Jo Mar 18, 2026
Transparent conducting oxide (TCO) films have been widely used as transparent electrodes in the optoelectronic devices such as flat panel displays and thin-film solar cells. Among them, Al-doped ZnO (AZO) films are being studied most due to their rich resources of Al and good electrical and optical properties.
The sputtering ambient has an influence on the microstructure, composition and electrical and optical properties of ZnO based films deposited by sputtering.
Some studies showed that adding appropriate amount of H2 into sputtering ambient leads to enhancement of the electrical properties of films. This encouraged many attempts to improve the properties of doped ZnO films by adding H2. However, there is little literature that dealt with the effects of H2 content on the properties of doped ZnO films deposited at low temperature and at high temperature.
Ri Kang Hyon, a section head at the Faculty of Material Science and Technology, compared the influence of H2 addition to sputtering ambient on the microstructural and electrical properties of AZO films deposited by r.f. magnetron sputtering at low temperature (100 ℃) and high temperature (400 ℃).
The results showed that for the AZO films prepared at comparatively low temperature around 100 ℃, small addition of H2 to sputtering ambient was favorable for enhancing the electrical properties of films, but for those at high temperature around 400℃, any addition of H2 was unfavourable at all.
For more information, please refer to his paper “Influence of hydrogen addition to sputtering ambient on the properties of AZO films deposited by sputtering” in “Physica Scripta” (SCI).
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Jo Mar 17, 2026
Selective laser melting (SLM) is one of the most popular advanced manufacturing techniques. SLM is an additive manufacturing (AM) technique that enables production of complicated metal products with high precision and flexibility and acceptable surface finish. It uses a high-intensity laser beam as the energy source to selectively melt metallic powder, which is dictated by 3D CAD data.
SLM enables production of critical parts which are impossible by various traditional metal forming techniques such as casting, forging, extrusion and metal cutting. Unlike the traditional manufacturing techniques, it manufactures 3D objects by gradually adding metal powder layer by layer according to the CAD model. With no need for any dies or tools, it may help to shorten design and production cycles and save time and costs for production.
SLM process parameters affect the multiple quality attributes of SLM-built parts. Thus, it is important to develop a new optimization methodology of SLM process parameters for improving the multiple quality attributes of SLM-built parts. It is a multi-objective optimization (MOO) problem. The multiple quality attributes are converted into a single overall quality index (OQI) using multi-attribute decision-making (MCDM) method, and the MOO problem is converted into a single objective optimization (SOO) one. The optimization results may differ according to the applied MCDM method.
In order to solve this problem, Yang Ji Yon, a post-graduate student of the Faculty of Material Science and Technology, proposed a reasonable process optimization methodology for improving multiple quality attributes of SLM-built parts using integrated OQI (I-OQI) combined with multiple OQIs obtained from multiple MADM methods.
She applied the proposed methodology to optimizing the process parameters such as laser power (LP), scan speed (SS) and overlap rate (OR) for improving five quality attributes of SLM-built AlSi10Mg alloy such as tensile strength, hardness, relative density, volumetric energy density and build rate.
The optimal values of the SLM process parameters obtained from Taguchi and grid search optimization methods were LP 320 W, SS 900 mm/s and OR 0.25.
The proposed methodology could be actively applied to the SLM process optimization of not only Al alloys but also various metal/alloys.
For further details, you can refer to her paper “Process Optimization for Improving Multiple Quality Attributes of AlSi10Mg Alloys Manufactured by Selective Laser Melting Based on Integrated Overall Quality Index” in “Russian Journal of Non-Ferrous Metals” (SCI).
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Jo Mar 16, 2026
Pyrochlore, which contains some rare metals such as tantalum and niobium and many yttrium group rare earths such as erbium and ytterbium, is of very high commercial value. Therefore, it is very important to efficiently recover valuable metals from pyrochlore.
To date, tantalum-niobium ores such as pyrochlore have been treated by using various methods including alkali digestion, acid leaching and chlorination. At present, NaOH or KOH melting digestion method is not applied to the industry due to its low digestion rate, high energy consumption, high reagent consumption and dangerous operations. The consumption of alkali in the pressure leaching is lower than that in the melting digestion, but it is also not applied to the industry due to its operation difficulties. Concentrates are digested at 120-200℃ with concentrated sulfuric acid in the sulfuric acid leaching, which has some drawbacks such as low digestion rate, complex process and high reagent consumption. In the hydrofluoric acid leaching, concentrates are leached at 90-100℃ with 60% HF. This method is now widely used in the industrial processes due to its high tantalum leaching rate (>85%) and easy production of high-purity tantalum. However, the wastes of about 10-15 tons containing fluorine are produced when 1 ton of concentrates is treated, which leads to serious environmental pollution. What is more, the tantalum leaching rate decreases below 85% when low-grade niobium-tantalum concentrates are treated, so this method causes wastage of resources.
Recently, the KOH sub-molten salt (SMS) leaching has been applied to treating ilmenite, vanadium slag, chromite ore and fergusonite, bringing successful results. This technology has several advantages including low environmental pollution, low reagent consumption, mild degradation conditions and high recovery of valuable metals.
Considering all the preceding studies, Kang Chung Su, a section head at the Institute of Analysis, investigated a new decomposition method of pyrochlore concentrate into high KOH solution in order to effectively recover tantalum and niobium from pyrochlore concentrates while reducing environmental pollution at the same time.
The results showed that when the pyrochlore concentrate with a particle size of less than 75㎛ is added to 80% KOH solution in a mass ratio of KOH to concentrate 3:1, and decomposed at 300℃ for 2h at the stirring rate of 80r/min, 95% decomposition rate of pyrochlore concentrate is guaranteed.
You can find more information in his paper “Study on the Environmental Friendly Decomposition Method of Pyrochlore Concentrate in High KOH Solution” in “Proceedings of KUTIC-2025”.
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Jo Mar 15, 2026
The gain and phase information are the important characteristic quantities of frequency domain for stability analysis and control design.
Many researchers have used LMI as an important tool for stability analysis and control design. Although LMI has a limitation that the feasibility is not guaranteed in some cases, it has been widely used in various control problems because it does not require specific assumptions.
Pak Ji Min, president of Kim Chaek University of Technology, presented a solution to the multivariable version of new Ψ-control and H∞/Ψ-mixed control problems with the phase design criterion that enables solving of some control design problems which cannot be achieved by the H∞-control theory.
First, he derived a new phase condition involving linear matrix inequality (LMI) for multi-input multi-output (MIMO) system. He then proved that the phase condition includes the positive real one for a given system and is guaranteed by the bounded real condition for the corresponding transformed system.
Second, he developed new LMI-based solutions to multivariable Ψ-control for both state feedback and dynamic output feedback. He performed H∞/Ψ-mixed control design by combining H∞-control and Ψ-control.
Finally, he illustrated through design examples the significance of phase criterion in the control design, and the effectiveness of the proposed solutions.
For more information, you can refer to his paper “LMI-Based Solution to Multivariable Ψ-Control and H∞/Ψ-Mixed Control Problems” in “Proceedings of KUTIC-2025”.
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Jo Mar 13, 2026
In physical exploration including magnetic prospecting, it is a basic requirement to explore in a regular network of standards. However, due to the various obstacles encountered in the survey, measurement is generally not performed in a regular network. Therefore, it is very important to study inversion algorithms with high noise reduction ability and increase the accuracy of sampling of the measured data at irregular intervals.
Ri Hyon Sok, a researcher at the Faculty of Earth Science and Technology, proposed a method of using the Fourier transform-based robust estimation method for processing magnetic prospecting data measured at disproportionate intervals, based on its high sampling accuracy and high noise enhancement capability, and demonstrated the advantage of the proposed method though model experiments and application.
The results of model calculations and field applications show that the magnetic prospecting analysis by the Fourier transform-based robust estimation method is superior to the existing magnetic susceptibility tracking imaging.
For more information, please refer to his paper “Study on the Application of Fourier Transform-Based Robust Optimization for Magnetic Inversion” in “Proceedings of KUTIC-2025”.
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Jo Mar 11, 2026
Mt. Paektu volcano is the largest intraplate stratovolcano located at the border of the Democratic People’s Republic of Korea (DPRK) and China. It is of great interest to volcanologists worldwide due to 3 factors: 1) its geographical location (nearly 1 400km far away from the subduction region of the Pacific plate); 2) one of the largest eruptions during the past 2 000 years and 3) a 2002-2005 unrest episode showing its potential for future activity.
One key focus of study on volcanoes is the depth and geometry of a magmatic system. Especially, resistivity is sensitive to the presence of fluids and magma, and can provide fundamental information on a variety of volcanic activities.
Originally, some researchers suggested that MT data revealed a conductivity anomaly at approximately 20km depth beneath the volcano. Later, some other ones conducted a 3-D inversion for a MT dataset along about 120km profile, proposed a resistivity model beneath the volcano and asserted that three relatively high conductive zones exist at the depths of 3-5km, 10-16km and 40-60km.
However, much of the geophysical work in the international literature is largely based on the data from China.
To delineate the resistivity structure beneath the DPR Korea side of the volcano, Kim Kang Sop, an institute head at the Faculty of Earth Science and Technology, collected magnetotelluric (MT) measurements in the frequency range of 0.0017-320Hz at about 60 sites to produce a 3D resistivity model, showing the presence of 3 conductors within the top 20km of crust.
He employed a 5-channel MT receiver, three inductive magnetic sensors and two electrical dipoles with Pb-PbCl2 electrodes manufactured at Kim Chaek University of Technology (KUT).
He conducted a 3D inversion using the ModEM3D code.
His research results are consistent with previous MT and seismic studies.
You can find the details in his paper “Magnetotelluric Constraints on the Magmatic System Beneath Mt. Paektu Volcano” in “Proceedings of KUTIC-2025”.
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