1,700 research outputs found
From TLS survey to 3d solid modeling for documentation of built heritage: The case study of porta savonarola in Padua
It is a matter of fact that 3D visualisation and proper documentation of cultural objects helps to preserve the history and memories of historic buildings, archaeological sites and cultural landscapes, and supports economic growth by stimulating cultural tourism. Preservation, visualisation and recreation of valuable historical and architectural objects and places has always been a serious challenge for specialists in the field. Today, the rapid developments in the fields of close-range photogrammetry, terrestrial laser scanning (TLS) and computer vision (CV) enable to carry out highly accurate 3D models so as to be extremely effective and intuitive for users who have stringent requirements and high expectations. In this note we present the results of the survey and 3D modeling of an ancient gate, Porta Savonarola, located within the remains of the medieval town walls surrounding the historical city center of Padua, Italy. The work has been undertaken within the framework of the project \u201cWalls Multimedia Museum\u201d (WMM) promoted by the local private association \u201cPadua Walls Committee\u201d. The goal of the project was to develop a prototype of an \u201cextended\u201d virtual museum, spreaded along most interesting locations of the town walls. The survey of the ancient gate was performed with a Leica C10 and P20 terrestrial laser scanners. Once the acquired scans were properly merged together, a solid model was generated from the global point cloud, and plans and elevations were extracted from it for restoration purposes. A short multimedia video was also created for the \u201cWalls Multimedia Museum\u201d, showing both the outer and inner part of the gate. In the paper we will discuss all the steps and challenges addressed to provide the 3D solid model of Porta Savonarola from the TLS data
COMPARISON OF LOW COST PHOTOGRAMMETRIC SURVEY WITH TLS AND LEICA PEGASUS BACKPACK 3D MODELS
This paper considers Leica backpack and photogrammetric surveys of a mediaeval bastion in Padua, Italy. Furhtermore, terrestrial
laser scanning (TLS) survey is considered in order to provide a state of the art reconstruction of the bastion. Despite control points
are typically used to avoid deformations in photogrammetric surveys and ensure correct scaling of the reconstruction, in this paper
a different approach is considered: this work is part of a project aiming at the development of a system exploiting ultra-wide band
(UWB) devices to provide correct scaling of the reconstruction. In particular, low cost Pozyx UWB devices are used to estimate
camera positions during image acquisitions. Then, in order to obtain a metric reconstruction, scale factor in the photogrammetric
survey is estimated by comparing camera positions obtained from UWB measurements with those obtained from photogrammetric
reconstruction. Compared with the TLS survey, the considered photogrammetric model of the bastion results in a RMSE of 21.9cm, average error 13.4cm, and standard deviation 13.5cm. Excluding the final part of the bastion left wing, where the presence of several poles make reconstruction more difficult, (RMSE) fitting error is 17.3cm, average error 11.5cm, and standard deviation 9.5cm. Instead, comparison of Leica backpack and TLS surveys leads to an average error of 4.7cm and standard deviation 0.6cm (4.2 cm and 0.3 cm, respectively, by excluding the final part of the left wing)
GRB 970228 Revisited: Evidence for a Supernova in the Light Curve and La te Spectral Energy Distribution of the Afterglow
At the time of its discovery, the optical and X-ray afterglow of GRB 970228
appeared to be a ringing endorsement of the previously untried relativistic
fireball model of gamma-ray burst (GRB) afterglows, but now that nearly a dozen
optical afterglows to GRBs have been observed, the wavering light curve and
reddening spectrum of this afterglow make it perhaps the most difficult of the
observed afterglows to reconcile with the fireball model. In this Letter, we
argue that this afterglow's unusual temporal and spectral properties can be
attributed to a supernova that overtook the light curve nearly two weeks after
the GRB. This is the strongest case yet for a GRB/supernova connection. It
strengthens the case that a supernova also dominated the late afterglow of GRB
980326, and the case that GRB 980425 is related to SN 1998bw.Comment: Accepted to The Astrophysical Journal (Letters), 14 pages, LaTe
From survey to fem analysis for documentation of built heritage: The case study of villa revedin-bolasco
In the last decade advances in the fields of close-range photogrammetry, terrestrial laser scanning (TLS) and Computer Vision (CV) have enabled to collect different kind of information about a Cultural Heritage objects and to carry out highly accurate 3D models. Additionally, the integration between laser scanning technology and Finite Element Analysis (FEA) is gaining particular interest in recent years for structural analysis of built heritage, since the increasing computational capabilities allow to manipulate large datasets. In this note we illustrate the approach adopted for surveying, 3D modeling and structural analysis of Villa Revedin-Bolasco, a magnificent historical building located in the small walled town of Castelfranco Veneto, in northern Italy. In 2012 CIRGEO was charged by the University of Padova to carry out a survey of the Villa and Park, as preliminary step for subsequent restoration works.
The inner geometry of the Villa was captured with two Leica Disto D3a BT hand-held laser meters, while the outer walls of the
building were surveyed with a Leica C10 and a Faro Focus 3D 120 terrestrial laser scanners. Ancillary GNSS measurements were
also collected for 3D laser model georeferencing. A solid model was then generated from the laser global point cloud in Rhinoceros software, and portion of it was used for simulation in a Finite Element Analysis (FEA). In the paper we discuss in detail all the steps and challenges addressed and solutions adopted concerning the survey, solid modeling and FEA from laser scanning data of the historical complex of Villa Revedin-Bolasco
Maximizing Vanadium Redox Flow Battery Efficiency: Strategies of Flow Rate Control
Vanadium redox flow batteries (VRFBs) are one of the most promising technologies for large-scale energy storage due to their flexible energy and power capacity configurations. The energy losses evaluation assumes a very important rule on the VRFB characterization in order increase the efficiency of the battery. Very few papers describe the relations between hydraulic, electrical and chemical contributions to the system energy losses, especially in a large size VRFB system. In the first part a fluid dynamics characterization of a 9kW / 27 kWh VRFB test facility has been conducted. In particular, we will consider the internal resistance as the sum of an ohmic and a transport resistance. Secondly, an overall loss assessment based on both numerical and experimental results has been carried out. Finally, some improvements in the battery management strategy and in stack engineering are proposed, that results from this work and can help the future designer to develop more efficient VRFB stack with a compact design
Enhancing the efficiency of kW-class vanadium redox flow batteries by flow factor modulation: An experimental method
he paper presents a control method of the electrolyte flow factor in kW-class Vanadium Redox Flow Batteries that minimizes transport losses without affecting the battery's electrical performance. This method uses experimental data acquired on a 9 kW/27 kWh test facility at varying operating conditions. The effects of overpotentials on the polarization curves are then modeled as non-linear electrical resistances that vary with the stack current, state of charge and electrolyte flow rates. Our analysis of these variables shows that the optimal performance is found if the flow factor is modulated during operation according to stack current and the battery state, so as to minimize the overall flow-dependent losses. The optimal profiles have been identified as functions of the battery's operating conditions. Based on these results, a dynamic control for the electrolyte flow rates has been implemented at a software level (i.e. without modifying the hardware of the test facility), which is capable of maximizing the round-trip efficiency and exceeds the performance achieved with a constant flow factor strategy, as proposed in previous literature. The implementation of the optimal flow rate control requires a preliminary test campaign to collect performance data, which are then used in the control protocol to manage the battery's operation. This scheme is easily implementable at a software level in other industrial redox flow batteries
Modelling a Coupled Thermoelectromechanical Behaviour of Contact Elements via Fractal Surfaces
A three-dimensional coupled thermoelectromechanical model for electrical connectors is here proposed to evaluate local stress and temperature distributions around the contact area of electric connectors under different applied loads. A micromechanical numerical model has been developed by merging together the contact theory approach, which makes use of the so-called roughness parameters obtained from experimental measurements on real contact surfaces, with the topology description of the rough surface via the theory of fractal geometry. Particularly, the variation of asperities has been evaluated via the Weierstrass-Mandelbrot function. In this way the micromechanical model allowed for an upgraded contact algorithm in terms of effective contact area and thermal and electrical contact conductivities. Such an algorithm is subsequently implemented to construct a global model for performing transient thermoelectromechanical analyses without the need of simulating roughness asperities of contact surfaces, so reducing the computational cost. A comparison between numerical and analytical results shows that the adopted procedure is suitable to simulate the transient thermoelectromechanical response of electric connectors
DIGITAL MODEL OFWALLS OF PADUA LOWRELIEF
Photogrammetry has been widely used in the recent years in a number of applications, e.g. cultural heritage, surveying buildings and infrastructures. Despite nowadays its use is quite common, most of the used photogrammetric softwares are commercial. This paper aims at comparing the use of a free Matlab tool that is being developed at the University of Padova mostly for educational purposes with that of a commercial (and widely used) software (Agisoft PhotoScan). Despite the above mentioned free Matlab tool is designed to work for airborne photogrammetric, in this work it is used in a slightly different case: the 3D reconstruction of a low relief of the walls of Padova, which is on the fac¸ade of the church Santa Maria del Giglio, Venice, Italy
Comparison of discrete return and waveform terrestrial laser scanning for dense vegetation filtering
Abstract. In this paper we present the results of the comparison between two terrestrial laser scanners (TLS), a discrete return system (Riegl LMS-Z620) and an echo-digitizing system (Riegl VZ-400), employed for the survey of a dense forested area, in the italian Alps. The site is actually undergoing a strong debate among the inhabitants and local government authorities about the exploitation of the area as a huge quarry to produce building material. The dispute originates from the uncertainty about the instability of the underlying mountain slope, which was interested in 1966 by a landslide. The whole area was surveyed with the two laser scanners on February 2011 during the vegetation dormant period. A slight different processing workflow was applied to the collected datasets: the VZ-400 scans were pre-filtered by exploiting the "calibrated relative reflectance" readings and the multi-target capability provided by this laser scanning system. Next, two different spatial filters were applied to both the resulting georeferenced 3D models, in order to eliminate as much vegetation as possible: iterative filter and a custom morphological filter, developed by the authors. Achieved results show that for both datasets, the iterative and the morphological filters perform quite well for eliminating the vegetation, though some manual editing is still required since vegetation does not feature a prevalent growing direction. Furthermore, the comparison between the number of points left in the final DTMs shows that the VZ-400 provided a one order of magnitude denser point cloud wrt. the LMS-Z620. This demonstrates that a TLS with multi-target capability can potentially provide a more detailed DTM even in presence of dense vegetation
INTEGRAZIONE DI TECNICHE DI RILEVAMENTO PER IL CONTROLLO DI STABILITĂ€ DI UNA STRUTTURA STORICA
RIASSUNTO
Negli anni recenti, la possibilitĂ offerta dal laser scanner terrestre di acquisire grandi quantitĂ di dati in tempi relativamente brevi, con
un grado di precisione e dettaglio elevati, ha spinto l’interesse di topografi, ingegneri, architetti e archeologi a considerare il laser a
scansione come uno strumento di rilevamento fondamentale per la modellazione 3D di oggetti e ambienti facenti parte del Patrimonio
Culturale di una nazione. Prova di tale fenomeno è costituito dall’ampia varietà di oggetti che sino ad oggi sono stati sottoposti a
scansione: dal piccolo pezzo di ceramica alla statua di marmo, dall’edificio storico ad un intero sito archeologico. D’altra parte, nel
panorama dei possibili impieghi del laser a scansione, la sua applicazione per il controllo di stabilitĂ di una struttura o edificio di
interesse storico appare tutt’ora un campo di ricerca poco indagato. Al fine di approfondire questa tematica di ricerca, è stato attivato
un progetto triennale volto a verificare la possibilitĂ di utilizzare in modo integrato una molteplicitĂ di tecniche di rilevamento per il
controllo della stabilitĂ di una struttura storica caratterizzata da una geometria complessa. In particolare, tale progetto prevede di
utilizzare strumentazione laser scanner terrestre, stazione totale, flessimetri, fotogrammetria e termografia per effettuare una serie di
rilievi a cadenza semestrale del Teatro Anatomico dell’Università di Padova. Lo scopo del progetto in questione è quello di verificare
la stabilitĂ nel tempo di questo tipo di struttura, considerando in particolare gli effetti del decadimento organico delle parti in legno.
In questa nota vengono quindi presentati i risultati ottenuti finora, ponendo particolare attenzione ai problemi e difficoltĂ insorte nel
rilievo laser scanner e modellazione 3D di una struttura di interesse storico e culturale caratterizzata da una geometria inusuale e
alquanto complessa.
ABSTRACT
The chance provided by terrestrial laser scanners to achieve, in short time, very dense, accurate and detailed 3D data drew in recent
years the interest of surveyors, engineers, architects and archaeologists towards the laser scanning technique as an invaluable
surveying mean for 3D modeling of sites and artifacts of cultural heritage. A wide variety of objects, e.g., small pieces of pottery,
statues, buildings, and large areas of archaeological sites, have been scanned and modeled for various purposes like preservation,
reconstruction, study, and museum exhibitions. However, the use of TLS systems for stability control is still a research field not
much investigated. In the view of insight investigation on this topic, a three-years project has been established in order to evaluate
the use of multiple surveying techniques for the stability control of a complex historical structure. To this aim, terrestrial laser
scanning (TLS), total station (TS), deflectometers, photogrammetry and thermography are being employed to perform on a 6 month
basis a set of surveys of the Anatomy Theatre, one of the oldest, most important and best-known historical “medical” buildings.
Located inside the Palazzo del Bo’, the building seat of the University of Padua, Italy. The main goal of this work is to verify the
stability over the time of this kind of structure, given the inherent organic decay of the wooden parts.
In this paper we present the results obtained from the repeated surveys and highlight issues and difficulties related to the laser
scanning of an unusual geometry such as the one provided by the Anatomy Theatre of the University of Padua
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