Jo Aug 6, 2024
A historical site Puyong Pavilion in Haeju City was built at the beginning of the sixteenth century during the feudal Joson dynasty.
It is a unique architecture built on the stone columns in a lotus pond.
The Puyong Pavilion forms an L-shape with a building called “Unghyang Pavilion”.
The pavilion is supported by tens of columns erected in the middle of a pond which is as large as one thousand several hundred square meters. The columns are standing on the border but no columns in the center, so the whole inside is uninterrupted for parties or something.
The Puyong Pavilion preserves the structural features of a typical pavilion and blends the surrounding environment and architecture, thus demonstrating the excellent building techniques of the Korean ancestors.
The charming scenery of the pavilion which felt like floating gently over the lotus pond gradually became widely known, which developed a saying “Missing the Puyong Pavilion denies that you have been to Haeju”.
The sound of raindrops falling onto the lotus flowers in full bloom in the pond at night was so pleasant to the ear that huge numbers of people gathered there when it was raining. It soon started to be called one of the Eight Scenes of Haeso (Haeso means ‘province with the sea in the west’).
As the scene of the pavilion became the pride of Haeju and one of the Eight Scenes of Haeso, many poems, songs and legends came into being, which are still being passed down.
Though it was severely destroyed during the past Fatherland Liberation War, the Puyong Pavilion was restored to its original state by the earnest instructions of President
The pavilion, which was used as a pleasure resort for feudal rulers in the past, turned into an excellent cultural recreation center for working people under the care of the Workers’ Party of Korea. It now serves as a place for education in patriotism that instills the national pride and self-confidence into the people.
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Jo Aug 4, 2024
The silicon steel plate is widely used as core materials of various devices such as a transformer and an electromotor. However, in order to solve the energy problem, it is very important to develop soft magnetic materials with less iron loss.
Fe-based amorphous and nano-crystalline alloys are widely used because of its low cost and iron loss about one fifth to one third of silicon steel plates. But, they are restricted to some degree in application because the value of maximum flux density of these materials is about 80% of silicon steel plates. Therefore, researches to develop soft magnetic materials with higher maximum flux density and lower core loss have been performed. As a result, new Fe-based nano-crystal soft magnetic materials have been developed. Among them, Fe-Cu-B system nano-crystalline soft magnetic materials are attracting a great deal of attention.
In most studies, the experimental results of the influence of copper, silicon and boron on the magnetic properties were analyzed, but the thermodynamic changing process was not described in detail.
Jo Chol Min, a researcher at the Faculty of Materials Science and Technology, has conducted a study to thermodynamically solve the influence of Cu addition on the crystallization of the Fe-based nano-crystalline soft magnetic alloy fabricated by the melt spinning method. In addition, he has analyzed the influence of silicon and boron on the magnetic properties of Fe-based nano-crystalline soft magnetic alloys to determine the reasonable composite.
He found that the crystallization activation energy of Fe-based alloys containing copper was lower than copper-free alloys, which indicates that copper is effective to accelerate the crystallization of alloys and increase the magnetic property. He also demonstrated that in crystallization heat treatment, the maximum flux density and coercive force of the Fe-based nano-crystalline soft magnetic alloy containing copper were the best with 2% of Si.
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Jo Aug 2, 2024
The altar remains of the feudal Joson age have been newly discovered at the vertex of a talus in Hyangdo Peak Basin by Lake Chon on the top of Mt. Paektu.
The base of the altar remains is almost square with each side of 36 meters while the surface is 15 meters long and 12 meters wide. The remains are approximately nine meters thick.
Two inscriptions were found there. One was on a flat oval-shaped natural rock of about 140 centimeters in length and 80 centimeters in width while the other was on a plain rock 26 centimeters long and 20 centimeters wide.
The former consists of 25 characters and the latter has 26 letters. The summary of these two inscriptions implies that various kinds of memorial services were held there during the feudal Joson dynasty.
The altar remains are of great significance in studying the history of Mt Paektu more deeply.
The remains, a material evidence that Korean ancestors set up an altar for memorial services on Mt. Paektu as early as in ancient times, prove that Korean nation has historically regarded Mt. Paektu as the ancestral mountain and the holy mountain of the nation.
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Jo Jul 30, 2024
People want to live in a cleaner environment and more developed living conditions. Various harmful substances such as toxic materials, gas, dust and dirt come into being from the daily life of people. These substances pollute air, water, soil, etc. and destroy ecological environment, thus doing direct or indirect harm to people.
As an acidic igneous rock containing quartz, feldspars and mica as essential minerals, granite is widely used for decoration of the outer walls of buildings. However, during the processing of granite, granite waste in which 30% is dust is generated. This waste is used as construction filler for building materials, but most of it is left in the open air or landfilled. Consequently, soil, underground water and source of stream are polluted and the concentration of dust in the air is increased. Especially, the particle size of fine granite dust (FGD) is so small that exerts severe harmful influence on the environment.
Recycling of this FGD into eco-friendly material can be very profitable to the economy as well as environment protection.
Ri Chol Ju, a researcher at the Faculty of Earth Science and Technology, has proposed a method of synthesizing zeolite from waste granite powder with low energy (fusing at the temperature of 800℃) and at low cost (using an effective solvent-sodium carbonate).
The results showed that 13X zeolite can be successfully synthesized through pretreatment at the relatively low temperature from what is manufactured by separating chemically stable quartz from FGD.
This method could be applied to all the waste produced from the processing of other rocks containing crystalline quartz.
If you need some more information, please refer to his paper “Hydrothermal synthesis of 13X zeolite by using feldspars separated from waste granite powder” in “International journal of environmental science and technology” (SCI).
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Jo Jul 28, 2024
Development and use of natural energy plays an important role in guaranteeing the sustainable development of economy and satisfying the energy demands. In this field, study on the solar energy is particularly important. Recently, the efficiency of perovskite solar cells (PSCs) which have become the focus of solar energy development almost reached the efficiency of silicon solar cells and therefore a lot of efforts are being made to ensure the stability of solar cells.
The stability of PSCs primarily depends on the stability of perovskite which performs the function of light absorber in devices. For this reason, many researchers are trying to improve the heat and humidity stability of perovskite.
Recently, it has been found that ion liquid, which has been studied in several fields including medicine due to its special properties such as high viscosity, low vapor pressure and incombustibility, can be used as an additive or a solvent for perovskite precursor to improve the performance and stability of PSCs.
Ion liquid, well known as an eco-friendly harmless solvent, has polarity that can solve perovskite precursor, so it can replace the toxic DMF or DMSO that have been conventionally used for fabrication of PSCs.
Kang Jin Hyok, a researcher at the Faculty of Information Science and Technology, investigated the influence of ion liquid methylammonium acetate (MAAc) on the characteristics of perovskite and the performance of hole transport material (HTM)-free PSCs with carbon electrode when it is used as a solvent of precursor for preparing perovskite.
The perovskite was prepared by solid–gas reaction between dimethylammonium lead iodide (DMAPbI3) and methylamine (MA). DMAPbI3 was solved by ion liquid MAAc instead of DMF and it was used as a precursor.
The perovskite film based on ion liquid was more uniform and denser than the one based on DMF, thus improving the crystallinity and crystal size of perovskite. The analysis result showed that the nonradiative recombination of cells decreased and the open circuit voltage could be improved when using MAAc instead of DMF.
For further details, you can refer to his paper “The characteristics of hole-transport material-free perovskite solar cells with carbon electrode made by using ion liquid methylammonium acetate solvent” in “Results in Optics” (SCI).
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Jo Jul 26, 2024
Increasing the measurable distance and the displacement measurement limit of a self-mixing displacement sensor poses one of the most important problems to improve the sensor’s performance.
In order to solve the problem, there has to be found an estimation method of the optical feedback factor for a strong feedback regime.
The hardship of the estimation in this regime is brought about by a strong speckle noise and the restriction of normalization methods presented hitherto.
Kim Chol Hyon, a section head at the Faculty of Physical Engineering, has found an approach to improving the accuracy of the self-mixing sensor, which can work even for long range and large displacement, by deciding the region of the optical feedback factor based on the ratio of fringe height and by using it and the fringe counting method.
The experiments showed that the SM displacement sensor based on the new approach will be a great help to the enlargement of the measurement range of the sensor.
If further information is needed, please refer to his paper “Amelioration of accuracy of displacement measurement in strong feedback regime based on region decision: enlargement of measurement range of self-mixing displacement sensor” in “Optics Communications” (SCI).
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