Generation of self-oscillations from a singly resonant periodically poled potassium titanyl phosphate crystal frequency doubler

We report on the generation of self-oscillations from a continuously pumped singly resonant frequency doubler based on a periodically poled potassium titanyl phosphate crystal （PPKTP）. The sustained square-wave and staircase curve of self-oscillations are obtained when the incident pump powers are below and above the threshold of subharmonic-pumped parametric oscillation （SPO）, respectively. The self-oscillations can be explained by the competition between the phase shifts induced by cascading nonlinearity and thermal effect, and the influence of fundamental nonlinear phase shift by the generation of SPO. The simulation results are in good agreement with the experiment data.

Stability analysis of a liquid crystal elastomer self-oscillator under a linear temperature field

Self-oscillating systems abound in the natural world and offer substantial potential for applications in controllers,micro-motors,medical equipments,and so on.Currently,numerical methods have been widely utilized for obtaining the characteristics of self-oscillation including amplitude and frequency.However,numerical methods are burdened by intricate computations and limited precision,hindering comprehensive investigations into self-oscillating systems.In this paper,the stability of a liquid crystal elastomer fiber self-oscillating system under a linear temperature field is studied,and analytical solutions for the amplitude and frequency are determined.Initially,we establish the governing equations of self-oscillation,elucidate two motion regimes,and reveal the underlying mechanism.Subsequently,we conduct a stability analysis and employ a multi-scale method to obtain the analytical solutions for the amplitude and frequency.The results show agreement between the multi-scale and numerical methods.This research contributes to the examination of diverse self-oscillating systems and advances the theoretical analysis of self-oscillating systems rooted in active materials.

Coupling processes between self-oscillation of formation pressure and periodic migration-accumulation of natural gases in Yinggehai Basin, South China Sea

The modeling of formation pressure in Yinggehai shows that DF1-1 diapir has oscilla-torily released thermal fluids twice since 5.0 Ma, which may be controlled by the multi-structural subsidences and their accompanying thermal events. Using thermal indicators of formation temperature by DST, I/S mixed clay minerals, homogeneous temperature of inorganic fluid inclusion and δ13C of methane to trace the thermal fluid migrating order and path, we found that there are two orders of natural gas migration-accumulation in the upper site over the top of the overpres-sured compartment. Based on the oscillatory development of formation pressure, we postulate there would exist earlier (before 5.0 Ma) gas accumulation in their deeper site.

Experiment, acoustic model for the self-oscillation of coaxial swirl injector and its influence to combustion of liquid rocket engine

During the experiment of gas/liquid coaxial swirl injector conducted with air and water under atmosphere environment, it is observed that the injector may selfoscillate. The self oscillation periodically occurs and vanishes with the increasing velocity of the gas flow.A theoretical model is presented based on the experiment investigation. Simulation of the acoustic process has been performed and conclusions consistent with the experiment can be drawn from the theoretical model, which explains the exPeriment phenomena quite well. At last, the comparison between phenomena of the self oscillation and some experiments of LRE indicates that some instability phenomena in oxygen/hydrogen propellant rocket engine may be the related to self oscillation in coaxial injectors

Self-Oscillating Structural Polymer Gels

self-oscillating polymer gel has become a distinguished class of smart soft materials. Here we fabricated and demonstrated a self-oscillating structural gel network with the incorporation of the Belousov-Zhabotinsky (BZ) reaction. The structural polymer gel oscillates at a macroscopic level with remarkably faster kinetics compared to a normal gel of similar chemical compositions. The structural polymer gel also displays larger oscillating amplitude compared to the normal gel because of the increased diffusion of fluids surrounding the gel particles. This type of structural polymer gels can be harnessed to provide novel and feasible applications in a wide variety of fields, such as drug delivery, nanopatterning, chemical and biosensing, and photonic crystals.

Tropical cyclone, as powerful natural self-oscillatory systems, and wind-energetic a way of struggle against it—The analysis of a cyclone from a position of the theory of vibrations

It is considered three phases of development of a tropical cyclone: the origin, the steady-state regime and the termination, coinciding with three phases of self-oscillatory process: oscillation buid-up, dynamic balance and failure of self-oscillations. The rough size of energy of a cyclone, as column of air rotating with high speed, at initial and final stages of development and comparison of the received sizes with nuclear and hydrogen bombs is calculated. The model of the electronic oscillator with negative active conductivity by the numerical solution of the equation of the Van-der-Pol is analyzed. Formal coincidence of transient in this model with increase of capacity of vortical air formation, that allows to make mnemonic model of a cyclone in the form of volume self-oscillatory system is shown. The numerical solution of the made equations allows to construct schedules of dynamic process for each of particles of the investigated environment. The general recipe on restraint of development of a cyclone by compulsory entering into it of attenuation is given. Realization of this recipe by means of group of platforms with powerful wind-electrogenerator and the fans and uses of a principle of negative feedback is shown. The results of laboratory experiment confirming idea, taken as a principle struggle against an arising air whirlwind, by transformation of a laminar stream in chaotic, turbulent are resulted. For fuller check offered a wind-energetic method of struggle against a cyclone carrying out of more scale experiment is necessary.

Self-Oscillating Mixer(SOM) With 0.18 μm CMOS Technology

self-oscillating mixer is introduced in this paper, with fundamental signal generated by the oscillator subcircuit in the process of mixing. The oscillator core consumes 3 mA of the current from a 1.8 V DC supply and leads to an output power of –0.88 dBm per oscillator, and a measured phase noise of –91, –102 and –107 dBc/Hz at 100 KHz, 600 KHz and 1 MHz from the carrier, respectively. The proposed mixer achieved IIP3 of 0 dBm in the process of mixing, with conversation gain of 1.93 dB. Designing and simulation the circuit was done in 0.18 μm CMOS technology by ADS2010.

Canards in a rheodynamic model of cardiac pressure pulsations

This paper reports on the canard phenomenon occurring in a rheodynamic model of cardiac pressure pulsations. By singular perturbation techniques the corresponding parameter value at which canards exist is obtained. The physiological significance of canards in this model is given.

Nonlinear dynamics of self-oscillating polymer gels

Self-oscillating polymer gels driven by Belousov-Zhabotinsky (BZ) chemical reaction are a new class of functional gels that have a wide range of potential applications (e.g., autonomously functioning membranes, actuate artificial muscles). However, the precise control of these gels has been an issue due to limited investigations of the influences of key system parameters on the characteristics of BZ gels. To address this deficiency, we studied the self-oscillating behavior of BZ gels using the nonline-ar dynamics theory and an Oregonator-like model, with focus placed upon the influences of various system parameters. The analysis of the oscillation phase indicated that the dynamic response of BZ gels represents the classical limit cycle oscillation. We then investigated the characteristics of the limit cycle oscillation and quantified the influences of key parameters (i.e., ini-tial reactant concentration, oxidation and reduction rate of catalyst, and response coefficient) on the self-oscillating behavior of BZ gels. The results demonstrated that sustained limit cycle oscillation of BZ gels can be achieved only when these key pa-rameters meet certain requirements, and that the pattern, period and amplitude of the oscillation are significantly influenced by these parameters. The results obtained in this study could enable the controlled self-oscillation of BZ gels system. This has several potential applications such as controlled drug delivery, miniature peristaltic pumps and microactuators.

Third harmonic distortion calculation of a self-oscillating power amplifier

It is difficult to analyze the harmonic distortion of a self-oscillating power amplifier (SOPA),because the SOPA is a hard nonlinear system without an external clock.The single or multiple sinusoidal inputs describing function (DF) method is commonly used to linearize a nonlinear element,but this method considers only the components at the same frequencies as the input signals (i.e.,fundamental components) at the nonlinear element's output.In this paper,besides the fundamental components,the third harmonic components are also calculated at the output of a comparator with three sinusoidal inputs,to create a linearized model of the comparator,and thus of the SOPA.The third harmonic distortion of the SOPA is calculated.The models of the zeroth and the first order SOPA are verified by behavioral simulation using MATLAB.

Synthesis and Characterization of Self-oscillating P(AA-co-AM)/PEG SemiIPN Hydrogels Based on a p H Oscillator in Closed System

Various semi-interpenetrating polymer network（semi-IPN） hydrogels composed of pore-forming agent polyethylene glycol（PEG）, acrylic acid（AA） and acrylamide（AM） were prepared by using free radical polymerization with a two-step method. The chemical structures of the synthesized hydrogels were characterized by FTIR spectroscopy and the morphologies were studied by scanning electron microscopy（SEM） method. The swelling properties, such as the p Hresponsive behavior, salt sensitivity, oscillatory swelling/de-swelling behaviors in different solutions with various p H values and self-oscillating behaviors in bath p H oscillator were investigated in detail. The results revealed that the prepared hydrogels exhibited high p H sensitivity and excellent salt sensitivity when the p H values of the medium changes from 3.0 and 7.0 and well reversible properties by undergoing a number of swelling/de-swelling recycles. In particular, the hydrogels exhibited self-oscillation behavior in a closed system containing Br O3？-SO32？-Fe（CN）64？-H＋. This study may create a new possibility as biomaterial for new self-walking actuators and other devices.

A novel BIST scheme for circuit aging measurement of aerospace chips

The avionics working environment is bad, easy to accelerate aging of circuits. Circuit aging is one of the important factors that influence the reliability of avionics, so circuit aging testing is of great significance to improve the reliability of avionics. As continuing aging would degrade circuit performance, aging can be monitored through precise measurement of performance degradation. However, previous methods for predicting circuit performance have limited prediction accuracy. In this paper, we propose a novel Built-In Self-Test（BIST） scheme for circuit aging measurement, which constructs self-oscillation loops employing parts of critical paths and activates oscillations by specific test patterns. An aging signature counter is then used to capture the oscillation frequency and in turn measure the aging state of the circuit. We propose to implement this measurement process by BIST. Experimental results show that the proposed in-field aging measurement is robust with respect to process variations and can achieve a precision of about 90%. The application of this scheme has a certain value to improve the reliability of avionics systems.

Hydrodynamic simulations of terahertz oscillation in double-layer graphene

We have theoretically studied current self-oscillations in double-layer graphene n+nn+ diodes driven by dc bias with the help of a time-dependent hydrodynamic model. The current self-oscillation results from resonant tunneling in the double-layer graphene structure. A detailed investigation of the dependence of the current self-oscillations on the applied bias has been carried out. The frequencies of current self-oscillations are in the terahertz(THz) region. The double-layer graphene n+nn+ device studied here may be presented as a THz source at room temperature.