• 전기의세계
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• v.38 no.3
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• pp.19-25
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• 1989

Observer에 의한 상태추정방식을 사용하여 실제 플랜트제어를 구현하는 방법을 살펴보고자 한다. 제어분야에 있어서 디지탈화는 컴퓨터기술의 진보와 함께 꾸준히 발전하여 왔으며 산업의 여러 현장에서 그 우수성이 입증되고 있다. 종래의 아나로그제어에 전적으로 의존하고 있던 플랜트제어도 아나로그 방식을 디지탈화한 여러 제어방식이 출현, 현재 점차로 적용되고 있다. 더우기 시스템의 파라메타들과 상ㅌ변수 등의 추정에 의한 고도의 현대제어는 그 물리적, 열역학적 해석이 정확히 주어짐으로 보다 우수한 플랜트제어를 가능하게 하고 있다. 미국이나 일본의 경우 시스템 모델링에 의한 플랜트 제어로의 접근이 이미 60년대와 70년대에 걸쳐 활발히 진행되어 현재는 엔지니어링 차원으로의 시도가 이루어지고 있다. 현대제어이론의 발전플랜트에의 적용은 제어의 질의 향상 뿐만아니라 효율향상과 기기수명 측면에서도 그 효과가 상당하여, 앞으로 이에 대한 활발한 연구와 실제 적용을 기대해 본다.

• Journal of Korean Society of Transportation
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• v.29 no.6
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• pp.97-106
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• 2011

Mode choice model is an essential element for estimating- the demand of new means of transportation in the planning stage as well as in the establishment phase. In general, current demand analysis model developed for the mode choice analysis applies common parameters of utility function in each region which causes inaccuracy in forecasting mode choice behavior. Several critical problems from using common parameters are: a common parameter set can not reflect different distribution of coefficient for travel time and travel cost by different population. Consequently, the resulting model fails to accurately explain policy variables such as travel time and travel cost. In particular, the nonlinear logit model applied to aggregation data is vulnerable to the aggregation error. The purpose of this paper is to consider the regional characteristics by adopting the parameters fitted to each area, so as to reduce prediction errors and enhance accuracy of the resulting mode choice model. In order to estimate parameter of each area, this study used Household Travel Survey Data of Metropolitan Transportation Authority. For the verification of the model, the value of time by marginal rate of substitution is evaluated and statistical test for resulting coefficients is also carried out. In order to crosscheck the applicability and reliability of the model, changes in mode choice are analyzed when Seoul subway line 9 is newly opened and the results are compared with those from the existing model developed without considering the regional characteristics.

• Journal of Korean Society of Forest Science
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• v.86 no.1
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• pp.17-24
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• 1997

As the first step to estimate the potential natural vegetation distribution of the globe, the best spherical interpolation method was developed to the temperature and precipitation which have close relation to the distribution pattern of world natural vegetation. For developing the interpolation method, a named Light Climatic Dataset composed of 1,060 stations around the globe was randomly divided into halves of feeding side and target side. The discrepancy between the observed and estimated values at the target stations was compared with combinations of parameters and methods. The estimated values were calculated to each combination which is all-out, constant radius and constant station methods in the selection of the feeding stations, n square reciprocal and negative exponential functions in weighting function of distance between feeding stations and each target, and oval weighting in direction of the feeding stations from each target. As a result, it turned out that the spherical interpolation with negative exponential weighting function fed from the constant radius stations ovally weighed yields the best estimates both for temperature and for precipitation. The parameters for temperature are $30^{\circ}$ in constant radius, 0.78 in negative exponential function and 0.4 in oval weighting, and for precipitation are $30^{\circ}$, 0.53 and 0.4, respectively.

• The KIPS Transactions:PartC
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• v.15C no.1
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• pp.31-36
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• 2008

The clock frequency difference of sensor nodes is one of main parameters in TOF estimation and affect to degrade ranging algorithms to estimate positions of mobile nodes in wireless sensor networks. The specification of IEEE802.15.4a describes asynchronous TWR and SDS-TWR insensitive to frequency difference without any additional network synchronization. But the TWR and SDS-TWR can not eliminate sufficiently the effect of frequency difference of node pair, packet processing delay and its difference. Especially use of low cost oscillator with wide range offset, sensor node with different hardware and software can make the positioning errors worse. We propose an estimation method of frequency differences, and apply the measured frequency differences to TWR and SDS-TWR. We evaluate the performance of the proposed algorithm with simulation, and make certain that the proposed method enhances the performance of existing algorithms with positioning errors less than 25 cm.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.04a
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• pp.4-10
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• 1995

이동가입자 수신단에서의 평균 수신전력 레벨이 핸드오버 임계값과 수신기 임계값 사이에 있는 영역을 핸드오버 영역이라고 하며, 이동가입자가 핸드오버 영역이라고 하며, 이동가입자가 핸드오버 영역에 머무르는 시간을 핸드오버 지속시간(Handover Duration Time)으로 정의한다. 본 논문에서는 이동통신 시스템에서 트래픽 모델링시 중요한 파라메타중 하나인 핸드오버 지속시간에 대한 분포를 추정한다. 첫번째로 핸드오버 지속시간의 분포군을 선택하기 위해 시뮬레이션 결과로부터 얻어진 샘플 데이타를 이용하여 점 통계량, 히스토그램, 확률도의 방법을 적용하며, 두번째로 구체적인 분포를 결정하기 위해서 모수(parameter)의 값들을 추정하는데, 본 논문에서는 모수를 추정하기 위해서 최우추정량을 사용하여 모수의 값들을 산출하고 이를 토대로 적합도 검정을 수행한다. 최종적인 분석 결과 핸드오버 지속시간은 감마 분포를 따르는 것을 제시하였다.

• The KIPS Transactions:PartB
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• v.9B no.4
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• pp.421-428
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• 2002

The local prediction method utilizing embedding vector loses the prediction power when the parameter r estimation is not exact for predicting the chaos time series induced from the high order differential equation. In spite of the fact that there have been a lot of suggestions regarding how to estimate the delay time ($\tau$), no specific method is proposed to apply to any time series. The inclinded linear model, which utilizes inclinded netter, yields satisfying degree of prediction power without estimating exact delay time ($\tau$). The usefulness of this approach has been indicated not only theoretically but also in practical situation when the method w8s applied to economical time series analysis.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.1
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• pp.72-85
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• 2001

A study for the structural strength evaluation on the doubler plate subjected to the biaxial in-plane compression has been performed through the systematic evaluation process. In order to estimate the proper static strength of doubler plate, elasto-plastic large deflection analysis is introduced including the contact effect between main plate and doubler. The characteristics of stiffness and strength variation are discussed based on their results. A1so, in order to compare the doubler structure with the original strength of main plate without doubler, a simple formula for the evaluation of the equivalent flat plate thickness is derived based on the additional series analysis of flat plate structure. Using this derived equation, the thickness change of a equivalent flat plate is analyzed according to the variation of various design parameters of doubler plate and some design guides are suggested in order to maintain the original strength of main plate without doubler reinforcement. Finally, correlation between derived equivalent flat plate formula and the developed buckling strength formulas by author et a1. is discovered and these relations are formulated for the future development of simple strength evaluation formula of doubler plate structure.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.4
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• pp.92-105
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• 2000

A study for the structural strength evaluation on the slender doubler plate has been performed through the systematic evaluation process. In order to estimate the proper static strength of doubler plate subjected to the longitudinal in-plane compression, elasto-plastic large deflection analysis is introduced including the contact effect between main plate and doubler. The characteristics of stiffness and strength variation are discussed based on their results. Also, in order to compare the doubler structure with the original strength of main plate without doubler, a simple formula for the evaluation of the equivalent flat plate thickness is derived based on the additional series analysis of flat plate structure. Using this derived equation, the thickness change of a equivalent flat plate is analyzed according to the variation of various design parameters of doubler plate and some design guides are suggested in order to maintain the original strength of main plate without doubler reinforcement. Finally, correlation between derived equivalent flat plate formula and the developed buckling strength formulas by author et al. is discovered and these relations are formulated for the future development of simple strength evaluation formula of doubler plate structure.

• Journal of Korean Society of Transportation
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• v.2 no.1
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• pp.69-88
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• 1984

통행시간가치에 대한 연구는 독립변수를 이용한 통행시간과 비용에 의한 선택모형 을 대개 사용하여 왔다. 통행시간과 비용에 대한 매개함수를 추정한 후에 통행시간가치를 교통시간과 비용의 $\ulcorner$파라메타$\lrcorner$비로써 얻고 있다. 그러나 통행시간가치에 관한 신뢰구간과 통계적 유의성을 설정하기 위한 적절한 과정은 아직 연구되지 않고 있으나 $\ulcorner$로-짓$\lrcorner$ 모형 자체에 대하여는 되어있다. 본 논문은 통행시간가치를 측정하기 위한 기존의 방향을 비평적 으로 검토하여 본 것으로 통행시간가치를 통계적 유의성 검증을 위한 표준화 과정은 아직 이론적으로 정립 가능하다고 생각되지 않지만 통행시간가치평가의 간편식을 제시하여 보았 다. 간편식에 의하여 제시된 결과에 의하면 선택모형에 입각한 통행시간가치의 통계적신뢰 구간이 매우 큰 것으로 나타났는바 이에 대한 선택모형에 입각한 통행시간가치 측정을 위한 과정의 타당성에 대한 많은 의문이 아직도 남는다 하겠다.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.2088-2090
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• 1997

This paper consists of the speed sensorless vector control of induction motors with the estimation of rotor resistance. In the application of variable-speed induction motor drives, if an inaccurate rotor resistance is used because the rotor resistance can change due to skin effects and temperature variables, it is difficult to achieve a collect field orientation. In this paper, to overcome these difficulties adaptive algorithm is designed for rotor resistance identification. The proposed adaptive algorithm for rotor resistance estimation in the synchronous reference frame is applied by sliding mode current controller satisfing persistent excitation(PE) condition. Adaptive flux observer is here used for the purpose of estimating rotor flux and speed in the speed sensorless scheme. Computer simulations are carried out to verify the validity of the proposed algorithm.