Probing the feeding and feedback of activity near and far     

S. García-Burillo  F. Combes  J. Graciá-Carpio  A. Usero  M. Guélin 《Astrophysics and Space Science》2008,313(1-3):261-265

High-resolution CO maps are an essential tool to search for observational evidence of AGN fueling in galaxy nuclei. While their capabilities will be surpassed by ALMA, current mm-interferometers can already provide relevant information on scales which are critical for the process of angular momentum transfer in fueling the AGN. In this context we present the latest results issued from the NUclei of GAlaxies (NUGA) project, a high-resolution (0.5^′′–1^′′) CO survey of low luminosity AGNs conducted with the IRAM Plateau de Bure interferometer (PdBI). The use of more specific molecular tracers of dense gas can probe the feedback influence of activity on the chemistry and energy balance in the interstellar medium of nearby galaxies, a prerequisite to understanding how feedback operate at higher redshift galaxies. We discuss the results obtained in an ongoing study devoted to probe the feedback of activity from nearby Seyferts to high-redshift QSO.  相似文献   

Can We Constrain Solar Interior Physics by Studying the Gravity-Mode Asymptotic Signature?     

R. A. García  S. Mathur  J. Ballot 《Solar physics》2008,251(1-2):135-147

Gravity modes are the best probes to infer the properties of the solar radiative zone, which represents 98% of the Sun’s total mass. It is usually assumed that high-frequency g modes give information about the structure of the solar interior whereas low-frequency g modes are more sensitive to the solar dynamics (the internal rotation). In this work, we develop a new methodology, based on the analysis of the almost constant separation of the dipole gravity modes, to introduce new constraints on the solar models. To validate this analysis procedure, several solar models – including different physical processes and either old or new chemical abundances (from, respectively, Grevesse and Noels (Origin and Evolution of the Elements 199, Cambridge University Press, Cambridge, 15, 1993) and Asplund, Grevesse, and Sauval (Cosmic Abundances as Records of Stellar Evolution and Nucleosynthesis CS-336, Astron. Soc. Pac., San Francisco, 25?–?38, 2005)) – have been compared to another model used as a reference. The analysis clearly shows that this methodology has enough sensitivity to distinguish among some of the models, in particular, among those with different compositions. The comparison of the models with the g-mode asymptotic signature detected in GOLF data favors the ones with old abundances. Therefore, the physics of the core – obtained through the analysis of the g-mode properties – is in agreement with the results obtained in the previous studies based on the acoustic modes, which are mostly sensitive to more external layers of the Sun.  相似文献   

Evaluation of approximate methods to estimate residual drift demands in steel framed buildings          下载免费PDF全文

Jorge Ruiz‐García  Carlos Chora 《地震工程与结构动力学》2015,44(15):2837-2854

This paper presents the evaluation of two approximate methods recently proposed in the literature to estimate residual (permanent) drift demands at the end of earthquake excitation for seismic assessment of buildings. Both methods require an estimate of the peak (maximum) interstory drift demand and the corresponding drift demand at significant yielding of the building. Additionally, an approximate method is proposed as part of this study. The introduced method follows a coefficient‐based approach similar to the Coefficient Method included in several US documents. For evaluating the approximate methods, five moment‐resisting steel framed buildings having different number of stories were analyzed under four sets of earthquake ground motions. Quantification of the accuracy of the approximate methods to estimate residual drift demands with respect to results from nonlinear time‐history analyses was performed through error measures computed for each building and each set of earthquake ground motions. Results show that the mean standard error tends to increase as the seismic hazard level increases. Between the two methods, the method introduced by Erochko et al. seems more effective in predicting residual drift demands than that proposed in the FEMA P‐58 recommendations in the USA. It is demonstrated that including additional sources of stiffness and strength in the modeling approach constrains the amplitude of residual drift demands. As a beneficial consequence, the accuracy of both approximate methods in predicting residual drift demands is significantly improved (i.e., mean standard error decreases). The introduced method also provides similar accuracy than the approximate methods available in the literature. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

The 3D Attenuation Structure of Deception Island (Antarctica)   总被引：1，自引：1，他引：0  

J. Prudencio  L. De Siena  J. M. Ibáñez  E. Del Pezzo  A. García-Yeguas  A. Díaz-Moreno 《Surveys in Geophysics》2015,36(3):371-390

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Source Parameters of Earthquakes Recorded Near the Itoiz Dam (Northern Spain)     

A. Jiménez  J. M. García-García  M. D. Romacho  A. García-Jerez  F. Luzón 《Pure and Applied Geophysics》2015,172(11):3163-3177

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Nonstationary matrix covariances: compact support,long range dependence and quasi-arithmetic constructions   总被引：3，自引：3，他引：0  

William Kleiber  Emilio Porcu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(1):193-204

Flexible models for multivariate processes are increasingly important for datasets in the geophysical, environmental, economics and health sciences. Modern datasets involve numerous variables observed at large numbers of space–time locations, with millions of data points being common. We develop a suite of stochastic models for nonstationary multivariate processes. The constructions break into three basic categories—quasi-arithmetic, locally stationary covariances with compact support, and locally stationary covariances with possible long-range dependence. All derived models are nonstationary, and we illustrate the flexibility of select choices through simulation.  相似文献   

Spatial average aquifer recharge through atmospheric chloride mass balance and its uncertainty in continental Spain   总被引：1，自引：0，他引：1       下载免费PDF全文

Francisco J. Alcalá  Emilio Custodio 《水文研究》2014,28(2):218-236

The atmospheric chloride mass balance (CMB) method allows spatial evaluations of the average diffuse aquifer recharge by rainfall () in large and varied territories when long‐term steady conditions can be assumed. Often, the distributed average CMB variables necessary to calculate have to be estimated from the available variable‐length data series, which may be of suboptimal quality and spatial coverage. This paper explains the use of these data and the reliability of the results in continental Spain, chosen as a large and varied territory. The CMB variables have been regionalized by ordinary kriging at the same 4976 nodes of a 10 km × 10 km grid. Nodal values vary from 14 to 810 mm year^–1, 90% ranging from 30 to 300 mm year^–1. The recharge‐to‐precipitation ratios vary from 0.03 in low‐permeability formations and semiarid areas to 0.65 in some carbonate massifs. Integrated average results for the whole of continental Spain yield a potential aquifer recharge of 64 km³ year^?1, the net recharge over permeable formations (40% of the territory) being 32 km³ year^?1. Two main sources of uncertainty affecting (given by the coefficient of variation, CV), induced by the inherent natural variability of the variables (CV_R) and from mapping (), have been segregated. The average CV_R is 0.13 and could be improved with longer data series. The average is 0.07 and may be decreased with better data coverage. The estimates were compared with other regional and local recharge estimates, being 4% and 1% higher, respectively. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

A test for directional-linear independence,with applications to wildfire orientation and size     

Eduardo García-Portugués  Ana M. G. Barros  Rosa M. Crujeiras  Wenceslao González-Manteiga  José Pereira 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(5):1261-1275

A nonparametric test for assessing the independence between a directional random variable (circular or spherical, as particular cases) and a linear one is proposed in this paper. The statistic is based on the squared distance between nonparametric kernel density estimates and its calibration is done by a permutation approach. The size and power characteristics of various variants of the test are investigated and compared with those for classical correlation-based tests of independence in an extensive simulation study. Finally, the best-performing variant of the new test is applied in the analysis of the relation between the orientation and size of Portuguese wildfires.  相似文献   

Crustacean assemblages in a polluted estuary from South-Western Spain     

J. Emilio Sánchez-Moyano  Isabel García-Asencio 《Marine pollution bulletin》2010,60(10):1890-1897

The spatial-temporal variation in crustacean assemblages of the Odiel-Tinto estuary, one of the most polluted areas in the world, was studied in 2000, 2002 and 2004. The crustacean assemblages were mainly established according to the natural gradient from estuarine to marine environment (based on water and sediment characteristics such as dissolved oxygen, salinity, granulometry or organic content). Pollutants such as copper, zinc or phosphates could also explain partially this pattern based on BIOENV and canonical correspondence analyses. However, there were clear symptoms of perturbation, mainly in the inner areas, such as a low number of species and a low abundance, especially in relation to the typical estuarine species (e.g. Cyathura carinata, Corophium spp.). This study provides baseline information which can be used as a reference point in a long-term perspective.  相似文献   

Removal of Arsenic by Alumina: Effects of Material Size,Additives, and Water Contaminants          下载免费PDF全文

Victor K. Tchieda  Emilio D'Amato  Agostina Chiavola  Mariapaola Parisi  Angelo Chianese  Mohamed Amamra  Andrei Kanaev 《洁净——土壤、空气、水》2016,44(5):496-505

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