نتایج جستجو برای: Time-Frequency Domain

تعداد نتایج: 2571320  

Journal: :فیزیک زمین و فضا 0
جلیل ناصری کارشناس ارشد ژئوفیزیک، شرکت eni حمیدرضا سیاهکوهی دانشیار، گروه فیزیک زمین، مؤسسة ژئوفیزیک دانشگاه تهران، ایران

in seismic exploration studies different types of techniques are used to recognize seismic features in terms of their temporal and spatial spectra. variations in frequency content are sensitive to subtle changes in reflection information (castro de matos et al., 2003). in this study the joint time-frequency analysis is used for seismic texture recognition. discrete wavelet transform (dwt) witho...

Journal: :فیزیک زمین و فضا 0
احسان ذبیحی نائینی حمیدرضا سیاهکوهی

spectral decomposition is a powerful tool for analysis of seismic data. fourier transform determines the frequency contents of a signal. but for analysis of non-stationary signals, 1-d transform to frequency domain is not sufficient. in early years, transforming of seismic traces into time and frequency domain was done via windowed fourier transform, called a short time fourier transform (stft)...

ژورنال: فیزیک زمین و فضا 2018

Time-frequency filtering is an acceptable technique for attenuating noise in 2-D (time-space) and 3-D (time-space-space) reflection seismic data. The common approach for this purpose is transforming each seismic signal from 1-D time domain to a 2-D time-frequency domain and then denoising the signal by a designed filter and finally transforming back the filtered signal to original time domain. ...

ژورنال: ژئوفیزیک ایران 2020
Mahjoobeh Meskaranian Peyman Pour Moghaddam

This study derives the discretized adjoint states full waveform inversion (FWI) in both time and frequency domains based on the Lagrange multiplier method. To achieve this, we applied adjoint state inversion on the discretized wave equation in both time domain and frequency domain. Besides, in this article, we introduce reliability tests to show that the inversion is performing as it should be ...

Journal: :بینا 0
ابراهیم جعفرزاده پور e jafarzadehpour تهران- میرداماد- میدان محسنی- خیابان شهید شاه نظری- دانشکده علوم توانبخشی- گروه بینایی سنجی

purpose: comparison of the results of visual evoked potential (vep) in time domain and frequency domain between multiple sclerosis (ms) suspected patients and normal indivisuals. method: eleven ms suspected patients with normal visual findings and 20 normal individuals were tested by vep. results were compared between two groups. results: the time domain results showed no significant difference...

Journal: :مهندسی بیوسیستم ایران 0
احمد بناکار استادیار دانشگاه تربیت مدرس مفداد خزایی دانشجوی دکتری

in this paper, a smart method is designed in order to classify healthy and illness ducks using their emission voice. for this purpose, firstly, the birds based on their healthy condition are divided into the different categories and then their voices are saved using a microphone and data acquisition card. gained signals were transformed from time-domain signal to frequency domain using fast fou...

ژورنال: فیزیک زمین و فضا 2018

Spatial aliasing is an unwanted side effect that produces artifacts during seismic data processing, imaging and interpolation. It is often caused by insufficient spatial sampling of seismic data and often happens in CMP (Common Mid-Point) gather. To tackle this artifact, several techniques have been developed in time-space domain as well as frequency domain such as frequency-wavenumber, frequen...

Journal: :IEEE Transactions on Vehicular Technology 2020

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