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141.
Marco Rahm David Schurig Daniel A. Roberts Steven A. Cummer David R. Smith John B. Pendry 《Photonics and Nanostructures》2008,6(1):87-VII
The technique of applying form-invariant, spatial coordinate transformations of Maxwell’s equations can facilitate the design of structures with unique electromagnetic or optical functionality. Here, we illustrate the transformation-optical approach in the designs of a square electromagnetic cloak and an omni-directional electromagnetic field concentrator. The transformation equations are described and the functionality of the devices is numerically confirmed by two-dimensional finite element simulations. The two devices presented demonstrate that the transformation optic approach leads to the specification of complex, anisotropic and inhomogeneous materials with well directed and distinct electromagnetic behavior. 相似文献
142.
T. A. Nguyen H. T. Dung 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):173-177
Using the Born expansion of the Green tensor, we consider the
spontaneous decay rate of an excited atom placed in the vicinity of
a rectangular plate. We discuss the limitations of the commonly used
simplifying assumption that the plate extends to infinity in the lateral
directions and examine the effects of the atomic dipole moment
orientation, atomic position, and plate boundary and thickness on the atomic
decay rate. In particular, it is shown that
due to the plate finite size, the spontaneous decay may be inhibited
even when the atom is situated very close to the surface, and that
in the boundary region, the
spontaneous decay rate can be strongly modified. 相似文献
143.
In this paper, a new type of resonant Brewster filters (RBF) with surface relief structure for the multiple channels is first presented by using the rigorous coupled-wave analysis and the S-matrix method. By tuning the depth of homogeneous layer which is under the surface relief structure, the multiple channels phenomenon is obtained. Long range, extremely low sidebands and multiple channels are found when the RBF with surface relief structure is illuminated with Transverse Magnetic incident polarization light near the Brewster angle calculated with the effective media theory of sub wavelength grating. Moreover, the wavelengths of RBF with surface relief structure can be easily shifted by changing the depth of homogeneous layer while its optical properties such as low sideband reflection and narrow band are not spoiled when the depth is changed. Furthermore, the variation of the grating thickness does not effectively change the resonant wavelength of RBF, but have a remarkable effect on its line width, which is very useful for designing such filters with different line widths at desired wavelength. 相似文献
144.
The(2 1)-dimensional nonlinear Schr(o)dinger(NLS)equation with spatially inhomogeneous nonlinearities is investigated,which describes propagation of light in(2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities.New types of optical modes and nonlinear effects in optical media are presented numerically.The results reveal that the regular split of beam can be obtained in (2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities,by adjusting the guiding parameter.Furthermore,the stability of beam regular split is discussed numerically,and the results reveal that the beam regular split is stable to the finite initial perturbations. 相似文献
145.
146.
A. Grusková J. Sláma R. Dosoudil D. Kevická V. Jančárik J. Lipka 《Czechoslovak Journal of Physics》2002,52(2):135-138
The M-type barium ferrite is doped with either Co2+-Ti4+ or Co2+-Zr4+ pairs to reduce its intrinsically high uniaxial magnetic anisotropy in order to make fine particles for magnetic recording. The magnetic parameters were investigated by magnetic measurements and the Mössbauer spectroscopy. Compounds (BaF) obtained from BaCo
x
(Ti,Zr)
x
Fe12-2x
O19 with 0x1.0 have been prepared by the modified citrate method with the initial ratio of Ba:Fe equal to 1:10.8. The substitution of Co - Ti or Co - Zr for Fe3+ ions affects mainly the positions 2a and 4f
2. Ba ferrite with the substitution x 0.8 is promising for perpendicular recording media applications. 相似文献
147.
We analyze the effective diffusivity of a passive scalar in a two-dimensional, steady, incompressible random flow that has
mean zero and a stationary stream function. We show that in the limit of small diffusivity or large Peclet number, with convection
dominating, there is substantial enhancement of the effective diffusivity. Our analysis is based on some new variational principles
for convection diffusion problems and on some facts from continuum percolation theory, some of which are widely believed to
be correct but have not been proved yet. We show in detail how the variational principles convert information about the geometry
of the level lines of the random stream function into properties of the effective diffusivity and substantiate the result
of Isichenko and Kalda that the effective diffusivity behaves likeɛ
3/13 when the molecular diffusivityɛ is small, assuming some percolation-theoretic facts. We also analyze the effective diffusivity for a special class of convective
flows, random cellular flows, where the facts from percolation theory are well established and their use in the variational
principles is more direct than for general random flows. 相似文献
148.
Fluorimetric Determination of Histamine in Fish Using Micellar Media and Fluorescamine as Labelling Reagent 总被引:1,自引:0,他引:1
Adamou R Coly A Douabalé SE Saleck ML Gaye-Seye MD Tine A 《Journal of fluorescence》2005,15(5):679-688
An analytical method based on the use of fluorescamine to produce a fluorescent derivative with histamine and combined with
micellar-enhanced fluorescence detection of the formed complex is developed for the sensitive and rapid determination of histamine
in fishes. The fluorescence properties of the obtained complex in water and micellar solutions of sodium dodecyl sulfate (SDS),
cetyltrimethylammonium chloride (CTAC) and brij-700 are reported. Physicochemical variables influencing the sensitivity of
the method (pH, micellar, fluorescamine and NaCl relative concentrations) have been optimized. The stability of the formed
complex, as shown by kinetic study, depends on the pH of the solution. Linear calibration curves allowing an effective histamine
determination were established with large linear dynamic range (LDR), and low limits of detection (LOD) between 0.5 and 33
ng mL−1, according to the solvent. Application to the analysis of fish samples (sardines) yielded satisfactory results. The method
seems to be suitable for environmental fish quality control.
Presented in part, at the 39th IUPAC Congress and the 86th Conference of the Canadian Society for Chemistry, August, 10–15,
2003, Ottawa (Canada). 相似文献
149.
Alexander?B.?Balakin Winfried?ZimdahlEmail author 《General Relativity and Gravitation》2005,37(10):1731-1751
The material tensor of linear response in electrodynamics is constructed out of products of two symmetric second rank tensor
fields which in the approximation of geometrical optics and for uniaxial symmetry reduce to “optical” metrics, describing
the phenomenon of birefringence. This representation is interpreted in the context of an underlying internal geometrical structure
according to which the symmetric tensor fields are vectorial elements of an associated two-dimensional space. 相似文献
150.
Min Zhang Lu Bai Tao Yuan Lewei Li Zhensen Wu 《International Journal of Infrared and Millimeter Waves》2005,26(2):315-327
An effective technique to characterize multilayered millimeter wave structure with vertical via-holes connected is presented. The advantage of this method is the closed-form Greens functions in spatial domain for general electric and magnetic sources in multilayered medium are obtained easily in terms of the two-level discrete complex image method (DCIM) with the high-order Sommerfeld identities, which only four elements of Greens functions in spectral domain are needed. In addition, the curl operators in mixed potential integral equations (MPIE) are avoided effectively from the Greens functions in this paper. A low temperature co-fired ceramic (LTCC) aperture coupled antenna with vertical via-holes connected is analyzed to prove the accuracy and efficiency of this technique on three-dimensional (3-D) multilayered structure with vertical components. 相似文献