Jo May 18, 2022
Sim Jae Rim, a section head at the Faculty of Materials Science and Technology, has established a way of making WC-Co-B4C system electrode material for electric spark alloying and an alloying process by this material so that the service life of tools and machine parts could get more than 2.5 times as long.
B4C in the material has a good effect on the formation of alloying layers since it plays the role as flux which decreases the amount of oxide scale made during electric spark alloying. It also decreases the amount of oxides of low hardness and helps the formation of carbides of high hardness.
The reasonable electric conditions for electric spark alloying by WC-Co-B4C system electrode material are short circuit current I=9A, U=24V, C=420㎌ and t=2min/cm2. The thickness and hardness of an electric spark alloying layer by the new material are higher, that is, 90㎛ and 23.5GPa respectively, compared to 70㎛ and 19.5GPa by previous WC-Co system electrode material.
Electric spark alloying by WC-Co-B4C system electrode material forms alloying layers of high hardness on the surfaces of tools and machine parts, which leads to the lengthening of their working life.
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Jo May 16, 2022
The research team led by Ri Ju Hyok, a section head at the Faculty of Heat Engineering, has designed and built a cryogenic liquid tank for storage of oxygen liquid.
The tank is manufactured to store oxygen liquid produced by cryogenic distillation process for a certain period and to supply it in either liquid or gas form.
It is composed of an inner body for storage of oxygen liquid, an outer body, a pipeline for injection and exhaustion, safety factors including checker valves, safety valves, pressure control valves, a level meter and manometers and a self-evaporator for increasing the pressure inside the tank.
The space between the inner and outer bodies is filled with thermal insulation material expanded perlite and made vacuous to reduce evaporation loss and to keep cool.
The problem of preserving the cold to minimize cold loss by a heat bridge was solved, which decreased daily loss to only 0.3~0.8%.
The degree of vacuum in the insulated space is 1.3Pa, and the total heat conductivity of the expanded perlite is 0.017W/(m•K).
With all these advantages it can also be used for storage of other cryogenic liquids like nitrogen, argon, etc. as well as oxygen.
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Jo May 13, 2022
Kim Myong Il, a vice dean at the Faculty of Communications, has invented an indoor antenna for mobile communication.
Compared with previous antennas, this antenna has several advantages ― it ensures enough matching, gain and horizontal omni pattern in a wide band of frequencies; it is easy to feed, produce and assemble; it is light, good-looking and easy to install.
Consisting of a cone monopole, a double cone reflection panel, a curved plastic protection lid and coaxial feeding structure, the antenna assumes horizontal omni pattern in a wide range of frequency such as GSM, WCDMA, LTE, etc. With the gain of 3dBi, it can provide indoor mobile communication service in areas such as the underground of a building where mobile communication service cannot reach.
As a wide-range radiator, a cone monopole has top and bottom panels made of metal (Oblique angle is 25.5, radii are 12mm and 21mm respectively.), with an impedance of 50Ω and a wide radiation area. So it is of nearly omni directional pattern on the horizontal plane.
Vertical radiation can be controlled by a double cone reflection panel consisting of a primary cone reflection panel, a plain reflection panel, an upper cone reflection panel for coaxial feeding and it can bring a gain of 3dBi.
The inner conductor of a feeding coaxial cable is connected to the bottom panel and the outer conductor is linked to the reflection panel. The impedance of the antenna can be controlled by inserting an inclined line between the cone monopole and the reflection panel. Therefore, the impedance of the antenna remains constant in a wide frequency range. What is more, it is easy to install on the wall and it is covered tightly with a radome made of glass fiber plastic in order to prolong the life span and give a good-looking appearance.
In a wider frequency range(756~1 063/1 670~2 777MHz) than in the frequency range of former wire monopoles, the gain is 3.2dBi, which is 1.1dBi higher than former antennas (2.1dBi), so the service bound gets 1.4 times wider than before. The antenna is light, easy to install and meets aesthetic requirements.
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Jo May 11, 2022
Kim Ryul, a researcher at the Faculty of Electronics, has developed a new insulation bushing for a 10kV electric boiler that conforms to the operating conditions of the boiler and guarantees high reliability.
Unlike prior bushings of a cylindrical shape for a 3-phase 3kV electric boiler, a newly-developed one is of a conical shape, satisfies the operating conditions for a 10kV electric boiler and is more reliable and lighter. As its head has been changed into a ring type, they can increase yield, which means it can help reduce the level of environmental pollution and save raw and other materials
The new bushing is lighter by 0.7 times each, which means it has now become cheaper to make.
What is more, it is 2.4 times higher in dielectric strength, 3.3 times in working voltage, 1.25 times in output power, 2.7 times in 5-minute upkeep water pressure and 0.65 times lower in maximum current, which offers a scientific guarantee of the operating conditions and reliability of a 10kV electric boiler.
The yield has increased up to 93%.
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Jo May 6, 2022
Ssirum (Korean wrestling), part of the superior national heritage created and developed by the Korean people from ancient times, is a traditional sporting event where two people who grasp each other’s thigh bands compete to bring down the opponents onto the ground using their hands, legs and bodies.
Korean ssirum, registered as part of the intangible heritage of the World Heritage Committee of UNESCO, has a long history and tradition.
Korean Ssirum is said to have made a start in Ancient Korea and have been perfected in Koguryo.
Although several nations and countries including Mongolia and Japan did have similar strength events called ssirum, Koguryo ssirum had some unique features ― wrestlers wearing heavy cloth bands around either thighs and no garments on their upper bodies competed in strength with their chins tucked on the opponents’ shoulders in bare feet; ssirum was well organized according to strict rules; wrestlers were trained to be professional.
Unlike Koguryo ssirum, however, Mongolian ssirum allowed wrestlers to wear shoes and upper garments similar to leather waistcoats.
Meanwhile, influenced by Korean ssirum, the Japanese did ssirum with thigh bands, bare upper body and bare feet. This explains Japanese ssirum originated from Korean ssirum.
This assertion is also supported by the figures discovered in Inbe Hachimanyama Tomb (around 6th century) situated on the basin of the Ginogawa River in Wakayama Prefecture, Japan.
Figure 10 of strong man erected in the east of the group of tombs bears a close resemblance to Koguryo ssirum wrestlers.
It proves that Japanese ssirum was not invented and developed in Japan itself, but introduced from Koguryo.
Such information is also found in “Japanese History” and other Japanese historical records.
In a word, Korean ssirum, which was developed in Ancient Korea and perfected in Koguryo, was disseminated through the neighbouring countries of the same blood Paekje, Silla and Kaya to the Japanese archipelago, exerting a significant influence upon the cultural development of the island country.
Indeed, the time-honoured and superior culture and tradition created by the Korean nation from olden times was introduced into other countries, thus leaving an indelible mark in their history of cultural development.
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Jo May 3, 2022
The contests came to an end on April 25, 2022.
The first contest, which was held on April 8 to 11, drew 20 000-odd contestants from tens of countries and regions including our country, China and India. More than 130 participants competed in Division 1, over 600 in Division 2, over 4 600 in Division 3 and over 15 500 in Division 4. Division 1 set forth 5 problems, none of which were challenge problems.
A total of 27 contestants won the first place in Division 1 ― 19 from the DPRK, 3 from China, 2 from India, 2 from Japan and 1 from the US.
10 out of the 19 winners of our country are students at Kim Chaek University of Technology.
As much as 70.37% of the world winners are from the DPRK, and 37.037% are from KUT. KUT students add up to 52.63% of the 19 DPRK winners.
In the meantime, a student from KUT took the first place in Division 2.
Several KUT students who were absent from the Codechef March Long Challenge due to the national coding challenge held in the same period took part in this contest, which bestowed on KUT the honour of having many winners.
The second contest went on from 22 to 25. 18 000-odd contestants from tens of countries and regions including our country, China and India took part. Over 70 contestants competed in Division 1, more than 900 in Division 2, over 3 300 in Division 3 and over 14 000 in Division 4.
4 from our country and 1 from Japan made a total of 5 winners in Division 1.
Half the 4 DPRK winners are students from Kim Chaek University of Technology.
Our country and KUT make up 80% and 40% of the world winners, respectively.
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