Ambulatory Blood Pressure Monitoring

Hypertension is a major health care concern. With office and home blood pressure monitoring giving insufficient information, ambulatory blood pressure monitoring has emerged as the investigation of choice for hypertension

An Investigation of Dissimilar Welding Joint of AISI 304L Stainless Steel with Pure Copper by Nd:YAG Pulse Laser: Optimization of Tensile Strength

Nd:YAG laser welding process has successfully used for joining a dissimilar metal AISI 304L stainless steel and pure copper plates. In this study, a statistical design of experiment (DOE) was used to optimize selected LBW parameters (laser power, welding speed and pulse duration). Taguchi approach was used to design the experimental layout, each factors having four levels. Joint strength was determined using the universal testing machine (UTM). The results were analysed using analyses of variance (ANOVA) and the signal-to-noise (S/N) ratio for the optimal parameters, and then compared with the base material. And the Response can be predicted by fuzzy logic experimental results point to that the laser-welded joints are improved successfully by optimizing the input parameters using the Taguchi fuzzy approach. Also find out the effect of the focusing position on the response

Structural and electronic properties of nanocrystalline silicon thin film solar cells fabricated by hot wire and ECR-plasma CVD techniques

Nanocrystalline silicon has become the material of interest recently, for solar cell applications and also in the fabrication of thin film transistors. The material contains crystalline grains surrounded by amorphous tissues and when used as intrinsic layer in solar cell devices, greatly enhances the device stability against the light induced degradation which is a critical problem with amorphous silicon solar cells. The conventional PECVD techniques used for the deposition of high efficiency devices have a major drawback of very low growth rates. This project deals with a systematic study of structural and electronic properties of nanocrystalline Si:H films and devices fabricated using a relatively new technique called the Hot Wire CVD (HWCVD). In addition, we study the influence of ions on the crystalline ratio, grain size and orientation of the nanocrystalline films. Our apparatus allows us to add plasma ions separately from the primary growth process, which is growth using only radicals that are generated by the thermal dissociation of silane and hydrogen at the hot wire. In this way, we have also deposited the first ever nanocrystalline silicon solar cells by the combined HWCVD and Electron Cyclotron Resonance (ECR) PECVD technique.;While hot wire deposition of nanocrystalline Si:H has been studied in the past, virtually all previous work utilized a close-proximity hot wire deposition condition that creates a varying temperature profile during deposition because of the intense heating of the growing film due to radiation from the filament. In contrast, in this work, we use a remote filament to minimize sample heating, a conclusion verified by experimental measurements of surface temperatures during growth conditions. We have found that low energy ion bombardment, by either inert (helium) or reactive (hydrogen) ions significantly helps in crystallization of the film. We also systematically study the influence of hydrogen dilution on grain size and grain orientation of the film. It is found that higher hydrogen dilution suppresses the \u3c220\u3e grains and leads to more random nucleation. It is found that \u3c220\u3e orientation is the thermodynamically preferred growth direction and \u3c111\u3e grains are created due to random nucleation which is enhanced by increasing the ion bombardment from the plasma source. We have also studied the fragmentation pattern of silane in ECR PECVD using a quadruple mass spectrometer. The study revealed the dominant radicals in both nc-Si and a-Si depositions for varying power and chamber pressures.;In the second part of this work, we focus primarily on the fabrication and analysis of the electronic properties of solar cells using nanocrystalline intrinsic layers. Apart from measuring the regular I-V characteristics and quantum efficiency, we investigate the critical device properties such as the defect densities in the intrinsic layer and the diffusion length of the minority carriers. By correlating the device results with the structural properties of the films, we are able to conclude that the maximum diffusion length and the minimum defect density can only be attained by depositing the intrinsic layers that are close to the transition to amorphous phase. Although few studies have been done on this transition regime of the deposited films, most of them have concentrated only on the film properties such as conductivity ratios and crystalline fractions. This work clearly describes why transition region is ideal for the fabrication of high efficiency solar cells and what are the critical deposition parameters that are involved in their design

An experimental analysis and optimization of machining rate and surface characteristics in WEDM of Monel-400 using RSM and desirability approach

In the present work, an experimental investigation on wire electrical discharge machining (WEDM) of Monel-400 has been presented. Monel-400 is a nickel- copper-based alloy, mostly employed in ships and corrosion- resisting applications. Four input WEDM parameters namely discharge current (Ip), pulse-on time (Ton), pulseoff time (Toff) and servo voltage (SV) have been investigated and modeled for two performance characteristics namely machining rate (MR) and surface roughness (SR). Effect of WEDM parameters has been discussed using response surface graphs. Using analysis of variance, quadratic model is found significant for MR while two factors interaction (2FI) model has been suggested for SR. To optimize multi-performance characteristics, desirability function has been employed. Corresponding to highest desirability, the optimal combination of discharge parameters is Ip: 103 A; Ton: 113 ls; Toff: 37 ls and SV: 50 V. The effect of discharge energy on surface morphology has also been examined. High discharge energy increases the extent of surface damage and results in large size and overlapped craters on machined surface. Low discharge energy and high value of Toff result in minimum defects on machined surface. Trim cutting operations were performed at low discharge energy using different wire offset values. Result shows that surface finish can be improved significantly after a single trim cut irrespective of high discharge energy in rough cut