6,854 research outputs found
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
Structural studies of phosphorus induced dimers on Si(001)
Renewed focus on the P-Si system due to its potential application in quantum
computing and self-directed growth of molecular wires, has led us to study
structural changes induced by P upon placement on Si(001)-. Using
first-principles density functional theory (DFT) based pseudopotential method,
we have performed calculations for P-Si(001) system, starting from an isolated
P atom on the surface, and systematically increasing the coverage up to a full
monolayer. An isolated P atom can favorably be placed on an {\bf M} site
between two atoms of adjacent Si dimers belonging to the same Si dimer row. But
being incorporated in the surface is even more energetically beneficial due to
the participation of the {\bf M} site as a receptor for the ejected Si. Our
calculations show that up to 1/8 monolayer coverage, hetero-dimer structure
resulting from replacement of surface Si atoms with P is energetically
favorable. Recently observed zig-zag features in STM are found to be consistent
with this replacement process. As coverage increases, the hetero-dimers give
way to P-P ortho-dimers on the Si dimer rows. This behavior is similar to that
of Si-Si d-dimers but are to be contrasted with the Al-Al dimers, which are
found between adjacent Si dimers rows and in a para-dimer arrangement. Unlike
Al-Si system P-Si does not show any para to ortho transition. For both systems,
the surface reconstruction is lifted at about one monolayer coverage. These
calculations help us in understanding the experimental data obtained using
scanning tunneling microscope.Comment: To appear in PR
The Central Charge of the Warped AdS^3 Black Hole
The AdS/CFT conjecture offers the possibility of a quantum description for a
black hole in terms of a CFT. This has led to the study of general AdS^3 type
black holes with a view to constructing an explicit toy quantum black hole
model. Such a CFT description would be characterized by its central charge and
the dimensions of its primary fields. Recently the expression for the central
charges (C_L, C_R) of the CFT dual to the warped AdS^3 have been determined
using asymptotic symmetry arguments. The central charges depend, as expected,
on the warping factor. We show that topological arguments, used by Witten to
constrain central charges for the BTZ black hole, can be generalized to deal
with the warped AdS^3 case. Topology constrains the warped factor to be
rational numbers while quasinormal modes are conjectured to give the dimensions
of primary fields. We find that in the limit when warping is large or when it
takes special rational values the system tends to Witten's conjectured unique
CFT's with central charges that are multiples of 24.Comment: 6 pages, Latex fil
Phase Mixing of Nonlinear Plasma Oscillations in an Arbitrary Mass Ratio Cold Plasma
Nonlinear plasma oscillations in an arbitrary mass ratio cold plasma have
been studied using 1-D particle-in-cell simulation. In contrast to earlier work
for infinitely massive ion plasmas it has been found that the oscillations
phase mix away at any amplitude and that the rate at which phase mixing occurs,
depends on the mass ratio () and the amplitude. A
perturbation theoretic calculation carried upto third order predicts that the
normalized phase mixing time depends on the amplitude
and the mass ratio as . We have confirmed this scaling in our simulations and
conclude that stable non-linear oscillations which never phase mix, exist only
for the ideal case with and . These cold plasma results
may have direct relevance to recent experiments on superintense laser beam
plasma interactions with applications to particle acceleration, fast ignitor
concept etc.Comment: pp 10 and two figures in PS forma
Hypoxia in the northern Gulf of Mexico: Does the science support the Plan to Reduce, Mitigate, and Control Hypoxia?
We update and reevaluate the scientific information on the distribution, history, and causes of continental shelf hypoxia that supports the 2001 Action Plan for Reducing, Mitigating, and Controlling Hypoxia in the Northern Gulf of Mexico (Mississippi River/Gulf of Mexico Watershed Nutrient Task Force 2001), incorporating data, publications, and research results produced since the 1999 integrated assessment. The metric of mid-summer hypoxic area on the Louisiana-Texas shelf is an adequate and suitable measure for continued efforts to reduce nutrients loads from the Mississippi River and hypoxia in the northern Gulf of Mexico as outlined in the Action Plan. More frequent measurements of simple metrics (e.g., area and volume) from late spring through late summer would ensure that the metric is representative of the system in any given year and useful in a public discourse of conditions and causes. The long-term data on hypoxia, sources of nutrients, associated biological parameters, and paleoindicators continue to verify and strengthen the relationship between the nitrate-nitrogen load of the Mississippi River, the extent of hypoxia, and changes in the coastal ecosystem (eutrophication and worsening hypoxia). Multiple lines of evidence, some of them representing independent data sources, are consistent with the big picture pattern of increased eutrophication as a result of long-term nutrient increases that result in excess carbon production and accumulation and, ultimately, bottom water hypoxia. The additional findings arising since 1999 strengthen the science supporting the Action Plan that focuses on reducing nutrient loads, primarily nitrogen, through multiple actions to reduce the size of the hypoxic zone in the northern Gulf of Mexico
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