Calculation Error's Correction of Three-Component Geomagnetic Field's Marine Survey

2013 ◽  
Vol 756-759 ◽  
pp. 323-326
Author(s):  
Xing Le Zhu ◽  
Chang Han Xiao ◽  
Zhen Ning Yao
Keyword(s):  
Wavelet Transform ◽  
High Frequency ◽  
Geomagnetic Field ◽  
Low Frequency ◽  
Frequency Component ◽  
Frequency Noise ◽  
Calculation Error ◽  
High Frequency Noise ◽  
Multi Scale ◽  
Simulation Results

In order to eliminate calculation error, wavelet transform is used to remove noise when navigational data is used to calculate truth-value of three-component geomagnetic field. By introducing Euler attitude rotation matrix, the computing value of geomagnetic vector is decomposed by multi-scale wavelet transform in each frequency. The high-frequency noise is removed and the accurate value of geomagnetic field can be got by rebuilding low-frequency component. Simulation results indicate that the calculated value is identical with setting value and has high precision, which means the method has great applied importance and instructional significance for practical measurement of marine three-component geomagnetic field.

Aerodynamic noise from an asymmetric airfoil with perforated extension plates at the trailing edge

2020 ◽  
pp. 1475472X2097838
Author(s):  
CK Sumesh ◽  
TJS Jothi
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Pore Diameter ◽  
Low Frequency ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Trailing Edge ◽  
High Frequency Noise ◽  
Displacement Thickness

This paper investigates the noise emissions from NACA 6412 asymmetric airfoil with different perforated extension plates at the trailing edge. The length of the extension plate is 10 mm, and the pore diameters ( D) considered for the study are in the range of 0.689 to 1.665 mm. The experiments are carried out in the flow velocity ( U∞) range of 20 to 45 m/s, and geometric angles of attack ( αg) values of −10° to +10°. Perforated extensions have an overwhelming response in reducing the low frequency noise (<1.5 kHz), and a reduction of up to 6 dB is observed with an increase in the pore diameter. Contrastingly, the higher frequency noise (>4 kHz) is observed to increase with an increase in the pore diameter. The dominant reduction in the low frequency noise for perforated model airfoils is within the Strouhal number (based on the displacement thickness) of 0.11. The overall sound pressure levels of perforated model airfoils are observed to reduce by a maximum of 2 dB compared to the base airfoil. Finally, by varying the geometric angle of attack from −10° to +10°, the lower frequency noise is seen to increase, while the high frequency noise is observed to decrease.

Effects of Noise Frequency on Performance and Annoyance for Women and Men

1981 ◽  
Vol 52 (2) ◽  
pp. 435-441 ◽  
Author(s):  
Kelli F. Key ◽  
M. Carr Payne
Keyword(s):  
Sex Differences ◽  
Magnitude Estimation ◽  
High Frequency ◽  
Ambient Noise ◽  
Direct Relationship ◽  
Low Frequency ◽  
Frequency Noise ◽  
Complex Task ◽  
High Frequency Noise ◽  
Noise Frequency

Effects of noise frequencies on both performance on a complex psychomotor task and annoyance were investigated for men ( n = 30) and women ( n = 30). Each subject performed a complex psychomotor task for 50 min. in the presence of low frequency noise, high frequency noise, or ambient noise. Women and men learned the task at different rates. Little effect of noise was shown. Annoyance ratings were subsequently obtained from each subject for noises of various frequencies by the method of magnitude estimation. High frequency noises were more annoying than low frequency noises regardless of sex and immediate prior exposure to noise. Sex differences in annoyance did not occur. No direct relationship between learning to perform a complex task while exposed to noise and annoyance by that noise was demonstrated.

Stereoscopic Images Enhancement Based on Edge Sharpening of Wavelet Coefficients

2014 ◽  
Vol 511-512 ◽  
pp. 490-494 ◽  
Author(s):  
Yi Min Qiu ◽  
Shi Hong Chen ◽  
Yi Zhou ◽  
Xin Hai Liu
Keyword(s):  
Wavelet Transform ◽  
High Frequency ◽  
Low Frequency ◽  
Subjective Assessment ◽  
Wavelet Coefficients ◽  
Stereoscopic Images ◽  
Multi Scale ◽  
Image Edge ◽  
Frequency Approximation ◽  
Edge Sharpening

This paper proposed a new image enhancement algorithm based on edge sharpening of wavelet coefficients for stereoscopic images. Our scheme uses the multi-scale characteristic of wavelet transform, decomposes the original image into low frequency approximation sub-graph and several high frequency direction. Under the multi-scale, the low frequency approximation sub-graph is processed by edge sharpening method. Then the low frequency sub-graph decomposes in multi-scale again. At last, the low frequency approximation graph after four layers decompose sharpening and the high frequency approximation of the decomposed sub-graph will be refactored to get the new image. Experimental results show that whether PSNR or visual effect, or the subjective assessment of the DMOS value, the proposed method has better enhanced performance than the conventional edge sharpening and wavelet transform. And it has good image edge enhancement, details protection. Meanwhile, the proposed algorithm has the same computational complexity with wavelet transform.

scholarly journals Seismic section image detail enhancement method based on bilateral texture filtering and adaptive enhancement of texture details

2020 ◽  
Vol 27 (2) ◽  
pp. 253-260
Author(s):  
Xiang-Yu Jia ◽  
Chang-Lei DongYe
Keyword(s):  
High Frequency ◽  
Structural Information ◽  
Low Frequency ◽  
Frequency Noise ◽  
Seismic Section ◽  
Multi Scale ◽  
Adaptive Enhancement ◽  
Enhancement Method ◽  
Frequency Components ◽  
Texture Filtering

Abstract. The seismic section image contains a wealth of texture detail information, which is important for the interpretation of the formation profile information. In order to enhance the texture detail of the image while keeping the structural information of the image intact, a multi-scale enhancement method based on wavelet transform is proposed. Firstly, the image is wavelet decomposed to obtain a low-frequency structural component and a series of high-frequency texture detail components. Secondly, bilateral texture filtering is performed on the low-frequency structural components to filter out high-frequency noise while maintaining the edges of the image; adaptive enhancement is performed on the high-frequency detail components to filter out low-frequency noise while enhancing detail. Finally, the processed high- and low-frequency components reconstructed by wavelets can obtain a seismic section image with enhanced detail. The method of this paper enhances the texture detail information in the image while preserving the edge of the image.

Effect of Stimulus Duration on Localization of Direction of Noise Stimuli

1970 ◽  
Vol 13 (4) ◽  
pp. 826-838 ◽  
Author(s):  
Willard R. Thurlow ◽  
James R. Mergener
Keyword(s):  
Stimulus Duration ◽  
Head Movement ◽  
High Frequency ◽  
Thermal Noise ◽  
Low Frequency ◽  
Frequency Noise ◽  
Noise Sources ◽  
Minimum Duration ◽  
High Frequency Noise ◽  
Efficient Performance

Localization of the direction of bursts of thermal noise was measured for both high-frequency and low-frequency bands, as a function of duration of bursts. Durations of 0.3, 1, 2, and 5 sec were used. Subjects were free to move their heads to aid in localization. Subjects were not specially trained in sound localization. With increase in stimulus duration, perception of elevation was slightly improved for low-frequency noise, probably due to increased information from head movement. A minimum duration of the order of 2 sec appears necessary to allow subjects to achieve maximum performance (which still is not very good for these low-frequency stimuli). Perception of the elevation of the high-frequency noise sources we used was relatively good even at the briefest duration; however, variability of judgment was larger at the shorter durations. Perception of front-back source position was much improved for both low-frequency and high-frequency noise when stimulus duration was increased. The results are understandable in terms of the increased possibility for head movement with increase in stimulus duration. It appears that one should use a minimum stimulus duration of about 2 sec if one wishes subjects to approach their most efficient performance.

Evidence for the existence of locally-generated body waves in the short-period noise at the Large Aperture Seismic Array, Montana

1972 ◽  
Vol 62 (1) ◽  
pp. 13-29 ◽  
Author(s):  
H. M. Iyer ◽  
John H. Healy
Keyword(s):  
Statistical Analysis ◽  
Phase Velocity ◽  
High Frequency ◽  
Seismic Noise ◽  
Average Velocity ◽  
Low Frequency ◽  
Body Waves ◽  
Frequency Noise ◽  
High Frequency Noise ◽  
Short Period

Abstract The approximate hexagonal configuration of LASA subarrays enables their use as omnidirectional arrays. This property is used to study the phase velocity of short-period seismic noise at different frequencies. It is found that the noise in the low-frequency band consists mainly of surface waves traveling with average velocities in the range 3.0 to 3.5 km/sec. The high-frequency noise, in the band 0.45 to 1.0 Hz, has an average velocity of about 6.0 km/sec. It is quite likely that the high-frequency noise has the nature of locally-generated body waves. Statistical analysis of Pg velocities observed during a crustal refraction experiment at LASA lends support to this hypothesis.

Impact of effective mass changes with mole-fraction on the analog/radio frequency benchmarking parameters in junctionless GaxIn1−xAs/GaAs field-effect transistor

2021 ◽  
pp. 2150238
Author(s):  
Mahdi Vadizadeh ◽  
Mohammad Fallahnejad
Keyword(s):  
Radio Frequency ◽  
Effective Mass ◽  
Mole Fraction ◽  
High Frequency ◽  
Cutoff Frequency ◽  
Frequency Noise ◽  
Noise Performance ◽  
High Frequency Noise ◽  
Gaas Structure ◽  
Simulation Results

In this paper, for the first time, changes in the effective mass (EM) of electron and hole with mole fraction are taken into account for extracting the benchmarking parameters of analog/radio frequency (RF) and high-frequency noise performance of junctionless (JL)-Ga[Formula: see text]In[Formula: see text]As/GaAs via simulation. In the JL-Ga[Formula: see text]In[Formula: see text]As/GaAs structure, considering changes in the effective mass with mole fraction is called a with-EM state, while the JL-Ga[Formula: see text]In[Formula: see text]As/GaAs structure without considering the changes in effective mass with mole fraction is called a without-EM state. The simulation results show that, per [Formula: see text], the maximum transconductance in the with-effective mass (EM) state is [Formula: see text] mS/[Formula: see text]m, which is reduced by 8% compared to the without-EM state. The JL-Ga[Formula: see text]In[Formula: see text]As/GaAs device in the with-EM state has the unity gain cutoff frequency of [Formula: see text] GHz, minimum noise figure of [Formula: see text] db, and available associated gain of [Formula: see text] db. The [Formula: see text] and [Formula: see text] parameters in the with-EM state decreased by 10% and 38%, respectively, compared to the without-EM state. Moreover, [Formula: see text] in the with-EM state increased by 65% compared to the without-EM state. Our simulation results indicated that an increase in electron effective mass with the increased [Formula: see text] can limit the analog/RF frequency and high-frequency noise performance of the JL-Ga[Formula: see text]In[Formula: see text]As/GaAs device.

scholarly journals Medical image fusion based on quaternion wavelet transform

2020 ◽  
Vol 14 ◽  
pp. 174830262093129
Author(s):  
Zhang Zhancheng ◽  
Luo Xiaoqing ◽  
Xiong Mengyu ◽  
Wang Zhiwen ◽  
Li Kai
Keyword(s):  
Wavelet Transform ◽  
Image Fusion ◽  
High Frequency ◽  
Medical Image ◽  
Low Frequency ◽  
Frequency Component ◽  
High Frequency Component ◽  
Medical Image Fusion ◽  
Quaternion Wavelet Transform ◽  
Fused Image

Medical image fusion can combine multi-modal images into an integrated higher-quality image, which can provide more comprehensive and accurate pathological information than individual image does. Traditional transform domain-based image fusion methods usually ignore the dependencies between coefficients and may lead to the inaccurate representation of source image. To improve the quality of fused image, a medical image fusion method based on the dependencies of quaternion wavelet transform coefficients is proposed. First, the source images are decomposed into low-frequency component and high-frequency component by quaternion wavelet transform. Then, a clarity evaluation index based on quaternion wavelet transform amplitude and phase is constructed and a contextual activity measure is designed. These measures are utilized to fuse the high-frequency coefficients and the choose-max fusion rule is applied to the low-frequency components. Finally, the fused image can be obtained by inverse quaternion wavelet transform. The experimental results on some brain multi-modal medical images demonstrate that the proposed method has achieved advanced fusion result.

Burial Process of a Seismic Station by Moving Dunes in Tarim Basin

2020 ◽  
Vol 91 (5) ◽  
pp. 2936-2941
Author(s):  
Xiaofeng Liang ◽  
Sicheng Zuo ◽  
Shilin Li ◽  
Yongge Feng
Keyword(s):  
High Frequency ◽  
Noise Level ◽  
Seismic Station ◽  
Low Frequency ◽  
Seismic Signal ◽  
Frequency Noise ◽  
Temperature Record ◽  
Environment Change ◽  
Broadband Seismometer ◽  
High Frequency Noise

Abstract A temporary seismometer vault was buried by a moving sand dune in the Taklimakan Desert at northwestern China in October 2019. The dune gradually covered the solar panel and the power supply to the seismic station was subsequently cut off. Here, we show that the burial process can be diagnosed according to the temperature record from the thermometer in the data-logger, an ultra-low-frequency seismic signal, and the change of high-frequency noise level from the continuous seismograms recorded by the broadband seismometer. The ultra-low-frequency seismic signal reflects the thermoelastic effect of the suspension spring in the seismometer corresponding to the temperature gradient in the sensor vault. At the same time, the variation of high-frequency noise level correlates well with the temperature profile and the ultra-low-frequency seismic signal, indicating the ground wind intensity. The peak frequency shifts and their different responses on three-component waveforms for the high-frequency noise might reflect the distance from the moving dunes to the station and their moving directions. This observation shows a potential usage of continuous seismograms to study rapid environment change around a temporary seismic station.

Effect of Perforated Tabs on the Noise Field of an Axisymmetric Jet

2013 ◽  
Vol 307 ◽  
pp. 250-256
Author(s):  
G. Fayaaz Hussain ◽  
Afthab Shaban Nasser ◽  
Mohammad Mohiudeen Nawaz ◽  
Bikash Kumar Mondal ◽  
N. Karthikeyan
Keyword(s):  
High Frequency ◽  
Supersonic Jet ◽  
Low Frequency ◽  
Frequency Noise ◽  
Noise Levels ◽  
Convergent Nozzle ◽  
High Frequency Noise ◽  
Axisymmetric Jet ◽  
Underexpanded Jets ◽  
Mach Numbers

Effect of triangular tabs with circular perforations on the acoustic far-field of an axisymmetric jet issued from a convergent nozzle of exit diameter of 30.16 mm was studied for both subsonic and sonic underexpanded cases. It was found that the noise in the low frequency range (Strouhal number < 0.29) reduced in both subsonic and supersonic jet mach numbers with a penalty in high frequency noise. OASPL plots showed that overall noise levels in subsonic jets increased due to the introduction of tabs except for far downstream angles where the noise levels reduced by 2 dB. Overall noise levels in underexpanded jets decreased in all directions and at all jet mach numbers without the penalty of high frequency noise. Comparison between tabs without perforation and perforated tabs showed that both the tabs were equally effective.

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