• 대한수학회지
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• 제50권5호
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• pp.1129-1163
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• 2013

Based on finite element discretization, two linearization approaches to the defect-correction method for the steady incompressible Navier-Stokes equations are discussed and investigated. By applying $m$ times of Newton and Picard iterations to solve an artificial viscosity stabilized nonlinear Navier-Stokes problem, respectively, and then correcting the solution by solving a linear problem, two linearized defect-correction algorithms are proposed and analyzed. Error estimates with respect to the mesh size $h$, the kinematic viscosity ${\nu}$, the stability factor ${\alpha}$ and the number of nonlinear iterations $m$ for the discrete solution are derived for the linearized one-step defect-correction algorithms. Efficient stopping criteria for the nonlinear iterations are derived. The influence of the linearizations on the accuracy of the approximate solutions are also investigated. Finally, numerical experiments on a problem with known analytical solution, the lid-driven cavity flow, and the flow over a backward-facing step are performed to verify the theoretical results and demonstrate the effectiveness of the proposed defect-correction algorithms.

• 대한기계학회논문집B
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• 제21권3호
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• pp.341-349
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• 1997

The characteristics of defect correction method are discussed in a sample heat conduction problem showing the numerical solution of the error correction equation can predict the error of the numerical solution of the original governing equation. A way of using defect correction method combined with the existing algorithm for the incompressible fluid flow, is proposed and subsequently tested for the driven square cavity problem. The error correction equations for the continuity equation and the momentum equations are considered to estimate the errors of the numerical solutions of the original governing equations. With this new approach, better velocity and pressure fields can be obtained by correcting the original numerical solutions using the estimated errors. These calculated errors also can be used to estimate the orders of magnitude of the errors of the original numerical solutions.

• Journal of applied mathematics & informatics
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• 제32권3_4호
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• pp.511-527
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• 2014

This paper provides a new application similar to the Local Defect Correction (LDC) technique to solve Poisson problem -u"(x) = f(x) with Dirichlet boundary conditions. The exact solution is supposed to have high activity in some region of the domain. LDC is combined with a fourth order compact scheme which is recently developed in Abbas (Num. Meth. Partial differential equations, 2013). Numerical tests illustrate the interest of this application.

• 핵의학기술
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• 제18권2호
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• pp.28-32
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• 2014

심근 관류 SPECT 검사 중 환자의 움직임은 관류 결손과 인공물을 발생시켜 정확한 진단에 영향을 줄 수 있는 인자이다. 움직임으로 왜곡된 데이터를 보정하는 방법으로 움직임 보정방법이 개발되었고 각 방법마다 사용된 알고리즘이 다르기에 상황에 비교하고자 한다. 실험에 사용된 장비는 GE Ventri Gamma Camera와 Anthropomorphic Torso Phantom을 이용하였다. 팬텀을 환자 조건과 동일하게 하기 위하여 심근에 74 kBq/mL, 연부조직 1.1 kBq/mL, 폐 2.6 kBq/mL, 간 9.6 kBq/mL의 Tl-201을 주입하여 제작하고, 움직이는 상황에서 결손의 변화 관찰 목적으로 심근의 Anterior wall에 임의로 결손을 삽입하였다. 움직이지 않는 정상군과 일정간격(2 cm, 3 pixel) 상하 1회 이동, 상하 반복 이동, 좌우 1회 이동, 좌우 반복 이동한 데이터에 나누어 영상 획득하고 MDC, Hopkins, Stasis 방법을 적용하여 Polar map과 정량분석 Score로 비교 하였다. 환자와 동일한 조건으로 회전각 $6^{\circ}$, 50sec/frame으로 영상 획득하고, OSEM (2 iterations, 10 subsets), Butterworth filter (order 10; cutoff frequency; 0.32 cycle per pixel)를 적용, scatter correction, 감쇠보정은 적용하지 않았다. 팬텀 실험에서 세 가지 방법들에서 MDC 방법이 Visual 인공물 없이 잘 보정하였으나, 환자의 데이터에 이를 적용 하였을 때, 환자마다 움직임 보정방법 적용 결과들이 일정하지 않았다. 이는, 환자의 움직임이 일정하지 않고, 장기내의 동위원소의 비율도 다르기에 발생한다고 생각되며 추가적인 연구와 상황에 맞는 움직임 보정방법의 유동적인 사용이 필요하다고 사료된다.

• 대한수학회지
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• 제49권3호
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• pp.549-569
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• 2012

In this paper asymptotic error expansions for mixed finite element approximations to a class of second order elliptic optimal control problems are derived under rectangular meshes, and the Richardson extrapolation of two different schemes and interpolation defect correction can be applied to increase the accuracy of the approximations. As a by-product, we illustrate that all the approximations of higher accuracy can be used to form a class of a posteriori error estimators of the mixed finite element method for optimal control problems.

• Journal of Chest Surgery
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• 제12권3호
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• pp.225-232
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• 1979

A 15-year-old girl underwent successful surgical correction of double-outlet right ventricle [S.D.L.] subaortic ventricular septal defect, patent foramen ovale, and pulmonary hypoplasia with valvular stenosis. The operation consisted of an internal baffling connecting the left ventricle to the aorta through the ventricular septal defect. The pulmonary stenosis was corrected with the method of connection the right ventricle to the pulmonary artery bifurcation using the Hancock valve[18mm] contained conduit. This rare type of DORV seemed to be suitable for corrective surgery, and the patient`s condition is very good until present time (post operative 7 months).

• Journal of Chest Surgery
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• 제33권2호
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• pp.139-145
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• 2000

Background: The purpose of this study is to review the clinical course after the correction of noncomplicated ventricular septal defect and to analyze the morbidity and risk factors of postoperative complications and evaluate residual defect during the follow-up period. Material and Method: From September 1994 to June 1998 24 patients(median age 10 months) underwent surgery under the diagnosis of ventricular septal defect. We made a retrospective review of the clinical records including the operation notes critical care unit records echocardiography results and the follow-up records. Result: There was no early mortality nd late mortality. There was no postoperative complete conduction block. Respiratory complication was the most common complication. The body weight age type of ventricular septal defect associated anomalies and operative procedure were not related to the incidence of complications. residual ventricular septal defects aortic valve regurgitation and tricuspid valve regurgitation were insignificant in postoperative hemodynamics, Conclusions: Correction of the noncomplicated ventricular septal defect was done without mortality and complete heart block. Aggressive preoperative medical treatment and early surgical treatment may decrease postoperative complications. Postoperative residual shunt and tricuspid regurgitation were not problematic during the follow-up

• 한국광학회:학술대회논문집
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• 한국광학회 2007년도 동계학술발표회 논문집
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• pp.62-63
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• 2007

• Journal of Chest Surgery
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• 제27권8호
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• pp.650-655
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• 1994

The author analyzed 99patients with VSD weighting less than 10kg of body weight who underwent surgical correction from 1981 to 1992 at cardiovascular department of Hanyang University hospital. Patients occupied 29.3% of total cases who were underwent surgical corrections for congenital heart diseases during that time. Of the 99 patients, 51 patients were male [52%] and 48 patients[48%] were female. Age ranged from 28 days to 36 months with mean age of 13.6 months. Mean body weight was 7.53kg. According to Kirklin`s anatomical classification, type II defect was most common [61.6%]. Associated anomaly was found in 48 patients [48.5%]. Patent foramen ovale was most commonly associated cardiac anomaly [14.1%] and followed by atrial septal defect [12.1%], patent ductus arteriosus [10.1%]. Cardiac catheterization data were analyzed. The most common range of Qp/Qs, Rp/Rs, Pp/Ps were above 3.0, 0.1 - 0.25, and above 0.75 respectively. Among the indications of surgical correction, there were pulmonary hypertention in 69 patients, congestive heart failure in 44 patients, frequent respiratory infection in 47 patients, growth retardation in 33 patients. The most common surgical approach and method for VSD closure were right atriotomy[48.3%] and dacron patch closure[93.3%]. Complication rate was 13.1% [13 cases], and overall mortality was 17.1% [17 cases]. The cause of death consisted of low cardiac output syndrome[11 cases], acute renal failure[3 cases], sepsis[2 cases] and pulmonary insufficiency[1 case] in order of frequency.

• Archives of Plastic Surgery
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• 제37권4호
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• pp.492-495
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• 2010

Purpose: Facial tumor excision is a common cause of lower eyelid defect in old patients. Many methods have been introduced for the reconstruction of lower eyelid. However, conventional surgical method can cause various complications like scar, ectropion and unnatural color matching. Thus, we introduce a simple and aesthetically acceptable method for the reconstruction of lower eyelid defect. Methods: Three elderly patients with skin cancer in the unilateral lower eyelid were operated by the new method. Following a wide excision of skin cancer, subcilliary incision of lower blepharoplasty was carried out. Elevated skin flap of lower eyelid was redrapped for the correction of defect and the remnant skin from lateral portion of lower eyelid was used for full thickness skin graft (FTSG) to correct the remaining defect. Results: All grafts survived and color match of the graft was excellent without ectropion. Furthermore, wrinkles of the lower eyelid were improved after the blepharoplasty. Conclusion: Lower eyelid defect resulting from wide excision of malignant tumor in old patients could be reconstructed successfully by modifying the conventional lower eyelid blepharoplasty along with FTSG using the remnant skin.