Nonlinear convection of a viscoelastic fluid with inclined temperature gradient

The energy method is used to analyze the viscoelastic fluid convection problem in a thin horizontal layer, subjected to an applied inclined temperature gradient. The boundaries are considered to be rigid and perfectly conducting. Both linear and nonlinear stability analyses are carried out. The eigenvalue problem is solved by the Chebyshev Tau-QZ method and comparisons are reported between the results of the linear theory and energy stability theory.Received: 12 March 2004, Accepted: 19 April 2004, Published online: 17 September 2004PACS: 47.20 Ky, 47-27 Te, 83.60 Wc Correspondence to: P.N. Kaloni     

On a Nonlinear Discretized LKR System: Reductions and Underlying Virasoro Symmetry Algebras

A differential-difference version of the Loewner–Konopelchenko–Rogers (LKR) system is constructed by discretization of the spatial variables in the continuous LKR system. The differential-difference LKR system admits a diversity of significant reductions. The symmetry algebras of the discrete LKR system and its reductions are shown to possess underlying Kac–Moody–Virasoro type structure. A discrete dromion-like solution of the LKR system is constructed via finite symmetry group transformation.     

Isomerization of 2-seleno-1,3,2-diazaphospholidine derivatives

For the first time the isomerization of 1,3,2-diazaphospholidine-2-selenide derivatives in refluxing benzene in the presence of trace water was observed, and the structure of isomerized product was determined by X-ray diffraction, IR, ¹H NMR, ³¹P NMR, and elemental analysis. The mechanism of isomerization was also proposed. The isomerized phosphoroheterocycle (C₂₆H₃₈N₃O₅PSe, Mr = 582.52) is orthorhombic with space group Pbca, a = 17.1010(9) Å, b = 16.6404(9) Å, c = 20.7517(11) Å, V = 5905.3(5) ų, Z = 8, Dr = 1.310 g/cm³, λ = 0.71073 Å, μ (Mo Kα) = 1.363 mm^?1, F(000) = 2432. The structure was refined to R1 = 0.0482, wR2 = 0.1204 for 5214 unique reflections with I > 2σ(I). Intramolecular and intermolecular hydrogen bonds are observed in the crystal packing.     

哈密顿Ermakov系统的形式不变性

把形式不变性的方法用于研究哈密顿Ermakov系统，从哈密顿Ermakov系统的形式不变性出发，运用比较系数法得到与形式不变性相应的点对称变换生成元的表达式及势能所满足的偏微分方程.结果表明，在点对称变换下，只有自治的哈密顿Ermakov系统才具有形式不变性. 关键词： 哈密顿Ermakov系统 拉格朗日函数 点对称变换 形式不变性     

Search for high dimensional integrable models

The possible high dimensional integrable models are studied in three different aspects: (i) starting from a strong symmetry operator of a known (1+1) -dimensional integrable model, we can construct a type of (n+1)-dimensional integrable models, high dimensional breaking soliton equations; (ii) from every concrete realization of the generalized Virasoro algebra, we can get many high dimensional integrable models in the meaning that the models possess generalized Virasoro symmetry algebra; (iii) starting from the Schwartz equations which possess conformal invariance, we can also get various high dimensional integrable models in the meaning that they possess Painlevé property. Project supported by the National Natural Science Foundation of China and the Natural Science Foundation of Zhejiang Province.     

EIGENVECTORS OF SYSTEM OF HAMMERSTEIN INTEGRAL EQUATIONS IN BANACH SPACES ANDAPPLICATIONS

1IntroductionLetEbeaBanachspaceandI=[O,l].ConsiderthesystemofHammersteinintegralequationsinE:wherekiEC[IxI,R'](i=1,2)arenonnegative,fieC[IxExE,E](i=1,2)andyt,YEC[I,E].Inthispaper,weinvestigatetheexistenceofeigenvectorsofsystem(l)bymeansoffixedpointindextheory.WealsogivesomeapplicationstoasystelllofSturm-Liouvilleproblemsofordinarydtherentialequations.Iuwl1atfollows,PdenotesthenormalconeofEwithanormalconstantN(see[1,2l):95u5vimplieslluII5N11vIl,whereoisthezeroelementofE.ExEisaBana…     

Femtosecond time-resolved energy transfer from CdSe nanoparticles to phthalocyanines

The first real-time observation of the early events during energy transfer from a photoexcited CdSe nanoparticle to an attached phthalocyanine molecule are presented in terms of a femtosecond spectroscopic pump–probe study of the energy transfer in conjugates of CdSe nanoparticles (NPs) and silicon phthalocyanines (Pcs) with 120 fs time resolution. Four different silicon phthalocyanines have been conjugated to CdSe NPs. All of these have proven potential for photodynamic therapy (PDT). In such NP-Pc conjugates efficient energy transfer (ET) from CdSe NPs to Pcs occurs upon selective photoexcitation of the NP moiety. Spectral analysis as well as time-resolved fluorescence up-conversion measurements revealed the structure and dynamics of the investigated conjugates. Femtosecond transient differential absorption (TDA) spectroscopy was used for the investigation of the non-radiative carrier and ET dynamics. The formation of excitons, trapped carriers states, as well as stimulated emission was monitored in the TDA spectra and the corresponding lifetimes of these states were recorded. The time component for energy transfer was found to be between 15 and 35 ps. The ET efficiencies are found to be 20-70% for the four Pc conjugates, according to fluorescence quenching experiments. Moreover, as a result of the conjugation between NP and the Pcs the photoluminescence efficiency of the Pc moieties in the conjugates do not strictly follow the quantum yields of the bare phthalocyanines. PACS 73.63.Bd     

On Stratified Shear Flow in Sea Straits of Arbitrary Cross Section

Equations and theorems governing the flow of an inviscid, incompressible, continuously-stratified fluid in a gradually varying channel with an arbitrary cross section are developed. The stratification and longitudinal velocity are assumed to be uniform in the transverse direction, an assumption that is supported under the assumption of gradual topographic variations. Extended forms of Long's model and the Taylor–Goldstein equation are developed. Interestingly, the presence of topographic variation does not alter the necessary condition for instability (Richardson number     ) nor the bounds on unstable eigenvalues (the semi-circle theorem). The former can be proved using a new technique introduced herein. For the special case of homogeneous shear flow, generalized versions of the theorems of Rayleigh and Fjørtoft do depend on the form of the topography, though no general tendency toward stabilization or destabilization is apparent. Previous results on the bounds and enumeration of neutral modes are also extended. The results should be of use in the hydraulic interpretation of exchange flow in sea straits.     

周期极化掺镁不同组分LiNbO3晶体的研究

利用气相平衡扩散法研制出掺镁不同组分的LiNbO3晶体 ,并对其极化特性进行了研究 .研究表明晶体的开关电场和自发极化不仅与晶体组分 [Li] [Nb]比有关而且与掺镁量有关 ,[Li] [Nb]比为 0 973掺入 2mol%MgO的近化学比LiNbO3晶体的开关电场仅为 1 8kV mm ,是同成分晶体的 1 12 ,且其极化结构的质量要远好于同成分LiNbO3晶体和近化学比LiNbO3晶体 .     

Characterization of heat-treated CN films fabricated by dual-facing-target sputtering for soft X-ray multilayer mirrors

The structural characterization of heat-treated CN films fabricated by dual-facing-target sputtering for soft X-ray multilayer mirrors was performed by means of X-ray diffraction (XRD), Raman spectroscopy (RS) and X-ray photoelectron spectroscopy (XPS). The XRD analyses indicate a graphization process in the CN films during thermal annealing. The Raman analyses imply that the primary bonding in the CN films is sp². In other words, the formation of the sp³ bonding in the CN films can be suppressed effectively by doping with N atoms, and thus the thickness expansion resulting from the changes in the density of CN films during annealing can be decreased considerably. This result is also clarified by the increased conductivity measured. The XPS results give the information of the existence of the strong covalent bonding between N and C atoms, which can slow down the tendency of the structural relaxation during annealing. These results suggest that CN films suitable for soft X-ray multilayers used at high-temperature environments can be obtained by reactive dual-facing-target sputtering. With the low-angle X-ray diffraction measurements, we do observe the enhanced thermal stability of CoN/CN multilayers. Received: 2 October 1998 / Accepted: 21 April 1999 / Published online: 23 September 1999