OALib Journal期刊

ISSN: 2333-9721




2019 ( 2 )

2018 ( 144 )

2017 ( 141 )

2016 ( 284 )


匹配条件: “precursor wave of low frequency” ,找到相关结果约17298条。

Zhang Shuliang,Liu Ruichun,Ning Yaling,Tang Leili,Li Bin,

大地测量与地球动力学 , 2009,
Abstract: The changes of some precursory observation in Shanxi area before Wenchuan Ms8.0 earthquake on May 12,2008 were analysed,and following conclutions are drawn.Firstly,the precursor waves of low frequent are main characters of the precursory change before the earthquake,and its superior period are 64-128 min.Secondly,the distribution of the abnormal points is in the same direction with the primary rupture of Wenchuan Ms8.0 earthquake.Thirdly,low-frequency precursory waves occured in a crowded time,mainly from 1...
Experimental Data for Study on the Shielding Effect of Electromagnetic Wave  [PDF]
Chen-Ching Ting, Chien-Chih Chen
Engineering (ENG) , 2011, DOI: 10.4236/eng.2011.37093
Abstract: This article presents some new experimental data for study the shielding effect of electromagnetic wave. The frequencies of electromagnetic wave are mainly focused on emission of daily electrical equipments, which are normally called “low frequency electromagnetic waves”. In this work, a water pump with maximum magnetic field intensity of ca. 2300 mG was applied as emission source of the electromagnetic wave. Experimental measurements used various shielding materials with the major constituent iron (Fe) in the form of plate for studying shielding effect of electromagnetic wave. The studied parameters were different thicknesses and gaps of the plate. The results show that pure iron plate has the best effect for shielding the magnetic field and its transmission ratio of magnetic field is proportional to distance between the emission source and the shielding plate. Moreover, the shielding plate close to the emission source received better protection.
Application of microspectral luminescent analysis to study the intracellular metabolism in single cells and cell systems  [PDF]
Natalia A. Karnaukhova, Larisa A. Sergievich, Valery N. Karnaukhov
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.25054
Abstract: Spectral luminescent analysis of single cells and cellular systems enable us to reveal the initial changes of intracellular metabolism that can followed by human diseases or failure in biocenosis. Two cytodiagnostic systems of de-vices and techniques have been developed: 1) Microspectrofluorimeters registering the fluo-rescent spectra of individual cells or intracellular organelles used for fundamental investigations of cell reactions and for discovering and studying new dimensionless fluorescent characteristic parameters reflecting the biochemical or physiological properties of the cells; 2) Double- and multi-wave microfluorimeters for rapid registration of fluorescent characteristic para- meters for many cells to obtain statistical information about cell population. These techni- ques are useful especially in medical and eco-logical investigations.
Seasonal Variation of Stationary and Low-Frequency Rossby Wave Rays
Lu Keli,Zhu Yongchun,
Lu Keli
,Zhu Yongchun

大气科学进展 , 1994,
Abstract: The wave rays and their seasonal variation of stationary and low-frequency Rossby waves are studied by using the Runge-Kutta scheme. The results show that for stationary waves the rays can reach lower latitudes in winter, and are limited in higher latitudes in summer. The main differences between the stationary and low-frequency wave rays are that low-frequency waves can propagate across the equator and the easterlies will not be an obstacle on their propagation. It explained to some extent the interaction of disturbances between the Northern and Southern Hemispheres. The lower wave frequencies and the stronger easterly flow are, the more difficult low-frequency waves will be to propagate across the equator. The waves with 20-day period are easier to propagate across the equator than that with 50-day period. The winter is the most favorable season for low-frequency waves to propagate into another hemisphere.
A New Current Conveyor Full-Wave Rectifier for Low Frequency/Small Signal Medical Applications  [PDF]
Adisak Monpapassorn
Circuits and Systems (CS) , 2018, DOI: 10.4236/cs.2018.93006
Abstract: This paper presents a new current conveyor (CCII+) full-wave rectifier for low frequency/small signal medical applications. The proposed rectifier is based on the current conveyor full-wave rectifier proposed previously, but the proposed rectifier is better in view of no need diodes to rectify, and no need bias sources to overcome the zero crossing error. It needs only two CCII+s, two resistors, and three simple current mirrors, which is easy for IC implementation and for building in many countries. The PSPICE simulation with the current conveyor CCII+ in the current feedback opamp AD844 IC and the 2N2222 bipolar current mirror shows the good low frequency/small signal rectification, the operation voltage of down to 6 \"\".
CISK-related Rossby Waves in the Tropical Atmosphere
Jiang Guorong,

大气科学进展 , 1996,
Abstract: In terms of a baroclinic quasi-geostrophic waveufiltering technique in connection with a dimensionless parameter,n(z),of condensation-released latent heat that indicates the CISK mechanism,a model is established for describing tropical atmosphere CISK-Rossby waves alongside its analytical solution. Theoretical study shows that thereexists pronounced difference between Rossby waves, CISK-involving and classic, and the former can be used to interpret some aspects of the low--frequency oscillation in the tropical atmosphere.
Nonlinear Three-Wave Interaction among Barotropic Rossby Waves in a Large-scale Forced Barotropic Flow
Luo Dehai,

大气科学进展 , 1999,
Abstract: In this paper. the coupling equations describing nonlinear three-wave interaction amongRossby waves including the forcing of an external vorticity source are obtained. Under certainconditions, the coupling equations with a constant amplitude forcing, the stability analysis indicates that when the amplitude of the external forcing increases to a certain extent, a pitchforkbifurcation occurs. Also. it is shown fi-o m numerical results that the bifurcation can lead to chaoticbehavior of" strange" attractor. For the obtained three-variable equation, when the amplitude ofmodulated external forcing gradually increases, a Period-doubling bifurcation is found to lead tochaotic behavior. Thus, in a nonlinear three-wave coupling model in the large-scale forcedbarotropic atmospheric flow, chaotic behavior can be observed. This chaotic behavior can explainin part 30-60-day low-flequency oscillations observed in mid-high latitudes.
The propagation of disturbances excited by low-frequency oscillations in the tropics
The Propagation of Disturbances Excited by Low-Frequency Oscillations in the Tropics

Lu Peisheng,

大气科学进展 , 1993,
Abstract: The propagation of disturbances excited by low-frequency oscillations in the tropics is investigated by applying the theory of wave packet dynamics. For simplicity, a linearized barotropic model is adopted and the zonal circulation is taken as basic current. Suppose that the disturbances or waves are superimposed on jet-like westerly basic current and excited by the forcing in the tropics. We have (1) only the eastward propagating (m>0,n>0 and σ>0) low-frequency disturbances and the stationary (σ = 0) waves can propagate into the middle and high latitudes in the Northern Hemisphere; the others, such as the westward propagating low-frequency wave (m>0,n<0, σ<0) and the high-frequency waves, are restricted only in the vicinity of source region; (2) a stationary wave (σ = 0) reaches a given latitude even more quickly than some low-frequency ones (σ>0) due to the fact that the group velocity of stationary wave is larger; (3) there is a whole wave train excited by the forcing in the tropics and extended into the middle and high latitudes, if the amplitude of the source is independent on time, especially, the low-frequency wave (σ>0) is of travelling type propagating along the ray; (4) if the source lasts only for an interval of time, namely, its amplitude also has the character of low-frequency oscillation, the excited wave train is not always a whole one, but is restricted in the vicinity of source region in the beginning, extended from the source region to the middle and high latitudes in its saturated stage, after that it gradually becomes weaker and weaker and is detectable only in some area at high latitude, and eventually disappears. Undoubtedly, case (4) is closer to the reality, even though case (3) gives a more impressive wavy pattern.
A Diagnostic Study on the Relationship between the Assembling of Low Frequency Waves in the Pacific Ocean and the Abnormality of the Subtropical High
Zhang Jianwen,Yu Shihua,
Zhang Jianwen
,Yu Shihua

大气科学进展 , 1998,
Abstract: By use of the filter analysis technique, the Complex Empirical Othogonal Function (CEOF) method and the ECMWF/WMO 2.5o× 2.5o grid data of the geopotential heights during the summer months in 1988, an interseasonal process that the western Pacific subtropical high (WPSH) was anomalously far to the north in the first and second ten days of July is studied. It has been found that in the western Pacific subtropical region in the first and second ten days of July, it is the continuous assembly of low frequency geopotential waves (LFGWs) that leads to the abnormality of WPSH. This abnormality emerges with the enhancement of wave assembling and ceases while the wave assembling situation disappears. The structure of the low frequency assembling waves corresponds to the struc-ture of subtropical high in its abnormal period. The effect of the assembling waves on the abnormality of subtropical high can be considered as the accumulation of disturbance energy carried by the low frequency waves from different directions in the western Pacific region.

Yang Yufen,

电子与信息学报 , 1990,
Abstract: A frequency tripler covering 210-270 GHz frequency band with a peak efficiency of 5.8% is lescribed. The maximum output power occurs at input power of 30-50 mW. The frequency tripler consists of an input waveguide WR-12, an output waveguide WR-4 and a coxial low pass filter between them.

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