• Journal of the Korea Concrete Institute
• /
• v.12 no.3
• /
• pp.3-10
• /
• 2000

In this study, we compared a plain mortar with the CAS-system shrinkage compensation mortar for Ondol that is Korean traditional heating system. The Ondol mortar is necessary to have properties as non-crack, fine flatness and stability for thermal changes. especially, mortar'crack prevention is to be most important property in Ondol mortar. To develope the stable material on the crack-prevention, we used to calcium-sulfo-aluminate(CSA)system in shrinkage compensation mortar. And so, we confirmed the effects of calcium-sulfo-aluminate(CSA) system for mortar's physical properties such as setting time, compressive strength and expansion ratio for crack prevention. The initial and final setting time of the CSA mortar is faster than plain mortar about 2hours. And, Compressive strength increased about 20% that plain mortar. The crack length per unit area, plain mortar is 0.426∼0.481m/m2. The Results of apartment construction field test, the shrinkage compensation mortar is excellent about the crack-reduce effect.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2010.05a
• /
• pp.433-434
• /
• 2010

This research was conducted length variation test for analyze the characteristics of shrinkage of concrete pavement along with changes of respective kinds of fibers. As a result, fiber-reinforced concrete has showed tendency that of enhanced performance compared to Plain in every kinds of shrinkage resistance performance especially on drying shrinkage. For the case of using domestic polypropylene fiber, a drying shrinkage has resulted in about 75% decrease compared to Plain.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1996.04a
• /
• pp.141-145
• /
• 1996

The primary purpose of this study is to investigate reusal techniques of by-product produced the combined heat power plant in the construction field, which may contribute to the savings of construction materials and the conservation of enviornment. This study is compared and evaluated by testing the chemical resistance, adiabatic temperature rising test, creep and drying shrinkage. As the result of the study, the following conclusions are derived : (1) hydration heat of the fly ash concrete is less than the plain concrete in adiabatic temperature rising test, (2) the fly axh concrete (FA 30%) is similar to the plain concrete in the chemical resistamce, (3) the fly ash concrete (FA 10, 30%) is similar to the plain concrete in drying shrinkage, but the fly ash concrete (FA 50%) is highly increased, (4) the fly ash concrete (FA 30%) is less than the plain concrete in creep test.

• Journal of the Korean Society of Safety
• /
• v.12 no.4
• /
• pp.191-200
• /
• 1997

This paper discusses prediction of the sound pressure level produced by simple engine exhaust systems(plain pipe, plain expansion chamber pipe, plain expansion chamber with internally extended inlet and outlet pipe, perforated pipe enclosed in a plain expansion chamber) and a computer program has been developed which predicts the sound pressure level and the frequency spectrum. The program utilizes unsteady flow gas dynamic theory and acoustic theory to predict the pressure-time history in the exhaust system and the mass flow rate-time history at the open end of the system and the sound pressure levels(1/3 Octave band levels) and the frequency spectrum in semi-anechoic room. The predictions are compared with measured levels and show a high degree of correlation.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.1163-1167
• /
• 2003

Effective properties of ceramic matrix plain woven textile composites were calculated using finite element analysis. The considered geometry is a unit cell of plain weave and the analysis was performed by commercial finite element program, ANSYS. The materials for analysis are 3 types for matrix, 1 type for fiber with various volume fraction. The result indicates that the effective properties of ceramic matrix composites can be controlled by the volume fraction. The result can be used for numerical analysis using ceramic matrix composites.

• Speech Sciences
• /
• v.3
• /
• pp.109-117
• /
• 1998

This paper tests whether the VOT (Voice Onset Time) contributes to the perception of tense and plain stops in Korean in the initial position. Previous studies have yielded opposite results regarding the role of the VOT in the distinction of these two stop categories. One the one hand, Lisker and Abramson (1964), Kim (1965), and Han and Weitzman (1970) suggest that the Korean plain and tense stops exhibit overlapping values of VOT and thus that, unlike many other languages, the VOT fails to serve as a cue to separate these stop categories. On the other hand, Silva (1991, 1992), and Lee (1991, 1994) use similar methods, but find that the VOT serve as the cue. In this study, the differences in the acoustic measurement with respect to the VOT of Korean plain and tense stops in initial prevocalic position will be tested preceptually, in seeking to determine whether these acoustic differences are used by listeners to distinguish these two stop types.

• Proceedings of the KSRS Conference
• /
• 2007.10a
• /
• pp.422-425
• /
• 2007

Traditionally, surface energy fluxes are obtained by model simulations or empirical equations with auxiliary meteorological data. These methods may not effectively represent the surface heat fluxes in a regional scale due to scene variability. On the other hand, remote sensing has the advantage to acquire data of a large area in an instantaneous view. The remotely sensed data can be further used to retrieve surface radiation and heat fluxes over a large area. In this study, the airborne and satellite images in conjunction with meteorological data and ground observations were used to estimate the surface heat fluxes over Taiwan's Chaiyi Plain. The results indicate that surface heat fluxes can be properly determined from both airborne and satellite images. The correlation coefficient of surface heat fluxes with in situ corresponding observations is over 0.60. We also observe that the remotely sensed data can efficiently provide a long term monitoring of surface heat fluxes over Taiwan's Chaiyi Plain.

• Advanced Composite Materials
• /
• v.18 no.3
• /
• pp.209-219
• /
• 2009

Carbon nanotubes (CNTs) have shown great potential for the reinforcement of polymers or fiber-reinforced composites. In this study, mechanical properties of multi-walled carbon nanotube (MWNT)-filled plain-weave glass/epoxy composites intended for use in radar absorbing structures were evaluated with regard to filler loading, microstructure, and fiber volume fraction. The plain-weave composites containing MWNTs exhibited improved matrix-dominant and interlaminar fracture-related properties, that is, compressive and interlaminar shear strength. This is attributed to strengthening of the matrix rich region and the interface between glass yarns by the MWNTs. However, tensile properties were only slightly affected by the addition of MWNTs, as they are fiber-dominant properties.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2009.11a
• /
• pp.171-174
• /
• 2009

This study analyzes the change of the basic characteristics of pavement concrete according to the reinforcement of macro-fiber and the results of the study can be summarized as follows. In the case of the compressive strength of the concrete, the fiber reinforced pavement concrete shows a small decreasing level compared to the basic mixing of pavement concrete (hereafter referred as 'Plain') based on the aging of 28 days. In particular, the polypropylene fiber made in Korea represents a decrease in the strength about 12% compared with that of the Plain. In the case of the tensile strength, it shows certain improvements in the tensile performance compared with that of the Plain. In particular, in the case of the polyvinyl alcohol fiber that shows the largest improvement in tensile performance, it shows an increase in its strength about 21%. In the case of the bending strength, there are no improvements in its strength in the fiber reinforced concrete compared to that of the Plain.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2004.04a
• /
• pp.250-253
• /
• 2004

Emphasis has been placed on thin plate fabrication of plain woven carbon fabric reinforced Al matrix composites using liquid pressing process. The composite has potential applications for PDP rear plate. The process is to use the low pressure for infiltration of Al melt into plain woven carbon fabric as the Al melt is pressurized directly. The minimum pressure required for the infiltration was calculated from force balance equation, permeability measurements and compaction behavior of carbon fiber. Also, the melting temperature and the holding time have been optimized. In order to measure coefficient of thermal expansion (CTE) of the composites, the thermal strain measurement using strain gage was performed and the thermal conductivity of the composites was measured using laser flash method. The constituent materials of the composite are PAN type carbon fibers as reinforcements and 6061 Al alloys as matrices.