基于改进遗传算法的重力固体潮独立分量分析

重力固体潮信号中的潮汐谐波相互独立,所以,对重力固体潮的谐波分析,就需要提取出各个谐波中的独立成分.据此,在原有独立分量分析算法的基础上,与智能优化算法相结合,提出了一种新的独立分量分析法,基于遗传算法的独立分量分析.对经典遗传算法进行改进,给出了改进后遗传算法的基本原理,讨论了遗传算法独立分量分析的实现过程.同时,应用该方法对重力固体潮信号进行处理,有效地从重力固体潮信号中提取出三个独立分量:长周期波分量、日波分量和半日波分量,以及各成分的特征频率.该方法可行有效,为地球物理信号的分析提供了一个有效的处理方法.     

易县台BBVS-120地震计记录重力固体潮能力分析

以河北省易县台BBVS-120甚宽频带地震计为研究对象,验证其垂直向地震记录波形中包含的长周期成分为重力固体潮,并运用小波变换方法提取地震记录中的固体潮信息;同时,通过对提取的固体潮信息进行Venedikov调和分析证明,易县地震台BBVS-120甚宽频带地震计可以记录重力固体潮信息。     

张家口地震台地形变数字化与模拟资料对比研究

介绍了张家口地震台的基本现状及形变数字化仪器的改造情况。从长期趋势、短期趋势和固体潮形态变化等方面,对地形变模拟观测和数字化观测资料进行了对比,对资料的连续性、稳定性、一致性和固体潮观测精度进行了分析,得出数字化资料总体评价。并针对数字化观测存在的问题提出了具体建议。     

基于分布估计算法对重力固体潮信号独立主成分分析及谐波提取

固体潮信号是地球自转在月球和太阳作用下产生的混合复杂信号.本文提出一个重力固体潮信号的正交分解模型,通过将重力固体潮信号谐波分量,分解在两个正交的方向上,以提取独立的谐波分量.为了实现这一分解,本文采用独立成分分析算法进行验证分析.独立成分分析主要用于提取信号中的独立成分,但一般的独立成分分析算法具有对初始值敏感,收敛较早熟等问题.本文利用分布估计算法的学习概率模型全局寻优,克服独立成分分析算法缺点.通过实验仿真分析,改进算法可将重力固体潮信号成功分离出以下独立的谐波状态:半日波信号、日波信号、长周期波信号.并且,这些分离出的独立成分与本文提出的重力固体潮信号正交分解模型一致,分别对应于模型中的正交谐波分量.     

地震的发生与固体潮

固体潮是指由月亮和太阳的引力而引起的地球弹性变形现象。通过对全球地震资料的分析,已明确了固体潮对地震的发生有着不可忽视的影响(Tsuruoka,et al,1995;鶴岡 弘,1995)。不过,由固体潮引起的地球内部的应力变化,充其量为10~3 Pa的     

易县地震台数字化观测与模拟观测资料对比研究

介绍了易县地震台的基本现状及形变数字化仪器改造情况,并从长期趋势、短期趋势和固体潮形态变化等方面对易县地震台形变模拟观测和数字化观测资料进行了对比。对数模两种观测资料的连续性、稳定性、一致性和固体潮观测精度进行了分析,得出数字化资料总体评价,并对数字化资料存在的问题提出具体建议。     

地震场景下重力固体潮信号互相关谱分析与异常信息提取

重力固体潮信号包括能量相对强的日波、半日波分量,和能量相对弱的长周期波分量.为了在能量差异大的谐波分量中,有效提取地震场景下的异常信息,本文根据重力固体潮信号的产生机理,提出了一种重力固体潮信号正交分解模型,将强弱不同的潮汐谐波分量,分解到不同的正交方向.同时利用一种新型智能优化算法,改进独立成分分析方法,有效分离出重力固体潮信号中对应于不同正交方向的独立成分.对独立成分分量的谱相关分析,可以揭示各谐波分量的调制关系,地震场景下的谐波分量间存在异常的调制信息.但自相关运算会使强的分量更强,而弱的分量更弱,湮没弱的异常调制信息.因此,本文采用独立成分间的互相关谱,可以更完整地提取出潮汐谐波的异常信息,在此基础上,通过对云南的地震实例分析,提取出重力固体潮信号中异常的调制信息,并引入了理论计算值做参考,凸出了实际重力固体潮信号中存在明显的异常信息,发现长周期谐波分量的误差率远远大于日波、半日波的误差率,说明相比于日波、半日波,长周期波能更好的反映重力固体潮信号存在的异常信息.     

江苏地区地电场变化特征与差异性分析

处理、分析了江苏省4个台的地电场日变化资料,结合地磁场水平分量H、线应变理论固体潮,研究了地电场日变化特征和差异,得到：（1）4个台地电场日变化明显,主要以12小时的半日波成分最强,8小时周期和全日波成分次之;（2）地电场日变化存在地磁场和固体潮影响。靠近海边及湖泊的台站,受固体潮的影响较为明显,各方向还具有明显的固体潮半月波,但没有像固体潮一样大小的波;而远离江、海、湖的一些台站观测到的地电场日变与地磁水平分量比较相关,其差异性与台站的位置、电性结构有关系。     

涉县地震台数字化观测与模拟观测资料对比研究

介绍了涉县地震台站基本现状及其形变数字化仪器改造情况,并从长期趋势、短期趋势和固体潮形态变化等方面对涉县台形变模拟观测和数字化观测资料进行形态对比,对数模两种观测资料的连续性、稳定性、一致性和固体潮观测精度进行分析研究,得出数字化资料总体评价结论。针对涉县数字化资料存在的问题和解决办法提出具体建议。     

基于一种单纯形邻域与多角色进化策略算法的重力固体潮信号独立成分分析

在重力固体潮信号中,反映地球、太阳、月亮等天体相对运动的潮汐谐波是相互独立的.所以,在重力固体潮的谐波分析中,只有提取出谐波中的独立成分,才能与相应的天体潮汐谐波对应.据此,本文提出一个重力固体潮信号的分解模型.该模型描述地球自转产生的潮汐谐波与月球、太阳相对于地球轨道变化产生的潮汐谐波的正交分解关系.为了从信号处理的角度实现这一模型描述的正交分解关系,本文提出了一种基于单纯形邻域与多角色进化策略的智能优化算法的独立成分分析方法,对重力固体潮信号进行独立成分分析,有效地从重力固体潮信号中提取出三个独立分量:一个为反映月球、太阳相对于地球轨道变化产生的长周期波系分量,一个为反映地球自转产生的日波系分量,一个为反映地球自转产生的半日波系分量.最终,从这些分解出的独立分量中进一步提取出具体谐波成分.     

SCIENCE CHINA Earth Sciences SUBJECT INDEX TO VOLUME 57(2014)

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Distribution of throughfall and stemflow in multi‐strata agroforestry,perennial monoculture,fallow and primary forest in central Amazonia,Brazil

The partitioning of rain water into throughfall, stemflow and interception loss when passing through plant canopies depends on properties of the respective plant species, such as leaf area and branch angles. In heterogeneous vegetation, such as tropical forest or polycultural systems, the presence of different plant species may consequently result in a mosaic of situations with respect to quantity and quality of water inputs into the soil. As these processes influence not only the water availability for the plants, but also water infiltration and nutrient leaching, the understanding of plant effects on the repartitioning of rain water may help in the optimization of land use systems and management practices. We measured throughfall and stemflow in a perennial polyculture (multi‐strata agroforestry), monocultures of peach palm (Bactris gasipaes) for fruit and for palmito, a monoculture of cupuaçu (Theobroma grandiflorum), spontaneous fallow and primary forest during one year in central Amazonia, Brazil. The effect on rain water partitioning was measured separately for four useful tree species in the polyculture and for two tree species in the primary forest. Throughfall at two stem distances, and stemflow, differed significantly between tree species, resulting in pronounced spatial patterns of water input into the soil in the polyculture system. For two tree species, peach palm for fruit (Bactris gasipaes) and Brazil nut trees (Bertholletia excelsa), the water input into the soil near the stem was significantly higher than the open‐area rainfall. This could lead to increased nutrient leaching when fertilizer is applied close to the stem of these trees. In the primary forest, such spatial patterns could also be detected, with significantly higher water input near a palm (Oenocarpus bacaba) than near a dicotyledonous tree species (Eschweilera sp.). Interception losses were 6·4% in the polyculture, 13·9 and 12·3% in the peach palm monocultures for fruit and for palmito, respectively, 0·5% in the cupuaçu monoculture and 3·1% in the fallow. With more than 20% of the open‐area rainfall, the highest stemflow contributions to the water input into the soil were measured in the palm monocultures and in the fallow. Copyright © 1999 John Wiley & Sons, Ltd.     

A Monte Carlo study of rainfall forecasting with a stochastic model

A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.     

Anthropogenic Eutrophication and Red Tide Outbreak in Lacustrine Systems of the Kashmir Himalaya

Red tide, a recurrent phenomenon has become conspicuous in several Kashmir lake ecosystems since 1991. The responsible organism (Euglena pedunculata), a rare flagellate rediscovered in the Kashmir Himalaya (Khan 1993) caused first and unprecedented red tide outbreak, constituting a maximum of 96% of resident numerical phytoplankton density in Dal Lake. At present, conflicting hypotheses exist on the generation of causal assemblage(s) imparting redness to waters: Jeeji Bai (1991) linked its origin to acid precipitation – a fallout of burning oil‐fields during the Gulf War – whilst Khan (1993) holds local factor(s) responsible. Field/experimental studies support the latter contention that the influx of untreated sewage, in unison with warm temperatures, high levels of PhAR, iron and interruption to hydrological flow‐pattern together with absence/or reduction in grazing activity created conducive environmental milieu for red tide outbreak. Dal Lake “red tide” drifted the bloom‐inoculum to other waters, including Lake Wular, where additional ecological niches were carved out, threatening the aesthetic value and biological diversity of Kashmir lakes. Ecological monitoring indicates frequent seasonal red tide occurrence in Dal Lake (including summer‐autumn event of 1998) which testifies its unabated eutrophication status. Further studies are needed on ecological adaptability and biogeographic distribution of this rare and unique red tide‐causing flagellate.