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排序方式: 共有86条查询结果,搜索用时 15 毫秒
51.
Rachid Amrani Frederic Pichot Jean Podlecki Alain Foucaran Larbi Chahed Yvan Cuminal 《Journal of Non》2012,358(17):1978-1982
Using argon as a diluent of Silane, hydrogenated amorphous and nanorocrystalline silicon films Si:H were prepared by radio-frequency (13.56 MHz) plasma enhanced chemical vapor deposition (rf-PECVD). The deposition rate and crystallinity varying with the deposition pressure and rf power, were systematically studied. Structural analysis (Raman scattering spectroscopy and X-ray diffraction), combined with optical measurements spectroscopy were used to characterize the films. The argon dilution of silane for all samples studied was 95% by volume, and the substrate temperature was 200 °C. The deposition pressure was varied from 400 mTorr to 1400 mTorr and varying rf power from 50 to 250 W. The structural evolution studies, shows that beyond 200 W of rf power, an amorphous-nanocrystalline transition was observed, with an increase in crystalline fraction by increasing rf power and working pressure. The films were grown at high deposition rates. The deposition rates of the films near the amorphous-nanocrystalline phase transition region were found in the range 6–10 Å/s. A correlation between structural and optical properties has been found and discussed. 相似文献
52.
Abdelkader Belfedal Yahya Bouizem Jamal Dine Sib Larbi Chahed 《Journal of Non》2012,358(11):1404-1409
Thin films of hydrogenated amorphous germanium (a-Ge:H) deposited at high growth rate by radiofrequency (RF) glow discharge with 1 sccm GeH4 diluted in 40 sccm H2 have been studied. The effect of the films thicknesses on the defect density and on the structural parameters was carefully investigated by means of infrared spectroscopy, optical transmission measurements, and the photothermal deflection spectroscopy (PDS) technique. The results of this investigation show that when the films thicknesses increase, the total hydrogen content (CH) decreases and the hydrogen-bonding configuration changes. The results of these changes appear clearly on the defects density and on the microstructure parameter of the films, while the disorder parameter EOV and the optical gap ET remain practically constant (EOV ≈ 45 ± 2 meV, ET = 1.08 ± 0.02 eV). The improvement of these parameters is mainly due to the incorporation of the hydrogen in the bulk of the material as the monohydride groups (Ge-H) rather than the polyhydride groups (Ge-H2 and Ge-H2n) when the films thicknesses increase. 相似文献
53.
Ali Ghoumaid Farid Benamira Larbi Guechi Zohra Khiat 《Central European Journal of Physics》2013,11(1):78-88
We present a rigorous path integral treatment of a dynamical system in the axially symmetric potential $V(r,\theta ) = V(r) + \tfrac{1} {{r^2 }}V(\theta ) $ . It is shown that the Green’s function can be calculated in spherical coordinate system for $V(\theta ) = \frac{{\hbar ^2 }} {{2\mu }}\frac{{\gamma + \beta \sin ^2 \theta + \alpha \sin ^4 \theta }} {{\sin ^2 \theta \cos ^2 \theta }} $ . As an illustration, we have chosen the example of a spherical harmonic oscillator and also the Coulomb potential for the radial dependence of this noncentral potential. The ring-shaped oscillator and the Hartmann ring-shaped potential are considered as particular cases. When α = β = γ = 0, the discrete energy spectrum, the normalized wave function of the spherical oscillator and the Coulomb potential of a hydrogen-like ion, for a state of orbital quantum number l ≥ 0, are recovered. 相似文献
54.
Fazia Derridj Karima Si Larbi Julien Roger Safia Djebbar Henri Doucet 《Tetrahedron》2012,68(36):7463-7471
The palladium-catalyzed direct arylation at C2 or C5 of free NH2 substituted thiophene derivatives was found to proceed in moderate to high yields using a variety of aryl halides. The choice of potassium acetate as the base was found to be crucial to inhibit the amination reaction and to promote the direct arylation. 相似文献
55.
Hanène M Ameur E Larbi KM Piras A Porcedda S Falconieri D Marongiu B Farhat F Chemli R 《Natural product research》2012,26(9):810-820
This study is outlined to probe the chemical composition of essential oil and in vitro antioxidant activity of Juniperus oxycedrus ssp. macrocarpa (S. & m.) Ball. and Juniperus oxycedrus L. ssp. rufescens (L. K.) berries, collected from four sites, according to their maturity phase. The chemical composition of the hydrodistilled essential oil was analysed by GC-MS. Forty-eight compounds were identified, accounting for approximately 79.8-98.9% of the oil. The main constituents were α-pinene, germacrene D, myrcene, abietadiene and cis-calamenene, their mean percentage vary according to their phenological stage. The antioxidant activity of the samples was determined by the ABTS and DPPH radical scavenging activities. Hawaria essential oil extracted from mature berries showed the highest antioxidant capacity. 相似文献
56.
Mohamed Larbi Kadri Jalel Ben Abdallah Thouraya Nouri Baranger 《Comptes Rendus Mecanique》2011,339(10):674-681
This Note deals with the identification of internal planar cracks inside a three-dimensional elastic body via two approaches relying on domain decomposition using elastostatic measurements. These approaches consist in recasting the problem in terms of primal or dual Steklov–Poincaré equations. The primal approach is a straightforward continuation to the elastic Cauchy problem of the work presented in J. Ben Abdallah (2007) [1] which is devoted to the Cauchy problem for the scalar Laplace equation. The numerical performances of these formulations are compared. 相似文献
57.
Multiconfiguration self-consistent field and multiconfiguration reference interaction including the Davidson’s correction techniques were employed to calculate the potential energy curves (PECs) of the BeS/BeS+ electronic states correlating to the 4/5 lowest dissociation limits. After nuclear motion treatment, we deduced reliable spectroscopic data for the neutral and cationic bound states. For BeS, the transition moments and spin-orbit couplings were also evaluated and used later with the PECs to deduce the rovibronic transition probabilities and the radiative lifetimes in the low-lying states, and to investigate the unimolecular decomposition processes of BeS (X1Σ+, A1Π, 3Σ+ and B1Σ+) leading to Be(1Sg) + S(3Pg). The prominent mechanism is a spin-orbit induced predissociation via the repulsive BeS(13Σ−) state. Finally, we give the single ionization spectrum of BeS (X1Σ+) populating the BeS+ (X2Π, 12Σ−, 12Σ+, 12Δ, 22Σ+, 22Π and 32Π) electronic states. The adiabatic ionisation energy of BeS is estimated to be ∼9.15 eV. 相似文献
58.
It is shown that in blends of PE having different melting temperatures the morphology depends drastically on the cooling rate. In these heterogeneous PE, the correlation relationship L = r between the long period L of the solid state and the dimension of the coils r in the liquid state is observed only in rapidly quenched materials. In slowcooled materials the SAXS spectra are interpreted in terms of segregation of two types of PE, on a scale of the order of the dimension of the coils, the arrangement of the crystalline lamellae being paracrystalline and statistical. 相似文献
59.
60.
Larbi Alaoui 《Semigroup Forum》1997,54(1):135-153
First are given results on the norm-continuity of translation semigroups and their asymptotic behavior. Secondly a cell cycle
model is studied from the point of view of linear translation semigroups theory. Existence and norm-continuity of the solution
semigroup and the property of exponential asynchronous growth are established for this model. 相似文献