Iterchanging Discrete Event Simulationprocess Interaction Modelsusing The Web Ontology Language - Owl

Discrete event simulation development requires significant investments in time and resources. Descriptions of discrete event simulation models are associated with world views, including the process interaction orientation. Historically, these models have been encoded using high-level programming languages or special purpose, typically vendor-specific, simulation languages. These approaches complicate simulation model reuse and interchange. The current document-centric World Wide Web is evolving into a Semantic Web that communicates information using ontologies. The Web Ontology Language OWL, was used to encode a Process Interaction Modeling Ontology for Discrete Event Simulations (PIMODES). The PIMODES ontology was developed using ontology engineering processes. Software was developed to demonstrate the feasibility of interchanging models from commercial simulation packages using PIMODES as an intermediate representation. The purpose of PIMODES is to provide a vendor-neutral open representation to support model interchange. Model interchange enables reuse and provides an opportunity to improve simulation quality, reduce development costs, and reduce development times

A FAULT TOLERANT, DATA FUSION SYSTEM FOR NAVIGATION APPLICATIONS TO A DUCTED FAN VTOL UAV

A Fault Tolerant, Data Fusion (FTDF) algorithm for a Ducted Fan Unmanned Aerial Vehicle (DFUAV) Navigation System is presented. The algorithm have two parts: Gradient Descent (GD) for the Attitude and Heading Reference System (AHRS) and an Interacting Multiple Model (IMM) for position estimation. The GD methodology was designed to fuse the gyroscope, accelerometer, and geomagnetic sensors. The IMM algorithm is able to identify and compensate for multiple sensors data failures. There are three parts in the presentation. Firstly, system identification and the Allan Variance method is used to build dynamic models and noise models for multiple Sensors and Actuators. Secondly, a GD filter is developed for application to the Inertial Measurement Unit (IMU) consisting of tri-axis gyroscopes, accelerometers and magnetometers. The GD filter implementation incorporates magnetic distortion and gyroscope bias drift compensation. The filter uses a quaternion representation, allowing accelerometer and magnetometer data to be used in an analytically derived and optimized algorithm to compute the direction of the gyroscope measurement error as a quaternion derivative. . Finally, the IMM algorithm is used to combine data from multiple sensors simultaneously. This filter uses multiple models that incorporate sensor failures. The probabilities of these models being correct is generated by the IMM. These probabilities can be used to identify sensor failures and compensate for these failures

Graphical Programming of Simulation Models in an Object-Oriented Environment

Graphical programming has been used in conjunction with conventional simulation languages via block diagrams or activity networks. Its beneficial effects on programming and modeling in simulation have been accepted by everyone involved in these languages. However, none of these conventional techniques is truely interactive. Given the level of the current hardware and software technology, it is possible to design a very good graphical programming system which supports an interactive incremental programming style in specifications of simulation models. The benefit of such a visual system would go beyond the modeling phase of a simulation study and it might as well be realized in understanding the behavior of complex problems, in being a communication and training medium for the user and developers, and finally in presenting the simulation results. In this study, the graphical programming methodology has been investigated from the perspective of object-oriented simulation. The truely interactive and graphical orientation of some of the object-oriented languages (e.g., Smalltalk-80) has opened up new avenues of research in this very important topic. Today, the nature of this type of research will be not whether it can be done but how the known techniques should be combined to yield the highest benefit

An approach to teaching computer simulation

The thesis proposes a method for teaching computer simulation. The method involves the use of a large-scale real-life project which had been carried out by the author on a consultancy basis. This project has been developed into a teaching package which is intended for a wide spectrum of students, thus little knowledge of mathematics is assumed. This method has been found to be the most successful one by the author in over twenty years of experience with different types of students and this particular package has been tried successfully with a group of students in Hong Kong. The.real system and the relevant problems involved are first described and considered. From this an extremely simplified version is then extracted. Solution methods are considered and the usefulness of simulation demonstrated. The tools required for a simulation are then introduced, the simulation language used being GPSS which is considered by the author to be the most appropriate on the basis of ease of learning and future usefulness. In a series of steps realistic complications are added to this simple system while in parallel the required extra elements of the simulation language are introduced building up to the final simulation of the real system by the students who will by then have a thorough grasp of GPSS. They will also have had the experience of developing a full-scale simulation model. At this stage the students will be in a position to apply their knowledge and experience to problems in other fields and the author hopes that the lecturer will be motivated to develop similar projects for teaching in other areas

Modeling of systems

The handbook contains the fundamentals of modeling of complex systems. The classification of mathematical models is represented and the methods of their construction are given. The analytical modeling of the basic types of processes in the complex systems is considered. The principles of simulation, statistical and business processes modeling are described. The handbook is oriented on students of higher education establishments that obtain a degree in directions of “Software engineering” and “Computer science” as well as on lecturers and specialists in the domain of computer modeling

NASA/ASEE Summer Faculty Fellowship Program

This document is a collection of technical reports on research conducted by the participants in the 1996 NASA/ASEE Summer Faculty Fellowship Program at the Kennedy Space Center (KSC). This was the twelfth year that a NASA/ASEE program has been conducted at KSC. The 1996 program was administered by the University of Central Florida in cooperation with KSC. The program was operated under the auspices of the American Society for Engineering Education (ASEE) with sponsorship and funding from the Office of Educational Affairs, NASA Headquarters, Washington, DC and KSC. The KSC Program was one of nine such Aeronautics and Space Research Program funded by NASA in 1996. The NASA/ASEE Program is intended to be a two-year program to allow in-depth research by the University faculty member. The editors of this document were responsible for selecting appropriately qualified faculty to address some of the many problems of current interest to NASA/KSC

A comparison of CMS Tier0-dataflow scenarios using the Yasper simulation tool

The CMS experiment at CERN will produce large amounts of data in short time periods. Because the data buffers at the experiment are not large enough, this data needs to be transferred to other storages. The CMS Tier0 will be an enormous job processing and storage facility at the CERN site. One part of this Tier0, called the Tier0 input buffer, has the task to readout the experiment data buffers and to supply these data to other tasks that need to be carried out with it (such as storing). It has to make sure that no data is lost. This thesis compares different scenarios to work with a set of disk servers in order to accomplish the Tier0 input buffer tasks. To increase the performance per disk server, write and read actions on the same disk server are separated. To find the optimal moments a disk server should change from accepting and writing items to supplying items to other tasks, the combination of various parameters, such as the usage of a particular queuing discipline (like FIFO, LIFO, LPTF and SPTF) and the state of the disk server has been studied. To make the actual comparisons a simulation of dataflow models of the different scenarios has been used. These simulations have been performed with the Yasper simulation tool. This tool uses Petri Net models as its input. To be more certain that the models represent the real situation, some model parts have been remodelled in a tool called GPSS. This tool is not using Petri Nets as its input model; instead it uses queuing models described in a special GPSS language. The results of the simulations show that the best queuing discipline to be used with the Tier0 input buffer is the LPTF discipline. In particular in combination with a change moment as soon as a disk server has been readout completely