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journal of Advanced dielectrics 2021年第3期11卷 39-44页

作者： B.R.Moya A.C.silva A.Peláiz-Barranco j.d.s.guerra Grupo de Ferroelétricos e Materiais Multifuncionais Instituto de Física Universidade Federal de Uberlandia UberlandiaMinas Gerais 38408-100Brazil departamento de Física e Química UNESP Campus de Ilha SolteiraSao Paulo 15385-000Brazil Grupo de Materiales Ferroicos Facultad de Física-Instituto de Ciencia y Tecnología de Materiales Universidad de La Habana La Habana 10400Cuba

(1-x)(Bi_(0.5)Na_(0.5))TiO_(3)-xBaTiO_(3) lead-free ceramics have been obtained from the conventional solid-state reaction sintering *** structural properties were investigated from X-ray diffraction and Raman spectroscopy *** revealed well-crystallized ceramic samples with perovskite *** properties,obtained from scanning electron microscopy measurements,have shown high density with very low porosity *** dielectric response,analyzed as a function of the temperature and several frequencies,showed very broad peaks with a strong frequency dependence of the temperature for the maximum dielectric permittivity for the modified *** were analyzed considering the influence of the BaTiO3 content on the studied physical properties.

关键词： Lead-free BNT Raman spectroscopy dielectric response

switching and energy-storage characteristics in PLZT 2/95/5 antiferroelectric ceramic system

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journal of Advanced dielectrics 2016年第4期6卷 1-4页

作者： A.Pelaiz-Barranco Y.Mendez-Gonzalez j.d.s.guerra Xiucai Wang Tongqing Yang Facultad de Fisica-IMRE Universidad de La Habana San Lazaroy LVedadoLa Habana 10400Cuba Grupo de Ferroeletricos e Materiais Multifuncionais Instituto de Fsica Universidade Federal de Uberlandia38408-100Uberlandia-MGBrazil Functional Materials Research Laboratory College for Materials Science and EngineeringTongji University4800 CaoanShanghai 201804P.R.China

switching mechanisms and energy-storage properties have been investigated in(Pb_(0.98)La_(0.02)T(Zr_(0.95)Ti_(0.05)T_(0.995O_(3)) antiferroelectric *** electric field dependence of polarization(P–E hysteresis loops)indicates that both the ferroelectric(FE)and antiferroelectric(AFE)phases coexist,being the AFE more stable above 100℃.It has been observed that the temperature has an important influence on the switching *** the other hand,the energy-storage density,which has been calculated from the P–E hysteresis loops,shows values higher than 1 j/cm^(3) for temperatures above 100℃ with around 73%of efficiency as *** properties indicate that the studied ceramic system reveals as a promising AFE material for energy-storage devices application.

关键词： Antiferroelectrics energy-storage switching.

EVIdENCEs OF A sTRUCTURAL PHAsE TRANsITION IN THE NEW Pb(Zr_(y)Ti_(1-y))O_(3)MOdIFIEd TELLURITE GLAss-CERAMIC COMPOsITE

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journal of Advanced dielectrics 2011年第2期1卷 185-190页

作者： j.d.s.guerra C.R.HATHENHER Grupo de Ferroeletricos e Materiais Multifuncionais Instituto de Fisica Universidade Federal de Uberlandia 38400-902UberlandiaMGBrazil

The physical properties of the new TeO_(2)-B_(2)O_(3)-PbO_(2)(TBP)-based glass system,obtained from the usual melt-quench method,have been investigated taking into account the infuence of the Pb(Zr_(y)Ti_(1-y))O_(3)(PZT)ferroelectric system.A crystalline-like structure,which characterizes a glass-ceramic-like state,promoted by the ferroelectric phase,has been revealed from the X-ray diffraction results for the sample with higher PZT *** the other hand,results on the dielectric response revealed noticeable dielectric anomalies,which until now have not been *** fact,the dielectric and ferroelectric properties suggest the existence of a structural phase transition induced by the PZT crystalline phase,which indeed have been related to the ferroelectric polar-phase regions embedded into the glass matrix.

关键词： Tellurite glasses ferroelectrics glass-ceramics dielectric properties

debye's temperature and heat capacity for sr_(0.15)Ba_(0.85)Bi_(2)Nb_(2)O_(9) relaxor ferroelectric ceramic

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journal of Advanced dielectrics 2016年第1期6卷 1-4页

作者： A.Pelaiz-Barranco Y.Gonzalez-Abreu P.saint-Gregoire j.d.s.guerra F.Calderón-Piñar Facultad de Fisica-IMRE Universidad de La Habana San Lazaro y LVedadoLaHabana 10400Cuba department of sciences and Arts University of Nîmes 30021 Nîmes Cedex 01France Grupo de Ferroeletricos e Materiais Multifuncionais Instituto de Fisica Universidade Federal de Uberlandia.38400-902Uberlandia-MGBrazil

A lead-free relaxor ferroelectric,sr_(0.15)Ba_(0.85)Bi_(2)Nb_(2)O_(9),was synthesized via solid-state reaction and the temperature-dependence of the heat capacity was measured in a wide temperature *** dielectric permittivity was also measured between 500 Hz and 5 MHz in the same temperature *** anomaly has been detected in the heat capacity curve for the whole temperature range covered in the present experiments,while broad peaks have been observed in the dielectric permittivity with high frequency dispersion.A typical relaxor behavior has been observed from the dielectric *** debye's temperature has showed a minimum value near the freezing *** results are discussed considering the spin-glass model and the high frequency dispersion,which has been observed for the studied relaxor system.

关键词： Relaxors ferroelectrics heat capacity ceramics

Exploring the electromechanical response and electric field-induced dielectric anomalies in PMN-PT electroceramics

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journal of Advanced dielectrics 2021年第3期11卷 32-38页

作者： j.d.s.guerra C.A.Guarany E.C.Lima E.B.Araújo j.E.Garcia Grupo de Ferroelétricos e Materiais Multifuncionais Instituto de Física Universidade Federal de Uberlandia UberlandiaMinas Gerais 38408-100Brazil Universidade Federal do Tocantins Porto Nacional Tocantins 77500-000Brazil departamento de Física e Química Universidade Estadual Paulista Ilha Solteira–Sao Paulo 15385-000Brazil department of Physics Universitat Politècnica de Catalunya–BarcelonaTech Barcelona 08034Spain

Electromechanical and dielectric properties of PMN-PT ferroelectric ceramics are *** particular,dielectric response studies focus on the investigation of the influence of the dC applied electric field on the dielectric permittivity as a function of temperature and *** reveal an electric field driven dielectric anomaly in the dielectric permittivity curves,e(E),which in turn prevails in the whole ferroelectric phase region and continuously vanishes for temperatures near the paraelectric-ferroelectric phase transition temperature.A schematic model for the domains dynamics of the studied material is proposed taking into account the simultaneous contribution of both 90°and 180°domains walls.

关键词： Ferroelectrics PMN-PT domain-walls dielectric response electric field

Relaxor ferroelectric behavior:An approach considering both the dipolar and electrical conductivity contributions

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journal of Advanced dielectrics 2021年第3期11卷 51-55页

作者： C.Carreras-Casas O.García-Zaldívar A.Peláiz-Barranco Y.González-Abreu F.Calderón-Pinar j.d.s.guerra Grupo de Materiales Ferroicos Facultad de Física-Instituto de Ciencia y Tecnología de Materiales Universidad de La Habana La Habana 10400Cuba Grupo de Ferroelétricos e Materiais Multifuncionais Instituto de Física Universidade Federal de Uberlandia UberlandiaMinas Gerais38408-100Brazil

The relaxor behavior of PLZT ferroelectric ceramics has been analyzed in a wide frequency and temperature ranges,below and above the temperature for the formation of the so-called polar nano-regions(PNRs).An approximation to the dynamical behavior of the PNRs has been discussed using Cole-Cole’s relaxation model and jonscher’s Universal Relaxation *** analysis considers both the dipolar contribution and those ones associated with dC and AC electric conductivities,this latter not being previously reported in the literature for relaxor *** effectiveness of the developed model has been verified from the agreement between the experimental data and the theoretical *** study also offers an indirect method to predict the dC component of the electrical conductivity.

关键词： Relaxor ferroelectrics dielectric response modeling conductivity Cole-Cole

Generalized polynomial chaos expansion by reanalysis using static condensation based on substructuring

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Applied Mathematics and Mechanics(English Edition) 2024年第5期45卷 819-836页

作者： d.LEE s.CHANG j.LEE department of Automotive Engineering Hanyang UniversitySeoul 04763Republic of Korea school of Mechanical Engineering Chungnam National UniversityDaejeon 34134Republic of Korea department of Mechanical Robotics and Energy EngineeringDongguk UniversitySeoul 04620Republic of Korea

This paper presents a new computational method for forward uncertainty quantification(UQ)analyses on large-scale structural systems in the presence of arbitrary and dependent random *** method consists of a generalized polynomial chaos expansion(GPCE)for statistical moment and reliability analyses associated with the stochastic output and a static reanalysis method to generate the input-output data *** the reanalysis,we employ substructuring for a structure to isolate its local regions that vary due to random *** allows for avoiding repeated computations of invariant substructures while generating the input-output data *** substructuring with static condensation further improves the computational efficiency of the reanalysis without losing ***,the GPCE with the static reanalysis method can achieve significant computational saving,thus mitigating the curse of dimensionality to some degree for UQ under high-dimensional *** numerical results obtained from a simple structure indicate that the proposed method for UQ produces accurate solutions more efficiently than the GPCE using full finite element analyses(FEAs).We also demonstrate the efficiency and scalability of the proposed method by executing UQ for a large-scale wing-box structure under ten-dimensional(all-dependent)random inputs.

关键词： forward uncertainty quantification(UQ) generalized polynomial chaos expansion(GPCE) static reanalysis method static condensation substructuring

Kick-start for metabolomics in liver disease

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World journal of Hepatology 2024年第9期16卷 1206-1210页

作者： Armando guerra-Ruiz Laboratory Medicine University Hospital Marques de ValdecillaSantander 39008CantabriaSpain Commission on Biochemical Assessment of Liver disease Spanish Society of Clinical Chemistry(SEQC-ML)Barcelona 08025CataloniaSpain digestive diseases Valdecilla Research Institute(IDIVAL)Santander 39011CantabriaSpain

It is not complicated for the clinician to diagnose a patient with advanced fibrosis or liver cirrhosis when he has already presented some decompensation of his liver ***,it is in the earliest stages when the patient's prognosis can be modified the *** liver disease is generally asymptomatic,not invasive markers are of great *** the era of omics,it is time for metabolomics to accompany genomics and proteomics,which are more established in the diagno-stics and prognostics clinical ***,understood as the compre-hensive evaluation of the metabolites present in the organism in a specific phys-iological situation,has undoubted advantages in the study and identification of serum markers relevant to a specific *** year,I read with interest two articles published in this journal:“Baseline metabolites could predict responders with hepatitis B virus-related liver fibrosis for entecavir or combined with FuzhengHuayu tablet”by dai et al and“Metabolomics in chronic hepatitis C:decoding fibrosis grading and underlying pathways”by Ferrasi et *** papers illuminate the power of metabolomics to provide us with new tools in the management of liver *** this editorial,I comment on these studies and others,and note how they can contribute to our understanding of liver disease in more than one way.

关键词： Metabolomics Liver disease Biomarkers Hepatology Mass spectrometry Hepatitis Clinical biochemistry

synthesis of coral-like structures of Pr-Yb co-doped YIG: structural,optical, magnetic and antimicrobial properties

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journal of Rare Earths 2024年第3期42卷 543-554,I0004页

作者： A.Fernandez Francisca P.Araujo Y.guerra s.Castro-Lopes j.Matilla-Arias Idglan s.de Lima Edson C.silva-Filho josy A.Osajima F.Guerrero R.Pena-Garcia Federal University of Piau Graduate Program in Materials Science and EngineeringTeresinaPIBrazil Federal Rural University of Pernambuco Academic Unit of Cabo de Santo AgostinhoCabo de Santo AgostinhoPEBrazil Federal University of Piaui Department of PhysicTeresinaPBrazil Federal University of Pernambuco Graduate Program in Materials ScienceRecifePEBrazil University of Granma Departmentof Basic Sciences and Applied InformaticsFaculty of Technical SciencesBayamoCuba Federal University of Amazonas Department of PhysicManausAMBrazil Federal University of Pernambuco Department of PhysicRecifePEBrazil

Coral-like structures of the Y_(3-x)Pr_(x)Fe_(5-y)Yb_(y)O_(12),(0.00 ≤ x ≤ 0.04, 0.00 ≤ y ≤ 0.02) compound were synthesized using the sol-gel method. structural investigation certified the YIG cubic crystal structure formation, without any secondary phase. It is shown that, the relatively large ionic radius of the dopant cations results in an expansion of the lattice parameter, variations in the Iona-O-Iondangle, Iona-O,Iond-O and Ionc-O bond distances and decrease in the average crystallite size. Fourier transform infrared(FTIR) and Raman measurements are essential to testify the single-phase formation of YIG crystal structure and are observed changes in the stretching and vibrational modes, respectively. The morphological study, energy dispersive spectroscopy(Eds) spectra and textural properties show corallike structures, peaks associated with Pr^(3+) and Yb^(3+) atoms and the effect of dopants on surface area,diameter, and pore volume, respectively. The optical analysis from diffuse reflectance spectra witnessed an increase in the optical gap band, a decrease in Urbach energy and blue shift in the charge transfer,correlated with the expansion of the unit cell due to the dopant's insertion in the YIG structure. A typical ferrimagnetic behavior is exhibited by the Y_(3-x)Pr_(x)Fe_(5-y)Yb_(y)O_(12)compound. The saturation magnetization(M_(s)), cubic anisotropy constant(K_(1)) and coercive field(H_(c)) increase with the Pr^(3+)cations content, as consequence of their magnetic nature and distribution around of Fe^(3+)ions due to the coexistence with the Yb^(3+). Finally, for the first time, antibacterial tests by mean of the direct contact method were performed for YIG co-doped with Pr^(3+)and Yb^(3+)and it is shown that, relatively high dosages of Pr^(3+) cations favored the activity against s. aureus, therefore, a new biological property for YIG doped with rare earths is presented.

关键词： Yttrium iron garnet(YIG) Coral-like structures Rare earths Band gap energy Magnetic properties Antimicrobial properties

Atomistic Investigation of shock-Induced Amorphization within Micro-shear Bands in Hexagonal Close-Packed Titanium

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Acta Metallurgica sinica(English Letters) 2024年第9期37卷 1590-1600页

作者： Z.C.Meng K.G.Wang T.Ali d.Li C.G.Bai d.s.Xu s.j.Li A.H.Feng G.j.Cao j.H.Yao Q.B.Fan H.Wang R.Yang Institute of Metal Research Chinese Academy of SciencesShenyang 110016China school of Materials science and Engineering University of Science and Technology of ChinaShenyang 110016China Interdisciplinary Centre for Additive Manufacturing(ICAM) School of Materials and ChemistryUniversity of Shanghai for Science and TechnologyShanghai 200093China school of Materials science and Engineering Tongji UniversityShanghai 201804China Key Laboratory for Light-Weight Materials Nanjing Tech UniversityNanjing 210009China National Key Laboratory of science and Technology on Materials Under shock and Impact School of Materials Science and EngineeringBeijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401135China

The mechanical response of a single crystal titanium sample against(0001)α surface impact was investigated using molecular dynamics ***,non-uniform plastic deformation was observed in the *** high strain rates,amorphization occurred near the edge of the contact region where severe shear strain induced a large number of stacking faults(sFs)and *** contrast,the central part of the contact region underwent less deformation with significantly fewer ***,instead of amorphization by consuming sFs and dislocations,there was a gradual increase in the density of dislocations and sFs during the process of *** local amorphous regions eventually grew into shear bands.

关键词： shock compression Amorphization shear band Titanium Molecular dynamics