Directional Chiral Optical Emission by Electron-Beam-Excited Nano-Antenna

Manipulating directional chiral optical emissions on a nanometer scale is significant for material science research. The electron-beam-excited nanoantenna provides a favorable platform to tune optical emissions at the deep subwavelength scale. Here we present an L-shaped electron-beam-excited nanoantenna(LENA) with two identical orthogonal arms. By selecting different electron-beam impacting sites on the LENA, either the lefthanded circularly polarized(LCP) or the right-handed circularly polarized(RCP) emission can be excited. The LCP and RCP emissions possess different emission directionality, and the emission wavelength depends on the arm length of the LENA. Further, we show a combined nanoantenna with two LENAs of different arm lengths.Induced by the electron beam, LCP and RCP lights emit simultaneously from the nanoantenna with different wavelengths to different directions. This approach is suggested to be informative for investigating electron-photon interaction and electron-beam spectroscopy in nanophotonics.

Composite excitation multi-extension direction defect magnetic flux leakage detection technology

In the traditional pipeline magnetic flux leakage(MFL)detection technology,circumferential or axial excitation is mainly used to excite the magnetic field of defects.However,the domestic and foreign pipeline detection devices currently in operation are mainly axial excitation MFL detection tools,in which circumferential cracks can be clearly identified,but the detection sensitivity of axial cracks is not high,thus forming a detection blind zone.Therefore,a composite excitation multi-extension direction defect MFL detection method is proposed,which can realize the simultaneous detection of axial and circumferential defects.On the basis of the electromagnetic theory Maxwell equation and Biot Savart law,a mathematical model of circumferential and axial magnetization is firstly established.Then finite element simulation software is used to establish a model of a new type of magnetic flux leakage detection device,and a simulation analysis of crack detection in multiple extension directions is carried out.Finally,under the conditions of the relationship model between the change rate of leakage magnetic field and external excitation intensity under unsaturated magnetization and the multi-stage coil magnetization model,the sample vehicle towing experiment is carried out.The paper aims to analyze the feasibility and effectiveness of the new magnetic flux leakage detection device for detecting defects in different extension directions.Based on the final experimental results,the new composite excitation multi extension direction leakage magnetic field detector has a good detection effect for defects in the axial and circumferential extension directions.

Characteristics of horizontal ground motion measures along principal directions

Ground motion records are often used to develop ground motion prediction equations （GMPEs） for a randomly oriented horizontal component, and to assess the principal directions of ground motions based on the Arias intensity tensor or the orientation of the major response axis. The former is needed for seismic hazard assessment, whereas the latter can be important for assessing structural responses under multi-directional excitations. However, a comprehensive investigation of the pseudo-spectral acceleration （PSA） and of GMPEs conditioned on different axes is currently lacking. This study investigates the principal directions of strong ground motions and their relation to the orientation of the major response axis, statistics of the PSA along the principal directions on the horizontal plane, and correlation of the PSA along the principal directions on the horizontal plane. For these, three sets of strong ground motion records, including intraplate California earthquakes, inslab Mexican earthquakes, and interface Mexican earthquakes, are used. The results indicate that one of the principal directions could be considered as quasi-vertical. By focusing on seismic excitations on the horizontal plane, the statistics of the angles between the major response axis and the major principal axis are obtained; GMPEs along the principal axes are provided and compared with those obtained for a randomly oriented horizontal component; and statistical analysis of residuals associated with GMPEs along the principal directions is carried out.

Exploration of magnetic field generation of H_(3)^(2+)by direct ionization and coherent resonant excitation

Coherent electronic dynamics are of great significance in photo-induced processes and molecular magnetism.We theoretically investigate electronic dynamics of triatomic molecule H_(3)^(2+) by circularly polarized pulses,including electron density distributions,induced electronic currents,and ultrafast magnetic field generation.By comparing the results of the coherent resonant excitation and direct ionization,we found that for the coherent resonant excitation,the electron is localized and the coherent electron wave packet moves periodically between three protons,which can be attributed to the coherent superposition of the ground A′state and excited E+state.Whereas,for the direct single-photon ionization,the induced electronic currents mainly come from the free electron in the continuum state.It is found that there are differences in the intensity,phase,and frequency of the induced current and the generated magnetic field.The scheme allows one to control the induced electronic current and the ultrafast magnetic field generation.

Direct driven wind energy conversion system based on hybrid excitation synchronous machine

A novel direct-drive type wind power generation system based on hybrid excitation synchronous machine（HESM）is introduced in this paper.The generator is connected to an uncontrollable rectifier,and a fully controlled voltage-sourceinverter is used to connect the system to utility grid.An intermediate DC bus exists between the rectifier and inverter.A new control strategy is proposed which achieves the maximum power point tracking（MPPT） with the control of excitation current of HESM and stabilizes the DC link voltage with the control of inverter output current simultaneously.Specially-designed buck circuit is used to control the excitation current of HESM,and grid voltage-oriented vector control strategy is employed to realize the decoupling of the inverter output power.Simulation results and experiment in 3 kW lab prototype show an excellent static and dynamic performance of the proposed system.

ANALYSIS OF COUPLING INFLUENCES OF LABYRINTH SEAL PARAMETERS ON CROSS COUPLED STIFFNESS AND DIRECT DAMPING COEFFICIENT

Labyrinth seal can cause steam-exciting, the structural and operating parameters of labyrinth seal have effect on stability of rotor-system. For investigating the coupling influences of the structure and operating parameters of labyrinth seals on dynamic coefficients, a model of calculating dynamic coefficients of labyrinth seals is presented using a two control volume model. The coupling influences of parameters on cross-coupled stiffness and direct damping of labyrinth seal are discussed. In the conclusion, a reference of preventing steam-exciting vibration and optimum determination of design parameters of labyrinth seals are provided.

水下振动台竖向动水附加质量特征与机理试验研究

工程结构与水体耦合抗震研究需求越来越大,推动了水下振动台的建设与发展,水下振动台竖向动水附加质量及特征直接影响其设计和自身性能。本文通过试验方法,共设计135个工况,台面负载20 t惯性质量块,分别考虑不同激励量级、不同频率、不同水深,研究水下振动台竖向动水附加质量特征,并试探从机理层面进行解释。试验结果表明:激励量级与动水附加质量之间相关性较为复杂,不同频率之间存在分组现象,水深比(水深/台面直径)可作为水下振动台设计重要参数,不同水下振动台动水附加质量最小值频率拐点不同。试验研究为水下振动台设计以及模型试验可靠性等提供参考。

不同地震激励方向下隔震曲线梁桥易损性分析

为进一步评估隔震曲线梁桥在地震激励下的抗震性能,从地震易损性角度出发并兼顾考虑地震激励方向对其易损性的影响。利用APDL建立采用板式橡胶支座的隔震曲线梁桥有限元模型,从PEER中选取同一地震事件中的近断层地震动,按规范规定比例输入水平双向地震动进行非线性动力时程分析,结合地震响应与损伤指标计算得到各构件地震易损性曲线;考虑地震激励方向的变化,通过MATLAB编程绘制得到桥梁结构构件(桥墩与支座)以及整体系统的地震易损性曲面,分析探讨地震激励方向对隔震曲线梁桥易损性的影响。结果表明:不同极限状态下各桥墩切向损伤条件概率明显大于其径向,各支座的切向与径向易损性相差不大,但仍是各支座的切向易损性略大于径向易损性;桥梁各构件(桥墩与支座)切向易损性对地震激励方向均表现出很强依赖性,而径向易损性对其的依赖性相对较弱,且伴随损伤等级的提高,构件易损性对地震激励方向更加敏感;桥梁整体系统易损性对地震激励方向的变化不太敏感,且因各构件响应之间的相关性较高,其系统易损性更接近于易损性最大的构件——易损性下限;当进行隔震曲线梁桥抗震性能评估时,应考虑不同地震激励方向对其地震易损性的影响,从而使得易损性分析结果更加合理,能够更加真实地反映隔震曲线梁桥的实际损伤状态。

定向井抽油杆柱纵横扭耦合振动仿真研究

抽油杆柱是由接箍与抽油杆通过螺纹连接组成的细长杆柱。对抽油杆柱动力学行为的研究是预防抽油杆柱失效破坏,降低油井运行成本的基础。针对抽油杆柱的纵横扭耦合振动,提出杆管摩擦力产生的绕轴扭矩是扭转振动的激励这一观点。考虑摩擦力对杆柱纵横扭耦合振动的影响,建立了具有初弯曲的定向井抽油杆柱在顶端位移激励、底端载荷激励、弯曲井眼轨道激励与油管约束条件下的纵横扭耦合振动仿真模型。采用四阶龙格-库塔法实现了对仿真模型的求解和对杆柱动力学行为的仿真模拟。仿真结果表明:杆柱的纵横扭耦合振动对杆柱纵向、横向振动仿真结果均有影响,相对来说对纵向振动的影响并不明显;油井造斜段的杆管接触力大,杆柱受压段的杆管碰撞严重,因此油井的造斜段与杆柱的受压段为杆管偏磨的危险点;正常预紧情况下,杆柱的扭转振动不足以导致抽油杆柱脱扣,但当接箍螺纹预紧力降至杆柱的最大扭矩以下后,扭转振动即可能导致抽油杆柱脱扣。

Shear wave velocity prediction:A review of recent progress and future opportunities

Shear logs,also known as shear velocity logs,are used for various types of seismic analysis,such as determining the relationship between amplitude variation with offset(AVO)and interpreting multiple types of seismic data.This log is an important tool for analyzing the properties of rocks and interpreting seismic data to identify potential areas of oil and gas reserves.However,these logs are often not collected due to cost constraints or poor borehole conditions possibly leading to poor data quality,though there are various approaches in practice for estimating shear wave velocity.In this study,a detailed review of the recent advances in the various techniques used to measure shear wave(S-wave)velocity is carried out.These techniques include direct and indirect measurement,determination of empirical relationships between S-wave velocity and other parameters,machine learning,and rock physics models.Therefore,this study creates a collection of employed techniques,enhancing the existing knowledge of this significant topic and offering a progressive approach for practical implementation in the field.

Behavior of composite rigid frame bridge under bi-directional seismic excitations

Pushover analysis and time history analysis are conducted to explore the bi-directional seismic behavior of composite steel-concrete rigid frame bridge, which is composed of RC piers and steel-concrete composite girders. Both longitudinal and transverse directions excitations are investigated using OpenSees. Firstly, the applicability of pushover analysis based on the funda- mental mode is discussed. Secondly, an improved pushover analysis method considering the contribution of higher modes is proposed, and the applicability on composite rigid frame bridges under bi-directional earthquake is verified. Based on this method, an approach to predict the displacement responses of composite rigid frame bridge under random hi-directional seismic excitations by revising the elasto-plastic demand curve is also proposed. It is observed that the developed method yield a good estimate on the responses of composite rigid frame bridges under bi-directional seismic excitations.

W^(6+)离子的电子碰撞电离研究

采用细致能级扭曲波方法计算了W^(6+)离子基态[Kr]4d^(10)5s^(2)4f^(14)5p^(6)和亚稳态[Kr]4d^(10)5s^(2)4f145p^(5)5d^(1),[Kr]4d^(10)5s2^(4)f^(13)5p^(6)5d^(1),[Kr]4d^(10)5s^(2)4f^(14)5p^(5)5f1,[Kr]4d^(10)5s^(2)4f^(13)5p^(6)5f^(1)的电子碰撞单电离(EISI)截面.为了考虑亚稳态离子对电离的贡献,本文采用了3种模型来确定母离子束中处于长寿命能级的比值.与Pindzola和Griffin(1997 Phys.A 561654)的理论结果和Stenke等(1995 J.Phys.B:At.Mol.Opt.Phys.282711)实验结果进行比较,发现在考虑了亚稳态的贡献后本文结果与Stenke等的实验结果吻合得很好.

舰载设备在基础运动激励下的动力响应分析方法

为了解决舰载设备在基础运动激励下的动力响应问题,本文通过对比惯性载荷法、大质量法、大刚度法、直接激励法的动力学方程,探讨不同方法的特点和应用条件,并给出相应的算例与结果分析,为开展舰载设备的动力响应计算提供理论依据及方法。

多方向振动能量收集装置输出特性分析

针对一种压电振动能量收集装置输出特性展开研究,以实现多方向、宽频振动能量收集。首先,建立压电悬臂梁单自由度振动系统的微分方程,分析外激励下悬臂梁的输出响应。在此基础上,采用COMSOL建立多悬臂梁式振动能量回收装置有限元模型,并进行模态、输出电压及输出功率等分析,仿真结果表明振动能量回收装置在不同方向激励时均具有较高的电压、功率输出。此外,进一步讨论了装置的在不同方向激励下宽频输出特性,结果显示其在200~400 Hz频带范围内具有多个幅值相当的峰值。

基于自激振动激励器的流动控制汽车减阻研究

为了降低汽车行驶时的空气阻力,文章采用一种基于内部结构流固耦合的自激振动激励器以产生高速、高频的脉冲微射流进行主动流动控制。通过ANSYS双向流固耦合仿真模拟激励器的工作过程,分析其产生的脉冲射流速度和频率,再从不同工作参数和结构参数对其激励特性的影响进行研究;将该激励器沿Ahmed类车体模型尾部的分离边缘布置,研究其对车体尾迹区流动拓扑结构的影响,并通过空气阻力系数分析其减阻效果。结果表明,自激振动激励器产生的脉冲微射流可以有效地控制减阻,最高可达7.12%的减阻效果。该研究为主动流动控制减阻提供了新思路。

Research on a direct torque control for an electrically excited synchronous motor drive with low ripple in flux and torque

The electrically excited synchronous motor(ESM)has typically small synchronous inductance values and quite low transient values because of the damper windings mounted on the rotor.Therefore,the torque and stator flux linkage ripples are high in the direct torque control(DTC)drive of the ESM with a torque and flux linkage hysteresis controller(basic DTC).A DTC scheme with space vector modulation(SVM)for the ESM was investigated in this paper.It is based on the compensation of the stator flux link-age vector error using the space vector modulation in order to decrease the torque and flux linkage ripples and produce fixed switching frequency under the principle that the torque is controlled by the torque angle in the ESM.Compared with the basic DTC,the results of the simulation and experiment show that the torque and flux linkage ripples are reduced,the maximum current value is decreased during the startup,and the current distortion is much smaller in the steady-state under the SVM-DTC.The field-weakening control is incorporated with the SVM-DTC successfully.

大兆瓦等级中速永磁风力发电机电磁激振谐响应分析

半直驱风力发电机具有中速永磁的特点,与成熟的直驱永磁发电机相比,在转速、频率、结构、永磁固定方式、冷却方式及通风结构都存在很大不同。它兼顾了直驱的可靠、高效和双馈的低成本、小体积等优势,在近年风电整机价格的持续走低的背景下,有了较快的发展和提升。半直驱风力发电机电磁激振谐响应分析因为具有多学科耦合、建模复杂等特点,研究难度较高。本文通过对大兆瓦等级中速永磁风力发电机的设计研究,形成了电磁激励载荷的分析与提取、机电耦合分析模型的简化与建立、谐响应分析、真机试验测试对比等一整套方法,系统解决了电磁激振谐响应分析的难题。

CO_(2)震源的槽波勘探现场实验及前景讨论

震源是地震记录的源头,是地震勘探的关键部分,直接影响地震信号质量,常规炸药震源在高瓦斯矿井受到了十分严格的管制,因此,亟需研究适合于矿井地震勘探的新型震源。基于此,在突出矿井中厚煤层工作面开展了新型CO_(2)震源的槽波勘探实验,基于理论计算、数值模拟及现场实测等方法,进行了新型CO_(2)震源激发地震信号的运动学及动力学特性研究,结果表明:在异巷激发-接收透射勘探及同巷激发-接收透射勘探地震剖面上均出现典型的纵波、横波及槽波,其中槽波主频最高,振幅能量最强;异巷激发-接收的透射槽波频宽为200~350 Hz,槽波埃里震相约为260 Hz,同巷激发-接收的透射槽波振幅能量集中在250~450 Hz,槽波埃里震相约为280 Hz;2 kg液态CO_(2)震源理论能量超过140 g的TNT当量;因此,CO_(2)震源激发下地震信号的频率及振幅满足矿井地震勘探需求。相对于巷帮激发的炸药震源而言,CO_(2)震源集中力源的激发方式有利于槽波发育,以及CO_(2)震源具有深孔激发的优势,避开了巷道及围岩松动圈的影响,定向聚能作用于煤。同时,CO_(2)震源激发具有方向性,利用CO_(2)震源聚能方向性优势进行构造精细勘探是下一步重点研究方向;CO_(2)相变致裂技术常被用于煤层卸压增透,借用CO_(2)震源有望实现对掘进工作面前方的瓦斯富集异常、应力变化异常的随掘随探。

结构非平稳随机响应的混合型精细时程积分

演变随机激励的调制函数取各种不同形式时，相应的虚拟激励对应精细时程积分的不同形式。混合地应用这些形式于结构响应时变功率谱分析，可高效地获得达到计算机精度的数值结果。

曲率半径对城市曲线桥梁地震反应的影响

以某城市立交工程匝道桥为工程背景,采用MIDAS软件建立了全桥的有限元分析模型。采用反应谱方法研究了不同的曲率半径及地震激励方向对曲线桥梁地震反应的影响。结果表明:曲率半径对曲线桥梁前3阶自振频率影响比较明显;不同曲率半径及地震激励方向对曲线桥梁各墩地震反应的影响较大;应用0°～180°旋转激励法输入反应谱可以获得各个桥墩的最不利地震反应,且与《公路桥梁抗震设计细则》中规定的输入方法所得结果基本一致。