Jo Jan 16, 2026
Point-type smoke sensors detect fire through sensor signals that are changed by smoke, which occurs early from the fire. However, the drawback of these smoke sensors is the drift of sensor signals due to the sensitivity to environmental changes. This can be the cause of occasional false alarms.
The first reason for sensor signal change in smoke sensors is seasonal changes in temperature and humidity. Secondly, in the case of an ionic smoke sensor, the accumulation of dust layers on the surface of radiation source decreases the ion current and the leakage of current between the electrodes causes the sensor signal to change. Inherent noise caused by the uncertainty of the radioactive decay for ionization is another reason, which is inversely proportional to the square root of the radioactivity. Lastly, the radiation sources used for the ionic smoke sensor are not uniform, so the sensitivities and signals of the sensors are also different, which also degrades the accuracy of fire alarm in a fire monitor based on a fixed threshold.
By these factors, sensor signals tend to increase or decrease slowly with time. If these signals are higher than a fixed threshold already set, the false alarm can be heard in the absence of fire, and if they are lower, they may generate the alarm late for real fires or may not generate the alarm at all. Therefore, smoke sensors or fire monitors need to adjust the threshold actively according to the sensor signals.
Jo Jin Song, a researcher at the Institute of Analysis, designed and verified a compensation algorithm that can automatically adjust the threshold for point-type smoke sensors or fire monitors.
The algorithm does not fix the threshold that is the criterion for identifying fire presence, but it can adjust it gradually to the change of sensor signals to improve the accuracy of alarm.
This algorithm can be applied to almost all point-type smoke sensors or fire monitors for active fire detection.
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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 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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