硒对极大螺旋藻生长及含硒量的影响   总被引：15，自引：0，他引：15  

周志刚  钟罡  刘志礼 《海洋科学》1997,21(5):42-45

用０．４ｍｇ／Ｌ硒培养极大螺旋藻时，３５℃与１６０μｍｏｌ／ｍ＾２．ｓ的光温条件有利于螺旋藻生长和对硒的累积，在此种光温条件下，４０ｍｇ／Ｌ硒以下均促进藻的生长，其中１２ｍｇ／Ｌ硒的效果最大；超过６０ｍｇ／Ｌ硒就有抑制作用；４００ｍｇ／Ｌ硒以下藻即死亡。  相似文献   

Statistical analysis of the largest possible earthquake magnitudes on the Ecuadorian coast for selected return periods     

Sandra García-Bustos  Jimmy Landín  Ricardo Moreno  A.S.E. Chong  Maurizio Mulas  Mónica Mite 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2020,14(1):56-68

ABSTRACT

In this work, we have studied the largest earthquake magnitudes on the Ecuadorian coast by using the principles of Extreme Value Analysis based on its two approaches: Block Maxima and Peaks-over-Threshold. First, before modelling the recorded earthquakes, the K-means clustering technique was applied to determine a classification according to the level of magnitude of the earthquakes. Then, models based on the Extreme Value theory of earthquake magnitudes were developed for each of the four clusters that were found, and finally, the best-fitted models were those known as Fréchet and Gumbel ones. The zone with the greatest earthquake magnitudes on the Ecuadorian coast is located between the north of the province of Manabí and the south of the province of Esmeraldas, with a return period of 50 years for an earthquake with magnitude greater than 7.7 M_W.  相似文献   

Torn between extremes: the ups and downs of phytoplankton     

A.?BeckmannEmail author  I.?Hense 《Ocean Dynamics》2004,54(6):581-592

We present a model to investigate the success and resulting patterns of phytoplankton migration, based on motility which depends exclusively on the internal energy and nutrient state of the cells. The model consists of migrating and non-migrating sub compartments for phytoplankton, and migration is a function of the prescribed threshold values for internal quotas. The different modes of phytoplankton behavior are evaluated in the framework of a coupled physical–biological model that includes wind-driven up- and downwelling. The results show that (1) migration is almost always advantageous with respect to biomass, (2) a wide variety of migration patterns (e.g., subsurface maxima, surface-avoidance behavior) can be reproduced by a relatively simple treatment of motility, (3) multiple deep chlorophyll maxima can be explained as the result of certain threshold values in combination with negligible vertical movement of the water, and (4) descending tongues of high phytoplankton concentration may be caused by migratory behavior and not necessarily by subduction due to frontal convergence. Thus, our model offers explanations for a large variety of observed phytoplankton distributions and migration patterns.The comments of two anonymous reviewers are gratefully acknowledged.  相似文献   

用最小绝对偏差方法(LAD)估计极值分布参数的探讨   总被引：2，自引：3，他引：2  

吴香华  秦伟良  王新蕾  俞书平 《气象科学》2006,26(3):260-264

数理统计问题中的最小绝对偏差方法(Least Absolute Deviation)由于具有良好的稳健性,近年来备受重视。本文所研究的是如何将最小绝对偏差法及非线性回归模型相结合,应用于极值分布的参数估计,并与经典的参数估计法相比较。通过对徐州市降雨量数据的研究表明,改进后的参数估计法不仅提高了模型拟和的精确度,而且有良好的稳定性,可以推广到相关气象要素的预测、预报研究中。其中,将LAD法运用于极值分布模型是一个新的尝试。  相似文献   

施氏獭蛤的生态观察   总被引：3，自引：1，他引：2  

蔡英亚  劳赞  陈东 《广东海洋大学学报》2005,25(1):39-42

施氏獭蛤(LutrariasieboldiiReeve)属暖水性贝类,分布于热带—亚热带海区,在我国东海和南海都有。据在广西和海南沿海的调查,它生活在潮下带至水深78m的沙或沙泥底质中。营埋栖生活,深度达21cm。生活海区的水温为8~32℃,盐度11 .50~33 00,pH值8. 2~8 .4,透明度4~7m。食物以底栖硅藻和有机碎屑为主。繁殖期在5~9月。其肉供食用,是较珍贵的食品,可以发展人工增养殖。  相似文献   

Assessing changes in the rainfall regime in Nigeria between 1961 and 2004     

Theophilus Odeyemi Odekunle  Samuel A. Adejuwon 《GeoJournal》2007,70(2-3):145-159

The study assessed changes in the rainfall regime in Nigeria between 1961 and 2004 in terms of (a) absolute seasonality—the length of dry and wet season; (b) relative seasonality—rainfall contrast during the year; (c) number of rainfall maxima and minima; and (d) timing of rainfall maxima and minima. Trends in the mean monthly surface locations of the Inter-tropical Discontinuity (ITD) were also examined as a prominent factor of the rainfall regime. Changes in the regime were examined over four time slices: 1961–1971, 1972–1982, 1983–1993 and 1994–2004. The results show that, in the area of single rainfall maximum regime, the length of the wet season has increased from 4 months (in 1961–1971) to 5 months (since 1972–1982). The rainfall relative seasonality has consistently been ‘most rain in 3 months or less’. The rainfall maxima still indicate single rainfall maximum but shift in the peak from August to July. Rainfall during the months of June to September appears to have witnessed declining trends over the first three time slices. The last time slice however indicates trends towards a wetter condition. For the area of double maxima rainfall regime, the length of the wet season has consistently been 8 months. The rainfall relative seasonality has consistently been ‘rather seasonal with a short drier season’. The rainfall maxima and minima still indicate double rainfall maxima with August as the month of the minimum but shift in the primary peak from July to September. The northward latitudinal distance of the surface location of the ITD from the equator indicates significant upward trends during the months of May to September only and for a period of 1983–2000. The trend results of the ITD appears to account for most of the observed changes in the rainfall regime in Nigeria.  相似文献   

Singularity detection of the thin bed seismic signals with wavelet transform     

李庆春  朱光明 《地震学报(英文版)》2000,13(1):61-66

IntroductionIn1977,Sheriff(1977)provedthedetectiftglimitthatwasdefinedasminimumthicknessofthereflectionthinbedtobel/30wavelength.Applyingthesingularitydetectionprinciplewithwavelettransforminthispaper,weanalyzethereflectionseismicsignalsofthethinbed...  相似文献   

波面极大值处水质点水平加速度的统计分布     

文凡 《中国海洋大学学报(自然科学版)》2000,30(4)

基于 L onguet- Higgins线性海浪模型 ,在二维情况下导出海浪波面极大值处水质点水平加速度分布律 ,其分布遵从正态分布。在分布中引入新的谱宽度参量 [(m2 m4 - m23 ) / m2 m4 ]12 。以Neumann谱为模式计算波面极大值处质点加速度分布。  相似文献   

THE STATISTICAL DISTRIBUTION OF THE SPATIAL MAXIMA OF A WAVY SEA SURFACE   总被引：2，自引：0，他引：2  

孙孚  丁平兴  管长龙 《中国海洋湖沼学报》1994,12(1):1-12

A statistical distribution of the maxima of a random function in two space variables is suggested to fit with stereo observations of the sea surface. The presented distribution is a complicated mix of Gaussian, Rayleighian and Maxwellian distributions and determined by three parameters of the directional spectrum, According to the changes of the three parameters it may approach the above three distributions respectively in special cases so that it has more probability of fitting stereo data better In addition, the fact that these parameters can be directly estimated from observed data is briefly in the paper.  相似文献   

Cryptophyta Flagellates of Meromictic Lakes Shira and Shunet(Khakassia,Russia):Mechanisms of Vertical Distribution and Trophic Role     

Yuri BARKHATOV  Elena KHROMECHEK  Alexander TOLOMEEV  Igor PROKOPKIN 《《地质学报》英文版》2014,88(Z1):50-52

正1 Introduction Many of the stratified lakes are characterized by the presence of large populations of cryptomonads in their chemocline zones(Reynolds,1992;Gervais et al,2003;Pedro's-Alio'et al.,1995).These populations are adapted to low light intensity and high sulfide concentration;they have a mixotrophic ability and form the so-called"deep chlorophyll maxima"(Gervais,1998;Marsha"and Laybourn-Parry,2002).A similar Cryptomonas sp.  相似文献