Accurate measurement of flow parameters is important in gas-solid two-phase flow,and such flow has to be dealt with in many processes involving bulk solids handling and transportation.The circular electrostatic sensor...Accurate measurement of flow parameters is important in gas-solid two-phase flow,and such flow has to be dealt with in many processes involving bulk solids handling and transportation.The circular electrostatic sensor is one of those used for gas-solid flow measurement.In this paper,the finite element method(FEM)is used to establish the mathematical model of the sensor,the spatial sensitivity characteristics of the sensors is analyzed,and the analytic model is improved by the nonlinear least square method and the iterative method.Finally,the correlation coefficients between the experimental results and the improved processing are compared and analyzed,and the mathematical expression of the model is improved.The feasibility and practicability of the improved model are verified.展开更多
Based on an electrical resistance tomography(ERT) sensor and the data mining technology,a new voidage measurement method is proposed for air-water two-phase flow.The data mining technology used in this work is a least...Based on an electrical resistance tomography(ERT) sensor and the data mining technology,a new voidage measurement method is proposed for air-water two-phase flow.The data mining technology used in this work is a least squares support vector machine(LS-SVM) algorithm together with the feature extraction method,and three feature extraction methods are tested:principal component analysis(PCA),partial least squares(PLS) and independent component analysis(ICA).In the practical voidage measurement process,the flow pattern is firstly identified directly from the conductance values obtained by the ERT sensor.Then,the appropriate voidage measurement model is selected according to the flow pattern identification result.Finally,the voidage is calculated.Experimental results show that the proposed method can measure the voidage effectively,and the measurement accuracy and speed are satisfactory.Compared with the conventional voidage measurement methods based on ERT,the proposed method doesn't need any image reconstruction process,so it has the advantage of good real-time performance.Due to the introduction of flow pattern identification,the influence of flow pattern on the voidage measurement is overcome.Besides,it is demonstrated that the LS-SVM method with PLS feature extraction presents the best measurement performance among the tested methods.展开更多
Wearable electronic devices have received increasing interests because of their excellent flexibility,stretchability,and human friendliness.As the core components,flexible strain sensors integrated with wide working r...Wearable electronic devices have received increasing interests because of their excellent flexibility,stretchability,and human friendliness.As the core components,flexible strain sensors integrated with wide working range,high sensitivity,and environment stability,especially in moisture or corrosive environments,remain a huge challenge.Herein,synergistic carbon nanotubes(CNTs)/reduced graphene oxide(rGO)dual conductive layer decorated elastic rubber band(RB)was successfully developed and treated with hydrophobic fumed silica(Hf-SiO_(2))for preparing superhydrophobic strain sensor.As expected,stable entangled CNTs layer and ultrasensitive microcracked rGO layer endow the sensor with extremely low detection limit(0.1%),high sensitivity(gauge factor is 685.3 at 482%strain),wide workable strain range(0–482%),fast response/recovery(200 ms/200 ms)and favorable reliability and reproducibility over 1000 cycles.Besides,the constructed Hf-SiO_(2) coating also makes the sensor exhibit excellent superhydrophobicity,self-cleaning property,and corrosion-resistance.As a proof of concept,our prepared high-performance strain sensor can realize the full-range monitoring of human motions and physiological signals even in the water environment,including pulse,vocalization,joint bending,running,and gesture recognition.Interestingly,it can also be knitted into a tactile electronic textile for spatial pressure distribution measurement.Thus,this study provides a universal technique for the preparation of high-performance strain sensors with great potential applications in the field of next-generation intelligent wearable electronics.展开更多
An index guiding photonic crystal fiber used in gas sensing applications is presented. The dependency of the confinement loss and relative sensitivity on the fiber parameters and wavelength is numerically investigated...An index guiding photonic crystal fiber used in gas sensing applications is presented. The dependency of the confinement loss and relative sensitivity on the fiber parameters and wavelength is numerically investigated by using the full-vectorial finite element method （FEM）. The simulations showed that the gas sensing sensitivity increased with an increase in the core diameter and a decrease in the distance between centers of two adjacent holes. Increasing the hole size of two outer cladding rings, this structure simultaneously showed up to 10% improved sensitivity, and the confinement loss reached 6x 10-4 times less than that of the prior sensor at the wavelength of 1.5 μm. This proved the ability of this fiber used in gas and chemicals sensing applications.展开更多
Silica-based fiber tips are used in a variety of spectroscopic, micro- or nano-scopic optical sensor applications and photonic micro-devices. The miniaturization of optical sensor systems and the technical implementat...Silica-based fiber tips are used in a variety of spectroscopic, micro- or nano-scopic optical sensor applications and photonic micro-devices. The miniaturization of optical sensor systems and the technical implementation using optical fibers can provide new sensor designs with improved properties and functionality for new applications. The selective-etching of specifically doped silica fibers is a promising method in order to form complex photonic micro structures at the end or within fibers such as tips and cavities in various shapes useful for the all-fiber sensor and imaging applications. In the present study, we investigated the preparation of geometrically predefined, nanoscaled fiber tips by taking advantage of the dopant concentration profiles of highly doped step-index fibers. For this purpose, a gas phase etching process using hydrofluoric acid （HF） vapor was applied. The shaping of the fiber tips was based on very different etching rates as a result of the doping characteristics of specific optical fibers. Technological studies on the influence of the etching gas atmosphere on the temporal tip shaping and the final geometry were performed using undoped and doped silica fibers. The influence of the doping characteristics was investigated in phosphorus-, germanium-, fluorine- and boron-doped glass fibers. Narrow exposed as well as protected internal fiber tips in various shapes and tip radiuses down to less than 15 nm were achieved and characterized geometrically and topologically. For investigations into surface plasmon resonance effects, the fiber tips were coated with nanometer-sized silver layers by means of vapour deposition and finally subjected to an annealing treatment.展开更多
基金Science and Technology on Electronic Test and Measurement Laboratory(No.9140C12040515X)
文摘Accurate measurement of flow parameters is important in gas-solid two-phase flow,and such flow has to be dealt with in many processes involving bulk solids handling and transportation.The circular electrostatic sensor is one of those used for gas-solid flow measurement.In this paper,the finite element method(FEM)is used to establish the mathematical model of the sensor,the spatial sensitivity characteristics of the sensors is analyzed,and the analytic model is improved by the nonlinear least square method and the iterative method.Finally,the correlation coefficients between the experimental results and the improved processing are compared and analyzed,and the mathematical expression of the model is improved.The feasibility and practicability of the improved model are verified.
基金Supported by the National Natural Science Foundation of China (60972138)
文摘Based on an electrical resistance tomography(ERT) sensor and the data mining technology,a new voidage measurement method is proposed for air-water two-phase flow.The data mining technology used in this work is a least squares support vector machine(LS-SVM) algorithm together with the feature extraction method,and three feature extraction methods are tested:principal component analysis(PCA),partial least squares(PLS) and independent component analysis(ICA).In the practical voidage measurement process,the flow pattern is firstly identified directly from the conductance values obtained by the ERT sensor.Then,the appropriate voidage measurement model is selected according to the flow pattern identification result.Finally,the voidage is calculated.Experimental results show that the proposed method can measure the voidage effectively,and the measurement accuracy and speed are satisfactory.Compared with the conventional voidage measurement methods based on ERT,the proposed method doesn't need any image reconstruction process,so it has the advantage of good real-time performance.Due to the introduction of flow pattern identification,the influence of flow pattern on the voidage measurement is overcome.Besides,it is demonstrated that the LS-SVM method with PLS feature extraction presents the best measurement performance among the tested methods.
基金supported by the National Natural Science Foundation of China(12072325)the National Key R&D Program of China(2019YFA0706802)the 111 Project(D18023)。
文摘Wearable electronic devices have received increasing interests because of their excellent flexibility,stretchability,and human friendliness.As the core components,flexible strain sensors integrated with wide working range,high sensitivity,and environment stability,especially in moisture or corrosive environments,remain a huge challenge.Herein,synergistic carbon nanotubes(CNTs)/reduced graphene oxide(rGO)dual conductive layer decorated elastic rubber band(RB)was successfully developed and treated with hydrophobic fumed silica(Hf-SiO_(2))for preparing superhydrophobic strain sensor.As expected,stable entangled CNTs layer and ultrasensitive microcracked rGO layer endow the sensor with extremely low detection limit(0.1%),high sensitivity(gauge factor is 685.3 at 482%strain),wide workable strain range(0–482%),fast response/recovery(200 ms/200 ms)and favorable reliability and reproducibility over 1000 cycles.Besides,the constructed Hf-SiO_(2) coating also makes the sensor exhibit excellent superhydrophobicity,self-cleaning property,and corrosion-resistance.As a proof of concept,our prepared high-performance strain sensor can realize the full-range monitoring of human motions and physiological signals even in the water environment,including pulse,vocalization,joint bending,running,and gesture recognition.Interestingly,it can also be knitted into a tactile electronic textile for spatial pressure distribution measurement.Thus,this study provides a universal technique for the preparation of high-performance strain sensors with great potential applications in the field of next-generation intelligent wearable electronics.
文摘An index guiding photonic crystal fiber used in gas sensing applications is presented. The dependency of the confinement loss and relative sensitivity on the fiber parameters and wavelength is numerically investigated by using the full-vectorial finite element method （FEM）. The simulations showed that the gas sensing sensitivity increased with an increase in the core diameter and a decrease in the distance between centers of two adjacent holes. Increasing the hole size of two outer cladding rings, this structure simultaneously showed up to 10% improved sensitivity, and the confinement loss reached 6x 10-4 times less than that of the prior sensor at the wavelength of 1.5 μm. This proved the ability of this fiber used in gas and chemicals sensing applications.
文摘Silica-based fiber tips are used in a variety of spectroscopic, micro- or nano-scopic optical sensor applications and photonic micro-devices. The miniaturization of optical sensor systems and the technical implementation using optical fibers can provide new sensor designs with improved properties and functionality for new applications. The selective-etching of specifically doped silica fibers is a promising method in order to form complex photonic micro structures at the end or within fibers such as tips and cavities in various shapes useful for the all-fiber sensor and imaging applications. In the present study, we investigated the preparation of geometrically predefined, nanoscaled fiber tips by taking advantage of the dopant concentration profiles of highly doped step-index fibers. For this purpose, a gas phase etching process using hydrofluoric acid （HF） vapor was applied. The shaping of the fiber tips was based on very different etching rates as a result of the doping characteristics of specific optical fibers. Technological studies on the influence of the etching gas atmosphere on the temporal tip shaping and the final geometry were performed using undoped and doped silica fibers. The influence of the doping characteristics was investigated in phosphorus-, germanium-, fluorine- and boron-doped glass fibers. Narrow exposed as well as protected internal fiber tips in various shapes and tip radiuses down to less than 15 nm were achieved and characterized geometrically and topologically. For investigations into surface plasmon resonance effects, the fiber tips were coated with nanometer-sized silver layers by means of vapour deposition and finally subjected to an annealing treatment.
