排序方式: 共有4条查询结果,搜索用时 0 毫秒
1
1.
In this article, we study isometric immersions of nearly Kähler manifolds into a space form (especially Euclidean space) and show that every nearly Kähler submanifold of a space form has an umbilic foliation whose leafs are 6-dimensional nearly Kähler manifolds. Moreover, using this foliation we show that there is no non-homogeneous 6-dimensional nearly Kähler submanifold of a space form. We prove some results towards a classification of nearly Kähler hypersurfaces in standard space forms. 相似文献
2.
Bahaedin Nikrooz Morteza Zandrahimi Hadi Ebrahimifar 《Journal of Sol-Gel Science and Technology》2012,63(3):286-293
Silica coating for the protection of stainless steel (SS) surfaces was prepared using tetraethoxysilane and methyltriethoxysilane as precursors via an acid-catalysed (H2SO4) sol?Cgel method and was deposited on ferritic SS AISI 430 by dip coating. The surface morphology was studied using a scanning electron microscope equipped with energy-dispersive X-ray, phase analysis was carried out by X-ray diffraction, and isothermal oxidation was carried out at 800?°C for 200?h. Corrosion properties were examined by electrochemical impedance spectroscopy and resistance polarization methods in an aqueous medium containing 3.5?wt?% NaCl. The results indicated that silica coating improved high-temperature oxidation resistance of AISI 430 in chloride media. 相似文献
3.
Considering the synthesis of new compounds, we developed heterocyclic chemistry. We also helped to improve the classical synthetic route for the synthesis of quinoxalines and phenazines through implement in terms of solvent‐free reaction. For the condensation of 1,2‐dicarbonyls and o‐phenylenediamines under solvent‐free conditions at room temperature, tungstate sulfuric acid (TSA) was found to be an efficient and reusable reagent. The high yield of the pure products and simple preparation of the catalyst have allowed the synthesis of several phenazines and quinoxalines using this methodology. 相似文献
4.
Anti-corrosion silica coating was prepared via the sol–gel method for AZ91D magnesium alloy using tetraethoxysilane and methyltriethoxysilane
as precursors. Silica coating was deposited on fluorinated magnesium alloy substrates by dip coating. The surface morphology
of the silica coating was characterized by scanning electron microscope (SEM). The corrosion properties were studied by electrochemical
impedance measurements and polarisation technique in 3.5 wt% Sodium chloride solution. The results showed an improvement in
the corrosion performance from these coatings. A three-factor, three-level design of experiment (DOE) with response surface
methodology including a Box–Behnken design was run to evaluate the main and interaction effects of several independent formulation
variables, which included precursor ratios MTES/TEOS (X1), sintering temperature (X3) and sol dilution (X2) which measured the volume of the diluted sol divided by the initial volume of sol. The dependent variables included the
corrosion current derived from the polarisation curve (icor = Y1) and the coating resistance derived from the Nyquist curve (Rcoat = Y2). Optimizations were predicted to yield Y1 and Y2 values of 1.57018E–7A cm−2 and 14279 Ω cm2, when X1, X2, and X3 were 3.36, 1.52 and 222, respectively. 相似文献
1