• Multiscale and Multiphysics Mechanics
• /
• v.1 no.3
• /
• pp.225-231
• /
• 2016

The formation of silicon-on-nothing (SON) structure during an annealing process from the silicon substrate including the trench structures has been considered as an effective technique to construct the structure that has an empty space under the closed flat surface. Previous studies have demonstrated the mechanism of the formation of SON structure, which is based on the surface diffusion driven by the minimization of their surface energy. Also, it has been fragmentarily shown that the morphology of SON structure can be affected by the initial design of trench (e.g., size, number) and the annealing conditions (e.g., temperature, pressure). Based on the previous studies, here, we report a comprehensive study for the design of the cavity-embedded structure (i.e., SON structure). To do this, a dynamic model has been developed with the phase field approach. The simulation results represent that the morphology of SON structures could be detailedly designed, for example the position and thickness of cavity, the thickness of top and bottom layer, according to the design parameters. This study will give us an advantage in the effective design of SON structures.

• Multiscale and Multiphysics Mechanics
• /
• v.1 no.1
• /
• pp.53-64
• /
• 2016

Amyloid fibrils have recently been considered as an interesting material, since they exhibit the excellent mechanical properties such as elastic modulus in the order of 10 GPa, which is larger than that of other protein materials. Despite recent findings of these excellent mechanical properties for amyloid fibrils, it has not been fully understood how these excellent mechanical properties are achieved. In this work, we have studied the nanomechanical deformation behaviors and properties of amyloid fibrils such as their elastic modulus as well as fracture strength, by using atomistic simulations, particularly steered molecular dynamics simulations. Our simulation results suggest the important role of the length of amyloid fibrils in their mechanical properties such that the fracture force of amyloid fibril is increased when the fibril length decreases. This length scale effect is attributed to the rupture mechanisms of hydrogen bonds that sustain the fibril structure. Moreover, we have investigated the effect of boundary condition on the nanomechanical deformation mechanisms of amyloid fibrils. It is found that the fracture force is critically affected by boundary condition. Our study highlights the crucial role of both fibril length and boundary condition in the nanomechanical properties of amyloid fibrils.

• Journal of Powder Materials
• /
• v.26 no.2
• /
• pp.119-125
• /
• 2019

Piezoelectric energy harvesting technology is attracting attention, as it can be used to convert more accessible mechanical energy resources to periodic electricity. Recent developments in the field of piezoelectric energy harvesters (PEHs) are associated with nanocomposites made from inorganic piezoelectric nanomaterials and organic elastomers. Here, we used the $BaTiO_3$ nanoparticles and piezoelectric poly(vinylidene fluoride) (PVDF) polymeric matrix to fabricate the nanocomposites-based PEH to improve the output performance of PEHs. The piezoelectric nanocomposite is produced by dispersing the inorganic piezo-ceramic nanoparticles inside an organic piezo-polymer and subsequently spin-coat it onto a metal plate. The fabricated organic-inorganic piezoelectric nanocomposite-based PEH harvested the output voltage of ~1.5 V and current signals of ~90 nA under repeated mechanical pushings: these values are compared to those of energy devices made from non-piezoelectric polydimethylsiloxane (PDMS) elastomers and supported by a multiphysics simulation software.

• Geomechanics and Engineering
• /
• v.16 no.5
• /
• pp.503-512
• /
• 2018

Globally there is an increasing need to reduce the greenhouse gas emissions and increase the use of renewable sources of energy. The storage of solar thermal energy is a crucial aspect for implementing the solar energy for space heating in high latitudes, where solar insolation is high in summer and almost negligible in winter when the domestic heating demand is high. To use the solar heating during winter thermal energy storage is required. In this paper, equations representing the single U-tube heat exchanger are implemented in weak form edge elements in COMSOL Multiphysics(R) to speed up the calculation process for modelling of a borehole storage layout. Multiple borehole seasonal solar thermal energy storage scenarios are successfully simulated. After 5 years of operation, the most efficient simulated borehole pattern containing 168 borehole heat exchangers recovers 69% of the stored seasonal thermal energy and provides 971 MWh of thermal energy for heating in winter.

• Journal of the Korean institute of surface engineering
• /
• v.52 no.3
• /
• pp.171-179
• /
• 2019

We have developed a numerical model to analyze flow dynamics and heat transfer characteristics of the cooling water in a circular rotating magnetron cathode by a moving boundary grid method realized in a commercial multiphysics package, CFD-ACE+. The numerical model is composed of a target, dual mass rotating cathode and cooling water connections. When the inlet and outlet of the cooling water are offset by the same distance from the rotation axis, the temperature at the center is higher by $50^{\circ}C$ at maximum. At 5 mm away from the target surface, the temperature profile showed typical center high characteristic. At heat input of 30 kW, the maximum temperature change of the cooling water hits $6^{\circ}C$ within 0.5 sec under 60 rpm. With a cooling water configuration of center in/edge out, the temperature of the center region of the target gets lowered. Within 100 seconds of plasma operation time, the cooling water temperature keeps getting higher.

• The Korean Journal of Physiology and Pharmacology
• /
• v.23 no.5
• /
• pp.295-303
• /
• 2019

A heart simulator, UT-Heart, is a finite element model of the human heart that can reproduce all the fundamental activities of the working heart, including propagation of excitation, contraction, and relaxation and generation of blood pressure and blood flow, based on the molecular aspects of the cardiac electrophysiology and excitation-contraction coupling. In this paper, we present a brief review of the practical use of UT-Heart. As an example, we focus on its application for predicting the effect of cardiac resynchronization therapy (CRT) and evaluating the proarrhythmic risk of drugs. Patient-specific, multiscale heart simulation successfully predicted the response to CRT by reproducing the complex pathophysiology of the heart. A proarrhythmic risk assessment system combining in vitro channel assays and in silico simulation of cardiac electrophysiology using UT-Heart successfully predicted drug-induced arrhythmogenic risk. The assessment system was found to be reliable and efficient. We also developed a comprehensive hazard map on the various combinations of ion channel inhibitors. This in silico electrocardiogram database (now freely available at http://ut-heart.com/) can facilitate proarrhythmic risk assessment without the need to perform computationally expensive heart simulation. Based on these results, we conclude that the heart simulator, UT-Heart, could be a useful tool in clinical medicine and drug discovery.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.24 no.5
• /
• pp.365-371
• /
• 2019

This study shows the feasibility of the parameter of the 1st RC parallel equivalent circuit as a factor of the heat generation of lithium-ion cell. The internal resistance of a lithium-ion cell consists of ohmic and polarization resistances. The internal resistances at various SOCs of the lithium-ion cell are obtained via an electrical characteristic test. The internal resistance is inversely obtained through the amount of heat generated during the experiment. By comparing the resistances obtained using the two methods, the summation of ohmic and polarization resistances is identified as the heating factor of lithium-ion battery. Finally, the amounts of heat generated from the 2C, 3C, and 4C-rate discharge experiments and the COMSOL multiphysics simulation using the summation of ohmic and polarization resistances as the heating parameter are compared. The comparison shows the feasibility of the electrical parameters of the 1st RC parallel equivalent circuit as the heating factor.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.20 no.1
• /
• pp.103-109
• /
• 2021

Fine chips generated by machining have an impact on machine failure and quality of machined products, it is necessary to remove the chips, so the microchip collection and removal device by rotating conveyor belt with neodymium permanent magnets was developed. In this research, to solve the problem for reducing the existing microchips in the tank, a micro-chip removal device by rotating conveyor belt with neodymium permanent magnets developed. In the development of micro-chip removal device, 3D CATIA modeling was used, and the flow analysis and the electromagnetic force analysis were performed with COMSOL Multiphysics program. To evaluate the performance of the prototypes produced, design of experiments (DOE) is used to obtain the effect of neodymium conveyor movement speed on chip removal for the ANOVA analysis of recovered powders. An experiment was conducted to investigate the effect of the conveyor feed rate on the chip removal performance in detail. As a result of the experiment, it was confirmed that the slower the feeding speed of the fine chip removing device, the more efficient the chip removal.

• Current Applied Physics
• /
• v.18 no.11
• /
• pp.1235-1239
• /
• 2018

We present a novel process to fabricate three-dimensional (3D) metallic patterns from 3D printed polymeric structures utilizing different hygroscopic swelling behavior of two different polymeric materials. 3D patterns are printed with two different polymers as cube shape. The surface of the 3D printed polymeric structures is plated with nickel by an electroless plating method. The nickel patterns on the surface of the 3D printed cube shape structure are formed by removing sacrificial layers using the difference in the rate of hygroscopic swelling between two printing polymer materials. The hygroscopic behavior on the interfaced structure was modeled with COMSOL Multiphysics. The surface and electrical properties of the fabricated three-dimensional patterns were analyzed and characterized.

• Korean Journal of Materials Research
• /
• v.32 no.7
• /
• pp.313-319
• /
• 2022

Double-layer capacitors (DLCs) are developed with high surface electrodes to achieve a high capacitance value. In the present work, the initial bulk concentration of 1 mol/m³ and 3 mol /m³ are selected to show the consequential effects on the performance of a double-layer capacitor. A 1D model of COMSOL Multiphysics has been developed to analyze the electric field and potential in cell voltage, the electric displacement field and polarization induced by the field, and energy density in a double-layer structure. The electrostatics and the electric circuit modes in COMSOL are used to simulate the electrochemical processes in the double-layer structure. The analytical analysis of a double-layer capacitor with different initial bulk concentrations is investigated by using Poisson-Nernst-Plank equations. From the simulation results, the differential capacitance changes as a function of compact layer thickness and initial bulk concentration. The energy density varies with the differential capacitance and voltage window. The values of energy density are dominated by the interaction of ions in the solution and electrode surface.