Book review     

Louis J. Maher Jr. 《Mathematical Geosciences》1987,19(6):575-577

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Inhomogeneous shearing related to rock composition: evidence from a major late-Panafrican shear zone in the Tuareg shield (Algeria)     

Bernard Henry  Mohamed E. M. Derder  Boualem Bayou  Mehdi A. Guemache  Omar Nouar  Aziouz Ouabadi  Hamou Djellit  Mohamed Amenna  Abderahmane Hemmi 《Swiss Journal of Geoscience》2008,101(2):453-464

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Reliability‐based control algorithms for nonlinear hysteretic systems based on enhanced stochastic averaging of energy envelope          下载免费PDF全文

Omar El‐Khoury  Abdollah Shafieezadeh 《地震工程与结构动力学》2017,46(14):2381-2397

Current reliability‐based control techniques have been successfully applied to linear systems; however, incorporation of stochastic nonlinear behavior of systems in such control designs remains a challenge. This paper presents two reliability‐based control algorithms that minimize failure probabilities of nonlinear hysteretic systems subjected to stochastic excitations. The proposed methods include constrained reliability‐based control (CRC) and unconstrained reliability‐based control (URC) algorithms. Accurate probabilistic estimates of nonlinear system responses to stochastic excitations are derived analytically using enhanced stochastic averaging of energy envelope proposed previously by the authors. Convolving these demand estimates with capacity models yields the reliability of nonlinear systems in the control design process. The CRC design employs the first‐level and second‐level optimizations sequentially where the first‐level optimization solves the Hamilton–Jacobi–Bellman equation and the second‐level optimization searches for optimal objective function parameters to minimize the probability of failure. In the URC design, a single optimization minimizes the probability of failure by directly searching for the optimal control gain. Application of the proposed control algorithms to a building on nonlinear foundation has shown noticeable improvements in system performance under various stochastic excitations. The URC design appears to be the most optimal method as it reduced the probability of slight damage to 8.7%, compared with 11.6% and 19.2% for the case of CRC and a stochastic linear quadratic regulator, respectively. Under the Kobe ground motion, the normalized peak drift displacement with respect to stochastic linear quadratic regulator is reduced to 0.78 and 0.81 for the URC and CRC cases, respectively, at comparable control force levels. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Early warning system for rainfall-triggered landslides based on real-time probabilistic hazard assessment     

Correa  Oscar  García  Francisco  Bernal  Gabriel  Cardona  Omar Darío  Rodriguez  Carlos 《Natural Hazards》2020,100(1):345-361

Natural Hazards - A methodology to define rainfall-landslide thresholds, using a probabilistic model in which the accumulated rainfall at any time is treated as a random variable, is proposed. The...  相似文献   

Near-surface foundation level assessment from seismic measurements: a case study of north Jeddah City,Saudi Arabia     

Mogren  Saad  Aldahri  Maher  Abdelrahman  Kamal  Zahran  Hani 《Arabian Journal of Geosciences》2020,13(5):1-22

In this study, a comprehensive assessment on the generation mechanism, distribution characteristics, and extension rules of structure cracks was conducted by in situ monitoring and field investigation in the Chengchao Iron Mine. Structure cracks are affected by many factors, e.g., surface deformation, structure strength, occurrence position, and machine vibration. They initially occur in a structure when the strength of the structure is not enough to resist the inner strain as surface deformation increases. In contrast, increases in width and length of structure crack exert stress release in the structure and thus decrease structure deformation surrounding the crack. A great ground crack may adversely aggravate structure cracking and release the stress of surrounding rock masses. In addition, micro cracks in rock masses provide favorable conditions for the generation and extension of cracks, resulting that cracks occur in shaft walls more easily and extend towards the deeper. The initial distribution of cracks is generally consistent with such micro cracks. Subsequently, cracks in deep rock masses will extend along the strike of the mined-out area as surface deformation increases. Sensibilities to cracking of structures are changed by their different strain resistances and become stronger from bolt-shotcrete shaft, bolt-shotcrete tunnel, and brick-concrete building to brick wall. Based on distribution characteristics of cracks and wave velocity in rock masses, the overlaying strata affected by underground mining can be divided into four zones: broken zone, broken transition zone, crack generation zone, and micro deformation zone.  相似文献   

Estuarine resources use by juvenile Flagfin mojarra (Eucinostomus melanopterus) in an inverse tropical estuary (Sine Saloum,Senegal)     

Ndombour Gning  François Le Loc'h  Omar T. Thiaw  Catherine Aliaume  Guy Vidy 《Estuarine, Coastal and Shelf Science》2010

The Flagfin mojarra, Eucinostomus melanopterus, is a marine spawner whose young individuals are common in the Sine Saloum inverse estuary (Senegal). The species offers the opportunity to study both the use of the estuarine nursery resources and the impact of the particular environment of the inverse estuary on these resources. This will lead to a better understanding of the functioning of the nursery. We investigated the resources used by juvenile Flagfin mojarra by coupling stomach contents and stable isotopes methods.  相似文献   

Modelling large-scale effects of estuarine and morphodynamic gradients on distribution and abundance of the sandy beach isopod Excirolana armata     

Juan Pablo Lozoya  Julio Gómez  Omar Defeo 《Estuarine, Coastal and Shelf Science》2010

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Equilibrium and Stability of Prominence Flux Ropes     

Bryan H. Fong  Omar A. Hurricane  Steven C. Cowley 《Solar physics》2001,201(1):93-117

Realistic models of solar prominence flux ropes are numerically constructed. The models are in 2.5 dimensions, including the effects of non-isothermal temperature, density and gravity, and pressure. Stability of the equilibria to pressure- and gravity-driven instabilities is numerically investigated, using the ballooning formalism of fusion plasma theory. The equilibrium models can become unstable to pressure- and gravity-driven modes at plasma parameters characteristic of prominences.  相似文献   

Reply to Comment on “The Keisarhjelmen detachment records Silurian–Devonian extensional collapse in Northern Svalbard”          下载免费PDF全文

Alvar Braathen  Per Terje Osmundsen  Harmon Maher  Morgan Ganerød 《地学学报》2018,30(4):322-324

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Intraurban variability of PM10 and PM2.5 in an Eastern Mediterranean city     

Rawad Massoud  Alan.L Shihadeh  Mohamed Roumié  Myriam Youness  Jocelyne Gerard  Nada Saliba  Rita Zaarour  Maher Abboud  Wehbeh Farah  Najat Aoun Saliba 《Atmospheric Research》2011,101(4):893-901

The results of the first large scale chemical characterization of PM10 and PM2.5 at three different sites in the urban city of Beirut, Lebanon, are presented. Between May 2009 and April 2010 a total of 304 PM10 and PM2.5 samples were collected by sampling every sixth day at three different sites in Beirut. Observed mass concentrations varied between 19.7 and 521.2 μg m^? 3 for PM10 and between 8.4 and 72.2 μg m^? 3 for PM2.5, respectively. Inorganic concentrations accounted for 29.7–35.6 μg m^? 3 and 46.0–53.5 μg m^? 3 of the total mass of PM10 and PM2.5, respectively. Intra-city temporal and spatial variations were assessed based on the study of three factors: correlation coefficients (R) for PM and chemical components, coefficient of divergence (CODs), and source apportionment using positive matrix factorization (PMF). Based on R and COD of PM concentrations, the three sites appear homogeneous. However, when individual elements were compared, heterogeneity among sites was found. This latter was attributed to the variability in the percent contribution of biogenic and local anthropogenic source factors such as traffic related sources and dust resuspension. Other factors included the proximity to the Mediterranean sea, the population density and the topographical structure of the city. Hence, despite its small size (20.8 km²), one PM monitoring site does not reflect an accurate PM level in Beirut.  相似文献