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排序方式: 共有152条查询结果,搜索用时 194 毫秒
1.
A numerical study of the steady forced convection heat transfer from an unconfined circular cylinder
Forced convection heat transfer from an unconfined circular cylinder in the steady cross-flow regime has been studied using
a finite volume method (FVM) implemented on a Cartesian grid system in the range as 10 ≤ Re ≤ 45 and 0.7 ≤ Pr ≤ 400. The numerical results are used to develop simple correlations for Nusselt number as a function of the pertinent dimensionless
variables. In addition to average Nusselt number, the effects of Re, Pr and thermal boundary conditions on the temperature field near the cylinder and on the local Nusselt number distributions
have also been presented to provide further physical insights into the nature of the flow. The rate of heat transfer increases
with an increase in the Reynolds and/or Prandtl numbers. The uniform heat flux condition always shows higher value of heat
transfer coefficient than the constant wall temperature at the surface of the cylinder for the same Reynolds and Prandtl numbers.
The maximum difference between the two values is around 15–20%. 相似文献
2.
A simple wet chemical method is used to prepare zinc oxide nanoflowers (ZnO NFs) which were subjected to various characterization techniques such as XRD, FTIR, UV–Vis, FE-SEM, and XPS. XRD pattern indicates pure, crystalline, and monodispersed form with hexagonal wurtzite phase. The 3-D flower shape morphology with hexagonal ZnO nanorods was confirmed in FE-SEM. The synthesized ZnO NFs was used to study catalytic behavior in Kabachnik–Fields reaction under controlled ultrasound cavitation technique. High surface-to-volume ratio of ZnO NFs and the effect of ultrasonication enhances the yield of α-aminophosphonate. The catalyst was recycled and reused four times without any significant loss of its catalytic activity. Moreover, existing method becomes attractive and practical due to its easy, clean, fast, cost-effective, and eco-friendly procedure. 相似文献
3.
Sarika Goyal 《Mathematische Nachrichten》2019,292(10):2189-2202
In this article, we study the eigenvalues of p‐fractional Hardy operator where , , , and Ω is an unbounded domain in with Lipschitz boundary containing 0. The weight function V may change sign and may have singular points. We also show that the least positive eigenvalue is simple and it is uniquely associated to a nonnegative eigenfunction. Moreover, we proved that there exists a sequence of eigenvalues as . 相似文献
4.
Sridevi V. Shinde Sarika Sinha Prof. Dr. Kumaravel Somasundaram Prof. Dr. Ashoka G. Samuelson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(39):12278-12291
Neutral half‐sandwich organometallic ruthenium(II) complexes of the type [(η6‐cymene)RuCl2(L)] ( H1 – H10 ), where L represents a heterocyclic ligand, have been synthesized and characterized spectroscopically. The structures of five complexes were also established by single‐crystal X‐ray diffraction confirming a piano‐stool geometry with η6 coordination of the arene ligand. Hydrogen bonding between the N? H group of the heterocycle and a chlorine atom attached to Ru stabilizes the metal–ligand interaction. Complexes coordinated to a mercaptobenzothiazole framework ( H1 ) or mercaptobenzoxazole ( H6 ) showed high cytotoxicity against several cancer cells but not against normal cells. In vitro studies have shown that the inhibition of cancer cell growth involves primarily G1‐phase arrest as well as the generation of reactive oxygen species (ROS). The complexes are found to bind DNA in a non‐intercalative fashion and cause unwinding of plasmid DNA in a cell‐free medium. Surprisingly, the cytotoxic complexes H1 and H6 differ in their interaction with DNA, as observed by biophysical studies, they either cause a biphasic melting of the DNA or the inhibition of topoisomerase IIα activity, respectively. Substitution of the aromatic ring of the heterocycle or adding a second hydrogen‐bond donor on the heterocycle reduces the cytotoxicity. 相似文献
5.
6.
Bharti U. N. Verma Kingsuk Mukhopadhyay 《Journal of Thermal Analysis and Calorimetry》2011,104(3):1071-1075
The ligand [2-(1,2,3,4-thiatriazole-5-yliminomethyl)-phenol] (L) is a schiff base derived from condensation reaction of 1,2,3,4-thiatriazole-5-ylamine
and Salicylaldehyde. Synthesis of the ligand (L) and the complex [Cu(II)(L)2]·2H2O have been studied in our previous work (Bharti et al., Asian J Chem 23(2):773–776, 2011). Thermal decomposition behavior
of synthesized Cu(II) complex has been investigated by thermo gravimetric (TG) analysis at heating rate of 10 °C min−1 under nitrogen atmosphere. The mechanism of decomposition of Cu(II) complex has been established from TG data. Kinetic parameters
such as order of reaction (n), activation energy (E
a), frequency factor (Z) and entropy of activation (∆S
≠) were calculated by using Freeman and Carroll (J Phys Chem 62:394–397, 1958) as well as Doyle’s methods as modified by Zsako
(J Phys Chem 72(7):2406–2411, 1968). 相似文献
7.
The synthesis of the Rhodococcus erythropolis siderophores heterobactins A and B, and the structurally related Nocardia heterobactin, is described. Two approaches for the assembly of these asymmetric ligand donor chelators are explored. In the first approach, a scheme predicated on the biosynthesis of the Paracoccus denitrificans siderophore, parabactin, is employed. In this approach, the central donor synthon is added last. In the second scheme, the central donor and the terminal 2,3-dihydroxybenzoyl fragment are first fixed to the ligand’s d-ornithine backbone. This is followed by condensation with the cyclic ornithine hydroxamate glycine segment. The schemes offer a flexible approach to other heterobactins. Job’s plots suggest that heterobactin A and Nocardia heterobactin form 1:1 ligand/metal complexes, while heterobactin B forms a 3:2 ligand/metal complex. 相似文献
8.
The present study describes the potential of the synchrotron radiation based X-ray fluorescence spectroscopy technique for the rapid, sensitive, user friendly and simultaneous monitoring of the changes in the elemental profile of the wheat seedlings stressed by excess manganese (Mn). For this, X-ray fluorescence spectra of the leaves of the control and Mn treated wheat seedlings have been recorded by synchrotron radiation X-ray of energy 15?keV. The analyses of the recorded spectra show the presence of elements chlorine, potassium, calcium, manganese, iron, copper, nickel, and zinc. A calibration-free approach, PyMca has been used for the quantitative estimation of the detected elements in the leaves of the control and Mn treated wheat seedlings. The excess supply of Mn to wheat seedlings results in the accumulation of manganese in the leaves of the seedlings. The accumulation of manganese in wheat seedlings negatively affects the uptake and translocation of calcium, potassium, and iron while it has stimulating effect on the uptake of copper and zinc. 相似文献
9.
Q.M. Zhang Z.-Y. Cheng V. Bharti 《Applied Physics A: Materials Science & Processing》2000,70(3):307-312
This paper presents experimental results showing that in a certain composition range and under a proper electron-irradiation treatment, a normal ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer can be converted into a material exhibiting many typical features of relaxor ferroelectrics, suggesting that this is a new class of relaxor ferroelectric material. Furthermore, the irradiated copolymer can generate giant electrostriction (ƽ%) with a high elastic energy density. The X-ray diffraction results obtained from the irradiated copolymer under electric field, indicate that the observed polarization and strain responses are mainly due to the local phase transformation from a non-polar phase to a polar phase. 相似文献
10.
S. B. Beri K. B. Bhalla R. Bhanja A. Bharti V. S. Bhatia G. Claesson S. Garpman S. K. Gupta V. K. Gupta N. Y. Herrstrom B. Jakobsson R. Joseph G. L. Kaul G. Kaur M. Kaur S. Kitroo V. Kumar S. Lokanathan I. Lund L. K. Mangotra I. S. Mitra S. Mookerjee B. Norén A. Oskarsson I. Otterlund Y. Prakash S. Persson N. K. Rao S. Sankhyadhar S. Satti M. M. Sherif K. Söderström S. K. Tuli 《Zeitschrift für Physik A Hadrons and Nuclei》1987,327(4):431-441
40Ar-emulsion interactions are studied, to investigate the question of anomalons, in twoG- 5 emulsion stacks. In about 4600 primary interactions, projectile fragments of Z≧2 for all generations have been followed until they interact or leave the stack. After careful estimation of charges of these fragments, variation of their mean free paths is studied as a function of distance from the preceding interaction. Generation effect,N h dependence and production angle effect are investigated. In addition multi-chain events are analysed separately. Our results do not show anomalons at the 6% level and are consistent with non-occurrence of anomalons. However, this experiment is not sensitive enough to rule out anomalons (with a mfp of the order of 2 to 3 cm) produced at about 1% (or less) level. 相似文献