• Journal of Ship and Ocean Technology
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• v.6 no.2
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• pp.37-50
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• 2002

In the present numerical simulation of viscous free surface flow around a ship, two-fluids in-compressible Reynolds-averaged Navier-Stokes equations with the standard $\textsc{k}-\varepsilon$turbulence model are discretized on a regular grid by using a finite volume method. A local level-set method is introduced for capturing the free surface movement and the influence of the viscous layer and dynamic boundary condition of the free surface are implicitly considered. Partial differential equations in the level-set method are discretized with second order ENO scheme and explicit Euler scheme in the space and time integration, respectively. The computational results for the Series-60 model with $C_B=0.6$ show a good agreement with the experimental data, but more validation studies for commercial complicated hull forms are necessary.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.8
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• pp.1215-1220
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• 2008

To obtain the shape of the free surface more accurately, computations are carried out by a finite volume method using unstructured meshes and an interface capturing method. Free-surface flow, which is very important in the fields of ship and marine engineering, is numerically simulated for flows of both water and air. Control volumes are used with an arbitrary number of faces and allows a local mesh refinement. The integration is of second order, with a midpoint rule integration and linear interpolation. The method is fully implicit and uses quadratic interpolation. The solution method of pressure-correction type solves sequentially equations of momentum, continuity, conservation, and two-equations turbulence model. Comparison are quantitatively made between the computation and experiment in order to confirm the solution method.

• Bulletin of the Korean Chemical Society
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• v.22 no.2
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• pp.241-243
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• 2001

• Radiation Oncology Journal
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• v.29 no.4
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• pp.219-227
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• 2011

Purpose: This study evaluated the treatment effectiveness and proper radiation dose of helical tomotherapy (HT) in spine oligometastases from gastrointestinal cancers. Materials and Methods: From 2006 to 2010, 20 gastrointestinal cancer patients were treated with HT for spine oligometastases (31 spine lesions). The gross tumor volume (GTV) was the tumor evident from magnetic resonance imaging images fused with simulation computed tomography images. Clinical target volume (CTV) encompassed involved vertebral bodies or dorsal elements. We assumed that the planning target volume was equal to the CTV. We assessed local control rate after HT for 31 spine metastases. Pain response was scored by using a numeric pain intensity scale (NPIS, from 0 to 10). Results: Spine metastatic lesions were treated with median dose of 40 Gy (range, 24 to 51 Gy) and median 5 Gy per fraction (range, 2.5 to 8 Gy) to GTV with median 8 fractions (range, 3 to 20 fraction). Median biologically equivalent dose (BED, ${\alpha}/{\beta}$ = 10 Gy) was 52 $Gy_{10}$ (range, 37.5 to 76.8 $Gy_{10}$) to GTV. Six month local control rate for spine metastasis was 90.3%. Overall infield failure rate was 15% and outfield failure rate was 75%. Most patients showed pain relief after HT (93.8%). Median local recurrence free survival was 3 months. BED over 57 $Gy_{10}$ and oligometastases were identified as prognostic factors associated with improved local progression free survival (p = 0.012, P = 0.041). Conclusion: HT was capable of delivering higher BED to metastatic lesions in close proximity of the spinal cord. Spine metastases from gastrointestinal tumors were sensitive to high dose radiation, and BED (${\alpha}/{\beta}$ = 10 Gy) higher than 57 $Gy_{10}$ could improve local control.

• Nuclear Engineering and Technology
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• v.41 no.8
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• pp.1045-1052
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• 2009

A calculation model is developed to predict the transient free surface flow on the containment floor following a loss-of-coolant accident (LOCA) of pressurized water reactors (PWR) for the use of debris transport evaluation. The model solves the two-dimensional Shallow Water Equation (SWE) using a finite volume method (FVM) with unstructured triangular meshes. The numerical scheme is based on a fully explicit predictor-corrector method to achieve a fast-running capability and numerical accuracy. The Harten-Lax-van Leer (HLL) scheme is used to reserve a shock-capturing capability in determining the convective flux term at the cell interface where the dry-to-wet changing proceeds. An experiment simulating a sudden break of a water reservoir with L-shape open channel is calculated for validation of the present model. It is shown that the present model agrees well with the experiment data, thus it can be justified for the free surface flow with accuracy. From the calculation of flow field over the simplified containment floor of APR1400, the important phenomena of free surface flow including propagations and interactions of waves generated by local water level distribution and reflection with a solid wall are found and the transient flow rates entering the Holdup Volume Tank (HVT) are obtained within a practical computational resource.

• Journal of Korean Port Research
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• v.13 no.1
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• pp.167-174
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• 1999

Numerical analysis of two-fluid flows for both water and air is carried out. Free-Surface flows with an arbitrary deformation have been simulated around two dimensional submerged hydrofoil. The computation is performed using a finite volume method with unstructured meshes and an interface capturing scheme to determine the shape of the free surface. The method uses control volumes with an arbitrary number of faces and allows cell-wise local mesh refinement. the integration in space is of second order based on midpoint rule integration and linear interpolation. The method is fully implicit and uses quadratic interpolation in time through three time levels The linear equation systems are solved by conjugate gradient type solvers and the non-linearity of equations is accounted for through picard iterations. The solution method is of pressure-correction type and solves sequentially the linearized momentum equations the continuity equation the conservation equation of one species and the equations or two turbulence quantities.

• Journal of Mechanical Science and Technology
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• v.14 no.7
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• pp.789-795
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• 2000

Free-surface flows with an arbitrary deformation, induced by a submerged hydrofoil, are simulated numerically, considering two-fluid flows of both water and air. The computation is performed by a finite volume method using unstructured meshes and an interface capturing scheme to determine the shape of the free surface. The method uses control volumes with an arbitrary number of faces and allows cell wise local mesh refinement. The integration in space is of second order, based on midpoint rule integration and linear interpolation. The method is fully implicit and uses quadratic interpolation in time through three time levels. The linear equations are solved by conjugate gradient type solvers, and the non-linearity of equations is accounted for through Picard iterations. The solution method is of pressure-correction type and solves sequentially the linearized momentum equations, the continuity equation, the conservation equation of one species, and the equations for two turbulence quantities. Finally, a comparison is quantitatively made at the same speed between the computation and experiment in which the grid sensitivity is numerically checked.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.133-140
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• 1998

A Navier-Stokes code based on a unstructured finite volume method is used to simulate the MIT flapping foil experiment. A low Reynolds number $k-{\varepsilon}$ turbulence model is used to close the Reynolds averaged Navier-Stokes equations. Computations are carried out for a domain involving two flapping foils and a downstream hydrofoil. The computational domain is meshed with unstructured quadrilateral elements, partly structured. Numerical solutions show good agreement with experiment. Unsteadiness inside boundary layer is entrained when a unsteady vortex impinge on the blade surface. It shoves that local peak value inside the boundary layer and also local minimum near the edge of boundary layer as it developes along the blade surface. The unsteadiness inside the boundary layer is almost isolated from the free stream unsteadiness and being convected at local boundary layer speed, less than the free stream value.

• Journal of Korean Neurosurgical Society
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• v.39 no.2
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• pp.102-108
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• 2006

Objective : The management of diffuse astrocytomas is one of the most controversial areas in clinical neurooncology. There are numerous reviews and editorials outlining the difficulties in the management of these lesions. In this study, we assess the role of Gamma Knife radiosurgery[GKS] for diffuse astrocytomas. Methods : Twenty-three patients with a diffuse astrocytoma were treated with GKS as a primary or adjuvant method from February 1995 to October 2003. The mean marginal dose was $13.6\;[8.5{\sim}17.5]Gy$ and the mean maximal dose was $27.3\;[17.0{\sim}35.0]Gy$. Local control and the pattern of radiologic response were evaluated. The probable factors affecting local control, such as tumor volume, margin dose, previous history of craniotomy or stereotactic biopsy, and the presence or absence of previous radiotherapy were statistically analyzed. The average duration of follow-up was 39.7 [$11.3{\sim}101.5$] months after GKS. Results : Of the 23 lesions treated, 16 lesions [69.6%] were controlled during the follow-up period. The mean progression-free interval was 57.4 months and the 5-year progression-free rate was 68%. Only tumor volume was found to be a statistically significant factor for local control. Smaller tumors were better controlled by GKS; it was significantly effective in tumors with less than $10cm^3$ volume. Conclusion : GKS could be a valuable therapeutic modality both as a primary treatment and as a postoperative adjuvant therapy in some selected cases.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.12
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• pp.1072-1087
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• 2008

A mixed volume and boundary integral equation method (Mixed VIEM-BIEM) is used to calculate the plane elastostatic field in an isotropic elastic half-plane containing an isotropic or anisotropic inclusion and a void subject to remote loading parallel to the traction-free boundary. A detailed analysis of stress field at the interface between the isotropic matrix and the isotropic or orthotropic inclusion is carried out for different values of the distance between the center of the inclusion and the traction-free surface boundary in an isotropic elastic half-plane containing three different geometries of an isotropic or orthotropic inclusion and a void. The method is shown to be very accurate and effective for investigating the local stresses in an isotropic elastic half-plane containing multiple isotropic or anisotropic inclusions and multiple voids.