• KIEE International Transactions on Power Engineering
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• v.5A no.2
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• pp.132-137
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• 2005

In Korea, the protection systems against the instability of the nation's power system are insufficient in contrast with many other countries. In addition, there have just been studies carried out on detecting power system instability, while only a few studies pertaining to protection plans against instability exist. This paper focuses on systems to protect against the instability phenomena in the Korean power system. In this paper, we survey possible contingencies in the Korean power system and suggest outline and specs of the SPS (System Protection Scheme) against faults on the 765 kV line, based on simulations. It is concluded that event-based SPS for transient stability is appropriate for the Korean power system. In the simulations, the most severe contingency on the Korean power system is the fault on 765 kV transmission lines. If one of these lines is tripped by a fault, synchronism may be lost on the power plants near this line because of heavy power flow carried by them. In addition, undervoltage in the Metropolitan region is a serious problem in this case since this region receives about half its total power flow through these lines. In order to prevent a synchronism loss, some power plants have to be rejected according to the situations in the simulations.

• Journal of Powder Materials
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• v.10 no.3
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• pp.176-180
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• 2003

Pure WC powders which does not include a binder phase were consolidated by spark plasma sintering (SPS) process at 1600~185$0^{\circ}C$ for 0~30 min under 50 MPa. Microstructure alid mechanical properties of binderless WC prepared by SPS were investigated. With increasing sintering temperature, sintered density and Vickers hardness of binderless WC increased. The fracture toughness of binderless WC was 7~15 MPa $m^{1/2}$ depending on the sintered density and decreased with increasing the Vickers hardness. It is found that the binderless WC prepared by SPS at 175$0^{\circ}C$ for 10 min under 50 MPa showed nearly full densification with fine-grained structure and revealed excellent mechanical properties of high hardness (~HV 2400) and considerably high fracture toughness (~7 MPa $m^{1/2}$).

• Journal of Powder Materials
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• v.12 no.1
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• pp.70-78
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• 2005

Mechanical alloying using high-energy ball mill and subsequent spark plasma sintering (SPS) process was applied to understand mechanical alloying processing of Al-Fe alloy system. The thermal stability of mechanically alloyed Al-Fe alloy was intended to be enhanced by SPS process. Various analytical techniques including particle size analysis, density measurement, micro-Vickers hardness test, SEM, TEM, and X-ray diffractometry were adopted to find optimum processing conditions for mechanical alloying and subsequent SPS and to estimate thermal stability of the prepared alloy. It was found from the treatment of mechanically alloyed Al-8wt.%Fe powder mixture that needle-shaped $Al_3Fe$ precipitates was formed in the Al-Fe matrix, and the alloy compact showed enhanced densification and reached its full density with little loss of its fine microstructure. After heat treatment at $500^{\circC}$, it was also shown that the thermal stability of Al-8wt.%Fe alloy fabricated in the present study was enhanced, which was due to its fine microstructure developed by fast densification of SPS.

• Journal of Powder Materials
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• v.11 no.2
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• pp.158-164
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• 2004

W-Cu composite has been used for the applications requiring both high strength, good thermal and electrical conductivity. A graded combination of W and Cu will reduce thermal stress concerned with heat conduction, maintaining good thermal conductivity and high mechanical strength. In the present work, an attempt was made to fabricate continuous W-Cu FGM by preparing the graded porous structure of W skeleton using spark plasma sintering (SPS) process followed by infiltrating Cu. The graded porous structure was prepared at 150$0^{\circ}C$ for 60s under pressure of 15MPa by SPS process using a graphite mold with varying crr)ss section in the longitudinal direction. Infiltration of Cu was performed at 115$0^{\circ}C$ for 1 hour under $H_2$. W-Cu composite with graded Cu composition of 14 to 27 wt％ was finally prepared. In this process the gradient of composition could be conveniently controlled by varying the gradient of cross sectional area of graphite mold, temperature and pressure.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1340-1352
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• 2008

In this study, S-wave velocity range is gauged in every field test method at the total 5 locations in the marine deposits in Incheon area. field test method is accomplished the SPT(Standard Penetration Test), CPT(Cone Penetration Test), SPS(Suspension PS Logger), SCPT (Seismic Cone Penetration Test) and so on. The S-wave velocity of SCPT in the downhole test method is measured lower than SPS logger at the N value > 15 range. But at the N value < 15 range, SPS logger and SCPT result is measured same. In this result, although the soil strength of the downhole test method increased, the rate of S-wave velocity is tend to be slowed. This result shows that the downhole test is difficult to apply at the place that the intensity of soil is more extreme and harder soil. And it shows that the existing Imai(1982) type that is mostly used within the country is not suitable for the marine deposits. Thus, the empirical formula that can show the range of S-wave velocity in each N value for domestic soil is needed.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2003.04a
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• pp.126-126
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• 2003

Sucrose-phosphate synthase (SPS) is a key regulatory enzyme in sucrose synthesis. To investigate the role of SPS in carbon partitioning, we produced transgenic rice plants overexpressing a cyanobacterial SPS from Synechocystis sp. PCC 6803. The gene was expressed under the control of the maize Ubil promoter in transgenic plants. Southern and Northern blot analyses confirmed the integration and the expression of the transgene in four transgenic rice lines. All of the four transgenic! lines analyzed showed abnormal vegetative and reproductive developments. Analysis of SPS activities and primary metabolites in the transgenic rice plants will be presented.

• Restorative Dentistry and Endodontics
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• v.26 no.1
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• pp.64-76
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• 2001

Despite the improvements in bond strengths of dentin adhesives and resin-modified glass ionomers, the marginal seal of cervical restorations remains a concern. Microleakage at poorly sealed margins can result in staining, post-operative sensitivity, pulpal irritation, and recurrent caries. The objective of this study was to evaluate the effect of surface penetrating sealant(SPS) on the microleakage of cervical restorations. 45 extracted human teeth were selected, and Class V preparations were prepared on the both buccal and lingual surface of the teeth to the following dimensions : 1.5mm axially, 3mm mesiodistally, and 3mm incisogingivally. After cervical restoration with composite resin, compomer, glass ionomer each restoration was treated as three methods: No Tx., Scotchbond Multipurpose Adhesive$^{\circledR}$, Fortify$^{\circledR}$. The sections were examined with a stereomicroscope to determine the extent of microleakage at enamel and dentin margins. The results of this study were as follows. 1. All groups showed some microleakage. 2. Gingival cavity wall with cementum margin showed significantly higher leakage value than occlusal cavity wall with enamel margin. 3. The group treated with SPS showed significantly lower leakage value than no treated group(p<0.05). But there is no difference between Fortify$^{\circledR}$ and Scotchbond Multipurpose adhesive$^{\circledR}$. The results of this study suggest that SPS are effective in reducing microleakage of class V restorations. But it is certain that some microleakage still occurred despite the application of SPS.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.199-201
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• 2003

전력산업의 경쟁도입 환경으로 인한 송전서비스에 대한 증가된 수요를 보여주고 있다. NERC의 1997-2000 신뢰도 평가 보고서에 의하면 과거 10년동안 대부분의 송전시스템 추가는 지역적 보강을 위해 이루어졌다. 전 계통의 시스템 능력을 강화시키는 큰 송전시스템의 증설은 거의 이루어지지 않았다. SPS는 비정상적 계통 상황을 검출하고 미리 계획된 동작을 수행함으로써 비정상적 상황을 회피하여 정상적 계통을 유지하게 한다. SPS는 계통의 송전능력을 증가시키는데 자주 이용된다. 새로운 송전설비 증설의 대안으로 비용면에서 값싼 SPS가 활용되어지는 것이다. SPS가 정확하게 동작한다면 상정사고에 대한 시스템 능력을 매우 향상된다. 그러나 미리 정의된 상황을 검출하는데 실패하거나 미리 계획된 교정동작을 수행하는데 실패한다면 매우 심각한 결과를 초래한다. IEEE-CIGRE 설문조사에서 보여주듯이 SPS 동작 실패는 비용면에서 매우 높은편으로 응답되었다. 따라서 단순 비용 평가를 통해 SPS를 도입을 결정할 수 없다. 경제적 위험 평가를 통해 SPS가 있을때와 없을때의 위험을 평가하여 의사결정에 반영하여야 한다. 본 논문에서는 SPS의 위험을 평가하는 절차를 보여주고 산업에서 SPS 경험들을 소개하도록 한다.

• Journal of Powder Materials
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• v.12 no.5 s.52
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• pp.351-356
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• 2005

Nanoscale Al powder with thin layer of alumina was produced by Wire Electric Explosion (WEE) process. Spark-Plasma Sintering (SPS) was performed for the produced powder to confirm the effectiveness of SPS like so-called 'surface-cleaning effect' and so on. Crystallite size and alumina content of produced powder varied with the ratio of input energy to sublimation energy of Al wire ($e/e_s$): Increase in ($e/e_s$) resulted in the decrease of crystallite size and the increase of alumina content. Shrinkage curve during SPS process showed that the oxide surface layer could not be destroyed near the melting point of Al. It implied that there was not enough or no spark-plasma effect during SPS for Al/Alumina powder.

• Korea Trade Review
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• v.44 no.6
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• pp.119-134
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• 2019

This study focuses on a recent WTO SPS dispute related to Korea Import Bans and Testing and Certification Requirements for Radionuclides (DS495) in order to learn from the case and take proactive measures to prevent potential import restrictions by Japan on Korean seafood. Korean-Radionuclides (Japan) emphasizes the importance of sufficient scientific evidence, especially scientific information from relevant international organizations, in an effort to take preventive measures towards Japan's restrictions on Korean seafood imports. Japan claims that a novel parasite, Kudoa septempuctata, in Korean flatfish causes food poisoning. As food poisoning is a serious concern, there is a low possibility that Japan's enhanced monitoring measures would be more trade restrictive than required as prescribed in Article 5.6 of the WTO SPS Agreement. In addition, Korea is the biggest exporter of olive flounder to Japan. Hence, the possibility that similar conditions could be established is low in relation to non-discriminatory principles under the WTO SPS Agreement. Accordingly, we should collect relevant scientific evidence, improve domestic sanitary management of fishery products, and seek export diversification so that we prepare for potential import restrictions by Japan and minimize implications.