Interaction between a laser beam and semiconductor nanowires: application to the raman spectrum of Si nanowires

One presents in this work the study of the interaction between a focused laser beam and Si nanowires (NWs). The NWs heating induced by the laser beam is studied by solving the heat transfer equation by finite element methods (FEM). This analysis permits to establish the temperature distribution inside the NW when it is excited by the laser beam. The overheating is dependent on the dimensions of the NW, both the diameter and the length. When performing optical characterisation of NWs using focused laser beams, one has to consider the temperature increase introduced by the laser beam. An important issue concerns the fact that the NW's diameter has subwavelength dimensions, and is also smaller than the focused laser beam. The analysis of the thermal behaviour of the NWs under the excitation with the laser beam permits the interpretation of the Raman spectrum of Si NWs. It is demonstrated that the temperature increase induced by the laser beam plays a major role in shaping the Raman spectrum of Si NWs

Evaluation offreeze-thaw damage in concrete by ultrasonic imaging

This work studies the use of ultrasonic imaging as an evaluation tool in concrete subjected to freeze–thaw (F–T) cycles. To evaluate the damage in this deterioration process, ultrasonic velocity and attenuation images have been generated from concrete specimens with and without air-entraining agents. Two parameters have been proposed from these ultrasonic images according to our experimental setup: the non-assessable area proportion (NAAP) and a weighted average velocity in terms of the NAAP. The proposed parameters have been compared with the recommended failure criteria of the ASTM and Rilem standards, which employ ultrasonic contact measurements. The principal advantage of the use of ultrasonic images and the proposed methodology in comparison with the ultrasonic velocity measurements by contact is the possibility of detection of incipient damage caused by accelerated freeze–thaw cycles

Thermal conductivity measurements of macroscopic frozen salt ice analogues of Jovian icy moons in support of the planned JUICE mission

14 páginas, 16 figuras, 2 tablascThe study of thermal properties of frozen salt solutions representative of ice layers in Jovian moons is crucial to support the JUpiter ICy moons Explorer (JUICE) (ESA) and Europa Clipper (NASA) missions, which will be launched in the upcoming years to make detailed observations of the giant gaseous planet Jupiter and three of its largest moons (Ganymede, Europa, and Callisto), due to the scarcity of experimental measurements. Therefore, we have conducted a set of experiments to measure and study the thermal conductivity of macroscopic frozen salt solutions of particular interest in these regions, including sodium chloride (NaCl), magnesium sulphate (MgSO4 ), sodium sulphate (Na2 SO4 ), and magnesium chloride (MgCl2 ). Measurements were performed at atmospheric pressure and temperatures from 0 to −70 ◦C in a climatic chamber. Temperature and calorimetry were measured during the course of the experiments. An interesting side effect of these measurements is that they served to spot phase changes in the frozen salt solutions, even for very low salt concentrations. A small sample of the liquid salt-water solution was set aside for the calorimetry measurements. These experiments and the measurements of thermal conductivity and calorimetry will be valuable to constrain the chemical composition, physical state, and temperature of the icy crusts of Ganymede, Europa, and Callisto.This project received financial support of The European Space Agency (ESA) contracts No.: RFP/3-15589/18/ES/CM and 4000126441/19/ES/CM: ‘Measurements of thermal and dielectric properties of ices in support to future radar measurements of Jovian Icy moons’, The Unidad de Excelencia ‘Mar ́ıa de Maeztu’ MDM-2017-0737– Centro de Astrobiolog ́ıa (INTA-CSIC), The Spanish Ministry of Science, Innovation and Universities AYA2017-85322-R and PID2020-118974GB-C21 (AEI/FEDER, UE), Retos Investigaci ́on BIA2016-77992-R (AEI/FEDER, UE), and ‘Explora Ciencia y Explora Tecnolog ́ıa’ [AYA2017-91062- EXP]. We are grateful to Anezina Solomonidou for assistance in the project proposal. The view expressed in this article can in no way be taken to reflect the official opinion of the European Space Agency. We thank the reviewer of this article for his constructive comments.Peer reviewe

An open-access database and analysis tool for perovskite solar cells based on the FAIR data principles

Large datasets are now ubiquitous as technology enables higher-throughput experiments, but rarely can a research field truly benefit from the research data generated due to inconsistent formatting, undocumented storage or improper dissemination. Here we extract all the meaningful device data from peer-reviewed papers on metal-halide perovskite solar cells published so far and make them available in a database. We collect data from over 42, 400 photovoltaic devices with up to 100 parameters per device. We then develop open-source and accessible procedures to analyse the data, providing examples of insights that can be gleaned from the analysis of a large dataset. The database, graphics and analysis tools are made available to the community and will continue to evolve as an open-source initiative. This approach of extensively capturing the progress of an entire field, including sorting, interactive exploration and graphical representation of the data, will be applicable to many fields in materials science, engineering and biosciences. © 2021, The Author(s)

The Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory is a second generation water Cherenkov detector designed to determine whether the currently observed solar neutrino deficit is a result of neutrino oscillations. The detector is unique in its use of D2O as a detection medium, permitting it to make a solar model-independent test of the neutrino oscillation hypothesis by comparison of the charged- and neutral-current interaction rates. In this paper the physical properties, construction, and preliminary operation of the Sudbury Neutrino Observatory are described. Data and predicted operating parameters are provided whenever possible.Comment: 58 pages, 12 figures, submitted to Nucl. Inst. Meth. Uses elsart and epsf style files. For additional information about SNO see http://www.sno.phy.queensu.ca . This version has some new reference

Measurement of the νe and total 8B solar neutrino fluxes with the Sudbury Neutrino Observatory phase-III data set

This paper details the solar neutrino analysis of the 385.17-day phase-III data set acquired by the Sudbury Neutrino Observatory (SNO). An array of 3He proportional counters was installed in the heavy-water target to measure precisely the rate of neutrino-deuteron neutral-current interactions. This technique to determine the total active 8B solar neutrino flux was largely independent of the methods employed in previous phases. The total flux of active neutrinos was measured to be 5.54-0.31+0.33(stat.)-0.34+0.36(syst.)×106 cm-2 s-1, consistent with previous measurements and standard solar models. A global analysis of solar and reactor neutrino mixing parameters yielded the best-fit values of Δm2=7.59-0.21+0.19×10 -5eV2 and θ=34.4-1.2+1.3degrees

Characterization of mortar samples using ultrasonic scattering attenuation

AbstractIn this paper, volume fraction and size of aggregates in highly dispersive materials have been estimated using ultrasonic techniques. Estimations were made by obtaining the best fit between experimental scattering attenuation and theoretical predictions obtained from an N-phase extension of the dynamic generalized self-consistent method (DGSCM) proposed by Yang [J. Appl. Mech. 70 (2003) 575]. Furthermore, a time-frequency procedure has been designed to estimate frequency-dependent scattering attenuation from experimental measures. The research was conducted with several cement mortar specimens made by taking into account different aggregate-to-cement ratio and water-to-cement ratio. Estimations of both size and volume fraction, were made and good agreements was found between experimental attenuation curves and theoretical predictions

Monitoring of Freeze-Thaw Cycles in concrete using an embedded micro-Sensor and Strain gauges

This paper deals with the study of internal stress produced during freeze-thaw (F-T) cycles using two non-destructive measurement approaches: the first approach devoted to continuous and internal monitoring using an embedded sensor based on amorphous ferromagnetic microwire during the cycles, and the second one, measuring the strain variations at the surface of the specimens by means of strain gauges. Also, measurements of ultrasonic pulse velocity through the concrete specimens were taken simultaneously during the freeze-thaw cycles. The objectives of this paper are to investigate the internal strain of freeze-thaw exposure providing a new way of measurement. These inspections may provide great reference for further research on the development of a calculation modelling of deterioration process in concrete structures under a freeze-thaw environment

Beam Solar Irradiation Assessment for Sonora, Mexico

AbstractLocated in north western Mexico, the State of Sonora has an excellent quality solar resource, with the highest solar irradiation levels in the country. In less than 1% of its vast arid territory, it receives enough solar power to satisfy the energy demand of the entire country. In spite of its huge solar potential, there has been little work on the measurement of solar radiation in this area. At a few locations, global solar radiation has been measured for some years. Also there have been some works reporting evaluation of solar irradiation based on empirical models or satellite images. Because of the very small amount of precipitation on most of its territory, Sonora is ideal for the implementation of concentrated solar power (CSP). Beam solar radiation data is necessary for the sizing and assessment of CSP plants. Unfortunately, very little information is available on this solar radiation component for Sonora. The present work reports on the results of recent measurements of beam and solar global radiation for the area of the city of Hermosillo, in the center of the state. The obtained results are compared with other available information obtained by indirect methods, such as satellite based or empirical climate data based models. The yearly available energy as well as the utilizable energy for certain irradiance levels is evaluated