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1993

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Articles 391 - 404 of 404

Full-Text Articles in Physics

The Effects Of Granularity On The Microwave Surface Impedance Of High Kappa Superconductors, Stephen Keith Remillard Jan 1993

The Effects Of Granularity On The Microwave Surface Impedance Of High Kappa Superconductors, Stephen Keith Remillard

Dissertations, Theses, and Masters Projects

The microwave surface impedance of granular high temperature superconductors is an important figure of merit for technological applications. Because the behavior of the granular materials deviates significantly from that of the ideal defect free superconductors, the loss mechanisms are not fully understood. This dissertation seeks to quantify the contribution of granularity to centimeter wave and millimeter wave losses. By understanding these losses, the superconductive coupling between neighboring grains can also be understood.;The weakly coupled grain model is used as a phenomenological description of the microwave surface impedance. The granular superconducting surface is modelled as an effective resistively shunted Josephson ...


A Study Of Molecular Order And Motion In Nematic Liquid Crystal Mixtures, Jon Michael Goetz Jan 1993

A Study Of Molecular Order And Motion In Nematic Liquid Crystal Mixtures, Jon Michael Goetz

Dissertations, Theses, and Masters Projects

Materials which flow like fluids, but possess anisotropic properties like molecular crystals, are called 'liquid crystals'. Studies of liquid crystals contribute to our understanding of how molecular orientation influences macroscopic properties. This thesis presents experimental and theoretical investigations of molecular order and dynamics in nematic liquid crystal systems. First, deuterium nuclear magnetic resonance is used to determine the degree of orientational order of both components of a liquid crystal mixture simultaneously. The temperature dependence of the four order parameters is interpreted using a newly developed mean field theory of nematic binary mixtures composed of biaxial molecules. Next, mean field theory ...


Anomalies For Pedestrians, Br Holstein Dec 1992

Anomalies For Pedestrians, Br Holstein

Barry R Holstein

The subject of anomalies, i.e., quantum mechanical symmetry breaking, is addressed using only basic quantum mechanics. Examples from different areas of physics are examined


Study Of The Violation Of Parity In Nuclear Beta-Decay Via A Relative Beta-Polarization Measurement With Polarized In-107 Nuclei, N Severijns, R Prieels, M Allet, J Camps, P Demoor, J Deutsch, F Gimenonogues, Br Holstein, Bh King, O Naviliatcuncici, I Pepe, Pa Quin, P Schuurmans, R Siebelink, W Vanderpoorten, J Vanhaverbeke, L Vanneste, J Wouters Dec 1992

Study Of The Violation Of Parity In Nuclear Beta-Decay Via A Relative Beta-Polarization Measurement With Polarized In-107 Nuclei, N Severijns, R Prieels, M Allet, J Camps, P Demoor, J Deutsch, F Gimenonogues, Br Holstein, Bh King, O Naviliatcuncici, I Pepe, Pa Quin, P Schuurmans, R Siebelink, W Vanderpoorten, J Vanhaverbeke, L Vanneste, J Wouters

Barry R Holstein

No abstract provided.


Solvable Quantum Mechanical Examples Of Broken Supersymmetry, Asim Gangopadhyaya Dec 1992

Solvable Quantum Mechanical Examples Of Broken Supersymmetry, Asim Gangopadhyaya

Asim Gangopadhyaya

We construct several analytically solvable examples of broken supersymmetry in non-relativistic quantum mechanics. Our examples are motivated from known shape-invariant potentials obeying unbroken supersymmetry and are obtained from them via suitable mapping procedures.


Quantum Correlations And 3 Body Decays At A Phi-Factory, Jf Donoghue, Br Holstein, Af Perez Dec 1992

Quantum Correlations And 3 Body Decays At A Phi-Factory, Jf Donoghue, Br Holstein, Af Perez

Barry R Holstein

No abstract provided.


Phenomenographic Research And The Measurement Of Understanding: An Investigation Of Students' Conceptions Of Speed, Distance And Time, P Ramsden, Geoff Masters, Andrew Stephanou, E Walsh, E Martin Dec 1992

Phenomenographic Research And The Measurement Of Understanding: An Investigation Of Students' Conceptions Of Speed, Distance And Time, P Ramsden, Geoff Masters, Andrew Stephanou, E Walsh, E Martin

Prof Geoff Masters AO

No abstract provided.


Physics Students' Understanding Of Relative Speed: A Phenomenographic Study, Eleanor Walsh, Gloria Dall'alba, John Bowden, Elaine Martin, Ference Marton, Geoff Masters, Paul Ramsden, Andrew Stephanou Dec 1992

Physics Students' Understanding Of Relative Speed: A Phenomenographic Study, Eleanor Walsh, Gloria Dall'alba, John Bowden, Elaine Martin, Ference Marton, Geoff Masters, Paul Ramsden, Andrew Stephanou

Prof Geoff Masters AO

It is important that students of physics develop both quantitative and qualitative understanding of physical concepts and principles. Although accuracy and reliability in solving quantitative problems is necessary, a qualitative understanding is required in applying concepts and principles to new problems and in real-life situations. If students are not able to understand what underlies quantitative problem-solving procedures nor interpret the solution in physical terms, it is questionable whether they have developed an adequate understanding of physics. The research reported here is part of a larger phenomenographic study that is concerned with the assessment of physics students' understanding of some basic ...


Equivalence Theorem And Global Anomalies, John Donoghue, Jusak Tandean Dec 1992

Equivalence Theorem And Global Anomalies, John Donoghue, Jusak Tandean

John Donoghue

In the presence of some forms of global anomalies, the equivalence theorem, which relates the interactions of longitudinal gauge bosons to those of the Goldstone bosons, is not always valid. This can occur when the Goldstone sector contains an anomaly which is canceled in the gauge currents by the effects of a different sector of the theory. The example of the standard model without Higgs particles is used to illustrate this phenomena.


Quantum Correlations In Three Body Ö Decay, John Donoghue, Barry Holstein, Antonio Perez Dec 1992

Quantum Correlations In Three Body Ö Decay, John Donoghue, Barry Holstein, Antonio Perez

John Donoghue

The decays of neutral kaons produced in ~b decay, (~-~KLKs, exhibit interesting quantum mechanical interference. The effects of this phenomenon on searches for CP violation have been previously been worked out for two body decays where the decay amplitude is a simple constant. For three body modes, where the matrix element varies across the kinematically allowed region, the quantum correlations will enhance or cancel certain terms in the decay distribution. We work out the results for two interesting modes q)~(nn)(nnT) and ~b~(3n)(3n). In the former case, the quantum correlation allows the isolation of the direct emission ...


Photon-Photon Scattering, Pion Polarizability And Chiral Symmetry, John Donoghue, Barry Holstein Dec 1992

Photon-Photon Scattering, Pion Polarizability And Chiral Symmetry, John Donoghue, Barry Holstein

John Donoghue

Recent attempts to detect the pion polarizability via analysis of γγ → ππ measurements are examined. The connection between calculations based on dispersion relations and on chiral perturbation theory is established by matching the low energy chiral amplitude with that given by a full dispersive treatment. Using the values for the polarizability required by chiral symmetry, predicted and experimental cross sections are shown to be in agreement. 


Electromagnetic Self Energies Of Pseudoscalar Mesons And Dashen's Theorem, John Donoghue, Barry Holstein, Daniel Wyler Dec 1992

Electromagnetic Self Energies Of Pseudoscalar Mesons And Dashen's Theorem, John Donoghue, Barry Holstein, Daniel Wyler

John Donoghue

The calculation of the electromagnetic mass shifts of pi, K mesons is studied using a model incorporating chiral symmetry and vector dominance. Significant SU(3) breaking to Dashen s theorem is found, allowing a resolution of the long-standing discrepancy between the quark-mass ratio (md —m„)/I, found from g->3pi decay and that from the K+-K0 mass difference. 


Sliding Mode Control Of The Systems With Uncertain Direction Of Control Vector, Sergey V. Drakunov Dec 1992

Sliding Mode Control Of The Systems With Uncertain Direction Of Control Vector, Sergey V. Drakunov

Sergey V. Drakunov

No abstract provided.


Doping And Pressure Studies On Ybbipt, A. Lacerda, R. Movshovich, M. F. Hundley, Paul C. Canfield, D. Arms, G. Sparn, J. D. Thompson, Z. Fisk, N. E. Philips, H.-R. Ott Dec 1992

Doping And Pressure Studies On Ybbipt, A. Lacerda, R. Movshovich, M. F. Hundley, Paul C. Canfield, D. Arms, G. Sparn, J. D. Thompson, Z. Fisk, N. E. Philips, H.-R. Ott

Paul C. Canfield

The compound YbBiPt exhibits an extremely large low‐temperature C/T (γ∼8 J K−2 mol−1/Yb) which, if due solely to a renormalized effective mass, would make this material the heaviest correlated electron system known to date. In the Kondo model, the very large γ corresponds to a small characteristic energy scale that is expected to be pressure dependent. We have studied the effect of chemical pressure on YbBiPt single crystals by heat‐capacity measurements on Y and Lu‐doped samples. We have also made preliminary low‐temperature measurements under hydrostatic pressure of the heat capacity (300 ...