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Jain M.,Indian Institute of Technology Roorkee | Gupta R.,Institute of Basic Science
Computers and Industrial Engineering | Year: 2013

The present investigation deals with the reliability analysis of a repairable system consisting of single repairman who can take multiple vacations. The system failure may occur due to two types of faults termed as major and minor. When the system has failed due to minor faults, it is perfectly recovered by the repairman. If the system failure is due to major faults, there are some recovery levels/procedures that recover the faults imperfectly with some probability. However, the system cannot be repaired in 'as good as new' condition. It is assumed that the repairman can perform some other tasks when either the system is idle or waiting for recovery from the faults. The life time of the system and vacation time of the repairman are assumed to be exponential distributed while the repair time follows the general distribution. By assuming the geometric process for the system working/vacation time, the supplementary variable technique and Laplace transforms approach are employed to derive the reliability indices of the system. We propose the replacement policy to maximize the expected profit after a long run time. The validity of the analytical results is justified by taking numerical illustrations. © 2013 Elsevier Ltd. All rights reserved. Source


Jain M.,Indian Institute of Technology Roorkee | Gupta R.,Institute of Basic Science
International Journal of Reliability, Quality and Safety Engineering | Year: 2011

The redundancy is a widely spread technology of building computing systems that continue to operate satisfactorily in the presence of faults occurring in hardware and software components. The principle objective of applying redundancy is achieve reliability goals subject to techno-economic constraints. Due to a plenty of applications arising virtually in both industrial and military organizations especially in embedded fault tolerance systems including telecommunication, distributed computer systems, automated manufacturing systems, etc., the reliability and its dependability measures of redundant computer-based systems have become attractive features for the systems designers and production engineers. However, even with the best design of redundant computer-based systems, software and hardware failures may still occur due to many failure mechanisms leading to serious consequences such as huge economic losses, risk to human life, etc. The objective of present survey article is to discuss various key aspects, failure consequences, methodologies of redundant systems along with software and hardware redundancy techniques which have been developed at the reliability engineering level. The methodological aspects which depict the required steps to build a block diagram composed of components in different configurations as well as Markov and non-Markov state transition diagram representing the structural system has been elaborated. Furthermore, we describe the reliability of a specific redundant system and its comparison with a non redundant system to demonstrate the tractability of proposed models and its performance analysis. © 2011 World Scientific Publishing Company. Source


Singh P.K.,Institute of Basic Science
Indian Journal of Pure and Applied Physics | Year: 2010

Pressure P, bulk modulus K and its first and second pressure derivatives K′ and K″, and the Grüneisen parameter y and its volume derivative q for NaCl crystal down to a compression, V/Vo = 0.65 have been studied. These properties have been calculated along different isotherms at selected temperatures in the range 300-1050 K using Holzapfel AP2 equation of state. The results obtained have been found to be in good agreement with the data reported in the literature. A reciprocal üf-primed equation, quadratic in PIK, has been found to satisfy the relationship between P, K and K' along with different isotherms, and is also consistent with the values of K" at different compressions and temperatures. Volume dependence of the Grüneisen parameter has been discussed in terms of the existing recent formulations. Source


Singh P.K.,Institute of Basic Science
Indian Journal of Pure and Applied Physics | Year: 2011

K-primed equations of state for solids are more advantageous than the conventional pressure-volume relationships for studying higher derivatives of bulk modulus and thermoelastic properties. The reciprocal K-primed quadratic equation is consistent with the first-principles results determined from the augmented plane wave method for metals, non-metals and diatomic solids, has been studied in the present paper. The values of pressure, bulk modulus and its pressure derivative based on the first-principles in case of different solids are found to satisfy the reciprocal K-primed quadratic equation. Source


Singh P.K.,Institute of Basic Science
Indian Journal of Physics | Year: 2012

We have studied high derivative thermoelastic properties such as the pressure derivatives of bulk modulus and the volume dependence of the Grüneisen parameter in case of MgO for a wide range of pressures down to compression V/V0 = 0.6, and temperatures up to 3,000 K approaching the melting temperature. We have used the isothermal pressure- volume equation of state (EOS) based on the adapted polynomial expansion of second order (AP2) due to Holzapfel. The results for the P-V-T relationships and high derivative properties have been obtained using the Holzapfel AP2 EOS. The pressure derivatives of bulk modulus and volume derivatives of the Grüneisen parameter have been determined using the free volume theory. A relationship between the pressure derivative of bulk modulus and the ratio of pressure and bulk modulus has been found to hold good. © 2012 IACS. Source

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