Discrete distributions with bathtub-shaped hazard rates

Discrete distributions with bathtub shaped hazard rates have recently become of interest in reliability modelling and analysis. In the present work, we address the problem of obtaining distributions having such hazard rates when the lifetime is discrete. The methods considered here include discretising continuous bathtub models, construction using the score function, construction from decreasing hazard rate distributions and some other methods currently available in the continuous case. We discuss properties and applications of the discretised quadratic hazard model which has a bathtub shaped hazard rate

Damping in Torsional Vibrations of Embedded Footings

The existing theoretical models to explain the dynamic behavior of embedded footings, overestimate the real response by neglecting damping forces which are inevitable as a result of slip at the interface of the embedded footing and soil. Many researchers in the field of Soil Dynamics have suggested that the inclusion of friction damping and internal damping in the mathematical model is necessary to improve the reliability of theoretical predictions. In this paper, results of the experimental investigations on full scale model embedded footings subjected to torsional mode of vibration have been presented. The results have been analyzed making use of three theoretical models, as developed by, Novak and Sachs (1973); Sankaran et al (1978) and Sankaran et al (1980). The importance of d-ping in predicting the dynamic response is brought out by a comparison of field vibratory test data with the corresponding values predicted by each of the above mentioned theoretical models

Comparison of Computed and Measured Performance of a Pulsed Inductive Thruster Operating on Argon Propellant

Pulsed inductive plasma accelerators are electrodeless space propulsion devices where a capacitor is charged to an initial voltage and then discharged through a coil as a high-current pulse that inductively couples energy into the propellant. The field produced by this pulse ionizes the propellant, producing a plasma near the face of the coil. Once a plasma is formed if can be accelerated and expelled at a high exhaust velocity by the Lorentz force arising from the interaction of an induced plasma current and the magnetic field. A recent review of the developmental history of planar-geometry pulsed inductive thrusters, where the coil take the shape of a flat spiral, can be found in Ref. [1]. Two concepts that have employed this geometry are the Pulsed Inductive Thruster (PIT)[2, 3] and the Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD)[4]. There exists a 1-D pulsed inductive acceleration model that employs a set of circuit equations coupled to a one-dimensional momentum equation. The model was originally developed and used by Lovberg and Dailey[2, 3] and has since been nondimensionalized and used by Polzin et al.[5, 6] to define a set of scaling parameters and gain general insight into their effect on thruster performance. The circuit presented in Fig. 1 provides a description of the electrical coupling between the current flowing in the thruster I1 and the plasma current I2. Recently, the model was upgraded to include an equation governing the deposition of energy into various modes present in a pulsed inductive thruster system (acceleration, magnetic flux generation, resistive heating, etc.)[7]. An MHD description of the plasma energy density evolution was tailored to the thruster geometry by assuming only one-dimensional motion and averaging the plasma properties over the spatial dimensions of the current sheet to obtain an equation for the time-evolution of the total energy. The equation set governing the dynamics of the coupled electrodynamic-current sheet system is composed of first-order, coupled ordinary differential equations that can be easily solved numerically without having to resort to much more complex 2-D finite element plasma simulations

Cold bonded pelletization of iron ore fines

Cold bonding processes have been developed with a view to conserve energy in pellet hardening step. The incorporation of the reductant and fluxes in the pellet also ensures a blast furnace burden that is hanogeneous with resultant smooth operations of the furnace. The present paper deals with the studies conducted on tha production of ccmposite iron are pellets using iron are fines, leco char. hydrated lime and natural silica flour as well as rice husk silica. The results indicate that the composite pellets with rice husk has superior strength compared to the pellets with natural crystalline form of silica. Studies on CaO-HZD-rice husk silica reaction systffil revealed that a gel like calciun silicate hydrate (CSH-I) is formed during the steaming operation that is responsible for the strengthaning of the composite pellet. The studies on the kinetics of the hydrothermal reaction revealed that the reaction is diffusion controlled and the product fanned is calcium silicate hydrate. The reducibility studies indicated good reducibility with minimun swelling

Instability in turmeric (Curcuma Zonga L.) production in India

The factors responsible for the instability in turmeric (Curcuma longa) production in India were studied. Instability analysis showed that yield instability increased marginally in the eighties. However, the decrease in area instability more than compensated for the increase in yield instablitity resulting in reduction of production instability. Decomposition analysis showed that yield instability was the dominant factor affecting production instability. Therefore future development programmes should envisage stabilisation of yield which will stabilise production. The yield instability could be reduced by investing on research towards evolving of cultivars suitable for existing agroclimatic conditions. &nbsp

Twisted Conjugacy Classes in Lattices in Semisimple Lie Groups

Given a group automorphism $\phi:\Gamma\to \Gamma$, one has an action of $\Gamma$ on itself by $\phi$-twisted conjugacy, namely, $g.x=gx\phi(g^{-1})$. The orbits of this action are called $\phi$-conjugacy classes. One says that $\Gamma$ has the $R_\infty$-property if there are infinitely many $\phi$-conjugacy classes for every automorphism $\phi$ of $\Gamma$. In this paper we show that any irreducible lattice in a connected semi simple Lie group having finite centre and rank at least 2 has the $R_\infty$-property.Comment: 6 page

Correlations between biometrical characters in vanilla (Vanilla planifolia Andrews)

A study was undertaken to fmd out the extent of association among growth attributes of vanilla (Vanilla planifolia) and to develop a model for determination of vine length based on biometrical observations. The characters, number of nodes, number of leaves and internodal length were significantly and positively correlated with vine length. The multiple regression equation derived exhibited a precision of 82.5 per cent. &nbsp

Correlations between biometrical characters in vanilla (Vanilla planifolia Andrews)

A study was undertaken to fmd out the extent of association among growth attributes of vanilla (Vanilla planifolia) and to develop a model for determination of vine length based on biometrical observations. The characters, number of nodes, number of leaves and internodal length were significantly and positively correlated with vine length. The multiple regression equation derived exhibited a precision of 82.5 per cent. &nbsp