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131.
通过横流太平洋往返两个航次随船调查,研究了采用气象导航对减少燃油消耗和保证船舶安全、班期等,不但有定的经济效益,而且是一种非常有效的航运管理方法。 相似文献
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The Holocence paleolimnology of Lake Sämbosjön is described using geochemical and diatom analyses. The objective of this study is the reconstruction of major changes in trophic state and productivity, and to interpret the major causative processes. The accumulation of organic matter indicates a relatively high productivity in early Holocene, and the diatom analysis indicates a relatively high trophic state and pH. A succeeding decrease in productivity and trophic state and lowering in pH is recorded from about 8000 BP. If lake development had been primarily edaphically conditioned, viz. determined by nutrient supply from catchment soils, such a progressive oligotrophication would represent the common development of temperate lakes. Between about 6000 BP and 4000 BP Lake Sämbosjön was characterized by relatively stable productivity and pH. From about 4000 BP the analyses reveal an increase again in trophic state, productivity, and in pH. This eutrophication, which continued throughout the late Holocene, was caused by an exceptionally strong human influence on the catchment of Lake Sämbosjön. The increased supply of nutrients from cleared and deforested catchment soils changed the trophic state and provided the basis for increased lake productivity. 相似文献
134.
澜沧—耿马地震震源动力学参数研究 总被引:8,自引:5,他引:8
本文使用沧澜—耿马地震主震后在震区建立的数字地震仪记录,用波谱法测算澜沧—耿马余震的震源动力学参数。就这些参数的统计特征,对该双主震型两主震区的地下介质不同状态予以讨论。 相似文献
135.
在我国东部沿海修建地下水封石洞油库若干问题的探讨 总被引:2,自引:0,他引:2
随着我国大陆架油、气田不断被发掘、开采,石油储运问题已指日可待。我国海岸线的基岩岸约占全长的2/3以上,其中,块状结晶岩体又占基岩岸的一半以上,这就给水封油库的布置提供了良好的基础。在油库的选择和兴建中,应加强对建库岩体和主要结构面、地应力及其分布的充分研究,以期能对洞库稳定问题、地下水位及水量的合理确定问题有所裨盖、 相似文献
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Immature Torbanite and the resistant biopolymer (PRB A) isolated from extant B. braunii were previously compared using bulk spectroscopic methods. In the present work, analysis of 400°C pyrolysis products and pyrolysis residues provided further information on their structure and possible relationships. It appears that such polymers are based upon unbranched, saturated, cross-linked hydrocarbon chains up to C31. In addition to these bridging structures, a substantial part of the alkyl chains is singly bound, as esters of unbranched, saturated or cis unsaturated, even fatty acids. These esters are sterically protected, against chemical degradations, by the network of the bioand geopolymer.Quantitative and qualitative observations derived from 400°C pyrolysis confirm that the chemical structure of PRB A and immature Torbanite are closely related. The pyrolysis residues show a similar evolution and numerous common features are noted, with respect to the nature and the distribution of the major constituents of the pyrolysates (hydrocarbons and fatty acids). Accordingly, Botryococcus provides what seems to be the first example of a close structural relationship between a biopolymer produced in large amounts by an extant alga and the geopolymer of an immature kerogen. The essential role of PRB A in Torbanite formation is ascertained. Moreover, it is found that the resistant biopolymer does not undergo important structural changes during the first stages of diagenesis. Thus, owing to steric protection, the esters of immature Torbanite show a distribution quite close to the one of PRB A esters, with exclusively even constituents and a large contribution of unsaturated acids.Recent observations pointed to the possible genesis of some algal kerogens principally by selective preservation of resistant macromolecules. Such a type of formation is clearly predominant in Torbanite, where the bulk of the fossil organic matter corresponds to a selectively preserved and weakly altered, resistant biopolymer, while incorporation of lipids into the kerogen structure during diagenesis seems to play a minor role. 相似文献
138.
本文通过对桩的荷载传递和沉降分析,研判了桩的极限载荷的极限状态,并结合工程实例予以说明。根据文献提供的资料,建议桩的极限荷载宜采用S-logP法确定。 相似文献
139.
本文根据白家疃台60年代以来的短周期地震记录图,分析了区域震相的强度比。研究表明:Sn/Lg波的强度比波传播路径上岩石层热结构、热状态及强地震活动等均有相关性,并就这种相关性对于强地震成因及其预测研究的直接意义进行了讨论。 相似文献
140.