This work presents an investigation of a piezoelectric sensor based energy harvesting system, which collects energy from the surrounding environment. Increasing costs and scarcity of fossil fuels is a great concern today for supplying power to electronic devices. Furthermore, generating electricity by ordinary methods is a complicated process. Disposal of chemical batteries and cables is polluting the nature every day. Due to these reasons, research on energy harvesting from renewable resources has become mandatory in order to achieve improved methods and strategies of generating and storing electricity. Many low power devices being used in everyday life can be powered by harvesting energy from natural energy resources. Power overhead and power energy efficiency is of prime concern in electronic circuits. In this work, an energy harvester is modeled and simulated in Simscape™ for the functional analysis and comparison of achieved outcomes with previous work. Results demonstrate that the harvester produces power in the 0 μW to 100 μW range, which is an adequate amount to provide supply to low power devices. Power efficiency calculations also demonstrate that the implemented harvester is capable of generating and storing power for low power pervasive applications.

Long delays between harvesting and crushing of sugarcane lead to excessive deterioration in the quality of sugarcane. The aim of this project was to develop a computer based model of sugarcane harvesting and delivery systems that could be used to investigate methods of reducing harvest-to crush delays. A literature review was conducted and simulation modelling was chosen as the most appropriate modelling technique for the situation of sugarcane harvesting and delivery and the purposes of this project. The Arena modelling system was chosen as the simulation software with which to construct the model. A model was developed on the scale of a particular sugar mill and the area of farms supplying it with cane. The Sezela mill on the south coast of KwaZulu-Natal, South Africa was chosen as a case study on which to develop and test the model. The model integrated a harvesting and transport section which represented all the individual farms or combinations of farms in the area with a millyard section. After the model had been verified and validated, it was used to investigate the effect of a number of different scenarios of harvesting and delivery systems and schedules on harvest-to-crush delays in the Sezela mill area. The results of the experimental runs performed with the model indicated that the most significant decreases in harvest-to-crush delays could be brought about by matching harvesting, delivery and milling cycles as closely as possible. It was also evident that burn-to-cut delays where daily burning is not practised constitute a large proportion of overall harvest-to crush delays. The model proved to be useful in making comparisons between systems and in providing a holistic view of the problem of harvest-to-crush delays. Recommendations for future developments of the model include adding a mechanical harvesting component and making the model more easily applicable to other mill areas. / Thesis (M.Sc.Eng.)-University of Natal, 1998.

Au cours des dernières décennies, la popularité des plantes médicinales s’est accrue auprès des civilisations occidentales de sorte que la quantité de plantes récoltées, la plupart provenant de populations sauvages, a grandement augmenté. Dans ce contexte, l’objectif principal de mon mémoire est d’évaluer l’impact de la récolte de deux plantes médicinales (Sarracenia purpurea et Rhododendron groenlandicum) utilisées par la Nation Crie du Nord du Québec. Pour y parvenir, des parcelles expérimentales, simulant différentes intensités de récolte (S. purpurea) et différentes méthodes de récolte (R. groenlandicum), ont été mises en place, puis des suivis annuels de la reprise ont été réalisés. Les résultats obtenus suggèrent que les techniques de récolte chez R. groenlandicum devraient exclure les nouvelles pousses, leur exploitation causant une forte mortalité. Par ailleurs, chez S. purpurea, la récolte de 20 % des individus semble peu dommageable, mais critique lorsque plus de 50 % des plants sont récoltés. Un modèle démographique pour S. purpurea a aussi été construit à partir des observations de terrain. Ce modèle a permis de réaliser des projections temporelles en variant les taux de récoltes ainsi que les intervalles entre les récoltes. Les résultats indiquent qu’une récolte de 20 % des individus est acceptable une fois tous les 20 ans. Pour une récolte plus régulière, 5 % tous les trois ans serait soutenable. Mon projet permettra d’assurer une exploitation soutenable de deux plantes médicinales ayant un grand potentiel pour le traitement du diabète de type II. / Over the past few decades, the popularity and use of medicinal plants have increased in Western civilisation. Consequently, harvesting plants from wild populations has increased. Using this perspective, the principal goal of my thesis is to assess the impact of harvest on two medicinal plants (Sarracenia purpurea and Rhododendron groenlandicum) used by the Cree Nation of Northern Québec. To achieve my goal, the simulation of four harvesting intensities (S. purpurea) and of two harvesting methods (R. groenlandicum) were setup in experimental plots and an annual follow up were conducted on establishment and growth. Results show that harvesting methods used on R. groenlandicum should exclude new shoots, since their exploitation results in high mortality rates. For S. purpurea, harvesting of individuals does not seem harmful under 20% of harvest, but is critical when 50% or more are collected. Furthermore, a matrix population model of S. purpurea demography was built from field observations. This model was used to simulate population projection in time under different levels of harvest when varying the number of years between harvests. These results demonstrate that collecting 20% of individuals should be done only once every 20 years to remain sustainable. A more efficient and regular harvest of 5% every three years would be sustainable. My project allowed defining acceptable levels of harvest in order to insure sustainable exploitation of two Cree medicinal plants bearing interesting potential for treating type II diabetes related symptoms.

Au cours des dernières décennies, la popularité des plantes médicinales s’est accrue auprès des civilisations occidentales de sorte que la quantité de plantes récoltées, la plupart provenant de populations sauvages, a grandement augmenté. Dans ce contexte, l’objectif principal de mon mémoire est d’évaluer l’impact de la récolte de deux plantes médicinales (Sarracenia purpurea et Rhododendron groenlandicum) utilisées par la Nation Crie du Nord du Québec. Pour y parvenir, des parcelles expérimentales, simulant différentes intensités de récolte (S. purpurea) et différentes méthodes de récolte (R. groenlandicum), ont été mises en place, puis des suivis annuels de la reprise ont été réalisés. Les résultats obtenus suggèrent que les techniques de récolte chez R. groenlandicum devraient exclure les nouvelles pousses, leur exploitation causant une forte mortalité. Par ailleurs, chez S. purpurea, la récolte de 20 % des individus semble peu dommageable, mais critique lorsque plus de 50 % des plants sont récoltés. Un modèle démographique pour S. purpurea a aussi été construit à partir des observations de terrain. Ce modèle a permis de réaliser des projections temporelles en variant les taux de récoltes ainsi que les intervalles entre les récoltes. Les résultats indiquent qu’une récolte de 20 % des individus est acceptable une fois tous les 20 ans. Pour une récolte plus régulière, 5 % tous les trois ans serait soutenable. Mon projet permettra d’assurer une exploitation soutenable de deux plantes médicinales ayant un grand potentiel pour le traitement du diabète de type II. / Over the past few decades, the popularity and use of medicinal plants have increased in Western civilisation. Consequently, harvesting plants from wild populations has increased. Using this perspective, the principal goal of my thesis is to assess the impact of harvest on two medicinal plants (Sarracenia purpurea and Rhododendron groenlandicum) used by the Cree Nation of Northern Québec. To achieve my goal, the simulation of four harvesting intensities (S. purpurea) and of two harvesting methods (R. groenlandicum) were setup in experimental plots and an annual follow up were conducted on establishment and growth. Results show that harvesting methods used on R. groenlandicum should exclude new shoots, since their exploitation results in high mortality rates. For S. purpurea, harvesting of individuals does not seem harmful under 20% of harvest, but is critical when 50% or more are collected. Furthermore, a matrix population model of S. purpurea demography was built from field observations. This model was used to simulate population projection in time under different levels of harvest when varying the number of years between harvests. These results demonstrate that collecting 20% of individuals should be done only once every 20 years to remain sustainable. A more efficient and regular harvest of 5% every three years would be sustainable. My project allowed defining acceptable levels of harvest in order to insure sustainable exploitation of two Cree medicinal plants bearing interesting potential for treating type II diabetes related symptoms.