• Journal of Broadcast Engineering
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• v.11 no.3 s.32
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• pp.326-335
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• 2006

Design criteria far a block code which guarantees minimized PAPR of the OFDM signals are proposed in this paper. Encoding procedure of the minimum PAPR codes (MPC) is composed of searching a seed codeword, circular shifting the register elements, and determining codeword inversion. It is shown that the PEP is invariant to the circular shift of register elements and codeword inversion. Based on such properties, systematic encoding rule for MPC is proposed. In addition proposed encoding rule can reduced greatly the size of look up table for MPC.

• Analytical Science and Technology
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• v.15 no.3
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• pp.214-220
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• 2002

The interfacial accumulation of the chromium-cupferron complex and the catalytic wave of its redox process is characterized by cyclic voltammetry. One cathodic peak is observed in the forward scan at -1.45 V. Scanning in the reverse direction produces a inverted peak at -1.39 V, which is indicative of a catalytic process. The optimal conditions of inverted peak were found to be 1 mM borate buffer solution(pH 9.48) containing $1{\times}10^{-4}M$ cupferron, holding potential of -1.8 V and scan rate of 20 mV/s. Using main peak, a preconcentration time of 1 min results in a detection limit of $3.2{\times}10^{-10}M$.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.10
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• pp.76-81
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• 2013

A new phase frequency detector based digital phase-locked loop (PLL) of 125 MHz was designed using the 130 nm CMOS technology library consisting of inverting edge detectors along with a typical digital phase-locked loop to reduce the lock time and jitter for mid-frequency applications. XOR based inverting edge detectors were used to obtain a transition earlier than the reference signal to change the output more quickly. The HSPICE simulator was used in a Cadence environment for simulation. The performance of the digital phase-locked loops with the proposed phase frequency detector was compared with that of conventional phase frequency detector. The PLL with the proposed detector took $0.304{\mu}s$ to lock with a maximum jitter of approximately 0.1142 ns, whereas the conventional PLL took a minimum of $2.144{\mu}s$ to lock with a maximum jitter of approximately 0.1245 ns.

• Investigative Magnetic Resonance Imaging
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• v.3 no.1
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• pp.60-65
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• 1999

Purpose : The purpose of this study was to evaluate the image quality, contrast characteristics, and possible clinical utility of Medium Tau Inversion Recovery(MTIR) sequence with white matter suppression in patients with brain cortical lesion. Materials and methods : Two normal volunteers and twenty-one patients with cortical lesion were scanned with MTIR as well as other MR imaging sequences. Gray-white matter contrast was evaluated objectively using region-of-interest calculations, including percent contrast and contrast-to-noise ratio(CNR). MTIR sequence was visually compared with other sequences in 21 patients with cortical lesion including conspicuity and detection rate. Results : MTIR sequence had the highest present contrast and CNR between the gray matter and white matter. In twenty-one cases of cortical lesion including cortical dysplasia, MTIR sequence improved delineation and conspicuity of lesion, but MTIR sequence could not detect new lesions. Conclusion : The MTIR sequence well delineated the cortical lesions, particularly in including cortical dysplasia. It may be used as an adjunctive imaging sequence in case of poor gray and white matter differentiation with conventional T1-weighted sequences.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.10
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• pp.859-867
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• 2007

The objective of this study is to develop and validate a numerical method which can handle the multi-rotor aerodynamic characteristics. For the purpose of power estimation, table look-up method is implemented to the existing unsteady panel code that is coupled with a time-marching free wake model. Also, the Reynolds number scaling is implemented for the application to various regions of Reynolds number. The computed results are validated against the available experimental data for coaxial and tandem rotors. In the validation case for the coaxial rotor, more accurate result is acquired when the thickness effect is considered. The wake instability problem occurs at a particular separation distance between the rotors for tandem rotors. The wake instability is avoided by setting the single-rotor wake geometry as the initial wake geometry for the multi-rotor analysis. The estimated result for rotor separation effect is compared with the result of the momentum theory.

• The Transactions of the Korea Information Processing Society
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• v.6 no.12
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• pp.3652-3661
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• 1999

To support multimedia applications such as a multimedia communication systems and multimedia broadcasting, an operating system need to predict their timing-constraints. So, In this real-time systems, we must solve the priority inversion problem that may make the behavior of unpredictable systems and need a real-time server model that provides a better preemptability and minimizes a system overhead. In current real-time systems, the single thread server model, the worker model and the dynamic server model are being used for synchronization but they cannot propose an effective structure for managing shared resources. In this paper, the priority inheritance protocol is used to solve the priority inversion problem and the hybrid prioritized worker model is proposed, which can provide a more effective structure and a faster response time minimizing a system overhead. The hybrid prioritized worker model is to combine the static and the dynamic prioritized worker model, and have a better performance than other models in response time which is an important factor in a real-time system.

• The Korean Journal of Financial Management
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• v.18 no.1
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• pp.107-128
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• 2001

금융기관이 직면하는 시장위험관리와 관련된 연구는 이자율과 주식가격 변동위험, 또는 환율과 이자율 변동위험만을 고려한 자산배분모델이므로 그 모형의 정교성에도 불구하고 국제금융기관의 시장위험관리 모형으로 이용하기에는 부족한 점이 있다. 시장위험인 VAR를 측정하는 방법 중 포트폴리오 VAR 측정방법인 델타-노말 방법을 응용하여 금융기관이 시장위험을 종합적으로 관리하는 한편, 기대수익을 최대화시키는 자산-부채의 최적배분에 대한 모형을 유도할 수 있다. 본 논문은 포트폴리오 접근법을 이용하여 금융기관의 시장위험을 종합적으로 관리할 수 있는 모형을 개발하는 동시에 미국, 일본, 영국, 독일의 주요 금융자산의 가격변동자료를 바탕으로 실증적 분석을 시도하였다. 이론적 모형과 관련하여 국제금융기관이 시장위험을 통제하는 한편 목표수익을 달성하는데 필요한 $m_1$ 종류의 국내자산과 부채의 규모, $m_2$ 종류의 외화자산과 부채의 규모를 동시적으로 결정할 수 있는 모델을 개발하였다. 이 모형은 금융기관의 위험포지션과 목표수익이 변동함에 따라 재구성되어야 할 국내외 자산과 부채의 포트폴리오에 대한 종류와 규모를 구체적으로 파악할 수 있게 한다. 실증분석을 위해 미국에 본점을 두고 미국, 일본, 영국, 독일에서 영업활동을 하는 국제금융기관이 16개의 국내외 금융자산을 이용 가능한 것으로 가정하였다. 1995년 1월부터 1999년 6월까지 이들 금융자산의 월별자료와 각 국 통화의 대 U.S. 달러 환율을 이용하여 목표이익 10,000천 달러를 실현하는 한편 이자율과 환율 위험을 최소화시키는 자산, 부채의 적정구성에 관한 결과를 제시하였다.구의 성과로는 특정 투자자 집단이 주가의 움직임에 따라 매매를 하는 수동적 전략의 의미보다는 적극적으로 주가를 움직이는 주체로서 외국인투자자와 일부 기관투자자의 존재를 확인할 수 있었다는 점이며, 주가 움직임에 따른 개인투자자와 일부 기관 투자자의 수동적 매매 스타일과 기관투자자 사이의 투자스타일의 이질성을 통계적으로 확인할 수 있었다는 데에 있다.남아 각국과 우리나라간에는 주가변동에 시차가 없는 것으로 나타났다. 그러나 각국간 표준시차 및 거래소 거래시간을 고려하면 미국, 영국, 독일의 경우에도 그 시차는 1일이내이거나 거의 시차가 없는 것으로 판단된다. 발견되어 선물의 선도효과가 지배적임을 발견하였다.적 일정하게 하는 소비행동을 목표로 삼고 소비와 투자에 대한 의사결정을 내리고 있음이 실증분석을 통하여 밝혀졌다. 투자자들은 무위험 자산과 위험성 자산을 동시에 고려하여 포트폴리오를 구성하는 투자활동을 행동에 옮기고 있다.서, Loser포트폴리오를 매수보유하는 반전거래전략이 Winner포트폴리오를 매수보유하는 계속거래전략보다 적합한 전략임을 알 수 있었다. 다섯째, Loser포트폴리오와 Winner포트폴리오를 각각 투자대상종목으로써 매수보유한 반전거래전략과 계속거래 전략에 대한 유용성을 비교검증한 Loser포트폴리오와 Winner포트폴리오 각각의 1개월 평균초과수익률에 의하면, 반전거래전략의 Loser포트폴리오가 계속거래전략의 Winner포트폴리오보다 약 5배정도의 높은 1개월 평균초과수익률을 실현하였고, 반전거래전략의 유용성을 충분히 발휘하기 위하여 장단기의 투자기간을 설정할 경우에 6개월에서 36개월로 이동함에 따라 6개월부터 24개월까지는 초과수익률이 상승하지만,

• Journal of radiological science and technology
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• v.32 no.1
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• pp.95-99
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• 2009

The purpose of this research is to seek SPAIR's reversal time (TI) which satisfies two conditions ; maintaining the suppression ability of fat tissue and simultaneously minimizing the inhomogeneity of fat tissue in T2 high-speed spin echo 3.0T magnetic resonance image (MRI) of the brain, and to compare SPAIR with STIR which is fat-suppression technique. The reversal times (TI) of SPAIR protocol are set to 1/2, 1/3, 1/6 and 1/12 of SPAIR TR (420 msec), namely 210 msec (8 people), 140 msec (26 people), 70 msec (26 people) and 35 msec (18 people) and STIR TI is set with 250 msec (26 people). With these parameter sets, we acquired the axis direction 104 images of the brain. In ROI ($50\;mm^2$) of output image, signal intensities of the fatty tissue, the muscular tissue, and the background were measured and the CNRs of fatty tissue and the muscular tissue were calculated. The inhomogeneity of the fatty tissue is SD/mean, where SD is the standard deviation and 'mean' is a average fatty tissue signal. Consequently, SPAIR TI is determined on either 1/3 or 1/6 of TR (420 ms) ; 140 ms or 70 ms. Because the difference of statistics in fat-suppression ability and inhomogeneity of fatty tissue is very small (p < 0.001), Selecting 140 ms seems to be better choice for the image quality. Meanwhile, Comparing SPAIR (TI : 140 ms) with STIR, the fat-suppression is not able to be considered statistically (p < 0.252), but the image quality is able to be considered statistically (p < 0.01). In conclusion, SPAIR is better than STIR in the image quality.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.349-352
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• 2001

The transient response in TDFA(Thulium-Doped Fiber Amplifier) is theoretically investigated. The TDFA has the spectral gain band in 1.47 ${\mu}{\textrm}{m}$. The transient model includes the transient buildup of the population inversion, the pump power, the signal power and their transient variation along the fiber amplifier. The results of numerical analysis can predict the gain saturation and recovery time at the fiber amplifier. It also shows the gain saturation and recovery effect depending on the pumping and saturation rate.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.248-249
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• 2007

본 연구에서는 능동 구동형 유기 발광 소자(AMOLED)에 쓰이는 수소화된 비정질 실리콘(a-Si:H)의 전류 안정성(stability)을 개선하기 위한 새로운 구동방법(driving method)을 제안한다. 제안된 방식은 한 프레임 시간 중 특정 시간동안 비정질 실리콘 박막 트랜지스터(Thin Film Transistor, TFT)에 음의 화상데이터전압을 인가함으로써 열화(degradation)를 억제한다. 비정질 실리콘 박막트랜지스터의 열화를 회복하기 위한 음의 화상데이터의 진폭은 실제 이미지를 표현하는 이전에 인가한 양의 화상데이터에 의해 결정된다. 본 연구에서 제안된 구동방식을 시뮬레이션을 통하여 화소 회로의 동작을 검증하였고, 이를 통해 비정질 실리콘 박막 트랜지스터의 열화가 억제되는 것과 화면의 균일성(screen uniformity) 개선하고자 한다.