Power Spectrum Method Research Articles

Gear Tooth Failure Detection by the Resonance Demodulation Technique and the Instantaneous Power Spectrum Method – A Comparative Study

The role of gears in industry for speed and torque variation purposes is obvious. The gearbox diagnostic methods have been improved quickly in recent years. In this paper, two of the newest methods, the resonance demodulation technique (R.D), and the instantaneous power spectrum technique (IPS) are applied to gearbox vibration signals and their capabilities in fault detection are compared. Yet, the important role of time averaging should not be dispensed with, as it is the primary step for both techniques. In the present study, the mathematical method of these techniques, according to the mathematical vibration model of gears, is introduced, these techniques are applied to the test rig data, and finally the results of both methods are compared. The results indicate that in each method, the location of fault can be estimated and it is located in the same angular position in both methods. The IPS method is applicable to severe faults, whereas the resonance demodulation technique is a simple tool to recognize the fault at each severity and at the early stages of fault generation.

A Study of Digital Watermark Algorithm Based on HVS for Halftone Images

Special printing material and special techniques are used for the purpose of fighting against the piracy of the presswork. But these methods require high standard technology and high production costs. Using digital watermark can guarantee a strong and low cost protection for the presswork. Existing digital watermark algorithms for halftone images are mostly applied to FM (Frequency Modulation) screening and these algorithms usually complete the embedding process by modulating the coefficients of the frequency domain. Such algorithms are relatively complex, and they are easy to lose information so that it will make a lower detection probability. Moreover, in the actual printing process, AM (Amplitude Modulation) screening is the more mature and more widely used method compared with FM screening. The subject of this article is monochrome presswork generated by AM screening. The structure of this article is as follows: The first section uses the principle of HVS (Human Visual System) model to select the area in which the watermark will be embedded. The second section uses different screening threshold matrixes to create the printing dots in the selected area. In this way, a texture of certain direction is formed. The last section uses Fourier Power Spectrum method to detect the texture features of the screened image to complete the detection of the watermark. The result of the experiment shows that this algorithm can generate a digital watermark of good transparency and high detection effectiveness. It combines a unique AM screening approach to complete the embedding process. All the processes do not require any additional equipment, and the embedding and detection process are quite simple.

Reconstruction of October Mean Temperature since 1796 in Wuying Based on Tree Ring Data

The monthly mean temperature for October in the Fenglin National Natural Reserve of Wuying, in Heilongjiang province, was reconstructed for the period running from 1796 to 2004 using RES tree ring chronology. The explained variance of the reconstruction is 34.8%. In the past 209 years, there are 4 colder and 4 warmer periods according to the reconstructed series. A period of 3.33-year is found significant based on the power spectrum method. Abrupt changes are also detected in the reconstructed series with 30-year time scale based on the smoothing t-test, smoothing F-test and Le Page test methods. Significant abrupt changes in mean value are observed for around 1871 and 1900, and a significant abrupt change in standard deviation is observed for around 1851. CitationYin, H., H. Liu, L. Huang, et al., 2010: Reconstruction of October mean temperature since 1796 in Wuying based on tree ring data. Adv. Clim. Change Res.,1, doi: 10.3724/SP.J.1248.2010.00100.

Identification of Fractal Scale Parameter of Machined Surface Profile

In order to identify fractal scale parameters of machined surface profile accurately, the precisions of different parameter identification methods, such as power spectrum method, structure function method and variance method, are analyzed and compared. Based on discrete power spectrum function and variance method, a revised method of scale parameter identification is advanced. Results show that, in contrast with other methods, the new method could identify more accurate parameter. Those methods are adopted to identify parameters of machined surface profile. The variation of fractal parameters with surface roughness is studied. Research indicated that the preferred method to identify fractal scale parameter is the revised method; otherwise, significant error may occur in the results of parameter identification.

An investigation into observational characteristics of rainfall and temperature in Central Northeast India—a historical perspective 1889–2008

Mann–Kendall non-parametric test was employed for observational trend detection of monthly, seasonal and annual precipitation of five meteorological subdivisions of Central Northeast India (CNE India) for different 30-year normal periods (NP) viz. 1889–1918 (NP1), 1919–1948 (NP2), 1949–1978 (NP3) and 1979–2008 (NP4). The trends of maximum and minimum temperatures were also investigated. The slopes of the trend lines were determined using the method of least square linear fitting. An application of Morelet wavelet analysis was done with monthly rainfall during June–September, total rainfall during monsoon season and annual rainfall to know the periodicity and to test the significance of periodicity using the power spectrum method. The inferences figure out from the analyses will be helpful to the policy managers, planners and agricultural scientists to work out irrigation and water management options under various possible climatic eventualities for the region. The long-term (1889–2008) mean annual rainfall of CNE India is 1,195.1 mm with a standard deviation of 134.1 mm and coefficient of variation of 11%. There is a significant decreasing trend of 4.6 mm/year for Jharkhand and 3.2 mm/day for CNE India. Since rice crop is the important kharif crop (May–October) in this region, the decreasing trend of rainfall during the month of July may delay/affect the transplanting/vegetative phase of the crop, and assured irrigation is very much needed to tackle the drought situation. During the month of December, all the meteorological subdivisions except Jharkhand show a significant decreasing trend of rainfall during recent normal period NP4. The decrease of rainfall during December may hamper sowing of wheat, which is the important rabi crop (November–March) in most parts of this region. Maximum temperature shows significant rising trend of 0.008°C/year (at 0.01 level) during monsoon season and 0.014°C/year (at 0.01 level) during post-monsoon season during the period 1914–2003. The annual maximum temperature also shows significant increasing trend of 0.008°C/year (at 0.01 level) during the same period. Minimum temperature shows significant rising trend of 0.012°C/year (at 0.01 level) during post-monsoon season and significant falling trend of 0.002°C/year (at 0.05 level) during monsoon season. A significant 4–8 years peak periodicity band has been noticed during September over Western UP, and 30–34 years periodicity has been observed during July over Bihar subdivision. However, as far as CNE India is concerned, no significant periodicity has been noticed in any of the time series.

Quantitative Analysis of Asymmetrical Cortical Activity Based on Power Spectrum Changes

The present study intends to quantitatively analyze power changes in blood oxygenation level-dependent (BOLD) signals, and to investigate functional asymmetry of cortical activity in motor areas during sequential finger movements. A power spectrum method was employed, mainly in contrast with the signal magnitude analysis, to investigate functional asymmetry of motor area cortical activity. Six right-handed subjects were included in the functional magnetic resonance imaging (fMRI) experiments. Both bi-handed and single-handed movements were analyzed. The power spectrum method demonstrated that right-handed subjects exhibited a larger power difference in BOLD signals between task and rest states in the right motor area than in the left motor area. These results showed that more nerve cells were evoked in the right motor area of right-handed subjects. In addition, the power spectrum method was confirmed to be a valid quantitative-analysis method for brain asymmetry analyses.

Chaotic bubbles and phase locking for a shaker system in the vicinity of three coexisting critical points

In this paper, the dynamical model of the shaker system, Poincaré maps, Jacobian matrix and power spectrum are established. Different phase-locking phenomena and chaotic bubbles are investigated in the vicinity of three coexisting critical points including Hopf–Hopf bifurcation point, 1:3 resonance point and 1:4 resonance point. In two strong resonance cases, phase-locking dynamics and associated bifurcations are easily to occur. Coexisting attractors have also been introduced to provide mechanisms for chaotic bubbles with connections between pieces. The occurrence of phase locking on doubling torus to multi-period leads to interruption of torus-doubling bifurcation. Isolated chaotic bubbles are birth via period-doubling bifurcation of such a multi-period. Phase-locking phenomena on T2 torus are also observed in such a neighborhood of critical points. The number of periods on torus by phase locking can be identified by power spectrum methods. The system parameters may be optimized by studying of phase-locking dynamics of this system.

S0505-1-4 ピエゾアクチュエータの駆動信号波形と境界層中に励起される速度変動波の関係([S0505-1]乱流遷移(1))

The characteristics of the velocity fluctuation waves excited by a piezo actuator are investigated. The actuator is driven by two kinds of signals: a sinusoidal and a rectangular signal. In order to investigate the characteristics, two methods are chosen. They are the power spectrum method and the correlation coefficient method. The comparison of the power spectrum peaks of the two cases shows that the fluctuation waves grow along the flow direction at different growth ratios. It is also found that the waveform changes for the rectangular signal case.

The Periodicity Analysis of the Light Curve of 3C 279 and Implications for the Precession Jet

ABSTRACTWe have analyzed the light curves of 3C 279 at 22 GHz, 37 GHz, optical R band, and X-ray (2–10 KeV), and found evidence of quasi-periodic outbusts. The light curves show that 3C 279 is an extremely active object. A period of P = 130.6 ± 1.3 days was consistently confirmed by three methods: the power-spectrum method, the discrete correlation function (DCF) method, and the Jurkevich method. Based on the relationship between observed period Pobs and the precession period Pp given by Rieger and our result, the precession period of jet in 3C 279 is Pp ≃ 29.6 yr, which is completely consistent with the precession period of jet of about 30 yr obtained by Carrara et al.. This suggests that there is a precession jet in 3C 279 and the variability period of about 130.6 days that we obtained is most likely caused by the helical motion of the jet.

Study on Fractal Characteristic of Surface Micro-Topography of Micro-WEDM

The surface micro-topography of micro-WEDM is random, disordered and multi-scale and has been proved that it is fractal with the characteristic of self-affinity within a certain scale on the basic of the fractal geometry theory. According to the characterization of W-M fractal function, the principles of three evaluation methods about power spectrum method, structure function method and wavelet criterion have been described. The advantages and disadvantages of them evaluating the fractal property of the surface micro-topography of micro-WEDM have been compared in this paper. The experimental results indicate that the wavelet criterion is more stable and dependable than the other two methods, so the fractal dimension D of the surface micro-topography of micro-WEDM has been calculated using it. The result shows that the fractal dimension has the tendency of decrease with the increase of root mean square deviation (Sq) value while it is not absolutely monotonic, which can be used as a beneficial supplement to traditional evaluation parameters of surface roughness.

Dynamic Scaling and Fractal Behavior of Phase Dispersion in Multicomponent Polymer Blends

Dynamic scaling and fractal behavior of phase dispersion in a binary polymer mixture of polypropylene with poly(cis-butadiene) rubber during processing in a batch mixer was studied by means of a back small-angle laser scattering (BSALS) online system. In the late stage of phase dispersion, a special fractal behavior was found; different overlapped line groups existed simultaneously and the temporal distribution was stochastic. We defined the special behavior as quasi-self-similarity and calculated the fractal dimension, D p, by using the power spectrum method. The results show that the evolution of different fractal dimensions with time is consistent with average chord length of the dispersed phase.

Root cause diagnosis of plant-wide oscillations using the concept of adjacency matrix

Oscillations are a common type of plant-wide disturbances whose effects propagate to many units and thus may impact overall process performance. It is important to detect and diagnose such oscillations early in order to rectify the situation. Many frequency domain tools such as the power spectrum and spectrum envelope methods are capable of detecting the oscillation frequency. However, few methods are available for locating the root cause which is the main objective of oscillation diagnosis. This paper proposes a new method to diagnose the root cause of plant-wide oscillations using the adjacency matrix. A novel feature of the new method is that it utilizes the information in the process flowsheet. The method is not data-based and it can be carried out without using any data. However, this method complements the data based methods very well and it is best used in combination with other data-based methods to provide powerful diagnosis of plant-wide oscillations. This paper is the subject of a newly proposed complete procedure for detection and diagnosis of plant-wide oscillation. Two industrial case studies are also presented to demonstrate the applicability of the proposed procedure.

Possible effect of solar activity on variation of the tree-rings of a 500 a platycladus orientalis at the Mausoleum of Emperor Huang

The variation of the tree-ring’s index of a platycladus orientalis at the Mausoleum of Emperor Huang and of a long series of sunspots relative number during AD1470–1974 are analyzed by using the wavelet power spectrum method, and their variation characters are also discussed. It is determined that the tree-ring’s variation has cycles of approximate 2–7, 11, 93 and 150 a. Two data series are used for analyzing sunspot relative number (SSN) variation. First, the analysis of the annual average SSN during AD1700–1974 proved that variation cycles are about 11, 50, and 93 a; then, the data during AD1465–1975 obtained from the decadal average SSN train over 7000 a reconstructed on the geomagnetic data is analyzed and its variation cycles are about 50, 90, and 160 a. Besides the tree-rings cycle of 2–7 a is commonly considered to be related to ENSO, while 11 a cycle is related to solar Schwabe cycle; in addition, it is possible that the cycles of 90 and150 a are likely to be related to solar Gleissberg cycle and Suess cycle. The correlations between them are possibly due to the effect of solar activity on the climate and additionally on the tree’s growth.

Interpretation of Magnetic Anomalies and Estimation of Depth of Magnetic Crust in Slovakia

The magnetic map of Slovakia used in the paper was compiled as part of a project titled Atlas of Geophysical maps and profiles in 2001. The residual magnetic data were analyzed to produce Curie point estimates. To remove distortion of magnetic anomalies caused by the Earth’s magnetic field, reduction to pole transformation was applied to the magnetic anomalies using the magnetization angle of the induced magnetization. Anomalies reduced to the pole tend to be better correlated with tectonic structures. We applied a 3-km upward continuation to the residually compiled magnetic anomalies in order to remove effects of topography. The depth of magnetic dipoles was calculated by an azimuthally averaged power spectrum method for the entire area. Such estimates can be indicative of temperatures in the crust, since magnetic minerals lose their spontaneous magnetization according to Curie temperature of the dominant magnetic minerals in the rocks. The computed Curie point depths in the Slovakia region vary between 15.2 km and 20.9 km. Heat flow higher than 100 mWm−2 occurs at the central volcanics and eastern part of Slovakia, where the Curie point depths values are shallow. The correlation between Curie point depths, heat flow and crust depth was investigated for two E-W cross sections. Heat flow and Curie point depth values are correlated with each other however, these values could not be correlated with crust depth. The Curie point isotherm, which separates magnetic and non-magnetic parts of the crust, is represented in two cross sections.

Impairment of the autonomic nervous function during decompression sickness in swine

Dysautonomia has been observed in many cardiac diseases; however, its effect in decompression sickness (DCS) has not been well examined largely due to the difficulty in obtaining experimental data in human or animal subjects. In this study, we examine how DCS affects the autonomic nervous system's (ANS) dynamics in swine. Baseline and post-DCS electrocardiograms were obtained via telemetry recordings and compared. These data were analyzed using both the power spectrum method and our recently developed principal dynamic mode (PDM) analysis. PDM is able to separate the dynamic tones of the sympathetic and parasympathetic nervous systems. Both methods demonstrated a statistically significant decrease (>55%; P < 0.05) in the dynamics of both branches of the autonomic nervous system in the swine with DCS compared with the control condition. In cardiac diseases such as myocardial infarction, ANS imbalance is often associated with a significant increase in sympathetic tone, which may or may not be counterbalanced by parasympathetic nervous activity. However, the effect of DCS is such that both branches of the ANS are depressed >55% compared with the control condition, suggesting impairment, but not imbalance, of the ANS.

Two-and-Three-Dimensional Crustal Thickness of the Eastern Pontides (NE Turkey)

The Eastern Pontide orogenic belt is divided into three subzones (northern, southern and axial zones) based on present lithologies and facies associations. NE-SW-, NW-SE- and E-W-trending fault systems, which play an important role in palaeotectonics and neotectonics of the Eastern Pontides, separate these zones. Three different methods were used to estimate the Moho depth from observed gravity value, namely (i) empirical relationship between Moho depth and Bouguer anomaly; (ii) spectral analysis of the radial wave number and; (iii) by the gravity inversion method. Power spectrum, a statistical approach, is a widely used technique to determine the depth of geological sources successfully. The empirical linear relations between the Bouguer anomalies and seismically determined crustal thicknesses have been used to compute depths to the Conrad and Moho discontinuities, which are consistent with the average depths obtained from the power spectrum method. The crustal structure was also determined from the inversion of a Bouguer anomaly profile along longitude 39°. Gravity inversion results are consistent with those obtained from the empirical relations and power spectrum methods. We calculated the maximum crustal thickness of 43.8 km in the studied region by using the gravity inversion method, which also showed that crustal thickness increases from north to south.

Generation of super smooth surface in compression of aluminum

In order to obtain fundamental information about generation of super smooth surface in metal forming, a simple compression test of aluminum strips is carried out. The tool and specimen surfaces are observed on the nanometer scale by atomic force microscope (AFM). It is found that the specimen surface asperities are smoothed to the almost same surface roughness as the tool on the nanometer scale at about 20% compressive strain. The maximum height in scanning range 20×20 μm2 and 500×500 nm2 are attained to 8 nm and 1 nm at the smoothest position of the specimen profiles, respectively. The tool and specimen surfaces are examined by the power spectrum method and the zeroset method of fractal analysis.

Measurement of Plethysmogram and Statistical Method for Analysis

The plethysmogram is measured at different points of human body by using the photo interrupter, which sensitively depends on the physical and mental situation of human body. In this paper the statistical method of the data-analysis is investigated to discuss the dependence of plethysmogram on stress and aging. The first one is the representation method based on the return map, which provides usuful information for the waveform, the flucuation in phase and the fluctuation in amplitude. The return map method makes it possible to understand the fluctuation of plethymogram in amplitude and in phase more clearly and globally than in the conventional power spectrum method. The second is the Lisajous plot and the correlation function to analyze the phase difference between the plethysmograms of the right finger tip and of the left finger tip. The third is the R-index, from which we can estimate “the age of the blood flow”. The R-index is defined by the global character of plethysmogram, which is different from the usual APG-index. The stress- and age-dependence of plethysmogram is discussed by using these methods.

Basinal Structure Of Yola Arm Of The Upper Benue Trough Nigeria; Evidence From Aeromagnetic Data

Aeromagnetic data interpretation of the Yola arm of the Upper Benue Trough has previously been carried out. However, no detail modeling of the Crustal Structures has been undertaken. Two composite reduced Aeromagnetic maps on a scale of 1:250,000 were digitized and processed using computer techniques. Analytical Signal, Power Spectrum and Upward Continuation methods were used prior to modeling of the subsurface structures. Forward and inverse modelings were done to determine the subsurface basin configuration. The result shows two sub-basins; the Lau and Yola sub-basins. The variations in sediment thickness within the Lau sub-basin is in the range of 2.0 – 4.5 km and in the Yola sub-basin 2.0 – 3.0 km respectively. The basin configurations from the modeled profiles depict that of horst and graben features resulting to variation in sediment thickness evident in Lau (Barwa to Yanga) subsector and Yola (Muleng) axis. The upward continuation revealed lineament trends in the NE-SW Yola (Muleng) axis and NW-SE Lau (Barwa to Yanga) subsector. Keywords : Upper Benue Trough, Basin configuration upward continuation, Analytical signal, power spectrum. Global Journal of Geological Sciences Vol. 6 (2) 2008: pp. 175-183

Implementation of a Fourier matched filter in CMB analyses

Aims. Implement a matched filter (MF) cross-correlation algorith m in multipole space and compare it to the standard Angular Cross Power Spectrum (ACPS) method. Apply both methods on a Integrated Sachs Wolfe (ISW) - Large Scale Structure (LSS) cross correlation scenario and study how sky masks influence the multipo le range where the cross correlation signal arises and its co mparison to theoretical predictions. Methods. The MF requires the inversion of a multipole covariance matrix that, under non-full sky coverage ( fsky < 1), is generally non-diagonal and singular. We choose a Singular Value Decomposition (SVD) approach that enables the identificatio n of those modes carrying most of the information from those more likely to introduce numerical noise, (that are dropped from the analysis). We compare the MF to the ACPS in ISW-LSS Monte Carlo simulations, focusing on the effect that a limited sky coverage has on the cross-correlation results. Results. Within the data model s = t+αm where t is Gaussian noise and m is a known filter, we find that the MF performs comparatively better than the ACPS for smaller values of fsky and scale dependent (non-Poissonian) noise fields. In the co ntext of ISW studies both methods are comparable, although the MF performs slightly more sensitively under more restrictive masks (smaller values of fsky). A preliminary analytical study of the ISW‐LSS cross correlation signal to noise (S/N) ratio shows that most of it should be found in the very large scales (50% of the S/N at l< 10, 90% at l< 40− 50), and this is confirmed by Monte Carlo simulations. The statistical significance of our cross-correlation stat istics reaches its maximum when considering l∈ [2, lmax], with lmax∈ [5, 40] for all values of fsky observed, despite of the smoothing and power aliasing that aggressive masks introduce in Fourier space. This l-confinement of the ISW-LSS cross correlation should enable a safe distinction from other secondary effects arising at smaller (higher l-s) angular scales.