Jo Jul 21, 2026
The impact energy, which is the main performance index of a rock drill, was estimated by many researchers in an indirect way because of the difficulty of direct measurements.
Those measurement methods are difficult to apply to the performance tests of mass-produced drills as they require modification of the structure of percussion drills or preparation of standardized rock samples.
In view of these practical requirements, Han Tok Hyong, an institute head at the Faculty of Mining Engineering, proposed a new structure of impact energy measurement device and analyzed its performance and availability through simulation.
The analysis results show that the stress wave transmitted through the drill rod is converted into the pressure wave of oil filled inside the cylinder. Its maximum value is 15-28MPa, varying with position. Therefore, a suitable location of the measurement point can raise measurement accuracy while extending the service life of the sensor.
The proposed device can be used effectively in the field of impact energy measurement of rock drills due to its simple structure and high reliability. Especially, as it is possible to estimate impact energy without altering the structure of rock drills, it can be used in performance testing processes in rock drill plants.
For more information, please refer to his paper “Simulation Study of Hydraulic Measuring Device for Impact Energy Estimation in Performance Test of Rock Drill” in “Proceedings of KUTIC-2025”.
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Jo Jul 20, 2026
Electric motors and drives consume approximately 40% of the electrical energy generated worldwide. In industrial applications, electric motors account for about 70% of energy consumption. Thus, it can be said that one way to save electrical energy is to increase the efficiency of electric motors.
SynRMs have been preferred in industry for their low cost, simple structure, field weakening capability, small loss, and high torque-to-volume ratio. High efficiency, power factor and torque-to-volume ratio depend on the saliency. It is determined by the synchronization and steady state performance according to starting winding parameters and barrier dimension.
An Se Gwang, a researcher at the Faculty of Electrical Engineering, designed a line-start synchronous reluctance motor (LS-SynRM) with reference to a 1kW induction motor, and determined the optimum rotor structure parameters.
The comparison of the rotor structure of these two motors with the same stator showed that the LS-SynRM has lighter rotor structure by 27.1%.
He determined the optimum dimensions for good synchronization performance and high power factor to be as follows: the diameter of starting winding ds2=4mm, the bridge thickness H=5.5mm, the yoke thickness Y0=5mm, and the barrier thickness B0=3mm.
You can find details in his paper “Determination of Reasonable Rotor Structure Parameters of Line Start Synchronous Reluctance Motor with Round Bar” in “Proceedings of KUTIC-2025”.
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Jo Jul 19, 2026
The precise orbit of a satellite is determined from the exact position and velocity estimated by the dynamic solution obtained from the motion differential equation of a satellite in the inertial space satisfying the Newton second law and by the data measured by some means such as on-board GPS. Because the dynamic solution is from GCRF and the measurement data is from ITRF, coordinates transformation is needed. Therefore, the uncertainty of the coordinates transformation affects the accuracy of position determination of satellites.
Precise ITRF/GCRF transformation is generally conducted using the earth originate parameter (EOP) provided by international earth rotation service (IERS). EOP data is updated every day. ITRF/GCRF transformation methods using the EOP data are classified into the classical equinox-based method and the modern CIO-based approach.
The latter is simpler in procedure than the former as it needs neither ecliptic nor equinox, and it is considered as a suitable method for improving the calculation speed as it can tabulate data necessary for coordinates transformation.
CIO-based approaches include precise theory method, series method and numerical interpolation method. The method using the series can improve the calculation speed by decreasing the order of the series, but it degrades the accuracy of coordinates transformation. Therefore, necessary data in the astrodynamics calculations are tabulated and interpolated to improve the calculation accuracy and speed.
Cha Pong Il, a section head at the Faculty of Aerospace Engineering, proposed a method for reducing the calculation time in precise ITRF/GCRF transformation and verified its effectiveness through simulation.
The simulation results show that the calculation time by the classical equinox-based method is equal to about 195s, while the time by the precise theory method is about 98s, but the numerical interpolation method maintains its accuracy with the calculation time of less than 1s. It means that the numerical interpolation method decreases calculation load and improves calculation speed significantly.
If further information is needed, you can refer to his paper “A Method for the Reduction of the Calculation Cycle in Precise ITRF/GCRF Transformation using the Numerical Interpolation Technology” in “Proceedings of KUTIC-2025”.
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Jo Jul 17, 2026
A nozzle is a device that splits liquid into fine droplets to spray them into the surrounding space. It has been widely used in various systems and devices including cooling, dust collection and spray systems. The tangential pressure swirl nozzle finds particularly wide use in various industrial and agricultural fields such as combustion engines, spray drying, cooling, plating, etc., due to its simple structure and good spray properties. Therefore, investigating the factors influencing the water spray characteristics of tangential pressure swirl nozzles is of great importance for proper installation and use of nozzles.
So far, the effect of the swirl chamber diameter, outlet diameter and swirl chamber cone angle on the water spray characteristics of a tangential pressure swirl nozzle has been studied, but that of the liquid incidence angle has not been considered.
Kim Song Won, a section head at the Faculty of Thermal Engineering, has experimentally studied the spray distribution, spray angle, etc. of a tangential pressure swirl nozzle and carried out a CFD simulation to analyze the effect of liquid incidence angle on the spray characteristics and determine the optimum incidence angle.
Through the study, he has concluded that it is necessary to take measures to prevent U-tube bundles from sagging down in the design and manufacture of reheater bundles.
For more information, you can refer to his paper “Experimental and CFD Study on Spray Characteristics of Tangential Pressure Swirl Nozzle” in “Proceedings of KUTIC-2025”.
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Jo Jul 16, 2026
Many programs have been in use for accurate evaluation of the efficiency of thermal systems and for their optimal design. Cyclepad is a good example. It has been developed for an analysis and the optimal design of different thermodynamic cycles.
However, Cyclepad has the disadvantage of needing the input and output of each computational module to be single phase only. Therefore, it failed to support accurate analyses of systems using wet steam and accurate calculation of the thermal properties of the working fluid at the transition points.
In addition to Cyclepad, some other programs for optimizing a second-order system using different optimization algorithms have also been developed, but they have not proved to be useful.
Pak Myong Guk, an institute head at the Faculty of Thermal Engineering, has proposed an improved random tunneling algorithm (RTA) to effectively solve a constrained mixed-variable global optimization problem, and based on it, he has conducted a thermal sequence efficiency analysis of the Rankine cycle and developed an optimization system for it.
With CAD technique introduced, the newly-developed program is effective for designing various Rankine cycles and for optimizing the efficiency of the Rankine cycle by applying improved IRTA.
For further details, you can refer to his paper “Development of Rankine Cycle Optimization CAD” in “Proceedings of KUTIC-2025”.
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Jo Jul 15, 2026
In recent years, many modal identification methods based on continuous wavelet transform have been developed. The time variation of the instantaneous amplitude and phase of each mode component within measured signals can be observed on time-frequency planes, where measured signals are decomposed to a series of curves called ridges which directly express the amplitude and phase of each mode component at the time of wavelet analysis. Thus, the extraction of ridges and the value of the CWT along the ridges are used to identify modal parameters.
What is important here is to determine ridges. When the frequency window of a wavelet function includes only one natural frequency, ridges accurately represent modal parameters. Therefore, ridges have to be considered carefully in the application of this method.
Ri Yong Ho, a researcher at the School of Science and Engineering, mathematically investigated the distortion of a ridge when the frequency window of wavelet function includes two closely-spaced natural frequencies.
He demonstrated the correctness of the analytical result in detail through numerical simulation.
If further information is needed, you can refer to his paper “Research of Characteristics of a Ridge for the Closely Spaced Two Modes in Time-Frequency Domain” in “Proceedings of KUTIC-2025”.
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