Stretched exponential kinetics for photoinduced birefringence in azo dye doped PVA films

We fabricated azo dye (methylorange) doped poly vinyl alcohol (MO/PVA) thin films and measured the photoinduced birefringence (PIB) kinetics for several pump beam intensities and for various MO concentrations by using the pump-probe technique. A novel approach to explain the transient behaviors of the photoinduced anisotropy is presented by employing an empirical stretched exponential time response in the course of the trans-cis-trans photoisomerization of azo molecules and is compared with the experimental data, showing excellent agreement. The stretched exponent is estimated to be β = 0.34 ± 0.04, revealing amorphous nature of the MO/PVA system.     

Bonding and correlation analysis of various Si2CO isomers on the potential energy surface

At various levels of theory, singlet and triplet potential energy surfaces (PESs) of Si₂CO, which has been studied using matrix isolation infrared spectroscopy, are investigated in detail. A total of 30 isomers and 38 interconversion transition states are obtained at the B3LYP/6‐311G(d) level. At the higher CCSD(T)/6‐311+G(2d)//QCISD/6‐311G(2d)+ZPVE level, the global minimum ¹1 (0.0 kcal/mol) corresponds to a three‐membered ring singlet O‐cCSiSi (¹A′). On the singlet PES, the species ¹2 (0.2 kcal/mol) is a bent SiCSiO structure with a ¹A′ electronic state, followed by a three‐membered ring isomer Si‐cCSiO (¹A′) ¹3 (23.1 kcal/mol) and a linear SiCOSi ¹4 (¹Σ⁺) (38.6 kcal/mol). The isomers ¹1, ¹2, ¹3 , and ¹4 possess not only high thermodynamic stabilities, but also high kinetic stabilities. On the triplet PES, two isomers ³1 (³B₂) (18.8 kcal/mol) and ³7 (³A″) (23.3 kcal/mol) also have high thermodynamic and kinetic stabilities. The bonding natures of the relevant species are analyzed. The similarities and differences between C₃O, C₃S, SiC₂O, and SiC₂S are discussed. The present results are also expected to be useful for understanding the initial growing step of the CO‐doped Si vaporization processes. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Synthesis and positive inotropic evaluation of 1-(benzylamino)-3-(4,5-di-hydro[1,2,4]trizaolo[4,3-a]quinolin-7-yloxy)propan-2-ol derivatives

In an attempt to search for more potent positive inotropic agents,a series of 1-(benzylamino)-3-(4,5-dihydro[1,2,4]trizaolo[4,3- a]quinolin-7-yloxy)propan-2-ol derivatives was synthesized in four steps using 6-hydroxy-3,4-dihydro-2(1H)-quinolinone as a starting material,and their positive inotropic activities were evaluated by measuring the coronary blood flow(CBF)and the left ventricular pressure(LVP)followed by calculating the rate of pressure development(dp/dt_(max)values)in the preparation of rat Lan...     

$CP(n)\times CP(m)$上向量丛的全Stiefel-Whitney类

The possible form of the total Stiefel-Whitney classes of vector bundles on CP（n） × CP（m） is determined in this paper.     

Global Well-Posedness for Navier–Stokes Equations with Small Initial Value in $${B^{0}_{n,\infty}(\Omega)}$$

We prove global well-posedness for instationary Navier–Stokes equations with initial data in Besov space \({B^{0}_{n,\infty}(\Omega)}\) in whole and half space, and bounded domains of \({{\mathbb R}^{n}}\), \({n \geq 3}\). To this end, we prove maximal \({L^{\infty}_{\gamma}}\) -regularity of the sectorial operators in some Banach spaces and, in particular, maximal \({L^{\infty}_{\gamma}}\) -regularity of the Stokes operator in little Nikolskii spaces \({b^{s}_{q,\infty}(\Omega)}\), \({s \in (-1, 2)}\), which are of independent significance. Then, based on the maximal regularity results and \({b^{s_{1}}_{q_{1},\infty}-B^{s_{2}}_{q_{2,1}}}\) estimates of the Stokes semigroups, we prove global well-posedness for Navier–Stokes equations under smallness condition on \({\|u_{0}\|_{B^{0}_{n,\infty}(\Omega)}}\) via a fixed point argument using Banach fixed point theorem.     

Mechanism of Electrospinning for Poly(amic acid)/Polyacrylonitrile Fiber Fabrication

A poly(amic acid) (PAA) solution in xylene was prepared for electrospinning in order to fabricate fibers. However, jet breaking occurred at the point of the occurrence of whipping instability, resulting in forming micro-particles. This was an exceptional jet behavior compared with the general electro-spraying process that occurs directly from the surface of the polymer droplet. It is important to understand the mechanism of electrospinning and the instability of PAA in order to form fibers for mat deposition. Thus, the behavior of the jet breaking was clearly observed by a high-speed camera and the dynamic behavior of the jet was explored by an image analysis technique. Furthermore, polyacrylonitrile (PAN) was added to the PAA/xylene solution with various concentrations to change the elongation viscosity. Uniform diameter fibers were obtained by increasing the content of PAN to the level that the drag force between the polymer chains increased enough to overcome the drawing force. As a result the optimum content ratio of the PAA/PAN mixed solution to obtain the desired fiber spinning and deposition was determined as being 5:5.     

冰浆在蓄冰槽内的蓄冰特性及其均匀度研究

对动态冰蓄冷中蓄冰槽蓄冰过程的动态特性进行实验研究,分析了影响蓄冰形成富冰层形状变化的参数:入口冰浆流量、固相含量、初始液面高度及入口管布置。分析实验结果,总结实验规律表明:冰浆流量与固相含量对富冰层变形影响较大,其它因素次之;增大上述两参数能够有效提高堆积富冰层的均匀性,提高蓄冰槽的有效利用率。     

In situ Reaction and Radiation Protection Properties of Gd(AA)3/NR Composites

Summary: For the first time, a series of Gd(AA)₃/NR (natural rubber) composites for X‐ray shielding were prepared by an in situ reaction method. Occurrence of the in situ polymerization of Gd(AA)₃ in composites during vulcanization of NR with peroxide greatly improves the dispersion level of the shielding phase by the remarkable reduction of Gd(AA)₃ particle size and the formation of small sized poly‐Gd(AA)₃ from the matrix. As expected and assumed, the X‐ray shielding properties of all composites apparently increase with the increase of the degree of dispersion of Gd(AA)₃ in composites.

The ability of the composites to shield X‐ray radiation increases with an increase in Gd(AA)₃ content and as the degree of in situ polymerization of Gd(AA)₃ increases (i.e., as t tends towards t₁₀₀).     

挖掘机工作载荷谱识别方法研究

为了快速准确地识别挖掘机等工程机械的工作载荷谱,基于时域内动应变响应与载荷的关系,提出一种新的工作载荷谱识别方法。首先,采集工作中的挖掘机结构上若干测点工作应变谱;其次建立有限元模型,通过有限元方法计算挖掘机在各种可能外载的单位载荷下的应变;最后,建立实测响应与数值模拟测点单位应变之间的关系,通过时间迭代求解结构响应与载荷间关系的线性方程组得到工作载荷谱。为说明方法的实用性和有效性,通过在结构上选择的7个基底测点的假设应变谱和数值模拟单位应变,获得挖掘机样机的工作载荷谱。文章最后讨论了在本文所提方法基础之上求解结构关键位置疲劳应力的方法。     

Multiple peak recordings in flow injection analysis

The quality and level of the information provided by conventional flow-injection systems can readily be enhanced by simple modifications. The different possibilities available for obtaining several peaks per injected sample are reviewed. Among the topics are simultaneous and sequential multidetection, multicomponent determinations (including speciation), reaction-rate methods, and automatic amplification of conventional analyte concentration ranges.