Transmitted ultrasonic wave simulation （TUWS） in a digital core is one of the important elements of digital rock physics and is used to study wave propagation in porous cores and calculate equivalent velocity. When ...Transmitted ultrasonic wave simulation （TUWS） in a digital core is one of the important elements of digital rock physics and is used to study wave propagation in porous cores and calculate equivalent velocity. When simulating wave propagates in a 3D digital core, two additional layers are attached to its two surfaces vertical to the wave-direction and one planar wave source and two receiver-arrays are properly installed. After source excitation, the two receivers then record incident and transmitted waves of the digital rock. Wave propagating velocity, which is the velocity of the digital core, is computed by the picked peak-time difference between the two recorded waves. To evaluate the accuracy of TUWS, a digital core is fully saturated with gas, oil, and water to calculate the corresponding velocities. The velocities increase with decreasing wave frequencies in the simulation frequency band, and this is considered to be the result of scattering. When the pore fluids are varied from gas to oil and finally to water, the velocity-variation characteristics between the different frequencies are similar, thereby approximately following the variation law of velocities obtained from linear elastic statics simulation （LESS）, although their absolute values are different. However, LESS has been widely used. The results of this paper show that the transmission ultrasonic simulation has high relative precision.展开更多
The methods were studied to improve the cooling performance of the absorption refrigeration system(ARS) driven by low-grade solar energy with ultrasonic wave, while the mechanism of ultrasonic wave strengthening boili...The methods were studied to improve the cooling performance of the absorption refrigeration system(ARS) driven by low-grade solar energy with ultrasonic wave, while the mechanism of ultrasonic wave strengthening boiling mass transfer in LiB r solution was also analyzed with experiment. The experimental results indicate that, under the driving heat source of 60–100 oC and the ultrasonic power of 20–60 W, the mass flux of cryogen water in Li Br solution is higher after the application of ultrasonic wave than auxiliary heating with electric rod of the same power, so the ultrasonic application effectively enhances the heat utilization efficiency. The distance H from ultrasonic transducer to vapor/liquid interface significantly affects mass transfer enhancement, so an optimal Hopt corresponding to certain ultrasonic power is beneficial to reaching the best strengthening effect for ultrasonic mass transfer. When the ultrasonic power increases, the mass transfer obviously speeds up in the cryogen water; however, as the power increases to a certain extent, the flux reaches a plateau without obvious increment. Moreover, the ultrasound-enhanced mass transfer technology can reduce the minimum temperature of driving heat source required by ARS and promote the application of solar energy during absorption refrigeration.展开更多
Electropolymerization of pyrrole under ultrasonic field at 20kHz was performed in a series of aqueous and propylene carbonate (PC) solutions. The ultrasonic wave with moderate intensity at the power of 44W, which is t...Electropolymerization of pyrrole under ultrasonic field at 20kHz was performed in a series of aqueous and propylene carbonate (PC) solutions. The ultrasonic wave with moderate intensity at the power of 44W, which is the power threshold of the ultrasonic generator used in this work to produce cavitation effect, enhance the conductivity and tensile strength of the polypyrrole films as prepared. However, too high intensity of the ultrasonic wave is harmful to the polymerization.展开更多
This paper presents a novel non-contact method for evaluating the resonant frequency of a microstructure, Firstly, the microstructure under test is excited by ultrasonic waves. This excitation method does not impose a...This paper presents a novel non-contact method for evaluating the resonant frequency of a microstructure, Firstly, the microstructure under test is excited by ultrasonic waves. This excitation method does not impose any undefined load on the specimen like the electrostatic excitation and also this is the first actual use of ultrasonic wave for exciting a microstructure in the literature. Secondly, the amplitudes of the microstructure are determined by image edge detection using a Mexican hat wavelet transform on the vibrating images of the microstructure. The vibrating images are captured by a CCD camera when the microstructure is vibrated by ultrasonic waves at a series of discrete high frequencies （〉30 kHz）. Upon processing the vibrating images, the amplitudes at various excitation frequencies are obtained and an amplitude-frequency spectrum is obtained from which the resonant frequency is subsequently evaluated. A micro silicon structure consisting of a perforated plate （192 × 192 μm） and two cantilever beams （76 × 43 μm） which is about 4 μm thickness is tested. Since laser interferometry is not required, thermal effects on a test object can be avoided. Hence, the setup is relatively simple. Results show that the proposed method is a simple and effective approach for evaluating the dynamic characteristics of microstructures.展开更多
Structural health monitoring employs different tools and techniques to provide a prediction for damages that occur in various structures.Damages such as debond and cracks in concrete-filled steel tube column(CFST)are ...Structural health monitoring employs different tools and techniques to provide a prediction for damages that occur in various structures.Damages such as debond and cracks in concrete-filled steel tube column(CFST)are serious defects that threaten the integrity of the structural members.Ultrasonic waves monitoring applied to the CFST column is necessary to detect damages and quantify their size.However,without appropriate signal processing tools,the results of the monitoring process could not be crucial.In this research,a monitoring process based on a Multiphysics numerical simulation study was carried out.Two signal processing tools:short time Fourier transform(STFT)and Welch Power Spectral Density Estimate(PSD)were used to analyse the captured raw signals.The STFT spectrogram was effective in identifying the different size of damage based on a graphical interpretation.The results show that the increasing of frequency of the excited signal give a better results.The increase in peak magnitude values in Welch PSD was found to be proportionate to the change in damage length whereas the damage depth has a less effect.The results for the crack size identification were less promising than those of debond damage because of the different type of the signal’s propagation path.Simulation process conducted by COMSOL software has proved the validity of the adopted signal processing techniques in detecting such damages in CFST columns.展开更多
Analyze and compare the basic principles of ultrasonic detection of voids in concrete,choose ZBL-U520/510 non-metallic ultrasonic detector,and use the opposite detection method to test the void size in the joints of p...Analyze and compare the basic principles of ultrasonic detection of voids in concrete,choose ZBL-U520/510 non-metallic ultrasonic detector,and use the opposite detection method to test the void size in the joints of prefabri-cated concrete structures.The results show that:ultrasonic method by testing the waveform,sound,and speed of sound analysis can effectively determine the position of the defect,and through the conversion formula can estimate the void size.Ultrasonic parameters are used to distinguish the internal defects of Assembly concrete.Sometimes there are diferent results with different para-meters.It is difficult for engineers to directly determine the internal de fects.Fuzzy comprehensive ev aluation can establish an overall evaluation of things or objects controlled by multiple factors by establishing membership functions.Through the inspection of engineering examples:the fuzzy comprehensive judgment method has no difference between the judgment of some good quality points and the judg-ment results of the original criteria,but for some abnormal points or points near the critical value,the advantages of fiuzzy criteria can be achieved.The judgment process will be more scientific by considering several parameters in a comprehen-sive manner and digtizing the original subjective judgments.展开更多
The feasibility of gas kick early detection outside the riser was analyzed based on gas-liquid multiphase flow theory.Then an experimental platform for gas kick early detection based on Doppler ultrasonic wave was est...The feasibility of gas kick early detection outside the riser was analyzed based on gas-liquid multiphase flow theory.Then an experimental platform for gas kick early detection based on Doppler ultrasonic wave was established and the propagation experiments in two-phase flow of gas-water(sucrose solutions)were conducted.The time and frequency domains of the Doppler ultrasonic wave signals during the experiments were analyzed.The results show that:(1)No matter the pump was on or off,the detected average Doppler ultrasonic signal voltage increased first and then decreased with the increase of the gas void fraction,and had a quadratic function relation with gas void fraction,so the average voltage change of the monitored signals can be used to deduce the approximate gas void fraction.The Doppler ultrasonic wave signal voltage was significantly reduced in magnitude and variation in the solution with higher viscosity,and the viscosity has stronger impact on the magnitude of signal than density.(2)When the pump was stopped,the Doppler shift increased with the increase of gas void fraction,and the two showed a nearly linear relation,so the detected amount of Doppler shift can reflect the variation of gas void fraction quantitatively.When the pump was on,the sound energy produced by frequency converter had a more significant impact on amplitude spectrum than gas void fraction,so it is impossible to determine whether gas kick occurs by frequency domain signal analysis.(3)This method is a non-contact measurement,with no contact with the drilling fluid and no disruption to the drilling operation.It can quantitatively characterize the gas void fraction according to the change of Doppler ultrasonic signal,enabling earlier detection of gas kick.展开更多
During offshore deepwater drilling,the strata with abnormal pressure are often encountered and gas invasion and overflow occur easily.If they cannot be detected and controlled in time,blowout may happen and even get o...During offshore deepwater drilling,the strata with abnormal pressure are often encountered and gas invasion and overflow occur easily.If they cannot be detected and controlled in time,blowout may happen and even get out of control,which will cause considerable economic loss and irreparable casualties and may even damage the marine ecologic environment seriously.How to monitor overflow early during deepwater drilling is a global research hot,focus and difficulty at present.In order to provide theoretical guidance for the early monitoring of overflow in the riser during offshore deepwater drilling,this paper designed an experimental device for the early monitoring of gas invasion based on the propagation principle of Doppler ultrasonic wave.Then,the installation mode and angle of Doppler probe were optimized.Finally,the propagation of Doppler ultrasonic wave in the gaseliquid two-phase flow with a void fraction of 0-46% and a liquid flow velocity of 0-0.7 m/s was experimentally studied,and the change laws of Doppler ultrasonic wave with void fraction were revealed.And the following research results are obtained.First,when the void fraction changes,the signal voltage will jump up and down at different amplitudes and frequencies on the basis of initial curve.The signal voltage amplitude increases firstly and then decreases with the increase of void fraction.Second,when the increase amplitude of mean signal voltage caused by multiple reflection is greater than the attenuation degree of ultrasonic wave,the mean signal voltage increases.Otherwise,the signal voltage decreases.Third,the fitting curve of mean signal voltage scatters and void fraction under different flow velocities and void fractions during pump stopping and starting present a change law of quadratic function.In conclusion,void fraction can be quantitatively predicted based on the measured signal voltage,so as to provide guidance for the early monitoring of riser overflow and well kill operation during offshore deepwater drilling.展开更多
Rock joints are one of the vital discontinuities in a natural rock mass.How to accurately and conveniently determine joint normal stiffness is therefore significant in rock mechanics.Here,first,seven existing methods ...Rock joints are one of the vital discontinuities in a natural rock mass.How to accurately and conveniently determine joint normal stiffness is therefore significant in rock mechanics.Here,first,seven existing methods for determining joint normal stiffness were introduced and reviewed,among which MethodⅠ(the indirect measurement method),MethodⅡ(the direct determination method),MethodⅢ(the across-joint strain gauge measurement method)and MethodⅣ(the deformation measuring ring method)are via destructive uniaxial compression testing,while MethodⅤ(the best fitting method),MethodⅥ(the rapid evaluation method)and MethodⅦ(the effective modulus method)are through wave propagation principles and nondestructive ultrasonic testing.Subsequently,laboratory tests of intact and jointed sandstone specimens were conducted following the testing requirements and pro-cedures of those seven methods.A comparison among those methods was then performed.The results show that Method I,i.e.the benchmark method,is reliable and stable.MethodⅡhas a conceptual drawback,and its accuracy is acceptable at only very low stress levels.Relative errors in the results from MethodⅢare very large.With MethodⅣ,the testing results are sufficiently accurate despite the strict testing environment and complicated testing procedures.The results from MethodⅤare greatly unstable and significantly dependent on the natural frequency of the transducers.The joint normal stiffness determined with MethodⅥis stable and accurate,although data processing is complex.MethodⅦcould be adopted to determine the joint normal stiffness corresponding to the rock elastic deformation phase only.Consequently,it is suggested that MethodsⅠ,ⅣandⅥshould be adopted for the mea-surement of joint normal stiffness.The findings could be helpful in selecting an appropriate method to determine joint normal stiffness and,hence,to better solve discontinuous rock mass problems.展开更多
Three kinds of lower rank bituminous coals from Yanzhou mine and Tengxian mine from Shandong Province were treated and hydrogenated in the study. The test re- sults show that the performance of hydrogenation liquefact...Three kinds of lower rank bituminous coals from Yanzhou mine and Tengxian mine from Shandong Province were treated and hydrogenated in the study. The test re- sults show that the performance of hydrogenation liquefaction of the pretreated coals is improved markedly. Under the test condition of H2 initial pressure 8.2 MPa, addition of FeSO4·7H2O and S as catalyst, final reacting temperature 400 ℃ and reacting time 1.5 h, the oil yield of pretreated YZ1 coal is 69.76% compared with 62.53% of oil yield of un- treated YZ1. Seminally the oil yield of pretreated YZ2 coal is 55.43% compared with 20.88% of untreated YZ2 coal. The results of tests also prove that the improving degree of hydrogenation liquefaction of the pretreated coals is related with radiation duration when the radiation frequency and radiation power of ultrasonic wave are fixed.展开更多
[Objectives]The extraction conditions of formula oolong tea were investigated by an orthogonal experiment.[Methods]The technical conditions were optimized by the 4C method,and the application of formula oolong tea ext...[Objectives]The extraction conditions of formula oolong tea were investigated by an orthogonal experiment.[Methods]The technical conditions were optimized by the 4C method,and the application of formula oolong tea extract in cigarettes was studied.[Results]①In the experimental range,the best sensory evaluation effect of formula oolong tea extract was obtained with extraction conditions of 70%ethanol as extraction solvent,extraction time h,extraction temperature 25℃,and ultrasonic frequency 80 kHz,and follow-up low-temperature concentration,low-temperature sedimentation and low-temperature centrifugation.②The effects of different centrifugal speeds on the quality of formula oolong tea extract were explored.The formula oolong tea extract obtained under the conditions of 3000 r/min and centrifugal time of 10 min showed the best evaluation effect with soft and delicate smoke,rich smoke fragrance,good comfort and refreshing mouthfeel.③The effective aroma components in the formula oolong tea extract were qualitatively analyzed by GC-MS.[Conclusions]This study provides high-quality raw materials and a theoretical basis for the research of independent flavor blending in cigarette industry enterprises.展开更多
It takes flavonoid extraction rate as indicator and adopts the method of orthogonal experiment to study process of total flavonoid in Trollius chinensis through ultrasonic wave assisted extraction, microwave assisted ...It takes flavonoid extraction rate as indicator and adopts the method of orthogonal experiment to study process of total flavonoid in Trollius chinensis through ultrasonic wave assisted extraction, microwave assisted extraction and backflow extraction, as well as optimization of process parameter. The result indicates that in terms of extraction efficiency, microwave extraction method is better than ultrasonic radiation extraction method, which is better than backflow extraction method. Optimal process parameter through backflow extraction is： backflow temperature 60℃, fluid material ratio 1：20, ethanol density 65%, backflow time 60min; optimal process parameter through ultrasonic wave assisted extraction is： ultrasonic radiation temperature 70℃, fluid material ratio 1：20, ethanol density 65%, ultrasonic wave radiation time 45rain; optimal process parameter of microwave assisted extraction is： microwave radiation temperature 60℃, fluid material ratio 1：20, ethanol density 75%, microwave radiation time 45min.展开更多
In many applications in aluminium industry, the number of inclusion-critical products increases and the quality of those products depend on the inclusion concentration and size. In order to improve the quality of alum...In many applications in aluminium industry, the number of inclusion-critical products increases and the quality of those products depend on the inclusion concentration and size. In order to improve the quality of aluminium products and the effectiveness of the processes, a reliable and cheaper on-line detection method is needed. Ultrasonic detection has been used in steel industry, but relatively rare in aluminium industry, although it would theoretically allow for an online non-intrusive detection of the cleanliness of the melt. In this work, the current information on ultrasonic inclusion detection was gathered and recommendations were provided on the Prerequisites for a set-up for ultrasonic detection of non-metallic inclusions in aluminium as a contribution on previous works. It has been concluded that ultrasonic waves seem promising, and should be experimented more on an industrial level to have a clear view on the potentials of the method.展开更多
Aim To develop a high speed and high resolution dynamic rangefinding device for the measurement of large distances.Methods The device was comprised of an ultrasonic transmitter and a receiver,and a receiver , and a co...Aim To develop a high speed and high resolution dynamic rangefinding device for the measurement of large distances.Methods The device was comprised of an ultrasonic transmitter and a receiver,and a receiver , and a continuous ultrasonic wave amplitude-modulated by a low- frequency acoustic signal was used. The rangefinding was achieved by detecting the phase difference between the transmitted and received ultrasonic signals. The design principle. hard- ware implementation , experimental results and performance analysis of the device are included. Results and Conclusion Experiments show that the accuracy of the device are included. within 1.5m while its dynamic data update rate can be up to 40kHz.展开更多
The output of an ultrasonic wave-driven nanogenerator(NG)has been found to depend on the excitation conditions and geometry.Incidence angle tests indicate that the effective area of an NG determines the amount of powe...The output of an ultrasonic wave-driven nanogenerator(NG)has been found to depend on the excitation conditions and geometry.Incidence angle tests indicate that the effective area of an NG determines the amount of power that can be generated.The output power of an NG is also directly related to its distance from the ultrasonic source.A sinusoidal profile of the electrical output was observed when an NG was moved inside a long tube filled with water with the ultrasonic source located at one end.This is due to the oscillation of the wave intensity inside the tube as a function of the distance from the excitation source.展开更多
High cement bond quality is required to keep an oil well from hydraulic commu- nication between zones. In the cement bond evaluation, the ultrasonic echo method is widely used for its capability of channeling azimuth ...High cement bond quality is required to keep an oil well from hydraulic commu- nication between zones. In the cement bond evaluation, the ultrasonic echo method is widely used for its capability of channeling azimuth detection. Full waveforms reflected from the cased hole are simulated for different bonding conditions by the generalized transfer matrix method. Because of the high acoustic impedance of casing, the amplitudes of the reflected waves from the cement and the formation are small and cannot easily be used to evaluate the cementing condition. The wave that can propagate into the cement and the formation through the casing concentrates closely on the casing resonant frequency. To reduce the amplitude of the reflected wave from the casing inner surface and highlight the part of the reflected wave which carries the cementing quality information, the reflected full wave is filtered according to the casing resonant frequency. There are several wave packets in the filtered waveform. When the amplitude of the second wave packet is low, the cement bonds well with the casing, otherwise poorly. A low amplitude third wave packet is an indication of a good bond of the cement with the formation, otherwise poor. To reveal the sensitivity of the reflection wave amplitudes to the incident angle, reflected full waveform is modeled when an acoustic beam with finite width is incident on the casing. It is shown that the bond evaluation method based on filtered wave packets is valid for incident angle less than 5 degrees.展开更多
A model evaluating the signal loss of the double transmitted acoustic beams through random rough surfaces was established based on the Fresnel approximation and phase- screen approximation. A simple analytical solutio...A model evaluating the signal loss of the double transmitted acoustic beams through random rough surfaces was established based on the Fresnel approximation and phase- screen approximation. A simple analytical solution was achieved using the exponential substi- tution approach to remove the nonlinear integral terms. The factors that affect the signal of double transmissions from random rough surfaces were analyzed. The research results demon- strated that the signal loss is not only related to the root-mean-squire height of the roughness, but also to the distance of wave traveling in the materials. The model can be very helpful for improving the reliability of NDT (Non-Destructive Testing).展开更多
In order to cvaluate the fiber / matrix interfaccs in a fiber reinforced compo site, a mathematical algorithm is prescnted for predicting the scattering cross scction of a cylindrical three-layered medium and the soun...In order to cvaluate the fiber / matrix interfaccs in a fiber reinforced compo site, a mathematical algorithm is prescnted for predicting the scattering cross scction of a cylindrical three-layered medium and the sound attenuation due to scattering in the composite. When the thickness of the fiber / matrix interface layer is small compared to the wavelength, two stiffness constants are used to simulate the boundary condi tions and a simplified method for predicting the sound scattering is developed. Nu mcrical computations have been made for the relations of longitudinal wave attcnuation coefficients in a glass fiber / aluminum composite with the interface properties and wave frequency.展开更多
Renal calculi are inhomogenous, heterogeneous and complex in nature. There is a large variation in their chemical composition due to food habits of patients and hence geography of the inhabitants in different parts of...Renal calculi are inhomogenous, heterogeneous and complex in nature. There is a large variation in their chemical composition due to food habits of patients and hence geography of the inhabitants in different parts of the world. Ultrasonic studies are made to investigate various physical and other constants of such renal calculi. A double-probe through transmission technique is used to study various propagation parameters. The ultrasonic waves displayed on cathode-ray oscilloscope are complex and complicated in nature. Complete analysis of such wave patterns is given in the present study. The data reported would help in the design of an u ltrasonic lithotripter.展开更多
Ultrasonic guided wave inspection is an effective non-destructive testing method which can be used for stress level evaluation in steel strands.Unfortunately the propagation velocity of ultrasonic guided waves changes...Ultrasonic guided wave inspection is an effective non-destructive testing method which can be used for stress level evaluation in steel strands.Unfortunately the propagation velocity of ultrasonic guided waves changes due to temperature shift making the prestress measurement of steel strands inaccurate and even sometimes impossible.In the course of solving the problem,this paper reports on quantitative research on the temperature dependence of ultrasonic longitudinal guided wave propagation in long range steel strands.In order to achieve the generation and reception of a chosen longitudinal mode in a steel strand with a helical shaped surface,a new type of magnetostrictive transducer was developed,characterized by a group of thin clips and three identical permanent magnets.Excitation and reception of ultrasonic guided waves in a steel strand were performed experimentally.Experimental results shows that in the temperature range from-4℃to 34℃,the propagation velocity of the L(0,1)mode at 160 kHz linearly decreased with increasing temperature and its temperature dependent coefficient was 0.90(m·s-1·(℃)-1)which is very close to the theoretical prediction.The effect of dimension deviation between the helical and center wires and the effect of the thermal expansion of the steel strand on ultrasonic longitudinal guided wave propagation were also analyzed.It was found that these effects could be ignored compared with the change in the material mechanical properties of the steel strands due to temperature shift.It was also observed that the longitudinal guided wave mode was somewhat more sensitive to temperature changes compared with conventional ultrasonic waves theoretically.Therefore,it is considered that the temperature effect on ultrasonic longitudinal guided wave propagation in order to improve the accuracy of stress measurement in prestressed steel strands.Quantitative research on the temperature dependence of ultrasonic guided wave propagation in steel strands provides an important basis for the compensation of temperature effects in stress measurement in steel strands by using ultrasonic guided wave inspection.展开更多
基金supported by the Open Fund of the Key Laboratory of Exploration Technologies for Oil and Gas Resources(Yangtze University)the Ministry of Education(No.K2014-06)the Reservoir Geophysical Research Center at Yangtze University
文摘Transmitted ultrasonic wave simulation （TUWS） in a digital core is one of the important elements of digital rock physics and is used to study wave propagation in porous cores and calculate equivalent velocity. When simulating wave propagates in a 3D digital core, two additional layers are attached to its two surfaces vertical to the wave-direction and one planar wave source and two receiver-arrays are properly installed. After source excitation, the two receivers then record incident and transmitted waves of the digital rock. Wave propagating velocity, which is the velocity of the digital core, is computed by the picked peak-time difference between the two recorded waves. To evaluate the accuracy of TUWS, a digital core is fully saturated with gas, oil, and water to calculate the corresponding velocities. The velocities increase with decreasing wave frequencies in the simulation frequency band, and this is considered to be the result of scattering. When the pore fluids are varied from gas to oil and finally to water, the velocity-variation characteristics between the different frequencies are similar, thereby approximately following the variation law of velocities obtained from linear elastic statics simulation （LESS）, although their absolute values are different. However, LESS has been widely used. The results of this paper show that the transmission ultrasonic simulation has high relative precision.
基金Project(51275180)supported by the National Natural Science Foundation of ChinaProject(S201304416899)supported by the Natural Science Foundation of Guangdong Province,ChinaProject(sybzzxm201213)supported by Doctorate Dissertation Funds of Guangdong Province,China
文摘The methods were studied to improve the cooling performance of the absorption refrigeration system(ARS) driven by low-grade solar energy with ultrasonic wave, while the mechanism of ultrasonic wave strengthening boiling mass transfer in LiB r solution was also analyzed with experiment. The experimental results indicate that, under the driving heat source of 60–100 oC and the ultrasonic power of 20–60 W, the mass flux of cryogen water in Li Br solution is higher after the application of ultrasonic wave than auxiliary heating with electric rod of the same power, so the ultrasonic application effectively enhances the heat utilization efficiency. The distance H from ultrasonic transducer to vapor/liquid interface significantly affects mass transfer enhancement, so an optimal Hopt corresponding to certain ultrasonic power is beneficial to reaching the best strengthening effect for ultrasonic mass transfer. When the ultrasonic power increases, the mass transfer obviously speeds up in the cryogen water; however, as the power increases to a certain extent, the flux reaches a plateau without obvious increment. Moreover, the ultrasound-enhanced mass transfer technology can reduce the minimum temperature of driving heat source required by ARS and promote the application of solar energy during absorption refrigeration.
基金This work was supported by the National Natural Science Foundation of China.
文摘Electropolymerization of pyrrole under ultrasonic field at 20kHz was performed in a series of aqueous and propylene carbonate (PC) solutions. The ultrasonic wave with moderate intensity at the power of 44W, which is the power threshold of the ultrasonic generator used in this work to produce cavitation effect, enhance the conductivity and tensile strength of the polypyrrole films as prepared. However, too high intensity of the ultrasonic wave is harmful to the polymerization.
基金supported by the National Natural Science Foundation of China(10772086 and 10727201)the National University of Singapore(R-265-000-140-112)
文摘This paper presents a novel non-contact method for evaluating the resonant frequency of a microstructure, Firstly, the microstructure under test is excited by ultrasonic waves. This excitation method does not impose any undefined load on the specimen like the electrostatic excitation and also this is the first actual use of ultrasonic wave for exciting a microstructure in the literature. Secondly, the amplitudes of the microstructure are determined by image edge detection using a Mexican hat wavelet transform on the vibrating images of the microstructure. The vibrating images are captured by a CCD camera when the microstructure is vibrated by ultrasonic waves at a series of discrete high frequencies （〉30 kHz）. Upon processing the vibrating images, the amplitudes at various excitation frequencies are obtained and an amplitude-frequency spectrum is obtained from which the resonant frequency is subsequently evaluated. A micro silicon structure consisting of a perforated plate （192 × 192 μm） and two cantilever beams （76 × 43 μm） which is about 4 μm thickness is tested. Since laser interferometry is not required, thermal effects on a test object can be avoided. Hence, the setup is relatively simple. Results show that the proposed method is a simple and effective approach for evaluating the dynamic characteristics of microstructures.
文摘Structural health monitoring employs different tools and techniques to provide a prediction for damages that occur in various structures.Damages such as debond and cracks in concrete-filled steel tube column(CFST)are serious defects that threaten the integrity of the structural members.Ultrasonic waves monitoring applied to the CFST column is necessary to detect damages and quantify their size.However,without appropriate signal processing tools,the results of the monitoring process could not be crucial.In this research,a monitoring process based on a Multiphysics numerical simulation study was carried out.Two signal processing tools:short time Fourier transform(STFT)and Welch Power Spectral Density Estimate(PSD)were used to analyse the captured raw signals.The STFT spectrogram was effective in identifying the different size of damage based on a graphical interpretation.The results show that the increasing of frequency of the excited signal give a better results.The increase in peak magnitude values in Welch PSD was found to be proportionate to the change in damage length whereas the damage depth has a less effect.The results for the crack size identification were less promising than those of debond damage because of the different type of the signal’s propagation path.Simulation process conducted by COMSOL software has proved the validity of the adopted signal processing techniques in detecting such damages in CFST columns.
基金The authors are grateful for the financial support received from the National Key R&D Program(2017YFF0205003)Hebei Province Higher Education Science and Technology Research Project(ZD2018249)Special funded by the Beijing Institute of Housing and Urban-Rural Science and Technology.
文摘Analyze and compare the basic principles of ultrasonic detection of voids in concrete,choose ZBL-U520/510 non-metallic ultrasonic detector,and use the opposite detection method to test the void size in the joints of prefabri-cated concrete structures.The results show that:ultrasonic method by testing the waveform,sound,and speed of sound analysis can effectively determine the position of the defect,and through the conversion formula can estimate the void size.Ultrasonic parameters are used to distinguish the internal defects of Assembly concrete.Sometimes there are diferent results with different para-meters.It is difficult for engineers to directly determine the internal de fects.Fuzzy comprehensive ev aluation can establish an overall evaluation of things or objects controlled by multiple factors by establishing membership functions.Through the inspection of engineering examples:the fuzzy comprehensive judgment method has no difference between the judgment of some good quality points and the judg-ment results of the original criteria,but for some abnormal points or points near the critical value,the advantages of fiuzzy criteria can be achieved.The judgment process will be more scientific by considering several parameters in a comprehen-sive manner and digtizing the original subjective judgments.
基金Supported by Natural Science Foundation of China(51991363)National Program on Key Basic Research Project(973 Program)(2015CB251200)Changjiang Scholars and Innovative Research Team Project(IRT_14R58)
文摘The feasibility of gas kick early detection outside the riser was analyzed based on gas-liquid multiphase flow theory.Then an experimental platform for gas kick early detection based on Doppler ultrasonic wave was established and the propagation experiments in two-phase flow of gas-water(sucrose solutions)were conducted.The time and frequency domains of the Doppler ultrasonic wave signals during the experiments were analyzed.The results show that:(1)No matter the pump was on or off,the detected average Doppler ultrasonic signal voltage increased first and then decreased with the increase of the gas void fraction,and had a quadratic function relation with gas void fraction,so the average voltage change of the monitored signals can be used to deduce the approximate gas void fraction.The Doppler ultrasonic wave signal voltage was significantly reduced in magnitude and variation in the solution with higher viscosity,and the viscosity has stronger impact on the magnitude of signal than density.(2)When the pump was stopped,the Doppler shift increased with the increase of gas void fraction,and the two showed a nearly linear relation,so the detected amount of Doppler shift can reflect the variation of gas void fraction quantitatively.When the pump was on,the sound energy produced by frequency converter had a more significant impact on amplitude spectrum than gas void fraction,so it is impossible to determine whether gas kick occurs by frequency domain signal analysis.(3)This method is a non-contact measurement,with no contact with the drilling fluid and no disruption to the drilling operation.It can quantitatively characterize the gas void fraction according to the change of Doppler ultrasonic signal,enabling earlier detection of gas kick.
基金Project supported by the Major Program of National Natural Science Foundation of China“Formation mechanism and safety control of barriers for multi-phase flow in natural gas hydrate wellbores”(No.:51991363)the National Program on Key Basic Research Project“Basic study on safe and efficient drilling for offshore deepwater petroleum development”(No.:2015CB251200)the Natural Science Foundation of Shandong Province“Flow pattern conversion mechanism of gaseliquid reverse multi-phase flow in annulus during bullheading”(No.:ZR2020ME095).
文摘During offshore deepwater drilling,the strata with abnormal pressure are often encountered and gas invasion and overflow occur easily.If they cannot be detected and controlled in time,blowout may happen and even get out of control,which will cause considerable economic loss and irreparable casualties and may even damage the marine ecologic environment seriously.How to monitor overflow early during deepwater drilling is a global research hot,focus and difficulty at present.In order to provide theoretical guidance for the early monitoring of overflow in the riser during offshore deepwater drilling,this paper designed an experimental device for the early monitoring of gas invasion based on the propagation principle of Doppler ultrasonic wave.Then,the installation mode and angle of Doppler probe were optimized.Finally,the propagation of Doppler ultrasonic wave in the gaseliquid two-phase flow with a void fraction of 0-46% and a liquid flow velocity of 0-0.7 m/s was experimentally studied,and the change laws of Doppler ultrasonic wave with void fraction were revealed.And the following research results are obtained.First,when the void fraction changes,the signal voltage will jump up and down at different amplitudes and frequencies on the basis of initial curve.The signal voltage amplitude increases firstly and then decreases with the increase of void fraction.Second,when the increase amplitude of mean signal voltage caused by multiple reflection is greater than the attenuation degree of ultrasonic wave,the mean signal voltage increases.Otherwise,the signal voltage decreases.Third,the fitting curve of mean signal voltage scatters and void fraction under different flow velocities and void fractions during pump stopping and starting present a change law of quadratic function.In conclusion,void fraction can be quantitatively predicted based on the measured signal voltage,so as to provide guidance for the early monitoring of riser overflow and well kill operation during offshore deepwater drilling.
基金supported by the Shenzhen Fundamental Research Program(Grant No.JCYJ20220818095605012)the National Natural Science Foundation of China(Grant No.51909026)the Fund of Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization(Grant No.2020-08).
文摘Rock joints are one of the vital discontinuities in a natural rock mass.How to accurately and conveniently determine joint normal stiffness is therefore significant in rock mechanics.Here,first,seven existing methods for determining joint normal stiffness were introduced and reviewed,among which MethodⅠ(the indirect measurement method),MethodⅡ(the direct determination method),MethodⅢ(the across-joint strain gauge measurement method)and MethodⅣ(the deformation measuring ring method)are via destructive uniaxial compression testing,while MethodⅤ(the best fitting method),MethodⅥ(the rapid evaluation method)and MethodⅦ(the effective modulus method)are through wave propagation principles and nondestructive ultrasonic testing.Subsequently,laboratory tests of intact and jointed sandstone specimens were conducted following the testing requirements and pro-cedures of those seven methods.A comparison among those methods was then performed.The results show that Method I,i.e.the benchmark method,is reliable and stable.MethodⅡhas a conceptual drawback,and its accuracy is acceptable at only very low stress levels.Relative errors in the results from MethodⅢare very large.With MethodⅣ,the testing results are sufficiently accurate despite the strict testing environment and complicated testing procedures.The results from MethodⅤare greatly unstable and significantly dependent on the natural frequency of the transducers.The joint normal stiffness determined with MethodⅥis stable and accurate,although data processing is complex.MethodⅦcould be adopted to determine the joint normal stiffness corresponding to the rock elastic deformation phase only.Consequently,it is suggested that MethodsⅠ,ⅣandⅥshould be adopted for the mea-surement of joint normal stiffness.The findings could be helpful in selecting an appropriate method to determine joint normal stiffness and,hence,to better solve discontinuous rock mass problems.
文摘Three kinds of lower rank bituminous coals from Yanzhou mine and Tengxian mine from Shandong Province were treated and hydrogenated in the study. The test re- sults show that the performance of hydrogenation liquefaction of the pretreated coals is improved markedly. Under the test condition of H2 initial pressure 8.2 MPa, addition of FeSO4·7H2O and S as catalyst, final reacting temperature 400 ℃ and reacting time 1.5 h, the oil yield of pretreated YZ1 coal is 69.76% compared with 62.53% of oil yield of un- treated YZ1. Seminally the oil yield of pretreated YZ2 coal is 55.43% compared with 20.88% of untreated YZ2 coal. The results of tests also prove that the improving degree of hydrogenation liquefaction of the pretreated coals is related with radiation duration when the radiation frequency and radiation power of ultrasonic wave are fixed.
文摘[Objectives]The extraction conditions of formula oolong tea were investigated by an orthogonal experiment.[Methods]The technical conditions were optimized by the 4C method,and the application of formula oolong tea extract in cigarettes was studied.[Results]①In the experimental range,the best sensory evaluation effect of formula oolong tea extract was obtained with extraction conditions of 70%ethanol as extraction solvent,extraction time h,extraction temperature 25℃,and ultrasonic frequency 80 kHz,and follow-up low-temperature concentration,low-temperature sedimentation and low-temperature centrifugation.②The effects of different centrifugal speeds on the quality of formula oolong tea extract were explored.The formula oolong tea extract obtained under the conditions of 3000 r/min and centrifugal time of 10 min showed the best evaluation effect with soft and delicate smoke,rich smoke fragrance,good comfort and refreshing mouthfeel.③The effective aroma components in the formula oolong tea extract were qualitatively analyzed by GC-MS.[Conclusions]This study provides high-quality raw materials and a theoretical basis for the research of independent flavor blending in cigarette industry enterprises.
文摘It takes flavonoid extraction rate as indicator and adopts the method of orthogonal experiment to study process of total flavonoid in Trollius chinensis through ultrasonic wave assisted extraction, microwave assisted extraction and backflow extraction, as well as optimization of process parameter. The result indicates that in terms of extraction efficiency, microwave extraction method is better than ultrasonic radiation extraction method, which is better than backflow extraction method. Optimal process parameter through backflow extraction is： backflow temperature 60℃, fluid material ratio 1：20, ethanol density 65%, backflow time 60min; optimal process parameter through ultrasonic wave assisted extraction is： ultrasonic radiation temperature 70℃, fluid material ratio 1：20, ethanol density 65%, ultrasonic wave radiation time 45rain; optimal process parameter of microwave assisted extraction is： microwave radiation temperature 60℃, fluid material ratio 1：20, ethanol density 75%, microwave radiation time 45min.
文摘In many applications in aluminium industry, the number of inclusion-critical products increases and the quality of those products depend on the inclusion concentration and size. In order to improve the quality of aluminium products and the effectiveness of the processes, a reliable and cheaper on-line detection method is needed. Ultrasonic detection has been used in steel industry, but relatively rare in aluminium industry, although it would theoretically allow for an online non-intrusive detection of the cleanliness of the melt. In this work, the current information on ultrasonic inclusion detection was gathered and recommendations were provided on the Prerequisites for a set-up for ultrasonic detection of non-metallic inclusions in aluminium as a contribution on previous works. It has been concluded that ultrasonic waves seem promising, and should be experimented more on an industrial level to have a clear view on the potentials of the method.
文摘Aim To develop a high speed and high resolution dynamic rangefinding device for the measurement of large distances.Methods The device was comprised of an ultrasonic transmitter and a receiver,and a receiver , and a continuous ultrasonic wave amplitude-modulated by a low- frequency acoustic signal was used. The rangefinding was achieved by detecting the phase difference between the transmitted and received ultrasonic signals. The design principle. hard- ware implementation , experimental results and performance analysis of the device are included. Results and Conclusion Experiments show that the accuracy of the device are included. within 1.5m while its dynamic data update rate can be up to 40kHz.
文摘The output of an ultrasonic wave-driven nanogenerator(NG)has been found to depend on the excitation conditions and geometry.Incidence angle tests indicate that the effective area of an NG determines the amount of power that can be generated.The output power of an NG is also directly related to its distance from the ultrasonic source.A sinusoidal profile of the electrical output was observed when an NG was moved inside a long tube filled with water with the ultrasonic source located at one end.This is due to the oscillation of the wave intensity inside the tube as a function of the distance from the excitation source.
基金supported by the National Natural Science Foundation of China(41174110,41204092)
文摘High cement bond quality is required to keep an oil well from hydraulic commu- nication between zones. In the cement bond evaluation, the ultrasonic echo method is widely used for its capability of channeling azimuth detection. Full waveforms reflected from the cased hole are simulated for different bonding conditions by the generalized transfer matrix method. Because of the high acoustic impedance of casing, the amplitudes of the reflected waves from the cement and the formation are small and cannot easily be used to evaluate the cementing condition. The wave that can propagate into the cement and the formation through the casing concentrates closely on the casing resonant frequency. To reduce the amplitude of the reflected wave from the casing inner surface and highlight the part of the reflected wave which carries the cementing quality information, the reflected full wave is filtered according to the casing resonant frequency. There are several wave packets in the filtered waveform. When the amplitude of the second wave packet is low, the cement bonds well with the casing, otherwise poorly. A low amplitude third wave packet is an indication of a good bond of the cement with the formation, otherwise poor. To reveal the sensitivity of the reflection wave amplitudes to the incident angle, reflected full waveform is modeled when an acoustic beam with finite width is incident on the casing. It is shown that the bond evaluation method based on filtered wave packets is valid for incident angle less than 5 degrees.
文摘A model evaluating the signal loss of the double transmitted acoustic beams through random rough surfaces was established based on the Fresnel approximation and phase- screen approximation. A simple analytical solution was achieved using the exponential substi- tution approach to remove the nonlinear integral terms. The factors that affect the signal of double transmissions from random rough surfaces were analyzed. The research results demon- strated that the signal loss is not only related to the root-mean-squire height of the roughness, but also to the distance of wave traveling in the materials. The model can be very helpful for improving the reliability of NDT (Non-Destructive Testing).
文摘In order to cvaluate the fiber / matrix interfaccs in a fiber reinforced compo site, a mathematical algorithm is prescnted for predicting the scattering cross scction of a cylindrical three-layered medium and the sound attenuation due to scattering in the composite. When the thickness of the fiber / matrix interface layer is small compared to the wavelength, two stiffness constants are used to simulate the boundary condi tions and a simplified method for predicting the sound scattering is developed. Nu mcrical computations have been made for the relations of longitudinal wave attcnuation coefficients in a glass fiber / aluminum composite with the interface properties and wave frequency.
文摘Renal calculi are inhomogenous, heterogeneous and complex in nature. There is a large variation in their chemical composition due to food habits of patients and hence geography of the inhabitants in different parts of the world. Ultrasonic studies are made to investigate various physical and other constants of such renal calculi. A double-probe through transmission technique is used to study various propagation parameters. The ultrasonic waves displayed on cathode-ray oscilloscope are complex and complicated in nature. Complete analysis of such wave patterns is given in the present study. The data reported would help in the design of an u ltrasonic lithotripter.
基金supported by National Natural Science Foundation of China(Grant No.10602004,Grant No.50975006)Beijing Municipal Natural Science Foundation of China(Grant No.2072003)+1 种基金Beijing Municipal Talent Developing Project of China(Grant No.20081B0501500173)Beijing Municipal Nova Program of China(Grant No.2008A015)
文摘Ultrasonic guided wave inspection is an effective non-destructive testing method which can be used for stress level evaluation in steel strands.Unfortunately the propagation velocity of ultrasonic guided waves changes due to temperature shift making the prestress measurement of steel strands inaccurate and even sometimes impossible.In the course of solving the problem,this paper reports on quantitative research on the temperature dependence of ultrasonic longitudinal guided wave propagation in long range steel strands.In order to achieve the generation and reception of a chosen longitudinal mode in a steel strand with a helical shaped surface,a new type of magnetostrictive transducer was developed,characterized by a group of thin clips and three identical permanent magnets.Excitation and reception of ultrasonic guided waves in a steel strand were performed experimentally.Experimental results shows that in the temperature range from-4℃to 34℃,the propagation velocity of the L(0,1)mode at 160 kHz linearly decreased with increasing temperature and its temperature dependent coefficient was 0.90(m·s-1·(℃)-1)which is very close to the theoretical prediction.The effect of dimension deviation between the helical and center wires and the effect of the thermal expansion of the steel strand on ultrasonic longitudinal guided wave propagation were also analyzed.It was found that these effects could be ignored compared with the change in the material mechanical properties of the steel strands due to temperature shift.It was also observed that the longitudinal guided wave mode was somewhat more sensitive to temperature changes compared with conventional ultrasonic waves theoretically.Therefore,it is considered that the temperature effect on ultrasonic longitudinal guided wave propagation in order to improve the accuracy of stress measurement in prestressed steel strands.Quantitative research on the temperature dependence of ultrasonic guided wave propagation in steel strands provides an important basis for the compensation of temperature effects in stress measurement in steel strands by using ultrasonic guided wave inspection.
