• 한국산학기술학회논문지
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• 제17권10호
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• pp.426-431
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• 2016

근래 조선소의 해양 프로젝트 비중이 증가함에 따라 작업 안전 환경과 공정 모니터링에 대한 요구 사항이 강화되고 있다. 이에 주요 조선소에서는 IT 기술을 접목하여 공정을 실시간으로 모니터링하고 작업자의 안전을 위해 작업 환경을 감지하기 위한 연구가 진행되고 있다. 조선소의 안벽 공정은 진수 후 안벽에 다수의 선박을 계류하고 선박 내부에서 의장 시스템 등의 마무리 공사 위주로 진행되며, 동시에 1,000여명 이상이 투입되어 진행되므로 인원의 관리와 안전 환경의 관리에 어려움이 많다. 본 연구에서는 이러한 안벽에서의 안전 작업을 위한 작업 환경을 모니터링하고 공정 진행 상황을 감지하기 위한 시스템의 개념 설계를 수행하였다. 현장 적용성을 높이기 위해 초기 투자비와 유지 운영비를 고려하여 6가지 구성 요소로 전체 시스템을 구성하였으며, 조선소 현장의 통신 환경을 고려하여 Wi-Fi와 LoRa 통신을 혼용하였고 현장에서의 데이터 송수신 기초 실험을 통해 그 적용성을 확인하였다. 설계된 시스템의 적용을 통해 안벽에 계류된 선박의 작업에 투입된 인원 현황, 작업 구역별 안전 현황을 실시간으로 감지하고 이를 기반으로 위험 상황 발생 시 단계별 알람을 발생하여 신속한 대피 및 대처가 가능하도록 함으로써 인명 손실 및 피해를 최소화 할 수 있다.

• 인터넷정보학회논문지
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• 제21권1호
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• pp.231-236
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• 2020

본 논문은 드론 운영개념에 따라 체공시간, 총 운영시간, 적정 소요량 등 작전운용성능과 소요량의 과학적 검증이 필요하나, 이를 체계적으로 분석할 수 있는 방법론이 없어 본 연구를 수행하였다. 본 연구는 임무기반한 모의분석을 통한 검증 6단계의 분석 방법론 연구 및 제안을 통해 드론의 운용개념 기반의 최적 ROC와 소요량을 제시할 수 있으며, 그 결과 기술적, 경제적 효과를 제시 하였다.

• Journal of Information Processing Systems
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• 제15권1호
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• pp.181-188
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• 2019

A production system is a management system that supports all activities to perform production operations at the manufacturing site. From the point-of-view of a smart factory, smart manufacturing systems redesigned the concept of onsite production systems to fit the entire system and its necessary functional composition. In this study, we select the key functions needed to build a smart factory for a PCB line and propose a new six-step model for the deployment of a smart manufacturing system by integrating essential functions. The smart manufacturing system newly classified the production and operation tasks of PCB manufacturing and selected necessary functions through requirement analysis and benchmarking of advanced companies. The selected production operation tasks are mapped to the functions of the system and configured into seven modules, and the optimal deployment model is presented to allow flexible responses to the characteristics of the tasks. These methodologies are first presented in this study, and the proposed model was applied to the PCB line to confirm that they had significant changes in the work method, qualitative effects, and quantitative effects. Typically, lead time and WIP have reduced by about 50%.

• The Journal of Korean Physical Therapy
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• 제36권1호
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• pp.27-32
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• 2024

Purpose: This study was conducted to verify the effect of applying a pressure biofeedback unit on walking ability and knee joint function while performing knee joint extensor strengthening exercises using resistance exercise equipment in total knee replacement (TKR) patients. Methods: This study was conducted on twelve patients receiving rehabilitation treatment after being admitted to a rehabilitation hospital post-TKR. Of these, six were allocated to a feedback group with a pressure biofeedback unit, and the other 6 were allocated to a control group without a pressure biofeedback unit. The subjects performed an exercise program for 45 minutes per session, five times a week, for two weeks. Walking ability and knee joint function were evaluated and analyzed before and after exercise. Results: The feedback group showed significantly better improvements in walking speed, gait cycle, step length on the non-operation side, time on the foot on the operation side, K-WOMAC stiffness, and K-WOMAC function than the control group (p<0.05). Conclusion: When strengthening the knee joint extensor muscles using resistance exercise equipment in TKR patients, the provision of a pressure biofeedback unit was found to improve walking ability and knee joint function by inducing concentric-eccentric contraction of the knee joint extensor muscles. Therefore, the study shows that exercise based on the provision of a pressure biofeedback unit should be considered when strengthening knee joint extensor muscles to improve the walking ability and knee joint function of TKR patients in clinical practice.

• 한국자동차공학회논문집
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• 제12권3호
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• pp.51-58
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• 2004

Optimization of engine desist and operation parameters using a genetic algorithm was demonstrated for direct injection diesel engine combustion. A micro genetic algorithm and a modified KIVA-3V code were used for the analysis and optimization of the engine combustion. At each generation of the optimization step the micro genetic algorithm generated five groups of parameter sets, and the five cases of KIVA-3V analysis were to be performed either in series or in parallel. The micro genetic algorithm code was also parallelized by using MPI programming, and a multi-CPU parallel supercomputer was used to speed up the optimization process by four times. An example case for a fixed engine speed was performed with six parameters of intake swirl ratio, compression ratio, fuel injection included angle, injector hole number, SOI, and injection duration. A simultaneous optimization technique for the whole range of engine speeds would be suggested for further studies.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1586-1592
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• 2017

Voltage sourced converter (VSC) based direct-current (DC) grid has the ability to control power flow flexibly and securely, thus it has become one of the most valid approaches in aspect of large-scale renewable power generation, oceanic island power supply and new urban grid construction. To solve the optimal power flow (OPF) problem in DC grid, an adaptive particle swarm optimization (PSO) algorithm based on fuzzy control theory is proposed in this paper, and the optimal operation considering both power loss and voltage quality is realized. Firstly, the fuzzy membership curve is used to transform two objectives into one, the fitness value of latest step is introduced as input of fuzzy controller to adjust the controlling parameters of PSO dynamically. The proposed strategy was applied in solving the power flow issue in six terminals DC grid model, and corresponding results are presented to verify the effectiveness and feasibility of proposed algorithm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.363-366
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• 1996

A FB-ZVS(Full Bridge Zero Voltage Switching) PWM DC/DC converter for electric vehicles is simulated and implemented in this paper. The converter considered is a step-down DC/DC converter with the ratings of 312/13.5V and 1.35kW. The steady state operation of this converter is divided into six operating modes in case of continuous current mode and eight operating modes in case of discontinuous current mode. Digital simulations using PSpice are carried out to verify the steady-state analysis. A prototype converter was built in the laboratory. MOSFETs were used for swithching devices and fast recovery diodes to reduce the charge storage problem of a pn-junction.

• 실천공학교육논문지
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• 제12권1호
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• pp.213-230
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• 2020

지금까지 학교 교육은 교육 예산 및 시설, 프로그램 등이 다양하게 투입되었지만 그 성과 평가는 명확하게 이루어지지 못했다. 본 연구는 전국 고등학교에서 학생들을 위한 교육 지원의 효율성을 분석하는 모델을 제시하였다. 학생 교육지원이 비슷한 학교의 운영 효율성을 분석하기 위하여 1차적으로 EM 군집분석을 수행한 후, 군집별로 상대적 효율성을 Network DEA를 이용하여 분석하였다. 본 연구에서 Network DEA는 학교 인프라 측면의 6개 투입요소, 1차적 산출 요소인 학업지속자, 학교 프로그램 측면의 10개 2차 투입 요소, 2차적 산출 요소인 진학자와 취업자, 연결 변수인 1인당도서관이용률을 고려하여 분석하였다. 효율성 분석 결과를 기반으로 벤치마킹할 대상을 선정하기 위해 유클리드 거리 계산방법을 적용하여 Tier분석을 수행하였다. 본 연구에서는 전국의 일반계고등학교와 직업계고등학교에서의 학생 교육지원 데이터를 수집하여 교육 지원의 효율성을 분석하는 모델을 적용하였다. 단계적 벤치마킹방안은 벤치마킹 대상 선택의 문제점을 보완하기 위해 비효율적인 학교의 요소를 고려하여 단계적으로 효율성 개선 대상을 선정하도록 제안하였다. 학생 교육지원 효율성이 낮은 학교가 학생 교육지원의 효율적 운영을 위한 단계적 벤치마킹을 하는데 기초적 자료로 활용될 것으로 기대된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.500-504
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• 1997

Current source inverter drives of auto sequentially commutated type are very popular in high power applications, because of simple power circuit configuration with four quadrant operation. But the six-step current output create harmonic problems and the input power factor of such a drive is not always good. In this respect pulse width modulated drives using gate turn off thyristors ( GTO ) are finding application, especially in traction drives. However the switching and snubber loses of a GTO do not permit the inverter switching frequency go beyond a few hundred hertz.This will again introduce low frequency harmonic problems. Multi level inverters of the 3-level and 5-level can be considered as an alternative to overcome the low switching frequency harmonic problem of the 2-level GTO inverters. But with multi level inverters the complexity of the power circuit increases. In this paper a combination of multi level ( 2-level and 3-level ) inverters and multi phase induction motor ( 3-phase and 6-phase) configurations are presented for high power VSI drives for traction applications with reduced inverter switching frequency requirements coupled with reduced voltage rating for the power switch.

• Nuclear Engineering and Technology
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• 제42권3호
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• pp.319-328
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• 2010

Bonded tendons have been used in reactor buildings at some operating nuclear power plants in Korea. Assessing prestress force on these bonded tendons has become an important pending problem in efforts to assure continued operation beyond their design life. The System Identification (SI) technique was thus developed to improve upon the existing indirect assessment technique for bonded tendons. As a first step, this study analyzed the sensitivity of the key parameters to prestress force, and then determined the optimal parameters for the SI technique. A total of six scaled post-tensioned concrete beams with bonded tendons were manufactured. In order to investigate the correlation of the natural frequency and the displacement to prestress force, an impact test, a Single Input Multiple Output (SIMO) sine sweep test, and a bending test using an optical fiber sensor and compact displacement transducer were carried out. These tests found that both the natural frequency and the displacement show a good correlation with prestress force and that both parameters are available for the SI technique to predict prestress force. However, displacements by the optical fiber sensor and compact displacement transducer were shown to be more sensitive than the natural frequency to prestress force. Such displacements are more useful than the natural frequency as an input parameter for the SI technique.