In this work, artificial neural networks (ANNs) are used to characterize the convective heat transfer rate that occurs during the evaporation of a refrigerant flowing inside tubes of very small diameter. An experimental setup based on an inverse Rankine refrigeration cycle is used to obtain the heat transfer data in an R-134a refrigerant mini-tube evaporator set operated under constant heat flux conditions. A considerable amount of data was acquired to map the thermal performance of the evaporative process under analysis, 75% of which were used for training the ANN and 25% were reserved for prediction purposes. Several neural network configurations were trained and the most accurate was selected to predict the thermal behavior. The results obtained in this investigation reveal the convenience of using ANNs as an accurate predictive tool for determination of convective heat transfer rates inside mini-tube evaporators.

Cactus prickly pear (Tuna) harvest is a complicated operation that continues in a rudimentary way, in the majority of cases manual and with the help of tools such as knives and rods which sometimes affect the fruit. In this research is analyzing the possibility of building a tool that meets the characteristics sufficient for a good harvest, one of the factors to consider is access due to the restrictive features of the cactus prickly pear (height and distribution of the joints), forcing the use of tools to achieve it (with sometimes unfavorable results). This is how arises the need to create a device that adapts to the needs and solve the problem of harvest of tuna. Field studies which were fundamental to the design, such studies were obtained measurements and tests of strength, which were carried out with instruments properly designed for the type of fruit. Generated a picker mechanism of cactus prickly pear (tunas), which according to your design could achieve a high level of harvest compared to which today has, thanks to the configuration of the mechanism and the way they get their movements lead to a suitable environment for personnel performing this activity. All Rights Reserved

Objective: To establish a local market and generate the value chain of horseradish tree (Moringa oleifera) as a food product to produce dietary supplements. Design/Methodology/Approach: We propose a strategy to introduce horseradish tree to the island of Ometepe, Nicaragua, based on the concept of value chain analysis and the characteristic of sustainability. Four analysis aspects were taken into consideration: a) production, b) sustainability, c) socioeconomic, and d) political. Likewise, requirements and barriers to the introduction of horseradish tree as a sustainable food product were identified. Results: Using synthetic fertilizers or pesticides is not recommended for the commercial production of horseradish tree leaf powder. From the polyculture farming of horseradish tree alone a $7,500-$8,000 USD yield in a 1-ha plot has been projected in the local economy for the first year and between $14,200 and $15,200 USD in the following years. Study Limitations/Implications: Although the horseradish tree contributes to an improved nutrition, the consumption of the fresh parts of this species involves a change in the food culture. Findings/Conclusions: Horseradish tree leaf powder is a viable alternative organic food and has the potential to respond to malnutrition in Ometepe, Nicaragua. It also represents a net profit between $5,050 and $5,600 USD in the first year and between $11,200 and $12,200 USD in subsequent years.

La región de Rioverde, San Luís Potosí, México, tiene 15 132 ha de riego; los suelos irrigados corresponden a Phaeozems, Vertisoles, Chernozems y Solonchaks. Durante más que 20 años, el laboratorio del Distrito de Desarrollo Rural 130 ha acumulado datos del análisis de dichos suelos; sin embargo, se carece de análisis de tal información, que permita conocer la variación de las propiedades físicas y químicas y la fertilidad de los suelos de la región, así como las repercusiones del riego en dichas propiedades. El objetivo de este estudio fue caracterizar los suelos agrícolas irrigados de dicha región, con base en la información de laboratorio existente. La información se procesó con el paquete Excel 97 para Windows 98, y se sometió a un análisis multivariable de ordenación mediante componentes principales. Los suelos se caracterizan con base en textura, materia orgánica, reacción, conductividad eléctrica, porcentaje de sodio intercambiable, fósforo y potasio asimilables. Se concluye con base en el análisis multivariable de las muestras de suelo que con sólo la determinación de los porcentajes de arena, arcilla y materia orgánica se puede conocer el estado actual de los suelos del área de estudio y las prácticas de manejo requeridas para su aprovechamiento racional.

ResumenEn la región de Rioverde la producción elote se caracteriza por el uso de cultivares tradicionales (criollos), baja densidad ajustada a la fertilidad residual del cultivo hortícola previo y bajos rendimientos de elote y grano; los costos de producción mínimos permiten rentabilidad alta en la producción de elote, pero baja en grano por su menor precio. En este trabajo se comparó el rendimiento y rentabilidad de cinco cultivares tradicionales y cuatro mejorados, utilizados para elote, sembrados en forma tradicional o intensiva. Se experimentó en dos localidades con suelo similar (Phaeozems), pero con diferente agua para riego (pozos o manantiales con aguas menos alcalinas). Se evaluaron dieciocho tratamientos resultantes de combinar nueve cultivares (parcelas menores) con dos sistemas de producción (parcelas mayores), asignados en un diseño experimental de parcelas divididas en bloques completos al azar con cinco repeticiones. En ambas localidades no hubo diferencias significativas en rendimiento de elote debidas al sistema de producción, pero el rendimiento de grano y forraje fue estadísticamente menor con el sistema tradicional. En ambas localidades y sistemas de producción al menos un cultivar mejorado superó estadísticamente a los cultivares tradicionales en rendimiento de elote y de maíz. AbstractIn the Rioverde region green corn ear (Zea mays L.) production is characterized by the use of traditional cultivars (land races), low density planting adjusted to residual fertility from previous vegetable crops, and low yields either of green ear or grain. Due to the minimum production costs for green corn ear and low selling prices for grain, profitability with green ear is higher than with grain. Profitability and yield of five traditional cultivars of corn for grain and green corn ear plus forage were compared with four improved grain cultivars sown under traditional and intensive systems. The experiments were established in lands of two villages with similar soils (Phaeozems) but using two sources of water (well and spring with less alkaline water). The 18 treatments resulting from combining nine cultivars (small plots) and two production systems (large plots), were allocated in an experimental design of split -plots in random blocks with five replicates. In both locations there were not significant differences in green corn ear yield owing to production system, but grain and green forage yield was significantly lower under the traditional system. In both production systems and locations, at last one improved cultivar exceeded statistically the traditional ones in green corn ear and grain production. IntroducciónEl elote dulce (Zea mays L.) es un cultivo comercial muy importante en muchas partes del mundo, debido a su gran demanda para los propósitos de congelación, enlatado y de mesa (Mallikarjunaswamy et al., 1999). Por lo tanto, el maíz dulce se ha clasificado generalmente como uno de los cinco cultivos más valiosas en Florida, EUA, donde se fertiliza con hasta 500 kg N ha -1 (He et al., 2009). Cuando...