Search results for "Mechanical engineering"
showing 10 items of 4245 documents
Evidence for long-lived, optically generated quenchers of excitons in single-walled carbon nanotubes.
2011
The nonlinear dependence of near-infrared photoluminescence (PL) emission on excitation intensity has been measured for individual nanotubes representing six different (n,m) species. Significant deviations from linearity are observed for intensities as low as ~100 W/cm(2), and an approximate inverse correlation is found between nonlinearity and PL action cross section (brightness). A model in which all PL nonlinearity arises from exciton-exciton annihilation is insufficient to account for the experimental data using realistic parameters. It is proposed that additional nonlinear quenching arises from photoinduced quenching states or species with longer lifetimes than emissive excitons. Evide…
Lit environments quality: A software for the analysis of luminance maps obtained with the HDR imaging technique
2013
Abstract Energy performance of lighting systems has assumed a significant role in the assessment of buildings’ consumptions and consequently lighting design is aimed to reduce installed power but at the same time to achieve an excellent lighting quality both for visual and health purposes. Lighting design is nowadays essentially based on illuminance values on visual tasks and surrounding areas, but today designers’ and researchers’ interest is focused on the analysis of luminance maps obtained through video luminance meters or with numeric simulation tools. Luminance maps availability focus the attention on a more accurate study of the light reaching the eyes (luminance), rather than on the…
Surface water RO permeate remineralization through minerals recovery from brines
2022
Assisted-Reverse Electrodialysis (A-RED) technology was applied following reverse osmosis (RO) of a surface water resource in order to recover minerals from its brine and directly remineralize the RO unit's permeate. Four different sets of cation/anion exchange membranes were benchmarked using single- and mixed-salts synthetic solutions as well as real brine and permeate streams produced from three-stage reverse osmosis applied to Seine River water. The process, operating under equal permeate and brine channel flows (2 cm/s velocities) and applied voltage varying from 0 to 10 V, showed viable remineralization results. Optimal recovery at 10 V applied allowed increasing permeate mineral cont…
Effect of operating conditions and feedstock composition on the properties of manganese oxide or quartz charcoal pellets for the use in ferroalloy in…
2020
peer-reviewed The full text of this article will not be available until the embargo expires on the 26/12/2021 This study investigates the effect of heat treatment temperature on the properties of charcoal composite pellets used for the reduction of ferroalloys. The heavy fraction of biooil was used as a binder for the charcoal ore pellet preparation. The effect of heat treatment temperature on the pellet shrinkage was related to the degree of reduction which varied with feedstock and ore composition. The results showed that the size and shape of the charcoal pellets were not affected by the biooil devolatilization. Manganese charcoal pellets showed higher electrical resistance during pyroly…
Scanning electron microscopy characterization of ZnSe single crystals grown by solid-phase recrystallization
2000
ZnSe single crystals were grown from n-type microcrystalline boules by a Solid Phase Recrystallization (SPR) method. The recrystallizations were performed under different atmospheres, Ar or Se, and pressures to investigate the influence of growth conditions on the structural features of the resulting crystals. The samples were mechanically and mechano-chemically polished in a bromine methanol solution and, then, etched in HCl for a short time, before characterization. The homogeneity and the nature of defects in the crystals were studied by Cathodoluminescence (CL) in the scanning electron microscope (SEM). CL measurements show the existence of slip bands in the recrystallized samples, like…
Buckling and nonlinear dynamics of elastically coupled double-beam systems
2016
Abstract This paper deals with damped transverse vibrations of elastically coupled double-beam system under even compressive axial loading. Each beam is assumed to be elastic, extensible and supported at the ends. The related stationary problem is proved to admit both unimodal (only one eigenfunction is involved) and bimodal (two eigenfunctions are involved) buckled solutions, and their number depends on structural parameters and applied axial loads. The occurrence of a so complex structure of the steady states motivates a global analysis of the longtime dynamics. In this regard, we are able to prove the existence of a global regular attractor of solutions. When a finite set of stationary s…
A numerical solution that determines the temperature field inside phase change materials: application in buildings
2013
The use of novel building materials that contain active thermal components would be a major advancement in achieving significant heating and cooling energy savings. In the last 40 years, Phase Change Materials or PCMs have been tested as thermal mass components in buildings, and most studies have found that PCMs enhance the building energy performance. The use of PCMs as an energy storage device is due to their relatively high fusion latent heat; during the melting and/or solidification phase, a PCM is capable of storing or releasing a large amount of energy. PCMs in a wall layer store solar energy during the warmer hours of the day and release it during the night, thereby decreasing and sh…
Vegetation growth parameters and leaf temperature: Experimental results from a six plots green roofs' system
2016
Abstract The paper provides a contribution for populating database of three physical parameters needed to model energy performance of buildings with green roofs: “coverage ratio” ( σ f ), leaf area index (LAI) and leaf temperature ( T f ). On purpose, six plant species were investigated experimentally: Phyla nordiflora, Aptenia lancifolia , Mesembryanthenum barbatus , Gazania nivea, Gazania uniflora , and Sedum . Proper ranges of the cited parameters have been found for each species. The here indicated ranges of σ f values refer to different growth levels of the species in the same lapse of time, that is four months. Single measured LAI values are also reported for the same plants. As for t…
Impact of building automation control systems and technical building management systems on the energy performance class of residential buildings: An …
2014
Abstract The paper focuses on the evaluation of the impact on residential buildings of building automation control (BAC) and technical building management (TBM) systems. This work shows how the control, monitoring and automation functions considered by the European Standard EN 15232 can considerably influence the energy performance of a single-family test house and, consequently, its energy performance class. The study puts into evidence that the benefit that can be drawn from the installation of BAC and TBM systems depends on the type of technical appliances in the household and on the starting energy performance class. Finally, the economic impact due to the introduction of BACS or TBM fu…
On the hyperporous non-linear elasticity model for fusion-relevant pebble beds
2010
Abstract Packed pebble beds are particular granular systems composed of a large amount of small particles, arranged in irregular lattices and surrounded by a gas filling interstitial spaces. Due to their heterogeneous structure, pebble beds have non-linear and strongly coupled thermal and mechanical behaviours whose constitutive models seem limited, being not suitable for fusion-relevant design-oriented applications. Within the framework of the modelling activities promoted for the lithiated ceramics and beryllium pebble beds foreseen in the Helium-Cooled Pebble Bed breeding blanket concept of DEMO, at the Department of Nuclear Engineering of the University of Palermo (DIN) a thermo-mechani…