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An Exploration of the Titrating-Delay Match-to-Sample Procedure with Pigeons

Description: The delayed matching‐to‐sample (DMTS) procedure involves the insertion of a delay between the offset of a sample stimulus and the onset of an array of comparison stimuli; one of which is designated as the “correct” match for the sample on each trial. The procedure has served as the base preparation in which the effects of environmental variables on short‐term remembering and is, in many ways, responsible for a refined understanding of the phenomenon. Despite its utility, however, there are a few problems with the DMTS procedure – first, the procedure doesn’t adjust for individual differences and second, the conventional dependent measure, percent of correct trials, is not as sensitive as one might like. The titrating-delay matching to sample (TDMTS) procedure is a variant of the DMTS procedure in which the delays between sample and comparison are adjusted as a function of the subject’s performance. Stable measures of adjusted delay are not only sensitive measures of the performance of interest but they are also automatically tuned to differences across individuals. The study reported here continues our efforts to understand the dynamics of the TDMTS procedure so that it can be used to ask important questions related to short‐term remembering.
Date: December 2011
Creator: Friedel, Jonathan E.
Partner: UNT Libraries

Application of simple ramsauer model to neutron total cross sections

Description: The simple nuclear Ramsauer model has been used successfully to fit neutron cross sections for three decades, but has not been widely used because the foundations of the model seem to be so unrealistic. We have shown that the Glauber calculations with the inclusion of refraction and optical model calculations essentially validate this simple model for neutron total cross sections in the neutron energy range of 5-50 MeV. This model yields a simple formula for parameterizing the energy dependence of the neutron cross section. We have applied the model to nuclei ranging from vanadium to bismuth. With the addition of a single parameter, we can improve these fits to less than 1.5%.
Date: April 29, 1997
Creator: Bauer, R.W.; Anderson, J.D.; Grimes, S.M. & Madsen, V.A.
Partner: UNT Libraries Government Documents Department

Parameterization of hysteresis effects in accumulator quadrupole magnets

Description: The hysteresis curves of two Accumulator sample magnets have been measured, one large quadrupole and one small quadrupole. Based upon these measurements, a parameterization of hysteresis effects is deduced and generalized to other magnets. The goal is to incorporate the best knowledge of the magnets we have into the Accumulator model, on which lattice measurements are based and which is used to calculate an accurate first guess at the E-835 deceleration tables. Since a well-defined sequence of current cycles is performed during Accumulator operations, some simplifying hypotheses can be applied.
Date: November 3, 1999
Creator: Stancari, Giulio
Partner: UNT Libraries Government Documents Department

A Monte Carlo Study of the Robustness and Power of Analysis of Covariance Using Rank Transformation to Violation of Normality with Restricted Score Ranges for Selected Group Sizes

Description: The study seeks to determine the robustness and power of parametric analysis of covariance and analysis of covariance using rank transformation to violation of the assumption of normality. The study employs a Monte Carlo simulation procedure with varying conditions of population distribution, group size, equality of group size, scale length, regression slope, and Y-intercept. The procedure was performed on raw data and ranked data with untied ranks and tied ranks.
Date: December 1984
Creator: Wongla, Ruangdet
Partner: UNT Libraries

Influence of the deuteron energy on the testing volume of IFMIF and its impact on other parameters

Description: The influence of the energy of the deuteron beam on irradiation parameters of IFMIF is analyzed. The main purpose of this paper is to identify possible positive and negative impacts on irradiation parameters that an increase in the deuteron energy of the beam can cause. Several parameters of the facility, such as neutron generation rate, number of neutrons with energy above 20 MeV at the source and in the test assembly, volume with dpa rate above a threshold value, gas production, and gradient of the atomic displacement rate, are analyzed and conclusions are drawn based on the calculated values. It is shown that an increase in the deuteron energy to 40 MeV does not produce a significant negative impact for the elements analyzed, but instead is beneficial in producing nuclear responses more similar to a fusion environment than the lower deuteron energies.
Date: September 1, 1995
Creator: Gomes, I.C. & Smith, D.L.
Partner: UNT Libraries Government Documents Department

Consideration on Isochronal Anneal Technique: From Measurement to Physics

Description: The isochronal anneal technique used to predict isothermal anneal behavior of MOS devices is analyzed as a function of experimental parameters. The effects of detrapping of trapped holes and compensating electrons are discussed.
Date: March 9, 1999
Creator: Flament, O.; Fleetwood, D.M.; Leray, J.L. & Paillet, P.
Partner: UNT Libraries Government Documents Department

Deep convection in the Arctic: The evaluation of results from an OGCM with a new convection parameterization

Description: The current generation of ocean general circulation models (OGCMS) uses a convective adjustment scheme to remove static instabilities and to parameterize shallow and deep convection. In simulations used to examine climate-related scenarios, investigators found that in the Arctic regions, the OGCM simulations did not produce a realistic vertical density structure, did not create the correct quantity of deep water, and did not use a time-scale of adjustment that is in agreement with tracer ages or observations. A possible weakness of the models is that the convective adjustment scheme does not represent the process of deep convection adequately. Consequently, a penetrative plume mixing scheme has been developed to parameterize the process of deep open-ocean convection in OGCMS. This new deep convection parameterization was incorporated into the Semtner and Chervin (1988) OGCM. The modified model (with the new parameterization) was run in a simplified Nordic Seas test basin: under a cyclonic wind stress and cooling, stratification of the basin-scale gyre is eroded and deep mixing occurs in the center of the gyre. In contrast, in the OGCM experiment that uses the standard convective adjustment algorithm, mixing is delayed and is wide-spread over the gyre.
Date: January 1, 1995
Creator: Paluszkiewicz, T.; Hibler, L.F. & Romea, R.D.
Partner: UNT Libraries Government Documents Department

Resolving kinematic redundancy with constraints using the FSP (Full Space Parameterization) approach

Description: A solution method is presented for the motion planning and control of kinematically redundant serial-link manipulators in the presence of motion constraints such as joint limits or obstacles. Given a trajectory for the end-effector, the approach utilizes the recently proposed Full Space Parameterization (FSP) method to generate a parameterized expression for the entire space of solutions of the unconstrained system. At each time step, a constrained optimization technique is then used to analytically find the specific joint motion solution that satisfies the desired task objective and all the constraints active during the time step. The method is applicable to systems operating in a priori known environments or in unknown environments with sensor-based obstacle detection. The derivation of the analytical solution is first presented for a general type of kinematic constraint and is then applied to the problem of motion planning for redundant manipulators with joint limits and obstacle avoidance. Sample results using planar and 3-D manipulators with various degrees of redundancy are presented to illustrate the efficiency and wide applicability of constrained motion planning using the FSP approach.
Date: February 1996
Creator: Pin, F.G. & Tulloch, F.A.
Partner: UNT Libraries Government Documents Department

Polarization and charge limit studies of strained GaAs photocathodes

Description: This thesis presents studies on the polarization and charge limit behavior of electron beams produced by strained GaAs photocathodes. These photocathodes are the source of high-intensity, high-polarization electron beams used for a variety of high-energy physics experiments at the Stanford Linear Accelerator Center. Recent developments on P-type, biaxially-strained GaAs photocathodes have produced longitudinal polarization in excess of 80% while yielding beam intensities of {approximately} 2.5 A/cm{sup 2} at an operating voltage of 120 kV. The SLAC Gun Test Laboratory, which has a replica of the SLAC injector, was upgraded with a Mott polarimeter to study the polarization properties of photocathodes operating in a high-voltage DC gun. Both the maximum beam polarization and the maximum charge obtainable from these photocathodes have shown a strong dependence on the wavelength of illumination, on the doping concentration, and on the negative electron affinity levels. The experiments performed for this thesis included studying the effects of temperature, cesiation, quantum efficiency, and laser intensity on the polarization of high-intensity beams. It was found that, although low temperatures have been shown to reduce the spin relaxation rate in bulk semiconductors, they don`t have a large impact on the polarization of thin photocathodes. It seems that the short active region in thin photocathodes does not allow spin relaxation mechanisms enough time to cause depolarization. Previous observations that lower QE areas on the photocathode yield higher polarization beams were confirmed. In addition, high-intensity, small-area laser pulses were shown to produce lower polarization beams. Based on these results, together with some findings in the existing literature, a new proposal for a high-intensity, high-polarization photocathode is given. It is hoped that the results of this thesis will promote further investigation on the properties of GaAs photocathodes.
Date: March 1, 1997
Creator: Saez, P.J.
Partner: UNT Libraries Government Documents Department

Revised lattice for the APS storage ring

Description: As a result of more detailed engineering studies of vacuum chamber components and related accelerator physics studies, the circumference of the APS storage ring is increased by 44 m to a value of 1104 m. The increase is 1.1 m for each of the 40 sectors. The insertion region straight section is lengthened by 0.52 m to 6.72 m. This allows full 20-cm vacuum chamber transition sections leading into and out of the 5.2-m insertion devices. Computer studies using TBCI and MAFIA-T3 have indicated that 20-cm-long transition regions reduce the transverse coupling impedance to an Acceptable low value. The results for 10-cm transition length were marginal.
Date: August 1, 1989
Creator: Crosbie, E.A.
Partner: UNT Libraries Government Documents Department

Analysis of thomsen parameters for finely layered VTI media

Description: The range of Thomsen`s anisotropy parameters {epsilon} and {delta} for vertical transversely isotropic (VTI) media when the anisotropy is due to fine layering of isotropic elas-tic materials is considered. We show that {epsilon} lies in the range -3/8 {<=} {epsilon} {<=} {1/2}[<v{sub p}{sup 2}><v{sup p}{sup -2}>-1], for finely lay-ered media having constant density; smaller positive and all negative values of {epsilon} occur for media with large fluctuations in the Lam{acute e} parameter {lambda} We show that sign({delta}) = sign (<v{sub p}{sup -2}> - <v{sub s}{sup -2}><v{sub s}{sup 2}/v{sub p}{sup 2}>) for constant density media, so {delta} can be either positive or negative. Among all theoretically possible random media, posi-tive and negative {delta} are equally likely in finely layered media limited to two types of constituent layers. Lay-ered media having large fluctuations in Lam{acute e} {lambda} are the ones most likely to have positive {delta}. Since Gassmann`s results for fluid-saturated porous media show that the effects of fluids influence only the {lambda} Lam{acute e} constant, not the shear modulus {mu}, these results suggest that positive {delta} occurring together with positive but small {epsilon} may be indicative of changing fluid content in layered earth.
Date: April 1, 1997
Creator: Berryman, J.G. & Berge, P.A.
Partner: UNT Libraries Government Documents Department

Spent nuclear fuel project design basis capacity study

Description: A parametric study of the Spent Nuclear Fuel Project system capacity is presented. The study was completed using a commercially available software package to develop a summary level model of the major project systems. A base case, reflecting the Fiscal Year 1998 process configuration, is evaluated. Parametric evaluations are also considered, investigating the impact of higher fuel retrieval system productivity and reduced shift operations at the canister storage building on total project duration.
Date: July 22, 1998
Creator: Cleveland, K.J.
Partner: UNT Libraries Government Documents Department

Use of a dynamic subgrid-scale model for large-eddy simulation of the planetary boundary layer

Description: Large-eddy simulation (LES) of the planetary boundary layer (PBL) is very sensitive to the subgrid-scale (SGS) model used when the strength of SGS motions begins to approach that of the resolved motions. This can typically occur near the ground and in strongly stable or sheared conditions. The underlying algebraic relations of Germano and least-squares local evaluation of dynamic parameters used in many dynamic SGS models require that the flow field be adequately resolved. This requirement is met throughout most of the PBL, but difficulty arises near the ground under non-convective conditions where energy-containing eddies are resolved, constrained in size due to the presence of a solid boundary. Adding grid resolution near the ground is an obvious approach, which is tried in this study. A more computationally efficient alternative is to include a parameterization that achieves a better match between the LES fields and similarity in the surface layer.
Date: May 1, 1997
Creator: Cederwall, R.T. & Street, R.L.
Partner: UNT Libraries Government Documents Department

Explicit simulation and parameterization of mesoscale convective systems. Final report, November 1, 1993--April 30, 1997

Description: This research has focused on the development of a parameterization scheme for mesoscale convective systems (MCSs), to be used in numerical weather prediction models with grid spacing too coarse to explicitly simulate such systems. This is an extension to cumulus parameterization schemes, which have long been used to account for the unresolved effects of convection in numerical models. Although MCSs generally require an extended sequence of numerous deep convective cells in order to develop into their characteristic sizes and to persist for their typical durations, their effects on the large scale environment are significantly different than that due to the collective effects of numerous ordinary deep convective cells. These differences are largely due to a large stratiform cloud that develops fairly early in the MCS life-cycle, where mesoscale circulations and dynamics interact with the environment in ways that call for a distinct MCS parameterization. Comparing an MCS and a collection of deep convection that ingests the same amount of boundary layer air and moisture over an extended several hour period, the MCS will generally generates more stratiform rainfall, produce longer-lasting and optically thicker cirrus, and result in different vertical distributions of large-scale tendencies due to latent heating and moistening, momentum transfers, and radiational heating.
Date: August 12, 1997
Creator: Cotton, W.R.
Partner: UNT Libraries Government Documents Department

Inverse modeling of a multistep outflow experiment fordetermining hysteretic hydraulic properties

Description: A new, closed-form hysteretic model of the capillary pressure-saturation and relative permeability-saturation relationship has been implemented into ITOUGH2. The hysteretic capillary pressure function is based on the van Genuchten model, with a modified version of the dependent domain model of Mualem to describe the scanning curves. Hysteresis in the relative permeability relations is considered to be mainly a result of nonwetting fluid entrap- ment. The hysteresis model was used in combination with inverse modeling techniques to examine the potential of a simple drainage- imbibition experiment to determine hysteretic hydraulic properties.
Date: May 1, 1998
Creator: Faybishenko, B.; Finsterle, S. & Sonnenborg, T.O.
Partner: UNT Libraries Government Documents Department

Selective, deep Si trench etching with dimensional control

Description: The recent development of a high-aspect ratio Si etch (HARSE) process has enabled the fabrication of a variety of Si structures where deep trench etching is necessary. The HARSE process relies on the formation of a sidewall etch inhibitor to prevent lateral etching of the Si structures during exposure to an aggressive SF{sub 6}/Ar plasma etch chemistry. The process yields highly anisotropic profiles with excellent dimensional control for high aspect ratio features. In this study, Si etch rates and etch selectivities to photoresist are reported as a function of chamber pressure, cathode rf-power, ICP source power, and gas flow. Si etch rates > 3 {micro}m/min with etch selectivities to resist > 75:1 were obtained. Lateral dimensional control, etch selectivities to SiO{sub 2} and Si{sub 3}N{sub 4}, and aspect ratio dependent etching (ARDE) will also be discussed.
Date: August 1, 1998
Creator: Shul, R.J.; Willison, C.G. & Zhang, L.
Partner: UNT Libraries Government Documents Department

QA lessons learned for parameter control from the WIPP Project

Description: This paper provides a summary of lessons learned from experiences on the Waste Isolation Pilot Plant (WJPP) Project in implementation of quality assurance controls surrounding inputs for performance assessment analysis. Since the performance assessment (PA) process is inherent in compliance determination for any waste repository, these lessons-learned are intended to be useful to investigators, analysts, and Quality Assurance (QA) practitioners working on high level waste disposal projects. On the WIPP Project, PA analyses for regulatory-compliance determination utilized several inter-related computer programs (codes) that mathematically modeled phenomena such as radionuclide release, retardation, and transport. The input information for those codes are the parameters that are the subject of this paper. Parameters were maintained in a computer database, which was then queried electronically by the PA codes whenever input was needed as the analyses were run.
Date: January 1, 1998
Creator: Richards, R.R.
Partner: UNT Libraries Government Documents Department


Description: A comprehensive benchmark program was developed by Brookhaven National Laboratory (BNL) to perform an evaluation of state-of-the-art methods and computer programs for performing seismic analyses of coupled systems with non-classical damping. The program, which was sponsored by the US Nuclear Regulatory Commission (NRC), was designed to address various aspects of application and limitations of these state-of-the-art analysis methods to typical coupled nuclear power plant (NPP) structures with non-classical damping, and was carried out through analyses of a set of representative benchmark problems. One objective was to examine the applicability of various analysis methods to problems with different dynamic characteristics unique to coupled systems. The examination was performed using parametric variations for three simple benchmark models. This paper presents the comparisons and evaluation of the program participants' results to the BNL exact solutions for the applicable ranges of modeling dynamic characteristic parameters.
Date: April 2, 2000
Creator: XU,J. & DEGRASSI,G.
Partner: UNT Libraries Government Documents Department

Low damage, highly anisotropic dry etching of SiC

Description: A parametric study of the etching characteristics of 6H p{sup +} and n{sup +} SiC and thin film SiC{sub 0.5}N{sub 0.5} in Inductively Coupled Plasma NF{sub 3}/O{sub 2} and NF{sub 3}/Ar discharges has been performed. The etch rates in both chemistries increase monotonically with NF{sub 3} percentage and rf chuck power. The etch rates go through a maximum with increasing ICP source power, which is explained by a trade-off between the increasing ion flux and the decreasing ion energy. The anisotropy of the etched features is also a function of ion flux, ion energy and atomic fluorine neutral concentration. Indium-tin-oxide (ITO) masks display relatively good etch selectivity over SiC (maximum of {approximately} 70:1), while photoresist etches more rapidly than SiC. The surface roughness of SiC is essentially independent of plasma composition for NF3/O2 discharges, while extensive surface degradation occurs for SiCN under high NF{sub 3}:O{sub 2} conditions.
Date: March 1, 1998
Creator: Wang, J. J.; Hong, J.; Lambers, E. S.; Pearton, S. J.; Ren, F.; Ostling, M. et al.
Partner: UNT Libraries Government Documents Department

Rate of Pu(IV) polymer formation in nitric acid solutions. A parametric study

Description: The kinetics of Pu(IV) polymer formation has been examined with the intent of developing a simple mathematical equation that would predict the appearance of polymer. The fundamental polymerization rate has been found to be dependent on [Pu(IV)]{sup 1} {sup 2} and [HNO{sub 3}]{sup -6}. The activation energy for polymer formation is real temperature dependent, varying from 66.9 kJ/mol (16 kcal/mol) at 25{sup 0}C to 150.5 kJ/mol (36 kcal/mol) at 105{sup 0}C. These relationships have guided the developement of an empirical model that gives time to form 2% polymer in hours, t = [Pu/sub T/]/sup a/[HNO{sub 3}]/sup b/ Ae/sup c/T/, where a = -1.6, b = 4.6, c = 12.300 K, and A = 7.66 x 10{sup -16} h M{sup -3}; [Pu/sub T/] is the total plutonium concentration, mol/L; and [HNO{sub 3}] is the makeup nitric acid concentration, mol/L. 11 references, 26 figures, 1 table.
Date: July 1, 1984
Creator: Toth, L.M. & Osborne, M.M.
Partner: UNT Libraries Government Documents Department


Description: This research presents a new method to improve analytical model fidelity for non-linear systems. The approach investigates several mechanisms to assist the analyst in updating an analytical model based on experimental data and statistical analysis of parameter effects. The first is a new approach at data reduction called feature extraction. This is an expansion of the update metrics to include specific phenomena or character of the response that is critical to model application. This is an extension of the classical linear updating paradigm of utilizing the eigen-parameters or FRFs to include such devices as peak acceleration, time of arrival or standard deviation of model error. The next expansion of the updating process is the inclusion of statistical based parameter analysis to quantify the effects of uncertain or significant effect parameters in the construction of a meta-model. This provides indicators of the statistical variation associated with parameters as well as confidence intervals on the coefficients of the resulting meta-model, Also included in this method is the investigation of linear parameter effect screening using a partial factorial variable array for simulation. This is intended to aid the analyst in eliminating from the investigation the parameters that do not have a significant variation effect on the feature metric, Finally an investigation of the model to replicate the measured response variation is examined.
Date: October 1, 2000
Creator: Schultz, J.F. & Hemez, F.M.
Partner: UNT Libraries Government Documents Department

Effect of Mo on pitting corrosion of ferritic steels in bromide and chloride solutions

Description: A model for pitting corrosion of stainless steels, independent of changes of passive film properties, was tested using Fe-18%Cr-x%Mo alloys in bromide and chlorine solutions. In 1M LiCl the pitting potential improved from {minus}50 mV{sub sce} to about 1200 mV{sub sce} on increasing Mo from 2% to 10%. In 1M LiBr the pitting potential increased from 125 to only 560 mV{sub sce}. Active dissolution kinetics of these steels in saturated solutions in a simulated pit were measured. Tafel lines for dissolution moved to more noble potentials with increases in Mo, indicating Mo inhibited dissolution rates. The potential increases were found to be equal to the increases in pitting potential for both halides. Agreement was interpreted in terms maintaining high halide concentrations in the pit by high rates of active metal dissolution. Bromide was less effective suggesting it interacted with Mo adsorbed on the dissolving surface.
Date: December 1, 1997
Creator: Kaneko, M. & Isaacs, H.S.
Partner: UNT Libraries Government Documents Department