After an aerial object enters the water, physical changes to sounds in the water caused by the accompanying bubbles are quite complex. As a result, traditional signal analyzing methods cannot identify the real physica...After an aerial object enters the water, physical changes to sounds in the water caused by the accompanying bubbles are quite complex. As a result, traditional signal analyzing methods cannot identify the real physical object. In view of this situation, a novel method for analyzing the sounds caused by an aerial object’s entry into water was proposed. This method analyzes the vibrational mode of the bubbles by using empitical mode decomposition. Experimental results showed that this method can efficiently remove noise and extract the broadband pulse signal and low-frequency fluctuating signal, producing an accurate resolution of entry time and frequency. This shows the improved performance of the proposed method.展开更多
Evaluation of quality of singing is an issue subjectively realized by the experts. This paper presents the results of the analysis of the vibrato parameter in the singing. The well-known fact is the existence of vibra...Evaluation of quality of singing is an issue subjectively realized by the experts. This paper presents the results of the analysis of the vibrato parameter in the singing. The well-known fact is the existence of vibrato of sufficient quality in the voices of professional singers. The authors focus here on the choral voices to assess the quality of their singing from the point of view of the vibrato parameter. The method presented here is developed to evaluate the vibrato while singing under conditions close to the real ones. The study was carried out on the recordings of the members of an academic choir. As a result of tests it was found that not all singers present the same quality of vibrato in terms of deviation of vibrato confidence （STDCV）.展开更多
Nonlinear behavior of glow discharge plasmas is experimentally investigated.The glow is generated between a barrier semiconductor electrode,Chromium doped namely Gallium Arsenide（Ga As：Cr）,as a cathode and an Indiu...Nonlinear behavior of glow discharge plasmas is experimentally investigated.The glow is generated between a barrier semiconductor electrode,Chromium doped namely Gallium Arsenide（Ga As：Cr）,as a cathode and an Indium–Tin Oxide（ITO） coated glass electrode as an anode,in reverse bias.The planar nature of electrodes provides symmetry in spatial geometry.The discharge behaves oscillatory in the time domain,with single and sometimes multiperiodicities in plasma current and voltage characteristics.In this paper,harmonic frequency generation and transition to chaotic behavior is investigated.The observed current–voltage characteristics of the discharge are discussed in detail.展开更多
A ship is operated under an extremely complex environment, and waves and winds are assumed to be the stochastic excitations. Moreover, the propeller, host and mechanical equipment can also induce the harmonic response...A ship is operated under an extremely complex environment, and waves and winds are assumed to be the stochastic excitations. Moreover, the propeller, host and mechanical equipment can also induce the harmonic responses. In order to reduce structural vibration, it is important to obtain the modal parameters information of a ship. However, the traditional modal parameter identification methods are not suitable since the excitation information is difficult to obtain. Natural excitation technique-eigensystem realization algorithm （NExT-ERA） is an operational modal identification method which abstracts modal parameters only from the response signals, and it is based on the assumption that the input to the structure is pure white noise. Hence, it is necessary to study the influence of harmonic excitations while applying the NExT-ERA method to a ship structure. The results of this research paper indicate the practical experiences under ambient excitation, ship model experiments were successfully done in the modal parameters identification only when the harmonic frequencies were not too close to the modal frequencies.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
Water hammer diagnostics is an important fracturing diagnosis technique to evaluate fracture locations and other downhole events in fracturing.The evaluation results are obtained by analyzing shut-in water hammer pres...Water hammer diagnostics is an important fracturing diagnosis technique to evaluate fracture locations and other downhole events in fracturing.The evaluation results are obtained by analyzing shut-in water hammer pressure signal.The field-sampled water hammer signal is often disturbed by noise interfer-ence.Noise interference exists in various pumping stages during water hammer diagnostics,with significantly different frequency range and energy distribution.Clarifying the differences in frequency range and energy distribution between effective water hammer signals and noise is the basis of setting specific filtering parameters,including filtering frequency range and energy thresholds.Filtering spe-cifically could separate the effective signal and noise,which is the key to ensuring the accuracy of water hammer diagnosis.As an emerging technique,there is a lack of research on the frequency range and energy distribution of effective signals in water hammer diagnostics.In this paper,the frequency range and energy distribution characteristics of field-sampled water hammer signals were clarified quantita-tively and qualitatively for the first time by a newly proposed comprehensive water hammer segmentation-energy analysis method.The water hammer signals were preprocessed and divided into three segments,including pre-shut-in,water hammer oscillation,and leak-off segment.Then,the three segments were analyzed by energy analysis and correlation analysis.The results indicated that,one aspect,the frequency range of water hammer oscillation spans from 0 to 0.65 Hz,considered as effective water hammer signal.The pre-shut-in and leak-off segment ranges from 0 to 0.35 Hz and 0e0.2 Hz respectively.Meanwhile,odd harmonics were manifested in water hammer oscillation segment,with the harmonic frequencies ranging approximately from 0.07 to 0.75 Hz.Whereas integer harmonics were observed in pre-shut-in segment,ranging from 6 to 40 Hz.The other aspect,the energy distribution of water hammer signals was analyzed in different frequency ranges.In 0e1 Hz,an exponential decay was observed in all three segments.In 1-100 Hz,a periodical energy distribution was observed in pre-shut-in segment,an exponential decay was observed in water hammer oscillation,and an even energy distri-bution was observed in leak-off segment.In 100-500 Hz,an even energy distribution was observed in those three segments,yet the highest magnitude was noted in leak-off segment.In this study,the effective frequency range and energy distribution characteristics of the field-sampled water hammer signals in different segments were sufficiently elucidated quantitatively and qualitatively for the first time,laying the groundwork for optimizing the filtering parameters of the field filtering models and advancing the accuracy of identifying downhole event locations.展开更多
文摘After an aerial object enters the water, physical changes to sounds in the water caused by the accompanying bubbles are quite complex. As a result, traditional signal analyzing methods cannot identify the real physical object. In view of this situation, a novel method for analyzing the sounds caused by an aerial object’s entry into water was proposed. This method analyzes the vibrational mode of the bubbles by using empitical mode decomposition. Experimental results showed that this method can efficiently remove noise and extract the broadband pulse signal and low-frequency fluctuating signal, producing an accurate resolution of entry time and frequency. This shows the improved performance of the proposed method.
基金supported by the Ministry of Science and Higher Education of Poland,under Grant No.NN516 517539
文摘Evaluation of quality of singing is an issue subjectively realized by the experts. This paper presents the results of the analysis of the vibrato parameter in the singing. The well-known fact is the existence of vibrato of sufficient quality in the voices of professional singers. The authors focus here on the choral voices to assess the quality of their singing from the point of view of the vibrato parameter. The method presented here is developed to evaluate the vibrato while singing under conditions close to the real ones. The study was carried out on the recordings of the members of an academic choir. As a result of tests it was found that not all singers present the same quality of vibrato in terms of deviation of vibrato confidence （STDCV）.
基金supported by the Scientific Research Project Fund of Middle East Technical University,under project # BAP-08-11-2016-044
文摘Nonlinear behavior of glow discharge plasmas is experimentally investigated.The glow is generated between a barrier semiconductor electrode,Chromium doped namely Gallium Arsenide（Ga As：Cr）,as a cathode and an Indium–Tin Oxide（ITO） coated glass electrode as an anode,in reverse bias.The planar nature of electrodes provides symmetry in spatial geometry.The discharge behaves oscillatory in the time domain,with single and sometimes multiperiodicities in plasma current and voltage characteristics.In this paper,harmonic frequency generation and transition to chaotic behavior is investigated.The observed current–voltage characteristics of the discharge are discussed in detail.
基金Supported by the National Natural Science Foundation of China（51079027）
文摘A ship is operated under an extremely complex environment, and waves and winds are assumed to be the stochastic excitations. Moreover, the propeller, host and mechanical equipment can also induce the harmonic responses. In order to reduce structural vibration, it is important to obtain the modal parameters information of a ship. However, the traditional modal parameter identification methods are not suitable since the excitation information is difficult to obtain. Natural excitation technique-eigensystem realization algorithm （NExT-ERA） is an operational modal identification method which abstracts modal parameters only from the response signals, and it is based on the assumption that the input to the structure is pure white noise. Hence, it is necessary to study the influence of harmonic excitations while applying the NExT-ERA method to a ship structure. The results of this research paper indicate the practical experiences under ambient excitation, ship model experiments were successfully done in the modal parameters identification only when the harmonic frequencies were not too close to the modal frequencies.
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support from the National Natural Science Foundation of China(No.52374019).
文摘Water hammer diagnostics is an important fracturing diagnosis technique to evaluate fracture locations and other downhole events in fracturing.The evaluation results are obtained by analyzing shut-in water hammer pressure signal.The field-sampled water hammer signal is often disturbed by noise interfer-ence.Noise interference exists in various pumping stages during water hammer diagnostics,with significantly different frequency range and energy distribution.Clarifying the differences in frequency range and energy distribution between effective water hammer signals and noise is the basis of setting specific filtering parameters,including filtering frequency range and energy thresholds.Filtering spe-cifically could separate the effective signal and noise,which is the key to ensuring the accuracy of water hammer diagnosis.As an emerging technique,there is a lack of research on the frequency range and energy distribution of effective signals in water hammer diagnostics.In this paper,the frequency range and energy distribution characteristics of field-sampled water hammer signals were clarified quantita-tively and qualitatively for the first time by a newly proposed comprehensive water hammer segmentation-energy analysis method.The water hammer signals were preprocessed and divided into three segments,including pre-shut-in,water hammer oscillation,and leak-off segment.Then,the three segments were analyzed by energy analysis and correlation analysis.The results indicated that,one aspect,the frequency range of water hammer oscillation spans from 0 to 0.65 Hz,considered as effective water hammer signal.The pre-shut-in and leak-off segment ranges from 0 to 0.35 Hz and 0e0.2 Hz respectively.Meanwhile,odd harmonics were manifested in water hammer oscillation segment,with the harmonic frequencies ranging approximately from 0.07 to 0.75 Hz.Whereas integer harmonics were observed in pre-shut-in segment,ranging from 6 to 40 Hz.The other aspect,the energy distribution of water hammer signals was analyzed in different frequency ranges.In 0e1 Hz,an exponential decay was observed in all three segments.In 1-100 Hz,a periodical energy distribution was observed in pre-shut-in segment,an exponential decay was observed in water hammer oscillation,and an even energy distri-bution was observed in leak-off segment.In 100-500 Hz,an even energy distribution was observed in those three segments,yet the highest magnitude was noted in leak-off segment.In this study,the effective frequency range and energy distribution characteristics of the field-sampled water hammer signals in different segments were sufficiently elucidated quantitatively and qualitatively for the first time,laying the groundwork for optimizing the filtering parameters of the field filtering models and advancing the accuracy of identifying downhole event locations.
