Jo Nov 28, 2025
Terbium belongs to the lanthanide or “rare earth elements (REE)” group of elements in the periodic table. However, rare earth elements are dispersed and they are not generally found concentrated as rare earth minerals (REM) in economically exploitable ore deposits. Terbium only occurs in trace quantities even in its ores. It is found in some minerals such as bastnaesite, monazite, xenotime, euxenite and gadolinite ores, but in low concentrations, on the order of 1%.
Terbium and its compounds are used as phosphors. Terbium phosphors give off a green light when struck by electrons. Phosphorescent terbium compounds are used in cathode ray tubes, light-emitting diodes, lasers, sensors, etc. Thus, terbium extraction processes need to be further studied and improved to include more economical and profitable methods.
Choe Kyong Mun, a researcher at the General Assay Office, has investigated the electrochemical behaviors of terbium in TbCl3-1-ethyl-3-methyl-imidazolium tetrafluoroborate [EMIm]BF4 electrolytes and TbCl3-1-ethyl-3-methyl-imidazolium dicyanamide [EMIm]DCA.
X-ray diffraction analysis results of electrodeposits from TbCl3-[EMIm]BF4 electrolytes and TbCl3-[EMIm]DCA electrolyte prove that metallic terbium is obtained.
For more information, please refer to his paper “Electrochemical behaviors of terbium from TbCl3-EMImBF4 and TbCl3-EMImDCA ionic liquid electrolytes: a comparative study” in “Journal of Solid State Electrochemistry” (SCI).
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Jo Nov 27, 2025
A protective relay plays a crucial role in the normal operation of a power system and the reliable supply of electrical power. The reliable operation of an electrical power transformer is very important in maintaining uninterrupted power supply. In a protective scheme for a transformer, high speed of protection and reliable operation against clear faults are essential.
Many advanced algorithms for power system protection have been implemented on the relay protection devices based on microprocessors in programming form. To be candid, there are no references showing the results related to the design and implementation of a multi-function protective relay for a power transformer.
Im Jung Bin, a researcher at the Faculty of Electrical Engineering, has proposed a method for implementing a modularized multi-functional hardware transformer protective relay based on Field programmable gate array (FPGA) for higher speed operation of protection.
Taking the advantage of parallelism feature of FPGA, the proposed hardware transformer relay can process multi-channel input signals at high speed in real time, and concurrently estimate and process protective logics with different functions. By using a single Altera CycloneⅢ EP3C40Q240CN8 and configuring different-function protective relays, this relay allows high-speed operation which is a basic demand for protection.
This relay can operate within 1.1 cycle of power frequency.
You can find details in his paper “A Structure of Transformer Protective Relay for Implementing a High-speed Operation of Many Protective Functions Using a Parallel Processing Feature of FPGA” in “Journal of Electrical Power & Energy Systems” (EI).
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Jo Nov 26, 2025
Airlift pumps are considered an effective means of lifting deep ocean water due to their several advantages such as high reliability, simple structure, low cost and convenient maintenance.
The airlift pump is a fluid machine for raising liquids or slurries through a vertical pipe by injecting compressed air into the pipe near its mid position or lower end part, and its performance is therefore related to the state of multi-phase upflow in the pipe.
Rim Un Ryong, a researcher at the Faculty of Shipbuilding and Ocean Engineering, has conducted a numerical analysis of steady air–water two-phase flow in a vertical pipe of an airlift system based on a one-dimensional multi-fluid model.
He calculated the depth distributions of 6 physical quantities such as volumetric fractions and axial velocities of two phases, air density and pressure by solving the governing equations or by integrating the vector form of nonhomogeneous ordinary differential equation for two-phase flow interval.
He applied the proposed numerical model to a 7.86-meter-long vertical pipe and compared the results with antecedent theoretical and experimental results to validate its accuracy. The results showed good agreement.
If further information is needed, please refer to his paper “Numerical analysis of air–water two-phase upflow in artificial upwelling of deep ocean water by airlift pump” in “Computers and Fluids” (SCI).
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Jo Nov 25, 2025
Ocean wave energy has great potential to cope with increasing energy demand since it is renewable, sustainable and green energy and its overall resource is estimated to be around 2TW.
Some wave energy devices can be modeled as submerged oscillating bodies, which requires a deep understanding of hydrodynamic interaction between ocean waves and submerged bodies.
Many numerical methods have been proposed for bodies in irregular or arbitrary shapes, but it is important to specify boundary conditions on a virtual cylindrical surface between mean free surface and seabed.
Rim Un Ryong, a researcher at the Faculty of Shipbuilding and Ocean Engineering, has investigated three-dimensional linear interaction between a submerged oscillating body in arbitrary shape and the regular water wave with finite depth.
First, he derived an exact Dirichlet-to-Neumann (DtN) boundary condition on a virtual cylindrical surface, where the virtual surface was chosen to enclose the body and extract an interior subdomain with finite volume from the horizontally unbounded water domain.
Then, he applied the DtN boundary condition to solve the interaction between the body and the linear wave in the interior subdomain with the boundary integral equation.
He has validated the proposed method via a submerged vertical cylinder. The result shows a good agreement with the analytical results of precedent papers.
For more information, please refer to his paper “Free surface wave interaction with a submerged body using a DtN boundary condition” in “Theoretical and Computational Fluid Dynamics” (SCI).
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Jo Nov 24, 2025
A single-tuned harmonic filter is a passive harmonic filter widely used to eliminate harmonics in power systems.
Minimizing the impedance of the filter at the corresponding harmonic frequency makes the harmonic voltage produced by the harmonic current generated by the non-linear load a minimum. This is the principle of filtering in a single-tuned harmonic filter.
While eliminating the corresponding harmonic, the single-tuned harmonic filter affects the fundamental power factor. That is because the single-tuned harmonic filter itself is capacitive at the fundamental frequency. In the past, most power systems were inductive at the fundamental frequency, so in general, their capacitive characteristics played a positive role in raising the power factor of power systems. But nowadays, with the widespread use of power electronic devices, there have been more and more loads that are non-inductive at the fundamental frequency in the power systems. In this case, using conventional single-tuned harmonic filters results in the decrement of the fundamental power factor and the increment of transmission loss. In order to overcome these disadvantages, it is necessary to develop a new type of filter that eliminates harmonics but does not influence the fundamental power factor.
Ji Kuk Ryol, an institute head at the Faculty of Electrical Engineering, has proposed a novel single-tuned harmonic filter, which can remove harmonics with the fundamental power factor unchanged.
The proposed filter can be applied to filtering the harmonics made by a load whose fundamental power factor is 1 or capacitive.
You can find more information in his paper “Novel Single Tuned Harmonic Filter not Affecting Fundamental Power Factor” in “Journal of Electrical Power & Energy Systems” (EI).
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Jo Nov 23, 2025
Sensing nitrogen oxide gas is important for measuring pollution gas and detecting pollution sources from vehicles and chemical processes in the atmosphere and for diagnosing the diseases of human body by measuring NO2 gas from breathing. Therefore, it is necessary to measure the range of dilute concentration and to develop a less power-consuming electrochemical method.
Kim Yong Hyok, a researcher at the Faculty of Electronics, has designed the structure of a new NO2 gas sensor and conducted a qualitative analysis of its performance. In addition, he has established its manufacturing process and experimentally analyzed the bias voltage properties.
The new sensor can linearly sense NO2 gas of up to 100ppm.
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