Tight K-Frames in Hilbert Spaces

k-框架是框架的一种推广.本文在HIlbErT空间将紧框架推广到k-框架上,引入紧k-框架的概念.通过紧k-框架的算子k和合成算子给出紧k-框架的算子刻画,并利用紧k-框架的算子k给出紧k-框架成为紧框架的一个充要条件.还讨论紧k-框架的构造以及两个紧k-框架集的包含与涉及的算子k的相互关系.K-frames are the generalizations of frames.In this paper,we introduce the definition of a tight K-frame in a Hilbert space,then we give a characterization for tight K-frames by the synthesis operator and the operator K.By means of the operator K,we also obtain a necessary and sufficient condition for tight K-frames to be tight frames.In the end we make a discussion on the construction for tight K-frame and the correlations between two tight K-frames and the involved operator K.国家自然科学基金(61170324); 天元基金(11226099); 福建省自然科学基金(2012J01005); 福建省教育厅资助科技项目(JA11100); 福州大学科研启动项目(022410); 福州大学科技发展基金项目(2012-XQ-29

Simultaneous determination of four phthalate esters in water samples using ultrasound-assisted dispersive liquidliquid microextraction coupled with highperformance liquid chromatography

建立了采用超声辅助分散液液微萃取技术结合高效液相色谱法(UA-DLLME-HPLC)对4种邻苯二甲酸酯(PAEs)进行富集、检测的方法,并成功应用于实际水样分析。实验中采用富集因子来评价萃取效率,考察并优化了影响萃取效率的主要因素,包括萃取剂类型和用量、分散剂类型和用量、超声时间、离子强度、萃取时间和pH值等。结果表明:在最佳萃取条件下,该法对4种PAEs(邻苯二甲酸二甲酯、邻苯二甲酸二乙酯、邻苯二甲酸二丁酯和邻苯二甲酸二正辛酯)具有较高的富集能力,富集因子分别为71、144、169和159;检出限分别为3.78、1.77、3.07和3.30μg/L。对实验室自来水、某品牌矿泉水以及湖水分别加..

Preparation of SiNO Ceramic by Pyrolysis Nitridation of Polycarbosilane

系统研究了热解和氧化条件对聚碳硅烷氮化热解法制备SInO陶瓷的影响.研究发现,氮化脱碳反应主要发生在800℃之前,且脱碳彻底,碳质量分数低于1%;在氮气气氛下继续烧成,最终生成陶瓷的氮质量分数可达35.65%.氮化前对聚碳硅烷进行氧化交联可提高陶瓷产率至61.84%,但是产物中氮质量分数显著降低到20%以下,产物为无定型态的SInO陶瓷.SiNO ceramic has very excellent comprehensive properties and is one of the best candidates for ceramic matrix composites.In this work,influences of pyrolysis and curing conditions on the SiNO ceramic prepared with pyrolysis nitridation are systematically studied.The results show that decarbonization is completed before 800 ℃ with carbon residue lower than 1%(by mass).After pyrolysis in N2,nitrogen content is as high as 35.65%(by mass).Oxidation curing before ammonolysis can improve ceramic yield.The ceramic yield is 61.84%(by mass)but the nitrogen content decreases significantly(below 20%)by mass,and the product is amorphous SiNO ceramic.Therefore,high-yield and low-carbon-content SiNO ceramic can be prepared with pyrolysis nitridation of polycarbosilane.国家自然科学基金(51002127

社会转型与文化转型·海峡两岸圆桌论坛·实录

徐新建(四川大学教授、人类学高级论坛副秘书长):大家好。今天的话题围绕"文化转型"展开。据我所知这既是人类学圈的一个新提法,也是一个有争议的话题。我想请徐杰舜教授首先交代一下议题的来源和这次圆桌对话的意义。虽然在座有部分学者参与谋划了很久,但多数人是没有参与的。今天上午周大鸣教授做了简短的表态,强调提"文化转型"的目的是一种抗争,也就是人类学和社会学的抗争,后者提出的"社会转型"几乎主导了现实社会的思想和实践。我想,这已涉及了知识生产和学术政治,值得各位关注。下面就请徐杰舜老师做简要说明