Studies on the growth aspects of organic L-alanine maleate: a promising nonlinear optical crystal

A organic nonlinear optical material, L-alanine maleate (LALM) was synthesized. Bulk Single crystals of LALM have been grown by slow cooling method with a solution pH of 5. The solubility of L-alanine maleate has been deter-mined for various temperatures. Large size sin-gle crystal of 2.0 x 1.2 x 0.8 cm3 has been grown with reasonable growth rate along the three crystallographic directions by optimizing the growth parameters. The structure of LALM crys- tal was studied by single-crystal X-ray diffrac-tion analysis. The presence of functional groups was confirmed by Fourier transform infrared spectroscopy. The LALM crystal was analysed for its thermal and mechanical behaviours. The grown crystals have also been subjected to linear and non-linear optical property studies. From these studies, it is inferred that the LALM crystals exhibit better thermal and mechanical stabilities with improved optical properties. Thus satisfies the essential requirements for optical device fabrication.

POSTBUCKLING RESPONSE OF CANTILEVER BEAMS OF NON-LINEAR ELASTIC MATERIAL SUBJECTED TO SUBTANGENTIAL FOLLOWER FORCES

This paper deals with the problem of the postbuckling response of a thin cantilever beam ofnon-linear material, subjected to subtangential follower forces. Based on the well-knownBernoulli-Euler bending moment-curvature relation, the proposed problem is reduced to a specialeigenvalue problem of non-linear differential equation. An approximate solution is achieved byusing a simple and very effective technique, which leads to reliable results even in the case of verylarge deflections. The initial postbuckling path depending on the subtangential follower forces inequilibrium is then obtained. Moreover, the individual and coupling effect of the subtangential fol-lower force, the material non-linearity and the beam slenderness ratio on the initial postbucklingpath are also discussed in detail.

Dynamic Response Analysis of Bird Strike on Aircraft Windshield Based on Damage-modified Nonlinear Viscoelastic Constitutive Relation

Damage-modified nonlinear viscoelastic constitutive equation and failure criterion are introduced and the three-dimensional incremental forms are deduced based on the updated Lagrangian approach. A simple tensile test model and a split Hopkinson pressure bar model are built to verify the accuracy of the subroutine implemented within the non-linear finite element program LS-DYNA. A numerical model of bird strike on windshield is established to study the responses of windshield under three different bird velocities at three sites. The bird is represented by a cylinder with a hemisphere at each end and the contact-impact coupling algorithm is used in this study. It is found that the implemented subroutine can properly describe the mechanical behavior of polymethyl methaerylate under low and high strain rates and large deformation, and can be used validly.

Determination of elastic moduli of composite medium containing bimaterial matrix and non-uniform inclusion concentrations

Reservoir porous rocks usually consist of more than two types of matrix materials, forming a randomly heterogeneous material. The determination of the bulk modulus of such a medium is critical to the elastic wave dispersion and attenuation. The elastic moduli for a simple matrix-inclusion model are theoretically analyzed. Most of the efforts assume a uniform inclusion concentration throughout the whole single-material matrix. However, the assumption is too strict in real-world rocks. A model is developed to estimate the moduli of a heterogeneous bimaterial skeleton, i.e., the host matrix and the patchy matrix. The elastic moduli, density, and permeability of the patchy matrix differ from those of the surrounding host matrix material. Both the matrices contain dispersed particle inclusions with different concentrations. By setting the elastic constant and density of the particles to be zero, a double-porosity medium is obtained. The bulk moduli for the whole system are derived with a multi-level effective modulus method based on Hashin＇s work. The proposed model improves the elastic modulus calculation of reservoir rocks, and is used to predict the kerogen content based on the wave velocity measured in laboratory. The results show pretty good consistency between the inversed total organic carbon and the measured total organic carbon for two sets of rock samples.

Room-temperature phosphorescence from purely organic materials

Room-temperature phosphorescence（RTP） materials have attracted great attention due to their involvement of excited triplet states and comparatively long decay lifetimes.In this short review,recent progress on enhancement of RTP from purely organic materials is summarized.According to the mechanism of phosphorescence emission,two principles are discussed to construct efficient RTP materials：one is promoting intersystem crossing（ISC） efficiency by using aromatic carbonyl,heavyatom,or/and heterocycle/heteroatom containing compounds;the other is suppressing intramolecular motion and intermolecular collision which can quench excited triplet states,including embedding phosphors into polymers and packing them tightly in crystals.With aforementioned strategies,RTP from purely organic materials was achieved both in fluid and rigid media.

Discovery of the low temperature phase barium metaborate (BBO) and its significance in the search for new type nonlinear optical materials

1 History of discovery of the low temperature phase barium metaborate （BBO）——an excel-lent new-type ultraviolet radiation frequency-doubling crystalline materialTHE first laser excitation in 1960 with ruby （α-Al2O3: Cr） as a laser crystal and the first dou-bling of frequency （347. 15 nm） in 1961 by irradiating quartz crystal （α-SiO2） with a 694. 3nm laser beam have laid the basis for the study of laser and nonlinear optical （NLO） crystals,

Macroscopic Self-Organized Electrochemical Patterns in Excitable Tissue and Irreversible Thermodynamics

In this paper we make the assertion that the key to understand the emergent properties of excitable tissue (brain and heart) lies in the application of irreversible thermodynamics. We support this assertion by pointing out where symmetry break, phase transitions both in structure of membranes as well as in the dynamic of interactions between membranes occur in excitable tissue and how they create emergent low dimensional electrochemical patterns. These patterns are expressed as physiological or physiopathological concomitants of the organ or organism behavior. We propose that a set of beliefs about the nature of biological membranes and their interactions are hampering progress in the physiology of excitable tissue. We will argue that while there is no direct evidence to justify the belief that quantum mechanics has anything to do with macroscopic patterns expressed in excitable tissue, there is plenty of evidence in favor of irreversible thermodynamics. Some key predictions have been fulfilled long time ago and they have been ignored by the mainstream literature. Dissipative structures and phase transitions appear to be a better conceptual context to discuss biological self-organization. The central role of time as a global coupling agent is emphasized in the interpretation of the presented results.

乙烯基非交联电缆屏蔽料性能与分散剂含量关系研究

非交联绝缘材料具有优异的电气机械性能,同时生产能耗少、可回收利用,成为目前电缆绝缘料的研究热点,但与之匹配的非交联半导电屏蔽料的研究还鲜有报道。导电炭黑的分散性对屏蔽料的性能影响重大。文中选用线性低密度聚乙烯(LLDPE)为基体树脂,白油为分散剂,采用熔融共混法制备了非交联电缆屏蔽料。研究了白油含量对屏蔽料中炭黑分散、结晶性能、体积电阻率和机械性能的影响。结果表明添加白油会促进炭黑的分散,但白油含量过大会降低屏蔽料的结晶度,增加其体积电阻率并降低拉伸强度和断裂伸长率。当白油含量为2 wt%时,屏蔽料体积电阻率最小,力学性能最佳。该研究为非交联半导电屏蔽料在乙烯基非交联电缆的应用研究提供了参考。

基于自动微分的桁架结构材料非线性分析

基于深度学习技术,提出一种基于自动微分技术的桁架结构材料非线性问题求解方案。以各杆件的位移参数作为优化变量,采用随机算法初始化杆件位移,并对结构荷载分段。在每个荷载段中,先通过几何关系由位移参数求得杆件的应变,并由材料的本构关系计算出各杆件的应力,由节点力平衡方程构建损失函数。为了使得损失函数最小,再结合自动微分技术,构建损失函数与节点位移的计算图,以快速求解损失函数关于结点位移的梯度。最后,根据梯度下降法对杆件位移进行迭代优化,直至满足收敛条件。以桁架结构作为研究对象,基于线性强化模型,求解了不同桁架的材料非线性问题,并将计算结果与有限元解进行对比。结果表明,此方案在弹塑性问题分析中的可行性,且求解结果具备较高的精度。

非齐次线性方程组在求解最优玻璃料方中的应用

浮法玻璃生产中料方成分的变更或波动对成品玻璃质量有显著的影响。通过解析原料及其所含化合物的数据结构,确定各种原料的用量,挖掘最接近目标料方的优化方案,是浮法玻璃料方计算领域中的重要研究内容。研究发现,原料及其所含化合物、目标料方可用非齐次线性方程组的系数矩阵、常数项列向量表示,计算最优料方中各原料的用量问题可以转化为非齐次线性方程组求解。在方程组有解的情况下,求解得到最优料方;在方程组无解但有最优解的情况下,通过搭配使用非齐次线性方程组和最小二乘法可以求解最优料方。此计算方案能维持或提高料方计算结果的精度,同时也能提高原料工程师在计算料方中的工作效率,从而产生实际的经济效益,可广泛应用于浮法玻璃料方计算。

Simple non-fullerene electron acceptors with unfused core for organic solar cells

Two simple electron acceptors based on unfused bithiophene core and 1,1-dicyanomethylene-3-indanone end group were easily prepared via three synthetic steps. These acceptors exhibited broad absorption in the range of 300 nm to 800 nm, aligned energy levels and high crystallinity. When combined with a wide band gap donor polymer in non-fullerene solar cells, an initial power conversion efficiency of 2.4% was achieved. The relatively low efficiencies were due to the large phase separation in blended thin films, which is originated from their high aggregation tendency in thin films. Our results suggest that these electron acceptors with unfused core are promising candidates for commercial application of solar cells due to the low cost starting materials and facile synthesis.

金属有机框架及其复合材料在葡萄糖无酶电化学传感器中的应用

糖尿病是全球发病率上升最快的慢性病之一,有效监测糖尿病患者的血糖水平对于糖尿病的控制与治疗至关重要。电化学方法作为众多血糖监测技术中的一种,因其简便性、快速响应和高灵敏度而受到青睐。传统的贵金属材料具有独特的物理化学性质,在葡萄糖检测中表现出良好的传感能力,但高昂的成本阻碍了其用作基础电化学传感材料。相较而言,过渡金属在自然界中储备量大、化学性质稳定、制备工艺简单,因此在葡萄糖传感领域中表现出一定的应用潜力,现已成为主流的研究方向。金属有机框架(MOF)是由过渡金属离子和有机配体组成的多孔配位聚合物,其独特的结构多样性、高比表面积和生物相容性,使其在传感器领域中表现出巨大的潜力。特别是,近年来通过对MOF进行调节,如合成双金属MOF、MOF与导电材料相复合等,提高MOF及其复合材料的电化学活性,实现在无酶参与情况下对葡萄糖的电催化氧化,这在无酶传感器的研发中尤为重要。总结了近年来MOF及其复合材料在葡萄糖无酶传感器中的应用,包括单金属MOF、双金属MOF、MOF与金属相复合材料、MOF与碳材料相复合材料等。阐述了MOF及其复合材料检测葡萄糖的机理,讨论了各类MOF基葡萄糖传感器的优缺点。最后,指出了MOF葡萄糖无酶传感器材料存在的问题,同时对MOF在未来葡萄糖无酶传感器中的发展作出了展望。

Scale, Complexity, and Cybersecurity Risk Management

Elementary information theory is used to model cybersecurity complexity, where the model assumes that security risk management is a binomial stochastic process. Complexity is shown to increase exponentially with the number of vulnerabilities in combination with security risk management entropy. However, vulnerabilities can be either local or non-local, where the former is confined to networked elements and the latter results from interactions between elements. Furthermore, interactions involve multiple methods of communication, where each method can contain vulnerabilities specific to that method. Importantly, the number of possible interactions scales quadratically with the number of elements in standard network topologies. Minimizing these interactions can significantly reduce the number of vulnerabilities and the accompanying complexity. Two network configurations that yield sub-quadratic and linear scaling relations are presented.

新型有机非线性光学分子MC-FTC的合成

设计和合成了一种新型的有机非线性光学分子 ,2 二氰基甲叉 3 氰基 4 [2 (N ,N 二 乙酰氧基乙基氨基苯乙烯基 ) 3 正丁基噻吩基 5 乙烯基 ] 5 ,5 二甲基 2 ,5 二氢呋喃 (MC FTC) .报道了它的详细合成方法 ,给出了反应路线和产物及各个中间体的化学结构 ,并通过IR ,UV/Vis ,NMR 。

酞菁及相关化合物在非线性光学中的应用

酞菁 (PcS)及其相关化合物具有二维 1 8π电子离域体系 ,它是研究非线性光学响应的重要目标化合物 .这些大环具有可裁剪性 ,可对酞菁的化学结构和非线性光学响应进行调制 .在分子水平上对酞菁进行分子设计做了较为全面地综述 ,并综述了酞菁的二阶和三阶非线性 (NLO)性质 ,以及在光限制方面的应用 .

行波效应下大跨钢管混凝土拱桥的非线性地震响应分析

对大跨度钢管混凝土拱桥在三维地震激励下进行了非线性时程分析。几何非线性分析采用修正拉格朗日描述(U.L列式法),材料非线性采用钢管混凝土统一理论并考虑等效紧箍力,通过对某大跨度钢管混凝土拱桥的非线性地震响应分析,研究了几何非线性、材料非线性、阻尼比及行波效应对拱桥地震响应的影响。结果表明:几何非线性对钢管混凝土拱桥地震响应的影响程度与结构的地震响应幅度有关;阻尼比和行波效应对钢管混凝土拱桥地震响应的影响是显著的;材料非线性对拱肋位移和轴力的影响较小,但对拱肋的面内外弯矩影响较大。

换流变压器出线装置电场分布与绝缘结构优化

在复合电压作用下,换流变压器出线装置的电场分布不均匀。为此,根据实际结构建立了电场仿真模型,分析出线装置在交流、直流及极性反转电压作用下的电场分布,以及温度对其电场分布的影响。采用非线性绝缘材料并通过几何形状优化法实现了对出线装置电场分布的均化。研究表明:交流电压下,出线装置上的最大电场强度出现在均压球附近的油隙中;直流电压下,出线装置的最大电场强度出现在均压球上表面的绝缘层中。在极性反转电压下,由于空间电荷的作用,变压器油承担较高的电场强度。随着温度的降低,变压器油和绝缘纸板中的电场分布越趋不均匀,采用非线性绝缘材料可有效改善出线装置中的电场分布。

开挖过程的非线性理论分析

本文从岩土介质力学非线性和变形破坏过程自组织非线性的角度对开挖过程岩土体非线性行为进行了探讨。以此为依据，分析了岩土从微观破坏、滑移面形成、直至整体变形破坏全过程的自组织发生机理，在此基础上，建立了伴随开挖过程岩土体变形破坏的非线性动力学描述方程。

衬底负偏压对线性离子束DLC膜微结构和物性的影响

采用一种新型线性离子束PVD技术制备出大面积类金刚石薄膜(DLC膜),研究了衬底负偏压对薄膜微结构和物性的影响.结果表明:制备出的类金刚石薄膜在300 mm×100 mm范围内纵向厚度均方差约10-12 nm,横向薄膜厚度均方差约2-4 nm.随着衬底偏压的提高,薄膜中sp^3键的含量先增加后减小,在衬底偏压为-100 V时sp^3键的含量最大;DLC膜的残余应力、硬度和弹性模量与sp^3键的含量呈近似线性的关系,在衬底偏压为-100 V时其最大值分别为3.1 GPa、26 GPa和230 GPa.DLC薄膜的摩擦学性能与薄膜中sp^3碳杂化键的含量密切相关,但是受衬底偏压的影响不大,其摩擦系数大多小于0.25.偏压对磨损的影响很大,在偏压比较低(0～-200 V)时,薄膜的磨损率约为10^(-8)mm^3/N·m,偏压升高到300 V磨损率急剧提高到10^(-7)mm^3/N·m.

植物花后光合性能与物质转运的研究进展

植物花后光合性能及物质运转对籽粒产量具有重要贡献,在植物整株物质生产中具有重要价值。本文重点从植物花后叶绿素的含量、绿色非叶器官的结构与功能、花后叶片和绿色非叶器官的光合性能及其物质运转等方面综述了花后植物的光合性能及物质转运的研究进展。研究植物花后不同冠层或穗位光合同化物的生产及转运情况,明确植物花后绿色非叶器官的光合途径及机制,可以为植物高产或超高产研究提供理论依据,进一步了解其对储藏过程中种子老化劣变的影响,为解决粮食及种子储藏问题探寻新思路。