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41.
Ognjen?GrujicEmail authorView authors OrcID profile Alessandra?Menafoglio Guang?Yang Jef?Caers 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(7):1955-1971
In this paper we propose Universal trace co-kriging, a novel methodology for interpolation of multivariate Hilbert space valued functional data. Such data commonly arises in multi-fidelity numerical modeling of the subsurface and it is a part of many modern uncertainty quantification studies. Besides theoretical developments we also present methodological evaluation and comparisons with the recently published projection based approach by Bohorquez et al. (Stoch Environ Res Risk Assess 31(1):53–70, 2016. https://doi.org/10.1007/s00477-016-1266-y). Our evaluations and analyses were performed on synthetic (oil reservoir) and real field (uranium contamination) subsurface uncertainty quantification case studies. Monte Carlo analyses were conducted to draw important conclusions and to provide practical guidelines for all future practitioners. 相似文献
42.
Jef Vandenberghe 《寒旱区科学》2021,13(2):177-178
正Hugh French passed away unexpectedly on May 11, 2019, at the age of 76. His influence on the research and teaching in the fields of periglacial environment, permafrost and civil engineering can hardly be overstated. Out of his numerous international contacts, impressive publication records, memberships of international organizations and committees, and awards(Guglielmin and Murton, 2019), 相似文献
43.
In this paper, we present three diverse types of applications of extreme value statistics in geology, namely: earthquakes magnitudes, diamond values, and impact crater size distribution on terrestrial planets. Each of these applications has a different perspective toward tail modeling, yet many of these phenomena exhibit heavy or long tails which can be modeled by power laws. It is shown that the estimation of important tail characteristics, such as the extreme value index, is directly linked to the interpretation of the underlying geological process. Only the most extreme data are useful for studying such phenomena, so thresholds must be selected above which the data become power laws. In the case of earthquake magnitudes, we investigate the use of extreme value statistics in predicting large events on the global scale and for shallow intracontinental earthquakes in Asia. Large differences are found between estimates obtained from extreme value statistics and the usually applied standard statistical techniques. In the case of diamond deposits, we investigate the impact of the most precious stones in the global valuation of primary deposits. It is shown that in the case of Pareto-type behavior, the expected value of few extreme stones in the entire deposit has considerable influence on the global valuation. In the case of impact crater distributions, we study the difference between craters distributions on Earth and Mars and distributions occurring on other planets or satellites within the solar system. A striking result is that all planets display the same distributional tail except for Earth and Mars. In a concluding account, we demonstrate the apparent loghyperbolic variation in all of the above-mentioned examples. 相似文献
44.
中国北方更新世极端冷期冬季风的快速变化 总被引:5,自引:3,他引:2
对黄土高原中部洛川和西峰黄土堆积的“上、下粉砂层”进行了间隔 5~ 6 cm的详细采样 ,测量了 80 0多个样品的粒度分布和磁化率值 ,根据沉积速率模式建立了一个相对独立的、较精确的时间标尺。结果表明 ,中国北方更新世极端冷期的黄土堆积记录了东亚冬季风频繁的和较大幅度的千年尺度变化。冬季风加强事件一般持续约1.8~ 2 .4ka。亚轨道时间尺度冬季风变化的可能原因是 ,在极端冷期赤道和极地气温差增大 ,纬向西风环流加强引起的大气环流和蒙古高亚不稳定 ,从而引起东亚冬季风千年尺度变化。在极端冷期降雨量和平均温度低于某个阈值的时候 ,虽然夏季风强度存在变化 ,但不足以影响磁铁矿和磁赤铁矿的形成 ,所以那时磁化率的变化不能很好地记录夏季风气候变化。 相似文献
45.
Ayenew Melese Endalew Christof Debaer Nick Rutten Jef Vercammen Mulugeta Admasu Delele Herman Ramon Bart M. Nicolaï Pieter Verboven 《Boundary-Layer Meteorology》2011,138(1):139-162
The effect of tree foliage on sprayer airflow through pear trees in a fruit orchard was studied and modelled in detail. A
new three-dimensional (3-D) computational fluid dynamics model that integrates the 3-D canopy architecture with a local closure
model to simulate the effect of the stem and branches and leaves of trees separately on airflow was developed. The model was
validated with field observations made in an experimental orchard (pcfruit, Sint-Truiden, Belgium) in spring and summer 2008
and was used to investigate the airflow from three air-assisted orchard sprayers (Condor V, Duoprop and AirJet quatt). Velocity
magnitudes were measured before and behind leafless and fully-leafed pear canopies across the row while the operating sprayers
are passing along the row, and were compared with the simulations. The simulation results predicted the measured values well
with all the local relative errors within 20%. The effect of foliar density on airflow from the three air assisted sprayers
was manifested by changing the magnitude and direction of the sprayers’ air velocity behind the canopy, especially at the
denser regions of the canopy and by changing the pattern of velocity decay horizontally along the jet. The developed methodology
will also allow a thorough investigation of atmospheric airflow in canopy structures. 相似文献
46.
A multi-resolution workflow to generate high-resolution models constrained to dynamic data 总被引:2,自引:0,他引:2
Céline Scheidt Jef Caers Yuguang Chen Louis J. Durlofsky 《Computational Geosciences》2011,15(3):545-563
Distance-based stochastic techniques have recently emerged in the context of ensemble modeling, in particular for history
matching, model selection and uncertainty quantification. Starting with an initial ensemble of realizations, a distance between
any two models is defined. This distance is defined such that the objective of the study is incorporated into the geological
modeling process, thereby potentially enhancing the efficacy of the overall workflow. If the intent is to create new models
that are constrained to dynamic data (history matching), the calculation of the distance requires flow simulation for each
model in the initial ensemble. This can be very time consuming, especially for high-resolution models. In this paper, we present
a multi-resolution framework for ensemble modeling. A distance-based procedure is employed, with emphasis on the rapid construction
of multiple models that have improved dynamic data conditioning. Our intent is to construct new high-resolution models constrained
to dynamic data, while performing most of the flow simulations only on upscaled models. An error modeling procedure is introduced
into the distance calculations to account for potential errors in the upscaling. Based on a few fine-scale flow simulations,
the upscaling error is estimated for each model using a clustering technique. We demonstrate the efficiency of the method
on two examples, one where the upscaling error is small, and another where the upscaling error is significant. Results show
that the error modeling procedure can accurately capture the error in upscaling, and can thus reproduce the fine-scale flow
behavior from coarse-scale simulations with sufficient accuracy (in terms of uncertainty predictions). As a consequence, an
ensemble of high-resolution models, which are constrained to dynamic data, can be obtained, but with a minimum of flow simulations
at the fine scale. 相似文献
47.
Conditioning Facies Simulations with Connectivity Data 总被引:3,自引:3,他引:0
Philippe Renard Julien Straubhaar Jef Caers Grégoire Mariethoz 《Mathematical Geosciences》2011,43(8):879-903
When characterizing and simulating underground reservoirs for flow simulations, one of the key characteristics that needs
to be reproduced accurately is its connectivity. More precisely, field observations frequently allow the identification of
specific points in space that are connected. For example, in hydrogeology, tracer tests are frequently conducted that show
which springs are connected to which sink-hole. Similarly well tests often allow connectivity information in a petroleum reservoir
to be provided. 相似文献
48.
Jef Vandenberghe Hugh M. French Aldar Gorbunov Sergei Marchenko Andrey A. Velichko Huijun Jin Zhijiu Cui Tingjun Zhang Xudong Wan 《Boreas: An International Journal of Quaternary Research》2014,43(3):652-666
This paper accompanies a map that shows the extent of permafrost in the Northern Hemisphere between 25 and 17 thousand years ago. The map is based upon existing archival data, common throughout the Northern Hemisphere, that include ice‐wedge pseudomorphs, sand wedges and large cryoturbations. Where possible, a distinction is made between areas with continuous permafrost and areas where permafrost is either spatially discontinuous or sporadic. The associated mean annual palaeo‐temperatures that are inferred on the basis of present‐day analogues increase understanding of the possible changes in permafrost extent that might accompany current global warming trends. Areas with relict permafrost and areas that were formerly exposed due to lower sea level (submarine permafrost) are also mapped. Mapping is mostly limited to lowland regions (areas approximately <1000 m a.s.l.). Striking features that appear from the map are (i) the narrow permafrost zone in North America, which contrasts with the broader LPM permafrost zone in Eurasia (that may be related to different snow thickness or vegetation cover), (ii) the zonal extent of former LPM permafrost (that may reflect sea‐ice distribution), which contrasts with the present‐day pattern of permafrost extent (especially in Eurasia) and (iii) the relatively narrow zones of LPM discontinuous permafrost (that may indicate strong temperature gradients). 相似文献
49.
Liang Zhao Huijun Jin Chuanchuan Li Zhijiu Cui Xiaoli Chang Sergey S. Marchenko Jef Vandenberghe Tingjun Zhang Dongliang Luo Dongxin Guo Gengnian Liu Chaolu Yi 《Boreas: An International Journal of Quaternary Research》2014,43(3):688-698
Recent investigations into relict periglacial phenomena in northern and western China and on the Qinghai–Tibet Plateau provide information for delineating the extent of permafrost in China during the Late Pleistocene. Polygonal and wedge‐shaped structures indicate that, during the local Last Glacial Maximum (LLGM, between ~35 and 10.5 ka BP), the southern limit of latitudinal permafrost in northern China advanced southward at least to ~38–40°N in the east and to ~37–39°N in the west. This represents an advance of about 5–10° of latitude beyond present‐day permafrost limits. The lower limits of elevationally controlled permafrost on the Qinghai–Tibet Plateau and its peripheries were about 1000 m lower: this permafrost was largely continuous during the LLGM. This suggests a cooling of between 4 and 10°C, or more. This paper discusses the extent of permafrost during the LLGM and presents maps that have been constructed on the basis of extensive and integrative analysis of all reliable and pertinent data. The results indicate that the extent of LLGM permafrost in China was between ~3.8 and 4.3×106 km2. This is 80 to 100% more than that of ~2.15×106 km2 in the 1970s, and 120 to ~150% more than that of ~1.75×106 km2 today. 相似文献
50.
Antoine Bertoncello Tao Sun Hongmei Li Gregoire Mariethoz Jef Caers 《Mathematical Geosciences》2013,45(7):873-893
Geostatistical simulation methods aim to represent spatial uncertainty through realizations that reflect a certain geological concept by means of a spatial continuity model. Most common spatial continuity models are either variogram, training image, or Boolean based. In this paper, a more recent spatial model of geological continuity is developed, termed the event, or surface-based model, which is specifically applicable to modeling cases with complex stratigraphy, such as in sedimentary systems. These methods rely on a rule-based stacking of events, which are mathematically represented by two-dimensional thickness variations over the domain, where positive thickness is associated with deposition and negative thickness with erosion. Although it has been demonstrated that the surface-based models accurately represent the geological variation present in complex layered systems, they are more difficult to constrain to hard and soft data as is typically required of practical geostatistical techniques. In this paper, we develop a practical methodology for constraining such models to hard data from wells and thickness data interpreted from geophysics, such as seismic data. Our iterative methodology relies on a decomposition of the parameter optimization problem into smaller, manageable problems that are solved sequentially. We demonstrate this method on a real case study of a turbidite sedimentary basin. 相似文献