Jo Aug 10, 2026
The age of relics is determined by the amount of natural radiation that they were exposed to in the soil. Among the relics unearthed in our country are many ceramics showing the excellent culture of the nation. Quartz, the main component of ceramics, is compatible with thermoluminescence measurements because of the peculiarity of ceramics manufacture, and the relationship between the thermoluminescence intensity and the irradiated dose can be used to calculate the annual dose and to estimate the age of ceramics. The accuracy of the age is determined by the accuracy of thermoluminescence intensity measurements at the time of heating a quartz sample at a constant rate, and by the accuracy of annual dose estimates.
Kim Sung Ryol, a researcher at the Institute of Analysis, proposed a heating rate stabilization method for reproducibility and accuracy of thermoluminescence intensity and a method for estimating the annual dose rate from a ceramic sample in the soil by MCNP.
Unlike before, he applied heating temperature control to the set-point tracking method to ensure stability and to achieve correct detection of the peaks obtained from the thermoluminescence curve. In addition, he developed an MCNP-based annual dose rate assessment program to ensure the speediness of dating.
It was verified that the internal and external dose simulation calculation functions of the newly-developed computational system are in good agreement with the measurements reported in the literature and that it can be used to determine the annual dose rate of a real object.
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Jo Aug 9, 2026
The working principle of electron microscopes is to form an image by using electron beams and electron lenses instead of light beams and optical lenses in optical microscopes. The design and focusing characteristics of magnetic lenses determine the main parameters of electron microscopes. The electro-optical (EO) system of transmission electron microscopy can be classified into illumination and imaging systems. The former consists of an electron gun and a focusing lens while the latter is made up of a sample chamber, an objective lens and intermediate and projective lenses. In an EO system, lenses are the most important components and the one that plays a crucial role among lenses is an objective lens.
There are many studies in the literature on the method of calculating the focal length of magnetic lenses in transmission electron microscopes, but these calculations are empirical, based on only pole-piece diameter, gap and the number of excitation turns in a magnetic lens. The effect of the change of various factors such as other structural dimensions, magnetic lens material and magnetic circuit configuration on the focal length is not mentioned, .
In magnetic lenses, the pole-piece diameter and the gap are of primary importance, but the magnetic circuit constituting the lens, the position of the magnetic flux-making coil, and other structural dimensions will influence the magnetic field distribution and the focal length. Therefore, the conventional focal length calculation method presents many problems in the design of real magnetic lenses.
Kim Hak Chol, a researcher at the Faculty of Electronics, proposed a new method of calculating the focal length by simulating the magnetic field distribution and trajectory of a magnetic lens.
Using a simulation tool, he set the structure dimensions, excitation conditions and material settings just like real ones and calculated the magnetic field distribution based on them. Then, he determined the focal length from the trajectory data by means of the method of calculating the focal length based on the electro-optical theory.
Unlike conventional focal length calculations, the proposed method can improve the accuracy of magnetic lens design, with all the factors affecting the focal length in consideration.
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Jo Aug 7, 2026
Accurate quantitative evaluation of the performance of pneumatic rock drills is important to improve the performance and put the design on a scientific basis.
A rock drill receives energy from a compressor or a hydraulic system and transfers impact energy through the drill and bit to crush rocks. Impact energy, the main performance index of rock drills, was estimated by many researchers in an indirect way because direct measurement is difficult.
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, Pak Chol Hyok, a researcher at the Faculty of Mining Engineering, proposed a new structure of impact energy measurement device and analyzed its performance 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, suitable location of measurement points can raise measurement accuracy while extending the service life of the sensor.
The newly proposed measuring device is more reliable and more convenient to operate than the method of determining the impact energy by stress wave measurement.
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Jo Aug 6, 2026
Generally, the design of small acoustic devices for mobile phones uses acoustic analysis techniques involving equivalent circuits. This acoustic analysis technique is an approach to find acoustic parameter values on acoustic equivalent circuits from the size values of angular acoustic device by the classical acoustic theory-based acoustic theory equation, and to predict acoustic properties electronically based on their acoustic parameters. Thus, it provides simple modeling and it does not take a long time to interpret. However, this acoustic analysis technique cannot predict exact acoustic characteristics because it cannot represent the variation of acoustic parameters due to the change of the “position relationship” or “geometry” in acoustic devices.
Han Myong U, a researcher at the Faculty of Communication, proposed an acoustic parameter estimation method which verifies, by finite element method, the structure of resonance frequency response due to the acoustic porthole position that could not be explained by the original equivalent circuit analysis method, and explains acoustic weight and acoustic capacity.
A genetic algorithm has been used for traditional acoustic parameter estimation, but it requires a very long time to estimate the correct factor because it depends on the search by mutations around the optimal solution. The proposed estimation method uses a hybrid genetic algorithm that switches to simulated annealing that performs well local retrieval after convergence to some extent around the optimal solution by a genetic algorithm.
He compared the measured results with the simulation results by the proposed method to validate its effectiveness. The results showed that the proposed estimation approach can accurately estimate acoustic capacity with respect to resonant frequency, and acoustic mass parameters, and it is possible to estimate acoustic parameters with respect to the position or shape of a compact acoustic device.
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Jo Aug 4, 2026
Lithium has been used as molten salt in aluminum electrolytic baths, as an additive in glass and ceramic manufacturing, and for lubricant production. With the development of science and technology, the application range of lithium has been further extended—it is particularly widely used in the fields of battery, rubber, refining, refrigeration, welding, medicine, aviation and nuclear power. Lithium isotope 6Li has become the main material of thermonuclear reactions, and lithium is an important energy source for the development of human society, with its wide use in thermonuclear reactions and high-energy lithium batteries. Among more than 130 lithium minerals known so far, the most industrially-valued mineral is spodumene.
Spodumene is being separated by various methods, among which flotation is dominant for lithium ore.
Previous studies on the flotation of spodumene mainly focused on cleaning using anion collectors, which indicates that reagent systems are different depending on the type and amount of gangue minerals present in the ore.
Kim Song Chol, a researcher at the Faculty of Mining Engineering, investigated the effects of several reagents on the flotation performance of spodumene via flotation experiments, and evaluated the mechanism of various components in fatty acid soap on spodumene surface via quantitative mechanical simulations.
The results of an individual experiment and an optimization experiment showed that a concentrate with Li2O grade of 2.55% can be obtained with recovery of 76.89% in roughing flotation.
The simulation results of the interaction energy between spodumene {110} surface and several kinds of fatty acid soap showed the following order of adsorption strength; sodium linoleic acid > sodium linolic acid > sodium oleic acid > sodium palmitin acid > sodium stearic acid.
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Jo Aug 3, 2026
The Ryongwang Pavilion is located in Taedongmun-dong, Central District, Pyongyang.
It was built in the mid-6th century in the period of Koguryo Kingdom and rebuilt several times afterwards. The present site of the pavilion was originally the site of a general’s terrace in the east of the keep of the Walled City of Pyongyang during the period of the kingdom. As the walled city was renovated and named Sogyong during the Koryo Dynasty, the pavilion was rebuilt in the same place and named Sansu Pavilion in 1111. It was repaired several times later and rebuilt in 1670 during the feudal Joson dynasty and renamed Ryongwang Pavilion.
It has been known as one of the eight scenic spots in the northwestern part of Korea from olden times for the beautiful scenery. It was also called the “most beautiful pavilion” and “Manhwa Pavilion”. On the pavilion is a calligraphic hanging board inscribed with the letters “The most beautiful place in the world”.
The pavilion showcasing the excellent architecture of the Koreans is associated with the patriotic struggles of the ancestors who repulsed foreign invasions.
Although it was badly damaged by the brutal bombing by the enemy during the Fatherland Liberation War, it was restored soon in the postwar period. It is now under good preservation as a national treasure and serves as a cultural recreation site for working people.
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