Repository logo

Browsing by Issue Date, starting with "2019-06-14"

Filter results by year or month
Now showing 1 - 2 of 2
  • Utilization of non-conformal wheel surfaces for railway dynamics
    Publication . Marques, Filipe; Magalhães, Hugo; Pombo, João; Ambrosio, Jorge; Flores, Paulo
    The dynamic analysis of railway systems using multibody systems formulation is nowadays a reliable tool for several studies, in which the wheelrail contact interaction has significant importance. The definition of contacting geometries affects directly the dynamic response of the system. For sake of simplicity and computational efficiency, some authors simplify the wheel profile to avoid its concave part. This work intends to study the impact of utilizing a simplified non-conformal profile instead of a real wheel profile. For this purpose, an Hertzian-based contact force model is used to compute either the normal and creep forces. A wheelset rolling over a straight track is used as demonstration case. The results show that although the location of the contact points is similar, the use of simplified wheel profile may have an extensive impact on the dynamic response of the system.
    2019-06-14Conference object Restricted access Show more
  • Ball milling modified SAPO-11 based catalysts for n-Decane hydroisomerization
    Publication . Ferreira, Luisa; Ribeiro, Filipa; Fernandes, Auguste; Martins, Angela
    Bifunctional Pt/SAPO-11 catalysts were prepared using as acid matrix the microporous silico-aluminophosphate, SAPO-11, synthesized under microwave radiation. After synthesis, the material was physically modified using a ball mill, changing the grinding time but keeping frequency constant. The metal function (0.5 wt.% Pt) was introduced through mechanical mixture with commercial Pt loaded alumina. The catalysts were characterized by several techniques: powder X-Ray Diffraction, pyridine adsorption followed by infrared spectroscopy, low temperature N-2 adsorption, Hg intrusion porosimetry and electronic microscopy (SEM). The characterization data show modifications of structural and textural properties of the samples as the milling time increases. The catalytic behaviour of Pt/SAPO-11 materials was studied for hydroisomerization of long chain n-alkanes, using n-decane as model molecule, aiming to increase the production of mono-branched isomers. The catalytic results show that, under optimized milling conditions (60 min; 50 Hz) the selectivity into mono-branched isomers increased when compared with parent catalyst.
    2019-06-14Journal article Restricted access Show more