基于正极性或-符合展开的易测性网络

为提高数字电路的可测性，提出了可实现任意逻辑函数的正极性或-符合网络的易测性实现，并给出了测试网络中所有单固定故障的通用测试集．该实现基于逻辑函数的正极性或-符合展开，网络的同或部分分别采用了串联和树形结构．为提高可测性，同或串的实现结构只需增加1个控制端及1个观察端，同或树的实现结构只需增加3个控制端及1个观察端．对于1个n变量的逻辑函数，两种实现结构下通用测试集的基数分别为（n＋4）和（n＋5）．这样短的通用测试集非常适合用内建自测试实现，从而有效地缩短测试时间．     

用导数法证明不等式的思维策略——例谈2007年高考试题中不等式证明问题

纵观2007年全国各省、市的高考试题,用"导数法"证明不等式依然是考试的热点、重点和难点.应用导数证明不等式是导数的一个重要应用,思路虽然简单,但在实际操作中,需要构造函数这一创造性的思维,因此如何更有效、更快捷、更合理地构造函数是使不等式获证的关键,而有效的思维策略会使得在解决这类问题时更有方向感.笔者结合2007年高考试题中的不等式证明问题,谈谈解决此类问题的思维策略.……     

Multi-agent controlled teleportation of multi-qubit quantum information via two-step protocol

Utilizing both the general quantum teleportation and the two-step protocol, a new method is presented by which multi-qubit quantum information can be teleported in a much easier way from a sender Alice to a receiver Bob via the control of many agents in a network than by Yang et al＇s method. In this method, only all the agents collaborate with Bob can the unknown states in Alice＇s qubits be fully reconstructed in Bob＇s qubits. Comparisons between the method and Yang et al＇s method are made. Results show that, in this method, the preparation difficulty of initial states and the identification difficulty of entangled states are considerably reduced, new method is more feasible in technique, and Hadamard operations are not needed at all.     

基于球壳内壁反射的球形换能器自易校准方法

基于球形换能器发射的脉冲球面声波及其在同心球壳内壁的反射,应用机电互易定理,导出了在球面波发射回波声场中,用于校准球形换能器的互易常数.以此为基础,提出一种使用封闭球壳反射器的自易校准方法,通过一次测量即可得到球形换能器的5个基本电声参数.进一步,将自易法校准所得的电压灵敏度换算成平面波声场中定义的标准灵敏度,给出了换...     

地方高等师范院校化学实验课程体系的构建与实践

构建了化学实验教学新体系,即＂二体系三层次＂的化学实验课程体系。其中二体系为基础化学实验课程和综合化学实验课程;在三层次中,基本操作实验为第一层次,基础性、设计性实验为第二层次,综合性实验为第三层次。该体系的建立、实践、推广凸现了地方高等师范院校化学专业实验课程的特色与优势。     

Neutron diffraction study on composite compound Nd2Co7

The crystallographic and the magnetic structures of the composite compound Nd₂Co₇ at 300 K are investigated by a combined refinement of X-ray diffraction data and high-resolution neutron diffraction data. The compound crystallizes into a hexagonal Ce₂Ni₇-type structure and consists of alternately stacking MgZn₂-type NdCo₂ and CaCu₅-type NdCo₅ structural blocks along the c axis. A magnetic structure model with the moments of all atoms aligning along the c axis provides a satisfactory fitting to the neutron diffraction data and coincides with the easy magnetization direction revealed by the X-ray diffraction experiments on magnetically pre-aligned fine particles. The refinement results show that the derived atomic moments of the Co atoms vary in a range of 0.7 μ_B-1.1 μ_B and the atomic moment of Nd in the NdCo₅ slab is close to the theoretical moment of a free trivalent Nd³⁺ ion, whereas the atomic moment of Nd in the NdCo₂ slab is much smaller than the theoretical value for a free Nd³⁺ ion. The remarkable difference in the atomic moment of Nd atoms between different structural slabs at room temperature is explained in terms of the magnetic characteristics of the NdCo₂ and NdCo₅ compounds and the local chemical environments of the Nd atoms in different structural slabs of the Nd₂Co₇ compound.     

Analysis of superconducting cavity quench events at SSRF

Quench is important and dangerous to superconducting RF cavities. This paper illustrates the mechanism of quench and how a quench detector works, and analyzes the quench events happening during beam operations and cavity conditioning. We find that the quench protection is mostly triggered by some reasons such as fluctuation of cavity voltage, multipacting or arc, rather than a real cavity thermal breakdown. The results will be beneficial to optimize the operation parameters of superconducting cavities, to discover the real reasons for beam trip by quench interlock, and to improve the operation stability of superconducting RF systems.     

邻近555nm区域目视光谱分析的操作技巧

看谱分析至今在一些机械工厂仍普遍使用,鉴于看谱仪器的生产厂家占有一定的市场份额,在一段时期内还不会被其它的仪器完全取代。本工作介绍了邻近555nm区域目视光谱分析的操作方法。从检测钢铁样品中钼开始,认识或记忆这条钼的谱线,可有助于掌握钼谱线周围的其它元素谱线,具有一定联想的效果,帮助初学者认识、记忆及操作。     

倡导“双轮驱动”,发掘学习潜能

1问题的提出在一次反证法的公开教学中,执教老师依照教材要求,通过对概念的讲解、反证法的操作流程及说明、举例与练习,有序地实施教学,在本节课小结时,向学生提出了这样一个问题:我们为什么要学习反证法?回答出人意料.一位学生说是为了做作