• 제어로봇시스템학회논문지
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• 제18권5호
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• pp.496-501
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• 2012

An equilibrium point of a WIP (Wheeled Inverted Pendulum) with changing its center of gravity is derived and validated by various numerical simulations. Generally, the WIP has two equilibrium points which are unstable and stable one. The unstable one is interested in this study. To keep the WIP over the unstable equilibrium point, the WIP is consistently being adjusted. A state feedback controller for the WIP needs a control reference for the equilibrium point. The control reference can be obtained by studying an equilibrium point of the WIP based on statics. By using Lagrange method, this study is deriving dynamic equations of the WIP both with and without changing its center of gravity. Various numerical simulations are carried out to show the validation of the equilibrium point.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.220-222
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• 1998

This paper presents a method, which develops an ability of Zero-phase Overcurrent Relay. Zero-phase current is very useful factor of Fault decision in Protect Relaying system. Actually, the setting-point value of Designed Relay, using Zero-phase current, is fixed. So in the case of deciding fault, Fixed setting-point value is not suitable for changing Load. and cause errors in Distributions system. For solving this problem, This paper proposes the Changed setting point value Algorithm, which can be adaptive for changing Distributions system using Zero-phase current r.m.s. indexes. The results of simulation under Load changing and High impedance fault show that proposed algorithm is useful for changing Distributions system and decreasing errors.

• 한국치위생학회지
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• 제7권4호
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• pp.395-403
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• 2007

The purpose of this study is to investigate the main factors that affect turnover of Dental Hygienists so that it leads to preventing high turnover and long-term service in their position. Data were obtained from 112 dental hygienists who are currently working for dental clinics from September 17th 2007 to October 16th 2007 via questionnaires. For this study, the demographic factors and unique characteristics of Dental Hygienists are considered as well as all the variables of statistic. The results derived from using SPSS 11.0 are as follows: 1. The average of job related factors is 2.55 point, the average of job satisfaction is 2.59 point, the average of salary related factor is 2.24 point and the average of changing their occupation is 2.85 point. 2. The difference between the factors related to age and changing their occupation shows the highest level on job related factors.(pM0.033) in the age between 26 and 30. 3. Dental Hygienists who are in their occupation for 6years to 9 years answer that salary would be the main reason to change their jobs. 4. For married dental hygienists, salary related factor is the main reason to make them change their occupation.(pM0.002)

• Journal of Acupuncture Research
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• 제21권3호
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• pp.43-59
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• 2004

Objective : In Modern society, patients with facial nerve paralysis are increasing because of many factors - irregular life, cold, overwork and stress etc. We have troubles in presuming the prognosis, though how to diagnosis and examine facial nerve paralysis are many. Methods : A clinical study was done on 89 patients who were diagnosed and treated as facial nerve paralysis(Bell's palsy) from January 2001 to May 2003 at the Dep. of Acupuncture and Moxibustion, college of Oriental Medicine, Woo-suk University. We classified 89 patients as the Sasang(四象) constitution, contributing factor, season, age and existence of diabetes items and analyzed, as we would research differences of changing point-Period from on set of Bell's palsy to the day which the change begins to be seen at the face- and improvement -Period which Bell's palsy is improved from on set to H-B grade II. Results : 1. Among the Sasang constitution, Soeumin($10.67{\pm}3.77days$) were faster than other constitutions, but Soyangin($16.25{\pm}6.75days$) were slower than other constitutions in changing point. Taeumin($4.12{\pm}1.49weeks$) were shorter than other constitutions, but Soyangin($4.88{\pm}2.11weeks$) were longer than other constitutions in improvement. 2. Among contributing factors, overwork and stress group were slower than other contributing factors in changing point($13.95{\pm}6.52days$), and longer than others in improvement($4.67{\pm}1.87weeks$). 3. Changing point and improvement of season, age, and existence of diabetes had the difference of the average according to an each item, but they were not statistically significant. 4. In 89 patients with Bell's palsy, average changing-point was $13.11{\pm}5.99$(days) and average improvement was $4.47{\pm}1.82$(weeks). Their correlation was 0.687 and statistically significance(P<0.01), therefore we could decide that their relation is highly correlation.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 추계학술대회 논문집
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• pp.234-237
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• 2003

As the maximum power operating point (MPOP) of photovoltaic (PV) power systems changes with changing atmospheric conditions, the efficiency of maximum power point tracking (MPPT) is important in PV power systems. Many MPPT techniques have been considered in the past, but techniques using microprocessors with appropriate MPPT algorithms are favored because of their flexibility and compatibility with different PV arrays. Although the efficiency of these MPPT algorithms is usually high, it drops noticeably in case of rapidly changing atmospheric conditions. In this paper, we proposed a new MPPT control method called improved perturb and observe method (ImP&O), anda simple voltage and current characteristic equation of a PV array for PV array simulator. Experimental results verify the accuracy and excellent performance of the proposed MPPT method. ImP&O algorithm is very simple, and has successful tracked the MPOP, even in case of rapidly changing atmospheric conditions.

• 한국수자원학회논문집
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• 제43권7호
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• pp.645-655
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• 2010

본 논문에서는 각각의 시점에서의 변화확률을 산정하여 변화시점을 추정하는 Barry and Hartigan (BH)의 베이지안 변화시점 추정방법(Bayesian changing points estimation method)을 이용하여 측우기 관측자료계열(CWK)과 근대우량계 관측자료계열(MRG)간의 변화에 대한 상대확률적 절점의 발생여부를 분석하였다. 어떠한 자연 현상도 완전히 동일하게 재현되지 않기때문에 시간적인 순서를 고려하지못하는 통계적 방법은 구체적인발생시간을 예측하기 어렵다는 점에서 자료의 변화량 파악은 가능하나 변화시점을 명확히 추정하는데 한계가 있다. 이러한 배경에서, 본 논문에서는 각 시점에서의 변화확률을 산정하여 변화시점을 추정하는 BH 베이지안 방법을 적용하여 CWK와 MRG의 각 강우특성별로 상대확률적인 변화시점 분석을 통하여 CWK와 MRG 간의 동질성 분석을 실시하였다. 분석 결과, CWK의 정성적인(본질적인) 통계적 특성은 MRG와 큰 차이가 없는 것으로 나타났다. 다만, 관측정밀도의 한계로 인한 정량적인 차이가 존재하는 것으로 분석되었다.

• 제어로봇시스템학회논문지
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• 제15권5호
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• pp.525-529
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• 2009

Most of FLC received input data from error e and change-of-error e' with no relation with system complexity. Basic scheme follows typical PD and PI or PID Controller and that has been developed through fixed ME In this paper, We studied the relationship between MF and system response and system response through changing Fuzzy variable of consequence MF and propose the simple FLC using this relationship. The response of FLC is changed according to the width of Fuzzy variable of consequence MF. As changing the Fuzzy variable of consequence MF shows various nonlinear characteristic, we studied the relation between response and MF using analytical method. We designed the effective FLC using three-variable MF and nine rules and took simulation for verification. In this study, we propose the method to design system with FLC in stability point which is an impotent characteristic of designing system. The circle criterion which is adapted to analysis the nonlinear system is put to use for proposed method. Since SISO FLC has a time-invariant and odd characteristic we can use the critical point not disk which is generally used to determine the stability in the circle criterion, to determine the stability. Using this, we can get the maximum critical point plot of SISO FLC with changing the consequence fuzzy variables. The predetermined critical point plot of FLC can be used to decide the region of the system to be stable. This method is effectively used to design the SISO FLC.

• 대한수학회보
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• 제47권2호
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• pp.411-422
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• 2010

By using the fixed point index theory, we investigate the existence of at least two positive solutions for p-Laplace equation with sign-changing nonlinear terms $(\varphi_p(u'))'+a(t)f(t,u(t),u'(t))=0$, subject to some boundary conditions. As an application, we also give an example to illustrate our results.

• Journal of Power Electronics
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• 제10권5호
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• pp.528-537
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• 2010

A novel decision reference based method for the maximum power point tracking (MPPT) of PV arrays is presented in this paper. The proposed decision reference was derived from a simplified solar cell model. This method solves the problems of conventional MPPT algorithms, such as oscillation of the operating point at the steady state and confusion under rapidly changing insolation. It is shown by simulation and experimental results that the method properly tracks a rapidly changing insolation profile. The signal to noise ratio (SNR) of the new decision reference is also higher than those of conventional P&O and INC methods. An updating subroutine was included in the proposed MPPT algorithm to compensate for temperature and aging effects.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권3호
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• pp.133-141
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• 2002

Most maximum power point tracking(MPPT) control algorithm is based on Perturb and Observe(P&O) and Incremental Conductance(IncCond). In comparison with P&O and IncCond algorithm, the dynamic and tracking characteristic of IncCond algorithm is better than P&O algorithm in condition of rapidly changing solar radiation. But in the case of digital implementation, the InCond algorithm has error en decision of maximum power operation point(MPOP). To solve this problem, this paper proposes a improved IncCond algorithm, which can determine the MPOP correctly by inserting the test signal in control input. This paper proposes a novel MPPT control algorithm for the digitally implemented photovoltaic system in condition of rapidly changing solar radiation. To verify the validity of the proposed control algorithm. the computer simulation and experiment are carried out.