Jo Jul 9, 2024
Superhydrophobic materials find their applications in self-cleaning, resistance reduction, corrosion protection, and anti-fogging due to their unique hydrophobicity. Lotus, a natural superhydrophobic material (SHP), has a contact angle (CA) of 162° because it has teat-like microstructures with a diameter of 5-9㎛ and nanostructures with a diameter of 124nm. One of the interesting applications of SHP materials is their self-cleaning ability to prevent and remove contamination of material surface by itself.
Superhydrophobic materials can be prepared by various methods, such as physical and chemical decomposition, chemical etching, anode oxidation, laser etching, chemical vapor deposition, sol-gel method, etc. The sol-gel method is a promising method for large-scale applications (metal, glass, ceramics and plastics), which can improve the mechanical durability of superhydrophobic materials and reduce fabrication cost.
Hollow ash is 10-20% in fly ash, a waste produced by coal-fired power plants. Hollow ash has excellent thermal insulation properties due to its porosity in the particles, so it is widely used as an insulating material.
Kim Jong Ho, a researcher at the Faculty of Chemistry, has formed a thermal barrier layer by using a composite solution of MMA-BA co-polymers and hollow ash, and investigated the functional coatings with high thermal insulation efficiency, self-cleaning ability and anticontamination performance. Based on the literature, he prepared mixed solutions of MMA-BA co-polymers and silica sol by using methyl methacrylate, butyl acrylate, methacrylate-β-hydroxyethyl ester and o-xylene. To maximize the thermal barrier properties and superhydrophobicity of the coatings, he carefully studied the effects of various factors such as the ratio of raw materials, coating thickness, and morphology.
Thermal characterization of the prepared films showed that the thermal insulation effect of the films was enhanced when hollow ash was added to the MMA-BA co-polymers solution.
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Jo Jul 7, 2024
Among the precious cultural legacies created by the Korean nation is Nine-storey Tower at Anguk Temple. This stone tower of the Koryo age is at Anguk Temple in Ponghak-dong, Phyongsong City.
The tower is built of granite. It is 6.23 meters tall with the square plane.
The tower consists of platforms, body and head. Every side of the lower platform is engraved with two lotus patterns the bottoms of which are decorated with bracken leaf patterns in the middle.
The upper platform is a lot higher than the lower one. All the sides of the platforms have three pillars each to be divided into two parts.
The roofing stones are pretty tall and three layers of eaves supports are overhanging.
The middle parts of the eaves edge are hollow and the both ends are smoothly raised. The vestiges of windbells are found at the end of the angle rafters.
On the top of the tower is a globular stone.
The whole tower feels like shooting up without much ascending reduction of distances between the roofing stones but with fair height of platforms, bodystone and roofing stones.
This stone tower is a precious legacy that demonstrates the skills of the Korean people in building stone towers. It is in good preservation and care thanks to the policy of the Workers’ Party of Korea on protecting the national inheritance.
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Jo Jul 5, 2024
Flexibility is a key concept in the management of modern manufacturing systems. The principal motivation is to achieve rapid response to manager’s demands by improving the efficiency of a job-shop while retaining its flexibility. To achieve this goal, the term flexible manufacturing system (FMS) is defined. FMS is an integrated computer controlled complex of automated material handling devices and numerically controlled machine tools that can process medium-sized volumes of a variety of part types. Flexible manufacturing systems have many potential advantages including high flexibility and high machine utilization rate.
As scheduling is the core of this control system, it plays a decisive role in achieving a goal. FMS scheduling problems are more difficult than those of conventional production systems because of a number of reasons such as machine setup times, part routing and operations scheduling. Flexible manufacturing system scheduling problems are very difficult, so mathematical modeling methods need to be improved to solve them.
Pak Myong Chol, a researcher at the Robotics Institute, designed a scheduler based on a self-adaptive genetic algorithm and obtained the optimal solution for the job-shop schedule. Then, he constructed a flexible production simulation system with the scheduling module and Flexsim and conducted a simulation based on the optimized part scheduling.
The simulation results verified that it is possible to reduce the total machining completion time, increase machine utilization and realize process optimization.
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Jo Jul 3, 2024
Korean parents have a traditional custom of giving a special party to their children celebrating their first birthday.
Traditionally, rice cakes such as steamed rice cake, sorghum cake coated with red-bean jam and five-colored half-moon-shaped rice cake stuffed with beans and flavored with pine needles and fruits of the season including dates, apples, pears, persimmons, etc. were prepared on the table, and things like rice, thread, brush, book and bow were placed in front. Grown-ups, watching the baby’s cute tricks at the table, wished them normal growth, future happiness, great talents and good fortune.
Dishes prepared for first birthday were the same for both sexes, but objects were different.
For boys, a bow and arrow and a book and brush were prepared to the effect that parents wanted them to be a brave warrior or a scholar.
For girls, a reel of thread, a ruler, a pair of scissors, etc. were prepared. These show the desire of parents for their daughters to be good at needle work.
The custom of giving a first-birthday party reflects the love and desire of our people for their children to be excellent persons who defend the country and promote the happiness of their families.
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Jo Jul 2, 2024
ASPEN PLUS, a chemical process design system, is widely used for solving scientific and technological problems arising in the process, device design and process operation, for production of chemicals.
Process simulation techniques have been widely used in the development of new processes because of their high economic effectiveness and scientific accuracy. So far, many researchers have used ASPEN PLUS to simulate gasification processes.
Choe Hyon Il, a researcher at the Faculty of Metal Engineering, has developed an entrained-flow gasification compartment model, which consists of sub-models of pyrolysis, combustion and gasification, by combining the modules provided by Aspen Plus, and analyzed the effects of operating conditions, i.e., oxygen to coal ratio, steam to coal ratio and pressure, on the composition of coal gas.
The results are as follows.
As the oxygen to coal ratio increases from 0.7 to 0.9, the CO content increases by 16% in the outlet gas and the H2 content decreases by about 20%. The CO2 content starts to increase when the oxygen to coal ratio is greater than 0.85. When the steam to coal ratio varies from 0.12 to 0.6, the CO content in the outlet coal gas is reduced by 50% and the H2 content by 29%. As the pressure increases, the effective content in the outlet coal gas decreases, but it is not very large, and especially the effect becomes weaker above 300kPa.
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Jo Jul 1, 2024
Ryonggok School is located at the southern foot of Mt Ryongak in Pyongyang.
It was a private institution of the feudal Joson dynasty for educating rising generations.
The school was first built in 1656 and rebuilt in 1713, which is still preserved.
In line with the general requirements of private schools, it is divided into two zones ― lecture halls and temple.
If you go through the outer gate into the yard, you will find an eastern lecture hall on the right and a western lecture hall on the left. A flight of steps in the north of the yard leads up to the inner gate. If you walk through the inner gate, you will see a temple. To the northwest of the temple is a pavilion for a monument.
Ryonggok School, one of the typical private schools of the country, is a precious cultural legacy that shows the appearance and architecture of educational institutions in the years of the feudal Joson dynasty.
President
Thanks to the policy of the Workers’ Party of Korea on protecting national heritage, Ryonggok School is in good preservation and maintenance.
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