Semantic Enablement for Spatial Data Infrastructures

Building on abstract reference models, the Open Geospatial Consortium (OGC) has established standards for storing, discovering, and processing geographical information. These standards act as a basis for the implementation of specific services and Spatial Data Infrastructures (SDI). Research on geo‐semantics plays an increasing role to support complex queries and retrieval across heterogeneous information sources, as well as for service orchestration, semantic translation, and on‐the‐fly integration. So far, this research targets individual solutions or focuses on the Semantic Web, leaving the integration into SDI aside. What is missing is a shared and transparent Semantic Enablement Layer for SDI which also integrates reasoning services known from the Semantic Web. Instead of developing new semantically enabled services from scratch, we propose to create profiles of existing services that implement a transparent mapping between the OGC and the Semantic Web world. Finally, we point out how to combine SDI with linked data.     

Finite element simulations of the behavior of piled‐raft foundations using a multiphase model

Finite element simulations of the behavior of a piled raft foundation have been carried out using a multiphase model conceived as an improved homogenization approach. According to this model, the ground reinforced by a group of piles is treated as a homogeneous continuous medium. In this approach, no specific interface elements are necessary to account for the mechanical interaction between the piles and the ground: this interaction is described by means of two scalar parameters, one stiffness parameter and one which can easily be derived from the maximum ground‐pile friction. The implementation of the model into a finite element code provides an efficient tool for the analysis of the influence of the pile number or length on the settlement and bearing capacity of a square piled raft foundation and of the way the total applied load is shared between the raft and the piles. Results are compared with a standard 3D finite element analysis. The comparison highlights the fact that the proposed approach remains to be improved to account for tip resistance. Copyright © 2012 John Wiley & Sons, Ltd.     

Sedimentologic evidence for outburst floods from the Laurentide Ice Sheet margin in Wisconsin, USA: implications for tunnel-channel formation

Clast-supported boulder gravel in outwash-fans along the glacial-maximum margin of the Laurentide Ice Sheet in Wisconsin indicates the occurrence of outburst floods. These sediments, with clast intermediate axes of up to 2 m, are located downstream of tunnel channels and were deposited shortly before cessation of glaciofluvial activity on each fan. Since tunnel channels with fans are widespread along the ice-sheet margin in the western Great Lakes region, these outburst floods were probably common. Paleodischarge estimates derived from the boulder deposits are poorly constrained, but values of at least several hundred m³ s⁻¹ are likely. Four potential water sources for the floods exist: an extreme surface-melt event, an extreme precipitation event, drainage of supraglacial lakes, or drainage of stored subglacial meltwater. We focus on the storage of subglacial meltwater behind the ice-sheet margin, as proglacial permafrost was present as ice advanced to its maximum extent, and a frozen-bed zone upstream from the margin probably impeded drainage through groundwater aquifers. Decay of this permafrost ‘seal’ would have eventually allowed trapped water to drain through the tunnel channels. We suggest that the 2-m boulders were entrained in an outburst of subglacial water that enlarged a pre-existing channel cut by ablation-derived flows.     

Nuclear magnetic resonance studies of ancient buried wood—II. Observations on the origin of coal from lignite to bituminous coal

Coalified logs ranging in age from Late Pennsylvania to Miocene and in rank from lignite B to bituminous coal were analyzed by ¹³C nuclear magnetic resonance (NMR) utilizing the cross-polarization, magic-angle spinning technique, as well as by infrared spectroscopy. The results of this study indicate that at least three major stages of coalification can be observed as wood gradually undergoes transformation to bituminous coal. The first stage involves hydrolysis and loss of cellulose from wood with retention and differential concentration of the resistant lignin. The second stage involves conversion of the lignin residues directly to coalified wood of lignitic rank, during which the oxygen content of intermediate diagenetic products remains constant as the hydrogen content and the carbon content increases. These changes are thought to involve loss of methoxyl groups, water, and C₃ side chains from the lignin. In the third major stage of coalification, the coalified wood increases in rank to subbituminous and bituminous coal; during this stage the oxygen content decreases, hydrogen remains constant, and the carbon content increases. These changes are thought to result from loss of soluble humic acids that are rich in oxygen and that are mobilized during compaction and dewatering. Relatively resistant resinous substances are differentially concentrated in the coal during this stage. The hypothesis that humic acids are formed as mobile by-products of the coalification of lignin and function only as vehicles for removal of oxygen represents a dramatic departure from commonly accepted views that they are relatively low-molecular-weight intermediates formed during the degradation of lignin that then condense to form high-molecular-weight coal structures.     

Quantitative assessment of the reliability of chironomid remains in paleoecology: effects of count density and sample size

Random distributions for a wide range (1–100,000) of chironomid head capsules (HC) were simulated on a 1-m² surface. The number of HC found in circular surfaces equivalent to standard core diameters (90 and 63 mm) was estimated 1000 times, over the range of tested densities. For each number of HC found in the samples, the range of simulated densities was estimated using a threshold probability (p > 0.95). This enabled us to develop equations to infer HC density from sample counts. Because of the threshold probability for comparable sample counts, the equations yield higher estimated densities under a random distribution than for a regular distribution. The probability of sampling at least one HC was >0.95 for densities of 900 HC m^?2 for the 90-mm core and 1400 HC m^?2 for the 63-mm core. For a specific sample count, the range of actual densities was ~10 times higher for the 63-mm core than the 90-mm core. Comparison with field larval densities revealed that most densities were too low to be suitable for annually resolved reconstruction of a quantitative signal, using current corer sizes, although a large number of populations can support sub-decadal analyses. Nonetheless, some lakes exhibit population sizes large enough to reconstruct robust quantitative estimates of past chironomid abundances. This work provides guidance to reconstruct species dynamics and fine-scale time series analyses in paleoecology.     

Cross-scale: multi-scale coupling in space plasmas

Most of the visible universe is in the highly ionised plasma state, and most of that plasma is collision-free. Three physical phenomena are responsible for nearly all of the processes that accelerate particles, transport material and energy, and mediate flows in systems as diverse as radio galaxy jets and supernovae explosions through to solar flares and planetary magnetospheres. These processes in turn result from the coupling amongst phenomena at macroscopic fluid scales, smaller ion scales, and down to electron scales. Cross-Scale, in concert with its sister mission SCOPE (to be provided by the Japan Aerospace Exploration Agency—JAXA), is dedicated to quantifying that nonlinear, time-varying coupling via the simultaneous in-situ observations of space plasmas performed by a fleet of 12 spacecraft in near-Earth orbit. Cross-Scale has been selected for the Assessment Phase of Cosmic Vision by the European Space Agency.      

Automatic revision of rules used to guide the generalisation process in systems based on a trial and error strategy

Automating the generalisation process, a major issue for national mapping agencies, is extremely complex. Several works have proposed to deal with this complexity using a trial and error strategy. The performance of systems based on such a strategy is directly dependent on the quality of the control knowledge (i.e. heuristics) used to guide the trials. Unfortunately, most of the time, the definition and updation of knowledge is a fastidious task. In this context, automatic knowledge revision can not only improve the performance of the generalisation, but also allow it to automatically adapt to various usages and evolve when new elements are introduced. In this article, an offline knowledge revision approach is proposed, based on a logging of the system and on the analysis of outcoming logs. This approach is dedicated to the revision of control knowledge expressed by production rules. We have implemented and tested this approach for the automated generalisation of groups of buildings within a generalisation model called AGENT, from initial data that reference a scale of approximately 1:15,000 compared with the target map's scale of 1:50,000. The results show that our approach improves the quality of the control knowledge and thus the performance of the system. Moreover, the approach proposed is generic and can be applied to other systems based on a trial and error strategy, dedicated to generalisation or not.