Phase spectrum estimation of the seismic wavelet is an important issue in high-resolution seismic data processing and interpretation. On the basis of two patterns of constant-phase rotation and root transform for wave...Phase spectrum estimation of the seismic wavelet is an important issue in high-resolution seismic data processing and interpretation. On the basis of two patterns of constant-phase rotation and root transform for wavelet phase spectrum variation, we introduce six sparse criteria, including Lu’s improved kurtosis criterion, the parsimony criterion, exponential transform criterion, Sech criterion, Cauchy criterion, and the modified Cauchy criterion, to phase spectrum estimation of the seismic wavelet, obtaining an equivalent effect to the kurtosis criterion. Through numerical experiments, we find that when the reflectivity is not a sparse sequence, the estimated phase spectrum of the seismic wavelet based on the criterion function will deviate from the true value. In order to eliminate the influence of non-sparse reflectivity series in a single trace, we apply the method to the multi-trace seismogram, improving the accuracy of seismic wavelet phase spectrum estimation.展开更多
This paper, using Karnopp's model of friction force and phase plane method, studies the stick-slip motion of the flexible drive mechanism. It is explained that a sudden drop of friction force is the essential sour...This paper, using Karnopp's model of friction force and phase plane method, studies the stick-slip motion of the flexible drive mechanism. It is explained that a sudden drop of friction force is the essential source of stick-slip motion when the sliding is impending. A new criterion for occurrence of stick-slip motion is established. The stick-slip region and the stable region in a parameter plane are separated by a critical parameter curve. Moreover, for the stick-slip motion of the flexible drive mechanism without viscous damping, a parameter expression is obtained. The results may be used in design of the flexible drive mechanism.展开更多
The flow patterns and their transitions of oil-water two-phase flow in horizontal pipes were studied. The experiments were conducted in two kinds of horizontal tubes, made of plexiglas pipe and stainless steel pipe wi...The flow patterns and their transitions of oil-water two-phase flow in horizontal pipes were studied. The experiments were conducted in two kinds of horizontal tubes, made of plexiglas pipe and stainless steel pipe with 40mm ID respectively. No. 46 mechanical oil and tap water were used as working fluids. The superficial velocity ranges of oil and water were: 0.04-1.2m·s^-1 and 0.04-2.2 m·s^-1, respectively. The flow patterns were identified by visualization and by transient fluctuation signals of differential pressure drop. The flow patterns were defined according to the relative distribution ofoil and water phases in the pipes. Flow pattern maps were obtained for both pipelines. In addition, semi-theoretical transition criteria for the flow patterns were proposed, and the proposed transitional criteria are in reasonable agreement with available data in liquid-liquid systems.展开更多
In this paper, the phase characteristic disturbance model for baseband direct sequence spread spectrum (DSSS) signal in additive white Gaussian noise (AWGN) environment is established, and the probability density func...In this paper, the phase characteristic disturbance model for baseband direct sequence spread spectrum (DSSS) signal in additive white Gaussian noise (AWGN) environment is established, and the probability density function (PDF) of phase characteristic disturbance is obtained. Then a novel receiver model for baseband DSSS signal based on maximum likelihood (ML) criterion is proposed. The simulation results show that, comparing with correlation scheme, the performance of the proposed method for baseband DSSS signal is 1dB worse in AWGN environment. However, if there is narrow interference in the AWGN environment, the proposed method will show better performance up to 2.5dB, and it has good adaptive resistance to narrowband interference located in different frequency points. This method could be used as an alterative communication scheme for military circumstance when existing strong narrowband interference of various frequencies.展开更多
基金supported by the Major Basic Research Development Program of China (973 Project No. 2007CB209608)
文摘Phase spectrum estimation of the seismic wavelet is an important issue in high-resolution seismic data processing and interpretation. On the basis of two patterns of constant-phase rotation and root transform for wavelet phase spectrum variation, we introduce six sparse criteria, including Lu’s improved kurtosis criterion, the parsimony criterion, exponential transform criterion, Sech criterion, Cauchy criterion, and the modified Cauchy criterion, to phase spectrum estimation of the seismic wavelet, obtaining an equivalent effect to the kurtosis criterion. Through numerical experiments, we find that when the reflectivity is not a sparse sequence, the estimated phase spectrum of the seismic wavelet based on the criterion function will deviate from the true value. In order to eliminate the influence of non-sparse reflectivity series in a single trace, we apply the method to the multi-trace seismogram, improving the accuracy of seismic wavelet phase spectrum estimation.
基金supported by National Key Basic Research Development Program (Grant No. 2007CB209600)National Major Science and Technology Program (Grant No. 2008ZX05010-002)
文摘This paper, using Karnopp's model of friction force and phase plane method, studies the stick-slip motion of the flexible drive mechanism. It is explained that a sudden drop of friction force is the essential source of stick-slip motion when the sliding is impending. A new criterion for occurrence of stick-slip motion is established. The stick-slip region and the stable region in a parameter plane are separated by a critical parameter curve. Moreover, for the stick-slip motion of the flexible drive mechanism without viscous damping, a parameter expression is obtained. The results may be used in design of the flexible drive mechanism.
基金National Natural Science Foundation of China (No.59995462 and 10172069)
文摘The flow patterns and their transitions of oil-water two-phase flow in horizontal pipes were studied. The experiments were conducted in two kinds of horizontal tubes, made of plexiglas pipe and stainless steel pipe with 40mm ID respectively. No. 46 mechanical oil and tap water were used as working fluids. The superficial velocity ranges of oil and water were: 0.04-1.2m·s^-1 and 0.04-2.2 m·s^-1, respectively. The flow patterns were identified by visualization and by transient fluctuation signals of differential pressure drop. The flow patterns were defined according to the relative distribution ofoil and water phases in the pipes. Flow pattern maps were obtained for both pipelines. In addition, semi-theoretical transition criteria for the flow patterns were proposed, and the proposed transitional criteria are in reasonable agreement with available data in liquid-liquid systems.
基金supported by the National Basic Research Program (973 Program) of China under Grant No.2007CB310606National Key Technologies R&D Program under Grant No.2009ZX03004-001
文摘In this paper, the phase characteristic disturbance model for baseband direct sequence spread spectrum (DSSS) signal in additive white Gaussian noise (AWGN) environment is established, and the probability density function (PDF) of phase characteristic disturbance is obtained. Then a novel receiver model for baseband DSSS signal based on maximum likelihood (ML) criterion is proposed. The simulation results show that, comparing with correlation scheme, the performance of the proposed method for baseband DSSS signal is 1dB worse in AWGN environment. However, if there is narrow interference in the AWGN environment, the proposed method will show better performance up to 2.5dB, and it has good adaptive resistance to narrowband interference located in different frequency points. This method could be used as an alterative communication scheme for military circumstance when existing strong narrowband interference of various frequencies.
