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Formation of micro structured doped and undoped hydrogenated silicon thin films
No full textThe microcrystalline hydrogenated-silicon (mu c-Si: H) (also called polymorphous silicon) consisting a two-phase mixture of amorphous and structured silicon is being used for electronic or optoelectronic based thin-film devices. The pc-Si: H thin films are deposited using radio frequency (13.56 MHz) Plasma Enhanced Chemical Vapour Deposition (RF-PECVD) by varying doping gases (diborane (B2H6) and phosphine (PH3)) flow and hydrogen-silane dilution ratio (R = H-2/SiH4) to optimize the crystalline fraction and electrical conductivity. Micro-Raman spectroscopy is used to investigate these effect on the transition fraction regime from amorphous into micro-structured silicon. Qualitative and quantitative properties have been studied by deconvolution of the micro Raman spectra which allows to determine the crystalline fraction in the film and also some investigation regarding the correlation between electrical and structural properties are presented for different annealing temperature (from 300 to 550 degrees C) and various film thickness ranges (10-100 nm). In this work, we present the characterization of thin films (both doped and undoped) deposited at the temperature of 250 degrees C on quartz substrate after annealed at 550 degrees C in N-2-ambient, as a result crystallinity percentage up to 90% for p-type, 96% for n-type and 80% for undoped films are achieved. A detailed characterization of the microcrystalline silicon (mu c-Si: H) has been demonstrated in this paper: structural properties through Raman spectroscopy, electrical properties through Four-point probe station and optical properties using Ellipsometer
DNN Based Speech Enhancement for Unseen Noises Using Monte Carlo Dropout
No full textIn this work, we propose the use of dropout as a Bayesian estimator for increasing the generalizability of a deep neural network (DNN) for speech enhancement. By using Monte Carlo (MC) dropout, we explore whether the DNN can accomplish better enhancement in unseen noisy conditions. Two DNNs are trained on speech corrupted with five different noises at three SNRs, one using conventional dropout and other with MC dropout and tested on speech with unseen noises. Speech samples are obtained from the TIMIT database and noises from NOISEX-92. In another experiment, we train five DNN models separately on speech corrupted with five different noises, at three SNRs. The model precision estimated using MC dropout is used as a proxy for squared error to dynamically select the best of the DNN models based on their performance on each frame of test data. The first set of experiments aims at improving the performance of an existing DNN with conventional dropout for unseen noises, by replacing the conventional dropout with MC dropout. The second set of experiments aims at finding an optimal way of choosing the best DNN model for de-noising when multiple noise-specific DNN models are available, for unseen noisy conditions
A Survey on Static Modeling of Miniaturized Pneumatic Artificial Muscles With New Model and Experimental Results
No full textPneumatic artificial muscles (PAMs) are linear pneumatic actuators consisting of a flexible bladder with a set of in-extensible fibers woven as a sheath on the outside. Upon application of pressure, the actuators contract or expand based on the angle of winding of the braid. Due to the similarity in properties of the actuators with biological muscles and the advantages thereof, these are increasingly being used in many robotic systems and mechanisms. This necessitates the development of mathematical models describing their mechanics for optimal design as well as for application in control systems. This paper presents a survey on different mathematical models described in the literature for representing the statics of PAM. Since it is observed that the validity of existing static models, based on energy balance methods, is not consistent with changes in parameters when applied to their miniaturized versions of pneumatic artificial muscles (MPAM), a new model has been proposed. The model takes into account material properties of the bladder as well as the end-effects which are prominent for MPAMs. Experiments conducted on fabricated MPAMs, of different diameters and lengths, show that the proposed model predicts the pressure-deformation characteristics of MPAMs with maximum error of less than 7%
Seasonal variation in stable isotope compositions of waters from a Himalayan river: Estimation of glacier melt contribution
No full textStable isotopic compositions (delta O-18 and delta D) in water samples collected from Parbati River in Himachal Pradesh, India, during 2002-2005 were measured to delineate the contributions from different sources in different seasons. A seasonal cycle with high delta O-18 and delta D values (in parts per thousand) during the spring (March to May; -9.2, -58.6), intermediate values during the winter (December to February; -10.1, -65.6), and low values during the south-west monsoon (July to September; -10.9, -71.8) is observed. The d-excess values (15.2 +/- 2.1 parts per thousand) are higher compared with the global meteoric waters indicating significant contribution (similar to 26%) of moisture carried by western disturbances. Higher delta-values during the spring are ascribed to enhanced contribution from snow melt. The lower delta-values during the monsoon are due to various Rayleigh effects (altitude, continental, and amount effects) and large-scale convection effect on rains. A three component-mixing model using the isotopic data and some plausible end member isotopic values was applied to identify contributions to the river discharge from different sources such as groundwater or subsurface base flow, glacier/surface snow melt, and the monsoon rain. Meltwater from glacier and snow combines with the base flow in spring season. South-west monsoon rain and glacier melt along with the base flow constitute the monsoon discharge. The post-monsoon season and winter are dominated by groundwater contribution. About 80% of the discharge is contributed by glacier melts in spring season. In the rainy monsoon season, glacier/snow melt contributes similar to 41% of the discharge. The mean annual glacier melt contribution to the river water is estimated to be 44 +/- 15%. The present estimate along with some previous studies suggest that glacier contribution to the river discharge increased from similar to 35% to 50% during the period 1990 to 2011. This is consistent with recent data on glacier retreats in the Himalayan region
Reusable Fe2O3-nanoparticle catalysed efficient and selective hydroboration of carbonyl compounds
No full textThe first Fe2O3-nanoparticle catalysed hydroboration of aromatic and aliphatic aldehydes and ketones with HBpin (pin = OCMe2CMe2O) is reported. The reaction proceeds under mild conditions (room temperature) and is moderately sensitive to air. This process is applicable to a broad range of substrates with high functional group compatibility. Moreover, aldehydes are selectively hydroborated over other reducible functional groups, such as ketone, nitrile, hydroxide, alkene, amide, ester, nitro and halide groups
HIGH-PERFORMANCE OPTIC DISC SEGMENTATION USING CONVOLUTIONAL NEURAL NETWORKS
No full textWe present a framework for robust optic disc segmentation using convolutional neural networks. Optic disc is an important anatomical landmark in the fundus image used for the diagnosis of ophthalmological pathologies. Our objective is to develop a system for unsupervised, early and robust detection of diseases such as glaucoma. We introduce the FineNet, which generates a high-resolution optic disc segmentation map (1024x1024) from retinal fundus images. The network is trained on three publicly available datasets, MESSIDOR, DRIONS-DB, and DRISHTI-GS. The proposed framework generalizes well as it performs reliably even on test images that have a significant variability. For experimental evaluation, we perform a five-fold cross-validation and achieve accurate optic disc localization in 99.4% of cases. Moreover, for optic disc segmentation we achieve an average Dice coefficient and Jaccard coefficient of 0.958 and 0.921, respectively
Supervisory Control Architecture for Standalone Solar Photo-Voltaic Power Generation System
No full textSolar Photo-Voltaic (SPV) based power generation system is an attractive alternative to diesel based counterparts for standalone or dual-mode AC micro-grids. Typically, a suitably sized battery-based energy storage system is required alongside PV that supplies power when solar energy and the grid are unavailable. In this work, a supervisory control architecture is proposed for the operation of such an SPV micro-grid system with battery storage. Three sub-modes of operation of the SPV converter, namely, Charger (CHGR), Maximum Power Point Tracking (MPPT) and Virtual Battery Emulation (VBE) modes are deployed to suitably control the system and manage power flow under varying conditions of battery voltage, load power, and solar insolation. The novel VBE mode emulates a parallel battery bank with the aid of the SPV converter and its appropriate control. This reduces the battery discharge and thus ensuring the extension of its cycle life. A finite state machine is presented that facilitates digital implementation of the proposed supervisory control scheme. Experimental results of various modes on a 1.2 kW SPV system prototype are presented for performance verification
Cascaded Active Neutral Point Clamped and Flying Capacitor Inverter Topology for Induction Motor Drives Applications
No full textThis paper proposes a novel multilevel architecture using active neutral point clamped inverter cascaded with a flying capacitor inverter to form a multilevel inverter topology with higher number of voltage levels for induction motor drives. All the capacitors in the topology can be balanced irrespective of any modulation index or power factor. This topology can be generalized for higher number of voltage levels. The front end DC sources required are of very low value and it can be further halved when using a reconfigured six phase induction machine for higher power. The low value DC sources can be stacked battery cells, hence the topology can find extensive applications in electric vehicles. Detailed experimental results are shown for the steady state and transient operations of the inverter. The proposed topology will be a viable scheme for high power applications
Comparison of the Fast and Slow Climate Response to Three Radiation Management Geoengineering Schemes
No full textGeoengineering has been proposed as a backup approach to rapidly cool the Earth and avoid damages associated with anthropogenic climate change. In this study, we use the NCAR Community Earth System Model to conduct a series of slab-ocean and prescribed sea surface temperature simulations to investigate the climate response to three proposed radiation management geoengineering schemes: stratospheric aerosol increase (SAI), marine cloud brightening (MCB), and cirrus cloud thinning (CCT). Our simulations show that different amounts of radiative forcing are needed for these three schemes to compensate global mean warming induced by a doubling of atmospheric CO2. With radiative forcing defined in terms of top-of-atmosphere energy imbalances in prescribed sea surface temperature simulations with land temperature adjustments, radiative forcing efficacy for SAI is about 15% smaller than that of CO2, and the efficacy for MCB and CCNCCT is about 10% larger than that of CO2. In our simulations, different forcing efficacies are associated with different feedback processes for these forcing agents. Also, these geoengineering schemes produce different land-ocean temperature change contrasts. The apparent hydrological sensitivity, that is, change in equilibrium global mean precipitation per degree of equilibrium temperature change, differs substantially between CO2, SAI, MCB, and CCNCCT forcings, which is mainly a result of different precipitation responses during fast adjustment. After removing the component of fast adjustment, the northward movement of the Intertropical Convergence Zone in response to these forcing agents is tightly related with changes in the interhemispheric energy exchange and hemispheric temperature gradient. Plain Language Summary To counteract the CO2-induced global warming effect, a number of geoengineering methods have been proposed. One proposed method (sulfate aerosol injection) is to inject sulfate aerosols or its precursors (SO2) into the stratosphere to deflect more sunlight back to space. Another method (marine cloud brightening) is to seed low-level marine stratocumulus clouds to reflect more sunlight. A third method, the intentional reduction of the coverage and optical thickness of high-level cirrus cloud (cirrus cloud thinning), could potentially reduce global warming by modifying the longwave radiative effect of cirrus clouds. In this study, we compare the climate response to these three geoengineering schemes that are designed to offset global mean surface warming caused by an abrupt doubling of atmospheric CO2. Our simulations show that to offset the same amount of CO2-induced global mean warming, different amounts of radiative forcing are needed, implying that the efficacy of climate forcing is different for different geoengineering schemes. Also, for the same amount of cooling achieved, cirrus cloud thinning produces a much smaller reduction in precipitation than does stratospheric aerosol injection or marine cloud brightening. Due to the different natures of imposed forcing, these different geoengineering schemes also produce different land-sea temperature contrasts
Fabrication of low cost and versatile internal field pulsed nuclear magnetic resonance spectrometer to study the magnetic materials
No full textWe have built a low cost and versatile pulsed internal field nuclear magnetic resonance (IFNMR) spectrometer and used it to study ferromagnetic materials. Initially optimization of the instrument has been tested with nuclear quadrupole resonance (NQR) active nuclei. Ferromagnetic materials like bulk iron, bulk cobalt and carbon coated cobalt nanopowder have been used as the testing materials for our spectrometer. Preliminary results obtained from the present spectrometer have been compared with the earlier reports and are in good agreement. The specifications and performance standard of the instrument match quite well with standard instruments elsewhere in the world which is testified with the observation of NMR echo signals in the above mentioned materials confirming the quality of the spectrometer. Additionally NMR signals from the grain boundaries are observed in Co@C nanomaterials which prove the sensitivity of the spectrometer