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51.
An analysis is made of steady two-dimensional oblique stagnation-point flow and radiative heat transfer of an incompressible viscous fluid towards a shrinking sheet which is shrunk in its own plane with a velocity proportional to the distance from a fixed point. Here the axis of the stagnation flow and that of the shrinking sheet are not aligned. A similarity transformation reduces the Navier-Stokes equations to a set of non-linear ordinary differential equations and are solved numerically using a shooting technique. The analysis of the results obtained shows that multiple solutions exist for a certain range of the ratio of the shrinking velocity to the free stream velocity. The effect of non-alignment for the wall shear stress and the horizontal velocity components are discussed. Streamline patterns are also shown for shrinking at the sheet with aligned and non-aligned cases. It is found that the temperature at a point in the fluid decreases with increase in effective Prandtl number (Pr eff ). The results pertaining to the present study indicate that as Pr eff increases, the rate of heat transfer also increases. The reported results are in good agreement with the available published work in the literature. 相似文献
52.
53.
S. Supriya Guddekoppa S. Ananthnag Vijayendra S. Shetti B.M. Nagaraja Gurumurthy Hegde 《应用有机金属化学》2020,34(3):e5384
A new heterogeneous catalyst was synthesized by immobilizing Pd on areca nut kernel-derived carbon nanospheres (CNSs). The CNSs, without any further activation processes, accommodated 3% of Pd on their surface. The new Pd/CNS material was used for the reduction of nitroarenes and Suzuki–Miyaura coupling of bromoarenes with aryl boronic acids. The reactions were conducted under microwave irradiation at 160 °C using 12 mol% of Pd/CNS (0.36% actual Pd content). The reduction of nitroarenes into their respective amino compounds was achieved in 10–20 min (conversion up to 100%); by contrast, the Suzuki–Miyaura reactions yielded up to 98% at 150 °C with 10 mol% of Pd/CNS catalyst. The products were identified using gas chromatography and nuclear magnetic resonance spectroscopy. The catalyst was isolated from reaction mixture and reused without any significant loss in the activity. Thus, the present work introduces one-pot-derived porous CNSs as efficient catalytic support to Pd, establishing an alternative to existing Pd/C in terms of cost and efficiency. 相似文献
54.
Satarupa Acharjee Tapan Kumar Maity Subir Samanta Supriya Mana Tania Chakraborty Tanushree Singha 《合成通讯》2013,43(23):3015-3024
AbstractThe present study describes the synthesis of novel chalcone based 1-{3-[3-(substituted phenyl) prop-2-enoyl] phenyl} thioureas (4a-c) using Claisen Schmidt condensation and investigates their protective role in diabetic conditions and associated oxidative stress. Spectral properties for the synthesized compounds were studied. Novel compounds were screened for antihyperglycemic effect in streptozotocin (STZ)-induced diabetic rats in a 6?week study and compound 4b exhibited significant (p?≤?.05) results similar to the standard drug glipizide. Treatment of diabetic animals with compound 4b (10 and 20?mg/kg, body weight) for 12?weeks, reduced the increased blood glucose level significantly (p?≤?.01) and restored attenuated serum biochemical parameters to normal levels. Altered antioxidant enzyme activity was also considerably (p?≤?.01) restored to the standard normal range. β-apoptotic TUNEL assay indicated that compound 4b (AI: 1.2?±?0.05) could prevent further β-cell death in the pancreas of diabetic animals in a dose-dependent manner, which highlights its potentiality as an effective antihyperglycemic agent. 相似文献
55.
Advantages and limitations of the existing models for practical forecasting of stock market volatility have been identified.
Support vector machine (SVM) have been proposed as a complimentary volatility model that is capable to extract information
from multiscale and high-dimensional market data. Presented results for SP500 index suggest that SVM can efficiently work
with high-dimensional inputs to account for volatility long-memory and multiscale effects and is often superior to the main-stream
volatility models. SVM-based framework for volatility forecasting is expected to be important in the development of the novel
strategies for volatility trading, advanced risk management systems, and other applications dealing with multi-scale and high-dimensional
market data. 相似文献
56.
A Sierpinski gasket fractal network model is studied in respect of its electronic spectrum and magneto-transport when each ‘arm’ of the gasket is replaced by a diamond shaped Aharonov–Bohm interferometer, threaded by a uniform magnetic flux. Within the framework of a tight binding model for non-interacting, spinless electrons and a real space renormalization group method we unravel a class of extended and localized electronic states. In particular, we demonstrate the existence of extreme localization of electronic states at a special finite set of energy eigenvalues, and an infinite set of energy eigenvalues where the localization gets ‘delayed’ in space (staggered localization). These eigenstates exhibit a multitude of localization areas. The two terminal transmission coefficient and its dependence on the magnetic flux threading each basic Aharonov–Bohm interferometer is studied in details. Sharp switch on–switch off effects that can be tuned by controlling the flux from outside, are discussed. Our results are analytically exact. 相似文献
57.
A. Borah S. Ghosh S. Nandy 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):221-225
The novel inelastic collision properties of two-soliton interaction for an n-component coupled higher order nonlinear Schr?dinger equation are studied. Some interesting features of three soliton interactions,
related to the integrability of the n-component coupled higher order nonlinear Schr?dinger equation are also discussed.
Received 17 April 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: abhijit@iitg.ernet.in
RID="b"
ID="b"e-mail: sasanka@iitg.ernet.in
RID="c"
ID="c"e-mail: sudipta@iitg.ernet.in 相似文献
58.
Yang SM Shie JJ Fang JM Nandy SK Chang HY Lu SH Wang G 《The Journal of organic chemistry》2002,67(15):5208-5215
By the promotion of samarium diiodide, thiophene-2-carboxylate reacted with 2 equiv of ketones at the C-4 and C-5 positions to give diols such as 2 and 9. Because the intermediary organosamarium species were oxophilic but not too basic, the double hydroxyalkylations with various ketone substrates, including alkyl aryl ketones, acetylthiophenes, cyclohexanone, alpha-tetralone, and alpha-phenylacetophenones, were realized without complication of side reactions. The diol products underwent an acid-catalyzed dehydration to give dienes such as 3 and 10, which were treated with DDQ to give either polysubstituted thiophenes (e.g., 4 and 11) or benzothiophenes (e.g., 5, 13, and 14) depending on the reaction conditions. Oxidative annulations of 4,5-diarylthiophenes 11 and 4,5,6,7-tetraphenylbenzothiophenes 14 were carried out by photochemical or chemical methods to give the sulfur-containing polycyclic aromatic compounds, such as phenanthro[9,10-b]thiophene-2-carboxylate, piceno[13,14-b]thiophene-2-carboxylate, and tribenzo[fg,ij,rst]pentapheno[15,16-b]thiophene-2-carboxylates. This method is applicable to the preparation of polysubstituted thiophenes, benzothiophenes, and the related compounds possessing liquid crystalline, photochromic, and other functional properties. 相似文献
59.
Small hydrogen-bonded water clusters have received much attention and are the subject of both theoretical and chemical research. The crystalline molecular host provides an environment for the stabilization of various topologies of water clusters. The present article deals with (H2O)
n
clusters, identified/observed crystallographically in respective crystalline hydrates. The structural details of water decamers, octamers, hexamers, tetramers, and dimers are described systematically. 相似文献
60.
Chullikkattil P. Pradeep Sabbani Supriya Panthapally S. Zacharias Samar K. Das 《Polyhedron》2006,25(18):3588-3592
A tetra-nuclear copper(II) complex [Cu4(C54H46N4O14)(OH)2] · 10H2O (1) has been synthesized starting from l-tyrosine, NaOH, 2,6-diformyl-4-methylphenol (dfp) and CuSO4 · 5H2O. Compound 1 crystallizes from an ethanol–water mixture in triclinic space group. In the crystal of 1, two binuclear copper units, related by a center of symmetry, are bridged by two hydroxo bridges and results in the formation of a tetra-nuclear {Cu4} structure. Five lattice water molecules, located in the asymmetric unit, interact among themselves and form an unusual form of a water nonamer. In the crystal, the water nonamer is again hydrogen bonded to the next nonamer forming a chainlike polymer. Each {Cu4} complex unit attaches four such water nonamer chains. Variable temperature magnetic data fit to the Bleaney–Bower’s equation with a Curie type of impurity of S = 0.5. The best fit of the magnetic data to this equation yielded 2J = −217, g = 2.019 and a TIP value of 60 × 10−6 cm3 mol−1. 相似文献