• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.7
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• pp.76-85
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• 1999

GDI(Gasoline Direct Injection( engine technology is well known as a new technology since it can improve fuel consumption and meet future emission regulations. But the GDI has many difficulties to be solved, such as complexity of injection control mode, unburned hydrocarbon, and restricted power. A 2-D shape combustion chamber was adopted to investigate mixture formation and combustion characteristics of GDI engine. Spray and combustion experiments were performed by changing the injection timing. injection pressure an din-cylinder flow in Rapid Compression and Expansion Machine(RCEM).Through the experiments, the detailed characteristics of fuel spray and combustion was analyzed by visualizing the in-cylinder phenomena according to the change of injection condition, and the optimal fuel injection timing and fuel injection pressure were obtained.

• 기계와재료
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• v.22 no.1
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• pp.54-64
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• 2010

공작기계의 고속화, 다축화, 복잡화에 따른 열변형 오차가 공작기계에서 발생하는 오차의 대부분을 차지하고 있다. 이러한 열변형 오차를 최소화 하기 위해 공작기계의 발열부에 차가운 오일을 공급하여 냉각함으로써, 열변형을 제거하는 장치가 오일쿨러이다. 오일쿨러는 제어 방법에 따라 On-off, 가스 바이패스, 인버터 방식 등이 사용된다. 초정밀 공작기계에는 주로 가스 바이패스 및 인버터 방식이 사용되는데, 인버터 방식의 경우 고가(高價)인 관계로 주로 옵션 형태로 사용된다. 가스 바이패스 방식 오일쿨러는 인버터 방식에 비해 가격이 저렴하고 구조가 간다하며 정밀한 온도제어를 할 수 있지만 부하가 낮은 경우 구조적인 한계로 인해 온도제어 불안정을 발생시킨다. 본 연구에서는 기존 바이패스 방식 오일쿨러에서 나타나는 문제점을 해결하고 보다 정밀한 온도제어를 위해 2개의 전자밸브를 갖는 듀얼 밸브 방식 오일쿨러 시스템을 개발하였다. 개발된 듀얼 밸브 오일쿨러 시스템의 성능검증을 위해 정격운전, DIN 8602 규격, ISO/DIS 230-3 운전모드에서 성능을 비교/분석하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.377-381
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• 2006

This paper identifies GNSS education and training program under Geomatic field of study. GNSS education programs is evaluated $vis-{\grave{a}}-vis$ new-products. Data on Geomatic knowledge generation in the era of the GNSS derivatives over the 1975 - 2003 period are examined. The emerging trends and patterns; in particular for selected Asian nations will be dissected in detail. The knowledge indicator used in this study is the patent ownership against the background of emergence of new core technologies and innovations in the field of GNSS. Looking at the dismal performance of Geomatic professionals in terms of innovative activities in most part of Asian and Malaysia in particular, is it there is something that holding up these professionals from doing so? With our universities and numerous polytechnics offering Geomatic program, more is expected from them. Is it a problem of lack or inadequacy of skills? Or is it these professionals are too busy and being narrowly focused on doing something else?

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.558-559
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• 2010

국제표준화 기구 및 표준화 단체는 각국에 1개씩 존재하고 있다고 보면 된다. 그중 표준화활동을 어느 정도 체계적으로 관리, 활동하는냐에 따라 수많은 표준(안)이 개발되고, 국제표준화기구의 승인을 요청하느냐에 따라 ICT 기업 매출과 직접적인 영향을 받을 것이다. 국제적으로는 ITU, ISO, ISO/IEC JTC1, ATIS, BSI, AFNOR, DIN, TTA 등 무수히 많은 표준화기구 및 단체 등이 활동하고 있다. 본고에서는 정보통신 분야의 최고 기구인 ITU-PP를 중심으로 논의하고자 하며, 이러한 국제표준화기구와 ICT 기업과의 생존관계를 위한 국제회의 유치가 ICT 분야 및 산업 발전에 미치는 영향을 분석 제시하고자 한다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.1
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• pp.119-129
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• 2002

Reinforced concrete haunched beams have been used for enhancement of shear resistance of beams to avoid the stress concentration. But American and British codes do not give my formula for the design of haunched beams. The purpose of this research is to experimentally investigate the shear failure of reinforced concrete punched beams for various haunch inclinations and shear span-to-depth ratios. The experimental results showed that even though shear behavior of haunched beam were similar to that of resembled rectangular beams, shear span-to-depth ratios and inclinations of haunch had effects on shear cracking strength.

• Proceedings of the KSPS conference
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• 2005.11a
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• pp.137-140
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• 2005

In this study we investigated the cognitive neuropsychological characteristics and the underlying mechanism in a letter-by-letter reading dyslexic patient after cerebral infarct of left posterior cerebral artery using fMRl, The results of cognitive neuropsychological assesment are visual perception was appropriate, and semantic categorization, picture naming and picture-word matching tasks were above83% correct, respectively. However, she was very poor in lexical decision task. The selective reading impairment is thought to result from the disruption of the left occipitotemporal region included fusiform gyrus. In fMRl results, the activation level increase din the right occipitotemporal region included fusiform gyrus compared with normal group in compensation for left impairment and more increased in pseudo word reading task than word reading on account of familiarity.

• Communications of the Korean Mathematical Society
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• v.24 no.4
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• pp.605-615
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• 2009

In this paper, we develop a reliable algorithm which is called the variation of parameters method for solving sixth-order boundary value problems. The proposed technique is quite efficient and is practically well suited for use in these problems. The suggested iterative scheme finds the solution without any perturbation, discritization, linearization or restrictive assumptions. Moreover, the method is free from the identification of Lagrange multipliers. The fact that the proposed technique solves nonlinear problems without using the Adomian's polynomials can be considered as a clear advantage of this technique over the decomposition method. Several examples are given to verify the reliability and efficiency of the proposed method. Comparisons are made to reconfirm the efficiency and accuracy of the suggested technique.

• Korean Journal of Remote Sensing
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• v.21 no.3
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• pp.221-228
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• 2005

Baekdusan is a Cenozoic stratovolcano in which a series of micro-seismic events and gaseous emissions have been reported in 1990s. Two-pass DInSAR technique was applied to determine displacement in the volcano by using 10 ERS SAR and 41 JERS-1 SAR datasets. Most interferometric phases out of 58 JERS-1 differential interferograms showed concentric fringe patterns that correlated with elevation. From an analysis of fringe-duration relation, the fringe patterns were found to be severely distorted specifically by stratified troposphere. To estimate the tropospheric delay, we used the data in the Sobaeksan located about 20 km away from the summit of Baekdusan. The maximum and mean magnitudes of the phase delay in the Baekdusan were respectively 13.8 cm and 3.8 cm over 1200 m in altitude. After removing tropospheric effects, a mean inflation rate was estimated to be about 3 mm per year from 1992 to 1998. Although the inflation rate of the volcano is inconclusive without ground truth data, the results indicate that there exists slow upward deformation in the Baekdusan volcano.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2746-2752
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• 2021

The environmental effects of China's nuclear energy consumption in a dynamic framework of the pollution haven hypothesis are examined. This study uses a dynamic autoregressive distributed lag simulation approach. Empirical evidence confirms that the pollution haven hypothesis does not exist for China; i.e., foreign direct investment plays a promising role in influencing environmental outcomes. Furthermore, empirical results concluded positive contribution of nuclear energy in pollution mitigation. From the results it is expected that encouraging foreign investment to increase generation of nuclear energy would benefit environmental quality by reducing CO₂ emissions.

• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.54-59
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• 2019

The main objective of nuclear reactor safety is to maintain the nuclear fuel in a thermally safe condition with enough safety margins during normal operation and anticipated operational occurrences. In this research, core flow bypass is studied under the conditions of the unavailability of safety systems. As core bypass occurs, the core flow rate is assumed to decrease exponentially with a time constant of 25 s to new steady state values of 20, 40, 60, and 80% of the nominal core flow rate. The thermal hydraulic code PARET is used through these calculations. Reactor thermal hydraulic stability is reported for all cases of core flow bypass.