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| 1 | Power system low frequency oscillation monitoring and analysis based on multi-signal online identification显示文摘The advance in the wide-area measurement system (WAMS) is driving the power system to the trend of wide-area monitoring and control.The Prony method is usually used for low frequency oscillation online identification.However,the identified amplitude and phase information is not sufficiently used.In this paper,the amplitude is adopted to detect the occurrence of the oscillation and to obtain the mode observability of the sites.The phase is adopted to identify the oscillation generator grouping and to obtain the mode shapes.The time varying characteristics of low frequency oscillations are studied.The behaviors and the characters of low frequency oscillations are displayed by dynamic visual techniques.Demonstrations on the '11.9' low frequency oscillation of the Guizhou Power Grid substantiate the feasibility and the validation of the proposed methods. | YUAN Ye1,2,SUN YuanZhang2,CHENG Lin2,CHEN Gang2 & WANG Peng3 1 State Nuclear Electric Power Planning Design and Research Institute,Beijing 100032,China 2 State Key Laboratory of Power Systems,Deptment of Electrical Engineering,Tsinghua University,Beijing 100084,China 3 EEE School,Nanyang Technological University,Singapore | 2010 | Science China(Technological Sciences)2010，53，9： | 13 |
| 2 | The Seasonal Climate and Low Frequency Oscillation in the Simulated Mid-Holocene Megathermal Climate显示文摘The mid-Holocene climate about 6000 years ago was simulated by using the atmospheric general circulation model. The orbital parameters for 6 ka BP (before present) were prescribed and other forcing factorswere set in the modern conditions. Results show that the large-scale climate change in the Aflican-Asianmonsoon areas during the summer-time is strongly compared to the present climate. while the changes inother seasons and regions are generally weak. The results also revealed the change of the low frequencyoscillation in the atmosphere. | 王会军 | 2000 | Advances in Atmospheric Sciences2000，17，3： | 12 |
| 3 | Modulatory effect of International standard Scalp Acupuncture on brain activation in the elderly as revealed by resting-state fMRI显示文摘The specific mechanisms by which acupuncture affects the central nervous system are unclear. In the International Standard Scalp Acupuncture system, acupuncture needles are applied at the middle line of the vertex, anterior parietal-temporal oblique line, and the posterior parietal-temporal oblique line. We conducted a single-arm prospective clinical trial in which seven healthy elderly volunteers (three men and four women;50–70 years old) received International Standard Scalp Acupuncture at MS5 (the mid-sagittal line between Baihui (DU20) and Qianding (DU21)), the left MS6 (line joining Sishencong (EX-HN1) and Xuanli (GB6)), and the left MS7 (line joining DU20 and Qubin (GB7)). After acupuncture, resting-state functional magnetic resonance imaging demonstrated changes in the fractional amplitude of low frequency fluctuations and regional homogeneity in various areas, showing remarkable enhancement of regional homogeneity in the bilateral anterior cingulate, left medial frontal gyrus, supramarginal gyrus, right middle frontal gyrus, and inferior frontal gyrus. Functional connectivity based on a seed region at the right middle frontal gyrus (42, 51, 9) decreased at the bilateral medial superior frontal gyrus. Our data preliminarily indicates that the international standard scalp acupuncture in healthy elderly participants specifcally enhances the correlation between the brain regions involved in cognition and implementation of the brain network regulation system and the surrounding adjacent brain regions. The study was approved by the Ethics Committee of the China-Japan Union Hospital at Jilin University, China, on July 18, 2016 (approval No. 2016ks043). | Wai-Yeung Chung Song-Yan Liu Jing-Chun Gao Yi-Jing Jiang Jing Zhang Shan-Shan Qu Ji-Ping Zhang Xiao-Long Tan Jun-Qi Chen Sheng-Xu Wang | 2019 | Neural Regeneration Research2019，14，12： | 8 |
| 4 | Experimental studies on extremely low frequency pulsed magnetic field inhibiting sarcoma and enhancing cellular immune functions显示文摘The previous observation with an electron microscope showed that extremely low frequency (ELF) pulsed magnetic field (PMF) (with the maximum intensity of 0. 6-2. 0 T, gradient of 10-100 T. M-1, pulse width of 20-200 ms and frequency of 0. 16-1. 34 Hz) inhibited the growth of S-180 sarcoma in mice and enhanced the ability of immune cell’s dissolving sarcoma cells. In this study, the DNA contents of nuclei were assayed by using Faulgen Staining method. With an electron microscope and cell stereoscopy technology it was observed that magnetic field affected the sarcoma cell’s metabolism, lowered its malignancy, and restrained its rapid and heteromorphic growth. The magnetic field enhanced the cellular immune ability and the reaction of lymphocytes and plasma. Since ELF pulsed magnetic fields can inhibit the growth of sarcomas and enhance the cellular immune ability, it is possible to use it as a new method to treat cancer. | 张沪生 叶晖 张传清 曾繁清 黄兴鼎 张晴川 李宗山 杜碧 | 1997 | Science China(Life Sciences)1997，40，4： | 8 |
| 5 | Low frequency vibration control of railway vehicles based on ahigh static low dynamic stiffness dynamic vibration absorber显示文摘In order to control the low frequency vibration of railway vehicles, a vertical two degrees of freedom(2DOF) low frequency dynamic vibration absorber(DVA) based on acceleration is proposed. Parameters of the dynamic vibration absorber are put forth to control the low frequency vibration of car body bouncing and pitching. Next, the acceleration power spectrum density(PSD)and ride quality of the car body are calculated based on the pseudo excitation method(PEM) and covariance algorithm,respectively. According to the requirement of 2DOF low frequency DVA, the isolators with high static low dynamic stiffness(HSLDS) are designed. A high-speed train dynamic model containing HSLDS isolators is established to validate the effects on the car body vibration. The results reveal that the 2D low frequency DVA can significantly reduce the vibration of the car body bouncing and pitching. Thus, the ride quality of the vehicle is increased, and passenger comfort is improved. | SUN Yu GONG Dao ZHOU JinSong SUN WenJing XIA ZhangHui | 2019 | Science China(Technological Sciences)2019，62，1： | 6 |
| 6 | Carrier dynamic overlapping switching frequency optimal pulse width modulation method for modular multilevel converters显示文摘Modular multilevel converters(MMCs) operate in the low modulation index region in many applications.However, when utilized at the low modulation index region, large harmonics appear in the output voltage, which degrade the performance of the MMC. To improve the harmonic characteristic in the low modulation index, the carrier dynamic overlapping switching frequency optimal pulse width modulation(CDOSFOPWM) method is proposed for the MMC here. The whole modulation index region is divided into three regions: high modulation index region, middle modulation index region, and low modulation index region. The carrier amplitude, carrier overlap ratio, and frequency of triangular carriers are chosen dynamically according to the modulation index region of the modulation signals, to achieve the optimal harmonic characteristic in the whole modulation index region and maintain the switching loss. The number of on-state submodules(SMs) can be calculated by CDOSFOPWM, and the selection of SMs is performed by a reducing switching frequency voltage balancing algorithm. Finally, the proposed method is verified by simulation and experimental results. | Fayun ZHOU Qianming XU An LUO Zhixing HE Yan LI Ning XIE Yichao WANG | 2018 | Journal of Modern Power Systems and Clean Energy2018，6，6： | 5 |
| 7 | Wigner-Hough transform based on slice's entropy and its application to multi-LFM signal detection显示文摘To enhance the capacity of the radar-reconnaissance interception receiver recognizing linear frequency modulated(LFM) at a low signal-noise ratio, this paper presents WignerHough transform(WHT) of the LFM signal and its corresponding characteristics, derives the probability density functions of the LFM signal and Gaussian white noise within WHT based on entropy(WHTE), dimension under different assumptions and puts forward a WHT algorithm based on entropy of slice to improve the capacity of detecting the LFM signal. Entropy of the WHT domain slice is adopted to assess the information size of polar radius or angle slice, which is converted into the weight factor to weight every slice. Double-deck weight is used to weaken the influences of noise and disturbance terms and WHTE treatment and signal detection procedure are also summarized. The rationality of the algorithm is demonstrated through theoretical analysis and formula derivation, the efficiency of the algorithm is verified by simulation comparison between WHT, fractional Fourier transform and periodic WHT, and it is highlighted that the WHTE algorithm has better detection accuracy and range of application against strong noise background. | Hongwei Wang Xiangyu Fan You Chen Yuanzhi Yang | 2017 | Journal of Systems Engineering and Electronics2017，28，4： | 5 |
| 8 | Vibration stimuli and the differentiation of musculoskeletal progenitor cells: Review of results in vitro and in vivo显示文摘Due to the increasing burden on healthcare budgets of musculoskeletal system disease and injury, there is a growing need for safe, effective and simple therapies. Conditions such as osteoporosis severely impact onquality of life and result in hundreds of hours of hospital time and resources. There is growing interest in the use of low magnitude, high frequency vibration(LMHFV) to improve bone structure and muscle performance in a variety of different patient groups. The technique has shown promise in a number of different diseases, but is poorly understood in terms of the mechanism of action. Scientific papers concerning both the in vivo and in vitro use of LMHFV are growing fast, but they cover a wide range of study types, outcomes measured and regimens tested. This paper aims to provide an overview of some effects of LMHFV found during in vivo studies. Furthermore we will review research concerning the effects of vibration on the cellular responses, in particular for cells within the musculoskeletal system. This includes both osteogenesis and adipogenesis, as well as the interaction between MSCs and other cell types within bone tissue. | Jennifer Helen Edwards Gwendolen Clair Reilly | 2015 | World Journal of Stem Cells2015，7，3： | 4 |
| 9 | Low-frequency and broadband vibration energy harvester driven by mechanical impact based on layer-separated piezoelectric beam显示文摘Vibration energy harvesting is to transform the ambient mechanical energy to electricity. How to reduce the resonance frequency and improve the conversion efficiency is very important. In this paper, a layer-separated piezoelectric cantilever beam is proposed for the vibration energy harvester(VEH) for low-frequency and wide-bandwidth operation, which can transform the mechanical impact energy to electric energy. First,the electromechanical coupling equation is obtained by the Euler-Bernoulli beam theory.Based on the average method, the approximate analytical solution is derived and the voltage response is obtained. Furthermore, the physical prototype is fabricated, and the vibration experiment is conducted to validate the theoretical principle. The experimental results show that the maximum power of 0.445 μW of the layer-separated VEH is about3.11 times higher than that of the non-impact harvester when the excitation acceleration is 0.2 g. The operating frequency bandwidth can be widened by increasing the stiffness of the fundamental layer and decreasing the gap distance of the system. But the increasing of operating frequency bandwidth comes at the cost of reducing peak voltage. The theoretical simulation and the experimental results demonstrate good agreement which indicates that the proposed impact-driving VEH device has advantages for low-frequency and wide-bandwidth. The high performance provides great prospect to scavenge the vibration energy in environment. | Dongxing CAO Wei XIA Wenhua HU | 2019 | Applied Mathematics and Mechanics(English Edition)2019，40，12： | 4 |
| 10 | CEOF ANALYSIS OF ATMOSPHERIC LOW FREQUENCY OSCILLATION IN LOWER LATITUDE REGION AND FREQUENCY MODULATION PHENOMENA OF LOW FREQUENCY SIGNALS显示文摘The low frequency oscillation of the low level atmospheric circulation in lower latitudes region is studied by usingthe CEOF method and other normal spectral analysis methods.It is found that in the atmospheric motion frequencyspectrum,there exist certain frequency bands with relatively-concentrated energy among low frequency bands,andthere is nonlinear interaction of frequency modulation among peak signals.It is this modulating action that leads to thechange of the temporal-spatial features of frequency and phase of these low frequency signals.In the paper,the propa-gation picture of low frequency waves modulated and its influence on midium-range variation of summer monsoon arealso discussed. | 罗坚 喻世华 | 1995 | Acta meteorologica Sinica1995，9，2： | 4 |
| 11 | ANALYSIS ON THE SOURCE AND SINK OF KINETIC ENERGY OF ATMOSPHERIC 30—60 DAY PERIOD OSCILLATION AND THE PROBABLE CAUSES显示文摘Based on ECMWF daily grid point data in summer (May—August),1981,the distributionfeatures of the source and sink of kinetic energy of atmosphere 30—60 day oscillation,including itshorizontal distribution characteristics and its vertical structure characteristics,are investigatedsystematically with diagnostic analysis methods over a latitude belt between 80°N and 60°S.Also,theprobable reasons for the existence of the source and sink of low frequency kinetic energy (LFKE) arediscussed preliminarily.Results show that the horizontal distribution of the sources and sinks ofkinetic energy of atmospheric 30—60 day oscillation is extremely different.The significant sourcesand sinks of LFKE mainly exist in the oceans and the coastal regions of continents or islands in themid-high latitudes.It is also found that,in the vertical direction,the sources and sinks of kineticenergy of 30—60 day oscillation display barotropic structure in the mid-high latitudes of bothhemispheres,but dispaly baroclinic structure in the equtorial region,and in the horizontal direction,the sources and sinks mainly display zonal wave-like distribution.The source and sink of LFKE aredeterminded by ageostrophic wind effect,frictional effect,interaction between sub-grid-scalesystems,nonlinear interaction,and the flux-divergence of LFKE transported by transient wind.There are some regional reasons for the generation of sources and sinks which are not completelyidentical in different areas. | 李清泉 朱乾根 | 1995 | Acta meteorologica Sinica1995，9，4： | 3 |
| 12 | Propagation of interplanetary shock excited ultra low frequency (ULF) waves in magnetosphere-ionosphere-atmosphere——Multi-spacecraft “Cluster” and ground-based magnetometer observations显示文摘The ultra low frequency (ULF) wave in magnetosphere can act as an important means for solar wind energy inward transmission.This paper quantitatively analyzes the propagation process of the ULF wave triggered by the interplanetary shock propagating from inner magnetosphere equatorial plane along magnetic field lines to the top of the ionosphere and below ionosphere propagating process and establishes a relatively complete magnetosphere-ionosphere-atmosphere propagation model which can be used to study the relationship between the amplitude of the ULF waves triggered by the interplanetary shock wave in magnetospheric space and the magnetic effect caused by the ULF waves.After a comparison with recent observations,we found that: in the event during November 7,2004 that an interplanetary shock wave interacted with the magnetosphere,Cluster satellites observed that electric field fluctuations and the band-pass filtered result of ground stations meridional component had similar characteristics.Comparing with the geomagnetic measurement near the footprints,we found that the electric field disturbance in the magnetosphere spread along the ground magnetic field lines in the form of the ULF waves and changed into geomagnetic disturbance.The result reveals that the ULF wave is in contact with the ground geomagnetic observation.The ULF waves couple with ionized components in ionosphere and spread to the ground in the form of electromagnetic waves.In this research,we believe that the magnetosphere,ionosphere and ground magnetic effects caused by interplanetary shock wave are the same physical phenomena responding in different locations.Based on the overall consideration of entire electromagnetic response to the interplanetary shock wave,we found that the correlation between CLUSTER multi-satellite observation and geomagnetic station observation is due to the ULF wave propagated in magnetosphere-ionosphere-atmosphere system,and we quantitatively interpreted this response process. | WANG ChengRui1,2,ZONG QiuGang1,3 & WANG YongFu1 1 Institute of Space Physics and Applied Technology,Peking University,Beijing 100871,China 2 Sate Key Laboratory of Space Weather,Chinese Academy of Sciences,Beijing 100190,China 3 Center for Atmospheric Research,600 Suffolk Street,University of Massachusetts Lowell,MA 01854,USA | 2010 | Science China(Technological Sciences)2010，53，9： | 3 |
| 13 | A Diagnostic Study on the Relationship between the Assembling of Low Frequency Waves in the Pacific Ocean and the Abnormality of the Subtropical High显示文摘ADiagnosticStudyontheRelationshipbetwentheAsemblingofLowFrequencyWavesinthePacificOceanandtheAbnormalityoftheSubtropicalHighZ... | 章建文 喻世华 | 1998 | Advances in Atmospheric Sciences1998，15，2： | 3 |
| 14 | Effects of extremely low frequency magnetic fields on gap junctional intercellular communication and its mechanism显示文摘The study on biological effect of electromagnetic fields has been paid close attention in recent years. Gap junctional intercellular communication (GJIC) plays an important role in the maintenance of cell proliferation and differentiation, and in the multistage process of carcinogenesis. A series of researches showed that xtremely low frequency (ELF) magnetic fields not only enhance the inhibition of GJIC induced by 12-O-tetradecanoylphorbol-13-acetate, but also inhibit GJIC directly when the intensity is equal to or more than 0.4 mT, and that the mechanisms of GJIC inhibition by ELF magnetic fields are due to hyperphosphorylation of connexin 43, which is mediated by protein kinase C-activated signal transduction, and the internalization of connexin 43 from plasma membrane to cytoplasm. | CHIANG Huai , HU Genlin and XU Zhengping(Microwave Laboratory, Zhejiang University School of Medicine, Hangzhou 310031, China) | 2002 | Progress in Natural Science:Materials International2002，12，3： | 2 |
| 15 | Meridional wind forced low frequency disturbances in the tropical ocean | 林一骅 季仲贞 曾庆存 | 1999 | Progress in Natural Science:Materials International1999，9，7： | 2 |
| 16 | Effect of particle size on the preparation and microwave absorption properties of FeSiAl magnetically soft alloy hollow microspheres显示文摘FeSiAl magnetically soft alloy hollow microspheres(MSAHMs) were prepared by self-reactive quenching technology based on Fe + Si + AI + KNO_3 reactive systems, in order to obtain absorbents with light weight, low frequency and high efficiency. Firstly, twice-balling adhesive precursor method was used to obtain FeSiAl magnetically soft alloy agglomerate powders. Then agglomerate powders with the mesh number of 150-240, 240-325 and 325-400 were sprayed through the flame field into the quenching water. At last, FeSiAl MSAHMs with coarse(average at 86.97 μm), medium(average at 52.16 μm) and fine particles(average at 31.80 μm) were got. Effect of particle size on the phases and microwave absorption properties in low frequency band was studied by XRD and vector network analyzer. The results show that,Fe_3 Si_(0.7)Al_(0.3) and Fe_3 Si_(0.5)Al_(0.5) appear in the phase components of FeSiAl MSAHMs,which is important to improve the microwave absorption properties in low frequency. In addition, the real part(ε′) and imaginary part(ε″) of complex permittivity, the real part(μ′) and imaginary part(μ″) of complex permeability of FeSiAl MSAHMs all present the trend of fine particles > medium particles > coarse particles. The microwave absorption properties in low frequency are improved with the increasing of particle size, and the absorption peak moves to lower frequency range. The properties of fine particles are the best. Their matching thickness of samples is at 5 mm, and the minimum reflectivity is-43 dB at this thickness. The absorption frequency band lower than-10 dB is 4.6-7.6 GHz with a bandwidth of 3 GHz. | Xu-dong Cai Xiao-jun Jiang Wei Xie Jing-yang Mu De-fei Yin | 2018 | Defence Technology(防务技术)2018，14，5： | 2 |
| 17 | Effect of Rare Earth Elements on Low Frequency Fatigue Cyclic Softening of Hot Rolled Steel 60CrMnMo at High Temperature显示文摘EffectofRareEarthElementsonLowFrequencyFatigueCyclicSofteningofHotRolledSteel60CrMnMoatHighTemperatureYangQingxiang;WuHaoquan... | 杨庆祥 吴浩泉 任学军 郭景海 | 1995 | Journal of Rare Earths1995，13，1： | 2 |
| 18 | 静息态脑区的活动特征研究显示文摘静息态脑区的活动处于一种相对稳定的状态。但是,静息态机能性磁共振成像(functional Magnetic Resonance Imaging,fMRI)实验中,被试者可能会受到各种噪声的影响,因此,统计分析所得到的静息态脑区的活动强度和体素数都可能受此影响。为了更进一步研究静息态脑区的活动特点,分别对16名被试采集了8′14″的静息态fMRI数据,将这些数据按照时间等分为5个部分,对每个部分分别采用低频振幅方法进行分析。实验结果显示:楔前叶和后扣带皮层包含活动体素的个数随时间变化较小,处于一种相对稳定的状态;额内侧皮层和顶下小叶中活动体素个数随时间变化差异较大,处于不是很稳定的状态。实验结果表明,静息态脑区中,楔前叶和后扣带皮层对于外界噪声的干扰不敏感,额内侧皮层和顶下小叶对于外界噪声比较敏感。 | 杜培锋 杨剑 吕胜富 钟宁 | 2011 | 北京教育学院学报(自然科学版)2011，6，2： | 2 |
| 19 | The relationship between low frequency atmospheric oscillation and SST in equatorial Pacific显示文摘Based on analyzing the tropical Pacific SST and ECMWF data in the 1980s, the inverse characteristics between low frequency atmospheric oscillation (LFO), including intrasea-sonal oscillation and half-year oscillation and the SST anomalies in the tropical Pacific (SSTA) have been found. The positive SSTA corresponds to the weak LFO, the negative SSTA to the strong LFO. The correlation field further demonstrates this kind of negative correlation and points out that the anomalous LFO in Indonesia plays an important role in the variation of SSTA in the tropical centre-eastern Pacific. | Chongyin Li Guilong Li | 1999 | Chinese Science Bulletin1999，44，12： | 2 |
| 20 | LOW FREQUENCY OSCILLATION IN EAST ASIA DURING THE 1991 EXCESSIVELY HEAVY RAIN OVER THE CHANGJIANG-HUAIHE RIVER BASIN显示文摘The activity of low frequency oscillation (LFO) widely exists in East Asia during the period of1991 excessively heavy rain over the Changjiang-Huaihe River Basin (Jianghuai).Both the rainfallamount of Jianghuai and the atmosphere from subtropical area to mid-high latitudes have thedominant period of 10—20 d,while the atmospheres in tropical area and high latitudes have thedominant period of 30—60 d.Compared with normal Meiyu season,the anomaly of the 1991 Meiyu process may be reflectedin the following two low frequency synoptic events:(a) The Meiyu process onsets extremely early(in the second dekad of May,which is nearly one month earlier than in normal Meiyu) and isimmediately followed by the first episode of heavy rain.(b) In the first dekad of July,there occursthe heaviest episode of rainfall of the whole Meiyu season,and it is even the heaviest rainfall forthe recent 30 years in China.For these two periods,corresponding to the adjustment of large-scalesituation from“double blocking high”to“bipolar blocking high”,the propagation direction of LFOin East Asia has a distinct seasonal variation,from eastward/northward propagation (passingthrough Jianghuai) during the first episode to westward/southward propagation during the thirdepisode.Oscillations of different frequency bands are superposed in phase.The LFO activity of thecold and warm/moist airs over Jianghuai can be strengthened through those LFO propagationprocesses in East Asia,although they may have different directions in three episodes.Particularly,the eastward (westward) propagation in low latitudes makes the southwest (southeast) airflowtransport intensively the low frequency warm/moist air to the south of Jianghuai from the IndianOcean (tropical West Pacific Ocean) in the first (third) episode.Such warm/moist airs meet andinteract with the cold air which vigorously invades Jianghuai persistently,and finally three episodesof heavy rain occur in mode of LFO. | 陆尔 丁一汇 | 1997 | Acta meteorologica Sinica1997，11，1： | 2 |
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