In this paper, using a Gaussian distribution of wave normal angle X=tan0, and considering contributions of harmonic resonances n up to ＋5, we analyze the effect of normal angle on diffusion coefficients induced by gy...In this paper, using a Gaussian distribution of wave normal angle X=tan0, and considering contributions of harmonic resonances n up to ＋5, we analyze the effect of normal angle on diffusion coefficients induced by gyroresonance between chorus waves and electrons with energies 0.1 and 1.0 MeV on the dayside and nightside at L=4.5. When pitch angle a~〉10~, for 0.1 and 1,0 MeV electrons on the dayside and nightside, diffusion coefficients of five orders （-2, -1, 0, 1, 2） decrease with in- creasing normal angle peak, leading to the total diffusion coefficients decreasing with increasing peak. When ae〈10~, for 1.0 MeV electrons on the dayside and 0.1 MeV electrons on the dayside and nightside, the positive order diffusion coefficients are generally smaller than the same negative order ones; in the meanwhile, diffusion coefficients of orders （-2, 1, 2） are very small, the dominant order n=-I diffusion coefficients change very little, hence the total diffusion coefficients almost remain un- changed. However, for 1.0 MeV electrons on the nightside, diffusion coefficients of orders （-2, 1, 2） which are larger than those of the order （-1） resonance increase with increasing peak, hence the total diffusion coefficients increase with increasing peak. The current results show that the wave normal angle plays an important role in the quantitative analysis of gyroresonance between chorus waves and electrons in the outer radiation belt.展开更多
This paper proposes a method of simultaneous determination of the four layer parameters （mass density, longitudinal velocity, the thickness and attenuation） of an immersed linear-viscoelastic thin layer by using the...This paper proposes a method of simultaneous determination of the four layer parameters （mass density, longitudinal velocity, the thickness and attenuation） of an immersed linear-viscoelastic thin layer by using the normally-incident reflected and transmitted ultrasonic waves. The analytical formula of the layer thickness related to the measured trans- mitted transfer functions is derived. The two determination steps of the four layer parameters are developed, in which acoustic impedance, time-of-flight and attenuation are first determined by the reflected transfer functions. Using the derived formula, it successively calculates and determines the layer thickness, longitudinal velocity and mass density by the measured transmitted transfer functions. According to the two determination steps, a more feasible and simplified measurement setups is described. It is found that only three signals （the reference waves, the reflected and transmitted waves） need to be recorded in the whole measurement for the determination of the four layer parameters. A study of the stability of the determination method against the experimental noises and the error analysis of the four layer parameters are made. This study lays the theoretical foundation of the practical measurement of a linear-viscoelastic thin layer.展开更多
We present an efficient three-dimensional coupled-mode model based on the Fourier synthesis technique. In principle, this model is a one-way model, and hence provides satisfactory accuracy for problems where the forwa...We present an efficient three-dimensional coupled-mode model based on the Fourier synthesis technique. In principle, this model is a one-way model, and hence provides satisfactory accuracy for problems where the forward scattering dominates. At the same time, this model provides an efficiency gain of an order of magnitude or more over two-way coupled-mode models. This model can be applied to three-dimensional range-dependent problems with a slowly varying bathymetry or internal waves. A numerical example of the latter is demonstrated in this work. Comparisons of both accuracy and efficiency between the present model and a benchmark model are also provided.展开更多
The aim of this paper is to present an analytical expression for the streamwise velocity distribution in a non-uniform flow in the presence of waves; the correlation between the horizontal and vertical velocity compon...The aim of this paper is to present an analytical expression for the streamwise velocity distribution in a non-uniform flow in the presence of waves; the correlation between the horizontal and vertical velocity components has been compreheusively examined. Different from previous researches which attributed the deviation of velocity from the classical log-law to the wave Reynolds stress, i.e. - ρ uv^- only, this study demonstrates that the momentum flux caused by mean velocities, i.e., u^- and v^-, is also responsible for the velocity deviation, and it is found that the streamwise velocity for a flow in the presence of non-zero wall-normal velocity does not follow the classical log-law, but the modified log-law proposed in this study based on simplified mixing-length theorem. The validity of the modified log-law has been verified by use of available experimental data from published sources for combined wave-current flows, and good agreement between the predicted and observed velocity profiles has been achieved.展开更多
Selection of proper reference genes (RGs) is an essential step needed for accurate normalization of results from genomic studies. Expression of RGs is regulated by many factors such as species, age, gender, type of ti...Selection of proper reference genes (RGs) is an essential step needed for accurate normalization of results from genomic studies. Expression of RGs is regulated by many factors such as species, age, gender, type of tissue, the presence of disease, and the administration of therapeutic treatment. The aim of the present study was to identify optimal RGs in a set of blood samples collected at different time points (0, 24, 48, 72 h) from horses following administration of extracorporeal shock wave therapy (ESWT). The mRNA expression of twelve RGs: HPRT1, ACTB, HSP90A, SDHA, GUSB, B2M, UBC, NONO, TBP, H6PD, RPL32, GAPDH was determined using real time quantitative polymerase chain reaction (qPCR). An SAS program developed on the algorithm of geNorm, SASqPCR, was used to determine stability of the expression and the number of optimal RGs. The results showed that the range of quantification cycle (Cq) values of the evaluated genes varied between 17 and 26 cycles, and that one optimal RG, ACTB, was sufficient for normalization of gene expression. Results of stability of expression demonstrated that ACTB was the optimal choice for all the samples studied. Notably, in samples collected at 72 h post ESWT, TBP showed a significant change in the expression level, and was not suitable for use as a RG. These results substantiate the importance of validating and selecting an appropriate RG.展开更多
In this paper, the improved version of the meshless singular boundary method (ISBM) is developed for analyzing the hydrodynamic performance of bottom-standing submerged breakwaters in regular normally incident waves. ...In this paper, the improved version of the meshless singular boundary method (ISBM) is developed for analyzing the hydrodynamic performance of bottom-standing submerged breakwaters in regular normally incident waves. Both the single and dual prismatic breakwaters of rectangular and trapezoidal forms are examined. Only the impermeable breakwaters are considered in this study. The physical problem is cast in terms of the Laplace equation governing an irrotational flow and incompressible fluid motion with the appropriate mixed-type boundary conditions, and it is solved numerically using the ISBM. The numerical results are presented in terms of the hydrodynamic quantities of reflection and transmission coefficients. The values are first validated against the data of previous studies, computed, and discussed for a variety of structural conditions, including the height, width, and spacing of breakwater submergence. An excellent agreement is observed between the ISBM results and those of other methods. The breakwater width is found to feature marginal effects compared with the height. The present method is shown to accurately predict the resonant conditions at which the maximum reflection and transmission occur. The trapezoidal breakwaters are found to generally present a wide spectrum of reflections, suggesting that they would function better than the rectangular breakwaters. The dual breakwater systems are confirmed to perform much better than single structures.展开更多
A simplified finite element model of a human thorax had been developed for probing into the mechani- cal response in simple and complex blast environments. The human thorax model was first created by CT images with bl...A simplified finite element model of a human thorax had been developed for probing into the mechani- cal response in simple and complex blast environments. The human thorax model was first created by CT images with blast loading applied via a coupled arbitrary Lagrangian- Eulerian method, allowing for a variety of loads to be considered. The goal is to analyze the maximum stress distri- butions of lung tissue and peak inward thorax wall velocity and to know the possible regions and levels of lung injury. In parallel, a mathematical model has been modified from the Lobdell model to investigate the detailed percentage of lung injury at each level. The blast loadings around the human tho- rax were obtained from the finite element model, and were then applied in the mathematical model as the boundary con- ditions to predict the normalized work of the human thorax lung. The present results are found in agreement with the modified Bowen curves and the results predicted by Axels- son＇s model.展开更多
For acoustic detection of internal waves, the core issue is to obtain the temporal and spatial distribution of the sound speed profile(SSP). In the inversion process, the SSP is usually expressed by a few parameters t...For acoustic detection of internal waves, the core issue is to obtain the temporal and spatial distribution of the sound speed profile(SSP). In the inversion process, the SSP is usually expressed by a few parameters through expansion. However, information about internal waves may sometimes be hard to read directly from the inversion results. The aim of this paper is to characterize the internal waves directly though expansion coefficients. By deducing the dynamic equations of the internal waves, an orthogonal basis called the hydrodynamic normal modes(HNMs) can be extracted from a certain number of SSP samples. Unlike the existing widely used empirical orthogonal functions(EOFs), the HNMs have a more explicit physical meaning that is directly related to internal wave activity. The HNMs are then used to expand the SSP time series, and the expansion coefficients are derived.Eventually, information about internal waves can be read directly from the time derivative of the expansion coefficients of the first two modes. In this study, this method is applied to thermistor string profiles from the northern shelf of the South China Sea, where the SSP shows evident spatial and temporal variations due to internal waves. The results show that the SSP can be described approximately by the first two modes with adequate precision. The special oscillation structure of the time derivative of the expansion coefficients can be used to detect internal solitary waves. The expansion coefficients can also give information on internal solitary wave amplitude and width. According to theoretical and experimental analysis, it can be concluded that the internal waves monitoring method introduced in this paper is effective. The HNMs method is simple to apply and depends less on sample data than EOFs. It could be used as an efficient alternative to EOFs to expand the use of the SSP in highly variable areas, where internal waves are intensive.展开更多
This paper presents a mathematical model of linear acoustic wave propagation in fluids. The benefits of a mathematical model over a normal mode analysis are first discussed, then the mathematical model for acoustic pr...This paper presents a mathematical model of linear acoustic wave propagation in fluids. The benefits of a mathematical model over a normal mode analysis are first discussed, then the mathematical model for acoustic propagation in the test medium is developed using computer simulations. The approach is based on a analytical solution to the homogeneous wave equation for fluid medium. A good agreement between the computational presented results with published data.展开更多
Methods of finding quasi-normal modes of non-rotating relativistic stars have been well established, however, none of the existing treatments which take spacetime and fluid oscillations fully into account can determin...Methods of finding quasi-normal modes of non-rotating relativistic stars have been well established, however, none of the existing treatments which take spacetime and fluid oscillations fully into account can determine modes of long decay time, e.g., the p and g mode series, or the f modes for stars with low compactness ratio （M/R）. In this paper we show how the quasi-normal modes of long lifetime can be determined through refinements of a treatment originally due to Detweiler and Lindblom. The determination of the p mode series has been argued in the literature to have implication on the life time of gravitational wave sources and stellar stability. In this paper we 1） provide detailed steps in our treatment to facilitate future effort in this direction; 2） correct mistakes in the literature on the formulation; and 3） analyse the accuracy of the quasi-normal mode frequencies obtained and the limitations of the treatment.展开更多
The submarine pipelines that are buried in the Yellow River subaqueous delta can be subject to fluctuant local-liquefied soil caused by storm wave action, possibly causing pipeline damage. An experimental investigatio...The submarine pipelines that are buried in the Yellow River subaqueous delta can be subject to fluctuant local-liquefied soil caused by storm wave action, possibly causing pipeline damage. An experimental investigation was carried out in a wave flume to study the horizontal normal force on buried rigid pipelines in fluctuant liquefied soil. In this experiment, the soil bed was made of silt from the Yellow River Delta, whereas a steel pipe served as pipeline. Under the experimental conditions, the normal force range on the pipeline in fluctuant liquefied soil was several times higher than that in stable soil, specifically on the side of the pipeline exposed to the wave direction. The resultant force of the horizontal normal forces on the buried pipeline grew by about one order of magnitude after soil liquefaction.展开更多
Normal-mode summation is the most rapidly used method in calculating synthetic seismograms. How- ever, normal-mode summation is mostly applied to point sources. For earthquakes triggered by faults extending for as lon...Normal-mode summation is the most rapidly used method in calculating synthetic seismograms. How- ever, normal-mode summation is mostly applied to point sources. For earthquakes triggered by faults extending for as long as several 100 km, the seismic waves are usually simulated by point source summation. In this paper, we attempt to follow a different route, i.e., directly calculate the excitation of each mode, and use normal-mode sum- mation to obtain the seismogram. Furthermore, we assume the finite source to be a ＂line source＂ and numerically calculate the transverse component of synthetic seismo- grams for vertical strike-slip faults. Finally, we analyze the features in the Love waves excited by finite faults.展开更多
In this paper, we look for solutions to the following Schrödinger-Bopp-Podolsky system with prescribed L<sup>2</sup>-norm constraint , where q ≠ 0, a, ρ> 0 are constants. At firs...In this paper, we look for solutions to the following Schrödinger-Bopp-Podolsky system with prescribed L<sup>2</sup>-norm constraint , where q ≠ 0, a, ρ> 0 are constants. At first, by the classical minimizing argument, we obtain a ground state solution to the above problem for sufficiently small ρwhen . Secondly, in the case p = 6, we show the nonexistence of positive solutions by using a Liouville-type result. Finally, we argue by contradiction to investigate the orbital stability of standing waves for .展开更多
The purpose of this paper is to consider 1D Riemann shock tube to investigate the formation and propagation of compression waves leading to formation, propagation and reflection of 1D normal shocks using simplified ma...The purpose of this paper is to consider 1D Riemann shock tube to investigate the formation and propagation of compression waves leading to formation, propagation and reflection of 1D normal shocks using simplified mathematical models commonly used in the published work as well as using complete mathematical models based on Conservation and Balance Laws (CBL) of classical continuum mechanics and constitutive theories for compressible viscous medium derived using entropy inequality and representation theorem. This work is aimed at resolving compression waves, the shock structure, shock formation, propagation and reflection of fully formed shocks. Evolutions obtained from the mathematical models always satisfy differentiability requirements in space and time dictated by the highest order of the derivatives of the dependent variables in the mathematical models investigated. All solutions reported in this paper including boundary conditions and initial conditions are always analytic. Solutions of the mathematical models are obtained using the space-time finite element method in which the space-time integral forms are space-time variationally consistent ensuring unconditionally stable computations during the entire evolution. Solution for a space-time strip or slab is calculated and is time marched upon convergence to obtain complete evolution for the desired space-time domain, thus ensuring time accurate evolutions. The space-time local approximation over a space-time element of a space-time strip or slab is p-version hierarchical with higher-order global differentiability in space and time, i.e., we consider scalar product approximation spaces in which k = (k<sub>1</sub>, k<sub>2</sub>) are the order of the space in space and time and p = (p<sub>1</sub>, p<sub>2</sub>) are p-levels of the approximations in space and time. Model problem studies are presented for different mathematical models and are compared with solutions obtained from the complete mathematical model based on CBL and constitutive theories for viscous compressible medium to illustrate the deficiencies and shortcomings of the simplified and approximate models in simulating correct physics of normal shocks.展开更多
Pseudowaves, known as burst-ion signals, which are different from plasma normal modes, exist frequently in ion- wave excitation experiments when launching the waves by applying a pulsed voltage to a negatively biased ...Pseudowaves, known as burst-ion signals, which are different from plasma normal modes, exist frequently in ion- wave excitation experiments when launching the waves by applying a pulsed voltage to a negatively biased grid. In previous experiments, only one kind of the pseudowave was observed. In this paper, we report the observation and identification of double pseudowaves in an ion-beam-plasma system. These pseudowaves originate from two ion groups： the burst of the beam ions and the burst of the background ions. It was observed that the burst of the background ions was in the case of high ion beam energy, while the burst of the beam ions was in the case of low ion beam energy. By observing the dependence of the signal velocities on the characteristics of the excitation voltage, these pseudowaves can be identified. It was also observed that the burst ion signal originating from the background ions can interact with slow beam mode and that originating from the beam ions can interact with fast beam mode.展开更多
Einstein guessed that the macroscopic electromagnetic wave is built by thousands of photons, however, no one has offered a theory about how the macroscopic electromagnetic wave is built from photons. A concrete theory...Einstein guessed that the macroscopic electromagnetic wave is built by thousands of photons, however, no one has offered a theory about how the macroscopic electromagnetic wave is built from photons. A concrete theory about photons is needed to answer this question. Current theory for photons is Maxwell’s equation which has the solution of waves, but it is difficult to describe the photon as a particle. There is the paradox problem of wave-particle duality. This article offers one solution to solve this problem by introducing the normalized mutual energy flow. The interaction of the retarded wave and advanced wave produce the mutual energy flow. The mutual energy flow satisfies the mutual energy flow theorem. The mutual energy flow theorem tells us that the energy that goes through each surface between the emitter and the absorber is all same. That means the mutual energy flow is different in comparison to the waves. The wave, for example, the retarded wave, its amplitude is decreased with the distance from the source to the point of the field. The mutual energy flow does not decrease. The author noticed this and claimed that the photon is the mutual energy flow. In this article the author updated this claim that the photon is the normalized mutual energy flow. Here the normalization of mutual energy flow will normalize the mutual energy flow to the energy of a photon, which is E = hf. E is the energy of the photon;h is Planck constant;f is the frequency of the light. This normalization is similar to the normalization in quantum mechanics. After this normalization the relation between an electromagnetic wave and photon as a particle becomes clear. This article will prove that the macroscopic wave of an electromagnetic field can be built by thousands of normalized mutual energy flows, which describes the photons. The mutual energy flow is an interaction of the retarded wave and the advanced wave. The retarded wave and the advanced wave satisfy the Maxwell equations. There are two additional waves which are the time-reversal waves which satisfy time-reversal Maxwell equations. The advanced wave and the two time-reversal waves are all real and physical electromagnetic fields. The time-reversal waves cancel all self-energy flows of the retarded wave and advanced wave. Hence, the waves do not carry any energy, the energy is only transferred by the normalized mutual energy flows which are the photons. Hence, all energy is transferred by the photon instead of waves. This offers a solution to paradox of the duality of wave-particle.展开更多
文摘In this paper, using a Gaussian distribution of wave normal angle X=tan0, and considering contributions of harmonic resonances n up to ＋5, we analyze the effect of normal angle on diffusion coefficients induced by gyroresonance between chorus waves and electrons with energies 0.1 and 1.0 MeV on the dayside and nightside at L=4.5. When pitch angle a~〉10~, for 0.1 and 1,0 MeV electrons on the dayside and nightside, diffusion coefficients of five orders （-2, -1, 0, 1, 2） decrease with in- creasing normal angle peak, leading to the total diffusion coefficients decreasing with increasing peak. When ae〈10~, for 1.0 MeV electrons on the dayside and 0.1 MeV electrons on the dayside and nightside, the positive order diffusion coefficients are generally smaller than the same negative order ones; in the meanwhile, diffusion coefficients of orders （-2, 1, 2） are very small, the dominant order n=-I diffusion coefficients change very little, hence the total diffusion coefficients almost remain un- changed. However, for 1.0 MeV electrons on the nightside, diffusion coefficients of orders （-2, 1, 2） which are larger than those of the order （-1） resonance increase with increasing peak, hence the total diffusion coefficients increase with increasing peak. The current results show that the wave normal angle plays an important role in the quantitative analysis of gyroresonance between chorus waves and electrons in the outer radiation belt.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10534040 and 40674059)the State Key Laboratory of Acoustics (IACAS) (Grant No. 200807)
文摘This paper proposes a method of simultaneous determination of the four layer parameters （mass density, longitudinal velocity, the thickness and attenuation） of an immersed linear-viscoelastic thin layer by using the normally-incident reflected and transmitted ultrasonic waves. The analytical formula of the layer thickness related to the measured trans- mitted transfer functions is derived. The two determination steps of the four layer parameters are developed, in which acoustic impedance, time-of-flight and attenuation are first determined by the reflected transfer functions. Using the derived formula, it successively calculates and determines the layer thickness, longitudinal velocity and mass density by the measured transmitted transfer functions. According to the two determination steps, a more feasible and simplified measurement setups is described. It is found that only three signals （the reference waves, the reflected and transmitted waves） need to be recorded in the whole measurement for the determination of the four layer parameters. A study of the stability of the determination method against the experimental noises and the error analysis of the four layer parameters are made. This study lays the theoretical foundation of the practical measurement of a linear-viscoelastic thin layer.
基金Supported by the National Natural Science Foundation of China under Grant No 11774374the Natural Science Foundation of Shandong Province of China under Grant No ZR2016AL10
文摘We present an efficient three-dimensional coupled-mode model based on the Fourier synthesis technique. In principle, this model is a one-way model, and hence provides satisfactory accuracy for problems where the forward scattering dominates. At the same time, this model provides an efficiency gain of an order of magnitude or more over two-way coupled-mode models. This model can be applied to three-dimensional range-dependent problems with a slowly varying bathymetry or internal waves. A numerical example of the latter is demonstrated in this work. Comparisons of both accuracy and efficiency between the present model and a benchmark model are also provided.
文摘The aim of this paper is to present an analytical expression for the streamwise velocity distribution in a non-uniform flow in the presence of waves; the correlation between the horizontal and vertical velocity components has been compreheusively examined. Different from previous researches which attributed the deviation of velocity from the classical log-law to the wave Reynolds stress, i.e. - ρ uv^- only, this study demonstrates that the momentum flux caused by mean velocities, i.e., u^- and v^-, is also responsible for the velocity deviation, and it is found that the streamwise velocity for a flow in the presence of non-zero wall-normal velocity does not follow the classical log-law, but the modified log-law proposed in this study based on simplified mixing-length theorem. The validity of the modified log-law has been verified by use of available experimental data from published sources for combined wave-current flows, and good agreement between the predicted and observed velocity profiles has been achieved.
文摘Selection of proper reference genes (RGs) is an essential step needed for accurate normalization of results from genomic studies. Expression of RGs is regulated by many factors such as species, age, gender, type of tissue, the presence of disease, and the administration of therapeutic treatment. The aim of the present study was to identify optimal RGs in a set of blood samples collected at different time points (0, 24, 48, 72 h) from horses following administration of extracorporeal shock wave therapy (ESWT). The mRNA expression of twelve RGs: HPRT1, ACTB, HSP90A, SDHA, GUSB, B2M, UBC, NONO, TBP, H6PD, RPL32, GAPDH was determined using real time quantitative polymerase chain reaction (qPCR). An SAS program developed on the algorithm of geNorm, SASqPCR, was used to determine stability of the expression and the number of optimal RGs. The results showed that the range of quantification cycle (Cq) values of the evaluated genes varied between 17 and 26 cycles, and that one optimal RG, ACTB, was sufficient for normalization of gene expression. Results of stability of expression demonstrated that ACTB was the optimal choice for all the samples studied. Notably, in samples collected at 72 h post ESWT, TBP showed a significant change in the expression level, and was not suitable for use as a RG. These results substantiate the importance of validating and selecting an appropriate RG.
基金supported by the Direction Général des Enseignements et de la Formation Supérieure of Algeria under Grant CNEPRU number G0301920140029
文摘In this paper, the improved version of the meshless singular boundary method (ISBM) is developed for analyzing the hydrodynamic performance of bottom-standing submerged breakwaters in regular normally incident waves. Both the single and dual prismatic breakwaters of rectangular and trapezoidal forms are examined. Only the impermeable breakwaters are considered in this study. The physical problem is cast in terms of the Laplace equation governing an irrotational flow and incompressible fluid motion with the appropriate mixed-type boundary conditions, and it is solved numerically using the ISBM. The numerical results are presented in terms of the hydrodynamic quantities of reflection and transmission coefficients. The values are first validated against the data of previous studies, computed, and discussed for a variety of structural conditions, including the height, width, and spacing of breakwater submergence. An excellent agreement is observed between the ISBM results and those of other methods. The breakwater width is found to feature marginal effects compared with the height. The present method is shown to accurately predict the resonant conditions at which the maximum reflection and transmission occur. The trapezoidal breakwaters are found to generally present a wide spectrum of reflections, suggesting that they would function better than the rectangular breakwaters. The dual breakwater systems are confirmed to perform much better than single structures.
文摘A simplified finite element model of a human thorax had been developed for probing into the mechani- cal response in simple and complex blast environments. The human thorax model was first created by CT images with blast loading applied via a coupled arbitrary Lagrangian- Eulerian method, allowing for a variety of loads to be considered. The goal is to analyze the maximum stress distri- butions of lung tissue and peak inward thorax wall velocity and to know the possible regions and levels of lung injury. In parallel, a mathematical model has been modified from the Lobdell model to investigate the detailed percentage of lung injury at each level. The blast loadings around the human tho- rax were obtained from the finite element model, and were then applied in the mathematical model as the boundary con- ditions to predict the normalized work of the human thorax lung. The present results are found in agreement with the modified Bowen curves and the results predicted by Axels- son＇s model.
基金The National Natural Science Foundation of China under contract No.41406041the Natural Science Foundation of Guangdong Province under contract No.2014A030310256+1 种基金the Project of Enhancing School with Innovation of Guangdong Ocean University under contract No.GDOU2016050246the Excellent Young Teachers Program of GDOU under contract No.HDYQ2015010
文摘For acoustic detection of internal waves, the core issue is to obtain the temporal and spatial distribution of the sound speed profile(SSP). In the inversion process, the SSP is usually expressed by a few parameters through expansion. However, information about internal waves may sometimes be hard to read directly from the inversion results. The aim of this paper is to characterize the internal waves directly though expansion coefficients. By deducing the dynamic equations of the internal waves, an orthogonal basis called the hydrodynamic normal modes(HNMs) can be extracted from a certain number of SSP samples. Unlike the existing widely used empirical orthogonal functions(EOFs), the HNMs have a more explicit physical meaning that is directly related to internal wave activity. The HNMs are then used to expand the SSP time series, and the expansion coefficients are derived.Eventually, information about internal waves can be read directly from the time derivative of the expansion coefficients of the first two modes. In this study, this method is applied to thermistor string profiles from the northern shelf of the South China Sea, where the SSP shows evident spatial and temporal variations due to internal waves. The results show that the SSP can be described approximately by the first two modes with adequate precision. The special oscillation structure of the time derivative of the expansion coefficients can be used to detect internal solitary waves. The expansion coefficients can also give information on internal solitary wave amplitude and width. According to theoretical and experimental analysis, it can be concluded that the internal waves monitoring method introduced in this paper is effective. The HNMs method is simple to apply and depends less on sample data than EOFs. It could be used as an efficient alternative to EOFs to expand the use of the SSP in highly variable areas, where internal waves are intensive.
文摘This paper presents a mathematical model of linear acoustic wave propagation in fluids. The benefits of a mathematical model over a normal mode analysis are first discussed, then the mathematical model for acoustic propagation in the test medium is developed using computer simulations. The approach is based on a analytical solution to the homogeneous wave equation for fluid medium. A good agreement between the computational presented results with published data.
基金supported by the Science Foundation of the Education Department of Hunan Province of China (Grant No. 07c578)in part by the US National Science Foundation NRACthe McDonnell Center for the Space Sciences of the Washington University(Grant No. MCA93S025)
文摘Methods of finding quasi-normal modes of non-rotating relativistic stars have been well established, however, none of the existing treatments which take spacetime and fluid oscillations fully into account can determine modes of long decay time, e.g., the p and g mode series, or the f modes for stars with low compactness ratio （M/R）. In this paper we show how the quasi-normal modes of long lifetime can be determined through refinements of a treatment originally due to Detweiler and Lindblom. The determination of the p mode series has been argued in the literature to have implication on the life time of gravitational wave sources and stellar stability. In this paper we 1） provide detailed steps in our treatment to facilitate future effort in this direction; 2） correct mistakes in the literature on the formulation; and 3） analyse the accuracy of the quasi-normal mode frequencies obtained and the limitations of the treatment.
基金funded by the National Natural Science Foundation of China (No. 41576039)
文摘The submarine pipelines that are buried in the Yellow River subaqueous delta can be subject to fluctuant local-liquefied soil caused by storm wave action, possibly causing pipeline damage. An experimental investigation was carried out in a wave flume to study the horizontal normal force on buried rigid pipelines in fluctuant liquefied soil. In this experiment, the soil bed was made of silt from the Yellow River Delta, whereas a steel pipe served as pipeline. Under the experimental conditions, the normal force range on the pipeline in fluctuant liquefied soil was several times higher than that in stable soil, specifically on the side of the pipeline exposed to the wave direction. The resultant force of the horizontal normal forces on the buried pipeline grew by about one order of magnitude after soil liquefaction.
基金supported by the National Natural Science Foundation of China (Grant No. 41674050)MOST grant (2012CB417301)
文摘Normal-mode summation is the most rapidly used method in calculating synthetic seismograms. How- ever, normal-mode summation is mostly applied to point sources. For earthquakes triggered by faults extending for as long as several 100 km, the seismic waves are usually simulated by point source summation. In this paper, we attempt to follow a different route, i.e., directly calculate the excitation of each mode, and use normal-mode sum- mation to obtain the seismogram. Furthermore, we assume the finite source to be a ＂line source＂ and numerically calculate the transverse component of synthetic seismo- grams for vertical strike-slip faults. Finally, we analyze the features in the Love waves excited by finite faults.
文摘In this paper, we look for solutions to the following Schrödinger-Bopp-Podolsky system with prescribed L<sup>2</sup>-norm constraint , where q ≠ 0, a, ρ> 0 are constants. At first, by the classical minimizing argument, we obtain a ground state solution to the above problem for sufficiently small ρwhen . Secondly, in the case p = 6, we show the nonexistence of positive solutions by using a Liouville-type result. Finally, we argue by contradiction to investigate the orbital stability of standing waves for .
文摘The purpose of this paper is to consider 1D Riemann shock tube to investigate the formation and propagation of compression waves leading to formation, propagation and reflection of 1D normal shocks using simplified mathematical models commonly used in the published work as well as using complete mathematical models based on Conservation and Balance Laws (CBL) of classical continuum mechanics and constitutive theories for compressible viscous medium derived using entropy inequality and representation theorem. This work is aimed at resolving compression waves, the shock structure, shock formation, propagation and reflection of fully formed shocks. Evolutions obtained from the mathematical models always satisfy differentiability requirements in space and time dictated by the highest order of the derivatives of the dependent variables in the mathematical models investigated. All solutions reported in this paper including boundary conditions and initial conditions are always analytic. Solutions of the mathematical models are obtained using the space-time finite element method in which the space-time integral forms are space-time variationally consistent ensuring unconditionally stable computations during the entire evolution. Solution for a space-time strip or slab is calculated and is time marched upon convergence to obtain complete evolution for the desired space-time domain, thus ensuring time accurate evolutions. The space-time local approximation over a space-time element of a space-time strip or slab is p-version hierarchical with higher-order global differentiability in space and time, i.e., we consider scalar product approximation spaces in which k = (k<sub>1</sub>, k<sub>2</sub>) are the order of the space in space and time and p = (p<sub>1</sub>, p<sub>2</sub>) are p-levels of the approximations in space and time. Model problem studies are presented for different mathematical models and are compared with solutions obtained from the complete mathematical model based on CBL and constitutive theories for viscous compressible medium to illustrate the deficiencies and shortcomings of the simplified and approximate models in simulating correct physics of normal shocks.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11575183 and 11705201)
文摘Pseudowaves, known as burst-ion signals, which are different from plasma normal modes, exist frequently in ion- wave excitation experiments when launching the waves by applying a pulsed voltage to a negatively biased grid. In previous experiments, only one kind of the pseudowave was observed. In this paper, we report the observation and identification of double pseudowaves in an ion-beam-plasma system. These pseudowaves originate from two ion groups： the burst of the beam ions and the burst of the background ions. It was observed that the burst of the background ions was in the case of high ion beam energy, while the burst of the beam ions was in the case of low ion beam energy. By observing the dependence of the signal velocities on the characteristics of the excitation voltage, these pseudowaves can be identified. It was also observed that the burst ion signal originating from the background ions can interact with slow beam mode and that originating from the beam ions can interact with fast beam mode.
文摘Einstein guessed that the macroscopic electromagnetic wave is built by thousands of photons, however, no one has offered a theory about how the macroscopic electromagnetic wave is built from photons. A concrete theory about photons is needed to answer this question. Current theory for photons is Maxwell’s equation which has the solution of waves, but it is difficult to describe the photon as a particle. There is the paradox problem of wave-particle duality. This article offers one solution to solve this problem by introducing the normalized mutual energy flow. The interaction of the retarded wave and advanced wave produce the mutual energy flow. The mutual energy flow satisfies the mutual energy flow theorem. The mutual energy flow theorem tells us that the energy that goes through each surface between the emitter and the absorber is all same. That means the mutual energy flow is different in comparison to the waves. The wave, for example, the retarded wave, its amplitude is decreased with the distance from the source to the point of the field. The mutual energy flow does not decrease. The author noticed this and claimed that the photon is the mutual energy flow. In this article the author updated this claim that the photon is the normalized mutual energy flow. Here the normalization of mutual energy flow will normalize the mutual energy flow to the energy of a photon, which is E = hf. E is the energy of the photon;h is Planck constant;f is the frequency of the light. This normalization is similar to the normalization in quantum mechanics. After this normalization the relation between an electromagnetic wave and photon as a particle becomes clear. This article will prove that the macroscopic wave of an electromagnetic field can be built by thousands of normalized mutual energy flows, which describes the photons. The mutual energy flow is an interaction of the retarded wave and the advanced wave. The retarded wave and the advanced wave satisfy the Maxwell equations. There are two additional waves which are the time-reversal waves which satisfy time-reversal Maxwell equations. The advanced wave and the two time-reversal waves are all real and physical electromagnetic fields. The time-reversal waves cancel all self-energy flows of the retarded wave and advanced wave. Hence, the waves do not carry any energy, the energy is only transferred by the normalized mutual energy flows which are the photons. Hence, all energy is transferred by the photon instead of waves. This offers a solution to paradox of the duality of wave-particle.
