An Algebra for Spatiotemporal Data: From Observations to Events     

Karine Reis Ferreira  Gilberto Camara  Antônio Miguel Vieira Monteiro 《Transactions in GIS》2014,18(2):253-269

Recent technological advances in geospatial data gathering have created massive data sets with better spatial and temporal resolution than ever before. These large spatiotemporal data sets have motivated a challenge for Geoinformatics: how to model changes and design good quality software. Many existing spatiotemporal data models represent how objects and fields evolve over time. However, to properly capture changes, it is also necessary to describe events. As a contribution to this research, this article presents an algebra for spatiotemporal data. Algebras give formal specifications at a high‐level abstraction, independently of programming languages. This helps to develop reliable and expressive applications. Our algebra specifies three data types as generic abstractions built on real‐world observations: time series, trajectory and coverage. Based on these abstractions, it defines object and event types. The proposed data types and functions can model and capture changes in a large range of applications, including location‐based services, environmental monitoring, public health, and natural disasters.  相似文献   

Occurrence of shallow cold flows in the winter atmospheric boundary layer of interior of Alaska     

Gilberto J. Fochesatto  John A. Mayfield  Derek P. Starkenburg  Matthew A. Gruber  James Conner 《Meteorology and Atmospheric Physics》2015,127(4):369-382

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Geochemical and statistical characterization of the phosphate facies of the Farim‐Saliquinhé phosphate mineralization (Guinea‐Bissau)     

Gilberto Charifo  António M. Ferreira  José A. Almeida  Jean‐Pierre Prian 《Resource Geology》2014,64(1):58-75

The Eocene Farim‐Saliquinhé phosphate mineralization (FSPM) is a buried sedimentary deposit located in the northern part of Guinea‐Bissau, discovered and spatially constrained during the 1980s by the French Geological Survey (BRGM). In the present work some of the data collected at that time are reworked in the framework of the development of a 3D geological and geochemical model of this mineralization. We show the usefulness of two classical multivariate statistical methods – principal component analysis (PCA) and cluster analysis (CA) – applied to eight geochemical variables (P₂O₅, SiO₂, Al₂O₃, Fe₂O₃, CaO, MgO, F and CO₂) measured in 247 samples from phosphate facies, for differentiation of samples taken from the different phosphate facies recognized in the FSPM, namely the main ore FPA (30 to 35% high grade phosphate), the calcareous low grade phosphate FPB (10 to 20% P₂O₅) (both Lutetian), and a mineralized Upper Eocene to Lower Oligocene cover (mainly including the FPO level and a silico‐aluminous phosphate bed), overlying the FPA, which can also be considered a third set of phosphate facies associated with the FSPM.  相似文献   

Evaluation of uniaxial contact models for moat wall pounding simulations     

Patrick J. Hughes  Gilberto Mosqueda 《地震工程与结构动力学》2020,49(12):1197-1215

Moat wall pounding occurs when a base-isolated building displaces beyond the provided clearance and collides with the surrounding retaining wall, inducing very high floor accelerations and interstory drifts. Previous studies on moat wall pounding typically employ simplified models of the superstructure, with a uniaxial contact spring used to model the entire moat wall. Consequently, researchers have developed sophisticated contact models to estimate the normal-direction contact force that is generated during seismic pounding. This study examines how the choice in contact model affects the seismic response of a base-isolated building subjected to impact-inducing ground excitation. Five widely used state-of-the-art contact models are summarized and implemented into an experimentally-calibrated numerical model of a base-isolated moment frame. Results of nonlinear dynamic time history analyses are shown in detail for one ground motion, followed by a larger parametric study across 28 near-fault ground motions. This work shows that peak impact force and base acceleration are moderately sensitive to the choice in contact model, while upper floor accelerations and interstory drifts are practically not affected.  相似文献