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A passive source ranging method based on the frequency warping transform of the vertical intensity flux in shallow water 被引量:1
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作者 Yu-Bo Qi Shi-Hong Zhou +3 位作者 Meng-Xiao Yu Shu-Yuan Du Mei Sun Ren-He Zhang 《Chinese Physics B》 SCIE EI CAS CSCD 2019年第5期145-149,共5页
The phase of cross-correlation function of two different normal modes contains source range information, which can be extracted by warping transform due to the dispersive characteristics of the shallow water waveguide... The phase of cross-correlation function of two different normal modes contains source range information, which can be extracted by warping transform due to the dispersive characteristics of the shallow water waveguide. The autocorrelation function of the received pressure or particle velocity contains both modal autocorrelation component(MAC) and modal cross-correlation component(MCC), with the former part usually treated as interference for source ranging. Because the real part of the vertical intensity flux(RPVIF) only contains MCC, a passive impulsive source ranging method based on the frequency warping transform of RPVIF with a single vector receiver in shallow water is presented. Using a waveguide-invariant-based frequency warping operator, the cross-correlation components of two different modes in the vertical intensity flux are warped into separable impulsive sequences, the time delays of which are subsequently used for source ranging. The advantages of source ranging based on warping the vertical intensity flux compared with warping the pressure autocorrelation function are pointed out, and the experiment results are also presented. 展开更多
关键词 passive source RANGING VERTICAL INTENSITY flux frequency WARPING TRANSFORM normal mode
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Effect of ultra-low frequency repetitive transcranial magnetic stimulation on dysphagia in elderly patients with acute cerebral infarction and quality of life
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作者 Yun-Feng Yang Ju-Hua Liu +1 位作者 Li Liu Wen-Ju Dong 《Journal of Hainan Medical University》 2020年第3期54-59,共6页
Objective:To investigate the clinical effect of ultra-low frequency repetitive transcranial magnetic stimulation on dysphagia in elderly patients with acute cerebral infarction and its impact on quality of life.Method... Objective:To investigate the clinical effect of ultra-low frequency repetitive transcranial magnetic stimulation on dysphagia in elderly patients with acute cerebral infarction and its impact on quality of life.Methods:60 elderly patients with dysphagia caused by acute cerebral infarction were randomly divided into rTMS group and control group,30 cases in each group.Both groups received routine drug therapy and swallowing function training.rTMS group was additionally treated by ultra-low frequency(10mHZ)repetitive transcranial magnetic stimulation for 14 days.The changes of NIHSS score andADL score and NSE serum level and Wa Tian drinking water experiment and Fujishima Ichiro dysphagia scale score and SWAL-QOL score and SF-36 score were observed between the two groups before and after treatment.The clinical effect was evaluated by Wa Tian drinking water experiment.Results:After treatment,The clinical effective rate in rTMS group was significantly higher compared with that in the control group(P<0.05),NIHSS score and serum NSE level were significantly lower compared with the control group(P<0.05),ADL score and Fujishima Ichiro dysphagia score and SWAL-QOL score and SF-36 scores were significantly higher compared with the control group(P<0.05).After treatment,SF-36 total score(or SWAL-QOL Score)was negatively correlated with NSE serum level and NIHSS score,which was positively correlated with ADL score and Fujishima Ichiro dysphagia scale score score.Conclusion:Ultra-low frequency rTMS therapy can reduce NSE level,effectively improve dysphagia in elderly patients with acute cerebral infarction and significantly improve the elderly patients'life quality. 展开更多
关键词 ultra-low frequency REPETITIVE TRANSCRANIAL Magnetic Stimulation The elderly patient Acute cerebral INFARCTION DYSPHAGIA NSE SF-36 scale Life quality
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A high-performance electromagnetic energy harvester for scavenging ultra-low frequency vibration energy of human foot movement
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作者 HU JiaJun QIAN Shuo +9 位作者 WU Hui HU DongXu NIU LiXin BI XiaoXue ZHANG Jie HOU XiaoJuan GENG WenPing MU JiLiang HE Jian CHOU XiuJian 《Science China(Technological Sciences)》 SCIE EI CAS CSCD 2024年第5期1391-1400,共10页
In our daily lives,low-frequency kinetic energy primarily manifests as vibrations.However,effective harnessing of lowfrequency kinetic energy remains a formidable challenge.This paper proposes a rope-driven rotor that... In our daily lives,low-frequency kinetic energy primarily manifests as vibrations.However,effective harnessing of lowfrequency kinetic energy remains a formidable challenge.This paper proposes a rope-driven rotor that rotates around an axis and consists of an ultra-high-molecular-weight polyethylene(UHMWPE)wire wrapped around a metal shaft.The rotor can convert ultra-low frequency vibration/linear motion into rapid rotation by pressing the top at low frequencies and driving the rope for a quick release.The harvester can generate up to 36.25 m W power using a 0.1-mm-diameter UHMWPE wire as the rotor when periodically pressed down to 20 mm at a frequency of 1 Hz.A simple power generation floor is assembled,generating 28.58-m W power with a matching load at a frequency of 1.5 Hz.Moreover,the harvester can increase the charging voltage of a 0.47-F supercapacitor from 0 to 6.8 V within 10 min.In addition,the harvester can harvest energy through a light finger press motion,and the energy obtained can also support the continuous operation of multiple electronic devices concurrently.This study introduces an effective method for harvesting ultra-low frequency energy and has great prospects in the field of power generation floor and human movement energy harvesting. 展开更多
关键词 electromagnetic energy harvester rope-shaft coupling structure human motion ultra-low frequency
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Propagation effects of low frequency electromagnetic waves in production well 被引量:2
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作者 Song Xijin Guo Baolong +1 位作者 Dang Ruirong Wang Xuelong 《Petroleum Science》 SCIE CAS CSCD 2012年第2期182-191,共10页
The frequency domain electromagnetic method has already been widely used for tomographic imaging or electromagnetic well logging. However, different from open hole logging, the metal casing existing in production well... The frequency domain electromagnetic method has already been widely used for tomographic imaging or electromagnetic well logging. However, different from open hole logging, the metal casing existing in production well logging has a strong shielding effect on the electromagnetic waves, thus bringing some difficulties to the application of the frequency domain electromagnetic method in production well logging. According to the relation of the field source geometry to the ring around the mandrel, the general expressions of frequency domain electromagnetic responses in axially symmetrical layered conductive medium are deduced. The propagation effects caused by the low-frequency electromagnetic waves in cased hole are also analyzed. The distribution curves of eddy current density and magnetic flux density along the radial direction in the mandrel indicate that the eddy loss within the mandrel is proportional to the transmission signal frequency and the mandrel conductivity. The secondary field responses of different casing materials show that the transmission frequency has an important effect on the ability of electromagnetic waves penetrating the metal casing. The transmission frequency should be ultra-low in order to enable the electromagnetic signal to penetrate the casing easily. The numerical results of frequency responses for different casing physical parameters show that the casing thickness has a significant impact on the choice of the transmission frequency. It is also found that the effect of the casing radius on the transmission frequency can be neglected. 展开更多
关键词 Propagation effects eddy current density magnetic flux density production well frequency response
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SIMULATION OF TEMPERATURE FIELD IN ULTRA-HIGH FREQUENCY INDUCTION HEATING AND VERIFICATION 被引量:2
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作者 李奇林 徐九华 苏宏华 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2013年第2期155-161,共7页
An experimental and numerical study on the temperature field induced in the ultra-high frequency induction heating is carried out.With an aim of predicting the thermal history of the workpiece,the influence factors of... An experimental and numerical study on the temperature field induced in the ultra-high frequency induction heating is carried out.With an aim of predicting the thermal history of the workpiece,the influence factors of temperature field,such as the induction frequency,the dimension of coil and the gap between coil and workpiece,are investigated considering temperature-dependent material properties by using FLUX 2Dsoftware.The temperature field characteristic in ultra-high induction heating is obtained and discussed.The numerical values are compared with the experimental results.A good agreement between them is observed with 7.9% errors. 展开更多
关键词 ultra-high frequency induction heating temperature field flux 2Dsoftware
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Cascaded quasi-zero stiffness nonlinear low-frequency vibration isolator inspired by human spine 被引量:4
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作者 Guoxin JIN Zhenghao WANG Tianzhi YANG 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2022年第6期813-824,共12页
Human motion induced vibration has very low frequency,ranging from 2 Hz to 5 Hz.Traditional vibration isolators are not effective in low-frequency regions due to the trade-off between the low natural frequency and the... Human motion induced vibration has very low frequency,ranging from 2 Hz to 5 Hz.Traditional vibration isolators are not effective in low-frequency regions due to the trade-off between the low natural frequency and the high load capacity.In this paper,inspired by the human spine,we propose a novel bionic human spine inspired quasi-zero stiffness(QZS)vibration isolator which consists of a cascaded multi-stage negative stiffness structure.The force and stiffness characteristics are investigated first,the dynamic model is established by Newton’s second law,and the isolation performance is analyzed by the harmonic balance method(HBM).Numerical results show that the bionic isolator can obtain better low-frequency isolation performance by increasing the number of negative structure stages,and reducing the damping values and external force values can obtain better low-frequency isolation performance.In comparison with the linear structure and existing traditional QZS isolator,the bionic spine isolator has better vibration isolation performance in low-frequency regions.It paves the way for the design of bionic ultra-low-frequency isolators and shows potential in many engineering applications. 展开更多
关键词 bionic spine inspired vibration isolator harmonic balance method(HBM) quasi-zero stiffness(QZS) ultra-low frequency vibration isolation
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Research on Slot-pole Combination in High-power Direct-drive PM Vernier Generator for Fractional Frequency Transmission System 被引量:3
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作者 Zhidong Yuan Shaofeng Jia +2 位作者 Deliang Liang Xiuli Wang Yong Yang 《CES Transactions on Electrical Machines and Systems》 CSCD 2022年第4期445-453,共9页
Offshore wind energy is an important part of clean energy,and the adoption of wind energy to generate electricity will contribute to the implementation of the carbon peaking and carbon neutrality goals.The combination... Offshore wind energy is an important part of clean energy,and the adoption of wind energy to generate electricity will contribute to the implementation of the carbon peaking and carbon neutrality goals.The combination of the fractional frequency transmission system(FFTS) and the direct-drive wind turbine generator will be beneficial to the development of the offshore wind power industry.The use of fractional frequency in FFTS is beneficial to the transmission of electrical energy,but it will also lead to an increase in the volume and weight of the generator,which is unfavorable for wind power generation.Improving the torque density of the generator can effectively reduce the volume of the generators.The vernier permanent magnet machine(VPM) operates on the magnetic flux modulation principle and has the merits of high torque density.In the field of electric machines,the vernier machine based on the principle of magnetic flux modulation has been proved its feasibility to reduce the volume and weight.However,in the field of low-speed direct-drive machines for high-power fractional frequency power generation,there are still few related researches.Therefore,this paper studies the application of magnetic flux modulation in fractional frequency and high-power direct-drive wind turbine generators,mainly analyzes the influence of different pole ratios and different pole pairs on the generator,and draws some conclusions to provide reference for the design of wind turbine generators. 展开更多
关键词 Direct-drive wind turbine generators Fractional frequency transmission system Pole ratio The magnetic flux modulation Vernier machine
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一种融合字词双通道的Domain-Flux僵尸网络检测方法 被引量:1
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作者 李晓冬 宋元凤 李育强 《计算机科学》 CSCD 北大核心 2023年第12期337-342,共6页
Domain-Flux是僵尸网络中常用的一种命令与控制信道隐蔽技术,其能有效躲避网络安全设备的检测。针对现有检测方法中对Domain-Flux域名信息提取不全面,无法有效捕获词典类域名关键分类特征的问题,提出了一种融合字词双通道的Domain-Flux... Domain-Flux是僵尸网络中常用的一种命令与控制信道隐蔽技术,其能有效躲避网络安全设备的检测。针对现有检测方法中对Domain-Flux域名信息提取不全面,无法有效捕获词典类域名关键分类特征的问题,提出了一种融合字词双通道的Domain-Flux僵尸网络检测方法。在字符向量和词根向量两个通道上分别采用卷积神经网络(CNN)和双向长短期记忆网络(BiLSTM)提取局部特征和全局特征,丰富输入域名的特征信息,提升分类性能。其中,字符向量通道针对随机字符域名提取局部空间特征,而词根向量通道基于TF-IDF算法,引入类内因子将词根重要性加权到词向量中,然后提取域名单词组合序列前后的时序特征。实验结果表明,与单一采用TextCNN或BiLSTM的模型相比,融合字词双通道的模型检测准确率分别提高7.12%和5.86%,针对词典类Domain-Flux的检测也具有更高的精确率。 展开更多
关键词 Domain-flux 僵尸网络 TF-IDF 卷积神经网络 双向长短期记忆网络
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双频DC-DC变换器的磁集成技术
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作者 高圣伟 李永宵 +1 位作者 田金锐 刘磊 《电工技术学报》 EI CSCD 北大核心 2024年第13期4025-4036,共12页
双频Buck变换器由两个降压单元级联构成,具有动态响应快,开关损耗小等优势。然而不足的是磁件占据了整个系统的大部分体积与重量,降低了系统的功率密度。针对这一问题,提出一种三段式绕制磁集成技术,将磁件以解耦的方式集成在一副磁心... 双频Buck变换器由两个降压单元级联构成,具有动态响应快,开关损耗小等优势。然而不足的是磁件占据了整个系统的大部分体积与重量,降低了系统的功率密度。针对这一问题,提出一种三段式绕制磁集成技术,将磁件以解耦的方式集成在一副磁心中。该文首先建立集成磁件的磁路等效模型,通过抵消各绕组之间的耦合作用推导出解耦条件,并详细阐述了磁心的选取、匝数以及气隙的设计原则。其次,利用有限元仿真平台对所提集成磁件进行建模分析,与现有的集成方法相比,磁通密度分布更为均匀,磁心的利用率得到了有效提升。最后,搭建一台48 V/12 V、108 W的实验样机,体积和重量同分离磁件相比降低了31.2%和25.3%,提高了系统的功率密度,验证了该集成方法理论分析的正确性和可行性。 展开更多
关键词 双频BUCK变换器 解耦集成 有限元仿真 磁通密度 功率密度
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永磁同步电机全转速范围无位置传感器控制
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作者 刘计龙 付康壮 +2 位作者 麦志勤 李科峰 张伟伟 《国防科技大学学报》 EI CAS CSCD 北大核心 2024年第4期114-124,共11页
为解决IF控制启动速度偏慢、启动转矩能力薄弱等问题,采用高频脉振电压注入法完成电动机零低速启动,并结合中高速区有效磁链法形成全转速范围无位置传感器复合控制策略。为了实现两种控制方法的平滑切换,提出一种基于转速过渡区与状态... 为解决IF控制启动速度偏慢、启动转矩能力薄弱等问题,采用高频脉振电压注入法完成电动机零低速启动,并结合中高速区有效磁链法形成全转速范围无位置传感器复合控制策略。为了实现两种控制方法的平滑切换,提出一种基于转速过渡区与状态机结合的滞环切换策略,所提策略将全转速范围划分为零低速区、过渡区以及中高速区,电动机由中高速区进入过渡区时提前开启高频脉振电压注入法,使其位置估计过程达到稳定,为切换做好准备。为了减小注入高频电压对有效磁链法位置估计过程的冲击,在转速过渡区采用软开启的方式实现高频脉振电压注入法的投入与退出。针对转速过渡区两种位置估计方法同时工作时的耦合问题,设置了双同步旋转坐标系,实现了转子位置估计的解耦控制。在一台三相永磁同步电机上对所提方法的有效性进行了验证。 展开更多
关键词 永磁同步电机 无位置传感器控制 高频脉振电压注入法 有效磁链法 复合控制
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夏季欧亚环流的低频振荡对长江流域降水影响的多尺度诊断
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作者 杨丹 王黎娟 鲍瑞娟 《地球科学与环境学报》 CAS 北大核心 2024年第1期54-66,共13页
长江流域夏季降水与欧亚中高纬大气低频振荡密切相关,定量诊断不同尺度环流异常对降水的贡献,对于提高旱涝灾害预测准确率具有重要意义。利用ERA5逐日再分析资料和CN05.1逐日降水资料,通过定义环流指数(CI),将夏季欧亚环流划分为两脊一... 长江流域夏季降水与欧亚中高纬大气低频振荡密切相关,定量诊断不同尺度环流异常对降水的贡献,对于提高旱涝灾害预测准确率具有重要意义。利用ERA5逐日再分析资料和CN05.1逐日降水资料,通过定义环流指数(CI),将夏季欧亚环流划分为两脊一槽(DR)型和两槽一脊(DT)型,并探究了其低频特征以及不同尺度环流异常对长江流域降水的影响。结果表明:两类环流型是环流指数低频循环周期中的两个不同位相,均具有10~30 d振荡周期,对长江流域低频降水有着重要影响。其主要表现为:①两类环流型对应的500 hPa低频环流场在欧亚中高纬呈现正、负位势高度异常交替的波列结构,具有明显向东传播的特征,平均传播速度约为每天5°(经度);②当DR型达峰值位相时,850 hPa低频风场中鄂霍次克海反气旋南侧的东北风引导中高纬干冷空气向长江流域入侵,与来自南海反气旋西侧的西南气流交汇,使太平洋和南海的大量水汽向长江流域输送,低频降水正异常滞后于环流2 d达到最强,DT型的特征则与之相反;③欧亚环流对长江流域低频降水的影响以大于30 d的背景水汽条件和10~30 d低频尺度环流的共同作用为主导,小于10 d的天气尺度环流次之,大于30 d的背景环流较前二者作用偏弱,并且水汽辐合项约为水汽平流项贡献的3倍,先由湿平流提供充足的水汽条件,再通过较强的水汽辐合产生降水。 展开更多
关键词 异常环流 夏季降水 多尺度诊断 低频振荡 传播特征 水汽通量 长江流域
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Critical analysis of the ULF power depression as a possible Tohoku earthquake precursor
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作者 Vyacheslav A Pilipenko Valery A Martines-Bedenko +1 位作者 Akimasa Yoshikawa Kirolosse M Girgis 《Earthquake Science》 2024年第5期407-414,共8页
Among electromagnetic methods of short-term earthquake prediction,an approach is being actively developed based on the phenomenon of magnetic ultra-low-frequency(ULF)power depression occurring a few days before an ear... Among electromagnetic methods of short-term earthquake prediction,an approach is being actively developed based on the phenomenon of magnetic ultra-low-frequency(ULF)power depression occurring a few days before an earthquake.In particular,a nighttime geomagnetic power depression in the band 0.03-0.05 Hz was observed approximately 5 days before the catastrophic Tohoku 2011 earthquake.To verify the reliability of this method,we performed an extended analysis using data from magnetometer arrays JMA,MAGDAS,PWING,and INTERMAGNET.The selected stations included sites close to the epicenter(<300 km)and remote points(~10000 km).The band-integrated spectral power of nighttime magnetic noise decreased significantly from March 6-9,several days before the earthquake.However,such variations occur simultaneously not only at nearby stations but also at distant stations.During this event,the ULF power depression was caused by low global geomagnetic activity,as evidenced by the planetary index SME.Thus,the depression of geomagnetic ULF noise cannot be considered a reliable short-term precursor. 展开更多
关键词 earthquake forecast seismo-electromagnetic phenomena ultra-low frequency(ULF)pulsations
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源于宇宙弦的引力波暴及其电磁共振效应
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作者 王丽丽 史金磊 +4 位作者 严建军 张祎 杨轲 赵琳 杨静静 《云南大学学报(自然科学版)》 CAS CSCD 北大核心 2024年第1期53-58,共6页
引力波为宇宙学模型的检验提供了新方法,宇宙弦环震荡会激发较强的尖端引力辐射,甚高频波段的引力波可以通过电磁共振效应来探测.文章基于修正的宇宙弦模型,以p和?为自由参数,主要研究了宇宙弦环震荡产生的甚高频引力波特性h,以及在电... 引力波为宇宙学模型的检验提供了新方法,宇宙弦环震荡会激发较强的尖端引力辐射,甚高频波段的引力波可以通过电磁共振效应来探测.文章基于修正的宇宙弦模型,以p和?为自由参数,主要研究了宇宙弦环震荡产生的甚高频引力波特性h,以及在电磁共振方案中产生的物理效应.通过数值计算保守估计引力波暴的量纲为1的振幅强度可以达到10^(-28)~10^(-25).在电磁共振效应下产生的信号光子流强度N_(x)^(1)达到10^(4)~10^(8)s^(-1),信噪比强度S为10^(-20)~10^(-14).与其它类型的此频段引力波相比较,此类引力波更可能在未来被探测器探测到. 展开更多
关键词 宇宙弦 甚高频引力波探测器 信号光子流 信噪比
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Application of ESMD Method to Air-Sea Flux Investigation 被引量:8
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作者 Hui-Feng Li Jin-Liang Wang Zong-Jun Li 《International Journal of Geosciences》 2013年第5期8-11,共4页
The ESMD method can be seen as a new alternate of the well-known Hilbert-Huang transform (HHT) for non-steady data processing. It is good at finding the optimal adaptive global mean fitting curve, which is superior to... The ESMD method can be seen as a new alternate of the well-known Hilbert-Huang transform (HHT) for non-steady data processing. It is good at finding the optimal adaptive global mean fitting curve, which is superior to the common least-square method and running-mean approach. Take the air-sea momentum flux investigation as an example, only when the non-turbulent wind components is well extracted, can the remainder signal be seen as actual oscillations caused by turbulence. With the aid of —5/3 power law for the turbulence, a mode-filtering approach based on ESMD decomposition is developed here. The test on observational data indicates that this approach is very feasible and it may greatly reduce the error caused by the non-turbulent components. 展开更多
关键词 Extreme-Point Symmetric MODE DECOMPOSITION (ESMD) AIR-SEA flux Hilbert-Huang Transform (HHT) Fourier frequency Spectrum Empirical MODE DECOMPOSITION (EMD) Wind MOMENTUM flux
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磁悬浮轴承横向磁通传感器设计与分析 被引量:1
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作者 金超武 叶周铖 +1 位作者 周瑾 徐园平 《仪器仪表学报》 EI CAS CSCD 北大核心 2023年第9期226-236,共11页
横向磁通传感器因结构紧凑和高检测精度在磁悬浮轴承系统中具有广阔的应用前景。随磁悬浮轴承技术的发展,对横向磁通传感器的检测性能提出了更高要求。为进一步提升横向磁通传感器的性能,满足磁悬浮转子高精度位移监测需求,本文针对灵... 横向磁通传感器因结构紧凑和高检测精度在磁悬浮轴承系统中具有广阔的应用前景。随磁悬浮轴承技术的发展,对横向磁通传感器的检测性能提出了更高要求。为进一步提升横向磁通传感器的性能,满足磁悬浮转子高精度位移监测需求,本文针对灵敏度指标对传感器进行设计与分析。通过建立传感器的数学模型和电磁场有限元分析,研究了激励频率和线圈参数之间的关系。对传感器线圈匝数与灵敏度的相关性进行了数值研究,从检测转子的角度分析了趋肤效应对传感器灵敏度的影响。设计了传感器信号处理电路实现由位移信号到电压信号的转换,并搭建实验平台对传感器的输出特性进行测量。实验结果表明,当灵敏度为20 mV/μm、检测范围为±500μm时,传感器的线性度为0.69%,且具有良好的动态特性,适用于磁悬浮轴承系统的转子高精度径向位置检测。 展开更多
关键词 横向磁通传感器 磁悬浮轴承系统 灵敏度 激励频率
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基于优化PWM的定子磁链轨迹跟踪控制研究
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作者 李杰 肖宇松 宋文祥 《电机与控制应用》 2023年第6期8-14,共7页
在异步电机的高性能控制方案中,为了降低开关损耗,采用优化脉宽调制(PWM)实现低开关频率下较小的电流谐波畸变。但在调制模式频繁切换时,优化PWM会产生电流和转矩冲击。因此,研究了将优化脉冲在线移位的闭环定子磁链轨迹跟踪控制方法,... 在异步电机的高性能控制方案中,为了降低开关损耗,采用优化脉宽调制(PWM)实现低开关频率下较小的电流谐波畸变。但在调制模式频繁切换时,优化PWM会产生电流和转矩冲击。因此,研究了将优化脉冲在线移位的闭环定子磁链轨迹跟踪控制方法,提出了由基于自控电机的降阶观测器与电机电流模型观测器组成的双观测器模型,实现了基波分量观测。结合电流谐波最小脉宽调制(CHMPWM)开关角,利用其重构参考磁链与实际磁链的差值,实现定子磁链轨迹跟踪。提出了无差拍下修正开关角小于2时的脉冲模式调整方案,消除了系统的动态调制误差,实现了低开关频率下异步电机的高性能控制。在开关频率为300 Hz以下的NPC型三电平逆变器上的仿真和试验证明了定子磁链轨迹跟踪控制策略的有效性。 展开更多
关键词 低开关频率 优化PWM 定子磁链 轨迹跟踪控制 动态性能优化
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考虑边缘磁通的LCT新型六电容频域解析模型
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作者 金平 张佳鑫 周天睿 《电机与控制学报》 EI CSCD 北大核心 2023年第7期40-49,共10页
基于有限元的松耦合变压器(LCT)设计往往只能考虑电场或磁场效应,存在计算复杂、耗时,不能得到参数间较为直观的物理关系,以及不能进行频域设计等问题;为此以相邻式磁罐变压器为例,在考虑气隙边缘磁通效应的基础上,提出了一种新型六电... 基于有限元的松耦合变压器(LCT)设计往往只能考虑电场或磁场效应,存在计算复杂、耗时,不能得到参数间较为直观的物理关系,以及不能进行频域设计等问题;为此以相邻式磁罐变压器为例,在考虑气隙边缘磁通效应的基础上,提出了一种新型六电容频域解析模型。采用磁路法和静电能量等效法分别计算了互感、漏感和分布电容参数,采用回路电流法建立了频域模型,然后采用频域分析法,对比研究了不同分布参数模型的传输特性。最后,通过有限元方法验证了考虑边缘磁通效应的电感模型的准确性,仿真和实验结果表明了本文松耦合变压器分布电容模型解析计算的正确性,同时相较于其他现有模型,提出了从频域角度分析的LCT六电容模型,并获得了比现有方法准确性更高的计算模型。 展开更多
关键词 松耦合变压器 边缘磁通效应 解析法 分布电容 频域模型 传输特性
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考虑交叉耦合效应的混合励磁开关磁链电机转子位置估计
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作者 刘旭 郑志康 曹阳 《电机与控制学报》 EI CSCD 北大核心 2023年第7期50-58,共9页
针对使用高频电压注入法估计混合励磁开关磁链永磁(HESFPM)电机转子位置时,由于直轴和交轴之间的交叉耦合效应使得转子位置估计精确度降低的问题,提出了一种对交叉耦合效应进行角度补偿的HESFPM电机励磁绕组高频电压注入位置估计方法。... 针对使用高频电压注入法估计混合励磁开关磁链永磁(HESFPM)电机转子位置时,由于直轴和交轴之间的交叉耦合效应使得转子位置估计精确度降低的问题,提出了一种对交叉耦合效应进行角度补偿的HESFPM电机励磁绕组高频电压注入位置估计方法。通过电枢绕组α、β轴高频电流响应估计转子位置,分析了交叉耦合效应对所提出的高频电压注入位置估计精确度的影响,通过离线方法测量出该效应导致的交叉饱和角,并进行无位置传感器控制在线角度补偿。最后,通过12槽10极HESFPM样机进行实验验证,实验结果表明电机运行在不同转速、负载工况下,所提方法能够有效减小位置估计直流偏置误差,具有良好动态跟随性能。 展开更多
关键词 混合励磁开关磁链永磁电机 转子位置估计 励磁绕组高频注入 交叉耦合效应 角度补偿 直流偏置误差
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一种改进的高铁牵引变流器反馈线性化控制策略 被引量:2
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作者 喻文倩 刘志刚 +2 位作者 张友刚 苟竞 刘嘉蔚 《电工技术学报》 EI CSCD 北大核心 2023年第8期2136-2147,共12页
针对车网系统存在的低频振荡现象,提出一种结合虚拟磁链和滑模观测器的反馈线性化虚拟惯量控制策略,在减少传感器数量的同时,提高系统的鲁棒性。首先,该文分析现有积分器的缺点,提出改进的虚拟磁链观测器,在消除直流偏置影响的同时可以... 针对车网系统存在的低频振荡现象,提出一种结合虚拟磁链和滑模观测器的反馈线性化虚拟惯量控制策略,在减少传感器数量的同时,提高系统的鲁棒性。首先,该文分析现有积分器的缺点,提出改进的虚拟磁链观测器,在消除直流偏置影响的同时可以进行滤波;然后,阐述所提控制策略的推导过程,包括反馈线性化控制、滑模观测器、虚拟惯量控制以及虚拟磁链观测器的设计;最后,在Simulink和硬件在环仿真平台中建立车网系统仿真模型,将该文所提控制方式与传统dq控制以及基于滑模观测器的反馈线性化虚拟惯量控制方式进行对比。仿真和实验结果表明,所提控制策略具有更好的静态和动态特性,能有效地抑制低频振荡的发生。 展开更多
关键词 虚拟磁链观测器 低频振荡 反馈线性化控制 虚拟惯量 高速铁路
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高频红外碳硫仪测定地球化学样品中有机碳 被引量:1
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作者 赵林强 甘黎明 +3 位作者 邓攀直 门倩妮 何涛 王鹏 《化学分析计量》 CAS 2023年第8期40-44,共5页
利用高频红外碳硫仪,建立盐酸预处理-红外吸收法测定地球化学样品中有机碳含量的分析方法。对样品的称取量、助熔剂的添加量、盐酸溶液的体积分数等条件进行了优化。高频红外碳硫分析仪专用陶瓷坩埚经过1200℃高温处理后,能够有效降低... 利用高频红外碳硫仪,建立盐酸预处理-红外吸收法测定地球化学样品中有机碳含量的分析方法。对样品的称取量、助熔剂的添加量、盐酸溶液的体积分数等条件进行了优化。高频红外碳硫分析仪专用陶瓷坩埚经过1200℃高温处理后,能够有效降低空白值。优化后的分析条件为:确定称样量为50 mg,使用体积分数为40%的盐酸溶液,选择0.5 g纯铁屑和1.5 g钨粒作为助熔剂;对土壤和水系沉积物等不同类型的地球化学样品进行6次测定,选择国家一级标准物质作为实验对象,其检测结果的相对误差为0.23%~3.63%,相对标准偏差为0.592%~4.551%,符合《多目标区域地球化学调查规范》规定,满足分析测试要求。该方法测定结果准确、稳定,流程短、操作简单,适用于地球化学样品中有机碳含量的测定。 展开更多
关键词 有机碳 高频红外碳硫仪 助熔剂 盐酸
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