铽掺杂纳米晶GaN薄膜的室温可见发光

利用直流磁控反应式共溅射方法制备了GaN：Tb薄膜。XRD结果显示,该薄膜为纳米晶结构,根据Scherrer公式,计算得到了GaN薄膜晶粒的平均大小为4．8nm;紫外可见谱表明在可见光区薄膜的平均透过率大于75％,同时利用Tauc公式计算得到了薄膜的光学带隙为3．07eV;测量了薄膜的室温光致发光谱,获得了Tb^3＋在可见光区（位于497．0,552．4,594．2以及627．8nm）的本征发光。     

pH值对微波协助乙二醇法制备PtRu/C催化剂的影响

以微波协助乙二醇工艺合成了碳负载不同粒径大小的PtRu/C纳米催化剂, 主要考察了溶液pH值对PtRu粒子大小的影响. 利用紫外可见光谱、能量散射X射线谱、透射电镜和X射线衍射谱对PtRu纳米催化剂进行了表征. 结果表明, pH值是一个对PtRu粒子大小有着重要影响的因素. TEM结果显示随着溶液pH值的增加, PtRu粒径从3.5 nm减小到1.5 nm. 当溶液pH值达到11.0时, 由于金属粒子被保护, 合成的催化剂中金属载量明显减少. 溶液pH 值在9.0 右合成的PtRu/C催化剂具有适宜粒径(2.4 nm)和均匀分布的金属颗粒, 具有最好的甲醇电氧化活性.     

纳米银修饰的压电晶体传感器用于水中痕量氰化物测定的研究

以压电石英晶体(PQC)技术为基础,研究了光化学方法沉积纳米银粒子到PQC电极表面的过程及机理.将该电极用于检测水中痕量的氰化物,与普通商品PQC的银膜相比, 这种新鲜产生的金属纳米银传感层可改善分析性能(检测信号加强3倍).结果显示该PQC电极频率的变化与氰化物的浓度在0.1 ～10 μmol/L范围内呈线性关系, 检出限(2.2 μg/L)较世界卫生组织(WHO)对饮用水氰化物含量的指导值低1 ～2个数量级.详细研究了光化学沉积银过程中的各种影响因素以及检测氰化物过程中的主要影响因素:纳米银粒子的大小及涂层厚度、背景缓冲溶液、pH及样品中共存物质的干扰等.     

浅谈中国化学会《有机化合物命名原则2017》的教学要点

比较了中国化学会《有机化合物命名原则2017》与1980版命名原则的不同,指出了新版的主要变化之处。通过举例,说明母体氢化物、特性基团的概念、含义及其在命名有机化合物时的重要意义。归纳出命名有机物时确定母体氢化物和主特性基团所依据原则和方法,梳理出命名有机化合物的一般步骤,并通过实例来说明2017版命名原则的实施方法。     

Particle number size distribution and new particle formation （NPF） in Lanzhou,Western China

Particle number size distribution from 10 to 10,000 nm was measured by a wide-range particle spectrometer (WPS-1000XP) at a downwind site north of downtown Lanzhou, western China, from 25 June to 19 July 2006. We first report the pollution level, diurnal variation of particle concentration in different size ranges and then introduce the characteristics of the particle formation processes, to show that the number concentration of ultrafine particles was lower than the values measured in other urban or suburban areas in previous studies. However, the fraction of ultrafine particles in total aerosol number concentration was found to be much higher. Furthermore, sharp increase of ultrafine particle concentration was frequently observed at noon. An examination of the diurnal pattern suggests that the burst of the ultrafine particles was mainly due to nucleation process. During the 25-day observation, new particle formation (NPF) from homogeneous nucleation was observed during 33% of the study period. The average growth rate of the newly formed particles was 4.4 nm/h, varying from 1.3 to 16.9 nm/h. The needed concentration of condensable vapor was 6.1 × 10⁷ cm^?3, and its source rate was 1.1 × 10⁶ cm^?3 s^?1. Further calculation on the source rate of sulphuric acid vapor indicated that the average participation of sulphuric acid to particle growth rate was 68.3%.     

一个考虑沉积物孔径分布特征的水合物相平衡模型

天然气水合物的相平衡条件一直是水合物相关研究的重点和难点. 本文探讨了沉积物孔隙大小及其分布特征对水合物相平衡条件的影响机理, 提出了有效孔隙半径的概念, 并利用沉积物孔隙大小分布特征, 假设孔径分布呈正态分布, 建立了水合物饱和度和有效孔隙半径之间的定量关系; 与传统的van der Waals-Platteeuw相平衡模型相结合, 提出了一个考虑沉积物孔隙大小及其分布特征的相平衡模型. 相对于传统模型, 本模型所表达的相平衡条件不再是二维平面的p-T曲线, 而是温度、压力以及水合物饱和度之间的三维定量关系. 这一特征使得所建模型既能较为真实地反映水合物形成与分解机理, 又能有效地考虑孔隙大小分布对水合物相平衡条件的影响. 通过与实验数据对比, 证明了所建模型的预测结果优于其他模型. 本模型在温度和压力条件确定的情况下还可以预测沉积物中水合物的饱和度, 因此, 可用于地层中水合物储量计算.     

如何编制初中数学开放性试题

教材中的数学题多数是封闭型试题,这些已经不能完全满足数学素质教育的要求,不利于培养学生的创新意识和创新能力.为了改变这种情况,使数学教学更多地体现以学生为主体的积极探究精神,使数学教学更有利于学生创造精神的培养,适当增加开放题是必要的.也就是说,我们可以把中学数学教材中一     

倒数的作用也不少

同学们都知道,乘积是1的两个数叫做互为倒数,其中一个数叫做另一个数的倒数.为方便起见,利用式子表示:如果ab=1,那么a叫做b的倒数,即a的倒数是b,或b的倒数是a.利用倒数的关系有时可以帮助我们解决不少问题呢,下面举例说明,或许对你今后的学     

Spark-generated bubble collapse near or inside a circular aperture and the ensuing vortex ring and droplet formation

This paper aims to study the oscillation of a sparkgenerated submerged bubble located near or inside a circular aperture made in a flat plate using high-speed visualization technique. In the case of a bubble oscillating near an aperture the initial free surface of the water was set at the bottom surface of the plate. The effects of aperture size and bubblefree surface distance on the bubble behavior as well as on the ensuing droplet dynamics are investigated. It was found that the direction of the bubble reentrant jet was towards the aperture or away from it respectively when the normalized aperture size was smaller or greater than a certain critical value. In addition, a toroidal vortex ring was observed to form, which rotated inwards as it moved away from the aperture. It was also found that if the bubble was incepted at a distance sufficiently away from a supercritical size aperture a single droplet could be produced. In the case of a bub- ble initiated in the middle of a circular aperture submerged just beneath the water free surface, the bubble was found to take the shape of an ellipsoid during its expansion. Then a reentrant jet was initiated and pierced the bubble from its top side.     

Linear and nonlinear excitations in complex plasmas with nonadiabatic dust charge fluctuation and dust size distribution

Both linear and nonlinear excitation in dusty plasmas have been investigated including the nonadiabatic dust charge fluctuation and Gaussian size distribution dust particles. A linear dispersion relation and a Korteweg-de Vries-Burgers equation governing the dust acoustic shock waves are obtained. The relevance of the instability of wave and the wave evolution to the dust size distribution and nonadiabatic dust charge fluctuation is illustrated both analytically and numerically. The numerical results show that the Gaussian size distribution of dust particles and the nonadiabatic dust charge fluctuation have strong common influence on the propagation of both linear and nonlinear excitations.