Predicting the hydrodynamic load on a body entering the water is important in the field of marine engineering. When a ship moves in water, water entry adversely affects ship motion and can even damage the ship structure.

Therefore, water entry problems have been widely investigated with experimental, theoretical and numerical methods.

According to preceding researches, however, the moving particle semi-implicit (MPS) method has not been widely applied to water entry problems.

Pak Chol Jun, a researcher at the Faculty of Naval Architecture and Ocean Engineering, has investigated hydrodynamic load acting on a two-dimensional (2D) wedge during water entry by means of the widely-used moving particle semi-implicit (MPS) method.

First, he proposed two techniques for enhancing the performance of MPS and a symmetry domain technique for reducing the computational cost. Additionally, he proposed a fluid–solid coupling algorithm using the MPS method.

The comparison results to verify the accuracy of the proposed techniques show that the MPS with the proposed schemes can provide reliable numerical prediction for water entry problems.

For further details, you can refer to his paper “Numerical Investigation on Water Entry of Two-dimensional Wedges with a Moving Particle Semi-implicit Method” in “Journal of Marine Science and Application” (SCOPUS).

Chip inductors are widely used in electronics applications including information, automotive and aerospace. In particular, the chip inductor is an integral fundamental component of antenna fabrication and at the same time, it is the main component of RF oscillator circuits such as low noise or power amplifiers and voltage-controlled oscillators.

So far, research on chip inductors has been active for a long time, and recently, the need for miniaturization and high-speed electronics has urgently led to the improvements in their reliability and performance.

Most chip inductors are made of copper electrodes and BaTiO₃. During manufacture, especially during service, parts of the chip inductor are exposed to the stress by mechanical, thermal and electrical loads. Therefore, multiple reliability tests including thermal shock, substrate bending and temperature cycling tests are typically required to ensure the reliability of the chip inductor when applied to some high-tech applications.

Kim Mi Gyong, a researcher at the Faculty of Electronics, conducted fatigue life prediction, on the basis of the observation of the region of maximum stress and the extent of cross-section deformation occurring during the operation of the chip inductor.

She constructed a 3D model similar to the real device and obtained the results by finite element analysis under the bending load with four-point bending conditions. The simulation results show that the stress distribution inside the chip inductor will be different with the increase in the number of turns of the chip inductor, which will affect the lifetime of the device.

The proposed method enables more detailed and more practical fatigue life prediction of devices including multilayer ceramic capacitors (MLCC) and chip resistors with similar structures as well as multilayer chip inductors.

For more information, you can refer to her paper “Fatigue life prediction of chip inductor using finite element analysis” in “International Journal of Applied Research” (SCI).

Electrochemical gas sensors are currently widely used in environmental industries due to their superior properties such as high sensitivity and gas selectivity, fast response and reproducibility, and low power consumption. Various kinds of gas sensors have already been commercialized and produced in series and there is a continuous effort to further improve their properties.

As reported in the previous literature, several sensor electrode structures have been used in the fabrication of electrochemical sensors, but there is no description of which structure is the most suitable for generation of current.

With an attempt to design a suitable electrode structure for widely-used electrochemical gas sensors, Kim Yong Hyok, a researcher at the Faculty of Electronics, has performed a simulation analysis of the electrolyte potential and current density of the sensor using COMSOL Multiphysics.

The simulation results show that the sensor of a circular ring-shaped electrode structure has larger current density among the two types of sensors designed. He has also performed an analysis and an experiment of the current density distribution for the variation of the electrode area of sensors with the circular ring-shaped electrode structure and for the variation of the gap between the electrodes. As a result, he has found that the larger the area of working electrodes and the smaller the gap between electrodes, the larger the current density.

For more information, you can refer to his paper “Current Characteristics with Electrode Structure and Geometric Changes of Electrochemical Gas Sensor” in “Journal of The Electrochemical Society” (SCI).