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71.
《应用有机金属化学》2017,31(11)
A new, simple and cheap dispersive liquid–liquid microextraction (DLLME) procedure was optimized for the preconcentration of trace amounts of Ni(II) as a prior step to its determination by flame atomic absorption spectrometry (FAAS). It is based on the microextraction of nickel, where appropriate amounts of the extraction solvent (CHCl3), disperser solvent (ethanol) and chelating agent, name 5‐[(Z)‐isoxazol‐3‐yl‐diazenyl]‐2‐methyl‐quinolin‐8‐ol (MMD), were firstly synthesized/characterized and used. Various parameters that affect the extraction procedure such as pH, centrifugation rate and time, the chelating agent (MMD) concentration and sampling volume on the recovery of Ni(II) were investigated. The preconcentration of a 20 ml sample solution was thus enhanced by a factor of 80. The resulting calibration graph was linear in the range of 0.24–10 mg L−1 with a correlation coefficient of 0.9998. The limit of detection (3 s/b) obtained under optimal conditions was 1.00 μg L−1. The relative standard deviation for certified reference material determinations was 1.2%. The accuracy of the method was verified by the determination of Ni(II) in the certified reference material of wastewater (Waste water CWW TMD). The proposed procedure was successfully applied to the determination of Ni(II) in some fake jewelry and cosmetics samples. 相似文献
72.
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
73.
基于Drude模型研究了异向介质的色散磁导率对调制不稳定性的影响. 结果表明,在反常色散情形,赝五阶非线性在异向介质的负折射区中增大了调制频谱的范围及增益值,这与常规正折射介质中出现的现象正好相反;自陡峭效应在异向介质中有可能为负值,但无论正负,也无论在正折射区还是负折射区,它都抑制调制不稳定性的产生;二阶非线性色散效应在正、负折射区中分别促进和抑制调制不稳定性的产生. 在正常色散情形,由于二阶非线性色散效应的作用,使本来在常规正折射介质中不可能出现的调制不稳定性现象也能出现,这一特性为在正常色散区形成孤 相似文献
74.
75.
J. Colliander M. Keel G. Staffilani H. Takaoka T. Tao 《Journal of the American Mathematical Society》2003,16(3):705-749
The initial value problems for the Korteweg-de Vries (KdV) and modified KdV (mKdV) equations under periodic and decaying boundary conditions are considered. These initial value problems are shown to be globally well-posed in all -based Sobolev spaces where local well-posedness is presently known, apart from the endpoint for mKdV and the endpoint for KdV. The result for KdV relies on a new method for constructing almost conserved quantities using multilinear harmonic analysis and the available local-in-time theory. Miura's transformation is used to show that global well-posedness of modified KdV is implied by global well-posedness of the standard KdV equation.
76.
J. E. Colliander J.-M. Delort C. E. Kenig G. Staffilani 《Transactions of the American Mathematical Society》2001,353(8):3307-3325
The three bilinearities for functions are sharply estimated in function spaces associated to the Schrödinger operator . These bilinear estimates imply local wellposedness results for Schrödinger equations with quadratic nonlinearity. Improved bounds on the growth of spatial Sobolev norms of finite energy global-in-time and blow-up solutions of the cubic nonlinear Schrödinger equation (and certain generalizations) are also obtained.
77.
This study presents the electromagnetic wave propagation through the frequency-dispersive and lossy double-negative slab embedded
between two different semi-infinite media. The double-negative slab is realized by using two models, the Lorentz and Drude
medium models. The properties and the required equations for the frequency-dispersive and lossy double-negative slab, the
Lorentz medium and Drude medium are given in detail. After the construction of the problem, the reflection and transmission
coefficients are derived for both TE and TM waves. Then, the reflected, transmitted and loss powers are determined using these
coefficients. Finally, in the numerical results, the mentioned powers for TE and TM waves are computed and illustrated as
a function of the incidence angle, the frequency and the slab thickness when the damping frequency changes. 相似文献
78.
3D FDTD Implementation for Scattering of Electric Anisotropic Dispersive Medium Using Recursive Convolution Method 总被引:1,自引:0,他引:1
Lixia Yang 《International Journal of Infrared and Millimeter Waves》2007,28(7):557-565
The finite-difference time-domain method based on recursive convoltion method (RC-FDTD) for the electric anisotropic dispersive
medium is discussed in detail. To exemplify the availability of the three-dimensional RC-FDTD algorithm, the backscattering
Radar-Cross-Section(RCS) of a non-magnetized plasma sphere is computed, and the numerical results are the same as the one
of the Shift Operater-FDTD method, and show that the RC-FDTD method is correct and efficient. In addition, the co-polarized
and cross-polarized backscattering time-domain of a magnetized plasma sphere are obtained by the RC-FDTD algorithm. The results
show that when the external magnetic field is implemented, the cross-polarized component appear, evidently. 相似文献
79.
The temporal and spectral properties of ultrashort pulsed Laguerre-Gaussian (LG) beams propagating in dispersive media are studied both theoretically and numerically. It is shown that the on-axis pulse broadens with increasing propagation distance and the on-axis spectrum is blueshifted. For the off-axis spectrum the blueshifts decrease and then the spectrum becomes redshifted as the radial distance increases. The propagation of ultrashort pulsed LG beams in free space and of ultrashort pulsed Gaussian beams can be regarded as special cases of our results, and some interesting properties are discussed. 相似文献
80.
Domenico Finco 《Reports on Mathematical Physics》2007,59(3):379-388
We discuss the asymptotic wave function of a quantum system in ?3 composed by heavy and light particles, in the case where the light particles are in scattering states and no interaction is assumed among particles of the same kind. We first review a recent result concerning the case of K heavy and N light particles, where the one-particle potential acting on each heavy particle decays at infinity. Then we consider the case of one light particle interacting with a system of harmonic oscillators and prove the same kind of result following, with some modification, the proof of the previous case. A possible application to the analysis of the scattering of a light particle from condensed matter is also outlined. 相似文献