• 한국전자통신학회논문지
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• 제11권3호
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• pp.277-282
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• 2016

페브리-페로 공진루프에서 광궤환이 가간섭성 광섬유 레이저의 주파수 천이도에 미치는 영향을 연구하였다. Er+3가 도핑 된 광궤환 방식 광섬유 레이저는 두 개의 광섬유브래그격자로 이루어진 페브리-페로 공진기에서 단방향 광궤환이 이루어지도록 구성하였다. 광궤환은 그렇지 않은 경우와 비교하여 광섬유레이저의 선폭 감소에 효과적인 것으로 나타났다. 위의 구성을 사용한 세 가지 광섬유 레이저는 모두 자기헤테로다인 선폭 측정 장치의 해상도 한계인 3kHz 이내로 나타났다. 마크-젠더 주파수 천이도 측정 장치의 한쪽 선로에 200m 길이의 광지연 선로를 두고 측정한 결과는 광궤환 방식 광섬유 레이저의 주파수 천이도가 광궤환이 없는 광섬유 레이저 보다 우수한 300kHz/sec으로 나타났다.

• 센서학회지
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• 제5권3호
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• pp.17-24
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• 1996

이 논문은 압력센서의 압저항 소자 값에 영향을 미치는 실리론 박막의 잔류응력과 4개 저항의 특성 차에 의해 발생하는 오프셋과 온도 드리프트 특성을 보상하기 위하여 2중 브리지구조의 압력센서에 대하여 연구한 것이다. 압력 변화에 무관한 브리지회로의 각 저항 소자를 압력 변화를 감지하는 브리지회로의 각 저항 소자 가까이 배치하여 각 브리지회로의 출력을 감산하므로 오프셋과 온도 드리프트를 소자내부에서 제거하는 것이다. 이 방법에 의해 오프셋과 온도 드리프트 성분의 약 95%가 제거되었다. 제작된 압력센서의 감도는 $0.9\;kgfcm^{-2}$ full-range에 대해서 $11.7\;mV/Vkg/cm^{-2}$ 이었다.

• Smart Structures and Systems
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• 제33권2호
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• pp.119-131
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• 2024

Drift angle is a significant index for diagnosing post-event structures. A common way to estimate this drift response is by using modal parameters identified under natural excitations. Although the modal parameters of shear structures cannot be identified accurately in the real environment, the identification error has little impact on the estimation when measurements from several floors are used. However, the estimation accuracy falls dramatically when there is only one accelerometer. This paper describes the susceptibility of single sensor identification to modelling error and simulations that preliminarily verified this characteristic. To make a robust evaluation from measurements of one floor of shear structures based on imprecisely identified parameters, a novel scheme is devised to approximately correct the mode shapes with respect to fictitious frequencies generated with a genetic algorithm; in particular, the scheme uses constrained minimization to take both the mathematical aspect and the realistic aspect of the mode shapes into account. The algorithm was validated by using a full-scale shear building. The differences between single-sensor and multiple-sensor estimations were analyzed. It was found that, as the number of accelerometers decreases, the error rises due to insufficient data and becomes very high when there is only one sensor. Moreover, when measurements for only one floor are available, the proposed method yields more precise and appropriate mode shapes, leading to a better estimation on the drift angle of the lower floors compared with a method designed for multiple sensors. As well, it is shown that the reduction in space complexity is offset by increasing the computation complexity.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.589-592
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• 1998

One of the main techniques for diagnosing heart disease is by examining the electrocardiogram(ECG). The earlier noise reduction techniques can not effectively cancellation complex noise from the noisy ECG such powrline interference, baseline drift, muscle artifact. In this paper, we performed the extrude noise from and recovering the ECG signal using wavelets transform that has recently been applying to various fields.

• 한국잡초학회지
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• 제7권3호
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• pp.337-347
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• 1987

Oxyfluorfen 살포(撒布)에 따른 과수종류(果樹種類) 및 품종간(品種間)의 표류비수(漂流飛數) 및 휘산해(揮散害) plastic house에서 조사(調査)하였고, 또한 사과에 대한 살포시기별(撒布時期別) 약해반응(藥害反應)을 포장(圃場)에서 비교(比較)하였다. 가. 수종(數種) 및 품종별(品種別) 약해반응(藥害反應) (1) 발아율감소(發芽率減少)에 미치는 oxyfluorfen의 해(害)를 보면 표류비산해(漂流飛散害) 및 휘산해(煇散害)가 비슷한 정도(程度)로 영향을 주었고 과수종류별(果樹種類別)로는 배와 복숭아가 사과보다 심하였다. (2) 신초당(新梢當) 엽수감소율(葉數減少率)은 사과와 복숭아가 배보다 컸으며 잎의 피해증상(被害症狀)은 배에서 가장 빨리 그러고 심하게 발현되었고 복숭아에서는 가장 경미하고 완만하였다. 피해요인별(被害要因別)로 보면 사과와 배에서는 표류비산해(漂流飛散害)와 휘산해(煇散害)를, 복숭아는 주로 휘산해(煇散害)를 받는 경향이었다. (3) 신초생장억제정도(新梢生長抑制程度)는 복숭아에 비하여 사과와 배에서 컷고, 배는 억제(抑制)가 급진적(急進的)이었으나 사과는 비교적 완만하게 진행(進行)되었다. 약해요인별(藥害要因別)로는 표류비산해(漂流飛散害)와 휘산해(煇散害)가 비슷한 정도(程度)로 나타났다. 나. 약제처리시기별(藥劑處理時期別) 약해반응(藥害反應) (1) Oxyfluorfen은 사과유목(幼木)의 발아(發芽)를 지연시켰는데 지연정도(程度)는 발아기(發芽期) 이전(以前)의 살포(撒布)가 발아기(發芽期)에서 발아완료기(發芽完了期) 사이에 살포(撒布)한 것보다 적었으나 최종 발아(發芽)된 수(數)는 oxyfluorfen 살포(撒布)에 의한 영향을 받지 않았다. 피해엽수(被害葉數)는 처리시기간(處理時期間)에 차이(差異)가 없었으나 피해정도(被害程度)는 발아전(發芽前) 살포(撒布)가 가벼웠다. (2) 신초당(新梢當) 엽수(葉數)와 묘목당(苗木當) 총신초생장량(總新梢生長量) oxyfluorfen의 어느 시기처리(時期處理)에서나 발아후(發芽後) 약 40일까지는 감소(減少)가 인정되었으나 신초생장(新梢生長)이 왕성한 5월 중순 이후에는 처리간(處理間)의 차이(差異)가 거의 없어졌다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.237-238
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• 2010

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 춘계 학술발표회논문집
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• pp.302-310
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• 2003

Cracking of slabs will be caused by applied load and volume changes during the life of a structure and thus it reduces flexural stiffness of slabs. The effect of slab cracking must be considered for appropriate modeling of the flexural stiffness for frame members used in structural analysis. Analytical and experimental study was undertaken to estimate the stiffness reduction of slabs. In the analytical approach, the trend of slab stiffness reduction related to gravity and lateral loads is found and the stiffness reduction factor ranged from a half to a quarter in ACI building code is reasonable when defining range. Analyzing results of the test by Hwang and Moehle for 0.5% drift show that the differences of rotational stiffness on the connection types is found and good results of lateral stiffness using the value of one-third is obtained.

• Structural Engineering and Mechanics
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• 제54권1호
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• pp.19-33
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• 2015

Open ground storey (OGS) buildings are characterized by the sudden reduction of stiffness in the ground storey with respect to the upper infilled storeys. During earthquakes, this vertical irregularity may result in accumulated damage in the ground storey members of OGS buildings without much damage in the upper storeys. Hence, the structural design of OGS buildings needs special attention. The present study suggests a modification of existing displacement-based design (DBD) procedure by proposing a new lateral load distribution. The increased demands of ground storey members of OGS buildings are estimated based on non-linear time history analysis results of four sets of bare and OGS frames having four to ten storey heights. The relationship between the increased demand and the relative stiffness of ground storey (with respect to upper storeys) is taken as the criterion for developing the expression for the design lateral load. It is also observed that under far-field earthquakes, there is a decrease in the ground storey drift of OGS frames as the height of the frame increases, whereas there is no such reduction when these frames are subjected to near-field earthquakes.

• Structural Engineering and Mechanics
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• 제81권4호
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• pp.429-441
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• 2022

A probabilistic assessment of the seismic-excited buildings with a multiple-tuned-mass-damper (MTMD) system is carried out in the presence of uncertainties of the structural model, MTMD system, and the stochastic model of the seismic excitations. A free search optimization procedure of the individual mass, stiffness and, damping parameters of the MTMD system based on the snap-drift cuckoo search (SDCS) optimization algorithm is proposed for the optimal design of the MTMD system. Considering a 10-story structure in three cases equipped with single tuned mass damper (STMS), 5-TMD and 10-TMD, sensitivity analyses are carried out using Sobol' indices based on the Monte Carlo simulation (MCS) method. Considering different seismic performance levels, the reliability analyses are done using MCS and kriging-based MCS methods. The results show the maximum structural responses are more affected by changes in the PGA and the stiffness coefficients of the structural floors and TMDs. The results indicate the kriging-based MCS method can estimate the accurate amount of failure probability by spending less time than the MCS. The results also show the MTMD gives a significant reduction in the structural failure probability. The effect of the MTMD on the reduction of the failure probability is remarkable in the performance levels of life safety and collapse prevention. The maximum drift of floors may be reduced for the nominal structural system by increasing the TMDs, however, the complexity of the MTMD model and increasing its corresponding uncertainty sources can be caused a slight increase in the failure probability of the structure.

• Journal of Astronomy and Space Sciences
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• 제12권2호
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• pp.265-274
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• 1995

The purpose of perigee kick motor firing is to place a satellite into transfer orbit and that of apogee kick motor firing is to place the satellite into geosynchonous orbit in order to increase the semi-major axis of the transfer orbit and reduce the inclination of the transfer orbit. Because apogee motor firing is always accompanied with injection errors, the satellite is not placed into geosynchonous orbit but into a near-geosynchonous orbit, also knows as a drift orbit. Thus, the orbital maneuver to correct drift orbit into gteosynchonous orbit is required, this maneuver is called the station acquisition. For reduction of expenditure and performance of mission, we estimate $\Delta$V budget and required fuel allowance for station acquisition. As the uncertainty of drift orbit by injection error of perigee and apogee kick motor firing prevents us from obtaining exact $\Delta$V budget, statistical Monte Carlo simulation technique is used in order to get optimal $\Delta$V budget and required fuel allowance with a probability of 99%. With respect to Korea satellite launched by Delta-2 launch vehicle in 1995, Monte Carlo analysis is used in order to get various orbital parameters, $\Delta$V budget and required fuel allowance for station acquisition with a probability of 99%.