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The Efficacy of Common Fit Indices for Enumerating Classes in Growth Mixture Models When Nested Data Structure is Ignored: A Monte Carlo Study

Description: This article investigates whether the correct number of classes can still be retrieved when a higher level of nesting in multilevel growth mixture model (MGMM) is ignored.
Date: March 30, 2017
Creator: Chen, Qi; Luo, Wen; Palardy, Gregory J.; Glaman, Ryan & McEnturff, Amber
Partner: UNT College of Education

Information Content of Iron Butterfly Arbitrage Bounds

Description: Informed traders trade options on underlying securities to lower transaction costs and increase financial leverage for price trend and variance strategies. Options markets play a significant role in price discovery by incorporating private information about future prices for an underlying security into option prices. I generate a new model-free volatility measure to calculate the "distance from arbitrage bounds" from minute-by-minute option series for the S&P 500 index and 30 individual underlying stocks. These iron butterfly arbitrage bounds (IBBs) use intraday call and put option prices from the Bloomberg database. Narrow and wide IBBs are expected to reveal the options market valuation of volatility by market participants. Data series is gathered by using successive one-minute intervals from the Bloomberg database. The data comprise the most recent bid and ask option prices and volumes. I collect S&P 500 index values and index options and use 30 underlying stock prices and option prices for the contracts that have the largest option trading volume during the sampling interval. These bid and ask prices reflect the information generated by intraday price pressures implied by S&P 500 index options or stock options. Consistent with the option micro-structure literature, I find that the IBB measure for actively traded stock options attains its highest level immediately after the open of the market, declines steadily throughout the first trading hour and remains relatively stable until market close. However, index IBBs behave differently. S&P 500 index option IBB attains its lowest level during the first hour of the trading day, then increases and remains relatively stable until market close. I present new evidence regarding the dynamic relation between stock returns and innovations in expected volatility by using the minute-by-minute change in implied volatility (IV) as a proxy. Unlike the relationship between individual stock returns and their respective changes in implied ...
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Date: December 2016
Creator: Kochan, Mucahit
Partner: UNT Libraries

Hydraulic Characteristics and Water-Supply Potential of the May 1975 Aquifers in the Vicinity of the Wastewater Treatment Plant, South Bend, Indiana

Description: Abstract: An intensive study was made of a 24-square mile (62-square kilometer) area surrounding the South Bend wastewater treatment plant to document the effects of dewatering about 40 feet (12 meter) of the 130-feet (40-meter) thick aquifer during construction at the plant, define the hydrologic system in order to allow development of a predictive model and select and evaluate one possible water-supply development plan as a model demonstration. Model-simulated water levels agree very well with those observed, both before and during dewatering. Model results indicate that the hydrologic system can sustain withdrawal of 28 million gallons per day (106,300 cubic meter per day) indefinitely with little effect on ground-water levels. The quantity that would be diverted from the St. Joseph River is less than 10 percent of the estimated minimum daily flow.
Date: May 1975
Creator: Marie, James R.
Partner: UNT Libraries Government Documents Department

Adaptation of the Minerals Management Service's Oil-Weathering Model for Use in the Gulf of Mexico Region

Description: The Minerals Management Service's open-ocean, oil-weathering model has been updated extensively for use on personal computers to determine what oil-weathering processes are wind and/or temperature dependent. Provides detailed user's instructions on how to use the model, examples demonstrating the model, and program listings.
Date: October 1992
Creator: Kirstein, Bruce E.
Partner: UNT Libraries Government Documents Department

A Theory of Teaching

Description: The problem with which this study is concerned is the development of a mathematical model and theory of teaching. The mathematical model consists of a set of abstract axioms. The fundamental elements or terms of the axioms are undefined. These primitive or undefined terms obtain their definitions only implicitly through the axioms.
Date: December 1971
Creator: Jenkins, Conley
Partner: UNT Libraries

The Biopsychosocial Approach to Understanding, Subtyping, and Treating Depression: Results from the National Comorbidity Survey - Replication.

Description: The most effective and useful way to diagnose and subtype depression has been a long debated topic which even now does not have a definite answer. The biopsychosocial approach to diagnosis may be a solution to this problem by linking various etiologies to symptom presentation. The biopsychosocial model, in regard to depression, takes into account biological risk factors/contributors, psychological or cognitive risk factors/contributors, and social risk factors/contributors to depression when making diagnosis and subtyping determinations. However, the most effective way to use this model in the assessment, diagnosis, and treatment of depression is not yet clear. In this study, the utility of the biopsychosocial model as an effective approach to conceptualizing and treating depression was assessed by testing hypotheses that showed that etiological contributors are related to the presence and differential presentation of depression, and that these etiologically-based subtypes of depression respond differently to different forms of treatment. These hypotheses were tested using data from the National Comorbidity Survey - Replication (NCS-R). Results showed that the biopsychosocial model can effectively predict the presence, severity and chronicity of depression, and may inform specific biopsychosocially-based subtypes. No conclusions could be drawn regarding success in treatment based on the biopsychosocial model. Future directions for research based on the current study are discussed.
Date: May 2011
Creator: McGill, Brittney C.
Partner: UNT Libraries

Notes on the construction and testing of model airplanes

Description: Here, it is shown that the construction of an airplane model can and should be simplified in order to obtain the most reliable test data. General requirements for model construction are given, keeping in mind that the general purpose of wind tunnel tests on a model airplane is to obtain the aerodynamic characteristics, the static balance, and the efficiency of controls for the particular combination of wings, tail surfaces, fuselage, and landing gear employed in the design. These parts must be exact scale reproductions. Any appreciable variation from scale reproduction must be in the remaining parts of the model, i.e., struts, wires, fittings, control horns, radiators, engines, and the various attachments found exposed to the wind in special airplanes. Interplane bracing is discussed in some detail.
Date: January 1922
Creator: Diehl, Walter S.
Partner: UNT Libraries Government Documents Department

Front-Tracking Model for Convective Transport in Flowing Ground Water

Description: Abstract: This report describes a finite-difference numerical model that simulates the convective transport of water or tracer particles through porous media. It can be applied to one- or two-dimensional problems involving either steady-state or transient flow. The model tracks representative water or tracer particles, initially located along specified lines, as they move in response to the ground-water velocity field. Aquifer properties may be both anisotropic and nonhomogeneous. Included in the report is a listing of the program along with input formats and test problem results. The front-tracking model provides a useful first approximation for determining the movement of solutes in an aquifer, particularly in cases where dispersion and dilution is of minor consideration.
Date: 1983
Creator: Garabedian, Stephen P. & Konikow, Leonard F.
Partner: UNT Libraries Government Documents Department

Method Rendering It Possible, in Testing Airplane Wing Models at the Eiffel Laboratory, to Obtain Comparable Polars, Whether the Supports Are Attached to the Upper or Lower Side of Model

Description: Report presenting an examination of the errors that result from testing an aircraft model and applying the results to full-sized airplanes. An investigation is carried out to determine how to obtain comparable polars regardless of whether the supports are attached to the upper or lower side of the model.
Date: November 1922
Creator: Eiffel, G.
Partner: UNT Libraries Government Documents Department

The Aerodynamic Characteristics of a Model Wing Having a Split Flap Deflected Downward and Moved to the Rear

Description: "Tests were made on a model wing with three different sized split trailing-edged flaps, in the NACA 7 by 10 foot wind tunnel. The flaps were formed of the lower rear portion of the wing and were rotated downward about axes at their front edges. The lift, drag, and center of pressure were measured with the axis in its original position and also with it moved back in even steps to the trailing edge of the main wing, giving in effect an increase in area. The split flaps when deflected about their original axis locations gave slightly higher maximum lift coefficients than conventional trailing-edge flaps, and the lift coefficients were increased still further by moving the axes toward the rear" (p. 1).
Date: May 1932
Creator: Weick, Fred E. & Harris, Thomas A.
Partner: UNT Libraries Government Documents Department

Some Aspects of the Comparison of Model and Full-Scale Tests

Description: This paper was delivered before the Royal Aeronautical Society as the 1925 Wilbur Wright Memorial lecture. It treats the subject of scale effect from the standpoint of the engineer rather than the physicist, in that it shows what compromises are necessary to secure satisfactory engineering model test data and how these test data compare with full scale or with theoretical values. The paper consists essentially of three parts: (1) a brief exposition of the theory of dynamic similarity, (2) application of the theory to airplane model tests, illustrated by test data on airfoils from the National Advisory Committee for Aeronautics variable-density wind tunnel, and (3) application of the theory to propeller testing, illustrated by comparisons of model and full-scale results.
Date: 1926
Creator: Taylor, D. W.
Partner: UNT Libraries Government Documents Department

An Application of the Rocket-Propelled-Model Technique to the Investigation of Low-Lift Buffeting and the Results of Preliminary Tests

Description: "The rocket-propelled-model technique has been applied to the investigation of low-lift buffeting. Results of preliminary tests show that severe buffeting, wing dropping, and normal-force changes occur almost simultaneously near zero lift over a Mach number range near 0.9 on unswept wings 12 percent thick. On unswept wings 7 percent thick, buffeting did not occur; however, mild wing dropping and normal-force changes were experienced" (p. 1).
Date: September 2, 1952
Creator: Mason, Homer P. & Gardner, William N.
Partner: UNT Libraries Government Documents Department

On a Pioneering Polymer Electrolyte Fuel Cell Model

Description: "Polymer Electrolyte Fuel Cell Model" is a seminal work that continues to form the basis for modern modeling efforts, especially models concerning the membrane and its behavior at the continuum level. The paper is complete with experimental data, modeling equations, model validation, and optimization scenarios. While the treatment of the underlying phenomena is limited to isothermal, single-phase conditions, and one-dimensional flow, it represents the key interactions within the membrane at the center of the PEFC. It focuses on analyzing the water balance within the cell and clearly demonstrates the complex interactions of water diffusion and electro-osmotic flux. Cell-level and system-level water balance are key to the development of efficient PEFCs going forward, particularly as researchers address the need to simplify humidification and recycle configurations while increasing the operating temperature of the stack to minimize radiator requirements.
Date: July 7, 2010
Creator: Weber, Adam Z. & Meyers, Jeremy P.
Partner: UNT Libraries Government Documents Department


Description: This project had goals of advancing the performance capabilities of the numerical general circulation model EULAG and using it to produce a fully operational atmospheric global climate model (AGCM) that can employ either static or dynamic grid stretching for targeted phenomena. The resulting AGCM combined EULAG's advanced dynamics core with the "physics" of the NCAR Community Atmospheric Model (CAM). Effort discussed below shows how we improved model performance and tested both EULAG and the coupled CAM-EULAG in several ways to demonstrate the grid stretching and ability to simulate very well a wide range of scales, that is, multi-scale capability. We leveraged our effort through interaction with an international EULAG community that has collectively developed new features and applications of EULAG, which we exploited for our own work summarized here. Overall, the work contributed to over 40 peer-reviewed publications and over 70 conference/workshop/seminar presentations, many of them invited. 3a. EULAG Advances EULAG is a non-hydrostatic, parallel computational model for all-scale geophysical flows. EULAG's name derives from its two computational options: EULerian (flux form) or semi-LAGrangian (advective form). The model combines nonoscillatory forward-in-time (NFT) numerical algorithms with a robust elliptic Krylov solver. A signature feature of EULAG is that it is formulated in generalized time-dependent curvilinear coordinates. In particular, this enables grid adaptivity. In total, these features give EULAG novel advantages over many existing dynamical cores. For EULAG itself, numerical advances included refining boundary conditions and filters for optimizing model performance in polar regions. We also added flexibility to the model's underlying formulation, allowing it to work with the pseudo-compressible equation set of Durran in addition to EULAG's standard anelastic formulation. Work in collaboration with others also extended the demonstrated range of validity of soundproof models, showing that they are more broadly applicable than some had previously thought. Substantial testing of EULAG ...
Date: May 8, 2012
Creator: Gutowski, William J.; Prusa, Joseph M. & Smolarkiewicz, Piotr K.
Partner: UNT Libraries Government Documents Department

Modeling and Diagnostics of Fuel Cell Porous Media for Improving Water Transport

Description: When a fuel cell is operating at high current density, water accumulation is a significant cause of performance and component degradation. Investigating the water transport inside the fuel cell is a challenging task due to opacity of the components, the randomness of the porous materials, and the difficulty in gain access to the interior for measurement due to the small dimensions of components. Numerical simulation can provide a good insight of the evolution of the water transport under different working condition. However, the validation of those simulations is remains an issue due the same experimental obstacles associated with in-situ measurements. The discussion herein will focus on pore-network modeling of the water transport on the PTL and the insights gained from simulations as well as in the validation technique. The implications of a recently published criterion to characterize PTL, based on percolation theory, and validate numerical simulation are discussed.
Date: July 1, 2011
Creator: Allen, Jeff & M'edici, Ezequiel
Partner: UNT Libraries Government Documents Department

Fracture Toughness Prediction for MWCNT Reinforced Ceramics

Description: This report describes the development of a micromechanics model to predict fracture toughness of multiwall carbon nanotube (MWCNT) reinforced ceramic composites to guide future experimental work for this project. The modeling work described in this report includes (i) prediction of elastic properties, (ii) development of a mechanistic damage model accounting for matrix cracking to predict the composite nonlinear stress/strain response to tensile loading to failure, and (iii) application of this damage model in a modified boundary layer (MBL) analysis using ABAQUS to predict fracture toughness and crack resistance behavior (R-curves) for ceramic materials containing MWCNTs at various volume fractions.
Date: September 1, 2013
Creator: Henager, Charles H. & Nguyen, Ba Nghiep
Partner: UNT Libraries Government Documents Department

Task 3: PNNL Visit by JAEA Researchers to Participate in TODAM Code Applications to Fukushima Rivers and to Evaluate the Feasibility of Adaptation of FLESCOT Code to Simulate Radionuclide Transport in the Pacific Ocean Coastal Water Around Fukushima

Description: Four JAEA researchers visited PNNL for two weeks in February, 2013 to learn the PNNL-developed, unsteady, one-dimensional, river model, TODAM and the PNNL-developed, time-dependent, three dimensional, coastal water model, FLESCOT. These codes predict sediment and contaminant concentrations by accounting sediment-radionuclide interactions, e.g., adsorption/desorption and transport-deposition-resuspension of sediment-sorbed radionuclides. The objective of the river and coastal water modeling is to simulate • 134Cs and 137Cs migration in Fukushima rivers and the coastal water, and • their accumulation in the river and ocean bed along the Fukushima coast. Forecasting the future cesium behavior in the river and coastal water under various scenarios would enable JAEA to assess the effectiveness of various on-land remediation activities and if required, possible river and coastal water clean-up operations to reduce the contamination of the river and coastal water, agricultural products, fish and other aquatic biota. PNNL presented the following during the JAEA visit to PNNL: • TODAM and FLESCOT’s theories and mathematical formulations • TODAM and FLESCOT model structures • Past TODAM and FLESCOT applications • Demonstrating these two codes' capabilities by applying them to simple hypothetical river and coastal water cases. • Initial application of TODAM to the Ukedo River in Fukushima and JAEA researchers' participation in its modeling. PNNL also presented the relevant topics relevant to Fukushima environmental assessment and remediation, including • PNNL molecular modeling and EMSL computer facilities • Cesium adsorption/desorption characteristics • Experiences of connecting molecular science research results to macro model applications to the environment • EMSL tour • Hanford Site road tour. PNNL and JAEA also developed future course of actions for joint research projects on the Fukushima environmental and remediation assessments.
Date: March 29, 2013
Creator: Onishi, Yasuo
Partner: UNT Libraries Government Documents Department

ab initio Solubility Prediction of Non-Electrolytes in Ternary Solvents Using a Combination of Jouyban-Acree and Abraham Models

Description: Article on the ab initio solubility prediction of non-electrolytes in ternary solvents using a combination of Jouyban-Acree and Abraham models.
Date: February 1, 2008
Creator: Jouyban, Abolghasem; Khoubnasabjafari, Maryam; Hamidi, Ali A. & Acree, William E. (William Eugene)
Partner: UNT College of Arts and Sciences

Flavor changing neutral currents and the third family

Description: We consider a Two Higgs Doublet Model with Flavor Changing Scalar Neutral Currents arising at the tree level. All the most important constraints are taken into account and the compatibility with the present Electroweak measurements is examined. The Flavor Changing couplings involving the third family are not constrained to be very small and this allows us to predict some interesting signals of new physics.
Date: September 16, 1996
Creator: Reina, L.
Partner: UNT Libraries Government Documents Department

Thermochemical investigations of crystalline solutes in non-electrolyte solutions: Mathematical representation of solubility data and the development of predictive solubility equations in systems with specific and non-specific interactions.

Description: Understanding the thermodynamic properties of multicomponent mixtures is of critical importance in many chemical and industrial applications. Experimental measurements become progressively difficult as the number of solution components increases -- producing the need for predictive models. Problems in development of predictive models arise if the mixture has one or more components that interact through molecular complexation or association. Experimental solubilities of anthracene and pyrene dissolved in binary systems containing one or more alcohols were measured in order to address this problem. Alcohols examined in this study were: 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 3-methyl-1-butanol, and 1-octanol. In binary solvent mixtures containing only a single self-associating alcoholic solvent, the alkane cosolvents studied were: n-hexane, n-heptane, n-octane, 2,2,4-trimethylpentane, cyclohexane, methylcyclohexane, tert-butylcyclohexane. Predictive solubility equations were developed using mobile order theory. This approach differs from classical solution models by representing hydrogen bonding with a probability term rather than with expressions derived from stepwise equilibria or expressions to represent hypothetical solution aggregates. Results were compared with the predicted solubilities found from using expressions developed using the Kretschmer-Wiebe and Mecke-Kempter approaches for modeling associated solutions. It was found that the mobile order approach provided reasonably accurate predictions for the solute solubilities in the systems studied. The limitations and applications for mathematical methods of representing experimental isothermal solubility data were also studied for 72 systems. Two possible descriptive forms for this mathematical representation were suggested based on the various nearly ideal binary solvent (NIBS) and modified Wilson models.
Date: May 2008
Creator: Zvaigzne, Anita Ilze
Partner: UNT Libraries