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81.
本文提出和研究了一般的斜半平面和角形区域的具有离散参数齐次随机场的线性预测问题,求出了它们的预测值与预测误差,分别推广了[2],[3],[4]的结果。 相似文献
82.
Yûji Kida 《Journal of Number Theory》1982,14(3):340-352
Hurwitz-type relations of Iwasawa's λ2?-invariants and the 2-ranks of the “narrow” ideal class groups in the 2-extensions of J-fields are given under the assumption of the vanishing of μ2-invariants. 相似文献
83.
试图用李群方法来分析流体及渗流的运动规律.对于流形上流体、渗流力学方程的研究,物理空间的流动中的拓扑结构只要具有李群的性质,便可以此来进行流动分析.这是将李群理论直接、直地应用于渗流力学的一种方法.李群方法将众多求解特定类型的渗流微分方程方法统一到共同的概念之下.李群无穷小变换方法为寻找微分方程的闭合形式的解提供的广泛的应用,补充了求解渗流力学方程的数学物理技巧. 相似文献
84.
TiO2 nanoparticles with different shapes and sizes were synthesised by the sol-gel route in Water/Brij78/Hexane reverse microemulsions.
The aqueous cores of these microemulsions were used as nanoreactors to control sol-gel reactions. We studied the effect of
water/surfactant mole ratio (W
0) on the morphology, and textural properties of the final products. The materials thus obtained were characterised by different
techniques. Thermogravimetric and differential thermal analysis (TG-DTA) was used to study the thermal behaviour of the products
and X-ray diffraction (XRD) to identify the crystalline phases. The morphological and textural properties of the products
were determined by scattering electron microscopy (SEM) and the Brunauer-Emmett-Teller (BET) method, respectively. We also
studied the influence of thermal treatment on the structure and size of the TiO2 particles. The effect of W
0 on the anatase-rutile phase transition temperature was investigated. 相似文献
85.
Saida Mnasri Néji Besbes Najoua Frini-Srasra Ezzeddine Srasra 《Comptes Rendus Chimie》2012,15(5):437-443
The purified Tunisian clay G and the commercialized American clay W were pillared with zirconium, aluminum and mixed pillars zirconium–aluminum, cerium–zirconium, cerium–aluminum, and cerium–zirconium–aluminum. These different clays were used in the synthesis of 2,2-dimethyl-1,3-dioxolane 3 by acetalyzation of acetone 2 with ethylene glycol 1 under autogenously pressure and without solvent. Results indicate that the yield of product 3 depends of the nature and the acidity of the clay used and the time of reaction. 相似文献
86.
S. Ben Khalifa B. Gruzza G. Bremond F. Saidi L. Bèji 《Journal of luminescence》2008,128(10):1611-1616
Porous GaAs layers were formed by electrochemical etching of p-type GaAs(1 0 0) substrates in HF solution. A surface characterization has been performed on p-type GaAs samples using X-ray photoelectron spectroscopy (XPS) technique in order to get information about the chemical composition, particularly on the surface contamination. According to the XPS spectra, the oxide layer on as-received porous GaAs substrates contains As2O3, As2O5 and Ga2O3. Large amount of oxygen is present at the surface before the surface cleaning.Compared to untreated GaAs surface, room temperature photoluminescence (PL) investigations of the porous layers reveal the presence of two PL bands: a PL peak at ∼871 nm and a “visible” PL peak at ∼650-680 nm. Both peak wavelengths and intensities varied from sample to sample depending on the treatment that the samples have undergone. The short PL wavelength at 650-680 nm of the porous layers is attributed to quantum confinement effects in GaAs nano-crystallites. The surface morphology of porous GaAs has been studied using atomic force microscopy (AFM). Nano-sized crystallites were observed on the porous GaAs surface. An estimation of the mean size of the GaAs nano-crystals obtained from effective mass theory and based on PL data was close to the lowest value obtained from the AFM results. 相似文献
87.
88.
仿生自组装纳米复合薄膜的制备与摩擦行为研究 总被引:7,自引:0,他引:7
利用分子自组装法在玻璃表面制备未聚合与聚合(丙烯酸十二醇酯/二氧化硅)有机-无机有序交替的层次纳米复合薄膜,并对其摩擦学行为进行了探讨。结果表明:未聚合或聚合薄膜的结构类似于海洋贝类的贝壳结构,与钢球对摩时都有较好的减摩性,摩擦系仅为0.1;而聚合薄膜的抗磨性能大幅提高,其失效循环次数为未聚合薄膜的6倍。 相似文献
89.
90.
Feten Béji Sonia Taktouk Jihène Ben Kraïem Salem S. Al‐Deyab Hassen Amri 《Journal of heterocyclic chemistry》2015,52(5):1576-1579
We present herein an efficient and rapid method for the synthesis of N,1‐dialkyl‐4‐(2‐hydroxyethyl)‐5‐oxopyrrolidine‐3‐carboxamides based on the conversion of γ‐lactone to γ‐lactam via the conjugate addition of primary amines to an ethyl α‐functionalized acrylate followed by intramolecular cyclization. 相似文献