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The Spectrophotometric Determination of Boron in Plutonium Using an Oxalate Separation.

Description: An improved method for the determination of boron in plutonium is reported. Precipitation of plutonium (III) acid oxalate prior to color development with curcumin results in increased precision, greater speed, and lower costs. Results are presented of a statistical study involving all variables.
Date: June 25, 1953
Creator: Newell, Donald M.
Partner: UNT Libraries Government Documents Department

Dimensional Mutation and Spacelike Singularities

Description: I argue that critical string theory on a Riemann surface of genus h >> 1 crosses over, when the surface approaches the string scale in size, to a background of supercritical string theory with effective central charge as large as 2h. Concrete evidence for this proposal is provided by the high energy density of states (realized on the Riemann surface side by strings wrapping nontrivial elements of the fundamental group) and by a linear sigma model which at large h approximates the time evolution through the initial transition. This suggests that cosmological singularities arising in negatively curved FRW backgrounds may be replaced by a phase of supercritical string theory.
Date: October 28, 2005
Creator: Silverstein, Eva
Partner: UNT Libraries Government Documents Department

Geometric Transitions, Topological Strings, and Generalized Complex Geometry

Description: Mirror symmetry is one of the most beautiful symmetries in string theory. It helps us very effectively gain insights into non-perturbative worldsheet instanton effects. It was also shown that the study of mirror symmetry for Calabi-Yau flux compactification leads us to the territory of ''Non-Kaehlerity''. In this thesis we demonstrate how to construct a new class of symplectic non-Kaehler and complex non-Kaehler string theory vacua via generalized geometric transitions. The class admits a mirror pairing by construction. From a variety of sources, including super-gravity analysis and KK reduction on SU(3) structure manifolds, we conclude that string theory connects Calabi-Yau spaces to both complex non-Kaehler and symplectic non-Kaehler manifolds and the resulting manifolds lie in generalized complex geometry. We go on to study the topological twisted models on a class of generalized complex geometry, bi-Hermitian geometry, which is the most general target space for (2, 2) world-sheet theory with non-trivial H flux turned on. We show that the usual Kaehler A and B models are generalized in a natural way. Since the gauged supergravity is the low energy effective theory for the compactifications on generalized geometries, we study the fate of flux-induced isometry gauging in N = 2 IIA and heterotic strings under non-perturbative instanton effects. Interestingly, we find we have protection mechanisms preventing the corrections to the hyper moduli spaces. Besides generalized geometries, we also discuss the possibility of new NS-NS fluxes in a new doubled formalism.
Date: June 29, 2007
Creator: Chuang, Wu-yen
Partner: UNT Libraries Government Documents Department

Collaborative Visualization for Large-Scale Accelerator Electromagnetic Modeling

Description: In the Phase I SBIR we proposed a ParaView-based solution to provide an environment for individuals to actively collaborate in the visualization process. The technical objectives of Phase I were: (1) to determine the set of features required for an effect collaborative system; (2) to implement a two-person collaborative prototype; and (3) to implement key collaborative features such as control locking and annotation. Accordingly, we implemented a ParaView-based collaboration prototype with support for collaborating with up to four simultaneous clients. We also implemented collaborative features such as control locking, chatting, annotation etc. Due to in part of the flexibility provided by the ParaView framework and the design features implemented in the prototype, we were able to support collaboration with multiple views, instead of a simple give as initially proposed in Phase I. In this section we will summarize the results we obtained during the Phase I project. ParaView is complex, scalable, client-server application framework built on top of the VTK visualization engine. During the implementation of the Phase I prototype, we realized that the ParaView framework naturally supports collaboration technology; hence we were able to go beyond the proposed Phase I prototype in several ways. For example, we were able to support for multiple views, enable server-as well as client-side rendering, and manage up to four heterogeneous clients. The success we achieved with Phase I clearly demonstrated the technical feasibility of the ParaView based collaborative framework we are proposing in the Phase II effort. We also investigated using the web browser as one of the means of participating in a collaborative session. This would enable non-visualization experts to participate in the collaboration process without being intimidated by a complex application such as ParaView. Hence we also developed a prototype web visualization applet that makes it possible for interactive visualization over ...
Date: August 25, 2010
Creator: Schussman, Greg
Partner: UNT Libraries Government Documents Department

Low temperature heat capacity of scandium and alloys of scandium

Description: The heat capacity of three electrotransport purified scandium samples has been measured from 1 to 20/sup 0/K. The resultant electronic specific heat constant and Debye temperature are 10.337 +- 0.015 mJ/gm-atom K/sup 2/ and 346.7 +- 0.8/sup 0/K respectively, and these values are believed to be truly representative of intrinsic scandium. Alloying studies have also been carried out to investigate the band structure of scandium based on the rigid band model, with zirconium to raise the electron concentration and magnesium to lower it. The results are then compared to the theoretical band structure calculations. Low temperature heat capacity measurements have also been made on some dilute Sc-Fe alloys. An anomaly is observed in the C/T vs. T/sup 2/ plot, but the C vs. T curve shows no evidence of magnetic ordering down to 1/sup 0/K, and electrical resistance measurement from 4 to 0.3/sup 0/K also indicates that no magnetic ordering took place.
Date: December 1, 1977
Creator: Tsang, T. W.E.
Partner: UNT Libraries Government Documents Department

Flux flow and proximity effects in aligned Pb--Cd eutectic lamellar structures

Description: A high speed directional solidification technique was used to fabricate lamellar Pb-Cd and (Pb-Mg)--(Cd-Mg) superconductor-normal metal composites in which all the lamellae are oriented perpendicular to the broad surface of the sample. These lamellar composites are found to behave like a large number (approximately 1000) of superconducting-normal-superconducting junctions. For the Pb-Cd eutectic system, the critical current densities and critical fields have shown no dependence upon the lamellar periods between 1.0 and 3.1 microns. The critical current density of the aligned lamellar Pb-Cd structures was enhanced approximately 50% when compared to quenched eutectic alloy and to pure Pb. The superconducting transition temperature, T/sub c/, varies inversely with the square of the thickness of the superconducting material as expected from Ginzburg-Landau theory. Upon annealing, the Pb lamellae change from type II to type I superconductivity.
Date: September 1, 1977
Creator: Spencer, C. R.
Partner: UNT Libraries Government Documents Department

Alternate HSA design requirements

Description: The requirements definition and a small amount of conceptual layout work which was performed for ERDA to provide assistance to NASA in conjunction with a program to develop advanced heat source assembly designs for use in the Brayton Isotope Power Systems (BIPS) are summarized.
Date: March 8, 1977
Partner: UNT Libraries Government Documents Department

Brayton isotope power system. Phase I (Ground demonstration system) configuration control document (CCD)

Description: The Brayton Isotope Power System (BIPS) Ground Demonstration System (GDS) configuration is defined. The GDS is configured to be similar to a conceptual flight system design referred to herein as the BIPS Flight System (FS). The Brayton Isotope Power System is being developed by the ERDA as a 500 to 2000 W/sub e/, 7 year life 3.5 W/sub e/ per pound space power system. The system was a closed Brayton dynamic system to convert energy from an isotope heat source at a net efficiency exceeding 25%. This CCD is for the first phase of the ERDA program to have a qualified system ready for launch by June 30, 1981. Phase I is a 36 month effort to provide a conceptual design of the flight system and design, fabricate and test a ground demonstration system. The baseline system is predicated on using two of the multihundred-watt isotope heat sources being developed for the ERDA by GE. The Ground Demonstration System will simulate, as closely as possible, the Brayton Isotope Power Flight System and will utilize components and technology being developed by NASA for the Mini-Brayton rotating unit (AIRPHX), recuperator (AIRLA) and heat source assembly (GE). The Ground Demonstration System includes a performance test and a 1000-hour endurance test.
Date: September 25, 1975
Partner: UNT Libraries Government Documents Department