Nitrogen-doped carbon quantum dots(N-CQDs)are nanocomposites that can be synthesized by the hydrothermal method.In this work,N-CQDs with the size of 3.2±1.7 nm was prepared from 1 g citric acid and 2 g urea precu...Nitrogen-doped carbon quantum dots(N-CQDs)are nanocomposites that can be synthesized by the hydrothermal method.In this work,N-CQDs with the size of 3.2±1.7 nm was prepared from 1 g citric acid and 2 g urea precursor in 10 mL water.Electrochemiluminescence(ECL)of the prepared N-CQDs with K2S2O8 as a coreactant was found to reach a high ECL efficiency up to 109%relative to that of the Ru(bpy)_(3)^(2+)/K_(2)S_(2)O_(8),coreactant system,revealing their great potential for electroanalysis.It is probably because that N elements were doped well in this N-CQDs and increased presence of surface states per mass of N-CQDs.From the spooling ECL spectroscopy,it can be found that the ECL spectra exhibited both a red shift compared with their photoluminescence(PL)spectrum and a wavelength shift during the potentiodynamic scan in the ECL evolution and devolution processes,due to various emissive excited states of N-CQDs leading to higher ECL efficiency.This work gives an insight into development of high ECL efficiency N-CQDs for bioanalytical and light emitting applications.展开更多
The 2D digital simplified flow valve is composed of a pilot-operated valvedesigned with both rotary and linear motions of a single spool, and a stepper motor under continualcontrol. How the structural parameters affec...The 2D digital simplified flow valve is composed of a pilot-operated valvedesigned with both rotary and linear motions of a single spool, and a stepper motor under continualcontrol. How the structural parameters affect the static and dynamic characteristics of the valve isfirst clarified and a criterion for stability is presented. Experiments are designed to test theperformance of the valve. It is necessary to establish a balance between the static and dynamiccharacteristics in deciding the structural parameters. Nevertheless, it is possible to maintain thedynamic response at a fairly high level, while keeping the leakage of the pilot stage at anacceptable level. One of the features of the digital valve is stage control. In stage control thenonlinearities, such as electromagnetic saturation and hysteresis, are greatly reduced. To a largeextent the dynamic response of the valve is decided by the executing cycle of the control algorithm.展开更多
The finite element method （FEM） and particle image velocimetry （PIV） technique are utilized to get the flow field along the inlet passage, the chamber, the metering port and the outlet passage of spool valve at th...The finite element method （FEM） and particle image velocimetry （PIV） technique are utilized to get the flow field along the inlet passage, the chamber, the metering port and the outlet passage of spool valve at three different valve openings. For FEM numerical simulation, the stream function ψ-vorticity ω forms of continuity and Navier-Stokes equations are employed and FEM is applied to discrete the equations. Homemade simulation codes are executed to compute the values of stream function and vorticity at each node in the flow domain, then according to the correlation between stream function and velocity components, the velocity vectors of the whole field are calculated. For PIV experiment, pulse Nd： YAG laser is exploited to generate laser beam, cylindrical and spherical lenses are combined each other to produce 1.0 mm thickness laser sheet to illuminate the object plane, Polystyrene spherical particle with diameter of 30-50 μm is seeded in the fluid as a tracing particles, Kodak ES 1.0 CCD camera is employed to capture the images of interested, the images are processed with fast Fourier transform （FFT） cross-correlation algorithm and the processing results is displayed. Both results of numerical simulation and PIV experimental show that there are three main areas in the spool valve where vortex is formed. Numerical results also indicate that the valve opening have some effects on the flow structure of the valve. The investigation is helpful for qualitatively analyzing the energy loss, noise generating, steady state flow forces and even designing the geometry structure and flow passage.展开更多
Precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke was derived. The computational fluid dynamics was used to analyze the flow features of the sloping U-shape not...Precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke was derived. The computational fluid dynamics was used to analyze the flow features of the sloping U-shape notch on the spool, such as mass flow rates, flow coefficients, effiux angles and steady state flow forces under different operating conditions. At last, the reliability of the mathematical model of the flow area for the sloping U-shape notch orifice on the spool was demonstrated by the comparison between the orifice area curve derived and the corresponding experimental data provided by the test. It is presented that the bottom arc of sloping U-shape notch （ABU） should not be omitted when it is required to accurately calculate the orifice area of ABU. Although the theoretical flow area of plain bottom sloping U-shape notch （PBU） is larger than that of ABU at the same opening, the simulated mass flow and experimental flow area of ABU are both larger than these of PBU at the same opening, while the simulated flow force of PBU is larger than that of ABU at the same opening. Therefore, it should be prior to adapt the ABU when designing the spool with proportional character.展开更多
We demonstrate coherent transfer of an ultra-stable optical frequency at 192.8 THz over 50-km spooled fiber. Random phase noise induced by environmental disturbance through fiber is detected and suppressed by feeding ...We demonstrate coherent transfer of an ultra-stable optical frequency at 192.8 THz over 50-km spooled fiber. Random phase noise induced by environmental disturbance through fiber is detected and suppressed by feeding a correctional signal into an acousto-optic modulator. After being compensated, the fiber-induced frequency instability is 2×10-17 at 1-s averaging time and reaches 8×10-20 after 16 h. The noise floor of the compensation system could be as low as 2×10-18 at 1-s averaging time.展开更多
To increase the efficiency and reliability of the thermodynamics analysis of the spool valve, the precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke and thermal-...To increase the efficiency and reliability of the thermodynamics analysis of the spool valve, the precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke and thermal-hydraulic bond graph based on the conservation of mass and energy were introduced. Subsequently, the connection rule for the bond graph elements and the method to construct the complete thermal-hydraulic system model were proposed. On the basis of heat transfer analysis of a typical hydraulic circuit containing the spool valve, the lumped parameter for mathematical model of the system was given. At last, the reliability of the mathematical model of the flow area and the thermal-hydraulic system for the sloping U-shape notch orifice on the spool were demonstrated by the test. The good agreement between the simulation results and experimental data demonstrates the validity of the modeling method.展开更多
In hydraulic area,independent metering control(IMC)technology is an effective approach to improve system efficiency and control flexibility.In addition,digital hydraulic technology(DHT)has been verified as a reasonabl...In hydraulic area,independent metering control(IMC)technology is an effective approach to improve system efficiency and control flexibility.In addition,digital hydraulic technology(DHT)has been verified as a reasonable method to optimize system dynamic performance.Integrating these two technologies into one component can combine their advantages together.However,few works focused on it.In this paper,a twin spools valve with switching technologycontrolled pilot stage(TSVSP)is presented,which applied DHT into its pilot stage while appending IMC into its main stage.Based on this prototype valve,a series of numerical and experiment analysis of its IMC performance with both simulated load and excavator boom cylinder are carried out.Results showed fast and robust performance of pressure and flow compound control with acceptable fluctuation phenomenon caused by switching technology.Rising time of flow response in excavator cylinder can be controlled within 200 ms,meanwhile,the recovery time of rod chamber pressure under suddenly changed condition is optimized within 250 ms.IMC system based on TSVSP can improve both dynamic performance and robust characteristics of the target actuator so it is practical in valve-cylinder system and can be applied in mobile machineries.展开更多
A study of the magnetic field with an unsaturated iron core in tokamak equilibrium using a spool model is described in detail. The application of this model to the J-TEXT tokamak shows that the calculated results are ...A study of the magnetic field with an unsaturated iron core in tokamak equilibrium using a spool model is described in detail. The application of this model to the J-TEXT tokamak shows that the calculated results are in good agreement with those measured experimentally. At present this scheme is used to give the plasma configuration during J-TEXT＇s operation.展开更多
A digital electro-hydraulic 4-port differential pressure control valve with a novel principle and structure is presented. The valve is designed by applying the regulating pressure technique of a capillary damping tube...A digital electro-hydraulic 4-port differential pressure control valve with a novel principle and structure is presented. The valve is designed by applying the regulating pressure technique of a capillary damping tube and also making full use of double freedom of the spool motion. Thevalve can implement digitizing interface easily. The theoretical analysis and experimental resultsshow that the valve is not only very simple in structure and convenient in use, but also has manygood properties, such as fast response, no-null-shift, etc.展开更多
Environmental vibration causes mechanical deformation in optical fibers, which induces excess frequency noise in fiber-stabilized lasers. In order to solve such a problem, we propose an ultralow acceleration sensitivi...Environmental vibration causes mechanical deformation in optical fibers, which induces excess frequency noise in fiber-stabilized lasers. In order to solve such a problem, we propose an ultralow acceleration sensitivity fiber spool with symmetrically mounted structure. By numerical analysis with the finite element method, we obtain the optimal geometry parameters of the spool with which the horizontal and vertical acceleration sensitivity can be reduced to 3.25 × 10^-12/g and 5.38 × 10^-12/g respectively. Moreover, the structure features the insensitivity to the variation of geometry parameters,which will minimize the influence from numerical simulation error and manufacture tolerance.展开更多
基金funded by the Natural Sciences and Engineering Research Council of Canada(NSERC,DG RGPIN-2013-201697,DG RGPIN-2018-06556,DG RGPIN-2023-05337,SPG STPGP-2016-493924(Z.D.))New Frontiers in Research Fund,NFRFR-2021-00272(Z.D.)+2 种基金National Natural Science Foundation of China(22004034(X.Q.))Natural Science Foundation of Hunan Province(China)(2020JJ5226(X.Q.))China Scholarship Council(CSC,201908430010(X.Q.)).
文摘Nitrogen-doped carbon quantum dots(N-CQDs)are nanocomposites that can be synthesized by the hydrothermal method.In this work,N-CQDs with the size of 3.2±1.7 nm was prepared from 1 g citric acid and 2 g urea precursor in 10 mL water.Electrochemiluminescence(ECL)of the prepared N-CQDs with K2S2O8 as a coreactant was found to reach a high ECL efficiency up to 109%relative to that of the Ru(bpy)_(3)^(2+)/K_(2)S_(2)O_(8),coreactant system,revealing their great potential for electroanalysis.It is probably because that N elements were doped well in this N-CQDs and increased presence of surface states per mass of N-CQDs.From the spooling ECL spectroscopy,it can be found that the ECL spectra exhibited both a red shift compared with their photoluminescence(PL)spectrum and a wavelength shift during the potentiodynamic scan in the ECL evolution and devolution processes,due to various emissive excited states of N-CQDs leading to higher ECL efficiency.This work gives an insight into development of high ECL efficiency N-CQDs for bioanalytical and light emitting applications.
基金This project is supported by National Natural Science Foundation of China (No.50075082).
文摘The 2D digital simplified flow valve is composed of a pilot-operated valvedesigned with both rotary and linear motions of a single spool, and a stepper motor under continualcontrol. How the structural parameters affect the static and dynamic characteristics of the valve isfirst clarified and a criterion for stability is presented. Experiments are designed to test theperformance of the valve. It is necessary to establish a balance between the static and dynamiccharacteristics in deciding the structural parameters. Nevertheless, it is possible to maintain thedynamic response at a fairly high level, while keeping the leakage of the pilot stage at anacceptable level. One of the features of the digital valve is stage control. In stage control thenonlinearities, such as electromagnetic saturation and hysteresis, are greatly reduced. To a largeextent the dynamic response of the valve is decided by the executing cycle of the control algorithm.
文摘The finite element method （FEM） and particle image velocimetry （PIV） technique are utilized to get the flow field along the inlet passage, the chamber, the metering port and the outlet passage of spool valve at three different valve openings. For FEM numerical simulation, the stream function ψ-vorticity ω forms of continuity and Navier-Stokes equations are employed and FEM is applied to discrete the equations. Homemade simulation codes are executed to compute the values of stream function and vorticity at each node in the flow domain, then according to the correlation between stream function and velocity components, the velocity vectors of the whole field are calculated. For PIV experiment, pulse Nd： YAG laser is exploited to generate laser beam, cylindrical and spherical lenses are combined each other to produce 1.0 mm thickness laser sheet to illuminate the object plane, Polystyrene spherical particle with diameter of 30-50 μm is seeded in the fluid as a tracing particles, Kodak ES 1.0 CCD camera is employed to capture the images of interested, the images are processed with fast Fourier transform （FFT） cross-correlation algorithm and the processing results is displayed. Both results of numerical simulation and PIV experimental show that there are three main areas in the spool valve where vortex is formed. Numerical results also indicate that the valve opening have some effects on the flow structure of the valve. The investigation is helpful for qualitatively analyzing the energy loss, noise generating, steady state flow forces and even designing the geometry structure and flow passage.
基金Project(51004085)supported by the National Natural Science Foundation of China
文摘Precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke was derived. The computational fluid dynamics was used to analyze the flow features of the sloping U-shape notch on the spool, such as mass flow rates, flow coefficients, effiux angles and steady state flow forces under different operating conditions. At last, the reliability of the mathematical model of the flow area for the sloping U-shape notch orifice on the spool was demonstrated by the comparison between the orifice area curve derived and the corresponding experimental data provided by the test. It is presented that the bottom arc of sloping U-shape notch （ABU） should not be omitted when it is required to accurately calculate the orifice area of ABU. Although the theoretical flow area of plain bottom sloping U-shape notch （PBU） is larger than that of ABU at the same opening, the simulated mass flow and experimental flow area of ABU are both larger than these of PBU at the same opening, while the simulated flow force of PBU is larger than that of ABU at the same opening. Therefore, it should be prior to adapt the ABU when designing the spool with proportional character.
基金supported by the National Natural Science Foundation of China(Grant Nos.11127405,11334002,and 11374102)the National Basic Research Program of China(Grant No.2012CB821302)
文摘We demonstrate coherent transfer of an ultra-stable optical frequency at 192.8 THz over 50-km spooled fiber. Random phase noise induced by environmental disturbance through fiber is detected and suppressed by feeding a correctional signal into an acousto-optic modulator. After being compensated, the fiber-induced frequency instability is 2×10-17 at 1-s averaging time and reaches 8×10-20 after 16 h. The noise floor of the compensation system could be as low as 2×10-18 at 1-s averaging time.
基金Project(51175518)supported by the National Natural Science Foundation of China
文摘To increase the efficiency and reliability of the thermodynamics analysis of the spool valve, the precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke and thermal-hydraulic bond graph based on the conservation of mass and energy were introduced. Subsequently, the connection rule for the bond graph elements and the method to construct the complete thermal-hydraulic system model were proposed. On the basis of heat transfer analysis of a typical hydraulic circuit containing the spool valve, the lumped parameter for mathematical model of the system was given. At last, the reliability of the mathematical model of the flow area and the thermal-hydraulic system for the sloping U-shape notch orifice on the spool were demonstrated by the test. The good agreement between the simulation results and experimental data demonstrates the validity of the modeling method.
基金Supported by National Natural Science Foundation of China(Grant Nos.52005441,51890885)open Foundation of the State Key Laboratory of Fluid Power and Mechatronic Systems(Grant No.GZKF-201906)+1 种基金Zhejiang Province Natural Science Foundation of China(Grant No.LQ21E050017)China Postdoctoral Science Foundation(Grant Nos.2021M692777,2021T140594).
文摘In hydraulic area,independent metering control(IMC)technology is an effective approach to improve system efficiency and control flexibility.In addition,digital hydraulic technology(DHT)has been verified as a reasonable method to optimize system dynamic performance.Integrating these two technologies into one component can combine their advantages together.However,few works focused on it.In this paper,a twin spools valve with switching technologycontrolled pilot stage(TSVSP)is presented,which applied DHT into its pilot stage while appending IMC into its main stage.Based on this prototype valve,a series of numerical and experiment analysis of its IMC performance with both simulated load and excavator boom cylinder are carried out.Results showed fast and robust performance of pressure and flow compound control with acceptable fluctuation phenomenon caused by switching technology.Rising time of flow response in excavator cylinder can be controlled within 200 ms,meanwhile,the recovery time of rod chamber pressure under suddenly changed condition is optimized within 250 ms.IMC system based on TSVSP can improve both dynamic performance and robust characteristics of the target actuator so it is practical in valve-cylinder system and can be applied in mobile machineries.
基金supported by National Basic Research Program ('973'Program)of China (No.2008CB717805)
文摘A study of the magnetic field with an unsaturated iron core in tokamak equilibrium using a spool model is described in detail. The application of this model to the J-TEXT tokamak shows that the calculated results are in good agreement with those measured experimentally. At present this scheme is used to give the plasma configuration during J-TEXT＇s operation.
文摘A digital electro-hydraulic 4-port differential pressure control valve with a novel principle and structure is presented. The valve is designed by applying the regulating pressure technique of a capillary damping tube and also making full use of double freedom of the spool motion. Thevalve can implement digitizing interface easily. The theoretical analysis and experimental resultsshow that the valve is not only very simple in structure and convenient in use, but also has manygood properties, such as fast response, no-null-shift, etc.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11034008 and 11274324)the Key Research Program of the Chinese Academy of Sciences(Grant No.KJZD-EW-W02)
文摘Environmental vibration causes mechanical deformation in optical fibers, which induces excess frequency noise in fiber-stabilized lasers. In order to solve such a problem, we propose an ultralow acceleration sensitivity fiber spool with symmetrically mounted structure. By numerical analysis with the finite element method, we obtain the optimal geometry parameters of the spool with which the horizontal and vertical acceleration sensitivity can be reduced to 3.25 × 10^-12/g and 5.38 × 10^-12/g respectively. Moreover, the structure features the insensitivity to the variation of geometry parameters,which will minimize the influence from numerical simulation error and manufacture tolerance.
