The physical properties and the effect of effective surface area (ESA) on the sensing properties of tin dioxide [SnO₂] thin films in air and propane [C₃H₈] atmosphere as a function of operating temperature and gas concentration have been studied in this paper. SnO₂ thin films with different estimated thicknesses (50, 100 and 200 nm) were deposited on glass substrates by the chemical spray technique. Besides, they were prepared at two different deposition temperatures (400 and 475 °C). Tin chloride [SnCl₄∙5H₂O] with 0.2 M concentration value and ethanol [C₂H₆O] were used as tin precursor and solvent, respectively. The morphological, and structural properties of the as-prepared films were analyzed by AFM and XRD, respectively. Gas sensing characteristics of SnO₂ thin solid films were measured at operating temperatures of 22, 100, 200, and 300 °C, and at propane concentration levels (0, 5, 50, 100, 200, 300, 400, and 500 ppm). ESA values were calculated for each sample. It was found that the ESA increased with the increasing thickness of the films. The results demonstrated the importance of the achieving of a large effective surface area for improving gas sensing performance. SnO₂ thin films deposited by spray chemical were chosen to study the ESA effect on gas sensing properties because their very rough surfaces were appropriate for this application.

Chromium and ruthenium-doped zinc oxide (ZnO:Cr) and (ZnO:Ru) thin solid films were deposited on soda-lime glass substrates by the sol-gel dip-coating method. A 0.6 M solution of zinc acetate dihydrate dissolved in 2-methoxyethanol and monoethanolamine was used as basic solution. Chromium (III) acetylacetonate and Ruthenium (III) trichloride were used as doping sources. The Ru incorporation and its distribution profile into the films were proved by the SIMS technique. The morphology and structure of the films were studied by SEM microscopy and X-ray diffraction measurements, respectively. The SEM images show porous surfaces covered by small grains with different grain size, depending on the doping element, and the immersions number into the doping solutions. The sensing properties of ZnO:Cr and ZnO:Ru films in a propane (C₃H₈) atmosphere, as a function of the immersions number in the doping solution, have been studied in the present work. The highest sensitivity values were obtained for films doped from five immersions, 5.8 and 900, for ZnO:Cr and ZnO:Ru films, respectively. In order to evidence the catalytic effect of the chromium (Cr) and ruthenium (Ru), the sensing characteristics of undoped ZnO films are reported as well.

This paper shows a novel design of a gas sensor system based on artificial neural networks and Floating-gate MOS Transistors (FGMOS). Two types of circuits with FGMOS transistors of minimum dimensions were designed and simulated by Simulink of Matlab; simulations and experimental measurements results were compared obtaining good expectations. The reason of using FGMOS is that ANN can also be implemented with these kinds of devices, since ANN’s based on FGMOS are able to produce pseudo Gaussian-functions. These functions give a reliable option to determine the gas concentration. A sensitive thin film can be deposited on the FGMOS’s floating gate, which produces a charge variation due to the chemical reaction between the sensitive layer and the gas species, modifying the threshold voltage thereby a correlation of drain current of the FGMOS with gas concentration can be obtained. Therefore, a generator circuit was implemented for the pseudo Gaussian signal with FGMOS. This system can be applied in environments with dangerous species such as CO2, CO, methane, propane, among others. Simulations demonstrated that the implemented proposal has a good performance as an alternative method for sensing gas concentrations, compared with conventional sensors.

La alineación de espejos segmentados es crucial en diversas aplicaciones ópticas; la implementación en el diseño arquitectónico ofrece nuevas posibilidades estéticas y funcionales. En este trabajo se emplea el interferómetro de Michelson para lograr una alineación óptima de espejos segmentados, corrigiendo la posición y orientación de cada segmento de espejo, garantizando una superficie reflectante continua y homogénea. Además, se presenta la integración del software AutoCAD para el diseño de los sistemas de soporte y alineación, así como el uso de impresión 3D para la fabricación de piezas personalizadas que aseguren una fijación precisa y estable de los espejos. Los resultados indican que la interferometría, combinada con herramientas de diseño asistido por computadora y fabricación de piezas de filamento plástico, no sólo mejora la precisión en la alineación de espejos, sino que también amplía las posibilidades creativas en el diseño interior y exterior, aportando tanto funcionalidad como estética.

En este trabajo se describe la relevancia de la conversión de señales eléctricas discretas a señales en el dominio del tiempo, en otras palabras, la conversión digital analógica. Para ello existe el convertidor digital a analógico (CDA), el cual permite la utilización de señales en modo de corriente o voltaje variantes en el tiempo, las cuales se utilizan para interactuar con el mundo real, ya que por lo general las señales analógicas son utilizadas por los actuadores, las bocinas, las antenas, etc. Los CDA constan de varios subcircuitos como las fuentes y espejos de corriente, los pares diferenciales, los arreglos R-2R y, se explican y diseñan para conformar un CDA completo, la simulación y el diseño asistido por computadora de un CDA utilizando transitores de la tecnología CMOS, fueron cruciales para este diseño.

Lithium has become a critical raw material, and research interest has expanded beyond pegmatites and brines toward unconventional sedimentary environments, although continental red-bed successions remain largely underexplored. This study presents a preliminary mineralogical and geochemical characterization of the basal interval of the Middle Jurassic Cahuasas Formation, Molango Rift System, Hidalgo, Mexico. Polarized-light microscopy, ICP–OES, XRF, XRD, Raman spectroscopy, FTIR, XPS, and SEM–EDS were combined. ICP–OES yielded a mean lithium concentration of $115.00\pm 4.58$ ppm, approximately 4.8 times the upper continental crust average of 24 ppm, but only 1.7 times the average shale concentration. XRD indicates a mineral assemblage dominated by quartz and chlorite, with diffraction matches to the reference pattern (Al_0.05Li_0.05Si_0.95O₂; PDF 96-900-2384). The Raman spectra contain a band at 707 cm⁻¹, reproduced in all analyzed spectra, consistent with a possible $\alpha$-spodumene-type contribution. FTIR, SEM–EDS, and XRF indicate a silicate–aluminosilicate matrix, while a weak XPS signal at 54.50 eV is compatible with Li 1s. The basal interval of the Cahuasas Formation is documented as hosting previously unreported lithium enrichment. These results provide preliminary evidence of a localized lithium anomaly, with diffraction matches to the reference pattern of a Li–Al-bearing phase. Given its preliminary nature, this study is limited to characterizing the anomaly and clarifying the mineralogical species present, without addressing genetic processes or economic aspects.