1차원 유한요소망 연속기법을 이용한 시간영역 탄성파의 역해석

강준원,Kang, Jun Won 한국전산구조공학회 2013 한국전산구조공학회논문집 Vol.26 No.4

이 논문에서는 반무한 고체영역의 표면에서 측정한 변위응답의 시간이력으로부터 유한요소망 연속기법을 이용해 탄성파 속도의 공간적 분포를 추정하는 역해석 문제를 소개한다. 반무한 영역에서의 역해석을 위해서는 해석 대상이 되는 유한영역의 경계에서 파동의 반사가 일어나지 않도록 하는 것이 중요하다. 이를 위해 유한영역의 경계면에 perfectly-matchedlayers(PMLs)라는 수치적 파동흡수층을 도입하였고, PML을 경계로 하는 유한영역에서 역해석 문제를 정의하였다. 이 문제를 탄성파동방정식을 구속조건으로 하는 최적화 문제로 표현하였으며, 라그랑주 승수법에 기초한 비구속 최적화 기법에 의해 탄성파속도의 최적 분포를 결정하였다. 해의 정확도와 수렴성을 높이기 위해 유한요소망 연속기법을 도입하여 점진적으로 밀도가 증가하는 유한요소망에 대해 연속적으로 역해석을 수행하였다. 1차원 예제들을 통해 유한요소망 연속기법을 이용한 역해석으로부터 탄성파속도의 분포를 정확히 추정할 수 있음을 확인하였으며, 측정 응답에 노이즈가 존재하는 경우에도 제안한 역해석 기법은 목표 탄성파속도 분포에 근사한 결과를 도출하였다. This paper introduces a mesh continuation scheme for a one-dimensional inverse medium problem to reconstruct the spatial distribution of elastic wave velocities in heterogeneous semi-infinite solid domains. To formulate the inverse problem, perfectly-matched-layers(PMLs) are introduced as wave-absorbing boundaries that surround the finite computational domain truncated from the originally semi-infinite extent. To tackle the inverse problem in the PML-truncated domain, a partial-differential-equations(PDE)-constrained optimization approach is utilized, where a least-squares misfit between calculated and measured surface responses is minimized under the constraint of PML-endowed wave equations. The optimization problem iteratively solves for the unknown wave velocities with their updates calculated by Fletcher-Reeves conjugate gradient algorithms. The optimization is performed using a mesh continuation scheme through which the wave velocity profile is reconstructed in successively denser mesh conditions. Numerical results showed the robust performance of the mesh continuation scheme in reconstructing target wave velocity profile in a layered heterogeneous solid domain.

내화피복을 적용한 강합성보의 구조화재해석

강준원,강문수,윤혜진,Jun Won Kang,Moon Soo Kang,Hyejin Yoon 한국전산구조공학회 2023 전산구조공학 Vol.36 No.2

This paper presents the effects of fire-resistant materials on the temperature and vertical deflection of a composite beam exposed to fire through nonlinear thermo-mechanical analysis. The fire was modeled using the standard fire curve proposed in American Society for Testing and Materials (ASTM) E119. Fire-resistant materials were modeled by reducing the heat transfer coefficient from the air layer to the beam. The temperature and vertical deflection of the uncoated composite beam were measured using a laboratory fire test, and the results of the structural fire analysis were verified through comparison with experimental results. By introducing the fire-resistance effect, the reduction in the temperature and deflection of the beam for the ASTM E119 standard fire can be reasonably estimated. Based on a case study of the heat transfer coefficient, the fire-resistant effect on the thermo-mechanical response of a composite beam in the event of a fire is presented.

당뇨 환자에서 연성 콘택트렌즈 착용에 의한 중심각막두께 및 각막내피세포의 변화

강준원,신기철,Joon Won Kang,Ki Cheul Shin 대한안과학회 2014 대한안과학회지 Vol.55 No.10

Purpose: To evaluate the changes in central corneal thickness and corneal endothelium in contact lens-wearing diabetic patients. Methods: This study included 113 patients who visited the Department of Ophthalmology, Konkuk University Medical Center from August 2006 to August 2007. Ultrasound pachymetry and noncontact specular microscopy were performed on the right eyes of 26 diabetic patients who regularly wore soft contact lenses (group 1), 27 diabetic patients who did not wear soft contact lenses (group 2), 30 soft contact lens-wearers without diabetes mellitus (DM) (group 3), and 30 normal subjects who did not wear soft contact lenses (group 4). Central corneal thickness, corneal endothelial cell density, endothelial cell coefficient of variation, and percentage of hexagonal endothelial cells were compared between the groups. Results: Average duration of diabetes in groups 1 and 2 was 4.38 and 4.41 years, respectively, and average duration of soft contact lens wear in groups 1 and 3 was 5.27 and 3.65 years, respectively. The central cornea was significantly thicker and the endothelial cell density was significantly lower in group 1 than in groups 3 and 4. The cell size coefficient of variation was higher in group 1 than in groups 2 and 4 and higher in group 3 than in group 4. The percentage of hexagonal cells was significantly lower in group 3 than in group 4. Conclusions: Central corneal thickness and endothelial cell density are more affected by DM than contact lens use, and corneal endothelial cell morphology is influenced more by contact lens use than DM. Contact lens use in diabetic patients significantly influences all characteristics of the corneal endothelium compared with those in normal subjects. Patients with DM should be advised not to wear contact lenses.J Korean Ophthalmol Soc 2014;55(10):1426-1431

The Formation of Assimilable Organic Carbon ( AOC ) in Ozonated Water and the Determination of AOC with Achinetobacter calcoaceticus

강준원,김종배 ( Joon Wun Kang,Jong Bae Kim ) 한국물환경학회 1995 한국물환경학회지 Vol.11 No.2

상수원수의 생분해도를 평가하는 방법으로 AOC(동화가능유기탄소)방법을 사용하여 보았다. van der Kooij가 제시하였던 기존의 AOC방법은 P17, NOX의 특정균주를 사용하였으며 본 연구에서는 낙도강수의 오존처리수에서 분리한 Acinetobacter calcoaceticus균주로 부터 AOC 측정 방법을 제시하였다. 본 실험에서 분리동정한 이 균주는 오존처리수에서 분리되는 세균의 대표적인 것이었으나, 오존처리를 하지않은 원수에서는 전혀분리되지 않았다. 분리균주의 생물활성도를 평가하기 위하여 sodium acetate와 oxalate를 영양원으로하여 탄소원의 농도 대비 세균증식수의 상관관계를 고찰한 결과 기존의 Pl7, NOX균주와 유사한 Yield Coefficient값을 관찰할 수 있었다. 이 균주를 사용한 AOC측정 방법의 가장 큰 장점은 세균의 증식속도가 Pl7, 또는 NOX에 비하여 매우 빠르기 때문에 AOC측정에 소요되는 배양시간을 단축할 수 있는 큰 잇점이 있다. 실증 Plant실험결과, AOC농도가 오존처리한 후 증가되었으며 염소소독 후에도 감소하지 않았다 이와같은 조건에서, 후-오존처리리공정후에 AOC의 농도를 줄일 수 있는 생물활성탄과같은 후처리공정을 설치하는것이 바람직 하다고 본다. The effect of ozone application in the drinking water on the production of assimilable organic carbon (AOC) was evaluated. The typical procedure to determine AOC is suggested by van der Kooij, which is the method of bacterial growth measurement by colony forming units using the strain P17 and/or NOX. The bacterial indicator species used for this study is Acinetobncter calcoaceticus which was isolated and identified ozonating the Nakdong river water. This strain could never be isolated from the raw water, but this strain was the predominant isolate in the ozonated water. Within a short incubation time, this organism was found to replicate well on acetate and oxalate as a sole carbon source. The yield coefficient of this organism for acetate and oxalate are the same order of magnitude of the value of P17 and NOX. The advantage of AOC determination using A. calcoaceticus might be the shortening of assay time due to the more rapid growth of this organism compared with that of P17 and NOX. With the full scale experiments, A.calcoaceticus was found to increase after ozonation, but did not decrease upon chlorination. The addition of biological treatment process such as biological activated carbon (BAC) filters after post-ozonation may appear to be an ideal solution to reduce the AOC concentration.

시간영역 Gauss-Newton 전체파형 역해석 기법의 성능평가

강준원,Kang, Jun Won,Pakravan, Alireza 한국전산구조공학회 2013 한국전산구조공학회논문집 Vol.26 No.4

본 논문에서는 물성이 균일하지 않은 반무한 고체영역의 탄성파속도 분포를 재구성하기 위한 시간영역 Gauss-Newton 전체파형 역해석 기법을 소개한다. 반무한 영역을 유한 계산영역으로 치환하기 위하여 유한영역의 경계에 수치적 파동흡수 경계조건인 perfectly-matched-layers(PMLs)를 도입하였다. 이 역해석 문제는 PML을 경계로 하는 영역에서의 탄성파동방정식을 구속조건으로 하는 최적화 문제로 성립되며, 표면에서 측정된 변위응답과 혼합유한요소법에 의해 계산된 응답간의 차이를 최소화함으로써 미지의 탄성파속도 분포를 결정한다. 이 과정에서 Gauss-Newton-Krylov 최적화 알고리즘과 정규화기법을 사용하여 탄성파속도의 분포를 반복적으로 업데이트하였다. 1차원 수치예제들을 통해 Gauss-Newton 역해석으로 부터 재구성된 탄성파속도의 분포가 목표값에 충분히 근사함을 보였으며, Fletcher Reeves 최적화 알고리즘을 사용한 기존의 역해석 결과에 비해 수렴율이 현저히 개선되고 계산 소요시간이 단축됨을 확인할 수 있었다. This paper presents a time-domain Gauss-Newton full-waveform inversion method for the material profile reconstruction in heterogeneous semi-infinite solid media. To implement the inverse problem in a finite computational domain, perfectly-matchedlayers( PMLs) are introduced as wave-absorbing boundaries within which the domain's wave velocity profile is to be reconstructed. The inverse problem is formulated in a partial-differential-equations(PDE)-constrained optimization framework, where a least-squares misfit between measured and calculated surface responses is minimized under the constraint of PML-endowed wave equations. A Gauss-Newton-Krylov optimization algorithm is utilized to iteratively update the unknown wave velocity profile with the aid of a specialized regularization scheme. Through a series of one-dimensional examples, the solution of the Gauss-Newton inversion was close enough to the target profile, and showed superior convergence behavior with reduced wall-clock time of implementation compared to a conventional inversion using Fletcher-Reeves optimization algorithm.

TCE , PCE 존재하에서 오존 / 과산화수소 정수처리공정에 의한 부산물 생성에 관한 연구

강준원,박훈수 ( Joon Wun Kang,Hoon Soo Park ) 한국물환경학회 1996 한국물환경학회지 Vol.12 No.2

A bench scale investigation was conducted of by products of trichloroethylene(TCE) and tetrachloroethylene(PCE) oxidation by the ozone/hydrogen peroxide advanced oxidation process(AOP). Post-chlorination of ozone/peroxide treated water was also investigated. Byproducts analyzed for TCE and PCE destruction in the ozone/peroxide experiments were chloral hydrate and di-and trichloroacetic acid (DCA and TCA). In TCE spiked (500∼700 ppb) ozone/peroxide runs, chloral hydrate was formed up to the level of 0.2 ppb and was slowly destroyed as the run progressed. Dichloroacetic acid and trichloroacetic acid was produced by the oxidation of TCE and PCE, respectively. In the post-chlorination experiments of PCE Spiked ozone/peroxide runs, concentration of chloral hydrate, DCA, and TCA were higher in the chlorinated water, but the levels seems to be quite below the maximum contamination level goal(MCLG) of USEPA.

치료 증례 간세포암 부신 전이의 경동맥화학색전술을 이용한 치료 보고

강준원 ( Joon Won Kang ),정진욱 ( Jin Wook Chung ),윤창진 ( Chang Jin Yoon ),채홍석 ( Hong Suk Chae ),박재형 ( Jae Hyung Park ),정아영,( Jean Jung ) 대한간암학회 2002 대한간암학회지 Vol.2 No.-

하수처리 : 활성탄의 인 흡착 특성에 관한 동력학적 연구

강준원 ( Jun Won Kang ),서정범 ( Jseng Bsem Seo ) 대한상하수도학회 2006 공동추계 학술발표회 논문집 Vol.2006 No.-

Pentafluoroethane(HFC-125)+Propane(R-290) 혼합냉매의 공비점 측정에 관한 실험적 연구

강준원(Jun-One Kang),박영무(Young-Moo Park),유재석(Jaisuk Yoo),이종화(Jong-Hwa Lee) 대한기계학회 2002 대한기계학회 기타 간행물 Vol.2002 No.11

방사선 , 자외선 및 초음파 조사방법을 이용한 폐수처리

강준원(Joon Wun Kang),이경혁(Kyung Hyuk Lee),이면주(Myun Joo Lee) 大韓環境工學會 1997 대한환경공학회지 Vol.19 No.1