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  • ItemArtigo
    On the gas heating effect of helium atmospheric pressure plasma jet
    (2023-05-01) do Nascimento, Fellype ; Gerling, Torsten ; Kostov, Konstantin Georgiev ; Universidade Estadual Paulista (UNESP) ; Leibniz Institute for Plasma Science and Technology-INP
    Plasma medicine is an emerging research field which has been driven by the development of plasma sources suitable to generate low temperature plasmas. In many cases, such devices can operate without a gas flow, producing a plasma discharge from the ambient air. However, the most common case is the use of a working gas at a given flow rate to produce a plasma jet. Helium (He) is one of the gases commonly used as the carrier gas to generate cold atmospheric pressure plasma jets (CAPPJs) due mainly to the easiness to ignite a gas discharge with it. However, in this work it was observed that most of the heating of a He CAPPJ can come just from the expansion of the He gas. This was found through measurements of gas temperature (T gas ), using fiber optic temperature (FOT) sensors, and thermal output, using both FOT and infrared imaging with the He flow impinging on a copper (Cu) plate. Such findings were achieved through comparisons of T gas and the temperature on the Cu (T Cu ) plate in the conditions with and without discharge ignition, as well as comparing T gas in the free gas/jet mode with and without discharge ignition. It was verified that the T gas values increased as the distance from the gas outlet was enlarged, especially at low He flow rates, even without discharge ignition. Despite the temperature increase with distance, it is possible to produce plasma jets with temperatures lower than 40 °C at low He flow rates.
  • ItemArtigo
    Mechanical Properties, Corrosion Behavior, and In Vitro Cell Studies of the New Ti-25Ta-25Nb-5Sn Alloy
    (2023-03-01) Silva, Kerolene Barboza da ; Carobolante, João Pedro Aquiles ; Rajan, S. Sudhagara ; Júnior, Celso Bortolini ; Sabino, Roberta Maia ; Seixas, Maurício Rangel ; Nakazato, Roberto Zenhei ; Popat, Ketul C. ; Claro, Ana Paula Rosifini Alves ; Universidade Estadual Paulista (UNESP) ; Colorado State University (CSU)
    This study aims to characterize a new Ti-25Ta-25Nb-5Sn alloy for biomedical application. Microstructure, phase formation, mechanical and corrosion properties, along with the cell culture study of the Ti-25Ta-25Nb alloy with Sn content 5 mass% are presented in this article. The experimental alloy was processed in an arc melting furnace, cold worked, and heat treated. For characterization, optical microscopy, X-ray diffraction, microhardness, and Young’s modulus measurements were employed. Corrosion behavior was also evaluated using open-circuit potential (OCP) and potentiodynamic polarization. In vitro studies with human ADSCs were performed to investigate cell viability, adhesion, proliferation, and differentiation. Comparison among the mechanical properties observed in other metal alloy systems, including CP Ti, Ti-25Ta-25Nb, and Ti-25Ta-25-Nb-3Sn showed an increase in microhardness and a decrease in the Young’s modulus when compared to CP Ti. The potentiodynamic polarization tests indicated that the corrosion resistance of the Ti-25Ta-25Nb-5Sn alloy was similar to CP Ti and the experiments in vitro demonstrated great interactions between the alloy surface and cells in terms of adhesion, proliferation, and differentiation. Therefore, this alloy presents potential for biomedical applications with properties required for good performance.
  • ItemArtigo
    Simultaneous Treatment of Both Sides of the Polymer with a Conical-Shaped Atmospheric Pressure Plasma Jet
    (2023-01-01) Kodaira, Felipe Vicente de Paula ; Leal, Bruno Henrique Silva ; Tavares, Thayna Fernandes ; Quade, Antje ; Hein, Luis Rogerio de Oliveira ; Chiappim, William ; Kostov, Konstantin Georgiev ; Universidade Estadual Paulista (UNESP) ; Leibniz Institute for Plasma Science and Technology—INP
    A conical-shaped atmospheric pressure plasma jet (CS-APPJ) was developed to overcome a standard limitation of APPJs, which is their small treatment area. The CS-APPJs increase the treatment area but use the same gas flow. In the present work, polypropylene samples were treated by CS-APPJ and characterized by scanning electron microscope (SEM), the contact angle, Fourier-transformed infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). It was observed that the treatment co-occurs on the face directly in contact with the plasma and on the opposite face (OF) of the samples, i.e., no contact. However, the treatment changed the chemical composition on each side; the OF is rougher than the direct contact face (DCF), probably due to the oxygen groups in excess at the DCF and nitrogen in quantity at the OF. Although simultaneous treatment of both sides of the sample occurs for most atmospheric plasma treatments, this phenomenon is not explored in the literature.
  • ItemArtigo
    Different Radial Modification Profiles Observed on APPJ-Treated Polypropylene Surfaces according to the Distance between Plasma Outlet and Target
    (2022-11-01) Nascimento, Fellype do ; Leal, Bruno Silva ; Quade, Antje ; Kostov, Konstantin Georgiev ; Universidade Estadual Paulista (UNESP) ; Leibniz Institute for Plasma Science and Technology—INP
    The plasma jet transfer technique relies on a conductive wire at floating potential, which, upon entering in contact with a primary discharge, is capable of igniting a small plasma plume at the distal end of a long flexible plastic tube. In this work, two different long tube configurations were employed for the surface modification of polypropylene (PP) samples using argon as the working gas. One of the jet configurations has a thin copper (Cu) wire, which was installed inside the long tube. In the other configuration, the floating electrode is a metallic mesh placed between two plastic tubes in a coaxial arrangement. In the first case, the tip of the Cu wire is in direct contact with the working gas at the plasma outlet, whereas, in the second, the inner plastic tube provides an additional dielectric barrier that prevents the conductor from being in contact with the gas. Water contact angle (WCA) measurements on treated PP samples revealed that different surface modification radial profiles are formed when the distance (d) between the plasma outlet and target is changed. Moreover, it was found that the highest WCA reduction does not always occur at the point where the plasma impinges the surface of the material, especially when the d value is small. Through X-ray photoelectron spectroscopy (XPS) analysis, it was confirmed that the WCA values are directly linked to the oxygen-functional groups formed on the PP surfaces after the plasma treatment. An analysis of the WCA measurements along the surface, as well as their temporal evolution, together with the XPS data, suggest that, when the treatment is performed at small d values, the plasma jet removes some functional groups at the point where the plasma hits the surface, thus leading to peculiar WCA profiles.
  • ItemArtigo
    Different configurations of transferred atmospheric pressure plasma jet and their application to polymer treatment
    (2023-01-01) Nascimento, Fellype do ; Quade, Antje ; Canesqui, Mara Adriana ; Kostov, Konstantin Georgiev ; Universidade Estadual Paulista (UNESP) ; Leibniz Institute for Plasma Science and Technology eV ; Universidade Estadual de Campinas (UNICAMP)
    The employment of atmospheric pressure plasma jets (APPJs) in a large sort of applications is limited by the adversities related to the size of the treated area and the difficulty to reach the target. The use of devices that employ long tubes in their structure has contributed significantly to overcome these challenges. In this work, two different plasma systems employing the jet transfer technique are compared. The main difference between the two devices is how the long plastic tube was assembled. The first one uses a copper wire placed inside a long plastic tube. The other device has a metallic mesh installed in a concentric arrangement between two coaxial plastic tubes. As a result, the two APPJ systems exhibit different properties, with the wire assembly being more powerful, also presenting higher values for the electrical current and rotational temperature when compared to the mesh mounting. X-ray photoelectron spectroscopy (XPS) demonstrates that both configurations were capable of inserting O-containing functional groups on the polypropylene (PP) surface. However, the transferred plasma jet with wire assembly was able to add more functional groups on the PP surface. The results from XPS analysis were corroborated with water contact angle measurements (WCA), being that lower WCA values were obtained when the PP surface presented higher amounts of O-containing groups. Furthermore, the results suggest that the APPJ with wire configuration is more appropriate for material treatments, while the transferred jet with mesh arrangement tends to present lower electrical current values, being more suitable for biological applications.
  • ItemResenha
    Non-Thermal Atmospheric Pressure Plasma Application in Endodontics
    (2023-05-01) Muniz, Ana Bessa ; Vegian, Mariana Raquel da Cruz ; Pereira Leite, Lady Daiane ; da Silva, Diego Morais ; Moreira Milhan, Noala Vicensoto ; Kostov, Konstantin Georgiev ; Koga-Ito, Cristiane Yumi ; Universidade Estadual Paulista (UNESP)
    The failure of endodontic treatment is frequently associated with the presence of remaining microorganisms, mainly due to the difficulty of eliminating the biofilm and the limitation of conventional irrigation solutions. Non-thermal atmospheric pressure plasma (NTPP) has been suggested for many applications in the medical field and can be applied directly to biological surfaces or indirectly through activated liquids. This literature review aims to evaluate the potential of NTPP application in Endodontics. A search in the databases Lilacs, Pubmed, and Ebsco was performed. Seventeen manuscripts published between 2007 and 2022 that followed our established inclusion criteria were found. The selected manuscripts evaluated the use of NTPP regarding its antimicrobial activity, in the direct exposure and indirect method, i.e., plasma-activated liquid. Of these, 15 used direct exposure. Different parameters, such as working gas and distance from the apparatus to the substrate, were evaluated in vitro and ex vivo. NTPP showed a disinfection property against important endodontic microorganisms, mainly Enterococcus faecalis and Candida albicans. The antimicrobial potential was dependent on plasma exposure time, with the highest antimicrobial effects over eight minutes of exposure. Interestingly, the association of NTPP and conventional antimicrobial solutions, in general, was shown to be more effective than both treatments separately. This association showed antimicrobial results with a short plasma exposure time, what could be interesting in clinical practice. However, considering the lack of standardization of the direct exposure parameters and few studies about plasma-activated liquids, more studies in the area for endodontic purposes are still required.
  • ItemArtigo
    Observational constraints on varying fundamental constants in a minimal CPC model
    (2023-02-01) Cuzinatto, R. R. ; Holanda, R. F.L. ; Pereira, S. H. ; University of Ottawa ; Universidade Federal de Alfenas ; Universidade Federal do Rio Grande do Norte ; Universidade Estadual Paulista (UNESP)
    A minimal model based on the Co-varying Physical Couplings (CPC) framework for gravity is proposed. The CPC framework is based on the assumptions of a metric-compatible four-dimensional Riemannian manifold, where a covariantly conserved stress-energy tensor acts as source of the field equations, which are formally the same as Einstein field equations, but where the couplings {G, c, Λ} are allowed to vary simultaneously. The minimal CPC model takes Λ as a genuine constant while c and G vary in an entangled way that is consistent with Bianchi identity and the aforementioned assumptions. The model is constrained using the most recent galaxy cluster gas mass fraction observational data. Our result indicates that the functions c(z) and G(z) = G0 (c/c0)4 are compatible with constant couplings for the two different parametrizations of c = c(z) adopted here.
  • ItemArtigo
    Fuzzy Soft Skills Assessment through Active Learning Sessions
    (2023-01-01) Novais, André Seixas de ; Matelli, José Alexandre ; Silva, Messias Borges ; Federal Institute of Rio de Janeiro ; Universidade Estadual Paulista (UNESP)
    This research aims to present a Fuzzy Expert System with psychologist expertise that seeks to assist professors, researchers and educational institutions in assessing the level of incorporation of students’ Soft Skills while attending Active Learning sessions. The difficulties encountered by higher education institutions, researchers and professors in evaluating subjective and behavioral components, such as Soft Skills, was one of the problems that motivated the undertaking of this research. The theoretical framework on which this work is based includes the development and evaluation of Soft Skills in students, some concepts and characteristics about Active Learning and the main attributes and properties of Fuzzy Logic. This research is of an exploratory applied nature, a qualitative and quantitative approach is proposed, in which the methodological triangulation between the bibliographic analysis, the case study and the modeling and implementation of the expert system called Fuzzy Soft Skills Assessment was used to achieve the objective proposed.
  • ItemArtigo
    Dimensionless models of representative parameters of the spray obtained from effervescent atomizers
    (2023-04-01) Amaro, Jordan ; Gamboa, Alexander R. ; Mendiburu, Andrés Z. ; dos Santos, Leila Ribeiro ; de Carvalho, João A. ; Universidade Estadual Paulista (UNESP) ; Federal University of Rio Grande Do Sul (UFRGS) ; Technological Institute of Aeronautics (ITA)
    The goal of this study was to develop dimensionless models to estimate characteristic parameters associated with the atomization of light heating oil in effervescent atomizers. Parameters like the integral Sauter mean diameter (ID32), the spray cone half-angle (γ/2) and the liquid concentration half-angle (α/2) are considered. An analytical method was developed to determine the coefficient and exponents of an optimized dimensionless model. A total of seven dimensionless models (M1 – M7) were taken into consideration, from which seven models (M1 – M7) were used to estimate ID32, and five models (M3 – M7) were used to estimate γ/2 and α/2. In order to establish each set of models (M1 – M7 and M3 – M7), a total of 255 experimental results obtained from 34 effervescent atomizers of the outside-in gas injection configuration were used. The model M3 was selected to estimate ID32, γ/2 and α/2, returning values of R2 equal to 0.895, 0.762 and 0.809, respectively. The dimensionless models showed very good accuracy; therefore, the analytical method developed to propose dimensionless models is also validated.
  • ItemResenha
    Flammability Limits: A Comprehensive Review of Theory, Experiments, and Estimation Methods
    (2023-03-16) Mendiburu, Andrés Z. ; Carvalho, João A. ; Ju, Yiguang ; Federal University of Rio Grande do Sul (UFRGS) ; Universidade Estadual Paulista (UNESP) ; Princeton University ; International Research Group for Energy Sustainability (IRGES)
    Flammability limits play an important role in combustion research, industrial applications, and fire safety. This article provides a comprehensive review of recent developments in the fundamental understanding of flammability limits and their experimental determination as well as estimation methods for pure fuels and fuel mixtures. The article begins with a discussion of the importance and challenges of determining flammability limits. It then presents the theoretical, computational, and experimental methods available to understand the mechanism of flammability limits and to quantify them. The experimental setups using cylindrical and spherical vessels to determine the flammability limits are discussed. The effects of buoyancy, thermal radiation, and flame stretch are examined. The relationship between the fundamental flammability limits and the extinction limits of stretched flames via strain and radiation is presented. The effects of initial temperature, pressure, mixtures of different fuels, and diluents are examined, and available estimation methods are presented. Finally, the flammability limits of renewable and alternative fuels are addressed and strategies for estimating the flammability limits of these fuels are presented.
  • ItemArtigo
    Optical and Structural Properties of PEO-Like Plasma Polymers
    (2002-01-01) Mota, Rogério Pinto ; Bigansolli, Antonio Renato ; Antunes, Érica Freire ; Rangel, Elidiane Cipriano ; Da Cruz, Nilson Cristino ; Honda, Roberto Yzumi ; Algatti, Mauricio Antonio ; Aramaki, Emilia Akemi ; Kayama, Milton Eiji ; Universidade Estadual Paulista (UNESP)
    This paper deals with the study of optical, structural and biocompatible properties of PEO-like plasma polymerized films resulting from RF excited diethylene glycol dimethyl ether (CH 3 O(CH 2 CH 2 O) 2 CH 3 diglyme) glow discharges. The study was carried out using visible-ultraviolet and FTIR spectroscopies and contact angle measurements. FTIR spectra of plasma polymerized diglyme showed a stronger presence of ethylene glycol groups in film structure for lower RF power levels. The contact angle measurements for water revealed an increasing from 30° to 62,5° when the RF power was varied from 2 to 45 W, indicating the decreasing of the hydrophilic character of diglyme films with the increasing of RF power. This trend is in agreement with FTIR results. The data from visible-ultraviolet reflectance and transmittance spectra revealed alterations on optical properties of plasma polymerized diglyme films. The film's optical gap varied from 3.8 to 3 eV for RF power running from 5 to 45 W.
  • ItemArtigo
    Experimental observation of ethanol–air premixed flames propagating inside a closed tube with high aspect ratio
    (2023-02-01) Serra, Aguinaldo M. ; Andrade, José C. ; Silva, Lucas M. ; Santos, José C. ; Silveira, Julia C. ; de Carvalho, João A. ; Mendiburu, Andrés Z. ; National Space Research Institute (INPE) ; Universidade Estadual Paulista (UNESP) ; Federal University of Rio Grande do Sul (UFRGS) ; International Research Group for Energy Sustainability (IRGES)
    The present article aims to experimentally observe the flame propagation of ethanol–air mixtures in a tube closed at both ends with an aspect ratio of 27.68. The mixtures were prepared with equivalence ratios ranging from 0.8 to 1.1. The tests were performed for initial pressures of 20, 40, and 60 kPa. The phenomenon of flame front inversion was observed in all experiments. This phenomenon is also known as tulip flame. It was also observed that the flame front inverted several times at the equivalence ratios of 1.0 and 1.1. After the initial deceleration, the velocity oscillated with a high amplitude at these equivalence ratios. An analysis of the available experimental data was performed to better understand the conditions that allow the flame velocity oscillations to occur. It was found that these oscillations manifest when the following conditions are met: (a) closed channels, (b) sufficiently high laminar flame velocity and (c) sufficiently high aspect ratio. Moreover, this phenomenon is coupled with pressure waves that develop inside the duct. The relationship between the distance for the formation of the flattened flame front and the laminar flame velocity was used to define a characteristic time that correlates with the available experimental data.
  • ItemArtigo
    Substitution of Natural Gas by Biomethane: Operational Aspects in Industrial Equipment
    (2023-01-01) Carvalho, Felipe Solferini de ; Reis, Luiz Carlos Bevilaqua dos Santos ; Lacava, Pedro Teixeira ; Araújo, Fernando Henrique Mayworm de ; Carvalho Jr, João Andrade de ; Aeronautics Institute of Technology ; Rio de Janeiro State University ; Universidade Estadual Paulista (UNESP)
    Global gas markets are changing as natural gas (NG) is replaced by biomethane. Biomethane is produced by upgrading biogas, which can have a molar concentration of methane to over 98%. This renewable energy has been injected into the pipeline networks of NG, which offers the possibility to increase its usage in industrial and residential applications. However, the expectation of the increase in biomethane proportion on the NG grids could increase the fluctuations on the composition of the NG–biomethane mixture in amplitude and frequency. In this context, the injection of biomethane into the existing network of NG raises a discussion about the extent to which variations in gas quality will occur and what permissible limits should exist, as variations in combustion characteristics can affect the operation of the combustion processes, with consequences for consumers, distributors and gas producers. This study describes a gas quality analysis with regard to the use of biomethane in industrial equipment, mixed or not mixed with NG, taking into account the indicators for gas interchangeability and provides a discussion on the necessary gas quality level to be achieved or maintained for efficient combustion in equipment originally designed to operate with NG. NG and biomethane real data collected for 92 consecutive days in 2022 and provided by two different companies in Brazil were used for this study. It is shown that the maximum deviation of the Wobbe Index (WI) of 5%, which is allowed for industrial plants, does not work for the operation of furnaces at temperatures of 1200 °C or more. In addition, it is shown that the WI, as defined in relation to the calorific value of the fuel, may allow inappropriate substitution of fuel gases, which is likely to reduce the range of blending of biomethane in NG pipelines. The results can be assessed to analyze how the addition of biomethane to NG grids will impact the WI and the equipment operation parameters such as the air-to-gas ratio, products-to-gas ratio, adiabatic flame temperature and furnace temperature.
  • ItemArtigo
    Techno-Economic and Environmental Assessment of Municipal Solid Waste Energetic Valorization
    (2022-12-01) Machin, Einara Blanco ; Pedroso, Daniel Travieso ; Acosta, Daviel Gómez ; Silva dos Santos, Maria Isabel ; de Carvalho, Felipe Solferini ; Machín, Adrian Blanco ; Neira Ortíz, Matías Abner ; Arriagada, Reinaldo Sánchez ; Travieso Fernández, Daniel Ignacio ; Braga Maciel, Lúcia Bollini ; Arcos, Daniel Cuevas ; Reyes, Yanet Guerra ; de Carvalho Júnior, Joao Andrade ; Universidad de Concepción ; Universidad del Bío-Bío ; Universidade Estadual Paulista (UNESP) ; Propulsion and Energy ; Universidad de Camagüey ; University of Pinar del Rio
    In 2019, Chile generated 20 million tons of waste, 79% of which was not properly disposed of, thereby providing an attractive opportunity for energy generation in advanced thermochemical conversion processes. This study presents a techno-economic and environmental assessment of the implementation of Waste-Integrated Gasifier-Gas Turbine Combined Cycle (WIG-GTCC) technology as an alternative for Municipal Solid Waste (MSW) treatment. The studied case assesses the conversion of 14.61 t·h−1 of MSW, which produces a combustible gas with a flow rate of 34.2 t·h−1 and LHV of 5900 kJ·kg−1, which, in turn, is used in a combined cycle to generate 19.58 MW of electrical power. The proposed economic assessment of the technology uses the energy generation processes as a reference, followed by a model for an overall economic evaluation. The results have shown that the profit could be up to USD 24.1 million, and the recovery of investment between 12 and 17 years would improve the environmental impacts of the current disposal technology. The WIG-GTCC has the most efficient conversion route, emitting 0.285 kg CO2eq/kWh, which represents 48.21% of the potential yield of global warming over 100 years (GWP100) of incineration and 58.51% of the GWP100 of the standard gasification method. The WIG-GTCC would enable the energetic valorization of MSW in Chile, eliminate problems associated with landfill disposal, and increase opportunities for decentralized electricity generation.
  • ItemArtigo
    Gaussian processes reconstruction of the dark energy potential
    (2022-11-01) Jesus, J. ; Valentim, R. ; Escobal, A. ; Pereira, S. ; Benndorf, D. ; Universidade Estadual Paulista (UNESP) ; Universidade Federal de São Paulo (UNIFESP)
    Scalar Fields (SF) have emerged as natural candidates for dark energy as quintessential or phantom fields, as they are the main ingredient of inflation theories. Instead of assuming some form for the scalar field potential, however, this work reconstructs the SF potential directly from observational data, namely, Hubble and SNe Ia data. We show that two popular forms for the SF potentials, namely, the power-law and the quadratic free-field, are compatible with the reconstructions thus obtained, at least for some choices of the priors of the matter density and curvature parameters and for some redshift intervals.
  • ItemArtigo
    Mapping for BPS Solitons of Scalar Field Potentials in 1 + 1 Dimensions and Family of Solutions
    (2023-02-01) Amaro de Faria, A. C. ; de Souza Dutra, A. ; Dresseno, J. E. ; Lourenço, R. E. ; Federal Technological University of Parana - UTFPR-GP ; Universidade Estadual Paulista (UNESP) ; Federal Technological University of Parana - UTFPR
    We analyze a method for solving a second-order nonlinear differential equation in 1 + 1 dimensions, applying it to some nonlinear systems. A particular solution for systems with this dimensionality is known as kink. In this study, we focus on revealing that any kink in 1 + 1 dimensions, accruing from models with one scalar field, can be straightforwardly obtained from a scalar field solution to a first-order linear differential equation with constant coefficients. This is accomplished by a suitable field transformation and we examine a few models and analyze how the introduction of an underlying scalar field can shed new light on models with one scalar field. In this work, in contrast to what is expected, we show that any kink in (1 + 1) dimensions, originating from models with just one scalar field, can be obtained from a master linear first-order differential equation using a convenient field transformation, which leads to a linear differential equation for the transformation function. A general approach is introduced and discussed, including a few subsequent cogent and important physical applications. This approach for certain values of parameters presents symmetry breaking like the λϕ4 model. The other parameter values correspond to a model with no minima, presenting kink configurations for the scalar field. In this study, we focus on revealing that any kink in (1 + 1) dimensions, accruing from models with one scalar field, can be obtained from the master linear first-order differential equation. This is accomplished through a convenient field transformation, obeying a linear differential equation for the transformation function. After analyzing a few models, we present a new one using the method developed in this work.
  • ItemArtigo
    Insights into the origin of the enhanced electrical conductivity of Pd-Sb2O3 nanoparticles: A combined experimental and theoretical study
    (2023-02-05) Gonçalves, Rosana A. ; Kuznetsov, Aleksey ; Ciapina, Eduardo G. ; Quade, Antje ; Teodoro, Marcio D. ; Baldan, Maurício R. ; Berengue, Olivia M. ; Universidade Estadual Paulista (UNESP) ; Universidad Técnica Federico Santa Maria 6400 ; INP Greifswald ; Universidade Federal de São Carlos (UFSCar) ; National Institute of Space Research (INPE)
    Supported metal nanocrystallites play a paramount role in catalysis, electrocatalysis, and gas sensing, among other fields. Although the majority of studies are focused on the modification of the composition, size and morphology of the active metallic phase to meet specific needs, the influence of the properties of the support on the overall behavior of such materials is often neglected. In a previous publication, we described for the first time the use of antimony trioxide (Sb2O3) as a new support material for Pd nanoparticles for the electrochemical oxidation of ethanol in alkaline media. Despite its high catalytic activity, information for the intrinsic fundamental properties of Pd-Sb2O3, such as the electrical conductivity and presence of defects, is still lacking. In this work, we combined both experimental techniques and theoretical simulations to gain further knowledge into some relevant physicochemical properties of the Pd-Sb2O3 system. An increase in electrical conductivity of 1000x is found in the Sb2O3 phase after the deposition of a small amount (4.9% weight) of Pd, which cannot be explained by the metallic phase; rather, oxygen vacancies in the Sb2O3 (as indicated by photoluminescence experiments) are likely the origin of such behavior. Theoretical calculations performed by density functional theory show that oxygen vacancies not only lead to distortion in chemical bonds but also change the overall reactivity of the system, corroborating X-ray photoelectron spectroscopy and electrochemical experiments.
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    Ecological efficiency of renewable and non-renewable energy generation power systems considering life cycle assessment
    (2022-11-01) de Paula Santos, Caio Felipe ; Bimestre, Thiago Averaldo ; Tuna, Celso Eduardo ; Silveira, José Luz ; Universidade Estadual Paulista (UNESP) ; Universidade Federal do ABC (UFABC)
    The world consumption of electricity has been increasing exponentially over the years; consequently, there is an increase in atmospheric emissions. In addition, the diversity of electricity generation sources is increasing, and renewable sources are becoming more popular because they are considered renewable energy sources with low atmospheric emissions. This work presents an original contribution from a comprehensive technical review of the current state of the art of the ecological efficiency method and the application of life cycle analysis in electricity generation systems, both renewable and non-renewable. As an original contribution, this article aims, for the first time, to solve the ecological efficiency difficulty in finding values for renewable energy generation systems and thus be able to compare with conventional systems when investigating the influence of life cycle analysis results. The results show that for full load operation, the minimum ecological efficiency was approximately 76.93% for hydro plants, 84.72% for solar PV and 95.10% for wind power. The contributions of this work can make public policy decision-making in the choices of energy generation systems simplifying the understanding of laypeople and experts during the process, making them understand that the consequences of indirect greenhouse gas emissions are as harmful or more than direct emissions, as they are not normally accounted for on plants.
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    A note on higher rank descriptions of massless and massive spin-1 particles
    (Elsevier B.V., 2022-10-13) Dalmazi, D. ; Barbosa, F. A. da Silva ; Santos, A. . L. R. dos ; Universidade Estadual Paulista (UNESP)
    The Maxwell theory can be written as a first order model with the help of a two-form auxiliary field, such master action allows the proof of duality between 1-form and D - 3 forms. Here we show that the replacement of the two-form auxiliary field by an arbitrary (non symmetric) rank-2 tensor leads to a new massless spin-1 dual theory in terms of a partially antisymmetric rank3 tensor. In the massive spin-1 case we have a non symmetric generalization of the massive two-form theory (Kalb-Ramond). The coupling of the massive non symmetric spin-1 model to matter fields is investigated via master actions. We also show that massive models with severe discontinuity in their massless limit can also be obtained from Kaluza-Klein dimensional reduction of massless higher rank tensors which become Stueckelberg fields after the reduction. (c) 2022 Elsevier Inc. All rights reserved.
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    (Fundacao Getulio Vargas, 2022-11-01) Figueiredo Facin, Ana Lucia ; Franco Paes Leme Barbosa, Ana Paula ; Matsumoto, Cristiane ; Safady Da Gama Cruz, Ana Flavia ; Salerno, Mario Sergio ; Universidade Estadual Paulista (UNESP) ; Universidade de São Paulo (USP)
    Digital transformation (DT) arises in debates about trends in various industries, mainly in value creation through the innovation of products and services and how they are negotiated. DT poses new challenges to organizations, which this research aims to identify by answering: What is the structure of the literature on DT, and what themes have gained prominence in the last five years? This research conducted a systematic literature review with bibliometric analysis and content analysis. The bibliometric analysis highlighted the following discussions: strategic renewal amid DT; implementation of technologies in Industry 4.0; digitization to enable servitization; DT as an engine of innovation in business models; digital innovation management; and DT to change the consumer experience. The analyses point out avenues for further research and raise important questions for decision-makers in companies that want to reap the benefits of DT.