Error analysis of the piston estimation method in dispersed fringe sensor

Dispersed fringe sensor(DFS) is an important phasing sensor of next-generation optical astronomical telescopes. The measurement errors induced by the measurement noise of three piston estimation methods for the DFS including leastsquared fitting(LSF) method, frequency peak location(FPL) method and main peak position(MPP) method, are analyzed theoretically and validated experimentally in this paper. The experimental results coincide well with the theoretical analyses.The MPP, FPL, LSF are used respectively when the DFS operates with broadband light(central wavelength: 706 nm,bandwidth: 23 nm). The corresponding root mean square(RMS) value of estimated piston error can be achieved to be1 nm, 3 nm, 26 nm, respectively. Additionally, the range of DFS with the FPL can be more than 100 μm at the same time. The FPL method can work well both in coarse and fine phasing stages with acceptable accuracy, compared with LSF method and MPP method.     

Studies on convergence and scaling law of Thomson backscattering spectra in strong fields

With the saddle point analysis method for the Bessel function structure and property, the convergence problem and the scaling laws of Thomson backscattering spectra are solved and studied in both cases that are for the plane wave laser field without and with applied external constant magnetic field. Some unclear points appeared in previous work are clarified. The extension of the method to a general situation for the laser field with an arbitrary polarization is discussed. We also make a simple analysis and discussion about the optimal spectra dependence of field parameters and its implication to practical applications.     

Theoretical research on the spin-Hamiltonian parameters of the square-planar CuS46− clusters in Cu(II)–dithiophosphonate complexes

The spin-Hamiltonian parameters (g-factors g_//, g_⊥ and hyperfine structure constants A_//, A_⊥) of the square-planar CuS^{6 ?}₄ clusters in Cu(II)–bis [4-ethoxphenyl-O-alkyl]-dithiophosphonate complexes are computed with the high-order perturbation formulas based on the two-mechanism model. The model includes the contributions to spin-Hamiltonian parameters from the vastly-utilised crystal-field (CF) mechanism concerning the CF excited states and the generally-omitted charge-transfer (CT) mechanism due to CT excited states. The energy levels of CF and CT excited states needed in the calculation are obtained from the observed optical spectra. The calculated results are in rational accordance with the experimental values. The signs of constants A_// and A_⊥ are suggested and the reasons of the very small g-shifts |?g_i| (= | g_i ? g_e |, where g_e ≈ 2.0023 and i = // or ⊥) are discussed.     

Stabilities,electronic and magnetic properties of Cu-doped nickel clusters: a DFT investigation

In this paper, we investigate the electronic and magnetic properties of Cu-doped nickel clusters by means of density functional theory. The stabilities of these clusters have also been studied in terms of the binding energies, second-order difference of energies, fragmentation energies and HOMO–LUMO energy gaps. The obtained results reveal that the N₄Cu, N₅Cu and Ni₇Cu clusters are found to be more stable that than all other clusters. Higher HOMO–LUMO gap was observed for Ni₅Cu cluster (2.265 eV), indicating its higher chemical stability. A half-metallic behaviour has also been observed for the Ni_nCu clusters, which suggests that these clusters can be employed as nanocatalysts for several catalytic processes, particularly for hydrogenation and dehydrogenation reactions. The magnetism calculations show that the magnetic moment is mostly located on the Ni atoms, and the contribution of the Cu atom to the total magnetic moment in the Ni_nCu clusters is very small. Furthermore, partial density of states analysis indicates that the 3d orbitals in Ni atoms are mostly responsible for the magnetic behaviour of these clusters, and the s orbitals have a very little contribution to the total magnetic moment.     

Generalization of the variational principle and the Hohenberg and Kohn theorems for excited states of Fermion systems

Through the entanglement of a collection of K non-interacting replicas of a system of N interacting Fermions, and making use of the properties of reduced density matrices the variational principle and the theorems of Hohenberg and Kohn are generalized to excited states. The generalization of the variational principle makes use of the natural orbitals of an N-particle density matrix describing the state of lowest energy of the entangled state. The extension of the theorems of Hohenberg and Kohn is based on the ground-state formulation of density functional theory but with a new interpretation of the concept of a ground state: It is the state of lowest energy of a system of KN Fermions that is described in terms of the excited states of the N-particle interacting system. This straightforward implementation of the line of reasoning of ground-state density functional theory to a new domain leads to a unique and logically valid extension of the theory to excited states that allows the systematic treatment of all states in the spectrum of the Hamiltonian of an interacting system.     

Influence of magnetic powders on the tribological performance of a novel magnetic brake material

By adding magnetic powders into matrix material, it has been proved to be a creative approach to improve tribological properties of brake materials. In this paper, a novel magnetic brake material with Nd–Fe–B and nano-Fe₃O₄ was developed, and the influential mechanism of these two magnetic powders and their content on the friction and wear performance was deeply discussed. Firstly, some experiments were carried out to investigate the tribological performance and influential mechanisms of four groups of brake pad samples with different magnetic powders. Furthermore, based on these results, further experiments for investigating the influence that Nd–Fe–B contents have on the tribological properties were conducted. According to the theoretical analysis about experiments, it was concluded that nano-Fe₃O₄ is beneficial to promote the formation of friction film and has certain lubricant effects. However, Nd–Fe–B has double effects on the formation of friction film. It will have positive effects when its content is less than a certain value. Otherwise, it will destroy the structure of friction film. Conclusively, it is believed that this study will be significantly valuable and meaningful for developing new brake materials and improving safety reliability of mechanical brakes.     

原子核层次的手征对称性

对称性及其破缺是基本的科学问题。手征对称性在自然界中广泛存在,大至星系旋臂、行星自转,小到矿物晶体、有机分子、基本粒子,都与手征对称性密切相关。原子核层次的手征对称性概念于1997年提出,随后成为核物理研究的热点问题。目前,实验上已经在核素图上的80,100,130和190质量核区发现了30多例可能具有手征对称性的原子核。简要介绍原子核中的手征对称性概念;手性原子核的预言、识别以及实验验证;并通过展示手性原子核结构的多样性（M_χD）,回顾了理论和实验研究进展;介绍最新发现的原子核中手性和空间反射对称性的联立自发破缺,对未来手性原子核研究的前景进行了展望。Symmetry and its breaking are basic scientific problems. Chiral symmetries are common in nature, for example, the macroscopic spiral arms of galaxies and the rotation of planets; the microscopic spirals of the mineral crystalline, the organic molecules and the elementary particles. The concept of chirality in atomic nuclei was first proposed in 1997. Since then many efforts have been made to understand chiral symmetry and its spontaneous breaking in atomic nuclei. Up to now, more than 30 candidates of chiral nuclei have been reported in the 80, 100, 130, and 190 mass regions. The concept of the chirality in atomic nuclei, the prediction, the signal, and the experimental verification of the chiral nuclei are briefly introduced; the recent theoretical and experimental progress are reviewed, in particular the existence of multiple chiral doublets (M_χD), i.e., more than one pair of chiral doublet bands in one single nucleus; the simultaneous spontaneous breaking of chiral and reflection symmetry in the newly observed atomic nuclei is introduced, together with a prospect on the future study on nuclear chiral symmetry.     

熔盐包层设计与氚增殖比的计算

通过对聚变堆设计包层进行先后的一维、三维氚增殖比计算与分析,确定合适的模块材料、明确的模块划分以及相应的模块厚度,最终找到了合适的满足氚自持(TBR=1.3162)的熔盐设计包层。     

On thermodynamic self-consistency of generic axiomatic-nonextensive statistics

Generic axiomatic-nonextensive statistics introduces two asymptotic properties,to each of which a scaling function is assigned.The first and second scaling properties are characterized by the exponents c and d,respectively.In the thermodynamic limit,a grand-canonical ensemble can be formulated.The thermodynamic properties of a relativistic ideal gas of hadron resonances are studied,analytically.It is found that this generic statistics satisfies the requirements of the equilibrium thermodynamics.Essential aspects of the thermodynamic self-consistency are clarified.Analytical expressions are proposed for the statistical fits of various transverse momentum distributions measured in most-central collisions at different collision energies and colliding systems.Estimations for the freezeout temperature(T_(ch)) and the baryon chemical potential(μ_b) and the exponents c and d are determined.The earlier are found compatible with the parameters deduced from Boltzmann-Gibbs(BG) statistics(extensive),while the latter refer to generic nonextensivities.The resulting equivalence class(c,d) is associated with stretched exponentials,where Lambert function reaches its asymptotic stability.In some measurements,the resulting nonextensive entropy is linearly composed on extensive entropies.Apart from power-scaling,the particle ratios and yields are excellent quantities to highlighting whether the particle production takes place(non)extensively.Various particle ratios and yields measured by the STAR experiment in central collisions at 200,62.4 and 7.7 GeV are fitted with this novel approach.We found that both c and d 1,i.e.referring to neither BG-nor Tsallis-type statistics,but to(c,d)-entropy,where Lambert functions exponentially rise.The freezeout temperature and baryon chemical potential are found comparable with the ones deduced from BG statistics(extensive).We conclude that the particle production at STAR energies is likely a nonextensive process but not necessarily BG or Tsallis type.     

一种简便的计算层析系统X射线硬化校正方法

以实物拍摄为依据,用一种最简便的修正方法解决计算机X射线层析术成像时由于硬化效应引起的切片图灰度失真问题。用高性能数字X射线机FAXITRON MX-20(射线管焦点20μm,探测板灰度等级16位)对不同厚度的物体进行透射成像,测得对应的透射光强度,并利用新创的指数拟合法得到理想的拟合曲线,由此推导硬化效应的指数校正公式;最后利用实验室的微型计算机层析设备进行扇形束扫描,并逆投影重建生成计算层析断层图像,验证了该校正方法的实用性。该指数拟合法的误差不到常用的二阶多项式拟合法的1/3,对物体计算层析重构,硬化校正以前有明显的“杯状”伪迹,切片灰度不均匀,用指数法修正以后该伪迹消失,切片灰度均匀。