3D Numerical investigation of a rounded corner square cylinder for supercritical flows

Nivedan Vishwanath,Aditya K. Saravanakumar,Kush Dwivedi,Kalluri R.C. Murthy,Pardha S. Gurugubelli,Sabareesh G. Rajasekharan 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.35 No.1

Tall buildings are often subjected to steady and unsteady forces due to external wind flows. Measurement and mitigation of these forces becomes critical to structural design in engineering applications. Over the last few decades, many approaches such as modification of the external geometry of structures have been investigated to mitigate wind-induced load. One such proven geometric modification involved the rounding of sharp corners. In this work, we systematically analyze the impact of rounded corner radii on the reducing the flow-induced loading on a square cylinder. We perform 3-Dimensional (3D) simulations for high Reynolds number flows (Re=1 × 105) which are more likely to be encountered in practical applications. An Improved Delayed Detached Eddy Simulation (IDDES) method capable of capturing flow accurately at large Reynolds numbers is employed in this study. The IDDES formulation uses a k-ω Shear Stress Transport (SST) model for near-wall modelling that prevents mesh-induced separation of the boundary layer. The effects of these corner modifications are analyzed in terms of the resulting variations in the mean and fluctuating components of the aerodynamic forces compared to a square cylinder with no geometric changes. Plots of the angular distribution of the mean and fluctuating coefficient of pressure along the square cylinder’s surface illustrate the effects of corner modifications on the different parts of the cylinder. The windward corner’s separation angle was observed to decrease with an increase in radius, resulting in a narrower and longer recirculation region. Furthermore, with an increase in radius, a reduction in the fluctuating lift, mean drag, and fluctuating drag coefficients has been observed.

International patenting activity in the field of carbon nanotubes

R.K Gupta,I. Dwivedy 한국물리학회 2005 Current Applied Physics Vol.5 No.2

Carbon nanotubes (CNT) are unique nanostructures with remarkable electronic and mechanical properties and could be used, for example, in nanometre-sized electronics or to strengthen polymer materials. Today, both SWNT and MWNT are being used as key components in the production of high-strength composites, and advanced sensors, electronic and optical devices, catalysts, batteries and fuel cells. Patenting activity in this sub-field of nanotechnology registered a spurt during the last 12 years..implying a breakthrough bringing about a technological paradigm shift in the field of fullerene since carbon nanotubes are fullerene-related structures. CNT is, thus, one of the key technologies likely to revolutionize information technology, materials and medicine and the present study aim to examine technological developments in this field based on international patenting activity during the period of 1991.2003.

Zinc, Copper and Cobalt Concentrations in Blood During Inflammation of the Mammary Gland in Dairy Cows

Naresh, R.,Dwivedi, S.K.,Dey, S.,Swarup, D. Asian Australasian Association of Animal Productio 2001 Animal Bioscience Vol.14 No.4

A study was undertaken to record the utilization of some micro-elements during inflammation of the mammary gland. Two groups of twenty five animals each suffering from subclinical and clinical mastitis were selected for the study. All the animals were maintained on identical diets. Blood zinc level in cows with subclinical mastitis ($5.66{\pm}0.52$) was significantly (p<0.05) lower than that of healthy cows ($8.46{\pm}1.10ppm$). No significant difference was, however, recorded in blood copper and cobalt levels between healthy and mastitic cows.

Antioxidant Defense and Lipid Peroxide Level in Liver and Kidneys of Lead Exposed Rats

Patra, R.C.,Swarup, D.,Dwivedi, S.K. Asian Australasian Association of Animal Productio 2000 Animal Bioscience Vol.13 No.10

An experiment was carried out with 48 IVRI 2CQ rats 6-8 week old, weighing 50-100 g, to study the effect of lead exposure on antioxidant defense, lipid peroxide level, status of thiol groups and concentration of lead in the liver and kidneys at the end of the exposure and also after withdrawal of lead administration. Twenty four rats were given lead at a daily dose rate of 1 mg lead/2 ml of distilled water/kg body weight as lead acetate solution intraperitoneally for a period of 30 days. Another 24 control rats received 2 ml of sterile normal saline solution (0.85% NaCl)/kg body weight in an identical manner. A many-fold increase in concentration of lead was associated with a non-significant (p>0.05) decrease in the activities of superoxide dismutase (SOD) in the liver (27%) and kidneys (12%) and catalase in kidneys (22%). A significant (p<0.05) increase in lipid peroxide level was recorded in the liver (40%) compared with control values. There were significant (p<0.05) decreases in the total thiol and protein bound thiol contents in liver and an increase in non-protein bound thiol groups in the kidneys of lead exposed rats. During the 10 day observation period after withdrawal of lead administration, no significant change was observed with respect to any of the above parameters indicating that a 10 day withdrawal period was not enough for restoration of normality. It is concluded that the magnitude of response and the resultant changes in the lipid peroxide concentration, and the activities of SOD and catalase were not identical in the liver and kidneys of lead-exposed rats.

Evaluation of Ascorbic Acid Treatment in Clinical and Subclinical Mastitis of Indian Dairy Cows

Naresh, Ram,Dwivedi, S.K.,Swarup, D.,Patra, R.C. Asian Australasian Association of Animal Productio 2002 Animal Bioscience Vol.15 No.6

A study was carried out to assess the therapeutic effect of ascorbic acid in mastitis of dairy cows. The herd with a population of 250-275 lactating cows was screened for clinical and subclinical mastitis for a period of 5 months. Based on inclusion and exclusion criteria, eighteen animals each with clinical and subclinical mastitis in one quarter only were selected as study population. Twelve cows (group A) with normal udder and health were also selected as a healthy control. Clinical mastitis cows were grouped as B (n=12) and C (n=6). Cows of group B were treated with ascorbic acid at 25 mg/kg, subcutaneously for 5 consecutive days and intramammary infusion (Ampicillin sodium 75 mg and Cloxacillin sodium 200 mg/infusion) based on antibiotic sensitivity test, till complete recovery. Group C cows received only intramammary infusion till the complete recovery. Eighteen subclinical mastitis cows were divided in group D (n=12) and E (n=6). Cows of group D were treated with ascorbic acid at 25 mg/kg subcutaneously for 5 consecutive days while group E did not receive any treatment. California mastitis test (CMT), somatic cell count (SCC), physical changes of udder and milk were used to diagnose and classify the mastitis. Evaluation of the therapy was based on CMT score and physical changes of udder and milk. Sample size calculation was also performed but was not followed for control groups due to scarcity of cases. Adequate blinding was done when and where required to avoid the biases. Confounding variables like herd, age of the cow, stage of the lactation, season and geographical region were duly considered and adequate blocking was followed. Ascorbic acid was administered in clinical and subclinical cases even after cure considering its immunostimulatory and healing inducing effects. The recovery rate was faster in cases of clinical mastitis treated with ascorbic acid along with an intramammary infusion (group B) than the quarters of group C cows. Quarter wise the average duration/number (3.16${\pm}$0.11 days) of antimicrobial intramammary infusion was significantly (p<0.01) less in group B than that of average duration/number (5.33${\pm}$0.20 days) of group C. Subclinical mastitis cows treated with ascorbic acid showed 83.33% recovery while 16.77% did not respond to treatment till last day of study. Cows of group E (untreated) did not recovered from the mastitis. Subjective parameters viz. swelling, pain reflex of udder and physical changes in milk from quarter of ascorbic acid treated cows (group B) disappeared earlier than that of group C cows. It is concluded from this study that the ascorbic acid might be useful as an adjunct in case of clinical mastitis to get quick recovery with less number of intramammary infusions. High recovery rate in subclinical mastitis quarters of group D cows is appreciable and opens a new avenue to conduct further trials in a larger population in various field conditions. However, the pharmacology of ascorbic acid with particular reference to health of mammary gland needs to be investigated.

Synthesis and ferroelectric behavior of Gd doped BNT ceramics

Vijayeta Pal,R.K. Dwivedi,O.P. Thakur 한국물리학회 2014 Current Applied Physics Vol.14 No.1

In the present work, polycrystalline (Bi1xGdx)0.5Na0.5TiO3 (BGNT) ceramics with low amount of rare earth ion Gd3þ (x ¼ 0, 0.02, 0.03, 0.04) have been synthesized by a semiewet technique. XRD patterns show single phase formation for all the samples with a rhombohedral structure at room temperature. FESEM images show decrease in grain size with Gd concentration. The temperature dependence of dielectric constant has revealed that the depolarization temperature ‘Td’ decreases with increasing x and the temperature ‘Tm’ of maximum dielectric constant increases initially for x ¼ 0.02 thereafter decreases. All the samples have shown saturated hysteresis (PeE) loop at room temperature. The BGNT ceramic system for composition, x ¼ 0.02 exhibits improved piezoelectric properties and strong ferroelectricity. With increasing temperature, polarization has been found to be reduced and deformed PeE loops are observed around ‘Td’.

Investigation on the Effect of Asymmetric Cyclic Loading on Ratcheting Deformation and Bulk Texture Development in HSLA Steel

Pushpendra Kumar Dwivedi,R. Vinjamuri,S. K. Sahoo,Krishna Dutta 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

Ratcheting deformation in association with bulk texture evolution in HSLA steel is studied in this investigation. The cyclicdeformation behaviors and damage modes of the specimens are obtained at room temperature, employing asymmetric stresscontrolledtests under various combinations of mean stress and stress amplitudes. Bulk texture measurements of the specimensare done adopting an X-ray diffraction analysis. The results exhibit an increase in strain accumulation from 0.23 to 30.61%associated with a sharp reduction in ratcheting life from 3320 to 880 cycles by the increment in mean stress/stress amplitude. A continuous cyclic softening until the final failure is observed for all the ratcheting tests. It is noticed that variation of meanstress is more detrimental than stress amplitude in controlling strain accumulation while the effect of stress amplitude is morepronounced than mean stress for the reduction of ratcheting life. The fracture surface morphology indicates typical striationformation in the crack propagation region along with overload failure. The bulk texture studies indicate that there is a transitionbetween ‘ϒ’ fiber and ‘ζ’ fiber during all loading conditions. The texture intensity is increased from 5.71 to 11.68 withprogressive ratcheting strain accumulation. Here also, influence of stress amplitude is more significant than the mean stress.

Maximization of the usage of coronary CTA derived plaque information using a machine learning based algorithm to improve risk stratification; insights from the CONFIRM registry

van Rosendael, Alexander R.,Maliakal, Gabriel,Kolli, Kranthi K.,Beecy, Ashley,Al’Aref, Subhi J.,Dwivedi, Aeshita,Singh, Gurpreet,Panday, Mohit,Kumar, Amit,Ma, Xiaoyue,Achenbach, Stephan,Al-Mallah, Mou Elsevier 2018 Journal of cardiovascular computed tomography Vol.12 No.3

<P><B>Abstract</B></P> <P><B>Introduction</B></P> <P>Machine learning (ML) is a field in computer science that demonstrated to effectively integrate clinical and imaging data for the creation of prognostic scores. The current study investigated whether a ML score, incorporating only the 16 segment coronary tree information derived from coronary computed tomography angiography (CCTA), provides enhanced risk stratification compared with current CCTA based risk scores.</P> <P><B>Methods</B></P> <P>From the multi-center CONFIRM registry, patients were included with complete CCTA risk score information and ≥3 year follow-up for myocardial infarction and death (primary endpoint). Patients with prior coronary artery disease were excluded. Conventional CCTA risk scores (conventional CCTA approach, segment involvement score, duke prognostic index, segment stenosis score, and the Leaman risk score) and a score created using ML were compared for the area under the receiver operating characteristic curve (AUC). Only 16 segment based coronary stenosis (0%, 1–24%, 25–49%, 50–69%, 70–99% and 100%) and composition (calcified, mixed and non-calcified plaque) were provided to the ML model. A boosted ensemble algorithm (extreme gradient boosting; XGBoost) was used and the entire data was randomly split into a training set (80%) and testing set (20%). First, tuned hyperparameters were used to generate a trained model from the training data set (80% of data). Second, the performance of this trained model was independently tested on the unseen test set (20% of data).</P> <P><B>Results</B></P> <P>In total, 8844 patients (mean age 58.0 ± 11.5 years, 57.7% male) were included. During a mean follow-up time of 4.6 ± 1.5 years, 609 events occurred (6.9%). No CAD was observed in 48.7% (3.5% event), non-obstructive CAD in 31.8% (6.8% event), and obstructive CAD in 19.5% (15.6% event). Discrimination of events as expressed by AUC was significantly better for the ML based approach (0.771) vs the other scores (ranging from 0.685 to 0.701), P < 0.001. Net reclassification improvement analysis showed that the improved risk stratification was the result of down-classification of risk among patients that did not experience events (non-events).</P> <P><B>Conclusion</B></P> <P>A risk score created by a ML based algorithm, that utilizes standard 16 coronary segment stenosis and composition information derived from detailed CCTA reading, has greater prognostic accuracy than current CCTA integrated risk scores. These findings indicate that a ML based algorithm can improve the integration of CCTA derived plaque information to improve risk stratification.</P>

Structural and Transport Properties of B-site Cu Doped La<SUB>0.80</SUB>Sr<SUB>0.20</SUB>MnO₃ Thin Film on LaAlO₃ by Spray Pyrolysis

Pawan Kumar,Ravikant Prasad,P. K. Siwach,R. K. Dwivedi,H. K. Singh 한국자기학회 2008 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-