• Journal of Power Electronics
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• 제15권3호
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• pp.730-740
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• 2015

This paper presents model reference adaptive system speed estimators based on Type-1 and Type-2 fuzzy logic controllers for the speed sensorless direct torque and flux control of an induction motor drive (IMD) using space vector pulse width modulation. A Type-1 fuzzy logic controller (T1FLC) based adaptation mechanism scheme is initially presented to achieve high performance sensorless drive in both transient as well as in steady-state conditions. However, the Type-1 fuzzy sets are certain and cannot work effectively when a higher degree of uncertainties occurs in the system, which can be caused by sudden changes in speed or different load disturbances and, process noise. Therefore, a new Type-2 FLC (T2FLC) - based adaptation mechanism scheme is proposed to better handle the higher degree of uncertainties, improve the performance, and is also robust to different load torque and sudden changes in speed conditions. The detailed performance of different adaptation mechanism schemes are performed in a MATLAB/Simulink environment with a speed sensor and sensorless modes of operation when an IMD is operates under different operating conditions, such as no-load, load, and sudden changes in speed. To validate the different control approaches, the system is also implemented on a real-time system, and adequate results are reported for its validation.

• 대한지리학회지
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• 제51권3호
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• pp.367-380
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• 2016

본 연구에서는 우리나라에서 발생한 저체중아 출생 집계 자료를 공간적으로 지도화하기 위한 기법들을 검토 비교하고, 이를 기반으로 우리나라의 LBW 지도를 작성하였다. 표준화사망률이나 조사망률 등은 역학 분야에서 지속적으로 광범위하게 사용되고 있는 지표이다. 그러나 이러한 표준화사망률은 집계 단위의 샘플 수에 영향을 많이 받는다는 단점을 가지고 있다. 이에, 본 연구에서는 베이지언 기법을 활용하여 샘플 수에 따른 통계적 변동성을 감소시키고자 하였다. 이를 위해 경험적 베이지언 기법과 풀 베이지언 기법을 모두 활용하였고, 결과적으로 유사한 통계량을 산출한 것을 확인할 수 있었다. 반면, SMR 기반의 통계량은 높은 분산을 가지고 있음을 확인하였다. 연구의 결과에 따른 통계 지도는 우리나라 저체중아 출생의 높은 위험도를 가지는 지역들을 파악할 수 있도록 한다.

• 한국음향학회지
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• 제35권3호
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• pp.234-242
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• 2016

본 논문에서는 양이형 음성 음질개선 시스템에 적용 가능한 잡음 상관도 온라인 추정 알고리즘을 제안한다. 양이형 시스템에서 공간 상관도(spatial coherence) 정보를 이용해 잡음의 파워 스펙트럼을 추정하거나 음질 개선 이득을 형성하는 기술들이 다수 연구되어 왔다. 이때 잡음 상관도는 통상적으로 수학적으로 모델링된 실수의 고정 값을 사용하여왔다. 하지만 실생활에서 접하게 되는 잡음의 상관도는 음향 환경에 따라 변화하는 특성을 가지게 되며 이때 발생하는 오차는 음질 개선 알고리즘의 정확도를 떨어뜨리는 원인이 된다. 따라서 본 논문에서는 변화하는 잡음의 상관도를 온라인으로 업데이트하여 정확한 잡음 상관도를 추정함으로써 양이형 음질 개선 알고리즘의 성능을 향상 시키고자 하였다. 잡음의 상관도는 음성 부재 구간에서 업데이트 될 수 있으며 실험 결과 제안 알고리즘이 기존의 수학적 모델에 비해 음질 개선 알고리즘의 성능을 향상시킴을 볼 수 있다.

• 응용통계연구
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• 제26권3호
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• pp.441-452
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• 2013

국내 영화 산업은 투자 배급사 멀티플렉스로 수직 계열화된 대기업 중심으로 온라인 구전 마케팅이 활발히 진행되고 있다, 최근에는 대기업 계열의 멀티플렉스 영화관 중심으로 3D 4D 영화포맷 복합상영을 통해 up-selling을 통한 흥행성과 극대화를 도모하고 있다. 영화산업 기술진보와 흥행여건 변화에 따라, 기존 관객 수 대신 매출액을 흥행성과로 정의하고, 국내 개봉 상업영화를 대상으로 축소추정기법을 포함한 여러 회귀모형을 적용하였다. 특히 LASSO회귀의 경우, 교차타당성 방법을 이용한 예측오차가 가장 적고 흥행성과에 설명력이 높은 변수 순으로 의미 있는 독립변수들을 빠르고 효율적으로 선택할 수 있었다. 2013년도 1분기 개봉 영화를 대상으로 실증분석 결과, 개봉 후 온라인 평점과 빈도 모두 영향력이 높았으나, 개봉 전에는 온라인 평점만 효과적인 것으로 나타났다. 상영포맷 또한 흥행성과에 유의한 영향을 미치는 것으로 나타났다.

• 제어로봇시스템학회논문지
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• 제21권2호
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• pp.145-149
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• 2015

This paper introduces a sway suppression control for container cranes with unknown payloads and sway rates. With no priori knowledge concerning the magnitude of payload mass and sway rate, the proposed control maintains superior sway suppressing and trolley positioning against external disturbances. The proposed scheme combines a second order sliding mode control and an adaptive control to cope with unknown payloads. A second order sliding mode control without feedback of the sway rate is first designed, which is based on a class of feedback linearization methods for stabilization of the under-actuated sway dynamics of the container. Under applicable restrictions of the magnitude of payload inertia and sway rate, a linear regression model is obtained, and an adaptive control with a payload estimator is then designed, which is based on Lyapunov stability methods for the fast attenuation of trolley oscillations in the vicinity of the target position. The asymptotic stability of the overall closed-loop system is assured irrespective of variations of rope length. Simulation are shown in the existence of initial sway and external wind disturbances.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.246-250
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• 2000

A distinctive feature in vibration control of a large civil infrastructure is the existence of large disturbances, such as wind, earthquake, and sea wave forces. Those disturbances govern the behavior of the structure, however, they cannot be precisely measured, especially for the case of wind-induced vibration control. The sliding mode fuzzy control (SMFC), which is of interest in this study, may use not only the structural response measurement but also the wind force measurement. Hence, an adaptive disturbance estimation filter is introduced to generate a wind force vector at each time instance based on the measured structural response and the stochastic information of the wind force. The structure of the filter is constructed based on an auto-regressive with auxiliary input model. A numerical simulation is carried out on a benchmark problem of a wind-excited building. The results indicate that the overall performance of the proposed SMFC is as good as the other methods and that most of the performance indices improve as the adaptive disturbance estimation filter is introduced.

• Journal of Power Electronics
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• 제11권4호
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• pp.464-470
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• 2011

In this paper, the feasibility of applying a position sensorless control technique to hybrid electric vehicles (HEVs) is practically evaluated. The proposed position estimator has a straightforward structure with properties that combines the model and the saliency tracking-based rotor position estimation for interior permanent magnet synchronous motors (IPMSMs). The proposed method can be used in the event of sensor loss or sensor recovery to sustain continuity of operations. The developed system takes into account the estimated position transition between two distinct sensorless methods. The transition is enhanced by introducing a synchronized transition algorithm based on a single tracking observer. Extensive experimental results are presented to verify the principles and show a reliable estimation performance over the entire speed range including standstill under 150% load conditions.

• 로봇학회논문지
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• 제6권2호
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• pp.97-107
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• 2011

This paper describes efficient flight control algorithms for building a reconfigurable ad-hoc wireless sensor networks between nodes on the ground and airborne nodes mounted on autonomous vehicles to increase the operational range of an aerial robot or the communication connectivity. Two autonomous flight control algorithms based on adaptive gradient climbing approach are developed to steer the aerial vehicles to reach optimal locations for the maximum communication throughputs in the airborne sensor networks. The first autonomous vehicle control algorithm is presented for seeking the source of a scalar signal by directly using the extremum-seeking based forward surge control approach with no position information of the aerial vehicle. The second flight control algorithm is developed with the angular rate command by integrating an adaptive gradient climbing technique which uses an on-line gradient estimator to identify the derivative of a performance cost function. They incorporate the network performance into the feedback path to mitigate interference and noise. A communication propagation model is used to predict the link quality of the communication connectivity between distributed nodes. Simulation study is conducted to evaluate the effectiveness of the proposed reconfigurable airborne wireless networking control algorithms.

• 대한조선학회논문집
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• 제46권3호
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• pp.362-371
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• 2009

Shipbuilding is a typical 'build to order' industry. It has a business model that generates revenues from building various ships and offshore products in accordance with owner's requirements at each production stage. Under uncertainty in shipping market, it is very essential for the shipbuilder to prepare the fast and competitive decision for product portfolio strategy in order to maximize contribution margin by exploiting production facilities and constraints. In this study, we introduce the unique decision supporting methodology for the optimal product portfolio sets based on Theory of Constraints(TOC). This methodology is established by adopting the concept of Drum Buffer Rope(DBR) in constraints planning and Throughput Accounting (TA) in management accounting of TOC. In addition, Decision Supporting System(DSS) is implemented. This DSS system provides a throughput estimator with reflecting the cost structure of shipbuilding industry and a resource simulator built on heuristic algorithms to operate major constraint-resources in shipyard such as dock, quay and pre-erection area etc. Several examples are presented to show that the proposed methodology and system can effectively support the strategic decision-making process of a global shipbuilding company.

• The Journal of Asian Finance, Economics and Business
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• 제7권10호
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• pp.161-169
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• 2020

The condition of mining companies that exploit natural resources in their business processes underline this research to emphasize on social and environmental issues. After twelve years of government regulation on CSR practices, this study investigates the factors that influence mining companies in disclosing information about corporate social responsibility based on legitimacy, stakeholders, and agency theory. Thus, independent variables are foreign ownership, company size, leverage, and the board of commissioners. The dependent variable is the corporate social reporting disclosure that is measured using GRI indexing. For sampling, we have used thirty-four Indonesian mining companies listed in IDX during the 2014-2018. out of which only fifty-two companies meet the sample criteria. All data should pass the classical assumption test to get the best estimator. Multiple linear regression is used to test the hypothesis, and the results show that the model is good, and can explain 60% of the dependent variable. Based on F-test, all four variables affect CSR practices simultaneously. The findings of this study suggest that foreign ownership and firm size influences CSR disclosure in a positive direction. However, this study did not support the hypothesis that leverage negatively affects CSR disclosure and board size measures positively affect CSR disclosure.