drainage (AMD). The genome of one of these strains, Thiomonas sp. 3As, was sequenced, annotated, and examined, revealing specific adaptations allowing this bacterium to survive and grow in its highly toxic environment. In order to explore genomic diversity as well as genetic evolution in Thiomonas spp., a comparative genomic hybridization (CGH) approach was used on eight different strains of the Thiomonas genus, including five strains of the same species. Our results suggest that the Thiomonas genome has evolved through the gain or loss of genomic islands and that this evolution is influenced by the specific environmental conditions in which the strains live

Scalability of the air transportation system and development of multi-airport systems : a worldwide perspective

Thesis (Ph. D.)--Massachusetts Institute of Technology, Engineering Systems Division, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 227-235).With the growing demand for air transportation and the limited ability to increase capacity at some key points in the air transportation system, there are concerns that in the future the system will not scale to meet demand. This situation will result in the generation and the propagation of delays throughout the system, impacting passengers' quality of travel and more broadly the economy. This thesis proposes the investigation of the mechanisms by which the air transportation system has scaled to meet demand in the past and is expected to do so in the future using a multi-level engineering systems approach.The air transportation system was first analyzed at the U.S. national level using network abstractions. In order to investigate limits in scaling of the U.S. air transportation network, theories of scale-free and scalable networks were used. It was found that the U.S. air transportation network was not scale-free due to capacity constraints at major airports, also preventing it from being scalable. However, the construction and analysis of a new network for which sets of two or more significant airports that serve passenger traffic in a metropolitan region (i.e. multi-airport systems) were aggregated into single nodes showed that it was scale-free and scalable. These results were also supported by a time series analysis of airport and multi-airport system growth. These analyses demonstrated the importance of regional level scaling mechanisms (i.e. development of multi-airport systems) in the ability of the air transportation system to adapt and scale to meet demand.(cont.) Given the importance of multi-airport systems, an in-depth multiple-case study analysis of 59 multi-airport systems worldwide was performed. This analysis was used to develop a feedback model that captures the fundamental processes that govern the evolution of multi-airport systems. Multi-airport systems were found to evolve according to two fundamental mechanisms: (1) the construction of new airports and (2) the emergence of secondary airports through the use of existing non-utilized airports. Several differences and similarities in the occurrence of these dynamics were identified across world regions. It was found that in the United States and Europe, the construction of new large airports occurred prior to or during World War II and to a minor extent during the 1960s and 1970s. More recently, significant limitations to the development of new airports (e.g. opposition from local communities) and changes in the airline industry (e.g. emergence and growth of low-cost carriers) led multi-airport systems in the United States and Europe to evolve through the emergence of secondary airports. In the Asia-Pacific region, multi-airport systems have predominantly evolved through the construction of new airports, due to fewer available airports, high projections of demand and weaker opposition to the construction of airports.The analyses and insights from this thesis were also used to analyze and better understand the evolution of future multi-airport systems and provide recommendations for infrastructure management policies and multi-airport system development strategies.(cont.) In the United States and in Europe, there is the need to protect non-utilized exiting airport infrastructure (both civil and military airports) that can later be used to accommodate demand through the emergence of secondary airports. In parts of Asia where the existing under-utilized airport infrastructure is weak and where projections of high volume of demand -with high uncertainty- are high, there is the need to apply a dynamic approach to develop multi-airport systems. This approach includes actions such as reserving land area for future airport development and keeping original airports open since this option has proven to be useful and successful in the other regions of the world (i.e. United States and Europe). In some parts of Asia, such as India, where the military airport infrastructure is more developed than in other parts, there is also the need, as in the United States and Europe, to protect these airports since they may become future secondary airports following the airport status conversion dynamics that were observed in Europe.by Philippe A. Bonnefoy.Ph.D

Discovery of a low-mass companion to the F7V star HD 984

ISSN:0035-8711ISSN:1365-2966ISSN:1365-871

GEM-GEP Rapport final, Le Risque Sismique à Nice: Apports Méthodologiques, Résultats et Perspectives Opérationnelles

Rapport distribué lors de la Journée du Risque Sismique à Nice - Rendu des résultats GEM-GEP le 7 avril 2005.les bâtiments publics les plus sensibles. Ce projet a été réalisé par le CETE-Méditerranée.1. Le choix des séismes de scénarios et l’évaluation de l’aléa: Le choix des deux séismes de scénarios retenus, 1644 et 1887, se base sur la connaissance de l’aléa régional. Il est tenu compte des effets de site potentiels (topographiques et sédimentaires) sur la ville de Nice.2. La vulnérabilité: La méthode développée pour l’analyse de la vulnérabilité met en œuvre trois étapes : Une délimitation de secteurs homogènes pour le bâti (27 sur Nice) ; Puis par secteur, un échantillonnage statistique des bâtiments ; et enfin, une estimation de la vulnérabilité moyenne par quartier.3. Le risque: Les scénarios sismiques réalisés sur Nice se traduisent par des estimations statistiques de l’importance et de la distribution spatiale des dommages sur le bâti. Les résultats de GEMGEP ont permis d’approfondir et de compléter la connaissance de l’aléa et de la vulnérabilité initiée avec GEMITIS