A Ginzburg–Landau model for material aging depending on temperature

ABSTRACT

We consider a model describing the behavior of a body subject to aging and fatigue. These phenomena are supposed to be affected by both mechanical and thermal effects. The material is assumed to be viscoelastic where the stress–strain relation is based on a new fractional derivative proposed in Caputo and Fabrizio. The order of derivative is regarded as a new variable whose evolution is ruled by a Ginzburg–Landau equation. The model also includes an evolutive equation for the temperature deducing from the first law of thermodynamics. In this article, thermodynamic compatibility is shown and some numerical simulations are performed.     

含分数阶导数项的随机Duffing振子的稳态响应分析

本文对一个含有分数阶导数项阻尼的、Gaussian白噪声激励下的Duffing振子进行了稳态响应分析。首先,基于能量平衡理论,运用等效线性化方法,计算等效系统的线性阻尼及自然频率,建立统计意义下的等效线性化系统。然后,利用平均法建立随机Ito方程,得到随机响应的Markovian近似;给出描述振子振幅概率密度函数演化的Fokker-Planck方程,并得到它的稳态解。进一步,对于含有响应振幅的等效线性系统,借助由Laplace变换得到的转换函数,得到原系统的条件功率谱密度,结合振幅的稳态概率密度作为权重函数,给出原系统功率谱密度的估计,以及响应的统计量的估计。数值模拟的结果说明所提出的功率谱密度的近似解析表达式是可靠的,它甚至适用于Duffing振子具有强非线性回复力的情形,因为它可以较好的表现出功率谱密度共振频谱加宽及多峰现象的出现。     

硅氧树脂 Si-O 键伸缩振动模式ATR红外光谱研究

在303~393 K 温度范围内,采用变温傅里叶变换衰减全反射红外光谱(ATR-FTIR)技术分别测定硅氧树脂的一维红外光谱、二阶导数红外光谱和四阶导数红外光谱。研究发现,在1800~600 cm-1范围内,聚硅氧树脂主要存在着 CH 3伸缩振动模式(νCH3)、CH 3变形振动模式(δCH3)、CH 3摇摆振动模式(ρCH3)、Si-O 伸缩振动模式(νSi-O )和 Si-C 伸缩振动模式(νSi-C )。在1100~1000 cm-1范围内,以νSi-O 为研究对象,研究了温度对硅氧树脂分子结构的影响。实验发现,随着测定温度的升高,硅氧树脂νSi-O 的主要红外吸收频率出现了明显的红移现象。进一步研究了硅氧树脂νSi-O 的二维红外光谱,考查温度对于νSi-O 红外吸收强度的影响。研究发现,随着测定温度的升高,硅氧树脂νSi-O 红外吸收强度的变化快慢顺序为：1024 cm-1>1096 cm-1>1010 cm-1>1076 cm-1>1083 cm-1>1064 cm-1。本研究拓展了 ATR-FTIR 技术在硅氧树脂材料热变性方面的研究范围。     

Controlling the Chromaticity of Small‐Molecule Light‐Emitting Electrochemical Cells Based on TIPS‐Pentacene

This work demonstrates a novel proof‐of‐concept to implement pentacene derivatives as emitters for the third generation of light‐emitting electrochemical cells based on small‐molecules (SM‐LECs). Here, a straightforward procedure is shown to control the chromaticity of pentacene‐based lighting devices by means of a photoinduced cycloaddition process of the 6,13‐bis(triisopropylsilylethynyl) (TIPS)‐pentacene that leads to the formation of anthracene‐core dimeric species featuring a high‐energy emission. Without using the procedure, SM‐LECs featuring deep‐red emission with Commission Internationale d'Eclairage (CIE) coordinates of x = 0.69/y = 0.31 and irradiance of 0.4 μW cm^?2 are achieved. After a careful optimization of the cycloaddition process, warm white devices with CIE coordinates of x = 0.36/y = 0.38 and luminances of 10 cd m^?2 are realized. Here, the mechanism of the device is explained as a host–guest system, in which the dimeric species acts as the high‐energy band gap host and the low‐energy bandgap TIPS‐pentacene is the guest. To the best of the knowledge, this work shows the first warm white SM‐LECs. Since this work is based on the archetypal TIPS‐pentacene and the photoinduced cycloaddition process is well‐knownfor any pentacenes, this proof‐of‐concept could open a new way to use these compounds for developing white lighting sources.     

比值导数波谱法在食品混合色素检测中的应用

探讨比值导数波谱法中相同除数因子下的不同零交点波长对食品混合色素检测的影响。用此法对柠檬黄、胭脂红及亮蓝等色素组成的三混体系进行分析 ,结果为平均回收率为 98.8%～ 10 5 .8% ,RSD为 0 .0 1%～ 5 .3 9%。说明不同零交点波长的检测结果无显著性差异。     

Novel translinear differential implementation of rational functions with squared denominators

This paper presents a novel generic translinear differential output stage that is useful for the implementation of rational functions with a squared denominator. As a proof of concept, such output stage is used to implement the first derivative of a rational activation function. Simulated results are presented for an implementation on a 0.35 µm CMOS process showing an almost perfect fit with the theoretical expressions. Copyright © 2013 John Wiley & Sons, Ltd.     

二聚脂肪酸应用研究进展

介绍了二聚脂肪酸的化学结构及其物理和化学性质,并对国内外二聚脂肪酸的制备、其衍生物的合成及应用研究进展进行了综述。建议我国应重视和加强二聚酸及其衍生物的开发应用研究,在借鉴国外应用研究的基础上,提出了目前应重视的研究领域和行业,以提高我国二聚酸及其衍生物的研究开发水平。     

具有甜味抑制作用的2-(4-甲氧基苯氧基)丙酸衍生物的构效关系

2-(4-甲氧基苯氧基)丙酸（2-(4-methoxyphenoxy) propionic acid,HPMP）是一种应用广泛的高效甜味抑制剂,但其构效关系尚不清晰。本实验旨在研究HPMP苯环对位疏水基团的变化对甜味抑制效果的影响,为探索新型甜味抑制化合物提供理论依据,以期改善高能食品、运动食品、传统高糖食品的食用品质。本实验合成HPMP及其4 种衍生物,构建甜味抑制效果的电子舌评价方法,考察HPMP及其衍生物对蔗糖、果糖、木糖醇、山梨糖醇甜度的影响。结果表明,电子舌能够反映HPMP的甜味抑制规律,其结果与感官评价结果具有良好的相关性,可作为甜味抑制效果的评价工具。HPMP及其衍生物对4 种甜味剂都有一定的甜味抑制作用。当不同的烷氧基修饰对位时,电子舌甜度抑制率随取代基体积的增大逐渐降低,甲基、氯原子等较小的疏水性基团修饰的衍生物在甜味抑制方面与HPMP效果相当,推测对位疏水取代基的空间体积大小是影响甜味抑制效果的关键因素。     

POSS-enhanced shape-memory copolymer of polynorbornene derivate and polycyclooctene through ring-opening metathesis polymerization

A copolymer consisting of polycyclooctene (PCOE) and poly(5-norbornene-exo,exo-2,3-dicarboxylic anhydride) (PNBEDCA) was firstly synthesized through ring-opening metathesis polymerization, and then the obtained copolymer P(COE-co-NBEDCA) was readily modified by grafting reaction of NBEDCA units with polyhedral oligomeric silsesquioxanes (POSS) to afford a novel functionalized copolymer P(COE-co-NBEDCA-g-POSS), in which carboxyl and POSS as side chains attached to polynorbornene backbones. The copolymers were characterized by means of thermogravimetry, wide-angle X-ray diffraction, and stress–strain measurements. The shape memory effect of the copolymer was evaluated by dynamical mechanical analysis and shape recovery speed. Having the properties of the good shape fixity and the large shape recovery, the POSS-enhanced copolymer is expected to use as a potential shape memory material.     

Identification of (-)(E)-N-[2(S)-Hydroxy-2-(4-hydroxyphenyl) ethyl]ferulamide, a natural product isolated from Croton pullei: theoretical and experimental analysis

Ferulic acid (FA) and its derivatives (FADs) are known for a variety of biological activities, such as photo-protective agent, antioxidant, antiatherogenic and antiplasmodial activities. During structural definition of a FAD isolated from Croton pullei, the possibility of a heterologous series made this definition difficult. In this regard, computational simulations were performed using theoretical calculations at DFT level to predict Infrared (IR) and Nuclear Magnetic Resonance (NMR) data. The IR and NMR (13)C and (1)H data were compared with the theoretical calculations performed for three structural possibilities of a heterologous series. The theoretical results were compared with the experimental data through linear regression in order to define the most probable structure and showed satisfactory values.