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 $E_c$ 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 $^{90}$Zr and $^{208}$Pb nuclei for several Skyrme type effective nucleon-nucleon interactions having a wide range of nuclear matter incompressibility ($K_{nm} \sim 215 - 275$ MeV) and symmetry energy ($J \sim 27 - 37$ MeV) indicate that the net uncertainty ($\delta E_c \sim 0.3$ 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

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 $\kappa$ associated with isovector giant dipole resonance, the quantity $L$ which is directly related to the slope of the symmetry energy and the Landau parameter $G_0^\prime$. However, restricting $\kappa$, $L$ and $G_0^\prime$ to vary within acceptable limits reduces the maximum value for the critical density $\tilde\rho_{cr}$ by $\sim 25$. We also show that among the various quantities characterizing the symmetric nuclear matter, $\tilde\rho_{cr}$ depends strongly on the isoscalar effective mass $m^*/m$ and surface energy coefficient $E_s$. For realistic values of $m^*/m$ and $E_s$ we get $\tilde\rho_{cr} = 2\rho_0$ to $3\rho_0$ ($\rho_0 = 0.16$fm$^{-3}$).Comment: 10 pages, 3 figures. Physicsl Review C (in press