Stay cables in cable-stayed bridges are prone to large amplitude oscillations under external excitations.The vibration of the cables is predominantly measured by using accelerometers to measure the acceleration.The dy...Stay cables in cable-stayed bridges are prone to large amplitude oscillations under external excitations.The vibration of the cables is predominantly measured by using accelerometers to measure the acceleration.The dynamic displacement is then usually obtained indirectly from the double integration of the acceleration data.This paper reports an experimental method of measuring the displacement of stayed cables using a digital video camera.With the newly developed videogrammetric technique,the video clips are transferred into image frames,from which the shape and location of the target are identified.The displacement time history is then captured.The technique is applied to a cable-stayed bridge to measure the dynamic displacement of stay cables.The displacement is compared with the acceleration data in the frequency and time domains.The results show that the displacement measured by the digital video camera is comparable to the counterparts integrated from the acceleration data.The vibration frequencies identified from the acceleration are finally used to estimate the tension forces of the cables.The results show that the tension forces have insignificant changes after one year’s operation.展开更多
The temperature effects on the electrical performance of a large area multicrystalline silicon solar cell with back-contact technology have been studied in a desert area under ambient conditions using the current shun...The temperature effects on the electrical performance of a large area multicrystalline silicon solar cell with back-contact technology have been studied in a desert area under ambient conditions using the current shunt measuring technique. Therefore, most of the problems encountered with traditional measuring techniques are avoided. The temperature dependency of the current shunt from 5oC up to 50oC has been investigated. Its temperature coefficient proves to be negligible which means that the temperature dependency of the solar cell is completely independent of the current shunt. The solar module installed in a tilted position at the optimum angle of the location, has been tested in two different seasons (winter and summer). The obtained solar cell short circuit current, open circuit voltage and output power are correlated with the measured incident radiation in both seasons and all results are discussed.展开更多
In many situations such as the cores of a rotating electrical machine and the T joints of a multiphase transformer, the local flux density varies with time in terms of both magnitude and direction, i.e. the flux densi...In many situations such as the cores of a rotating electrical machine and the T joints of a multiphase transformer, the local flux density varies with time in terms of both magnitude and direction, i.e. the flux density vector is rotating. Therefore, the magnetic properties of the core materials under the rotating flux density vector excitation should be properly measured, modeled and applied in the design and analysis of these electromagnetic devices. This paper presents an extensive review on the development of techniques and apparatus for measuring the rotational core losses of soft magnetic materials based on the experiences of various researchers in the last hundred years.展开更多
With the development of science and technology in China, the measuring technique in water resources and hydropower engineering is also developing constantly. Measuring technique in water resources and hydropower engin...With the development of science and technology in China, the measuring technique in water resources and hydropower engineering is also developing constantly. Measuring technique in water resources and hydropower engineering is an important link in water conservancy and hydropower projects, which can improve the survey efficiency of water conservancy and hydropower projects and promote the rapid development of China's water conservancy and hydropower projects. This paper will analyze the current situation of measuring technique development of water conservancy and hydropower projects and explore how to improve the measuring efficiency of water conservancy and hydropower projects.展开更多
Heteromorphism leaf area of garden trees was measured by CAD-vector method.It was showed that all the coefficients of variation were below 1% when measurement accuracy was relatively high.This method was fit for accur...Heteromorphism leaf area of garden trees was measured by CAD-vector method.It was showed that all the coefficients of variation were below 1% when measurement accuracy was relatively high.This method was fit for accuracy area measurement of abnormity leaf,pests and disease leaf,big leaf,small leaf and so on.展开更多
Borehole overcoring stress measurement with an improved hollow inclusion technique was carried out at 10 points on 3 levels in Jinchuan nickel mine which is situated in north-west of China. Through the measurement, 3-...Borehole overcoring stress measurement with an improved hollow inclusion technique was carried out at 10 points on 3 levels in Jinchuan nickel mine which is situated in north-west of China. Through the measurement, 3-D in situ stress state at the measuring points and distribution characteristics of the stress field in the mine were obtained. The stress state in Jinchuan mine is dominated by the horizontal tectonic stress field. The maximum principal stress is horizontal which is about twice the weight of the overburden and its orientation is approximately vertical to the regional tectonic line. The difference between two horizontal principal stresses is quite large which is an important reason to cause failure of underground excavations.展开更多
Reliable information of in--situ stress state is necessary for the design andconstruction of most important rock projects. As most rock projects are getting deeper and deeper,traditional techniques of in--situ stress ...Reliable information of in--situ stress state is necessary for the design andconstruction of most important rock projects. As most rock projects are getting deeper and deeper,traditional techniques of in--situ stress measurement are not very suitable. The current techniquesof in--situ stress measurement and their insufficiency for use at great depth are analyzed. Somebasic ideas of the development of new techniques and the improvement of current techniques for useat great depth are provided.展开更多
The purpose of this study is to develop a standard methodology for measuring the surface free energy (SFE),and its component parts of bamboo fiber materials.The current methods was reviewed to determine the surface te...The purpose of this study is to develop a standard methodology for measuring the surface free energy (SFE),and its component parts of bamboo fiber materials.The current methods was reviewed to determine the surface tension of natural fibers and the disadvantages of techniques used were discussed.Although numerous techniques have been employed to characterize surface tension of natural fibers,it seems that the credibility of results obtained may often be dubious.In this paper,critical surface tension estimates were obtained from computer aided machine vision based measurement.Data were then analyzed by the least squares method to estimate the components of SFE.SFE was estimated by least squares analysis and also by Schultz' method.By using the Fowkes method the polar and disperse fractions of the surface free energy of bamboo fiber materials can be obtained.Strictly speaking,this method is based on a combination of the knowledge of Fowkes theory. SFE is desirable when adhesion is required,and it avoids some of the limitations of existing studies which has been proposed.The calculation steps described in this research are only intended to explain the methods.The results show that the method that only determines SFE as a single parameter may be unable to differentiate adequately between bamboo fiber materials,but it is feasible and very efficient.In order to obtain the maximum performance from the computer aided machine vision based measurement instruments,this measurement should be recommended and kept available for reference.展开更多
One of the detection objectives of the Chinese Asteroid Exploration mission is to investigate the space environment near the Main-belt Comet(MBC,Active Asteroid)311P/PANSTARRS.This paper outlines the scientific object...One of the detection objectives of the Chinese Asteroid Exploration mission is to investigate the space environment near the Main-belt Comet(MBC,Active Asteroid)311P/PANSTARRS.This paper outlines the scientific objectives,measurement targets,and measurement requirements for the proposed Gas and Ion Analyzer(GIA).The GIA is designed for in-situ mass spectrometry of neutral gases and low-energy ions,such as hydrogen,carbon,and oxygen,in the vicinity of 311P.Ion sampling techniques are essential for the GIA's Time-of-Flight(TOF)mass analysis capabilities.In this paper,we present an enhanced ion sampling technique through the development of an ion attraction model and an ion source model.The ion attraction model demonstrates that adjusting attraction grid voltage can enhance the detection efficiency of low-energy ions and mitigate the repulsive force of ions during sampling,which is influenced by the satellite's surface positive charging.The ion source model simulates the processes of gas ionization and ion multiplication.Simulation results indicate that the GIA can achieve a lower pressure limit below 10-13Pa and possess a dynamic range exceeding 10~9.These performances ensure the generation of ions with stable and consistent current,which is crucial for high-resolution and broad dynamic range mass spectrometer analysis.Preliminary testing experiments have verified GIA's capability to detect gas compositions such as H2O and N2.In-situ measurements near 311P using GIA are expected to significantly contribute to our understanding of asteroid activity mechanisms,the evolution of the atmospheric and ionized environments of main-belt comets,the interactions with solar wind,and the origin of Earth's water.展开更多
The system principle and configuration of the double differential pressure method for measuring oil tank level are presented. The fundamental method and circuit of fiber optic transmission are analyzed .The accuracy a...The system principle and configuration of the double differential pressure method for measuring oil tank level are presented. The fundamental method and circuit of fiber optic transmission are analyzed .The accuracy and security of level measurement in the oil tanks have been greatly improved.展开更多
Electrochemical techniques of the corrosion measurements of reinforcing steeI in concrete have been evaluated. These techniques include half-cell potential measurements, impressed voltage method, impressed current met...Electrochemical techniques of the corrosion measurements of reinforcing steeI in concrete have been evaluated. These techniques include half-cell potential measurements, impressed voltage method, impressed current method and potentiostatic polarization technique. The results of corrosion behaviour of the steel in both 5%NaCl and 5%MgSO4 show that each electrochemical technique provides some information about the condition of the steel bar or the corrosivity of the environment being evaluated, yet none provides a complete data regarding the corrosion resistance of reinforcing steel in aggressive media展开更多
An electrochemical probe measurement system for detecting an electrogenerated etchant in solution is developed.Concentration distribution of electrogenerated etchant bromine as close as 8 micrometer to the surface of ...An electrochemical probe measurement system for detecting an electrogenerated etchant in solution is developed.Concentration distribution of electrogenerated etchant bromine as close as 8 micrometer to the surface of macrodisk is studied quantitatively.展开更多
Different methods of measuring a propagating laser beam quality are summarized.The disadvantages in traditional way in measuring a laser beam quality is analyzed and the insufficiencies of the Shack-Hartmannin method ...Different methods of measuring a propagating laser beam quality are summarized.The disadvantages in traditional way in measuring a laser beam quality is analyzed and the insufficiencies of the Shack-Hartmannin method which is commonly using wave front technique at present is pointed out.Finally,the transmission intensity equation based(TIE-based)measuring way in a laser beam quality evaluation and the corresponding advantages are discussed,which is believed to be a deve-l oping trend in laser beam evaluation.展开更多
Nitrogen oxides(NO_(x))are crucial in tropospheric photochemical ozone(O_(3))production and oxidation capacity.Currently,the widely used NO_(x)measurement technique is chemiluminescence(CL)(CL-NO_(x)),which tends to o...Nitrogen oxides(NO_(x))are crucial in tropospheric photochemical ozone(O_(3))production and oxidation capacity.Currently,the widely used NO_(x)measurement technique is chemiluminescence(CL)(CL-NO_(x)),which tends to overestimate NO_(2)due to atmospheric oxidation products of NO_(x)(i.e.,NO_(z)).We developed and characterized a NO_(x)measurement system using the cavity attenuated phase shift(CAPS)technique(CAPS-NO_(x)),which is free from interferences with nitrogen-containing species.The NO_(x)measured by the CAPS-NO_(x)and CL-NO_(x)analyzers were compared.Results show that both analyzers showed consistent measurement results for NO,but the NO_(2)measured by the CAPS-NO_(x)analyzer(NO_(2)_CAPS)was mostly lower than that measured by the CL-NO_(x)analyzer(NO_(2)_CL),which led to the deviations in O_(3)formation sensitivity regime and O_(x)(=O_(3)+NO_(2))sources(i.e.,regional background and photochemically produced O_(x))determined by the ozone production efficiencies(OPE)calculated from NO_(2)_CL and NO_(2)_CAPS.Overall,OPE_CL exceeded OPE_CAPS by 18.9%,which shifted 3 out of 13 observation days from the VOCs-limited to the transition regime when judging using OPE_CL,as compared to calculations using OPE_CAPS.During the observation period,days dominated by regional background O_(x)accounted for 46%and 62%when determined using NO_(2)_CL and NO_(2)_CAPS,respectively.These findings suggest that the use of the CL-NO_(x)analyzer tends to underestimate both the VOCs-limited regime and the regional background O_(x)dominated days.The newly built CAPS-NO_(x)analyzer here can promote the accurate measurement of NO_(2),which is meaningful for diagnosing O_(3)formation regimes and O_(x)sources.展开更多
This review gives a short introduction into the principles of ultrasonic measurement techniques for liquids, using cavity resonators. Guidelines for the resonator design in broad-band ultrasonic stxctroscopy as well a...This review gives a short introduction into the principles of ultrasonic measurement techniques for liquids, using cavity resonators. Guidelines for the resonator design in broad-band ultrasonic stxctroscopy as well as in high-resolution single-frequncy or narrowband applications are presented. Deviations of the field configuration in real cells frtxn that in an ideal resonator are discussed and relations for the mode spectrum of cavity fields are given. Recent resonator measurement procedures and methods of data evaluation are mentioned briefly. Some examples of measurements show the extended usability of ultrasonic resonator techniques in basic science and in a wide range of applications for rrkaterials characterization, in manufacturing processes, as well as in control routines.展开更多
An active measurement method and its principle was introduced consideringthe low success rate,special difficulty,and long measurement time of the direct gas pressuremeasurement currently used in coal roadways.The tech...An active measurement method and its principle was introduced consideringthe low success rate,special difficulty,and long measurement time of the direct gas pressuremeasurement currently used in coal roadways.The technology of drilling,boreholesealing depth,borehole sealing length,sealing control of the measuring process,compensatorycomputation of gas loss quantity and other key techniques were discussed.Finally,based on the latest instrument the authors developed,a series of experiments of directgas pressure measurement in the coal roadways of the Jincheng and Tongchuanmine district,were carried out.The experimental results show that active gas pressuremeasurement technique has advantages as follows:(1) the application scope of direct gaspressure measurement technique is wide and it does not have the restriction of coalhardness,coal seam fissure and other conditions;(2) the measured results are credible,which can be tested by the same gas pressure value acquired from a different borehole inthe same place;(3) the measurement process is convenient and quick,it takes about 2 to3 days to acquire the gas pressure value in a coal seam.展开更多
Using the Differential Absorption Lidar (DIAL) technique, two types of approaches, namely, reflection from retroreflector / topographic target and backscatter from atmosphere, are available for studying remotely the a...Using the Differential Absorption Lidar (DIAL) technique, two types of approaches, namely, reflection from retroreflector / topographic target and backscatter from atmosphere, are available for studying remotely the atmospheric NO, concentration. The Argon ion lidar system at the Indian Institute of Tropical Meteorology (IITM), Pune, India has been used for the measurements by following both the path-averaged and range-resolved approaches. For the former, a topographic target (hill) is used for determining path-averaged surface concentration. In the latter, spectral properties of atmospheric attenuation is used for making range-resolved measurements in the surface layer. The results of the observations collected by following both approaches are presented. The average surface NO2 concentration was found to vary between 0.01 and 0.105 ppm and the range-resolved measurements exhibited higher values suggesting treatment of the lidar data for scattering and extinction effects due to atmospheric aerosols and air molecules, and atmospheric turbulence. Certain modifications that are suggested to the experimental set-up, data acquisition and analysis to improve the measurements are briefly described.展开更多
Recently, optical techniques have attracted great attention due to their excellent non-destructive, non-contact, high-resolution, and full-field characteristics. Applications can be found in diverse fields such as pre...Recently, optical techniques have attracted great attention due to their excellent non-destructive, non-contact, high-resolution, and full-field characteristics. Applications can be found in diverse fields such as precision mechanics and manufacturing, aerospace and automotive testing and inspection, materials science, and biomedical engineering. Advances in Optical Techniques for Me- chanical Measurements presents the latest research progresses in several widely used optical techniques with applications in preci- sion mechanical engineering.展开更多
For strain measurement on offshore jacket platform in deep water, waterproof of strain foil is always an important issue, especially, due to the high pressure in deep water. The waterproof is difficult in two places, ...For strain measurement on offshore jacket platform in deep water, waterproof of strain foil is always an important issue, especially, due to the high pressure in deep water. The waterproof is difficult in two places, one is between the matrix structure and the protection structure, and another is between the lead wires and the protection structure. The surround protection technique discussed in this paper is conventional and ideal, and can be operative for a long time, up to five years. In this method, a metal case and tube is added on the local position, which increases the local rigidity, but the effect on the measurement of strain is not well studied. In this paper, the effect of the surround protection technique on the strain measurement is studied by using numerical and experimental methods, and the results show that the measurement error is well in the range permitted by engineering practice.展开更多
This paper carries out tbe experirnent study on the correlation between am stress-strain process of rock samples and the acoustie parameter change of rock by using the measurement system of KS acoustic wave data proce...This paper carries out tbe experirnent study on the correlation between am stress-strain process of rock samples and the acoustie parameter change of rock by using the measurement system of KS acoustic wave data processing device. On the spot, the stability of surrounding rock is studied by means of experiments on the relationship between the change process (from elastie to plastic failure zone) in surrounding rock of roadway and the change law of acoustic parameters of rock. These acoustie parameters inelude wave amplitude, spectral amplitude, spectrum area, spectral density,wave veloeity and attenuation coefficient etc.展开更多
基金Supported by the Research Grants Council of the Hong Kong Special Administrative Region of China(No.PolyU 5298/11E)the Hong Kong Polytechnic University(No.A-PD0H).
文摘Stay cables in cable-stayed bridges are prone to large amplitude oscillations under external excitations.The vibration of the cables is predominantly measured by using accelerometers to measure the acceleration.The dynamic displacement is then usually obtained indirectly from the double integration of the acceleration data.This paper reports an experimental method of measuring the displacement of stayed cables using a digital video camera.With the newly developed videogrammetric technique,the video clips are transferred into image frames,from which the shape and location of the target are identified.The displacement time history is then captured.The technique is applied to a cable-stayed bridge to measure the dynamic displacement of stay cables.The displacement is compared with the acceleration data in the frequency and time domains.The results show that the displacement measured by the digital video camera is comparable to the counterparts integrated from the acceleration data.The vibration frequencies identified from the acceleration are finally used to estimate the tension forces of the cables.The results show that the tension forces have insignificant changes after one year’s operation.
文摘The temperature effects on the electrical performance of a large area multicrystalline silicon solar cell with back-contact technology have been studied in a desert area under ambient conditions using the current shunt measuring technique. Therefore, most of the problems encountered with traditional measuring techniques are avoided. The temperature dependency of the current shunt from 5oC up to 50oC has been investigated. Its temperature coefficient proves to be negligible which means that the temperature dependency of the solar cell is completely independent of the current shunt. The solar module installed in a tilted position at the optimum angle of the location, has been tested in two different seasons (winter and summer). The obtained solar cell short circuit current, open circuit voltage and output power are correlated with the measured incident radiation in both seasons and all results are discussed.
文摘In many situations such as the cores of a rotating electrical machine and the T joints of a multiphase transformer, the local flux density varies with time in terms of both magnitude and direction, i.e. the flux density vector is rotating. Therefore, the magnetic properties of the core materials under the rotating flux density vector excitation should be properly measured, modeled and applied in the design and analysis of these electromagnetic devices. This paper presents an extensive review on the development of techniques and apparatus for measuring the rotational core losses of soft magnetic materials based on the experiences of various researchers in the last hundred years.
文摘With the development of science and technology in China, the measuring technique in water resources and hydropower engineering is also developing constantly. Measuring technique in water resources and hydropower engineering is an important link in water conservancy and hydropower projects, which can improve the survey efficiency of water conservancy and hydropower projects and promote the rapid development of China's water conservancy and hydropower projects. This paper will analyze the current situation of measuring technique development of water conservancy and hydropower projects and explore how to improve the measuring efficiency of water conservancy and hydropower projects.
文摘Heteromorphism leaf area of garden trees was measured by CAD-vector method.It was showed that all the coefficients of variation were below 1% when measurement accuracy was relatively high.This method was fit for accuracy area measurement of abnormity leaf,pests and disease leaf,big leaf,small leaf and so on.
文摘Borehole overcoring stress measurement with an improved hollow inclusion technique was carried out at 10 points on 3 levels in Jinchuan nickel mine which is situated in north-west of China. Through the measurement, 3-D in situ stress state at the measuring points and distribution characteristics of the stress field in the mine were obtained. The stress state in Jinchuan mine is dominated by the horizontal tectonic stress field. The maximum principal stress is horizontal which is about twice the weight of the overburden and its orientation is approximately vertical to the regional tectonic line. The difference between two horizontal principal stresses is quite large which is an important reason to cause failure of underground excavations.
文摘Reliable information of in--situ stress state is necessary for the design andconstruction of most important rock projects. As most rock projects are getting deeper and deeper,traditional techniques of in--situ stress measurement are not very suitable. The current techniquesof in--situ stress measurement and their insufficiency for use at great depth are analyzed. Somebasic ideas of the development of new techniques and the improvement of current techniques for useat great depth are provided.
基金the National Natural Science Foundation of China(No.31101085)the Scientific Research and Development Foundation for Start-up Projects of Zhejiang Agriculture and Forestry University (No.2034020044)
文摘The purpose of this study is to develop a standard methodology for measuring the surface free energy (SFE),and its component parts of bamboo fiber materials.The current methods was reviewed to determine the surface tension of natural fibers and the disadvantages of techniques used were discussed.Although numerous techniques have been employed to characterize surface tension of natural fibers,it seems that the credibility of results obtained may often be dubious.In this paper,critical surface tension estimates were obtained from computer aided machine vision based measurement.Data were then analyzed by the least squares method to estimate the components of SFE.SFE was estimated by least squares analysis and also by Schultz' method.By using the Fowkes method the polar and disperse fractions of the surface free energy of bamboo fiber materials can be obtained.Strictly speaking,this method is based on a combination of the knowledge of Fowkes theory. SFE is desirable when adhesion is required,and it avoids some of the limitations of existing studies which has been proposed.The calculation steps described in this research are only intended to explain the methods.The results show that the method that only determines SFE as a single parameter may be unable to differentiate adequately between bamboo fiber materials,but it is feasible and very efficient.In order to obtain the maximum performance from the computer aided machine vision based measurement instruments,this measurement should be recommended and kept available for reference.
基金Supported by the National Natural Science Foundation of China(42474239,41204128)China National Space Administration(Pre-research project on Civil Aerospace Technologies No.D010301)Strategic Priority Research Program of the Chinese Academy of Sciences(XDA17010303)。
文摘One of the detection objectives of the Chinese Asteroid Exploration mission is to investigate the space environment near the Main-belt Comet(MBC,Active Asteroid)311P/PANSTARRS.This paper outlines the scientific objectives,measurement targets,and measurement requirements for the proposed Gas and Ion Analyzer(GIA).The GIA is designed for in-situ mass spectrometry of neutral gases and low-energy ions,such as hydrogen,carbon,and oxygen,in the vicinity of 311P.Ion sampling techniques are essential for the GIA's Time-of-Flight(TOF)mass analysis capabilities.In this paper,we present an enhanced ion sampling technique through the development of an ion attraction model and an ion source model.The ion attraction model demonstrates that adjusting attraction grid voltage can enhance the detection efficiency of low-energy ions and mitigate the repulsive force of ions during sampling,which is influenced by the satellite's surface positive charging.The ion source model simulates the processes of gas ionization and ion multiplication.Simulation results indicate that the GIA can achieve a lower pressure limit below 10-13Pa and possess a dynamic range exceeding 10~9.These performances ensure the generation of ions with stable and consistent current,which is crucial for high-resolution and broad dynamic range mass spectrometer analysis.Preliminary testing experiments have verified GIA's capability to detect gas compositions such as H2O and N2.In-situ measurements near 311P using GIA are expected to significantly contribute to our understanding of asteroid activity mechanisms,the evolution of the atmospheric and ionized environments of main-belt comets,the interactions with solar wind,and the origin of Earth's water.
文摘The system principle and configuration of the double differential pressure method for measuring oil tank level are presented. The fundamental method and circuit of fiber optic transmission are analyzed .The accuracy and security of level measurement in the oil tanks have been greatly improved.
文摘Electrochemical techniques of the corrosion measurements of reinforcing steeI in concrete have been evaluated. These techniques include half-cell potential measurements, impressed voltage method, impressed current method and potentiostatic polarization technique. The results of corrosion behaviour of the steel in both 5%NaCl and 5%MgSO4 show that each electrochemical technique provides some information about the condition of the steel bar or the corrosivity of the environment being evaluated, yet none provides a complete data regarding the corrosion resistance of reinforcing steel in aggressive media
文摘An electrochemical probe measurement system for detecting an electrogenerated etchant in solution is developed.Concentration distribution of electrogenerated etchant bromine as close as 8 micrometer to the surface of macrodisk is studied quantitatively.
基金National Basic Research Program of China(973Plan) (No.2010CB327806)National Natural Science Foundation of China(No. 61070165)
文摘Different methods of measuring a propagating laser beam quality are summarized.The disadvantages in traditional way in measuring a laser beam quality is analyzed and the insufficiencies of the Shack-Hartmannin method which is commonly using wave front technique at present is pointed out.Finally,the transmission intensity equation based(TIE-based)measuring way in a laser beam quality evaluation and the corresponding advantages are discussed,which is believed to be a deve-l oping trend in laser beam evaluation.
基金supported by the Natural Science Foundation of Guangdong Province(No.2020A1515110526)the Key-Area Research and Development Programof Guangdong Province(No.2020B1111360003)the National Natural Science Foundation of China(No.42305096).
文摘Nitrogen oxides(NO_(x))are crucial in tropospheric photochemical ozone(O_(3))production and oxidation capacity.Currently,the widely used NO_(x)measurement technique is chemiluminescence(CL)(CL-NO_(x)),which tends to overestimate NO_(2)due to atmospheric oxidation products of NO_(x)(i.e.,NO_(z)).We developed and characterized a NO_(x)measurement system using the cavity attenuated phase shift(CAPS)technique(CAPS-NO_(x)),which is free from interferences with nitrogen-containing species.The NO_(x)measured by the CAPS-NO_(x)and CL-NO_(x)analyzers were compared.Results show that both analyzers showed consistent measurement results for NO,but the NO_(2)measured by the CAPS-NO_(x)analyzer(NO_(2)_CAPS)was mostly lower than that measured by the CL-NO_(x)analyzer(NO_(2)_CL),which led to the deviations in O_(3)formation sensitivity regime and O_(x)(=O_(3)+NO_(2))sources(i.e.,regional background and photochemically produced O_(x))determined by the ozone production efficiencies(OPE)calculated from NO_(2)_CL and NO_(2)_CAPS.Overall,OPE_CL exceeded OPE_CAPS by 18.9%,which shifted 3 out of 13 observation days from the VOCs-limited to the transition regime when judging using OPE_CL,as compared to calculations using OPE_CAPS.During the observation period,days dominated by regional background O_(x)accounted for 46%and 62%when determined using NO_(2)_CL and NO_(2)_CAPS,respectively.These findings suggest that the use of the CL-NO_(x)analyzer tends to underestimate both the VOCs-limited regime and the regional background O_(x)dominated days.The newly built CAPS-NO_(x)analyzer here can promote the accurate measurement of NO_(2),which is meaningful for diagnosing O_(3)formation regimes and O_(x)sources.
文摘This review gives a short introduction into the principles of ultrasonic measurement techniques for liquids, using cavity resonators. Guidelines for the resonator design in broad-band ultrasonic stxctroscopy as well as in high-resolution single-frequncy or narrowband applications are presented. Deviations of the field configuration in real cells frtxn that in an ideal resonator are discussed and relations for the mode spectrum of cavity fields are given. Recent resonator measurement procedures and methods of data evaluation are mentioned briefly. Some examples of measurements show the extended usability of ultrasonic resonator techniques in basic science and in a wide range of applications for rrkaterials characterization, in manufacturing processes, as well as in control routines.
基金Supported by National Basic Research Program of China(2005cb221504)National Key Technologies R & D Program of China(2006BAK03B01)
文摘An active measurement method and its principle was introduced consideringthe low success rate,special difficulty,and long measurement time of the direct gas pressuremeasurement currently used in coal roadways.The technology of drilling,boreholesealing depth,borehole sealing length,sealing control of the measuring process,compensatorycomputation of gas loss quantity and other key techniques were discussed.Finally,based on the latest instrument the authors developed,a series of experiments of directgas pressure measurement in the coal roadways of the Jincheng and Tongchuanmine district,were carried out.The experimental results show that active gas pressuremeasurement technique has advantages as follows:(1) the application scope of direct gaspressure measurement technique is wide and it does not have the restriction of coalhardness,coal seam fissure and other conditions;(2) the measured results are credible,which can be tested by the same gas pressure value acquired from a different borehole inthe same place;(3) the measurement process is convenient and quick,it takes about 2 to3 days to acquire the gas pressure value in a coal seam.
文摘Using the Differential Absorption Lidar (DIAL) technique, two types of approaches, namely, reflection from retroreflector / topographic target and backscatter from atmosphere, are available for studying remotely the atmospheric NO, concentration. The Argon ion lidar system at the Indian Institute of Tropical Meteorology (IITM), Pune, India has been used for the measurements by following both the path-averaged and range-resolved approaches. For the former, a topographic target (hill) is used for determining path-averaged surface concentration. In the latter, spectral properties of atmospheric attenuation is used for making range-resolved measurements in the surface layer. The results of the observations collected by following both approaches are presented. The average surface NO2 concentration was found to vary between 0.01 and 0.105 ppm and the range-resolved measurements exhibited higher values suggesting treatment of the lidar data for scattering and extinction effects due to atmospheric aerosols and air molecules, and atmospheric turbulence. Certain modifications that are suggested to the experimental set-up, data acquisition and analysis to improve the measurements are briefly described.
文摘Recently, optical techniques have attracted great attention due to their excellent non-destructive, non-contact, high-resolution, and full-field characteristics. Applications can be found in diverse fields such as precision mechanics and manufacturing, aerospace and automotive testing and inspection, materials science, and biomedical engineering. Advances in Optical Techniques for Me- chanical Measurements presents the latest research progresses in several widely used optical techniques with applications in preci- sion mechanical engineering.
文摘For strain measurement on offshore jacket platform in deep water, waterproof of strain foil is always an important issue, especially, due to the high pressure in deep water. The waterproof is difficult in two places, one is between the matrix structure and the protection structure, and another is between the lead wires and the protection structure. The surround protection technique discussed in this paper is conventional and ideal, and can be operative for a long time, up to five years. In this method, a metal case and tube is added on the local position, which increases the local rigidity, but the effect on the measurement of strain is not well studied. In this paper, the effect of the surround protection technique on the strain measurement is studied by using numerical and experimental methods, and the results show that the measurement error is well in the range permitted by engineering practice.
文摘This paper carries out tbe experirnent study on the correlation between am stress-strain process of rock samples and the acoustie parameter change of rock by using the measurement system of KS acoustic wave data processing device. On the spot, the stability of surrounding rock is studied by means of experiments on the relationship between the change process (from elastie to plastic failure zone) in surrounding rock of roadway and the change law of acoustic parameters of rock. These acoustie parameters inelude wave amplitude, spectral amplitude, spectrum area, spectral density,wave veloeity and attenuation coefficient etc.
