It is well known that the layout of a large wind turbine cluster aects the energyoutput of the wind farm. The individual placement and distances betweenturbines will in uence the wake spreading and the wind velocity decit. Manyanalytical models and simulations have been made trying to calculate this, butstill there is a lack of experimental data to conrm the models. This thesis isdescribing the preparations and the execution of an experiment that has beenconducted using about 250 small rotating turbine models in a wind tunnel. Theturbine models were developed before the experiment and the characteristicswere investigated. The main focus was laid on special eects occurring in largewind turbine clusters, which were named Global Turbine Array Eects.It was shown that the upstream wind was little aected by a large windfarm downstream, even though there existed a small dierence in wind speedbetween the undisturbed free stream and the wind that arrived to the rstturbines in the wind farm. The dierence in wind speed was shown to beunder 1% of the undisturbed free stream. It was also shown that the densityof the wind farm was related to the reduced wind velocity, with a more densefarm the reduction could get up to 2.5% of the undisturbed free stream at theupstream center turbine. Less velocity decit was observed at the upstreamcorner turbines in the wind farm.When using small rotating turbine models some scaling requirements hadto be considered to make the experiment adaptable to reality. It was concludedthat the thrust coecient of the turbine models was the most important parameterwhen analysing the eects. One problem discussed was the low Reynoldsnumber, an eect always present in wind tunnel studies on small wind turbinemodels.A preliminary investigation of a photo measuring technique was also performed,but the technique was not fully developed. The idea was to take oneor a few photos instantaneously and then calculate the individual rotationalspeed of all the turbine models. It was dicult to apply the technique becauseof uctuations in rotational speed during the experiment, therefore thecalculated values could not represent the mean value over a longer time period.

In this work we have prepared Si and SI(1-X)GE(X) nanocrystals by rf magnetron cosputtering method. The eect of annealing parameters and Ge content of x on the structural and optical properties sandwiched SiO2/SiO2: Si: Ge/SiO2 nanostructures have been investigated. For characterization we have used cross-sectional high resolution electron microscope (HREM), X-ray diraction (XRD), Raman spectroscopy (RS), Fourier transform infrared (FTIR), photoluminescence (PL), and temperature dependent PL (TDPL) techniques. It was shown that Ge content of x, annealing temperature, and annealing time are important parameters aecting the structural and optical properties of the nanocrystals. We have observed a uniform SI(1-X)GE(X) nanocrystal formation upon annealing at relatively low temperatures and short annealing time. However, Ge-rich SI(1-X)GE(X) nanocrystals do not hold their compositional uniformity when annealed at high temperatures for enough long time. A segregation process leads to the separation of Ge and Si atoms from each other and formation of Si-rich core covered by a Ge-rich shell. Related to the optical properties of Si and SI(1-X)GE(X) nanocrystals, influence of annealing treatments and Ge content of x on the simultaneous observation and relative contribution of quantum confined and interface related radiative emission to PL spectra are investigated. On the other hand, temperature dependent photoluminescence (TDPL) measurements have been applied to investigate in detail the involving PL mechanisms and the competing thermally activated emission process and the thermally activated escape process of carriers into nonradiative recombination centers and/or tunneling of the excitons into the interface or to larger nanocrystals.

Membrane structures are commonly used in many elds. The studies of thesestructures are of increasing interest. The two projects focus on the evaluations ofequilibrium states for uid-pressurized membranes under dierent loading conditions,and the corresponding instability behavior.The rst part of the current work discusses the instability behavior of a thin,planar, circular and initially horizontal membrane subjected to downwards or upwards uid pressure. The membrane structures exhibit large deformations under uid pressure. Various instability behaviors have been observed for dierent loadingparameters. Limit and bifurcation points have been detected for dierent loadingconditions. Dierent loading parameters have been used to interpret the instabilitybehavior. The eects on instability of parameters, the initial states of the membrane,and the chosen mesh have been discussed.The second part of the current work discusses instability behavior of a thin,spherical and closed membrane containing gas and uid placed on a horizontal rigidand non-friction plane. A multi-parametric loading has been described. By addingthe practically relevant controlling equations, the complex equilibrium paths werefollowed using the generalized path following algorithm, and the stability conclusionswere made dierently, according to the considered load parameters and theconstraints. A generalized eigenvalue analysis was used to evaluate the stabilitybehavior including the constraint eects. Fold line evaluations were performed toanalyze the parametric dependence of the instability behavior. A solution surfaceapproach was used to visualize the mechanical response under this multi-parametricsetting. / <p>QC 20151029</p>