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Selected Works

1992

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Articles 1 - 14 of 14

Full-Text Articles in Physics

The Elastic Moduli Of Simple Two-Dimensional Isotropic Composites: Computer Simulation And Effective Medium Theory, K. A. Snyder, E. J. Garboczi, Anthony Roy Day Dec 1992

The Elastic Moduli Of Simple Two-Dimensional Isotropic Composites: Computer Simulation And Effective Medium Theory, K. A. Snyder, E. J. Garboczi, Anthony Roy Day

Anthony Roy Day

An algorithm, combining digital-image with spring network techniques, has been developed that enables computation of the elastic moduli of random two-dimensional multiphase composites. This algorithm is used to study the case of isotropic, randomly centered, overlapping circular inclusions in an isotropic elastic matrix. The results of the algorithm for the few-inclusion limit, as well as the case where both phases have the same shear moduli, agree well with the exact results for these two problems. The case where the two phases have the same Poisson’s ratio, but different Young’s moduli, is also studied, and it is shown that ...


Bend Elastic-Modulus Of A Bent And Straight Dimeric Liquid-Crystal, Gregory A. Dilisi Apr 1992

Bend Elastic-Modulus Of A Bent And Straight Dimeric Liquid-Crystal, Gregory A. Dilisi

Gregory A. DiLisi

Light scattering measurements in the nematic phase are reported for two dimers based upon the monomer 4,4'-dipentyloxyphenylbenzoate. One dimer has an even number of methylene units in the spacer and, in consequence, is approximately straight in the all-trans conformation. The other dimer has one less methylene unit in the spacer and is, therefore, bent at the spacer group. We find that the ratio of the twist to splay elastic modulus is nearly the same for both species, but that the ratio of the bend to splay modulus is considerably smaller in the bent dimer.


Viscoelastic Properties Of A Liquid-Crystalline Monomer And Its Dimer, Gregory A. Dilisi, Charles Rosenblatt, Anselm C. Griffin, Uma Hari Mar 1992

Viscoelastic Properties Of A Liquid-Crystalline Monomer And Its Dimer, Gregory A. Dilisi, Charles Rosenblatt, Anselm C. Griffin, Uma Hari

Gregory A. DiLisi

Quasielastic-light-scattering measurements are reported for a dialkoxyphenylbenzoate monomer and its dimer in their respective nematic phases. The splay and twist elastic moduli of the dimer are found to be nearly independent of molecular length. The dimer's bend modulus, however, shows an anomalous increase with decreasing temperature well below the nematic-isotropic phase transition. Monomer viscosities are consistent with typical literature values, although y, /g, pf y and gb,„d seem to be larger than expected for the dimer, where y& is the twist viscosity. The results are discussed in terms of viscoelastic properties of semiflexible rods. The elastic properties in ...


Light Quark Masses Beyond Leading Order, John Donoghue, Daniel Wyler Jan 1992

Light Quark Masses Beyond Leading Order, John Donoghue, Daniel Wyler

John Donoghue

We describe the measurement of the light quark mass ratios when one calculates to second order in the quark masses. At this order there is an ambiguity in the meaning of the quark mass, which afBicts the past attempts to provide a model-independent measurement of the ratios. We argue that this is similar to the regularization-scheme dependence of coupling constants. We study the anomalous Ward identities and the effects of strong CP violation in an attempt to resolve the ambiguity. The ambiguity persists even with singlet fields, such as the g', but can be resolved by observing the 9 dependence ...


Anchoring Strength Coefficient Of A Monomer And Its Dimer At A Polymer-Coated Interface, Gregory A. Dilisi, Charles Rosenblatt, Robert B. Akins, Anselm Griffin, Uma Hari Dec 1991

Anchoring Strength Coefficient Of A Monomer And Its Dimer At A Polymer-Coated Interface, Gregory A. Dilisi, Charles Rosenblatt, Robert B. Akins, Anselm Griffin, Uma Hari

Gregory A. DiLisi

The dialkoxyphenylbenzoate monomer ‘5005’ (C5H11OC6H4COOC6H4OC5H11) and its dimer were aligned parallel to a buffed polyimide-coated glass substrate. A magnetically induced Freedericksz transition in both thick and thin cells was used in conjunction with a capacitance technique to determine the anchoring strength coefficient Was a function of temperature in the nematic phase. It was found that for both monomer and dimer, Wincreases with decreasing temperature. The anchoring coefficient for the dimer, however, was found to be an order of magnitude larger than for the monomer at comparable reduced temperatures. The splay elastic moduli were also determined for both species, and found ...


Chiral Symmetry Tests In Nonleptonic K Decay, J. Kambor, John Donoghue, Barry Holstein, J. Missimer, D. Wyler Dec 1991

Chiral Symmetry Tests In Nonleptonic K Decay, J. Kambor, John Donoghue, Barry Holstein, J. Missimer, D. Wyler

John Donoghue

The existence of empirical tests for the validity of chiral perturbation theory in the analysis of nonleptonic kaon decay is pointed out in the context of K-> 2pi, 3pi processes. Comparison with existing data reveals good agreement with the chiral constraints. 


Components Of A Chiral Coefficient, John Donoghue, Barry Holstein Dec 1991

Components Of A Chiral Coefficient, John Donoghue, Barry Holstein

John Donoghue

One of the coefficients that parametrizes the chiral Lagrangian of QCD is expressible in terms of a sum rule for which the integrand is known from experiment. We confront two model calculations of this coeScient with the behavior of the data. The model related to vector dominance reproduces the sumrule behavior very well, whereas a one-loop chiral quark model calculation fails badly. The sum rule allows one to identify those ingredients which are needed to make the quark method more realistic. 


Mass Ratios Of Light Quarks, John Donoghue, Barry Holstein, Daniel Wyler Dec 1991

Mass Ratios Of Light Quarks, John Donoghue, Barry Holstein, Daniel Wyler

John Donoghue

We derive a consistent set of light quark mass ratios which are compatible with the available constraints of chiral symmetry treated to next-to-leading order. Also required as input is resonance saturation of a set of low-energy amplitudes, in particular for the pion and kaon electromagnetic mass difference. The results (mz +m„) /m, =1/15.5, (mz —m„)/m, =1/29 are modestly different from previous values, and resolve the long-standing puzzle of the g 3pi decay rate. 


Two Component Semileptonic Form Factors, Gustavo Burdman, John Donoghue Dec 1991

Two Component Semileptonic Form Factors, Gustavo Burdman, John Donoghue

John Donoghue

In the semileptonic decays of a heavy quark to a light quark, present models disagree in an essential fashion concerning the shape of the form factors. Both the heavy quark limit of QCD and dispersion relations suggest that the correct form factors contain two distinct contributions. We discuss these as applied to the B->piev and B->pev decays. We also describe the inconsistencies of available phenomenological models and discuss how they must be modified.


Optical Transformations In Three-Space: Simulations With A Pc, Raymond G. Wilson, Sean M. Mccreary, Jeffrey L. Thompson Dec 1991

Optical Transformations In Three-Space: Simulations With A Pc, Raymond G. Wilson, Sean M. Mccreary, Jeffrey L. Thompson

Raymond Wilson

Using Fourier transform and convolution techniques, it is illustrated how all aspects of Fraunhofer diffraction of virtually any aperture real or complex can be calculated and displayed in two- and three-space using an IBM-compatible PC. Details of program commands using software Matlab are illustrated as well as results of plotting software Surfer. Fresnel diffraction is illustrated using Fourier transformation.


Nuclear Emp Hardening Approach As The Basis For Unified Electromagnetic Environmental Effects Protection, George H. Baker Iii Dec 1991

Nuclear Emp Hardening Approach As The Basis For Unified Electromagnetic Environmental Effects Protection, George H. Baker Iii

George H Baker

Operation DESERT STORM demonstrated the clear military advantage that was provided by our sophisticated electronic C4I and weapons systems. High tech means so dominate the battlefield that the outcome of future conflicts could be decided by electronics attrition rather than human casualties. However, the electromagnetic threat landscape is highly complex. The already formidable list of environments (EMI, lighting, ESD, EMP, HERO, TEMPEST, EW, etc.) is lengthened by emerging threats from high power microwave (HPM) and ultra-wide band (UWB) electromagnetic weapons. Many of these environments overlap in the frequency and amplitude of the electrical stresses they create.

The large number of ...


Sliding-Mode Observers Based On Equivalent Control Method, Sergey V. Drakunov Dec 1991

Sliding-Mode Observers Based On Equivalent Control Method, Sergey V. Drakunov

Sergey V. Drakunov

No abstract provided.


Multi-Ball Collisions, Terry L. Smith, Jay S. Huebner Dec 1991

Multi-Ball Collisions, Terry L. Smith, Jay S. Huebner

Jay S Huebner

Explanation to use the "double-ball" demonstration as a model for the supernova core bounce.


Union Of Chiral And Heavy Quark Symmetries, John Donoghue Dec 1991

Union Of Chiral And Heavy Quark Symmetries, John Donoghue

John Donoghue

We describe the chiral symmetric couplings of pions to heavy mesons (B or D), valid in the portion of phase space where the pions have low momentum. In order to include consistently all low energy excitations, the vector mesons (B* or D*) must appear explicitly in the effective lagrangian. The result is then invariant under both the chiral and heavy quark symmetries. We include matrix elements relevant for various weak decays.