毛细现象液面形状特性分析

毛细管插入液面时,液体会由于表面张力作用而上升,这就是毛细现象.大多数学者在计算毛细现象中液面上升高度时,直接假定液面为球帽型,计算液柱重力势能时,将液体近似为圆柱体,忽略球帽的重力势能.本文严格计算了液面的形状,发现当液面较窄时(小于液面上升高度),这种近似是合理的.但液面较宽时,近似计算结果与实际情况偏离较大.本文在特殊情况下验证了描述液面接触角的杨氏方程的正确性.     

科学饮食 营造健康生活

饮食是人类生存的根本,是生命的源泉。伴随着人民生活水平的提高和对餐饮业需求的增长,饮食健康成了一道靓丽的风景。饮食文化、合理膳食、科学烹调和饮食习惯引起了人们广泛关注。     

Acylation of nitriles to β-ketonitriles catalyzed by a heterometallic alkoxide cluster of neodymium and sodium： NdNa8（O^tBu）10（OH）

Catalytic acylation of nitriles with esters in the presence of 10 mol% NdNa8(OtBu)10(OH) is developed.The procedure is suitable for both enolizable and nonenolizable esters and affords β-ketonitriles in moderate to high yields.The heterometallic alkoxide cluster NdNa8(OtBu)10(OH) is structurally characterized by X-ray diffraction,and a mechanism for the production of β-ketonitriles using the cluster is proposed and verified.     

化学振荡的间接扰动法测定磷酸苯酯

根据磷酸苯酯在碱性磷酸酶的催化作用下水解生成的苯酚对化学振荡体系(溴酸钠-硫酸-苹果酸-大环铜配合物)产生的干扰作用,首次建立一种分析测定磷酸苯酯二钠二水(DPPD)的新方法.其分析结果表明:当磷酸苯酯二钠二水的浓度在2.0×10-6~6.0×10-4mol.L-1范围内时,其浓度对数与振荡体系的振幅的改变值△A呈良好的线性关系,相关系数为0.996 49.     

当代改编民歌的发展特点及演唱分析——以《孟姜女》《玛依拉变奏曲》为例

随着时代的发展,人们对民族音乐的发展提出了更高的要求.短小易唱的民间曲调已不能满足人们的审美情趣与欣赏水平,在技术上也难以充分展示演唱者的专业水平.因此,一批优秀的、具有创新意识的作曲家开始探寻民族声乐的创新之路,他们在传统民歌音乐的基础上用现代创作技法结合现代审美意识对其进行改编,创作出一批集民族性、艺术性、科学性于一体的优秀改编民歌,为我国民族声乐的繁荣发展贡献了力量.同时,对演唱者技能的提高、艺术表现力的丰富、艺术修养的完善起到重要作用.     

基于结构化模型驱动的稳控装置动作模拟仿真方法

提出了一种基于结构化模型驱动的稳控装置动作模拟仿真方法.通过对稳控装置模型的结构化,将其稳控策略组织为四元表形式(即故障、运行方式、潮流水平和控制策略),并将其控制策略分解为控制方式、控制量、控制量实施原则、控制对象队列和约束5个基本元素,在此基础上归纳出直接型、顺序型、循环型和最优型四种基本的控制策略结构化模型.进一...     

An important functional group,benzo[1,3]dioxole,of alkaloids induces the formation of the human telomeric DNA G-quadruplex

Over the past few decades, numerous molecules have been discovered or designed to interact efficiently and selectively with a peculiar DNA structure named G-quadruplex. Some of these molecules have been developed as anticancer agents. To aid the design of anticancer agents, the ability of alkaloids possessing Protoberberine and Benzophenanthridine groups to induce the formation of G-quadruplexes were studied using CD spectroscopy. By careful examination of their structures, we found that a benzo[1,3]dioxole group plays an important role in influencing their inductive properties. The more functional groups the alkaloids have, the stronger their G-quadruplex inductive ability.     

Investigation of silicon on insulator fabricated by two-step O+ implantation

In this paper, we investigated the dose window of forming a continuous buried oxide (BOX) layer by single implantation at the implantation energy of 200 keV. Then, an improved two-step implantation process with second implantation dose of 3×10¹⁵ cm^?2 was developed to fabricate high quality separation by implanted oxygen (SIMOX) silicon on insulator (SOI) wafers. Compared with traditional single implantation, the implantation dose is reduced by 18.2%. In addition, the thickness and uniformity of the BOX layers were evaluated by spectroscopic ellipsometry. Defect-free top Si as well as atomic-scale sharp top Si/buried oxide interfaces were observed by transmission electron microscopy, indicating a high crystal quality and a perfect structure of the SOI fabricated by two step implantation. The top Si/BOX interface morphology of the SOI wafers fabricated by single or two-step implantation was also investigated by atomic force microscopy.     

多丝正比计数器的优化设计

由于低水平放射性测量中样品计数率非常低,使用多丝正比计数器进行α放射性测量时,本底主要由探测器内壁材料中的α放射性成分贡献.考虑到测量系统本身的放射性干扰一直是制约测量能力的重要因素,降低测量系统本底是α辐射测量的重点.采取在传统多丝正比室添加屏蔽丝的方法,并通过Garfield程序模拟正比室在不同参数设置下电子漂移过程得到正比室各项参数的最优解.模拟结果表明,优化后的正比室可以对不同入射方向的α粒子进行筛选,有效抑制探测器本底,从而得到最优的正比室结构设计参数.     

Semi-global stabilization via homogeneous output feedback for a class of nonlinear time-delay systems

The semi-global stabilization problem for a class of nonlinear systems with state time-delay is addressed in this paper. By using Lyapunov-Krasovskii functional method and homogeneous domination approach, a homogeneous observer and an output feedback controller with a scaling gain are designed. Then the scaling gain is adjusted such that the closed-loop system is semi-global asymptotically stable. A numerical example is presented to illustrate the effectiveness of the obtained results in this paper.