A new silicon micro flow sensor with multiple temperature sensing elements was proposed and numerically simulated in considering wide range flow measuring properties.The micro flow sensor has three pairs of temperatur...A new silicon micro flow sensor with multiple temperature sensing elements was proposed and numerically simulated in considering wide range flow measuring properties.The micro flow sensor has three pairs of temperature sensing elements with a central heater compared with typical sensor which has only a temperature sensing element on each side of a central heater.A numerical analysis of the micro flow sensor by Finite Difference Formulation for Heat Transfer Equation was performed.The nearest pair of temperature sensor showed very good linear sensitivity between 0 to 0.4m/s flow and saturated from 0.75m/s flow.However the furthest pair of temperature sensor showed some flow sensitivity even though the flow rate of 2.0m/s.Thus,this suggested new micro flow meter with multiple temperature sensing elements could be used as a thermal mass flow sensor which has accuracy sensitivity for very wide flow range.展开更多
Any phenomenon in nature is potential to be an inspiration for us to propose new ideas.Lateral line is a typical example which has attracted more interest in recent years.With the aid of lateral line,fish is capable o...Any phenomenon in nature is potential to be an inspiration for us to propose new ideas.Lateral line is a typical example which has attracted more interest in recent years.With the aid of lateral line,fish is capable of acquiring fluid information around,which is of great significance for them to survive,communicate and hunt underwater.In this paper,we briefly introduce the morphology and mechanism of the lateral line first.Then we focus on the development of artificial lateral line which typically consists of an array of sensors and can be installed on underwater robots.A series of sensors inspired by the lateral line with different sensing principles have been summarized.And then the applications of artificial lateral line systems in hydrodynamic environment sensing and vortices detection,dipole oscillation source detection,and autonomous control of underwater robots have been reviewed.In addition,the existing problems and future foci in this field have been further discussed in detail.The current works and future foci have demonstrated that artificial lateral line has great potentials of applications and contributes to the development of underwater robots.展开更多
A passive simulation method based on the six degrees of freedom(6-DOF)model and dynamic mesh is proposed according to the working principle to study the dynamic characteristics of the turbine flow sensors.This simulat...A passive simulation method based on the six degrees of freedom(6-DOF)model and dynamic mesh is proposed according to the working principle to study the dynamic characteristics of the turbine flow sensors.This simulation method controls the six degrees of freedom of the impeller using the user-defined functions(UDF)program so that it can only rotate under the impact of fluid.The impeller speed can be calculated in real-time,and the inlet speed can be set with time to obtain the dynamic performance of the turbine flow sensors.Based on this simulation method,three turbine flow sensors with different diameters were simulated,and the reliability of the simulation method was verified by both steady-state and unsteady-state experiments.The results show that the trend of meter factor with flow rate acquired from the simulation is close to the experimental results.The deviation between the simulation and experiment results is low,with a maximum deviation of 2.88%.In the unsteady simulation study,the impeller speed changed with the inlet velocity of the turbine flow sensor,showing good tracking performance.The passive simulation method can be used to predict the dynamic performance of the turbine flow sensor.展开更多
The qualitative and quantitative assessment of gas flow has become increasingly relevant in the use of everyday systems. The micro flow sensor, developed by Innovative Sensor Technology AG （Switzerland）, is by princ...The qualitative and quantitative assessment of gas flow has become increasingly relevant in the use of everyday systems. The micro flow sensor, developed by Innovative Sensor Technology AG （Switzerland）, is by principle a calorimetric flow sensor produced as a micro system on a glass substrate by means of photolithography and glass etching technology. These structures are arranged as a platinum micro heater and sensor in a Wheatstone bridge. The subsequent etching process produces an exposed area of polyimide membrane that is only a few microns thick and includes the resistive sensor structure as the active area. In addition, the RTD （resistance temperature detector） technology included on the sensor allows for the implementation of a variety of electronic biasing and signal processing modes. Since the sensor can be powered and the bridge can be measured in both CTA （constant temperature anemometer） and calorimetric mode, new possibilities are presented for both low and high flow rates with regard to temperature compensation, self-calibration and self-monitoring.展开更多
Computational Fluid Dynamics(CFD)simulation is one of the important methods to study the performance and influencing factors of turbine flow sensors.According to the working characteristics of the turbine flow sensor,...Computational Fluid Dynamics(CFD)simulation is one of the important methods to study the performance and influencing factors of turbine flow sensors.According to the working characteristics of the turbine flow sensor,the passive simulation method based on the six degrees of freedom(6-DOF)model and dynamic mesh is proposed in this paper.The reliability of the simulation method is verified by steady-state experiments and unsteady-state experiments.The results show that the trend of meter factor with flow rate acquired from the simulation is close to the experimental results,and the deviation between the simulation result and the experiment result is low with a maximum deviation of 2.88%.In the unsteady simulation study,the impeller speed changes with the inlet velocity of the turbine flow sensor,which has a good follow-up.The passive simulation method can be used to predict the dynamic performance of the turbine flow sensor.展开更多
A novel chemiluminescence (CL) sensor for NH4+ combined with flow injection analysis is presented in this paper. It is based on the inhibition effect of NH4+ on the CL reaction between luminol, immobilized electrostat...A novel chemiluminescence (CL) sensor for NH4+ combined with flow injection analysis is presented in this paper. It is based on the inhibition effect of NH4+ on the CL reaction between luminol, immobilized electrostatically on an anion-exchange column, and hypochlorous acid electrogenerated on-line. The sensor responds linearly to NH4+ concentration in 1.0x10(-6)-4.0x10(-9) g/ml range. A complete analysis could be performed in 1 min. The system is stable for 200 determination.展开更多
Drawing inspiration from natural creatures that utilize flow fluctuations to evade predators and track prey,our human beings harness insights into flow dynamics through the development of flow sensors.The past few dec...Drawing inspiration from natural creatures that utilize flow fluctuations to evade predators and track prey,our human beings harness insights into flow dynamics through the development of flow sensors.The past few decades have witnessed a significant development in such sensors,evolving from bulky catheters designed for industrial settings to miniaturized,versatile and flexible devices tailored for wearable scenarios.This work presents a comprehensive overview of recent advances in flexible and thin-film-based flow sensors.First,the primary working mechanisms of these sensors,including thermal,piezoresistive,piezoelectric,and acoustic principles,are introduced,highlighting their challenges and alternative solutions.Subsequently,applications are categorized and demonstrated based on the type of flow including airflow,blood flow,breath,and water flow.Finally,future trends in flexible flow sensors are explored,indicating their pivotal roles in wide research and industry fields such as underwater robotics,human-machine interfaces,and bioelectronics.展开更多
A novel grain flow sensor consists of an impact plate and a PVDF(Polyvinylidene Fluoride)piezoelectric film was developed in this research.The kinetic model of the grain flow sensor was built to analyze the steady and...A novel grain flow sensor consists of an impact plate and a PVDF(Polyvinylidene Fluoride)piezoelectric film was developed in this research.The kinetic model of the grain flow sensor was built to analyze the steady and transient vibration disturbances which had a significant influence on performance of the sensor,and the results showed that damping ratio of the sensor was the key factor to improve accuracy of the sensor.To maximize damping ratio of the sensor,the thickness of the impact plate and damping material were optimized according to a loss factor model of the free damping structure.The optimized results indicated the most appropriate thickness ratio of damping material and the impact plate was 6.A test rig equipped with the novel grain flow sensor and weight sensors which could simulate field situations was built to investigate the performance of the sensor,on which test experiments under different feed flows were conducted.The results showed that the maximum error of the sensor was 3.02%and the mean error was 2.15%,which revealed that the novel grain flow sensor could be used to measure grain flow.Comparing with conventional grain flow sensors,the novel grain flow sensor has the features of high accuracy,simple structure and flexible signal processing methods.展开更多
This article summarizes our studies on micro flow sensors fabricated on a flexible polyimide circuit board by a low-cost hybrid process of thin-film deposition and circuit printing. The micro flow sensor has merits of...This article summarizes our studies on micro flow sensors fabricated on a flexible polyimide circuit board by a low-cost hybrid process of thin-film deposition and circuit printing. The micro flow sensor has merits of flexibility, structural simplicity, easy integrability with circuits, and good sensing performance. The sensor, which adheres to an object surface, can detect the surface flow around the object. In our study, we install the fabricated micro flow sensors on micro aerial vehicles （MAVs） to detect the surface flow variation around the aircraft wing and deduce the aerodynamic parameters of the MAVs in flight. Wind tunnel experiments using the sensors integrated with the MAVs are also conducted.展开更多
The grain yield data collected by the intelligent yield measurement system of the combine harvester is generated into a field plot yield distribution map,which is of great significance for guiding agricultural product...The grain yield data collected by the intelligent yield measurement system of the combine harvester is generated into a field plot yield distribution map,which is of great significance for guiding agricultural production.However,in the process of drawing the yield map,the combine harvester is affected by vibration during operation and the generated error data in the process of collecting data which will cause the drawing results to be inaccurate.This study researched two factors that cause errors,then,the influence of vibration interference on the measurement signal was eliminated by filtering,vibration isolation,and designing a double-plates differential grain flow sensor.Three methods were taken to eliminate random errors,gross errors and systematic errors,including using the arithmetic average value to replace the true value,the 3σcriterion,and removing the filling time data and the delaying time data.Finally,the grain yield distribution map was obtained through Matlab and Excel.The results showed that the interference frequency above 50 Hz could be eliminated by filtering,but it was difficult to filter the low-frequency signal which was close to the grain impact frequency.The vibration amplitude was reduced to 14.29%by adding a vibration isolation plate,and the SNR was increased from−4.67 dB to 29.21 dB by combining low-pass filtering and damping vibration isolation.When the grain feeding rate was 2 kg/s,the natural vibration amplitude of the sensor after difference was about 0.02 V and evenly distributed around the zero voltage 0.2 V.The influence of positive and negative offset on the average value of grain impact signal could be ignored,and the signal-to-noise ratio was increased from 29.21 dB to 62.49 dB.The results of field experiments showed that the yield map drawn can clearly display the yield value of the harvest area,which is used to guide agricultural production.展开更多
The signals generated by electromagnetic flow sensors used for slurry fluids are often affected by noise interference produced by interaction with the slurry itself.In this study,the power spectrum characteristics of ...The signals generated by electromagnetic flow sensors used for slurry fluids are often affected by noise interference produced by interaction with the slurry itself.In this study,the power spectrum characteristics of the signal are studied,and an attempt is made to determine the relationship between the characteristics of the related noise and the velocity and concentration of the slurry fluid.Dedicated experiments are conducted and the related power spectrum curve is obtained processing the signal measured by the sensor with Matlab.Numerical simulations are also carried out in the frame of an Eulerian approach in order get additional insights into the considered problem through comparison with the experimental results.The following conclusions are drawn:(1)The intensity of noise is directly proportional to the number of solid particles colliding with the electrode of the electromagnetic flow sensor per unit time,and to the square of the average velocity of the flow layer near the pipe wall.(2)With an increase in the slurry noise intensity,the power spectrum curve shifts upward in the logarithmic coordinate system(and vice versa).展开更多
The dependence of flow volume on the pressure difference between the ports of a U-tube was determined for both laminar and turbulent flows of a magnetic fluid.The results showed that the dependence was linear in the c...The dependence of flow volume on the pressure difference between the ports of a U-tube was determined for both laminar and turbulent flows of a magnetic fluid.The results showed that the dependence was linear in the case of laminar flow but was non-linear in the case of turbulent flow.In addition,the inductance and the voltage difference across two coils around the arms of the U-tube were calculated.The voltage difference was proportional to the flow volume and inversely proportional to the square of the coil length.These theoretical and experimental results demonstrate that the design of magnetic-fluid-based flow sensors is feasible.展开更多
Oil-gas-water three-phase flow in the pipe is commonly encountered in the petroleum and nature gas industry. Its flow patterns are complex and always changeable, so it’s difficult to be measured and is becoming one o...Oil-gas-water three-phase flow in the pipe is commonly encountered in the petroleum and nature gas industry. Its flow patterns are complex and always changeable, so it’s difficult to be measured and is becoming one of the most important subjects. Moreover, most of the oil fields in China are in such a high water fraction period that measures must be taken to meet the needs of the actual production. A conductance sensor which is widely used in the measurements of oil-water two-phase flow is used to measure the flow rate of the three-phase flow based on the research of the characteristics and the correlation theory, and a new technical solution which is suitable for measuring the oil-gas-water three-phase flow is established. A series of tests demonstrate that it’s feasible to use the conductance sensor in the measurements of oil- gas-water three-phase flow.展开更多
Patterned flow sensor cell consisting of single-walled carbon nanotubes (SWCNTs) network and polydimethylsiloxane (PDMS) are fabricated,based on the process of vacuum filtration,photolithography,and plasma etching.The...Patterned flow sensor cell consisting of single-walled carbon nanotubes (SWCNTs) network and polydimethylsiloxane (PDMS) are fabricated,based on the process of vacuum filtration,photolithography,and plasma etching.The sensor cell is a composite thin film and packaged to form a flow sensor,and then tested in different flow rates with different liquids,such as deionized (DI) water and NaCl solution.The induced-voltage increases with increasing flowing velocity and liquid concentration.The relation between induced-voltage and sensor cell conductivity is tested in the same liquid at the same flow rate.The higher the conductivity is,the higher the induced-voltage is.Some of the SWCNTs are fixed in the PDMS matrix,simultaneously some of them protrude above the composite thin film,which are exposed to the liquid and contribute to the voltage generation.The fabrication method can make the flow sensor scaled down to dimensions on the order of micrometers,which makes it suitable in very small liquid volumes.展开更多
Water outlets for washing hands and medical equipment are essential for preventing hospital infection. The present study clarified the effects of water flow volume on the identification and quantitative evaluation of ...Water outlets for washing hands and medical equipment are essential for preventing hospital infection. The present study clarified the effects of water flow volume on the identification and quantitative evaluation of bacteria found around spouts in the 17 hand-washing stations. Pseu-domonas aeruginosa was detected from 4 sta-tions before adjustment and 2 after adjustment. Although no significant difference was identified in the detection rate of P. aeruginosa (p = 0.368), when combining P. aeruginosa and glucose non-fermentative Gram-negative bacilli (NFB), the number of stations with P. aeruginosa and/or NFB decreased significantly from 15 before adjustment to 9 after adjustment (p = 0.023). Before adjust-ment, quantity of bacteria was “2+” for 3 stations and “1+” for 7 stations, but was “1+” for 3 stations and “2+” for 0 stations after adjustment. These results show that quantity of bacteria could be reduced from spouts by adjusting flow volume. These results were also supported by experiments for cleanliness using Adenosine 5’-triphosphate bioluminescence me- thod.展开更多
文摘A new silicon micro flow sensor with multiple temperature sensing elements was proposed and numerically simulated in considering wide range flow measuring properties.The micro flow sensor has three pairs of temperature sensing elements with a central heater compared with typical sensor which has only a temperature sensing element on each side of a central heater.A numerical analysis of the micro flow sensor by Finite Difference Formulation for Heat Transfer Equation was performed.The nearest pair of temperature sensor showed very good linear sensitivity between 0 to 0.4m/s flow and saturated from 0.75m/s flow.However the furthest pair of temperature sensor showed some flow sensitivity even though the flow rate of 2.0m/s.Thus,this suggested new micro flow meter with multiple temperature sensing elements could be used as a thermal mass flow sensor which has accuracy sensitivity for very wide flow range.
基金This work was supported in part by grants from the National Natural Science Foundation of China(NSFC,No.91648120,61633002,51575005)the Beijing Natural Science Foundation(No.4192026).
文摘Any phenomenon in nature is potential to be an inspiration for us to propose new ideas.Lateral line is a typical example which has attracted more interest in recent years.With the aid of lateral line,fish is capable of acquiring fluid information around,which is of great significance for them to survive,communicate and hunt underwater.In this paper,we briefly introduce the morphology and mechanism of the lateral line first.Then we focus on the development of artificial lateral line which typically consists of an array of sensors and can be installed on underwater robots.A series of sensors inspired by the lateral line with different sensing principles have been summarized.And then the applications of artificial lateral line systems in hydrodynamic environment sensing and vortices detection,dipole oscillation source detection,and autonomous control of underwater robots have been reviewed.In addition,the existing problems and future foci in this field have been further discussed in detail.The current works and future foci have demonstrated that artificial lateral line has great potentials of applications and contributes to the development of underwater robots.
基金The National Natural Science Foundation of China(No.62173122)the Hebei Key Project of Natural Science Foundation(No.F2021201031)。
文摘A passive simulation method based on the six degrees of freedom(6-DOF)model and dynamic mesh is proposed according to the working principle to study the dynamic characteristics of the turbine flow sensors.This simulation method controls the six degrees of freedom of the impeller using the user-defined functions(UDF)program so that it can only rotate under the impact of fluid.The impeller speed can be calculated in real-time,and the inlet speed can be set with time to obtain the dynamic performance of the turbine flow sensors.Based on this simulation method,three turbine flow sensors with different diameters were simulated,and the reliability of the simulation method was verified by both steady-state and unsteady-state experiments.The results show that the trend of meter factor with flow rate acquired from the simulation is close to the experimental results.The deviation between the simulation and experiment results is low,with a maximum deviation of 2.88%.In the unsteady simulation study,the impeller speed changed with the inlet velocity of the turbine flow sensor,showing good tracking performance.The passive simulation method can be used to predict the dynamic performance of the turbine flow sensor.
文摘The qualitative and quantitative assessment of gas flow has become increasingly relevant in the use of everyday systems. The micro flow sensor, developed by Innovative Sensor Technology AG （Switzerland）, is by principle a calorimetric flow sensor produced as a micro system on a glass substrate by means of photolithography and glass etching technology. These structures are arranged as a platinum micro heater and sensor in a Wheatstone bridge. The subsequent etching process produces an exposed area of polyimide membrane that is only a few microns thick and includes the resistive sensor structure as the active area. In addition, the RTD （resistance temperature detector） technology included on the sensor allows for the implementation of a variety of electronic biasing and signal processing modes. Since the sensor can be powered and the bridge can be measured in both CTA （constant temperature anemometer） and calorimetric mode, new possibilities are presented for both low and high flow rates with regard to temperature compensation, self-calibration and self-monitoring.
基金supported by National Natural Science Foundation of China,China(62173122)Hebei Key Project of Natural Science Foundation(F2021201031)Beijing-Tianjin-Hebei Collaborative Innovation Community Construction Project(20540301D)
文摘Computational Fluid Dynamics(CFD)simulation is one of the important methods to study the performance and influencing factors of turbine flow sensors.According to the working characteristics of the turbine flow sensor,the passive simulation method based on the six degrees of freedom(6-DOF)model and dynamic mesh is proposed in this paper.The reliability of the simulation method is verified by steady-state experiments and unsteady-state experiments.The results show that the trend of meter factor with flow rate acquired from the simulation is close to the experimental results,and the deviation between the simulation result and the experiment result is low with a maximum deviation of 2.88%.In the unsteady simulation study,the impeller speed changes with the inlet velocity of the turbine flow sensor,which has a good follow-up.The passive simulation method can be used to predict the dynamic performance of the turbine flow sensor.
文摘A novel chemiluminescence (CL) sensor for NH4+ combined with flow injection analysis is presented in this paper. It is based on the inhibition effect of NH4+ on the CL reaction between luminol, immobilized electrostatically on an anion-exchange column, and hypochlorous acid electrogenerated on-line. The sensor responds linearly to NH4+ concentration in 1.0x10(-6)-4.0x10(-9) g/ml range. A complete analysis could be performed in 1 min. The system is stable for 200 determination.
基金supported by the National Natural Science Foundation of China(52105593,52475610)the“Pioneer”and“Leading Goose”R&D Program of Zhejiang(2023C03007).
文摘Drawing inspiration from natural creatures that utilize flow fluctuations to evade predators and track prey,our human beings harness insights into flow dynamics through the development of flow sensors.The past few decades have witnessed a significant development in such sensors,evolving from bulky catheters designed for industrial settings to miniaturized,versatile and flexible devices tailored for wearable scenarios.This work presents a comprehensive overview of recent advances in flexible and thin-film-based flow sensors.First,the primary working mechanisms of these sensors,including thermal,piezoresistive,piezoelectric,and acoustic principles,are introduced,highlighting their challenges and alternative solutions.Subsequently,applications are categorized and demonstrated based on the type of flow including airflow,blood flow,breath,and water flow.Finally,future trends in flexible flow sensors are explored,indicating their pivotal roles in wide research and industry fields such as underwater robotics,human-machine interfaces,and bioelectronics.
基金the Key Technologies R&D Program of Liaoning Province(Y5L7160701)National High-tech R&D Program of China(863Program)(2013AA040403).
文摘A novel grain flow sensor consists of an impact plate and a PVDF(Polyvinylidene Fluoride)piezoelectric film was developed in this research.The kinetic model of the grain flow sensor was built to analyze the steady and transient vibration disturbances which had a significant influence on performance of the sensor,and the results showed that damping ratio of the sensor was the key factor to improve accuracy of the sensor.To maximize damping ratio of the sensor,the thickness of the impact plate and damping material were optimized according to a loss factor model of the free damping structure.The optimized results indicated the most appropriate thickness ratio of damping material and the impact plate was 6.A test rig equipped with the novel grain flow sensor and weight sensors which could simulate field situations was built to investigate the performance of the sensor,on which test experiments under different feed flows were conducted.The results showed that the maximum error of the sensor was 3.02%and the mean error was 2.15%,which revealed that the novel grain flow sensor could be used to measure grain flow.Comparing with conventional grain flow sensors,the novel grain flow sensor has the features of high accuracy,simple structure and flexible signal processing methods.
文摘This article summarizes our studies on micro flow sensors fabricated on a flexible polyimide circuit board by a low-cost hybrid process of thin-film deposition and circuit printing. The micro flow sensor has merits of flexibility, structural simplicity, easy integrability with circuits, and good sensing performance. The sensor, which adheres to an object surface, can detect the surface flow around the object. In our study, we install the fabricated micro flow sensors on micro aerial vehicles （MAVs） to detect the surface flow variation around the aircraft wing and deduce the aerodynamic parameters of the MAVs in flight. Wind tunnel experiments using the sensors integrated with the MAVs are also conducted.
基金supported by the Open Project of the Key Laboratory of Modern Agricultural Equipment and TechnologyMinistry of Education of the PRC(Grant No.JNZ201911)the Youth Talent Development and Program of Jiangsu University,and the Key Laboratory of Agricultural Equipment and Intelligent High Technology Research of Jiangsu Province.
文摘The grain yield data collected by the intelligent yield measurement system of the combine harvester is generated into a field plot yield distribution map,which is of great significance for guiding agricultural production.However,in the process of drawing the yield map,the combine harvester is affected by vibration during operation and the generated error data in the process of collecting data which will cause the drawing results to be inaccurate.This study researched two factors that cause errors,then,the influence of vibration interference on the measurement signal was eliminated by filtering,vibration isolation,and designing a double-plates differential grain flow sensor.Three methods were taken to eliminate random errors,gross errors and systematic errors,including using the arithmetic average value to replace the true value,the 3σcriterion,and removing the filling time data and the delaying time data.Finally,the grain yield distribution map was obtained through Matlab and Excel.The results showed that the interference frequency above 50 Hz could be eliminated by filtering,but it was difficult to filter the low-frequency signal which was close to the grain impact frequency.The vibration amplitude was reduced to 14.29%by adding a vibration isolation plate,and the SNR was increased from−4.67 dB to 29.21 dB by combining low-pass filtering and damping vibration isolation.When the grain feeding rate was 2 kg/s,the natural vibration amplitude of the sensor after difference was about 0.02 V and evenly distributed around the zero voltage 0.2 V.The influence of positive and negative offset on the average value of grain impact signal could be ignored,and the signal-to-noise ratio was increased from 29.21 dB to 62.49 dB.The results of field experiments showed that the yield map drawn can clearly display the yield value of the harvest area,which is used to guide agricultural production.
基金National Key Research and Development Program of China Subproject(No.2016YFD0700103)Natural Science Foundation of Henan(Nos.202300410124&19HASTIT021)+1 种基金Key Research and Development Program of Yunnan Province(No.2018ZC001)the National Natural Science foundation of China under Grant No.61801288.
文摘The signals generated by electromagnetic flow sensors used for slurry fluids are often affected by noise interference produced by interaction with the slurry itself.In this study,the power spectrum characteristics of the signal are studied,and an attempt is made to determine the relationship between the characteristics of the related noise and the velocity and concentration of the slurry fluid.Dedicated experiments are conducted and the related power spectrum curve is obtained processing the signal measured by the sensor with Matlab.Numerical simulations are also carried out in the frame of an Eulerian approach in order get additional insights into the considered problem through comparison with the experimental results.The following conclusions are drawn:(1)The intensity of noise is directly proportional to the number of solid particles colliding with the electrode of the electromagnetic flow sensor per unit time,and to the square of the average velocity of the flow layer near the pipe wall.(2)With an increase in the slurry noise intensity,the power spectrum curve shifts upward in the logarithmic coordinate system(and vice versa).
基金supported by the National Natural Science Foundation of China (60471004)the Beijing Natural Science Foundation (4062028)
文摘The dependence of flow volume on the pressure difference between the ports of a U-tube was determined for both laminar and turbulent flows of a magnetic fluid.The results showed that the dependence was linear in the case of laminar flow but was non-linear in the case of turbulent flow.In addition,the inductance and the voltage difference across two coils around the arms of the U-tube were calculated.The voltage difference was proportional to the flow volume and inversely proportional to the square of the coil length.These theoretical and experimental results demonstrate that the design of magnetic-fluid-based flow sensors is feasible.
文摘Oil-gas-water three-phase flow in the pipe is commonly encountered in the petroleum and nature gas industry. Its flow patterns are complex and always changeable, so it’s difficult to be measured and is becoming one of the most important subjects. Moreover, most of the oil fields in China are in such a high water fraction period that measures must be taken to meet the needs of the actual production. A conductance sensor which is widely used in the measurements of oil-water two-phase flow is used to measure the flow rate of the three-phase flow based on the research of the characteristics and the correlation theory, and a new technical solution which is suitable for measuring the oil-gas-water three-phase flow is established. A series of tests demonstrate that it’s feasible to use the conductance sensor in the measurements of oil- gas-water three-phase flow.
基金the National High-Tech Research & Development Program of China (2007AA04Z348)China Postdoctoral Science Foundation (20080440139)
文摘Patterned flow sensor cell consisting of single-walled carbon nanotubes (SWCNTs) network and polydimethylsiloxane (PDMS) are fabricated,based on the process of vacuum filtration,photolithography,and plasma etching.The sensor cell is a composite thin film and packaged to form a flow sensor,and then tested in different flow rates with different liquids,such as deionized (DI) water and NaCl solution.The induced-voltage increases with increasing flowing velocity and liquid concentration.The relation between induced-voltage and sensor cell conductivity is tested in the same liquid at the same flow rate.The higher the conductivity is,the higher the induced-voltage is.Some of the SWCNTs are fixed in the PDMS matrix,simultaneously some of them protrude above the composite thin film,which are exposed to the liquid and contribute to the voltage generation.The fabrication method can make the flow sensor scaled down to dimensions on the order of micrometers,which makes it suitable in very small liquid volumes.
文摘Water outlets for washing hands and medical equipment are essential for preventing hospital infection. The present study clarified the effects of water flow volume on the identification and quantitative evaluation of bacteria found around spouts in the 17 hand-washing stations. Pseu-domonas aeruginosa was detected from 4 sta-tions before adjustment and 2 after adjustment. Although no significant difference was identified in the detection rate of P. aeruginosa (p = 0.368), when combining P. aeruginosa and glucose non-fermentative Gram-negative bacilli (NFB), the number of stations with P. aeruginosa and/or NFB decreased significantly from 15 before adjustment to 9 after adjustment (p = 0.023). Before adjust-ment, quantity of bacteria was “2+” for 3 stations and “1+” for 7 stations, but was “1+” for 3 stations and “2+” for 0 stations after adjustment. These results show that quantity of bacteria could be reduced from spouts by adjusting flow volume. These results were also supported by experiments for cleanliness using Adenosine 5’-triphosphate bioluminescence me- thod.
