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Highly electroactive N–Fe hydrothermal carbons and carbon nanotubes for the oxygen reduction reaction

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Journal of Energy Chemistry 2020年第11期29卷 260-270页

作者： R.G.Morais N.Rey-Raap J.L.Figueiredo M.F.R.Pereira Associate Laboratory LSRE-LCM Departamento de Engenharia QuimicaFaculdade de EngenhariaUniversidade do PortoR.Dr.Roberto Frias s/n4200-465PortoPortugal

Glucose-derived carbons were prepared by hydrothermal carbonization of glucose followed by carbonization or activation to obtain carbon materials with different microporosities. These microporous carbons and carbon nanotubes(CNTs) were functionalized with melamine and/or iron(Ⅱ) phthalocyanine(FePc)following three different methodologies:(i) Functionalization with melamine via thermal treatment,(ii)incorporation of the lowest amount of FePc reported in the literature via incipient wetness impregnation followed by thermal treatment and(iii) functionalization with melamine followed by Fe Pc *** chemical and textural characterization of the prepared materials and their electrochemical assessment allowed to understand the role of microporosity in the incorporation of FePc and its effect on the oxygen reduction reaction(ORR). It was observed that FePc was preferentially incorporated inside the porous structure, especially in samples with more developed microporosity. However, functionalization with melamine modified the textural properties and the surface chemistry, favoring the incorporation of FePc on the surface. Regarding the electrochemical performance, the presence of FePc greatly enhanced the electroactivity of the microporous catalysts. An onset potential of 0.88 V and a four-electron pathway were obtained for glucose-derived carbons, whereas the limiting current densities and kinetic current densities rose by 126% and 222%, respectively, in comparison to the base sample. Notwithstanding, the highest electrochemical activity was observed for the sample prepared with CNTs, due to the synergy between the active metal centers and their highly graphitic carbon structure. The electrochemical parameters of CNTFeP csurpass the commercial Pt/C. The half-wave potential is 40 mV higher, the limiting current density increases by 17%, and a negligible production of by-products(< 1%) was observed.

关键词： Iron(Ⅱ)phthalocyanine Hydrothermal carbons Carbon nanotubes Oxygen reduction reaction Electrocatalysis

Non-destructive microstructural analysis by electrical conductivity:Comparison with hardness measurements in different materials

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Journal of Materials Science & Technology 2019年第3期35卷 360-368页

作者： Gon?alo L.Sorger J.P.Oliveira Patrick L.Inácio Norbert Enzinger Pedro Vila? R.M.Miranda Telmo G.Santos department of Engineering design and Production School of Engineering Aalto University department of Materials Science and Engineering The Ohio State University UNIdeMI Departamento de Engenharia Mecanica e Industrial Faculdade de Ciências e Tecnologia Universidade Nova de Lisboa IMAT-Institute of Materials Science Joining and FormingTU Graz

The use of non-destructive evaluation(Nde) techniques for assessing microstructural changes in processed materials is of particular importance as it can be used to assess, qualitatively, the integrity of any material/structure. Among the several Nde techniques available, electrical conductivity measurements using eddy currents attract great attention owing to its simplicity and reliability. In this work, the electrical conductivity profiles of friction stir processed Ti6Al4 V, Cu, Pb, S355 steel and gas tungsten arc welded AISI 304 stainless steel were determined through eddy currents and four-point probe. In parallel, hardness measurements were also performed. The profiles matched well with the optical macrographs of the materials: while entering in the processed region a variation in both profiles was always observed. One particular advantage of electrical conductivity profiles over hardness was evident: it provides a better resolution of the microstructural alterations in the processed materials. Moreover, when thermomechanical processing induces microstructural changes that modify the magnetic properties of a material,eddy currents testing can be used to qualitatively determine the phase fraction in a given region of the material. A qualitative relation between electrical conductivity measurements and hardness is observed.

关键词： Non-destructive evaluation techniques Electrical conductivity Hardness Friction stir processing Gas tungsten arc welding

An advanced anaerobic biofilter with effluent recirculation for phenol removal and methane production in treatment of coal gasification wastewater

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Journal of Environmental Sciences 2016年第9期28卷 23-33页

作者： Yajie Li Salma Tabassum Zhenjia Zhang School of Environmental Science and Engineering Shanghai Jiao Tong University LCM-Laboratory of Catalysis and Materials Associate Laboratory LSRE-LCMDepartamento de Engenharia QuímicaFaculdade de EngenhariaUniversidade do Porto

An advanced anaerobic biofilter（AF） was introduced for the treatment of coal gasification wastewater（CGW）,and effluent recirculation was adopted to enhance phenol removal and methane *** results indicated that AF was reliable in treating diluted CGW,while its efficiency and stability were seriously reduced when directly treating raw ***,its performance could be greatly enhanced by effluent *** optimal effluent recirculation of 0.5 to the influent,concentrations of chemical oxygen demand（COD） and total phenol in the effluent could reach as low as 234.0 and 14.2 mg/L,***,the rate of methane production reached 169.0 m L CH_4/L/*** CGW seemed to restrain the growth of anaerobic microorganisms,especially methanogens,the inhibition was temporary and reversible,and anaerobic bacteria presented strong *** activities of methanogens cultivated in CGW could quickly recover on feeding with glucose wastewater（GW）.However,the adaptability of anaerobic bacteria to the CGW was very poor and the activity of methanogens could not be improved by long-term *** analysis using the Haldane model,it was further confirmed that high effluent recirculation could result in high activity for hydrolytic bacteria and substrate affinity for toxic matters,but only suitable effluent recirculation could result in high methanogenic activity.

关键词： Coal gasification wastewater Effluent recirculation Methane production Anaerobic biofilters

Quasinormal Modes of the Planar Black Holes of a Particular Lovelock Theory

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Communications in Theoretical Physics 2018年第12期69卷 689-694页

作者： Dan Wen Kai Lin Wei-Liang Qian faculdade de engenharia de Guaratingueta Universidade Estadual Paulista Hubei Subsurface Multi-Scale Imaging Key Laboratory Institute of Geophysics and GeoinformaticsChina University of Geosciences Escola de engenharia de Lorena Universidade de Sao Paulo

In this work, we study the scalar quasinormal modes of a planar black hole metric in asymptotic anti-de Sitter spacetime derived from a particular Lovelock theory. The quasinormal frequencies are evaluated by adopting the Horowitz-Hubeny method as well as a matrix formalism. Also, the temporal evolution of small perturbations is studied by using finite difference method. The roles of the dimension of the spacetime, the parameter of the metric k, as well as the temperature of the background black hole, are discussed. It is observed that the particular form of the metric leads to quasinormal frequencies whose real parts are numerically insignificant. The black hole metric is found to be stable against small scalar perturbations.

关键词： quasinormal modes Lovelock theory Horowitz-Hubeny method matrix method

Evaluation of bearing, gears and gearboxes performance with different wind turbine gear oils

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Friction 2015年第4期3卷 275-286页

作者： Ramiro Carneiro MARTINS Carlos M.C.G.FERNANdeS Jorge H.O.SEABRA INEGI Universidade do PortoPortoPortugal faculdade de engenharia Universidade do PortoPortoPortugal

The oil viscosity specification for wind turbine gear oils is ISO VG 320,although there are quite different viscosity indexes oils for that viscosity *** work evaluates the behaviour of different base oil formulations,since polyalphaolefin(PAO),mineral,ester and polyalkeleneglycol(PAG)that withstand quite different viscosity *** oils evaluation was done in rolling bearing tests and gear *** behaviour was compared for operating conditions in the range observable in a wind turbine *** experimental results showed considerable differences between the different oils and it was observed that depending on the contact type the relative behaviour of the lubricants would change,i.e.,the best lubricant for the rolling bearing would not imply the best result on the gear *** gear geometry is also very important toward the transmission efficiency,once using a low loss gear concept a decrease of up to 25%in torque loss could be *** models were implemented with the purpose of performing a better simulation of the mechanical system and also to obtain the friction coefficient promoted by the tested oils.

关键词： gears rolling bearings friction coefficient lubricants efficiency

Theoretical Study of Fully developed Turbulent Flow in a Channel, Using Prandtl’s Mixing Length Model

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Journal of Applied Mathematics and Physics 2018年第4期6卷 677-692页

作者： Luigi A. Antonialli Aristeu Silveira-Neto faculdade de engenharia mecanica Universidade Federal de Uberlandia Uberlandia Minas Gerais Brazil

This research used the common decomposition of the velocity and pressure in an average part and a fluctuating part, for high Reynolds number, of the Navier-Stokes equation, which leads to the classic problem of turbulent closure. The Prandtl’s mixing length model, based on the Boussinesq hypothesis and traditionally used for free shear flows, was chosen and adapted for internal flows to solve the closure problem. For channel flows, Johann Nikuradse proposed a model for the Prandtl mixing length. In the present paper, which has an academic character, the authors made a return to the model of the mixing length of Prandtl and the model of Nikuradse, to solve turbulent flows inside a plane channel. It was possible to develop an ordinary differential model for the velocity in the direction of the flow whose solution occurs computationally in a simple but extremely accurate way when compared with Direct Numerical Simulation databases. For the viscous stress on the wall, it was possible to determine the exact mathematical solution of the ordinary differential equation. It is a model of great academic value and even to be used as reference for verification of computational codes destined to the solution of complete numerical and computational models.

关键词： Mixing Length Channel Pipe Turbulent Flow

Assessing the estrogenic potency in a Portuguese wastewater treatment plant using an integrated approach

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Journal of Environmental Sciences 2010年第10期22卷 1613-1622页

作者： Mário S.Diniz Rita Maurício Mira Petrovic Maria J.López de Alda Leonor Amaral Isabel Peres Damiá Barceló Fernando Santana Universidade Nova de Lisboa Faculdade de Ciencias e TecnologiaREQUIMTEDep.de Quimica Universidade Nova de Lisboa Faculdade de Ciencias e TecnologiaDep.de Ciencias e Engenharia do Ambiente department of Environmental Chemistry-IIQAB-CSIC c/Jordi Girona

The estrogenic potency of a wastewater treatment plant （WWTP） was evaluated using chemical and biological analyses, which showed that after the station treatment processes some of the selected endocrine disruptor compounds （EDCs） were still present in the treated effluent （e.g., bisphenol A, alkylphenols, estrone）. Thus, the most common endocrine EDCs were identified and quantified and the overall estrogenicity of the treated effluent assessed by integrating the results. Male goldfish （Carassius auratus） were used as biological indicators in a 28-day experiment. Vitellogenin （Vtg）, gonadosomatic and hepatosomatic indices, steroids （17β-estradiol and 11-ketotestosterone） and histopathology were biomarkers used in fish to evaluate WWTP treated effluent estrogenicity, in combination with instrumental analyses. The results showed a significant increase （P 〈 0.01） in plasma and liver Vtg, which were significantly correlated （r = 0.66; P 〈 0.01）. The gonadosmatic index was significantly （P 〈 0.01） reduced in exposed fish. The steroid analyses revealed significant elevations in 17β-estradiol and depressed 11-ketotestosterone concentrations. The histological examinations show changes in exposed fish gonads, such as regressed testes and in some cases （43% to 75%） the development of ovo-testis in fish exposed to 50% and 100% treated effluent.

关键词： Carassius auratus endocrine disruptors vitellogenin steroids intersex

A Robust, Fully Adaptive Hybrid Level-Set/Front-Tracking Method for Two-Phase Flows with an Accurate Surface Tension Computation

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Communications in Computational Physics 2010年第6期8卷 51-94页

作者： Hector D.Ceniceros Alexandre M.Roma Aristeu Silveira-Neto Millena M.Villar department of Mathematics University of California Santa BarbaraCA 93106USA departamento de Matematica Aplicada Universidade de Sao PauloCaixa Postal 66281CEP 05311-970Sao Paulo-SPBrasil faculdade de engenharia mecanica Universidade Federal de UberlandiaCEP 38400-902Uberlandia-MGBrasil

We present a variable time step,fully adaptive in space,hybrid method for the accurate simulation of incompressible two-phase flows in the presence of surface tension in two *** method is based on the hybrid level set/front-tracking approach proposed in[*** and ***,***.,205,391-400,2005].Geometric,interfacial quantities are computed from front-tracking via the immersed-boundary setting while the signed distance(level set)function,which is evaluated fast and to machine precision,is used as a fluid *** surface tension force is obtained by employing the mixed Eulerian/Lagrangian representation introduced in[***,***-Khalik,*** and ***,***.,203,493-516,2005]whose success for greatly reducing parasitic currents has been *** use of our accurate fluid indicator together with effective Lagrangian marker control enhance this parasitic current reduction by several orders of *** resolve accurately and efficiently sharp gradients and salient flow features we employ dynamic,adaptive mesh *** spatial adaption is used in concert with a dynamic control of the distribution of the Lagrangian nodes along the fluid interface and a variable time step,linearly implicit time integration *** present numerical examples designed to test the capabilities and performance of the proposed approach as well as three applications:the long-time evolution of a fluid interface undergoing Rayleigh-Taylor instability,an example of bubble ascending dynamics,and a drop impacting on a free interface whose dynamics we compare with both existing numerical and experimental data.

关键词： Front-tracking immersed boundary method level set method adaptive mesh re-finements semi-implicit methods multilevel multigrid closest point transform semi-backward difference formula

Effect of pier shape and pier alignment on the equilibrium scour depth at single piers

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International Journal of Sediment Research 2016年第3期31卷 244-250页

作者： Cristina Fael Rui Lana António Cardoso faculdade de engenharia Universidade da Beira InteriorEdificio Ⅱ das EngenhariasCalcada Fonte da Lameiro Instituto Superior de engenharia/Universidade do Algarve Instituto Superior Tecnico Universidade de Lisboa

The equilibrium scour depth at uniform single bridge piers depends on a large number of variables,including the pier horizontal cross-section shape and its alignment angle towards the flow *** influence of these variables has been studied by only a few researchers,mostly,on the basis of tests that were far from approaching *** experimental study aims at revisiting the influence of piers’ shape and alignment on local scouring for length-width ratios smaller than or equal to 4,by increasing the experimental *** five long-duration laboratory tests were run under steady,clear-water flow,close to the threshold for initiation of sediment *** pier shapes were considered:circular,rectangular square-nosed,rectangular round-nosed,oblong,and zero-spacing(packed) pile-groups;the tested skew-angles were 0°,30°,45°,60°,and 90°.It was concluded that i) the shape factor can be taken as 1.0,for rectangular round-nosed and oblong cross-section piers,and as 1.2,for rectangular squarenosed and packed pile-group cross-section piers,ii) the shape factor does not vary significantly with the duration of tests,this way confirming the robustness of the shape factors reported to date,iii) the effect of shape is present at skewed piers although the associated coefficients remain in the narrow range of1.0-1.2,and iv) for length-width ratios smaller than 4,the shape factor is of the same order of magnitude as the skew angle factor and should not be neglected.

关键词： Scour Pier shape Pier alignment