• Journal of Energy Engineering
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• v.4 no.1
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• pp.85-94
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• 1995

본 연구에서는 최근 차량용 대체연료로서 주목받고 있는 천연가스의 연소특성을 규명하기 위해 밀폐된 정적연소실을 이용, 당량비, 초기압력 및 점화위치 변화에 따른 연소실험을 행하였으며, 그 결과 다음과 같은 결론을 얻었다. 메탄-공기 예혼합기의 화염전파과정은 이론혼합기 부근에서 구면형으로 진행되는데 반해, 과농 또는 과박 혼합기 그리고 점화위치가 연소실 벽면에 가까울수록 타원형으로 진행되며, 초기압력이 증가함에 따라 화염전파는 느려진다. 화염전파속도와 연소 속도는 초기압력이 낮고 점화위치가 연소실 중심에 가까울수록 빠르며, 당량비 1.0∼1.1 사이에서 최대치를 보인다.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1103-1107
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• 2009

최근 기상이변에 따른 국지성 호우 등으로 인하여 지역별로 홍수량 차이가 많이 나고 있는 상황으로 유역내 중요시설물 및 인명의 보호를 위해서는 유역의 특성을 정확하게 반영한 홍수분석이 필수적인 실정이다. 유역 주요지점의 정확한 홍수량을 산정하기 위해서는 지역특성이 반영된 호우를 선정하고, 유출모의를 위한 유역특성이 잘 구현되어야 한다. 이를 위해서는 홍수량산정에 영향을 주는 매개변수의 정확한 산정이 필요하며 본 연구에서는 미공병단(US Army Corps)에서 개발하여 배포한 차세대 프로그램인 HEC-HMS(v3.3)를 이용하여 집중시간, 저류상수, Curved Number, 감수상수, 초기손실, 초기기저유량, Threshold 등 7가지 매개변수에 대한 최적화를 수행하였다. 종래에는 첨두홍수량을 중시하여 집중시간과 저류상수는 최적화하고 나머지 변수들은 실측치 및 계산값을 적용하였으나, 금번 연구에서는 첨두홍수량 및 총유출량 모두 관측값에 최대한 일치하도록 7가지 매개변수를 최적화하는 방안 및 최적화시 초기값 선정이 매개변수 최적화에 미치는 영향을 연구하였다. 매개변수 최적화 순서는 먼저 전체적인 평균유출량 또는 평균유출고가 실측치와 모의치 간에 일치하도록 CN, RC를 보정하고 다음 단계로 첨두발생시간이 일치하도록 Tc, K를 보정하고, 마지막으로 홍수 수문곡선의 형태를 결정하는 나머지 매개변수를 조정하여 전체적인 수문곡선의 형태와 첨두홍수량이 일치하도록 수행하였으며, Tc, K, CN 등의 중요 매개변수는 신뢰구간(계산치의 0.8${\sim}$1.2)을 설정하여 목적함수의 수렴을 유도하였다. 위를 이용하여 수렴된 매개변수들로 강우-유출 모의를 분석한 결과를 기존 홍수사상과 비교한 결과 상당히 근접한 결과를 도출할 수 있어, 매개변수는 7가지 모두에 대한 최적화를 가능한 것으로 연구되었으나 목적함수들의 수렴되는 과정에 대해서는 좀 더 심도있는 고찰이 필요할 것으로 판단된다.

• Korean Journal of Food Science and Technology
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• v.34 no.1
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• pp.30-36
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• 2002

To use overproduction muskmelon effectively, muskmelon vinegar was prepared by two stage fermentations of alcohol and acetic acid. In the alcohol fermentation using muskmelon, alcohol content showed maximum value (7.47%) in $17.83^{\circ}Brix$ of initial sugar concentration and 82.65 h of fermentation time. Acetic acid content in alcohol fermentation revealed minimum value (0.46%) in $12.17^{\circ}Brix$ of initial sugar concentration and 60.56 h of fermentation time. The fermentation conditions for minimum residual sugar were $10.02^{\circ}Brix$ of initial sugar concentration and 105.61 h of fermentation time. The optimum conditions predicted for each corresponding physical properties of acetic acid fermentation were 200 rpm (agitation rate), 250 h (fermentation time) in acetic content and 200 rpm, 150 h in residual alcohol content.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4
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• pp.157-165
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• 1992

IMS, a precision coordinate measuring system using theodolites, is being used to survey and align precision mechanical structures. Compared to conventional mechanical devices for precision measurement, such as CMM (Coordinate Measuring Machine), the target objects of IMS have little limitations in their sizes and shapes, and can be measured in place. Also since IMS displays the coordinate values in real-time, it is possible to perform measurement and alignment of the objects simultaneously. In this paper, the elements and functions of IMS are introduced and a mathematical model of the new software, which utilizes an altered version of the 'Bundle' adjustment algorithm of analytical photogrammetry for the specific use of IMS, is demonstrated. Differences of the mathematical model of IMS from that of analytical photogrammetry are discussed by following the steps of the 'Measurement' option in the 'Main Menu' of the software. A new IMS calibration method is proposed to calculate better first approximations for the 4 unknown theodolite parameters and the coordinates of target objects. The software provides the 'Bundle' procedure for the first approximations of the unknowns before the real-time measurement. It also provides an opportunity of 'bundling' to re-adjust the collected positional data at the end of the measurement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.485-496
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• 2006

Practical stability design method of main members of cable-stayed bridges is proposed and discussed through a design example. For this purpose, initial tensions of stay cables and axial forces of main members are firstly determined using initial shaping analysis of bridges under dead loads. And then the effective buckling length using system elastic/inelastic buckling analysis and bending moments considering $P-{\delta}-{\Delta}$ effect by second-order elastic analysis are calculated for main girder and pylon members subjected to both axial forces and moments, respectively. Particularly, three load combinations of dead and live loads, in which maximum load effects due to live loads are obtained, are taken into account and effects of live loads on effective buckling lengths are investigated.

• Management & Information Systems Review
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• v.35 no.1
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• pp.143-154
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• 2016

In this research, The new CEO is expected to increase a reporting income through earning management for individual benefit such as a good reputation, high compensation and CEO' s contract extension in the early years of service, of which may influence value relevance of the accounting numbers. We investigate the change of value relevance from 2004 to 2014, compare firms with a change of CEO and firms with non-change of CEO and analysis the value relevance in the early years and in the late years of the new CEO. The results of research are as follows. First, value relevance of EPS of firms with change of CEO are decreased, whereas value relevance of BPS are increased in the regression of all sample. Second, value relevance of EPS are decreased, whereas value relevance of BPS are increased in the early years of the new CEO. This research makes a contribution to provide the first proof about influence of value relevance by the earning management in the early years of the new CEO in Korea.

• 대한치과보철학회:학술대회논문집
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• 1995.12a
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• pp.35-35
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• 1995

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 1998.06a
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• pp.285-286
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• 1998

• Journal of the korean academy of Pediatric Dentistry
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• v.41 no.1
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• pp.64-71
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• 2014

Mesiodens is defined as a supernumerary tooth in the premaxillary region. It can cause several clinical manifestations in normal eruption and position of adjacent teeth, such as displacement and impaction. Although the mesiodens accompanied by a clinical complication is indicated for removal, the optimal time of mesiodens removal is still controversial. Some authors suggest immediate intervention defining the removal of mesiodens as soon as possible after the first detection. On the other hand, others recommend delayed intervention which denotes the removal of mesiodens after complete root development of adjacent teeth. This case report is presented with three cases of spontaneous correction and proper alignment of rotated maxillary central incisors by extraction of mesiodens when the crowns of rotated incisors were completely formed while the roots of them were at an early developmental stage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1351-1360
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• 1999

In frequency selective channels, conventional PN code acquisition schemes are not ideal candidates. This is because they are primarily designed for the AWGN channel. In this paper, a direct-sequence spread-spectrum(DSSS) PN code acquisition system based on digital matched filtering (DMF) with automatic threshold control(ATC) algorithm is presented and analyzed with regards to probability of detection and probability of false alarm. These two important probabilities, the probability of detection ($P_D$) and the probability of false alarm ($P_{FA}$) are derived and analyzed in considering Doppler shift, sampling rate, mean acquisition time, and PN chip rate in frequency selective Rayleigh fading channel when using serial-search method as detection technique. From computer simulation results of a DMF acquisition system model, it is shown that the performance of the acquisition system using ATC algorithm is better than that of constant threshold system.