氢键概念的形成和发展

1902年,瑞士化学家维尔纳对氯化铵结构的解释为氢键概念的形成奠定了基础。1920年,美国化学家拉提麦尔和罗德布什首先认识了水中的氢键：2个八隅体所持的氢核构成的“弱键(weak bond)”。1928年,美国化学家鲍林在解释[FHF]^-的结构时首次使用“氢键(hydrogen bond)”一词,但并未对氢键的概念进行明确定义。1939年,鲍林在《化学键的本质》中明确提出了氢键的概念,并解释了氢键的性质,自此,氢键的概念正式形成。近年来,科学家经过深入研究发现了氢键的新类型：π型氢键、双氢键、金属氢键和单电子氢键。随着科学思想和科学技术的发展,关于氢键的认识也会越来越深入。     

运用微粒观开发复分解反应教学价值的实践与研究

在酸、碱、盐教学中以复分解反应条件教学为例, 应用“微粒观”统领酸、碱、盐教学。基于“微粒观”构建了本节课的知识结构层级图, 剖析了学生的认识发展过程, 通过教学实践总结、归纳了若干教学策略, 从而突破学生学习难点, 提高学生的迁移和应用能力, 并为高中进一步学习离子反应做好铺垫。     

理、化、生不同专业大学生关于能量概念的认识现状研究

能量概念是科学教育的一个核心概念,也是近年来国际科学教育研究的一个热点话题。在柳秀峰、Wilson等人的研究基础上,构建了能量概念的认识模型。基于该模型,并结合国内物理、化学和生物等不同专业的中学、大学教材中涉及的能量相关概念,笔者编制了调查问卷,对北京师范大学物理、化学和生物等不同专业的共280名大学生进行了测查和访谈。通过Rasch模型和SPSS统计分析发现,不同学科背景的学生对能量概念的认识角度和水平存在差异,而且存在一些偏差认识。基于学生的认识现状,笔者最后构建了关于能量概念认识的难度进阶,并对能量概念的教学提出了建议。     

π-CONJUGATED OLIGOMERS IN SUPRAMOLECULAR CRYSTALS AND THEIR OPTOELECTRONIC FUNCTIONS

Functional organic molecular materials and conjugated oligomers or polymers now allow the low-cost fabrication of thin films for insertion into new generations of electronic and optoelectronic devices. The performance of these devices relies on the understanding and optimization of several complementary processes. Our goal is to discuss the relationship between the molecular stacking structures and their optoelectronic properties that are of importance in all these areas. The concept of intermolecular interaction should be taken here in the special sense that is inter-dipole coupling. Specifically, we will address the impact of inter-dipole interaction between adjacent molecules in aggregate state on the solid-state emission properties.     

Monte-Carlo simulation of a compact gamma-ray detector using wavelength-shifting fibers coupled to a YAP scintillation crystal

The production and transportation of fluorescent light produced in wavelength-shifting fibers (WSFs) coupled to YAP scintillation crystal is simulated using the GEANT4 codes.An advantage of the wavelength-shifting fiber readout technique over a direct readout with a position-sensitive photo-sensor is the reduced requirement for position sensitive photomultiplier tube photocathode area.With this gamma-ray detector,the gamma camera is small and flexible and has larger effective field of view and low cost.Simulation results show that a) a mean 12 of photons per 59.5 keV gamma ray interaction is produced in the WSF located nearest to the incident gamma ray,and a spatial resolution of 3.6 mm FWHM is obtained,b)a mean 27 of photons per 140 keV gamma ray interaction is produced and a spatial resolution of 3.1 mm FWHM is obtained.Results demonstrate the feasibility of this concept of a compact gamma-ray detector based on wavelength-shifting fibers readout.However,since the very low photoelectron levels,it is very important to use a photon counting device with good single photo-electron response to readout the WSFs.     

Schopenhauer's Prolegomenon to Fuzziness

Prolegomenon means something said in advance of something else. In this study, we posit that part of the work by Arthur Schopenhauer (1788–1860) can be thought of as a prolegomenon to the existing concept of fuzziness. His epistemic framework offers a comprehensive and surprisingly modern framework to study individual decision making and suggests a bridgeway from the Kantian program into the concept of fuzziness, which may have had its second prolegomenon in the work by Frege, Russell, Wittgenstein, Peirce and Black. In this context, Zadeh's seminal contribution can be regarded as the logical consequence of the Kant-Schopenhauer representation framework.     

灵敏度控制思想在主动膜系设计中的快速实现算法

 基于斜入射薄膜制备实践中镀膜误差对光谱性能的严重退化影响的认识,提出了一种基于灵敏度控制思想的主动膜系设计方法。在深入分析了镀膜中膜层结构参数误差的分布规律的基础上,运用膜系光谱系数关于膜层参数的导数计算的解析模型,建立了膜系灵敏度的定量计算模型和快速实现算法。以一45°入射高精度消偏振增透膜的设计实验为例,探讨了灵敏度控制思想在膜系设计中的可行性、快速性和有效性。结果表明,这一新型设计方法不会显著增加程序时间消耗,能获得具有良好可镀制性能的薄膜,对于正入射和宽角度入射膜同样适用,而且可以避免昂贵的失败试镀和采样,有助于缩短新薄膜的生产周期,特别是对于高精度斜入射薄膜的重复性制备具有重要意义。     

Fluorescent azophenol-quinazoline dyad as multichannel reversible pH indicator in aqueous media: an innovative concept on diazo based dyads

A novel azophenol-quinazoline dyad 1 has been designed, synthesized and demonstrated as an efficient reversible multichannel pH indicator through distinct signalling in aqueous media. Owing to the competence between highly fluorescent quinazoline moiety and a well known fluorescence quencher diazo group, dyad 1 is moderately fluorescent in nature. Under acidic conditions 1 displays diverse fluorogenic changes (blue emission at pH 4.25; green at pH 1.80) while under basic condition (pH 11.80) chromogenic changes were observed.     

On the applicability of the “abt” concept

Kaiser's “abt” concept rests on the experimental establishment of a linear relation between band width at half height, b_0.5, and capacity ratio, k, according to His column specification quantity, h_real, is dependent on the square of the slope a, obtained from a linear regression analysis based on this relation. It is shown in the present paper that an improvement of the experimental conditions leading to a lower extra-column contribution to band broadening, b, introduces a tendency towards a negative curvature in the plot at low k values. The mean slope increases, and an uncritical linear regression would yield an h_real-value which is higher than before and which would be in the opposite direction to the requirements of a reliable column specification. Generally the linear regression analysis has to be moved to higher k regions in cases of curvature, especially as it is also shown that h_real is an estimation of the traditional HETP value, H∞, that would be obtained when k approaches infinity. This theoretically expected relation is a strong motivation for the use of h_real as a column specification, since the b_0.5-value associated with H∞ is expected to be practically independent of b.     

基于约束概念格的天体光谱局部离群数据挖掘系统

寻找特殊的、未知的天体是人类探索宇宙奥妙所追求的目标之一,天体光谱数据挖掘是实现该目标的一种有效方法。约束概念格是一种新的概念格结构,具有构造效率高、提取知识针对性和实用性强等特点。针对天体光谱数据在特征子空间中的局部偏离,采用VC++ 6.0和Oracle 9i作为开发工具,设计与实现了基于约束概念格的天体光谱局部离群数据挖掘系统,并对软件模块功能和体系结构,以及天体光谱数据预处理、约束概念格构造方法、基于链表结构的概念格构造、局部离群数据挖掘方法等关键技术进行了详细描述。运行结果表明,该系统实现天体光谱数据局部离群数据挖掘是可行的、有价值的,从而为寻找未知的、特殊的天体提供了一种新途径。