Inter-growth bismuth layer-structured ferroelectrics（BLSFs）, Bi_4Ti_3O_（12）-Na_（0.5）Bi_（4.5）Ti_4O_（15）（BIT-NBT）, were successfully synthesized using the traditional solid-state reaction method. X-ray diffr...Inter-growth bismuth layer-structured ferroelectrics（BLSFs）, Bi_4Ti_3O_（12）-Na_（0.5）Bi_（4.5）Ti_4O_（15）（BIT-NBT）, were successfully synthesized using the traditional solid-state reaction method. X-ray diffraction（XRD） Rietveld refinements were conducted using GSAS software. Good agreement and low residual are obtained. The XRD diffraction peaks can be well indexed into I2 cm space group. The inter-growth structure was further observed in the high-resolution TEM image. Dielectric and impedance properties were measured and systematically analyzed. At the temperature range 763-923 K（below T_c）, doubly ionized oxygen vacancies（OVs） are localized and the short-range hopping leads to the relaxation processes with an activation energy of 0.79-1.01 eV. Above T_c, the doubly charged OVs are delocalized and become free ones, which contribute to the long-range dc conduction. The reduction in relaxation species gives rise to a higher relaxation activation energy ~ 1.6 eV.展开更多
Based on the principles of electrical conduction and transformation, a model was put forward for the electrical conversion of piezoelectric damping composites, and a related formula was derived. The results show that ...Based on the principles of electrical conduction and transformation, a model was put forward for the electrical conversion of piezoelectric damping composites, and a related formula was derived. The results show that the best effect of conversion can be achieved by reducing the imaginary part of the impedance and matching the frequency. The optimal damping effect at a certain frequency requires resistance of conductive phase （R） satisfying the condition of R=I/（ωC）, but this condition may cause the damping effect at other frequencies to deviate away from the optimum condition. It is suggested that in order to make the damping effect more efficient and objective, frequency matching should be considered during the design of piezoelectric damping composites.展开更多
Induction motors have been widely used across industry,particularly with smaller loads and fixed speed services.Existing works focus on fault detection of induction motors without considering the shutdown time and pro...Induction motors have been widely used across industry,particularly with smaller loads and fixed speed services.Existing works focus on fault detection of induction motors without considering the shutdown time and production in industry.Therefore,this work aims to monitor the health conditions of the induction motor continuously through electrical signature analysis(ESA).The proposed technique is capable of predicting different kinds of faults,i.e.,rotor faults,stator phase imbalances,and supply cable faults at early stages.Moreover,ESA in real time is implemented.Thereafter,these current spectra were analyzed in frequency domain and compared with healthy current spectra.Performance evaluation is implemented by observing these spectra under different faulty conditions.A comparative study is made and analyzed through MATLAB simulations.展开更多
Characteristic period is an important parameter of the seismic design response spectrum. There is important theoretical significance and engineering application value to the study of the characteristic period of seism...Characteristic period is an important parameter of the seismic design response spectrum. There is important theoretical significance and engineering application value to the study of the characteristic period of seismic design response spectrum of ultra high voltage （UHV） electrical equipment. In this paper, 1448 horizontal earthquake records within the world scope including the United States and Japan for Site Class m were analyzed. Results show that both magnitude and epicentral distance have great influence on the characteristic period. About 80 % of characteristic periods of strong earthquake records are about 0. 9s. Statistical analysis was conducted on the seismic hazard assessment results of 312 projects of China in recent years, and it is found that about 70 % of characteristic periods are about 0. 9s. Combined with the related code comparison and analysis, it is suggested that the characteristic period of the seismic design response spectrmn of UHV electrical equipment should select 0. 9s in order to effectively guarantee the seismic safety of UHV electrical equipment.展开更多
CONSPECTUS:Microscopy has long expanded humanity’s understanding of the microscopic world,transcending limitations of the naked eye.The atomic force microscope(AFM),in particular,marks a major advancement in this fie...CONSPECTUS:Microscopy has long expanded humanity’s understanding of the microscopic world,transcending limitations of the naked eye.The atomic force microscope(AFM),in particular,marks a major advancement in this field,enabling nanoscale investigations of materials through direct physical probing of their surface.Unlike traditional microscopes that use light or electrons,AFM’s unique methodology allows for both imaging on the atomic scale and precise manipulation of a material’s mechanical,electrical,and chemical properties.A key advantage also lies in its capacity for multimodal analysis,where multiple properties can be simultaneously measured to provide comprehensive insights into material behavior.In the current landscape of miniaturizing electronics and optimizing energy materials,the interplay between mechanical and electrical properties has gained particular importance.The precise integration of these properties is vital for advancing nanotechnology,and AFM allows the elucidation of these effects on the nanoscale.This is especially relevant for multifunctional materials that respond to both mechanical and electrical stimuli,and as surface properties exert a pronounced influence on material behavior at reduced scales,the capabilities of the AFM have informed the design and characterization of many smart,dielectric,and energy materials over the past decades.In this article,we present our group’s recent works on the integration of mechanical and electrical analyses using AFM-based characterization techniques.We begin by tracing the progression from early piezoresponse force microscopy(PFM)studies,which investigated domain growth and switching characteristics in ferroelectric films,as well as the surface charge dynamics of polar domains.Based on these foundations,we introduce a surface scraping-based method of imaging-charge gradient microscopy-for rapid characterization of these domains and showcase a novel three-dimensional lithography technique that exploits asymmetric wear rates of up and down domains.This method underscores the strongly coupled interactions between the mechanical and electrical properties of dielectrics,with the potential for scaling to device-relevant dimensions.The discussion then transitions from piezoelectric electromechanical dynamics to ionic electrochemical phenomena,where electrical stimuli similarly induce mechanical surface deformations detectable by an AFM tip.We explore a multimodal approach in electrochemical strain microscopy(ESM)to investigate functional components in composite materials,demonstrating how friction mapping can be employed to identify specific material components.Additionally,we introduce mechanically and electrically modulated spectroscopy techniques,including nanoindentation,PFM hysteresis,and current−voltage spectroscopy,emphasizing the potential of spectroscopic methods to be customized for eliciting targeted material response.Finally,the challenges and future directions in AFM-based research are addressed,as we offer approaches to enhance the reliability,accuracy,and data throughput of AFM measurements.We anticipate that these integrated approaches,which bridge mechanical and electrical analyses at the nanoscale,will accelerate material discovery and fuel innovation across diverse fields,from energy storage to nanoelectronics.展开更多
A type of combined optical fiber interferometric acoustic emission sensor is proposed. The sensor can be independent on the laser source and make light interference by matching the lengths of two arms,so it can be use...A type of combined optical fiber interferometric acoustic emission sensor is proposed. The sensor can be independent on the laser source and make light interference by matching the lengths of two arms,so it can be used to monitor the health of large structure. Theoretical analyses indicate that the system can be equivalent to the Michelson interferometer with two optical fiber loop reflectors,and its sensitivity has been remarkably increased because of the decrease of the losses of light energy. PZT is powered by DC regulator to control the operating point of the system,so the system can accurately detect feeble vibration which is generated by ultrasonic waves propagating on the surface of solid. The amplitude and the frequency of feeble vibration signal are obtained by detecting the output light intensity of interferometer and using Fourier transform technique. The results indicate that the system can be used to detect the acoustic emission signals by the frequency characteristics.展开更多
Electrical power network analysis and computation play an important role in the planning and operation of the power grid,and they are modeled mathematically as differential equations and network algebraic equations.Th...Electrical power network analysis and computation play an important role in the planning and operation of the power grid,and they are modeled mathematically as differential equations and network algebraic equations.The direct method based on Gaussian elimination theory can obtain analytical results.Two factors affect computing efficiency:the number of nonzero element fillings and the length of elimination tree.This article constructs mapping correspondence between eliminated tree nodes and quotient graph nodes through graph and quotient graph theories.The Approximate Minimum Degree(AMD)of quotient graph nodes and the length of the elimination tree nodes are composed to build an Approximate Minimum Degree and Minimum Length(AMDML)model.The quotient graph node with the minimum degree,which is also the minimum length of elimination tree node,is selected as the next ordering vector.Compared with AMD ordering method and other common methods,the proposed method further reduces the length of elimination tree without increasing the number of nonzero fillings;the length was decreased by about 10%compared with the AMD method.A testbed for experiment was built.The efficiency of the proposed method was evaluated based on different sizes of coefficient matrices of power flow cases.展开更多
In a home energy management system(HEMS),appliances are becoming diversified and intelligent,so that certain simple maintenance work can be completed by appliances themselves.During the measurement,collection and tran...In a home energy management system(HEMS),appliances are becoming diversified and intelligent,so that certain simple maintenance work can be completed by appliances themselves.During the measurement,collection and transmission of electricity load data in a HEMS sensor network,however,problems can be caused on the data due to faulty sensing processes and/or lost links,etc.In order to ensure the quality of retrieved load data,different solutions have been presented,but suffered from low recognition rates and high complexity.In this paper,a validation and repair method is presented to detect potential failures and errors in a domestic energy management system,which can then recover determined load errors and losses.A Kernel Extreme Learning Machine(K-ELM)based model has been employed with a Radial Basis Function(RBF)and optimised parameters for verification and recognition;whilst a Dual-spline method is presented to repair missing load data.According to the experiment results,the method outperforms the traditional B-spline and Cubic-spline methods and can effectively deal with unexpected data losses and errors under variant loss rates in a practical home environment.展开更多
Blasting is one of the most important operations in the mining projects that has effective role in the whole operation physically and economically. Unsuitable blasting pattern may lead to unwanted events such as poor ...Blasting is one of the most important operations in the mining projects that has effective role in the whole operation physically and economically. Unsuitable blasting pattern may lead to unwanted events such as poor fragmentation, back break and fly rock. Multi attribute decision making(MADM) can be useful method for selecting the most appropriate blasting pattern among previously performed patterns. In this work, initially, from various already performed patterns, efficient and inefficient patterns are determined using data envelopment analysis(DEA). In the second step, after weighting impressive attributes using experts' opinion, elimination Et choice translating reality(ELECTRE) was used for ranking the efficient patterns and recognizing the most appropriate pattern in the Sungun Copper Mine, Iran. According to the obtained results, blasting pattern with the hole diameter of 15.24 cm, burden of 3 m, spacing of 4 m and stemming of 3.2 m has selected as the best pattern and has selected for future operation.展开更多
Influence of the gassing materials, such as PA6, PMMA, and POM on the dielectric properties of air are investigated. In this work, the fundamental electron collision cross section data were carefully selected and vali...Influence of the gassing materials, such as PA6, PMMA, and POM on the dielectric properties of air are investigated. In this work, the fundamental electron collision cross section data were carefully selected and validated. Then the species compositions of the air–organic vapor mixtures were calculated based on the Gibbs free energy minimization. Finally, the Townsend ionization coefficient, the Townsend electron attachment coefficient and the critical reduced electric field strength were derived from the calculated electron energy distribution function by solving the Boltzmann transport equation. The calculation results indicated that H;O with large attachment cross sections has a great impact on the critical reduced electric field strength of the air–organic vapor mixtures. On the other hand, the vaporization of gassing materials can help to increase the dielectric properties of air circuit breakers to some degree.展开更多
By using an optical system simulator, we investigated the tunable delay-line with an optical SSB modulator and an optical fiber loop, where the delay can be controlled by the electric signal fed to the modulator.
The procedure by means of which the occurrence time of an impending mainshock can be identified by analyzing in natural time the seismicity in the candidate area subsequent to the recording of a precursory seismic ele...The procedure by means of which the occurrence time of an impending mainshock can be identified by analyzing in natural time the seismicity in the candidate area subsequent to the recording of a precursory seismic electric signals（SES） activity is reviewed. Here, we report the application of this procedure to an MW5.4 mainshock that occurred in Greece on 17 November 2014. This mainshock（which is pretty rare since it is the strongest in that area for more than half a century） was preceded by an SES activity recorded on 27 July 2014, and the results of the natural time analysis reveal that the system approached the critical point（mainshock occurrence） early in the morning on 15 November 2014.展开更多
the power network fault detection system can only analyze all kinds of fault signal in stationary sequence： the internal grid and external disturbance presents degeneration, tiny, signal intensity changes randomly fl...the power network fault detection system can only analyze all kinds of fault signal in stationary sequence： the internal grid and external disturbance presents degeneration, tiny, signal intensity changes randomly fluctuate, that will cause the system to detect the fault isolation ability of confusion and small fault signal is not strong; The article propose a method of power network fault detection for based on GSM, Through the underlying sensing equipment acquisition abnormal information of current, voltage power in the network and GSM networking scheme can filter the interference factors in extraction of fault information from and attribute value. The embedded gateway take STM32 chip as the core to monitoring data processing, to achieve a unified data management and user remote access, realizing method of system software are given, to construct the monitor management information platform. The actual test system show that, identification diagnosis ability of fault signal separation ability and small signal increases 17%, also meet the requirements.展开更多
Due to the pandemic’s widespread effects on daily life in the past few years,evaluating and analyzing the impact of COVID-19 on large cities in China accurately and timely has become increasingly significant.The exis...Due to the pandemic’s widespread effects on daily life in the past few years,evaluating and analyzing the impact of COVID-19 on large cities in China accurately and timely has become increasingly significant.The existing research lacks studies on the electricity consumption of residents and non-residents during the pandemic.So based on the four-year electricity consumption data of a large city in China,this paper examines COVID-19’s impact from the perspective of residential and nonresidential electricity consumption through the COVID-19-Power framework and its extended version that predicts electricity consumption in 2020 without the outbreak of COVID-19 for comparison with the actual values.For residential electricity consumption,through comparative analysis of different administrative districts on geographic location and historical electricity consumption habits,the impact of the pandemic on residential electricity consumption is found to be relatively small.For nonresidential electricity consumption,we infer that power-related factors including real estate development and investment,etc.contribute to perception of the special impacts of the pandemic.We conduct predictive analysis of non-residential electricity consumption for different administrative districts by geographic location,different electricity consumption categories.We verify the significant negative impact of the pandemic on the real estate sector by the analysis of electricity consumption across different sectors.Through these research results,details about the impact of the pandemic on people’s lives and electrical load in China’s large cities can be captured by power enterprises to adjust power supply strategies more effectively and pertinently.展开更多
An equivalent circuit model for the analysis and design of terahertz （THz） metamaterial filters is presented.The proposed model,derived based on LMC equivalent circuits,takes into account the detailed geometrical pa...An equivalent circuit model for the analysis and design of terahertz （THz） metamaterial filters is presented.The proposed model,derived based on LMC equivalent circuits,takes into account the detailed geometrical parameters and the presence of a dielectric substrate with the existing analytic expressions for self-inductance,mutual inductance,and capacitance.The model is in good agreement with the experimental measurements and full-wave simulations.Exploiting the circuit model has made it possible to predict accurately the resonance frequency of the proposed structures and thus,quick and accurate process of designing THz device from artificial metamaterials is offered.展开更多
We investigate the lateral shift of a TM-polarized light beam reflected from Otto configuration under grazing incidence. It is found that the lateral shift is strongly dependent on the thickness of the air-gap layer. ...We investigate the lateral shift of a TM-polarized light beam reflected from Otto configuration under grazing incidence. It is found that the lateral shift is strongly dependent on the thickness of the air-gap layer. By employing the pole-null representation, we demonstrate that the lateral shift is closely related to the null of the reflection function. The numerical simulations for a Gaussian beam are performed to demonstrate the validity of our theoretical analvsis.展开更多
Four coaxial cylinder dielectric barrier discharge micro-plasma reactors were designed for the noncatalytic decomposition of pure CO_(2) into CO and O_(2) at low temperature and ambient pressure.The influence of segme...Four coaxial cylinder dielectric barrier discharge micro-plasma reactors were designed for the noncatalytic decomposition of pure CO_(2) into CO and O_(2) at low temperature and ambient pressure.The influence of segmented outer electrodes on the electrical characteristics and the reaction performance was investigated.Experimental results indicated that the introduction of segmented outer electrodes can significantly promote the decomposition of CO_(2).Encouragingly,the highest conversion of 13.1% was obtained at an applied voltage of 18 kV,which was a substantial increase of 39.4% compared to the traditional device.Compared with other types of dielectric barrier discharge plasma reactors,the proposed segmented outer electrode micro-plasma reactor can give a higher CO_(2) conversion and acceptable energy efficiency.The increase in conversion can be attributed mainly to the enhanced corona discharge caused by the fringe effect at electrode edges,the increase in energy density and the increase in the number of micro-discharges.In addition,detailed electrical characterization was performed to reveal some trends in the electrical behavior of proposed reactors.展开更多
A fiber Bragg grating （FBG） hydrophone with high sensitivity was demonstrated. This hydrophone used a rubber diaphragm and a copper hard core as the sensing element. To compensate the hydrostatic pressure, a capilla...A fiber Bragg grating （FBG） hydrophone with high sensitivity was demonstrated. This hydrophone used a rubber diaphragm and a copper hard core as the sensing element. To compensate the hydrostatic pressure, a capillary tube was fixed at the end of the hydrophone. Theoretical analysis of the acoustic pressure sensitivity was given in this letter. Experiments were carried out to test the frequency response of the hydrophone. The result shows that when the Young＇s modulus of the diaphragm is higher, a flatter frequency response will be obtained.展开更多
We present a resolution testing system of ultraviolet （UV） imager. In this system, an UV Czerny-Turner monochromator with a small f-number is designed to get more energy as an UV radiation source, and its stray ligh...We present a resolution testing system of ultraviolet （UV） imager. In this system, an UV Czerny-Turner monochromator with a small f-number is designed to get more energy as an UV radiation source, and its stray light is rejected effectively by light traps. And UV diffuser is employed in order to get uniform light distribution on the resolving power test target. We also design a novel UV collimator which makes infinite UV testing targets. It can reduce the difficulty of optical design and the machining cost, and utilize UV energy at maximum extent. This facility has been applied in the imaging quality evaluation of the UV instrument, and the results accord with the theoretical analysis.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51562014,51262009,and 51602135)
文摘Inter-growth bismuth layer-structured ferroelectrics（BLSFs）, Bi_4Ti_3O_（12）-Na_（0.5）Bi_（4.5）Ti_4O_（15）（BIT-NBT）, were successfully synthesized using the traditional solid-state reaction method. X-ray diffraction（XRD） Rietveld refinements were conducted using GSAS software. Good agreement and low residual are obtained. The XRD diffraction peaks can be well indexed into I2 cm space group. The inter-growth structure was further observed in the high-resolution TEM image. Dielectric and impedance properties were measured and systematically analyzed. At the temperature range 763-923 K（below T_c）, doubly ionized oxygen vacancies（OVs） are localized and the short-range hopping leads to the relaxation processes with an activation energy of 0.79-1.01 eV. Above T_c, the doubly charged OVs are delocalized and become free ones, which contribute to the long-range dc conduction. The reduction in relaxation species gives rise to a higher relaxation activation energy ~ 1.6 eV.
基金supported by the National Natural Science Foundation of China (No. 90305003)the 863’ projects of China (Nos. 2009AA03Z427 and 2008AA030705)the Science & Technology Pillar Program of Sichuan Province Science and Technology Plan Foundation (No.200910GZ00690251)
文摘Based on the principles of electrical conduction and transformation, a model was put forward for the electrical conversion of piezoelectric damping composites, and a related formula was derived. The results show that the best effect of conversion can be achieved by reducing the imaginary part of the impedance and matching the frequency. The optimal damping effect at a certain frequency requires resistance of conductive phase （R） satisfying the condition of R=I/（ωC）, but this condition may cause the damping effect at other frequencies to deviate away from the optimum condition. It is suggested that in order to make the damping effect more efficient and objective, frequency matching should be considered during the design of piezoelectric damping composites.
基金Fundamental Research Funds for the Central Universities,China(No.2232019D3-51)Shanghai Sailing Program,China(No.19YF1402100)。
文摘Induction motors have been widely used across industry,particularly with smaller loads and fixed speed services.Existing works focus on fault detection of induction motors without considering the shutdown time and production in industry.Therefore,this work aims to monitor the health conditions of the induction motor continuously through electrical signature analysis(ESA).The proposed technique is capable of predicting different kinds of faults,i.e.,rotor faults,stator phase imbalances,and supply cable faults at early stages.Moreover,ESA in real time is implemented.Thereafter,these current spectra were analyzed in frequency domain and compared with healthy current spectra.Performance evaluation is implemented by observing these spectra under different faulty conditions.A comparative study is made and analyzed through MATLAB simulations.
基金founded by the Earthquake Science and Technology Spark Plan of China(XH12063)
文摘Characteristic period is an important parameter of the seismic design response spectrum. There is important theoretical significance and engineering application value to the study of the characteristic period of seismic design response spectrum of ultra high voltage （UHV） electrical equipment. In this paper, 1448 horizontal earthquake records within the world scope including the United States and Japan for Site Class m were analyzed. Results show that both magnitude and epicentral distance have great influence on the characteristic period. About 80 % of characteristic periods of strong earthquake records are about 0. 9s. Statistical analysis was conducted on the seismic hazard assessment results of 312 projects of China in recent years, and it is found that about 70 % of characteristic periods are about 0. 9s. Combined with the related code comparison and analysis, it is suggested that the characteristic period of the seismic design response spectrmn of UHV electrical equipment should select 0. 9s in order to effectively guarantee the seismic safety of UHV electrical equipment.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT,RS-2023-00222411 and RS-2023-00247245)supported by the National Research Foundation of Korea(NRF)Grant,funded by the Korean Government(NRF-2022K1A4A7A04095892),for supporting the Korean−German collaboration.
文摘CONSPECTUS:Microscopy has long expanded humanity’s understanding of the microscopic world,transcending limitations of the naked eye.The atomic force microscope(AFM),in particular,marks a major advancement in this field,enabling nanoscale investigations of materials through direct physical probing of their surface.Unlike traditional microscopes that use light or electrons,AFM’s unique methodology allows for both imaging on the atomic scale and precise manipulation of a material’s mechanical,electrical,and chemical properties.A key advantage also lies in its capacity for multimodal analysis,where multiple properties can be simultaneously measured to provide comprehensive insights into material behavior.In the current landscape of miniaturizing electronics and optimizing energy materials,the interplay between mechanical and electrical properties has gained particular importance.The precise integration of these properties is vital for advancing nanotechnology,and AFM allows the elucidation of these effects on the nanoscale.This is especially relevant for multifunctional materials that respond to both mechanical and electrical stimuli,and as surface properties exert a pronounced influence on material behavior at reduced scales,the capabilities of the AFM have informed the design and characterization of many smart,dielectric,and energy materials over the past decades.In this article,we present our group’s recent works on the integration of mechanical and electrical analyses using AFM-based characterization techniques.We begin by tracing the progression from early piezoresponse force microscopy(PFM)studies,which investigated domain growth and switching characteristics in ferroelectric films,as well as the surface charge dynamics of polar domains.Based on these foundations,we introduce a surface scraping-based method of imaging-charge gradient microscopy-for rapid characterization of these domains and showcase a novel three-dimensional lithography technique that exploits asymmetric wear rates of up and down domains.This method underscores the strongly coupled interactions between the mechanical and electrical properties of dielectrics,with the potential for scaling to device-relevant dimensions.The discussion then transitions from piezoelectric electromechanical dynamics to ionic electrochemical phenomena,where electrical stimuli similarly induce mechanical surface deformations detectable by an AFM tip.We explore a multimodal approach in electrochemical strain microscopy(ESM)to investigate functional components in composite materials,demonstrating how friction mapping can be employed to identify specific material components.Additionally,we introduce mechanically and electrically modulated spectroscopy techniques,including nanoindentation,PFM hysteresis,and current−voltage spectroscopy,emphasizing the potential of spectroscopic methods to be customized for eliciting targeted material response.Finally,the challenges and future directions in AFM-based research are addressed,as we offer approaches to enhance the reliability,accuracy,and data throughput of AFM measurements.We anticipate that these integrated approaches,which bridge mechanical and electrical analyses at the nanoscale,will accelerate material discovery and fuel innovation across diverse fields,from energy storage to nanoelectronics.
基金the Fundamental Research Foundation of Harbin Engineering University, (grant number HEUF 04017)
文摘A type of combined optical fiber interferometric acoustic emission sensor is proposed. The sensor can be independent on the laser source and make light interference by matching the lengths of two arms,so it can be used to monitor the health of large structure. Theoretical analyses indicate that the system can be equivalent to the Michelson interferometer with two optical fiber loop reflectors,and its sensitivity has been remarkably increased because of the decrease of the losses of light energy. PZT is powered by DC regulator to control the operating point of the system,so the system can accurately detect feeble vibration which is generated by ultrasonic waves propagating on the surface of solid. The amplitude and the frequency of feeble vibration signal are obtained by detecting the output light intensity of interferometer and using Fourier transform technique. The results indicate that the system can be used to detect the acoustic emission signals by the frequency characteristics.
基金supported in part by the National Key Basic Research and Development Program of China(No.2017YFE0132100)the Tsinghua-Toyota Research Fund(No.20203910016)the BNRist Program(No.BNR2020TD01009)。
文摘Electrical power network analysis and computation play an important role in the planning and operation of the power grid,and they are modeled mathematically as differential equations and network algebraic equations.The direct method based on Gaussian elimination theory can obtain analytical results.Two factors affect computing efficiency:the number of nonzero element fillings and the length of elimination tree.This article constructs mapping correspondence between eliminated tree nodes and quotient graph nodes through graph and quotient graph theories.The Approximate Minimum Degree(AMD)of quotient graph nodes and the length of the elimination tree nodes are composed to build an Approximate Minimum Degree and Minimum Length(AMDML)model.The quotient graph node with the minimum degree,which is also the minimum length of elimination tree node,is selected as the next ordering vector.Compared with AMD ordering method and other common methods,the proposed method further reduces the length of elimination tree without increasing the number of nonzero fillings;the length was decreased by about 10%compared with the AMD method.A testbed for experiment was built.The efficiency of the proposed method was evaluated based on different sizes of coefficient matrices of power flow cases.
文摘In a home energy management system(HEMS),appliances are becoming diversified and intelligent,so that certain simple maintenance work can be completed by appliances themselves.During the measurement,collection and transmission of electricity load data in a HEMS sensor network,however,problems can be caused on the data due to faulty sensing processes and/or lost links,etc.In order to ensure the quality of retrieved load data,different solutions have been presented,but suffered from low recognition rates and high complexity.In this paper,a validation and repair method is presented to detect potential failures and errors in a domestic energy management system,which can then recover determined load errors and losses.A Kernel Extreme Learning Machine(K-ELM)based model has been employed with a Radial Basis Function(RBF)and optimised parameters for verification and recognition;whilst a Dual-spline method is presented to repair missing load data.According to the experiment results,the method outperforms the traditional B-spline and Cubic-spline methods and can effectively deal with unexpected data losses and errors under variant loss rates in a practical home environment.
文摘Blasting is one of the most important operations in the mining projects that has effective role in the whole operation physically and economically. Unsuitable blasting pattern may lead to unwanted events such as poor fragmentation, back break and fly rock. Multi attribute decision making(MADM) can be useful method for selecting the most appropriate blasting pattern among previously performed patterns. In this work, initially, from various already performed patterns, efficient and inefficient patterns are determined using data envelopment analysis(DEA). In the second step, after weighting impressive attributes using experts' opinion, elimination Et choice translating reality(ELECTRE) was used for ranking the efficient patterns and recognizing the most appropriate pattern in the Sungun Copper Mine, Iran. According to the obtained results, blasting pattern with the hole diameter of 15.24 cm, burden of 3 m, spacing of 4 m and stemming of 3.2 m has selected as the best pattern and has selected for future operation.
基金supported by the National Key Basic Research Program of China(973 Program)2015CB251002National Natural Science Foundation of China under Grant 51521065,51577145+1 种基金the Fundamental Research Funds for the Central UniversitiesShaanxi Province Natural Science Foundation 2013JM-7010
文摘Influence of the gassing materials, such as PA6, PMMA, and POM on the dielectric properties of air are investigated. In this work, the fundamental electron collision cross section data were carefully selected and validated. Then the species compositions of the air–organic vapor mixtures were calculated based on the Gibbs free energy minimization. Finally, the Townsend ionization coefficient, the Townsend electron attachment coefficient and the critical reduced electric field strength were derived from the calculated electron energy distribution function by solving the Boltzmann transport equation. The calculation results indicated that H;O with large attachment cross sections has a great impact on the critical reduced electric field strength of the air–organic vapor mixtures. On the other hand, the vaporization of gassing materials can help to increase the dielectric properties of air circuit breakers to some degree.
文摘By using an optical system simulator, we investigated the tunable delay-line with an optical SSB modulator and an optical fiber loop, where the delay can be controlled by the electric signal fed to the modulator.
基金support of the geoelectrical stations of the SES telemetric network by Basil Dimitropoulos,Spyros Tzigkos and George Lampithianakis
文摘The procedure by means of which the occurrence time of an impending mainshock can be identified by analyzing in natural time the seismicity in the candidate area subsequent to the recording of a precursory seismic electric signals（SES） activity is reviewed. Here, we report the application of this procedure to an MW5.4 mainshock that occurred in Greece on 17 November 2014. This mainshock（which is pretty rare since it is the strongest in that area for more than half a century） was preceded by an SES activity recorded on 27 July 2014, and the results of the natural time analysis reveal that the system approached the critical point（mainshock occurrence） early in the morning on 15 November 2014.
文摘the power network fault detection system can only analyze all kinds of fault signal in stationary sequence： the internal grid and external disturbance presents degeneration, tiny, signal intensity changes randomly fluctuate, that will cause the system to detect the fault isolation ability of confusion and small fault signal is not strong; The article propose a method of power network fault detection for based on GSM, Through the underlying sensing equipment acquisition abnormal information of current, voltage power in the network and GSM networking scheme can filter the interference factors in extraction of fault information from and attribute value. The embedded gateway take STM32 chip as the core to monitoring data processing, to achieve a unified data management and user remote access, realizing method of system software are given, to construct the monitor management information platform. The actual test system show that, identification diagnosis ability of fault signal separation ability and small signal increases 17%, also meet the requirements.
文摘Due to the pandemic’s widespread effects on daily life in the past few years,evaluating and analyzing the impact of COVID-19 on large cities in China accurately and timely has become increasingly significant.The existing research lacks studies on the electricity consumption of residents and non-residents during the pandemic.So based on the four-year electricity consumption data of a large city in China,this paper examines COVID-19’s impact from the perspective of residential and nonresidential electricity consumption through the COVID-19-Power framework and its extended version that predicts electricity consumption in 2020 without the outbreak of COVID-19 for comparison with the actual values.For residential electricity consumption,through comparative analysis of different administrative districts on geographic location and historical electricity consumption habits,the impact of the pandemic on residential electricity consumption is found to be relatively small.For nonresidential electricity consumption,we infer that power-related factors including real estate development and investment,etc.contribute to perception of the special impacts of the pandemic.We conduct predictive analysis of non-residential electricity consumption for different administrative districts by geographic location,different electricity consumption categories.We verify the significant negative impact of the pandemic on the real estate sector by the analysis of electricity consumption across different sectors.Through these research results,details about the impact of the pandemic on people’s lives and electrical load in China’s large cities can be captured by power enterprises to adjust power supply strategies more effectively and pertinently.
基金supported by the National Natural Science Fondation of China (Nos. 61028011,61007034,and 60977064)the U.S. National Science Foundation+1 种基金the Tianjin Sci-Tech Program (Nos. 09ZCKFGX01500 and 10JCYBJC01400)the 111 Program of China (No. B07014)
文摘An equivalent circuit model for the analysis and design of terahertz （THz） metamaterial filters is presented.The proposed model,derived based on LMC equivalent circuits,takes into account the detailed geometrical parameters and the presence of a dielectric substrate with the existing analytic expressions for self-inductance,mutual inductance,and capacitance.The model is in good agreement with the experimental measurements and full-wave simulations.Exploiting the circuit model has made it possible to predict accurately the resonance frequency of the proposed structures and thus,quick and accurate process of designing THz device from artificial metamaterials is offered.
基金the National Natural Science Foundation of China(No.60377025)the Shanghai Educational Development Foundation(No.2007CG52)the Shanghai Leading Academic Discipline Program(No.T0104)
文摘We investigate the lateral shift of a TM-polarized light beam reflected from Otto configuration under grazing incidence. It is found that the lateral shift is strongly dependent on the thickness of the air-gap layer. By employing the pole-null representation, we demonstrate that the lateral shift is closely related to the null of the reflection function. The numerical simulations for a Gaussian beam are performed to demonstrate the validity of our theoretical analvsis.
基金financially supported by the National Key Research and Development Program of China(Grant No.2016YFB0600701).
文摘Four coaxial cylinder dielectric barrier discharge micro-plasma reactors were designed for the noncatalytic decomposition of pure CO_(2) into CO and O_(2) at low temperature and ambient pressure.The influence of segmented outer electrodes on the electrical characteristics and the reaction performance was investigated.Experimental results indicated that the introduction of segmented outer electrodes can significantly promote the decomposition of CO_(2).Encouragingly,the highest conversion of 13.1% was obtained at an applied voltage of 18 kV,which was a substantial increase of 39.4% compared to the traditional device.Compared with other types of dielectric barrier discharge plasma reactors,the proposed segmented outer electrode micro-plasma reactor can give a higher CO_(2) conversion and acceptable energy efficiency.The increase in conversion can be attributed mainly to the enhanced corona discharge caused by the fringe effect at electrode edges,the increase in energy density and the increase in the number of micro-discharges.In addition,detailed electrical characterization was performed to reveal some trends in the electrical behavior of proposed reactors.
基金Key Projects Program of Chinese Acadelny of Sciences under Grant No.CXJJ-177.
文摘A fiber Bragg grating （FBG） hydrophone with high sensitivity was demonstrated. This hydrophone used a rubber diaphragm and a copper hard core as the sensing element. To compensate the hydrostatic pressure, a capillary tube was fixed at the end of the hydrophone. Theoretical analysis of the acoustic pressure sensitivity was given in this letter. Experiments were carried out to test the frequency response of the hydrophone. The result shows that when the Young＇s modulus of the diaphragm is higher, a flatter frequency response will be obtained.
基金the National Natural Science Foundation of China under Grant No.40675083.
文摘We present a resolution testing system of ultraviolet （UV） imager. In this system, an UV Czerny-Turner monochromator with a small f-number is designed to get more energy as an UV radiation source, and its stray light is rejected effectively by light traps. And UV diffuser is employed in order to get uniform light distribution on the resolving power test target. We also design a novel UV collimator which makes infinite UV testing targets. It can reduce the difficulty of optical design and the machining cost, and utilize UV energy at maximum extent. This facility has been applied in the imaging quality evaluation of the UV instrument, and the results accord with the theoretical analysis.
