519 research outputs found
Irreversibility at zero temperature from the perspective of the environemnt
We address the emergence of entropy production in the non-equilibrium process
of an open quantum system from the viewpoint of the environment. By making use
of a dilation-based approach akin to Stinespring theorem, we derive an
expression for the entropy production that comprises two fundamental
contributions. The first is linked to the rate of creation of correlations
between system and environment whereas the second highlights the possibility
for the environment to modify its state in light of its coupling to the system.
Both terms are shown to be associated with irreversible currents within the
system and the environment, which pinpoint the emergence of irreversibility in
the Markovian limit. Finally, we discuss how such a change of perspective in
the study of entropy production has fecund implications for the study of
non-Markovian open-system dynamics
Evaluation of band gap energy of TiO2 precipitated from titanium sulphate
The determination of the band gap energy () of semiconductors powder materials can be performed from diffuse reflectance spectroscopy (DRS) measurements. For this purpose, the classical theory proposed by Kubelka and Munk (K-M) and the so-called plot Tauc, both discussed here, have been largely employed. We investigate the values of anatase TiO2 particles synthesized by precipitation of titanyl sulphate in the presence of 5% ammonia solution and titanium and iron salts. Based on K-M function and Tauc plot and considering that the TiO2 anatase phase is an indirect band gap semiconductor, our results indicate that the samples subjected to a mechanochemical treatment (mill rotation speed equal to 300 rpm) present substantially lower values compared to those reported by other authors in a recent work(undefined
Photocatalytic asphalt mixtures: semiconductors' impact in skid resistance and texture
Photocatalytic asphalt mixtures have the capability of mitigating air quality problems and degrade oils/greases by using semiconductors. The techniques to do so can change their functional characteristics. This study aimed to analyse the functionalization effect on the essential surface characteristics, such as macrotexture, skid resistance, and microtexture. AC 14 and AC 6 mixtures were functionalised with nano-TiO2 and micro-ZnO by spraying and bulk incorporation. Mean Profile Depth, British Pendulum and microtexture amplitude parameters were evaluated. TiO2 application seemed to smooth the surface slightly. In dry condition, the skid resistance of functionalised asphalt and control mixtures was similar. In wet condition, the functionalization caused a maximum decrease of 7% in skid resistance. The amplitude parameters were not affected by any functionalization technique except the skewness of AC 14 with 6% TiO2 by bulk incorporation. Furthermore, the application of the semiconductors can be used without high impacts in texture and skid resistance.This work was partially financed by FCT (Fundacao para a Ciencia e a Tecnologia) under the project [PTDC/FIS/120412/2010]: "Nanobased concepts for Innovative & Eco-sustainable constructive material's surfaces" and project [PEst-OE/ECI/UI4047/2014]. Also, the first author would like to acknowledge FCT for the PhD scholarship [SFRH/BD/137421/2018]
Applied optics in the development of smart asphalt mixtures
The functionalization of asphalt mixtures is carried out in order to provide new capabilities to the road pavements, with major social, environmental and financial benefits. Optical characterization techniques as well as optical processes like photocatalysis play a major role in the development of new asphalt mixtures with smart functions. These advanced capabilities which are being developed in asphalt mixtures are: photocatalytic, superhydrophobic, self-cleaning, de-icing/anti-ice, self-healing, thermochromic, and latent heat thermal energy storage. The main objective of this research work is to stress the importance of optics and photonics technologies giving an overview of advanced functionalized smart asphalt mixtures.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020.
This work was partially financed by FCT - Fundação para a Ciência e a Tecnologia - under the projects of the Strategic Funding UIDB/04650/2020, MicroCoolPav project EXPL/EQU-EQU/1110/2021, and NanoAir project PTDC/FISMAC/6606/2020
Photocatalytic performance of textiles coated with titanium dioxide-reduced graphene oxide system for degradation of crude petroleum under similar solar irradiation
The pollution caused by oil and its toxic derivatives presents a considerable risk to the public health and the environment. This work is devoted to the study of the influence of TiO2 nanoparticles immobilized on three types of textiles materials (Cotton, Entretela, and Polylactic Acid-PLA) coated with reduced graphene oxide (RGO) to be used for degradation of crude petroleum under simulated solar irradiation. The morphological studies of the functionalized textiles substrates were performed by using Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy, which indicated an excellent dispersion and adhesion of nanoparticles of about 60% (atomic %Ti) on the textile fibers covered with RGO after washing. Ultraviolet-visible Diffuse Reflectance spectra suggest a reduction in the band gap energy of TiO2 up to 2.86 eV due to the presence of RGO. The functionalized textiles presented at least 60% of photocatalytic efficiency measured by Rhodamine B degradation, decreasing less than 12% after the rigorous washing. The excitation/emission Synchronous Fluorescence Spectroscopy and Fourier-transform Infrared spectroscopies demonstrated a great potential for photocatalytic degradation of the functionalized textiles substrates as the appearance of the hydroxyl, carboxyl, and the C-O bands confirm the photoinduced oxidation of the organic compounds implying with high prospects in petroleum and wastewater treatment areas. Moreover, this environmentally friendly, sustainable, and inclusive research work can be included in clean technologies, contributing to the novel socio-economic model recognized as "Green Recovery".[GRAPHICS].This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and the project PTDC/FIS-MAC/6606/2020. Also, the third author would like to acknowledge the FCT for the Ph.D. scholarship (SFRH/BD/137421/2018). Moreover, the authors would like to acknowledge Sociedade Nacional de Combusti ' veis de Angola (Sonangol), which partially provided the crude oil samples
Advancements in phase change materials in asphalt pavements for mitigation of urban heat island effect: bibliometric analysis and systematic review
This research presents a dual-pronged bibliometric and systematic review of the
integration of phase change materials (PCMs) in asphalt pavements to counteract the urban heat
island (UHI) effect. The bibliometric approach discerns the evolution of PCM-inclusion asphalt
research, highlighting a marked rise in the number of publications between 2019 and 2022. Notably,
Chang’an University in China has emerged as a leading contributor. The systematic review
addresses key questions like optimal PCM types for UHI effect mitigation, strategies for PCM
leakage prevention in asphalt, and effects on mechanical properties. The findings identify
polyethylene glycols (PEGs), especially PEG2000 and PEG4000, as prevailing PCMs due to their
wide phase-change temperature range and significant enthalpy during phase transitions. While
including PCMs can modify asphalt’s mechanical attributes, such mixtures typically stay within
performance norms. This review emphasises the potential of PCMs in urban heat management and
the need for further research to achieve optimal thermal and mechanical balanceThis research was partially funded by the Portuguese Foundation for Science and
Technology (FCT) under the framework of the projects MicroCoolPav EXPL/EQU-EQU/1110/2021,
NanoAir PTDC/FIS-MAC/6606/2020, UIDB/04650/2020, and UIDB/04029/2020. This research was
also supported by the doctoral Grant PRT/BD/154269/2022 financed by the FCT, and with funds
from POR Norte-Portugal 2020 and State Budget, under MIT Portugal Program. I.R.S. would like to
acknowledge the FCT for funding (2022.00763.CEECIND). V.C.B. acknowledges the Fundação
Cearense de Apoio ao Desenvolvimento CientÃfico e Tecnológico (Funcap), MLC-0191-
00144.01.00/22 (Edital Mulheres na Ciência), and the National Council for Scientific and
Technological Development (CNPq), Process 404978/2021-5—Call CNPq/MCTI/FNDCT N°
18/2021—Faixa B—Consolidated Groups
The Structure and Dynamics of the Upper Chromosphere and Lower Transition Region as Revealed by the Subarcsecond VAULT Observations
The Very high Angular resolution ULtraviolet Telescope (VAULT) is a sounding
rocket payload built to study the crucial interface between the solar
chromosphere and the corona by observing the strongest line in the solar
spectrum, the Ly-a line at 1216 {\AA}. In two flights, VAULT succeeded in
obtaining the first ever sub-arcsecond (0.5") images of this region with high
sensitivity and cadence. Detailed analyses of those observations have
contributed significantly to new ideas about the nature of the transition
region. Here, we present a broad overview of the Ly-a atmosphere as revealed by
the VAULT observations, and bring together past results and new analyses from
the second VAULT flight to create a synthesis of our current knowledge of the
high-resolution Ly-a Sun. We hope that this work will serve as a good reference
for the design of upcoming Ly-a telescopes and observing plans.Comment: 28 pages, 11 figure
Mitigation of urban heat island effects by thermochromic asphalt pavement
Asphalt road pavements are usually dark and, consequently, have a low albedo. Therefore, they absorb energy as heat, increasing the Urban Heat Island (UHI) effect, which impacts the environment, energy consumption, and human health. Through the functionalization with thermochromic materials (TM), this work aims to develop a smart asphalt pavement able to change its surface color, increasing the reflectance, and thus mitigate this phenomenon. To achieve this goal, asphalt substrates were functionalized by a surface spray coating of a thermochromic solution (TS) containing aqueous solution of thermochromic microcapsules (thermocapsules), dye, and epoxy resin. To evaluate the functionalization features, Fourier Transform Infrared Spectroscopy (FTIR), and Thermal Differential test (TDT) with cyclic temperature variation were performed in the functionalized asphalt binder. Moreover, Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectrometry (EDS), a Quick Ultraviolet Accelerated Weathering Test (QUV) with Colorimetry test, and an adaptation of the Accelerated Polishing Test (APT) were performed on the functionalized asphalt mixture. The results indicate that the functionalization of asphalt substrates with TS exhibits a reversible color-change ability, higher luminosity values when subjected to temperatures above 30 C, and wear resistance
Highly ionized Fe X-ray lines at energies 7.7-8.6 keV
Fe XXV lines at 1.85 A (6.70 keV) and nearby Fe XXIV satellites have been
widely used for determining the temperature of the hottest parts of solar flare
and tokamak plasmas, though the spectral region is crowded and the lines are
blended during flare impulsive stages. The aim of this work is to show that
similarly excited Fe lines in the 7.7--8.6 keV (1.44--1.61 A) region have the
same diagnostic capability with the advantage of not being so crowded. Spectra
in the 7.7--8.6 keV range are synthesized using the CHIANTI spectral package
for conditions (temperature, turbulent velocities) appropriate to solar flares.
The calculated spectra show that the Fe lines in the 7.7--8.6 keV are well
separated even when turbulent velocities are present, and Fe XXIV/Fe XXV line
ratios should therefore provide valuable tools for diagnosing flares and
tokamak plasmas. It is concluded that Fe lines in the 7.7--8.6 keV range are
ideal for the measurement of flare temperature and for detecting the presence
of low-energy nonthermal electrons present at flare impulsive stages. An
indication of what type of instruments to observe this region is given.Comment: 6 pages, 7 figures. Accepted for publication in Astronomy and
Astrophysic
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