• Transactions on Electrical and Electronic Materials
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• 제14권6호
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• pp.308-311
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• 2013

The effect of an electric field on the ac electrical treeing in various epoxy/reactive diluent systems was studied in a needle-plate electrode geometry. Diglycidyl ether of bisphenol A (DGEBA) type epoxy was used as a base resin, and 1,4-butanediol diglycidyl ether (BDGE) or polyglycol (PG) as a reactive diluent was introduced to the DGEBA system, in order to decrease the viscosity of the DGEBA epoxy system. BDGE was acted as a chain extender, and PG acted as a flexibilizer, after the curing reaction. To measure the treeing initiation time and the propagation rate, three constant alternating currents (ac) of 10, 13 and 15 kV/4.2 mm (60 Hz) were applied to the specimen, in a needle-plate electrode arrangement, at $30^{\circ}C$ of insulating oil bath. When 10 kV/4.2 mm (60 Hz) was applied, the treeing initiation time and the propagation rate in the DGEBA system were 356 min and $1.10{\times}10^{-3}$ mm/min, respectively, those in the DGEBA/BDGE system were 150 min and $1.14{\times}10^{-3}$ mm/min, respectively. Those in the DGEBA/PG system were 469 min and $1.05{\times}10^{-3}$ mm/min, respectively. As 15 kV/4.2 mm (60 Hz) was applied, the propagation rate in the DGEBA system was $5.41{\times}10^{-3}$ mm/min, and that in the DGEBA/PG system was $1.42{\times}10^{-3}$ mm/min. These values meant that PG could be used as a reactive diluent in the DGEBA system, without the deterioration of the insulation breakdown property.

• 대한토목학회논문집
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• 제37권3호
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• pp.603-610
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• 2017

최근 집중호우, 잦은 강설, 급격한 기온차이 등 환경변화의 가속화에 따라 균열, 단차, 포트홀 등 다양한 형태의 도로 파손이 급증하고 있다. 이중 포트홀 관련 사고는 파손 특징상 대형사고를 유발하며 08년 기준 5년간 약 5배 이상 증가하였다. 매년 포트홀로 인한 인명피해, 차량파손 등 직 간접적인 피해가 증가함에 따라 보다 신속하고 효율적인 관리 대책이 필요하다. 따라서 본 연구에서는 포트홀 규모, 면적과의 상관관계를 통해 체적 보정계수와 보수재료 물량산출 알고리즘을 제시하였다. 제시된 물량산출 알고리즘의 검증을 위해 수도권 지역 15개소의 포트홀을 측정한 결과 통상적으로 개소당 약 5~7 kg까지 발생하던 재료 잔량이 1~2 kg까지 감소하는 것으로 나타났다. 작업자의 주관적인 판단에 의존하여 시공하고 있는 실정에서 포트홀 체적 감지 자동화 통합시스템은 재료/자원 절감뿐 아니라 적정한 보수물량 산정을 통해 다짐상태 등 포장 품질향상에 기여할 수 있을 것이다.

• 환경영향평가
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• 제21권5호
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• pp.617-629
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• 2012

This study aims to find out critical areas of a soil loss and propose feasible measures to reduce the water quality deterioration by a soil lose. As a study area, the So-ok stream catchment locating at the upper area of Daecheong Reservoir is selected and intensive field observation was carried out. RUSLE model is applied to assess the impact of the pollution migration by a soil ross from the critical areas during storms on the water quality of Chusori embayment. As results, total amount of the soil ross assessed against to the critical area on which major type of land use is a orchard for fruits is 54.3 ton/ha/yr and that of an abandoned mine site is about 200 ton/ha/year. In particular as effective measures, a plantation of an appropriate species of fruit trees and an application of ecologic restoration schemes are proposed against to the orchard and the abandoned mine site, respectively.

• 한국항공우주학회지
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• 제32권4호
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• pp.43-52
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• 2004

본 논문에서는 아리랑 1호의 실제 비행데이터를 이용하여 지상에서 정밀궤도결정을 수행한 후 얻을 수 있는 성능에 대해 분석하였다. 분석에 사용된 궤도결정 알고리즘은 바예 시안 최소자승법을 작용한 배치필터이며, 궤도결정 정밀도 평가를 위해 중첩법 (Overlap Method) 을 이용하였다. 또한, 미국 NORAD 의 TLE (Two-Line Element) 및 지상추적 데이터를 이용한 궤도결정 결과들과의 비교, 분석도 수행하였다. 궤도결정 정밀도에 영향을 미칠 수 있는 요인, 즉 관측데이터 종류 및 탑재시계 편류 (On-Board Time Drift)에 의한 정밀도 변화에 대해서도 분석되어졌다. 본 연구결과, 중첩법 평가에 의한 30시간 GPS 항행해 위치 성분만을 이용한 궤도결정 정밀도는 5m RMS 수준이었으며, GPS 항행해 중 속도 성분은 궤도결정 시 사용하지 않는 것이 바람직하며, 타 관측데이터를 이용한 궤도결정 결과와의 비교를 통해 심각한 시각 바이어스에 의한 뚜렷한 정밀도 저하는 없음을 알 수 있었다.

• Journal of Korean Neurosurgical Society
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• 제58권5호
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• pp.448-453
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• 2015

Objective : Recently, the survival of patients with hepatocellular carcinoma (HCC) has been prolonged with improvements in various diagnostic tools and medical treatment modalities. Consequently, spine metastases from HCC are being diagnosed more frequently. The accurate prediction of prognosis plays a critical role in determining a patient's treatment plan, including surgery for patients with spinal metastases of HCC. We investigated the clinical features, surgical outcomes, and prognostic factors of HCC presenting with spine metastases, in patients who underwent surgery. Methods : A retrospective review was conducted on 33 HCC patients who underwent 36 operations (three patients underwent surgical treatment twice) from February 2006 to December 2013. The median age of the patients was 56 years old (range, 28 to 71; male : female=30 : 3). Results : Overall survival was not correlated with age, sex, level of metastases, preoperative Child-Pugh classification, preoperative ambulatory function, preoperative radiotherapy, type of operation, administration of Sorafenib, or the Tokuhashi scoring system. Only the Tomita scoring system was shown to be an independent prognostic factor for overall survival. Comparing the Child-Pugh classification and ambulatory ability, there were no statistically differences between patients pre- and post-operatively. Conclusion : The Tomita scoring system represents a practicable and highly predictive prognostic tool. Even though surgical intervention may not restore ambulatory function, it should be considered to prevent deterioration of the patient's overall condition. Additionally, aggressive management may be needed if there is any ambulatory ability remaining.

• 한국결정성장학회지
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• 제7권2호
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• pp.284-291
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• 1997

V-Ti(V-rich) 수소저장합금을 기초(base)로 하여 2가지 타입(type)의 전극을 제조하였다. 첫째로 V-Ti 합금에 Ni 분말을 혼합하여 성형한 후 급속가열방법으로 소결하여 전극을 제조하였다. 둘째로 Ni을 V-Ti 합금과 합금화한 V-Ti-Ni 3원계 수소저장합금에 Ni, PTFE 분말을 혼합하여 냉간압축으로 성형하여 전극을 제조하였다. 이와같이 제조된 전극으로 싸이클에따른 충/방전 실험을 한 결과, 모든 전극에 있어 10싸이클 이내에 퇴화(degradation)가 일어났다. 충방전 실험후 전해질내의 조성분석결과 Ti에 비해 V이 많이 전해질 내에 용해되었으며 합금원소의 용해에 의한 표면 형상의 변화가 관찰되었고, 전극표면에 매우 passive 한 Ti-oxide($TiO_2$)가 형성되었다. Ti-oxide($TiO_2$)는 전기전도도가 매우 낮고, 수소에대한 확산계수(diffusivity)도 낮기때문에 전극표면에 형성된 $TiO_2$층은 충/방전 싸이클동안 방전용량을 크게 감소시키는 것으로 나타났다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 1998년도 공동 심포지엄 및 추계학술발표회
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• pp.119-122
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• 1998

Chemical analysis, measurement of pumping rates of 60 production wells and depth to water tables of 57 monitoring wells were carried to protect depletion of water resources and deterioration of water quality for the commercial portable ground-water. Borehole depth of production well averages 149m(31 boreholes), casing depth is 28m(29 boreholes), production rate is 70 $m^3$/day and depth to water table of monitoring well is 23.26m, respectively. The geology of 60 wells can be divided into Daebo granite(20), Okchun metarmorphic complex(18), Precambrian granitic gneiss(15), Bulguksa granite(4), Cheju volcanics(2), Cretaceous sedimentary rock(1). Average electrical conductivity and pH are 152$\mu$S/cm, and 7.35, respectively. The contents of major cation and anion predominantly $Ca^{2+}$>N $a^{+}$>M $g^{2+}$> $K^{+}$ and HC $O_{3}$$^{－}$ >S $O_{4}$$^{2-}$>Cl￣>F￣. Water type is predominantly $Ca^{2+}$-HC $O_{3}$$^{－}$(81.7%). It's possible that water chemistry of some wells were affected not only by the geology of boreholes penetrated but by inflows of surface water or shallow ground-water. Therefore, it is strongly necessary to steadily monitor the water quality and hydrogeologic conditins of production wells.ells.ls.ells.

• 한국환경과학회지
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• 제21권2호
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• pp.241-251
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• 2012

The emissions of several air pollutants ($NO_x$, CO, VOCs, etc.) for the replacement of all diesel buses by Compressed Natural Gas (CNG) buses were estimated in the Busan Metropolitan Area (BMA). These emissions were calculated from emission factors considering the different driving speeds with bus routes, distance traveled, and deterioration factors. For the purpose of this study, three categories of fuel type were selected: (1) the combination of diesel (65%) and CNG buses (35%) (DSL+CNG case), (2) all diesel buses (DSL case), and (3) all CNG buses (CNG case). The emissions of $NO_x$ and CO in the CNG case were estimated to be significant decreases (by about 50% and 98%, respectively) relative to the DSL case. Conversely, the emission of VOCs (980.7 ton/year) in the CNG case were a factor of 3.3 higher than that (299.8 ton/year) in the DSL case. In addition, the diurnal variations of emissions between two city buses (e.g. diesel and CNG) and all other vehicles were distinctly different because the two city buses operate at a regular time interval. Our overall results suggest the possibility that the pollutant emissions from the CNG buses can exert less influence on air quality in the target area than those from the diesel buses.

• 통상정보연구
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• 제11권2호
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• pp.173-201
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• 2009

As a result of overemphasizing the goods sector in trade structure, Korea does not meet properly the global trend which has the key role of 'trade in services' as the service economy have been expanded. Hereafter, it is easily forecasted that trade in services will be one of the main factors for Korea's competitiveness and engine of growth. Nevertheless, because Korea does not equip the concreteness of governance for trade in services, it is possible that the efficiency deterioration of trade volume, confusion of Korea's trade policy, conflict among trading countries, and discordance between the interested parties may be occurred. This paper analyzes the governance system of Korea for trade in services in order to enhance the competitiveness reflecting the importance of trade in services and to draw some strategies for remodeling the service governance system. It is expected to raise the efficiency of Korea's trade policy by constructing the systematic governance for trade in services, and to remove lots of latent risks during global transactions by improving the imbalance between manufacturing and service part for the development of trade in services in Korea. Analysis revealed itself the result that Korea is weak enough to can not identify the governance system about trade in services. Except 'Extent of Services' article of the Foreign Trade Act, Korea has not prepared the governance system for trade in services so that governance system have been scattered overly or decentralized. Problems about trade in services are not limited to enterprise's side, but extended to all the players including government agency whole, academic world and research institute. Therefore, the governance of trade in services should be strengthened and systematized by making the model law for trade in services(provisional name : Master Law for Trade in Services or Promotion Law for Trade in Services) by formatting type of fundamental law or separate legislation. If the bill legislation does not meet the conditions, the Foreign Trade Act should be totally reformed to Omnibus Trade Act concept including trade in services.

• 콘크리트학회지
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• 제9권4호
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• pp.197-205
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• 1997

폴리머 콘크리트를 오버레이 콘크리트로서 기존 시멘트 콘크리트 위에 타설할 경우 폴리머 콘크리트의 경화수축으로 말미암아 전단응력, 수직응력 및 축응력이 발생되며 이러한 응력은 폴리머 콘크리트와 기존 시멘트 콘크리트 사이의 접착성능에 영향을 미쳐 결국 역학적 성질 및 내구성이 저하될 수 있다. 오버레이 콘크리트의 수축응력은 본 실험에서 실시한 구속된 오버레이 콘크리트의 구속해제에 의한 수축변형량과 탄성계수로서 구할 수 있다. 본 연구에서는 폴리머 종류, 오버레이 콘크리트 두께, 양생시간과 온도에 따른 폴리머 콘크리트 및 폴리머 시멘트 콘크리트의 수축에 의한 축응력을 측정하여 폴리머 콘크리트를 각종 교량등의 오버레이 콘크리트로 사용하멩 있어서 기초적 자료를 제공하고자 하였다. 연구결과, 폴리머 콘크리트의 경화수축응력은 폴리머의 종류, 양생온도, 재령 및 두께에 의해 영향을 크게 받는 것으로 나타났다.