In real life, we often observe circular data (for example, in the fields of geology, meteorology, oceanography and medicine, among others). However, the common practice is to ignore the periodic feature of such observations employing the usual available methods, which often ends in misleading results in terms of inferential measures. The loss of statistical power is a serious issue if the method is applied to clinical trials involving human subjects. In the present article, heuristic procedures for testing equality of treatment effects are developed in the context of clinical trials with the assumption that responses are circular in nature. The developed procedures are studied empirically in terms of statistical power and are compared to relevant existing competitors. The procedures are further applied to a real clinical trial on cataract surgery.

Non-existence of distributions with constant coefficient of variation(CV) is investigated within the discrete Power Series and Modified Power Series families of distributions. The development is used to revisit and comment on the problem of existence of a better but biased estimator.

In this paper a new family of minimum divergence estimators based on the Brègman divergence is proposed, where the defining convex function has an exponential nature. These estimators avoid the necessity of using an intermediate kernel density and many of them also have strong robustness properties. It is further demonstrated that the proposed approach can be extended to construct a class of generalized estimating equations, where the pool of the resultant estimators encompass a large variety of minimum divergence estimators and range from highly robust to fully efficient based on the choice of the tuning parameters. All of the resultant estimators are M-estimators, where the defining functions make explicit use of the form of the parametric model. The properties of these estimators are discussed in detail; the theoretical results are substantiated by simulation and real data examples. It is observed that in many cases, certain robust estimators from the above generalized class provide better compromises between robustness and efficiency compared to the existing standards.

Covariate adjusted response adaptive designs are developed with ordinal categorical responses for phase III clinical trial involving multiple treatments. Stochastic ordering principle is used to order the treatments according to effectiveness and consequently allocation functions are developed by combining the cumulative odds ratios suitably. The performance of the proposed designs is investigated through relevant exact as well as large sample measures. To investigate the performance in a real situation, a real clinical trial involving lung cancer patients is further redesigned using the proposed allocation design.

The objective of Content-Based Image Retrieval (CBIR) methods is essentially to extract, from large (image) databases, a specified number of images similar in visual and semantic content to a so-called query image.To bridge the semantic gap that exists between the representation of an image by low-level features (namely, colour, shape, texture) and its high-level semantic content as perceived by humans, CBIR systems typically make use of the relevance feedback (RF) mechanism.RF iteratively incorporates user-given inputs regarding the relevance of retrieved images, to improve retrieval efficiency.One approach is to vary the weights of the features dynamically via feature reweighting.In this work, a novel approach has been proposed for improving the retrieval accuracy of CBIR system which incorporates RF based on feature reweighting using discriminant analysis.Results of a number of experiments have been presented to illustrate the significant improvement is retrieval accuracy with the proposed approach.

A number of allocation designs are developed for continuous and binary treatment outcomes to assign a higher number of subjects to the treatment doing better in course of the trial. However, if the response is circular in nature, the definition of a better treatment differs from that under the linear response and hence the already developed designs lack appropriateness. In the current work, redefining the notions of superiority, we develop an allocation function in the context of circular treatment outcomes. Using a response-adaptive route for practical implementation, we study the resulting design both theoretically and numerically and finally illustrate the performance for a real-life example on cataract surgery.

Our earlier studies using cellulose acetate membrane for the removal of radioactive species from ammonium diuranate filtrate effluents (ADUF) indicated promising performance in terms of very good decontamination factors (DF) and volume reduction factors (VRF). In view of the inherently short membrane life of cellulose acetate membrane, studies were carried out to assess the potential of polyamide (PA) based reverse osmosis (RO), nanofiltration (NF), and ultrafiltration (UF) membranes. Experiments based on real effluents corresponding to specific activity levels of microcuries/liter containing about 4% ammonium nitrate yielded decontaminated streams containing nanocuries/liter levels of radiocontaminants both for RO and NF membranes. UF membrane failed to give reasonable decontamination factors and hence was found unsuitable for the purpose. Due to very high ammonium nitrate solute rejection of PA membranes under RO condition, it was not possible to get high volume reduction factors. However, NF membranes have shown the potential to achieve very high VRF with good decontamination factors owing to their poor ammonium nitrate rejection characteristics and the consequent maintenance of permeate fluxes. The studies indicate the viability of the NF process for the treatment of ammonium diuranate filtrate effluents in large scale.

A reverse osmosis process has been found to be effective for the separation of radiocontaminants from ammonium diuranate effluents in a uranium metal plant. Pilot-plant-scale experiments were conducted using cellulosic membranes in a plate module system and actual plant effluents containing more than about 40,000. ppm of ammonium and nitrate species and having radiocontaminants corresponding to specific activities of about 10(-3) Ci/m3 beta/gamma emitters. The results indicated that more than 95% by volume of the treated effluents were within disposal limits, while the remaining contained the concentrate, which can be treated for possible containment.