Recently, attempts have been made to use fiber-reinforced plastic composites as aircraft structural materials, but aluminum alloys still have 70% utilization as airborne fuselage materials. In particular, high-alloy duralumin Du16 has been used as the main material for manufacturing aircraft fuselage surfaces and blades.

The body material of an airplane varies in its nature with the speed of flight, so it is very important to determine whether a given alloy can be used as a body material for subsonic and supersonic aircrafts.

Previous studies show that the grain growth of duralumin alloy at annealing temperatures above 300 °C leads to poor mechanical properties, but they failed to deal with annealing at temperatures below that. What is more, they did not cover the changes in the texture and property with temperature when the body of an airplane is heated during the flight.

Therefore, Ri Hyon Song, a researcher at the Faculty of Materials Science and Technology, has measured the fuselage heating temperature range by means of simulation analysis and investigated the changes in the texture and property with annealing temperature.

First, he designed a model of a supersonic aircraft and conducted a simulation analysis of the temperature distribution of the body surface according to flight speed. Then, he performed hardness and microstructure observation experiments.

The results showed that Du16 alloy does not degrade its hardness at 100℃ for 8 hours of annealing, and above 300℃, the hardness is gradually degraded with time.

Hyonmu Gate is the north gate of the northern castle of the Walled City of Pyongyang of Koguryo on Moran Hill.

The gate was named after the mythological turtle symbolizing the God of the North, one of the four gods in charge of the four directions.

It was first built in the sixth century when the Walled City of Pyongyang was being built during the Koguryo dynasty and underwent repair and rebuilding several times during the Koryo dynasty. The present gate was rebuilt in 1714. After that, it underwent thorough repairs in 1855 and 1954.

The gate is made up of an embankment, the extension of the castle wall, and a tower on it.

Like the castle wall, the embankment is built with stones faced in the form of quadrangular pyramid that are placed one upon another to avoid longitudinally straight joint lines. There is an arched gate in the middle of it.

There are battlements on the embankment that is about 2.5 meters tall. The gatehouse is a single-eaves gabled house which is three kans (7.05m) in length and one kan in width.

Hyonmu Gate is a precious cultural legacy demonstrating the ardent patriotism and advanced castle gate architecture of the Korean ancestors.

The International Conference―2025 of Kim Chaek University of Technology will be held in November 2025 in Pyongyang, the capital of the Democratic People’s Republic of Korea (DPR Korea).

“Kim Chaek University of Technology International Conference―2025” aims to discuss recent achievements in a broad range of science and technology on the subject “Science and Technology―Power for Development and Strategic Means”.

We warmly welcome you (educators and scientists at home and abroad) to this conference to exchange valuable experiences and knowledge by presenting your latest academic findings/achievements and ideas in all areas of science and technology.