Efficiency Enhancement of Coaxial-Cavity Electron Cyclotron Resonance Maser by Tapering Guide Magnetic Field

A coaxial-cavity cyclotron resonance maser (CRM) oscillator with tapered guide magnetic field is proposed. It is shown that the transmission quality can be improved by tapering the guide magnetic field. Simulation indicates that the efficiency of a millimeter-wave gyrotron oscillator may be reached up to 38.7% by optimizing the tapered magnetic field.     

极值图论与度序列

本文简要概述极值图论与度序列的最新研究进展，同时提出了一些有待进一步解决的问题和猜想．     

不等式约束优化问题的一个势函数

基于Carroll(1961)建立的罚函数，本文给出了不等式约束优化问题的一个势函数，并且讨论了该函数的性质．最后证明了在此基础上建立的对偶算法具有Q-线性收敛性．     

排球比赛中的二传最优过程

为了研究排球比赛中的二传最优过程 ,本文基于决策论的理论和方法建立了排球二传最优过程的数学模型 .通过对模型的分析研究分别给出了最大概率准则和最大期望准则下的最优传球方式 .本文所得到的结果对排球队的训练和比赛有一定的指导意义 .     

基于BP神经网络的企业未来获利能力智能综合评价

分析了相关分析——多指标综合评价法在确定企业未来获利能力方面的优点和不足 ;并在其基础上提出了基于 BP神经网络的多指标综合评价法 ;仿真试验证明了基于 BP神经网络的多指标综合评价法的有效性     

Two New Diterpene Acetylxylosides from Aster veitchianus

Two new acetylxylosides,ent-manool-13-O-β-D-2′-acetylxylopyranoside(1)and entmanool-13-O-β-D-2′,4′-diacetylxylopyranoside(2)were isolated from Aster veitchianus.Their structures were elucidated by spectroscopic methods.     

CdZnTe核探测器的蒙特卡罗模拟的初步研究

以CdZnTe核探测器的工作原理为依据,探测器内反应的随机性和反应产生的电子空穴对数目的统计规律为物理模型,应用Visual C + + 自行编制了蒙特卡罗模拟软件.模拟了γ射线在CdZnTe探测器中的响应能谱,并将模拟结果与实际器件的测试结果进行了比较讨论.模拟能谱与实际测得的能谱的主峰符合较好.此外,通过分析⁵⁷Co源辐照下探测效率与器件厚度的关系,可以推测探测效率达到最大时所对应CdZnTe探测器的理想厚度     

Synthesis,characterization, and micellization of an epoxy‐based amphiphilic diblock copolymer of ϵ‐caprolactone and glycidyl methacrylate by enzymatic ring‐opening polymerization and atom transfer radical polymerization

Amphiphilic diblock copolymer polycaprolactone‐block‐poly(glycidyl methacrylate) (PCL‐b‐PGMA) was synthesized via enzymatic ring‐opening polymerization (eROP) and atom transfer radical polymerization (ATRP). Methanol first initiated eROP of ?‐caprolactone (?‐CL) in the presence of biocatalyst Novozyme‐435 under anhydrous conditions. The resulting monohydroxyl‐terminated polycaprolactone (PCL–OH) was subsequently converted to a bromine‐ended macroinitiator (PCL–Br) for ATRP by esterification with α‐bromopropionyl bromide. PCL‐b‐PGMA diblock copolymers were synthesized in a subsequent ATRP of glycidyl methacrylate (GMA). A kinetic analysis of ATRP indicated a living/controlled radical process. The macromolecular structures were characterized for PCL–OH, PCL–Br, and the block copolymers by means of nuclear magnetic resonance, gel permeation chromatography, and infrared spectroscopy. Differential scanning calorimetry and wide‐angle X‐ray diffraction analyses indicated that the copolymer composition (?‐CL/GMA) had a great influence on the thermal properties. The well‐defined, amphiphilic diblock copolymer PCL‐b‐PGMA self‐assembled into nanoscale micelles in aqueous solutions, as investigated by dynamic light scattering and transmission electron microscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5037–5049, 2007     

57Fe Mössbauer Study of Magnetic Nanowires

Hyperfine Interactions - Nanowires of metal, alloy, compound, and ferrite have been electrodeposited in anodic aluminium oxide templates. The structure and magnetic properties of the nanowires are...     

Two New Ionone Derivatives from Rhododendron przewalskii Maxim

Two new ionone derivatives,named rhododendrone and rhododendronside,were isolated from the alcohoilc extract of the aerial parts of Rhododendron przwalskii Maxim.Their structures were elucidated on the basis of spectroscopic analysis.