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Journal of Magnesium and Alloys 2024年第3期12卷 1186-1203页

作者： Biaobiao Yang Javier LLorca IMDEA Materials Institute C/Eric Kandel 2GetafeMadrid 28906Spain Department of Materials Science Polytechnic University of Madrid/Universidad Politécnica de MadridE.T.S.de Ingenieros de CaminosMadrid 28040Spain

A large number of anomalous extension twins,with low or even negative twinning Schmid factors,were found to nucleate and grow in a strongly textured Mg-1Al alloy during tensile deformation along the extruded *** deformation mechanisms responsible for this behaviour were investigated through in-situ electron back-scattered diffraction,grain reference orientation deviation,and slip trace-modified lattice *** was found that anomalous extension twins nucleated mainly at the onset of plastic deformation at or near grain boundary triple *** were associated with the severe strain incompatibility between neighbour grains as a result from the differentbasal slip-induced lattice ***,the anomalous twins were able to grow with the applied strain due to the continuous activation ofbasal slip in different neighbour grains,which enhanced the strain *** results reveal the complexity of the deformation mechanisms in Mg alloys at the local level when deformed along hard orientations.

关键词： Magnesium Extension twinning In-situ electron back-scattered diffraction basal slip Deformation mechanisms.

Fe含量对粉末冶金Cu-Fe合金显微组织与性能的影响

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Transactions of Nonferrous Metals Society of China 2024年第5期34卷 1571-1587页

作者：张平袁晓波曾梓名滕剑威周芸合杨标标李云平中南大学粉末冶金国家重点实验室长沙410083 Institute for Materials Research Tohoku UniversitySendai 980-8577Japan IMDEA Materials Institute C/Eric Kandel 2GetafeMadrid 28906Spain Department of Materials Science Polytechnic University of Madrid/Universidad Politécnica de MadridE.T.S.de Ingenieros de CaminosMadrid 28040Spain

研究Fe含量对粉末冶金Cu-Fe合金显微组织及性能的影响。采用电火花等离子烧结、冷轧以及时效处理工艺制备4种不同铁含量(5%、10%、20%和40%,质量分数)的Cu-Fe合金。研究结果表明,随着Fe含量从5%(质量分数)增加到40%(质量分数),Fe相由离... 详细信息

研究Fe含量对粉末冶金Cu-Fe合金显微组织及性能的影响。采用电火花等离子烧结、冷轧以及时效处理工艺制备4种不同铁含量(5%、10%、20%和40%,质量分数)的Cu-Fe合金。研究结果表明,随着Fe含量从5%(质量分数)增加到40%(质量分数),Fe相由离散球形分布演变为连续交错分布,Fe相尺寸从0.29μm增加到1.20μm;时效态的Cu-Fe合金的屈服强度从411.5 MPa提高到788.8 MPa,电导率从62.5%(IACS)降低到42.0%(IACS)。在以上结果的基础上,提出一种混合法则计算Cu基体、初级Fe相和次级Fe相对屈服强度的贡献,可较好地预测Fe含量高于10%(质量分数)合金的力学性能。

关键词：铜铁合金粉末冶金快速凝固力学性能强度计算

Influence of parameters on the microstructure of a duplex stainless steel joint welded by a GMAW welding process

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Progress in Natural Science:Materials International 2022年第4期32卷 415-423页

作者： Sandra Chacón-Fernández Antonio Portolés García Gerardo Romaní Labanda Universidad Politécnica de Madrid Escuela Técnica Superior de Ingenieros Industriales UPM

Duplex stainless steels（DSSs） are widely used in industry for their desirable properties. Any fusion welding technique modifies the microstructure and, consequently, the properties of the material. This paper presents a parametric study of the variables that determine the energy contribution（current, voltage and welding speed） and the structural modifications produced during gas metal arc welding. The analysis comprises metallographic study,phase balance, dimensioning of the weld beads and tensile and hardness tests. The influence of the variables studied on the thermal cycles obtained（temperatures reached and cooling rate） was determined by using a finite element model. The results showed that, in addition to the indicated parameters, the parameter power transfer per volume（W/m3） and the geometry in the bead must be controlled due to their influence on the heat flow distribution and phase balance.

关键词： Welding Heat input GMAW Duplex stainless steels (DSS) Finite element model (FEM)

Experimental study on lightweight expanded clay at particle level:Breakage of isolated grains

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第7期15卷 1846-1858页

作者： Elías Roces-Alonso Jose Estaire Miriam Martín-Ruiz Jesús González-Galindo ETS de ingenieros de Caminos Universidad Politécnica de MadridSpain Laboratorio de Geotecnia CEDEXMadridSpain

In this study,more than 1500 particles of lightweight expanded clay aggregate(LECA)are individually loaded up to breakage,following different patterns of contact(from 2 to 7)using a purpose-built ***,a statistical model for predicting the number of fragments into which a grain breaks as a function of the number of contacts and their diameter is *** number of fragments is found to follow a statistical binomial-type distribution function that depends on the number of *** addition,a model based on Bayesian networks,capable of assessing the number of fragments and their size(measured as normalized weight)as a function of the number of contacts,is *** proposed method is applicable when performing discrete element method(DEM)simulations on granular media in which grain breakage plays a relevant role.

关键词： Lightweight expanded clay aggregate(LECA) Grain fragmentation Grain breakage Biaxial grain load

Decoupled Photovoltaic Power Ramp-rate Calculation Method for Perturb and Observe Algorithms

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Journal of Modern Power Systems and Clean Energy 2022年第4期10卷 932-940页

作者： Jose Miguel Riquelme-Dominguez Francisco M.Gonzalez-Longatt Sergio Martinez Electrical Engineering Department Escuela Tecnica Superior de Ingenieros IndustrialesUniversidad Politecnica de Madrid28006 MadridSpain Department of Electrical Engineering Information Technology and CyberneticsUniversity of South-Eastern Norway3918 PorsgrunnNorway

As photovoltaic energy increasingly penetrates in power systems,transmission system operators have started to request its participation in providing ancillary *** of the demanded services is the power ramp-rate control(PRRC),which attempts to limit the power ramps produced by intermittent irradiance *** order to achieve the desired objective,solutions based on storage systems or modifying the maximum power point tracking(MPPT)in perturb and observe(P&O)algorithms are commonly *** starting point in PRRC is the determination of the instantaneous power ramprate,and different methods have been proposed in the literature for its ***,the accuracy and computational speed of existing procedures can be improved,which may be critical in situations with rapid irradiance *** this paper,a decoupled photovoltaic power ramp-rate calculation method is presented,in which the effect of variable irradiance and the P&O algorithm are computed *** proposed method has been theoretically demonstrated and tested through simulation and experimental *** results show that it can improve the previous methods in terms of accuracy and computation *** validation with hardware-inthe-loop demonstrates the suitability of the proposed method for real-time applications,even in presence of noisy measurements.

关键词： Hardware-in-the-loop maximum power point tracking perturb and observe photovoltaic power ramp-rate control ramp-rate calculation method

Revisiting the analytical solutions for ultimate bearing capacity of pile embedded in rocks

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第6期15卷 1506-1519页

作者： A.Picardo M.A.Millán R.Galindo A.Alencar Escuela Técnica Superior de Arquitectura Universidad Politécnica de MadridMadrid28040Spain Escuela Técnica Superior de ingenieros de Caminos Canales y Puertos de MadridUniversidad Politécnica de MadridMadrid28040Spain

This paper investigates the validity and shortcomings of the existing analytical solution for the ultimate bearing capacity of a pile embedded in a rock mass using the modified HoekeBrown failure *** this criterion is considered a reference value for empirical and numerical calculations,some limitations of its basic simplifications have not been clarified *** research compares the analytical results obtained from the novel discontinuity layout optimization(DLO)method and the numerical solutions from the finite difference method(FDM).The limitations of the analytical solution are considered by comparing different DLO failure modes,thus allowing for the first time a critical evaluation of its scope and conditioning for *** of up to 40%in the bearing capacity and unrealistic failure modes are the main issues in the analytical *** main aspects of the DLO method are also analyzed with an emphasis on the linearization of the rock failure criterion and the accuracy resulting from the discretization *** analysis demonstrates DLO as a very efficient and accurate tool to address the pile tip bearing capacity,presenting considerable advantages over other methods.

关键词： Discontinuity layout optimization(DLO) Analytical solution Bearing capacity Deep foundations HoekeBrown failure criterion Finite difference method(FDM)

Active Learning and Dynamic Pricing Policies

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American Journal of Operations Research 2014年第2期4卷 90-100页

作者： María-Jesús Vázquez-Gallo Macarena Estévez Santiago Egido Conento S.L.U. Madrid Spain Department Civil Engineering Technical University of Madrid Madrid Spain solute ingenieros San Sebastián de los Reyes Madrid Spain

In this paper, we address the problem of dynamic pricing to optimize the revenue coming from the sales of a limited inventory in a finite time-horizon. A priori, the demand is assumed to be unknown. The seller must learn on the fly. We first deal with the simplest case, involving only one class of product for sale. Furthermore the general situation is considered with a finite number of product classes for sale. In particular, a case in point is the sale of tickets for events related to culture and leisure;in this case, typically the tickets are sold months before the event, thus, uncertainty over actual demand levels is a very a common occurrence. We propose a heuristic strategy of adaptive dynamic pricing, based on experience gained from the past, taking into account, for each time period, the available inventory, the time remaining to reach the horizon, and the profit made in previous periods. In the computational simulations performed, the demand is updated dynamically based on the prices being offered, as well as on the remaining time and inventory. The simulations show a significant profit over the fixed-price strategy, confirming the practical usefulness of the proposed strategy. We develop a tool allowing us to test different dynamic pricing strategies designed to fit market conditions and seller's objectives, which will facilitate data analysis and decision-making in the face of the problem of dynamic pricing.

关键词： Dynamic Pricing Demand Learning Revenue Management

The relation between ductility at high temperature and solid solution in Mg alloys

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Journal of Magnesium and Alloys 2022年第1期10卷 241-256页

作者： D.F.Shi C.M.Cepeda-Jiménez M.T.Pérez-Prado IM DEA Materials Institute C/Eric Ka ridel228906 GetafeMadridSpain Department of Materials Science Polytechnic University of Madrid/Universidad Politecnica de MadridE.T.S.de Ingenieros de Caminos28040MadridSpain Department of Physical Metallurgy CENIMCSICAv.Gregorio del Amo 828040 MadridSpain

This work investigates the effect of solid solution on ductility and on the activation of individual deformation mechanisms at moderate temperatures and at quasi-static strain rates in Mg-Zn and Mg-Al alloys. With that aim, four solid solution Mg-Zn and Mg-Al binary alloy ingots containing 1 and 2 wt.% solute atoms were subjected to hot rolling and subsequent annealing to generate polycrystals with similar average grain size and basal-type texture for each composition. The activity of the different slip systems after tensile testing at 150°C and at 250°C was evaluated in pure Mg and in the alloys by EBSD-assisted slip trace analysis. In addition, segregation of Zn and Al atoms at grain boundaries during the thermo-mechanical processing was characterized by HAADF-STEM and EDX. It was found that while the addition of Al and Zn atoms to pure Mg does not lead to major changes in the mechanical strength at the investigated temperatures, it does enhance ductility significantly, especially at 250℃. Our results show that this increase in ductility cannot be attributed to a higher activation of non-basal systems in the alloys, as reported earlier, as the incidence of non-basal systems is indeed considerably higher in pure Mg. This work suggests, on the contrary, that the ductility increase may be attributed to the presence of a more homogenous basal activity in the alloys due to a lower degree of orientation clustering, to grain boundary solute segregation, and to a higher slip diffusivity at grain interiors.

关键词： Magnesium solute segregation Slip trace analysis Ductility Deformation mechanisms

GROUNDWATER MASS TRANSPORT AND HOMOGENEOUS EQUILIBRIUM CHEMISTRY IN THE PRESENCE OF FLUX BOUNDARY CONDITIONS

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Acta Mathematicae Applicatae Sinica 1991年第2期7卷 165-172页

作者：管志成 Zhejiang Universityonsidering a solute transport problem deseribed by some algebraic and partial differentialequations with the presence of flux boundary conditions we reduce the problem to a fixed point oneand use a priori estimates to prove the existence and uniqueness of the global solutions.

Considering a solute transport problem deseribed by some algebraic and partial differentialequations with the presence of flux boundary conditions, we reduce the problem to a fixed point oneand use a priori estimates ... 详细信息

关键词： GROUNDWATER MASS TRANSPORT AND HOMOGENEOUS EQUILIBRIUM CHEMISTRY IN THE PRESENCE OF FLUX BOUNDARY CONDITIONS

Effect of Ti additions on microstructure and mechanical properties of Cu-Cr-Zr alloy

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Journal of Materials Science & Technology 2023年第32期163卷 69-80页

作者： Chenying Shi Muzhi Ma Biaobiao Yang Yuling Liu Yushen Huang Yong Du State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China School of Materials Science and Engineering Central South UniversityChangsha 410083China IMDEA Materials Institute C/Eric Kandel 2Getafe28906 MadridSpain Department of Materials Science Polytechnic University of Madrid/Universidad Politécnica de MadridE.T.S.de Ingenieros de Caminos28040 MadridSpain

Ti additions in Cu–Cr–Zr alloys are useful for achieving high mechanical *** this work,the influence of Ti contents(0.25 wt%,0.6 wt%,and 1.02 wt%)on the microstructure,mechanical,and electrical properties of Cu–Cr–Zr alloys has been investigated experimentally,along with thermodynamic and kinetic *** electrical conductivity decreased but the hardness/strength increased with increasing Ti *** lower electrical conductivity is due to increased electron scattering through the solution of more Ti atoms in the Cu *** for the higher hardness/strength,it is mainly owing to higher dislocation density and finer FCC-Cr ***,a model considering the size distributions of precipitates is adopted to calculate precipitation strengthening *** calculated yield strengths are consistent with the experimental ones for the *** thermodynamic and kinetic calculations reveal that increasing Ti content can facilitate the nucleation of FCC-Cr but enhance its activation energy,hence hindering the growth *** present work study can provide an effective strategy for producing copper alloys with expected performance.

关键词： Cu-Cr-Zr-Ti alloy Mechanical and electrical properties Microstructure Precipitation behavior Thermodynamic and kinetic calculations