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Repositório IC-Online

Institution's Scientific Repository

 

IC-Online, the Institutional Repository of Scientific Information of the Polytechnic of Leiria (IPLeiria), is part of the RCAAP Project (Open Access Scientific Repositories of Portugal). Its main objectives are to organise, preserve and disseminate the scientific production of the Polytechnic of Leiria (IPLeiria), helping to increase the visibility and impact of the institution's scientific publications.

The IC-Online Repository includes various types of digital documents, such as articles from national and international scientific journals, papers from congresses and conferences, master's dissertations and doctoral theses, among others.

Email repositorio@ipleiria.pt

Recent Submissions

Heat inactivation of Listeria innocua in broth and food products under non-isothermal conditions
Publication . Miller, Fátima A.; Ramos, Bárbara F.; Gil, Maria M; Brandão, Teresa R.S.; Teixeira, Paula; Silva, Cristina L.M.
The objective of this work was to study the effect of three linear temperature profiles (heating rates of 1.5, 1.8 and 2.6 °C/min, from 20 to 65 °C) on Listeria innocua inactivation in liquid medium. The inactivation was also analyzed in artificially contaminated parsley (heating rate of 1.8 °C/min) and throughout a frying process, using a pre-cooked frozen food as case study. Inactivation showed a sigmoidal behaviour and all data was fitted with a Gompertz-inspired model. Results demonstrated that, in liquid media, Listeria inactivation is influenced by the temperature profile used. As heating rate increases, the shoulder decreases and the tail effect disappears. If Listeria was in parsley, its heat resistance increased (for identical experimental conditions in broth). Besides model adequacy was proven in all studied situations, the heating rate affected parameters’ precision.
2011-01Journal article Open access Show more
On the quantification of the controlling regimes in automotive catalytic converters
Publication . Santos, H.; Costa, M.
The conversion of pollutants in automotive catalytic converters is influenced by a number of physical and chemical processes that take place in the gaseous and solid phases as the exhaust gases flow through the converter. A detailed understanding of the complex processes involving flow dynamics, heat and mass transport and heterogeneous surface reactions is of crucial importance to improve the converter design. The main objective of the present study is to quantify the magnitudes of the external and internal mass transfer as well as chemical reaction limiting processes as a function of the converter operating temperature. To this end, experimental data, obtained for a three way catalyst (TWC) under real world operating conditions, are analyzed and compared against analytical expressions that allow for the quantification of the different limiting processes involved. The results demonstrate that (i) the external mass transfer resistance overlaps the reaction resistance only at moderate operating temperatures and not immediately above the ignition temperature as generally considered in the literature, (ii) the transport phenomena (external and internal mass transfer) represents 90% of the total resistance for temperatures higher than 792 K, (iii) the internal mass transfer in the porous washcoat presents a larger resistance than the external mass transfer from the bulk fluid to the washcoat wall even at high operating temperatures, and (iv) based on the quantification of the individual resistances as a function of the TWC operating temperature, it was demonstrated both the influence of the substrate cell density and of the effective diffusivity on the TWC conversions.
2010-12-03Journal article Open access Show more
Biomimetic composite coating on rapid prototyped scaffolds for bone tissue engineering
Publication . Arafat, M. Tarik; Lam, Christopher X.F.; Ekaputra, Andrew K.; Wong, Siew Yee; Li, Xu; Gibson, Ian
The objective of this present study was to improve the functional performance of rapid prototyped scaffolds for bone tissue engineering through biomimetic composite coating. Rapid prototyped poly(ε-caprolactone)/tri-calcium phosphate (PCL/TCP) scaffolds were fabricated using the screw extrusion system (SES). The fabricated PCL/TCP scaffolds were coated with a carbonated hydroxyapatite (CHA)-gelatin composite via biomimetic co-precipitation. The structure of the prepared CHA-gelatin composite coating was studied by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Compressive mechanical testing revealed that the coating process did not have any detrimental effect on the mechanical properties of the scaffolds. The cell-scaffold interaction was studied by culturing porcine bone marrow stromal cells (BMSCs) on the scaffolds and assessing the proliferation and bone-related gene and protein expression capabilities of the cells. Confocal laser microscopy and SEM images of the cell-scaffold constructs showed a uniformly distributed cell sheet and accumulation of extracellular matrix in the interior of CHA-gelatin composite-coated PCL/TCP scaffolds. The proliferation rate of BMSCs on CHA-gelatin composite-coated PCL/TCP scaffolds was about 2.3 and 1.7 times higher than that on PCL/TCP scaffolds and CHA-coated PCL/TCP scaffolds, respectively, by day 10. Furthermore, reverse transcription polymerase chain reaction and Western blot analysis revealed that CHA-gelatin composite-coated PCL/TCP scaffolds stimulate osteogenic differentiation of BMSCs the most, compared with PCL/TCP scaffolds and CHA-coated PCL/TCP scaffolds. These results demonstrate that CHA-gelatin composite-coated rapid prototyped PCL/TCP scaffolds are promising for bone tissue engineering.
2011-02Journal article Open access Show more
Destination Brand Experience: A Study Case in Touristic Context of the Peneda-Gerês National Park
Publication . Martins, Hugo; Carvalho, Paulo; Almeida, Nuno
Based on the scientific literature, this paper emphasises the destination brand experience (DBE) (multidimensional construct and second-order factor) in order to analyse the implications it plays regarding visitors’ satisfaction, their intentions to revisit and their intentions to recommend it. In terms of methodology, a confirmatory factor analysis was used to test the model and the research hypotheses. The sample was composed of 507 tourists who visited the Peneda-Gerês National Park in Northern Portugal. Results showed an acceptable fit. The items of each construct were very strong. Positive significant results were found for all the considered hypotheses, particularly regarding the association of sensory DBE and behavioural DBE (subdimensions of the DBE scale) with satisfaction. The sensory DBE and affective DBE subdimensions of the DBE scale were meaningfully associated with visitors’ intentions to recommend. Satisfaction was a strong mediator for sensory DBE impact on their intention to revisit and to recommend, and a less strong effect was found for satisfaction as a mediator for behavioural DBE impact on intentions to revisit and to recommend. The theoretical contribution of this study aimed to deepen the analysis of the DBE construct in its multidimensional aspect and its relationship with other constructs. The results are discussed in relation to their theoretical and practical relevance.
2021-10-20Journal article Open access Show more
An element enriched formulation for simulation of splitting failure
Publication . Dias-da-Costa, D.; Veludo, J.; Alfaiate, J.; Júlio, E.
Radial cracking propagation is often related to the bond transfer mechanism induced by slippage of a deformed bar. However, this failure pattern can also develop in other situations, namely: (i) concrete pipes submitted to an excessive inner pressure or (ii) concrete structures exposed to adverse environmental conditions under which corrosion or frost develops. In this paper a new contribution for the simulation of radial splitting failure is given. A discrete strong discontinuity formulation is presented which is fully capable of embedding radial discontinuities into axisymmetric finite elements. Numerical examples are used to show: (i) the capability of fully softening the applied inner pressure and (ii) mesh independence. Comparison with two published analytical approaches is performed for varying brittleness numbers. Finally, the model is applied to the simulation of both plain and reinforced concrete cylinders subjected to increasing inner pressure. A good agreement with experimental data is obtained.
2011-01Journal article Open access Show more