Surface energy changes produced by ultraviolet-ozone irradiation of poly(methylmethacrylate), polycarbone and polytetrafluoroethylene

Contact angles of water and methylene iodide were measured as a function of UV/O3 treatment time for three polymers: poly(methylmethacrylate) (PMMA), polycarbonate, and polytetrafluoroethylene (PTFE). Surface roughnesses were also measured. Surface free energies were then calculated using relationships developed by Kaelble and Neumann. The surface energy of polycarbonate was found to increase (60 percent) during UV/O3 treatment. However, calculations on PMMA were hampered by the formation of a water soluble surface product. On PTFE surfaces, the UV/O3 treatment etched the surface causing large increases in surface roughness, rendering contact angle measurements impossible. It is concluded that care must be taken in interpreting contact angle measurements and surface energy calculations on UV/O3 treated polymer surfaces

Prediction of RCF Damage on Underground Metro Lines

London Underground (LUL) is one of the largest metro networks in the world and carried nearly 1.5 billion passengers in 2015. This increasing passenger demand leads to higher axle loads and shorter headways in the railway operations. However, this has a detrimental impact on the damage generated at the wheel-rail interface. In spite of the advances in rolling stock and track engineering, new developments in material manufacturing methods and rail inspection technology, cracking in rails still remains a major concern for infrastructure managers in terms of safety and maintenance costs. In this study, field data from two metro lines on the LUL network was analysed to identify the distribution and severity of the different damage types. Detailed vehicle dynamics route simulations were conducted for the lines and the calculated wheel-rail forces were investigated to assess the applicability current models for the prediction of rail damage on metro lines. These models include the Whole Life Rail Model (WLRM), previously developed for Great Britain (GB) main line tracks, and Shakedown theory. The influence of key factors such as curve radius, different friction conditions, track irregularities and wheel-rail profiles on the wheel-rail contact interface have been evaluated and compared with outputs from simulations on mainline routes. The study found that the contact patch energy (Tγ) and the interaction between wear and RCF in rails were highly influenced by the characteristics of metro tracks. It was also shown that both the Tγ and Shakedown methods can provide successful prediction of damage susceptibility of rails. However, in order to increase the accuracy of damage predictions and to ascertain the severity of different damage types, the duty conditions which are observed by the rail and the changes in contact conditions resulting from the successive vehicle passes should be considered in the modelling

Reproductive performance of native and imported dairy cows in the Tadla region (Morocco)

Parmi les performances de reproduction des vaches laitières dans la région du Tadla (Maroc) sur une période de 4 années, l’âge à la première insémination artificielle (IA) a été de 573,4 ± 35,6 jours et à l’âge au premier vêlage de 853,8 ± 103,5 jours, l’intervalle vêlage-1ère IA de 75,5 ± 35,6 jours. Celui-ci a été plus court chez les femelles importées que chez les natives. La race Montbéliarde a été inséminée plus tôt que la race Prim’Holstein. Le taux de réussite en 1ère IA a été de 53,2% avec de larges variations inter-annuelles et inter-élevages. Les Prim’holstein ont été mieux fécondées que les autres races. 18,2% des vaches ont nécessité 3 IA ou plus et l’indice coïtal a été de 1,8 ±1,3. La campagne, l’élevage et la race ont affecté significativement le taux de femelles ayant nécessité 3 IA ou plus. La race Prim’holstein française a manifesté un taux inférieur à celui de la race Prim’holstein canadienne. L’intervalle vêlage - insémination fécondante a été de 119,2 ± 83,8 jours. Ce paramètre a varié très significativement selon l’année, l’élevage, la race et le numéro de lactation. La race Montbéliarde a présenté undélai moyen de fécondation plus court que la race Prim’Holstein Canadienne