Jo May 10, 2024
Nowadays numerical simulation is an essential tool for stability analysis of mining engineering, and constructing a more realistic numerical model is important to ensure the accuracy and reliability of mining engineering design.
In recent years, many researchers have made significant progress in the study to quickly obtain more realistic structural elements of stopes and to apply them to production practice by performing numerical simulations of mining areas with FLAC3D. However, the model construction parts in these programs are quite difficult to use for building large and complex 3D mining models, particularly, for multi-seam and multi-boundary geological bodies.
Han Un Chol, a researcher at the Science Engineering Institute has proposed a new method of quickly converting a 3D solid model into a numerical one for stability analysis of geotechnical and mining structures by combining ANSYS, FLAC3D and SURPAC.
First, he carried out a detailed analysis of the data structure used in these three programs and presented a transformation technique between the data. Then, he converted the integrated 3D solid model made by SURPAC into a numerical model of ANSYS, and meshed it as tetrahedral elements, and consecutively, converted the meshed model of ANSYS into a grid model of FLAC3D for numerical simulation.
Finally, he applied the proposed method to numerical analysis of pillar stability in the sublevel open stopes in the target mine. It was shown that the model transformation time can be reduced to 1/50 and the accuracy of the numerical model can be increased by more than 20%.
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Jo May 9, 2024
Steamed rice cake (paeksolgi in Korean where paek means ‘white’) is named after its colour which is as white as snow. It was first introduced as paeksolgo in “Kyuhapchongso”, a book of the early nineteenth century.
Snow-white steamed rice cake reflects our people’s honesty and faithfulness. Steamed rice cake has been regarded as indispensable for several occasions like a party given to a hundred-day-old baby, the first birthday of a baby, a wedding, etc.
The custom of preparing steamed rice for hundred-day-old babies is associated with parents’ wish for them to grow up healthily and honestly like snow-white steamed rice cake.
Sharing with neighbors the dishes including steamed rice cake prepared for the day, Korean people have exchanged congratulatory remarks and shared joy with one another for good harmony and unity. Such beautiful characteristics are still being handed down.
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Jo May 6, 2024
To estimate the lifetime of welding joints of steam pipes working at high temperatures and high pressures is of great importance for the stability and maximum economic efficiency of steam power plants. Long-term exposure of heat-resistant steels at high temperature leads to deterioration in the mechanical properties because of the changes in the microstructure. Alloying elements and microstructures significantly affect the heat resistance in the welds of low alloy heat resistant steel at high temperature.
In order to illustrate the changing nature of heat resistance, Ri Won Jun, a researcher at the Faculty of Materials Science and Technology, investigated the mechanical properties (ultimate strength, yield strength, elongation, hardness, etc.) of pipe materials and their welding joints with respect to the content of elements in carbides, their morphology and change in the metallic structures. Also, he conducted an experiment by using zirconium instead of vanadium for electrodes to evaluate the microstructure of deposited metal, mechanical properties at room temperature, metallic structures analysis, carbide analysis, scale resistance, short-term creep strength and long-term creep strength.
As a result, he drew the following conclusions.
First, the metallographic study showed that Zr series has less migrant tendency of the grain boundary than V series at high temperatures for a long time. And the comparison of mechanical properties with hybrid carbides showed that Zr series is superior to V series in all indices.
Second, the experiment for oxidation inclination at high temperature showed that the value of scale oxidation of Zr series is 1.4 times higher than that of V series, indicating that Zr series is more stable at high temperature.
Third, the metal deposited by the stick electrode coated with Zr has no ferrite segregation and the primary structure is finer than that with V.
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Jo May 5, 2024
The crater of Mt Paektu full of mysteries gives a view of extraordinary falls, too.
In the rainy season, the cliffs of the crater are covered with falling water, forming crater waterfalls. When a strong northwesterly wind blows up the slopes of the crater, it changes the downward flow into “upward waterfalls” like spout from a fountain. These extraordinary “upward waterfalls” are seen in the spring thaw from May to June and in the rain spell from July to August.
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Jo May 3, 2024
PhD. Associate Prof. Kwon Chang Dok, a section head at the Faculty of Mining Engineering, is a competent scientist who has made a distinguished contribution to the agricultural development of the country and to the improvement of the people’s living standard. Having developed a paddy rice cultivation method by electrical pulse water treatment, he has introduced and generalized it to a huge number of farms across the country in the last nine years.
Finding that the water treatment technology highly effective in floatation and leaching of nonferrous mineral significantly influences the growth of animals and plants by activating water, he started research for introducing it to stockbreeding, fish farming and vegetable farming followed by paddy rice farming. Starting from a 500-phyong (1 phyong = 3.954 sq. yds) test rice field, he rapidly expanded the area year by year. As a result, he made proud successes of increased yield of a huge amount of rice in a hundred thousand jongbo (1 jongbo = 2.451 acres) of paddy-fields in 2023.
In the course of making a lot of scientific research successes, he was highly appreciated by Chairman
During those days, he moved into a new flat in Kyongru-dong in April, 2022, and he had the greatest honor of having a significant photo session with the respected Comrade
Now he is full of enthusiasm to devote all his talent, wisdom and passion to open up a breakthrough for the economic development of the country with torchlight of science and technology, bearing in mind the trust and expectation of the Party and the fatherland that put him forward as a state top-honor scientist & technician.
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Jo Apr 29, 2024
Investment casting is widely used to make complex castings with high dimensional accuracy at low cost. The impellers of centrifugal pumps have many thin-walled regions and structures of uneven thickness in parts, so shrinkage defects can occur in these areas.
Also, their complex internal cavities cause excessive variations in the velocities of molten metal flowing into the shell mold. This results in gas and non-metal inclusion defects in castings. Therefore, it is important to avoid these casting defects occurring in investment casting of impellers.
Kim Yu Chol, a section head at the Faculty of Materials Science and Technology, has succeeded in making centrifugal pump impellers with no defects by optimal design of runner/riser system and mold tilt angle with ProCast software, thus enhancing the quality of castings and reducing production hours. The sprue was used as a kind of riser to feed shrinkage of casting and enhance casting yield. The shell mold was tilted at various tilt angles to eliminate gas and inclusions during pouring.
You can find the details in his paper “Improvement of quality and yield for investment casting of centrifugal pump impeller by tilting mold and optimizing runner/riser system” in “The International Journal of Advanced Manufacturing Technology” (SCI).
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