改进型非对称Y分叉内全反射光开关特性分析

提出一种改进型非对称Y分叉内全反射光开关,较详细地分析了结构参量对光开关消光比和损耗的影响,优化设计后开关的消光比可大幅度提高,并给出了一种优化设计的方案.     

细水雾遮蔽红外辐射的蒙特卡洛模拟及透射场分析

基于蒙特卡洛法,对水雾遮蔽热辐射衰减建立了光子状态序列的追踪模型.利用该模型对水雾粒子的多重散射进行模拟,分析了影响水雾消光性能的消光系数、水雾浓度、不对称因子等参数,发现不对称因子也是影响水雾隐身性能的重要参数.研究表明:对于消光系数相同的介质,不对称因子越小越有利于衰减目标热辐射强度,而采用朗伯比尔定律则不能获得此结论;在雾粒子半径远大于红外波长的情况下,提高水雾的浓度并减小粒子半径可有效提高水雾的衰减作用.     

Asymmetric multimode interference isolator based on nonreciprocal phase shift

This paper presents an asymmetric multimode interference-based (MMI) optical isolator, by utilizing the magneto-optical nonreciprocal phase shift (NPS). Equivalent beam propagation method (BPM) simulation of symmetric and asymmetric isolators are performed using configuration of Air/Ce:YIG/SiO₂ on silicon substrate for integration. The asymmetric isolator is found to be much more compact in size and efficient in isolation compared with symmetric isolator. Simulation results show that the isolation of asymmetric structure is 23.8 dB higher than that of symmetric one. It is mainly because both symmetric mode and anti-symmetric mode are excited in asymmetric structure and hence can interfere destructively. The proposed device may play an important role in the optical communication systems and photonic integrated devices.     

线偏振周期量级脉冲中H-强场光解离的不对称性

Photodetachment of H^- irradiated by linearly polarized few-cycle laser field is investigated by time-dependent Schr?dinger equation numerically. The photo-electron left-right asym-metry parameter as a function of carrier-envelop (CE) phase of few-cycle pulses is attained. We confirm the asymmetry of photoelectron distribution in H^- photodetachment and find that the maximal asymmetry parameter of H^- is equal to that of H atom under the same conditions but the corresponding CE phases are quite different. Thus a CE phase shift ap-pears. Compared to that of H atom and field free electron, the zero asymmetry CE phase shift is sensitively affected by Coulomb field. The Coulomb effect on the asymmetry of H^- photodetachment mainly behaves in the CE phase shift of H^- instead of the amplitude of asymmetry parameter curve.     

Just noticeable differences of open quotient and asymmetry coefficient in singing voice

This study aims to explore the perceptual relevance of the variations of glottal flow parameters and to what extent a small variation can be detected. Just Noticeable Differences (JNDs) have been measured for three values of open quotient (0.4, 0.6, and 0.8) and two values of asymmetry coefficient (2/3 and 0.8), and the effect of changes of vowel, pitch, vibrato, and amplitude parameters has been tested. Two main groups of subjects have been analyzed: a group of 20 untrained subjects and a group of 10 trained subjects. The results show that the JND for open quotient is highly dependent on the target value: an increase of the JND is noticed when the open quotient target value is increased. The relative JND is constant: ΔO_q/O_q = 14% for the untrained and 10% for the trained. In the same way, the JND for asymmetry coefficient is also slightly dependent on the target value–an increase of the asymmetry coefficient value leads to a decrease of the JND. The results show that there is no effect from the selected vowel or frequency (two values have been tested), but that the addition of a vibrato has a small effect on the JND of open quotient. The choice of an amplitude parameter also has a great effect on the JND of open quotient.     

Development and study of novel non-contact ultrasonic motor based on principle of structural asymmetry

The article presents novel design of non-contact rotary ultrasonic motor consisting of ring-shaped stator vibrating in in-plane flexural mode and rotor provided with blades. In contrast to other motors with similar design proposed motor relies on the use of standing ultrasonic waves. This simplifies design and electronic control of motor and becomes possible due to introduction of artificial asymmetry, for example by tilting one or several blades of the rotor relative to the surface normal. Operating principle of the proposed motor is based on acoustic radiation torque exerted on rotor by ultrasonic waves propagating in air or fluid gap between rotor and stator. This torque is calculated using finite element method by means of COMSOL Multiphysics software. Dynamics of rotor is studied using MathCad software and general theory of nonlinear conservative oscillators. Role of asymmetry is explained on the basis of comparative analysis of potential functions and phase trajectories for symmetric and asymmetric cases. It is shown that direction of rotation is determined by structural parameters of motor, particularly tilting direction (clockwise or counter-clockwise) of the blades. Conceptual design of motor with bidirectional rotation is described. Direction and velocity of rotation in the proposed conceptual design can be potentially controlled by changing excitation frequency of stator.     

(2R，3R)-和(2S，3S)-2-(4-羟基-3-甲氧基)-3-羟甲基-1，4-苯并二氧六环-6-醛的对映选择性合成

1,4-苯并二氧六环木脂素类天然产物多数具有增加胆碱乙酰化酶和抗肝毒等活性 ,其活性主要源于 1 ,4-苯并二氧六环官能团 [1] . 1 ,4-苯并二氧六环木脂素的消旋全合成已有报道 [2 ] ,但其不对称合成还是空白[3] .我们发展了一条对映选择性合成 1 ,4-苯并二氧六环木脂素的简捷有效的路线 .基于前面的工作 [4 ] ,我们发现 1 ,4-苯并二氧六环醛类衍生物是合成此类天然产物的关键中间体 ,选择 2 - (4-羟基- 3-甲氧基 ) - 3-羟甲基 - 1 ,4-苯并二氧六环 - 6-醛 (1 )作为目标分子 ,其合成路线如下 :Reagents and conditions:( ) Me OH,H2 SO4,9…     

Chemical ordering and thermodynamic properties of HgNa liquid alloys

We have studied the thermodynamic properties and microscopic structures of HgNa liquid alloy at 673 K on the basis of regular associated solution model. The concentrations of ApB type complex in a regular associated solution of Hg and Na have been determined. We have then used the concentration of complex to calculate the free energy of mixing, enthalpy of mixing, entropy of mixing, activity, concentration fluctuations in long wavelength limit S_CC(0) and the Warren-Cowley short-range parameter α₁. The analysis suggests that heterocoordination leading to the formation of complex Hg₄Na is likely to exist in the liquid and is of a strongly interacting nature. The theoretical analysis reveals that the pairwise interaction energies between the species depend considerably on temperature and the alloy is more ordered towards Hg-rich region.     

Fluorescence line narrowing spectroscopy of Eu in zinc-thallium-tellurite glass

The environment of Eu³⁺ in zinc-thallium-tellurite glass of the molar composition 60TeO₂-30TlO_0.5-9.9ZnO-0.1Eu₂O₃ was investigated by laser-induced fluorescence line narrowing (FLN) techniques using Eu³⁺ as a local site probe. From the site selective luminescence spectra of Eu³⁺ at 7 K, the energies of the Stark components of the ⁷F₁ and ⁷F₂ states were recorded and then the crystal field parameters B_nm were calculated assuming a C_2v site symmetry. The ratios B₂₂/B₂₀ and B₄₄/B₄₀ for each excitation energy within ⁷F₀-⁵D₀ transition were obtained and compared with the values calculated for Eu³⁺ in other types of glasses.