Direct Multi-grid Methods for Linear Systems with Harmonic Aliasing Patterns

Multi-level numerical methods that obtain the exact solution of a linear system are presented. The methods are devised by combining ideas from the full multi-grid algorithm and perfect reconstruction filters. The problem is stated as whether a direct solver is possible in a full multi-grid scheme by avoiding smoothing iterations and using different coarse grids at each step. The coarse grids must form a partition of the fine grid and thus establishes a strong connection with domain decomposition methods. An important analogy is established between the conditions for direct solution in multi-grid solvers and perfect reconstruction in filter banks. Furthermore, simple solutions of these conditions for direct multi-grid solvers are found by using mirror filters. As a result, different configurations of direct multi-grid solvers are obtained and studied

Development of flow focusing device for the visualization of leukocyte rolling adhesion

La microfluídica es un área de la microtecnología basada en chips de PDMS que está siendo utilizada cada vez más en multitud de aplicaciones. Una de estas aplicaciones es la investigación biomédica. La microfluídica o “Lab on a Chip” se ha convertido en una manera de realizar experimentos biomédicos y diagnósticos de una manera barata, rápida y eficaz. Cuando se realizan estudios sobre la extravasación leucocitaria utilizando chips microfluídicos, podemos observar la inconsistencia en la trayectoria de rodadura de los leucocitos debido a un flujo laminar. En este trabajo de fin de grado presentamos un método para centrar la interfaz de células en el centro de canal microfluídico. Cuando las células circulan por los sistemas microfluídicos, las células tienden a circular de manera aleatoria por los canales. Por tanto, con el sistema propuesto en este trabajo, dichas células serán redirigidas a la porción central del canal con el fin de recrear el fenómeno de rodadura presente en nuestro sistema circulatorio y así obtener información más detallada. Los resultados de este trabajo muestran la utilidad y la versatilidad de este dispositivo para experimentos relacionados

Practical Calculation of Expected and Unexpected Losses in Operational Risk by Simulation Methods

This paper explores the difficulties involved in quantitative measurement of operational risk and proposes simulation methods as a practical solution to obtain the distribution of total losses. It also introduces an example of the estimation of expected and unexpected losses, as well as Value-at-Risk (VaR), arising from operational risk.Operational risk; loss distribution; Value-at-Risk (VaR); simulation methods; Basel II

Evaluation of herb pastures for New Zealand dairy systems : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Sciences at Massey University, Manawatu, New Zealand

Chicory (Cichorium intybus L.) and plantain (Plantago lanceolata L.) sown in pure swards or both herbs sown with red clover (Trifolium pratense L.) and white clover (T. repens L.) are able to produce large amounts of high-quality forage in summer and autumn, when production and quality of perennial ryegrass (Lolium perenne L.) are often limited. There have been many cases of poor persistence of chicory with current management practices, but there is limited information for plantain and the herb-clover mix pastures when grazed in dairy systems. Additionally, the presence of bioactive compounds in plantain has created interest in their potential effect on rumen fermentation. The objectives of this research were to evaluate the effect of grazing frequency, two and four weeks, on the agronomic characteristics and diet selection of chicory, plantain, and herb-clover mix pastures, with dairy cows during two growing seasons (2011-2012; 2012-2013) and to examine the effect of the bioactive compounds in plantain on in vitro rumen fermentation. Chicory plants grazed every two weeks, rather than every four weeks, did not develop large taproots, and consequently stored less carbohydrate reserves (fructan and fructose) and failed to develop extra shoots. Chicory grazed every two weeks failed to persist, while chicory grazed every four weeks persisted only for the two growing seasons. For plantain the grazing frequency did not affect its plant density nor taproot diameter; however, the number of shoots per plant increased when grazed every two weeks compared to every four weeks. Overall, plantain and herb-clover mix pastures were more productive and persistent than chicory. The three pastures produced high-quality feed for dairy cows. Dairy cows preferred the herb-clover mix pasture, rather than pure chicory or plantain swards, and selected indiscriminately between chicory, plantain, and red clover. The diet selection for chicory and plantain varied between seasons and was affected by the vertical access and horizontal distribution of the species in the swards. The presence of bioactive compounds, aucubin and acteoside in plantain reduced the ammonia concentration during fermentation and probably causes less urea to be excreted in the cow‘s urine when grazing plantain. In conclusion, the herb-clover mix performed best due to its high herbage production and nutritive value and greater grazing preference by dairy cows, plus its potential to reduce the nitrogen lost from dairy systems