• Bulletin of the Korean Chemical Society
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• v.21 no.1
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• pp.69-74
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• 2000

Applicability of Thermal field flow fractionation (ThFFF) was investigated for the analysis of masticated natural rubber (NR) adhesives produced bya hot melt mastication process. An optimum ThFFF condition for NR analysis was found by using tetrahydrofuran (THF) as a solvent/carrier and a field-programming. Low flowrate (0.3 mL/min) was used to avoid stopping the flow for the sample relaxation. Measured molecular weight distribution was used to monitor degradation of rubber during the mastication process. Rubber samples collected at three different stages of the mastication process and were analyzed by ThFFF. It was found that in an anaerobic process rubber degradation occurs at the resin-mixing (compounding) zone as well as in the initial break-down zone, while in an aerobic process most of degradation occurs at the initial breakdown zone. It was also found that E-beam radiation on NR causes a slight increase in the NR molecular weight due to the formation of a branched structure.

• The Journal of the Korea Contents Association
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• v.18 no.2
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• pp.290-300
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• 2018

The point of discovering a new technique using colored glass and clay is to improve the existing inconveniences, which is compatible with the mutual physical property of ceramics clay and glass. It is easy to express the decoration of colored glass in vertical ceramics, but the aesthetic expression is limited due to the rust flowing down on horizontal ceramics. So the point is the discovery of a new expressive method that do not melt down in vertical objects. A new technique is to crush finely and dilute the colored glass using clay, and brushing it to the wall. Additionally, inlaid technique and paste brush technique were applied to further enhance aesthetic end. The plastic method is oxidation and reduction, and the coloration was different due to the plasticity method. Particularly, partial cutting of engraved color glass leads to forming gray-line soft gradation. This effect will be good to apply to production of work and industrial ceramics.

• Journal of Korean Institute of Industrial Engineers
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• v.16 no.2
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• pp.135-147
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• 1990

A nuclear power plant can be viewed as a large complex man-machine system where high system reliability is obtained by ensuring that sub-systems are designed to operate at a very high level of performance. The chance of severe accident involving at least partial core-melt is very low but once it happens the consequence is very catastrophic. The prediction of risk in low probability, high-risk incidents must be examined in the contest of general engineering knowledge and operational experience. Engineering knowledge forms part of the prior information that must be quantified and then updated by statistical evidence gathered from operational experience. Recently, Bayesian procedures have been used to estimate rate of accident and to predict future risks. The Bayesian procedure has advantages in that it efficiently incorporates experts opinions and, if properly applied, it adaptively updates the model parameters such as the rate or probability of accidents. But at the same time it has the disadvantages of computational complexity. The predictive distribution for the time to next incident can not always be expected to end up with a nice closed form even with conjugate priors. Thus we often encounter a numerical integration problem with high dimensions to obtain a predictive distribution, which is practically unsolvable for a model that involves many parameters. In order to circumvent this difficulty, we propose a method of approximation that essentially breaks down a problem involving many integrations into several repetitive steps so that each step involves only a small number of integrations.

• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.990-1001
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• 2004

The retention of a molten pool vessel cooled by internal vessel reflooding and/or external vessel reactor cavity flooding has been considered as one of severe accident management strategies. The present numerical study investigates the effect of both internal and external vessel mixed cooling on an internally heated molten pool. The molten pool is confined in a hemispherical vessel with reference to the thermal behavior of the vessel wall. In this study, our numerical model used a scaled-down reactor vessel of a KSNP (Korea Standard Nuclear Power) reactor design of 1000 MWe (a Pressurized Water Reactor with a large and dry containment). Well-known temperature-dependent boiling heat transfer curves are applied to the internal and external vessel cooling boundaries. Radiative heat transfer has been considered in the case of dry internal vessel boundary condition. Computational results show that the external cooling vessel boundary conditions have better effectiveness than internal vessel cooling in the retention of the melt pool vessel failure.

• Journal of the Korean Geotechnical Society
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• v.32 no.12
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• pp.33-43
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• 2016

In order to analyze ground relaxation and cavity formation mechanism due to deteriorated sewer pipe, field test was carried out and a numerical assessments were compared with the field test results. An artificial underground cavity was intended using the ice block overlaying the buried pipe and confirmed that the cavity and relaxation of the surrounding ground were gradually formed as the ice block starts to melt down. Such mechanism was highly suspected to be involved with soil particle interlocking as a soil compaction was a typical process for the buried pipes. In exploring such mechanism numerically, commercially available DEM (Discrete Element Method) code PFC2D was used and the interlocking induced cavern behaviors were successfully simulated and compared with field test results by utilizing the clump logic imbedded in PFC code.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.3
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• pp.73-79
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• 2012

This paper describes the machining characteristics of the sintered carbide and die steel(STD-11) by electric discharge drilling with various tubular electrodes. Electrical discharge machining(EDM) removes material from the workpiece by a series of electrical sparks that cause localized temperatures high enough to melt or vapourize the vicinity of the charge. In the experiment. four types of electrode which have different diameter are used with the application of continuous direct current and axial electrode feed. The controlled factors include the dimension of the electrode. In drilling by EDM, the dielectric flushed down the interior of the rotating tube electrode, in order to order to facilitate the removal of machining debris the hole. The expansion increase with increasing the thickness of material and the diameter of electrode and the expansion of sintered carbide is 1.75 times large then that of die steel. The taper of machined hole decrease with increasing the thickness of material. The crater sixe of die steel is larger then thet of sintered carbide and the surface roughness of sintered carbide is 1.58 tims larger then that of die steel.

• Korean journal of food and cookery science
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• v.20 no.6 s.84
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• pp.658-666
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• 2004

In order to develop and commercialize high quality frozen soy yogurt, the effects of industrial proteases and commercial mixed cultures were examined on the functional properties and the sensory attributes of frozen soy yogurt. For quality improvement, soy protein isolates were primarily hydrolyzed by either Flavourzyme or Neurtrase, industrial Proteases, to reduce the beany flavor and increase the functional properties of the protein. The viable cell count of lactic acid bacteria was higher in the soy protein hydrolysates than whenuntreated. ABT-5 (L. acidophilus, Bifidobacterium lactis, and S. thermophilus) resulted in higher acid tolerance, bile acid tolerance and melt-down percent values than those with YC-X11 (Lactobacillus bulgaricus and Streptococci thermophilus). The overrun of frozen soy yogurt was improved by both Flavourzyme $(193.3\%)$ and Neurtrase $(156.7\%)$ treatments. With regard to thesensory characteristics, Flavourzyme improved the beany flavor, astringency taste, mouth feel and overall quality of frozen soy yogurts fermented with ABT-5. Further studies onproduct formulation will be needed to commercialize the frozen soy yogurt for the market.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.2
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• pp.94-99
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• 1995

Potassium lithium niobate (KLN) crystals, grown by the micro pulling down $({\mu}-PD)$ method, have been considered on the interchange between incongruent melt composition and second harmonic generation (SHG) properties because of the sensitive interaction. Correlation between the composition of crystals and the wavelength of SHG applications from ultra - violet to green region was found. Also, the ${\mu}-PD KLN$ KLN crystals showed a homogeneity of noncritical phase matching and an excellent SHG property which is converted to blue laser light with half wavelength by the red irradiation.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.282-282
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• 2011

Low power consuming operation of phase-change random access memory (PRAM) can be achieved by confining the switching volume of phase change media into nanometer scale. Ge2Sb2Te5 (GST) is one of the best materials for the phase change random access memory (PRAM) because the GST has two stable states, namely, high and low resistance values, which correspond to the amorphous and crystalline phases of GST, respectively. However, achieving the fast operation speed at lower current requires an alternative chalcogenide material to replace the GST and shrinking the dimension of programmable volume. In this paper, we have fabricated nanoscale contact area on Ge2Sb2Te5 thin films with trimming process. The GST material was fabricated by melt quenching method and the GST thin films were deposited with thickness of 100 nm by the electron beam evaporation system. As a result, the reset current can be safely scaled down by reducing the device contact area and we could confirmed the phase-change characteristics by applying voltage pulses.

• Journal of Korea Foundry Society
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• v.36 no.5
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• pp.147-152
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• 2016

Aluminum has been used as an alternative material for copper, due to its good electrical and thermal conductivities. However, small quantities of transition elements such as Ti and V affect the conductivities of aluminum. Therefore, in this study, the influence of B addition to reduce the effects of Ti and V on the conductivities of aluminum was investigated. Both the electrical and thermal conductivities of aluminum were improved with addition of B up to 0.05 wt%, while the conductivities were gradually reduced with an excess amount of B. SEM-EDS and XRD results exhibited that B reacted with Ti and V element to form diborides, such as $TiB_2$ and $VB_2$ phase, and those diborides tended to settle down to the bottom of the crucible because their densities were higher than that of aluminum melt. As a result, B reduced the deleterious effects of Ti and V, and the electrical and thermal conductivities of aluminum were improved.