The microstructure and electrical properties of ZnO-Bi2O3-Yb2O3 based varistor ceramics were investigated with various temperature effects from 900°C to 1050°C.From the results,it was observed that the incre...The microstructure and electrical properties of ZnO-Bi2O3-Yb2O3 based varistor ceramics were investigated with various temperature effects from 900°C to 1050°C.From the results,it was observed that the increase of sintering temperature offers a reduced capacitive effect from 0.460 nF to 0.321 nF.Furthermore,the grain sizes of varistors were varied from 6.8μm to 9.8μm.The consequence of such smaller grain sizes provided a better voltage gradient of about 895 V/mm for the disc sintered at 900°C and fallen drastically to 410 V/mm for the sample sintered at 1050°C.In addition,there was an increase of non-linearity index to a maximum value of 36.0 and reduced leakage current of 0.026 mA/cm2.However,the density of the varistor decreased with an increase of temperature from 5.41 g/cm3 to 5.24 g/cm3.With this base,the influence of varistor capacitance and high voltage gradient were scrutinized and it led an improved transition speed of the varistor assembly from non-conduction to conduction mode during intruding nanosecond transients.展开更多
This study evaluates the seasonal cycle of the activity of convectively coupled equatorial waves(CCEWs),including mixed Rossby-gravity(MRG) and tropical depression-type(TD-type) waves,based on the twentieth century ex...This study evaluates the seasonal cycle of the activity of convectively coupled equatorial waves(CCEWs),including mixed Rossby-gravity(MRG) and tropical depression-type(TD-type) waves,based on the twentieth century experiments of 18 global climate models(GCMs) from the Coupled Model Intercomparison Project phase 3(CMIP3).The ensemble result of the 18 GCMs shows that the observed seasonal cycle of MRG and TD-type wave activity cannot be well reproduced.The seasonal transition of wave activity from the southern hemisphere to the northern hemisphere is delayed from April in the observations to May in the simulations,indicating that the simulated active season of tropical waves in the northern hemisphere is delayed and shortened.This delayed seasonal transition of tropical wave activity is associated with a delayed seasonal transition of simulated mean precipitation.The mean precipitation in April and May shows a double-ITCZ problem,and the horizontal resolution is important to the delayed seasonal transition of wave activity.Because of the coincident seasonal cycle of MRG and TD-type wave activity and tropical cyclone(TC) geneses,the delayed seasonal transition of wave activity may imply a similar problem of TC genesis in the GCMs,namely,a delayed and shortened TC season in the northern hemisphere.展开更多
Chemical synaptic couplings are more common than electric(gap junction) connections in neurons.In this paper,the firing synchronizations induced by chemical synaptic coupling in chemically delayed scale-free networks ...Chemical synaptic couplings are more common than electric(gap junction) connections in neurons.In this paper,the firing synchronizations induced by chemical synaptic coupling in chemically delayed scale-free networks of modified Hodgkin-Huxley neurons have been studied.It was found that the chemical coupling-induced synchronization transitions are delay-dependent and much different for various delay lengths.In the absence of delay,the neurons exhibit a transition from chaotic bursting(CB) to bursting synchronization(BS) with desynchronized spikes in each burst;for smaller delay lengths,the firing evolves from CB to spiking synchronization(SS),but for larger delay lengths,there are transitions from CB to intermittently multiple SS behaviors.These findings show that the chemical coupling-induced firing synchronization transitions strongly depend on the chemical delay lengths,and intermittently multiple SS can only occur for larger delay lengths.This result would be helpful for better understanding the joint roles of the chemical coupling and chemical delay in the firing activity of the neurons.展开更多
According to the time&space conversion relations and different frequency phase detection principle,an ultra-high precision time&frequency measurement method is proposed in this paper.The higher accuracy and st...According to the time&space conversion relations and different frequency phase detection principle,an ultra-high precision time&frequency measurement method is proposed in this paper.The higher accuracy and stability of the speed of light and electromagnetic signals during the transmission in space or a specific medium enable the measurement of short time interval which uses the coincidence detection of signal’s transmission delay in length.The measurement precision better than 10 picoseconds can be easily obtained.The method develops the length vernier utilizing the stability of signal’s transmission delay,minimizes the fuzzy region of phase coincidence between the standard frequency signal and the measured signal,approaches the best phase coincidences and therefore improves the measurement precision which is higher than the precision provided by the traditional methods based on frequency processing.Besides,the method costs less than the traditional methods and can also solve the problem of the measurement of super-high frequency.Experimental results show the method can improve the measurement precision to 10 12/s in the time&frequency domain.展开更多
文摘The microstructure and electrical properties of ZnO-Bi2O3-Yb2O3 based varistor ceramics were investigated with various temperature effects from 900°C to 1050°C.From the results,it was observed that the increase of sintering temperature offers a reduced capacitive effect from 0.460 nF to 0.321 nF.Furthermore,the grain sizes of varistors were varied from 6.8μm to 9.8μm.The consequence of such smaller grain sizes provided a better voltage gradient of about 895 V/mm for the disc sintered at 900°C and fallen drastically to 410 V/mm for the sample sintered at 1050°C.In addition,there was an increase of non-linearity index to a maximum value of 36.0 and reduced leakage current of 0.026 mA/cm2.However,the density of the varistor decreased with an increase of temperature from 5.41 g/cm3 to 5.24 g/cm3.With this base,the influence of varistor capacitance and high voltage gradient were scrutinized and it led an improved transition speed of the varistor assembly from non-conduction to conduction mode during intruding nanosecond transients.
基金supported financially by the National Basic Research Program of China (Grant No.2010CB950403)the National Natural Science Foundation of China (Major Research,Grant No. 40890151+2 种基金Grant Nos.40921160379 and 41105047)supported by the National Science Council (Grant No. NSC98-2745-M-001-005-MY3)supported by the National Science Foundation and the Office of Science (BER) of the U.S. Department of Energy
文摘This study evaluates the seasonal cycle of the activity of convectively coupled equatorial waves(CCEWs),including mixed Rossby-gravity(MRG) and tropical depression-type(TD-type) waves,based on the twentieth century experiments of 18 global climate models(GCMs) from the Coupled Model Intercomparison Project phase 3(CMIP3).The ensemble result of the 18 GCMs shows that the observed seasonal cycle of MRG and TD-type wave activity cannot be well reproduced.The seasonal transition of wave activity from the southern hemisphere to the northern hemisphere is delayed from April in the observations to May in the simulations,indicating that the simulated active season of tropical waves in the northern hemisphere is delayed and shortened.This delayed seasonal transition of tropical wave activity is associated with a delayed seasonal transition of simulated mean precipitation.The mean precipitation in April and May shows a double-ITCZ problem,and the horizontal resolution is important to the delayed seasonal transition of wave activity.Because of the coincident seasonal cycle of MRG and TD-type wave activity and tropical cyclone(TC) geneses,the delayed seasonal transition of wave activity may imply a similar problem of TC genesis in the GCMs,namely,a delayed and shortened TC season in the northern hemisphere.
基金supported by the Natural Science Foundation of Shandong Province of China (ZR2009AM016)
文摘Chemical synaptic couplings are more common than electric(gap junction) connections in neurons.In this paper,the firing synchronizations induced by chemical synaptic coupling in chemically delayed scale-free networks of modified Hodgkin-Huxley neurons have been studied.It was found that the chemical coupling-induced synchronization transitions are delay-dependent and much different for various delay lengths.In the absence of delay,the neurons exhibit a transition from chaotic bursting(CB) to bursting synchronization(BS) with desynchronized spikes in each burst;for smaller delay lengths,the firing evolves from CB to spiking synchronization(SS),but for larger delay lengths,there are transitions from CB to intermittently multiple SS behaviors.These findings show that the chemical coupling-induced firing synchronization transitions strongly depend on the chemical delay lengths,and intermittently multiple SS can only occur for larger delay lengths.This result would be helpful for better understanding the joint roles of the chemical coupling and chemical delay in the firing activity of the neurons.
基金supported by the National Natural Science Foundation of China (Grant No. U1304618)the Open Fund of Key Laboratory of Precision Navigation and Timing Technology of Chinese Academy of Sciences(Grant No. 2012PNTT01)+5 种基金the Postdoctoral Grant of China (Grant Nos. 2011M501446, 2012T50798)the Basic and Advanced Technology Research Foundation of Henan Province under Grant (Grant No. 122300410169)The Key Science and Technology Foundation of Henan Province under Grant (Grant No. 132102210180)the Doctor Fund of Zhengzhou University of Light Industry under (Grant No. 2011BSJJ031)the Scientific Research Fund of Zhengzhou University of Light Industry under (Grant No. 2012XJJ009)the Fundamental Research Funds for the Central Universities(Grant No. K5051204003)
文摘According to the time&space conversion relations and different frequency phase detection principle,an ultra-high precision time&frequency measurement method is proposed in this paper.The higher accuracy and stability of the speed of light and electromagnetic signals during the transmission in space or a specific medium enable the measurement of short time interval which uses the coincidence detection of signal’s transmission delay in length.The measurement precision better than 10 picoseconds can be easily obtained.The method develops the length vernier utilizing the stability of signal’s transmission delay,minimizes the fuzzy region of phase coincidence between the standard frequency signal and the measured signal,approaches the best phase coincidences and therefore improves the measurement precision which is higher than the precision provided by the traditional methods based on frequency processing.Besides,the method costs less than the traditional methods and can also solve the problem of the measurement of super-high frequency.Experimental results show the method can improve the measurement precision to 10 12/s in the time&frequency domain.
