Aplicación de internet de las cosas (IoT) para entornos de invernadero optimizados

Esta revisión presenta la investigación más avanzada sobre sistemas IoT para entornos de invernadero optimizados. Los datos fueron analizados usando métodos descriptivos y estadísticos para inferir relaciones entre Internet de las cosas (IoT), tecnologías emergentes, agricultura de precisión, agricultura 4.0 y mejoras en la agricultura comercial. La discusión se sitúa en el contexto más amplio de IoT en la mitigación de los efectos adversos del cambio climático y el calentamiento global en la agricultura a través de la optimización de parámetros críticos como la temperatura y la humedad, la adquisición inteligente de datos, el control basado en reglas y la resolución de las barreras para la adopción comercial de sistemas IoT en la agricultura. Los recientes eventos meteorológicos severos e inesperados han contribuido a los bajos rendimientos y pérdidas agrícolas; este es un desafío que se puede resolver a través de la agricultura de precisión mediada por tecnología. Los avances tecnológicos han contribuido con el tiempo al desarrollo de sensores para la prevención de heladas, el control remoto de cultivos, la prevención de riesgos de incendio, el control preciso de nutrientes en cultivos de invernadero sin suelo, la autonomía energética mediante el uso de energía solar y la alimentación, el sombreado y la iluminación inteligentes. control para mejorar los rendimientos y reducir los costos operativos. Sin embargo, abundan los desafíos particulares, incluida la adopción limitada de tecnologías inteligentes en la agricultura comercial, el precio y la precisión de los sensores. Las barreras y los desafíos deberían ayudar a guiar futuros proyectos de investigación y desarrollo y aplicaciones comerciales

Response of Asymmetric Slim Floor Beams in Parametric-Fires

State-of-the-art slim floor systems are a newest addition to the composite construction industry and several types are currently being used for building and construction purposes. Asymmetric slim floor beams are a type of slim floor systems which consist of a rolled section with a larger bottom flange. The larger bottom flange induces asymmetry and offers an efficient use of the material strength as a composite beam. It also offers a larger area to support the steel decking and pre-cast slab units during the construction of floor. Experimental and analytical investigations on response of asymmetric slim floor beams have shown that these beams offer a higher fire resistance in comparison to the conventional composite systems with down-stand steel beams. Previous investigations on these beams have been conducted in standard fire exposure conditions, hence, their response to natural fire scenarios still deems further examination. This study addresses response of asymmetric slim floor beams in natural fire exposure conditions. For this purpose, finite element models developed and verified by the authors are employed to study the thermal and structural response of slim floor beams in fast and slow parametric-fire exposures. Results obtained show that the asymmetric slim floor beams behave differently in parametric-fires in comparison to that in standard fire exposure conditions. Asymmetric slim floor beams continued to support the loads for the whole duration of parametric fires without undergoing excessive deflections and offering a better fire resistance. Unlike in case of the standard fire where the temperatures keep on increasing throughout the duration, temperatures on the slim floor beams decrease after reaching a maximum point in parametric-fires. It was found that for fast parametric-fires, the thermal gradient across the section is more severe as compared to that for the slow parametric-fires at earlier stages of fire exposure. In case of the fast parametric-fires, the rise and fall of temperatures on the slim floor beams are rapid while in case of the slow parametric-fire, these variations in temperatures are subtle. It was observed that the structural response of slim floor beams in standard and parametric fires depends on the average temperature across the steel section. Deflections predicted for the beams were found to be directly related to these average temperatures. Outcomes of this study will benefit in understanding the response of asymmetric slim floor beams in natural fire conditions and will aid to develop simple fire design methods for future use

Effect of Air-Gap on Performance of Fabricated Slim Floor Beams in Fire

Fabricated slim floor beams are produced by welding a steel plate to the bottom flange of an I-shaped steel section. The welded steel plate makes them structurally efficient and serves as a platform to support the steel decking of composite floor and the pre-cast concrete slabs. During their fabrication, an air-gap is induced between the steel plate and the bottom flange. Previous experimental investigations have shown that this air-gap has an influence on their thermal behaviour at elevated temperatures. Though the air-gap presence has an influence on their thermal performance, no investigations have yet been conducted to analyse its effects on their structural response in fire. This research investigates the effects of air-gap on structural response of fabricated slim floor beams in fire. During this study, finite element modelling is performed to simulate the response of fabricated slim floor beams and the predicted behaviour is verified against the available test data from literature. The validated finite element model is then employed to perform parametric studies to investigate the effects of the presence and size of the air-gap on their response in fire. Results obtained show that the presence of the air-gap has a significant influence on structural response of these beams at elevated temperatures. On the other hand, the size of air-gap has no or negligible effect on their thermal behaviour as well as on their structural response in fire. It was found that the presence of the air-gap restricts temperatures on the bottom flange and helps in achieving an improved fire resistance. As the presence of the air-gap is found to be helpful and beneficial, findings from this research can be used to develop similar designs for structural members as an efficient and inexpensive way to improve their behaviour in fire

Numerical evaluation on shell buckling of empty thin-walled steel tanks under wind load according to current American and European design codes

Liquid storage steel tanks are vertical above-ground cylindrical shells and as typical thin-walled structures, they are very sensitive to buckling under wind loads, especially when they are empty or at low liquid level. Previous studies revealed discrepancies in buckling resistance of empty tanks between the design method proposed by the American Standard API 650 and the analytical formulas recommended by the European Standard EN1993-1-6 and EN1993-4-2. This study presents a comparison between the provisions of current design codes by performing all types of numerical buckling analyses recommended by Eurocodes (i.e. LBA-linear elastic bifurcation analysis, GNA-geometrically nonlinear elastic analysis of the perfect tank and GNIA-geometrically nonlinear elastic analysis of the imperfect tank). Such analyses are performed in order to evaluate the buckling resistance of two existing thin-walled steel tanks, with large diameters and variable wall thickness. In addition, a discussion is unfolded about the differences between computational and analytical methods and the conservatism that the latter method imposes. An influence study on the geometric imperfections and the boundary conditions is also conducted. Investigation on the boundary conditions at the foot of the tank highlights the sensitivity to the fixation of the vertical translational degree of freedom. Further, it is indicated that the imperfection magnitude recommended by the EN1993-1-6 is extremely unfavorable when applied to large diameter tanks. Comments and conclusions achieved could be helpful in order to evaluate the safety of the current design codes and shed more light towards the most accurate one

A NEW LIGHTWEIGHT STEEL BRIDGE FOUNDED IN PEAT Optimal Design and Soil Improvement

peer reviewedThis paper presents the planned design for a new steel road bridge in the Tenagi valley, Kavala, Greece. The plans are for a single span steel truss trough bridge with a span of 67 m over an irrigation channel. The new bridge will replace an existing reinforced concrete one that is no longer in service due to excessive rotation of its single pier and deck failure. The major challenge associated with the design of the new bridge is the poor soil characteristics in the region. The soil is composed of peat to a depth of over 200 m. Optimization of the type, shape, and size of the bridge superstructure is critical in order to minimize soil intervention. In this article, the effects of several types of deck (a reinforced concrete deck, a fiber reinforced polymer deck, and a steel deck are considered) on the weight of the steel truss are examined. Shape optimization of the truss is conducted with the truss height as a variable. Beyond minimizing the weight of the bridge, soil improvement techniques such as deep soil mixing and the preloading of embankments must also be implemented to minimize settlement and increase the bearing capacity of the soil