000128   Singh A K;Prabhu C M R (Faculty of Engineering and Technology, Multimedia University, Melaka, Malaysia, Email: c.m.prabu@unu.edu.my) : Design of low power SRAM cell for write/read operations. Asian J Phys 2008, 17(2), 273-8.

A new design approach for SRAM cell is proposed to reduce the power consumption/dissipation during write/read operation. Mainly used two tail transistors, one n-MOS and other p-MOS, in the respective inverter to avoid the charging or discharging of the respective nodes. The proposed circuit is simulated with the help of MICROWIND3 and DSCH 3 in advanced MOSIS technology for different size and power supplies. Our designed SRAM cell consumes approximately 50% less power than the conventional SRAM. Power dissipation is also found to be lower than the conventional SRAM. Most of the write operation is '0' and our circuit shows a better stability in the write '0' operation. In the read operations, power consumption is approximately the same as the conventional cell. The only drawback of our circuit is that it uses two extra transistors than the conventional one.

4 illus, 3 tables, 15 ref

000127   Rahman M;Choudhury P K (Faculty of Engineering, Multimedia University, Jalan Multimedia, 63100 Cyberjaya, Selangor, Malaysia, Email: pkchoudehury@yahoo.com) : Particle physics with extra dimensions: state-of-the-art. Asian J Phys 2008, 17(2), 263-72.

Extra dimensions (EDs), if they exist, have many implications in particle physics beyond the standard model (SM). They may solve the hierarchy problem without relying on supersymmetry or technicolor. The validity of string theory largely relies on the existence of EDs. Therefore, searches for EDs constitute a promising direction in particle physics. In the present article we review the state-of-the-art of the research in both theoretical and experimental arena.

41 ref

000126   Pathmanathan S S;Abdul-Rashid H A;Choudhury P K (Faculty of Engineering, Multimedia University, Cyberjaya-63100, Setangor,Malaysia, Email: pkchoudhury@yahoo.com) : An experimental investigation of double-pass erbium-doped optical amplifier with tunable band-pass filter. Asian J Phys 2008, 17(2), 241-4.

Presents an experimental investigation of the performance characteristics of a double pass erbium-doped fiber amplifier (DFA) with tunable band-pass filter (TBFs). The TBF is essentially used to suppress the undesired amplified spontaneous emission (ASE). Both co- and counter- 1480 nm pumpings are considered. Gain and noise figure of the EDFA are measured. The results show that the signal achieves a higher gain in the case of double-pass amplification with TBF. No significant improvement is achieved when co- and counter-pumpings are employed.

4 illus, 17 ref

000125   Misra D K (Electrical Engineering and Computer Science Dep, University of Wisconsin - Milwaukee, P.O. Box 784, Milwaukee, WE53201, USA, Email: misra@csd.uwm.edu) : A survey of the techniques for nondestructive electrical characterization of materials at microwave frequencies. Asian J Phys 2008, 17(2), 193-202.

Nondestructive methods for the electrical characterization of materials are desired in many industrial and scientific applications. It includes in-vivo characterization of biological mediums, in-situ measurements of various structures, and non-contact testing of disbands in composites. These methods are based on the measurement of reflection and/or transmission of electromagnetic signals interacting with the sample material. A radio frequency or microwave signal is applied to the material-under-test via a suitable sensor that is sometimes placed near the sample medium. The same sensor may be used to collect the echo signal carrying the characteristics of the sample material. Rectangular as well as circular aperture waveguides, coaxial lines, microstrip lines, coplanar waveguides, and dipole antennas have been employed for such measurements. These techniques require an electrical equivalent model of the sensor to extract the sample characteristics. Free-space methods have been used mostly at the millimeter waves and optical range where the signal beam incident on the sample is monitored to find the material properties. This paper reviews the current status of these techniques including a summary of recent admittance models of the sensor. Selected experimental and computational results are included along with the limitations of the technique.

5 illus, 2 tables, 70 ref

000124   Lakhtakia A;Polo J A (Engineering Science & Mechanics Dep, Pennsylvania State University, University Park, PA 16802, USA, Email: akhlesh@psu.edu) : Morphological influence on surface- wave propagation at the planar interface of a metal film and a columnar thin film. Asian J Phys 2008, 17(2), 185-91.

The selection of a higher vapor deposition angle when growing a columnar thin film (CTF) leads to surface-wave propagation at a planar metal-CTF interface with phase velocity of lower magnitude and shorter propagation range. Acordingly, a higher angle of plane-wave incidence is required to excite that surface wave in a modified Kretschmann configuration.

2 illus, 2 tables, 15 ref

000123   Joshi P S (NO, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400 005, Email: psj@tifr.res.in) : On the genericity of spacetime singularities. Pramana J Phys 2007, 69(1), 119-35.

Considers the genericity aspects of spacetime singularities that occur in cosmology and in gravitational collapse. The singularity theorems (that predict the occurrence of singularities in general relativity) allow the singularities of gravitational collapse to be either visible to external observers or covered by an event horizon of gravity. It is shown that the visible singularities that develop as final states of spherical collapse are generic. Some consequences of this fact are discussed.

27 ref

000122   Inderjit Singh;Kumar U;Kesari V;Jain P K;Basu B N (School of Electrical Sciences, Vellore Institute of Technology, Vellore, Email: pkjain_vns@hotmail.com) : Electromagnetic analysis of ohmic quality factor for the tapered gyrotron cavity. Asian J Phys 2008, 17(2), 289-96.

A simple electromagnetic method has been presented, by dividing the input- and output-taper sections of cavity into numbers of non-tapered circular steps, to calculate the ohmic quality factor of tapered cavity of a gyrotron. The energy stored in cavity and power loss on cavity-wall, have been estimated in sinusoidal field profile. For the typically chosen non-tapered cavity, the calculated value of ohmic quality factor, in the present paper, was found within 4% of the results calculated using two of previously published expressions. The validation/ comparison of results against simulation software: MAGIC have been made and found within 3%. Further, the effect of structure dimensions, namely, length of mid-section of the cavity, input-taper angle and output-taper angle, on value of the ohmic quality factor for a tapered gyrotron cavity have been studied. It is found that the ohmic quality factor for a tapered gyrotron cavity, other parameters remaining constant, increases with decrease of length of mid-section and input-taper angle, and with increase of output-taper angle. Out of input- and output-taper angles, the latter was found more sensitive controlling parameter for the ohmic quality factor and hence frequency selectivity as well as ohmic heating in a tapered cavity. Furthermore, the contours of length of mid-section and ohmic quality factor were plotted to provide flexibility to the designer in optimising the structure parameters of tapered cavity of a gyrotron.

4 illus, 22 ref

000121   Hossain N;Mishra V;Hasnayeen M A;Faidz A R (Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor, Malaysia, Email: faidzrahman@mmu.edu.my) : Modeling of the power budget of remotely pumped long haul OFCS incorporated with pre-EDFA and DRA. Asian J Phys 2008, 17(2), 253-62.

Focuses on the modeling of the power budget of remotely pumped long haul optical fiber communication system (OFCS) incorporated with an Erbium doped fiber amplifier in the pre-length (Pre-EOFA) and distributed Raman amplifier (DRA). Signal loss in the post- and pre-length as well as signal gain by the Pre-EOFA and ORA are simulated to determine the maximum achievable transmission distance of a remotely pumped long haul OFCS incorporated with pre-EDFA and ORA. Design parameters of pre-EOFA are optimized using the numerical simulation of EOFA rate equation model in order to optimize the pre-EOFA. ORA mathematical model is solved numerically to analyze the signal propagation characteristics through the pre-length due to ORA. The results obtained from the numerical simulation of EDFA and DRA mathematical model are used in the modeling of the power budget of remotely pumped long haul OFCS incorporated with pre-EOFA and ORA. The developed model can be used to design and analyze the performance of a long haul OFCS link and to optimize the system performance.

7 illus, 2 tables, 14 ref

000120   Dixit M;Lakhtakia A (CATMAS - Computational & Theoretical Materials Sciences Group, Enginee, Pennsylvania State University, University Park, PA 16802-6812, USA, Email: akhlesh@psu.edu) : Electrically controlled Bragg resonances of an ambichiral electro-optic structure: oblique incidence. Asian J Phys 2008, 17(2), 213-23.

The Pockels effect can increase the effective birefringence of ambichiral, electro-optic rejection filters made of maªterials with a 42m point group symmetry, when a de electric field is applied parallel to the axis of non homogeneity. The reflectances and the transmittances of such an ambichiral structure for obliquely incident plane waves are solvable through a boundary-value problem that is formulated using the frequency-domain Maxwell equations, the constitutive equations that contain the Pockels effect, and standard algebraic techniques for handling 4x4 matrix ordinary differential equations. The Bragg resonance peaks, for different circular-polarized-incidence conditions, blueshift as the angle of incidence increases. These blueshifts are unaffected by the sign of the dc electric field.

7 illus, 12 ref

000119   Das S R (Physics and Astronomy Dep, University of Kentucky, Lexington, KY 40506, USA, Email: das@pa.uky.edu) : String theory and cosmological singularities. Pramana J Phys 2007, 69(1), 93-108.

In general relativity space-like or null singularities are common: they imply that 'time' can have a beginning or end. Well-known examples are singularities inside black holes and initial or final singularities in expanding or contracting universes. In recent times, string theory is providing new perspectives of such singularities which may lead to an understanding of these in the standard framework of time evolution in quantum mechanics. Describes some of these approaches.

2 illus, 27 ref

000118   Chaubey V K (Electical & Electronics Engineering Group, Birla Institute of Technology and Sciences, Pilani-333 031, Email: vke@bits-pilani.ac.in) : Modeling and simulation of all-optical intelligent routed networks under traffic control protocols. Asian J Phys 2008, 17(2), 245-52.

The network protocol and efficient node architecture increases the data transport capability of an optical wavelength division multiplexed system. Presents a simple analytical model for an optical router capable of implementing specific routing algorithm controlled by efficient protocols. The router is modeled as a processor to implement the instructions through appropriate optical hardware components to support packet stacking, switching or routing the bursty traffic. An analytical node model has been developed to simulate the traffic throughput under the appropriate link and node operating conditions. The node performance for the source initiated and the destination initiated protocols has been reported to show the superiority of the performance through bandwidth utilization via reservation control protocols. The simulation results validate their analytical model and show that the network performance is well-controlled by the Implemented protocols and network design parameters.

6 illus, 28 ref

000117   Brill D;Khetarpal P;Kaul V (Physics Dep, University of Maryland, College Park, MD 20782, USA, Email: brill@physics.umd.edu) : Horizons in 2+1-dimensional collapse of particles. Pramana J Phys 2007, 69(1), 109-18.

A simple, geometrical construction is given for three-dimensional spacetimes with negative cosmological constant that contain two particles colliding head-on. Dependªing on parameters like particle masses and distance, the combined geometry will be that of a particle, or of a black hole. In the black hole case the horizon is calculated. It is found that the horizon typically starts at a point and spreads into a closed curve with corners, which propagate along spacelike caustics and disappear as the horizon passes the particles.

5 illus, 10 ref

000116   Ashtekar A (Institute for Gravitational Physics and Geommetry, Physics Dep, Penn State University, University Park, PA 16802, USA) : Black hole dynamics in general relativity. Pramana J Phys 2007, 69(1), 77-92.

Basic features of dynamical black holes in full, non-linear general relativity are summarized in a pedagogical fashion. Qualitative properties of the evolution of various horizons follow directly from the celebrated Raychaudhuri equation.

2 illus, 22 ref

000115   Ahmadi N;Nouri-Zonoz M (Physics Dep, University of Tehran, North Karegar Ave., Tehran 14395-547, Iran, Email: nahmadi@ut.ac.ir) : Raychaudhuri equation in quantum gravitational optics. Pramana J Phys 2007, 69(1), 147-57.

The equation of Raychaudhuri is one of the key concepts in the formulation of the singularity theorems introduced by Penrose and Hawking. Taking into account QED vacuum polarization, studies the propagation of a bundle of rays in a background gravitational field through the perturbative deformation of Raychaudhuri's equation. In a sense, this could be seen as another semiclassical study in which geometry is treated classically but matter (which means the photon here) is allowed to exhibit quantum characteristics that are encoded in its coupling to the background curvature.

1 illus, 16 ref