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Experimental Investigation of Moving Pressure Disturbances and Shock Waves and Correlation with One-Dimensional Unsteady-Flow Theory

Description: Note presenting experimental pressure-time measurements along with schileren photographs of the unsteady-flow phenomena initiated in constant-cross-sectional-area passages. The methods of calculation of the flow phenomena are based on the assumptions of one-dimensional, nonviscous, unsteady flow.
Date: July 1949
Creator: Huber, Paul W.; Fitton, Cliff E., Jr. & Delpino, F.
Partner: UNT Libraries Government Documents Department

Initial Performance of the Keck AO Wavefront Controller System

Description: The wavefront controller for the Keck Observatory AO system consists of two separate real-time control loops: a tip-tilt control loop to remove tilt from the incoming wavefront, and a deformable mirror control loop to remove higher-order aberrations. In this paper, we describe these control loops and analyze their performance using diagnostic data acquired during the integration and testing of the AO system on the telescope. Disturbance rejection curves for the controllers are calculated from the experimental data and compared to theory. The residual wavefront errors due to control loop bandwidth are also calculated from the data, and possible improvements to the controller performance are discussed.
Date: March 1, 2001
Creator: Johansson, E M; Acton, D S; An, J R; Avicola, K; Beeman, B V; Brase, J M et al.
Partner: UNT Libraries Government Documents Department

Inflation in the postmodern era

Description: In this lecture I will review some recent progress in improving the accuracy of the calculation of density perturbations resulting from inflation. 26 refs., 3 figs., 2 tabs.
Date: December 1, 1996
Creator: Kolb, E.W.
Partner: UNT Libraries Government Documents Department

Psychosocial Influences on Bulimic Symptoms: Investigation of an Emprical Model

Description: The emerging consensus among investigators seems to be that bulimia is a multidetermined disorder with a number of contributing factors, including biological components, sociocultural factor, personality, and family characteristics (Garfinkel & Garner, 1982). An etiological model was examined in this study integrating two important theoretical perspectives in the bulimia literature: the stress-coping perspective (Cattanach & Rodin, 1988) and the family systems perspective (Minuchin et al., 1978). Five latent variables: Family Characteristics, Coping Resources, Psychological Disturbance, Environmental Stressors, and Bulimia were represented by twelve measured variables. Structural Equation Modeling analysis allowed for the simultaneous examination of the hypothesized interrelationships between model variables. Findings confirmed a direct impact of psychological disturbances on bulimic symptoms. Hypothesized indirect relationships of family characteristics, coping resources and environmental stressors to bulimia were confirmed. Treatment implications as well as directions for future research were discussed.
Date: August 1996
Creator: Owen-Nieberding, Amy
Partner: UNT Libraries

On fluid flow in a heterogeneous medium under nonisothermal conditions

Description: An asymptotic technique, valid in the presence of smoothly-varying heterogeneity, provides explicit expressions for the velocity of a propagating pressure and temperature disturbance. The governing equations contain nonlinear terms due to the presence of temperature-dependent coefficients and due to the advection of fluids with differing temperatures. Two cases give well-defined expressions in terms of the parameters of the porous medium: the uncoupled propagation of a pressure disturbance and the propagation of a fully coupled temperature and pressure disturbance. The velocity of the coupled disturbance or front, depends upon the medium parameters and upon the change in temperature and pressure across the front. For uncoupled flow, the semi-analytic expression for the front velocity reduces to that associated with a linear diffusion equation. A comparison of the asymptotic travel time estimates with calculations from a numerical simulator indicates reasonably good agreement for both uncoupled and coupled disturbances.
Date: November 1, 2010
Creator: D.W., Vasco
Partner: UNT Libraries Government Documents Department

First Order Perturbation Effects in Iron-Dominated Two-DimensionalSymmetrical Multipoles

Description: The effects of several perturbations are investigated. They are: modification of the shape of a pole, error excitation, displacement, and rotation of a pole. The effects are described in terms of changes of multipole coefficients. General relationships between some of these coefficients are described, and formulae are derived that allow their calculation for a model 2N-pole magnet. Numerical values of these coefficients are given for a quadrupole, sextupole, and octupole.
Date: April 1, 1969
Creator: Halbach, K.
Partner: UNT Libraries Government Documents Department

Active vibration damping in the presence of uncertainties.

Description: Several control design techniques including PlD, LQG, and PPF are investigated For adive vibration damping of a cantilever beam with uncertain boundary conditions. Step disturbances were used to evaluate the performance of the designed controllers.
Date: January 1, 2002
Creator: Farrar, C. R. (Charles R.); Eisenhour, T. A. (Travis A.); Hatchett, S. (Sam) & Salazar, I. (Isaac)
Partner: UNT Libraries Government Documents Department

Bursting Frequency Predictions for Compressible Turbulent Boundary Layers

Description: A computational method for the prediction of the bursting frequency associated with the coherent streamwise structures in high-speed compressible turbulent boundary layers is presented. The structures are described as wavelike disturbances of the turbulent mean flow. A direct resonance theory is used to determine the frequency of bursting. The resulting hydrodynamic linear stability equations are discretized by using a Chebyshev collocation method. A global numerical method capable of resolving the entire eigenvalue spectrum is used. Realistic turbulent mean velocity and temperature profiles are applied. For all of the compressible turbulent boundary layers calculated, the results show at least one frequency that satisfies the resonance condition. A second frequency can be identified for cases with high Reynolds numbers. An estimate is also made for the profile distribution of the temperature disturbance.
Date: October 1, 2002
Creator: LIOU, WILLIAM W. & FANG, YICHUAN
Partner: UNT Libraries Government Documents Department

Observations of magnetospheric substorms occurring with no apparent solar wind/IMF trigger

Description: An outstanding topic in magnetospheric physics is whether substorms are always externally triggered by disturbances in either the interplanetary magnetic field or solar wind, or whether they can also occur solely as the result of an internal magnetospheric instability. Over the past decade, arguments have been made on both sides of this issue. Horwitz and McPherron have shown examples of substorm onsets which they claimed were not externally triggered. However, as pointed out by Lyons, there are several problems associated with these studies that make their results somewhat inconclusive. In particular, in the McPherron et al. study, fluctuations in the B{sub y} component were not considered as possible triggers. Furthermore, Lyons suggests that the sharp decreases in the AL index during intervals of steady IMF/solar wind, are not substorms at all but rather that they are just enhancements of the convection driven DP2 current system that are often observed to occur during steady magnetospheric convection events. In the present study, we utilize a much more comprehensive dataset (consisting of particle data from the Los Alamos energetic particle detectors at geosynchronous orbit, IMP 8 magnetometer and plasma data, Viking UV auroral imager data, mid-latitude Pi2 pulsation data, ground magnetometer data and ISEE1 magnetic field and energetic particle data) to show as unambiguously as possible that typical substorms can indeed occur in the absence of an identifiable trigger in the solar wind/IMF.
Date: March 1, 1996
Creator: Henderson, M.G.; Reeves, G.D.; Belian, R.D. & Murphree, J.S.
Partner: UNT Libraries Government Documents Department

Monthly report to LLNL from the Budker INP. Novosibirsk, September, 1992

Description: The experiments on a plasma equilibrium response to externally applied disturbance of the magnetic field of a dipole type have been done on the GDT facility. The disturbance was produced by a pair of the coils installed at the end tank so as it was localized in the expander region. The results were compared with the theoretical predictions based on a hydromagnetic model of plasma equilibrium in the magnetic field treated in a long thin approximation. It was found that the measured displacements of the plasma column from a geometrical axis of the device varies linearly with the current in the disturbing coils at least up to 5cm at the midplane. The data was processed to subtract the displacement measured for zero current that apparently caused by a small disturbance of the magnetic field by soft-iron-made parts of the equipment placed near the device inside the experimental hall and, in part, also by misalignments of the main coils. Theoretically predicted slope of the displacement-field amplitude dependence is to be inversely proportional to a pressure-weighted curvature averaged along the device. The authors believe this allows the use of the data for the measurements of this value. The slopes have been calculated for the GDT parameters under different assumptions on Kp parameter that define an upper limit of integration of the pressure-weighted curvature in the near-end wall region in the expanders.
Date: September 1, 1992
Creator: Ivanov, A.A. & Kotelnikov, I.A.
Partner: UNT Libraries Government Documents Department

The method of boundary perturbation, and its application to wakefield calculations

Description: The boundary perturbation method, suggested by Zhang and (independently) by Chatard-Moulin, Cooper, and their colleagues, is employed to the wakefield calculations for geometrical discontinuities in accelerators. Results are compared with that obtained from the mesh calculations using TBCI. When the perturbation is small and the geometry is suitable for TBCI, agreement is good. Discrepancies observed in other cases are also discussed.
Date: December 31, 1990
Creator: Chou, W.
Partner: UNT Libraries Government Documents Department

The magnetospheric trough

Description: The authors review the history of the concepts of the magnetospheric cold-ion trough and hot-electron trough and conclude that the two regions are actually essentially the same. The magnetospheric trough may be viewed as a temporal state in the evolution of convecting flux tubes. These flux tubes are in contact with the earth`s upper atmosphere which acts both as a sink for precipitating hot plasma sheet electrons and as a source for the cold ionospheric plasma leading to progressive depletion of the plasma sheet and refilling with cold plasma. Geosynchronous plasma observations show that the rate of loss of plasma-sheet electron energy density is commensurate with the precipitating electron flux at the low-latitude edge of the diffuse aurora. The rate at which geosynchronous flux tubes fill with cold ionospheric plasma is found to be consistent with previous estimates of early-time refilling. Geosynchronous observations further indicate that both Coulomb collisions and wave-particle effects probably play a role in trapping ionospheric material in the magnetosphere.
Date: March 4, 1997
Creator: Thomsen, M. F.; McComas, D. J.; Elphic, R. C. & Borovsky, J. E.
Partner: UNT Libraries Government Documents Department

Transient effect in high intensity proton linear accelerators

Description: We study the possible mechanism of the separatrix destruction during the transient in the linear accelerator. This effect is due to the parametric resonance of the beam in the longitudinal plane caused by the perturbations of electromagnetic field. The magnitude of time-space perturbations of the electromagnetic field depends on the disperse feature of resonator and the beam intensity. In the paper we discuss how to avoid this effect or to decrease its influence.
Date: September 1, 1993
Creator: Senichev, Yu
Partner: UNT Libraries Government Documents Department

Power Quality Evaluation of 480-V, 2-MVA UPS Systems

Description: A mobile 480-V, 2-MVA UPS System utilizing battery energy storage was installed at S and C Electric Company's Polymer Products Fabrication Building in Chicago, Illinois in May 1999 to provide uninterrupted power to the building for up to 15 seconds in the event of a voltage sag or momentary interruption in the local utility supply. Similar units can be applied at medium voltage through the application of a step-up transformer to provide momentary power disturbance ride through of up to 30 seconds for loads up to 15 MVA at system voltages ranging from 4.16 kV to 34.5 kV. A power quality evaluation of the installation was performed over a six-month period from July 1999 to early January 2000. This paper describes the details and results of this power quality evaluation, which involved two phases. Phase I involved the collection and review of power disturbance data and the effects on process equipment, while Phase II involved power quality monitoring of utility source and building load voltages and currents over a period of six months. Review of power disturbance data and equipment power-disturbance ride-through characteristics during Phase I of the project indicated that the polymer fabrication process in the building is affected by the tripping of motors driving hydraulic pumps for the thermal set molding machines. The tripping of these motors may have resulted in direct production losses in 1998 of approximately $468,000. The monitoring conducted during Phase II of the project showed that the PureWave UPS operated as intended during 12 utility voltage sag events to protect the building's load against momentary power disturbances. In addition, the unit operated successfully during many staged interruptions involving opening of a source-side circuit breaker.
Date: June 21, 2000
Creator: Camm, E. H.; Corey, Garth P. & Roberts, S. B.
Partner: UNT Libraries Government Documents Department

Removing Barriers to Utility Interconnected Photovoltaic Inverters

Description: The Million Solar Roofs Initiative has motivated a renewed interest in the development of utility interconnected photovoltaic (UIPV) inverters. Government-sponsored programs (PVMaT, PVBONUS) and competition among utility interconnected inverter manufacturers have stimulated innovations and improved the performance of existing technologies. With this resurgence, Sandia National Laboratories (SNL) has developed a program to assist industry initiatives to overcome barriers to UIPV inverters. In accordance with newly adopted IEEE 929-2000, the utility interconnected PV inverters are required to cease energizing the utility grid when either a significant disturbance occurs or the utility experiences an interruption in service. Compliance with IEEE 929-2000 is being widely adopted by utilities as a minimum requirement for utility interconnection. This report summarizes work done at the SNL balance-of-systems laboratory to support the development of IEEE 929-2000 and to assist manufacturers in meeting its requirements.
Date: October 3, 2000
Creator: Gonzalez, S.; Bonn, R.H. & Ginn, J.W.
Partner: UNT Libraries Government Documents Department

Macroscopic Description of Pressure-anisotropy-driven Collective Instability in Intense Charged Particle Beams

Description: The macroscopic warm-fluid model developed by Lund and Davidson [Phys.Plasmas 5, 3028 (1998)] is used in the smooth-focusing approximation to investigate detailed stability properties of an intense charged particle beam with pressure anisotropy, assuming small-amplitude electrostatic pertubations about a waterbag equilibrium.
Date: May 30, 2000
Creator: Strasburg, Sean & Davidson, Ronald C.
Partner: UNT Libraries Government Documents Department

Psychopathic Traits and Insecure Attachment Patterns in Community-based Subgroups

Description: There is a growing body of research on psychopathic traits in non-clinical populations. This emerging research has documented the prevalence of psychopathic traits in the general population and demonstrated that psychopathy has a similar latent structure as well as similar correlates (e.g., violent behavior, alcohol abuse, and lower intelligence) to forensic/offender samples. Relatedly, there is strong evidence insecure attachment patterns in adulthood are associated with many personality disorders, including psychopathy, but only a few studies have examined the relationship between attachment and psychopathic traits in non-clinical samples (albeit, convenience samples of college students). Thus, two aims of the current study are to: 1) describe and explore the manifestation and expression of psychopathic traits in a large, community-based sample and 2) examine associations between adult attachment disturbances and psychopathic traits in diverse sociodemographic subgroups. Using a cross-sectional design, results showed mean-level psychopathy factor score differences existed only when considering single sociodemographic factors (e.g., age), not an interaction of those factors. Psychopathy factor profiles were also consistent across groups, with higher levels of lifestyle followed by interpersonal, affective, and antisocial traits reported. Regarding the second aim, findings indicated support for the positive association between disturbed attachment patterns in adult relationships and psychopathic traits, although these associations differed in males and females of different age groups. Finally, there was some support for attachment processes acting as a social development pathway toward psychopathy, as insecure attachments in adulthood partially mediated the relationships between age and interpersonal, affective, and lifestyle traits of psychopathy.
Date: August 2014
Creator: Carter, Rachel M.
Partner: UNT Libraries

Consolidated fuel reprocessing program: a mathematical model for liquid flow transients in a rotary dissolver

Description: A model describing the liquid outlet response to perturbations in the flow to a compartmented rotary dissolver has been developed. The model incorporates stagewise differential material balances coupled with the general equation for flow over a weir to calculate acid concentrations and liquid volumes in each stage. Data were taken from step-change flow experiments conducted on a 0.5-t/d rotary dissolver. The predicted response of the model was in good agreement with the data from the dissolver experiments. All constants in the model were obtained by independent tests. The model appears to be applicable over a wide range of dissolver operating conditions; however, temperature fluctuations and the presence of solids were not addressed.
Date: October 1, 1980
Creator: Lewis, B. E. & Weber, F. E.
Partner: UNT Libraries Government Documents Department

The feed-out process: Rayleigh-Taylor and Richtmyer-Meshkov instabilities in thin, laser-driven foils

Description: Eight beams carrying a shaped pulse from the NOVA laser were focused into a hohlraum with a total energy of about 25 kJ. A planar foil was placed on the side of the hohlraum with perturbations facing away from the hohlraum. All perturbations were 4 {micro}m in amplitude and 50 {micro}m in wavelength. Three foils of pure aluminum were shot with thicknesses and pulse lengths respectively of 86 {micro}m and 2. 2 ns, 50 {micro}m and 4.5 ns, and 35 {micro}m with both 2.2 ns and 4. 5 ns pulses. Two composite foils constructed respectively of 32 and 84 {micro}m aluminum on the ablative side and 10 {micro}m beryllium on the cold surface were also shot using the 2.2 ns pulse. X-ray framing cameras recorded perturbation growth using both face- and side-on radiography. The LASNEX code was used to model the experiments. A shock wave interacted with the perturbation on the cold surface generating growth from a Richtmyer-Meshkov instability and a strong acoustic mode. The cold surface perturbation fed-out to the Rayleigh-Taylor unstable ablation surface, both by differential acceleration and interface coupling, where it grew. A density jump did not appear to have a large effect on feed-out from interface coupling. The Rayleigh-Taylor instability`s vortex pairs overtook and reversed the direction of flow of the Richtmyer-Meshkov vortices, resulting in the foil moving from a sinuous to a bubble and spike configuration. The Rayleigh-Taylor instability may have acted as an ablative instability on the hot surface, and as a classical instability on the cold surface, on which grew second and third order harmonics.
Date: April 1, 1998
Creator: Smitherman, D.P.
Partner: UNT Libraries Government Documents Department

Pulsating Hydrodynamic Instability and Thermal Coupling in an Extended Landau/Levich Model of Liquid-Propellant Combustion -- I. Inviscid Analysis

Description: Hydrodynamic (Landau) instability in combustion is typically associated with the onset of wrinkling of a flame surface, corresponding to the formation of steady cellular structures as the stability threshold is crossed. In the context of liquid-propellant combustion, such instability has recently been shown to occur for critical values of the pressure sensitivity of the burning rate and the disturbance wavenumber, significantly generalizing previous classical results for this problem that assumed a constant normal burning rate. Additionally, however, a pulsating form of hydrodynamic instability has been shown to occur as well, corresponding to the onset of temporal oscillations in the location of the liquid/gas interface. In the present work, we consider the realistic influence of a nonzero temperature sensitivity in the local burning rate on both types of stability thresholds. It is found that for sufficiently small values of this parameter, there exists a stable range of pressure sensitivities for steady, planar burning such that the classical cellular form of hydrodynamic instability and the more recent pulsating form of hydrodynamic instability can each occur as the corresponding stability threshold is crossed. For larger thermal sensitivities, however, the pulsating stability boundary evolves into a C-shaped curve in the (disturbance-wavenumber, pressure-sensitivity) plane, indicating loss of stability to pulsating perturbations for all sufficiently large disturbance wavelengths. It is thus concluded, based on characteristic parameter values, that an equally likely form of hydrodynamic instability in liquid-propellant combustion is of a nonsteady, long-wave nature, distinct from the steady, cellular form originally predicted by Landau.
Date: March 1, 1999
Creator: Margolis, Stephen B. & Williams, Forman A.
Partner: UNT Libraries Government Documents Department