Evaluating pixel and object based image classification techniques for mapping plant invasions from UAV derived aerial imagery : Harrisia pomanensis as a case study

Invasive alien plants (IAPs) not only pose a serious threat to biodiversity and water resources but also have impacts on human and animal wellbeing. To support decision making in IAPs monitoring, semi-automated image classifiers which are capable of extracting valuable information in remotely sensed data are vital. This study evaluated the mapping accuracies of supervised and unsupervised image classifiers for mapping Harrisia pomanensis (a cactus plant commonly known as the Midnight Lady) using two interlinked evaluation strategies i.e. point and area based accuracy assessment. Results of the point-based accuracy assessment show that with reference to 219 ground control points, the supervised image classifiers (i.e. Maxver and Bhattacharya) mapped H. pomanensis better than the unsupervised image classifiers (i.e. K-mediuns, Euclidian Length and Isoseg). In this regard, user and producer accuracies were 82.4% and 84% respectively for the Maxver classifier. The user and producer accuracies for the Bhattacharya classifier were 90% and 95.7%, respectively. Though the Maxver produced a higher overall accuracy and Kappa estimate than the Bhattacharya classifier, the Maxver Kappa estimate of 0.8305 is not significantly (statistically) greater than the Bhattacharya Kappa estimate of 0.8088 at a 95% confidence interval. The area based accuracy assessment results show that the Bhattacharya classifier estimated the spatial extent of H. pomanensis with an average mapping accuracy of 86.1% whereas the Maxver classifier only gave an average mapping accuracy of 65.2%. Based on these results, the Bhattacharya classifier is therefore recommended for mapping H. pomanensis. These findings will aid in the algorithm choice making for the development of a semi-automated image classification system for mapping IAPs.The South African National Department of Environment Affairs through its funding of the South African National Biodiversity Institute Invasive Species Programme, project number P038.http://www.elsevier.com/ locate/ isprsjprs2018-07-30hj2018Geography, Geoinformatics and Meteorolog

Manufacturability improvements of high frequency transformers

M.Ing. (Electrical and Electronic Engineering)In order to improve the industrialisation of modern power converters, its physical size must be reduced, material must be utilised more efficiently and its manufacturability improved. Consequently, many converters are operated in the ultrasonic frequency range, where the size of its constituent components are considerably reduced. Even at high frequencies of operation, however, magnetic components are still the largest and heaviest components in converters, and do not utilise materials to their maximum benefit. The aim of this work is to investigate the possibility of improving the industrialisation of power electronic converters by making use of a novel, multiple core magnetic component structure, called the distributed transformer. Existing magnetic component structures are evaluated from a materials point of view and the concept of distributed magnetic components introduced. A generalised transformer model is developed for the distributed transformer and pertinent design considerations discussed. A 1.5 kw battery charger industrialised by Spoornet is based on the CukDC-DC converter and is used as a case study. A conventional monolithic isolation transformer is used in its construction after a complete mathematical analysis of the converter topology, and compared with the equivalent distributed transformer configuration. The distributed transformer is then compared with the conventional monolithic transformer and evaluated in terms of its physical and electrical performance, design and ease of manufacture

The effect of vasodilatation as obtained by lumbar sympathectomy on the growth of bones in normal young animals

The effect of changes in the circulation of blood on the metabolism of bone in general is well known to surgeons. The bones adjacent to an acute inflammatory process may share in the regional hyperaemis and undergo considerable osteoporosis. One of the most notable examples of this process has been observed in the upper cervical vertebrae in association with acute inflammatory lesions of the pharnyx and of the glands in the neck which may lead to osteoporosis of such a degree as to produce spontaneous fracture of a vertebra

Die amp van die evangelis in die Ned. Gerf. Kerk

Verhandeling (B. Th.) -- Universiteit van Stellenbosch, 1990.Full text to be digitised and attached to bibliographic record