基于优化参数的地震P、S波震相到时自动拾取及质量评估

准确拾取P、S波震相到时是深入开展地震波研究工作的基础,本文改进了自动拾取参数优化函数算法和质量评估方案,引入了拾取到时优化方案,使用基于参数优化的频带-带宽拾取算法、AICD拾取算法和峰度拾取算法对腾冲地区7个宽频带地震台站记录的地震资料开展了地震P、S波到时自动拾取,对拾取结果进行了优化和质量判定.结果表明：经参数优化、拾取优化后,采用3种方法自动拾取的P、S波到时与人工拾取到时的时差在0.1 s内的记录占比分别达到74.66%、70.98%.这些参数值均优于算法改进前的同类参数,证明了优化方法的可靠性.     

Use of magnetic measures to assess soil redistribution following deforestation in hilly region

Limited information is available about the use of magnetic susceptibility property to determine soil redistribution in hilly areas of the semi-arid regions. This study was conducted to evaluate the use of magnetic properties to determine soil redistribution along a hill slope following deforestation. The study area is located in the Quaternary hilly region of Lordegan district in west Iran. Ten transects were established in two land uses that included natural Querqus forested and cultivated lands. Soil samples were collected at different positions along the slope and magnetic properties (χlf, χhf, SIRM, ARM, and χfd) and selected physico-chemical properties were determined. The results (based on the χfd, SIRM/ARM) showed that the magnetic susceptibly in the calcareous materials is pre-dominantly derived during the pedogenic processes and the superparamagnetic particles which were transported to lower positions of hill slope following deforestation. The results confirmed that this methodology could be applied for monitoring soil redistribution along the slope in calcareous hilly areas in the semi-arid regions.     

DEMETER卫星磁场波形数据分析方法初探

为充分利用法国DEMETER地震电磁卫星中心提供的磁场波形数据对地震事件进行分析研究,详细介绍了峰度演化方法,并对峰度演化方法的有效性进行了检验.最后将峰度演化方法应用于汶川地震前后DEMETER卫星所记录到的实际数据.分析研究发现.所采用的方法能够较好的处理DEMETER卫星记录到的磁场波形数据:汶川地震发生之前较长...     

Occurrence probability of a freak wave in a nonlinear wave field

The Edgeworth’s form of a cumulative expansion of the probability density function (PDF) of surface elevation expands the maximum wave height distribution to predict the occurrence probability of freak waves. This study investigated the enhancement of the occurrence probability of freak waves due to the fourth order moment of surface elevation, kurtosis, change and found that the nonlinear effects on the occurrence probability of a freak wave linearly depends on kurtosis for a small number of waves N=250. The statistical theory was compared with field data, and freak waves sometimes appear when not expected by the Rayleigh theory, but they were predicted by the proposed theory.     

Effects of wave breaking on wave statistics for deep-water random wave train

The experimental studies of the breaking effects on wave statistics for deep-water random waves are presented. It is especially focused on the behavior of kurtosis of surface elevations due to wave breaking. Wave breaking suppresses the maximum limit of kurtosis of the surface elevation, although skewness depends on characteristic wave steepness. The mean instantaneous wave steepness of breaking waves defined using the zero-down-crossing method was much lower than expected from the Stokes waves.     

基于Kurtosis-IHS的遥感影像融合

针对传统IHS遥感影像融合的光谱扭曲和易引入噪声问题,提出了一种基于Kurtosis-IHS的遥感影像融合方法：从多光谱图像强度分量与全色图像最优逼近的角度出发,迭代求解多光谱各波段图像融合系数,减少光谱失真;根据全色图像的峭度获取其细节分量,达到抑制噪声的目的;最后使用基于Kurtosis-IHS的融合公式得到融合结果.实验选取2组实际遥感数据,结果表明,融合方法在CC、ERGAS、RASE、RMSE及SID 5个光谱性能评价指标上均优于传统的IHS、PCA、DWT及NSCT融合方法,在第二组遥感影像融合测试中,Kurtosis-IHS方法比传统IHS方法的5个指标分别提高了41.80％、57.09％、57.11％、57.11％、49.74％;在含噪环境下,融合方法的融合结果PSNR值均达到最大.所提出的Kurtosis-IHS方法优于传统的IHS融合方法,在提高空间分辨率的同时,具有较好地保持光谱信息及有效抑制噪声的优点.     

Morphologic evolution of bifurcated reaches in a macrotidal estuary with mountain streams

A macrotidal estuary with mountain streams(MEMS) is characterized by rapidly rising and falling flood peaks and large tidal ranges and is a typical estuary type with strong flow dynamics that is found worldwide. Understanding the morphodynamic evolution of MEMSs has great significance for river management. The roles of the mountain stream river flood process and macrotides on the morphology evolution still needs further quantitative study. Taking the Oujiang Estuary as an example, the evolution ...     

The Relationship between Skewness and Kurtosis of A Diffusing Scalar

It has been demonstrated that in turbulent dispersion, there exists a quadratic relationship between the skewness (S) and kurtosis (K) statistics obtained from continuous, elevated sources of scalar contaminant released into both convective and stable atmospheric boundary layers. Specifically, one observes that where A and B are empirically fitted constants that depend on the flow. For two reasons, this is potentially useful information in regard to modelling the probability density function (PDF) of a diffusing scalar. First, since many PDFs have a signature relationship between their skewness and kurtosis, candidate models can immediately be either accepted or rejected depending upon whether they conform to the quadratic curve that is observed experimentally. Second, if one intends to model the PDF by inverting a limited number of moments, the task is reduced when there is a functional relationship between the standardized third and fourth moments. The aforementioned relationship has been corroborated by others who have examined data over a wide range of experimental configurations. However, from one flow to another, there appears to be a non-negligible variability in the two fitting constants of the quadratic curve. In this paper we put forth a framework to help explain this phenomenon, and we also attempt to predict how these parameters vary in space and/or time. Our point is illustrated with well-resolved data from a wind-tunnel, grid-turbulence, plume experiment.