23 research outputs found

    On the different convex hulls of sets involving singular values

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    We give a representation formula for the convex, polyconvex and rank one convex hulls of a set of n Ă— n matrices with prescribed singular value

    Tracking the evolution of riverbed morphology on the basis of uav photogrammetry

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    Unmanned aerial vehicle (UAV) photogrammetry has recently become a widespread technique to investigate and monitor the evolution of different types of natural processes. Fluvial geomorphology is one of such fields of application where UAV potentially assumes a key role, since it allows for overcoming the intrinsic limits of satellite and airborne-based optical imagery on one side, and in situ traditional investigations on the other. The main purpose of this paper was to obtain extensive products (digital terrain models (DTMs), orthophotos, and 3D models) in a short time, with low costs and at a high resolution, in order to verify the capability of this technique to analyze the active geomorphic processes on a 12 km long stretch of the French–Italian Roia River at both large and small scales. Two surveys, one year apart from each other, were carried out over the study area and a change detection analysis was performed on the basis of the comparison of the obtained DTMs to point out and characterize both the possible morphologic variations related to fluvial dynamics and modifications in vegetation coverage. The results highlight how the understanding of different fluvial processes may be improved by appropriately exploiting UAV-based products, which can thus represent a low-cost and non-invasive tool to crucially support decisionmakers involved in land management practices

    The new landslide inventory of Tuscany (Italy) updated with PS-InSAR: geomorphological features and landslide distribution

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    In this paper, the updating of the landslide inventory of Tuscany region is presented. To achieve this goal, satellite SAR data processed with persistent scatter interferometry (PSI) technique have been used. The updating leads to a consistent reduction of unclassified landslides and to an increasing of active landslides. After the updating, we explored the characteristics of the new inventory, analysing landslide distribution and geomorphological features. Several maps have been elaborated, as sliding index or landslide density map; we also propose a density-area map to highlight areas with different landslide densities and sizes. A frequency-area analysis has been performed, highlighting a classical negative power-law distribution. We also explored landslide frequency for lithology, soil use and several morphological attributes (elevation, slope gradient, slope curvature), considering both all landslides and classified landslide types (flows, falls and slides)

    UAV-based multitemporal remote sensing surveys of volcano unstable flanks: a case study from Stromboli

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    UAV-based photogrammetry is becoming increasingly popular even in application fields that, until recently, were deemed unsuitable for this technique. Depending on the characteristics of the investigated scenario, the generation of three-dimensional (3D) topographic models may in fact be affected by significant inaccuracies unless site-specific adaptations are implemented into the data collection and processing routines. In this paper, an ad hoc procedure to exploit high-resolution aerial photogrammetry for the multitemporal analysis of the unstable Sciara del Fuoco (SdF) slope at Stromboli Island (Italy) is presented. Use of the technique is inherently problematic because of the homogeneous aspect of the gray ash slope, which prevents a straightforward identification of match points in continuous frames. Moreover, due to site accessibility restrictions enforced by local authorities after the volcanic paroxysm in July 2019, Ground Control Points (GCPs) cannot be positioned to constrain georeferencing. Therefore, all 3D point clouds were georeferenced using GCPs acquired in a 2019 (pre-paroxysm) survey, together with stable Virtual Ground Control Points (VGCPs) belonging to a LiDAR survey carried out in 2012. Alignment refinement was then performed by means of an iterative algorithm based on the closest points. The procedure succeeded in correctly georeferencing six high-resolution point clouds acquired from April 2017 to July 2021, whose time-focused analysis made it possible to track several geomorphological structures associated with the continued volcanic activity. The procedure can be further extended to smaller-scale analyses such as the estimation of locally eroded/accumulated volumes and pave the way for rapid UAV-based georeferenced surveys in emergency conditions at the SdF

    Louis I. Kahn and Richard Kelly: collaborative design in creation of the luminous environment

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    As one of the most prominent architects of the twentieth century, Louis I. Kahn aspired to use natural light to shape his architecture. The lighting designer Richard Kelly, one of his close collaborators, had significant influence on modern architectural lighting design in the twentieth century. Kahn and Kelly designed the luminous environments in three art-gallery and museum buildings, The Yale University Art Gallery, the Kimbell Art Museum and the Yale Center for British Art. Collaboration between the architect and the lighting designer resulted in well-resolved lighting solutions. This research investigated the collaboration between Louis I. Kahn and Richard Kelly from both theoretical and pragmatic perspectives. In terms of the theoretical perspective, a detailed overview of their collaborative work is provided through literature review. In terms of the pragmatic perspective, the background of their cooperation and the technical details are presented. In addition, daylighting performance analysis of these three buildings through digital modelling was undertaken. This study found that the lighting design solutions produced together by Louis I. Kahn and Richard Kelly, especially the way of using daylight, have had significant impact on architectural space and the luminous environment. More importantly, this kind of collaborative working method could provide a useful reference and guidance for contemporary architecture and lighting design

    Subsidence mapping at regional scale using persistent scatters interferometry (PSI): The case of Tuscany region (Italy)

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    In this paper the mapping of subsidences in Tuscany (Italy) is presented. To achieve our goal satellite SAR data processed with persistent scatters interferometry (PSI) technique have been used. Several subsiding areas have been identified and three of them have been analyzed in detail and subsequently compared with literature work both to validate the results and to analyze the evolution of the identified subsidences. In general, this comparison confirmed the quality of the analyses and, furthermore, lead to the identification of an important ground uplift close to Prato city, an area that was historically affected by subsidence

    Potential benefit of nizatidine in female patients with idiopathic xerostomia: A pilot study

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    Xerostomia is a frequent salivary complaint, especially in elderly people, typically caused by Sjogren’s syndrome, uncontrolled diabetes mellitus, radiation to the head and neck, chemotherapy, and different medications. Above all, drugs are the most common reason of reduced salivation, and the medications most commonly implicated are tricyclic antidepressants, antipsychotics, atropinics, beta-blockers and antihistamines. Nizatidine is a histamine H2-receptor antagonist used in the treatment of peptic ulcer and gastro-esophageal reflux disease. In the past, salivary secretion has been reported to increase when nizatidine was administered to healthy volunteers, patients with dry mouth and patients with primary Sjo¨ gren’s syndrome. In the present study, we tried to analyze the efficacy of nizatidine on both dry mouth symptoms and salivary secretion in patients affected by idiopathic xerostomia

    The platysma myocutaneous flap (PMF) for head and neck reconstruction: A retrospective and multicentric analysis of 91 T1-T2 patients.

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    The platysma myocutaneous flap (PMF) was first applied to intraoral reconstructions in 1978. PMF is not only an alternative to microvascular flaps but it also represents an excellent reconstructive choice especially in cases where free tissue transfer cannot be carried out. Failure and complications rate have been described as varying from 18 to 45% and this is why this flap should not be used in specific cases such as in the presence of cervical metastases and in cases of mandibulectomy and simultaneous reconstruction with alloplastic materials. The purpose of this study is to examine the experience and results obtained in three different and independent institutes where PMF has been adopted in 91 patients for head and neck cancer reconstructions. The authors report their departments\u2019 separate but simultaneous experiences with PMF for small and middle-size soft tissue defects in a 10-year period
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