• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
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• pp.438-444
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• 1997

Recently, optical disk drives are increasingly demanded to have higher speed as well as high information density, especially for applications like CD-ROM drives. To this end, improvement of their optical pick-up structure and control is recognized the very challenging issue. In this paper, the 2-D motion of the pick-up is first analytically modelled to identify the cause and effect of the troublesome cross coupling between auto-focusing and tracking directions. Subsequently, the overall system equations are derived to include the dynamics of the related components in the auto-focusing servo system. While its unmeasurable parameters being estimated by the least square error method, a simple but decent linear model can be obtained within its operating frequency range. To design the high speed and robust positional servo controller, the design specifications are detailed and H$\sub$.inf./ control method is employed based on the simple model. Using the pickup in a commercial 8 fold speed CD-ROM drive as an example, performance of the designed controller is verified by realtime experiments.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(1)
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• pp.367-373
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• 1996

H$_{\infty}$ robust control theory is applied to the nuclear steam generator level control. Nuclear steam generator has the properties such as nonlinearity, non-minimum phase, and so, has some difficulties on level control. In a nuclear plant, it is more important to keep the operating variables under certain safety limits against various uncertainties than to meet the optimal performance. The designed H$_{\infty}$ controller shows robust level control against modelling error, disturbance in the nonlinear simulation. As the H$_{\infty}$ controller has both robustness and design transparency, it is adequate to the automation of level control and in licensibility

• Computers and Concrete
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• 제24권1호
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• pp.7-17
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• 2019

The complex phenomenon of the bond formation in geopolymer is not well understood and therefore, difficult to model. This paper present applied statistical models for evaluating the compressive strength of geopolymer. The applied statistical models studied are divided into three different categories - linear regression [least absolute shrinkage and selection operator (LASSO) and elastic net], tree regression [decision and bagging tree] and kernel methods (support vector regression (SVR), kernel ridge regression (KRR), Gaussian process regression (GPR), relevance vector machine (RVM)]. The performance of the methods is compared in terms of error indices, computational effort, convergence and residuals. Based on the present study, kernel based methods (GPR and KRR) are recommended for evaluating compressive strength of Geopolymer concrete.

• 융합신호처리학회논문지
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• 제7권3호
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• pp.108-115
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• 2006

본 논문에서는 주행하는 차선 내에 존재하는 선행차량의 위치측정 및 차량까지의 거리를 정확히 인식하기 위해 차량의 요동에 기인되는 피칭오차를 보정하여 계측하는 알고리듬을 제안하였다. 선행 차량까지의 거리를 정확히 계측하기 위하여 2 차원 영상좌표로부터 사영기하학을 적용하여 3 차원 좌표를 얻을 수 있는 카메라 Calibration 알고리듬을 확립하고, View Frustum(V.F.) 모델을 이용하여 직선부분에 대한 도로의 영상 모델을 제시하였다. 기 발표된 많은 연구논문들은 도로가 평면이라 가정하여 도로와 차량사이의 기하적인 변화에 따른 오차 특성을 고려하지 않은 경우가 많다. 이를 보완하고자 본 논문에서는 카메라 Calibration 알고리듬을 적용하여 실세계 좌표계와 영상좌표 계 사이의 기하해석으로 사영행렬을 추출하였고, V.F. 모델을 이용하여 소실점의 기하적인 해석을 통하여 차량의 피칭변화 에 따른 오차특성을 보정하였다. 실험결과 거리의 오차를 현저하게 줄일 수 있어 피칭변화에 강인함을 확인할 수 있었다.

• 대한수학회보
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• 제29권1호
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• pp.125-135
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• 1992

In various viscus flow problems it has been the custom to replace the convective derivative by the ordinary partial derivative in problems for which the data are small. In this paper we consider the Benard Convection problem with small data and compare the solution of this problem (assumed to exist) with that of the linearized system resulting from dropping the nonlinear terms in the expression for the convective derivative. The objective of the present work is to derive an estimate for the error introduced in neglecting the convective inertia terms. In fact, we derive an explicit bound for the L$_{2}$ error. Indeed, if the initial data are O(.epsilon.) where .epsilon. << 1, and the Rayleigh number is sufficiently small, we show that this error is bounded by the product of a term of O(.epsilon.$^{2}$) times a decaying exponential in time. The results of the present paper then give a justification for linearizing the Benard Convection problem. We remark that although our results are derived for classical solutions, extensions to appropriately defined weak solutions are obvious. Throughout this paper we will make use of a comma to denote partial differentiation and adopt the summation convention of summing over repeated indices (in a term of an expression) from one to three. As reference to work of continuous dependence on modelling and initial data, we mention the papers of Payne and Sather [8], Ames [2] Adelson [1], Bennett [3], Payne et al. [9], and Song [11,12,13,14]. Also, a similar analysis of a micropolar fluid problem backward in time (an ill-posed problem) was given by Payne and Straughan [10] and Payne [7].

• 산업기술연구
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• 제28권B호
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• pp.91-99
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• 2008

Applicability of existing methods of predicting consolidation settlement was assessed by analyzing results of centrifuge tests modelling self-weight consolidation of soft marine clay. From extensive literature review about self-weight consolidation of soft marine clays located in southern coast in Korea, constitutive relationships of void ratio-effective stress-permeability and typical self-weight consolidation curves with time were obtained by centrifuge model experiments. For the condition of surcharge loading, exact solution of consolidation settlement curve was obtained by Terzaghi's consolidation theory and was compared with the results predicted by currently available methods such as Hyperbolic method, Asaoka's method, Hoshino's method and ${\sqrt{S}}$ method. All methods were found to have their own inherent error to predict final consolidation settlement. From results of analyzing the self-weight consolidation with time by using those methods, Asaoka's method predicted the best. Hyperbolic method predicted relatively well in error range of 2~24% for the case of showing the linearity in the relationship between T vs T/S in the stage of consolidation degree of 60~90 %. For the case of relation curve of T vs $T/S^2$ showing the lineality after the middle stage, error range from Hoshino method was close to those from Hyperbolic method. However, Hoshino method is not able to predict the final settlement in the case of relation curve of T vs $T/S^2$ being horizontal. For the given data about self-weight consolidation after the middle stage, relation curve of T vs T/S from ${\sqrt{S}}$ method shows the better linearity than that of T vs $T/{\sqrt{s}}$ from Hyperbolic method.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.149-153
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• 2006

강우는 물과 에너지 순환에서 가장 중요한 역할을 한다. 이 연구에서는 원격탐사를 이용하여 추출한 강우자료의 불확실성 (uncertainty)이 수치수문모형에서 수문인자 (토양함수, 토양온도, 유출, 증발산, 열전도 등)를 모의할 때 공간 스케일의 영향을 검토해 보았다. 지상강우관측을 이용하여 보정된 WSR-88D (NEXRAD)에 의해 추출한 강우자료와 현장에서 측정된 기상자료를 입력 자료로 사용하여, 오프라인 CLM(Community Land Model) 수문모형을 세 가지의 다른 공간 스케일 $0.25^{\circ},\;0.5^{\circ}\;and\;1.0^{\circ}$에 대하여 수행하였다. 이어서 현장에서 측정된 기상자료는 고정시키고 동시공간에 해당하는 IR (Infrared) 밴드를 기반으로 하는 인공위성 강우자료로 대치시켜 같은 모형을 수행하여 비교 검토하였다. 이 연구에서는 물리적 이론을 기반으로 하는 CLM수문모형의 매개변수는 지표면-대기의 수문반응 (land-atmosphere interaction)을 적절하게 묘사하도록 정의되었다고 가정한다. 모형의 실험결과는 강우입력의 불확실성이 수문반응의 공간분포 결과에 어떻게 영향을 미치는지를 보여준다. 이 연구는 수문모형을 수행할 때 수문반응의 불확실성에 대한 정보를 제공해 주며, 결국은 기후 변화에 따른 수자원의 재분배를 이해하는데 이바지 할 것이다.

• Asian-Australasian Journal of Animal Sciences
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• 제33권3호
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• pp.408-415
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• 2020

Objective: The aim of the paper was to compare the fit of data derived from daily automatic milking systems (AMS) and monthly test-day records with the use of lactation curves; data was analysed separately for primiparas and multiparas. Methods: The study was carried out on three Polish Holstein-Friesians (PHF) dairy herds. The farms were equipped with an automatic milking system which provided information on milking performance throughout lactation. Once a month cows were also subjected to test-day milkings (method A4). Most studies described in the literature are based on test-day data; therefore, we aimed to compare models based on both test-day and AMS data to determine which mathematical model (Wood or Wilmink) would be the better fit. Results: Results show that lactation curves constructed from data derived from the AMS were better adjusted to the actual milk yield (MY) data regardless of the lactation number and model. Also, we found that the Wilmink model may be a better fit for modelling the lactation curve of PHF cows milked by an AMS as it had the lowest values of Akaike information criterion, Bayesian information criterion, mean square error, the highest coefficient of determination values, and was more accurate in estimating MY than the Wood model. Although both models underestimated peak MY, mean, and total MY, the Wilmink model was closer to the real values. Conclusion: Models of lactation curves may have an economic impact and may be helpful in terms of herd management and decision-making as they assist in forecasting MY at any moment of lactation. Also, data obtained from modelling can help with monitoring milk performance of each cow, diet planning, as well as monitoring the health of the cow.

• 한국컴퓨터정보학회논문지
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• 제17권1호
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• pp.81-85
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• 2012

대형 금융회사는 다양하고 급속하게 변화하는 비즈니스 환경 및 복잡한 업무요건들에 대해 금융정보 데이터의 생성과 변경을 효율적으로 정확하게 처리하고 데이터 처리 오류와 시행착오를 최소화하기 위한 시스템을 구축하기 위해 다양한 분야에서 연구와 노력이 진행되고 있다. 이 논문에서는 다양한 연구 분야 중 금융 데이터 모델링에 안정성, 정확성, 편의성을 제공하고 이에 따르는 영향도 분석 할 수 있으며 신규 모델 적용 시 기존 모델간의 매핑 정보를 제공하여 모델과 데이터베이스간의 효율적이고 편리하게 운용 할 수 있는 메타시스템을 구축했다. 이러한 메타데이터 시스템을 통해 모델링과 표준화 데이터를 관리하면 데이터에 대한 변경이 발생할 경우 데이터 표준화부터 데이터베이스까지 일원화된 체계로 모델 변경 작업을 진행할 수 있고 일관성 있는 고품질 데이터 모델을 유지 및 관리할 수 있다.

• 한국해안해양공학회지
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• 제9권1호
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• pp.43-55
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• 1997

니토층의 압밀과 침식 및 파랑에 의한 유동화에 대한 이론과 실험결과를 개략적으로 고찰하였으며, 영광 해역의 기존자료를 재분석하여 주기적 및 비수기적 압밀과 유동화를 겪는 해저 니토층의 전단강도 연직분포의 시간변화 이력의 중요성에 관하여 정성적의로 논하였다. 기존의 실내설험 결과 및 영광 해역의 현장자료에 따르면, 저면의 압밀과 유동화를 고려하지 않고 니토 혹은 오염물질을 수치모의할 경우 ,유체역학적 작용력과 수주내 농도증가 사이에 시간차이를 유발할 수 있다. 이러한 시간차이는, 특히 파랑에너지가 비교적 큰 대조차 환경에서 저면으로부터 기인하는 고농도 물질의 이동방향 측면, 즉 물질수지 측면에서 심각한 오차를 발생시킬 수 있다