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11,771 Matching Results
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Reduction of Tropical Cloudiness by Soot
Measurements and models show that enhanced aerosol concentrations can augment cloud albedo not only by increasing total droplet cross-sectional area, but also by reducing precipitation and thereby increasing cloud water content and cloud coverage. Aerosol pollution is expected to exert a net cooling influence on the global climate through these conventional mechanisms. Here we demonstrate an opposite mechanism through which aerosols can reduce cloud cover and thus significantly offset aerosol-induced radiative cooling at the top of the atmosphere on a regional scale. In model simulations the daytime clearing of trade cumulus is hastened and intensified by solar heating in dark haze (as found over much of the northern Indian Ocean during the northeast monsoon).
Date:
May 8, 2000
Creator:
Ackerman, A. S.; Toon, O. B.; Stevens, D. E.; Heymsfield, A. J. & Ramanathan, V.
Object Type:
Report
System:
The UNT Digital Library
Education Vouchers: Constitutional Issues and Cases
This report details the constitutional standards that currently apply to indirect school aid programs and summarizes all of the pertinent Supreme Court decisions, with particular attention to Zelman. It also summarizes the pending case of Davey v. Locke and other recent and ongoing state and lower federal court cases concerning vouchers.
Date:
May 20, 2003
Creator:
Ackerman, David M.
Object Type:
Report
System:
The UNT Digital Library
NATO Enlargement: Senate Advice and Consent
None
Date:
May 2, 2003
Creator:
Ackerman, David M.
Object Type:
Report
System:
The UNT Digital Library
The Role of Global Observations for Climate and Other Applications
Most of the current earth-observing systems have been designed primarily for the needs of weather forecasting. Weather forecasting is an initial condition problem; the success of the forecast is heavily dependent on the quality of the specified initial state of the atmosphere. Thus, weather forecasting observing systems tend to focus on determining the 3D values of the state variables of the system namely temperature, humidity, and wind vector. While weather forecasting requires accurate observations, spatial patterns and relative accuracy across those patterns are the primary concern. Climate, on the other hand, is a boundary condition problem, i.e., climate simulation depends on knowing the energy fluxes into and out of the system, and quantities such as CO2 that affect the flow of those energy fluxes in the system. Consequently, climate-observing systems must extend beyond measurements of state variables to flux measurements of radiation energy and water. We focus on these two cycles because the dominant forms of energy transfer in the climate system (solar energy, thermal infrared energy, evaporation, and condensation) involve these two quantities. Further, because climate is a search for small system trends and imbalances in the midst of large weather variability, climate observations require a much higher degree …
Date:
May 1, 2005
Creator:
Ackerman, T.P.
Object Type:
Report
System:
The UNT Digital Library
The Role of Global Observations for Climate and Other Applications
Most of the current earth-observing systems have been designed primarily for the needs of weather forecasting. Weather forecasting is an initial condition problem; the success of the forecast is heavily dependent on the quality of the specified initial state of the atmosphere. Thus, weather forecasting observing systems tend to focus on determining the 3D values of the state variables of the system – namely temperature, humidity, and wind vector. While weather forecasting requires accurate observations, spatial patterns and relative accuracy across those patterns are the primary concern. Climate, on the other hand, is a boundary condition problem, i.e., climate simulation depends on knowing the energy fluxes into and out of the system, and quantities such as CO2 that affect the flow of those energy fluxes in the system. Consequently, climate-observing systems must extend beyond measurements of state variables to flux measurements of radiation energy and water. We focus on these two cycles because the dominant forms of energy transfer in the climate system (solar energy, thermal infrared energy, evaporation, and condensation) involve these two quantities. Further, because climate is a search for small system trends and imbalances in the midst of large weather variability, climate observations require a much higher …
Date:
May 1, 2005
Creator:
Ackerman, TP
Object Type:
Report
System:
The UNT Digital Library
Cation distribution in a Fe-bearing K-feldspar from Itrongay,Madagascar. A combined neutron- and X-ray single crystal diffractionstudy
We determined the cation distribution and ordering of Si, Al and Fe on the tetrahedral sites of a monoclinic low-sanidine from Itrongay, Madagascar, by combined neutron- and X-ray single-crystal diffraction. The cation distribution was determined by means of a simultaneous refinement using neutron- and X-ray data, as well as by combining scattering densities obtained from separate refinements with chemical data from a microprobe experiment. The two methods give the same results and show that Fe is fully ordered on T1, whereas Al shows a high degree of disorder. Based on this and previously published temperature-dependent X-ray data, we conclude that it is preferential ordering of Fe on T1 even at high temperature, rather than a high diffusion kinetics of Fe, which causes this asymmetry in ordering behavior between Al and Fe. The preferential ordering of Fe3+ relative to Al3+ in T1 is consistent with its 25 percent larger ionic radius.
Date:
May 2, 2005
Creator:
Ackermann, Sonia; Kunz, Martin; Armbruster, Thomas; Schefer,Jurg & Hanni, Henry
Object Type:
Article
System:
The UNT Digital Library
B physics: evidence for the exclusive decay b^+/-_c -> j/psi pi^+ and measurement of the mass of the b^+/-_c meson
We report the first evidence of a fully reconstructed decay mode of the B{sub c}{sup {+-}} meson in the channel B{sub c}{sup {+-}} {yields} J/{psi}{sup {+-}}, with J/{psi} {yields} {mu}{sup +}{mu}{sup -}. The analysis is based on an integrated luminosity of 360 pb{sup -1} in p{bar p} collisions collected by the Collider Detector at Fermilab. We observe 18.9 {+-} 5.7 signal events on a background of 10.0 {+-} 1.4 events and the fit to the J/{psi}{pi}{sup {+-}} mass spectrum yields a B{sub c}{sup {+-}} mass of 6287.0 {+-} 4.8(stat) {+-} 1.1(syst) MeV/c{sup 2}.
Date:
May 25, 2005
Creator:
Acosta, D.
Object Type:
Report
System:
The UNT Digital Library
B physics: first evidence for b_s0 --> phi phi decay and measurements of branching ratio and a_cp for b+ --> phi k+
We present the first evidence of charmless decays of the B{sub s}{sup 0} meson, the decay B{sub s}{sup 0} {yields} {phi}{phi}, and a measurement of the Branching Ratio BR(B{sub s}{sup 0} {yields} {phi}{phi}) using 180 pb{sup -1} of data collected by the CDF II experiment at the Fermilab Tevatron collider. In addition, the BR and direct CP asymmetry for the B{sup +} {yields} {phi}K{sup +} decay are measured.
Date:
May 31, 2005
Creator:
Acosta, D.
Object Type:
Report
System:
The UNT Digital Library
Electroweak physics: search for zz and zw production in p anti-p collisions at s**(1/2) = 1.96 tev
We present a search for ZZ and ZW vector boson pair production in p{bar p} collisions at {radical}s = 1.96 TeV using the leptonic decay channels ZZ {yields} llvv, ZZ {yields} lll'l' and ZW {yields} lll'v. In a data sample corresponding to an integrated luminosity of 194 pb{sup -1} collected with the Collider Detector at Fermilab, 3 candidate events are found with an expected background of 1.0 {+-} 0.2 events. We set a 95% confidence level upper limit of 15.2 pb on the cross section for ZZ plus ZW production, compared to the standard model prediction of 5.0 {+-} 0.4 pb.
Date:
May 18, 2005
Creator:
Acosta, D.
Object Type:
Report
System:
The UNT Digital Library
Qcd physics: study of jet shapes in inclusive jet production in ppbar collisions at sqrt s = 1.96 tev
We present a search for excited and exotic electrons (e*) decaying to an electron and a photon, both with high transverse momentum. We use 202 pb{sup -1} of data collected in p{bar p} collisions at {radical}s = 1.96 TeV with the CDF II detector. No signal above standard model expectation is seen for associated ee* production. We discuss the e* sensitivity in the parameter space of the excited electron mass M{sub e*} and the compositeness energy scale {Lambda}. In the contact interaction model, we exclude 132 GeV/c{sup 2} < M{sub e*} < 879 GeV/c{sup 2} for {Lambda} = M{sub e*} at 95% confidence level (C.L.). In the gauge-mediated model, we exclude 126 GeV/c{sup 2} < M{sub e*} < 430 GeV/c{sup 2} at 95% C.L. for the phenomenological coupling f/{Lambda} {approx} 10{sup -2} GeV{sup -1}.
Date:
May 8, 2005
Creator:
Acosta, D.
Object Type:
Report
System:
The UNT Digital Library
A Fundamental Study of Dispersed Multiphase Flows at Small Scales
The purpose of the research supported by this grant was two-fold: I, to continue our earlier studies on the rheology of suspensions of non-colloidal particles; and, II, to study the transport of a nano-sized particle through a fluid-filled nano-channel using molecular dynamics simulations. In I, we investigated, by means of Stokesian Dynamics simulations, the dynamics of concentrated suspensions and discovered that their statistical properties could be described, even for particle concentrations up to 20%, by means of an analytical theory of pair-particle interactions, provided that pair-doublets are assumed to be totally absent. We also provided a quantitative explanation of the fascinating banding phenomenon of particle axial segregation which was observed when a suspension of neutrally buoyant particles was sheared in a partially filled horizontal Couette device or in a rotating horizontal cylinder. In II, independently of the shape and the relative size of the particle, we find two distinct regimes as a function of the degree of wetting, with a sharp transition between them. Specifically, in a highly wetting suspending fluid, the particle moves through the cylinder with an average axial velocity in agreement with that obtained from the solution of the continuum Stokes equations. In contrast, in the case …
Date:
May 3, 2005
Creator:
Acrivos, Andreas; Khusid, Boris & Koplik, Joel
Object Type:
Report
System:
The UNT Digital Library
Performance Evaluation for Modular, Scalable Cooling Systems with Hot Aisle Containment in Data Centers
Scientific and enterprise data centers, IT equipment product development, and research data center laboratories typically require continuous cooling to control inlet air temperatures within recommended operating levels for the IT equipment. The consolidation and higher density aggregation of slim computing, storage and networking hardware has resulted in higher power density than what the raised-floor system design, coupled with commonly used computer rack air conditioning (CRAC) units, was originally conceived to handle. Many existing data centers and newly constructed data centers adopt CRAC units, which inherently handle heat transfer within data centers via air as the heat transfer media. This results in energy performance of the ventilation and cooling systems being less than optimal. Understanding the current trends toward higher power density in IT computing, more and more IT equipment manufacturers are designing their equipment to operate in 'conventional' data center environments, while considering provisions of alternative cooling solutions to either their equipment or supplemental cooling in rack or row systems. Naturally, the trend toward higher power density resulting from current and future generations of servers has, in the meanwhile, created significant opportunities for precision cooling suppliers to engineer and manufacture packaged modular and scalable systems. The modular and scalable cooling …
Date:
May 1, 2009
Creator:
Adams, Barbara J
Object Type:
Report
System:
The UNT Digital Library
Composition and structure of sputter deposited erbium hydride thin films
Erbium hydride thin films are grown onto polished, a-axis {alpha} Al{sub 2}O{sub 3} (sapphire) substrates by reactive ion beam sputtering and analyzed to determine composition, phase and microstructure. Erbium is sputtered while maintaining a H{sub 2} partial pressure of 1.4 x 10{sup {minus}4} Torr. Growth is conducted at several substrate temperatures between 30 and 500 C. Rutherford backscattering spectrometry (RBS) and elastic recoil detection analyses after deposition show that the H/Er areal density ratio is approximately 3:1 for growth temperatures of 30, 150 and 275 C, while for growth above {approximately}430 C, the ratio of hydrogen to metal is closer to 2:1. However, x-ray diffraction shows that all films have a cubic metal sublattice structure corresponding to that of ErH{sub 2}. RBS and Auger electron that sputtered erbium hydride thin films are relatively free of impurities.
Date:
May 10, 2000
Creator:
Adams, David P.; Romero, Juan A.; Rodriguez, Mark A.; Floro, Jerrold A. & Banks, James C.
Object Type:
Article
System:
The UNT Digital Library
Applying Agile Methods to Weapon/Weapon-Related Software
This white paper provides information and guidance to the Department of Energy (DOE) sites on Agile software development methods and the impact of their application on weapon/weapon-related software development. The purpose of this white paper is to provide an overview of Agile methods, examine the accepted interpretations/uses/practices of these methodologies, and discuss the applicability of Agile methods with respect to Nuclear Weapons Complex (NWC) Technical Business Practices (TBPs). It also provides recommendations on the application of Agile methods to the development of weapon/weapon-related software.
Date:
May 2, 2007
Creator:
Adams, Dennis; Armendariz, Maria; Blackledge, Mike; Campbell, Frank; Cloninger, Mack; Cox, Larry et al.
Object Type:
Report
System:
The UNT Digital Library
Tank Characterization Report for Single Shell Tank (SST) 241-TX-118
None
Date:
May 5, 2000
Creator:
Adams, M. R.
Object Type:
Report
System:
The UNT Digital Library
Studies of the Transformations of Sulfur Containing Heterocycles by Transition Metal Cluster Compounds. Final Report, June 1, 1995 - October 31, 1999
Report on results of research on the catalytic macrocyclization reactions of thietane and thiolactones by metal carbonyl complexes.
Date:
May 16, 2001
Creator:
Adams, Richard D.
Object Type:
Report
System:
The UNT Digital Library
MOBILE SYSTEMS FOR DILUTION OF HIGHLY ENRICHED URANIUM AND URANIUM CONTAINING COMPONENTS
A mobile melt-dilute (MMD) module for the treatment of aluminum research reactor spent fuel is being developed. The process utilizes a closed system approach to retain fission products/gases inside a sealed canister after treatment. The MMD process melts and dilutes spent fuel with depleted uranium to obtain a fissile fraction of less than 0.2. The final ingot is solidified inside the sealed canister and can be stored safely either wet or dry until final disposition or reprocessing. The MMD module can be staged at or near the research reactor fuel storage sites to facilitate the melt-dilute treatment of the spent fuel into a stable non-proliferable form.
Date:
May 2, 2007
Creator:
Adams, T
Object Type:
Article
System:
The UNT Digital Library
Searches for new phenomena with lepton final states at the Tevatron
Numerous searches for new phenomena have been carried out using data from proton-antiproton collisions at Fermilab's Tevatron. Final states with leptons give signatures which are relatively unique and generally have small backgrounds. We present many of the latest results from the CDF and D0 collaborations from 0.4-1.2 fb{sup -1} of data. Topics include supersymmetry, extra gauge bosons, Randall-Sundrum gravitons, excited electrons and neutral, long-lived particles.
Date:
May 1, 2007
Creator:
Adams, T.
Object Type:
Article
System:
The UNT Digital Library
Renaissance of the ~1 TeV Fixed-Target Program
This document describes the physics potential of a new fixed-target program based on a {approx} TeV proton source. Two proton sources are potentially available in the future: the existing Tevatron at Fermilab, which can provide 800 GeV protons for fixed-target physics, and a possible upgrade to the SPS at CERN, called SPS+, which would produce 1 TeV protons on target. In this paper we use an example Tevatron fixed-target program to illustrate the high discovery potential possible in the charm and neutrino sectors. We highlight examples which are either unique to the program or difficult to accomplish at other venues.
Date:
May 1, 2009
Creator:
Adams, T.; Appel, Jeffrey A.; Arms, Kregg Elliott; Balantekin, A. B.; Conrad, Janet Marie; Cooper, Peter S. et al.
Object Type:
Article
System:
The UNT Digital Library
Verification Survey of the Building 315 Zero Power Reactor-6 Facility, Argonne National Laboratory-East, Argonne, Illinois
Oak Ridge Institute for Science and Education (ORISE) conducted independent verification radiological survey activities at Argonne National Laboratory’s Building 315, Zero Power Reactor-6 facility in Argonne, Illinois. Independent verification survey activities included document and data reviews, alpha plus beta and gamma surface scans, alpha and beta surface activity measurements, and instrumentation comparisons. An interim letter report and a draft report, documenting the verification survey findings, were submitted to the DOE on November 8, 2006 and February 22, 2007, respectively (ORISE 2006b and 2007).
Date:
May 25, 2007
Creator:
Adams, W. C.
Object Type:
Report
System:
The UNT Digital Library
PILOT-SCALE HYDRAULIC TESTING OF RESORCINOL FORMALDEHYDE ION EXCHANGE RESIN
Savannah River National Laboratory (SRNL) performed pilot-scale hydraulic/chemical testing of spherical resorcinol formaldehyde (RF) ion exchange (IX) resin for the River Protection Project-Hanford Tank Waste Treatment & Immobilization Plant (WTP) Project. The RF resin hydraulic cycle testing was conducted in two pilot-scale IX columns, 1/4 and 1/2 scale. A total of twenty-three hydraulic/chemical cycles were successfully completed on the spherical RF resin. Sixteen of these cycles were completed in the 24-inch IX Column (1/2 scale column). Hydraulic testing showed that the permeability of the RF resin remained essentially constant, with no observed trend in the reduction of the permeability as the number of cycles increased. The permeability during the pilot-scale testing was 3 times better than the design requirements of the WTP full-scale IX system. The RF resin bed showed no tendency to form fissures or pack more densely as the number of cycles increased. Particle size measurements of the RF resin showed no indication of particle size change (for a given chemical) with cycles and essentially no fines formation. The permeability of the resin bed was uniform with respect to changes in bed depth. Upflow Regeneration and Simulant Introduction in the IX columns revealed another RF resin benefit; negligible …
Date:
May 28, 2009
Creator:
Adamson, D.
Object Type:
Article
System:
The UNT Digital Library
Measurement of the atmospheric muon charge ratio at TeV energies with MINOS
The 5.4 kton MINOS far detector has been taking charge-separated cosmic ray muon data since the beginning of August, 2003 at a depth of 2070 m.w.e. in the Soudan Underground Laboratory, Minnesota, USA. The data with both forward and reversed magnetic field running configurations were combined to minimize systematic errors in the determination of the underground muon charge ratio. When averaged, two independent analyses find the charge ratio underground to be N{sub {mu}}+/N{sub {mu}}-=1.374{+-}0.004(stat)-0.010{sup +0.012}(sys). Using the map of the Soudan rock overburden, the muon momenta as measured underground were projected to the corresponding values at the surface in the energy range 1-7 TeV. Within this range of energies at the surface, the MINOS data are consistent with the charge ratio being energy independent at the 2 standard deviation level. When the MINOS results are compared with measurements at lower energies, a clear rise in the charge ratio in the energy range 0.3-1.0 TeV is apparent. A qualitative model shows that the rise is consistent with an increasing contribution of kaon decays to the muon charge ratio.
Date:
May 1, 2007
Creator:
Adamson, P.; Andreopoulos, C.; Arms, K.E.; Armstrong, R.; Auty, D.J.; Avvakumov, S. et al.
Object Type:
Article
System:
The UNT Digital Library
Operational performance of a bunch by bunch digital damper in the Fermilab Main Injector
We have implemented a transverse and longitudinal bunch by bunch digital damper system in the Fermilab Main Injector, using a single digital board for all 3 coordinates. The system has been commissioned over the last year, and is now operational in all MI cycles, damping beam bunched at both 53MHz and 2.5MHz. We describe the performance of this system both for collider operations and high-intensity running for the NuMI project, operating with a full ring and sometimes with only a few buckets populated.
Date:
May 1, 2005
Creator:
Adamson, P.; Ashmanskas, W. J.; Foster, G. W.; Hansen, S.; Marchionni, A.; Nicklaus, D. et al.
Object Type:
Article
System:
The UNT Digital Library
Lebanon: Background and U.S. Relations
This report provides an overview of Lebanese politics, recent events in Lebanon, and current issues in U.S.-Lebanon relations and will be updated to reflect major developments.
Date:
May 19, 2009
Creator:
Addis, Casey L.
Object Type:
Report
System:
The UNT Digital Library