1,527 research outputs found
Numerical simulations of components produced by fused deposition 3D printing
Three-dimensional printing technology using fused deposition modeling processes is becoming more and more widespread thanks to the improvements in the mechanical properties of materials with the addition of short fibers into the polymeric filaments. The final mechanical properties of the printed components depend, not only on the properties of the filament, but also on several printing parameters. The main purpose of this study was the development of a tool for designers to predict the real mechanical properties of printed components by performing finite element analyses. Two different materials (nylon reinforced with glass or carbon fibers) were investigated. The experimental identification of the elastic material model parameters was performed by testing printed fully filled dog bone specimens in two different directions. The obtained parameters were used in numerical analyses to predict the mechanical response of simple structures. Blocks of 20 mm × 20 mm × 160 mm were printed in four different percentages of a triangular infill pattern. Experimental and numerical four-point bending tests were performed, and the results were compared in terms of load versus curvature. The analysis of the results demonstrated that the purely elastic transversely isotropic material model is adequate for predicting behavior, at least before nonlinearities occur
Energy Efficiency of Hybrid-Power HetNets: A Population-like Games Approach
In this paper, a distributed control scheme based on population games is proposed. The controller is in charge of dealing with the energy consumption problem in a Heterogeneous Cellular Network (HetNet) powered by hybrid energy sources (grid and renewable energy) while guaranteeing appropriate quality of service (QoS) level at the same time. Unlike the conventional approach in population games, it considers both atomicity and non-anonymity. Simulation results show that the proposed population-games approach reduces grid consumption by up to about 12% compared to the traditional best-signal level association policy.U.S. Air Force Office of Scientific Research FA9550-17-1-0259Ministerio de Cultura y Deporte DPI2016-76493-C3-3-RMinisterio de Economía y Empresa DPI2017-86918-
Analysis of strain rate behavior of an Al 6061 T6 alloy
Abstract In order to simulate complex scenario like ballistic impact, correct material calibration is fundamental. The material in the area involved by impact can experience high deformation and damage in a very limited time. As a consequence dynamic tests on the materials are needed in order to calibrate constitutive law able to describe the material behavior in terms of hardening and in particular strain rate. According to the fact that no guidelines are available on testing methods, different types of testing techniques have been used to generate data under dynamic conditions. Several dynamic tests, are carried out on Al 6061 T6 specimens and the experimental data elaborated. The developed procedure is useful to take into account also the thermal phenomena generally affecting high strain-rate tests due to the adiabatic overheating related to the conversion of plastic work. The method presented requires strong effort both from experimental and numerical point of view; anyway it allows to precisely identifying the parameters of a material models. This could provide great advantages when high reliability of the material behavior is necessary
Numerical simulations of tungsten targets hit by LHC proton beam
The unprecedented energy intensities of modern hadron accelerators yield special
problems with the materials that are placed close to or into the high intensity beams. The
energy stored in a single beam of LHC particle accelerator is equivalent to about 80 kg of
TNT explosive, stored in a transverse beam area with a typical value of 0.2 mm×0.2 mm. The
materials placed close to the beam are used at, or even beyond, their damage limits. However,
it is very difficult to predict structural efficiency and robustness accurately: beam-induced
damage for high energy and high intensity occurs in a regime where practical experience does
not exist. The interaction between high energy particle beams and metals induces a sudden
non uniform temperature increase. This provokes a dynamic response of the structure
entailing thermal stress waves and thermally induced vibrations or even the failure of the
component. This study is performed in order to estimate the damage on a tungsten component
due to the impact with a proton beam generated by LHC. The solved problems represent some
accidental cases consequent to an abnormal release of the beam: the energy delivered on the
components is calculated using the FLUKA code and then used as input in the numerical
simulations, that are carried out via the FEM code LS-DYNA
Relationship between exhaled air temperature and exhaled nitric oxide in childhood asthma
Airway inflammation is a characteristic of asthma. Exhaled nitric oxide (eNO) has been demonstrated to be related to actual levels of airway inflammation in asthmatic patients. The purpose of this study was to investigate whether the temperature of exhaled air is related to eNO levels. Temperature of exhaled air and eNO were measured in 52 asthmatic children with a cross-sectional design. A significant relationship was demonstrated between eNO and temperature of peak and plateau exhaled air temperature. The relationship between both the peak and the plateau values and eNO was more evident when it was corrected for environmental temperature. These results suggest a relationship between exhaled nitric oxide and the temperature of exhaled air in asthmatic patients not treated with systemic steroids
Therapeutic Effects of Vitamin D in Asthma and Allergy
In recent years, low vitamin D status has been proposed as a putative risk factor for allergic diseases. A growing body of literature reports low vitamin D levels in atopic patients and supports an association between vitamin D deficiency and risk of adverse asthma and allergies outcomes. Therefore, it has been speculated that vitamin D supplementation may either prevent or reduce the risk of allergic diseases. Birth cohort studies addressing the role of vitamin D intake during pregnancy have shown conflicting results regarding allergy outcomes in offspring. Currently, only a few studies have tried to supplement vitamin D in asthmatic patients, often as an add-on therapy to standard asthma controller medications, and results are not all consistent. There is emerging data to show that vitamin D can enhance the antiinflammatory effects of glucocorticoids and potentially be used as adjuvant therapy in steroid-resistant asthma. Recent in vivo data suggest that vitamin D supplementation may also reduce the severity of atopic dermatitis. This review examines the existing relevant literature focusing on vitamin D supplementation in the treatment of allergic diseases
Microbiota network and mathematic microbe mutualism in colostrum and mature milk collected in two different geographic areas: Italy versus Burundi
Human milk is essential for the initial development of newborns, as it provides
all nutrients and vitamins, such as vitamin D, and represents a great source of
commensal bacteria. Here we explore the microbiota network of colostrum and
mature milk of Italian and Burundian mothers using the auto contractive map
(AutoCM), a new methodology based on artificial neural network (ANN)
architecture. We were able to demonstrate the microbiota of human milk to be a
dynamic, and complex, ecosystem with different bacterial networks among different
populations containing diverse microbial hubs and central nodes, which change
during the transition from colostrum to mature milk. Furthermore, a greater
abundance of anaerobic intestinal bacteria in mature milk compared with colostrum
samples has been observed. The association of complex mathematic systems such as
ANN and AutoCM adopted to metagenomics analysis represents an innovative approach
to investigate in detail specific bacterial interactions in biological
samples
Flunisolide Decreases Exhaled Nitric Oxide and Nitrotyrosine Levels in Asthmatic Children
Background. Exhaled nitric oxide (FeNO) has been reported to be elevated in the oxidative stress involved in asthmatic patients, and the reaction of nitric oxide (NO) with superoxide anions results in the formation of nitrotyrosine. The purpose of this study was to investigate the effect of inhaled steroid treatment on nitrotyrosine levels collected by exhaled breath condensate (EBC) and on FeNO. Methods. This was a single-blind placebo-controlled study. The lung function, FeNO, and nitrotyrosine levels were evaluated in 10 asthmatic children. Results. The nitrotyrosine levels were stable during the placebo period (T0 = 1.16 ng/ml versus T1 = 1.05 ng/ml; NS.), whereas they decreased after the treatment with flunisolide (T2 = 1.14 ng/ml versus T3 = 0.88 ng/ml; P < .001). No significant reduction in FeNO levels was observed after placebo treatment (T0 = 38.4 ppb versus T1 = 34.7 ppb, NS.). In contrast, FeNO values decreased significantly being at T3 = 14.9 ppb (T1 versus T3; P = .024). Conclusions. This study shows that corticosteroid treatment reduces nitrotyrosine levels in EBC of asthmatic subjects
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