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Journal of Magnesium and Alloys 2018年第4期6卷 356-365页

作者： I.L.Lehr S.B.Saidman Instituto de ingeniería Electroquímica y Corrosión(INIEC) Departamento de Ingeniería QuímicaUniversidad Nacional del Sur(UNS)CONICETBahía BlancaArgentina

In order to improve the corrosion resistance of AZ91D magnesium alloy,a coating was formed by a potentiostatic technique from a solutions containing Ce(NO_(3))_(3),Na_(2)MoO_(4)and citric acid(H_(3)Cit).The degree of corrosion protection achieved was evaluated in simulated physiological solution by monitoring the open circuit potential,polarization techniques and electrochemical impedance spectroscopy(EIS).Surface analysis techniques(SEM,EDS,X-ray diffraction and X-ray photoelectron spectroscopy(XPS))were used for coating *** film is mainly composed by cerium and molybdenum oxides and magnesium oxides and *** obtained results show that the corrosion resistance of the coated electrodes has been increased *** improvement in the anticorrosive performance is in part due to the corrosion inhibition properties of H_(3)Cit.

关键词： Cerium and molybdenum-based coatings AZ91D alloy Citric acid Anticorrosive properties

Oxidative degradation of Thermoplastic Starch Induced by UV Radiation

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Journal of Renewable Materials 2019年第4期7卷 383-391页

作者： Mayte M.Quispe Olivia V.López Marcelo A.Villar Planta Piloto de ingeniería Química PLAPIQUI(UNS CONICET)Bahía Blanca(8000)Argentina departamento de ingeniería Química Universidad Nacional del Sur(UNS)Bahía Blanca(8000)Argentina

Among biopolymers,thermoplastic starch(TPS)is a good candidate to obtain biomaterials because of its natural origin,biodegradable character,and *** to ultraviolet(UV)radiation causes significant degradation of starch-based materials,inducing photooxidative reactions which result in breaking of polymer chains,production of free radical,and reduction of molar *** changes produce a deterioration of TPS mechanical properties,leading to useless materials after an unpredictable *** this work,changes induced on TPS by UV radiation,analyzing structural properties and mechanical behavior,are *** was obtained through thermo-mechanical processing of native corn starch in the presence of water(45%w/w)and glycerol(30%w/w)as *** were obtained by thermocompression and,before testing,specimens were conditioned to reduce material *** process was performed by exposing TPS to 264 h UV radiation in a weathering test ***’s weight loss was determined *** changes were studied by Fourier Transform Infrared Spectroscopy(FTIR)and morphological modifications were analyzed by Scanning Electron Microscopy(SEM).Reduction of weight average molar mass was measured by Static Light Scattering(SLS).Changes in mechanical properties were studied from tensile *** 96 h exposure,TPS specimens presented a weight reduction of 4-6%,mainly attributed to plasticizers lost by *** observations showed that UV radiation induced morphological changes on TPS,evidenced by an increment of specimens *** FTIR,it was detected the presence of an additional band located at 1726 cm-1 in samples submitted to UV radiation,attributed to the formation of-C=O *** average molar mass of native starch was in the order of 107 g *** exposure to UV radiation decreased significantly its molar mass,confirming molecular degradation of the *** TPS was exposed during 48 h,it

关键词： Thermoplastic starch UV radiation structural properties mechanical behavior

Behavior of ductile steel X-braced RC frames in seismic zones

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Earthquake Engineering and Engineering Vibration 2019年第4期18卷 845-869页

作者： Eber Alberto Godínez-Domínguez Arturo Tena-Colunga Facultad de ingeniería Universidad Autónoma de Chiapas Tuxtla Gutiérrez 29050 Mexico departamento de Materiales Universidad Autónoma Metropolitana México City 02200 Mexico

A satisfactory ductile performance of moment-resisting reinforced concrete concentric braced frame structures (RC-MRCBFs) is not warranted by only following the provisions proposed in Mexico’s Federal District Code (MFDC-04). The nonlinear behavior of low to medium rise ductile RC-MRCBFs using steel X-bracing susceptible to buckling is evaluated in this study. The height of the studied structures ranges from 4 to 20 stories and they were located for design in the lakebed zone of Mexico City. The design of RC-MRCBFs was carried out considering variable contribution of the two main lines of defense of the dual system (RC columns and steel braces). In order to observe the principal elements responsible for dissipating the earthquake input energy, yielding mappings for diff erent load-steps were obtained using both nonlinear static and dynamic analyses. Some design parameters currently proposed in MFDC-04 as global ductility capacities, overstrength reduction factors and story drifts corresponding to diff erent limit states were assessed as a function of both the considered shear strength and slenderness ratios for the studied RC-MRCBFs using pushover analyses. Additionally, envelopes of response maxima of dynamic parameters were obtained from the story and global hysteresis curves. Finally, a brief discussion regarding residual drifts, residual drift ratios, mappings of residual deformations in steel braces and residual rotations in RC beams and columns is presented. From the analysis of the obtained results, it is concluded that when a suitable design criterion is considered, good structural behavior of RC-MRCBFs with steel-X bracing can be obtained. It is also observed that the shear strength balance has an impact in the height-wise distribution of residual drifts, and an important “shake-down” eff ect is obtained for all cases. There is a need to improve design parameters currently proposed in MFDC to promote an adequate seismic performance of RC-MRCBFs.

关键词： RC braced-frames seismic design nonlinear dynamic analyses steel-X bracing overstrength collapse mechanism story drifts residual drifts

Robust Disturbance Rejection Based Control with Extended-state Resonant Observer for Sway Reduction in Uncertain Tower-cranes

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International Journal of Automation and computing 2019年第6期16卷 812-827页

作者： Horacio Coral-Enriquez Santiago Pulido-Guerrero John Cortés-Romero Programa de ingeniería Mecatrónica Facultad de IngenieríaUniversidad de San Buenaventura sede BogotáCra.8H No 172-20 Edif.DBBogotáOf204Colombia departamento de ingeniería Eléctrica y Electrónica Facultad de IngenieríaUniversidad Nacional de Colombia sede BogotáCra.30 No 45-03 Edif.453BogotáOf222Colombia

In this paper, the problem of load transportation and robust mitigation of payload oscillations in uncertain tower-cranes is addressed. This problem is tackled through a control scheme based on the philosophy of active-disturbance-rejection. Here, a general disturbance model built with two dominant components: polynomial and harmonic, is stated. Then, a disturbance observer is formulated through state-vector augmentation of the tower-crane model. Thus, better performance of estimations for system states and disturbances is achieved. The control law is then formulated to actively reject the disturbances but also to accommodate the closed-loop system dynamics even under system uncertainty. The proposed control schema is validated via experimentation using a small-scale tower-crane,and compared with other relevant active disturbance rejection control(ADRC)-based techniques. The experimental results show that the proposed control scheme is robust under parametric uncertainty of the system, and provides improved attenuation of payload oscillations even under system uncertainty.

关键词： Active disturbance rejection control(ADRC) extended state observer(ESO) tower-crane control resonant observer disturbance observer linear matrix inequality

Discretized Miller approach to assess effects on boundary layer ingestion induced distortion

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Chinese Journal of Aeronautics 2017年第1期30卷 235-248页

作者： Esteban Valencia Víctor Hidalgo devaiah Nalianda Laskaridis Panagiotis Riti Singh departamento de ingeniería Mecánica Facultad de Ingeniería Mecánica Escuela Politécnica Nacional Ladron de Guevara E11-253 Quito 17-01-2759 Ecuador School of Engineering Cranfield University Bedford MK430AL United Kingdom

The performance of propulsion configurations with boundary layer ingestion（BLI） is affected to a large extent by the level of distortion in the inlet flow field. Through flow methods and parallel compressor have been used in the past to calculate the effects of this aerodynamic integration issue on the fan performance; however high-fidelity through flow methods are computationally expensive, which limits their use at preliminary design stage. On the other hand, parallel compressor has been developed to assess only circumferential distortion. This paper introduces a discretized semi-empirical performance method, which uses empirical correlations for blade and performance calculations. This tool discretizes the inlet region in radial and circumferential directions enabling the assessment of deterioration in fan performance caused by the combined effect of both distortion patterns. This paper initially studies the accuracy and suitability of the semiempirical discretized method by comparing its predictions with CFD and experimental data for a baseline case working under distorted and undistorted conditions. Then a test case is examined,which corresponds to the propulsor fan of a distributed propulsion system with BLI. The results obtained from the validation study show a good agreement with the experimental and CFD results under design point conditions.

关键词： BLI Correlations Distortion Embedded propulsors Empirical Mean-line analysis Turbomachinery

Analysis of the role of diffraction in topographic site effects using boundary element techniques

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Earthquake Science 2013年第5期26卷 341-350页

作者： Juan Gomez Doriam Restrepo Juan Jaramillo Camilo Valencia departamento de ingeniería Civil Universidad EAFITMedellín Colombia

The role played by the diffraction field on the problem of seismic site effects is studied. For that purpose we solve and analyze simple scattering problems under P and SV in-plane wave assumptions, using two well known direct boundary-element-based numerical methods. After establishing the difference between scattered and diffracted motions, and introducing the concept of artificious and physically based incoming fields, we obtain the amplitude of the Fourier spectra for the diffracted part of the response： this is achieved after establishing the connection between the spatial distribution of the transfer function over the studied simple topographies and the diffracted field. From the numerical simulations it is observed that this diffracted part of the response is responsible for the amplification of the surface ground motions due to the geometric effect. Furthermore, it is also found that the diffraction field sets in a fingerprint of the topographic effect in the total ground motions. These conclusions are further supported by observations in the time-domain in terms of snapshots of the propagation patterns over the complete computational model. In this sense the geometric singularities are clearly identified as sources of diffraction and for the considered range of dimensionless frequencies it is evident that larger amplifications are obtained for the geometries containing a larger number of diffraction sources thus resulting in a stronger topographic effect. The need for closed-form solutions of canonical problems to construct a robust analysis method based on the diffraction field is identified.

关键词： Seismic site effects Topographiceffects Elastic wave scattering Diffractionof in-plane waves

deposition of carbon nanotubes onto glass fibers using ultrasound standing waves

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Frontiers of Materials Science 2021年第3期15卷 471-475页

作者： Julio Alejandro RODRÍGUEZ-GONZÁLEZ Carlos RUBIO-GONZÁLEZ Alfonso PÉREZ-SÁNCHEZ Centro de ingeniería y desarrollo industrial Departamento de EnergíaAv.Pie de la Cuesta#702Col.Desarrollo San PabloC.P.76125QuerétaroQroMexico

Carbon nanotubes(CNTs)are special types of carbon nanostructures with exceptional physical and mechanical properties such as high elastic modulus,high electrical and thermal conductivities,as well as high surface area and large aspect ratios[1].Given their tubular structure and size,CNTs are conceptualized as one-dimensional nanostructures with a crystalline structure of carbon sp2 hybridization formed by carbon–carbon covalent bonds[1].

关键词： carbon fibers exceptional

Effect of laser shock processing on erosive resistance of 6061-T6 aluminum

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Transactions of Nonferrous Metals Society of China 2016年第6期26卷 1522-1530页

作者： J.IBARRA E.RODRíGUEZ O.JIMéNEZ G.GóMEZ-ROSAS M.FLORES J.VERDUZCO J.CHáVEZ Universidad de Guadalajara Departamento de Ingeniería de Proyectos Universidad de Guadalajara Departamento de Física Centro Universitario de Ciencias Exactas e Ingenierías

Application of laser shock processing （LSP） on 6061-T6 aluminum was made in order to evaluate its response to the erosive wear by silica sand. Impact angles of 15° , 30° , 60° and 90° were tested, two particle speeds （37 and 58 m/s） and two LSP irradiation conditions were used. Erosion marks were characterized by 3D profilometry and SEM analysis was conducted to identify the erosion mechanisms for each tested angle. The results showed a maximum erosive wear at low impact angles （ductile type behavior）. Erosion strength and the erosion mechanisms were not affected by the application of LSP and they were attributed to the high strain rate of the erosion phenomena. A few differences encountered on the erosion plots were explained on the basis of the surface roughness left by the LSP process. The maximum mass loss and the maximum erosion penetration happened in different impact angles （15° and 30° , respectively）. Finally, a well-defined erosion mechanism transition was observed, from cutting action at low impact angle, to crater formation at 90° of incidence.

关键词： 6061-T6 aluminum erosive wear laser shock processing

Endophytes versus biotrophic and necrotrophic pathogens—are fungal lifestyles evolutionarily stable traits?

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Fungal Diversity 2013年第3期60卷 125-135页

作者： Luis delaye Graciela García-Guzmán Martin Heil departamento de ingeniería Genética Centro de Investigación y de Estudios Avanzados(CINVESTAV)IrapuatoGuanajuatoMexico departamento de Ecología Evolutiva Instituto de EcologíaUNAMMéxico CityMexico

Endophytes infect living plant tissues without causing symptoms of ***,many of them contribute to the resistance phenotype of their ***,fungal endophytes are generally closely related to plant pathogens,fungi that either develop within living host tissue(biotrophic fungi)or that kill the host cells and then live in the dead tissue(necrotrophic fungi).We adopted a phylogenetic approach to investigate whether these strategies represent evolutionarily stable lifestyles and to elucidate their general phylogenetic *** analysed 163 fungal strains for which we found information on the sequence of the 5.8S rRNA gene and the flanking internal transcribed spacer regions,the identity of the host plant and the concrete phenotypic outcome of the infection.A Maximum-Likelihood analysis combined with ancestral character mapping by maximum parsimony revealed that some fungal lineages had switched multiple times between a necrotrophic and an endophytic *** character mapping indicated a minimum of four changes from an endophytic to a necrotrophic lifestyle,four changes in the opposite direction and eight changes among these lifestyles for which the direction could not be determined *** contrast,biotrophs formed five clusters that did not contain necrotrophs or *** biotrophy evolves there is apparently no regression to one of the other two *** conclude that biotrophy usually represents a derived and evolutionarily stable trait,whereas fungi easily can switch between an endophytic and necrotrophic lifestyle at the evolutionary and even the ecological *** experimental studies should focus on the environmental or genetic changes that cause the rapid switches between these two phenotypically different lifestyles.

关键词： Disease expression Fungi Plant pathogens Phylogenetic effects

detection of DC series arc in more electric aircraft power system based on optical spectrometry

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High Voltage 2020年第1期5卷 24-29页

作者： Jun Jiang Mingxin Zhao Zhe Wen Chaohai Zhang Ricardo Albarracín Center for More Electric Aircraft Power System Nanjing University of Aeronautics and AstronauticsNanjing 211106People's Republic of China departamento de ingeniería Eléctrica ElectrónicaAutomática y Física AplicadaEscuela Técnica Superior de Ingeniería y Diseño IndustrialUniversidad Politécnica de MadridRonda de Valencia 328012 MadridSpain

Series arcing faults have been recognised as a hazardous phenomenon in the power system of more electric aircraft(MEA),especially with the increasing voltage level and power *** of the electrical method,the optical method can be used as an approach to detect arc fault with the advantages of fast response and immunity to electromagnetic *** is the basis of optical arc detection to determine the distribution spectrum range of direct current(DC)arc *** at series arc optical detection in the MEA DC system,a DC series arc test platform was established to measure the series arc *** spectrum was disassembled though empirical mode decomposition to extract characteristic wavelengths of arc light and denoised by means of wavelet decomposition and reconstruction(wavelet transformation)to reduce equipment *** resolve the baseline drift,the baseline of the arc spectrum measured was calculated and corrected based on Savitzky−*** experimental results indicate that there are several series arc characteristic spectra of the MEA DC system,including 309.3 and 324.5 nm in the ultraviolet ***,the arc spectrum with different metals,copper and aluminium,were contrasted,indicating the arc spectral behaviour is related to the melting/boiling point and chemical properties of the anode *** measurement of the series arc spectrum makes it more effective to apply optical detection in the MEA discharging faults diagnosis.

关键词： power system series