• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3286-3288
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• 1999

The electrostatically actuated test structure was presented to measure the micro mechanical characteristics of micromaterials as thin films forming the microactuators. The test structure was fabricated by the surface micromachining processes and driven by the electrostatic force, In order to measure the fracture toughness, the sharp notch in the test structure was introduced by the etching process. On the basis of the beam bending theory, the elastic modulus was measured by using the microcantilevr beam and the mechanical displacement, curvature and deflection curve under the electrostatic force was evaluated by using the electrostatic structure.

• Asian Journal of Atmospheric Environment
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• v.10 no.2
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• pp.114-123
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• 2016

A change in chemical compositions of Asian dust (AD) particles can dramatically alter their optical properties, cloud-forming properties, and health effects. The present study was undertaken to evaluate this aging of AD particles by means of two complementary methods (i.e., the traditional spot test and the most advanced micro-PIXE analytical technique) for single particle analysis. Size-classified particles were sampled at the rural peninsula of Korea (Byunsan, 35.37N; 126.27E) during AD event and non-AD period in 2004. Sulfate was principally enriched on the particles in the size range of $7.65-10.85{\mu}m$ collected during AD event. The average number fraction of coarse particles ($>2.05{\mu}m$) containing chloride was 16.2% during AD event. Relatively low particles containing nitrate compared to those containing sulfate and chloride were found in AD event. Micro-PIXE elemental maps indicated that a large number of AD particles were internally mixed with man-made zinc. The highest peaks of EC and OC concentrations were appeared at $0.01-0.43{\mu}m$ particle aerodynamic diameter. High EC concentration in $PM_1$ was might be caused by the Saemangeum Seawall Project that was being conducted during our field measurement.

• Journal of Energy Engineering
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• v.26 no.2
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• pp.73-79
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• 2017

In nucleation assisted crystallization process formed $CO_2$ leaves as colloid gas and is used as the template by the rapidly growing crystals in the nucleation site. This emulsion of $CaCO_3$ micro-crystals & $CO_2$ micro-bubbles forms hollow particles. Formed hollow particles are double walled, both internal and external faces belonging to the cleavage aragonites which separate the surrounding water from the enclosed gas cavity. Hence, the reverse reaction of $CO_2$ with water forming Carbonic Acid is not possible and the pH stability is maintained. In fact every excess $CaCO_3$ crystals are buffering any carbonic acid left over. This $CO_2$ based nucleation technology prevents scale formation in water channels, but it also helps to reduce the previously formed scales. This process takes out water dissolved $CO_2$ in almost-visible micro-bubbles forms that helps reducing previously formed scale over a period of time (depends on the usage period). The aragonite crystals can't form scale because of its stable molecular structure and neutral surface electro potentiality.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.6
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• pp.577-585
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• 2015

We fabricated multi-scale such as macro-, micro-, and multi-scale wrinkles by using repetitive volume dividing (RVD) method and thermal curing process. Also wrinkle surface was modified with coating of a self-assembled monolayer (SAM). We measured the contact angle of each wrinkled surface, and observed the behavior of droplets on sloping surface. Through experimental study, we found out that the contact angle was much higher in case of multi-scale and SAM coated wrinkles. And micro-scale wrinkle showed a high contact angle comparing with that of macro-scale wrinkle. Dynamic behaviors of a water droplet like sliding velocity on diverse wrinkled surfaces were dependent on their static contact angles. These results showed that hydro-dynamic characteristics were changed depending on the wrinkle structure and the material forming the wrinkle. These dynamic characteristics can be utilized in bio-chip, microfluidics, and many others in order to control easily chemical reactivity.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.61-67
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• 2006

Sandwich structures, which are composed of a thick core between two faces, are commonly used in many engineering applications because they combine high stiffness and strength with low weight. Accordingly, the usage of sandwich structure is very widely applied to the aircraft, the automobile and marine industry, etc., because of these advantages. In this paper, we have investigated the buckling protection of an inner structure plate and the useful corrugated configuration for contact, and the fabrication method of the inner structure plate for large area using the continuous molding process. Also, we have guaranteed the accuracy of the molding process through the micro corrugated mold fabrication and secured the accuracy and analyzed aspect properties of the inner structure plate fabricated for a large area using the partial mold process. We have compared molding simulation according to the aspect thickness of the corrugated configuration with the molding experiment results.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.378.1-378.1
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• 2014

In this study, we investigated that the resistance switching characteristics of Nb-doped HfO2 films with increasing Nb doping concentration. The Nb-doped HfO2 based ReRAM devices with a TiN/Nb-doped HfO2/Pt/Ti/SiO2 were fabricated on Si substrates. The Nb-doped HfO2 films were deposited by reactive dc magnetron co-sputtering at $300^{\circ}C$ and oxygen partial ratio of 60% (Ar: 16sccm, O2: 24sccm). Microstructure of Nb-doped HfO2 films and atomic concentration were investigated by XRD, TEM, and XPS, respectively. The Nb-doped HfO2 films showed set/reset resistance switching behavior at various Nb doping concentrations. The process voltage of forming/set is decreased and whereas the initial current level is increased in doped HfO2 films. However, the switching properties of Nb-doped HfO2 were changed above the specific doping concentration of Nb. The change of resistance switching behavior depending on doping concentration was discussed in terms of concentration of non-lattice oxygen and micro-structure of Nb-doped HfO2.

• Journal of the Korean Solar Energy Society
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• v.40 no.4
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• pp.23-33
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• 2020

The loss in photovoltaic power due to hailstorms has been highlighted as a major issue in the sustained growth of the PV power plant industry. This study investigates the safety of a solar module by conducting a numerical analysis of a hail test according to the IEC 61215 standard. Our study aims to elucidate the detailed behavior between the ice and solar modules and the micro-cracks forming on solar modules during hailstorms. To analyze the impact of hail, we used the ANSYS AUTODYN software to evaluate the impact characteristics on a solar module with different front glass thicknesses. The simulations show that a solar module with a glass thickness of 4.0 mm results in excellent durability against hail. The results indicate the feasibility of using simulations to analyze and predict micro-cracks on solar modules tailored to various conditions, which can be used to develop new solar modules.

• The Journal of the Korea Contents Association
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• v.9 no.6
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• pp.17-24
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• 2009

This paper proposes a new e-learning model which introduces a participant method based on concepts of open source as well as UCC of web2.0 and achieves learner-centered learning. It is possible for learner to participate actively in creation of micro-contents and reorganize contents using various micro-content with one's learning strategies in consideration of one's own intellectual power, learning objectives and propensity to learn. The learner can achieve the learner-oriented learning through this procedure and select micro-contents in order to reorganize the personalized learning contents to take advantage of social network among learners. The higher effectiveness of learning would be expected by forming connectedness among learners using social network.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.423-424
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• 2009

• Korean Journal of Metals and Materials
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• v.50 no.4
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• pp.316-323
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• 2012

The aim of this study is to investigate the effect of post heat treatment on bonding properties of roll cladded Ti/MS/Ti materials. First grade Ti sheets and SPCC mild steel sheets were prepared and then Ti/MS/Ti clad materials were fabricated by a cold rolling and post heat treatment process. Microstructure and point analysis of the Ti/MS interfaces were performed using the SEM and EDX Analyser. Diffusion bonding was observed at the interfaces of Ti/MS. The thickness of the diffusion layer increased with post heat treatment temperature and the diffusion layer was verified as having $({\epsilon}+{\zeta})+({\zeta}+{\beta}-Ti)$ intermetallic compounds at $700^{\circ}C$ and an $({\zeta}+{\beta}-Ti)$ intermetallic compound at $800^{\circ}C$, respectively. The micro Knoop hardness of mild steel decreased with post heat treatment temperature; however, those of Ti decreased at a range of $500{\sim}600^{\circ}C$ and showed a uniform value until $800^{\circ}C$ and then increased rapidly up to $900^{\circ}C$. The micro Knoop hardness value of the diffusion layer increased up to $700^{\circ}C$ and then saturated with post heat treatment. A T-type peel test was used to estimate the bonding forces of Ti/Mild steel interfaces. The bonding forces decreased up to $800^{\circ}C$ and then increased slightly with post heat treatment. The optimized temperature ranges for post heat treatment were $500{\sim}600^{\circ}C$ to obtain the proper formability for an additional plastic deformation process.