Input-absorptive high-order wideband balun bandpass filters with quasi-elliptic-type response

2022 52th European Microwave Conference (EuMC), 27-29 September 2022, Milan, Italy.A class of input-reflectionless high-order wideband balun bandpass filters (BPFs) with quasi-elliptic-type response are reported. They consist of two main circuit parts: 1) a three-port reflective-type high-order balun BPF network and 2) a resistivelyterminated microstrip T-junction that is shunt connected at the unbalanced port. The reflective-type balun BPFs developed with 5th- and 6th-order Chebyshev equal-ripple responses are firstly described. By replacing the last two virtually-short-circuit-ended quarter-wavelength transmission-line (TL) stubs with opencircuit-ended half-wavelength TL stubs, their balun counterparts with two close-to-passband transmission zeros (TZs) are then presented. As design example, a 5th-order input-reflectionless quasi-elliptic-type wideband balun BPF is theoretically discussed. Furthermore, for experimental-validation purposes, a proof-ofconcept two-layer microstrip prototype of 5th-order balun BPF is simulated and tested. Its measured metrics are 2.05-GHz center frequency, 3-dB fractional bandwidth of 63.61% for the two output ports, input-power-matching levels higher than 10 dB, and stopband-power-rejection levels above 26.1 dB from DC to 5 GHz.European CommissionAgencia Estatal de Investigació

Multilayered balanced wideband bandpass filter with high filtering selectivity

2021 IEEE MTT-S International Microwave Filter Workshop (IMFW), 17-19 Nov. 2021, Peruggia, Italy.A type of multilayered balanced wideband bandpass filter (BPF) with high filtering selectivity is presented. It is composed of two back-to-back cascaded microstrip-tomicrostrip vertical transitions using slotline stepped-impedance resonators (SIRs). Under differential-mode excitation, a sharprejection fifth-order wideband filtering transfer function with two paired close-to-passband transmission zeros can be attained in the proposed balanced BPF. Moreover, high common-mode suppression levels within the differential-mode passband range are achieved. For experimental-demonstration purposes, a microstrip prototype of the devised balanced wideband BPF architecture is developed and tested. It exhibits a measured differential-mode fifth-order high-selectivity wideband filtering response with center frequency of 4.015 GHz, 3-dB fractional bandwidth of 38.06%, and minimum in-band power-insertionloss level of 0.947 dB. The common-mode suppression levels are above 20 dB from 2.075 to 5.588 GHz.European CommissionAgencia Estatal de Investigació

Two-layered microstrip diplexer based on high-selectivity wideband bandpass filters

2022 IEEE Radio and Wireless Symposium (RWS), 16-19 Jan. 2022, Las Vegas, NV, USA.This paper presents a microstrip diplexer based on two high-selectivity wideband bandpass filters (BPFs) in a twolayered structure. Both the lower and upper channels are designed with third-order microstrip-to-microstrip vertical transitions using open-circuit-ended slotline stepped-impedance resonators (SIRs). Specifically, open-circuit-ended microstrip lines on the top and bottom layers for the lower channel are employed, whereas the upper channel is equipped with short-circuit-ended ones. Thus, owing to the slotline SIRs, two close-to-passband transmission zeros (TZs) leading to sharp-rejection capabilities for both BPF channels are attained. The theoretical foundations and RF operating principles of the devised diplexer are discussed in detail. For practical-validation purposes, a two-layered microstrip wideband diplexer prototype is designed, simulated, and tested. It features two three-pole high-selectivity filtering responses for the measured lower and upper channels that are centered at 1.52 GHz and 2.76 GHz, and exhibit 3-dB fractional bandwidths of 60% and 24.93%, respectively.European CommissionAgencia Estatal de Investigació

Estudio de la relación entre la Radiación Ultravioleta-B ambiental y diagnósticos de cáncer de piel entre 1990 y 2010, así como los principales factores de riesgo de exposición actual a dicho agente en agricultores de las zonas altas de Cartago.

Proyecto de Graduación (Bachillerato en Ingeniería en Seguridad Laboral e Higiene Ambiental) Instituto Tecnológico de Costa Rica. Escuela de Seguridad Laboral e Higiene Ambiental, 2014.La radiación ultravioleta (RUV) ha incrementado por los cambios medioambientales de los últimos siglos; sobre todo al fenómeno de cambio climático el cual incluye el proceso de efecto invernadero. La RUV-B es la RUV biológicamente más perjudicial para la piel (cáncer de piel) y ojos (cataratas), produce quemaduras solares y otros efectos biológicos como; envejecimiento prematuro y supresión del sistema inmunológico. En Costa Rica el cáncer de piel es una de las enfermedades que ha ido tomando avance sobre la salud de los costarricenses. El presente estudio pretende describir de forma general la relación entre la RUV-B ambiental y los diagnósticos de cáncer de piel entre 1990 y 2010, así como los principales factores de riesgo de exposición actual a dicho agente en agricultores de las zonas altas de Cartago. Para ello se realizó un estudio descriptivo que incluyó una correlación entre diagnósticos de cáncer de piel y la RUV-B, datos suministrados por instituciones gubernamentales. Se realizaron entrevistas y observaciones de los factores ocupacionales de riesgo por exposición a los rayos del sol en agricultores de Pacayas, Tierra Blanca y Llano Grande. Como principales resultados se demostró que los diagnósticos de cáncer de piel aumentan mientras que la RUV-B presenta comportamientos heterogéneos, además se mostró que no se correlacionan a través de los años; así mismo se encontró que la población agrícola actual se caracteriza por tener noción de los efectos de RUV, más no utilizan mecanismos eficientes para protegerse contra el sol, además, presentan tiempos prolongados de exposición que aumentan el riesgo de desarrollar cáncer de piel. Por lo tanto, el estudio muestra valores de RUV poco constantes (sin tendencia homogénea y constante a crecer o decrecer), y diagnósticos de cáncer de piel mayores en la segunda década; no se encontró correlación positiva entre estas dos variables. Por otra parte, los valores de RUV encontrados son elevados en comparación con estudios similares y que las condiciones actuales de exposición a RUV aumentan el riesgo de desarrollar cáncer de piel por la exposición acumulada a RUV-B y las malas prácticas de protección.Instituto Tecnológico de Costa Rica. Escuela de Seguridad Laboral e Higiene Ambiental

Synthesis and reactivity of new mixed dicyclopentadienyl Group 4 metal complexes with the doubly bridged bis(dimethylsilanediyl)-cyclopentadiene-(η5-cyclopentadienyl) ligand

The monocyclopentadienyl titanium complex [Ti{(C5H4)(SiMe2)2(η5-C5H3)} Cl3] 3 and the dichloro mixed dicyclopentadienyl Group 4 metal complexes [M(η5-C5R5){(C5H4)(SiMe2)2(η5-C5H3)} Cl2] (R=H; M=Ti 4, Zr 5, Hf 6; R=Me; M=Ti 7) containing the doubly bridged bis(dimethylsilanediyl)-cyclopentadiene-(η5-cyclopentadienyl) ligand were prepared in high yields by reaction of the monolithium salt Li[(C5H4)(SiMe2)2(C5H3)] 2 with equimolar amounts of TiCl4 or the monocyclopentadienyl complexes [Cp′MCl3], respectively. Reactions of the chloro complexes with various alkylating agents afforded the chloroalkyl [M(η5-C5H5){(C5H4)(SiMe2)2(η5-C5H3)}ClR] (M=Ti; R=Me 8, Et 9; M=Zr, R=Me 10, Et 11, CH2Ph 12; M=Hf, R=CH2Ph 13) and dialkyl [M(η5-C5R5){(C5H4)(SiMe2)2(η5-C5H3)}Me2] (M=Ti; R=H 14, Me 15; M=Zr; R=H 16, compounds. Formation of the heterodinuclear complex [Zr(η5-C5H5)Cl2(η5-C5H3)(SiMe2)2(η5-C5H3)Ti(NMe2)3] 17 with amine elimination was observed by 1H-NMR spectroscopy when complex 5 was reacted with Ti(NMe2)4. The catalytic activity of compounds 3–5 for ethylene polymerization has been studied using MAO as cocatalyst

Improvement of sol-gel prepared tungsten trioxide photoanodes upon doping with ytterbium

The development of efficient and stable photoelectrodes keeps on being critical in the implementation of practical water splitting devices. Sol-gel synthesized tungsten trioxide thin film electrodes modified with ytterbium have been prepared on conducting glass substrates. All the obtained electrodes were found to be composed of monoclinic WO3, which is the photoactive crystal phase of WO3 for water oxidation. The photoelectrochemical behavior of both WO3 and WO3:Yb nanostructured electrodes in 0.1 M HClO4 is apparently characterized by a low degree of recombination. Ytterbium addition to tungsten trioxide improves its photoelectrochemical response as larger photocurrents are obtained without a significant change of the onset potential. This behavior is attributed primarily to a surface effect rather than to bulk doping. The addition of H2O2 to the aqueous electrolyte gives rise to both an increment in photocurrent and a shift of the photocurrent onset potential toward less positive values, which can be linked to the fact that hydrogen peroxide acts as an efficient hole scavenger. The implications of these findings in the mechanism of water photooxidation on WO3 are discussed.Financial support of the Spanish Ministry of Economy and Competitiveness through project MAT2015-71727-R (FONDOS-FEDER) is gratefully acknowledged. A. K. D.-G. thanks the Mexican government (CONACyT) for the award of a doctoral grant

Segregation-induced grain boundary electrical potential in ionic oxide materials: A first principles model

A first principles continuum analytical model for cationic segregation to the grain boundaries in complex ceramic oxides is presented. The model permits one to determine the electric charge density and the segregation-induced electric potential profiles through the grain and can be extrapolated to the range of nanostructured grain sizes. The theoretical predictions are compared with existing data for yttria-stabilized tetragonal zirconia polycrystals. The implications for physical properties (mainly high temperature plasticity and hardening behaviour) are then discussed.Gobierno de España MAT2009-14351-C02-01, MAT2009-14351-C02-0

High-order input-reflectionless quasi-elliptic-type wideband bandpass filter using dual-mode slotline resonator

2022 Asia-Pacific Microwave Conference (APMC), 29 November to 02 December 2022, Yokohama, Japan.A high-order input-reflectionless quasi-elliptic-type wideband bandpass filter (BPF) that exploits a complementary-diplexer-based topology is reported. Firstly, a fourth-order wideband microstrip-to-microstrip vertical transition employing a dual-mode slotline resonator as the reflective-type BPF channel is designed. It features a sharp-rejection BPF response with two close-to-passband transmission zeros (TZs). To attain broadband input-reflectionless behavior, a shunt resistively-terminated microstrip π-shape network is used as the absorptive bandstop-filter (BSF) channel. The RF theoretical operational principle of the conceived broadband BPF is detailed. Compared to prior-art high-order input-/two-port-reflectionless wideband BPFs, the proposed BPF features not only improved passband flatness at the passband edges, but also relatively-high stopband power-attenuation levels and power-absorption ratios. For experimental-validation purposes, a two-layer fourth-order BPF microstrip prototype centered at 1 GHz is developed and tested.European CommissionAgencia Estatal de Investigació

Quais são os fatores que influenciam a utilização das redes sociais como meio para servir a pedagogia?

Social networks are a key element in young people's and teenagers' leisure time. But their influence goes beyond the field of entertainment further reaching educational and training environments. These tools can support and improve student learning, but it is clear that they can also be an inconvenience or a potential danger for the youth. The purpose of this research is to describe the profiles of teachers who use social networks as resources for their teaching, both inside and outside the classroom. It also seeks to know the characteristics that influence their incorporation as learning elements. For this reason, a secondary exploitation of the PISA 2018 database is carried out. It contains the data of 21, 621 teachers of the secondary education level from the 19 regions of Spain. Multilevel analysis is used as a method of data analysis. The results point out differences in use according to the Autonomous Communities, showing the importance of the age of the teacher and the number of years of experience, both for their use in the classroom and to cover their training needs. Quality teaching requires a commitment to technological resources; therefore, decisive to know these elements in order to design teachers and educational institutions.As redes sociais são um elemento-chave nos tempos livres dos jovens e dos adolescentes. Mas a sua influência vai para além do campo do entretenimento, atingindo o ambiente educativo e de formação. Essas ferramentas podem apoiar e melhorar a aprendizagem dos estudantes, mas é evidente que também podem ser um incômodo ou um perigo potencial para os jovens. O objetivo desta investigação é descrever os perfis dos professores que utilizam as redes sociais como recursos para o seu ensino, tanto dentro como fora da sala de aula. Procura também conhecer as características que influenciam a sua incorporação como elementos de aprendizagem. Por esta razão, é realizada uma exploração secundária da base de dados PISA 2018. Ela contém os dados de 21.621 professores do ensino secundário das 19 regiões de Espanha. A análise multinível é utilizada como um método de análise de dados. Os resultados apontam para diferenças de utilização de acordo com as Comunidades Autônomas, mostrando a importância da idade do professor e o número de anos de experiência, tanto para a sua utilização na sala de aula como para cobrir as suas necessidades de formação. Um ensino de qualidade requer um compromisso com os recursos tecnológicos; por conseguinte, é decisivo conhecer esses elementos para planear professores e instituições de ensin