A Time-Transformed Leapfrog Scheme

We present a time-transformed leapfrog scheme combined with the extrapolation method to construct an integrator for orbits in N-body systems with large mass ratios. The basic idea can be used to transform any second-order differential equation into a form which may allow more efficient numerical integration. When applied to gravitating few-body systems this formulation permits extremely close two-body encounters to be considered without significant loss of accuracy. The new scheme has been implemented in a direct N-body code for simulations of super-massive binaries in galactic nuclei. In this context relativistic effects may also be included.     

地磁低点位移异常类型特征与地震活动

通过对大量的地磁低点位移异常震例研究,结果表明: ① 地磁低点位移异常的形态、空间展布有明显的地区特征。异常大致可分为: 大范围异常和区域性异常二大类, 还可细分为 5个类型 ; ② 地磁低点位移异常与我国的地质活动构造有较密切的联系。 异常范围的大小、形态与异常所在地区的活动构造的规模、展布形态特征,以及这一地区即将发生的地震强度有关。     

Effect of non-linear soil deformation on the interaction among energy piles

This study investigates the effect of non-linear soil deformation on the displacement interaction among energy piles. The work is based on interaction factor analyses of full-scale pile group tests, whose results are compared with experimental evidence. The results presented highlight the tendency of interaction factor analyses that ignore non-linear soil deformation to overestimate the interaction and the displacement of energy pile groups. This outcome, in accordance with previous studies for conventional pile groups subjected to mechanical loads, may be considered in the analysis and design of energy pile groups subjected to thermal (and mechanical) loads through the interaction factor method.     

腾格里沙漠地区水化学特征

水资源极为匮乏的腾格里沙漠区内所赋存的水主要有两种类型。一种是沙下潜水 ,主要是周边山区由高向低缓慢地向沙漠区运移所致 ,分布较为普遍 ;另一种是沙漠湖水 ,它是在沙漠区内之低洼地段 ,由于沙下潜水的长期溢出汇集于大小不等的长条状湖泊之中 ,以湖表水 (咸水和卤水 )的形式存在。沙下潜水矿化度在 0 .5～ 1 g/L之间 ,为本区的饮用水。湖表水咸苦 ,矿化度较高 ,就同一湖区而言 ,也有咸水和卤水之分 ,咸水矿化度为每升数十克 ,卤水则在 1 0 0～ 440 g/L之间 ,已达到了盐湖类沉积阶段     

BIBLIOGRAPHIE

Abstract

Time series modelling approaches are useful tools for simulating and forecasting hydrological variables and their change through time. Although linear time series models are common in hydrology, the nonlinear time series model, the Generalized Autoregressive Conditional Heteroscedasticity (GARCH) model, has rarely been used in hydrology and water resources engineering. The GARCH model considers the conditional variance remaining in the residuals of the linear time series models, such as an ARMA or an ARIMA model. In the present study, the advantages of a GARCH model against a linear ARIMA model are investigated using three classes of the GARCH approach, namely Power GARCH, Threshold GARCH and Exponential GARCH models. A daily streamflow time series of the Matapedia River, Quebec, Canada, is selected for this study. It is shown that the ARIMA (13,1,4) model is adequate for modelling streamflow time series of Matapedia River, but the Engle test shows the existence of heteroscedasticity in the residuals of the ARIMA model. Therefore, an ARIMA (13,1,4)-GARCH (3,1) error model is fitted to the data. The residuals of this model are examined for the existence of heteroscedasticity. The Engle test indicates that the GARCH model has considerably reduced the heteroscedasticity of the residuals. However, the Exponential GARCH model seems to completely remove the heteroscedasticity from the residuals. The multi-criteria evaluation for model performance also proves that the Exponential GARCH model is the best model among ARIMA and GARCH models. Therefore, the application of a GARCH model is strongly suggested for hydrological time series modelling as the conditional variance of the residuals of the linear models can be removed and the efficiency of the model will be improved.

Editor D. Koutsoyiannis; Associate editor C. Onof

Citation Modarres, R. and Ouarda, T.B.M.J., 2013. Modelling heteroscedasticty of streamflow times series. Hydrological Sciences Journal, 58 (1), 1–11.     

地磁低点位移法的改进

中低纬度地磁场平静太阳日变化Z分量的极小值出现的时刻常被用于地震预报,即"低点位移"法,但现有算法的时间格式和人工绘制突变界线的模式会产生较大的误差,本文在第一部分针对这些误差改进了原有算法.第一项是改进了地磁低点时间的格式,第二项是引入了Voronoi剖分技术替代人工画线.前者过滤了假的突变界线,消除了系统误差;后者建立了突变界线与地磁台网低点数据之间的解析关系,使它们一一对应,消除了随机误差.本文第二部分内容是提出了新的时间格式与数字化突变界线的计算公式,并用程序实现计算任务.本文第三部分内容是在对地磁台网的低点时间跟踪的过程中,捕捉到了甘肃省周边几次地震前的地磁低点位移现象,并分析这些案例,在结论中证明该方法的可靠性.     

内蒙古东乌珠穆沁旗舒哈迪铅锌多金属矿成矿特征

舒哈迪铅锌多金属矿床赋存在发育于奥陶系中统多宝山组细碧岩、石英角斑岩岩系中的断裂构造蚀变带内,矿体呈脉状、透镜状,受舒哈迪背斜构造及其伴生的断裂构造控制,铅锌矿石成分简单,伴生有银和铜.围岩蚀变主要为黄铁矿化、硅化、绿泥石化、绿帘石化、绢云母化和碳酸盐化,具有不明显的分带性.成矿物质来源于奥陶系中统多宝山组变质岩系,成矿热液来源于隐伏的岩浆侵入体,矿床成因属于岩浆热液充填（脉）型铅锌多金属矿床,矿床形成时代为燕山早-中期.     

新滩滑坡后两岸边坡的位移监测及形变趋势

本文介绍新滩滑坡后两岸边坡监测的工作,对边坡变形提出了趋势意见。认为新滩斜坡目前正处于整体稳定下的局部调整阶段,变形缓慢平稳,但要注视广家崖的危岩动态;链子崖仍有趋势性的倾江形变。5—6号缝围成的7万方危岩及江段的5万方危岩体尚有一触即崩之势,须加强监视。     

A DIAGNOSTIC ANALYSIS OF AIR TEMPERATURE ANOMALY MODE OVER CHINA IN 2009/2010 WINTER BASED ON GENERALIZED EQUILIBRIUM FEEDBACK ASSESSMENT (GEFA) METHOD

By using the observed monthly mean data over 160 stations of China and NCAR/NCEP reanalysis data, the generalized equilibrium feedback assessment(GEFA) method, combined with the methods of EOF analysis, correlation and composite analysis, is used to explore the influence of different SST modes on a wintertime air temperature pattern in which it is cold in the northeast and warm in the southwest in China. The results show that the 2009/2010 winter air temperature oscillation mode between the northern and southern part of China is closely related to the corresponding sea surface temperature anomalies(SSTA) and its associated atmospheric circulation anomalies. Exhibiting warming in Northeast China and cooling in Southwest China, the mode is significantly forced by the El Nio mode and the North Atlantic SSTA mode, which have three poles. Under the influence of SSTA modes, the surface northerly flow transported cold air to North and Northeast China, resulting in low temperatures in the regions. Meanwhile, the mid-latitude westerlies intensify and the polar cold air stays in high latitudes and cannot affect the Southwest China, resulting in the warming there.     

浙江省年平均气温百年序列的构建

长时间气温序列是气候变化研究的基础,早期气温观测台站的缺乏在某种程度上限制了区域性气温长序列的建立。将局部台站的气温观测值向代表全区水平的气温观测值转化,亦是一种有效利用早期少数气温站点构建区域性气温长序列的重要途径。基于浙江省气温观测台站资料的统计分析,提出了局部台站观测值全局修正（GAoSV）的气温长序列建立方式,并利用该方式构建了浙江省年平均气温百年序列。研究结果表明：省级区域内气温局部台站观测与全区台站观测,两者的气温年值变化具有高度的趋同相关性,所提出的GAoSV气温序列构建方式可在少数气温观测台站的情况下,有效保证全区气温序列的构建可信度,且随着观测台站数量增多,其构建可信度会进一步增大,该方式尤其适合早期气温观测台站稀缺（仅有1～2个）的省市级气温长序列的建立。以GAoSV方式建立的浙江省年平均气温百年序列显示,1905-2012年浙江省年平均气温总体在逐渐升高,增温速率约为0．11℃／10a,1980-2012年期间气温的上升趋势更为明显,增温速率约为0．51℃／10a。