Jo Nov 25, 2025
Ocean wave energy has great potential to cope with increasing energy demand since it is renewable, sustainable and green energy and its overall resource is estimated to be around 2TW.
Some wave energy devices can be modeled as submerged oscillating bodies, which requires a deep understanding of hydrodynamic interaction between ocean waves and submerged bodies.
Many numerical methods have been proposed for bodies in irregular or arbitrary shapes, but it is important to specify boundary conditions on a virtual cylindrical surface between mean free surface and seabed.
Rim Un Ryong, a researcher at the Faculty of Shipbuilding and Ocean Engineering, has investigated three-dimensional linear interaction between a submerged oscillating body in arbitrary shape and the regular water wave with finite depth.
First, he derived an exact Dirichlet-to-Neumann (DtN) boundary condition on a virtual cylindrical surface, where the virtual surface was chosen to enclose the body and extract an interior subdomain with finite volume from the horizontally unbounded water domain.
Then, he applied the DtN boundary condition to solve the interaction between the body and the linear wave in the interior subdomain with the boundary integral equation.
He has validated the proposed method via a submerged vertical cylinder. The result shows a good agreement with the analytical results of precedent papers.
For more information, please refer to his paper “Free surface wave interaction with a submerged body using a DtN boundary condition” in “Theoretical and Computational Fluid Dynamics” (SCI).
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Jo Nov 24, 2025
A single-tuned harmonic filter is a passive harmonic filter widely used to eliminate harmonics in power systems.
Minimizing the impedance of the filter at the corresponding harmonic frequency makes the harmonic voltage produced by the harmonic current generated by the non-linear load a minimum. This is the principle of filtering in a single-tuned harmonic filter.
While eliminating the corresponding harmonic, the single-tuned harmonic filter affects the fundamental power factor. That is because the single-tuned harmonic filter itself is capacitive at the fundamental frequency. In the past, most power systems were inductive at the fundamental frequency, so in general, their capacitive characteristics played a positive role in raising the power factor of power systems. But nowadays, with the widespread use of power electronic devices, there have been more and more loads that are non-inductive at the fundamental frequency in the power systems. In this case, using conventional single-tuned harmonic filters results in the decrement of the fundamental power factor and the increment of transmission loss. In order to overcome these disadvantages, it is necessary to develop a new type of filter that eliminates harmonics but does not influence the fundamental power factor.
Ji Kuk Ryol, an institute head at the Faculty of Electrical Engineering, has proposed a novel single-tuned harmonic filter, which can remove harmonics with the fundamental power factor unchanged.
The proposed filter can be applied to filtering the harmonics made by a load whose fundamental power factor is 1 or capacitive.
You can find more information in his paper “Novel Single Tuned Harmonic Filter not Affecting Fundamental Power Factor” in “Journal of Electrical Power & Energy Systems” (EI).
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Jo Nov 23, 2025
Sensing nitrogen oxide gas is important for measuring pollution gas and detecting pollution sources from vehicles and chemical processes in the atmosphere and for diagnosing the diseases of human body by measuring NO2 gas from breathing. Therefore, it is necessary to measure the range of dilute concentration and to develop a less power-consuming electrochemical method.
Kim Yong Hyok, a researcher at the Faculty of Electronics, has designed the structure of a new NO2 gas sensor and conducted a qualitative analysis of its performance. In addition, he has established its manufacturing process and experimentally analyzed the bias voltage properties.
The new sensor can linearly sense NO2 gas of up to 100ppm.
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Jo Nov 21, 2025
In marine engineering, it is prone to encounter free surface flow problems. Typically, a boat moving on water causes nonlinear free surface flows accompanied by spray. A high-speed boat, in particular, experiences considerable resistance due to the spray, and some high-speed boats such as seaplanes and hovercrafts suffer great damage in their propulsion systems. Thus, predicting nonlinear free surface flow is an important issue for developing high-speed boats with high performance.
For the simulation of free surface flows, some computational fluid dynamics approaches called mesh-based method have been proposed. These methods are suitable for the flow of low-speed boats but not suitable for high-speed boats.
Other approaches called mesh-free method or particle method have been proposed for free surface flows. Moving particle semi-implicit (MPS), smoothed particle hydrodynamics (SPH) and particle finite element method (PFEM) are typical mesh-free methods widely used for nonlinear free surface flows. In many studies, mesh-free methods have been applied successfully to lots of problems in the marine engineering field.
Pak Chol Jun, a researcher at the Faculty of Shipbuilding and Ocean Engineering, has proposed an improved MPS method with some modifications for simulating the flow around a moving body. To improve the original MPS method, he proposed the intermediate velocity of wall particles, Laplacian compensation in the domain close to the boundary, a technique to prevent fluid particles from penetrating the wall boundary, and a handling technique for the open boundary.
He applied the improved MPS method to hydrostatic pressure and sloshing problems to validate its performance. The comparison of the numerical results with the analytical results and experimental data showed that Laplacian compensation remarkably enhances the accuracy of MPS method.
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Jo Nov 20, 2025
Automatic Guided Vehicles (AGVs) are material handling equipment traveling on a network guide path. AGVs can be interfaced with other equipment for production and storage. Increasing the efficiency of automatic guided vehicle (AGV) scheduling is one of the important issues to improve the productivity of manufacturing enterprises.
Ri Il Chol, a researcher at the Faculty of Automation Engineering, has established a multi-objective mathematical model for scheduling multi-load AGVs carrying production materials and cutting tool consumables.
The objective function includes three objectives: the total moving distance of AGVs, the standard deviation of AGV workload and the standard deviation of the difference between the latest delivery time and the predicted time of tasks. Then, he implemented the assignment and ordering of tasks performed by AGV by implementing neighborhood search strategy using an improved harmony search algorithm.
He has applied the proposed harmony search algorithm to a virtual manufacturing enterprise to evaluate its performance.
The computational results show that the proposed harmony search algorithm outperforms the genetic algorithm.
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Jo Nov 19, 2025
Rod coal briquette is a kind of porous material consisting of solid coal particles, liquid phase moisture, stream and air, and study of drying process of coal briquette is that of porous material.
Most researchers proposed some mathematical models of drying inside porous material by convective heat. They are classified into diffusion model, theory model based on osmosis evaporation, and models based on Whitaker’s continuum theory and non-equilibrium thermodynamics.
Study on heat and mass transfer in porous material was conducted for a long period and it developed from the basic theory of heat and moisture transfer mechanism into the modern comprehensive and logical scientific theory. However, most studies were focused on the drying of wood, grain and paper, and not on rod coal briquette.
Pak Kyong Il, a researcher at the Faculty of Metal Engineering, designed a tunnel-type dryer for reducing coal consumption while reducing the cracking of briquettes and increasing their strength by improving the thermal working state of a tunnel dryer with low recovery and high coal consumption required for drying.
Compared to the conventional dryers, the newly-designed one has many advantages. First, drying time per batch is reduced by 4h from 24h to 20h. Second, 48kg of coal is saved for drying a ton of coal briquettes. Third, cracking rate is reduced by 23%.
In addition, cold compressive strength and hot compressive strength, and hot abrasive strength are raised by 10-11% and 4-5%, respectively, to improve the quality of briquettes used for iron production in small blast furnaces.
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