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The Use of Evidence-based Practices in the Provision of Social Skills Training for Students with Autism Spectrum Disorders: a National Survey of School Psychologists' Training, Attitudes, and Practices
The purpose of this exploratory study was to examine school psychologists' use of evidence- based practices (EBP), in general, and more specifically in the area of social skills training (SST) for students with autism spectrum disorders (ASD). Study participants, consisting of 498 school psychologists from across the nation, participated in an online survey that gathered information about their training, attitudes, and practices. The frequency with which specific EBP practices for social skills training for students with ASD was examined, as was prediction of use of these practices. Multiple-regression analyses revealed multiple independent variables that were predictors for overall use of EBP. Results indicated that over half of the participants provide SST for students with ASD. Although the majority of participants indicated that their graduate program included at least one course with information about ASD and EBP practices, in general, nearly half indicated that their coursework did not include any courses that directly addressed social skills training for students with ASD. Confirmatory factor analysis (CFA) was used to determine the extent to which the data fit the factor model. Participants' perception of the importance placed on EBP by their school district, scores on the openness subscale of the Evidence Based Practices …
Date:
August 2011
Creator:
Austin, Jennifer E.
System:
The UNT Digital Library
TRISO Fuel Performance: Modeling, Integration into Mainstream Design Studies, and Application to a Thorium-fueled Fusion-Fission Hybrid Blanket
This study focused on creating a new tristructural isotropic (TRISO) coated particle fuel performance model and demonstrating the integration of this model into an existing system of neutronics and heat transfer codes, creating a user-friendly option for including fuel performance analysis within system design optimization and system-level trade-off studies. The end product enables both a deeper understanding and better overall system performance of nuclear energy systems limited or greatly impacted by TRISO fuel performance. A thorium-fueled hybrid fusion-fission Laser Inertial Fusion Energy (LIFE) blanket design was used for illustrating the application of this new capability and demonstrated both the importance of integrating fuel performance calculations into mainstream design studies and the impact that this new integrated analysis had on system-level design decisions. A new TRISO fuel performance model named TRIUNE was developed and verified and validated during this work with a novel methodology established for simulating the actual lifetime of a TRISO particle during repeated passes through a pebble bed. In addition, integrated self-consistent calculations were performed for neutronics depletion analysis, heat transfer calculations, and then fuel performance modeling for a full parametric study that encompassed over 80 different design options that went through all three phases of analysis. Lastly, …
Date:
November 28, 2011
Creator:
Powers, J J
System:
The UNT Digital Library
Target Visualization at the National Ignition Facility
As the National Ignition Facility continues its campaign to achieve ignition, new methods and tools will be required to measure the quality of the targets used to achieve this goal. Techniques have been developed to measure target surface features using a phase-shifting diffraction interferometer and Leica Microsystems confocal microscope. Using these techniques we are able to produce a detailed view of the shell surface, which in turn allows us to refine target manufacturing and cleaning processes. However, the volume of data produced limits the methods by which this data can be effectively viewed by a user. This paper introduces an image-based visualization system for data exploration of target shells at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory. It aims to combine multiple image sets into a single visualization to provide a method of navigating the data in ways that are not possible with existing tools.
Date:
November 21, 2011
Creator:
Potter, D
System:
The UNT Digital Library
A measurement of neutrino oscillations with muon neutrinos in the MINOS experiment
Experimental evidence has established that neutrino flavor states evolve over time. A neutrino of a particular flavor that travels some distance can be detected in a different neutrino flavor state. The Main Injector Neutrino Oscillation Search (MINOS) is a long-baseline experiment that is designed to study this phenomenon, called neutrino oscillations. MINOS is based at Fermilab near Chicago, IL, and consists of two detectors: the Near Detector located at Fermilab, and the Far Detector, which is located in an old iron mine in Soudan, MN. Both detectors are exposed to a beam of muon neutrinos from the NuMI beamline, and MINOS measures the fraction of muon neutrinos that disappear after traveling the 734 km between the two detectors. One can measure the atmospheric neutrino mass splitting and mixing angle by observing the energy-dependence of this muon neutrino disappearance. MINOS has made several prior measurements of these parameters. Here I describe recently-developed techniques used to enhance our sensitivity to the oscillation parameters, and I present the results obtained when they are applied to a dataset that is twice as large as has been previously analyzed. We measure the mass splitting {Delta}m{sub 23}{sup 2} = (2.32{sub -0.08}{sup +0.12}) x 10{sup -3} eV{sup …
Date:
January 1, 2011
Creator:
Coleman, Stephen James & Coll., /William-Mary
System:
The UNT Digital Library
Suppressed Charmed B Decay
This thesis describes the measurement of the branching fractions of the suppressed charmed B{sup 0} {yields} D{sup (*)-} a{sub 0}{sup +} decays and the non-resonant B{sup 0} {yields} D{sup (*)-} {eta}{pi}{sup +} decays in approximately 230 million {Upsilon}(4S) {yields} B{bar B} events. The data have been collected with the BABAR detector at the PEP-II B factory at the Stanford Linear Accelerator Center in California. Theoretical predictions of the branching fraction of the B{sup 0} {yields} D{sup (*)-} a{sub 0}{sup +} decays show large QCD model dependent uncertainties. Non-factorizing terms, in the naive factorization model, that can be calculated by QCD factorizing models have a large impact on the branching fraction of these decay modes. The predictions of the branching fractions are of the order of 10{sup -6}. The measurement of the branching fraction gives more insight into the theoretical models. In general a better understanding of QCD models will be necessary to conduct weak interaction physics at the next level. The presence of CP violation in electroweak interactions allows the differentiation between matter and antimatter in the laws of physics. In the Standard Model, CP violation is incorporated in the CKM matrix that describes the weak interaction between quarks. Relations …
Date:
November 28, 2011
Creator:
Snoek, Hella Leonie & /Vrije U., Amsterdam
System:
The UNT Digital Library
Studies of the structure and function of Mms6, a bacterial protein that promotes the formation of magnetic nanoparticles
Here we report structural and functional studies of Mms6, a biomineralization protein that can promote the formation in vitro of magnetic nanoparticles with sizes and morphologies similar to the magnetites synthesized by magnetotactic bacteria. We found the binding pattern of Mms6 to ferric ion to be two-phase and multivalent. We quantatively determined that Mms6 binds one Fe{sup 3+} with a very high affinity (K{sub d} = 10{sup -16} M). The second phase of iron binding is multivalent and cooperative with respect to iron with a K{sub d} in the {mu}M range and a stoichiometry of about 20 ferric ion per protein molecule. We found that Mms6 exists in large particles of two sizes, one consisting of 20-40 monomeric units and the other of 200 units. From proteolytic digestion, ultracentrifugation and liposome fusion studies, we found that Mms6 forms a large micellar quaternary structure with the N-terminal domain self-assembling into a uniformly sized micelle and the C-terminal domain on the surface. The two-phase iron-binding pattern may be relevant to iron crystal formation. We propose that the first high affinity phase may stabilize a new conformation of the C-terminal domain that allows interaction with other C-terminal domains leading to a structural change …
Date:
May 15, 2011
Creator:
Wang, Lijun
System:
The UNT Digital Library
Mesoporous silica nanoparticles as smart and safe devices for regulating blood biomolecule levels
Stimuli-responsive end-capped MSN materials are promising drug carriers that securely deliver a large payload of drug molecules without degradation or premature release. A general review of the recent progress in this field is presented, including a summary of a series of hard and soft caps for drug encapsulation and a variety of internal and external stimuli for controlled release of different therapeutics, a discussion of the biocompatibility of MSN both in vitro and in vivo, and a description of the sophisticated stimuli-responsive systems with novel capping agents and controlled release mechanism. The unique internal and external surfaces of MSN were utilized for the development of a glucose-responsive double delivery system end-capped with insulin. This unique system consists of functionalized MSNs capable of releasing insulin when the concentration of sugar in blood exceeds healthy levels. The insulin-free nanoparticles are then up taken by pancreatic cells, and release inside of them another biomolecule that stimulates the production of more insulin. The in vivo application of this system for the treatment of diabetes requires further understanding on the biological behaviors of these nanoparticles in blood vessels. The research presented in this dissertation demonstrated the size and surface effects on the interaction of MSNs …
Date:
May 15, 2011
Creator:
Zhao, Yan
System:
The UNT Digital Library
Search for heavy metastable particles decaying to quark pairs at CDF
We report on the search for heavy metastable particles that decay into quark pairs with a macroscopic lifetime (c{tau} {approx} 1 cm) using data taken with the CDF II detector at Fermilab. We use a data driven background approach, where they build probability density functions to model Standard Model secondary vertices from known processes in order to estimate the background contribution from the Standard Model. No statistically significant excess is observed above the background. Limits on the production cross section in a Hidden Valley benchmark phenomenology are set for various Higgs boson masses as well as metastable particle masses and lifetimes.
Date:
March 1, 2011
Creator:
Kwang, Shawn Andrew
System:
The UNT Digital Library
Study of the production of the sigma b*+- with the CDF detector at the Tevatron
The composition of matter is a topic in which the man has been interested throughout History. Since the introduction of the atom by Democritus in the 5th century BC until the establishment of the Standard Model, our successful theory that contains our current knowledge on the matter and their interactions, it has come a long way trying to solve this fundamental question. The efforts of many of the greatest minds to perform crucial experiments and develop theoretical models have helped to get deeper insight into the origin of the matter. Today we know that indivisible atoms postulated by Democritus are no longer true, and they are actually composed of a nucleus made of protons and neutrons (nucleons) with orbiting electrons through electromagnetic interactions. Also the nucleons are not fundamental particles but are composed of more fundamental ones called quarks. According to the present state of our knowledge, matter is composed of two types of particles: quarks and leptons. Leptons are believed to be fundamental particles and can occur freely in nature. Quarks are also fundamental particles, and there are no free in nature, but are confined to form hadrons. The hadrons may consist of a quark and an antiquark (mesons) …
Date:
February 1, 2011
Creator:
Calancha Paredes, Constantino & /Madrid, CIEMAT /Madrid U.
System:
The UNT Digital Library
Organic Light-Emitting Diodes (OLEDs) and Optically-Detected Magnetic Resonance (ODMR) studies on organic materials
Organic semiconductors have evolved rapidly over the last decades and currently are considered as the next-generation technology for many applications, such as organic light-emitting diodes (OLEDs) in flat-panel displays (FPDs) and solid state lighting (SSL), and organic solar cells (OSCs) in clean renewable energy. This dissertation focuses mainly on OLEDs. Although the commercialization of the OLED technology in FPDs is growing and appears to be just around the corner for SSL, there are still several key issues that need to be addressed: (1) the cost of OLEDs is very high, largely due to the costly current manufacturing process; (2) the efficiency of OLEDs needs to be improved. This is vital to the success of OLEDs in the FPD and SSL industries; (3) the lifetime of OLEDs, especially blue OLEDs, is the biggest technical challenge. All these issues raise the demand for new organic materials, new device structures, and continued lower-cost fabrication methods. In an attempt to address these issues, we used solution-processing methods to fabricate highly efficient small molecule OLEDs (SMOLEDs); this approach is costeffective in comparison to the more common thermal vacuum evaporation. We also successfully made efficient indium tin oxide (ITO)-free SMOLEDs to further improve the efficiency of …
Date:
November 30, 2011
Creator:
Cai, Min
System:
The UNT Digital Library
Search for the Standard Model Higgs Boson in Missing Transverse Energy and $b$-quark Final States Using Proton-Antiproton Collisions at 1.96 TeV
A search for the standard model Higgs boson is performed in 6.4 fb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV, collected with the D0 detector during Run II of the Fermilab Tevatron. The final state considered is a pair of jets originating from b quarks and missing transverse energy, as expected from p{bar p} {yields} ZH {yields} {nu}{bar {nu}}b{bar b} production. The search is also sensitive to the WH {yields} {ell}{nu}b{bar b} channel, where the charged lepton is not identified. Boosted decision trees are used to discriminate signal from background. Good agreement is observed between data and expected backgrounds, and a limit is set at 95% C.L. on the section multiplied by branching fraction of (p{bar p} {yields} (Z/W)H) x (H {yields} b{bar b}). For a Higgs boson mass of 115 GeV, the observed limit is a factor of 3.5 larger than the value expected from the standard model.
Date:
March 1, 2011
Creator:
Dorland, Tyler M. & /Washington U., Seattle
System:
The UNT Digital Library
Antineutrino Oscillations in the Atmospheric Sector
This thesis presents measurements of the oscillations of muon antineutrinos in the atmospheric sector, where world knowledge of antineutrino oscillations lags well behind the knowledge of neutrinos, as well as a search for {nu}{sub {mu}} {yields} {bar {nu}}{sub {mu}} transitions. Differences between neutrino and antineutrino oscillations could be a sign of physics beyond the Standard Model, including non-standard matter interactions or the violation of CPT symmetry. These measurements leverage the sign-selecting capabilities of the magnetized steel-scintillator MINOS detectors to analyze antineutrinos from the NuMI beam, both when it is in neutrino-mode and when it is in antineutrino-mode. Antineutrino oscillations are observed at |{Delta}{bar m}{sub atm}{sup 2}| = (3.36{sub -0.40}{sup +0.46}(stat) {+-} 0.06(syst)) x 10{sup -3} eV{sup 2} and sin{sup 2}(2{bar {theta}}{sub 23}) = 0.860{sub -0.12}{sup +0.11}(stat) {+-} 0.01(syst). The oscillation parameters measured for antineutrinos and those measured by MINOS for neutrinos differ by a large enough margin that the chance of obtaining two values as discrepant as those observed is only 2%, assuming the two measurements arise from the same underlying mechanism, with the same parameter values. No evidence is seen for neutrino-to-antineutrino transitions.
Date:
May 1, 2011
Creator:
Himmel, Alexander I. & /Caltech
System:
The UNT Digital Library
Measurement of CP Violation in B Anti-B Mixing on the Recoil of Partially Reconstructed Anti-B0 to D* L- Anti-Nu/L Using Kaon Tags
After its formulation in 1960's the Standard Model of Fundamental Interactions has gone through an impressive series of successes, begun with the discovery of neutral weak currents [1] and the experimental observations of the massive carriers of weak interactions, the W{sup {+-}} and Z{sup 0} bosons [2], [3]. High precision measurements performed at LEP and SLAC test the validity of the theory to an unprecedented level of accuracy and do not show any significant deviations with respect to the Standard Model predictions. One of the attractive features of the Standard Model is the description of the phenomena which violate the matter-antimatter symmetry (CP), and this violation uniquely depends (in the quark sector) on a weak phase in the matrix describing the couplings among different quark flavors. CP-violation was discovered in 1964 as a tiny effect in the mixing of the K{sup 0} - {bar K}{sup 0} system [12] but, after a few decades of study of the physics of K mesons, no strong confirmation of the Standard Model can be obtained on the mechanism which generates CP-violation. On the other hand the physics of B mesons is suitable for a pretty large number of measurements which can confirm or disprove …
Date:
November 16, 2011
Creator:
Gaz, Alessandro & U., /Padua
System:
The UNT Digital Library
Search for CP violation in singly Cabibbo suppressed four-body D decays
We search for CP violation in a sample of 4.7 x 10{sup 4} singly Cabibbo suppressed D{sup 0} {yields} K{sup +} K{sup -} {pi}{sup +}{pi}{sup -} decays and 1.8(2.6) x 10{sup 4} D{sub (s)}{sup +} {yields} K{sub S}{sup 0} K{sup +} {pi}{sup +} {pi}{sup -} decays. CP violation is searched for in the difference between the T-odd asymmetries, obtained using triple product correlations, measured for D and {bar D} decays. The measured CP violation parameters are A{sub T}(D{sup 0}) = (1.0 {+-} 5.1(stat) {+-} 4.4(syst)) x 10{sup -3}, A{sub T}(D{sup +}) = (-11.96 {+-} 10.04(stat) {+-} 4.81(syst)) x 10{sup -3} and A{sub T}(D{sub s}{sup +}) = (-13.57 {+-} 7.67(stat) {+-} 4.82(syst)) x 10{sup -3}. This search for CP violation showed that the T-odd correlations are a powerful tool to measure the CP violating observable A{sub T}. The relative simplicity of an analysis based on T-odd correlations and the high quality results that can be obtained, allow to consider this tool as fundamental to search for CP violation in four-body decays. Even if the CP violation has not been found, excluding any New Physics effect to the sensitivity of about 0.5%, it is still worth to search for CP violation in …
Date:
June 22, 2011
Creator:
Martinelli, Maurizio & U., /Bari
System:
The UNT Digital Library
Measuring neutrino oscillation parameters using $\nu_\mu$ disappearance in MINOS
MINOS is a long-baseline neutrino oscillation experiment. It consists of two large steel-scintillator tracking calorimeters. The near detector is situated at Fermilab, close to the production point of the NuMI muon-neutrino beam. The far detector is 735 km away, 716m underground in the Soudan mine, Northern Minnesota. The primary purpose of the MINOS experiment is to make precise measurements of the 'atmospheric' neutrino oscillation parameters ({Delta}m{sub atm}{sup 2} and sin{sup 2} 2{theta}{sub atm}). The oscillation signal consists of an energy-dependent deficit of {nu}{sub {mu}} interactions in the far detector. The near detector is used to characterize the properties of the beam before oscillations develop. The two-detector design allows many potential sources of systematic error in the far detector to be mitigated by the near detector observations. This thesis describes the details of the {nu}{sub {mu}}-disappearance analysis, and presents a new technique to estimate the hadronic energy of neutrino interactions. This estimator achieves a significant improvement in the energy resolution of the neutrino spectrum, and in the sensitivity of the neutrino oscillation fit. The systematic uncertainty on the hadronic energy scale was re-evaluated and found to be comparable to that of the energy estimator previously in use. The best-fit oscillation parameters …
Date:
February 1, 2011
Creator:
Backhouse, Christopher James
System:
The UNT Digital Library
Forward-Backward Asymmetry at High Mass in $t\bar{t}$ Production in $p\bar{p}$ Collisions at $\sqrt{s} = 1.96$ TeV
Current understanding of particle physics postulates that there are 17 fundamental particles that interact via four fundamental forces - gravity, the strong force, the weak force, and the electromagnetic force. These fundamental particles can be classified by their spins into bosons, which are the force-carrying particles with integer spins, and fermions, which have half-integer spins. Fermions can be further divided into quarks and leptons. The particles and three of the four forces - all but gravity - are described by the Standard Model, a local SU(3) x SU(2) x U(1) gauge theory. Electromagnetic and weak interactions as described by Electroweak Theory or Quantum Electrodynamics, SU(2) x U(1). Strong interactions are described by Quantum Chromodynamics or QCD, SU(3). Fermions are grouped into three generations as shown in Table 1.1. Each generation consists of a leptonic doublet containing a charged and a neutral lepton and a weak isospin doublet containing two quarks. The first generation, containing the electron, the electron neutrino, the up quark, and the down quark, is the lightest generation and is thus the most frequently found in nature. The second generation contains the muon, the muon neutrino, the strange quark, and the charm quark. The third generation contains the …
Date:
April 1, 2011
Creator:
Eppig, Andrew
System:
The UNT Digital Library
Measurement of low $p_{T}$ $D^{0}$ meson production cross section at CDF II.
In this thesis we present a study of the production of D{sup 0} meson in the low transverse momentum region. In particular the inclusive differential production cross section of the D{sup 0} meson (in the two-body decay channel D{sup 0} {yields} K{sup -}{pi}{sup +}) is obtained extending the published CDF II measurement to p{sub T} as low as 1.5 GeV/c. This study is performed at the Tevatron Collider at Fermilab with the CDF II detector.
Date:
May 1, 2011
Creator:
Mussini, Manuel & U., /Bologna
System:
The UNT Digital Library
Observation of the doubly strange b-Baryon Omega(b)-
This thesis reports the first experimental evidence of the doubly strange b-baryon {Omega}{sub b}{sup -} (ssb) following the decay channel {Omega}{sub b}{sup -} {yields} J/{psi}(1S) {mu}{sup +}{mu}{sup -} {Omega}{sup -} {Lambda} K{sup -} p {pi}{sup -} in p{bar p} collisions at {radical}s = 1.96 Tev. Using approximately 1.3 fb{sup -1} of data collected with the D0 detector at the Fermilab Tevatron Collider, they observe 17.8 {+-} 4.9(stat) {+-} 0.8(syst) {Omega}{sub b}{sup -} signal events at 6.165 {+-} 0.010(stat) {+-} 0.013(syst) GeV/c{sup 2} with a corresponding significance of 5.4 {sigma}, meaning that the probability of the signal coming from a fluctuation in the background is 6.7 x 10{sup -8}. The theoretical model we have to describe what we believe are the building blocks of nature and the interactions between them, is known as Standard Model. The Standard Model is the combination of Electroweak Theory and Quantum Chromodynamics into a single core in the attempt to include all interactions of subatomic particles except those due to gravity in a simple framework. This model has proved highly accurate in predicting certain interactions, but it does not explain all aspects of subatomic particles. For example, it cannot say how many particles there should be …
Date:
February 1, 2011
Creator:
Hernandez Orduna, de Jesus, Jose
System:
The UNT Digital Library
Study of the top quark electric charge at the CDF experiment
We report on the measurement of the top quark electric charge using the jet charge tagging method on events containing a single lepton collected by the CDF II detector at Fermilab between February 2002 and February 2010 at the center-of-mass energy {radical}s = 1.96 TeV. There are three main components to this measurement: determining the charge of the W (using the charge of the lepton), pairing the W with the b-jet to ensure that they are from the same top decay branch and finally determining the charge of the b-jet using the Jet Charge algorithm. We found, on a sample of 5.6 fb{sup -1} of data, that the p-value under the standard model hypothesis is equal to 13.4%, while the p-value under the exotic model hypothesis is equal to 0.014%. Using the a priori criteria generally accepted by the CDF collaboration, we can say that the result is consistent with the standard model, while we exclude an exotic quark hypothesis with 95% confidence. Using the Bayesian approach, we obtain for the Bayes factor (2ln(BF)) a value of 19.6, that favors very strongly the SM hypothesis over the XM one. The presented method has the highest sensitivity to the top quark …
Date:
September 1, 2011
Creator:
Bartos, Pavol
System:
The UNT Digital Library
Magnetic spectroscopy and microscopy of functional materials
Heusler intermetallics Mn{sub 2}Y Ga and X{sub 2}MnGa (X; Y =Fe, Co, Ni) undergo tetragonal magnetostructural transitions that can result in half metallicity, magnetic shape memory, or the magnetocaloric effect. Understanding the magnetism and magnetic behavior in functional materials is often the most direct route to being able to optimize current materials for todays applications and to design novel ones for tomorrow. Synchrotron soft x-ray magnetic spectromicroscopy techniques are well suited to explore the the competing effects from the magnetization and the lattice parameters in these materials as they provide detailed element-, valence-, and site-specifc information on the coupling of crystallographic ordering and electronic structure as well as external parameters like temperature and pressure on the bonding and exchange. Fundamental work preparing the model systems of spintronic, multiferroic, and energy-related compositions is presented for context. The methodology of synchrotron spectroscopy is presented and applied to not only magnetic characterization but also of developing a systematic screening method for future examples of materials exhibiting any of the above effects. The chapter progression is as follows: an introduction to the concepts and materials under consideration (Chapter 1); an overview of sample preparation techniques and results, and the kinds of characterization methods employed …
Date:
January 28, 2011
Creator:
Jenkins, C.A.
System:
The UNT Digital Library
A measurement of the 2 neutrino double beta decay rate of Te-130 in the CUORICINO experiment
CUORICINO was a cryogenic bolometer experiment designed to search for neutrinoless double beta decay and other rare processes, including double beta decay with two neutrinos (2{nu}{beta}{beta}). The experiment was located at Laboratori Nazionali del Gran Sasso and ran for a period of about 5 years, from 2003 to 2008. The detector consisted of an array of 62 TeO{sub 2} crystals arranged in a tower and operated at a temperature of #24;10 mK. Events depositing energy in the detectors, such as radioactive decays or impinging particles, produced thermal pulses in the crystals which were read out using sensitive thermistors. The experiment included 4 enriched crystals, 2 enriched with {sup 130}Te and 2 with {sup 128}Te, in order to aid in the measurement of the 2{nu}{beta}{beta} rate. The enriched crystals contained a total of #24;350 g {sup 130}Te. The 128-enriched (130-depleted) crystals were used as background monitors, so that the shared backgrounds could be subtracted from the energy spectrum of the 130- enriched crystals. Residual backgrounds in the subtracted spectrum were fit using spectra generated by Monte-Carlo simulations of natural radioactive contaminants located in and on the crystals. The 2{nu}{beta}{beta} half-life was measured to be T{sup 2{nu}}{sub 1/2} = [9.81{+-} #6;0.96(stat){+-} 0.49(syst)]#2;x10{sup …
Date:
November 3, 2011
Creator:
Kogler, Laura
System:
The UNT Digital Library
Phase-field investigation on the non-equilibrium interface dynamics of rapid alloy solidification
The research program reported here is focused on critical issues that represent conspicuous gaps in current understanding of rapid solidification, limiting our ability to predict and control microstructural evolution (i.e. morphological dynamics and microsegregation) at high undercooling, where conditions depart significantly from local equilibrium. More specifically, through careful application of phase-field modeling, using appropriate thin-interface and anti-trapping corrections and addressing important details such as transient effects and a velocity-dependent (i.e. adaptive) numerics, the current analysis provides a reasonable simulation-based picture of non-equilibrium solute partitioning and the corresponding oscillatory dynamics associated with single-phase rapid solidification and show that this method is a suitable means for a self-consistent simulation of transient behavior and operating point selection under rapid growth conditions. Moving beyond the limitations of conventional theoretical/analytical treatments of non-equilibrium solute partitioning, these results serve to substantiate recent experimental findings and analytical treatments for single-phase rapid solidification. The departure from the equilibrium solid concentration at the solid-liquid interface was often observed during rapid solidification, and the energetic associated non-equilibrium solute partitioning has been treated in detail, providing possible ranges of interface concentrations for a given growth condition. Use of these treatments for analytical description of specific single-phase dendritic and cellular operating point …
Date:
August 15, 2011
Creator:
Choi, Jeong
System:
The UNT Digital Library
Optimization of Operating Parameters for Minimum Mechanical Specific Energy in Drilling
Efficiency in drilling is measured by Mechanical Specific Energy (MSE). MSE is the measure of the amount of energy input required to remove a unit volume of rock, expressed in units of energy input divided by volume removed. It can be expressed mathematically in terms of controllable parameters; Weight on Bit, Torque, Rate of Penetration, and RPM. It is well documented that minimizing MSE by optimizing controllable factors results in maximum Rate of Penetration. Current methods for computing MSE make it possible to minimize MSE in the field only through a trial-and-error process. This work makes it possible to compute the optimum drilling parameters that result in minimum MSE. The parameters that have been traditionally used to compute MSE are interdependent. Mathematical relationships between the parameters were established, and the conventional MSE equation was rewritten in terms of a single parameter, Weight on Bit, establishing a form that can be minimized mathematically. Once the optimum Weight on Bit was determined, the interdependent relationship that Weight on Bit has with Torque and Penetration per Revolution was used to determine optimum values for those parameters for a given drilling situation. The improved method was validated through laboratory experimentation and analysis of published …
Date:
May 25, 2011
Creator:
Hamrick, Todd
System:
The UNT Digital Library
Measurement of branching fractions of B decays to K1(1270)pi and K1(1400)pi and determination of the CKM angle alpha from B0 --> a1(1260) - pi-
In the Standard Model, CP violation in weak interactions involving quarks is parameterized by an irreducible complex phase in the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing-matrix. The precise determination of the CKM elements is a necessary ingredient for a stringent test of the Standard Model predictions, and is a crucial input for reducing the theoretical error in many New Physics searches with flavor, e.g., in the kaon sector. The unitarity of the CKM matrix is typically expressed as a triangle relationship among its parameters, where the area of the so-called Unitarity Triangle visually depicts the amount of asymmetry between the decays of B particles and their antimatter counterparts. In the past few years, the BABAR and Belle experiments have been able to measure all three angles of the triangle from CP asymmetry measurements. The first asymmetry measurements in B particle decays, about ten years ago, allowed to determine {beta}, which is now known to better than 5% precision. The angles {alpha} and {gamma}, measured in much rarer processes, required several years of data taking before analyses could yield reliable answers. A remarkable feature is that the direct measurement of the angles of the Unitarity Triangle generates an area that is consistent with the …
Date:
February 7, 2011
Creator:
Stracka, Simone & /SLAC, /Milan U.
System:
The UNT Digital Library