Mixed-mode oscillations and slow manifolds in the self-coupled FitzHugh Nagumo system

We investigate the organization of mixed-mode oscillations in the self-coupled FitzHugh-Nagumo system. These types of oscillations can be explained as a combination of relaxation oscillations and small-amplitude oscillations controlled by canard solutions that are associated with a folded singularity on a critical manifold. The self-coupled FitzHugh-Nagumo system has a cubic critical manifold for a range of parameters, and an associated folded singularity of node-type. Hence, there exist corresponding attracting and repelling slow manifolds that intersect in canard solutions. We present a general technique for the computation of two-dimensional slow manifolds (smooth surfaces). It is based on a boundary value problem approach where the manifolds are computed as one-parameter families of orbit segments. Visualization of the computed surfaces gives unprecedented insight into the geometry of the system. In particular, our techniques allow us to find and visualize canard solutions as the intersection curves of the attracting and repelling slow manifolds. © 2008 American Institute of Physics

Efficient computation of quasiperiodic oscillations in nonlinear systems with fast rotating parts

We present a numerical method for the investigation of quasiperiodic oscillations in applications modeled by systems of ordinary differential equations. We focus on systems with parts that have a significant rotational speed. An important element of our approach is to change coordinates into a co-rotating frame. We show that this leads to a dramatic reduction of computational effort in the case that gravitational forces can be neglected. As a practical example we study a turbocharger model for which we give a thorough comparison of results for a model with and without gravitational forces

Extraction and accuracy assessment of DTMs derived from remotely sensed and field surveying approaches in GIS framework

© Published under licence by IOP Publishing Ltd. Generating a high precision continuous surface is a key capability required in most geographic information system (GIS) applications. In fact the most commonly used surface type is a digital elevation model (DEM). Recently, there are some sources of remote sensing data that provide DEM information such as; LiDAR, InSAR and ASTER GDEM which ranged from very high to low spatial resolution. However, new methods of topographic field surveying still highly on demand e.g. Differential GPS and Total station devices. In both method of capturing the terrain elevation the post processing need to be applied to create a continuous surface from point clouds. Geostatistical analysis were used to interpolate the taken sample points from site into continuous surface. In current research, we examined the height accuracy of LiDAR point clouds and total station dataset with three non-adoptive interpolation models including, invers distance weightage (IDW), nearest neighbour (NN) and radial basis function (RBF) based on referenced DGPS points. RMSE and R square regression analysis were conducted to reveal the most accurate approaches in pilot study area. The results showed Lidar surveying (less than 0.5 meter RMSE) has higher height accuracy compared to Total station surveying (above 1 meter in RMSE) to extract DTM in flat area; while consumed less computational processing time. Moreover, IDW was the best and accurate interpolation model in both datasets to generate raster cautious terrain model

Academic Performance of Less Endowed High School Students in the Kwame Nkrumah University of Science and Technology

This paper investigates the academic performance of students from less endowed senior high schools in the Kwame Nkrumah University of Science and Technology (KNUST). Questionnaires were administered to 152 (123 males and 29 females) fourth year students who enrolled for various programmes at KNUST in 2007 through the less endowed admission policy. The items included in the questionnaires were student characteristics (e.g. age, gender, university entrance score, number of siblings) and parental characteristics (e.g. educational attainments and occupation). We found that 61.8% were high performing students (11.8% first class and 50% second class upper). We also found that among the less endowed socio-economic group, university entrance score had a significant positive influence on their academic performance at 5% level of significance. Again, it was discovered that if parental factors were not controlled for, being male had a significant positive influence on the performance of less endowed students at 5% significance level. These findings have very important policy implications for Ghana, especially policies aimed at improving participation of students from less endowed schools in public universities.Keywords: Performance, less endowed, student, admission, universit