1,720,978 research outputs found
An approximate analytic solution to a non-linear ODE for air jet velocity decay through tree crops using piecewise linear emulations and rectangle functions
Full text linkThe velocity of air that crosses the canopy of tree crops when using orchard sprayers is a variable that aects pesticide dispersion in the environment. Therefore, having an equation to describe air velocity decay through the canopy is of interest. It was necessary to start from a more general non-linear ordinary dierential equation (ODE) obtained from the momentum theorem. After approximating the non-linearity with some piecewise linear terms, analytic solutions were found. Subsequently, to obtain a single equation for velocity decay, a combination of these solutions was proposed by using rectangle functions formed through the hyperbolic tangent function. This single equation was assessed in comparison to the experimental value obtained on a vineyard row by measuring the air velocity at exit of canopy. The results have shown good correspondence, with a mean relative error of 6.6%; moreover, there was no significant dierence. To simplify, a combination of only two linearized solutions was also proposed. Again, there was no significant dierence between the experimental value and the predicted one, but the mean relative error between the two equations was 3.6%
Durability test on an agricultural tractor engine fuelled with pure biodiesel (B100)
No full textThe performance of a 118-kW tractor fuelled by pure biodiesel was monitored during a long-term field experiment with approximately 800 h of engine function. The objective was to demonstrate that B100, a pure biodiesel fuel, is a viable alternative to traditional diesel oil in terms of long-term mechanical reliability. A bench test on the new engine, performed by attaching a test stand to the power take-off of the tractor, showed an expected reduction in power (-9%) and torque (-7%) and an increase in specific consumption (+13%) when biodiesel was used as a complete substitute to diesel oil. Furthermore, with the same setup, the exhaust gas had a Bosch smoke index equal to 50% of the value for the same engine fuelled with diesel oil. After these initial tests, the tractor was set up for normal field operations, in which both the engine curves and lubricant quality were periodically monitored. These surveys indicated no significant reduction in engine performance; however, the lubricant was consequently diluted and contaminated by biodiesel, which caused the lubricant properties to considerably worsen. However, on the basis of the chemical-physical analysis, reducing the oil change interval from 200 h (manufacturer's indications for the engine when operating with diesel oil) to 100 h would compensate for this progressive quality decline. At the end of the trials, the engine was disassembled to check the condition of its components; wear and lacquer-like coating phenomena were observed, and their levels were acceptable. The obtained results demonstrated that B100 can effectively substitute for diesel oil in a standard compression-ignition engine: the power change is not perceptible during normal operation of a tractor, and no particular problem will arise in the engine during its life if the lubricant is changed every 100 h
Exergetic analysis and exergy loss reduction in the milk pasteurization for Italian cheese production
Full text linkThe cheese industry has high energy consumption, and improvements to plant efficiency may lead to a reduction of its environmental impact. A survey on a sample of small-medium Italian cheese factories was carried out in order to assess the efficiency of heat recovery of the milk pasteurization equipment for the cheese production. Then, an exergetic analysis to calculate the related exergy loss was carried out together with a cost-benefit analysis to identify the optimized value of the heat efficiency. The exergy loss reduction was determined throughout an exergy analysis that takes into account this last value and the comparison with the previous exergy losses. Finally, the feasibility and the consequent additional reduction of exergy losses were verified, if a cogeneration heat and power (CHP) combined to the pasteurization equipment is assumed. Results show a current heat recovery efficiency of 93.2% in the Italian cheese factories; a close connection between the exergetic losses and the efficiency of the heat recovery exchanger; the optimized recovery efficiency equal to 97.3% obtained from the cost-benefit analysis; a related important exergetic loss reduction of −45% in the heat exchangers, as a second result of the exergetic analysis; a similar reduction of the exergy loss (−42%) of the whole system, as a third result of the exergetic analysis; a total exergy loss reduction of 22.9 kJ kg−1milk, which corresponds to a lower environmental impact due to CO2 reduction; a further reduction of the exergy loss of −10% when the cogeneration heat and power CHP are used
Assessment of the efficiency of tractor transmissions using acceleration tests
No full textA theoretical model that could be useful for investigating the performance of ground vehicles using acceleration tests was developed. The model takes into account all of the forces acting on a moving vehicle to give a description of its kinematics: the rolling friction of the propulsion devices, their slip on the soil, aerodynamic resistance, road slope and traction developed by the engine. In the methodology of applying the model, the experimental data collected during acceleration tests on a flat and sloping road from a standing start to reach a given distance or a stated speed are used to determine the average efficiency of the transmission of three tractors with different equipment (a mechanical full-powershift drive and two different hydro-mechanical continuously-variable ratio transmissions - CVT). The same model was also used to predict tractor performance during other acceleration tests. The results of the CVT tests suggest that there probably is an influence of the transmission architecture that takes precedence over the general type of the transmission
Technical and economic evaluation of maceration of red grapes for production everyday wine.
Full text linkFor red wines, the phase of maceration is fundamental as it affects important features such as colour, aroma and flavour. For wines for everyday consumption these features must provide an easily drinkable product with a good quality basis that is consistent over time. In recent years two methods of maceration seem to guarantee these objectives better than others, while also allowing good work organization and automation: hot maceration and pneumo-carbonic pumping over.
These techniques have been evaluated in a large winery, defining their production potential, labour requirements, energy consumptions and economic costs. Chemical and sensory evaluations were carried out on wines produced from grapes with the same characteristics
Evaluation of physical and antioxidant properties of O/W emulsions based on turmeric-enriched soybean oil and carrot juice
No full textLe emulsioni alimentari rappresentano valide strategie per arricchire la dieta con molecole bioattive. Il presente lavoro si è focalizzato sulla valutazione delle proprietà fisico-chimiche e antiossidanti di emulsioni O/A a base di olio di soia alla curcuma e succo di carota in presenza di emulsionanti e/o addensanti e/o acidulanti
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Rappresentare il paesaggio. Utilizzo delle nuove tecnologie grafiche nel Roden Crater’s project di James Turrell
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