Jo May 13, 2025
Mesocellular silica foam (MCF) is a kind of new mesoporous silica material found in 1999, with the largest pore size (up to 50nm) of all mesoporous materials synthesized to date, which has the three dimensional cubic mesopore structure of a typical foam phase. The specific surface area reaches 1 000m2/g, and the pore size and pore volume are large. Relatively large spherical pores are interconnected by small pores.
Compared to the mesoporous materials of MCM and SBA series with relatively small pore size, MCF has large specific surface area and pore size and it is scalable. Its specific 3D foam structure characteristics have a great theoretical research significance and wide application prospect in various fields. For example, as a catalyst support, it is beneficial to the mass transfer and diffusion of reactants and products by increasing the metal loading. Recently, several studies have applied it to the esterification solidification of alcohol, hydrogenation, dehydrogenation, CO2 adsorption, hydrogen peroxide synthesis, etc., which has shown its excellent performance.
Plasma treatment, a gas phase treatment technique combined with a kind of physical and chemical method, has several advantages like no pollution, low energy consumption, no water consumption and no use of chemical reagents. In particular, low temperature plasma treatment causes physical and chemical changes near the surface of materials to be treated, while maintaining their own properties. Therefore, low temperature plasma treatment is of great importance in the functionalization of materials surface.
Mun Se Hyon, a researcher at the Institute of Nano Science and Technology, has carried out a surface modification treatment in the mesoporous material pore channel using dielectric barrier discharge (DBD) with 3D mesocellular silica foam (MCF) as a support, and investigated the effect of plasma treatment conditions on the reaction on MCF surface.
First, he synthesized mesocellular silica foam (MCF) by sol-gel method and treated the surface of MCF by DBD to enhance its surface activity. After plasma treatment, he modified amine groups on the MCF pore channel surface.
To investigate the effect of plasma treatment on the mesoporous material MCF support, he modified amine groups on both treated and untreated MCF surfaces. Then, he compared the specific surface area of catalyst support MCF-NH2 synthesized by the two methods and the amount of -OH in the pore channel via nitrogen adsorption and desorption analysis (BET), infrared spectroscopy (IR) and thermo gravimetric (TG) analysis.
The results showed that plasma treatment greatly influences the pore structure of the mesoporous material MCF, and even the activity of the MCF surface obtained.
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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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