154,188 research outputs found
Engineering the accurate distortion of an object's temperature-distribution signature
It is up to now a challenge to control the conduction of heat. Here we
develop a method to distort the temperature distribution signature of an object
at will. As a result, the object accurately exhibits the same temperature
distribution signature as another object that is predetermined, but actually
does not exist in the system. Our finite element simulations confirm the
desired effect for different objects with various geometries and compositions.
The underlying mechanism lies in the effects of thermal metamaterials designed
by using this method. Our work is of value for applications in thermal
engineering.Comment: 11 pages, 4 figure
A Note on Pretzelosity TMD Parton Distribution
We show that the transverse-momentum-dependent parton distribution, called as
Pretzelosity function, is zero at any order in perturbation theory of QCD for a
single massless quark state. This implies that Pretzelosity function is not
factorized with the collinear transversity parton distribution at twist-2, when
the struck quark has a large transverse momentum. Pretzelosity function is in
fact related to collinear parton distributions defined with twist-4 operators.
In reality, Pretzelosity function of a hadron as a bound state of quarks and
gluons is not zero. Through an explicit calculation of Pretzelosity function of
a quark combined with a gluon nonzero result is found.Comment: improved explanation, published version in Phys. Lett.
Image Properties of Embedded Lenses
We give analytic expressions for image properties of objects seen around
point mass lenses embedded in a flat CDM universe. An embedded lens in
an otherwise homogeneous universe offers a more realistic representation of the
lens's gravity field and its associated deflection properties than does the
conventional linear superposition theory. Embedding reduces the range of the
gravitational force acting on passing light beams thus altering all quantities
such as deflection angles, amplifications, shears and Einstein ring sizes.
Embedding also exhibits the explicit effect of the cosmological constant on
these same lensing quantities. In this paper we present these new results and
demonstrate how they can be used. The effects of embedding on image properties,
although small i.e., usually less than a fraction of a percent, have a more
pronounced effect on image distortions in weak lensing where the effects can be
larger than 10%. Embedding also introduces a negative surface mass density for
both weak and strong lensing, a quantity altogether absent in conventional
Schwarzschild lensing. In strong lensing we find only one additional quantity,
the potential part of the time delay, which differs from conventional lensing
by as much as 4%, in agreement with our previous numerical estimates.Comment: 17 pages, 6 figure
Comment on "Superconducting gap anisotropy vs. doping level in high-T_c cuprates" by C. Kendziora et al, PRL 77, 727 (1996)
In a recent paper Kendziora et al concluded that the superconducting gap in
overdoped Bi-2212 is isotropic. From data obtained from electronic Raman
scattering measurements, their conclusion was based on the observation that
pair breaking peaks occured at approximately the same frequency in different
scattering geometries and that the normalized scattering intensity at low
energies was strongly depleted. We discuss a different interpretation of the
raw data and present new data which is consistent with a strongly anisotropic
gap with nodes. The spectra can be successfully described by a model for Raman
scattering in a d_{x^{2}-y^{2}} superconductor with spin fluctuations and
impurity scattering included.Comment: 1 page revtex plus 1 postscript figur
Investigation of a novel elastic-mechanical wheel transmission under light duty conditions
A novel 'Elastic Engagement and Friction Coupled' (EEFC) mechanical transmission has been proposed recently in which the power is transmitted through elastic tines on the surfaces of the driving and driven wheels. This study introduces new variations of EEFC mechanical wheel transmission ( broadly emulating a gear-pair) with small contact areas for use under light duty conditions. Because a drive of this type inevitably has a strong statistical component, theoretical analysis of the geometrical and mechanical relationships has been attempted by using linear modeling and empirical weightings. Several simple forms of the EEFC wheel transmission are tested under limiting ( slip) conditions for transmission force and transmission coefficients against normal load. Normalized standard deviation of these parameters is used to summarize noise performance. Models and experiments are in reasonable agreement, suggesting that the model parameters reflect important design considerations. EEFC transmissions appear well suited to force regimes of a few tenths of a newton and to have potential for use in, for example, millimetre-scale robots
Transonic Shocks In Multidimensional Divergent Nozzles
We establish existence, uniqueness and stability of transonic shocks for
steady compressible non-isentropic potential flow system in a multidimensional
divergent nozzle with an arbitrary smooth cross-section, for a prescribed exit
pressure. The proof is based on solving a free boundary problem for a system of
partial differential equations consisting of an elliptic equation and a
transport equation. In the process, we obtain unique solvability for a class of
transport equations with velocity fields of weak regularity(non-Lipschitz), an
infinite dimensional weak implicit mapping theorem which does not require
continuous Frechet differentiability, and regularity theory for a class of
elliptic partial differential equations with discontinuous oblique boundary
conditions.Comment: 54 page
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