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When implementing an appropriate windowing, the interference from a Cognitive Radio (CR) system to licensed systems (primary users) will be significantly reduced. Consequently, power allocated to subcarriers can be increased, especially subcarriers having far spectral distance to primary user bands can be allocated full of its maximum possible power. In this paper, we propose a new class of sub-optimal subcarrier power allocation algorithm that significantly reduces complexity of OFDMA-based CR systems. Two sub-optimal proposals, called Pre-set Filling Range (PFR) and Maximum Filling Range (MFR) are studied. Investigations show that this new power allocating algorithm allows CR systems obtain high throughput while retaining low complexity.
This paper represented Autoregressive
Neural Network (ARNN) and meant threshold methods for recognizing eye movements for control of an electrical
wheelchair using EEG technology. The eye movements such as eyes open, eyes
blinks, glancing left and glancing right related to a few areas of human brain
were investigated. A Hamming low pass filter was applied to remove noise and
artifacts of the eye signals and to extract the frequency range of the measured
signals. An autoregressive model was employed to produce coefficients
containing features of the EEG eye signals. The coefficients obtained were
inserted the input layer of a neural network model to classify the eye
activities. In addition, a mean threshold
algorithm was employed for classifying eye movements. Two methods were
compared to find the better one for applying in the
wheelchair control to follow users to reach the
desired direction. Experimental results of controlling the wheelchair in the
indoor environment illustrated the effectiveness
of the proposed approaches.
In this work, the vibration characteristics of a piezoelectric ceramic disk with different dimensional ratio are studied by simulation method. Computational finite element modeling combined with the computational programs has allowed for the prediction of the effect, the change of diameter-to-thickness ratio on the resonant characteristics, the vibration modes as well as comparing the physic properties of piezoceramics. Three types of piezoelectric materials were chosen, piezoelectric materials (PZT) and Pb-free piezoelectric materials Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3(BZT-50BCT), BaTiO3 for research.