Earth rotation parameter estimation by GPS observations

The methods of Earth rotation parameter （ERP） estimation based on IGS SINEX file of GPS so- lution are discussed in detail. There are two different ways to estimate ERP： one is the parameter transformation method, and the other is direct adjustment method with restrictive conditions. By comparing the estimated results with independent copyright program to IERS results, the residual systemic error can be found in estimated ERP with GPS observations.     

Parametric study on performance of bridge retrofitted by unseating prevention devices

1 Introduction Structural retro?t techniques (Roberts, 2005), such as restrainers, concrete shear keys, steel jackets, CFRPshells, base isolators, or dampers have been widely studied and implemented in actual structures based on the experiences learned from past earthquakes. In the Chi-Chi earthquake (EERI, 2001), the damage to simply-supported PCI girder bridges provided a different view from which to examine the function of a rubber bearing system for simply- supported bridges (NCREE,…     

3D viscous-spring artificial boundary in time domain

After a brief review of studies on artificial boundaries in dynamic soil-structure interaction, a three-dimensional viscous-spring artificial boundary （VSAB） in the time domain is developed in this paper. First, the 3D VSAB equations in the normal and tangential directions are derived based on the elastic wave motion theory. Secondly, a numerical simulation technique of wave motion equations along with the VSAB condition in the time domain is studied. Finally, numerical examples of some classical elastic wave motion problems are presented and the results are compared with the associated theoretical solutions, demonstrating that high precision and adequate stability can be achieved by using the proposed 3D VSAB. The proposed 3D VSAB can be conveniently incorporated in the general finite element program, which is commonly used to study dynamic soil-structure interaction problems.     

Mechanical compression release device in steel bracing system for retrofitting RC frames

1 Introduction Braced steel frames are commonly used to resist seismic loads. Their seismic behavior was extensively studied during the past decades (Bertero et al.., 1989; Roeder, 1989; Jain, 1978). Their design is governed by the buckling behavior of the bracing members (ASCE, 1994,2002; CSA, 1994). To prevent or delay the seismic buckling of compressive members in concentrically braced frames in steel structures, a great number of methods have been proposed. These include the use of sp…     

A Modified Form of Mild-Slope Equation with Weakly Nonlinear Effect

Nonlinear effect is of importance to waves propagating from deep water to shallow water.Thenon-linearity of waves is widely discussed due to its high precision in application.But there are still someproblems in dealing with the nonlinear waves in practice.In this paper,a modified form of mild-slope equa-tion with weakly nonlinear effect is derived by use of the nonlinear dispersion relation and the steady mild-slope equation containing energy dissipation.The modified form of mild-slope equation is convenient to solvenonlinear effect of waves.The model is tested against the laboratory measurement for the case of a submergedelliptical shoal on a slope beach given by Berkhoff et al,The present numerical results are also comparedwith those obtained through linear wave theory.Better agreement is obtained as the modified mild-slope e-quation is employed.And the modified mild-slope equation can reasonably simulate the weakly nonlinear ef-fect of wave propagation from deep water to coast.     

红外波段太阳观测技术方法研究

1m红外太阳塔是我国未来重点发展的地面太阳观测设备 ,本文的所有工作均围绕着与此相关的红外波段太阳观测技术方法展开。1 .针对望远镜实验平台—云台太阳光谱仪 ,建立了光谱仪分光流量模型 ,并用多种实验手段验证了其可靠性。利用该模型计算了FeⅠ 1 .56μm红外太阳光谱的分光流量 ,分析了实验观测的可行性及改进方案。2 .针对探测器实验平台—PtSi红外焦平面阵列相机 ,建立了FeⅠ 1 .56μm光谱观测信噪比模型 ,模拟了各种噪声对观测的影响。在此基础上 ,在国内首次成功进行了FeⅠ1 .56μm红外太阳光谱的面阵观测实验。3 .在红外观测实验所处的高背景低对比度条件下 ,讨论了红外太阳光谱观测的图像处理方法 ,分析了观测中出现的干涉条纹的来源及解决办法 ,初步建立起了一整套红外太阳光谱与成像的定标方法和图像处理方法。4 .首次利用PVA材料 ,设计研制了一套FeⅠ 1 .56μm近红外Stokes参量偏振仪 ,并将该偏振仪安装在美国国立天文台McMath望远镜上进行了观测实验。针对一太阳黑子 ,通过扫描进行了二维的Stokes参量观测。同时建立了一套从Stokes参量反演磁矢量场的方法 ,并将反演的结果与怀柔太阳磁场望远镜的观测结果进行了比对。5.针对 1m红外太阳塔的太阳光谱仪系统 ,给出了垂直多波段光谱仪和红外     

小气候、雪盖及土壤湿度对高山生态系统功能的影响

1 Introduction High mountain landscapes above the tree-line are often regarded as close to nature, although human impact has obviously changed the environment, partly exceeding its carrying capac- ity (L?ffler, 2000). Due to their fragility regarding expected environmental changes and an increasing land use pressure in many regions, high mountain landscapes recently became a major focus within the discussion on a sustainable development in a worldwide (Messerli and Ives, 1997), and regional p…     

Decollements in slate belts,examples from the European variscides and the Qin Ling Belt of Central China

Decollements are conspicuous features of collision belts as a result of shortening and shearing of rocks of different competencies in response to intracontinental subduction and crustal stacking. When these decollements occur at upper levels, the classical thin skin tectonics of the foredeeps without important internal strain results; at mid crustal levels slaty cleavage and foliation development occurs. In the more internal parts of the chains, in the lower crust, near the crust mantle boundary, the more severe conditions (granulitic metamorphism) result in ductile deformation in the deepest parts of the mountain belts. Examples of middle and lower crust are well documented in Central China and the Variscan Belt of Europe from field evidence and deep seismic profiling.From these examples it appears more and more likely that most of the mid-crustal slate belts showing vertical slaty cleavage at the erosion surface overly flat decollements.At greater depth large decollements must occur as well in the lower continental crust and at crust-mantle boundary. Typical features of the deep seismic vertical profiles such as the strongly layered lower crust may represent the image of such deep decollements.

---

Zusammenfassung Abscherungen sind charakteristische Strukturen von Kollisions-Orogenen. Sie sind das Ergebnis von Verkürzung und Scherung verschieden kompetenter Gesteine infolge intrakontinentaler Subduktion und Krustenüberlagerung. Zu unterscheiden sind Überschiebungen oberer Zonen, wie in den Randgebirgsbereichen ohne bedeutende innere Deformation, von internen metamorphen Zonen mit Schieferung und Plättung. In den tiefen Krustenzonen und im Krusten-Mantelbereich gehen sie einher mit hochgradiger Metamorphose, allgemein in der Granulitfazies.Beispiele der mittleren und tiefen Zonen sind gut erschlossen im paleozoischen Orogen Zentralchinas und im Variszikum Europas und belegt sowohl durch die Geologie wie tiefenseismische Profile. Diese Beispiele zeigen mehr und mehr, daß geschieferte Gebirgsstockwerke mit an der Oberfläche steilstehender Schieferung von flachen Abscherungen unterlagert werden.Die typische Erscheinung einer seismisch gut geschichteten Strukturierung der Unterkruste könnte in dieser Hinsicht als Deckenbahnen interpretiert werden.

---

Résumé Les décollements sont des structures typiques des chaînes de collision. Ils résultent du raccourcissement et du cisaillement de roches de différentes compétences en réponse à la subduction continentale et à l'empilement crustal. On peut distinguer des décollements superficiels surtout dans les bassins d'avant chaîne où les roches charriées ont subi une déformation interne faible à nulle (plis et chevauchements sans schistosité). Des décollements plus profonds dans le tiers supérieur de la croûte accompagnés de schistosité et de foliation, dans les parties plus internes métamorphiques des chaînes. Enfin des décollements très profonds à la base de la croûte ou entre croûte et manteau, accompagnés ou suivis d'un métamorphisme de haut degré, généralement granulitique.Ces deux derniers types de décollement sont clairement exprimés dans la chaîne Varisque d'Europe et dans la chaîne Paléozoïque Qin Ling de Chine Centrale. Il apparaît ainsi de plus en plus évident que la plupart des zones plissées à schistosité verticale, non liées à des décrochements, passent en profondeur à de grands décollements plats. On les met en évidence sur le terrain ou/et grâce à des profils de sismique réflexion écoute longue. Des aspects caractéristiques de ces profils comme par exemple la croûte inférieure litée pourraient représenter l'image sismique de tels décollements profonds.

---

. , . , .: , . / , . , , , . , . , - . .

     

The correlation between geochemical data and SPOT satellite imagery of lateritic terrain in southern Mali

Detailed geochemical mapping of superficial lateritic formations is compared with recent high-resolution SPOT satellite images in the Dagadamou prospect in southern Mali.The two main landscape features standing out in SPOT images are expressed by thematic indices derived from multispectral data. They reflect the distribution of vegetation cover and the distinction between silty clay soils in the valleys and ferruginous duricrust exposed on the plateaus. Geochemical differentiation factors are closely related to the nature of sampled materials and reflect the relative amounts of major constituent minerals estimated by normative calculation.Duricrust samples with high Fe and Al content are also enriched in trace elements, P, V, Cr, As, Mo, Nb and Cu, immobilized in the weathering profile with secondary oxihydroxide minerals.Soils of flats are composed mainly of quartz and kaolinite; they also concentrate heavy minerals characterized by high contents of Zr, Ti, Ce and Y.Accumulation of detrital material at the periphery of duricrust plateaus is marked by a geochemical halo of higher contents in Zr and quartz at their periphery. This feature is clearly visible on SPOT imagery as a zone of high reflectance, devoid of vegetation.The density of vegetation on duricrust is related to its kaolinite content. Its distribution is characterized by a striped pattern, which is probably controlled by bedrock lithological structures preserved in the lateritic cover.This study shows the relationships, both direct and indirect, existing between spectral reflectance and geochemical composition of superficial lateritic formations. Many other landscape features identified with high resolution on SPOT images provide complementary information, which could be very helpful at various stages of geological and mineral exploration in lateritic terrain.     

Intercomparison of NO column measurements during MAP/GLOBUS 1985

Column measurements of nitric oxide were made using several techniques during the MAP/GLOBUS campaign in France in September 1985. The data sets are nearly co-located and simultaneous, therefore allowing a valid intercomparison of the various measurement methods. The range of altitudes sampled differs from instrument to instrument. This complicates the comparison because the data sets are to some extent complementary. The NO distributions apparently vary significantly from day to day, and possibly over shorter timescales. Changes in dynamics may be responsible for these variations. The results from the instruments which measure in the infrared and the ultraviolet are self-consistent, and show good agreement with photochemical predictions. On 19 September, when the intercomparison was made, the profile measured by the in-situ chemiluminescent instrument differed significantly from the predicted profile, and the measured columns were generally higher.