50 resultados para Carracci, Annibale, 1560-1609.


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Seasonal investigations of size-fractionated biomass and production were carried out from February 1992 to May 1993 in Jiaozhou Bay, China. Microplankton assemblages were separated into three fractions: pico-(0.7-2 mu m), nano- (2-20 mu m) and netplankton (20-200 mu m). The biomass was measured as chlorophyll a (Chl a), particulate organic carbon (POC) and particulate organic nitrogen (PON). The production was determined by C-14 and N-15 tracer techniques. The seasonal patterns in biomass, though variable, were characterized by higher values in spring and lower values in autumn and summer (for Chl a only). The seasonal patterns in production, on the other hand, were more clear with higher values occurring in summer and spring, and lower values occurring in autumn and winter. Averaged over the whole study period, the respective proportions of total biomass accounted for by net-, nano- and picoplankton were 26, 45 and 29% for Chl a, 32, 33 and 35% for POC, and 26, 32 and 42% for PON. The contributions to total primary production by net-, nano- and picoplankton were 31, 35 and 34%, respectively. The respective proportions of total NH4+-N uptake accounted for by net-, nano- and picoplankton were 28, 33 and 39% in the daytime, and 10, 29 and 61% at night. The respective contributions to total NO3--N uptake by net-, nano- and picoplankton were 37, 40 and 23% in the daytime, and 13, 23 and 64% at night. Some comprehensive ratios, including C/N biomass ratio, Chl a/C ratio, C uptake/Chl a ratio, C:N uptake ratio and the f-ratio, were also calculated size separately, and their biological and ecological meanings are discussed.

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Through 2-3-year (2003-2005) continuous eddy covariance measurements of carbon dioxide and water vapor fluxes, we examined the seasonal, inter-annual, and inter-ecosystem variations in the ecosystem-level water use efficiency (WUE, defined as the ratio of gross primary production, GPP, to evapotranspiration, ET) at four Chinese grassland ecosystems in the Qinghai-Tibet Plateau and North China. Representing the most prevalent grassland types in China, the four ecosystems are an alpine swamp meadow ecosystem, an alpine shrub-meadow ecosystem, an alpine meadow-steppe ecosystem, and a temperate steppe ecosystem, which illustrate a water availability gradient and thus provide us an opportunity to quantify environmental and biological controls on ecosystem WUE at different spatiotemporal scales. Seasonally, WUE tracked closely with GPP at the four ecosystems, being low at the beginning and the end of the growing seasons and high during the active periods of plant growth. Such consistent correspondence between WUE and GPP suggested that photosynthetic processes were the dominant regulator of the seasonal variations in WUE. Further investigation indicated that the regulations were mainly due to the effect of leaf area index (LAI) on carbon assimilation and on the ratio of transpiration to ET (T/ET). Besides, except for the swamp meadow, LAI also controlled the year-to-year and site-to-site variations in WUE in the same way, resulting in the years or sites with high productivity being accompanied by high WUE. The general good correlation between LAI and ecosystem WUE indicates that it may be possible to predict grassland ecosystem WUE simply with LAI. Our results also imply that climate change-induced shifts in vegetation structure, and consequently LAI may have a significant impact on the relationship between ecosystem carbon and water cycles in grasslands.

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本文以863-512型号项目为背景,从运动特性、运动描述、运动控制以及运动规划等几个方面研究履带式移动机器人的行动规划技术;首先从理论上分析了履带式移动机器人的内在运动传递机理,指出了其区别于轮式移动载体的独特的运动特性,尤其是在其转向特性方面,得出了履带式移动机器人运动角速度几乎不可控原理、原地转弯转不准问题、以及履带式车辆行动规划时所要遵循的规则等重要结论,针对履带式移动机器人的纵向运动控制问题,讨论了其速度控制模型,提出了一种速度测量与控制的简单、准确、可靠的方法。在磺向运动方面,提出了一种基于FM-LIKE和AM-LIKE相结合的复合控制技术,解决了难度较大的方向控制问题。最后提供了实验结果,证明了上述方法与结论的正确性。上述方法与结论,作为863-512某型号任务的一部分,业已通过验收。

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The recent years research indicated that middle-south section of Da Hinggan Mountains metallogenic belt has two periods(Hercynian and Yanshanian) characteristics of metallogenesis, as well as the most of ore deposits in the area closely relate to Permian strata. Longtoushan ore deposit discovered in 2004 is an Ag-Pb-Zn polymetallic ore deposit born in Permian and located in the east hillside of the metallogenic belt, which has considerable resources potentials. It has important research value for its good metallogenic location and blank research history. Base on the detail field geology studies, the geology characteristics of "two stages and three kinds of metallogensis" has established. According to further work through geochemistry research including trace element, REE, S, Pb and Sr isotope, as well as petrography, microtemperature measurement, Laser Raman analysis and thermodynamics calculation of fluid inclusion, origin and characteristic of the ore-forming material and fluid has been discussed. And a new technology of single pellet Rb-Sr isochrones has been tried for dating its born time. Bae on above work, study of ore deposit comparison has been carried out, and metallogesis controlling factor and geological prospecting symbol have been summarized. Finally, metallogenic model and prospecting model have been established. According to above, the next step work direction has been proposed. Main achievement of the paper are listed as follow: 1.Longtoushan ore deposit has experienced two metallogenic periods including hot-water sedimentation period and hydrothermal reformation period. There are three kinds of metallizing phase: bedded(or near-bedded) phase, vein-shaped phase and pipe-shaped phase. The mian metallogenic period is hot-water sedimentation period. 2.Ore deposit geochemistry research indicated that the metal sulfides have charcateristic of hot-water sedimentation metallogensis, but generally suffered later hydrothermal transformation. The barite mineral isotope content is homogenous, showing the seabed hot-water sedimentation origin characteristic. Wall rock, such as tuff is one of metallogenic material origins. Both of Pb model age and Rb-Sr isochrone research older age value than that of strata, possibly for been influenced by hydrothermal transformation, and interfusion of ancient basis material. 3.There are two kinds of main metallogenic fluid inclusion in barite of the Longtoushan ore deposit, which are rich gas phase( C type) and liquid phase (D type). Their size is 2~7um, and principal components is H2O. Both kinds of fluid inclusion have freezing point temperature -7.1~-2.4℃ and -5.5~-0.3℃, salinity 4.0~10.6wt% and 0.5~8.5wt%, homogeneous temperature 176.8~361.6℃ and 101.4~279.9℃, which peak value around 270℃ and 170℃, respectively. Density of the ore-forming fluid is 0.73~0.97g/cm3, and metallogenic pressure is 62.3×105~377.9×105Pa. Above characteristic of the fluid inclusion are well geared to that of ore deposit originated in seabed hot-water sedimentation. 4.Through the comparison research, that Longtoushan ore deposit has main characteristic of hot-water sedimentation ore deposit has been indicated. Ore-forming control factor and prospecting symbol of it has been summarized, as well as metallogenic model and prospecting model. Next step work direction about prospecting has also been proposed finally.

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依托GIS与RS技术,以广西省都安瑶族自治县为研究载体,采用TM影像为背景资料.辅以地形图、土地利用图、地质图、土壤图以及GPS实测数据库等相关资料综合分析,建立石漠化分级的遥感影像解译指标体系,生成都安县石漠化分级分布图和数字化土壤类型图;运用GIS空间分析功能.定量探讨不同级别石漠化与土壤类型之间的空间相互关系。