成都地面气温与风速年极大值的渐近分布及参数估计     

孟庆珍  唐谟智 《成都信息工程学院学报》1997,(4)

利用１９３３～１９９２年期间成都地面最高气温和地面最大风速年极值的记录，通过统计推断，找出了成都地面最高气温年极值和地面最大风速年极值遵循的渐近分布——Ｗｅｉｂｕｌ分布和Ｇｕｍｂｅｌ分布，并讨论了它们的参数估计方法。  相似文献   

Potential benefits of increased application of water to paddy fields in Taiwan     

Yu‐Chuan Chang  Chun‐E. Kan  Gwo‐Fong Lin  Chao‐Lin Chiu  Yuan‐Chuan Lee 《水文研究》2001,15(8):1515-1524

The potential benefits of increased application of water to paddy fields in Taiwan are investigated in this paper. A conceptual model is used to represent the hydrological system of the paddy field. A technique is presented to estimate the parameters of the model. Field experiments also are performed for parameter estimation and model verification. The simulated results are in good agreement with the observed during model verification. With parameters estimated from the field data, the model is used to simulate the effects of applying water beyond current practice. The simulation results show that the downward percolation increases when the irrigation water increases. However, the percolation reaches a capacity rate no matter how large the amount of water applied. This phenomenon results from the existence of a hard layer below the paddy field. The effects of raising the height of levees around paddy fields are also studied. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

成都地面风速年极值的4种分布函数拟合结果的比较   总被引：4，自引：0，他引：4  

孟庆珍  杜健 《成都信息工程学院学报》2001,16(2):97-104

分别用Webukk分布，Gumbel分布，Pearson Ⅲ分布和对数正态分布拟合成都1993－1997年间地面风速年极大值的渐近分布，其结果表明Gumbel分布和对数正态分布拟合效果最好。  相似文献   

日像仪的电磁干扰分析     

王威  陈志军  刘玉英  颜毅华  姬国枢 《天文研究与技术》2006,3(2):176-182

讨论了日像仪的干扰容限，列出了干扰源分布，估算出干扰测试仪灵敏度。计算了同步卫星干扰及干扰时间预测，也分析了中低轨道卫星干扰问题。对移动通信基站产生的干扰作了传播分析、计算，对脉冲雷达干扰作了谱分析及保守计算。  相似文献   

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陶本藻 《大地测量与地球动力学》2002,22(1):11-15

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Estimation of areal specific yield in sands using the central limit theorem     

Stephen B. K. Tan  E. B. Shuy  Lloyd H. C. Chua  Ngonidzashe Mzila 《水文研究》2006,20(18):3975-3987

A new approach is demonstrated that permits a reliable estimate of specific yield using published values of the van Genuchten water retention parameters and effective grain sizes and the measured effective grain sizes of soil samples. The specific yield distribution of the soil texture was computed using the published values of the van Genuchten parameters. The specific yield values and the published values of effective grain sizes were then used to construct a specific yield–effective grain size curve, which estimates the ‘point’ specific yield of the soil samples. Applying the central limit theorem, the point specific yields could be transformed into an ‘areal’ specific yield for a study area. Compared with other commonly used approaches, the present procedure requires relatively low computational efforts and readily obtainable data. It is cost effective and does not depend on soil texture classification. More importantly, it incorporates the depth to water table and the variations in grain sizes inherent in natural soil conditions in the estimation. The approach developed was applied for estimating the specific yield of an unconfined sandy aquifer created by land reclamation in the equatorial region. The values obtained were compared with field measurements and the typical ranges of specific yield from the literature. Instead of a single estimate of the specific yield, the method yields a confidence interval with a high confidence level of 95% and with a narrower range than the typical ranges from the literature. In addition, the estimated values are close to the field measurements; hence, the procedure provides a cost‐effective alternative to field measurement. The applicability of the present approach could be extended to sites with heterogeneity in the horizontal direction. Nevertheless, the applicability of the present approach for layered soil profiles requires further evaluations. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

调相白噪声背景中高稳频率源参数估计     

李孝辉  张慧君  边玉敬 《时间频率学报》2002,25(1):18-22

调相白噪声背景中高稳频率源参数的估计是一个应用广泛的信号处理问题 ,给出了利用平方拟合估计频率源参数的方法 ,它是最小平方误差意义下的估计 ,并根据模拟的数据对这种方法作了验证。  相似文献   

Difference between model parameter estimation and curve fitting     

Jason E. Curoe  R. E. Nasburg 《Mathematical Geology》1985,17(4):483

Within a single well, a least-squares model such as Ø = a +bT _sonic may be appropriate, insofar as random errors in core measurement and in sonic tool response are concerned. However, if several wells are in the reservoir, and if structural variation across the field exists, no single least-squares solution will adequately describe all wells with the same precision. Interpolation, via a cubic spline, is offered as an alternative to model this type of variation. However, to control both inter- and intra-well variability, a combination of least squares and interpolation is the model of choice.  相似文献   

成都地区降水时空分布变化   总被引：3，自引：0，他引：3  

李昕翼  肖国杰  白爱娟  施娟 《气象科技》2011,39(4):417-422

分析成都地区12个气象观测站50年（1960—2009年）逐日降水资料的时空分布变化规律得出：成都地区年降水量、汛期有雨日降雨强度、最大日降水量均呈现出逐渐下降的趋势。降水量主要集中在夏季,盛夏7、8两个月降水量占全年降水总量的47%;降水空间分布的主要类型为东—西走向,即降水量的地区分布趋势是西部多于东部;对降水量的M-K突变检验表明,大部分地方存在年降水总量的突变。  相似文献   

2009年石家庄暴雪过程降雪雷达估测   总被引：1，自引：1，他引：0  

匡顺四  王丽荣  张秉祥  孙云  刘金平 《气象科技》2011,39(3):326-331

介绍了天气形势和采用多普勒雷达资料进行降雪估测的原理,利用雷达与降雪加密观测资料,对2009年11月10—12日石家庄地区暴雪过程采用卡尔曼滤波法进行降雪估测。研究表明：①卡尔曼滤波降雪估测法对石家庄地区的降雪估测效果较好,尤其是对较强降雪（大于等于2 mm/h）的估测。②采用卡尔曼滤波估测法对石家庄地区进行降雪估测,要根据不同的地理特征和雷达反射率因子、回波顶高等特征采用不同的仰角进行降雪估测,与雷达降水估测的仰角选取有一定的差别。因此,充分利用雷达产品与降雪加密观测资料能够估测降雪分布,可以为决策服务提供一定的科学依据。  相似文献