Defect and Diffusion Forum Vols. 312-315

Abstract: Zinc oxide (ZnO) nanostructures with different kind of morphologies were synthesized on glass substrates via the hydrothermal aqueous chemical growth method utilizing c-axis oriented ZnO thin film as seeded catalyst. By preparing ZnO thin film at different molar concentrations between 0.2~1.0 M, oval shaped ZnO nanostructures mixed with ZnO nanowires and rod shaped ZnO nanostructures mixed with ZnO nanowires were produced after immersion process into 0.0002 M zinc nitrate solution for 24 hour. The XRD spectra show synthesized ZnO nanostructures were ZnO hexagonal wurtzite crystalline. The photoluminescence (PL) measurement indicates the luminescences of the samples were depending on the shapes of ZnO nanostructure.

Abstract: Nanostructured zinc oxide (ZnO) thin films were prepared through sol-gel method and spin-coating technique. ZnO thin films then were annealed at temperature of 350°C, 400°C, 450°C and 500°C. The thin films were characterized using field emission scanning electron microscope (FESEM), UV-VIS-NIR spectrophotometer and photoluminescence (PL) spectrofluorometer for morphology and optical properties study. The morphology study indicates that the particle size of ZnO increased with annealing temperatures. All thin films are optically transparent (~ 80 % in transmittance) in the visible light-NIR region. PL spectra reveal improved UV emission with annealing temperatures up to 500°C.

Abstract: This paper presents ongoing work for the definition of an optimal design strategy for retrofitting educational buildings. The term “optimal design” refers to the selection of different retrofitting solutions to ensure an energy efficient building that can be developed which will not compromise hygrothermal comfort, indoor air quality, health and durability. In this paper, a selection model of thermal insulation thickness of envelope elements is developed, aiming the control of surface condensation and upgrade of hygrothermal comfort. The mathematical formulation of this model leads to a nonlinear program with linear objective function. The software Gmas/Minos was chosen to solve the optimization problem and to develop a calculation program to solve this specific application. The software Energy-Plus developed by the US Department of Energy was used to simulate hygrothermal performance of the building, providing results for a comparison with the developed simulation tool. The paper presents an example of an optimal design problem for a specific classroom of a retrofit educational building.

Abstract: The physical and structural properties of cold-set whey protein isolate gels are largely influenced by the protein concentration and the denaturation conditions, namely temperature and holding time. In this work, we systematically varied the protein concentration, the temperature and holding time of denaturation in order to screen their impact on the resulting heat denatured whey protein isolate (HD-WPI) solution viscosity and gel elasticity. The gelation of the HD-WPI solutions was induced, at room temperature, through the addition of magnesium chloride. Based on the assumption that solution turbidity is associated with light scattered by protein aggregates, an aggregate concentration was computed for the HD-WPI solutions. For all experimental conditions, HD-WPI solution viscosities and gels Young modulus data fall, respectively, on two single curves when plotted against the computed aggregates concentration. Three concentration regimes corresponding to non gelling solutions, weak gels and strong gels could be identified. In this study was verified that cold-set gels produced upon addition of Mg2+ had a large spectrum of elastic properties.

Abstract: In this work the water vapour adsorption was studied, during the initial states of absorption, for different piles of granules held in a cylindrical container. A diffusion model was presented for the description of the physical phenomenon whereby water vapour penetrates along the piles of cylindrical pores. The differential mass balance equation was solved numerically using a finite-difference method. The numerical solutions were tested through the measurement of water vapour mass uptake for different piles of silica gel and breakfast cereals (popcorns), being observed that they are in good agreement with the experimental values.

Abstract: This paper describes the application of the cylindrical pore model to the study of water vapour adsorption in piles of spherical particles packed in cylindrical containers. The differential mass balance equations were solved numerically using a finite-difference method and the numerical solutions obtained were in good agreement with the experimental data. The experiments were carried out through the measurement of water vapour mass uptake for different piles of silica gel and popcorns (breakfast cereals).

Abstract: In the present work, three different mathematical models that can be applied to simulate the supercritical fluid extraction from herbaceous matrices were studied: Single-Sphere Model I (SS I), Single-Sphere Model II (SS II) and Characteristic Time Model (CTM). It was tested and compared the agreement between models results and available experimental data reported in literature.

Abstract: The coating of surfaces by plasma spraying is an important manufacturing process with many industrial applications. In the last several decades, numerical modeling of plasma spraying processes has met with considerable attention [1,2,3]. That is in order to well understand the complex phenomena the plasma spray involves, for economic constraints and to well predict the plasma-inflight-particles exchanges since this affects directly the coating formability and microstructure. This study deals with the investigation of plasma jets using an axisymmetric LB thermal model. Plasma jets have been very successful in many applications (such as spraying, cutting, welding,…). The excellent choice of high performance plasma gases and spraying materials has been the subject of several experimental and numerical efforts. An excellent choice will be the response of efficient numerical studies and the results of experimental tests. Plasma jets are high temperature flows (>8000K). Therefore, all diffusion parameters involved in conservation equations are temperature dependent. In the following, we present a plasma jet investigation in an axisymmetric LBM (Jian’s model [4]). In the context of our knowledge, it is the first attempt to tackle this field by using the LBM. Further reading on solution procedure, the model implementation and assumptions may be found in [5,6].

Abstract: The seepage analysis in geotechnical problems, namely in excavations, was typically performed assuming saturated conditions in the ground. It is now know that the flow in the non saturated part of the ground assumes also relevant importance and hence it is vital to characterize its behaviour. The Soil Water Characteristic Curve (SWCC) of the soil is probably the most important parameter in defining this behaviour and particularly for estimating the permeability of the soil. This paper presents the definition of the SWCC for a granite residual soil using pressure plates and the filter paper method. Based on experimental data some equations are adjusted and the results obtained are discussed. At the end of the paper some predictions of the non saturated permeability of the ground are also performed.

Abstract: We present the results of an experimental investigation of the evaporation of a liquid meniscus in a high aspect ratio micro-channel. The study investigates evaporation rates of a stationary liquid meniscus in a high aspect ratio microchannel, the wall of which is electrically heated using transparent resistive coating. Four different liquids are used as working fluids. We report on the dependence of the measured overall evaporation rate on the applied power. The results indicate, and consistently, that the evaporation rate increases with the applied power then peaks before declining. In order to gain insight into these results, we used thermographic infra red imaging to map the temperature field on the external wall of the microchannel. The measurements show that there is a good correlation between the maximum in the evaporative rate and the onset of instabilities of the interface. These instabilities, to our mind, are induced by an increasing temperature gradient along the microchannel wall around the three phase contact line region. These instabilities are revealed by a high speed camera used to record the behaviour of the interface during evaporation.