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Physical Sciences and Mathematics Commons™

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2002

Brigham Young University

Articles 1 - 30 of 33

Full-Text Articles in Physical Sciences and Mathematics

Level Oriented Formal Model For Asynchronous Circuit Verification And Its Efficient Analysis Method, Eric G. Mercer, Tomoya Kitai, Chris Myers, Yusuke Oguro, Tomohiro Yoneda Dec 2002

Level Oriented Formal Model For Asynchronous Circuit Verification And Its Efficient Analysis Method, Eric G. Mercer, Tomoya Kitai, Chris Myers, Yusuke Oguro, Tomohiro Yoneda

Faculty Publications

Using a level-oriented model for verification of asynchronous circuits helps users to easily construct formal models with high readability or to naturally model datapath circuits. On the other hand, in order to use such a model on large circuits, techniques to avoid the state explosion problem must be developed. This paper first introduces a level-oriented formal model based on time Petri nets, and then proposes its partial order reduction algorithm that prunes unnecessary state generation while guaranteeing the correctness of the verification.

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Controlling Laser High-Order Harmonic Generation Using Weak Counter-Propagating Light, Sergei Leonidovich Voronov Dec 2002

Controlling Laser High-Order Harmonic Generation Using Weak Counter-Propagating Light, Sergei Leonidovich Voronov

Theses and Dissertations

Laser high-order harmonic generation in the presence of relatively weak interfering light is investigated. The interfering pulses intersect the primary harmonic-generating laser pulse at the laser focus. The interfering light creates a standing intensity and phase modulation on the field, which disrupts microscopic phase matching and shuts down local high harmonic production. Suppression of the 23rd harmonic (by two orders of magnitude) is observed when a counter-propagating interfering pulse of light is introduced. A sequence of counter-propagating pulses can be used to shut down harmonic production in out-of-phase zones of the generating volume to achieve quasi phase matching. Harmonic emission …

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Biaxial Strain-Modified Valence And Conduction Band Offsets Of Zinc-Blende Gan, Gap, Gaas, Inn, Inp, And Inas, And Optical Bowing Of Strained Epitaxial Ingan Alloys, Gus L. W. Hart, P. R. C. Kent, Alex Zunger Dec 2002

Biaxial Strain-Modified Valence And Conduction Band Offsets Of Zinc-Blende Gan, Gap, Gaas, Inn, Inp, And Inas, And Optical Bowing Of Strained Epitaxial Ingan Alloys, Gus L. W. Hart, P. R. C. Kent, Alex Zunger

Faculty Publications

Using density-functional calculations, we obtain the (001) biaxial strain dependence of the valence and conduction band energies of GaN, GaP, GaAs, InN, InP, and InAs. The results are fit to a convenient-to-use polynomial and the fits provided in tabular form. Using the calculated biaxial deformation potentials in large supercell empirical psuedopotential calculations, we demonstrate that epitaxial strain reduces the InGaN alloy bowing coefficient compared to relaxed bulk alloys.

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Coordinated Target Assignment And Intercept For Unmanned Air Vehicles, Erik P. Anderson, Randal W. Beard, Michael A. Goodrich, Timothy W. Mclain Dec 2002

Coordinated Target Assignment And Intercept For Unmanned Air Vehicles, Erik P. Anderson, Randal W. Beard, Michael A. Goodrich, Timothy W. Mclain

Faculty Publications

This paper presents an end-to-end solution to the cooperative control problem represented by the scenario where unmanned air vehicles (UAVs) are assigned to transition through known target locations in the presence of dynamic threats. The problem is decomposed into the subproblems of: 1) cooperative target assignment; 2) coordinated UAV intercept; 3) path planning; 4) feasible trajectory generation; and 5) asymptotic trajectory following. The design technique is based on a hierarchical approach to coordinated control. Simulation results are presented to demonstrate the effectiveness of the approach.

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Statistical Cataloging Of Archival Data For Luminosity Class Iv-V Stars, B. J. Taylor Nov 2002

Statistical Cataloging Of Archival Data For Luminosity Class Iv-V Stars, B. J. Taylor

Faculty Publications

This paper is one of a pair in which temperatures and metallicity catalogs for class IV-V stars are considered. The temperature catalog described here is derived from a calibration based on stellar angular diameters. If published calibrations of this kind are compared by using color-index transformations, temperature-dependent differences among the calibrations are commonly found. However, such differences are minimized if attention is restricted to calibrations based on Johnson V-K. A calibration of this sort from Di Benedetto (1998) is therefore tested and adopted. That calibration is then applied to spectroscopic and photometric data, with the latter predominating. Cousins R-I photometry …

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Statistical Cataloging Of Archival Data For Luminosity Class Iv-V Stars - Ii. The Epoch 2001 [Fe/H] Catalog, B. J. Taylor Nov 2002

Statistical Cataloging Of Archival Data For Luminosity Class Iv-V Stars - Ii. The Epoch 2001 [Fe/H] Catalog, B. J. Taylor

Faculty Publications

This paper describes the derivation of an updated statistical catalog of metallicities. The stars for which those metallicities apply are of spectral types F, G, and K, and are on or near the main sequence. The input data for the catalog are values of [Fe/H] published before 2002 February and derived from lines of weak and moderate strength. The analyses used to derive the data have been based on one-dimensional LTE model atmospheres. Initial adjustments which are applied to the data include corrections to a uniform temperature scale which is given in a companion paper (see Taylor 2003). After correction, …

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Modeling The Multicast Address Allocation Problem, Daniel Zappala, Chris Gauthierdickey, Virginia Lo Nov 2002

Modeling The Multicast Address Allocation Problem, Daniel Zappala, Chris Gauthierdickey, Virginia Lo

Faculty Publications

To support IP multicast, domains must assign a unique multicast address to each application from a limited, globally-shared address space. We examine the performance of several classes of address allocation algorithms withln the context of the MASC architecture. This study is the first of its kind to model the generalized multicast address allocation problem and consider non-contiguous allocation algorithms. We find that prefix-based allocation outperforms our non-contiguous algorithm, despite the apparent advantages of non-contiguous allocation. We also verify the benefits of using worst-fit for new allocations.

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A Theoretical Framework For The Multicast Address Allocation Problem, Daniel Zappala, Chris Gauthierdickey, Virginia Lo, Timothy Singer Nov 2002

A Theoretical Framework For The Multicast Address Allocation Problem, Daniel Zappala, Chris Gauthierdickey, Virginia Lo, Timothy Singer

Faculty Publications

The multicast address allocation problem requires Internet domains to allocate unique addresses to multicast applications from a globally-shared space. We develop a theoretical framework for multicast allocation algorithms that is influenced by subcube allocation in hypercube computer systems. Based on this framework we derive complexity results for the address allocation problem and describe several new allocation algorithms that use a hypercube model for address representation.

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Horizon Occlusion Culling For Real-Time Rendering Of Hierarchical Terrains, Parris K. Egbert, Brandon Lloyd Oct 2002

Horizon Occlusion Culling For Real-Time Rendering Of Hierarchical Terrains, Parris K. Egbert, Brandon Lloyd

Faculty Publications

We present a technique to perform occlusion culling for hierarchical terrains at run-time. The algorithm is simple to implement and requires minimal pre-processing and additional storage, yet leads to 2-4 times improvement in framerate for views with high degrees of occlusion. Our method is based on the well-known occlusion horizon algorithm. We show how to adapt the algorithm for use with hierarchical terrains. The occlusion horizon is constructed as the terrain is traversed in an approximate front to back ordering. Regions of the terrain are compared to the horizon to determine when they are completely occluded from the viewpoint. Culling …

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Rf Rendez-Blue: Reducing Power And Inquiry Costs In Bluetooth-Enabled Mobile Systems, Eric S. Hall, Charles D. Knutson, David K. Vawdrey Oct 2002

Rf Rendez-Blue: Reducing Power And Inquiry Costs In Bluetooth-Enabled Mobile Systems, Eric S. Hall, Charles D. Knutson, David K. Vawdrey

Faculty Publications

In resource-limited mobile computing devices, Bluetooth wireless technology imposes a weighty burden due to inefficient power utilization and a sluggish device discovery process. Buttressing Bluetooth with Radio Frequency Identification (RFID) technology by performing an operation we call “Rendez-Blue” alleviates these limitations. In the Rendez-Blue process, an RFID signal is used as a cue to “wake-up” a sleeping Bluetooth radio. This ensures that the Bluetooth radio is active only when needed, significantly reducing power consumption. In addition, RFID is used to communicate Bluetooth device information, allowing the user to bypass the traditional 10.24-second discovery process.

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Performance Evaluation Of Path Searching Heuristics For Multicast Qos Routing, Daniel Zappala, Dayi Zhou Oct 2002

Performance Evaluation Of Path Searching Heuristics For Multicast Qos Routing, Daniel Zappala, Dayi Zhou

Faculty Publications

Quality of Service routing for multicast enables a group member to find and install a branch of the multicast tree that can meet its QoS constraints. The most promising protocols in this area use receiver-oriented path searching heuristics to find feasible routes. In this paper, we examine the performance of the path searching heuristics used by these protocols, to determine which techniques are the most effective. We find that several low-overhead path searching heuristics are effective, and that generic path searching can work as well as targeted, QoS-specific searching.

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Compact Focusing Von Hamos Spectrometer For Quantitative X-Ray Spectroscopy, Larry V. Knight, A. P. Shevelko, Yu S. Kasyanov, O. F. Yakushev Oct 2002

Compact Focusing Von Hamos Spectrometer For Quantitative X-Ray Spectroscopy, Larry V. Knight, A. P. Shevelko, Yu S. Kasyanov, O. F. Yakushev

Faculty Publications

A compact focusing crystal spectrometer based on the von Hamos scheme is described. Cylindrically curved mica and graphite crystals with a radius of curvature of R = 20 mm are used in the spectrometer. A front illuminated charge-coupled device (CCD) linear array detector makes this spectrometer useful for real-time spectroscopy of laser-produced plasma x-ray sources within the wavelength range of lambda= 1.8-10 Angstroms. Calibration of crystals and the CCD linear array makes it possible to measure absolute photon fluxes. X-ray spectra in an absolute intensity scale were obtained from Mg, Ti, and Fe laser-produced plasmas, with a spectral resolution lambda/delta …

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Bluetooth: An Emerging Technology For Wireless Personal Area Networks, Eric S. Hall, Charles D. Knutson, David K. Vawdrey Oct 2002

Bluetooth: An Emerging Technology For Wireless Personal Area Networks, Eric S. Hall, Charles D. Knutson, David K. Vawdrey

Faculty Publications

Look under your desk or behind your computer. See that rat’s nest of wires and cables? Almost every cable or wire that tethers us to our devices (or our devices to one another) is unnecessary. Bluetooth wireless technology promises to reduce the cabling chaos that afflicts us all. Bluetooth is a recently developed technology that uses radio frequency (RF) transceivers to provide point-to-multipoint wireless connectivity within a personal space. Bluetooth was designed for both voice and data communication at low per-unit costs while consuming little power. To achieve the cost and power goals, Bluetooth limits connectivity to a sphere of …

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Algebraic Methods For Computer Aided Geometric Design, Thomas W. Sederberg, Jianmin Zheng Aug 2002

Algebraic Methods For Computer Aided Geometric Design, Thomas W. Sederberg, Jianmin Zheng

Faculty Publications

CAGD draws from several branches of mathematics and computer science, such as approximation theory, differential geometry, and numerical analysis. This chapter reviews some of the tools of algebra and algebraic geometry that have been brought to bear on problems in CAGD.

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Construction And Testing Of A Low-Finesse Fabry-Perot Interferometer For Use In Atomic Spectroscopy, Nathan C. Moody Aug 2002

Construction And Testing Of A Low-Finesse Fabry-Perot Interferometer For Use In Atomic Spectroscopy, Nathan C. Moody

Student Works

I built a low-finesse confocal cavity with aluminum mirrors for use in the imaging of ultra-cold calcium ion plasmas. The confocal cavity provides stability at large mirror separations, a condition necessary for achieving both low finesse and narrow peak widths. Additionally, the finesse in the case of coherent input is effectively doubled compared to multi-mode resonance. The cavity was tested using a GaN diode laser input at 397nm. The transmission obtained indicated that the finesse of the cavity was slightly lower than the prediction based on measurements of the mirror reflectivities and the assumption of incoherent input.

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Simulations Of The Instability Of The M = 1 Self-Shielding Diocotron Mode In Finite-Length Non-Neutral Plasmas, Grant W. Mason, Ross L. Spencer Aug 2002

Simulations Of The Instability Of The M = 1 Self-Shielding Diocotron Mode In Finite-Length Non-Neutral Plasmas, Grant W. Mason, Ross L. Spencer

Faculty Publications

The "self-shielding" m = 1 diocotron mode in Malmberg-Penning traps has been known for over a decade to be unstable for finite length non-neutral plasmas with hollow density profiles. Early theoretical efforts were unsuccessful in accounting for the exponential growth and/or the magnitude of the growth rate. Recent theoretical work has sought to resolve the discrepancy either as a consequence of the shape of the plasma ends or as a kinetic effect resulting from a modified distribution function as a consequence of the protocol used to form the hollow profiles in experiments. Both of these finite length mechanisms have been …

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A Formal Method To Analyze Framework-Based Software, Trent N. Larson Aug 2002

A Formal Method To Analyze Framework-Based Software, Trent N. Larson

Theses and Dissertations

Software systems are frequently designed using abstractions that make software verification tractable. Specifically, by choosing meaningful, formal abstractions for interfaces and then designing according to those interfaces, one can verify entire systems according to behavioral predicates. While impractical for systems in general, framework-based software architectures are a type of system for which formal analysis can be beneficial and practical over the life of the system. We present a method to formally analyze behavioral properties of framework-based software with higher-order logic and then demonstrate its utility for a significant, modern system.

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Intelligent Segmentation Tools, William A. Barrett, Eric N. Mortensen, L. Jack Reese Jul 2002

Intelligent Segmentation Tools, William A. Barrett, Eric N. Mortensen, L. Jack Reese

Faculty Publications

Intelligent Scissors and Intelligent Paint are complementary interactive image segmentation tools that allow a user to quickly and accurately select objects of interest using simple gesture motions with a mouse. With Intelligent Scissors. when the cursor position comes in proximity to an object edge, a live-wire boundary “snaps” to, and wraps around the object of interest. The Intelligent Paint tool uses the cursor position to sample the image data interior to the object and grows the current region, in discrete, snapping increments, to include similar neighboring regions. Both techniques make use of a watershed algorithm called toboganning. Wth Intelligent Scissors, …

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Vibrational Modes Of Thin Oblate Clouds Of Charge, Thomas G. Jenkins, Ross L. Spencer Jul 2002

Vibrational Modes Of Thin Oblate Clouds Of Charge, Thomas G. Jenkins, Ross L. Spencer

Faculty Publications

A numerical method is presented for finding the eigenfunctions (normal modes) and mode frequencies of azimuthally symmetric non-neutral plasmas confined in a Penning trap whose axial thickness is much smaller than their radial size. The plasma may be approximated as a charged disk in this limit; the normal modes and frequencies can be found if the surface charge density profile sigma(r) of the disk and the trap bounce frequency profile wz(r) are known. The dependence of the eigenfunctions and equilibrium plasma shapes on nonideal components of the confining Penning trap fields is discussed. The results of the calculation are compared …

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An Enterprise-Based Grid Resource Management System, Mark J. Clement, Joseph Ekstrom, Quinn O. Snell, Kevin B. Tew Jul 2002

An Enterprise-Based Grid Resource Management System, Mark J. Clement, Joseph Ekstrom, Quinn O. Snell, Kevin B. Tew

Faculty Publications

As the Internet began its exponential growth into a global information environment, software was often unreliable, slow and had difficulty in interoperating with other systems. Supercomputing node counts also continue to follow high growth trends. Supercomputer and grid resource management software must mature into a reliable computational platform in much the same way that web services matured for the Internet. DOGMA The Next Generation (DOGMA-NG) improves on current resource management approaches by using tested off-the-shelf enterprise technologies to build a robust, scalable, and extensible resource management platform. Distributed web service technologies constitute the core of DOGMA-NG’s design and provide fault …

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Machine-Learned Contexts For Linguistic Operations In German Sentence Realization, Eric K. Ringger, Simon Corston-Oliver, Michael Gamon, Robert Moore Jul 2002

Machine-Learned Contexts For Linguistic Operations In German Sentence Realization, Eric K. Ringger, Simon Corston-Oliver, Michael Gamon, Robert Moore

Faculty Publications

We show that it is possible to learn the contexts for linguistic operations which map a semantic representation to a surface syntactic tree in sentence realization with high accuracy. We cast the problem of learning the contexts for the linguistic operations as classification tasks, and apply straightforward machine learning techniques, such as decision tree learning. The training data consist of linguistic features extracted from syntactic and semantic representations produced by a linguistic analysis system. The target features are extracted from links to surface syntax trees. Our evidence consists of four examples from the German sentence realization system code-named Amalgam: case …

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Network Simplification Through Oracle Learning, Tony R. Martinez, Joshua Menke, Adam Peterson, Michael E. Rimer May 2002

Network Simplification Through Oracle Learning, Tony R. Martinez, Joshua Menke, Adam Peterson, Michael E. Rimer

Faculty Publications

Often the best artificial neural network to solve a real world problem is relatively complex. However, with the growing popularity of smaller computing devices (handheld computers, cellular telephones, automobile interfaces, etc.), there is a need for simpler models with comparable accuracy. The following research presents evidence that using a larger model as an oracle to train a smaller model on unlabeled data results in 1) a simpler acceptable model and 2) improved results over standard training methods on a similarly sized smaller model. On automated spoken digit recognition, oracle learning resulted in an artificial neural network of half the size …

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Optimization By Varied Beam Search In Hopfield Networks, Tony R. Martinez, Xinchuan Zeng May 2002

Optimization By Varied Beam Search In Hopfield Networks, Tony R. Martinez, Xinchuan Zeng

Faculty Publications

This paper shows that the performance of the Hopfield network for solving optimization problems can be improved by a varied beam search algorithm. The algorithm varies the beam search size and beam intensity during the network relaxation process. It consists of two stages: increasing the beam search parameters in the flrst stage and then decreasing them in the second stage. The purpose of using such a scheme is to provide the network with a better chance to find more and better solutions. A large number of simulation results based on 200 randomly generated city distributions of the 10-city traveling salesman …

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Improving Speech Recognition Learning Through Lazy Training, Tony R. Martinez, Michael E. Rimer, D. Randall Wilson May 2002

Improving Speech Recognition Learning Through Lazy Training, Tony R. Martinez, Michael E. Rimer, D. Randall Wilson

Faculty Publications

Multi-layer backpropagation, like most learning algorithms that can create complex decision surfaces, is prone to overfitting. We present a novel approach, called lazy training, for reducing the overfit in multiple-layer networks. Lazy training consistently reduces generalization error of optimized neural networks by more than half on a large OCR dataset and on several real world problems from the UCI machine learning database repository. Here, lazy training is shown to be effective in a multi-layered adaptive learning system, reducing the error of an optimized backpropagation network in a speech recognition system by 50.0% on the TIDIGITS corpus.

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Probabilistic Connections In Relaxation Networks, Dan A. Ventura May 2002

Probabilistic Connections In Relaxation Networks, Dan A. Ventura

Faculty Publications

This paper reports results from studying the behavior of Hopfield-type networks with probabilistic connections. As the probabilities decrease, network performance degrades. In order to compensate, two network modifications - input persistence and a new activation function - are suggested, and empirical results indicate that the modifications significantly improve network performance.

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Rapid Heterogeneous Ad Hoc Connection Establishment: Accelerating Bluetooth Inquiry Using Irda, Trevor Clifton, Derek D. Joos, Charles D. Knutson, Ryan W. Woodings Mar 2002

Rapid Heterogeneous Ad Hoc Connection Establishment: Accelerating Bluetooth Inquiry Using Irda, Trevor Clifton, Derek D. Joos, Charles D. Knutson, Ryan W. Woodings

Faculty Publications

Bluetooth device discovery is a time-intensive phase of the Bluetooth connection-establishment procedure. In this paper we propose a technique that integrates existing IrDA technology with Bluetooth technology to improve the ad hoc connection establishment time of Bluetooth devices. We accomplish this improvement by first establishing an IrDA connection between two devices equipped with both Bluetooth and IrDA capabilities and then exchanging Bluetooth device discovery information via the established IrDA connection. As a result of this cooperative exchange, the devices are able to bypass the time-intensive Bluetooth device discovery procedure. Our research shows that IrDA-assisted Bluetooth connection establishment is up to …

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A Comparison Of Coalescent Estimation Software, Kristen Piggott Shepherd Mar 2002

A Comparison Of Coalescent Estimation Software, Kristen Piggott Shepherd

Theses and Dissertations

Coalescent theory is a method often used by population geneticists in order to make inferences about evolutionary parameters. The coalescent is a stochastic model that approximates ancestral relationships among genes. An understanding of the coalescent pattern of a sample of sequences, along with some knowledge of the mutations that have occurred, provides information about the evolutionary forces that have acted on the population. Processes such as migration, recombination, variable population size, or natural selection are the forces that affect the genealogies and lead to genetic variability in a sample. Coalescent theory provides a statistical description of the variability in the …

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Pattern Classification Using A Quantum System, Dan A. Ventura Mar 2002

Pattern Classification Using A Quantum System, Dan A. Ventura

Faculty Publications

We consider and compare three approaches to quantum pattern classification, presenting empirical results from simulations.

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Negative Band Gap Bowing In Epitaxial Inas/Gaas Alloys And Predicted Band Offsets Of The Strained Binaries And Alloys On Various Substrates, Gus L. W. Hart, Kwiseon Kim, Alex Zunger Feb 2002

Negative Band Gap Bowing In Epitaxial Inas/Gaas Alloys And Predicted Band Offsets Of The Strained Binaries And Alloys On Various Substrates, Gus L. W. Hart, Kwiseon Kim, Alex Zunger

Faculty Publications

We use pseudopotential theory to provide (1) the band offsets of strained GaAs and InAs on various substrates and (2) the energies Ev(x) of the valence and conduction bands of InxGa1-xAs alloy, as a function of composition. Results are presented for both the bulk alloy and for the alloy strained on InP or GaAs. We predict that while Ex(x) bows downward for relaxed bulk alloys, it bows upward for strained epitaxial alloys. The calculated alloy offsets are used to discuss electron and hole localization in this system.

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The Algebra And Geometry Of Curve And Surface Inversion, Thomas W. Sederberg, Eng-Wee Chionh, Kent Ridge Jan 2002

The Algebra And Geometry Of Curve And Surface Inversion, Thomas W. Sederberg, Eng-Wee Chionh, Kent Ridge

Faculty Publications

An inversion equation takes the Cartesian coordinates of a point on a parametric curve or surface and returns the parameter value(s) of that point. A 2-D curve inversion equation has the form t = f(x,y)/g(x,y). This paper shows that practical insight into inversion can be obtained by studying the geometry of the implicit curves f(x,y) = 0 and g(x,y) = 0. For example, the relationship between the singular locus of the parametric curve and the lowest possible degree of an inversion equation can be understood in this way. Also, insight is given into what parameter value will be returned if …

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