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This task may be solved with the aid of inverse
scattering method.
1f there are many neurons in the nonlinear
network then coontinuous component of spectrum
plaies more important role.It can be characterized
by scattering koefficient RC ).But this koefficient
can be found from the initial light distribution at
the detector plane, because this distribution is
Fourier transform of Rí ). Then it is necessary to
use Helfand-Levitan equation.
2.6 Losses in the networks
Basic philosophy adopted in our discussion is
absence of attenuation in network.Within some time
period this statement is correct.But the length of
network is proportional of l0sses. As it is
determined in /11/, spectral components suffer
changes with the time
+
[ ydt’
(42) n +) -n(0)exp(- &) > r
It means that amplitude and velocity of soliton
reduce with cource of time.This effect may be used
while adjusting losses at some sections of network.
Discrete components of spectrum suffer changes due
to attenuation too.
3. MODEL OF NEURON
Examine laboratory prototype of neuron.Each of
them has receiving element.For this it is possible
to choose capacity of photodetector.It has constant
component CO and nonlinear one. Then all equi valent
scheme can be represented as long line where
inductor is an element of connection and neuron is
nonlinear itself (see Fig.4).
b)
Figure 4, Electrical model of neuronlike
network
As one can see main element their is nonlinear
capacity.This system with the aid of differential
amplifiers produces nonlinear capacity through
logarithmic and exponential transforms.The impedance
of system consisting of amplifiers has capacity
character. Inductance may be formed by convertors.
Extent of nonlinearity was choosen in two types:
m
Un C = cori+« M» y
Uo Uo
Corresponding circuits are represented at Fig.5 a,b.
Üne can show, that for circuit, represented at Fig.5
C = CO In({1+ J
C = Co (1+A)
where À is realized as function of U
In the case a)
21
ase d (t Mn)
and in case b)
Ra
A= CAL) Re
Potential UO shifts constant charges
and enables to regulate the extent of nonlinearity.
Electrical network consisting of such neuronlike
elements was simulated using CAD system DISFS
(for micro VAX type computer) to obtain real non-
linear waves.
When signal is small and UO is close to zero,
network functionates as a linear one.The second type
of nonlinearity leads to different but important
results. There are more strong losses. Initial
conditions were defined as potentials at all knots.
This procedure is equivalent to carrying in non-
linear capacities of initial charges in addition to
constant charges.Boundary conditions were choosen as
fixed at the ends of line.
First type of nonlinearities produces as well
continuous component but less than in second type.
Simulation has shown that if nonlinearity declines
from logarithmic form, contribution of discrete
spectrum becomes less. If neuron is perfect and
network consists of finite guantity of neurons then
this network has only discrete components.
Level of initial potential UO is important
parameter of network.There are worked out method of
regulating this value making use information from
another networks.
This idea may be realized with the aid of two
neighbour networks.First should be network discussed
above and second is one with elements which are
in capacitors
connected by linear links. This system will average
out charge (00) at all elements. Charge ao
determines potential UO. Furthemore let us place
near every nonlinear network, network for production
Qoi and connect all them together. We obtain
ms. Qoc
L7 1
where n — number of neurons.
Then whole system acquire property to estimate
integral influence of receiving matrix. For pictures
which produce almost homogeneous light distribution
at the detector plane constant level of UO will
transform optical field to high part of spectrum. If
there are bright points at the receiving matrix,
then they will be transformed to strong solitons.
This method enables to pick out bright points.
However, if there are many of those points, then
efficiency of average charge method for all network
decreases, In that situation it is necessary to
devide linear networks into several groups. And
every of them will have own average charge. It would
enable to pick out isolated bright points and even
lines (envisaging network as a whole).
Third method consists in accidental connections
of different groups of linear networks. But this
case supposes analysis of picture using several
sequences. Consequently it may find application only
when change of external illuminance happens slowly.
It should be stressed that charge DO changes
initial conditions.
If boundary conditions are cyclic then solitons
move round the cycle and after some period of time
initial picture restores. These experiments have
shown that theoretical suggestions were close to
characteristics of real network.
4. EXPERIMENTAL INVESTIGATIONS
Experimental investigations had for an object