Features of induced synchronization of a bistable oscillator with chaotic dynamics

The features of induced synchronization of a Chua oscillator with a nonlinear element admitting cubic approximation have been numerically simulated for a system where the autonomous operation admits regular or chaotic regimes determined by losses in the oscillatory circuit. The cases of deterministic synchronization (under the action of a harmonic external driving signal) and chaotic synchronization (chaotic control) have been considered. It is established that, outside the band of synchronous oscillations that corresponds to the deterministic synchronization, the external harmonic signal stimulates the transformation of regular oscillations into chaos with the motions switched between two attractors. In cases of chaotic synchronization, there is a residual “noise” in the form of differential chaotic oscillations, which grows with increasing non-identity of the driving and driven signals.     

Controlled chaos in an oscillator with additional oscillatory circuit

A system comprising the classical van der Pol oscillator coupled with an additional oscillator circuit is considered in the presence of an algorithm ensuring chaotization of the self-sustained oscillations. A mathematical model of the system is described and the results of numerical analysis illustrating the new method of chaotizing coupling are presented.     

Chaotic attractors formed using bistable systems

A new method of nonautonomous excitation of chaotic oscillations is proposed which makes use of bistable systems. The formation of an original chaotic attractor in a bistable system, representing decaying motions between two basins of attraction, is demonstrated by numerical methods.     

Noncontacting measurement of thickness of thin titanium silicidefilms using spectroscopic ellipsometer

Spectroscopic ellipsometry has gained increasing attention in semiconductor process control because the technique is nondestructive and noncontacting. This paper demonstrates the capability of spectroscopic ellipsometer to measure the thickness of conducting thin films of titanium silicide. Unlike cross section TEM measurement, this technique does not involve elaborate process of sample preparation. This technique does not require calibration and is used to determine thickness of silicide films from few tens of angstrom up to tens of nanometer. The thickness of titanium silicide film measured at a single point, using spectroscopic ellipsometer and TEM analysis differs by only 4%     

Kinetic responses of murine sarcoma cells to radiation and hyperthermia in vivo and in vitro

Cells of a solid mouse mammary sarcoma that can be cultured in vitro and which, upon inoculation, grow in vivo into new tumors, were exposed either in vivo or in vitro to doses of 300 or 600 rads of X-rays and/or to a temperature of 43 degrees for 1 hr. DNA histograms obtained with flow cytofluorometry were sampled at regular time intervals after treatments in order to obtain information on the cells' postexposure kinetics. X-irradiation of exponentially growing cells induced the expected G2 block; heat exposure caused cells to accumulate in S and G2. The sequential treatment (300 rads followed by 1 hr of hyperthermia) resulted in a mitotic delay that was longer than the sum of the delays of the individual treatments. The proliferative behavior of cycling cells in the tumor treated with a dose of X-rays was qualitatively similar to that seen for exponentially growing cells in vitro; however, marked differences were seen after 43 degrees exposure. The heat treatment of tumors in vivo caused a significant decrease in the tumor cell density as compared to the X-ray treatment alone. Sequential X-ray and heat treatment induced a higher fraction of cycling cells than that found in control tumors. However, X-ray or heat treatment alone caused no significant recruitment of resting cells into cycle 1 day after treatment. A model that permits estimation of the fraction of resting cells in a tumor is described.     

Controlled stochastization of oscillations in a chaotic delayed-feedback system

A mathematical model of the ring autooscillatory system, which possesses chaotic dynamics and comprises a nonlinear amplifier with a differentiating element in the feedback chain, a nonlinear oscillatory circuit, and a delay line, is considered. Numerical analysis has been performed for irregularly varying initial conditions. These conditions were set by the solutions of equations describing chaos that simulated intrinsic noises of a real autooscillatory system. It is shown that the irregularly varying conditions of excitation can lead to stochastization of the chaotic oscillations, in which case the oscillatory process becomes irreproducible.     

Chaotic oscillations in a system of coupled triggers

A circuit consisting of two triggers coupled by a capacitance is studied. The equations of motion are presented with a cubic approximation for the nonlinear terms. It is shown by numerical analysis that chaotic oscillations can be excited. A mechanism for the transition of the oscillations to chaos is described. Pis’ma Zh. Tekh. Fiz. 25, 1–6 (March 26, 1999)