Jo Apr 17, 2026
Functionally graded material (FGM) shells and plates, which eliminate interface problems and stress concentrations of composite laminated structures, are regarded as main structures for mechanical engineering, civil engineering, marine, automotive and many other applications. Recently, many scholars have paid their attention to numerical and experimental studies for mechanical behavior of various structures made of functionally graded materials.
Various methods such as Haar wavelet method, Jacobi–Ritz method, spectral-Tchebychev method, dynamic stiffness method, finite element method and meshfree method have been employed for the numerical analysis of composite structures. In recent years, the meshfree method that needs no meshes for discretization of problem domains has attracted significant attention of many scholars.
Kwak Song Hun, a researcher at the Faculty of Mechanical Science and Technology, has proposed a meshfree Jacobi-radial point interpolation (Jacobi-RPI) method for free vibration and stochastic response analyses of functionally graded eccentric sectorial and annular plates.
He adopted the Hamilton’s principle to establish motion equations of functionally graded material (FGM) eccentric sectorial plates in the framework of first order shear deformation theory (FSDT). He transformed the eccentric sectorial plate into a simple square domain by using the coordinate mapping technique, and approximated the displacement components of the sectorial plate by using the meshfree Jacobi-RPI shape function. He obtained motion equations of FGM eccentric annular plates by coupling the equations of several sectorial plates.
He has validated the accuracy and reliability of the proposed method through a sufficient number of numerical studies for the free vibration and dynamic response analysis of eccentric sectorial and annular plates.
For more information, please refer to his paper “A meshfree approach for free vibration and stationary stochastic response analyses of functionally graded eccentric sectorial and annular plates” in “Journal of the Brazilian Society of Mechanical Sciences and Engineering” (SCI).
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Jo Apr 16, 2026
The mixed refrigerant is a mixture of several simple refrigerants in a certain proportion. In refrigeration cycles, the mixed refrigerant is generally less energy-consuming compared to its pure components. In addition, the ozone layer destruction coefficient (ODP) and the global warming coefficient (GWP) are low.
Typical mixed refrigerants include R12/R13, R22/R13, R22/R23, R134a/R23, R22/R14, R22/R23/R14, R134a/R23/R14, R600a/R23/R14, R600a/R23/R50, etc.
R600a has zero ODP and GWP, no poisoning, high latent heat of vaporization and high refrigeration efficiency. R508B is an azeotropic mixture consisting of R23 and R116, an environmentally friendly refrigerant with ODP of 0. In automatic cascade refrigeration systems, the composition ratio of mixture has a great influence on the system performance.
Ri Ju Hyok, a researcher at the Faculty of Thermal Engineering, constructed an automatic cascade refrigeration system using mixed refrigerant R600a/R508B, and analyzed its cycle characteristics, based on the thermal properties of the environmentally friendly mixed refrigerant R600a/R508B calculated by the Helmholtz energy mixture model. Then, by using Aspen Plus program, he analyzed the effect of various parameters on the cycle characteristics and optimized them.
Based on the optimization results, he built an experimental setup of an automatic cascade refrigeration system and carried out some performance experiments to confirm that the cycle characteristics analysis was relatively accurate.
You can find more information in his paper “Auto Cascade Refrigeration Process for Environmental Protection using Mixed Refrigerant R600a/R508B” in “Proceedings of KUTIC-2025”.
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Jo Apr 15, 2026
Selecting a suitable mining method in consideration of surface subsidence caused by underground mining, safety of stope and mining recovery rate under mining and geological conditions of a certain target is very important for safe mining, protection of surface structures and minimization of coal loss.
The results of previous studies show that better results can be obtained by analyzing the surface subsidence characteristics caused by the influence of mining operations using numerical simulation methods that can well reflect the nonlinear relationship between rock mass movement and deformation parameters.
Hong Kun Ui, dean of the Faculty of Mining Engineering, numerically investigated a suitable mining method in consideration of the surface subsidence and the safety of stope by using FLAC3D and SURPAC software with a change of stope pillar size in the case of mining thick coal seams with dip of 30° by using different room and pillar methods.
The numerical simulation results showed that when the interval between stope pillars is 4m, the maximum subsidence of surface is about 2.2cm, which ensures stope safety.
He introduced his method to Kaechon coal mine and proved its reliability.
For more details, you can refer to his paper “Numerical Simulation Analysis for the Selection of Suitable Mining Method in Consideration of the Surface Subsidence and the Safety of Stope and the Mining Recovery Rate” in “Proceedings of KUTIC-2025”.
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Jo Apr 14, 2026
Vanadium redox flow batteries (VRFBs) are large-scale electrochemical energy storage systems that enable the supply of stable and reliable power from wind or solar energy. Proton exchange membrane fuel cells (PEMFCs) are efficient and environmentally friendly electro-chemical energy conversion systems that produce only water and heat with clean hydrogen produced using renewable energy as fuel. On the other hand, EHC is an advanced electrochemical system that is indispensable for hydrogen energy cycle systems that purify and compress hydrogen simultaneously.
Sulfonated polyetheretherketone (SPEEK) membranes have been widely regarded as inexpensive proton exchange membranes for electrochemical energy systems such as VRFBs, PEMFCs and EHC due to their ease of fabrication, low cost, good proton conductivity, and excellent thermal and chemical stability.
General requirements for these applications are high proton conductivity, chemical and mechanical stability and impermeability of fuels and oxidants.
In order to improve the performance of membranes, Ju Il Myong, a researcher at the Faculty of Chemical Engineering, developed SPEEK/TiO2 nanopaper composite membranes with TiO2 nanopaper as a backbone and SPEEK polymer as a proton conducting medium, and evaluated their physicochemical properties.
Compared to pristine membranes, the SPEEK/TiO2 nanopaper composite membranes show nearly twice tensile strength, about 1/3 of vanadium permeability and low hydrogen gas permeability, and better performance and long lifetime in VRFB, PEMFC and EHC systems. The experimental results show that SPEEK/TiO2 nanopaper composite membranes can replace commercial Nafion® membranes in electrochemical energy systems.
If more information is needed, please refer to his paper “SPEEK/TiO2 Nanopaper Composite Membranes for Electrochemical Energy Systems” in “Proceedings of KUTIC-2025”.
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Jo Apr 13, 2026
Recently, environmental protection has become a very important issue in the world. Many enterprises are recycling as much waste material as possible from their production processes, and they are concerned about energy consumption and environmental issues of production processes.
Generally, biological sewage treatment is widely applied to treating sewage containing a large amount of organic matter including farm sewage and domestic sewage. The most energy-consuming process in these methods is the blowing equipment of the aeration system for supplying dissolved oxygen to sewage. Therefore, improving aeration facilities to increase oxidation efficiency is important to reduce power consumption.
Use of microbubbles in the aeration process of biological sewage treatment has been reported to significantly improve sewage treatment parameters, especially with a significant reduction in energy consumption.
Ji Chol Hyok, a researcher at the Instititute of Nano Science and Technology, investigated the effect of introducing fluidic oscillation into a sewage aerator to enhance oxygen transfer efficiency and generate smaller bubbles.
The experimental results showed that the overall wastewater treatment parameters were improved in microbubble aeration combined with FOs.
You can find more information in his paper “Improving the Efficiency of Biological Sewage Treatment by Applying Porous Membrane Microbubble Generating System Coupled with Fluidic Oscillators” in “Proceedings of KUTIC-2025”.
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Jo Apr 12, 2026
The dependence of the differential negative resistance of a unijunction transistor (UJT) on external behavior is used to develop a new family of microelectronic transistors for measuring temperature, magnetic field, light radiation and pressure. The magnetic sensitivity of UJT in the presence of an externally applied magnetic field depends on this current magnetic effect. To our knowledge, there are no published results regarding the magnetic sensitivity of structures with p+ diffusion rings and surface recombination center regions.
Kim Sang Hyok, a section heat at the Institute of Semiconductor, proposed a unijunction transistor (UJT) of a new structure with enhanced galvanomagnetic effects by using a p+ diffusion ring and improved magnetic sensitivity by forming a recombination region on the surface with an emitter.
He fabricated the device on an n-type <111> orientation silicon mono-crystalline wafer with resistivity of 200Ω·cm and thickness of 250㎛ by using the standard CMOS technology.
The experimental results show that it had the highest magnetic sensitivity of 80V/T when the ratio of Emitter-Base 1 distance to diffusion length is about 1:0 and the width of the Base layer limited by the p+ diffusion loop is twice the Emitter width.
You can find more information in his paper “A New Structure of High-Sensitivity Magnetically Unijunction Transistor” in “Proceedings of KUTIC-2025”.
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