共查询到18条相似文献，搜索用时 156 毫秒
1.
陶跃跃 《南京气象学院学报》2018,10(6):723-730
本文研究了一类具有异步控制器的离散马尔可夫Lur''e跳变系统的稳定性及l2增益性能.通过引入隐马尔可夫模型（HHM）来描述所设计的控制器和原始系统之间出现的异步现象.利用线性矩阵不等式（LMI）方法分析了闭环系统的稳定性和l2增益性能.然后提出了一个充分条件使得闭环系统随机稳定,并使得从扰动到系统输出的l2增益达到最小.同时,通过求解给定条件来设计一个由线性状态反馈和扇形有界非线性输出反馈组成的异步控制器.最后,给出了一个数值仿真例子来验证所提方法的有效性. 相似文献
2.
在完全考虑非绝热加热项作用的前提下,从原始方程出发,推导出改进后的非地转湿Q矢量(Qq),以及用其散度作强迫项的ω方程,将其应用于一次梅雨锋暴雨诊断分析,结果表明:改进后的非地转湿Q矢量对同时刻地面降水的反映能力较岳彩军改进的湿Q矢量(QM)、原非地转湿Q矢量(Q*)、非地转Q矢量(Q#)有显著的提高;在整个梅雨锋暴雨过程中,500hPa高度上的Qq矢量散度辐合场的辐合强度及其辐合中心位置对同时刻的降水强度及雨区位置有非常好的指示作用;Qq矢量的垂直分布揭示了次级环流的方向和强弱,暴雨位于次级环流的上升支附近。 相似文献
3.
薛艳梅 《南京气象学院学报》2015,7(5):475-480
研究了n维α带小波紧框架的结构,给出了m个函数生成n维α带小波紧框架的充分条件,并给出构造该小波紧框架的显式算法,最后给出了构造小波紧框架的数值算例. 相似文献
4.
5.
应用Leray-Schauder非线性二择一原理研究二阶动力系统x+k2x=f(t,x)+e(t)非平凡周期解的存在性,其中0<k<π/T,f∈C((R/TZ)×RN\{0},RN)在原点具有排斥的奇性.不需要任何的强制性条件,既可以处理强奇性,也可以处理弱奇性. 相似文献
6.
利用2010年1-2月深圳LAP3000型风廓线雷达资料, 对湍流耗散率进行了估算, 针对典型晴天条件下的湍流耗散率ε、折射率结构常数C2n、水平风速和风切变, 分析了其时空变化特征。得出如下结论: (1) 深圳地区低空大气ε的量级在10-7~10-1 m-2·s-3之间, 与理论模拟值基本一致; (2) 时间分布特征为, 2 km以下ε有很明显的日变化特征, 夜晚和上午ε较大, 下午及傍晚减少;(3) 空间分布特征表现为, ε随高度大致呈递减分布;ε量级达10-2.5 m2·s-3所在高度可作为深圳地区2010年1月14-15日边界层顶高度的判断依据。 相似文献
7.
In the context of August 1982- July 1983 radiation balance data of the Qinghai-Xizang Plateau, detailed study is made of the relation between the active-surface temperature and surface temperature, proposing two parameterization schemes on surface long-wave radiation(SLWR)of the form U=kδσ(T0+273)4 and U=δσ[(T0+273)4+△T)]4, where k and △T are indicated by parameterization equations, separately, others being in conventional notation. Retrieved verification shows the two formulae to be of the same fitting accuracy with the mean relative error of 3.6% and suitable for computing instantaneous and mean flux density, alongside analyzed daily and annual variations of k and △T. Eventually. SLWR in the target area is investigated and its climatic characteristics examined. 相似文献
8.
根据图像和检测算子的特性,以相关性为准则,使用遗传算法对图像小波变换的尺度进行选择,从而构成一种自适应的高斯小波尺度空间.融合该空间下不同尺度检测的图像边缘,使得整幅图像的边缘细节丰富清晰,具有更好的抗噪性能.对测试图像使用Canny算法、单尺度、二进尺度和自适应尺度小波进行边缘检测,验证了该算法在去除噪声和准确定位方面的有效性. 相似文献
9.
王廷秀 《南京气象学院学报》2017,9(4):391-394
本文简要讨论Gronwall不等式的研究进展,并给出关于如下的一类非线性Volterra积分不等式的一个结果：w(u(t))≤g(t))+∑i=1n∫αi(t0)αi(t)fi(t,s)∏j=1mHij(u(s))Gij(maxs-h≤ξ≤s u (ξ))ds. 相似文献
10.
The characteristics of net radiation (Rn)(0.3--10 μm) in Lhasa and
Haibei in the Tibetan Plateau were analyzed based on long-term in-situ
measurements of surface radiation data. The monthly average of daily
Rn reached a minimum during the winter period followed by an increase
until May and then a decline until January. This variation is consistent
with solar activity. The annual mean daily total Rn values were 0.92 MJ
m-2 d-1 and 0.66 MJ m-2d-1 in Lhasa and Haibei,
respectively.
A relationship between Rn and broadband solar radiation (Rs) was
demonstrated by a good linear correlation at the two sites. Rn can be an
accurate estimate from Rs. The estimated Rn values were similar to the
observed values, and the relative deviations between the estimates and
measurements of Rn were 2.8% and 3.8% in Lhasa and Haibei,
respectively. The application of the Rn estimating model to other
locations showed that it could provide acceptable estimated Rn values from the Rs data. Furthermore, we analyzed the influence of clouds on
Rn by different clear index (Ks), defined as the ratio of Rs to the
extraterrestrial solar irradiance on a horizontal surface. The results
indicate that more accurate results are associated with increased cloudy
conditions. The influence of the albedo was also considered, but its
inclusion in the model resulted in only a slight improvement. Because
surface albedo is not usually measured, an expression based solely on global
solar radiation could be of more extensive use. 相似文献
11.
介绍了小波变换和维纳滤波相结合的图像小波域维纳滤波去噪算法，在分析该算法最小均方误差期望的基础上提出一种改进算法。指出在进行维纳滤波之前，阈值化处理可以有效提高维纳滤波的性能。用标准测试图像的处理结果来比较改进前后两种算法的效果。 相似文献
12.
13.
V. Tutiš 《Meteorology and Atmospheric Physics》1992,50(4):189-195
Summary A special analytical solution is derived for the classical orographic configuration of two-dimensional, stratified, linear, non-hydrostatic and dry model (without friction and Coriolis force). The well-known differential equation for the vertical velocity involves the vertical distribution of the Scorer parameterl
2(z) and in this casel
2 is specified such that the lower atmosphere has a stable duct near the surface and is capped by a layer which acts as a good reflector.Examination of the solution for the vertical amplitude in the vicinity of singularities indicates the dominant lee wavelength and observations confirm that in comparable settings resonant trapped gravity waves develop in the lee of mountains. Comparison with a real atmospheric lee-wave events gives good predictions for the wavelength and wave drag, but, as in other linear models, the amplitude is underestimated.With 2 Figures 相似文献
14.
采用可精确刻画雷达回波强度数据统计特征的小波域高斯尺度混合（GSM）模型作为雷达图像先验模型,进行天气雷达图像插值,在提高图像分辨率的同时有效重建降水回波中局部强回波值、小尺度变化细节等一些重要空间分布统计特征。分析和总结雷达回波强度数据小波频率域统计特点,建立小波域GSM模型;匹配天气雷达图像小波系数和GSM模型,利用贝叶斯理论估计更小尺度的小波系数,进行小波逆变换,完成高分辨率天气雷达图像插值。试验表明,该算法能从低分辨率图像中估计出高分辨率高频系数,且所利用的先验模型充分考虑降水数据本身的特点,可有效捕获降水回波结构的非高斯特征和局部相关特性,重建雷达图像中的局部变化细节。 相似文献
15.
H. A. R. De Bruin W. M. L. Meijninger Ann-Sofi Smedman Mikael Magnusson 《Boundary-Layer Meteorology》2002,105(1):129-148
The friction velocity (u*) and the sensible heat flux density (H) determined with a displaced-beam small aperture scintillometer (DBSAS) and a hot-film eddy correlation system are compared. Random errors in the DBSAS are relatively small, compared to scatter found with two eddy-correlation systems. Assuming that the hot-film system yields the true fluxes, theDBSAS appears to overestimate u* when u* is less than 0.2 m s-1 and to underestimate u* at high wind speeds. This implies that the DBSAS measurements of theinner scale length of turbulence, l0, a direct measure for the dissipation rate of kinetic turbulent energy, are biased. Possible causes for these results are discussedin detail. A correction procedure is presented to account for effects of random noise and of so-called inactive turbulence or sensor vibrations. The errors in u* cause errors in the DBSAS measurements of the structure parameter of temperature CT
2. The derived H appears to be less sensitive to errors in l0 and CT
2, because errors in these quantities tend to cancel out. 相似文献
16.
Aerodynamic roughness of vegetated surfaces 总被引：2，自引：0，他引：2
Ido Seginer 《Boundary-Layer Meteorology》1974,5(4):383-393
Available experimental results indicate that as the density of roughness elements over a horizontally homogeneous surface is varied, the roughness length, z
0, varies in a manner that exhibits a maximum at intermediate density values. In an attempt to explain this behaviour, the available analytical solutions for the wind profile inside dense homogeneous canopies were reviewed. The review indicated that the variation of z
0 with density depends on the interrelationship between the leaf density, a, and the mixing length, l. In view of this finding, a numerical model was devised based on a simple rule for constructing mixing-length profiles in the canopy. The rule states that the actual value of l is the maximum possible under the two constraints: l l
i and ¦dl/dz¦ k, where k is the von Karman constant and the intrinsic mixing length, l
i, is a function of the local internal structure of the canopy. The model which ensures a smooth transition from dense to thin canopy, was used to reproduce the observed maximum of z
0. The model is also capable of handling vertically non-homogeneous canopies. 相似文献
17.
Zbigniew Sorbjan 《Boundary-Layer Meteorology》2012,142(1):21-31
Empirical similarity functions of the Richardson number, obtained from bin-averaged data in the lower part of the stable boundary
layer, show an undesired dependence on height at which the observations are collected. A correction of this flaw is proposed
and tested by employing the neutral mixing length l
o
as a similarity scale for height. The function of height describing l
o
is assumed to be linear in the surface layer, and approaching a specified value with increasing height. The modification
does not alter the dependence of similarity functions on the Richardson number, and is shown to be supported by the Cooperative
Atmospheric-Surface Exchange Study-1999 (CASES-99) data. 相似文献
18.
Statistical analysis of microphysical properties and the parameterization of effective radius of warm clouds in Beijing area 总被引：1，自引：0，他引：1
Zhaoze Deng Chunsheng Zhao Qiang Zhang Mengyu Huang Xincheng Ma 《Atmospheric Research》2009,93(4):888-896
In this paper warm cloud microphysical parameters including cloud droplet number concentration (Nc), liquid water content (ql) and effective radius (re) from 75 flights around the Beijing area during 2005 and 2006 are summarized. Average Nc (cm− 3) for Cu, Sc, Ac, As and Ns are 376 ± 290, 257 ± 226, 147 ± 112, 60 ± 35 and 60 ± 84, respectively. Many records of high Nc above 1000 cm− 3 are observed. The large standard deviations indicate a large variation of Nc and ql in this region. The maxima of ql reach 1.4 g m− 3 in Cu and 1.0 g m− 3 in Sc, respectively. Different parameterizations of effective radius are examined with the in-situ data in this area. There are different ways to obtain the prefactor representing the relationship between effective radius and mean volume radius. Significant systematic errors are found to be at the large sizes when the prefactor is expressed with relative dispersion under the Gamma Distribution. Fixed prefactor of 1, which was widely used, even produces much larger error. A prefactor of 1.22 is found to be better than the former two methods by fitting with the observed data. The effective radius is further parameterized as functions of mean volume radius, liquid water content and cloud droplet number concentration. We suggest that the effective radius can be parameterized as re,p ≈ 1.20rv + 0.22–1.28/rv2, which is a practical and more accurate scheme without too much computation complexity. 相似文献