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21.
N. Kleemann 《Mathematical Methods in the Applied Sciences》2012,35(12):1365-1391
This paper studies conical diffraction problems with non‐smooth grating structures. We prove the existence, uniqueness and regularity results for solutions in weighted Sobolev spaces of Kondratiev type. An a priori estimate that follows from these results is then used to prove shape differentiability of solutions. Finally, a characterization of the shape derivative as a solution of a modified transmission problem is given. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
22.
T. Woike U. Dörfler L. Tsankov G. Weckwerth D. Wolf M. Wöhlecke T. Granzow R. Pankrath M. Imlau W. Kleemann 《Applied physics. B, Lasers and optics》2001,72(6):661-666
The purity and the concentrations of the constituents Sr, Ba, Nb and Cr were determined in single crystals of chromium-doped
Sr0.61Ba0.39Nb2O6 (SBN) by instrumental neutron activation analysis (INAA) and X-ray fluorescence analysis (XRF). Experiments with different
Cr concentrations CCr reveal constant Sr and Ba concentrations as well as a decreasing Nb concentration with an increasing CCr. Therefore, Cr is incorporated at Nb lattice sites. The distribution coefficient of Cr is 1.2 between 100 and about 7000 ppm
Cr and 1 above. From measurements of the holographic two-beam coupling gain Γ for different CCr, we deduced response times for the buildup of holographic gratings. The saturation value of Γ depends in a nonlinear manner
on CCr and reaches its maximum at about 6000 ppm Cr. The inverse photorefractive response time of the grating erasure depends linearly
on the erasure intensity for all doping concentrations. Thus a one-center model can be assumed for the charge transport in
SBN:Cr.
Received: 8 December 2000 / Revised version: 23 January 2001 / Published online: 21 March 2001 相似文献
23.
24.
M. E. Guzhva V. V. Lemanov P. A. Markovin W. Kleemann 《Physics of the Solid State》1997,39(4):618-624
Temperature-induced variations of light refraction and dielectric permittivity in single-crystal Sr1−x
BaxTiO3 (x=0.02, 0.05, 0.07, and 0.14), Sr1−x
CaxTiO3 (x=0.014), and in nominally pure strontium titanate have been studied within the 17–300 K temperature range. The spontaneous
polar contribution to the refractive index has been isolated. It was used to calculate the temperature and concentration dependences
of the polarization autocorrelation function 〈P
s
2〉
in the Sr1−x
BaxTiO3 system. For x⩽0.07, the polarization P
s=〈P
s
2
〉1/2 varies proportional to (x−x
g)1/2, where x
g=0.0027 is the new critical concentration in Sr1−x
BaxTiO3, below which short-range polar order vanishes.
Fiz. Tverd. Tela (St. Petersburg) 39, 704–710 (April 1997) 相似文献
25.
26.
Reactions of Phosphorous Bis(dimethylamide) and Phosphoric Tris(methylamide) with PCI3 From the products of the reaction between phosphorous bis(dimethylamide) and PCl3 in the presence of pyridine the pentakis(dimethylamide) of acid can be isolated. The reaction between phosphoric tris(methylamide) and PCl3 in the presence of pyridine yields crystalline O = P[NCH3? PCl2]3 which can be converted into O = P[NCH3? PF2]3 with SbF3 or AsF3. The nmr data of the new compounds and some by-products of the reaction are given and discussed. 相似文献
27.
28.
29.
Ch. Binek T. Kato W. Kleemann O. Petracic D. Bertrand F. Bourdarot P. Burlet H. Aruga Katori K. Katsumata K. Prokes S. Welzel 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):35-40
In order to clarify the nature of the additional phase transition at H
1
(
T
) <
H
c
(
T
) of the layered antiferromagnetic (AF) insulator FeBr
2
as found by Aruga Katori et al. (1996) we measured the intensity of different Bragg-peaks in different scattering geometries. Transverse AF ordering is observed
in both AF phases, AF I and AF II. Its order parameter exhibits a peak at T
1
=
T
(
H
1
) in temperature scans and does not vanish in zero field. Possible origins of the step-like increase of the transverse ferromagnetic
ordering induced by a weak in-plane field component when entering AF I below T1 are discussed.
Received 27 September 1999 and Received in final form 6 December 1999 相似文献
30.
P. Lehnen W. Kleemann Th. Woike R. Pankrath 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):633-637
The linear birefringence (LB) of Sr
0.61-x
Ba
0.39
Nb
2
O
6
:Ce
3+
x (SBN61:Ce) has been measured as a function of temperature within the range of . Large tails have been observed above the ferroelectric phase transition temperatures T
c
= 350, 328, 320 and 291 K for the concentrations x
= 0, 0.0066, 0.0113 and 0.0207, respectively. Within an Ornstein-Zernike analysis the critical exponents , and are determined. It suggests that pure SBN61 belongs to the 3D Ising universality class. Doping with Ce
3+
ions, which seem to act as random fields, enhances the relaxor properties. The critical exponents and of SBN61:Ce shift against those of the three-dimensional random-field Ising model.
Received 1 October 1999 相似文献