Performance assessment and economic perspectives of integrated PEM fuel cell and PEM electrolyzer for electric power generation

The study presents a complete one-dimensional model to evaluate the parameters that describe the operation of a Proton Exchange Membrane (PEM) electrolyzer and PEM fuel cell. The mathematical modeling is implemented in Matlab/Simulink® software to evaluate the influence of parameters such as temperature, pressure, and overpotentials on the overall performance. The models are further merged into an integrated electrolyzer-fuel cell system for electrical power generation. The operational description of the integrated system focuses on estimating the overall efficiency as a novel indicator. Additionally, the study presents an economic assessment to evaluate the cost-effectiveness based on different economic metrics such as capital cost, electricity cost, and payback period. The parametric analysis showed that as the temperature rises from 30 to 70 °C in both devices, the efficiency is improved between 5-20%. In contrast, pressure differences feature less relevance on the overall performance. Ohmic and activation overpotentials are highlighted for the highest impact on the generated and required voltage. Overall, the current density exhibited an inverse relation with the efficiency of both devices. The economic evaluation revealed that the integrated system can operate at variable load conditions while maintaining an electricity cost between 0.3-0.45 $/kWh. Also, the capital cost can be reduced up to 25% while operating at a low current density and maximum temperature. The payback period varies between 6-10 years for an operational temperature of 70 °C, which reinforces the viability of the system. Overall, hydrogen-powered systems stand as a promising technology to overcome energy transition as they provide robust operation from both energetic and economic viewpoints

Ensamble de batoideos costeros en el norte del Perú: Conocimiento preliminar: Assemblage of coastal batoids in northern Peru: Preliminary knowledge

Abstract.- This preliminarily study aims at increasing our understanding of an assemblage of coastal batoids on the northern coast of Peru by determining species composition, body size structure and its behaviour in marine-coastal zone of Los Órganos, Piura Region, Peru. During 20 field trips, between the years 2016, 2017, and 2019, eighty-six individuals were sampled belonging to eight species: Zapteryx xyster (n= 22), Narcine entemedor (n= 11), Urobatis tumbesensis (n= 7), Urotrygon chilensis (n= 40), Pseudobatos planiceps (n= 1), Urobatis halleri (n= 1), Gymnura crebripunctata (n= 2), Aetobatus laticeps (n= 2). In the study area, a predominance of adult females was observed for Z. xyster, N. entemedor and U. chilensis. These preliminary results suggest that during the morning some batoid species (i.e., Z. xyster, N. entemedor, U. chilensis) use the coastal zone to rest since they are found inactive and partially or totally buried in the sand - N. entemedor could be also hunting through ambush. Future studies should determine if this is a gestation area for some of these batoid species

Caracterización de condiciones de trabajo y efectos sobre la salud de vendedores ambulantes

Identificar cuáles son las enfermedades más frecuentes derivadas de las condiciones de trabajo de los vendedores ambulantesEn el presente trabajo de investigación se describirán las condiciones de trabajo y los efectos de estas sobre la salud de las personas que se desempeñan como vendedores ambulantes. El objetivo es analizar cuáles son las enfermedades que más inciden en su salud derivadas de la práctica de su oficio, así como también los posibles riesgos y peligros a los que se exponen las personas que se desempeñan en este gremio, estableciendo puntos de referencia, que nos permitan entender cuáles son realmente sus condiciones laborales; a partir de ellas sugerir recomendaciones, protocolos y prácticas de autocuidado con la intención de prevenir de peligros, y malas prácticas que puedan afectar su calidad de vida. Por otro lado, se plantea la identificación y valoración del peligro, la descripción de las condiciones de salud prevalentes entre este gremio, mediante una investigación de tipo monografía. Lo anterior se realiza a partir de la revisión bibliográfica existente de autores que han realizado investigaciones acerca de las condiciones de trabajo, riesgos asociados, y enfermedades más recurrentes en este gremio; por medio de esta, se podrá clasificar los peligros y establecer medidas de contro

Estratégia de ambientes de trabalho saudáveis no setor informal: perspectiva dos atores envolvidos

Objective: This research examines the perspective of informal workers and occupational health and safety technicians on implementing the strategy for healthy workplaces in informal work units (UTI, for its abbreviation in Spanish) of the Usaquen district (Bogota, Colombia). Method: A descriptive study in 16 UTIs using qualitative tools. Direct observation was conducted in 16 UTIs, and 17 workers (men and women) were surveyed on knowledge, attitudes, and practices. Semistructured interviews were conducted with two occupational health and safety technicians. Results: The workers who have been part of the strategy demonstrate adequate knowledge of the occupational hazards. This fact has led to take some positive preventive measures in the UTIs (e.g., order, signposting). However, most knowledge about risks and their prevention is not shown during workers’ practices. The participants identified workers’ time availability and the program’s short duration as the main barriers to implementing the strategy. Discussion and Conclusions: From the participants’ perspective, the strategy for healthy workplaces has had some benefits. However, it is important to overcome the identified barriers. These types of strategies require continuity so that the training is translated into health benefits for workers. The activities perceived as the most effective are those articulated with the legal regulations of UTIs. This research contributes to the scientific literature on informal workers’ occupational health and the few qualitative studies on occupational health and safety.Objetivo: esta investigación buscó examinar la perspectiva de trabajadores informales y tecnólogos de salud ocupacional sobre la implementación de la estrategia de entornos de trabajo saludables en las unidades de trabajo informal (UTI) de la localidad de Usaquén (Bogotá, Colombia). Método: estudio descriptivo en 16 UTI utilizando herramientas cualitativas. Se hizo observación directa en 16 UTI y encuestas de conocimientos, actitudes y prácticas a 17 trabajadores (hombres y mujeres). Se hicieron entrevistas semiestructuradas a dos tecnólogos en salud ocupacional. Resultados: los trabajadores que han sido parte de la estrategia tienen un conocimiento satisfactorio de los riesgos ocupacionales. Esto ha llevado a algunas medidas positivas de prevención en las UTI (p. ej. orden, señalización). Sin embargo, la mayoría de conocimientos sobre los riesgos y su prevención no se manifiestan en prácticas de los trabajadores. Los participantes identificaron como principales barreras para la implementación de la estrategia el tiempo disponible por parte de los trabajadores y la corta duración del programa. Discusión y Conclusiones: desde la perspectiva de los participantes, la estrategia de entornos de trabajo saludables ha presentado algunos beneficios. Sin embargo, es importante que las barreras identificadas sean superadas. Este tipo de estrategias requieren de continuidad para que la capacitación se manifieste en beneficios de salud para los trabajadores. Las actividades que fueron percibidas como las más efectivas son aquellas que están articuladas con requerimientos legales de las UTI. Esta investigación aporta a la literatura científica sobre la salud ocupacional en trabajadores informales y a los pocos estudios cualitativos en salud ocupacional.Objetivo: Buscou-se examinar a perspectiva de trabalhadores informais e tecnólogos em saúde ocupacional sobre a implementação da estratégia de ambientes de trabalho saudáveis ​​nas unidades informais de trabalho (UIT) do município de Usaquén (Bogotá, Colômbia). Método: estudo descritivo em 16 UITs por meio de ferramentas qualitativas. Foi realizada observação direta em 16 UITs e enquetes de conhecimentos, atitudes e práticas a 17 trabalhadores (homens e mulheres). Além disso, realizaram-se entrevistas semiestruturadas com dois tecnólogos em saúde do trabalhador. Resultados: os trabalhadores que têm sido parte da estratégia possuem um conhecimento satisfatório dos riscos ocupacionais. Isso tem levado a algumas medidas preventivas positivas nas UITs (por exemplo, ordem, sinalização). Porém, grande parte do conhecimento sobre os riscos e sua prevenção não se manifesta nas práticas dos trabalhadores. Os participantes identificaram como principais entraves à implementação da estratégia o tempo disponível por parte dos trabalhadores e a curta duração do programa. Discussão e conclusões: na perspectiva dos participantes, a estratégia de ambiente de trabalho saudável apresentou alguns benefícios. No entanto, é importante que as barreiras identificadas sejam superadas. Esses tipos de estratégias requerem continuidade para que a formação se manifeste em benefícios à saúde dos trabalhadores. As atividades que foram percebidas como mais eficazes são aquelas que são articuladas com as exigências legais das UITs. Esta pesquisa contribui para a produção científica sobre saúde ocupacional em trabalhadores informais e aos poucos estudos qualitativos na área de saúde ocupacional

Diversity of the egg tertiary membranes in some elasmobranch species and comments on the actual yolk-sac viviparous reproductive mode: Diversidad de las membranas terciarias en algunas especies de elasmobranquios y comentarios sobre el modo reproductivo vivíparo saco-vitelino actual

After fertilization, elasmobranch eggs (mostly megalecithal) are encapsulated in a tertiary membrane of different complexity, in the oviducal gland. The gross morphological characteristics of this membrane in elasmobranchs are highly variable, attaining it most sophisticates’ forms within the oviparous species. The purpose of this study was to contribute to the knowledge of the elasmobranch tertiary membranes, in both viviparous and oviparous species, and to discuss the relation with their role in protecting the embryos their development. In addition, the limitations of yolk-sac viviparity as a single reproductive mode category are commented, suggesting a new arrangement of taxa within that reproductive mode and new terminology. Data on tertiary membranes in elasmobranchs come from a large number of sources ranging from 1977 to date. Specimens were captured on board of commercial and scientific research cruises, from the following some major geographic regions: South Western Atlantic, South Western Pacific, and different areas of the Mediterranean Sea. In all, our records of tertiary membranes belong to ten species of sharks of five orders; Hexanchiformes, Squatiniformes, Heterodontiformes, Lamniformes, Carcharhiniformes, and eight species of rays and skates, of four orders: Rajiformes, Rhinopristiformes, Torpediniformes and Myliobatiformes. The reproductive modes reported for all this species were both lecithotrophic (yolk-sac viviparity, short single oviparity) and matrotrophic (ovotrophy, placentotrophy, limited and lipidic histotrophy). Six morphological and structural major patterns were detected within the yolk-sac viviparous species (type I to VI); a thin, diaphanous, shapeless membrane; candle capsules; oviparous-like tough egg capsule, and cases where no tertiary membrane was present

Copper catalyzed sun fuel generation by CO2 and H2O reduction

Heterogeneous copper-based catalysts have been investigated for the photocatalytic H2O and CO2 reduction. Ex situ and in situ synthesized catalysts supported on inert silica have been developed for the photocatalytic proton reduction. The best supported photocatalyst achieved a significantly higher activity compared to the initial homogeneous precursor. In a second project highly porous photocatalysts have been synthesized, applied in aqueous CO2 reduction and characterized by in situ XAS, EPR and UV-vis measurements. An improved catalytic performance was observed by the addition of oxygen

La imprenta en México : epítome : (1539-1810)

ctb20

Boletín 2607 de registros. Del 29 de Marzo al 04 de Abril de 2003

Servicios registralesCONTENIDORegistros público