• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.12
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• pp.1615-1624
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• 2000

Algebraic Reynolds Stree (ARS) model is applied in order to analyze the turbulent flow of wall-attaching offset jet and to evaluate the predictability of model. The applied numerical schemes are the upwind scheme and the skew-upwind scheme. The numerical results show a good prediction in the first order calculations(i.e., reattachment length, mean velocity, pressure), however, slight deviations in the second order(i.e., kinetic energy and turbulence intensity). Comparing with the previous results using the k-$\varepsilon$ model, the ARS model predicts better than the standard k-$\varepsilon$ model, however, slightly worse than the k-$\varepsilon$ model including the streamline curvature modification. Additionallay this study can reconfirm that the skew-upwind scheme has approximately 25% improved predictability than the upwind scheme.

• Journal of Korea Water Resources Association
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• v.30 no.1
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• pp.15-22
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• 1997

The flow in meandering channel has a great influence on curved bank revetment in river morphology. It is difficult to state generalized cirteria for channel improvement applicable to any paricular river. But it is very important to provide some principles and guidelines for design engineers. The objective of this experimental study in fixed bed model is to povide effective data that find out maximum velocity size by the mean velocity and the radius of curvature in curved channel, for the purpose of improving small stream without hydraulic modeling test each time.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.1
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• pp.11-25
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• 1991

The steady, incompressible developing 3-dimensional turblent flow in a square sectioned curved duct has been investigated by using partially-parabolic equation and Finite Analytic Method. The calculation of turbulent flow field is performed using 2-equation K-$\epsilon$ turbulence model, modified wall function, simpler algorithm and numerically generated body fitted coordinates. Iso-mean velocity contours at the various sections are compared with the existing experimental data and elliptic solutions by other authors. In the region of $0^{\circ}<{\theta}<71^{\circ}$, present results agree with the experimental data much better than the elliptic solution for the similar number of grid points. Furthermore, for the same tolerance, the present solution converges four times faster than the elliptic solution.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.52-53
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• 2017

Through the case study, we surveyed an applicability of digital fabrication in irregular-shaped building construction project. By digital fabrication, we mean is a precision manufacturing method has been used in aircraft, ship and car manufacturing industry. We collected construction-completed "LotteWorld Tower Podium" project data and analyzed its process in terms of construction quality andduration. The result shows that digital fabrication is considered a competitive technology that enabled to complete the project in seven months within 3mm surface curvature threshold. The digitalfabrication is expected to apply on a number of irregular-shaped building construction project.

• Journal of the Korean Mathematical Society
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• v.42 no.3
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• pp.447-455
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• 2005

In this article, we introduce the notion of pointwise 1-type Gauss map of the first and second kinds and study surfaces of revolution with such Gauss map. Our main results state that surfaces of revolution with pointwise 1-type Gauss map of the first kind coincide with surfaces of revolution with constant mean curvature; and the right cones are the only rational surfaces of revolution with pointwise 1-type Gauss map of the second kind.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.30-37
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• 2003

Lineaments along the Yangsan and Ulsan fault systems were extracted through aerial photograph interpretation in the southeastern part of Korean Peninsula. Lineaments can be classified into five ranks on the basis of certainty and divided by curvatures. Mean strikes of all lineament by aerial photograph interpretation is dominant in NS ~N05$^{\circ}$E direction along the Ulsan fault system and Nl5-20$^{\circ}$E direction along the Yangsan fault system respectively. The curvature of lineament around Yangsan Fault is different from around the Ulsan Fault system, the former shows that straight lineament is dominant but the latter curved lineaments are dominant. It indicates that the Quaternary faults around Ulsan Fault would be appeared as reverse fault.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.4
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• pp.426-434
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• 1988

Series expansion is applied to solve the laminar boundary layer equations for the problem of natural convection from vertical cylinder with uniform surface heat flux. The series in terms of transverse curvature parameter ${\xi}$ is extended to five terms and is well converged by applying the Shanks transform twice. In case of natural convection from a vertical cylinder heated with uniform surface heat flux, it is possible to consider the vertical cylinder as vertical plate under the condition of D/L${\geq}$A/$(Gr_L^*)^{1/5}$, where A is in the range of 5.7~55.2. Also, mean Nusselt number ${\overline{Nu_L}}$ can be represented as $C_1(Ra_L^*)^{1/5}$, where $C_1$ is a constant which depends on Pr and is in the range of 0.5~0.8.

• Journal of the Korean Mathematical Society
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• v.58 no.1
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• pp.109-122
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• 2021

In this paper, we consider the problem of finding the hypersurface Mn in the Euclidean (n + 1)-space ℝn+1 that satisfies an equation of mean curvature type, called singular minimal hypersurface equation. Such an equation physically characterizes the surfaces in the upper half-space ℝ+3 (u) with lowest gravity center, for a fixed unit vector u ∈ ℝ3. We first state that a singular minimal cylinder Mn in ℝn+1 is either a hyperplane or a α-catenary cylinder. It is also shown that this result remains true when Mn is a translation hypersurface and u is a horizantal vector. As a further application, we prove that a singular minimal translation graph in ℝ3 of the form z = f(x) + g(y + cx), c ∈ ℝ - {0}, with respect to a certain horizantal vector u is either a plane or a α-catenary cylinder.

• Bulletin of the Korean Mathematical Society
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• v.59 no.6
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• pp.1567-1594
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• 2022

In this article, we first introduce the notion of commuting Ricci tensor and pseudo-anti commuting Ricci tensor for Hopf hypersurfaces in the homogeneous nearly Kähler 𝕊³ × 𝕊³ and prove that the mean curvature of hypersurface is constant under certain assumptions. Next, we prove the nonexistence of Ricci soliton on Hopf hypersurface with potential Reeb vector field, which improves a result of Hu et al. on the nonexistence of Einstein Hopf hypersurfaces in the homogeneous nearly Kähler 𝕊³ × 𝕊³.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.10
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• pp.121-129
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• 1995

The objective of this research is to develop an effective inspection planning strategy for sculptured surfaces by using 3-dimensional Coordinate Measuring Machine (CMM). First, the CAD/CAM database is generated by using the Bezier surface patch mathod and variable cutter step size approach for design and machining of the workpiece model. Then, optimum measuring point locations are determained based on the mean curvature analysis to obtain more effective inspection results for the given sample numbers. An optimal probe sequence generation method is proposed by implementing the Traveling Salesperson (TSP) algorithm and new guide point selection methods are suggested based on the concepts of the variable distance between the first and second guide points. Finally, simulation study and experimental work show the effectiveness of the proposed strategy.