Volume 65 (2014): Issue 3 (May 2014)

This paper provides an innovative practical realization of a memristor based chaotic circuit. The first part discusses the mathematical analysis of the proposed system, including calculation of an eigenvalues, bifurcation diagram and largest Lyapunov exponents. Another parts deal with circuitry realization and the influence of parasitic properties of active elements. The circuit simulations obtained by PSpice environment and the practical measurement results on a breadboard are presented in the last part of this paper. The main aim of this work is an innovative realization of the memristor based chaotic circuit with one type of energy-storage element (linear passive capacitor) and with simpler construction in comparison to other circuits. The next contribution consists in verification of designed circuit with respect to influence of parasitic properties of active elements to chaos destruction.

The main aim of this paper is to present solution of triple-input single-output (TISO) filter with independently adjustable pole frequency, quality factor, bandwidth and also gain. Filter is universal, operates in current mode and includes only one active element - the so-called Controlled-Gain Voltage Differencing Current Conveyor (CG-VDCC) with two controllable parameters: transconductance (g_m) and gain of output currents (B_X ). Implementation of CG-VDCC element in 0.18 μm CMOS technology is also included and this model is used in proposed filter simulations.

An efficient procedure for classification of transient phenomena in distribution systems is proposed in this paper. The proposed method has been applied to classify some transient phenomena such as inrush current, load switching, capacitor switching and single phase to ground fault. The new scheme is based on wavelet transform algorithm. All of the events for feature extraction and test are simulated using Electro Magnetic Transient Program (EMTP). Results show high accuracy of proposed method.

In this paper further theoretical investigations to understand and elucidate recently raised questions on the characteristics of lightning return-strokes curried out. Using Antenna Theory (AT) model, which is extended to take into account the channel inclination, the electromagnetic fields expressions for vertical dipole are completed, and an inclined channel is properly modeled, vertical electric and azimuthally magnetic fields are computed at different distances (close, intermediate and far distance ranges). The computations show that amplitudes and wave forms of the electromagnetic fields at close and intermediate lightning environment are considerably affected by the channel inclination.

Terrain exploration robots can be of great usefulness in critical navigation circumstances. However, the challenge is how to guarantee a control for covering a full terrain area. That way, the application of a chaotic oscillator to control the wheels of an autonomous mobile robot, is introduced herein. Basically, we describe the realization of a random number generator (RNG) based on a double-scroll chaotic oscillator, which is used to guide the robot to cover a full terrain area. The resolution of the terrain exploration area is determined by both the number of bits provided by the RNG and the characteristics of step motors. Finally, the experimental results highlight the covered area by painting the trajectories that the robot explores.

The paper suggests a new and efficient method for location of nonlinear loads on a grid. It is based on measuring of distortion power. The paper reviews different definitions of distortion power and proves that the method is feasible independently on particular definition. The obtained results of simulation and measurement confirm the effectiveness and applicability of the method. The proposed solution is suitable for software update of existing electronic power-meters or can be implement as hardware upgrade.

The monitoring of runway surfaces, for the detection of ice formation or presence of water, is an important issue for reducing maintenance costs and improving traffic safety. An innovative sensor was developed to detect the presence of ice or water on its surface, and its repeatability, stability and reliability were assessed in different simulations and experiments, performed both in laboratory and in the field. Three sensors were embedded in the runway of the Turin-Caselle airport, in the north-west of Italy, to check the state of its surface. Each sensor was connected to a GPRS modem to send the collected data to a common database. The entire system was installed about three years ago, and up to now it shows correct work and automatic reactivation after malfunctions without any external help. The state of the runway surface is virtual represented in an internet website, using the Internet of Things features and opening new scenarios.

The amorphous silicon carbide/crystalline silicon heterojunction was prepared and analyzed. The current-voltage (I − V ) measurements showed the barrier properties of prepared sample. Biased impedance spectra of Al/a-SiC/c-Si(p)/Al heterojunction under the standard illumination are reported and analyzed. AC measurements in the illuminated conditions were processed in order to identify electronic behavior using equivalent AC circuit which was suggested and obtained by fitting the measured impedance data. A phenomenon of negative capacitance/resistance in certain frequency range has been observed.

In this paper, linearization of the optimal compression function is done and hierarchical coding (by coding the regions firstly and then the cells inside the region) is applied, achieving simple and fast process of coding and decoding. The signal at the entrance of the scalar quantizer is modeled by Laplacian probability density function. It is shown that the linearization of inner regions very little influences distortion and therefore only the last region should be optimized. Two methods of optimization of the last region are proposed, that improve performances of the scalar quantizer, and obtained SQNR (signal-to-quantization noise ratio) is close to that of the nonlinear optimal compression function.

Ultra-wideband (UWB) signals with a large bandwidth has some advantages like multipath immunity, low transmission power, good resolution for ranging and detecting geo locations, as well as it can resist to narrow-band interference. These signals are used for transmission in short distance with high throughput. In this paper, we have analyzed different modulation schemes for performance comparison in terms of BER with UWB Gaussian second derivative monopulse and wavelet-based monopulse. The simulation results demonstrate that wavelet-based monopulse provides better performance in comparison to the other two monopulses.

In this paper, an automated system for oscillator phase noise measurement is described. The system is primarily intended for use in academic institutions, such as smaller university or research laboratories, as it deploys standard spectrum analyzer and free software. A method to compensate the effect of instrument intrinsic noise is proposed. Through series of experimental tests, good performances of our system are verified and compliance to theoretical expectations is demonstrated.