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Artificial Intelligence and Soft Computing: Behavioral ... - Arteimi.info

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The most common non-linear functions used for synaptic inhibition are:<br />

• sigmoid function<br />

• tanh function<br />

• signum function<br />

• step function<br />

Sigmoid <strong>and</strong> tan hyperbolic (tanh) functions are grouped under soft nonlinearity,<br />

whereas signum <strong>and</strong> step functions are under hard type non-linearity.<br />

These functions are presented graphically in fig. 14.2 for convenience.<br />

The schematic diagram of an artificial neuron, based on the above<br />

modeling concept, is presented in fig. 14.3.<br />

x1<br />

x2<br />

xn<br />

w1<br />

w2<br />

wn<br />

Dendrons<br />

n<br />

∑ wi xi<br />

i = 1 Net<br />

Cell body<br />

Axon<br />

out<br />

Net<br />

Synapse<br />

Fig. 14.3: An electrical equivalent of the biological neuron.<br />

14.3 Topology of <strong>Artificial</strong> Neural Nets<br />

Depending on the nature of problems, the artificial neural net is organized in<br />

different structural arrangements (topologies). Common topologies (vide fig.<br />

14.4) are:<br />

out

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