Stability analysis of a liquid crystal elastomer self-oscillator under a linear temperature field

Self-oscillating systems abound in the natural world and offer substantial potential for applications in controllers,micro-motors,medical equipments,and so on.Currently,numerical methods have been widely utilized for obtaining the characteristics of self-oscillation including amplitude and frequency.However,numerical methods are burdened by intricate computations and limited precision,hindering comprehensive investigations into self-oscillating systems.In this paper,the stability of a liquid crystal elastomer fiber self-oscillating system under a linear temperature field is studied,and analytical solutions for the amplitude and frequency are determined.Initially,we establish the governing equations of self-oscillation,elucidate two motion regimes,and reveal the underlying mechanism.Subsequently,we conduct a stability analysis and employ a multi-scale method to obtain the analytical solutions for the amplitude and frequency.The results show agreement between the multi-scale and numerical methods.This research contributes to the examination of diverse self-oscillating systems and advances the theoretical analysis of self-oscillating systems rooted in active materials.

Liquid crystal-integrated metasurfaces for an active photonic platform

Metasurfaces have opened the door to next-generation optical devices due to their ability to dramatically modulate electromagnetic waves at will using periodically arranged nanostructures.However,metasurfaces typically have static optical responses with fixed geometries of nanostructures,which poses challenges for implementing transition to technology by replacing conventional optical components.To solve this problem,liquid crystals(LCs)have been actively employed for designing tunable metasurfaces using their adjustable birefringent in real time.Here,we review recent studies on LCpowered tunable metasurfaces,which are categorized as wavefront tuning and spectral tuning.Compared to numerous reviews on tunable metasurfaces,this review intensively explores recent development of LC-integrated metasurfaces.At the end of this review,we briefly introduce the latest research trends on LC-powered metasurfaces and suggest further directions for improving LCs.We hope that this review will accelerate the development of new and innovative LC-powered devices.

ENERGY CONSERVATION FOR THE WEAK SOLUTIONS TO THE 3D COMPRESSIBLE NEMATIC LIQUID CRYSTAL FLOW

In this paper,we establish some regularity conditions on the density and velocity fields to guarantee the energy conservation of the weak solutions for the three-dimensional compressible nematic liquid crystal flow in the periodic domain.

THE EXISTENCE AND UNIQUENESS OF TIME-PERIODIC SOLUTIONS TO THE NON-ISOTHERMAL MODEL FOR COMPRESSIBLE NEMATIC LIQUID CRYSTALS IN A PERIODIC DOMAIN

In this paper,we are concerned with a three-dimensional non-isothermal model for the compressible nematic liquid crystal flows in a periodic domain.Under some smallness and structural assumptions imposed on the time-periodic force,we establish the existence of the time-periodic solutions to the system by using a regularized approximation scheme and the topological degree theory.We also prove a uniqueness result via energy estimates.

Multi-dimensional multiplexing optical secret sharing framework with cascaded liquid crystal holograms

Secret sharing is a promising technology for information encryption by splitting the secret information into different shares.However,the traditional scheme suffers from information leakage in decryption process since the amount of available information channels is limited.Herein,we propose and demonstrate an optical secret sharing framework based on the multi-dimensional multiplexing liquid crystal(LC)holograms.The LC holograms are used as spatially separated shares to carry secret images.The polarization of the incident light and the distance between different shares are served as secret keys,which can significantly improve the information security and capacity.Besides,the decryption condition is also restricted by the applied external voltage due to the variant diffraction efficiency,which further increases the information security.In implementation,an artificial neural network(ANN)model is developed to carefully design the phase distribution of each LC hologram.With the advantage of high security,high capacity and simple configuration,our optical secret sharing framework has great potentials in optical encryption and dynamic holographic display.

基于不确定度评估研究ID-LC-MS/MS法检测鸡蛋中氟虫腈砜残留量的关键控制点

为了控制检测结果准确性,以鸡蛋粉中氟虫腈砜残留分析标准物质[GBW(E)100779]为测试样,采用“自下而上”法对基于多功能净化柱(PAC柱)净化的同位素稀释液相色谱串联质谱(ID-LC-MS/MS)法进行测量不确定度评估。“鱼骨图”分析表明,不确定度分量主要来源有样品称样量、内标溶液添加体积、标准工作溶液浓度及其移取体积。内标溶液添加体积引入的不确定度最大,对检测结果不确定度的贡献率为68.59%;万分之一天平称量引入的不确定度可忽略不计。同位素内标的添加过程是ID-LC-MS/MS法检测的关键控制点,参考基准的合理选择和目标物的完全提取是准确测量的前提。进一步用LC-MS/MS法对参考物质、稀释剂和内标溶液的适用性进行了评估,并基于国家有证标准物质[GBW(E)100779]对提取方法进行了优化。研究结果有利于提升鸡蛋食品安全的检测质量和质控水平,为精准检测质控方案的设计提供新思路。

HPLC及LC-MS测定榛子中氯吡苯脲和多菌灵残留

本文采用高效液相色谱法(HPLC)和液相色谱-质谱法(LC-MS)对干果榛子中氯吡苯脲和多菌灵残留量进行含量测定.HPLC和LC-MS均使用C18色谱柱,含量测定采取等度洗脱,流动相:甲醇-水(55∶45,体积比);体积流量:1.0 mL·min-1;测定波长:260 nm;柱温:30℃.LC-MS采取电喷雾离子源,梯度洗脱,体积流量:0.6 mL·min-1,柱温:30℃.结果表明,榛子中氯吡苯脲与多菌灵存在残留,氯吡苯脲质量浓度在1.00~10.00μg·mL-1范围内线性关系良好,加样回收率在95.58%~100.58%;多菌灵质量浓度在1.005~15.075μg·mL-1范围内具有良好的线性关系,加样回收率在95.61%~104.39%.实验证明,HPLC与LC-MS相结合的方法具有操作简便、灵敏度高、检出限低等优点,能有效地检测到榛子样品中膨大剂氯吡苯脲及杀菌剂多菌灵的残留,并确定其残留量,线性关系和回收率结果均令人满意.根据被检测的8批样品中氯吡苯脲和多菌灵两项农药残留量推断,作为一般干果食用榛子是安全的.

Flat multifunctional liquid crystal elements through multi-dimensional information multiplexing

Flat optical elements have attracted enormous attentions and act as promising candidates for the next generation of optical components.As one of the most outstanding representatives,liquid crystal(LC)has been widely applied in flat panel display industries and inspires the wavefront modulation with the development of LC alignment techniques.However,most LC elements perform only one type of optical manipulation and are difficult to realize the multifunctionality and light integration.Here,flat multifunctional liquid crystal elements(FMLCEs),merely composed of anisotropic LC molecules with space-variant orientations,are presented for multichannel information manipulation by means of polarization,space and wavelength multiplexing.Specifically,benefiting from the unique light response with the change of the incident polarization,observation plane,and working wavelength,a series of FMLCEs are demonstrated to achieve distinct near-and far-field display functions.The proposed strategy takes full advantage of basic optical parameters as the decrypted keys to improve the information capacity and security,and we expect it to find potential applications in information encryption,optical anti-counterfeiting,virtual/augmented reality,etc.

A review of liquid crystal spatial light modulators:devices and applications

Spatial light modulators,as dynamic flat-panel optical devices,have witnessed rapid development over the past two decades,concomitant with the advancements in micro-and opto-electronic integration technology.In particular,liquid-crystal spatial light modulator(LC-SLM)technologies have been regarded as versatile tools for generating arbitrary optical fields and tailoring all degrees of freedom beyond just phase and amplitude.These devices have gained significant interest in the nascent field of structured light in space and time,facilitated by their ease of use and real-time light manipulation,fueling both fundamental research and practical applications.Here we provide an overview of the key working principles of LC-SLMs and review the significant progress made to date in their deployment for various applications,covering topics as diverse as beam shaping and steering,holography,optical trapping and tweezers,measurement,wavefront coding,optical vortex,and quantum optics.Finally,we conclude with an outlook on the potential opportunities and technical challenges in this rapidly developing field.

基于LC-MS/MS测定人体类固醇激素的研究进展

类固醇激素是一类具有环戊烷多氢菲结构的化合物,由细胞色素P450酶催化形成,在调节机体代谢、促进性器官发育等方面起着重要作用。临床上将类固醇激素水平作为肾上腺疾病、精神类疾病等的诊断指标。液相色谱-串联质谱(LC-MS/MS)联用技术因具有高灵敏度、高通量和高专属性的特点,已成为类固醇临床测定的首选方法。本文综述了LC-MS/MS在内源性类固醇激素测定中的应用,特别是在样品前处理、色谱条件和质谱条件优化等方面的研究进展,为临床上类固醇激素的诊断检测提供参考。

Singularity Formation forthe General Poiseuille Flow of Nematic Liquid Crystals

We consider the Poiseuille flow of nematic liquid crystals via the full Ericksen-Leslie model.The model is described by a coupled system consisting of a heat equation and a quasilinear wave equation.In this paper,we will construct an example with a finite time cusp singularity due to the quasilinearity of the wave equation,extended from an earlier resultonaspecial case.

采用丙烯酸酯双单体的高空间频率透射式体全息H-PDLC光栅的研制

全息聚合物分散液晶(holographic-polymer dispersed liquid crystal, H-PDLC)体全息光栅因其化学状态稳定、制作简单、价格低廉等优势为全息光波导耦合器件提供了一个更优的思路。本文提出了采用复合型丙烯酸酯类高/低折射率匹配调制的H-PDLC透射式体光栅的研制。首先结合耦合波理论及分子扩散理论介绍了H-PDLC光栅的形成机理。然后,通过实验对不同官能度单体的光栅材料进行筛选,并研究其全息衍射特性。在此基础上,进一步采用提高引发剂含量的方式优化了高频体全息H-PDLC光栅性能。实验结果表明,该双单体的H-PDLC配方可实现在可见光波段透过率大于90%,在空间频率为973 lp/mm下,衍射效率达到90%,响应带宽为99 nm;在2 941 lp/mm下,衍射效率为75.4%,响应带宽为29 nm。该H-PDLC光栅作为波导显示系统的耦合器件有可观的应用前景。

基于卷积神经网络的TFT-LCD引脚导电性能检测

针对导电粒子粘连严重影响TFT-LCD引脚质量检测精度问题,提出融入K均值聚类特征选择的卷积神经网络引脚导电性能二分类图像检测方法。基于引脚附着粒子数量合格与否的判别标准,建立引脚图像检测的合格与不合格二分类模型。根据监督学习机理,构建包含2 000张引脚图像的数据集。为了提高检测精度,针对不同引脚图像中导电粒子与背景之间灰度阈值存在差异的特点,提出融入K均值聚类特征选择的卷积神经网络引脚图像粒子数量分类算法。进一步应用10折交叉验证法对算法的有效性进行了评估,检测正确率达到96.0%,比极大类间方差法提高了8%,比分水岭法提高了5.5%。

基于LC-OPA的空间激光通信技术进展

液晶相控阵既可以在空间激光通信技术建立多点间空间激光通信链路,又能代替压电偏摆镜的精瞄方式。阐述液晶相控阵应用趋势;通过对液晶相控阵中液晶分子电致双折射和多缝衍射光束偏转原理,提出替压电偏摆镜配合终端进行瞄准捕获跟踪的方案;以“一对二”空间激光通信终端为例,提出基于液晶相控阵多点间空间激光通信终端方案和链路工作模式,分析方案优势,并进行未来展望。

NOVEL POLYMER WIDE VIEWING ANGLE COMPENSATION FILMS FOR LIQUID CRYSTAL DISPLAYS(LCDS)

We report on generating uniaxial negative birefringent compensation films, made of specifically designedpolyimides. These polymers were synthesized via a polycondensation of dianhydride [such as 2, 2' -bis(3, 4-dicarboxyphenyl)hexafluoropropane dianhydride] and 2, 2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl. The uniaxial negative birefringent (n_x =n_y > n_z) polyimide substrates are achieved using a solution-casting method in conventional solvents, which exhibit thedesirable optical phase retardation [(n_x - n_z)×d] values from 50 to 400 nm varying with the film thickness. In thesepolyimide films, the long chain rigid molecules adopt intrinsic planar orientaion. In detail, the majority of phenylene-imiderings and phenylenes preferentially adopt nearly planar conformations parallel to the film substrae. In addition, these filmsalso possess high transparency (or transmittance) and little color shift. The unique color dispersion curve indicates that thistype of materials is very suitable for the applications in LCDs due to an excellent mimic for the retardation color dispersioncurve with respect to LC molecules. Significantly low in-plane retardation (< 1 nm) allows this new technology based film toachieve sufficiently high contrast ratio while highly negative retardation dramatically suppresses the gray scale inversion toimprove the viewing angle performance in a variety of new mode LCDs.

Calculating the dielectric anisotropy of nematic liquid crystals:a reinvestigation of the Maier-Meier theory

This paper investigates the average dielectric permittivity （^-ε） in the Maier-Meier theory for calculating the dielectric anisotropy （△ε） of nematic liquid crystals.For the reason that ^-ε of nematics has the same expression as the dielectric permittivity of the isotropic state,the Onsager equation for isotropic dielectric was used to calculate it.The computed ^-ε shows reasonable agreement with the results of the numerical methods used in the literature.Molecular parameters,such as the polarizability and its anisotropy,the dipole moment and its angle with the molecular long axis,were taken from semi-empirical quantum chemistry （MOCPAC/AM1） modeling.The calculated values of △ε according to the Maier-Meier equation are in good agreement with the experimental results for the investigated compounds having different core structures and polar substituents.

STUDIES ON CRITICAL CONCENTRATION OF LIQUID CRYSTALLINE ETHYLCELLULOSE

Critical concentrations of lyotropic liquid crystalline ethylcellulose in more than ten solvents were determined using both Abbe refractometer and polarized microscopy. Critical concentration C-crit of forming Liquid crystal phase decreased with increasing solubility parameter delta of solvent until approaching the delta of polymer. Although the alcohols used as solvents had the same variation rule, the critical concentration values of their solutions were much higher, due to their excessive large hydrogen bond component of delta. The experiments of using mixed solvents which showed good linear relation between C-crit and delta also proved this rule. A technique of Transmission Optical Analysis was first used to estimate the concentration dependence of critical phase transition temperature T-crit of EC, and a T-C phase diagram could be drawn.

Effect of Polymer Network Morphology on the Performance of Polymer Dispersed Liquid Crystal (PDLC) Composite Films

The effects of the morphologies of liquid crystal (LC) droplets left in polymer network on the performance of polymer dispersed liquid crystal composite films were investigated.By adjusting the relative content range of the crosslinking and diluents,the morphologies of polymer network can be changed.Therefore,the properties of PDLC composite films with imparity polymer morphologies were obtained by experiments and the finite element simulation.Results of the experimental and finite element simulation showed that the electro-optical properties of PDLC composite films were inversely proportional to the domain size of the polymer network and the mechanical properties were proportional to the domain size of the polymer network.

QuEChERS-LC-MS/MS测定姜油树脂、姜精油中8种农药残留及膳食风险评估

本研究建立了QuEChERS-液相色谱-串联四极杆质谱(LC-MS/MS)法测定姜油树脂、姜精油样品中噻虫嗪、吡虫啉、噻虫胺等8种农药残留,通过方法优化,选择乙腈-水-正己烷体系提取样品,QuEChERS方法净化提取液,在电喷雾离子源正离子模式下电离,多反应监测(MRM)模式下测定,并采用基质匹配标准曲线内标法进行定量分析。结果表明,8种农药在1~32μg/L浓度范围内的线性关系良好,相关系数(R 2)均大于0.99,方法检出限和定量限分别为0.03~0.16、0.10~0.53 mg/kg;3种不同加标水平下的回收率均在70%~119%之间,相对标准偏差(RSD)均小于20%。采用该方法测定实际样品,其中,噻虫嗪、吡虫啉、噻虫胺阳性样本的检出率较高,分别为56%、58%、52%,残留量大于1 mg/kg的样本量占比分别为12%、16%、10%,最高残留量分别为2.16、1.92、2.01 mg/kg,其他5种农药的检出率均低于20%。基于实际样品中农药残留中位值评估干姜片、姜精油和姜油树脂中噻虫嗪、吡虫啉、噻虫胺的慢性膳食摄入风险,评估结果远小于100%,表明农药残留的慢性摄入风险较小。

Captiva EMR-Lipid技术结合UPLC-MS/MS快速测定牛羊产品中甲苯咪唑及其代谢物的残留量

建立了牛羊产品中甲苯咪唑及其代谢物羟基甲苯咪唑、氨基甲苯咪唑的通过式净化-超高效液相色谱-串联质谱测定的分析方法。样品经0.2%氨化乙腈溶液振荡提取,冷冻离心后,经Captiva EMR-Lipid小柱净化,直接进样分析。以安捷伦SB-C_(18)色谱柱(2.1 mm×100 mm,1.8μm)进行分离,以0.1%甲酸水和乙腈为流动相进行梯度洗脱,电喷雾正离子(ESI^(+))模式电离、多反应监测(MRM)模式进行检测,采用基质匹配标准工作曲线,内标法定量。结果表明,甲苯咪唑及其代谢物在0.2~50 ng/mL范围内线性良好,相关系数均大于0.999,甲苯咪唑及其代谢物的检出限(S/N>3)为0.3μg/kg,三水平的加标回收率在80.5%~108.0%之间,RSD为1.1%~5.8%。该方法操作简便、结果准确,克服了目前方法前处理繁琐、检测周期长等不足,适用于牛羊产品中甲苯咪唑及其代谢物残留量的快速检测。