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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Automatic simplification of models in a hierarchical, modular discrete event simulation environment.

Sevinc, Suleyman. January 1988 (has links)
This research is concerned with the simplification of discrete event simulation models. Specifically, the necessary concepts and tools are investigated for the automatic generation of simplified versions of a discrete event model. The simplification process developed utilizes observations of model behavior. It is based on Zeigler's DEVS formalism developed in his book "Multifacetted Modelling and Discrete Event Simulation". Therefore, the simplified models that are generated adhere to all the canons of this formalism. The implementation is designed as an extension to DEVS-Scheme, a hierarchical modular discrete event modelling and simulation environment. It consists of two layers: the lower layer observes the model behavior and the higher layer generates the code from the observation data obtained at the lower layer. The resulting system allows one to generate simplified models at any level of the model structure hierarchy. A local area network model base is developed and used to demonstrate the validity and complexity reduction of the simplified models relative to the models from which they are extracted.


Massoumi, Mehran Mokhtar, 1961- January 1987 (has links)
Every effective simulation system should offer enough flexibility to allow thorough examination of the simulation object. HPSIM is a non-interactive function level Hardware Program SIMulator which is used to simulate synchronous clock mode sequential circuits. HPSIM, although a powerful design tool, lacks the flexibility to let the user carry out a "trial and error" simulation or inspect the behavior of the circuit for several inputs without having to prepare separate input files and re-run the entire program for every input. This thesis explores the drawbacks of HPSIM and offers solutions to produce a more effective design tool. The result is the interactive version of HPSIM or HPSIM/I which includes all features of HPSIM plus several added capabilities.


Wang, Yung-Hsin, 1957- January 1987 (has links)
The hierarchical abstract simulator is a multicomponent, multilevel discrete event model where each processor communicates with other processors by message passing. A methodology was developed to map the hierarchical abstract simulator onto distributed simulator architectures. The Intel's Personal Super Computer (iPSC) family with a concurrent-processing architecture is well suited for such simulation implementation. This thesis presents an alternative mapping realization of the hierarchical abstract simulator by using Intel's FORTRAN 286, FORTRAN 77 with extensions, on the iPSC computer (Hypercube). Algorithms for the hierarchical abstract simulator are provided in high level pseudo codes. A summary of iPSC system overview and programming concepts is described. Also, two examples are given for the illustration of our hypercube implementation. Finally, some experimental runs were made on the implementation, and comparisons of the performance (execution time) between sequential and parallel processor assignment are made.

Realistic evaluation of terrain by intelligent natural agents (RETINA)

Burgess, Rene G. 09 1900 (has links)
Approved for public release; distribution is unlimited / US Army and Joint constructive simulations require human operators to observe the exercise in progress, conduct analysis of the results, and provide a realistic reports and assessment of the action presented on their screens to the desired training audience. Current software tools provide excellent mathematical assessments (such as center of mass calculations, optimal routes, and sensor ranges) but poor human-like assessment of data (most likely route, probable enemy intention, etc.). This Thesis presents an artificial intelligence architecture specifically designed to reduce that manpower requirement by describing a concept for computer modeling that can produce realistic human-like assessment results. Specific concepts described are approaches for conducting a digital terrain assessment, development of avenues of approach, deployment of templated forces to a specific piece of terrain, and then a method of adjusting the templated force to react to actual sightings and known information. Also included are more detailed discussions and implementation details for use of gas diffusion as a method of analyzing avenues of approach through digital terrain. This approach seems quite promising as a method of modeling human movement tendencies and appears superior to classic path finding or optimal route selection methods. / Lieutenant Colonel, United States Army

Application of computer simulation methods to the study of Platinum Group minerals

Ntoahae, Petros Senauoa January 2005 (has links)
Thesis (PhD)(Mineral Sciences), University of Limpopo, 2005 / Computer simulation studies of a few representative Platinum-Group- Minerals (PGM), which are of industrial importance to the mining industry in South Africa were carried out. The electronic, structural and optical properties of PGM (PtS, PdPt3S4, PtAs2 and Pt4As4S4) were calculated within the framework of the density functional theory. We have used both the pseudopotential planewave and the Tight Binding Linear Muffin-Tin Orbital (TB-LMTO) methods to complement each other, since there is not much experimental data available for these systems. In the TB-LMTO method, the radii of overlapping Muffin Tin (MT) spheres were chosen to provide an efficient packing of space while ensuring that the overlap between the spheres remains small. The ground state structural properties were obtained by self-consistent energy minimization with respect to the atomic volume. The predicted equilibrium volume is within less than 15% of experiment. We have also found non-metallic semi-conducting behaviour for the three systems, PtS, PdPt3S4 and PtAs2 using both ab initio techniques. On the other hand, Pt4As4S4 was predicted to be metallic. We argue that the strong bonding between the Pt 5d and the S(As) 3p(4p) states plays a crucial role in the formation of the band gap in the semiconducting. The optical properties of PtS, PdPt3S4 and PtAs2 were calculated, and their reflectance spectra were found to be in good agreement with the experimental measurements. Full relaxation of both the volume and the internal parameters was carried out using the plane-wave pseudopotential method. It was found that the internal parameters as well as the bond lengths decrease with hydrostatic compression particularly for the cubic PtAs2, Pt4As4S4 and tetragonal PdPt3S4, and PtS has no internal parameters. The bulk moduli were calculated for these representatives of PGM and there are currently no experimental results available. We have derived a new set of potential models for PtS, PdPt3S4, PtAs2 and Pt4As4S4 structures. The models were used to study the pressure dependence of lattice constant for all the four systems and agree well with our electronic structure methods. However, PtS display anomaly under hydrostatic pressure, by expanding along c-lattice constant with increased pressure, for which there are no experimental evidence. We then modelled the structure and stabilities of PtAs2 and Pt4As4S4 of the dry and hydrated surfaces for low and high index surfaces, and predicted the {100} surface to be the most stable in both cases. It is further shown that molecular absorption of water has a stabilising effect on all the surfaces of the two structures. Stepped surfaces were created for {510} and {610} for both PtAs2 and Pt4As4S4 in order to model more realistic surfaces under dry condition with one dimensional defects, and then acute stepped were found to be the most stable compared to the obtuse steps. The three surfaces expressed in the equilibrium morphology of PtAs2, {100}, {210} and {102}, are in good agreement with experiment. / National Research Foundation (NRF), Royal Society(RS) and University of Limpopo (Turfloop campus)

Simulation-based search for hybrid system control and analysis

Neller, Todd William. January 1900 (has links)
Thesis (Ph.D)--Stanford University, 2000. / Title from pdf t.p. (viewed April 3, 2002). "June 2000." "Adminitrivia V1/Prg/20000830"--Metadata.

Tactical HF field expedient antenna performance /

Turkes, Gurkan. January 1990 (has links) (PDF)
Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, March 1990. / Thesis Advisor(s): Adler, Richard W. Second Reader: Jauregui, Stephen. "March 1990." Description based on signature pages as viewed on August 26, 2009. DTIC Identifier(s): Directional antennas, Computerized simulation, Tactical antennas, Buried radials, Elevated radials, High frequency, Lossy soils, Theses. Author(s) subject terms: Computer Simulation, Numerical Electromagnetics Code (NEC), Tactical HF Field Antennas. Includes bibliographical references. Also available online.

Advanced research into moving target imaging using multistatic radar

Riedl, Grant H. January 2009 (has links) (PDF)
Thesis (M.S. in Applied Physics)--Naval Postgraduate School, December 2009. / Thesis Advisor: Borden, Brett. Second Reader: Walters, Donald. "December 2009." Description based on title screen as viewed on January 29, 2010. Author(s) subject terms: Moving Target Imaging, multistatic radar, computer simulation. Includes bibliographical references (p. 31). Also available in print.

Perception & role of 3-D visualizations in planning a case study of the Northwest Passage Scenic Byway's viewshed protection & visualization project /

Balke, Kyle. January 2010 (has links)
Thesis (MS)--University of Montana, 2010. / Contents viewed on February 4, 2010. Title from author supplied metadata. Includes bibliographical references.

Realistic evaluation of terrain by intelligent natural agents (RETINA) /

Burgess, René G. January 2003 (has links) (PDF)
Thesis (M.S. in Modeling, Virtual Environments and Simulation)--Naval Postgraduate School, September 2003. / Thesis advisor(s): Chris Darken, John Hiles. Includes bibliographical references (p. 87-90). Also available online.

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