1,727 Matching Results

Search Results

Advanced search parameters have been applied.

The Dielectric Constant of Galvinoxyl

Description: The molecules in many substances are know to undergo at characteristic temperatures a change in their rotational freedom in the solid state, signifying either a change in structure of the material of the onset of limited rotation of the molecule about some symmetry axis. The purpose of this research was to determine from dielectric constant measurements over the 100°K-420°K temperature range whether or not the organic free radical galvinoxyl and its diamagnetic parent molecule, dihydroxydiphenylmethane, undergo any such transitions.
Date: May 1968
Creator: Mizell, Michael E.
Partner: UNT Libraries

Electrodeposit of Nickel

Description: The purpose of this study is to investigate the varying conditions in types of solutions, concentrations of solutions, hydrogen-ion concentration, current densities and potentials in the electro deposition of nickel.
Date: August 1937
Creator: Rohrer, Charles Stephen
Partner: UNT Libraries

Two-Dimensional Carrier-Carrier Screening in a Quantum Well

Description: The behavior of carrier-carrier screening is investigated in a GaAs-GaAIAs quantum well structure by measuring the band-to-band polarization dephasing with femtosecond photon echoes. The variation of the electron-hole polarization dephasing time with the carrier concentration reveals the two-dimensional character of the short range screening between the interacting carriers.
Date: July 1, 1991
Creator: Bigot, J.-Y.; Portella, M.T.; Schoenlein, R.W.; Cunningham, J.E. & Shank, C.V.
Partner: UNT Libraries Government Documents Department

An Experimental Study of the Electrodeposition of Lead

Description: This thesis aimed to study some of the general principles underlying electrodeposition together with experimental facts regarding the effects of changing constituents of the plating solutions, variations in hydrogen-ion concentrations, and variation in current density used in the electrodeposition of lead.
Date: June 1937
Creator: Roberts, Ira Clifford
Partner: UNT Libraries

Design and Manufacture of Molding Compounds for High Reliability Microelectronics in Extreme Conditions

Description: The widespread use of electronics in more avenues of consumer use is increasing. Applications range from medical instrumentation that directly can affect someone's life, down hole sensors for oil and gas, aerospace, aeronautics, and automotive electronics. The increased power density and harsh environment makes the reliability of the packaging a vital part of the reliability of the device. The increased importance of analog devices in these applications, their high voltage and high temperature resilience is resulting in challenges that have not been dealt with before. In particular packaging where insulative properties are vital use polymer resins modified by ceramic fillers. The distinct dielectric properties of the resin and the filler result in charge storage and release of the polarization currents in the composite that have had unpredictable consequences on reliability. The objective of this effort is therefore to investigate a technique that can be used to measure the polarization in filled polymer resins and evaluate reliable molding compounds. A valuable approach to measure polarization in polymers where charge release is tied to the glass transition in the polymer is referred to as thermally stimulated depolarization current (TSDC) technique. In this dissertation a new TSDC measurement system was designed and fabricated. The instrument is an assembly of several components that are automated via a LabVIEW program that gives the user flexibility to test different dielectric compounds at high temperatures and high voltage. The temperature control is enabled through the use of dry air convection heating at a very slow rate enabling controlled heating and cooling. Charge trapping and de-trapping processes were investigated in order to obtain information on insulating polymeric composites and how to optimize it. A number of material properties were investigated. First, polarization due to charges on the filer were investigated using composites containing charged and uncharged particles using ...
Access: This item is restricted to UNT Community Members. Login required if off-campus.
Date: December 2016
Creator: Garcia, Andres
Partner: UNT Libraries

Methods of Calculation of Resistance to Polarization (Corrosion Rate) Using ASTM G 59

Description: The corrosion rate of a metal (alloy) can be measured using: (1) Immersion tests or weight loss such as in ASTM G 1 and G 31 or (2) Electrochemical techniques such as in ASTM G 59. In the polarization resistance (PR) or linear polarization method (G 59), the resistance to polarization (Rp) of a metal is measured in the electrolyte of interest in the vicinity of the corrosion potential (E{sub corr}). This polarization resistance can be mathematically converted into corrosion rates (CR). A plot of E vs. I in the vicinity of E{sub corr} is generated by increasing the potential at a fixed rate of 0.1667 mV/s and measuring the output current. The polarization resistance (Rp) is defined as the slope of a potential (E) (Y axis) vs. Current (I) (X axis) plot in the vicinity of the corrosion potential (E{sub corr}). When the potential is ramped and the current is measured, E is the independent variable and I is the dependent variable. In a proper mathematical plot, E should be represented in the X axis and I in the Y axis. However, in the conventions of the corrosion community, E is always plotted in the Y axis and I in the X axis. Therefore, how this plot of Delta E/Delta I is analyzed is a matter of current debate.
Date: February 5, 2006
Creator: Wong, L L; King, K J; Martin, S I & Rebak, R B
Partner: UNT Libraries Government Documents Department

Direct Measurements of an increased threshold for stimulated Brillouin scattering with polarization smoothing in ignition hohlraum plasmas

Description: We demonstrate a significant reduction of stimulated Brillouin scattering by polarization smoothing. The intensity threshold is measured to increase by a factor of 1.7 {+-} 0.2 when polarization smoothing is applied. The results were obtained in a high-temperature (T{sub 3} {approx_equal} 3 keV) hohlraum plasma where filamentation is negligible in determining the backscatter threshold. These results are explained by an analytical model relevant to ICF plasma conditions that modifies the linear gain exponent to account for polarization smoothing.
Date: November 8, 2007
Creator: Froula, D; Divol, L; Berger, R L; London, R; Meezan, N; Neumayer, P et al.
Partner: UNT Libraries Government Documents Department

qSF wavefront triplication in a transversely isotropicmaterial

Description: Triplication of a wavefront, also classically known as birefringence, can and does occur in transversely isotropic (TI) media. With the growing interest in shear waves, and in particular, converted shear waves, it becomes necessary to study this phenomenon, and the bright spots that accompany it. In a plane that includes the medium's rotational symmetry axis, there may exist a range of angles within which the qSV wave, whose polarization lies in that plane, may propagate at three distinct velocities. The region of the qSV wave curve where this can occur always corresponds to the region of the qSV slowness curve where the closed qSV curve about the origin is concave. When the range of angles is small and the three arrivals are close together, the usual situation, the qSV wave within that small range will be significantly brighter than in other directions. When the range of angles is large, the two cusps of the wave surface, on the borders of the region of triplication will both be bright spots.
Date: June 1, 2004
Creator: Schoenberg, Michael & Daley, Thomas M.
Partner: UNT Libraries Government Documents Department


Description: The stable spin direction in the RHIC rings is vertical. With one or two partial helical Siberian snakes in the AGS, the stable spin direction at extraction is not vertical. Interleaved vertical and horizontal bends in the transport line between AGS and the RHIC rings also tend to tip the spin away from the vertical. In order to maximize polarization in RHIC, we examined several options to improve the matching of the stable spin direction during beam transfer from the AGS to each of the RHIC rings. While the matching is not perfect, the most economical method appears to be a lowering of the injection energy by one unit of G{gamma} from 46.5 to 45.5.
Date: June 23, 2006
Partner: UNT Libraries Government Documents Department

p-Carbon polarimetry at RHIC.

Description: The polarization measurement through elastic ({rvec p},C) reaction plays a crucial role in the polarized proton beam operation of Relativistic Heavy Ion collider at Brookhaven National Laboratory. As well as measuring the polarization, the unknown analyzing power A{sub N} of elastic ({rvec p},C) is determined as well in combination with the absolute polarization measurement by a H-jet polarimeter. The systematic uncertainty of the Run05 measurements are discussed as well as introducing the experimental apparatus of the polarimeter system.
Date: September 10, 2007
Creator: Nakagawa,I.; Makdisi,Y.; Alekseev, I.; Bazilesky, A.; Bravar, A.; Bunce, G. et al.
Partner: UNT Libraries Government Documents Department

Probing Ferroelectricity in PbZr0.2Ti0.8O3 with Polarized Soft X-rays

Description: The reduction in symmetry associated with the onset of ferroelectric order in PbZr{sub 0.2}Ti{sub 0.8}O{sub 3} (PZT) thin films leads to a pronounced difference at the Ti L{sub 3,2} absorption edges between spectra measured with the x-ray linear polarization perpendicular and parallel to the ferroelectric polarization. We introduce a general method to analyze the observed difference spectra using atomic multiplet calculations. Moreover, we find experimental evidence for structural changes in PZT induced by the reversal of the ferroelectric polarization.
Date: June 7, 2010
Creator: Arenholz, E.; van der Laan, G.; Fraile-Rodriguez, A.; Yu, P.; He, Q. & Ramesh, R.
Partner: UNT Libraries Government Documents Department

Global polarization measurement in Au+Au collisions

Description: The system created in non-central relativisticnucleus-nucleus collisions possesses large orbital angular momentum. Dueto spin-orbit coupling, particles produced in such a system could becomeglobally polarized along the direction of the system angular momentum. Wepresent the results of Lambda and anti-Lambda hyperon global polarizationmeasurements in Au+Au collisions at sqrt sNN=62.4 GeV and 200 GeVperformed with the STAR detector at RHIC. The observed globalpolarization of Lambda and anti-Lambda hyperons in the STAR acceptance isconsistent with zero within the precision of the measurements. Theobtained upper limit, lbar P Lambda, anti-Lambda rbar<= 0.02, iscompared to the theoretical values discussed recently in theliterature.
Date: August 2, 2007
Creator: Abelev, B.I.; Adams, J.; Aggarwal, M.M.; Ahammed, Z.; Amonett,J.; Anderson, B.D. et al.
Partner: UNT Libraries Government Documents Department

Spin Tracking Studies for Beam Polarization Preservation in theNLC Main Damping Rings

Description: We report results from studies of spin dynamics in the NLC Main Damping. Our studies have been based on spin tracking particles through the lattice under a range of conditions. We find that there are a number of spin resonances close to the nominal operating energy of 1.98 GeV; however, the effects of the resonances are weak, and the widths are narrow. We do not expect that any significant depolarization of the beam will occur during the store time.
Date: July 26, 2004
Creator: Wolski, Andrzej & Bates, Daniel
Partner: UNT Libraries Government Documents Department

Measurement of the Polarization in Elastic Electron ProtonScattering

Description: We have measured the (illegible) scattering (?-illegible) of electrons (?-illegible) from a polarized proton target. (illegible) between (?-illegible) imaginary part of the two-photon-(illegible) (illegible) photon-exchange amplitude could produce (?-illegible) (illegible) results indicate no asymmetry within (illegible) 1 to 2% at four(?-illegible)-momentum transfer (illegible) (illegible) 0.98 (GeV/c){sup 2}.
Date: March 1, 1970
Creator: Powell, Thomas; Chamberlain, Owen & Borghini, Michel
Partner: UNT Libraries Government Documents Department

The Mechanism of Proton Polarization in High-EnergyCollisions

Description: Recently experimental evidence has accumulated showing that high-energy collisions of protons with various nuclei induce a considerable polarization in proton beams, and a mechanism has been proposed to account for this effect.
Date: June 9, 1954
Creator: Chamberlain, Owen; Segre, Emilio; Tripp, Robert; Wiegand, Clyde & Ypsilantis, Thomas
Partner: UNT Libraries Government Documents Department

The RHIC Optically-Pumped Polarized H Ion Source.

Description: The depolarization factors in the multi-step spin-transfer polarization technique and basic limitations on maximum polarization in the OPPIS (Optically-Pumped Polarized H{sup -} Ion Source) are discussed. Detailed studies of polarization losses in the RHIC OPPIS and the source parameters optimization resulted in the OPPIS polarization increase to 86-90%. This contributed to increasing polarization in the AGS and RHIC to 65-70%.
Date: September 10, 2007
Creator: Zelenski,A.; Zelenski, A.; Kokhanovski, S.; Kponou, A.; Ritter, J. & Zubets, V.
Partner: UNT Libraries Government Documents Department


Description: The depolarization factors in the multi-step spin-transfer polarization technique and basic limitations on maximum polarization in the OPPIS (Optically-Pumped Polarized H{sup -} Ion Source) are discussed. Detailed studies of polarization losses in the RHIC OPPIS and the source parameters optimization resulted in the OPPIS polarization increase to 86-90%. This contributed to increasing polarization in the AGS and RHIC to 65-70%.
Date: June 25, 2007
Partner: UNT Libraries Government Documents Department