Design Optimization of Vena Cava Filters: An application to dual filtration devices (open access)

Design Optimization of Vena Cava Filters: An application to dual filtration devices

Pulmonary embolism (PE) is a significant medical problem that results in over 300,000 fatalities per year. A common preventative treatment for PE is the insertion of a metallic filter into the inferior vena cava that traps thrombi before they reach the lungs. The goal of this work is to use methods of mathematical modeling and design optimization to determine the configuration of trapped thrombi that minimizes the hemodynamic disruption. The resulting configuration has implications for constructing an optimally designed vena cava filter. Computational fluid dynamics is coupled with a nonlinear optimization algorithm to determine the optimal configuration of trapped model thrombus in the inferior vena cava. The location and shape of the thrombus are parameterized, and an objective function, based on wall shear stresses, determines the worthiness of a given configuration. The methods are fully automated and demonstrate the capabilities of a design optimization framework that is broadly applicable. Changes to thrombus location and shape alter the velocity contours and wall shear stress profiles significantly. For vena cava filters that trap two thrombi simultaneously, the undesirable flow dynamics past one thrombus can be mitigated by leveraging the flow past the other thrombus. Streamlining the shape of thrombus trapped along the …
Date: December 3, 2009
Creator: Singer, M. A.; Wang, S. L. & Diachin, D. P.
System: The UNT Digital Library
MODELING TRANSPORT IN THE DOWN GRADIENT PORTION OF THE 200-PO-1 OPERABLE UNIT AT THE HANFORD SITE (open access)

MODELING TRANSPORT IN THE DOWN GRADIENT PORTION OF THE 200-PO-1 OPERABLE UNIT AT THE HANFORD SITE

Remedial Investigations are underway for the 200-PO-l Operable Unit (OU) at the U.S. Department of Energy's Hanford Site in Washington State. To support the baseline risk assessment and evaluation of remedial alternatives, fate and transport modeling is being conducted to predict the future concentration of contaminants of potential concern in the 200-PO-1 OU. This study focuses on modeling the 'down gradient' transport of those contaminants that migrate beyond the 3-D model domain selected for performing detailed 'source area' modeling within the 200-PO-1 OU. The down gradient portion is defined as that region of the 200-PO-1 OU that is generally outside the 200 Area (considered 'source area') of the Hanford Site. A 1-D transport model is developed for performing down gradient contaminant fate and transport modeling. The 1-D transport model is deemed adequate based on the inferred transport pathway of tritium in the past and the observation that most of the contaminant mass remains at or near the water table within the unconfined aquifer of the Hanford Formation and the Cold-Creek/Pre-Missoula Gravel unit. The Pipe Pathway feature of the GoldSim software is used to perform the calculations. The Pipe Pathway uses a Laplace transform approach to provide analytical solutions to a …
Date: December 3, 2009
Creator: Mehta, S.; Aly, Ah; Miller, C. W. & Mayenna, A
System: The UNT Digital Library
POTENTIAL USE OF ACTIVATED CARBON TO RECOVER TC-99 FROM 200 WEST AREA GROUNDWATER AS AN ALTERNATIVE TO MORE EXPENSIVE RESINS HANFORD SITE RICHLAND WASNINGTON (open access)

POTENTIAL USE OF ACTIVATED CARBON TO RECOVER TC-99 FROM 200 WEST AREA GROUNDWATER AS AN ALTERNATIVE TO MORE EXPENSIVE RESINS HANFORD SITE RICHLAND WASNINGTON

Recent treatability testing performed on groundwater at the 200-ZP-1 Operable Unit at the Hanford Site in Richland, Washington, has shown that Purolite{reg_sign} A530E resin very effectively removes Tc-99 from groundwater. However, this resin is expensive and cannot be regenerated. In an effort to find a less expensive method for removing Tc-99 from the groundwater, a literature search was performed. The results indicated that activated carbon may be used to recover technetium (as pertechnetate, TCO{sub 4}{sup -}) from groundwater. Oak Ridge National Laboratory used activated carbon in both batch adsorption and column leaching studies. The adsorption study concluded that activated carbon absorbs TCO{sub 4}{sup -} selectively and effectively over a wide range of pH values and from various dilute electrolyte solutions (< 0.01 molarity). The column leaching studies confirmed a high adsorption capacity and selectivity of activated carbon for TCO{sub 4}{sup -}. Since activated carbon is much less expensive than Purolite A530E resin, it has been determined that a more extensive literature search is warranted to determine if recent studies have reached similar conclusions, and, if so, pilot testing of 200-ZP-1 groundwater wi11 likely be implemented. It is possible that less expensive, activated carbon canisters could be used as pre-filters to …
Date: December 3, 2009
Creator: Byrnes, M. E.; Rossi, A. J. & Tortoso, A. C.
System: The UNT Digital Library
RESULTS FROM RECENT SCIENCE AND TECHNOLOGY INVESTIGATIONS TARGETING CHROMIUM IN THE 100D AREA HANFORD SITE WASHINGTON USA (open access)

RESULTS FROM RECENT SCIENCE AND TECHNOLOGY INVESTIGATIONS TARGETING CHROMIUM IN THE 100D AREA HANFORD SITE WASHINGTON USA

Sodium dichromate was used in Hanford's 100D Area during the reactor operations period of 1950 to 1964 to retard corrosion in the reactor cooling systems. Some of the sodium dichromate was released to the environment by spills and/or leaks from pipelines used to deliver the chemical to water treatment plants in the area. As a result, hexavalent chromium [Cr(VI)] has migrated through the vadose zone to the groundwater and contaminated nearly 1 km{sup 2} of groundwater to above the drinking water standard of 48 {micro}g/L. Three technology tests have recently been completed in this area to characterize the source area of the plumes and evaluate alternative methods to remove Cr(VI) from groundwater. These are (1) refine the source area of the southern plume; (2) test electrocoagulation as an alternative groundwater treatment technology; and (3) test the ability to repair a permeable reactive barrier by injecting micron or nanometer-size zero-valent iron (ZVI). The projects were funded by the US Department of Energy as part of a program to interject new technologies and accelerate active cleanup. Groundwater monitoring over the past 10 years has shown that Cr(VI) concentrations in the southern plume have not significantly diminished, strongly indicating a continuing source. Eleven …
Date: December 3, 2009
Creator: Petersen, S. W.; Thompson, K. M. & Tonkin, M. J.
System: The UNT Digital Library
SAVANNAH RIVER SITE R REACTOR DISASSEMBLY BASIN IN SITU DECOMMISSIONING (open access)

SAVANNAH RIVER SITE R REACTOR DISASSEMBLY BASIN IN SITU DECOMMISSIONING

The US DOE concept for facility in-situ decommissioning (ISD) is to physically stabilize and isolate in tact, structurally sound facilities that are no longer needed for their original purpose of, i.e., generating (reactor facilities), processing(isotope separation facilities) or storing radioactive materials. The 105-R Disassembly Basin is the first SRS reactor facility to undergo the in-situ decommissioning (ISD) process. This ISD process complies with the105-R Disassembly Basin project strategy as outlined in the Engineering Evaluation/Cost Analysis for the Grouting of the R-Reactor Disassembly Basin at the Savannah River Site and includes: (1) Managing residual water by solidification in-place or evaporation at another facility; (2) Filling the below grade portion of the basin with cementitious materials to physically stabilize the basin and prevent collapse of the final cap - Sludge and debris in the bottom few feet of the basin will be encapsulated between the basin floor and overlying fill material to isolate if from the environment; (3) Demolishing the above grade portion of the structure and relocating the resulting debris to another location or disposing of the debris in-place; and (4) Capping the basin area with a concrete slab which is part of an engineered cap to prevent inadvertent intrusion. The …
Date: December 3, 2009
Creator: Langton, C.; Blankenship, J.; Griffin, W. & Serrato, M.
System: The UNT Digital Library
Large Time Projection Chambers for Rare Event Detection (open access)

Large Time Projection Chambers for Rare Event Detection

The Time Projection Chamber (TPC) concept [add ref to TPC section] has been applied to many projects outside of particle physics and the accelerator based experiments where it was initially developed. TPCs in non-accelerator particle physics experiments are principally focused on rare event detection (e.g. neutrino and darkmater experiments) and the physics of these experiments can place dramatically different constraints on the TPC design (only extensions to the traditional TPCs are discussed here). The drift gas, or liquid, is usually the target or matter under observation and due to very low signal rates a TPC with the largest active mass is desired. The large mass complicates particle tracking of short and sometimes very low energy particles. Other special design issues include, efficient light collection, background rejection, internal triggering and optimal energy resolution. Backgrounds from gamma-rays and neutrons are significant design issues in the construction of these TPCs. They are generally placed deep underground to shield from cosmogenic particles and surrounded with shielding to reduce radiation from the local surroundings. The construction materials have to be carefully screened for radiopurity as they are in close contact with the active mass and can be a signification source of background events. The TPC …
Date: November 3, 2009
Creator: Heffner, M
System: The UNT Digital Library
Oligo and Poly-thiophene/Zno Hybrid Nanowire Solar Cells (open access)

Oligo and Poly-thiophene/Zno Hybrid Nanowire Solar Cells

We demonstrate the basic operation of an organic/inorganic hybrid single nanowire solar cell. End-functionalized oligo- and polythiophenes were grafted onto ZnO nanowires to produce p-n heterojunction nanowires. The hybrid nanostructures were characterized via absorption and electron microscopy to determine the optoelectronic properties and to probe the morphology at the organic/inorganic interface. Individual nanowire solar cell devices exhibited well-resolved characteristics with efficiencies as high as 0.036percent, Jsc = 0.32 mA/cm2, Voc = 0.4 V, and a FF = 0.28 under AM 1.5 illumination with 100 mW/cm2 light intensity. These individual test structures will enable detailed analysis to be carried out in areas that have been difficult to study in bulk heterojunction devices.
Date: November 3, 2009
Creator: Briseno, Alejandro L.; Holcombe, Thomas W.; Boukai, Akram I.; Garnett, Erik C.; Shelton, Steve W.; Frechet, Jean J. M. et al.
System: The UNT Digital Library
Integrated Genomic Analysis Identifies Clinically Relevant Subtypes of Glioblastoma Characterized by Abnormalities in PDGFRA, IDH1, EGFR, and NF1 (open access)

Integrated Genomic Analysis Identifies Clinically Relevant Subtypes of Glioblastoma Characterized by Abnormalities in PDGFRA, IDH1, EGFR, and NF1

The Cancer Genome Atlas Network recently cataloged recurrent genomic abnormalities in glioblastoma multiforme (GBM). We describe a robust gene expression-based molecular classification of GBM into Proneural, Neural, Classical, and Mesenchymal subtypes and integrate multidimensional genomic data to establish patterns of somatic mutations and DNA copy number. Aberrations and gene expression of EGFR, NF1, and PDGFRA/IDH1 each define the Classical, Mesenchymal, and Proneural subtypes, respectively. Gene signatures of normal brain cell types show a strong relationship between subtypes and different neural lineages. Additionally, response to aggressive therapy differs by subtype, with the greatest benefit in the Classical subtype and no benefit in the Proneural subtype. We provide a framework that unifies transcriptomic and genomic dimensions for GBM molecular stratification with important implications for future studies.
Date: September 3, 2009
Creator: Verhaak, Roel GW; Hoadley, Katherine A; Purdom, Elizabeth; Wang, Victoria; Qi, Yuan; Wilkerson, Matthew D et al.
System: The UNT Digital Library
Numerical Tests and Properties of Waves in Radiating Fluids (open access)

Numerical Tests and Properties of Waves in Radiating Fluids

We discuss the properties of an analytical solution for waves in radiating fluids, with a view towards its implementation as a quantitative test of radiation hydrodynamics codes. A homogeneous radiating fluid in local thermodynamic equilibrium is periodically driven at the boundary of a one-dimensional domain, and the solution describes the propagation of the waves thus excited. Two modes are excited for a given driving frequency, generally referred to as a radiative acoustic wave and a radiative diffusion wave. While the analytical solution is well known, several features are highlighted here that require care during its numerical implementation. We compare the solution in a wide range of parameter space to a numerical integration with a Lagrangian radiation hydrodynamics code. Our most significant observation is that flux-limited diffusion does not preserve causality for waves on a homogeneous background.
Date: September 3, 2009
Creator: Johnson, B M & Klein, R I
System: The UNT Digital Library
Physics of Neutralization of Intense Charged Particle Beam Pulses by a Background Plasma (open access)

Physics of Neutralization of Intense Charged Particle Beam Pulses by a Background Plasma

Neutralization and focusing of intense charged particle beam pulses by a background plasma forms the basis for a wide range of applications to high energy accelerators and colliders, heavy ion fusion, and astrophysics. For example, for ballistic propagation of intense ion beam pulses, background plasma can be used to effectively neutralize the beam charge and current, so that the self-electric and self-magnetic fields do not affect the ballistic propagation of the beam. From the practical perspective of designing advanced plasma sources for beam neutralization, a robust theory should be able to predict the self-electric and self-magnetic fields during beam propagation through the background plasma. The major scaling relations for the self-electric and self-magnetic fields of intense ion charge bunches propagating through background plasma have been determined taking into account the effects of transients during beam entry into the plasma, the excitation of collective plasma waves, the effects of gas ionization, finite electron temperature, and applied solenoidal and dipole magnetic fields. Accounting for plasma production by gas ionization yields a larger self-magnetic field of the ion beam compared to the case without ionization, and a wake of current density and self-magnetic field perturbations is generated behind the beam pulse. A solenoidal …
Date: September 3, 2009
Creator: Kaganovich, I. D.; Davidson, R. C.; Dorf, M. A.; Startsev, E. A.; Sefkow, A. B.; Friedman, A. F. et al.
System: The UNT Digital Library
SYNTHESIS OF NON-RADIOACTIVE SLURRIES TO SIMULATE THE PROCESSING BEHAVIOR OF PARTICLES IN RADIOACTIVE WASTE SLURRIES 626-G (open access)

SYNTHESIS OF NON-RADIOACTIVE SLURRIES TO SIMULATE THE PROCESSING BEHAVIOR OF PARTICLES IN RADIOACTIVE WASTE SLURRIES 626-G

Process development using non-radioactive analogs to high-level radioactive waste slurries is an established cost effective alternative to working with actual samples of the real waste. Current simulated waste slurries, however, do not capture all of the physical behavior of real waste. New methods of preparing simulants are under investigation along with mechanisms for altering certain properties of finished simulants. These methods have achieved several notable successes recently in the areas of rheology and foaminess. Particle size is also being manipulated more effectively than in the past, though not independently of the rheological properties. The interaction between rheology and foaminess has exhibited counter-intuitive behavior with more viscous slurries being less foamy even though drainage of liquid from the foam lamellae should be inhibited by higher viscosities.
Date: September 3, 2009
Creator: Koopman, D.; Lambert, D.; Eibling, R.; Newell, J. & Stone, M.
System: The UNT Digital Library
Ab initio no core calculations of light nuclei and preludes to Hamiltonian quantum field theory (open access)

Ab initio no core calculations of light nuclei and preludes to Hamiltonian quantum field theory

Recent advances in ab initio quantum many-body methods and growth in computer power now enable highly precise calculations of nuclear structure. The precision has attained a level sufficient to make clear statements on the nature of 3-body forces in nuclear physics. Total binding energies, spin-dependent structure effects, and electroweak properties of light nuclei play major roles in pinpointing properties of the underlying strong interaction. Eventually,we anticipate a theory bridge with immense predictive power from QCD through nuclear forces to nuclear structure and nuclear reactions. Light front Hamiltonian quantum field theory offers an attractive pathway and we outline key elements.
Date: August 3, 2009
Creator: Vary, J. P.; Maris, P.; Shirokov, A. M.; Honkanen, H.; li, J.; Brodsky, S. J. et al.
System: The UNT Digital Library
Assembly and Characterization of a Prototype Laser-Optical Firing System (open access)

Assembly and Characterization of a Prototype Laser-Optical Firing System

The design, assembly and characterization of the latest generation of a small, ruggedized laser-optical firing system will be discussed. This work builds upon earlier results in an effort to continue the development of robust fiber-coupled laseroptical firing systems.[1][2] This newest prototype strives to improve on earlier designs, while continuing to utilize many of the environmentally proven opto-mechanical sub-assemblies.[2][3] One area of improvement involves the implementation of a second optical safing and arming component. Several additional design improvements were also incorporated to address shortcomings uncovered during environmental testing.[4][5] These tests and the subsequent failure analysis were performed at the laser sub-system level. Four identical prototypes were assembled and characterized. The performance of the units were evaluated by comparing a number of parameters including laser output energy, slope efficiency, beam divergence, spatial intensity profile, fiber injection and splitter-coupler transmission efficiency. Other factors evaluated were the ease of alignment, repeatability of the alignment process and the fabrication of the fiberoptical cables. The experimentally obtained results will be compared and contrasted to the performance of earlier prototypes.
Date: August 3, 2009
Creator: Morelli, Gregg L
System: The UNT Digital Library
A Bottom-Up Approach to SUSY Analyses (open access)

A Bottom-Up Approach to SUSY Analyses

This paper proposes a new way to perform event generation and analysis in searches for new physics at the LHC. An abstract notation is used to describe the new particles on a level which better corresponds to detector resolution of LHC experiments. In this way the SUSY discovery space can be decomposed into a small number of eigenmodes each with only a few parameters, which allows to investigate the SUSY parameter space in a model-independent way. By focusing on the experimental observables for each process investigated the Bottom-Up Approach allows to systematically study the boarders of the experimental efficiencies and thus to extend the sensitivity for new physics.
Date: August 3, 2009
Creator: Horn, Claus
System: The UNT Digital Library
Conceptual Design of the Drive Beam for a PWFA-LC (open access)

Conceptual Design of the Drive Beam for a PWFA-LC

Plasma Wake-Field Acceleration (PWFA) has demonstrated acceleration gradients above 50 GeV/m. Simulations have shown drive/witness bunch configurations that yield small energy spreads in the accelerated witness bunch and high energy transfer efficiency from the drive bunch to the witness bunch, ranging from 30% for a Gaussian drive bunch to 95% for bunch with triangular shaped longitudinal profile. These results open the opportunity for a linear collider that could be compact, efficient and more cost effective than the present microwave technologies. A concept of a PWFA-based Linear Collider (PWFA-LC) has been developed by the PWFA collaboration. Here we will describe the conceptual design and optimization of the drive beam, which includes the drive beam linac and distribution system. We apply experience of the CLIC drive beam design and demonstration in the CLIC Test Facility (CTF3) to this study. We discuss parameter optimization of the drive beam linac structure and evaluate the drive linac efficiency in terms of the drive beam distribution scheme and the klystron/modulator requirements.
Date: August 3, 2009
Creator: Pei, S.; Hogan, M. J.; Raubenheimer, T. O.; Seryi, A.; Braun, H. H.; Corsini, R. et al.
System: The UNT Digital Library
Connecting Reionization to the Local Universe (open access)

Connecting Reionization to the Local Universe

We present results of combined N-body and three-dimensional reionization calculations to determine the relationship between reionization history and local environment in a volume 1 Gpc h{sup -1} across and a resolution of about 1 Mpc. We resolve the formation of about 2 x 10{sup 6} halos of mass greater than {approx} 10{sup 12} M{sub {circle_dot}} at z = 0, allowing us to determine the relationship between halo mass and reionization epoch for galaxies and clusters. For our fiducial reionization model, in which reionization begins at z {approx} 15 and ends by z {approx} 6, we find a strong bias for cluster-size halos to be in the regions which reionized first, at redshifts 10 < z < 15. Consequently, material in clusters was reionized within relatively small regions, on the order of a few Mpc, implying that all clusters in our calculation were reionized by their own progenitors. Milky Way mass halos were on average reionized later and by larger regions, with a distribution most similar to the global one, indicating that low mass halos are nearly uncorrelated with reionization when only their mass is taken as a prior. On average, we find that most halos with mass less than 10{sup …
Date: August 3, 2009
Creator: Alvarez, Marcelo A.; Busha, Michael; Abel, Tom; Wechsler, Risa H. & /KIPAC, Menlo Park
System: The UNT Digital Library
Constraining the Scatter in the Mass-Richness Relation of maxBCG Clusters With Weak Lensing and X-ray Data (open access)

Constraining the Scatter in the Mass-Richness Relation of maxBCG Clusters With Weak Lensing and X-ray Data

We measure the logarithmic scatter in mass at fixed richness for clusters in the maxBCG cluster catalog, an optically selected cluster sample drawn from SDSS imaging data. Our measurement is achieved by demanding consistency between available weak lensing and X-ray measurements of the maxBCG clusters, and the X-ray luminosity-mass relation inferred from the 400d X-ray cluster survey, a flux limited X-ray cluster survey. We find {sigma}{sub lnM|N{sub 200}} = 0.45{sub -0.18}{sup +0.20} (95%CL) at N{sub 200} {approx} 40, where N{sub 200} is the number of red sequence galaxies in a cluster. As a byproduct of our analysis, we also obtain a constraint on the correlation coefficient between lnL{sub X} and lnM at fixed richness, which is best expressed as a lower limit, r{sub L,M|N} {ge} 0.85 (95% CL). This is the first observational constraint placed on a correlation coefficient involving two different cluster mass tracers. We use our results to produce a state of the art estimate of the halo mass function at z = 0.23 - the median redshift of the maxBCG cluster sample - and find that it is consistent with the WMAP5 cosmology. Both the mass function data and its covariance matrix are presented.
Date: August 3, 2009
Creator: Rozo, Eduardo; U., /Ohio State; Rykoff, Eli S.; /UC, Santa Barbara; Evrard, August; U., /Michigan et al.
System: The UNT Digital Library
Damping Effect Studies for X-band Normal Conducting High Gradient Standing Wave Structures (open access)

Damping Effect Studies for X-band Normal Conducting High Gradient Standing Wave Structures

The Multi-TeV colliders should have the capability to accelerate low emittance beam with high rf efficiency, X-band normal conducting high gradient accelerating structure is one of the promising candidate. However, the long range transverse wake field which can cause beam emittance dilution is one of the critical issues. We examined effectiveness of dipole mode damping in three kinds of X-band, {pi}-mode standing wave structures at 11.424GHz with no detuning considered. They represent three damping schemes: damping with cylindrical iris slot, damping with choke cavity and damping with waveguide coupler. We try to reduce external Q factor below 20 in the first two dipole bands, which usually have very high (R{sub T}/Q){sub T}. The effect of damping on the acceleration mode is also discussed.
Date: August 3, 2009
Creator: Pei, S.; Li, Z.; Tantawi, S. G.; Dolgashev, V. A. & Wang, J.
System: The UNT Digital Library
A Domino Theory of Flavor (open access)

A Domino Theory of Flavor

We argue that the fermion masses and mixings are organized in a specific pattern. The approximately equal hierarchies between successive generations, the sizes of the mixing angles, the heaviness of just the top quark, and the approximate down-lepton equality can all be accommodated by many flavor models but can appear ad hoc. We present a simple, predictive mechanism to explain these patterns. All generations are treated democratically and the flavor symmetries are broken collectively by only two allowed couplings in flavor-space, a vector and matrix, with arbitrary {Omicron}(1) entries. Repeated use of these flavor symmetry breaking spurions radiatively generates the Yukawa couplings with a natural hierarchy. We demonstrate this idea with two models in a split supersymmetric grand unified framework, with minimal additional particle content at the unification scale. Although flavor is generated at the GUT scale, there are several potentially testable predictions. In our minimal model the usual prediction of exact b-{tau} unification is replaced by the SU(5) breaking relation m{sub {tau}}/m{sub b} = 3/2, in better agreement with observations. Other SU(5) breaking effects in the fermion masses can easily arise directly from the flavor model itself. The symmetry breaking that triggers the generation of flavor necessarily gives rise …
Date: August 3, 2009
Creator: Graham, Peter W. & Rajendran, Surjeet
System: The UNT Digital Library
Empirical Assessment of Shareholder Incentive Mechanisms Designs under Aggressive Savings Goals: Case Study of a Kansas"Super-Utility" (open access)

Empirical Assessment of Shareholder Incentive Mechanisms Designs under Aggressive Savings Goals: Case Study of a Kansas"Super-Utility"

Achieving significant reductions in retail electric sales is becoming a priority for policymakers in many states and is echoed at the federal level with the introduction of legislation to establish a national energy efficiency resource standard. Yet, as the National Action Plan on Energy Efficiency (NAPEE) pointed out, many utilities continue to shy away from seriously expanding their energy efficiency program offerings because they claim there is insufficient profit motivation, or even a financial disincentive, when compared to supply-side investments. In response to an information request from the Kansas Corporation Commission staff, we conducted a financial analysis to assess the utility business case in Kansas for pursuing more aggressive energy efficiency that complies with recent state legislation. Kansas' utilities are vertically integrated and don't face retail competition. With historically low retail rates and modest experience with energy efficiency, the achievement of rapid and substantial sales reductions from energy efficiency will require a viable utility business model. Using a conglomerate of the three largest utilities in Kansas, we quantitatively illustrate the tradeoff between ratepayer and shareholder interests when a 1percent reduction in incremental sales is achieved through energy efficiency both with and without the impact of future carbon regulation. We then …
Date: August 3, 2009
Creator: Cappers, Peter & Goldman, Charles
System: The UNT Digital Library
FLASH Beam-off RF Measurements and Analyses (open access)

FLASH Beam-off RF Measurements and Analyses

None
Date: August 3, 2009
Creator: Pei, S.; Adolphsen, C.; Carwardine, J. & Walker, N. J.
System: The UNT Digital Library
A Fusing Switch for Fault Suppression in the SNS High Voltage Converter Modulators (open access)

A Fusing Switch for Fault Suppression in the SNS High Voltage Converter Modulators

The High Voltage Converter Modulators (HVCMs) at the Spallation Neutron Source (SNS) have operated in excess of a combined 250,000 hours. Performance and reliability improvements to the HVCM are ongoing to increase modulator availability as accelerator system demands increase. There is a relatively large amount of energy storage in the HVCMs, {approx}180 kJ. This energy has the potential to dump into unsuppressed faults, cause damage, and increase the time to repair. The 'fusing switch' concept involves isolation of this stored energy from the location of the most common faults. This paper introduces this concept and its application to the HVCMs.
Date: August 3, 2009
Creator: Kemp, Mark A.; Burkhart, Craig; Nguyen, Minh N. & Anderson, David E.
System: The UNT Digital Library
Galaxy Mergers and Dark Matter Halo Mergers in LCDM: Mass, Redshift, and Mass-Ratio Dependence (open access)

Galaxy Mergers and Dark Matter Halo Mergers in LCDM: Mass, Redshift, and Mass-Ratio Dependence

We employ a high-resolution LCDM N-body simulation to present merger rate predictions for dark matter halos and investigate how common merger-related observables for galaxies - such as close pair counts, starburst counts, and the morphologically disturbed fraction - likely scale with luminosity, stellar mass, merger mass ratio, and redshift from z = 0 to z = 4. We provide a simple 'universal' fitting formula that describes our derived merger rates for dark matter halos a function of dark halo mass, merger mass ratio, and redshift, and go on to predict galaxy merger rates using number density-matching to associate halos with galaxies. For example, we find that the instantaneous merger rate of m/M > 0.3 mass ratio events into typical L {approx}> fL{sub *} galaxies follows the simple relation dN/dt {approx_equal} 0.03(1+f)Gyr{sup -1} (1+z){sup 2.1}. Despite the rapid increase in merger rate with redshift, only a small fraction of > 0.4L{sub *} high-redshift galaxies ({approx} 3% at z = 2) should have experienced a major merger (m/M > 0.3) in the very recent past (t < 100 Myr). This suggests that short-lived, merger-induced bursts of star formation should not contribute significantly to the global star formation rate at early times, in …
Date: August 3, 2009
Creator: Stewart, Kyle R.; Bullock, James S.; Barton, Elizabeth J.; /UC, Irvine; Wechsler, Risa H. & /KIPAC, Menlo Park /SLAC
System: The UNT Digital Library
Gas-Rich Mergers in LCDM: Disk Survivability and the Baryonic Assembly of Galaxies (open access)

Gas-Rich Mergers in LCDM: Disk Survivability and the Baryonic Assembly of Galaxies

We use N-body simulations and observationally-normalized relations between dark matter halo mass, stellar mass, and cold gas mass to derive robust expectations about the baryonic content of major mergers out to redshift z {approx} 2. First, we find that the majority of major mergers (m/M > 0.3) experienced by Milky Way size dark matter halos should have been gas-rich, and that gas-rich mergers are increasingly common at high redshift. Though the frequency of major mergers into galaxy halos in our simulations greatly exceeds the observed late-type galaxy fraction, the frequency of gas-poor major mergers is consistent with the observed fraction of bulge-dominated galaxies across the halo mass range M{sub DM} {approx} 10{sup 11} - 10{sup 13} M{sub {circle_dot}}. These results lend support to the conjecture that mergers with high baryonic gas fractions play an important role in building and/or preserving disk galaxies in the universe. Secondly, we find that there is a transition mass below which a galaxy's past major mergers were primarily gas-rich and above which they were gas poor. The associated stellar mass scale corresponds closely to that marking the observed bimodal division between blue, star-forming, disk-dominated systems and red, bulge-dominated systems with old populations. Finally, we find …
Date: August 3, 2009
Creator: Stewart, Kyle R.; Bullock, James S.; /UC, Irvine; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC; Maller, Ariyeh H. et al.
System: The UNT Digital Library