No description available.

The aim of the work described in this thesis was to investigate the hydrodynamic characteristics of two panel demersal trawls and to develop methods for predicting net drag and shape. The investigation started with a comprehensive analysis of existing data on net performance. Tentative prediction formulae for net performance were developed. The effects of groundgear, sweep length, buoyancy and net taper rate on the drag and shape were examined. Four experiments were then carried out to improve knowledge of the hydrodynamic characteristics of trawls. 1) Groundgear friction drag was measured for the three main types (bobbin, disc and rockhopper), with these parts rigged to have the same shape as in fishing conditions on both mud and sand; 2) The effect of buoyancy and wing spread on net drag and shape were investigated on five models nets having distinct differences in design in a flume tank; 3) Netting panel drag at low angles of attack (0o to 15o) was investigated. The effects of netting parameters (ie setting angle, Reynolds number, angle of attack, d/a ratio, solidity and so on), on the coefficient of drag based on twine area, were examined. The measurements significantly increased and improved knowledge of the hydrodynamic features of netting at low angles of attack; 4) Observations were made on flow through netting in a small flume tank, by measurement of velocity profiles and by visualisation. The velocity profiles at different positions showed the effects of setting angle, mesh type and angle of attack on water flow through the netting. Visualisation of flow through netting revealed details of the process of water flow. This study has provided a group of empirical equations to predict drag and shape and a sufficient data on groundgear friction and panel drag to enable analytical calculation of net drag with satisfactory accuracy.

The measured drag characteristics of a variety of cable fairings are reviewed and compared with those of bare cables. The effect of cable inclination angle has been studied and an empirical rule developed for dealing with faired cables, the hydrodynamic properties of which are shown to depend significantly on the section shape of the fairing. Non-dimensional cable functions are tabulated for both bare and faired cable profiles and applied to show how the addition of fairings can improve the towing performance of a given system. Simple formulae are developed for calculating faired cable system properties and for assessing the effect of fish drag.

The dynamic motion of floating wind turbines is studied using numerical simulations. Floating wind turbines in the deep ocean avoid many of the concerns with land-based wind turbines while allowing access to strong stable winds. The full three-dimensional Navier-Stokes equations are solved on a regular structured grid, using a level set method for the free surface and an immersed boundary method for the turbine platform. The tethers, the tower, the nacelle and the rotor weight are included using reduced order dynamic models, resulting in an efficient numerical approach which can handle nearly all the nonlinear wave forces on the platform, while imposing no limitation on the platform motion. Wind is modeled as a constant thrust force and rotor gyroscopic effects are accounted for. Other aerodynamic loadings and aero-elastic effects are not considered. Several tests, including comparison with other numerical, experimental and grid study tests, have been done to validate and verify the numerical approach. Also for further validation, a 100:1 scale model Tension Leg Platform (TLP) floating wind turbine has been simulated and the results are compared with water flume experiments conducted by our research group. The model has been extended to full scale systems and the response of the tension leg and spar buoy floating wind turbines has been studied. The tension leg platform response to different amplitude waves is examined and for large waves a nonlinear trend is seen. The nonlinearity limits the motion and shows that the linear assumption will lead to over prediction of the TLP response. Studying the flow field behind the TLP for moderate amplitude waves shows vortices during the transient response of the platform but not at the steady state, probably due to the small Keulegan-Carpenter number. The effects of changing the platform shape are considered and finally the nonlinear response of the platform to a large amplitude wave leading to slacking of the tethers is simulated. For the spar buoy floating wind turbine, the response to regular periodic waves is studied first. Then, the model is extended to irregular waves to study the interaction of the buoy with more realistic sea state. The results are presented for a harsh condition, in which waves over 17 m are generated, and linear models might not be accurate enough. The results are studied in both time and frequency domain without relying on any experimental data or linear assumption. Finally a design study has been conducted on the spar buoy platform to study the effects of tethers position, tethers stiffness, and platform aspect ratio, on the response of the floating wind turbine. It is shown that higher aspect ratio platforms generally lead to lower mean pitch and surge responses, but it may also lead to nonlinear trend in standard deviation in pitch and heave, and that the tether attachment points design near the platform center of gravity generally leads to a more stable platform in comparison with attachment points near the tank top or bottom of the platform.

Sistemas não-lineares podem apresentar um comportamento periódico, no qual o ponto de equilíbrio no diagrama de fase, quando se plota uma variável de estado versus outra variável de estado, é substituído por uma órbita circular, denominada ciclo limite. A estimação de parâmetros desses sistemas não é uma tarefa simples, devido a não convexidade do problema de otimização. A fim de estimar parâmetros em tais modelos, este trabalho propõe um método que quantifica o comportamento oscilatório do sistema em função do valor dos parâmetros, adicionando essa informação, na forma de uma penalidade à função objetivo do problema de otimização associado reduzindo a não convexidade do problema, conduzindo o modelo a produzir o comportamento oscilatório. Para avaliar a metodologia, primeiramente foi estudado o modelo de Jöbses et al. (1986), onde foi comparada metodologia proposta com abordagens disponíveis na literatura. A metodologia proposta também foi aplicada a modelos relativos à produção de petróleo offshore, onde foram considerados: o modelo simplificado de Meglio et al. (2009), com três estados dinâmicos, representando apenas a região do sistema pipeline/riser, o modelo estendido de Diehl et al. (2017), com seis estados dinâmicos, representando a dinâmica das regiões anular/tubing e pipeline/riser e, por fim, a aplicação real, onde foram estimados os parâmetros desse último modelo com os dados de planta de produção offshore de uma plataforma de petróleo nacional. Os resultados mostraram que o método proposto foi capaz de garantir o comportamento oscilatório, diferentemente das outras abordagens, reduzindo a não convexidade do problema de estimação e forçando o comportamento dinâmico do sistema a produzir o ciclo limite, mesmo quando a otimização fosse inicializada a partir de valores fora da região de ciclo limite. / Non-linear systems may present a periodic behavior, where the phase diagram equilibrium point, obtained by plotting a state variable versus another state variable, is replaced by a circular orbit called limit cycle. The parameters estimation in these systems is not an easy task due to the non-convexity of the optimization problem. In order to estimate parameters in these models, this work proposes a method that quantifies the system oscillatory behavior in function of the parameters values, adding this information in the form of a penality to the objective function of the associated optimization problem, reducing the non-convexity and leading the model to produce an oscillatory behavior. Firstly, to evaluate the methodology, it was studied the Jöbses et al. (1986) model, where the proposed methodology was compared to the approaches available in the literature. The methodology was also applied to models related to offshore oil production, where it was considered: the simplified Meglio et al. (2009) model, with three dynamical states, representing only the pipeline/riser region, the Diehl et al. (2017) extended model, with six dynamical states, representing the dynamics of the anular/tubing and pipeline/riser region and, lastly, to a real application, where the parameters were estimated with the Diehl et al. (2017) model using real data obtained from a national oil plataform. The results showed that the proposed approach was able to ensure the oscillatory behavior, differently of other approaches, reducing the non-convexity of the estimation problem and forcing the dynamical behavior of the system to produce the limit cycle, even when the optimization was initializated with values outside the region of the limit cycle.

Thesis (M.S.)--Massachusetts Institute of Technology, Alfred P. Sloan School of Management, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND DEWEY. / Includes bibliographical references. / by Dongwei Chen. / M.S.

No description available.

Pang Ho Yin, Dennis. / "Architecture Department, Chinese University of Hong Kong, Master of Architecture Programme 2010-2011, design report." / Includes bibliographical references (p. 55). / Chapter 00 --- Introduction / Chapter 0.1 --- Content --- p.0-1 / Chapter 0.2 --- Statement --- p.0-2 / Chapter 01 --- Fundamental issue / Chapter 1.1 --- Sea Water Level Rises / Chapter 1.1.1 --- Global Warming --- p.1-3 to 1-4 / Chapter 1.1.2 --- Sinking Cities / Chapter 1.1.2.1 --- Venice / Chapter 1.1.2.2 --- Amsterdam / Chapter 1.2 --- Reclamation Issues --- p.1-6 / Chapter 1.2.1 --- Area of reclamated Land in the world --- p.1-7 / Chapter 1.2.2 --- The Influence After Reclamation --- p.1-8 / Chapter 1.3 --- High Population in Coastal Cities / Chapter 1.3.1 --- Population Distribution in the world --- p.1-9 / Chapter 1.3.2 --- Limitation of the development of the coastal cities --- p.1-10 / Chapter 1.4 --- Attitude towards the Environment / Chapter 1.4.1 --- Not Rescue Project --- p.1-11 to 1-12 / Chapter 1.4.2 --- High Density to Low Density --- p.1-13 / Chapter 1.4.3 --- Slow Traffic/Mass Traffic instead of Private Traffic --- p.1-13 / Chapter 1.5 --- Case Study --- p.1-14 to 1-17 / Chapter 02 --- Research Study / Chapter 2.1 --- Urban Development Study / Chapter 2.1.1 --- Geometry / Chapter 2.1.1.1 --- Ideal Cases --- p.2-18 / Chapter 2.1.1.2 --- Real Cases --- p.2-19 / Chapter 2.1.1.3 --- Further Expansion --- p.2-20 / Chapter 2.1.1.4 --- Coastal Cities --- p.2-21 / Chapter 2.1.2 --- City Function / Chapter 2.1.2.1 --- Financial --- p.2-22 / Chapter 2.1.2.2 --- Tourism --- p.2-23 / Chapter 2.1.2.3 --- Low Density --- p.2-24 / Chapter 2.1.2.4 --- Coastal Cities --- p.2-25 / Chapter 2.1.3 --- Density Control --- p.2-26 / Chapter 2.1.3.1 --- New Town --- p.2-27 / Chapter 2.1.3.2 --- Green Belt --- p.2-28 / Chapter 2.1.4 --- City Transformation / Chapter 2.1.4.1 --- Reason --- p.2-29 / Chapter 2.1.4.2 --- Method --- p.2-30 / Chapter 2.1.4.3 --- Potential Site --- p.2-31 to 2-32 / Chapter 2.2 --- Comparing Cases / Chapter 2.2.1 --- Background information --- p.2-33 / Chapter 2.2.1.1 --- Area --- p.2-34 / Chapter 2.2.1.2 --- Populaion and density --- p.2-35 / Chapter 2.2.1.3 --- Land Use --- p.2-36 / Chapter 2.2.2 --- Living Style / Chapter 2.2.2.1 --- As A Leisure Land --- p.2-37 to 2-39 / Chapter 2.2.2.2 --- Transportation system --- p.2-40 / Chapter 03 --- Design Strategy / Chapter 3.1 --- Site Selection / Chapter 3.1.1 --- Conditon --- p.3-44 / Chapter 3.1.2 --- Land Use --- p.3-45 / Chapter 3.1.3 --- Other Approach / Chapter 3.1.3.1 --- Reclamation + Dam --- p.3-46 / Chapter 3.1.3.2 --- Moving to Higher Land/Inner Land --- p.3-47 / Chapter 3.1.3.3 --- Artificial Island --- p.3-48 / Chapter 3.1.4 --- Program --- p.3-49 / Chapter 3.2 --- Prelinimary Design / Chapter 3.2.1 --- Master layout plan --- p.3-50 to 3-52 / Chapter 3.2.2 --- Sectional Design --- p.3-53 to 3-54 / Chapter 04 --- Conclusion / Chapter 4.1 --- Conclusion and Expectation --- p.4-55 / Chapter 4.2 --- Reference --- p.4-56

Magister Commercii - MCom / 1. Taxes are an important source of government revenue (income). A failure by the government to collect sufficient taxes to cover for its ever increasing expenditures, engenders fiscal problems. Amongst others the government is compelled to borrow to finance its budget short fall. In this instance, should the government borrow domestically or offshore to finance its short fall . 2. Amongst the theories discussed in this paper, are the views of the Neoclassical Keynesian and the Ricardi an schools of thought. Further more, South African theories on government debt are also discussed. 3. There is a considerably large number of indicators that can be used to determine an appropriate level of both domestic and foreign debt of a country. Certain well establish criteria such as the ratio of foreign interest payments to exports, the ratio of foreign debt to gross domestic product, the ratio of·govemment debt to gross domestic product and the ratio of foreign debt to exports, are amongst the pool of indicators that can be used. However, the following indicators have been identified as the most commonly used in the analysis of budget deficits, and they are; ratio of deficit before borrowing and debt repayment to GDP, the ratio of government debt to GDP, the ratio of interest payments to government expenditure, the level of real interest rates relative to economic growth and the net asset value or net worth of the government. 4. Deficit financing refer to the ways in which the budgetary gap is financed. Overreliance on domestic borrowing may mean high real interest rates and falling investment, and overreliance on foreign borrowing can cause appreciating real exchange rates and unsustainable external indebtedness, amongst others. 5. Amongst the available remedies for debt ills in this country, is the suggestion to significantly cut government expenditure. However, realities currently confronting the authorities, like the increase in public servants as a result of the abolishment of homelands and the constitutionally guaranteed employment of civil servants from the old order, automatically put pressure on public consumption. 6. On the international front, South Africa is underborrowed. In this regard favour should go more for offshore borrowing. Certainly South Africa has to generate the means of meeting debt obligations by running a surplus of exports over imports of goods and services. The bulk of the country's debt is of domestic origin which account for well over 90 % of total debt. The current anti inflationary monetary policy with its concomitant high interest rates, makes domestic borrowing more costly.

L'énergie éolienne est une des composantes d'une politique énergétique permettant de réaliser un développement durable. Ces dernières années, des parcs éoliens offshore ont été installés. Ces parcs bénéficient d'un vent plus fort et plus régulier en mer que sur terre. Pour un choix judicieux des lieux d'implantation des parcs éoliens, il est nécessaire de disposer d'une cartographie du potentiel éolien. Ces cartes doivent être à haute résolution spatiale pour détecter les variations du potentiel à l'échelle d'un parc éolien. La cartographie du potentiel éolien se fait au travers de la description de la variation spatiale des paramètres statistiques caractérisant la climatologie du vent. Pour une estimation précise de ces paramètres statistiques, il est nécessaire d'avoir des mesures de vitesse et de direction du vent à haute résolution temporelle. Cependant, aucune source de données, actuelle, n'allie la haute résolution spatiale et la haute résolution temporelle. On propose une méthode de fusion de données permettant de tirer profit de la haute résolution spatiale de certains instruments de télédétection (les radars à ouverture synthétiques) et de la haute résolution temporelle d'autres instruments de télédétection (les radars diffusomètres). La méthode de fusion est appliquée à un cas d'étude et les résultats sont évalués. Les résultats montrent la pertinence de la fusion de données pour la cartographie du potentiel éolien offshore.