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991.
C.H. Song J. Ma Y.Y. Yao X.M. Lu Y.N. Wang C.L. Choy 《Solid State Communications》2004,129(12):775-780
Bi4Ti3O12 (BiT), Bi3.25La0.75Ti3O12 (BLT), Bi4−x/3Ti3−xNbxO12 (BTN) and Bi3.25−x/3La0.75Ti3−xNbxO12 (BLTN) thin films have been prepared by pulsed laser deposition. BTN and BLTN films exhibit a maximum in the remanent polarization Pr at a Nb content x=0.018. At this Nb content, the BLTN film has a Pr value (25 μC/cm2) that is much higher than that of BiT and a coercive field similar to that of BiT. The polarization of this BLTN film is fatigue-free up to 109 switching cycles. The high fatigue resistance is mainly due to the substitution of Bi3+ ions by La3+ ions at the A site and the enhanced Pr arises largely from the replacement of Ti4+ ions by Nb5+ ions at the B site. The mechanisms behind the effects of the substitution at the two sites are discussed. 相似文献
992.
In this paper, non-axisymmetric guided wave propagation in circular cylindrical, anisotropic structures is studied in a frequency range up to 1 MHz. The investigations are carried out with carbon fibre reinforced tubes. The aim is the experimental determination of their effective linear elastic material properties in a non-destructive way. Therefore, an analytical model of the dispersion equation is fitted to the experimentally detected dispersion curves by systematically adjusting the desired material properties. A total least square scheme accompanied by an outlier detection criterion is used for this optimization task. Since the raw data of the measured dispersion curves contain a lot of noise, these outliers have to be detected and excluded, to achieve accurate results. Good agreement is found between the measured curves and the analytically calculated curves based on the estimated parameters. This fact indicates a high accuracy of the determined material properties. 相似文献
993.
A theorem proved by R. Høegh-Krohn in Comm. Math. Phys. 38(1974), 195–224, which yields a possibility to define states of systems of quantum particles by their values on the products
, where \mathfraka
t
, t
are time automorphisms and F
j
are multiplication operators, is generalized and extended. In particular, it is shown that the algebras generated by such products with F
j
taken from the families of multiplication operators satisfying certain conditions are dense in the algebras of observables in the -weak topology, in which normal states are continuous. This result was obtained for the systems with two types of kinetic energy: the usual one expressed by means of the Laplacian; the relativistic kinetic energy defined by a pseudo-differential operator. 相似文献
994.
We consider the connection problem for the Heun differential equation, which is a Fuchsian differential equation that has four regular singular points. We consider the case in which the parameters in this equation satisfy a certain set of conditions coming from the eigenvalue problem of the non-commutative harmonic oscillators. As an application, we describe eigenvalues with multiplicities greater than 1 and the corresponding odd eigenfunctions of the non-commutative harmonic oscillators. The existence of a rational or a certain algebraic solution of the Heun equation implies that the corresponding eigenvalues has multiplicities greater than 1.The research of the author is supported in part by a Grant-in-Aid for Scientific Research (B) (No. 15340005) from the Ministry of Education, Culture, Sports, Science and Technology.Mathematics Subject classifications (2000). primary, 34M35, secondary, 33E20.This revised version was published online in March 2005 with corrections to the cover date. 相似文献
995.
S.A. Nepijko M. Klais G. Schönhense N. Cramer Z. Celinski C.M. Schneider S. Zennaro N. Zema N.N. Sedov 《Applied Physics A: Materials Science & Processing》2003,76(5):809-815
Micromagnetic properties of the Fe19Ni81 (5 nm)/NiO (50 nm)/Fe19Ni81 (30 nm) structured system have been investigated in a photoemission electron microscope in the magnetic X-ray circular dichroism
operating mode. The microstructured Fe19Ni81 (5 nm) film contained two-dimensional islands with the aspect ratio varying from 1:1 to 10:1, and the linear size of their
long axis comprised 24, 12 and 6 μm. It is shown that the magnetic domains have the direction of magnetization preferentially
parallel and antiparallel to the magnetic field direction in which this system was prepared. Their number is determined by
the particles’ sizes, their shape as well as by the direction of the external magnetizing field and can be characterized by
a non-monotonic size dependence. The magnetization of domains with different lateral sizes was found to be 0.4 T with an accuracy
better than 20%.
Received: 29 May 2002 / Accepted: 17 July 2002 / Published online: 22 November 2002
RID="*"
ID="*"Corresponding author. Fax: +49-6131/392-3807, E-mail: nepijko@mail.uni-mainz.de 相似文献
996.
R. Frömter H.P. Oepen J. Kirschner 《Applied Physics A: Materials Science & Processing》2003,76(6):869-871
The basics of the scanning electron microscope with polarization analysis are briefly reviewed, emphasizing the achievable
magnetic resolution and image contrast. The design of an optimized spin-polarization detector based on the well-established
LEED scattering principle is presented. Results of first tests are reported.
Received: 2 September 2002 / Accepted: 2 September 2002 / Published online: 5 March 2003
RID="*"
ID="*"Corresponding author. Fax: +49-40/42838-6368, E-mail: RFroemte@PHYSnet.Uni-Hamburg.de 相似文献
997.
A. Krasyuk A. Oelsner S.A. Nepijko A. Kuksov C.M. Schneider G. Schönhense 《Applied Physics A: Materials Science & Processing》2003,76(6):863-868
Owing to its parallel image acquisition, photoemission electron microscopy is well suited for real-time observation of fast
processes on surfaces. Pulsed excitation sources like synchrotron radiation or lasers, fast electric pulsers for the study
of magnetic switching, and/or time-resolved detection can be utilised. A standard approach also being used in light optical
imaging is stroboscopic illumination of a periodic (or quasi-periodic) process. Using this technique, the time dependence
of the magnetic field in a pulsed microstrip line has been imaged in real time exploiting Lorentz-type contrast. Similarly,
the corresponding field-induced changes in the magnetisation of cobalt microstructures deposited on the microstrip line have
been observed exploiting magnetic X-ray circular dichroism as a contrast mechanism. The experiment has been performed at the
UE 56/1-PGM at BESSY II (Berlin) in the single-bunch mode.
Received: 2 September 2002 / Accepted: 2 September 2002 / Published online: 5 March 2003
RID="*"
ID="*"Corresponding author. Fax: +49-6131/392-3807, E-mail: krasyuk@mail.uni-mainz.de 相似文献
998.
999.
For a strictly decreasing sequence an
n=0 of nonnegative real numbers converging to zero, we construct a continuous 2-periodic function f such that RT
n(f) = an, n=0,1,2,..., where RT
n(f) are best approximations of the function f in uniform norm by trigonometric rational functions of degree at most n. 相似文献
1000.
S.?Dey S.S.?Dasgupta C.C.?Dey P.?Bhattacharya 《The European Physical Journal A - Hadrons and Nuclei》2003,16(2):193-197
A kinematically complete experiment has been performed to study the α-n final-state interaction (FSI) in the α + d ↦α + p
+ n break-up reaction at 50 MeV incident energy for the alpha-particles. For this, we have chosen four pairs of correlation
angles for the outgoing alpha and protons. These are ( θα = 18°, θp = 42°), ( θα = 20°, θp = 45°), ( θα = 22°, θp = 42°) and ( θα = 22°, θp = 47°), selected kinematically where the allowed phase spaces are in favor of the α-n final-state interaction. Our experimental
data show strong α-n FSI in all the selected configurations. Also, the FSI is found to be stronger at the lower alpha-particle
energy when two FSI peaks appear in the same configuration.
Received: 17 June 2002 / Accepted: 3 October 2002 / Published online: 4 February 2003
RID="a"
ID="a"e-mail: dey_s2001@yahoo.com; Present address: 445 Waupelani Drive, Apt. F3, State College, PA 16801, USA.
Communicated by M. Gar?on 相似文献