Brilliant LeaderShip

On Munsu Hill

It was April 6, Juche 36(1947). On the day President Kim Il Sung climbed Munsu Hill after attending a grand commemoration ceremony of tree-planting. The President was heartbroken at the sight of the ...

Spring Fragrance on International Women’s Day

On March 8 over a decade ago, there was a performance in the presence of Chairman Kim Jong Il. The women who were enjoying the performance together with him could ...

Criterion of Service Activity

One day in March some years ago, the respected Comrade Kim Jong Un visited the newly built Mirae Shop. Acknowledging that the shop was well built as befits the model of commercial establishments ...

Story of Coming Back

One night after midnight, the respected Comrade Kim Jong Un visited a unit of the Korean People’s Army. He took hours to give valuable instructions concerning the work of the unit. Then, tenderly ...

Teaching in Detail

One spring day Chairman Kim Jong Il visited the park of Mangyongdae Schoolchildren’s Palace (then) for memorial tree-planting. Lest the Chairman, who was always busy with the state affairs, should waste much time ...

Historic Significance Elucidated by the Chairman

Chairman Kim Jong Il was conducting the revolutionary activities at Kim Il Sung University when one day in February, Juche 51 (1962), he shared with his fellow students comments on the Chongsan-ri ...

News

Jo Mar 26, 2024

Induction channel furnace (ICF) is widely used for melting, holding and casting metals and alloys in many processing industries because it has high overall efficiency, low electric power consumption and operation costs, better degassing and homogenization of melt and low oxide and slag formation. However, thermal stresses in the refractory lining caused by high temperature and flow of molten metal may cause premature erosion of the lining and failure of the inductor, and so it is difficult to repair the furnace. In addition, the furnace for steel melting often experiences shortened operating life and quicker needs for a repair cycle due to high temperature of molten metal and severe erosion of lining, so it is rarely used.

In order to solve these problems and make easy operation, it is important to improve the structure and to numerically simulate Joule heat generation and molten metal flow in the channel.

Song Hak Myong, a lecturer at the Mechanical Engineering Department, has designed a new type of channel of three-phase ICF for steel melting and investigated temperature distribution of the channel by a coupled simulation on the electromagnetism-heat-fluid using COMSOL Multiphysics 5.4.

ICF consists of molten metal bath and induction unit that is made up of iron core, inductor and channel. If one three-phase induction unit is fixed to the furnace body, it will lead to decrease in electrical unbalance and ease of furnace repair.

According to his simulation results, the optimal design parameters (with maximum S/N ratio) for three-phase ICF are as follows:

• Type of channel: Elliptic

• Dimensions of channel: 85×90 mm2

• Existence of protruding part: Yes

• Setting angle of channel: 30°

The local superheating temperature is relatively low (20.8–22.9K) and the maximum local superheating temperature is similar to the maximum local superheating temperature 33K in the channel of the twin channel induction furnaces.

It is one of the ways to prevent early erosion and expansion of refractory lining by local superheating in the channel and to increase its repair cycle.

The proposed method could be used for reducing manufacturing cost and regularizing operation through optimizing the parameters of induction furnace needed for aimed melting and flow.

If further information is needed, please refer to his paper “ Simulation on Temperature in Channel of Three-phase Induction Channel Furnace for Steel Melting Using COMSOL Multiphysics and Taguchi Method” in “International Journal of Metalcasting” (SCI).

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Jo Mar 23, 2024

As modern industrial processes become more complex with the development of technology, more advanced monitoring methodologies are required to keep high efficiency and safe operation. In order to improve monitoring performance, it is important to identify the operational phase of a process by evaluating all measurable variables comprehensively. Multiple operational characteristic that occurs in most industrial processes like chemical processes by their physical and chemical properties, variations in market requirement and product specification, catalyst degradation, etc. has become an important factor to be considered in process monitoring.

Since most multimode monitoring approaches with the mode-identification are only based on the similarity of process mean, the identification of transitions and faults is possible only after the cluster of process data should be formed or neighbour modes could be analyzed. Furthermore, mode-identification based approach seems to be inappropriate to monitoring of process with lots of modes not only because it requires a large amount of off-line data but also because its capability of adapting to unexpected states may not be acceptable.

Song Kwang Rim, a researcher at the Faculty of Automation Engineering, has proposed an online transition-identification based monitoring procedure for industrial process with multiple operational modes using process variability.

Firstly, he detected the change point in the dynamical behavior of multimode process by the log determinant of covariance matrix.

Second, based upon the analysis of the change behavior of process variability during transition and fault state, he developed new statistics to identify the transition.

Finally, he adopted an adaptive monitoring strategy to monitor multimode processes by the single model using the transition-identification.

Then, he conducted three case studies through TE benchmark to verify the usefulness and effectiveness of the proposed approach.

The result showed that the proposed approach has high ability to identify transitions and faults and to cope with the occurrence of new modes.

The details of this are found in his paper “Monitoring Industrial Processes with Multiple Operation Modes: a Transition-Identi¦cation Approach Based on Process Variability” in “Industrial & Engineering Chemistry Research” (SCI).

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Jo Mar 22, 2024

Numerical modeling and simulations of plasma is an indispensable means to overcome the technical limit in measuring plasma parameters, which has been performed by many researchers. Unlike conventional numerical modeling, lattice Boltzmann method (LBM) is a meso-scale scheme based on Boltzmann kinetic theory, which has some advantages such as relatively simple computational structure, easy handling on complex boundaries and possible parallel computation. Recently, the LBM has been widely used to simulate not only single phase flow but also multi-component and/or multi-phase thermal fluid transfer, electric and magnetic fields, acoustic fields and radiative transport. However, the previous models for plasma were limited to 2D schemes, so they were not enough to analyze 3D mechanism of arc dynamics.

Therefore, Kim Ju Song, a lecturer at the Faculty of Physical Engineering, has suggested a 3D lattice Boltzmann model to numerically simulate thermal fluid flow in non-transferred arc torch with swirl and validated its accuracy by comparing it with results in literature.

The Boltzmann model was built for local thermodynamic equilibrium. The boundary conditions were considered for both macro- and micro-parameters, and the curved boundaries were handled for the cathode and the anode.

The simulation results demonstrate that the maximal temperatures appear at positions downstream from cathode and the axial velocity profiles are remarkably different according to the swirl number and that the position in the maximal axial velocity shifts toward the cathode with increase in the swirl number.

For more information about it, please refer to his paper “Numerical Analysis for Argon Arc Plasma Jet Flow by Three-Dimensional Thermal Lattice Boltzmann Model” in “Bulletin of the Lebedev Physics Institute” (SCI).

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Students on “Risang” Local Network (1)

“Risang”, homepage for distance education of Kim Chaek University of Technology, has been making the part-time learners realize their ideal to the full.

Nov 11, 2022