Mismatched Load Protected Solid State Amplifier of 1W CWRF Output in Frequency Range of 28 - 46 MHz

This project work is associated with the concept, design, fabrication and testing of a continuous wave radio frequency (cwrf) solid state amplifier. This amplifier of gain more than 20dB with 10mW input, will be developed for general application in the frequency range of 28 to 46 MHz. This Low Power Amplifier (LPA) will be made to exhibit a feature of protection from finite mismatched load that causes Voltage Standing Wave Ratio (VSWR) and consequent failure of the solid state device. The rf and microwave circuits including amplifiers are designed for standard 50 transmission line components and load. In case of perfectly matched load, only incident waves exist without any reflection i.e. 1:1 VSWR and maximum power is transferred to the load. In practice, mismatched load persists where reflected waves along with the forward waves gives rise to standing waves that cause damage to the solid state devices due to various reasons. In order to protect the device, the amplifier to be developed, will be treated with various protections so that load mismatch is managed in the most optimised manner. DOI: 10.17762/ijritcc2321-8169.15056

Resonant Raman of OH/OD vibrations and photoluminescence studies in LiTaO3 thin film

Resonant Raman spectra (RRS) of O-H and O-D vibration and libration modes, their combinations and higher harmonics have been observed in LiTaO3 polycrystalline thin films. RRS peaks are superimposed on photoluminescence (PL) spectrum. Monochromatic light from a xenon lamp is used as excitation source. PL spectrum shows two broad peaks, first near the band gap in UV (4.4-4.8eV) and another in the sub band gap region (< 4.0 eV). Band gap PL along with RRS peaks are reported for the first time. Photoluminescence excitation spectrum (PLE) shows a peak at 4.8 eV. Peak positions and full width at half maximum (FWHM) of RRS peaks depend upon the excitation energy. Dispersions of the fundamental and the third harmonic of the stretching mode of O-H with excitation energy are about 800 cm-1/eV and 2000 cm-1/eV respectively. This dispersion is much higher than reported in any other material.Comment: 20 page

Distortion Analysis of CMOS Based Analog Circuits

The amplifiers are the vital part of the analog circuit designs. The linearity of the CMOS is of most important concern in the design of many analog circuits. There are several aspects regarding nonlinear distortion analysis in analog circuits implemented in CMOS technology. Basically, the investigations visualize the nature of the total harmonic distortion (THD) dependence on the amplitude and frequency of the input signals. In this paper, the basic building blocks of analog integrated circuits such as Common source amplifier with diode connected load and Differential amplifier with current mirror load have been presented for distortion analysis. The MOSFET model used for simulation is BSIM3 SPICE model from 0.13-μm and BSIM4 SPICE model from 22-μm CMOS process technology. HSPICE circuit simulator tool is used for distortion analysis of CMOS circuits. It is evident that the above function gives remarkable insight of the nonlinear behavior of the considered circuits and it is worth considering for further investigations

Kinetically Decoupled Electrical and Structural Phase Transitions in VO2

Vanadium dioxide (VO2) has drawn significant attention for its near room temperature insulator to metal transition and associated structural phase transition. The underlying Physics behind the temperature induced insulator to metal and concomitant structural phase transition in VO2 is yet to be fully understood. We have investigated the kinetics of the above phase transition behaviors of VO2 with the help of resistivity measurements and Raman spectroscopy. Resistance thermal hysteresis scaling and relaxation measurements across the temperature induced insulator to metal transition reveal the unusual behaviour of this first-order phase transition, whereas Raman relaxation measurements show that the temperature induced structural phase transition in VO2 follows usual behaviour and is consistent with mean field prediction. At higher temperature sweeping rates decoupling of insulator to metal transition and structural phase transition have been confirmed. The observed anomalous first order phase transition behavior in VO2 is attributed to the unconventional quasi particle dynamics, i.e. significantly lowered electronic thermal conductivity across insulator to metal transition, which is confirmed by ultrafast optical pump-probe time domain thermoreflectance measurements.Comment: 25 pages, 8 figure

Multiple exciton generation in VO2

Multiple exciton generation (MEG) is a widely studied phenomenon in semiconductor nanocrystals and quantum dots, aimed at improving the energy conversion efficiency of solar cells. MEG is the process wherein incident photon energy is significantly larger than the band gap, and the resulting photoexcited carriers relax by generating additional electron-hole pairs, rather than decaying by heat dissipation. Here, we present an experimental demonstration of MEG in a prototype strongly correlated material, VO2, through photocurrent spectroscopy and ultrafast transient reflectivity measurements, both of which are considered the most prominent ways for detecting MEG in working devices. The key result of this paper is the observation of MEG at room temperature (in a correlated insulating phase of VO2), and the estimated threshold for MEG is 3Eg. We demonstrate an escalated photocurrent due to MEG in VO2, and quantum efficiency is found to exceed 100%. Our studies suggest that this phenomenon is a manifestation of expeditious impact ionization due to stronger electron correlations and could be exploited in a large number of strongly correlated materials.Comment: 6 pages, 5 figures, Physical Review

Effect of physiotherapy on single breath count and breath holding time in COVID-19 patients

Background: The novel Coronavirus is known to primarily affect the respiratory system and physiotherapy treatment is integral to combat this infection. However, the assessment of pulmonary function poses a difficult challenge considering the risk of spread of infection and sanitisation of the devices used. Single breath count (SBC) and breath holding time (BHT) can be thus adopted as bedside assessment tests for pulmonary function following physiotherapy treatment.Method: In this a retrospective observational study of 51 COVID-19 patients, mean age 51.7±14.56 years, on room air, admitted in the step-down units of a tertiary care hospital. Patients received standard physiotherapy treatment, within safe hemodynamic limits. Pre and post treatment session SBC was recorded in 32 patients and BHT in 19 patients. Three reading were noted and the best of three readings were used for analysis.Results: The paired t test was used to analyse SBC and BHT. Mean pre and post SBC was 18.25±8.96 and 23.31±9.96 respectively with a mean difference of 5.06 and p<0.0001. Mean pre and post BHT were 19.37 and 23.05 seconds respectively with a mean difference of 3.68 and p<0.0001.  Statistically significant difference in the pre and post treatment session SBC and BHT was observed, indicating a positive effect of physiotherapy treatment on pulmonary function.Conclusion: Physiotherapy treatment shows significant improvement in the pulmonary function in COVID-19 patients. SBC and BHT tests can be used as assessment and prognostic tools for pulmonary function in COVID-19 patients

Chemical Protection Studies of Activated Carbon Spheres based Permeable Protective Clothing Against Sulfur Mustard, a Chemical Warfare Agent

Technological advancements in the field of chemical threat have made it possible to create extremely dangerous chemical warfare agents (CWA). Hence, the effective protection of personnel is very important in a chemical warfare&nbsp;scenario amidst the current climate of terrorism awareness. In particular, body protection plays a substantial role in the chemical defence considering the urgency of situation in the nuclear, biological and chemical environment. Activated carbon spheres (ACS) based permeable chemical protective clothing (coverall) was developed for protection against CWA. The adsorbent material i.e, ACS used in this protective clothing provided higher adsorption capacity (1029 mg/g in terms of iodine) and low thermal burden (34 °C WBGT index) compared to earlier indigenously developed NBC suit. This article focuses on the extensive evaluation of chemical protective clothing against&nbsp;sulfur mustard (HD), a CWA. The results revealed that the developed protective clothing provided more than 24 h protection against HD. This chemical protective suit is light weight (&lt; 2.75 kg for XL size). It also has higher air permeability (&gt; 30 cm3/s/cm2) as well as less water vapour resistance (&lt; 9.6 m2Pa/W). With continued innovations in materials and attention to key challenges it is expected that advanced, multifunction chemical protective suit will play a pivotal role in the CWA protection scenario

Radiographic Findings and Association With Clinical Severity and Outcomes in Critically Ill Patients With COVID-19

PURPOSE: To describe evolution and severity of radiographic findings and assess association with disease severity and outcomes in critically ill COVID-19 patients. MATERIALS AND METHODS: This retrospective study included 62 COVID-19 patients admitted to the intensive care unit (ICU). Clinical data was obtained from electronic medical records. A total of 270 chest radiographs were reviewed and qualitatively scored (CXR score) using a severity scale of 0-30. Radiographic findings were correlated with clinical severity and outcome. RESULTS: The CXR score increases from a median initial score of 10 at hospital presentation to the median peak CXR score of 18 within a median time of 4 days after hospitalization, and then slowly decreases to a median last CXR score of 15 in a median time of 12 days after hospitalization. The initial and peak CXR score was independently associated with invasive MV after adjusting for age, gender, body mass index, smoking, and comorbidities (Initial, odds ratio [OR]: 2.11 per 5-point increase, confidence interval [CI] 1.35-3.32, P= 0.001; Peak, OR: 2.50 per 5-point increase, CI 1.48-4.22, P= 0.001). Peak CXR scores were also independently associated with vasopressor usage (OR: 2.28 per 5-point increase, CI 1.30-3.98, P= 0.004). Peak CXR scores strongly correlated with the duration of invasive MV (Rho = 0.62, P\u3c 0.001), while the initial CXR score (Rho = 0.26) and the peak CXR score (Rho = 0.27) correlated weakly with the sequential organ failure assessment score. No statistically significant associations were found between radiographic findings and mortality. CONCLUSIONS: Evolution of radiographic features indicates rapid disease progression and correlate with requirement for invasive MV or vasopressors but not mortality, which suggests potential nonpulmonary pathways to death in COVID-19