Jo Apr 9, 2023
Kuryong Falls is a famous waterfall in the zone of Kuryong Pool in Outer Kumgang of Mt. Kumgang, a world-famous scenic spot.
From ancient times, it has been accepted as one of the three famous waterfalls of our country along with Pakyon Falls in Kaesong and Taesung Falls on Mt. Solak, and what is more, it is known as number one of the four famous waterfalls on Mt. Kumgang.
At the bottom of the waterfall is a pool shaped like a large stone mortar dug by the falling waters.
The pool got the name Kuryong as legend has it that there lived nine dragons defending Mt. Kumgang in old days, and the water falling down into the pool was called Kuryong Falls (“Kuryong” means “nine dragons”). Above the falls is Sangphaltam (eight pools), which is well known for the legend about “eight fairies of Mt. Kumgang”.
Pak Sin Jong, researcher at the Academy of Social Sciences
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Jo Apr 6, 2023
Recently, large floating structures such as oil storage facilities and floating airports have appeared for the purpose of utilizing sea space and exploiting ocean resources. Many researchers have been developing artificial protective structures such as submerged breakwaters to prevent or decrease the actions of incident wave towards a coast. Therefore, it is necessary to estimate wave motion at a place where such structures are installed, and it is also important to consider the cases of undulated seabeds or bathymetric regions.
Rim Un Ryong, a researcher at the Faculty of Shipbuilding and Ocean Engineering, has studied three-dimensional water wave motion over undulated seabeds. For wave motion in sea water of finite depth, a fluid domain is usually unbounded horizontally but bounded vertically by free water surfaces and seabeds.
To study local wave motion over undulated regions only, he suggested a novel Dirichlet-to-Neumann (DtN) boundary condition on an artificial cylindrical surface by which a fluid domain is divided into an interior region with finite volume and an exterior region. Then, he applied the DtN boundary condition and other boundary conditions on mean free water surfaces and undulated seabeds in order to determine the solution to wave motion in the interior region by using Boundary Integral Equation (BIE). Upon verification of a submerged square cylinder, he extended the present model to the case of an array of rounded-rectangular cylinders or circular paraboloidal shoals.
The proposed model can be applied to assess wave motion over an undulated seabed when an undulated region is local and its surrounding region is horizontal and unbounded.
More information about this is found in his paper “An exact DtN artificial boundary condition for motion analysis of water wave with undulated seabed” in “Wave Motion” (SCI).
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Jo Apr 5, 2023
A catapult, a bow that works in a mechanical way, was one of the excellent weapons of Koguryo.
It was made up of two parts ― a bow and a body. The bow was for loading shooting force on the arrow and the body was for holding and directing the arrow.
Our country has the longest history of a catapult in the East. A catapult was of two types ― single-shot and multi-shot.
The most well-known multi-shot catapult was a three-arrow-shot catapult of our country in the middle ages.
Upgraded from the Koguryo’s single-shot catapult, the three-arrow-shot catapult could hold many arrows and discharge three arrows at a time.
Other countries did not have such a multi-shot catapult in those days.
The catapults invented by our resourceful ancestors were absolutely unique in structure, way of working and manufacturing technique, so they are still attracting admiration of people.
A great number of people are particularly impressed by the line of sight inscribed on the catapult that can be seen only on modern weapons.
That is why even weapon experts from other countries praised, “The simple but clever construction of a catapult amazes modern people. It is so interesting since it works like a today’s rifle. As an invention 2 000 years ago, it is absolutely amazing.”
Indeed, the catapult of Koguryo demonstrates our ancestors’ extraordinary creative wisdom and talent.
Kim Kwang Jo, researcher at the Academy of Social Sciences
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Jo Apr 3, 2023
The knotty problems in displacement reconstruction based on self-mixing (SM) technique are estimation of self-mixing interferometry parameters and normalization of SM signals (SMSs) since they are all very time-consuming and based on complex algorithms. This has an unfavorable effect on the real-time and low-cost natures of an SM displacement sensor.
Kim Chol Hyon, a researcher at the Faculty of Physical Engineering, has presented a simple method of displacement retrieval with a high resolution, which does not require any parameter estimation and normalization.
According to his study, when C changes during the operation of a self-mixing sensor, a single fringe, in a strict sense, does not correspond to a half wavelength and, therefore, this causes inaccuracy in displacement reconstruction. On the basis of it, he has proposed a very simple method called fringe scaling for displacement reconstruction, which does not require any normalization of SMSs and parameter estimation. This method provides a high resolution of λ0/10 and in addition, it can be employed for all feedback regimes including weak, moderate and strong regimes.
The proposed method is based on the scaling of individual fringes in SMSs and speckle noise proof. The simplicity of the method will make a great contribution to lowering the cost of SM displacement sensors and improving their reliability and resolution.
For more information, please refer to his paper “Normalization-free displacement reconstruction method based on fringe scaling” in “Applied optics” (SCI).
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Jo Apr 1, 2023
Jang Ji Yon (1864―1921) is the writer of the editorial “Let’s wail bitterly and loudly.”, which denounced the evil crimes of the Japanese imperialists that fabricated the “Ulsa Five-Point Treaty” in 1905, and expressed the burning indignation over the national ruin.
A patriotic literary man Jang Ji Yon, with burning love for the country and nation, was very active in writing literature for conveying the proud tradition of literature and art of our nation. One typical example is the compilation of “Taedong Selection of Poems” in Juche 8 (1919).
The book is divided into 12 volumes and 6 books. Volume 1 contains “Song of konghu” by Ryo Ok in Ancient Korea and other poems by over 150 persons including Ulji Mun Dok, Choe Chi Won, Jong Ji Sang, Ri Kyu Bo and Ri Je Hyon, who did some creative activities in the period from the Three Kingdoms to Koryo. Works by more than 1 700 persons during the feudal Joson dynasty are found from Volume 2 to Volume 10. Volume 11 and Volume 12 have poems composed by some women and Buddhist monks like Sosandaesa and Samyongdang, and other fine ones by unknown writers.
The compilation of this book by Jang Ji Yon was aimed at restoring the national spirit fading out under the cruel colonial rule of Japanese imperialists and at protecting and preserving the national poetry inheritance. “Taedong selection of poems” serves as an important reference for research into the development history of our national literature since it is a collection of a large number of national poems and songs that shows the long development history of our national poetry in a systematic and detailed way by means of those composed in each period.
Kim Son Yong, researcher at the Academy of Social Sciences
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Jo Mar 30, 2023
A research team led by Kye Myong Ho, an institute head at the Faculty of Metal Engineering, has developed an energy dispersive X-ray fluorescence (EDXRF) analyzer.
The analyzer has several advantages: nondestructive analysis without any chemical reagents, simultaneous analysis of several elements in a short time, very simple structure, wide range of concentration standardless analysis and convenience in use.
It is made up of a high voltage power unit, an x-ray tube, a semiconductor detector, a multi-channel pulse height analyzer, a control circuit, a vacuum pump and analysis software.
The maximum power of the x-ray tube is 50W and the energy resolution of the semiconductor detector is 149eV. The analyzer enables measurement in the vacuum and its measuring time is below 5 minutes.
The analytical software is used for instrument control, qualitative analysis, semi-quantitative analysis, calibration curve drawing and quantitative analysis.
In the software, the voltage and current of the x-ray tube are set according to elements, and fluorescence spectrum is collected. Semi-quantitative analysis is available by standardless analysis. For semi-quantitative analysis, the kind of sample must be selected before measuring. You can also make a quantitative analysis by a standard curve. First, you should select the standard curve for a sample, and then quantitative analysis result is presented.
EDXRF analyzer can be widely used for analysing element concentration of substances such as alloy, mineral, cement, precious metals and catalyzers in the fields like metal, chemical, building materials, mining industries, prospecting and archaeology.
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