• Journal of the Korean Society for Precision Engineering
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• v.30 no.8
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• pp.802-808
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• 2013

Thermal barrier coating (TBC) is used to protect substrates and extend the operating life of gas turbines in power plant and aeronautical applications. The major causes of failure of such coatings is spallation, which results from thermal stress due to a thermal expansion coefficient mismatch between the top coating and the bond coating layers. In this paper, the effects of the material properties and the thickness of the top coating layer on thermal stresses were evaluated using the finite element method and the equation for the thermal expansion coefficient mismatch stress. In addition, we investigated a design technique for the top coating whereby thermal resistance is exploited.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.275-278
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• 2000

In this paper, we carried out fundamental experiments to use steel manufacturing slag as a concrete aggregate. Generally, there are two types of slag, the blast-furnace slag and the steel manufacturing slag. The latter is classified by the difference of manufacturing method of steel into the convertor slag and the electric-furnace slag. The steel manufacturing slag mainly contains $SiO_2$ and CaO as the chemical composition. The reaction with water and a little of free CaO in the steel manufacturing slag made the expansion of volume change, Therefore, we primarily investigated physical properties, expansion mechanism, pH value, aging effect and aging methods in the steel manufacturing slag, Then compressive strength of concrete with steel slag aggregate is measured.

• Journal of Hydrogen and New Energy
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• v.27 no.4
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• pp.349-356
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• 2016

Volumetric capacity metrics at cryogenic condition are critical for technological and commercial development. It must be calculated and reported in a uniform and consistent manner to allow comparisons among different materials. In this paper, we propose a simple and universal protocol for the determination of volumetric capacity of sorbent materials at cryogenic condition. Usually, the sample container volume containing porous sample at RT can be directly determined by a helium expansion test. At cryogenic temperatures, however, this direct helium expansion test results in inaccurate values of the sample container volume for microporous materials due to a significant helium adsorption, resulting significant errors in hydrogen uptake. For reducing this container volume error, therefore, we introduced and applied the indirect method such as 'volume correction using a non-porous material', showing a reliable cold volume correction.

• Korean Management Science Review
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• v.19 no.1
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• pp.29-38
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• 2002

Due to the rapid increase In the Internet traffic volume, ISPs are faced with the definite need of the expansion of server capacity. In order to Provide prompt services for customers and still prevent excessive facility cost, it is critical to determine the optimum level of internet server capacity. The purpose of this Paper is to provide a simple but effective strategy on the expansion of servers capacity according to the increase in internet traffic. We model an internet server as an M/G/m/m queueing system and derive an efficient method to compute the loss probability which, In turn, Is used as a basis to determine proper server capacity. The Process of estimating the traffic parameter values at each server based on log data analysis is also given. All the procedures are numerically demonstrated through the process of analyzing actual log data collected from a game company.

• Communications of the Korean Mathematical Society
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• v.27 no.1
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• pp.107-116
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• 2012

Here, by using the symbolical method introduced by Burchnall and Chaundy, we aim at constructing certain expansion formulas for the generalized hypergeometric function $_pF_q$. In addition, using our expansion formulas for $_pF_q$, we present formulas of an analytic continuation of the Clausen hypergeometric function $_3F_2$, which are much simpler than an earlier known result. We also give some integral representations for $_3F_2$.

• Journal of the Korean Chemical Society
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• v.22 no.3
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• pp.117-127
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• 1978

Slater type orbitals, located at two different points A and B, are expressed in a common coordinate system by expanding the spherical harmonics and the radial part of these orbitals in terms of the reference point A. Master formulas for two center overlap integrals are derived, using the general expansion formulas of slater type atomic orbitals. Two center overlap integrals for $CH_4,\;H_2O,\;NH_3,\;C_2H_6\;and\;PH_3$molecules are evaluated, using master formulas for two center overlap integrals. The results are in agreement with those of two center overlap integrals of Mulliken.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.05a
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• pp.255-256
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• 2012

In this study, strain properties of high strength concrete using light weight aggregate which is widely used in recent years are evaluated. For these purpose, thermal strain, transient creep were measured in prestressed condition as 0, 20, 40% of specimen strength at target temperature with 60MPa specimens which was using normal and light weight aggregate. As a result, light weight aggregate is more advantageous for the control of strain than normal aggregate because of its low thermal expansion.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.11 no.5
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• pp.323-331
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• 1986

By solving the current distribution, natual frequencies, and the amplitude of natural modes about the perfect conducting scatterer of revolution are presented. Singularity expansion method is applied to slove the time-domain response based on the simplified E-field integral equation by the application of the extended boundary conditin for the perfect conductin scatterer of revolution.

• The Transactions of the Korea Information Processing Society
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• v.7 no.5
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• pp.1482-1490
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• 2000

With the increasing availability of information in electronic form, it becomes more important and feasible to have automatic methods to retrieve relevant information in the Internet. A deficiency of traditional information retrieval systems is that search terms are often different from those indexed by the systems. Thus, users ma either retrieve wrong information or miss what they really want. In this paper, e used an automatic query expansion based expansion based on term distribution to enhance the performance of information retrieval. Also this thesis proposed the method for setting the threshold according to area distribution in order choose additional terms.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.9
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• pp.94-102
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• 2010

The spindle is the main component in machine tools. To develop high speed machine tools, a lot of studies have been carried out for high speed spindle. Bearing is very important part in spindle. The bearing clearance is influenced by shrink fit and thermal expansion during operation. The designer must take into account the reduction of shrink fits. The aims of this study are to grasp the shrink fits and behavior of a bearing which is a deeply connected with fatigue life of bearing and performance of spindle through FEM(Finite Element Method). This paper proposed optimum value of shrink fit considering deformation of spindle and stress of fitting area using design of experiments. Thus, the proposed formula can be used to obtain bearing internal clearance.