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1.
Investigating the propagation mechanism of unmodelled systematic errors on coordinate time series estimated using least squares 总被引：6，自引：8，他引：6
The propagation of unmodelled systematic errors into coordinate time series computed using least squares is investigated,
to improve the understanding of unexplained signals and apparent noise in geodetic (especially GPS) coordinate time series.
Such coordinate time series are invariably based on a functional model linearised using only zero and first-order terms of
a (Taylor) series expansion about the approximate coordinates of the unknown point. The effect of such truncation errors is
investigated through the derivation of a generalised systematic error model for the simple case of range observations from
a single known reference point to a point which is assumed to be at rest by the least squares model but is in fact in motion.
The systematic error function for a one pseudo-satellite two-dimensional case, designed to be as simple but as analogous to
GPS positioning as possible, is quantified. It is shown that the combination of a moving reference point and unmodelled periodic
displacement at the unknown point of interest, due to ocean tide loading, for example, results in an output coordinate time
series containing many periodic terms when only zero and first-order expansion terms are used in the linearisation of the
functional model. The amplitude, phase and period of these terms is dependent on the input amplitude, the locations of the
unknown point and reference point, and the period of the reference point's motion. The dominant output signals that arise
due to truncation errors match those found in coordinate time series obtained from both simulated data and real three-dimensional
GPS data. 相似文献
2.
Giulia Zuecco Chiara Marchina Ylenia Gelmini Anam Amin H. J. van Meerveld Daniele Penna Marco Borga 《水文研究》2021,35(3):e14095
Ressi is a small (2.4 ha) forested catchment located in the Italian pre-Alps. The site became an experimental catchment to investigate the water fluxes in the soil–plant–atmosphere continuum and the impact of vegetation on runoff generation in 2012. The elevation of the catchment ranges from 598 to 721 m a.s.l. and the climate is humid temperate. The bedrock consists of rhyolites and dacites; the soil is a Cambisol. The catchment is covered by a dense forest, dominated by beech, chestnut, maple, and hazel trees. The field set up includes measurements of the rainfall in an open area, streamflow at the outlet, soil moisture at various depths and locations, and depth to water table in six piezometers at a 5- or 10-min interval. Samples of precipitation, stream water, shallow groundwater and soil water are collected monthly for tracer analysis (stable isotopes (2H and 18O), electrical conductivity and major ions), and during selected rainfall–runoff events to determine the contribution of the various sources to runoff. Since 2017, soil and plant water samples have been collected to determine the sources of tree transpiration. Data collected in the period 2012–2016 are publicly available. Data collection is ongoing, and the data set is expected to be updated on an annual basis to include the most recent measurements. 相似文献
3.
Filippo Santucci de Magistris Anna d’Onofrio Augusto Penna Rodolfo Puglia Francesco Silvestri 《Natural Hazards》2014,74(3):2005-2035
The prediction of the variability of the seismic ground motion in a given built-up area is considered an effective tool to plan appropriate urban development, to undertake actions on seismic risk mitigation and to understand the damage pattern caused by a strong-motion event. The procedures for studying the seismic response and the seismic microzonation of an urban area are well established; nevertheless, some controversial points still exists and are discussed here. In this paper, the selection of a reference input motion, the construction of a subsoil model and the seismic response analysis procedures are discussed in detail, based on the authors’ experience in two Italian case histories: the seismic microzonation of the city of Benevento, which was a predictive study, and the simulation of seismic response and damage distribution in the village of San Giuliano di Puglia, which was a retrospective analysis. 相似文献
4.
Gabriella Della Penna 《Celestial Mechanics and Dynamical Astronomy》1999,75(2):103-124
A model for planetary precession is investigated using analytical and numerical techniques. A Hamiltonian function governing
the model is derived in terms of action-angle Andoyer-Déprit variables under the assumption of equatorial symmetry. As a first
approximation a simplified Hamiltonian with zero-eccentricity is considered and stability estimates are derived using KAM
theory. A validation of the analytical results is performed computing Poincaré surfaces of section for the circular and elliptical
model. We also investigate the role of the eccentricity and its connection with the appearance of resonances. Special attention
is devoted to the particular case of the Earth–Moon system.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
Using the applied element method for modelling calcium silicate brick masonry subjected to in‐plane cyclic loading 
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下载免费PDF全文 The response of calcium silicate unreinforced masonry construction to horizontal cyclic loading has recently become the focus of experimental and numerical research, given its extensive use in some areas of the world that are now exposed to induced earthquakes (eg, north of the Netherlands). To assess the seismic behaviour of such construction, a relatively wide range of modelling methodologies are available, amongst which the discrete elements approach, which takes into account the intrinsic heterogeneity of a brick‐mortar assembly, can probably be deemed as the most appropriate computational procedure. On the other hand, however, since discrete elements numerical methods are based on a discontinuum domain, often they are not able to model every stage of the structural response adequately, and because of the high computational burden required, the analysis scale should be chosen carefully. The applied element method is a relatively recent addition to the discrete elements family, with a high potential for overcoming the aforementioned limitations or difficulties. Initially conceived to model blast events and concrete structures, its use in the earthquake engineering field is, of late, increasing noticeably. In this paper, the use of the applied element method to model the in‐plane cyclic response of calcium silicate masonry walls is discussed and scrutinised, also through the comparison with experimental results of in‐plane cyclic shear‐compression tests on unreinforced masonry walls. 相似文献
6.
Post-earthquake damage data represent an invaluable source of information for the seismic vulnerability assessment of the exposed building stock, as they are a direct evidence of the actual buildings’ performance under real seismic events. This paper exploits a robust and homogeneous database of damage data collected after the 2009 L’Aquila (Italy) earthquake, to derive damage probability matrices for several building typologies representative of the Italian building stock. To this aim, the first part of the work investigates several issues related to the definition of damage to be associated with each inspected building. Different approaches and damage conversion rules are applied, pointing out advantages and weaknesses of each one. Considering the widespread seismic damage observed on masonry infill panels and partitions of reinforced concrete constructions, the impact of this type of non-structural damage on empirical damage and functional loss distributions is explored. The second part of the study proposes different possible interpretations of the repartition of the observed damage in the different damage levels, showing in some cases a bimodal trend. Two novel hybrid procedures are outlined and compared with the classical binomial approach for predicting the subdivision of damage in the different levels. The application of the proposed methodologies to the different building typologies allows the selection, for each one, of the method providing the best fit to empirical results. The parameters required for the application of the optimal approach are reported in the paper, so that results can be used for forecasting the expected seismic damage in sites with similar seismic hazard and exposed buildings. 相似文献
7.
A framework for the seismic assessment of existing masonry buildings accounting for different sources of uncertainty 下载免费PDF全文
下载免费PDF全文 The current formulation of Eurocode 8 Part 3 and the Italian building code for the seismic assessment of existing buildings accounts for epistemic (knowledge‐based) uncertainties by means of the identification of knowledge levels with associated values of the so‐called confidence factors, applied only as a reduction of material strengths. This formulation does not always produce consistent results and it does not explicitly account for other sources of uncertainty. The paper proposes a probabilistic methodology for the quantification of appropriately defined factors, allowing consideration of the different sources of uncertainty involved in the seismic assessment of masonry buildings by means of nonlinear static analyses. This simple approach, also including an alternative formulation of the confidence factors related with material properties, allows to obtain results which are consistent with the acquired level of knowledge and correctly account for the different sources of uncertainty without requiring to carry out any stochastic nonlinear analysis. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
8.
Andrea Penna Paolo Morandi Maria Rota Carlo Filippo Manzini Francesca da Porto Guido Magenes 《Bulletin of Earthquake Engineering》2014,12(5):2255-2273
The earthquake sequence started on May \(20\) th 2012 in Emilia (Italy) affected a region where masonry constructions represent a large part of the existing building stock and the construction of new modern masonry buildings is a common practice. The paper is focused on the performance of common architectural configurations, typical for residential or business use. The large majority of old masonry buildings is made of fired clay bricks. The seismic performance of these buildings is particularly interesting since major past earthquakes in Italy affected areas with mainly stone masonry structures. Apart from examples showing systematic or peculiar structural deficiencies governing the vulnerability of several buildings, the overall seismic performance of these structures to repeated shaking, with PGA as large as 0.25–0.3 g was rather good, despite the major part of them were only conceived for carrying vertical loads. In fact, seismic design is mandatory in the area only since 2003. Modern low-rise masonry buildings erected after this date and incorporating seismic design and proper detailing resulted in most cases practically undamaged. The examples reported in the paper allow an evaluation of the superior performance of seismically designed modern masonry buildings in comparison to older ones. 相似文献
9.
Accoroni S Romagnoli T Colombo F Pennesi C Di Camillo CG Marini M Battocchi C Ciminiello P Dell'Aversano C Dello Iacovo E Fattorusso E Tartaglione L Penna A Totti C 《Marine pollution bulletin》2011,62(11):2512-2519
Intense blooms of the benthic dinoflagellate Ostreopsis cf. ovata have occurred in the northern Adriatic Sea since 2006. These blooms are associated with noxious effects on human health and with the mortality of benthic organisms because of the production of palytoxin-like compounds. The O. cf. ovata bloom and its relationships with nutrient concentrations at two stations on the Conero Riviera (northern Adriatic Sea) were investigated in the summer of 2009. O. cf. ovata developed from August to November, with the highest abundances in September (1.3 × 106 cells g−1 fw corresponding to 63.8 × 103 cells cm−2). The presence of the single O. cf. ovata genotype was confirmed by a PCR assay. Bloom developed when the seawater temperature was decreasing. Nutrient concentrations did not seem to affect bloom dynamics. Toxin analysis performed by high resolution liquid chromatography-mass spectrometry revealed a high total toxin content (up to 75 pg cell−1), including putative palytoxin and all the ovatoxins known so far. 相似文献
10.
A nonlinear macroelement model for the seismic analysis of masonry buildings 总被引：1，自引：0，他引：1 下载免费PDF全文
下载免费PDF全文 The macroelement technique for modelling the nonlinear response of masonry panels is particularly efficient and suitable for the analysis of the seismic behaviour of complex walls and buildings. The paper presents a macroelement model specifically developed for simulating the cyclic in‐plane response of masonry walls, with possible applications in nonlinear static and dynamic analysis of masonry structures. The model, starting from a previously developed macroelement model, has been refined in the representation of flexural–rocking and shear damage modes, and it is capable of fairly simulating the experimental response of cyclic tests performed on masonry piers. By means of two internal degrees of freedom, the two‐node macroelement permits to represent the coupling of axial and flexural response as well as the interaction of shear and flexural damage. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献