Jo Oct 27, 2022
The Korean people possessed of special love for their children had a custom of adorning the sleeves of their children’s coats with small pieces of coloured cloth.
Pieces of coloured cloth in rainbow-like harmony of colours ― mainly red, green, blue, yellow, pink, purple, white, etc. ― are usually attached to sleeves. Some of them are plain and some have patterns like flowers and butterflies and letters.
The breast of a rainbow-striped garment is decorated with striped or triangular pieces of cloth in various colours and the body is made in colours like green, jade green, yellow and pink for a good harmony of colours with the sleeves.
Rainbow-striped garments include saektongjogori, saektongkhunjogori, saektongmagoja, saektongturumagi, etc.
From ancient times, mothers in our country have dressed their sons and daughters in colourful coats and jackets distinguishable from casual ones on their first birthdays, which is a peculiar custom of the Korean people. Such customs are never found in other countries.
Since these clothes not only look beautiful and smart, but are to a children’s taste as well, they have been worn on first birthdays, birthdays and holidays and other visiting occasions.
The beautiful manners and customs peculiar to the Korean people have been improved by constant supplement of fresh elements over a long period and rainbow-striped garments have been developed into the ones representative of the national features.
Kim Kyong Il, researcher at the Academy of Social Sciences
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Jo Oct 26, 2022
In sedimentology, stratigraphic sequences and cycles are ordered by time spans and physical scales such as thickness, and bounded by discontinuities including unconformities or flooding surfaces.
Song Man Hyok, a section head at the Faculty of Earth Science and Technology, has proposed a spectral analysis method based on wavelet transform (WT) maxima and used it as a quantitative tool to identify multiorder stratigraphic boundaries and cycles in well log data.
The proposed spectral analysis is based on quantitative analysis of the center frequencies and resolutions of Gaussian wavelets in time and frequency, and it uses a combination of the WT maxima based on both the first order Gaussian wavelet with a high time resolution and the seventh order Gaussian wavelet with a high frequency resolution.
WT maxima spectra, which can characterize the evolution of WT maxima across scales and periods along WT maxima lines concerned with sequence boundaries, are used to detect dominant spectral peaks corresponding to the time-period domain WT maxima and to determine WT maxima spectral slopes.
The WT maxima spectral slopes are helpful for discriminating sequence boundaries from intrasequence cyclic variations in well log data, and the time-period domain WT maxima are used to relate the detected boundaries to relevant cycles.
He has introduced interval WT maxima spectra and stationary indexes related to the WT maxima spectra as indicators that could be used for hierarchical ordering of the boundaries and cycles.
Application of the proposed method to well log data shows that this method is efficient in identifying multi-order sequences that relate well to the Milankovitch cycles.
The detailed information about this is found in his paper “Spectral Analysis Based on Wavelet Transform Maxima: Identification of Multi-order Stratigraphic Boundaries and Cycles” presented to the SCI Journal “Mathematical Geosciences”.
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Jo Oct 24, 2022
Korean traditional dishes have developed in the course of a long history and they are widely-known to the world for their original flavor, aroma, appearance and colour and for their diversity in kind.
Korean traditional dishes have several good qualities.
First of all, Korean traditional dishes taste exceptionally good.
The original taste of each dish is guaranteed by several sorts of seasonings including soy, bean paste, peppered bean paste, sesame oil, garlic, spring onion and ginger harmoniously mixed with main ingredients ― various kinds of cereals, vegetables, fish, edible herbs, fruit, etc. that are grown in our country. For example, vinegared soy is used for oily dishes while vinegared hot pepper paste or mustard paste is used for slices of raw fish. Minced raw beef is mixed with sesame oil.
Secondly, Korean traditional dishes are wonderful in harmony of colour and delicious-looking.
Fruit of Schizandra chinensis or red pepper is used to make dishes red, and pine pollen or yolk of an egg is added for yellow colour. Green is made by wormwood or green soybeans, and black is made by black sesame or boletus. Fruit like ginkgo nuts or pine nuts are used to decorate dishes. Korean traditional dishes such as sinsollo, yakbap (sweet rice dish mixed with sugar, dates, chestnuts, pine nuts, sesame oil, etc.) and Pyongyang raengmyon (cold noodle) bring water to mouths for their natural colour and beautiful and good-tasting appearance.
Thirdly, diverse and scientific ways of cooking and cultural and hygienic ways of table setting are another feature of Korean traditional dishes.
Fermenting and aging like making kimchi, fermented rice cake and fermented fish together with boiling, baking, frying and stewing are the major ways of cooking, which not only make dishes delicious but also improve people’s health and prevent or cure diseases. As for table setting, cold and pungent dishes are served on small plates while those that are not pungent are put in large bowls. Besides, every food container has their lids for preserving the warmth and aroma of the contents and preventing them from going bad.
The last feature is the diversity.
The Korean people have lived on rice from olden times and the rice alone is made into many kinds including boiled white rice, bean-mixed rice, rice cooked with red-beans, bibimbap (mixed with spices, vegetables, meat, etc.), boiled millet, etc. They have made many kinds of rice cake as special dishes ― glutinous rice cake, rice cake steamed on a layer of pine needles, rice cake with flower patterns imprinted, cake made of rice flour and wormwood paste, steamed rice cake, etc. to name a few. Kimchi, which is original and widely known to the world, is diverse in its kind: whole cabbage kimchi, pickled sliced radishes, watery kimchi made of sliced radish, radish pickles with wild garlic, pickled mustard leaves and stems, etc. The number of Korean dishes is beyond enumeration ― dishes cooked in different seasons, those for traditional holidays and those cooked in different parts and so on.
Korean national dishes with a long history and tradition are still being developed and enriched in conformity with the aesthetic senses of the times and the demands of the people.
Pak Sung Gil, researcher at the Academy of Social Sciences
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Jo Oct 22, 2022
In general, commercialized medium-sized asynchronous wind turbines are fully-automated facilities designed to operate in a parallel connection to the grid; in case of isolated operation, they need to be combined with diesel generators.
Choe Ki Yong, an institute head at the Faculty of Automation Engineering, has studied a method of producing electricity of maximal quality with the wind, by constructing a new stand-alone hybrid (medium-sized asynchronous wind turbines, UPS with battery and photovoltaic array) power system without a diesel generator.
He has proposed a new architecture of a stand-alone hybrid power system which consists of a medium-sized asynchronous wind turbine, a UPS, a current limiter (reactor), a photovoltaic array, and consumer and dump loads; Accordingly, a supervisory control and data acquisition (SCADA) for this system has been suggested along with the operation strategies depending on the output power of the UPS and the wind turbine, consumer load and the battery voltage of UPS.
The case study was confirmed through the simulation results of the operation of a new stand-alone hybrid (two 110 kW asynchronous wind turbines, 250 kVA UPS with battery, reactor, 36 kW photovoltaic array, consumer and dump loads) power system.
The results of the simulation showed that the system frequency change of the new stand-alone hybrid power system was 60±0.5 Hz and that of the wind + diesel stand-alone hybrid system was 60±1 Hz, for the sudden change of consumer load and gust.
More information can be found in his paper “New architecture and SCADA for stand-alone hybrid (medium-sized asynchronous wind turbine + UPS with battery + photovoltaic array) power system without diesel generator” presented to the SCI Journal “Wind Energy”.
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Jo Oct 21, 2022
Janggu (a long Korean drum that tapers in the middle) is one of the representative national percussion instruments loved and enjoyed by the Korean people for a long period of time.
Janggu originated in Koguryo. According to historical records, it was called “yogo” as it was a drum carried at the waist. “Yogo”, which looks similar to present janggu, is painted on the murals in Tomb No.4 and Tomb No. 5 of Jian Five Tombs, Koguryo tombs, and it is recorded in a number of historical books that Koguryo had a yogo. This shows that yogo was a predecessor of janggu and the Korean people have used it since the period of Koguryo.
Yogo, made by Koguryo people, was handed down to the people in Palhae. The yogo from Koguryo and Palhae was improved to be similar to the present janggu during the Koryo and the feudal Joson dynasties, and it was called janggo.
Janggu is a percussion instrument of an extraordinary shape, which has two resonance boxes that are linked together.
Its balanced and beautiful look aroused people’s attachment to janggu. The left-hand side with a big resonance box is called kungphyon, while the right-hand side with a small box is chaephyon. You play it by hitting the sides with a janggu stick in the right hand. The kungphyon is made of thick skin and the chaephyon is made of thin skin.
In the respect of a tone and a sound, the kungphyon produces low soft sounds while the chaephyon makes high sharp sounds. Therefore, the janggu plays the role of two drums and expresses satisfactorily a variety of Korean rhythms and exquisite tunes.
As the janggu had a very wide range of applications for a long period of time and made progress in various playing techniques, it played the role of a conductor in a small orchestra and it was even used as a solo instrument.
With rhythms of various characters that excite a national zest, the janggu makes a great contribution to improving the performances of national music and it is also used as stage props in a music and dance.
With a time-honoured tradition, the janggu has been developed in every way. It is a proud national percussion instrument that is still loved by the Korean people and makes a positive contribution to the development of national music and the cultural and emotional life.
Ri Yong Ho, section head at the Academy of Social Sciences
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Jo Oct 20, 2022
The microgrid has more flexibility and reliability to fulfill the system stability, power quality requirement, etc. However, the voltage unbalance might occur when the unbalanced loads including single-phase loads between two phases or between one phase and the neutral are connected in the microgrids. The unbalanced voltages occurred in the microgrids may cause problems with power quality such as power system instability, additional power losses, and adverse effects on the motors and power electric converters.
In order to provide highly reliable and good quality power to the distributed loads, the power-converter based DGs can be used as the distributed active filter to compensate the voltage imbalance, for which the imbalance power should be shared among the distributed generations in the islanded microgrid.
In the islanded microgrids, the droop control method has been widely used for power sharing, but the mismatched line impedance was not considered in most literature for accurate power sharing. With the help of the low-bandwidth communication, the centralized control method was proposed to compensate the voltage imbalance and to share the imbalance power. However, the single point of failure feature results in limited flexibility and low reliability.
In recent years, consensus-based distributed control schemes have been studied for distributed voltage imbalance compensation with accurate sharing of the negative-sequence current among the DGs. However, this method may cause differences in negative-sequence voltage among the DGs to incur the circulating negative-sequence currents in the microgrid.
Kim Sung Hyok, a researcher at the Faculty of Electronics, has proposed a method whereby virtual impedance is adopted to regulate the DG equivalent impedance at the fundamental negative-sequence for sharing the imbalance power in proportion to the DG power rating with consideration of mismatched line impedance. In that case, the line equivalent impedance is defined as the serial combination of the line impedance and the virtual impedance controlled by the DG unit at the fundamental negative-sequence.
In order to ensure the accurate imbalance power sharing regardless of the impact of mismatched line impedance, the discrete form of the consensus algorithm is considered to design the communication law for the global average of per unit imbalance power discovery.
The global average of the imbalance power is used to find the virtual negative-sequence impedance correction term by the designed consensus algorithm. Here, the per unit imbalance power mismatch is fed to a proportional-integral (PI) controller to discover the virtual negative-sequence impedance correction term.
The virtual negative-sequence impedance is regulated adaptively to eliminate the imbalance power sharing mismatch. Accordingly, the load imbalance power is accurately shared among the DGs.
The virtual negative-sequence impedance regulation based on the consensus algorithm is developed to accurately regulate the line equivalent impedance regardless of the detection of line impedance.
The effectiveness of the proposed method has been verified by the simulation and experiment results.
You can find more information about this in his paper “Distributed virtual negative-sequence impedance control for accurate imbalance power sharing in islanded microgrids” presented to the SCI Journal “Sustainable Energy, Grids and Networks”.
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