1,721,139 research outputs found
Quantum vortex creep: Hall and dissipative tunneling
No full textWithin the framework of the path-integral approach, we study the quantum vortex creep for the situation where both the Hall and the dissipative dynamics are simultaneously present. We calculate the relaxation rate and the crossover temperature separating the thermal activation and the quantum tunneling processes for anisotropic or multilayer superconductors. The results are compared with the available experimental data. (C) 1998 Elsevier Science B.V. All rights reserved
Electron-hole cotunneling effect in coupled single-electron transistors
No full textWe have found theoretically that parallel coupled single-electron transistors undergo a unique crossover from a cotunneling-only state to a predominantly sequential-tunneling state. As a result of the competition between the cotunneling and the sequential tunneling in the course of the crossover, a current dip instead of the usual current peak is observed
Quantum theory of nucleation in magnetic films
No full textEmploying two sublattice model, quantum nucleation has been studied in ferromagnetic or antiferromagnetic thin film by applying an external magnetic field at an arbitrary angle. For antiferromagnetic film with non-compensated sublattices the crossover from the ferromagnetic to antiferromagnetic quantum nucleation is discussed. It is found that quantum nucleation is more pronounced in antiferromagnetic film than in ferromagnetic one. (C) 2001 Elsevier Science B.V. All rights reserved
Quantum coherence in biaxial nanomagnets with a large transverse magnetic field
No full textWe study quantum coherence of the biaxial spin system with a large magnetic field along an arbitrary direction in the plane of hard and medium axes. Within the framework of the instanton method we present the analytic formula of the oscillation rate as a function of magnitude and direction of the magnetic field, and discuss its thermal effect. These features are expected to be tested in existing experimental techniques
Thickness-profile measurement of transparent thin-film layers by white-light scanning interferometry
No full textWhite-light scanning interferometry is increasingly used for precision profile metrology of engineering surfaces, but its current applications are limited primarily to opaque surfaces with relatively simple optical reflection behavior. A new attempt is made to extend the interferometric method to the thickness-profile measurement of transparent thin-film layers. An extensive frequency-domain analysis of multiple reflection is performed to allow both the top and the bottom interfaces of a thin-film layer to be measured independently at the same time by the nonlinear least-squares technique. This rigorous approach provides not only point-by-point thickness probing but also complete volumetric film profiles digitized in three dimensions. (C) 1999 Optical Society of America
Development of an Efficient Eigenproblem Solver for Optimizing Structural Dynamics of a Large Size Finite Element Model
No full text
A geometry constraint handling technique for stiffener layout optimization problem
Full text linkBeam stiffeners have frequently been used for raising natural frequencies of base structures. In stiffener layout optimization problems, most of the previous researches considering the position and/or the length of the stiffener as design variables dealt with structures having just simple convex shapes such as a square or rectangle. The reason was because concave shape structures have difficulties in formulating geometry constraints. In this paper, a new geometry constraint handling technique, which can define both convex and concave feasible regions and measure a degree of geometry constraint violation, was proposed. Evolution strategies (ESs) was utilized as an optimization tool. In addition, the constraint-handling technique of EVOSLINOC (EVOlution Strategies for scalar optimization with LInear and NOnlinear Constraints) was utilized to solve constrained optimization problems. From numerical examples, the proposed geometry constraint handling technique was verified and proved that the technique can easily be applied to structures in not only convex but also concave shapes, even with a protrusion or interior holes. (c) 2004 Elsevier Ltd. All rights reserved
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