Internal Flow Simulation of High-Performance Solid Rockets using a k-ω Turbulence Model

For technological reasons many high-performance solid rocket motors are made from segmented propellant grains with non-uniform port geometry. In this paper parametric studies have been carried out to examine the geometric dependence of transient flow features in solid rockets with non-uniform ports. Numerical computations have been carried out in an inert simulator of solid propellant rocket motor with the aid of a standard k-ωturbulence model. It was seen that the damping of the temperature fluctuation is faster in solid rocket with convergent port than with divergent port geometry. We inferred that the damping of the flow fluctuations using the port geometry is a meaningful objective for the suppression and control of the instability and/or pressure/thrust oscillations during the starting transient of solid rockets.     

Low temperature micro Raman and laser induced upconversion and downconversion spectra of europium doped silver tungstate Ag<Subscript>2−3x</Subscript>Eu<Subscript>x</Subscript>WO<Subscript>4</Subscript> nanorods

All the red emitting europium-doped silver tungstate α-Ag_2?3xEu_xWO₄ (x = 0.01–0.08 mol) phosphor reported herein crystalise as nanorods. The nanorods were structurally characterised by X-ray powder diffraction, Rietveld refinement, low temperature (20 to ?190 °C) micro-Raman spectroscopy . The morphology of the nanorods reported herein was confirmed by field emission scanning electron microscopy. The optical properties were studied using low temperature (20 to ?190 °C) high resolution laser excited upconversion and downconversion luminescence.     

Pattern conserving data structure and algorithms for computations on dendritic trees

The linked list is offered as a pattern conserving data structure, useful for storing neuronal dendritic trees. A BASIC language algorithm is described. Modifications of this algorithm for building linked lists, graphing dendritic trees, and tarry ordering trees are presented. Brief mention is made of the last in first out stack as a alternative data structure for computations on dendritic trees.     

Compact effector optics for processing in limited physical access situations

A major advantage of fiber-optic beam delivery in laser materials processing is the ability to guide the laser power to the location where it is needed, leaving the laser itself remote and protected from the process. This is of special importance if the processing is to be performed in a hazardous environment. Particular problems are faced by the nuclear industry where weld repair and surface treatment work are required inside radioactive installations. By use of fiber beam delivery, only part of the delivery system and effector optics become contaminated, but the expensive laser system does not. However, in many cases the region where repair is required is not only radioactive but has only limited physical access, e.g., inside tubes or into corners, which prevents use of standard effector optics. We present a new design to deal with such constraints of a 2-mm outer diameter employing a hollow waveguide and gas shielding. This design is optically characterized and its performance assessed in welding and surface treatment applications. The potential of this compact effector optics in limited physical access situations is clearly demonstrated.     

Discovering applications of higher order functions through proof planning

The close association between higher order functions (HOFs) and algorithmic skeletons is a promising source of automatic parallelisation of programs. A theorem proving approach to discovering HOFs in functional programs is presented. Our starting point is proof planning, an automated theorem proving technique in which high-level proof plans are used to guide proof search. We use proof planning to identify provably correct transformation rules that introduce HOFs. The approach has been implemented in the Clam proof planner and tested on a range of examples. The work was conducted within the context of a parallelising compiler for Standard ML.Received February 2001Revised March 2004 and November 2004Accepted November 2004 by D. J. Cooke