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Probing Ferroelectricity in PbZr0.2Ti0.8O3 with Polarized Soft X-rays (open access)

Probing Ferroelectricity in PbZr0.2Ti0.8O3 with Polarized Soft X-rays

The reduction in symmetry associated with the onset of ferroelectric order in PbZr{sub 0.2}Ti{sub 0.8}O{sub 3} (PZT) thin films leads to a pronounced difference at the Ti L{sub 3,2} absorption edges between spectra measured with the x-ray linear polarization perpendicular and parallel to the ferroelectric polarization. We introduce a general method to analyze the observed difference spectra using atomic multiplet calculations. Moreover, we find experimental evidence for structural changes in PZT induced by the reversal of the ferroelectric polarization.
Date: June 7, 2010
Creator: Arenholz, E.; van der Laan, G.; Fraile-Rodriguez, A.; Yu, P.; He, Q. & Ramesh, R.
Object Type: Article
System: The UNT Digital Library
MATERIAL TRACKING USING LANMAS (open access)

MATERIAL TRACKING USING LANMAS

LANMAS is a transaction-based nuclear material accountability software product developed to replace outdated and legacy accountability systems throughout the DOE. The core underlying purpose of LANMAS is to track nuclear materials inventory and report transactions (movement, mixing, splitting, decay, etc.) to the Nuclear Materials Management and Safeguards System (NMMSS). While LANMAS performs those functions well, there are many additional functions provided by the software product. As a material is received onto a site or created at a site, its entire lifecycle can be tracked in LANMAS complete to its termination of safeguards. There are separate functions to track material movements between and within material balance areas (MBAs). The level of detail for movements within a MBA is configurable by each site and can be as high as a site designation or as detailed as building/room/rack/row/position. Functionality exists to track the processing of materials, either as individual items or by modeling a bulk process as an individual item to track inputs and outputs from the process. In cases where sites have specialized needs, the system is designed to be flexible so that site specific functionality can be integrated into the product. This paper will demonstrate how the software can be used …
Date: June 7, 2010
Creator: Armstrong, F.
Object Type: Article
System: The UNT Digital Library
Landsat and the Data Continuity Mission (open access)

Landsat and the Data Continuity Mission

This report discusses the U.S. Landsat Mission, which has collected remotely sensed imagery of the Earth's surface for more than 35 years. The two satellites currently in orbit are operating beyond their designed life and may fail at any time. Most Landsat data is used by federal agencies. Efforts to commercialize Landsat operations have not been successful. This report discusses issues facing Congress regarding funding for new Landsat satellites.
Date: June 7, 2010
Creator: Behrens, Carl E.
Object Type: Report
System: The UNT Digital Library
Recent Results on Flavor Physics from BaBar (open access)

Recent Results on Flavor Physics from BaBar

The authors report an update to their previous measurement of the CKM element |V{sub ub}| using exclusive B {yields} {pi}{ell}{nu} decays. In the charm sector they have performed a measurement of f{sub D{sub s}} using D{sub s}{sup +} {yields} {tau}{sup +}{nu}{sub {tau}} decays, they have measured the mixing parameter y{sub CP} using the lifetime ratio <{tau}{sub K{pi}}>/<{tau}{sub hh}> in D{sup 0} decays, and they have also searched for CP violation using T-odd correlations in D{sup 0} decays to K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}. Finally, in the tau sector they have performed a search for the lepton flavor violating decays {tau}{sup {+-}} {yields} e{sup {+-}}{gamma} and {tau}{sup {+-}} {yields} {mu}{sup {+-}}{gamma}.
Date: June 7, 2010
Creator: Benitez, Jose
Object Type: Article
System: The UNT Digital Library
Asian Carp and the Great Lakes Region (open access)

Asian Carp and the Great Lakes Region

This report describes non-indigenous Asian carp migrating to the United States, their potential impacts on the ecosystem, federal responses, and litigation.
Date: June 7, 2010
Creator: Buck, Eugene H.; Upton, Harold F.; Stern, Charles V. & Nichols, James E.
Object Type: Report
System: The UNT Digital Library
Quantum Simulations for Dense Matter (open access)

Quantum Simulations for Dense Matter

High pressure systems are important, for example, to understand the interiors of giant planets (Jupiter and Saturn), for experiments at NIF (the National Ignition Facility at Livermore) related to inertially confined fusion and for other interests of DOE. In this project, we are developing innovative simulation methods (Quantum Monte Carlo methods) to allow more accurate calculation of properties of systems under extreme conditions of pressure and temperature. These methods can use the power of current day supercomputers made of very many processors, starting from the basic equations of physics to model quantum phenomena important at the microscopic scale. During the grant period, we have settled two important questions of the physics of hydrogen and helium under extreme conditions. We have found the pressures and temperatures when hydrogen and helium mix together; this is important to understand the difference of the interiors of the planets Jupiter and Saturn. Secondly, we have shown that there exists a sharp transition as a function of pressure between molecular and atomic liquid hydrogen at temperatures below 2000K. This prediction can be confirmed with high pressure experiments.
Date: June 7, 2010
Creator: Ceperley, David M.
Object Type: Report
System: The UNT Digital Library
Ultraviolet Behavior of N = 8 supergravity (open access)

Ultraviolet Behavior of N = 8 supergravity

In these lectures the author describes the remarkable ultraviolet behavior of N = 8 supergravity, which through four loops is no worse than that of N = 4 super-Yang-Mills theory (a finite theory). I also explain the computational tools that allow multi-loop amplitudes to be evaluated in this theory - the KLT relations and the unitarity method - and sketch how ultraviolet divergences are extracted from the amplitudes.
Date: June 7, 2010
Creator: Dixon, Lance J.
Object Type: Article
System: The UNT Digital Library
Mine-Resistant, Ambush-Protected (MRAP) Vehicles: Background and Issues for Congress (open access)

Mine-Resistant, Ambush-Protected (MRAP) Vehicles: Background and Issues for Congress

This report covers the 2007 Department of Defense (DOD) major procurement initiative to replace most up-armored High Mobility, Multi-Wheeled Vehicles (HMMWVs) with Mine-Resistant, Ambush-Protected (MRAP) vehicles. It looks at the cost and subsequent budgets of this initiative. Among potential issues for congressional consideration are the status of older, unused MRAPS in Afghanistan that are reportedly not being used because of their size and weight; possible redundancies with the MRAP, M-ATV, and the Joint Light Tactical Vehicle (JLTV) programs; and actual Marine M-ATV requirements.
Date: June 7, 2010
Creator: Feickert, Andrew
Object Type: Report
System: The UNT Digital Library
ENHANCEMENT OF ENVIRONMENTAL SAMPLING THROUGH AN IMPROVED AIR MONITORING TECHNIQUE (open access)

ENHANCEMENT OF ENVIRONMENTAL SAMPLING THROUGH AN IMPROVED AIR MONITORING TECHNIQUE

Environmental sampling (ES) is a key component of International Atomic Energy Agency (IAEA) safeguarding approaches throughout the world. Performance of ES (e.g. air, water, vegetation, sediments, soil and biota) supports the IAEAs mission of drawing conclusions concerning the absence of undeclared nuclear material or nuclear activities in a State and has been available since the introduction of safeguards strengthening measures approved by the IAEA Board of Governors (1992-1997). A recent step-change improvement in the gathering and analysis of air samples at uranium/plutonium bulk handling facilities is an important addition to the international nuclear safeguards inspector's toolkit. Utilizing commonly used equipment throughout the IAEA network of analytical laboratories for particle analysis, researchers are developing the next generation of ES equipment for air grab and constant samples. Isotopic analysis of collected particles from an Aerosol Contaminant Extractor (ACE) silicon substrate has been performed with excellent results in determining attribute and isotopic composition of chemical elements present in an actual test-bed sample. The new collection equipment will allow IAEA nuclear safeguards inspectors to develop enhanced safeguarding approaches for complicated facilities. This paper will explore the use of air monitoring to establish a baseline environmental signature of a particular facility that could be used …
Date: June 7, 2010
Creator: Hanks, D.
Object Type: Article
System: The UNT Digital Library
Application of Adaptive Beamforming to Signal Observations at the Mt. Meron Array, Israel (open access)

Application of Adaptive Beamforming to Signal Observations at the Mt. Meron Array, Israel

None
Date: June 7, 2010
Creator: Harris, D B
Object Type: Report
System: The UNT Digital Library
The Jurisprudence of Justice John Paul Stevens: Selected Opinions on the Jury's Role in Criminal Sentencing (open access)

The Jurisprudence of Justice John Paul Stevens: Selected Opinions on the Jury's Role in Criminal Sentencing

This report discusses Justice John Paul Stevens' opinions on the Jury's role in criminal sentencing. Justice Stevens has played a critical role in the Supreme Court's interpretation of a jury's role in criminal sentencing. In 2000, he wrote the majority opinion for the Court in Apprendi v. New Jersey, a landmark case in which the Court held that a judge typically may not increase a sentence beyond the range prescribed by statute unless the increase is based on facts determined by a jury "beyond a reasonable doubt." In 2005, he wrote one of two majority opinions in United States v. Booker, in which the Court applied the Apprendi rule to the Federal Sentencing Guidelines. In those two cases and in several other cases on this issue during the past few decades, Justice Stevens has been a leading voice, articulating a broad interpretation of the jury trial and due process rights at issue.
Date: June 7, 2010
Creator: Henning, Anna C.
Object Type: Report
System: The UNT Digital Library
Doctoral Lecture Recital: 2010-06-07 – Steven Hunter, trombone transcript

Doctoral Lecture Recital: 2010-06-07 – Steven Hunter, trombone

Recital presented at the UNT College of Music Recital Hall in partial fulfillment of the Doctor of Musical Arts (DMA) degree.
Date: June 7, 2010
Creator: Hunter, Steven
Object Type: Sound
System: The UNT Digital Library
Trade Remedies and the WTO Rules Negotiations (open access)

Trade Remedies and the WTO Rules Negotiations

At the November 2001 Ministerial meeting of the World Trade Organization (WTO) in Doha, Qatar, member countries launched a new round of trade talks known as the Doha Development Agenda (DDA). This report examines trade remedy issues in DDA in three parts. The first part provides background information and contextual analysis. The second section focuses on how these issues fit into the DDA. A third section provides a more specific overview of major reform proposals that are being considered.
Date: June 7, 2010
Creator: Jones, Vivian C.
Object Type: Report
System: The UNT Digital Library
Afghanistan: Post-Taliban Governance, Security, and U.S. Policy (open access)

Afghanistan: Post-Taliban Governance, Security, and U.S. Policy

This report discusses the current political state of Iran, focusing particularly on the influence of the Taliban and other militant groups and on the leadership of Afghan President Hamid Karzai. This report also discusses the U.S.-Iran relationship and U.S. efforts under the Obama Administration to provide military, reconstructive, and stabilization aid.
Date: June 7, 2010
Creator: Katzman, Kenneth
Object Type: Report
System: The UNT Digital Library
Lifetime Tests on a High Ohms/Square Metalized High Crystalline Polypropylene Film Capacitor with Application to a Marx Modulator (open access)

Lifetime Tests on a High Ohms/Square Metalized High Crystalline Polypropylene Film Capacitor with Application to a Marx Modulator

This paper presents accelerated lifetime tests on a polypropylene film capacitor. Experimental parameters (20% droop, 5 Hz repetition rate) simulate anticipated operating conditions encountered in the SLAC P2 Marx. Elevated film electric field stress is utilized as the acceleration parameter. Results indicate that, for the particular film of interest, a film stress of {approx}290 V/{mu}m corresponds to a 10{sup 5} hour lifetime. In addition, the voltage scaling exponent for this film is 13.1.
Date: June 7, 2010
Creator: Kemp, Mark A.; Burkhart, Craig & Tang, Tao
Object Type: Article
System: The UNT Digital Library
S09 Symposium KK, Structure-Property Relationships in Biomineralized and Biomimetic Composites (open access)

S09 Symposium KK, Structure-Property Relationships in Biomineralized and Biomimetic Composites

The technical presentations and discussions at this symposium disseminated and assessed current research and defined future directions in biomaterials research, with a focus on structure-function relationships in biological and biomimetic composites. The invited and contributed talks covered a diverse range of topics from fundamental biology, physics, chemistry, and materials science to potential applications in developing areas such as light-weight composites, multifunctional and smart materials, biomedical engineering, and nanoscaled sensors. The invited speakers were chosen to create a stimulating program with a mixture of established and junior faculty, industrial and academic researchers, and American and international experts in the field. This symposium served as an excellent introduction to the area for younger scientists (graduate students and post-doctoral researchers). Direct interactions between participants also helped to promote potential future collaborations involving multiple disciplines and institutions.
Date: June 7, 2010
Creator: Kisailus, David; Estroff, Lara; Gupta, Himadri S.; Landis, William J. & Zavattieri, Pablo D.
Object Type: Report
System: The UNT Digital Library
A Moving Window Technique in Parallel Finite Element Time Domain Electromagnetic Simulation (open access)

A Moving Window Technique in Parallel Finite Element Time Domain Electromagnetic Simulation

A moving window technique for the finite element time domain (FETD) method is developed to simulate the propagation of electromagnetic waves induced by the transit of a charged particle beam inside large and long structures. The window moving along with the beam in the computational domain adopts high-order finite-element basis functions through p refinement and/or a high-resolution mesh through h refinement so that a sufficient accuracy is attained with substantially reduced computational costs. Algorithms to transfer discretized fields from one mesh to another, which are the key to implementing a moving window in a finite-element unstructured mesh, are presented. Numerical experiments are carried out using the moving window technique to compute short-range wakefields in long accelerator structures. The results are compared with those obtained from the normal FETD method and the advantages of using the moving window technique are discussed.
Date: June 7, 2010
Creator: Lee, Lie-Quan; Candel, Arno; Ng, Cho & Ko, Kwok
Object Type: Article
System: The UNT Digital Library
Critical Infrastructures: Background, Policy, and Implementation (open access)

Critical Infrastructures: Background, Policy, and Implementation

This report discusses the evolution of a national critical infrastructure policy and the institutional structures established to implement it. Critical infrastructure includes physical assets used to produce and distribute services such as electricity (including the power plants and electric grid), communications, and computers. The report highlights five issues of Congressional concern: identifying critical assets; assessing vulnerabilities and risks; allocating resources; information sharing; and regulation.
Date: June 7, 2010
Creator: Moteff, John D.
Object Type: Report
System: The UNT Digital Library
Compact, Intelligent, Digitally Controlled IGBT Gate Drivers for a PEBB-Based ILC Marx Modulator (open access)

Compact, Intelligent, Digitally Controlled IGBT Gate Drivers for a PEBB-Based ILC Marx Modulator

SLAC National Accelerator Laboratory has built and is currently operating a first generation prototype Marx klystron modulator to meet ILC specifications. Under development is a second generation prototype, aimed at improving overall performance, serviceability, and manufacturability as compared to its predecessor. It is designed around 32 cells, each operating at 3.75 kV and correcting for its own capacitor droop. Due to the uniqueness of this application, high voltage gate drivers needed to be developed for the main 6.5 kV and droop correction 1.7 kV IGBTs. The gate driver provides vital functions such as protection of the IGBT from over-voltage and over-current, detection of gate-emitter open and short circuit conditions, and monitoring of IGBT degradation (based on collector-emitter saturation voltage). Gate drive control, diagnostic processing capabilities, and communication are digitally implemented using an FPGA. This paper details the design of the gate driver circuitry, component selection, and construction layout. In addition, experimental results are included to illustrate the effectiveness of the protection circuit.
Date: June 7, 2010
Creator: Nguyen, M. N.; Burkhart, C.; Olsen, J. J. & Macken, K.
Object Type: Article
System: The UNT Digital Library
Development Status of The ILC Marx Modulator (open access)

Development Status of The ILC Marx Modulator

The ILC Marx Modulator is under development as a lower cost alternative to the 'Baseline Conceptual Design' (BCD) klystron modulator. Construction of a prototype Marx is complete and testing is underway at SLAC. The Marx employs solid state elements, IGBTs and diodes, to control the charge, discharge and isolation of the modules. The prototype is based on a stack of sixteen modules, each initially charged to {approx}11 kV, which are arranged in a Marx topology. Initially, eleven modules combine to produce the 120 kV output pulse. The remaining modules are switched in after appropriate delays to compensate for the voltage droop that results from the discharge of the energy storage capacitors. Additional elements will further regulate the output voltage to {+-}0.5%. The Marx presents several advantages over the conventional klystron modulator designs. It is physically smaller; there is no pulse transformer (quite massive at these parameters) and the energy storage capacitor bank is quite small, owing to the active droop compensation. It is oil-free; voltage hold-off is achieved using air insulation. It is air cooled; the secondary air-water heat exchanger is physically isolated from the electronic components. This paper outlines the current developmental status of the prototype Marx. It presents …
Date: June 7, 2010
Creator: Nguyen, M.; Beukers, T.; Burkhart, C.; Larsen, R.; Olsen, J. & Tang, T.
Object Type: Article
System: The UNT Digital Library
Proton-Nucleus Scattering Approximations and Implications for LHC Crystal Collimation (open access)

Proton-Nucleus Scattering Approximations and Implications for LHC Crystal Collimation

In particle accelerators, scattered protons with energies close to the incident particles may travel considerable distances with the beam before impacting on accelerator components downstream. To analyze such problems, angular deflection and energy loss of scattered particles are the main quantities to be simulated since these lead to changes in the beam's phase space distribution and particle loss. Simple approximations for nuclear scattering processes causing limited energy loss to high-energy protons traversing matter are developed which are suitable for rapid estimates and reduced-description Monte Carlo simulations. The implications for proton loss in the Large Hadron Collider due to nuclear scattering on collimation crystals are discussed.
Date: June 7, 2010
Creator: Noble, Robert
Object Type: Article
System: The UNT Digital Library
X-Ray Emitting GHz-Peaked Spectrum Galaxies: Testing a Dynamical-Radiative Model with Broad-Band Spectra (open access)

X-Ray Emitting GHz-Peaked Spectrum Galaxies: Testing a Dynamical-Radiative Model with Broad-Band Spectra

In a dynamical-radiative model we recently developed to describe the physics of compact, GHz-Peaked-Spectrum (GPS) sources, the relativistic jets propagate across the inner, kpc-sized region of the host galaxy, while the electron population of the expanding lobes evolves and emits synchrotron and inverse-Compton (IC) radiation. Interstellar-medium gas clouds engulfed by the expanding lobes, and photoionized by the active nucleus, are responsible for the radio spectral turnover through free-free absorption (FFA) of the synchrotron photons. The model provides a description of the evolution of the GPS spectral energy distribution (SED) with the source expansion, predicting significant and complex high-energy emission, from the X-ray to the {gamma}-ray frequency domain. Here, we test this model with the broad-band SEDs of a sample of eleven X-ray emitting GPS galaxies with Compact-Symmetric-Object (CSO) morphology, and show that: (i) the shape of the radio continuum at frequencies lower than the spectral turnover is indeed well accounted for by the FFA mechanism; (ii) the observed X-ray spectra can be interpreted as non-thermal radiation produced via IC scattering of the local radiation fields off the lobe particles, providing a viable alternative to the thermal, accretion-disk dominated scenario. We also show that the relation between the hydrogen column densities …
Date: June 7, 2010
Creator: Ostorero, L.; Moderski, R.; Stawarz, L.; Diaferio, A.; Kowalska, I.; Cheung, C. C. et al.
Object Type: Article
System: The UNT Digital Library
Isotopic Abundances and Ratios in Arsenic Irradiated by High-Energy Neutrons (open access)

Isotopic Abundances and Ratios in Arsenic Irradiated by High-Energy Neutrons

None
Date: June 7, 2010
Creator: Parker, W E & Hall, J M
Object Type: Report
System: The UNT Digital Library
Development of Controlled Pitch Nano Arrays for Application in Nano Scale Based Proportional Counters (open access)

Development of Controlled Pitch Nano Arrays for Application in Nano Scale Based Proportional Counters

Proportional counters (PCs) are a type of gas-filled radiation detection device capable of distinguishing between a wide range of radiation types and energies. In this application, however, these devices are limited by high power consumption and high bias potentials required to operate in the proportional detection regime. Previous work performed with a single carbon nanotube (CNT) anode has shown that nanoscale-based PCs can operate at bias potentials of 10V rather than the 1000V range required for PCs. ''Proof of concept'' experiments with a single CNT as the anode exhibit a small detection volume and consequently required long count times (24 hrs). To make this a practical detector technology (i.e., decrease the count time), the effective detection volume has to be increased. Experimental data and electric field modeling show that if the pitch (spacing between individual nanotubes) of the arrays is too small, the electric field of the individual nanostructure will collapse and the nanoscale array will behaved as a single macro-scale field with the associated high bias potential required to reach the proportional region. Electric-field modeling of the affect of nanostructure pitch on the electric field distribution of these arrays predicted that a pitch of about two-and-a-times the height of …
Date: June 7, 2010
Creator: Sexton, L.; Serkiz, S. & Siegfried, M.
Object Type: Article
System: The UNT Digital Library