Thermodynamic Analysis of Reaction and Process Simu...

Jo Aug 8, 2025

Spraying is a surface treatment technique whereby the heat source such as an arc or gas flame melts the spraying material and the compressed gas injects it to form a coating on the metal surface. Unlike surface alloying, the coating component is never or rarely diluted by the base metal because it melts none or very little of the base material.

In order to coat mechanical components with mechanical abrasions or casting defects on their surface, the self-propagating high-temperature synthesis method (SHS) is incorporated into the oxygen-acetylene flame spaying. Compared to plasma spraying, oxygen-acetylene flame spraying is cheap, but it is not available for materials with high melting points due to its low flame speed and flame temperature. However, combining the oxygen-acetylene flame spraying with the SHS method is the solution.

Therefore, there have been many studies to spray Al-Fe₂O₃ materials with good internal friction performance, low cost and high melting points by combining the oxygen-acetylene frame spraying and the SHS method. However, they dealt only with the spraying process and the structures and properties of coating layers in the system, but not reactive thermodynamic analyses.

The desired reaction during spraying and the formation of the structure can be found by reaction thermodynamic analysis. Hence, Jegal Tok Song, a researcher at the Faculty of Materials Science and Technology, has formed an Al₂O₃-Fe composite coating layer with Fe₂O₃ and Al powder, cheap belongings to the SHS reaction system, and performed a reactive thermodynamic analysis and a simulation of a spraying process.

First, he verified the possibility of reaction by calculating the adiabatic temperature of the system and the Gibbs free energy of theoretically possible reactions. Then, he performed a differential thermal analysis to determine the temperature for reactions. Finally, he determined the optimum spraying conditions by using Fluent.

The results of his study can also be applied to other reaction systems that involve SHS methods for spraying.

Sungin Hall Demonstrates Architecture of Koryo Age

Jo Aug 6, 2025

Sungin Hall is a shrine built at the end of the Koryo age, standing together with Sungnyong Hall by the Pyongyang Students and Children’s Palace.

It was first built in 1325 in the late period of Koryo. It underwent three thorough repairs in 1352 and 1428 and finally in 1954 immediately after the Fatherland Liberation War, to be in the present state.

Sungin Hall, which was originally comprised of 10-odd buildings including the main building, was damaged by the aggressors during the Imjin Patriotic War and the Fatherland Liberation War, as a result of which only the main building, the gate and the monument pavilion survived. The central building alone was moved next to Sungnyong Hall in 1977.

This building for ancestor worship was promoted in its name in 1612 to be called Sungin Hall. It is a precious historical relic that demonstrates the excellent architecture of Koryo, providing a lot of information for studying the architectural history of Korea.

Improvement of CII Estimation by Introduction of Co...

Jo Aug 5, 2025

In the initial IMO Strategy for reducing greenhouse gas (GHG) emissions from ships, the level of ambition for CII of international shipping was quantified by CO₂ emissions per transport work, the average of overall international shipping.

This is a severe rule for ships with only short voyage because the greater the navigation distance is, the lower the CO₂ emissions per unit transport work are. In addition, short voyage ships might be evaluated as poor in the CII assessment because of the small transport workday, although measures have been taken to improve energy efficiency. Consequently, all ships will refuse short-term navigation, resulting in a conversion to land transport in some areas. This will lead to an increase in CO₂ emissions.

Ri Hyok, a researcher at the Faculty of Shipbuilding and Ocean Engineering, has proposed a relatively fair CII calculation method by introducing a correction factor for an ordinary freight vessel, taking short-voyage and long-voyage into account.

He confirmed the accuracy of correction factors with operational data of ships of less than 35 000 DWT.