35,406 research outputs found
Bulk superconductivity in Bi4O4S3 revealed by specific heat measurement
Specific heat experiments on a well-characterized polycrystalline sample of
the BiS2 based superconductor Bi4O4S3 revealed that it shows a crear specific
heat anomaly at about Tc = 4.4 K, consistent with Tc from the resistivity and
dc susceptibility. This observation indicates the superconductivity of Bi4O4S3
to be bulk in nature
Anomalous microwave response of high-temperature superconducting thin-film microstrip resonator in weak dc magnetic fields
We have studied an anomalous microwave (mw) response of superconducting
YBa_{2}Cu_{3}O_{7-delta} (YBCO) microstrip resonators in the presence of a weak
dc magnetic field, H_{dc}. The surface resistance (R_{s}) and reactance (X_{s})
show a correlated non-monotonic behaviour as a function of H_{dc}. R_{s} and
X_{s} were found to initially decrease with elevated H_{dc} and then increase
after H_{dc} reaches a crossover field, H_{c}, which is independent of the
amplitude and frequency of the input mw signal within the measurements. The
frequency dependence of R_{s} is almost linear at fixed H_{dc} with different
magnitudes (H_{c}). The impedance plane analysis
demonstrates that r_{H}, which is defined as the ratio of the change in
R_{s}(H_{dc}) and that in X_{s}(H_{dc}), is about 0.6 at H_{dc}<H_{c} and 0.1
at H_{dc}>H_{c}. The H_{dc} dependence of the surface impedance is
qualitatively independent of the orientation of H_{dc}.Comment: REVTex 3.1, 5 pages, 6 EPS figures, submitted to Physica
Bioenergy
In contrast to fossil fuels, the use of biofuels for thermal applications and power generation provides significant environmental advantages. Since Bio-Oil is extracted from organic wastes, it is a CO2 Neutral technique and can generate CO2 credits. In the present scenario energy sectors and individual entrepreneurs can opt a new way of power generation using the most abundantly available renewable source of energy in the form of Biomass wastes. Rice husks, groundnut shells, powdery husks, sugar cane (baggasse), corn cobs are some of the carbonaceous biomass fuels. Among the Biomass resources Coconuts are the abundant renewable resource of Energy available all around the world. Literature review showed that limited research studies had been carried out on yielding the product from coconut shell pyrolysis. The objective of present work is to envisage the methodology of generating power from biomass wastes using pyrolysis techniques. Pyrolysis is a thermal decomposition technique which decomposes carbonaceous biowastes into liquids, gases, and char (solid residue) in the absence of oxygen. Bio-Oil can be used as a fuel in diesel engine with modifications in fuel pump, linings, and the injection system. High carbonaceous Bio-Oil extracted from pyrolysis of coconut shell can be used in oil burners for thermal applications and in combustion boilers to generate electricity. Also can be blended with standard diesel fuels to form a pollution free green bio-diesel fuel. Hence biofuels based power generation system would be a boon to the energy crisis in an environmental friendly way using coconut shells for rural electrification
Measurement of Scattering Rate and Minimum Conductivity in Graphene
The conductivity of graphene samples with various levels of disorder is
investigated for a set of specimens with mobility in the range of
cm/V sec. Comparing the experimental data with the
theoretical transport calculations based on charged impurity scattering, we
estimate that the impurity concentration in the samples varies from cm. In the low carrier density limit, the conductivity exhibits
values in the range of , which can be related to the residual
density induced by the inhomogeneous charge distribution in the samples. The
shape of the conductivity curves indicates that high mobility samples contain
some short range disorder whereas low mobility samples are dominated by long
range scatterers.Comment: 4 pages 4 figure
Sparse Feature Extraction for Activity Detection Using Low-Resolution IR Streams
In this paper, we propose an ultra-low-resolution infrared (IR) images based activity recognition method which is suitable for monitoring in elderly care-house and modern smart home. The focus is on the analysis of sequences of IR frames, including single subject doing daily activities. The pixels are considered as independent variables because of the lacking of spatial dependencies between pixels in the ultra-low resolution image. Therefore, our analysis is based on the temporal variation of the pixels in vectorised sequences of several IR frames, which results in a high dimensional feature space and an "n<; <; p" problem. Two different sparse analysis strategies are used and compared: Sparse Discriminant Analysis (SDA) and Sparse Principal Component Analysis (SPCA). The extracted sparse features are tested with four widely used classifiers: Support Vector Machines (SVM), Random Forests (RF), K-Nearest Neighbours (KNN) and Logistic Regression (LR). To prove the availability of the sparse features, we also compare the classification results of the noisy data based sparse features and non-sparse based features respectively. The comparison shows the superiority of sparse methods in terms of noise tolerance and accuracy
Predictable Disruption Tolerant Networks and Delivery Guarantees
This article studies disruption tolerant networks (DTNs) where each node
knows the probabilistic distribution of contacts with other nodes. It proposes
a framework that allows one to formalize the behaviour of such a network. It
generalizes extreme cases that have been studied before where (a) either nodes
only know their contact frequency with each other or (b) they have a perfect
knowledge of who meets who and when. This paper then gives an example of how
this framework can be used; it shows how one can find a packet forwarding
algorithm optimized to meet the 'delay/bandwidth consumption' trade-off:
packets are duplicated so as to (statistically) guarantee a given delay or
delivery probability, but not too much so as to reduce the bandwidth, energy,
and memory consumption.Comment: 9 page
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