• 응용통계연구
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• 제8권1호
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• pp.1-7
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• 1995

표본조사에서 추정하고자 하는 모비율이 낮으면 많은 표본을 추출해야 한다. 이 때 단위표본의 비용이 높아 추출할 수 있는 표본의 크기가 제한된다면 추정량의 분산을 줄일 수 있는 방법을 신중히 고려해야 할 것이다. 본 논문에서는 모집단에 대한 사전 정보가 있어 이를 이용하여 층화추출하는 경우에 층의 표본크기의 새로운 배분방법을 제안하고 기존의 배분방법들과 비교해 본다.

• Transactions on Control, Automation and Systems Engineering
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• 제3권4호
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• pp.289-292
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• 2001

This paper concerns with a receding horizon estimator (RHE) for discrete-time linear systems subject to constraints on the estimate. In solving the optimization for every horizons, the past all measurement data outside the horizon is discarded and thus the arrival cost is not considered. The RHE in the current work is a finite impulse response (FIR) structure which has some good inherent properties. The proposed RHE can be represented in the simple matrix form for the unconstrained case. Various numerical examples demonstrate how including constraints in the RHE can improve estimation performance. Especially, in the application to the unknown input estimation, it will be shown how the FIR structure in the RHE can improve the estimation speed.

• Journal of Advanced Marine Engineering and Technology
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• 제24권6호
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• pp.102-109
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• 2000

In this industrial induction motor speed and torque controlled drive system, the closed loop control usually requires the measurement of speed or position of amotor. However a sensorless drive of an induction motor has several advantages ; low cost and mechanical simplicity. Thus this paper investigates a field oriented control method without speed and flux sensors. The proposed control strategy is based on the Model Reference Adaptive System(MRAS) using a new flux estimator which replaces integrators with two lag circuits as the reference model. This algorithm may overcome several shortages of conventional MRAS such as integrator problems, small EMF at low speed. The simulation and experimental results indicate good speed responses.

• 품질경영학회지
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• 제28권2호
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• pp.123-134
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• 2000

In the survey, it is very hard to get the complete response. Because the respondents tend to refuse to the questionnaire with something like incomes of the individual or may not be at home in the survey time. These nonresponses are classified into two groups as the item nonresponse and the unit nonresponse. When the nonresponse happen to the special item of the questionnaire, it is caned item nonresponse. On the other hand the unit nonresponse occurs to the totally missing in questionnaire. In this paper, we only consider to the unit nonresponse situation. We propose that the optimal estimator which is minimized the variance of the estimator under a fixed cost function for the survey and response.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.931-938
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• 2016

Application of vector control scheme for consumer products is enlarging to improve control performance. For the field-oriented control, accurate position detection is essential and generally requires expensive sensors. On the other hand, cost-reduction is important in home appliances, so that binary-type Hall-effect sensors are commonly used rather than using an expensive sensor such as an encoder. The control performance is directly influenced by the accuracy of the position information, and there exist non-uniformities related to Hall sensors in electrical and mechanical aspects, which result in distorted position information. Therefore, to get high-precision position information from low-resolution Hall sensors, this paper proposes a new position estimator consisting of a Kalman filter and feedforward compensation scheme, which generates a linearly changing position signal. The efficacy of the proposed scheme is verified by simulation and experimental results carried out with a 48-pole permanent magnet motor.

• 한국건설관리학회논문집
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• 제11권4호
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• pp.22-31
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• 2010

프로젝트 초기단계에서 산정된 공사비는 발주자의 중요한 의사결정에 영향을 미치므로 그 중요성이 강조되고 있지만, 정보의 부족으로 인하여 주로 견적전문가의 경험과 지식에 의존하여 진행된다. 이것은 현재 문제와 가장 유사한 과거 사례를 선택하여 사용하는 사례기반추론으로 발전되었다. 사례기반추론 모델의 예측 성능은 속성 가중치의 산정 결과에 많은 영향을 받으므로, 정확한 속성 가중치의 산정이 요구된다. 기존의 연구는 수학적 방법 또는 전문가의 주관적 판단을 이용하는 방법을 사용한다. 본 연구는 기존 연구의 문제점을 보완하기 위해 유전자 알고리즘을 이용한 사례기반추론 공사비 예측 모델을 제안한다. 공사비 예측 모델은 최근이웃 조회 방법의 과정에 의해 추출한 사례의 공사비 정보를 이용하여 예측 대상의 공사비를 산정한다. 검증 결과 AACE에서 정의한 견적시기별 예측 정확도와 표준화 회귀계수 동일가중치를 사용한 방법보다 높은 오차율을 나타내었다. 따라서 본 연구는 유전자 알고리즘을 도입하여 예측 성능을 향상시키고, 사례기반추론 방법을 사용하여 사용자가 이해하기 용이한 해결책 도출과정을 제시하였다는데 그 의미가 있다.

• 한국디지털건축인테리어학회논문집
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• 제10권3호
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• pp.11-18
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• 2010

Cost estimation through fast and correct quantity take offs are crucial in the process of construction project. The existing methods for cost estimation are mainly based on 2D-based drawings and the estimation result tends to be different according to the estimator's experience, the quality and quantity of used information and estimation time. To solve these problems, the domestic construction industry have recently tried to use the data extracted from 3D data modeling based on BIM(Building Information Modeling) in order to achieve more accurate and objective cost estimation. However it tends to increase dramatically the quantity of information that can be used in cost estimation by estimators. Therefore in order to achieve quality information data from 3D data modeling, the characteristics of the project should be reflected on the 3D model and it is most important to extract information only for cost estimation from the whole 3D model fast and accurately. Thus this study aims to propose the 3D modeling method through Data Normalization which maximizes the usability of 3D Data modeling in cost estimation process.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.883-889
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• 2009

The importance of cost estimate in early stage such has been increasing due to market change and severe competition in construction industry. Because the adjustable budget is only 20% after design stage, most of the crucial decisions to influence cost is made in the early stage. However, in the early stage, the project scope is not defined completely so that estimator has inaccurate information to make critical decision. Therefore, this research suggests the cost estimate method using case-based reasoning. Case-based reasoning is appropriate for the early cost estimating, as it has the strength of rapidity and convenience in cost estimation. This research analyzes 84 actual data of public apartment on the scale of 11~15 stories. In order to extract the most similar case, at the first step this research identifies influence factors and calculates attribute similarity. In case-based reasoning, the most challenging task is determining attribute weight. At the third step, this research calculates case similarity which is aggregated attribute similarity multipled by attribute weight. Finally, extracts the most similar case which has the highest score of case similarity.

• 응용통계연구
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• 제22권2호
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• pp.387-402
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• 2009

In this paper we have considered the problem of estimating the population mean $\bar{Y}$ of the study variable y using auxiliary information in presence of non-response. Classes of estimators for $\bar{Y}$ in the presence of non-response on the study variable y only and complete response on the auxiliary variable x is available, have been proposed in different situations viz., (i) population mean $\bar{X}$ is known, (ii) when population mean $\bar{X}$ and variance $S^2_x$ are known; (iii) when population mean $\bar{X}$ is not known: and (iv) when both population mean $\bar{X}$ and variance $S^2_x$ are not known: single and two-phase (or double) sampling. It has been shown that various estimators including usual unbiased estimator and the estimators reported by Rao (1986), Khare and Srivastava (1993, 1995) and Tabasum and Khan (2006) are members of the proposed classes of estimators. The optimum values of the first phase sample size n', second phase sample size n and the sub sampling fraction 1/k have been obtained for the fixed cost and the fixed precision. To illustrate foregoing, we have carried out an empirical investigation to reflect the relative performance of all the potentially competing estimators including the one due to Hansen and Hurwitz (1946) estimator, Rao (1986) estimator, Khare and Srivastava (1993, 1995) and Tabasum and Khan (2006) estimator.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.168-180
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• 2018

In order to achieve the high quality output voltage of single-phase voltage source inverters, in this paper an Adaptive Complementary Sliding Mode Control (ACSMC) is proposed. Firstly, the dynamics model of the single-phase inverter with lumped uncertainty including parameter variations and external disturbances is derived. Then, the conventional Sliding Mode Control (SMC) and Complementary Sliding Mode Control (CSMC) are introduced separately. However, when system parameters vary or external disturbance occurs, the controlling performance such as tracking error, response speed et al. always could not satisfy the requirements based on the SMC and CSMC methods. Consequently, an ACSMC is developed. The ACSMC is composed of a CSMC term, a compensating control term and a filter parameters estimator. The compensating control term is applied to compensate for the system uncertainties, the filter parameters estimator is used for on-line LC parameter estimation by the proposed adaptive law. The adaptive law is derived using the Lyapunov theorem to guarantee the closed-loop stability. In order to decrease the control system cost, an inductor current estimator is developed. Finally, the effectiveness of the proposed controller is validated through Matlab/Simulink and experiments on a prototype single-phase inverter test bed with a TMS320LF28335 DSP. The simulation and experimental results show that compared to the conventional SMC and CSMC, the proposed ACSMC control strategy achieves more excellent performance such as fast transient response, small steady-state error, and low total harmonic distortion no matter under load step change, nonlinear load with inductor parameter variation or external disturbance.