A model for step‐stress accelerated life testing

Modern technology is producing high reliability products. Life testing for such products under normal use condition takes a lot of time to obtain a reasonable number of failures. In this situation a step‐stress procedure is preferred for accelerated life testing. In this paper we assume a Weibull and Lognormal model whose scale parameter depends upon the present level as well as the age at the entry in the present stress level. On the basis of that we propose a parametric model to the life distribution for step‐stress testing and suggest a suitable design to estimate the parameters involved in the model. A simulation study has been done by the proposed model based on maximum likelihood estimation. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2003     

India’s Taliban Dilemma: To Contain or to Engage?

India’s Afghanistan policy in the 1990s is termed a zero-sum game of influence with Pakistan. New Delhi’s aversion to the pro-Pakistan Taliban regime is considered a marker of this rivalry. This paper revisits India’s approach towards Afghanistan and examines if New Delhi was necessarily averse to engaging with pro-Pakistan political factions during 1990s. Based on fresh primary interviews with former Indian policymakers, media archives, and official reports, the paper shows that India engaged with and accommodated pro-Pakistan factions after the Soviet withdrawal in 1989 until 1996. The Taliban’s rise to power in Kabul in September 1996 challenged India’s engage-with-all approach. Nonetheless, the decision to sever ties with the Taliban and to bolster anti-Taliban factions was highly debated in New Delhi. Many in India saw the Taliban as a militant Islamist force sponsored by Pakistan. For others, however, it was an ethno-nationalist movement representing Pashtun interests, and not necessarily under Islamabad’s control.     

Analysis of down times of jib cranes—A stochastic approach

In this paper a case study dealing with the maintenance problem of jib cranes is presented. A jib crane is viewed as a complex system whose performance is observed as a single realization over period of time. After pointing out limitations of existing stochastic models to analyze the observed realization a new family of bivariate stochastic processes is introduced. The data of jib crane is analyzed using new model and cross‐validated using part of the data set. It is noted that the new family of stochastic processes is useful to analyze bivariate data where one of the variables is finitely valued and the other is nonnegative and continuous. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 231–243, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10006