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A relative high power in the alpha band (8 - 13Hz) at a particular EEG position is believed to indicate an active inhibitory state of the corresponding cortical site. According to this hypothesis an active inhibitory state corresponds to a lower engagement of the cortical site and is accompanied by a higher engagement of other sites (possibly neighboring ones). In this project the influence of a repetitive visual stimulation on the alpha band was investigated. A special attention was paid to the difference between the individual alpha frequency and alpha power before and after the stimulation. Data was analyzed by using the matching pursuit time-frequency distribution that provides better resolution in time and frequency than STFT or Wigner-Ville transforms.

A brain computer interface (BCI) is a communication or control system which does not need any neuromuscular activity to produce the message or action. Therefore it can be a communication solution for those people with severe neuromuscular disorders as well as for healthy people in practical applications in entertainment, and communication restoration. SSVEPs are oscillatory responses elicited by a flickering light stimulus that can be recorded in the electroencephalogram(EEG). It is a repetitive evoked potential whose constituent discrete frequency components remain constant in amplitude and phase over aninfinitive long time period. The SSVEP response consists of a number of sinusoids with frequencies given by the stimulus flickering frequency and a number of harmonics. This study is based on brain computer interfaces based on steady-state-visual-evoked-potentials. Thebrain regions where the response is produced has been demonstrated along this work to be stable for a certain frequency and so on spatial filters that discriminate the regions responsible of the SSVEP response have been consider a good solution. We present an approach to automatically obtain the optimum spatial filter to detect the SSVEP at a given stimulation frequency using short signal segments where the stimulation is presented at intermittent periods interspersed with breaks. The best harmonic combination is calculated and asan output all the necessary tools for a suitable detection, thresholdand detection filters.

LEDs are strong candidates for future illumination applications dueto their much lower consumption of energy compared to conventional lighting options. One of key problems in development of LEDs is successful thermal management during illumination. Therefore, current research ongoing related to high power LEDs is focusing on improvementof cooling performance of them to enhance light output efficiency, durability and reliability of these devices.The goal of current studyis a first characterization of the LEDs arrays cooling with microchanneled flows. The flow and heat transfer characterization of a 5 LED array on top of water driven microchannels are performed and the junction temperature change with flow rate and thermal resistance isstudied. Experimental results show that the microchannel cooler reduces the junction temperature of LED array and improves the heat dissipation capability of the LEDs themselves.X At very low Reynolds numbers, there are discrepancies found between literature data and ourexperimental results. These discrepancies are explained by uncertainty in general measurements at microscale, including geometrical dimensions and operating parameters. It is demonstrated that the uncertainty in f*Re is dominated by the microchannel width and height measurements. Even a very accurate pressure drop measurements are oftenovershadowed by the geometry measurement uncertainties. In addition,the channel geometry is often not exactly the desired geometry dueto manufacturing difficulties associated withsmall scales. Therefore, the flow behavior is different from the expectations based on theory. Nusselt number variation with Reynolds number is investigated. Nusselt number is almost linearly increasing with Reynolds number inthe low Reynolds number range as also observed in literature. In fact, Nusselt number is expected to be constant in fully developed laminarflow according to the classical laminar flow theory. This does not hold for several reasons such as entrance region effects, unclearboundary conditions in microchannel cross section, multi directional heat transfer, flow configuration as also explained in details previously.