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).

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”.

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”.