Jo Jun 3, 2025
Nowadays, with the development of positioning technology, people have become able to obtain the position information of objects in the global range easily, more accurately and in large quantities. In order to reduce the amount of information about the trajectory of moving objects or the location of geographical objects, it is necessary to simplify the polyline consisting of nodes representing the location information.
The Douglas-Peucker (DP) algorithm is known as an accurate and efficient one for simplifying polyline. In order to simplify the trajectory of moving objects in the global domain with DP algorithm, geodetic distance computation in spherical space is necessary.
In the implementation of the DP algorithm on the Earth’s ellipsoid, it is impossible to avoid spending much time on geodetic distance computation, and the main problem is a huge computational effort.
Kim Song Chol, a section head at the IT Institute, has investigated the performance of DP algorithm in spherical space for trajectory simplification of moving objects.
He proposed a method of using geodetic coordinates as spherical coordinates and evaluated its accuracy. The geodetic distance error was about 0.22~0.55% of the maximum geodetic distance. With this error, the results of implementing the DP algorithm in spherical space have been experimentally found to be more accurate. In addition, the computational speed has been proved to be very fast and applicable to the global scale.
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Jo Jun 2, 2025
The Elephant Rock of Pidan Island is a natural monument located in Sindo County of North Phyongan Province.
When the sea water entered the Korean West Sea area at the end of the fourth glacial period, the rocks on the relatively high hills exposed above the sea formed an extraordinary topography by a long time of abrasion and weathering.
The rock has been called Elephant Rock as it resembles an elephant.
The rock is 40 meters long and 15 meters high, with the top of 8 meters in width.
The “trunk” is 9 meters round.
At the “head” of the rock is a small rock resembling an “ivory” and in the middle of the “trunk” is a small hole. Grass is growing on the rock.
The rock is submerged and exposed by the tide. When it is submerged, it looks like an elephant swimming in the water, and when it is exposed, it looks like being caught in the marshland.
The Elephant Rock, which is of significance in studying the change in the nature after the formation of the Korean West Sea, is a natural monument adding beauty to the beachscape.
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Jo May 30, 2025
The time-dependent Ginzburg-Landau (TDGL) equations are a useful computational tool for characterizing the spatiotemporal variance of an order parameter that represents the phase transition in mesoscopic type-II superconductors. Especially, they are used to simulate the dynamics of magnetic vortex for designing superconducting materials with high critical current density.
Therefore, simulation of type-II superconductors using TDGL equations is essential for understanding magnetic vortex dynamics and studying superconducting critical characters such as critical current density and critical magnetic field. Numerical simulations for it are conducted by the finite difference method (FDM), the finite element method (FEM), the lattice Boltzmann method (LBM), etc.
Ryu Yu Gwang, a researcher at the Faculty of Physical Engineering, has investigated the influences of surface defects on the motion of magnetic vortices in a mesoscopic type-II superconductor with randomly distributed pinning centers through the simulations of TDGL equations by using COMSOL Multiphysics.
Two kinds of surface defects are located in the boundary: one is pinning centers and the other is geometric defects along with pinning centers.
In the simulation, he analyzed the magnetization curves, the vorticity and the density of superconducting electrons for both different contents of pinning centers and various geometric defects.
For the pinning centers as surface defects, the maximum magnetization values as a function of the contents exponentially decrease, and the field where the first vortex penetrates and the field where the complete transition from superconducting to a normal state in the system occurs are reduced.
For the geometric defects as surface defects, the density of superconducting electrons and the magnetization curves depend on their size and form. In addition, a threshold in the size of geometric defects in which the motion of vortices and vorticity change, exists.
You can find the details in his paper “The Influence of Surface Defects on Motion of Magnetic Vortices in Mesoscopic Type-II Superconductor with Randomly Distributed Pinning Centers” in “Journal of Superconductivity and Novel Magnetism” (SCI).
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Jo May 29, 2025
Stroke remains a tremendous public health burden with approximately 795 000 people affected every year. Stroke is the leading cause of major long-term disability of adults and the third leading cause of death in developed countries. Urinary tract infection is a frequent problem after stroke.
Although prior scoring systems for UTI after stroke have been developed, Pak In Hui, a researcher at the Faculty of Biology and Medicine Engineering, has developed a simple scoring system of our own for all types of stroke.
The study was designed on retrospective data. The population included 1 496 patients with stroke who were admitted at the Neurology Department of Hospital of Pyongyang University of Medical Sciences between January, 2010 and August, 2019. The patients were diagnosed by means of CT and MRI.
You can find the details in her paper “The Development of Simple Scoring System to Predict Urinary Tract Infection (UTI) in Patients with Stroke” in “International Journal of Endocrinology” (SCI).
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Jo May 28, 2025
It is well known that accurately modeling the radiative heat transfer process at high temperature of several thousand to tens of thousands of K is a main factor in evaluating the efficiency of rocket propellants, pulverized coal combustion and thermal plasma. In particular, as radiative transfer equation (RTE) mathematically explaining heat radiation in the absorbing, emitting and scattering media has a calculus characteristic, its solution exists only in extremely limited geometries and conditions.
To analyze the radiative heat transfer in high temperature systems such as plasma, it is essential to determine the temperature distribution of the plasma, which requires the distribution of radiant intensity to be determined. Therefore, computational models for analyzing the temperature distribution of system and the radiant intensity distribution are required, and it is important to establish a methodology for combining these two computational models and to apply them to practice to improve accuracy.
Pak In Ae, a researcher at the Faculty of Physical Engineering, has proposed a new Discrete Ordinate-Lattice Boltzmann Method (DO-LBM) by combining DOM and LBM to analyze radiative heat transfer in a two-dimensional irregular enclosure that involves absorbing, emitting and scattering media.
Through the comparison with other methods, she has confirmed that the DO-LBM is more simple and accurate and can reduce computational cost of simulating radiative heat transfer in a complex boundary structure.
For more information, please refer to her paper “Discrete-Ordinate-Lattice-Boltzmann Method for analyzing radiative heat transfer: Application to two-dimensional irregular enclosure” in “Mathematics and Computers in Simulation” (SCI).
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