A micromachined vertical cavity tunable filter with AlGaAs/GaAs distributed Bragg reflector is presented.This filter can be electrostatic tuning over a range of 28nm with an applied voltage of 7V.
Based on a daily precipitation observation dataset of 743 stations in China from 1951 2004, the F distribution function is used to calculate the probability distribution of daily precipitation and to define extreme pr...Based on a daily precipitation observation dataset of 743 stations in China from 1951 2004, the F distribution function is used to calculate the probability distribution of daily precipitation and to define extreme precipitation events. Based on this, the relationship of ENSO and the frequency of extreme precipitation events is studied. Results reveal that ENSO events have impact on extreme precipitation events, with different magnitudes at different regions and seasons. In general, during winter and spring, extreme precipitation events occur more often during E1 Nino events than during La Nina events. While during summer and autumn, the opposite is found. The relationship of a two season-lag ENSO and extreme precipitation frequency shows different pattern. Extreme precipitation events occur more often in several regions if an ENSO warm phase happened in the central-eastern tropical Pacific two seasons before. No similar impacts of El Nino and La Nina on the frequency of extreme precipitation events are found.展开更多
The effect of riblets surface on flat plate boundary layer development hasbeen measured with laser Doppler velocimeter (LDV). In the present experiment, although the development of boundary layer can be divided into t...The effect of riblets surface on flat plate boundary layer development hasbeen measured with laser Doppler velocimeter (LDV). In the present experiment, although the development of boundary layer can be divided into three regions, the laminarboundary layer region is increased, and the transition occurs at a larger Reynolds number.The Reynolds number of transition to turbulence Rextr is 4. 3 tinies as great as that in thesmooth flat plate case. In the turbulent boundary layer region, greater value of integralconstant C is obtained in log-law for velocity distribution. This indicates that the ribletssurface has obviously drag reduction characteristics. The maximum value of turbulence intensity and its position are less than the smooth surface results in the turbulent boundarylayer region.展开更多
According to dispersion theory of coda of local events, using near-field data of aftershocks recorded by two mobile digital stations at the Tianxin and Yunlong after the Wuding, Yunnan Ms=6.5 main-shock and sampling a...According to dispersion theory of coda of local events, using near-field data of aftershocks recorded by two mobile digital stations at the Tianxin and Yunlong after the Wuding, Yunnan Ms=6.5 main-shock and sampling at different central frequencies (1.5-sim;20 Hz), spatial distribution features of coda attenuation ratio β(f) are studied. The results show that there exists obvious non-uniformity of coda attenuation ratio β(f) given by the two stations in small region. When f less than or equal 6.0 Hz the coda attenuation ratio β(f) observed on both sides of earthquake-generating fault are basically identical. Yunlong station is located on east side and Tianxin station on west side. The corresponding Qc(f) is in the range of 66-120. However, in the range of high frequency (f greater than or equal 6.0 Hz) the coda in near field going through major fault encounters a strong absorption from the fracture zone. The β(f) going through the fault observed at Yunlong station is 30% lower than that in Tianxin station in which the seismic waves do not go through the fault. The reason for the difference in space distribution of coda attenuation is discussed. The results also show that factor A0(f) of wave source is not only related to the source strength, but also to frequency f. The mean free path L of S wave obtained using 1.5-20 Hz is respectively 30 km on east side of the fault and 40 km on west side, from which it is verified that there is a stronger dispersion body when seismic waves go through the fracture zone.展开更多
For the linear mixed model with skew-normal random effects, this paper gives the density function, moment generating function and independence conditions. The noncentral skew chi-square distribution is defined and its...For the linear mixed model with skew-normal random effects, this paper gives the density function, moment generating function and independence conditions. The noncentral skew chi-square distribution is defined and its density function is shown. The necessary and sufficient conditions under which a quadratic form is distributed as noncentral skew chi-square distribution are obtained. Also, a version of Cochran＇s theorem is given~ which modifies the result of Wang et al. （2009） and is used to set up exact tests for fixed effects and variance components of the proposed model. For illustration, our main results are applied to a real data problem.展开更多
文摘A micromachined vertical cavity tunable filter with AlGaAs/GaAs distributed Bragg reflector is presented.This filter can be electrostatic tuning over a range of 28nm with an applied voltage of 7V.
基金supported by the program under Grant No.2007BAC29B04
文摘Based on a daily precipitation observation dataset of 743 stations in China from 1951 2004, the F distribution function is used to calculate the probability distribution of daily precipitation and to define extreme precipitation events. Based on this, the relationship of ENSO and the frequency of extreme precipitation events is studied. Results reveal that ENSO events have impact on extreme precipitation events, with different magnitudes at different regions and seasons. In general, during winter and spring, extreme precipitation events occur more often during E1 Nino events than during La Nina events. While during summer and autumn, the opposite is found. The relationship of a two season-lag ENSO and extreme precipitation frequency shows different pattern. Extreme precipitation events occur more often in several regions if an ENSO warm phase happened in the central-eastern tropical Pacific two seasons before. No similar impacts of El Nino and La Nina on the frequency of extreme precipitation events are found.
文摘The effect of riblets surface on flat plate boundary layer development hasbeen measured with laser Doppler velocimeter (LDV). In the present experiment, although the development of boundary layer can be divided into three regions, the laminarboundary layer region is increased, and the transition occurs at a larger Reynolds number.The Reynolds number of transition to turbulence Rextr is 4. 3 tinies as great as that in thesmooth flat plate case. In the turbulent boundary layer region, greater value of integralconstant C is obtained in log-law for velocity distribution. This indicates that the ribletssurface has obviously drag reduction characteristics. The maximum value of turbulence intensity and its position are less than the smooth surface results in the turbulent boundarylayer region.
基金National Key Fundamental Research Plan (Mechanism and Prediction of Continental Strong Earthquake( - Moving Test Field in Wester
文摘According to dispersion theory of coda of local events, using near-field data of aftershocks recorded by two mobile digital stations at the Tianxin and Yunlong after the Wuding, Yunnan Ms=6.5 main-shock and sampling at different central frequencies (1.5-sim;20 Hz), spatial distribution features of coda attenuation ratio β(f) are studied. The results show that there exists obvious non-uniformity of coda attenuation ratio β(f) given by the two stations in small region. When f less than or equal 6.0 Hz the coda attenuation ratio β(f) observed on both sides of earthquake-generating fault are basically identical. Yunlong station is located on east side and Tianxin station on west side. The corresponding Qc(f) is in the range of 66-120. However, in the range of high frequency (f greater than or equal 6.0 Hz) the coda in near field going through major fault encounters a strong absorption from the fracture zone. The β(f) going through the fault observed at Yunlong station is 30% lower than that in Tianxin station in which the seismic waves do not go through the fault. The reason for the difference in space distribution of coda attenuation is discussed. The results also show that factor A0(f) of wave source is not only related to the source strength, but also to frequency f. The mean free path L of S wave obtained using 1.5-20 Hz is respectively 30 km on east side of the fault and 40 km on west side, from which it is verified that there is a stronger dispersion body when seismic waves go through the fracture zone.
基金supported by National Natural Science Foundation of China(Grant No.11401148)Ministry of Education of China,Humanities and Social Science Projects(Grant Nos.14YJC910005,10YJC790184)+2 种基金Zhejiang Provincial Natural Science Foundation of China(Grant No.LY14A010030)Zhejiang Provincial Philosophy and Social Science Planning Project of China(Grant No.13NDJC089YB)Houji Scholar Fund of Northwest A and F University,China
文摘For the linear mixed model with skew-normal random effects, this paper gives the density function, moment generating function and independence conditions. The noncentral skew chi-square distribution is defined and its density function is shown. The necessary and sufficient conditions under which a quadratic form is distributed as noncentral skew chi-square distribution are obtained. Also, a version of Cochran＇s theorem is given~ which modifies the result of Wang et al. （2009） and is used to set up exact tests for fixed effects and variance components of the proposed model. For illustration, our main results are applied to a real data problem.
