In order to realize the automatic recognition and classification of cracks with different depths,in this study,several deep convolutional neural networks including AlexNet,ResNet,and DenseNet were employed to identify...In order to realize the automatic recognition and classification of cracks with different depths,in this study,several deep convolutional neural networks including AlexNet,ResNet,and DenseNet were employed to identify and classify cracks at different depths and in various materials.An analysis process for the automatic classification of crack damage was presented.The image dataset used for model training was obtained from scanning experiments on aluminum and titanium alloy plates using an ultrasonic phased-array flaw detector.All models were trained and validated with the dataset;the proposed models were compared using classification precision and loss values.The results show that the automatic recognition and classification of crack depth can be realized by using the deep learning algorithm to analyze the ultrasonic phased array images,and the classification precision of DenseNet is the highest.The problem that ultrasonic damage identification relies on manual experience is solved.展开更多
Soil aggregate stability is a fundamental measure for evaluating soil structure.While numerous tests exist for assessing soil aggregate stability,ultrasonic agitation(UA)is widely recognized for its effectiveness.None...Soil aggregate stability is a fundamental measure for evaluating soil structure.While numerous tests exist for assessing soil aggregate stability,ultrasonic agitation(UA)is widely recognized for its effectiveness.Nonetheless,a significant limitation of UA is the lack of standardized methodologies and stability assessment criteria,resulting in inconsistency and incomparability across studies.Several critical factors influence the assessment of soil aggregate stability,including sample preparation(e.g.,drying,sieving,and settling duration),initial and final aggregate size classes,the definition of final energy form and its calculation,variations in instrumentation and laboratory procedures,and the absence of standardized criteria.Unlike some stability methods,UA produces a broad range of results,with dispersion energy varying significantly(0.5–13440 J g^(-1))across different soil and aggregate types due to divergent procedural settings.These settings encompass factors such as initial power and amplitude,temperature fluctuation,soil/water ratio,probe specification(diameter and insertion depth),and the choice of liquid used during the process.Furthermore,UA faces challenges related to limited reproducibility,raising doubts about its status as a standard stability assessment method.To address these issues,standardization through predefined procedures and stability criteria has the potential to transform UA into a precise and widely accepted method for both qualitative and quantitative assessments of soil stability.In this comprehensive review,we outline the challenges in standardizing UA,elucidate the factors contributing to dispersion energy variation,and offer practical recommendations to establish standardized protocols for UA in soil aggregate stability assessments.展开更多
In this work,the effect of ultrasonic vibration modes on the mechanical properties and relaxation of residual stress in 6061-T6 aluminum alloy was studied.A new ultrasonic vibration Johnson-Cook model was proposed,and...In this work,the effect of ultrasonic vibration modes on the mechanical properties and relaxation of residual stress in 6061-T6 aluminum alloy was studied.A new ultrasonic vibration Johnson-Cook model was proposed,and the relaxation and distribution of residual stress under ultrasonic vibration were predicted and analyzed using the finite element method(FEM).The mechanical properties of 6061-T6 aluminum alloy under different ultrasonic vibration modes were analyzed through experiments involving notched specimen tensile testing and scanning electron microscopy(SEM)analysis.The findings indicate that ultrasonic vibration treatment during deformation,unloading,and load-holding,as well as treatment with its natural ultrasonic frequency,can effectively release residual stress;however,treatment with its natural frequency has the highest rate of release up to 65.4%.Ultrasonic vibration treatment during deformation better inhibits fracture under the same conditions.The FEM results are in good agreement with the experimental results,and it can be used as a valid tool for predicting residual stress release under ultrasonic vibration.展开更多
In practical applications,noble metal doping is often used to prepare high performance gas sensors,but more noble metal doping will lead to higher preparation costs.In this study,CeO_(2)/ZnO-Pd with low palladium cont...In practical applications,noble metal doping is often used to prepare high performance gas sensors,but more noble metal doping will lead to higher preparation costs.In this study,CeO_(2)/ZnO-Pd with low palladium content was prepared by ultrasonic method with fast response and high selectivity for acetone sensing.With the same amount of palladium added,the selectivity coefficient of CeO_(2)/ZnO-Pd is 1.88 times higher than that of the stirred sensor.Compared with the pure PdO-doped CeO_(2)/ZnO-PdO material,the content of Pd in CeO_(2)/ZnO-PdO is about 30%of that in CeO_(2)/ZnO-PdO,but the selectivity coefficient for acetone is 2.56 times higher.The CeO_(2)/ZnO-Pd sensor has a higher response(22.54)to 50×10^(−6) acetone at 300℃and the selectivity coefficient is 2.57 times that of the CeO_(2)/ZnO sensor.The sensor has a sub-second response time(0.6 s)and still has a 2.36 response to 330×10^(−9) of acetone.Ultrasonic doping makes Pd particles smaller and increases the contact area with gas.Meanwhile,the composition of n-p-n heterojunction and the synergistic effect of Pd/PdO improve the sensor performance.It shows that ultrasonic Pd doping provides a way to improve the utilization rate of doped metals and prepare highly selective gas sensors.展开更多
A new method for optimizing a butterfly-shaped linear ultrasonic motor was proposed to maximize its mechanical output. The finite element analysis technology and response surface methodology were combined together to ...A new method for optimizing a butterfly-shaped linear ultrasonic motor was proposed to maximize its mechanical output. The finite element analysis technology and response surface methodology were combined together to realize the optimal design of the butterfly-shaped linear ultrasonic motor. First, the operation principle of the motor was introduced. Second, the finite element parameterized model of the stator of the motor was built using ANSYS parametric design language and some structure parameters of the stator were selected as design variables. Third, the sample points were selected in design variable space using latin hypercube Design. Through modal analysis and harmonic response analysis of the stator based on these sample points, the target responses were obtained. These sample points and response values were combined together to build a response surface model. Finally, the simplex method was used to find the optimal solution. The experimental results showed that many aspects of the design requirements of the butterfly-shaped linear ultrasonic motor have been fulfilled. The prototype motor fabricated based on the optimal design result exhibited considerably high dynamic performance, such as no-load speed of 873 ram/s, maximal thrust of 27.5 N, maximal efficiency of 43%, and thrust-weight ratio of 45.8.展开更多
SiC nanoparticles reinforced magnesium matrix composites were fabricated by ultrasonic method.The AZ91 alloy and SiC nanoparticles with the average diameter of 50 nm were used as the matrix alloy and the reinforcement...SiC nanoparticles reinforced magnesium matrix composites were fabricated by ultrasonic method.The AZ91 alloy and SiC nanoparticles with the average diameter of 50 nm were used as the matrix alloy and the reinforcement,respectively.The addition of nanoparticles was 0.1%,0.3%,and 0.5%(mass fraction) of the composites.The results of microstructural evaluation and mechanical properties indicate that the nanoparticles can be dispersed into magnesium alloys efficiently and uniformly with the aid of ultrasonic vibration.As compared with the matrix alloys,the grains of composites were refined and the mechanical properties of composites were improved significantly.The SEM and DSC analyses show that the SiC nanoparticles can act as the heterogeneous nucleation of α-Mg.Also,the strengthening mechanism responsible for the composites reinforced with SiC nanoparticles was discussed.展开更多
To find the optimal location for large-aperture telescopes is a goal of astronomy. Chinese Antarctic astronomy has begun to flourish in recent years, and it is an urgent need in basic astronomical work to measure and ...To find the optimal location for large-aperture telescopes is a goal of astronomy. Chinese Antarctic astronomy has begun to flourish in recent years, and it is an urgent need in basic astronomical work to measure and analyze the optical turbulence spatiotemporal distribution in the Antarctic region. We analyzed turbulence data measured by a mobile atmospheric parameter measurement system from 30 December 2013 to 10 February 2014 at Antarctic Taishan Station. Because there is a discrepancy between the refractive index structure constant Cn2 measured by an ultrasonic anemometer with a single-point temperature structure function method and by micro-thermometer, a new method to measure C,2 with a temperature spectrum method is proposed herein. Through comparing long-term continuous Cn2 data derived from ultrasonic anemometer with those via the new method and micro-thermometer, trend, magnitude and measured weak turbulence of-2× 10-16m-2/3 are generally satisfactory. The reason for the discrepancy in Cn2 measurement between the ultrasonic anemometer with the old method and micro-thermometer is investigated.展开更多
An example of using ultrasonic method to detect the compactness of complicated concrete-filled steel tube in certain high-rise building was discussed in this study.Because of the particularity of the complicated concr...An example of using ultrasonic method to detect the compactness of complicated concrete-filled steel tube in certain high-rise building was discussed in this study.Because of the particularity of the complicated concrete-filled steel tubular column,the plane detection method and embedded sounding pipe method were adopted in the process of effectively detecting the column.According to the results of the plane detection method and embedded sounding pipe method,the cementing status of steel tube and concrete can be concluded,which cannot be judged by the hammering method in the rectangular steel tube-reinforced concrete.展开更多
The effect of vibratory stress relief （VSR） is usually evaluated with the indirect method of observing the change of amplitude frequency response characteristics of structures. A new kind of evaluating method of VSR...The effect of vibratory stress relief （VSR） is usually evaluated with the indirect method of observing the change of amplitude frequency response characteristics of structures. A new kind of evaluating method of VSR based on the ultrasonic time-of-arrival method （UTM）, which can obtain the residual stress directly through measuring the propagation time of ultrasonic wave in the material, is presented. At first, the principle of the measuring method of residual stress based on UTM is analyzed. Then the measuring system of the method is described, which is in virtue of ultrasonic flaw detector and high-sampling-rate digital oscillograph. And a set of calibration system that contains a piece of standard specimen is also introduced. Experimental results prove the relation between the residual stress and the propagation time of ultrasonic in workpieces. Finally, the measuring and calibration systems are applied in evaluating the effect of VSR. The final test results show that the method is effective.展开更多
[Objectives]To study the optimal extraction process of total flavonoids in Rhodiola rosea L.,and further facilitate the development and utilization of Rhodiola rosea L. [Methods]With Rhodiola crenulata as raw material...[Objectives]To study the optimal extraction process of total flavonoids in Rhodiola rosea L.,and further facilitate the development and utilization of Rhodiola rosea L. [Methods]With Rhodiola crenulata as raw material,ethanol as extractant,ultrasonic extraction as the extraction method,the single factor method was first used for preliminary investigation of effect of ethanol volume fraction,solid-liquid ratio,extraction temperature and extraction time on the flavonoids extraction rate,and then the Box-Behnken response surface method was used to optimize the extraction process of total flavonoids in R. crenulata. [Results] The optimal extraction conditions: ethanol concentration of 72%;solid-liquid ratio of 1∶ 43; extraction temperature of 66℃; extraction time of 50 min. Under these conditions,the extraction rate of total flavonoids from R. crenulata was 2. 591%. [Conclusions] The results showed that the method of response surface was reasonable and feasible for the optimization of ultrasonic extraction of total flavonoids from R. crenulata.展开更多
The double-threshold method has been widely used in ultrasonic flow measurement to determine time-of-flight(TOF)due to its low cost and ease of implementation.Performance of this method is negatively affected by the c...The double-threshold method has been widely used in ultrasonic flow measurement to determine time-of-flight(TOF)due to its low cost and ease of implementation.Performance of this method is negatively affected by the cycle-skip phenomenon which occurs frequently under inconstant working conditions,especially varied fluid temperature.This paper proposes a method to suppress the phenomenon to facilitate reliable determination of TOF in ultrasonic flow measurement.First,the double-threshold method is used to generate a feature point to segment the signal.Second,based on the correlation coefficient and signal power,judgement factors of individual signal periods are calculated to determine signal onset.Finally,a valid zero crossing which has a constant lag from the onset is selected to determine the TOF.Thus,the cycle-skip phenomenon is suppressed.Two additional modifications are proposed to eliminate the influence of varied signal frequency and low sampling rate.The proposed method was validated by an experiment based on an ultrasonic water flow sensor.Results showed that the frequently appearing cycle-skip phenomenon can be successfully suppressed by the proposed method.展开更多
In order to optimize the wood internal quality detection and evaluation system and improve the comprehensive utilization rate of wood,this paper invented a set of log internal defect detection and visualization system...In order to optimize the wood internal quality detection and evaluation system and improve the comprehensive utilization rate of wood,this paper invented a set of log internal defect detection and visualization system by using the ultrasonic dry coupling agent method.The detection and visualization analysis of internal log defects were realized through log specimen test.The main conclusions show that the accuracy,reliability and practicability of the system for detecting the internal defects of log specimens have been effectively verified.The system can make the edge of the detected image smooth by interpolation algorithm,and the edge detection algorithm can be used to detect and reflect the location of internal defects of logs accurately.The content mentioned above has good application value for meeting the requirement of increasing demand for wood resources and improving the automation level of wood nondestructive testing instruments.展开更多
Taken kiwi fruit as raw material, this paper extracted kiwi fruit seed oil with ultrasonic-assisted enzyme, researched the influence of factors such as liquid-to-solid ratio, granularity, type of enzyme, ultrasonic po...Taken kiwi fruit as raw material, this paper extracted kiwi fruit seed oil with ultrasonic-assisted enzyme, researched the influence of factors such as liquid-to-solid ratio, granularity, type of enzyme, ultrasonic power, treating time, enzymolysis temperature, enzymolysis time, pH and enzyme additive on oil extraction, and optimized the extracting technology of kiwi fruit seed oil with response surface method. The result shows that the best technical parameter is: material granularity: 60, liquid-to-solid ratio: 1:10 (g/mL), ultrasonic power: 400 W, treating time: 30 min, enzyme amount: 2.50%, pH: 9.2, enzymolysis temperature: 53°C, enzymolysis time: 2.80 h;and the extracting ratio under such condition is 92.57%.展开更多
To preserve the environment for civilization,we should remove the pollutants like toxic dyes by friendly and cost efficacious method.In this study,the effect of surfactants or mixed surfactants on physicochemical,opti...To preserve the environment for civilization,we should remove the pollutants like toxic dyes by friendly and cost efficacious method.In this study,the effect of surfactants or mixed surfactants on physicochemical,optical and adsorption properties of ternary mixed oxide CeO_(2)-ZrO_(2)-Al_(2) O_3(CZA) are investigated.The ternary mixed oxide CZA was prepared by surfactants or mixed surfactants assisted ultrasonic coprecipitation method.The physicochemical and optical properties are estimated by different techniques like XRD,TEM,EDX,FTIR,S_(BET) and UV-Vis/DR.The CZA_T and CZA_C have hybrid shapes and high surface area.The adsorption properties of ternary mixed oxides adsorbents were characterized by sono-removing anionic dyes such as Congo red(CR) and Remazol red RB-133(RR).The different factors like contact time,different dye concentrations and temperatures also studied.The kinetics and isotherms applications showed that,the adsorption process was followed pseudo second order kinetics and the Freundlich isotherm model.Also,the adsorption is spontaneous and endothermic process through the thermodynamic study.Finally,the results showed that the ternary mixed oxide nano-adsorbent(CeO_(2)-ZrO_(2)-Al_(2) O_3) is promising and functional materials for anionic dye sweep from wastewater.展开更多
The strength curves of lightweight aggregate concrete （LWAC） were tested based on detecting LWAC with density of 1 400-1 900 kg/m3 and LWAC with strength grade of LC15-LC50 by rebound method and ultrasonic-rebound c...The strength curves of lightweight aggregate concrete （LWAC） were tested based on detecting LWAC with density of 1 400-1 900 kg/m3 and LWAC with strength grade of LC15-LC50 by rebound method and ultrasonic-rebound combined method.The results show that the common measured strength curves tested by above two methods can not satisfy the required accuracy of LWAC strength test.In addition,specified compressive strength curves of testing LWAC by rebound method and ultrasonic-rebound combined method are obtained,respectively.展开更多
The damage characteristic of particle reinforced metal matrix composite (PMMC) was studied by ultrasonic non-destructive evaluation method. After the sample was damaged induced by tensile load, the ultrasonic wave tha...The damage characteristic of particle reinforced metal matrix composite (PMMC) was studied by ultrasonic non-destructive evaluation method. After the sample was damaged induced by tensile load, the ultrasonic wave that propagated in the sample were collected. The damage parameter was defined by ultrasonic parameter and the wave signals were analyzed by correlation method. The results show that with the increase of tensile load, the damage parameter increases and the correlation coefficient decreases. The fracture section morphologies of PMMC under tensile load were observed by SEM. It is found that there are many concaves in the metal matrix. Therefore the damage evolution can be concluded. The initial damage is induced by void nucleation, growth and subsequent coalescence in the matrix or interface separation.展开更多
Background Ultrasonic tactile representation utilizes focused ultrasound to create tactile sensations on the bare skin of a user's hand that is not in contact with a device.This study is a preliminary investigatio...Background Ultrasonic tactile representation utilizes focused ultrasound to create tactile sensations on the bare skin of a user's hand that is not in contact with a device.This study is a preliminary investigation on whether different ultrasonic haptic rendering methods have an impact on the perceptual threshold.Methods This study conducted experiments with the adaptive step method to obtain participants'perceptual thresholds.We examine(1)whether different parts on the palm of the hand have different perceptual thresholds;(2)whether the perceptual threshold is different when the ultrasonic focus point is stationary and when it moves in different trajectories;(3)whether different moving speeds of the ultrasonic focus point have an influence on the perceptual threshold;and(4)whether the addition of a DC offset to the modulating wave has an impact on the perceptual threshold.Results The results show that the center of the palm is more sensitive to ultrasonic haptics than the fingertip;compared with a fast-moving focus point,the palm is more sensitive to a stationary and slow-moving focus point.When the modulating wave has a DC offset,the palm is sensitive to a much smaller modulation amplitude.Conclusion For the future ultrasonic tactile representation systems,dynamic adjustment of intensity is required to compensate the difference in perceptual thresholds under different rendering methods to achieve more realistic ultrasonic haptics.展开更多
The operating principle of a lead screw linear ultrasonic motor using bending vibration modes is analyzed. The simplified beam bending vibration model is used to analyze the dynamics characteristics of the motor. Moti...The operating principle of a lead screw linear ultrasonic motor using bending vibration modes is analyzed. The simplified beam bending vibration model is used to analyze the dynamics characteristics of the motor. Motion trajectory equations are derived for driving points of the stator. The motor operation and driving mechanisms are investigated. The vibration modes and the construction of the motor are analyzed by using the finite element method （FEM）. A prototype motor is built and its stator dimension is 13 mm × 13 mm× 30 mm. The motor is experimentally characterized and the maximum output force of 5- 2 N is obtained.展开更多
Al/Co co-doped α-Ni（OH）2 samples were prepared by either ultrasonic co-precipitation method （Sample B） or co-precipitation method （Sample A）. The crystal structure and particle size distribution of the prepared...Al/Co co-doped α-Ni（OH）2 samples were prepared by either ultrasonic co-precipitation method （Sample B） or co-precipitation method （Sample A）. The crystal structure and particle size distribution of the prepared samples were examined by X-ray diffraction （XRD） and laser particle size analyzer, respectively. The results show that Sample B has more crystalline defects and smaller average diameter than Sample A. The cyclic voltammetry and electrochemical impedance spectroscopy measurements indicate that Sample B has better electrochemical performance than Sample A, such as better reaction reversibility, lower charge-transfer resistance and better cyclic stability. Proton diffusion coefficient of Sample B is 1.96×10-10cm2/s, which is two times as large as that （9.78×10-11cm2/s） of Sample A. The charge-discharge tests show that the discharge capacity （308 mA·h/g） of Sample B is 25 mA·h/g higher than that of Sample A （283 mA·h/g）.展开更多
Phase aberration correction for medical ultrasound systems has attracted a great deal of attention. Since phased array techniques are now widely employed for industrial non-destructive testing （NDT） applications in ...Phase aberration correction for medical ultrasound systems has attracted a great deal of attention. Since phased array techniques are now widely employed for industrial non-destructive testing （NDT） applications in various fields, the problem of phase aberrations in the process of NDT testing is considered. The technique of cross-covariance for phase aberration correction is presented. The performance of the technique for phase aberration correction is tested by means of echo signals obtained in practical non-destructive testing experiment. The results show that the technique has the better accuracy of phase correction.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52222504 and 52241502)the Natural Science Talents Foundation of Shaanxi Province(No.2021JC-04).
文摘In order to realize the automatic recognition and classification of cracks with different depths,in this study,several deep convolutional neural networks including AlexNet,ResNet,and DenseNet were employed to identify and classify cracks at different depths and in various materials.An analysis process for the automatic classification of crack damage was presented.The image dataset used for model training was obtained from scanning experiments on aluminum and titanium alloy plates using an ultrasonic phased-array flaw detector.All models were trained and validated with the dataset;the proposed models were compared using classification precision and loss values.The results show that the automatic recognition and classification of crack depth can be realized by using the deep learning algorithm to analyze the ultrasonic phased array images,and the classification precision of DenseNet is the highest.The problem that ultrasonic damage identification relies on manual experience is solved.
基金support from the National Natural Science Foundation of China(No.42177299)the Guangdong Province Key Areas Research and Development Plan Project,China—Key Preparation Technology and Application of Green and Efficient Agricultural Input Controlled-Release Materials(No.2023B0202080002)。
文摘Soil aggregate stability is a fundamental measure for evaluating soil structure.While numerous tests exist for assessing soil aggregate stability,ultrasonic agitation(UA)is widely recognized for its effectiveness.Nonetheless,a significant limitation of UA is the lack of standardized methodologies and stability assessment criteria,resulting in inconsistency and incomparability across studies.Several critical factors influence the assessment of soil aggregate stability,including sample preparation(e.g.,drying,sieving,and settling duration),initial and final aggregate size classes,the definition of final energy form and its calculation,variations in instrumentation and laboratory procedures,and the absence of standardized criteria.Unlike some stability methods,UA produces a broad range of results,with dispersion energy varying significantly(0.5–13440 J g^(-1))across different soil and aggregate types due to divergent procedural settings.These settings encompass factors such as initial power and amplitude,temperature fluctuation,soil/water ratio,probe specification(diameter and insertion depth),and the choice of liquid used during the process.Furthermore,UA faces challenges related to limited reproducibility,raising doubts about its status as a standard stability assessment method.To address these issues,standardization through predefined procedures and stability criteria has the potential to transform UA into a precise and widely accepted method for both qualitative and quantitative assessments of soil stability.In this comprehensive review,we outline the challenges in standardizing UA,elucidate the factors contributing to dispersion energy variation,and offer practical recommendations to establish standardized protocols for UA in soil aggregate stability assessments.
基金Project(51775480)supported by the National Natural Science Foundation of ChinaProjects(E2018203143,E2022203050)supported by the Natural Science Foundation of Hebei Province,China。
文摘In this work,the effect of ultrasonic vibration modes on the mechanical properties and relaxation of residual stress in 6061-T6 aluminum alloy was studied.A new ultrasonic vibration Johnson-Cook model was proposed,and the relaxation and distribution of residual stress under ultrasonic vibration were predicted and analyzed using the finite element method(FEM).The mechanical properties of 6061-T6 aluminum alloy under different ultrasonic vibration modes were analyzed through experiments involving notched specimen tensile testing and scanning electron microscopy(SEM)analysis.The findings indicate that ultrasonic vibration treatment during deformation,unloading,and load-holding,as well as treatment with its natural ultrasonic frequency,can effectively release residual stress;however,treatment with its natural frequency has the highest rate of release up to 65.4%.Ultrasonic vibration treatment during deformation better inhibits fracture under the same conditions.The FEM results are in good agreement with the experimental results,and it can be used as a valid tool for predicting residual stress release under ultrasonic vibration.
基金Project(2023JJ10005)supported by the Natural Science Foundation of Hunan Province,ChinaProjects(51772082,51804106)supported by the National Natural Science Foundation of China。
文摘In practical applications,noble metal doping is often used to prepare high performance gas sensors,but more noble metal doping will lead to higher preparation costs.In this study,CeO_(2)/ZnO-Pd with low palladium content was prepared by ultrasonic method with fast response and high selectivity for acetone sensing.With the same amount of palladium added,the selectivity coefficient of CeO_(2)/ZnO-Pd is 1.88 times higher than that of the stirred sensor.Compared with the pure PdO-doped CeO_(2)/ZnO-PdO material,the content of Pd in CeO_(2)/ZnO-PdO is about 30%of that in CeO_(2)/ZnO-PdO,but the selectivity coefficient for acetone is 2.56 times higher.The CeO_(2)/ZnO-Pd sensor has a higher response(22.54)to 50×10^(−6) acetone at 300℃and the selectivity coefficient is 2.57 times that of the CeO_(2)/ZnO sensor.The sensor has a sub-second response time(0.6 s)and still has a 2.36 response to 330×10^(−9) of acetone.Ultrasonic doping makes Pd particles smaller and increases the contact area with gas.Meanwhile,the composition of n-p-n heterojunction and the synergistic effect of Pd/PdO improve the sensor performance.It shows that ultrasonic Pd doping provides a way to improve the utilization rate of doped metals and prepare highly selective gas sensors.
基金Projects(51275235, 50975135) supported by the National Natural Science Foundation of ChinaProject(U0934004) supported by the Natural Science Foundation of Guangdong Province, ChinaProject(2011CB707602) supported by the National Basic Research Program of China
文摘A new method for optimizing a butterfly-shaped linear ultrasonic motor was proposed to maximize its mechanical output. The finite element analysis technology and response surface methodology were combined together to realize the optimal design of the butterfly-shaped linear ultrasonic motor. First, the operation principle of the motor was introduced. Second, the finite element parameterized model of the stator of the motor was built using ANSYS parametric design language and some structure parameters of the stator were selected as design variables. Third, the sample points were selected in design variable space using latin hypercube Design. Through modal analysis and harmonic response analysis of the stator based on these sample points, the target responses were obtained. These sample points and response values were combined together to build a response surface model. Finally, the simplex method was used to find the optimal solution. The experimental results showed that many aspects of the design requirements of the butterfly-shaped linear ultrasonic motor have been fulfilled. The prototype motor fabricated based on the optimal design result exhibited considerably high dynamic performance, such as no-load speed of 873 ram/s, maximal thrust of 27.5 N, maximal efficiency of 43%, and thrust-weight ratio of 45.8.
基金Project(2007CB613706) supported by the National Basic Research Program of ChinaProject(00900054R4001) supported by Innovation Project for Talents of BJUTProject(00900054K4004) supported by the Science Foundation for Youths of BJUT
文摘SiC nanoparticles reinforced magnesium matrix composites were fabricated by ultrasonic method.The AZ91 alloy and SiC nanoparticles with the average diameter of 50 nm were used as the matrix alloy and the reinforcement,respectively.The addition of nanoparticles was 0.1%,0.3%,and 0.5%(mass fraction) of the composites.The results of microstructural evaluation and mechanical properties indicate that the nanoparticles can be dispersed into magnesium alloys efficiently and uniformly with the aid of ultrasonic vibration.As compared with the matrix alloys,the grains of composites were refined and the mechanical properties of composites were improved significantly.The SEM and DSC analyses show that the SiC nanoparticles can act as the heterogeneous nucleation of α-Mg.Also,the strengthening mechanism responsible for the composites reinforced with SiC nanoparticles was discussed.
基金supported by the National Natural Science Foundation of China (Grant no. 41275020)supported by the Chinese Polar Environment Comprehensive Investigation & Assessment Programs (Grant nos. CHINARE2013-02-03, CHINARE2014-02 -03, and CHINARE201502-03)+1 种基金the Polar Science Innovation Fund for Young Scientists of Polar Research Institute of China (Grant no. CX20130201)the Shanghai Natural Science Foundation (Grant no. 14ZR1444100).
文摘To find the optimal location for large-aperture telescopes is a goal of astronomy. Chinese Antarctic astronomy has begun to flourish in recent years, and it is an urgent need in basic astronomical work to measure and analyze the optical turbulence spatiotemporal distribution in the Antarctic region. We analyzed turbulence data measured by a mobile atmospheric parameter measurement system from 30 December 2013 to 10 February 2014 at Antarctic Taishan Station. Because there is a discrepancy between the refractive index structure constant Cn2 measured by an ultrasonic anemometer with a single-point temperature structure function method and by micro-thermometer, a new method to measure C,2 with a temperature spectrum method is proposed herein. Through comparing long-term continuous Cn2 data derived from ultrasonic anemometer with those via the new method and micro-thermometer, trend, magnitude and measured weak turbulence of-2× 10-16m-2/3 are generally satisfactory. The reason for the discrepancy in Cn2 measurement between the ultrasonic anemometer with the old method and micro-thermometer is investigated.
文摘An example of using ultrasonic method to detect the compactness of complicated concrete-filled steel tube in certain high-rise building was discussed in this study.Because of the particularity of the complicated concrete-filled steel tubular column,the plane detection method and embedded sounding pipe method were adopted in the process of effectively detecting the column.According to the results of the plane detection method and embedded sounding pipe method,the cementing status of steel tube and concrete can be concluded,which cannot be judged by the hammering method in the rectangular steel tube-reinforced concrete.
基金This project is supported by National Natural Science Foundation of China(No.50305036).
文摘The effect of vibratory stress relief （VSR） is usually evaluated with the indirect method of observing the change of amplitude frequency response characteristics of structures. A new kind of evaluating method of VSR based on the ultrasonic time-of-arrival method （UTM）, which can obtain the residual stress directly through measuring the propagation time of ultrasonic wave in the material, is presented. At first, the principle of the measuring method of residual stress based on UTM is analyzed. Then the measuring system of the method is described, which is in virtue of ultrasonic flaw detector and high-sampling-rate digital oscillograph. And a set of calibration system that contains a piece of standard specimen is also introduced. Experimental results prove the relation between the residual stress and the propagation time of ultrasonic in workpieces. Finally, the measuring and calibration systems are applied in evaluating the effect of VSR. The final test results show that the method is effective.
基金Supported by Tibetan 13th Five-Year Agricultural Product Processing and Product Development Project
文摘[Objectives]To study the optimal extraction process of total flavonoids in Rhodiola rosea L.,and further facilitate the development and utilization of Rhodiola rosea L. [Methods]With Rhodiola crenulata as raw material,ethanol as extractant,ultrasonic extraction as the extraction method,the single factor method was first used for preliminary investigation of effect of ethanol volume fraction,solid-liquid ratio,extraction temperature and extraction time on the flavonoids extraction rate,and then the Box-Behnken response surface method was used to optimize the extraction process of total flavonoids in R. crenulata. [Results] The optimal extraction conditions: ethanol concentration of 72%;solid-liquid ratio of 1∶ 43; extraction temperature of 66℃; extraction time of 50 min. Under these conditions,the extraction rate of total flavonoids from R. crenulata was 2. 591%. [Conclusions] The results showed that the method of response surface was reasonable and feasible for the optimization of ultrasonic extraction of total flavonoids from R. crenulata.
基金Project supported by the Science Fund for Creative Research Groups of National Natural Science Foundation of China(No.51821093)。
文摘The double-threshold method has been widely used in ultrasonic flow measurement to determine time-of-flight(TOF)due to its low cost and ease of implementation.Performance of this method is negatively affected by the cycle-skip phenomenon which occurs frequently under inconstant working conditions,especially varied fluid temperature.This paper proposes a method to suppress the phenomenon to facilitate reliable determination of TOF in ultrasonic flow measurement.First,the double-threshold method is used to generate a feature point to segment the signal.Second,based on the correlation coefficient and signal power,judgement factors of individual signal periods are calculated to determine signal onset.Finally,a valid zero crossing which has a constant lag from the onset is selected to determine the TOF.Thus,the cycle-skip phenomenon is suppressed.Two additional modifications are proposed to eliminate the influence of varied signal frequency and low sampling rate.The proposed method was validated by an experiment based on an ultrasonic water flow sensor.Results showed that the frequently appearing cycle-skip phenomenon can be successfully suppressed by the proposed method.
文摘In order to optimize the wood internal quality detection and evaluation system and improve the comprehensive utilization rate of wood,this paper invented a set of log internal defect detection and visualization system by using the ultrasonic dry coupling agent method.The detection and visualization analysis of internal log defects were realized through log specimen test.The main conclusions show that the accuracy,reliability and practicability of the system for detecting the internal defects of log specimens have been effectively verified.The system can make the edge of the detected image smooth by interpolation algorithm,and the edge detection algorithm can be used to detect and reflect the location of internal defects of logs accurately.The content mentioned above has good application value for meeting the requirement of increasing demand for wood resources and improving the automation level of wood nondestructive testing instruments.
文摘Taken kiwi fruit as raw material, this paper extracted kiwi fruit seed oil with ultrasonic-assisted enzyme, researched the influence of factors such as liquid-to-solid ratio, granularity, type of enzyme, ultrasonic power, treating time, enzymolysis temperature, enzymolysis time, pH and enzyme additive on oil extraction, and optimized the extracting technology of kiwi fruit seed oil with response surface method. The result shows that the best technical parameter is: material granularity: 60, liquid-to-solid ratio: 1:10 (g/mL), ultrasonic power: 400 W, treating time: 30 min, enzyme amount: 2.50%, pH: 9.2, enzymolysis temperature: 53°C, enzymolysis time: 2.80 h;and the extracting ratio under such condition is 92.57%.
文摘To preserve the environment for civilization,we should remove the pollutants like toxic dyes by friendly and cost efficacious method.In this study,the effect of surfactants or mixed surfactants on physicochemical,optical and adsorption properties of ternary mixed oxide CeO_(2)-ZrO_(2)-Al_(2) O_3(CZA) are investigated.The ternary mixed oxide CZA was prepared by surfactants or mixed surfactants assisted ultrasonic coprecipitation method.The physicochemical and optical properties are estimated by different techniques like XRD,TEM,EDX,FTIR,S_(BET) and UV-Vis/DR.The CZA_T and CZA_C have hybrid shapes and high surface area.The adsorption properties of ternary mixed oxides adsorbents were characterized by sono-removing anionic dyes such as Congo red(CR) and Remazol red RB-133(RR).The different factors like contact time,different dye concentrations and temperatures also studied.The kinetics and isotherms applications showed that,the adsorption process was followed pseudo second order kinetics and the Freundlich isotherm model.Also,the adsorption is spontaneous and endothermic process through the thermodynamic study.Finally,the results showed that the ternary mixed oxide nano-adsorbent(CeO_(2)-ZrO_(2)-Al_(2) O_3) is promising and functional materials for anionic dye sweep from wastewater.
文摘The strength curves of lightweight aggregate concrete （LWAC） were tested based on detecting LWAC with density of 1 400-1 900 kg/m3 and LWAC with strength grade of LC15-LC50 by rebound method and ultrasonic-rebound combined method.The results show that the common measured strength curves tested by above two methods can not satisfy the required accuracy of LWAC strength test.In addition,specified compressive strength curves of testing LWAC by rebound method and ultrasonic-rebound combined method are obtained,respectively.
基金Project(104014) supported by Fok' Ying Tong Education Foundation, China Project(05B008) supported by the Scientific Research Fund of Hunan Provincial Education Department, China
文摘The damage characteristic of particle reinforced metal matrix composite (PMMC) was studied by ultrasonic non-destructive evaluation method. After the sample was damaged induced by tensile load, the ultrasonic wave that propagated in the sample were collected. The damage parameter was defined by ultrasonic parameter and the wave signals were analyzed by correlation method. The results show that with the increase of tensile load, the damage parameter increases and the correlation coefficient decreases. The fracture section morphologies of PMMC under tensile load were observed by SEM. It is found that there are many concaves in the metal matrix. Therefore the damage evolution can be concluded. The initial damage is induced by void nucleation, growth and subsequent coalescence in the matrix or interface separation.
基金the National Key Research and Development Program(2016YFB1001304)and the National Natural Science Foundation of China(61631010).
文摘Background Ultrasonic tactile representation utilizes focused ultrasound to create tactile sensations on the bare skin of a user's hand that is not in contact with a device.This study is a preliminary investigation on whether different ultrasonic haptic rendering methods have an impact on the perceptual threshold.Methods This study conducted experiments with the adaptive step method to obtain participants'perceptual thresholds.We examine(1)whether different parts on the palm of the hand have different perceptual thresholds;(2)whether the perceptual threshold is different when the ultrasonic focus point is stationary and when it moves in different trajectories;(3)whether different moving speeds of the ultrasonic focus point have an influence on the perceptual threshold;and(4)whether the addition of a DC offset to the modulating wave has an impact on the perceptual threshold.Results The results show that the center of the palm is more sensitive to ultrasonic haptics than the fingertip;compared with a fast-moving focus point,the palm is more sensitive to a stationary and slow-moving focus point.When the modulating wave has a DC offset,the palm is sensitive to a much smaller modulation amplitude.Conclusion For the future ultrasonic tactile representation systems,dynamic adjustment of intensity is required to compensate the difference in perceptual thresholds under different rendering methods to achieve more realistic ultrasonic haptics.
基金Supported by the National Natural Science Foundation of China(50575103, 50735002)~~
文摘The operating principle of a lead screw linear ultrasonic motor using bending vibration modes is analyzed. The simplified beam bending vibration model is used to analyze the dynamics characteristics of the motor. Motion trajectory equations are derived for driving points of the stator. The motor operation and driving mechanisms are investigated. The vibration modes and the construction of the motor are analyzed by using the finite element method （FEM）. A prototype motor is built and its stator dimension is 13 mm × 13 mm× 30 mm. The motor is experimentally characterized and the maximum output force of 5- 2 N is obtained.
基金Project (10774030) supported by the National Natural Science Foundation of ChinaProject (2008J1-C161) supported by the Science and Technology Program of Guangzhou City of China
文摘Al/Co co-doped α-Ni（OH）2 samples were prepared by either ultrasonic co-precipitation method （Sample B） or co-precipitation method （Sample A）. The crystal structure and particle size distribution of the prepared samples were examined by X-ray diffraction （XRD） and laser particle size analyzer, respectively. The results show that Sample B has more crystalline defects and smaller average diameter than Sample A. The cyclic voltammetry and electrochemical impedance spectroscopy measurements indicate that Sample B has better electrochemical performance than Sample A, such as better reaction reversibility, lower charge-transfer resistance and better cyclic stability. Proton diffusion coefficient of Sample B is 1.96×10-10cm2/s, which is two times as large as that （9.78×10-11cm2/s） of Sample A. The charge-discharge tests show that the discharge capacity （308 mA·h/g） of Sample B is 25 mA·h/g higher than that of Sample A （283 mA·h/g）.
基金National Natural Science Foundation of China(No.61201412)Ntural Science Foundation of Shanxi Province(No.2012021011-5)
文摘Phase aberration correction for medical ultrasound systems has attracted a great deal of attention. Since phased array techniques are now widely employed for industrial non-destructive testing （NDT） applications in various fields, the problem of phase aberrations in the process of NDT testing is considered. The technique of cross-covariance for phase aberration correction is presented. The performance of the technique for phase aberration correction is tested by means of echo signals obtained in practical non-destructive testing experiment. The results show that the technique has the better accuracy of phase correction.
