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Natan Micheletti Loris Foresti Sylvain Robert Michael Leuenberger Andrea Pedrazzini Michel Jaboyedoff Mikhail Kanevski 《Mathematical Geosciences》2014,46(1):33-57
This paper explores the use of adaptive support vector machines, random forests and AdaBoost for landslide susceptibility mapping in three separated regions of Canton Vaud, Switzerland, based on a set of geological, hydrological and morphological features. The feature selection properties of the three algorithms are studied to analyze the relevance of features in controlling the spatial distribution of landslides. The elimination of irrelevant features gives simpler, lower dimensional models while keeping the classification performance high. An object-based sampling procedure is considered to reduce the spatial autocorrelation of data and to estimate more reliably generalization skills when applying the model to predict the occurrence of new unknown landslides. The accuracy of the models, the relevance of features and the quality of landslide susceptibility maps were found to be high in the regions characterized by shallow landslides and low in the ones with deep-seated landslides. Despite providing similar skill, random forests and AdaBoost were found to be more efficient in performing feature selection than adaptive support vector machines. The results of this study reveal the strengths of the classification algorithms, but evidence: (1) the need for relying on more than one method for the identification of relevant variables; (2) the weakness of the adaptive scaling algorithm when used with landslide data; and (3) the lack of additional features which characterize the spatial distribution of deep-seated landslides. 相似文献
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Carlos Frajuca Fabio da Silva Bortoli Natan Vanelli Garcia Nadja Simao Magalhaes 《Astronomische Nachrichten》2024,345(2-3):e230177
An experimental set up was proposed to determine the speed of gravitational signals traveling in air or in some other medium. It involves two vibrating masses—the emitters, which will be the sources of periodic tidal gravitational signals—and one sapphire-made mass that will act as a detector, positioned between the two emitters. The detector is planned to be suspended in vacuum and cooled down to 4.2 K, and its vibrational amplitude should be measured by a microwave signal (with ultra-low phase-noise) that is expected to resonate with the whispering gallery modes inside the detector. The mechanical and electrical quality factors of sapphire are quite high, yielding a very narrow detection band that reduces the detector sensitivity while amplifying the phase difference of the emitters' signals. The frequencies of the normal modes of the detector were previously determined using a finite element program. In this work, these frequencies are applied to the calculation of a first estimate of the sensitivity of the experiment. 相似文献
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Our aim is to theorize the shifting relationship between cities and the biosphere in ways that can incorporate vanguard scientific, technical and social innovations. We specify that the city (a) generates third natures - specific new environments - such as heat islands, that today are destructive of the biosphere, and (b) that the city has systemic properties that correspond to those of the biosphere, but today are mostly flattened out of action through the ruptures that dominate today's articulation between cities and biosphere. That is to say, our specific project agrees with the problematizing of the category “nature,” which pertains to our presence in the biosphere. But we do not take Harvey's more absolute statement that the city itself is nature nor do we confine our analysis only to Latourian natures-cultures. Our analysis is less centered in the work of correcting a false binary, as is the case with both Latour and Harvey, notwithstanding their different objects of study. We focus on the complex in-between space that is the site of both the transactions between city and biosphere, as well as the site of the ruptures that characterize these transactions. 相似文献
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Jordanova V.K. Thorne R.M. Farrugia C.J. Dotan Y. Fennell J.F. Thomsen M.F. Reeves G.D. McComas D.J. 《Solar physics》2001,204(1-2):361-375
We study the development of the terrestrial ring current during the time interval of 13–18 July, 2000, which consisted of
two small to moderate geomagnetic storms followed by a great storm with indices Dst=−300 nT and Kp=9. This period of intense geomagnetic activity was caused by three interplanetary coronal mass ejecta (ICME) each driving
interplanetary shocks, the last shock being very strong and reaching Earth at ∼ 14 UT on 15 July. We note that (a) the sheath
region behind the third shock was characterized by B
z fluctuations of ∼35 nT peak-to-peak amplitude, and (b) the ICME contained a negative to positive B
z variation extending for about 1 day, with a ∼ 6-hour long negative phase and a minimum B
z of about −55 nT. Both of these interplanetary sources caused considerable geomagnetic activity (Kp=8 to 9) despite their disparity as interplanetary triggers. We used our global ring current-atmosphere interaction model
with initial and boundary conditions inferred from measurements from the hot plasma instruments on the Polar spacecraft and the geosynchronous Los Alamos satellites, and simulated the time evolution of H+, O+, and He+ ring current ion distributions. We found that the O+ content of the ring current increased after each shock and reached maximum values of ∼ 60% near minimum Dst of the great storm. We calculated the growth rate of electromagnetic ion cyclotron waves considering for the first time wave
excitation at frequencies below O+ gyrofrequency. We found that the wave gain of O+ band waves is greater and is located at larger L shells than that of the He+ band waves during this storm interval. Isotropic pitch angle distributions indicating strong plasma wave scattering were
observed by the imaging proton sensor (IPS) on Polar at the locations of maximum predicted wave gain, in good agreement with model simulations. 相似文献
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Investigating the geomorphological potential of freely available and accessible structure‐from‐motion photogrammetry using a smartphone 
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下载免费PDF全文 We test the acquisition of high‐resolution topographic and terrain data using hand‐held smartphone technology, where the acquired images can be processed using technology freely available to the research community. This is achieved by evaluating the quality of digital terrain models (DTM) of a river bank and an Alpine alluvial fan generated with a fully automated, free‐to‐use, structure‐from‐motion package and a smartphone integrated camera (5 megapixels) with terrestrial laser scanning (TLS) data used to provide a benchmark. To evaluate this approach a 16.2‐megapixel digital camera and an established, commercial, close‐range and semi‐automated software are also employed, and the product of the four combinations of the two types of cameras and software are compared. Results for the river bank survey demonstrate that centimetre‐precision DTMs can be achieved at close range (10 m or less), using a smartphone camera and a fully automated package. Results improve to sub‐centimetre precision with either higher‐resolution images or by applying specific post‐processing techniques to the smartphone DTMs. Application to an entire Alpine alluvial fan system shows the degradation of precision scales linearly with image scale, but that (i) the expected level of precision remains and (ii) difficulties in separating vegetation and sediment cover within the results are similar to those typically found when using other photo‐based techniques and laser scanning systems. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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We describe a design for a compact cooled spectrograph which incorporates two cameras and two collimators to achieve high throughput from 0.8 to 2.5m. The spectrograph utilizes multiple NICMOS 3 arrays, specially mounted to minimize their separation in the spectral dimension. This accommodates the broad wavelength range while providing extensive coverage in the spatial dimension. 相似文献
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Dotan Shaked Gelband Yael Edelman‐Furstenberg Mordechai Stein Abraham Starinsky 《Sedimentology》2019,66(7):2950-2975
The study focuses on the formation of lacustrine dolomite in late Miocene lakes, located at the East Mediterranean margins (Northern Israel). These lakes deposited the sediments of the Bira (Tortonian) and Gesher (Messinian) formations that comprise sequences of dolostone and limestone. Dolostones are bedded, consist of small‐sized (<7 μm), Ca‐rich (52 to 56 mol %) crystals with relatively low ordering degrees, and present evidence for replacement of CaCO3 components. Limestones are comprised of a wackestone to mudstone matrix, freshwater macrofossils and intraclasts (mainly in the Bira Formation). Sodium concentrations and isotope compositions differ between limestones and dolostones: Na = ~100 to 150 ppm; ~1000 to 2000 ppm; δ18O = ?3·8 to ?1·6‰; ?2·0 to +4·3‰; δ13C = ?9·0 to ?3·4‰; ?7·8 to 0‰ (VPDB), respectively. These results indicate a climate‐related sedimentation during the Tortonian and early Messinian. Wet conditions and positive freshwater inflow into the carbonate lake led to calcite precipitation due to intense phytoplankton blooms (limestone formation). Dry conditions and enhanced evaporation led to precipitation of evaporitic CaCO3 in a terminal lake, which caused an increased Mg/Ca ratio in the residual waters and penecontemporaneous dolomitization (dolostone formation). The alternating lithofacies pattern reveals eleven short‐term wet–dry climate‐cycles during the Tortonian and early Messinian. A shift in the environmental conditions under which dolomite formed is indicated by a temporal decrease in δ18O of dolostones and Na content of dolomite crystals. These variations point to decreasing evaporation degrees and/or an increased mixing with meteoric waters towards the late Messinian. A temporal decrease in δ13C of dolostones and limestones and appearance of microbial structures in close association with dolomite suggest that microbial activity had an important role in allowing dolomite formation during the Messinian. Microbial mediation was apparently the main process that enabled local growth of dolomite under wet conditions during the latest Messinian. 相似文献
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