Jo Aug 1, 2022
“Turtle ship” is the very first iron-clad battleship designed by a distinguished patriotic general Ri Sun Sin after being appointed admiral of Left Jolla Province in 1591.
According to the historical book “Richungmugongjonso”, the structure, building method and performance of turtle ships are roughly as follows.
A turtle ship was 35 metres long, 11.8 metres wide and 5.2 metres high, with 10 oars at each side and about 70 muzzles. The sails could be either raised or lowered if necessary.
The front part of the ship looked like the head of a turtle, where sulphur and nitre were burnt to produce smoke which was supposed to be emitted through the mouth to prevent enemy from noticing it.
It had two muzzles at the top of the turtle head and one muzzle on each side of the door. There were 12 muzzles on the right and left siding walls respectively on which some colours were fixed.
The roof of the ship was made up of large planks to look like a turtleback. There was a narrow way for our warriors only on the turtleback the rest part of which sharp objects like spears and daggers were fixed all over to keep enemies away. In the centre of the ship were 26 chambers, two of which were filled with ironware, five of which stored weapons like guns, arrows and bows, dynamite, swords, etc. and 19 of which were used as bedrooms for warriors. One of the remaining 2 chambers was captain’s cabin and the other one was a bedroom for commanding officers.
As warriors and combat equipment were protected inside the ship and they could look out from inside but nobody could look in from outside, it was possible for warriors in the ship to fire guns on all sides at hundreds of enemy ships at the same time. Some parts of the ship were iron-clad and the rest parts were covered with thick planks. Therefore, contemporary gun fire could never break it down nor burn it down.
Stout and stable in structure and incredible in speed, turtle ships equipped with various kinds of weapons and guns (12 at the right and left, 2 at the front, total 14) and loaded with as many warriors as 160 was an incomparably powerful warship in those days that was capable of destroying any enemy ship. In addition, the reasonable size and shape of the ship ensured good navigability.
Turtle ship, built in an original way by the Korean people, who had exploited and defended the sea from the early times, made a great contribution to defending the country by inflicting disastrous defeat on the Japanese invaders in several sea battles including the battle on the sea off Sachon during the Japanese invasion of Korea in 1592.
Outside Korea, it was not until the Crimean War (1853~1856), which broke out 440 years after the turtle ship, that three iron-clad ships were built. However, they were hardly used because they were too slow and cumbersome.
In conclusion, the first ever iron-clad ship turtle ship is a priceless national heritage that demonstrates the resourcefulness and creative talents of the Korean nation and at the same time it is a common asset of mankind that holds a prominent position in the world history of armament.
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Jo Jul 29, 2022
O Un Suk, a lecturer at the Faculty of Applied Mathematics, has studied the relations of core, Weber set and Shapley value to one another under the condition of strong convexity / weak concavity.
A cooperative game with transferable utility, a TU-game for short, is defined as a pair (N, v) , where N is a finite set of players and v is a mapping that assigns a real number v(S) to each coalition S⊆N. v(φ) is set 0.
One of the important problems in the cooperative game theory is to select an efficient payoff vector, i.e., a way of sharing among players the total worth of the game when they all join a grand coalition. For this aim, various solution concepts have been developed.
The solutions playing an important role in selecting efficient payoff vectors include Core, Weber set, and Shapley value.
In many real situations, however, not all subsets of N can be realized as coalitions or they are not feasible. The interest in subcollections of the power set of N is inspired by the fact that in case of restricted communication or cooperation structure, the standard model of a cooperative game is not applicable. A game on concept lattices is a good example.
A game on concept lattices is a cooperative TU-game defined on concepts, where a concept is a pair (S, S') of S, a subset of players or objects, and S' a subset of attributes.
Such games induce a game on extents and a game on intents.
The inclusion of the Weber set in core plays an important role in the studies of the stability of the Shapley value (inclusion of the Shapley value into the core) because the Shapley value is defined as a mean value of all vertices of the Weber set.
The Weber set does not become the subset of the core under convexity in games on concept lattices different from classical cooperative games. Thus, the concept of strong convexity is introduced in games on extents.
Strong convexity means that the larger coalition each player joins in, the greater the average creation value of them gets.
The following theorem shows that the extent Weber set becomes a subset of the extent core in strongly convex games on extents.
Theorem 1. The extent Weber set is included in the extent core if a game on extents is strongly convex.
Corollary 1. The extent Shapley value assigns an element of the extent core if a game on extents is strongly convex.
The condition of strong convexity is a sufficient condition that guarantees the extent Shapley value to be in the extent core in the games on extents. Therefore, in convex games, not strongly convex, the extent Shapley value may belong to the extent core.
Similarly, it becomes possible to define weak concavity in games on intents as they are in dual relation with games on extents. Then, it can be proved that the intent Weber set is the subset of the intent core under weak convexity.
It is concluded that the extent/intent Shapley value can be used as a rational solution to this game if a game on extents/intents is convex/concave.
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Jo Jul 28, 2022
In the early 15th century, some talented musicians in Korea including Pak Yon and Hwang Hyo Song invented a system of lettered musical notes in rectangles capable of expressing the pitch, length and time of a sound fairly adequately.
Musical characters, key signatures, etc. written in rectangles like those on a chessboard denoted both the pitches and the lengths of sounds. That was an original quantitative system of musical notes that was invented for the first time in the history of eastern music.
The earliest musical notes in rectangles was “Sejong Sillok Akpo” devised and compiled in 1430 and published in 1453 by some talented musicians in the palace led by Pak Yon (1378~1458).
It was based on a fixed “degree” system where the initials (hwang, tae, thae, hyop, ko, jung, yu, rim, i, nam, mu, ung) of 12 musical notes with absolute pitches were written in 32 rectangles in a row.
Later it was improved into a 5-note system in 16 rectangles in a row, which is none other than “Sejo Sillok Akpo” published in 1464.
With the appearance of the lettered musical notes expressed in rectangles, the shortcomings of the previous musical notes arranged in a row and kuumyukpo, which failed to show tone length, were overcome, and poems and songs were able to be precisely expressed. This made a great stride in the expression of music.
As mentioned above, the musical notes devised by some musicians including Pak Yon in the early 15th century are of great musical significance as they are far superior over previous ones and the earliest in the history of the East, too.
Indeed, the Korean nation is a wise and resourceful nation that left a remarkable trace in the pages of musical history.
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Jo Jul 26, 2022
Formal Concept Analysis (FCA) is considered to be a major formalism for knowledge extraction, reduction, representation and analysis. The core of the mathematical theory of FCA is formal concept lattice.
Determination and description problems on the formal concept lattice are basic ones of FCA. The determination problem is “How can one determine the concept lattice of a given context?” and the description problem is “How can one describe the concept lattice of a given context?”. The most communicative description of the concept lattice is known to be given by Hasse diagrams. However, it is difficult for any information retrieval software to autonomously understand the hierarchy of the concepts from Hasse diagrams. If the hierarchy of the concept lattice is described with a matrix corresponding to Hasse diagrams, any software will be able to autonomously understand the hierarchy of the concepts by the hierarchy-matrix.
In order to obtain such matrix, matrix-correspondence of finite topological spaces obtained by the introduction of Scott topology into the finite concept lattices must be employed and then a new hierarchy-matrix describing the hierarchy of the concept lattice be generated. This idea is based on the matrix-correspondence of finite topological spaces and the fact that Scott topology base is a collection of upper sets of every element. This hierarchy-matrix embodies all the information of the Hasse diagram and is well adapted for use to software.
Pak Chol Hong, a researcher at the Faculty of Applied Mathematics, has proposed a method for generating a new hierarchy-matrix, estimating the connectivity of concepts by the hierarchy-matrix, describing the Hasse diagram via a hierarchy-matrix and generating the hierarchy-matrix via the Hasse diagram in a given finite concept lattice.
The results can also be discussed in universal lattices. If the description of the concept lattices via the hierarchy-matrix is linked up with the determination of the concept lattices, then the formal concept analysis will be used more effectively in several areas of information retrieval, knowledge mining and database management.
Meanwhile, he has proposed that the finite concept lattice is an algebraic lattice and a topological lattice with respect to the Scott topology and the category of finite concept lattices as objects and monotonic mappings as morphisms. These results seem helpful to categorical research into FCA.
More information about this is in his paper “Describing hierarchy of concept lattice by using matrix” presented to SCI Journal “Information Sciences”.
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Jo Jul 24, 2022
Jang Ui Jun, a researcher at the Faculty of Earth Science and Technology, has developed a plasma water treatment device, an experimental device for education and research, which enables experiments for improving the quality of groundwater and surface water to be conducted in combination with laboratory conditions and field characteristics, and verified its utility.
In general, water treatment devices for improving the quality of groundwater or surface water include chlorine sterilizers, various kinds of filters such as activated carbon filters, UV disinfecters, ozone sterilizers and plasma sterilizers.
A plasma water treatment device, one of advanced water treatment devices, is able to overcome the limitations of the above-mentioned water treatment devices and conduct sterilization and water treatment comprehensively and efficiently by means of active chemical species as well as ultraviolet and ozone.
It consists of a power supply unit for geneartion of pulsed high voltage, a plasma reactor, a water sample tank and a water control valve and a tank for treated water.
Using this plasma water treatment device, we can do experiments the aim of which is to reduce the contents of various water quality indicators contained in contaminated surface water or groundwater, especially some elements such as Fe2+, to remove bacteria including Escherichia coli, and to improve water quality.
This device, compared to the aeration method, helps increase the rate of oxidation of Fe2+ ions in water by more than 2.5 times and raise recognition effect by providing visual effects.
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Jo Jul 21, 2022
In recent decades, temperature/pH dual responsive amphiphilic polymers have attracted the interest of researchers as they can perform certain functions by changing hydrophilic and hydrophobic balances corresponding to changes in the external environment. These types of amphiphilic polymers are very useful, especially for drug delivery, tissue engineering, biotechnology and other related fields.
However, most temperature/pH dual responsive polymers are prepared with petroleum chemical monomers as main raw material. This results in its limited applicability due to their toxicity and poor biocompatibility. In recent years, many researchers have focused their work on biomass derivatives to improve the temperature/pH dual responsiveness of polymers.
Jong Kwang Hyok, a section head at the Faculty of Applied Chemistry, has successfully synthesized a novel type of temperature/pH dual responsive polymer, PyHES (2-hydroxy-3-(2-propynyloxy) propyl hydroxyethyl starch)-DMAET (2-(dimethylamino) ethanethiol).
He prepared temperature-responsive polymer PyHES via hydrophobic modification of hydroxyl groups in hydroxyethyl starch (HES) with propynylglycidyl ether (PGE); subsequently, he connected a pH-responsive tertiary amine group to the propynyl group via a thiol-yne click reaction.
As PyHES-DMAET has pH-responsive amino groups and hydrophobic thioether groups, its aqueous solution exhibits excellent temperature/pH dual sensitivity, i.e., a good transference between hydrophobic (or self-assembly) and hydrophilic (or swelling) states resulting from changes in temperature/pH values. These properties can be exploited for hydrophobic drug release.
The experimental results showed that drug release reached 96% at 37℃ and a pH of 6.5, and that the drug-loading capacity of PyHES-DMAET increased with the degree of substitution (DS) of the hydrophobic propynyl groups in the PyHES, and the maximum drug-loading capacity for doxorubicin (DOX) achieved in the study was 33 wt%.
More information about this is in his paper “Temperature and pH dual responsive 2-(dimethylamino)ethanethiol modified starch derivatives via a thiol-yne reaction for drug delivery” presented to SCI Journal “Colloid and Polymer Science”.
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