Gyldén Model: The Slowly Changing Equivalent Gravitational Parameter

In the Gyldén problem, the case of slowly changing equivalent gravitational parameter (e.g.p.) is studied. Assuming the following law for the variation of the e.g.p.: μ (t) = μ₀+ εμ (εt), ε< μ₀, we obtained a) a O(ε⁴ T⁴)-approximation of the solution, on a shortened time scale (0,T), with T of order o(ε^-1),for the general case (i.e. the support function μ is O(1)-valued and admits an expansion in power series of its argument), and b) a O(ε²)-approximation of the solution, on a natural timescale of order O(1/ε), for the case of a bounded variation rate (i.e. the support function μ and its derivative are both O(1)-valued). For the study of the first problem we introduced a type of Lissajous variables and used the Lie-Hori normalization scheme; for the second problem we used the Delaunay variables and applied the von Zeipel method for approximate integration. The physical interpretation of the results is in both cases the same: within the corresponding limits of approximation, the variation of e.g.p. (i) has no effect on the size of the osculating ellipse, (ii) it sets the pericenter in slow rotation and (iii) it introduces a secular variation in the longitudes. This revised version was published online in July 2006 with corrections to the Cover Date.     

内蒙古区域数值预报对探空和地面观测资料的敏感性试验研究

基于内蒙古睿图预报系统的低分辨率版本和WRFDA-FSO诊断工具,评估2021年7月现有探空和地面观测对内蒙古睿图预报系统预报的影响。该方法计算代价相对低廉,并允许根据观测变量、观测类型、气压层次、地理区域等观测的子集对观测影响进行划分。代价函数为以干总能量为度量的背景场和分析场的预报误差之间的差异。结果表明:观测影响的总体总和为负,观测对预报起正贡献作用。对12 h预报误差减小贡献最大的观测来自探空观测的动力变量(U、V风分量)。而单时次单位数量平均观测影响,探空观测的贡献约为地面观测的1/2。探空观测对12 h预报误差减小从近地面层至模式层顶均保持正贡献作用,并在对流层中低层和对流层高空急流层存在两个极大值区域;地面观测在850 hPa以下低层正贡献占比明显。探空观测在被同化系统同化时均总体具有有利的影响,也反映出探空观测数据稳定、质量较高的特征;地面观测对12 h预报误差减小起正贡献作用次数最多的区域在河套地区尤为显著。同时,探讨了需进一步提高地面观测资料同化率的问题。     

Holocene peatland development and hydrological variability inferred from bog‐pine dendrochronology and peat stratigraphy – a case study from southern Sweden

Dendrochronological analysis was applied to subfossil remains of Scots pine (Pinus sylvestris L.) buried in a South Swedish peat deposit. In combination with peat stratigraphy, this approach was explored for its potential to provide information on the local hydrological and depositional history at the site, forming the basis for a regional palaeohydrological analysis. A 726‐year ring‐width chronology was developed and assigned an absolute age of 7233–6508 cal a BP (5284–4559 BC) through cross‐dating with German bog‐pine chronologies, whereas two short additional records of older ages were radiocarbon dated. Registration of growth positions of individual trees allowed assessment of the spatial dynamics of the pine population in response to hydrological changes and peatland ontogeny. Annually resolved growth variability patterns in the pine population reveal several establishment and degeneration phases, probably reflecting fluctuations in bog‐surface wetness. A major establishment phase at 7200–6900 cal a BP reflects the onset of a period of lowered groundwater level, also indicated by increased peat humification, and a development consistent with regional temperature and lake level reconstructions revealed from other proxies. This study demonstrates that subfossil bog‐pine populations may provide annually to decadally resolved reconstructions of local groundwater variability, which are highly relevant in a long‐term palaeoclimatic context. Copyright © 2012 John Wiley & Sons, Ltd.     

Reverse time migration of CMP-gathers an effective tool for the determination of interval velocities

One of the most important steps in the conventional processing of reflection seismic data is common midpoint (CMP) stacking. However, this step has considerable deficiencies. For instance the reflection or diffraction time curves used for normal moveout corrections must be hyperbolae. Furthermore, undesirable frequency changes by stretching are produced on account of the dependence of the normal moveout corrections on reflection times. Still other drawbacks of conventional CMP stacking could be listed.One possibility to avoid these disadvantages is to replace conventional CMP stacking by a process of migration to be discussed in this paper. For this purpose the Sherwood-Loewenthal model of the exploding reflector has to be extended to an exploding point model with symmetry to the lineP _EX M whereP _EX is the exploding point, alias common reflection point, andM the common midpoint of receiver and source pairs.Kirchhoff summation is that kind of migration which is practically identical with conventional CMP stacking with the exception that Kirchhoff summation provides more than one resulting trace.In this paper reverse time migration (RTM) was adopted as a tool to replace conventional CMP stacking. This method has the merit that it uses the full wave equation and that a direct depth migration is obtained, the velocityv can be any function of the local coordinatesx, y, z. Since the quality of the reverse time migration is highly dependent on the correct choice of interval velocities such interval velocities can be determined stepwise from layer to layer, and there is no need to compute interval velocities from normal moveout velocities by sophisticated mathematics or time consuming modelling. It will be shown that curve velocity interfaces do not impair the correct determination of interval velocities and that more precise velocity values are obtained by avoiding or restricting muting due to non-hyperbolic normal moveout curves.Finally it is discussed how in the case of complicated structures the reverse time migration of CMP gathers can be modified in such a manner that the combination of all reverse time migrated CMP gathers yields a correct depth migrated section. This presupposes, however, a preliminary data processing and interpretation.     

Miscellaneous information

Miscellaneous information     

Moravian and Silesian nationalities: A new phenomenon in the ethnic map of the Czech Lands?

In the 1991 population census, 1.4 million inhabitants of the Czech Republic applied for Moravian or Silesian nationality, which did not exist before.They expressed their consciousness of territorial appurtenance to the historical provinces of Moravia and Silesia and by this declaration they set it above the appurtenance to the Czech nation. New social cleavage thus developed in ethnically almost homogeneous environment of the Czech Republic, which constitutes a potential threat of the further splitting of the State. Trying to find the causes of such a phenomenon, the author deals with the territorial differentiation of these inhabitants and factors which influenced it. The close interconnection with political demands is stressed. The insensive centralizing measures of the communist regime are considered as the direct impulses of the present development. The phenomenon is understood as a specific manifestation of the posttotalitarian social crisis in Central and Eastern Europe.     

若干特殊地表风蚀的风洞实验研究

经风洞模拟实验,本文对四种特殊地表在净风和挟沙风情况下的风蚀特性,进行了定量的研究。揭示了原始地表结构受人为破坏后,其抗风蚀能力急剧降低的特点。探讨了风成沙粒配、戈壁风蚀平衡与风蚀有关的几个问题。     

遥感影像信息在澳门、磨刀门海域工程建设中的应用及其效益

本文介绍了计算机处理和光学处理相结合的信息提取方法并得到显著效益。根据澳门海域和磨刀门海域工程建设中的实际需要,成功地运用遥感影像信息为澳门海域工程物理模型试验提供了模型水流流态与原型水流流态相似性的验证,为磨刀门海域围垦工程提供了水下潜坝的动态影像信息,并取得了较好的社会效益和经济效益。