• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2910-2912
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• 2000

Since the heavy-duty power manipulator has high ratio gear reducers at its joints, its dynamic characteristics are much slower than that of the master manipulator and it is likely to encounter the saturation in the input magnitude when it is used as the slave manipulator in telemanipulator systems. This paper proposes a force reflecting position control scheme for 2 axes heavy-duty power manipulator which compensates control input saturation. A series of experiments is shown to give an excellent tracking performance regardless of saturation.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.294-295
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• 2017

태양광발전시스템은 설비 사용률을 최대화하기 위하여 PV 모듈을 최대 전력점에서 운전하는 MPPT(Maximum Power Point Tracking) 제어가 반드시 필요하다. 기존의 MPPT 알고리즘은 경사법에 기반을 두기 때문에 일정한 MPPT 주기마다 일정한 크기의 PWM Duty 비의 자극을 주고, 그에 따른 출력 전력의 변화를 감지하여 최대 전력점을 향한 다음 운전점을 찾는다. 이러한 MPPT 알고리즘을 실제 날씨 환경에 적용할 때 최대전력을 생산하기 위한 최적의 MPPT 주기와 PWM Duty 비의 변량은 다양한 일사량의 프로파일 형태에 따라 달라진다. 그러므로 최적의 MPPT 주기와 PWM Duty 비의 변량을 결정하기 위해서는 실제 날씨 환경에서 다양한 일사량 프로파일의 패턴에 대한 분석이 필수적이다. 본 논문에서는 대한민국 중부지역의 전형적인 맑은 날씨와 흐린 날씨에서 실제 일사량을 측정, 분석하여 MPPT 목표 효율을 최대화할 수 있는 MPPT 주기를 제시하였다.

• Journal of Korean society of Dental Hygiene
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• v.17 no.6
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• pp.1067-1080
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• 2017

Objectives: This study analyzed the perception towards clinical practice education content held by dental hygiene students in dental institutions and their perceived importance of dental hygienists' clinical duties. Methods: The subjects of this study were 182 dental hygienists who were working at dental institutions in Seoul, Gyeonggi, and Chungcheong areas. A survey was conducted with a self-administered questionnaire. In the questionnaire, the clinical practice contents were classified into observation, preparation, and performance, and the importance of clinical duty was measured with a 3-point scale. For the clinical practice contents and the importance of duty, descriptive statistics and chi-square test were performed, and the study results were analyzed using STATA 11.0. Results: With regard to clinical practice contents, observation was mainly performed in oral & maxillofacilal radiology, preventive dentistry, periodontal medicine and oral medicine. In primary care and infection control, practice and observation were mainly performed. In the department of orthodontics and pediatric dentistry, observation and preparation were mainly conducted, while in oral surgery, conservative dentistry observation, preparation and practice were all conducted. With regard to clinical practice contents according to the dental institution, there were statistically significant differences in the type of dental institution and the duty (p>0.05). In terms of the importance of dental hygienist's duty, infection control, toothbrushing education for each patient, removal of plaque, and patient education after surgery were considered important. Conclusions: For clinical practice of the dental hygiene department, the education contents should be standardized in accordance with the importance of the dental hygienist's duty, a protocol for operation of practice should be developed, and a method of standardization of evaluation should be sought in the future.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.6
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• pp.527-534
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• 2017

This paper proposes a new DC link voltage controller for a single-phase power factor correction (PFC) boost converter. The load current of the PFC boost converter affects the capacitor current, whereas the load current changes the output voltage. However, previous works that compensate output current have failed to consider the relationship between load current and duty. Thus, they also fail to maintain a constant output voltage if the load fluctuates under the conditions of a non-rated input voltage. By considering the duty in the load current compensation, the proposed method improves the load transient response regardless of the input voltage. To demonstrate its effectiveness, the proposed method is compared with other control methods by conducting PSM simulations and experiments under a rapidly changing load.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.10
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• pp.4754-4773
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• 2018

In sensor medium access control (SMAC) protocol, sensor nodes can only access the channel in the scheduling and listening period. However, this fixed working method may generate data latency and high conflict. To solve those problems, scheduling duty in the original SMAC protocol is divided into multiple small scheduling duties (micro duty MD). By applying different micro-dispersed contention channel, sensor nodes can reduce the collision probability of the data and thereby save energy. Based on the given micro-duty, this paper presents an adaptive duty cycle (DC) and back-off algorithm, aiming at detecting the fixed duty cycle in SMAC protocol. According to the given buffer queue length, sensor nodes dynamically change the duty cycle. In the context of low duty cycle and low flow, fair binary exponential back-off (F-BEB) algorithm is applied to reduce data latency. In the context of high duty cycle and high flow, capture avoidance binary exponential back-off (CA-BEB) algorithm is used to further reduce the conflict probability for saving energy consumption. Based on the above two contexts, we propose an improved SMAC protocol, micro duty adaptive SMAC protocol (MDA-SMAC). Comparing the performance between MDA-SMAC protocol and SMAC protocol on the NS-2 simulation platform, the results show that, MDA-SMAC protocol performs better in terms of energy consumption, latency and effective throughput than SMAC protocol, especially in the condition of more crowded network traffic and more sensor nodes.

• Journal of Distribution Science
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• v.14 no.10
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• pp.47-57
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• 2016

Purpose - This study's purpose is to investigate the market structure of the Korean duty free shop industry that has received recent attention from researchers and practitioners. By raising the question of whether or not the Korean duty free shop industry is unequivocally monopolistic, a wider viewpoint is provided. The study seeks to offer insights and managerial implications for marketers and policy makers who are in charge of regulating major Korean duty free shops. Research design, data, and methodology - The authors use secondary data from various sources, including Korea Customs Service and the Moodie Report, to investigate the structure of the duty free shop industry of Korea. Based on several theories, they present various criteria and statistical evidence such as K-firm concentration ratio, HHI, consumer substitutability, excess profit, and marketing costs. Results - In terms of consumer substitutability, it is difficult to confirm whether or not the Korean duty free shop industry is monopolistic. Notwithstanding monopoly characteristics in terms of market share, neither the company Lotte nor Shilla appear to have market dominating power. It is not easy for either of them to control prices or to achieve a much lower operational profit ratio due to a dominant bargaining power. Moreover, the license is not an economic rent. In this situation, it is not easy for these companies to obtain an excessive profit. Conclusions - Considering that most global duty free shops are trying to go upscale to improve bargaining power, it does not seem likely that rigid regulations are needed in the industry. Even though the Korean duty free industry ostensibly has a monopolistic structure, government and policy-makers should look beyond the surface. They should take global and other reasonable criteria into consideration when they establish or change regulation policies. Thorough understanding and appropriate support are needed for the Korean duty free shop industry. Additionally, duty free shops should position themselves as global companies struggling against unlimited international competition, rather than Korean domestic companies. At the same time, they need to give customers appropriate information about the benefits they provide.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.966-967
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• 2015

본 논문은 BLDC 팬모터의 속도제어 선형성(linearity)에 관한 것이다. PWM으로 모터의 속도를 제어할 때에 입력 duty cycle이 증가함에 따라 모터 속도가 선형적으로 증가하지 않는 문제가 발생한다. 모터를 구동하는 드라이브 IC의 출력 PWM duty cycle을 속도제어의 입력값에 해당하는 입력 PWM duty cycle과 비선형적으로 출력함으로써, 모터 속도의 입력 PWM duty cycle에 대해 선형성을 향상시켰다. 또한, 비휘발성 메모리에 설정값을 저장하여 선형성 정도를 조절가능하도록 하였다. 0.35um CMOS 공정으로 단상 BLDC 모터 드라이브 IC를 설계 및 제작하고, 모터 샘플을 이용하여 PWM 입력 duty cycle과 모터 속도와의 선형성 정도를 측정하였다.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.21 no.2
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• pp.47-61
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• 2013

A concession business at Incheon Int'l airport has achieved a huge success since its grand opening of 2001. However the duty-free market became matured due to downtown duty free stores and on-line stores. Thus this paper tried to research and suggest strategic planning of VMD at Incheon airport's duty-free after analyzing the relationship among the components of duty-free store's VMD, brand awareness, brand image and customer's loyalty. Components of VMD are constructed in harmony, attractiveness, trendiness and Trust, which are independent variables. In addition, brand awareness and brand image are chosen as control variables. Customer loyalty is also designated as a dependant variable. Focusing those variables, this paper tried to find out the effect of VMD components to brand and consumer loyalty. According to the research result, it is proven attractiveness and harmony have a significant positive impact on brand awareness and brand image. It is also found out brand awareness and image have a positive impact on passenger's loyalty on duty-free stores at Incheon airport.

• Journal of Distribution Science
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• v.16 no.8
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• pp.39-50
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• 2018

Purpose - The ultimate purpose of this research is to analyze the influence of personal disposition on shopping value and behavioral intention by expanding the theory of planned behavior (TPB). Research design, data, and methodology - An attempt was made to examine the effects of personal disposition (reflecting duty-free shop characteristics) on three selective actions of consumers - compulsive buying, variety seeking, and price sensitivity. We conducted a questionnaire survey with the users of airport duty-free shops, downtown duty-free shops (offline), and online duty-free shops. In total, 410 copies of the questionnaire were analyzed using a structural equation model. Results - According to the results, compulsive buying, variety seeking, and price sensitivity significantly affected shopping value. Shopping value and subjective norms both had significant effects on attitude, the major variable in the TPB, and attitude had the greatest effect on behavioral intention, followed by subjective norms and perceived behavioral control in descending order. Conclusions - This study has academic implications in that it extends the existing theories of planned behavior and applies it to consumer characteristics and shopping value. It has practical implications as well in that it provides basic data that can be used to establish concrete marketing strategies for duty-free shop owners targeting segmented markets by closely examining customer desires.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.470-475
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• 2002

Instantaneous following PWM control technique is pulsed nonlinear dynamic control method. This new control technique using analog integrator is proposed to control the duty ratio D of do-dc converter. In this control method, the duty ratio of a switch is exactly equal In or proportional to the control reference in the steady state or in a transient. Proposed control method compensates power source perturbation in one switching cycle, and the average value of the dynamic reference in one switching cycle. There is no steady state error nor dynamic error between the control reference and the average value of the switched variable. Experiments with buck converter have demonstrated the robustness of the control method and verified theoretical prediction. The control method is very general and applicable to all type PWM