Tuning Bandgap and Energy Stability of Organic-Inorganic Halide Perovskites through Surface Engineering

Organohalide perovskite with a variety of surface structures and morphologies have shown promising potential owing to the choice of the type of heterostructure dependent stability. We systematically investigate and discuss the impact of 2-dimensional molybdenum-disulphide (MoS2), molybdenum-diselenide (MoSe2), tungsten-disulphide (WS2), tungsten-diselenide (WSe2), boron- nitiride (BN) and graphene monolayers on band-gap and energy stability of organic-inorganic halide perovskites. We found that MAPbI3ML deposited on BN-ML shows room temperature stability (-25 meV~300K) with an optimal bandgap of ~1.6 eV. The calculated absorption coefficient also lies in the visible-light range with a maximum of 4.9 x 104 cm-1 achieved at 2.8 eV photon energy. On the basis of our calculations, we suggest that the encapsulation of an organic-inorganic halide perovskite monolayers by semiconducting monolayers potentially provides greater flexibility for tuning the energy stability and the bandgap.Comment: 19 pages (single sided), 5 figures, 1 Tabl

Learning Surrogate Models of Document Image Quality Metrics for Automated Document Image Processing

Computation of document image quality metrics often depends upon the availability of a ground truth image corresponding to the document. This limits the applicability of quality metrics in applications such as hyperparameter optimization of image processing algorithms that operate on-the-fly on unseen documents. This work proposes the use of surrogate models to learn the behavior of a given document quality metric on existing datasets where ground truth images are available. The trained surrogate model can later be used to predict the metric value on previously unseen document images without requiring access to ground truth images. The surrogate model is empirically evaluated on the Document Image Binarization Competition (DIBCO) and the Handwritten Document Image Binarization Competition (H-DIBCO) datasets

CFD Analysis of Stirling Cryocoolers

The application of cryocoolers are in various fields of modern day applications for adequate refrigeration at specified temperature with low power input, long lifetime, high reliability and maintenance free operation with minimum vibration and noise, compactness and light weight. The demand of Stirling cryocoolers has increased due to the ineffectiveness of Rankin cooling systems at lower temperatures. With the rise in applications of Stirling cryocoolers, especially in the field of space and military, several simulations of Stirling cryocoolers were developed. In this project, so far a detailed analysis has been carried out on previous developed model with computed lengths of different sections of the cryocooler. The previous models have been developed by solving governing partial differential equations mathematically. The regenerator efficiency had been taken 100% in the previous analysis and with performing Schmidt analyses taking sinusoidal variations of pressure and volume, previous model geometry parameters were calculated. The CFD analysis has been done in this project taking the previous model and a UDF for the movement of the piston has been developed in C++ language. The regenerator parameters have been calculated from the results of the analysis. Simulations are done on Stirling cryocooler with adiabatic conditions at the cold space side and later with a heat load of 0.25 W at cold end and their results were compared. An attempt has also been made in determining the optimum frequency of operation of the proposed model of Stirling cryocooler by comparing the minimum cool down temperature attained by them with different frequencies of operation