Abstract
Ultraviolet-induced Luminescence (UVL) is the property of some materials of emitting light once illuminated by a source of UV radiation. This feature is characteristic of some mediums and ...pigments, such as some red lakes, widely used for the realisation of works of art. On the one hand, UVL represents a like strike for a researcher in the cultural heritage field: in fact, UVL allows to characterise the state of conservation of the paintings and, in some cases, to recognize at glance some of the materials used by the artists. On the other hand, the contribution of UVL to the study of the artefacts is almost always limited to qualitative observation, while any speculation about the cause of the luminescence emission relies on the observer’s expertise. The aim of this paper is to overcome this paradigm, moving a step toward a more quantitative interpretation of the luminescence signal. The obtained results concern the case study of pictorial materials by Giuseppe Pellizza da Volpedo (1868–1907, Volpedo, AL, Italy) including his iconic masterpiece
Quarto Stato
(1889–1901), but the method has general validity and can be applied whenever the appropriate experimental conditions occur. Once designed an appropriate set-up, the statistical comparison between the acquisitions performed on
Quarto Stato
, on a palette belonged to the master, on drafts made by the author himself and on a set of ad hoc prepared samples both with commercial contemporary pigments and prepared with the traditional recipe, shed some light on which materials have been employed by the artist, where they have been applied and support some intriguing speculations on the use of the industrial lakes in the
Quarto Stato
painting.
The efficiency of generating electricity from heat using concentrated solar power plants (which use mirrors or lenses to concentrate sunlight in order to drive heat engines, usually involving ...turbines) may be appreciably increased by operating with higher turbine inlet temperatures, but this would require improved heat exchanger materials. By operating turbines with inlet temperatures above 1,023 kelvin using closed-cycle high-pressure supercritical carbon dioxide (sCO
) recompression cycles, instead of using conventional (such as subcritical steam Rankine) cycles with inlet temperatures below 823 kelvin
, the relative heat-to-electricity conversion efficiency may be increased by more than 20 per cent. The resulting reduction in the cost of dispatchable electricity from concentrated solar power plants (coupled with thermal energy storage
) would be an important step towards direct competition with fossil-fuel-based plants and a large reduction in greenhouse gas emissions
. However, the inlet temperatures of closed-cycle high-pressure sCO
turbine systems are limited
by the thermomechanical performance of the compact, metal-alloy-based, printed-circuit-type heat exchangers used to transfer heat to sCO
. Here we present a robust composite of ceramic (zirconium carbide, ZrC) and the refractory metal tungsten (W) for use in printed-circuit-type heat exchangers at temperatures above 1,023 kelvin
. This composite has attractive high-temperature thermal, mechanical and chemical properties and can be processed in a cost-effective manner. We fabricated ZrC/W-based heat exchanger plates with tunable channel patterns by the shape-and-size-preserving chemical conversion of porous tungsten carbide plates. The dense ZrC/W-based composites exhibited failure strengths of over 350 megapascals at 1,073 kelvin, and thermal conductivity values two to three times greater than those of iron- or nickel-based alloys at this temperature. Corrosion resistance to sCO
at 1,023 kelvin and 20 megapascals was achieved
by bonding a copper layer to the composite surface and adding 50 parts per million carbon monoxide to sCO
. Techno-economic analyses indicate that ZrC/W-based heat exchangers can strongly outperform nickel-superalloy-based printed-circuit heat exchangers at lower cost.
Photonics is essential in life science research and the continuous development of methods offers researchers tools of unprecedented sensitivity. Sensors are key to the exploitation of the most ...advanced biophotonic techniques with highly demanding specifications in terms of single photon sensitivity, time resolution, miniaturisation real-time processing and data throughput. Silicon photomultipliers and Single Photon Avalanche Diode (SPAD) imagers represent the state-of-the-art in photon detection with single photon sensitivity, photon number resolving capability and the possibility to integrate on chip advanced functionalities. As a consequence, they can be the platform for the next generation biophotonic instruments and methods.
This paper summarises the main biophotonic techniques and reports exemplary applications of Silicon Photomultipliers and SPAD imagers for fluorescence, chemiluminescence, time correlated single photon counting and imaging. Achievements and current limitations are addressed, pointing as well to the most recent technology advances and highlighting the possible pathways for the near future.
In this paper the problem of high-precision motion control of remotely operated vehicles (ROVs) in the proximity of the seabed through vision-based motion estimation is addressed. The proposed ...approach consists of the integration of a cheap monocular vision system for the estimate of the vehicle's linear motion with a conventional dual-loop hierarchical architecture for kinematics and dynamics control. Results obtained by operating at sea the Romeo ROV are presented, demonstrating the system capability in performing station-keeping in the presence of external disturbance and relatively high accuracy in horizontal motion control.
Abstract
Brachytherapy is a radiotherapy procedure performed with radioactive sources implanted into the patient's body, close to the area affected by cancer. This is a reference procedure for the ...treatment of prostate and gynecologic cancer due to the reduction of the dose released close to organs at risk (e.g., rectum, bladder, colon). For this reason, real-time dose verification and source localisation are essential for an optimal treatment plan. The ORIGIN collaboration aims to achieve this goal through a 16-fibre sensor system, designed
to house a small volume of scintillating material in a transparent fibre tip to enable point-like measurements.
The selected scintillating materials feature a decay time of about 500 μs and the signal associated with the primary
γ
-ray interaction results in the emission of a sequence of single photons distributed over time. Therefore, the dosimeter requires a detector with single-photon sensitivity and a system designed to provide dose measurements by photon counting.
Uniformity of fibre response, system stability and reproducibility of measurements are key features of the dosimeter. The characterisation of the 16-channel dosimeter system equipped with thermo-electrically cooled Silicon Photomultipliers, carried out in the laboratory using an X-ray cabinet, is discussed and the results are compared with an earlier version equipped with SiPMs operated at room temperature.
A first dual-readout fibre calorimeter readout with Silicon Photomultipliers was designed, constructed and tested on beam. This first test completed the proof-of-concept and pointed out some issues ...to be address in future beam tests. Possible solutions and strategies to overcome these challenges are summarized in this paper.
IDEA (Innovative Detector for Electron–positron Accelerators) is a detector concept designed for a future leptonic collider operating as a Higgs factory. It is based on innovative detector ...technologies developed over years of R&D. In September 2018, prototypes of the proposed sub-detectors have been tested for the first time on a beam line at CERN. The preliminary results from this test of a full slice of the IDEA detector and standalone measurements of dual read-out calorimeter prototypes are presented.
Among manufacture techniques for SiC ceramics, reactive infiltration has proven to be the most efficient. However, materials manufactured with this technique present minimum 10% of unreacted silicon. ...Si hinders the performance of the material. The replacement of Si with a MexSiy can improve the performance of the composite. Since Me–Si alloys wet carbon materials, they are suitable candidates to be used as infiltrants in SiC/MexSiy composite production via reactive infiltration. To optimize the process, it is necessary to identify the mechanisms involved in infiltration and the parameters governing them. A basic wetting study can provide a clear understanding of the operative mechanisms and allow obtaining accurate parameters. In this work, the wetting behavior of silicon-cobalt alloys on carbon materials was studied using the sessile drop technique. The influence of temperature, composition and carbon crystallinity was evaluated, observing a strong dependence of process kinetics and reactivity with temperature and carbon crystallinity.
A cosmic ray muon detection system is proposed for stability monitoring in the field of civil engineering, in particular for the static monitoring of historical buildings, where conservation ...constraints are severe and the time evolution of the deformation phenomena under study may be of the order of months or years. The stability monitoring of the wooden vaulted roof of the Palazzo della Loggia, located in the town of Brescia, Italy, has been considered as a case study. The feasibility, as well as the performance and limitations of a stability monitoring system based on cosmic ray tracking have been studied by Monte Carlo simulations. A study of possible systematic uncertainties is presented along with a realistic design for the construction of a measurement system prototype.
Tests of a dual-readout fiber calorimeter with SiPM light sensors Antonello, M.; Caccia, M.; Cascella, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2018, Letnik:
899, Številka:
C
Journal Article
Recenzirano
Odprti dostop
In this paper, we describe the first tests of a dual-readout fiber calorimeter in which silicon photomultipliers are used to sense the (scintillation and Čerenkov) light signals. The main challenge ...in this detector is implementing a design that minimizes the optical crosstalk between the two types of fibers, which are located very close to each other and carry light signals that differ in intensity by about a factor of 60. The experimental data, which were obtained with beams of high-energy electrons and muons as well as in lab tests, illustrate to what extent this challenge was met. The Čerenkov light yield, a limiting factor for the energy resolution of this type of calorimeter, was measured to be about twice that of the previously tested configurations based on photomultiplier tubes. The lateral profiles of electromagnetic showers were measured on a scale of millimeters from the shower axis and significant differences were found between the profiles measured with the scintillating and the Čerenkov fibers.
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