Jo May 11, 2025
Chongbaek Juniper growing in Chongbaek-ri, Kumya County, South Hamgyong Province was planted around 1550. It is 10 meters tall, with the root collar of 5.4 meters round and the canopy of 18 meters from east to west and 21 meters from north to south.
At the height of 50 centimeters, it spreads in three big branches that are 2.6 meters, 2.1 meters and 2.2 meters round, respectively.
It looks like a collection of small clouds from a short distance and like a large furled umbrella from a long distance.
The oldest and largest tree on the eastern coast is a natural monument that is significant for studying the size and age of juniper trees and adds beauty to this area.
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Jo May 9, 2025
Plasma technology has been widely used in various forms in the fields of functional materials, new materials synthesis, metal cutting, ozone generation, air purification, food, environmental, chemical, mechanical industries, etc. In particular, surface treatment of objects based on plasma has been studied by many researchers because it can improve several properties of the surface and broaden its application.
Dielectric barrier discharge is a very effective non-equilibrium plasma generation method that prevents the transition into spark and arc discharge that occurs in the discharge gap by inserting dielectric into the discharge space. Corona discharge is also an effective method of non-equilibrium plasma generation at atmospheric pressure. However, its discharge area is small and the power density is not high. Hence, if corona discharge and dielectric barrier discharge are properly combined, the discharge is more uniform and stable due to the corona effect at the corona electrode in the discharge space and high power density atmospheric pressure discharge can be realized.
The discharge formed by high frequency and high pressure after the insertion of dielectric into the corona discharge space is called dielectric barrier corona discharge (DBCD). Treatment of the surface of resin or cloth by DBCD can improve the surface properties by changing the adhesion, resistance, dyeing, painting, gloss, wear resistance, hydrophobicity, etc.
Kim Jin Hyok, a researcher at the Institute of Nano Science and Technology, has generated dielectric barrier corona discharge using quartz glass as dielectric in the atmosphere, treated the surface of Tetron fabric by passing it through the discharge space, and considered the change of its characteristics. At high frequency, high pressure power supply of 15 kHz and 18kV, he treated the Tetron fabric with varying discharge power, treatment speed and number of treatments, and measured the change of water penetration time to compare its surface characteristics.
As a result, he has found the following.
First, the higher the discharge power is, the shorter the water penetration time gets and the better the hydrophobicity becomes. When the slower the treatment speed is, i.e., the longer the treatment time for the unit area of the Tetron fabric is, the higher the treatment efficiency is, which leads to the shorter water penetration time. The more the number of treatment is, the better the surface properties become and the shorter the water penetration time gets.
From these characteristics, he determined the optimal surface treatment parameters by the Taguchi method. They are 900W of discharge power, 7cm/s of treatment migration rate and 4 rounds of treatment. Under these conditions, water penetration time is 9.2s.
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Jo May 7, 2025
The Ancestral Apple Tree is in Ryongjon-ri, Pukchong County of North Hamgyong Province, a place famous for apples.
In October, 1959, President
In June, 2002, Chairman
This long-lived apple tree over the age of 100 is still growing healthily.
Its root collar is 1.2 meters round and the canopy is as wide as 6 meters. It blossoms in May with long and deep green leaves.
This oldest tree in our country is a precious natural monument of significance for judging the maximum age of apples and studying the characteristics of their varieties.
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Jo May 6, 2025
A torque converter, equipped between engine and transmission, is a complex turbo-machine to transfer power from engine to transmission by means of interaction of moving fluid and blade cascades. A torque converter is widely used in vehicle transmissions and industrial power transmissions because of its outstanding automatic torque amplification, good acceleration performance and absorption of excessive vibration.
The design of blade cascades is the kernel part of a torque converter design. The blade cascades consist of complex surfaces and 3D curves, so it is very difficult to design and optimize them. There are two parts in the design of blade cascades: modeling of blade surface and its performance evaluation based on CFD analysis.
Kim Myong Hak, a researcher at the Robotics Institute, has proposed a practical torque converter design approach based on CFD analysis.
First, he built a 3D model of torque converter blades by ANSYS BladeGen and predicted their performance by CFD simulations. Second, he modeled the angle and thickness distribution curves at the core and shell of blades by Bezier curves, and improved the performance of the torque converter by controlling the control point of Bezier curves based on CFD simulation results. As a result, he established the methodology for designing torque converters with the required performance saving computation time and costs.
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Jo May 5, 2025
Among the precious and beautiful natural monuments in the DPRK is Kimhwa Elm Tree.
Kimhwa Elm Tree, growing on the shore of the Kumsong River about one kilometer south-east of the seat of Kimhwa County of Kangwon Province, is 500-odd years old.
It is 21 meters tall, with the root collar of 5.7 meters round, the chest-height of 5.2 meters round and the canopy of about 22 meters.
The first branches stretch southwards at the height of 4.5 meters while the second and the third ones stretch westwards and southwards at the heights of 7 and 10 meters, respectively.
It has a total of 12 big branches.
This large old tree adds natural beauty to the surroundings and it is of great significance in the academic research.
The natural monument, Kimhwa Elm Tree, is still growing vigorously, further enriching the treasure house of the natural cultural heritage.
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Jo Apr 29, 2025
The exhaustion of fossil fuel resources and constant evil effect of the global warming due to greenhouse gas emission needs the introduction of new kinds of energy system. Now, hydrogen energy system is attracting a great deal of attention as a reasonable energy system that can solve almost all kinds of environmental problems.
Proton exchange membrane (PEM) water electrolysis is considered as a main option to integrate and to miniaturize hydrogen energy systems. An advantage of PEM water electrolysis is short start-up time, high current density, high pressurized hydrogen production possibility and no use of corrosive solutions like alkali.
The kinds and properties of an anodic porous transport layer (PTL) play an important role in water management and ohmic resistance reduction. Some materials such as porous carbon materials (carbon fiber or carbon paper) and metals (Ti or Ni) can be used as the PTLs of PEM water electrolyzers.
Jang Tae Il, a researcher at the Institute of Nano Science and Technology, has concluded that the hot-pressed carbon paper is a superior PTL for improving the conductivity of the catalyst coated layer (CCL), and intensified his research to use carbon paper as an anodic PTL.
First, he found that anti-oxidized and hydrophilically treated carbon paper could be used as anodic PTL. Then, during the formation of a micro protective layer (MPL) by protective agents, he conducted plasma treatment of the hydrophobized carbon paper followed by impregnation with the hydrophilic polymer Nafion solution before repeating immersion-drying processes several times and heat treatment at 140℃ for 30 min to use carbon paper as anodic PTL.
PEM water electrolyzer prepared with the hydrophilic anodic PTL displayed desirable performance; initial voltage at 1.2A·cm-2 of current density at 80℃ was 1.76±0.02V, and finally measured voltage 1.84±0.02V after 6 270h of testing.
For more information, please refer to his paper “Hydrophilic treatment of carbon paper for anodic porous transport layer in proton exchange membrane water electrolyzer” in “Reaction Kinetics, Mechanisms and Catalysis” (SCI).
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