361 research outputs found
Novel architecture for human re-identification with a two-stream neural network and attention ,echanism
This paper proposes a novel architecture that utilises an attention mechanism in conjunction with multi-stream convolutional neural networks (CNN) to obtain high accuracy in human re-identification (Reid). The proposed architecture consists of four blocks. First, the pre-processing block prepares the input data and feeds it into a spatial-temporal two-stream CNN (STC) with two fusion points that extract the spatial-temporal features. Next, the spatial-temporal attentional LSTM block (STA) automatically fine-tunes the extracted features and assigns weight to the more critical frames in the video sequence by using an attention mechanism. Extensive experiments on four of the most popular datasets support our architecture. Finally, the results are compared with the state of the art, which shows the superiority of this approach
Casimir interactions of an object inside a spherical metal shell
We investigate the electromagnetic Casimir interactions of an object
contained within an otherwise empty, perfectly conducting spherical shell. For
a small object we present analytical calculations of the force, which is
directed away from the center of the cavity, and the torque, which tends to
align the object opposite to the preferred alignment outside the cavity. For a
perfectly conducting sphere as the interior object, we compute the corrections
to the proximity force approximation (PFA) numerically. In both cases the
results for the interior configuration match smoothly onto those for the
corresponding exterior configuration.Comment: 4 pages, 3 figure
Constraints on stable equilibria with fluctuation-induced forces
We examine whether fluctuation-induced forces can lead to stable levitation.
First, we analyze a collection of classical objects at finite temperature that
contain fixed and mobile charges, and show that any arrangement in space is
unstable to small perturbations in position. This extends Earnshaw's theorem
for electrostatics by including thermal fluctuations of internal charges.
Quantum fluctuations of the electromagnetic field are responsible for
Casimir/van der Waals interactions. Neglecting permeabilities, we find that any
equilibrium position of items subject to such forces is also unstable if the
permittivities of all objects are higher or lower than that of the enveloping
medium; the former being the generic case for ordinary materials in vacuum.Comment: 4 pages, 1 figur
Casimir potential of a compact object enclosed by a spherical cavity
We study the electromagnetic Casimir interaction of a compact object
contained inside a closed cavity of another compact object. We express the
interaction energy in terms of the objects' scattering matrices and translation
matrices that relate the coordinate systems appropriate to each object. When
the enclosing object is an otherwise empty metallic spherical shell, much
larger than the internal object, and the two are sufficiently separated, the
Casimir force can be expressed in terms of the static electric and magnetic
multipole polarizabilities of the internal object, which is analogous to the
Casimir-Polder result. Although it is not a simple power law, the dependence of
the force on the separation of the object from the containing sphere is a
universal function of its displacement from the center of the sphere,
independent of other details of the object's electromagnetic response.
Furthermore, we compute the exact Casimir force between two metallic spheres
contained one inside the other at arbitrary separations. Finally, we combine
our results with earlier work on the Casimir force between two spheres to
obtain data on the leading order correction to the Proximity Force
Approximation for two metallic spheres both outside and within one another.Comment: 12 pages, 6 figure
Casimir Force at a Knife's Edge
The Casimir force has been computed exactly for only a few simple geometries,
such as infinite plates, cylinders, and spheres. We show that a parabolic
cylinder, for which analytic solutions to the Helmholtz equation are available,
is another case where such a calculation is possible. We compute the
interaction energy of a parabolic cylinder and an infinite plate (both perfect
mirrors), as a function of their separation and inclination, and ,
and the cylinder's parabolic radius . As , the proximity force
approximation becomes exact. The opposite limit of corresponds to a
semi-infinite plate, where the effects of edge and inclination can be probed.Comment: 5 pages, 3 figures, uses RevTeX; v2: expanded conclusions; v3: fixed
missing factor in Eq. (3) and incorrect diagram label (no changes to
results); v4: fix similar factor in Eq. (16) (again no changes to results
Casimir spring and compass: Stable levitation and alignment of compact objects
We investigate a stable Casimir force configuration consisting of an object
contained inside a spherical or spheroidal cavity filled with a dielectric
medium. The spring constant for displacements from the center of the cavity and
the dependence of the energy on the relative orientations of the inner object
and the cavity walls are computed. We find that the stability of the force
equilibrium can be predicted based on the sign of the force, but the torque
cannot be.Comment: 5 pages, 4 figure
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A Review of Techniques on Gait-Based Person Re-Identification
Copyright (c) 2023 Babak Rahi, Maozhen Li and Man Qi. Person re-identification at a distance across multiple non-overlapping cameras has been an active research area for years. In the past ten years, short-term Person re-identification techniques have made great strides in accuracy using only appearance features in limited environments. However, massive intra-class variations and inter-class confusion limit their ability to be used in practical applications. Moreover, appearance consistency can only be assumed in a short time span from one camera to the other. Since the holistic appearance will change drastically over days and weeks, the technique, as mentioned above, will be ineffective. Practical applications usually require a long-term solution in which the subject's appearance and clothing might have changed after the elapse of a significant period. Facing these problems, soft biometric features such as Gait has stirred much interest in the past years. Nevertheless, even Gait can vary with illness, ageing and emotional states, walking surfaces, shoe types, clothes types, carried objects (by the subject) and even environment clutters. Therefore, Gait is considered as a temporal cue that could provide biometric motion information. On the other hand, the shape of the human body could be viewed as a spatial signal which can produce valuable information. So extracting discriminative features from both spatial and temporal domains would benefit this research. This article examines the main approaches used in gait analysis for re-identification over the past decade. We identify several relevant dimensions of the problem and provide a taxonomic analysis of current research. We conclude by reviewing the performance levels achievable with current technology and providing a perspective on the most challenging and promising research directions.This research received no external funding
Classical Casimir interaction in the plane-sphere geometry
We study the Casimir interaction in the plane-sphere geometry in the
classical limit of high temperatures. In this limit, the finite conductivity of
the metallic plates needs to be taken into account. For the Drude model, the
classical Casimir interaction is nevertheless found to be independent of the
conductivity so that it can be described by a single universal function
depending only on the aspect ratio where is the interplate distance
and the sphere radius. This universal function differs from the one found
for perfect reflectors and is in principle amenable to experimental tests. The
asymptotic approach of the exact result to the Proximity Force Approximation
appears to be well fitted by polynomial expansions in .Comment: Updated version with minor modifications and addition of a referenc
Fluctuation induced quantum interactions between compact objects and a plane mirror
The interaction of compact objects with an infinitely extended mirror plane
due to quantum fluctuations of a scalar or electromagnetic field that scatters
off the objects is studied. The mirror plane is assumed to obey either
Dirichlet or Neumann boundary conditions or to be perfectly reflecting. Using
the method of images, we generalize a recently developed approach for compact
objects in unbounded space [1,2] to show that the Casimir interaction between
the objects and the mirror plane can be accurately obtained over a wide range
of separations in terms of charge and current fluctuations of the objects and
their images. Our general result for the interaction depends only on the
scattering matrices of the compact objects. It applies to scalar fields with
arbitrary boundary conditions and to the electromagnetic field coupled to
dielectric objects. For the experimentally important electromagnetic Casimir
interaction between a perfectly conducting sphere and a plane mirror we present
the first results that apply at all separations. We obtain both an asymptotic
large distance expansion and the two lowest order correction terms to the
proximity force approximation. The asymptotic Casimir-Polder potential for an
atom and a mirror is generalized to describe the interaction between a
dielectric sphere and a mirror, involving higher order multipole
polarizabilities that are important at sub-asymptotic distances.Comment: 19 pages, 7 figure
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