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201.
张训华 《海洋地质与第四纪地质》1994,14(4):95-100
本文简要介绍了局控项目《中国海区1∶50万区域地质编图(大连幅)》重力异常图、磁力异常图的编制过程,给出了一种以计算机为手段、实现编图自动化的新方法,并分析了该方法与以往编图方法的不同和优点,以国际分幅在中国海区开展区域地质编图尚属首次,在既无海区地质调查规范,又无海区地质调查编图规范的情况下,这一工作无异具有开创性。从理论上系统总结出一套切实可行的编图方法,对于编制中国海区区域地质调查编图规范以 相似文献
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Japanese fisheries production in the Japan/East Sea between 1958 and 2003 increased to their peak (1.76 million tons) in the late 1980s and decreased abruptly with the collapse of Japanese sardine. Catch results for 58 fisheries and various environmental time-series data sets and community indices, including mean trophic level (MTL) and Simpson’s diversity index (DI), were used to investigate the impacts of fishing and climate changes on the structure of the fish community in the Tsushima warm current (TWC) region of the Japan/East Sea. The long-term trend in fisheries production was largely dependent on the Japanese sardine that, as a single species, contributed up to 60% of the total production in the Japanese waters of the Japan/East Sea during the late 1980s. Excluding Japanese sardine, production of the small pelagic species was higher during 1960s and 1990s but lower during 1970s and 1980s. This variation pattern generally corresponds with the trend in water temperature, warmer before early 1960s and after 1990s but colder during 1970s and 1980s. The warm-water, large predatory fishes and cold water demersal species show opposite responses to the water temperature in the TWC region, indicating the significant impact of oceanic conditions on fisheries production of the Japan/East Sea. Declines in demersal fishes and invertebrates during 1970s and 1980s suggested some impact of fishing. MTL and DI show a similar variation pattern: higher during 1960s and 1990s but lower during 1970s and 1980s. In particular, the sharp decline during the 1980s resulted from the abundant sardine catches, suggesting that dominant species have a large effect on the structure of the fish community in the Japan/East Sea. Principal component analysis for 58 time-series data sets of fisheries catches suggested that the fish community varied on inter-annual to inter-decadal scales; the abrupt changes that occurred in the mid-1970s and late 1980s seemed to correspond closely with the climatic regime shifts in the North Pacific. These results strongly suggest that the structure of the fish community in the Japan/East Sea was largely affected by climatic and oceanic regime shifts rather than by fishing. There is no evidence showing “fishing down food webs” in the Japan/East Sea. However, in addition to the impacts of abrupt shifts that occurred in the late 1980s, the large predatory and demersal fishes seem to be facing stronger fishing pressure with the collapse of the Japanese sardine. 相似文献
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Jos Rafael García‐March Antonio Manuel García‐Carrascosa lvaro Luís Pea 《Marine Ecology》2002,23(3):207-217
Abstract. Pinna nobilis Linnaeus 1758 is an endemic bivalve mollusc in the Mediterranean Sea, where it inhabits seagrass meadows, especially Posidonia oceanica (L.) Delile. It is the largest bivalve in the Mediterranean, reaching lengths up to 120 cm. In its natural habitat, P. nobilis lives with the anterior part of the valve buried in the seabed, attached to Posidonia rhizomes by byssus threads. This habit makes it impossible to measure its total length directly in situ. As the only way to determine the individual age is the relationship between age and total length, several equations have been proposed to estimate total length by relating it to the unburied parts of the shell. Such measurements are essential to ecological studies that consider age, growth, and population dynamics, and that evaluate the environmental factors that affect this species.Accurately estimating total length depends on the accuracy and precision of the method employed to measure the unburied shell parts. In this paper, we point out the lack of precision of the instruments and methods used until now; we also demonstrate the reason for this imprecision. A new device to measure unburied parts of Pinna nobilis with a precision comparable to that obtained when measuring extracted valves is described. This device is unaffected by substratum type and reduces measurement time. The latter is a very important feature, because these procedures are usually performed whilst SCUBA diving. Finally, a growth equation has been fitted to the measurements obtained with the new device from a population located in Moraira (Alicante, western Mediterranean). 相似文献
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从数据管理及后期应用的角度提出了数据平台的要领,讨论了该数据平台的物理结构、逻辑结构,在分类与组织的基础上给出了相应的数据字典。同时,还基于该平台探讨了测井曲线库及图形库的建设方法,并实现了具体功能。 相似文献
210.
The upper layer (above 140 m depth) temperature in the western Philippine Sea near Taiwan was sampled using a coastal monitoring
buoy (CMB) with 15 attached thermistors during July 28–August 7, 2005. The data were collected every 10 min at 1, 3, 5, 10,
15, and 20 m using the CMB sensors, and every 15 sec at 15 different depths between 25 m and 140 m. Internal waves and solitons
were identified from the time-depth plot of the temperature field. Without the internal waves and solitons, the power spectra,
structure functions, and singular measures (representing the intermittency) of temperature field satisfy the power law with
multi-scale characteristics at all depths. The internal waves do not change the basic characteristics of the multifractal
structure. However, the internal solitons change the power exponent of the power spectra drastically, especially in the low
wave number domain; they also break down the power law of the structure function and increase the intermittency parameter.
The physical mechanisms causing these different effects need to be explored further. 相似文献