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22,567 Matching Results
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Measurement of the b jet cross-section in events with a Z boson in p anti-p collisions at s**(1/2) = 1.96-TeV
None
Date:
May 1, 2006
Creator:
Abulencia, A.; Acosta, D.; Adelman, Jahred A.; Affolder, T.; Akimoto, T.; Albrow, M. G. et al.
Object Type:
Article
System:
The UNT Digital Library
Measurement of the ratio of branching fractions B(D0 ---> K+ pi-) / B(D0 ---> K- pi+) using the CDF II Detector
The authors present a measurement of R{sub B}, the ratio of the branching fraction for the rare decay D{sup 0} {yields} K{sup +}{pi}{sup -} to that for the Cabibbo-favored decay D{sup 0} {yields} K{sup -}{pi}{sup +}. Charge conjugate decays are implicitly included. A signal of 2005 {+-} 104 events for the decay D{sup 0} {yields} K{sup +}{pi}{sup -} is obtained using the CDF II detector at the Fermilab Tevatron collider. The data set corresponds to an integrated luminosity of 0.35 fb{sup -1} produced in {bar p}p collisions at {radical}s = 1.96 TeV. Assuming no mixing, they find R{sub B} = [4.05 {+-} 0.21(stat) {+-} 0.11(syst)] x 10{sup -3}. This measurement is consistent with the world average, and comparable in accuracy with the best measurements from other experiments.
Date:
May 1, 2006
Creator:
Abulencia, A.; Acosta, D.; Adelman, Jahred A.; Affolder, T.; Akimoto, T.; Albrow, M.G. et al.
Object Type:
Article
System:
The UNT Digital Library
Search for a neutral Higgs boson decaying to a W boson pair in p antip collisions at s**(1/2) = 1.96-TeV
The authors present the results of a search for standard model Higgs boson production with decay to WW*, identified through the leptonic final states e{sup +}e{sup -} {bar {nu}}{nu}, e{sup {+-}}{mu}{sup {-+}} {bar {nu}}{nu} and {mu}{sup +} {mu}{sup -} {bar {nu}}{nu}. This search uses 360 pb{sup -1} of data collected from p{bar p} collisions at {radical}s = 1.96 TeV by the upgraded Collider Detector at Fermilab (CDF II). They observe no signal excess and set 95% confidence level upper limits on the production cross section times branching ratio for the Higgs boson to WW* or any new scalar particle with similar decay products. These upper limits range from 5.5 to 3.2 pb for Higgs boson masses between 120 and 200 GeV/c{sup 2}.
Date:
May 1, 2006
Creator:
Abulencia, A.; Acosta, D.; Adelman, Jahred A.; Affolder, T.; Akimoto, T.; Albrow, M.G. et al.
Object Type:
Article
System:
The UNT Digital Library
Search for new physics in lepton + photon + X events with 305 pb**-1 of p anti-p collisions at s**(1/2) = 1.96-TeV
The authors present results of a search for anomalous production of events containing a charged lepton ({ell}, either e or {mu}) and a photon ({gamma}), both with high transverse momentum, accompanied by additional signatures, X, including missing transverse energy (E{sub T}) and additional leptons and photons. We use the same kinematic selection criteria as in a previous CDF search, but with a substantially larger data set, 305 pb{sup -1}, a p{bar p} collision energy of 1.96 TeV, and the upgraded CDF II detector. We find 42 {ell}{gamma}E{sub T} events versus a standard model expectation of 37.3 {+-} 5.4 events. The level of excess observed in Run I, 16 events with an expectation of 7.6 {+-} 0.7 events (corresponding to a 2.7{sigma} effect), is not supported by the new data. In the signature of {ell}{ell}{gamma} + X we observe 31 events versus an expectation of 23.0 {+-} 2.7 events. In this sample we find no events with an extra photon or E{sub T} and so find no events like the one ee{gamma}{gamma}E{sub T} event observed in Run I.
Date:
May 1, 2006
Creator:
Abulencia, A.; Acosta, D.; Adelman, Jahred A.; Affolder, T.; Akimoto, T.; Albrow, M.G. et al.
Object Type:
Article
System:
The UNT Digital Library
Top quark mass measurement from dilepton events at CDF II with the matrix-element method
We describe a measurement of the top quark mass using events with two charged leptons collected by the CDF II detector from p{bar p} collisions with {radical}s = 1.96 TeV at the Fermilab Tevatron. The likelihood in top mass is calculated for each event by convoluting the leading order matrix element describing q{bar q} {yields} t{bar t} {yields} b{ell}{nu}{sub {ell}}{bar b}{ell}{prime} {nu}{sub {ell}}, with detector resolution functions. The presence of background events in the data sample is modeled using similar calculations involving the matrix elements for major background processes. In a data sample with integrated luminosity of 340 pb{sup -1}, we observe 33 candidate events and measure M{sub top} = 165.2 {+-} 6.1(stat.) {+-} 3.4(syst.) GeV/c{sup 2}. This measurement represents the first application of this method to events with two charged leptons and is the most precise single measurement of the top quark mass in this channel.
Date:
May 1, 2006
Creator:
Abulencia, A.; Acosta, D.; Adelman, Jahred A.; Affolder, T.; Akimoto, T.; Albrow, M.G. et al.
Object Type:
Article
System:
The UNT Digital Library
Longevity of duct tape in residential air distribution systems: 1-D, 2-D, and 3-D joints
The aging tests conducted so far showed that duct tape tends to degrade in its performance as the joint it is applied to requires a geometrical description of a higher number of space dimensions (1-D, 2-D, 3-D). One-dimensional joints are the easiest to seal with duct tape, and thus the least to experience failure. Two-dimensional joints, such as the flexible duct core-to-collar joints tested in this study, are less likely to fail than three-dimensional collar-to-plenum joints, as the shrinkage could have a positive effect in tightening the joint. Three-dimensional joints are the toughest to seal and the most likely to experience failure. The 2-D flexible duct core-to-collar joints passed the six-month period of the aging test in terms of leakage, but with the exception of the foil-butyl tape, showed degradation in terms hardening, brittleness, partial peeling, shrinkage, wrinkling, delamination of the tape layers, flaking, cracking, bubbling, oozing and discoloration. The baking test results showed that the failure in the duct tape joints could be attributed to the type of combination of the duct tape and the material it is applied to, as the duct tape behaves differently with different substrates. Overall, the foil-butyl tape (Tape 4) had the best results, …
Date:
May 30, 2002
Creator:
Abushakra, Bass
Object Type:
Report
System:
The UNT Digital Library
Thermodynamics of higher dimensional black holes
We discuss the thermodynamics of higher dimensional black holes with particular emphasis on a new class of spinning black holes which, due to the increased number of Casimir invariants, have additional spin degrees of freedom. In suitable limits, analytic solutions in arbitrary dimensions are presented for their temperature, entropy, and specific heat. In 5 + 1 and 9 + 1 dimensions, more general forms for these quantities are given. It is shown that the specific heat for a higher dimensional black hole is negative definite if it has only one non-zero spin parameter, regardless of the value of this parameter. We also consider equilibrium configurations with both massless particles and massive string modes. 16 refs., 3 figs.
Date:
May 1, 1986
Creator:
Accetta, F.S. & Gleiser, M.
Object Type:
Report
System:
The UNT Digital Library
HCCl Combustion: Analysis and Experiments
Homogeneous charge compression ignition (HCCI) is a new combustion technology that may develop as an alternative to diesel engines with high efficiency and low NOx and particulate matter emissions. This paper describes the HCCI research activities being currently pursued at Lawrence Livermore National Laboratory and at the University of California Berkeley. Current activities include analysis as well as experimental work. On analysis, we have developed two powerful tools: a single zone model and a multi-zone model. The single zone model has proven very successful in predicting start of combustion and providing reasonable estimates for peak cylinder pressure, indicated efficiency and NOX emissions. This model is being applied to develop detailed engine performance maps and control strategies, and to analyze the problem of engine startability. The multi-zone model is capable of very accurate predictions of the combustion process, including HC and CO emissions. The multi-zone model has applicability to the optimization of combustion chamber geometry and operating conditions to achieve controlled combustion at high efficiency and low emissions. On experimental work, we have done a thorough evaluation of operating conditions in a 4-cylinder Volkswagen TDI engine. The engine has been operated over a wide range of conditions by adjusting the intake …
Date:
May 4, 2001
Creator:
Aceves, S. M.; Flowers, D. L.; Martinez-Frias, J.; Smith, J. R.; Dibble, R.; Au, M. et al.
Object Type:
Article
System:
The UNT Digital Library
Certification Testing and Demonstration of Insulated Pressure Vessels for Vehicular Hydrogen Storage
Insulated pressure vessels are cryogenic-capable pressure vessels that can be fueled with liquid hydrogen or ambient-temperature compressed hydrogen. This flexibility results in multiple advantages with respect to compressed hydrogen tanks or low-pressure liquid hydrogen tanks. Our work is directed at verifying that commercially available aluminum-lined, fiber-wrapped pressure vessels can be safely used to store liquid hydrogen. A series of tests have been conducted, and the results indicate that no significant vessel damage has resulted from cryogenic operation. Future activities include a demonstration project in which the insulated pressure vessels will be installed and tested on two vehicles. A draft standard will also be generated for certification of insulated pressure vessels.
Date:
May 22, 2002
Creator:
Aceves, S. M.; Martinez-Frias, J. & Espinosa-Loza, F.
Object Type:
Article
System:
The UNT Digital Library
Certification Testing and Demonstration of Insulated Pressure Vessels for Vehicular Hydrogen and Natural Gas Storage
We are working on developing an alternative technology for storage of hydrogen or natural gas on light-duty vehicles. This technology has been titled insulated pressure vessels. Insulated pressure vessels are cryogenic-capable pressure vessels that can accept either liquid fuel or ambient-temperature compressed fuel. Insulated pressure vessels offer the advantages of cryogenic liquid fuel tanks (low weight and volume), with reduced disadvantages (fuel flexibility, lower energy requirement for fuel liquefaction and reduced evaporative losses). The work described in this paper is directed at verifying that commercially available pressure vessels can be safely used to store liquid hydrogen or LNG. The use of commercially available pressure vessels significantly reduces the cost and complexity of the insulated pressure vessel development effort. This paper describes a series of tests that have been done with aluminum-lined, fiber-wrapped vessels to evaluate the damage caused by low temperature operation. All analysis and experiments to date indicate that no significant damage has resulted. Future activities include a demonstration project in which the insulated pressure vessels will be installed and tested on two vehicles. A draft standard will also be generated for obtaining insulated pressure vessel certification.
Date:
May 22, 2002
Creator:
Aceves, S. M.; Martinez-Frias, J.; Espinosa-Loza, F.; Schaffer, R. & Clapper, W.
Object Type:
Article
System:
The UNT Digital Library
HCCI Combustion: Analysis and Experiments
Homogeneous charge compression ignition (HCCI) is a new combustion technology that may develop as an alternative to diesel engines with high efficiency and low NOx and particulate matter emissions. This paper describes the HCCI research activities being currently pursued at Lawrence Livermore National Laboratory and at the University of California Berkeley. Current activities include analysis as well as experimental work. On analysis, we have developed two powerful tools: a single zone model and a multi-zone model. The single zone model has proven very successful in predicting start of combustion and providing reasonable estimates for peak cylinder pressure, indicated efficiency and NOX emissions. This model is being applied to develop detailed engine performance maps and control strategies, and to analyze the problem of engine startability. The multi-zone model is capable of very accurate predictions of the combustion process, including HC and CO emissions. The multi-zone model h as applicability to the optimization of combustion chamber geometry and operating conditions to achieve controlled combustion at high efficiency and low emissions. On experimental work, we have done a thorough evaluation of operating conditions in a 4-cylinder Volkswagen TDI engine. The engine has been operated over a wide range of conditions by adjusting the …
Date:
May 14, 2001
Creator:
Aceves, Salvador M.; Flowers, Daniel L.; Martinez-Frias, Joel; Smith, J. Ray; Dibble, Robert; Au, Michael et al.
Object Type:
Article
System:
The UNT Digital Library
Tritium distribution in the MHTGR
The {sup 3}H production, transport and environmental release from the 350 MW(t) Modular High Temperature Gas Cooled Reactor was analyzed. The analysis was performed using a modified TRITGO computer code, plant data base from the Preliminary Safety Information Document and materials property data from the Fuel Design Data Manual, Issue F. The analysis indicates that most of the {sup 3}H produced in the reactor is retained by the fuel particles and the structural graphite elements. The single largest source of {sup 3}H is ternary fission in the fuel particles, of which 95% is retained by the particles. The {sup 3}H released from the core and the {sup 3}H produced by {sup 3}He activation are largely removed by the Helium Purification System. Assuming zero leakage of water from the secondary system, the average predicted {sup 3}H activity in the secondary water of 0.35 {mu}Ci/g is much greater than the allowable activity of 5 pCi/g for direct discharge into the environment. If any of the secondary water has to be discharged, it must be diluted prior to discharge. 10 refs., 9 figs.
Date:
May 1, 1988
Creator:
Acharya, R.
Object Type:
Report
System:
The UNT Digital Library
Fission product plateout/liftoff/washoff test plan. Revision 1
A test program is planned in the COMEDIE loop of the Commissariat a l`Energy Atomique (CEA), Grenoble, France, to generate integral test data for the validation of computer codes used to predict fission product transport and core corrosion in the Modular High Temperature Gas-Cooled Reactor (MHTGR). The inpile testing will be performed by the CEA under contract from the US Department of Energy (DOE); the contract will be administered by Oak Ridge National Laboratory (ORNL). The primary purpose of this test plan is to provide an overview of the proposed program in terms of the overall scope and schedule. 8 refs, 3 figs.
Date:
May 1, 1988
Creator:
Acharya, R. & Hanson, D.
Object Type:
Report
System:
The UNT Digital Library
HRB-22 preirradiation thermal analysis
This report describes the preirradiation thermal analysis of the HRB-22 capsule designed for irradiation in the removable beryllium (RB) position of the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL). CACA-2 a heavy isotope and fission product concentration calculational code for experimental irradiation capsules was used to determine time dependent fission power for the fuel compacts. The Heat Engineering and Transfer in Nine Geometries (HEATING) computer code, version 7.2, was used to solve the steady-state heat conduction problem. The diameters of the graphite fuel body that contains the compacts and the primary pressure vessel were selected such that the requirements of running the compacts at an average temperature of < 1,250 C and not exceeding a maximum fuel temperature of 1,350 C was met throughout the four cycles of irradiation.
Date:
May 1, 1995
Creator:
Acharya, R. & Sawa, K.
Object Type:
Report
System:
The UNT Digital Library
Oxidation of 316 stainless steel and other alloys in prototypic GCFR environments
The oxidation behavior of type 316 stainless steel and candidate advanced alloys for the gas-cooled fast reactor (GCFR) is being investigated at General Atomic Company. The test program consists of oxidation tests in prototypic GCFR environments. Two tests have been completed to date and a third test is under way. The first test was performed in an environment containing a hydrogen/water ratio of 10. The oxidation behavior of all the alloys was good to excellent in this environment. Preferential oxidation of chromium was responsible for this behavior. The second test was performed in an environment containing a hydrogen/water ratio of 0.25, where both chromium and iron oxides are thermodynamically stable. Some of the alloys and some of the ribbed type 316 stainless steel test specimens showed unacceptable oxidation resistance in this environment. In the third test, presently under way, two different pretreatment procedures are being used to control the poor oxidation behavior observed in the second test. Early results show some degree of success.
Date:
May 1, 1980
Creator:
Acharya, R.T.
Object Type:
Article
System:
The UNT Digital Library
Monitoring the Migrations of Wild Snake River Spring/Summer Chinook Salmon Juveniles, 2007-2008 Report of Research.
This report provides results from an ongoing project to monitor the migration behavior and survival of wild juvenile spring/summer Chinook salmon in the Snake River Basin. Data reported is from detections of PIT tagged fish during late summer 2007 through mid-2008. Fish were tagged in summer 2007 by the National Marine Fisheries Service (NMFS) in Idaho and by the Oregon Department of Fish and Wildlife (ODFW) in Oregon. Our analyses include migration behavior and estimated survival of fish at instream PIT-tag monitors and arrival timing and estimated survival to Lower Granite Dam. Principal results from tagging and interrogation during 2007-2008 are listed below: (1) In July and August 2007, we PIT tagged and released 7,390 wild Chinook salmon parr in 12 Idaho streams or sample areas. (2) Overall observed mortality from collection, handling, tagging, and after a 24-hour holding period was 1.4%. (3) Of the 2,524 Chinook salmon parr PIT tagged and released in Valley Creek in summer 2007, 218 (8.6%) were detected at two instream PIT-tag monitoring systems in lower Valley Creek from late summer 2007 to the following spring 2008. Of these, 71.6% were detected in late summer/fall, 11.9% in winter, and 16.5% in spring. Estimated parr-to-smolt survival …
Date:
May 26, 2009
Creator:
Achord, Stephen; Sandford, Benjamin P. & Hockersmith, Eric E.
Object Type:
Report
System:
The UNT Digital Library
Monitoring the Migrations of Wild Snake River Spring/Summer Chinook Salmon Juveniles, 2004-2005 Annual Report.
None
Date:
May 1, 2006
Creator:
Achrod, Stephen; Sandford, Benjamin P. & Hockersmith, Eric E. (National Marine Fisheries Services, Northwest Fisheries Science Center, Fish Ecology Division, Seattle, WA)
Object Type:
Report
System:
The UNT Digital Library
Variability of Ocean Heat Uptake: Reconciling Observations and Models
This study examines the temporal variability of ocean heat uptake in observations and in climate models. Previous work suggests that coupled Atmosphere-Ocean General Circulation Models (A-OGCMs) may have underestimated the observed natural variability of ocean heat content, particularly on decadal and longer timescales. To address this issue, we rely on observed estimates of heat content from the 2004 World Ocean Atlas (WOA-2004) compiled by Levitus et al. (2005). Given information about the distribution of observations in WOA-2004, we evaluate the effects of sparse observational coverage and the infilling that Levitus et al. use to produce the spatially-complete temperature fields required to compute heat content variations. We first show that in ocean basins with limited observational coverage, there are important differences between ocean temperature variability estimated from observed and infilled portions of the basin. We then employ data from control simulations performed with eight different A-OGCMs as a test-bed for studying the effects of sparse, space- and time-varying observational coverage. Subsampling model data with actual observational coverage has a large impact on the inferred temperature variability in the top 300 and 3000 meters of the ocean. This arises from changes in both sampling depth and in the geographical areas sampled. Our …
Date:
May 5, 2005
Creator:
AchutaRao, K. M.; Santer, B. D.; Gleckler, P. J.; Taylor, K.; Pierce, D.; Barnett, T. et al.
Object Type:
Article
System:
The UNT Digital Library
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
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
Measurement of Separate Cosmic-Ray Electron And Positron Spectra with the Fermi Large Area Telescope
None
Date:
May 13, 2013
Creator:
Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Barbiellini, G.; Bastieri, D. et al.
Object Type:
Article
System:
The UNT Digital Library
Fermi LAT Observations of Cosmic-Ray Electrons From 7 GeV to 1 TeV
None
Date:
May 28, 2013
Creator:
Ackermann, M.; Ajello, M.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G. et al.
Object Type:
Article
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