超导故障限流器的研究现状及其应用

超导故障限流器(Superconducting Fault Current Limiter,SFCL)是利用超导体的基本特性,有效限制电力系统故障短路电流,提高电网安全性和稳定性的一种新型电力设备。文中在综合大量文献的基础上,对超导故障限流器进行了一种较为系统的分类。基于该种分类,结合目前国内外的研究现状,就电阻型、磁屏蔽型、饱和铁芯电抗器型、桥路型SFCL的工作原理作了详细的分析介绍,还给出了它们在电力系统中的安装位置。最后,对超导故障限流器的研究中存在的问题及其发展趋势做了说明。     

Memory Effects in High-Dimensional Systems Faithfully Identified by Hilbert–Schmidt Speed-Based Witness

A witness of non-Markovianity based on the Hilbert–Schmidt speed (HSS), a special type of quantum statistical speed, has been recently introduced for low-dimensional quantum systems. Such a non-Markovianity witness is particularly useful, being easily computable since no diagonalization of the system density matrix is required. We investigate the sensitivity of this HSS-based witness to detect non-Markovianity in various high-dimensional and multipartite open quantum systems with finite Hilbert spaces. We find that the time behaviors of the HSS-based witness are always in agreement with those of quantum negativity or quantum correlation measure. These results show that the HSS-based witness is a faithful identifier of the memory effects appearing in the quantum evolution of a high-dimensional system with a finite Hilbert space.     

精品课程教材《高分子物理实验》建设的体会——三个及时融入

中国科学技术大学"高分子物理实验"课程是2006年安徽省精品课程,作者结合教学研究和精品课程建设经验,总结出了"三个及时融入"的教材建设理念,本文结合实例对该理念的具体含义进行了阐述.     

Thermodynamics of a Fluid of Hard D-dimensional Spheres: Percus-Yevick and Carnahan-Starling-like Results for D = 4 and 5

Abstract

The equations of state (EOS) of four and five dimensional hyperspheres have been calculated using Leutheusser's ansatz. In five dimensions these, and the correlation functions, are compared with the results obtained from the analytic solution of the Percus—Yevick (PY) approximation. It is shown that the ansatz reproduces extremely well the PY results. However, in both approximations neither the virial, Z_v , nor the compressibility, Z_c , EOS reproduce well the available molecular dynamics (MD) results. Yet a linear combination of Z_v and Z_c , following the Carnahan—Starling EOS for hard spheres, are in excellent agreement with the MD results in four and five dimensions.     

A cohomological obstruction for global quasi-bi-Hamiltonian fields

We introduce the notion of integrating factor for a 1-form which is an inner product of a vector fields and a 2-form, and the notion of weakly bi-Hamiltonian field also, which is locally quasi-bi-Hamiltonian. A cohomological class in some first cohomology space is associated to such vector fields when this is weakly bi-Hamiltonian and defined relatively to the above 1-form. This class is a cohomological obstruction to the existence of a global integrating factor for the 1-form.     

Two-dimensional optical micro-scanner on silicon technology

A two-dimensional optical micro-scanner, which main components are two mobile flat and a concave micro-mirrors, is designed such that, all optical components can be fabricated on the same substratum. The optical parameters, which physical dimensions are between 50 and 500 μm, are obtained within the geometrical optics. The optical performance is evaluated by means of the MTF and Rayleigh resolution criteria, given 80% of modulation for a frequency of 8 cycles/mm with a Gaussian source, the resolution limit is 30 μm.     

Second graders articulating ideas about linear functional relationships

In this paper, we explore the ideas that second grade students articulate about functional relationships. We adopt a function-based approach to introduce elementary school children to algebraic content. We present results from a design-based research study carried out with 21 second-grade students (approximately 7 years of age). We focus on a lesson from our classroom teaching experiment in which the students were working on a problem that involved a linear functional relationship (y = 2x). From the analysis of students’ written work and classroom video, we illustrate two different approaches that students adopt to express the relationship between two quantities. Students show fluency recontextualizing the problem posed, moving between extra-mathematical and intra-mathematical contexts.     

Facile Synthesis of Bis(crown ether)benzils: Prospective Building Blocks for Metal Ion Sensors

A new facile synthetic route to benzils containing fragments of 12-crown-4, 15-crown-5, and 18-crown-6 by oxidation of corresponding stilbenes was developed. The first representative of a new family of fluorescent sensors was obtained by reaction of bis(15-crown-5)benzil with o-phenylenediamine. The latter exhibits great fluorescence enhancement upon association with K⁺ and Rb⁺ compared to Na⁺ and Cs⁺.