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排序方式: 共有145条查询结果,搜索用时 15 毫秒
1.
In this paper, we prove some existence results for the Webster scalar curvature problem on the three dimensional CR compact manifolds locally conformally CR equivalent to the unit sphere S3 of C2. Our methods are based on the techniques related to the theory of critical points at infinity. 相似文献
2.
Mouna Smida Jérome Lhôste Mohamed Dammak Santiago Garcia-Granda 《Arabian Journal of Chemistry》2019,12(8):2519-2523
Crystal structure of Fe2F5(H2O)(Htaz)(taz)(Hdma) which crystallizes in the triclinic system space group with unit cell parameters a = 8.8392(5) Å, b = 9.1948(5) Å, c = 9.5877(5) Å, α = 82.070(3)°, β = 63.699(3)°, γ = 89.202(3)°, Z = 2, and V = 690.91(7) Å3, was synthesized under hydrothermal conditions at 393 K for 72 h, by a mixture of FeF2/FeF3, 1,2,4-triazole molecule (Htaz), and hydrofluoric acid solution (HF 4%) in dimethylformamide solvent (DMF). The main feature of this material is the coexistence of two oxidation states for iron atoms (Fe2+, Fe3+) in the unit cell, which associate by opposite fluorine corners of FeF5N and FeF2N4 octahedra, and/or triazole molecule which originates the 2D produces material. The structure determination, performed from single crystal X-ray diffraction data, lead to the R1/WR2 reliability factors 0.031/0.087. Thermal stability studies (TG/DTG/DTA) show that the decomposition provides in the temperature range 473–773 K and no mass loss was detected before 473 K. Mass spectrometry (MS) has been used. The optical absorption of the solid was measured at the corresponding λmax using UV–vis diffuse-reflectance spectrum. 相似文献
3.
4.
Zghal Imen Farjas Jordi Camps Jaume Sánchez-Rodríguez D. Dammak Mohamed Roura-Grabulosa Pere 《Journal of Thermal Analysis and Calorimetry》2020,140(5):2087-2096
Journal of Thermal Analysis and Calorimetry - Thermal energy storage (TES) has been identified as a breakthrough concept in development of renewable technologies. However, the main challenges are... 相似文献
5.
Isolation and structure determination of a novel furanic ester from the aerial part of Prasium majus
The aerial part of Prasium majus provided a new furanic ester, 2-2-[(5-formyl-6[(5-formylfuran-2-yl)methoxy] succinic acid dimethyl ester, (+/-)-hiziprafuran. Its structure was principally established by one- and two-dimensional NMR spectroscopy. 相似文献
6.
We study the expansion of real numbers with negative base (?β), and prove that if $\mathbb{Z^{-}}$ or $\mathbb{Z^{+}} \subset \mathop {\rm Fin}\nolimits \, (-\beta)$ , then β is a Pisot number. 相似文献
7.
Sami Baraket Makkia Dammak Taieb Ouni Frank Pacard 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2007,24(6):875-895
Using some nonlinear domain decomposition method, we prove the existence of branches of solutions having singular limits for some 4-dimensional semilinear elliptic problem with exponential nonlinearity. 相似文献
8.
Finite element method for the stress analysis of isotropic cylindrical helical spring 总被引:4,自引:0,他引:4
Dammak Fakhreddine Taktak Mohamed Abid Said Dhieb Abderrazek Haddar Mohamed 《European Journal of Mechanics - A/Solids》2005,24(6):1068-1078
This paper presents an efficient two nodes finite element with six degrees of freedom per node, capable to model the total behaviour of a helical spring. The formulation, which includes the shear deformation effects, is based on the assumed forces hybrid approach. The resultant forces approximation verifies exactly the resultant equilibrium equations. The developed model proves its accuracy compared with other elements. This element permits to get the distribution of different stresses along the spring and through the wire surface by only one element. 相似文献
9.
Mohammed Hichem Mortad 《Proceedings of the American Mathematical Society》2005,133(2):455-464
We give classes of unbounded real-valued for which is self-adjoint on , , where is the wave operator defined on .
10.
A selection of steroids, glycerides, clerodane diterpenoids, and a beta-hydroxy fatty acid methyl ester, all previously isolated from Ajuga pseudoiva leaves, were tested for their antibacterial activity toward three Gram- rods and one Gram+ coccus using the dilution method; MIC values were determined. The results suggested some importance for a free beta-hydroxy group in the fatty acid ester and also in the glycerides and clerodane derivatives; the absolute configurations of the latter, notably at C2, had little influence on activity. 相似文献