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Random Vibrations: Assessment of the State of the Art
Random vibration is the phenomenon wherein random excitation applied to a mechanical system induces random response. We summarize the state of the art in random vibration analysis and testing, commenting on history, linear and nonlinear analysis, the analysis of large-scale systems, and probabilistic structural testing.
Date:
February 23, 1999
Creator:
Paez, Thomas L.
System:
The UNT Digital Library
Utilizing Gauss-Hermite Quadrature to Evaluate Uncertainty in Dynamic System Response
Probabilistic uncertainty is a phenomenon that occurs to a certain degree in many engineering!~ applications. The effects that the uncertainty has upon a given system response is a matter of some concern. Techniques which provide insight to these effects will be required as modeling and prediction become a more vital tool in the engineering design process. As might be expected, this is a difficult proposition and the focus of many research efforts. The purpose of this paper is to outline a procedure to evaluate uncertainty in dynamic system response exploiting Gauss-Hermite numerical quadrature. Specifically numerical integration techniques are utilized in conjunction with the Advanced Mean Value method to efficiently and accurately estimate moments of the response process. A numerical example illustrating the use of this analytical tool in a practical framework is presented.
Date:
November 17, 1998
Creator:
Field, Richard V.; Paez, Thomas L. & Red-Horse, John R.
System:
The UNT Digital Library
Conservatism in least favorable response analysis and testing
In order to assure that mechanical structures can meet design requirements it is desirable to test a structure using an input which is conservative but not a severe overtest. One method available for the specification of shock tests is the method of least favorable response. This method can be used analytically or in the laboratory and is guaranteed to provide tests which are conservative, at least in one sense. When the impulse response function, or equivalently the frequency response function, is available between a point of interest on a structure and the input point of the structure, and when we know the real function which envelops the modulus of the Fourier transform of all possible inputs which might excite the structure, then the method of least favorable response can be used to find an upper bound on the response which the point of interest on the structure can realize. We use this in the analysis of structural peak response. In the laboratory the least favorable response is generated experimentally, for example, by testing the structural unit on a shake table. If the structure survives the laboratory test, then we assume that it could survive any input in the class of …
Date:
January 1, 1980
Creator:
Paez, Thomas L.
System:
The UNT Digital Library
PEGASUS: a multi-megawatt nuclear electric propulsion system
With the Space Transportation System (STS), the advent of space station Columbus and the development of expertise at working in space that this will entail, the gateway is open to the final frontier. The exploration of this frontier is possible with state-of-the-art hydrogen/oxygen propulsion but would be greatly enhanced by the higher specific impulse of electric propulsion. This paper presents a concept that uses a multi-megawatt nuclear power plant to drive an electric propulsion system. The concept has been named PEGASUS, PowEr GenerAting System for Use in Space, and is intended as a ''work horse'' for general space transportation needs, both long- and short-haul missions. The recent efforts of the SP-100 program indicate that a power system capable of producing upwards of 1 megawatt of electric power should be available in the next decade. Additionally, efforts in other areas indicate that a power system with a constant power capability an order of magnitude greater could be available near the turn of the century. With the advances expected in megawatt-class space power systems, the high specific impulse propulsion systems must be reconsidered as potential propulsion systems. The power system is capable of meeting both the propulsion system and spacecraft power requirements.
Date:
June 1, 1985
Creator:
Coomes, Edmund P.; Cuta, Judith M.; Webb, Brent J. & King, David Q.
System:
The UNT Digital Library
Problems and potentialities of stable isotopes as tracers for studying pollutant behavior under field conditions
None
Date:
January 1, 1974
Creator:
Matwiyoff, N. A.; Cowan, G. A.; Ott, D. G. & McInteer, B. B.
System:
The UNT Digital Library
Some history of liquid scintillator development at Los Alamos
The early developments in liquid scintillation counting made at Los Alamos Scientific Laboratory are reviewed. Most of the work was under the direction of F.N. Hayes and included counter development and applications as well as synthesis and chemistry of liquid scintillators.
Date:
January 1, 1979
Creator:
Ott, Donald G.
System:
The UNT Digital Library
Deformation mechanism maps: a review with applications
None
Date:
January 1, 1974
Creator:
Notis, Michael R.
System:
The UNT Digital Library
One-carbon /sup 13/C-labeled synthetic intermediates. Comparison and evaluation of preparative methods
Frequently the biggest stumbling block to the synthesis of a structurally complex labeled compound is obtaining the required low molecular weight, structurally simple, isotopic intermediates. Selection of a particular scheme from various alternatives depends on the available capabilities and quantity of product desired, as well as on anticipated future requirements and need for related compounds. Many of the newer reagents for organic synthesis can be applied effectively to isotopic preparations with improvements of yields and simplification of procedures compared to established classical methods. New routes developed for higher molecular weight compounds are sometimes not directly adaptable to the one-carbon analogs, either because of isolation difficulties occasioned by physical properties or by chemical reactivities peculiar to their being first members of homologous series. Various routes for preparation of carbon-13 labeled methanol, formaldehyde, and cyanide are compared.
Date:
January 1, 1978
Creator:
Ott, Donald G.
System:
The UNT Digital Library
Experimental Evaluation of a Simulation Model for Wrap-Around Heat Exchanger, Solar Storage Tanks
The thermal performance of a commercially available 80 gallon, solar storage tank with an integral wrap-around heat exchanger is characterized experimentally an indoor test stand. The experimental results are used to evaluated the accuracy of a previously developed simulation model. Heat input on the collector side of the heat exchanger is held constant causing the heat transfer to reach a quasi-steady state. Temperatures in the heat exchanger and tank increase with time, however, the temperature differences across the heat exchanger remain nearly constant. Several combinations of heat input and collector loop flow are investigated. The development of the tank temperature profiles over time and the overall heat transfer performance predicted by the model are compared with experimental results. The influence of an electric auxiliary heater located in the top of the solar storage tank on the heat exchanger performance is investigated. Experimental normalization of the model is considered and modifications to the model and experiments are recommended.
Date:
May 1, 1995
Creator:
Miller, Jeffrey A. & Hittle, Douglas C.
System:
The UNT Digital Library
Shock sensitivity of LX 04 at elevated temperatures
Hazard scenarios can involve multiple stimuli, such as heating followed by fragment impact (shock). The shock response of LX-04 (85 weight % HMX and 15 weight % Viton binder) preheated to temperatures hear 170C is studied in a 10.2 cm bore diameter gas gun using embedded manganin pressure gauges. The pressure histories at various depths in the LX-04 targets and the run distances to detonation at several input shock pressures are measured and compared to those obtained in ambient temperature LX-04. The hot LX-04 is significantly more shock sensitive than ambient LX-04. Ignition and Growth reactive flow models are developed for ambient and hot LX-04 to allow predictions of impact scenarios that a can not be tested directly.
Date:
July 1, 1997
Creator:
Urtiew, P. A.; Tarver, C. M.; Forbes, J. W. & Garcia, F.
System:
The UNT Digital Library
Will Rogers High School: The Public Works Administration, Progressive Education, and a Modern School
This article details the pedagogical planning and architectural design of Tulsa's Will Rogers High School.
Date:
Winter 2007
Creator:
Ambler, Cathy
System:
The Gateway to Oklahoma History
Enigma and Battleground: The Development of Oklahoma's Public Two-Year Colleges
Article details the effects of philosophical and political issues on the development of junior colleges in Oklahoma.
Date:
Winter 2009
Creator:
Simpson, Michael W.
System:
The Gateway to Oklahoma History
Understanding gas-surface interactions from direct force measurements using a specialized torsion balance
The first comprehensive measurements of the magnitude and direction of the forces exerted on surfaces by molecular beams are discussed and used to obtain information about the microscopic properties of the gas-surface interactions. This unique approach is not based on microscopic measurements of the scattered molecules. The reduced force coefficients are introduced as a new set of parameters that completely describe the macroscopic average momentum transfer to a surface by an incident molecular beam. By using a specialized torsion balance and molecular beams of N{sub 2}, CO, CO{sub 2}, and H{sub 2}, the reduced force coefficients are determined from direct measurements of the force components exerted on surface of a solar panel array material, Kapton, SiO{sub 2}-coated Kapton, and Z-93 as a function of the angle of incidence ranging from 0{degrees} to 85{degrees}. The absolute flux densities of the molecular beams were measured using a different torsion balance with a beam-stop that nullified the force of the scattered molecules. Standard time-of-flight techniques were used to determine the flux-weighted average velocities of the various molecular beams ranging from 1600 m/s to 4600 m/s. The reduced force coefficients can be used to directly obtain macroscopic average properties of the scattered molecules, such …
Date:
December 31, 1996
Creator:
Cook, Steven R. & Hoffbauer, Mark A.
System:
The UNT Digital Library
Performance of CdZnTe detectors passivated with energetic oxygen atoms
Noise caused by surface-leakage current can degrade the performance of CdZnTe spectrometers, particularly devices with closely spaced contacts such as coplanar grid detectors. In order to reduce surface leakage, the authors are treating CdZnTe detector surfaces with energetic, neutral oxygen atoms. Energetic oxygen atoms react with the surface to form a resistive oxide layer. Because the reaction is effective at room temperature, deleterious heating of the substrate is avoided. In most cases, leakage current and noise are shown to decrease significantly after treatment. The effect of the treatment on the performance of coplanar grid detectors is presented.
Date:
December 1, 1998
Creator:
Prettyman, T. H.; Hoffbauer, M. A. & Rennie, J.
System:
The UNT Digital Library
Experimental and Modeling Study of Laminar Flame Speeds for Alkyl Aromatic Components Relevant to Diesel Fuels
None
Date:
March 8, 2013
Creator:
Dirrenberger, Patricia; Herbinet, Olivier; Bounaceur, Roda; Glaude, Pierre-Alexandre; Battin-Leclerc, Frederique; Mehl, Marco et al.
System:
The UNT Digital Library
A detailed kinetic modeling study of toluene oxidation in a premixed laminar flame
An improved chemical kinetic model for the toluene oxidation based on experimental data obtained in a premixed laminar low-pressure flame with vacuum ultraviolet (VUV) photoionization and molecular beam mass spectrometry (MBMS) techniques has been proposed. The present mechanism consists of 273 species up to chrysene and 1740 reactions. The rate constants of reactions of toluene, decomposition, reaction with oxygen, ipso-additions and metatheses with abstraction of phenylic H-atom are updated; new pathways of C{sub 4} + C{sub 2} species giving benzene and fulvene are added. Based on the experimental observations, combustion intermediates such as fulvenallene, naphtol, methylnaphthalene, acenaphthylene, 2-ethynylnaphthalene, phenanthrene, anthracene, 1-methylphenanthrene, pyrene and chrysene are involved in the present mechanism. The final toluene model leads to an overall satisfactory agreement between the experimentally observed and predicted mole fraction profiles for the major products and most combustion intermediates. The toluene depletion is governed by metathese giving benzyl radicals, ipso-addition forming benzene and metatheses leading to C{sub 6}H{sub 4}CH{sub 3} radicals. A sensitivity analysis indicates that the unimolecular decomposition via the cleavage of a C-H bond has a strong inhibiting effect, while decomposition via C-C bond breaking, ipso-addition of H-atom to toluene, decomposition of benzyl radicals and reactions related to C{sub 6}H{sub …
Date:
December 18, 2009
Creator:
Tian, Zhenyu; Pitz, William J.; Fournet, Rene; Glaude, Pierre-Alexander & Battin-Leclerc, Frederique
System:
The UNT Digital Library
Chemical Kinetic Characterization of Combustion Toluene
A study is performed to elucidate the chemical kinetic mechanism of combustion of toluene. A detailed chemical kinetic mechanism for toluene was improved by adding a more accurate description of the phenyl + O{sub 2} reaction channels. Results of the chemical kinetic mechanism are compared with experimental data obtained from premixed and nonpremixed systems. Under premixed conditions, predicted ignition delay times are compared with new experimental data obtained in shock tube. Also, calculated species concentration histories are compared to experimental flow reactor data from the literature. Critical conditions of extinction and ignition were measured in strained laminar flows under nonpremixed conditions in the counterflow configuration. Numerical calculations are performed using the chemical kinetic mechanism at conditions corresponding to those in the experiments. Critical conditions of extinction and ignition are predicted and compared with the experimental data. For both premixed and nonpremixed systems, sensitivity analysis was used to identify the reaction rate constants that control the overall rate of oxidation in each of the systems considered.
Date:
March 20, 2001
Creator:
Pitz, W. J.; Seiser, R.; Bozzelli, J. W.; Da Costa, I.; Fournet, R.; Billaud, F. et al.
System:
The UNT Digital Library
Influence of calculated gap closure and fission product inventory on FRAP-T4 cladding failure analysis under PCI conditions. [BWR; PWR]
The results of power ramp tests and associated cladding failure analyses, performed as part of FRAP-T4 independent verification studies, are discussed. The 90 ramp tests considered are characterized in terms of relevant fuel design and operating parameters. The use of alternative gap closure and fuel deformation models is shown to strongly affect results of the current stress dependent failure probability model. The influence of both mechanical and chemical failure mechanisms is established by interpreting the concurrent effects of both the ramp-induced stress levels and the relative amounts of retained fission gas available for promoting stress corrosion. A relatively simple modeling approach is outlined which meets the basic mechanistic requirements for calculating pellet cladding interaction (PCI) failure probability.
Date:
January 1, 1978
Creator:
Coleman, Dennis R.
System:
The UNT Digital Library
MEMS design rule checking: a batch approach for remote operation
This paper describes a design rule checking (DRC) tool developed as an aid for designing microelectromechanical structures (MEMS) using AutoCAD running on a Windows NT workstation. The application suite, MEMSdrc, consists of: a graphical user interface integrated into AutoCAD to invoke DRC, translation and interface software to communicate with a commercial IC layout design checking software package, and routines to interactively display and review the results. The user interface provides the capability to select a checking window area and specific DRC rules to be applied to the design. The MEMS structures, defined as 2D AutoCAD geometry are translated first into DXF format, then to GDSII format. A remote process transfers the files to a Unix workstation where Mentor Graphics ICverify is invoked to perform the layout design rule checks. Upon completion, the results are translated into DXF geometry and returned back to the Windows NT workstation to be overlaid onto the original design. A set of icons are provided for the user to interactively review the results inside of AutoCAD using a first/next/previous technique.
Date:
January 1, 1998
Creator:
Yarberry, Victor R.
System:
The UNT Digital Library
Comparison of measured and calculated helium production in nickel using newly evaluated neutron cross sections for /sup 59/Ni
Fusion reactors will produce high levels of helium in surrounding materials with a helium (appm)-to-displacement ratio of about 10-to-1 in stainless steel. This high ratio can be obtained in mixed-spectrum reactors, which are used for fusion materials testing, due to unusually high thermal neutron cross sections for the sequential reactions /sup 58/Ni(n,..gamma..)/sup 59/Ni(n,..cap alpha..)/sup 56/Fe. The high-energy (approx. 340 keV)/sup 56/Fe recoils also add significantly to the displacement damage at the rate of one DPA per 567 appm helium. Until now, the calculation of helium production in nickel has been done in a semi-empirical manner due to a lack of evaluated cross sections for /sup 59/Ni. However, this approach cannot be readily transferred between different reactors since we do not know the contributions from epithermal neutrons in different neutron spectra. A new evaluation of the /sup 59/Ni cross sections has recently been completed, permitting us to calculate all of the required reaction rates for any given neutron spectrum. Radiometric dosimetry and helium measurements have recently been completed for several different mixed-spectrum reactors. Precise comparisons of the helium production cross sections and measurements can thus be made in well-characterized neutron spectra. Data are presented for several recent fusion materials irradiations in …
Date:
January 1, 1983
Creator:
Greenwood, L. R.; Kneff, D. W.; Skowronski, R. P. & Mann, F. M.
System:
The UNT Digital Library
Dosimetry and cross section measurements at RTNS II
Numerous measurements have been conducted at TRNS-II in order to map the neutron field for materials irradiations, to measure activation cross sections, and to measure helium production cross sections. Experiments of up to two weeks duration irradiated large numbers of activation dosimetry and helium samples both close to the source and throughout the target room. Many other samples have been irradiated in piggy-back positions over periods lasting many months. All of these experiments fall into four main classes, namely, fluence-mapping, activation dosimetry, the production of long-lived isotopes, and helium generation measurements. Radiometric dosimetry and activation cross section measurements were performed at Argonne National Laboratory; helium production was measured at Rockwell International Corporation. This paper briefly summarizes the principal results of our measurements at RTNS-II; references are given for more detailed publications. 14 refs., 4 figs.
Date:
January 1, 1987
Creator:
Greenwood, L. R. & Kneff, D. W.
System:
The UNT Digital Library
Chromosome aberrations and loss of some cell functions following in vitro exposure to retorted oil shale. [Cultured cells were exposed to processes oil shale particles (spent shales)]
An investigation of cellular level effects of processed oil shale from a simulation of modified in situ retorting was undertaken as part of an assessment of the toxicity and mutagenicity of oil shale. Complete assessment of the health hazards associated with physical contact, inhalation, or ingestion of oil shale has not been examined in humans and until it becomes practical to assess these hazards in man, we must rely upon well established in vitro detection procedures in addition to whole animal testing. CHO cells and L-2 rat lung epithelial cell lines were exposed in vitro to processed oil shale particles at different intervals following exposure. Cells were analyzed for chromosome alterations, cell colony forming ability, DNA synthesis, and cell transformation. The results of these studies demonstrate that retorted oil shale, under these experimental conditions, does modify cells in vitro. Chromosome aberrations increased with dose, cell colony forming ability decreased exponentially with dose, and the rate of DNA synthesis was affected, however cell transformation was not demonstrated after 3 months.
Date:
January 1, 1979
Creator:
Stroud, Agnes N.
System:
The UNT Digital Library
Hanford site Computer Automated Mapping Information System (CAMIS)
The Computer Automated Mapping Information System (CAMIS) provides sitewide, networked access to CAD based geographically referenced data. CAMIS allows multiple organizations to maintain and share their data. Information collected and managed according to site-wide standards, enables each organization to focus their limited resources on data issues tied to their own discipline without having to collect or manage reference data outside their respective domains. Sharing information also minimizes redundant data and helps improve the overall quality of the sites` data resources.
Date:
September 1, 1995
Creator:
Rush, Steven F.
System:
The UNT Digital Library
An Exercise in Pride: Celebrating the Oklahoma Semi-centennial
This article takes a look back at the semi-centennial celebration of 1957 as Oklahoma prepares to celebrate the centennial of 1907 statehood in 2007.
Date:
Summer 2007
Creator:
Mullins, Bill
System:
The Gateway to Oklahoma History