Quantitative thickness estimation of thin-layer is a great challenge in seismic exploration, especially for thin-layer below tuning thickness. In this article, we analyzed the seismic response cha- racteristics of rhy...Quantitative thickness estimation of thin-layer is a great challenge in seismic exploration, especially for thin-layer below tuning thickness. In this article, we analyzed the seismic response cha- racteristics of rhythm and gradual type of thin-layer wedge models and presented a new method for thin-layer thickness estimation which uses relative peak frequency increment. This method can de- scribe the peak frequency to thickness relationship of rhythm and gradual thin-layers in unified equa- tion while the traditional methods using amplitude information cannot. What＇s more, it won＇t be in- fluenced by the absolute value of thin-layer reflection coefficient and peak frequency of wavelet. The unified equations were presented which can be used for rhythm and gradual thin-layer thickness cal- culation. Model tests showed that the method we introduced has a high precision and it doesn＇t need to determine the value of top or bottom reflection coefficient, so it has a more wide application in practice. The application of real data demonstrated that the relative peak frequency increment attribute can character the plane distribution feature and thickness characteristic of channel sand bodies very well.展开更多
nonlinear magnitude frequency equation has been derived in this paper on the assumption that all seismicity systems hold fractal characteristics, and according to the differences of relevant coefficients in the equati...nonlinear magnitude frequency equation has been derived in this paper on the assumption that all seismicity systems hold fractal characteristics, and according to the differences of relevant coefficients in the equation, seis-micity systems are classified into two types: type I, the whole earthquake activity is controlled by only one great unified system; type II, the whole earthquake activity is controlled by more than one great system. One type of seismicity system may convert to the other type, generally. For example, a type I system will change to a type II system prior to the occurrence of a strong earthquake in North China. This change can be regarded as an index for earthquake trend estimation. In addition, the difference between b value in nonlinear magnitude frequency equation and that in linear equation and the term dΔM related to the coefficients of nonlinear terms obtained in this paper are proved to be a pair of available parameters for medium short term earthquake prediction.展开更多
The complexity of seismicity and the relation of magnitude and frequency are discussed in this paper on the basis of nonlinear dynamics and multifractal theory. We argue that seismic active systems normally have multi...The complexity of seismicity and the relation of magnitude and frequency are discussed in this paper on the basis of nonlinear dynamics and multifractal theory. We argue that seismic active systems normally have multifractal characteristics, either for the spatial-temporal distribution or the intensity distribution of events. In the view of multifractal theory the nonlinear characteristics of the magnitude-frequency relation are discussed and the formulation is revised. Also, one example of the variance of bq estimated based on the recent New Zealand catalogue is enumerated.展开更多
High-frequency magnetic properties, such as core loss, coercivity and amplitude permeabilityof a newly-developed nanocrystalline Fe72.5Cu1Nb2V2Si13.5B9 alloy in the wide ranges of f =20-103 kHz, Bm = 0.01~0.6 T and Bm...High-frequency magnetic properties, such as core loss, coercivity and amplitude permeabilityof a newly-developed nanocrystalline Fe72.5Cu1Nb2V2Si13.5B9 alloy in the wide ranges of f =20-103 kHz, Bm = 0.01~0.6 T and Bmf = 10~40 (T.kHz) have been measured. A largeamount of experimental data have been fitted by a computer, thus obtaining several expressionsrepresenting the influence of frequency on high-frequency magnetic properties, that are useful inpractical applications.展开更多
Based on vibration analysis, single-layered graphene sheet （SLGS） with multiple attached nanoparticles is developed as nanoscale mass sensor in thermal environments. Graphene sensors are assumed to be in simplysuppo...Based on vibration analysis, single-layered graphene sheet （SLGS） with multiple attached nanoparticles is developed as nanoscale mass sensor in thermal environments. Graphene sensors are assumed to be in simplysupported configuration. Based on the nonlocal plate the- ory which incorporates size effects into the classical theory, closed-form expressions lot the frequencies and relative fre- quency shills of SLGS-based mass sensor are derived using the Galerkin method. The suggested model is justified by a good agreement between the results given by the present model and available data in literature. The effects of tem- perature difference, nonlocal parameter, the location of the nanoparticle and the number of nanoparticles on the relative frequency shift of the mass sensor are also elucidated. The obtained results show that the sensitivity of the SLGS- based mass sensor increases with increasing temperature difference.展开更多
Grazing exclusion (GE) is the most effective rangeland restoration technique which facilitates species diversity and forage quality. This study aimed at assessing short-term impact of GE and continuously grazed rangel...Grazing exclusion (GE) is the most effective rangeland restoration technique which facilitates species diversity and forage quality. This study aimed at assessing short-term impact of GE and continuously grazed rangeland on relative frequency, dry matter yield and nutritive value of dominant grasses in an area invaded by Euryops floribundus. A plot of 2.5 ha was measured and the boundaries demarcated using tape measure and steal pins, the plot was further divided into two subplots of 1ha each which were 5 m apart. One subplot was fenced and protected from grazing livestock, while one subplot was grazed continuously and not fenced. Three parallel belt transects of 100 m × 2 m with 3 m apart were laid out in both subplots. Woody plants occurring within the transects were identified and recorded to determine density. In each subplot, a 0.25 m<sup>2</sup> quadrant measuring was thrown randomly to take detailed records on plant species, relative frequency of species and herbage biomass. Four dominant species at the two sites were harvested to determine the nutritive value. Results indicate that grazing exclusion (GE) facilitates grass species diversity, subsequently sixteen and thirteen grasses species were recorded in the GE and uncontrolled grazed (UG) sites, respectively. Eragrostis chloromelas (21.7%), and Themeda triandra (13.2%) had high relative frequencies in the GE site. Highest biomass production was recorded in the GE site (1400 kg·ha<sup>-1</sup>) compared to UG site (1102 kg·ha<sup>-1</sup>). Crude protein content was relatively lower at UG site (5.4% - 5.8%) as compared to GE site (7.2% - 7.8%). It was concluded that, GE showed a positive impact on a relative frequency (%), dry matter yield and crude protein content. UG creates a conducive environment for Euryops recruitment. Further studies are required to examine the impact of GE in long-term trial setup.展开更多
An algorithm for GPS receiver performing to mitigate cross correlations between weak satellite signal and strong satellite signals is presented.By using the tracking result of strong signal,the cross-correlation and c...An algorithm for GPS receiver performing to mitigate cross correlations between weak satellite signal and strong satellite signals is presented.By using the tracking result of strong signal,the cross-correlation and cross correlation sequence between weak signals and strong signal can be computed,further modifying the local generate C/A code to drive the cross correlation to zero. The advantage of this method is that it does not require estimation of the strong signal amplitude and it partially independent of the data bit value.Simulation result shows it can eliminate the interference of 75%,and this method is at the cost of sensitivity loss of 0.28dB.展开更多
The propagation characteristics of elasto-thermodiffusive Lamb waves in a homogenous isotropic,thermodiffusive,elastic plate have been investigated in the context of linear theory of generalized thermodiffusion.After ...The propagation characteristics of elasto-thermodiffusive Lamb waves in a homogenous isotropic,thermodiffusive,elastic plate have been investigated in the context of linear theory of generalized thermodiffusion.After developing the formal solution of the mathematical model consisting of partial differential equations,the secular equations have been derived by using relevant boundary conditions prevailing at the surfaces of the plate for symmetric and asymmetric wave modes in completely separate terms.The secular equations for long wavelength and short wavelength waves have also been deduced and discussed.The amplitudes of displacement components,temperature change and mass concentration under the Lamb wave propagation conditions have also been obtained.The complex transcendental secular equations have been solved by using a hybrid numerical technique consisting of irreducible Cardano method along with function iteration technique after splitting these in a system of real transcendental equations.The numerically simulated results in respect of phase velocity,attenuation coefficient,specific loss factor and relative frequency shift of thermoelastic diffusive waves have been presented graphically in the case of brass material.展开更多
基金supported by the Fundamental Research Funds for the Central Universities,Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20110022120004)China National Key S&T Project on Marine Carbonate Reservoir Characterization(No.2011ZX05004003)
文摘Quantitative thickness estimation of thin-layer is a great challenge in seismic exploration, especially for thin-layer below tuning thickness. In this article, we analyzed the seismic response cha- racteristics of rhythm and gradual type of thin-layer wedge models and presented a new method for thin-layer thickness estimation which uses relative peak frequency increment. This method can de- scribe the peak frequency to thickness relationship of rhythm and gradual thin-layers in unified equa- tion while the traditional methods using amplitude information cannot. What＇s more, it won＇t be in- fluenced by the absolute value of thin-layer reflection coefficient and peak frequency of wavelet. The unified equations were presented which can be used for rhythm and gradual thin-layer thickness cal- culation. Model tests showed that the method we introduced has a high precision and it doesn＇t need to determine the value of top or bottom reflection coefficient, so it has a more wide application in practice. The application of real data demonstrated that the relative peak frequency increment attribute can character the plane distribution feature and thickness characteristic of channel sand bodies very well.
文摘nonlinear magnitude frequency equation has been derived in this paper on the assumption that all seismicity systems hold fractal characteristics, and according to the differences of relevant coefficients in the equation, seis-micity systems are classified into two types: type I, the whole earthquake activity is controlled by only one great unified system; type II, the whole earthquake activity is controlled by more than one great system. One type of seismicity system may convert to the other type, generally. For example, a type I system will change to a type II system prior to the occurrence of a strong earthquake in North China. This change can be regarded as an index for earthquake trend estimation. In addition, the difference between b value in nonlinear magnitude frequency equation and that in linear equation and the term dΔM related to the coefficients of nonlinear terms obtained in this paper are proved to be a pair of available parameters for medium short term earthquake prediction.
基金State natural Science foundation of China (40074013).
文摘The complexity of seismicity and the relation of magnitude and frequency are discussed in this paper on the basis of nonlinear dynamics and multifractal theory. We argue that seismic active systems normally have multifractal characteristics, either for the spatial-temporal distribution or the intensity distribution of events. In the view of multifractal theory the nonlinear characteristics of the magnitude-frequency relation are discussed and the formulation is revised. Also, one example of the variance of bq estimated based on the recent New Zealand catalogue is enumerated.
文摘High-frequency magnetic properties, such as core loss, coercivity and amplitude permeabilityof a newly-developed nanocrystalline Fe72.5Cu1Nb2V2Si13.5B9 alloy in the wide ranges of f =20-103 kHz, Bm = 0.01~0.6 T and Bmf = 10~40 (T.kHz) have been measured. A largeamount of experimental data have been fitted by a computer, thus obtaining several expressionsrepresenting the influence of frequency on high-frequency magnetic properties, that are useful inpractical applications.
文摘Based on vibration analysis, single-layered graphene sheet （SLGS） with multiple attached nanoparticles is developed as nanoscale mass sensor in thermal environments. Graphene sensors are assumed to be in simplysupported configuration. Based on the nonlocal plate the- ory which incorporates size effects into the classical theory, closed-form expressions lot the frequencies and relative fre- quency shills of SLGS-based mass sensor are derived using the Galerkin method. The suggested model is justified by a good agreement between the results given by the present model and available data in literature. The effects of tem- perature difference, nonlocal parameter, the location of the nanoparticle and the number of nanoparticles on the relative frequency shift of the mass sensor are also elucidated. The obtained results show that the sensitivity of the SLGS- based mass sensor increases with increasing temperature difference.
文摘Grazing exclusion (GE) is the most effective rangeland restoration technique which facilitates species diversity and forage quality. This study aimed at assessing short-term impact of GE and continuously grazed rangeland on relative frequency, dry matter yield and nutritive value of dominant grasses in an area invaded by Euryops floribundus. A plot of 2.5 ha was measured and the boundaries demarcated using tape measure and steal pins, the plot was further divided into two subplots of 1ha each which were 5 m apart. One subplot was fenced and protected from grazing livestock, while one subplot was grazed continuously and not fenced. Three parallel belt transects of 100 m × 2 m with 3 m apart were laid out in both subplots. Woody plants occurring within the transects were identified and recorded to determine density. In each subplot, a 0.25 m<sup>2</sup> quadrant measuring was thrown randomly to take detailed records on plant species, relative frequency of species and herbage biomass. Four dominant species at the two sites were harvested to determine the nutritive value. Results indicate that grazing exclusion (GE) facilitates grass species diversity, subsequently sixteen and thirteen grasses species were recorded in the GE and uncontrolled grazed (UG) sites, respectively. Eragrostis chloromelas (21.7%), and Themeda triandra (13.2%) had high relative frequencies in the GE site. Highest biomass production was recorded in the GE site (1400 kg·ha<sup>-1</sup>) compared to UG site (1102 kg·ha<sup>-1</sup>). Crude protein content was relatively lower at UG site (5.4% - 5.8%) as compared to GE site (7.2% - 7.8%). It was concluded that, GE showed a positive impact on a relative frequency (%), dry matter yield and crude protein content. UG creates a conducive environment for Euryops recruitment. Further studies are required to examine the impact of GE in long-term trial setup.
文摘An algorithm for GPS receiver performing to mitigate cross correlations between weak satellite signal and strong satellite signals is presented.By using the tracking result of strong signal,the cross-correlation and cross correlation sequence between weak signals and strong signal can be computed,further modifying the local generate C/A code to drive the cross correlation to zero. The advantage of this method is that it does not require estimation of the strong signal amplitude and it partially independent of the data bit value.Simulation result shows it can eliminate the interference of 75%,and this method is at the cost of sensitivity loss of 0.28dB.
文摘The propagation characteristics of elasto-thermodiffusive Lamb waves in a homogenous isotropic,thermodiffusive,elastic plate have been investigated in the context of linear theory of generalized thermodiffusion.After developing the formal solution of the mathematical model consisting of partial differential equations,the secular equations have been derived by using relevant boundary conditions prevailing at the surfaces of the plate for symmetric and asymmetric wave modes in completely separate terms.The secular equations for long wavelength and short wavelength waves have also been deduced and discussed.The amplitudes of displacement components,temperature change and mass concentration under the Lamb wave propagation conditions have also been obtained.The complex transcendental secular equations have been solved by using a hybrid numerical technique consisting of irreducible Cardano method along with function iteration technique after splitting these in a system of real transcendental equations.The numerically simulated results in respect of phase velocity,attenuation coefficient,specific loss factor and relative frequency shift of thermoelastic diffusive waves have been presented graphically in the case of brass material.
