A method using a Fourier series is demonstrated to optimize an LED array for local dimming applications in liquid crystal display backlighting. The same optimization method is also suitable for LED displays in which the Moiré effect must be suppressed during photography with a minimum loss of spatial resolution. Initially, the angular intensity profile of a Lambertian LED is modelled when backlighting a Lambertian rear projection screen and compared to experimental data. An array of optimized LEDs and the resulting screen intensity pattern is then derived such that an intensity distribution with an intensity deviation of less than 2% is achieved. The angular intensity profile of the LED is modified using adjustable Fourier coefficients optimized according to an algorithm. The algorithm is designed to achieve an illuminated screen area of maximum size for a bounded LED backlight array to appear uniform in intensity to an observer. This Fourier series approach provides an elegant method to optimize the intensity profile of LED backlight arrays without the use of ray tracing. A lens was designed in order to provide this optimized intensity profile as well as created and tested. / Thesis / Master of Science (MSc)

The diploma thesis deals with the evaluation of the quality of customers using fuzzy logic based on the evaluation of their orders. The thesis consists of three parts. The first part is the theoretical basis of the thesis, which explains the issue of fuzzy logic. The second is the analytical part, in which the company ZKN METAL s.r.o. was introduced, for which a specific solution is subsequently proposed in the third and last part of the thesis. This solution is processed in the form of two models. The first of the models is processed in the MS Excel program and the second is modeled using the MATLAB programming environment. Both models are set in a user-intuitive environment and they are compared with each other afterwards.

The fabrication of low cost, high efficiency solar cells is imperative in competing with existing energy technologies. Many research groups have explored using III-V materials and thin-film technologies to create high efficiency cells; however, the materials and manufacturing processes are very costly as compared to monocrystalline silicon (Si) solar cells. Since commercial Si solar cells typically have efficiencies in the range of 17-19%, techniques such as surface texturing, depositing a surface-passivating film, and creating multi-junction Si cells are used to improve the efficiency without significantly increasing the manufacturing costs. This research focused on two of these techniques: (1) a tandem junction solar cell comprised of a thin-film perovskite top cell and a wafer-based Si bottom cell, and (2) Si solar cells with single- and double-layer silicon nitride (SiNx) anti-reflection coatings (ARC). The perovskite/Si tandem junction cell was modeled using a Matlab analytical program. The model took in material properties such as doping concentrations, diffusion coefficients, and band gap energy and calculated the photocurrents, voltages, and efficiencies of the cells individually and in the tandem configuration. A planar Si bottom cell, a cell with a SiNx coating, or a nanostructured black silicon (bSi) cell can be modeled in either an n-terminal or series-connected configuration with the perovskite top cell. By optimizing the bottom and top cell parameters, a tandem cell with an efficiency of 31.78% was reached. Next, planar Si solar cells were fabricated, and the effects of single- and double-layer SiNx films deposited on the cells were explored. Silicon nitride was sputtered onto planar Si samples, and the refractive index and thicknesses of the films were measured using ellipsometry. A range of refractive indices can be reached by adjusting the gas flow rate ratios of nitrogen (N2) and argon (Ar) in the system. The refractive index and thickness of the film affect where the minimum of the reflection curve is located. For Si, the optimum refractive index of a single-layer passivation film is 1.85 with a thickness of 80nm so that the minimum reflection is at 600nm, which is where the photon flux is maximized. However, using a double-layer film of SiNx, the Si solar cell performance is further improved due to surface passivation and lowered surface reflectivity. A bottom layer film with a higher refractive index passivates the Si cell and reduces surface reflectivity, while the top layer film with a smaller refractive index further reduces the surface reflectivity. The refractive indices and thicknesses of the double-layer films were varied, and current-voltage (IV) and external quantum efficiency (EQE) measurements were taken. The double-layer films resulted in an absolute value increase in efficiency of up to 1.8%.

Tato diplomová práce se zabývá vytvořením modelu signálu impedančního měření srdce (ICG signál). Impedanční kardiografie podává informaci o změně srdečního objemu během srdečního cyklu. Modelování signálu předchází statistická analýza vzájemné pozice ICG signálu vzhledem k dalším mechanickým srdečním signálům. Konstrukce modelu vychází z reálných nasnímaných signálů. Konečný ICG model je začleněn do již existujícího modelu mechanických interakcí mezi srdcem a plícemi. Výsledkem je funkční model kardio-respiračních interakcí, který bude sloužit v dalších částech výzkumu laboratoře PRETA.