Jo Apr 28, 2026
Composite shell structures with varying thickness are often used in different industrial fields because it could exhibit structural advantages at minimum material cost.
Recently, many works have been reported for static and dynamic analyses of different structures with variable thickness. 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 numerical analysis of composite structures. In recent years, the meshfree method has attracted significant attention of many scholars.
Jo Ju Chol, a researcher at the Faculty of Mechanical Science and Technology, developed a meshfree Jacobi-radial point interpolation (Jacobi-RPI) method for free vibration and stochastic response analyses of laminated composite sectorial and annular plates with straight fibers and variable thickness.
First, he adopted the Hamilton’s principle to establish the equations of motion of the laminated composite sectorial plate with straight fiber and variable thickness in the framework of first-order shear deformation theory (FSDT). Then, he approximated the displacement components of the plate by using the meshfree Jacobi-RPI shape function. As the laminated annular plate with straight fiber is not symmetrical, he obtained its motion equations by combining the equations of several sectorial plates.
He validated the accuracy and reliability of the proposed method through a sufficient number of numerical studies.
For more details, you can refer to his paper “A meshfree formulation for free vibration and stationary stochastic response analyses of laminated composite annular plate with straight fibers and variable thickness” in “Acta Mech” (SCI).
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Jo Apr 26, 2026
As is known, in a ball screw–driven servomechanism, the servo motor and the ball screw can be connected directly or via a tooth belt drive, a gear pair or a commercial reducer. However, more complex systems cause more kinematic errors in the machines, so in precision machine tools, the former is more common, but in conventional machine tools it is more economical to use the latter. This is because the latter can improve the resolution in an open system, replace the output of a high-speed low-torque servo motor with the output of a low-speed high-torque unit, significantly reduce the load inertia torque in terms of the motor shaft to favor inertial matching and has the potential to significantly reduce electric consumption by reducing the size of the motor. Especially, tooth belt drives are commercially available and inexpensive but have a relatively small backlash compared to other speed reducers, which makes them a large part of industrial applications. On the other hand, since the former is a special case of the latter, the results of the latter study can also be applied to the former. Certainly, the study on optimal selection of the key components of ball screw–driven servomechanisms with tooth belt drives is a subject of great socio-economic significance.
Jang Rim Chol, a researcher at the Faculty of Mechanical Science and Technology, proposed a method for determining the optimal combination of the key components (servo motor, ball screw, and tooth pulley pair) of a ball screw–driven servomechanism with a tooth belt drive transmission. The proposed method deals with a more generalized optimization problem because it focuses on the optimization of a ball screw–driven servomechanism with a reducer (tooth belt drive transmission) unlike previous works that focused only on the optimization of a system where the servo motor and the ball screw are directly connected.
The proposed method enables optimal selection of the key components of a ball screw–driven servomechanism for different purposes including machine tools, without subjective selection or prediction of some components or some parameters for different objective functions.
You can find the details in his paper “Selection of key components in ball screw–driven servomechanisms with toothed belt drive transmission for machine tools through combinational optimization” in “The International Journal of Advanced Manufacturing Technology” (SCI).
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Jo Apr 24, 2026
Hydrogen, the cleanest future fuel, can replace fossil fuel based on carbon. During the past decades, many methods for hydrogen production and storage have been studied for practical use. In particular, storage and transport of hydrogen has recently become a focus of intensive research for large-scale application of hydrogen energy systems.
One of the major challenges in the quest for feasible hydrogen-fueled vehicles is to develop lightweight materials with high hydrogen densities (>5wt %) which can absorb and release hydrogen in the range of 1-10 bar and 298-473 K.
Recently, perovskite materials have emerged as a multifunctional material for photovoltaics, luminescence, photocatalytics and hydrogen storage applications.
Ri Sol Hyang, a lecturer at the Faculty of Online Education, theoretically investigated the materials properties such as structural, electronic and lattice dynamics properties and mechanical and dynamical stabilities of the hydride perovskites ACaH3 (A = Li, Na) in cubic phase for its application as a hydrogen storage material by using the first-principles calculations.
The results show that cubic LiCaH3 is regarded as a potential H2 storage material due to its high H2 storage capacity, stability and suitable dehydrogenation temperature.
For more information, please refer to her paper “Perovskite-type hydrides ACaH3 (A = Li, Na): computational investigation on materials properties for hydrogen storage applications” in “RSC Advances” (SCOPUS).
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Jo Apr 23, 2026
Aluminium is widely used as a core material in the production of various kinds of cables, and the problem of improving its structure and properties is widely discussed.
In order to use aluminum wires, it is important to improve their mechanical properties. Therefore, pure aluminum is not used as a core, but increasing the properties of the core by alloying, complexing, coating, and adding trace elements has become a worldwide trend.
Currently, there is a growing worldwide interest in the preparation of composites with enhanced carbon nanotubes with excellent mechanical, thermal and electrical properties, and a number of researchers have achieved some successes.
According to previous reports, carbon nanotube reinforced aluminum matrix composites have been prepared by powder metallurgy, in situ synthesis, deposition, etc., and these techniques have the disadvantage of complex manufacturing processes and low productivity.
Jon Song Won, a researcher at the Faculty of Material Science and Technology, prepared CNT-Al composite wires by a novel method of direct addition of carbon nanotubes to aluminum molten steel, rather than conventional powder metallurgy and in situ synthesis. Then, he investigated the effects of carbon nanotubes on the microstructure and mechanical properties of CNT-Al composites and the dispersion properties of carbon nanotubes.
The results show that increase in the CNT content improves the mechanical properties of the composite and decreases the particle size of the composite, and that the carbon nanotubes were co-injected with inert gas (N2) to achieve the best performance with a strength limit of 250MPa, elongation of 4.2% and bending number of 6 times.
For more information, please refer to his paper “Effect of Carbon Nanotubes on Microstructure and Mechanical Properties of Carbon Nanotube Reinforced Aluminum Composites” in “Russian Journal of Non-Ferrous Metals” (SCI).
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Jo Apr 22, 2026
Enamel is widely used in various industrial fields because it has excellent properties such as beautiful color, gloss, excellent corrosion resistance, wear resistance and fire resistance, high temperature stability, etc. Enamel is a composite material consisting of glass coating that is melted and chemically bonded on a metal or its alloy. The physicochemical and mechanical properties of enamel coatings including corrosion resistance and wear resistance are mostly determined by enamel material called frit. The most widely used enamel frit is a glass material composed of inorganic materials that are added to the borosilicate-based glass material to provide physical properties such as acid resistance, alkali resistance, heat resistance and wear resistance.
The final physicochemical and mechanical properties of material are controlled by the crystallization process occurring during the calcination process. Therefore, it is important to know crystallization kinetics well in order to optimize the parameters affecting the properties.
The crystallization kinetics of different silicate-based glasses has been studied much in several methods. However, few investigations have been done on the crystallization kinetics of sodium borosilicate-based glass.
Kim Kwang Myong, a researcher at the Institute of Nano Science and Technology, investigated the non-isothermal crystallization behavior of sodium borosilicate-based glass materials used as a bottom material of low carbon steel enamel by DSC method.
In order to study the crystallization process of Na2O-B2O3-SiO2 based materials, he prepared sodium borosilicate-based glass materials used as ground coating material of steel enamel by melting and quenching.
He analyzed the experimental data by the methods proposed by preceding researchers to provide theoretical support for the preparation of good-quality sodium borosilicate-based glasses and to design a practical procedure.
You can find the details in his paper “Non-isothermal crystallization kinetics of sodium borosilicate-based glass” in “Reaction Kinetics, Mechanism and Catalyst” (SCI).
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Jo Apr 21, 2026
So far, there has been a little imperfection in the analytical theory of radiation heat transfer. Although there is a calculation formula for non-transparent bodies, more universal calculation formulae for partially transparent bodies have not yet been found.
Today, various types of plastic films are most commonly used to cover greenhouses. However, plastic films are partially transparent to long-wave thermal radiation. Up to now, the radiation heat transfer in the buildings like solar greenhouses has been analyzed using the repeated reflection method.
Preceding authors calculated the radiation heat transfer of radiation systems containing partially transparent bodies such as glasses or films by using different methods, but they did not perform detailed quantitative and qualitative analyses of radiation components when radiation passes through partially transparent bodies. Also, the number of determinants increased considerably because different studies developed formulae with individual radiation components. Therefore, only computer-based calculations were able to determine heat fluxes of resultant radiation or transmission radiation, and some calculation time was required. Furthermore, studies on the determination of radiation heat fluxes using the multiple reflection method and the ray tracing method were more complex than using the effective radiation method. Introduction of computers into technical calculations enabled calculation of radiation heat fluxes in greenhouses by the repeated reflection method, but programming also required a lot of effort. In a word, it was more complex and less intuitive than the effective radiation method.
Kim Chol Gon, a researcher at the Faculty of Thermal Engineering, derived universalized formulae to briefly and explicitly calculate radiation heat fluxes in radiation systems with partially transparent bodies including solar greenhouses and solar collectors, using the effective radiation method (i.e., the radiosity method). Then, he proved that calculated characteristics of the daily temperature variation in a single-roofed solar plastic film greenhouse by using derived formulae are the same as those calculated by using the repeated reflection method.
These formulae can be fully applied to calculating radiation heat fluxes in all radiation systems with partially transparent bodies such as solar greenhouses and solar collectors. They can also be effectively applied to radiation heat calculations of public houses and buildings with windows.
For more information, please refer to his paper “The formula for calculating radiative heat fluxes in systems with partially transparent structures” in “Thermal Engineering” (SCOPUS).
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