Jo Jul 8, 2026
Currently, SCR (Silicon Controlled Rectifier) is widely used in power electronic devices to convert and control electrical energy.
If a rapidly rising anodic voltage is applied between the anode and the cathode without giving a gate trigger signal, the device is open even if it is much smaller than the breakover voltage under forward-off conditions. This turn-on mode is called dU/dt turn-on or dU/dt failure.
In thyristor fabrication, Al or Ni is used as electrode materials. Unlike the electrode structure of Al elements of p type, the emitter shorts structure was proposed for Ni electrode SCR, but it was not so useful because the emitter shorts effect was not significant and macroscopic shorts structure was found. One of the reasons is that the surface doping concentration of the shunt contact cannot be as high as the emitter region due to the limitation of emitter surface doping concentration when the device is fabricated, and the other is that the Al electrode structure does not suffer from the base-layer ohm contact problems, but the Ni electrode structure does not have ideal ohm contact. Therefore, increasing the p2 region surface doping concentration in a thyristor of Ni electrode structure is very important to improve the forward and reverse blocking voltage symmetry and dU/dt capability.
In order to enhance the cathode emitter shorts effect of SCR of Ni electrode structure, Kim Won Man, a researcher at the Institute of Semiconductor, has proposed a cathode groove etch scheme in which the surface doping concentration in the region p2 can be increased to the emitter region surface doping concentration value, and analyzed the relationship between the dU/dt capability and cathode groove etching structure parameters of the device.
The results show that forward and reverse blocking voltage symmetry is within 5% and the critical forward blocking voltage rise rate dU/dt is improved by 1.5 times.
His study results can be applied to power thyristors including TRIAC (Bidirectional Thyristor) with Ni electrodes and GTO (Gate-Turn-0ff Thyristor).
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Jo Jul 6, 2026
The Kaesong Chomsongdae Observatory is an astronomical observatory from the period of Koryo Kingdom which is situated in the west of Manwoltae in Kaesong Municipality.
In view of its present position and the records of the History of Koryo, the observatory is believed to have been built in the early period of Koryo, when the Yongyong Palace was being built on Manwoltae. Now there remains only its granite platform. Originally, there were astronomical observation instruments on the platform.
The plane of the platform was square and the platform consisted of stone pillars and stone floors laid on the pillars. The platform is 2.8 metres high and each side of it is 2.6 metres long. The pillar stones number five, four standing at the four corners and one in the middle. The sides of the platform face the cardinal points. It was constructed accurately and solidly.
From the early period of its foundation Koryo had national agencies in charge of astronomical and meteorological observation to do relevant observation at astronomical observatories and record the results meticulously. The records of sunspots observed from 1105 to the closing years of Koryo number over 150.
The Kaesong Chomsongdae Observatory is a valuable legacy showing the state of astronomical observation and high architecture of Korea at that time.
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Jo Jun 30, 2026
Real-time and omnidirectional observation of the ocean is of great significance in protecting the marine environment while enabling mankind to effectively develop and utilize marine resources. In particular, ocean currents and wind observation are very important in the observation of marine environmental quality. Ocean currents are the large-scale and relatively stable flow of seawater, which is one of the most important and universal forms of motion of the sea water, playing an important role in the stability of the global climate and ecological balance, and having many adverse effects on the livelihood and production of coastal people and the exploitation and utilization of the ocean. As a result, current measurement technology has been one of the main focuses of the oceanography. In addition, ocean wind observation has important significances in ensuring navigation safety, preventing disasters, assisting climate research, improving environmental protection and promoting resource exploitation and fisheries production.
Currently, ocean observation is mainly carried out by oceanographic buoys, unmanned vessel surveillance and satellite remote sensing. Ocean observation buoys, which have the longest history of development, can be mainly divided into two types; underwater observation buoys for specified points and surface drifting buoys that drift along the ocean current.
Of course, observations by unmanned ships and satellite remote sensing have been applied in ocean water measurement, but they cannot accurately measure ocean water at exact locations required by users, and real-time and long-term measurements are more difficult. In ocean water measurement using observation buoys, accurate measurement data can be directly measured and wirelessly transmitted in real time at any location required by observers.
Kim Chol Min, a researcher at the Faculty of Naval Architecture and Ocean Engineering, analysed the influence of the yaw and pitch characteristics of observation buoys on the measurement of the direction of the ocean current and wind direction, proposed a simple and reasonable measurement method, and verified its effectiveness through simulations and experiments.
The simulations and experiments demonstrated high accuracy of ocean current and wind direction measurements. The absolute error of the ocean current direction measurement is less than 0.5%, and 16 wind directions were accurately measured.
For further details, please refer to his paper “One method to measuring ocean current and wind direction from marine buoys” in “Journal of Atmospheric and Oceanic Technology” (SCI).
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Jo Jun 29, 2026
The opinion dynamics model which is being widely investigated by physicists can be largely divided into two types: discrete opinion models and continuous opinion models. The former uses a finite number of values to express agents’ opinions. The latter, unlike the discrete opinion models, takes a real number to represent agents’ opinions.
Some researchers studied the SJT model, one of the continuous opinion models. They proposed two thresholds: an acceptance threshold (d1) and a repulsion threshold (d2). According to their rules, when the difference in the inner opinion between two randomly selected agents is smaller (or larger) than d1 (or d2), the agents simultaneously update their opinions in the direction where their difference gets smaller (or bigger).
Jang Paek San, a researcher at the Institute of Nano Science and Technology, proposed a modified SJT model with a new opinion updating mechanism. Unlike the previous works, every individual affects the others’ opinions and the extent of the influence depends only on the magnitude in the opinion difference. To incorporate the convergence parameter of the assimilation effect and the divergence parameter of the repulsion effect into one parameter, he introduced a new function and used Monte Carlo simulations to study the opinion evolution process of the new model.
The simulation results showed that as d1 increases, the number of opinion clusters increases, but with increasing d2, the opinion dynamics changes from a bipolarization of opinions to a consensus of opinions.
For more information, you can refer to his paper “Social Judgment Theory model with continuous interaction between assimilation and repulsion mechanisms” in “SN Social Sciences” (SCI).
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Jo Jun 28, 2026
The introduction of a self-mixing (SM) displacement sensor into the measurement of mechanical vibration is an effective choice due to the characteristics of the SM interferometry (SMI). This is because the SMI has very favorable advantages for field measurement, for instance, high measurement accuracy, adaptability to any reflective surface, low cost, etc. Moreover, the compactness of SM sensors makes it easy to develop a hand-held portable device.
The key to developing a hand-held SM sensor is how to remove the hand-induced parasitic vibration. Since the removal of parasitic vibration is important for the accuracy of SMI, there have been many studies, divided into hardware-based and software-based methods.
Jang Kum Hyang, a researcher at the Institute of Mirae Industrial Technology, proposed a method of removing the hand-induced parasitic vibration based on data fitting, which is very simple and suitable for a hand-held self-mixing displacement sensor for the measurement of mechanical vibration.
The measurement accuracy that the proposed method provides is less than 30 nm.
If further information is needed, please refer to his paper “Removal of parasitic vibration in a self-mixing measurement for mechanical vibration based on data fitting” in “Applied optics” (SCI).
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Jo Jun 26, 2026
Previous papers suggested an end processing function, an enhanced smooth continuous condition and a method to overcome the defects of the precedent modified analytic embedded atom method (EAM) potentials considering the farther neighbor atoms by fitting model parameters to one or two structure energy differences. The structure energy differences and the binding energy curves as a function of volume calculated by these potentials are better than the calculation results by precedent modified analytic EAM (MAEAM) considering the farther neighbor atoms in the agreement with the experimental results and the Rose equation curves. The original MAEAM proposed only one many-body potential form for body-centered cubic (BCC), facet-centered cubic (FCC) and hexagonal close packed (HCP) metals. So, this potential has been frequently used in the calculation of the properties of metals and alloys. However, as the MAEAM considering farther neighbor atoms suggested different potential forms for different structures, using this potential is inconvenient and the application examples are rare. But it still gives better results than the original MAEAM.
Therefore, it is necessary to adopt a common potential form which can be applied to all kinds of metals such as the original MAEAM, simultaneously considering the farther neighbor atoms.
Ho In Chol, a researcher at the Faculty of Information Science and Technology, suggested a common pair potential form which can be applied to the three kinds of the typical structures of metals and explain the structure stabilities, the structure energy differences and the dependence of binding energies on lattice constants well.
The results by the common-form potentials of the modified EAM for the BCC transition metals Cr, Fe and Mo are in good agreement with experimental data and other calculation results, and significantly better than the precedent potentials for the BCC metals.
For further details, please refer to his paper “Common potential form of modified embedded atom method and BCC transition metals Cr, Fe, and Mo” in “Indian Journal of Physics” (SCI).
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