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241.
Armando Bazzani Stefano Marmi Giorgio Turchetti 《Celestial Mechanics and Dynamical Astronomy》1989,47(4):333-359
We prove that non resonant isochronous symplectic maps in a neighborhood of an elliptic fixed point are stable for exponentially long times with the inverse of the distance from the fixed point. In the proof we make use of the majorant series method together with an idea for optimizing remainder estimates first applied to Hamiltonian problems by Nekhoroshev. 相似文献
242.
Z. Schenková V. Schenk I. Kalogeras R. Pichl P. Kottnauer C. Papatsimba G. Panopoulou 《Journal of Seismology》2007,11(3):345-353
Macroseismic intensity, a useful measure of earthquake effects, is still applied in a wide range of seismological applications
like seismic hazard assessments, attenuation relationships, etc. Isoseismals represent the spatial distribution of macroseismic
intensities, and their shapes depend on source properties, lithosphere structures, tectonic line orientations, site geology,
and topography. The applications ask for both the higher number of isoseismal maps, and their standardization and homogenization.
The point kriging gridding method for an automatic computer drawing of isoseismal maps was delivered. Smoothing rates and
numerical parameters used in the kriging algorithm were tested on macroseismic data of Greek earthquakes representing different
tectonic and geomorphological regimes. The optimum kriging default option was defined. Its application for four Greek earthquakes
is presented and discussed from the viewpoint of a broad use in recent macroseismology.
The online version of the original article can be found at . 相似文献
243.
Suzette G. A. Flantua John H. van Boxel Henry Hooghiemstra John van Smaalen 《Climate Dynamics》2007,29(7-8):697-712
Climate changes affect the abundance, geographic extent, and floral composition of vegetation, which are reflected in the
pollen rain. Sediment cores taken from lakes and peat bogs can be analysed for their pollen content. The fossil pollen records
provide information on the temporal changes in climate and palaeo-environments. Although the complexity of the variables influencing
vegetation distribution requires a multi-dimensional approach, only a few research projects have used GIS to analyse pollen
data. This paper presents a new approach to palynological data analysis by combining GIS and spatial modelling. Eastern Colombia
was chosen as a study area owing to the migration of the forest–savanna boundary since the last glacial maximum, and the availability
of pollen records. Logistic regression has been used to identify the climatic variables that determine the distribution of
savanna and forest in eastern Colombia. These variables were used to create a predictive land-cover model, which was subsequently
implemented into a GIS to perform spatial analysis on the results. The palynological data from the study area were incorporated
into the GIS. Reconstructed maps of past vegetation distribution by interpolation showed a new approach of regional multi-site
data synthesis related to climatic parameters. The logistic regression model resulted in a map with 85.7% predictive accuracy,
which is considered useful for the reconstruction of future and past land-cover distributions. The suitability of palynological
GIS application depends on the number of pollen sites, the distribution of the pollen sites over the area of interest, and
the degree of overlap of the age ranges of the pollen records. 相似文献
244.
Isoseismal maps drawing by the kriging method 总被引:1,自引:0,他引:1
Z. Schenková V. Schenk I. Kalogeras R. Pichl P. Kottnauer C. Papatsimba G. Panopoulou 《Journal of Seismology》2007,11(1):121-129
Macroseismic intensity, a useful measure of earthquake effects, is still applied in a wide range of seismological applications
like seismic hazard assessments, attenuation relationships, etc. Isoseismals represent the spatial distribution of macroseismic
intensities and their shapes depend on source properties, lithosphere structures, tectonic line orientations, site geology
and topography. The applications ask for both the higher number of isoseismal maps and their standardization and homogenization.
The point kriging gridding method for an automatic computer drawing of isoseismal maps was delivered. Smoothing rates and
numerical parameters used in the kriging algorithm were tested on macroseismic data of Greek earthquakes representing different
tectonic and geomorphological regimes. The optimum kriging default option was defined. Its application for four Greek earthquakes
is presented and discussed from viewpoint of a broad use in recent macroseismology.
An erratum to this article can be found at 相似文献
245.
In this study, a Markov Random Field (MRF) approach is used to locate source boundary positions which are difficult to identify
from Bouguer gravity and magnetic maps. As a generalized form of Markov Chains, the MRF approach is an unsupervised statistical
model based algorithm and is applied to the analysis of images, particularly in the detection of visual patterns or textures.
Here, we present a dynamic programming based on the MRF approach for boundary detection of noisy and super-positioned potential
anomalies, which are produced by various geological structures. In the MRF method, gravity and magnetic maps are considered
as two-dimensional (2-D) images with a matrix composed of N1 × N2 pixels. Each pixel value of the matrix is optimized in real time with no a priori processing by using two parameter sets; average steering vector (θ) and quantization level (M). They carry information about the correlation of neighboring pixels and the locality of their connections. We have chosen
MRF as a processing approach for geophysical data since it is an unsupervised, efficient model for image enhancement, border
detection and separation of 2-D potential anomalies. The main benefit of MRF is that an average steering vector and a quantization
level are enough in evaluation of the potential anomaly maps. We have compared the MRF method to noise implemented synthetic
potential field anomalies. After satisfactory results were found, the method has been applied to gravity and magnetic anomaly
maps of Gelibolu Peninsula in Western Turkey. Here, we have observed Anafartalar thrust fault and another parallel fault northwest
of Anafartalar thrust fault. We have modeled a geological structure including a lateral fault, which results in a higher susceptibility
and anomaly amplitude increment. We have shown that the MRF method is effective to detect the broad-scale geological structures
in the Gelibolu Peninsula, and thus to delineate the complex tectonic structure of Gelibolu Peninsula. 相似文献
246.
A. Kirfel T. Lippmann P. Blaha K. Schwarz D. F. Cox K. M. Rosso G. V. Gibbs 《Physics and Chemistry of Minerals》2005,32(4):301-313
A generalized X-ray scattering factor model experimental electron density distribution has been generated for the orthosilicate forsterite, using an essentially extinction and absorption free set of single crystal diffraction data recorded with intense, high energy synchrotron X-ray radiation (E=100.6 keV). A refinement of the model converged with an R(F)=0.0061. An evaluation of the bond critical point, bcp, properties of the distribution at the (3, –1) stationary points for the SiO and MgO bonded interactions, yielded values that agree typically within ~5%, on average, with theoretical values generated with quantum chemical computational strategies, using relatively robust basis sets. On the basis of this result, the modeling of the experimental distribution is considered to be adequate. As the bcp properties increase in magnitude, the MgO and SiO bonds decrease in length as calculated for a number of rock forming silicates. As asserted by Coppens (X-ray charge densities and chemical bonding. Oxford University Press, Oxford, 1997), large negative 2(rc) values, characteristic of shared interactions involving first row atoms, may not be characteristic of closed shell covalent bonded interactions involving second row Si, P and S atoms bonded to O. This study adds new evidence to the overall relatively good agreement between theoretical bcp properties generated with computational quantum strategies, on the one hand, and experimental properties generated with single crystal high energy synchrotron diffraction data on the other. The similarity of results not only provides a basis for using computational strategies for studying and modeling structures, defects and the reactivity of representative structures, but it also provides a basis for improving our understanding of the crystal chemistry of earth materials and the character of the SiO bonded interaction. 相似文献
247.
E.W. Grafarend 《Journal of Geodesy》2005,78(10):594-615
Harmonic maps are generated as a certain class of optimal map projections. For instance, if the distortion energy over a meridian strip of the International Reference Ellipsoid is minimized, we are led to the Laplace–Beltrami vector-valued partial differential equation. Harmonic functions x(L,B), y(L,B) given as functions of ellipsoidal surface parameters of Gauss ellipsoidal longitude L and Gauss ellipsoidal latitude B, as well as x(,q), y(,q) given as functions of relative isometric longitude =L–L0 and relative isometric latitude q=Q–Q0 gauged to a vector-valued boundary condition of special symmetry are constructed. The easting and northing {x(b,),y(b,)} of the new harmonic map is then given. Distortion energy analysis of the new harmonic map is presented, as well as case studies for (1) B[–40°,+40°], L[–31°,+49°], B0= ±30°, L0=9° and (2) B[46°,56°], L{[4.5°, 7.5°]; [7.5°, 10.5°]; [10.5°,13.5°]; [13.5°,16.5°]}, B0= 51°, L0 {6°,9°,12°,15°}. 相似文献
248.
Computer-assisted navigation systems provide navigation information to automobile drivers and are now available. They are capable of storing, processing and displaying information about street networks. The display typically mimics a printed street map. The underlying capabilities of these systems present unique opportunities for geographers to study spatial cognition, wayfinding, spatial search, the impact of spatial information on trip behavior, and market responses to potentially different travel patterns. Such systems are reviewed and key areas for future research are identified. 相似文献
249.
在地图的色彩设计中,设计人员不仅要考虑色彩单独使用的效果,而且要考虑地图上各素的色彩配合,即各种色彩在图面上的整体感受效果。电子地图由于有极大的色彩选择空间,背景色不局限于白色,因而选色、配色比纸质地图更加复杂。用哪种简称颜色作为背景视觉效果较好?图面上各要素的色彩如何配合?针对这两个问题,作者设计了电子地图的一个色彩感受实验-色彩配合实验,利用自编的电子地图视觉感受测试构件(TEVP)进行了实验 相似文献
250.
A first generation of probabilistic seismic hazard maps of the Italian country are presented. They are based on seismogenic zoning deriving from a kinematic model of the structural tectonic units and on an earthquake catalogue with the foreshock and aftershock events filtered out. The following ground motion parameters have been investigated and mapped using attenuation equations based on strong-motion recordings of Italian earthquakes: peak ground acceleration and velocity; Arias intensity; strong motion duration; and the pseudovelocity and pseudoacceleration spectral values at 14 fixed frequencies both for the vertical and the largest horizontal component. A Poissonian model of earthquake occurrence is assumed as a default and the hazard maps are presented in terms of ground motion values expected to be exceeded at a 10% probability level in 50 years (return period 475 years) according to the requirement of Eurocode 8 for the seismic classification of national territories, as well as in terms of exceedance probabilities of selected ground motion values. Finally, as a tentative study, the use of hybrid methods (implementing both seismogenic zones and structures), renewal processes (including earthquake forecasting) and the influence of site effects (as the basis for the planning of earthquake scenarios) were explored. 相似文献