• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.4
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• pp.297-306
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• 2014

Recently nano-materials are gaining more importance in the construction industry due to its enhanced energy efficiency, durability, economy, and sustainability. Nano-silica addition to cement based materials can control the degradation of the fundamental calcium-silicate-hydrate reaction of concrete caused by calcium leaching in water as well as block water penetration and therefore lead to improvements in durability. In this paper, the influence of synthesized nano silica from locally available rice husk on the mechanical properties and corrosion resistant properties of OPC (Ordinary Portland Cement) has been studied by conducting various experimental investigations. Micro structural properties have been assessed by conducting Scanning Electron Microscopy, Thermo gravimetry and Differential Thermal Analysis, X-Ray Diffraction analysis, and FTIR studies. The experimental results revealed that NS reacted with calcium hydroxide crystals in the cement paste and produces Calcium Silicate Hydrate gel which enhanced the strength and acts as a filler which filled the nano pores present in concrete. Hence the strength and corrosion resistant properties were enhanced than the control.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.7
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• pp.456-461
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• 2015

In this study, the frequency properties of electrostatic capacity and dielectric loss for the samples with different types of filler has been measured in through the applied frequency range of 7 kHz ~3,000 kHz at temperature of $80^{\circ}C$, $110^{\circ}C$, $140^{\circ}C$, $170^{\circ}C$. The results of this study are as follows. When the sample is degradated at the temperature of $80^{\circ}C$, $110^{\circ}C$, $140^{\circ}C$, $170^{\circ}C$ and the frequency range of 7 kHz ~3,000 kHz is applied, It found that the electrostatic capacity of the sample with Polyimide film is larger than the sample with Grass fiber. It found that the dielectric loss for the sample with Polyimide film is larger than the sample with Grass fiber with increasing frequency and temperature in the $80^{\circ}C$, $110^{\circ}C$, $140^{\circ}C$, $170^{\circ}C$ range. Also, the dielectric loss decreased with increasing frequency. In case of the sample with Polyimide film, It found that the electrostatic capacity decreased with increasing temperature, and the dielectric loss gradually decreased with increasing frequency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.12
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• pp.1772-1780
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• 2003

An optimal soot blowing system has been developed for an optimal operation of power utility boilers by both minimization of the use of steam and the number of soot blowers worked during soot blowing. Traditionally, the soot blowing system has been operated manually by operators. However, it causes the reduction of power and thermal performance degradation because all soot blowers installed in the plant should be worked simultaneously even there are lots of tubes those are not contaminated by slagging or fouling. Heat transfer area is divided into four groups, furnace, convection area including superheater, reheater and economizer, and air preheater in the present study. The condition of cleanness of the tubes is calculated by several parameters obtained by sensors. Then, a part of soot blowers works automatically where boiler tubes are contaminated. This system has been applied in a practical power plant. Therefore, comparison has been done between this system and manual operation and the results are discussed.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.903-908
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• 2001

A web-based client/server program, MOVIDIK(Motor-Operated-Valve Integrated Database Information of KEPCO) has been developed to perform a design basis safety evaluation for a motor-operated-valve(MOV) in the nuclear power plant. The MOVIDIK consists of seven analysis modules and one administrative module. The analysis module calculates a differential pressure on the valve disk, thrust/torque acting at a valve stem, maximum allowable stress, thermal-overload-relay selection, voltage degradation, actuator output and margin. In addition, the administrative module manages user information, approval system and code information. MOVIDIK controls a huge amount of evaluation data and piles up the safety information of safety-related MOV. The MOVIDIK will improve the efficiency of safety evaluation work and standardize the analysis process for the MOV.

• Journal of Power System Engineering
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• v.8 no.3
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• pp.18-22
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• 2004

Boiler is one of the most important utilities providing steam to turbine in order to supply mechanical energy in thermal power plant. It is composed of thousands of tubes for high efficient heat transfer. The material for boiler tubes is used in such high temperature and pressure condition as $540^{\circ}C$, 22MPa. The boiler tube material is required to resist creep damage, fatigue cracking, and corrosion damages. 2.25%Cr-1Mo steel is used for conventional boiler tubes, and austenitenite stainless steel is used for higher temperature boiler tubes. But the temperature and pressure of steam in power plant became higher for high plant efficiency. So, the property of boiler tube material must be upgaded to fit the plant property. Several boiler tube material was developed to fit such conditions. X20CrMoV12.1 steel is also developed in 1980's and used for superheater and reheater tubes in supercritical boilers. The material has martensite microstructures which is difficult to evaluate the degradation. In this thesis, degrade the X20CrMoV12.1 steel at high temperatures in electric furnace, and evaluate hardness with Vickers hardness tester and strengths with Indentation tester.

• Journal of the Korean Applied Science and Technology
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• v.15 no.3
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• pp.21-26
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• 1998

Polyvinyl alcohol[PVA] is useful for the production of water-soluble packaging, paper, textile sizes. PVA and Chitosan are known as biodegradable polymers. PVA/chitosan blend films were prepared by solution blends method in the weight ratio of chitosan for the purpose of useful biodegradable films. Thermal and mechanical properties of PVA/chitosan blend films such as DSC, impact strength, tensile strength and morphology by SEM were determined. As a result, The ratio of 10.0wt% PVA/chitosan blend films were similar to PVA. Blend films were completely degraded pH 4.0 better than 7.0, 10.0 in the buffer solution. Also, Blend films were rapidly degraded enzyme(${\beta}-glucosidase$) solution better than pH solution by Enzymolysis.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.385-392
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• 2003

Sol-gel preparation technique using a chemical reaction of metal alkoxides has been widely used for the fabrication of various materials including ceramics. However, its mechanism has been studied till now because a number of chemical ways are possible from various alkoxides and additives. In this study, the mechanism of hydrolysis, condensation, and polymerization of alkoxides were investigated from the fabrication of lead-zirconate-titanate (PbZr$\_$x/Ti$\_$l-x/O$_3$; PZT) thin film that is used as various micro-actuator, transducer, and sensor because of its high electro-mechanical coupling factors and thermal stability. Furthermore, the fabrication process and characteristics of self-patternable PZT film using photosensitive stabilizer were studied in order to resolve the problem of physical damage and properties degradation during dry etching for device fabrication. Using an optimum condition to prepare the self-patternable PZT film, more than 5000 ${\AA}$ thick self-patternable PZT film could be fabricated by three times coating. The PZT film showed 28.4 ${\mu}$c/cm$^2$ of remnant polarization (Pr) and 37.0 kV/cm of coercive field (E$\_$c/).

• Composites Research
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• v.17 no.1
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• pp.47-54
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• 2004

Vacuum hot pressing has been used for the development of titanium metal matrix composites using foil-fiber-foil technique. Subsequent micro-mechanical characteristics of the composites are then investigated by means of several experimental methods. The levels of consolidation, together with mechanism based failure processes of the materials have been analyzed by employing a thermo-acoustic emission technique. As shown by the results, fiber strength degradation occurs during the consolidation, and particularly residual stresses results from the thermal expansion mismatch between fiber and matrix materials during cooling process are incorporated in the changes of mechanical properties of the finished products. In industrial applications, both qualitative and quantitative evaluations of the material-mechanical characteristics are particularly important, and therefore must be included in process development. The present paper represents a methodology by which this can be achieved.

• Analytical Science and Technology
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• v.9 no.1
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• pp.1-12
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• 1996

The thermally labile compounds with hydroxyl group generate the [${MNH_4}^+$] ion, [$MH^+$] and [$MH^+-OH$] ion by ion-molecule reaction in LC/TSP/MS. But these ions create the trouble in the estimation of molecular weight of an unknown compound because the margin of [${MNH_4}^+$] ion and [$MH^+$] ion is same to that of [$MH^+$] ion and [$MH^+-OH$] ion. If it is compensated for the results by using of the $CF_3COOD+NH_4OH$ LC eluent, the molecular weight of analyte will be able to be confirmed. And this study was tried to recognize whether the fragment ions of thermally labile compound are generated by electron impact or by thermal degradation in ion source.

• Korean Journal of Materials Research
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• v.18 no.9
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• pp.486-491
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• 2008

The effect of annealing treatment conditions on the interfacial adhesion energy between electrolessplated Ni film and polyimide substrate was evaluated using a $180^{\circ}$ peel test. Measured peel strength values are $26.9{\pm}0.8,\;22.4{\pm}0.8,\;21.9{\pm}1.5,\;23.1{\pm}1.3,\;16.1{\pm}2.0\;and\;14.3{\pm}1.3g/mm$ for annealing treatment times during 0, 1, 3, 5, 10, and 20 hours, respectively, at $200^{\circ}C$ in ambient environment. XPS and AES analysis results on peeled surfaces clearly reveal that the peeling occurs cohesively inside polyimide. This implies a degradation of polyimide structure due to oxygen diffusion through interface between Ni and polyimide, which is also closely related to the decrease in the interfacial adhesion energy due to thermal treatment in ambient conditions.