Abstract

Aircraft hazards were evaluated to determine the total annual probability of an aircraft crash occurring at any structure located on the US Department of Energy (DOE) reservation in Oak Ridge, Tennessee. This report documents the use of an accepted methodology for calculating the probability of an aircraft crash as applied to the three Oak Ridge plant sites including the adjoining facilities. Based on the data contained herein, the evaluation concluded that the probability of an aircraft crash occurrence at a single facility is generally considered ``not credible`` as defined in DOE/OR-901. Additionally, reevaluation of probabilities would be necessary if significant changes were made to local air traffic. The probability of an aircraft crash could increase as a result of the opening of any new airport or heliport in the vicinity; a greater volume of air traffic from McGhee Tyson airport in Knoxville, should the airport status change from feeder airport to hub airport; the rerouting of commercial and/or military flights at the McGhee Tyson airport; and finally, a change in direction or the addition of a federal airway. At one time, DOE planned to establish a zone of prohibited airspace over the Y-12 plant; if the plans are enacted inmore » the future, the probability of an aircraft crash at the Y-12 plant could decrease. Pilots since have been voluntarily requested not to fly below 3000 feet over the Y-12 plant. Also, the Federal Aviation Administration plans to reroute air traffic in the spring of 1993 on federal airway V16. However, the section of V16 which traverses the three plant sites and five adjoining facilities will not be altered. If this plan is implemented, the air traffic over the Oak Ridge facilities would not be affected significantly, and the probability of an aircraft crash as determined herein would be unchanged.« le Document type: Report

Abstract

This report presents design principles and algorithms for building a fast-time scheduler of arrival aircraft based on a FCFS (first-come-first-served) scheduling protocol and non FCFS. The algorithms provide the conceptual and computational foundation for the Traffic Management Advisor (TMA) of the Centre/terminal radar approach control facilities (TRACON) automation system, that's it an arrival manager (AMAN concept). The primary objective of the scheduler is to assign arrival aircraft to a favourable landing runway and schedule then to land at times that minimize delays. In order to solve the problem a fast time simulator platform was selected by Eurocontrol (the European Organisation for the Safety of Air Navigation) named AirTOp. Many problems in that module, as for example the lack of information about the code, the fact that for changing one small parameter, the process involved takes more than 2 or 4 months or the fact that EUROCONTROL is paying a special license only to use this specific module has brought to think in a better solution. This solutions entails the creation of a separate module from zero, a plugin, due to AirTOp is providing and API (Application Programming Interface) where the user can create, retrieve or modify the data during the simulations. The creation of this module was made in Java due to AirTOp is programmed in Java and allows easily the creation of a plugin. A plugin is an external module that can use some information from the main software, and allows the user to model and create some new information, such as a new AMAN. In the creation of the AMAN plugin two solution has been tested, in order of complexity to continue programming, an FCFS time schedule algorithm (First Come First Served) and a non-FCFS time schedule algorithm. By the end of this project a full AMAN was created in Java with Eclipse, helping the Air Traffic Controllers to manage the situation with better solutions, it can reduce the average delays up to 20% (depending of the case) and it improves the time constraint feasibility in a 17%. A full deployment and distribution of this plugin has been made for the ATM/RDS/ATS unit in Eurocontrol, unit in charge of the research and development for the Air Traffic Management and Air Traffic Services improvements and innovations. In addition a user guide for the creation of a plugin has been created, explaining all required steps to develop a generic plugin.

Abstract

Today, mobility and persistence are important aspects of distributed computing- . They have many fields of use such as load balancing, fault tolerance and dynamic reconfiguration of applications. In this context, Java provides many useful mechanisms for the mobility of code via dynamic class loading, and the mobility or persistence of data via object serialization. However, Java does not provide any mechanism for the mobility/persistence of computation (i.e., threads). We designed and implemented a new mechanism, called , that is used to build thread mobility or thread persistence. Therefore, a running Java thread can, at an arbitrary state of its execution, migrate to a remote machine where it resumes its execution, or be checkpointed on disk for possible subsequent recovery. With our services, migrating a thread is simply performed by the call of our primitive, and checkpointing/recovering a thread is performed by the call of our and primitives. Several projects have recently addressed the issue of Java thread serialization, e.g., Sumatra, Wasp, JavaGo, Brakes, JavaGoX, Merpati. Some of them have attempted to minimize the overhead incurred by the thread serialization mechanism on thread performance, but none of them has been able to completely avoid this overhead. We propose a generic Java thread serialization mechanism that does not impose any performance overhead on serialized threads. This is achieved thanks to the use of type inference and dynamic de-optimization techniques. In this paper, we describe the design and implementation details of our thread serialization prototype in Sun Microsystems' JDK. We report on experiments conducted with our prototype, present a comparative performance evaluation of the main thread serialization techniques, and confirm the elimination of the performance overhead with our thread serialization mechanism. Document type: Report