• Journal of the Microelectronics and Packaging Society
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• v.30 no.3
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• pp.73-77
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• 2023

In this study, we developed a Multi-level FeRAM (Ferroelectrics random access memory) device utilizing different ferroelectric materials and analyzed its operation through C-V analysis using simulations. To achieve Multi-level operation, we proposed an MFM (Multi-Ferroelectric Material) structure by depositing two different ferroelectric materials with distinct properties horizontally on the same bottom electrode and subsequently adding a gate electrode on top. By analyzing C-V peaks based on the polarization phenomenon occurring under different voltage conditions for the two materials, we confirmed the feasibility of achieving Multi-level operation, where either one or both of the materials can be polarized. Furthermore, we validated the process for implementing the proposed structure using semiconductor fabrication through process simulations. These results signify the significance of the new structure as it allows storing multiple states in a single memory cell, thereby greatly enhancing memory integration.

• Journal of Hydrogen and New Energy
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• v.14 no.2
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• pp.122-130
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• 2003

Li/S 이차전지의 유황양극의 전기전도도를 향상시키고 유황이 충방전시 전해질내로 용출되는 것을 방지하기 위하여 multi-walled carbon nanotubes (MWNTs)를 thermal CVD 방법으로 제조하여 유황양극에 첨가하였다. 실험결과 첫 사이클에서 Li/S 이차전지의 방전용량은 485mAh/g-sulfur이었고, MWNT 첨가 이후에 유황양극의 cycle life와 rate-capability가 향상되는 것을 관찰할 수 있었다. 그러므로 MWNT는 polysulfide를 유황양극에 흡착시키는 동시에 good electric conductor로서 작용한다는 것을 알 수 있었다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.176-179
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• 2001

When the preform is composed of more than two layers with different in-plane permeability in resin transfer molding, effective average permeability should be determined for the flow analysis in the mold. The most frequently used averaging scheme is the weighted average scheme, but it does not account for the transverse flow between adjacent layers. A new averaging scheme is proposed predicting the effective permeability of the multi-layered preform, which accounts for the transverse flow effect. The new scheme is verified by measuring the effective permeability of the multi-layered preforms and the difference in each flow front position.

• Composites Research
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• v.15 no.5
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• pp.44-52
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• 2002

To study numerically the mechanical behaviors of advanced composite materials considering the microscopic phenomena as well as the macroscopic properties and behaviors, a multi-scale modeling and analysis by the mathematical homogenization method with the help of the finite element method(FEM) are reviewed. The hierarchical modeling strategy and the formulation are briefly described first to give some idea of the multi-scale framework. The latter half of this article focuses on the verification of the multi-scale analysis by the homogenization method in its applications to real advanced materials. The first example is the verification of the predicted macroscopic(homogenized) properties based on the microstructure of porous ceramics. In spite of the complexity of the random microstructure, the error between the predicted and the measured values was only 1%. Next, two applications to the process simulation of fiber reinforced polymer matrix composites are presented. The permeability characteristics are evaluated for sheared weave fabrics for resin transfer molding(RTM) simulation, and the thermoforming of FRTP sheet is analyzed considering the large deformation of the knit structure during the deep-draw forming was verified by comparison with the experimental results.

• Journal of the Korean Ceramic Society
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• v.39 no.7
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• pp.622-627
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• 2002

Multi-layer composites consisting of silicon nitride, silicon nitride-silicon carbide and boron nitride-alumina layers were prepared fly stacking the corresponding ceramic tapes. The composites demonstrated self-diagnostic capability and non-catastrophic failure behavior. The composites consisting of many thin layers exhibited high strength and stepwise increase of the electrical resistance during the flexure test. The strength of the composite with too thick silicon nitride layers was low and the electrical resistance was abruptly increased to the detection limit of the digital multi-meter during the test. An extensive crack branching was observed in the weak (BN + Al$_2$O$_3$)layer.

• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.832-836
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• 2003

Multi-layer ceramic composites were prepared by tape casting followed by hot pressing using silicon nitride layer with silicon nitride whiskers, silicon nitride layer with silicon carbide particles and boron nitride-alumina layer. The whiskers were aligned during the casting. As the whisker content of the silicon nitride layer was increased up to 10 wt％, the flexural strength of the multi-layer composite was increased. However, further increase of the whisker content in the layer resulted in a rapid decrease of the strength of the composite. The results suggest that the strength of multi-layer ceramic composite showing non-catastrophic failure behavior can be significantly improved by incorporating the aligned whiskers in the layers.

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.65-65
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• 2008

• Steel and Composite Structures
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• v.27 no.1
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• pp.27-33
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• 2018

In this study, a mixed-interpolated tensorial component 4 nodes method (MITC4) is treated as a numerical analysis model for topology optimization using multiple materials assigned within Reissner-Mindlin plates. Multi-material optimal topology and shape are produced as alternative plate retrofit designs to provide reasonable material assignments based on stress distributions. Element density distribution contours of mixing multiple material densities are linked to Solid Isotropic Material with Penalization (SIMP) as a design model. Mathematical formulation of multi-material topology optimization problem solving minimum compliance is an alternating active-phase algorithm with the Gauss-Seidel version as an optimization model of optimality criteria. Numerical examples illustrate the reliability and accuracy of the present design method for multi-material topology optimization with Reissner-Mindlin plates using MITC4 elements and steel materials.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.238-241
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• 2007

We present an innovative method of multi-physics application involving energetic materials. Energetic materials are related to reacting flows in extreme environments such as fires and explosions. They typically involve high pressure, hish temperature, strong non-linear shock waves, and high strain rate deformation of metals. We use an Eulerian methodology to address these problems. Our approach is naturally free from large deformation of materials that makes it suitable for high strain-rate multi-material interaction problems. Furthermore we eliminate the possible interface smearing by using the level sets. We have devised a new level set based tracking framework that can elegantly handle large gradients typically found in reacting gases and metals. We show several work-in-progress applications of our algorithm including the Taylor impact test, explosive venting and additional confined explosion problems of modem interest.

• Journal of the Korean housing association
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• v.11 no.1
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• pp.171-181
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• 2000

The purpose of the resent research is to investigate the characteristics of sound insulation at the circular voided concrete slab in the multi-housing. In order to do this research, the method for field measurement of floor impact sound level was used following the Korea Standard F2810-1996. For the multi-housing, three kinds of circular voided concrete slabs are used to measure the characteristics of sound insulation.The results are as follows; 1.The main factor affecting the characteristics of sound insulation at the circular voided concrete slab in the multi-housing is sound-absorbing materials in the circular tube. 2. The main factor to effect the difference of sound pressure level is circular tube in the concrete slab. 3. The forms of circular tubes effect the characteristics of sound insulation at the circular tube. 4. Sound Pressure Level resulting from the piping direction of circular tubes in little different to octave band level.More study will be needed about the depth and distance of sound insulation materials, and the components of sound insulation materials for the multi-housing.