• Proceedings of the KSME Conference
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• 2002.08a
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• pp.83-86
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• 2002

Numerical simulations are conducted for laminar flow past a sphere rotating In the transverse direction, in order to investigate the effect of the rotation on the characteristics of flow over a sphere. The Reynolds numbers considered are Re=100, 250 and 300 based on the free-stream velocity and the sphere diameter, and the rotational speeds are in the range of $0{\leq}{\omega}{\leq}1$, where ${\omega}^{\ast}$ is the maximum velocity on the sphere surface normalized by the free-stream velocity. At ${\omega}^{\ast}=0$ (without rotation), the flow past the sphere experiences steady axisymmeoy, steady planar-symmetry and unsteady planar-symmetry, respectively, at Re=100, 250 and 300. However, with rotation, the flow becomes planar-symmetric for all the cases investigated and the symmetry plane is orthogonal to the axis of the rotation. The flow is also steady or unsteady depending on both the Reynolds number and the rotational speed, and the vortical structures behind the sphere are significantly modified by the rotation. For example, at Re=300, hairpin vortices completely disappear in the wake at ${\omega}^{\ast}=0.4\;and\;0.6$, and at ${\omega}^{\ast}=1$ vortical structures of a high frequency are newly generated due to the shear layer instability. It is also shown that with increasing rotational speed, the time-averaged drag and lift coefficients increase monotonically.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.111-116
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• 2000

A semi-infinite interfacial crack propagated with constant velocity in two bonded anisotropic strip under out-of-plane clamped displacements is analyzed. The asymptotic stress and displacement fields near the crack tip are obtained, where the results get more general expressions applicable not only to isotropic/orthotropic materials but also to the extent of the anisotropic material having one plane of elastic symmetry for the interfacial crack. The dynamic stress intensity factor is obtained as a closed form, which is decreased as the velocity of crack propagation increases. The critical velocity where the stress intensity factor comes to zero is obtained, which agrees with the lower value between the critical values of parallel crack merged in the material 1 and 2 adjacent to the interface. The dynamic energy release rate is also obtained as a form related to the stress intensity factor.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.195.1-195.1
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• 2005

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.5
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• pp.632-639
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• 2014

Mechanical stress and the vacuum level are the two main factors dominating the quality factor of a resonator operated in the vacuum range 1 mTorr to 10 Torr. This means that if the quality factor of a resonator is very insensitive to the mechanical stress in the vacuum range, it is sensitive to mainly the ambient vacuum level. In this paper, a wafer-level packaged MEMS resonator with a highly vacuum-sensitive quality factor is presented. The proposed device is characterized by a package with out-of-plane symmetry and a suspending structure with only a single anchor. Out-of-plane symmetry helps prevent deformation of the packaged device due to thermal mismatch, and a single-clamped structure facilitates constraint-free displacement. As a result, the proposed device is very insensitive to mechanical stress and is sensitive to mainly the ambient vacuum level. The average quality factors of the devices packaged under pressures of 50, 100, and 200 mTorr were 4987, 3415, and 2127, respectively. The results demonstrated the high controllability of the quality factor by vacuum adjustment. The mechanical robustness of the quality factor was confirmed by comparing the quality factors before and after high-temperature storage. Furthermore, through more than 50 days of monitoring, the stability of the quality factor was also certified.

• Wind and Structures
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• v.11 no.5
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• pp.345-359
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• 2008

An experimental investigation of the flow over the rectangular body located in close proximity to a ground board was reported using the particle image velocimetry (PIV) technique. The present experiments were conducted in a closed-loop open surface water channel with the Reynolds number, $Re_H=1.2{\times}10^4$ based on the model height. In addition to the PIV measurements, flow visualization studies were also carried out. The PIV technique provided instantaneous and time-averaged velocity vectors map, vorticity contours, streamline topology and turbulent quantities at various locations in the near wake. In the vertical symmetry plane, the upperbody flow is separated from the sharp top leading edge of the model and formed a large reverse flow region on the upper surface of the model. The flow structure downstream of the model has asymmetric double vortices. In the horizontal symmetry plane, identical separated flow regions occur on both vertical side walls and a pair of primary recirculatory bubbles dominates the wake region.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.25 no.1
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• pp.50-63
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• 2016

Successful treatment in the anterior esthetic prosthetic can be a balance between aesthetics in the facial, tooth, and periodontal tissue in the oral. In the case of facial symmetry of patients with normal occlusal plane, If you establish criteria of finding balance of aesthetics such as a several books and articles and manufacture a prostheses by the established-criteria, you can manufacture a harmonious and aesthetic prostheses without any trouble. However, in the case of patients with facial asymmetry, if you manufacture a tooth as patient's facial aesthetic symmetry by force even facial asymmetry case, you can't get a result not only aesthetic but also functional prostheses. Also, to produce the prosthetic of harmonious and aesthetic with periodontal tissue, and excellent self-cleansing function, you must apply to the form of the prosthetic changed dental environment.

• Proceedings of the KSMRM Conference
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• 2002.11a
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• pp.133-133
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• 2002

Purpose： The purpose of paper is to implement software to visualize brain fiber tract using a 24-bit color coding scheme and to test its feasibility. Materials and Methods： MR imaging was performed on GE 1.5 T Signa scanner. For diffusion tensor image, we used a single shot spin-echo EPI sequence with 7 non-colinear pulsed-field gradient directions： (x, y, z)：(1,1,0),(-1,1,0),(1,0,1),(-1,0,1),(0,1,1),(0,1,-1) and without diffusion gradient. B-factor was 500 sec/$\textrm{mm}^2$. Acquisition parameters are as follows： TUTE=10000ms/99ms, FOV=240mm, matrix=128${\times}$128, slice thickness/gap=6mm/0mm, total slice number=30. Subjects consisted of 10 normal young volunteers (age：21∼26 yrs, 5 men, 5 women). All DTI images were smoothed with Gaussian kernel with the FWHM of 2 pixels. Color coding schemes for visualization of directional information was as follows. HSV(Hue, Saturation, Value) color system is appropriate for assigning RGB(Red, Green, and Blue) value for every different directions because of its volumetric directional expression. Each of HSV are assigned due to (r,$\theta$,${\Phi}$) in spherical coordinate. HSV calculated by this way can be transformed into RGB color system by general HSV to RGB conversion formula. Symmetry schemes： It is natural to code the antipodal direction to be same color(antipodal symmetry). So even with no symmetry scheme, the antipodal symmetry must be included. With no symmetry scheme, we can assign every different colors for every different orientation.(H =${\Phi}$, S=2$\theta$/$\pi$, V=λw, where λw is anisotropy). But that may assign very discontinuous color even between adjacent yokels. On the other hand, Full symmetry or absolute value scheme includes symmetry for 180$^{\circ}$ rotation about xy-plane of color coordinate (rotational symmetry) and for both hemisphere (mirror symmetry). In absolute value scheme, each of RGB value can be expressed as follows. R=λw｜Vx｜, G=λw｜Vy｜, B=λw｜Vz｜, where (Vx, Vy, Vz) is eigenvector corresponding to the largest eigenvalue of diffusion tensor. With applying full symmetry or absolute value scheme, we can get more continuous color coding at the expense of coding same color for symmetric direction. For better visualization of fiber tract directions, Gamma and brightness correction had done. All of these implementations were done on the IDL 5.4 platform.

• Geomechanics and Engineering
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• v.4 no.1
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• pp.19-37
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• 2012

This paper presents the results of analytical and numerical analyses of the effects of performing a pressuremeter test or driving a pile in clay. The geometry of the problem has been simplified by the assumptions of plane strain and axial symmetry. Pressuremeter testing or installation of driven piles has been modelled as an undrained expansion of a cylindrical cavity. Stresses, pore water pressures, and deformations are found by assuming that the clay behaves like normally consolidated modified Cam clay. Closed-form solutions are obtained which allow the determination of the principal effective stresses and the strains around the cavity. The analysis which indicates that the intermediate principal stress at critical state is not equal to the mean of the other two principal stresses, except when the clay is initially isotropically consolidated, also permits finding the limit expansion and excess pore water pressures by means of the Almansi finite strain approach. Results are compared with published data which were determined using finite element and finite difference methods.

• Journal of the Korean Mathematical Society
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• v.49 no.3
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• pp.475-491
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• 2012

In 1950 a class of generalized Petersen graphs was introduced by Coxeter and around 1970 popularized by Frucht, Graver and Watkins. The family of $I$-graphs mentioned in 1988 by Bouwer et al. represents a slight further albeit important generalization of the renowned Petersen graph. We show that each $I$-graph $I(n,j,k)$ admits a unit-distance representation in the Euclidean plane. This implies that each generalized Petersen graph admits a unit-distance representation in the Euclidean plane. In particular, we show that every $I$-graph $I(n,j,k)$ has an isomorphic $I$-graph that admits a unit-distance representation in the Euclidean plane with a $n$-fold rotational symmetry, with the exception of the families $I(n,j,j)$ and $I(12m,m,5m)$, $m{\geq}1$. We also provide unit-distance representations for these graphs.

• International Journal of Automotive Technology
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• v.6 no.3
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• pp.277-283
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• 2005

Formability simulation of automotive panels at early design phases can reduce product and tooling development time and cost. However, for the simulation to be effective in leading the design process, fast and reliable results should be achieved with limited design definition and minimum modeling effort. In this paper, nonlinear finite element analysis is used to develop an automated process for the formability simulation of automotive body panels at early design phases. Due to the limited design definition at early design phases, the automated simulation process is based on the plane strain analysis for selected number of typical sections along the panel. Therefore, an entire panel can be analyzed with few sections. The state of plane strain can be easily induced, during simulation through symmetry and applied boundary conditions that simplify the modeling process. To study the reliability and effectiveness of the developed simulation process, the analytical results are compared with measured results of production automotive body side panels. The comparison demonstrates that the developed simulation process is reliable and can be effective for analyzing sheet metal formability, in early vehicle development phases.