Elucidating iron doping induced n- to p- characteristics of Strontium titanate based ethanol sensors

Neha Sarin,Monu Mishra,Govind Gupta,Ivan P. Parkin,Vandna Luthra 한국물리학회 2018 Current Applied Physics Vol.18 No.2

A series of pure and iron doped strontium titanate, (SrFexTi1-xO3; x = 0, 0.1 and 0.2) powders were synthesized, characterized and used to fabricate ethanol sensors for low concentration. X-Ray Diffraction (XRD) technique was used to confirm the single phase formation. Microstructural properties of the powders were investigated using scanning electron microscopy (SEM). Electrical conductivity of all the samples at room temperature (RT) was measured. Sensors were optimized for best responsiveness by varying the operating temperature from 350 °C to 500 °C.The sensor with doping x = 0.2 exhibited best sensing response at 400 °C for ethanol gas. The undoped sensor demonstrated a decrease in resistance on exposure to ethanol gas whereas Fe-doped sensors showed increase in resistance. The doping induced changeover from n to p behavior in the sensing response on doping has been investigated and corroborated with an observed shift in the Fermi level position by X-ray photoelectron spectroscopy (XPS). The disparity in gas sensing response clearly demonstrates inter-connection of multiple influencing factors such as electrical conductivity, morphology, porosity and change in chemical composition on doping. The sensors were exposed to ethanol, nitrogen dioxide, carbon monoxide, butane gases at concentration between 5 ppm and 50 ppm. The sensor exhibited much reduced relative response to all gases other than ethanol which can be utilized for wide range of applications.

Ideal Strategy for the Management of CHB in Asia : Is It Better to Treat Chronic Hepatitis B(CHB) as early as possible?: cons.

( Shiv Kumar Sarin ) 대한간학회 2004 Clinical and Molecular Hepatology(대한간학회지) Vol.10 No.1(S)

Predictors of steroid non-response and new approaches in severe alcoholic hepatitis

Shiv Kumar Sarin,Shvetank Sharma 대한간학회 2020 Clinical and Molecular Hepatology(대한간학회지) Vol.26 No.4

Severe alcoholic hepatitis (SAH) remains a disease with high mortality. Steroid is the main stay and has been shown to give modest 28-day survival benefit in carefully selected patients, but no 90-day survival benefit. Since non-responders have high incidence of infections and increased mortality, it would be worthwhile to identify them before starting steroid therapy. A high and rising bilirubin, urinary acetyl carnitine >2,500 ng/mL, high asiloglycoprotein positive microparticles, and specific features in liver biopsy could predict steroid non-response at baseline. There is an ever-growing need to find new and effective therapies for SAH patients. Besides aggressive nutrition, granulocyte colony stimulating factor, fecal microbiota transplantation, and plasma exchange appear promising therapies and provide a hope for steroid ineligible or steroid non-responsive patients. Suppression of hepatic inflammation, preventing new bacterial or fungal infections, and enhancing liver regeneration will remain the key targets for next generation therapies.

Orthogonally blocked mixture component–amount designs via projections of F-squares

M. L. AGGARWAL,Poonam Singh,Vandana Sarin,Bushra Husain 한국통계학회 2012 Journal of the Korean Statistical Society Vol.41 No.1

Orthogonal block designs for Scheffé’s quadratic model have been considered previously by Draper et al. (1993), John (1984), Lewis et al. (1994) and Prescott, Draper, Dean, and Lewis (1993). Prescott and Draper (2004) obtained mixture component–amount designs via projections of standard mixture designs, viz., the simplex-lattice, the simplex-centroid and the orthogonally blocked mixture designs based on latin squares. Aggarwal, Singh,Sarin, and Husain (2009) considered the case of components assuming equal volume fractions and obtained mixture designs in orthogonal blocks using F-squares. In this paper,we construct orthogonal blocks of two and three mixture component–amount blends by projecting the class of four component mixture designs presented by Aggarwal et al. (2009).

Hydrogels formed through regulated self-organization of gradually charging chitosan in solution of xanthan

Shchipunov, Yury,Sarin, Sergei,Kim, Il,Ha, Chang-Sik Royal Society of Chemistry 2010 GREEN CHEMISTRY Vol.12 No.7

<P>Hydrogels are prepared by means of progressive acidification of xanthan solution containing dispersed chitosan particles in noncharged state at pH a little larger than p<I>K</I><SUB>a</SUB> of this polysaccharide. The following pH shift causes gradual charging of chitosan macromolecules that are involved into electrostatic interactions with oppositely charged xanthan. This triggered self-regulating processes of polysaccharide self-organization into supramolecular structures. Fibrillation or capsulation was observed that depended on the charge mixing ratio between chitosan and xanthan. The jellification of solutions took place in a case of fibrillar morphology. The strongest hydrogels were found where a fine and dense network of aligning fibrils of mean diameter of around 30 nm were generated. Where oppositely charged polysaccharides self-organized into capsules, the hydrogel was not formed because of the absence of cross-links between particles that could reach few mm in diameter and had mechanically strong shell.</P> <P>Graphic Abstract</P><P>Monolithic hydrogels or capsules are formed through the electrostatic interactions of anionic polysaccharide with chitosan that are gradually charged in the course of a progressive pH decrease by chemical acidulant. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b925138c'> </P>

Chitosan bionanocomposites prepared in the self-organized regime

Postnova, Irina,Sarin, Sergei,Silant’ev, Vladimir,Ha, Chang-Sik,Shchipunov, Yury De Gruyter 2015 Pure and Applied Chemistry Vol.87 No.8

<P><B>Abstract</B></P><P>Bionanocomposites in the self-organized regime are prepared when chitosan is gradually charged in the course of progressive change of pH by hydrolyzing<I>D</I>-glucono-<I>δ</I>-lactone in solutions of nanoparticles bearing negative charges on their surface. This novel approach is applicable to the formation of monolithic hydrogels and films. Here bionanocomposites of chitosan with clay nanoparticles of saponite and sepiolite having various geometry and with oxidized multiwall carbon nanotubes are considered. Structural organization of hydrogels and films is studied by scanning and transmission electron microscopy as well as small angle X-ray scattering. Jellification is caused by generation of three-dimensional network from fibrils, whereas films have pronounced stratified layer (nacre-like) structure from stacked nanoparticles and aligned chitosan macromolecules. Special attention is paid to mechanical properties of films that are improved drastically with introducing nanoparticles.</P>

Computationally efficient variational Bayesian method for PAPR reduction in multiuser MIMO‐OFDM systems

Davinder Singh,Rakesh Kumar Sarin 한국전자통신연구원 2019 ETRI Journal Vol.41 No.3

This paper investigates the use of the inverse‐free sparse Bayesian learning (SBL) approach for peak‐to‐average power ratio (PAPR) reduction in orthogonal frequency‐division multiplexing (OFDM)‐based multiuser massive multiple‐input multiple‐output (MIMO) systems. The Bayesian inference method employs a truncated Gaussian mixture prior for the sought‐after low‐PAPR signal. To learn the prior signal, associated hyperparameters and underlying statistical parameters, we use the variational expectation‐maximization (EM) iterative algorithm. The matrix inversion involved in the expectation step (E‐step) is averted by invoking a relaxed evidence lower bound (relaxed‐ELBO). The resulting inverse‐free SBL algorithm has a much lower complexity than the standard SBL algorithm. Numerical experiments confirm the substantial improvement over existing methods in terms of PAPR reduction for different MIMO configurations.

Is South Asia an Optimum Currency Area?

( Biswash Gauchan ),( Vishal Sarin ) 세종대학교 경제통합연구소 2018 Journal of Economic Integration Vol.33 No.3

We assess whether the South Asian Association of Regional Cooperation is an Optimum Currency Area by analyzing the symmetry of structural shocks. The result shows that SAARC countries experience asymmetric patterns of shocks, which implies the region is not yet ready for a common currency. However, we also find the increased number of positive correlation such as GDP growth, inflation, exchange rates movements and supply shocks compared to the results in the previous studies. Thus, macroeconomic convergence is ongoing among the countries, which can underpin the basis for greater monetary cooperation.

Inspection of Ceramic Coatings Using Nanoindentation and Frequency Domain Photoacoustic Microscopy

Steen, T.L.,Basu, S.N.,Sarin, V.K.,Murray, T.W. The Korean Society for Nondestructive Testing 2006 한국비파괴검사학회지 Vol.26 No.6

The elastic properties and thickness of mullite environmental barrier coatings grown through chemical vapor deposition (CVD) on silicon carbide substrates were measured using frequency domain photoacoustic microscopy. In this technique, extremely narrow bandwidth surface acoustic waves are generated with an amplitude modulated laser source. A photorefractive crystal based interferometer is used to detect the resulting surface displacement. The complex displacement field is mapped as a function of source-to-receiver distance in order to extract the wavelength of the surface acoustic wave at a given excitation frequency, and the phase velocity is determined. The coatings tested exhibited spatial variations in thickness and mechanical properties. The measured surface wave dispersion curves were used to extract an effective value for the elastic modulus and the coating thickness. Nanoindentation was used to validate the measurements of the effective elastic modulus. The average elastic modulus measured through the coating thickness using nanoindentation is compared to the effective modulus found using the photoacoustic system. Optical microscopy is used to validate the thickness measurements. The results indicate that the photoacoustic microscopy technique can be used to estimate the effective elastic properties in coatings exhibiting spatial inhomogeneities, potentially providing valuable feedback for the optimization of the CVD growth process.

Slotted Implantable Patch Antenna for ISM Band Application and Its Usage in WiMAX with an I-Shaped Defected Ground Structure

Adil Al Ayubi,Shikha Sukhija,Rakesh Kumar Sarin 한국전기전자재료학회 2017 Transactions on Electrical and Electronic Material Vol.18 No.6

A slotted implantable patch antenna with microstrip feeding is proposed for industrial, scientific, and medical bandapplications. The result is verified by implanting the antenna in animal tissue. Further, by varying the ground width andintroducing a defect into the ground structure, the antenna becomes applicable for worldwide interoperability for microwaveaccess operations. A simulation is performed using Empire XCcel software. An Agilent vector network analyzer is used foranalyzing the return loss performance. Simulated and measured results are compared. Antennas with and without defectedground structure both have key advantages including low profile, desirable return loss, good impedance matching andrequired bandwidth.