• Journal of Power Electronics
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• 제18권2호
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• pp.395-406
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• 2018

Marine controlled-source electromagnetic transmitters (MCSETs) are important in marine electromagnetic exploration systems. They play a crucial role in the exploration of solid mineral resources, marine oil, and gas and in marine engineering evaluation. A DC-DC controlled-source circuit is typically used in traditional MCSETs, but using this circuit in MCSETs causes several problems, such as large voltage ringing of the high-frequency diode, heating of the insulated-gate bipolar transistor (IGBT) module, high temperature of the high-frequency transformer, loss of the duty cycle, and low transmission efficiency of the controlled-source circuit. This paper presents a clamping-diode circuit for MCSET (CDC-MCSET). Clamping diodes are added to the controlled-source circuit to reduce the loss of the duty ratio and the voltage peak of the high-frequency diode. The temperature of the high-frequency diode, IGBT module, and transformer is decreased, and the service life of these devices is prolonged. The power transmission efficiency of the controlled-source circuit is also improved. Saber simulation and a 20 KW MCSET are used to verify the correctness and effectiveness of the proposed CDC-MCSET.

• Journal of Power Electronics
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• 제19권2호
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• pp.529-539
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• 2019

The modular multilevel converter (MMC) has become a promising topology for high-voltage direct current (HVDC) transmission systems. To control a MMC system properly, the ac-side current, circulating current and submodule (SM) capacitor voltage are taken into consideration. This paper proposes a low-computation indirect model predictive control (IMPC) strategy that takes advantages of the conventional MPC and has no weighting factors. The cost function and duty cycle are introduced to minimize the tracking error of the ac-side current and to eliminate the circulating current. An optimized merge sort (OMS) algorithm is applied to keep the SM capacitor voltages balanced. The proposed IMPC strategy effectively reduces the controller complexity and computational burden. In this paper, a discrete-time mathematical model of a MMC system is developed and the duty ratio of switching state is designed. In addition, a simulation of an eleven-level MMC system based on MATLAB/Simulink and a five-level experimental setup are built to evaluate the feasibility and performance of the proposed low-computation IMPC strategy.

• 전기전자학회논문지
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• 제18권2호
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• pp.220-227
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• 2014

이 논문은 Dead-time을 갖는 톱니파 발생기를 이용하여 공통모드와 차동모드 피드백 루프를 구현한 Single-Inductor Dual-Output DC-DC Converter 설계에 관한 내용을 제시하고 있다. 제어회로에는 공통모드와 차동모드 피드백 루프를 Dead-time을 갖는 톱니파 발생기를 이용하여 동시에 사용하였다. 차동모드 피드백 루프에서 duty를 생성하기 위해서 전류 분배기 회로를 사용하여 공통모드 피드백에 의한 duty에 따라 dead-time이 유동적으로 변하는 톱니파형을 만드는 회로인 Dead-time을 갖는 톱니파 발생기를 추가하여 차동모드 피드백 회로를 구성하였다. 0.35um 공정을 사용하여 설계한 SIDO DC-DC Converter는 2.5V 입력으로부터 2.8V와 4.2V의 전압을 출력하며 최대 전력변환 효율은 95%이다. 출력간의 Cross regulation은 출력전류가 2배씩 증가할 경우 Boost1과 Boost2의 출력전압은 각각 3.57%, 4% 수준을 보이고 있다.

• 한국통신학회논문지
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• 제40권11호
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• pp.2178-2187
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• 2015

무선 개인화 네트워크 환경에서는 통신 장치의 경량화 정책으로 인하여 에너지 효율이 크게 요구되며, 이러한 시장 요구를 만족시키기 위하여 수많은 통신 프로토콜들이 연구되어 왔다. 특히 Bluetooth Low Energy 기술은 Duty Cycle 방식과 주파수 호핑 방식을 모두 채택하여 저전력 통신 기술의 대표 기술로 시장 선점을 주도하고 있다. 하지만 대부분의 저전력 통신 기술들은 Duty Cycle 채택 등의 이유로 Broadcast 통신 방식에서의 신뢰성 문제를 해결하기 힘들다. 본 논문에서는 IoT 환경에서 발생될 수 있는 Broadcast 통신 요구를 Bluetooth Low Energy 환경에서 해결하기 위한 에너지 고효율의 MAC 프로토콜을 제안하고, Master 장치와 Slave 장치의 Broadcast 전송 효율에 대한 분석을 통하여 제안 방식의 객관적 성능을 검증한다.

• Journal of Power Electronics
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• 제18권3호
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• pp.789-801
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• 2018

Model predictive direct power control (MPDPC) is a widely recognized high-performance control strategy for a three-phase grid-connected pulse width modulation (PWM) rectifier. Unlike those of conventional grid-connected PWM rectifiers, the active and reactive powers of permanent magnet synchronous generator (PMSG)-connected PWM rectifiers, which are used in electromagnetic transmitters, cannot be calculated as the product of voltage and current because the back electromotive force (EMF) of the generator cannot be measured directly. In this study, the predictive power model of the rectifier is obtained by analyzing the relationship among flux, back EMF, active/reactive power, converter voltage, and stator current of the generator. The concept of duty cycle control in the proposed MPDPC is introduced by allocating a fraction of the control period for a nonzero vector and rest time for a zero vector. When nonzero vectors and their duration in the predefined cost function are simultaneously evaluated, the global power ripple minimization is obtained. Simulation and experimental results prove that the proposed MPDPC strategy with duty cycle control for the PMSG-connected PWM rectifier can achieve better control performance than the conventional MPDPC-SVM with grid-connected PWM rectifier.

• 전기학회논문지P
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• 제65권4호
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• pp.309-315
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• 2016

NCS is the nation-wide standard designed to standardize and systematize the capability(knowledge, technology and attitude) required for personnel to undertake their task in industrial site according to industry field and level of the task. In order to cope with rapidly changing labor market, individual has to be equipped with ability required for each relevant duty field. And company also requires worker to have basic working ability, professional knowledge or technical capability for relevant duty. Especially, the core competency, a fundamental element for all tasks, has been recognized as critical part not just in social level but also in company level. In that sense, the necessity of adding the core competence into regular education program has been vastly demanded. This study mainly deals with development of NCS-based learning module for information capability that most of industrial field want their employee to be equipped as basic skill. And, in particular, education achievement analysis for computer application capability, a subordinate capabilities of information capability, and its application method are mainly described.

• 한국화재소방학회논문지
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• 제21권1호
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• pp.60-68
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• 2007

산불 발생 시 산불현장에 투입되는 지상진화대의 안전한 작업유도와 산불 현장 정보를 신속히 파악하기 위해 진화업무를 수행하는 지상진화대의 위치를 실시간으로 모니터링하는 것은 필수적이다. 본 연구에서는 CDMA(Code Division Multiple Access) 데이터 망을 이용하여 GPS로부터 수신되는 지상진화대의 위치를 실시간으로 전송하여 지상진화대의 정확한 위치탐지와 이동경로를 모니터링 함으로서 안전한 진화작업 유도와 산불 현장정보를 제공하고자 한다.

• 대한의용생체공학회:의공학회지
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• 제30권6호
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• pp.521-528
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• 2009

This study is about to evaluation of postural stability according to characteristics of electrical stimulation on the ankle muscles. We measured body sway(center of pressure, COP) when various parameters of electrical stimulation was applied to ankle muscles in stable and unstable posture. Subjects consisted of 10 young adults, and electrical stimulation was delivered on right and left of tibialis anterior and Achilles tendon. The body sway was measured during electrical stimulation of three duty cycle and frequencies in stable posture and three amplitudes of sensory threshold in unstable posture. Consequently, the COP Shift is higher during electrical stimulation of 1/30(duty ratio) and 100Hz(frequency) in stable posture. In unstable posture, 100% amplitude of sensory threshold induced postural stability. These findings are important for the rehabilitation system of postural stability and the use of electrical stimulation as somatosensory information.

• 융복합기술연구소 논문집
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• 제5권1호
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• pp.1-5
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• 2015

SI thermochemical hydrogen production process achieves water splitting into hydrogen and oxygen through three chemical reactions. The process is comprised of three sections and one of them is HI decomposition into $H_2$ and $I_2$ called as Section III. The production of $H_2$ included processes involving EED for concentrating a product stream from Section I. Additionally an $I_2$ crystallization would be considered to reduce burden on EED by removing certain amount of $I_2$ out of a process stream prior to EED. In this study, the current thermodynamic model of SI process was briefly described and the calculation results of the applied Electrolytes NRTL model for phase equilibrium calculations was illustrated for ternary systems of Section III. We calculated temperature and heat duty of an $I_2$ crystallizer and heat duty of heaters using UVa model and heat balance equation of simulation tool. The results were expected to be used as operation information in optimizing HI decomposition process and setting up material balance throughout SI process.

• 대한지역사회영양학회지
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• 제13권6호
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• pp.890-902
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• 2008

The purpose of this study was to develop a standardized job description for dietitians working in the public health nutrition area. Work-oriented job analysis methodology was employed for the study purpose. Subjects of 38 dietitians currently working at health centers in 2002 were recruited. Based on the focus group interview with 7 public health nutritionists and 7 professors, information about task elements was collected. Questionnaires measuring work performance and self-perception of importance of the selected task elements were administered. Reliability and validity of this instrument were tested by Chronbach's alpha and factor analysis. SAS PC package program was used for the statistical analysis. The final developed job description for public health nutritionists included 5 duties, 20 tasks and 93 task elements. The results of this study can be summarized as follows; 1) 5 duty areas are A. plan and evaluation of public health nutrition services, B. developing nutrition education materials, C. implementing nutrition services, D. networking community, and E. self development. 2) Each duty area from A to E was composed with 6, 2, 6, 4, 2 tasks, respectively. 3) Each duty area from A to E was composed with 24, 8, 38, 14, 9, and 2 task elements, respectively.