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81.
The preservation of the organic-walled microbiota of the Lakhanda Lagerstätte in the Kumakha mudstone succession of the late Mesoproterozoic Lakhanda Group (Uchur-Maya region, southeast Siberia) is a result of unusually favorable paleoecologic, taphonomic, and diagenetic conditions. Well known for its marked taxonomic diversity and exquisite preservation, the biota inhabited a warm, shallow, epicontinental basin rich in nutrients into which were dispersed clay minerals, from weathering of continental crust, and minor amounts of volcanic detritus. The fossils were preserved by compression in fine-grained smectite–illite–kaolinite mudstones deposited in a sulfur-deficient disoxic and anoxic environment. Subsequently, the long-term (1 Ga) tectonic stability of the southeast margin of the Siberian platform has provided an exceptional environment for the preservation of the microfossil assemblage without significant diagenetic alteration. Conclusions drawn here from studies of the paleoecology, taphonomy, and diagenesis of the Lakhanda Lagerstätte may provide a globally useful model in the search for additional evidence of the Precambrian rise to dominance of eukaryotes in the Earth's biosphere. 相似文献
82.
Pole-to-pole moisture conditions for the IGY 总被引:1,自引:0,他引:1
Summary A study of the mean atmospheric humidity conditions on a planetary scale during the IGY covering the calendar year 1958 is presented. The fields of mean precipitable water content and of the zonal and meridional transports of water vapor are analyzed for the entire globe. Zonally averaged values of the various quantities at several levels are presented in tabular form and compared whenever possible with previous results or indirectly are analyzed on the basis of information obtained from different sources. The structure of these fields is studied and the corresponding implications for the general circulations of the atmosphere are discussed. Finally the zonal water balance for all the globe is discussed and its implications analyzed. 相似文献
83.
The formulation of a new land surface scheme (LSS) with vegetation dynamics for coupling to the McGill Paleoclimate Model (MPM) is presented. This LSS has the following notable improvements over the old version: (1) parameterization of deciduous and evergreen trees by using the models climatology and the output of the dynamic global vegetation model, VECODE (Brovkin et al. in Ecological Modelling 101:251–261 (1997), Global Biogeochemical Cycles 16(4):1139, (2002)); (2) parameterization of tree leaf budburst and leaf drop by using the models climatology; (3) parameterization of the seasonal cycle of the grass leaf area index; (4) parameterization of the seasonal cycle of tree leaf area index by using the time-dependent growth of the leaves; (5) calculation of land surface albedo by using vegetation-related parameters, snow depth and the models climatology. The results show considerable improvement of the models simulation of the present-day climate as compared with that simulated in the original physically-based MPM. In particular, the strong seasonality of terrestrial vegetation and the associated land surface albedo variations are in good agreement with several satellite observations of these quantities. The application of this new version of the MPM (the green MPM) to Holocene millennial-scale climate changes is described in a companion paper, Part II.
相似文献
Yi WangEmail: Phone: +1-514-3987448Fax: +1-514-3986115 |
84.
加卸载响应比(LURR)理论的实验研究 总被引:13,自引:1,他引:13
利用大尺度岩石试件破坏声发射实验,对加卸载响应比(Load/Unload Response Ratio)理论进行了实验研究。实验采用的加载条件力求能够模拟地下岩石的复杂受力过程。在加载过程中,岩石试件内部出现的损伤用声发射技术进行了记录。实验数据经过分析之后所得的结论与加卸载响应比理论预测的结果相符合。把加卸载响应比值Y的变化情况与声发射事件定位的过程相对比,也可以进一步看出岩石材料内部的损伤发展过程与加卸载响应比Y值的变化具有一致性。而高Y值的异常情况出现,又是在材料发生最终破坏之前,所以,可以用加卸载响应比理论定量地分析岩石试件损伤演化情况,从而对岩石材料的破坏及地震做出预测。实验结果再一次验证了加卸载响应比理论。 相似文献
85.
Victor A. Avdyushev 《Celestial Mechanics and Dynamical Astronomy》2003,87(4):383-409
Mainly, the author focuses on Baumgarte's method and its applications in satellite, asteroid, stellar and planetary problems. In the paper arguments are given for the use of energy relations for stabilization in the elliptical two-body problem. Stabilizing properties of Baumgarte's equations and others are discussed. A simple approach is proposed for stabilizing the equations of almost circular motion. By using Baumgarte's technique, the author derives stabilized equations of perturbed restricted three-body problem. It is shown experimentally that stabilization in the problems mentioned above can raise the accuracy of numerical integration by several orders. 相似文献
86.
Lara Alejandro Bucci Felipe Palma Cristobal Munizaga Juan Montre-Águila Victor 《Natural Hazards》2021,109(2):1935-1957
Natural Hazards - Chilean geography exposes the country to high-level risks such as earthquakes and tsunamis. The disasters of 1930, 1960, 2010, and 2014 testify to the continuous link between... 相似文献
87.
Giovanni Dolif Andre Engelbrecht Alessandro Jatobá Antônio José Dias da Silva José Orlando Gomes Marcos R. S. Borges Carlos A. Nobre Paulo Victor R. de Carvalho 《Natural Hazards》2013,65(3):1831-1847
Natural disasters, particularly those triggered by heavy rainfall, may cause major damage and death. However, if an accurate early warning is issued, the damage can be mitigated. In Latin America and Brazil, characteristics of socioeconomic development often lead to a disorderly growth of cities and, consequently, occupation and irregular construction in risk areas. Therefore, forecasts of heavy rainfall, as well as preventative and mitigatory actions based on meteorological data/alerts, are essential to saving lives and minimizing material loss. An event that would have benefited from such actions is that which occurred in the mountainous region of Rio de Janeiro in January 2011, when over 800 people lost their lives. This work describes the first research initiative on resilience engineering domain in systems to forecast heavy rains in Rio de Janeiro. The results indicate important sources of brittleness in the system that supports the work of meteorologists, mainly related to the technical and organizational framework, and suggests that the main source of resilience in dealing with critical situations is the tacit knowledge of experts. 相似文献
88.
Victor Fernandez Nascimento Nazli Yesiller Keith C Clarke Jean Pierre Henry Balbaud Ometto Pedro R. Andrade Anahi Chimini Sobral 《地理信息系统科学与遥感》2017,54(5):657-677
??The proper management of solid waste (SW) is a global environmental challenge. A major issue is the proper disposal of SW while balancing a wide range of criteria and working with different spatial data. In this study, we used geographic information system as a tool to perform multi-criteria decision analysis with an analytical hierarchy process to develop an environmental impact susceptibility model (EISM) for landfills. The model was applied to the state of California, USA and results are presented herein. In particular, the EISM considers factors such as geology, pedology, geomorphology, water resources, and climate as represented by 13 associated environmental indicators. The results of the EISM indicate that more than 75% of California’s territory is situated in areas with very low, low, and medium environmental impact susceptibility categories. However, in the remaining 25% of the state’s land, 61 landfills are located in the high and very high categories. These results are alarming because during the period from 2000 to 2015, these 61 landfills received approximately 308 million tons of SW, which corresponds to more than 57% of all SW disposed in California. The model results can be used toward mitigating the environmental impacts of these facilities. 相似文献
89.
Julia Suso Pere Blay Almudena Robert Victor Reglero Chris J. Eyles 《Astrophysics and Space Science》2001,276(1):299-309
LEGRI has been operating successfully on MINISAT-01 since its switch-on the 22nd of May 1997. HouseKeeping (HK) data have been continuously receivedfor nearly two years by LEGRI SOC in Valencia, and subsequently checked on adaily basis and then stored for long term monitoring analysis.LEGRI HouseKeeping data include three critical operating parameters:temperature, power and polarisation voltages. Six temperature sensors arespread over the different LEGRI units: Detector Unit, Data Processing Unit,High Voltage Unit and Star Sensor. Voltages are measured at eight differentpoints. Detector Unit temperature and polarisation voltage are thecritical parameters for LEGRI operation. Solid state detectors aresensitive to changes not only in polarisation but also in temperature.Around one and a half million of measurements for each of the HK fourteen parameters have been recorded and analysed. The data show a very remarkablestability, within the expected margins, and the averages are very close to theoptimal design values. Special attention has been paid to the detectorpolarisation voltages analysis with a mean value of 286 ± 2 V when the detectors are operating. Thermal control over all the LEGRI units shows a remarkable stability in their temperatures.On the detector plane a mean value of T
det = 13 ± 2 °C has been found.We can therefore conclude that LEGRI as a system has been operating withinits optimal design conditions. We also want to point out the excellentperformance of the MINISAT-01 thermal control system. 相似文献
90.