Jo Jan 26, 2026
Today, the application range of nanofibers are widening day by day because of their excellent properties that are different from conventional materials.
Nowadays, electrospinning is widely used as a versatile and convenient method for the production of nano-sized fibers. However, the difficulty in the production of nanofibers by single-needle electrospinning is that it has low production efficiency. To solve this problem, several types of electrospinning methods have been developed, which can be divided into two broad categories. One is needleless electrospinning and the other is multi-needle electrospinning. Between them, multi-needle electrospinning plays an important role in preparing specific structures because it is able to control the properties of fibers.
So, when the number and density of nozzles are increased in the multi-needle electrospinning, the intended electric field of the nozzles gets more distorted due to electrical interactions between the nozzles, which destabilizes the flow of the polymer solution jet and negatively affects the quality of the obtained fibers. Therefore, the uniformity of the electric field distribution at the spinneret needle tip in the multi-needle electrospinning process is a key factor for producing good quality fibers.
Jang Kum Chol, a researcher at the Institute of Nano Science and Technology, proposed a trapezoidal wave (TW) arranged multi-needle electrospinning spinneret with auxiliary electrodes (AEs), and conducted a study to further enhance the electric field uniformity by optimizing the AE parameters by Taguchi method.
The optimization results showed that the uniformity of electric field was best when the distance between the spinneret and the auxiliary electrode was equal to 21 mm, the arrangement angle of auxiliary electrode 120゜, the spacing between two adjacent needles of auxiliary electrode 18 mm, the needle length of auxiliary electrode 13 mm, the needle diameter of auxiliary electrode 2.5 mm.
For more information, please refer to his paper “Optimization of parameters of auxiliary electrodes for electric field uniformity around spinneret needles in multi-needle electrospinning by using Taguchi method” in “Journal of Electrostatics” (SCI).
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Jo Jan 25, 2026
With the rapid development of economy, energy consumption increases gradually every year, and coal slurries are used in various thermal machines, especially in internal combustion engines, in accordance with the global strategy of saving and replacing oil.
In the production of CWS fuel, the ration of raw coal and additives and the relevant process are important for improving the quality and saving the cost.
Pak Song Chol, researcher at the Faculty of Physics, conducted an experimental study to convert coal-water-oil slurry (CWOS) into an alternative fuel (AF) for internal combustion engines by high-voltage discharge (HVD) and dielectric barrier discharge (DBD) plasmas.
He prepared CWOS by adding oil to the coal-water mixture in a relevant ratio. Then, he converted the CWOS to AF by passing high-voltage discharge and DBD plasma with gas emission and liquefaction reactions through it.
The result showed that after HVD and DBD plasma treatments, the CWOS has the average coal size reduced from 12.95 to 8.26㎛, improved dispersibility, less deposits, and calorific value enhanced by 35%.
The plasma-treated CWOS is similar to other liquid fuels in terms of rheological property and calorific value. It is therefore concluded that it can be directly employed to fuel combustion in the internal combustion engines with a little design modification.
The details can be found in his paper “Enhancement of calorific value and dispersion stability of coal-water-oil slurry by discharge plasmas: application of high voltage discharge and dielectric barrier discharge” in “International Journal of Coal Preparation and Utilization” (SCI).
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Jo Jan 23, 2026
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).
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Jo Jan 22, 2026
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).
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Jo Jan 21, 2026
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).
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Jo Jan 20, 2026
The use of known model information in the design of an active disturbance rejection controller reduces the magnitude of the “total disturbance” and consequently improves the control performance.
Based on Takagi–Sugeno (T-S) fuzzy modeling, Choe Hak Jin, a researcher at the Faculty of Metallic Engineering, proposed a new method for incorporating the known nonlinear dynamics of the plant into a linear active disturbance rejection controller (LADRC),
In order to evaluate the effectiveness of the proposed method, he performed simulations of a cart inverted pendulum.
The simulation results show that the estimation burden of the extended state observer is reduced and the control performance is improved in the proposed method than in the conventional model-assisted LADRC that can incorporate only linear model information, and that the proposed cascade control scheme has good disturbance rejection, transient response and robustness at the same time.
If further information is needed, please refer to his paper “A cascade control scheme with T-S fuzzy model-assisted linear active disturbance rejection controller for position tracking of cart inverted pendulum” in “International Journal of Dynamics and Control” (SCI).
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