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51.
Costas Dounas Ian Davies George Triantafyllou Panayota Koulouri George Petihakis Christos Arvanitidis George Sourlatzis Anastasios Eleftheriou 《Continental Shelf Research》2007
Disturbance of the seabed resulting from bottom trawling affects ecosystem processes, such as the rate and magnitude of nutrient regeneration. The potential responses of the plankton community arising from such effects can be modelled, provided that reliable data on the effects on nutrient fluxes are available. In a north Cretan outer continental shelf and upper slope fishing ground (Heraklion Bay, Crete, Eastern Mediterranean) we applied a new field instrument which can simulate the passage of trawl groundropes across the sea floor and made direct seasonal measurements of the rate of dissolved and particulate nutrient releases resulting from seabed disturbance. These observational data were then integrated in a 3D ecosystem model. Results revealed that bottom trawling may trigger off considerable productivity pulses, in addition to pulses from the natural seasonal cycle. 相似文献
52.
THE DEVELOPMENT OF SYMMETRIC DISTURBANCE SUPERPOSED ON BAROCLINIC FRONTAL ZONE UNDER THE ACTION OF DEFORMATION FIELD* 下载免费PDF全文
The development of symmetric disturbance superposed on the background field of Hoskins-Bretherton (1972) frontogenesis model is investigated by means of WKBJ approach,It is found that the forcing of large-scale deformation,the frontal circulation and the spatial-temporal variations of stability parameters (F2,N2,M2) can bring about the development of symmetric disturbance,even though the frontal baroclinic flow is symmetric stable (F2N2-M2>0),The frontogenetical process of deformation confluence zone and the ascending branch of frontal circulation are in favor of the development of symmetric disturbance,The actions of ageostrophic shear in frontal zone and the variation of stability parameters are dependent on the structure of disturbance. 相似文献
53.
夏季西风带定常扰动对东北亚阻塞高压的影响 总被引:6,自引:4,他引:6
利用ECMWF 1980~1988年9年的格点资料,分析了定常扰动与东北亚阻塞高压之间的关系。分析结果表明:定常扰动的分布对阻塞高压维持日数有着重要的影响,定常扰动的季节变化可以很好地说明阻塞高压冬季多在太平洋和大西洋上发生和维持,而夏季多在东北亚地区发生和维持的特征。此外,从定常扰动的分布可以看到,不仅中高纬地区上空的正距平强度可以影响着阻塞高压的发生和维持,其南侧的负距平强度也同样重要地影响着阻塞高压。分析结果还表明:不仅定常扰动的水平结构对阻高有着重要影响,其垂直结构亦有着重要影响。最后,对夏季定常扰动进行了波数域分析,表明在夏季定常扰动的作用主要通过其中所包含的行星波、特别是行星波1波来实现,定常扰动中行星波部分的振幅变化是影响阻塞高压发生和维持的重要物理机制。 相似文献
54.
55.
用中国地磁台站的资料,研究了S_q逐日变化的形态学特征,用理论模型计算了磁层环电流、部分环电流、场向电流、磁尾电流、Chapman-Ferraro电流的地磁效应.在消除了这些磁层电流体系的影响之后,得到了电离层潮汐风发电机电流产生的磁场S_q变化.对1973年的资料研究表明,S_q发电机电流的逐日变化主要表现在强度上,即使在磁扰期间,也可以分离出形态稳定的S_q变化.由此提出了一种新的地磁指数——S_q指数,用来描述S_q发电机电流强度的逐日变化. 相似文献
56.
本文介绍渤海辽东湾实验区AI平台丛式定向井最后钻完的3口侧钻绕障井。在有邻井和本井套管磁干扰情况下,特别是与邻井间距最小仅为0.6m,采用陀螺定向侧钻以及导向钻井技术相结合,安全顺利的钻完了这3口井。总结和介绍了侧钻、防碰的工艺特声,以及安全措施。研究和分析了使用陀螺定向侧钻,钻速与造斜率,井眼轨迹合理控制等问题。 相似文献
57.
58.
The terrestrial noise in the differencial data of geomagnetic total field recorded at 21h in North China was fitted by using
the geomagnetic vector data from Beijing Observatory. The terrestrial noise level and its spatial feature in this region was
discussed. A method, which may be useful for justifying the quality of fitting, was provided in this paper. The analysis indicates
that the terrestrial noise is one of the important noise in tectonomagnetic study. It is shown that the susceptibility effect
is quite small and the orientation effect is the main component in the terrestrial noise in North China. The rough spatial
feature of the magnetic anomaly in crustal substance was infered from the spatial feature of terrestrial noise. The measurement
precision and the source noise level of data at 21h in this region were obtained in the analysis of residual noise.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 441–447, 1993. 相似文献
59.
ABSTRACTSoil structure-dependent parameters can vary rapidly as a consequence of perturbing events such as intense rainfall. Investigating their short-term changes is therefore essential to understand the general behaviour of a porous medium. The aim of this study is to gain insight into the effects of wetting, perturbation and recovery processes through different sequences of Beerkan infiltration experiments performed on a sandy-loam soil. Two different three-run infiltration experiments (LHL and LLL) were carried out by pouring water at low (L, non-perturbing) and high (H, perturbing) heights above the soil surface and at short time intervals (hours, days). The results demonstrate that the proposed method allows one to capture short-term variations in soil structure-dependent parameters. The developed methodology is expected to simplify the parameterization of hydrological models with temporally variable soil hydraulic properties. 相似文献
60.
Unicellular gametophytes ofUndaria pinnatifida (Harv.) Sur. were isolated in Qingdao, P. R. China in April 1993 and in Tokushima, southern Japan in March 1995. Different
intraspecific crossings by using unicellular male and female gametophytes were successfully undertaken in Sept. of 1995 in
Qingdao. Sporophytes were transplanted to two different locations for open sea cultivation. One was at Zhanqiao (ZQ) Bay where
the water current was slower than that of another location—Taipingjiao(TPJ). A total of 218 adult sporophytes were harvested
on January 12 and 18 from TPJ and ZQ respectively. For eacn combination, 10 sporophytes were cultivated. Analysis of the morphological
characteristics of adult sporophytes indicated that the longest length between two bases of the serration of pinnate blades
(W2) is a morphological characteristic that can be transferred from the parent plant to the next generations regardless of
environmental variations. There was evidence that W2 was apparently determined by sex-linked factors, i.e., by male parental
gametophyte. Sporophytes from certain crossing combinations showed more vigorous growth than those from other crossing combinations.
It is therefore possible to select gametophyte strains which can be used as parental gametophytes for the seedling production
of sporophytes with more vigorous growth within shorter cultivation period. The morphology of hybrids from a Qingdao strain
and a Tokushima cultivated strain resembled that of both parental plants in frond features (wrinkled or smooth) and W2. Sporophyll
formation also varied with strains. The fact that adult sporophytes resulting from the same crossing combinations have identical
morphological characteristics under the same environmental conditions indicates the possibility of a new way to select strains
which are expected to be ideal for commerical production by purposely selecting, propagating, and seeding unicellular gametophytes
for sporeling production through freeliving techniques of gametophytes.
Project 39400102 supported by NSFC, also supported by National Climbing Plan B (PD-B642); and Bioengineering Center, SSTC. 相似文献