• 대한의용생체공학회:의공학회지
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• 제28권6호
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• pp.798-802
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• 2007

The synthetic focusing in the ultrasonic imaging systems has been formed in the way that one element transmits a circular wave and receives an echo signal. The amplitude of the signal transmitted from one element is too small to propagate a long distance so that the SNR(Signal to Noise Ratio) is very low in an image obtained by the synthetic focusing. To solve this problem, a defocusing method which uses several elements has been proposed. In this method, the SNR is improved due to using several elements to transmit the circular wave. But if the number of transmitting elements increases, the phase distortion is severe in the defocusing method. In this paper, we propose a new method that can generate a circular wave using a lot of elements without phase distortion. At first, we generate limited plane waves with different propagation angles and then superpose them to make a circular wave. We show that the circular wave can be used to improve SNR in the real-time 3D ultrasonic imaging as well as the synthetic focusing through computer simulation and experiments.

• 대한전기학회논문지
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• 제39권12호
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• pp.1296-1305
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• 1990

Common enclosure type SF6 circuit breakers have been developed in many countries for their compact design and economical merits, but their performance testing method is one of the difficult problems because of the limitation of testing capacity. This paper studies a three phase synthetic testing circuit which consists of 4-unit circuits based on the current injection method. This new synthetic testing circuit can be used in both ways of three phase testing up to 242kV rating and single phase testing up to 800kV rating.

• Journal of Electrical Engineering and Technology
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• 제7권5호
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• pp.778-783
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• 2012

The synthetic short-circuit making test to adequately stress the circuit breaker has been specified as the mandatory test duty in the IEC 62271-100. The purpose of this test is to give the maximum pre-arcing energy during making operation. And this requires the making operation with symmetrical short-circuit current that is established when the breakdown between contact gap occurs near the crest of the applied voltage. Also, if the interrupting chamber of circuit breakers is designed as the type of common enclosure or the operation is made by the gang operated mechanism that three-phase contacts are operated by one common mechanism, three-phase synthetic making test is basically required. Therefore, several testing laboratories have developed and proposed their own test circuits to properly evaluate the breaker performance. With these technical backgrounds, we have developed the new alternative three-phase making circuit.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.505-508
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• 2000

The success of target reconstruction in SAR(Synthetic Aperture Radar) imaging system is greatly dependent on the coherent detection. Primary causes of incoherent detection are uncompensated target or sensor motion, random turbulence in propagation media, wrong path in radar platform, and etc. And these appear as multiplicative phase error to the echoed signal, which consequently, causes fatal degradations such as fading or dislocation of target image. In this paper, we present iterative phase error estimation scheme which uses echoed data in all temporal frequencies. We started with analyzing wave equation for one point target and extend to overall echoed data from the target scene - The two wave equations governing the SAR signal at two temporal frequencies of the radar signal are combined to derive a method to reconstruct the complex phase error function. Eventually, this operation attains phase error correction algorithm from the total received SAR signal. We verify the success of the proposed algorithm by applying it to the simulated spotlight-mode SAR data.

• 한국전자파학회논문지
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• 제29권2호
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• pp.109-117
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• 2018

비선형적으로 회전하는 표적의 inverse synthetic aperture radar(ISAR) 영상을 형성하기 위해서는 표적의 수신 신호에 적절한 회전운동 보상기법을 수행해 주어야 한다. 대표적인 회전운동 보상기법인 prominent point processing(PPP)은 산란점의 위상정보를 이용하여 비선형 회전성분을 선형화하는 기법이다. 본 논문에서는 integrated cubic phase function(ICPF)을 이용하여 산란점의 위상정보를 추정한 다음 PPP를 수행하여 ISAR 영상을 형성하는 방법을 제안한다. ICPF는 다수의 산란점으로부터 중첩된 신호가 수신되었을 때 1차원 영역(domain)의 최댓값을 찾는 작업을 수행함으로써 산란점의 위상정보를 추정할 수 있다. 시뮬레이션 결과 ICPF를 이용한 산란점 위상정보 추정 후 PPP를 수행함으로써 지배적 산란점이 존재하지 않는 환경에서 실시간으로 높은 품질의 ISAR 영상을 획득하였다.

• 한국응용과학기술학회지
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• 제21권2호
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• pp.140-147
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• 2004

An aqueous solution of a commercial liquid synthetic detergent for kitchen use was photodecomposed in the presence of titanium dioxides powder under an atmosphere of air at room temperature. Titanium dioxides were prepared by sol-gel method from titanium iso-propoxide at different R ratio($H_2O$/titanium iso-propoxide) and calcined at $500^{\circ}C$. All titanium dioxides were characterized by XRD, BET surface area analyzer and UV-VIS spectrometer. The surface area of titanium dioxides prepared at R ratio=6 appeared higher volume about 20% than commercial $TiO_2$ catalysts. XRD patterns of titania particles were observed mixing phase together with rutile and anatase type. Titanium dioxides prepared by sol-gel method show higher activity about 6% than commercial $TiO_2$ catalysts on the photocatalytic degradation of a commercial liquid synthetic detergent for kitchen. The concentration of the detergent decreased to about 90% of its initial value at illumination times of 2 hour. Illumination for 30 minutes decreased the concentration of oxygen to about one-fifth of the initial value.

• 한국안전학회지
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• 제16권3호
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• pp.76-82
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• 2001

An aqueous solution of a commercial liquid synthetic detergent for kitchen use was photodecomposed in the presence of titanium dioxides ponder under an atmosphere of air at room temperature. Titanium dioxides were prepared by sol-gel method from titanium iso-propoxide at different R R ratio($H_2O$/titanium iso-propoxide) and calcined at $500^{\circ}C$. All titanium dioxides m characterized by XRD, BET surface area analyzer and UV-VIS spectrometer. The surface mea of titanium dioxides prepared at R ratio=6 appeared higher volume about 20% than commercial $TiO_2$ catalyses. XRD patterns of titania particles were observed mixing phase together with rutile and anatase type. Titanium dioxides prepared by sol-gel method show higher activity about 6% than commercial $TiO_2$ catalysts on the Photocatalytic foundation of a commercial liquid synthetic detergent for kitchen. The concentration of the detergent decreased to about 90%, of its initial value at illumination times of 2 hour. illumination for 30 minutes decreased the concentration of oxygen to about one-fifth of the initial value.

• 대한의용생체공학회:의공학회지
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• 제23권2호
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• pp.87-99
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• 2002

본 논문에서는 대상테의 움직임이 합성구경 기법에 미치는 영향을 조사하고, 이를 토대로 합성구경 기법의 움직임 긱함을 극복할 수 있는 방법을 제안하였다. 제안한 방법은 일정한 관심영역 내에서 대상테의 대표적인 축방향 움직임을 추정하고 이에 의한 집속 지연 오타만을 관심영역의 모든 영상점에 대하여 동일하게 보상하는 영역 기반의 움직임 보상 기법을 사용한다. 이때 대표 움직임은 관심영역 내에서 접속된 신호의 에너지가 최대가 되는 점에서의 움직임을 상호상관을 이용하여 계산할 수 있다. 또한 자기상관 기반의 도플러 평균 주파수 추정 기법을 이용하여 관심영역 내의 대표적인 축방향 움직임(대표 움직임 속도)을 추정하는 방법을 제안하였다. 모의 실험과 실제 인체 실험 결과 두 방법 모두 합성구경 영상의 움직임 오류를 제거함으로써 양방향 동적접속의 구현을 가능하게 하여 초음파 영상의 해상도 및 SNR을 현저히 개선시킬 수 있음을 확인하였다. 또한 자기상관 방법은 훨씬 적은 계산량으로 상호상관 방법과 거의 동일한 성능을 제공함을 확인하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.1389-1392
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• 2009

A series of new symmetric TTF derivatives were designed and synthesized. This facile synthetic method provides an opportunity to prepare TTF-based LC candidates. This series of compounds exhibited smectic A phase based on coplanar TTF core. One of the LC compounds was used as a semiconductor layer to fabricate OTFT.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.179.2-179.2
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• 2003

We have developed the novel one-pot synthetic method for regioselective and stereoselective N-protected amines through the reaction of various ethers with chlorosulfonyl isocyanate (CSI). Also, we found a novel technique to compare directly the stability of carbocations in the solution phase and established the stability order of the various carbocations. And we reported the cleavage of benzyl and p-methoxybenzyl protecting groups of alcohols and phenols in the presence of other functional groups using CSI. (omitted)