Non-sinusoidal Oscillation Research Articles

Simulation and Study on Non-Sinusoidal Oscillation Control System of Continuous Casting Mold

The paper describes the composition and working principle of the mold oscillation control system. The mathematical model of hydraulic servo control system is established. The total system transfer function is established by MATLAB program. By using the SIMULINK module, we determined various components’ parameter values. We got different simulation curves and Bode plots by inputting non- sinusoidal function and carrying out the dynamic simulation to the mold oscillation mathematical model, we also analyzed stability of the whole system to verify the accuracy of system design.

On the Sensitivity of Period Searches

AbstractAstronomical time series are special in that time sampling in them is uneven yet often with periodic gaps due to daytime, moon and seasons. There is therefore a need for special-purpose time-series analysis (TSA) methods. The emergence of massive CCD photometric surveys from the ground and space raises the question of an automatic period search in ≫ 105 light curves. We caution that already at the planning stage it is important to account for the effects of time sampling and analysis methods on the sensitivity of detections. We present a transparent scheme for the classification of period-search methods. We employ tools for evaluating the performance of those methods, according to the type of light curves investigated. In particular we consider sinusoidal and non-sinusoidal oscillations as well as eclipse or transit light curves. From these considerations we draw recommendations for the optimum analysis of astronomical time series. We present briefly the capability of an automatic period-search package Tatry. Finally we discuss the role of Monte Carlo simulations in the analysis of detection sensitivity. As an example, we demonstrate a practical method to account for the bandwidth (multi-trial) penalty in the statistical evaluation of detected periods.

Effect of Non-Sinusoidal Oscillation Parameters on Mold Flux Consumption Rate

According to the rule of non-sinusoidal oscillation of continuous casting mold, a mathematical model was established to study the effects of oscillation parameters on the consumption rate of mold flux. The results indicated that the mold flux consumption rate is remarkably affected by the non-sinusoidal factor. This proves that the non-sinusoidal oscillation of mold contributes to increase the flux consumption. Moreover, the amplitude and frequency of mold oscillation have effects on mold flux consumption rate. The non-sinusoidal oscillation parameters must be optimized.

Modeling and Optimization of Mould Non-Sinusoidal Oscillation Process

A model on non-sinusoidal oscillation of continuous casting mould was established to study the pressure in flux channel. The effects of oscillation parameters on the pressure in flux channel were researched. The non-sinusoidal oscillation parameters were optimized. When the casting speed is 1.8 m·min-1, the optimized oscillation parameters are: non-sinusoidal factor (α) is 0.198, oscillation amplitude (s) is ±4mm and oscillation frequency (f) is 165min-1. When the casting speed is 2.0 m·min-1, the optimized oscillation parameters are: α is 0.186, s is ±4.5mm and f is 155min-1. These optimized oscillation parameters are proved applicable in practice.

An Investigation of Mechanical Non-Sinusoidal Oscillation of Continuous Casting Mold

In this paper, a new technique to set up non-sinusoidal oscillations of the mold in continuous casting is presented. The waveform functions of this non-sinusoidal oscillation technique and operational parameters are analyzed and the design to realize the non-sinusoidal oscillation of mold is presented. It is anticipated that this technique will be widely applied as it has many advantages such as lower investment and maintenance cost, simple equipment which is easy to manufacture and maintain.

Study on Deformed Limacon Gear and Motion Optimization of Its Serial Mechanism

In order to obtain the nonsinusoidal oscillation wave of continuous caster molds, a vibration generator comprised of an eccentric shaft and a new kind of noncircular gears called deformed limacon gear pair is proposed. The pitch curve equations of limacon gears are described based on the cosine rule. According to the closed property of noncircular pitch curves and residue theorem, the center distance between a limacon gear and its conjugate gear is deduced, as well as their transmission ratio and the pitch curve equations of the conjugate gear. Subsequently, the mathematical model of deformed limacon gears with dissymmetrical transmission ratio in one period is established and the kinematic formula of the serial mechanism is presented for optimization by a modified genetic algorithm. Here, a computer program is developed for optimizing the gear linkage mechanism to meet requirements in practice and results show that expected motion can be achieved by deformed gear linkage mechanism, which can provide a new choice for application.

Research on the Elastic Vibration Response of New Non-sinusoidal Oscillation System for the Mold

A new type of non-sinusoidal oscillation system for the mold made up of anti-parallel equal-crank four-bar linkage and the cascaded whole-leaf spring oscillation mechanism.Elastic dynamic model coupled by torsional and linear vibration is set up with lumped parameter method and equations of motion is also built.Elastic vibration response is solved in time domain,which shows motion law of mold becomes distortion in some working frequency.In frequency domain,it is given that resonance is the cause of distortion motion of mold by FFT,and harmonic increases with bigger amplitudes in these frequencies.Furthermore,effects on the motion law of excitations are analyzed,which proves that the inner excitations with multi-frequency determine the resonance frequency of the system and external excitation only influence resonance peak value.So the study can provide theoretical basis for application of the system and research on the kinematic stability of the non-sinusoidal oscillation system.

A New Non-Sinusoidal Oscillation Waveform for Continuous Casting Mold

A new non-sinusoidal oscillation waveform which is shown by waveform distortional rate was advanced. The amplitude, oscillation frequency, waveform distortional rate and casting velocity were established for a computer model of the continuous casting process. The range of waveform distortional rate was ascertained. The choosing method of amplitude and oscillation frequency was given. These offered a theory basis to the application of the advanced technique. Industrial scale experiments showed the new type waveform is effective on improving the quality of continuous casting slab and reducing breakout.

Dynamic pressure in mould flux channel during mould non-sinusoidal oscillation

Based on the lubrication theory of mould flux, a mathematical model of dynamic pressure in mould flux channel was developed, and the distribution of dynamic pressure and its variation during non-sinusoidal oscillation were investigated. The effects of casting speed and non-sinusoidal oscillation parameters, including the degree of non-sinusoidal operation (non-sinusoidal factor), amplitude and frequency of oscillation on the dynamic pressure in the mould flux channel, were studied. The results indicate that the maximum negative pressure is decreased, and the maximum positive pressure is increased with increasing non-sinusoidal factor. The optimum value of non-sinusoidal factor is ∼0·2. With increasing amplitude and frequency of oscillation, both the negative and positive pressure are increased; moreover, the increment of positive pressure is obviously greater than that of negative pressure; especially when the oscillation frequency is increased, the increment of negative pressure is very little. When the casting speed is enhanced, the negative pressure is increased, but the positive pressure is decreased. Therefore, if the casting speed is increased, the oscillation amplitude needs to be increased, as well as the oscillation frequency needs to be decreased properly. With these adjustments, the positive pressure in mould flux channel is nearly unchanged. The actions of strand demoulding and cracks welding are kept effective. Moreover, the negative pressure in mould flux channel is increased properly, which causes the flux consumption to increase, so the mould lubrication is improved. Finally, the strand surface quality is improved greatly, and breakout can be avoided. The applicability of the optimised non-sinusoidal oscillation parameters for the two kinds of casting speed has been proven by industrial practice.

Testing for cycles in multiple time series

In practice, it is often impossible to assess the validity of the smoothness assumptions crucial to standard tests for singularities in the spectrum. We therefore propose new tests which are completely insensitive to sharp peaks in the absolutely continuous part of the spectrum. Using Neyman Pearson tests of Bayesian mixtures we first derive admissible tests under simplifying assumptions and then show that under realistic assumptions our test statistics remain the same. The tests are designed to have high power especially against alternatives containing oscillations which are positively correlated with each other. Motivated by a biological dataset with non-sinusoidal oscillations, we finally extend our approach by including higher harmonics.

Mould lubrication and friction behaviour with hydraulic oscillators in slab continuous casting

It is very important to obtain reliable lubrication from casting powder both at the meniscus and in the gap between strand and mould as it affects slab surface quality and caster productivity. With knowledge of mould friction, a quantitative insight into the behaviour of powder during caster operation is possible. In the present research, the friction was studied based on a slab continuous caster equipped with hydraulic oscillators. The effects of mould oscillation and the abrupt change of casting speed on mould friction force were evaluated, and the characteristics of lubrication behaviour in a casting sequence were investigated. In particular, a comparison between the mould friction force between sinusoidal oscillation mode and non-sinusoidal oscillation mode was made. Finally, the characteristics of friction before a breakout are discussed. The experimental and analytical results may contribute to the development of mould friction online measurement and more clearly learn the lubrication behaviour in different conditions.

Fuzzy PID control of mould non-sinusoidal oscillator driven by permanent magnet synchronous motor

Mould non-sinusoidal oscillation is one of the key techniques to development of the high efficiency continuous casting and the mould non-sinusoidal oscillator is the pivotal mechanism. A mold non-sinusoidal oscillation mechanism, which is driven by a field-oriented control permanent magnet synchronous motor (PMSM), with fuzzy PID control proposed in this study. The machine design of the mold oscillation servo-mechanism is developed. The rod and four bar-linkage of the mould oscillation mechanism are assumed to be rigid and the kinematic analysis of this mechanism is introduced. A fuzzy PID controller is designed to control the angular speed of the PMSM, the performance of the proposed controller is verified by simulation experiments.

Optimisation of non-sinusoidal oscillation parameters for slab continuous casting mould with high casting speed

Friction force and flux channel pressure of the meniscus in a continuous casting mould were calculated based on the influence of frequency, amplitude and factor of non-sinusoidal oscillation on the effectiveness of mould oscillation and the stress state of the initial solidifying shell while casting SPHC ([C] ≤ 0.08%) steel grade at 2·0 m min−1 speed. On the basis of these calculations, an oscillation synchrocontrol model reflecting the relations between casting speed and each oscillation parameter was established. The relevant oscillation parameters were determined as casting speed increased from 2·0 m min−1 to 2·2 m min−1. The results show that the frequency should be decreased and the amplitude and non-sinusoidal oscillation factor should be increased with casting speed to improve the oscillation effectiveness and the stress state of the solidifying shell. The values of frequency, amplitude and non-sinusoidal oscillation factor were chosen to be 140 min−1, ±4·5 mm and 0·25, respectively, at a casting speed of 2·2 m min−1.

Asymmetry and non-zero mean of neuronal oscillations: What is essential for the generation of evoked responses?

Evoked responses (ERs) from magneto- and electroencephalographic recordings (MEG/EEG) are the primary real-time objective measures of cognitive and perceptual processes in the human brain. For the past fifty years, only two mechanisms for the generation of ERs have been discussed in the literature: „additive“ responses and „phase resetting“ of ongoing oscillations. Recently we introduced a novel mechanism for the generation of ERs (Nikulin et al., 2007), which can be deduced entirely from the properties of the ongoing neuronal oscillations, e.g., alpha oscillations. We have shown analytically and experimentally that neuronal oscillations with a non-zero mean (i.e., the integrated field of one oscillatory cycle is not zero) is a sufficient prerequisite for oscillations to contribute to evoked responses through a mechanism of amplitude modulation. Recently in another study (Mazaheri and Jensen, 2008) it was proposed that an „amplitude fluctuation asymmetry index“ (AFA, the amplitude asymmetry of peaks and troughs around zero) might reveal whether or not an amplitude modulation of oscillations contributes to ERs. Necessarily, oscillations with a non-zero mean will have a non-zero AFA index. Critically, however, the reverse is not true in general, because – as we show here – the AFA index is sensitive also to the non-sinusoidal (e.g., comb-like) shape of neuronal oscillations. We prove analytically and experimentally that the amplitude modulation of non-sinusoidal oscillations with zero mean cannot give rise to evoked responses. Consequently, it is not possible to infer from the AFA index of an oscillation whether its amplitude modulation will contribute to an evoked response. It is therefore crucial to choose methodological approach that is specifically sensitive to the non-zero-mean properties of neuronal oscillations in order to be able to make conclusions about the contribution of the novel ER mechanism to the measured data.

Non-sinusoidal Wave and Process Parameters of Anti-parallel Four-bar Linkage

Based on the non-sinusoidal generating device of elliptic gear, a non-sinusoidal oscillation generating device for continuous casting mould driven by anti-parallel four-bar linkage is developed, and its prototype is manufactured. The new device features compact and rational structure, high reliability, and easy realization of static and dynamic balances, so both its working performance and cost are superior to those of elliptic gear. Through motion analysis, the displacement, velocity and acceleration functions of the non-sinusoidal wave generated by anti-parallel four-bar linkage are obtained with simple formulas. The analytical formulas of the process parameters are deduced, and the variation rules with basal parameters of non-sinusoidal oscillation are analyzed. Through geometric parameters substitution, these formulas can be transformed into corresponding formulas of non-sinusoidal wave of elliptic gear, and the calculation is simple and can obtain accurate solution, thereby providing theoretical basis for accurate calculation of process parameters and accurate control of process in the practical application.

The Shell Surface Force Caused by Mould Friction during Slab Continuous Casting

In continuous casting, the lubrication and friction between the mould and the initial solidified strand shell play an important role for achieving the high speed casting and producing a good surface quality of the product. Investigation of the frictional behavior is therefore essential for getting a better online control of the mould processes. In the present work, the measurement of shell surface force caused by mould friction was performed during the slab continuous casting. Friction force was calculated to investigate the periodical variations as well as the effect of tensions and pressures on the solidified shell. Also the comparison of the mould friction in sinusoidal and non-sinusoidal mould oscillation was made. This research provided the test foundations and technical supports for studying the mechanical behavior of casting mould and optimizing the casting variables.

Low-frequency Resonance of Mold Driven by Oval Gears

In production practice,some continuous casters suffer from severe resonance during their starting although the vibration frequency of mold is much lower than the natural frequency of the vibration system.The resonance can cause shake of liquid steel level and,more seriously,even industrial accident such as breakout.In view of this phenomenon,the torsional vibration model of non-sinusoidal oscillation system driven by oval gears is built up.And the dynamics equations are deduced.Low-frequency resonance is discussed.Factors which influence the resonance frequency are considered.A solid foundation for solving the running smooth problem of the mold and for better application of the oscillation device is laid.

Effect of tubular inhomogeneities on filter properties of thick ascending limb of Henle’s loop

We used a simple mathematical model of rat thick ascending limb (TAL) of the loop of Henle to predict the impact of spatially inhomogeneous NaCl permeability, spatially inhomogeneous NaCl active transport, and spatially inhomogeneous tubular radius on luminal NaCl concentration when sustained, sinusoidal perturbations were superimposed on steady-state TAL flow. A mathematical model previously devised by us that used homogeneous TAL transport and fixed TAL radius predicted that such perturbations result in TAL luminal fluid NaCl concentration profiles that are standing waves. That study also predicted that nodes in NaCl concentration occur at the end of the TAL when the tubular fluid transit time equals the period of a periodic perturbation, and that, for non-nodal periods, sinusoidal perturbations generate non-sinusoidal oscillations (and thus a series of harmonics) in NaCl concentration at the TAL end. In the present study we find that the inhomogeneities transform the standing waves and their associated nodes into approximate standing waves and approximate nodes. The impact of inhomogeneous NaCl permeability is small. However, for inhomogeneous active transport or inhomogeneous radius, the oscillations for non-nodal periods tend to be less sinusoidal and more distorted than in the homogeneous case and to thus have stronger harmonics. Both the homogeneous and non-homogeneous cases predict that the TAL, in its transduction of flow oscillations into concentration oscillations, acts as a low-pass filter, but the inhomogeneities result in a less effective filter that has accentuated non-linearities.

Harmonic resonance in non-sinusoidal oscillation of mold

In production practice,some continuous casters,for which the molds undergo non-sinusoidal oscillation,suffer from severe resonance during their starting although the running frequency is much lower than the natural frequency of the os-cillation system.The resonance can cause mold level fluctua-tion and even breakout.To get an insight view of this problem,the dynamic model of the oscillation mechanism is built up.The vibration excitation is deduced.Harmonic analysis is ap-plied on non-sinusoidal excitation.The method to determine resonance interval is given.Factors concern the harmonic components are analyzed.Harmonic resonance analysis is car-ried on a practical oscillation system adopted by a certain iron plant.Also,a test to check the motion states of the mold is done.The test data support the theoretical results very well,which explains why the mold reciprocation table vibrates heavily in lateral direction.And harmonic resonance is verified.Harmonic resonance has general sense in non-sinusoidal oscillation of the mold.So harmonic resonance should be analyzed if only the mold undergoes non-sinusoidal oscillation.

Current-induced voltage oscillations in superconducting Y1Ba2Cu3O7-δ

We investigated influence of bidirectional square wave current with long periods and dc current on the evolution of the voltage-time (V - t) curves in superconducting polycrystalline bulk Y1Ba2Cu3O7-δ (YBCO) material at the temperatures near the critical temperature. In a well-defined range of amplitudes and periods of driving current, and temperatures, novel type of non-linear dynamic responses was observed by means of the V-t curves. It was seen that such a non-linear response to bidirectional square wave current sometimes reflects itself as regular sinusoidal-like voltage oscillations. The sinusoidal-like and non-sinusoidal oscillations were discussed mainly in terms of the dynamic competition between pinning and depinning and significant relaxation effects which appear in this competing process. The density fluctuations associated with the current induced self-magnetic flux (SMF) lines and semi-elastic coupling of SMF lines with the pinning centers were also considered as possible physical mechanisms in the interpretation of the experimental results.