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Projeto de investigaĆ§Ć£o
NANOMATERIALS-BASED INNOVATIVE ENGINEERING SOLUTION TO ENSURE SUSTAINABLE SAFEGUARD TO INDOOR AIR
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Fullāsize experimental assessment of the aerodynamic sealing of low velocity air curtains
Publication . Viegas, JoĆ£o Carlos Godinho; Carrasco, Levi; Pinto, LuĆs; Morais, JoĆ£o; Aelenei, Daniel; Morais, Paulo; DEC - Departamento de Engenharia Civil; UNINOVA-Instituto de Desenvolvimento de Novas Tecnologias; CTS - Centro de Tecnologia e Sistemas; MDPI - Multidisciplinary Digital Publishing Institute
Vertical air curtains are often used to separate two different zones to reduce contaminant transfer or even to provide aerodynamic sealing from one zone to the other. In this isothermal full-size experimental research work, the contaminant transfer between zones is reduced using an air extraction from the ācontaminatedā compartment and an air curtain. This work correlates the min-imum exhaust air flow rate required to reach the aerodynamic sealing at the opening connecting two different zones with the jet nozzle velocity for small nozzle thicknesses (5 mm, 10 mm and 16 mm), particularly for Reynolds numbers below 3800. Following the experimental study, a general physical law that relates the jet parameters (angle, nozzle thickness and jet velocity at the nozzle) with the average velocity through the opening (for the condition of acceptable contaminant tight-ness) was obtained. The results showed that the average velocity of the flow across a door protected by an air curtain required to keep the aerodynamic sealing varies linearly with Re. The slope, how-ever, is different below and above Re = 3820.
Gate-tunable electroluminescence in Aviram-Ratner-type molecules: Kinetic description
Publication . Petrov, Elmar G.; Gorbach, Victor V.; Ragulya, Andrey V.; Lyubchik, Andrey; Lyubchik, Svetlana; DQ - Departamento de QuĆmica; LAQV@REQUIMTE; AIP - American Institute of Physics
A theoretical study of the mechanisms of electroluminescence (EL) generation in photoactive molecules with donor and acceptor centers linked by saturated Ļ-bonds (molecules of the Aviram-Ratner-type) is presented. The approach is based on the kinetics of single-electron transitions between many-body molecular states. This study shows that the EL polarity arises due to asymmetric coupling of molecular orbitals of the photochromic part of the molecule to the electrodes. The gate voltage controls the power of the EL through the occupancy of the excited singlet state. The shifting of the orbital energies forms a resonant or a non-resonant path for the transmission of electrons through the molecule. The action of the gate voltage is reflected in specific critical voltages. An analytical dependence of the critical voltages on the energies of molecular states involved in the formation of EL, as well as on the gate voltage, was derived for both positive and negative polarities. Conditions under which the gate voltage lowers the absolute value of the bias voltage that is responsible for the activation of the resonance mechanism of EL formation were also established. This is an important factor in control of EL in molecular junctions.
Features of superexchange nonresonant tunneling conductance in anchored molecular wires
Publication . Petrov, Elmar G.; Shevchenko, Yevgen V.; Snitsarev, Vladislav; Gorbach, Victor V.; Ragulya, Andrey V.; Lyubchik, Svetlana; DQ - Departamento de QuĆmica; LAQV@REQUIMTE; AIP - American Institute of Physics
A modified superexchange model is used to clarify the physical mechanisms for the formation of nonresonant tunneling conductance in terminated molecular wires. Due to the specific relationship between its key parameters, this model has wider areas of applicability compared to the flat-barrier model and the standard superexchange model, which are widely involved for the physical interpretation of experimental results. Moreover, the results obtained in the two latest models appear in the modified model as characteristic limiting cases. Our estimates show that the exponential decay of conductance, characterized by an attenuation factor Ī² (per repeating unit), is limited by the conditions Ī² ā¤ 1.2 and Ī² ā„ 3.7 for the flat-barrier and standard models, respectively. At the same time, the modified superexchange model yields Ī² > 0, which, thus, allows us to analyze the tunneling conductance in molecular wires containing both saturated and conjugated bonds. We also show that for a small number of N repeating wire units (about 3-6 depending on the value of Ī²), the exponential dependence of conductance on N is violated and, accordingly, contact conductance is not identical to conductance at N = 0. Formulas are found which, on the basis of experimental data, make it possible to establish the values of superexchange parameters as well as indicate the conditions of possible hybridization between the orbitals of the anchor groups and the adjacent end units belonging to the interior wire region. One example is the establishment of features in the tunneling conductance of terminated alkane chains caused by the nature of their anchor groups.
Experimental Study on the Aerodynamic Sealing of Air Curtains
Publication . Viegas, Joao Carlos; Oliveira, Fernando; Aelenei, Daniel; DEC - Departamento de Engenharia Civil; MDPI - Multidisciplinary Digital Publishing Institute
Controlling the air quality is of the utmost importance in today's buildings. Vertical air curtains are often used to separate two different climatic zones with a view to reduce heat transfer. In fact, this research work proposes an air curtain aimed to ensure a proper separation between two zones, a clean one and a contaminated one. The methodology of this research includes: (i) small-scale tests on water models to ensure that the contamination does not pass through the air curtain, and (ii) an analytical development integrating the main physical characteristics of plane jets. In the solution developed, the airflow is extracted from the contaminated compartment to reduce the curtain airflow rejected to the exterior of the compartment. In this research work, it was possible to determine the minimum exhaust flow necessary to ensure the aerodynamic sealing of the air curtain. This article addresses the methodology used to perform the small-scale water tests and the corresponding results.
Optical properties, photocatalytic and bactericide activity of pure and Ag-decorated Zr, al-doped ZnO
Publication . Akhkozov, Leonid; Gorban, Oksana; Danilenko, Igor; Gorban, Sergii; Volkova, Galina; Bryukhanova, Iryna; Shapovalova, Olesya; Lyubchik, Svetlana; Konstantinova, Tetyana; LAQV@REQUIMTE
Structure, optical and photocatalytic properties for wide band gap oxide doped zinc oxide are investigated by XRD, ESR and UV-visible spectroscopy. It was shown the introduction of Al2O3 or ZrO2 led to form of structural defects in zinc oxide matrix. According ESR data a small amount of ZrO2 (0.01 mol.%) in ZnO forms a defects of donor nature, while the same amount of Al2O3 in ZnO matrix led forming as acceptor and as donor defects. Observed tail and shift of optical band gap confirmed ESR data. It was shown the increasing of donor defects in structure ZnO led to increase of photocatalytic activity to phenol degradation. It was shown the dopant types also determined a kind of intermediates of phenol degradation and possible mechanism. For Ag-decorated doped ZnO it is also shown that mechanism of phenol degradation contain a redox cycle. It was shown the bactericide activity of Ag-decorated ZrO2-doped ZnO to S.aureus is better than E.coli.
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Entidade financiadora
European Commission
Programa de financiamento
H2020
NĆŗmero da atribuiĆ§Ć£o
690968