27,311 research outputs found
Fate of silver nanoparticles in constructed wetlands : a microcosm study
Nano-enabled materials are produced at growing volumes which increases the likelihood of nanoparticles being released into the environment. Constructed wetlands (CWs) are likely to receive wastewater containing nanoparticles leaching from products during usage. Therefore, we investigate the retention of silver nanoparticles (Ag-NPs) in microcosms simulating CWs treating domestic wastewater. The effects of aeration and organic matter content on the Ag-NP removal efficiencies are studied in particular. CWs remove most of the Ag (80-90%) and the largest fraction of Ag is found in/on the biofilm. Detailed electron microscopy analyses suggest that Ag-NPs are transformed into Ag2S in all microcosm experiments. The good correlation between total suspended solids (TSS) and the Ag concentration measured in the effluent indicates that Ag-NPs are bound to the solids in the effluent. Aeration of the microcosms does not affect the release of Ag-NPs from the systems but increasing organic matter leads to increased amounts of Ag passing the CWs, correlating with the increased release of TSS from the CWs. These results suggest that Ag-NPs are retained with the (suspended) solids in CWs and that the removal efficiency of TSS is an important factor determining the discharge of Ag-NPs from CWs
The Influence of Colour on Radiometric Performances of Agricultural Nets
The whole construction parameters of the net, combined with the shape of the structure, the position of the sun and the sky conditions affect the radiometric performance of the permeable covering system. The radiometric properties of the permeable membrane influence the quality of the agricultural production and the aesthetic characteristics of the netting system. Moreover, the colour of the material and the light reflection- especially of the wavelengths visible for the human eye (VIS, 380-760nm)- is an interesting criterion to determine the aesthetic value of the net structure and its environmental impact. In order to investigate the influence of the threads colour on the radiometric properties of the net, a set of field tests were performed by means of a spectroradiometer in combination with an experimental setup 120x120x50cm covered with membranes formed by threads with different colour. A second set of experiments were performed, on the same kind of nets, in laboratory by means of a combination of a large integrating sphere and a small one: the transmissivity from a direct (tauDIR) and diffuse ((tauDIF) source and the reflectivity from diffuse source (¿) of 50x50cm samples were measured in the PAR range. The evaluation of the transmissivity values shows that the colour of a net influence spectral distribution of the radiation passing through the net absorbing their complementary colours. The transmissivity of black nets is almost constant in the visible range and the reduction of the incoming radiation is proportional to the solidity of the net. In the PAR range transparent and black nets doesn¿t cause an alteration of the spectrum of solar radiation and transmittance is almost constant with a slight growth in nets having lower porosity
Proposal of a novel design for linear superconducting motor using 2G tape stacks
This paper presents a new design for a su-
perconducting linear motor (SLM). This SLM uses stacks
of second-generation (2G) superconducting tapes, which
are responsible for replacing yttrium barium copper oxide
bulks. The proposed SLM may operate as a synchronous
motor or as a hysteresis motor, depending on the load
force magnitude. A small-scale linear machine prototype
with 2G stacks was constructed and tested to investigate
the proposed SLM topology. The stator traveling magnetic
field wave was represented by several Nd-Fe-B permanent
magnets. A relative movement was produced between the
stator and the stack, and the force was measured along the
displacement. This system was also simulated by the finite
element method, in order to calculate the induced currents
in the stack and determine the electromagnetic force. The
H-formulation was used to solve the problem, and a power
law relation was applied to take into account the intrin-
sically nonlinearity of the superconductor. The simulated
and measured results were in accordance. Simulated re-
sults were extrapolated, proving to be an interesting tool to
scale up the motor in future projects. The proposed motor
presented an estimated force density of almost 500 N/kg,
which is much higher than any linear motor.This work was supported in part by the following agencies: CNPq/CAPES/INERGE, CNPq—Ci ˆ encias sem Fronteiras, FAPERJ, Catalan Government 2014- SGR-753, CONSOLIDER Excellence Network MAT2014-56063-C2-1-R and MAT2015-68994-REDC, Eurofusion EU COST ACTIONS MP1201/ MP1014/PPPT-WPMAG 2014, EUROTAPES FP7-NMP-Large-2011- 280432, FORTISSIMO FP7-2013-ICT-609029, and Spanish Govern- ment Agencies—Severo Ochoa Programme Centres of Excellence in R&D. (Corresponding author: Guilherme G. Sotelo.
Knowledge based cloud FE simulation of sheet metal forming processes
The use of Finite Element (FE) simulation software to adequately predict the outcome of sheet metal forming processes is crucial to enhancing the efficiency and lowering the development time of such processes, whilst reducing costs involved in trial-and-error prototyping. Recent focus on the substitution of steel components with aluminum alloy alternatives in the automotive and aerospace sectors has increased the need to simulate the forming behavior of such alloys for ever more complex component geometries. However these alloys, and in particular their high strength variants, exhibit limited formability at room temperature, and high temperature manufacturing technologies have been developed to form them. Consequently, advanced constitutive models are required to reflect the associated temperature and strain rate effects. Simulating such behavior is computationally very expensive using conventional FE simulation techniques. This paper presents a novel Knowledge Based Cloud FE (KBC-FE) simulation technique that combines advanced material and friction models with conventional FE simulations in an efficient manner thus enhancing the capability of commercial simulation software packages. The application of these methods is demonstrated through two example case studies, namely: the prediction of a material's forming limit under hot stamping conditions, and the tool life prediction under multi-cycle loading conditions
Finite element simulation of semi-finishing turning of Electron Beam Melted Ti6Al4V under dry and cryogenic cooling
open6noIn the last few years, important step forwards have been made on Finite Element Simulation of machining operations. Wrought Ti6Al4V alloy has been deeply investigated both numerically and experimentally due to its wide application in the industry. Recently, Additive Manufacturing technologies as the Electron Beam Melting and the Direct Melting Laser Sintering are more and more employed in the production of biomedical and aeronautical components made of Ti6Al4V alloy. Fine acicular microstructures are generated by the application of additive manufacturing technologies, affecting the mechanical properties and the machinability. By the consequence, this peculiarity has to be considered in modelling the material behaviour. In this work, a numerical analysis of cylindrical external turning on Electron Beam Melted (EBM) Ti6Al4V alloy is presented. A Johnson-Cook constitutive equation was implemented as a flow stress model and adapted with respect to the wrought Ti6Al4V alloy. The model was calibrated and validated through the cutting forces and temperatures measurements acquired under dry and cryogenic lubricating conditions.openBordin, A; Imbrogno, S.; Rotella, G.; Bruschi, S.; Ghiotti, A.; Umbrello, D.Bordin, Alberto; Imbrogno, S.; Rotella, G.; Bruschi, Stefania; Ghiotti, Andrea; Umbrello, D
A mobile antineutrino detector with plastic scintillators
We propose a new type segmented antineutrino detector made of plastic
scintillators for the nuclear safeguard application. A small prototype was
built and tested to measure background events. A satisfactory unmanned field
operation of the detector system was demonstrated. Besides, a detailed Monte
Carlo simulation code was developed to estimate the antineutrino detection
efficiency of the detector.Comment: 23 pages, 11 figures; accepted for publication in Nuclear Instruments
and Methods in Physics Research
Logistic regression for simulating damage occurrence on a fruit grading line
Many factors influence the incidence of mechanical damage in fruit handled on a grading line. This makes it difficult to address damage estimation from an analytical point of view. During fruit transfer from one element of a grading line to another, damage occurs as a combined effect of machinery roughness and the intrinsic susceptibility of fruit. This paper describes a method to estimate bruise probability by means of logistic regression, using data yielded by specific laboratory tests. Model accuracy was measured via the statistical significance of its parameters and its classification ability. The prediction model was then linked to a simulation model through which impacts and load levels, similar to those of real grading lines, could be generated. The simulation output sample size was determined to yield reliable estimations. The process makes it possible to derive a suitable line design and the type of fruit that should be handled to maintain bruise levels within European Union (EU) Standards. A real example with peaches was carried out with the aid of the software implementation SIMLIN®, developed by the authors and registered by Madrid Technical University. This kind of tool has been demanded by inter-professional associations and grading lines designers in recent year
Mechanical Properties of Growing Melanocytic Nevi and the Progression to Melanoma
Melanocytic nevi are benign proliferations that sometimes turn into malignant
melanoma in a way that is still unclear from the biochemical and genetic point
of view. Diagnostic and prognostic tools are then mostly based on dermoscopic
examination and morphological analysis of histological tissues. To investigate
the role of mechanics and geometry in the morpholgical dynamics of melanocytic
nevi, we study a computation model for cell proliferation in a layered
non-linear elastic tissue. Numerical simulations suggest that the morphology of
the nevus is correlated to the initial location of the proliferating cell
starting the growth process and to the mechanical properties of the tissue. Our
results also support that melanocytes are subject to compressive stresses that
fluctuate widely in the nevus and depend on the growth stage. Numerical
simulations of cells in the epidermis releasing matrix metalloproteinases
display an accelerated invasion of the dermis by destroying the basal membrane.
Moreover, we suggest experimentally that osmotic stress and collagen inhibit
growth in primary melanoma cells while the effect is much weaker in metastatic
cells. Knowing that morphological features of nevi might also reflect geometry
and mechanics rather than malignancy could be relevant for diagnostic purpose
Advances in Repurposing and Recycling of Post-Vehicle-Application Lithium-Ion Batteries
Increased electrification of vehicles has increased the use of lithium-ion batteries for energy storage, and raised the issue of what to do with post-vehicle-application batteries. Three possibilities have been identified: 1) remanufacturing for intended reuse in vehicles; 2) repurposing for non-vehicle, stationary storage applications; and 3) recycling, extracting the precious metals, chemicals and other byproducts. Advances in repurposing and recycling are presented, along with a mathematical model that forecasts the manufacturing capacity needed for remanufacturing, repurposing, and recycling. Results obtained by simulating the model show that up to a 25% reduction in the need for new batteries can be achieved through remanufacturing, that the sum of repurposing and remanufacturing capacity is approximately constant across various scenarios encouraging the sharing of resources, and that the need for recycling capacity will be significant by 2030. A repurposing demonstration shows the use of post-vehicle-application batteries to support a semi-portable recycling platform. Energy is collected from solar panels, and dispensed to electrical devices as required. Recycling may be complicated: lithium-ion batteries produced by different manufacturers contain different active materials, particularly for the cathodes. In all cases, however, the collecting foils used in the anodes are copper, and in the cathodes are aluminum. A common recycling process using relatively low acid concentrations, low temperatures, and short time periods was developed and demonstrated
- …