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1Surface structure of cleaved (001) USB2 single crystal surface

Description: We have achieved what we believe to be the first atomic resolution STM images for a uranium compound USb2 taken at room temperature. The a, b, and c lattice parameters in the images confirm that the tetragonal USb2crystals cleave on the (00 I) basal plane as expected. Our calculations indicate a symmetric cut between Sb planes to be the most favorable cleavage plane and U atoms to be responsible for most ofthe density of states measured by STM. Since the spacing between Sb atoms and between U atoms is the same, STM topography only cannot unambiguously identify the surface atom species.
Date: January 1, 2009
Creator: Chen, Shao-ping
Partner: UNT Libraries Government Documents Department

2008 Wind Energy Projects, Wind Powering America (Poster)

Description: The Wind Powering America program produces a poster at the end of every calendar year that depicts new U.S. wind energy projects. The 2008 poster includes the following projects: Stetson Wind Farm in Maine; Dutch Hill Wind Farm in New York; Grand Ridge Wind Energy Center in Illinois; Hooper Bay, Alaska; Forestburg, South Dakota; Elbow Creek Wind Project in Texas; Glacier Wind Farm in Montana; Wray, Colorado; Smoky Hills Wind Farm in Kansas; Forbes Park Wind Project in Massachusetts; Spanish Fork, Utah; Goodland Wind Farm in Indiana; and the Tatanka Wind Energy Project on the border of North Dakota and South Dakota.
Date: January 1, 2009
Partner: UNT Libraries Government Documents Department

[2009 Directory of Texas Daily Newspapers]

Description: The 2009 Director of the Texas Daily Newspapers, published by the Texas Daily Newspaper Association. The text document details the origins of the Texas Daily Newspaper and gives in lenght details on the officers, directors, staff and services that TDNA provides.
Date: 2009
Creator: Texas Daily Newspaper Association
Partner: UNT Libraries Special Collections

3D design activities at Fermilab: Opportunities for physics

Description: Fermilab began exploring the technologies for vertically integrated circuits (also commonly known as 3D circuits) in 2006. These technologies include through silicon vias (TSV), circuit thinning, and bonding techniques to replace conventional bump bonds. Since then, the interest within the High Energy Physics community has grown considerably. This paper will present an overview of the activities at Fermilab over the last 3 years which have helped spark this interest.
Date: January 1, 2009
Creator: Yarema, Raymond; Deptuch, Grezgorz; Hoff, Jim; Shenai, Alpana; Trimpl, Marcel; Zimmerman, Tom et al.
Partner: UNT Libraries Government Documents Department

Ab-initio calculations of the hydrogen-uranium system. Part I: Surface phenomena, absorption, transport and trapping

Description: Density functional theory was applied to the initial steps of uranium hydriding: surface phenomena, absorption, bulk transport and trapping. H adsorbs exothermically to the (0 0 1) surface, yet H absorption into the bulk is endothermic, with off-center octahedral absorption having the lowest absorption energy of 0.39 eV, relative to molecular H{sub 2}. H absorption in interstitial sites causes a local softening of the bulk modulus. Diffusion of H in unstrained {alpha}-U has a barrier of 0.6 eV. The energy of H absorption adjacent to the chemical impurities C, S, Si was lowered by an amount proportional to the size of the impurity atom, and the resulting lattice strain Si > S > C. Thus, impurities may promote hydriding by providing surfaces or prestrained zones for H uptake.
Date: January 1, 2009
Creator: Taylor, Christopher D & Lillard, R Scott
Partner: UNT Libraries Government Documents Department

Accelerating the disposition of transuranic waste from LANL - 9495

Description: Los Alamos National Laboratory (LANL) was established during World War II with a single mission -- to design and build an atomic bomb. In the 65 years since, nuclear weapons physics, design and engineering have been the Laboratory's primary and sustaining mission. Experimental and process operations -- and associated cleanout and upgrade activities -- have generated a significant inventory of transuranic (TRU) waste that is stored at LANL's Technical Area 54, Material Disposal Area G (MDA G). When the Waste Isolation Pilot Plant (WIPP) opened its doors in 1999, LANL's TRU inventory totaled about 10,200 m{sup 3}, with a plutonium 239-equivalent curie (PE Ci) content of approximately 250,000 curies. By December 2008, a total of about 2,300 m3 (61,000 PE Ci) had been shipped to WIPP from LANL. This has resulted in a net reduction of about 1,000 m{sup 3} of TRU inventory over that time frame. This paper presents progress in dispositioning legacy and newly-generated transuranic waste (TRU) from ongoing missions at the LANL. The plans for, and lessons learned, in dispositioning several hundred high-activity TRU waste drums are reviewed. This waste population was one of the highest risks at LANL. Technical challenges in disposition of the high-activity drums are presented. These provide a preview of challenges to be addressed in dispositioning the remaining 6,800 m{sup 3} of TRU stored above ground and 2,400 m{sup 3} of TRU waste that is 'retrievably' stored below-grade. LANL is using subcontractors for much of this work and has formed a strong partnership with WIPP and its contractor to address this cleanup challenge.
Date: January 1, 2009
Creator: Shepard, Mark D; Stiger, Susan G; Blankenhorn, James A; Rael, George J & Moody, David C
Partner: UNT Libraries Government Documents Department

Adaptive anisotropic meshing for steady convection-dominated problems

Description: Obtaining accurate solutions for convection–diffusion equations is challenging due to the presence of layers when convection dominates the diffusion. To solve this problem, we design an adaptive meshing algorithm which optimizes the alignment of anisotropic meshes with the numerical solution. Three main ingredients are used. First, the streamline upwind Petrov–Galerkin method is used to produce a stabilized solution. Second, an adapted metric tensor is computed from the approximate solution. Third, optimized anisotropic meshes are generated from the computed metric tensor by an anisotropic centroidal Voronoi tessellation algorithm. Our algorithm is tested on a variety of two-dimensional examples and the results shows that the algorithm is robust in detecting layers and efficient in avoiding non-physical oscillations in the numerical approximation.
Date: January 1, 2009
Creator: Nguyen, Hoa; Gunzburger, Max; Ju, Lili & Burkardt, John
Partner: UNT Libraries Government Documents Department

Adaptive management: a paradigm for remediation of public facilities

Description: Public facility restoration planning traditionally focused on response to natural disasters and hazardous materials accidental releases. These plans now need to integrate response to terrorist actions. Therefore, plans must address a wide range of potential vulnerabilities. Similar types of broad remediation planning are needed for restoration of waste and hazardous material handling areas and facilities. There are strong similarities in damage results and remediation activities between unintentional and terrorist actions; however, the uncertainties associated with terrorist actions result in a re-evaluation of approaches to planning. Restoration of public facilities following a release of a hazardous material is inherently far more complex than in confined industrial settings and has many unique technical, economic, social, and political challenges. Therefore, they arguably involve a superset of drivers, concerns and public agencies compared to other restoration efforts. This superset of conditions increases complexity of interactions, reduces our knowledge of the initial conditions, and even condenses the timeline for restoration response. Therefore, evaluations of alternative restoration management approaches developed for responding to terrorist actions provide useful knowledge for large, complex waste management projects. Whereas present planning documents have substantial linearity in their organization, the 'adaptive management' paradigm provides a constructive parallel operations paradigm for restoration of facilities that anticipates and plans for uncertainty, multiple/simUltaneous public agency actions, and stakeholder participation. Adaptive management grew out of the need to manage and restore natural resources in highly complex and changing environments with limited knowledge about causal relationships and responses to restoration actions. Similarities between natural resource management and restoration of a facility and surrounding area(s) after a disruptive event suggest numerous advantages over preset linearly-structured plans by incorporating the flexibility and overlap of processes inherent in effective facility restoration. We discuss three restoration case studies (e.g., the Hart Senate Office Building anthrax restoration, Rocky Flats actinide remediation, ...
Date: January 1, 2009
Creator: Janecky, David R; Whicker, Jeffrey J & Doerr, Ted B
Partner: UNT Libraries Government Documents Department

Advanced Fuel Cycle Economic Analysis of Symbiotic Light-Water Reactor and Fast Burner Reactor Systems

Description: The Advanced Fuel Cycle Economic Analysis of Symbiotic Light-Water Reactor and Fast Burner Reactor Systems, prepared to support the U.S. Advanced Fuel Cycle Initiative (AFCI) systems analysis, provides a technology-oriented baseline system cost comparison between the open fuel cycle and closed fuel cycle systems. The intent is to understand their overall cost trends, cost sensitivities, and trade-offs. This analysis also improves the AFCI Program’s understanding of the cost drivers that will determine nuclear power’s cost competitiveness vis-a-vis other baseload generation systems. The common reactor-related costs consist of capital, operating, and decontamination and decommissioning costs. Fuel cycle costs include front-end (pre-irradiation) and back-end (post-iradiation) costs, as well as costs specifically associated with fuel recycling. This analysis reveals that there are large cost uncertainties associated with all the fuel cycle strategies, and that overall systems (reactor plus fuel cycle) using a closed fuel cycle are about 10% more expensive in terms of electricity generation cost than open cycle systems. The study concludes that further U.S. and joint international-based design studies are needed to reduce the cost uncertainties with respect to fast reactor, fuel separation and fabrication, and waste disposition. The results of this work can help provide insight to the cost-related factors and conditions needed to keep nuclear energy (including closed fuel cycles) economically competitive in the U.S. and worldwide. These results may be updated over time based on new cost information, revised assumptions, and feedback received from additional reviews.
Date: January 1, 2009
Creator: Shropshire, D. E.
Partner: UNT Libraries Government Documents Department

Advances in Dust Detection and Removal for Tokamaks

Description: Dust diagnostics and removal techniques are vital for the safe operation of next step fusion devices such as ITER. In the tokamak environment, large particles or fi bers can fall on the electrostatic detector potentially causing a permanent short. An electrostatic dust detector developed in the laboratory is being applied to the National Spherical Torus Experiment (NSTX). We report on the development of a gas puff system that uses helium to clear such particles from the detector. Experiments at atmospheric pressure with varying nozzle designs, backing pressures, puff durations and exit fl ow orientations have given an optimal confi guration that effectively removes particles from a 25 cm² area. Similar removal effi ciencies were observed under a vacuum base pressure of 1 mTorr. Dust removal from next step tokamaks will be required to meet regulatory dust limits. A tri-polar grid of fi ne interdigitated traces has been designed that generates an electrostatic traveling wave for conveying dust particles to a “drain.” First trials with only two working electrodes have shown particle motion in optical microscope images.
Date: January 1, 2009
Creator: Campos, A. & Skinner, C.H.
Partner: UNT Libraries Government Documents Department

Algorithms for optimal dyadic decision trees

Description: A new algorithm for constructing optimal dyadic decision trees was recently introduced, analyzed, and shown to be very effective for low dimensional data sets. This paper enhances and extends this algorithm by: introducing an adaptive grid search for the regularization parameter that guarantees optimal solutions for all relevant trees sizes, revising the core tree-building algorithm so that its run time is substantially smaller for most regularization parameter values on the grid, and incorporating new data structures and data pre-processing steps that provide significant run time enhancement in practice.
Date: January 1, 2009
Creator: Hush, Don & Porter, Reid
Partner: UNT Libraries Government Documents Department

American Leadership for the Global Climate Crisis

Description: This paper discusses several key areas where U.S. policy should be reshaped, both domestically and internationally, to ensure we lead the world towards a safe, sustainable future. We should: Establish a price for carbon by adopting an ambitious 2020 emissions reduction target. Make investments and adopt policies to stimulate a green economy. Lead the world toward an effective and equitable global climate agreement Support efforts to stop emissions from deforestation and degradation in developing countries. Contribute to global financing mechanisms for climate mitigation and adaptation in the developing world. Ensure that climate change-related impacts are addressed under the Endangered Species Act. Improve science and information to prepare communities and ecosystems for unavoidable climate change. Build public support for sustained action to fight climate change
Date: January 2009
Creator: WWF (Organization)
Partner: UNT Libraries

Analysis and algorithms for a regularized Cauchy problem arising from a non-linear elliptic PDE for seismic velocity estimation

Description: In the present work we derive and study a nonlinear elliptic PDE coming from the problem of estimation of sound speed inside the Earth. The physical setting of the PDE allows us to pose only a Cauchy problem, and hence is ill-posed. However we are still able to solve it numerically on a long enough time interval to be of practical use. We used two approaches. The first approach is a finite difference time-marching numerical scheme inspired by the Lax-Friedrichs method. The key features of this scheme is the Lax-Friedrichs averaging and the wide stencil in space. The second approach is a spectral Chebyshev method with truncated series. We show that our schemes work because of (1) the special input corresponding to a positive finite seismic velocity, (2) special initial conditions corresponding to the image rays, (3) the fact that our finite-difference scheme contains small error terms which damp the high harmonics; truncation of the Chebyshev series, and (4) the need to compute the solution only for a short interval of time. We test our numerical scheme on a collection of analytic examples and demonstrate a dramatic improvement in accuracy in the estimation of the sound speed inside the Earth in comparison with the conventional Dix inversion. Our test on the Marmousi example confirms the effectiveness of the proposed approach.
Date: January 1, 2009
Creator: Cameron, M.K.; Fomel, S.B. & Sethian, J.A.
Partner: UNT Libraries Government Documents Department

Analysis of error floor of LDPC codes under LP decoding over the BSC

Description: We consider linear programming (LP) decoding of a fixed low-density parity-check (LDPC) code over the binary symmetric channel (BSC). The LP decoder fails when it outputs a pseudo-codeword which is not a codeword. We propose an efficient algorithm termed the instanton search algorithm (ISA) which, given a random input, generates a set of flips called the BSC-instanton and prove that: (a) the LP decoder fails for any set of flips with support vector including an instanton; (b) for any input, the algorithm outputs an instanton in the number of steps upper-bounded by twice the number of flips in the input. We obtain the number of unique instantons of different sizes by running the ISA sufficient number of times. We then use the instanton statistics to predict the performance of the LP decoding over the BSC in the error floor region. We also propose an efficient semi-analytical method to predict the performance of LP decoding over a large range of transition probabilities of the BSC.
Date: January 1, 2009
Creator: Chertkov, Michael; Chilappagari, Shashi; Vasic, Bane & Stepanov, Mikhail
Partner: UNT Libraries Government Documents Department

Analysis of Godiva-IV delayed-critical and static super-prompt-critical conditions

Description: Super-prompt-critical burst experiments were conducted on the Godiva-IV assembly at Los Alamos National Laboratory from the 1960s through 2005. Detailed and simplified benchmark models have been constructed for four delayed-critical experiments and for the static phase of a super-prompt-critical burst experiment. In addition, a two-dimensional cylindrical model has been developed for the super-prompt-critical condition. Criticality calculations have been performed for all of those models with four modern nuclear data libraries: ENDFIB-VI, ENDF/8-VII.0, JEFF-3.1 , and JENDL-3.3. Overall, JENDL-3.3 produces the best agreement with the reference values for k{sub eff}.
Date: January 1, 2009
Creator: Mosteller, Russell D & Goda, Joetta M
Partner: UNT Libraries Government Documents Department

Analytical Study of Stress State in HTS Solenoids

Description: A main challenge for high field solenoids made of in High Temperature Superconductor (HTS) is the large stress developed in the conductor. This is especially constraining for BSCCO, a brittle and strain sensitive ceramic material. To find parametric correlations useful in magnet design, analytical models can be used. A simple model is herein proposed to obtain the radial, azimuthal and axial stresses in a solenoid as a function of size, i.e. self-field, and of the engineering current density for a number of different constraint hypotheses. The analytical model was verified against finite element modeling (FEM) using the same hypotheses of infinite rigidity of the constraints and room temperature properties. FEM was used to separately evaluate the effect of thermal contractions at 4.2 K for BSCCO and YBCO coils. Even though the analytical model allows for a finite stiffness of the constraints, it was run using infinite stiffness. For this reason, FEM was again used to determine how much stresses change when considering an outer stainless steel skin with finite rigidity for both BSCCO and YBCO coils. For a better understanding of the actual loads that high field solenoids made of HTS will be subject to, we have started some analytical studies of stress state in solenoids for a number of constraint hypotheses. This will hopefully show what can be achieved with the present conductor in terms of self-field. The magnetic field (B) exerts a force F = B x J per unit volume. In superconducting magnets, where the field and current density (J) are both high, this force can be very large, and it is therefore important to calculate the stresses in the coil.
Date: January 1, 2009
Creator: Barzi, E. & Terzini, E.
Partner: UNT Libraries Government Documents Department

Annex VI to the Protocol of Environmental Protection to the Antarctic Treaty : message from the President of the United States transmitting Annex VI on liability arising from environmental emergencies to the Protocol on Environmental Protection to the Antarctic Treaty (Annex VI), adopted on June 14, 2005

Description: This amendment to the Antarctic Treaty deals with preventing and managing environmental emergencies in the Antarctica Treaty area.
Date: 2009
Creator: United States. President (2009- : Obama) & Clinton, Hillary Rodham
Partner: UNT Libraries

Anomalous diffusion and scaling in coupled stochastic processes

Description: Inspired by problems in biochemical kinetics, we study statistical properties of an overdamped Langevin processes with the friction coefficient depending on the state of a similar, unobserved, process. Integrating out the latter, we derive the Pocker-Planck the friction coefficient of the first depends on the state of the second. Integrating out the latter, we derive the Focker-Planck equation for the probability distribution of the former. This has the fonn of diffusion equation with time-dependent diffusion coefficient, resulting in an anomalous diffusion. The diffusion exponent can not be predicted using a simple scaling argument, and anomalous scaling appears as well. The diffusion exponent of the Weiss-Havlin comb model is derived as a special case, and the same exponent holds even for weakly coupled processes. We compare our theoretical predictions with numerical simulations and find an excellent agreement. The findings caution against treating biochemical systems with unobserved dynamical degrees of freedom by means of standandard, diffusive Langevin descritpion.
Date: January 1, 2009
Creator: Bel, Golan & Nemenman, Ilya
Partner: UNT Libraries Government Documents Department

Application of x-ray tomography to optimization of new NOx/NH3 mixed potential sensors for vehicle on-board emissions control

Description: Mixed potential sensors for the detection of hydrocarbons, NO{sub x}, and NH{sub 3} have been previously developed at Los Alamos National Laboratory (LANL). The LANL sensors have a unique design incorporating dense ceramic-pelletlmetal-wire electrodes and porous electrolytes. The performance of current-biased sensors using an yttria-stabilized zirconia (YSZ) electrolyte and platinum and La{sub 0.8}Sr{sub 0.2}CrO{sub 3} electrodes is reported. X-ray tomography has been applied to non-destructively examine internal structures of these sensors. NO{sub x} and hydrocarbon response of the sensors under various bias conditions is reported, and very little NO{sub x} response hysteresis was observed. The application of a 0.6 {mu}A bias to these sensors shifts the response from a hydrocarbon response to a NO{sub x} response equal for both NO and NO{sub 2} species at approximately 500 {sup o}C in air.
Date: January 1, 2009
Creator: Nelson, Mark A; Brosha, Eric L; Mukundan, Rangachary & Garzon, Fernando H
Partner: UNT Libraries Government Documents Department