The method using pulsed eddy currents to determine the thickness of a conduction plate is extended to enable the simultaneous measurement of the plate thickness and material properties. For optimal performance, a prob...The method using pulsed eddy currents to determine the thickness of a conduction plate is extended to enable the simultaneous measurement of the plate thickness and material properties. For optimal performance, a probe must be designed depending on the thickness range that should be accessible. The need for a calibration of the material properties of a conducting plate to enable the measurement of its thickness has been removed. All that is needed is a probe with known dimensions and suitable hardware to create a current pulse and measure a transient magnetic induction.展开更多
Horizontal gas-liquid two-phase flows widely exist in chemical engineering,oil/gas production and other important industrial processes.Slug flow pattern is the main form of horizontal gas-liquid flows and characterize...Horizontal gas-liquid two-phase flows widely exist in chemical engineering,oil/gas production and other important industrial processes.Slug flow pattern is the main form of horizontal gas-liquid flows and characterized by intermittent motion of film region and slug region.This work aims to develop the ultrasonic Doppler method to realize the simultaneous measurement of the velocity profile and liquid film thickness of slug flow.A single-frequency single-channel transducer is adopted in the design of the field-programmable gate array based ultrasonic Doppler system.A multiple echo repetition technology is used to improve the temporal-spatial resolution for the velocity profile.An experiment of horizontal gas-liquid two-phase flow is implemented in an acrylic pipe with an inner diameter of 20 mm.Considering the aerated characteristics of the liquid slug,slug flow is divided into low-aerated slug flow,high-aerated slug flow and pseudo slug flow.The temporal-spatial velocity distributions of the three kinds of slug flows are reconstructed by using the ultrasonic velocity profile measurement.The evolution characteristics of the average velocity profile in slug flows are investigated.A novel method is proposed to derive the liquid film thickness based on the instantaneous velocity profile.The liquid film thickness can be effectively measured by detecting the position and the size of the bubbles nearly below the elongated gas bubble.Compared with the time of flight method,the film thickness measured by the Doppler system shows a higher accuracy as a bubble layer occurs in the film region.The effect of the gas distribution on the film thickness is uncovered in three kinds of slug flows.展开更多
AIM:To access the agreement of intraocular pressure(IOP)values obtained from biomechanically corrected tonometer[Corvis ST(CST)],non-contact tonometer(NCT),and Goldmann applanation tonometer(GAT)in children with NCT m...AIM:To access the agreement of intraocular pressure(IOP)values obtained from biomechanically corrected tonometer[Corvis ST(CST)],non-contact tonometer(NCT),and Goldmann applanation tonometer(GAT)in children with NCT measured-IOP(NCT-IOP)values of 22 mm Hg or more,and related factors.METHODS:A total of 51 eyes with NCT-IOP≥22 mm Hg in children aged 7 to 14y were examined and IOP was measured by CST,NCT,and GAT.Based on GAT measured IOP(GAT-IOP),ocular hypertension(OHT)group(≥22 mm Hg,24 eyes)and the non-OHT group(<22 mm Hg,27 eyes)were defined.We compared the agreement of the three measurements,i.e.,CST measured IOP(CST-IOP),GAT-IOP,and NCT-IOP,and further analyzed the correlation between the differences in tonometry readings,central corneal thickness(CCT),axial length(AL),optic disc rim volume,and age.RESULTS:Compared with the OHT group,thicker CCT,larger rim volume,and higher differences between NCTIOP and GAT-IOP,were found in the non-OHT group.The differences between CST-IOP and GAT-IOP were lower than the differences between NCT-IOP and GAT-IOP in both groups.The mean differences in CST-IOP and GAT-IOP were 1.26 mm Hg(95%limit of agreement ranged from 0.1 to 2.41 mm Hg,OHT group)and 1.20 mm Hg(95%limit of agreement ranged from-0.5 to 3.00 mm Hg,non-OHT group),and the mean differences in NCT and GAT were 3.90 mm Hg(95%limit of agreement ranged from-0.19 to 9.70 mm Hg,OHT group)and 6.00 mm Hg(95%limit of agreement ranged from 1.50 to 10.50 mm Hg,non-OHT group).The differences between CST-IOP and GAT-IOP were not related to CCT,age,and AL in both groups;while the differences between NCT-IOP and GAT-IOP were related to CCT in the OHT group(r=0.93,P<0.001)and to CCT and AL in the non-OHT group(r=0.66,P<0.001,r=-0.81,P<0.001).CONCLUSION:The accuracy of NCT in the diagnosis of pediatric OHT is low.The agreement of CST-IOP and GATIOP was significantly higher in children with and without OHT than in those with NCT-IOP and GAT-IOP.Therefore,CST can be used as a good alternative for IOP measurement in children.The impacts of CCT and AL on NCT measurement need to be fully considered when managing childhood IOP.展开更多
The special ultrasonic testing system has been developed for thickness measurement of plasma sprayed coatings. The ultrasonic immersion method was used to obtain stable coupling condition and avoid other disadvantages...The special ultrasonic testing system has been developed for thickness measurement of plasma sprayed coatings. The ultrasonic immersion method was used to obtain stable coupling condition and avoid other disadvantages of contact method. Spherical acoustic lens were designed to focus ultrasonic beam so as to improve beam directivity and concentrate ultrasonic energy. To increase testing precision and avoid mussy wave signals, moderate pulse width and frequency of the transducer has been selected. The displacement of transducer in X-Y-Z directions was precisely manipulated by step-controlled system to insure the accuracy of focus length and repetition of measurement. Optimized testing conditions (with the transducer of center frequency of 10 MHz and crystal diameter of 8 mm, focus length of 9.5 mm, diameter of focal column of 0. 1 mm and length of focal column of 0.27 mm) were selected to determine the thickness between 285 -414 μm of ZrO2 coatings plasma sprayed on the nickel based superalloy. The frequency interval of the periodic extremums in ultrasonic power spectra decreases with increasing coating thickness. The ultrasonic results accord with those of metallographical method.展开更多
In eddy current testing, the law of attenuation of eddy current(EC) is of great concern. In conductive half space under the excitation of uniform magnetic field, the EC density decreases exponentially in the depth dir...In eddy current testing, the law of attenuation of eddy current(EC) is of great concern. In conductive half space under the excitation of uniform magnetic field, the EC density decreases exponentially in the depth direction. However, in conductor with finite thickness tested by coil, the distribution of EC in the depth direction is more complicated. This paper studies the characteristics of EC attenuation in metallic plate of finite thickness. Simulation results show that there is an EC reflection at the bottom of plate, which changes the law of EC attenuation. A new concept, namely the equivalent attenuation coefficient, is proposed to quantify the speed of EC attenuation. The characteristics of EC attenuation are utilized to explain the nonmonotonic relation between coil voltage and plate thickness. Procedure of selecting frequency is discussed. Thereafter, measurement of plate thickness is carried out and accurate result is obtained.展开更多
A novel thickness measurement method for surface insulation coating of silicon steel based on NIR spectrometry is explored.The NIR spectra of insulation coating of silicon steel were collected by acousto-optic tunable...A novel thickness measurement method for surface insulation coating of silicon steel based on NIR spectrometry is explored.The NIR spectra of insulation coating of silicon steel were collected by acousto-optic tunable filter(AOTF) NIR spectrometer.To make full use of the effective information of NIR spectral data,discrete binary particle swarm optimization(DBPSO) algorithm was used to select the optimal wavelength variates.The new spectral data,composed of absorbance at selected wavelengths,were used to create the thickness quantitative analysis model by kernel partial least squares(KPLS) algorithm coupled with Boosting.The results of contrast experiments showed that the Boosting-KPLS model could efficiently improve the analysis accuracy and speed.It indicates that Boosting-KPLS is a more accurate and robust analysis method than KPLS for NIR spectral analysis.The maximal and minimal absolute error of 30 testing samples is respectively-0.02 μm and 0.19 μm,and the maximal relative error is 14.23%.These analysis results completely meet the practical measurement need.展开更多
AIM:To evaluate the central corneal thickness(CCT)measurements of premature infantsMETHODS:The premature infants who were born between 25-34wk of gestational age(GA)were retrieved for the study.All CCT measurements we...AIM:To evaluate the central corneal thickness(CCT)measurements of premature infantsMETHODS:The premature infants who were born between 25-34wk of gestational age(GA)were retrieved for the study.All CCT measurements were performed within the first 2d of their life under topical anesthesia by using an ultrasonic pachymeter.RESULTS:The mean CCT of 200 eyes was 647.79±63.94μm.The mean CCT of the right and left eyes were similar(647.30±64.72μm and 648.29±63.47μm consecutively).The mean CCT of the girls was 642.08±54.89μm and the boys was 653.07±71.14μm,with no statistically significant difference(P】0.05).But there was a negative correlation of the CCT with GA and birth weight(BW)(P【0.01).CONCLUSION:The CCT values of premature babies were negatively correlated with GA and BW.展开更多
Elasticity is of profound significance to evaluating the function of a biological soft tissue. When the elasticity of a tissue is macroscopically changed, it means that the biological function of the tissue is abnorma...Elasticity is of profound significance to evaluating the function of a biological soft tissue. When the elasticity of a tissue is macroscopically changed, it means that the biological function of the tissue is abnormal and some disease or injury may occur. In the present work, an elastometer is developed to measure the elasticity of biological soft tissues. The measurement is based on the indentation method and the force is measured by the bending of the cantilever. The force-indentation data of the soft tissue is experimentally measured by this elastometer and Young's modulus of the tissue is calculated using the Hertz-Sneddon model. For comparison, a numerical model for the indentation method is established using the finite element method. The difference between the actual modulus and the measured modulus is discussed. The effect of the thickness of the specimen on the measurement is investigated. Young's moduli of beef, porcine liver and porcine kidney are experimentally measured. The results indicate that our elastometer is effective in measuring Young's modulus of a soft tissue quantitatively.展开更多
For a ship in service,seawater corrosion is unavoidable. In order to ensure navigation safety and master the steel plate thickness in service ship,thickness of the ship steel plate must be tested periodically by a sci...For a ship in service,seawater corrosion is unavoidable. In order to ensure navigation safety and master the steel plate thickness in service ship,thickness of the ship steel plate must be tested periodically by a scientific method. After consideration of an actual situation of thickness measurement,the bearing mechanism of ultrasonic thickness meter probe has been designed on the basis of wall-climbing robot,and preliminary experiments have been carried out. The device is mainly used for thickness measurement of a large area of ship hull plate when the docking ship has been sandblasted. Efficiency and safety can be improved to finish thickness measurement by using the device.展开更多
Through optimizing the eletric parameters of the resistance-capacitance (R-C)oscillation,a measuring instrument is developed for measurement of EHL oil filmthickness.Actual measurement was made with space bearings and...Through optimizing the eletric parameters of the resistance-capacitance (R-C)oscillation,a measuring instrument is developed for measurement of EHL oil filmthickness.Actual measurement was made with space bearings and actual measurements arein good agreement with theoretical calculations.展开更多
The paper briefly introduces the Contamination Line Method for foil thickness measurement in transmission electron microscopy and compares it with four conventional methods: the convergent beam diffraction method, the...The paper briefly introduces the Contamination Line Method for foil thickness measurement in transmission electron microscopy and compares it with four conventional methods: the convergent beam diffraction method, the contamination spot method, the methods hased on characteristic X-ray emission and continuous X-ray emission on the application, aperation and accuracy etc.展开更多
Several methods for investigating the thickness uniformity of polymer thin films are presented as well as their measurement principles. A comparison of these experimental methods is given.The cylindrical lightwave ref...Several methods for investigating the thickness uniformity of polymer thin films are presented as well as their measurement principles. A comparison of these experimental methods is given.The cylindrical lightwave reflection method is found to can obtain the thickness distribution along a certain direction.It is a simple and suitable method to evaluate the film thickness uniformity.展开更多
Luquire et al. ' s impedance change model of a rectangular cross section probe coil above a structure with an arbitrary number of parallel layers was used to study the principle of measuring thicknesses of multi-l...Luquire et al. ' s impedance change model of a rectangular cross section probe coil above a structure with an arbitrary number of parallel layers was used to study the principle of measuring thicknesses of multi-layered structures in terms of eddy current testing voltage measurements. An experimental system for multi-layered thickness measurement was developed and several fitting models to formulate the relationships between detected impedance/voltage measurements and thickness are put forward using least square method. The determination of multi-layered thicknesses was investigated after inversing the voltage outputs of the detecting system. The best fitting and inversion models are presented.展开更多
In Quepos,Pacific of Costa Rica,it was finished on 2010 the first phase of a marina,including two mix breakwaters,with rubble mound(rocks and concrete units),and 25 circular steel sheet piles cofferdam cells,filled wi...In Quepos,Pacific of Costa Rica,it was finished on 2010 the first phase of a marina,including two mix breakwaters,with rubble mound(rocks and concrete units),and 25 circular steel sheet piles cofferdam cells,filled with sand and gravel.The maintenance plan,considers tracking sheet pile corrosion,comparing'actual'against expected rates,checking structural limits,and programming countermeasures if accelerated corrosion is identified.Specific control sections,along the breakwaters,both inside and outside the basin,were established.In each section,thicknesses were measured every meter from the top of the steel cell to seabed using an ultrasonic equipment,and an underwater transducer.Both land crew,and divers for submerged portions,were used.The measurements campaigns are for several years from 2011 to 2016.Sectors of the breakwater with varied corrosion attack levels could be differentiated.Also,corrosion rates and lifespans were estimated,both general for the structures,and specific for each section and level.In turn,this allowed to identify maintenance priorities,defining sites where measures of corrosion protection should initiate,as well,to have confidence in the structural capacity and safety of the breakwaters.展开更多
To detect overlapped echoes due to the thin pavement layers,we present a thickness measurement approach for the very thin layer of pavement structures.The term "thin" is relative to the incident wavelength o...To detect overlapped echoes due to the thin pavement layers,we present a thickness measurement approach for the very thin layer of pavement structures.The term "thin" is relative to the incident wavelength or pulse.By means of independent component analysis of noisy signals received by a single radar sensor,the overlapped echoes can be successfully separated.Once the echoes from the top and bottom side of a thin layer have been separated,the time delay and the layer thickness determination follow immediately.Results of the simulation and real data verify the feasibility of the presented method.展开更多
Based on the development of the non-contact measurement system of free-formsurface, NURBS reconstruction of measurement points of freeform surface is effectively realized bymodifying the objective function and recursi...Based on the development of the non-contact measurement system of free-formsurface, NURBS reconstruction of measurement points of freeform surface is effectively realized bymodifying the objective function and recursive procedure and calculating the optimum number ofcontrol points. The reconstruction precision is evaluated through Ja-cobi's transformation method.The feasibility of the measurement system and effectiveness of the reconstruction algorithm aboveare proved by experiment.展开更多
文摘The method using pulsed eddy currents to determine the thickness of a conduction plate is extended to enable the simultaneous measurement of the plate thickness and material properties. For optimal performance, a probe must be designed depending on the thickness range that should be accessible. The need for a calibration of the material properties of a conducting plate to enable the measurement of its thickness has been removed. All that is needed is a probe with known dimensions and suitable hardware to create a current pulse and measure a transient magnetic induction.
基金supported by the National Natural Science Foundation of China(41974139,42274148,42074142)。
文摘Horizontal gas-liquid two-phase flows widely exist in chemical engineering,oil/gas production and other important industrial processes.Slug flow pattern is the main form of horizontal gas-liquid flows and characterized by intermittent motion of film region and slug region.This work aims to develop the ultrasonic Doppler method to realize the simultaneous measurement of the velocity profile and liquid film thickness of slug flow.A single-frequency single-channel transducer is adopted in the design of the field-programmable gate array based ultrasonic Doppler system.A multiple echo repetition technology is used to improve the temporal-spatial resolution for the velocity profile.An experiment of horizontal gas-liquid two-phase flow is implemented in an acrylic pipe with an inner diameter of 20 mm.Considering the aerated characteristics of the liquid slug,slug flow is divided into low-aerated slug flow,high-aerated slug flow and pseudo slug flow.The temporal-spatial velocity distributions of the three kinds of slug flows are reconstructed by using the ultrasonic velocity profile measurement.The evolution characteristics of the average velocity profile in slug flows are investigated.A novel method is proposed to derive the liquid film thickness based on the instantaneous velocity profile.The liquid film thickness can be effectively measured by detecting the position and the size of the bubbles nearly below the elongated gas bubble.Compared with the time of flight method,the film thickness measured by the Doppler system shows a higher accuracy as a bubble layer occurs in the film region.The effect of the gas distribution on the film thickness is uncovered in three kinds of slug flows.
基金Supported by Medical Science Research Project of Hebei Province in 2023(No.20231818).
文摘AIM:To access the agreement of intraocular pressure(IOP)values obtained from biomechanically corrected tonometer[Corvis ST(CST)],non-contact tonometer(NCT),and Goldmann applanation tonometer(GAT)in children with NCT measured-IOP(NCT-IOP)values of 22 mm Hg or more,and related factors.METHODS:A total of 51 eyes with NCT-IOP≥22 mm Hg in children aged 7 to 14y were examined and IOP was measured by CST,NCT,and GAT.Based on GAT measured IOP(GAT-IOP),ocular hypertension(OHT)group(≥22 mm Hg,24 eyes)and the non-OHT group(<22 mm Hg,27 eyes)were defined.We compared the agreement of the three measurements,i.e.,CST measured IOP(CST-IOP),GAT-IOP,and NCT-IOP,and further analyzed the correlation between the differences in tonometry readings,central corneal thickness(CCT),axial length(AL),optic disc rim volume,and age.RESULTS:Compared with the OHT group,thicker CCT,larger rim volume,and higher differences between NCTIOP and GAT-IOP,were found in the non-OHT group.The differences between CST-IOP and GAT-IOP were lower than the differences between NCT-IOP and GAT-IOP in both groups.The mean differences in CST-IOP and GAT-IOP were 1.26 mm Hg(95%limit of agreement ranged from 0.1 to 2.41 mm Hg,OHT group)and 1.20 mm Hg(95%limit of agreement ranged from-0.5 to 3.00 mm Hg,non-OHT group),and the mean differences in NCT and GAT were 3.90 mm Hg(95%limit of agreement ranged from-0.19 to 9.70 mm Hg,OHT group)and 6.00 mm Hg(95%limit of agreement ranged from 1.50 to 10.50 mm Hg,non-OHT group).The differences between CST-IOP and GAT-IOP were not related to CCT,age,and AL in both groups;while the differences between NCT-IOP and GAT-IOP were related to CCT in the OHT group(r=0.93,P<0.001)and to CCT and AL in the non-OHT group(r=0.66,P<0.001,r=-0.81,P<0.001).CONCLUSION:The accuracy of NCT in the diagnosis of pediatric OHT is low.The agreement of CST-IOP and GATIOP was significantly higher in children with and without OHT than in those with NCT-IOP and GAT-IOP.Therefore,CST can be used as a good alternative for IOP measurement in children.The impacts of CCT and AL on NCT measurement need to be fully considered when managing childhood IOP.
文摘The special ultrasonic testing system has been developed for thickness measurement of plasma sprayed coatings. The ultrasonic immersion method was used to obtain stable coupling condition and avoid other disadvantages of contact method. Spherical acoustic lens were designed to focus ultrasonic beam so as to improve beam directivity and concentrate ultrasonic energy. To increase testing precision and avoid mussy wave signals, moderate pulse width and frequency of the transducer has been selected. The displacement of transducer in X-Y-Z directions was precisely manipulated by step-controlled system to insure the accuracy of focus length and repetition of measurement. Optimized testing conditions (with the transducer of center frequency of 10 MHz and crystal diameter of 8 mm, focus length of 9.5 mm, diameter of focal column of 0. 1 mm and length of focal column of 0.27 mm) were selected to determine the thickness between 285 -414 μm of ZrO2 coatings plasma sprayed on the nickel based superalloy. The frequency interval of the periodic extremums in ultrasonic power spectra decreases with increasing coating thickness. The ultrasonic results accord with those of metallographical method.
基金Supported by National Natural Science Foundation of China(Grant No.51277154)Xiamen Key Laboratory of Optoelectronic Transducer Technology+1 种基金Fujian Key Laboratory of Universities and Colleges for Transducer TechnologyInnovative Talents Program of Far East NDT New Technology&Application Forum
文摘In eddy current testing, the law of attenuation of eddy current(EC) is of great concern. In conductive half space under the excitation of uniform magnetic field, the EC density decreases exponentially in the depth direction. However, in conductor with finite thickness tested by coil, the distribution of EC in the depth direction is more complicated. This paper studies the characteristics of EC attenuation in metallic plate of finite thickness. Simulation results show that there is an EC reflection at the bottom of plate, which changes the law of EC attenuation. A new concept, namely the equivalent attenuation coefficient, is proposed to quantify the speed of EC attenuation. The characteristics of EC attenuation are utilized to explain the nonmonotonic relation between coil voltage and plate thickness. Procedure of selecting frequency is discussed. Thereafter, measurement of plate thickness is carried out and accurate result is obtained.
基金National High Technology Research and Development Program of China(2009AA04Z131)Natural Science Foundation of China (50877056)
文摘A novel thickness measurement method for surface insulation coating of silicon steel based on NIR spectrometry is explored.The NIR spectra of insulation coating of silicon steel were collected by acousto-optic tunable filter(AOTF) NIR spectrometer.To make full use of the effective information of NIR spectral data,discrete binary particle swarm optimization(DBPSO) algorithm was used to select the optimal wavelength variates.The new spectral data,composed of absorbance at selected wavelengths,were used to create the thickness quantitative analysis model by kernel partial least squares(KPLS) algorithm coupled with Boosting.The results of contrast experiments showed that the Boosting-KPLS model could efficiently improve the analysis accuracy and speed.It indicates that Boosting-KPLS is a more accurate and robust analysis method than KPLS for NIR spectral analysis.The maximal and minimal absolute error of 30 testing samples is respectively-0.02 μm and 0.19 μm,and the maximal relative error is 14.23%.These analysis results completely meet the practical measurement need.
文摘AIM:To evaluate the central corneal thickness(CCT)measurements of premature infantsMETHODS:The premature infants who were born between 25-34wk of gestational age(GA)were retrieved for the study.All CCT measurements were performed within the first 2d of their life under topical anesthesia by using an ultrasonic pachymeter.RESULTS:The mean CCT of 200 eyes was 647.79±63.94μm.The mean CCT of the right and left eyes were similar(647.30±64.72μm and 648.29±63.47μm consecutively).The mean CCT of the girls was 642.08±54.89μm and the boys was 653.07±71.14μm,with no statistically significant difference(P】0.05).But there was a negative correlation of the CCT with GA and birth weight(BW)(P【0.01).CONCLUSION:The CCT values of premature babies were negatively correlated with GA and BW.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11274342,11304353,11404245 and 11474042
文摘Elasticity is of profound significance to evaluating the function of a biological soft tissue. When the elasticity of a tissue is macroscopically changed, it means that the biological function of the tissue is abnormal and some disease or injury may occur. In the present work, an elastometer is developed to measure the elasticity of biological soft tissues. The measurement is based on the indentation method and the force is measured by the bending of the cantilever. The force-indentation data of the soft tissue is experimentally measured by this elastometer and Young's modulus of the tissue is calculated using the Hertz-Sneddon model. For comparison, a numerical model for the indentation method is established using the finite element method. The difference between the actual modulus and the measured modulus is discussed. The effect of the thickness of the specimen on the measurement is investigated. Young's moduli of beef, porcine liver and porcine kidney are experimentally measured. The results indicate that our elastometer is effective in measuring Young's modulus of a soft tissue quantitatively.
基金Supported by the National Natural Science Foundation of China(No.51309116)
文摘For a ship in service,seawater corrosion is unavoidable. In order to ensure navigation safety and master the steel plate thickness in service ship,thickness of the ship steel plate must be tested periodically by a scientific method. After consideration of an actual situation of thickness measurement,the bearing mechanism of ultrasonic thickness meter probe has been designed on the basis of wall-climbing robot,and preliminary experiments have been carried out. The device is mainly used for thickness measurement of a large area of ship hull plate when the docking ship has been sandblasted. Efficiency and safety can be improved to finish thickness measurement by using the device.
基金The Project is supported by the doctoral foundation of the National Education Committee of China
文摘Through optimizing the eletric parameters of the resistance-capacitance (R-C)oscillation,a measuring instrument is developed for measurement of EHL oil filmthickness.Actual measurement was made with space bearings and actual measurements arein good agreement with theoretical calculations.
文摘The paper briefly introduces the Contamination Line Method for foil thickness measurement in transmission electron microscopy and compares it with four conventional methods: the convergent beam diffraction method, the contamination spot method, the methods hased on characteristic X-ray emission and continuous X-ray emission on the application, aperation and accuracy etc.
文摘Several methods for investigating the thickness uniformity of polymer thin films are presented as well as their measurement principles. A comparison of these experimental methods is given.The cylindrical lightwave reflection method is found to can obtain the thickness distribution along a certain direction.It is a simple and suitable method to evaluate the film thickness uniformity.
基金This work was supported by National Natural Science Foundation of China (Grant No. 40476005 and 40233032), the Ministry of Science and Technology, China (Grant No. 2005DIB3J114), and the "863 Project" (Grant No. 2006AA04Z206 and 2006AA09Z152).
文摘Luquire et al. ' s impedance change model of a rectangular cross section probe coil above a structure with an arbitrary number of parallel layers was used to study the principle of measuring thicknesses of multi-layered structures in terms of eddy current testing voltage measurements. An experimental system for multi-layered thickness measurement was developed and several fitting models to formulate the relationships between detected impedance/voltage measurements and thickness are put forward using least square method. The determination of multi-layered thicknesses was investigated after inversing the voltage outputs of the detecting system. The best fitting and inversion models are presented.
文摘In Quepos,Pacific of Costa Rica,it was finished on 2010 the first phase of a marina,including two mix breakwaters,with rubble mound(rocks and concrete units),and 25 circular steel sheet piles cofferdam cells,filled with sand and gravel.The maintenance plan,considers tracking sheet pile corrosion,comparing'actual'against expected rates,checking structural limits,and programming countermeasures if accelerated corrosion is identified.Specific control sections,along the breakwaters,both inside and outside the basin,were established.In each section,thicknesses were measured every meter from the top of the steel cell to seabed using an ultrasonic equipment,and an underwater transducer.Both land crew,and divers for submerged portions,were used.The measurements campaigns are for several years from 2011 to 2016.Sectors of the breakwater with varied corrosion attack levels could be differentiated.Also,corrosion rates and lifespans were estimated,both general for the structures,and specific for each section and level.In turn,this allowed to identify maintenance priorities,defining sites where measures of corrosion protection should initiate,as well,to have confidence in the structural capacity and safety of the breakwaters.
文摘To detect overlapped echoes due to the thin pavement layers,we present a thickness measurement approach for the very thin layer of pavement structures.The term "thin" is relative to the incident wavelength or pulse.By means of independent component analysis of noisy signals received by a single radar sensor,the overlapped echoes can be successfully separated.Once the echoes from the top and bottom side of a thin layer have been separated,the time delay and the layer thickness determination follow immediately.Results of the simulation and real data verify the feasibility of the presented method.
基金Acknowledgments: The study is one of branches of a key project of Chinese National Programs for Foundation Research and Development, thanks for the supporting from the National Nature Science Foundation. The new method to measure thickness of wager film has applied an utility model patent in China (No. 200620098211.4).
基金This project is supported by Provincial Natural Science Foundation of Zhejiang of China (No.599026).
文摘Based on the development of the non-contact measurement system of free-formsurface, NURBS reconstruction of measurement points of freeform surface is effectively realized bymodifying the objective function and recursive procedure and calculating the optimum number ofcontrol points. The reconstruction precision is evaluated through Ja-cobi's transformation method.The feasibility of the measurement system and effectiveness of the reconstruction algorithm aboveare proved by experiment.