A mathematical model of blood flow and convective diffusion processes in constricted bifurcated arteries

Chakravarty S.,Sen S. The Korean Society of Rheology 2006 Korea-Australia rheology journal Vol.18 No.2

Of concern in the present theoretical investigation is the study of blood flow and convection-dominated diffusion processes in a model bifurcated artery under stenotic conditions. The geometry of the bifurcated arterial segment having constrictions in both the parent and its daughter arterial lumen frequently appearing in the diseased arteries causing malfunction of the cardiovascular system, is constructed mathematically with the introduction of suitable curvatures at the lateral junction and the flow divider. The streaming blood contained in the bifurcated artery is treated to be Newtonian. The flow dynamical analysis applies the two-dimensional unsteady incompressible nonlinear Wavier-Stokes equations for Newtonian fluid while the mass transport phenomenon is governed by the convection diffusion equation. The motion of the arterial wall and its effect on local fluid mechanics is, however, not ruled out from the present model. The main objective of this study is to demonstrate the effects of constricted flow characteristics and the wall motion on the wall shear stress, the concentration profile and on the mass transfer. The ultimate numerical solutions of the coupled flow and diffusion processes following a radial coordinate transformation are based on an appropriate finite difference technique which attain appreciable stability in both the flow phenomena and the convection-dominated diffusion processes.

Propulsion System Modeling and Control of a Warhead with Multi-thruster Configuration

Rajtilok Chakravarty,Nachiket Wadwankar,N. Ananthkrishnan,V.S. Renganathan,Hyun Ko,Ji-Hyung Lee 한국추진공학회 2013 한국추진공학회 학술대회논문집 Vol.2013 No.12

A novel internal pressure controller is developed for a Kinetic Energy Interceptor (KEI) equipped with a multi-thruster configuration. To that end, first the propulsion system model for solid fuel with a tubular grain burning configuration is detailed. Subsequently the internal pressure control logic design and implementation is laid out and a closed loop simulation is successfully demonstrated where varying chamber pressure is demanded and met by the controller by varying the thruster throat areas appropriately.

Dynamic response of heat and mass transfer in blood flow through stenosed bifurcated arteries

S. Chakravarty,S. Sen 한국유변학회 2005 Korea-Australia rheology journal Vol.17 No.2

The present study deals with a mathematical model describing the dynamic response of heat and mass transfer in blood flow through bifurcated arteries under stenotic condition. The geometry of the bifurcated arterial segment possessing constrictions in both the parent and the daughter arterial lumen frequently appearing in the diseased arteries causing malfunction of the cardiovascular system, is formulated mathematically with the introduction of the suitable curvatures at the lateral junction and the flow divider. The blood flowing through the artery is treated to be Newtonian. The nonlinear unsteady flow phenomena is governed by the Navier-Stokes equations while those of heat and mass transfer are controlled by the heat conduction and the convection-diffusion equations respectively. All these equations together with the appropriate boundary conditions describing the present biomechanical problem following the radial coordinate transformation are solved numerically by adopting finite difference technique. The respective profiles of the flow field, the temperature and the concentration and their distributions as well are obtained. The influences of the stenosis, the arterial wall motion and the unsteady behaviour of the system in terms of the heat and mass transfer on the blood stream in the entire arterial segment are highlighted through several plots presented at the end of the paper in order to illustrate the applicability of the present model under study.

Efficient keV X-ray Generation from Irradiation of in-situ Produced Silver Clusters by Ti:sapphire Laser Pulses

U. Chakravarty,P. A. Naik,S. R. Kumbhare,P. D. Gupta 한국광학회 2009 Current Optics and Photonics Vol.13 No.1

An experimental study of energy absorption and x-ray emission from ultrashort laser pulse irradiation of in-situ produced solid clusters has been performed. Silver clusters produced by a 30 mJ, 300 ps laser pulse were irradiated up to an intensity of 3×1017 W/cm2 by a 70 mJ, 45 fs compressed laser pulse from the same Ti:sapphire laser. Absorption of the laser light exceeding 70% was observed, resulting in an x-ray yield (>1 keV) of ~60 μJ/ pulse. This may constitute a much simpler means of intense x-ray generation using ultrashort laser pulses as compared to the irradiation of structured / pre-deposited cluster targets, and it offers higher x-ray conversion efficiency than that from gas clusters and planar solid targets.

Evaluation of Shungit -A Non-Petro Performance Filler in Tyre Compounds and Studies with Silica filler

( A. Chakravarty ),( S. N. Chakravarty ) 한국고무학회 2007 고무기술 Vol.8 No.2

Shungit are natural composite materials having unusual structure, consist of uniformly distributed highly dispersed crystalline silicate particles in amorphous carbon matrix. It`s main component is fullerene like Shungit carbon (upto 80%). Studies with Shungit, a non petro based performance carbon filler, in additional quantity to Carbon black in typical automotive tyre carcass, bead & apex and tread compounds as well as replacement of silica filler have been carried out and reported here. Rheological / Rheometric studies, Physico-mechanical properties determination, Dynamic Mechanical analysis & Rubber Process Analyzer studies were carried out with different compounds. Compound mixing was carried out in Brabender Plasticoder. Technological properties of rubber compound with Shungit were considerably improved with respect to Mooney viscosity and time of premature vulcanization start (Scorch Safety). DMA analysis shows lower tan delta value with Shungit containing compound. RPA studies also indicate lower heat development and tan delta. Results indicate that Shungit can replace, fully or partly, Silica in tyre tread compounds containing Carbon black.

A mathematical model of blood flow and convective diffusion processes in constricted bifurcated arteries

S. Chakravarty,S. Sen 한국유변학회 2006 Korea-Australia rheology journal Vol.18 No.2

Of concern in the present theoretical investigation is the study of blood flow and convection-dominated diffusion processes in a model bifurcated artery under stenotic conditions. The geometry of the bifurcated arterial segment having constrictions in both the parent and its daughter arterial lumen frequently appearing in the diseased arteries causing malfunction of the cardiovascular system, is constructed mathematically with the introduction of suitable curvatures at the lateral junction and the flow divider. The streaming blood contained in the bifurcated artery is treated to be Newtonian. The flow dynamical analysis applies the two-dimensional unsteady incompressible nonlinear Navier-Stokes equations for Newtonian fluid while the mass transport phenomenon is governed by the convection diffusion equation. The motion of the arterial wall and its effect on local fluid mechanics is, however, not ruled out from the present model. The main objective of this study is to demonstrate the effects of constricted flow characteristics and the wall motion on the wall shear stress, the concentration profile and on the mass transfer. The ultimate numerical solutions of the coupled flow and diffusion processes following a radial coordinate transformation are based on an appropriate finite difference technique which attain appreciable stability in both the flow phenomena and the convection-dominated diffusion processes.

인도 역사의 한 문제로서 유럽

디페쉬 차크라바르티(Dipesh Chakravarty),김은실 (번역자),문금영 (번역자) 문화과학사 2001 흔적 Vol.- No.1

Influence of Temperature and Humidity on Pregnancy Rate of Murrah Buffaloes under Subtropical Climate

Dash, Soumya,Chakravarty, A.K.,Sah, V.,Jamuna, V.,Behera, R.,Kashyap, N.,Deshmukh, B. Asian Australasian Association of Animal Productio 2015 Animal Bioscience Vol.28 No.7

Heat stress has adverse effects on fertility of dairy animals. Decline in fertility is linearly associated with an increase in combination of both temperature and humidity. The purpose of this study was to investigate the relationship between temperature humidity index (THI) and the pregnancy rate of Murrah buffaloes in a subtropical climate. The effects of genetic and non-genetic factors viz., sire, parity, period of calving and age group at first calving were found non-significant on pregnancy rate. The effect of THI was found significant (p<0.001) on pregnancy rate of Murrah buffaloes calved for first time and overall pregnancy rate. The threshold THI affecting the pregnancy rate was identified as THI 75. The months from October to March showed THI<75 and considered as non heat stress zone (NHSZ), while months from April to September were determined as heat stress zone (HSZ) with $THI{\geq}75$. The lowest overall pregnancy rate (0.25) was obtained in July with THI 80.9, while the highest overall pregnancy rate (0.59) was found in November with THI 66.1. May and June were identified as critical heat stress zone (CHSZ) within the HSZ with maximum decline (-7%) in pregnancy rate with per unit increase in THI. The highest overall pregnancy rate was estimated as 0.45 in NHSZ with THI value 56.7 to 73.2. The pregnancy rate was found to have declined to 0.28 in HSZ with THI 73.5 to 83.7. However, the lowest pregnancy rate was estimated as 0.27 in CHSZ with THI value 80.3 to 81.6.

Observation of novel coexistence of Kondo effect and room temperature magnetism in AlN/Al/AlN trilayer thin film

Nath Deena,Chakravarty Sujay,Deshpade U.P.,Arasu A.V. Thanikai,Baskaran R.,Shekar N.V. Chandra 한국물리학회 2022 Current Applied Physics Vol.34 No.-

In this work for the first time, we are reporting the unusual observation of the Kondo effect with the coexistence of room temperature ferromagnetism in AlN/Al/AlN trilayer thin film. The grown film shows resistivity minimum at a temperature of ~48K, which shifts to the lower temperature on the application of magnetic fields. After considering various possibilities for an upturn in resistivity, we found that the Kondo scattering is responsible for upturn at low temperature. The simultaneous presence of ferromagnetism and Kondo scattering is explained by spatial variation of nitrogen vacancy defects from the film surface to the Al sandwich layer. Furthermore, magneto-transport properties of the film measured at different temperature exhibits both negative and positive components described by localized magnetic moment model for the spin scattering of carriers and two-band model, respectively. This work provides insight into the novel co-existence of ferromagnetism and Kondo effect in crystalline AlN.

Detection of Polymorphism of Growth Hormone Gene for the Analysis of Relationship between Allele Type and Growth Traits in Karan Fries Cattle

Pal, Aruna,Chakravarty, A.K.,Bhattacharya, T.K.,Joshi, B.K.,Sharma, Arjava Asian Australasian Association of Animal Productio 2004 Animal Bioscience Vol.17 No.10

The present study was conducted to detect polymorphism at growth hormone gene in Karan Fries bulls. A 428 bp fragment of growth hormone gene spanning over $4^{th}$exon, $4^{th}$intron and $5^{th}$ exon was amplified and digested with AluI restriction enzyme to identify polymorphism at this locus. Karan Fries bulls were found to be polymorphic at this locus. Two genotypes LL and LV were identified in Karan Fries with higher allelic frequency for L allele. In Karan Fries males, the average birth weight, 3 months body weight and daily body weight gains of LL homozygotes were significantly higher than that of LV heterozygotes. Genetic distances of KF bulls with respect to genotype along with 3 months body weight and average daily body weight gain forms a single cluster of bulls with LL genotype, while individuals with LV genotype forms three distinct clusters indicating more influence of L allele on growth traits.