No abstract

No abstract

No abstract

Recently Jammalamadaka and Mangalam [2003. Non-parametric estimation for middle censored data. J. Nonparametric Statist. 15, 253--265] introduced a general censoring scheme called the "middle-censoring'' scheme in non-parametric set up. In this paper we consider this middlecensoring scheme when the lifetime distribution of the items is exponentially distributed and the censoring mechanism is independent and non-informative. In this set up, we derive the maximum likelihood estimator and study its consistency and asymptotic normality properties. We also derive the Bayes estimate of the exponential parameter under a gamma prior. Since a theoretical construction of the credible interval becomes quite difficult, we propose and implement Gibbs sampling technique to construct the credible intervals. Monte Carlo simulations are performed to evaluate the small sample behavior of the techniques proposed. A real data set is analyzed to illustrate the practical application of the proposed methods.

The charge transport properties of bulk heterojunction solar cells formed by blending poly-(3-hexylthiophene) (P3HT) and [6,6] phenyl C61 butyric acid methyl ester (PCBM) were improved by doping with single walled carbon nanotubes (SWNTs). The SWNTs used were not functionalized, and contained both metallic and semiconducting tubes. Their work function was found to be 4.89 eV. Unlike P3HT:PCBM interface, the P3HT:SWNT interface has been inefficient for charge generation. Using SWNTs at concentrations below 1 wt. %, the solar cell efficiency increased from 2.86% to 3.52% for 80 nm devices and from 2% to 3% in 125 nm devices at low light intensities. In both cases, the increment is because of higher fill factor with no change in short circuit current density and open circuit voltage. At higher light intensities, a 43% increase in fill factor and a 37% increase in short circuit current density were obtained, which doubled the efficiency. These improvements were primarily because of reduced recombination through improved charge extraction by SWNTs.