Temperature and pressure dependence of 35Cl NQR in NaClO3 and Ba(ClO3)2·H2O

Pressure and temperature dependence of 35Cl nuclear quadrupole resonance (NQR) has been investigated in NaClO3 and Ba(ClO3)2·H2O. NQR frequencies are measured in the temperature range 77–300 K and up to 5 kbar pressure. The torsional frequency of the ClO3 pyramid and its variation with both pressure and temperature are evaluated from the NQR frequencies under the harmonic approximation. In general, the pressure effect on the internal motions is found to be less in Ba (ClO3)2·H2O compared to NaClO3. When the samples are cooled to 77 K the pressure coeffecient of NQR frequency becomes nearly zero in sodium chlorate, whereas it retains a value of 6 kHz kbar−1 in barium chlorate. This behaviour follows from the fact that at 77K, the torsional frequency in NaClO3 is unaffected by the application of pressure while it increases at the rate 12 cm−1 kbar−1 in Ba(ClO3)2·H2O.

Free vibration of rectangular beams of arbitrary depth

The state space approach is extended to the two dimensional elastodynamic problems. The formulation is in a form particularly amenable to consistent reduction to obtain approximate theories of any desired order. Free vibration of rectangular beams of arbitrary depth is investigated using this approach. The method does not involve the concept of the shear coefficientk. It takes into account the vertical normal stress and the transverse shear stress. The frequency values are calculated using the Timoshenko beam theory and the present analysis for different values of Poisson's ratio and they are in good agreement. Four cases of beams with different end conditions are considered.Die Zustandsraum-Technik wird auf zweidimensionale elastodynamische Probleme ausgedehnt. Die Formulierung ist besonders geeignet für die Aufstellung von Näherungstheorien beliebigen Grades. Freie Schwingungen von Rechteckbalken beliebiger Höhe wurden mit Hilfe dieser Technik untersucht. Das Verfahren umgeht den Begriff des Schubbeiwertsk. Es berücksichtigt die senkrechte Normalbeanspruchung und die Querkraft. Die Frequenzwerte werden mit Hilfe der Balkentheorie von Timoshenko und der vorliegenden Analyse berechnet, und zwar für verschiedene Werte der Querdehnzahl. Die berechneten Werte befinden sich in guter Übereinstimmung. Vier Fälle von Balken mit verschiedenen Endbedingungen werden untersucht.

Five-fold quasiperiodic tilings generated by inflated rhombuses with identical boundaries: possible application to the growth of quasicrystals

In order to generate normal Penrose tilings by inflation/deflation, decisions have to be made regarding the matching of the rhombuses/tilings with their neighbours. We show here that this decision-making problem can be avoided by adopting a deflation/inflation procedure which uses the decorated rhombuses with identical boundaries. The procedure enables both kinds of inflated rhombuses to match in any orientation along their edges. The tilings so generated are quasiperiodic. These structures appear to have a close relationship with the growth mechanism of quasicrystals.

Resonant absorption of Alfven waves and the associated phenomenon of magnetic reconnection

It is proposed that the mathematical analysis of the Alfven wave equation in inhomogeneous magnetic fields which explain the resonance absorption of Alfven surface waves near a resonant layer can also be used to show that the magnetic reconnection process can arise near the zero-frequency resonant layer driven by VLF Alfven surface waves. It is suggested that the associated phenomena of resonant absorption and magnetic reconnection can account for the recent observations of intense magnetic activity in the long-period geomagnetic micropulsation range, at cusp latitudes, during flux transfer events.

Path integral quantisation of topological field theories

Conditions for quantum topological invariance of classically topological field theories in the path integral formulation are discussed. Both the three-dimensional Chern-Simons system and a Witten-type topological field theory are shown to satisfy these conditions.

Optimal explicit terminal guidance for a launch vehicle

It is observed that general explicit guidance schemes exhibit numerical instability close to the injection point. This difficulty is normally attributed to the demand for exact injection which, in turn, calls for finite corrections to be enforced in a relatively short time. The deviations in vehicle state which need corrective maneuvers are caused by the off-nominal operating conditions. Hence, the onset of terminal instability depends on the type of off-nominal conditions encountered. The proposed separate terminal guidance scheme overcomes the above difficulty by minimizing a quadratic penalty on injection errors rather than demanding an exact injection. There is also a special requirement in the terminal phase for the faster guidance computations. The faster guidance computations facilitate a more frequent guidance update enabling an accurate terminal thrust cutoff. The objective of faster computations is realized in the terminal guidance scheme by employing realistic assumptions that are accurate enough for a short terminal trajectory. It is observed from simulations that one of the guidance parameters (P) related to the thrust steering angular rates can indicate the onset of terminal instability due to different off-nominal operating conditions. Therefore, the terminal guidance scheme can be dynamically invoked based on monitoring of deviations in the lone parameter P.

Analogues of the Wiener-Tauberian and Schwartz theorems for radial functions on symmetric spaces

We prove a Wiener Tauberian theorem for the L-1 spherical functions on a semisimple Lie group of arbitrary real rank. We also establish a Schwartz-type theorem for complex groups. As a corollary we obtain a Wiener Tauberian type result for compactly supported distributions.

The Reproducing Kernel DMS-FEM: 3D Shape Functions and Applications to Linear Solid Mechanics

We propose a family of 3D versions of a smooth finite element method (Sunilkumar and Roy 2010), wherein the globally smooth shape functions are derivable through the condition of polynomial reproduction with the tetrahedral B-splines (DMS-splines) or tensor-product forms of triangular B-splines and ID NURBS bases acting as the kernel functions. While the domain decomposition is accomplished through tetrahedral or triangular prism elements, an additional requirement here is an appropriate generation of knotclouds around the element vertices or corners. The possibility of sensitive dependence of numerical solutions to the placements of knotclouds is largely arrested by enforcing the condition of polynomial reproduction whilst deriving the shape functions. Nevertheless, given the higher complexity in forming the knotclouds for tetrahedral elements especially when higher demand is placed on the order of continuity of the shape functions across inter-element boundaries, we presently emphasize an exploration of the triangular prism based formulation in the context of several benchmark problems of interest in linear solid mechanics. In the absence of a more rigorous study on the convergence analyses, the numerical exercise, reported herein, helps establish the method as one of remarkable accuracy and robust performance against numerical ill-conditioning (such as locking of different kinds) vis-a-vis the conventional FEM.

High-pressure studies on the critical composition in Ge—As—Te glasses

High-pressure resistivity measurements have been performed on G37.5AsxTe92.5-x (x = 20, 40, 45, 50 and 55) and Ge10AsxTe90-x (x = 15, 20, 35, 40, 45 and 50) glasses. The glasses show reversible metallization behaviour under pressure. The pressure derivative of the logarithm of the resistivity of the glasses is a minimum at glass compositions corresponding to the average coordination number [r] = 2.60. This behaviour is interpreted on the basis of the existence of a critical composition in glasses with a layered structure.

Pulsed laser deposition of strontium titanate thin films for dynamic random access memory applications

Polycrystalline strontium titanate (SrTiO3) films were prepared by a pulsed laser deposition technique on p-type silicon and platinum-coated silicon substrates. The films exhibited good structural and dielectric properties which were sensitive to the processing conditions. The small signal dielectric constant and dissipation factor at a frequency of 100 kHz were about 225 and 0.03 respectively. The capacitance-voltage (C-V) characteristics in metal-insulator-semiconductor structures exhibited anomalous frequency dispersion behavior and a hysteresis effect. The hysteresis in the C-V curve was found to be about 1 V and of a charge injection type. The density of interface states was about 1.79 x 10(12) cm(-2). The charge storage density was found to be 40 fC mu m(-2) at an applied electric field of 200 kV cm(-1). Studies on current-voltage characteristics indicated an ohmic nature at lower voltages and space charge conduction at higher voltages. The films also exhibited excellent time-dependent dielectric breakdown behavior.

Stabilizing trench's algorithm to invert symmetric toeplitz matrices

Presented here is a stable algorithm that uses Zohar's formulation of Trench's algorithm and computes the inverse of a symmetric Toeplitz matrix including those with vanishing or nearvanishing leading minors. The algorithm is based on a diagonal modification of the matrix, and exploits symmetry and persymmetry properties of the inverse matrix.