Jo Jan 9, 2023
A research team led by Hong Sung Chol, a researcher at the Faculty of Heat Engineering, has developed and introduced various types of energy conservational boilers.
Energy conservational unpowered boiler with a package of fire-tube heaters combined with fin array in box type
The boiler satisfies heat requirements needed for production and heating with a small amount of fuel. It costs little to manufacture and install. It is simple in its composition and principle and easy to reset the load. It has the highest heat output for furnaces of the same volume. In addition, for the same heat output, it consumes a lot less fuel and material than other fire-tube heaters. Especially, it is very convenient to introduce them as they are standardized in 10 heat outputs with seven optimized indicators to ensure the scientific accuracy, economy and promptness of introduction in consideration of its various types and conditions of installation. The boiler makes the most use of the produced heat by preheating water from the heat included in waste ash, by using the flue gas from heating and by keeping boiler walls warm. Compared with conventional boilers of the same furnace volume, it provides three times as much heat output (η=88~93%), consumes less fuel by 1/4 [fuel consumption of 162kW hot water heater: B=100~110kg/d(Qar=20MJ/㎏)] and material by over 1/2, and reduces the number of boilers for a unit heating area.
Energy conservational steam bath boiler
It is made up of the cylindrical body that produces both heat and hot water at the same time by recycling wasted heat, a water heater, a feed water inlet, a hot water outlet, a fuel inlet, a fire-grate and a chimney. The annular upper and lower heaters inside the body and the outer collecting heater and economizer outside the body maintain the temperature of a sauna at over 75~85℃ and produce hot water of 40~50℃ at 2~2.5t/h. (fuel consumption B=40kg/d)
Boiler for hot water tank
In the boiler is a hot water heater in the shape of a nest which is combined with a plate and a water pipe. The hot water system consumes no electricity and is operated by natural ventilation and cycle. It can produce hot water of 65~75℃ at 40~45t/d. (fuel consumption B=60kg/d)
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Jo Jan 8, 2023
The site of Anhak Palace, a royal palace of Koguryo, covers a large area of Anhak-dong, Taesong District, Pyongyang City.
It was built when the capital of Koguryo moved from present-day Jian, Jilin to Pyongyang. Anhak Palace was for normal times, while Fort on Mt. Taesong was for emergency.
The palace site is surrounded by earthen castle walls. Each side of the square castle is 622 meters. The area of the site is as large as about 380 000㎡. In the castle, 52 palaces stand with the eaves facing one another on the total floor space of 31 458㎡.
A moat was dug outside around the walls of the castle to reinforce the defence. There were three castle gates on the southern wall and one on the eastern, western and northern walls each.
The palaces in the castle were disposed along the north-south central axis.
The palaces constituted five architectural groups ― outer palace, inner palace, bedchamber palace, eastern palace and western palace.
The outer palace was for great state ceremonies and the inner palace was for ordinary state affairs. The bedchamber palace was the king’s dwelling place.
The eastern palace was the Crown prince’s palace, and in the western palace were people serving in the palace and administration facilities. In the palace castle were laid out ponds in various sizes and gardens with artificial slopes. The site of Anhak Palace gives us a glimpse into the excellent architecture of that time. Such system of Koguryo’s royal palaces was introduced into Paekje and Silla, the countries of the same blood, and the later feudal royal palaces of our country.
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Jo Jan 6, 2023
There are many multicriteria decision-making (MCDM) methods applicable to material selection. They are simple additive weighting (SAW) method, weighted product method (WPM), analytic hierarchy process (AHP) method, analytic network process (ANP) method, technique for order preference by similarity to ideal solution (TOPSIS) method, gray relational analysis (GRA), VIse Kriterijumska Optimizacija Kompromisno Resenje (VIKOR) method, preference ranking organization method for enrichment evaluations (PROMETHEE), extended PROMETHEE (EXPROM) method, elimination and et choice translating reality (ELECTRE) method, complex proportional assessment (COPRAS) method, preference selection index (PSI) method, range of value method (ROVM), rank sum ratio (RSR) method, graph theory and matrix approach (GTMA), multi-objective optimization on the basis of ratio analysis (MOORA), quadrant constellation graph-based method, etc. These methods may produce considerable differences in the material selection results.
However, it is unknown which MCDM method produces more rational results and there is no rational method to determine final overall performance scores of alternative materials.
Yang Won Chol, a researcher at the Faculty of Materials Science and Technology, has proposed a new method to determine final overall performance scores and final ranks of alternative materials by combining the results from different MCDM methods in material selection.
The steps are as follows.
First, the overall performance scores and ranks of the alternative materials are calculated using some different MCDM methods.
Second, mean values of the rank correlation coefficients between the rankings obtained from different MCDM methods are calculated before the mean values are assigned as the priority weights of each MCDM method.
Finally, the weighted mean values of the overall performance scores obtained from different MCDM methods are calculated. They are determined as final overall performance scores of alternative materials.
To illustrate the effectiveness, he applied the proposed method to selecting the best tool holder materials using some well-known MCDM methods such as SAW, TOPSIS, GRA, VIKOR, PROMETHEE, and RSR methods.
Conclusively, the following conclusions were drawn:
(i) The proposed method can determine not only the final ranks but also the final overall performance scores of alternative materials by combining the results obtained from individual MCDM methods.
(ii) The proposed method reflects the priority weights of individual MCDM methods to the final overall performance scores and ranks of alternative materials.
(iii) The proposed method may be more reasonable, clearer and simpler than previous methods.
(iv) The proposed method could widely be used to get more reasonable, appropriate, and robust material selection results by combining different available MCDM methods.
If further information is needed, please refer to his paper “A New Material Selection Method Based on Weighted Mean Values of Overall Performance Scores from Different Multicriteria Decision-Making Methods” published in the SCI Journal “Advances in Materials Science and Engineering”.
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Jo Jan 4, 2023
Hansan Great Victory, Jinju Great Victory and Haengju Great Victory, the major great victories won in the battles against Japanese invaders during the Imjin Patriotic War, are called Imjin 3 Great Victories.
Hansan Great Victory
In July, 1592, Admiral Ri Sun Sin in command of Jollado naval force decoyed 73 enemy ships in Kyonnaeryang in the southern sea of Kyongsang Province to the sea off Hansan Island with the tactics of allurement and encirclement. There, they annihilated 59 enemy ships and thousands of enemy soldiers.
Jinju Great Victory
In October, 1592, the warriors and people in Jinju Fort repelled the attack of Japanese invaders mercilessly under the command of Kim Si Min, thus defending the fort successfully.
Haengju Great Victory
In February, 1593, the defending warriors and women in the fort on Mt. Haengju achieved a great victory under the command of Kwon Ryul by fighting bravely to repulse the attack of ten times as many Japanese invaders.
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Jo Jan 3, 2023
Thin-walled structures such as ship and offshore structures basically consist of a number of plates stiffened by different types of stiffeners.
Continuous welding may be used for attaching stiffeners to plates, but this technique requires a large amount of welding, adds weight to the structures, and increases construction costs. In order to reduce the costs of labour and materials and save weight of the stiffened plate structures, non-continuous welding is frequently applied to the attachment of plates and stiffeners. This method of fabrication also lowers the magnitudes of welding residual stresses more than continuous welding.
Over the past few decades, the buckling and collapse behaviors of continuously welded stiffened plates under different loading conditions have been widely investigated in order to develop analytical, empirical, numerical and experimental methods.
However, little has been studied on the behavior of intermittently welded stiffened plates and, furthermore, only some numerical and experimental studies have been carried out.
Mun Ji Song, a section head at the Mirae Academy of Science and Technology, has proposed a simplified method for ultimate strength estimation of intermittently welded stiffened plates under uniaxial compression. The plate and stiffener of a stiffened plate were considered as individual beam-columns. The whole span of an intermittently welded stiffened plate was divided into welded and non-welded segments. For modeling the behavior of the intermittently welded stiffened plate, the differential equations which describe the bending of the beam-columns in welded and non-welded segments were considered.
Special attention was paid to the following two cases.
i) Case 1
It was assumed that beam-columns 1 and 2 are deformed in contact and deflections of the beam-columns 1 and 2 are equal to each other.
ii) Case 2
In this case, it was assumed that beam-columns 1 and 2 are deformed in non-contact and behaviors of the beam-columns 1 and 2 are independent of each other.
Based on the model, the Euler limit load of the intermittently welded stiffened plate was calculated. The intermittently welded stiffened plate was changed into a continuously welded one with the equivalent Euler limit load. The Paik’s empirical formulation was used to estimate the ultimate strength of the changed continuously welded stiffened plate under uniaxial compression.
The proposed method demonstrated a good agreement with FEA results. This suggests that ultimate strength of chained and staggered welded stiffened plates can be estimated by the proposed method.
For more information, please refer to his paper “Study on Ultimate Strength Estimation of Intermittently Welded Stiffened Plates under Uniaxial Compression” published in the SCI Journal “Marine Structures”.
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Jo Jan 2, 2023
The knowledge and visions of the map experts in our country in the fifteenth century were not restricted to the country but broaden to the world.
It resulted in two world maps: “Honilgangriryoktaeguktojido” in the early 15th century and “Chonhado” in 1469.
They are elaborate enough to show several tens of names of places in Europe, Africa and even the Middle and Near East
For clear distinction of different parts like lands, seas and deserts, seas are painted in blue and deserts in black, which ensures high visual effect as a map.
They contain not only the maps of our country and the world but also separate ones of other individual countries including then China, Japan, etc.
In conclusion, our ancestors, creators of time-honored and brilliant culture, made great progress in geography, too.
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