Nonperiodic Waveforms Research Articles

MAXIMUM ACTIVE POWER TRANSMISSION EFFICIENCY AND POWER FACTOR DEFINITION IN HYBRID SYSTEMS WITH ARBITRARY WAVEFORMS

Based on a theorem giving the maximum available active power with constant transmission losses valid for arbitrary waveforms it is possible rigorously generalize the definitions of power factor based on the definition of apparent power as the maximum power available. Then it could be applied to systems with non-symmetric, non-sinusoidal, and eventually time-varying (ie non-periodic) waveforms or DC grids. By this way, the application may be extended to hybrid multi-wire systems with asymmetrical phases, with different voltages, frequencies or waveforms (i.e. non-sinusoidal waves, such as rectangular or PWM) and even DC, which can be combined eventually sharing the neutral conductor.

Effects of Surface Roughness on Direct Plasma Bonding between Silicone Rubbers Fabricated with 3D-Printed Molds.

This study presents the effects of surface roughness on the adhesion strength of plasma-treated rubbers that are widely used in soft robotics. The rubbers are designed with 11 molds of different patterns and fabricated from liquid silicones for mutual comparison. Several specimens with nonperiodic and periodic surface waveforms are quantitatively analyzed based on the correlation between surface roughness and adhesion strength. The surface roughness of three-dimensional (3D) printed molds under different printing conditions is compared to that of the standard specimens molded by a smooth acrylic plate and four sandpapers. The surface profiles are measured by a stylus profiler, analyzed using fast Fourier transform, and subsequently quantified using the experimental roughness parameters, R a and R ku *. The kurtosis ratio R ku * is proposed to simultaneously evaluate the sharpness, total height, and peak density to identify contact surfaces. A 90° peel test is also conducted to evaluate the adhesion strength, considering the designed pattern and printing orientation relative to the peeling direction. Microstructural analysis of the specimens is performed to investigate the peeling mechanism and molding quality using scanning electron and digital microscopes. Correlations between adhesion strength and surface roughness are obtained through the evaluation of the plasma-treated silicone specimens. R ku * is significant in determining the surface properties of the effective contact area, particularly for rough surfaces, and further contributes to an effective evaluation when the parameter R a is used simultaneously. The results suggest that the plasma bonding of silicone rubbers fabricated with 3D-printed molds is effective in enhancing the adhesion strength of soft robots or stretchable devices.

Maximum Active Power Transmission Efficiency and Apparent Power Definition with Arbitrary Waveforms

A proof of the theorem giving the maximum available active power with constant transmission losses (i.e., maximum efficiency) valid for arbitrary waveforms, is proposed. This makes it possible to rigorously generalize the definitions of power factor based on the definition of apparent power as the maximum power available to apply them to systems with non-symmetric, non-sinusoidal, and eventually time-varying (i.e., non-periodic) waveforms or DC grids, thus extending its application to hybrid multi-wire systems with asymmetrical phases, with different voltages, frequencies or waveforms (i.e., non-sinusoidal waves, such as rectangular or PWM) and even DC, which can be combined eventually sharing the neutral conductor. Finally, an example of application to a hybrid system composed of DC and unbalanced load inverter-based non-sinusoidal AC subsystems is included.

Design of Ultra-Compact On-Chip Discrete Phase Filters for Broadband Dispersion Management

This paper provides an in-depth theoretical and numerical analysis of a group-velocity dispersion (GVD) management scheme for broadband waveforms using ultra-compact on-chip discrete spectral phase filters based upon waveguide Bragg gratings (WBGs) in a silicon-on-insulator (SOI) platform. Through this technique, mm-long discrete phase filters can be designed to impart a target arbitrary GVD profile on a high-rate (typically, $\geq\!10$ GHz) periodic pulsed waveform, including fully customized and extremely large second and higher-order dispersion terms (e.g., equivalent to 10,000 km of a standard single-mode fiber), over a broad frequency bandwidth (up to $\sim\!3$ THz, demonstrated here). The capabilities and limitations of this technique to impart a target GVD profile over an arbitrary (generally, non-periodic) broadband signal are also studied. We show that customized GVD lines can be efficiently implemented offering a net group-delay excursion in the hundreds-of-ps range using mm-long integrated discrete phase filters. Additionally, we suggest and numerically demonstrate a simple and practical strategy to improve significantly the performance of the discrete phase filtering approach for application on non-periodic waveforms, by combining the discrete phase filter with a suitable periodic resonance (frequency-comb) amplitude filter. An extensive tolerance analysis is conducted, and we conclude that the proposed SOI design framework is well within practical fabrication requirements as well as robust to the expected variability in the main WBG device design parameters.

Respiration Symptoms Monitoring in Body Area Networks

This work presents a framework that monitors particular symptoms such as respiratory conditions (abnormal breathing pattern) experienced by hyperthyreosis, sleep apnea, and sudden infant death syndrome (SIDS) patients. The proposed framework detects and monitors respiratory condition using S-Band sensing technique that leverages the wireless devices such as antenna, card, omni-directional antenna operating in 2 GHz to 4 GHz frequency range, and wireless channel information extraction tool. The rhythmic patterns extracted using S-Band sensing present the periodic and non-periodic waveforms that correspond to normal and abnormal respiratory conditions, respectively. The fine-grained amplitude information obtained using aforementioned devices is used to examine the breathing pattern over a period of time and accurately identifies the particular condition.

Very-low-SNR cognitive receiver based on wavelet preprocessed signal patterns and neural network

A pattern-based cognitive communication system (PBCCS) that optimizes non-periodic RF waveforms for security applications is proposed. PBCCS is a cross-layer approach that merges the channel encoding and modulation. The transmitter encodes sequences of bits into continuous signal patterns by selecting the proper symbol glossaries. The cognitive receiver preprocesses the received signal by extracting a limited set of wavelet features. The extracted features are fed into an artificial neural network (ANN) to recover the digital data carried by the distorted symbol. The PBCCS system offers a flexible management for robustness against a high noise level and increases the spectral efficiency. In this study, the spectral efficiency and robustness of a PBCCS scheme for an additive white Gaussian noise (AWGN) channel is investigated. The results show that at an SNR of −5 dB, a 3-bit glossary achieves a bit error rate (BER) of 10−5. Also, the link spectral efficiency (LSE) of the proposed system is 2.61 bps/Hz.

Enhanced Performances of a Photocatalytic Reactor for Wastewater Treatment Using Controlled Modulation of Leds Light

One of the main limitations related to the industrial utilization of a photocatalytic process is the use of UV lamps that have several disadvantages such as the low quantum efficiency (QE). One of the approaches to increase the QE consists in the use of controlled periodic illumination (CPI). In this regard, Light Emitting Diodes (LEDs) are the best choice as light sources, since they can be electronically controlled by using LED dimming techniques, allowing variable turn-on and turn-off times on a microsecond time-scale. The aim of this work is to investigate the influence of controlled modulation of LEDs light on the performances of a photocatalytic reactor for wastewater treatment using TiO2 immobilized on glass spheres (TiO2/GS). The experiments were realized with a pyrex cylindrical batch photoreactor irradiated by three power UV-LEDs and placed surrounding the external body of the cylindrical photoreactor. The system adopted for the controlled modulation of LEDs light is composed by a photovoltaic panel (PV), a dc–dc converter dedicated to the maximum power point tracking of the PV panel and a dc–dc converter dedicated to drive the UV LEDs. A system controller is also included, whose goal is to ensure matching between the maximum available PV power, the LED power and the resulting low-frequency LEDs dimming modulation. The experimental results showed that the use of certain types of duty-cycle dimming modulation waveforms, including periodic and non-periodic waveforms and combinations of them, have been discovered to improve the photo-catalytic reactor performances. In particular, the use of a modulation of LEDs dimming like sinusoidal and pseudo-sinusoidal waveforms is more effective than the fixed dimming. The best results in terms of methylene blue degradation (about 25% in less than 1 h) have been achieved with a pseudo- sinusoidal waveform.

Ultrafast Spectroscopy Based on Temporal Focusing and Its Applications

The whole family of the parametric spectro-temporal analyzer (PASTA) system has enriched the capability of our tool box in ultrafast spectrum measurements. The advent of the dispersive stretching technology started the era of the temporal spectrum analyzer, and it is easy to implement with stable results, while only capable of short pulses at low-repetition-rate. To enlarge the temporal observation window, a time-lens is first incorporated in the single-lens PATSA system. It can characterize stationary sources as well as some nonperiodic waveforms. To further enhance the observation flexibility, a pair of time-lens structure is introduced to perform the telescope/wide-angle PASTA. Leveraging the merit of instantaneous response, as well as the flexible lens structure; here, we present a 100-MHz frame rate PASTA system, with 17 times zoom in/out ratio for different observation ranges. Each configuration has its optimum application range. As a proof of concept and also for the first time, we demonstrate some of its bio-imaging applications, including the time-stretch microscopy and the tomography systems.

Experimental investigation of the incremental conductance maximum power point tracking algorithm at high perturbation rates

One of the most commonly utilised maximum power point tracking (MPPT) algorithms for photovoltaic (PV) generators is the incremental conductance (INC) algorithm. Yet, the operating characteristics of this algorithm at high perturbation frequencies, when the system response to MPPT perturbations is never allowed to settle, have not been addressed in the literature. This study characterises system behaviour in this operating mode experimentally for a standalone PV system with a dc motor–pump load. Results show that the INC algorithm operating at a high perturbation rate offers higher energy utilisation efficiency and better system performance despite the resulting non-periodic waveforms of the system.

Operating Characteristics of the P&O Algorithm at High Perturbation Frequencies for Standalone PV Systems

The perturb and observe (P&O) algorithm is one of the most commonly utilized maximum power point tracking (MPPT) control schemes for photovoltaic (PV) generators. However, the operation of this algorithm at high perturbation frequencies, when the system response to MPPT perturbations is never allowed to settle, has not been given adequate attention in the literature. This paper characterizes system behavior in this mode of operation for standalone PV systems feeding resistive loads and motor-pump loads. Simulation and experimental results show that the P&O algorithm operating at a high perturbation frequency may offer higher energy utilization efficiency and better system performance, despite the resulting nonperiodic waveforms of the system.

Exposure of Working Population to Pulsed Magnetic Fields

Reference values of exposure for working population at extremely low frequency electromagnetic fields have been stated in ICNIRP Guidelines of 1998, and accepted by European Parliament in 2004. Nevertheless, quantification of coupling mechanism under pulsed field conditions is still an open question. The effect of complex non-sinusoidal or non-periodic waveforms is not univocally defined and several ways of estimating it have been proposed. This paper compares different ways of assessing effects of pulsed electromagnetic fields with frequency spectrum below 100 kHz and compare them to the eddy currents induced in one realistic model of human body by a resistance spot welding system supplied by in pulsed medium frequency direct current mode.

Tracking control of hysteretic piezoelectric actuator using adaptive rate-dependent controller

With the increasing popularity of actuators involving smart materials like piezoelectric, control of such materials becomes important. The existence of the inherent hysteretic behavior hinders the tracking accuracy of the actuators. To make matters worse, the hysteretic behavior changes with rate. One of the suggested ways is to have a feedforward controller to linearize the relationship between the input and output. Thus, the hysteretic behavior of the actuator must first be modeled by sensing the relationship between the input voltage and output displacement. Unfortunately, the hysteretic behavior is dependent on individual actuator and also environmental conditions like temperature. It is troublesome and costly to model the hysteresis regularly. In addition, the hysteretic behavior of the actuators also changes with age. Most literature model the actuator using a cascade of rate-independent hysteresis operators and a dynamical system. However, the inertial dynamics of the structure is not the only contributing factor. A complete model will be complex. Thus, based on the studies done on the phenomenological hysteretic behavior with rate, this paper proposes an adaptive rate-dependent feedforward controller with Prandtl–Ishlinskii (PI) hysteresis operators for piezoelectric actuators. This adaptive controller is achieved by adapting the coefficients to manipulate the weights of the play operators. Actual experiments are conducted to demonstrate the effectiveness of the adaptive controller. The main contribution of this paper is its ability to perform tracking control of non-periodic motion and is illustrated with the tracking control ability of a couple of different non-periodic waveforms which were created by passing random numbers through a low pass filter with a cutoff frequency of 20 Hz.

Random Noise Radar/Sodar With Ultrawideband Waveforms

Random noise waveforms with ultrawide bandwidth improve the range resolution and reduces the probability of intercept in radar/sodar. As a result of the nonperiodic waveform, the range ambiguity is removed as well. By transmitting a sine signal that is phase or frequency modulated by random noise, autocorrelation functions with improved side lobe suppression in range can be formed. There are great similarities in the signal-processing algorithms applied in noise radar and sodar. The much slower propagation velocity of sound compared to light reduces the signal bandwidth but increases the time of measurement, however. In both sodar and radar, the range resolution is determined by the wavelength band occupied by the transmitted waveform, while the velocity resolution is controlled by the ratio of wavelength and time of measurement. The slower sound velocity also enhances the range/Doppler ambiguity problem in sodar when periodic waveforms are applied. This ambiguity could be suppressed if nonperiodic waveforms are introduced, such as random noise. In this paper, fundamental similarities and differences on system level between sodar and radar are first discussed, and signal-processing algorithms applied in random noise radar/sodar are reviewed. In particular, the noise floor of the ambiguity function and its relationship to spectrum width and time of measurement are analyzed, including improved side lobe suppression using mismatched filtering. The signal-processing algorithms were tested on raw data from sodar measurements on moving targets, buildings, vegetation, and water surfaces. An adaptive filter algorithm for suppression of the increased noise floor from dominant reflectors was derived and successfully applied to both sodar and stepped frequency radar data

Compensation-based nonactive power definition

This paper presents a new definition of nonactive current from which the definitions of instantaneous active and nonactive power are also derived. The definitions are consistent with the traditional power definitions and valid for single-phase and polyphase systems, as well as periodic and nonperiodic waveforms. The definitions are applied to a shunt compensation system. The paper elaborates on the compensation of three different cases of nonperiodic current: single-phase disturbance, three-phase subharmonics, and three-phase stochastic current. Simulation results give credibility to the applicability of the definition for a diversity of load currents. According to different compensation cases and the goals to be achieved, different averaging time intervals for the compensator are chosen which will determine the compensator's energy storage requirement and the extent of residual distortion in the source current.

Evaluation of a shunt active power conditioner with a modified control scheme under nonperiodic conditions

Nonperiodic waveforms are produced in power systems under various operating conditions; it is convenient to suppress such waveforms via the active filter dedicated to harmonics. An active power conditioner is scrutinised and modified to treat both periodic and nonperiodic waveform distortions. A new consistent and practical index to assess the distortion of nonstationary and nonperiodic signals is established. Its fidelity and potential for real applications are also addressed. The conditioner operation is examined under nonperiodic load currents with different types of nonperiodicity. The proposal is compared with both Fryze's and instantaneous power control techniques. The active conditioner is shown to be competent in compensating periodic and nonperiodic current distortions.

Instantaneous and full compensation in three-phase systems

Fundamental results of the generalized instantaneous power theory have been applied for power factor correction in three-phase systems. Instantaneous and full compensation were considered to set the differences between compensation in general conditions (periodic or nonperiodic waveforms) and compensation in steady states (periodic waveforms). An active power filter is simulated as reactive power compensator to confirm the theory.

General theory for the spectral evolution of nonlinear Rayleigh waves

The spectral theory developed by Zabolotskaya [J. Acoust. Soc. Am. 91, 2569–2575 (1992)] for nonlinear Rayleigh waves in isotropic solids is generalized to include fields with nonperiodic waveforms and nonplanar spatial dependencies. Model equations for cylindrical waves and diffracting beams that have been used in previous work, and which were obtained in an ad hoc manner, are derived here rigorously from first principles. The present theory for plane waves, which is derived using Hamiltonian formalism, is shown to be equivalent to the theory obtained by Parker [Int. J. Eng. Sci. 26, 59–75 (1988)], whose derivation is based on a different approach.

Simulation of mixed switched-capacitor/digital networks with signal-driven switches

The simulation of mixed switched-capacitor/digital (SC/D) networks containing capacitors, independent and linear-dependent voltage sources, switches controlled either by periodic or nonperiodic Boolean signals, latched comparators, and logic gates is considered. A unified linear switched-capacitor network (SCN) and mixed SC/D network simulator, SWITCAP2, and its applications to several widely used and novel nonlinear SCNs are discussed. The switches may be controlled by periodic waveforms and by nonperiodic waveforms from the outputs of comparators and logic gates. The signal-dependent modification of network topology through the comparators, logic gates, and signal-driven switches makes the modeling of various nonlinear switched-capacitor circuits possible. Simulation results for a pulse-code modulation (PCM) voice encoder, a sigma-delta modulator, a neural network, and a phase-locked loop (PLL) are presented to demonstrate the flexibility of the approach.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Birth and death of the double scroll

The “double scroll” is a chaotic attractor observed from an extremely simple electronic circuit made of 4 linear circuit elements (2 capacitors, 1 inductor and 1 resistor) and a 2-terminal nonlinear resistor characterized by a 3 segment piecewise-linear v-i characteristic. This nonlinear resistor can be built in the laboratory using 2 transistors and diodes. The qualitative behavior of the double scroll attractor has been described elsewhere where each cross section of the double scroll attractor is shown to consist of 2 tightly wound spirals. Our objective in this paper is to present a bifurcation analysis of this circuit in terms of 2 basic parameters. Various bifurcation phenomena such as Hopf bifurcation, period-doubling cascades, Rössler's spiral and screw-type attractors, periodic windows, Shilnikov phenomenon, double scroll, and boundary crisis are described. In particular, special emphasis is given to the mechanisms leading to the birth and the death of the double scroll attractor. All bifurcation phenomena described in this paper are observed not only experimentally but also confirmed by digital computer simulations. Moreover, an analytical foundation of the double scroll family of equations has been developed and used to explain, in a rigorous way, all observed bifurcation phenomena. In addition, Rössler's spiral-type and screw-type attractors have been observed from the same circuit where the nonlinear resistor has only one break point, i.e., it is described by a 2-segment piecewise-linear v-i characteristic. This means that extremely complicated non-periodic (chaotic) waveforms can arise in the simplest third order uncoupled electrical circuit in which all elements except one (a resistor) are linear and passive, and in which the constitutive relation of the nonlinear resistor is made of the simplest conceivable nonlinearity; namely, 2 straight-line segments.

Analysis and computation for nonlinear elastic surface waves of permanent form

Linear elastic surface waves are nondispersive. All wavelengths travel at the Rayleigh wave speed c R. This absence of frequency dispersion means that nonlinear waves of permanent form cannot be determined as a small perturbation from a sinusoidal wavetrain. By representing the general Rayleigh wave of the linear theory in terms of a pair of conjugate harmonic functions, waves which propagate without distortion are characterized as those having surface elevation profiles which satisfy a certain nonlinear functional equation. In the small-strain limit, this reduces to a quadratic functional equation. Methods for the analysis of this equation are presented for both periodic and nonperiodic waveforms. For periodic waveforms, the infinite system of quadratic equations for the Fourier coefficients of the profile is solved numerically in the case of a certain ‘harmonic’ elastic material. Two distinct families of profiles having phase speed differing from the linearized Rayleigh wave speed are found. Additionally, two families of exceptional waveforms are found, describing profiles which travel at the Rayleigh wave speed.