• Proceedings of the Materials Research Society of Korea Conference
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• 1995.11a
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• pp.89-89
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• 1995

• BioChip Journal
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• v.12 no.4
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• pp.280-286
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• 2018

Hydrogel scaffolds composed of multiple components are promising platform in tissue engineering as a transplantation materials or artificial organs. Here, we present a new fabrication method for implementing multi-layered macroscopic hydrogel scaffold composed of multiple components by controlling height of hydrogel layer through precise control of ultraviolet (UV) energy density. Through the repetition of the photolithography process with energy control, we can form several layers of hydrogel with different height. We characterized UV energy-dependent profiles with single-layered PEGDA posts photocrosslinked by the modular methodology and examined the optical effect on the fabrication of multi-layered, macroscopic hydrogel structure. Finally, we successfully demonstrated the potential applicability of our approach by fabricating various macroscopic hydrogel constructs composed of multiple hydrogel layers.

• Transactions of Materials Processing
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• v.22 no.1
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• pp.17-22
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• 2013

Tube hydroforming is a technology that utilizes hydraulic pressure to form a tube into desired shapes inside die cavities. Due to its advantages, such as weight reduction, increased strength, improved quality, and reduced tooling cost, single-layered tube hydroforming is widely used in industry. However in some special applications, it is necessary to produce multi-layered tubular components which have corrosion resistance, thermal resistance, conductivity, and abrasion resistance. In this study, a hollow forming process to fabricate a part from multi-layered tubes for structural purposes is proposed. To accomplish a successful hydroforming process, an analytical model that predicts optimal load path for various parameters such as tube material properties, thickness of tubes, diameter of holes and the number of holes was developed. Tubular hydroforming experiments to fabricate a hollow part were performed and the optimal loading path developed by the analytical model was successfully verified. The results show that the proposed hydroforming process can effectively produce hollow parts with multi-layered tube without defects such as wrinkling or fracture.

• Journal of Bio-Environment Control
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• v.29 no.4
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• pp.320-325
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• 2020

This study aimed to analyze thermo-keeping and economic feasibility by utilizing silica aerogel, which has been attracting attention as a new material, complementing the disadvantages of the conventional multi-layered thermal screen, and producing and installing multi-layered thermal screen. The multi-layered thermal screen used in the experiment was produced in two combinations using a non-woven fabric containing silica aerogel and measured and compared the temperature and fuel consumption changes due to differences in practice with the multi-layered thermal screen being sold and used on the market. Experimental results show that the temperature and relative humidity changes due to the differences of the multi-layered thermal screens in the single-span greenhouse and the multi-span greenhouse were small but remained almost the same temperature and relative humidity. It is judged that this shows that the multi-layered thermal screen using silica aerogel is not inferior to the conventional multi-layered thermal screen. As a result of a comparative analysis of heating energy, the aerogel-based multi-layered thermal screen reduced fuel consumption by about 15% in the single-span greenhouse and about 20% in the multi-span greenhouse compared to the conventional multi-layered thermal screen. It is clear that heating energy is saved as a greenhouse size and duration increase. It was found that the silica aerogel-based multi-layered screen was more breathable and warmer than the conventional multi-layered thermal screen, but It was found that the multi-layered screen used in the multi-span greenhouse was heavier and stiff compared with the conventional multi-layered thermal screen, indicating less workability and operability. Therefore, improvements were applied to the multi-layered screens used in the single-span greenhouses. It was confirmed that the replacement of internal insulation materials reduced thickness and improved stiffness so that there could be sufficient possibility for farmers to use.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.322-323
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• 2008

Multi layered thin films with ZnS/$Na_3AlF_6$/ZnS were deposited on glass substrate by thermal evaporator precess and simulated by using EMP(Essential Macleod Program). EMP is a comprehensive software package to design and analyse the optical characteristics of multi-layered thin film. ZnS and $Na_3AlF_6$ were selected as a high refractive index and low refractive index material respectively. Additionally Cu was chosen as mid reflective material. Optical properties including color effect were systematically studied. in terms of different optical thickness of low refractive index material. The optical thickness of $Na_3AlF_6$ was changed as 0.25, 0.5, 0.75 and $1.0\lambda$. The film with 0.25, 0.5, 0.75 and $1.0\lambda$. of optical thickness showed mixed color range between bluish green and red purple, yellowish green and bluish green, purple and mixed color range of green and purple respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.231-231
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• 2010

Thermoelectric properties of a multi-layered thin film, which was composed with indium selenide and bismuth telluride, were investigated. The structure of the layered thin film is Bi-Te /In-Se/Bi-Te and it was prepared on sapphire substrate by RF magnetron sputter using stoichiometric $Bi_2Te_3$ (99.9%) and $In_2Se_3$(99.99%) target at room temperature. Then, it was annealed at temperature range of 150 - $500^{\circ}C$ in Ar ambient. Structural characterizations were done using X-ray diffraction(XRD, BRUKER, D8, 60kW) and transmission electron microscopy (TEM, FEI, Tecnai, F30 S-Twin), respectively. Cross-section of multi-layer structure was observed by Scanning electron microscopy (SEM). The resistivity and Seebeck coefficient of these samples were also measured by conventional equipment at room temperature. The maximum value of power factor was $1.16\;{\mu}W/k^2m$ at annealing temperature of $400^{\circ}C$.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.155-158
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• 2004

In resin transfer molding, the preform similar to product shape is placed into a mold cavity. Rapid flow front without void formation is important for the composites processing. Multi-layered preform of sandwich is selected. Experiments is carried out using redial flow. An analytical modeling is performed and compared with experimental results. Accurate prediction of flow advance in the preform is of use for reducing the time consumption in the process and enhancing product properties of the final part.

• The Journal of the Acoustical Society of Korea
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• v.41 no.4
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• pp.375-388
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• 2022

This paper deals with the process of obtaining sound transmission loss of a cylindrical silencer lined with multi-layered poroelastic sound absorbing materials. The Biot model and the Johnson-Champoux-Allard-Lafarge (JCAL) model were used to deal with waves propagating in multi-layered poroelastic materials. The boundary conditions required for analysis of the silencer were obtained and the numerical process of finding modes was explained. A numerical experiment was conducted on the 2-layered silencer using the modes and the transmission loss converged with the first 12 modes. Finally, the mode matching method proposed in this research was validated by being compared with the results calculated from Finite Element Method (FEM) about different kinds of sound absorbing materials.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.882-887
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• 2001

This paper deals with the effect of mass-spring-mass resonance that is a characteristics of the multi-layered panels in order to enhance sound insulation performance. From theoretical and experimental investigation, it is evident that tuning mass-spring-mass resonance by controlling elastic modulus of the core materials is very important to improve the STC value without increasing the weight of panels, resulting in enhancing STC value more than 10 dB.

• Journal of Magnetics
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• v.7 no.2
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• pp.45-50
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• 2002

A magnetic field annealing is firstly used for nanostructured Sm-Co/Co films, prepared by magnetron sputtering method. The effects of magnetic field annealing on single-layered Sm-Co films are different from those on multi-layered Sm-Co/Co films. A detailed analysis of microstructures and magnetic properties is made by means of HRTEM, Auger electron spectroscopy, XRD and Physical Property Measurement System (PPMS). From magnetic properties and microstructure analysis, it was confirmed that these differences originate from the effects of magnetic field annealing on crystallization behavior of the films. The relationship between magnetic properties and microstructures explains a different demagnetization process of single-layered and multilayered films. For the single-layered Sm-Co films, magnetic-field-annealing makes the main phases change from $CaCu_5/ to Zn_2Th_{17}$ structure, resulting in a decrease of coercivity. The results show that the magnetic-field-annealing is useful to improve the properties of nanostructured Sm-Co(30 nm)/Co(10 nm) films, which ascribe to improving the pinning effectiveness in coercivity mechanism and decreasing the magnetostatic interaction of films. A very high coercivity about 0.7 T was obtained from nanoscaled multi-layered Sm-Co(30 nm)-/Co(10 nm) films.