Sinusoidal Components Research Articles

Nova metoda za estimaciju parametara složenoharmonijskog energetskog signala

A systematic analytical procedure for simultaneous estimation of the fundamental frequency, the amplitudes and phases of harmonic waves was proposed in this paper, which enabled fast and precise estimation with a small numerical error. Individual sinusoidal components have been extracted from the input complex-harmonic signal with finite-impulse response (FIR) comb filters. The proposed algorithm is based on the application of partial derivate of the processed and filtered input signal, after which it is performed weighted estimation procedure to better estimate the size of the values of the fundamental frequency, amplitude and the multi-sinusoid signal phase. The designed algorithm can be used in the signal reconstruction and estimation procedures, spectral processing, in procedures for the identification of the system that is observed, as well as other important signal processing areas. Through the simulation check, the effectiveness of the proposed algorithm was assessed, which confirmed its high performance.

Aging Monitoring Method for Lithium-Ion Batteries Using Harmonic Analysis

Monitoring the aging battery cells is important to maintain battery performance. Capacity is a key indicator of battery aging diagnosis, but capacity can be estimated differently depending on the C-rate. Battery impedance monitoring using electrochemical impedance spectroscopy (EIS) is also recognized as a battery diagnostic method. However, EIS is inefficient when diagnosing a large number of individual battery cells due to complex computation and measurement time. In this article, a harmonic analysis method for monitoring aging battery is proposed. The proposed diagnostic technique applies the designed 1-kHz sinusoidal signal, comprising a sinusoidal current component and a direct current component, to the battery. Harmonics are generated when signals passing through nonlinear systems are distorted. A battery is an asymmetric nonlinear system with different bidirectionality. Comparing the simulation and experimental results, we confirmed that the harmonic signatures are the indicators that distinguish between a normal and an aging battery. Moreover, the proposed in situ technique can be applied during charge/discharge cycles, even in the case of an apparent reduction of even harmonics.

Estimation of steady water flux density in a porous medium by Fourier analysis of temperature variations in a cyclic heat pulse system

We tested a novel theoretical model that determines the steady water flux density in a porous medium from Fourier analysis of temperature variations induced by a cyclic heat pulse system. The model depends on the thermal diffusivity of the medium and on the relative spatial variation of the amplitude and phase of the first order sinusoidal component of the heat wave. The model was tested by using a hydraulic column made of a PVC pipe filled with sawdust. The sensor consisted of two hypodermic needles spaced 7 mm apart. One needle contained a heater and a thermocouple while the other contained only a thermocouple. Different combinations of heating and cooling cycles were tested. The flow was controlled by pressure head and volumetrically measured at the outlet of the tube. The experimental results supported the theoretical model. In particular, the convective index defined in terms of the variations of amplitude and phase of the first component of the heat wave was linearly related to the measured flux density, as predicted. The model was independent of the different combinations of heating and cooling cycles. The estimated water flux density was strongly related to the measured flux density (R2>0.99), having the same slope for the different combinations. The first results of this new approach of cyclic heat pulse system are very promising and suggest further studies and field applications.

Excess semiannual variation in historical temperature records

AbstractThe annual temperature cycle of the Earth closely follows the annual cycle of solar flux. At temperate latitudes, both driving and response cycles are well described by a strong annual sinusoidal component and a nonvanishing semiannual component. A new analysis of historical weather station records from the United States determines persistent annual and semiannual variation with high precision. Historical annual temperature ranges are consistent with prior studies. Semiannual temperature cycles are much stronger than expected based on the semiannual solar driving. Instead, these cycles were consistent with multiplicative effects of two annual cycles. Our methods provide a quantitative window into the climate's nonlinear response to solar driving, which is of potential value in testing climate models.

Lift Equivalence and Cancellation for Airfoil Surge–Pitch–Plunge Oscillations

A NACA 0018 airfoil in freestream velocity is oscillated in longitudinal, transverse, and angle-of-attack directions with respect to the freestream velocity, known as surge, plunge, and pitch. The lift-based equivalence method introduces phase shifts between these three motions to construct in-phase sinusoidal components for maximum lift, waveform construction. Lift cancellation is also determined with the exact negative pitch and plunge motion amplitudes found from the equivalence method to achieve out-of-phase wave destruction. Lift cancellation occurs when a combination of these motions is sought to obtain a constant lift magnitude throughout the oscillation cycle. To achieve both equivalence and cancellation of lift, a prescribed pure pitch amplitude through the Theodorsen theory equates the corresponding equivalent plunge amplitude and pitch–plunge phase shift. These Theodorsen, linear superposition findings of pitch–plunge are leveraged toward the Greenberg theory to determine a closed-form, surge–pitch–plunge solution through the addition of a surge–plunge phase shift and optimal surge amplitude for lift cancellation. The lift cancellation surge–pitch–plunge amplitudes define the equivalence amplitude investigated here and theoretically limit the experiment to combinations of the first lift harmonic of the Greenberg theory. The analytical results are then compared with experimental lift force measurements and dye visualization. The normalized lift differences due to unsteady wake and boundary-layer behavior are examined to explore the extents of the Greenberg theory for these cases of lift-based equivalence and cancellation.

Numerical modelling of the oscillatory flow effect around submarine pipeliness

This work describes the dynamics of an underwater pipeline subjected to an incident flow composed of a uniform flow and a sinusoidal component. The motion equations of the pipeline and the fluid flow around the pipeline are solved simultaneously with a numerical model that considers in-line oscillations (one degree of freedom) and a second numerical model that additionally includes cross flow (two degrees of freedom). The amplitude response and drag forces on the pipe are compared for both models considering parameters such as the difference between the excitation and natural frequencies of pipelines and the relative value between the sinusoidal and uniform components of the incident flow. Important differences in numerical predictions of both models are observed when the excitation frequency is greater than the natural frequency of the system and when the amplitude of the oscillatory component of the incident flow is greater than the amplitude of the uniform flow.

Distribution of seasonality of calving patterns and milk production in dairy herds across the United States

Calving patterns and milk production are seasonal throughout the United States; however, the distribution of seasonality, and the extent to which this seasonality is due to direct effects of climate on milk production and reproductive performance or farm management, is not well quantified. Summer-to-winter (SW) ratios have been used as measures of seasonality, but other measures such as low-to-peak (LP) ratios have been proposed. Our objectives were (1) to describe the distribution of seasonality in calving pattern and milk production among herds in the United States, (2) to compare SW and LP ratios of calving pattern and milk production, (3) to quantify the effect of a seasonal calving pattern, parity, and percentage of dry cows on seasonality of milk production, and (4) to describe the association between seasonality in calving pattern and milk production, herd size, and daily milk production per cow. The final data set contained Dairy Herd Improvement Association lactation records from 2015 from 5,292 (calving pattern) and 5,200 (milk production) herds for 41 states in the United States. We used generalized linear regression models with 1 sinusoidal curve to model calving pattern and milk production per cow for each herd. For milk production, a model adjusting for days in milk (DIM) and the interaction of DIM and parity (ADJ) and a model that was not adjusted (NO) were run. Both models included the effect of the percentage of dry cows. We used SW and LP ratios calculated from the parameters of the sinusoidal component of the models as measures of seasonality. The variability within states for all seasonality measures was large. The median LP ratio of calving pattern was 0.61, and small herds were more seasonal (LP ratio 0.56) than large herds (LP ratio 0.75). For milk production, the median LP ratio-NO was 0.88, and the LP ratio-ADJ was 0.90. Small herds were more seasonal (0.89) than large herds (0.92) when their LP ratios-ADJ were compared. States in the south of the United States were the most seasonal for calving patterns and milk production. Adjusting for DIM and parity increased the LP ratio of milk production by 8.9% for 66% of the herds. Adjusting for the percentage of dry cows increased the LP ratio in 72.9% of the herds by a median value of 21.8%. The correlations between SW and LP ratios were weak. Herds that were more seasonal for milk production had a lower average daily milk per cow than less-seasonal herds. In conclusion, seasonality in calving patterns and milk production among herds varied greatly across the United States. Sinusoidal models with covariates allowed for quantification of the effects of calving pattern, DIM, and parity on the seasonality in milk production. The LP ratios captured the maximum seasonality better than SW ratios did.

Reduction of a noise influence with sinusoidal signal meters

The purpose of the article is to suggest digital processing methods of sinusoidal signal measurements data as well as compensation of sinusoidal noises. This kind of task arises, for example, in implementation of feeder control of electrical power networks, in which an additional ELF voltage source is included between the controlled network and the ground. A leakage current measuring device for this frequency should be installed on each feeder. The suggestion is to use averaging of the sinusoidal signal over several periods to reduce the effect of random interference. For this purpose, several periods of the signal are stored in digital form, measured after equidistant moments of time. Time sampling frequency is selected at least an order of magnitude higher than the frequency of the signal being measured. Then the values “bound” to a particular signal phase are averaged. In addition, it was proposed to use the approximation of the obtained points by a trigonometric polynomial. A series of averaged values corresponding to one period are approximated for this purpose by the sum of the constant component as well as the cosine and sinusoidal components. For approximation, the least squares method is used, which provides the minimum discrepancy between the measured values and the analytical function. The measurement result is presented in a complex form, i.e. as a sum of cosine (actual) and sinusoidal (imaginary) components. As a result, it is possible to isolate oneself from noise and measure the sinusoidal signal with high precision.

Detecting abandoned farmland using harmonic analysis and machine learning

It is critical to inventory abandoned farmland soon after it is generated, to better manage agricultural resources and to prevent negative consequences that would otherwise follow. This study aims to distinguish abandoned farmlands from active croplands—rice paddy and agricultural fields—by discerning the phenological trajectories over a short-term period of three years (Jan. 2016 to Dec. 2018) in Gwanyang City in South Korea. For Support Vector Machine (SVM) classification, we fully utilized parameters derived from harmonic analyses of the three vegetation indices (VIs: NDVI, NDWI, and SAVI) extracted from Sentinel-2A imagery. The harmonic analyses proved that higher-order sinusoid components produced better fitting to explain the trajectory of the VIs—the maximum adjusted R2 was 95.23%—and the multiple VIs diversified the attributes for the classifications. Consequently, the higher-order harmonic components and the additional VIs increased the accuracy when used in SVM classification. The best performing classification was achieved with a composite of harmonic terms derived from the three VIs, yielding overall accuracy of 90.72%, Kappa index of 0.858, and user’s accuracy for abandoned farmland of 93.40%. The proposed method here would greatly improve the process of detecting abandoned farmland, despite a relatively short observation period, and enable a rapid response to the occurrence of abandonment.

Neural Tracking of Band-Limited Sine-Wave Speech in Normal Hearing and Cochlear Implant Listeners

A sine-wave speech represents complex speech with a limited number of sinusoidal components. Functionally, its strategy draws a close similarity to the signal processing strategy in cochlear implant (CI) which transmits speech envelope information in limited number of channels. In this study, we investigated how synchronous cortical activities to speech envelope relates to the speech intelligibility of sine-wave speech in different bandwidths with both normal hearing (NH) and CI listeners. 12 NH and four CI participants were recruited. We divided our NH participants into two groups: 1) Six NH listeners, 2) six NH listening to CI simulation synthesized using a noise vocoder. In our third group, 3) four CI users, one of them participated in only behavioral tests. Neural tracking was obtained using multi-channel electroencephalogram (EEG) system and cross-checked with behavioural performance, speech perception scores and speech quality ratings. Our result showed that intelligible sine-wave speech can be built with a small number of sinusoidal components selected from the original speech spectrum. Our cross-correlation analysis between cortical activities and speech envelope fluctuation showed an increasing trend in their synchrony with sine-wave speech built using more sinusoidal components for both group 2) and 3). Cortical entrainment to speech envelope is more observable in CI users compared to NH listened to CI simulated sine-wave speech. Our result have implications for understanding of neural tracking in terms of spectrally degraded speech perception in NH and CI individuals. Keywords: Sinusoidal model, electroencephalogram (EEG), cortical entrainment, speech intelligibility, hearing prosthesis. Read more →

Frequency Estimation in Interpolated Discrete Fourier Transform With Generalized Maximum Sidelobe Decay Windows for the Control of Power

The study presented in this article demonstrates that the sin p time window family is an extension of class I Rife–Vincent windows to a more general class, i.e., generalized maximum sidelobe decay (GMSD) windows. The presented frequency characteristics and other useful formulas derived for GMSD windows allow the derivation of a method to estimate the frequency of a sinusoidal component of a multifrequency signal based on the interpolated discrete Fourier transform. The presented estimation method is a significant generalization of methods already known. The method uses GMSD windows and takes into account the conjugate component in the spectrum. The method can be widely used, and, in particular, it allows for fast and accurate estimation of the frequency for a short data record (even below 1–2 signal periods). One of the many possible applications is frequency estimation in a power control system, which was studied in the accuracy analysis.

Low Frequency Injection as a Method of Low-Level DC Microgrid Communication

This paper provides a simple low-level unidirectional global communication method for DC microgrids, and requires no hardware modifications to the microgrid and interfacing power electronic converters. The underlying premise to this communication method is injecting low-frequency low-voltage sinusoidal components into the DC microgrid power lines. This method deviates from the common bit-level communication scheme by relating parameters and commands with certain frequency components. Communication structures are included as a basis for communication protocols, and a detection method is proposed for detecting the injected frequencies. The injection method, communication structure, and detection method are implemented on a live-scale DC microgrid.

Computation and Analysis of Electric Field Distribution Under Lightning Impulse Voltage for 1000-kV Gas-Insulated-Switchgear Spacer

The electric field distribution is critical to the insulation structure design of 1000-kV gas-insulated-switchgear (GIS) equipment. At present, it is not difficult to obtain the electric field distribution under commercial frequency sinusoidal voltage; however, for lightning impulse voltage, the electric field distribution is commonly substituted by electrostatic analysis under the peak voltage. As a result, this treatment may not embody the characteristics of the dielectric constant changing with frequency. In this paper, a frequency-domain mathematical model for transient analysis is established. The measured broadband frequency dielectric spectrum for the medium of a GIS spacer is well fitted by a H–N function model with three relaxation peaks. The transient analysis for a 1000-kV GIS spacer is realized by superposing the responses to the sinusoidal and direct current components of the lightning impulse waveform. The potential and electric field regulation for a 1000-kV GIS spacer under lightning impulse voltage is presented and analyzed. Furthermore, the computed results from traditional electrostatic analysis are introduced for comparison. The results indicate that the electrostatic analysis increases the computed electric field strength at the surface of the GIS spacer, while it decreases that at the interface between the GIS spacer and center conductor. It could provide computational support for the insulation structure design of 1000-kV GIS spacers.

Elimination of aperiodic components of measuring elements of relay protection

The authors propose the algorithms to calculate the actual values of currents and their derivatives. The algorithms allow a sharp reduction in the aperiodic components of currents in the calculated actual values and their derivatives. The algorithms are developed to calculate the instantaneous values of positive- and negative-sequence currents when the information obtained during a time interval equal to two milliseconds or less is used. An algorithm is devised to calculate the sinusoidal components of the currents in the presence of aperiodic components in the samples. To eliminate the disoperation of digital relay protection and improve the accuracy of fault location, it is necessary to eliminate the influence of aperiodic components in the currents drawn to the measuring devices of relay protection. The algorithm completely eliminates the aperiodic component at any time constants and is implemented by four samples of currents. The four samples of currents separated by three sampling intervals are sufficient for calculating all the parameters of currents, including the positive and negative-sequence currents, in particular in the case when the magnetic cores of current transformers reach saturation. The proposed methods for setting the industrial frequency parameters to avoid the aperiodic components in short-circuit currents are based on the algorithms that process the data from three and four samples of currents.

Tide‐Storm Surge Interactions in Highly Altered Estuaries: How Channel Deepening Increases Surge Vulnerability

AbstractWe develop idealized analytical and numerical models to study how storm surge amplitudes vary within frictional, weakly convergent, nonreflective estuaries. Friction is treated using Chebyshev polynomials. Storm surge is represented as the sum of two sinusoidal components, and a third constituent represents the semidiurnal tide (D2). An empirical fit of storm surge shows that two sinusoidal components adequately represent storm surge above a baseline value (R2 = 0.97). We find that the spatial transformation of surge amplitudes depends on the depth of the estuary, and characteristics of the surge wave including time scale, amplitude, asymmetry, and surge‐tide relative phase. Analytical model results indicate that surge amplitude decays more slowly (larger e‐folding) in a deeper channel for all surge time scales (12–72 hr). Deepening of an estuary results in larger surge amplitudes. Sensitivity studies show that surges with larger primary amplitudes (or shorter time scales) damp faster than those with smaller amplitudes (or larger time scales). Moreover, results imply that there is a location with maximum sensitivity to altered depth, offshore surge amplitude, and time scale and that the location of observed maximum change in surge amplitude along an estuary of simple form moves upstream when depth is increased. Further, the relative phase of surge to tide and surge asymmetry can change the spatial location of maximum change in surge. The largest change due to increased depth occurs for a large surge with a short time scale. The results suggest that both sea level rise and channel deepening may also alter surge amplitudes.

Majorana bound states in nanowire-superconductor hybrid systems in periodic magnetic fields

We study how the shape of a periodic magnetic field affects the presence of Majorana bound states (MBS) in a nanowire-superconductor system. Motivated by the field configurations that can be produced by an array of nanomagnets, we consider spiral fields with an elliptic cross-section and fields with two sinusoidal components. We show that MBS are robust to imperfect helical magnetic fields. In particular, if the amplitude of one component is tuned to the value determined by the superconducting order parameter in the wire, the MBS can exist even if the second component has a much smaller amplitude. We also explore the effect of the chemical potential on the phase diagram. Our analysis is both numerical and analytical, with good agreement between the two methods.

Spectral integration of infrasound at threshold.

The present study investigated the effect of the number of spectral components on the threshold in quiet of infrasound stimuli. Stimuli with one, two, or three sinusoidal components were presented monaurally to the ear with a low-distortion infrasound reproduction system. All components of the complex tones had the same level relative to their respective pure-tone threshold. The data are consistent with the assumption of a (perceptually weighted) intensity integration at threshold: The level at threshold for each component is 3 dB lower when two components were presented simultaneously. Thresholds decrease further, when a three-tone complex is used.

Partial discharge characteristics of oil-paper insulation for on-board traction transformers under superposed inter-harmonic AC voltages

Oil-paper insulation of higher voltage winding and traction winding in on-board traction transformers frequently withstand large AC fluctuation voltages mainly combined with AC and inter-harmonic components. This paper presents the characteristics of partial discharge (PD) of oil-paper insulation under superimposed inter-harmonic AC voltages. The experimental results show that the addition of the inter-harmonic to the fundamental sinusoidal component results in variation of peak voltage and dv/dt along the phase. This superimposed inter-harmonic AC voltages has a significant impact on PD including partial discharge inception voltage (PDIV), breakdown voltage, PD repetition rate, and phase resolved partial discharge (PRPD). In addition, a dynamic characterization method of PD statistical parameters is proposed to determine the developing trend. The critical values and inflection points of PD are obtained. Besides, the theoretical mechanism is expounded to better interpret and understand the influence of inter-harmonic component on PD properties. These methods will provide the dynamic datasets and more information for insulation condition assessment of on-board traction transformer.

Wave excitation force estimation of wave energy floats using extended Kalman filters

In many advanced control strategies the wave excitation force is key to determining the control input. However, it is often difficult to measure the excitation force on a Wave Energy Converter (WEC). The use of Kalman filters to estimate the wave excitation force based on readily available measurement data can potentially fill the gap between the development of WEC control strategies and the data that is available. Two different estimation methods using an nonlinear Extended Kalman Filter are tested on experimental wave tank data for a heaving semi-submerged float. The first method relies on directly including the excitation force as a state in the first order dynamics—which allows the “random walk” of the Kalman filter to identify an estimate of the excitation force. The second method of estimation involves modeling the wave excitation force as a harmonic oscillator comprised of sinusoidal components. Both methods are evaluated for a variety of incident waves and additional sensitivity analyses are performed to investigate the susceptibility of these estimation methods to changes in the model, measurement noise, and sampling rate.

Research on Sinusoidal Error Compensation of Moiré Signal Using Particle Swarm Optimization

In this paper, the sinusoidal error compensation method based on particle swarm optimization (PSO) is researched to reduce the subdivision precision loss caused by sinusoidal error in a grating moire signal. On the basis of the principle of arctangent subdivision of a grating moire signal, the subdivision error caused by sinusoidal error is quantitatively analysed. In view of the sinusoidal error compensation method, the signal compensation method involves complex calculations and occupies many resources; therefore, a sinusoidal error angle compensation method is proposed. The principle of the sinusoidal error angle compensation method based on the PSO algorithm is explained in detail. Aiming at the large calculation amount of the PSO algorithm, the appropriate PSO parameters are selected experimentally, and the complexity of the PSO algorithm is minimized while ensuring the fitting accuracy. The parameters of the signal waveform equation are solved using the PSO algorithm on the field-programmable gate array (FPGA) platform. According to the parameters solved, a lookup table for sinusoidal error compensation is designed. The grating system platform is built to verify the effect of the compensation scheme on the FPGA platform. The results show that the compensation method can effectively reduce the sinusoidal error component in the signal, and the subdivision error is reduced from 0.95” to 0.56” in the time domain. Consequently, the zero-order, first-order, second-order and third-order components are considerably suppressed. The compensation scheme can realize the sinusoidal error compensation of the grating moire signal and effectively improve the measurement accuracy of the grating encoder.