1,720,999 research outputs found
Shading Screens Characterization by Means of Wind Tunnel Experiments and CFD Modeling
No full textThe use of shading screens in the protected cultivation sector is widespread, due to the fact they allow both to reduce the heat load and thus to control temperature, and to have lower and uniform levels of light intensity inside greenhouses. An extended selection of shading screens is available on the market, with different colors, material, and textures. The choice of the best screen depends on the specific application and needs of the grower. Despite the positive action of the screens, some screens can also negatively affect ventilation and indoor climate, since their porosity can generate extra mass, heat and momentum transfer resistance. Most studies have evaluated the screen-related parameters, such as permeability and porosity, and the screen effect on ventilation referring to screens with simple and regular textures, which is not the case of the new screen types. The reliability of the literature models for these parameters’ estimation of new type of screens is not certain. In this work, these parameters have been evaluated for three new screen types, available on the market, under different approaches. An experimental approach based on image analysis together with wind tunnel tests has been set up to yield the permeability and inertial coefficient. On the other hand, another methodology is based on the detailed modeling of the shading screen and on the CFD simulation to obtain the relation between air velocity through a screen and the relative pressure drop, avoiding any experiment. A representative section of the screen has been chosen for CFD simulations and the numerical results have been validated by comparison with Particle Image Velocimetry (PIV) data. This has allowed both to improve the model and to evaluate its effectiveness in simulating this specific fluid dynamics domain. By these novel approaches, the basis for extending the knowledge about the characterization of the screens used in agriculture have been laid
Assessment of geometrical and seasonal effects on the natural ventilation of a pig barn using CFD simulations
Full text linkAirflow in naturally ventilated barns usually presents high variability with time and it is rather difficult to estimate because of the presence and interaction of the animals. On the other hand, appropriate ventilation is an essential requirement to ensure animal welfare and efficient and sustainable production. In this regard, the computational fluid dynamic simulations represent a powerful and useful tool and, in this paper, CFD simulations are used to investigate and assess the geometrical and seasonal effects on the natural ventilation of an existing pig barn sited in the northern Italy and composed of six wings converging on a central body. First, the effects of the complex barn geometry on the ventilation parameters have been investigated by outdoor simulations with eight wind scenarios on a closed envelope building model. From these analyses, both the interaction among the different wings and the influence of the surrounding buildings, have been carefully evaluated and a dimensionless parameter, called ventilation rate ratio, has been proposed and applied to the case study barn to assess the effects of the building geometry on the ventilation efficiency. Then, starting from the statistical analysis of the free-field ventilation at the site, seven additional wind scenarios have been analysed on a different model of the barn, to evaluate the efficiency of indoor natural ventilation during summer and winter seasons, when the most extreme conditions for animal welfare take place. The ventilation resulted very different during the years from season to season, but also presented valuable differences in the same season, from wing to wing. The outcomes of the paper provide useful indications on the present conditions of the structure and they could be used as decision-making information for the management of the livestock building to identify the most favourable pens for the different finishing pig groups at different fattening stages but also for the planning of the most suitable ventilation retrofitting interventions
Turning agricultural wastes into biomaterials: Assessing the sustainability of scenarios of circular valorization of corn cob in a life-cycle perspective
Full text linkCircular economy plays a key role in increasing the sustainability of the agricultural sector, given the countless possibilities of transforming crop residues and recycling precious resources. The maize cultivation process produces a significant amount of residual organic materials, commonly left on the field, as a soil conditioner and source of nutrients even if some parts, such as the cob, play a minor role in these actions. The solutions for the valorization of this remnant depend on economic and environmental factors and the evaluation of the environmental performances of the processes in a life-cycle perspective is important to compare the overall sustainability of the valorization alternatives, maximizing their environmental added value. This work reports the results of Life Cycle Analysis, from cradle-to-gate of corn cob valorized as a raw material in two scenarios: corn cob pellet and corn cob abrasive grits to use as blasting or finishing media. A comparative study has been performed with two products available on the market and with the same functions. The results show that cob-based products have lower impact than those currently used. The work provides indication for evaluating the benefits of turning agricultural wastes in natural-based materials and intends to promote circular economy processes in agriculture production
Masquelet technique to treat a septic nonunion after nailing of a femoral open fracture
No full textSeptic nonunion is one of the most serious complications after an open fracture because both the infection and the bone defect need to be dealt with. Treatment is always protracted and expensive, and the result is uncertain. In the 1980s, Masquelet first described the technique of the induced membrane and autologous bone grafting to manage critical size bone defects. In septic nonunions, the described approach, characterised by two different surgical steps, allows a radical approach to manage the infection, and gives a significant biological stimulus to bone healing. In this case, we present a 35-year-old male patient with an open grade II femoral shaft fracture (AO / OTA 32C3). The patient was initially treated with an intramedullary nail and the resulting septic nonunion was subsequently managed with the induced membrane technique and a double-plate osteosynthesis to protect the biological chamber
Numerical simulations for the optimisation of ventilation system designed for wine cellars
No full textThe wine-ageing process is one of the most important phases of the wine production and it can be considerably affected by the micro-climatic conditions inside the ageing rooms. Underground wine cellars in small-medium wineries are designed with natural ventilation systems, able to maintain optimal indoor condition. However, critical factors emerge, such as mold growth or wine evapo-transpiration, where ventilation proved to be poorly designed, insufficient in the first case or excessive in the second one. The zones around the wooden barrels proved to be the most sensitive and problematic. These areas are the most investigated in terms of temperature and humidity values but surprisingly not in terms of air velocity. In this paper, a ventilation system has been designed and optimised to support the lack of ventilation, by means of computational fluid dynamics modelling. Eight configurations have been performed and analysed, identifying the best two according to the air velocity range. Specific parameters have been defined to appreciate the application limits of each configuration. These parameters can be used as reference for system design in similar studies and applications and can help scholars and professionals to identify the optimal configurations for the implementation and proper placement of the system inside a cellar
Environmental assessment of design choices of green walls based for materials combination and plants
Full text linkPurpose: Green infrastructures have been considered as a sustainable solution to deal with the problems in dense urban spaces. This acceptance has led to the use of various materials and methods in designing and producing green infrastructures. The purpose of this study is to emphasize the components and materials used in the green walls system. By determining the environmental impact of each element, it can be replaced with another component with the same function. This approach ultimately leads to the sustainable design of systems. Methods: Accordingly, two green wall systems were selected for the environmental assessment using the life cycle assessment method. Data related to all processes and components involved in each system are reviewed for a 10-year lifespan. For each system, eight different scenarios of component composition are considered. The functional unit is 1 square meter and the ILCD method is used to evaluate the impact of the life cycle. OpenLCA software and Ecoinvent® v3.7 database are used to model and analyze all 16 scenarios. Results: The results clearly show that the components and materials used in the production and construction of the green wall system have a very high impact on the environmental performance of these systems. A better design can be achieved by doing an environmental assessment, identifying the undesirable components in the system, and replacing them. Different scenarios' results show the potential to improve the environmental performance of systems in all impact categories. This highlights the great importance of the green wall system's design, material selection and maintenance methods. Conclusions: Considering the ability of the LCA method to identify the weak and strong points of the systems, the lack of using this method in the design phase is strongly sensed. With this method's help, it is possible to produce more sustainable systems. On the other hand, the studies conducted in the field of green walls are limited compared to other green infrastructures. At the same time, the design of the green wall system can be changed based on geographical location, weather conditions, access to raw materials and consumer needs. As the number of studies on these systems increases in different places and weather conditions, it can help the stability of these systems
Damage control distrettuale nelle fratture da trauma ad alta energia della tibia prossimale: indicazioni, tecnica, complicanze e scelta del trattamento definitivo
Full text linkIntroduzione. Le problematiche dei tessuti molli sono state storicamente le più frequenti ed importanti complicanze delle fratture da trauma ad alta energia delle tibia prossimale. Il damage control della lesione mediante un fissatore esterno femoro-tibiale a ponte viene eseguito in queste fratture per stabilizzare le lesioni ossee e dei tessuti molli e per ripristinare la lunghezza e l’asse dell’arto. Alcuni autori hanno riportato i risultati di questa strategia di trattamento, con un decremento significativo delle complicanze dei tessuti molli e buoni risultati clinici e radiografici. Metodi. È stata valutata una popolazione di 24 casi di fratture da trauma da alta energia della tibia prossimale in 23 pazienti, trattati mediante applicazione di un fissatore esterno femoro-tibiale a ponte in urgenza seguito da una fissazione interna definitiva a distanza. I casi trattati con fissazione esterna definitiva sono stati esclusi, tra questi tutti i casi di frattura esposta oltre il grado IIIB di Gustilo-Anderson e i casi trattati mediante fasciotomie per sindrome compartimentale. Sono stati registrati il tipo di frattura e l’entità del danno dei tessuti molli, la configurazione del fissatore esterno temporaneo, il tempo di conversione a sintesi definitiva, i risultati clinici e radiografici e le complicanze. I dati ottenuti sono stati confrontati con quanto riportato in letteratura. Risultati. Le fratture erano prevalentemente a morfologia complessa, del tipo V e VI secondo Schatzker nel 70,8% dei casi e del tipo C3 secondo lo classificazione AO nel 63% dei casi. Nel 50% dei casi era presente un danno severo dei tessuti molli, per la presenza di esposizione del focolaio (25%) o di fratture chiuse tipo Tscherne II e III (25%). La configurazione anteriore per la fissazione esterna è stata la più utilizzata (66,7%) per la sua versatilità e rapidità di applicazione. Non sono state notate differenze tra i differenti montaggi in termini di risultato clinico e complicanze, le quali non sono state riscontrate. Il tempo di conversione a fissazione interna è stato in media di 6 giorni, utilizzando più frequentemente due placche contrapposte. I risultati clinici sono stati molto soddisfacenti, con pochi casi di viziosa consolidazione e nessuna pseudoartrosi. L’incidenza di complicanze dei tessuti molli è stata molto bassa, con un solo caso di infezione superficiale di ferita con deiscenza parziale (4,3%). Discussione. L’utilizzo di un fissatore esterno a ponte è un metodo sicuro ed efficace per diminuire l’incidenza di complicanze dei tessuti molli nelle fratture da trauma ad alta energia della tibia prossimale, mantenendo buoni risultati clinici e radiografici. Non vi sono differenze tra i diversi montaggi per la stabilizzazione a ponte della lesione se i principi di sicurezza sono rispettati e gli obiettivi di efficace stabilizzazione e ripristino di asse e lunghezza vengono perseguiti. Deve essere attentamente selezionata la tecnica di osteosintesi della frattura, riservando alla fissazione esterna definitiva i casi più compless
Assessing the environmental performance of plastic-based and felt-based green wall systems in a life-cycle perspective
Full text linkWith the remarkable growth of cities and the increase of built-up areas, mitigation of urban heat island effects has become one of the most crucial challenges in social and environmental sustainability with significant impacts on public health. This has led to an increasing development of urban green infrastructure. Among those nature-based solutions, green wall systems have been receiving a growing attention, being a passive technology with their ability to reduce greenhouse gas emissions, adapt to climate change, improve air quality and reduce the heat island effect in urban environments. Despite that growing interest in studying the functions and features of such green systems, and the various types of living walls nowadays available, most studies evaluate their energy efficiency and performance only during the use phase. This study aimed to assess the overall environmental performances of two types of green walls in a life cycle perspective, considering the embodied energy, greenhouse gas emissions, materials and energy consumption, and embodied carbon. After collecting inventory data related to all components and processes of each system, a life cycle assessment with cradle to gate approach has been performed to compare the performances of a felt-based system without organic growth medium and a system based on plastic modules with organic growth medium. The main impacts have been detected in the production stage and materials used in systems structure. By comparing the results achieved in the 16 impact categories analyzed, the felt-based system showed the highest overall impact, with the use of fertilizers and aluminum components playing a crucial part. Polypropylene used to produce the panels, water used for plant irrigation and potting soil composition are the main environmental impact contributors in the plastic-based system. The results pointed out the importance of accurate choice of materials for the design and production of green walls
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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