메탄/공기 층류 부분예혼합화염의 상세 라디칼(OH*, CH* 그리고 C₂*) 정보와 배기매출물에 관한 실험적 연구

정용기,오정석,전충환,장영준,Jeong Yong Ki,Oh Jeong Seog,Jeon Chung Hwan,Chang Young June 대한기계학회 2005 大韓機械學會論文集B Vol.29 No.2

An experimental study was performed to investigate the effects of partially premixing, varying the equivalence ratios from $0.79{\sim}{\infty}$, on NOx emissions and chemiluminescence of excited $OH^{\ast},\;CH^{ast}\;C_2^{\ast}$ radicals in laminar partially premixed flames. the signal from the electronically excited state of $OH^{\ast},\;CH^{ast}\;C_2^{\ast}$ was detected through a band pass filter with a photo multiplier tube, which are processed to the intensity ratio ($C_2^{\ast}/CH^{\ast},\;C_2^{\ast}/OH^{\ast},\;and\;CH^{\ast}/OH^{\ast}$) to reveal the correlation with local equivalence ratio. And measurements of NOx emission were made to investigate the relationship between visible flame appearance, chemiluminescence, and EINOX. The results demonstrated that (1) the flames at ${\phi}<1.59$ exhibited classical double flame structure, at ${\phi}>4.76$, the flames exhibited diffusion flame structure, and the intermediate flames at $1.59<{\phi}<4.76$ was a merged flame, (2) the $OH^{\ast}$ peak was located inside the $CH^{\ast}\;and\;C_2^{\ast}$ radical for all measured conditions and the emission intensity ratio of $C_2^{\ast}/CH^{\ast}\;and\;C_2^{\ast}/OH^{\ast}$ were identified as good marker for local equivalence ratio over a range of ${\phi}=0.79{\sim}1.2\;and\;CH^{\ast}/OH^{\ast}\;is\;0.79<{\phi}<1.9$. However, it was difficult to predict the equivalence ratio in partially premixed flames using this system for ${\phi}>2.38$, (3) the minimum NOX emission index (EINOx) is obtained for a equivalence ratio of 3.19 in the intermediate flames.

메탄 공기 층류 부분 예혼합화염에서 예혼합 정도에 따른 화염구조와 질소산화물의 배출에 미치는 영향에 관한 연구

오정석(Jeong Seog Oh),정용기(Yong Ki Jeong),전층환(Chung Hwan Jeon),장영준(Young June Chang) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11

It is shown that the effect of variable parameters on flame structures and NOx emissions in the laminar<br/> partially premixed methane-air flames with a co-axial Bunsen burner. Objectives of this paper is to<br/> understand the effects of flow variables on NOx emissions and the flame structure with OH<br/> chemiluminescence, including reconstructed image by abel inversion processing at each conditions. A fuel<br/> flowrate of 200 [cc/min] was fixed and the amount of air was varied from 400 to 1200 [cc/min]. The<br/> experimental variables were equivalence ratio( ), fuel split percentage( ) and inner tube recess(x/D). Flow<br/> conditions were ranged from 1.36~4.76(equivalence ratio), 50~100(fuel split percentage) and 0~20(inner<br/> tube recess). NOx analyzer and ICCD camera with a OH filter were used as a main experimental<br/> apparatus. In addition, Abel inversion, which is a kind of tomography and valuable to estimate a<br/> two-dimensional structure of co-axial flames from cubical information, was employed for combustion<br/> diagnostics. Results from this study indicate that the main effects depend on equivalence ratio and next<br/> sigma, x/D for NOx production and OH formation. Throughout Abel inversion, we could affirm the<br/> maximum position and the tendency of OH radical intensity by variants at five axial heights above the<br/> burner exit.

이중동축 메탄/공기 층류 부분 예혼합화염에서의 화염구조와 자발광 배출 특성 안쪽관 연료주입의 영향

오정석(Jeong Seog Oh),정용기(Yong Ki Jeong),전충환(Chung Hwan Jeon),장영준(Young June Chang) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11

In this study, the effect of central fuel injection on a coaxial laminar CH₄/air flame was experimented at the defined premixing condition(φ=1.90, σ=50/75/100%, x/D=10). The partial premixing parameter are the equivalence ratio that total fuel is fixed at 200cc/min, the fuel split degree which means the percentage of fuel entering the outer tube to the total amount, and the mixing distance indicating the nonreactant mixture's homogeneity between inner tube top and burner exit. The object is to investigate the flame structure and chemiluminescence characteristics of laminar partial premixed flame as changing mixing parameters. The radical signal was acquired from ICCD camera and PMT. Each intensity was compared with Abel inverted value for measuring the effect of background light on the peak signal location and the intensity at central preheat zone. The results show that the peak location of each radical was broaden as the fuel split degree increasing because the mixing quality was enhanced. and OH* is a good indicator for flame front between reaction and preheat zone. At last C₂* has the same tendency with CH* but a thinner reaction zone than CH* due to a rapid decay on the burned gas side.

양극성 반고관절 성형술을 이용한 대퇴 경부 골절의 치료

오정환,조병주,안의환 건국대학교 의과학연구소 1998 건국의과학학술지 Vol.8 No.-

Problems of nonunion, avascular necrosis of the femoral head, and loss of fixation are frequently encountered in the management of femoral neck fractures and high complication rates after closed or open reduction and internal fixation technique were reported due to poor bone quality or lack of cooperation in elderly patients. So, another option of hemiarthroplasty for the management of the femoral neck fractures were recommended, especially in elderly patients. We reviewed 20 bipolar hemiarthroplasties which had been performed from April, 1990 to March, 1996 for the femoral neck fractures and followed up for a minimum of 1 year and are reporting their results.

이종마찰압접재의 변형 및 균열 성장 거동 : STS304 와 SM15C재를 중심으로 For STS304 and SM15C

오정국,오환섭,박준건 조선대학교 동력자원연구소 1997 動力資源硏究所誌 Vol.19 No.1

In this study, behavior of crack growth and fracture under static tensile load in friction welded dissimilar materials, and necking phenomenon occuring at tensile yeilding point is shown. Crack is observed in heat affected zone including fine ferrite region of SM15C and heat affected zone of STS304. Plastic flow was occured by friction welding process, so direction of crack is inclined with welded surface. Fracture behavior of similar material is subject to joint of void, but dissimilar material is liable to joint of micro crack. Fibrous zone with the view of macroscope and dimple pattern with the view of microscope is observed at fracture surface.

흉ㆍ쇄관절 후방탈구 : A Case Report

오정환,오창남,정도혁 대한스포츠의학회 1994 대한스포츠의학회지 Vol.12 No.2

Injuries to the sternoclavicular joint are not frequent, and the posterior dislocation of the sternoclavicular joint is much more rare. As the diagnosis is not easy with simple radiographic technique, special techniques are required. A case of the traumatic posterior dislocation of the sternoclavicular joint had been reported in our literature up to now. We also experienced a case of the retrosternal dislocation of the clavicle which had been caused by a ski injury and had a satisfactory clinical result with a closed reduction in a long-term follow-up. So we are reporting this case with a review of the literatures along with the injury mechanism.

이종접합재 접합 계면근방 균열의 응력 및 파괴특성

오정국,차용훈,오환섭,박준건,박경식 朝鮮大學校 機械技術硏究所 1998 機械技術硏究 Vol.1 No.1

현재까지 이종마찰압접재의 강도측정은 실험 (7)-(15)에 의해 구해져 왔다. 하지만 최근 이종마찰압접재의 효율성을 인정하여 여러 실용 부품에 응용하려는 연구가 한창 진행중이다. 이종마찰압접재에 대한 저자들(1)-(6)의 기초실험결과 일반적인 단종재와는 상이한 파괴거동(3)이 관찰되었고, 파괴역학적인 관점에서 정성적인 data 확보가 필요하게 되었다. 따라서 본 연구에서는 인장시험시 이종마찰압접재의 접합강도와 미소균열들에 의한 파괴거동을 파괴역학적 관점에서 해석적으로 고찰하여 보고자 경계요소법(BEM ; Boundary Element Method)을 이용하여 접합계면을 포함하는 접합부를 중심으로 계면상의 응력분포와 계면의 중앙에 결함이 균열로써 존재하는 경우의 응력분포와 인장시험시 열영향부에서 관찰된 균열의 모델링을 통한 균열선단에서의 응력해석을 행하였고, 그 결과 얻어진 중요한 내용을 요약하면 다음과 같다. 계면의 중앙에 균열이 존재하는 접합계면의 표면부에서 응력의 특이성이 발생하며 탄성계수의 비가 증가할수록 특이성이 증가함이 관찰되었다. 탄성계수의 비가 일정한 경우 균열의 크기가 변화하여도 계면의 표면부에서 발생하는 특이성은 거의 같은 값을 갖게 되며, 탄성계수의 비가 증가할수록 표면부의 응력 특이성의 크기는 증가한다. 이종마찰압접재의 인장시험시 관찰된 균열을 모델링 하여 해석한 결과 최대 응력 기준으로 살펴볼 때 인접한 균열선단에서의 응력분포는 균열을 합체시키는 방향으로 작용함을 알 수 있다. In this study stress distribution on the interface and stress near tip of the sub-interface crack in the dissimilar friction welded material is analyzed by using of BEM( Boundary Element Method). Stress singularity near surface of model to analyze is observed for various crack length and ratio of elastic modulus. Tensile and shear stress distribution near two neithbor sub-interface crack tips are analyzed. Existance of singularity near surface on the interface is particular situation so that we need to investigate for dissimilar friction welded materials by means of numerical analysis method.

이종마찰압접재 계면의 기계·금속조직학적 거동 및 파면특성 : STS304와 SM15C재를 중심으로 For STS304 and SM15C

오환섭,박경식,박준건,오정국,백영남 慶熙大學校 材料科學技術硏究所 1998 材料科學技術硏究論集 Vol.11 No.-

In this study is behavior of crack propagation and fracture under static tensile load, shear load, rotary bending fatigue load in friction welded dissimilar materials. Crack was observed in fine ferrite zone of SM15C and heat affected zone of STS304. Plastic flow was occured by friction welding process, so direction of crack is inclined with welded surface. Fatigue fracture most occurred in SM15C heat affected zone around interface. Fibrous zone with the view of macroscope and dimple pattern with the view of microscope were observed at fracture surface. Result is more metal micrstructure dependence than stress dependence by mechanical and metallic mechanics.

조갑하 외골증 : 1례 보고 A Case Report

오정환,김보현 건국대학교 의과학연구소 1995 건국의과학학술지 Vol.5 No.-

Subungual exostosis is not uncommon disease entity which orthopaedic surgeon tend to neglect as a trivial one, even though it causes a troublesome discomfort and pain. Its etiology is not well defined and various differential diagnosis are required. We experienced a case of subungual exostosis in the distal phalanx of the great toe and reporting this case with a review of the literatures. Complete local excision is required, but damage to the nail bed should be avoided.

슬개골 골절과 동반된 후방 십자인대 손상

오정환,신규철 건국대학교 의과학연구소 1994 건국의과학학술지 Vol.4 No.-

Patellar fractures result from direct and/or indirect forces. The majority of the patellar fractures result from direct injuries and a fall on the knee or a direct blow sustained in the vehicular trauma is one of the common causes. Patellar fractures from indirect forces occur when the intrinsic strength of the patella is exceeded by the pull of the musculotendinous and ligamentous units attaching to it and typically occurs in the act of stumbling or partially falling. Posterior cruciate ligament disruption is generally caused by a posteriorly directed force on the proximal tibia, and hyperextension with abduction or external rotation movements have been also described in the production of posterior cruciate ligament injuries. Posterior cruciate ligament injuries are apt to be negelected frequently, and ipsilateral femoral shaft fracture or posterior dislocation of the hip also may be seen with direct injuries to the patella, but patellar fractures are rarely associated with posterior cruciate ligament injuries. So we are reporting four cases of the posterior cruciate ligament injuries as one of the combined entity, which had been neglected and associated with the patellar fracture after a review of the literatures.