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Effect of Aerodynamic Hysteresis on Critical Flutter Speed at Stall

Description: Memorandum presenting a theoretical analysis of the effect of aerodynamic hysteresis on stalling flutter. The results were applied to a given airfoil and correlation of the experimental and theoretical results was found possible by assuming that the angle of aerodynamic lag varies as the slope of the static-lift curve. It was shown that the phenomenon of stalling flutter can at least in some cases be explained on the basis of an aerodynamic lag or hysteresis effect.
Date: June 18, 1948
Creator: Mendelson, Alexander
Partner: UNT Libraries Government Documents Department

Some Considerations of Hysteresis Effects on Tire Motion and Wheel Shimmy

Description: "A theoretical study is made of the influence of tire hysteresis effects on the rolling motion and wheel shimmy of landing gears. The results of this study indicate that hysteresis forces and moments have a noticeable secondary influence on the landing-gear rolling behavior. Comparisons of the available experimental data with the corresponding theoretical predictions provide a fair confirmation of the theory" (p. 1).
Date: June 1957
Creator: Smiley, Robert F.
Partner: UNT Libraries Government Documents Department

Dependence of Magnetic Hysteresis upon Wave Form

Description: Report issued by the Bureau of Standards over studies on magnetic hysteresis and its dependence upon wave form. Methods and equipment used during the studies are presented and discussed. This report includes tables, and illustrations.
Date: 1909
Creator: Lloyd, Morton G.
Partner: UNT Libraries Government Documents Department

Flip-Flop Modes in Symmetric and Asymmetric Colliding-Beam Storage Rings

Description: A model of self-consistent beam blow-up in a colliding beam storage ring is described which explains the appearance of flip-flop modes in both symmetric and asymmetric beam systems. It derives the strong-strong steady-states and their stabilities from the weak-strong behavior. This model agrees well with the observed flip-flop behavior in storage rings, including the hysteresis seen when the beams are flipped from one asymmetric steady state to the other. It can be used to predict the behavior of proposed facilities in which the two colliding beams are characterized by different parameters.
Date: August 1, 1989
Creator: Tennyson, J.L.
Partner: UNT Libraries Government Documents Department

Contact Hysteresis and Friction of Alkanethiol SAMs on Au

Description: Nanoindentation has been combhed with nanometer-scale friction measurements to identi~ dissipative mechanisms responsible for friction in hexadecanethiol self-assembled monolayer on Au. We have demonstrated that friction is primarily due to viscoelastic relaxations within the films, which give rise to contact hysteresis when deformation rates are within the ranges of 5 and 200 k. We observe that this contact hysteresis increases with exposure to air such that the friction coefficient increases from 0.004 to 0.075 when films are exposed to air for 40 days. Both hysteresis and friction increase with probe speed, and we present a model of friction that characterizes this speed dependence and which also predicts a linear dependence of friction on normal force in thin organic films. Finally, we identify several short-term wear regimes and identify that wear changes dramatically when fdms age.
Date: October 14, 1998
Creator: Houston, J.E. & Kiely, J.D.
Partner: UNT Libraries Government Documents Department

Large melting point hysteresis of Ge nanocrystals embedded inSiO2

Description: The melting behavior of Ge nanocrystals embedded within SiO{sub 2} is evaluated using in situ transmission electron microscopy. The observed melting point hysteresis is large ({+-} 17%) and nearly symmetric about the bulk melting point. This hysteresis is modeled successfully using classical nucleation theory without the need to invoke epitaxy.
Date: May 4, 2006
Creator: Xu, Q.; Sharp, I.D.; Yuan, C.W.; Yi, D.O.; Liao, C.Y.; Glaeser,A.M. et al.
Partner: UNT Libraries Government Documents Department

Fabricating Optical Fiber Imaging Sensors Using Inkjet Printing Technology: a pH Sensor Proof-of-Concept

Description: We demonstrate the feasibility of using Drop-on-Demand microjet printing technology for fabricating imaging sensors by reproducibly printing an array of photopolymerizable sensing elements, containing a pH sensitive indicator, on the surface of an optical fiber image guide. The reproducibility of the microjet printing process is excellent for microdot (i.e. micron-sized polymer) sensor diameter (92.2 {+-} 2.2 microns), height (35.0 {+-} 1.0 microns), and roundness (0.00072 {+-} 0.00023). pH sensors were evaluated in terms of pH sensing ability ({le}2% sensor variation), response time, and hysteresis using a custom fluorescence imaging system. In addition, the microjet technique has distinct advantages over other fabrication methods, which are discussed in detail.
Date: March 1, 2005
Creator: Carter, J C; Alvis, R M; Brown, S B; Langry, K C; Wilson, T S; McBride, M T et al.
Partner: UNT Libraries Government Documents Department

Low temperature elastic constants and nonlinear acoustic response in rocks and complex materials

Description: The 'P-M Space' model of Guyer and McCall has some success in describing the large nonlinear effects ('slow dynamics') observed by Johnson et al. in rocks. The model uses elements which couple classical nonlinear elasticity with hysteretic components. The actual processes and scales corresponding to the model elements are not yet defined, however it is reasonable to seek energy scales by studying the low-temperature dependence of the elastic constants. We have measured qualitative elastic properties of basalt and Berea sandstone from room temperature down to 4 K using Resonant Ultrasound Spectroscopy (RUS). A simple elastic solid should show a monotonic increase in the elastic constants as temperature decreases. The basalt samples show this gross behavior but the sandstone shows a very unexpected anomalous regime between 40 K and 200 K where the elastic constants decrease with decreasing temperature. Both rocks show temperature-dependent structure in both the modulus and internal friction, and also significant hysteresis, indicating history and rate-dependent properties. This data provides insight into the time and energy scales of dynamical effects observed in sandstones.
Date: January 1, 2001
Creator: Darling, T. W. (Timothy W.); Ulrich, T. J. (Timothy J.); Johnson, P. A. (Paul A.) & Tencate, J. A. (James A.)
Partner: UNT Libraries Government Documents Department

Scaling Behavior of Barkhausen Avalanches along the Hysteresis loop in Nucleation-Mediated Magnetization Reversal Process

Description: We report the scaling behavior of Barkhausen avalanches for every small field step along the hysteresis loop in CoCrPt alloy film having perpendicular magnetic anisotropy. Individual Barkhausen avalanche is directly observed utilizing a high-resolution soft X-ray microscopy that provides real space images with a spatial resolution of 15 nm. Barkhausen avalanches are found to exhibit power-law scaling behavior at all field steps along the hysteresis loop, despite their different patterns for each field step. Surprisingly, the scaling exponent of the power-law distribution of Barkhausen avalanches is abruptly altered from 1 {+-} 0.04 to 1.47 {+-} 0.03 as the field step is close to the coercive field. The contribution of coupling among adjacent domains to Barkhausen avalanche process affects the sudden change of the scaling behavior observed at the coercivity-field region on the hysteresis loop of CoCrPt alloy film.
Date: October 14, 2008
Creator: Im, Mi-Young; Fischer, Peter; Kim, D.-H. & Shin, S.-C.
Partner: UNT Libraries Government Documents Department

Beam based measurements of hysteresis effects in Fermilab main injector magnets

Description: Operation of the Fermilab Main Injector is sensitive to magnetic field differences due to hysteretic effects. Measurements using the beam are reported with various current ramps. This will provide magnetic field information for accelerator operations with better ramp control than is available from magnet test facility data. This makes possible improved low field reproducibility with mixed 120 GeV and 150 GeV operation of the Main Injector.
Date: May 27, 2003
Creator: Capista, Bruce C. Brown and David P
Partner: UNT Libraries Government Documents Department

Design for Fermilab main injector magnet ramps which account for hysteresis

Description: Although the dominant fields in accelerator electromagnets are proportional to the excitation current, precise control of accelerator parameters requires a detailed understanding of the fields in Main Injector magnets including contribution from eddy currents, magnet saturation, and hysteresis. Operation for decelerating beam makes such considerations particularly significant. Analysis of magnet measurements and design of control system software is presented. Field saturation and its effects on low field hysteresis are accounted for in specifying the field ramps for dipole, quadrupole and sextupole magnets. Some simplifying assumptions are made which are accepted as limitations on the required ramp sequences. Specifications are provided for relating desired field ramps to required current ramps for the momentum, tune, and chromaticity control.
Date: May 1, 1997
Creator: Brown, B.C.; Bhat, C.M.; Harding, D.J.; Martin, P.S. & Wu, G.
Partner: UNT Libraries Government Documents Department

Magnetic field strength and shape measurements of the Fermilab main injector quadrupoles

Description: All of the new quadrupoles for the Fermilab Main Injector ring have been built and measured. The magnets are 2.95 m and 2.54 m in length with a 41.7 mm bore. In operation, the magnets run from 1.61 T/m at 8. 9 GeV/c to 15.7 T/m at 120 GeV/c and 19.6 T/m at 150 GeV/c. These points correspond to injection, Main Injector fixed target physics and antiproton production, and extraction for transfer to the Tevatron. Good field uniformity is required to ensure a stable beam over the whole acceleration cycle. A significant octupole is included to assist in resonant extraction. The performance of these quadrupoles, in both integrated strength and field uniformity, is presented. All magnets produced meet the accelerator requirements.
Date: May 1, 1997
Creator: Harding, D.J.; Brown, B.C. & DiMarco, H.H.
Partner: UNT Libraries Government Documents Department

Direct Measurement of Extension and Force in Conductive Polymer Gel Actuators

Description: The synthesis of a polythiophene-based conductive polymer gel is described. Preliminary measurements of the electrochemically driven extension and force response of this gel are reported when driven under the action of an applied square-wave potential. Over each square wave interval (i.e., one oxidation pulse followed by one reduction pulse), the axial change in dimension was found to be approximately 2%. Some hysteresis was noted in that the cylindrical specimens did not return to their original axial dimension. The axial pressure generated by the expansion of the gel against a fixed surface was also measured and found to be on the order of 15 kPa.
Date: February 1, 2001
Creator: Goods, S.H.; Whinnery, L.L.; Irvin, D.J. & Korellis, J.S.
Partner: UNT Libraries Government Documents Department

Numerical simulations of magnetic reversal in layered spring magnets.

Description: This report summarizes the results of numerical investigations of magnetic reversal in layered spring magnets. A one-dimensional model is used of a film consisting of several atomic layers of soft material on top of several atomic layers of hard material. Each atomic layer is taken to be uniformly magnetized, and spatial inhomogeneities within an atomic layer are neglected. The state of such a system is described by a chain of magnetic spin vectors. Each spin vector behaves like a spinning top driven locally by the effective magnetic field and subject to damping (Landau-Lifshitz-Gilbert equation). A numerical integration scheme for the LLG equation is presented that is unconditionally stable and preserves the magnitude of the magnetization vector at all times. The results of numerical investigations for a bilayer in a rotating in-plane magnetic field show hysteresis with a basic period of 2{pi} at moderate fields and hysteresis with a basic period of {pi} (or any multiple thereof) at strong fields.
Date: January 24, 2001
Creator: Jiang, J.S.; Kaper, H.G. & Leaf, G.K.
Partner: UNT Libraries Government Documents Department

Magnetic domain structure and magnetization reversal in submicron-scale Co dots

Description: We present a magnetic force microscopy (MFM) analysis of arrays of submicron-scale Co dots fabricated by interference lithography. The dots are thin (180-300 A) and are elliptical in shape. MFM of these structures reveals that they relax into highly ordered remanent states whose symmetry and configuration are governed by their shape anisotropy. In particular, when the dots are saturated along the easy-axis, a uniformly magnetized state persists at remanence. However, when the dots are saturated in hard-axis, they relax into a single-vortex state in which the circulation can have either sign. Both remanent states are characterized by smoothly varying magnetization patterns and a high degree of uniformity across the array. We attribute the ordered behavior of these structures to the film microstructure, which allows the shape anisotropy to dominate over magnetocrystalline anisotropy. By imaging a series of minor-loop remanent states, we show that magnetization reversal in these structures occurs via the nucleation and annihilation of a single vortex. Magnetic hysteresis loop measurements are consistent with these observations and provide additional details. Furthermore, we present the results of micromagnetic simulations, which are in excellent agreement with both the MFM images and the hysteresis loop measurements.
Date: February 17, 1998
Creator: Fernandez, A.
Partner: UNT Libraries Government Documents Department

Extension of the stability of motions in a combustion chamber by non- linear active control based on hysteresis

Description: This report presents the first quantitative data establishing the details of hysteresis whose existence in dynamical behavior was reported by Sterling and Zukoski. The new idea was demonstrated that the presence of dynamical hysteresis provides opportunity for a novel strategy of active nonlinear control of unsteady motions in combustors. A figure shows the hysteresis exhibited for the amplitude of pressure oscillations as a function of equivalence ratio in a combustor having a recirculation zone, in this case a dump combustor.
Date: July 1, 1996
Creator: Knoop, P.; Culick, F.E.C. & Zukoski, E.E.
Partner: UNT Libraries Government Documents Department

Parameterization of hysteresis effects in accumulator quadrupole magnets

Description: The hysteresis curves of two Accumulator sample magnets have been measured, one large quadrupole and one small quadrupole. Based upon these measurements, a parameterization of hysteresis effects is deduced and generalized to other magnets. The goal is to incorporate the best knowledge of the magnets we have into the Accumulator model, on which lattice measurements are based and which is used to calculate an accurate first guess at the E-835 deceleration tables. Since a well-defined sequence of current cycles is performed during Accumulator operations, some simplifying hypotheses can be applied.
Date: November 3, 1999
Creator: Stancari, Giulio
Partner: UNT Libraries Government Documents Department

Final Scientific Report - "Improved Fuel Efficiency from Nanocomposite Tire Tread"

Description: Rolling resistance, a measure of the energy lost as a tire rotates while moving, is a significant source of power and fuel loss. Recently, low rolling resistant tires have been formulated by adding silica to tire tread. These "Green Tires" (so named from the environmental advantages of lower emissions and improved fuel economy) have seen some commercial success in Europe, where high fuel prices and performance drive tire selection. Unfortunately, the higher costs of the silica and a more complicated manufacturing process have prevented significant commercialization - and the resulting fuel savings - in the U.S. In this project, TDA Research, Inc. (TDA) prepared an inexpensive alternative to silica that leads to tire components with lower rolling resistance. These new tire composite materials were processed with traditional rubber processing equipment. We prepared specially designed nanoparticle additives, based on a high purity, inorganic mineral whose surface can be easily modified for compatibility with tire tread formulations. Our nanocomposites decreased energy losses to hysteresis, the loss of energy from the compression and relaxation of an elastic material, by nearly 20% compared to a blank SBR sample. We also demonstrated better performance than a leading silica product, with easier production of our final rubber nanocomposite.
Date: December 30, 2005
Creator: Myers, Dr. Andrew
Partner: UNT Libraries Government Documents Department

Measures of trajectory ensemble disparity in nonequilibrium statistical dynamics

Description: Many interesting divergence measures between conjugate ensembles of nonequilibrium trajectories can be experimentally determined from the work distribution of the process. Herein, we review the statistical and physical significance of several of these measures, in particular the relative entropy (dissipation), Jeffreys divergence (hysteresis), Jensen-Shannon divergence (time-asymmetry), Chernoff divergence (work cumulant generating function), and Renyi divergence.
Date: June 3, 2011
Creator: Crooks, Gavin & Sivak, David
Partner: UNT Libraries Government Documents Department

Enhanced Coarse-Graining for Multiscale Modeling of Elastomers

Description: One of the major goal of the researchers is to reduce energy loss including nanoscale to the structural level. For instance, around 65% of fuel energy is lost during the propulsion of the automobiles, where 11% of the loss happens at tires due to rolling friction. Out of that tire loss, 90 to 95% loss happens due to hysteresis of tire materials. This dissertation focuses on multiscale modeling techniques in order to facilitate the discovery new rubber materials. Enhanced coarse-grained models of elastomers (thermoplastic polyurethane elastomer and natural rubber) are constructed from full-atomic models with reasonable repeat units/beads associated with pressure-correction for non-bonded interactions of the beads using inverse Boltzmann method (IBM). Equivalent continuum modeling is performed with volumetric/isochoric loading to predict macroscopic mechanical properties using molecular mechanics (MM) and molecular dynamics (MD). Glass-transition and rate-dependent mechanical properties along with hysteresis loss under uniaxial deformation is predicted with varying composition of the material. A statistical non-Gaussian treatment of a rubber chain is performed and linked with molecular dynamics in order predict hyperelastic material constants without fitting with any experimental data.
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Date: December 2016
Creator: Uddin, Md Salah
Partner: UNT Libraries

Excitation Curves of small quadrupoles for tev I Beam Line Use

Description: Excitation curves for at least one magnet of each length of TeV I Small Quadrupole have been measured utilizing the MIF-TeV I VAX standard measurement system. Since the standard measurement sequence does not include this sort of excitation curve, the standard reports issued on the magnet does not contain this data. Measurements were taken with the gradient probe SQ25 (probe ID No.40) centered in the aperture and extending through the field length to integrate the strength of the magnet. The parameter BETA2 reported below is the probe calibration factor for this probe in meters**2. The gradient strength of the magnet in Tesla-meters/meter is obtained from the measured flux by dividing by BETA2. The data were collected from MEAS BASE runs in which the measurement probe flux is recorded in a baseline measurement sequence. The hysteresis of the magnet is set by ramping to the specified maximum current then back to zero. The integrator is zeroed at zero current and the integrator voltage recorded one or more times. The current is then ramped successively to the measurement current where the integrator voltage is recorded, to full field and back to zero where the integrator voltage is again recorded for each current at which data is desired. After correction for drift, amplifier gain and integrator Re, the data is recorded in the Reduced data files. This report collects this data for measurements on several magnets. The data at non-zero currents are converted to Tesla and reported also in Tesla/Amp. In order to prepare the report entirely with the DATATRIEVE query language, the usual averaging of Probe Up and Probe Down measurements was not carried out. The reader is invited instead to look at both sets of data to observe that the error to be canceled is small. In addition, this report may ...
Date: February 1, 1985
Creator: Brown, B.
Partner: UNT Libraries Government Documents Department

Tune Variations due to Septum Stray Field F. Pederson &

Description: Two types of antiproton instabilities due to trapped ions are harmful in the AA. One is a coherent instability occurring when an ion pocket resonates with a 3-Q mode (hiccups), the other is excitation of 11th and 15th order non-linear resonances due to the non-linear focusing fields from localized ion clouds trapped in uncleared potential well pockets. Accumulation with a good injection yield of antiprotons forces us to locate the tune of the dense core in the general area of the array of 15th order resonances. To avoid harmful blow-up of the dense core the tune is located between the resonances 11Q{sub H} + 4Q{sub V} = 34, 10Q{sub H} + 5Q{sub V} = 34, and 11Q{sub H} = 25, requiring a tune of Q{sub H} = 2.2722 to be maintained with a precision of a few 10{sup -4} (Fig. 4). Different angles of the injection and ejection trajectories require the septum current to be changed from 3860 A during accumulation to 3920 A, during ejection mode. Variations in the septum stray field due to these changes in current cause tune changes in the order of 10{sup -3}. In addition, at a given septum current, a pronounced hysteresis of the stray field causes tune variations of about the same order of magnitude, so also the past history of the septum excitation must be carefully controlled to obtain a reproducible tune.
Date: October 12, 1986
Creator: Rinolfi, L.
Partner: UNT Libraries Government Documents Department

A pore network model for adsorption in porous media

Description: Using a pore network model to represent porous media we investigate adsorption-desorption processes over the entire range of the relative pressure, highlighting in particular capillary condensation. The model incorporates recent advances from density functional theory for adsorption-desorption in narrow pores (of order as low as 1 nm), which improve upon the traditional multi-layer adsorption and Kelvin's equation for phase change and provide for the dependence of the critical pore size on temperature. The limited accessibility of the pore network gives rise to hysteresis in the adsorption-desorption cycle. This is due to the blocking of larger pores, where adsorbed liquid is allowed to but cannot desorb, by smaller pores containing liquid that may not desorb. By allowing for the existence of supercritical liquid in pores in the nm range, it is found that the hysteresis area increases with an increase in temperature, in agreement with experiments of water adsorption-desorption in rock samples from The Geysers. It is also found that the hysteresis increases if the porous medium is represented as a fractured (dual porosity) system. The paper finds applications to general adsorption-desorption problems but it is illustrated here for geothermal applications in The Geysers.
Date: January 26, 1995
Creator: Satik, Cengiz & Yortsos, Yanis C.
Partner: UNT Libraries Government Documents Department