Searching an information is essential part of the Internet today. There are many algorithms and methods for effective web search engines, where the results are more or less relevant. Web pages for better visibility and usability use SEO techniques which improve final query results. The result of this work is full-text web search engine for images and texts. Aim of this work is to make introduction to knowledge of the web search engines and provide own design of web search indexing architecture which will be used for futher educational process.

In this paper is presented the 3D model of Chua's circuit boundary surfaces. This represents the boundary between the two attractors - chaos and a stable limit cycle. In the first part is described short history of Chua’s circuit and sequential circuits boundary surface modelling and visualization. Second part describes 3D modeling of boundary surface. Three dimensional model of boundary surface is created by appropriate combination lot of 2D cross-sections in surface u1=const using triangulation. The modelling and visualization of boundary surface represents modelling and visualization of large graphical data set and is timeconsuming process.

This paper presents a simplified control scheme for three-phase three-level series active power filter to compensate all load voltage perturbations such us harmonic unbalances, sags and swells. The standard configuration of three-phase series active power filter uses the two-level three-phase voltage source inverter with hysteresis controller. This configuration presents some drawbacks and is limited to low power systems. Today three-level (NPC) inverter is one of the most successfully employed topology in various industrial applications. In this paper a new scheme to increase the capability of series Active Power Filter (APF) voltage controller based on three-level inverter using simplified Pulse Width Modulation (PWM), is proposed. The control strategy adopted use instantaneous reactive power theory, easy to implement and gives good performance for all load voltage perturbations. The numerical simulation results carried with MATLAB-Simulink and SimPowerSystem Toolbox show the effectiveness of the proposed control scheme.