光折变晶体(BaSr)TiO3感应自泵浦相位共轭及光学双稳的理论分析

给出光折变晶体感应自泵浦相位共轭的一种理论解释，利用数值计算求解相应的耦合波方程，得出感应自泵浦相位共轭光与诱导光之间在一定条件下所呈现的双稳关系以及可逆尖和不可逆感应的特性，其分析结构与笔者先前得到的实验结果吻合。     

Ultrathin Multilayer Films Incorporating Keggin-type Heteropolyanion Clusters

In recent years, there has been considerable interest in the fabrication of self-assembled ultrathin multilayer films, because of their availability to form nanostructured materials with tailored architecture and properties1. The layer-by-layer (LBL) self-assembly, initially developed for pairs of oppositely charged polyelectrolytes2, is an unusually simple and versatile technique to built up of ultrathin multilayer films. A special feature of the multilayer films is that the composition, t…     

Time‐resolved spectroscopy study of donor–acceptor‐type copolymers in a monodisperse system: The effect of ratio between the acceptor and the donor

The photoexcitation processes of two donor–acceptor‐type copolymers PCFBT with different ratios between the donor and the acceptor ( PCFBT_0.5 and PCFBT_0.1 ) in the solution system are systematically studied. If the number of the donor is equal to that of the acceptor in one repeat unit (such as PCFBT_0.5 ), intrachain charge transfer (ICT) can occur and participate in the relaxation of the excited state after photoexcitation. When the number of donors is much larger than that of acceptors (such as PCFBT_0.1 ) in one repeat unit, the ICT character can disappear, and the localized exciton decay process is dominant in the relaxation of the copolymer, which also involves an excitation intensity‐independent vibrational thermal relaxation process at the initial time. The results further the understanding of the basic structure‐property relationship. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 992–996     

An experimental investigation of one- and two-degree of freedom VIV of cylinders

In the paper,an experiment investigation was conducted for one-and two-degree of freedom vortex-induced vibration(VIV) of a horizontally-oriented cylinder with diameter of 11 cm and length of 120 cm.In the experiment,the spring constants in the cross-flow and in-line flow directions were regulated to change the natural vibration frequency of the model system.It was found that,in the one-degree of freedom VIV experiment,a "double peak" phenomenon was observed in its amplitude within the range of the reduced velocities tested,moreover,a "2T" wake appeared in the vicinity of the second peak.In the two-degree of freedom VIV experiment,the trajectory of cylinder exhibited a reverse "C" shape,i.e.,a "new moon" shape.Through analysis of these data,it appears that,besides the non-dimensional in-line and cross-flow natural vibration frequency ratios,the absolute value of the natural vibration frequency of cylinder is also one of the important parameters affecting its VIV behavior.     

Biocompatible and pH‐responsive triblock copolymer mPEG‐b‐PCL‐b‐PDMAEMA: Synthesis,self‐assembly,and application

A series of well‐defined amphiphilic triblock copolymers [polyethylene glycol monomethyl ether]‐block‐poly(ε‐caprolactone)‐block‐poly[2‐(dimethylamino)ethyl methacrylate] (mPEG‐b‐PCL‐b‐PDMAEMA or abbreviated as mPEG‐b‐PCL‐b‐PDMA) were prepared by a combination of ring‐opening polymerization and atom transfer radical polymerization. The chemical structures and compositions of these copolymers have been characterized by Fourier transform infrared spectroscopy, ¹H NMR, and thermogravimetric analysis. The molecular weights of the triblock copolymers were obtained by calculating from ¹H NMR spectra and gel permeation chromatography measurements. Subsequently, the self‐assembly behavior of these copolymers was investigated by fluorescence probe method and transmission electron microscopy, which indicated that these amphiphilic triblock copolymers possess distinct pH‐dependent critical aggregation concentrations and can self‐assemble into micelles or vesicles in PBS buffer solution, depending on the length of PDMA in the copolymer. Agarose gel retardation assays demonstrated that these cationic nanoparticles can effectively condense plasmid DNA. Cell toxicity tests indicated that these triblock copolymers displayed lower cytotoxicity than that of branched polyethylenimine with molecular weight of 25 kDa. In addition, in vitro release of Naproxen from these nanoparticles in pH buffer solutions was conducted, demonstrating that higher PCL content would result in the higher drug loading content and lower release rate. These biodegradable and biocompatible cationic copolymers have potential applications in drug and gene delivery. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1079–1091, 2010     

An amperometric ethanol sensor based on foam nickel electrode

An amperometric sensor using foam nickel electrode as the working electrode for the measurement of ethanol in alkaline solution has been developed. Cyclic voltammetry and chronoamperometry are employed to analyze electrochemical behavior of the electrode. The results show that the oxidation of ethanol is more efficient on the foam nickel electrode than that on the nickel foil electrode. The sensor exhibits a good linear relationship between response current and ethanol concentration in the range of 4 to 1400 ppm with a detection limit of 0.8 ppm. The sensitivity and the response time of the sensor are 4.63 μA/ppm and 10 s respectively. Additionally, the sensor has 60 days shelf-life time at least.     

Rapidity distributions in unequal nuclei collision at high energies and hydrodynamic model

The mechanism of high-energyA′?A collisions (A>A′, A′ ^1/3?1) and the space-time evolution of the fluid formed in the collision are analysed. The corresponding 1+1 dimensional hydrodynamic equations are set up. The average rapidity distributions are estimated and compared with cosmic ray data. The origin of the unsymmetry of rapidity distributions is explained.     

119Sn and121Sb Mössbauer studies of BaSn1−x Sb x O3 Perovskite system

The relations between the electrical characteristics of BaSn_1?x Sb _x O₃ perovskite system and the contents of BaO, Sb₂O₃ and silicate sintering agent were studied by X-ray diffraction analysis and Mössbauer spectroscopy. It was found that the electrical conductivity is related to the substitution of Sb³⁺ for Sn⁴⁺, the content of sintering agent and the phase constitutents in samples. BaSnO₃, Ba₃Sn₂O₇, Ba₂SnO₄ and SnO₂ phases might appear in different fractions when the contents of BaO change from 0.5 mole to 3.5 mole. In low antimony percentage condition, pentavalent Sb³⁺ ions inserted in Sn⁴⁺ sites and formed the donor center. In high antimony percentage (x≥0.20) condition, the existence of an insulating phase (BaSb₂O₆) was confirmed.     

STURM COMPARISON THEOREM OF SOLUTION FOR SECOND ORDER NONLINEAR DIFFERENTIAL EQUATIONS

In this paper, we establish some differential identities and obtain some Sturm comparison theorems for the second order nonlinear differential equation by using them.and generalize some classicial Sturm comparison theorems.