Spatial variability of mechanical resistance to penetration evaluated with mobile unit on haplic vertisol cultivated with mango

Since the advent of mechanized farming and intensive use of agricultural machinery and implements on the properties, the soil began to receive greater load of machinery traffic, which can cause increased soil compaction. The aim of this study was to evaluate the spatial variability of soil mechanical resistance to penetration (RP) in the layers of 0.00-0.10, 0.10-0.20, 0.20-0.30 and 0.30-0.40m, using geostatistics in an area cultivated with mango in Haplic Vertisol of the northeastern semi-arid, with mobile unit equipped with electronic penetrometer. The RP data was collected in 56 points from an area of 3 ha, and random soil samples were collected to determine the soil moisture and texture. For RP data analysis we used descriptive statistics and geostatistics. The soil mechanical resistance to penetration presented increased variability, with adjustment of the spherical and exponential semivariograms in the layers. We found that 42% of the area in the layer of 0.10-0.20m showed RP values above 2.70 MPa. Maximum values of RP were found in the layer of 0.19-0.27m, predominantly in 56% of the area.

Energy demand in citrus production under varied operational efficiency values

Citrus orchards are very important in Brazil, especially in São Paulo State, where occupy an area of 600,000 ha approximately. To identify sustainability degree of citrus production system, an energy analysis allows evaluating efficiency of direct and indirect applied inputs. Thus, this study aimed to evaluate citrus production system under energetic point of view, in which invested energy is paid back with citrus production; being compared within three scenarios for operational field efficiency. As result, by sensitivity analysis was determined that fuel was the main energy demander, followed by pesticides and fertilizers. In operational work capacity analysis, all combinations between efficiency (minimum, typical and maximum) and yield levels became positive in the seventh year, except for the combination minimum efficiency and 10 % less yield, positive in the eighth year. The best combination (maximum efficiency and 10 % more yield) has promoted investment payoff around the sixth and seventh year. By this study, it is possible to determine the total energy demand to produce citrus and indentify the applied inputs that need more attention by the decision-makers. Labor and seedlings can be ommited for further studies with citrus, since they were irrelevant. Management of agricultural machinery may pose an important role on decreasing environmental impact of citrus production.

Mechanical damage during harvest and loading affect orange postharvest quality

Brazil is the world’s largest orange producer; however, part of this production is lost during postharvest. This loss can be minimized by controlling incidence of physical damage throughout the harvest and loading operations. Impacts can negatively modify quantitative and qualitative fruits aspects. The main goal of this study was to measure the impact magnitude in two types of harvest (manual and detachment) and during all steps from picking into bags until loading for transport to the processing industry and additionally evaluating, in laboratory, the physico-chemical quality of the fruit subjected to various impacts, similar to those found in the field. In order to evaluate the impact magnitude, an instrumented sphere was used (760 mm, Techmark, Inc, USA). The following physico-chemical parameters were evaluated during 6-days of storage: weight loss, soluble solids contents, titratable acidity, ascorbic acid content, pH, firmness and peel color. The greatest impacts were observed during harvest, during the detachment practice, and when loading and unloading from bulk storage, with average acceleration values between 249.5 and 531.52G. The impact incidence in oranges were responsible for reducing the soluble solids, titratable acidity, ascorbic acid and weight by to 5.5%; 8.7%; 4.6% and 0.5%, respectively, compared to the control. Impacts during harvest and the various pre-industry manipulation steps must be controlled as they interfere in postharvest quality and physiology of ‘Valência’ oranges.

Quality of peanut mechanical sowing in function of seeding density and size of the seeds

ABSTRACTPeanut crop (Arachis hypogaeaL.) mechanization has been improved over the years; however there are drawbacks that affect the quality of operations. Thus, this article’s objectives were to evaluate the operational performance of the mechanized sowing of peanut crop according to seeding densities (10, 14, and 18 seeds m-1) and seed sizes (21 and 23 mm). It was observed that the seeds of 23 mm had shorter average number of days to emergence and a higher percentage of emergences, occurring the opposite to the seeding density of 18 seeds m-1. The higher the seeding density, the largest was the plant stand, whereas the 23 mm seed obtained the best results and the same with the seeding density of 14 seeds m-1 that had a higher percentage of normal spacing. The densities of 14 and 18 seeds m-1 reflected in higher yields, being always superior to the 23 mm seeds.

Monitoring of mechanical sugarcane harvesting through control charts

ABSTRACT Statistical process control in mechanized farming is a new way to assess operation quality. In this sense, we aimed to compare three statistical process control tools applied to losses in sugarcane mechanical harvesting to determine the best control chart template for this quality indicator. Losses were daily monitored in farms located within Triângulo Mineiro region, in Minas Gerais state, Brazil. They were carried over a period of 70 days in the 2014 harvest. At the end of the evaluation period, 194 samples were collected in total for each type of loss. The control charts used were individual values chart, moving average and exponentially weighted moving average. The quality indicators assessed during sugarcane harvest were the following loss types: full grinding wheel, stumps, fixed piece, whole cane, chips, loose piece and total losses. The control chart of individual values is the best option for monitoring losses in sugarcane mechanical harvesting, as it is of easier result interpretation, in comparison to the others.

Thermal efficiency of individual shelters for girolando calves in brazilian semi-arid regions

ABSTRACT The objective of this research was to evaluate the thermal efficiency of roofs used on individual shelters during milk-feeding stage of Girolando calves. The research was conducted at a farm located in a dry region of Pernambuco state, Brazil. The experimental design was completely randomized, with 27 Holstein × Gir dairy crossbred calves housed in shelters with three roofing materials (fibre cement tile, recycled tile, and thatched roofs). The recycled tiles and thatched roofs provided reductions of 18.7 and 14.6% in radiant thermal load, respectively. Regardless the roofing material, all animals increased their respiratory rate to maintain thermal equilibrium.

Reproductive efficiency of asymptomatic Theileria equi carriers mares submitted to an embryo transfer program

This study aimed to assess and evaluate the effects of Theileria equi infection on embryonic recovery, gestation and early embryonic loss. Thirteen Mangalarga Marchador Theileria equi positive donors (diagnosed through nested-PCR) and 40 embryos receptors were used. Donors were submitted to two embryo collections in two consecutive estrous cycles (GId); after, the same mares were treated with imidocarb dipropionate (1.2mg/kg IM.) in order to collect more embryos in two more estrous cycles (GIId). Receptors were divided into two groups (control and with treated) with 20 animals each, where one group was the control (GIr) and the other one (GIIr) treated with 1.2mg/kg IM of imidocarb dipropionate assessing the gestation rate at 15, 30, 45 and 60 days. After 52 embryo collections, the embryonic recovery rates were 53.84% (14/26) and 65.38% (17/26) (p> 0.05) for GId and GIId, respectively. The gestation rate was 70% (14/20) (p>0.05) at 15, 30, 45 and 60 days in group GIr and for GIIr was 85% (17/20) (p>0.05) at 15 days, 80% (16/20) (p>0.05) at 30, 45 and 60 days. The treatment with imidocarb dipropionate did not cause significant improvement in the reproductive efficiency at an ET program.

Critical aspects on the behavior of material from the mechanical tool-workpiece interaction in single point diamond turning

Some material aspects such as grain size, purity and anisotropy exert an important influence on surface quality, especially in single point diamond turning. The aim of this paper is to present and discuss some critical factors that can limit the accuracy of ultraprecision machining of non-ferrous metals and to identify the effects of them on the cutting mechanism with single point diamond tools. This will be carried out through observations of machined surfaces and chips produced using optical and scanning electron microscopy. Solutions to reduce the influence of some of these limiting factors related with the mechanism of generation of mirror-like surfaces will be discussed.

BEM/FEM non-linear model applied to transient analysis with viscous damping

In this article a two-dimensional transient boundary element formulation based on the mass matrix approach is discussed. The implicit formulation of the method to deal with elastoplastic analysis is considered, as well as the way to deal with viscous damping effects. The time integration processes are based on the Newmark rhoand Houbolt methods, while the domain integrals for mass, elastoplastic and damping effects are carried out by the well known cell approximation technique. The boundary element algebraic relations are also coupled with finite element frame relations to solve stiffened domains. Some examples to illustrate the accuracy and efficiency of the proposed formulation are also presented.

Non-linear analysis of laminated metal matrix composites by an integrated micro/macro-mechanical model

The present paper describes an integrated micro/macro mechanical study of the elastic-viscoplastic behavior of unidirectional metal matrix composites (MMC). The micromechanical analysis of the elastic moduli is based on the Composites Cylinder Assemblage model (CCA) with comparisons also draw with a Representative Unit Cell (RUC) technique. These "homogenization" techniques are later incorporated into the Vanishing Fiber Diameter (VFD) model and a new formulation is proposed. The concept of a smeared element procedure is employed in conjunction with two different versions of the Bodner and Partom elastic-viscoplastic constitutive model for the associated macroscopic analysis. The formulations developed are also compared against experimental and analytical results available in the literature.

Turbulent heat transfer and pressure drop in pinned annular regions

Experiments were performed to determine average heat transfer coefficients and friction factors for turbulent flow through annular ducts with pin fins. The measurements were carried out by means of a double-pipe heat exchanger. The total number of pins attached to the inner wall of the annular region was 560. The working fluids were air, flowing in the annular channel, and water through the inner circular tube. The average heat transfer coefficients of the pinned air-side were obtained from the experimental determination of the overall heat transfer coefficients of the heat exchanger and from the knowledge of the average heat transfer coefficients of the circular pipe (water-side), which could be found in the pertinent literature. To attain fully developed conditions, the heat exchanger was built with additional lengths before and after the test section. The inner circular duct of the heat exchanger and the pin fins were made of brass. Due to the high thermal conductivity of the brass, the small tube thickness and water temperature variation, the surface of the internal tube was practically isothermal. The external tube was made of an industrial plastic which was insulated from the environment by means of a glass wool batt. In this manner, the outer surface of the annular channel can be considered adiabatic. The results are presented in dimensionless forms, in terms of average Nusselt numbers and friction factors as functions of the flow Reynolds number, ranging from 13,000 to 80,000. The pin fin efficiency, which depends on the heat transfer coefficient, is also determined as a function of dimensionless parameters. A comparison of the present results with those for smooth sections (without pins) is also presented. The purpose of such a comparison is to study the influence of the presence of the pins on the pressure drop and heat transfer rate.

Modelling of mechanical properties of CRFC composites under flexure loading

Carbon Fibre Reinforced Carbon (CFRC) Composites are increasing their applications due to their high strength and Young’s Modulus at high temperatures in inert atmosphere. Although much work has been done on processing and structure and properties relationship, few studies have addressed the modelling of mechanical properties. This work is divided in two parts. In the first part, a modelling of mechanical properties was carried out for two bi-directional composites using a model based on the Bernoulli-Euler theory for symmetric laminated beams. In the second part, acoustic emission (AE) was used as an auxiliary technique for monitoring the failure process of the composites. Differences in fracture behaviour are reflected in patterns of AE.

Using passive techniques for vibration damping in mechanical systems

This paper examines two passive techniques for vibration reduction in mechanical systems: the first one is based on dynamic vibration absorbers (DVAs) and the second uses resonant circuit shunted (RCS) piezoceramics. Genetic algorithms are used to determine the optimal design parameters with respect to performance indexes, which are associated with the dynamical behavior of the system over selected frequency bands. The calculation of the frequency response functions (FRFs) of the composite structure (primary system + DVAs) is performed through a substructure coupling technique. A modal technique is used to determine the frequency response function of the structure containing shunted piezoceramics which are bonded to the primary structure. The use of both techniques simultaneously on the same structure is investigated. The methodology developed is illustrated by numerical applications in which the primary structure is represented by simple Euler-Bernoulli beams. However, the design aspects of vibration control devices presented in this paper can be extended to more complex structures.

Is there correlation between the turbulent eddies size and mechanical hemolysis ?

Hemolytic profile of an artificial device chronically implanted in the cardiovascular system may represent the difference between the success and failure in its long-term performance. Last decades have witnessed efforts on the development of methods capable of predicting red blood cell damage in artificial organs. However, all of them have had limited success to predict hemolysis. The primary cause of this problem is that such models do not take into consideration structures of turbulent flow. The present paper demonstrates that microscopic measurable occurrences of the turbulent flow may be linked to red blood cell trauma. This study suggests that if the smallest turbulent eddies dimension is under 10 m m hemolysis is not dependent on the exposure time and the red blood cells damage depends only on the dissipation of the turbulent energy in the erythrocyte membrane. The analysis reported here opens the possibility of mapping the flow field in artificial assist devices based on the smallest eddy length scales. This is a promising new trend and should be considered in the designing requirements of the next generations of artificial organs.

Effect of particle morphology on the mechanical and thermo-mechanical behavior of polymer composites

Fiber reinforced polymer composites have been used in many applications, such as in automobile, aerospace and naval industries, due basically to their high strength-to-weight and modulus-to-weight, among other properties. Even though particles are usually not able to lead to the level of reinforcement of fibers, particle reinforced polymer composites have been proposed for many new applications due to their low cost, easy fabrication and isotropic properties. In this work, polymer composites were prepared by incorporating glass particles of different morphologies on poly(aryl sulfones) matrices. Particles with aspect ratios equal to 1, 2.5 and 10 were used. The prepared composites were characterized using electron microscopy and thermal analysis. Mechanical properties of the composites were evaluated using a four-point bending test. The thermo-mechanical behavior of the obtained composites was also investigated. The results showed that the morphology of the particles alter significantly the mechanical properties of composites. Particles with larger values of aspect ratio led to large elastic modulus but low levels of strain at failure. This result was explained by modeling the thermo-mechanical behavior of the composites using a viscoelastic model. Parameters of the model, obtained from a Cole-Cole type of plot, demonstrated that interactions at the polymer-reinforcing agent interface were higher for composites with large aspect ratio particles. Higher levels of interactions at interfaces can lead to higher degrees of stress transfer and, consequently, to composites with large elastic modulus, as experimentally observed.