Mohit Agarwal

Locally weighted projection regression for predicting hydraulic parameters

With the advent of electronics and control technology many new computing approaches are being made available for their use to the general scientific community including hydraulic engineers. One such latest technique coming under the category of data driven modelling is locally weighted projection regression (LWPR). In the present work, the suitability of this technique to solve two problems of uncertain nature, namely prediction of littoral drift and that of scour downstream of a flip bucket spillway, is assessed. Although traditional techniques to predict these hydraulic phenomena exist, they may not always yield satisfactory results owing to the complexity of underlying physical processes. Alternative approaches in this regard should therefore be welcome. For the prediction of littoral drift field measurements of waves and sediments collected near the beach of Karwar along the west coast of India are used while the scour prediction is based on laboratory model observations. It is found that the estimation of the rate of littoral drift as well as that of the spillway scour made by this new computing approach is better than traditional empirical formulae and further it rivals the results of the other and previously attempted data driven methods like artificial neural networks and genetic programming. There is thus a case to apply the LWPR technique in future to a variety of problems in hydraulic engineering.

Influence of RF power on magnetron sputtered AZO films

Al-doped Zinc Oxide (AZO) transparent conducting films are prepared on glass substrate by RF magnetron sputtering under different RF power with a 3 inch diameter target of 2 wt% Al2O3 in zinc oxide. The effect of RF power on the structural, optical and electrical properties of AZO films was investigated by X-ray Diffraction (XRD), Hall measurement and UV-Visible spectrophotometry. The XRD data indicates a preferential c-axis orientation for all the films. All films exhibit high transmittance (<90%) in visible region. Films deposited at 60 W power exhibit lowest resistivity of 5.7×10−4ωcm. Such low-resistivity and high-transmittance AZO films when prepared using low RF power at room temperature could find important applications in flexible electronics.

Temperature dependent analysis of heterojunction silicon solar cells: Role of intrinsic layer thickness

Temperature dependent dark current voltage characteristics of p type hydrogenated amorphous silicon/intrinsic a-Si: H/n-type crystalline silicon solar cells with varying the intrinsic layer thickness are discussed to elucidate the dominant current transport phenomena in such structures. The a-Si:H films were deposited by Hot-Wire chemical vapor deposition (HWCVD) technique. The charge carrier conduction behavior of the a-Si:H/c-Si junction is strongly influenced by the intrinsic layer. The structure without intrinsic layer shows recombination at the interface whereas multi tunneling capture emission (MTCE) process is dominant after inserting a thin intrinsic layer in between the p-a-Si:H/n-c-Si interface.

Isotropic etching of polycrystalline silicon wafer by acidic solution

In photovoltaic technology, texturing of base wafer has great importance since it reduces the reflectance of incident light that leads to improvement in the conversion efficiency. Due to different orientations present in polycrystalline silicon wafer an isotropic etching and the texturing without grain boundary delineation is great challenge. In this study, an attempt has been made to get isotropic etching by acidic solution. The volume ratios of HF/HNO3/ CH3COOH have been chosen in such a way that it fell in lower part of iso-etch curve where the solution is HNO3 rich. The presence of high concentration of HNO3 leads to the rapid oxidation of silicon surface and hence makes the etching rate limited through the diffusion of HF into the SiO2. This study shows the isotropic etching of poly-Si wafer which is confirmed by scanning electron microscopy. Moreover, the reflectance measurements show that the average reflectance reduces from 20.5 to 8.5 % over 350 to 800 nm range.