The Coulomb Resonances, the Quasi-Real Photons and Electro-Disintegration of Nuclei by High-Energy Electrons

Various aspects of the influence of the quasi-real photons and the Coulomb resonances on the formation of the crosssection of inelastic scattering of high energy electrons on atomic nuclei are investigated. Emiss is the energy that disappears in the processes of knocking-on of protons in the reactions . A new hypothesis that interprets the origin of the energy losses is proposed. Specific experiments that can confirm or refute this hypothesis are proposed as well. The “regularized” cross-sections of electro-disintegration of nuclei by high-energy electrons are calculated in the framework of the nuclear shell model. It is shown that for the experimental verification of the existence of Coulomb resonances, it is necessary to investigate the processes at relatively small angles of scattering. The peculiarities of numerical methods that are crucial in the investigation of inelastic scattering of high-energy electrons on nuclei in the framework of the nuclear shell model are analyzed in this work as well. The cross-sections of the scattering of high-energy electrons on the angle are calculated. It is shown that the orthogonality of the wave functions of a knocked-on proton in the initial and final states plays an important role in the interpretation of this process.

Analysis and Simulation of a High Performance Quasi Resonant PWM Inverter for Solar Power Generation

A quasi resonant pulse width modulation（PWM） inverter is used in a solar power system to convert the solar panel and battery charger＇s direct current（DC） output to alternating current（AC）.Although much has been published about DC to AC PWM inverters,none of the previous work has shown modeling and simulation results for DC to AC inverters.In this study,we suggest a new topology for a quasi resonant PWM inverter.Experimental results are also presented.

Fabry–Prot resonance coupling associated exceptional points in a composite grating structure

The exceptional point（EP） is a significant and attractive phenomenon in an open quantum system. The scattering properties of light are similar to those in the open quantum system, which makes it possible to achieve EP in the optic system. Here we investigate the EP in a Fabry–P′erot（F–P） resonant coupling structure. The coupling between different types of F–P resonances leads to a near zero reflection, which results in a degeneration of eigenstates and thus the appearing of EP. Furthermore, the multi-wavelength EPs and unidirectional invisibility can be achieved which may be used in integrated photonics systems.

A novel receiver-transmitter metasurface for a high-aperture-efficiency Fabry-Perot resonator antenna

This paper presents a novel coupled receiver-transmitter metasurface(MS)which is used to realize a high-aperture-efficiency Fabry-Perot resonator antenna.The unit cell of the MS adopts a slot-coupling procedure to realize energy transmission from the receiver patch to the radiator patch.This approach makes it easier to independently control the transmission magnitude and phase.Based on this characteristic,the transmission coefficients of different unit cells on the MS can be optimized by a genetic algorithm.Then,nearly uniform electric amplitude and phase distribution across the aperture field of the antenna are achieved.Therefore,the gain and aperture efficiency of the antenna are improved.A prototype of the optimized antenna is fabricated and measured to validate the design.The measured gain of the fabricated antenna reaches 17.3 dBi with an aperture efficiency of 94.5%.A higher aperture efficiency is obtained with the proposed antenna which has a low profile and simple structure.

High-sensitivity refractive index sensors based on Fano resonance in a metal-insulator-metal based arc-shaped resonator coupled with a rectangular stub

A metal-insulator-metal(MIM)-based arc-shaped resonator coupled with a rectangular stub(MARS) structure is proposed. This structure can generate two tunable Fano resonances originating from two different mechanisms. The structure has the advantage of being sensitive to the refractive index, and this feature makes it favorable for application in various microsensors. The relationship between the structural parameters and Fano resonance is researched using the finite element method(FEM) based on the software COMSOL Multiphysics 5.4. The simulation reveals that the sensitivity reaches1900 nm/refractive index unit(RIU), and the figure of merit(FOM) is 23.75.

Topographicaly Forced Thre-Wave Quasi-Resonant and Non-Resonant Interactions among Barotropic Rossby Waves on an Infinite Beta-Plane

In this paper, we first apply the assumption h=εh' of topographic variation ( h is the nondimensional topographic height and is a small parameter) to obtain nonlinear equations describing three-wave quasi-resonant and non-resonant interactions among Rossby waves for zonal wavenumbers 1—3 over a wavenumber-two bottom topography (WTBT). Some numerical calculations are made with the fourth-order Rung-Kutta Scheme. It is found that for the case without topographic forcing, the period of three-wave quasi-resonance (TWQR) is found to be independent of the zonal basic westerly wind, but dependent on the meridional wavenum ber and the initial amplitudes. For the fixed initial data, when the frequency mismatch is smaller and the meridional wavelength is moderate, its period will belong to the 30-60-day period band. However, when the wavenumber-two topography is included, the periods of the forced quasi-resonant Rossby waves are also found to be strongly dependent on the setting of the zonal basic westerly wind. Under the same conditions, only when the zonal basic westerly wind reaches a moderate extent, intraseasonal oscillations in the 30-60-day period band can be found for zonal wavenumbers 1-3. On the other hand, if three Rossby waves considered have the same meridional wavenumber, three-wave non-resonant interaction over a WTBT can occur in this case.When the WTBT vanishes, the amplitudes of these Rossby waves are conserved. But in the presence of a WTBT, the three Rossby waves oscillate with the identical period.The period, over a moderate range of the zonal basic westerly wind, is in the intraseasonal, 30-60-day range.

ANALYSIS OF ZERO-VOLTAGE QUASI-RESONANT BOOST DC-DC CONVERTER

The zero-voltage quasi-resonant boost switching DC-DC converter has been inves-tigated by using the time averaging equivalent circuit approach of periodically switching linearnetworks.The DC steady state and AC small signal characteristics of the converter are also given.

Resonant perfect absorption of molybdenum disulfide beyond the bandgap

Light absorption and radiation are fundamental processes in optical science and engineering.Materials with perfect absorption properties play an important role in numerous optical applications.Following the meteoric rise of MoS_(2)material,global opportunities and challenges coexist due to its extremely weak light-matter interaction capability beyond its energy band.In this work,we designed a kind of sandwich resonance structure and investigated MoS_(2)as a perfect absorber in the infrared spectrum that should be transparent according to the optical band theory.The infrared absorption properties of W or Au/MoS_(2)/Au models at 800 nm-2400 nm were systematic simulated.By optimizing the structural parameters,the resonant wavelength of perfect absorption can be modulated from 830 nm to 1700 nm with angle insensitivity and polar independence.Moreover,we discovered that the bandwidth of absorption exceeding 50%of the W-top model reaches500 nm,while that of the Au-top model is less than 100 nm,indicating that the top metal material has a great influence on the resonance absorption spectrum.Our work provides a practical route for enhancing and manipulating the light-matter interactions of low-dimensional materials beyond their own band gaps,which will be critical in the future design and implementation of optoelectronic devices and systems.

基于双补偿下垂—MQPR的直驱式风电机组并网控制

为了实现直驱式永磁风力发电系统安全稳定并网,提出一种基于双补偿下垂与多重准比例谐振(multiple quasi proportional resonance,MQPR)相结合的并网控制策略。该策略源于传统下垂控制,在电压控制环节引入直流电压补偿量,能快速调节直流母线电压达到稳定;在电流控制环节引入电容电流补偿量,能有效减小滤波电容造成的电流误差影响;同时,设计出MQPR控制器替代内环电流的PI控制器,可以滤除系统中多次谐波电流。通过建立仿真模型,与双闭环PI和传统下垂控制策略进行对比,验证所提控制策略的有效性。

多电平级联H桥逆变器通用型离散模型及分岔与混沌行为特性分析

多电平级联H桥逆变器内部功率器件多、等效开关频率高、开关组合状态繁杂、离散数学模型建立难度大,其分岔、混沌动力学行为难以进行系统性分析。基于虚拟遍历法建立了具有N个单元的多电平级联H桥逆变器通用型离散映射数学模型;引入对交流变量跟踪性能更佳的准比例谐振控制器,并重点分析了比例增益、谐振增益、单元数量N变化以及主电路和控制电路中其他参数变化情况下的分岔、混沌行为特性;对比分析了引入混沌抑制前后系统稳定性变化情况。从方法论角度分别采用根轨迹图和折叠图验证了稳定性分析结果的正确性,并通过PSIM仿真和实验验证了相关结论的正确性和抑制分岔与混沌行为的有效性。

基于SSO多扰动输入机理分析的DFIG-GSC功率振荡抑制策略研究

电网次同步振荡(SSO)已成为桎梏新能源发展的主要问题之一,针对SSO下双馈感应发电机(DFIG)中网侧变流器(GSC)的功率振荡问题展开研究。首先,建立SSO对GSC的多扰动输入数学模型,探究不同扰动输入的性质以及其对GSC系统的影响,明确了针对物理量扰动以及信号扰动分别采用补偿与滤除两种不同的抑制方法。其次,针对锁相环(PLL)输出误差经过坐标变换产生耦合振荡的问题,建立PLL输出误差角度的频域数学模型,并通过设计一种改进PLL消除其输出误差对GSC的信号扰动影响。同时,设计一种准谐振控制器的自适应算法,并提出基于自适应准谐振控制器的DFIG-GSC功率振荡抑制策略,消除SSO对GSC的物理扰动影响;最后,通过搭建具有SSO模拟环境的DFIG实验平台,验证本文所提控制策略的有效性。

主动磁轴承系统建模与准谐振自抗扰振动抑制

为了建立更准确的磁轴承数学模型,优化其控制性能,对磁轴承的电磁力非线性特性和系统固有干扰源进行了分析,通过转子动力学分析建立了含干扰源的主动磁轴承径向耦合系统模型。为抑制系统的振动,提出了一种磁轴承准谐振自抗扰振动抑制方法。通过扩张状态观测器实现系统解耦,简化控制流程,提升系统抗干扰能力;在此基础上,并入准谐振控制器对正弦周期性振动进行抑制。与传统方法相比,该方法控制结构简单,所需整定参数较少。仿真与试验结果表明,所提方法可以有效降低转子位移振动幅值,系统内常见的1、3、5倍频周期性振动得到显著抑制,具有良好的振动抑制效果。

基于双闭环控制的三相四线制逆变器控制研究

三相四线制逆变器具有更好的不平衡负载驱动能力,被广泛用于不间断电源等领域。对于这种离网模式下的逆变器而言,通常使用电压电流双闭环控制模式对输出进行控制。提出一种无需坐标变换的电压电流双闭环控制,实现输出三相之间完全解耦。由于准比例谐振(Quasi Proportional Resonance,QPR)控制对交流信号的控制效果更好,因此电压外环采用QPR控制,电流内环采用比例控制。实验证明了所提控制方法的有效性。

扩展P-ROQR环流抑制策略在船舶MMC-MVDC电力系统中的应用

为了解决船舶中压直流(MVDC)电力系统中应用的模块化多电平变换器(MMC)存在的环流问题,分析自阻型MMC的拓扑结构及环流产生机理,采用基于2阶广义积分器(SOGI)的滤波器过滤环流中的直流分量。对于环流中的交流分量,提出一种基于比例降阶准比例谐振控制器的新型环流抑制器对其进行抑制。在MATLAB/Simulink软件中搭建船舶自阻型MMC-MVDC电力系统模型。仿真结果表明:所提策略能有效抑制环流中的交流分量;自阻型MMC应用于逆变侧时具有直流故障闭锁能力。所提策略应用于船舶MMC-MVDC电力系统的环流抑制效果优异,同时具有减少桥臂电流畸变,稳定子模块电容电压的作用。

基于改进型QPR的并网逆变器复合控制策略

针对准比例谐振(QPR)控制对高次谐波和直流抑制能力差等问题,提出了一种改进型QPR控制与直流前馈补偿的复合控制策略。该策略在QPR控制的基础上加入了高次谐波补偿,并在控制基波电流的电流外环上加入含积分控制器的直流分量补偿环节。在对并网电流所含3、5、7次谐波进行抑制的同时,降低了并网电流中所含直流分量。仿真结果表明,与QPR控制相比,所提控制策略直流含量从0.05降为0.01,总谐波畸变率下降了1.48%,具有较好的抑制效果。

金属光栅覆盖分布式布拉格反射镜结构的透射增强效应

为了采用易于直接激发的塔姆等离激元(Tamm plasmon polaritons,TPPs)实现透射增强现象,本文提出了一种由一维金属光栅覆盖分布式布拉格反射镜(distributed Bragg reflector,DBR)构成的层状结构.采用有限元法分析了入射光波在DBR-金属交界面上激发TPPs并产生能量高度局域的物理过程.研究表明入射TM光波在金属-DBR交界面上激发的TPPs可以有效地激发金属狭缝内的SPPs模式,当SPPs模式在狭缝内满足类FP谐振的条件就可以使入射光波在该结构中的产生透射增强.在此基础上,分析了狭缝宽度及其占空比对透射谱峰的定量影响.结果显示:周期确定时随着狭缝宽度的增大,峰值透射率则呈现先增大后减小的变化趋势;宽度确定时随着占空比的增大,峰值透射率会呈现单调降低的变化趋势,而透射峰中心波长呈现近似线性蓝移趋势,这为灵活调节异常透射的中心波长提供了一种有效手段.

基于数值优化方法的Halbach磁体无源匀场方法研究

小型化的核磁共振谱仪由于其便携性的优势,成了当下核磁共振领域的研究热点.近年来,Halbach磁体在小型化核磁共振波谱仪领域得到了广泛应用.永磁体磁场的不均匀性对无源匀场方法提出了较高的要求.因此,本文基于机械可调的Halbach永磁体阵列结构进行了无源匀场研究.首先研制了由12个机械可调的磁块构成的Halbach磁体,并建立了磁块位置和磁场均匀性的最小二乘问题,随后利用了一种结合Levenberg-Marquardt法和拟牛顿法的优化算法,通过改变磁块的径向位置来优化磁场的均匀性.通过这种方法,成功将1.03 T的Halbach磁体中心区域(半径为2.5 mm)的均匀度从7391×10^(-6)提升到154.23×10^(-6).本文提出的匀场方法相对于传统的无源匀场方法更加灵活和简便,有望应用于核磁共振波谱仪和其他需要高磁场均匀度的仪器.

基于谐振改进型单自由度自抗扰控制器的PMSM转速波动抑制策略

高性能系统期望电机输出平滑且稳定的转速。然而,永磁同步电机驱动系统的转速环遭受多源扰动影响,导致电机输出转速呈现非周期和周期波动。为了抑制转速环中多源扰动,该文提出一种谐振改进型单自由度自抗扰控制器(active disturbance rejection controller,ADRC)。单自由度ADRC保留了传统ADRC对非周期扰动的抑制能力。在此基础上,该文采用准谐振控制器拓展单自由度ADRC观测器在特定频率处的带宽,以进一步提高单自由度ADRC对周期扰动的抑制能力。因此,所提方法可以同时抑制转速的非周期和周期波动进而提高转速的控制性能。此外,该文利用Nyquist稳定判据分析所提方法的稳定性。最后,通过实验验证所提方法的有效性。

准谐振与有源钳位反激变换器的性能比较和分析

高频、高效和高功率密度已成为AC-DC变换器重要的设计指标。传统准谐振反激变换器因其漏感能量多借助无源电阻元件以热能形式释放,不具备ZVS特性,限制了功率密度的进一步提升,而有源钳位反激变换器能弥补准谐振反激变换器的不足。先简述准谐振反激变换器与有源钳位反激变换器的工作原理,接着分析准谐振与有源钳位反激变换器主要性能指标差异,然后设计并制作两款48 W的准谐振反激变换器样机和有源钳位反激变换器样机以便获得相关的试验数据,作为性能比较分析的依据。

准谐振Flyback变换器分析与设计

设计了一台65 W输出的准谐振反激变换器(QR-Flyback)。分析了QR-Flyback的谷底开通原理与开关损耗减小机制,对比了系统在不同工况下的频率特点与损耗特征,总结了变频控制的优势与不足。结合NCP1380控制器的跳频控制功能,对系统各部分的硬件电路参数进行详细设计,有效提升了整机效率。最后,通过仿真和实验验证了理论分析与参数设计的可行性。