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21.
研究(?)Ri的由Ri(i=1,2,…,p)的序所诱导的序,证明(?)Ri在一定条件下作成一个有单位元的f环,并在有单位元的K-f环上的格序模范畴中引入保格R1(?)R2映射,进一步定义了张量积,使张量积概念在不同序环的序模范畴得到拓展. 相似文献
22.
Radially oriented Nd-Fe-B rings are prepared by backward extrusion of fine grained melt-spun powder. Melt-spun powder with the nominal composition of Nd30.5Febal.Co6.0Ga0.6Al0.2B0.9 (wt%) is used as starting material. The effects of process variables, such as deformation temperature (Td), strain rate (ε) and height reduction (Δh%), on the magnetic properties of the rings are investigated. A scanning electron microscope (SEM) equipped with an energy spectrum device is used to study the metallograph and microfracture of the extruded rings. The Br and (BH)max reach the optimum values at Td=800℃, ε =0.01 mm/s, and Δh% =70%. It is found by SEM observations that the particle boundaries, which seemingly correspond to the interfaces of the starting melt-spun powders, emerge after the corrosion of metallography specimens. This is helpful for studying the effects of powder-powder interface on the local deformation and deformation homogeneity in the rings. For different spatial positions of the extruded rings, there are characteristic metallographies and microfractures. The upper end of the rings has the least deformation and worst texture, and therefore the worst magnetic properties. The magnetic properties in the radial direction increase slightly along the axis from the bottom to the middle, then steeply decrease at the upper end of the ring. The deformation and the formation-of-texturing processes are discussed. The deformation and the texturing formation of melt-spun Nd-Fe-B alloys probably involve grain boundary sliding and grain rotation, the solution-precipitation process and preferential growth of Nd2Fe14B nanograins along the easy growth a-axis. 相似文献
23.
K.I. Petsas A. Gatti L.A. Lugiato C. Fabre 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):501-512
We investigate the spatial behaviour of the quantum-noise-reduction spectrum of the vacuum state emitted by a degenerate optical
parametric oscillator below threshold. In view of possible experimental implementations, we consider a mode-degenerate resonator
and two matching lenses and show that, for the realistic case of a finite-width pump, significant level of squeezing can be
observed in a very small region of the beam.
Received 25 September 2002 Published online 11 February 2003 相似文献
24.
25.
The optical limiting properties of acid blue29 solutions in different solvents are investigated. Experiments are performed using a CW He-Ne Laser beam at 632.8 nm wavelength and 35 mW power. The strength of the optical limiting action is dramatically influenced by the solvent. Multiple diffraction rings were observed when the samples were exposed to laser radiation. The effect of concentration, solvent and laser intensity on the diffraction rings are studied experimentally. Our results show that the nonlinear refraction is the dominant mechanism to explain the optical limiting behavior in acid blue29. 相似文献
26.
介观金属双环系统中的持续电流和量子能谱 总被引:7,自引:1,他引:7
崔元顺 《原子与分子物理学报》2006,23(3):527-531
基于电荷的不连续性,对处于外磁场中的介观双环系统进行量子化.假设系统在电荷表象中具有变换的对称性,通过求解电流和Hamilton算符的本征值方程,给出介观金属环互感系统中的量子电流和能谱关系;分析和研究了介观金属环中量子电流和能谱的性质.结果表明,持续电流和量子能谱不仅与外磁场、介观双环参数有关,而且还明显地依赖于电荷的量子化性质. 相似文献
27.
通过实验及仿真研究了三角谐振环组合新型六边形谐振环金属线复合周期结构左手材料.仿真研究了以金属铜三角开口谐振环(SRRs)为基本单元的周期结构负磁导率材料,与闭口环(CSRRs)结果对比发现三角开口谐振环能产生很好的谐振效果即能产生负磁导率,并且多层单元仿真发现多个谐振环耦合能提高谐振频率并加宽谐振频段;设计、制作并实验和仿真研究了三角开口环为基本单元的六边形谐振环金属线复合周期结构左手材料,仿真结果在98GHz附近出现良好负折射效应,实验验证在93—108 GHz出现良好负折射效应,与仿真结果具有良好的一致性.该研究对新型周期结构左手材料的研究、设计和研制具有重要的科学意义和应用前景.
关键词:
左手材料
三角环组成的六边形谐振环
负折射 相似文献
28.
M. Hausmann J. Stadlmann F. Attallah K. Beckert P. Beller F. Bosch H. Eickhoff M. Falch B. Franczak B. Franzke H. Geissel Th. Kerscher O. Klepper H.-J. Kluge C. Kozhuharov Yu.A. Litvinov K.E.G. Löbner G. Münzenberg N. Nankov F. Nolden Yu.N. Novikov T. Ohtsubo T. Radon H. Schatz C. Scheidenberger M. Steck Z. Sun H. Weick H. Wollnik 《Hyperfine Interactions》2001,132(1-4):289-295
A novel method for mass measurements of short-lived exotic nuclides is presented. Exotic nuclides were produced and separated
in flight at relativistic energies with the fragment separator (FRS) and were injected into the experimental storage ring
(ESR). Operating the ESR in the isochronous mode we performed mass measurements of neutron deficient fragments of 84Kr with half-lives larger than 50 ms. However, this experimental technique is applicable in a half-life range down to a few
μs. A mass resolving power of 110000 (FWHM) has been achieved. Results are presented for the masses of 68As, 70,71Se and 73Br.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
29.
REN Ji-Rong WANG Ji-Biao LI Ran XU Dong-Hui DUAN Yi-Shi 《理论物理通讯》2008,50(9):777-780
Two kinds of topological soliton (skyrmion and magnetic vortex ring) in ferromagnets are studied. They have the common topological origin, a tensor Hαβ = n→·(δαn→×βδn→), which describes the non-trivial distribution of local orientation of magnetization n→ at large distances in space. The topological stability of skyrmion is protected by the winding number. Knot-like topological defect as magnetic vortex rings is also studied. On the assumption that magnetic vortex rings are geometric lines, we present their δ-function distribution in ferromagnetic materials. Furthermore, it is briefly shown that Hopf invariant is a proper topological invariant to describe the topology of magnetic vortex rings. 相似文献
30.
We study electron energies in a double concentric quantum ring with anisotropy in the rims heights in the presence of the external magnetic field applied along the symmetry axis. To this end, we consider a model in which the thickness grows linearly from the axis up to the inner rim with a slope different from one between the inner and the outer rims. The anisotropy in the rims heights originated by the presence in the structure of various valleys we simulate by periodic dependence of the slope on the radial direction. We show that the wave functions of the electron confined in such structure can be found analytically if the slopes in all radial directions are the same, and by using a simple exact diagonalization procedure otherwise. The behavior of the electron energies as functions of the magnetic field, rings radii and rims heights, as well as the number of the valleys and their depths is consistently described with our formalism. The entanglement of the states with different radial and orbital quantum numbers, the period and the amplitude of the Aharonov–Bohm oscillations are very sensible to any variations of the rims heights. 相似文献