The effects of HALS in the prevention of photo-degradation of acrylic clear topcoats and wooden surfaces

A study of the photocatalytic degradation of an acrylic dispersion based coating and its prevention using hindered amine light stabilizers (HALS) was carried out on solid films by exposing them to Xenon arc light. The degradation rates were compared using FTIR-ATR techniques by plotting the differential build up of the hydroxyl and hydroperoxide bands as function of exposure time. UV-Vis spectroscopic studies were carried out as well to obtain data about the light stabilization of organic UV Absorbers (UVA) and inorganic UV screeners by HALS. The effectiveness of an aqueous primer comprising a specific lignin stabilizing HALS in combination with clear topcoats with UVA or UV screeners in the prevention of photo-induced discolouration of wooden surfaces was investigated by measuring the colour change during exposure time. It was shown, that the usage of HALS was effective in reducing the degradation speed of clear coats with UVA and UV screeners. Results obtained by UV-Vis spectroscopic analysis during the exposure cycle showed an inhibition of the photo-degradation of the UVA themselves, while no positive effect occurred on inorganic UV screeners. A lignin stabilizer containing aqueous primer with a specific HALS as active component, showed some promising results in combination with transparent topcoats comprising organic UVA and inorganic UV screeners, except ZnO, where a strong antagonistic effect occurred.     

修饰β-环糊精／4-（N，N-二甲氨基）-苯甲酸-2′-乙基己基酯笼型包结物研究

用分子光谱法研究了甲基-β-环糊精(M-CD)和羟丙基-β-环糊精(HP-CD)与4-(N,N-二甲氨基)-苯甲酸-2′-乙基己基酯(EHDAB)分子间的包结作用.结果表明,柔性的2′-乙基己基和刚性的芳香端都包结在M-CD和HP-CD空腔中,形成了2∶1笼型主-客体包结物.疏水性2′-乙基己基在包结物的热力学稳定性中起重要作用,亲水性M-CD和HP-CD将EHDAB增溶在水中,提高了EHDAB分子的紫外吸收程度,M-CD和HP-CD空腔抑制了光诱导EHDAB分子内扭转电荷转移,显著提高了EHDAB的光化学稳定性,增强了其抗氧化性,降低了酸碱性水解程度,包结物的热稳定性与所用主体环糊精相当.     

An elastic oscillation model for goods in a shortage market

I.IntroductionTheelasticrelation.elasticreplacementandgenerallyelastictheor}'amonggoods,sincetheconceptofelasticit}'ineconomicswasintroducedbyK.Marxeinthemiddleoflastcentury,havebeenlargel}'andwidelydiscussed.Fromthephysicalfact.thevariouskindsofelasticit…     

On the Design of the Piecewise Linear Vibration Absorber

This paper explores the potential of the piecewise linearvibration absorber in a system subject to narrow band harmonic loading.Such a spring is chosen because the design of linear springs is commonknowledge among engineers. The two-degrees-of-freedom system is solvedby using the Incremental Harmonic Balance method, and response aspectssuch as stiffness crossing frequency and jump behaviour are discussed.The effects of mass, stiffness, natural frequency ratios, and stiffnesscrossing positions on the suppression zone are probed. It is shown thata hardening absorber can deliver a wider bandwidth than a linear oneover a range of frequencies. The absorber parameters needed to producegood designs have been determined and the quality of the realizedsuppression zone is discussed. Design guidelines are formulated to aidthe parameter selection process.     

多极板电流变阀应用于避震器之研究

以流动模式(flow mode)多极板之电流变阀(electrorheological valve) 进行避震器阻尼力特性的研究.由于电极板的大小直接影响到流体流动的剪力及避震器的阻尼力,因此使用多极板型式来探讨避震器的特性.设计有1～5个流道之并联及1～3个流道之串联多极板电流变阀的电流变避震器,并使用自制的电流变液进行实验.由研究结果显示,流动式并联极板之电流变避震器,一个流道之阻尼力最大,流道极板增加则阻尼力反而下降,而流动式串联多极板之电流变避震器之阻尼力则随极板数递增,故需要高阻尼力之避震器较适合使用串联多极板型式.     

GeSe基薄膜太阳电池模拟研究

硫化亚锗(GeSe)具有合适的禁带宽度、高的吸收系数和高的载流子迁移率等优异的光电特性,且组分简单、低毒和储量丰富,特别适合作为光伏吸收材料。本文基于新型太阳电池吸收层材料GeSe构筑了结构为金属栅线/AZO/i-ZnO/CdS/GeSe/Mo/玻璃的薄膜太阳电池,分别模拟分析了缓冲层和吸收层的厚度、掺杂浓度,以及吸收层体缺陷密度对器件性能的影响。经过优化CdS缓冲层厚度和掺杂浓度以及GeSe吸收层厚度和掺杂浓度,器件获得高达27.59%的转换效率。这些结果表明GeSe基薄膜太阳电池有成为高效光伏器件的潜力。     

混合谐振模式宽带长波红外超表面吸收器研究

为了满足红外探测器件集成化和对红外宽光谱范围吸收的需求,设计了一种工作在长波红外波段(8~14μm)的超宽带、高吸收、极化不敏感的超材料吸收器。通过在金属-介质-金属三层异质的超材料吸收器结构的顶部金属周围镶嵌一层介质形成超表面,以增加谐振强度和吸收带宽。在8~13.6μm的带宽范围内,该结构有超过90%的平均吸收率,覆盖了大部分长波红外大气窗口波段,对红外探测领域有着重要意义。研究结果表明:镶嵌的金属-介质组成的介质波导模式和谐振腔模式的结合以及传播型表面等离激元模式的激发是形成宽带高吸收的主要原因,并且谐振模式的谐振波长可以通过相关参数来进行调控。本文的研究结果为可调谐宽带长波红外吸收材料的设计提供参考,该设计方法可推广到中波红外波段、甚至长波红外或其它波段。     

基于少模光纤被动调Q柱矢量光光纤激光器

通过单模光纤和少模光纤熔融拉锥耦合的方法制备出模式转换器,而后将一层多壁的碳纳米管薄膜作为可饱和吸收体覆盖到拉锥光纤的锥区,形成一种可饱和吸收体柱矢量光器件.结合调Q光纤激光器和模式转换器件的优势,可以简单高效地产生脉冲柱矢量光束,并得到具有峰值功率高、模式纯度高等特点的脉冲高阶模式激光输出.通过实验实现了中心波长为1560nm、最大单脉冲能量和最大峰值功率分别为116nJ和57mW的稳定调Q脉冲输出.通过调节光路中的偏振控制器,可以分别实现径向和角向偏振的调Q脉冲激光的输出.     

Simulation of nonlinear optical absorption in ZnSe:Co crystals

The paper presents theoretical approach to simulation of nonlinear optical absorption in zinc selenide crystals doped with cobalt (II) ions (ZnSe:Co²⁺), which was reported by us earlier (Opt. Laser Technology, V. 35, (2003), 169). We used ZnSe:Co²⁺ crystals as saturable absorbers for generation of giant-pulse eye-safe laser radiation. It was found that minimal optical losses (maximal final transmission) occurred for ZnSe samples containing 1.6×10¹⁹ cm⁻³ of Co²⁺ ions. Band structure and photoinduced molecular dynamics simulations were performed to explain the parabolic dependence of optical losses versus Co²⁺ concentration. The minimum was shown to be the result of photoinduced anharmonic electron–phonon interaction.     

含负克尔效应半导体可饱和吸收镜的五镜腔飞秒钛宝石激光器的理论分析

基于半导体可饱和吸收镜(SESAM)的负克尔效应，对含SESAM的五镜腔进行了理论计算和分析.结果表明，由于SESAM的负克尔效应，与没有SESAM的相比，锁模激光器的稳区在上稳区的内边缘有明显扩展，这使得激光器锁模启动的工作点更加靠近直流运转时的稳区边缘，从而获得更大的非线性因子.这说明SESAM的可饱和吸收机理具有锁模自启动效应外，其负克尔效应也有助于锁模的自启动. 关键词： 半导体可饱和吸收镜 负克尔效应 五镜腔