• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.5
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• pp.11-17
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• 2007

The appearance inspection of various electronic products and parts has been executed by the eyesight of human. But inspection by eyesight can't bring about uniform inspection result. Because the appearance inspection result by eyesight of human is changed by condition of physical and spirit of the checker. So machine vision inspection system is currently used to many appearance inspection fields instead of the checker. However the inspection result of machine vision is changed by the illumination of workplace. Therefore we have used a power-law transformation and histogram specification in this paper for improvement of vision inspection accuracy. As a result of these power-law transformation and histogram specification algorithm, we could increase the exactness of vision inspection and prevent system error from physical and spirit condition of human. Also this system has been developed only using PC, CCD Camera and Visual C++ for universal workplace.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.4
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• pp.39-47
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• 1992

Derivation of reasonable design low flows was attempted by comparative analysis of design low flows was derived by Power and SMEMAX transformations for the normalizations of skewed distribution and by Type m extremal distribution presented in the first report of this study with annual low flows in the five watersheds of main river basins in Korea. The results were anslyzed and summarized as follows. 1.Basic statistics of annual low flows for the selected watersheds were calculated by using Power and SMEMAX transformations. 2.Power thansformation has found to be the best for the normalization of skewed distribution among others including log, square root and SMEMAX transformations. 3.Design low flows for the selected watersheds were derived by the Power and SMEMAX transformations. 4.Judging by the relative suitabilities of the Type III extremal distribution, Power and SMEMAX transformation, it was found that design low flows of all methods are closer to the observed data within 10 years of the return period and those of Power transformation can be acknowledzed as a reasonable one among others from the viewpoint of the median between values of Type m extremal distribution and SMEMAX transformation in addition to closing the observed than others over 10 years of the return period.

• Journal of the Korean Data and Information Science Society
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• v.16 no.2
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• pp.271-281
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• 2005

Zokian(1993) and Li and Li(1996) developed TARCH(Threshold ARCH) model, considering the asymmetries in volatility. The models are based on Engle(1982)'s ARCH model and Bollerslev(1986)'s GARCH model. However, two TARCH models can be expressed a common model through Box Cox Power transformation, which was used by Higgins and Bera(1992) for developing NARCH(nonlinear ARCH) model. This article shows the PTARCH(Power transformation TARCH) model is necessary in some condition, and it checks the fact that PTARCH model has better performance comparing estimates and RMSE(Root Mean Square Error) with those of Zakoian's TARCH model and Li and Li's TARCH model. PTARCH model would give contribution in asymmetric study as well as heteroscedastic study.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.3
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• pp.228-236
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• 2007

An analytical solution for long waves propagating over an asymmetric trench is derived. The water depth inside the trench varies in proportion to a power of distance from the center of the trench. The mild-slope equation, governing equation, is transformed into second order ordinary differential equation with variable coefficients by using the long wave assumption and then the analytical solution is obtained by using the power series technique. The analytical solution is confirmed by comparison with the numerical solution. After calculating the analytical solution under various conditions, the results are analyzed.

• The Journal of the Korea Contents Association
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• v.12 no.3
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• pp.434-441
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• 2012

An analytic solution to the extended mild-slope equation was derived for waves propagating over an axi-symmetric pit. The water depth inside the pit was in proportion to a power of radial distance from the center of pit. The equation was transformed into the ordinary differential equation using the method of separation of variables. The coefficients of differential terms were expressed as an explicit form composing of the phase and group velocities. The bottom curvature and the square of bottom slope terms, which were added to the extended mild-slope equation, were expressed as power series. Finally, using the Frobenius series, the analytic solution to the extended mild-slope equation was derived. The present analytic solution was validated by comparing with the numerical solution obtained from FEM.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.116-116
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• 2023

대규모 댐과 같은 수공구조물의 파괴시 상당한 피해가 발생하므로 구조물설계시 가능최대강수량(PMP) 기준이 적용된다. 포락선 방법은 가장 극심했던 강우량의 포락선을 작성하여 PMP를 산정하는 방법으로 기상 및 강수량자료가 부족시 PMP 추정이 어려운 경우에 사용한다. 포락선의 근사식은 지속시간의 거듭제곱인 멱함수 형태로 나타내며, 우리나라의 경우 1일을 전후로 계수와 차수가 다른 식을 사용한다. 이러한 근사식은 우리나라의 이상홍수 발생빈도 및 규모가 커짐에 따라 검토될 필요성이 있다. 또한, PMP 산정시 활용하는 제한된 수의 지상관측자료는 시공간적 변동성을 완전히 포착할 수 없어 한계가 있다. 본 연구는 이러한 한계를 극복하기 위하여 기상레이더 자료를 기반으로 우리나라 전역의 최대 강우깊이-지속시간 관계를 분석 및 새로운 PMP 포락선을 제시한다. 활용한 레이더는 CMAX(Column Maximum)로 2009~2018년간 10분 단위자료를 수집하였다. 레이더 자료와 비교하기 위하여 지상관측자료 AWS를 함께 수집하였다. AWS는 1997~2022년간 1분 단위자료로 우리나라 전역의 547개 지점관측자료를 활용하였다. 레이더자료는 Z-R 관계식으로 변환하여 가외치(outlier)를 제거 및 보정하였다. 그 후, 정규 크리깅기법으로 생성한 지상관측 강우장과 병합하는 CM(Conditional Merging)기법을 적용하였다. 우리나라 최대 강우깊이-지속시간 관계를 산정한 결과, 기존 포락선의 값이 낮게 산정되었음을 확인하였다. 이는 기후변화 등에 따라 최근 극한 호우가 발생한 것으로 판단된다. 또한, 실제 근사식은 멱함수 거동에서 벗어난 형태로 나타났고, 지점관측자료가 기상레이더 값보다 과소추정되는 경향을 확인하였다. 특히 같은 기간에서 확인하였을 때, 강우지속시간이 짧을수록 AWS값과 레이더자료의 강수량이 2배 정도 차이를 보여 지점관측소가 없는 지역의 국지성 호우 존재를 확인할 수 있었다. 추후, 미래에 더 긴 레이더 시계열을 사용한다면, 더욱 신뢰성 있는 자료로 활용할 수 있을 것으로 판단한다.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.11-13
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• 2007

The appearance inspection of various electronic products and parts has been executed by the eyesight of human. But inspection by eyesight can't bring about uniform inspection result. Because the appearance inspection result by eyesight of human is changed by condition of physical and spirit of the checker. So machine vision inspection system is currently used to many appearance inspection fields instead of the checker. However the inspection result of machine vision is changed by the illumination of workplace. Therefore we have used a power-law transformation in this paper. for improvement of vision inspection accuracy and could increase inspection accuracy of vision system. Also this system has been developed only using PC, CCD Camera and Visual C++ for universal workplace.

• The Korean Journal of Applied Statistics
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• v.23 no.1
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• pp.49-61
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• 2010

The time series dependencies of Financial volatility are frequently measured by the autocorrelation function of power-transformed absolute returns. It is known as the Taylor property that the autocorrelations of the absolute returns are larger than those of the squared returns. Hass (2009) developed a simple method for detecting the Taylor property in absolute-value-GAROH(1,1) (AVGAROH(1,1)) model. In this article, we fitted AVGAROH(1,1) model for various Korean financial time series and observed the Taylor property.

• Korean Journal of Ecology and Environment
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• v.41 no.3
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• pp.320-330
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• 2008

For twenty-nine aquatic insect taxa common to mountain headwater streams in central Korean peninsula, body length-dry mass and -ash free dry mass relationships were developed by using a natural log transformed power function. Most of the predicted mass at length of this study was rather similar to those of other studies. Taxa with higher predicted mass at length than predicted by others tend to have soft exoskeleton and move by stretching and contracting their body. Ash rate in average was 10% of dry mass and was not significantly different among functional feeding groups.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.23 no.4
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• pp.153-178
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• 2018

Most operational uses of wind speed data require measurements at, or estimates generated for, the reference height of 10 m above mean sea level (AMSL). On the Ieodo Ocean Research Station (IORS), wind speed is measured by instruments installed on the lighthouse tower of the roof deck at 42.3 m AMSL. This preliminary study indicates how these data can best be converted into synthetic 10 m wind speed data for operational uses via the Korea Hydrographic and Oceanographic Agency (KHOA) website. We tested three well-known conventional empirical neutral wind profile formulas (a power law (PL); a drag coefficient based logarithmic law (DCLL); and a roughness height based logarithmic law (RHLL)), and compared their results to those generated using a well-known, highly tested and validated logarithmic model (LMS) with a stability function (${\psi}_{\nu}$), to assess the potential use of each method for accurately synthesizing reference level wind speeds. From these experiments, we conclude that the reliable LMS technique and the RHLL technique are both useful for generating reference wind speed data from IORS observations, since these methods produced very similar results: comparisons between the RHLL and the LMS results showed relatively small bias values ($-0.001m\;s^{-1}$) and Root Mean Square Deviations (RMSD, $0.122m\;s^{-1}$). We also compared the synthetic wind speed data generated using each of the four neutral wind profile formulas under examination with Advanced SCATterometer (ASCAT) data. Comparisons revealed that the 'LMS without ${\psi}_{\nu}^{\prime}$ produced the best results, with only $0.191m\;s^{-1}$ of bias and $1.111m\;s^{-1}$ of RMSD. As well as comparing these four different approaches, we also explored potential refinements that could be applied within or through each approach. Firstly, we tested the effect of tidal variations in sea level height on wind speed calculations, through comparison of results generated with and without the adjustment of sea level heights for tidal effects. Tidal adjustment of the sea levels used in reference wind speed calculations resulted in remarkably small bias (<$0.0001m\;s^{-1}$) and RMSD (<$0.012m\;s^{-1}$) values when compared to calculations performed without adjustment, indicating that this tidal effect can be ignored for the purposes of IORS reference wind speed estimates. We also estimated surface roughness heights ($z_0$) based on RHLL and LMS calculations in order to explore the best parameterization of this factor, with results leading to our recommendation of a new $z_0$ parameterization derived from observed wind speed data. Lastly, we suggest the necessity of including a suitable, experimentally derived, surface drag coefficient and $z_0$ formulas within conventional wind profile formulas for situations characterized by strong wind (${\geq}33m\;s^{-1}$) conditions, since without this inclusion the wind adjustment approaches used in this study are only optimal for wind speeds ${\leq}25m\;s^{-1}$.