• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1456-1462
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• 2008

This study conducted a direct shear test to evaluate friction properties on contact surface of waste resources including turban shell, gastropod shell and PET bottle film. The contact surface that was considered for computation of shear strength in contact surface were turban shell/turban shell, gastropod shell/gastropod shell, and PET bottle film/PET bottle film. As a result of test, friction angle was found to be $16.7^{\circ}$ for contact surface of turban shell/turban shell, $35.4^{\circ}$ for gastropod shell/gastropod shell, and about $11^{\circ}$ for PET bottle film/PET bottle film. Using the results, the author aims to provide a possibility for application of waste resource in the field.

• 한국기계가공학회지
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• 제19권2호
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• pp.47-54
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• 2020

Themo-mechanical analysis was carried out using the finite element method for the steel shell of a cupola furnace. When the outer surface of the shell was cooled with water to within the temperature range of 35-80 ℃ during operation of the cupola, the inner surface of the shell was expected to exhibit a temperature of 65-248 ℃ based on heat transfer analysis. The shell was also expected to have an equivalent stress range of 100-280 MPa in the outer surface over the temperature range examined. Upon cooling the shell to obtain an outer surface temperature <80 ℃, the maximum equivalent stress of the shell did not exceed the yield strength. Although the temperature of the outer surface varied between 35 and 80 ℃ periodically due to the cooling control problem, the fatigue stress at the outer surface of the shell was calculated to be within the fatigue strength. During a non-operational period to examine the system between furnace operations, the thermal stress presented in the shell was sufficiently low to reach the desired yield strength and fatigue limit.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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• pp.295-302
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• 2001

In the present study, we propose the framework which directly links shell finite element to the surface geometric modeling. For the development of a robust shell element, partial mixed variational functional is provided. The NURBS is used to generate the general free form of parameterized shell surfaces. Employment of NURBS makes shell finite element handle the arbitrary geometry of the smooth shell surfaces. The proposed shell finite element model linked with NURBS surface representation provides efficiency for design and analysis and can be directly extended to surface shape optimization problems in future work.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.505-511
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• 2002

In the present study, we visualize the linkage framework between geometric modeling and shell finite element based on B-spline representation. For the development of a consistent shell element, geometrically exact shell elements based on general curvilinear coordinates is provided. The NUBS(Non Uniform B-Spline) is used to generate the general free form shell surfaces. Employment of NUBS makes shell finite element handle the arbitrary geometry of the smooth shell surfaces. The proposed shell finite element .model linked with NUBS surface representation provides efficiency for the integrated design and analysis of shell surface structures. The linkage framework can potentially provide efficient integrated approach to the shape topological design optimizations for shell structures.

• 대한기계학회논문집A
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• 제31권1호
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• pp.105-112
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• 2007

The linkage framework of geometric modeling based on NURBS(Non-Uniform Rational B-Spline) surface and shell finite analysis is developed in the present study. For this purpose, geometrically exact shell finite element is implemented. NURBS technology is employed to obtain the exact geometric quantities for the analysis. Especially, because NURBS is the most powerful and wide-spread method to represent general surfaces in the field of computer graphics and CAD(Computer Aided Design) industry, the direct computation of surface geometric quantities from the NURBS surface equation without approximation shows great potential for the integration between geometrically exact shell finite element and geometric modeling in the CAD systems. Some numerical examples are given to verify the performance and accuracy of the developed linkage framework. In additions, trimmed surfaces with some cutouts are considered for more practical applications.

• 한국세라믹학회지
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• 제40권9호
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• pp.902-908
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• 2003

Au/TiO$_2$ core-shell 구조 나노 미립자가 졸-겔법에 의해서 제조되었고, TiO$_2$ shell의 형상과 결정성이 TEM과 UV-Vis. absorption spectrometer에 의해서 조사되었다. Au/TiO$_2$ core-shell 나노 미립자는 Au 콜로이드 에탄올 수용액 중에서 TOAA(Titanium Oxide Acethylacetonate)의 가수분해에 의해 합성될 수 있었다. Au 나노 미립자의 표면에 형성된 TiO$_2$ shell의 두께는 약 1 nm이었다. TiO$_2$ shell의 결정성을 조사하기 위하여. TiO$_2$가 피복된 Au 콜로이드 에탄올 용액에 254 nm의 자외선과 $^{60}$Co의 방사선을 조사하였다. Au 나노 미립자의 surface plasmon 현상은 방사선이 조사되었을 때만 나타났고, 이 결과로부터 TiO$_2$ shell은 비정질 상태임을 알 수 있었으며, Au의 분산성 향상을 위해 표면에 처리된 MUA(Mercaptoundecanoic Acid)층은 전자의 이동을 방해하는 장애물로 작용하지 않음을 확인할 수 있었다.

• 한국재료학회지
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• 제20권1호
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• pp.1-6
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• 2010

Geopolymer materials are attractive as inorganic binders due to their superior mechanical and eco-friendly properties. In the current study, geopolymer-based cement was prepared using aluminosilicate minerals from fly-ash with KOH as an alkaline-activator and $Na_2SiO_3$ as liquid glass. Then, calcium carbonate powder from a clam shell was mixed with the geopolymer and the mixture was coated on a concrete surface to provide points of attachment for environmental organisms to grow on the geopolymers. We investigated the effect of the shell powder grain size on the microstructure and bonding property of the geopolymers. A homogeneous geopolymer layer coated well on the concrete surface via aluminosilicate bonding, but the adhesiveness of the shell powder on the geopolymer cement was dependent on the grain size of the shell powder. Superior adhesive characteristics were shown in the shell powder of large grain size due to the deep penetration into the geopolymer by their large weight. This kind of coating can be applied to the adhesiveness of eco-materials on the surface of seaside or riverside blocks.

• 한국염색가공학회지
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• 제15권4호
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• pp.65-72
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• 2003

Poly(ethylene-co-vinylacetate) (EVA) microspheres were prepared by a thermally induced phase separation. Poly(vinyl Alcohol) (EVAL) microsphere with Core-Shell Structure were synthesized by a saponification on sheath of EVA microspheres. The size of EVA core/EVAL shell microsphere was decreased from $4.09\mu{m}\;to\;2.55\mu{m}$ by partial saponification of $NaOH/Na_2SO_4$/methanol(2 : 1 : 1 by weight) at $60^\circ{C}$ for 4h to produce a saponified surface layer of about 60% of original radius. In this process, the surface layer of EVAL microsphere was dissolved partially and morphology of surface was not showed. Add-on of cotton and silk printed with EVA core/EVAL shell microsphere was increased and that of printed PET was decreased. In case of EVA core/EVAL shell microsphere, Hand of cotton and silk printed was flexible and fullness.

• Smart Structures and Systems
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• 제25권6호
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• pp.643-655
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• 2020

Active control of nonlinear vibration of stiffened functionally graded (SFG) cylindrical shell is studied in this paper. The system is subjected to axial and transverse periodic loads in the presence of thermal uncertainty. The material composition is considered to be continuously graded in the thickness direction, also these properties depend on temperature. The relations of strain-displacement are derived based on the classical shell theory and the von Kármán equations. For modeling the stiffeners on the cylindrical shell surface, the smeared stiffener technique is used. The Galerkin method is used to discretize the partial differential equations of motion. Some comparisons are made to validate the SFG model. For suppression of the nonlinear vibration, the linear and nonlinear control strategies are applied. For control objectives, the piezoelectric actuator is attached to the external surface of the shell and the thin ring piezoelectric sensor is attached to the middle internal surface of shell. The effect of PID, feedback linearization and sliding mode control on the suppression of vibration for SFG cylindrical shell is presented.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.794-801
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• 2006

The linkage framework of geometric modeling and analysis based on the NURBS technology is developed in this study. The NURBS surfaces are generated by interpolating the given set of data points or by extracting the necessary information to construct the NURBS surface from the IGES format file which is generated by the commercial CAD systems in the present study. Numerical examples shows the rate of displacement convergence according to the paramterization methods of the NURBS surface. NURBS can generate quadric surfaces in an exact manner. It is the one of the advantages of the NURBS. A trimmed NURBS surface that is often encountered in the modeling process of the CAD systems is also presented in the present study. The performance of the developed geometrically exact shell element integrated with the exact geometric representations by the NURBS equation is compared to those of the previous reported FE shell elements in the selected benchmark problems.