Polymorphic phase boundary in piezoelectric oxides

The design of phase boundaries has now become a consolidated strategy to improve the functional properties of piezoelectric oxides because of the unique properties that may be obtained in their vicinity. In particular, polymorphic phase boundaries (PPBs) have attracted significant interest in recent years because they represent a significant breakthrough in terms of enhanced piezoelectric activity of lead-free piezoelectric oxides. PPBs are temperature-driven phase transitions where both intrinsic and extrinsic contributions maximize, thereby enhancing the macroscopic properties of piezoelectric materials. This tutorial discusses potassium–sodium–niobate-based systems as model materials to reveal some of the most relevant advances in the design of PPBs through compositional modifications. We focus on how PPBs can be modulated by engineered doping and also discuss the direct relation between PPBs and the enhancement of piezoelectric activity. Finally, we briefly describe the main experimental techniques for detecting PPBs.Postprint (author's final draft

Ferroelectric properties of Bi0.5(Na0.8K0.2)0.5TiO3 ceramics

Different processing conditions and the effect of secondary phases on ferroelectric properties of Bi0.5(Na0.8K0.2)0.5TiO3 (BNKT) are studied. Ceramic powders are prepared by solid state reaction and different sintering temperatures (temperatures between 1075 and 1150ºC) are analyzed. Finally, samples are characterized by X-ray diffraction, Raman microspectroscopy, Scanning Electron Microscopy, impedance spectroscopy, and density measurements. Through XRD patterns, the perovskite structure is stabilized; together with small peaks corresponding to a secondary phase associated with K2-xNaxTi6O13 phase. Moreover, the content of the secondary phase, d33 piezoelectric constant and dielectric properties increase with sintering temperature.Fil: Camargo, Javier Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Ramajo, Leandro Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Rubio Marcos, Fernando. Instituto de Ceramica y Vidrio de Madrid; EspañaFil: Castro, Miriam Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Study of processing conditions of Bi0.5(Na0.8K0.2)0.5TiO3

En este trabajo se estudian las condiciones de procesamiento de sistemas Bi0.5(Na0.8K0.2)0.5TiO3 (BNKT) que permitan obtener materiales cerámicos con buenas propiedades ferroeléctricas. Los reactivos de partida fueron activados mecanoquímicamente y mediante análisis térmico diferencial y termogravimetría (ATD-ATG) se determinaron las temperaturas de descomposición, mientras que por difracción de Rayos X (DRX) se identificaron las diferentes fases cristalinas. El efecto de la temperatura de sinterización en el sistema BNKT fue caracterizado mediante microespectroscopía Raman y espectroscopía de impedancia. Se determinó que las muestras sinterizadas a 1100 ºC no presentan fases secundarias, y proporcionan los mayores valores de densidad, y las menores pérdidas dieléctricas. En estas muestras mediante DRX no se registró la presencia de fases secundarias.In this paper, the improvement of the ferroelectric properties of Bi0.5(Na0.8K0.2)0.5TiO3 ceramics through the implementation of different processing conditions is studied. Ceramic powders were obtained by solid state reaction, after mechanochemical activation of the starting reagents. Thermal evolution of starting powders was analyzed by differential thermal analysis and thermogravimetry (DTA-TGA). Crystalline phases of powders, thermally treated at temperatures ranging between 550 and 800 ºC, were characterized by X-ray diffraction (XRD). The influence of the sintering temperature on the BNKT-system was characterized by Raman microspectroscopy, and impedance spectroscopy. It was found that samples sintered at 1100 ºC showed the highest density and the lowest dielectric loss values. Moreover, in these samples, secondary phases were not detected by XRD.Fil: Camargo, Javier Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Ramajo, Leandro Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Rubio-marcos, Fernando. Instituto de Cerámica y Vidrio; EspañaFil: Castro, Miriam Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentin

Aplicación de soporte para personal docente en dispositivo móvil : iPhone

Actualment és difícil no veure a gent de totes les edats amb algun tipus de Gadget electrònic. En forma de telèfons mòvils, GPS, agendes electròniques, reproductors de música, tablets o qualsevol altre dispositiu, el món digital ens aborda, la informació i les dades es digitalitzen i arriben fins a les nostres butxaques per ser accessibles en qualsevol moment. Es fa indispensable familiaritzar-se amb aquestes eines i per això s'introdueixen en els centres educatius de tot el món. En aquest projecte es combinen tots aquests fets per desenvolupar un herbari digital sobre un dispositiu mòbil, amb finalitat educativa i ús privat.Actualmente es difícil no ver a gente de todas las edades con algún tipo de Gadget electrónico. En forma de teléfono móvil, GPS, agendas electrónicas, reproductores de música, tablets o cualquier otro dispositivo, el mundo digital nos aborda, la informaciónn y los datos se digitalizan y llegan hasta nuestros bolsillos para ser accesibles en cualquier momento. Se hace indispensable familiarizarse con tales herramientas y por eso se introducen en los centros de educativos de todo el mundo. En este proyecto se combinan todos estos echos para desarrollar un herbario digital sobre un dispositivo móvil, con fines educativos y uso privado.Nowadays it's not difficult to see people of all ages with any type of electronic gadget such as mobile phones, GPS, PDAs, tablets and so on. The digital world surrounds us; information and data are digitalized and accessible at any time, anywhere. Therefore it is essential to familiarize ourselves with these tools. Already learners of young age have to be confronted with them in education centres so that they are prepared for the standards set in our society. This project takes all these facts into account to develop a digital herbarium on a mobile device, for educational and personal use.Nota: Aquest document conté originàriament altre material i/o programari només consultable a la Biblioteca de Ciència i Tecnologia

Enhancement of piezoelectric properties stability of submicron-structured piezoceramics obtained by spark plasma sintering

Grain-size effect on functional properties of piezoceramics is nowadays an important topic due to the potential applications of these materials at the submicron scale. In this context, we explore the effect of the grain size reduction on the functional properties stability of piezoceramics. Submicron- and micro-structured Pb(Zr,Ti)O3-based materials are taken as model samples to carry out this study. Rayleigh analysis is used to quantitatively evaluate the domain wall contribution. The results show that the stability of properties depends strongly on grain size. Specifically, the nonlinear response decreases significantly when the grain size is reduced to the submicron scale. This behavior can be explained by taking into account that a grain size reduction involves a grain boundary increment, which may clamp domain walls. The results suggest that grain size engineering may be an effective alternative to the widely used compositional engineering in order to control the undesirable nonlinear behavior in piezoceramics.Postprint (author's final draft

Transportation infrastructure network design in the presence of modal competition: computational complexity classification and a genetic algorithm

[EN] In this paper we analyze the computational complexity of transportation infrastructure network design problems, in the presence of a competing transportation mode. Some of these problems have previously been introduced in the literature. All problems studied have a common objective: the maximization of the number of travelers using the new network to be built. The differences between them are due to two factors. The first one is the constraints that the new network should satisfy: (1) budget constraint, (2) no-cycle constraint, (3) both constraints. The second factor is the topology of the network formed by the feasible links and stations: (1) a general network, (2) a forest. By combining these two factors, in total we analyze six problems, five of them are shown to be NP-hard, the sixth being trivial. Due to the NP-hardness of these problems, a genetic algorithm is proposed. Computational experiments show the applicability of this algorithm.Mozart Menezes and Juan A. Mesa were partially supported by project MTM2015- 67706-P (MINECO/FEDER,UE). Federico Perea was partially supported by the Spanish Ministry of Science, Innovation, and Universities, under projects "OPTEP-Port Terminal Operations Optimization" (No. RTI2018-094940-B-I00) and MTM2016-74983, fnanced with FEDER funds, and by the Universitat Politècnica de València under grant SP20180164 of the program Primeros Proyectos de Investigaciòn (PAID-06-18), Vicerrectorado de Investigaciòn, Innovaciòn y Transferencia. All this support is gratefully acknowledged.Perea Rojas Marcos, F.; Menezes, MBC.; Mesa, JA.; Rubio-Del-Rey, F. (2020). Transportation infrastructure network design in the presence of modal competition: computational complexity classification and a genetic algorithm. Top. 28(2):442-474. https://doi.org/10.1007/s11750-019-00537-xS442474282Balakrishnan A, Magnanti TL, Mirchandani P (1997) Network design. Annotated bibliography in combinatorial optimization. Wiley, New YorkBussieck M, Winter T, Zimmermann U (1997) Discrete optimization in public rail transport. Math Prog 79(1–3):415–444Chakroborty P (2003) Genetic algorithms for optimal urban transit network design. Comput Aided Civ Infrastruct Eng 18:184–200Chakroborty P, Dwivedi T (2002) Optimal route network design for transit systems using genetic algorithms. Eng Optim 34(1):83–100Desaulniers G, Hickman MD (2007) Public transit. Transportation Handbooks in operations research and management science, vol 14. Elsevier, Amsterdam, pp 69–127García-Archilla B, Lozano AJ, Mesa JA, Perea F (2013) GRASP algorithms for the robust railway network design problem. J Heuristics 19(2):399–422Garey M, Johnson DS (1979) Computers and Intractability: a guide to the theory of NP-completeness. W.H Freeman and Company, USGoel G, Karande C, Tripathi P, Wanga L (2010) Approximability of combinatorial problems with multi-agent submodular cost functions. ACM SIGecom Exch 9(1):1–4Grötschel M, Lovász L, Schrijver A (1981) The ellipsoid method and its consequences in combinatorial optimization. Combinatorica 1:169–197Grötschel M, Lovász L, Schrijver A (1993) Geometric algorithms and combinatorial optimization, 2nd edn. Springer-Verlag, New YorkGuihaire V, Hao JK (2008) Transit network design and scheduling: a global review. Transp Res Part A 42:1251–1273Jegelka SS (2012) Combinatorial problems with sub-modular coupling in machine learning and computer vision. Thesis ETH ZurichLaporte G, Mesa JA, Ortega FA (1995) Assessing the efficiency of rapid transit configurations. Top 5:95–104Laporte G, Mesa JA, Perea F (2010) A game theoretic framework for the robust railway transit network design problem. Transp Res Part B 44:447–459Magnanti TL, Wong RT (1984) Network design and transportation planning: models and algorithms. Transp Sci 18:1–55Marín A, García-Ródenas R (2009) Location of infrastructure in urban railway networks. Comput Oper Res 36(5):1461–1477Mesa JA, Boffey BT (1996) A review of extensive facility location in networks. Eur J Oper Res 95:592–603Nayeem MA, Rahman MK, Rahman MS (2014) Transit network design by genetic algorithm with elitism. Transp Res Part C 46:30–45Nemhauser GL, Wolsey LA (1999) Integer and combinatorial optimization. Wiley, AmsterdamPerea F, Mesa JA, Laporte G (2014) Adding a new station and a road link to a road-rail network in the presence of modal competition. Transp Res Part B 68:1–16Puerto J, Ricca F, Scozzari A (2018) Extensive facility location problems on networks: an updated review. TOP 26(2):187–226Schmidt M, Schöbel A (2014) Location of speed-up subnetworks. Ann Oper Res 223(1):379–401Schöbel A (2012) Line planning in public transportation: models and methods. OR Spectr 34(3):491–510Sourirajan K, Ozsen L, Uzsoy R (2009) A genetic algorithm for a single product network design model with lead time and safety stock considerations. Eur J Oper Res 197(2):599–608Székely L, Wang H (2005) On subtrees of trees. Adv Appl Math 34:138–155Ukkusuri SV, Mathew TV, Waller ST (2007) Robust transportation network design under demand uncertainty. Comput Aided Civ Infrast Eng 22:6–1

Influence of the BaTiO3 addition to K0.5Na0.5NbO3 lead-free ceramics on the vacancy-like defect structure and dielectric properties

A study on the induced changes in the vacancy-like defect structure and the dielectric properties of K0.5Na0.5NbO3 ceramics by the addition of different amounts, between 0% and 7%, of BaTiO3 is presented. The samples were prepared by a mechanochemically activated solid-state reaction method. The structural evolution due to the orthorhombic to the tetragonal phase transition of the KNN doped samples was followed using X-ray diffraction and Raman spectroscopy. The use of positron annihilation lifetime spectroscopy allowed to identify the defect structure at sub-nanometric scale and the nature of the vacancy-like defects generated by the phase transition. The obtained results are discussed considering the lattice symmetry change and the defects structure formed due to the replacement of alkaline and niobium ions by barium and titanium ones. Additionally, changes in the dielectric properties are discussed in terms of the structural modifications of the different KNN-based ceramics involving different kinds of vacancy-like defects.Fil: Prado Espinosa, Fabiola Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Ramajo, Leandro Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Rubio Marcos, Fernando. Instituto de Cerámica y Vidrio de Madrid; EspañaFil: Macchi, Carlos Jorge. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Somoza, A.. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; ArgentinaFil: Castro, Miriam Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Light-driven motion of charged domain walls in isolated ferroelectrics

©2022 American Physical SocietyLight-induced ferroelectric domain wall motion turns out to be a promising phenomenon to de- velop new photo-controlled devices. However, the physical origin of this ligh-matter coupling when material is irradiated with visible light remains unclear. Here, a phenomenological model predicting the motion of charged domain walls (CDWs) is developed. The photo-induced electronic reconstruc- tion mechanism is proposed as the primary absorption mechanism, leading to a linear dependence for the polarization perturbation with the light intensity. Domain walls motion is then driven by the energetic difference between domains in a CDW array, such that the macroscopic polarization can be easily tuned.Postprint (author's final draft

Endothelial-specific deficiency of megalin in the brain protects mice against high-fat diet challenge

Background: The increasing risk of obesity and diabetes among other metabolic disorders are the consequence of shifts in dietary patterns with high caloric-content food intake. We previously reported that megalin regulates energy homeostasis using blood-brain barrier (BBB) endothelial megalin-deficient (EMD) mice, since these animals developed obesity and metabolic syndrome upon normal chow diet administration. Obesity in mid-life appears to be related to greater dementia risk and represents an increasing global health issue. We demonstrated that EMD phenotype induced impaired learning ability and recognition memory, neurodegeneration, neuroinflammation, reduced neurogenesis, and mitochondrial deregulation associated with higher mitochondrial mass in cortical tissue

Increased YKL-40 but Not C-Reactive Protein Levels in Patients with Alzheimer’s Disease

Neuroinflammation is a common feature in Alzheimer's (AD) and Parkinson's (PD) disease. In the last few decades, a testable hypothesis was proposed that protein-unfolding events might occur due to neuroinflammatory cascades involving alterations in the crosstalk between glial cells and neurons. Here, we tried to clarify the pattern of two of the most promising biomarkers of neuroinflammation in cerebrospinal fluid (CSF) in AD and PD. This study included cognitively unimpaired elderly patients, patients with mild cognitive impairment, patients with AD dementia, and patients with PD. CSF samples were analyzed for YKL-40 and C-reactive protein (CRP). We found that CSF YKL-40 levels were significantly increased only in dementia stages of AD. Additionally, increased YKL-40 levels were found in the cerebral orbitofrontal cortex from AD patients in agreement with augmented astrogliosis. Our study confirms that these biomarkers of neuroinflammation are differently detected in CSF from AD and PD patients