铒镱双掺的钒酸钇和铌酸锂晶体中的铒离子的上转换发光

利用J-O理论,计算了在铒、镱双掺的钒酸钇和铌酸锂晶体中的铒离子在室温下的晶场唯象参数Ωλ(λ=2,4,6)及辐射跃迁几率、无辐射跃迁几率和共振跃迁几率.考虑到铒、镱间的能量转移,写出了在这些晶体中的铒离子的速率方程.速率方程的解表明,在铒、镱双掺的钒酸钇晶体中的铒离子的550 nm的上转换发光,比它在铒、镱双掺的铌酸锂晶体中更为有效.这一理论结果与我们的实验观察结果一致.     

k—型卡接胶／聚乙烯吡咯烷酮共混水凝胶的国徽制备及性质研究

采用辐射技术制备了k-型卡接胶（ＫＣ）／聚乙烯基吡咯烷酮（ＰＶＰ）共混水凝胶,研究了共凝胶内ＫＣ含量、ＰＶＰ的分子量和辐照剂量等对ＫＣ／ＰＶＰ共混水凝胶性质的影响,实验发现,ＫＣ与高分子量的ＰＶＰ（k-90）共混后在一定剂量范围内辐照可得到高强度,高 胀行为的ＫＣ／ＰＶＰ共混水凝胶,随着共混水凝胶内ＫＣ含量的增加,凝胶强度及深胀性能均显著提高,分析表明,ＫＣ与高分子量的ＰＶＰ共混后,在较低剂量下ＫＣ的降解被抑制,从而获得一种由物理交联的ＫＣ和化学交联的ＰＶＰ形成的互穿网络（ＩＰＮ）凝胶。     

Cubic Lienard equation with quadradic damping (I)

1. IntroductionLienard equationdZx dx~ f(.)g g(x) = 0 (l.0)dtZ dthas been extensively studied with particular emphasis on the ekistence and uniqueness oflimit cycles (see e.g. [l--4] and references there in). The number of limit cycles of (l.0) hasbeen also investigated by several authors (see e.g. [5--8]).In the present paper we study the general cubic Lienard equation, namelydx da~ = y ~ F(x), Z ~ ~g(x) (1.1)dt' dtwhereF(x) = ale a,x: a,x', (l.2)g(x) = blx b,x' b,x'. (1.3)Clea…     

光互连技术在信号处理中的某些应用

叙述了近年来在天津大学研究及开发光互连网络的情况。这些研究围绕着解决信号传输中的延迟和通信带宽,开展的研究工作有：完成包括64个处理器的光电混合处理器阵列系统;giga—bit／s机群系统光互连链路;在链路中采用时分复用技术(TDM),实现了“虚拟并行传输”;在链路中设计了硬件路由功能,并组成光环网;在网络系统中实现波长路由,并建立了波长路由双环网,采用该技术可以避免路由延迟;在光互连网络中应用了MEMS光开关,实现了星型一环形二级结构;用同步光传输技术实现了多通道数据传输卡。     

HARMONIC AND SUBHARMONIC BIFURCATION IN THE BRUSSEL MODEL WITH PERIODIC FORCE

1.IntroductionABrusselatorisoneofthebestexaminedmodelchemicalreactionswhichconsistsoffourstepsItisshowninFig.1schematicallyandisrepreselltedbythefollowingsetofequationsffevedFebruary6,1995.*~workissupportedbytheNationalNaturalScienceFOundationmanYuan"TermsinChina.ThemodelweadoptistheoneduetoPrigogine,Lefever,andNicolis(Brusselator)t'.Fig.1.'TheschematicdiagramofBrusselmodel(AdditionalcirculararrowsrepreseDttheexistenceofautocatalysis.)Herexandystandfortheconcentrationsofreferencereacta…     

QUALITATIVE ANALYSIS FOR A MATHEMATICAL MODEL OF AIDS

In this paper a mathematical model of AIDS is investigated.The conditions of the existence of equilibria and local stability of equilibria are given.The existences of transcritical bifurcation and Hopf bifurcation are also considered.in particular,the conditions for the existence of Hopf bifurcation can be given in terms of the coefficients of the characteristic equation.The method extends the application of the Hopf bifurcation theorem to higher differential equations which occur in biological models,chemical models,and epidemiological models etc.     

锁相环路方程分界线环的研究及数值计算

<正> 1.引言文[1],[2],[3]对几种锁相环路方程作了定性研究,本文着重研究无噪声混合锁相环路方程的分界线环,并给出了分界线参数值的近似值,这可供实际工作者参考.而关于混合锁相环路的结构及数学模型可参看[5]第三章.     

捕食-食饵动力系统的定性分析

§1.引言G.W.Harrison 研究了一种比 Volterra 模型和 Freedman 模型更为真实的捕食-食饵相互作用的生物系统的数学模型:     

浑沌简介

浑沌现象涉及到数学、物理学、化学、生物学等许多学科.本文简要介绍浑沌理论的研究现状、判断和研究浑沌现象的方法.     

HOPF BIFURCATION AND OTHER DYNAMICAL BEHAVIORS FOR A FOURTH ORDER DIFFERENTIAL EQUATION IN MODELS OF INFECTIOUS DISEASE

ＨＯＰＦＢＩＦＵＲＣＡＴＩＯＮＡＮＤＯＴＨＥＲＤＹＮＡＭＩＣＡＬＢＥＨＡＶＩＯＲＳＦＯＲＡＦＯＵＲＴＨＯＲＤＥＲＤＩＦＦＥＲＥＮＴＩＡＬＥＱＵＡＴＩＯＮＩＮＭＯＤＥＬＳＯＦＩＮＦＥＣＴＩＯＵＳＤＩＳＥＡＳＥＪＩＮＧＺＨＵＪＵＮ（井竹君）（Ｉｎｓｔｉｔ...