Stability and accuracy in a hybrid test example     

Francisco J. Molina  Francesco Marazzi  Bernard Viaccoz  Anna Bosi 《地震工程与结构动力学》2013,42(3):469-475

This paper presents an example of the application of error monitoring techniques to the results of a pseudodynamic test performed at variable testing speeds. For the faster testing speeds, the control errors increased and the test reliability was lost in terms of accuracy and stability, as observed by the evolution of the monitoring parameters. The applied monitoring methods were the spatial model identification of frequency and damping distortions and the error energy, which have been proposed in previous publications. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Does the complexity in temporal precipitation disaggregation matter for a lumped hydrological model?     

Hannes Müller-Thomy  Anna E. Sikorska-Senoner 《水文科学杂志》2013,58(12):1453-1471

ABSTRACT

Flood peaks and volumes are essential design variables and can be simulated by precipitation–runoff (P–R) modelling. The high-resolution precipitation time series that are often required for this purpose can be generated by various temporal disaggregation methods. Here, we compare a simple method (M1, one parameter), focusing on the effective precipitation duration for flood simulations, with a multiplicative cascade model (M2, 32/36 parameters). While M2 aims at generating realistic characteristics of precipitation time series, M1 aims only at accurately reproducing flood variables by P–R modelling. Both disaggregation methods were tested on precipitation time series of nine Swiss mesoscale catchments. The generated high-resolution time series served as input for P–R modelling using a lumped HBV model. The results indicate that differences identified in precipitation characteristics of disaggregated time series vanish when introduced into the lumped hydrological model. Moreover, flood peaks were more sensitive than flood volumes to the choice of disaggregation method.  相似文献   

Location Performance and Detection Threshold of the Spanish National Seismic Network     

Antonino D’Alessandro  José Badal  Giuseppe D’Anna  Dimitris Papanastassiou  Ioannis Baskoutas  Nurcan M. Özel 《Pure and Applied Geophysics》2013,170(11):1859-1880

Spain is a low-to-moderate seismicity area with relatively low seismic hazard. However, several strong shallow earthquakes have shaken the country causing casualties and extensive damage. Regional seismicity is monitored and surveyed by means of the Spanish National Seismic Network, maintenance and control of which are entrusted to the Instituto Geográfico Nacional. This array currently comprises 120 seismic stations distributed throughout Spanish territory (mainland and islands). Basically, we are interested in checking the noise conditions, reliability, and seismic detection capability of the Spanish network by analyzing the background noise level affecting the array stations, errors in hypocentral location, and detection threshold, which provides knowledge about network performance. It also enables testing of the suitability of the velocity model used in the routine process of earthquake location. To perform this study we use a method that relies on P and S wave travel times, which are computed by simulation of seismic rays from virtual seismic sources placed at the nodes of a regular grid covering the study area. Given the characteristics of the seismicity of Spain, we drew maps for M _L magnitudes 2.0, 2.5, and 3.0, at a focal depth of 10 km and a confidence level 95 %. The results relate to the number of stations involved in the hypocentral location process, how these stations are distributed spatially, and the uncertainties of focal data (errors in origin time, longitude, latitude, and depth). To assess the extent to which principal seismogenic areas are well monitored by the network, we estimated the average error in the location of a seismic source from the semiaxes of the ellipsoid of confidence by calculating the radius of the equivalent sphere. Finally, the detection threshold was determined as the magnitude of the smallest seismic event detected at least by four stations. The northwest of the peninsula, the Pyrenees, especially the westernmost segment, the Betic Cordillera, and Tenerife Island are the best-monitored zones. Origin time and focal depth are data that are far from being constrained by regional events. The two Iberian areas with moderate seismicity and the highest seismic hazard, the Pyrenees and Betic Cordillera, and the northwestern quadrant of the peninsula, are the areas wherein the focus of an earthquake is determined with an approximate error of 3 km. For M _L 2.5 and M _L 3.0 this error is common for almost the whole peninsula and the Canary Islands. In general, errors in epicenter latitude and longitude are small for near-surface earthquakes, increasing gradually as the depth increases, but remaining close to 5 km even at a depth of 60 km. The hypocentral depth seems to be well constrained to a depth of 40 km beneath the zones with the highest density of stations, with an error of less than 5 km. The M _L magnitude detection threshold of the network is approximately 2.0 for most of Spain and still less, almost 1.0, for the western sector of the Pyrenean region and the Canary Islands.  相似文献   

2012 Urban Geography Plenary Lecture Topological City     

Anna Secor 《Urban geography》2013,34(4):430-444

The purpose of this paper is to explore the idea of the topological city, both by sharing some observations about the use of topology in critical human geography today and also by demonstrating how different modes of topological analyses of the city may work. This paper suggests that while topology is not new to the social sciences in general or geography in particular, an uptick in interest in topology in the past decade is likely due to its role in the work of Deleuze and Agamben. Topology, I suggest, can help geographers think in creative ways about spatial ontology, thereby offering some insights into the relationship between the subject and the city. I build this argument by discussing the topological workings of three cinematic cities: The Adjustment Bureau (2011), Midnight in Paris (2011), and Inception (2010). [Key words: topology, film, Lacan, subject, spatial theory.]  相似文献   

SEDIMENT SOURCES OF NEBKHAS IN THE SAHEL ZONE OF BURKINA FASO     

Anna Tengberg 《自然地理学》2013,34(4):259-275

Owing to the decline in rainfall and intensified land use in the Sahel during the past 25 years, wind erosion is causing increasing problems in this region. The aim of the present paper is to identify possible sources for the material found in nebkhas in northern Burkina Faso. Nebkhas are plant-obstacle dunes that frequently occur in semi-arid areas. Grain-size distributions of nebkha sediments and five other subenvironments were analyzed using univariate and multivariate methods. Quartz-grain surface textures were studied by Scanning Electron Microscopy (SEM).

The SEM and grain-size analyses together indicate that the nebkhas have experienced considerable recent aeolian abrasion and sorting as compared with the five other sub-environments. It was concluded that the material in the nebkhas investigated is local in origin and that it mainly has been eroded by wind from adjacent disturbed soils or deflated from loose material made available for wind erosion by sheet-wash processes. This means that wind erosion is an important process in the removal of topsoil in this Sahelian environment and that measures to reduce wind erosion should be taken to protect sensitive soils. [Key words: Nebkhas, wind erosion, Sahel, Burkina Faso.]  相似文献   

Generalized migration in frequency-wavenumber domain (MGF-K) in anisotropic media     

Andrzej Kostecki  Anna Półchłopek 《Acta Geophysica》2013,61(3):624-637

In this paper, the background of MGF-K migration in dual domain (wavenumber-frequency K-F and space-time) in anisotropic media is presented. Algorithms for poststack (zero-offset) and prestack migration are based on downward extrapolation of acoustic wavefield by shift-phase with correction filter for lateral variability of medium’s parameters. In anisotropic media, the vertical wavenumber was determined from full elastic wavefield equations for two dimensional (2D) tilted transverse isotropy (TTI) model. The method was tested on a synthetic wavefield for TTI anticlinal model (zero-offset section) and on strongly inhomogeneous vertical transverse isotropy (VTI) Marmousi model. In both cases, the proper imaging of assumed media was obtained.  相似文献   

Jet radio emission in Cygnus X-1 and its orbital modulation     

Anna Szostek  Andrzej A. Zdziarski 《Monthly notices of the Royal Astronomical Society》2007,375(3):793-804

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Spectro-Polarimetric Observations and Non-Lte Modeling of Ellerman Bombs     

Hector Socas-Navarro  Valentín Martínez Pillet  David Elmore  Anna Pietarila  Bruce W. Lites  Rafael Manso Sainz 《Solar physics》2006,235(1-2):75-86

Ellerman bombs are bright emission features observed in the wings of Hα, usually in the vicinity of magnetic concentrations. Here we show that they can also be detected in the Ca II infrared triplet lines, which are easier to interpret and therefore allow for more detailed diagnostics. We present full Stokes observations of the 849.8 and 854.2 nm lines acquired with the new spectro-polarimeter SPINOR. The data show no significant linear polarization at the level of 3 × 10⁻⁴. The circular polarization profiles exhibit measureable signals with a very intricate pattern of peaks. A non-LTE analysis of the spectral profiles emerging from these features reveals the presence of strong downflows (∼10 {km s⁻¹}) in a hot layer between the upper photosphere and the lower chromosphere. Visiting Astronomers, National Solar Observatory, operated by the Association of Universities for Research in Astronomy, Inc. (AURA), under cooperative agreement with the National Science Foundation. The National Center for Atmospheric Research (NCAR) is sponsored by the National Science Foundation, USA.  相似文献   

Fluid inclusion evidence for deep burial of the Tertiary accretionary wedge of the Carpathians     

Vratislav Hurai  Franti&#x;ek Marko  Antoni K. Tokarski  Anna wierczewska  Júlia Kotulov  Adrin Biro&#x; 《地学学报》2006,18(6):440-446

Hydrothermal quartz from mineralized joints of the Carpathian accretionary wedge contains immiscible aqueous, oil‐condensate, methane and carbon dioxide‐rich fluid inclusions. Distribution patterns of the inclusion trapping PT parameters point to a crack‐seal mechanism during upward and lateral migration of hot methane‐rich fluids from overpressured sediments at the base of the accretionary wedge. A simple equation is proposed to calculate depths from densities and trapping pressures of the buoyant inclusion fluids. In the Carpathian accretionary wedge, the paleofluid pressures of 52–306 MPa correspond to a 5‐ to 11‐km‐thick overburden. Prior to exhumation, thickness of the wedge must have attained 10–25 km, of which only c. 50% was preserved until recently. Anomalously high methane densities (up to 0.43 g cm^?3) recorded in the lowermost nappe sheets are provisionally interpreted as a result of supralithostatic overpressure due to thermal cracking of oil and kerogen to methane and pyrobitumen at temperatures above 200 °C.  相似文献   

Climate change and hydrology: next steps for climate models     

Chris Huntingford  John Gash  Anna Maria Giacomello 《水文研究》2006,20(9):2085-2087

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