Jo Feb 28, 2026
NOMA (Non-Orthogonal Multiple Access) is the main technology of 5th generation communication system for controlling the throughputs of users by using power allocation corresponding to information transmission time.
In the previous researches, they assumed that all users have the same channel weights in the aspects of power allocation and sum rate.
However, their assumption makes it difficult to simultaneously satisfy the sum rate and user fairness.
Kim Tong Jin, a researcher at the Faculty of Communication, proposed an improved energy harvesting scheme to achieve the maximum sum rate by using weighted users.
The proposed scheme is based on an energy harvesting model and the sum rate is expressed by the throughput of the Nth user.
He set the channel weight of the Nth user to be a certain value and calculated the weights of other users by using the weight of the Nth user so that all users have the same rate and the scheme has the maximum sum rate. Then, he assumed that the sum rate does not depend on the number of users and the channel weight of the Nth user. Under this assumption, he calculated the optimal information transfer time to maximize the sum rate.
He compared the new scheme with the previous one in terms of the channel weight for the Nth user and information transfer time. The results showed that when the number of users in one source block is increased, the sum rate and user fairness are improved significantly.
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Jo Feb 27, 2026
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).
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Jo Feb 26, 2026
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).
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Jo Feb 25, 2026
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).
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Jo Feb 24, 2026
The reliability of wire-bond IGBT modules is limited by the thermal and mechanical fatigue of the inter-bond line connections.
Han Ryong Hwan, a researcher at the Faculty of Electronics, has simulated thermo-mechanical stress distribution in solder joints and wire joints using the ANSYS with an attempt to define a rational linear bond shape for minimum thermo-mechanical stress.
He paid special attention to comparing the stresses in the flip-chip and the wire-bonding interconnect for various wire-bonding types of samples at constant temperature.
The results show that the thermal stress varies with the bending shape of the metal wire in the solders and connecting wires, and the thermal stress decreases with the increase in the number of bending.
You can find the details in his paper “Analysis Of Geometric Effects On The Thermo-Mechanical Stress In Al Bond Wire Interconnects In The Wire-bond IGBT Module” in “Recent Patents On Engineering” (SCI).
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Jo Feb 23, 2026
Since silicon single crystal is the base material of electronics industry, many electronic devices are based on it. Many electronic sensors are based on this material grown by the floating zone (FZ) process.
The crucial factors for growing silicon single crystal by the FZ process are the current density and frequency applied to the high-frequency (HF) inductor, the pull rate and rotational rate of the feed rod and single crystal and the pressure of the atmosphere. Precise determination of these parameters is very important for improving the quality of the grown crystal, and therefore, a lot of research has been focused on it.
In order to fabricate high-quality single crystals necessary to develop power semiconductor devices, Yu Nam Chol, a section head at the Faculty of Electronics, on the basis of the analysis of preceding studies, has performed three-dimensional transient simulations of the growth of FZ single crystal silicon using ANSYS, analyzed the influence of HF inductor type on the growth of single crystal and determined the optimum morphology.
The results show that stepped HF inductors form better temperature distribution in the melting zone than tilted HF inductors.
For more information, please refer to his paper “Modeling of HF Inductor and Influence on Electro-magnetic Field in Silicon FZ Process” in “Journal of Multiscale Modeling” (SCI).
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