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318,998 Matching Results
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318,998
Zr and Mo isotopic constraints on the origins of unusual types of presolar SiC grains.
Although most presolar silicon carbide grains form in asymptotic giant branch red giant stars (the so-called mainstream grains) or supernovae (the X-grains), there are a number of other minor types of grains whose origin is less clear. The dominant mechanisms of heavy element nucleosynthesis, the s-process and r-process, are thought to occur mainly in AGB stars and supernovae, respectively [1], and the isotopic patterns in heavy elements in presolar grains can be used to constrain their origins. We have previously reported that mainstream SiC grains have strong enrichments in the s-process isotopes of Sr, Zr and Mo [2-5] and that X-grains have an unusual Mo isotopic composition that differs from s- and r-process expectations [6,7]. We report here the first measurements of Zr and Mo isotopes in several grains of other rare types that were found in the same mount as the mainstream and X-grains reported previously.
Date:
March 1, 2000
Creator:
Pellin, M. J.; Davis, A. M.; Calaway, W. F.; Lewis, R. S.; Clayton, R. N. & Amari, S.
Object Type:
Article
System:
The UNT Digital Library
ZrH reactor lattice spacing (heat transfer considerations)
None
Date:
September 25, 1970
Creator:
Felten, L. D.
Object Type:
Report
System:
The UNT Digital Library
ZrH-reactor-technology program. Progress report, April-June 1974
The report on the 2 kW(e) reactor-organic Rankine system was drafted. This report details the design parameters of a minimum weight, 2 kW(e) reactor-organic Rankine system. The system is designed for 5 years unattended life in space. The reactor produces 16.2 kW of thermal power with a NaK outlet temperature of 800/sup 0/F and a 200/sup 0/F ..delta..T. The reactor contains 19 fuel elements, 1.25'' in diameter by 10'' long, hydrided to an N/sub H/ of 6.35. The terrestrial applications effort was oriented towards the establishment of the feasibility of utilizing the zirconium hydride reactor technology in a subsea application for supplying electrical power to deep water, and other environmentally severe, oil well installations. The overall system concept is shown. The power system is composed of three basic modules (i.e., a reactor module, a generator module, and a heat rejection system) mounted on a barge. The barge is then towed to the installation site and submerged to mate with a previously installed seafloor foundation. An assembly/disassembly sequence was drafted detailing the steps required to assemble the reactor module and to disassemble it after 4 years of operations.
Date:
July 12, 1974
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
ZrO sub 2 and ZrO sub 2 /SiC particle reinforced-MoSi sub 2 matrix composites
ZrO{sub 2}-MoSi{sub 2} and ZrO{sub 2}/SiC-MoSi{sub 2} composites were fabricated by hot pressing and hot pressing/HIP at 1700{degrees}C. No reactions between ZrO{sub 2}, SiC, and MoSi{sub 2} were observed. An amorphous silica glassy phase was present in all composites. Composites with unstabilized ZrO{sub 2} particles exhibited the highest room temperature fracture toughness, reaching a level three times that of pure MoSi{sub 2}. Both the room temperature toughness and 1200{degrees}C strength of ZrO/{sub 2}SiC-MoSi{sub 2} composites were higher than ZrO{sub 2}-MoSi{sub 2} composites, indicating beneficial effects of combined reinforcement phases. Low strength levels were observed at 1400{degrees}C due to the presence of the silica glassy phase. Elimination of glassy phases and refinements in microstructural homogeneity are processing routes important to the optimization of the mechanical properties of these types of composites. 18 refs., 7 figs.
Date:
January 1, 1991
Creator:
Petrovic, J. J.; Bhattacharya, A. K.; Honnell, R. E.; Mitchell, T. E. (Los Alamos National Lab., NM (United States)); Wade, R. K. (Arizona Materials Lab., Tucson, AZ (United States)) & McCellan, K. J. (Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Materials Science and Engineering)
Object Type:
Article
System:
The UNT Digital Library
THE ZrO$sub 2$-CaO-UO$sub 2$ CERAMIC FUEL FABRICATION FOR THE EBWR SPIKED CORE ELEMENTS. Final Report-Metallurgy Program 7.9.5
A series of experiments was proposed in which the thermal output of the EBWR is increased to 100 Mw. The increase in thermal enengy will be accomplished by inserting 32 spike elements in the initial fuel core. The fuel selected for the spike elements was a cubic solid solution in the system ZrO/sub 2/- CaO- UO/ sub 2/. The ceramic fuel was fabricated in the form of pellets by compacting a mixture of U/sub 3/O/sub 8/, CaCO/sub 3/, and ZrO/sub 2/. The pressed pellets were sintered in air at 1675 deg C plus or minus 25 deg C to form a cubic solid solution having a composition of 9.01 wt.% UO/sub 2/ (93% enriched), 9.07 wt.% CaO, and 81.92 wt.% ZrO/sub 2/. The procedures used in forming the fuel pellets are described. Following fabrication, the pellets were loosely inserted into Zircaloy-2 tubes for subsequent assembly into fuel elements. (auth)
Date:
May 1961
Creator:
Lied, R. C.; Lynch, E. D. & Handwerk, J. H.
Object Type:
Report
System:
The UNT Digital Library
ZrO sub 2 reinforced-MoSi sub 2 matrix composites
ZrO{sub 2} particle-MoSi{sub 2} matrix composites were fabricated by wet processing/hot pressing, using high quality unstabilized, partially stabilized, and fully stabilized ZrO{sub 2} powders. Composite room temperature indentation fracture toughness increased with increasing volume fraction of ZrO{sub 2} reinforcement. Unstabilized ZrO{sub 2} produced the highest composite fracture toughness, 7.8 MPa m{sup {1/2}} as compared to 2.6 MPa m{sup {1/2}} for pure MoSi{sub 2}. Unstabilized ZrO{sub 2} composites exhibited matrix microcracking, and the spontaneous tetragonal-to-monoclinic ZrO{sub 2} phase transformation induced significant plastic deformation in the MoSi{sub 2} matrix. Partially stabilized ZrO{sub 2} produced a lesser extent of composite fracture toughening, possibly as a result of an inhomogeneous ZrO{sub 2} particle distribution and presence of a glassy phase. 13 refs., 6 figs., 1 tab.
Date:
January 1, 1991
Creator:
Petrovic, J. J.; Honnell, R. E.; Mitchell, T. E. (Los Alamos National Lab., NM (USA)); Wade, R. K. (Arizona Materials Lab., Tucson, AZ (USA)) & McClellan, K. J. (Case Western Reserve Univ., Cleveland, OH (USA). Dept. of Materials Science and Engineering)
Object Type:
Article
System:
The UNT Digital Library
ZT-40 administrative plan
An administrative plan for the ZT-40 project has been developed. It describes baselines and procedures that will be used for the remainder of the construction phase of the project.
Date:
August 1, 1978
Creator:
Thomas, K.S. (comp.)
Object Type:
Report
System:
The UNT Digital Library
ZT-40M system design, modification, and installation
ZT-40 is a reversed field pinch experiment which had been operated as originally designed, with a ceramic discharge tube until November 1980. At that time, the experiment was shut down for major modifications. This paper will describe these modifications in general and discuss in detail the design of the energy system.
Date:
January 1, 1981
Creator:
Hammer, C. F.
Object Type:
Article
System:
The UNT Digital Library
ZT-P: an advanced air core reversed field pinch prototype
The ZT-P experiment, with a major radius of 0.45 m and a minor radius of 0.07 m, was designed to prototype the next generation of reversed field pinch (RFP) machines at Los Alamos. ZT-P utilizes an air-core poloidal field system, with precisely wound and positioned rigid copper coils, to drive the plasma current and provide plasma equilibrium with intrinsically low magnetic field errors. ZT-P's compact configuration is adaptable to test various first wall and limiter designs at reactor-relevant current densities in the range of 5 to 20 MA/m/sup 2/. In addition, the load assembly design allows for the installation of toroidal field divertors. Design of ZT-P began in October 1983, and assembly was completed in October 1984. This report describes the magnetic, electrical, mechanical, vacuum, diagnostic, data acquisition, and control aspects of the machine design. In addition, preliminary data from initial ZT-P operation are presented. Because of ZT-P's prototypical function, many of its design aspects and experimental results are directly applicable to the design of a next generation RFP. 17 refs., 47 figs.
Date:
January 1, 1986
Creator:
Schoenberg, K. F.; Buchenauer, C. J.; Burkhardt, L. C.; Caudill, L. D.; Dike, R. S.; Dominguez, T. et al.
Object Type:
Report
System:
The UNT Digital Library
ZTI: An ignition class reversed-field pinch
A cost-optimized conceptual design of an intermediate-step, ignition-class RFP device (ZTI)for the study of alpha-particle physics and burn control in a DT plasma is reported. With major and minor plasma radii R{sub T} = 2.4m and {tau}{sub p} = 0.4m, respectively, and for conservative extrapolations of experimental energy-confinement times, ion-density profiles, and impurity levels, the ZTI operating conditions during a 5-s period of constant fusion power are: toroidal plasma current I{sub {phi}} {approx equal} 9 MA, plasma temperature T {approx equal} 11 keV, plasma density n{sub i} {approx equal} 3 {times} 10{sup 20} m{sup {minus}3}, fusion power P{sub F} {approx equal} 100 MW, and physics Q-value Q{sub p} {approx equal} 5 for a total machine size that corresponds to P{sub F}/M{sub FPC} {approx equal} 590 kW/tonne. This physics design point was adopted as a strawman'' with which to examine the requirements of ohmic heating to DT ignition and to perform a cost-optimized magnetics design. The ZTl design reflects potentially significant cost savings relative to similar ignition-class tokamaks for device parameters that reside on the path to a viable commercial RFP reactor. The methodology and results of coupling realistic physics, engineering, and cost models through a multi-dimensional optimizer are reported for …
Date:
January 1, 1990
Creator:
Bathke, C. G.; Krakowski, R. A.; Miller, R. L. & Werley, K. A.
Object Type:
Article
System:
The UNT Digital Library
ZTI: Preliminary characterization of an ignition class reversed-field pinch
A preliminary cost-optimized conceptual design of an intermediate-step, ignition-class RFP device (ZTI) for the study of alpha-particle physics in a DT plasma is reported. The ZTI design reflects potentially significant cost savings relative to similar ignition-class tokamaks for device parameters that reside on the path to a viable commercial RFP reactor. Reductions in both device costs and number of steps to commercialization portend a significantly reduced development cost for fusion. The methodology and result and coupling realistic physics, engineering, and cost models through a multi-dimensional optimizer are reported for ZTI, which is a device that would follow the 2--4 MA ZTH on a {approx gt} 1996--98 timescale. 15 refs., 7 figs., 2 tabs.
Date:
January 1, 1990
Creator:
Bathke, C. G.; Krakowski, R. A.; Miller, R. L. & Werley, K. A.
Object Type:
Article
System:
The UNT Digital Library
Zuni Mountains, New Mexico as a potential dry hot rock geothermal energy Site
Many of the criteria for the successful exploitation of energy from dry hot rock are met in the Zuni Mountains, New Mexico. This area falls within a broad region of abnormally high heat flow on the Colorado Plateau. Within this region, a variety of evidence indicates that local ''hot spots'' may be present. These ''hot spots'' are prime targets for dry hot rock exploration. A site-evaluation program utilizing geological, geochemical-geochronological, and geophysical techniques is proposed to delineate the optimal sites for subsequent exploratory drilling.
Date:
December 1, 1975
Creator:
Laughlin, A. W. & West, F. G.
Object Type:
Report
System:
The UNT Digital Library
ZX Pulsed-Power Design
ZX is a new z-pinch accelerator planned as the next generation z-pinch driver at SNL, and as an intermediate step towards X-1. It is planned to drive either a single 50 MA z-pinch load, or two 25 to 30 MA z pinches. Three designs for the ZX accelerator are presented. All require 7 to 8 MV at the insulator stack to drive the z-pinch load to implosion in 100 to 120 ns. Two of the designs are based on the Z accelerator, and use water-line technology; a transit-time-isolated water adder, and a water transformer. The third design uses inductive-voltage adders in water. They also describe a low-inductance insulator stack design that helps minimize voltage requirements. This design is evaluated for water and vacuum break-down using JCM, THM, and magnetic-flashover-inhibition criteria.
Date:
August 2, 1999
Creator:
Corley, J. P.; Johnson, D. L.; McDaniel, D. H.; Spielman, R. B.; Struve, K. W. & Stygar, W. A.
Object Type:
Article
System:
The UNT Digital Library
ZZ ---> l+ l- v anti-v production in p anti-p collisions at s**(1/2) = 1.96-TeV
None
Date:
August 1, 2008
Creator:
Abazov, V. M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Object Type:
Article
System:
The UNT Digital Library