Wyniki wyszukiwania - BazTech

1

Design and analytical calculations of the width and arrangement of quantum well and barrier layers in GaN/AlGaN LED to enhance the performance

Sharma L., Sharma R.

Opto-Electronics Review

|

2021

|

Vol. 29, No. 4

141--147

EN

This research paper discusses an analytical approach to designing the active region of light emitting diodes to enhance its performance. The layers in the active region were modified and the effects of changing the width of quantum well and barrier layers in a multi-quantum light emitting diode on the output power and efficiency have been investigated. Also, the ratio of the quantum well width to the B layer width was calculated and proposed in this research paper. The study is carried out on two different LED structures. In the first case (i.e., first structure), the width of the quantum well layers is kept constant while the width of the B layers is varied. In the second case (i.e., second structure), both the quantum well and B layer widths are varied. Based on the simulation results, it has been observed that the LED power efficiency increases considerably for a given quantum well to B layers width ratio without increasing the production complexity. It is also seen that for a desired power efficiency the width of quantum well should be between 0.003 μm and 0.006 μm, and the range of B width (height) should be 2.2 to 6 times the quantum well width. The proposed study is carried out on the GaN-AlGaN-based multi-quantum well LED structure, but this study can be extended to multiple combinations of the semiconductor structures.

2

Performance Investigation of a Double Pipe Heat Exchanger under Different Flow Configuration by Using Experimental and Computational Technique

Kannojiya V., Gaur R., Yadav P., Sharma R.

Archive of Mechanical Engineering

|

2018

|

Vol. LXV, nr 1

27--41

EN

Heat exchangers are widely employed in numerous industrial applications to serve the heat recovery and cooling purpose. This work reports a performance analysis of a tube in tube heat exchanger for different flow configuration under variable operating conditions. The experimental investigation was performed on a U-shaped double pipe heat exchanger set up whereas Commercial Computational Fluid Dynamics code FLUENT along with k-ε turbulence modeling scheme was implemented for the simulation study. The flow solution was achieved by implementing k-ε turbulence modeling scheme and the simulation findings were compared with the experimental results. The experimental findings were in good agreement with the simulation results. The counter-flow configuration was found to be 29.4% more effective than the cocurrent one at low fluid flow rate. Direct relationship between heat transfer rate and flow rate is observed while effectiveness and LMTD showed inverse relationship with it. The significance of inlet temperature of hot and cold stream has been evaluated, they play crucial role in heat exchange process.

3

Axisymmetric vibration for micropolar porous thermoelastic circular plate

Kumar R., Kaushal P., Sharma R.

International Journal of Applied Mechanics and Engineering

|

2017

|

Vol. 22, no. 3

583--600

EN

The present investigation is concerned with a two dimensional axisymmetric problem in a homogeneous isotropic micropolar porous thermoelastic circular plate by using the eigen value approach. The Laplace and Hankel transform are used to solve the problem. The expression of displacements, microrotation, volume fraction field, temperature distribution and stresses are obtained in the transformed domain subjected to thermomechanical sources. A computer algorithm is developed for numerical computations. To obtain the resulting quantities in a physical domain, a numerical inversion technique is used. The resulting quantities are depicted graphically for a specific model. Some special cases are also deduced.

4

Common fixed point theorems via generalized condition (B) in quasi-partial metric space and applications

Tomar A., Beloul S., Sharma R., Upadhyay S.

Demonstratio Mathematica

|

2017

|

Vol. 50, nr 1

278--298

EN

The aim of this paper is to introduce generalized condition (B) in a quasi-partial metric space acknowledging the notion of Künzi et al. [Künzi H.-P. A., Pajoohesh H., Schellekens M. P., Partial quasi-metrics, Theoret. Comput. Sci., 2006, 365, 237-246] and Karapinar et al. [Karapinar E., Erhan M., Öztürk A., Fixed point theorems on quasi-partial metric spaces, Math. Comput. Modelling, 2013, 57, 2442-2448] and to establish coincidence and common fixed point theorems for two weakly compatible pairs of self mappings. In the sequel we also answer a rmatively two open problems posed by Abbas, Babu and Alemayehu [Abbas M., Babu G. V. R., Alemayehu G. N., On common fixed points of weakly compatible mappings satisfying generalized condition (B), Filomat, 2011, 25(2), 9-19]. Further in the setting of a quasi-partial metric space, the results obtained are utilized to establish the existence and uniqueness of a solution of the integral equation and the functional equation arising in dynamic programming. Our results are also justified by explanatory examples supported with pictographic validations to demonstrate the authenticity of the postulates.

5

Thermo-Mechanical Deformation and Stress Analysis of Hydroxyapatite/Titanium FGM plate by FEM

Sharma R., Jadon V. K., Singh B.

Mechanics and Mechanical Engineering

|

2016

|

Vol. 20, nr 4

499--513

EN

Hydroxyapatite(HA)/titanium(Ti) functionally graded materials(FGM) are latest materials used for medical implants, structural components in defense, in dentistry, in aviation, and other fields under various type of loads. A finite element analysis model is designed to study the behavior of a HA/Ti FGM plate under thermo-mechanical loadings. Simply supported plate subjected to mechanical and thermal loads on its top and bottom surface is considered with suitable temperature and loading function. The first-order shear deformation plate (FSDT) method is used to investigate the thermo mechanical behavior of functionally graded plate .The volume fraction of the FGM plate is varied smoothly and continuously along the thickness of the plate. Results are discussed for the deformation and stresses of HA/Ti FGM plate It is observed from the study that FGMs are able to resist higher temperatures and loads without delamination.

6

Spectroscopic investigations of polycrystalline InxSb20−xAg10Se70 (0 6 x 6 15) multicomponent chalcogenides

Sharma R., Sharma S., Kumar P., Chander R., Thangaraj R., Mian M.

Materials Science Poland

|

2016

|

Vol. 34, No. 4

794--799

EN

The composition dependence of physical properties of chalcogenides has recently been studied for their phase change properties and energy conversion. In the present work, we report the structure, composition, optical and Raman spectroscopy results for bulk polycrystalline InxSb20-xAg10Se70 (0 ≤ × ≤ 15) samples. The phase quantification and composition have been studied by using XRD and EDX techniques. The alloy composition up to 5 at.% of indium resulted in crystallization of AgSbSe2, while further increase in In content favored the formation of another chalcopyrite AgInSe2 phase yielding the solid solutions for this alloy system. A decrease in band gap up to x = 5 followed by its increase with an increase in indium concentration has been observed. The variations in shape and position of characteristic Raman bands has been used for understanding the structural modifications of the network with the variation in indium content.

7

Magneto-polar fluid flow through a porous medium of variable permeability in slip flow regime

Gaur P. K., Jha A. K., Sharma R.

International Journal of Applied Mechanics and Engineering

|

2016

|

Vol. 21, no. 2

323--339

EN

A theoretical study is carried out to obtain an analytical solution of free convective heat transfer for the flow of a polar fluid through a porous medium with variable permeability bounded by a semi-infinite vertical plate in a slip flow regime. A uniform magnetic field acts perpendicular to the porous surface. The free stream velocity follows an exponentially decreasing small perturbation law. Using the approximate method the expressions for the velocity, microrotation, and temperature are obtained. Further, the results of the skin friction coefficient, the couple stress coefficient and the rate of heat transfer at the wall are presented with various values of fluid properties and flow conditions.

8

Effects of Hall current on unsteady hydromagnetic free convection flow past an impulsively moving vertical plate with Newtonian heating

Seth G. S., Sarkar S., Sharma R.

International Journal of Applied Mechanics and Engineering

|

2016

|

Vol. 21, no. 1

187--203

EN

An investigation of unsteady hydromagnetic free convection flow of a viscous, incompressible and electrically conducting fluid past an impulsively moving vertical plate with Newtonian surface heating embedded in a porous medium taking into account the effects of Hall current is carried out. The governing partial differential equations are first subjected to the Laplace transformation and then inverted numerically using INVLAP routine of Matlab. The governing partial differential equations are also solved numerically by the Crank-Nicolson implicit finite difference scheme and a comparison has been provided between the two solutions. The numerical solutions for velocity and temperature are plotted graphically whereas the numerical results of skin friction and the Nusselt number are presented in tabular form for various parameters of interest. The present solution in special case is compared with a previously obtained solution and is found to be in excellent agreement.

9

Sharma R., Singh R.

International Journal of Occupational Safety and Ergonomics

|

2014

|

Vol. 20, No. 2

363--373

EN

The main aim of this paper was to identify job stressors, gender responses and association of psychosocial work stressors with prevalence of work related musculoskeletal disorders (MSDs) among foundry workers. The data were obtained with ergonomics checklist using Likert scale. The results of this study showed a high prevalence of MSDs among workers. The male workers were more prone to pain in neck while the female workers were more prone to MSDs in upper back and shoulders. Correlation analysis showed significant relationship of dimensions of work aspects with pain and discomfort. It proved that the work-related MSDs are the results of interaction of multiple stressors associated with work and work environment, and other personal factors. ANOVA indicated that the perception of work aspects as stressors differed significantly between male and female workers.

10

Research and practice of business ethics: indian case of Shreyans Paper Mills Ltd.

Sharma R., Saggar S.

Organizacja i Zarządzanie : kwartalnik naukowy

|

2011

|

nr 1

37-57

EN

Business enterprises are expected to meet standards of responsible business conduct that go beyond what had been expected traditionally. The study of business ethics needs to be probed at individual as well as organizational level. Business decisions are made by individuals making up the business, thus a number of factors affect ethical behavior in organizations. At the organization level it will focus on the role of organizational policies, practices, culture and business ethics internally and externally. After reviewing literature on business ethics in Western as well as Indian contexts the chapter presents the case of a private firm, Shreyans Paper Mills Ltd. where ethical business practices have been institutionalized. Established in 1979 and listed on Stock Exchange of India Shreyans Paper Mills Ltd manufactures writing and printing paper from non-conventional agro-based raw materials to the tune of 37,000 mts per annum at two locations in Punjab, India. The company is operating with a wide product mix with well accepted quality in the market based on non-conventional raw materials. Shreyans, as a responsible corporate citizen, strongly adheres to corporate governance principles to ensure that the resources of the company are used entrusted to generate value for its stakeholders. Apart from this, it is a recipient of 'Best Productivity Award' from Government of India, Labor Department in the years 1987-1988, 1988-1989 and 1989-1990. The case exemplifies how a company has enhanced its brand image and has achieved sustainable business growth with ethical business practices and concern for stakeholders.

PL

Współcześnie oczekujemy od przedsiębiorstw wypełniania standardów odpowiedzialnego postępowania w biznesie, które wykracza poza dotychczasowe, tradycyjne oczekiwania. Studiowanie etyki biznesu wymaga zarówno badań poszczególnych jednostek, osób, jak również badań realizowanych na poziomie organizacyjnym. Decyzje biznesowe są podejmowane przez jednostki tworzące, inicjujące określoną działalność, jednak liczne czynniki wpływają na zachowania etyczne w organizacjach. Na poziomie organizacyjnym uwzględniają one rolę organizacyjnej polityki, praktyk, kultury oraz etyki biznesu o charakterze wewnętrznym i zewnętrznym. Niniejszy rozdział, poza przeglądem literatury przedmiotu nt. etyki biznesu w świecie Zachodnim, jak i w kontekście indyjskim, prezentuje również przypadek prywatnego przedsiębiorstwa - Shreyans Paper Mills Ltd., gdzie etyczne praktyki biznesowe zostały zinstytucjonalizowane. Przedsiębiorstwo zostało utworzone w 1979 roku i jest notowane na indyjskiej giełdzie. Shreyans Paper Mills Ltd. jest wytwórcą papieru produkowanego z niekonwencjonalnych surowców rolnych w ilości 37 tys. m rocznie w dwóch lokalizacjach w Pendżabie w Indiach. Przedsiębiorstwo działa w szerokim asortymencie produktów o uznanej jakości na rynku surowców niekonwencjonalnych. Shreyans, jako odpowiedzialny obywatel, bardzo przestrzega zasad ładu korporacyjnego, zapewniając, iż powierzone zasoby przedsiębiorstwa są wykorzystywane dla tworzenia wartości dla jego interesariuszy. Ponadto, jest to laureat nagrody "Best Productivity Award" (Nagroda dla najlepszej wydajności) przyznawanej przez rząd Indii, Departament Pracy w latach 1987-1988, 1988-1989 oraz 1989-1990. Omawiany przypadek stanowi przykład wzmocnienia przez firmę wizerunku marki oraz osiągnięcia wzrostu zrównoważonego biznesu za pomocą etycznych praktyk w biznesie i troski o interesariuszy.

11

Modelling of thermoelastic Lamb waves in a plate bordered with viscous fluid of varying temperature

Sharma J. N., Sharma R.

International Journal of Applied Mechanics and Engineering

|

2010

|

Vol. 15, no 1

217-236

EN

The propagation of thermoelastic waves in a homogeneous isotropic, thermally conducting plate bordered with layers (or half-spaces) of a viscous fluid on both sides is investigated. The problem has been modeled by employing non classical theory of thermoelasticity to carry the investigation. The secular equations for governing the symmetric and antisymmetric wave motion of the plate, in completely separate terms, are derived. The results in the context of classical conventional coupled and uncoupled theories of thermoelasticity in case of viscous and inviscid fluid loadings have been obtained as particular cases from the present analysis. The regions of the secular equation, waves of short wavelength and waves of long wavelength have also been discussed and deduced. Finally, in order to illustrate the analytical results, the numerical solution is carried out for an aluminum-epoxy composite material plate bordered with layers (or half-spaces) of light and heavy water. The results have been deduced and compared with the existing ones in relevant publications available in the literature at various stages of this work.

12

Investigations of highly conducting and transparent Sc doped ZnO films grown by the sol-gel process

Sharma R., Shishodia P. K., Wakahara A., Mehra R. M.

Materials Science Poland

|

2009

|

Vol. 27, No. 1

225--237

EN

Highly transparent and conductive scandium doped zinc oxide (ZnO/Sc) films were prepared on Corning glass 7059 substrates by the sol-gel technique. The influence of scandium concentration (0-1.5 wt. %) and annealing temperature (300-500 °C) on the structural, optical and electrical properties was investigated. The average transmittance was found to be above 89% in the visible region. ZnO/Sc film having 0.5 wt. % of Sc and annealed at 400 °C exhibited a minimum resistivity of 3.52×10-4 ohmocm. The surface morphology of these films examined by SEM and AFM revealed formation of nano rods.

13

Development of validation of RP-HPLC method for simultaneous determination of pyridoxine hydrochloride, isoniazid, pyrazinamide and rifampicin in pharmaceutical formulation

Dhal S. K., Sharma R.

Chemia Analityczna

|

2009

|

Vol. 54, No. 6

1487-1500

EN

A simple, rapid and precise liquid chromatographic method for simultaneous determination of pyridoxine hydrochloride. isomazid, pyrazmamide and rifampicin in a tablet dosage form has been developed Chromatographic analysis was performed on a 250 x 4.6 mm I.D. C|8 column packed with 5 μm-in-size particles applying gradient elution with a mobile phase composed of acetonitrile (A) and 15 mmol L-1 potassium dihydrogen phosphate buffer of pH adjusted to 4.0 J: 0.1 with o-phosphoric acid (B). A:B ratio was 11:89 v/v for the initial 4.5 min. and then it was maintained at 50:50 v/v; the flow rate was 1 mL min-1UV detection was performed at 235 nm. The total run time was 20 mm. Retention times for pyridoxine hydrochloride, isoniazid, pyrazmamide and rifampicin were 3.687, 4.113, 5.041 and 12.829 min, respectively The method was validated with respect to linearity, accuracy, . precision, specificity and sensitivity in accordance with ICH guidelines. Limits of detection were 0.043. 0.063. 0.036 and 0.059 μg mL--1'and limits of quantification were 0.13, 0.19, 0.11 and 0.18 μg ml, ' for pyridoxine hydrochloride, isoniazid, pyrazinamide and rifampicin, respectively. High recovery and low coefficients of variance confirmed the suitability of the method for the simultaneous analysis of the four considered drugs.

PL

Opracowano prostą, szybką i precyzyjną procedurę jednoczesnego oznaczania chlorowodorku pirydoksyny, izoniazydu, pirazynamidu i rifampicyny w tabletkach za pomocą chromatografii cieczowej. Analizę chromatograficzną prowadzono przy użyciu kolumny 250 x 4,6 mm. napełnionej faząC18 o wielkości cząstek wynoszącej 5 urn. Zastosowano gradient fazy ruchomej składającej się z acetonitrylu (A) i buforu w postaci fosforanu dihydropotasowego o stężeniu 15 mmol L-1 i pH = 4 š 0, l ustalonego za pomocą kwasu o-fosforowego (B). Stosunek A i B wynosił 11:89 v/v przez 45 min, następnie był utrzymywany stosunek 50:50 v/v. Przepływ fazy ruchomej wynosił l mL min"1. Całkowity czas rozdzielania składników mieszaniny wynosił 20 min. Detekcję UV prowadzono przy 235 nm. Czasy retencji chlorowodorku pirydoksyny, izoniazydu, pirazynamidu i rifampicyny wynosiły odpowiednio 3.687; 4,113; 5,041 i 12,829 min. Opracowaną procedurę walidowano uwzględniając liniowość, dokładność, precyzję, specyficzność i czułość, zgodnie z zaleceniami Międzynarodowej Konferencji Harmonizacyjnej (ICH). Wykrywalności wynosiły 0.043; 0.063; 0.036 i 0,059μg mL-1a oznaczalności 0,13; 0,19; 0,11 i 0,18 μg mL-1 odpowiednio dla chlorowodorku pirydoksyny, izoniazydu, pirazynamidu i rifampicyny. Wysoki odzysk i małe współczynniki wariancji potwierdziły przydatność metody do jednoczesnej analizy czterech leków.

14

Generalized Rayleigh waves in thermoelastic solids under viscous fluid loading

Sharma J. N., Sharma R., Sharma Y. D.

International Journal of Applied Mechanics and Engineering

|

2008

|

Vol. 13, no 1

217-238

EN

The paper is aimed to study the propagation of Rayleigh surface waves in a homogeneous isotropic, thermally condueting, and elastic solid halfspace underlying a viscous liquid semi space in the context of generalized theories of thermoelasticity. The investigation is based on modelling the viscous liquid as a hypothetical solid in addition to conduction-convection condition of heat transfer at the interface. After developing the mathematical model, boundary conditions and formal solutions, the secular equations for a thermoelastic solid in closed form and isolated mathematical conditions for generalized Rayleigh waves (Stoneley waves), in complete forms are derived. The amplitude ratios of solid and liquid displacements and temperature change on the surface (interface) are obtained analytically. The surface particle motion has also been discussed and found to be elliptical. The semi-major and semi-minor axes, eccentricity and inclination of major axes with the wave normal are computed analytically and analyzed numerically. The results have been deduced and compared with the relevant publications available in the literature at the appropriate stages of the work. Finally, the numerical solution is carried out for an aluminum-epoxy composite material solid (half space) underlying water, in the case of both light and heavy semi spaces. The dispersion curves, attenuation coefficient profiles and amplitude ratios of surface displacements, temperature change in the solid half space for generalized Rayleigh waves are presented and illustrated graphically in order to illustrate and compare the theoretical results. The theory and numerical computations are found to be in close agreement. The present analysis is useful in electronics and navigation applications.

15

Development and validation of an RP-HPLC method for simultaneous analysis of drotaverine and omeprazole in a tablet dosage form

Panigrahi D., Sharma R.

Acta Chromatographica

|

2008

|

Vol. 20, no. 3

439-450

EN

A simple, rapid reversed-phase high-performance liquid chromatographic method has been developed and validated for simultaneous estimation of drotaverine and omeprazole in a tablet dosage form. A C 18 column was used with a 60:40 ( v/v ) mixture of methanol and ammonium acetate (0.1 M , pH 5, adjusted with orthophosphoric acid) as mobile phase at a flow rate of 1.5 mL min -1 . UV detection was performed at 319 nm. The method was validated for accuracy, precision, linearity, specificity and sensitivity in accordance with International Conference on Harmonisation guidelines. The method was successfully used for quantitative analysis of Ranipas-DV tablets. Total run time was 10 min, drotaverine and omeprazole were eluted with retention times of 7.969 and 6.538 min respectively. Validation revealed that the method is specific, accurate, precise, reliable and reproducible. Calibration plots were linear over the concentration ranges 5-40 µg mL -1 for drotaverine and 5-50 µg mL -1 for omeprazole, respectively. Limits of detection were 16.2 and 4.8 ng mL -1 and limits of quantification were 49.0 and 14.5 ng mL -1 for drotaverine and omeprazole, respectively. Recovery was in the range 100.66-100.94% and 102.42-102.89% for drotaverine and omeprazole, respectively, and the coefficient of variance was <2.0% for both. The high percentage recovery and low co-efficient of variation confirm the suitability of the method for simultaneous analysis of drotaverine and omeprazole in tablets.

16

Development and validation of an RP-HPLC method for simultaneous analysis of a three-component tablet formulation containing metformin hydrochloride, pioglitazone hydrochloride, and glibenclamide

Chaturvedi P. K., Sharma R.

Acta Chromatographica

|

2008

|

Vol. 20, no. 3

451-461

EN

A simple, rapid, and precise reversed-phase high-performance liquid chromatographic method for simultaneous analysis of metformin hydrochloride, pioglitazone hydrochloride, and glibenclamide in a tablet dosage form has been developed and validated. Chromatography was performed on a 25 cm × 4.6 mm i.d., 5-µm particle, C 18 column with 55:45 ( v/v ) acetonitrile - potassium dihydrogen phosphate buffer (pH adjusted to 3.0 š 0.1 with 5% orthophosphoric acid) as mobile phase at a flow rate of 1.5 mL min ?1 . UV detection was performed at 230 nm. Total run time was 10 min; metformin hydrochloride, pioglitazone hydrochloride, and glibenclamide were eluted with retention times of 1.362, 3.418, and 7.395 min, respectively. The method was validated for accuracy, precision, linearity, specificity, and sensitivity in accordance with ICH guidelines. Validation revealed the method is specific, rapid, accurate, precise, reliable, and reproducible. Calibration plots were linear over the concentration ranges 200-1000µg mL -1 for metformin hydrochloride, 200-1000 µg mL -1 for pioglitazone hydrochloride, and 50-300 µg mL -1 for glibenclamide. Limits of detection were 6.3, 15.4, and 8.2 ng mL -1 and limits of quantification were 19.09, 46.66, and 24.84 ng mL -1 for metformin hydrochloride, pioglitazone hydrochloride, and glibenclamide, respectively. The high recovery and low coefficients of variation confirm the suitability of the method for simultaneous analysis of the three drugs in tablets. The validated method was successfully used for quantitative analysis of triglycomate tablets.

17

Stability of stratified Walters' (Model B') viscoelastic fluid in stratified porous medium

Sunil D., Sharma R., Sharma V.

Studia Geotechnica et Mechanica

|

2004

|

Vol. 26, nr 1-2

35-52

PL

Przedstawiono liniową stabilność uwarstwionej cieczy Waltersa (model B') w uwarstwionym ośrodku porowatym. Rozważono przypadki zmian wykładniczych gęstości, lepkości, lepkosprężystości, porowatości i przepuszczalności środowiska. Stwierdzono, że w przypadku potencjalnie stabilnego uwarstwienia układ jest stabilny lub niestabilny w zależności od kinematycznej lepkosprężystości, która może osiągać wartość mniejszą lub większą od wartości otrzymanej przez podzielenie przepuszczalności środowiska przez jego porowatość. Stanowi to przeciwieństwo stabilności uwarstwionej cieczy Newtona. Jednakże układ jest niestabilny w przypadku zakłóceń wszystkich liczb falowych dla potencjalnie niestabilnego uwarstwienia. Jeżeli wprowadzi się pewne ograniczenia, to szybkość wzrostu zwiększa się lub zmniejsza wraz ze zwiększającymi się wartościami parametrów uwarstwienia. Oddzielnie omówiono wpływ zmiennego poziomego pola magnetycznego i jednorodnej rotacji. Szybkość wzrostu stabilności w zależności od prędkości Alfvena (w przypadku pola magnetycznego) oraz w zależności od prędkości kątowej (w przypadku rotacji) zbadano analitycznie i stwierdzono, że w pewnych warunkach zarówno pole magnetyczne, jak i rotacja mają sprzężony wpływ na stabilność.

EN

The linear stability of stratified Walters' (model B') fluid in stratified porous medium is presented. The case of exponentially varying density, viscosity, viscoelasticity, medium porosity and medium permeability is considered. It is found that for the potentially stable stratifications the system is stable or unstable, depending on the kinematic viscoelasticity which can be smaller or greater than the medium permeability divided by medium porosity. This is in contrast to the stability of stratified Newtonian fluid. However, the system is found to be unstable for disturbances of all wave numbers for potentially unstable stratifications. If some restrictions are imposed, then the growth rates are found to increase or decrease with increasing values of stratification parameters. The effects of variable horizontal magnetic field and uniform vertical rotation have also been discussed separately. The behaviour of growth rate with respect to the Alfven velocity (in the case of magnetic field) and angular velocity (in the case of rotation) are examined analytically and it is found that under certain conditions both magnetic field and rotation have a dual effect on this stability problem.

18

Thermosolutal instability of Walters' rotating fluid (Model B') in porous medium

Sharma R., Sunil, Chand S.

Archives of Mechanics

|

1999

|

Vol. 51, nr 2

181-191

EN

The thermosolutal instability of Walters' (Model B') fluid in porous medium is considered in the presence of uniform vertical rotation. For the case of stationary convection, the stable solute gradient and rotation have stabilizing effects on the system, whereas the medium permeability has a destabilizing (or stabilizing) effect on the system under certain conditions. The dispersion relation is also analysed numerically. It has also been shown that as rotation parameter increases, the stabilizing range of medium also increases. The kinematic viscoelasticity has no effect on the stationary convection. The stable solute gradient, rotation, porosity and kinematic viscoelasticity introduce oscillatory modes in the system, which did not occur in their absence. The sufficient conditions for the non-existance of overstability are also obtained.