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21.
The intersubband absorption in square and graded quantum wells under a laser field is calculated within the framework of the effective mass approximation. We conclude that, for quantum wells with different shapes, the laser field amplitude induces an important effect on the electronic and optical properties of the semiconductor structure. This gives a new degree of freedom in various device applications based on the intersubband transition of electrons. 相似文献
22.
Metal oxide layers formed from transition-metal foils oxidized by heating in air have been examined for their photoelectrolytic response. The metals examined are Y, Ti, Zr, Hf, V, Nb, Ta, Mo, W, and Pt. Weak photoeffects are observed for oxide layers of all of these metals. Sizable light-dependent oxygen gas evolution rates are found in Ti and also in W oxides. The spectral dependence of the oxygen response in these compounds is investigated, and interpretation is given of these experiments. 相似文献
23.
M. Ghoranneviss A. Shokouhy M. M. Larijani S. H. Haji Hosseini M. Yari A. Anvari M. Gholipur Shahraki A. H. Sari M. R. Hantehzadeh 《Pramana》2007,68(1):135-140
This work presents the results of a low-energy nitrogen ion implantation of AISI 304 type stainless steel (SS) at a moderate
temperature of about 500°C. The nitrogen ions are extracted from a Kauffman-type ion source at an energy of 30 keV, and ion
current density of 100 μA cm−2. Nitrogen ion concentration of 6 × 1017, 8 × 1017 and 1018 ions cm−2, were selected for our study. The X-ray diffraction results show the formation of CrN polycrystalline phase after nitrogen
bombardment and a change of crystallinity due to the change in nitrogen ion concentration. The secondary ion mass spectrometry
(SIMS) results show the formation of CrN phases too. Corrosion test has shown that corrosion resistance is enhanced by increasing
nitrogen ion concentration.
相似文献
24.
Abdul Rehman Khan Johnson MathewKhawla Al-Shayji Majed Sari 《European Polymer Journal》2002,38(5):1013-1023
The synthesis of copolyesteramides using para-acetamido benzoic acid (PABA) and polyethylene terephthalate (PET) by melt polymerization has been studied in detail. The performance of three transesterification catalysts are assessed for three different initial compositions, PABA 60 mol%/PET 40%, PABA 50 mol%/PET 50% and PABA 40 mol%/PET 60%. The polycondensations are found to obey second order kinetics, irrespective of whether the reaction was catalysed or not. The mechanism of initial stage polymerization kinetics of the copolymers has been fully explained.It is suggested that acetic acid is evolved only by the homopolymerization of PABA and that the insertion of a monomer of homopolymer of PABA into PET does not yield any acetic acid. A set of differential equations containing three different rate constants, k1 for homopolymerization of PABA, k2 for PET reaction with dimer of PABA and k3 for PABA reaction with copolymer of PABA and PET has been developed and numerically solved, to study the initial stage kinetics. The computed values of acetic acid are compared with the experimentally collected amount and the three rate constants are optimized using a differential algebraic optimization technique. The present model represents the data with an acceptable accuracy with an average % error of less than 5% between experimental and computed values for the entire experimental range. The correlation coefficient values range between 0.988 and 0.999.Differential scanning analysis of the copolyestermides indicates that 40 mol% PABA and 60% PET had the highest enthalpy values of the order of 18 kJ/mol. It is found that within the copolyesteramide series the degree of crystallinity increased with the increase of PET contents in the feed mixture to the batch reactor. 相似文献
25.
Sabri Cevik Bihter Şaşmaz Cengiz Yenikaya Ferdağ Çolak Musa Sari Orhan Büyükgüngör 《Russian Journal of Inorganic Chemistry》2010,55(4):494-500
The hydrothermal reaction of a mixture of V2O5, VCl3, 2,5-pyridinedicarboxylic acid and diluted H2SO4 for 68 h at 180°C gives a blue colored solution which yields prismatic blue crystals of IV 2 IV O2(SO4)2(H2O)6] (1) in 32% yield (based on V). Complex 1 was investigated by means of elemental analysis (C, H and S), TGA, FT-IR, manganometric titration, Single Crystal X-ray Diffraction Methods and also comparative antimicrobial activities. Crystal data for the compound: monoclinic space group P21/c and unit cell parameters are a = 7.3850(12) Å, b = 7.3990(7) Å, c = 12.229(2) Å, β = 108.976(12)° and Z = 2. Although structure of 1 as a natural mineral has been previously determined, this work covers new preparation method and full characterization of 1 along with comparison of antibacterial activity between 1 and the commercial vanadium(IV) oxide sulfate hydrate compounds, VOSO4 · xH2O (Riedel-de Haën and Alfa Aesar brand names). 1 was evaluated for the antimicrobial activity against gram-positive, gram-negative bacteria, yeasts and mould compared with the commercial VOSO4 · xH2O compounds. 1 showed weak activity against bacteria Bacillus cereus, Nocardia asteroides and yeast Candida albicans. A good antimicrobial activity was recorded against Cirtobacter freundii (15 mm). There are only a few reproducible well-defined vanadium(IV) starting materials to use for exploring the synthesis of new materials. VCl4, VO(acac)2, VOSO4 · xH2O and [V(IV)OSO4(H2O)4] · SO4 · [H2N(C2H4)2NH2] are common starting materials for such applications. In addition to these compounds, 1 can be used as an oxovanadium precursor. 相似文献
26.
An intense laser field effect on the intersubband transitions in quantum wells is theoretically investigated within the framework of the effective-mass approximation. Results obtained show that intersubbband optical transitions and energy levels in quantum wells can be significantly modified and controlled by an intense laser field. PACS 71.55.Eq; 73.21.Fg; 78.67.De 相似文献
27.
Sari M. Kunnari Raija Oilunkaniemi Risto S. Laitinen Markku Ahlgren 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(10):o610-o611
The novel title tetraselenacalix[4]arene, C16H8S4Se4 or [(C4H2S)Se]4, has a centrosymmetric cyclic molecular structure with approximate C2h molecular symmetry. The four thienyl rings are joined together by Se bridges and exhibit a syn–syn–anti–anti arrangement around the molecule. The lattice consists of skewed stacks of molecules, with chalcogen–chalcogen close contacts binding the stacks together, forming a two‐dimensional network of molecules. 相似文献
28.
Noora Ristolainen Ulla Vainio Santeri Paavola Mika Torkkeli Ritva Serimaa Jukka Seppl 《Journal of Polymer Science.Polymer Physics》2005,43(14):1892-1903
The properties of polypropylene composites can be tailored through the use of nanoclay fillers. The effectiveness of a metallocene‐catalyzed hydroxyl‐functional polypropylene in the compatibilization of polypropylene layered nanosilicate composites was studied, and the results were compared with those for a commercial maleic anhydride functionalized polypropylene. Polypropylene/organoclay nanocomposites were prepared by melt blending, and two polypropylene/compatibilizer/organoclay ratios, 90/5/5 and 70/20/10, were characterized. The organomodification of the clay was carried out with octadecylamine and N‐methylundecenylamine. The structure of the layered silicate was studied by transmission electron microscopy, wide‐angle X‐ray scattering, and small‐angle X‐ray scattering. The fracture surfaces of the composites and thus the efficiency of the compatibilizers to penetrate the galleries of the organoclays were characterized by scanning electron microscopy, and the melt viscosity was studied by stress‐controlled rotational rheometry. The nanostructure was observed with both alkyl amines used for intercalation. The fillers facilitated the processability of all the composites, consisting of equal amounts of compatibilizer and organoclay filler and, in some of the composites, containing twice as much compatibilizer as organoclay filler. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1892–1903, 2005 相似文献
29.
Murat Sari Gürhan Gürarslan Asuman Zeytinoğlu 《Numerical Methods for Partial Differential Equations》2011,27(5):1313-1326
In this article, up to tenth‐order finite difference schemes are proposed to solve the generalized Burgers–Huxley equation. The schemes based on high‐order differences are presented using Taylor series expansion. To establish the numerical solutions of the corresponding equation, the high‐order schemes in space and a fourth‐order Runge‐Kutta scheme in time have been combined. Numerical experiments have been conducted to demonstrate the high‐order accuracy of the current algorithms with relatively minimal computational effort. The results showed that use of the present approaches in the simulation is very applicable for the solution of the generalized Burgers–Huxley equation. The current results are also seen to be more accurate than some results given in the literature. The proposed algorithms are seen to be very good alternatives to existing approaches for such physical applications. © 2010 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 27: 1313‐1326, 2011 相似文献
30.
Branko Sarić 《Czechoslovak Mathematical Journal》2011,61(4):1017-1022
In this paper a full totalization is presented of the Kurzweil-Henstock integral in the multidimensional space. A residual function of the total Kurzweil-Henstock primitive is defined. 相似文献