1,342 research outputs found
Spatial dispersion and energy in strong chiral medium
Since the discovery of backward-wave materials, people have tried to realize
strong chiral medium, which is traditionally thought impossible mainly for the
reason of energy and spatial dispersion. We compare the two most popular
descriptions of chiral medium. After analyzing several possible reasons for the
traditional restriction, we show that strong chirality parameter leads to
positive energy without any frequency-band limitation in the weak spatial
dispersion. Moreover, strong chirality does not result in a strong spatial
dispersion, which occurs only around the traditional limit point. For strong
spatial dispersion where higher-order terms of spatial dispersion need to be
considered, the energy conversation is also valid. Finally, we show that strong
chirality need to be realized from the conjugated type of spatial dispersion.Comment: 6 pages, 2 figure
Axisymmetric Indentation Response of Functionally Graded Material Coating
In this chapter, the indentation response of the functionally graded material (FGM) coating is considered due to the contact between the coating and axisymmetric indenter. The mechanical properties of FGM coating is assumed to vary along the thickness direction. Three kinds of models are applied to simulate the variation of elastic parameter in the FGM coating based on the cylindrical coordinate system. The axisymmetric frictionless and partial slip contact problems are reduced to a set of Cauchy singular integral equations that can be numerically calculated by using the Hankel integral transform technique and the transfer matrix method. The effect of gradient of coating on the distribution of contact stress is presented. The present investigation will provide the guidance for the indentation experiment of coating
Gauss-Bonnet inflation with a constant rate of roll
We consider the constant-roll condition in the model of the inflaton
nonminimal coupling to the Gauss-Bonnet term. By assuming the first
Gauss-Bonnet flow parameter is a constant, we discuss the
constant-roll inflation with constant , constant and
constant , respectively. Using the Bessel function approximation, we
get the analytical expressions for the scalar and tensor power spectrum and
derive the scalar spectral index and the tensor to scalar
ratio to the first order of . By using the Planck 2018
observations constraint on and , we obtain some feasible
parameter space and show the result on the region. The
scalar potential is also reconstructed in some spectral cases
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