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Unsteady flow of a Maxwell nanofluid over a stretching surface in the presence of magnetohydrodynamie and thermal radiation effects

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Propulsion and Power Research 2017年第1期6卷 31-40页

作者： Macha madhu Naikoti Kishan Ali J.Chamkha Department of Mathematics Osmania UniversityHyderabad-7TSIndia Mechanical Engineering Department Prince Mohammad Bin Fahd UniversityAl-Khobar 31952Kingdom of Saudi Arabia

The problem of unsteady magnetohydrodynamic(MHD)boundary layer flow of a non-Newtonian Maxwell nanofluid over a stretching surface with thennal radiation is *** Maxwell model is used to characterize the non-Newtonian fluid *** appropriate similarity transformation Is employed to transform the governing partial differential equations of mass,momentum,energy and nanoparticle concentration into ordinary differential *** coupled non-linear ordinary differential equations are solved by using the variational finite element *** flow features and the heat transfer characteristics and nanoparticle volume fraction are analyzed and discussed in detail for several sets of values of the governing flow *** results for the skin-friction coefficient,local Nusselt number and the local Sherwood number are presented in tables for various values of the flow controlling parameters.

关键词： Unsteady flow Stretching surface Maxwell nanofluid Magnetohydrodynamic(MHD) Thermal radiation

Neural network modeling to evaluate the dynamic flow stress of high strength armor steels under high strain rate compression

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Defence Technology（防务技术） 2014年第4期10卷 334-342页

作者： Ravindranadh BOBBILI V.madhu A.K.GOGIA Defence Metallurgical Research Laboratory Hyderabad 500058 India

An artificial neural network(ANN) constitutive model is developed for high strength armor steel tempered at 500 C, 600 C and 650 C based on high strain rate data generated from split Hopkinson pressure bar(SHPB) experiments. A new neural network configuration consisting of both training and validation is effectively employed to predict flow stress. Tempering temperature, strain rate and strain are considered as inputs, whereas flow stress is taken as output of the neural network. A comparative study on Johnsone Cook(Je C) model and neural network model is performed. It was observed that the developed neural network model could predict flow stress under various strain rates and tempering temperatures. The experimental stressestrain data obtained from high strain rate compression tests using SHPB, over a range of tempering temperatures(500e650 C), strains(0.05e0.2) and strain rates(1000e5500/s) are employed to formulate Je C model to predict the high strain rate deformation behavior of high strength armor steels. The J-C model and the back-propagation ANN model were developed to predict the high strain rate deformation behavior of high strength armor steel and their predictability is evaluated in terms of correlation coefficient(R) and average absolute relative error(AARE). R and AARE for the Je C model are found to be 0.7461 and 27.624%, respectively, while R and AARE for the ANN model are 0.9995 and 2.58%, respectively. It was observed that the predictions by ANN model are in consistence with the experimental data for all tempering temperatures.

关键词：人工神经网络模型高应变率高强度装甲钢流变应力可预测性压缩评估

Effects of Sudden Stratospheric Warming Events on the Distribution of Total Column Ozone over Polar and Middle Latitude Regions

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Open Journal of Marine Science 2016年第2期6卷 302-316页

作者： Vazhathottathil madhu Department of Atmospheric Sciences School of Marine Sciences Cochin University of Science and Technology Cochin India

In winter the polar stratosphere is extremely cold. During the Sudden Stratospheric Warming events, the polar stratospheric temperature rises concurrently zonal-mean zonal flow weakens over a short period of time. As the zonal flow weakens, the stratospheric circulation becomes highly asymmetrical and the stratospheric polar vortex is displaced off the pole. The polar stratospheric temperature rises by 50°C and the stratospheric circumpolar flow reverses direction in a span of just few days. Sudden Stratospheric Warming (SSW) leads to significant changes in the rate of several chemical reactions which occur in the polar stratosphere. During such events, the dynamical fields in the polar stratosphere completely altered and columnar ozone changed. This study concentrated on the variability of winter polar vortex, meridional temperature gradient and associated changes in the Total Column Ozone (TCO) over the polar and middle latitude regions. It is found that changes in the amount of column ozone are positively correlated with polar lower stratospheric temperature with colder (warmer) temperature correlating with less (high) amount column ozone. But in the middle latitude region we observed negative correlations between ozone concentration and stratospheric temperature. In almost all cases there is sudden increase of ozone concentration over the pole and after few days the value is reduced when the warming effect is weak. During SSW events there observed an increase of 30 DU in TCO from the average value over the pole and if the SSW is strong TCO is found to rise by 50 DU. But in the middle latitude approximately 10 DU increase is noted. From the above results it may be concluded that variability of column ozone depends on dynamic and stratospheric chemistry over the poles and in middle latitude the variability can be attributed to the dynamical aspects. Anomaly of column ozone is higher during sudden stratospheric warming events over both polar and middle latitude reg

关键词： Stratospheric Sudden Warming Total Column Ozone Polar Vortex

Madden Julian Oscillations in Total Column Ozone, Air Temperature and Surface Pressure Measured over Cochin during Summer Monsoon 2015

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Open Journal of Marine Science 2016年第2期6卷 270-282页

作者： Vazhathottathil madhu Department of Atmospheric Sciences School of Marine Sciences Cochin University of Science and Technology Cochin India

The intra-seasonal variability plays a major role in the inter-annual variability of weather parameters such as rainfall, temperature and pressure which lead to extreme weather events in certain years. The active (more rainy days) and break (less rainy days) periods of Indian summer monsoon heavily depend on the intra-seasonal variability of weather parameters such as wind, pressure and temperature oscillations during the monsoon season. In the present analysis daily total column ozone, surface temperature and surface pressure measured over Cochin using Microtop II Ozonometer (sun Photometer) were used to study the Intra-Seasonal Variations (ISV) of the above parameters during the monsoon season, 2015. The dominant and significant intra-seasonal oscillations (ISOs) were identified using an advanced statistical method called the Discrete Mayer’s Wavelet (DMW) analysis. Two major ISOs such as Madden Julian Oscillations (MJO, 30 - 60 days) and quasi-bi weekly (12 - 16 days) oscillations were found in TCO, surface temperature and pressure. In TCO an additional mode of ISO with quasi tri-weekly periodicity was also found (16 - 22 day). It is observed that MJO mode is the dominant among all other modes and its positive and negative phases correlate with positive and negative anomalies of the above parameters. The ISO mode in the surface pressure shows an out of phase relation with the Indian summer monsoon rainfall which indicates the active and break periods of Indian summer monsoon. The contribution of MJO mode is dominant in the tropical atmosphere, which modulates the intra-seasonal variability. It is found that for the year 2015 total column ozone, surface pressure and surface temperature show an annual range of 30 DU, 4 hPa and 1°C, respectively.

关键词： Intra-Seasonal Oscillations Total Column Ozone (TCO) Madden Julian Oscillation Wavelet Analysis

Growth performance, and enteric and manure greenhouse gas emissions from Murrah calves fed diets with different forage to concentrate ratios

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Animal Nutrition 2018年第2期4卷 215-221页

作者： Vinu M.Nampoothiri madhu Mohini Bilal A.Malla Goutam Mondal Sujata PANDita Division of Animal Nutrition ICAR-National Dairy Research Institute Division of Animal Physiology ICAR-National Dairy Research Institute

The present study investigated the effects of different dietary forage to concentrate ratios on animal performance, and enteric and manure greenhouse gas emissions in growing *** male Murrah calves(153.5 ± 18.17 kg; 6 to 12 months) were randomly assigned to 3 dietary treatments and fed corn fodder, wheat straw and concentrate in 3 different proportions: 20:60:20(C20); 20:40:40(C40) and 10:30:60(C60), for a period of 120 *** dietary concentrate proportion had no significant(P > 0.05) effect on dry matter intake(DMI) but increased crude protein(CP) and total digestible nutrient intake(P 0.05).The apparent digestibility of dry matter, organic matter and CP were higher(P 0.05).Daily methane(CH_4) emission(g/d), CH_4 energy loss(MJ/d) and CH_4 yield(CH_4 g/kg organic matter intake [OMI], CH_4 g/kg digestible OMI, and CH_4% of metabolizable energy intake) were significantly higher for C20 compared with C60(P 0.05).Manure CH_4(g/kg DMI) and nitrous oxide(N_2O mg/kg nitrogen) emissions were not affected(P > 0.05), but N_2O emission on mg/kg DM basis was significantly higher(P < 0.05) from the manure of calves fed C60 than that for ***, increasing dietary concentrate proportion improved animal performance, and reduced enteric CH_4 emission(g/day) without any significant effect on manure N_2O(mg/kg nitrogen) and CH_4 emissions.

关键词： Concentrate proportion Growth Digestibility Manure Methane Nitrous oxide

Prediction of flow stress of 7017 aluminium alloy under high strain rate compression at elevated temperatures

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Defence Technology（防务技术） 2015年第1期11卷 93-98页

作者： Ravindranadh BOBBILI B.RAMAKRISHNA V.madhu A.K.GOGIA Defence Metallurgical Research Laboratory

An artificial neural network(ANN) constitutive model and JohnsoneC ook(Je C) model were developed for 7017 aluminium alloy based on high strain rate data generated from split Hopkinson pressure bar(SHPB) experiments at various temperatures. A neural network configuration consists of both training and validation, which is effectively employed to predict flow stress. Temperature, strain rate and strain are considered as inputs, whereas flow stress is taken as output of the neural network. A comparative study on Johnsone Cook(Je C) model and neural network model was performed. It was observed that the developed neural network model could predict flow stress under various strain rates and temperatures. The experimental stressestrain data obtained from high strain rate compression tests using SHPB over a range of temperatures(25 e300 C), strains(0.05e0.3) and strain rates(1500e4500 s 1) were employed to formulate JeC model to predict the flow stress behaviour of 7017 aluminium alloy under high strain rate loading. The JeC model and the back-propagation ANN model were developed to predict the flow stress of 7017 aluminium alloy under high strain rates, and their predictability was evaluated in terms of correlation coefficient(R) and average absolute relative error(AARE). R and AARE for the J-C model are found to be 0.8461 and 10.624%, respectively, while R and AARE for the ANN model are 0.9995 and 2.58%, respectively. The predictions of ANN model are observed to be in consistent with the experimental data for all strain rates and temperatures.

关键词： Aluminium alloy Artificial neural network Johnson-Cook model

Investigation of hepatoprotective activity of Cyathea gigantea(***.)leaves against paracetamol-induced hepatotoxicity in rats

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Asian Pacific Journal of Tropical Biomedicine 2012年第5期2卷 352-356页

作者： P madhu Kiran A Vijaya Raju B Ganga Rao A.U College of Pharmaceutical Sciences Andhra University

Objective:To investigate the hepatoprotective activity of methanolic leaf extract of Cyathea gigantea(***)against paracetamol induced liver damage in ***:The hepatoprotective activity for plant extract was investigated for paracetamol induced hepatoxicity in *** albino rats of either sex were divided into five groups of 6 animals each and are given orally the following treatment for seven *** normal control group was given 1%*** 1mL/kg bw,*** at dose of 1g/kg bw,*** given as toxic dose for inducing ***(50mg/kg.p.o.) was given as reference *** doses of C. gigantea extract i.e.,100 mg/*** 200 mg/kg,*** tested for hepatoprotective activity. The treatment was given for seven days and after 24 h of last treatment blood was collected from retro-orbital plexus and analysed for various serum parameters like serum glutamic-oxaloacetic transaminase(SGOT),serum glutamic pyruvic transaminase(SGPT),alkaline phosphatase(ALP),total bilirubin(TB)and total protein(TP)in different ***:The paracetamol intoxication lead to histological and biochemical *** treatment with methanolic leaf extract of *** reduced the elevated levels of SCOT,SGPT,ALP,TB and also reversed the hepatic damage towards normal which further supports the hepatoprotective activity of leaf extract of ***:The methanolic extract of leaves of *** at doses of 100 mg/kg bw and 200 mg/kg bw have significant effect on liver of paracetamol induced hepatotoxicity model in rats.

关键词： Hepatoprotective Cyathea gigantea Paracetamol Silymarin Hepatotoxicity

Spatial and Temporal Variability of Total Column Ozone over the Indian Subcontinent: A Study Based on Nimbus-7 TOMS Satellite

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Atmospheric and Climate Sciences 2014年第5期4卷 884-898页

作者： Vazhathottathil madhu Department of Atmospheric Sciences Cochin University of Science and Technology Cochin India

The distribution and variability of ozone is very important to the atmospheric thermal structures, and it can exert their greater influence on climate. Present study is based on Nimbus-7 TOMS overpass column ozone for a period of 14 years (1979-1992) over twelve selected Indian stations from south to north latitude and it explores the spatial and temporal variability of Total Column Ozone (TCO). For this investigation an advanced statistical methods such as Factor Analysis and Morlet wavelet transform are employed. Total column ozone variability over these stations is grouped into two clusters (Eigen value greater than 1) by the Multivariate Factor analysis. It is found that the Group I stations shows the same nature of variability mainly due the first factor as the primarily loading and whereas as the Group II stations shows the same nature of variability due to second factor as the primary loading. The correlation value of TCO decreases from 0.9 to 0.32 as we move from south to north stations (lower latitude to higher latitude). The total column ozone over tropical stations is maximum during monsoon season with peak in the month of June and that for the higher latitude stations is during the pre-monsoon season. Annual average of TCO for tropical stations is about 265 DU and that for subtropical stations is about 280 DU and a difference of 15 DU is noted in the annual average of TCO between tropical and subtropical stations. A large reduction in TCO is noted over the Indian subcontinent in the year 1985, the same year in which the ozone hole over Antarctica was discovered. It is also found that two prominent oscillations are present in total column ozone one with a periodicity of 16 to18 months and other with 28 to 32 months (QBO periodicity) apart from the annual oscillations. These oscillations are found to be significant at above 95% level of confidence when tested with Power Spectrum method. Tropical TCO shows high concentration during the westerly phase and lo

关键词： Total Column Ozone Quasi-Biennial Oscillation Interannual Variability Morlet Wavelet

Heat transfer and entropy generation analysis of non-Newtonian fluid flow through vertical microchannel with convective boundary condition

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Applied Mathematics and Mechanics(English Edition) 2019年第9期40卷 1285-1300页

作者： M. madhu N. S. SHASHIKUMAR B. MAHANTHESH B. J. GIREESHA N. KISHAN Department of Studies and Research in Mathematics Kuvempu University Shankaraghatta 577451 India Department of Mathematics Christ Deemed to be University Bangalore 560029 India Department of Mathematics Osmania University Telangana 500007 India

The entropy generation and heat transfer characteristics of magnetohydrodynamic (MHD) third-grade fluid flow through a vertical porous microchannel with a convective boundary condition are analyzed. Entropy generation due to flow of MHD non-Newtonian third-grade fluid within a microchannel and temperature-dependent viscosity is studied using the entropy generation rate and Vogel's model. The equations describing flow and heat transport along with boundary conditions are first made dimensionless using proper non-dimensional transformations and then solved numerically via the finite element method (FEM). An appropriate comparison is made with the previously published results in the literature as a limiting case of the considered problem. The comparison confirms excellent agreement. The effects of the Grashof number, the Hartmann number, the Biot number, the exponential space-and thermal-dependent heat source (ESHS/THS) parameters, and the viscous dissipation parameter on the temperature and velocity are studied and presented graphically. The entropy generation and the Bejan number are also calculated. From the comprehensive parametric study, it is recognized that the production of entropy can be improved with convective heating and viscous dissipation aspects. It is also found that the ESHS aspect dominates the THS aspect.

关键词： microchannel entropy generation Bejan number third-grade fluid magnetic field