scholarly journals Method for measuring the azimuth of an aerial target for a meter-range radar

2021 ◽  
pp. 26-31
Author(s):  
V. I. Ermoshkin ◽  
S. B. Shatkovsky ◽  
A. V. Shcherbinko ◽  
E. E. Fenyuk
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Antenna Array ◽  
New Method ◽  
Test Results ◽  
Radio Waves ◽  
Statistical Estimates ◽  
Pulse Processing ◽  
The Mean ◽  
Further Development

The purpose of the study is to develop a new method that increases the accuracy of measuring the azimuth of an air target for stationary radars of the meter range of radio waves with a fixed antenna array and a small number of antenna elements. For this, the known methods are considered and their disadvantages are revealed. The new method proposed by the authors uses a digital radiation pattern with a fast Fourier transform after intra-pulse processing of signals from the receiving elements of the antenna array at a given frequency. To refine the azimuth, an inverse fast Fourier transform is used, followed by signal processing and repeated measurement for each target with a small step. Calculations and test results are presented. Comparisons of statistical estimates of the mean and standard deviation of azimuth measurement tests by various methods are presented. The scientific novelty and directions for further development of the topic with the use of the results obtained have been established.

A Fast Method for Solving Contact Plasticity in a Half Space

2011 ◽  
Author(s):  
Zhanjiang Wang ◽  
Xiaoqing Jin ◽  
Shuangbiao Liu ◽  
Leon M. Keer ◽  
Jian Cao ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Residual Stresses ◽  
Fast Fourier Transform ◽  
Half Space ◽  
Three Dimensional ◽  
New Method ◽  
Fast Method ◽  
Discrete Convolution ◽  
Influence Coefficients ◽  
The One

This paper presents a new method of contact plasticity analysis based on Galerkin vectors to solve the eigenstresses due to eigenstrain. The influence coefficients relating eigenstrains to eigenstresses thus can be divided into four terms the one due to the eigenstrains in the full space, others due to the mirrored eigenstrains in the mirror half space. Each term can be solved fast and efficient by using the three-dimensional discrete convolution and fast Fourier transform (DC-FFT) or the three-dimensional discrete correlation and fast Fourier transform (DCR-FFT). The new method is used to analyze the contact plastic residual stresses in half space.

scholarly journals A study of acoustic characteristics of voluntary expiratory sounds produced before and immediately after swallowing

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Shoma Hattori ◽  
Shinji Nozue ◽  
Yoshiaki Ihara ◽  
Koji Takahashi
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Time Window ◽  
Maximum Amplitude ◽  
Comparison Method ◽  
Window Length ◽  
Acoustic Characteristics ◽  
The Mean ◽  
Time Waveform ◽  
The Relationship

AbstractTo evaluate the expiratory sounds produced during swallowing recorded simultaneously with videofluorographic examination of swallowing (VF) using fast Fourier transform (FFT), and to examine the relationship between dysphagia and its acoustic characteristics. A total of 348 samples of expiratory sounds were collected from 61 patients with dysphagia whose expiratory sounds were recorded during VF. The VF results were evaluated by one dentist and categorized into three groups: safe group (SG), penetration group (PG), and aspiration group (AG). The duration and maximum amplitude of expiratory sounds produced were measured as the domain characteristics on the time waveform of these sounds and compared among the groups. Time window-length appropriate for FFT and acoustic discriminate values (AD values) of SG, PG, and AG were also investigated. The groups were analyzed using analysis of variance and Scheffé's multiple comparison method. The maximum amplitude of SG was significantly smaller than those of PG and AG. The mean duration in SG (2.05 s) was significantly longer than those in PG (0.84 s) and AG (0.96 s). The AD value in SG was significantly lower than those in PG and AG. AD value detects penetration or aspiration, and can be useful in screening for dysphagia.

scholarly journals Periodic Noise Removal in Strain and Natural Images Using 2-D Fast Fourier Transform

2013 ◽  
pp. 90-94
Author(s):  
Mandeep Kaur ◽  
Dinesh Kumar ◽  
Ekta Walia ◽  
Manjit Sandhu
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Frequency Domain ◽  
Noise Removal ◽  
Natural Images ◽  
Periodic Pattern ◽  
Periodic Noise ◽  
Mean Filter ◽  
The Mean

This paper presents a 2-D FFT removal algorithm for reducing the periodic noise in natural and strain images. For the periodic pattern of the artifacts, we apply the 2-D FFT on the strain and natural images to extract and remove the peaks which are corresponding to periodic noise in the frequency domain. Further the mean filter applied to get more effective results. The performance of the proposed method is tested on both natural and strain images. The results of proposed method is compared with the mean filter based periodic noise removal and found that the proposed method significantly improved for the noise removal.

scholarly journals ANALISIS KEMUNCULAN SPREAD F DI ATAS KUPANG

2019 ◽  
Vol 4 (1) ◽  
pp. 8-16
Author(s):  
Adrianus Marselus Seran ◽  
Ali Warsito ◽  
Jehunias L. Tanesib
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
High Frequency ◽  
Satellite System ◽  
Radio Waves ◽  
Geomagnetic Disturbances ◽  
Ionospheric Layer ◽  
Spread F ◽  
F Distribution ◽  
Global Navigation

Abstrak  Telah  dilakukan dilakukan penelitian tentang kemunculan spread F di atas Kupang dengan menggunakan data hasil scalling ionogram pada tahun 2013 hingga 2015. Penelitian ini bertujuan untuk mengetahui kerakteristik kejadian spread F dan variasi tipe kemunculan spread F berdasarkan klimatologi kemunculannya  yang berdampak pada perambatan gelombang radio High Frequency (HF;3-30 MHz) dan sistem navigasi berbasis satelit yang dikenal Global Navigation Satelit System (GNSS). Kemunculan spread F mempunyai korelasi dengan kejadian sintilasi yang bersumber dari aktivitas matahari dan gelombang gravitasi yang umunya terjadi pada malam hari (18.00-06.00) LST. Hasil analisis kemunculan Spread F pada periode tahun 2013-2015 menunjukan bahwa kemunculan spead F tertinggi di tahun 2014 dengan tipe spread F frekuensi karena pada periode tahun 2014 masih merupakan puncak siklus matahari ke 24 meskipun dikatakan siklus  terlemah atau aktivitas mataharinya sangat minimum namun gangguan aktivitas matahari seperti flare dan CME awal bulan pertengahan bulan tahun 2014 sangat tinggi intensiasnya yang menimbulkan gangguan geomagnet pada lapisan ionosfer sangat besar dimana tipe spread F frekuensi disebabkan oleh gangguan geomagnet. Intensitas kejadian spread F terjadi di pertengahan tahun yakni bulan Juni dibandingkan dengan bulan-bulan awal dan akhir tahun yang tingkat kemunculannya rendah terutama pada fase ekuinoks. Jumlah kemunculan spread F maksimum terjadi pada tengah malam (22.00-03.00) LST dan minimum di awal dan di akhir malam. Analisis dalam domain frekuensi dengan menggunakan metode Fast Fourier Transform (FFT), menunjukan bahwa adanya kemunculan spread F selama 3 tahun (36 bulan) terjadi rentang waktu 200 hingga 600 hari. Frekuensi kemunculan spread F untuk tiap tahunnya adalah 0,1 sampai 0,2 perhari. Informasi ini menunjukan bahwa intensitas kemunculan spread F yang dapat mengganggu perambatang pelombang radio pada lapisan ionosfer di atas wilayah Kupang masih rendah dengan periode kejadian yaitu 365 hari atau 1 tahun selama 3 tahun  (2013-2015) dan dapat digunakan sebagai indicator peluang kejadian spread F setiap tahunnya. Kata kunci: Spread F; FFT; Kupang  Abstract  Research has been conducted on the emergence of the distribution of F above Kupang by using scaling ionogram data from 2013 to 2015. This study aims to study the characteristics of F distribution events and variations in the type of occurrence of F distribution based on their climatology appearance used in High Frequency radio wave moorings (HF ; 3-30 MHz) and a satellite-based navigation system called the Global Navigation Satellite System (GNSS). The appearance of spread F has an interaction with the scintillation event that originates from the activity of the sun and the wave of release that occurs at night (18.00-06.00) LST. The results of the analysis of the emergence of the F spread in the period 2013-2015 indicate that the appearance of the highest F spead in 2014 with the type of spread F frequency in the period of 2014 is still the peak of the 24th solar cycle which is expected to be protected or used by the minimum sun to be used to monitor solar activity such as flares and CME at the beginning of the middle of 2014 is very high, which causes geomagnetic disturbances in the ionospheric layer to be very large where the frequency F type spread is related to geomagnetic interference. The intensity of diffuse F events occurs in the middle of the year in June compared to the initial and end of the year with a low rate of occurrence in the equinox phase. The maximum number of occurrences of the F spread occurs at midnight (10:00 p.m.: 00: 00) LST and minimum at the beginning and end of the night. Analysis in the domain using the Fast Fourier Transform (FFT) method, showed that there were occurrences that spread F for 3 years (36 months) occurring in the range 200 to 600 days. The frequency of occurrence of spread F for each semester is 0.1 to 0.2 per day. This information shows that the intensity of the spread of occurrence of F that can be carried out by radio waves in the ionospheric layer above the Kupang region is still low with an event period of 365 days or 1 year for 3 years (2013-2015) and can be used as an Annual indicator. Keywords: Spread F; FFT; Kupang

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