This study evaluated the yield performance of the tomato hybrids 'DS0060', 'Thaise' and 'Trucker' in the open field and environments protected by agricultural film (F) and polycarbonate panels (P) ...during the Amazonian summer. In the protected environment, the crops produced significantly higher yields than in the open field. 'Thaise' has high thermotolerance and is adaptable to a wide temperature range, making it the best-performing hybrid in environment F. Highest yields were found for 'Thaise' in environment F or P (86.2 and 92.5 t ha-1) together with 'DS0060' and 'Trucker' in environment F (75.3 and 88.2 t ha-1), demonstrating the high yield potential in the interim growing season (January to April). In the open field, the fruit color was paler, fruit flesh firmer and ripening index lower. In environment F, the fruits contained highest levels of soluble solids, lycopene and β-carotene. 'Thaise' contained higher concentrations of these two compounds. Under environment P, the yield of the evaluated tomato hybrids increased considerably, indicating it as a promising possibility for tomato cultivation in tropical regions. 'Thaíse' stood out with high yield and good quality traits, when grown in an F or P environment. These results prove the viability of tomato production as interim crop in tropical regions, under high rainfall and heat, as well as the difference protected environments make for tomato cultivation, in particular the choice of the most suitable cover material for the crop, to ensure high yields coupled with desirable quality properties.
An alternative method called pulsed-DC powder-pack boriding process (PDCPB) is presented in this study. The main components of the PDCPB consisted of a metal box containing the specimen embedded in a ...powder mixture, and placed between two electrodes, which were connected to a DC power supply, and a programmable electronic control device producing the polarity changes during the process. A set of boriding conditions were carried out on the surfaces of AISI 316 L stainless steel and Inconel 718 superalloy using a constant current input of 5 A with polarity inversion cycles of 10 s. After the PDCPB, the boride layers were characterized by optical microscopy, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy.
The growth kinetics of the boride layers was established using a diffusion model that considered the mass balance equations at the growth interfaces, in which the boron diffusion coefficients in the layers were expressed as a function of the boriding temperatures to estimate the boron activation energies in the borided materials. The change of polarity in the electrodes allowed a uniform flux of boron during the process, obtaining similar layer thicknesses on the surfaces of the material exposed to the pulsed-DC field. Finally, the results showed that the growth rate of the layers was increased by the effect of the pulsed-DC field, whilst the boron activation energies, in the borided materials, decreased drastically compared to those obtained for the conventional powder-pack boriding process.
•A novel method denominated pulsed-DC powder-pack boriding is presented in this work.•Uniform boron fluxes were produced on the surfaces exposed to pulsed-DC field.•Pulsed-DC field developed similar layer thicknesses at the material surface.•Pulsed-DC field increased the growth kinetics of boride layer in treated materials.
In this work, a semianalytic solution for the acoustic streaming phenomenon, generated by standing waves in Maxwell fluids through a two-dimensional microchannel (resonator), is derived. The ...mathematical model is non-dimensionalized and several dimensionless parameters that characterize the phenomenon arise: the ratio between the oscillation amplitude of the resonator and the half-wavelength ($\eta =2A/\lambda _{a}$); the product of the fluid relaxation time times the angular frequency known as the Deborah number ($De=\lambda _{1}\omega$); the aspect ratio between the microchannel height and the wavelength ($\epsilon =2 H_{0}/\lambda _{a}$); and the ratio between half the height of the microchannel and the thickness of the viscous boundary layer ($\alpha =H_{0}/\delta _{\nu }$). In the limit when $\eta \ll 1$, we obtain the hydrodynamic behaviour of the system using a regular perturbation method. In the present work, we show that the acoustic streaming speed is proportional to $\alpha ^{2.65}De^{1.9}$, and the acoustic pressure varies as $\alpha ^{6/5}De^{1/2}$. Also, we have found that the growth of inner vortex is due to convective terms in the Maxwell rheological equation. Furthermore, the velocity antinodes show a high dependency on the Deborah number, highlighting the fluid's viscoelastic properties and the appearance of resonance points. Due to the limitations of perturbation methods, we will only analyse narrow microchannels.
•Borided AISI 316L steel wear maps provide a general view of its wear performance.•Wear maps in terms of load and sliding speed for ball-on-flat tests are reported.•Mild regime is characterized by ...grooving, material agglomeration and a tribofilm.•Debris, pitting and severe grooving predominate in the transition zone.
New results on wear maps of borided AISI 316L steel, obtained by powder-pack boriding process, are presented to provide a general visualization of its wear performance under different dry sliding conditions. Wear maps showed wear behavior in terms of specific wear rate, volume of material removed and coefficient of friction as a function of load (5–20 N) and sliding speed (5–30 mm/s). Specific wear rates between 5 × 10−6 to 9.7 × 10−6 mm3/Nm were found, corresponding to mild wear and the transition region to severe wear. Grooving, material agglomeration and the formation of a tribofilm characterize the mild zone as observed by SEM-EDS, while debris, pitting and severe grooving predominate in the transition zone.
New results about the wear resistance of nickel boride layers under dry sliding conditions were obtained in this work. For this purpose, an Inconel 718 superalloy was borided under different ...conditions: 1173 K with 2 h of exposure and 1223 K with 6 h of exposure, using the powder-pack process. Before the wear tests, the nickel boride layer was characterized by the depth-sensing Vickers microindentation technique to determine indentation properties such as hardness, Young's modulus, residual stresses and fracture toughness.
The dry sliding wear tests were performed on the borided Inconel 718 superalloy obtained for the two boriding conditions, and on the surface of the reference material (Inconel 718 superalloy), using the ball-on-flat technique, under a constant load of 20 N and considering relative wear distances between 50 and 200 m. In addition, the development of the failure mechanisms over the surface of the wear tracks was analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS) techniques.
For the overall set of experimental conditions, the results showed that the presence of nickel boride layers on the surface of the Inconel 718 superalloy increased the wear resistance compared with the reference material. However, the presence of a deeper zone of compressive residual stresses at the inner-zone of the nickel boride layer formed at 1223 K with 6 h of exposure, enhanced the wear resistance by approximately two- and three-fold compared with the values estimated for the nickel boride layer obtained at 1173 K with 2 h of exposure.
•New results about the sliding wear resistance of nickel boride layer were obtained•The wear resistance of the nickel boride layer is influenced by the layer thickness•Indentation properties of the boride layer are correlated with wear resistance•A thick nickel boride layer developed a deeper zone of compressive residual stresses•A deeper zone of compressive stresses increased the wear resistance of the layer
New results about the growth kinetics of nickel boride layers on an Inconel 718 superalloy were obtained. The nickel boride layers were developed by means of the powder-pack boriding process at ...1173–1223 K with different exposure times for each temperature. According to optical and scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and nanoindentation techniques, the microstructure of the boride layer consisted in three zones: a high content of Ni4B3 on the outer-zone of the borided surface, while Ni2B and Ni3B were revealed at the inner zone of the layer and diffusion zone, respectively. Moreover, the boriding growth kinetics of nickel boride layers was estimated using the Heat Balance Integral Method (HBIM) based on a numerical resolution of a system formed by differential algebraic equations, and considering that the evolution of the layers is governed by the parabolic growth law. For the range of boriding temperatures, the boron activation energies in the Ni4B3, Ni2B and Ni3B resulted in 233, 206 and 218 kJ mol−1, respectively.
•New results of growth kinetics of boride layer on Inconel 718 alloy were obtained.•The HBIM was used to evaluate the growth kinetics of Ni4B3, Ni2B and Ni3B phases.•Boron diffusion in Ni borides was obtained by a particular solution of DAE system.•The Q values were 233, 206 and 218 kJ mol −1 for Ni4B3, Ni2B and Ni3B phases.
•New results indicate that diffusion annealing doubled borided 1018 steel wear rate.•Fracture toughness of borided 1018 steel is higher after diffusion annealing.•Diffusion annealing increments the ...plasticity index of borided 1018 steel.•Diffusion annealing generates surface compressive stresses on borided 1018 steel.
Boriding improves the mechanical and chemical properties of steels. However, the discontinuity of mechanical properties at the FeB-Fe2B interphase can induce shear failure. As a solution, post-boriding treatments to dissolve the FeB layer are applied.
In this study, new results on the wear behavior of AISI 1018 steel exposed to powder-pack boriding process (PPBP) and to the diffusion annealing process (DAP), which were evaluated through ball-on-flat linear reciprocating wear tests under different sliding distances are presented. Vickers microhardness characterization was also performed. After DAP a change from tensile to compressive residual stresses at the surface of the material was found, as well as a two-fold increase in wear and fracture resistance. Failure mechanisms on the surface of the wear tracks, for both treatment conditions, were mainly grooving and adhered material as observed by scanning electron microscopy.
We examined the relationships between three eating behaviors and nine motives underlying food choices made by Brazilian adults. Using participant responses to the short version of the Three-Factor ...Eating Questionnaire and the Food Choice Questionnaire, we investigated eating behaviors (cognitive restriction, uncontrolled eating, and emotional eating) and motives for food choices (health, mood, convenience, sensory appeal, natural content, price, weight control, familiarity, and ethical concern). We used a structural equation model to test relationship pathways (β), with eating behaviors as independent variables and motives for food choices as dependent variables. Participants were 1297 individuals (69.5% female) with a mean age of 25.0 years (SD = 5.8). We confirmed the validity and reliability of the questionnaires in this sample. Restrictive eating behavior was significantly related to motives of health (β = .415), mood (β = .127), natural content (β = .364), weight control (β = .681), and ethical concern (β = .161). Emotional eating behavior was related to motives of mood (β = .277), health (β = −.137), and natural content (β = −.136). Uncontrolled eating behavior was related to motives of convenience (β = .226), sensory appeal (β = .121), price (β = .153), and familiarity (β = .090). We believe these findings can now help design future research and clinical interventions for managing people’s risky eating behaviors and promoting beneficial food choices.
Tribological maps on powder-pack borided and non-borided AISI 316L steel under a Hank’s solution medium, during linear reciprocating sliding wear tests with a ball-on-flat configuration, are ...presented with the aim of elucidating the role of the operating environment on wear mechanisms and tribological performance. 2D maps obtained by Response Surface Methodology showed the coefficient of friction, wear volume and specific wear rate as a function of load and sliding speed. Findings showed k for the non-borided AISI 316L steel was between 5.40 and 34.90 ×10−6 mm3/Nm, while it was between 2.37 and 4.91 ×10−6 mm3/Nm for the borided AISI 316L steel. Grooving, smearing, plastic deformation and the formation of a passive film were the identified wear mechanisms on the wear tracks using Scanning Electron Microscopy.
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•Sliding wear tests under Hank’s solution of borided AISI 316L steel are reported.•Wear maps in terms of load and sliding speed for wet sliding tests are reported.•2D maps of CoF and wear rate were obtained by Response Surface Methodology.•On borided AISI 316L steel a passive film predominated on the wear track surfaces.•A passive layer enhances wear performance under Hank’s solution for AISI 316L steel.
•CoB-Co2B layer was changed to Co2B by diffusion annealing on borided CoCrMo alloy.•The scratch resistance notably improved after a diffusion annealing process.•The accomplished layer avoids severe ...scratch failure mechanisms.•The scratch residual depth decreased around 60% with this procedure.•The enhanced layer reduced around 50% the volume loss in multipass scratch.
This work studies the effect of a diffusion annealing process in cobalt boride layers by progressive load scratch (PLST) and multipass scratch (MPST) tests. First, a double-phase CoB/Co2B layer was formed on CoCrMo alloy at 1000 °C for 6 h. Next, a single-phase Co2B layer was obtained through a diffusion annealing process. The scratch tests were conducted with a progressive load from 5 to 150 N in PLST, whereas in MPST, up to 400 passes were applied with a subcritical load of 38 N. Conducting the diffusion annealing process significantly improved the scratch resistance; in PLST, the achieved layer avoided severe failure mechanisms and decreased residual depth by 60%. In MPST, friction was reduced and the volume loss decreased around 50%.
