排序方式: 共有69条查询结果,搜索用时 15 毫秒
31.
Jabbar Khalafy Mahnaz Ezzati Mehdi Rimaz Ahmad Poursattar Marjani Hooman Yaghoobnejad Asl 《Journal of the Iranian Chemical Society》2014,11(4):1067-1074
A study concerning the new substituted cinnoline synthesis is described. The use of a one-pot three-component method allows a simple regioselective and efficient synthesis of cinnoline derivatives via reaction of arylglyoxals with 1,3-cyclohexanedione and dimedone in the presence of hydrazine hydrate. 相似文献
32.
Research on Chemical Intermediates - The main goal of this study is to modify the polyethersulfone membrane by the grafting hyperbranched polyethylene glycol (HB-PEG) via a two-step grafting... 相似文献
33.
Mojtaba Bagherzadeh Hooman Karimi Mojtaba Amini 《Journal of Coordination Chemistry》2017,70(17):2986-2998
Graphene oxide was an effective supporting material for immobilizing a dioxomolybdenum Schiff base complex via covalent interaction. The large surface of graphene oxide plays important roles to obtain a good degree of catalytic reaction. Catalytic capacity of the graphene-bound dioxomolybdenum Schiff base complex was investigated for the oxidation of various sulfides to sulfoxide compounds using hydrogen peroxide urea as an oxidant. The catalyst was characterized by various techniques including XRD, FTIR, TGA, SEM, UV–vis, and ICP-AES. The immobilized complex was very efficient with the extra benefits of easy recovery and recycling of the heterogeneous catalyst. The graphene oxide bound dioxomolybdenum Schiff base complex was reused for several runs without meaningful loss in catalytic activity. 相似文献
34.
A numerical study has been conducted to examine the heat transfer from a metal foam-wrapped solid cylinder in cross-flow.
Effects of the key parameters including the free stream velocity and characteristics of metal foam such as porosity, permeability,
and form drag coefficient on heat and fluid flow are examined. Being a determining factor in pressure drop and heat transfer
increment, the porous layer thickness is changed systematically to observe that there is an optimum layer thickness beyond
which the heat transfer does not improve while the pressure drop continues to increase. This has been verified by the application
of Bejan’s Intersection of Asymptotes method. Results have been compared to those of a finned-tube heat exchanger to observe
much higher heat transfer rate with reasonable excess pressure drop leading to a higher area goodness factor for metal foam-wrapped
cylinder. 相似文献
35.
This article presents a porous media transport approach to model the performance of an air-cooled condenser. The finned tube
bundles in the condenser are represented by a porous matrix, which is defined by its porosity, permeability, and the form
drag coefficient. The porosity is equal to the tube bundle volumetric void fraction and the permeability is calculated by
using the Karman–Cozney correlation. The drag coefficient is found to be a function of the porosity, with little sensitivity
to the way this porosity is achieved, i.e., with different fin size or spacing. The functional form was established by analyzing
a relatively wide range of tube bundle size and topologies. For each individual tube bundle configuration, the drag coefficient
was selected by trial and error so as to make the pressure drop from the porous medium approach match the pressure drop calculated
by the heat exchanger design software ASPEN B-JAC. The latter is a well-established commercial heat exchanger design program
that calculates the pressure drop by using empirical formulae based on the tube bundle properties. A close correlation is
found between the form drag coefficient and the porosity with the drag coefficient decreasing with increasing porosity. A
second order polynomial is found to be adequate to represent this relationship. Heat transfer and second law (of thermodynamics)
performance of the system has also been investigated. The volume-averaged thermal energy equation is able to accurately predict
the hot spots. It has also been observed that the average dimensionless wall temperature is a parabolic function of the form
drag coefficient. The results are found to be in good agreement with those available in the open literature. 相似文献
36.
We consider the possibility that the quark condensate formed by QCD confinement generates Majorana neutrino masses mν via dimension seven operators. No degrees of freedom beyond the Standard Model are necessary, below the electroweak scale. Obtaining experimentally acceptable neutrino masses requires the new physics scale Λ∼TeV, providing a new motivation for weak-scale discoveries at the LHC. We implement this mechanism using a Z3 symmetry which leads to a massless up quark above the QCD chiral condensate scale. We use non-helicity-suppressed light meson rare decay data to constrain Λ. Experimental constraints place a mild hierarchy on the flavor structure of dimension seven operators and the resulting neutrino mass matrix. 相似文献
37.
Davoudiasl H 《Physical review letters》2007,99(14):141301
It has recently been suggested that a scale-invariant "unparticle" sector with a nontrivial infrared fixed point may couple to the standard model (SM) via higher-dimensional operators. The weakness of such interactions hides the unparticle phenomena at low energies. We demonstrate how cosmology and astrophysics can place significant bounds on the strength of unparticle-SM interactions. We also discuss the possibility of a having a non-negligible unparticle relic density today. 相似文献
38.
39.
Polarization mode conversion in an optical microdisk resonator vertically coupled to a waveguide bus
Hooman Akhavan 《Optics Communications》2009,282(21):4224-4228
Due to the existence of non-zero, and asymmetrics cross-polarization coupling coefficients between a microdisk and a waveguide bus, high Q (∼10,000) overcoupled microdisks with minimal internal losses and sharp bending curvature (small radii) vertically coupled to a narrow-width ridge waveguide can be engineered as a proper candidate for a narrow-band polarization rotator. A semi-analytical calculation method is presented to realize microdisk-waveguide system as a polarization rotator. 相似文献
40.
Immiscible viscous liquid–liquid two-phase flow patterns and pressure drop characteristics in a circular microchannel have been investigated. Water and silicone oil with a dynamic viscosity of 863 mPa s were injected into a fused silica microchannel with an inner diameter of 250 μm. As the microchannel was initially filled with the silicone oil, an oil film was found to always form and remain on the microchannel wall. Different flow patterns were observed and classified over a wide range of water and oil flow rates. A flow pattern map is presented in terms of Re, Ca, and We numbers. Two-phase pressure drop data have also been collected and analyzed to develop a simple correlation for slug, annular and annular-droplet flow patterns in terms of superficial water and oil velocities. 相似文献