In this report a phase locked loop (PLL) system for grid voltage phase tracking has been investigated. The grid voltage phase angle contains critical information for connecting a power plant, such as a wave energy converter, to the grid. A synchronous reference frame PLL system with PI-regulator gains calculated with the symmetrical optimum method has been designed and simulations in SIMULINK have been made. For ideal grid conditions the phase angle was tracked fast and accurate. For non-ideal conditions the phase angle was tracked but with less accuracy, due to slow dynamics of the system, but still within acceptable margins. In order to test this system further it has to be implemented in a control system and tested when connected to the grid.

The objective of this study is to investigate how the development regarding the short-term nominal interest rate in Portugal would have differed from that set by the ECB 1999-2011 in a situation where they did not enter the European Monetary Union. To do this, we use the Taylor rule, which incorporates economic activities such as inflation and output and how these deviates from their target. Constructing the Taylor rule, we estimate its reaction functions using an Ordinary Least Square Regression on annual data from the period 1988-1998. The reaction functions serve as weights on the deviations for inflation and output. The result reached is that the interest rate set by the ECB since 1999 is far below that interest rate required by the Portuguese economic situation. Further, we discuss how the influence in the setting of the ECB interest rate differs considering the member countries size.

This study defines the optimum route planning for Electric Transmission Lines by Multicriteria Decision Analysis which is based on Geographic Information Systems (GIS). Determination of the optimum route is performed by using both the spatial and Euclidean distances between two points located on the Earth&rsquo / s surface. The criteria needed to be taken into account to define the route of the Electrical Transmission Lines were evaluated with help of the experts who are doing this business in the available system and for this study the decision about the usage of needed data such as landuse map, landuse capability map, geology map, road map, zone plan and digital elevation models is also made with their knowledge. A Matlab code, which computes the optimum distance between two transformers by using real distance (spatial distance) method and by considering materials mentioned above is written. The results are compared with the ones found from the Euclidian distance, which is the common distance finding method in the available commercial GIS softwares. The spatial resolution effect in finding the spatial distance is also analyzed. The routes obtained by two different distance computation methods are compared with the existing route. The economical expectations in finding the optimum route are also discussed.

The steady-state natural convection from vertically placed rectangular fins is investigated numerically by means of a commercial CFD program called ICEPAK. The effects of geometric parameters of fin arrays on the performance of heat dissipation from fin arrays are examined. In order to simulate the different fin configurations and compare the results with literature, two experimental studies from literature are selected. Optimum fin spacing for both studies are found numerically and compared with experimental studies. The models are first verified by simulating natural convection on vertically placed flat plate and comparing the results with literature. After verification 30 different fin array configurations for the first experimental case study and 15 different fin array configurations for the second experimental case study from literature are analyzed. It is observed that the present results agree very well with the optimum fin spacing results of the experimental studies. It is also observed that the empirical correlations in the literature are conservative and the numerically obtained correlations predict higher heat transfer rates.

Carbothermic production of hexagonal BN by using boric acid and ground colemanite mined from Bigadi&ccedil / Region in Turkey was investigated by subjecting pellets prepared from B2O3, activated carbon and colemanite mixtures to nitrogen gas at 1500&deg / C. Similar to CaCO3 addition, colemanite addition to the B2O3-C mixtures resulted in higher amounts of h-BN in the final products. As a result of the experiments conducted with colemanite and CaCO3 additions providing the same quantity of CaO to the initial mixtures, similar amounts of hexagonal BN in the reaction products were observed. As a result of the experiments conducted with different compositions of colemanite- B2O3- C mixtures, 5 wt % colemanite addition was determined to be the optimum composition giving the highest amount of hexagonal BN in the reaction products. Increasing duration of the experiments increased the amount and particle size of h-BN formed in the products. Optimum amount of colemanite addition resulted in higher amounts and coarser particles of h-BN in the products than the optimum amounts of CaCO3 addition.

No description available.

No description available.

No description available.

No description available.

No description available.