태백산맥 풍하측 대기 물뜀 발생에 관한 수치 실험

이재헌(Jaeheon Lee),강성락(Song-lak Kang) 한국방재학회 2022 한국방재학회논문집 Vol.22 No.6

태백산맥 풍하측 대기 물뜀에 대한 큰 에디 모사는 온난이상 이류와 음의 와도 대기 역류를 잘 보여주었다. 대기 물뜀은 상층 대기를 하층 대기로 유입한다. 모의된 물뜀 발생은 장애물의 유효 고도와 폭의 함수로 정리될 수 있었다: â > 10에 대해 ĥ ≥ 0.74, 이는 장애물의 고도와 폭으로 정의된 프루드 수로 Fra < 0 .1에 대해 Frh ≤ 1.35에 해당한다. 수치 실험에서, 부력 진동수(N) = 0.009 s-1에 대해 풍상측 평균 바람(U) ≤ 12 ms-1일 때 물뜀이 발생하였다. 물뜀 현상이 발생할 때 풍속은 30분 내외로 급격한 상승을 보였고, 초기 풍속이 강할수록 보다 강한 온난이상과 돌풍이 발생하였다. 본 연구는 산불 발생환경 조성 측면에서 대기 물뜀 현상을 이해하고, 이를 장애물 폭과 장애물 높이를 사용한 프루드 수의 함수로 설명하였다. 결과적으로 대기는 물뜀 현상이 발생할 시 보다 산불에 취약한 대기 환경을 형성할 수 있었고, 프루드 수의 함수로는 대기 물뜀과 관련된 산악파 파쇄가 잘 설명될 수 있었다. Large-eddy simulation of the lee-side hydraulic jump at the downwind side of the Taebaek Mountains demonstrates the advection of a warm anomaly and the atmospheric reverse roller of negative vorticity. The lee-side hydraulic jump entrains the upper-level atmospheric air into the lower-level atmosphere. The simulated lee-side hydraulic jump occurs under the following conditions on the effective height ĥ and width â of an obstacle: ĥ ≥ 0.74 for â > 10, which are equivalent to Frh ≤ 1.35 for Fra < 0 .1, where Frh and Fra are the Froude numbers defined in terms of the height and width of the obstacle, respectively. In detail, the hydraulic jump occurs when the upwind-side mean wind (U) ≤ 12 ms- 1 for the buoyancy frequency (N) = 0.009 s- 1. The wind speed dramatically increases within the 30-minute period when the hydraulic jump occurs. The stronger upwind causes a warmer anomaly and stronger downslope wind gust. This study situates the atmospheric hydraulic jump phenomenon with regard ro wildfire occurrence, and describes it using the Froude number for the width and height of the obstacle. It is shown that a more vulnerable atmospheric environment can be formed when the hydraulic jump occurs, and the wave-breaking of mountain waves related to the hydraulic jump can be predicted by the Froude number.

Statistical Process Control Procedure for Integral-Controlled Processes

Lee, Jaeheon,Park, Cangsoon 한국통계학회 2000 Communications for statistical applications and me Vol.7 No.2

Statistical process control(SPC) and engineering process control(EPC) are two strategies for quality improvement that have been developed independently. EPC seeks to minimize variability by adjusting compensatory variables in order to make the process level close to the target, while SPC seeks to reduce variability by monitoring and eliminating causes of variation. One purpose of this paper is to propose the IMA(0,1,1) model as the in-control process model. For the out-of-control process model we consider two cases; one is the case with a step shift in the level, and the other is the case with a change in the nonstationarity. Another purpose is to suggest the use of an integrated process control procedure with adjustment and monitoring, which can consider the proposed process model effectively. An integrated control procedure will improve the process control activity significantly for cases of the proposed model, when compared to the procedure of using either EPC or SPC, since EPC will keep the process close to the target and SPC will eliminate special causes.

Estimation of the Change Point in VSS X Control Charts

Lee, Jaeheon,Park, Changsoon 한국통계학회 2003 Communications for statistical applications and me Vol.10 No.3

Knowing the time of the process change could lead to quicker identification of the responsible special cause and less process down time, and it could help to reduce the probability of incorrectly identifying the special cause. In this paper, we propose a maximum likelihood estimator of the process change point when a Shewhart $\bar{X}$ chart with variable sample size (VSS) scheme signals a change in the process mean. Also we build a confidence interval for the process change point by using the likelihood function.

The Estimation for the Expected Cost Function in Automatic Process Control

Lee, Jaeheon 광주대학교 1996 産業技術硏究 Vol.7 No.-

자동공정관리의 목적은 품질특성치가 가능한 한 목표치에 근접하게 유지하도록 공정을 관리하는데 있다. 이러한 자동공정관리의 절차는 기대비용함수를 최소화하도록 설계되기 때문에, 기대비용함수의 추정에 관하여 많은 연구가 되어지고 있다. 본 논문에서는 간단하면서 개선된 기대비용함수의 추정식을 제안한다. 모의실험으로 이 추정식의 정확성을 비교한 결과, 제안된 추정방법은 기대비용함수를 추정하는데 있어서 충분히 좋은 결과를 주는 것으로 나타났다. The purpose of automatic process control(APC) is to regulate the process under study and to keep the quality characteristic to be as close to its target as possible. Because procedures for APC were designed to minimize the overall expected cost, many estimation methods for the expected cost function have been studied. In this paper, a simple and improved approximation method for this function is proposed. From simulation studies, it may be noted that the proposed method gives good performances in estimating the expected cost function.

Internal impingement of the shoulder in sports activity: common overuse injury

Jaeheon Lee,Hwa Pyung Kim,Min Soo Shon 대한정형외과 스포츠의학회 2023 Arthroscopy and Orthopedic Sports Medicine Vol.10 No.2

Sports-related shoulder injuries are a common condition and are particularly prevalent as an overuse injury caused by repeated microtrauma. This study aimed to provide updated information on pathophysiology, clinical diagnosis, effective treatment, and the importance of preventing internal impingement of the shoulder as a common overuse shoulder injury. Current literature indicates multiple factors that can contribute to developing internal impingement, including anatomical, biomechanical, and other pathologic lesion-associated factors. Internal impingement is diagnosed based on a thorough patient history and physical examination. Magnetic resonance imaging is a gold standard imaging to confirm the diagnosis and rule out other causes of shoulder pain. Treatment, and especially, shoulder internal impingement rehabilitation in athletes should be comprehensive, integrative, and systematic. The best way to prevent internal impingement is to strengthen and stretch the rotator cuff muscles and avoid overhead activities that cause pain. The first-line treatment option is nonsurgical treatment, while patients with more severe symptoms may require surgical treatment.

Development of non-woven carbon felt composite bipolar plates using the soft layer method

Lee, Dongyoung,Choe, Jaeheon,Nam, Soohyun,Lim, Jun Woo,Choi, Ilbeom,Lee, Dai Gil ELSEVIER (APPLIED SCIENCE) 2017 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.160 No.-

<P><B>Abstract</B></P> <P>Carbon fiber reinforced polymer composites are ideal substitutes for brittle graphite for electrically conductive bipolar plates because of their high mechanical property and productivity. Early composite bipolar plates suffered from high electrical contact resistance due to the resin-rich area formed on the surface. To decrease the electrical contact resistance, the “soft layer method” was developed, which exposed bare carbon fibers on the composite surface. This method significantly improved the electrical as well as mechanical properties of composite bipolar plates. The remaining problem for wider commercialization of composite bipolar plates is their high fabrication pressure.</P> <P>In this work, a non-woven carbon felt composite bipolar plate was developed to obtain improved electrical properties with low fabrication pressure. The soft layer method was also used to expose bare carbon fibers. Compared to conventional high fiber volume fraction composite bipolar plates, the developed bipolar plate exhibited superior electrical properties.</P>

A VSR Χ￣ Chart with Multi-state VSS and 2-state VSI Scheme

Lee, Jaeheon,Park, Changsoon 한국품질경영학회 2004 품질경영학회지 Vol.32 No.4

Variable sampling interval (VSI) control charts vary the sampling interval according to value of the control statistic while the sample size is fixed. It is known that control charts with 2-state VSI scheme, which uses only two sampling intervals, give good statistical properties. Variable sample size (VSS) control charts vary the sample size according to value of the control statistic while the sampling interval is fixed. In the VSS scheme no optimal results are known for the number of sample sizes. It is also known that the variable sampling rate (VSR) X￣ control chart with 2-state VSS and 2-state VSI scheme leads to large improvements in performance over the fixed sampling rate (FSR) X￣ chart, but the optimal number of states for sample size is not known. In this paper, the VSR X￣ charts with multi-state VSS and 2-state VSI scheme are designed and compared to 2-state VSS and 2-state VSI scheme. The multi-state VSS scheme is considered to achieve an additional improvement by switching from the 2-state VSS scheme. On the other hand, the multi-state VSI scheme is not considered because the 2-state scheme is known to be optimal. The 3-state VSS scheme improves substantially the sensitivity of the X￣ chart especially for small and moderate mean shifts.

강원도 미세먼지 분포에 대한 태백산맥의 영향

이재헌(Jaeheon Lee),강성락(Songlak Kang) 한국방재학회 2023 한국방재학회논문집 Vol.23 No.3

The purpose of this study was to empirically confirm that the Taebaek Mountains are one of the primary causes of the spatial difference in the concentration of particulate matter between the west (Yeongseo) and east (Yeongdong) sides of the mountain range in Gangwon Province in the Korean peninsula. We investigated the effects of the Taebaek Mountains by analyzing data on PM10 and PM2.5 concentrations, wind direction, and wind speed, collected over seven years from 2015 to 2021 in the Yeongseo and Yeongdong regions. Our results demonstrated that wind direction and speed could be considered significant features in the aerial transport of PM10 and PM2.5. When the concentrations were higher than normal, the reduction effect of the Taebaek mountain range on PM10 was clear, while the effect on PM2.5 was not as obvious. When wind blows from west to east across the Taebaek Mountains, the wind speed may increase on the Yeongdong; in these cases, the concentrations of PM10 and PM2.5 were much lower than at the Yeongseo. Moreover, with these westerly winds, when the wind speed at Yeongseo exceeded 2 m/s, the distribution range of high concentrations of PM10 and PM2.5 was narrower at Yeongseo and Yeongdong than when the wind speed was weaker.

특허 인용분석을 이용한 영향력 있는 특허를 찾는 방법 및 분석 시스템

이재헌(JaeHeon Lee) 한국정보과학회 2005 한국정보과학회 학술발표논문집 Vol.32 No.2

산업이 발전함에 따라 지적재산권에 대한 가치는 점점 중요해지고 있고, 기업의 흥망성쇄를 결정짓는 가장 큰 요인중 하나로 자리잡고 있다. 엄청난 비용을 투자하여 사업화하고 있던 세계 굴지의 기업들도 경쟁회사의 핵심특허 단 몇 건만으로 순식간에 몰락하는 경우도 발생하고 있다. 이제 지적재산권은 살아남기 위한 유일한 방어수단이자 공격수단이 되었다. 이와 같은 급박한 상황하에서 각 기업은 경쟁회사의 지적재산권을 분석하고, 이를 통해 자사의 연구개발 전략을 수립하기 위해 노력하고 있다. 그러나 이와 같은 분석작업은 다수의 전문가 일지라도 상당한 시일이 소요되는 방대한 작업이며, 이를 자동으로 실행하기 위해 많은 소프트웨어 회사들은 Clinent base 특허분석용 툴과 Web base site를 개발하여 서비스를 하고 있다. 그러나 이들 종래의 특허분석용 툴과 Web site들은 특허에대한 정량분석 정보와 정성분석 정보를 제공하지만 해당 특허가 기술분야에서 얼마나 영향력을 미치는 객관적으로 제시를 하지 못하고 있다. 본 논문에서는 개술 개발시 해당 분야의 특허 기술의 흐름을 빠르게 파악하고 동 기술 분야에서 영향력이 있는 특허의 랭킹을 제시하여 기술 개발시의 위험성을 줄이고자 하는데 그 목적이 있다. 이에 특허 출원시 인용했던 선행특허들의 인용 관계를 분석하여 특허간 연관관계를 규명하고, 각 기술 분야에서 영향력이 높은 특허를 찾는 방법과 시스템을 제시하고자 한다.

가솔린엔진의 냉각계 유로 변경을 통한 금속면 온도 및 전열에 관한 실험적 연구

이재헌(Jaeheon Lee),류택용(Taekyong Ryu),신승용(Seungyong Shin),최재권(Jaekwon Choi) 한국자동차공학회 2002 한국 자동차공학회논문집 Vol.10 No.1