• ETRI Journal
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• v.45 no.6
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• pp.1035-1045
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• 2023

We propose a novel graphics processing unit (GPU) algorithm that can handle a large-scale 3D fast Fourier transform (i.e., 3D-FFT) problem whose data size is larger than the GPU's memory. A 1D FFT-based 3D-FFT computational approach is used to solve the limited device memory issue. Moreover, to reduce the communication overhead between the CPU and GPU, we propose a 3D data-transposition method that converts the target 1D vector into a contiguous memory layout and improves data transfer efficiency. The transposed data are communicated between the host and device memories efficiently through the pinned buffer and multiple streams. We apply our method to various large-scale benchmarks and compare its performance with the state-of-the-art multicore CPU FFT library (i.e., fastest Fourier transform in the West [FFTW]) and a prior GPU-based 3D-FFT algorithm. Our method achieves a higher performance (up to 2.89 times) than FFTW; it yields more performance gaps as the data size increases. The performance of the prior GPU algorithm decreases considerably in massive-scale problems, whereas our method's performance is stable.

• Journal of Advanced Navigation Technology
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• v.22 no.5
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• pp.429-435
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• 2018

In radar systems, FFT (fast Fourier transform) operation is necessary to obtain the range and velocity of target, and the design of an FFT processor which operates at high speed is required for real-time implementation. The perfect shuffle network is suitable for high-speed FFT processor. In particular, twice perfect shuffle network based on radix-4 is preferred for very high-speed FFT processor. Moreover, radar systems that requires various velocity resolution should support scalable FFT points. In this paper, we propose a 8~1024-point scalable FFT processor based on twice perfect shuffle network algorithm and present hardware design and implementation results. The proposed FFT processor was designed using hardware description language (HDL) and synthesized to gate-level circuits using $0.65{\mu}m$ CMOS process. It is confirmed that the proposed processor includes logic gates of 3,293K.

• Journal of the Korean Society of Combustion
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• v.22 no.2
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• pp.1-8
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• 2017

To evaluate the combustion instability of a gas turbine combustor, the DMD technique was applied. The mode frequency results for each fuel composition were compared with FFT(Fast Fourier Transform) results. The damping coefficient, which is a quantitative parameter for combustion instability, was evaluated for 5 experimental cases. The flame transfer function (FTF) was calculated in the most unstable test case. In deriving the FTF, gain and phase were calculated using DMD technique. As a result of the analysis of the OH radical perturbation of the DMD, the heat release fluctuation was the highest at 100 Hz, at which the highest value of gain is observed. The frequency of FFT and FTF were different. In order to clarify the reason for this, FTF for various resonance frequencies was performed and it shows that the pattern of gain was similar to FFT.

• Journal of Advanced Navigation Technology
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• v.24 no.2
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• pp.85-91
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• 2020

Recently, a multi-mode radar system was designed for efficient operation of unmanned aerial vehicles (UAVs) in various environments, which has the advantage of being able to integrate and utilize methods of the pulse Doppler (PD) radar and the frequency modulated continuous wave (FMCW) radar. For the range detection part of the multi-mode radar signal processor (RSP), the hardware structure using the FFT processor and the IFFT processor is required to be designed in a way that improves efficiency on the area side. In addition, given the radar application environment that requires a variety of distance resolutions, FFT processors need to support variable-length operations. In this paper, the FFT processor and IFFT processor in multi-mode RSP range estimation are designed and proposed as hardware for a single FFT processor that supports variable length operation of 16-1024 points. The proposed FFT processor designed in hardware description language (HDL) and can be implemented with 7,452 logic elements and 5,116 registers.

• Journal of The Korean Astronomical Society
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• v.48 no.1
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• pp.67-73
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• 2015

We present a novel method to implement time-delayed propagation of radiation fields in cosmological radiative transfer simulations. Time-delayed propagation of radiation fields requires construction of retarded-time fields by tracking the location and lifetime of radiation sources along the corresponding light-cones. Cosmological radiative transfer simulations have, until now, ignored this "light-cone effect" or implemented ray-tracing methods that are computationally demanding. We show that radiative transfer calculation of the time-delayed fields can be easily achieved in numerical simulations when periodic boundary conditions are used, by calculating the time-discretized retarded-time Green's function using the Fast Fourier Transform (FFT) method and convolving it with the source distribution. We also present a direct application of this method to the long-range radiation field of Lyman-Werner band photons, which is important in the high-redshift astrophysics with first stars.

• 연구논문집
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• s.31
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• pp.77-88
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• 2001

In this paper, the critical vibration limits of a spindle unit for a high speed ball pen tip processing machine are studied. The vibration of the spindle is measured by FFT, and the influence of the vibration amplitude due to unbalance, bearing deflect, bite, and timing belts tension is analyzed. The critical vibration limits of the spindle is determined by the X, and Z directional vibrations of the spindle. Both FET and RMS values can be used to analyze the vibration characteristics of the spindle. From experimental results the limit line can be drawn for the spindle. The RMS value for the vibration limit is 3 G.

• International Journal of Highway Engineering
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• v.15 no.4
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• pp.31-42
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• 2013

PURPOSES : The purpose of this study is to eliminate the noise of the vehicle after measuring the friction noise obtained from the NCPX (Noble Close ProXimity) method. The pure friction noise between the tire and road pavement could be determined from filtering the compositeness of sound and the influence of the vehicle noise. METHODS: The noise magnitude could be determined by analyzing the sound pressure level (SPL) and sound power level (PWL) along with the noise frequency of a FFT (Fast Fourier Transform) analysis as well as CPB (Constant Percentage Bandwidth) analysis. RESULTS: When the test for measuring the friction noise originated somewhere between tire and road pavement is performed with NCPX method, it must be fulfilled by attaching the surface microphone near the tire. In this condition, the surface microphone can measure the friction noise occurred at between tire and pavement, the chassis noise from the engine and power transfer units, the fluctuating aerodynamic noise, and the turbulence noise directly affected to the surface microphone. By using the NCPX method, the noise occurred at the vehicle must be eliminated for measuring the friction noise between tire and pavement from the traffic noise. CONCLUSIONS: The vehicle's testing engine noise depends on the vehicle and road types. The effect of vehicle's engine noise is less than the friction noise occurred at between tire and pavement at less than 1% effect.

• Korean Journal of Optics and Photonics
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• v.33 no.3
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• pp.106-112
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• 2022

A two-dimensional optical code division multiple access (OCDMA) encoder/decoder, which is composed of add/drop filters and all-pass filters for delay operation, is proposed. An example design is presented, and its feasibility is illustrated through numerical simulations. The chip area of the proposed OCDMA encoder/decoder could be about one-third that of a previous OCDMA device employing delay waveguides. Its performance is numerically investigated using the transfer-matrix method combined with the fast Fourier transform. The autocorrelation peak level over the maximum cross-correlation level for incorrect wavelength hopping and spectral phase code combinations is greater than 3 at the center of the correctly decoded pulse, which assures a bit error rate lower than 10^-3, corresponding to the forward error-correction limit.

• Journal of Multimedia Information System
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• v.4 no.4
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• pp.225-232
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• 2017

Understanding actions in videos is an important task. It helps in finding the anomalies present in videos such as fights. Detection of fights becomes more crucial when it comes to sports. This paper focuses on finding fight scenes in Hockey sport videos using blur & radon transform and convolutional neural networks (CNNs). First, the local motion within the video frames has been extracted using blur information. Next, fast fourier and radon transform have been applied on the local motion. The video frames with fight scene have been identified using transfer learning with the help of pre-trained deep learning model VGG-Net. Finally, a comparison of the methodology has been performed using feed forward neural networks. Accuracies of 56.00% and 75.00% have been achieved using feed forward neural network and VGG16-Net, respectively.

• Fibers and Polymers
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• v.5 no.3
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• pp.177-181
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• 2004

Current efforts to establish links between geometrical features and mechanical performance of nonwoven fabrics in general, and of point-bonded (spot-bonded) nonwovens in particular has been made using the measurements of Fiber Orientation Distribution Function (ODF) and tensile modulus which occurs during controlled-deformation experiments. Image analysis technique (using the Fast Fourier Transform) was used to quantify the fiber orientation distribution. The results suggest that, within a typical window of processing conditions, the fiber orientation has a significant influence on the anisotropical behavior of nonwoven. The data also suggest that mechanical anisotropy of thermally point-bonded nonwovens is likely to be governed by different load transfer mechanism according to the applied macroscopic tensile direction.