• 한국지진공학회논문집
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• 제12권4호
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• pp.19-33
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• 2008

구조물에 고유한 진동수,모드형태 및 감쇠비 등과 같은 동적성능치를 추출하기 위하여 25층 및 42층 건물에 대하여 자연진동에 의한 동적계측실험을 수행하였다. 고려된 건물은 주요 횡하중 지지기구로서 코아벽체 혹은 전단벽체가 추가된 철근콘크리트건물이며, 입면 혹은 평면상으로 골조가 혼합된 구조형식을 나타낸다. 특히, 25층 건물은 측면에 위치한 코아벽체 이외에 상부로부터 내려오는 전단벽 구조가 4층 바닥이하에서 골조형식으로 전환되는 복잡한 구조이다. 이와 같은 이유 및 건물 주방향의 유사한 강성배치로 매우 근접하고 혼합된 모드형태가 예상되어 시스템판별 시 어려움이 예상된다. 현재까지 개발된 다양한 시스템판별법을 대상건물의 자연진동 실측기록에 적용하여 모달계수를 유도하였으며, 그 결과를 비교 분석하였다. 3개의 주파수영역 및 4개의 시간영역에 근거한 응답의존 시스템판별법이 고려되었다. 서로 다른 시스템판별법에 의하여 추출된 고유진동수 및 감쇠비는 대체로 상당한 일치를 보였으나, 모드형태는 사용된 방법에 따라 정도가 다르게 불일치를 나타냈다. 실험으로부터 추출한 성능치와 초기 유한요소해석 값을 비교해 본 결과 대상건물 모두 적어도 저차 3개의 고유진동수에서 2배 정도의 차이를 나타냈다. 실험과 해석결과의 일치를 위하여 몇몇 수동모델향상이 시도되었으며, 허용할 만한 결과를 획득하였다. 사용된 시스템판별법에 대하여 각자의 장, 단점에 대하여 기술하였으며, 본 연구와 같은 실제 대형구조물에 대하여 자동모델향상기법을 적용할 시 예상되는 문제점에 대하여 토의하였다.

• Nuclear Engineering and Technology
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• 제54권3호
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• pp.1037-1048
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• 2022

A radioactive isotope identification algorithm is a prerequisite for a low-resolution scintillation detector applied to an unmanned radiation monitoring system. In this paper, a sparse representation with dictionary learning approach is proposed and applied to plastic gamma-ray spectra. Label-consistent K-SVD was used to learn a discriminative dictionary for the spectra corresponding to a mixture of four isotopes (¹³³Ba, ²²Na, ¹³⁷Cs, and ⁶⁰Co). A Monte Carlo simulation was employed to produce the simulated data as learning samples. Experimental measurement was conducted to obtain practical spectra. After determining the hyper parameters, two dictionaries tailored to the learning samples were tested by varying with the source position and the measurement time. They achieved average accuracies of 97.6% and 98.0% for all testing spectra. The average accuracy of each dictionary was above 96% for spectra measured over 2 s. They also showed acceptable performance when the spectra were artificially shifted. Thus, the proposed method could be useful for identifying radioisotopes in gamma-ray spectra from a plastic scintillation detector even when a dictionary is adapted to only simulated data. Furthermore, owing to the outstanding properties of sparse representation, the proposed approach can easily be built into an insitu monitoring system.

• 드라이브 ㆍ 컨트롤
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• 제13권4호
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• pp.23-30
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• 2016

This paper presents a control-oriented dynamical model of a towing rope system with variable-length. In this system, a winch driven by a motor's torque uses the towing rope to pull a cart. In general, it is a difficult and complicated process to obtain an accurate mathematical model for this system. In particular, if the rope length is varied by operating the winch, the varying rope dynamics needs to be considered, and the key physical parameters need to be re-identified... However, real time parameter identification requires long computation time for the control scheme, and hence undesirable control performance. Therefore, in this article, the rope is modeled as a straight massless segment, with the mass of rope being considered partly with that of the cart, and partly as halfway to the winch. In addition, the changing spring constant and damping constant of the towing rope are accounted for as part of the dynamics of the winch. Finally, a reduced-order observer-based servomechanism controller is designed for the system, and the performance is evaluated by computer simulation.

• Fibers and Polymers
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• 제7권1호
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• pp.62-65
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• 2006

Making a good model is one of the most important aspects in the field of a control system. If one makes a good model, one is now ready to make a good controller for the system. The focus of this thesis lies on system modeling, the draft system in specific. In modeling for a draft system, one of the most common methods is the 'least-square method'; however, this method can only be applied to linear systems. For this reason, the draft system, which is non-linear and a time-varying system, needs a new method. This thesis proposes a new method (the MLS method) and demonstrates a possible way of modeling even though a system has input noise and system noise. This thesis proved the adaptability and convergence of the MLS method.

• 한국정밀공학회지
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• 제18권10호
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• pp.101-108
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• 2001

In this study, the static and dynamic characteristics of endmilling process were modelled and the analytic realization of chatter mechanism was discussed. In this reward, We have discussed on the comparative assessment of recursive time series modeling algorithms that cal represent time machining process and detect the abnormal machining behaviors in precision endmilling operation. In this study, simulation and experimental works were performed to show the malfunctional behaviors. For this purpose, new recursive algorithm(RLSM) was adopted for the oil-line system identification and monitoring of a machining process, we can apply these new algorithms in real process for detection of abnormal chatter. Also, The stability lobe of chatter was analysed by varying parameter of cutting dynamics in regenerative chatter mechanics.

• 대한기계학회논문집A
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• 제30권10호
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• pp.1209-1218
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• 2006

Precision servomechanisms are widely used in machine tool, semiconductor and flat panel display industries. It is important to improve contouring accuracy in high-precision servomechanisms. In order to improve the contouring accuracy, cross-coupled control systems have been proposed. However, it is very difficult to select the controller parameters because cross-coupled control systems are multivariable, nonlinear and time-varying systems. In this paper, in order to improve contouring accuracy of a biaxial servomechanism, a cross-coupled controller is adopted and an optimal tuning procedure based on an integrated design concept is proposed. Strict mathematical modeling and identification process of a servomechanism are performed. An optimal tuning problem is formulated as a nonlinear constrained optimization problem including the relevant controller parameters of the servomechanism. The objective of the optimal tuning procedure is to minimize both the contour error and the settling time while satisfying constraints such as the relative stability and maximum overshoot conditions, etc. The effectiveness of the proposed optimal tuning procedure is verified through experiments.

• 한국산업정보학회:학술대회논문집
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• 한국산업정보학회 1996년도 추계 학술 발표회 발표논문집
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• pp.217-227
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• 1996

The new filed of learning control develops controllers that learn to improve their performance at executing a given task , based on experience performing this specific task. In a previous work[6], authors presented a theory of indirect learning control based on use of indirect adaptive control concepts employing simultaneous identification and control. This paper develops improved indirect learning control algorithms, and studies the use of such controller indecentralized systems. The original motivation of the learning control field was learning in robots doing repetitive tasks such as on an asssembly line. This paper starts with decentralized discrete time systems. and progresses to the robot application, modeling the robot as a time varying linear system in the neighborhood of the nominal trajectory, and using the usual robot controllers that are decentralized, treating each link as if it is independent of any coupling with other links. The resultof the paper is to show that stability of the indirect learning controllers for all subsystems when the coupling between subsystems is turned off, assures convergence to zero tracking error of the decentralized indirect learning control of the coupled system, provided that the sample tie in the digital learning controller is sufficiently short.

• 한국소음진동공학회논문집
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• 제16권6호
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• pp.565-573
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• 2006

Acoustic analysis of a moving sound source required that the measured sound signals be do-Dopplerized and restored as of the original emission signals. The purpose of this research is development of beamforming technique can be applied to the rotor noise source identification. For the do-Dopplerization and reconstruction of emitted sound wave, Forward Propagation Method is applied to the time domain beamforming technique. And validation test were performed using rotating sound source constructed by bended pipe and horn driver. In the validation test using sinusoidal sound wave, sufficient performance of signal processing can be seen, and the effect of measuring duration for accuracy was compared. In the prop-rotor measurements, the acoustic source locations were successfully verified in varying positions for different frequencies and collective pitch angle, in hover condition.

• 반도체디스플레이기술학회지
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• 제23권2호
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• pp.87-91
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• 2024

SiO₂, renowned for its excellent insulating properties, has been used in the semiconductor industry as a valuable dielectric material. High-quality SiO₂ films find applications in gate spacers and interlayer insulation gap-fill oxides, among other uses. One of the prevalent methods for depositing these SiO₂ films is plasma enhanced chemical vapor deposition (PECVD) favored for its relatively low processing costs and ability to operate at low temperatures. However, compared to the increasingly utilized atomic layer deposition (ALD) method, PECVD exhibits inferior film characteristics such as uniformity. This study aims to produce SiO₂ films with uniformity as close as possible to those achieved by ALD through the adjustment of PECVD process parameters. we conducted a total of nine PECVD processes, varying the process time and gas flow rates, which were identified as the most influential factors on the PECVD process. Furthermore, ellipsometry analysis was employed to examine the uniformity variations of each process. The experimental results enabled us to elucidate the relationship between uniformity and deposition rate, as well as the impact of gas flow rate and deposition time on the process outcomes. Additionally, thickness measurements obtained through ellipsometer facilitate the identification of optimal process parameters for PECVD.

• 경영과정보연구
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• 제31권4호
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• pp.261-286
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• 2012

본 연구는 오늘날 기업에 관한 부정적 소문인 루머의 영향을 최소화하기 위한 관리 방안을 고찰하는데 목적이 있다. 즉, 기업-소비자동일시 수준에 따른 루머의 신뢰 정도와 그에 따른 확산정도를 파악하고 루머의 신뢰와 확산을 막고자 하는 기업이 루머반박을 했을 경우, 동일시 수준에 따른 반박효과의 차이를 살펴보았다. 연구결과를 요약하면 다음과 같다. 본 연구에서는 동일시 수준에 따라 악성루머에 대한 신뢰도 반응 확산의도 차이, 재구매 의도 차이가 있는지 확인해 보았으며, 동일시 수준에 따라 유의한 차이를 보였다. 동일시가 낮은 소비자가 루머에 대한 신뢰도가 높았고, 확산의도 또한 동일시가 낮은 소비자에서 높게 나타났다. 이에 반해, 재구매 의도는 동일시가 높은 소비자에게서 높게 나타났다. 따라서 기업-소비자 동일시 수준에 따라 루머에 대한 반응의 차이와 그 후 태도에 영향을 미치는 것으로 나타났다. 추가적으로, 기업이 반박기사를 냈을 경우, 동일시 수준에 따라, 반박 기사에 대한 반응이 다를 것이라 보았다. 동일시가 높은 소비자는 동일시가 낮은 소비자 보다 반박기사에 대한 신뢰도가 높게 나타났음을 확인할 수 있었다.