홀 확장된 판재의 에지마진 변화에 따른 피로특성 연구

이준현,이동석,이환우,Lee, Joon-Hyun,Lee, Dong-Suk,Lee, Hwan-Woo 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.11

This paper describes an experimental study on fatigue life extension by using cold working process in fastener hole of aircraft structure. Cold working process was applied for A12024-7351 specimens by considering the effect of edge margin on fatigue life. It is generally recognized that cold working process offers a protective zone around fastener hole of aluminum aircraft structure due to the residual compressive stresses which lead to retardation of crack growth. Thus this process provides the beneficial effect of increasing the fatigue life of the component. there by decreasing maintenance costs. It has also been successfully incorporated into damage tolerance and structural integrity programs. Cold working specimens were tested at constant amplitude peak cyclic stresses. Fatigue life of cold working specimen compared with that of specimen fabricated with base material. The increase of fatigue life for cold working specimen is discussed by both considering the effect of residual compressive stresses measured by X-ray diffraction technique and quantitative effect of edge margin.

이온층 고에너지 입자 상태와 저궤도 위성의 위성체 전위 사이의 상관관계

이준현,이은상,김관혁,선종호,이재진,이동훈,진호,Lee, Jun-Hyeon,Lee, Eun-Sang,Kim, Gwan-Hyeok,Seon, Jong-Ho,Lee, Jae-Jin,Lee, Dong-Hun,Jin, Ho 한국천문학회 2012 天文學會報 Vol.37 No.2

위성체의 전위는 위성 주변의 우주 환경에 크게 영향을 받는다. 본 연구에서는 과학기술위성 1호(STSAT-1)에 탑재된 LP(Langmuir Probe)와 ESA(Electro-Static Analyzer) 관측 자료를 이용하여 위성체의 전위에 위성 주변 고에너지 입자들이 미치는 영향을 분석하였다. 일반적으로 위성체가 대전되어 위성체의 부동전위가 감소할 때 위성 주변의 플라즈마 밀도는 감소하고 온도는 증가한다. 또한 DMSP 위성 등을 비롯한 이전 관측에서는 고에너지 입자의 플럭스가 증가하는 지역을 위성이 통과할 때 위성체의 전위가 감소하였다. 본 연구에서는 위성이 수 ~ 수 십 keV 정도의 고에너지 입자 플럭스가 증가한 후 감소하는 지역을 통과할 때에도 위성체의 전위가 감소하는 현상을 관측하였다. 고에너지 입자의 플럭스가 감소하는 지역에서 일어나는 위성의 대전현상을 통계적으로 분석해 보고 이러한 결과를 토대로 위성체 전위 변화에 우주환경 변화가 어떤 영향을 주는지 연구하였다.

알루미늄 평판의 표면결함에 대한 와전류 신호의 유한요소해석

이준현,이봉수,이민래,Lee Joon-Hyun,Lee Bong-Soo,Lee Min-Rae 대한기계학회 2005 大韓機械學會論文集A Vol.29 No.10

The detection mechanism of the flaw for the nondestructive testing using eddy current is related to the interaction of the induced eddy currents in the test specimen with flaws and the coupling of these interaction effects with the moving test probe. In this study, the two-dimensional electromagnetic finite element analysis(FEM) fur the eddy current signals of the aluminum plate with different depth of surface cracks is described and the comparison is also made between experimental and predicted signals analyzed by FEM. In addition, the characteristics of attenuation of the eddy current density due to the variation of the depth of a conductor are evaluated. The effective parameters for the application of eddy current technique to evaluate surface cracks are discussed by analyzing the characteristics of the eddy current signals due to the variation of crack depths.

진행위암의 복강경 보조 위 전절제술 - 개복 위 전절제술과의 후향적 비교 -

이준현,남유희,허훈,전해명,김욱,Lee, Jun Hyun,Nam, Yoo Hee,Hur, Hoon,Jeon, Hae Myung,Kim, Wook 대한위암학회 2008 대한위암학회지 Vol.8 No.3

목적: 상부 진행위암 환자에서 시행된 복강경 보조 위 전절제술의 초기 경험을 개복 위 전 절제술과 비교 분석하여 수술결과를 평가하고자 한다. 대상 및 방법: 2004년 4월부터 2008년 3월까지 복강경 보조 위 전 절제술과 $D1+{\beta}$ 이상의 림프절 절제술이 시행된 47명의 환자 중, 수술 후 진행위암으로 확진된 29명의 환자(LATG군)를 같은 시기에 개복 위 전 절제술을 시행한 35명의 환자(OTG군)와 임상병리학적 특징, 수술 후 결과, 재발 및 생존기간 등을 후향적으로 비교하였다. 결과: 두 군의 성비, 나이, 체질량 지수 및 병기 등에서 차이는 없었으나, 암종의 크기는 LATG군이 평균 6.1 cm로 OTG군의 9.2 cm에 비해 유의하게 작았으며, 근위부 절제연은 평균 3.6 cm로 OTG의 2.1 cm에 비해 유의하게 길었다. 수술시간은 LATG군이 평균 361.3분으로 OTG군의 289.0분보다 유의하게 길었으나, 출혈량, 합병증, 장 운동 회복일, 음식 섭취 시작일과 재원일에는 차이가 없었다. 수술 후 추적기간은 18.8개월(범위 3~46개월)이었으며 평균 생존기간은 LATG군 31개월과 OTG군 32개월, 무병 생존기간은 평균 28개월과 24개월로 유의한 차이는 없었다. 재발률은 LATG 군이 30.8%, OTG군은 34.3%였으며 재발부위는 두 군 모두 복막과 림프절이 가장 많았다. 결론: 대상 환자가 적은 후향적 연구지만 복강경 보조 위전 절제술은 진행위암의 치료에서 개복 위 전 절제술과 비교 시 수술과 연관된 합병증이나 생존기간, 재발율 등에서 유의한 차이가 없었음을 확인하였다. 그러나 환자의 예후에 대한 장기 추적 관찰과 전향적 연구가 필요할 것으로 생각된다. Purpose: The aim of this study was to compare the short-term operative outcomes of laparoscopy-assisted total gastrectomy (LATG) with those of open total gastrectomy (OTG) for patients suffering with advanced upper gastric cancer. Materials and Methods: Of the 47 patients who underwent LATG with $D1+{\beta}$ or D2 lymphadenectomy from July 2004 to March 2008, 29 patients with pathologically proven advanced gastric cancer were compared with 35 patients who underwent conventional OTG during the same time period. The comparison was based on the clinicopathological characteristics, the surgical outcome, the follow-up survival and tumor recurrence. Results: The patients' age, gender and body mass index were similar between the two groups. However, there were statistically differences in tumor size ($9.2{\pm}3.9$ vs $6.1{\pm}3.6cm$, P=0.002) and the proximal resected margin ($2.1{\pm}2.0$ vs $3.6{\pm}2.1cm$ P=0.004). There was no significant difference in most of the peri- and post-operative courses such as the time to first flatus, the time to starting a solid diet and the length of the hospital stay, except for a longer operating time (289.0 vs. 361.3 minutes, P<0.001) in the LATG group. The complication rate was higher in the LATG group (13.8%) than that in the OTG group (5.7%). The mean overall survival and disease free survival times were 32 and 31 months, and 24 and 28 months, respectively, with an average 18.8 months follow-up duration. The main recurrent sites were peritoneum and lymph node in both groups. Conclusion: The early results of the current study suggest that LATG for AGC is technically feasible and it does not show any inferiorities of the postoperative outcomes as compared to those of conventional open total gastrectomy.

수표교(水標橋) 칼럼 - 에너지강국을 향한 힘찬 도약 -그린에너지 전략로드맵 2011

이준현,Lee, Jun-Hyeon 대한전기협회 2011 전기저널 Vol.415 No.-

알루미나 세라믹에 대한 열충격 손상의 비파괴적 평가

이준현,이진경,송상헌,Lee, Jun-Hyeon,Lee, Jin-Gyeong,Song, Sang-Heon 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.8

The objective of this paper is to investigate the applicability of acoustic emission(AE) technique to monitor the progress of the thermal shock damage on alumina ceramic. For this purpose, alumina ceramic specimen was heated in the furnace and then was quenched in the water tank. When the specimen was quenched in the water tank, complex AE signals due to the initiation of micro-cracks and boiling effect were generated by the progress of thermal shock damage. These mixed AE signals have to be classified for monitoring the degree of the thermal shock damage of alumina ceramics. In this paper, the mixed AE signals generated from both the boiling effect and the crack initiation under thermal shock test was analyzed. The characteristics of AE signals were also discussed by considering the variation of bending strength and Yongs modulus of specimens.

레이저 유도 초음파 및 자기보상 기법을 이용한 재료의 표면균열 깊이 비파괴 평가

이준현,최상우,하상봉,Lee, Jun-Hyeon,Choe, Sang-U,Ha, Sang-Bong 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.4

It is required to evaluate nondestructively the crack depth of surface-breaking cracks for the assurance of safety of structure. Optical generation of ultrasound produces well defined pulses with a repeatable frequency content, that are free of any mechanical resonances; they are broad band and are ideal for the measurement of attenuation and scattering over a wide frequency range. Self-calibrating surface signal transmission measurement is very sensitive and practical tool for surface-breaking crack depth. In this paper, the self-calibrating technique by laser-based ultrasound is used to evaluate the depth of surface-breaking crack of material. It is suggested that the relationship between the signal transmission and crack depth can be used as a practical model for predicting the surface-breaking crack depths from the signal transmission measured in structure.

경계요소법을 이용한 다중결함의 SH형 초음파 산란장 해석에 관한 연구

이준현,이서일,Lee, Jun-Hyeon,Lee, Seo-Il 대한기계학회 1999 大韓機械學會論文集A Vol.23 No.11

Ultrasonic technique which is one of the most common nondestructive evaluation techniques has been applied to evaluate the integrity of structures by analyzing the characteristic of scattering sign al from internal defects. Therefore, a numerical analysis of ultrasonic scattering field due to defect profiles is absolutely needed for the accurate, quantitative estimation of internal defects. In this paper, the SH-wave scattering by multi-cavity defects and inclusion using Elastodynamic Boundary Element Method is studied. The effects of shape and distance of defects on transmitted and reflected fields are considered. The interaction of multi-cavity defects in SH-wave scattering is also investigated. Numerical calculations by the BEM have been carried out to predict near field solution of scattered fields of ultrasonic SH-wave. The presented results can be used to improve the detection sensitivity and pursue quantitative nondestructive evaluation for inverse problem.

직장암과 동반된 갑상선의 CASTLE 1예

이준현,이도상,백종민,손보성,박일영,성기영,Jun Hyun Lee,M,D,Do Sang Lee,M,D,Jong Min Baek,M,D,Bo Sung Son,M,D,Il Young Park,M,D,and Ki Young Sung,M,D 대한갑상선-내분비외과학회 2008 The Koreran journal of Endocrine Surgery Vol.8 No.4

CASTLE은 갑상선에서 발생하는 드문 종양이다. 이 종양은 이소성 갑상선 조직이나 갑상선 주위 또는 갑상선에서 가슴샘 발생과 관련된 잔류물에서 발생하며 일반적으로 갑상선 하부 2/3부위에 위치한다. 환자는 66세 남자환자로 직장암 수술을 위해 입원하였다. 과거력에서 35년 전에 폐결핵으로 우상부 폐엽절제술을 받았다. 수술 전 시행한 흉부 전산화 단층촬영에서 갑상선 결절이 우연히 발견되었다. 결절 흡인세포검사에서 역형성암종이 의심되었다. 원발성 종양에 대해 저위전방절제술과 갑상선 일엽절제술을 시행하였다. 최종 병리진단에서 CASTLE로 진단되어 잔여 갑상선 절제술, 중심구획 임파선 곽청술 및 방사선 치료를 시행하였다. 수술 후 15개월간 재발은 없었다. (Korean J Endocrine Surg 2008;8:266-268) Carcinoma showing thymus-like elements (CASTLE) is a rare neoplasm arising from the thyroid gland. This tumor is thought to originate from ectopic thymic tissue or remnants related to thymic development in or adjacent to the thyroid gland and usually located in the lower two-thirds of the thyroid gland. The patient was a 66-year-old man admitted to our hospital with rectal carcinoma for surgery. He had undergone a right upper lobectomy of the lung for the pulmonary tuberculosis 35 years previously. He underwent a chest computed tomography (CT) pre-operatively, and an incidental nodule of the thyroid gland was detected. Based on aspiration cytology of the nodule, the lesion was suspected to be an anaplastic carcinoma. He underwent a low anterior resection and thyroid lobectomy for a double primary neoplasm. On the final pathologic examination, the thyroid lesion was shown to be CASTLE. Therefore, completion thyroidectomy with lymph node dissection of the central compartment and radiotherapy were performed, and there was no evidence of recurrence 15 months post- operatively. (Korean J Endocrine Surg 2008;8:266-268)

재료내 기공결함에 의한 SH형 초음파 원거리 산란장의 신호특성에 대한 수치해석

이준현,이서일,박윤원,Lee, Jun-Hyeon,Lee, Seo-Il,Park, Yun-Won 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.1

In this study, the scattered far-field due to a cavity embedded in infinite media subjected to the incident SH-wave was calculated by the boundary element method. The effects of cavity shape and distance between internal cavity and internal point in infinite media were considered. The scattered far-field of the frequency domain was transformed into the signal of the time domain by using the Inverse Fast Fourier Transform(IFFT). It was found that the amplitude of scattered signal in time domain decreased with the increase of the distance between the detecting points of ultrasonic scattered field and the center of internal cavity in media. In addition, the time delay was clearly found in time domain waveform as the distance between the detecting points of ultrasonic scattered field and the center of internal cavity was gradually increased.