• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1401-1406
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• 2003

Performance of two vapor pressure correlation equations in a polynomial expression is compared. These are the Wagner-type equation and the Inverted form equation. The equations are fitted to correlate the data in the ASHRAE tables and from NIST Chemistry WebBook for 17 pure substances. Some observations on the exponents in the two polynomial equations are made, which results in a proposal of a new closed form vapor pressure equation. The new equation yields the accuracy comparable to that of the Wagner-type equation and better than that of the Inverted form equation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.717-720
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• 2000

Event-driven communication protocols such as CAN(Controller Area Network) have inherent packet delays due to the contention process for the use of network medium. These delays are stochastic in nature because most packets arrive at random time instants. The stochastic property of the delay adversely influences the control system's performance in terms of stability, responsiveness and steady-state error. Another problem for safety-critical application such as brake-by-wire systems is the reliability of the communication modules that can fail abruptly. This paper deals with two methods to overcome the above problems : (i) scheduling method that can maintain packet delays under some acceptable level, and (ii) redundancy management of communication modules that prescribes dual-redundancy modules' behavior when one of them fails.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.2
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• pp.38-44
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• 2008

In the present paper, we theoretically analyze the flow of magnetic fluids in a circular pipe with a vertical magnetic field and investigate the magnetic response by the external magnetic field. Theoretical study through the governing equation derived by Siliomis is carried out with numerical analysis by the Gauss Elimination Method. Using polar and magnetic effect parameters, theoretical equations and distributions for the velocity, apparent viscosity as the magnetic response are shown. Especially, in the region of strong magnetic field the specific property is appeared by finding a critical magnetic effect parameter for a polar effect parameter.

• Progress in Superconductivity
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• v.7 no.1
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• pp.11-16
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• 2005

Coupling of non-linear oscillators have long been an interesting problem for physicists. The coupling phenomena have been frequently observed in Josephson junction series array, which have been used for Josephson voltage standard. Interestingly pronounced self-generation effect has been found during recent development of Josephson arrays for programmable Josephson voltage standard. But the coupling effect between the self-generations is not fully understood yet. We present harmonically approximated analytical solutions for coupled self-generations in the Josephson arrays, i.e., Superconductor-Insulator-Normal metal-Insulator-Superconductor (SINIS) array, externally shunted Superconductor-Insulator-Supercondctor (es-SIS) array, Superconductor-Normal metal-Superconductor (SNS) array. We find that the coupling between the self-generated Josephson oscillations through microwave transmission line plays critical role in microwave property of the Josephson array.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.91-96
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• 2000

Glass fiber reinforced thermoplastic composites were manufactured by Rapid Press Consolidation Technique(RPCT) as functions of temperature, pressure and time in pre-heating, consolidation and solidification sections during the manufacturing processing. It was found that the material property is greatly affected by pre-heating temperature under vacuum, mold temperature and molding pressure. Among them, the temperature In the mold was the most critical factor in determining the mechanical properties and the molded conditions of specimen. The crystallinity of PET matrix was also investigated by differential scanning calorimetry(DSC) measurements for various processing conditions. The level of crystallinity($X_c$) depended strongly on the mold temperature, cooling rate and the type of composite. The difference in $X_c$ is believed to be one of important factors in characterizing the mechanical properties.

• Journal of the Korean Mathematical Society
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• v.54 no.5
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• pp.1573-1594
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• 2017

This paper deals with the existence and energy estimates of solutions for a class of degenerate nonlocal problems involving sub-linear nonlinearities, while the nonlinear part of the problem admits some hypotheses on the behavior at origin or perturbation property. In particular, for a precise localization of the parameter, the existence of a non-zero solution is established requiring the sublinearity of nonlinear part at origin and infinity. We also consider the existence of solutions for our problem under algebraic conditions with the classical Ambrosetti-Rabinowitz. In what follows, by combining two algebraic conditions on the nonlinear term which guarantees the existence of two solutions as well as applying the mountain pass theorem given by Pucci and Serrin, we establish the existence of the third solution for our problem. Moreover, concrete examples of applications are provided.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.05a
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• pp.311-313
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• 2012

Many efforts have been made and many tools have been developed in order to manage construction projects by a smart device such as a smart phone and smart pad. This research proposed a method to manage construction schedules via a smart device using Flash. The interactive and graphic property of Flash enables a field manager to manage schedules easily and efficiently. A prototype was implemented by Adobe Flex Builder, and it applied a sample network in a smart pad. Further studies would develop network diagrams such as CPM(Critical Path Method).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.149-150
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• 2005

According to the trend for electric power equipment of high capacity and reduction of its size, the needs for the new high performance electric equipments become more and more important. On of the possible solution is high temperature superconducting (HTS) power application. Following the successful development of practical HTS wires, there have been renewed activities in developing superconducting power equipment. HTS equipments have to be operated in a coolant such as liquid nitrogen ($LN_2$) or cooled by conduction-cooling method such as using Gifford-McMahon (G-M) cryocooler to maintain the temperature below critical level. In this paper, the dielectric strength of unfilled epoxy and filled epoxy in $LN_2$ was analyzed. The filled epoxy composite not only compensates for this fragile property but enhances its dielectric strength.

• Progress in Superconductivity
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• v.1 no.2
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• pp.141-145
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• 2000

Different twist pitches of multi filamentary BSCCO 2223 tapes using high resistivity sheath were fabricated to investigate the effect of twist pitches on the microstructure and critical current property. A conductor with a high resitstivity matrix is possible to allow larger twist pitch for reducing ac losses and reduce eddy current losses simultaneously. The $J_{ct}$ values of 10 mm and 5 mm twisted tapes drop faster than that of untwisted and 20 mm twisted tapes under increasing magneticfield, especially in low field regime (0 $\sim$ 0.03 T). It suggests that weak links in the former are more serious than in the latter, which is in accordance with the microstructure analysis.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.32 no.1
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• pp.26-32
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• 2000

The impact of major surface chemical properties of silica sols on the retention and drainage performance of the silica based micrparticle system, Compozil was investigated using four different silica sols. And the effect of silica properties on the interactions with cationic starch and cationic plyacrylamide has also been identified. The surface charge density and the stability over pH of silica sols were increased by introducing aluminosilicate anions at surface. It was found that the charge density of silica sols determined the addition level necessary to attain the maximum retention and drainage. When silica sols were combined with cationic starch, the change density of the product was the critical properties and the degree of microagregation was of minor importance. In the cationic polyacrylamide system the degree of colloid structure appeared to be a more critcial property than the charge density of silica sols.