An algorithm for detecting and estimating cycle slips in single-frequency GPS

An algorithm for detecting outliers and cycle slips in single-frequency GPS using a 3rd order polynomial model of the Kalman filter and for estimating the ambiguity by using optimal wavelet is presented in this paper. It is applicable to the carrier phase measurement with sample rate of one per second. The results of calculation with the GPS data aboard satellite Topex on 1995 June 22 show that the algorithm is so efficient that it can accurately estimate the ambiguity even for signals interrupted by a few seconds.     

Early warning research on salt-alkalization desertification in western Songnen Plain

Desertification is an environmental issue in the world. The salt-alkalization desertification land area formed by both primary and secondary salt-alkalization has extended in a large scale, which has become a significant eco-environmental problem. Based on the characteristics of eco-environment and the situation of desertification in western Songnen plain, this paper reports the analyzes of its formation in background and cause. An early warning system on the salt-alkalization desertification is established and the GIS technology is used to abstract the information of desertification evaluation index. Supported by the integrated technology of the GIS and ANN, the orientation and quantitative result of desertification are gained, which is helpful to the eco-environment protection and resource development in western Songnen Plain.     

Silicon limitation on primary production and its destiny in Jiaozhou Bay, China——Ⅳ：Study on cross-bay transect from estuary to ocean

The authors analyzed the data collected in the Ecological Station Jiaozhou Bay from May 1991 to November 1994, including 12 seasonal investigations, to determine the characteristics, dynamic cycles and variation trends of the silicate in the bay. The results indicated that the rivers around Jiaozhou Bay provided abundant supply of silicate to the bay. The silicate concentration there depended on river flow variation. The horizontal variation of silicate concentration on the transect showed that the silicate concentration decreased with distance from shorelines. The vertical variation of it showed that silicate sank and deposited on the sea bottom by phytoplankton uptake and death, and zooplankton excretion. In this way, silicon would endlessly be transferred from terrestrial sources to the sea bottom. The silicon took up by phytoplankton and by other biogeochemical processes led to insufficient silicon supply for phytoplankton growth. In this paper, a 2D dynamic model of river flow versus silicate concentration was established by which silicate concentrations of 0.028–0.062 μmol/L in seawater was yielded by inputting certain seasonal unit river flows (m³/s), or in other words, the silicate supply rate; and when the unit river flow was set to zero, meaning no river input, the silicate concentrations were between 0.05–0.69 μmol/L in the bay. In terms of the silicate supply rate, Jiaozhou Bay was divided into three parts. The division shows a given river flow could generate several different silicon levels in corresponding regions, so as to the silicon-limitation levels to the phytoplankton in these regions. Another dynamic model of river flow versus primary production was set up by which the phytoplankton primary production of 5.21–15.55 (mgC/m²·d)/(m³/s) were obtained in our case at unit river flow values via silicate concentration or primary production conversion rate. Similarly, the values of primary production of 121.98–195.33 (mgC/m²·d) were achieved at zero unit river flow condition. A primary production conversion rate reflects the sensitivity to silicon depletion so as to different phytoplankton primary production and silicon requirements by different phytoplankton assemblages in different marine areas. In addition, the authors differentiated two equations (Eqs. 1 and 2) in the models to obtain the river flow variation that determines the silicate concentration variation, and in turn, the variation of primary production. These results proved further that nutrient silicon is a limiting factor for phytoplankton growth. This study was funded by NSFC (No. 40036010), and the Director's Fund of the Beihai Sea Monitoring Center, the State Oceanic Administration.     

Morphological characters of the two-ribbon flare of 1981 May 13 and their explanation

We give a summary of the morphology of the two-ribbon flare of 1981 May 13. One striking feature is that the Ha flare began at about 0338' UT and the double-ribbon structure was formed about 0346, $\text{before}$ the impulsive phase of the radio 3 cm burst at 04 11 UT. The 3 cm radio burst flux beginning at 03 33 UT showed only slow, stepwise increases lasting half an hour until the impulsive phase and this type of increase is usually regarded to be a typical thermal process. Each step in the radio flux corresponded to a variation in the Ha flare, showing that the radio and Hα emissions during this period came from the same thermal source. In this paper, we explain this behaviour in terms of Hyder's model: we think that the magnetic trough supporting the solar prominence rose for some reason, causing the prominence matter (the dark filaments) to fall along the magnetic lines and to hit the chromosphere and trigger off the flare. We give rough estimates of the energy density, the height of prominence and the infall matter at the different radio increments. We also give a qualitative explanation for the appearances of the single-peak structure in the radio burst at 0411 and the covering of the sunspot shortly after at 04 13 and propose several possible mechanisms.     

康古尔塔格缝合带的变形机制

北天山东段康古尔塔格带是晚古生代塔里木板块和准噶尔板块碰撞的结果。它是一条复杂的、强烈的高应变带．并具有独特的变形机制、应变序列以及构造变形。本文运用构造－地层研究方法对该碰撞带的构造特征加以分析和研究。     

国外现代景观地理研究的主要发展趋势

景观地理是地理学传统的综合研究领域,近年来主要呈现出下列发展趋势:(1)从传统的经验综合走向系统综合;(2)研究方法和手段在不断革新;(3)基础研究的重心开始向景观的动态特征转移;(4)应用研究在进一步加强;(5)景观生态研究迅速发展。这些都标志着景观地理研究正处在一个新的转折和发展时期。     

Disintegration and age of basement metamorphic rocks in Qiangtang,Tibet, China

Comprehensive studies on lithologic association, provenance of metacongelometre, characteristics of metamorphism and deformation, and²⁰⁷Pb/²⁰⁶Pb-dating of single-zircon for metamorphic rocks distributed in Chabu-Chasang areas in Qiangtang block indicate that most of them belong to Middle Proterozoic metamorphic basement except silicilith member ascribed to Triassic. Disintegrated basement strata are called Gemuri group and Guoganjianianri group; they are different in histories of metamorphism and deformation. The single-zircon²⁰⁷Pb/²⁰⁶Pb-ages provide excellent evidence for the existence of an Archean continent nucleus around study areas. Some thermal event ages such as 929–1016 and 509–548 Ma are recorded in Gemuri group.