• 한국자동차공학회논문집
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• 제21권5호
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• pp.145-150
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• 2013

Recently, many vehicles have applied electric parts for saving fuel consumption and reducing levels of environmental pollution. ISG (integrated starter & generator) is one of main electric parts and can improve fuel efficiency by using idle stop & go function and regenerative braking system. However, if ISG driving inverter works under the continuously high load condition, it will make the performance and durability of the inverter decreased with rising temperature. In this study, we carried out the analysis on the fluid flow and thermal characteristics of the inverter. As a result, we found the MOSFET of the air cooled inverter was increased up to $116^{\circ}C$ over the limit temperature. On the other hand, the liquid cooled type inverter's MOSFET was decreased by about $17^{\circ}C$ compared to that of the air cooled inverter. Therefore, we verified the feasibility of the liquid cooled type using the present cooling structure.

• 산업경영시스템학회지
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• 제37권4호
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• pp.63-71
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• 2014

As power consumption increases, more power utilities are required to satisfy the demand and consequently results in tremendous cost to build the utilities. Another issue in construction of power utilities to meet the peak demand is an inefficiency caused by surplus power during non-peak time. Therefore, most power company considers power demand management with time-based electricity rate policy which applies different rate over time. This paper considers an optimal machine operation problem under the time-based electricity rates. In TOC (Theory of Constraints), the production capacities of all machines are limited to one of the bottleneck machine to minimize the WIP (work in process). In the situation, other machines except the bottleneck are able to stop their operations without any throughput loss of the whole manufacturing line for saving power utility cost. To consider this problem three integer programming models are introduced. The three models include (1) line shutdown, (2) block shutdown, and (3) individual machine shutdown. We demonstrate the effectiveness of the proposed IP models through diverse experiments, by comparing with a TOC-based machine operation planning considered as a current model.

• 산업공학
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• 제18권2호
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• pp.136-147
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• 2005

This paper introduces a simulation study regarding the operation of the Painted Body Storage (PBS) in an automobile factory. In the paint shop of the factory, same colored bodies are grouped together in order to increase the effectiveness of process, for example decrease the loss of cleaning the painting-gun when the color of body changes from one to another. However the production of automobiles in the assembly shop is a typical example of the mixed model assembly production. Therefore PBS locates between the paint shop and the assembly shop for control the input sequence of bodies to the assembly shop, and it enables to meet the smoothing requirement of assembly sequence. There are highly restricted constraints on the assembly sequence in a assembly shop. Those are spacing restriction and smoothing restriction. If such restrictions are violated, conveyor-stop or utility work will be necessary. Thus the major objective of PBS is to control the assembly sequence in a way to meet the two restrictions. In this paper a case study of PBS in an automotive factory is introduced. The storage/retrieval algorithms are suggested and the proposed system is verified using simulation models. Sensitivity analysis for operating factors is also conducted.

• 전기학회논문지
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• 제66권6호
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• pp.898-904
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• 2017

DFT(Discrete Fourier Transform) is one of the most widely used method to estimate the phasor of a relaying signal. The harmonics are eliminated by the DFT. However, high frequency components, except for harmonics, are not removed and cause an error in DFT-based phasor estimation process. This paper suggests high frequency noise reduction method by using a newly designed low-pass filter to estimate a signal phasor. When selecting a stop-band cut-off frequency of the low-pass filter, high frequency components generated by faults are considered. To reduce the phasor estimation delay caused by a low-pass filter, this paper proposes a low-pass filter whose settling time is reduced. An adverse effect of high frequency noise on DFT-based phasor estimation is reduced. To evaluate the performance of the proposed method, signals which are collected under a fault condition at a 345[kV] transmission system modeled by EMTP-RV are used.

• Journal of Platform Technology
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• 제9권1호
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• pp.23-31
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• 2021

최근 몇 년간 국내 산업에서 센서 오작동과 환경 모니터링의 부재로 인한 유해가스 방출 등으로 인명피해가 발생하고 이러한 유해 물질이 감지할 수 있는 환경 센서의 평가는 내구성 시험 및 위해성 검사 위주이기 때문에 센서의 측정 데이터에 대한 신뢰성 검증에는 한계가 있다. 본 플랫폼은 환경센서의 신뢰성을 검증하고 수집한 데이터를 통해 환경 분석을 위해 주요한 10종의 물질에 대해 측정하는 센서 보드와 각 센서의 성능 검증 체계를 설계하였다. 데이터를 수집하기 위해 센서 보드로 수집된 데이터를 LoRa 통신을 이용하여 데이터 신뢰성 평가 및 검증을 위한 서버로 전달되고 전달된 데이터를 모니터링 하기 위한 센서 데이터 플랫폼의 프로토타입을 제작하였다. 그리고 수집한 데이터를 이용하여 machine learning 기법을 통해 대기 환경을 분석하고 예측한다.

• 대한건축학회논문집:계획계
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• 제35권9호
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• pp.3-9
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• 2019

Modern cities have been clustered with spaces defined by specific functions, while standardized with well-defined areas. The monopoly of the function reduces the publicity of the space and hinders people's daily communication. Street also be overwhelmed by the function of being a "passage", traditional streets were losing their liminality. In fact, the street was a place of meeting, a place of events, and a place of freedom to broaden the choices of behavior. The freedom to stop or walk on one'sits own, be attracted by unforeseen events that are available on traditional streets, has become rare on the streets of big cities. Life has become dull and monotonous, too, through the modelling of the street system. Cities have become grim as communities are cut off and fragmented. In today's big cities, public attention to the liminality of the traditional streets need to be aroused so that people could gather freely and have a festival time.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.3985-3995
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• 2022

The emergence of new nanoscale technologies has imposed significant challenges to designing reliable electronic systems in radiation environments. A few types of radiation like Total Ionizing Dose (TID) can cause permanent damages on such nanoscale electronic devices, and current state-of-the-art technologies to tackle TID make use of expensive radiation-hardened devices. This paper focuses on a novel and different approach: using machine learning algorithms on consumer electronic level Field Programmable Gate Arrays (FPGAs) to tackle TID effects and monitor them to replace before they stop working. This condition has a research challenge to anticipate when the board results in a total failure due to TID effects. We observed internal measurements of FPGA boards under gamma radiation and used three different anomaly detection machine learning (ML) algorithms to detect anomalies in the sensor measurements in a gamma-radiated environment. The statistical results show a highly significant relationship between the gamma radiation exposure levels and the board measurements. Moreover, our anomaly detection results have shown that a One-Class SVM with Radial Basis Function Kernel has an average recall score of 0.95. Also, all anomalies can be detected before the boards are entirely inoperative, i.e. voltages drop to zero and confirmed with a sanity check.

• 한국산업정보학회논문지
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• 제19권4호
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• pp.53-63
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• 2014

이동 컴퓨팅 환경에서 사용자 움직임 판별은 해결해야 할 중요한 이슈중의 하나이다. 본 논문에서는 유클리디안 거리 유사도를 이용하여 스마트폰 사용자의 움직임을 인식하고 판별하기 위한 방법을 제시한다. 제안된 방법에서는 GPS와 가속 센서를 이용하여 데이터를 수집하고, 수집된 데이터를 이용하여, 사용자의 정지, 걷기, 뛰기, 차량이동을 판별한다. 제안된 방법의 타당성과 효율성을 검증하기 위하여, 안드로이드 시스템에 유클리디안 거리 유사도의 여러 변형을 이용한 응용프로그램을 구현하여 그 정확도를 측정하였다. 실험 결과, 사용자 움직임 종류를 90% 이상의 정확도를 가지고 판별해 내었다.

• 산업경영시스템학회지
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• 제39권3호
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• pp.129-138
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• 2016

The train-centric control systems development has some distinct points in that a big size of government budget is in general expended in there and the development duration seems to be long. In addition, the changes are ever made continuously in the capability and operational requirements for Trains. Thus, the impact of the potential changes in the required operational capability on the development activities can induce some type of project risks [7]. As such, proper management of project risk has been one of crucial subjects in the train systems development. All these notes combined together make it the significance of the safety management process be raised further up in the train-centric control systems development. As such, the underlying safety management process should be capable of appropriately handling the potential risks that can be created due to the unexpected changes and the long-term development period. The process should also be complemented for the safety consideration of train-centric control systems, for instance, stop. To study these aspect is the objective of the paper. To do so, a step-by-step approach to analyzing the safety management process is first presented. Then, to enhance the process some necessary and useful activities are added in terms of risk and safety management. Then, to pursue some enhancement on the process, a set of necessary and useful activities are added in terms of risk and safety management. The resultant process is further analyzed and tailored using a design structure matrix method. The resultant process is applied in a train-centric control development as a case study.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.99-99
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• 2011

Fuel cell systems are a completely different form of electricity source that has been used so far and is an aggregation of multiple technologies with multidisciplinary features that can be operated safely only when gas and electrical safety are being considered. Since fuel cells generate through electrochemical reactions there are difficulties in ensuring electricity safety, power quality assessment, effective control and reliability standards for system faults using conventional inspection techniques and even though they are necessary as a primary means for reduction of CO2 owing to the Climate Convention, electrical safety assessment and measures are required for the prevention of faults in residential facilities. Although small-scaled distributed power supplies can be utilized as important means of peak control and energy management measures, research is required for observing the effects on the system and the development of inspection technology to ensure stable operation, and the electrical safety of residential fuel cell systems need to be assessed and the problems derived for establishing electrical safety standards. From the year 2002, Japan has established laws on technical safety standards and development and rules on the product specifications and standards for the industrialization of hydrogen fuel cells. Also, a lot of effort have been made for the commercialization of fuel cells by building one-stop certification services. Internationally, the IEC TC 105 has established international standards based on fuel cells. In order to protect the national interest, the country should be able to respond accordingly meet global standards. In fact, in Korea, to comply with the international trend, Korea Energy Management Corporation is establishing a certified agenda for fuel cells and Korean Agency for Technology and Standards is enacting technical standards for fuel cells. The current terms of fuel cells are that research has been focused more on the quality and performance of manufactured products rather than stable power operation and maintenance over time. In this paper, by considering the household fuel cell as a power device, the safety standards of the fuel cell system for a reliable operation with the existing power system is being proposed.