We present a methodology to explore experimentally the formation of thermally induced long-range ground-state ordering in artificial spin-ice systems. Our novel approach is based on the ...thermalization from a square artificial spin-ice array of elongated ferromagnetic nanoislands made of a FeNi alloy characterized by a Curie temperature about 100 K lower than that of Permalloy (Ni81Fe19), which is commonly used for this kind of investigation. The decrease in M(T) when the sample is heated close to its Curie temperature reduces the shape anisotropy barrier of each island and allows us to bring the artificial spin-ice pattern above the blocking temperature of the islands, thus 'melting' the spin-ice system, without damaging the sample. The magnetization configuration resulting from the thermal excitation of the islands and the frustrated dipolar interactions among them can be then imaged by magnetic force microscopy or any other kind of magnetic microscopy imaging after cooling down the sample back to room temperature. This thermally induced melting-freezing protocol can be repeated as many times as desired on the same sample and the heating and cooling parameters (max T, heating and cooling rates, number of cycles, application of external fields) varied at will. Thereby, the approach proposed here opens up a pathway to the systematic experimental study of thermally induced frozen states in artificial spin-ice systems, which have been the subject of many recent theoretical studies due to their interesting physical properties but, because of the difficulties in obtaining them in real samples and in a controlled manner, remain experimentally an almost completely unexplored terrain.
▶ LSP is an effective surface treatment to improve fatigue properties of duplex stainless steel. ▶ Increasing pulse density, fatigue crack growth rate is reduced. ▶ Microstructure is not affected by ...LSP. ▶ Compressive residual stresses increases increasing pulse density.
Duplex stainless steels have wide application in different fields like the ship, petrochemical and chemical industries that is due to their high strength and excellent toughness properties as well as their high corrosion resistance. In this work an investigation is performed to evaluate the effect of laser shock processing on some mechanical properties of 2205 duplex stainless steel. Laser shock processing (LSP) or laser shock peening is a new technique for strengthening metals. This process induces a compressive residual stress field which increases fatigue crack initiation life and reduces fatigue crack growth rate. A convergent lens is used to deliver 2.5J, 8ns laser pulses by a Q-switched Nd:YAG laser, operating at 10Hz with infrared (1064nm) radiation. The pulses are focused to a diameter of 1.5mm. Effect of pulse density in the residual stress field is evaluated. Residual stress distribution as a function of depth is determined by the contour method. It is observed that the higher the pulse density the greater the compressive residual stress. Pulse densities of 900, 1600 and 2500pul/cm2 are used. Pre-cracked compact tension specimens were subjected to LSP process and then tested under cyclic loading with R=0.1. Fatigue crack growth rate is determined and the effect of LSP process parameters is evaluated. In addition fracture toughness is determined in specimens with and without LSP treatment. It is observed that LSP reduces fatigue crack growth and increases fracture toughness if this steel.
•Simulations explain the influence of advancing direction on residual stresses.•Fatigue life in laser peened stainless steel 316L specimens can be increased (+471%) by optimizing the pulse ...sequence.•3D FEM model allows to simulate massive parallel LSP over real geometries.•Good match between simulations and experimental results.
Laser shock peening (LSP) is considered as a well-established technology for inducing compressive residual stresses under the surface of metallic components. As a result, fatigue life is increased and the material becomes more resistant to corrosion and wear. This paper studies the effect of a significant parameter of LSP, the advancing direction of the laser scanning pattern, on the induced residual stress fields and the fatigue life of stainless steel 316L samples using experiments and 3D finite element analysis. The chosen material is of interest for nuclear and biomedical applications. Two different laser shock processing strategies (two different pulse sequences varying the advancing direction) were performed on the specimens. Their fatigue lives were compared revealing the decisive role played by the advancing direction of the treatment and the generated residual stresses. Fatigue life in laser peened specimens was increased from +166% to +471% by optimizing the pulse sequence. This improvement is explained by stress–strain analysis.
ABSTRACT
Recently, in 2020, Stark broadening parameters have been measured for spectral lines belonging to 75 vanadium ii (V ii) multiplets. For some of them, there are published calculations in the ...literature. However, these lines are not sufficient for the analysis of the lines present in the metal-poor star HD 8493. When new calculations by the Griem approximation are performed and compared with the experimental results, in some cases there is a difference of a factor of 7. It is clear that the problem lies, as already suggested some years ago in a theoretical paper by Douglas H. Sampson, in the poor approximation proposed by van Regemorter for the Gaunt factors used in the Griem approximation. In this work, we have performed broadening measurements of 3276.12 and 3715.46 Å V ii lines that confirmed the previous measurements of 2020. Subsequently, we performed a more accurate calculation using the procedure to calculate the Gaunt factors suggested by Sampson, obtaining results very close to the experimental values. These allowed us to assume that the calculations performed for 56 lines ranging between 3700 and 4600 Å (present in the photospheres of the Sun and the metal-poor star HD 8493), and without experimental information, are more accurate using the Gaunt factors proposed by Sampson.
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•Accurate estimation of uncertainty by Monte Carlo method is presented.•In the example proposed, hole depth is the most important uncertainty source.•Transverse sensitivity, Poisson’s ...ratio, thermal uncertainties can be ignored.•Guidelines are proposed to extend the results to other residual stress problems.•Monte Carlo method verifies GUM uncertainty framework.
Due to its simplicity and low cost, the hole drilling strain gauge method is one of the most popular techniques to determine residual stresses. The Standard ASTM E837-13 distinguish between constant and variable stresses in depth. Each type of measurement has an associated uncertainty. The goal should be the quantification and reduction in its magnitude to be acceptable for the purposes of the measurement. Uncertainty estimation associated with this method has not been addressed in depth. The present work deals with uncertainty calculation in the determination of non-uniform residual stresses by the integral method. A general estimation procedure by Monte Carlo method, where many uncertainty sources have been considered, is presented. In normal experiment condition, most of these sources are significant and the irrelevant ones have been identified. Monte Carlo method verifies that a measurement uncertainty evaluation with the GUM uncertainty framework can be performed.
•Full-scale MBR optimization strategies were identified through scenario analysis.•Model-based assessment was applied.•Effluent quality, operational risks and costs were considered.•Optimization ...strategies applied in a full-scale MBR achieved successful improvements.•The proposed methodology could be applied to other chemical engineering processes.
Despite the high number of advantages of membrane bioreactors (MBR), operational costs still remain as one of the main obstacles of this technology. In that sense, a full-scale MBR was studied in order to explore and identify viable optimization strategies for improving effluent quality and reducing operational costs through a model-based approach. Opportunities for optimization strategies, identified through the initial experimental phase, were focused on improving the nitrogen removal efficiencies and reducing the aeration energy costs through the aerobic DO set point and recirculation modifications. A mechanistic model was developed to reproduce the operation of the full-scale MBR and predict the effects of the optimization actions. Moreover, a qualitative risk model was also applied to ensure that the DO set point reduction did not negatively affect the microbiology of the activated sludge. The best viable control scenario was identified and then tested in the full-scale MBR. The results achieved maximum improvements on the nitrogen removal efficiencies of 27% and reduction on the aeration energy (7%) without affecting the sludge properties or the filtration performance. The model approached proved in this study and the optimization strategies identified can be generalized for municipal MBRs.
•3D FEM model allows to simulate LSP over extended areas with overlapped pulses in real geometries.•LSP pulse sequence is optimized taking into account edge effects in order to improve fatigue ...life.•Developed FEM model predicts the location of crack initiation in tested specimens.
Laser shock processing (LSP) is being considered as a competitive alternative technology to classical treatments for improving fatigue, corrosion cracking and wear resistance of metallic materials.The purpose of this paper is to present a fully 3D finite element model for predicting the residualstresses that result from the LSP of aluminum alloy Al2024-T351 samples of interest for aeronauticindustry in order to optimize the laser treatment to increase the fatigue life of the material. In order to correlate the simulation results with experimental data, three different laser shock processing strategies (pulse sequences) were performed on fatigue specimens and their fatigue life were compared. The starting points of cracks were identified by means of optical and scanning electron microscope examinations and a correlation with the maximum tensile stress regions predicted by the numerical model has been established.
Background Oxandrolone, an anabolic agent, has been administered for 1 year post burn with beneficial effects in pediatric patients. However, the long-lasting effects of this treatment have not been ...studied. This single-center prospective trial determined the long-term effects of 1 year of oxandrolone administration in severely burned children; assessments were continued for up to 4 years post therapy. Study Design Patients 0 to 18 years old with burns covering >30% of the total body surface area were randomized to receive placebo (n = 152) or oxandrolone, 0.1 mg/kg twice daily for 12 months (n = 70). At hospital discharge, patients were randomized to a 12-week exercise program or to standard of care. Resting energy expenditure, standing height, weight, lean body mass, muscle strength, bone mineral content (BMC), cardiac work, rate pressure product, sexual maturation, and concentrations of serum inflammatory cytokines, hormones, and liver enzymes were monitored. Results Oxandrolone substantially decreased resting energy expenditure and rate pressure product, increased insulin-like growth factor-1 secretion during the first year after burn injury, and, in combination with exercise, increased lean body mass and muscle strength considerably. Oxandrolone-treated children exhibited improved height percentile and BMC content compared with controls. The maximal effect of oxandrolone was found in children aged 7 to 18 years. No deleterious side effects were attributed to long-term administration. Conclusions Administration of oxandrolone improves long-term recovery of severely burned children in height, BMC, cardiac work, and muscle strength; the increase in BMC is likely to occur by means of insulin-like growth factor-1. These benefits persist for up to 5 years post burn.
Wastewater treatment selection is a complex task usually addressed by applying separate tools for the correct assessment of multi-criteria evaluation. Novedar_EDSS integrates technical, ...environmental, economic and social assessment capabilities in one single platform. The aim of this work is to evaluate and demonstrate the capabilities of this environmental decision support system (EDSS). For that purpose, 4 case studies of real projects were selected to validate the results in the EDSS by comparing them with those from the study of alternatives performed by the decision makers. Moreover, 1 conceptual case study was applied to support the selection of the most properly strategy for plant retrofitting. Results have demonstrated that the EDSS provides key aspects when deciding the retrofitting process to apply and, when compared to real projects, it recommends analogue treatments as those applied in the projects, ranking them in the same order. Therefore, results in the validation process performed show that this tool provides a reliable basis to support decision makers to select properly treatment alternatives in wastewater treatment plant pre-design.
•Validation of a decision support system for wastewater treatment is performed.•5 case studies are selected (4 real and 1 conceptual) for new plant and retrofitting.•Results in the tool are compared with process flow diagrams in the real case studies.•The tool recommends analogous treatments as those selected by decision-makers.•Reliability of the tool in pre-design of wastewater treatment plants is demonstrated.
Laser shock processing (LSP) or laser shock peening is a new technique for strengthening metals. This process induces a compressive residual stress field which increases fatigue crack initiation life ...and reduces fatigue crack growth rate. Specimens of 6061-T6 aluminum alloy are used in this investigation. A convergent lens is used to deliver 1.2
J, 8
ns laser pulses by a Q-switch Nd:YAG laser, operating at 10
Hz. The pulses are focused to a diameter of 1.5
mm onto a water-immersed type aluminum samples. Effect of pulse density in the residual stress field is evaluated. Residual stress distribution as a function of depth is assessed by the hole drilling method. It is observed that the higher the pulse density the larger the zone size with compressive residual stress. Densities of 900, 1350 and 2500
pulses/cm
2 with infrared (1064
nm) radiation are used. Pre-cracked compact tension specimens were subjected to LSP process and then tested under cyclic loading with
R = 0.1. Fatigue crack growth rate is determined and the effect of LSP process parameters is evaluated. Fatigue crack growth rate is compared in specimens with and without LSP process. In addition fracture toughness is determined in specimens with and without LSP treatment. It is observed that LSP reduces fatigue crack growth and increases fracture toughness in the 6061-T6 aluminum alloy.
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