1,721,122 research outputs found
EFFECTS OF EXISTING LANDSLIDES ON SEISMICALLY-INDUCED DISPLACEMENTS DUE TO INPUT-SLOPE INTERACTIONS
No full textNew procedure for deriving multifrequential dynamic equivalent signals: numerical implementation and case study based on italian accelerometric records
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The LEMA_DES approach for deriving dynamic equivalent signals: numerical modeling of input-slope interaction
No full textLevelled-energy multifrequencial analysis for deriving dynamic equivalent signals (LEMA_DES): application for an earthquake scenario.
Full text linkAn equivalent acceleration signal can be regarded as an acceleration time history, inferred from a reference acceleration record which can be defined in different ways on the basis of different equivalence criteria such as: 1) kinematic characteristics of the signal; 2) Fourier spectrum amplitude; 3) Fourier spectrum phase values; 4) response spectrum; 5) energy. The equivalent signals may be employed in technical-scientific applications, when common theoretical approaches or instrumental devices can hardly manage the whole complexity of the actual phenomena to be investigated. As their definition suggests, equivalent signals are full-fledged analogue tools for modelling natural processes (real prototypes) as physical analogues (equivalent prototypes). At this regard, the levelled-energy multifrequencial analysis for deriving dynamic equivalent signals (LEMA_DES) optimises the already existing ones, by obtaining acceleration signals that can be regarded as more constrained to the real actions. Following this approach, a dynamic equivalent signal is derived by selecting and processing a limited number of representative harmonic functions from the reference acceleration spectrum. The dynamic equivalent signal is sized on a reference prototype under criteria of energy, spectral and peak acceleration (PGA) equivalence. The LEMA_DES approach was tested on 48 acceleration records from 23 November, 1980 Irpinia earthquake and compared with more traditional approaches for deriving cyclic equivalent inputs. Moreover, a specifically derived LEMA_DES signal was applied to force a slope by a FDM numerical modelling, referred to the Calitri landslide case-history which was seismically-induced by the same considered earthquake
Seismic monitoring system for landslide hazard assessment and risk management at the drainage plant of the Peschiera Springs (Central Italy)
Full text linkThe assessment of landslide hazards and design of strategies for managing the related risk have been widely studied topics in the scientific community due to the settlements, infrastructures and tourist and cultural heritage sites that may be threatened by deformations involving unstable slopes. Engineering geological and geophysical techniques have been recently integrated in multidisciplinary approaches to study gravity-induced slope instabilities and monitor their evolution. The slope that hosts the Peschiera Springs drainage plant (Central Italy) is involved in a mass rock creep process associated with deep karst dissolution. Due to the importance of this infrastructure, which provides water to the Rome aqueduct, an accelerometric network was installed in 2008, and a nanoseismic array was added in 2014. In this paper, data recorded by the nanoseismic array were used to locate 397 microseismic events related to the slope instability process, distinguished into two types with different waveforms: 16 failures and 381 collapses. The failures were distributed throughout the slope, while the collapses exhibited two spatially separate clusters below the groundwater level, at a depth where karst processes produce cavities. The clusters were analysed as two distinct microseismic sources characterised by specific frequency-magnitude curves of events that describe their attitude to produce events of different magnitudes. Regarding the accelerometric network, an automated procedure was developed for quickly analysing the seismic records, which include signals from teleseisms and near- to far-field earthquakes that can induce deformation in the landslide-involved slope. The results obtained by the two seismic monitoring systems were integrated with the aim of implementing a landslide hazard matrix based on the statistical frequency of the occurrence of such events and their probability of exceedance during a reference period, providing a useful tool for managing the related landslide risk
Polydimethylsiloxane/divinylbenzene overcoated fiber and its application to extract and analyse wine volatile compounds by solid-phase microextraction and gas chromatography coupled to mass spectrometry: direct immersion, headspace or both?
No full textIn this study, a comparison of the efficiency of the commercially available polydimethylsiloxane/divinylbenzene (PDMS/DVB) overcoated (OC) fiber used in direct immersion (DI) or in headspace (HS), has been performed by extracting volatiles through solid-phase microextraction (SPME) from a red wine and from a wine model to confirm the results. It was also investigated if a combination of DI followed by HS in a single assay (DI-HS) can provide improvements as compared to the use in DI or in HS only. Furthermore, the use of OC fiber in HS mode was compared with the use of the triphasic phase (TP, in PDMS/CAR/DVB), known to provide good results in this application. To have information also on fiber specificity, the detected analytes were subdivided into three classes depending on their boiling point. Results show that: OC fiber gives slightly better performance as compared to TP fiber, demonstrating a high efficiency of the OC fiber also in HS mode. Then, comparing the use of the commercial OC fiber in HS, DI and in the combined DI-HS mode, explored for the first time in this study to extract volatiles from wine, the combination DI-HS resulted to provide a more balanced efficiency for all the three groups of analytes, thus being a good compromise when the analytes have a broad range of volatility. Principal component analysis (PCA) and the design of experiment (DoE) were exploited to plan experiments and to help interpreting the results, highlighting that the combined DI-HS approach can be successfully applied to the characterization of wines and of other matrices, where analytes of interest have a wide range of volatility
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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