Digital Commons Network^™

A Comparison Of Traffic Models: Part 1, Framework, Hong Lo, Wei-Hua Lin, Lawrence Liao, Elbert Chang, Jacob Tsao

Faculty Publications

This report defines a framework for comparing dynamic traffic models. It emphasizes four dimensions: functionality, traffic dynamics, route choice dy namics, and overall network performance. The first dimension compares the models through a check-list of model functions. Regarding the last three comparison dimensions, a total of five networks and twelve scenarios are defined. These test scenarios are designed to accentuate model properties and differences. Also included in the report are a list of performance measures for comparison purpose, and a discussion of the interpretation of results.

Dynamic Traffic Assignment For Automated Highway Systems: A Two-Lane Highway With Speed Constancy, H.-S. Jacob Tsao

Faculty Publications

Dynamic traffic assignment through analytical modeling and optimization has been widely accepted by the IVHS R&D community as a promising traffic control tool for understanding and relieving traffic congestion on conventional highways and city streets. Due to the completely controlled nature of AHS traffic, dynamic assignment of AHS traffic is even more promising. One added dimension of complexity associated with AHS dynamic traffic assignment is lane assignment. Lane changes, for fully utilizing AHS capacity or for exiting, incur disturbances to and hence reduction of longitudinal flow. Intelligent lane assignment is necessary to ensure a high rate of successful exiting, to …

Chemical Species Spatial Distribution And Relationship To Elevation And Snow Accumulation Rate Over The Greenland Ice Sheet, Qinzhao Yang, Paul A. Mayewski, E. Linder, Sallie I. Whitlow, Mark S. Twickler

Faculty Publications

Major chemical species (Cl−, NO−3, SO2−4, Na+, K+, Mg2+, Ca2+) from 24 snowpits (sampled at a resolution of 3 cm, total 2995 samples) collected from northern, central, and southern Greenland were used for this investigation. The annual and seasonal (winter and summer) concentration of each chemical species was calculated and used to study the spatial distribution of chemical species over the central portion of the Greenland Ice Sheet. A two‐sided t‐distribution test (α = 0.05) suggests that concentrations of major chemical species in snow do not vary significantly over this portion of central Greenland. The relationship between chemical concentration and …

Structural Phase Transition And Tc Distribution In Hf-Doped Lamno3 Investigated Using Perturbed-Angular-Correlation Spectroscopy, William E. Evenson, David D. Allred, Gary L. Catchen

Faculty Publications

Using perturbed-angular-correlation (PAC) spectroscopy, via the Hf-->Ta probe, we have measured Mn-site electric-field gradients (EFG's) at Ta nuclei in ceramic samples of LaMnO3. Two crystallographic phases coexist over a temperature interval of ≈16 K near the orthorhombic-to-rhombohedral transition at ≈724 K, which shows a thermal hysteresis of ≈1.7±0.2 K. Concurrently, in the two phases, we determined the temperature dependence of the EFG parameters, Vzz, ƞ, and δ, and the ratio of the probe concentrations A1/A2. To explain the apparent coexistence of two phases in this weakly first-order transition, we present a model that assumes a spatial distribution of Tc …

Sol-Gel Phase Transitions In Thermoreversible Gels: Onset Of Gelation And Melting, Y. Liu, R.B. Pandey

Faculty Publications

A Monte Carlo simulation model is propsed to study the phase transition and the structural evolution of thermoreversible gels with the coexistence of phase separation and gelation processes. Our model includes the mobility of all the species and the reversibilty of bonds of the clusters formed due to cross-linking reactions. These features provide a more realistic depiction of a polymer-solvent system. We attempt to elucidate the effects of interactions, solvents, polymer fraction, etc. on the phase behaviors of the thermoreversible gel. Sol-to-gel transition is studied in detail as a function of temperature, and the related critical exponents are evaluated. Two …

Measurement Of The Reaction Γ*P→Φp In Deep Inelastic E+P Scattering At Hera, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. R. Okrasinski, J. Repond, R. Stanek, R. L. Talaga, H. Zhang, Margarita C. K. Mattingly, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, R. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, I. Gialas, R. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam

Faculty Publications

The production of φ mesons in the reaction e+p → e+φp (φ → K+K-), for 7 < Q2 < 25 GeV2 and for virtual photon-proton centre of mass energies (W) in the range 42-134 GeV, has been studied with the ZEUS detector at HERA. When compared to lower energy data at similar Q2, the results show that the γp → p0p cross section rises strongly with W. This behaviour is similar to that previously found for the γ*p → p0p cross section. This strong dependence cannot be explained by production through soft pomeron exchange. It is, however, consistent with perturbative QCD expectations, where it reflects the rise of the gluon momentum density in the proton at small x. The ratio of σ(φ)/σ(p0), which has previously been determined by ZEUS to be 0.065 ± 0.013 (stat.) in photoproduction at a mean W of 70 GeV, is measured to be 0.18 ± 0.05 (stat.) ± 0.03 (syst.) at a mean Q2 of 12.3 GeV2 and mean W of ≈ 100 GeV and is thus approaching at large Q2 the value of 2/9 predicted from the quark charges of the vector mesons and a flavour independent production mechanism.

Effects Of Climate Change On Hypoxia In Coastal Waters: A Doubled Co2 Scenario For The Northern Gulf Of Mexico, Dubravko Justic, Nancy N. Rabalais, R. Eugene Turner

Faculty Publications

Projections of general circulation models suggest that freshwater discharge from the Mississippi River to the coastal ocean will increase 20% if atmospheric CO2 concentration doubles. This result is likely to affect water column stability, surface productivity, and global oxygen cycling in the northern Gulf of Mexico, which is the site of the largest (up to 16,500 km2) and most severe hypoxic zone (liter‒1) in the western Atlantic Ocean. We use a coupled physical-biological two-box model to investigate potential effects of climate change on seasonal oxygen cycling and hypoxia in river-dominated coastal waters. The model was developed and calibrated using comprehensive …

Morphometry Of Juvenile And Subadult Loligo Pealei And L. Plei From The Northern Gulf Of Mexico, Guillermo Sánchez, Harriet M. Perry, Christine B. Trigg, Michael Vecchione, Clyde Roper, Patricia M. Biesot

Faculty Publications

Two species of Loligo are abundant in northern Gulf waters: the long-finned squid, Loligo pealei. and the arrow squid, Loligo plei. Variability within species and similarities between the species often hamper accurate identification. The two species more closely resemble each other in areas of sympatry. and there is overlap in almost all of the diagnostic characters. Small specimens of Loligo are not easily identified. and there are few studies detailing their morphometry. Because of the taxonomic uncertainties associated with the identification of juveniles and subadults of L. pealei and L. plei, the species were differentiated by isoelectric …

Dynamics Of Conversion Of Conduction Electrons Into A Collective Charge-Density-Wave Current, Alexander S. Kovalev, Yuriy V. Pershin Dr, Alexander S. Rozhavsky

Faculty Publications

The exactly solvable model which describes the dynamics of transformation of conduction electrons into nonlinear charge-carrying excitations of charge-density waves in quasi-one-dimensional Peierls-Frohlich conductors is formulated and studied by the inverse scattering transformation method. The pair of self-trapped conduction electrons transform into a charged 2π kink localized in a single conducting chain and surrounded by dipoles in neighboring chains.

Robust Optimization Using Training Set Evolution, Tony R. Martinez, Dan A. Ventura

Faculty Publications

Training Set Evolution is an eclectic optimization technique that combines evolutionary computation (EC) with neural networks (NN). The synthesis of EC with NN provides both initial unsupervised random exploration of the solution space as well as supervised generalization on those initial solutions. An assimilation of a large amount of data obtained over many simulations provides encouraging empirical evidence for the robustness of Evolutionary Training Sets as an optimization technique for feedback and control problems.

Nutrient Changes In The Mississippi River And System Responses On The Adjacent Continental Shelf, Nancy N. Rabalais, R. Eugene Turner, Dubravko Justic, Quay Dortch, William J. Wiseman, Barun Sen Gupta

Faculty Publications

The Mississippi River system ranks among the world's top 10 rivers in freshwater and sediment inputs to the coastal ocean. The river contributes 90% of the freshwater loading to the Gulf of Mexico, and terminates amidst one of the United States' most productive fisheries regions and the location of the largest zone of hypoxia, in the western Atlantic Ocean. Significant increases in riverine nutrient concentrations and loadings of nitrate and phosphorus and decreases in silicate have occurred this century, and have accelerated since 1950. Consequently, major alterations have occurred in the probable nutrient limitation and overall stoichiometric nutrient balance in …

Heterogeneous Radial Basis Function Networks, Tony R. Martinez, D. Randall Wilson

Faculty Publications

Radial Basis Function (RBF) networks typically use a distance function designed for numeric attributes, such as Euclidean or city-block distance. This paper presents a heterogeneous distance function which is appropriate for applications with symbolic attributes, numeric attributes, or both. Empirical results on 30 data sets indicate that the heterogeneous distance metric yields significantly improved generalization accuracy over Euclidean distance in most cases involving symbolic attributes.

A Robust System For Natural Spoken Dialogue, Eric K. Ringger, James F. Allen, Bradford W. Miller, Teresa Sikorski

Faculty Publications

This paper describes a system that leads us to believe in the feasibility of constructing natural spoken dialogue systems in task-oriented domains. It specifically addresses the issue of robust interpretation of speech in the presence of recognition errors. Robustness is achieved by a combination of statistical error post-correction, syntactically- and semantically-driven robust parsing, and extensive use of the dialogue context. We present an evaluation of the system using time-to-completion and the quality of the final solution that suggests that most native speakers of English can use the system successfully with virtually no training.

Smith On Krauss, 'The Physics Of Star Trek', Anne Collins Smith

Faculty Publications

Review of Lawrence M. Krauss.The Physics of Star Trek. New York: Basic Books, 1995. xvi + 188 pp. $20.00(cloth), ISBN 978-0-465-00559-8.

Reviewed by Anne Collins Smith (Austin Community College) Published on H-PCAACA (May, 1996)

A Brief Introduction To Formal Methods, Paul E. Black, Kelly M. Hall, Michael D. Jones, Trent N. Larson, Phillip J. Windley

Faculty Publications

As hardware designs grow in size and complexity, current design methods are proving less adequate. Current methods for specification, design, and test are typically empirical or informal, that is, they are based on experience and argument. Formal methods are solidly based on mathematical logic systems and precise rules of inference. Formal methods offer a discipline which complements current methods so designers can successfully meet the demand for high performance systems. Formal methods covers a broad and diverse set of techniques aimed at improving computer correctness. This paper explains the role of specifications and implementation models in formal methods, and different …

Error Correction Via A Post-Processor For Continuous Speech Recognition, Eric K. Ringger, James F. Allen

Faculty Publications

This paper presents a new technique for overcoming several types of speech recognition errors by post-processing the output of a continuous speech recognizer. The post-processor output contains fewer errors, thereby making interpretation by higher-level modules, such as a parser, in a speech understanding system more reliable. The primary advantage to the post-processing approach over existing approaches for overcoming SR errors lies in its abilityto introduce options that are not available in the SR module’s output. This work provides evidence for the claim that a modern continuous speech recognizer can be used successfully in “black-box” fashion for robustly interpreting spontaneous utterances …

Simulations Of Electrostatic Modes Of Non-Neutral Plasmas With Small Aspect Ratio In A Penning Trap, Grant W. Mason, Ross L. Spencer, Jonathan A. Bennett

Faculty Publications

The dependence on induced charge, experimental geometry, and temperature of electrostatic modes in very low aspect ratio non-neutral plasmas in a Penning trap is considered. The modes are of interest as non-destructive diagnostics of the shape of the plasmas. These investigations include equilibrium calculations of plasma shapes and profiles at finite temperature and particle-in-cell simulations of axisymmetric modes. The results of the simulations are compared to the zero-temperature theory by Dubin [Phys. Rev. Lett. 66, 2076 (1991)] taken to first-order in the aspect ratio and to experimental measurements by Weimer et al. [Phys. Rev. A 49, 3842 (1994)]. In general, …

The Advanced Glycation End Product, NE-(Carboxymethyl)Lysine, Is A Product Of Both Lipid Peroxidation And Glycoxidation Reactions, Min-Xin Fu, Jesus R. Requena, Alicia J. Jenkins, Timothy J. Lyons, John W. Baynes, Suzanne R. Thorpe

Faculty Publications

Nepsilon-(Carboxymethyl)lysine (CML) is an advanced glycation end product formed on protein by combined nonenzymatic glycation and oxidation (glycoxidation) reactions. We now report that CML is also formed during metal-catalyzed oxidation of polyunsaturated fatty acids in the presence of protein. During copper-catalyzed oxidation in vitro, the CML content of low density lipoprotein increased in concert with conjugated dienes but was independent of the presence of the Amadori compound, fructoselysine, on the protein. CML was also formed in a time-dependent manner in RNase incubated under aerobic conditions in phosphate buffer containing arachidonate or linoleate; only trace amounts of CML were formed from …

Compressing Semi-Structured Text Using Hierarchical Phrase Identifications, Dan R. Olsen Jr., Craig G. Nevill-Manning, Ian H. Witten

Faculty Publications

The structure of this paper is as follows. We begin by identifying some characteristics of semi-structured text that have special relevance to data compression. We then give a brief account of a particular large textual database, and describe a compression scheme that exploits its structure. In addition to providing compression, the system gives some insight into the structure of the database. Finally we show how the hierarchical grammar can be generalized, first manually and then automatically, to yield further improvements in compression performance.

Grain-Boundary Structure Effects On Intergranular Stress Corrosion Cracking Of Alloy X-750, Brent L. Adams, Ted Olsen, N. Panayotou, Y. Pan

Faculty Publications

This work was supported by the Department of Energy under Grant No. DE-FG02-88ER 45355. TO was supported by the National Science Foundation during her 1993-94 stay at the Institute for Advanced Studies (Princeton) under grant DMS-9304580. The authors wish to acknowledge helpful discussion with Carol Nichols, John Hack, Gino Palumbo, Karl Aust, and Gary Was. It is well known that the properties and behavior of grain boundaries are strongly affected by local chemistry and atomic structure. This paper focuses on the mesoscale description of grain boundary structure (i.e. the five crystallographic degrees of freedom) and correlations with intergranular stress corrosion …

Theory, Science, And 'Micro-Macro' Bridges In Structural Social Psychology, Barry N. Markovsky

Faculty Publications

Social psychology stands to benefit from multilevel theories that link it to both lower and higher levels of analysis. Making the link, however, requires a level of theoretical rigor heretofore relatively uncommon in the social sciences. After refuting several common objections to this brand of theorizing, I offer a rationale and a set of criteria for multilevel theory construction.

Dynamics And Conformation Of Polymer Chains In A Porous Medium, Grace M. Foo, R.B. Pandey, D. Stauffer

Faculty Publications

No abstract provided.

On Tree-Partitions Of Graphs, Guoli Ding, Bogdan Oporowski

Faculty Publications

A graph G admits a tree-partition of width k if its vertex set can be partitioned into sets of size at most k so that the graph obtained by identifying the vertices in each set of the partition, and then deleting loops and parallel edges, is a forest. In the paper, we characterize the classes of graphs (finite and infinite) of bounded tree-partition-width in terms of excluded topological minors.

Rapidity Gaps Between Jets In Photoproduction At Hera, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, H. Zhang, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, R. Bruni, G. Cara Romeo, G. Castellini, M. Chiarini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, I. Gialas, R. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam, R. Nania, Margarita C. K. Mattingly

Faculty Publications

Photoproduction events which have two or more jets have been studied in the Wγp range 135 GeV < Wγp < 280 GeV with the ZEUS detector at HERA. A class of events is observed with little hadronic activity between the jets. The jets are separated by pseudorapidity intervals (Δη) of up to four units and have transverse energies greater than 6 GeV. A gap is defined as the absence between the jets of particles with transverse energy greater than 300 MeV. The fraction of events containing a gap is measured as a function of Δη. It decreases exponentially as expected for processes in which colour is exchanged between the jets, up to a value of Δη ∼ 3, then reaches a constant value of about 0.1. The excess above the exponential fall-off can be interpreted as evidence for hard diffractive scattering via a strongly interacting colour singlet object.

Towards A Loop Representation For Quantum Canonical Supergravity, Daniel Armand-Ugon, Rodolfo Gambini, Octavio Obregón, Jorge Pullin

Faculty Publications

We study several aspects of the canonical quantization of supergravity in terms of the Ashtekar variables. We cast the theory in terms of a GSU (2) connection and we introduce a loop representation. The solution space is similar to the loop representation of ordinary gravity, the main difference being the form of the Mandelstam identities. Physical states are in general given by knot invariants that are compatible with the GSU/(2) Mandelstam identities. There is an explicit solution to all the quantum constraint equations connected with the Chern-Simons form, which coincides exactly with the Dubrovnik version of the Kauffman polynomial. This …

A Note On Generators Of Least Degree In Gorenstein Ideals, Matthew Miller, Rafael H. Villarreal

Faculty Publications

No abstract provided.

Spectrum Generating Operators And Intertwining Operators For Representations Induced From A Maximal Parabolic Subgroup, Thomas Branson, Gestur Ólafsson, Bent Ørsted

Faculty Publications

We present a new method of calculating intertwining operators between principal series representations of semisimple Lie groups G. Working in the compact realization we find the eigenvalues of the operators on the K-types, and give several examples. Among the advantages of our method is its applicability to bundle-valued cases. © 1996 Academic Press, Inc.

Linear Programming With Inequality Constraints Via Entropic Perturbation, Jacob Tsao, Shu-Cherng Fang

Faculty Publications

A dual convex programming approach to solving linear programs with inequality constraints through entropic perturbation is derived. The amount of perturbation required depends on the desired accuracy of the optimum. The dual program contains only non-positivity constraints. An ϵ-optimal solution to the linear program can be obtained effortlessly from the optimal solution of the dual program. Since cross-entropy minimization subject to linear inequality constraints is a special case of the perturbed linear program, the duality result becomes readily applicable. Many standard constrained optimization techniques can be specialized to solve the dual program. Such specializations, made possible by the simplicity of …

A Simple Model For Nonequilibrium Fluctuations In A Fluid, Alejandro Garcia, F. Baras, M. Malek Mansour

Faculty Publications

Presents a train model that shows the long-range spatial correlations of fluctuations in nonequilibrium fluid systems. Illustration of model through analysis of flat-car trains running on parallel tracks; Simulation of train model in computers; Theoretical analysis for fluctuations in the train model; Relationship between train model and the fluctuating hydrodynamic theory of fluids.

Effects Of Wage Discrimination On Employment And Firm's Location, Yeung-Nan Shieh

Faculty Publications

No abstract provided.