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5,436 Matching Results
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Position Estimation of Tranceivers in Communication Networks
With the rapid development in wireless sensor networks, there is an important need for transceiver position estimation independent of Global Positioning Systems (GPS) [1,3]. While GPS might be useful for outdoor sensor nodes, it is not for indoor node localization. In this case, position estimation is possible through network range estimates from time-of-flight (TOF) measurements, a technique well suited to large bandwidth physical links, such as in ultra-wideband (UWB) communications. For example, in our UWB systems, with pulse duration less than 200 pico-seconds, range can easily be resolved to less than a foot. Assuming an encoded UWB or spread spectrum physical layer, we developed algorithms and simulation tools to test transceiver position localization. Simulations were designed to lend insight into system characteristics such as position error sensitivities to network geometry, to range estimation errors, and to number of sensor nodes.
Date:
October 13, 2003
Creator:
Kent, C. A. & Dowla, F. U.
Object Type:
Report
System:
The UNT Digital Library
Advanced Refrigerant-Based Cooling Technologies for Information and Communication Infrastructure (ARCTIC)
Faster, more powerful and dense computing hardware generates significant heat and imposes considerable data center cooling requirements. Traditional computer room air conditioning (CRAC) cooling methods are proving increasingly cost-ineffective and inefficient. Studies show that using the volume of room air as a heat exchange medium is wasteful and allows for substantial mixing of hot and cold air. Further, it limits cabinet/frame/rack density because it cannot effectively cool high heat density equipment that is spaced closely together. A more cost-effective, efficient solution for maximizing heat transfer and enabling higher heat density equipment frames can be accomplished by utilizing properly positioned âÃÂÃÂphase changeâÃÂàor âÃÂÃÂtwo-phaseâÃÂàpumped refrigerant cooling methods. Pumping low pressure, oil-free phase changing refrigerant through microchannel heat exchangers can provide up to 90% less energy consumption for the primary cooling loop within the room. The primary benefits of such a solution include reduced energy requirements, optimized utilization of data center space, and lower OPEX and CAPEX. Alcatel-Lucent recently developed a modular cooling technology based on a pumped two-phase refrigerant that removes heat directly at the shelf level of equipment racks. The key elements that comprise the modular cooling technology consist of the following. A pump delivers liquid refrigerant to finned …
Date:
December 13, 2012
Creator:
Salamon, Todd
Object Type:
Report
System:
The UNT Digital Library
Edge Gyrokinetic Theory and Continuum Simulations
None
Date:
September 13, 2007
Creator:
Xu, X. Q.; Xiong, Z.; Dorr, M. R.; Hittinger, J. A.; Bodi, K.; Candy, J. et al.
Object Type:
Article
System:
The UNT Digital Library
Review of free electron laser theory and experiments
A review of the major Free Electron Laser (FEL) experiments will be presented. These experiments are designed to produce radiation at wavelengths from the far infrared to the ultraviolet. Different categories of FELs (Compton, Raman, optical klystron, two stage, etc.), as well as the suitability of various types of electron accelerators to power FELs, will also be discussed. Potential applications of the FEL will be summarized.
Date:
January 13, 1984
Creator:
Prosnitz, D.
Object Type:
Article
System:
The UNT Digital Library
Theory of AC Loss in Cables with 2G HTS Wire
While considerable work has been done to understand AC losses in power cables made of first generation (1G) high temperature superconductor (HTS) wires, use of second generation (2G) HTS wires brings in some new considerations. The high critical current density of the HTS layer 2G wire reduces the surface superconductor hysteretic losses. Instead, gap and polygonal losses, flux transfer losses in imbalanced two layer cables and ferromagnetic losses for wires with NiW substrates constitute the principal contributions. Current imbalance and losses associated with the magnetic substrate can be minimized by orienting the substrates of the inner winding inward and the outer winding outward.
Date:
September 13, 2009
Creator:
Clem, J.R. & Malozemoff, A.P.
Object Type:
Article
System:
The UNT Digital Library
Introduction to the Theory and Analysis of Resolved (and Unresolved) Neutron Resonances via SAMMY
Neutron cross-section data are important for two purposes: First, they provide insight into the nature of matter, increasing our understanding of fundamental physics. Second, they are needed for practical applications (e.g., for calculating when and how a reactor will become critical, or how much shielding is needed for storage of nuclear materials, or for medical applications). Neutron cross section data in the resolved-resonance region are generally obtained by time-of-flight experiments, which must be carefully analyzed if they are to be properly understood and utilized. In this report, important features of the analysis process are discussed, with emphasis on the particular techniques used in the analysis code SAMMY. Other features of the code are also described; these include such topics as calculation of group cross sections (including covariance matrices), generation and fitting of integral quantities, and extensions into the unresolved-resonance region and higher-energy regions.
Date:
March 13, 2000
Creator:
Larson, N.
Object Type:
Article
System:
The UNT Digital Library
Hexagon Functions and the Three-loop Remainder Function
None
Date:
August 13, 2013
Creator:
Dixon, Lance J.; Drummond, James M.; von Hippel, Matt & Pennington, Jeffrey
Object Type:
Article
System:
The UNT Digital Library
Mad Cow Disease: Agricultural Issues for Congress
In December 2003 a Holstein dairy cow in Washington State tested positive for BSE (bovine spongiform encephalopathy, or mad cow disease), the first case discovered in the The United States and the second native casein North America. (Canada confirmed a third and then the fourth case in early January 2005.)
Date:
January 13, 2005
Creator:
Becker, Geoffrey S.
Object Type:
Report
System:
The UNT Digital Library
The Use of the Electrical Conductivity of Graphite as a Radiation Damage and Flux Monitor. Implications of the Results to the General Theory of Radiation Damage
A method for monitoring radiation damage irradiations using the change of the electrical conductivity of graphite is described. Results of monitoring operations in a number of locations are given. An attempt is made to explain the damage rate found in the converter at CP-3. An estimate of the flux spectrum in VT-4 and the converter of CP-3 is made and the damage rate is computed according to theories of Seitz and James. It is found that the experimental results are more in accord with the predictions of Seitz. A number of corrections to James' report, ORNL-307, are noted in an appendix. It is shown that some information about the fast flux spectrum can be inferred from the radiation damage rate.
Date:
July 13, 1953
Creator:
Primak, W. L. & Fuchs, L. H.
Object Type:
Report
System:
The UNT Digital Library
NEUTRON DIVISION ANNUAL PROGRESS REPORT FOR PERIOD ENDING SEPTEMBER 1, 1960
Research efforts in neutron physics are reported in the areas of light- water-moderated reactors, new reactors for BSF and TSF, critical experiments, experimental nuclear physics, experimental reactor physics, reactor theory, shielding research, radiation detector studies, plasma physics theory, and theoretical nuclear physics. Separate abstracts were prepared for the seventy sections of the report. (W.D.M.)
Date:
December 13, 1960
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
A Quantitative Study of Tethered Chains in Various Solution Conditions Using Langmuir Diblock Copolymer Monolayers
This article summarizes our investigations of tethered chain systems using Langmuir monolayer of polydimethysiloxane-poly styrene (PDMS-PS) diblock copolymers on organic liquids. In this system, the PDMS block adsorbs to the air surface while the PS block dangles into the subphase liquid. The air surface can be made either repulsive or attractive for the tethered PS chain segments by choosing a subphase liquid which has a surface tension lower or greater than that of PS, respectively. The segment profile of the PS block is determined by neutron reflection as a function of the surface density, the molecular weights of the PS and PDMS blocks, and the solution conditions. We cover the range of reduced surface density (SIGMA) characteristic of the large body of data in the literature for systems of chains tethered onto solid surfaces from dilute solution in good or theta solvent conditions (SIGMA < 12). We emphasize quantitative comparisons with analytical profile forms and scaling predictions. We find that the strong-stretching limit invoked in analytical SCF and scaling theories is not valid over this Z range. On the other hand, over a large portion of this range (SIGMA < 5) tethered layers are well described by a renormalization group …
Date:
August 13, 1999
Creator:
Kent, Michael S.
Object Type:
Article
System:
The UNT Digital Library
Two Topics in Pion Physics. [Part] 1. Photoproduction of Neutral Pions From Complex Nuclei and the Pair-Correlation Function. [Part] 2. The Relative Rate of Absorption of Negative Pions in Hydrogen and Deuterium
A simple theory of the photoproduction of pi /sup 0/ mesons from complex nuclei based on the impulse and closure approximation is studied. The theory is compared with an experiment of Goodwin, Anderson, and Kenney that shows the dependence of the number of decay gammas from pi /sup 0/ mesons photo- produced from various nuclei as a function of the atomic number at 45, 90, and 135 degrees for incident photon energies from threshold to 350 Mev. The dependence measured near threshold and at 45 degrees does not agree with the simple theory nor is it consistent with partial elastic production. By a method of Placzek and Wick the corrections to the simple theory are estimated, and found to be large near threshold. These corrections may explain the discrepancy between the theory and the experimental results. No information about the nuclear-pair correlation function is obtained. The impulse approximation is used to calculate the relative ratio of the radiative absorption rate of pi /sup -/ mesons absorbed in hydrogen and deuterium from an atomic s state. The calculated value of the ratio T = R( pi /sup -/ + d yields 2n + gamma )/R( pi /sup -/ + p yields …
Date:
August 13, 1962
Creator:
Traxler, R. H.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
TWENTY-FIVE GROUP REACTOR NUCLEAR DATA TAPE NEUTRON CROSS SECTIONS
A compilation is presented, in the twenty-five group Reactor Nuclear Data Tape format, of neutron cross sections for elements of major interest for GE- ANPD reactor analysis. The tabulated data are a reproduction of neutron cross section information contained on the Reactor Nuclear Data Tape, which was recently prepared. A brief outline of methods used in processing of the cross sections is also included. (auth)
Date:
June 13, 1961
Creator:
Zwick, J. W. & Kostigen, T. J.
Object Type:
Report
System:
The UNT Digital Library
An evaluation of the experimental determination of the effects of burnout and corrosion on spline worth
Efforts have been made to experimentally evaluate and to calculate the effect of reactor environment on splines. This report follows some of these efforts and relates them to operational experience. The use of splines in the Hanford Reactors has improved the efficiency and ease of operating the reactors. With the widespread use of splines, it is important to know the effect of reactor exposure to safely and efficiently use the splines in reactor operation.
Date:
July 13, 1964
Creator:
Blyckert, W. A.
Object Type:
Report
System:
The UNT Digital Library
Reactivity trends and prediction problems vs operating trends C, H, KE, and KW Reactors, 1954--1958
During the past several years higher pile power levels, variations in the uranium goal exposure, changes in reactor loadings, and resulting changes in operating practices have steadily increased reactivity transients following the reacotr shutdowns and start-ups. Consequently, since conditions influencing activity transient predictions have becomeincreasingly more varied, it has become more difficult to maintain prediction accuracy Trends related to operating practices, reactivity variables, and critical predictions have been presented previously for the years 1950 thorugh 1957. It is the purpose of this report to include the data for the year 1958. In addition to presenting the data for reference purposes this document discusses the trends in operting pratices reactivity variable evaluations, and the accuracy of reactivity predictions during the past five years. Bar graphs show the yearly averages of selected data obtained from the shutdown data sheets, montly reports, and routinereactivity balance reports. In addition to these averages a table presents maximum and minimum values wherever they are applicable.
Date:
March 13, 1959
Creator:
Goins, D. E.
Object Type:
Report
System:
The UNT Digital Library
Preliminary evaluation of neutron capture cross sections for /sup 144/Sm, /sup 145/Sm and /sup 145/Pm
We have made preliminary neutron-capture cross-section calculations of the Hauser-Feshbach type for the isotopes /sup 144/Sm, /sup 145/Sm, and /sup 145/Pm to investigate the production of radioactive /sup 145/Pm by neutron capture on the stable isotope /sup 144/Sm. The calculations were made for incident neutron energies from 2.5 MeV to about 1/sup -4/ or 10/sup -5/ MeV, wherever the first unbound resonance was estimated to occur in each case. At that energy, the calculated value was reduced by a somewhat arbitrary factor, and the excitation function extended down to thermal energy using a (E/sub n/)/sup -1/2/ energy dependence. Since very large uncertainties are associated with the position and magnitude of the first unbound resonance and the subsequent extrapolation back to thermal energy, the cross sections in this low-energy region should not be considered more accurate than +- a factor of 10. For incident neutron energies above each step, the calculations represent an average through the separated and overlapping resonance regions and may be accurate to better than +- a factor of 2. 18 refs., 7 figs., 5 tabs.
Date:
February 13, 1986
Creator:
Gardner, D. G. & Gardner, M. A.
Object Type:
Report
System:
The UNT Digital Library
L-shell photoabsorption spectroscopy for solid metals: Ti, V, Cr, Fe, Ni, Cu
Synchrotron radiation measurements of near-threshold and broad-range (400--1500 eV) absolute photoabsorption cross sections were made for five transition metals with {plus minus}10% overall uncertainties. Fine structure details of 2p-3d autoionizing resonances are shown with better than 1.0 eV resolution for solid metals: Ti, V, Cr, Fe, Ni, and Cu. Fine structure similar to what we measured can be produced using a multi-configuration Dirac Fock (MCDF) model if a statistical distribution is assumed for the initial atomic states. Calculations were performed in intermediate coupling with configuration interactions by Mau H. Chen. The results are compared with other experimental work and theoretical methodologies. 18 refs., 7 figs.
Date:
September 13, 1989
Creator:
Del Grande, N.K. (Lawrence Livermore National Lab., CA (USA))
Object Type:
Article
System:
The UNT Digital Library
Report of the QCD Working Group
We discuss some current problems associated with the applications of QCD to event rates in high energy collisions. Emphasis is given to the current ambiguities and uncertainties that exist in estimates of signals and backgrounds. The production of jets and isolated photons at hadron colliders is discussed in some detail. The problems of jet definition are addressed. Some features of the events underlying the hard scattering process are discussed. 72 refs., 32 figs., 3 tabs.
Date:
January 13, 1989
Creator:
Hinchliffe, I. & Shapiro, M. D.
Object Type:
Article
System:
The UNT Digital Library
A comparison of risk assessment techniques from qualitative to quantitative
Risk assessment techniques vary from purely qualitative approaches, through a regime of semi-qualitative to the more traditional quantitative. Constraints such as time, money, manpower, skills, management perceptions, risk result communication to the public, and political pressures all affect the manner in which risk assessments are carried out. This paper surveys some risk matrix techniques, examining the uses and applicability for each. Limitations and problems for each technique are presented and compared to the others. Risk matrix approaches vary from purely qualitative axis descriptions of accident frequency vs consequences, to fully quantitative axis definitions using multi-attribute utility theory to equate different types of risk from the same operation.
Date:
February 13, 1995
Creator:
Altenbach, T.J.
Object Type:
Article
System:
The UNT Digital Library
Modeling node bandwidth limits and their effects on vector combining algorithms
Each node in a message-passing multicomputer typically has several communication links. However, the maximum aggregate communication speed of a node is often less than the sum of its individual link speeds. Such computers are called node bandwidth limited (NBL). The NBL constraint is important when choosing algorithms because it can change the relative performance of different algorithms that accomplish the same task. This paper introduces a model of communication performance for NBL computers and uses the model to analyze the overall performance of three algorithms for vector combining (global sum) on the Intel Touchstone DELTA computer. Each of the three algorithms is found to be at least 33% faster than the other two for some combinations of machine size and vector length. The NBL constraint is shown to significantly affect the conditions under which each algorithm is fastest.
Date:
January 13, 1992
Creator:
Littlefield, R.J.
Object Type:
Report
System:
The UNT Digital Library
Modeling node bandwidth limits and their effects on vector combining algorithms
Each node in a message-passing multicomputer typically has several communication links. However, the maximum aggregate communication speed of a node is often less than the sum of its individual link speeds. Such computers are called node bandwidth limited (NBL). The NBL constraint is important when choosing algorithms because it can change the relative performance of different algorithms that accomplish the same task. This paper introduces a model of communication performance for NBL computers and uses the model to analyze the overall performance of three algorithms for vector combining (global sum) on the Intel Touchstone DELTA computer. Each of the three algorithms is found to be at least 33% faster than the other two for some combinations of machine size and vector length. The NBL constraint is shown to significantly affect the conditions under which each algorithm is fastest.
Date:
January 13, 1992
Creator:
Littlefield, R. J.
Object Type:
Report
System:
The UNT Digital Library
Optics in the Multipole Approximation: From Atomic Systems to Solids
Starting from the microscopic light-matter interaction in form of the minimal coupling Hamiltonian, the multipole approximation for the optical response of localized electrons in atomic systems is extended to delocalized electrons in solids. A spatial averaging procedure is used to derive the electromagnetic sources for macroscopic Maxwell's equations as well as the corresponding many particle Hamiltonian on a coarse grained length scale. The results are illustrated for semiconductor bulk material up to quadruple moments for the interband transitions, where gauge invariant equations of motion for the optical response are obtained.
Date:
September 13, 1999
Creator:
CHOW, WENG W.; KNORR, ANDREAS & KOCH, STEPHAN W.
Object Type:
Article
System:
The UNT Digital Library
The Panola Watchman (Carthage, Tex.), Vol. 129, No. 80, Ed. 1 Sunday, October 13, 2002
Semiweekly newspaper from Carthage, Texas that includes local, state, and national news along with advertising.
Date:
October 13, 2002
Creator:
unknown
Object Type:
Newspaper
System:
The Portal to Texas History
The Panola Watchman (Carthage, Tex.), Vol. 126, No. 82, Ed. 1 Wednesday, October 13, 1999
Semiweekly newspaper from Carthage, Texas that includes local, state, and national news along with advertising.
Date:
October 13, 1999
Creator:
unknown
Object Type:
Newspaper
System:
The Portal to Texas History