광섬유격자 온도센서의 정밀도 개선

이현욱,송민호,이준호,Lee, Hyun-Wook,Song, Min-Ho,Lee, June-Ho 한국광학회 2006 한국광학회지 Vol.17 No.3

전력시스템의 비정상적 동작에 의한 열적 현상을 감지하기 위하여 준분배형 광섬유격자 온도센서를 구현하였다. 2개의 기준격자와 4개의 센서격자를 사용하고, Fabry-Perot 가변파장필터를 사용하여 반사파장의 변화를 측정함으로써 각 센서 위치에서의 온도변화를 관측하였다. 측정의 정밀도를 높이기 위하여 광검출기의 신호를 가우시안 cure-fitting 알고리즘으로 처리한 후 계산된 파형에서 피크를 검출하였다. 실험을 통하여 기존의 피크검출방식에 비하여 높은 정밀도를 얻었으며, 반사 스펙트럼이 왜곡된 광섬유격자 센서의 출력검출에서도 뛰어난 오차보상 특성을 보여주는 것을 확인할 수 있었다. 2 Hz의 대역폭에서 $0.3^{\circ}C$의 정밀도를 얻었고, thermocouple 기준온도계와 비교한 온도측정실험에서 약 0.37 %의 선형화오차를 확인할 수 있었다. We propose the use of the Gaussian-curve fitting algorithm for the improvement of measurement accuracy in wavelengthscanned Fabry-Perot filter based demodulation systems. The peak locations of FBG sensors were calculated from the fitted curves rather than from distorted PD profiles, resulting in much better measurement accuracy than that of the highest-peak search algorithm. Also, the algorithm was proved to minimize measurement uncertainty of spectrally-distorted grating sensors. From our experimental results, a temperature resolution as small as ${\sim}0.3^{\circ}C$ was readily achieved by use of the Gaussian-curve fitting algorithm whereas the highest-peak search algorithm gave a temperature resolution larger than ${\sim}4^{\circ}C$.

압력용기용 A516 강의 미세조직에 미치는 탄소 당량과 냉각 속도의 영향

이현욱,강의구,김민수,신상용,Lee, Hyun Wook,Kang, Ui Gu,Kim, Min Soo,Shin, Sang Yong 한국재료학회 2019 한국재료학회지 Vol.29 No.8

In this study, the effect of carbon equivalent and cooling rate on microstructure and hardness of A516 steels for pressure vessel is investigated. Six kinds of specimens are fabricated by varying carbon equivalent and cooling rate, and their microstructures and hardness levels are analyzed. Specimens with low carbon equivalent consist of ferrite and pearlite. As the cooling rate increases, the size of pearlite decreases slightly. The specimens with high carbon equivalent and rapid cooling rates of 10 and $20^{\circ}C/s$ consist of not only ferrite and pearlite but also bainite structure, such as granular bainite, acicular ferrite, and bainite ferrite. As the cooling rate increases, the volume fractions of bainite structure increase and the effective grain size decreases. The effective grain sizes of granular bainite, acicular ferrite, and bainitic ferrite are ~20, ~5, and ${\sim}10{{\mu}m$, respectively. In the specimens with bainite structure, the volume fractions of acicular ferrite and bainitic ferrite, with small effective grains, increase as cooling rate increases, and so the hardness increases significantly.

모야모야병의 수술적 치료와 연관된 합병증과 그에 대한 치료

이현욱,홍승철,Lee, Hyun Wook,Hong, Seung-Chyul 대한신경외과학회 2000 Journal of Korean neurosurgical society Vol.29 No.8

선반가공공정에서 RSM을 이용한 가공공정의 포괄적 최적화

이현욱,권원태,Lee, Hyun-Wook,Kwon, Won-Tae 한국생산제조학회 2010 한국생산제조학회지 Vol.25 No.3

Optimization of the turning process has been concentrated on the selection of the optimal cutting parameters, such as cutting speed, feed rate and depth of cut. However, optimization of the cutting parameters does not necessarily guarantee the maximum profit. For the maximization of the profit, parameters other than cutting parameters have to be taken care of. In this study, 8 price-related parameters were considered to maximize the profit of the product. Regression equations obtained from RSM technique to relate the cutting parameters and maximum cutting volume with a given insert were used. The experiments with four combinations of cutting inserts and material were executed to compare the results that made the profit and cutting volume maximized. The results showed that the cutting parameters for volume and profit maximization were totally different. Contrary to our intuition, global optimization was achieved when the number of inserts change was larger than those for volume maximization. It is attributed to the faster cutting velocity, which decreases processing time and increasing the number of tool used and the total tool changing time.

전력 시스템 보호를 위한 광섬유 격자 온도센서의 정밀도 개선

이현욱(Hyun-Wook Lee),이준호(Jun-Ho Lee),송민호(Min-Ho Song) 한국조명·전기설비학회 2005 한국조명·전기설비학회 학술대회논문집 Vol.2005 No.5월

A distributed FBG temperature sensor system was constructed for the use in protection of electric power system. A F-P wavelength tunable filter is used converting temperature-induced wavelength variations to temporal peak locations. We used Gaussian line-fitted algorithm to alleviate the error caused by quantization and electrical noises. The experimental results showed much better accuracy than the raw peak-detection scheme.

광주시 신시가지구의 성장과 공간구조의 변화

이현욱 ( Hyun Wook Lee ) 한국도시지리학회 2007 한국도시지리학회지 Vol.10 No.2

환자와 의료 서비스 로봇을 위한 상호작용 시스템의 설계 및 구현

이현욱(Hyun Wook Lee),임재봉(Jae Bong Lim),전용수(Yong Su Jeon),김범준(Beom Jun Kim),백윤주(Yun Ju Baek) 한국통신학회 2020 한국통신학회 학술대회논문집 Vol.2020 No.2

신제품 개발 프로세스 변환의 성공 요인에 관한 사례연구

이현욱(Hyun Wook Lee),한정희(Jung Hee Han),김병근(Byung Keun Kim) 한국IT서비스학회 2016 한국IT서비스학회지 Vol.15 No.4

This paper investigates changing processes of new product development (NPD) systems. In order to continuously develop first-class products, world wide super-class products and hit products, R&D (Research & Development) must be competitive. Firms must achieve competitiveness in terms of quality and cost by launching new products. Most films focus on improving effectiveness and efficiency of NPD process. However, sometimes, they face to the critical challenge of transforming NPD processes entirely reflecting dramatic change of their core products. Transforming of NPD process is difficult in that it involves technological and organizational changes in marketing, R&D, Engineering and manufacturing systems. The purpose of this paper is to shed light on processes and factors affecting successful transformation of new product development systems. We present a case study on the changing processes of S company’s NPD process. S company has changed new product development systems successfully from a major IT equipment supplier to an automotive supplier. Empirical results show successful changes of 10 core NPD processes from understanding the market and customers process to after sales process. In case of transformation of NPD, adaption of attribute of business is crucial for success factors in the process innovation. This paper shows the bridging the gap between IT and automotive industrial dynamics and growth through adaption of two processes in the NPD.

광주광역시 도시공원의 분포특성과 이용행태 분석

이현욱 ( Hyun Wook Lee ) 한국도시지리학회 2009 한국도시지리학회지 Vol.12 No.3

지가를 이용한 도시규모별 토지이용예측

이현욱 ( Hyun-wook Lee ) 전남대학교 사회과학연구소 2022 현대사회과학연구 Vol.26 No.-

본 연구는 최고지가에 대한 비율을 이용하여 도시 내 토지이용에 대한 일반화를 시도한 것이다. 서울과 동경의 비교 연구에서 확인된 것을 가설로 세우고 규모를 달리하는 5개 도시를 대상으로 최고지가에 대한 비율을 이용하여 토지 이용을 예측해보고자 했다. 부산과 인천, 광주와 수원, 전주 5개 도시에 대해 검증해 본 결과, CBD 혹은 도심의 범위는 최고지가지점을 정점으로 도시규모에 따라 최고지가에 대한 10%~30% 범위 내에서 획정가능하였다. 또 도심과 분리되어 있는 동의 최고지가가 도시 최고지가의 30% 이상이 되면 부도심의 기능을 수행한다고 할 수 있다. 최고지가의 10%이상을 보이는 표준지들은 대부분 상업적으로 이용된다. 최고지가의 5% 이상의 비율을 보이는 표준지들은 주택과 상업이 혼재하는 이용을 보이지만 도시의 여건에 따라서 상업적 이용이 높거나 주거적 이용이 높게 나타난다. 최고지가의 3% 이하의 지가를 보이는 표준지들은 대도시의 경우 대부분 주거용으로 이용되지만 중규모의 도시에서는 농경지나 녹지 지역으로 이용되고 있었다. 가설 자체가 대도시로부터 얻어진 만큼 대도시에는 적합하였지만, 도시의 규모가 작아질수록 도시의 최고지가도 낮아지고 최고지가에 대한 비율 값도 낮아져서 토지이용이 예상과 달라지고 가설의 적합도도 낮아졌다. 그러나 최고 지가에 대한 비율은 간단한 일반화로서 토지이용분화의 이해에 유효하게 이용될 수 있다고 판단된다. This study attempted to generalize land use within the city using the ratio to the highest land value. Based on the hypotheses confirmed in the comparative study of Seoul and Tokyo, we tried to estimate land use using the ratio to the highest land value in five cities of different sizes. As a result of verifying five cities in Busan, Incheon, Gwangju, Suwon, and Jeonju, the range of CBD or downtown can be estimated as having about 10% to 30% of the highest land value with the peak at the highest land value depending on the size of the city. In addition, when the highest land value in a dong that is separated from CBD or downtown exceeds 30% of the highest land value in the city, it can perform the function of a sub-center. Most of the standard lots showing more than 10% of the highest land value are used commercially. Standard lots with a ratio of 5% of the highest land value show a mix of residential and commercial use. Standard lots of having about 3% of the highest land value are mostly used for residential land use in large cities, but are used as farmland or green areas in medium-sized cities. The hypothesis itself was suitable for large cities as it was obtained from large cities, the smaller the size of the city, the lower the highest land value in the city and the lower land values calculated as a ratio of the highest land value, so the land use was some different from the expectation and the fit of the hypothesis was ako lowered. However, as a simple generalization, the ratio to the highest land value can be effectively used to understand land use differentiation.