Shallow rectangular TLD for structural control implementation

A simple and practical model for the application of shallow rectangular tuned liquid damper (TLD) in structural vibration control is presented in this paper. The dynamic properties of shallow liquid in rectangular containers subjected to forced horizontal oscillation are analysed directly from the continuity and momentum equations of fluids. Following some practical assumptions, the nonlinear partial differential equations describing the wave movement of shallow liquid in rectangular containers are established and a numerical procedure for the solutions of these equations is proposed based on the finite element method. The formula for determining the control force provided by a shallow rectangular TLD is presented. The advantage of the proposed approach for the modeling of shallow rectangular TLD is that it simplifies a three-dimensional problem into a one-dimensional problem and therefore reduces the computation efforts significantly. The whole process forms a solid foundation and provides a simplified procedure for the design and analysis of shallow rectangular TLD.     

用偏光干涉法动态测量扭曲向列型液晶指向矢

提出一种基于双折射晶体劈的偏振态实时测量方法,并将该方法用于扭曲向列型液晶透射光的偏振态分析,实现了液晶分子平均指向矢的动态测量.利用基于晶体劈的偏光干涉法将待测光的偏振参量编码为两组干涉条纹,通过对干涉条纹定位实现偏振态的实时测量;再根据液晶指向矢的倾角、扭转角与透射光偏振态之间的关系,推算出液晶分子平均指向矢的动态信息.本实验测量液晶指向矢的速度为每秒5次,液晶平均指向矢的倾角、扭转角的测量准确度达到0.2°.本文研究为液晶分子平均指向矢的动态测量提供了一种有效途径.     

Analyzing and tailoring spectra of arbitrary microring resonator arrays based on six transfer cells and simulated annealing algorithm

A simple approach based on six transfer cells and simulated annealing algorithm for analyzing and tailoring the spectra of arbitrary microring resonator arrays is presented. Coupling coefficients, ring sizes, and waveguide lengths of microring resonator arrays can be arbitrary in this approach. After developing this approach, several examples are demonstrated and optimized for various configurations of microring resonator arrays. Simulation results show that this approach is intuitive, efficient, and intelligent for applications based on microring resonator arrays.     

Novel approach to study liquid crystal phase transitions using Legendre moments

A novel approach is proposed to investigate the phase transitions of cholesteric liquid crystals using the Legendre moments. The textures of cholesteric liquid crystals (cholesteryl butyrate, cholesteryl n-valerate, cholesteryl decanoate, and cholesteryl myristate) are captured as a function of temperature using high-resolution camera attached to the arthroscopic mode of polarizing optical microscope with hot stage. A recurrence formula is used to compute the Legendre moments of the liquid crystal textures based on the Legendre polynomial using MATLAB software. The abrupt change in the values of Legendre moments as a function of temperature gives the phase transitions of liquid crystals. The investigated transition temperatures of cholesteric liquid crystals are compared with other techniques.     

基于相控阵雷达模型的液晶光束偏转波控方法研究

针对闪耀光栅模型光束偏转角度数量分布有限的缺点,提出一种基于相控阵雷达模型的液晶光束偏转波控方法。该方法控制液晶电极间相位差,通过改变液晶电极间相位差控制出射光波束方向。使用傅里叶光学方法推导该模型最大偏转角度、光束偏转角度与电极间调制相位关系以及衍射效率和偏转角度的关系。实验证明该方法可实现任意分辨角的光波束扫描, 在0.15°光束扫描范围内实现优于20 μrad的连续光束偏转。     

Novel method for laser focal point positioning on the cover slip for TPP-based microfabrication and detection of the cured structure under optical microscope

Detection of a single cured structure in two-photon photopolymerization (TPP) based microstructure fabrication requires the laser focal spot to be exactly positioned on the cover slip. This is due to the fact that if the laser focal position is not exactly on the cover slip, the structure may not stick to the cover slip and flow away with the liquid during the washing and developing stages. In this paper, we report a scheme of laser spot positioning for the implementation of TPP process and the detection of a single cured microstructure under an optical microscope. For this, a novel yet very simple approach is devised and an uncomplicated procedure is developed. Experimental results are also included to prove the worthiness of the devised method.     

Entanglement assisted metrology

We propose a new approach to the measurement of a single spin state, based on nuclear magnetic resonance (NMR) techniques and inspired by the coherent control over many-body systems envisaged by quantum information processing. A single target spin is coupled via the magnetic dipolar interaction to a large ensemble of spins. Applying radio frequency pulses, we can control the evolution so that the spin ensemble reaches one of two orthogonal states whose collective properties differ depending on the state of the target spin and are easily measured. We first describe this measurement process using quantum gates; then we show how equivalent schemes can be defined in terms of the Hamiltonian and thus implemented under conditions of real control, using well established NMR techniques. We demonstrate this method with a proof of principle experiment in ensemble liquid state NMR and simulations for small spin systems.     

采用从头计算方法研究液态氦原子间等效对势

 提出了一种具有体心立方排列的原子团簇He₉模型,用于模拟液氦中邻近原子的近程平均分布特征,并运用量子从头计算方法和原子团簇理论计算技术,首次从理论上计算了液态氦原子间等效作用对势。计算给出的等效对势能较好地再现液氦的等温压缩线及冲击压缩线,所提出的液体等效结构的原子团簇模型能比较合理地描述液氦近程结构特征以及原子间多体相互作用规律。还将理论对势函数与经验Exp-6势进行了比较。     

Numerical modelling of foam Couette flows

A numerical computation based on a tensorial visco-elasto-plastic model based on continuous mechanics is compared to experimental measurements on liquid foams for a bidimensional Couette flow between two glass plates, both in stationary and transient cases. The main features of the model are elasticity up to a plastic yield stress, and viscoelasticity above it. The effect of the friction of the plates is taken into account. The numerical modelling is based on a small set of standard material parameters that are fully characterised. Shear localisation as well as acute transient observations are reproduced and agree with experimental measurements. The plasticity appears to be the fundamental mechanism of the localisation of the flow. Finally, the present approach could be extended from liquid foams to similar materials such as emulsions, colloids or wet granular materials, that exhibit localisation.     

Optical manipulation of microscale fluid flow

A novel optical method is used both to probe and to control dynamics in experiments on the spreading of microscale liquid films over solid substrates. The flow is manipulated by thermally induced surface-tension gradients that are regulated by controlling the absorption of light in the substrate. This approach permits, for the first time, the measurement of the dispersion relation for the well-known contact line instability; the measurements are compared with theoretical predictions from the slip model for spreading films. The experiments also demonstrate the use of feedback control to suppress instability. These results show that optical control can provide dynamically reconfigurable manipulations of fluid flow, thereby suggesting a general approach for constructing reprogrammable microfluidic devices.     

Nanosecond electrical discharges between semiconducting sulfide mineral particles in water

A model for developing electric discharges between sulfide mineral (pyrite) particles under high-voltage nanosecond pulses in a liquid medium (water) is considered. A possibility of electrical breakdowns of liquid gaps between particles under nanosecond pulses is shown. This probability and the energy released in discharge channels depend strongly on the sulfide conductivity.     

Implementation of the desired state of motion for a vessel with heavy liquid

A mode of precision control of a vessel with an ideal heavy liquid into the state of the desired motion is proposed and justified. The algorithm is implemented and tested for typical control functions. The application efficiency of the proposed approach for poorly controllable oscillation systems with an infinite number of degrees of freedom under conditions of resonance is established.     

Analytical approach for determining the surface shape of a liquid metal under laser cladding conditions

We propose an improvement of an analytical approach presented previously for determining the surface shape formed during laser cladding process at the goods manufacturing in additive technologies. The approach is based on the balance of pressures on the liquid metal surface, which occurs under the gravity and surface tension. A method generalization is proposed for the case of a curvilinear shape of a substrate, which allows determining the surface ge-ometry at arbitrary contact angles for single beads, vertical walls, and coatings formed by overlapping beads. The verification of the considered approach was carried out for laser cladding problems with the use of experimental data obtained by other authors.     

基于液体晃动干扰观测器的航天器混沌姿态H_∞控制

针对航天器受液体燃料晃动及内外周期性微小激励耦合影响产生混沌运动的问题,提出了基于神经网络干扰观测器的自适应H∞鲁棒控制方案,以实现充液航天器混沌姿态运动的消除与液体燃料晃动的抑制.基于神经网络的非线性逼近能力设计干扰观测器,自适应跟踪补偿液体晃动、参数不确定及外扰引起的耦合扰动,解决液体燃料晃动角速度及外扰不易直接测量的问题,提高控制器对系统不确定的自适应能力及液体晃动的抑制能力.同时考虑观测误差与模型不精确问题,利用H∞控制策略提高控制器的鲁棒性.通过与现有常用控制策略的对比仿真研究,验证了控制方案的有效性及优势.     

Density wave theory of freezing and the solid

The theory of the liquid to solid transition, in three as well as in two dimensions, is reviewed. The transition can be viewed either as the melting of the solid due to phonon or defect proliferation instabilities or alternatively as freezing of the liquid into a density wave state with crystalline symmetry. A theory due to Yussouff and the author, based on the latter idea, is discussed and its predictions are compared with experiment. It is shown that the theory leads to a new approach to the properties of a deformed (e.g., sheared) solid and of defects such as grain boundaries and dislocations in a solid. The approach brings out explicitly the structural nature of these properties, and is not restricted to small deviations from perfect periodicity (harmonic approximation) since the solid, the liquid and anything in between can be handled theoretically.     

Emission of phonons by vortex filaments and the decay of a turbulent state in the Bose condensate

A turbulence decay mechanism in the Bose condensate (superfluid liquid) that is associated with the emission of acoustic waves upon reconnection of vortex filaments is studied. An approach based on the master equation for the length distribution of vortex loops is developed. Evolution equations for the density of the vortex filaments in the quasistationary and non-quasistationary regimes are derived. The decay law is compared to the numerical simulation results.     

Dose Characteristics of the Ionization Chamber Based on TMS “Warm Liquid”

An ionization chamber is proposed, based on which dose characteristics of organosilicon liquid (tetramethylsilane (TMS)) featuring electronic conductivity at room temperature are studied with the purpose of its application for developing complex radiation detectors and dosimeters for planning beam therapy.     

向列相液晶中光致非线性效应的研究

分析了向列相液晶中的光致非线性效应.在此基础上,基于液晶显示器工作原理设计了光控光器件.提出简化模型并利用琼斯矩阵给出光在该模型中的传输理论;引入斜入射的控制光束代替外加电压来调控液晶盒中分子的排列,实现对出射信号光的位相和光强的光-光调控;利用5CB液晶的温度特性分析环境温度对光-光调控的影响.理论分析表明:出射光位...     

Parameter identification of new bidirectional tuned liquid column and sloshing dampers

A tuned liquid column and sloshing damper (TLCSD) is introduced in this study. It shows dynamic behavior of both tuned liquid column damper (TLCD) and tuned liquid damper (TLD) in the direction of two axes perpendicular with each other. As a preliminary study for applying the TLCSD to bidirectional control of building structures, one of objectives of this study is to derive analytical dynamics to investigate coupled effects due to TLCD and TLD. Another objective is to investigate the effect of coupled control force due to TLCD and TLD on the dynamic characteristic of the TLCSD based on analytical dynamics. Shaking table test is undertaken to experimentally grasp dynamic characteristics of TLCSD under white noise excitation with various amplitude levels. Its dynamic characteristics are expressed by the transfer function from the shaking table acceleration to the control force generated from a TLCSD. The analytical dynamics of TLCSD is derived from the equivalent linearized TMD model. The coupled dynamics of TLCSD is expressed in terms of those of both TLCD and TLD. Finally, the key parameters of both TLCD and TLD are identified based on the coupled dynamics proposed in this study, which include the mass ratio of horizontal liquid column to total liquid for a TLCD, and the participation factor of the fundamental liquid sloshing for a TLD and damping ratio for both cases.     

激光加载锡的动态破碎颗粒尺寸分布

基于Grady能量破坏准则,结合固体动态断裂碎块尺寸分布规律研究结果,提出了材料微层裂破碎颗粒质量分布改进模型,并对强激光加载下锡的熔化破碎实验进行了理论计算。研究显示,理论计算的锡的微层裂破碎颗粒分布数随直径变化规律与实验结果一致,模型进一步改进需考虑应变率变化等更多综合因素影响。