With decades of continuous coal mining, the mining conditions of coal seams are becoming increasingly unfavorable. Coal seams generally include thick coal seams, thin coal seams, uncomplex coal seams and complex coal seams, with different thicknesses and shapes.

Some coal seams have high thickness and inclination and complicated orientation. In such coal seams, it is difficult to use mining machinery such as a coal cutter-loader. To make more effective use of underground resources, it is necessary to mine not only suitable coal seams but also complex coal seams, that is, those for which machinery and equipment were unable to be used in the past because of poor mining conditions.

However, there has been little research on coal mining in coal seams with complex morphology, with high variation in thickness and inclination angle of coal seams.

Pak Jang Hyok, a researcher at the Faculty of Mining Engineering, has proposed a novel coal mining method (a diagonal collapse coal mining method), which can be applied to difficult-to-machine conditions due to the high variations of thickness and inclination angle of coal seams.

This is the method of coal excavation by drilling up tunnels with a diagonal angle, and the transportation of coal in the face is carried out by a chute without using special transport equipment.

The research results show that this method is best suited to apply to complex coal seams varying in inclination angles above 15°, and it can also be applied to coal seams varying in inclination angles below 15°, but it is preferable to take into account economic indices.

For more information, please refer to his paper “Numerical Simulation for the Determination of the Dip Angle of a Diagonal Collapse Coal Mining Method by EDEM Under Complex Anthracite Seam Conditions” in “Advances in Civil Engineering” (SCI).

Promoting seed germination is important for increasing grain production. It requires increasing tolerance to various types of stresses including drought and the disease tolerance of crops.

Wheat is one of the three major field crops along with maize and rice worldwide. In temperate regions, spring wheat sowing is mostly carried out in March and April. This period represents the seed dormancy due to low average ambient temperatures of 8–15 °C and low soil water content due to drought. Therefore, it is important to break the dormancy of wheat seeds, increase the germination rate of seeds, promote growth, and improve drought tolerance.

Choe Hak Chol, a researcher at the Faculty of Physics, evaluated the effects of the gliding arc discharge (GAD) plasma-treatment on the germination of dormant wheat seeds and old seeds at low ambient temperature.

The GAD plasma promoted the germination of dormant wheat seeds and old seeds at 10 °C. For wheat seeds treated by GAD plasma with a power of 400W, the germination potential, the germination rate, the percentage of germination and the sprout length showed clear increasing trends compared to untreated ones. The positive germination effects similar to the above were observed even for old seeds kept at 25 °C.

You can find more information in his paper “Gliding arc discharge plasma treatment for promoting germination of wheat seed at low ambient temperature” in “Journal of Vacuum Science and Technology A” (SCI).

Recently, many numerical and experimental studies on the mechanical behavior of functionally graded (FG) structures have been carried out as they are widely used in various fields of engineering due to their benefits such as high stiffness, light weight and high thermal resistance.

Sin Chol Nam, a section head at the Faculty of Mechanical Science and Technology, has proposed a meshfree Jacobi-radial point interpolation (Jacobi-RPI) method for the dynamic analysis of a functionally graded elliptical shell with varying thickness (FGESVT) in supersonic flow and thermal environment.

He assumed the material properties of FGESVT to vary along the direction perpendicular to the bottom surface. He considered the thermal stress due to the variation of environmental temperature by introducing the nonlinear part of the Green–Lagrange strain. He constructed a meshfree shape function by combining the radial basis with Jacobi polynomials with fast convergence, numerical stability and high accuracy. He expanded the displacement components of the FGESVT by using the meshfree Jacobi-RPI shape function. He obtained the equations of motion of the closed FGESVT by coupling the equations of several open shells.

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 open and closed FGESVT.

For more details, please refer to his paper “A meshfree method for thermodynamic analysis of functionally graded elliptical shell with varying thickness in supersonic flow” in “Archive of Applied Mechanics” (SCI).