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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Jo Feb 22, 2026
NTC (negative temperature coefficient) thermistor chips have been adopted effectively as temperature sensing units and temperature compensation units of reference voltage source for their specific characteristics of resistance inversely proportional to temperature.
The NTC consists of several inner electrodes which are enclosed by thermistor ceramic material and three-layer terminations which are connected to the ceramic body.
Many researches on the NTC have developed up to date, and the miniaturization and high speed of electronic devices urgently needs us to improve its reliability and operation characteristics.
Many factors influence the characteristics of the chips and the structures, and material properties are the main factors. The structure and material of solder which is used to mount chips onto the board (PCB) also affect their characteristics. The thermal stress occurs in sintering, soldering and operating processes and the mechanical stress occurs by the bending load of pressure.
Under these processes and conditions, the differences in the material properties such as thermal expansion coefficient and modulus of elasticity of NTC elements focus stresses on the boundary sides and if it lasts for a long time, the NTC might be brought to failure.
O Ryong Jin, a researcher at the Faculty of Electronics, by considering mainly the stress distribution of ceramic bodies, electrodes, boundaries of inner electrodes, soldered regions and three-layered terminations, conducted simulations for optimization of NTC design and analyzed the results.
The simulation results show that when the number of electrodes of NTC increases, the stress distribution in the NTC body changes, which affects the lifetime of NTC.
For more information, please refer to his paper “Residual Stress in Multilayer NTC Thermistors during Bending Test” in “GAS Journal of Engineering and Technology” (SCI).
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Jo Feb 20, 2026
Zinc oxide (ZnO) is one of the oxide semiconductor materials with excellent electrical, piezo-electrical and optical characteristics. It is widely used in many applications such as solar cells, gas sensors and field-emission displays. ZnO nanomaterials are also used in electronic, thermal and quantum devices, catalysis and wastewater disposal as adsorbents and photocatalysts.
For synthesis of ZnO nanoparticles, various techniques have been proposed and applied. Among them, the electrochemical synthesis method is widely used due to its simplicity, low-temperature operation, low energy consumption and great purity of synthesized products.
So Hyong Dok, a student at the Faculty of Material Science and Technology, has proposed a process optimization method, namely, TOPSIS-Taguchi method, for electrochemical synthesis of ZnO nanoparticles with respect to productivity and consumption using technique for order preference by similarity to ideal solution (TOPSIS) and Taguchi methods. TOPSIS is used to convert multiple responses into a single integrated response (IR), and Taguchi method is used to design experiments and find optimal process parameters (PPs) by optimizing multiple responses.
He determined the optimal pH, concentration (CC), voltage (VL), and conductivity (CD) to maximize the productivity of ZnO nanoparticles and minimize the specific energy consumption and specific electrode consumption.
The optimal PPs were pH of 5, CC of 0.05 M, VL of 8V and CD of 30ms/cm, and their effect ranking on the IR was CC (37.657%), CD (32.498%), pH (15.614%) and VL (14.231%).
The proposed method could be widely used not only to electrochemical synthesis process optimization of ZnO nanoparticles but also to various materials fabrication process optimization problems.
For more information, please refer to his paper “Process optimization for electrochemical synthesis of ZnO nanoparticles with respect to productivity and consumption using TOPSIS and Taguchi methods” in “Scientific Reports” (SCI).
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Jo Feb 19, 2026
In automatic control of industrial processes, the determination of controller parameters is very important to prevent dangerous accidents and to increase quality and production. However, it is not easy to calculate controller parameters suitable for real plants, since most real processes have immeasurable model uncertainties.
PID controllers are most frequently applied in many fields where automatic control including process control is necessary. A PID controller has a great variation in control performance depending on how the parameters are determined, and thus many methods have been developed to adjust the parameters appropriately.
Conventional feedback control methods may not be good for time-delay plants because the control action is lagged. A suitable alternative to this kind of plant is the predictive control.
Hong Kwang Hyok, a researcher at the Faculty of Automatics, has investigated an improved internal model control based PID (IMC-PID) controller by combining particle swarm optimization (PSO) together with predictive functional control (PFC) framework.
First, he determined the optimal filter time constant, which is the core element of IMC, using PSO algorithm. Then, by employing the PFC idea to eliminate the effect of delay, he constructed a modified PID control system with PFC features. According to the framework of PFC, he carried out output prediction of the plant with delay and determined the optimal manipulated value by the IMC-PID control strategy.
The control method he investigated proved effective through the control of a first plus dead time (FOPDT) plant.
If further details are needed, please refer to his paper “A novel optimal design of IMC-PID controller incorporating PSO and predictive functional control framework” in “Second International Conference on Electronics, Electrical, and Control System” (EI).
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