8,270 research outputs found
The role of critical current on point contact Andreev Reflection spectrum between a normal metal and a superconductor
The point contact spectrum between a normal metal and a superconductor often
shows unexpected sharp dips in the conductance at voltage values larger than
the superconducting energy gap. These dips are not predicted in the
Blonder-Tinkham-Klapwizk (BTK) theory, commonly used to analyse these contacts.
We present here a systematic study of these dips in a variety of contacts
between different combinations of a superconductor and a normal metal. From the
correlation between the characteristics of these dips with the contact area, we
can surmise that such dips are caused by the contact not being in the ballistic
limit. An analysis of the possible errors introduced while analysing such a
spectrum with the standard BTK model is also presented.Comment: 16 pages, PS, figure include
Superstrings in type IIB R-R plane-wave in semi-light-cone gauge and conformal invariance
We reconsider the analysis done by Kazama and Yokoi in arXiv:0801.1561
(hep-th). We find that although the right vacuum of the theory is the one
associated to massless normal ordering (MNO), phase space normal ordering (PNO)
plays crucial role in the analysis in the following way. While defining the
quantum energy-momentum (EM) tensor one needs to take into account the field
redefinition relating the space-time field and the corresponding world-sheet
coupling. We argue that for a simple off-shell ansatz for the background this
field redefinition can be taken to be identity if the interaction term is
ordered according to PNO. This definition reproduces the correct physical
spectrum when the background is on-shell. We further show that the right way to
extract the effective equation of motion from the Virasoro anomaly is to first
order the anomaly terms according to PNO at a finite regularization parameter
\eps and then take the \eps \to 0 limit. This prescription fixes an
ambiguity in taking the limit for certain bosonic and fermionic contributions
to the Virasoro anomaly and is the natural one to consider given the above
definition of the EM tensor.Comment: 22 page
Nonlinear translational symmetric equilibria relevant to the L-H transition
Nonlinear z-independent solutions to a generalized Grad-Shafranov equation
(GSE) with up to quartic flux terms in the free functions and incompressible
plasma flow non parallel to the magnetic field are constructed
quasi-analytically. Through an ansatz the GSE is transformed to a set of three
ordinary differential equations and a constraint for three functions of the
coordinate x, in cartesian coordinates (x,y), which then are solved
numerically. Equilibrium configurations for certain values of the integration
constants are displayed. Examination of their characteristics in connection
with the impact of nonlinearity and sheared flow indicates that these
equilibria are consistent with the L-H transition phenomenology. For flows
parallel to the magnetic field one equilibrium corresponding to the H-state is
potentially stable in the sense that a sufficient condition for linear
stability is satisfied in an appreciable part of the plasma while another
solution corresponding to the L-state does not satisfy the condition. The
results indicate that the sheared flow in conjunction with the equilibrium
nonlinearity play a stabilizing role.Comment: 26 pages, 16 figure
Characterization and comparative evaluation of novel planar electromagnetic sensors
The characterization of three types of novel planar electromagnetic sensors: 1) meander; 2) mesh; and 3) interdigital configuration, has been studied and their comparative performance has been evaluated based on their areas of applications. All of them are suitable for inspection and evaluation of system properties without destroying them. The experiments on fabricated sensors have been conducted and the results are presented here. The target application is to use a mixture of different types of sensors to detect plasti
A low-cost sensing system for quality monitoring of dairy products
The dairy industry is in need of a cost-effective, highly reliable, very accurate, and fast measurement system to monitor the quality of dairy products. This paper describes the design and fabrication works undertaken to develop such a system. The techniques used center around planar electromagnetic sensors operating with radio frequency excitation. Computer-aided computation, being fast, facilitates on-line monitoring of the quality. The sensor technology proposed has the ability to perform volumetric penetrative measurements to measure properties throughout the bulk of the product
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