Periodic Pulse Excitation Research Articles

Dynamical behavior of cardiac conduction system under external disturbances: simulation based on microcontroller technology

The heart rhythm is one of the most interesting aspects of the dynamic behavior of biological systems. Understanding heart rhythms is essential in the dynamic analysis of the heart. Each type of dynamic behaviour can describe normal or pathological physiology. The heart is made up of nodes ranging from SA node (natural pacemaker) to Purkinje fibers. The electric current originates in the sinus node and travels through the heart until it reaches the Purkinje fibers, causing after its passage through each of the nodes a heartbeat thus constituting the electrocardiogram (ECG). Since the origin of the electric current is the sinus node, in this article we study numerically and experimentally by microcontroller the influence of the sinus node on the propagation of electric current through the heart. A study of the sinus node in its autonomous state shows us that in their coupled state, the nodes of the heart qualitatively reproduce the time series of the action potential of this latter, which leads to the recording of the ECG. A study when the sinus node is subjected to periodic pulsed excitation assumed to come from blood pressure, with the blood pressure, shows that for some selected frequencies, it is found that the nodes of the heart and the ECG exhibit responses having the same shape and the same frequencies as those of the pulsatile blood pressure. This suggests the possibility of using such a conversion and excitation mechanism to replicate the functioning of cardiac conduction system. The chaotic analysis of the sinus node subjected to a sinusoidal type disturbance is also presented, it shows that in its chaotic state, the nodes of the heart, as well as the ECG, provide very high frequency signals. This requires the control of the sinus node (natural pacemaker) in such a situation.

Monitoring of Changes in Oxygen Concentration in Tissues by the Kinetics of Delayed Fluorescence of Exogenous Dyes

The dynamics of the consumption of oxygen during photodynamic processes and the subsequent restoration of its concentration in malignant tumors and healthy tissues of mice were studied in vitro by the kinetics of long-term luminescence of xanthene dyes. To assess changes in the oxygen concentration in tissues, delayed fluorescence can be used due to singlet–triplet annihilation of singlet oxygen and a sensitizer in the triplet state. Upon periodic pulse excitation of sensitizers, reversible quenching of delayed fluorescence was detected in tumors, which is associated with a decrease in the amount of oxygen in the tissues during photodynamic processes. A method for visualizing the restoration of the initial oxygen concentration in tissues is proposed.

Theoretical Modeling of the Nuclear‐Field Induced Tuning of the Electron Spin Precession for Localized Spins

This work is devoted to a theoretical analysis of the effect of nuclear‐induced field (Overhauser field) on the Larmor frequencies of electron spins under the periodic pulsed excitation. To describe the dynamical nuclear spin polarization, we use the model where the optically induced Stark field determines the magnitude and direction of the Overhauser field. The Stark field strongly depends on the detuning between the photon energy of excitation and the optical transition energy in the quantum system. Detailed calculations which show that the precession frequencies of fluorine donor‐bound electron spins in ZnSe deviate from the linear dependence of the Larmor frequencies on the external magnetic field have been performed. A similar effect is observed for the (In,Ga)As/GaAs quantum dots, where it has been shown that the Overhauser field strongly changes the spectrum of the electron spin precession frequencies.

Study on rail fastener failure testing based on fractal theory

The residual vibration of steel rail is rich in the mechanical properties, which include the constraint, that was, the degree of tightness of the fastener. The aim of this research is to characterize the tightness of rail fastener. A fractal analysis procedure based on 1-D curve length calculation is proposed, which applies a length unit to cover fastening the behavior of fasteners. Using the rail vibration data under periodic pulse excitation measured by a track fastener inspection vehicle, this method can derive the fractal dimension of fastener tightness directly (D∈ [1, 2)). Furthermore, 1-D curve length method is also introduced into multi-fractal spectrum analysis for investigating fine scale information. The statistical analysis demonstrates that, fractal dimension Dl, Dr, and multi-fractal parameters αfmax, ∆α can reflect the change process of the tightness of rail fasteners effectively. Therefore, it shows potential to use the fractal parameters of the rail vibration signal to characterize the tightness of the fastener.

Analysis of Multiconductor Transmission Lines with Nonlinear Terminations in Frequency Domain

The analysis of multiconductor transmission lines with arbitrary nonlinear terminations in the frequency domain is presented in this paper. The transmission line system can either be modeled by the R, L, G, C matrix for quasi-static approximation, or represented by the multi-port S-parameter for the full-wave consideration. The time-domain responses for both of the two transmission line formulations in nonlinear loading then are acquired by using the harmonic balance technique with the periodic pulse excitation in a few iteration processes. Numerical examples show the availability and versatile features of the proposed approach with confirmations of the literature and the commercial software results.

Study of semiconductor/electrolyte interface using the Fourier transformation of photovoltage response to periodic laser pulses

Charge transfer processes at the TiO 2/electrolyte interface have been studied using periodic short laser pulses (337 nm) as probe. A model has been developed to determine a number of semiconductor characteristics from the Fourier image of the photovoltage response induced by the periodic pulsed excitation. It has been shown that the capacitance of depletion and Helmholtz layers, flatband potential, doping density and dielectric constant of a semiconductor electrode as well as the surface recombination rate can be determined by this method, even for polycrystalline semiconductor films exhibiting non-linear Mott–Schottky dependencies.

Energy yield of photoluminescence in a system of particles with three energy levels on periodic pulse excitation

Within the framework of the probability method, we obtained analytical expressions for the luminescence power, absorption power, and energy yield of photoluminescence in a system of particles with three energy levels on periodic pulse excitation. It is shown that at certain periods and durations of exciting pulses the energy yield can be higher than under stationary excitation conditions.

Internal combustion engine noise analysis and production using a novel multipulse excited time series modeling technique.

Automobile manufacturers have learned that customers have well‐defined notions as to what an automobile engine should sound like for the various vehicle segments (luxury, sportscar, economy, etc.). Therefore, it is advantageous to model and synthesize various types of engine sounds for customer evaluation. Much work has been done in the area of speech modeling and synthesis based on physical assumptions of human speech production. The intent of this paper is twofold. First discussed are the similarities and differences between speech and engine noise modeling and synthesis problems. Second, application of techniques learned for speech synthesis to that of automotive noise production is demonstrated. Early models of speech production used periodic pulse excitation in a linear predictive coding (LPC) framework. This technique is used to synthesize engine noise. It is then compared to that of a new suboptimal multipulse method proposed by the authors. It is hoped that this paper will pave the path for a better understanding of the relationship between the two systems so that much of the work performed in speech analysis and production can be applied to the analysis and synthesis of automotive internal combustion engine sounds.

Steady-state response of vibrating systems to periodic pulse excitation

^anson, D. B., Helicoidal Surface Theory for Propeller Aerodynamics and AIAA Journal, Vol. 21, June 1983, pp. 881-889. Long, L. N., ''The Compressible Aerodynamics of Rotating Blades Using an Acoustic Formulation, Ph.D. Dissertation, School of Engineering and Applied Science, George Washington University, Washington, D.C., April 1983. Long, L. N., Aerodynamics of Propellers and Rotors Using an Acoustic Formulation in the Time Domain, AIAA Paper 831821, 1983. Farassat, F., Prediction of the Noise of Supersonic Propellers in Time Domain—New Theoretical Results, AIAA Paper 83-0743, April 1983. Ffowcs Williams, J. E. and Hawkings, D. L., Generated by Turbulence and Surfaces in Arbitrary Motion, Philosophical Transactions of the Royal Society of London, Vol. A264, 1969, pp. 321-342. Isom, M. P., Theory of Sound Radiated by a Hovering Transonic Helicopter Blade, Polytechnic Institute of New York, Rept. Poly-AE/AM 75-4, 1975. Farassat, F., Advanced Theoretical Treatment of Propeller Propeller Performance and Noise, von Karmn Institute for Fluid Dynamics, Lecture Series 1982-08, 1982. function, and tf the duration of the pulse within a period. The periodic pulse excitation F( t) is shown in Fig. 1. Assuming that steady-state conditions are obtained after sufficiently large n = N, the system response will satisfy the following conditions:

Ultrahigh-resolution coherence spectroscopy by means of periodic excitation with picosecond pulses

The feasibility of ultrahigh-resolution coherence spectroscopy with a train of picosecond light pulses from a synchronously pumped mode-locked and cavity-dumped dye laser is demonstrated. Narrow resonances of periodic pulse excitation are observed whenever the pulse repetition rate of the laser of a higher harmonic coincides with the frequency splitting of coherently excited levels. The zero-field hyperfine splitting of the Na-ground state (1771.6 MHz) could be measured in the 2100th order of the excitation rate with a resonance halfwidth of 800 Hz.

Relaxation of the space charge in the electroluminescence of ZnS-Cu phosphors

The relaxation of the space charge originating in the electroluminescence of ZnS-Cu phosphors excited by a pulse voltage is investigated by the method of electrical sounding after excitation is removed. It is shown that the main characteristics of the brightness wave for a periodic pulsed excitation are determined by the quantity of electrons and holes locked in the phosphor at the time the previous pulse acted, as well as by the rate of resorption of the space charge.