Most mineral and coal processing plants are forced to size their particulate streams in order to maximize the efficiency of their unit operations. Classifiers are generally considered to be more practical than screens for fine sizing, but the separation efficiency decreases dramatically for particles smaller than approximately 150 μm. In addition, classifiers commonly suffer from bypass, which occurs when a portion of the ultrafine particles (slimes) are misplaced by hydraulic carryover into the oversize product. The unwanted misplacement can have a large adverse impact on downstream separation processes. One method of reducing bypass is to inject water into the cyclone apex. Unfortunately, existing water injection systems tend to substantially increase the particle cut size, which makes it unacceptable for ultrafine sizing applications. A new apex washing technology was developed to reduce the bypass of ultrafine material to the hydrocyclone underflow while maintaining particle size cuts in the 25-50 m size range. Another method of reducing bypass is to retreat the cyclone underflow using multiple stages of classifiers. However, natural variations in the physical properties of the feed make it difficult to calculate the exact improvement offered by multistage classification in experimental studies. Therefore, several mathematical equations for multistage classification circuits were evaluated using mathematical tools to calculate the expected impact of multistage hydrocyclone circuits on overall cut size, separation efficiency and bypass. These studies suggest that a two-stage circuit which retreats primary underflow and recycles secondary overflow offers the best balance between reducing bypass and maintaining a small cut size and high efficiency. / Master of Science

[pt] Este trabalho formula um método para a determinação das funções de rede de um circuito linear genérico, utilizando a interpolação, em pontos do circuito de raio unitário no plano complexo, de funções racionais reais. O método desenvolvido independe de considerações de ordem topológica podendo, ser usado com programas de análise de circuitos baseados na análise nodal, o que o torna bastante rápido, apesar de menos precioso, que os métodos baseados em técnicas de gráficos de fluxo de sinal. / [en] This work describes a method for generating the coeficients of a network function of a general linear circuit, using the interpolation of a real rational function on points of the unit circle in the s plane. The method is independent of topological considerations and suitable for use with network analysis programs based on the nodal formulation of network equations, beeing faster but less precise, than methods using flow graph techniques.

This master´s thesis deals with a design and simulation of an audio power phono amplifier using vakuum tubes. The frequency response of suggested solution should comply with the norm specified by RIAA. It also describes a vacuum tube basic description and also its advantages for audio applications and principle of usage a magnetodynamic pick-up. Last part contains a design of microprocessor system and power supply.