• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.5
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• pp.313-319
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• 2000

In order to design the current carrying conductor for GIS, it is important to predict temperature-rise when rated current flows in the bus bar. However, it is not easy to apply the correct heat transfer coefficient on the boundary between different material for the thermal analysis. In this paper, the heat transfer coefficient which depends on parameters such like material constant, model geometry as well as ambient temperature, was calculated by analytic method. The calculated coefficient is used for the temperature rise prediction by F.E.M. The results show good agreement with experimental data.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.894-895
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• 2007

This paper presents coupled analysis between finite element method and analytic technique for predicting temperature rise of 25.8kV 25kA three-phase GIS bus bar. The power losses and temperature distribution of three-phase GIS bus bar model are analyzed by magneto-thermal finite element method. The heat transfer coefficients on the boundaries are analytically calculated by applying Nusselt number considering material constant and model geometry for the natural convection. And these are used as the input data to predict the temperature rise of three-phase GIS bus bar model by coupled magneto-thermal F.E.A. The predicted temperature of 25.8kV 25kA three-phase GIS bus bar model shows good agreement with the experimental data.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.19 no.3
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• pp.327-364
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• 2015

In this paper, a generalized guidance law with an arbitrary pair of guidance coefficients for impact angle control is proposed. Under the assumptions of a stationary target and a lag-free missile with constant speed, necessary conditions for the guidance coefficients to satisfy the required terminal constraints are obtained by deriving an explicit closed-form solution. Moreover, optimality of the generalized impact-angle control guidance law is discussed. By solving an inverse optimal control problem for the guidance law, it is found that the generalized guidance law can minimize a certain quadratic performance index. Finally, analytic solutions of the generalized guidance law for a first-order lag system are investigated. By solving a third-order linear time-varying ordinary differential equation, the blowing-up phenomenon of the guidance loop as the missile approaches the target is mathematically proved. Moreover, it is found that terminal misses due to the system lag are expressed in terms of the guidance coefficients, homing geometry, and the ratio of time-to-go to system time constant.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05a
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• pp.34-39
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• 1996

A consistent general order nodal method for solving the 3-D neutron diffusion equation in (x-y-z) geometry has ben derived by using a weighted integral technique and expanding the spatial variables by the Legendre orthogonal series function. The equation set derived can be converted into any order nodal schemes. It forms a compact system for general order of nodal moments. The method utilizes the analytic solutions of the transverse-integrated quasi -one dimensional equations and a consistent expansion for the spatial variables so that it renders the use of an approximation for the transverse leakages no necessary. Thus, we can expect extremely accurate solutions and the solution would converge exactly when the mesh width is decreased or the approximation order is increased since the equation set is consistent mathematically.

• Nuclear Engineering and Technology
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• v.30 no.2
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• pp.140-147
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• 1998

Basic concept of a cold neutron source for a 30 MW heavy water moderated reactor (HANARO) is developed. The source is a cold bottle located in a vertical hole near the reactor core. Since the bottle does not have sufficient volume for cooling, the optimum liquid mixture ratio is studied between liquid hydrogen and liquid deuterium. We also studied the variation of the gain depending on the volume of the bottle. The calculation is performed by a coupled MCNP model and by a semi-analytic approach. For the current geometry, 80% liquid deuterium mixture with liquid hydrogen gives the highest gain at 10 A neutron wave.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1721-1729
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• 2001

The performance of gas turbines is decreased as their operating hours increase. Fouling in the axial compressor is one of main reasons for the performance degradation of gas turbine. Airborne particles entering with air at the inlet into compressor adhere to the blade surface and result in the change of the blade shape, which is closely and sensitively related to the compressor performance. It is difficult to exactly analyze the mechanism of the compressor fouling because the growing process of the fouling is very slow and the dimension of the fouled depth on the blade surface is very small compared with blade dimensions. In this study, an improved analytic method to predict the motion of particles in compressor cascades and their deposition onto blade is proposed. Simulations using proposed method and their comparison with field data demonstrate the feasibility of the model. It if found that some important parameters such as chord length, solidity and number of stages, which represent the characteristics of compressor geometry, are closely related to the fouling phenomena. And, the particle sloe and patterns of their distributions are also Important factors to predict the fouling phenomena in the axial compressor of the gas turbine.

• Fire Science and Engineering
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• v.26 no.3
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• pp.79-84
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• 2012

In this study thermal characteristics of heat-responsive element considering conduction, convection and rate of change of element using Response Time Index (RTI) applied to sensitivity test of sprinkler head at home and aborad are theoretically investigated. Analytic solution of temperature distributions with radial direction and time is obtained form energy transport equations, non-homogeneous 2th order partial differential equation, applying to constant wall temperature and symmetric condition in order to analyze thermal characteristics of heat-responsive element for circular cylindrical geometry. Base on the results, the analytic method of this study is fundamental data to practical use for sensitivity test of sprinkler head and design of heat-responsive element.

• Journal for History of Mathematics
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• v.2 no.1
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• pp.9-27
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• 1985

Islam toot a great interest in the utility sciences such as mathematics and astronomy as it needed them for the religious reasons. It needeed geometry to determine the direction toward Mecca, its holiest place: arithmetic and algebra to settle the dates of the festivals and to calculate the accounts lot the inheritance; astronomy to settle the dates of Ramadan and other festivals. Islam expanded and developed mathematics and sciences which it needed at first for the religious reasons to the benefit of all mankind. This thesis focuses upon the golden age of Islamic culture between 7th to 13th century, the age in which Islam came to possess the spirit of discovery and learning that opened the Islamic Renaissance and provided, in turn, Europeans with the setting for the Renaissance in 14th century. While Europe was still in the midst of the dark age of the feudal society based upon the agricultural economy and its mathematics was barey alive with the efforts of a few scholars in churches, the. Arabs played the important role of bridge between civilizations of the ancient and modern times. In the history of mathematics, the Arabian mathematics formed the orthodox, not collateral, school uniting into one the Indo-Arab and the Greco-Arab mathematics. The Islam scholars made a great contribution toward the development of civilization with their advanced the development of civilization with their advanced knowledge of algebra, arithmetic and trigonometry. the Islam mathematicians demonstrated the value of numerals by using arithmetic in the every day life. They replaced the cumbersome Roman numerals with the convenient Arabic numerals. They used Algebraic methods to solve the geometric problems and vice versa. They proved the correlation between these two branches of mathematics and established the foundation of analytic geometry. This thesis examines the historical background against which Islam united and developed the Indian and Greek mathematics; the reason why the Arabic numerals replaced the Roman numerals in the whole world: and the influence of the Arabic mathematics upon the development of the modern mathematics.

• East Asian mathematical journal
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• v.32 no.4
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• pp.483-500
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• 2016

Ancient Greek mathematician Euclid left three books about mathematics. It's 'The elements', 'The data', 'On divisions of figure'. This study is based on the analysis of Euclid's 'On divisions of figure'. 'On divisions of figure' is a book about the construction of the shape. Because, there are thirty six proposition in 'On divisions of figure', among them 30 proposition are for the construction. In this study, based on the 'On divisions of figure' we explore the direction for construction education. The results were as follows. First, the proposition of 'On divisions of figure' shall include the following information. It is a 'proposition presented', 'heuristic approach to the construction process', 'specifically drawn presenting', 'proof process'. Therefore, the content of textbooks needs a qualitative improvement in this way. Second, a conceptual basis of 'On divisions of figure' is 'The elements'. 'The elements' includes the construction propositions 25%. However, the geometric constructions contents in middle school area is only 3%. Therefore, it is necessary to expand the learning of construction in the our country mathematics curriculum.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.125-129
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• 2009

In this paper automatic 3D wing shape modeling program is introduced. The program is developed in Visual Basic based on Net Framework 3.5 environment by using CATIA COM Library, and it is used together with CATIA system to model 3D wings with or without flaps. With this program users can easily construct wing models by specifying geometry parameters which are usually design variables with the aid of easy-to-use GUI environment, and specifying sectional airfoil data is done either by using analytic shape functions such as NACA series airfoils or by providing input files with point data describing the airfoil shape. When all the input parameters are provided, users can either work further with the model in the CATIA system which would be automatically started by the program or save the resultant model in the format of users choice. Unstructured grid generation program is also briefly described which can make grid generation task for a 3D wing easy and efficient one when used together with the wing modeling program by choosing STL format as the model's output format.