NISCAIR Online Periodicals Repository Collection: IJEMS Vol.14(1) [February 2007]

Design of Routh column polynomials for instability analysis of linear time invariant continuous systems

Mon, 29 Jan 2007 22:58:59 GMT

Title: Design of Routh column polynomials for instability analysis of linear time invariant continuous systems

Authors: Sivanandam, S N; Deepa, S N

Abstract: The analysis of unstable linear time-invariant continuous systems, employing the elements of columns from Routh table is brought out in this work. A linear time invariant continuous system represented in the form of characteristic equation can be analyzed for stability or instability with the help of Routh table. The elements of this table are generated using Routh multiplication rules and the sign changes in the first column, as well sign change anywhere in the table indicates unstable situation. If the sign change occurs at the end of the first column, it involves more computation. As a result, in this work, the other columns of the Routh array are studied, based on which Pseudo-Routh Polynomials are constructed and the instability is analyzed. It is to be noted that the information residing from the last column only traverses towards the first column. If the instability analysis is obtained from last column or last but one column itself, the entire Routh array need not be constructed, which helps in easier computation in higher degree polynomials. Examples are given to illustrate the proposed scheme.

Page(s): 81-86

Study of surface roughness in squeeze casting LM6 aluminium alloy using Taguchi method

Mon, 29 Jan 2007 22:58:59 GMT

Title: Study of surface roughness in squeeze casting LM6 aluminium alloy using Taguchi method

Authors: Vijian, P; Arunachalam, V P; Charles, S

Abstract: Squeeze casting combines the strength and integrity of forging with the economy and design flexibility of casting to produce components with better surface finish. The primary aim of this study was to analyze the influence of the process parameters on surface roughness in squeeze casting of LM6 aluminium alloy using Taguchi method. A three level orthogonal array L₉ (3⁴) was used to determine the S/N ratio (dB), and analysis of variance (ANOVA). The most significant process parameters affecting the surface roughness were identified using F test. The results indicated that squeeze pressure and die pre-heating temperature were the parameters responsible for causing appreciable improvement in the surface finish of the squeeze cast components.

Page(s): 7-11

Theoretical prediction of detonation pressure of CHNO high energy materials

Mon, 29 Jan 2007 22:58:59 GMT

Title: Theoretical prediction of detonation pressure of CHNO high energy materials

Authors: Keshavarz, M H

Abstract: A new simple method has been introduced to calculate maximum obtainable detonation pressure of any pure or mixed CHNO explosives. There is no need to use heat of formation and crystal density of explosive in this procedure. It is shown here how the atomic composition and structural parameters can be integrated into an empirical formula for predicting the detonation pressure of proposed explosives. Maximum performance obtained by new procedure for both pure and explosive formulations show good agreement with respect to measured detonation pressure.

Page(s): 77-80

Hydration of bamboo leaf ash blended Portland cement

Mon, 29 Jan 2007 22:58:59 GMT

Title: Hydration of bamboo leaf ash blended Portland cement

Authors: Singh, N B; Das, S S; Singh, N P; Dwivedi, V N

Abstract: Bamboo leaf ash (BLA) obtained at 600oC was found to be pozzolanic material. The pozzolanic activity was studied by using chemical methods, differential scanning calorimetry, X-ray diffraction and scanning electron microscopic techniques. Hydration behaviour of 20 wt% BLA blended ordinary Portland cement (OPC) was studied by using different experimental techniques and it was found that at 28 days of hydration the compressive strength value for 20 wt% BLA blended cement mortar was quite comparable to that of mortar made from OPC. The mechanism of pozzolanic activity has been discussed.

Page(s): 69-76