Solution-based synthesis of high yield CZTS (Cu₂ZnSnS₄) spherical quantum dots

Rajesh, G.,Muthukumarasamy, N.,Subramanian, E.P.,Venkatraman, M.R.,Agilan, S.,Ragavendran, V.,Thambidurai, M.,Velumani, S.,Yi, J.,Velauthapillai, D. Academic Press 2015 Superlattices and microstructures Vol.77 No.-

High yield CZTS quantum dots have been synthesized using simple precursors by chemical precipitation technique. Formation mechanism of CZTS spherical quantum dots also has been investigated. According to the mechanism, copper sulfide nuclei firstly forms, and serves as the starting point for the nucleation and growth of CZTS. X-ray diffraction pattern, X-ray photoelectron spectra (XPS) and Raman spectra reveals the formation of pure kesterite structure Cu<SUB>2</SUB>ZnSnS<SUB>4</SUB> nanoparticles. HRTEM analysis reveals the formation of CZTS quantum dots with an average particle size of ~8.3nm. The elemental distribution of CZTS quantum dots studied using STEM elemental mapping reveals that Cu, Zn, Sn and S are present in the sample. The photoluminescence spectra of CZTS exhibit a broad red emission band at 657nm. The optical band gap is shifted to the higher energy side and it shows the presence of quantum confinement effect.

Theoretical simulation on evolution of suspended sodium combustion aerosols characteristics in a closed chamber

Sujatha Pavan Narayanam,Amit Kumar,Usha Pujala,Subramanian V.,Srinivas C.V.,Venkatesan R.,Athmalingam S.,Venkatraman B. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.6

In the unlikely event of core disruptive accident in sodium cooled fast reactors, the reactor containmentbuilding would be bottled up with sodium and fission product aerosols. The behavior of these aerosols iscrucial to estimate the in-containment source term as a part of nuclear reactor safety analysis. In thiswork, the evolution of sodium aerosol characteristics (mass concentration and size) is simulated usingHAARM-S code. The code is based on the method of moments to solve the integro-differential equation. The code is updated to FORTRAN-77 and run in Microsoft FORTRAN PowerStation 4.0 (on Desktop). Thesodium aerosol characteristics simulated by HAARM-S code are compared with the measured values atAerosol Test Facility. The maximum deviation between measured and simulated mass concentrations is30% at initial period (up to 60 min) and around 50% in the later period. In addition, the influence ofhumidity on aerosol size growth for two different aerosol mass concentrations is studied. The measuredand simulated growth factors of aerosol size (ratio of saturated size to initial size) are found to bematched at reasonable extent. Since sodium is highly reactive with atmospheric constituents, the aerosolgrowth factor depends on the hygroscopic growth, chemical transformation and density variations besides coagulation. Further, there is a scope for the improvement of the code to estimate the aerosoldynamics in confined environment

Structural vibration control using resistively shunted piezoceramics

Kandagal, S.B.,Venkatraman, Kartik Techno-Press 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.14 No.5

Application of piezoceramic materials in actuation and sensing of vibration is of current interest. Potential and more popular applications of piezoceramics are probably in the field of active vibration control. However, the objective of this work is to investigate the effect of shunted piezoceramics as passive vibration control devices when bonded to a host structure. Resistive shunting of a piezoceramic bonded to a cantilevered duralumin beam has been investigated. The piezoceramic is connected in parallel to an electrical network comprising of resistors and inductors. The piezoceramic is a capacitor that stores and discharges electrical energy that is transformed from the mechanical motion of the structure to which it is bonded. A resistor across the piezoceramic would be termed as a resistively shunted piezoceramic. Similarly, an inductor across the piezoceramic is termed as a resonantly shunted piezoceramic. In this study, the effect of resistive shunting on the nature of damping enhancement to the host structure has been investigated. Analytical studies are presented along with experimental results.

HVS Weighted Progressive Image Transmission using LOT / CVQ

Chansik Hwang,S. Venkatraman,K. R. Rao 한국통신학회 1993 Asia-Pacific Conference on Communications Vol.2 No.1

Role of Anatomical Landmarks in Identifying Normal and Transitional Vertebra in Lumbar Spine Magnetic Resonance Imaging

Devimeenal Jagannathan,Venkatraman Indiran,Fouzal Hithaya,M. Alamelu,S. Padmanaban 대한척추외과학회 2017 Asian Spine Journal Vol.11 No.3

Study Design: Retrospective study. Purpose: Identification of transitional vertebra is important in spine imaging, especially in presurgical planning. Pasted images of the whole spine obtained using high-field magnetic resonance imaging (MRI) are helpful in counting vertebrae and identifying transitional vertebrae. Counting vertebrae and identifying transitional vertebrae is challenging in isolated studies of lumbar spine and in studies conducted in low-field MRI. An incorrect evaluation may lead to wrong-level treatment. Here, we identify the location of different anatomical structures that can help in counting and identifying vertebrae. Overview of Literature: Many studies have assessed the vertebral segments using various anatomical structures such as costal facets (CF), aortic bifurcation (AB), inferior vena cava confluence (IC), right renal artery (RRA), celiac trunk (CT), superior mesenteric artery root (SR), iliolumbar ligament (ILL) psoas muscle (PM) origin, and conus medullaris. However, none have yielded any consistent results. Methods: We studied the locations of the anatomical structures CF, AB, IC, RRA, CT, SR, ILL, and PM in patients who underwent whole spine MRI at our department. Results: In our study, 81.4% patients had normal spinal segmentation, 14.7% had sacralization, and 3.8% had lumbarization. Vascular landmarks had variable origin. There were caudal and cranial shifts with respect to lumbarization and sacralization. In 93.8% of cases in the normal group, ILL emerged from either L5 alone or the adjacent disc. In the sacralization group, ILL was commonly seen in L5. In the lumbarization group, ILL emerged from L5 and the adjacent disc (66.6%). CFs were identified at D12 in 96.9% and 91.7% of patients in the normal and lumbarization groups, respectively. The PM origin was observed from D12 or D12–L1 in most patients in the normal and sacralization groups. Conclusions: CF, PM, and ILL were good identification markers for D12 and L5, but none were 100% accurate.

IMAGE CODING USING A CLASSIFIED TRANSFORM VECTOR QUANTIZATION BASED ON LAPPED ORTHOGONAL TRANSFORM

Jae Yeal Nam,K. R. Rao,S. Venkatraman 대한전자공학회 1992 JTC-CSCC : Joint Technical Conference on Circuits Vol.- No.-

Comparison of the Adhesion and Proliferation Characteristics of HUVEC and Two Endothelial Cell Lines (CRL 2922 and CRL 2873) on Various Substrata

Boon Chin Heng,Yun Xia,Xiaobo Shang,Peter Rainer Preiser,S. K. Alex Law,Freddy Yin-Chiang Boey,Subbu S. Venkatraman 한국생물공학회 2011 Biotechnology and Bioprocess Engineering Vol.16 No.1

Endothelial cell coverage of blood-contacting devices is crucial to their eventual success in the clinic. Two established human cell lines derived from HUVEC (human umbilical vascular endothelial cells), CRL 2922and CRL 2873, have been widely utilized to study and model endothelial cell biology. However, it is not clear if these two cell lines would be useful for modeling primary endothelial cell interaction with newly-formulated biomaterials in tissue engineering applications. Hence, this study was conducted to compare the adhesion and proliferation characteristics of HUVEC grown on seven different substrata, tissue culture polystyrene (TCPS), gelatin,chitosan, poly-L-lysine, hyaluronan, poly-L-lactic acid (PLLA), and polylactic-co-glycolic acid (PLGA). The short-term adhesive behavior (2 h) of HUVEC on the various substrata was not closely-replicated by either CRL 2873 or CRL 2922. This was likely because the 2 h timeframe is too short for identification of differences in the interaction among the three cell types grown on various substrata. There was much faster proliferation of CRL 2922 on all seven substrata when compared to HUVEC and CRL 2873. Moreover, the proliferation rates of CRL 2922 on the various substrata showed little variation. In contrast, HUVEC and CRL 2873 displayed similar trends in proliferation rates, with gelatin and TCPS yielding the highest rates, and PLLA and PLGA yielding the lowest rates. Hence, CRL 2873 is better suited for modeling primary endothelial cell interaction with newly-formulated biomaterials than CRL 2922. The advantage of using CRL 2873 over HUVEC for biomaterial screening is that it is immortalized and displays much less inter-batch variability than primary culture.

VAULT PROTEIN-TEMPLATED ASSEMBLIES OF NANOPARTICLES

XIAO-YING QI,XIAO HUANG,HAI LI,YUSONG WANG,Yun Xia,MEENUBHARATHI NATARAJAN,JUN WEI,Subbu S. Venkatraman,HUA ZHANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2012 NANO Vol.7 No.1

Recombinant vault nanoparticles are used as stable nanoscale platforms for controlled self-assembly of various kinds of nanoparticles into the predefined multidimensional architectures. High-yield and uniform discoidal assemblies templated by vaults are constructed from gold nanospheres and quantum dots, while dimeric assemblies are formed from relatively-large gold nanocubes. The vault-templated approach appears to be mainly mediated by the surface and dimensional properties of nanoparticles while less affected by the chemical composition of nanoparticles, making it a universal strategy for fabrication of nanoassemblies with designed properties for potential applications.

A study on transport and plugging of sodium aerosol in leak paths of concrete blocks

Narayanam Sujatha Pavan,Sen Soubhadra,Kumari Kalpana,Kumar Amit,Pujala Usha,Subramanian V.,Chandrasekharan S.,Preetha R.,Venkatraman B. 한국원자력학회 2024 Nuclear Engineering and Technology Vol.56 No.1

In the event of a severe accident in Sodium Cooled Fast Reactors (SFR), the sodium combustion aerosols along with fission product aerosols would migrate to the environment through leak paths of the Reactor Containment Building (RCB) concrete wall under positive pressure. Understanding the characteristics of sodium aerosol transport through concrete leak paths is important as it governs the environmental source term. In this context, experiments are conducted to study the influence of various parameters like pressure, initial mass concentration, leak path diameter, humidity etc., on the transport and deposition of sodium aerosols in straight leak paths of concrete. The leak paths in concrete specimens are prepared by casting and the diameter of the leak path is measured using thermography technique. Aerosol transport experiments are conducted to measure the transported and plugged aerosol mass in the leak paths and corresponding plugging times. The values of differential pressure, aerosol concentration and relative humidity taken for the study are in the ranges 10–15 kPa, 0.65–3.04 g/m3 and 30–90% respectively. These observations are numerically simulated using 1-Dimensional transport equation. The simulated values are compared with the experimental results and reasonable agreement among them is observed. From the safety assessment view of reactor, the approach presented here is conservative as it is with straight leak paths.