The Average Star Formation Histories of Galaxies in Dark Matter Halos from z = 0-8 (open access)

The Average Star Formation Histories of Galaxies in Dark Matter Halos from z = 0-8

Presents a method to constrain average galaxy star formation rates, star formation histories, and the intracluster light as a function of halo mass.
Date: May 9, 2013
Creator: Behroozi, Peter S.; Wechsler, Risa H. & Conroy, Charlie
System: The UNT Digital Library
Brightness and Coherence of Synchrotron Radiation and FELs (open access)

Brightness and Coherence of Synchrotron Radiation and FELs

None
Date: May 9, 2013
Creator: Huang, Zhirong
System: The UNT Digital Library
Early Experiences With The OpenMP Accelerator Model (open access)

Early Experiences With The OpenMP Accelerator Model

None
Date: May 9, 2013
Creator: Liao, C.; Yan, Y.; de Supinsky, B.; Quinlan, D. & Chapman, B.
System: The UNT Digital Library
Microbunched Electron Cooling for Hadrons (open access)

Microbunched Electron Cooling for Hadrons

None
Date: May 9, 2013
Creator: Ratner, Daniel
System: The UNT Digital Library
120-Channel, Chronically Implantable, Wireless, Polymer Neural Interface (open access)

120-Channel, Chronically Implantable, Wireless, Polymer Neural Interface

None
Date: May 9, 2012
Creator: Tooker, A; Shah, K; Tolosa, V; Sheth, H; Felix, S; Delima, T et al.
System: The UNT Digital Library
Beam Measurements at LCLS (open access)

Beam Measurements at LCLS

None
Date: May 9, 2012
Creator: Frisch, J.; Akre, R.; Decker, F. J.; Ding, Y.; Dowell, D.; Emma, P. et al.
System: The UNT Digital Library
CW Room Temperature Re-Buncher for the Project X Front End (open access)

CW Room Temperature Re-Buncher for the Project X Front End

At Fermilab there is a plan to construct the Project X Injector Experiment (PXIE) facility - a prototype of the front end of the Project X, a multi-MW proton source based on superconducting linac. The construction and successful operations of this facility will validate the concept for the Project X front end, thereby minimizing the primary technical risk element within the Project. The room temperature front end of the linac contains an ion source, an RFQ accelerator and a Medium Energy Beam Transport (MEBT) section comprising a high bandwidth bunch selective chopper. The MEBT length is about 10 m, so three re-bunching CW cavities are used to support the beam longitudinal dynamics. The paper reports a RF design of the re-bunchers along with preliminary beam dynamic and thermal analysis of the cavities.
Date: May 9, 2012
Creator: Romanov, Gennady; Awida, Mohamed H.; Chen, Meiyu; Gonin, Ivan V.; Kazakov, Sergey; Kostin, Roman et al.
System: The UNT Digital Library
Efficient Laser-Induced 6 - 8 KeV X-Ray Production From Iron Oxide Aerogel and Foil-Lined Cavity Targets (open access)

Efficient Laser-Induced 6 - 8 KeV X-Ray Production From Iron Oxide Aerogel and Foil-Lined Cavity Targets

None
Date: May 9, 2012
Creator: Perez, F.; Kay, J. J.; Patterson, R.; Kane, J.; Villette, B.; Girard, F. et al.
System: The UNT Digital Library
Modeling Multi-Bunch X-band Photoinjector Challenges (open access)

Modeling Multi-Bunch X-band Photoinjector Challenges

An X-band test station is being developed at LLNL to investigate accelerator optimization for future upgrades to mono-energetic gamma-ray technology at LLNL. The test station will consist of a 5.5 cell X-band rf photoinjector, single accelerator section, and beam diagnostics. Of critical import to the functioning of the LLNL X-band system with multiple electron bunches is the performance of the photoinjector. In depth modeling of the Mark 1 LLNL/SLAC X-band rf photoinjector performance will be presented addressing important challenges that must be addressed in order to fabricate a multi-bunch Mark 2 photoinjector. Emittance performance is evaluated under different nominal electron bunch parameters using electrostatic codes such as PARMELA. Wake potential is analyzed using electromagnetic time domain simulations using the ACE3P code T3P. Plans for multi-bunch experiments and implementation of photoinjector advances for the Mark 2 design will also be discussed.
Date: May 9, 2012
Creator: Marsh, R A; Anderson, S G; Gibson, D J & Barty, C J
System: The UNT Digital Library
PACKAGING CERTIFICATION PROGRAM METHODOLOGY FOR DETERMINING DOSE RATES FOR SMALL GRAM QUANTITIES IN SHIPPING PACKAGINGS (open access)

PACKAGING CERTIFICATION PROGRAM METHODOLOGY FOR DETERMINING DOSE RATES FOR SMALL GRAM QUANTITIES IN SHIPPING PACKAGINGS

The Small Gram Quantity (SGQ) concept is based on the understanding that small amounts of hazardous materials, in this case radioactive materials (RAM), are significantly less hazardous than large amounts of the same materials. This paper describes a methodology designed to estimate an SGQ for several neutron and gamma emitting isotopes that can be shipped in a package compliant with 10 CFR Part 71 external radiation level limits regulations. These regulations require packaging for the shipment of radioactive materials, under both normal and accident conditions, to perform the essential functions of material containment, subcriticality, and maintain external radiation levels within the specified limits. By placing the contents in a helium leak-tight containment vessel, and limiting the mass to ensure subcriticality, the first two essential functions are readily met. Some isotopes emit sufficiently strong photon radiation that small amounts of material can yield a large dose rate outside the package. Quantifying the dose rate for a proposed content is a challenging issue for the SGQ approach. It is essential to quantify external radiation levels from several common gamma and neutron sources that can be safely placed in a specific packaging, to ensure compliance with federal regulations. The Packaging Certification Program (PCP) …
Date: May 9, 2012
Creator: Nathan, S.; Loftin, B.; Abramczyk, G. & Bellamy, S.
System: The UNT Digital Library
Project X RFQ EM Design (open access)

Project X RFQ EM Design

Project X is a proposed multi-MW proton facility at Fermi National Accelerator Laboratory (FNAL). The Project X front-end would consist of an H- ion source, a low-energy beam transport (LEBT), a CW 162.5 MHz radio-frequency quadrupole (RFQ) accelerator, and a medium-energy beam transport (MEBT). Lawrence Berkeley National Laboratory (LBNL) and FNAL collaboration is currently developing the designs for various components in the Project X front end. This paper reports the detailed EM design of the CW 162.5 MHz RFQ that provides bunching of the 1-10 mA H- beam with acceleration from 30 keV to 2.1 MeV.
Date: May 9, 2012
Creator: Romanov, Gennady; Hoff, Matthew; Li, Derun; Staples, John & Virostek, Steve
System: The UNT Digital Library
Dynamical Systems in Circuit Designer's Eyes (open access)

Dynamical Systems in Circuit Designer's Eyes

Examples of nonlinear circuit design are given. Focus of the design process is on theory and engineering methods (as opposed to numerical analysis). Modeling is related to measurements It is seen that the phase plane is still very useful with proper models Harmonic balance/describing function offers powerful insight (via the combination of simulation with circuit and ODE theory). Measurement and simulation capabilities increased, especially harmonics measurements (since sinusoids are easy to generate)
Date: May 9, 2011
Creator: Odyniec, M.
System: The UNT Digital Library
Exploring simultaneous single and coincident gamma-ray measurements for U/Pu assay in safeguards (open access)

Exploring simultaneous single and coincident gamma-ray measurements for U/Pu assay in safeguards

None
Date: May 9, 2011
Creator: Wang, T. F.; Horne, S. M.; Henderson, R. A.; Roberts, K. E. & Vogt, D. K.
System: The UNT Digital Library
Geothermal Energy Production from Actively-Managed CO2 Storage in Saline Formations (open access)

Geothermal Energy Production from Actively-Managed CO2 Storage in Saline Formations

None
Date: May 9, 2011
Creator: Buscheck, T A; Sun, Y; Hao, Y; Chen, M; Court, B; Celia, M A et al.
System: The UNT Digital Library
Waveguide Coupler for X-Band Deflectors (open access)

Waveguide Coupler for X-Band Deflectors

Technology developed for the NLC and for recent high gradient research may help building advanced {approx}fs beam diagnostics.
Date: May 9, 2011
Creator: Dolgashev, Valery
System: The UNT Digital Library
Characteristics of CoxTi1-xO2 thin films deposited by MOCVD (open access)

Characteristics of CoxTi1-xO2 thin films deposited by MOCVD

This paper deals with the growth and characterization of ferromagnetic cobalt doped TiO{sub 2} thin films deposited by liquid precursor metal organic chemical vapor deposition (MOCVD) using a new combination of the source materials Co(TMHD){sub 3}, tetrahydrofuran (THF), and titanium isopropoxide (TIP). An array of experiments reveals the intrinsic ferromagnetic nature of the grown films, and suggests that the magnetism is not generated by oxygen vacancies.
Date: May 9, 2008
Creator: McClure, A.; Kayani, A.; Idzerda, Y.U.; Arenholz, E. & Cruz, E.
System: The UNT Digital Library
Dendrimer Templated Synthesis of One Nanometer Rh and Pt Particles Supported on Mesoporous Silica: Catalytic Activity for Ethylene and Pyrrole Hydrogenation. (open access)

Dendrimer Templated Synthesis of One Nanometer Rh and Pt Particles Supported on Mesoporous Silica: Catalytic Activity for Ethylene and Pyrrole Hydrogenation.

Monodisperse rhodium (Rh) and platinum (Pt) nanoparticles as small as {approx}1 nm were synthesized within a fourth generation polyaminoamide (PAMAM) dendrimer, a hyperbranched polymer, in aqueous solution and immobilized by depositing onto a high-surface-area SBA-15 mesoporous support. X-ray photoelectron spectroscopy indicated that the as-synthesized Rh and Pt nanoparticles were mostly oxidized. Catalytic activity of the SBA-15 supported Rh and Pt nanoparticles was studied with ethylene hydrogenation at 273 and 293 K in 10 torr of ethylene and 100 torr of H{sub 2} after reduction (76 torr of H{sub 2} mixed with 690 torr of He) at different temperatures. Catalysts were active without removing the dendrimer capping but reached their highest activity after hydrogen reduction at a moderate temperature (423 K). When treated at a higher temperature (473, 573, and 673 K) in hydrogen, catalytic activity decreased. By using the same treatment that led to maximum ethylene hydrogenation activity, catalytic activity was also evaluated for pyrrole hydrogenation.
Date: May 9, 2008
Creator: Huang, Wenyu; Kuhn, John N.; Tsung, Chia-Kuang; Zhang, Yawen; Habas, Susan E.; Yang, Peidong et al.
System: The UNT Digital Library
FLUIDIZED BED STEAM REFORMING ENABLING ORGANIC HIGH LEVEL WASTE DISPOSAL (open access)

FLUIDIZED BED STEAM REFORMING ENABLING ORGANIC HIGH LEVEL WASTE DISPOSAL

Waste streams planned for generation by the Global Nuclear Energy Partnership (GNEP) and existing radioactive High Level Waste (HLW) streams containing organic compounds such as the Tank 48H waste stream at Savannah River Site have completed simulant and radioactive testing, respectfully, by Savannah River National Laboratory (SRNL). GNEP waste streams will include up to 53 wt% organic compounds and nitrates up to 56 wt%. Decomposition of high nitrate streams requires reducing conditions, e.g. provided by organic additives such as sugar or coal, to reduce NOX in the off-gas to N2 to meet Clean Air Act (CAA) standards during processing. Thus, organics will be present during the waste form stabilization process regardless of the GNEP processes utilized and exists in some of the high level radioactive waste tanks at Savannah River Site and Hanford Tank Farms, e.g. organics in the feed or organics used for nitrate destruction. Waste streams containing high organic concentrations cannot be stabilized with the existing HLW Best Developed Available Technology (BDAT) which is HLW vitrification (HLVIT) unless the organics are removed by pretreatment. The alternative waste stabilization pretreatment process of Fluidized Bed Steam Reforming (FBSR) operates at moderate temperatures (650-750 C) compared to vitrification (1150-1300 C). The …
Date: May 9, 2008
Creator: Williams, M
System: The UNT Digital Library
X-ray streak camera temporal resolution improvement using a longitudinal time-dependent field (open access)

X-ray streak camera temporal resolution improvement using a longitudinal time-dependent field

X-ray streak cameras (XSC) have been known to be one of the fastest detectors forultrafast X-ray science. A number of applications in material science, biochemistry, accelerator physics, require sub-picosecond resolution to study new phenomena. Inthis paper, we report on a new method which can potentially improve the temporal resolution of a streak camera down to 100 femtoseconds. This method uses a time-dependent acceleration field to lengthen the photoelectron bunch, significantlyimproving the time resolution as well as reducing the time dispersion caused byinitial energy spread and the effects fromthe space charge forces. A computer simulation of an XSC using this method shows significant improvement in the resolution.
Date: May 9, 2008
Creator: Qiang, Ji; Qiang, J.; Byrd, J.M.; Feng, J. & Huang, G.
System: The UNT Digital Library
Airbreathing Acceleration Toward Earth Orbit (open access)

Airbreathing Acceleration Toward Earth Orbit

As flight speed increases, aerodynamic drag rises more sharply than the availability of atmospheric oxygen. The ratio of oxygen mass flux to dynamic pressure cannot be improved by changing altitude. The maximum possible speed for airbreathing propulsion is limited by the ratio of air capture area to vehicle drag area, approximately Mach 6 at equal areas. Simulation of vehicle acceleration shows that the use of atmospheric oxygen offers a significant potential for minimizing onboard consumables at low speeds. These fundamental calculations indicate that a practical airbreathing launch vehicle would accelerate to near steady-state speed while consuming only onboard fuel, then transition to rocket propulsion. It is suggested that an aircraft carrying a rocket-propelled vehicle to approximately Mach 5 could be a realistic technical goal toward improving access to orbit.
Date: May 9, 2007
Creator: Whitehead, J C
System: The UNT Digital Library
An improved WRF for urban-scale and complex-terrain applications (open access)

An improved WRF for urban-scale and complex-terrain applications

None
Date: May 9, 2007
Creator: Lundquist, J K; Chow, F K; Mirocha, J D & Lundquist, K A
System: The UNT Digital Library
Pump Fed Propulsion for Mars Ascent and Other Challenging Maneuvers (open access)

Pump Fed Propulsion for Mars Ascent and Other Challenging Maneuvers

Returning Mars geology samples to Earth within science mission budgets requires a miniature launch vehicle (100-200 kg) for ascending from Mars to an orbital rendezvous. A Mars Ascent Vehicle must deliver a velocity change exceeding 4 km/s within minutes, entirely outside the capabilities of satellite propulsion. A possible solution is to scale down liquid launch vehicle principles to achieve stage propellant mass fractions near 90 percent. Feeding a high-pressure engine from thin-walled low pressure tanks permits stage hardware to be sufficiently lightweight and compact, if very high performance pumps can be made available. NASA's Mars Technology Program has funded refinement and testing of a miniature piston pump, powered by reacted propellant. A pump-fed bipropellant rocket stage remains to be developed. The technology could also benefit other future lunar and planetary science programs.
Date: May 9, 2007
Creator: Whitehead, J C
System: The UNT Digital Library
Renewables Portfolio Standards: A Factual Introduction toExperience from the United States (open access)

Renewables Portfolio Standards: A Factual Introduction toExperience from the United States

Renewables portfolio standards (RPS) have--since the late 1990s--proliferated at the state level in the United States. What began as a policy idea minted in California and first described in detail in the pages of the 'Electricity Journal' FPT has emerged as an important driver for renewable energy capacity additions in the United States. Over the years, articles in the 'Electricity Journal' have explored the RPS in more detail, identifying both its strengths and weaknesses. The present article provides an introduction to the history, concept, and design of the RPS, reviews early experience with the policy as applied at the state level, and provides a brief overview of Federal RPS proposals to date and the possible relationship between Federal and state RPS policies. Our purpose is to offer a factual introduction to the RPS, as applied and considered in the U.S. Though elements of state RPS design are summarized here, other publications provide a more thorough review of design lessons that emerge from that experience. In addition, the present article does not describe the results of economic analyses of Federal RPS proposals, though we do cite many of the analyses conducted by the U.S. DOE's Energy Information Administration (EIA).
Date: May 9, 2007
Creator: Wiser, R.; Namovicz, C.; Gielecki, M. & Smith, R.
System: The UNT Digital Library
Visualization Tools for Adaptive Mesh Refinement Data (open access)

Visualization Tools for Adaptive Mesh Refinement Data

Adaptive Mesh Refinement (AMR) is a highly effective method for simulations that span a large range of spatiotemporal scales, such as astrophysical simulations that must accommodate ranges from interstellar to sub-planetary. Most mainstream visualization tools still lack support for AMR as a first class data type and AMR code teams use custom built applications for AMR visualization. The Department of Energy's (DOE's) Science Discovery through Advanced Computing (SciDAC) Visualization and Analytics Center for Enabling Technologies (VACET) is currently working on extending VisIt, which is an open source visualization tool that accommodates AMR as a first-class data type. These efforts will bridge the gap between general-purpose visualization applications and highly specialized AMR visual analysis applications. Here, we give an overview of the state of the art in AMR visualization research and tools and describe how VisIt currently handles AMR data.
Date: May 9, 2007
Creator: Weber, Gunther H.; Beckner, Vincent E.; Childs, Hank; Ligocki,Terry J.; Miller, Mark C.; Van Straalen, Brian et al.
System: The UNT Digital Library