Amplitude Probability Distribution Research Articles

유빙 하중을 받는 내빙 선박의 피로손상도 추정Part I - 직접 해석법

In this study, a fatigue damage estimation for an ice-going vessel navigating through broken ice fields was carried out. A numerical model to simulate the interaction between ice and structure developed using the finite element method was introduced. Time series of stresses calculated by the proposed model and the corresponding fatigue analysis results are presented. The numerical model enables the long time analysis through an efficient interaction model, the application of the periodic media analysis and the convolution integral, and it allows the stress time history to be extracted directly using the finite element method. To describe the probability distribution of stress amplitudes, the 2-parameter Weibull model was applied to the calculated stress time history, and the fatigue damage was calculated using the Palmgren-Miner rule. Finally, the fatigue damage considering the ice conditions of the Baltic Sea was calculated using the proposed method and LR method, and the results were compared to each other.

Numerical simulation on the ice-induced fatigue damage of ship structural members in broken ice fields

A fatigue damage assessment for an ice-going ship navigating through broken ice fields was carried out using a numerical model to simulate the interactions between ice floes and structure. The stress history was obtained by a numerical model and the corresponding fatigue analysis results are presented. The stress time series required for fatigue analysis could be extracted directly using an efficient interaction model, the application of a periodic media analysis method, and the convolution integral. A 2-parameter Weibull model was applied to describe the probability distribution of the stress amplitude, and the fatigue damage was obtained using the Palmgren-Miner rule. Finally, the fatigue damage considering the actual ice conditions of the Baltic Sea was calculated using the proposed method and LR method, and each result was compared.

Ferroelectric switching and scale invariant avalanches in BaTiO3

Ferroelectric-field switching in $\mathrm{BaTi}{\mathrm{O}}_{3}$ generates ``Barkhausen noise'' when domain walls are displaced. We show by acoustic emission spectroscopy that electric-field switching of ${90}^{\ensuremath{\circ}}$ boundaries generates large strain fields, which emit acoustic phonons during ferroelectric hysteresis measurements. We use highly sensitive receivers (microphones) to measure the time sequences of noise in close analogy to noise patterns in ferroelastic and magnetic materials. Domain-wall interactions and jamming generate the ``crackling noise'' that follows scale invariant avalanche dynamics: the avalanche energy and amplitude probability distribution functions follow power laws with exponents $\ensuremath{\varepsilon}=1.65$ (energy) and \ensuremath{\tau}\ensuremath{'} = 2.25 (amplitudes). Aftershocks are very common and follow Omori law with probability $\ensuremath{\sim}{t}^{\ensuremath{-}p}$ where $t$ is the time elapsed after the main shock and $p$ is the Omori exponent $p\ensuremath{\sim}1$. The interevent times follow a double power-law distribution with exponents 0.9 for small times and 2.2 for the larger times. The scaling behavior is consistent with predictions of mean field theory.

Measurement based Characterization of Electromagnetic Noise for Industrial Internet of Things

The Industrial Internet of Things (IIOT) can help the manufacturing enterprises improve the production efficiency, reduce costs and achieve intelligent factory production. In this harsh scenario, however, the electromagnetic noise performs a severe impact on IIOT which uses low-power wireless sensor devices. In this article, we aim to characterize electromagnetic noise for IIoT systems based on the realistic measurement data collected in an automobile factory. The measurements were taken in time and frequency domain into account. By using the frequency-domain measurement data, we can extract the frequency occupation and power amplitude information of electromagnetic noise in 300MHz~3GHz band. By using the time-domain measurement data, the amplitude probability distribution (APD) could be obtained of electromagnetic noise at 315MHz, 779MHz and 916MHz bands. Then, an improved bell shaped spectrum is used to characterize the frequency spectrum of wide band electromagnetic noise.

Exploratory study on adequacy of upper extremity position during smartphone usage

This study compared the effects of the prone, side-lying, and sitting positions during smartphone use. Positions can cause discomfort in the upper extremity musculoskeletal system. Thirty healthy young adults were recruited and instructed to type on a smartphone for 5 min in each position and 5 min rest between each position. Electromyography data acquired from the upper extremity muscles were analysed using the amplitude probability distribution function (APDF) method. Wrist and elbow joint angles were assessed using the motion analysis system (MyoMotion). In 50% of APDFs, the flexor carpi ulnaris muscle displayed higher muscle activity in the side-lying position, whereas the abductor pollicis brevis (APB) and extensor carpi ulnaris (ECU) muscles showed higher muscle activity in the sitting position. In 90% of APDF, the upper trapezius, ECU, and APB muscles showed higher muscle activity in the sitting position. Additionally, the side-lying position showed a neutral wrist extension angle of 0° compared to the prone and sitting positions (p < 0.05). Using smartphones in the side-lying position is recommended to reduce overuse of the upper-extremity muscles and poor alignment of the wrists.

Workstation configuration and container type influence upper limb posture in grocery bagging

IntroductionRepetitive movements and awkward postures are two persistent injury risk factors for grocery store cashiers. Due to the recent rise in popularity of environmentally-friendly grocery bagging options, current recommendations for cashiers are likely outdated. Correspondingly, the objective of this study was to examine the effects of cashier-specific work demands, workstation configuration, and container type on upper limb postures during typical job activities. MethodsFifteen experienced cashiers bagged groceries at varying combinations of workstation height (low, medium, high) and container type (reusable bins, reusable bags, plastic bags). Upper limb movement was quantified with motion capture and amplitude probability distribution functions of humeral elevation and humeral axial internal rotation were used to assess the static (10th percentile), median (50th percentile), and peak (90th percentile) postural demands, which were then interpreted in the context of existing postural guidelines. ResultsHigh workstation height and reusable bags increased right arm elevation at peak posture by 15.7° compared to the low workstation height and reusable bin combination. However, reusable bins increased internal rotation demands of the right arm by 4.3° compared to other container types. Left arm elevation and internal rotation were consistently lower than right arm angles. ConclusionCashiers are encouraged to adjust the workstation to decrease the arm elevation and internal rotation required by higher workstation heights and tall containers, and to use both arms for scanning and packing, when possible, to reduce undesirable arm postures.

Surface roughness analysis in finishing end-milling of duplex stainless steel UNS S32205

Duplex stainless steel (DSS) UNS S32205 presents high resistance to oxidation, corrosion, and corrosion under stress associated with good mechanical properties, thus being widely used in oil exploration and chemical treatment systems. Due to these characteristics, studies on surface quality are justified in the machining of such materials. In this work, dry machining end-milling tests were performed with positive geometry cutting tools (coated carbide inserts with tip radius of 0.4 mm) with different cutting parameters. Each cutting parameter was evaluated in three levels, combined through Box-Behnken Design of experiments (BBD): cutting speed (30, 45, 60 m/min), feed per tooth (0.05, 0.1, 0.15 mm/tooth), and depth of cut (0.2, 0.4, 0.6 mm). Two surface roughness parameters (Ra and Rz) were measured in the machined surfaces under different cutting combinations. Roughness profiles were analyzed for the highest and lowest measured values of surface roughness, and Abbott-Firestone Curve (AFC) and amplitude-probability distribution (APD) represented its statistical profile. In this way, appropriate combination of cutting parameters for minimum Ra and Rz parameters obtained after finishing end-milling of UNS S32205 were determined, as well as AFC and APD of these values, thus allowing the characterization of the performance of tool-workpiece pair in DSS cutting, resulting in Ra and Rz values of 0.182 and 1.302 μm, respectively. Low surface roughness values were validated using BBD, representation of the statistical profile, and optimization of cutting parameters improved the little bibliographical material in DSS milling.

Quantitative evaluation method for liver fibrosis based on multi-Rayleigh model with estimation of number of tissue components in ultrasound B-mode image

The development of a quantitative diagnostic method for liver fibrosis using an ultrasound B-mode image is highly required. In our previous study, a multi-Rayleigh model was proposed to express a probability distribution of echo envelope amplitude from a fibrotic liver. Using the multi-Rayleigh model, a structure of fibrotic tissue can be quantitatively estimated. In this study, a method of estimating the number of tissue components was proposed to improve the accuracy of estimating a fibrotic tissue structure. Using threshold processing for a squared Mahalanobis distance of moments, which is a statistical property of echo envelope amplitude, the number of tissue components could be quantitatively estimated. The results of evaluation of clinical ultrasound B-mode images using the multi-Rayleigh model with estimation of the number of tissue components well reflected the tissue structural changes caused by liver fibrosis. It was concluded that our proposed method of estimating the number of tissue components improves the accuracy of liver fibrosis evaluation based on the multi-Rayleigh model.

МОДЕЛИРОВАНИЕ ЛОКАЦИОННЫХ СИГНАЛОВ, ОТРАЖЕННЫХ ОТ КРОМКИ ЗЕМЛЯ-МОРЕ

Introduction: Mathematical models of echo signals from underlying surfaces of the land and sea are used in synthesis and analysis of aircraft onboard radars which carry out the search, detection and tracking of objects. In these cases, the echoes are noise on whose background the information signals are selected and processed. When approximating the density of the reflected signal amplitude probability distribution, many researchers use the Rayleigh distribution density. To approximate the amplitude distribution of signals reflected by an underlying surface, the studies of high-precision radars characteristics often use log-normal distribution density, Weibull distribution density, compound distributions and some other distribution densities. Purpose: We develop a universal algorithm to simulate the fluctuations of radar signals reflected from the edge of land and sea. Results: We have obtained a simulation algorithm which allows you to simulate the fluctuations of a signal reflected from the edge of land and sea. As the distribution laws for amplitude and power of the signals reflected from underlying surfaces, we used the log-normal law for the reflections from the sea, and the Weibull distribution law for the reflections from the land. The algorithm synthesis technique allows you to use other distribution laws, too. The simulation algorithms for the signals reflected from the land or sea are special cases of the presented algorithm. Practical relevance: This algorithm can be used in the development of coastline mapping equipment, as well as in testing flarecraft takeoff and landing modes near ports.

A Simple Statistical Method for the Automatic Detection of Ripples in Human Intracranial EEG.

High frequency oscillations (HFOs) are a promising biomarker of epileptic tissue, but detection of these electrographic events remains a challenge. Automatic detectors show encouraging results, but they typically require optimization of multiple parameters, which is a barrier to good performance and broad applicability. We therefore propose a new automatic HFO detection algorithm, focusing on simplicity and ease of implementation. It requires tuning of only an amplitude threshold, which can be determined by an iterative process or directly calculated from statistics of the rectified filtered data (i.e. mean plus standard deviation). The iterative approach uses an estimate of the amplitude probability distribution of the background activity to calculate the optimum threshold for identification of transient high amplitude events. We tested both the iterative and non-iterative approaches using a dataset of visually marked HFOs, and we compared the performance to a commonly used detector based on the root-mean-square. When the threshold was optimized for individual channels via ROC curve, all three methods were comparable. The iterative detector achieved a sensitivity of 99.6%, false positive rate (FPR) of 1.1%, and false detection rate (FDR) of 37.3%. However, in an eight-fold cross-validation test, the iterative method had better sensitivity than the other two methods (80.0% compared to 64.4 and 65.8%), with FPR and FDR of 1.3, and 49.4%, respectively. The simplicity of this algorithm, with only a single parameter, will enable consistent application of automatic detection across research centers and recording modalities, and it may therefore be a powerful tool for the assessment and localization of epileptic activity.

Characteristics of Spark Discharge from Faulty Insulators

SUMMARYThe radiation field from the spark discharge on faulty insulators of distribution lines often influences broadcasting services of radio and television, and communication services. The spark discharge occurs due to loose connection in a metal‐fittings connection of strain insulators. The rust of metal‐fittings and the low‐tension of wire are causes of loose connection. In this paper, the generation conditions of spark discharge were clarified by the basic experiment. And the radiation field which includes frequency component of several GHz due to the spark discharge was measured using a 6.6 kV full‐scale distribution line, and the amplitude probability distribution of electric field was analyzed.

On-off intermittency in coupled chaotic thermoacoustic oscillations.

This paper documents on-off intermittency observed in coupled thermoacoustic chaotic oscillations. Mode competition between two or three oscillation modes engenders chaotic oscillations through quasiperiodic oscillations introduced by a local cross-sectional change in a gas-filled tube. Complete synchronization is then obtained by connecting two thermoacoustic chaotic oscillators via a rigid plate with an orifice. From the analysis of pressure fluctuations, theoretical statistical scaling laws related to the laminar phases, spectral density, and amplitude probability distribution are found to be satisfied in the coupled thermoacoustic oscillators, when the thermoacoustic complete synchronization breaks down through an on-off intermittency route with the decreased orifice size.

Experimental Research on Vibration Fatigue of CFRP and Its Influence Factors Based on Vibration Testing

A new research method based on vibration testing for the vibration fatigue of FRP was proposed in this paper. Through the testing on a closed-loop controlled vibration fatigue test system, the vibration fatigue phenomenon of typical carbon-fiber-reinforced plastic (CFRP) cantilevered laminate specimens was carefully studied. Moreover, a method based on the frequency response function was proposed to monitor the fatigue damage accumulation of specimens. On the basis of that, the influence factors that affect the vibration fatigue life of CFRP were experimentally studied. The influence of amplitude probability distribution of the vibration load spectrum on the fatigue life was deeply explored. Compared with Gaussian random vibration, the non-Gaussian random load has a significant impact on the vibration fatigue life of CFRP. The experimental results also showed that the magnitude of power spectral density (PSD) has a significant effect on the vibration fatigue life of specimens. For Gaussian vibration load, the frequency bandwidth almost has no effects on the vibration fatigue life of CFRP. However, for non-Gaussian vibration load, it has a great impact on the fatigue life. When PSD magnitude and frequency bandwidth are constant, the root mean square (RMS) is proportional to the vibration fatigue life of composites.

Influence of input device, work surface angle, and task on spine kinematics.

With the increase of tablet usage in both office and industrial workplaces, it is critical to investigate the influence of tablet usage on spine posture and movement. To quantify spine kinematics while participants interacted with a tablet or desktop computer. Fourteen participants volunteered for this study. Marker clusters were fixed onto body regions to analyze cervical and lumbar spine posture and sampled at 32 Hz (Optotrak Certus, NDI, Waterloo, Canada). Participants sat for one hour in total. Cervical and lumbar median angles and range of motion (10th to 90th % ile angles) were extracted from amplitude probability distribution functions performed on the angle data. Using a sloped desk surface at 15°, compared to a flat desk, influenced cervical flexion (p = 0.0228). Completing the form fill task resulted in the highest degree of cervical flexion (p = 0.0008) compared to the other tasks completed with cervical angles between 6.1°-8.5° higher than emailing and reading respectively. An interaction between device and task (p = 0.0061) was found for relative lumbar median spine angles. Increased lumbar flexion was recorded when using a computer versus a tablet to complete various tasks. Task influenced both cervical and lumbar spine posture with the highest cervical flexion occurring while completing a simulated data entry task. A work surface slope of 15° decreased cervical spine flexion compared to a horizontal work surface slope.

On-off intermittency in coupled chaotic thermoacoustic systems

We present chaos-chaos synchronization in coupled thermally induced acoustic gas oscillation systems. By introducing a local cross-sectional change in a gas-filled tube subjected to a temperature gradient, chaotic oscillations are found to be achieved through the mode competition. The chaos-chaos synchronization is then obtained by connecting the two thermoacoustic oscillators via a rigid plate with an orifice. Theoretical statistical scaling laws regarding the laminar phases, spectral density, and amplitude probability distribution are found to be satisfied in the coupled thermoacoustic oscillators, as presented from the analysis of pressure fluctuations when the thermoacoustic chaos-chaos synchronization breaks down with the decreased orifice size.

2-D Digital Predistortion Using Vector Quantization Method for Dual-Band Transmitters

This paper proposes a two-dimensional (2-D) digital predistortion (DPD) technique using vector quantization piecewise (VQP) method to compensate for nonlinearities of power amplifiers (PAs) in concurrent dual-band wireless transmitters. 2-D DPD architecture is used to extract the predistortion coefficients and linearize the PA in each band separately, which results in lower sampling rates of digital-to-analog and analog-to-digital converters compared to traditional 1-D method. Vector quantization method is introduced to divide the 2-D signal space into several regions in terms of signal amplitude probability distribution and subtle 2-D memory polynomial (MP) models are assigned to the regions, thus the proposed technique can linearize the PA in the whole signal amplitude range successfully due to the fact that PA nonlinearities are usually dependent on amplitude modulation characteristics strongly. The performance of dual-band wideband code division multiple access (WCDMA) signals which are 100 MHz apart is investigated. The simulation results show that when the region number is 16, 2-D VQP DPD implement can improve the PA's adjacent channel power ratio (ACPR) by about 13dBc, and it is 8 dB better than the 2-D PDD method.

Universal Inverse Power-Law Distribution for Fractal Fluctuations in Dynamical Systems: Applications for Predictability of Inter-Annual Variability of Indian and USA Region Rainfall

Dynamical systems in nature exhibit self-similar fractal space–time fluctuations on all scales indicating long-range correlations and, therefore, the statistical normal distribution with implicit assumption of independence, fixed mean and standard deviation cannot be used for description and quantification of fractal data sets. The author has developed a general systems theory based on classical statistical physics for fractal fluctuations which predicts the following. (1) The fractal fluctuations signify an underlying eddy continuum, the larger eddies being the integrated mean of enclosed smaller-scale fluctuations. (2) The probability distribution of eddy amplitudes and the variance (square of eddy amplitude) spectrum of fractal fluctuations follow the universal Boltzmann inverse power law expressed as a function of the golden mean. (3) Fractal fluctuations are signatures of quantum-like chaos since the additive amplitudes of eddies when squared represent probability densities analogous to the sub-atomic dynamics of quantum systems such as the photon or electron. (4) The model predicted distribution is very close to statistical normal distribution for moderate events within two standard deviations from the mean but exhibits a fat long tail that are associated with hazardous extreme events. Continuous periodogram power spectral analyses of available GHCN annual total rainfall time series for the period 1900–2008 for Indian and USA stations show that the power spectra and the corresponding probability distributions follow model predicted universal inverse power law form signifying an eddy continuum structure underlying the observed inter-annual variability of rainfall. On a global scale, man-made greenhouse gas related atmospheric warming would result in intensification of natural climate variability, seen immediately in high frequency fluctuations such as QBO and ENSO and even shorter timescales. Model concepts and results of analyses are discussed with reference to possible prediction of climate change. Model concepts, if correct, rule out unambiguously, linear trends in climate. Climate change will only be manifested as increase or decrease in the natural variability. However, more stringent tests of model concepts and predictions are required before applications to such an important issue as climate change. Observations and simulations with climate models show that precipitation extremes intensify in response to a warming climate (O’Gorman in Curr Clim Change Rep 1:49–59, 2015).

Probabilistic characteristics of noisy Van der Pol type oscillator with nonlinear damping

The exact Fokker–Planck equation for the joint probability distribution of amplitude and phase of a Van der Pol oscillator perturbed by both additive and multiplicative noise sources with arbitrary nonlinear damping is first derived by the method of functional splitting of averages. We truncate this equation in the usual manner using the smallness of the damping parameter and obtain a general expression for the stationary probability density function of oscillation amplitude, which is valid for any nonlinearity in the feedback loop of the oscillator. We analyze the dependence of this stationary solution on system parameters and intensities of noise sources for two different situations: (i) Van der Pol generator with soft and hard excitation regimes; (ii) Van der Pol oscillator with negative nonlinear damping. As shown, in the first case the probability distribution of amplitude demonstrates one characteristic maximum, which indicates the presence of a stable limit cycle in the system. The non-monotonic dependence of stationary probability density function on oscillation frequency is also detected. In the second case we examine separately three situations: linear oscillator with two noise sources, nonlinear oscillator with additive noise and nonlinear oscillator with frequency fluctuations. For the last two situations, noise-induced transitions in the system under consideration are found.

Reconstruction of Far-Field Tsunami Amplitude Distributions from Earthquake Sources

The probability distribution of far-field tsunami amplitudes is explained in relation to the distribution of seismic moment at subduction zones. Tsunami amplitude distributions at tide gauge stations follow a similar functional form, well described by a tapered Pareto distribution that is parameterized by a power-law exponent and a corner amplitude. Distribution parameters are first established for eight tide gauge stations in the Pacific, using maximum likelihood estimation. A procedure is then developed to reconstruct the tsunami amplitude distribution that consists of four steps: (1) define the distribution of seismic moment at subduction zones; (2) establish a source-station scaling relation from regression analysis; (3) transform the seismic moment distribution to a tsunami amplitude distribution for each subduction zone; and (4) mix the transformed distribution for all subduction zones to an aggregate tsunami amplitude distribution specific to the tide gauge station. The tsunami amplitude distribution is adequately reconstructed for four tide gauge stations using globally constant seismic moment distribution parameters established in previous studies. In comparisons to empirical tsunami amplitude distributions from maximum likelihood estimation, the reconstructed distributions consistently exhibit higher corner amplitude values, implying that in most cases, the empirical catalogs are too short to include the largest amplitudes. Because the reconstructed distribution is based on a catalog of earthquakes that is much larger than the tsunami catalog, it is less susceptible to the effects of record-breaking events and more indicative of the actual distribution of tsunami amplitudes.

Adaptive Strategies in the Leader Propagation Model for Lightning Shielding Failure Evaluation: Implementation and Applications

Lightning shielding failure accounts for the highest proportion of lightning accidents for transmission systems above 500 kV. The leader propagation model (LPM) was found to be effective in the analysis of lightning shielding failure of high-voltage transmission lines, especially for the ultrahigh voltage (UHV) transmission systems. However, it was generally inefficient to calculate the shielding failure rate by LPM, since the progress of lightning development must be simulated repeatedly, which is time-consuming, and no adaptive implementation of LPM has been reported. In this paper, adaptive strategies to accelerate the computation of shielding failure analysis by LPM were proposed, which include the adaptive time step control according to the electric field at the conductor surface, non-uniform lightning current sampling based on the lightning current amplitude probability distribution, and the adaptive lightning location sampling based on recursive adaptive Simpson’s method. The analysis results were validated by the field data of the UHV transmission line in Japan, and the efficiency of the adaptive strategies was shown by the shielding failure analysis of a typical 500 kV ac transmission line.