共查询到19条相似文献,搜索用时 125 毫秒
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在分子态结构的假设下, 利用手征么正模型研究了D0(2308)和B0的可能结构. 通过研究重子-赝标介子相互作用, 找到了一些可能的分子态. 结果表明: 在带奇异数的系统中, 存在一个质量为2.312±0.041GeV的DK束缚态, 它可以被解释为实验上发现的Ds0(2317). 与此同时, 在非奇异系统中, 存在一个与之对应的、质量为2.1GeV的宽度较大的态和一个对应的、质量为2.44GeV的宽度较小的态. 这两个态应对应于D0. 因此, 分子态结构只能是D0(2308)一个分量. 计算结果还预言了一些Bs0和B0态. 其中质量为5.725±0.039GeV的BK束缚态可以被解释为Bs0(5725), 而预言的B0(5536)和B0(5819)应为与Bs0(5725)相对应的非奇异态. 相似文献
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本文使用密度泛函理论设计了两个无需配体的具有Mg-Mg和Zn-Zn单键的团簇Mg2B7-和Zn2B7-. 这两种团簇的全局能量最低构型均以M22+(B73-)的形式存在,其中M-M单键处于准平面六边形形状的B7部分的上方. 化学键分析证实了这些团簇中Mg-Mg和Zn-Zn单键的存在,这些单键是在异常稳定的B73-的驱动下生成的. 该B73-部分同时具有σ和π双重芳香性. 计算得到Mg2B7-和Zn2B7-的垂直跃迁能分别为2.79 eV和2.94 eV. 相似文献
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本文基于最重要的"硬"产生机制,计算了Z0衰变产生Bc(或Bc)介子并伴有c(或c)和b(或b)两个重夸克喷注的产生率.指出在LEP上的下一次取数据中将产生出足够数目的Bc(或Bc)介子的性质成为可能. 相似文献
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强制体积磁致伸缩的数量级极小(10-10~10-9[(103/4π)(A/m)]-1),如通过测量三个互成直角方向的线磁致伸缩(10-6[(103/4π)(A/m)]-1)再正负迭加则很难测准。本文利用热力学关系:(dω/dH)T,p=-(dMs/dp)T,H,用静水压法在0.000 1~2.4 GPa范围测得七种非晶合金Fe81.6Si4.6B13.8、Fe46.3Co0.03Ni46.5Si3.75V0.92B2.5、Fe75Cr5Si5B15、Fe73.9Co8.3Si4.4B13.4、Fe75Ni5Si5B15、Fe78.75Cu1.25Si5B15和(Fe0.85Co0.15)82Cu0.4Si4.4B13.2的强制体积磁致伸缩及其随静水压p的变化。结果表明:(1)其中六种属于第一类压磁效应。(dω/dH)T,p在大部分压力下为正,p增加时Ms不断减小;(dω/dH)T,p仅在几个狭窄的压力范围为负。可归因于磁性原子与非磁性原子的化学短程序在压力下的变化。(2)非晶合金Fe78.75Cu1.25Si5B15属于第二类压磁效应。(dω/dH)T,p在绝大部分压力下为负。Ms反常升高与Cu的特殊作用有关。 相似文献
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150keV Ar离子辐照非晶态合金Fe39Ni39Mo2Si12B8、Fe40Ni40Si12B8、Fe39Ni39V2Si12B8、Fe77Cr2Si5B16和Fe78Si10B12,用扫描电子显微镜(SEM)观测研究了表面损伤形貌剂量变化的过程.低剂量时表面发泡形成.发泡随剂量增加受到溅射腐蚀,表面形成坑洞或针孔,针孔密度随剂量增加而增加,高剂量时,表面损伤以溅射为主,溅射对表面的腐蚀导致多孔粗糙的表面损伤结构建立,并且这些结构与靶材料有着密切的关系. 相似文献
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本文研究了B0-B0和B0-B0系统二体重子衰变中的CP不守恒效应.我们讨论了两种实验背景:(1)BB对在Z0共振峰不相干产生,(2)电荷共轭宇称C=+1的BB对在Υ(4S)共振峰以上产生.我们估算了检验该效应所需的bb对数目.对于衰B0→PP,Δ++Δ--和Δ0Δ0,Nbb~107—108. 相似文献
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Bridgman directional solidification and laser remelting experiments were carried out on Nd11.76Fe82.36B5.88 and Nd13.5Fe79.75B6.75 alloys. Microstructure evolutions along with solidification parameters (temperature gradient G, growth velocity V and initial alloy composition C
0) were investigated. A solidification microstructure selection map was established, based on the consideration of solidification
characteristics of peritectic T1 phase. In Bridgman directional solidification experiments, with the increasing growth velocities, the morphology of T1 phase changed from plane front or faceted plane front to dendrites. In laser remelting experiments, a transition from primary
γ-Fe dendrites to T1 dendrites was found. Theoretical predictions are in good agreement with experimental results.
Supported by the National Natural Science Foundation of China (Grant No. 50395100) 相似文献
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Dielectric permittivities (ε′,ε″) have been measured as functions of temperature (140-535 K) and frequency (500 Hz-2.0 MHz) in a (001)-cut Pb(In1/2Nb1/2)0.7Ti0.3O3 (PINT30%) single crystal grown by the modified Bridgman method with Pb(Mg1/3Nb2/3)0.71Ti0.29O3 (PMNT29%) seed crystal. A diffused phase transition was observed in the temperature region of ∼430-460 K with strong frequency dispersion. Above the Burns temperature TB≅510 K, the dielectric permittivity was found to follow the Curie-Weiss behavior, ε′=C/(T−TC), with parameters C=3.9×105 and TC=472 K. Below TB≅510 K, polar nanoclusters are considered to appear and are responsible for the diffused dielectric anomaly. Optical transmission, refractive indices, and the Cauchy equations were obtained as a function of wavelength at room temperature. The unpoled crystal shows almost no birefringence, indicating that the average structural symmetry is optically isotropic. The crystal exhibits a broad transparency in the wavelength range of ∼0.4-6.0 μm. 相似文献
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Zbigniew Koza 《Journal of statistical physics》1996,85(1-2):179-191
We examine the long-time behavior of A+B0 reaction-diffusion systems with initially segregated species A and B. All of our analysis is carried out for arbitrary (positive) values of the diffusion constantsD
A andD
B and initial concentrationsa
0 andb
0 of A's and B's. We divide the domain of the partial differential equations describing the problem into several regions in which they can be reduced to simpler, solvable equations, and we merge the solutions. Thus we derive general formulas for the concentration profiles outside the reaction zone, the location of the reaction zone center, and the total reaction rate. An asymptotic condition for the reaction front to be stationary is also derived. The properties of the reaction layer are studied in the mean-field approximation, and we show that not only the scaling exponents, but also the scaling functions are independent ofD
A,D
B,a
0 andb
0. 相似文献
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A. M. Glezer M. P. Plotnikova A. V. Shalimova N. S. Perov 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(9):1240-1244
The influence of severe plastic deformation in a Bridgman cell on the magnetic properties of amorphous alloys of metal-metalloid
type, Ni44Fe29Co15Si2B10, Fe74Si13B9Nb3Cu1, Fe57.5Ni25B17.5, Fe49.5Ni33B17.5, and Fe70Cr15B15, obtained by melt spinning, has been investigated. It is found that the saturation magnetization significantly changes (increases
or decreases), depending on the number of ferromagnetic and antiferromagnetic components in the alloy. It is suggested that
very high shear stress causes internal phase decomposition in the amorphous matrix into nanoscale regions, enriched or depleted
with ferromagnetic components. 相似文献
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Zoltán Perjés 《International Journal of Theoretical Physics》1974,10(4):217-227
A systematic approach to the geometric structure of stationary gravitational fields is presented. The algebraic type of the trace-free Ricci tensor together with the propagation properties of the eigenrays in the background 3-space defined by the Killing trajectories serve as a basis for classifying the solutions of the stationary field equations. The eigenrays are the integral curves belonging to the solutions A of the eigenvalue problemG
A
B
B=A,G
A
B
spinor representing the gravitational field in the background space. Many of the already known stationary metrics can be derived in the present scheme but new solutions of the field equations are also obtained. The possible types of the vacuum and electrovac fields are discussed in their connection with the corresponding exact solutions.Work honoured by a Fifth Gravity Research Foundation Award in 1973.Leverhulme Visiting Fellow. 相似文献
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Variable angle spectroscopic ellipsometry has been applied to characterize the optical constants of bulk Cu(In0.7Ga0.3)5Se8 and Cu(In0.4Ga0.6)5Se8 crystals grown by the Bridgman method. The spectra were measured at room temperature over the energy range 0.8-4.4 eV. Adachi’s model was used to calculate the dielectric functions as well as the spectral dependence of complex refractive index, absorption coefficient, and normal-incidence reflectivity. The calculated data are in good agreement with the experimental ones over the entire range of photon energies. The parameters such as strength, threshold energy, and broadening, corresponding to the E0, E1A, and E1B interband transitions, have been determined using the simulated annealing algorithm. 相似文献