Jo Sep 17, 2025
With the rapid development of plasma technology, plasma activated water has recently been introduced to agricultural sectors with the potential to increase the germination, growth and grain yield of crops.
Plasma discharge devices to activate water are currently divided into two types. One is to contact various chemical active species produced after plasma discharge in the gas phase with liquid to form secondary active species in it. This is achieved by plasma injection or natural diffusion of plasma activated species such as surface dielectric barrier discharge. The other one is the direct contact of liquid with plasma discharge, and the water is placed in the discharge space. This is achieved by direct plasma discharge between several electrodes, such as a needle electrode or a plate electrode, and water surfaces.
An Song Il, a researcher at the Institute of Nano Science and Technology, has performed water treatment by plasma flow which he formed by high-frequency high-pressure discharge and contacted with water, and compared the production of active species according to two discharge modes (discharge mode using dielectric barrier discharge and discharge mode using a spark discharge between two needle electrodes and water surfaces).
The experimental results show that the plasma treatment mode by dielectric barrier discharge was higher in the production of active species when compared with plasma activated water treated by spark discharge. Therefore, he has concluded that the discharge method using dielectric barrier discharge is superior for mass production of plasma activated water for agricultural applications.
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Jo Sep 16, 2025
In order to actively develop marine resources for sustainable economic development, it is necessary to identify the types, distribution locations and reserves of seabed mineral resources. All seabed work is impossible without seabed sample exploration, whether it is a study of seabed geological structure or seabed resource exploration.
Ri Jong Chol, a researcher at the Faculty of Shipbuilding and Ocean Engineering, has designed a gravity corer with a spring release mechanism for re-identification of a seabed phosphorite distribution area, and determined the critical velocity before the free fall of the corer designed for sample seabed phosphorites at the depths of 1 000-2 000m.
He has found that the range of critical velocity increases with the increase in the mass of the corer and the decrease in the stiffness of the spring, and that it decreases with the length of a lever arm.
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Jo Sep 15, 2025
Calculation of riser for steel casting is more important than that for other alloy castings because of the high shrinkage and pouring temperature of cast steels, which leads to severe shrinkage defects.
Among the different calculation methods, the cubic equation method can be used to calculate the shape and dimensions of riser in parametric forms, but it is not widely used due to the large computational amount.
Numerical simulations of the solidification process of cast are more and more used in the design of casting process because of the economy of time and effort as well as the increased accuracy. Many researchers have studied the process of the flow and solidification processes of castings using ProCAST. Most of them, however, found the optimum values by constructing initial design schemes and repeating simulations and modifications. Also, the inclusion of excess mass in the riser is unavoidable, which reduces casting yield.
Hence, it is necessary to establish a methodology to determine the optimum size of the riser while saving the time for simulations.
Ri Hak Song, a researcher at the Faculty of Materials Science and Technology, has set the hydro-powered Pelton turbine blade casting as the main research project, and optimized the riser by combining the numerical simulation analysis by ProCAST with the cubic equation method.
He performed a calculation of the riser by the cubic method and a numerical simulation by ProCAST, a simulation tool for casting processes, to identify the most suitable riser.
The results of the study show that the yield of riser calculated by the cubic method does not differ significantly with the change in the shape of riser, but the elliptical shape is the optimum shape of the riser, with the ratio of height to width of 1.3 and the yield of riser of 67.5%.
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Jo Sep 14, 2025
Ozone water is made by dissolving into water the gaseous ozone generated during the discharge of oxygen or air or the electrolysis of water.
There are several methods for ozone water production from generated ozone gas, such as porous, bubble tower, U-tube, spray tower, Venturi tube, etc. Among them, venturi-based ozone mixers are widely used, due to their excellent features such as cost, performance, installation area, power consumption, etc.
One of the important ways to increase the concentration of ozone water in the venturi ozone mixer is to increase the amount of ozone gas inhalation into the gas intake. Previous studies only considered the pressure change or velocity change inside the venturi, but not much work has been done on the inhalation volume at the intake.
Rim Chol Bom, a researcher at the Institute of Nano Science and Technology, has determined the optimum geometry of a venturi tube for ozone water production through computational fluid dynamics (CFD) simulations.
The numerical results are inlet diameter of 40mm, throat diameter of 12mm, converging angle of 27° and gas inlet diameter of 7mm, with inhalation rate of 0.100 6g/s.
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Jo Sep 12, 2025
Polyester fibers currently represent more than half of fibers in global use, and the most commonly-used of them is polyethylene terephthalate (PET), which has continued to increase in its production. In addition, with the improvement in the people’s living standard, the use cycle of textiles is getting much shorter, which leads to the production of textile waste, reaching 90% of global fiber production. On the other hand, resource depletion and environmental pollution have become a serious problem, and people have been better aware of the environmental system, which has encouraged positive efforts to recycle textile waste.
There are three main ways to reuse waste textiles, namely, mechanical, physical and chemical methods. In the chemical method, polyester is decomposed into monomers or oligomers before being separated and purified to obtain desired chemical products. This is a complete fiber-fiber cycle technique that can produce new textile fibers from waste textiles. In the 2010s, some countries synthesized PET for textile fibers by applying the chemical method to PET waste plastics to produce clothing such as suits, shirts, etc. Chemical recycling methods of post-consumer PET include glycolysis, hydrolysis and others. In glycolysis, in particular, Bis(2-hydroxyethyl terephthalate) monomer (BHET) and oligomer are obtained by trans-esterification between diol and ester groups of PET.
Since BHET is used as a PET synthetic feedstock, many studies have been carried out on glycolysis of PET. However, previous studies addressed glycolysis of relatively clean PET waste, and little attention has been paid to PET waste fibers containing various impurities such as dyes.
Ri Myong Chol, a researcher at the Faculty of Materials Science and Technology, has investigated the preparation of BHET by glycolysis of PET textile waste under microwave irradiation.
The experimental results show that high purity BHET used as a precursor for PET synthesis can be prepared by pre-decolorization of PET textile and glycolysis of PET before recrystallization of BHET.
When PET textile and PET plastics are glycolyzed under the same reaction conditions, the conversion of PET and the yield of BHET are higher in the fiber than in the plastics. The reason lies in the fact that the depolymerization reaction rate gets faster in the PET fiber because the specific surface area of fiber is much larger than that of plastics and the molecular weight of PET fiber is lighter than that of PET plastics.
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Jo Sep 10, 2025
Kwangbop Temple, situated in Taesong-dong, Taesong District, is one of the typical Buddhist temples in Pyongyang and the surrounding area. It was built during the period ruled by King Kwanggaetho of Koguryo and rebuilt in 1727. In July, 1952, during the Fatherland Liberation War, it was completely destroyed by the US imperialists’ bombing and it was restored to its original state in 1990.
Kwangbop Temple is comprised of Taeung Hall, eastern and western monasteries, five-storied octagonal pagoda, etc. The buildings are distributed symmetrically with the pagoda in the center. The way of siting buildings on the four sides of a pagoda was frequently found in the period of Koguryo.
Taeung Hall, the main building of the temple, is a magnificent two-storied gabled house. In the hall are placed three Buddhist statues including Shakyamuni Tathagata and some Buddhist images. The hall is painted colorfully in glittering gold.
The lotus pond transmitted from olden times and the monument to Kwangbop Temple erected in 1727 still remain around the temple. The legend about the nine dragons and ninety-nine ponds of Mt. Taesong, namely, Mt. Kuryong is recorded on the monument.
Kwangbop Temple on the picturesque Mt. Taesong is in good preservation and care as a national treasure and a precious cultural legacy demonstrating the advanced architectural skills of Korean ancestors in those times.
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