Search Results

Effects of Global Boundary and Local Collisionality on Magnetic Reconnection in a Laboratory Plasma

Description: The magnetic reconnection process is studied in a wide range of operating conditions in the well-controlled Magnetic Reconnection Experiment. The reconnection rate is observed to be a function of both global (i.e., system size) and local (collisionality) plasma parameters. When only local collisionality is lowered, the current sheet is shortened while effective resistivity is enhanced, both accelerating reconnection rates. At a fixed collisionality, the current sheet length increases with system size, resulting in the reduction of the reconnection rate. These results quantitatively agree with a generalized Sweet-Parker analysis.
Date: July 24, 2007
Creator: A. Kuritsyn, H. Ji, S.P. Gerhardt, Y. Ren, and M. Yamada
Partner: UNT Libraries Government Documents Department

Acoustic Wave Equations for a Linear Viscous Fluid and An Ideal Fluid

Description: The mathematical description of acoustic wave propagation within a time- and space-varying, and moving, linear viscous fluid is formulated as a system of coupled linear equations. This system is rigorously developed from fundamental principles of continuum mechanics (conservation of mass, balance of linear and angular momentum, balance of entropy) and various constitutive relations (for stress, entropy production, and entropy conduction) by linearizing all expressions with respect to the small-amplitude acoustic wavefield variables. A significant simplification arises if the fluid medium is neither viscous nor heat conducting (i.e., an ideal fluid). In this case the mathematical system can be reduced to a set of five, coupled, first-order partial differential equations. Coefficients in the systems depend on various mechanical and thermodynamic properties of the ambient medium that supports acoustic wave propagation. These material properties cannot all be arbitrarily specified, but must satisfy another system of nonlinear expressions characterizing the dynamic behavior of the background medium. Dramatic simplifications in both systems occur if the ambient medium is simultaneously adiabatic and stationary.
Date: July 1, 2002
Creator: ALDRIDGE, DAVID F.
Partner: UNT Libraries Government Documents Department

Fast Grid Search Algorithm for Seismic Source Location

Description: The spatial and temporal origin of a seismic energy source are estimated with a first grid search technique. This approach has greater likelihood of finding the global rninirnum of the arrival time misiit function compared with conventional linearized iterative methods. Assumption of a homogeneous and isotropic seismic velocity model allows for extremely rapid computation of predicted arrival times, but probably limits application of the method to certain geologic environments and/or recording geometries. Contour plots of the arrival time misfit function in the vicinity of the global minimum are extremely useful for (i) quantizing the uncertainty of an estimated hypocenter solution and (ii) analyzing the resolving power of a given recording configuration. In particular, simultaneous inversion of both P-wave and S-wave arrival times appears to yield a superior solution in the sense of being more precisely localized in space and time. Future research with this algorithm may involve (i) investigating the utility of nonuniform residual weighting schemes, (ii) incorporating linear and/or layered velocity models into the calculation of predicted arrival times, and (iii) applying it toward rational design of microseismic monitoring networks.
Date: July 1, 2000
Creator: ALDRIDGE,DAVID F.
Partner: UNT Libraries Government Documents Department

Cooperative Monitoring Center Occasional Paper/16: The Potential of Technology for the Control of Small Weapons: Applications in Developing Countries

Description: For improving the control of small arms, technology provides many possibilities. Present and future technical means are described in several areas. With the help of sensors deployed on the ground or on board aircraft, larger areas can be monitored. Using tags, seals, and locks, important objects and installations can be safeguarded better. With modern data processing and communication systems, more information can be available, and it can be more speedily processed. Together with navigation and transport equipment, action can be taken faster and at greater range. Particular considerations are presented for cargo control at roads, seaports, and airports, for monitoring designated lines, and for the control of legal arms. By starting at a modest level, costs can be kept low, which would aid developing countries. From the menu of technologies available, systems need to be designed for the intended application and with an understanding of the local conditions. It is recommended that states start with short-term steps, such as acquiring more and better radio transceivers, vehicles, small aircraft, and personal computers. For the medium term, states should begin with experiments and field testing of technologies such as tags, sensors, and digital communication equipment.
Date: July 1, 2000
Creator: ALTMANN, JURGEN
Partner: UNT Libraries Government Documents Department

Radiation dose assessment methodology and preliminary dose estimates to support US Department of Energy radiation control criteria for regulated treatment and disposal of hazardous wastes and materials

Description: This report provides unit dose to concentration levels that may be used to develop control criteria for radionuclide activity in hazardous waste; if implemented, these criteria would be developed to provide an adequate level of public and worker health protection, for wastes regulated under U.S, Environmental Protection Agency (EPA) requirements (as derived from the Resource Conservation and Recovery Act [RCRA] and/or the Toxic Substances Control Act [TSCA]). Thus, DOE and the US Nuclear Regulatory Commission can fulfill their obligation to protect the public from radiation by ensuring that such wastes are appropriately managed, while simultaneously reducing the current level of dual regulation. In terms of health protection, dual regulation of very small quantities of radionuclides provides no benefit.
Date: July 1, 1995
Creator: Aaberg, R.L.; Baker, D.A.; Rhoads, K.; Jarvis, M.F. & Kennedy, W.E. Jr.
Partner: UNT Libraries Government Documents Department

Hydrogeochemical and stream sediment reconnaissance of the National Uranium Resource Evaluation Program primarily for the Rocky Mountain states of New Mexico, Colorado, Wyoming, and Montana, and the State of Alaska. Semiannual progress report, October 1978-March 1979

Description: During this six-month period, Hydrogeochemical and Stream Sediment Reconnaissance samples were collected by the Los Alamos Scientific Laboratory (LASL) from 623 locations in Colorado for a special study. Additional special studies are planned for nine other areas in the Rocky Mountain states in fiscal year 1979, plus some cleanup reconnaissance sampling in parts of four quadrangles that overlap state borders. Preparations for reconnaissance sampling of the entire North Slope region of Alaska have been made but sampling is contingent upon receiving supplemental funds. Water samples from 6725 locations were analyzed for uranium by fluorometry or delayed-neutron counting (DNC). Water samples from 9390 locations were analyzed by emission spectroscopy for 12 other elements. Sediment samples from 14,414 locations were analyzed for uranium and 31 other elements by combined DNC and neutron activation analysis. Sediment samples from 9876 locations were analyzed for two additional elements by x-ray fluorescence. Nine LASL reconnaissance reports, one pilot study data release, one supplemental multielement data release, a multielement data release for three areas in western Alaska, and one quarterly report were open filed by the Department of Energy, Grand Junction Office during the six-month period. Numerous other reports are in various stages of completion and several will be open filed in the near future.
Date: July 1, 1979
Creator: Aamodt, P. L.; Bunker, M. E.; Waterbury, G. R. & Waller, R. A.
Partner: UNT Libraries Government Documents Department

J/{psi} production in p{anti p} collisions at {radical}s = 1.8 TeV

Description: The authors have studied J/{psi} production in p{anti p} collisions at {radical}s = 1.8 TeV with the D0 detector at Fermilab, using a {mu}{sup +}{mu}{sup {minus}} data sample corresponding to an integrated luminosity of 13 pb{sup {minus}1}. They have measured the inclusive J/{psi} production cross section as a function of J/{psi} transverse momentum p{sub T}. For the kinematic range p{sub T} > 8 GeV/c and {vert_bar}{eta}{vert_bar} < 0.6 they obtain Br(J/{psi} {yields} {mu}{sup +}{mu}{sup {minus}}) {center_dot} {sigma}(p{anti p} {yields} J/{psi} + X) = 1.93 {+-} 0.16(stat) {+-} 0.43(syst) nb. Using the muon impact parameter they have estimated the fraction of J/{psi} mesons coming from B meson decays to be f{sub b} = 0.35 {+-} 0.09 (stat) {+-} 0.10 (syst) and inferred the inclusive b production cross section. From the information on the event topology a fraction of non-isolated J/{psi} events has been measured to be f{sub non-isol} = 0.64 {+-} 0.09(stat) {+-} 0.06(syst). They have also obtained the fraction of events resulting from radiative decays of {chi}{sub c} states as f{sub {chi}} = 0.30 {+-} 0.07(stat) {+-} 0.07(syst). They discuss the implications of the measurements for charmonium production processes.
Date: July 1, 1995
Creator: Abachi, S.
Partner: UNT Libraries Government Documents Department

Measurement of B{sup 0} {minus} {bar B}{sup 0} mixing using dimuons at D0

Description: The D0 experiment at Fermilab has determined the B{sup 0} {minus} B{sup 0} mixing probability x using dimuon events produced in p{bar p} collisions at {radical}s = 1.8 TeV. Using a sample of 172 dimuon events, we have determined the time and flavor averaged mixing probability x to be 0.09 {plus_minus} 0.04(stat){plus_minus}0.03(sys) [preliminary] in agreement with the present world average.
Date: July 1995
Creator: Abachi, S.
Partner: UNT Libraries Government Documents Department

Measurement of inclusive triple differential dijet cross section, d{sup 3}{sigma}/dE{sub T}d{eta}{sub 1}d{eta}{sub 2} in p{bar p} collisions at {radical}s = 1.8 TeV

Description: Measurement of the inclusive triple differential dijet cross section, d{sup 3}{sigma}/dE{sub T}d{sub {eta}1}d{sub {eta}2}, at a center of mass energy {radical}s = 1.8 TeV with the D0 detector during the 1992--1993 run. The sensitivity of this measurement to different parton distribution functions is explored. A comparison of the data to NLO theory using different parton distributions functions indicates the need for a smaller gluon content in the x range accessible at the Tevatron than is predicted by current parton distribution sets.
Date: July 1995
Creator: Abachi, S.
Partner: UNT Libraries Government Documents Department

A measurement of the ratio of W + 1 jet to W + 0 jets cross sections and comparisons to QCD

Description: A preliminary measurement of the ratio, R{sup 10}, of the production cross sections for W + 1 Jet and W + 0 Jets processes at {radical}s = 1,800 GeV by the D0 Collaboration is presented. A comparison of this ratio is made to next-to-leading order calculations and the implications of these comparisons, especially for the extraction of a value for the strong coupling constant {alpha}{sub s}(M{sub W}{sup 2}), are discussed.
Date: July 1996
Creator: Abachi, S.
Partner: UNT Libraries Government Documents Department

Inclusive dimuon and b-quark production cross sections in p{bar p} collisions at {radical}s = 1.8 TeV

Description: We report on a preliminary measurement of the inclusive dimuon cross section in p{bar p} collisions at {radical}s = 1.8 TeV using the D0 detector at the Fermilab Tevatron. From these results, we extract the inclusive b-quark production cross section for the kinematic range {vert_bar}y{sup b}{vert_bar} < 1.0 and 9 GeV/c < p{sub T}{sup b min} < 25 GeV/c. The difference in azimuthal angle in the transverse plane for dimuon pairs from b{bar b} production is also shown.
Date: July 1, 1995
Creator: Abachi, S.; Abbott, B. & Abolins, M.
Partner: UNT Libraries Government Documents Department

Measurement of the {gamma} cross section at D0 using dimuons

Description: The D0 experiment has measured the {gamma} differential cross section in p{bar p} collisions at {radical}s = 1.8 TeV for {vert_bar}y{sup {gamma}}{vert_bar} < 0.7. We find the measured cross section to be a factor of five larger than the O({alpha}{sub s}{sup 3}) QCD prediction for p{sub T}{sup {gamma}} > 5 GeV/c.
Date: July 1995
Creator: Abachi, S.; Abbott, B. & Abolins, M.
Partner: UNT Libraries Government Documents Department