Jo Jan 13, 2026
When the hull roof frame with a large bending radius is made with L-shaped steel instead of a square pipe by a press, the die must be designed correctly considering the spring-back in order to ensure high accuracy.
Ri Song Min, a researcher at the Faculty of Mechanical Science and Technology, proposed a method of selecting a reasonable bending radius of the die by considering the stress, strain characteristics and spring-back of work-pieces in the process of bending the L-shaped steel that is used in the manufacture of the roof frames of vehicles including underground trains by means of a press, and conducted a simulation analysis. In addition, by measuring the amount of spring-back at the time of bending with constant force using a press to compare the experimental values with simulation values, he evaluated the accuracy of the simulation analysis, and compared the bending radii of the die to form an L-shaped steel product for roof frames.
He performed a finite element analysis at the ceiling and the corner sections, respectively. The finite element simulation analysis result of the process of bending the L-shaped steel shows that the bending radius of the die must be designed to be 7 782mm and 426mm for the ceiling and the corner sections, respectively.
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Jo Jan 9, 2026
PTN (Packet Transport Network) based on MPLS-TP (Multi-Protocol Label Switching-Transport Profile) does not rely on subscriber service signals. It provides real-time transmission and robust OAM (Operation, Administration and Maintenance) functions thanks to VPN (Virtual Private Network) technique using LSP (Label Switch Path) and PW (Pseudo-Wire) for transparent transport, thus being widely used in transport systems for mobile communication.
The PTN for 3rd generation mobile communication is operated in the centralized way, and it is difficult to apply to the next generation mobile communication.
Kim Myong Jun, a researcher at the Faculty of Communication, has proposed a method of how to apply MPLS-TP based PTN device using dedicated network processor WINPATH to the next generation systems, and verified its application possibility.
The experimental results show that transport network for next generation can adopt MPLS-TP based PTN device by the proposed method.
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Jo Jan 9, 2026
Radiation leaking into the surrounding environment has a detrimental effect on the human body, so it should be evaluated first to prevent it.
The most considerable radiation affecting the human body is gamma rays. This is because the penetrability of gamma rays is the strongest of all other kinds of radiation. Therefore, gamma dose measurement is of paramount importance for its dosimetry.
Radiation detectors for environmental radiation monitoring usually include scintillation detectors, ionization chambers, and automatic discharge counters. Among them, automatic discharge counter tubes are widely used for environmental radiation monitor fabrication because of their low cost and simple measurement circuitry. However, the automatic discharge counter tubes manufactured at home and abroad have the disadvantage of narrow energy band for dose estimation and low counting rate.
Pak Yong, a researcher at the Institute of Analysis, has designed a new environmental radiation monitor to measure radioactive contamination and environmental radiation.
By applying the time-count conversion method, he eliminated the effect of dead time in the GM counter tube and extended the counting rate measurement range from 2×103 to 105cells/s.
The proposed monitor enables measurement from 10nSv/h to 200mSv/h using two GM counters with improved properties.
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Jo Jan 8, 2026
The earth’s crust is in ceaseless movement by the physical and chemical process of lava underneath itself and the gravitation force between the earth and other celestial bodies including the sun and the moon. Monitoring the tilt change of the earth’s crust is critical to detect the signs of crustal deformation.
A tiltmeter is an instrument for monitoring the ultra-fine tilt change of the crust (about 150nrad/day). Nowadays, geophysical scientists and researchers predict the precursory activity of natural disasters including earthquakes and volcanoes by analyzing the monitored data of tilt change. The earth tide tiltmeter is so accurate and sophisticated that it is usually expensive.
Ri Hyok Min, a researcher at the Institute of Nano Science and Technology, developed a low-cost tiltmeter based on a capacitive micro-displacement sensor and conducted a calibration and field test.
The micro-displacement sensor is a differential capacitive one, which consists of two fixed plates and a movable plate. The movable plate is the bob of the vertical pendulum which reflects the tilt of the earth’s crust. The sensor signal is pre-amplified by the Low-Z type amplifier and then processed by the lock-in amplifier.
He calibrated the tiltmeter by using the heavy block method. He verified the measured data of the developed tiltmeter by using MATLAB. The prototype of the developed tiltmeter had been installed in the dedicated laboratory to be operated for 4 months.
The results show that the developed tiltmeter is simple and cheap for monitoring the tilt of the earth’s crust and it is useful for predicting the precursor of earthquakes and volcanoes.
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Jo Jan 7, 2026
The games for training martial arts in the period of Koryo included archery, fencing, spearing, horse-riding, Subak, ssirum, stone-throwing, running, etc.
These games reflecting the martial spirit of Koguryo were the improvement of the ways of playing and competition of those days.
During the Koryo dynasty, many archery grounds were built and game rules were made so that warriors and archery beginners could practise archery and have a match, and awarding ceremonies for them took place.
Horse riding developed, too. High riding skills like riding into and out of the fire as well as performing various tricks on the horseback were displayed in this period.
Subak of those days which was a combination of fistic fighting with kicking and heading was very powerful. The fact that there was a military unit specialized in Subak and national Subak matches were widely organized suggests that Subak was more popular than ever before.
In Koryo, ssirum was selected as an important martial art and ssirum games were held at every opportunity.
How much ssirum was encouraged and popular in those days is well explained by the fact that a Koryo king watched ssirum matches with warriors.
The strenuous effort of Koryo people to train martial arts including stone-throwing and running brought brilliant fruitions in anti-aggression wars for defending the sovereignty of the country and the dignity of the nation, and led to the great feats demonstrating the spirit of the Korean nation thereafter.
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Jo Jan 6, 2026
Line-start permanent magnet synchronous motor (LSPMSM) is a self-starting PMSM, which features both induction motor and conventional synchronous motor. The asynchronous torque generated by the stator-rotating magnetic field and its interaction with the squirrel cage rotor drives this motor. In normal operation, the rotor is driven at synchronous speed and the cage rotor is not actuated. Its operating principle is the same as that of a conventional synchronous motor. What is different is that the PMSM provides a permanent magnet (PM) with a magnetic field necessary for energy conversion, so it is simple in configuration and significantly high in energy density.
With the efficiency and power factor higher than induction motors, LSPMSMs have found wide application in various fields such as light industry, textile industry, oil industry, chemical industry and transportation. In particular, they have incomparable advantages over induction motors in respect of fans, compressors, pumps, etc. Therefore, there is a world trend to replace induction motors with them as they are stable in rotational speed and have high efficiency and power factor.
Many researchers have studied the starting, synchronizing and efficiency enhancement of LSPMSM and investigated the influence of various parameters. There is no research data available that detailed the rotor configuration, design method and manufacturing method for the induction motor to be modified to LSPMSM.
Ki Yong Chol, a researcher at the Faculty of Electrical Engineering, proposed a rotor configuration scheme to convert a three-phase low-power induction motor into LSPMSM, carried out the optimal design of the rotor, and simulated the motor characteristics under different operating conditions.
To verify the simulation results, he built a prototype and conducted a test. The test results were in good agreement with the simulation results, showing that the efficiency and power factor increased as compared with conventional induction motors.
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