Periodic Oscillatory Phenomenon in Fractional-Order Neural Networks Involving Different Types of Delays

This research is chiefly concerned with the stability and Hopf bifurcation for newly established fractional-order neural networks involving different types of delays. By means of an appropriate variable substitution, equivalent fractional-order neural network systems involving one delay are built. By discussing the distribution of roots of the characteristic equation of the established fractional-order neural network systems and selecting the delay as bifurcation parameter, a novel delay-independent bifurcation condition is derived. The investigation verifies that the delay is a significant parameter which has an important influence on stability nature and Hopf bifurcation behavior of neural network systems. The computer simulation plots and bifurcation graphs effectively illustrate the reasonableness of the theoretical fruits.

Precursory Vehicle Modelling

Chapter 4 considers a number of precursory car and bicycle models, as well as an important oscillatory phenomenon commonly referred to as shimmy. The chapter begins by considering a classical single-track car model that will be used to analyse such things as yaw stability, the effects of acceleration and braking, and some of the influences of cornering. After that, the Timoshenko–Young bicycle model that has steering and rolling freedoms is considered. Bicycle stability is then considered with the help of a point-mass bicycle model. Shimmy, including gyroscopic shimmy, is discussed in the concluding part of the chapter. The reader will also be introduced to the fundamental notions of oversteer and understeer.

Oscillatory growth for twisting crystals

We demonstrate the oscillatory phenomenon for the twisting growth of a triclinic crystal through in situ observation of the concentration field around the growing tip of a needle.

On Control Factors for the Oscillation of a Simplified Flip-Flop Jet Nozzle

The authors experimentally investigate a self-excited oscillatory phenomenon of a two-dimensional confined jet with a cylinder as a downstream target, especially for the effect of a streamwise target size a. As a result, the authors find that the jet’s dominant frequency fD can be approximately predicted by the proposed empirical formula (Hirata et al., 2011), whenever the jet stably oscillates at various values of the non-dimensional streamwise target size a/b where b denotes the length scale of the jet’s breadth. The effect of a/b upon the occurrence of the stable jet oscillation is negligible for a/b ≤ 10. Then, the occurrence of oscillations can be predicted by the proposed empirical formula (Hirata et al., 2009). On the other hand, for a/b > 10, the a/b effect is not negligible. In addition, the authors conduct numerical analyses, which reveal the two-dimensionality of the concerning phenomenon.

Impact of the spatial distribution of morphological pattern on the efficiency of electrocatalytic gas evolving reactions

The efficiency of electrocatalytic gas evolving reactions (hydrogen, chlorine and oxygen evolution) is a key challenge for the important industrial processes, such as chlor-alkali electrolysis or water electrolysis. Central issue for the aforementioned electrocatalytic processes is huge power consumption. Experimental results accumulated in the past, as well as some predictive models ("volcano" plots) indicate that altering the nature of the electrode material cannot significantly increase the activity of mentioned reactions. Consequently, it is necessary to find a qualitatively different strategy for improving the energy efficiency of electrocatalytic gas evolving reactions. Usually disregarded fact is that the gas evolution is an oscillatory phenomenon. Given the oscillatory behavior, a key parameter of macrokinetics of gas electrode is the frequency of gas-bubble detachment. Bearing in mind that the gas evolution greatly depends on the surface morphology, a methodology is proposed that establishes a rational link between the morphological pattern of electrode with electrode activity and stability. Characterization was performed using advanced analytical tools. Frequency of gas-bubble detachment is obtained in the configuration of scanning electrochemical microscopy (SECM) while the corrosion stability is analyzed using miniaturized scanning flow electrochemical cell connected to the mass spectrometer (SFC-ICPMS).

Generation of electrical self-oscillations in two-terminal switching devices based on the insulator-to-metal phase transition of VO2 thin films

We present the non-linear electrical properties of simple two-terminal switching devices based on vanadium dioxide (VO2) thin films. The current–voltage characteristics of such devices present negative differential resistance (NDR) regions allowing generating electrical self-oscillations across the investigated devices, with frequencies ranging from several kHz up to 1 MHz. We investigate and compare the factors determining the onset of oscillatory phenomenon in both voltage- and current-activated oscillations and explain its origin. For both activation modes, we will correlate the properties of electrical oscillations (amplitude and frequency) with the amplitude of the continuous excitation signal, the physical geometry of the devices or ambient temperature. We conclude by mentioning several possible applications for the oscillation generation in the radiofrequency (RF)/microwave domains (inverters, integrated a.c. signal generators, pressure and temperature sensors, etc.).