Earthquakes triggered by dynamic disturbances have been confirmed by numerous observations and experiments.In the past several decades,earthquake triggering has attracted increasing attention of scholars in relation t...Earthquakes triggered by dynamic disturbances have been confirmed by numerous observations and experiments.In the past several decades,earthquake triggering has attracted increasing attention of scholars in relation to exploring the mechanism of earthquake triggering,earthquake prediction,and the desire to use the mechanism of earthquake triggering to reduce,prevent,or trigger earthquakes.Natural earthquakes and large‐scale explosions are the most common sources of dynamic disturbances that trigger earthquakes.In the past several decades,some models have been developed,including static,dynamic,quasi‐static,and other models.Some reviews have been published,but explosiontriggered seismicity was not included.In recent years,some new results on earthquake triggering have emerged.Therefore,this paper presents a new review to reflect the new results and include the content of explosion‐triggered earthquakes for the reference of scholars in this area.Instead of a complete review of the relevant literature,this paper primarily focuses on the main aspects of dynamic earthquake triggering on a tectonic scale and makes some suggestions on issues that need to be resolved in this area in the future.展开更多
Dear Editor,This letter addresses the resilient model predictive control(MPC)problems for adaptive cruise control(ACC)systems under sensor attacks.In the light of vulnerabilities of ACC systems to sensor attacks,an in...Dear Editor,This letter addresses the resilient model predictive control(MPC)problems for adaptive cruise control(ACC)systems under sensor attacks.In the light of vulnerabilities of ACC systems to sensor attacks,an intrusion detection mechanism is proposed at the controller side to distinguish abnormal data.Then,the robust control gains are derived to design the terminal region constraint for MPC.展开更多
Federated learning is widely used to solve the problem of data decentralization and can provide privacy protectionfor data owners. However, since multiple participants are required in federated learning, this allows a...Federated learning is widely used to solve the problem of data decentralization and can provide privacy protectionfor data owners. However, since multiple participants are required in federated learning, this allows attackers tocompromise. Byzantine attacks pose great threats to federated learning. Byzantine attackers upload maliciouslycreated local models to the server to affect the prediction performance and training speed of the global model. Todefend against Byzantine attacks, we propose a Byzantine robust federated learning scheme based on backdoortriggers. In our scheme, backdoor triggers are embedded into benign data samples, and then malicious localmodels can be identified by the server according to its validation dataset. Furthermore, we calculate the adjustmentfactors of local models according to the parameters of their final layers, which are used to defend against datapoisoning-based Byzantine attacks. To further enhance the robustness of our scheme, each localmodel is weightedand aggregated according to the number of times it is identified as malicious. Relevant experimental data showthat our scheme is effective against Byzantine attacks in both independent identically distributed (IID) and nonindependentidentically distributed (non-IID) scenarios.展开更多
The 2022 Honghe M_(S)5.0 seismic event is intriguing due to its occurrence in the south of the Red River Fault,an area historically lacking seismic activities greater than M_(S)5.0.To elucidate the seismogenic mechani...The 2022 Honghe M_(S)5.0 seismic event is intriguing due to its occurrence in the south of the Red River Fault,an area historically lacking seismic activities greater than M_(S)5.0.To elucidate the seismogenic mechanism and scrutinize stress-triggered interactions,we calculated co-seismic and post-seismic Coulomb stress alterations induced by nine historical seismic events(M≥6.0).The analysis reveals that these substantial seismic events provoked co-seismic stress augmentations of 1.409 bar and postseismic stress increments of 0.159 bar.Noteworthy seismic events,such as the 1833 Songming,1877Shiping,1913 Eshan,and 1970 Tonghai earthquakes,catalyzed the occurrence of the Honghe earthquake.Areas of heightened future seismic risk include the southern region of the Red River Fault and the eastern segments of the Shiping-Jianshui and Qujiang faults.Additionally,we assessed the correlation between the spatial distribution of aftershocks and the Coulomb stress shift triggered by the mainshock,taking into account the influence of calculation parameter settings.展开更多
Negative Indian Ocean Dipole(nIOD)can exert great impacts on global climate and can also strongly influence the climate in China.Early nIOD is a major type of nIOD,which can induce more pronounced climate anomalies in...Negative Indian Ocean Dipole(nIOD)can exert great impacts on global climate and can also strongly influence the climate in China.Early nIOD is a major type of nIOD,which can induce more pronounced climate anomalies in summer than La Niña-related nIOD.However,the characteristics and triggering mechanisms of early nIOD are unclear.Our results based on reanalysis datasets indicate that the early nIOD and La Niña-related nIOD are the two major types of nIOD,and the former accounts for over one third of all the nIOD events in the past six decades.These two types of nIODs are similar in their intensities,but are different in their spatial patterns and seasonal cycles.The early nIOD,which develops in spring and peaks in summer,is one season earlier than the La Niña-related nIOD.The spatial pattern of the wind anomaly associated with early nIOD exhibits a winter monsoon-like pattern,with strong westerly anomalies in the equatorial Indian Ocean and eastly anomalies in the northern Indian Ocean.Opposite to the triggering mechanism of early positve IOD,the early nIOD is induced by delayed Indian summer monsoon onset.The results of this study are helpful for improving the prediction skill of IOD and its climate impacts.展开更多
In this study,a pulsed,high voltage driven hollow-cathode electron beam sources through an optical trigger is designed with characteristics of simple structure,low cost,and easy triggering.To validate the new design,t...In this study,a pulsed,high voltage driven hollow-cathode electron beam sources through an optical trigger is designed with characteristics of simple structure,low cost,and easy triggering.To validate the new design,the characteristics of hollow-cathode discharge and electron beam characterization under pulsed high voltage drive are studied experimentally and discussed by discharge characteristics and analyses of waveform details,respectively.The validation experiments indicate that the pulsed high voltage supply significantly improves the frequency and stability of the discharge,which provides a new solution for the realization of a high-frequency,high-energy electron beam source.The peak current amplitude in the high-energy electron beam increases from 6.2 A to 79.6 A,which indicates the pulsed power mode significantly improves the electron beam performance.Besides,increasing the capacitance significantly affects the highcurrent,lower-energy electron beam more than the high-energy electron beam.展开更多
This paper addresses the problem of event-triggered finite-time H<sub>∞</sub> filter design for a class of discrete-time nonlinear stochastic systems with exogenous disturbances. The stochastic Lyapunov-K...This paper addresses the problem of event-triggered finite-time H<sub>∞</sub> filter design for a class of discrete-time nonlinear stochastic systems with exogenous disturbances. The stochastic Lyapunov-Krasoviskii functional method is adopted to design a filter such that the filtering error system is stochastic finite-time stable (SFTS) and preserves a prescribed performance level according to the pre-defined event-triggered criteria. Based on stochastic differential equations theory, some sufficient conditions for the existence of H<sub>∞</sub> filter are obtained for the suggested system by employing linear matrix inequality technique. Finally, the desired H<sub>∞</sub> filter gain matrices can be expressed in an explicit form.展开更多
Triggering characteristics of triggered vacuum switch (TVS), including the discharge delay time, delay jitter, range of operational voltage and peak of pulsed current, are investigated. Both structure and experiment...Triggering characteristics of triggered vacuum switch (TVS), including the discharge delay time, delay jitter, range of operational voltage and peak of pulsed current, are investigated. Both structure and experimental circuit of TVS are presented. The results indicate that TVS, as a surface flashover triggering device with high dielectric permittivity material, is with excellent triggering characteristics. When the hold-off voltage reaches 120 kV, the minimum operational voltage is 1.3 kV, and the minimum discharge delay time and jitter are 100 ns and ±10 ns, respectively. The peak current is up to 240 kA when the operational voltage reaches 100 kV. TVS can well satisfy the main demands of high voltage and current applications, and can also be used under a multi-crowbar circuit.展开更多
Techniques of artificially-triggered lightning have provided a significantly useful means to directly measure various physical parameters of lightning discharge and to conduct research on protection methods of lightni...Techniques of artificially-triggered lightning have provided a significantly useful means to directly measure various physical parameters of lightning discharge and to conduct research on protection methods of lightning electromagnetic pulses.In this study,using capacitive and resistive dividers,current probes and optical fiber transmission devices,we measured and analyzed the induced overvoltage on the overhead transmission line and the overcurrent through Surge Protective Devices(SPD) when a lightning discharge was artificially triggered nearby on August 12,2008 at Conghua Field Lightning Experiment Site.The triggered lightning discharge contained an initial current stage and eight return strokes whose peak currents ranged from 6.6kA to 26.4kA.We found that overcurrents through SPD were induced on the power line both during the initial continuous current stage and the return stroke processes.During the return strokes,the residual voltage and the current through the SPD lasted up to the ms(millisecond) range,and the overcurrents exhibited a mean waveform up to 22/69μs with a peak value of less than 2kA.Based on the observed data,simple calculations show that the corresponding single discharge energy was much greater than the values of the high voltage pulse generators commonly used in the experiments regulated for SPD.The SPD discharge current peak was not synchronous to that of the residual voltage with the former obviously lagging behind the latter.The SPD discharge current peak was well correlated with the triggered lightning current peak and the wave-front current gradient.The long duration of the SPD current is one of the major reasons why the SPD was damaged even with a big nominal discharge current.展开更多
An extraordinary earthquake swarm occurred at Rushan on the Jiaodong Peninsula from October 1, 2013, onwards, and more than 12,000 aftershocks had been detected by December 31, 2015. All the activities of the whole sw...An extraordinary earthquake swarm occurred at Rushan on the Jiaodong Peninsula from October 1, 2013, onwards, and more than 12,000 aftershocks had been detected by December 31, 2015. All the activities of the whole swarm were recorded at the nearest station, RSH, which is located about 12 km from the epicenter. We examine the statistical characteristics of the Rushan swarm in this paper using RSH station data to assess the arrival time difference, ts p, of Pg and Sg phases. A temporary network comprising 18 seismometers was set up on May 6, 2014, within the area of the epicenter; based on the data from this network and use of the double difference method, we determine precise hypocenter locations. As the distribution of relocated sources reveals migration of seismic activity, we applied the mean-shift cluster method to perform clustering analysis on relocated catalogs. The results of this study show that there were at least 16 clusters of seismic activities between May 6, 2014, and June 30, 2014, and that each was characterized by a hypocenter spreading process. We estimated the hydraulic diffusivity, D, of each cluster using envelope curve fitting; the results show that D values range between 1.2 and 3.5 m2/d and that approximate values for clusters on the edge of the source area are lower than those within the central area. We utilize an epidemic-type aftershock sequence (ETAS) model to separate external triggered events from self-excited aftershocks within the Rushan swarm. The estimated parameters for this model suggest that α = 1.156, equiva- lent to sequences induced by fluid-injection, and that the forcing rate (μ) implies just 0.15 events per day. These estimates indicate that around 3% of the events within the swarm were externally triggered. The fact that variation in μ is synchronous with swarm activity implies that pulses in fluid pressure likely drove this series of earthquakes.展开更多
Dear editor,Recently,researchers have obtained many new results about the multi-agent systems(MASs)[1]-[3].In[1],the fixed-time cooperative control(FTCC)algorithm of linear MASs with matched disturbances was proposed....Dear editor,Recently,researchers have obtained many new results about the multi-agent systems(MASs)[1]-[3].In[1],the fixed-time cooperative control(FTCC)algorithm of linear MASs with matched disturbances was proposed.The nonholonomic chained-form dynamics case was considered in[2].In[3],the output tracking problem with data packet dropout was solved for high-order MASs.Moreover,delay frequently occurs because of the non-ideal data transmission[4],and the corresponding FTCC algorithm of MASs with delay was given in[5].展开更多
The plasma-jet triggered gas switch (PJTGS) could operate at a low working coefficient with a low jitter. We observed and analyzed the discharge process of the PJTGS at the lowest working coefficient of 47% with the...The plasma-jet triggered gas switch (PJTGS) could operate at a low working coefficient with a low jitter. We observed and analyzed the discharge process of the PJTGS at the lowest working coefficient of 47% with the trigger voltage of 40 kV and the pulse energy of 2 J to evaluate the effect of the plasma jet. The temporal and spatial evolution and the optical emission speclrum of the plasma jet were captured. And the spraying delay time and outlet velocity under different gas pressures were investigated. In addition, the particle in cell with Monte Carlo collision was employed to obtain the particle distribution of the plasma jet varying with time. The results show that, the plasma jet generated by spark discharge is sprayed into a spark gap within tens of nanoseconds, and its outlet velocity could reach 104 m s-1. The plasma jet plays a non-penetrating inducing role in the triggered discharge process of the PJTGS. On the one hand, the plasma jet provides the initial electrons needed by the discharge; on the other hand, a large number of electrons focusing on the head of the plasma jet distort the electric field between the head of the plasma jet and the opposite electrode. Therefore, a fast discharge originated from the plasma jet is induced and quickly bridges two electrodes.展开更多
To overcome hole-injection limitation of p^+-n emitter junction in 4H-SiC light triggered thyristor, a novel high- voltage 4H-SiC light triggered thyristor with double-deck thin n-base structure is proposed and demon...To overcome hole-injection limitation of p^+-n emitter junction in 4H-SiC light triggered thyristor, a novel high- voltage 4H-SiC light triggered thyristor with double-deck thin n-base structure is proposed and demonstrated by two- dimensional numerical simulations. In this new structure, the conventional thin n-base is split to double-deck. The hole- injection of p^+-n emitter junction is modulated by modulating the doping concentration and thickness of upper-deck thin n- base. With double-deck thin n-base, the current gain coefficient of the top pnp transistor in 4H-SiC light triggered thyristor is enhanced. As a result, the triggering light intensity and the turn-on delay time of 4H-SiC light triggered thyristor are both reduced. The simulation results show that the proposed 10-kV 4H-SiC light triggered thyristor is able to be triggered on by 500-mW/cm^2 ultraviolet light pulse. Meanwhile, the turn-on delay time of the proposed thyristor is reduced to 337 ns.展开更多
A new 4 H–SiC light triggered thyristor(LTT) with 7-shaped thin n-base doping profile is proposed and simulated using a two-dimensional numerical method. In this new structure, the bottom region of the thin n-base ...A new 4 H–SiC light triggered thyristor(LTT) with 7-shaped thin n-base doping profile is proposed and simulated using a two-dimensional numerical method. In this new structure, the bottom region of the thin n-base has a graded doping profile to induce an accelerating electric field and compensate for the shortcoming of the double-layer thin n-base structure in transmitting injected holes. In addition, the accelerating electric field can also speed up the transmission of photongenerated carriers during light triggering. As a result, the current gain of the top pnp transistor of the SiC LTT is further increased. According to the TCAD simulations, the turn-on delay time of the SiC LTT decreases by about 91.5% compared with that of previous double-layer thin n-base SiC LTT. The minimum turn-on delay time of the SiC LTT is only 828 ns,when triggered by 100 mW/cm^2 ultraviolet light. Meanwhile, there is only a slight degradation in the forward blocking characteristic.展开更多
A triggered surge protective device is designed and its discharge characteristics axe studied. The experimental results show that the triggered surge protective device has excellent surge protective characteristics. W...A triggered surge protective device is designed and its discharge characteristics axe studied. The experimental results show that the triggered surge protective device has excellent surge protective characteristics. When the gap distance is 5 mm, p. d is 90 Pa.mm and without an active energy trigger circuit, the DC breakdown voltage of the triggered surge protective device is 2.32 kV and the pulse breakdown voltage is 5.75 kV. Therefore, the pulse voltage ratio, which is defined as the specific value of pulse breakdown voltage and DC breakdown voltage, is 2.48. With a semiconductor ZnO flashover trigger device and an active energy coupling trigger circuit, the pulse breakdown voltage can be reduced to 3.32 kV, the pulse voltage ratio is 1.43 and the response time is less than 100 ns. These results are helpful in laying a theoretical foundation for further studies on triggered surge protective devices.展开更多
The spectra with wavelength range of 390 nm to 660 nm of triggered lightning were observed in Guangdong Area using a slitless spectrograph. The characteristics of the lightning spectra during the initial continuous cu...The spectra with wavelength range of 390 nm to 660 nm of triggered lightning were observed in Guangdong Area using a slitless spectrograph. The characteristics of the lightning spectra during the initial continuous current and return strokes were analyzed, and the differences between the metal section and air section of the lightning channel were compared. The results showed that the metal spectra were contained in the metal section during the initial continuous current. As for the lightning channel of the return strokes, the line spectra for both the metal section and the air section were identical;neither of the two sections contained the metal spectra, but the relative intensity of its emission spectrum was different. Owing to different radiation mechanisms, the spectral structures and luminance of the two sections were not the same. Combined with the current data, it was found that there was a good positive correlation between the total spectral strength and the transferred charge. The total intensity of the lightning channel spectrum increased with the height of the channel, indicating that the radiation sequence of the lightning channel was different. High temporal resolution observations showed that the spectral line duration could be divided into three categories, in which the lines with higher excitation energy appear first and decay rapidly, while those with lower excitation energy appear later but last longer.展开更多
This study aimed to examine the preparation of cationic lipid microbubble(CLM),and evaluate its physical and chemical properties and toxicity,measure the gene transfection efficiency by ultrasound triggered microbob...This study aimed to examine the preparation of cationic lipid microbubble(CLM),and evaluate its physical and chemical properties and toxicity,measure the gene transfection efficiency by ultrasound triggered microbobble destruction(UTMD) in combination with CLM.The CLM was prepared by the method of the thin film hydration,and its morphology was observed under the electron microscopy at 1st,3rd,7th,10th,and 14th day after preparation,respectively.The size,Zeta potential and stability of CLM were tested.The acute toxicity of CLM was assessed.The green fluorescent protein gene(EGFP) transfection efficiency was evaluated.The experiment grouping was as follows:naked plasmid group(P group),ultrasonic irradiation plus naked plasmid group(P-US group),naked plasmid plus CLM group(P-CLM group),naked plasmid plus ultrasound and CLM group(UTMD group).The expression of EGFP was detected by fluorescent microscopy and flow cytometry.The results showed that CLMs were spherical in shape,with the similar size and good distribution degree under the light and electron microscopies.The size of CLMs was varied from 250.4±88.3 to 399.0±99.8 nm and the Zeta potential of CLMs from 18.80±4.97 to 20.1±3.1 mV.The EGFP expression was the strongest in the UTMD group,followed by the P-CLM group,P-US group and P group.Flow cytometry results were consistent with those of fluorescent microscopy.The transfection efficiency was substantially increased in the P-US group,P-CLM group and UTMD group as compared with that in the P group,almost 7 times,10 times and 30 times higher than that in the P group respectively.It is suggested that CLMs prepared by the method of thin film hydration are uniform in diameter,and proved non-toxic.UTMD combined with CLM can significantly increase the transfection efficiency of EGFP to targeted cells.展开更多
Great earthquakes in mountain areas always trigger severe geologic hazards such as landslides, debris flows and rock falls, thereby causing tremendous property damage and casualties. On 19th June, 1781, a Ms 7.5 earth...Great earthquakes in mountain areas always trigger severe geologic hazards such as landslides, debris flows and rock falls, thereby causing tremendous property damage and casualties. On 19th June, 1781, a Ms 7.5 earthquake occurred in Tongwei of Pan'an, Gansu Province, west China,展开更多
In order to investigate the process of optically triggered discharge formation,a model of ion space-charge formation based on classical plane electrodes and revised for a characteristic hollow-cathode discharge(HCD)co...In order to investigate the process of optically triggered discharge formation,a model of ion space-charge formation based on classical plane electrodes and revised for a characteristic hollow-cathode discharge(HCD)configuration is proposed in this paper.The primary modified factor in our model is the penetrating electric-field parameter,which influences the ionization of trigger electrons and is calculated via particle simulation.Optical-trigger experiments are carried out using different voltages and under different seed-electron conditions,provided by two different photocathodes,Cu and Mg.The ion-accumulation rates calculated by our model are compared to the discharge-formation time,which is deduced from optical-trigger experiments.The results demonstrate that the process of positive space-charge formation is dominant in the HCD formation process or trigger delay,which is highly dependent on the seeding-electron density and applied voltage,and can therefore be quantitatively described by our model.Additionally,electron-beam generation is investigated by optically triggered HCD experiments on Mg-and Cu-photocathode-based devices.The results show that a more efficient trigger device is capable of generating an electron beam with higher amplitude and density.展开更多
基金supported by the National Natural Science Foundation of China(NSFC grants No.12172036,51774018)the Program for Changjiang Scholars and Innovative Research Team in University(PCSIRT,IRT_17R06)+2 种基金the Russian Foundation for Basic Research,Grant Number 20‐55‐53032Russian State Task number 1021052706247‐7‐1.5.4the Government of Perm Krai,research project No.С‐26/628.
文摘Earthquakes triggered by dynamic disturbances have been confirmed by numerous observations and experiments.In the past several decades,earthquake triggering has attracted increasing attention of scholars in relation to exploring the mechanism of earthquake triggering,earthquake prediction,and the desire to use the mechanism of earthquake triggering to reduce,prevent,or trigger earthquakes.Natural earthquakes and large‐scale explosions are the most common sources of dynamic disturbances that trigger earthquakes.In the past several decades,some models have been developed,including static,dynamic,quasi‐static,and other models.Some reviews have been published,but explosiontriggered seismicity was not included.In recent years,some new results on earthquake triggering have emerged.Therefore,this paper presents a new review to reflect the new results and include the content of explosion‐triggered earthquakes for the reference of scholars in this area.Instead of a complete review of the relevant literature,this paper primarily focuses on the main aspects of dynamic earthquake triggering on a tectonic scale and makes some suggestions on issues that need to be resolved in this area in the future.
基金supported in part by A*STAR under its RIE2020 Advanced Manufacturing and Engineering(AME)Industry Alignment Fund-Pre Positioning(IAF-PP)(Award A19d6a0053)the Agency for Science,Technology and Research(A*STAR)(I2001E0067)+2 种基金the Schaeffler Hub for Advanced Research at NTUNational Natural Science Foundation of China(62203142)the China Postdoctoral Science Foundation(2022M710966,2022TQ 0096)。
文摘Dear Editor,This letter addresses the resilient model predictive control(MPC)problems for adaptive cruise control(ACC)systems under sensor attacks.In the light of vulnerabilities of ACC systems to sensor attacks,an intrusion detection mechanism is proposed at the controller side to distinguish abnormal data.Then,the robust control gains are derived to design the terminal region constraint for MPC.
基金in part by the National Social Science Foundation of China under Grant 20BTQ058in part by the Natural Science Foundation of Hunan Province under Grant 2023JJ50033。
文摘Federated learning is widely used to solve the problem of data decentralization and can provide privacy protectionfor data owners. However, since multiple participants are required in federated learning, this allows attackers tocompromise. Byzantine attacks pose great threats to federated learning. Byzantine attackers upload maliciouslycreated local models to the server to affect the prediction performance and training speed of the global model. Todefend against Byzantine attacks, we propose a Byzantine robust federated learning scheme based on backdoortriggers. In our scheme, backdoor triggers are embedded into benign data samples, and then malicious localmodels can be identified by the server according to its validation dataset. Furthermore, we calculate the adjustmentfactors of local models according to the parameters of their final layers, which are used to defend against datapoisoning-based Byzantine attacks. To further enhance the robustness of our scheme, each localmodel is weightedand aggregated according to the number of times it is identified as malicious. Relevant experimental data showthat our scheme is effective against Byzantine attacks in both independent identically distributed (IID) and nonindependentidentically distributed (non-IID) scenarios.
基金funded by the Youth Seismic Regime Tracking Project of CEA(2023010129)。
文摘The 2022 Honghe M_(S)5.0 seismic event is intriguing due to its occurrence in the south of the Red River Fault,an area historically lacking seismic activities greater than M_(S)5.0.To elucidate the seismogenic mechanism and scrutinize stress-triggered interactions,we calculated co-seismic and post-seismic Coulomb stress alterations induced by nine historical seismic events(M≥6.0).The analysis reveals that these substantial seismic events provoked co-seismic stress augmentations of 1.409 bar and postseismic stress increments of 0.159 bar.Noteworthy seismic events,such as the 1833 Songming,1877Shiping,1913 Eshan,and 1970 Tonghai earthquakes,catalyzed the occurrence of the Honghe earthquake.Areas of heightened future seismic risk include the southern region of the Red River Fault and the eastern segments of the Shiping-Jianshui and Qujiang faults.Additionally,we assessed the correlation between the spatial distribution of aftershocks and the Coulomb stress shift triggered by the mainshock,taking into account the influence of calculation parameter settings.
基金The Basic Scientific Fund for National Public Research Institutes of China under contract No.2022S02the National Natural Science Foundation of China under contract No.41976021.
文摘Negative Indian Ocean Dipole(nIOD)can exert great impacts on global climate and can also strongly influence the climate in China.Early nIOD is a major type of nIOD,which can induce more pronounced climate anomalies in summer than La Niña-related nIOD.However,the characteristics and triggering mechanisms of early nIOD are unclear.Our results based on reanalysis datasets indicate that the early nIOD and La Niña-related nIOD are the two major types of nIOD,and the former accounts for over one third of all the nIOD events in the past six decades.These two types of nIODs are similar in their intensities,but are different in their spatial patterns and seasonal cycles.The early nIOD,which develops in spring and peaks in summer,is one season earlier than the La Niña-related nIOD.The spatial pattern of the wind anomaly associated with early nIOD exhibits a winter monsoon-like pattern,with strong westerly anomalies in the equatorial Indian Ocean and eastly anomalies in the northern Indian Ocean.Opposite to the triggering mechanism of early positve IOD,the early nIOD is induced by delayed Indian summer monsoon onset.The results of this study are helpful for improving the prediction skill of IOD and its climate impacts.
基金supported by National Natural Science Foundation of China(No.12102099)the National Key R&D Program of China(No.2021YFC2202700)the Outstanding Academic Leader Project of Shanghai(Youth)(No.23XD1421700),respectively。
文摘In this study,a pulsed,high voltage driven hollow-cathode electron beam sources through an optical trigger is designed with characteristics of simple structure,low cost,and easy triggering.To validate the new design,the characteristics of hollow-cathode discharge and electron beam characterization under pulsed high voltage drive are studied experimentally and discussed by discharge characteristics and analyses of waveform details,respectively.The validation experiments indicate that the pulsed high voltage supply significantly improves the frequency and stability of the discharge,which provides a new solution for the realization of a high-frequency,high-energy electron beam source.The peak current amplitude in the high-energy electron beam increases from 6.2 A to 79.6 A,which indicates the pulsed power mode significantly improves the electron beam performance.Besides,increasing the capacitance significantly affects the highcurrent,lower-energy electron beam more than the high-energy electron beam.
文摘This paper addresses the problem of event-triggered finite-time H<sub>∞</sub> filter design for a class of discrete-time nonlinear stochastic systems with exogenous disturbances. The stochastic Lyapunov-Krasoviskii functional method is adopted to design a filter such that the filtering error system is stochastic finite-time stable (SFTS) and preserves a prescribed performance level according to the pre-defined event-triggered criteria. Based on stochastic differential equations theory, some sufficient conditions for the existence of H<sub>∞</sub> filter are obtained for the suggested system by employing linear matrix inequality technique. Finally, the desired H<sub>∞</sub> filter gain matrices can be expressed in an explicit form.
基金supported by the New Century Talent Foundation of Ministry of Education of China (NCET-08-0438)
文摘Triggering characteristics of triggered vacuum switch (TVS), including the discharge delay time, delay jitter, range of operational voltage and peak of pulsed current, are investigated. Both structure and experimental circuit of TVS are presented. The results indicate that TVS, as a surface flashover triggering device with high dielectric permittivity material, is with excellent triggering characteristics. When the hold-off voltage reaches 120 kV, the minimum operational voltage is 1.3 kV, and the minimum discharge delay time and jitter are 100 ns and ±10 ns, respectively. The peak current is up to 240 kA when the operational voltage reaches 100 kV. TVS can well satisfy the main demands of high voltage and current applications, and can also be used under a multi-crowbar circuit.
基金A key project of China Meteorological Administration (CMATG2008Z07)Specialized Science Project for Public Welfare Industries (GYHY2007622)Key Science Project of the Guangzhou Regional Meteorological Center (GRMC2007B03)
文摘Techniques of artificially-triggered lightning have provided a significantly useful means to directly measure various physical parameters of lightning discharge and to conduct research on protection methods of lightning electromagnetic pulses.In this study,using capacitive and resistive dividers,current probes and optical fiber transmission devices,we measured and analyzed the induced overvoltage on the overhead transmission line and the overcurrent through Surge Protective Devices(SPD) when a lightning discharge was artificially triggered nearby on August 12,2008 at Conghua Field Lightning Experiment Site.The triggered lightning discharge contained an initial current stage and eight return strokes whose peak currents ranged from 6.6kA to 26.4kA.We found that overcurrents through SPD were induced on the power line both during the initial continuous current stage and the return stroke processes.During the return strokes,the residual voltage and the current through the SPD lasted up to the ms(millisecond) range,and the overcurrents exhibited a mean waveform up to 22/69μs with a peak value of less than 2kA.Based on the observed data,simple calculations show that the corresponding single discharge energy was much greater than the values of the high voltage pulse generators commonly used in the experiments regulated for SPD.The SPD discharge current peak was not synchronous to that of the residual voltage with the former obviously lagging behind the latter.The SPD discharge current peak was well correlated with the triggered lightning current peak and the wave-front current gradient.The long duration of the SPD current is one of the major reasons why the SPD was damaged even with a big nominal discharge current.
基金supported financially by the Science and Technology Development Plan Project of Shandong Province(2014GSF120007)Shandong Earthquake Agency,China Earthquake Administration(SD1250501)
文摘An extraordinary earthquake swarm occurred at Rushan on the Jiaodong Peninsula from October 1, 2013, onwards, and more than 12,000 aftershocks had been detected by December 31, 2015. All the activities of the whole swarm were recorded at the nearest station, RSH, which is located about 12 km from the epicenter. We examine the statistical characteristics of the Rushan swarm in this paper using RSH station data to assess the arrival time difference, ts p, of Pg and Sg phases. A temporary network comprising 18 seismometers was set up on May 6, 2014, within the area of the epicenter; based on the data from this network and use of the double difference method, we determine precise hypocenter locations. As the distribution of relocated sources reveals migration of seismic activity, we applied the mean-shift cluster method to perform clustering analysis on relocated catalogs. The results of this study show that there were at least 16 clusters of seismic activities between May 6, 2014, and June 30, 2014, and that each was characterized by a hypocenter spreading process. We estimated the hydraulic diffusivity, D, of each cluster using envelope curve fitting; the results show that D values range between 1.2 and 3.5 m2/d and that approximate values for clusters on the edge of the source area are lower than those within the central area. We utilize an epidemic-type aftershock sequence (ETAS) model to separate external triggered events from self-excited aftershocks within the Rushan swarm. The estimated parameters for this model suggest that α = 1.156, equiva- lent to sequences induced by fluid-injection, and that the forcing rate (μ) implies just 0.15 events per day. These estimates indicate that around 3% of the events within the swarm were externally triggered. The fact that variation in μ is synchronous with swarm activity implies that pulses in fluid pressure likely drove this series of earthquakes.
基金supported in part by the National Natural Science Foundation of China(62103099,61921004)the Natural Science Foundation of Jiangsu Province of China(BK20210214).
文摘Dear editor,Recently,researchers have obtained many new results about the multi-agent systems(MASs)[1]-[3].In[1],the fixed-time cooperative control(FTCC)algorithm of linear MASs with matched disturbances was proposed.The nonholonomic chained-form dynamics case was considered in[2].In[3],the output tracking problem with data packet dropout was solved for high-order MASs.Moreover,delay frequently occurs because of the non-ideal data transmission[4],and the corresponding FTCC algorithm of MASs with delay was given in[5].
文摘The plasma-jet triggered gas switch (PJTGS) could operate at a low working coefficient with a low jitter. We observed and analyzed the discharge process of the PJTGS at the lowest working coefficient of 47% with the trigger voltage of 40 kV and the pulse energy of 2 J to evaluate the effect of the plasma jet. The temporal and spatial evolution and the optical emission speclrum of the plasma jet were captured. And the spraying delay time and outlet velocity under different gas pressures were investigated. In addition, the particle in cell with Monte Carlo collision was employed to obtain the particle distribution of the plasma jet varying with time. The results show that, the plasma jet generated by spark discharge is sprayed into a spark gap within tens of nanoseconds, and its outlet velocity could reach 104 m s-1. The plasma jet plays a non-penetrating inducing role in the triggered discharge process of the PJTGS. On the one hand, the plasma jet provides the initial electrons needed by the discharge; on the other hand, a large number of electrons focusing on the head of the plasma jet distort the electric field between the head of the plasma jet and the opposite electrode. Therefore, a fast discharge originated from the plasma jet is induced and quickly bridges two electrodes.
基金supported by the National Natural Science Foundation of China(Grant No.51677149)
文摘To overcome hole-injection limitation of p^+-n emitter junction in 4H-SiC light triggered thyristor, a novel high- voltage 4H-SiC light triggered thyristor with double-deck thin n-base structure is proposed and demonstrated by two- dimensional numerical simulations. In this new structure, the conventional thin n-base is split to double-deck. The hole- injection of p^+-n emitter junction is modulated by modulating the doping concentration and thickness of upper-deck thin n- base. With double-deck thin n-base, the current gain coefficient of the top pnp transistor in 4H-SiC light triggered thyristor is enhanced. As a result, the triggering light intensity and the turn-on delay time of 4H-SiC light triggered thyristor are both reduced. The simulation results show that the proposed 10-kV 4H-SiC light triggered thyristor is able to be triggered on by 500-mW/cm^2 ultraviolet light pulse. Meanwhile, the turn-on delay time of the proposed thyristor is reduced to 337 ns.
基金Project supported by the National Natural Science Foundation of China(Grant No.51677149)
文摘A new 4 H–SiC light triggered thyristor(LTT) with 7-shaped thin n-base doping profile is proposed and simulated using a two-dimensional numerical method. In this new structure, the bottom region of the thin n-base has a graded doping profile to induce an accelerating electric field and compensate for the shortcoming of the double-layer thin n-base structure in transmitting injected holes. In addition, the accelerating electric field can also speed up the transmission of photongenerated carriers during light triggering. As a result, the current gain of the top pnp transistor of the SiC LTT is further increased. According to the TCAD simulations, the turn-on delay time of the SiC LTT decreases by about 91.5% compared with that of previous double-layer thin n-base SiC LTT. The minimum turn-on delay time of the SiC LTT is only 828 ns,when triggered by 100 mW/cm^2 ultraviolet light. Meanwhile, there is only a slight degradation in the forward blocking characteristic.
基金supported by National Natural Science Foundation of China(No.51177131)the New Century Talent Foundation of Ministry of Education of China(NCET-08-0438)
文摘A triggered surge protective device is designed and its discharge characteristics axe studied. The experimental results show that the triggered surge protective device has excellent surge protective characteristics. When the gap distance is 5 mm, p. d is 90 Pa.mm and without an active energy trigger circuit, the DC breakdown voltage of the triggered surge protective device is 2.32 kV and the pulse breakdown voltage is 5.75 kV. Therefore, the pulse voltage ratio, which is defined as the specific value of pulse breakdown voltage and DC breakdown voltage, is 2.48. With a semiconductor ZnO flashover trigger device and an active energy coupling trigger circuit, the pulse breakdown voltage can be reduced to 3.32 kV, the pulse voltage ratio is 1.43 and the response time is less than 100 ns. These results are helpful in laying a theoretical foundation for further studies on triggered surge protective devices.
基金supported by the Open Fund of the State Key Laboratory of Severe Weather of the Chinese Academy of Meteorological Sciences (Grant No. 2019LASW-B08)as a Basic Research Project of the Chinese Academy of Meteorological Sciences (Grant No. 2015Z006. 2016Z005)
文摘The spectra with wavelength range of 390 nm to 660 nm of triggered lightning were observed in Guangdong Area using a slitless spectrograph. The characteristics of the lightning spectra during the initial continuous current and return strokes were analyzed, and the differences between the metal section and air section of the lightning channel were compared. The results showed that the metal spectra were contained in the metal section during the initial continuous current. As for the lightning channel of the return strokes, the line spectra for both the metal section and the air section were identical;neither of the two sections contained the metal spectra, but the relative intensity of its emission spectrum was different. Owing to different radiation mechanisms, the spectral structures and luminance of the two sections were not the same. Combined with the current data, it was found that there was a good positive correlation between the total spectral strength and the transferred charge. The total intensity of the lightning channel spectrum increased with the height of the channel, indicating that the radiation sequence of the lightning channel was different. High temporal resolution observations showed that the spectral line duration could be divided into three categories, in which the lines with higher excitation energy appear first and decay rapidly, while those with lower excitation energy appear later but last longer.
基金supported by a grant from National Natural Sciences Foundation of China (No. 81071280)
文摘This study aimed to examine the preparation of cationic lipid microbubble(CLM),and evaluate its physical and chemical properties and toxicity,measure the gene transfection efficiency by ultrasound triggered microbobble destruction(UTMD) in combination with CLM.The CLM was prepared by the method of the thin film hydration,and its morphology was observed under the electron microscopy at 1st,3rd,7th,10th,and 14th day after preparation,respectively.The size,Zeta potential and stability of CLM were tested.The acute toxicity of CLM was assessed.The green fluorescent protein gene(EGFP) transfection efficiency was evaluated.The experiment grouping was as follows:naked plasmid group(P group),ultrasonic irradiation plus naked plasmid group(P-US group),naked plasmid plus CLM group(P-CLM group),naked plasmid plus ultrasound and CLM group(UTMD group).The expression of EGFP was detected by fluorescent microscopy and flow cytometry.The results showed that CLMs were spherical in shape,with the similar size and good distribution degree under the light and electron microscopies.The size of CLMs was varied from 250.4±88.3 to 399.0±99.8 nm and the Zeta potential of CLMs from 18.80±4.97 to 20.1±3.1 mV.The EGFP expression was the strongest in the UTMD group,followed by the P-CLM group,P-US group and P group.Flow cytometry results were consistent with those of fluorescent microscopy.The transfection efficiency was substantially increased in the P-US group,P-CLM group and UTMD group as compared with that in the P group,almost 7 times,10 times and 30 times higher than that in the P group respectively.It is suggested that CLMs prepared by the method of thin film hydration are uniform in diameter,and proved non-toxic.UTMD combined with CLM can significantly increase the transfection efficiency of EGFP to targeted cells.
基金support of China Geological Survey(Project No.12120114035901)NSFC(Award No.41472296 and No.41372374)
文摘Great earthquakes in mountain areas always trigger severe geologic hazards such as landslides, debris flows and rock falls, thereby causing tremendous property damage and casualties. On 19th June, 1781, a Ms 7.5 earthquake occurred in Tongwei of Pan'an, Gansu Province, west China,
文摘In order to investigate the process of optically triggered discharge formation,a model of ion space-charge formation based on classical plane electrodes and revised for a characteristic hollow-cathode discharge(HCD)configuration is proposed in this paper.The primary modified factor in our model is the penetrating electric-field parameter,which influences the ionization of trigger electrons and is calculated via particle simulation.Optical-trigger experiments are carried out using different voltages and under different seed-electron conditions,provided by two different photocathodes,Cu and Mg.The ion-accumulation rates calculated by our model are compared to the discharge-formation time,which is deduced from optical-trigger experiments.The results demonstrate that the process of positive space-charge formation is dominant in the HCD formation process or trigger delay,which is highly dependent on the seeding-electron density and applied voltage,and can therefore be quantitatively described by our model.Additionally,electron-beam generation is investigated by optically triggered HCD experiments on Mg-and Cu-photocathode-based devices.The results show that a more efficient trigger device is capable of generating an electron beam with higher amplitude and density.