首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 125 毫秒
1.
The first part of the paper gives a general equation for triple-crystal arrangement with perfect crystals on the assumption that the third crystal is rotated. It is shown that in the case of perfect crystals the shape of the reflection curve is practically independent of the vertical divergence. The case of mosaic crystals is also solved and the possibility of rotation by other than the third crystal is considered. A method is proposed for investigating the imperfection of a crystal which is different from methods used up to now. The paper is supplemented by some experimental results.
, . , . , , . , . .
  相似文献   

2.
3.
The magnetic properties of thin ferromagnetic films are studied taking into account the magnetic anisotropy term in the Hamiltonian. In the second approximation equations are obtained for the magnetization of the monatomic layers parallel to the surface of the thin film. From these equations one obtains the Curie temperature, which depends on the thickness of the thin film and the ratio a between the anisotropy constant and the exchange energy between two neighbours. A value can be chosen for such that the thin film becomes ferromagnetic only for a thickness greater than a definite value and in this manner the theoretical results can be fitted to the experimental data. The situation in cobalt thin films is dealt with in particular.
. , . , . , , - , . , , .


The author extends his thanks to the research workers of CIFA 1 as well as to Dr. L. Valenta for information on the same subject.  相似文献   

4.
The change in integrated intensity of the (200) reflections of a solid solution during the formation of G.P. zones was measured and compared with the change in the character of the diffuse streaks corresponding to them. It was found that the. formation of G.P. zones does not lead to a decrease in primary extinction despite the great changes in the distribution of the copper atoms. It was shown that the formation of a precipitate accompanied by the formation of crystallographically incoherent boundaries greatly decreases the primary extinction.
. II. 1-u 4%: [. . ]
(200) . . , . , . . , . , , , .
  相似文献   

5.
We consider a billiard in the punctured torus obtained by removing a small disk of radius >0 from the flat torus 2, with trajectory starting from the center of the puncture. In this case the phase space is given by the range of the velocity only. Let (), and respectively R(), denote the first exit time (length of the trajectory), and respectively the number of collisions with the side cushions when 2 is being identified with [0,1)2. We prove that the probability measures on [0, ) associated with the random variables and R are weakly convergent as 0+ and explicitly compute the densities of the limits. Research partially supported by ANSTI grant C6189/2000.  相似文献   

6.
7.
8.
The paper describes microscopic investigation into the spectral distribution of photo-luminescence and its polarization on hexagonal ZnS monocrystals in relation to the structural defects of such crystals. These observations, as well as birefringent observations, show that the values of the birefringence and the degree of polarization in different stripes of the same crystal are the same within the limits of observational errors.
ZnS: Cu
ZnS . , , , .


In conclusion the author would like to thank K. Pátek, L. Souková and M. Mokonová for providing the monocrystals and for fruitful discussions.  相似文献   

9.
The gamma-spectrum and coincidences of gamma-rays appearing in Dy155 Tb155 decay have been measured with the aid of a scintillation gamma-spectrometer. The Dy155 source has been obtained by a repeated chromatographic separation from Ho fraction produced by a spallations reaction Ta+p(E p=660 MeV). Dy155 appears as a decay product of Ho155 (T 1/2= =45 min). In the gamma-spectrum new transitions in the energy range of 1170–2000 keV have been observed. As a result of- coincidence measurements we get a new energy level (1820±15 keV) of Tb155.

, Dy155 . . .  相似文献   

10.
E. Hiyama 《Few-Body Systems》2004,34(1-3):79-84
From the viewpoint of critical stability, we discuss the three- and four-body structure of 6He, 7He, 4He, and 4H. With the + + N three-body model, 6He is found to have a three-layer structure of the matter distribution: core, a skin and neutron halo. Also the level structure of 7He with the three-body model of 5He + n + n is predicted. This stimulates a new study of neutron-rich and proton-rich hypernuclei. By performing a four-body calculation with both NNN and NNN channels and with both NN and NNN channels, we show that the N-N and -N couplings are very important in critical stability of few-body hypernuclear systems.  相似文献   

11.
We discuss stochastic Schrödinger operators and Jacobi matrices with wave functions, taking values in l so there are 2l Lyaponov exponents 1...l0 l+1...2l =–1. Our results include the fact that if 1=0 on a set positive measure, thenV is deterministic and one that says that {E|exactly 2j 's are zero} is the essential support of the a.c. spectrum of multiplicity 2j.Research partially supported by USNSF under grant DMS-8416049  相似文献   

12.
We study higher order bicovariant differential calculi on the quantum groups Oq(N) and Sp q (N). We show that the second antisymmetrizer exterior algebra u is the quotient of the universal exterior algebra u by the principal ideal generated by . Here denotes the unique up to scalars biinvariant 1-form. Moreover is central in u and u is an inner differential calculus. We show that the quadratic dual to the left-invariant algebra s L is isomorphic to the reflection equation algebra. Let be an arbitrary left-covariant first order differential calculus. We show that the dimension of the space of left-invariant 2-forms in the universal exterior algebra equals the number of linearly independent quadratic-linear relations in the quantum tangent space.  相似文献   

13.
The distribution of dislocations in a crystal of an Fe-4.2% Si alloy prepared from the melt is studied microscopically and, by X-ray diffraction after rendering them visible by anodic dissolving. The dislocations are also studied inside the crystal by successively grinding the surface. The density of the dislocations inside the blocks is determined by calculation from microphotos, the density of the dislocations forming the boundaries between the blocks by measuring the angles between the lattices of neighbouring blocks. It is found that the dislocations are distributed very unevenly in the crystal and most of them form complicated boundaries of blocks, similarly as with ionic crystals. The distribution of dislocations is also discussed from the point of view of their formation and conclusions are reached as to the preparation of single crystals having a smaller number of dislocations.
Fe-Si,
- Fe-4,2%Si, , . . , , — . , , . .


The author is indebted to Candidates of Mathematics and Physics, F. Kroupa and J. Kaczér, for careful reading and advice whereby they helped to give greater depth and accuracy to this paper. He thanks Z. Tahal and M. Honegrová for initiative shown in helping to prepare the single crystals and during exacting experimental work, and S. Kadeková for aid in adjusting the spectrometer.  相似文献   

14.
. , , , . .
The theory and structure of the temperature image
The paper describes the theory of the formation of a temperature image when there are large temperature differences and introduces the concept of temperature distortion of an image. It also deals with the geometrical distortion of the temperature image by the longitudinal thermal conductivity of the receiver layer and gives a solution of the corresponding differential equation of the temperature image for the case of a general linear line test and general circular concentric test. Equations are derived for the temperature distributions of the temperature images of some optical lineated and circular test objects and their geometrical distortion due to the thermal conductivity of the receiver layer is investigated.
  相似文献   

15.
We use a quite concrete and simple realization of sl q (2, ) involving finite difference operators. We interpret them as derivations (in the noncommutative sense) on a suitable graded algebra, which gives rise to the noncommutative scheme 1 II 1* as the counterpart of the standard 1 = Sl(2, )/B.  相似文献   

16.
Slow production via dd-CF using a two-layer arrangement is investigated. To determine its feasibility, experimental measurements are now in progress using the muonic X-ray detection method. The following experimental steps are being considered: (1) measurement of the number of stopped inside a solid H2/D2 layer by detecting p K X-rays, (2) hot d emission detection by placing a secondary target at a distance of 10–30 mm from the layer and by detecting specific delayed X-rays, (3) measurement of the disappearance of d emission as the added D2 layer is increased, (4) dd-CF measurement by detecting fusion protons, and (5) slow emission detection. Results of the initial test experiment are presented.  相似文献   

17.
The current and logarithm-of-the-current distributionsn(i) andn(ln i) on bond diluted two-dimensional random-resistor networks at the percolation threshold are studied by a modified transfer matrix method. Thek th moment (–9k8) of n(ln i) i.e., ln i&k, is found to scale with the linear sizeL as (InL)(k). The exponents (k) are not inconsistent with the recent theoretical prediction (k)=k, with deviations which may be attributed to severe finitesize effects. For small currents, ln n(y), yielding information on the threshold below which the multifractality of (i) breaks down. Our numerical results for the moments of the currents are consistent with other available results.  相似文献   

18.
The breakup of 12C states into three -particles is discussed in the context of the continuum three-body problem. New information from the -decay of 12N populating 0+, 1+, and 2+ states in 12C is presented. The breakup mechanism of the 1+ state at 12.71MeV is clarified, the spin of the 10.3MeV state is determined as 0+, and evidence for a previously unknown 2+ state at 14.1(2)MeV is given.  相似文献   

19.
Zusammenfassung Es wird theoretisch der Prozeß des Exzitonenzerfalls mit Hilfe der Ionisation durch das elektrostatische Feld der Störstelle untersucht. Die Wirkungsquerschnitte werden in zwei Grenzfällen bestimmt: bei einer kleinen und einer großen mittleren freien Bahn des Exzitons, die durch dessen Wechselwirkung mit den Phononen bedingt ist. Die Ergebnisse werden zum Studium des Exzitonenzerfalls an einer Vakanz nach einem Kupferion in Cu2O-Kristallen mit einem stöchiometrischen Sauerstoffüberschuß verwendet.
. : , . Cu20 .
  相似文献   

20.
The paper deals with the motion of 90° wedge domains in BaTiO3 in an alternating field of 50 c/s. The critical field, the positional hysteresis loops with double asymmetry, the production of wedges with polarization perpendicular to the field and 180° substructure in the wedges were studied. The differences between the behaviour of the wedges and the individual 90° walls are pointed out which are caused by differences in the energy balance of these formations and by different interactions with 180° processes. The upper limit of contribution of the wedge motion to the initial permittivity is estimated. The results are discussed from the phenomenological point of view.
90° BaTiO3
90° BaTiO3 , 50 Hz. , , , , , , 180° . 90° , 180° . , . .
  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号