Physics Commons^™

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 the effective …

Work-Function Anisotropies As An Origin Of Long-Range Surface Forces, Nancy Burnham, R Colton, H Pollock

Nancy A. Burnham

Unusual effects noticed in previous force microscopy data are explained by a model based on work-function anisotropies and their associated patch charges. Measurable forces between macroscopic bodies can be due to the interaction of patch charges, with important consequences in the fields of surface forces, contact mechanics, adhesion, Schottky barriers, and the surface properties of insulators.

The Elastic Moduli Of A Sheet Containing Circular Holes, Anthony Day, K. Snyder, E. Garboczi, M. Thorpe

Anthony Roy Day

We apply computer simulation techniques to obtain the clastic moduli of a matrix containing circular holes. As the area fraction of holes increases, the Young's modulus of the composite decreases from E0 until it eventually vanishes at the percolation threshold. We study three distinct geometries: (a) periodically centered circular holes on a honeycomb lattice, (b) periodically centered circular holes on a triangular lattice, and (c) randomly centered circular holes. All three cases have the same dilute limit that can be calculated exactly. By examining the narrow necks between adjacent circles, we have calculated the critical behavior for the regular cases …

Quark-Antiquark Condensates In Strong Magnetic Fields, Alec Schramm, Berndt Muller, Stefan Schramm

Alec J Schramm

We discuss the effect of large external magnetic fields on the QCD vacuum structure. We show that the deformed vacuum leads to substantial changes in the hadronic spectrum.

W Boson Condensation In P-P Collisions?, Alec Schramm, Stefan Schramm, Berndt Muller

Alec J Schramm

We address the question of whether W+/- boson condensation can occur in high-energy collisions.

Chiral Invariance And Electroweak Interactions Of Pions And Kaons, Br Holstein

Barry R Holstein

Electroweak interactions of pions and kaons are studied in the context of chiral perturbation theory. We demonstrate that the effective Lagrangian framework allows a consistent and predictive picture of such processes as well as a succinct way in which to represent the many previous studies of these reactions which have been performed using chiral models.

Displacement, Velocity, And Frames Of Reference: Phenomenographic Studies Of Students’ Understanding And Some Implications For Teaching And Assessment, John Bowden, Gloria Dall'alba, Elaine Martin, D Laurillard, Ference Marton, Geoff Masters, Paul Ramsden, Andrew Stephanou, E Walsh

Prof Geoff Masters AO

Student understanding of fundamental concepts in kinematics has been explored using the phenomenographic research method. University and high schoolphysics students were interviewed and their understandings of displacement, velocity, and frames of reference have been analyzed in particular problem contexts. Descriptions of the different ways students understand the concepts have been developed and relations between the different levels of understanding have been identified. The data highlight the contextual nature of learning and the need for teachers to focus on the nature of student understanding in specific contexts using questions that require qualitative explanation by students. In particular, it is demonstrated that …

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

Raymond Wilson

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

Sergey V. Drakunov

No abstract provided.

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.