22,395 research outputs found
Design and breadboard evaluation of the SPS reference phase control system concept
The total breadboard system includes one pilot transmitter, one pilot receiver, nine phase distribution units, and two power transponders. With this complement of equipment, segments of a typical phase distribution system can be assembled to facilitate the evaluation of significant system parameters. The achievable accuracy of a large phase distribution system, the sensitivity of the system to parameter variations, and the limitations of commercially available components in such applications were determined
Search for gamma rays of energy 10(15) eV from Cygnus X-3
Finite flux of excess radiation of energy 10 to the 15th power has been reported by two groups from the direction of Cygnus X-3, with the characteristic periodicity of 4.8 hrs. Samorski and Stamm find that the muon content of the showers generated by this excess radiation is about 77% of that in normal cosmic ray showers, whereas the expectation for gamma ray showers is less than 10%. It is thus difficult to understand the nature of the radiation arriving from the direction of Cygnus X-3. Samorski and Stamm measured the muon densities close to the core (approx. 10 m), where contamination due to other components is severe. Even though this does not explain the high ratio of muon densities, measurements should be carried out away from the core to establish the nature of the radiation. In order to establish the signal from Cygnus X-3 and its muon content with better statistical significance, an extensive air shower array, specifically designed for this purpose was operated at Kolar Gold Fields (longitude: 78 deg .3 E; latitude: + 12 deg .95; atmospheric depth: 920 q/square centimeters) since September, 1984. The details of the array and the accuracy of arrival direction measurements are discussed
Electronic phase separation in the rare earth manganates, (La1-xLnx)0.7Ca0.3MnO3 (Ln = Nd, Gd and Y)
All the three series of manganates showsaturation magnetization
characteristic of ferromagnetism, with the ferromagnetic Tc decreasing with
increasing in x up to a critical value of x, xc (xc = 0.6, 0.3, 0.2
respectively for Nd, Gd, Y). For x > xc, the magnetic moments are considerably
smaller showing a small increase around TM, the value of TM decreasing slightly
with increase in x or decrease in . The ferromagnetic compositions (x xc)
show insulator-metal (IM) transitions, while the compositions with x > xc are
insulating. The magnetic and electrical resistivity behavior of these
manganates is consistent with the occurrence of phase separation in the
compositions around xc, corresponding to a critical average radius of the
A-site cation, , of 1.18 A. Both Tc and TIM increase linearly when < rA
> > or x xc as expected of a homogenous ferromagnetic phase. Both Tc
and TM decrease linearly with the A-site cation size disorder at the A-site as
measured by the variance s2. Thus, an increase in s2 favors the insulating AFM
state. Percolative conduction is observed in the compositions with > <
rAc >. Electron transport properties in the insulating regime for x > xc
conforms to the variable range hopping mechanism. More interestingly, when x >
xc, the real part of dielectric constant (e') reaches a high value (104-106) at
ordinary temperatures dropping to a very small (~500) value below a certain
temperature, the value of which decreases with decreasing frequency.Comment: 27 pages; 11 figures, Submitted to J.Phys:Condens Matte
Mg II Absorption Systems in SDSS QSO Spectra
We present the results of a MgII absorption-line survey using QSO spectra
from the SDSS EDR. Over 1,300 doublets with rest equivalent widths greater than
0.3\AA and redshifts were identified and measured. We
find that the rest equivalent width ()
distribution is described very well by an exponential function , with
and \AA. Previously reported power law
fits drastically over-predict the number of strong lines. Extrapolating our
exponential fit under-predicts the number of \AA systems,
indicating a transition in near \AA. A combination of
two exponentials reproduces the observed distribution well, suggesting that
MgII absorbers are the superposition of at least two physically distinct
populations of absorbing clouds. We also derive a new redshift parameterization
for the number density of \AA lines:
and \AA. We find that the distribution steepens with decreasing redshift,
with decreasing from \AA at to \AA at
. The incidence of moderately strong MgII lines does not
show evidence for evolution with redshift. However, lines stronger than
\AA show a decrease relative to the no-evolution prediction with
decreasing redshift for . The evolution is stronger for
increasingly stronger lines. Since in saturated absorption lines is an
indicator of the velocity spread of the absorbing clouds, we interpret this as
an evolution in the kinematic properties of galaxies from moderate to low z.Comment: 50 pages, 26 figures, accepted for publication in Ap
Understanding of the phase transformation from fullerite to amorphous carbon at the microscopic level
We have studied the shock-induced phase transition from fullerite to a dense
amorphous carbon phase by tight-binding molecular dynamics. For increasing
hydrostatic pressures P, the C60-cages are found to polymerise at P<10 GPa, to
break at P~40 GPa and to slowly collapse further at P>60 GPa. By contrast, in
the presence of additional shear stresses, the cages are destroyed at much
lower pressures (P<30 GPa). We explain this fact in terms of a continuum model,
the snap-through instability of a spherical shell. Surprisingly, the relaxed
high-density structures display no intermediate-range order.Comment: 5 pages, 3 figure
MOBILE ROBOT SELF-PLANNING AND NAVIGATION BASED ON ARTIFICIAL LANDMARK LOCALIZATION METHOD AND BINOCULAR STEREO VISION
This paper describes design of artificial landmark based on colour model used for Self-planning in unstructured environment to a robot for its movement. This method provides less error in estimation when compared to existing methods. This project is an investigation into building a system which visually detects artificial landmarks to determine the landmarks within a location, decipher their position within that location and track the landmark throughout the location using Binocular stereo vision
Droplet Fluctuations in the Morphology and Kinetics of Martensites
We derive a coarse grained, free-energy functional which describes droplet
configurations arising on nucleation of a product crystal within a parent. This
involves a new `slow' vacancy mode that lives at the parent-product interface.
A mode-coupling theory suggests that a {\it slow} quench from the parent phase
produces an equilibrium product, while a {\it fast} quench produces a
metastable martensite. In two dimensions, the martensite nuclei grow as
`lens-shaped' strips having alternating twin domains, with well-defined front
velocities. Several empirically known structural and kinetic relations drop out
naturally from our theory.Comment: 4 pages, REVTEX, and 3 .eps figures, compressed and uuencoded,
Submitted to Phys. Rev. Let
Scanning Electron Probe Microanalysis
Scanning electron probe microanalysis has grown over the pastthree decades into a powerful technique for the microchemicalcharacterisation of materials. This paper describes the principles andvarious features of a typical microanalyser, and illustrates its uniquecapabilities in the study of materials by means of selected case histories
Quality Assessment of Ambulatory Electrocardiogram Signals by Noise Detection using Optimal Binary Classification
In order to improve the diagnostic capability in Ambulatory Electrocardiogram signal and to reduce the noise signal impacts, there is a need for more robust models in place. In terms of improvising to the existing solutions, this article explores a novel binary classifier that learns from the features optimized by fusion of diversity assessment measures, which performs Quality Assessment of Ambulatory Electrocardiogram Signals (QAAES) by Noise Detection. The performance of the proposed model QAAES has been scaled by comparing it with contemporary models. Concerning performance analysis, the 10-fold cross-validation has been carried on a benchmark dataset. The results obtained from experiments carried on proposed and other contemporary models for cross-validation metrics have been compared to signify the sensitivity, specificity, and noise detection accuracy
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