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203
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112
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106
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15,323 Matching Results
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Arithmetic averaging: A versatile technique for smoothing and trend removal
Arithmetic averaging is simple, stable, and can be very effective in attenuating the undesirable components in a complex signal, thereby providing smoothing or trend removal. An arithmetic average is easy to calculate. However, the resulting modifications to the data, in both the time and frequency domains, are not well understood by many experimentalists. This paper discusses the following aspects of averaging: (1) types of averages -- simple, cumulative, and moving; and (2) time and frequency domain effects of the averaging process.
Date:
December 31, 1993
Creator:
Clark, E. L.
Object Type:
Article
System:
The UNT Digital Library
Aspects of modeling uncertainty and prediction
Probabilistic assessment of variability in model prediction considers input uncertainty and structural uncertainty. For input uncertainty, understanding of practical origins of probabilistic treatments as well as restrictions and limitations of methodology is much more developed than for structural uncertainty. There is a simple basis for structural uncertainty that parallels that for input uncertainty. Although methodologies for assessing structural uncertainty for models in general are very limited, more options are available for submodels.
Date:
December 31, 1993
Creator:
McKay, M. D.
Object Type:
Article
System:
The UNT Digital Library
Assessment of the PIUS physics and thermal-hydraulic experimental data bases
The PIUS reactor utilizes simplified, inherent, passive, or other innovative means to accomplish safety functions. Accordingly, the PIUS reactor is subject to the requirements of 10CFR52.47(b)(2)(i)(A). This regulation requires that the applicant adequately demonstrate the performance of each safety feature, interdependent effects among the safety features, and a sufficient data base on the safety features of the design to assess the analytical tools used for safety analysis. Los Alamos has assessed the quality and completeness of the existing and planned data bases used by Asea Brown Boveri to validate its safety analysis codes and other relevant data bases. Only a limited data base of separate effect and integral tests exist at present. This data base is not adequate to fulfill the requirements of 10CFR52.47(b)(2)(i)(A). Asea Brown Boveri has stated that it plans to conduct more separate effect and integral test programs. If appropriately designed and conducted, these test programs have the potential to satisfy most of the data base requirements of 10CFR52.47(b)(2)(i)(A) and remedy most of the deficiencies of the currently existing combined data base. However, the most important physical processes in PIUS are related to reactor shutdown because the PIUS reactor does not contain rodded shutdown and control systems. …
Date:
December 31, 1993
Creator:
Boyack, B. E.
Object Type:
Report
System:
The UNT Digital Library
Asymptotic coherence of gluons and of q-bosons
In theoretical physics one of the most important aspects of coherent states is that they can often be simply and reliably used to investigate the quantum coherence and correlation properties of new dynamical, quantum field theories. First, this paper reviews the coherent/degenerate state treatment of the infra-red dynamics of perturbative QCD. This based on the asymptotic behavior of the Hamiltonian operator as {vert_bar}t{vert_bar} {yields} {infinity} in the interaction representation. Second, the paper reviews the usage of q-analogue coherent states {vert_bar}z>{sub q} to deduce coherence and uncertainty properties of the q-analogue quantized radiation field in the {vert_bar}z>{sub q} ``classical limit`` where {vert_bar}z{vert_bar} is large. Third, for future applications, a new ``projector`` definition of the usual coherent states and of the squeezed states is reported.
Date:
December 31, 1993
Creator:
Nelson, C. A.
Object Type:
Article
System:
The UNT Digital Library
Atmospheric gas. Annual report, August 1, 1992--July 31, 1993
This proposal requests support for a third year of funding to complete a modelling study of processes controlling the distribution and waters at an ocean location with detailed background measurements of biological physical properties. We determined concentrations of the gases O{sub 2}, Ar, N{sub 2}, and the stable isotope ratio ({sup 18}O/{sup 16}O) of molecular oxygen in surface waters at Station ALOHA in conjunction with the Global Ocean Flux Study (GOFS) Hawaiian Ocean Time-series project during the years 1989--90 and 1992--93, the latter currently being completed. Chemical tracers have been incorporated into an existing ocean mixed-layer model to simulate the physical processes controlling the distribution and seasonal cycle of dissolved gases in the upper ocean. The broad background of concurrent chemical, physical, and biological measurements at station ALOHA provides enough redundancy of ``ground truth`` to assess the model`s accuracy. Biological oxygen production estimated from modeled chemical tracers agrees with estimates based on measurements of carbon fluxes into the deep ocean and nitrate fluxes into the upper ocean during 1989--90, verifying for the first time the utility of chemical tracers for determining biological fluxes in the ocean. The results suggest that in the euphoric zone the net biological O{sub 2} production …
Date:
December 31, 1993
Creator:
Schudlich, R. & Emerson, S.
Object Type:
Report
System:
The UNT Digital Library
[Atomic and electronic structure of metals and alloys: Clean surfaces and chemisorbed molecules]
Ultrapure Tb was further purified and surface cleaning procedures developed for basal plane and (11{bar 2}0) surface of Tb. Structure of both surfaces was found to be relaxed: (0001) is contracted by 3.9% in the first and expanded by 1.4% in second interlayer spacing; (11{bar 2}0) is contracted by 3.3% in first layer and shows a change in registry. Thin films of Gd, Tb, Dy, Ho, and Er were grown on W{l_brace}110{r_brace} substrate in ultrahigh vacuum. Studies have been carried out on epitaxial systems involving Cu, Fe and Mn on Fe and Pt, Cu, and Pd substrates, respectively; new metastable crystalline phases have been found. Studies of possible ferromagnetism in 4d elements (Rh, Ru) and relativistic effects in electron band structure of Cu{l_brace}111{r_brace} have been completed and published. Plans for the following year are given.
Date:
December 31, 1993
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Atomic and electronic structure of metals and alloys: Rare earths, ultrathin films and surface alloys. Final report, [October 1, 1988--December 31, 1993]
The project has been productive: 47 refereed publications in about 5 years. While confined to the area of surfaces and thin films, the project has covered a wide range of physical properties and different materials: rare earths, bulk and surface alloys, metal surfaces, magnetism, and (especially) atomic and electronic structure of ultrathin films. Notable achievements include quantitative studies of atomic structure of clean rare-earth surfaces: Tb(0001), Tb(11{ovr 2}0), Gd(0001), and Gd(11{ovr 2}0). Surface alloys studied included Cu{l_brace}001{r_brace}c(2 {times} 2)-Au and Cu{l_brace}001{r_brace}c(2 {times} 2)-Pd. The most important achievement of the project lies in the application of quantitative low-energy electron diffraction to ultrathin films, particularly magnetic metals on nonmagnetic substrates (e.g., Fe on Ag{l_brace}001{r_brace}, etc.) (No data given.)
Date:
December 31, 1993
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Atomic and molecular data needs for fusion
Atomic and molecular processes in plasmas play a crucial role in the development of net energy producing magnetic fusion devices. In light of this fact, presented here is a survey of the broad needs of fusion energy research and a review of the status of the existing database. Emphasis is placed on the relatively new needs for data as novel materials are evaluated for use in the next devices, and as components such as the divertor take on more significance for demonstration and practical reactors. Also, examples are given of recent or ongoing data evaluation efforts, the role of national and international data centers is discussed, and some summarizing comments are given.
Date:
December 31, 1993
Creator:
Schultz, D. R.
Object Type:
Article
System:
The UNT Digital Library
Atomic processes in Inertial Electrostatic Confinement (IEC) devices
Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P. T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated neutron yields as high as 2*10{sup 10} neutrons/sec. These systems have considerable potential as small, inexpensive, portable neutron sources for assaying applications. Neutron tomography is also a potential application. Atomic physics effects strongly influence the performance of all of these systems. Important atomic effects include elastic scattering, ionization, excitation, and charge exchange. This paper discusses how an IEC system is influenced by these effects and how to design around them. Theoretical modeling and experimental results are presented.
Date:
December 31, 1993
Creator:
Nebel, R. A.; Turner, L.; Tiouririne, T. N.; Barnes, D. C.; Nystrom, W. D.; Bussard, R. W. et al.
Object Type:
Article
System:
The UNT Digital Library
Attempts to model the generation of new grain boundaries during the deformation of polycrystals
We explore ways by which new orientations (``nuclei``) can arise during essentially homogeneous deformation in polycrystals. All of these can be categorized as generating new large-angle boundaries: one is due to excessive storage of dislocations of one sign parallel to existing grain boundaries; another is due to reactions of cell walls with grain edges; and in the last, new boundaries are created surrounding a domain of different slip system distribution.
Date:
December 31, 1993
Creator:
Kocks, U. F.; Cotton, J. D.; Chen, S. R.; Wright, S. I.; Rollett, A. D.; Embury, J. D. et al.
Object Type:
Article
System:
The UNT Digital Library
Attrition and Changes in Size Distribution of Lime Sorbents During Fluidization in a Circulating Fluidized Bed Absorber. Double Quarterly Report, January 1--August 31, 1993
The experimental data of lime sorbent attrition obtained from attriton tests in a circulating fluidized bed absorber (CFBA) are represented. The results are interpreted as both the weight-based attrition rate and size-based attrition rate. The weight-based attrition rate constants are obtained from a modified second-order attrition model, incorporating a minimum fluidization weight, W{sub min}, and excess velocity. Furthermore, this minimum fluidization weight, or W{sub min} was found to be a function of both particle size and velocity. A plot of the natural log of the overall weight-based attrition rate constants (ln K{sub a}) for Lime 1 (903 MMD) at superficial gas velocities of 2 m/s, 2.35 m/s, and 2.69 m/s and for Lime 2 (1764 MMD) at superficial gas velocities of 2 m/s, 3 m/s, 4 m/s and 5 m/s versus the energy term, 1/(U-U{sub mf}){sup 2}, yielded a linear relationship. And, a regression coefficient of 0.9386 for the linear regression confirms that K{sub a} may be expressed in Arrhenius form. In addition, an unsteady state population model is represented to predict the changes in size distribution of bed materials during fluidization. The unsteady state population model was verified experimentally and the solid size distribution predicted by the model agreed …
Date:
December 31, 1993
Creator:
Lee, Sang-Kwun; Keener, T. C.; Cook, J. L. & Khang, Soon Jai
Object Type:
Report
System:
The UNT Digital Library
An attrition-resistant zinc titanate sorbent for sulfur. Final technical report, September 1, 1992--August 31, 1993
In the continuing search for good sorbent materials to remove sulfur for hot, coal-derived gases, zinc titanate sorbents have shown great promise. The objective of this project was to extend the work of prior investigators by developing improvements in the compressive strength and, therefore, the cycle life of these sorbents while maintaining good chemical reactivity. Fifteen formulations were prepared and evaluated. The best properties were obtained by blending relatively course (two micron) ZnO and TiO{sub 2} powders to obtain a composition of 50%Zn{sub 2}TiO{sub 4}-50%TiO{sub 2}. When sintered at 1000{degrees}C, it had a compressive strength of 28 MPa or 147 N/mm, which is four times higher than values obtained by prior investigators. It also performed well in thermogravimetric analysis measurements of reactivity, both in screening tests and in simulated coal gas.
Date:
December 31, 1993
Creator:
Swisher, J. H.
Object Type:
Report
System:
The UNT Digital Library
Auger, zero-energy photoelectron, coincidence spectroscopy (AZEPECO): Chemical-site-selective Auger electron spectroscopy
The Auger electron spectrum associated with decay of a core-hole on the terminal nitrogen and that associated with the central nitrogen of nitrous oxide, N{sub 2}O, are obtained individually through the use of a coincidence technique. Specifically, each of the two Auger electron spectra is obtained by detection of Auger electrons in coincidence with near zero energy (threshold) photoelectrons at the respective ionization thresholds. These zero energy electrons serve to identify the core-ionization continuum associated with the different Auger electrons. The salient features of the experimental spectra are in good agreement with theoretical calculations. The low counting rate generally associated with coincidence experiments, especially in the gas phase, is not encountered because the low energy electrons are collected over a 4{pi} solid angle. Also, velocity discrimination is accomplished by a spatial filter rather than by time-of-flight to utilize the maximum duty cycle of the synchrotron source. These data are believed to be the first examples of chemical-site-selective molecular Auger spectra.
Date:
December 31, 1993
Creator:
Lee, K.; Ji, D.; Hanson, D. M.; Hulbert, S. L. & Kuiper, P.
Object Type:
Article
System:
The UNT Digital Library
Automated remote monitoring of toxic gases with diode-laser-based sensor systems
There is a growing need for compact sensor systems that provide reliable and automated monitoring of toxic gases and pollutants. Near infrared (NIR) diode lasers, originally developed for the communications industry, have the necessary reliability for use in such automated sensor systems. The authors combine NTR lasers with its patented line-locked absorption techniques to create the DiRTiGAS family of automated sensor systems for continuous remote monitoring of gas concentration. A broad variety of small polyatomic gases can be detected using GaAs-based diode lasers. They report here tests on NO{sub 2}, O{sub 2}, NH{sub 3}, C{sub 2}H{sub 2}, and CO{sub 2} with two source modules operating at 760 and 1,540 nm, respectively. The DiRTiGAS family of remote sensors uses modular components which can be assembled in two basic configurations for process control and ambient air monitoring. The fiber-optic configuration uses a central control unit linked by a fiberoptic network to remote sensor heads. The long-path configuration uses a similar control unit and a distant retroreflective target to monitor the concentration in the intervening distances. A fieldable prototype longpath unit, and a fiber-optic head has been developed for process water vapor monitoring in exhaust stacks at temperatures up to 650 C. This …
Date:
December 31, 1993
Creator:
Goldstein, N.; Lee, J. & Bien, F.
Object Type:
Report
System:
The UNT Digital Library
Automatic differentiation, tangent linear models, and (pseudo) adjoints
This paper provides a brief introduction to automatic differentiation and relates it to the tangent linear model and adjoint approaches commonly used in meteorology. After a brief review of the forward and reverse mode of automatic differentiation, the ADIFOR automatic differentiation tool is introduced, and initial results of a sensitivity-enhanced version of the MM5 PSU/NCAR mesoscale weather model are presented. We also present a novel approach to the computation of gradients that uses a reverse mode approach at the time loop level and a forward mode approach at every time step. The resulting ``pseudoadjoint`` shares the characteristic of an adjoint code that the ratio of gradient to function evaluation does not depend on the number of independent variables. In contrast to a true adjoint approach, however, the nonlinearity of the model plays no role in the complexity of the derivative code.
Date:
December 31, 1993
Creator:
Bischof, C.H.
Object Type:
Article
System:
The UNT Digital Library
Automating the determination of 3D protein structure
The creation of an automated method for determining 3D protein structure would be invaluable to the field of biology and presents an interesting challenge to computer science. Unfortunately, given the current level of protein knowledge, a completely automated solution method is not yet feasible, therefore, our group has decided to integrate existing databases and theories to create a software system that assists X-ray crystallographers in specifying a particular protein structure. By breaking the problem of determining overall protein structure into small subproblems, we hope to come closer to solving a novel structure by solving each component. By generating necessary information for structure determination, this method provides the first step toward designing a program to determine protein conformation automatically.
Date:
December 31, 1993
Creator:
Rayl, K. D.
Object Type:
Article
System:
The UNT Digital Library
Base program on energy related research. Quarterly technical progress report, August--October 1993
Progress reports are presented for the following area of studies: oil and gas; advanced systems applications; environmental technologies; and applied energy science. Oil and gas includes the following tasks: CROW{sup TM} process modeling; and miscible-immiscible gas injection processes. Advanced systems applications covers: development and optimization of a process for the production of a premium solid fuel from Western U.S. coals; development of an on-line alkali monitoring probe; optimization of the recycle oil process for Eastern oil shale; and process support and development. Tasks in the environmental technologies are: solid waste management; and remediation of contaminated soils. Applied energy science covers heavy oil/plastics co-processing.
Date:
December 31, 1993
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Bat habitat research. Final technical report
This progress report describes activities over the current reporting period to characterize the habitats of bats on the INEL. Research tasks are entitled Monitoring bat habitation of caves on the INEL to determine species present, numbers, and seasons of use; Monitor bat use of man-made ponds at the INEL to determine species present and rates of use of these waters; If the Big Lost River is flowing on the INEL and/or if the Big Lost River sinks contain water, determine species present, numbers and seasons of use; Determine the habitat requirement of Townsend`s big-eared bats, including the microclimate of caves containing Townsend`s big-eared bats as compared to other caves that do not contain bats; Determine and describe an economical and efficient bat census technique to be used periodically by INEL scientists to determine the status of bats on the INEL; and Provide a suggestive management and protective plan for bat species on the INEL that might, in the future, be added to the endangered and sensitive list;
Date:
December 31, 1993
Creator:
Keller, B. L.; Bosworth, W. R. & Doering, R. W.
Object Type:
Report
System:
The UNT Digital Library
BATSE burst location accuracy and constraints on the fraction of repeating GRB sources
We use a one parameter model for GRB source repetition to investigate the ability of BATSE to detect source repetition and to place constraints on the fraction of repeating sources. From Monte Carlo simulations we find that the current uncertainty in BATSE burst locations severely limits our ability to confidently detect source repetition from distributions containing fewer than 10 {minus}15% repeaters. A fit of our repetition model to 260 BATSE catalog bursts yields a best-fit repeating fraction of f{sub r} = 21% with a 90% confidence region ranging from 5.5 to 32.5%. By modifying the size of the measurement errors in our simulations we show that the location and width of the confidence region depends sensitively on the burst location errors. With BATSEs present location accuracy analysis of larger samples of bursts will not appreciably improve the constraint on the repeating fraction.
Date:
December 31, 1993
Creator:
Strohmayer, T. E.; Fenimore, E. E. & Miralles, J. A.
Object Type:
Article
System:
The UNT Digital Library
Battery modeling for electric vehicle applications using neural networks
Neural networking is a new approach to modeling batteries for electric vehicle applications. This modeling technique is much less complex then a first principles model but can consider more parameters then classic empirical modeling. Test data indicates that individual cell size and geometry and operating conditions affect a battery performance (energy density, power density and life). Given sufficient battery data, system parameters and operating conditions a neural network model could be used to interpolate and perhaps even extrapolate battery performance under wide variety of operating conditions. As a result the method could be a valuable design tool for electric vehicle battery design and application. This paper describes the on going modeling method at Texas A and M University and presents preliminary results of a tubular lead acid battery model. The ultimate goal of this modeling effort is to develop the values necessary to be able to predict performance for batteries as wide ranging as sodium sulfur to zinc bromine.
Date:
December 31, 1993
Creator:
Swan, D. H.; Arikara, M. P. & Patton, A. D.
Object Type:
Article
System:
The UNT Digital Library
Beam position feedback system for the Advanced Photon Source
The Advanced Photon Source (APS) will implement both global and local beam position feedback systems to stabilize the particle and X-ray beams for the storage ring. The systems consist of 20 VME crates distributed around the ring, each running multiple digital signal processors (DSP) running at 4kHz sampling rate with a proportional, integral, and derivative (PID) control algorithm. The particle and X-ray beam position data is shared by the distributed processors through networked reflective memory. A theory of closed orbit correction using the technique of singular value decomposition (SVD) of the response matrix and simulation of its application to the APS storage ring will be discussed. This technique combines the global and local feedback systems and resolves the conflict among multiple local feedback systems due to local bump closure error. Maximum correction efficiency is achieved by feeding back the global orbit data to the local feedback systems. The effect of the vacuum chamber eddy current induced by the AC corrector magnet field for local feedback systems is compensated by digital filters. Results of experiments conducted on the X-ray ring of the National Synchrotron Light Source and the SPEAR at Stanford Synchrotron Radiation Laboratory will be presented.
Date:
December 31, 1993
Creator:
Chung, Y.
Object Type:
Article
System:
The UNT Digital Library
Beam transport
Transport and focusing of light ion beams for inertial confinement fusion is discussed, including transport schemes, gas breakdown research, and a strategy for divergence reduction.
Date:
December 31, 1993
Creator:
Olson, C. L.; Cuneo, M. E. & Desjarlais, M. P.
Object Type:
Article
System:
The UNT Digital Library
Beams 92: Proceedings. Volume 1: Invited papers, pulsed power
This report contains papers on the following topics: Ion beam papers; electron beam, bremsstrahlung, and diagnostics papers; radiating Z- pinch papers; microwave papers; electron laser papers; advanced accelerator papers; beam and pulsed power applications papers; pulsed power papers; and these papers have been indexed separately elsewhere.
Date:
December 31, 1993
Creator:
Mosher, D. & Cooperstein, G.
Object Type:
Article
System:
The UNT Digital Library
Beams 92: Proceedings. Volume 2, Ion beams, electron beams, diagnostics
This report contains papers on the following topics. Ion beam papers; electron beam papers; and these papers have been indexed separately elsewhere.
Date:
December 31, 1993
Creator:
Mosher, D.; Cooperstein, G. & Naval Research Lab., Washington, DC (United States)]
Object Type:
Article
System:
The UNT Digital Library