A dynamic solution is presented for the propagation of waves in an electric-magneto-elastic plate composed of piezoelectric, piezomagnetic materials and elastic matrix. The electric-magneto-elastic plate is polarized ...A dynamic solution is presented for the propagation of waves in an electric-magneto-elastic plate composed of piezoelectric, piezomagnetic materials and elastic matrix. The electric-magneto-elastic plate is polarized along the thickness direction. The generalized displacements are expressed as the sum of the gradient of a scalar (dilatation wave) and the curl of a vector (shear wave). With the help of dynamic equilibrium equations and geometric equations, we can obtain dynamic equations of the dilatation wave and the shear wave. The conclusion that the types of the dilatation waves and the shear waves remain unchanged after being reflected by the boundary can be obtained through the analysis of these kinetic equations. The dispersion properties and phase velocity surface of the dilatation and shear wave can be obtained by solutions of dynamic equilibrium equations. Influences of the piezoelectric and piezomagnetic parameters on wave characteristics are discussed.展开更多
Based on cavity resonance and sandwich composite plate （3D） theoretical model for frequency dispersion characterization theory, this paper presents a universal three-dimensional and displacement profile shapes of th...Based on cavity resonance and sandwich composite plate （3D） theoretical model for frequency dispersion characterization theory, this paper presents a universal three-dimensional and displacement profile shapes of the film bulk acoustic resonator （FBARs）. This model provides results of FBAR excited thickness-extensional and flexure modes, and the result of frequency dispersion is proposed in which the thicknesses and impedance of the electrodes and the piezoelectric material are taken into consideration; its further simplification shows good agreement with the modified Butterworth-Van-Dyke （MBVD） model. The displacement profile reflects the vibration stress distribution of electrode shapes and the lateral resonance effect, which depends on the axis ratio of the electrode shapes a/b. The results are consistent with the 3D finite element method modeling and laser interferometry measurement in general.展开更多
Air–sea exchange plays a vital role in the development and maintenance of tropical cyclones（TCs）. Although studies have suggested the dependence of air–sea fluxes on surface waves and sea spray, how these processe...Air–sea exchange plays a vital role in the development and maintenance of tropical cyclones（TCs）. Although studies have suggested the dependence of air–sea fluxes on surface waves and sea spray, how these processes modify those fluxes under TC conditions have not been sufficiently investigated based on in-situ observations.Using continuous meteorological and surface wave data from a moored buoy in the northern South China Sea,this study examines the effects of surface waves and sea spray on air–sea fluxes during the passage of Typhoon Hagupit. The mooring was within about 40 km of the center of Hagupit. Surface waves could increase momentum flux to the ocean by about 15%, and sea spray enhanced both sensible and latent heat fluxes to the atmosphere,causing Hagupit to absorb 500 W/m^2 more heat flux from the ocean. These results have powerful implications for understanding TC–ocean interaction and improving TC intensity forecasting.展开更多
High speed impact experiments of rectangular plate-shaped Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 bulk metallic glass（BMG） were performed using a two-stage light gas gun.Under spherical shock waves with impact velocities ...High speed impact experiments of rectangular plate-shaped Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 bulk metallic glass（BMG） were performed using a two-stage light gas gun.Under spherical shock waves with impact velocities ranging from 0.503 km/s to 4.917 km/s,obvious traces of laminated spallation at the back（free） surface and melting（liquid droplets） at the impact point were observed.The angles about 0掳,17掳,36掳,and 90掳to the shocking direction were shown in the internal samples because of the interaction between the compressive shock waves and the rarefaction waves.The compressive normal stress was found to induce the consequent temperature rise in the core of the shear band.展开更多
A first principles study of the electronic properties and bulk modulus （B0） of the fcc and bcc transition metals, transition metal carbides and nitrides is presented. The calculations were performed by plane-wave ps...A first principles study of the electronic properties and bulk modulus （B0） of the fcc and bcc transition metals, transition metal carbides and nitrides is presented. The calculations were performed by plane-wave pseudopotential method in the framework of the density functional theory with local density approximation. The density of states and the valence charge densities of these solids are plotted. The results show that B0 does not vary monotonically when the number of the valence d electrons increases. B0 reaches a maximum and then decreases for each of the four sorts of solids. It is related to the occupation of the bonding and anti-bonding states in the solid. The value of the valence charge density at the midpoint between the two nearest metal atoms tends to be proportional to B0.展开更多
Tunable and switchable Ba 0.5 Sr 0.5 TiO 3 film bulk acoustic resonators（FBARs） based on SiO 2 /Mo Bragg reflectors are explored,which can withstand high temperature for the deposition of Ba x Sr 1 x TiO 3（BST） fi...Tunable and switchable Ba 0.5 Sr 0.5 TiO 3 film bulk acoustic resonators（FBARs） based on SiO 2 /Mo Bragg reflectors are explored,which can withstand high temperature for the deposition of Ba x Sr 1 x TiO 3（BST） films at 800 C.The dc bias-dependent resonance may be attributed to the piezoelectricity of the BST film induced by an electrostrictive effect.The series resonant frequency is strongly dc bias-dependent and shifts downwards with dc bias increasing,while the parallel resonant frequency is only weakly dc bias-dependent and slightly shifts upwards at low dc bias（ 45 V） while downwards at higher dc bias.The calculated relative tunability of shifts at series resonance frequency is around 2.3% and the electromechanical coupling coefficient is up to approximately 8.09% at 60-V dc bias,which can be comparable to AlN FBARs.This suggests that a high-quality tunable BST FBAR device can be achieved through the use of molybdenum（Mo） as the high acoustic impedance layer in a Bragg reflector,which not only provides excellent acoustic isolation from the substrate,but also improves the crystallinity of BST films withstanding higher deposition temperature.展开更多
The formation bulk density is one of the most important rock properties required for reservoir evaluation and geomechanical analysis.In intervals where the formation bulk density logs are not acquired,the industry pra...The formation bulk density is one of the most important rock properties required for reservoir evaluation and geomechanical analysis.In intervals where the formation bulk density logs are not acquired,the industry practice is to estimate the formation bulk density from the compressional-wave velocity using empirical relationships.The major problems with the existing empirical relationships are:(1)they were developed primarily for specific lithologies(in most cases clean formations)and have failed to produce reasonable estimates when applied over a lithological column that consists of several stratigraphic units;(2)they are not applicable to rocks that contain microcracks/fractures.In this paper,a new formation bulk density prediction method that can be applied to a wide range of intact and fractured siliciclastic rocks is being proposed based on experimental data.The model is then validated using wireline log data acquired from an onshore well in the tertiary deltaic system of the Niger Delta basin.In the new model,the formation bulk density is expressed as a function of sonic velocity difference and shale volume factor.In general,an excellent agreement exists between the predicted and measured formation bulk density using the new technique.The statistical analysis shows that the new formation bulk density prediction model outperforms the most widely used empirical relationships with the least-root-mean square errors and least residual values.展开更多
The ultrasonic contact impedance technique and ultrasonic wave velocities have been widely used for non-destructive hardness measurement.Ultrasonic wave velocity shift provides through the thickness average hardness, ...The ultrasonic contact impedance technique and ultrasonic wave velocities have been widely used for non-destructive hardness measurement.Ultrasonic wave velocity shift provides through the thickness average hardness, however, the correlations are performed according to surface hardness. In order to accept this technique as a particular non-destructive method for determination of hardness, it is necessary to test it with industrial applications. A widely used joining(welding) technique is selected for this purpose. Samples of carbon steels with three different carbon contents, but similar composition, are annealed in order to obtain the softened samples with different hardness values. Rockwell B scale hardness of heat treated samples, which are assumed to be isotropic, are determined and correlated with ultrasonic wave velocity shifts. Effect of welding process on hardness is investigated using ultrasonic wave velocity shifts, and the results are verified with destructive hardness measurements.展开更多
Experiments on silt incipient motion under wave action were carried out. Under wave action, for different wave periods, water depths and bulk densities of silt, the shear stress or height of waves for incipient motion...Experiments on silt incipient motion under wave action were carried out. Under wave action, for different wave periods, water depths and bulk densities of silt, the shear stress or height of waves for incipient motion was determined, and a relation between the shear stress and bulk density of silt was established. Results indicate that the critical shear stress depends on the structure of the silt itself, related to the tightness between the grains （or bulk density）. Exterior condition is only an external cause of silt incipient motion, and the critical shear stress for the incipient motion is the token of exterior condition.展开更多
文摘A dynamic solution is presented for the propagation of waves in an electric-magneto-elastic plate composed of piezoelectric, piezomagnetic materials and elastic matrix. The electric-magneto-elastic plate is polarized along the thickness direction. The generalized displacements are expressed as the sum of the gradient of a scalar (dilatation wave) and the curl of a vector (shear wave). With the help of dynamic equilibrium equations and geometric equations, we can obtain dynamic equations of the dilatation wave and the shear wave. The conclusion that the types of the dilatation waves and the shear waves remain unchanged after being reflected by the boundary can be obtained through the analysis of these kinetic equations. The dispersion properties and phase velocity surface of the dilatation and shear wave can be obtained by solutions of dynamic equilibrium equations. Influences of the piezoelectric and piezomagnetic parameters on wave characteristics are discussed.
基金supported by the National Natural Science Foundation of China(Grant No.61275081)
文摘Based on cavity resonance and sandwich composite plate （3D） theoretical model for frequency dispersion characterization theory, this paper presents a universal three-dimensional and displacement profile shapes of the film bulk acoustic resonator （FBARs）. This model provides results of FBAR excited thickness-extensional and flexure modes, and the result of frequency dispersion is proposed in which the thicknesses and impedance of the electrodes and the piezoelectric material are taken into consideration; its further simplification shows good agreement with the modified Butterworth-Van-Dyke （MBVD） model. The displacement profile reflects the vibration stress distribution of electrode shapes and the lateral resonance effect, which depends on the axis ratio of the electrode shapes a/b. The results are consistent with the 3D finite element method modeling and laser interferometry measurement in general.
基金Zhejiang Provincial Natural Science Foundation of China under contract No.LR15D060001the National Program on Global Change and Air-Sea Interactions under contract No.GASI-IPOVAI-04the National Natural Science Foundation of China under contract Nos 41476021,41706034 and 41321004
文摘Air–sea exchange plays a vital role in the development and maintenance of tropical cyclones（TCs）. Although studies have suggested the dependence of air–sea fluxes on surface waves and sea spray, how these processes modify those fluxes under TC conditions have not been sufficiently investigated based on in-situ observations.Using continuous meteorological and surface wave data from a moored buoy in the northern South China Sea,this study examines the effects of surface waves and sea spray on air–sea fluxes during the passage of Typhoon Hagupit. The mooring was within about 40 km of the center of Hagupit. Surface waves could increase momentum flux to the ocean by about 15%, and sea spray enhanced both sensible and latent heat fluxes to the atmosphere,causing Hagupit to absorb 500 W/m^2 more heat flux from the ocean. These results have powerful implications for understanding TC–ocean interaction and improving TC intensity forecasting.
基金Project supported by the National Basic Research Program of China (Grant No. 2010CB731600)
文摘High speed impact experiments of rectangular plate-shaped Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 bulk metallic glass（BMG） were performed using a two-stage light gas gun.Under spherical shock waves with impact velocities ranging from 0.503 km/s to 4.917 km/s,obvious traces of laminated spallation at the back（free） surface and melting（liquid droplets） at the impact point were observed.The angles about 0掳,17掳,36掳,and 90掳to the shocking direction were shown in the internal samples because of the interaction between the compressive shock waves and the rarefaction waves.The compressive normal stress was found to induce the consequent temperature rise in the core of the shear band.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 50175082 and 10275049）, and the Fund for the Doctoral Program of Higher Education （Grant No 2002486016）.
文摘A first principles study of the electronic properties and bulk modulus （B0） of the fcc and bcc transition metals, transition metal carbides and nitrides is presented. The calculations were performed by plane-wave pseudopotential method in the framework of the density functional theory with local density approximation. The density of states and the valence charge densities of these solids are plotted. The results show that B0 does not vary monotonically when the number of the valence d electrons increases. B0 reaches a maximum and then decreases for each of the four sorts of solids. It is related to the occupation of the bonding and anti-bonding states in the solid. The value of the valence charge density at the midpoint between the two nearest metal atoms tends to be proportional to B0.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60871049 and 50972024)
文摘Tunable and switchable Ba 0.5 Sr 0.5 TiO 3 film bulk acoustic resonators（FBARs） based on SiO 2 /Mo Bragg reflectors are explored,which can withstand high temperature for the deposition of Ba x Sr 1 x TiO 3（BST） films at 800 C.The dc bias-dependent resonance may be attributed to the piezoelectricity of the BST film induced by an electrostrictive effect.The series resonant frequency is strongly dc bias-dependent and shifts downwards with dc bias increasing,while the parallel resonant frequency is only weakly dc bias-dependent and slightly shifts upwards at low dc bias（ 45 V） while downwards at higher dc bias.The calculated relative tunability of shifts at series resonance frequency is around 2.3% and the electromechanical coupling coefficient is up to approximately 8.09% at 60-V dc bias,which can be comparable to AlN FBARs.This suggests that a high-quality tunable BST FBAR device can be achieved through the use of molybdenum（Mo） as the high acoustic impedance layer in a Bragg reflector,which not only provides excellent acoustic isolation from the substrate,but also improves the crystallinity of BST films withstanding higher deposition temperature.
基金support provided by the Advanced Drilling Technology Laboratory Group, Memorial University of Newfoundland, Canada
文摘The formation bulk density is one of the most important rock properties required for reservoir evaluation and geomechanical analysis.In intervals where the formation bulk density logs are not acquired,the industry practice is to estimate the formation bulk density from the compressional-wave velocity using empirical relationships.The major problems with the existing empirical relationships are:(1)they were developed primarily for specific lithologies(in most cases clean formations)and have failed to produce reasonable estimates when applied over a lithological column that consists of several stratigraphic units;(2)they are not applicable to rocks that contain microcracks/fractures.In this paper,a new formation bulk density prediction method that can be applied to a wide range of intact and fractured siliciclastic rocks is being proposed based on experimental data.The model is then validated using wireline log data acquired from an onshore well in the tertiary deltaic system of the Niger Delta basin.In the new model,the formation bulk density is expressed as a function of sonic velocity difference and shale volume factor.In general,an excellent agreement exists between the predicted and measured formation bulk density using the new technique.The statistical analysis shows that the new formation bulk density prediction model outperforms the most widely used empirical relationships with the least-root-mean square errors and least residual values.
文摘The ultrasonic contact impedance technique and ultrasonic wave velocities have been widely used for non-destructive hardness measurement.Ultrasonic wave velocity shift provides through the thickness average hardness, however, the correlations are performed according to surface hardness. In order to accept this technique as a particular non-destructive method for determination of hardness, it is necessary to test it with industrial applications. A widely used joining(welding) technique is selected for this purpose. Samples of carbon steels with three different carbon contents, but similar composition, are annealed in order to obtain the softened samples with different hardness values. Rockwell B scale hardness of heat treated samples, which are assumed to be isotropic, are determined and correlated with ultrasonic wave velocity shifts. Effect of welding process on hardness is investigated using ultrasonic wave velocity shifts, and the results are verified with destructive hardness measurements.
基金This research was financially supported by the High Technology Research and Development Programof China(863 Program,Grant No.2002AA601011)
文摘Experiments on silt incipient motion under wave action were carried out. Under wave action, for different wave periods, water depths and bulk densities of silt, the shear stress or height of waves for incipient motion was determined, and a relation between the shear stress and bulk density of silt was established. Results indicate that the critical shear stress depends on the structure of the silt itself, related to the tightness between the grains （or bulk density）. Exterior condition is only an external cause of silt incipient motion, and the critical shear stress for the incipient motion is the token of exterior condition.
