• Environmental Engineering Research
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• 제16권1호
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• pp.47-51
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• 2011

The oxygen transfer rate is a parameter that characterizes the gas-liquid mass transfer in surface aerators. Gas-liquid transfer mechanisms in surface aeration tanks depend on two different extreme lengths of time; namely, macromixing and micromixing. Small scale mixing close to the molecular level is referred to as micromixing; whereas, macromixing refers to mixing on a large scale. Using experimental data and numerical simulations, macro- and micro-scale parameters describing the two extreme time scales were investigated. A scale up equation to simulate the oxygen transfer rate with micromixing times was developed in geometrically similar baffled surface aerators.

• East Asian Economic Review
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• 제19권2호
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• pp.189-220
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• 2015

Multi-scale representations are effective in characterising the time-frequency characteristics of financial return series. They have the capability to reveal the properties not evident with typical time domain analysis. Given the aforesaid, this study derives crucial insights from multi scale analysis to investigate the co-movements between Indian and emerging Asian equity markets using wavelet correlation and wavelet coherence measures. It is reported that the Indian equity market is strongly integrated with Asian equity markets at lower frequency scales and relatively less blended at higher frequencies. On the other hand the results from cross correlations suggest that the lead-lag relationship becomes substantial as we turn to lower frequency scales and finally, wavelet coherence demonstrates that this correlation eventually grows strong in the interim of the crises period at lower frequency scales. Overall the findings are relevant and have strong policy and practical implications.

• 한국음향학회지
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• 제14권2호
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• pp.50-61
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• 1995

본 논문에서는 음성 신호가 가지고 있는 중요한 특성을 유지하면서 발음 속도만을 변화시키는 시간축 변환 방법을 범용 디지탈 신호 처리 프로세서를 이용하여 실시간으로 구현하였다. 음성 신호 시간축 변환은 음성 신호의 발음 속도만을 변화시키기 때문에, 입력 신호와 변환 신호간의 시간적 차이가 발생하여 실시간 처리가 불가능하다. 본 논문에서는 이러한 입력, 변환 신호간의 시간차를 해결하기 위해서, 카세트 테이프 레코더의 모터 회전 속도를 조절하는 것과 같은 물리적 시간축 변환으로, 입력 음성 신호를 느리게 또는 빠르게 변환시켜 그 신호를 실시간 시스템의 입력으로 사용하였다. 카세트 레코더의 주행 속도만을 조절하는 물리적 변환은 원 신호의 피치 정보를 왜곡시켜, 원 음성의 특성을 변화시키기 때문에, 본 연구에서는 FIR 필터를 이용한 피치 보정 기법으로 왜곡된 신호를 원신호로 복원한 후, SOLA 시간축 변환 방법을 이용하여, 복원된 신호를 카세트 레코더의 모터 속도에 맞추어 시간축으로 변환하는 시스템을 실시간으로 구현하였다. 구현된 알고리듬으로 음성 신호를 시간축으로 변환하는 실험에서, 16비트 해상도를 가진 ADSP2101 프로세서로 구현한 결과와 컴퓨터 시뮬레이션 결과를 비교할 때 평균 구간 신호 대 오차비가 대략 20dB로 두 결과가 거의 유사함을 알 수 있었다.

• 한국컴퓨터정보학회논문지
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• 제21권11호
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• pp.31-38
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• 2016

In this paper, we propose multi-scale infrared target detection algorithm with varied filter size using integral image. Filter based target detection is widely used for small target detection, but it doesn't suit for large target detection depending on the filter size. When there are multi-scale targets on the sky background, detection filter with small filter size can not detect the whole shape of the large targe. In contrast, detection filter with large filter size doesn't suit for small target detection, but also it requires a large amount of processing time. The proposed algorithm integrates the filtering results of varied filter size for the detection of small and large targets. The proposed algorithm has good performance for both small and large target detection. Furthermore, the proposed algorithm requires a less processing time, since it use the integral image to make the mean images with different filter sizes for subtraction between the original image and the respective mean image. In addition, we propose the implementation of real-time embedded system using FPGA.

• Smart Structures and Systems
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• 제22권1호
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• pp.41-55
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• 2018

Damping ratio and frequency have influence on dynamic serviceability or instability such as vortex-induced vibration and displacement amplification due to earthquake and critical flutter velocity, and it is thus important to make determination of damping ratio and frequency accurate. As bridges are getting longer, small scale model test considering similitude law must be conducted to evaluate damping ratio and frequency. Analysis conditions modified by similitude law are applied to experimental test considering different scale ratios. Generally, Nyquist frequency condition based on natural frequency modified by similitude law has been used to determine sampling rate for different scale ratios, and total time length has been determined by users arbitrarily or by considering similitude law with respect to time for different scale ratios. However, Nyquist frequency condition is not suitable for multimode system with noisy signals. In addition, there is no specified criteria for determination of total time length. Those analysis conditions severely affect accuracy of damping ratio. The focus of this study is made on the determination of minimum analysis conditions for different scale ratios. Influence of signal to noise ratio is studied according to the level of noise level. Free initial value problem is proposed to resolve the condition that is difficult to know original initial value for free vibration. Ambient and free vibration tests were used to analyze the dynamic properties of a system using data collected from tests with a two degree-of-freedom section model and performed on full bridge 3D models of cable stayed bridges. The free decay is estimated with the stochastic subspace identification method that uses displacement data to measure damping ratios under noisy conditions, and the iterative least squares method that adopts low pass filtering and fourth order central differencing. Reasonable results were yielded in numerical and experimental tests.

• 가정과삶의질연구
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• 제9권2호
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• pp.241-251
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• 1991

The Purpose of this study was the development of scale to measure the Perceived Adequacy of Resources(PAR). A 38-item instrument was analysed with responses form 300 wives dwelling in Seoul. PAR was categorized housing, health, time money, interpersonal, knowledge/skills, community resources, Data were analysed by the method of Pearson's Correlation, Factor Analysis and Multiple Regression. Items were loaded eight resource categories such as time housing, money , health, knowledge, social support, community, psychological relationship. Internal consistency of the scale was high(Cronbach's α=.85) The result proposed PAR constructed 28 items.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.2293-2295
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• 2000

This paper describes the synthesis of robust decentralized controllers for uncertain large-scale discrete-time systems with time-delays in subsystem interconnections. Based on the Lyapunov method, a sufficient condition for robust stability, is derived in terms of a linear matrix inequality(LMI). The solutions of the LMI can be easily obtained using various efficient convex optimization techniques. A numerical example is given to illustrate the proposed method.

• 한국정보통신학회논문지
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• 제19권3호
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• pp.731-740
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• 2015

최근 기기간 통신에 따른 소규모 네트워크에 적합한 통신 방법들에 대한 관심이 급증하면서 수요가 증가하고 있다. 소규모 네트워크의 기본적 시스템은 TDMA(Time Division Multiple Access)방식이 사용될 수 있다. 하지만 TDMA는 동기화 방식이 복잡하고 추가 장비가 필요하며 비용적인 측면에서 비효율 적이다. 때문에 본 논문에서는 DESYNC(DESYNChronization)를 이용하여 소규모 네트워크에 적합한 동기화 방법을 제안한다. 기존 DESYNC는 동기화 완료까지의 시간이 걸리고 지연시간을 보장하지 않는다. 본 논문에서는 DESYNC 알고리즘을 개선하여 BC(Bridge Count)-DESYNC를 제안한다. BC-DESYNC는 통신 범위를 초과한 노드들 사이에 CU(Central Unit)을 배치하여 중앙제어장치 기능을 통해 노드들의 통신이 가능하도록 하며, Mimic DESYNC와 C-DESYNC를 이용하여 동기화 상태 완료 시간을 보장한다.

• 한국유체기계학회 논문집
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• 제20권1호
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• pp.48-52
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• 2017

Small-scale motor-generator sets have been used in laboratories for verification of real large wind turbines whose rated power are more than 1 MW. In this paper, a result of designing a small-scale motor-generator system, which is composed of motor, gear box, flywheel, and generator, is presented in the aspect of speed response. Design objective is to make a small-scale motor-generator system have the same time constant and optimal tip speed ratio region as a real MW wind turbine. A small-scale 3.5 kW motor-generator system for emulating response of a 2 MW wind turbine is considered and designed.

• 조명전기설비학회논문지
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• 제26권10호
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• pp.72-80
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• 2012

In general, electronic conveyor scales are installed in a relatively distributed manner on the crushed rock and sand production site. It is one of the time-consuming and difficult engineering works to monitor and control the plant operation status such as the management of measuring data, malfunction of belt conveyor, and fault of electronic conveyor scale. Therefore, to alleviate the inefficient problems and to monitor the operating plant in the online and remote control room, a remote calibration and real-time monitoring system, which is practically applied to the electronic conveyor scale system and verified by onsite experiment, is developed based on the LabVIEW.