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.
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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.
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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.
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Jo Aug 2, 2025
Pobun Hermitage is a Buddhist temple located on Mt. Ryongak. The present buildings underwent reconstruction during the feudal Joson dynasty.
The hermitage was built during the period of Koguryo, which is proved by the fact that the way of trimming the stones piled for the stereobate is the same as those for Koguryo citadels and that some convex roofing tiles and antefixes were discovered, as well as by the epitaph and other records.
With bluff cliffs in the background, Pobun Hermitage, which consists of five buildings including the main temple, is well suited to the topographical conditions of Mt. Ryongak.
The main temple of the hermitage erected on the raised stereobate is five kans (10.27 meters) long and three kans (6.2 meters) wide.
The hermitage, the precious national cultural heritage associated with the talent of the Korean people, is now in good preservation and care.
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Jo Jul 29, 2025
In wireless rechargeable sensor networks (WRSNs), charging request nodes (RNs) are characterized by several criteria which are contradictory.
Recently, on-demand charging scheduling schemes, which use two or more multicriteria decision-making (MCDM) methods, have been proposed. However, these schemes use a pairwise ratio scale which can magnify the actual pairwise difference between multicriteria, and do not take into account the trade-off between performance metrics.
Ri Man Gun, an institute head at the Faculty of Communications, has proposed an on-demand charging scheduling method based on a fuzzy cognitive network process (FCNP) which uses a fuzzy pairwise interval scale.
The proposed method, called an integrated FCNP-Q-learning-based scheduling (iFQS), first uses FCNP to exactly assign the relative weights to five multicriteria for charging prioritization and to three multicriteria for partial charging time (PCT) determination, respectively.
Then, in charging path planning with Q-learning, the BS uses these five criteria’s weights to design the reward function and select the most suitable next charging sojourn point. On the other hand, the three criteria’s weights are used to reasonably determine the PCT at charging sojourn points while achieving a desirable trade-off between charging metrics.
The results of the extensive simulation show that the iFQS significantly improves charging performance in comparison with the existing MCDM-based methods.
You can find the details in his paper “iFQS: An Integrated FCNP-Q-Learning-Based Scheduling Algorithm for On-Demand Charging in Wireless Rechargeable Sensor Networks” in “International Journal of Distributed Sensor Networks” (SCI).
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Jo Jul 28, 2025
We often see people with splints at the fracture site after operation on the fractures of arms, legs, wrists or ankles caused by various accidents or severe exercises. However, conventional splints are esthetically unpleasant and bulky. Moreover, patients feel uncomfortable if the splints are not customized and suitable for them. Also, their heavy weight can impose a great burden on patients, and their poor ventilation conditions might lead to several skin diseases in hot weather, thus prolonging the recovery time.
The Additive Manufacturing (AM) technique has been widely used in many medical practices, including fabrication of orthoses, thus, providing increased satisfaction to patients and effective rehabilitation therapy. Several papers have been published on the fabrication of customized orthoses using the Fused Deposition Modeling (FDM) technique. In particular, customized orthoses fabricated by FDM can provide patients with best comfort with reduced incidence of various complications due to air permeability.
Om Myong Song, a section head at the Faculty of Materials Science and Technology, has determined a reasonable structural dimension of orthopedic orthoses fabricated by FDM, using a finite element simulation based on the uniform design, the simple additive weighting method, the multiple linear regression model and the grid search optimization method.
The reasonable values for the structural dimension factors of the orthosis are shell thickness of 2.2mm, lattice thickness of 6.4mm, and number of ventilation holes of 15.
If further information is needed, you can refer to his paper “A reasonable approach to determine structural dimension of FDM fabricated orthopedic orthosis using finite element simulation and simple additive weighting method” in “Journal of Mechanical Engineering Science” (SCI).
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