弹道扰动引力无奇异性计算模型的建立     

刘晓刚  吴娟  姬剑锋 《地球物理学进展》2013,28(2)

利用地球重力场模型来计算飞行器轨道扰动引力,当飞行器飞越两极及其附近地区时,由于Legendre函数的一阶导数以及分母上所含余纬的正弦函数,将导致扰动引力的计算出现无穷大.本文推导了Legendre函数一阶导数以及球谐函数m (P)mn(cosθ)/sinθ无奇异性的计算公式,建立了飞行器轨道扰动引力各分量无奇异性的详细计算模型,并通过数值试验分析了扰动引力各分量在两极地区的变化趋势,从而彻底解决了利用地球重力场模型计算两极地区飞行器轨道扰动引力时存在的奇异性问题.  相似文献   

国外地震重防区农村地区安保工作的主要做法和经验     

胡爱真  哈辉  张守洁  徐传捷  陈有顺  赵国伟  纪淑果 《高原地震》2013,(3):50-57

通过对国外以美、日等发达国家为代表的经济发达地区,以智利、墨西哥等南美多地震国家为代表的发展中国家,以印度、伊朗等亚洲多地震但经济欠发达国家为代表的3种模式的农村地区防震安保工作的主要做法和经验的分析对比,以期对我国农村地区地震安保工作的发展和完善有一定的借鉴和启示作用。  相似文献   

山东诸城农居抗震性能分析对比     

冀东普  郭惠民 《高原地震》2013,(3):58-62

通过对山东诸城民居现状进行调查,发现其抗震性能较差。对山东农村民居在抗震设防中存在的突出问题进行了分析并提出了应对方案。  相似文献   

Power spectral characteristics of drought indices in the Ebro river basin at different temporal scales   总被引：3，自引：3，他引：0  

L. Telesca  S. M. Vicente-Serrano  J. I. López-Moreno 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(5):1155-1170

A deep spectral investigation of the monthly time series of Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) in 45 meteorological stations in the Ebro basin (Spain) from 1950 to 2006 for timescales ranging from 1 to 48 months was performed. In order to summarize the results for the whole basin, the spectral analysis was also carried out on the four principal components of SPI and SPEI. Results confirm that SPI and SPEI presents very similar spectral characteristics. At the shorter time scales, the signal of SPI and SPEI is characterized by purely random temporal fluctuations. The longer time scales tend to feature the signal as a smoothly varying time series or persistent, mostly due to the aggregated nature of the indices calculation. The comparative analysis of the spectral properties of the drought indices for all the 45 sites in the Ebro basin lead to the identification of global or regional effects discriminated by local effects. It was found that some periodical signals are common to almost all the sites, while others where only identified in specific meteorological stations.  相似文献   

Estimation and prediction of the spatial occurrence of fish species using Bayesian latent Gaussian models   总被引：3，自引：3，他引：0  

Facundo Muñoz  M. Grazia Pennino  David Conesa  Antonio López-Quílez  José M. Bellido 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(5):1171-1180

A methodological approach for modelling the occurrence patterns of species for the purpose of fisheries management is proposed here. The presence/absence of the species is modelled with a hierarchical Bayesian spatial model using the geographical and environmental characteristics of each fishing location. Maps of predicted probabilities of presence are generated using Bayesian kriging. Bayesian inference on the parameters and prediction of presence/absence in new locations (Bayesian kriging) are made by considering the model as a latent Gaussian model, which allows the use of the integrated nested Laplace approximation ( INLA ) software (which has been seen to be quite a bit faster than the well-known MCMC methods). In particular, the spatial effect has been implemented with the stochastic partial differential equation (SPDE) approach. The methodology is evaluated on Mediterranean horse mackerel (Trachurus mediterraneus) in the Western Mediterranean. The analysis shows that environmental and geographical factors can play an important role in directing local distribution and variability in the occurrence of species. Although this approach is used to recognize the habitat of mackerel, it could also be for other different species and life stages in order to improve knowledge of fish populations and communities.  相似文献   

Non-parametric copulas for circular–linear and circular–circular data: an application to wind directions     

Jose A. Carnicero  M. Concepción Ausín  Michael P. Wiper 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(8):1991-2002

This paper proposes a nonparametric approach to estimating the dependence relationships between circular variables and other circular or linear variables using copulas. The proposed method is based on the use of Bernstein copulas which are a very flexible class of non-parametric copulas which allows for the approximation of any kind of dependence structure, including non symmetric relationships. In particular, we present a simple procedure to adapt Bernstein copulas to the circular framework and guarantee that the constructed bivariate distributions are strictly continuous. We provide two illustrative case studies, the first on the relation between wind direction and quantity of rainfall in the North of Spain and the second on the dependence between the wind directions in two nearby buoys at the Atlantic ocean.  相似文献   

电性源时域地空电磁数据小波去噪方法研究   总被引：4，自引：2，他引：2       下载免费PDF全文

李肃义  林君  阳贵红  田培培  王远  于生宝  嵇艳鞠 《地球物理学报》2013,56(9):3145-3152

基于飞艇的时间域地空电磁探测系统,具有勘探深度大、效率高、空间分辨率高、飞行控制容易等优势.但在低空飞行测量过程中,飞艇飞行高度、航迹、姿态等受风向、大气气流、地形、地面局部温度场变化等影响而发生变化,导致固定在艇囊前端的接收线圈发生运动,切割大地磁场,产生了电磁噪声、运动噪声、基线漂移等,从而影响电磁数据的电阻率成像质量.因此,研究地空电磁信号中多种噪声的去除方法,对数据的反演解释非常重要.由于地空电磁信号中有效信号频带与部分噪声频带相重叠,使用传统滤波或消噪方法具有一定局限性.因此,本文提出一种综合小波去噪法:根据地空电磁信号的特点,采用sym8小波基;基于小波多分辨率分析原理,利用小波高尺度近似分量估计基线漂移,以校正电磁数据中的基线;基于小波阈值收缩原理,采用5层小波分解、极小极大阈值配合硬收缩函数的消噪方法,来压制数据中的其余噪声.最后,通过异常环模型的理论响应和实测数据进行算法的验证,结果表明这种综合消噪法对多种噪声均有很好的抑制作用,是一种实用有效的时间域地空电磁数据消噪方法.  相似文献   

An Overview of Thunderstorm-Related Research on the Atmospheric Electric Field, Schumann Resonances, Sprites, and the Ionosphere at Sopron, Hungary     

Gabriella Sátori  Michael Rycroft  Pál Bencze  Ferenc Märcz  József Bór  Veronika Barta  Tamás Nagy  Károly Kovács 《Surveys in Geophysics》2013,34(3):255-292

This paper gives a resume of the papers written in English which (a) describe some of the recording instruments in use at the Nagycenk Observatory (NCK) since the International Geophysical Year (IGY 1957–1958) and up to the present time, (b) summarise the most important and different types of observations associated with thunderstorms which have been made there, and (c) discuss their various geophysical interpretations. The paper describes the main results which have been obtained in four areas of thunderstorm associated atmospheric and geospace science within the context of Earth system science. These relate to the following parameters of atmospheric electricity: the vertical electric potential gradient just above the Earth’s surface and the air–Earth current as well as the point discharge current, Schumann resonance (SR) signals of the Earth-ionosphere cavity at 8, 14 and 20 Hz, transient luminous events (TLEs), and some aspects of the behaviour of the ionosphere. Deductions from these data sets are concerned with the global lightning activity and the conductivity of the air, with diurnal, seasonal, annual and long-term variations of the SR amplitudes and resonant frequencies in terms of migrating thunderstorm centres, with transient SR excitations and with sprites and other TLEs, and with ionospheric disturbances. The paper closes with some thoughts on future research directions based on the observations at NCK and Sopron and the results achieved since the IGY.  相似文献   

Residual drift demands in moment‐resisting steel frames subjected to narrow‐band earthquake ground motions     

Edén Bojórquez  Jorge Ruiz‐García 《地震工程与结构动力学》2013,42(11):1583-1598

This paper presents the main results of the evaluation of residual inter‐story drift demands in typical moment‐resisting steel buildings designed accordingly to the Mexican design practice when subjected to narrow‐band earthquake ground motions. Analytical 2D‐framed models representative of the study‐case buildings were subjected to a set of 30 narrow‐band earthquake ground motions recorded on stations placed in soft‐soil sites of Mexico City, where most significant structural damage was found in buildings as a consequence of the 1985 Michoacan earthquake, and scaled to reach several levels of intensity to perform incremental dynamic analyses. Thus, results were statistically processed to obtain hazard curves of peak (maximum) and residual drift demands for each frame model. It is shown that the study‐case frames might exhibit maximum residual inter‐story drift demands in excess of 0.5%, which is perceptible for building's occupants and could cause human discomfort, for a mean annual rate of exceedance associated to peak inter‐story drift demands of about 3%, which is the limiting drift to avoid collapse prescribed in the 2004 Mexico City Seismic Design Provisions. The influence of a member's post‐yield stiffness ratio and material overstrength in the evaluation of maximum residual inter‐story drift demands is also discussed. Finally, this study introduces response transformation factors, T_p, that allow establishing residual drift limits compatible with the same mean annual rate of exceedance of peak inter‐story drift limits for future seismic design/evaluation criteria that take into account both drift demands for assessing a building's seismic performance. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Evaporative losses from soils covered by physical and different types of biological soil crusts   总被引：3，自引：0，他引：3  

S. Chamizo  Y. Cantón  F. Domingo  J. Belnap 《水文研究》2013,27(3):324-332

Evaporation of soil moisture is one of the most important processes affecting water availability in semiarid ecosystems. Biological soil crusts, which are widely distributed ground cover in these ecosystems, play a recognized role on water processes. Where they roughen surfaces, water residence time and thus infiltration can be greatly enhanced, whereas their ability to clog soil pores or cap the soil surface when wetted can greatly decrease infiltration rate, thus affecting evaporative losses. In this work, we compared evaporation in soils covered by physical crusts, biological crusts in different developmental stages and in the soils underlying the different biological crust types. Our results show that during the time of the highest evaporation (Day 1), there was no difference among any of the crust types or the soils underlying them. On Day 2, when soil moisture was moderately low (11%), evaporation was slightly higher in well‐developed biological soil crusts than in physical or poorly developed biological soil crusts. However, crust removal did not cause significant changes in evaporation compared with the respective soil crust type. These results suggest that the small differences we observed in evaporation among crust types could be caused by differences in the properties of the soil underneath the biological crusts. At low soil moisture (<6%), there was no difference in evaporation among crust types or the underlying soils. Water loss for the complete evaporative cycle (from saturation to dry soil) was similar in both crusted and scraped soils. Therefore, we conclude that for the specific crust and soil types tested, the presence or the type of biological soil crust did not greatly modify evaporation with respect to physical crusts or scraped soils. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献