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1

Development and validation of HPLC assay method for marbofloxacin determination in veterinary chewable tablets

Oliveira K. R. W., Sversut R. A., Singh A. K., Amaral M. S., Kassab N. M.

Acta Chromatographica

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2019

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Vol. 31, no. 4

291--293

EN

The present study aimed to develop and validate an analytical method for determination of marbofloxacin (MAR) in veterinary chewable tablets. The isocratic reversed-phase chromatographic method was developed and validated using a Vertisep®, RP C18 column (150 mm × 4.6 mm, 5.0 μm). The mobile phase was composed of water–acetonitrile (55:45, v/v) with pH adjusted to 3.0 with ortho-phosphoric acid and a flow rate set at 0.4 mL/min. The proposed method was validated for linearity in a concentration range of 2.5 to 17.5 μg/mL with a correlation coefficient of 0.99991. The mean content of MAR found in chewable tablets was 104.40% with RSD below 2%. The accuracy expressed as average recovery of the proposed method was 98.74%, and the precision expressed as relative standard deviation among repeated analysis was 0.55%. The method has adequate sensitivity with detection and quantitation limits of 0.25 and 0.81 μg/mL, respectively. Based on the presented results and according to the ICH and AOAC guidelines on validation of analytical methods, the proposed method was considered precise, accurate with adequate sensitivity, and robust in the MAR quantitative analysis. Therefore, the method can be used in the quality control of chewable veterinary tablets containing MAR.

2

Natural convection in a hydrodynamically and thermally anisotropic non-rectangular porous cavity: effect of internal heat generation/absorption

Chandran P., Sacheti N. C., Bhadauria B. S., Singh A. K.

International Journal of Applied Mechanics and Engineering

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2018

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Vol. 23, no. 3

595--609

EN

Laminar natural convection in a trapezoidal porous vertical cavity has been investigated in this work. It is assumed that the porous enclosure is filled up with a permeable material subject to hydrodynamic and thermal anisotropy, the flow being governed by the Darcy law as applicable to a non-isotropic medium. It is further assumed that (i) there is heating at the left vertical wall and cooling at the right wall of the enclosure and (ii) the flow domain is subject to the presence of heat source or heat sink. The partial differential equations governing the resulting free convection have been solved numerically in the non-dimensional forms. There arises a number of parameters relating to buoyancy, internal heating, cavity aspect ratio and inclination of the upper surface to the horizontal. The influence of these parameters has been illustrated and analyzed through contours of streamlines and isotherms. We have also discussed the role of internal heating as well as anisotropy on the heat transfer characteristics.

3

Short-term optimal energy management in stand-alone microgrid with battery energy storage

Paliwal N. K., Singh A. K., Singh N. K.

Archives of Electrical Engineering

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2018

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Vol. 67, nr 3

499-–513

EN

The optimal energy management (OEM) in a stand-alone microgrid (SMG) is a challenging job because of uncertain and intermittent behavior of clean energy sources (CESs) such as a photovoltaic (PV), wind turbine (WT). This paper presents the effective role of battery energy storage (BES) in optimal scheduling of generation sources to fulfill the load demand in an SMG under the intermittency of theWT and PV power. The OEM is performed by minimizing the operational cost of the SMG for the chosen moderate weather profile using an artificial bee colony algorithm (ABC) in four different cases, i.e. without the BES and with the BES having a various level of initial capacity. The results show the efficient role of the BES in keeping the reliability of the SMG with the reduction in carbon-emissions and uncertainty of the CES power. Also, prove that the ABC provides better cost values compared to particle swarm optimization (PSO) and a genetic algorithm (GA). Further, the robustness of system reliability using the BES is tested for the mean data of the considered weather profile.

4

Impact of Inhomogeneity on SH-type Wave Propagation in an Initially Stressed Composite Structure

Saha S., Chattopadhyay A., Singh A. K.

Acta Geophysica

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2018

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Vol. 66, no. 1

1--19

EN

The present analysis has been made on the influence of distinct form of inhomogeneity in a composite structure comprised of double superficial layers lying over a half-space, on the phase velocity of SH-type wave propagating through it. Propagation of SH-type wave in the said structure has been examined in four distinct cases of inhomogeneity viz. when inhomogeneity in double superficial layer is due to exponential variation in density only (Case I); when inhomogeneity in double superficial layers is due to exponential variation in rigidity only (Case II); when inhomogeneity in double superficial layer is due to exponential variation in rigidity, density and initial stress (Case III) and when inhomogeneity in double superficial layer is due to linear variation in rigidity, density and initial stress (Case IV). Closed-form expression of dispersion relation has been accomplished for all four aforementioned cases through extensive application of Debye asymptotic analysis. Deduced dispersion relations for all the cases are found in well-agreement to the classical Love-wave equation. Numerical computation has been carried out to graphically demonstrate the effect of inhomogeneity parameters, initial stress parameters as well as width ratio associated with double superficial layers in the composite structure for each of the four aforesaid cases on dispersion curve. Meticulous examination of distinct cases of inhomogeneity and initial stress in context of considered problem has been carried out with detailed analysis in a comparative approach.

5

Magnetoelastic shear wave propagation in pre-stressed anisotropic media under gravity

Kumari N., Chattopadhyay A., Singh A. K., Sahu S. A.

Acta Geophysica

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2017

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Vol. 65, no. 1

189--205

EN

The present study investigates the propagation of shear wave (horizontally polarized) in two initially stressed heterogeneous anisotropic (magnetoelastic transversely isotropic) layers in the crust overlying a transversely isotropic gravitating semi-infinite medium. Heterogeneities in both the anisotropic layers are caused due to exponential variation (case-I) and linear variation (case-II) in the elastic constants with respect to the space variable pointing positively downwards. The dispersion relations have been established in closed form using Whittaker’s asymptotic expansion and were found to be in the well-agreement to the classical Love wave equations. The substantial effects of magnetoelastic coupling parameters, heterogeneity parameters, horizontal compressive initial stresses, Biot’s gravity parameter, and wave number on the phase velocity of shear waves have been computed and depicted by means of a graph. As a special case, dispersion equations have been deduced when the two layers and half-space are isotropic and homogeneous. The comparative study for both cases of heterogeneity of the layers has been performed and also depicted by means of graphical illustrations.

6

Development and validation of an isocratic HPLC method for simultaneous determination of quaternary mixtures of antihypertensive drugs in pharmaceutical formulations

Anderson J. F. F., Gerlin M. C. G., Sversut R. A., Oliveira L. C. S., Singh A. K., Amaral M. S., Kassab N. M.

Acta Chromatographica

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2017

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Vol. 29, no. 1

95--110

EN

The objective of this study was to develop and validate an assay method for simultaneous determination of atenolol, furosemide, losartan, and spironolactone in pharmaceutical formulations. A reverse-phase high-performance liquid chromatography procedure was developed, using a Kinetex® C-18 column (100 mm × 4.6 mm, 2.6 μm). The mobile phase was composed of metanol-water (75:25 v/v, pH 3.0, adjusted with phosphoric acid), with a flow rate of 0.4 mL min-1. All drugs were separated in less than 5 min. The method was validated according to International Conference on Harmonization (ICH) and Association of Official Analytical Chemists (AOAC) guidelines. The method showed linearity in a concentration range of 0.75–12.0 μg Ml-1 for atenolol (r = 0.9995), 0.30–12.00 μg Ml-1 for furosemide (r = 0.9997), 0.45–12.00 μg Ml-1 for losartan (r = 0.9995), and 0.45–12.0 μg Ml-1 for spironolactone (r = 0.9999). The method also showed repeatability and precision. The three-day average intra-day precisions were 101.35 ± 0.74% for atenolol, 95.84 ± 1.44% for furosemide, 98.90 ± 1.16% for losartan, and 97.19 ± 0.18% for spironolactone. Similarly, the inter-day precisions were 101.34 ± 0.72% for atenolol, 95.84 ± 0.1.50% for furosemide, 98.90 ± 1.17% for losartan, and 97.19 ± 0.83% for spironolactone. The method accuracy was also tested and validated - in this case, the average recovery values were 100.18 ± 1.20% for atenolol, 99.83 ± 1.54% for furosemide, 100.07 ± 0.95% for losartan, and 99.94 ± 0.93% for spironolactone. Finally, the method was successfully applied in the simultaneous determination of atenolol, furosemide, losartan, and spironolactone in magisterial formulas, as well as in commercial pharmaceutical formulations.

7

An Integrated Reverse Engineering Approach for Accuracy Control of Free-Form Objects

Pathak V. K., Nayak C., Singh A. K., Chaudhary H.

Archive of Mechanical Engineering

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2016

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Vol. LXIII, nr 4

647--663

EN

Computer-aided tools help in shortening and eradicating numerous repetitive tasks that reduces the gap between digital model and actual product. Use of these tools assists in realizing free-form objects such as custom fit products as described by a stringent interaction with the human body. Development of such a model presents a challenging situation for reverse engineering (RE) which is not analogous with the requirement for generating simple geometric models. Hence, an alternating way of producing more accurate three-dimensional models is proposed. For creating accurate 3D models, point clouds are processed through filtering, segmentation, mesh smoothing and surface generation. These processes help in converting the initial unorganized point data into a 3D digital model and simultaneously influence the quality of model. This study provides an optimum balance for the best accuracy obtainable with maximum allowable deviation to lessen computer handling and processing time. A realistic non trivial case study of free-form prosthetic socket is considered. The accuracy obtained for the developed model is acceptable for the use in medical applications and FEM analysis.

PL

Narzędzia wspomagania komputerowego pomagają skrócić lub wyeliminować powtarzające się wielokrotnie zadania w procesie redukowania różnic pomiędzy rzeczywistym produktem a jego modelem cyfrowym. Ich zastosowanie pomaga realizować obiekty o dowolnych kształtach, takie jak produkty dopasowane indywidualnie, przeznaczone do ścisłego współdziałania z ciałem człowieka. Opracowanie modeli podobnego rodzaju stanowi dla inżynierii odwrotnej wyzwanie nieporównywalnie trudniejsze od tego, jakim jest tworzenie modeli o prostych formach geometrycznych. Biorąc powyższe pod uwagę, autorzy zaproponowali alternatywną drogę tworzenia dokładniejszych modeli trójwymiarowych. W celu realizacji tego zadania trójwymiarowe chmury punktów są przetwarzane drogą filtracji, segmentacji, wygładzania siatki i generacji powierzchni. Zastosowane procesy przetwarzania pomagają przekształcić początkowy nieuporządkowany zbiór danych w model trójwymiarowy, wpływając jednocześnie na jakość tego modelu. W pracy zaproponowano kompromis pomiędzy osiąganiem najlepszej dokładności przy dopuszczalnych odchyłkach a zmniejszeniem obciążenia komputera i czasu przetwarzania danych. Rozważono realistyczny, nietrywialny przypadek modelu o złożonym kształcie – trzonu protezy kończyny. Dokładność uzyskanego modelu okazała się wystarczająca do zastosowań medycznych oraz do celów analizy MES.

8

Effect of Corrugation and Reinforcement on the Dispersion of SH-wave Propagation in Corrugated Poroelastic Layer Lying over a Fibre-reinforced Half-space

Singh A. K., Das A., Lakshman A., Chattopadhyay A.

Acta Geophysica

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2016

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Vol. 64, no. 5

1340--1369

EN

The presence of porosity and reinforcement in a medium is an important factor affecting seismic wave propagation and plays vital role in many geophysical prospects. Also, the presence of salt and ore deposits, mountains, basins, mountain roots, etc. is responsible for the existence of corrugated boundary surfaces of constituent layers. Such facts brought motivation for the present paper which deals with the propagation of SHwave in a heterogeneous fluid-saturated poroelastic layer with corrugated boundaries lying over an initially stressed fibre-reinforced elastic halfspace. Closed form of dispersion relation has been obtained and is found in well agreement to classical Love wave equation for isotropic case. The effect of corrugation, wave number, undulation, position parameter, horizontal compressive/tensile initial stress and heterogeneity on phase velocity has been analysed through numerical computation and graphical illustration. Moreover, comparative study exploring the effect of presence and absence of reinforcement in half-space on dispersion curve is the major highlight of the current study.

9

A Study of Early/Slow VLF Perturbations Observed at Agra, India

Pandey U., Singh A. K., Singh O. P., Singh B., Saraswat K.

Acta Geophysica

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2016

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Vol. 64, no. 3

755--771

EN

We present here the results of sub-ionospheric VLF perturbations observed on NWC (19.8 kHz) transmitter signal propagating in the Earth-ionosphere waveguide, monitored at our low latitude station Agra. During the period of observation (June-December 2011), we found 89 cases of VLF perturbation, while only 73 cases showing early character associated with strong lightning discharges. Out of 73 events, 64 (~84%) of the early VLF perturbations are found to be early/slow in nature; the remaining 9 events are early/fast. The onset duration of these early/slow VLF perturbations is up to ~ 5 s. A total of 54 observed early events show amplitude change lying between ± 3.0 dB, and phase change ± 12 degree, respectively, and found to occur mainly during nighttime. One of the interesting results we found is that the events with larger recovery time lie far away from the VLF propagation path, while events with smaller duration of recovery are within the ± 50-100 km of signal path. The World Wide Lightning Location Network (WWLLN) data is analysed to find the location of causative lightning and temporal variation. The lightning discharge and associated processes that lead to early VLF events are discussed.

10

Recent advancement in metal containing multicomponent chalcogenide glasses

Singh A. K.

Opto-Electronics Review

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2012

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Vol. 20, No. 3

226-238

EN

Amorphous semiconductors or chalcogenide glasses are the key materials in modern optoelectronics to make comfortable life of our society. Understanding of physical properties (like microstructure, thermal, optical, electrical) of these materials is important for their different uses. Predominant study of physical properties of the metal containing multicomponent chalcogenide glasses have attracted much attention, due to their interesting variable features and wide range of structural network modifications. Structural modifications in these materials are usually described with respect to the values of structural units (or average coordination number). In significance to this, the present work demonstrates the chronological development in the field of chalcogenide glasses along with scanning electron microscopy (SEM) morphologies. Optical, electrical and thermal correlative properties of recent developed Se93-xZn2Te5Inx (0 ≤ x ≤ 10) metallic multicomponent chalcogenide glasses are discussed. Variation in SEM morphology, refractive index (n), extinction coefficient (K), optical energy band gap (Eg), electrical conductivity (δav), crystallization activation energy (Ec) and glass forming ability (GFA) with structural units of Se-Zn-Te-In glasses have been demonstrated in this study. Subjected materials thermal, optical and electrical parameters have been achieved higher and lower in a respective manner at the threshold structural unit value (r)

11

The range of non-atomic measures on effect algebras

Khare M., Singh A. K.

Demonstratio Mathematica

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2010

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Vol. 43, nr 3

497-510

EN

The present paper deals with the study of superior variation m+, inferior variation m¯ and total variation |m| of an extended real-valued function m defined on an effect algebra L; having obtained a Jordan type decomposition theorem for a locally bounded real-valued measure m defined on L, we have observed that the range of a non-atomic function m defined on a D-lattice L is an interval (—m¯ (1), m+(1)). Finally, after introducing the notion of a relatively non-atomic measure on an effect algebra L, we have proved an analogue of Lyapunov convexity theorem for this measure.

12

Magnetogasdynamic shock waves in a non-uniform gas with heat conduction and radiation heat-flux

Vishwakarama J. P., Singh A. K.

International Journal of Applied Mechanics and Engineering

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2008

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Vol. 13, no 3

797-815

EN

The propagation of a cylindrical or spherical shock wave in an ideal gas with heat conduction and radiation heat-flux, in the presence of a spacially decreasing azimuthal magnetic field, is investigated. The initial density of the gas is assumed to obey a power law. The heat conduction is expressed in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient are assumed to vary with temperature and density. The shock wave is assumed to be driven by a piston moving with a variable velocity. Similarity solutions are obtained and the effects of variation of the heat transfer parameters and the variation of piston velocity (or initial density) and Alfven-Mach number are investigated.

13

Development of a mineral deposit as a sustainable economic unit

Sinha S. K., Singh A. K.

Gospodarka Surowcami Mineralnymi

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2008

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T. 24, z. 3/1

465-470

EN

Closure of a mine is more certain than starting it. Kamaishi mine of Japan is an example of the development of a mineral deposit as a sustainable economic unit, where revenue earned today is comparable, when the mine was operational. Alternative possible measures to be taken during active mining life have been suggested like Afforestation, Water Harvesting, Tourism etc. to earn the desired revenue during post mining period in the article.

PL

Zamknięcie kopalni jest bardziej pewne niż jej uruchomienie. Kopalnia Kamaishi w Japonii jest przykładem opracowania złoża mineralnego jako jednostki zrównoważonej ekonomicznie, gdzie dochody zarabiane obecnie są porównywalne z tymi z czasu, gdy kopalnia pracowała. Zaproponowano alternatywne środki do podjęcia w czasie aktywności kopalni, takie jak zalesianie, hodowle wodne, turystyka, itp., których celem jest wypracowanie żądanych dochodów w okresie po zakończeniu eksploatacji.

14

Non-isothermal hydromagnetic convection in a porous medium with heat sink: hypergeometric function solutions

Beg O. A., Takhar H. S., Beg T. A., Singh A. K.

International Journal of Applied Mechanics and Engineering

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2007

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Vol. 12, no 2

337-351

EN

The present paper deals with the free convection laminar boundary layer flow and heat transfer of an incompressible, electrically conducting, viscous fluid through a porous medium caused by stretching a porous wall in the presence of a heat source and under the influence of uniform magnetic field. Exact solutions of the basic equations of momentu m and energy ar e obtained after reducing them i n to non-linear ordinary differential equations and using confluent hypergeometric functions. The variations in the velocity field and temperature distribution with the Prandtl number (Pr), hydromagnetic parameter (M), permeability param eter (K), suction parameter (N), wall temperature parameler (S), and the heat sink parameter (Q) are obtained and depicted graphically. The skin-friction at the wall is also derived, and the numerical values for various physical parameters are also tabulaled. Magnetic field (M) is seen to reduce both longitudinal and translational velocities and also lower temperalures, aiding in controlling momentum and heat transfer during materiaIs processing. Suction (N) posivitely influences the transverse velocity but depresses the longitudinal velocity magnitudes as we II as decreasing tempcratures. Suction therefore also assists in controlling heat transfer in Ihe boundary layer. Increasing permeability parameter (K) depresses the longitudinal velocity but elevates transverse velocities and increases the skin friction at the wall. Both rising temperature (non-isothermal wall) parameter (S) and heat sink parameter (Q) decrease temperature values. The model finds applications in nucIear engineering control systems and MHD energy systems.

15

Achieving enhanced perceptual quality of stego-images for secure multimedia transmission

Singh H. V., Singh A. K., Balasubramanian S. K., Mohan A.

Image Processing & Communications

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2007

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Vol. 12, no 1

47-52

EN

This paper discusses a new method of hiding ASCII characters into still cover image. It is based on finding match between the bit of the randomly selected image pixel and the data bits. Higher nibbles are used for data hiding at a position indicated in the lower nibble using a 2-bit code word. Simulation results on IEEE standard Lena image hiding 800 ASCII text characters are given. It is shown that the proposed technique achieves up to 44.7 dB PSNR as against minimum required value of 35 dB for acceptable perceptual quality along with the bounds of the change in the original pixel value in the range ۭ. Therefore the proposed method retains enhanced perceptual quality of the original cover image in spite of hiding large number of text characters and offers high robustness as compared to the LSB insertion technique [1, 2]. In addition it is less prone to attacks by eaves droppers and therefore it can be effectively used for secure multimedia transmissions.

16

Transient natural convection between two vertical walls heated/cooled asymmetrically

Singh A. K., Paul T.

International Journal of Applied Mechanics and Engineering

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2006

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Vol. 11, no 1

143-154

EN

The present paper analyses a closed form solution for the transient free convective flow of a viscous and incompressible fluid between two vertical walls as a result of asymmetric heating or cooling of the walls. The convection currents between the walls occur due to a change in the temperature of the walls to that of the temperature of the fluid. The Laplace transform method has been used to find the solutions for the velocity and temperature fields by solving the governing partial differential equations. The numerical values obtained from the analytical solution show that the flow is initially in the downward direction near the cooled wall for negative values of the buoyancy force distribution parameter. The temperature field of both the air and water gradually decreases and becomes negative near the cooled wall for all negative values of the buoyancy force distribution parameter. The transient solution approaches a steady state when the non-dimensional time becomes comparable with the actual Prandtl number.

17

Transient free-convective flow in a vertical channel due to symmetric heating

Jha B. K., Singh A. K., Takhar H. S.

International Journal of Applied Mechanics and Engineering

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2003

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Vol. 8, no 3

497-502

EN

This paper presents a closed form solution for a transient free convective flow of a viscous and incompressible fluid in a vertical channel due to symmetric heating of channel walls. The Laplace transform technique has been used to obtain the expression for the velocity and temperature fields by solving the governing differential equations. The influence of the physical parameters on the velocity field, skin-friction, rate of heat transfer and volumetric flux of the fluid are carefully analysed. A correlation between the steady state time and the Prandtl number has been developed. It is observed that the nature of correlation is linear when the Prandtl number is greater than one while cubic for the Prandtl number is less than one.

18

Transient natural convection in a vertical channel

Paul T., Jha B. K., Singh A. K.

International Journal of Applied Mechanics and Engineering

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2001

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Vol. 6, no 4

913-922

EN

This paper describes a theoretical analysis of transient motion of a viscous incompressible fluid in a vertical channel. The motion of the fluid is caused by the buoyancy force arising from the temperature gradient as a result of constant heat flux at one wall and an adiabatic condition on the other wall. Expressions for the velocity and temperature fields are derived with the help of the Laplace transform technique. The influence of the various parameters is extensively discussed with the help of graphs. It has been observed that the temperature is not influenced by the presence of an adiabatic condition on the other plate for large values of the Prandtl number.

19

Exact solutions for the convective flow of fluids of different Prandtl numbers near an infinite vertical plate in a rotating system

Chandran P., Sacheti N. C., Singh A. K.

International Journal of Applied Mechanics and Engineering

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2001

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Vol. 6, no 3

573-590

EN

The partial differential equations governing the unsteady convective flow of a fluid have been solved exactly when the flow takes place near an infinite vertical plate in a system rotating with a constant angular velocity. Exact analytical solutions for the boundary layer velocity variables and skin friction components have been presented separately for the cases of fluids whose Prandtl numbers are less than or greater than unity. The influence of rotation on the temporal and spatial variations of these physical quantities has been discussed for two specific fluids, each belonging to the two separate Prandtl number categories considered. It is seen that the rotation parameter and the Prandtl number have significant effects on the boundary layer velocity and skin friction.

20

On the thermal boundary layer of a moving flat plate thermometer in the presence of Ohmic heating

Singh A. K., Chandran P., Sacheti N. C.

Applied Mechanics and Engineering

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2000

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Vol. 5, no 2

303-313

EN

The energy aspect of the boundary layer flow due to Ohmic heating and frictional forces at a moving flat plate has been analyzed based on similarity transformations. The flow is assumed to take place in the presence of an externally applied transverse magnetic field. The velocity and temperature profiles in the boundary layer have been shown by numerically integrating the governing nonlinear ordinary differential equations. Furthermore, the variations of temperature, both close to and away from the boundary plate, have been illustrated graphically as a function of the Prandtl number. The effects of the dissipative processes on the skin friction and plate temperature have been discussed. The magnetic field increases both the skin friction and the wall temperature, whereas, for a fixed magnetic field, the effect of boundary motion is to decrease them.