• Journal of the Korean Society of Safety
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• v.18 no.3
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• pp.101-108
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• 2003

Polymeric positive temperature coefficient(PTC) composites have been prepared by incorporating carbon black(CB) into high density polyethylene(HDPE), polyphenylene sulfide(PPS) and polybutylene terephthalate(PBT) matrices. A PTC effect was observed in the composite, caused by the large thermal expansion due to He consecutive melting of HDPE, PPS and PBT crystallites. This theory is based upon the premise that the PTC phenomenon is due to a critical separation distance between carbon particles in the polymer matrix at the higher temperature. The influence of PTC characteristics of the PPS/CB composite can be explained by DSC result. HDPE, one of prepared composition, exhibit the higher performance PTC behavior that decreaseing of negative temperature coefficient(NTC) effect and improved reproducibility by chemically crosslinking. Also, PBT/CB and PPS/CB composites exhibit the higher PTC peack temperature than HDPE/CB PTC composite, individually $200^{\circ}C$ and $230^{\circ}C$. These PTC composite put to good use in a number of safety application, such as self$.$controlled heater, over-current protectors, auto resettable switch, high temperature proctection sensor, etc.

• Journal of the Korean Society of Safety
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• v.23 no.6
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• pp.1-6
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• 2008

Machine operator and quality are affected by chip during cutting process to product machine parts. This paper presents a study of the influence of cutting conditions on the surface roughness obtained by turning using Taguchi method for safety of turning operator. In the machining of titanium alloy, high cutting temperature and strong chemical affinity between the tool and the work material are generated because of its low thermal conductivity and chemical reactivity. Therefore titanium alloys are known as difficult-to materials. An orthogonal array, the signal-to-noise ratio, the analysis of variance are employed to investigate the cutting characteristics of implant material bars using tungsten carbide cutting tools of throwaway type. Also Experimental results by orthogonal array are compared with optimal condition to evaluate advanced reliability. Required simulations and experiments are performed, and the results are investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.144-145
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• 2007

Phase change random access memory is one of the most promising candidates for next generation non-volatile memories. However, the high reset current is one major obstacle to develop a high density PRAM. One way of the reset current reduction is to develop the new phase change material. In this paper, to reduce the reset current for phase transition, we have investigated the effect of phase change material parameters using finite element analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.518-519
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• 2007

In this paper, the temperature distribution within ACSR conductor was precisely measured and examined, conducted as part of a serious of studies on large currents in transmission lines. According to measurements of the conductor temperature near a joint(sleeve and clamp), the electrical resistance of joint is lower than that of the same length conductor. The detailed results were presented in the text.

• Nuclear Engineering and Technology
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• v.12 no.3
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• pp.180-193
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• 1980

Subroutines to enable fast and accurate generation of water properties-enthalpy, specific volume, viscosity, thermal conductivity and saturation entropy-which are usually basic requirements for nuclear calculation of LWR, have been developed. The sources of data were quoted from “ASME Steam Tables (1967)” and their Revision (1975). It is ensured that the obtained values from this routine fall within 0.2% difference compared with the reference data, in the ranges of temperature and pressure for LWR nuclear calculation.

• Nuclear Engineering and Technology
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• v.45 no.3
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• pp.311-322
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• 2013

High-Cr martensitic steel HT-9 is one of the candidate materials for advanced nuclear energy systems. Thanks to its excellent thermal conductivity and irradiation resistance, ferritic/martensitic steels such as HT-9 are considered for in-core applications of advanced nuclear reactors. The harsh neutron irradiation environments at the reactor core region pose a unique challenge for structural and cladding materials. Microstructural and microchemical changes resulting from displacement damage are anticipated for structural materials after prolonged neutron exposure. Consequently, various irradiation effects on the service performance of in-core materials need to be understood. In this work, the fundamentals of radiation damage and irradiation effects of the HT-9 martensitic steel are reviewed. The objective of this paper is to provide a background introduction of displacement damage, microstructural evolution, and subsequent effects on mechanical properties of the HT-9 martensitic steel under neutron irradiations. Mechanical test results of the irradiated HT-9 steel obtained from previous fast reactor and fusion programs are summarized along with the information of irradiated microstructure. This review can serve as a starting point for additional investigations on the in-core applications of ferritic/martensitic steels in advanced nuclear reactors.

• Vacuum Magazine
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• v.3 no.3
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• pp.19-23
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• 2016

BNNTs (Boron nitride nanotubes) is an analogue of CNTs (Carbon Nanotubes) in terms of lattice structure. In BNNTs, a boron atom forms sp2 hybridized bonding with three nitrogen atoms, and so does a nitrogen with three boron atoms in the honeycomb structure. Its innovative properties, such as high thermal conductivity, neutron shielding capability, superb oxidation resistance at $900^{\circ}C$, excellent chemical resistance, and superior mechanical properties are advantageous for a wide range of applications, especially for electric device packages, neutron shielding, protective coating materials, and functional composites. In this paper, boron nitride nanotube synthesis, properties and application are reviewed.

• Transactions of Materials Processing
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• v.21 no.1
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• pp.5-12
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• 2012

The weight of the bipolar plate is one of the crucial aspects of improving power density in PEMFC stacks. Aluminum alloys have good mechanical properties such as density, electrical resistivity, and thermal conductivity. Furthermore, using aluminum in a bipolar plate instead of graphite reduces the bipolar plate cost and makes machining easier. Therefore in this study, an aluminum alloy was selected as the appropriate material for a bipolar plate. Results from feasibility experiments with the aim of developing fuel cells consisting of Al bipolar plates with multiple channels are presented. Dynamic loading was applied and the formability of micro channels was estimated as a function of punch pressure and die radius. Sheets of Al5052 with a thickness of 0.3mm were used. For a die radius of 0.1mm the formability was optimized with a sine wave dynamic load of 90kN at maximum pressure and 5 cycles of a sine wave punch travel. The experimental results demonstrate the feasibility of the proposed manufacturing technique for producing bipolar plates.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.142-145
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• 2008

Process simulation requires accurate and reliable data for a wide variety of material properties, ranging from thermal conductivity to flow stress curves. Traditionally such data are gathered from experimental sources, which has significant disadvantages in that not all of the required data is readily available, it may be from various sources that are themselves inconsistent, measurement of high temperature properties is expensive, and furthermore the properties can be sensitive to microstructure as well as to alloy composition. This article describes the development of a new multi-platform software program called JMatPro, which is based on CALPHAD methodology, for calculating the properties and behavior of multi-component alloys. A feature of the JMatPro is that the calculations are based on sound physical principles rather than purely statistical methods. Thus, many of the shortcomings of methods such as regression analysis can be overcome.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.436-442
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• 2005

Rapid development of electronic technology requires small size, high density packaging and high power of electronic devices. In this paper, characteristics on oscillating heat pipe according to operating conditions (environment temperature, charging ratio of working fluid, inclination) based on experimental study was investigated From the experimental results $25^{\circ}C$(environment temperature) R-141b (working fluid) $40\%$ (charging ratio) was best performace at others of inclination angle and the top heating mode of OCHP performed $80\%$ efficiency of the bottom heating mode.