• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.103-106
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• 2001

본 논문은 radix-2 FFT를 파이프라인 기법으로 구현할때의 성능 향상을 위한 메모리 어드레싱기법에 대한 새로운 구조를 제안하고자 한다. Fast Fourier Transform(FFT) 프로세서의 속도 및 성능은 파이프라인 싸이클과 클럭에 좌우되므로, 동시에 병렬로 처리하기 위한 입력 데이타에 access 하기 위해 사용되어지는 기존의 메모리 어드레싱 기법은 지연문제로 인해 FFT 프로세서 성능 저하의 원인이 된다. 이 기법은 정확한 메모리 뱅크를 선택하기 위한 주소부 패러티 체크가 필요 없으므로 수행 속도를 빠르게 하고, ROM에 저장된 Coefficient의 실수부와 허수부의 상호교환특성을 이용하여 Coefficient ROM을 반으로 줄일 수 있다. 이 논문에서 제안된 구조는 VHDL을 사용하여 설계하였고, 설계된 회로를 시뮬레이션 및 합성시켰다.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.169-173
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• 2001

In this paper, dc link ripple currents for three-phase ac/dc/ac PWM converters are ana lysed in a frequency domain. The expression of the harmonic currents is developed by using switching functions and exponential Fourier series expansion. The dc link ripple currents with regard to power factor and modulation index are investigated. In addition, the effect of the displacement angle between the switching periods of line-side converters and load-side inverters on the dc link ripple current is studied. The result of the dc link current analysis is helpful in specifying the dc link capacitor size and its lifetime estimation.

• Proceedings of the KIEE Conference
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• 2007.04c
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• pp.194-197
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• 2007

This paper proposes a linearization technique for the 3 level NPC type inverter, which increases the linear control range of inverter up to the 6-step inverter. The overmodulation range is divided into two modes depending on the modulation index(MI), In mode I, the reference angles are derived from the Fourier series expansion of the reference voltage corresponds to the MI. In mode II, the holding angles are also derived in the same way. Therefore, it is possible to obtain the linear control and the maximized utilization of PWM inverter output voltage.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.540-540
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• 2013

In this studying, we investigated the basic properties of N-doped plasma polymer. The N-doped ethylcyclohexane plasma polymer thin films were deposited by radio frequency (13.56 MHz) plasma-enhanced chemical vapor deposition method. Ethylcyclohexenewas used as organic precursor (carbon source) with hydrogen gas as the precursor bubbler gas. Additionally, ammonia gas [NH3] was used as nitrogen dopant. The as-grown polymerized thin films were analyzed using ellipsometry, Fourier-transform infrared [FT-IR] spectroscopy, Raman spectroscopy, FE-SEM, and water contact angle measurement. The ellipsometry results showed the refractive index change of the N-doped ethylcyclohexene plasma polymer film. The FT-IR spectrashowed that the N-doped ethylcyclohexene plasma polymer films were completely fragmented and polymerized from ethylcyclohexane.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.285-287
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• 1997

We have deposited hydrogen-free diamond-like carbon (DLC) films by pulsed laser deposition of graphite. Pulsed laser deposition (PLD) can be utilized to generate films with desired properties quite different from those of the starting material. Since DLC films grown by PLD using turbo pump are perpared without hydrogen, they have a higher density and a higher index of refraction than the hydrogenated DLC films. In this study, effects of the substrate temperature and laser energy density on the properties of DLC films were systematically investigated. The structure and properties of the films have been studied by scanning electron microscopy (SEM), Fourier Transform Infrared (FT-IR), X-ray diffraction (XRD), and Raman spectroscopy.

• Journal of the Korean Mathematical Society
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• v.49 no.2
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• pp.293-314
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• 2012

We prove that the Siegel modular form of D'Hoker and Phong that gives the chiral superstring measure in degree two is a lift. This gives a fast algorithm for computing its Fourier coefficients. We prove a general lifting from Jacobi cusp forms of half integral index t/2 over the theta group ${\Gamma}_1$(1, 2) to Siegel modular cusp forms over certain subgroups ${\Gamma}^{para}$(t; 1, 2) of paramodular groups. The theta group lift given here is a modification of the Gritsenko lift.

• Preventive Nutrition and Food Science
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• v.6 no.2
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• pp.112-116
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• 2001

Oxidized potato starch/polyethylene (PE) cast films were prepared with different percentages of linear low density PE (LLDPE), oxidized potato starch and prooxidant. For the determination of biodegradability of the films, lignocellulose-degrading Streptomyces viridosporus T7A (ATCC 39115) was used. Films were chemically disinfected and incubated with S. viridosporus by shaking at 100 rpm at 37$^{\circ}C$ for eight weeks. Hydroxyl indices of the films by Fourier-Transform Infrared Spectroscopy, mechanical Properties of the films by Instron and film morphology by scanning electron microscope (SEM) were measured. The hydroxyl index of the film containing the oxidized potato starch incubated with S. viridosporus T7A was higher than that of the corresponding control. All the films containing 5% and 10% oxidized starch showed a decrease of tensile strength on the films after incubation when the corresponding uninoculated film was compared. In the oxidized starch/PE film incubated with S. viridosporus T7A, partial destruction of starch and PE was examined by SEM.

• Carbon letters
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• v.16 no.2
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• pp.121-126
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• 2015

Carbon fibers are prepared by stabilizing pitch fibers accompanying electron beam (E-beam) irradiation. The carbon fibers pretreated by E-beam irradiation achieve a higher stabilization index than the carbon fibers that are only heat-stabilized. In addition, the carbon fibers subjected to E-beam irradiation in the stabilization step exhibit a comparable tensile strength to that of general purpose carbon fibers. The carbon fibers pretreated with an absorbed dose of 3000 kGy have a tensile strength of 0.54 GPa for a similar fiber diameter. Elemental, Fourier-transform infrared spectroscopy, and thermogravimetric analyses indicate that E-beam irradiation is an efficient oxidation and dehydrogenation treatment for pitch fibers by showing that the intensity of the aliphatic C-H stretching and aromatic $CH_2$ bending (out-of-plane) bands significantly decrease and carbonyl and carboxylic groups form.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.202-204
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• 2003

This paper introduces a new algorithm to calculate distortion power using complx THD(Total Harmonic Distortion) index. The proposed algorithm involves FFT(Fast Fourier Transform) to compute real and imaginary THDs of voltage and current. Case studies are presented to show the availability of the proposed method.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.223-226
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• 2001

In this paper, dc link ripple currents for three-phase ac/dc/ac PWM converters are analyzed in a frequency domain. The expression of the harmonic currents is developed by using switching functions and exponential Fourier series expansion. The dc link ripple currents with regard to power factor and modulation index are investigated. In addition, the effect of the displacement angle between the switching periods of line-side converters and load-side inverters on the do link ripple current is studied. The result of the do link current analysis is helpful in specifying the dc link capacitor size and its life time estimation.