Wavelets applied to simplification of digital terrain models     

Jan T. Bj⊘rke  Stein Nilsen 《International journal of geographical information science》2013,27(7):601-621

Wavelet thresholding is used to generate simplified terrain models. This non-linear filtering technique is adaptive in the sense that the large wavelet coefficients in areas of high relief are kept, whereas all coefficients smaller than a threshold value, representing smooth areas, are thrown away. The degree of detail in the simplified model is controlled by the number of wavelet coefficients retained. Two different areas are analysed using this method. The experiments show the smoothing effect of the thresholding, and how the main terrain features survive as the threshold value increases. At large threshold values the method introduces blocking artifacts in the model.  相似文献   

Statistics-based outlier detection for wireless sensor networks     

Y. Zhang  N.A.S. Hamm  N. Meratnia  A. Stein  M. van de Voort  P.J.M. Havinga 《International journal of geographical information science》2013,27(8):1373-1392

Wireless sensor network (WSN) applications require efficient, accurate and timely data analysis in order to facilitate (near) real-time critical decision-making and situation awareness. Accurate analysis and decision-making relies on the quality of WSN data as well as on the additional information and context. Raw observations collected from sensor nodes, however, may have low data quality and reliability due to limited WSN resources and harsh deployment environments. This article addresses the quality of WSN data focusing on outlier detection. These are defined as observations that do not conform to the expected behaviour of the data. The developed methodology is based on time-series analysis and geostatistics. Experiments with a real data set from the Swiss Alps showed that the developed methodology accurately detected outliers in WSN data taking advantage of their spatial and temporal correlations. It is concluded that the incorporation of tools for outlier detection in WSNs can be based on current statistical methodology. This provides a usable and important tool in a novel scientific field.  相似文献   

Untangling the influence of in-lake productivity and terrestrial organic matter flux on 4,250 years of mercury accumulation in Lake Hambre, Southern Chile     

Yvonne-Marie Hermanns  Antonio Martinez Cortizas  Helge Arz  Rüdiger Stein  Harald Biester 《Journal of Paleolimnology》2013,49(4):563-573

There is ongoing debate about the relative influence of aquatic production, flux, and sedimentation of aquatic and terrestrial organic matter on mercury accumulation in lake sediments. In this study, lake sediments spanning the past 4,250 years, were collected from remote, organic-rich Lake Hambre, Patagonia (53° S) and investigated for changes in the accumulation of pre-anthropogenic mercury and organic matter of aquatic and terrestrial origin. Natural mercury accumulation varied by up to a factor of four, comparable to the recent anthropogenic forcing of the mercury cycle (factor 3–5). Hydrogen and Oxygen indices (HI and OI, Rock–Eval©) and nitrogen/carbon ratios of the organic matter, combined with multi-element sediment data, reveal intense changes in aquatic productivity as well as influx of terrestrial organic matter into the lake. Evaluation of the multi-element dataset using Principal Component Analysis shows clear covariation of mercury with other soil-derived elements such as copper and yttrium. This covariance reflects a common transport mechanism, i.e. leaching of trace-element-bearing organic matter complexes from catchment soils. Correlation between changes in aquatic productivity and mercury concentrations occurs in some sections of the record, but we do not suggest they are linked by a direct causal relationship. Mass balance approaches suggest that mercury scavenging and accumulation in this organic-rich lake is controlled by the supply of mercury from catchment soils rather than the amount of organic material produced within the water column. A common controlling mechanism, i.e. changing climate, however, is thought to independently drive variations in both the flux of terrestrial organic matter mercury complexes and aquatic productivity.  相似文献   

Vulnerability of buildings to debris flow impact   总被引：5，自引：1，他引：4  

M. Jakob  D. Stein  M. Ulmi 《Natural Hazards》2012,60(2):241-261

Quantitative risk assessments (QRAs) for landslide hazards are increasingly being executed to determine an unmitigated level of risk and compare it with risk tolerance criteria set by the local or federal jurisdiction. This approach allows urban planning with a scientific underpinning and provides the tools for emergency preparedness. Debris-flow QRAs require estimates of the hazard probability, spatial and temporal probability of impact (hazard assessment) and vulnerability of the elements at risk. The vulnerability term is perhaps the most difficult to estimate confidently because (a) human death in debris flows is most commonly associated with building damage or collapse and is thus an indirect consequence and (b) the type and scale of building damage is very difficult to predict. To determine building damage, an intensity index (I _DF) was created as the product of maximum expected flow depth d and the square of the maximum flow velocity v (I _DF = dv ²). The I _DF surrogates impact force and thus correlates with building damage. Four classes of building damage were considered ranging from nuisance flood/sedimentation damage to complete destruction. Sixty-six well-documented case studies in which damage, flow depth and flow velocity were recorded or could be estimated were selected through a search of the global literature, and I _DF was plotted on a log scale against the associated damage. As expected, the individual damage classes overlap but are distinctly different in their respective distributions and group centroids. To apply this vulnerability model, flow velocity and flow depth need to be estimated for a given building location and I _DF calculated. Using the existing database, a damage probability (P _DF) can then be computed. P _DF can be applied directly to estimate the likely insurance loss or associated loss of life. The model presented here should be updated with more case studies and is therefore made openly available to international researchers who can access it at .  相似文献   

Earthquake Modelling at the Country Level Using Aggregated Spatio-Temporal Point Processes   总被引：1，自引：1，他引：0  

M. N. M. van Lieshout  A. Stein 《Mathematical Geosciences》2012,44(3):309-326

The goal of this paper is to derive a hazard map for earthquake occurrences in Pakistan from a catalogue that contains spatial coordinates of shallow earthquakes of magnitude 4.5 or larger aggregated over calendar years. We test relative temporal stationarity by the KPSS statistic and use the inhomogeneous J-function to test for inter-point interactions. We then formulate a cluster model, and de-convolve in order to calculate the hazard map, and verify that no particular year has an undue influence on the map. Within the borders of the single country, the KPSS test did not show any deviation from homogeneity in the spatial intensities. The inhomogeneous J-function indicated clustering that could not be attributed to inhomogeneity, and the analysis of aftershocks showed some evidence of two major shocks instead of one during the 2005 Kashmir earthquake disaster. Thus, the spatial point pattern analysis carried out for these data was insightful in various aspects and the hazard map that was obtained may lead to improved measures to protect the population against the disastrous effects of earthquakes.  相似文献   

余震密度随距离的衰减不代表动态应力触发过程     

K.R.-Dinger  R.S.Stein  S.Toda  魏志恒  冯蔚 《世界地震译丛》2011,(3)

分辨多数余震和后续主震是由静态应力触发(Stein,1999;Todaetal,2005;Parsons,2002)还是动态应力触发(Hilletal,1993;kilb,2003;Brodsky and Prejean,2005;Gomberg and Johnson,2005;Hill and Prejean,2007),对理解地震内在作用和预测地震危险性是有必要的(Freed,2005)。Felzer和Brodsky(2006)分析了2≤M<3和3≤M<4级主震后5min内余震的空间分布情况,发现距主震50km范围内M≥2余震具有特定的幂律衰减关系,且衰减曲线的斜率为-1.35。据此,他们认为余震随距离的衰减只能用动态触发来解释。基于上述假设我们进行了一系列的检验,但没有一个可通过检验,进而,本文中对这种衰减关系提出了另外一种解释。在距离2≤M<3主震300m以外的地方,主震前5min内的地震活动性衰减与主震后5min内的衰减没有显著的区别,表明主震对它静态触发区域以外的地方没有影响。表征余震基本特性的大森随时间衰减关系在距离主震10km以外的地方是不存在的。最后,发现在主震波前未到达之前的余震中发现了...  相似文献   

Numerical modeling of cyclic mobility based on fuzzy-set concepts in plasticity theory     

Yu Bao  Stein Sture 《Computers and Geotechnics》2011

In this paper, the application of an efficient, transparent and accurate kinematic-cyclic constitutive model based on the fuzzy-set concepts and incremental plasticity theory is presented to show its capability in modeling cyclic mobility of saturated granular soil. The nature and kinematic mechanism of the membership functions in the fuzzy-set constitutive model are illustrated. The model’s capability of modeling soil dilatancy is investigated. Important features of volume change and pore water pressure build-up related to soil cyclic mobility are captured. The formulation of the proposed model is relatively simple and it can be readily implemented in finite element codes. The enhanced fuzzy-set model is capable of simulating ground motion problems particularly related to cyclic mobility, soil liquefaction, and spreading behavior.  相似文献   

Black dimensional stones: geology, technical properties and deposit characterization of the dolerites from Uruguay   总被引：1，自引：1，他引：0  

Manuela Morales Demarco  Pedro Oyhantçabal  Karl-Jochen Stein  Siegfried Siegesmund 《Environmental Earth Sciences》2011,63(7-8):1879-1909

Dimensional stones with a black color occupy a prominent place on the international market. Uruguayan dolerite dikes of andesitic and andesitic–basaltic composition are mined for commercial blocks of black dimensional stones. A total of 16 dikes of both compositions were studied and samples collected for geochemical and petrographical analysis. Color measurements were performed on different black dimensional stones in order to compare them with the Uruguayan dolerites. Samples of the two commercial varieties (Absolute Black and Moderate Black) were obtained for petrophysical analysis (e.g. density, porosity, uniaxial compressive strength, tensile strength, etc.). Detailed structural analyses were performed in several quarries. Geochemistry and petrography determines the intensity of the black color. The Uruguayan dolerite Absolute Black is the darkest black dimensional stone analyzed in this study. The petrophysical properties of Uruguayan dolerites make them one of the highest quality black dimensional stones. Structural analyses show that five joint sets have been recognized: two sub-vertical joints, one horizontal and two diagonal. These joint sets are one of the most important factors that control the deposits, since they control the block size distribution and the amount of waste material.  相似文献   

26Al‐26Mg isotope systematics of the first solids in the early solar system     

Noriko T. Kita  Qing‐Zhu Yin  Glenn J. MacPherson  Takayuki Ushikubo  Benjamin Jacobsen  Kazuhide Nagashima  Erika Kurahashi  Alexander N. Krot  Stein B. Jacobsen 《Meteoritics & planetary science》2013,48(8):1383-1400

High‐precision bulk aluminum‐magnesium isotope measurements of calcium‐aluminum‐rich inclusions (CAIs) from CV carbonaceous chondrites in several laboratories define a bulk ²⁶Al‐²⁶Mg isochron with an inferred initial ²⁶Al/²⁷Al ratio of approximately 5.25 × 10^?5, named the canonical ratio. Nonigneous CV CAIs yield well‐defined internal ²⁶Al‐²⁶Mg isochrons consistent with the canonical value. These observations indicate that the canonical ²⁶Al/²⁷Al ratio records initial Al/Mg fractionation by evaporation and condensation in the CV CAI‐forming region. The internal isochrons of igneous CV CAIs show a range of inferred initial ²⁶Al/²⁷Al ratios, (4.2–5.2) × 10^?5, indicating that CAI melting continued for at least 0.2 Ma after formation of their precursors. A similar range of initial ²⁶Al/²⁷Al ratios is also obtained from the internal isochrons of many CAIs (igneous and nonigneous) in other groups of carbonaceous chondrites. Some CAIs and refractory grains (corundum and hibonite) from unmetamorphosed or weakly metamorphosed chondrites, including CVs, are significantly depleted in ²⁶Al. At least some of these refractory objects may have formed prior to injection of ²⁶Al into the protosolar molecular cloud and its subsequent homogenization in the protoplanetary disk. Bulk aluminum and magnesium‐isotope measurements of various types of chondrites plot along the bulk CV CAI isochron, suggesting homogeneous distribution of ²⁶Al and magnesium isotopes in the protoplanetary disk after an epoch of CAI formation. The inferred initial ²⁶Al/²⁷Al ratios of chondrules indicate that most chondrules formed 1–3 Ma after CAIs with the canonical ²⁶Al/²⁷Al ratio.  相似文献   

High-Resolution Non-Hydrostatic Simulations of Flash-Flood Episodes with Grid-Nesting and Ice-Phase Parameterization     

J. Stein  E. Richard  J. P. Lafore  J. P. Pinty  N. Asencio  S. Cosma 《Meteorology and Atmospheric Physics》2000,72(2-4):203-221

Summary ?Simulations of two heavy rainfall events south of the Alps have been conducted with a non-hydrostatic model at horizontal resolutions ranging from 40 to 2.5 km. Emphasis is placed on the assessment of two recent model developments: a detailed explicit mixed phase microphysical scheme and a two-way interactive grid nesting method. In the high-resolution simulations, the impact of the ice phase was found to be quite substantial, accelerating the propagation of the surface front and modifying the spatial distribution of the rainfall. Simulations carried out with two-way interactive grid nesting yielded more realistic overall precipitation patterns, particularly at the finest horizontal resolution. Received March 22, 1999/Revised June 28, 1999  相似文献