Magnetic field topology modeling under resonant magnetic perturbations on EAST

In order to understand the mechanism by which the resonant magnetic perturbation (RMP)mitigates or suppresses the edge-localized mode (ELM),the topological study of the edge magnetic field in ELM mitigation or suppression phase is a critical issue.To model the three-dimensional magnetic field topology superposed RMP on Experimental Advanced Superconducting Tokamak,a numerical model using the field line tracing method for both vacuum and ideal plasma response approximations is proposed.Using the numerical model,the topological change and the penetration depth of the stochastic field lines in the edge magnetic field are studied in an RMP experiment.Comparing profiles of minimum9 on edge stochastic field lines and the particle flux pattem,the ideal plasma response changes the field line penetration depth while remaining similar profile relative to vacuum approximation.To mitigate and suppress ELM strongly,the deep penetration of RMP fields and topological changes of the edge magnetic field is a key from our modeling.

Topological resonators based on hexagonal-star valley photonic crystals

In valley photonic crystals, topological edge states can be gained by breaking the spatial inversion symmetry without breaking time-reversal symmetry or creating pseudo-spin structures, making highly unidirectional light transmission easy to achieve. This paper presents a novel physical model of a hexagonal-star valley photonic crystal. Simulations based on the finite element method(FEM) are performed to investigate the propagation of TM polarized mode and its application to ring resonators. The results show that such a topologically triangular ring resonator exhibits an optimum quality factor Q of about 1.25×104, and Q has a maximum value for both frequency and the cavity length L. Our findings are expected to have significant implications for developing topological lasers and wavelength division multiplexers.

Design of small-scale gradient coils in magnetic resonance imaging by using the topology optimization method

A topology optimization method based on the solid isotropic material with penalization interpolation scheme is utilized for designing gradient coils for use in magnetic resonance microscopy. Unlike the popular stream function method, the proposed method has design variables that are the distribution of conductive material. A voltage-driven transverse gradient coil is proposed to be used as micro-scale magnetic resonance imaging（MRI） gradient coils, thus avoiding introducing a coil-winding pattern and simplifying the coil configuration. The proposed method avoids post-processing errors that occur when the continuous current density is approximated by discrete wires in the stream function approach. The feasibility and accuracy of the method are verified through designing the z-gradient and y-gradient coils on a cylindrical surface.Numerical design results show that the proposed method can provide a new coil layout in a compact design space.

Study of New Planar Resonator’s Topologies Little Perceptible in Variations of Substratum’s Height

The mobile communication (radio, mobile, satellite telephony…) insert band filters which are required to comply with stringent pass-band characteristics concerning the selectivity, the group delay, the insertion losses and the mass and volume. The mass and volume of payload electronic equipment is a significant contributor to the overall cost of space systems. Within this framework, many improvements were made in the design of filters and multiplexers which represent a considerable portion of the overall satellite payload. The High Temperature Superconducting (HTS) planar technology permits to realize compact size filtering devices. Moreover, it could also provide a superior performance not attainable by any other technology. However, not controllable parameters in the manufacturing processes (indistinctness of the engraving, the not uniformity of substratum thickness) do not allow to obtain a precision on the echo’s frequency and to keep a high quality factor. So, it is necessary to use method to tune the center frequency of filters after the fabrication or to study new resonator topologies which present lower sensitivity to LAIO3 substrate thickness. This last point is the object of this article.

Tailoring topological corner states in photonic crystals by near-and far-field coupling effects

We explore the behaviors of optically coupled topological corner states in supercell arrays composed of photonic crystal rods,where each supercell is a second-order topological insulator.Our findings indicate that the coupled corner states possess nondegenerate eigenfrequencies at theΓpoint,with coupled dipole corner states excited resonantly by incident plane waves and displaying a polarization-independent characteristic.The resonance properties of coupled dipole corner states can be effectively modulated via evanescently near-field coupling,while multipole decomposition shows that they are primarily dominated by electric quadrupole moment and magnetic dipole moment.Furthermore,we demonstrate that these coupled corner states can form surface lattice resonances driven by diffractively far-field coupling,leading to a dramatic increase in the quality factor.This work introduces more optical approaches to tailoring photonic topological states,and holds potential applications in mid-infrared topological micro-nano devices.

基于三相桥光储一体系统的建模与控制

为解决光伏发电具有波动性且伴有“弃光”现象的问题,提出了一种基于三相桥的光储一体转换器拓扑结构及相关控制策略。该结构能够实现光伏电源、蓄电池、负载之间的功率流动,并具有LLC谐振变换器的软开关性质、高效率、输入电压范围适应性更宽、高功率密度等优点。在控制策略方面,采用带有复合反馈的电导增量法来实现最大功率点跟踪;为实现双向DC-DC变换器共用电感和直流母线电压稳定,采用双频率控制方法确定电感,并实现电压外环电流内环双闭环控制;为保证输出负载电压稳定,LLC谐振转换器采用电压闭环的调频控制。最后,搭建了光储一体系统仿真模型与实验平台,仿真与实验结果表明:提出的新型光储一体系统结构简单,可以稳定运行且易于实现。

宽增益高效谐振型直流变换器技术

直流变换器广泛应用于电动汽车充电系统与光伏发电系统,如何适应输入/输出电压大范围变化,实现直流变换器的宽增益和高传输效率为学术界和工业界所关注。其中,LLC、LLC_LC、LLCLC谐振变换器虽具有高功率密度、低电磁干扰等特性,但存在磁元件与谐振网络参数设计难度大,造成变换器输出不稳定等不足,难以满足实际应用的要求。为此,提出了宽增益高效谐振型直流变换器技术。首先总结了谐振型直流变换器的基本原理,围绕其拓扑结构及调制策略的国内外研究进展,重点就宽增益与高效谐振型直流变换器应用需求进行阐述。然后分析了LLC_LC、LLCLC多模式PWM倍压整流变换器拓扑及调制策略。最后结合仿真与实验验证结果,证明了该宽增益高效谐振型直流变换器拓扑及其调制策略的有效性,最高可实现输出电压范围为1~6.2,转换效率达96.1%,具有较宽广的应用前景。

一种超宽电压增益双LLC谐振变换器及控制方法

为解决传统LLC谐振变换器在宽电压增益应用中所需开关频率范围过宽、总体效率较低等问题,文中提出一种多模式双LLC谐振变换器。该变换器基于半桥、全桥切换以及桥式、倍压整流切换的拓扑重构思路,以增益不同的4种模式实现较窄频率范围内的超宽输出电压,提高变换器效率的同时通过复用开关器件来降低成本。为了实现模式间的平滑过渡,针对所提变换器设计一种脉冲宽度频率调制控制方法,并根据模式切换特性进一步优化,提高模式切换速度。基于SiC开关器件,设计并搭建一台60~450 V输出电压、最大功率为900 W的实验样机,以验证所提拓扑及控制方法的可行性。

一类带p-Laplace算子的非线性二阶m点共振边值问题解的存在性

基于拓扑横截方法连同障碍带技巧,得到一类带p-Laplace算子的非线性二阶m点共振边值问题解的新的存在性结果,并给出应用举例。

Small-worldness of brain networks after brachial plexus injury: a resting-state functional magnetic resonance imaging study

Research on brain function after brachial plexus injury focuses on local cortical functional reorganization,and few studies have focused on brain networks after brachial plexus injury.Changes in brain networks may help understanding of brain plasticity at the global level.We hypothesized that topology of the global cerebral resting-state functional network changes after unilateral brachial plexus injury.Thus,in this cross-sectional study,we recruited eight male patients with unilateral brachial plexus injury（right handedness,mean age of 27.9±5.4years old）and eight male healthy controls（right handedness,mean age of 28.6±3.2）.After acquiring and preprocessing resting-state magnetic resonance imaging data,the cerebrum was divided into 90 regions and Pearson’s correlation coefficient calculated between regions.These correlation matrices were then converted into a binary matrix with affixed sparsity values of 0.1–0.46.Under sparsity conditions,both groups satisfied this small-world property.The clustering coefficient was markedly lower,while average shortest path remarkably higher in patients compared with healthy controls.These findings confirm that cerebral functional networks in patients still show smallworld characteristics,which are highly effective in information transmission in the brain,as well as normal controls.Alternatively,varied small-worldness suggests that capacity of information transmission and integration in different brain regions in brachial plexus injury patients is damaged.

Nuclear magnetic resonance for quantum computing： Techniques and recent achievements

Rapid developments in quantum information processing have been made, and remarkable achievements have been obtained in recent years, both in theory and experiments. Coherent control of nuclear spin dynamics is a powerful tool for the experimental implementation of quantum schemes in liquid and solid nuclear magnetic resonance （NMR） system, especially in liquid-state NMR. Compared with other quantum information processing systems, the NMR platform has the advantages such as the long coherence time, the precise manipulation, and well-developed quantum control techniques, which make it possible to accurately control a quantum system with up to 12-qubits. Extensive applications of liquid-state NMR spectroscopy in quantum information processing such as quantum communication, quantum computing, and quantum simulation have been thoroughly studied over half a century. This article introduces the general principles of NMR quantum information processing, and reviews the new-developed techniques. The review will also include the recent achievements of the experimental realization of quantum algorithms for machine learning, quantum simulations for high energy physics, and topological order in NMR. We also discuss the limitation and prospect of liquid-state NMR spectroscopy and the solid-state NMR systems as quantum computing in the article.

Resonance and antiresonance characteristics in linearly delayed Maryland model

The Maryland model is a critical theoretical model in quantum chaos.This model describes the motion of a spin-1/2particle on a one-dimensional lattice under the periodical disturbance of the external delta-function-like magnetic field.In this work,we propose the linearly delayed quantum relativistic Maryland model(LDQRMM)as a novel generalization of the original Maryland model and systematically study its physical properties.We derive the resonance and antiresonance conditions for the angular momentum spread.The“characteristic sum”is introduced in this paper as a new measure to quantify the sensitivity between the angular momentum spread and the model parameters.In addition,different topological patterns emerge in the LDQRMM.It predicts some additions to the Anderson localization in the corresponding tight-binding systems.Our theoretical results could be verified experimentally by studying cold atoms in optical lattices disturbed by a linearly delayed magnetic field.

基于补偿拓扑切换的MCR-WPT最大效率追踪方法

针对串联串联(S-S)和串联并联(S-P)补偿拓扑结构在大(小)负载场合传输效率低的问题,提出了基于补偿拓扑结构切换的磁耦合谐振式无线电能传输(MCR-WPT)系统最大效率追踪方法.通过建立S-S、S-P等效电路模型提取谐振补偿网络参数,将系统最大传输效率切换点的寻优过程划分成轻载与重载两种工作模式,并使用有源阻抗匹配的方式对系统最大效率点进行自适应追踪.仿真测试结果表明:所提方法在轻载模式下能够维持原有系统最大传输效率,约为84.5%;在重载模式下效率由84.5%提升至91.6%,验证了该方法的有效性.

基于LCC-S补偿式谐振拓扑的锂电池WPT系统研究

无线电能传输(wireless power transfer,WPT)系统具有安全、可靠、方便等优点。文章在分析WPT系统锂离子电池内阻及其典型充电方式的基础上,通过对WPT原理和谐振拓扑结构的研究,提出了基于LCC-S补偿式谐振拓扑的WPT系统。在电池等效负载变化的情况下,通过合理的参数设计,LCC-S补偿式谐振拓扑结构可以分别实现与负载无关的恒流模式和恒压模式,无需切换拓扑结构。在理论分析的基础上,设计了系统的参数,并通过MATLAB仿真系统搭建仿真模型,验证了研究中的恒流模式和恒压模式。

Floquet拓扑光子绝缘体研究进展(特邀)

拓扑光子学是光学领域一个重要的新兴研究方向,它的奇异光学响应特性颠覆了人们对光传播的理解,为人工操控光的传播提供了一种全新方法。Floquet拓扑光子绝缘体是拓扑光子学的一个重要分支,它利用周期性的驱动来探索物质的相变过程,发现了很多违反直觉的新奇物理现象。本文综述了近十年来Floquet拓扑光子绝缘体的主要研究进展。根据实现方式将其分为基于时间调制、基于空间调制、基于耦合谐振调制的三个大类进行详细论述。对于每一类Floquet拓扑光子绝缘体,从基础理论和物理实现平台两个方面论述了Floquet拓扑光子绝缘体的独特光学特性和奇异物理现象,并讨论了其潜在的应用前景。最后,总结了该领域当前面临的主要挑战,并对Floquet拓扑光子绝缘体的未来研究方向进行了展望。

地下变形三维测量装置的无线电能传输系统设计

针对地下变形三维测量装置供电缺陷的问题,在不影响传感单元测量的情况下采用传感单元的测量线圈作为传输线圈。根据测量线圈的特性进行建模与优化,利用磁耦合谐振式无线电能传输方式,搭建了一套能进行多个节点之间电能传输的系统。该系统采用硬件与软件相结合的方法,对传感单元的电量进行监测,采用蓝牙通信技术使电能能够自上而下的传输。实验中,通过采用串联补偿电容的方式搭建串串拓扑结构,优化以测量线圈为主的传输模型,整个电能传输系统能够实现3个节点的电能传输,系统在补偿电容为22 nF时传输效率达到最大为31%。

基于拓扑变换的共形超材料高增益微带贴片天线

微带贴片天线具有体积小、重量轻、剖面低、成本低、易于集成等优点,被广泛应用于各种通信、遥测和探测系统中。但是,微带贴片天线也存在定向增益低的缺点。为此,提出了一种加载共形超材料的高增益微带贴片天线。将方形开环谐振器(Split-ring resonator,SRR)拓扑变换为符合圆形衬底的SRR单元,SRR赋予抑制天线表面波的超材料效应。仿真结果表明,初始的圆形微带贴片天线的谐振频率为10 GHz,增益为6.12 dBi。加载10个拓扑SRR单元的天线的近场参数保持良好,远场增益为7.88 dBi,比初始天线增加了近2 dBi。

提升无线充电异物检测系统灵敏度的高阶复合谐振拓扑

针对无线充电系统中金属异物的检测需要,提出一种提升异物检测系统检测灵敏度的高阶复合谐振拓扑,解决了传统检测线圈边缘区域检测灵敏度低及存在检测盲区等问题。首先建立金属异物与检测线圈的互感耦合模型,阐释谐振拓扑对检测线圈阻抗变化的放大作用;其次在合理设计参数下分析复合谐振拓扑对检测灵敏度提升的可行性;然后根据谐振拓扑对线圈阻抗变化的放大特性设计一种高阶复合谐振拓扑,并对该拓扑结构中各器件参数进行优化;最后对所提出的高阶复合谐振拓扑的检测灵敏度及其具体实现电路进行实验验证。实验结果表明,针对检测线圈边角位置处的金属异物和曲别针等小尺寸异物,系统检测灵敏度可达62.31%和119.23%。在金属异物对检测线圈阻抗影响的微小变化下,所提出的高阶复合谐振拓扑具有足够高的检测灵敏度并可以完全消除检测盲区。

阻塞性睡眠呼吸暂停脑网络研究进展

阻塞性睡眠呼吸暂停(obstructive sleep apnea,OSA)是最常见的睡眠障碍之一,以睡眠时上呼吸道塌陷致部分或完全性气道阻塞及机体间歇性缺氧为特征,其发生与脑结构及功能网络的异常改变存在关联。随着MRI技术的快速发展,越来越多研究者关注网络属性变化与OSA病理生理机制的联系。本文综述了OSA脑结构和功能网络的研究进展,多角度分析OSA功能和结构网络属性改变的特点,讨论OSA神经病理改变与脑功能和结构网络属性变化的联系及机制,以期为临床寻找OSA神经影像标志物及理解OSA所致认知功能障碍的潜在神经影像学机制提供新的思路。

基于三SCC结构的LCCC-S型IPT系统设计

感应电能传输(inductive power transfer,IPT)系统中需要引入谐振补偿网络来消除电路中的无功损耗,而固定参数下的谐振补偿网络往往只能实现恒压或者恒流源输出,输出类型单一且不具有可控性。为解决这一问题,将常用的LCC型拓扑改进为LCCC型拓扑,并建立数学模型分析该拓扑的电路特性;其次,利用高频开关电容变换器取代单一的补偿电容,实现输出电压调节,并分析多阶受控开关电容(switch-controlled capacitor,SCC)变换器电路的工作原理以及开关管的移相调制条件;最后通过仿真和实验验证该IPT系统的可行性与有效性。仿真和实验结果表明:所构建的三SCC结构的LCCC-S型IPT系统具有软开关特性,控制方式简单;在不同负载和互感的条件下,可定向调节输出电压;在松耦合系数较低的情况下,系统的仿真效率平均为91.51%(最高为92.96%),实验效率平均为80.6%(最高为83.43%);调节过程中可以使IPT系统始终处于弱感性状态,保证了IPT系统在实现输出调整的同时依然具有较低的无功损耗。