• 한국수자원학회논문집
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• 제36권1호
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• pp.33-44
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• 2003

유황곡선은 하천유량의 변동성을 함축적으로 나타내고 있다. 본 연구는 인위적인 유량조절이 없는 자연하천의 무차원 유황곡선을 조사하여 보았다. 유황분석은 IHP대표유역과 대하천 주요 수위관측 지점의 수문자료를 토대로 수행하였다. 유황은 유역면적에 의존하나 유황계수는 판수계수를 제외하면 유역면적의 변화에 민감하지 않았으며 특히 풍수계수는 일정한 값을 나타내었다. 본 연구에서 평수량에 대한 갈수량 및 저수량의 비로 정의한 유황변동계수는 유역면적이 증가하면 작아지고 하천 경사의 증가에 따라 커진다. 저수유황변동에 비하여 갈수유황 변동이 유역면적의 변화에 영향을 받는 것으로 보여진다.

• 대한기계학회논문집B
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• 제24권5호
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• pp.709-717
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• 2000

Cyclic variability has long been recognized as limiting the range of operating conditions of spark ignition engines, in particular, under lean and highly diluted operation conditions. The cyclic combustion variations can be characterized by the pressure parameters, combustion parameters, and flame front parameters. The coefficient of variation in indicated mean effective pressure ($COV_{IMEP}$) defines the cyclic variability in indicated work per cycle, and it has been found that vehicle driveability problems usually result when $COV_{IMEP}$ exceeds about 10%. For analysis of the cyclic variability in SI engines at idling, the results show that cyclic variability by the $COV_{IMEP}$ or the coefficient of variation in maximum pressure can be explained and may be consequently reduced by the help of the optimum spark timings.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1435-1440
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• 2009

Geotechnical variability is a complex feature that results from many independent sources of uncertainties, and is mainly affected by inherent variability and measurement errors. This study evaluates the coefficient of variation (COV) of soil properties at Song-do region in Korea for evaluating inherent soil variability. Since soil variability is sensitive to soil layers and soil types, the COVs by soil layers (reclaimed layer and marine layer) and the COVs by soil types (clay and silt) were separately evaluated. It is observed that geotechnical variability of marine layer and clay is relatively smaller than that of reclamation layer and silt.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.215-216
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• 2007

• 한국환경과학회지
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• 제22권10호
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• pp.1305-1316
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• 2013

A long-term wind resource map was made to provide the key design data for the 2.5 GW Korean West-South Offshore Wind Project, and its reliability was validated. A one-way dynamic downscaling of the MERRA reanalysis meteorological data of the Yeongwang-Gochang offshore was carried out using WindSim, a Computational Fluid Dynamics based wind resource mapping software, to establish a 33-year time series wind resource map of 100 m x 100 m spatial resolution and 1-hour interval temporal resolution from 1979 to 2012. The simulated wind resource map was validated by comparison with wind measurement data from the HeMOSU offshore meteorological tower, the Wangdeungdo Island meteorological tower, and the Gochang transmission tower on the nearby coastline, and the uncertainty due to long-term variability was analyzed. The long-term variability of the wind power was investigated in inter-annual, monthly, and daily units while the short-term variability was examined as the pattern of the coefficient of variation in hourly units. The results showed that the inter-annual variability had a maximum wind index variance of 22.3% while the short-term variability, i.e., the annual standard deviation of the hourly average wind power, was $0.041{\pm}0.001$, indicating steady variability.

• 한국운동역학회지
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• 제18권4호
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• pp.49-57
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• 2008

이 연구는 고령자를 대상으로 탄성저항운동을 수행하였을 경우 운동 전 후로 보행 시 지면반력 신호 크기와 이들의 variability에 어떠한 영향을 미치는 가를 구명하고자 하였다. 이를 위하여 여성 고령자 12명을 대상으로 12주간 탄성저항운동을 실시하였으며, 운동 전 후로 보행 시 3방향 지면반력 신호의 주파수 크기와 variability 값을 산출하였다. FFT(fast Fourier transform)를 이용하여 주파수 분석을 하였으며, PSD(power spectral density)를 계산하였다. 총 대상자들의 변이 계수(SD/Mean*100)을 이용하여 집단 간 variability를 계산하였다. 그 결과 다음과 같은 결론을 얻었다. 지면반력 신호의 주파수 크기는 좌우 방향에서 운동 전보다 운동 후에 작은 값을 보였으며, 통계적으로도 유의한 차이(p<.05)가 나타났다. 지면반력 신호의 variability에서는 좌우 방향에서 운동 전보다 운동 후에 큰 값이 나타났으며, 통계적으로도 유의한 차이(p<.05)가 나타났다.

• 한국자원식물학회지
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• 제11권3호
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• pp.264-271
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• 1998

This study was conducted to investigate morphological characteristics of Korean local garlic varieties and to define the genetic variability and the correlations amongthe characters associated with yield. The plant height, the leaf sheath diameter, the nubmer of leaves, and bulb weight were significantly increased in the garlic plants from heavier seed bulbs. The proportation of six clove bulbs was more than 60% in Seosan variety and this was not realted with the number of cloves in seed bulb. While more than 70% bulbs in Jeoksung and Danyang varieties cultivated in paddy field were composed of 6 or 7 cloves, majority of the bulbs of Euisung and Danyang varieties cultivated in upland were composed of bulbs with 7 cloves or more. The highest genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) were observed in bulb weight. GCV and PCV also showed high value in leaf sheath diameter. Thus, there is a greater scope for selection of these characters. The small difference between PCV and GCV values in plant height indicates that the environmental influence would be limited in this character. High heritability was observed of plant height (56.76%) and bulb weight (45.95%). And the weight per bulb (34.24%) exhibited highest genitic advance followed by leaf sheath diameter (18.8%) and plant height (9.61%), and those would be the ideal characters for selelction.

• 한국운동역학회지
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• 제24권4호
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• pp.359-365
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• 2014

A study was conducted to investigate the possible effects of fatigue which was resulted from increased running time on the stability during a prolonged run. The purposes of this study were twofold: first, to determine the discrete and non-linear variability of GRF (ground reaction force) components between running times to know the body stability, and second, to determine the pattern between discrete and non-linear variability. Nineteens healthy young adult males served in this study as subjects who ran at their preferred running speed. GRF data for twenty strides were collected at 5, 65, and 125 minutes during run. Variance coefficient and Lyapunov Exponent techniques on the GRF data were used to calculate variability index for each of the running time conditions. There were no difference between discrete variabilities of three components of GRF, but non-linear variability of the Fz component of GRF was decreased by increasing running time (p<.01). No relationship was found between discrete and non-linear variability.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 2006년도 추계 학술대회
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• pp.211-216
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• 2006

Monitoring variability is a vital part of modem statistical process control. The conventional Shewhart Rand S charts address the setting where the in-control process readings have a constant variance. In some settings, however, it is the coefficient of variation, rather than the variance, that should be constant. This paper develops a chart, equivalent to the S chart, for monitoring the coefficient of variation using rational groups of observations.

• Journal of Mechanical Science and Technology
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• 제15권1호
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• pp.81-87
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• 2001

Cyclic variability limits the range of operating conditions of spark ignition engines, especially under lean and highly diluted operation conditions. The cyclic combustion variations can be characterized by pressure parameters, combustion related parameters, and flame-front related parameters. The coefficient of variation (COV) in indicated mean effective pressure (IMEP) defines the cyclic variability in indicated work per cycle.