Effects of Fermion Flavor on Exciton Condensation in Double Layer Systems

We use fermionic path integral quantum Monte Carlo to study the effects of fermion flavor on the physical properties of dipolar exciton condensates in double layer systems. We find that by including spin in the system weakens the effective interlayer interaction strength, yet this has very little effect on the Kosterlitz-Thouless transition temperature. We further find that, to obtain the correct description of screening, it is necessary to account for correlation in both the interlayer and intralayer interactions. We show that while the excitonic binding cannot completely surpress screening by additional fermion flavors, their screening effectiveness is reduced leading to a much higher transition temperatures than predicted with large-N analysis.Comment: 4 pages, 3 figure

Design of wideband vibration-based electromagnetic generator by means of dual-resonator

This paper describes the design of a wideband electromagnetic energy harvester that utilizes a novel dual-resonator method to improve the operational frequency range of the vibration-based generator. The device consists of two separate resonator systems (coil and magnet), which each comply with their respective resonance frequencies. This is because both resonators are designed in such a way that both magnet and coil components will oscillate at an additive phase angle, and hence create greater relative motion between the two dominating resonance frequencies, which realizes the wideband generator. Each resonator system consists of a distinctive cantilever beam, one attached with four magnets and steel keepers, the other attached with a copper coil and stainless steel holder as the free end mass. Both cantilevers are clamped and fitted to a common base that is subjected to a vibration source. Basic analytical models are derived and a numerical model is implemented in MATLAB-Simulink. Electromagnetic, structural modal and static mechanical analysis for the design of the prototype are completed using ANSYS finite element tools. For a 0.8 m s−2 acceleration, the open-loop voltage obtained from the experiment shows a good correlation with those from the simulation. Peak induced voltage is measured to be 259.5Vrms as compared to 240.9Vrms from the simulator at 21.3 Hz, which implies an error range of 7.7%. The results also indicate that there is a maximum of 58.22% improvement in the induced voltage within the intermediate region which occurs at the intersection point between the output response plots of two single resonator generators

The Effect of Cooling Rate on the Ductile- Brittle Bend-transition Temperature of Chromium Wire

Effect of cooling rate on ductile-brittle bend-transition temperature of chromium wir

Investigation of mechanical properties of chromium, chromium-rhenium, and derived alloys Twenty-third quarterly progress report, Oct. 1, 1965 - Mar. 31, 1966

Mechanical properties of chromium-rhenium alloy wire

Simultaneous sparse approximation via greedy pursuit

A simple sparse approximation problem requests an approximation of a given input signal as a linear combination of T elementary signals drawn from a large, linearly dependent collection. An important generalization is simultaneous sparse approximation. Now one must approximate several input signals at once using different linear combinations of the same T elementary signals. This formulation appears, for example, when analyzing multiple observations of a sparse signal that have been contaminated with noise. A new approach to this problem is presented here: a greedy pursuit algorithm called simultaneous orthogonal matching pursuit. The paper proves that the algorithm calculates simultaneous approximations whose error is within a constant factor of the optimal simultaneous approximation error. This result requires that the collection of elementary signals be weakly correlated, a property that is also known as incoherence. Numerical experiments demonstrate that the algorithm often succeeds, even when the inputs do not meet the hypotheses of the proof

Behavior of large-scale rectangular columns confined with FRP composites

This paper focuses on axially loaded, large-scale rectangular RC columns confined with fiber-reinforced polymer (FRP) wrapping. Experimental tests are conducted to obtain the stress-strain response and ultimate load for three field-size columns having different aspect ratios and/or corner radii. Effective transverse FRP failure strain and the effect of increasing confining action on the stress-strain behavior are examined. Existing strength models, the majority of which were developed for small-scale specimens, are applied to predict the structural response. Since some of them fail to adequately characterize the test data and others are complex and require significant calculation, a simple design-oriented model is developed. The new model is based on the confinement effectiveness coefficient, an aspect ratio coefficient, and a corner radius coefficient. It accurately predicts the axial ultimate strength of the large-scale columns at hand and, when applied to the small-scale columns studied by other investigators, produces reasonable results

Improved sparse approximation over quasi-incoherent dictionaries

This paper discusses a new greedy algorithm for solving the sparse approximation problem over quasi-incoherent dictionaries. These dictionaries consist of waveforms that are uncorrelated "on average," and they provide a natural generalization of incoherent dictionaries. The algorithm provides strong guarantees on the quality of the approximations it produces, unlike most other methods for sparse approximation. Moreover, very efficient implementations are possible via approximate nearest-neighbor data structure