8,737 Matching Results

Search Results

Parallel Texts

Description: Article discussing parallel texts and natural language processing.
Date: September 2005
Creator: Mihalcea, Rada, 1974- & Simard, Michel
Partner: UNT College of Engineering

The History Engine: Doing History with Digital Tools

Description: Article on the History Engine Project, an online archive consisting of thousands of narratives written and contributed by undergraduates.
Date: September 9, 2009
Creator: Nelson, Robert K.; Nesbit, Scott & Torget, Andrew J., 1978-
Partner: UNT College of Arts and Sciences

Functional analysis of members of the isoflavone and isoflavanone O-methyltransferase enzyme families from the model legume Medicago truncatula

Description: Article on a functional analysis of members of the isoflavone and isoflavanone O-methyltransferase enzyme families from the model legume Medicago truncatula.
Date: September 26, 2006
Creator: Deavours, Bettina E.; Liu, Chang-Jun; Naoumkina, Marina A.; Tang, Yuhong; Farag, Mohamed A.; Sumner, Lloyd W. et al.
Partner: UNT College of Arts and Sciences

Precision solid liner experiments on Pegasus II

Description: Pulsed power systems have been used in the past to drive solid liner implosions for a variety of applications. In combination with a variety of target configurations, solid liner drivers can be used to compress working fluids, produce shock waves, and study material properties in convergent geometry. The utility of such a driver depends in part on how well-characterized the drive conditions are. This, in part, requires a pulsed power system with a well-characterized current wave form and well understood electrical parameters. At Los Alamos, the authors have developed a capacitively driven, inductive store pulsed power machine, Pegasus, which meets these needs. They have also developed an extensive suite of diagnostics which are capable of characterizing the performance of the system and of the imploding liners. Pegasus consists of a 4.3 MJ capacitor bank, with a capacitance of 850 {micro}f fired with a typical initial bank voltage of 90 kV or less. The bank resistance is about 0.5 m{Omega}, and bank plus power flow channel has a total inductance of about 24 nH. In this paper the authors consider the theory and modeling of the first precision solid liner driver fielded on the LANL Pegasus pulsed power facility.
Date: September 1, 1995
Creator: Bowers, R.L.; Brownell, J.H. & Lee, H.
Partner: UNT Libraries Government Documents Department

Preliminary analysis of core capsule x-ray spectroscopy and image results for medium-to-high growth factor implosions

Description: Recent capsule implosions using indirect drive on NOVA have probed core and near-core capsule T{sub e}, {rho} and mix structure using non-trivial pulse shapes (i.e. with a foot). These experiments have been performed using smooth as well as artificially roughened capsules. They have been performed using basically 3 non-trivial pulse-shapes with 3 different types of capsules with correspondingly different growth regimes for Rayleigh-Taylor instabilities. These experiments have employed time-dependent spectroscopy, gated imaging and absolutely calibrated time-integrated imaging as x-ray diagnostics. The authors compare nominal and {open_quotes}modified{close_quotes} 1D calculations with the spectroscopic and time-integrated image results. They find that the core T{sub e} is less than calculated (not surprising), but also that the T{sub e} of the inner pusher is substantially higher (at least 20%) than predicted, with perhaps some enhanced mix of the PVA layer towards the core.
Date: September 1, 1995
Creator: Pollak, G.; Delamater, N. & Landen, N.
Partner: UNT Libraries Government Documents Department

Development of a high-power lithium-ion battery.

Description: Safety is a key concern for a high-power energy storage system such as will be required in a hybrid vehicle. Present lithium-ion technology, which uses a carbon/graphite negative electrode, lacks inherent safety for two main reasons: (1) carbon/graphite intercalates lithium at near lithium potential, and (2) there is no end-of-charge indicator in the voltage profile that can signal the onset of catastrophic oxygen evolution from the cathode (LiCoO{sub 2}). Our approach to solving these safety/life problems is to replace the graphite/carbon negative electrode with an electrode that exhibits stronger two-phase behavior further away from lithium potential, such as Li{sub 4}Ti{sub 5}O{sub 12}. Cycle-life and pulse-power capability data are presented in accordance with the Partnership for a New Generation of Vehicles (PNGV) test procedures, as well as a full-scale design based on a spreadsheet model.
Date: September 2, 1998
Creator: Jansen, A. N.
Partner: UNT Libraries Government Documents Department

Thermodynamic and nonstoichiometric behavior of the GdBa{sub 2}Cu{sub 3}O{sub x} system.

Description: Electromotive force (EMF) measurements of oxygen fugacities as a function of stoichiometry have been made on the GdBa{sub 2}Cu{sub 3}O{sub x} system in the temperature range {approximately}400-600 C by means of an oxygen titration technique with an yttria-stabilized zirconia electrolyte. Equations for the variation of oxygen partial pressure with composition and temperature have been derived from our EMF measurements. The shape of the 400 C isotherms as a function of oxygen stoichiometry for the Gd and Nd cuprate systems suggests the presence of miscibility gaps at values of x that are higher than those in the YBa{sub 2}Cu{sub 3}O{sub x} system. For a given oxygen stoichiometry, oxygen partial pressures above Gd-123 and Nd-123 cuprate systems are higher (above x = 6.5) than that for the Y-123 system. A thermodynamic assessment and intercomparison of our partial pressure measurements with the results of related measurements will be presented.
Date: September 29, 1998
Creator: Tetenbaum, M.
Partner: UNT Libraries Government Documents Department

AntiReflection Coating D

Description: Analytical expressions used to optimize AR coatings for single junction solar cells are extended for use in monolithic, series interconnected multi-junction solar cell AR coating design. The result is an analytical expression which relates the solar cell performance (through J{sub sc}) directly to the AR coating design through the device reflectance. It is also illustrated how AR coating design be used to provide an additional degree of freedom for current matching multi-junction devices.
Date: September 23, 1999
Creator: AIKEN,DANIEL J.
Partner: UNT Libraries Government Documents Department

Assembly and testing of a composite heat pipe thermal intercept for HTS current leads

Description: We are building high temperature superconducting (HTS) current leads for a demonstration HTS-high gradient magnetic separation (HGMS) system cooled by a cryocooler. The current leads are entirely conductively cooled. A composite nitrogen heat pipe provides efficient thermal communication, and simultaneously electrical isolation, between the lead and an intermediate temperature heat sink. Data on the thermal and electrical performance of the heat pipe thermal intercept are presented. The electrical isolation of the heat pipe was measured as a function of applied voltage with and without a thermal load across the heat pipe. The results show the electrical isolation with evaporation, condensation and internal circulation taking place in the heat pipe.
Date: September 1, 1995
Creator: Daugherty, M.A.; Daney, D.E.; Prenger, F.C.; Hill, D.D.; Williams, P.M. & Boenig, H.J.
Partner: UNT Libraries Government Documents Department

Pulsed optically-pumped polarized H{sup {minus}} ion source development

Description: Results are presented of pulsed optically-pumped polarized H{sup {minus}} ion source (OPPIS) development for high energy accelerators. An atomic hydrogen beam intensity of 2 {times} 10{sup 18} atoms/s within the polarizer acceptance was obtained with an atomic H injector at BINP. A pulsed polarized H{sup {minus}} ion current of about 10--20 mA should be obtainable using this injector. Limitations on beam characteristics due to space-charge were studied. A polarization scheme to avoid space-charge limitations is considered, in which charge-exchange and spin-exchange are combined.
Date: September 1, 1995
Creator: Zelenski, A.N.; Davydenko, V.I.; Dimov, G.I.; Levy, C.D.P.; Oers, W.T.H. van; Schmor, P.W. et al.
Partner: UNT Libraries Government Documents Department

Status report on the long-term stability of the Advanced Photon Source.

Description: Table 1 summarizes the average elevation changes and standard deviations as well as the points with the largest changes for each year. On average, hardly any settlements can be detected; however, local changes of +2.90 mm to {minus}2.31 mm have been measured. Looking at the low and high points, the settlement process is slowing down over time. Overall, the settlements observed match the expectations for this type of construction. To date no major realignment of the Advanced Photon Source (APS) storage ring has been necessary. The particle beam tracks with the settlements of the floor as long as these changes occur in a smooth fashion and not as sudden discontinuities [5]. From Figures 6 through 8 it is also apparent that settlements affect larger areas in the storage ring and experiment hall that impact the location of the source point as well as the location of the beamline user equipment. The limiting apertures of the insertion device chambers will make realignment of the APS storage ring a necessity at some point in the future. Currently simulations and machine studies we underway to provide an estimate of tolerable settlement limits before a realignment of certain sections of the storage ring would be required. In conclusion, the APS has been constructed on solid ground with an excellent foundation. Only small settlement changes are being observed; so far they are not impacting the operation of the accelerator. We are continuing to monitor deformations of the APS floor in anticipation of a future realignment of the accelerator components.
Date: September 21, 1998
Creator: Friedsam, H.
Partner: UNT Libraries Government Documents Department

Modeling the wind-fields of accidental releases with an operational regional forecast model

Description: The Atmospheric Release Advisory Capability (ARAC) is an operational emergency preparedness and response organization supported primarily by the Departments of Energy and Defense. ARAC can provide real-time assessments of atmospheric releases of radioactive materials at any location in the world. ARAC uses robust three-dimensional atmospheric transport and dispersion models, extensive geophysical and dose-factor databases, meteorological data-acquisition systems, and an experienced staff. Although it was originally conceived and developed as an emergency response and assessment service for nuclear accidents, the ARAC system has been adapted to also simulate non-radiological hazardous releases. For example, in 1991 ARAC responded to three major events: the oil fires in Kuwait, the eruption of Mt. Pinatubo in the Philippines, and the herbicide spill into the upper Sacramento River in California. ARAC`s operational simulation system, includes two three-dimensional finite-difference models: a diagnostic wind-field scheme, and a Lagrangian particle-in-cell transport and dispersion scheme. The meteorological component of ARAC`s real-time response system employs models using real-time data from all available stations near the accident site to generate a wind-field for input to the transport and dispersion model. Here we report on simulation studies of past and potential release sites to show that even in the absence of local meteorological observational data, readily available gridded analysis and forecast data and a prognostic model, the Navy Operational Regional Atmospheric Prediction System, applied at an appropriate grid resolution can successfully simulate complex local flows.
Date: September 11, 1995
Creator: Albritton, J.R.; Lee, R.L. & Sugiyama, G.
Partner: UNT Libraries Government Documents Department

Small-angle and surface scattering from porous and fractal materials.

Description: We review the basic theoretical methods used to treat small-angle scattering from porous materials, treated as general two-phase systems, and also the basic experimental techniques for carrying out such experiments. We discuss the special forms of the scattering when the materials exhibit mass or surface fractal behavior, and review the results of recent experiments on several types of porous media and also SANS experiments probing the phase behavior of binary fluid mixtures or polymer solutions confined in porous materials. Finally, we discuss the analogous technique of off-specular scattering from surfaces and interfaces which is used to study surface roughness of various kinds.
Date: September 18, 1998
Creator: Sinha, S. K.
Partner: UNT Libraries Government Documents Department

Stabilization of insertion electrodes for lithium batteries.

Description: This paper discusses the techniques that are being employed to stabilize LiMn{sub 2}O{sub 4} spinel and composite Li{sub x}MnO{sub 2} positive electrodes. The critical role that spinel domains play in stabilizing these electrodes for operation at both 4 V and 3 V is highlighted. The concept of using an intermetallic electrode MM{prime} where M is an active alloying element and M{prime} is an inactive element (or elements) is proposed as an alternative negative electrode (to carbon) for lithium-ion cells. An analogy to metal oxide insertion electrodes, such as MnO{sub 2}, in which Mn is the electrochemically active ion and O is the inactive ion, is made. Performance data are given for the copper-tin electrode system, which includes the intermetallic phases eta-Cu{sub 6}Sn{sub 5} and Li{sub 2}CuSn.
Date: September 3, 1998
Creator: Thackeray, M. M.
Partner: UNT Libraries Government Documents Department

Measurement of the CP violation parameter sin(2{beta}) in B{sup 0} {r_arrow}J/{psi} K{sub s}{sup 0} Decays

Description: A sample of {approximately} 400 B{sub d}{sup 0}/{bar B}{sub d}{sup 0} {r_arrow} J/{psi}K{sub s}{sup 0} decays collected in {bar p}p collisions by the CDF detector is used to directly measure the CP-violation parameter sin (2{beta}). They find sin(2{beta}) = 0.79{sub {minus}0.44}{sup + 0.41}, favoring the standard model expectation of a large CP violation in this B{sup 0} decay mode.
Date: September 2, 1999
Creator: Bauer, G.
Partner: UNT Libraries Government Documents Department