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61.
A.SH. Hussein Z. Hassan S.M. Thahab Abu Hassan M.A. Abid C.W. Chin 《Physica B: Condensed Matter》2011,406(6-7):1267-1271
We have studied the structural properties of undoped and Si-doped AlxGa1?xN/GaN/AlN on Si (1 1 1) substrate prepared by plasma-assisted molecular beam epitaxy (PA-MBE) using high-resolution X-ray diffraction (HR-XRD) and atomic force microscopy (AFM). In comparison with undoped AlGaN, the roughness and dislocation density on the surface of the AlGaN layer decrease with Si doping. Full width half maximum (FWHM) of the undoped and Si-doped samples were equal to 0.69° and 0.52°, respectively. This indicates that the Si doping improves the crystalline quality of the AlxGa1?xN layer compared with the undoped one. Raman scattering measurement reveals that the optical phonon modes of A1(LO) and E2(H) of the AlGaN show a one-mode and two-modes behavior, respectively. The Fourier-transform infrared reflectance (FTIR) investigation confirms the one-mode (two-mode) behavior of the LO (TO) phonon in our samples. This is in good agreement with Raman measurement. Finally, the barrier height (ΦB) of undoped and Si-doped AlxGa1?xN samples was found to be 0.86 and 0.74 eV, respectively. 相似文献
62.
Kevin Kam Fung Yuen 《Fuzzy Optimization and Decision Making》2014,13(1):105-130
Group decision making is the process to explore the best choice among the screened alternatives under predefined criteria with corresponding weights from assessment of a group of decision makers. The Fuzzy TOPSIS taking an evaluated fuzzy decision matrix as input is a popular tool to analyze the ideal alternative. This research, however, finds that the classical fuzzy TOPSIS produces a misleading result due to some inappropriate definitions, and proposes the rectified fuzzy TOPSIS addressing two technical problems. As the decision accuracy also depends on the evaluation quality of the fuzzy decision matrix comprising rating scores and weights, this research applies compound linguistic ordinal scale as the fuzzy rating scale for expert judgments, and cognitive pairwise comparison for determining the fuzzy weights. The numerical case of a robot selection problem demonstrates the hybrid approach leading to the much reliable result for decision making, comparing with the conventional fuzzy Analytic Hierarchy Process and TOPSIS. 相似文献
63.
(WO3)0.15(BiO1.5)0.85 exhibits a tetragonal structure derived from the fluorite subcell. The electrical conductivity of (WO3)0.15(BiO1.5)0.85 is lower than that of Y2O3-doped Bi2O3. The structure and electrical conductivity of samples formulated as (YO1.5)
x
(WO3)0.15(BiO1.5)0.85-
x
(x = 0.1, 0.2, 0.3, and 0.4) were investigated. The as-sintered (YO1.5)0.1(WO3)0.15(BiO1.5)0.75 exhibited a single cubic structure that is isostructural with δ-Bi2O3. For x = 0.2, 0.3, and 0.4, the as-sintered samples consisted of a cubic fluorite structure and rhombohedral Y6WO12. After heat treatment at 600 °C for 200 h, the cubic structures are stable for x = 0.1, 0.3, and 0.4. A transformation from cubic to rhombohedral phase after heat treatment at 600 °C for 200 h was observed
in the sample originally formulated as (YO1.5)0.2(WO3)0.15(BiO1.5)0.65. 相似文献
64.
65.
Synthesis and thermal properties of mesomorphic 1,1'-bis[ω-(4'-cyano-4-biphenyloxy)alkyl] ferrocenes
A new series of 1,1'-disubstituted ferrocene compounds of the type [(η5-C5H4(CH2)nOC6H4C6H4CN]2Fe (3a-d, n = 5, 6, 8, 11) incorporating a variable length alkyloxy cyanobiphenyl unit has been prepared and their mesomorphic properties have been investigated. Compounds 3b, c and d exhibit a thermotropic smectic C phase and 3c also exhibits a monotropic smectic A phase over a fairly wide range near ambient temperature. 相似文献
66.
A new technique has been developed to compute mean and fluctuating concentrations in complex turbulent flows. An initial distribution of material is discretised into any small clouds which are advected by a combination of the mean flow and large scale turbulence. The turbulence can be simulated either by Kinematic Simulation or by a stochastic model for the motion of each cloud centroid. The clouds also diffuse relative to their centroids; the statistics for this are obtained from a separate calculation of the growth of individual clouds in small scale turbulence, generated by Kinematic Simulation. The ensemble of discrete clouds is periodically rediscretised, to limit the size of the small clouds and prevent overlapping. The model is illustrated with simulations of dispersion in uniform flow and in a coastal flow, and the results are compared with analytic, steady state solutions where available. 相似文献
67.
Dong M Si YQ Sun SY Pu XP Yang ZJ Zhang LR Zhang LH Leung FP Lam CM Kwong AK Yue J Zhou Y Kriksunov IA Hao Q Lee HC 《Organic & biomolecular chemistry》2011,9(9):3246-3257
Human CD38 is a novel multi-functional protein that acts not only as an antigen for B-lymphocyte activation, but also as an enzyme catalyzing the synthesis of a Ca(2+) messenger molecule, cyclic ADP-ribose, from NAD(+). It is well established that this novel Ca(2+) signaling enzyme is responsible for regulating a wide range of physiological functions. Based on the crystal structure of the CD38/NAD(+) complex, we synthesized a series of simplified N-substituted nicotinamide derivatives (Compound 1-14). A number of these compounds exhibited moderate inhibition of the NAD(+) utilizing activity of CD38, with Compound 4 showing the highest potency. The crystal structure of CD38/Compound 4 complex and computer simulation of Compound 7 docking to CD38 show a significant role of the nicotinamide moiety and the distal aromatic group of the compounds for substrate recognition by the active site of CD38. Biologically, we showed that both Compounds 4 and 7 effectively relaxed the agonist-induced contraction of muscle preparations from rats and guinea pigs. This study is a rational design of inhibitors for CD38 that exhibit important physiological effects, and can serve as a model for future drug development. 相似文献
68.
Soni R Cheung FK Clarkson GC Martins JE Graham MA Wills M 《Organic & biomolecular chemistry》2011,9(9):3290-3294
Ru(II) complexes of TsDPEN containing two alkyl groups on the non-tosylated nitrogen atom are poor catalysts for asymmetric transfer hydrogenation of ketones and imines; this observation provides direct evidence for the importance of the N-H interaction in the transition state for ketone reduction. 相似文献
69.
70.
Metal/superconductor/semiconductor (Ag/Hg-1212/CdSe) hetero-nanostructures have been fabricated using pulse-electrodeposition
technique and are characterized by X-ray diffraction (XRD), full-width at half-maximum (FWHM) and scanning electron microscopy
(SEM) studies. The junction capacitance of Ag/Hg-1212, Hg-1212/CdSe and Ag/Hg-1212/CdSe heterojunctions is measured in dark
and under laser irradiation at room temperature. The nature of the junction formed and built-in-junction potentials were determined.
The increase in carrier concentration across the junction due to photo-irradiation has been observed. 相似文献