18,540 research outputs found
Management and Performance of APPLE Battery in High Temperature Environment
India's first experimental communication satellite, APPLE, carried a 12 AH Ni-Cd battery for supplying power during eclipse. Failure to deploy one of the two solar panels resulted in the battery operating in a high temperature environment, around 40 C. This also resulted in the battery being used in diurnal cycles rather than just half yearly eclipse seasons. The management and performance of the battery during its life of two years are described. An attempt to identify the probable degradation mechanisms is also made
Consequences of self-consistency violations in Hartree-Fock random-phase approximation calculations of the nuclear breathing mode energy
We provide for the first time accurate assessments of the consequences of
violations of self-consistency in the Hartree-Fock based random phase
approximation (RPA) as commonly used to calculate the energy of the
nuclear breathing mode. Using several Skyrme interactions we find that the
self-consistency violated by ignoring the spin-orbit interaction in the RPA
calculation causes a spurious enhancement of the breathing mode energy for spin
unsaturated systems. Contrarily, neglecting the Coulomb interaction in the RPA
or performing the RPA calculations in the TJ scheme underestimates the
breathing mode energy. Surprisingly, our results for the Zr and
Pb nuclei for several Skyrme type effective nucleon-nucleon
interactions having a wide range of nuclear matter incompressibility ( MeV) and symmetry energy ( MeV) indicate that
the net uncertainty ( MeV) is comparable to the
experimental one.Comment: Revtex file (11 pages), Accepted for the publication in Phys. Rev.
Feasibility and benefits of laminar flow control on supersonic cruise airplanes
An evaluation was made of the applicability and benefits of laminar flow control (LFC) technology to supersonic cruise airplanes. Ancillary objectives were to identify the technical issues critical to supersonic LFC application, and to determine how those issues can be addressed through flight and wind-tunnel testing. Vehicle types studied include a Mach 2.2 supersonic transport configuration, a Mach 4.0 transport, and two Mach 2-class fighter concepts. Laminar flow control methodologies developed for subsonic and transonic wing laminarization were extended and applied. No intractible aerodynamic problems were found in applying LFC to airplanes of the Mach 2 class, even ones of large size. Improvements of 12 to 17 percent in lift-drag ratios were found. Several key technical issues, such as contamination avoidance and excresence criteria were identified. Recommendations are made for their resolution. A need for an inverse supersonic wing design methodology is indicated
X-ray properties of the microquasar GRS 1915+105 during a variability class transition
We present a detailed X-ray study of the microquasar GRS 1915+105 during a
variability class transition observed in 2000 June with the PPCs of the Indian
X-ray Astronomy Experiment. We supplement this observation with data from the
RXTE archives. The source made a transition from a steady low-hard state to a
regular oscillatory behaviour in the light curve known as bursts or class `rho'
(Belloni et al. 2000) between 2000 May 11 and 17 and reverted back to the
low-hard state on 2000 June 27. A gradual change in the burst recurrence time
from about 75 s to about 40 s was observed which then increased to about 120 s
during the ~ 40 days of class `rho'. The regular bursts disappeared from the
X-ray light curves and the class transition was observed to occur within 1.5
hours on 2000 June 27 with the PPCs. A correlation is found between the
observed QPO frequency at 5-8 Hz in the quiescent phase and the average X-ray
intensity of the source during the class `rho'. We notice a strong similarity
between the properties of the source during the class `rho' and those during
the oscillatory phase of the observations of class `alpha'. From the timing and
spectral analysis, it is found that the observed properties of the source over
tens of days during the class `rho' are identical to those over a time scale of
a few hundreds of seconds in the class `alpha'. Examining the light curves from
the beginning of the RXTE/PCA and RXTE/ASM observations, it is found that the
change of state from radio-quiet low-hard state to high state occurs through
the X-ray classes `rho' and `alpha' which appear together during the state
transition. It is further inferred that the source switches from low-hard state
to the class `rho' through the intermediate class `alpha'.Comment: 10 pages with 9 figures, LaTex. To be appeared in MNRA
Probabilistic Super Dense Coding
We explore the possibility of performing super dense coding with
non-maximally entangled states as a resource. Using this we find that one can
send two classical bits in a probabilistic manner by sending a qubit. We
generalize our scheme to higher dimensions and show that one can communicate
2log_2 d classical bits by sending a d-dimensional quantum state with a certain
probability of success. The success probability in super dense coding is
related to the success probability of distinguishing non-orthogonal states. The
optimal average success probabilities are explicitly calculated. We consider
the possibility of sending 2 log_2 d classical bits with a shared resource of a
higher dimensional entangled state (D X D, D > d). It is found that more
entanglement does not necessarily lead to higher success probability. This also
answers the question as to why we need log_2 d ebits to send 2 log_2 d
classical bits in a deterministic fashion.Comment: Latex file, no figures, 11 pages, Discussion changed in Section
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Ultra-broad Mid-IR Supercontinuum Generation in Single, Bi and Tri Layer Graphene Nano-Plasmonic waveguides pumping at Low Input Peak Powers
This article presents four different plasmonic structures using Graphene which yielded an efficient plasmonic mode with low loss for Supercontinuum(SC) generation. At an operating wavelength of 1550 nm in these structures, we generated a multi-octave broadband SC spectrum ranging from 1.5 um-25 um at a low input peak power of 1 W. Due to pumping in the anomalous dispersion region with two Zero Dispersion Wavelengths (ZDWs) and the process of cross phase modulation with soliton fission, red-shifted dispersive waves were generated which led to large broadening from 1.5 um-25 um. Two other Supercontinua ranging from 1-10 um and 0.85-2.2 um also at low input peak powers of 2 W and 0.1 W respectively were generated. These three supercontinua are useful for applications in the fields of biomedical sensors, spectroscopy, fluorescence lifetime imaging and in the design of many other new optical devices. Furthermore, we have also discussed our results on behaviour of Graphene as a metal, even without the negative real value of dielectric constant
Critical densities for the Skyrme type effective interactions
We use the stability conditions of the Landau parameters for the symmetric
nuclear matter and pure neutron matter to calculate the critical densities for
the Skyrme type effective nucleon-nucleon interactions. We find that the
critical density can be maximized by adjusting appropriately the values of the
enhancement factor associated with isovector giant dipole resonance,
the quantity which is directly related to the slope of the symmetry energy
and the Landau parameter . However, restricting , and
to vary within acceptable limits reduces the maximum value for the
critical density by . We also show that among the
various quantities characterizing the symmetric nuclear matter,
depends strongly on the isoscalar effective mass and
surface energy coefficient . For realistic values of and we
get to (fm).Comment: 10 pages, 3 figures. Physicsl Review C (in press
Anomalous low level of cosmic ray intensity decreases observed during 1980
Past studies have revealed solar cycle changes in the sunspot activity, as well as in many other solar parameters, such as, solar flares and solar coronal holes. These solar features in turn produce the observed cyclic variations in the interplanetary plasma and fields. Both the cosmic ray intensity as well as the intensity of geomagnetic disturbances are affected by the interplanetary changes and produce 11/22 year periodicity. An anomalous situation has been noticed during the year 1980 (period of high sunspot activity), when both the geomagnetic disturbance index Ap, as well as the magnitude and number of Forbush decreases as small. Such an anomaly occurs, in spite of the fact that both the sunspot numbers and the energetic solar flares are almost maximum during the present solar cycle
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