Unsteady computation of flow field and convective heat transfer over tandem cylinders at subcritical Reynolds numbers

S. K. Dhiman,Arbind Kumar,J. K. Prasad 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.3

Unsteady flow and convective heat transfer over single and two tandem cylinders at constant-heat-flux condition in subcritical range of Reynolds number was numerically investigated. Two-dimensional computations were performed by adopting 3-equation k-kl-ω turbulence model using a commercial software FLUENT ® .The aim was to investigate the capabilities of k-kl-ω turbulence model for collective flow and heat transport conditions past cylindrical bodies and then to identify a critical spacing ratio for the maximum heat transport. The center-to-center spacing ratio (L/D) was varied in the range from 1.2 to 4.0. Instantaneous path lines and vorticity contours were generated to interpret the interaction of shear layer and vortices from upstream cylinder with the downstream cylinder. Comparison of pressure coefficients, fluctuating and average lift as well as drag coefficients, Strouhal number and the local and average Nusselt numbers with the available literatures indicated a reasonably good agreement. The combined outcome of flow field and heat transfer study revealed a critical spacing ratio of L/D = 2.2. Based on the present investigation, a correlation has been suggested to calculate overall average Nusselt number of the two cylinders placed in tandem.

Studies of Structural, Microstructure, Dielectric and Optical Properties of Bismuth-Based Complex Perovskite Modified Bismuth Ferrite: BiFeO3 –(Bi0.5 Na0.25 K0.25 )(Ti0.5 Mn0.5 )O3 Ceramics

S. K. Sourav,S. K. Parida,R. N. P. Choudhary,Umakant Prasad 한국전기전자재료학회 2023 Transactions on Electrical and Electronic Material Vol.24 No.5

This communication describes a solid-state reaction prepared bismuth oxide and related complex compounds (BNKMT) of a chemical composition (1-x)BiFeO3-x(Bi0.5 Na0.25 K0.25 Ti0.5 Mn0.5 O3), where x = 0.15 and 0.20. Structural studies of the complex system show rhombohedral crystal symmetry (#R3c). The homogeneous distribution of the grains and grain boundaries throughout the sample surface clearly defined grain boundaries, which play a significant part in the conductivity mechanism, as revealed by the analysis of scanning electron microscopy micrographs and electrical properties. An energydispersive X-ray analysis spectrum was used to verify the processed materials’ purity and composition. According to the analysis of the FTIR-ATR spectrum, the prepared samples show stretching bands that correspond to their constituent elements. A dielectric investigation confirmed that the Maxwell–Wanger type of dielectric dispersion is present in the samples. Studies of impedance parameters as a function of temperature and frequency result in a negative temperature coefficient of resistance behavior. While ac conductivity research supports the presence of a thermally activated relaxation process in the materials. Analysis of electric modulus discloses a non-Debye type relaxation mechanism in the studied sample. Because the samples are semiconducting at high temperatures, semi-circular arcs have been seen in both the Nyquist and Cole–Cole plots. When compared to BNKTM 15%, BNKTM 20% has a bandgap energy of 5.9 eV, according to the analysis of UV visible spectra.

Experimental investigation of Wheeler's hardening model for Pusan clays

Chung, S.G.,M. Suneel,K.N. Prasad,Rao, K.G. 東亞大學校建設技術硏究所 2004 硏究論文集 Vol.28 No.1

The present paper adopts Wheeler's model (1997) to evaluate its application to Pusan clays. A program of triaxial and consolidation tests on samples of Pusan clays at Yangsan, Korea was under taken to investigate the applicability of the model adopted. The model parameters are evaluated by describing the initial state of the soil. Model predictions are shown to be qualitatively consistent with experimental observations, but refinement seems to be required to have much better agreement between experimental results and model predictions.

Limitations in doxorubicin production from Streptomyces peucetius

Malla, S.,Prasad Niraula, N.,Singh, B.,Liou, K.,Kyung Sohng, J. G. Fischer 2010 Microbiological research Vol.165 No.5

Doxorubicin (DXR), produced by Streptomyces peucetius ATCC 27952, exhibits potent antitumor activity against various cancer cell lines. Considerable time has lapsed since the biosynthesis of DXR and its overproduction was first summarized. Based on biosynthetic studies and product analysis, various factors affecting its production by the parental strain, S. peucetius ATCC 27952, are reviewed to better circumvent any bottlenecks in DXR production, thereby providing ideas to genetically engineered industrial strains of S. peucetius.

Influence of Deaeration, Cl− Ion and Strong Oxidizer on the Active Behavior of the High Phosphorus Containing Pig Iron and Subsequent Effect on the Sacrificial Anode Behavior

Nisheeth Kr. Prasad,A. S. Pathak,S. Kundu,K. Mondal 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.9

The effect of deaeration, Cl−ion content and strong oxidizer on the active behavior of the high phosphorus pig iron (HPPI)samples was studied in 3.5% NaCl and 1 N HNO3solutions. Deaerating the 3.5% NaCl solution could effectively shift thecorrosion potential of the HPPI below the protective potential of the steel in seawater [− 0.778 V vs saturated calomelelectrode (SCE)], which has not been observed in the freely aerated 3.5% NaCl solution. Both the Cl−ion content and thedeaerated conditions restrict the formation of the stable iron phosphate on the surface and promote the dissolution of the pigiron as soluble iron phosphate hydrate (FePO4·2H2O). However, in the case of the freely aerated nitric acid solution, evenwith deaeration, the HPPI samples have shown more noble behavior as compared to the mild steel due to the strong oxidizingnature of nitric acid and the formation of a stable iron phosphate on the surface.

Analysis of High-Temperature Effects on InAs∕In0.3Al0.7As∕InSb∕In0.3Al0.7As pHEMTs on Accessing RF/Analog performance: A Machine Learning Predictive Modeling

G. Lakshmi Vara Prasad,Venkatagurunatham Naidu Kollu,M. Sailaja,S. Radhakrishnan,K. Jagan Mohan,A. Kishore Reddy,G. Rajesh Chandra 한국전기전자재료학회 2024 Transactions on Electrical and Electronic Material Vol.25 No.1

In this paper, we delve into the intriguing realm of Pseudo-morphic High Electron Mobility Transistors (pHEMTs) composed of InAs∕In0.3Al0.7As∕InSb∕In0.3Al0.7As layers, utilizing Silvaco-TCAD for simulation. Our focus centers on the assessment of RF and analog electrical characteristics, with a keen eye on the high-temperature eff ects. The influence of temperature on device performance is meticulously evaluated in comparison to a reference device operating at room temperature. Traditionally, the critical parameters such as threshold voltage ( Vth ), transconductance ( gm ), and Ion∕Ioff ratio have been calculated within the temperature range spanning from 300 K to 700 K. The primary pHEMT device in our study exhibits impressive attributes, featuring a drain current of 950 mA, a threshold voltage of -1.75 V, a high transconductance ( gm ) value of 650 mS/mm, an Ion∕Ioff ratio of 1 × 106 , a transition frequency ( ft ) soaring to 790 GHz, and a maximum frequency ( fmax ) reaching a staggering 1.4 THz. However, as we traverse the temperature spectrum, our findings unveil a compelling narrative. The impact of rising temperature is unequivocal, triggering a cascade of transformations within the device. Notably, as the temperature escalates, we observe a noticeable decrease in current, a reduction in transconductance ( gm ), and a diminishing Ion∕Ioff ratio. To unravel the intricacies of these temperature-induced effects, we introduce the infusion of Machine Learning (ML) into our analysis.

Predicting Barrett's Esophagus in Families: An Esophagus Translational Research Network (BETRNet) Model Fitting Clinical Data to a Familial Paradigm

Sun, Xiangqing,Elston, Robert C.,Barnholtz-Sloan, Jill S.,Falk, Gary W.,Grady, William M.,Faulx, Ashley,Mittal, Sumeet K.,Canto, Marcia,Shaheen, Nicholas J.,Wang, Jean S.,Iyer, Prasad G.,Abrams, Julia American Association for Cancer Research 2016 Cancer Epidemiology, Biomarkers & Prevention Vol.25 No.5

<P><B>Background:</B> Barrett's esophagus is often asymptomatic and only a small portion of Barrett's esophagus patients are currently diagnosed and under surveillance. Therefore, it is important to develop risk prediction models to identify high-risk individuals with Barrett's esophagus. Familial aggregation of Barrett's esophagus and esophageal adenocarcinoma, and the increased risk of esophageal adenocarcinoma for individuals with a family history, raise the necessity of including genetic factors in the prediction model. Methods to determine risk prediction models using both risk covariates and ascertained family data are not well developed.</P><P><B>Methods:</B> We developed a Barrett's Esophagus Translational Research Network (BETRNet) risk prediction model from 787 singly ascertained Barrett's esophagus pedigrees and 92 multiplex Barrett's esophagus pedigrees, fitting a multivariate logistic model that incorporates family history and clinical risk factors. The eight risk factors, age, sex, education level, parental status, smoking, heartburn frequency, regurgitation frequency, and use of acid suppressant, were included in the model. The prediction accuracy was evaluated on the training dataset and an independent validation dataset of 643 multiplex Barrett's esophagus pedigrees.</P><P><B>Results:</B> Our results indicate family information helps to predict Barrett's esophagus risk, and predicting in families improves both prediction calibration and discrimination accuracy.</P><P><B>Conclusions:</B> Our model can predict Barrett's esophagus risk for anyone with family members known to have, or not have, had Barrett's esophagus. It can predict risk for unrelated individuals without knowing any relatives' information.</P><P><B>Impact:</B> Our prediction model will shed light on effectively identifying high-risk individuals for Barrett's esophagus screening and surveillance, consequently allowing intervention at an early stage, and reducing mortality from esophageal adenocarcinoma. <I>Cancer Epidemiol Biomarkers Prev; 25(5); 727–35. ©2016 AACR</I>.</P>

Testicular Cell Indices and Peripheral Blood Testosterone Concentrations in Relation to Age and Semen Quality in Crossbred (Holstein Friesian×Tharparkar) Bulls

Rajak, S.K.,Kumaresan, A.,Gaurav, M.K.,Layek, S.S.,Mohanty, T.K.,Aslam, M.K. Muhammad,Tripathi, U.K.,Prasad, Shiv,De, S. Asian Australasian Association of Animal Productio 2014 Animal Bioscience Vol.27 No.11

Present study analyzed the changes in peripheral blood testosterone concentrations and testicular cytogram in relation to age and semen quality in crossbred males. Three different age groups of crossbred males viz. bull calves (6 months, n = 5), young bulls (15 months, n = 5) and adult bulls (4 to 6 years, n = 8) were utilized for the study. Testicular fine needle aspiration cytology technique was used to quantify testicular cytology and their indices. Peripheral blood testosterone concentrations were measured using enzyme-linked immunosorbent assay method. Semen samples collected from adult bulls were microscopically evaluated for quality parameters. Mean peripheral blood testosterone concentrations in bull calves, young bulls and adult bulls were $2.28{\pm}0.09ng/mL$, $1.42{\pm}0.22ng/mL$ and $5.66{\pm}1.08ng/mL$ respectively, and that in adult bulls were significantly different (p<0.01) from young bulls and bull calves. There was no significant difference between the proportion of different testicular cells in bull calves and young bulls. Between young and adult bulls, significant differences (p<0.01) were observed in the proportion of spermatocytes, spermatozoa, and sperm: Sertoli cell ratio. The proportions of Sertoli cells showed a significant difference (p<0.01) between the three age groups. The number of primary spermatocytes had a positive correlation with peripheral blood testosterone concentrations in bull calves (r = 0.719, p<0.01). Number of Sertoli cells per 100 germ cells was negatively correlated with blood testosterone concentration in young bulls (r = -0.713, p<0.01). Among different semen parameters in adult bulls, ejaculate volume (r = 0.790, p<0.05) had positive relationship, and sperm motility had significant negative correlation (r = -0.711, p<0.05) with testosterone concentrations. The number of Sertoli cells and Sertoli cell index had a positive correlation with various semen quality parameters (p<0.001). Results of the present study conclude that number of Sertoli cells and Sertoli cell index are good indicators of semen quality, but peripheral blood testosterone concentrations may not have a direct relationship with various seminal attributes in crossbred bulls.

Growth Performance and Caecal Fermentation in Growing Rabbits Fed on Diets Containing Graded Levels of Mulberry (Morus alba) Leaves

Prasad, Rajendra,Misra, A.K.,Sankhyan, S.K.,Mishra, A.S.,Tripathi, M.K.,Karim, S.A.,Jakhmola, R.C. Asian Australasian Association of Animal Productio 2003 Animal Bioscience Vol.16 No.9

Growth performance, nutrient digestibility and changes in caecal fermentation pattern was studied on four groups of 8 grower rabbits (soviet chinchilla) each, fed on diets containing 17 to 18% CP and $10.4-11.00MJ\;DE\;kg^{-1}$ feed. The complete diets contained mulberry leaves along with other feed ingredients at 0 (LH), 15 (ML15), 30 (ML30) and 45% (ML45) levels. In LH diet ground lucerne hay was added at 15% of the diet as roughage source. The diets were uniform in other nutritional parameters except the higher amount of hemicellulose (18.7 and 16.5%) in LH and ML15 diets. The performance of grower rabbits was better (p<0.05) on LH and ML15 diets in terms of twelve weeks weight (kg), total gain (g), average daily gain (ADG) and feed efficiency (%). Different levels of mulberry leaves in the diet did not influence the dry matter intake. Digestibility of nutrients for DM, OM, CP, NDF and energy was uniform in all the diets but the digestibility of CF, ADF and cellulose was higher (p<0.01) on ML15, ML30 and ML 45 diets. The hemicellulose digestibility was significantly higher (p<0.01) on LH (44.52%) and ML15 (48.00%) compared to ML30 (33.54%) and ML 45 (39.17%) diets. The nitrogen retention (% of intake) was higher (p<0.05) in LH and ML15 diets than ML30 and ML45 diets. The caecum weight as percent of intestine weight consistently increased (p<0.05) with increasing content of mulberry leaves in diets. Total nitrogen and $NH_3$-N was higher on LH and ML15 diets. It is concluded that incorporation of mulberry leaves can replace Lucerne hay in complete rabbit feed (15% in diet). Even at higher level i.e. 30 and 45% of the diet mulberry leaves based complete feed gave promising results.

Synthesis and Antimicrobial Activity of 1-Benzhydryl-sulfonyl-4-(3- (piperidin-4-yl) propyl)piperidine Derivatives against Pathogens of Lycopersicon esculentum: A Structure-activity Evaluation Study

K. Vinaya, R. Kavitha,C. S. Ananda Kumar,S. B. Benaka Prasad,S. Chandrappa,S. A. Deepak,S. Nanjunda Swamy,S. Umesha,K. S. Rangappa 대한약학회 2009 Archives of Pharmacal Research Vol.32 No.1

Several 1-benzhydryl-sulfonyl-4-(3-(piperidin-4-yl)propyl)piperidine derivatives 8(a-j) were prepared by the treatment of substituted benzhydryl chlorides with 4-(3-(piperidin-4-yl)propyl)piperidine followed by N-sulfonation with sulfonyl chlorides in the presence of dry methylene dichloride and triethyl amine. The synthesized compounds were characterized by 1H-NMR, IR, and elemental analysis. All the synthesized compounds were evaluated in vitro for their efficacy as antimicrobial agents by artificial inoculation technique against standard strains of two important bacterial viz., Xanthomonas axonopodis pv. vesicatoria and Ralstonia solanacearum as well as and two fungal pathogens namely Alternaria solani and Fusarium solani of tomato plants. We have briefly investigated the structure-activity relation studies and reveal that the nature of substitutions on benzhydryl ring and sulfonamide ring influences the antibacterial activity. Among the synthesized new compounds 8b, 8d, 8g, 8h, 8i, and 8j were showed significant potent antimicrobial activities compared to the standard drugs Chloramphenicol, Mancozeb.