Pound-Drever-Hall稳频误差信号线性动态范围及灵敏度分析

在Pound-Drever-Hall激光稳频方法中,误差信号的线性动态范围和灵敏度是影响稳频效果的重要指标。为了对Pound-Drever-Hall激光稳频性能进行优化,本文理论分析了调制频率、FP腔镜反射率和腔长对动态范围及灵敏度的影响,并通过实验仿真进行定量讨论和优化。实验结果表明,调制频率、反射率和腔长都分别与线性动态范围的大小有着紧密的联系,通过对这些参数的正确选取,以及对精度和灵活性要求的综合考虑,可以提升稳频系统的效果;而且对调制深度的优化可以提高误差信号灵敏度。

A Cultural Analysis of Pound's Mistranslation in the Poem "Blue, blue is the Grass

Ezra Pound is one of the founders of the American Imagist poetry, and Chinese Classic Poetry happened to be a great stimulus as the Renaissance from the Greeks to this poetry movement. Pound, who was deeply fascinated by Chinese poetry, has rendered many into English. Yet due to cultural differences, Pound’s translation has a lot of mistakes. And this paper aims at a cultural analysis of the mistranslation on a certain text to display its influence upon the Imagist Movement in the history of American Poetry.

Effects of Bagging with Paper Bags and Non-woven Bags on Flavor Compounds of Feicheng Peach

With Hongli Feicheng Peach as the test material, the effects of bagging with 4 kinds of paper bags and 3 kinds of non-woven bags on the soluble sugar, organic acids and aroma compounds in peach fruits were investigated using headspace solid-phase microextraction （HS-SPME） combined with gas chromatogra- phy-mass spectrometry （GC-MS） and high-performance liquid chromatography （HPLC）. The results showed that there were significant differences in sugar and acids contents of peach fruits between different bagging treatments. The sugar con- tent of peach fruits was increased when bagged with single-layer inner-black outer- yellow paper bags and double-layer inner-white outer-yellow paper bags. The organ- ic acid content in peach fruits bagged with all the types of bags except the single- layer inner-black outer-yellow paper bag was increased greatly. The count and rela- tive content of aroma compounds were all decreased after bagging. Combined with the detection results of soluble sugar, organic acids and aroma compounds, the sin- gle-layer inner-black outer-yellow paper bag was suitable for bagging of Hongli Fe- icheng peach.

Pound-Drever-Hall激光稳频系统线性化复频域建模及分析研究

Pound-Drever-Hall(PDH)稳频系统利用了调制光谱技术和外差探测技术,将激光频率锁定在F-P参考腔的中心频率上以实现稳频。鉴频曲线的线性区为PDH系统的频率快速捕获区。在此区域内,PDH误差信号与激光频率差成正比。本文建立了该频率快速捕获区的PDH稳频系统线性化复频域模型,研究了系统的稳定性和稳态误差。F-P参考腔作为稳频基准,其干扰对系统稳频性能影响极大。将F-P参考腔干扰作为噪声源,分析了系统的扰动误差。分析了系统动态性能,研究了频率锁定的暂态响应过程,给出了系统参数设计依据。

Stylistic Analysis of Ezra Pound's Cathay

Cathay by Ezra Pound is the masterpiece in modern poetry in the West,and it contains nineteen Chinese poems.Based on literary stylistic theory,Pound’s translation style in Cathay is analyzed from lexical categories,aspects of syntax and figures of speech etc.It is found that the vocabulary and sentences in Cathay are very simple and brief,and the language is rich of images,which is the exact reflection of Pound’s idea of Imagism.

正交解调Pound-Drever-Hall激光稳频技术实验研究

为了提高激光器的频率稳定度,设计了基于正交解调原理的Pound-Drever-Hall(PDH)稳频系统。该系统采用直接数字频率合成器同步产生三路同频正弦和余弦信号,其中一路正弦信号用作电光相位调制器的驱动信号,另两路正弦和余弦信号同时用作相位解调的参考信号。解调所得PDH稳频系统的误差信号用于反馈调节激光器腔长,使得激光器频率自动稳定到Fabry-Perot(F-P)参考腔的谐振频率上。建立了正交解调PDH稳频实验系统,实验结果表明,在1.5 h稳频时间内,激光器的频率漂移不超过±0.13 MHz,根据Allan方差计算得到其频率稳定度优于1.2×10^(-11)。这种稳频激光器可用作合成波绝对距离干涉测量系统的理想光源。

A modified Kelvin impact model for pounding simulation of base-isolated building with adjacent structures

Base isolation can effectively reduce the seismic forces on a superstructure, particularly in lowto medium-rise buildings. However, under strong near-fault ground motions, pounding may occur at the isolation level between the baseisolated building （BIB） and its surrounding retaining walls. To effectively investigate the behavior of the BIB pounding with adjacent structures, after assessing some commonly used impact models, a modified Kelvin impact model is proposed in this paper. Relevant parameters in the modified Kelvin model are theoretically derived and numerically verified through a simple pounding case. At the same time, inelasticity of the isolated superstructure is introduced in order to accurately evaluate the potential damage to the superstructure caused by the pounding of the BIB with adjacent structures. The reliability of the modified Kelvin impact model is validated through numerical comparisons with other impact models. However, the difference between the numerical results from the various impact analytical models is not significant. Many numerical simulations of BIBs are conducted to investigate the influence of various design parameters and conditions on the peak inter-story drifts and floor accelerations during pounding. It is shown that pounding can substantially increase floor accelerations, especially at the ground floor where impacts occur. Higher modes of vibration are excited during poundings, increasing the inter-story drifts instead of keeping a nearly rigid-body motion of the superstructure. Furthermore, higher ductility demands can be imposed on lower floors of the superstructure. Moreover, impact stiffness seems to play a significant role in the acceleration response at the isolation level and the inter-story drifts of lower floors of the superstructure. Finally, the numerical results show that excessive flexibility of the isolation system used to minimize the floor accelerations may cause the BIB to be more susceptible to pounding under a limited seismic gap.

内调制技术和Pound-Drever-Hall技术对894.6nm倍频腔的稳频比较

为了对抽运源的稳频技术做出对比和选择,采用内调制技术和相位调制光外差技术,以周期性极化KTP晶体作为非线性晶体,实现了894.6nm连续光两镜驻波倍频腔的稳频运转。结果表明,在不同注入光功率下,用这两种方法锁定倍频腔后获得的蓝光功率基本相同;在最大注入光功率为350m W时,获得178m W的447.3nm蓝光,相应的转化效率为50.8%;在最大注入光功率下,利用内调制技术和相位调制光外差稳频技术获得的蓝光在2h内功率起伏分别为3.4%和2.3%。该研究对获得稳定输出的447.3nm蓝光用来制备铯原子D1线的非经典光的实验是有帮助的。

Experimental study of a highway bridge with shape memory alloy restrainers focusing on the mitigation of unseating and pounding

This paper presents an experimental study to investigate the performance of shape memory alloy(SMA) restrainers for mitigating the pounding and unseating of highway bridges when subjected to seismic excitations.Mechanical property tests of the SMA wire used in the restrainers are conducted first to understand the pseudo-elastic characteristics of the material.Then,a series of shaking table tests are carried out on a highway bridge model.The structural responses of the highway bridge model equipped with SMA restrainers,installed in the form of deck-deck and deck-pile connections,are analyzed and compared with the uncontrolled structures.The test results of this study indicate that the SMA restrainers are not only effective in preventing unseating but also in suppressing the seismic-induced pounding of the highway bridge model used in this study.

Implications of seismic pounding on the longitudinal response of multi-span bridges-an analytical perspective

Seismic pounding between adjacent frames in multiple-frame bridges and girder ends in multi-span simply supported bridges has been commonly observed in several recent earthquakes.The consequences of pounding include damage to piers,abutments,shear keys,bearings and restrainers,and possible collapse of deck spans.This paper investigates pounding in bridges from an analytical perspective.A simplified nonlinear model of a multiple-frame bridge is developed including the effects of inelastic frame action and nonlinear hinge behavior,to study the seismic response to longitudinal ground motion.Pounding is implemented using the contact force-based Kelvin model,as well as the momentum-based stereomechanical approach.Parameter studies are conducted to determine the effects of frame period ratio,column hysteretic behavior,energy dissipation during impact and near source ground motions on the pounding response of the bridge.The results indicate that pounding is most critical for highly out-of-phase frames and is not significant for frame period ratios greater than 0.7.Impact models without energy dissipation overestimate the displacement and acceleration amplifications due to impact,especially for elastic behavior of the frames.Representation of stiffness degradation in bridge columns is essential in capturing the accurate response of pounding frames subjected to far field ground motion.Finally,it is shown that strength degradation and pounding can result in significant damage to the stiffer frames of the bridge when subjected to large acceleration pulses from near field ground motion records.

Earthquake induced pounding between adjacent buildings considering soil-structure interaction

Many closely located adjacent buildings have suffered from pounding during past earthquakes because they vibrated out of phase. Furthermore, buildings are usually constructed on soil; hence, there are interactions between the buildings and the underlying soil that should also be considered. This paper examines both the interaction between adjacent buildings due to pounding and the interaction between the buildings through the soil as they affect the buildings＇ seismic responses. The developed model consists of adjacent shear buildings resting on a discrete soil model and a linear visco- elastic contact force model that connects the buildings during pounding. The seismic responses of＇ adjacent buildings due to ground accelerations are obtained for two conditions： fixed-based （FB） and structure-soil-structure interaction （SSSI）. The results indicate that pounding worsens the buildings＇ condition because their seismic responses are amplified after pounding. Moreover, the underlying soil negatively impacts the buildings＇ seismic responses during pounding because the ratio of their seismic response under SSSI conditions with pounding to those without pounding is greater than that of the FB condition.

Dimensional analysis of earthquake-induced pounding between adjacent inelastic MDOF buildings

In this study the seismic pounding response of adjacent multi-degree-of-freedom(MDOF) buildings with bilinear inter-story resistance characteristics is investigated through dimensional analysis. The application of dimensional analysis leads to a condensed presentation of the response, and the remarkable self-similarity property for bilinear MDOF buildings with inelastic collision is uncovered. It is shown that when the response is expressed in the appropriate dimensionless form, response spectra for any intensity of the excitation collapse to a single master curve. The reduced Π set explicitly describes the interaction between the colliding structures. The effect of pounding on the MDOF building’s response is illustrated using three well-divided spectral regions(amplifi ed, de-amplifi ed and unaffected regions). Parametric studies are conducted to investigate the effects of the story stiffness of structures, the story stiffness ratio and mass ratio of adjacent buildings, the structural inelastic characteristics and the gap size values. Results show that(i) the infl uence of system stiffness ratio to the lighter and more fl exible building is more signifi cant in the fi rst spectral region, where the maximum response of the building is amplifi ed because of pounding; and(ii) the velocity and pounding force of the heavier and stiffer building is unexpectedly sensitive to the mass ratio of adjacent buildings.

Ezra Pound＇s Conversion to Confucianism

The paper aims to explore Pound＇s early discovery of Confucianism and his conversion to Confucianism. Pound＇s interest in Confucianism coincided with the time when Christianity, already ＂contaminated＂ by ＂historical diseases＂ in Pound＇s view, could not offer a valid vision by which to guide the spiritual life, resulting in losing self in a modem society. Pound discovers three main deficiencies of Christianity： lack of respect for individuality, the decline of ethics, and open attack upon nature, which could not provide solutions to Western problems. Pound turned to Confucianism to search the existence of modem man in the face of society, and nature, which results in Pound＇s Confucian medicine to cure Western moral obtuseness.

Ultra-deep adsorptive removal of thiophenic sulfur compounds from FCC gasoline over the specific active sites of CeHY zeolite

Adsorption desulfurization performance of Na Y,HY and Ce HY zeolites is evaluated in a miniature fixedbed flow by model gasoline containing with thiophene,tetrahydrothiophene,2-methylthiophene,benzothiophene or mixed sulfur compounds.The structural properties of adsorbents are characterized by XRD,N2-adsorption and XPS techniques.Adsorption desulfurization mechanisms of these sulfur compounds over the specific active sites of adsorbents as a major focus of this work,have been systematically investigated by using in situ FT-IR spectroscopy with single and double probing molecules.Desulfurization experimental results show that the Ce HY adsorbent exhibits superior adsorption sulfur capacity at breakthrough point of zero sulfur for ultra-deep removal of each thiophenic sulfur compound,especially in the capture of aromatic 2-methylthiophene(about ca.28.6 mgS/gadsorbent).The results of in situ FT-IR with single probing molecule demonstrate an important finding that high oligomerization ability of thiophene or 2-methylthiophene on the CeHY can promote the breakthrough adsorption sulfur capacity,mainly resulting from the synergy between Br?nsted acid sites and Ce(III)hydroxylated species active sites located in the supercages of Ce HY.Meanwhile,the result of in situ FT-IR with double probing molecules further reveals the essence of oligomerization reactions of thiophene and 2-methylthiophene molecules on those specific active sites.By contrast,the oligomerization reaction of benzothiophene molecules on the active sites of Ce HY cannot occur due to the restriction of cavity size of supercages,but they can be adsorbed on the Br?nsted acid sites via protonation,and on Ce(III)hydroxylated species and extra-framework aluminum hydroxyls species via direct"S-M"bonding interaction.As to the tetrahydrothiophene,adsorption mechanism is similar to that of benzothiophene,except in the absence of protonation.The paper can provide a new design idea of specific adsorption active sites in excellent desulfurization adsorbents for elevating higher quality of FCC gasoline in the future.

A Comparison of Pound's Poetic Ideas and Some Chinese Poetic Principles-Using the Translation of "The Jewel Stairs' Grievance" as a Case in Point

The prominent features of Li Bai's "The Jewel Stairs'Grievance" are precise diction;implicit meaning;an absent narrator;and a seamless unity of images and feelings.Pound's translation of it in Cathay reveals some kind of connections between some Chinese poetic principals and Pound's individual poetics.

The Function of Colour in Ezra Pound's Imagist Poetry

This paper is to explore the function of colour in Ezra Pound's Imagist poetry.As the position of image in poetry is raised,colour,as a part making up image,play a much more positive role in Pound's Imagist poems by defining the image to be more concrete and definite and reinforcing the theme directly.Pound's Imagist poetry includes his typical short Imagist poems and his poems in Cathay.

SYNTHESIS AND CHARACTERIZATION OF A NEW COMPOUND :K_6Ti_0.67Nb_15.33O_42

A new compound K6Ti0.67Nb15.33O42 was prepared for the first time by solid state reaction in K2O-Ni2O3-Nb2O5 ternary system. The new compound was characterized by electron probe, X-ray powder diffraction and DTA. The result of X-ray powder diffraction shows that K6Ti0.67Nb15.33O42 crystallizes the hexagonal system with unit cell parameters a = 9. 1341(5) A ,c=12. 090(1)A . and space group P62/mcm(193 ).

Underground blast effects on structural pounding

In the present study,actual three-dimensional structures are converted into a stick model of multi degree of-freedom(MDOF)systems for understanding the macro-behavior of structures.The study investigates the performance of three closely spaced,adjacent G+10,fixed-base MDOF systems with the mass aligned at the same levels and subjected to accidental underground blast loading.The acceleration time history of underground blast loading is generated based on past empirical relationships.The blast charge weight varies from 10 to 75 t while keeping the charge distance constant(R=100 m).The entire formulation is solved with the MATLAB solver,using the state space form solution.Three cases are considered,based on changing the position of the three stick systems.The first case considered left building rigid,middle building moderate rigid,and right building flexible.The second assumed left building flexible,middle building rigid,and right building moderate rigid.The third examined the left building as moderate rigid,the middle building as flexible,and the right building rigid.An analysis of the results shows that the arrangement with low stiffness,high stiffness,and moderately stiff buildings placed to the left,middle,and right side,respectively,yields minimum structural response when compared to the other two combinations.

Equivalent Kelvin Impact Model for Seismic Pounding Analysis of Bridges

Based on Hertz contact theory, a method to determine the parameters of Kelvin impact model for seismic pounding analysis of bridges is proposed. The impact stiffness of Kelvin model is determined by the ratio of maximum impact force to maximum contact deformation, which is calculated based on Hertz contact theory with considering the vibration effect. The restitution coefficient which has great influence on the damping coefficient of Kelvin impact model is investigated by numerical analysis. Numerical results indicate that the impact stiffness of Kelvin impact model increases with the increment of the Hertz contact stiffness, approaching velocity or the length ratio of short to long girders. Vibration effect has remarkable influence on the impact stiffness and cannot be neglected. The restitution coefficient decreases when approaching velocity increases or the length ratio of short girder to long girder decreasing. The practical ranges of impact stiffness and restitution coefficient are obtained as 3 × 10^8--6 × 10^8 N/m and 0.6-3.95 respectively.

Nonlinear analysis of pounding between decks of multi-span bridge subjected to multi-support and multi-dimensional earthquake excitation

The nonlinear analysis of pounding between bridge deck segments subjected to multi-support excitations and multi-dimensional earthquake motion was performed.A novel bottom rigid element(BRE)method of the current displacement input model for structural seismic analysis under the multi-support excitations was used to calculate structural dynamic response.In the analysis,pounding between adjacent deck segments was considered.The seismic response of a multi-span bridge subjected to the multi-support excitation,considering not only the traveling-wave effect and partial coherence effect,but also the seismic non-stationary characteristics of multi-support earthquake motion,was simulated using finite element method(FEM).Meanwhile,the seismic response of the bridge under uniform earthquake was also analyzed.Finally,comparative analysis was conducted and some calculation results were shown for pounding effect,under multi-dimensional and multi-support earthquake motion,when performing seismic response analysis of multi-span bridge.Compared with the case of uniform/multi-support/multi-support and multi-dimensional earthquake input,the maximum values of pounding force in the case of multi-support and multi-dimensional earthquake input increase by about 5 8 times;the absolute value of bottom moment and shear force of piers increase by about50%600%and 23.1%900%,respectively.A conclusion can be given that it is very necessary to consider the pounding effect under multi-dimensional and multi-support earthquake motion while performing seismic response analysis of multi-span bridge.