Helix parameters in bi- and multicomponent mixtures composed of orthoconic antiferroelectric liquid crystals with three ring molecular core

Eight types of bicomponent systems composed of antiferroelectric compounds with different polarity of achiral chain and different temperature dependence of helical pitch as well as three multicomponent mixtures composed of antiferroelectric compounds with opposite helical twist sense were studied. The phase miscibility was tested by polarising optical microscopy. The results of the helical pitch and helical twist sense measurements obtained by a spectrophotometric method of selectively reflected light and by polarimetric method, respectively, are presented. It was found that it is possible to control helical pitch length and temperature of helix twist inversion in antiferroelectric mixtures by controlling the ratio of compounds with left- and right-handed helix in such mixtures, although all of them have the same chiral terminal chain.     

Propylene Glycol and Ethoxylated Surfactant Effects on the Phase Behavior of Water/Sucrose Stearate/Oil System

In this work, we studied the phase behavior as function of temperature of water/sucrose stearate/propylene glycol/oil and water/sucrose stearate/ethoxylated mono‐di‐glyceride/oil systems. The oils were R (+)‐limonene, isopropylmyristate, and caprylic‐capric triglyceride. It was found that adding propylene glycol and ethoxylated mono‐di‐glyceride to the water/sucrose stearate/R (+)‐limonene and water/sucrose stearate/isopropylmyristate systems decreases the temperature and surfactants concentration needed for the formation of a microemulsion phase region and no three phase region is observed. In the case of water/sucrose stearate/caprylic‐capric triglyceride system a three phase region is observed. In the caprylic‐capric based system, it was found that increasing the propylene glycol and ethoxylated mono‐di‐glyceride contents decrease the phase inversion temperature and increases the efficiency. In the case where the mixed surfactants (sucrose stearate and ethoxylated mono‐di‐glyceride) were present in the system, the efficiencies observed are higher than those observed in the system based on the mixture of sucrose stearate and propylene glycol.     

The temperature and concentration dependence of helical pitch in the mixtures of antiferroelectric compounds with the opposite helical twist sense

The temperature dependence of helical pitch for members of an homologous series of orthoconic antiferroelectric compounds (3FmHPhF) and their bicomponent mixtures (m = 3 and 5 as well as m = 3 and 7) has been measured by the method of selective light reflection. The compounds have the same chiral centre but they have different temperature dependence of the helical pitch as well as the helical twisting sense in SmC*_A phase: right for member m = 3, left for m = 7, and both right and left for m = 5. For this last homologue, the change of twisting sense is connected with the appearance of the unwound structure. Concentration dependence on helical pitch was investigated in the mixtures. It was demonstrated that it is possible to obtain mixtures with desirable high pitch and also with totally unwound structure.     

Equilibrium Topology and Partial Inversion of Janus Drops: A Numerical Analysis

The equilibrium topology of an aqueous Janus emulsion of two oils, O1 and O2, with water, W, [(O1+O2)/W], is numerically evaluated with the following realistic interfacial tensions (γ): γ_O2/W=5 mN m⁻¹, γ_O1/O2=1 mN m⁻¹, and γ_O1/W varies within the range 4–5 mN m⁻¹, which is the limiting range for stable Janus drop topology. The relative significance of the two independently pivotal factors for the topology is evaluated, that is, the local equilibrium at the line of contact between the three liquids and the volume fraction of the two dispersed liquids within the drop. The results reveal a dominant effect of the local equilibrium on the fraction of the O2 drop surface that is covered by O1. In contrast, for a constant volume of O2, the impact of the interfacial tension balance on the limit of the coverage is modest for an infinite volume of O1. Interestingly, when the O1 volume exceeds this value, an emulsion inversion occurs, and the O1 portion of the (O1+O2)/W topology becomes a continuous phase, generating a (W+O2)/O1 Janus configuration.     

多光子反Jaynes-Cummings模型中混合态二能级原子的粒子数反转特性

利用多光子反Jaynes-Cummings模型研究了单模相干光场与混合态二能级原子相互作用时,二能级原子的粒子数反转特性.讨论了相干光场的平均光子数、跃迁光子数以及原子初始态的混合度等参量对粒子数反转的影响.结果表明：二能级原子的粒子数反转有周期性的崩塌和回复现象. 相干光场平均光子数和跃迁光子数的增加会改变原子的回复周期和崩塌的衰减时间;随相干光场平均光子数的增加粒子数反转的振荡频率增大;随着混合度的减少回复的周期性和崩塌的衰减时间不发生变化但粒子数反转的振荡幅度增大.     

遗传算法结合正则化方法反演海洋大气波导

针对正则化方法在解决实际反演问题时既能克服问题的不适定性又可以很大程度上抑制噪声和误差的传播, 本文提出了利用遗传算法结合正则化方法的新算法, 在遗传算法适应度函数中引入正则化项来反演波导参数; 然后对算法进行仿真试验, 结果表明新算法与传统遗传算法相比具有较高的反演精度, 并指出当噪声误差小于10%时, 算法具有较强的“去噪”性能; 最后利用机载雷达在Wallops岛探测的海表面处局部回波资料进行反演试验, 将反演结果与实测大气折射率廓线进行比较, 说明该算法的有效性. 新方法为海洋大气波导反演研究提供了一种新思路.     

循环跃迁的Δ 型三能级系统中的无反转激光

研究了在引入非相干抽运的情况下,循环跃迁的Δ型共振三能级系统中产生的无反转激光.利用主方程的方法, 导出了缀饰态中强相干场极限下布居数项和相干项的稳态近似解析解以及产生无反转激光所需要满足的条件;并利用数值模拟的方法讨论了布居数分布、 系统增益对探测场和相干场拉比频率的依赖性以及随时间的演化规律. 结果表明:无论各个参量取何值,共振Δ型三能级系统总是处于无粒子数反转的状态; 只要探测场或相干场之中有一个为强场,便可产生无反转激光; 当其中任意一个场远强于另一个场时,系统的无反转增益将不再依赖于任何一个场的拉比频率.     

大气湍流畸变对空间目标清晰干涉成像仿真研究

本文利用功率谱反演法分别展开对符合 Kolmogonov 统计规律和修正后的Von Karmen 统计规律的大气湍流畸变波前相位屏进行了数值模拟研究. 得到各种模型下相位屏对该成像系统干涉成像图. 仿真结果表明, 采用闭合相位原理, 基本可以消除大气湍流对光束波前的影响, 验证了采用相位闭合技术的优势.     

层状各向异性介质大地电磁联合反演研究

地壳和上地幔中存在的电性各向异性是地电模型、地下结构和构造模型间一个重要的联系因素. 近年来, 它引起了广泛的关注, 推动了对电性各向异性结构模型和反演理论新方法的研究. 本文在Marquardt反演理论的基础上, 引入权因子对其改进后用于大地电磁视电阻率和阻抗相位联合反演, 通过具体算例的分析, 验证了理论的正确性; 此外, 对西北某地大地电磁实测资料处理解释, 说明了程序的实用性并为今后研究深部电性构造提供了一种新的方法和途径.