نتایج جستجو برای: wigner function
تعداد نتایج: 1217365 فیلتر نتایج به سال:
In this paper the authors will try to discuss the applicability of Wigner-Ville Distribution for the digital analysis of auscultatory sounds. First of all, thte issues related to computer aided diagnosis are presented. Next, the methodology of research is shown and subsequently, the types of sounds are described. Another element of this work is the presentation of issues related to the digital ...
We consider a set of operators x̂ = (x̂1, . . . , x̂N ) with diagonal representatives P (n) in the space of generalized coherent states |n〉 : x̂ = ∫ dμ(n)P (n)|n〉〈n|. We regularize the coherent-state path integral as a limit of a sequence of averages 〈 〉L over polygonal paths with L vertices n1...L. The distribution of the path centroid P̄ = 1 L ∑L l=1 P (nl) tends to the Wigner function W (x), the ...
Boltzmann equation was successfully used for transport description and modeling in conventional semiconductor devices from the early development of semiconductor technology. Due to a rapid down scaling of transistor dimensions, with the 90 nm technology node being already industrially implemented, quantum effects becomes more pronounced, and the question of going beyond the semiclassical approa...
Much of the discussion of decoherence has been in terms of a particle moving in one dimension that is placed in an initial superposition state (a Schrödinger ”cat” state) corresponding to two widely separated wave packets. Decoherence refers to the destruction of the interference term in the quantum probability function. Here, we stress that a quantitative measure of decoherence depends not onl...
Classical molecular dynamics (MD) is a well established and powerful tool in various fields of science, e.g. chemistry, plasma physics, cluster physics and condensed matter physics. Objects of investigation are few-body systems and many-body systems as well. The broadness and level of sophistication of this technique is documented in many monographs and reviews, see for example [1, 2]. Here we ...
The Wigner function is a quasiprobability density over phase space (for reviews, see Lee[1], Cohen[2], or Hillery et al.[3]; a quasiprobability is generally not positive semi-definite), so in a quantum field theory setting it is not manifestly Lorentz covariant. Quasiprobabilities are conceptually interesting partly because Arthurs-Kelly type interpretations of positive definite Husimi function...
Based on a linear systems approach, we derive the Wigner distribution function (WDF) of a 4f imager with a volume holographic three-dimensional pupil; then we obtain the WDF of the volume hologram itself by using the shearing properties of the WDF. Two common configurations, plane and spherical wave reference volume holograms, are examined in detail. The WDF elucidates the shift variant nature ...
Coherent transport in mesoscopic devices is well described by the Schrödinger equation supplemented by open boundary conditions. When electronic devices are operated at room temperature, however, a realistic transport model needs to include carrier scattering. In this work, the kinetic equation for the Wigner function is employed as a model for dissipative quantum transport. Carrier scattering ...
This paper introduces a novel method of speech epoch extraction using a modified Wigner-Ville distribution. The Wigner-Ville distribution is an efficient speech representation tool with which minute speech variations can be tracked precisely. In this paper, epoch detection/extraction using accurate energy tracking, noise robustness, and the efficient speech representation properties of a modifi...
This paper presents an analysis of the representation of instantaneous frequency using time-frequency distributions of energy density domain. Similarity to the ”ideal” instantaneous frequency presentation is chosen as a criterion for comparison of various distributions. Although all the commonly used distributions suffer from the artifacts along frequency axis, it is shown that the Wigner distr...
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