The role of current velocity in structuring eelgrass (Zostera marina L.) meadows     

Mark S. Fonseca  Joseph C. Zieman  Gordon W. Thayer  John S. Fisher 《Estuarine, Coastal and Shelf Science》1983,17(4):367-380

Measurements of velocity profiles, bathymetry, and surface sediment characteristics across eelgrass (Zostera marina L.) meadows yielded information on community development processes and functional attributes of this ecosystem. Height/length ratios of the meadows were positively correlated with tidal current velocity. Low, medium, and high current regimes were separated by surface current velocities of approximately 50 and 90 cm s^?1. Z. marina can tolerate approximately 120–150 cm/sec current velocities in the areas studied. Per cent silt-clay and organic matter content of the surface sediments are negatively associated with shear velocity, suggesting that meadows in high current areas are sources while meadows in low current areas are sinks of autochthonous detritus. Current velocity maintains seagrass meadows at different equilibrium levels (relative climaxes). We theorize these different equilibrium levels provide unequal habitat utilization potentials for the associated faunal community.  相似文献   

A mathematical model for orientation data from macroscopic conical folds     

D. Kelker  C. W. Langenberg 《Mathematical Geology》1982,14(4):289-307

Statistical techniques are developed to classify folds into one of three classes: cylindrical, conical, or neither. A translated version of Bingham's distribution on the sphere is applied to orientation data fron conical folds. Iterative least-squares techniques are used to determine the best-fitting small circle (or cone), and confidence intervals for the cone axis and half apical angle are developed. Examples of a cylindrical and a conical fold are given. Another fold is neither cylindrical nor conical and is classified as pseudoconical. Relationships between the Bingham and Fisher distributions are presented.  相似文献   

Spectrophotometry observations of HR 8107     

S. C. Joshi  D. K. Ojha  J. B. SrivaStava 《Journal of Astrophysics and Astronomy》1989,10(1):113-118

HR 8107, a reported new Be star, has been observed spectrophotometrically. The energy distribution curve of the star has been compared with those of other stars of similar spectral and luminosity types and model atmospheres. On the basis of comparison with model atmospheres an effective temperature has been assigned to the star  相似文献   

脉冲星在银河系中空间分布的讨论(英文)     

吴鑫基  D.A.Leahy 《中国天文和天体物理学报》1989,(3)

已发表的三个脉冲星星表共有384颗。采用这个样本并用一种经验的方法修正观测选择效应,获得脉冲星按银心距离的分布和银河系中可能存在的脉冲星总数。一个明显的峰值在离银心5—7KPC处。脉冲星的总数为(8.4±3.7)×10~4。采用束因子值为5和平均寿命为9×10~6年,得到诞生率为每15—38年产生一颗。  相似文献   

Some observations on the effect of ozone treatment on suspended particulate matter in seawater     

Hasong Pak  James Kitchen  Percy Donaghay  J. Ronald  V. Zaneveld 《Estuarine, Coastal and Shelf Science》1981,13(3):327-336

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Knowledge based systems for risk assessment of the subsurface of contaminated sites     

S. Heynisch  A. Pekdeger  B. Richter  M. -Th. Schafmeister  W. Skala 《Mathematical Geology》1994,26(4):505-517

Computer-based risk evaluation methods are practical tools to compare automatically and evaluate contaminated sites. HYDRISK is an example of adequate knowledge-based systems: HYDRISK evaluates hydrogeological properties and chemical criteria relevant to contaminant transport with respect to the necessary remedial actions. It works at a high investigative level and enables geologists and engineers to draw differentiated conclusions for selecting remediation methods for the contaminated site. HYDRISK emphasizes space and time dependent aspects of the contaminant transport. It is supported by a geographic information system (GIS) to display the evaluation results. Some ideas on considering the spatiotemporal variability of relevant parameters by means of geostatistical methods and numerical models will be given.  相似文献   

DISTRIBUTIONS OF TOTAL, INORGANIC AND ORGANIC PHOSPHORUS IN THE SEDIMENTS NEAR THE HUANGHE RIVER ESTUARY   总被引：1，自引：0，他引：1  

林荣根  吴景阳 《中国海洋湖沼学报》1992,10(3):204-214

For some hundred surface sediment samples from five cores taken in two cruises near the Huanghe River Estuary, total phosphorus (TP (.inorganic phosphorus (IP (and organic phosphorus (OP)were determined.On the average, 527×10-6, 455×10~6 and 72×10-6 were found for TP,IP and OP for the surface sediments taken in the two cruises. The distribution of OP and IP was controlled by the sample particle size: OP content increased with the decreasing of the sample particle size, while the maximal value of IP was found in the silt fraction due to the existence of apatite in our samples. Vertical distributions reflected well the channel change of the Huanghe River. Results from the multiple regressions between the three forms of phosphorus and the percentages of different particle size agreed well with the analytical data.  相似文献   

RAPID ESTIMATION OF THE NUMBER OF COELUTING COMPONENTS IN LIQUID CHROMATOGRAPHY BY FACTOR ANALYSIS     

CHENGBOSHEN  THOMASJ.VICKERS  CHARLESK.MANN 《地理学报(英文版)》1991,(5)

Evaluation of the results of factor analysis of sets of spectroscopically detected chromatograms is carriedout by examining the shapes of the abstract factors.This is done either by visual inspection or by analysisof the power density spectra produced from them.Owing to constraints imposed by the column functionand the spectroscopic instrument function,the information content of the chromatograms necessarilyoccurs at low spatial frequencies.As a consequence,it appears as relatively broad features in the abstractchromatograms and as a peak in the low-frequency region of the corresponding power density plot.Onthe basis of examination of the power density distribution,a well-defined distinction is made betweenprimary and secondary abstract factors.The major uncertainty encountered in determining the numberof chemical components appears to arise from effects of contaminants in reagents.  相似文献   

Statistical control chart for regime identification in volcanic time series     

Chih-Hsiang Ho 《Mathematical Geology》1992,24(7):775-787

In an important paper, Mulargia et al. (1987) address the importance of quantitative and objective identification of different regimes of a volcano. They develop a procedure based on the two-sample Kolmogorov-Smirnov (K-S) statistic. The K-S test is a general-purpose test that discriminates between two data sets as belonging to two different regimes based on their empirical distribution functions. The empirical distribution function is designed to describe the aggregate behavior of the volcanic activity, and it is constructed from the orders of the length of the collected repose times in each data set. In this article, we use the idea of statistical process control to distinguish between the variation inherent in the observed repose times and the extraordinary variation that signals a real change in the regimes. We construct a table of control limits, and we demonstrate the procedure of regime identification based on a simple control chart. It shows a point outside the control limits almost as soon as the process enters a new regime. The basis of the statistical process control mechanism is a simple Poisson process, which is state of the art. The proposed control charting procedure is an eruption by eruption procedure, which follows the original chronological order of the eruptions. This procedure is applied to the eruptive history of the Mount Etna volcano. The application shows schematically that the procedure presents a visual interpretation of the identified regimes and can be practically translated for tabular or manual use.  相似文献   

湖北省棉花产量的变化与棉田布局的战略调整^*     

唐文雅 《地理研究》1988,7(3):34-43

本文揭示了湖北省棉花亩产的增长具有北高南低的特点,分析了鄂北地区种植棉花的自然优势和经济效盆大于江汉平原,从而提出湖北省棉花北移的战略调整的设想。  相似文献