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Oscillations with a period of two Cr monolayers were measured in the antiferromagnetic exchange coupling between Fe magnetizations separated by Cr. The coupling was measured on a sample consisting of a Au(20 A)/Fe(50 A)/Cr(0-18 A wedge) film deposited by a molecular-beam epitaxy on a Fe[lOO] single-crystal "whisker." The Cr and Fe grew monolayer by monolayer as monitored by reflection high-energy-electron diff'raction. The coupling was determined from the magneto-optic Kerr effect. It was antiferromagnetic for 5-18 A Cr with four strong peaks and a maximum value of -0.60 mJ/m^ for eight monolayers of Cr.

a b s t r a c tBuilding Integrated and Building Attached Photovoltaic (BIPV, BAPV) systems may suffer from lower performance than predicted as a result of not considered partial shading. New system architectures have been proposed to optimize performance. The common approach of these new architectures is to track the Maximum Power Point (MPP) of every solar module individually. A simulation model is developed to quantify the benefits and drawbacks of different PV system architectures. The model includes a shading evaluation of the installation with means of 3D modeling, irradiance calculations, PV cell modeling and finally an empirical power conversion model. The energy yield of three leading architectures is confirmed (string inverter, power optimizer, micro inverter) for clear and partial shading conditions by means of an outdoor field test. Results with the irradiance profile of the Netherlands show that the string inverter system outperforms MLPE in 2 out of 3 partial shading scenarios that were evaluated in this study. It is found that the energy yield benefit of MLPE has a seasonal and latitude variation with the highest contribution during winter months. Additionally a study was performed to evaluate the energy yield at different irradiance profiles. Results show that there is a marginal benefit of the micro inverter system at higher irradiance locations when partial shading is present. The analysis method can be used by PV installers and system designer to determine which is the optimal system architecture for maximum energy yield especially when partial shading is present.

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