On the design of dynamic associative neural memories

We consider the design problem for a class of discrete-time and continuous-time neural networks. We obtain a characterization of all connection weights that store a given set of vectors into the network, that is, each given vector becomes an equilibrium point of the network. We also give sufficient conditions that guarantee the asymptotic stability of these equilibrium points.     

Stabilization and disturbance rejection for the wave equation

We consider a system described by the one-dimensional linear wave equation in a bounded domain with appropriate boundary conditions. To stabilize the system, we propose a dynamic boundary controller applied at the free end of the system. The transfer function of the proposed controller is a proper rational function of the complex variable and may contain a single pole at the origin and a pair of complex conjugate poles on the imaginary axis, provided that the residues corresponding to these poles are nonnegative; the rest of the transfer function is required to be a strictly positive real function. We then show that depending on the location of the pole on the imaginary axis, the closed-loop system is asymptotically stable. We also consider the case where the output of the controller is corrupted by a disturbance and show that it may be possible to attenuate the effect of the disturbance at the output if we choose the controller transfer function appropriately. We also present some numerical simulation results which support this argument     

Boron nitride coatings of steel and graphite produced with a low pressure r.f. plasma

Boron nitride (BN) coatings were deposited onto die steel and graphite substrates with a low pressure r.f. plasma. The coatings were deposited onto substrates at temperatures of 550–620 °C from a gas mixture of argon, NH₃ and BCl₃. X-ray diffraction and scanning electron microscopy were employed to identify and to characterize the coatings. The coatings are mostly amorphous; however, the existence of small amounts of hexagonal BN was identified. The influence on the growth rate of the deposition time and the pressure in the reactor is described.     

Current-mode level restoration: circuit for multi-valued logic

The multi-valued logic circuits provide very small chip size, higher speed, and a small number of interconnections. However, the main drawback of these circuits is the lower noise margin and it is necessary to restore the nominal levels of the signal after a certain number of cascaded stages. A new current-mode CMOS restoration circuit is presented and evaluated.     

On the stabilization of a cable with a tip mass

In this note, we consider a vertical cable which is pinched at the upper end. A mass is attached at the lower end where a control force is also applied. We show that this hybrid system is uniformly stabilized by choosing a suitable control law for the control force depending on the velocity and angular velocity at the free end. Moreover for specific values of the feedback coefficients, we obtain the rate of decay of the energy of the system     

Wien bridge based RC chaos generator

A new circuit, which is formed by coupling a Chua diode with a Wien bridge oscillator in parallel, is presented. This circuit contains only resistors, capacitors and operational amplifiers. By choosing element values appropriately, this circuit is shown experimentally to exhibit various forms of chaotic behaviour     

Dynamic boundary control of a Euler-Bernoulli beam

A flexible beam, clamped to a rigid base at one end and free at the other end is considered. To stabilize the beam vibrations, a dynamic boundary force control and a dynamic boundary torque control applied at the free end of the beam are proposed. It is proved that with the proposed controls, the beam vibrations decay exponentially. The proof uses a Lyapunov functional, based on the energy functional of the system     

Orientation and stabilization of a flexible beam attached to arigid body: planar motion

The author considers a flexible structure modeled as a rigid body which rotates in inertial space; a light flexible beam is clamped to the rigid body at one end and free one is clamped at the other. It is assumed that the flexible beam performs only planar motion. The equations of motion are obtained by using free body diagrams. Two control problems are posed, namely the orientation and stabilization of the system. It is shown that suitable boundary controls applied to the free end of the beam and suitable control torques applied to the rigid body solve the problems posed above. The proofs are obtained by using the energy of the system as a Lyapunov functional