Jo Nov 10, 2023
Core and Weber set are the most important set-valued solution concepts in TU-games. The core is a set of efficient payoff vectors that satisfy coalitional rationality i.e., a coalition receives at least its own worth, while the Weber set is a convex hull of all marginal vectors. In TU-games, core is always contained in Weber set. Furthermore, a game is convex if and only if its core coincides with its Weber set.
Inclusion of Weber set into core plays an important role in studies of 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 marginal vectors.
O Un Suk, a lecturer at the Faculty of Applied Mathematics, has proved the stability of the extent/intent Shapley value using the inclusion of the extent/intent Weber set into the extent/intent core in games on concept lattices.
In games on extents, she introduced extent Weber set, newly defined strong convexity, and proved the inclusion of the extent Weber set into the extent core under this condition. Similarly, she proved that the intent Weber set is included into the intent core under the weak concavity in games on intents. Finally, she studied the relation between the game on extents and the game on intents, and derived a sufficient condition for stability of two Shapley values.
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Jo Nov 9, 2023
“Taedongjiji”, also called “Taedongbangyogo”, is a geography book of our country. It was written in the middle of the nineteenth century by Kim Jong Ho, a geographer and cartographer of those days. It is in 32 volumes and 15 books.
It was written at the same time as his republication of “Taedongyo Map” in 1864 reflecting the demand of the times concerning the development of commerce and transportation in our country in the nineteenth century.
The book contains a detailed description of about 40 items by counties and districts such as the statistics of population, disposition and power of army, kind and number of ships, customs, taxes, etc., all of which were impossible to show on the map.
The first part of the book shows a table of contents and a list of 65 references. Volume 1 is about the capital. Volumes 2 to 24 deal with the geography of 8 provinces of the country. Volume 25 covers mountains and streams and Volume 26 is about national defence. Volumes 27 and 28 are on transportation and communication each. Volumes from 29 to 32 give the historical geography of territory changed over the period from the ancient times to the Koryo dynasty.
The book is organized in a new system on the basis of the new practical data the author obtained from his field surveys over a long period of time and a great number of references.
In terms of system and description, “Taedongjiji” could not pass the limit of feudal stereotype and facts enumeration but it still serves as one of our country’s geographical legacies with its own characteristics as a modern geography book.
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Jo Nov 7, 2023
Game theory is a set of algebraic models to investigate behavior conflicting with each other. In practice, event players often have a game in uncertain conditions with lack of opponents’ strategies.
Especially, in such games as two-person zero-sum games, the payoff value of each player’s strategy is imperfect, so high accuracy of player modeling cannot be guaranteed. In general, statistical method processes uncertainty mathematically with lots of observed numerical value data, but observed data usually contain occasional fluctuation caused instantly by various reasons as well as essential information about opponents.
Being used as a technology of several variables which identifies common characteristic factors in an invariable set, statistical factor analysis uses probability methods for factor analysis. However, these methods include invariable assumptions about probability distribution so the results may not always be right. Also, there are some cases where modeling is not suitable in practice. Though modeling is not correct strictly, we can draw nearly right conclusions from those hypotheses if it is approximately suitable.
Game theoretical decision adoption is a decision-making problem which determines how the best result can be obtained when the result depends both on its own and on the opponent’s actions.
Some decision-making problems like a zero-sum game are inflexible in target weight according to the structure, so they are changed and affected by opponents. Information analysis methods used in the past are not sufficient to deal with these problems.
Kim Ok, a researcher at the Faculty of Information Science and Technology, has proposed an algorithm where a player’s model can be estimated by a small amount of game data in a two-person zero-sum game characterized by a monotonically decreasing function.
The algorithm is based on the analysis of game process profiles. First, she introduced ordered weight operators to the strategic sequence determination of players and defined a compensation function considering monotonically decreasing character of a two-person zero-sum game. Then, she evaluated the game payoff value of the strategy and conducted player modeling.
The proposed algorithm will contribute to enhancing the accuracy of player modeling in two-person zero-sum games.
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Jo Nov 4, 2023
“Chronicles of the Feudal Joson Dynasty” is a “government journal” where the 500-odd-year history of the feudal Joson dynasty from 1392 to 1910 is recorded in order of year, month and date classified by the kings.
It is in 1 763 volumes and over 900 books.
“Chronicles of the Feudal Joson Dynasty” is classified by the kings into “Thaejo Sillok” (Chronicles of Thaejo), “Jongjong Sillok” (Chronicles of Jongjong), “Thaejong Sillok” (Chronicles of Thaejong), “Sejong Sillok” (Chronicles of Sejong), etc.
With huge amount and rich contents that could hardly be found in the world, “Chronicles of the Feudal Joson Dynasty” is a precious treasure of our nation.
During the hard-fought Fatherland Liberation War decisive of the destiny of the country, President
Under the wise leadership of the great leaders possessed of ardent love for the nation, all the contents were translated into Korean, thus widely used these days for historical studies.
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Jo Nov 2, 2023
Radiation is an important process of thermal transfer together with conduction and/or convection. Particularly, in high temperature conditions such as burning of pulverized coal, propellants of rockets and thermal plasma, it contributes significantly to overall thermal transfer. However, due to the integro-differential characteristic of a radiative transfer equation for mathematically explaining thermal radiation in absorbing, emitting and scattering media, its algebraic solution is in existence only for extremely limited geometries and conditions. Thus, numerical methods have mainly been utilized to study radiative thermal transfer. Moreover, the advance on performance of modern computers and the interest increased for understanding thermal radiation have promoted the development of numerical methods to solve the radiative transfer equation at a low cost.
Several numerical methods, such as Monte Carlo method, zonal method, discrete ordinates method, finite element method, etc. were applied to model radiative behavior.
The discrete ordinates method (DOM) is a numerical technique proposed first for analyzing radiative thermal transfer in a slab-parallel medium, which has several advantages: low dimensional approximation with sufficient accuracy, modest computational requirement, and applicability into complex geometry.
There were some attempts to use the lattice Boltzmann method (LBM) as a tool to solve the radiative transfer equation, which has developed into an alternative and promising numerical scheme for simulating fluid flows.
Kim Yong Jun, a researcher at the Faculty of Physics Engineering, has developed a discrete ordinate-lattice Boltzmann method (DO-LBM) by combining the advantages of DOM and LBM that can be utilized as a direct tool to solve the radiative transfer equation.
The discrete ordinates scheme is used for angular discretization and the lattice Boltzmann model is applied for spatial discretization.
Introducing Chapmann-Enskog method and dimensionless numbers, he analyzed accuracy of the DO-LBM and non-negativity of the equilibrium distribution function. He compared his method with numerical results by modified discrete ordinates method. The result showed that analyzing radiative transfer in geometry with complex boundaries lowers computational cost more than modified discrete ordinates method often found in literature.
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Jo Nov 1, 2023
When a villager builds or moves into a new house, the whole village turns out to sincerely help them rejoicing over it as over their own. It has been our peoples’ fixed way of life from earlier ages.
On the day of moving into a new house, people in the neighbourhood regarded it as courtesy to help remove household goods or bring some kind of presents needed for housekeeping like a match or a gourd dipper, and the host would serve them with simple food in return.
This fine custom shows the good manners of our people, who have regarded being friendly with neighbours as moral norms of life and have kept to it traditionally.
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