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61.
The present paper deals with the hydrodynamics of a porous sphere placed in an arbitrary oscillatory Stokes flow. Unsteady
Stokes equation is used for the flow outside the porous sphere and Brinkman equation is used for the flow inside the porous
sphere. Corresponding Faxén’s law for drag and torque is derived and compared with few existing results in some special cases.
Examples like uniform flow, oscillatory shear flow and oscillating Stokeslet are discussed. Also, translational oscillation
of a weakly permeable sphere is discussed. 相似文献
62.
Study of Heat Transfer Control with Magnetic Field Using Higher Order Finite Difference Scheme 下载免费PDF全文
R. Sivakumar S. Vimala S. Damodaran & T. V. S. Sekhar 《advances in applied mathematics and mechanics.》2016,8(3):449-463
The control of convective heat transfer from a heated circular cylinder immersed
in an electrically conducting fluid is achieved using an externally imposed
magnetic field. A Higher Order Compact Scheme (HOCS) is used to solve the governing
energy equation in cylindrical polar coordinates. The HOCS gives fourth order
accurate results for the temperature field. The behavior of local Nusselt number, mean
Nusselt number and temperature field due to variation in the aligned magnetic field is
evaluated for the parameters 5≤$Re$≤40, 0≤$N$≤20 and 0.065≤$Pr$≤7. It is found that
the convective heat transfer is suppressed by increasing the strength of the imposed
magnetic field until a critical value of $N$, the interaction parameter, beyond which the
heat transfer increases with further increase in $N$. The results are found to be in good
agreement with recent experimental studies. 相似文献
63.
64.
Chandra Sekhar Reddy Gangireddy Radha Rani Chinthaparthi Veeranarayana Reddy Mudumala Madhav Mamilla Uma Ravi Sankar Arigala 《Heteroatom Chemistry》2014,25(3):147-156
The present work focuses on the study of catalytic activity of polystyrene‐supported p‐toluenesulfonic acid (PS/PTSA) and the synthesis of α‐aminophosphonates from the Kabachnik–Fields (KF) reaction under microwave irradiation in solvent‐free conditions. Recently, the catalytic activity of PS/PTSA was tested with good yields. This procedure is the simplest, most straightforward, environment friendly method for the synthesis of α‐aminophosphonates from simple to different substituted aldehyde substrates. Furthermore, this catalyst can be recovered and reused without loss of its catalytic activity. 相似文献
65.
Karmakar S Choudhury M Das AS Maiti A Majumdar S Mitra C 《Natural product research》2012,26(6):500-509
This study examined the efficacy of hydroalcoholic extract of dried clove buds, which is rich in phenolic compounds namely eugenol and eugenol derivatives (precursors of flavones, isoflavones and flavonoids), on different primary and secondary osteoporotic marker changes in an ovariectomised (OVX) rat model of osteoporosis. Female Wistar rats were randomly divided into three groups: sham-operated control (A), OVX (B) and OVX plus 50% hydroalcoholic extract of dried clove buds for 4 weeks (C). Results indicated that, compared to control, serum alkaline phosphatase (AP; 48.25%, p?0.01), serum tartrate-resistant acid phosphatase (TRAP; 63.48%, p?0.01), urinary calcium (14.70%, p?0.01), urinary phosphate (50.30%, p?0.01) and urinary creatinine (122.44%, p?0.01) were significantly altered in OVX rats. All these altered responses were significantly restored (AP: 27.53%, p?0.01; TRAP: 33.51%, p?0.01; calcium: 53.15%, p?0.01; phosphate: 27.49%, p?0.01; creatinine: 46.40%, p?0.01) by supplementation with hydroalcoholic extract of dried clove buds. Results of bone density, bone mineral content, bone tensile strength and histological analysis also showed similar trend of results, which supported initial observations of this study. It is proposed that hydroalcoholic extract of dried clove buds has bone-preserving efficacy against hypogonadal osteoporosis. 相似文献
66.
Das RS Singh B Mukhopadhyay S Banerjee R 《Dalton transactions (Cambridge, England : 2003)》2012,41(15):4641-4648
Gelatin-capped gold nano particles (GNPs) of diameter 23, 28 and 36 nm were prepared and characterized as almost monodispersed, near-spherical solids. In acidic media, these GNPs at their very low concentration level (~10(-13) M) catalyze the oxidation of hydrazine by the metallo-superoxide, [(NH(3))(4)Co(III)(μ-NH(2),μ-O(2))Co(III)(NH(3))(4)](NO(3))(4) (1). In the presence of a large excess of hydrazine over [1], the catalyzed oxidation is first-order in [1], [GNPs] and media alkalinity. The pure first-order dependence implies that the size as well as the nature of the catalyst remained unchanged during the reaction. The catalytic efficacies increased with increased total surface area of the GNPs. Increasing T(Hydrazine) (T(Hydrazine) is the analytical concentration of hydrazine) tends to saturate the first-order rate constant (k(o)) for hydrazine oxidation and a plot of 1/k(o)versus T(Hydrazine) was found to be linear at a particular [GNPs], indicating the GNPs assisted deprotonation of N(2)H(5)(+) to N(2)H(4). The rate constants show a non-linear behavior with temperature studied in the range 288-308 K. At a lower temperature interval, viz. 288-298 K, k(o) increases with increasing temperature whereas at temperature interval, viz. 303-308 K, k(o) decreases with temperature. Such a variation indicates the important process of absorption and desorption of the reactants on and from the surface. A plausible mechanism for the GNPs catalyzed oxidation of hydrazine is suggested. 相似文献
67.
José P.B. Silva Koppole C. Sekhar Sofia A.S. Rodrigues Anatoli Khodorov Javier Martín-Sanchez Mário Pereira Maria J.M. Gomes 《Current Applied Physics》2012,12(4):1144-1147
The effect of pulse amplitude on the ferroelectric and switching properties of pulsed laser deposited Ba0.8Sr0.2TiO3 thin films has been studied. The structural and morphological analysis revealed that the films had a well crystallized perovskite phase and grain size of about 30–40 nm. A well saturated P–E hysteresis loop was observed with a remnant polarization (Pr) ≈ 4.8 μC/cm2 and a coercive field ≈ 100 kV/cm at a frequency of 1 kHz. The Pr has been found to be decreased only 4.3% after passing 8.0 × 108 cycles. The analysis of switching response with nucleation limited switching model reveals that characteristic switching time (t0) variance is due to the random distribution of the local electric fields. The peak value of polarization current and t0 exhibits exponential dependence on reciprocal of pulse amplitude. 相似文献
68.
G. Chandra Sekhar Reddy M. Veera Narayana Reddy C. Radha Rani N. Bakthavatchala Reddy K. Uma Maheswara Rao S.K. Nayak C. Suresh Reddy 《Heteroatom Chemistry》2012,23(3):247-253
A new family of di(1‐oxo/thioxoper‐hydro‐1λ5‐[1,3,2]diazaphospholo[1,5‐a]pyridine‐1‐yl)(4‐substituted phenyl) boronates ( 4a – j ) has been synthesized in a two‐step process. A reaction of (±)‐piperidin‐2‐yl‐methanamine ( 1 ) phosphoryl/phosphorothioyl chloride in the presence of triethylamine in dry tetrahydrofuran formed the intermediate monochloride ( 2 ), which on condensation with p‐substituted phenylboronic acids ( 3a – j ) afforded the titled compounds ( 4a – j ). They were characterized by elemental, IR, 1H, 13C, 31P NMR, and mass spectral analyses. All these compounds showed moderate to high antiosteoclast and osteoblast activity. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:247–253, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21010 相似文献
69.
A uniform potential flow past a porous circular cylinder with a core of different permeability is discussed. The porous circular
cylinder is slightly deformed whose radius is r=r1(1+ecosm q){r=r_1(1+\epsilon \cos m \theta)} , where | e | << 1{\mid\epsilon\mid\ll 1} and m is a positive integer. Here r, θ are the polar coordinates and r
1 is the characteristic radius of the cylinder. The drag force exerted by the exterior flow on the surface of the cylinder
is calculated and it depends on the thickness of the porous material and on the permeabilities of the two porous regions.
As special cases, porous cylinder with hollow core, rigid core, and deformed cylinder is discussed. 相似文献
70.
The steady viscous incompressible and slightly conducting fluid flow around a circular cylinder with an aligned magnetic field is simulated for the range of Reynolds numbers 100 ? Re ? 500 using the Hartmann number, M. The multigrid method with defect correction technique is used to achieve the second order accurate solution of complete non-linear Navier–Stokes equations. The magnetic Reynolds number is assumed to be small. It is observed that volume of the separation bubble decreases and drag coefficient increases as M is increased. We noticed that the upstream base pressure increases slightly with increase of M whereas downstream base pressure decreases with increase of M. The effect of the magnetic field on the flow is discussed with contours of streamlines, vorticity, plots of surface pressure and surface vorticity. 相似文献