Dear Editor,This letter deals with the stabilization problem of nonlinear stochastic systems via self-triggered impulsive control(STIC), where the timing of impulsive control actions is not dependent on continuous sta...Dear Editor,This letter deals with the stabilization problem of nonlinear stochastic systems via self-triggered impulsive control(STIC), where the timing of impulsive control actions is not dependent on continuous state monitoring. In contrast to the existing self-triggered control method, novel self-triggered mechanism(STM) is proposed by incorporating a waiting time for stabilizing impulses. This allows for direct prediction of the next impulsive instant.展开更多
Dear Editor,This letter deals with the stabilization of a resilient model predictive control(MPC)algorithm with a dynamic event-triggered mechanism subject to Denial-of-Service(Do S)attacks.Different from previous wor...Dear Editor,This letter deals with the stabilization of a resilient model predictive control(MPC)algorithm with a dynamic event-triggered mechanism subject to Denial-of-Service(Do S)attacks.Different from previous works,this letter is based on the designed threshold function to dynamically trigger and gives the upper bound conditions for intersampling intervals with attack and attack-free scenarios to converge.展开更多
This study utilizes data from a 3D lightning location system,polarimetric radar,and current measurements from channels of triggered lightning flashes(TLFs)to analyze the structural characteristics of the parent thunde...This study utilizes data from a 3D lightning location system,polarimetric radar,and current measurements from channels of triggered lightning flashes(TLFs)to analyze the structural characteristics of the parent thunderstorms associated with negative TLFs in South China.The triggered-flash region(TFR)displays distinct stratiform cloud characteristics,including lower radar reflectivity heights and a predominance of ice crystals and dry snow above the 0℃ layer.In contrast,the thunderstorm convection core region(CCR)tends to have more graupel particles in the mixed-phase layers and exhibits an ice-water content peak approximately 3.4 times that of the TFR.The charge regions involved in discharges in TFRs exhibit a dipolar charge structure,with the-5℃ layer roughly dividing the upper positive and lower negative charge regions.Conversely,the CCRs feature a typical tripolar charge structure.The dominant dipole charge structure in the TFR results in an increase in the negative charge field below the negative charge region with height,providing a necessary condition for successfully triggering negative TLFs.Furthermore,the horizontal extent of TLFs is positively correlated with their duration and charge transfer.Regions where TLF channels with larger charge transfers propagate tend to have greater maximum radar reflectivity but lower average radar reflectivity compared to regions with TLFs with smaller charge transfer.展开更多
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
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
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
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
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
Triggered spark-gap switch is a popular discharge switch for pulse power systems.Previous studies have focused on planarizing this switch using thin film techniques in order to meet the requirements of compact size in...Triggered spark-gap switch is a popular discharge switch for pulse power systems.Previous studies have focused on planarizing this switch using thin film techniques in order to meet the requirements of compact size in the systems.Such switches are one-shot due to electrodes being too thin to sufficiently resist spark-erosion.Additionally,these switches did not employ any structures in securing internal gas composition,resulting in inconsistent performance under harsh atmospheres.In this work,a novel planar triggered spark-gap switch(PTS)with a hermetically sealed cavity was batched-prepared with printed circuit board(PCB)technology,to achieve reusability with low cost.The proposed PTS was inspected by micro-computed tomography to ensure PCB techniques meet the requirements of machining precision.The results from electrical experiments demonstrated that PCB PTS were consistent and reusable with lifespan over 20 times.The calculated switch voltage and circuit current were consistent with those derived from real-world measurements.Finally,PCB PTS was used to introduce hexanitrostilbene(HNS)pellets in a pulse power system to verify its performance.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
The identification of large-giant bedrock landslides triggered by earthquake aims to the landslide prevention and control. Previous studies have described the basic characteristics, distribution, and the formation mec...The identification of large-giant bedrock landslides triggered by earthquake aims to the landslide prevention and control. Previous studies have described the basic characteristics, distribution, and the formation mechanism of seismic landslides （Bijan Khazai et al., 2003; Chong Xu et al., 2013; Lewis a. Owen et al., 2008; Randall W. Jibson et al., 2006）. However, few researches have focused on the early identification indicators of large-giant bedrock landslides triggered by earthquake （David k. Keefer., 1984; Janusz Wasowski et al., 2011; Alexander L.Strom., 2009; Patrick Meunier et al., 2008; Shahriar Vahdani et al., 2002; Bijan Khazai et al., 2003）. This paper presents the identification indicators of large-giant bedrock landslides triggered by earthquake in the Longmenshan tectonic belt on the basic of their characteristics, distribution and the relationship between seismic landslides and the peak ground motion acceleration.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
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
According to the classic Karush-Kuhn-Tucker(KKT)theorem,at every step of incremental support vector machine(SVM)learning,the newly adding sample which violates the KKT conditions will be a new support vector(SV)and mi...According to the classic Karush-Kuhn-Tucker(KKT)theorem,at every step of incremental support vector machine(SVM)learning,the newly adding sample which violates the KKT conditions will be a new support vector(SV)and migrate the old samples between SV set and non-support vector(NSV)set,and at the same time the learning model should be updated based on the SVs.However,it is not exactly clear at this moment that which of the old samples would change between SVs and NSVs.Additionally,the learning model will be unnecessarily updated,which will not greatly increase its accuracy but decrease the training speed.Therefore,how to choose the new SVs from old sets during the incremental stages and when to process incremental steps will greatly influence the accuracy and efficiency of incremental SVM learning.In this work,a new algorithm is proposed to select candidate SVs and use the wrongly predicted sample to trigger the incremental processing simultaneously.Experimental results show that the proposed algorithm can achieve good performance with high efficiency,high speed and good accuracy.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
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
On April 14, 2010 at 07：49 （Beijing time）, a catastrophic earthquake with Ms 7. 1 occurred at the central Qinghai-Tibetan Plateau. The epicenter was located at Yushu county, Qinghai Province, China. A total of 2036...On April 14, 2010 at 07：49 （Beijing time）, a catastrophic earthquake with Ms 7. 1 occurred at the central Qinghai-Tibetan Plateau. The epicenter was located at Yushu county, Qinghai Province, China. A total of 2036 landslides were determined from visual interpretation of aerial photographs and high resolution remote sensing images, and verified by selected field investigations. These landslides covered a total area of about 1. 194km~. Characteristics and failure mechanisms of these landslides are listed in this paper, including the fact that the spatial distribution of these landslides is controlled by co- seismic main surface fault ruptures. Most of the landslides were small scale, causing rather less hazards, and often occurring close to each other. The landslides were of various types, including mainly disrupted landslides and rock falls in shallows and also deep-seated landslides, liquefaction induced landslides, and compound landslides. In addition to strong ground shaking, which is the direct landslide triggering factor, geological, topographical, and human activity also have impact on the occurrence of earthquake triggered landslides. In this paper, five types of failure mechanisms related to the landslides are presented, namely, the excavated toes of slopes accompanied by strong ground shaking; surface water infiltration accompanied by strong ground shaking; co- seismic fault slipping accompanied by strong ground shaking; only strong ground shaking; and delayed occurrence of landslides due to snow melt or rainfall infiltration at sites where slopes were weakened by co-seismic ground shaking. Besides the main co-seismic surface ruptures, slope fissures were also delineated from visual interpretation of aerial photographs in high resolution. A total of 4814 slope fissures, with a total length up to 77. lkm, were finally mapped. These slope fissures are mainly distributed on the slopes located at the southeastern end of the main co-seismic surface rupture zone, an area subject to strong compression during the earthquake.展开更多
BACKGROUND:Calcium calmodulin-dependent kinase II(CaMKII) can be more active in patients with left ventricular hypertrophy(LVH),which in turn causes phosphorylation of ryanodine receptors,resulting in inactivation and...BACKGROUND:Calcium calmodulin-dependent kinase II(CaMKII) can be more active in patients with left ventricular hypertrophy(LVH),which in turn causes phosphorylation of ryanodine receptors,resulting in inactivation and the instability of intracellular calcium homeostasis.The present study aimed to determine the effect of CaMKII-ryanodine receptor pathway signaling in rabbits with left ventricular hypertrophy and triggered ventricular arrhythmia.METHODS:Forty New Zealand rabbits were randomized into four groups(10 per group):sham group,LVH group,KN-93 group(LVH+KN-93),and ryanodine group(LVH+ryanodine).Rabbits in the LVH,KN-93,and ryanodine groups were used to establish a left ventricular hypertrophy model by the coarctation of the abdominal aorta,while those in the sham group did not undergo the coarctation.After eight weeks,action potentials(APs) were recorded simultaneously in the endocardium and epicardium,and a transmural electrocardiogram(ECG) was also recorded in the rabbit left ventricular wedge model.Drugs were administered to the animals in the KN-93 and ryanodine groups,and the frequency of triggered APs and ventricular tachycardia was recorded after the rabbits were given isoprenaline(1 μmol/L) and high-frequency stimulation.RESULTS:The frequency(animals/group) of triggered APs was 0/10 in the sham group,10/10 in the LVH group,4/10 in the KN-93 group,and 1/10 in the ryanodine group.The frequencies of ventricular tachycardia were 0/10,9/10,3/10,and 1/10,respectively.The frequencies of polymorphic ventricular tachycardia or ventricular fibrillation were 0/10,7/10,2/10,and 1/10,respectively.The frequencies of triggered ventricular arrhythmias in the KN-93 and ryanodine groups were much lower than those in the LVH group(P<0.05).CONCLUSIONS:KN-93 and ryanodine can effectively reduce the occurrence of triggered ventricular arrhythmia in rabbits with LVH.The CaMKII-ryanodine signaling pathway can be used as a new means of treating ventricular arrhythmia.展开更多
A novel NMOS triggered LIGBT(NTLIGBT) structure is proposed for electrostatic discharge(ESD) protection in this paper. The structure utilizes internal NMOS to trigger SCR-like structure in LIGBT. The trigger voltage i...A novel NMOS triggered LIGBT(NTLIGBT) structure is proposed for electrostatic discharge(ESD) protection in this paper. The structure utilizes internal NMOS to trigger SCR-like structure in LIGBT. The trigger voltage is significantly reduced because the embedded NMOS causes N+-drain/P-body junction being apt to avalanche breakdown. At the same time, the new parasitic PNP transistor including the newly added P+-region as a collector forms another path to bleed ESD current and then the conductivity modulation in the LIGBT is weakened. As a result, the holding voltage is increased. So, the proposed NTLIGBT structure has a narrow ESD design window. The simulation results show an improvement of 71.5% in trigger voltage and over 50% in holding voltage comparing with the conventional LIGBT structure.展开更多
Objectives This study aimed at investigating the cellular mechanism of isoproterenol （ISO） on delayed afterdepolarizations （DADs） and triggered activity （TA） of the noninfarcted myocardium in the myocardial infa...Objectives This study aimed at investigating the cellular mechanism of isoproterenol （ISO） on delayed afterdepolarizations （DADs） and triggered activity （TA） of the noninfarcted myocardium in the myocardial infarcted rabbit model.Methods Rabbits with the left anterior descending coronary artery occlusion were prepared and recovered for 8 wk （healed myocardial infarction, HMI）. Myocytes were isolated from regions of the noninfarcted left ventricular free wall. ISO was added to cellular surface by perfusion way. Action potentials and ion currents were recorded with whole-cell patch clamp. Results The results showed that treatment with ISO induced more DADs and TA events in HMI myocytes. Iti and IC,_L of myocytes treated with ISO were increased significantly compared with HMI cells, which contributed to DADs-related triggered arrhythmia. Conclusions The results suggested that more arrhythmia events of DADs and TA developed in myocytes with ISO treatment. The underlying mechanism was associated with the augment of I6 and calcium influxing展开更多
基金supported by the National Natural Science Foundation of China(62403393,12202058,62103118)the China Postdoctoral Science Foundation(2021T140160,2023 T160051)the Natural Science Foundation of Chongqing(CSTB 2023NSCQ-MSX0152)
文摘Dear Editor,This letter deals with the stabilization problem of nonlinear stochastic systems via self-triggered impulsive control(STIC), where the timing of impulsive control actions is not dependent on continuous state monitoring. In contrast to the existing self-triggered control method, novel self-triggered mechanism(STM) is proposed by incorporating a waiting time for stabilizing impulses. This allows for direct prediction of the next impulsive instant.
文摘Dear Editor,This letter deals with the stabilization of a resilient model predictive control(MPC)algorithm with a dynamic event-triggered mechanism subject to Denial-of-Service(Do S)attacks.Different from previous works,this letter is based on the designed threshold function to dynamically trigger and gives the upper bound conditions for intersampling intervals with attack and attack-free scenarios to converge.
基金funded by the Natural Science Foundation of China(Grant No.U2342215)Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province(Grant No.SCSF202302)。
文摘This study utilizes data from a 3D lightning location system,polarimetric radar,and current measurements from channels of triggered lightning flashes(TLFs)to analyze the structural characteristics of the parent thunderstorms associated with negative TLFs in South China.The triggered-flash region(TFR)displays distinct stratiform cloud characteristics,including lower radar reflectivity heights and a predominance of ice crystals and dry snow above the 0℃ layer.In contrast,the thunderstorm convection core region(CCR)tends to have more graupel particles in the mixed-phase layers and exhibits an ice-water content peak approximately 3.4 times that of the TFR.The charge regions involved in discharges in TFRs exhibit a dipolar charge structure,with the-5℃ layer roughly dividing the upper positive and lower negative charge regions.Conversely,the CCRs feature a typical tripolar charge structure.The dominant dipole charge structure in the TFR results in an increase in the negative charge field below the negative charge region with height,providing a necessary condition for successfully triggering negative TLFs.Furthermore,the horizontal extent of TLFs is positively correlated with their duration and charge transfer.Regions where TLF channels with larger charge transfers propagate tend to have greater maximum radar reflectivity but lower average radar reflectivity compared to regions with TLFs with smaller charge transfer.
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,
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 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We gratefully acknowledge support from the Natural Science Foundation of Jiangsu Province of China(Grant No.BK20151486).
文摘Triggered spark-gap switch is a popular discharge switch for pulse power systems.Previous studies have focused on planarizing this switch using thin film techniques in order to meet the requirements of compact size in the systems.Such switches are one-shot due to electrodes being too thin to sufficiently resist spark-erosion.Additionally,these switches did not employ any structures in securing internal gas composition,resulting in inconsistent performance under harsh atmospheres.In this work,a novel planar triggered spark-gap switch(PTS)with a hermetically sealed cavity was batched-prepared with printed circuit board(PCB)technology,to achieve reusability with low cost.The proposed PTS was inspected by micro-computed tomography to ensure PCB techniques meet the requirements of machining precision.The results from electrical experiments demonstrated that PCB PTS were consistent and reusable with lifespan over 20 times.The calculated switch voltage and circuit current were consistent with those derived from real-world measurements.Finally,PCB PTS was used to introduce hexanitrostilbene(HNS)pellets in a pulse power system to verify its performance.
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financially supported by the Geological Survey Project of China Geological Survey (grant no.1212011014032,1212011220134)
文摘The identification of large-giant bedrock landslides triggered by earthquake aims to the landslide prevention and control. Previous studies have described the basic characteristics, distribution, and the formation mechanism of seismic landslides （Bijan Khazai et al., 2003; Chong Xu et al., 2013; Lewis a. Owen et al., 2008; Randall W. Jibson et al., 2006）. However, few researches have focused on the early identification indicators of large-giant bedrock landslides triggered by earthquake （David k. Keefer., 1984; Janusz Wasowski et al., 2011; Alexander L.Strom., 2009; Patrick Meunier et al., 2008; Shahriar Vahdani et al., 2002; Bijan Khazai et al., 2003）. This paper presents the identification indicators of large-giant bedrock landslides triggered by earthquake in the Longmenshan tectonic belt on the basic of their characteristics, distribution and the relationship between seismic landslides and the peak ground motion acceleration.
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 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 the National Natural Science Foundation of China(Nos.U1509207 and 61325019)
文摘According to the classic Karush-Kuhn-Tucker(KKT)theorem,at every step of incremental support vector machine(SVM)learning,the newly adding sample which violates the KKT conditions will be a new support vector(SV)and migrate the old samples between SV set and non-support vector(NSV)set,and at the same time the learning model should be updated based on the SVs.However,it is not exactly clear at this moment that which of the old samples would change between SVs and NSVs.Additionally,the learning model will be unnecessarily updated,which will not greatly increase its accuracy but decrease the training speed.Therefore,how to choose the new SVs from old sets during the incremental stages and when to process incremental steps will greatly influence the accuracy and efficiency of incremental SVM learning.In this work,a new algorithm is proposed to select candidate SVs and use the wrongly predicted sample to trigger the incremental processing simultaneously.Experimental results show that the proposed algorithm can achieve good performance with high efficiency,high speed and good accuracy.
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sponsored by the National Natural Science Foundation,China(40821160550),supported by the National Natural Science Foundation of China (41202235 )the Basic Scientific Fund of the Institute of Geology, China Earthquake Administration (IGCEA1215)
文摘On April 14, 2010 at 07：49 （Beijing time）, a catastrophic earthquake with Ms 7. 1 occurred at the central Qinghai-Tibetan Plateau. The epicenter was located at Yushu county, Qinghai Province, China. A total of 2036 landslides were determined from visual interpretation of aerial photographs and high resolution remote sensing images, and verified by selected field investigations. These landslides covered a total area of about 1. 194km~. Characteristics and failure mechanisms of these landslides are listed in this paper, including the fact that the spatial distribution of these landslides is controlled by co- seismic main surface fault ruptures. Most of the landslides were small scale, causing rather less hazards, and often occurring close to each other. The landslides were of various types, including mainly disrupted landslides and rock falls in shallows and also deep-seated landslides, liquefaction induced landslides, and compound landslides. In addition to strong ground shaking, which is the direct landslide triggering factor, geological, topographical, and human activity also have impact on the occurrence of earthquake triggered landslides. In this paper, five types of failure mechanisms related to the landslides are presented, namely, the excavated toes of slopes accompanied by strong ground shaking; surface water infiltration accompanied by strong ground shaking; co- seismic fault slipping accompanied by strong ground shaking; only strong ground shaking; and delayed occurrence of landslides due to snow melt or rainfall infiltration at sites where slopes were weakened by co-seismic ground shaking. Besides the main co-seismic surface ruptures, slope fissures were also delineated from visual interpretation of aerial photographs in high resolution. A total of 4814 slope fissures, with a total length up to 77. lkm, were finally mapped. These slope fissures are mainly distributed on the slopes located at the southeastern end of the main co-seismic surface rupture zone, an area subject to strong compression during the earthquake.
基金supported by a grant from Surface Project of Natural Science Foundation of Fujian Province(2008J0075)
文摘BACKGROUND:Calcium calmodulin-dependent kinase II(CaMKII) can be more active in patients with left ventricular hypertrophy(LVH),which in turn causes phosphorylation of ryanodine receptors,resulting in inactivation and the instability of intracellular calcium homeostasis.The present study aimed to determine the effect of CaMKII-ryanodine receptor pathway signaling in rabbits with left ventricular hypertrophy and triggered ventricular arrhythmia.METHODS:Forty New Zealand rabbits were randomized into four groups(10 per group):sham group,LVH group,KN-93 group(LVH+KN-93),and ryanodine group(LVH+ryanodine).Rabbits in the LVH,KN-93,and ryanodine groups were used to establish a left ventricular hypertrophy model by the coarctation of the abdominal aorta,while those in the sham group did not undergo the coarctation.After eight weeks,action potentials(APs) were recorded simultaneously in the endocardium and epicardium,and a transmural electrocardiogram(ECG) was also recorded in the rabbit left ventricular wedge model.Drugs were administered to the animals in the KN-93 and ryanodine groups,and the frequency of triggered APs and ventricular tachycardia was recorded after the rabbits were given isoprenaline(1 μmol/L) and high-frequency stimulation.RESULTS:The frequency(animals/group) of triggered APs was 0/10 in the sham group,10/10 in the LVH group,4/10 in the KN-93 group,and 1/10 in the ryanodine group.The frequencies of ventricular tachycardia were 0/10,9/10,3/10,and 1/10,respectively.The frequencies of polymorphic ventricular tachycardia or ventricular fibrillation were 0/10,7/10,2/10,and 1/10,respectively.The frequencies of triggered ventricular arrhythmias in the KN-93 and ryanodine groups were much lower than those in the LVH group(P<0.05).CONCLUSIONS:KN-93 and ryanodine can effectively reduce the occurrence of triggered ventricular arrhythmia in rabbits with LVH.The CaMKII-ryanodine signaling pathway can be used as a new means of treating ventricular arrhythmia.
基金supported by National Natural Science Foundation of China(Grant No.61274080)
文摘A novel NMOS triggered LIGBT(NTLIGBT) structure is proposed for electrostatic discharge(ESD) protection in this paper. The structure utilizes internal NMOS to trigger SCR-like structure in LIGBT. The trigger voltage is significantly reduced because the embedded NMOS causes N+-drain/P-body junction being apt to avalanche breakdown. At the same time, the new parasitic PNP transistor including the newly added P+-region as a collector forms another path to bleed ESD current and then the conductivity modulation in the LIGBT is weakened. As a result, the holding voltage is increased. So, the proposed NTLIGBT structure has a narrow ESD design window. The simulation results show an improvement of 71.5% in trigger voltage and over 50% in holding voltage comparing with the conventional LIGBT structure.
基金This work was supported by the National Natural Science Foundation of China （No： 30770901）.
文摘Objectives This study aimed at investigating the cellular mechanism of isoproterenol （ISO） on delayed afterdepolarizations （DADs） and triggered activity （TA） of the noninfarcted myocardium in the myocardial infarcted rabbit model.Methods Rabbits with the left anterior descending coronary artery occlusion were prepared and recovered for 8 wk （healed myocardial infarction, HMI）. Myocytes were isolated from regions of the noninfarcted left ventricular free wall. ISO was added to cellular surface by perfusion way. Action potentials and ion currents were recorded with whole-cell patch clamp. Results The results showed that treatment with ISO induced more DADs and TA events in HMI myocytes. Iti and IC,_L of myocytes treated with ISO were increased significantly compared with HMI cells, which contributed to DADs-related triggered arrhythmia. Conclusions The results suggested that more arrhythmia events of DADs and TA developed in myocytes with ISO treatment. The underlying mechanism was associated with the augment of I6 and calcium influxing
