• Structural Engineering and Mechanics
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• v.43 no.3
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• pp.311-320
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• 2012

The higher-order asymptotic C(t) - $A_2(t)$ approach was employed to investigate the crack-tip stress of two collinear cracks in a power-law creeping material under the plane strain conditions. A comprehensive calculation was made of the single crack, collinear crack model with S/a = 0.4 and 0.8, by using the C(t) - $A_2(t)$ approach, HRR-type field and the finite element analysis; the latter two methods were used to check the constraint significance and the calculation accuracy of the C(t) - $A_2(t)$ approach, respectively. With increasing the creep time, the constraint $A_2$ was exponentially increased in the small-scale creep stage, while no discernible dependency of the constraint $A_2$ on the creep time was found at the extensive creep state. In addition, the creep time and the mechanical loads have no distinct influence on accuracy of the results obtained from the higher-order asymptotic C(t) - $A_2(t)$ approach. In comparison with the HRR-type field, the higher-order asymptotic C(t) - $A_2(t)$ solution matches well with the finite element results for the collinear crack model.

• Interaction and multiscale mechanics
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• v.6 no.2
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• pp.173-195
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• 2013

Meshfree methods are known to have the capability to overcome the strict regularization requirements and numerical instabilities that encumber the finite element method (FEM) in large deformation problems. They are also more naturally suited for problems involving material perforation and fragmentation. To take advantage of the high efficiency of FEM and high accuracy of meshfree methods, a coupled finite element (FE) and reproducing kernel (RK, one of the meshfree approximations) formulation is described in this paper. The coupling of FE and RK approximation is implemented in an evolutionary fashion, where the extent and location of the evolution is dependent on a triggering criteria provided by the material constitutive laws. To enhance computational efficiency, Gauss quadrature is applied to integrate both FE and RK domains so that no state variable transfer is required when mesh conversion is performed. To control the hourglassing that might occur with 1-point integrated hexahedral grids, viscous type hourglass control is implemented. Meanwhile, the FEM version of the K&C concrete (KCC) model was modified to make it applicable in both FE and RK formulations. Results using this code and the KCC model are shown for the modeling of concrete responses under quasi-static, blast and impact loadings. These analyses demonstrate that fragmentation phenomena of the sort commonly observed under blast and impact loadings of concrete structures was able to be realistically captured by the coupled formulation.

• Journal of the Korean Geotechnical Society
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• v.27 no.5
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• pp.45-59
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• 2011

This study introduces the diagrammatic Upper and Lower Bound (UB and LB) methods theoretically in order to derive the bearing capacity factor, $N_c$ in undrained clay and to compare with Prandtl's exact solution (1921). As a result of the theoretical study, an exact solution comes out when the UB and LB solutions are the same. In addition, the finite element analyses show that the failure loads approach to the bearing capacity factor of 5.14. Results of the FEA significantly depend on the finite element type, a number of elements, and a number of increments. From this study the exact solution defines that solutions from UB and LB are the same. However, this situation is very difficult to process, so we can confirm the exact solution as a range between UB and LB solutions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.425-426
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• 2012

• Bulletin of the Korean Mathematical Society
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• v.56 no.4
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• pp.929-937
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• 2019

The main purpose of this paper is to establish $H{\ddot{o}}lder$ estimates for the Cauchy transform in a class of finite/infinite type convex domains in $\mathbb{C}^2$.

• Bulletin of the Korean Mathematical Society
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• v.48 no.3
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• pp.601-609
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• 2011

Tensor product immersions of a given Riemannian manifold was initiated by B.-Y. Chen. In the present article we study the tensor product surfaces of two Euclidean plane curves. We show that a tensor product surface M of a plane circle $c_1$ centered at origin with an Euclidean planar curve $c_2$ has harmonic Gauss map if and only if M is a part of a plane. Further, we give necessary and sufficient conditions for a tensor product surface M of a plane circle $c_1$ centered at origin with an Euclidean planar curve $c_2$ to have pointwise 1-type Gauss map.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.50-52
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• 2001

The BLDC(Brushless DC) motor with the permanent magnet has many merits such as high efficiency and efficiency. These characteristics of the BLDC motor makes them one of the most popular motors in the world today. The C type ferrite magnet is many used in BLDC motor for high performance, especilly low price. Many papers have been written on the analysis of the BLDC motor with C type ferrite magnet. But, most of these target models are contained symmetric distribution of permanent magnet. In this paper, investigations are made on different distribution of permanent magnets for a understanding of the effects of unequal permanent magnet location on the unbalanced cogging torque. Motor torque and cogging torque are obtained by using the 2 dimensional finite element method.

• Communications of the Korean Mathematical Society
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• v.39 no.3
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• pp.739-756
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• 2024

The ordinary mean curvature vector field 𝗛 on a submanifold M of a space form is said to be proper if it satisfies equality Δ𝗛 = a𝗛 for a constant real number a. It is proven that every hypersurface of an Riemannian space form with proper mean curvature vector field has constant mean curvature. In this manuscript, we study the Lorentzian hypersurfaces with proper second mean curvature vector field of four dimensional Lorentzian space forms. We show that the scalar curvature of such a hypersurface has to be constant. In addition, as a classification result, we show that each Lorentzian hypersurface of a Lorentzian 4-space form with proper second mean curvature vector field is C-biharmonic, C-1-type or C-null-2-type. Also, we prove that every 𝗛₂-proper Lorentzian hypersurface with constant ordinary mean curvature in a Lorentz 4-space form is 1-minimal.

• Journal of Ocean Engineering and Technology
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• v.13 no.2 s.32
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• pp.168-175
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• 1999

In the present paper, a hull form for the turtle boat type incinerating vessel was developed based on the Finite source Distribution Method(FDM) and 1-$C_p$ method. In order to obtain proper hull form within the limited time and budget, a computer program OCL(Optimization of $C_p$ and LCB) was developed adn used. For the confirmation of the theoretical results by OCL, these theoretical results were compared with results of model test in the circulating water channel (CWC)in Chosun University.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.1
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• pp.131-137
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• 2009

In this paper, we have manufactured hole type PRAM unit cell using phase change material $Ge_2Sb_2Te_5$. The phase change material $Ge_2Sb_2Te_5$ was deposited on hole of 500 nm size using sputtering method. Reset current of PRAM unit cell was confirmed by measuring R-V characteristic curve. Reset current of manufactured hole type PRAM unit cell is 15 mA, 100 ns. And electro and thermal characteristics of hole type PRAM unit cell were analyzed by 3-D finite element analysis. From simulation temperature of PRAM unit cell was $705^{\circ}C$.