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951.
The structural and elastic properties of TaC in NiAs‐type structure under high pressure have been investigated using first principles calculations based on density functional theory. Results indicate that the incompressibility along the c‐axis of TaC exceeds that of diamond under higher pressure. Particularly, an interesting point singularity exists in its mechanical properties as the pressure increases from 20 GPa to 40 GPa. The minimal shear modulus, Young's modulus, Debye temperature, and maximum Poisson ratio of TaC are simultaneously obtained at 28 GPa. The calculations of hardness indicate that the NiAs‐type TaC crystal possesses excellent mechanical properties. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
952.
Luminescent CuInS2 nanocrystals have been synthesized in dodecanethiol using air-stable precursors. The nanocrystals were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The optical properties of the CuInS2 nanocrystals can be controlled by changing the reaction conditions, such as reaction time, temperature, and addition of ligands. It was found that the steady-state photoluminescence spectrum of the close-packed CuInS2 nanocrystals on glass substrate peaked at longer wavelength than that of the colloidal ones and the close-packed nanocrystals possessed a shorter luminescence decay time. This behavior was explained on the basis of Förster resonant energy transfer due to the shorter distance between nanocrystals on substrate. 相似文献
953.
Zhengwen Yang Dong Yan Zhiguo Song Dacheng Zhou Xue Yu Yong Yang Zhaoyi Yin Lei Yan Rongfei Wang Hangjun Wu Jianbei Qiu 《Journal of luminescence》2012,132(6):1550-1552
The SiO2: Tb, Yb inverse opals with photonic band gap at 465 or 543 nm were prepared, and an effect of photonic band gap on upconversion spontaneous emission from Tb3+ was investigated. The results show that the photonic band gap has a significant influence on the upconversion emission of the SiO2: Tb, Yb inverse opals. The upconversion luminescence of the Tb3+ ions is suppressed in the inverse opal compared with the luminescence of that of the reference sample. 相似文献
954.
Divalent europium-doped alkaline earth metal silicate phosphors, (Ba1?x?ySryEux)9Sc2Si6O24 (x=0.005–0.1, y=0–0.95), have been successfully prepared by solid-state reaction at 1350 °C. The analysis of X-ray diffraction shows that the compounds are in a single phase at the proper concentration of Sr2+. At room temperature, the Eu2+-activated Ba9Sc2Si6O24 phosphor exhibits a single emission band peaking at about 506 nm. With the increasing content of Sr2+, the luminescent intensity of (Ba1?x?ySryEux)9Sc2Si6O24 weakens, and the emission peak shifts towards red. Luminescence concentration quenching occurs when Eu2+ content x is more than 1 mol% in (Ba1?x?ySryEux)9Sc2Si6O24 (y=0/0.2). At low temperatures (Ba0.9?ySryEu0.1)9Sc2Si6O24 (y=0/0.2) phosphors have two emission bands corresponding to different Eu2+ crystallographic sites. The high energy peak (P1) is quenched at room temperature, while the low energy peak (P2) weakens much more slowly owing to the energy transfer from P1 to P2. 相似文献
955.
Chi-Ching Yang 《Journal of sound and vibration》2012,331(3):501-509
The main goal of this paper is to propose the single input robust adaptive sliding mode controllers to accomplish synchronization and anti-synchronization between two identical Φ6 Duffing or Van der Pol oscillators with unmodel dynamics and external disturbances. Unlike directly eliminating the nonlinear dynamics by active control and sliding mode control in the literature, the proposed sliding mode controllers include the equivalent control part, which is only proportional to the synchronized error states, and the switching control part, where the discontinuous control functions have adaptive feedback gains. Sufficient conditions are provided based on the Lyapunov stability theorem and numerical simulations are performed to verify the effectiveness of presented schemes. 相似文献
956.
Non-specular reflection of self-collimated beams in photonic-crystal-made prism and waveguide system
Fei Zhou Kui Han Yang Ge Faliang Ju Yifeng Shen Gang Tang 《Optics Communications》2012,285(12):2780-2784
We demonstrate a dual-beam-reflection phenomenon for a Gaussian beam illuminating at a Kretschmann configuration composed of a photonic-crystal-made prism and a dielectric waveguide. One reflection beam has a positive shift and the other has a negative shift. The finite-difference time-domain (FDTD) shows that the specific phenomenon takes place only when the corresponding quasi-guided mode supported in the Kretschmann configuration is excited. Field profile of the quasi-guided mode demonstrates a strong localized stationary field in the dielectric waveguide. We found that the maximum positive lateral shift (LS) is 14.27a (where a is the lattice constant), corresponding to 3.07 times of the incident wavelength, which is 0.7135 times of the beam waist and much larger than that in some previous reports. 相似文献
957.
A theoretical investigation about sensing mechanism of fluoride anion for (E)‐2‐(2‐(dimethylamino)ethyl)‐6‐(4‐hydroxystyryl)‐1H‐benzo[de]‐isoquinoline‐1,3 (2H)‐dione 下载免费PDF全文
In the present work, we theoretical study the sensing mechanism of a new fluoride chemosensor (E)‐2‐(2‐(dimethylamino)ethyl)‐6‐(4‐hydroxystyryl)‐1H‐benzo[de]‐isoquinoline‐1,3(2H)‐dione (the abbreviation is NIM ). Based on density functional theory and time‐dependent density functional theory methods, the fluoride anion response mechanism has been confirmed via constructing potential energy curve. The exothermal deprotonation process along with the intermolecular hydrogen bond O–H···F reveals the uniqueness of detecting F?. After capturing hydrogen proton forming NIM‐A anion configuration, a new absorption peak around 655 nm appears in dimethyl sulfoxide solvent. In addition, the emission of NIM can be quenched when adding F? has been also confirmed. Due to the twisted intramolecular charge transfer character NIM‐A‐S 1 form, we further verify the experimental phenomenon. The theoretical electronic spectra (vertical excitation energies and fluorescence peak) reproduced previous experimental results (ACS Appl. Mater. Interfaces 2014, 6, 7996), which not only reveals the rationality of our theoretical level used in this work but also confirms the correctness of geometrical attribution. In view of the excitation process, the strong intramolecular charge transfer process of S0 → S1 transition explain the redshift of absorption peak for NIM with the addition of fluoride anion. This work presents a straightforward sensing mechanism (deprotonation process) of fluoride anion for the novel NIM chemosensor. 相似文献
958.
959.
960.
L.T. Yang J.K. Liang G.B. Song J. Luo F.S. Liu H.F. Yang G.H. Rao 《Applied Physics A: Materials Science & Processing》2005,80(4):865-870
The compound FeSr2NdCu2O7+ (Fe1212) was successfully synthesized by solid-state reaction. X-ray diffraction data indicate that the sample is of single phase. Rietveld whole-pattern-fitting method was used to refine the crystal structure of samples prepared under different annealing conditions using the tetragonal system with space group P4/mmm. Magnetization measurements indicate that magnetic susceptibility changes with temperature in a Curie-type manner. Resistance measurements indicate that these samples have a semiconductor-like behavior. PACS 61.10.Nz; 74.72.Jt 相似文献