Identifiability of the Stochastic Frontier Models

This paper examines the identifiability of the standard single-equation stochastic frontier models with uncorrelated and correlated error components giving, inter alia, mathematical content to the notion of “near-identifiability” of a statistical model. It is seen that these models are at least locally identifiable but suffer from the “near-identifiability” problem. Our results also highlight the pivotal role played by the Signal to Noise Ratio in the “near-identifiablity” of the stochastic frontier models.Identification, Stochastic frontier model, Information Matrix, Signal to Noise Ratio

Dictionary based Image Compression via Sparse Representation

Nowadays image compression has become a necessity due to a large volume of images. For efficient use of storage space and data transmission, it becomes essential to compress the image. In this paper, we propose a dictionary based image compression framework via sparse representation, with the construction of a trained over-complete dictionary. The over-complete dictionary is trained using the intra-prediction residuals obtained from different images and is applied for sparse representation. In this method, the current image block is first predicted from its spatially neighboring blocks, and then the prediction residuals are encoded via sparse representation. Sparse approximation algorithm and the trained over-complete dictionary are applied for sparse representation of prediction residuals. The detail coefficients obtained from sparse representation are used for encoding. Experimental result shows that the proposed method yields both improved coding efficiency and image quality as compared to some state-of-the-art image compression methods

Estimation of Inefficiency using a Firm-specific Frontier Model

It has been argued that the deterministic frontier approach in inefficiency measurement has a major limitation as inefficiency is mixed with measurement error (statistical noise) in this approach. The result is that inefficiency is contaminated with noise. Later stochastic frontier approach improves the situation with allowing a statistical noise in the model which captures all other factors other than inefficiency. The stochastic frontier model has been used for inefficiency analysis despite its complicated form and estimation procedure. This paper introduced an extra parameter which estimates the amount of proportion that an error component shares in the observational error. An EM estimation approach is used for estimation of the model and a test procedure is developed to test the significance of presence of the error component in the observational error

A cross sectional study on the determinants of railway fatalities in different age groups

Background: Over the last few decades many railway accidents and fatalities have occurred in India as well as worldwide. Cities having a high economic activity and are complex spatial structures, are supported by transport systems. The evolution of mass rapid transport system in the form of sub-urban railway network has increased railway casualties in the cities as the railroads pass through residential and commercial zones.Methods:  This cross-sectional observational study was conducted at R. G. Kar medical college and hospital police Morgue attached to the department of forensic medicine and toxicology (FMT), Kolkata on the randomly selected medico legal postmortems over last 4 years.Results: Railway accidents were common in males with mean age group of 38.98 years and was almost identical with the female mean age. The accidents mostly occurred in the office hours during the day time. Chi square test of association gave significant results between the different age groups with sex and grievous injuries sustained the people. Injuries sustained by the train showed that they were found mostly over the head followed by spine and thorax. Major cause of death was due to head injuries.Conclusions: The article gives an idea about the relevant demographic profiles and association with the age-related factors that can be taken up as means to prevent the accidents

Estimation of Inefficiency using a Firm-specific Frontier Model

It has been argued that the deterministic frontier approach in inefficiency measurement has a major limitation as inefficiency is mixed with measurement error (statistical noise) in this approach. The result is that inefficiency is contaminated with noise. Later stochastic frontier approach improves the situation with allowing a statistical noise in the model which captures all other factors other than inefficiency. The stochastic frontier model has been used for inefficiency analysis despite its complicated form and estimation procedure. This paper introduced an extra parameter which estimates the amount of proportion that an error component shares in the observational error. An EM estimation approach is used for estimation of the model and a test procedure is developed to test the significance of presence of the error component in the observational error

Cost Optimal Design of a Single-Phase Dry Power Transformer

The Dry type transformers are preferred to their oil-immersed counterparts for various reasons, particularly because their operation is hazardless. The application of dry transformers was limited to small ratings in the earlier days. But now these are being used for considerably higher ratings.  Therefore, their cost-optimal design has gained importance. This paper deals with the design procedure for achieving cost optimal design of a dry type single-phase power transformer of small rating, subject to usual design constraints on efficiency and voltage regulation. The selling cost for the transformer has been taken as the objective function. Only two key variables have been chosen, the turns/volt and the height: width ratio of window, which affects the cost function to high degrees. Other variables have been chosen on the basis of designers’ experience. Copper has been used as conductor material and CRGOS as core material to achieve higher efficiency, lower running cost and compact design. The electrical and magnetic loadings have been kept at their maximum values without violating the design constraints. The optimal solution has been obtained by the method of exhaustive search using nested loops

Zinc contamination is an underestimated risk to amphibians: toxicity evaluation in tadpoles of Fejervarya limnocharis

Aquatic environments are often contaminated with zinc. Amphibian tadpoles are likely to be exposed to high concentrations of zinc present in these environments. We determined the acute and sub-chronic toxicity of ZnCl2 on Fejervarya limnocharis tadpoles under laboratory conditions. The LC50 values of ZnCl2 were found to be 5.81, 4.32, 3.79 and 3.61 mg/L at 24, 48, 72 and 96 h of exposure respectively. Long-term exposure to sub-lethal concentrations of ZnCl2 induced significant mortality in concentration and time dependent manner. Sub-lethal ZnCl2 exposure significantly altered survival, body length and body weight at metamorphosis. Micronucleus test and comet assay indicated the genotoxic potential of ZnCl2. Significant increase in DNA strand break was observed following ZnCl2 exposure equivalent to 1% of the of 24 h LC50 value. The findings indicate possible adverse to tadpoles inhabiting aquatic environments contaminated with zinc. In addition, the findings may be extrapolated to aquatic organisms of similar torphic status