利用λ/4波片测定任意波片的位相延迟角

讨论了利用λ/4波片测定任意波片位相延迟角的原理 ,介绍了实验测定的方法。

1998年东亚夏季风环流相互作用的低频耦合模态及其位相特征

利用1998年SCSMEX试验期降水观测资料和NCEP/NCAR再分析资料, 将物理量场在降水EOF分析得到的时间系数上展开,分析东亚夏季风环流低频变化特征。在揭示环流及我国东部降水异常观测事实的基础上,研究了它们之间相互作用的低频耦合模态及其可能机理,并讨论了低频位相变化与长江流域降水的关系,指出暴雨期次级环流是高低空环流相互作用的可能纽带。

正三角型结构三光纤出射光场干涉理论模型及其实验

利用三根光纤以正三角形的方式组合在一起 ,实现了三光纤Moir啨干涉 ,建立了纤端出射场干涉模型 ,并进行了理论计算 实验结果与理论计算结果符合较好

基于Talbot效应的掺镁铌酸锂二维六角位相阵列光栅的研究

本文系统研究了基于泰伯效应(Talbot)的位相可调掺镁铌酸锂二维六角位相阵列光栅及其光衍射成像,对光栅占空比 D、不同位相差φ、及泰伯分数β条件下的光栅近场光衍射强度分布进行了理论研究, 结果表明当光栅占空比 D = 52%、位相差φ = 0.75 π、泰伯分数β = 0.2 时, 光栅近场衍射光图像效果最佳. 实验设计与制备了掺镁铌酸锂二维六角位相阵列光栅,并对其进行了Talbot衍射光成像实验研究,得到了不同位相差和不同泰伯分数β条件下光栅近场衍射光图像,实验结果与理论研究结果相符.

Using a linear array to estimate the velocity of underwater moving targets

A new method uses a linear array that takes advantage of underwater physical sound fields to estimate the velocity of an underwater moving target. The mathematical model was established by considering the geometric relationship between the moving target installed with only two transducers to radiate sound of different frequencies and the linear array. In addition, deterministic maximum likelihood and signal phase matching algorithms were introduced to effectively find the directions of arrival （DOAs） of the sound sources of the two transducers installed on the target. Factors causing velocity measurement errors were considered. To track the target, a linear array with a compass, a pressure transducer, a signal conditioner and a digital recorder was configured. Relevant requirements for the array parameters were derived. The simulation showed that a 16-element array with an aperture of less than lm can measure velocity with relative error of no more＇, than 4% when including typical system errors. Anechoic pool and reservoir experiments confirmed these results.

外加电场调制二维六角位相阵列光分束器的研究

本文建立了外加电场调制二维六角位相阵列光分束器的倒格矢理论模型,利用数值模拟方法开展了阵列光分束器的理论研究,对可调位相差阵列光分束器进行了分析,得到了不同分数泰伯距离以及外加电场条件下的光强分布图.实验设计与制备了铌酸锂二维六角位相阵列光分束器,并对其进行了Talbot衍射光分束实验研究,当外加电压为0.5 kV(电场为1 kV/mm)时,观测到了Talbot衍射光分束现象,随着外加调制电场的增大,其衍射光分束图像越清晰,该实验结果和理论研究结果相符.

基于Talbot效应的可调位相差二维六角位相阵列器的理论研究和数值模拟

系统研究了基于Talbot效应的光栅阵列器,利用数值模拟方法开展了阵列器的理论研究,对二维振幅型与固定位相差型阵列器进行了分析,通过外加电场调制位相差可以很好的解决二维振幅型与固定位相差型阵列器后z处光强分布不可调节和工作易受温度影响的问题.推导了外加电场调制位相差位相型阵列器实现均匀光强分布的理论模型,并验证了Paturz等人的实验结果,为此种新型阵列器的研究提供了基础.

Thyristor Controlled Phase Shifter:A Comprehensive Survey

Thyristor control phase shifter (TCPS) is one of the new facilities implemented in power network, leading to the development of economically efficient and technically reliable system. This paper introduces the function of TCPS in power system, describes its working principle and structure, and suggests some simple models used in its study and briefly presents the comparison between different types of TCPSs and their applications.

Motion and orientation of cylindrical and cubic particles in pipe flow with high concentration and high particle to pipe size ratio

Lattice Boltzmann method was used to numerically investigate the motion and orientation distribution of cylindrical and cubic particles in pipe flow with high concentration and high particle to pipe size ratio. The transient impulse model of 3D collisions between particles and between particle and wall is proposed. The numerical results are qualitatively in agreement with and quantitatively comparable to the experiment data. The results show that the increases of both the cylindrical particle to pipe size ratio and the particle aspect ratio decrease the rotation about all axes. All rotations of cubic particles decrease with increasing the particle concentration. The cubic particles, rotating more drastically in the flow with large Reynolds number, rotate faster than the cylindrical particles with the same size. The cylindrical particles align with the flow direction more obviously with decreasing Reynolds numbers. However, the orientations of cubic particles are spread all over the range with no significant difference in magnitude, and the Reynolds numbers have no obvious effect on the orientations of cubic particles.

Phase Properties of Two-Mode Squeezing-Rotating Entangled Representation

By virtue of the squeezing-rotating entangled representation, we mainly establish the new two-mode phase operator and phase angle operat, or, which is a general form including the foregoing formalist in two-mode Fock space. In addition, the corresponding phase distribution function is given in the entangled representation. In terms of this definition, we also analyze the phase behavior of some simple two-mode states such as squeezing-rotatlng coherent state, squeezing-rotating vacuum state, and so on. It is found that the results exactly agree with the foregoing phase theory.

Evolution of TiNi precipitates in TiNi alloy during equal channel angular pressing

The evolution of Ti3Ni4 precipitates in Ti49.2Ni50.8 alloy during equal channel angular pressing(ECAP) and intermediate annealing was investigated by transmission electron microscopy. The solution-treated Ti49.2Ni50.8 alloy was aged at 450 ℃ for 10 to 60 min to obtain Ti3Ni4 precipitates ranging from 37 to 75 nm. After ECAP at 450 ℃ for one pass, Ti3Ni4 precipitates introduced by aging for 10 and 30 min totally dissolve into the matrix;however, those produced by aging for 60 min become smaller. The critical size of Ti3Ni4 precipitates to totally dissolve into matrix is determined to be in the range of 37-68 nm. The dislocation density of ECAP-processed samples depends on the initial size of Ti3Ni4 precipitates after aging. With increasing the duration of initial aging from 10 to 60 min, the dislocation density firstly increases and then decreases.

Rolling thin film oven test investigation for polymer modified asphalt

Rolling Thin Film Oven Test （RTFOT） is the AASHTO T240 standard method to simulate asphalt plant mix aging. But it has proven inadequate in aging polymer-modified asphalts （PMA）. NCHRP 9-10 offered a modified RTFOT （MRTFOT） by adding a steel rod in each bottle. Since construction temperature of PMA mixture is 10 ℃ -20 ℃ higher than that of conventional asphalt mixtures in the field, elevating RTFOT temperature for PMA is necessary for adequate aging and proper simulation. Six PMAs with various PG grades and sources were aged with RTFO at elevated temperatures. Some were also treated with MRTFOT for comparison. SHRP performance grade and phase angle were used as indicators to analyze the effects of RTFOT under different conditions. The results show that elevating the temperature is more effective than using rods. And PMA RTFOT temperature could be determined by equiviscous principle. From limited data, O. 25 Pa ~ s is tentatively proposed as critical viscosity for PMA, but still more work is necessary to validate this. Given the fact that equiviscous principle is seldom used in field practice, a simple approach was proposed： 173 ℃ is used for RTFOT of PG70 PMAs （grading herein from un-aged asphalts） , while 178 ℃ is for PMAs of PG76 or PG82 and 20 ℃ higher than standard 163 ℃ is necessary for PG 88 or stiffer PMAs.

Optimal Forward-Scattering Angles of Atmospheric Aerosols in North China

The accurate understanding of atmospheric aerosol extinction coefficients is very important for at- mospheric science research. To achieve a fast and simple method for determining the parameters, the selection of optimal forward-scattering angles of atmospheric aerosols is required. In this paper, the authors introduce the detec- tion basis of forward-scattering of atmospheric aerosols, and the authors verify the sensitivity of the phase function to the real part of the complex refractive index. The au- thors use the Jaenicke urban aerosol model to determine that forward-scattering angles near 33° are suitable. However, the optimal forward-scattering angles in North China are between 37° and 40°. Numerical simulation shows that certain types of particle size distribution of newly generated particles and pollution have limited in- fluences on the selection of forward-scattering angles. But the ranges of these insensitive angles shift - 10 degrees for dust intrusion, and the relative deviations of the phase function are less than 5.0% within extra angles of 0° to 3°. This study can serve as a reference for the selection of optimal forward-scattering angles for visibility meters and Present Weather Identifiers （PWIs） in addition to the de- tection of forward-scattering optical properties.

Angular Momentum Phase State Representation for Quantum Pendulum

To consummate the quantum pendulum theory whose Hamiltonian takes bosonic operator formalism and manifestly exhibits its dynamic behaviour in the entangled state representation, we introduce angular momentum state representation and phase state representation. It turns out that the angular momentum state is the partial wave expansion of the entangled state.

A Study on Tidal Force Triggering of the Wenchuan M_S8.0 Earthquake and Its Strong Aftershocks

By calculating the azimuth, phase angle and change rate of tidal force, and contrasting their rupture types, we find that in 6 of 11 reverse faulting earthquakes, the angles between the direction of the horizontal tidal force and compressive principal stress are within 33°, the vertical phase angles of all 8 strike-slip earthquakes are in the upward peak section and the vertical phase angles of two extensional normal faulting earthquakes are in the downward peak section. According to the above statistics, the mechanism of tidal force triggering of the Wenchnan Ms8. 0 Earthquake and its strong aftershocks is discussed.

Application Study on Synthesis Method of Earthquake Motion

For seismic design of structure and machinery, it is important to reproduce input earthquake motions that are likely to occur at a target site. Among the various methods used for generating artificial earthquake motions, the Synthesis Method of Trigonometric Function is used widely. In this method, artificial waves are reproduced by superimposing sine waves and then adding information about amplitude and phase in the frequency domain. In the Japanese architectural design code, the amplitude is standardized as the target response spectrum, and the phase can be defined by random numbers or by the phase of one observed wave. However, a random phase is distinctly different from the phase of an actual earthquake. Further, the phase of one observed wave is confined to the phase characteristic of the artificial wave of only one specific earthquake motion. In this paper, the authors introduce a new convenient method to reproduce artificial waves that not only satisfy the standardized spectrum property but also have the time-frequency characteristics of multiple observed waves. The authors show the feature of the artificial waves, discuss the merits of the method by comparing with existing methods, and report the tendencies of the non-liuear response by using simple model.

利用非线性光学效应进行红外信号探测和红外图象转换

一、引言激光问世后,使人们有可能把它作为得力助手,来发现和研究光学媒质在强光作用下所出现的一系列非线性光学效应和非线性光学理论,促使光学这门古老的学科以新的活力冲出物理学的边界而另树一帜。从1961年第一次观察到红宝石激光束在石英中的倍频现象起。

重视基础实验 提高理论教学效果——机械振动的几个示范试验

自然科学基础理论,是人们长期从事生产斗争和科学实验的经验总结,是培养又红又专科技人材所不可缺少的教学内容。近年来,由于“四人帮”的干扰和破坏,学校的基础理论研究和基础理论教学有所削弱,一些必要的基础实验没有给予应有的重视,严重破坏了无产阶级科技队伍的培养。对于“四人帮”的流毒和影响,决不能低估,必须竖决予以肃清,才能使学校的教育革命和科学研究沿着毛主席开辟的航道更加健康地发展。下面发表的理论力学安验是关于机械振动学基础实验的介绍,推荐给同志们一看。学员反映,做了这些实验以后,印象深刻,概念清晰,大表加探了对振动学一些基本概念的理解。因此,必须切实加强基础理论研究和教学,改革教学方法,加强科学实验,密切结合阶级斗争、生产斗争和科学实验的三大革命斗争寒际培养学员。如果我校各个专业都能做到像他们那样,认真搞好基础理论课教学和科学实验的结合,我们相信.一定能把培养学员的质量提高一大步。

Numerical Investigation of Flutter Stability in Subsonic Space Turbine Blisk with Emphasis on Cut-on/Cut-off Modes and Interblade Phase Angles

The so-called blisks,i.e.integrally bladed disks,are characterized by very low viscous material damping and make the flutter prediction much more critical.In that framework,a two-dimensional numerical study of a space turbine blisk featuring complex deformation of blades and high eigenfrequency(>40kHz)is performed.The simulations are based on unsteady Reynolds Averaged Navier Stokes computations linearized in the frequency domain and consist in the superposition of an unsteady linear(in time)pressure field,generated by a harmonic perturbation,upon a steady nonlinear(in space)flow.The aerodynamic damping coefficient is calculated over a range of nodal diameters,and the blades are predicted aeroelastically stable.However,violent changes occur and are rather critical since sudden and large deviations in stability appear.In that context,the nature of the waves propagating from the cascade are evaluated.Such an approach provides fundamental knowledge about the perturbations which can either propagate to the far-field(cut-on mode)or decay(cut-off mode).It is expected that the ability of the flow to damp or to amplify the blade motion is strongly affected by the way unsteady perturbations are transferred from the cascade to the far-field.The nature of the waves are first assessed from the aforementioned linearized results,then they are evaluated analytically and finally compared.A good agreement is found despite the strong assumptions of the analytical model.The results show a clear correlation between the cut-on/cut-off conditions and stability.The least stable configuration corresponds to cut-off mode at the inlet and no wave at the outlet.Without outgoing waves from the cascade,the blade is prone to be less stable:the energy from the blades vibration is necessarily dissipated or sent out by the cascade.

Theoretical analysis of stimulated polariton scattering from the A_1-symmetry modes of KNbO_3 crystal

Stimulated polariton scattering(SPS) based on noncollinear phase matching scheme from the A_1-symmetry modes of KNbO_3 crystal is investigated for generating terahertz(THz) wave. Frequency tuning characteristics of THz wave by varying the phase matching angle and pump wavelength are analyzed. The expression of the effective parametric gain length under the noncollinear phase matching condition is deduced. Parametric gain and absorption characteristics of THz wave in KNbO_3 are theoretically simulated. The characteristics of KNbO_3 for parametric oscillator(TPO) are compared with those of Mg O:LiNbO_3. The analysis results indicate that KNbO_3 is an excellent optical crystal for TPO to enhance the output of THz wave.