Optical simulation of in-plane-switching blue phase liquid crystal display using the finite-difference time-domain method

The finite-difference time-domain method is used to simulate the optical characteristics of an in-plane switching blue phase liquid crystal display.Compared with the matrix optic methods and the refractive method,the finite-difference timedomain method,which is used to directly solve Maxwell＇s equations,can consider the lateral variation of the refractive index and obtain an accurate convergence effect.The simulation results show that e-rays and o-rays bend in different directions when the in-plane switching blue phase liquid crystal display is driven by the operating voltage.The finitedifference time-domain method should be used when the distribution of the liquid crystal in the liquid crystal display has a large lateral change.

Comparison of Cloud Properties between Cloud Sat Retrievals and Airplane Measurements in Mixed-Phase Cloud Layers of Weak Convective and Stratus Clouds

Cloud microphysical properties including liquid and ice particle number concentration （NC）, liquid water content （LWC）, ice water content （IWC） and effective radius （RE） were retrieved from CloudSat data for a weakly convective and a widespread stratus cloud. Within the mixed-phase cloud layers, liquid-phase fractions needed to be assumed in the data retrieval process, and one existing linear （Pl） and two exponential （P2 and P3） functions, which estimate the liquid-phase fraction as a function of subfreezing temperature （from -20℃ to 0℃）, were tested. The retrieved NC, LWC, IWC and RE using Pl were on average larger than airplane measurements in the same cloud layer, Function P2 performed better than p1 or P3 in retrieving the NCs of cloud droplets in the convective cloud, while function Pl performed better in the stratus cloud. Function P3 performed better in LWC estimation in both convective and stratus clouds. The REs of cloud droplets calculated using the retrieved cloud droplet NC and LWC were closer to the values of in situ observations than those retrieved directly using the Pl function. The retrieved NCs of ice particles in both convective and stratus clouds, on the assumption of liquid-phase fraction during the retrieval of liquid droplet NCs, were closer to those of airplane observations than on the assumption of function P1.

Asymmetric dynamic phase holographic grating in nematic liquid crystal

A new scheme for recording a dynamic phase grating with an asymmetric profile in C60-doped homeotropically aligned nematic liquid crystal（NLC） was presented.An oblique incidence beam was used to record the thin asymmetric dynamic phase holographic grating.The diffraction efficiency we achieved is more than 40%,exceeding the theoretical limit for symmetric profile gratings.Both facts can be explained by assuming that a grating with an asymmetric saw-tooth profile is formed in the NLC.Finally,physical mechanism and mathematical model for characterizing the asymmetric phase holographic grating were presented,based on the photo-refractive-like（PR-like） effect.

Kerr effect and Kerr constant enhancement in vertically aligned deformed helix ferroelectric liquid crystals

In this article,we review recently achieved Kerr effect progress in novel liquid crystal（LC） material：vertically aligned deformed helix ferroelectric liquid crystal（VADHFLC）.With an increasing applied electric field,the induced inplane birefringence of LCs shows quadratic nonlinearity.The theoretical calculations and experimental details are illustrated.With an enhanced Kerr constant to 130 nm/V2,this VADHFLC cell can achieve a 2π modulation by a small efficient electric field with a fast response around 100 μs and thus can be employed in both display and photonics devices.

Low voltage transflective blue-phase liquid crystal display with a non-uniform etching substrate

A transflective polymer-stabilized blue-phase liquid crystal display（BP-LCD） with a non-uniform etching substrate is proposed.In-plane switching（IPS） electrodes on the bottom substrate are put on the different gaps,and the bottom substrate between the electrodes is etched into different depths in transmissive（T） and reflective（R） regions.This structure can balance the optical phase retardation in the two regions and is helpful to achieve well-matched voltag-dependent transmittance and reflectance curves.This transflective display has high optical efficiency,a wide viewing angle,and low operating voltage（approximately 6 V）.

Computational study of laser fragmentation in liquid:Phase explosion,inverse Leidenfrost effect at the nanoscale,and evaporation in a nanobubble

Laser fragmentation in liquid is an effective and environment-friendly processing technique capable of yielding colloidal nanoparticles and atomic clusters with a narrow size distribution. The advancement of this technique can be facilitated by an improved understanding of processes that control the sizes, shapes, and structures of the produced nanoparticles. In this work, the dependence of the fragmentation mechanisms on the energy density deposited by the laser pulse is investigated in atomistic simulations performed for 20 nm Au nanoparticles irradiated in water by 10 ps laser pulses. The simulations reveal that the decrease in the absorbed laser energy leads to sequential transitions from the regime of “strong” phase explosion, when all products of an explosive phase decomposition of the irradiated nanoparticle are promptly injected into the water surrounding a nanobubble formed around the nanoparticle, to two distinct regimes of nanoparticle fragmentation leading to the formation of a large central nanoparticle surrounded by smaller satellite fragments. First, in the regime of “mild” phase explosion, the central nanoparticle is produced by the reflection of some of the hot metal droplets generated by the explosive decomposition of the nanoparticle from the boundary of the nanobubble. This reflection is attributed to the inverse Leidenfrost effect acting at the nanoscale. The reflected droplets converge in the center of the nanobubble and coalesce into a single droplet that solidifies shortly after the collapse of the nanobubble. Further decrease in the absorbed laser energy brings the irradiation conditions below the threshold for the phase explosion and results in the formation of a core-satellite structure of the fragmentation products through an interplay of the intense evaporation from the surface of the irradiated nanoparticle, evolution of the nanobubble, and condensation of the metal vapor into clusters and small satellite nanoparticles. The computational predictions are related to the experimental observations, and the connections between the fragmentation mechanisms, the nanoparticle size distribution, and the generation of internal crystal defects are discussed.

Sonoluminescence as the PeTa Radiation, Part Three

This paper is the third in a series published in this journal during 2017-2018. These three papers present various stages in the development of the PeTa model for phenomena of the same physical nature: cavitational luminescence (CL), multi-bubble sonoluminescence (MBSL), single-bubble sonoluminescence (SBSL), and laser-induced bubble luminescence (LIBL). The basis of this model is the PeTa (Perel’man-Tatartchenko) effect—a nonequilibrium characteristic radiation under first-order phase transitions, for instance, vapour condensation. The third iteration of this model “Vapour bubble luminescence” (VBL) is presented in this paper. The essence of this model is as follows: with a local decrease of pressure or an increase of temperature in a tiny volume of the liquid, one or several bubbles filled with vapour will appear. Subsequently, a very rapid increase in pressure or a decrease in temperature of the bubble leads to super-saturation of the vapour inside the bubble, followed by its instantaneous condensation with the emission of condensation energy (this is the PeTa effect). A sharp decrease in pressure causes the collapse of the bubble accompanied by a shock wave in the liquid. VBL model is conveniently represented on the solid-liquid-vapour phase diagram. A better understanding of the physical nature of the phenomena under consideration could help to find their useful applications. To develop this idea further, we propose a design of a cavity-free pulsed laser on the basis of CL/MBSL/SBSL. An analysis of LIBL in cryogenic liquids is also given in this paper.

Studies on Liquid Crystalline Bis[4-(p-phenoxy)-phenylbenzoate]Alkyldicarboxylat

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Synthesis of Mixed Tail Triphenylene Discotic Liquid Crystals： Molecular Symmetry and Oxygen-Atom Effect on the Stabilization of Columnar Mesophases

Small change in chemical structure of discotic liquid crystals can cause big difference in their mesomorphism. Replacing of the alkoxy peripheral chains of triphenylene by oxygen-atom containing ester chains would result in novel mesomorphism. A series of mixed tail triphenylenes containing propoxyacetyloxy and alkoxy, abbreviated as C18H6（OCnH2n＋1）3（OCOCH2OC3H7）3, n=4-8, and hexa（propyloxyacetyloxy）triphenylene, C18H6（OCOCH2OC3H7）6 were synthesized. Thermal gravimetry analysis （TGA） of three discogens showed that they had good thermal stability till 350 ℃. The mesomorphism was investigated through differential scanning calorimetry （DSC） and polarized optical microscopy （POM）. The preliminary X-ray diffraction （XRD） results of one compound showed that it exhibited ordered hexagonal columnar （Colho） mesophase. These mixed tail triphenylene derivatives possessed much stable Colho mesophase and wider mesophase ranges than their hexaalkoxytriphenylene C18H6（OR）6 and hexaalkanoyloxytriphenylene C18H6（OCOR＇）6 analogues. The asymmetrical compounds 2,6,11-trialkoxy-3,7,10-tri（2-propyloxyacetyloxy）triphenylenes with n=5-8 displayed higher clearing points and wider temperature ranges than their symmetrical isomers 2,6,10-trialkoxy-3,7,11-tri（2-propyloxyacetyloxy）- triphenylenes, while C18H6（OCOCH2OC3H7）6 had the highest clearing point due to the β-oxygen-atom effect.

Controlling the Balance of Photoluminescence and Photothermal Effect in Cyanostilbene-Based Luminescent Liquid Crystals

Molecular motions of the luminescent liquid crystals(LLCs)show a significant effect on fluorescent emission and heat generation.In this article,a series of cyanostilbene-based LLCs(CSs:CS1-6,CS1-12,CS2-6 and CS2-12)are synthesized to investigate how the pho-toluminescence and photothermal effect balanced.Among these materials,the mesogens peripheried by single alkyl chains formed enantiotropic nematic(CS1-6)or smectic C(CS1-12)phase with different alkyl tail lengths.When the single aliphatic chain is re-placed by mini-dendrons,room temperature(RT)monotropic hexagonal columnar phase(CS2-12)or molecular liquid(CS2-6)is formed.The results revealed that all these materials exhibited high efficiency emission with the highest quantum yield reaching 59.0%.The photoluminescence and photothermal effect can be effectively tuned by dispersing CSs into a commercially available RT liquid crystal matrix 8CB,which output significantly improved photothermal conversion efficiency of 63.2%.Furthermore,the pho-tothermal can rapidly trigger the Smectic A-Nematic-Isotropic sequence transitions of 8CB doped with CSs.This work paves a way of adjusting the balance of photoluminescence and photothermal properties of the LLC materials.

Multiple Effects Tailoring the Self-organization Behaviors of Triphenylene Side-chain Liquid Crystalline Polymers via Changing the Spacer Length

Long-alkyl tail triphenylene （TP） side-chain liquid crystalline polymers （SCLCPs） with different spacer length （P-m-TP, m = 2, 3, 4, 6, 8, which is the number of carbon atom in the flexible alkyl spacers） have been successfully synthesized via free radical polymerization. The differential scanning calorimetry （DSC）, polarized light microscopy （POM）, ultraviolet-visible spectroscopy （UV- Vis）, wide-angle X-ray diffraction （WAXD） and small-angle X-ray scattering （SAXS） measurements were performed to investigate the influence of multiple effects on the self-organization behaviors of P-m-TP, including steric effect, decoupling effect and π-π stacking effect. The experimental results revealed that P-m-TP （m = 2, 3, 4） formed the columnar phase which was developed by the TP moieties and the main chain as a whole, suggesting that the side-chains had strong steric effect even though the number of spacer length （m） exceeded 4. In addition, the clearing points （Tis） of the polymers were above 300 ℃. When m = 6 and 8, the polymers displayed hexagonal columnar phase and exhibited the low Tis （91 and 80 ℃ respectively）, originating from the self-assembly of triphenylene due to the decoupling effect and π-π stacking effect. This work offers a viable and inspiring pathway to control the phase transition temperature and phase structure ofTP SCLCPs via simply tailoring the spacer length and increasing the alkyl tail length of TP.

Marangoni流动对液滴撞击过热液池影响的数值模拟

对液滴撞击过热液池的动态过程进行数值模拟,着重关注由液池表面不均匀温度引起的马兰戈尼效应(Marangoni effect)对液池内的流场和温度场演化过程的影响。当乙醇液滴落入过热油池后,液池表面温度随着液滴的靠近而迅速下降,从而在径向上产生很大的温度梯度。由此引发的沿径向向内的Marangoni力会与沿径向向外的蒸汽剪切应力相抗衡,进而在蒸汽层最薄的位置形成一个“热射流”结构。随着时间的推进,占据主导地位的Marangoni力逐渐将“热射流”向内推动,直至在液滴下方形成下沉羽流。此外,随着液池黏度的增加,液池内由表面蒸汽应力引起的流动将被抑制,进而导致界面附近的换热效率大幅下降。

非球形湿颗粒导向管喷动流化床流动特性

实际工业生产中颗粒多为非球形颗粒,对颗粒形状效应和液相作用机制的研究不足,是导向管喷动流化床在颗粒涂层改性、包膜等工业应用的关键限制因素。选取粒径、密度相似的球形和圆柱形非球形颗粒为实验物料,对比两种颗粒在不同气速和雾滴引入量下的压力脉动信号频谱分析、信息熵分析,并结合床内气固流动对流型进行划分,绘制非球形湿颗粒流动相图,进而探究喷动流化过程中颗粒形状效应及液相作用机制。相比于球形颗粒,粒径、密度相似的非球形颗粒有较小的最小喷动速度,在喷动过程中有两个及以上较低的主频峰且信息熵较大,显示出非球形颗粒在系统内较高的混乱程度,颗粒之间摩擦、碰撞等降低了导向管内颗粒的固体循环速率。液体的引入增大了环形区颗粒间液桥力,使最小流化速度变大,但液体挥发引起喷动气量增大,使最小喷动速度与最小喷动流化速度减小。在喷动流化流型下引入液体,球形颗粒导向管两端压降ΔpDT的脉动主频降低,而非球形颗粒ΔpDT的主频升高。而且非球形颗粒黏附液体后频谱分析结果显示幅值较大的单一主频峰,表明非球形湿颗粒压力脉动规律性的增强。

环肽α-amanitin在小鼠体内的毒性作用研究

目的研究环肽α-amanitin在动物体内的毒性作用。方法对小鼠尾静脉和腹腔注射给药,确定环肽α-amanitin对小鼠的半数致死量(LD50);研究α-amanitin对小鼠外周血血象和生化指标的影响,脏器指数、组织病理学改变,并定性检测中毒小鼠血液及组织中的α-amanitin。结果腹腔和尾静脉两种给药方式的LD50分别为0.742mg/kg和0.327mg/kg。对小鼠尾静脉注射0.327mg/kgα-amanitin24h后,小鼠白细胞(WBC)、红细胞(RBC)和血红蛋白(Hb)明显降低,同时尿素氮(BUN)和肌酐(Crea)明显增高,谷丙转氨酶、谷草转氨酶、总胆红素和结合胆红素(ALT、AST、TBIL和DBIL)值分别增高至空白对照组的24.0、9.6、26.3和37.0倍;作用48h后,小鼠肝脏和肾脏指数显著增高,细胞核碎裂和组织局灶性坏死,肝脏和肾脏组织中可检出α-amanitin。结论小鼠对α-amanitin毒性作用的敏感血液指标是BUN、Crea、ALT、AST、TBIL和DBIL;肝脏、肾脏是主要受损脏器,α-amanitin作用后期,可以蓄积在肝脏和肾脏。

考虑水盐相变的盐渍土基质吸力的温度效应

基质吸力是引起土体中水分迁移的驱动力,对探究土体中水盐迁移动态具有重要的意义。为研究由温度变化诱发的盐渍土孔隙溶液相变对土体基质吸力的影响,用pF meter测试了不同NaCl和Na_(2)SO_(4)比例的盐渍土在不同温度条件下的基质吸力。试验结果表明:在水盐相变发生前,盐渍土基质吸力随温度的降低呈线性增加;而当降温过程中有水盐相变发生时,土体基质吸力随温度的变化趋势会发生明显突变。NaCl和Na_(2)SO_(4)对土体水盐相变规律影响不同,使得含不同比例NaCl和Na_(2)SO_(4)的复合盐渍土基质吸力呈现较大的区别。2%NaCl+4%Na_(2)SO_(4)的盐渍土在19和-9℃附近发生盐结晶相变和二次相变,而4%NaCl+2%Na_(2)SO_(4)的盐渍土两次相变分别发生在11和-16℃附近。水盐相变导致土体液态含水率明显降低,进而引起复合盐渍土基质吸力在两个相变阶段均有明显增加。NaCl抑制土体中液态水发生冰水相变,Na_(2)SO_(4)容易在正温结晶,故Na_(2)SO_(4)主要影响土体正温时的盐结晶规律,NaCl则主要影响土体在负温条件下的冰晶产生规律;二者比例不同造成土体盐结晶温度和二次相变温度有明显差异,使得复合盐渍土的水盐相变规律更加复杂,其基质吸力随温度的变化更加难以预测。此外,该研究进一步探究了冰、盐结晶量对基质吸力变化的贡献,为深入理解盐渍土的相变过程和基质吸力之间的关系提供了有效参考。

煤层气低压采气管线气、液两相流演化分析

在煤层气田开发的中后期,为保持抽采速率,控制递减率,管网运行压力逐年降低。结合贝克流型分界法进行流型划分并对流型演化的影响因素进行分析,在煤层气采气管线中两相流发展演化的过程中通常为雾状流、环状流、层状流、波浪流、段塞流依次出现,影响流型发展的因素包含降温、合并、捕获、叠加、重力作用及特殊管段等。同时因相对流速变化或截流效应,高持液率的相态也会向低持液率的相态转化。对气液两相流的演化过程进行研究有助于系统分析积液产生的原因并采取科学的治理对策。为提高冬季管线运行效率,降低煤层气开发的操作成本,在进一步研究中需要深入分析两相流演化的各类影响因素,探索采取干预措施,为管线优化设计提供依据。

超高效液相色谱-串联质谱法快速测定蔬菜中4种异噻唑啉酮类化合物的含量

提出了超高效液相色谱-串联质谱法(UHPLC-MS/MS)快速测定蔬菜中5-氯-2-甲基-4-异噻唑啉-3-酮(CMIT)、2-甲基-4-异噻唑啉-3-酮(MIT)、1,2-苯并异噻唑啉-3-酮(BIT)、2-正辛基-4-异噻唑啉-3-酮(OIT)等4种异噻唑啉酮类化合物含量的方法。取10.0 g已匀浆的蔬菜样品,用10 mL乙腈超声提取30 min,离心,残渣重复提取一次,合并提取液,加入5 g氯化钠,振荡、静置后,于40℃氮吹至近干,用2 mL 10%(体积分数,下同)甲醇溶液溶解残渣。所得溶液过已活化的HLB固相萃取小柱,用5 mL 10%甲醇溶液淋洗,6 mL甲醇洗脱。洗脱液于40℃氮吹至近干后,用甲醇定容至1 mL,过0.22μm有机滤膜,滤液在ACQIUTY UPLC BEH SHIELD RP18色谱柱上分离,以不同体积比的甲醇-水混合液为流动相进行梯度洗脱,质谱分析采用多反应监测采集模式,电喷雾正离子扫描模式,基质匹配法绘制工作曲线。结果表明,4种异噻唑啉酮类化合物的质量浓度在一定范围内与对应的峰面积呈线性关系,检出限(3S/N)分别为0.5,0.5,0.5,0.025μg·kg^(-1)。在不同蔬菜基质中进行3个浓度水平的加标回收试验,回收率为68.8%~81.3%,测定值的相对标准偏差(n=6)均小于9.0%。方法用于20种蔬菜样品分析,仅一组韭菜样品中检出BIT,检出量为2.3μg·kg^(-1)。

亲脂性匹配色谱分离-超高效液相色谱-串联质谱法测定果蔬中21种三唑类杀菌剂

为了提高农药残留的色谱分离效率和降低基质效应,本研究提出亲脂性匹配色谱分离,选取三唑类杀菌剂为研究对象,建立了果蔬中21种三唑类杀菌剂的超高效液相色谱-串联质谱(Ultra performance liquid chromatography-tandem mass spectrometry,UPLC-MS/MS)检测方法。样品经乙腈提取,盐析分相,分散固相萃取净化,选用与三唑类杀菌剂具有相近亲脂性的色谱柱进行分离,探究不同亲脂性烷基键合相对基质效应、回收率以及三唑杀菌剂和基质组分色谱分离的影响。结果表明,亲脂性匹配色谱分离能够提高色谱分离效率,改善三唑杀菌剂和基质组分的色谱分离,21种三唑杀菌剂的基质效应为-8.3%~4.7%,在5~250μg/L浓度范围内线性关系良好,决定系数R2≥0.999,平均回收率为91.4%~108.1%,定量限为0.5~3.5μg/kg。该检测方法能够有效降低基质效应,使用溶剂校准曲线进行定量即可获得满意的回收率,显著提高了检测效率,具有简便、准确、灵敏度高等特点,适用于果蔬中三唑杀菌剂的检测。所述亲脂性匹配色谱分离,为农药残留的液相色谱-串联质谱法分析中液相色谱柱的选择和基质效应的降低提供了方法参考。

Gas-liquid phase coexistence and finite-size effects in a two-dimensional Lennard-Jones system

The gas-liquid phase coexistence in a two-dimensional Lennard-Jones system is investigated using Maxwell construction method together with molecular dynamics simulations.The results of phase coexistence in different truncations of the potential are compared with data obtained from the literature,and the corresponding critical properties calculated.The crossover from Ising-like to mean field behavior is observed and confirmed as the temperature approaches the critical point from below.Performing simulations on systems with different sizes,we find that a finite size effect is more significant than those shown in most of the previous results,and a lower critical temperature is obtained when the full extent of this finite size effect is considered.

大规模红外焦平面阵列探测器的有效像元率研究

随着大规模红外焦平面阵列探测器应用的日益广泛,用户对其有效像元率指标提出了越来越高的要求。分析了有效像元率提升的难点。通过优化基于垂直布里奇曼法的衬底生长以及表面加工等工艺,提高了液相外延材料质量,获得了低缺陷中波碲镉汞薄膜外延材料;通过开发碲镉汞探测器背面平坦化工艺和优化探测器与读出电路倒装互连工艺,提高了成品率。最终提升了有效像元率指标(大于99.8%),获得了良好的效果。