• Journal of the Korea Concrete Institute
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• v.12 no.6
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• pp.43-50
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• 2000

In this paper, a new splicing method was applied to design the girder section of bridges with the span length of 25m, 30m, 35m, 40m and 45m. A U-type precast prestressed section was also determined for each bridge. Additionally, the sectional area, beam depth and Guyon's efficiency factor of the spliced U-type sections in each span were analyzed in comparison with the present I-type PSC bridges. As a result, in spite of an increase of 31%∼50% in the sectional areas compared with the I-type precast girders, the spliced U-type the beam depth of the spliced U-type girder was designed as 2,050 mm compared with the I-type precast girder of 2,600mm in a 40m span bridge. The sectional efficiency factors of the spliced U-type sections were analyzed as 0.76∼0.99. It shows that the spliced U-type sections ar of a superior structural efficiency in contrast to the average sectional efficiency factor of 0.66 value in the I-type girders.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.12 s.189
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• pp.80-87
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• 2006

Seals are usually made from elastomer, a kind of rubber, and it has the non-linearity and hyper-elasticity. U-type seals are used to prevent the leakage of internal fluid sealed in hydraulic actuator because they have more excellent performance than O-rings or rectangular seals. As a core part of hydraulic actuator, U-type seal gives much effect on performance and reliability of actuator. This study considers an NBR U-type seal under high pressure of a hydraulic actuator, and provides its deformation, stress-strain characteristic and contact force using the non-linear finite element analysis. Analysis results are compared with the experimental ones performed by the self-developed testing equipment. Verification result shows that this study presents a good application process for the effective design of U-type seals under high operation pressure.

• Bulletin of the Society of Naval Architects of Korea
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• v.17 no.2
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• pp.33-42
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• 1980

This paper compared the seakeeping quality of U, V type ships in infinite depth by using the finite element method. From the calculated results, it is found that heaving and pitching motions of V type are comparatively better than those of U type ship in the water of infinite depth and the reversed phenomenon occures in the water of finite depth. And the seakeeping quality of U type is better than V type ship in larger ranges than the nondimensional wave number 2.0.

• East Asian mathematical journal
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• v.32 no.1
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• pp.117-128
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• 2016

In this paper, we study the viscoelastic Kirchhoff type equation with a nonlinear source $$u^{{\prime}{\prime}}-M(x,t,{\parallel}{\bigtriangledown}u(t){\parallel}^2){\bigtriangleup}u+{\int}_0^th(t-{\tau})div[a(x){\bigtriangledown}u({\tau})]d{\tau}+{\mid}u{\mid}^{\gamma}u=0$$. Under the smallness condition with respect to Kirchhoff coefficient and the relaxation function and other assumptions, we prove the uniform decay rate of the Kirchhoff type energy.

• Archives of Metallurgy and Materials
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• v.65 no.4
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• pp.1287-1291
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• 2020

The U-type ferrite is a kind of hexagonal ferrite, and it is known as a microwave absorber in the X-band. The magnetic and dielectric loss of the U-type ferrite change to the composition and coating layer, etc. In this study, the silicon oxide layer was coated on the substituted U-type ferrites to improve microwave absorption characteristics. The complex permittivity and complex permeability were measured using toroidal specimens that were press-molded and the measured frequency range was set from 2-18 GHz. The improvement of the microwave absorption rate was different according to the type of the substituted U-type ferrites. Only in the substituted U-type ferrites with nickel and zinc, an improvement in the microwave absorption rate due to enhancement of magnetic loss was confirmed. The highest microwave absorption was 99.9% at 9.6 GHz, which was S_Z_0.5U.

• East Asian mathematical journal
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• v.32 no.5
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• pp.659-675
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• 2016

In this paper, we study the generalized Kirchhoff type equation in the presence of past and finite history $$\large u_{tt}-M(x,t,{\tau},\;{\parallel}{\nabla}u(t){\parallel}^2){\Delta}u+{\normalsize\displaystyle\smashmargin{2}{\int\nolimits_0}^t}\;h(t-{\tau})div[a(x){\nabla}u({\tau})]d{\tau}\\\hspace{25}-{\normalsize\displaystyle\smashmargin{2}{\int\nolimits_{-{\infty}}}^t}\;k(t-{\tau}){\Delta}u(x,t)d{\tau}+{\mid}u{\mid}^{\gamma}u+{\mu}_1u_t(x,t)+{\mu}_2u_t(x,t-s(t))=0.$$ Under the smallness condition with respect to Kirchhoff coefficient and the relaxation function and other assumptions, we prove the expoential decay rate of the Kirchhoff type energy.

• East Asian mathematical journal
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• v.32 no.3
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• pp.399-412
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• 2016

In this paper, we study the viscoelastic Kirchhoff type equation with the following nonlinear source and time-varying delay $$u_{tt}-M(x,t,{\parallel}{\nabla}u(t){\parallel}^2){\Delta}u+{\int_{0}^{t}}h(t-{\tau})div[a(x){\nabla}u({\tau})]d{\tau}\\+{\parallel}u{\parallel}^{\gamma}u+{\mu}_1u_t(x,t)+{\mu}_2u_t(x,t-s(t))=0.$$ Under the smallness condition with respect to Kirchhoff coefficient and the relaxation function and other assumptions, we prove the uniform decay rate of the Kirchhoff type energy.

• Journal of the Korean Vacuum Society
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• v.15 no.3
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• pp.241-245
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• 2006

In this study, the characteristics of large area internal linear ICP sources of 1020mm X 920mm(substrate area is 880 X 660mm) were investigated using two different types of antenna, that is, a conventional serpentine-type antenna and a newly developed multiple U-type antenna. The multiple antenna showed a higher plasma density, a higher radical density, and more plasma stability compared to the serpentine-type antenna, and it appeared from the higher inductively coupling and less standing wave effect compared to the serpentine-type antenna. Using the multiple U-type antenna, the plasma density of $2\times10^{11}/cm^3$ with the plasma uniformity of 4% could be obtained using 15mTorr Ar and 5000W of RF power.

• Journal of the Korean Mathematical Society
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• v.58 no.6
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• pp.1327-1345
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• 2021

In this paper, we are concerned with a Liouville-type result of the nonlinear integral equation of Chern-Simons-Higgs type $$u(x)=\vec{\;l\;}+C_{\ast}{{\displaystyle\smashmargin{2}{\int\nolimits_{\mathbb{R}^n}}}\;{\frac{(1-{\mid}u(y){\mid}^2){\mid}u(y){\mid}^2u(y)-\frac{1}{2}(1-{\mid}u(y){\mid}^2)^2u(y)}{{\mid}x-y{\mid}^{n-{\alpha}}}}dy.$$ Here u : ℝⁿ → ℝ^k is a bounded, uniformly continuous function with k ⩾ 1 and 0 < α < n, $\vec{\;l\;}{\in}\mathbb{R}^k$ is a constant vector, and C_* is a real constant. We prove that ${\mid}\vec{\;l\;}{\mid}{\in}\{0,\frac{\sqrt{3}}{3},1\}$ if u is the finite energy solution. Further, if u is also a differentiable solution, then we give a Liouville type theorem, that is either $u{\rightarrow}\vec{\;l\;}$ with ${\mid}\vec{\;l\;}{\mid}=\frac{\sqrt{3}}{3}$, when |x| → ∞, or $u{\equiv}\vec{\;l\;}$, where ${\mid}\vec{\;l\;}{\mid}{\in}\{0,1\}$.

• Bulletin of the Korean Mathematical Society
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• v.49 no.1
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• pp.135-143
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• 2012

We present two kinds of construction methods for self-dual codes over $\mathbb{F}_2+u\mathbb{F}_2$. Specially, the second construction (respectively, the first one) preserves the types of codes, that is, the constructed codes from Type II (respectively, Type IV) is also Type II (respectively, Type IV). Every Type II (respectively, Type IV) code over $\mathbb{F}_2+u\mathbb{F}_2$ of free rank larger than three (respectively, one) can be obtained via the second construction (respectively, the first one). Using these constructions, we update the information on self-dual codes over $\mathbb{F}_2+u\mathbb{F}_2$ of length 9 and 10, in terms of the highest minimum (Hamming, Lee, or Euclidean) weight and the number of inequivalent codes with the highest minimum weight.