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91.
92.
P. Goovaerts 《Mathematical Geology》1998,30(5):511-534
This paper presents both estimation and simulation as optimization problems that differ in the optimization criteria, minimization of a local expected loss for estimation and reproduction of global statistics (semivariogram, histogram) for simulation. An intermediate approach is proposed whereby an initial random image is gradually modified using simulated annealing so as to better match both local and global constraints. The relative weights of the different constraints in the objective function allow the user to strike a balance between smoothness of the estimated map and reproduction of spatial variability by simulated maps. The procedure is illustrated using a synthetic dataset. The proposed approach is shown to enhance the influence of observations on neighboring simulated values, hence the final realizations appear to be better conditioned to the sample information. It also produces maps that are more accurate (smaller prediction error) than stochastic simulation ignoring local constraints, but not as accurate as E-type estimation. Flow simulation results show that accounting for local constraints yields, on average, smaller errors in production forecast than a smooth estimated map or a simulated map that reproduces only the histogram and semivariogram. The approach thus reduces the risk associated with the use of a single realization for forecasting and planning. 相似文献
93.
R. Müller J.-U. Grooß D. S. McKenna P. J. Crutzen C. Brühl J. M. Russell III L. L. Gordley J. P. Burrows A. F. Tuck 《Annales Geophysicae》1998,17(1):101-114
Severe chemical ozone loss has been detected in the Arctic in the winter and spring of 1995–96 by a variety of methods. Extreme reductions in column ozone due to halogen catalysed chemistry were derived from measurements of the Halogen Occultation Experiment (HALOE) on board the Upper Atmosphere Research Satellite in the Arctic vortex. Here, we discuss further aspects of the HALOE observations in the Arctic over this period. Potential problems, both in the data themselves and in the methodology of the data analysis are considered and the reason for the differences between the Arctic ozone losses deduced from HALOE data version 17 and 18 is analysed. Moreover, it is shown that HALOE measurements in the Arctic in winter and spring 1995–96 compare well with observations by other ground-based and satellite instruments. 相似文献
94.
新疆破坏性地震损失“盲估”方法 总被引:1,自引:1,他引:0
通过总结新疆近年来的震害预测研究成果和震害损失评估工作的实践,给出了震后损失快速评估方法-“盲估”方法。提出今后震灾评估的发展方向是建立震后趋势快速判定计算机管理系统。 相似文献
95.
为快速了解破坏性地震发生后建筑物破坏所造成的人员伤亡和经济损失,合理投入救灾所需人、财、物,便于领导决策和指挥,提出震后经济损失和人员伤亡快速预估方法。依据地震发生的基本参数、地震地质条件等预估灾害范围、建筑物破坏程度、经济损失、人员伤亡等情况,给出地震发生早期影响尺度的快速预测结果。 相似文献
96.
V.A. Osinov 《Soil Dynamics and Earthquake Engineering》1998,17(1):13-28
A theoretical investigation of plane waves in granular soils is presented. Dynamic equations are derived with the use of the hypoplasticity theory for granular materials. For numerical calculations the material parameters of Karlsruhe sand are used. Wave speeds as slopes of characteristics of the dynamic equations are calculated for various stresses and densities. It is shown that under certain conditions the dynamic equations lose hyperbolicity and the initial boundary value problem thus becomes ill-posed. Two types of ill-posedness are found, known as flutter ill-posedness and stationary discontinuity. The latter is shown to arise at higher shear stress than the former. A comparison is made between dynamic ill-posedness and stability of static equilibrium. With the use of the second-order work stability criterion it is found that the dynamic equations lose hyperbolicity when the static equilibrium under a dead load is still stable. Numerical solutions to the problem of propagation of boundary disturbance in a half-space are obtained. Owing to dilatancy and contractancy of the granular material, a purely transverse disturbance induces a longitudinal component of velocity in the wave, and vice versa. 相似文献
97.
上海旱地农田氮磷随地表径流流失研究 总被引:14,自引:0,他引:14
选择上海宝山罗店镇具有代表性的旱地蔬菜农田生态系统,从2004年3月到8月的近半年时间里,通过对径流及径流中侵蚀泥沙的氮磷流失情况的连续监测,研究了旱地农田施肥与氮磷流失污染之间的关系,探讨了农田氮磷的迁移特征及环境效应,主要结果表明:当季施用化肥的地表径流总流失量,总氮为32.77kg/hm^2,总磷为8.1kg/hm^2,随径流排出农田的氮素中有37.7%是当季施用的氮素化肥,磷素中有26.9%是当季施用的磷素化肥;从过量施肥与环境污染之间的“因”与“果”来看,减量15%施肥区相比常规施肥区的茄子的产量减少2.7%,但是其污染负荷却减少了13.4%,表明在化肥利用的有效性上或增施化肥与控制环境污染之间,应该寻找一个最佳的平衡点。 相似文献
98.
Roland Walter 《Astrophysics and Space Science》2007,309(1-4):5-9
INTEGRAL is operational since more than three years and producing high quality data that allows to detect fainter new hard
X-ray sources. The new sources, identified until now, are mostly active galactic nuclei and absorbed or transient high mass
X-ray binaries. TeV emission could be expected from the new high mass X-ray binaries accreting dense clumps of stellar wind.
INTEGRAL sources with TeV counterparts are discussed.
Based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially
the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic and Poland, and with the participation
of Russia and the USA. 相似文献
99.
Infrared Characteristics of Associated Sources of Water Masers 总被引:2,自引:0,他引:2
Jarken Esimbek 《中国天文和天体物理学报》2005,5(6):587-594
We present an analysis of the infrared properties of 1417 water masers collected from the literature published by December 2004. The associated infrared sources of the water masers were identified with IRAS and MSX (Midcourse Space Experiment) catalogues. There are 1252 water masers associated with IRAS sources within 1', which include 700 interstellar and 552 stellar sources. For 382 sources, the IRAS counterpart identification and the maser classification are new. We found the colors of the interstellar maser sources are much redder than those of the stellar ones at IRAS wavelength bands; 99% of the interstellar maser sources are above black body line, while 95% of the stellar masers are below. The distribution difference of the two kinds of masers shown in the color-color diagram is due to their different optical depths and temperature distributions of dust regions. There are 743 water masers with MSX counterparts, of which 552 are interstellar masers and 191 are stellar masers. MSX colors of the associated sources of water masers are here analyzed for the first time. The color differences among the MSX bands are small and the interstellar masers are redder than the stellar masers. There is a correlation between the intensity of the stellar water maser emission and that of the 12μm and 25μm emissions, while there is no correlation between the water maser emission and the 8 μm emission. The infrared intensity increases with increasing wavelength for the interstellar masers, while it is the opposite for stellar masers. These results may provide clues for the pumping of water maser and for the properties of the two kinds of maser emission regions. 相似文献
100.