• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.240-244
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• 2003

In this paper, we present the CFD and experimental results for flow characteristics as well as pressure fluctuation in a T-type ball valve. In the experiment, flow visualization for the wake is performed with a fluorescent dye. In CFD, the valve flow is simulated three-dimensionally using a commercial fluid analysis code, FLUENT 6.0. FFT analysis to the pressure fluctuation in the wake region is also calculated Analysis results show that the characteristic frequency of the wake flow is strongly dependent on the Reynolds number.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.3
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• pp.116-122
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• 2006

A fast scan digital-IF FFT receiver at the radio communication band is presented for spectrum monitoring applications. It is composed of three parts: RF front-end, fast LO board, and signal processing board. It has about 19GHz/s scan rate, multi frequency resolution from 10kHz to 2.5kHz, and high sensitivity of below -99dBm. The design and performance analysis of the digital-IF FFT receiver are presented.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.10
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• pp.530-538
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• 2004

A electromagnetic waves are used for sensing in insulation diagnosis at electric machine or equipment. When it a method, waves are transformed into the FFT(Fast Fourier Transform); a kind of the process for data transformation. In a general way, a scientist use frequncy band 30[㎒]～l[㎓] to applied field. If we are measured high frequency band, we will need to a high capacity hardware. Also a antenna has a fault on atmospheric phenomena, outside environment and the like. In this paper We proposed new method for detecting electric equipment faulty state using only electric voltage which is generally measured in the electric and electronic field. It is called the Partition-FFT The analytic method is this first divide measured voltage waves into equal parts, second each deal with give effect to the FFT, finally each results deal with a graphic method and gather graphic. We are compare Partition-FFT with discharge form by tracking tester. As the result it demonstrated that the Partition-FFT is applicable.

• Journal of IKEEE
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• v.23 no.2
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• pp.614-621
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• 2019

In this paper, we presents the integral equation-fast Fourier transform(IE-FFT) and block matrix preconditioner (BMP) to solve electromagnetic scattering problems of penetrable structures composed of dielectric or magnetic materials. IE-FFT can significantly improve the amount of calculation to solve the matrix equation constructed from the moment method(MoM). Moreover, the iterative method in conjunction with BMP can be significantly reduce the number of iterations required to solve the matrix equations which are constructed from electrically large structures. Numerical results show that IE-FFT and block matrix preconditioner can solve electromagnetic scattering problems for penetrable objects quickly and accurately.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.209-215
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• 2010

This paper describes a design of variable-length FFT/IFFT processor (VL_FCore) for OFDM-based multi-standard communication systems. The VL_FCore adopts in-place single-memory architecture, and uses a hybrid structure of radix-4 and radix-2 DIF algorithms to accommodate various FFT lengths in the range of $N=64{\times}2^k\;(0{\leq}k{\leq}7)$. To achieve both memory size reduction and the improved SQNR, a two-step conditional scaling technique is devised, which conditionally scales the intermediate results of each computational stage. The performance analysis results show that the average SQNR's of 64~8,192-point FFT's are over 60-dB. The VL_FCore synthesized with a $0.35-{\mu}m$ CMOS cell library has 23,000 gates and 32 Kbytes memory, and it can operate with 75-MHz@3.3-V clock. The 64-point and 8,192-point FFT's can be computed in $2.25-{\mu}s$ and $762.7-{\mu}s$, respectively, thus it satisfies the specifications of various OFDM-based systems.

• Journal of the Korean Magnetics Society
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• v.22 no.5
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• pp.178-182
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• 2012

This research suggested that the extraction of respiratory rate could be made possible by using frequency analysis in the data process for clip-type pulsimeter equipped with permanent magnet and Hall sensor. The pulse analysis included of cardiac motion information depending on variation of pulse waveforms is investigated by means of Fast Fourier Transformation (FFT). The peaks of FFT spectrums measured at 15, 20, 30, 40, and 50 tempos are coincided to each respiratory rate having 0.125 Hz, 0.16 Hz, 0.25 Hz, 0.33 Hz, and 0.41 Hz, respectively. The FFT spectrum using algorithm for the extraction of respiratory rate showed the best pulse waves measured during 300 s. Based upon these results, the clip-type pulsimeter could extract the effective respiratory rate reflecting physical effects.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.73-79
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• 1999

Finite element equations by using fast Fourier transformation were formulated for studying temperatures resulting from frictional heating in sliding systems. The equations include the effect of velocity of moving components. The program developed by using FFT-FEM that combines Fourier transform techniques and the finite element method, was applied to the sliding bearing system. Numerical prediction obtained by FFT-FEM was in an excellent agreement of experimental temperature measurements.

• Proceedings of the IEEK Conference
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• 2002.06a
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• pp.33-36
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• 2002

A new smart antenna scheme based on spatial FFT is proposed. By combining the output of spatial FFT, the proposed structure shows similar performance gain compared to ordinary smart antenna systems. Moreover. the proposed scheme could be easily integrated to general receiver without beam focusing module. The analysis and simulation results show that the performances of proposed scheme are comparable to ordinary smart antenna systems

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.255-256
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• 2002

In this paper, the frictional behavior according to the contact geometry was investigated using a micro-tribotester built inside a Scanning Electron Microscope (SEM) and an Atomic Force Microscope (AFM). FFT (Fast Fourier Transform) analysis for friction was conducted as a method to interpret the contact condition. From the experimental results, it could be concluded that the relative dimensions and distribution of contact asperities on the surface could be predicted by the power spectrum and main frequency in the FFT analysis of the friction signal.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.343-346
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• 1998

In this paper a radiation problem for a finite microstrip antenna structure is analyzed. For the analysis of finite structures we utilize the equivalent volume current. Intergral equation for the unknown equivalent volume current induced on a finite microstrip structure is derived and solved by the use of conjugate gradient-fast fourier. transform (CG-FFT) method. Some numerical examples are radiation patterns derived by the equivalent volume current solved by the conjugate gradient-fast fourier transform.