• 한국ITS학회 논문지
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• 제14권5호
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• pp.30-37
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• 2015

MIMO(Multiple Input Multiple Output) 시스템을 사용하여 주파수 선택적 페이딩 환경에서 동작하는 차세대 무선 통신 시스템의 데이터 전송 속도를 향상시키기 위한 연구가 현재 활발히 진행 중이다. 여러 개의 송신 안테나에서 송신된 시호들이 혼합되어 각 수신 안테나에 수신되는데 이렇게 혼합된 신호를 분리하기 위해서 직교 특성을 갖는 훈련신호가 필요하며, 이 훈련신호를 사용하여 신호의 동기화 및 채널 추정을 수행할 수 있어야 한다. 본 논문에서는 MIMO 통신 시스템에 사용 가능한 시퀀스들을 소개하고, 관심 영역에 대하여 우수한 자기 상관 특성을 갖는 변형된 WeCAN(weighted cyclic algorithm new) 시퀀스를 제안한다. 모의실험을 통해 각 훈련신호의 자기 상관도를 비교하였으며, 또한 도플러 주파수 변화와 다중경로 전달 페이딩 환경에서의 상관 특성을 비교하였다.

• Journal of Oral Medicine and Pain
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• 제26권1호
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• pp.17-25
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• 2001

The purpose of this study is to evaluate the relationship of menstrual cycle and halitosis by measuring the concentrations of Voltile Sulfur Compounds, secretion rate of unstimulated saliva, secretion rate of stimulated saliva and viscosity of saliva during the menstrual cycle. The subjects were 19 female dental students of Yonsei University who had relatively good alignment of the teeth. They hadn't taken antibiotics or oral contraceptive pills during the few months prior to the experiment, and they didn't have any dental caries involving the pulp or periodontal disease. Lady-$Q^{(R)}$(Alpain Korea, Korea), which confirms the ovulation using saliva, was used to find out the menstrual cycle of subjects. Their history was taken and their basal body temperature was measured. On the basis of these data, the amount of Volatile Sulfur Compounds, secretion rate of unstimulated saliva, secretion rate of stimulated saliva, viscosity of saliva were measured during 1 day of the proliferative phase, 3 days of ovulatory phase and 1 day of the luteal phase within the menstrual cycle. The results were as follows : 1. The amount of Volatile Sulfur Compounds, secretion rate of unstimulated saliva, secretion rate of stimulated saliva, and viscosity of saliva showed no statistically significant cyclic change during proliferative phase, ovulatory phase, and luteal phase(p<0.05). 2. Between the secretion rate of unstimulated saliva and secretion rate of stimulated saliva, there was significant correlation during proliferative phase and luteal phase(p<0.05) and there was no significant correlation during ovulatory phase but relatively close result was seen. 3. The amount of Volatile Sulfur Compounds during proliferative phase and luteal phase had statistically significant correlation(p<0.05). 4. Secretion rate of stimulated saliva during proliferative phase and ovulatory phase, proliferative phase and luteal phase, ovulatory phase and luteal phase had significant correlations (p<0.01).

• Structural Engineering and Mechanics
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• 제30권6호
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• pp.733-761
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• 2008

The failure of reinforced concrete structures in recent earthquakes caused concern about the performance of beam column joints. Confinement of joint is one of the ways to improve the performance of beam column joints during earthquakes. This paper describes an experimental study of exterior beam-column joints with two non-conventional reinforcement arrangements. One exterior beam-column joint of a six story building in seismic zone III of India was designed for earthquake loading. The transverse reinforcement of the joint assemblages were detailed as per IS 13920:1993 and IS 456:2000 respectively. The proposed nonconventional reinforcement was provided in the form of diagonal reinforcement on the faces of the joint, as a replacement of stirrups in the joint region for joints detailed as per IS 13920 and as additional reinforcement for joints detailed as per IS 456. These newly proposed detailing have the basic advantage of reducing the reinforcement congestion at the joint region. In order to study and compare the performance of joint with different detailing, four types of one-third scale specimens were cast (two numbers in each type). The main objective of the present study is to investigate the effectiveness of the proposed reinforcement detailing. All the specimens were tested under reverse cyclic loading, with appropriate axial load. From the test results, it was found that the beam-column joint having confining reinforcement as per IS: 456 with nonconventional detailing performed well. Test results indicate that the non-conventionally detailed specimens, Type 2 and Type 4 have an improvement in average ductility of 16% and 119% than their conventionally detailed counter parts (Type1 and Type 3). Further, the joint shear capacity of the Type 2 and Type 4 specimens are improved by 8.4% and 15.6% than the corresponding specimens of Type 1 and Type 3 respectively. The present study proposes a closed form expression to compute the yield and ultimate load of the system. This is accomplished using the theory of statics and the failure pattern observed during testing. Good correlation is found between the theoretical and experimental results.

• Bulletin of the Korean Chemical Society
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• 제33권2호
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• pp.415-419
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• 2012

Electrochemical characteristics of nitrite ion were investigated at a poly(methylene blue)-modified glassy carbon electrode by cyclic voltammetry and differential pulse voltammetry. The poly(methylene blue)-modified glassy carbon electrode exhibited enhanced anodic signals for nitrite. The effects of key parameters on the detection of nitrite were evaluated at the modified electrode, such as pH, accumulation time, and scan rate. Under optimum condition, the chemically modified electrode can detect nitrite in the concentration range $2.0{\times}10^{-6}$ to $5.0{\times}10^{-4}$ M with the detection limit of $2.0{\times}10^{-6}$ M and a correlation coefficient of 0.999. The detection of nitrite using the chemically modified electrode was not affected by common ions such as $Na^+$, $K^+$, $Ca^{2+}$, $Cl^-$, $HPO_4^{2-}$ and $H_2PO_4^- $. The modified electrode showed good stability and reproducibility. The practical application of the present method was successfully applied to the determination of nitrite ion in cabbage samples.

• 한국지반공학회지:지반
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• 제14권3호
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• pp.47-62
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• 1998

본 연구에서 제안한 교란상태 개념 (disturbed state concept, DSC)은 변형중인 재료는 상대적으로 손상되지 않은 상태(relative intact state: Rl)와 완전히 파괴된 상태(fully adjusted state. FA)가 혼합되어 있다는 기본가정에 기초를 두고 있다. 여기에서 사용된 두 가지 상태, 즉 Rl상태와 FA상태는 재료의 파괴정도를 정의하는 기준이 된다. 이와 같은 개념을 바탕으로 DSC는 반복 하중하에 있는 포화사질토의 거동특성에 대한'통합된 구성방정식을 제공한다. 포화사질토에 대한 본 모델의 계수들은 실삼축시첩(truly triaxial test)의 결과를 통해 산정된다. 또한 실내실험을 통하여 얻은 결과를 이용하여 본 모델에 대한 검증을 수행하였다. DSC모델을 이용한 역해석 해석대상 시험결과는 전반적으로 일치되는 경향을 보이고있다. 본 연구의 결과를 토대로, DSC 모델은 동하중하의 구화 사질토의 거동특성을 규명할 수 있다고 사료된다.

• BMB Reports
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• 제42권10호
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• pp.642-647
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• 2009

In this study, the effects of $Ca^{2+}$ and cyclic adenosine monophosphate (cAMP) on microsomal triglyceride (TG) transfer protein (MTP) activity were investigated in rat liver. MTP activity was high when liver contained low levels of cAMP, which was induced by administration of glucose, or high levels of total $Ca^{2+}$ and TG. However, MTP activity increased by high levels of $Ca^{2+}$ and TG was reduced in a dose-dependent manner by treatment with dibutyryl-cAMP (db-cAMP), a cAMP analogue. Conversely, when homogenates of liver from normal rats, with low levels of total $Ca^{2+}$ and high levels of cAMP, were incubated with thapsigargin, a $Ca^{2+}$-inducer, MTP activity was increased in a dose-dependent manner compared to control. Therefore, our results suggest that high levels of $Ca^{2+}$ cause hypertriglyceridemia through the elevation of MTP activity, as opposed to high levels of cAMP, which suppress MTP activity and inhibit hypertriglyceridemia.

• Applied Biological Chemistry
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• 제51권3호
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• pp.219-222
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• 2008

제3세대 제초성 cyclic imide 유도체를 탐색하기 위하여 peroxidizing 제초제로써 40개의 1-(4-chloro-2-fluoro-5-pro-pargyloxypheny)-3-thiourea 유도체(1-40) 중, 3-R-치환체의 발아 전 벼(Oryza sativa)와 논피(Echinochlo crusglli)에 대한 평균 제초활성 값들을 제시하였다. 그리고 Urea 유도체(1-40)와 protox 효소의 기질분자인 protogen사이의 분자구조 유사성을 검토하였다. 논피에 대하여 선택성을 나타내는 화합물은 diallyl-치환체(20)와 3-nitro-치환체(33)이었으며 allyl-치환체(8)가 가장 큰 제초활성$(pI_{50}=4.71)$과 유사성 지수(S=0.81) 값을 나타내었다. 그리고 aryl-치환체(21-40)와 Protogen 사이의 중첩된 부피(C)와 S값 사이에 상관성이 좋았다.

• Journal of Astronomy and Space Sciences
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• 제31권2호
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• pp.145-148
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• 2014

There was a research on the prolongation of solar cycle 23 by the solar cyclic variation of solar, interplanetary geomagnetic parameters by Oh & Kim (2013). They also suggested that the sunspot number cannot typically explain the variation of total solar irradiance any more. Instead of the sunspot number, a new index is introduced to explain the degree of solar activity. We have analyzed the frequency of sunspot appearance, the length of solar cycle, and the rise time to a solar maximum as the characteristics of solar cycle. Then, we have examined the predictability of solar activity by the characteristics of preceding solar cycle. We have also investigated the hemispheric variation of flare index for the periods that the leading sunspot has the same magnetic polarity. As a result, it was found that there was a good correlation between the length of preceding solar cycle and spotless days. When the length of preceding solar cycle gets longer, the spotless days increase. It is also shown that the shorter rise time to a solar maximum is highly correlated with the increase of sunspots at a solar maximum. Therefore, the appearance frequency of spotless days and the length of solar cycle are more significant than the general sunspot number as an index of declining solar activity. Additionally, the activity of flares leads in the northern hemisphere and is stronger in the hemisphere with leading sunspots in positive polarity than in the hemisphere with leading sunspots in negative polarity. This result suggests that it is necessary to analyze the magnetic polarity's effect on the flares and to interpret the period from the solar maximum to solar maximum as the definition of solar cycle.

• 한국통신학회논문지
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• 제33권11A호
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• pp.1079-1086
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• 2008

본 논문을 통해 GAS-CP-CDMA(우수한 자기상관 특성의 시퀀스를 사용하는 순한확장 CDMA) 시스템이 제안되었고 그 시스템의 상향링크의 신호대 잡음비 성능이 분석되었다. 다른 사용자를 구분하기 위해 위상이 편이된 시퀀스가 사용된다. GAS-CP-CDMA 시스템의 신호는 좋은 자기상관 특성 덕분에 동일 셀내의 다른 사용자 신호와 거의 간섭을 일으키지 않는다. 그러나 인접셀의 사용자 신호는 간섭을 일으킨다. CDMA 시스템에서 주파수 재사용율은 0.6 정도이다. 따라서 기존 CDMA 방식에서 인접셀로 부터 유입되는 간섭은 전체 간섭의 40% 정도가 된다. 수치분석은 주파수 재사용율에 대한 신호대 잡음비와, 사용자 수에 따른 신호대 잡음비 성능에 대해 수행되었으며, GAS-CP-CDMA 시스템은 기존 CDMA 시스템보다 우수한 성능을 가지는 것으로 분석되었다. 제안된 시스템의 상향링크 사용자 용량은 기존 CDMA 시스템의 약 2배로 증가됨을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.191-195
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• 2011

This study reports the root cause of the improved rate performance of $LiFePO_4$ after Cr doping. By measuring the chemical diffusion coefficient of lithium ($D_{Li}$) using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the correlation between the electrochemical performance of $LiFePO_4$ and Li diffusion is acquired. The diffusion constants for $LiFePO_4$/C and $LiFe_{0.97}Cr_{0.03}PO_4$/C measured from CV are $2.48{\times}10^{-15}$ and $4.02{\times}10^{-15}cm^2s^{-1}$, respectively, indicating significant increases in diffusivity after the modification. The difference in diffusivity is also confirmed by EIS and the $D_{Li}$ values obtained as a function of the lithium content in the cathode. These results suggest that Cr doping facilitates Li ion diffusion during the charge-discharge cycles. The low diffusivity of the $LiFePO_4$/C leads to the considerable capacity decline at high discharge rates, while high diffusivity of the $LiFe_{0.97}Cr_{0.03}PO_4$/C maintains the initial capacity, even at high C-rates.