• Journal of Welding and Joining
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• 제28권6호
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• pp.76-83
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• 2010

The purpose of this study is to propose a method to decide near-optimal settings of the constant current fuzzy control parameters using a controlled random search. This method tries to find the near-optimal settings of the constant current fuzzy control parameters through experiments. It has an advantage of being able to carry out searches in the search domain which includes some irregular points. The method suggested in this study was used to determine the fuzzy control parameters by which the desired welding current were formed during inverter DC resistance spot welding. The output variable was the ITAE (integral of time multiplied by the absolute error). This output variable was determined according to the input variables, which are the GE, GDE, and GDU. This study described how to obtained near-optimal welding current condition over a wide search space conducting a relatively small number of experiments.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2270-2273
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• 2003

Fuzzy logic control has been widely implemented in air conditioning and ventilation systems which has uncertainty or high robust system. Since the dynamic behaviors of the systems contain complexity and uncertainty in its parameters , several fuzzy logic controllers had been implemented to control room temperature in the field of air conditioning system. In this paper, the fuzzy logic control has been developed to control room temperature and humidity in the precision air conditioning systems. The nonlinear mathematical model was formulated using energy and continuity equations. MATLAB was used to simulate the fuzzy logic control of the multi-variable air conditioning systems. The simulation results show that fuzzy logic controller can reduce the steady-state errors of the room temperature and relative humidity in multivariable air conditioning systems. The offset are less than 0.5 degree Celsius and 3 percent in relative humidity respectively under random step disturbance in heating load and moisture load respectively

• 한국정밀공학회지
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• 제19권12호
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• pp.70-77
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• 2002

Necessity of the tole-operation has been increased in many fields. Since the Internet is inexpensive and available all over the world, it is a strong candidate for the transmission media of the tole-operation. However, the Internet has random time delays that may cause instability in the system especially if the tole -operation is bilateral. In the past few years many attempts have been made to overcome the random time delay, So far, they are still insufficient in terms of performance. The ‘Variable holding time’ is introduced to improve the performance of the ‘Event based tole-operation’ which controls a system with a non-time action reference. By holding each event for proper time, the system can quickly respond and be stabilized. The proper holding time should be selected based on the characteristics of the task that the system performs. The factors that reflect those characteristics are investigated. The fuzzy logic is employed to obtain the proper holding time for each event while the tole-operation system is in operation. The experimental results presented in this paper verify effectiveness of the proposed method.

• 한국지반공학회논문집
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• 제23권11호
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• pp.109-117
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• 2007

암반사면의 안정성 해석에는 다양한 원인에 의하여 불확실성이 개입하게 되며 경우에 따라 이러한 불확실성이 암반사면의 붕괴원인이 되기도 한다. 따라서 1980년대 이후부터 이러한 불확실성에 대한 중요성이 인식되었고 이를 정량화하기 위한 기법의 하나로 확률론적 해석기법이 제안되었다. 그러나 확률론적 해석기법은 불확실성에 대한 정보를 충분하게 획득할 수 있어 확률변수(random variable)치 확률특성을 정확하게 파악할 수 있다는 가정 하에 그 적용이 가능하다. 또한 불확실성중 공간적인 변동성이나 불균질성에 의한 불확실성은 확률론에 의해 쉽게 정량화될 수 있으나 측정오차나 측정수량의 부족 등에 의해 기인하는 불확실성은 확률론에 의해 다루기 어려운 것이 사실이다. 따라서 이러한 한계점을 보완하기 위해 퍼지집합이론(fuzzy set theory)의 활용이 제안되었다. 본 연구에서는 확률변수를 퍼지 숫자(fuzzy number)로 고려하여 퍼지집합이론을 활용하였고 이를 해석하기 위한 방법으로 몬테카를로기법(Monte Carlo simulation) 기법을 제안하였다. 이것은 퍼지숫자(fuzzy number)를 분석하기 위해 꼭지점(vertex) 기법이나 점추정법(point estimate method, PEM), 일계이차모멘트법(first order second moment method, FOSM)의 기법을 활용하였던 기존의 방법이 대표값만을 이용했던 단점을 보완할 수 있을 것으로 보인다. 제안된 기법의 적용성을 판단하기위해 현장을 선정하여 적용해 보았다. 결정론적 해석 결과 절리군 2는 안전한 것으로 절리군 4는 불안정한 것으로 해석되었다. 반면 확률론적 해석 결과 절리군 2의 경우 29.3%의 파괴확률을, 절리군 4의 경우 73.5%의 파괴확률을 보였다. 본 연구를 통해 제안된 기법을 활용하여 파괴확률을 계산해본 결과 절리군 2의 경우 33.5%, 절리군 4의 경우 73.5%로 확률론 해석기법의 결과와 유사하게 산정되었다. 따라서 본 연구에 의해 제안된 해석기법인 퍼지몬테카를로기법(Fuzzy Monte Carlo simulation) 기법이 이전의 해석결과와 유사한 해석결과를 보여주면서 자료의 분산이 많이 감소했다는 것을 알 수 있다.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2006년도 춘계학술대회 학술발표 논문집 제16권 제1호
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• pp.370-373
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• 2006

본 논문은 집합치 집합체 연산자를 정의하고 이들의 성질들을 조사한다. 또한 구간치 쇼케이적분에 의해 정의된 집합체 연산자를 정의 하고 이들의 특성들을 제시한다.

• Journal of Power Electronics
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• 제11권6호
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• pp.914-921
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• 2011

Commencing with incandescent light bulbs, every load today creates harmonics. Unfortunately, these loads vary with respect to their amount of harmonic content and their response to problems caused by harmonics. The prevalent difficulties with harmonics are voltage and current waveform distortions. In addition, Electronic equipment like computers, battery chargers, electronic ballasts, variable frequency drives, and switching mode power supplies generate perilous amounts of harmonics. Issues related to harmonics are of a greater concern to engineers and building designers because they do more than just distort voltage waveforms, they can overheat the building wiring, cause nuisance tripping, overheat transformer units, and cause random end-user equipment failures. Thus power quality is becoming more and more serious with each passing day. As a result, active power filters (APFs) have gained a lot of attention due to their excellent harmonic compensation. However, the performance of the active filters seems to have contradictions with different control techniques. The main objective of this paper is to analyze shunt active filters with fuzzy and pi controllers. To carry out this analysis, active and reactive current methods ($i_d-i_q$) are considered. Extensive simulations were carried out. The simulations were performed under balance, unbalanced and non sinusoidal conditions. The results validate the dynamic behavior of fuzzy logic controllers over PI controllers.

• The Journal of Asian Finance, Economics and Business
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• 제9권3호
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• pp.257-263
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• 2022

The objective of this study was to see how artificial intelligence applications affected organizational innovation in Jordanian commercial banks. Both independent and dependent variables were measured in three dimensions: expert systems, neural network systems, and fuzzy logic systems for artificial intelligence applications variable. Product innovation, process innovation, and management innovation for the organizational innovation variable. To achieve study objectives, a questionnaire was developed and distributed to a sample of one hundred fifty-three managers in Jordanian commercial banks, who were selected according to the simple random sampling method. Except for the neural network systems dimension, which comes in at an average level, the study indicated that there is a high level of organizational innovation and artificial intelligence applications. Furthermore, the findings revealed that artificial intelligence applications have a significant impact on organizational innovation in Jordanian commercial banks, with the most important artificial intelligence application being a fuzzy logic system. The study suggested keeping track of technological advancements in the field of artificial intelligence applications and incorporating them into banking operations by benchmarking with the best commercial bank practices and allocating a portion of the budget to technological applications and infrastructure development, as well as balancing between technology use and information security risks to ensure client privacy is protected.

• 한국생산제조학회지
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• 제21권4호
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• pp.683-690
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• 2012

In this work, the semi-active control of a large-sized bus suspension system with an MR damper was studied. An MR damper model that can aptly describe the hysteretic characteristics of an MR damper was adopted. Parameter values of the MR damper model were suitably modified by considering the maximum damping force of a passive damper used in the suspension system of a real large-sized bus. In addition, a fuzzy logic controller was developed for semi-active control of a suspension system with an MR damper. The vertical acceleration at the attachment point of the MR damper and the relative velocity between sprung and unsprung masses were used as input variables, while voltage was used as the output variable. Straight-ahead driving simulations were performed on a road with a random road profile and on a flat road with a bump. In straight-ahead driving simulations, the vertical acceleration and pitch angle were measured to compare the riding performance of a suspension system with a passive damper with that of a suspension with an MR damper. In addition, a single lane change simulation was performed. In the simulation, the lateral acceleration and roll angle were measured in order to compare the handling performance of a suspension system using a passive damper with that of a suspension system using an MR damper.

• 한국지능시스템학회논문지
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• 제19권3호
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• pp.371-374
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• 2009

이 논문에서는 사건과 확률변수를 각각 일반화한 이펙트와 옵저버블을 소개하였다. 그리고 $\sigma$-함수의 개념을 소개하고 이펙트 집합위에서의 확률측도로서의 $\sigma$-함수의 성질을 조사하였다.

• 디지털융복합연구
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• 제17권1호
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• pp.239-247
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• 2019

감정을 정확히 예측하는 것은 환자중심의 의료디바이스 개발 및 감성관련 산업에서 매우 중요한 이슈이다. 감정예측에 관한 많은 연구 중 감정 예측에 심박 변동성과 뉴로-퍼지 접근법을 적용한 연구는 없다. 본 연구는 HRV를 이용한 ANFEP(Adaptive Neuro Fuzzy system for Emotion Prediction)을 제안한다. ANFEP의 핵심 기능은 인공 신경망과 퍼지시스템을 통합해 예측 모델을 학습하는 ANFIS(Adaptive Neuro-Fuzzy Inference System)에 기반한다. 제안 모형의 검증을 위해 50명의 실험자를 대상으로 청각자극으로 감정을 유발하고, 심박변이도를 구하여 ANFEP 모형에 입력하였다. STDRR과 RMSSD를 입력으로 하고 입력변수 당 2개의 소속함수로 하는 ANFEP모형이 가장 좋은 결과를 나타났다. 제안한 감정예측 모형을 선형회귀 분석, 서포트 벡터 회귀, 인공신경망, 랜덤 포레스트와 비교한 결과 본 제안모형이 가장 우수한 성능을 보였다. 연구 결과는 보다 적은 입력으로 신뢰성 높은 감정인식이 가능함을 입증했고, 이를 활용해 보다 정확하고 신뢰성 높은 감정인식 시스템 개발에 대한 연구가 필요하다.