Some rare‐earth‐doped alkaline‐earth cerates (e.g., Nd2O3‐doped BaCeO3) are proton conductors that can act as solid state electrolytes in hydrogen or steam sensors, hydrogen pumps, steam electrolyzers, and fuel cells. In the present study, dense tapes of neodymia‐doped barium cerate were produced by the oxidation of malleable Ba‐CeH3‐Nd2O3precursor tapes. Precursor tapes were produced by cold‐rolling either blended or milled mixtures of Ba, CeH3, and Nd2O3 within a silver can. X‐ray diffraction, electron microprobe analyses, and thermogravimetric analyses were used to study the phase transformations resulting from heat treatments conducted at 300° to 900°C in pure, flowing oxygen. Barium peroxide and cerium dioxide, produced during oxidation at ≤300°C, reacted at ≤500°C to form barium cerate. The rate of formation of barium cerate depended on the degree of milling of the solid metal‐bearing precursor powder. Dense barium cerate tapes were obtained after heat treatment at 1080°C.
El proceso de producción de banano en El Cantón Milagro, Provincia del Guayas, Ecuador; es un proceso que presenta oportunidades de mejora desde el punto de vista gerencial. Por medio de la aplicación de un instrumento de recolección de información se buscó explicar mediante indicadores cualitativos los nudos críticos que se generan en el proceso productivo de 180 pequeños productores de la zona. En el análisis se identificó la recurrencia de los factores y la influencia de estos en los procesos gerenciales, lo que genera que la gestión económica de la zona se ralentice, y pierda competitividad y eficiencia. Entre los hallazgos se encontró que los nudos críticos más relevantes para la zona de estudio son: bajos niveles de planificación por parte de los productores, bajos niveles en la utilización de registros de control, bajos niveles en la productividad de la zona y el uso no controlado de agroquímicos en los cultivos. Como recomendaciones resultantes del análisis, se concluye que para la mejora de estos nudos se pueden incorporar acciones como: la planificación periódica de las actividades, la identificación de las necesidades del proceso, la revisión permanente de dificultades, la unificación de los criterios agronómicos de control para la minimización del impacto ambiental y el diseño e implementación de programas de asistencia técnica para la producción.
El plátano es un cultivo de gran importancia para el desarrollo social de muchas regiones, pero se requiere un cambio, orientando hacia la protección ambiental, utilizando diferentes alternativas naturales. De esta manera, el objetivo de la investigación fue: evaluar alternativas ecológicas para el control de Sigatoka negra (Mycosphaerella fijiensis Morelet) en el cultivo de plátano (Musa AAB) en la zona del sur del Lago de Maracaibo. Los tratamientos fueron: T1: testigo sin ningún tipo de aplicación de producto; T2: lixiviado de raquis de plátano; T3: vermicompost; T4: sulfa-Ca-Mg (caldo sulfocálcico); T5: dióxido de cloro (BioAus) y T6: Propizole 250 CE. Los datos fueron analizados utilizando la metodología de medidas repetidas a fin de evaluar las variables en estudio a través del tiempo, ajustando un modelo polinómico de segundo grado. Es viable la utilización de productos de origen biológico como alternativa ecológica para el manejo de M. fijiensis en plantaciones de plátano, a fin de disminuir el impacto negativo de los agroquímicos. Con aplicaciones semanales de alguna de las alternativas ecológicas, se podría mantener la hoja número tres como la más joven que presentó la enfermedad y grado tres o cuatro de incidencia de la misma.
INTRODUCTIONThe technical viability of advanced power plants will be critically dependent on the availability of suitable materials. Higher efficiencies can be achieved only by operating at temperatures that will exceed the capabilities of many of the conventional alloys. It is expected that maximum waterwall temperatures in high efficiency units will approach 600 to 625°C, with superheater and reheater outlet temperatures expected to go as high as 750°C. Similar or higher temperatures are expected for piping and headers. These higher operating temperatures may severely limit the serviceable lives of critical operating components due to an increase in the kinetics of oxidation/ corrosion mechanisms. Controls on emissions imposed by government regulatory agencies in the USA promoted the development of various strategies for lowering these emissions through changes in the way the fossil fuel was burned in a boiler. Staged coal firing provided a viable technology to meet stringent requirements on NO x emissions. However, it was found that during staged firing the substoichiometric firing conditions generate relatively high concentrations of total reduced sulfur species (TRS), unburned carbon, and pyrite particulate at the boiler waterwalls. Reduced sulfur species and reducing microclimates then are conducive to accelerated waterwall wastage by various sulfidation mechanisms.Higher operating waterwall temperatures will lead to accelerated scaling on the unprotected ID surface of waterwall tubing. This build-up of oxide will restrict heat transfer, and may, if metal temperatures are high enough, cause local overheating of the tube wall and premature failure. The consequent reduction in boiler availability will jeopardize the economic benefits of the higher efficiency plants. In addition, when the oxide reaches a critical thickness it will exfoliate from the surface of the tube, become entrained in the steam, and enter the turbine, where the high velocity impact of the oxide particles on critical turbine components can lead to significant losses in turbine efficiency. Although alternative materials with higher creep strength are being developed for these applications, the available data suggests that in many cases their oxidation behavior in steam is not satisfactory.Radical changes in the way the fuel is burned in the furnace of present-day steam generator have led to variations in the traditional wastage mechanisms, such as coal-ash corrosion. Standard high-temperature alloys, such as grades 304H or 310H, have been subjected to the effects of high-temperature carburization. Although the number of reported failures related to carburization to date has been small, the frequency of occurrence clearly is increasing, and the phenomenon has been acknowledged officially in a recent study of coal-ash corrosion [1].The purpose of the present report is to review recent test data that has served as the basis for the understanding of the major modes of degradation that affect current and future coal-fired power plants. Recommend...
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