• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.567-570
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• 2008

The present study investigated the applicability of the minium fludization velocity measuring method using linear regression analysis between the standard deviation of pressure fluctuation and gas velocity in multi-particle sand on a fluidized bed 0.109 in inner diameter. We measured minium fludization velocity according to the standard deviation of particle distribution in Gaussian distribution. The measured value compared with other researchers' equations. The minium fludization velocity derived from the linear regression analysis of the standard deviation of pressure fluctuation and pressure drop inside the bed. We also found that the minium fludization velocity of a multi-particle system using the standard deviation of pressure fluctuation must be measured at freely bubbling region.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.964-968
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• 2007

The measurement of floor impact sound have been standardized in KS 2810-1 and 2. The height of receiving microphones position is specified in the standard as 1.2m which is almost half height of apartment rooms as a listening position. In this study, receiving positions are investigated by measuring the distribution of sound pressure levels at 792 receiving microphone positions in the standard testing building. Standard impact sources, tapping machine and impact ball, are driven on the center position in the source room where is located at the above floor. It was found that the distribution of sound pressure levels in the receiving room indicates significant deviation at different frequencies there is more than 5dB drop at 63Hz but 2dB rise at 125Hz at a height of 1.2m when the impact ball is driven, in the other case of a generating tapping machine there is more than 2dB rise at 125Hz at a height of 1.2m due to room modes.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.2
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• pp.159-173
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• 1999

Based on air quality monitoring data('89~'97) operated by the Department of Environment, we provide various fundamental statistics for ground ozone. The purpose of this paper are to review the national ambient ozone standard, to study spatial distribution of ozone. Since we, in Korea, calculate average ozone level, to examine the occurrences of ozone level 3 times a day (1~8, 9~16, 17~24 hours), the method does not seem to be scientifically sound comparing to a running average method adapted by the USEPA. When we counted the number of cases with 8-h average O3 level exceeding 60ppb(8-h average standard in Korea)and 80 ppb (that in the U.S.A) and also when we calculated 8-hour average ozone level based on th US method, some regions were classified as non-attainment areas. Especially in Seoul, results of spatial distribution analysis showed that high level ozone over 80 ppb was observed at Kuui-Dong and Pangi-Dong in the eastern part and at Ssangmun-Dong in the northeastern part. Also, occurrences of ozone episode defined as number of days then ozone level exceeding 80 ppb for 3 consecutive hours were extensively reviewed in this paper.

• KIEAE Journal
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• v.10 no.6
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• pp.97-103
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• 2010

Sky simulator is a effective daylighting design tool that can evaluate three dimensional performance of lighting. Especially, the dome type sky simulator offer reliable and reproducible daylighting performance with different standard sky models. Recently, K university has developed the dome type sky simulator(sky dome) with the diameter of 6.5m and the height of 3.7m. The sky dome consists of a group of 145 large steel panels with 72 halogen lamps which are arranged in a circular array. The luminance distribution of the sky dome can be calibrated by changing the angle and the brightness of the lamps respectively. To allow more reliable prediction and evaluation of daylighting through the sky dome, It is essential to validate the sky luminance distribution of the sky dome. This study consider the validation of the comparisons between the measured and the calculated luminance values for the CIE standard overcast sky. Also, the error rate between the measured and the calculated luminance values were compared to the previous studies. The results indicated that the K university sky dome can reproduce reliable CIE standard overcast sky with the average relative error rate of 4.4% and root-mean-square error(RMSE) of 5.4%.

• Structural Engineering and Mechanics
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• v.18 no.3
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• pp.331-342
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• 2004

The vibration control problem of structures with random parameters is discussed, which is approximated by a deterministic one. A method for calculating the standard deviations of eigenvalues of the closed-loop systems is presented by using the random perturbation. The method presented in this paper will not require the distribution function of the random parameters of the systems other than their means and variances. Similarly, the distribution function of the random eigenvalues will not be computed other than their means and variances. The standard deviations of eigenvalues of the uncertain closed-loop systems can be used to estimate the stability robustness. The present method is applied to a vibration control system to illustrate the application. The numerical results show that the present method is effective.

• KIEAE Journal
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• v.5 no.4
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• pp.51-57
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• 2005

For the evaluating daylighting performance, field measurement, scale model test and a set of computer tools can be applied. For the scale model measurements, the sky simulator is a vital facility to represent the desired sky conditions consistently. Recently K university has developed a large size sky simulator, 6m-diameter and 3.7m-height, that is suitable for the international standard. To verify the reliability of the sky simulator, the luminance distribution on the inner sky surface was measured and compared with the CIE standard overcast sky model. It is found that the sky simulator can be reproduced the CIE standard overcast sky condition with 4.3% as mean difference. K university sky simulator is fully validated for usability and accuracy for daylighting researches.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.9
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• pp.616-623
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• 2001

Effects of the grating period fluctuation on the wavelength distribution have been studied by an effective index transfer matrix method in quarter wavelength shifted (QWS) DFB lasers. The wavelength distribution is expressed by a probability density that is an analytical function of the correlation coefficient and normalized standard deviation of the grating period fluctuation. The probability density function of wavelength distribution is shown to be nearly Gaussian, and its standard deviation increases with normalized standard deviation of the grating period fluctuation, and decreases with the negative correlation between adjacent half-periods.

• Applied Chemistry for Engineering
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• v.27 no.5
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• pp.546-550
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• 2016

Over 60~70% of the domestic soil contamination have occurred by petroleum products. B T E X including benzene, toluene, ethylbenzene, xylene and total petroleum hydrocarbon (TPH) have to be inspected for the contaminated soil by petroleum products. An accurate contamination analysis is necessary to estimate the are of contaminated soil and also establish an appropriate purification scheme. In this study, we analyzed a sectional TPH pattern for current domestic distributed petroleum products. Also, the TPH content was analyzed by compensating the defect of current Korea standard analytic methods for soil where the analytic range is just for $C_8{\sim}C_{40}$. The light distillate petroleum products such as gasoline and solvent 1 showed the maximum of 85% difference in the TPH content between the standard analytic and improved methods.

• Journal of Korean Society on Water Environment
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• v.39 no.4
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• pp.302-315
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• 2023

Distribution characteristics and altitudinal gradient of four species (E. strigata, E. separigata, E. orientalis-sachalinensis group) of the mayfly genus Ephemera (Order Ephemeroptera) were analyzed with probability distribution models (exponential, normal, lognormal, logistic, Weibull, gamma, beta, Gumbel). Data was collected from 23,846 sampling units of 6,787 sites in Korea from 2010 to 2021. The beta distribution model showed the best fit for positively skewed E. orientalis-sachalinensis and little-skewed E. strigata along with altitudinal gradient. The reversed lognormal distribution model showed the best-fit for negatively skewed E. separigata. E. orientalis-sachalinensis distributed at the range of altitude 1~700 m (mean 251 m, median 226 m, mode 124 m, and standard deviation 161 m), E. strigata distributed at the range of altitude 5~871 m (mean 474 m, median 478 m, mode 492 m, and standard deviation 200 m), E. separigata distributed at the range of altitude 7~846 m (mean 620 m, median 659 m, mode 760 m, and standard deviation 181 m). Altitudinal habitat suitability ranges were estimated to be 42~257 m for E. orientalis-sachalinensis, 335~644 m for E. strigata, and 641~824 m for E. separigata. Based on the altitudinal spectrum of suitability and altitude-related temperature analysis results, E. orientalis-sachalinensis was estimated to be thermophilic, E. strigata to be mesophilic, and E. separigata to be thermophobic. This is the first national-scale evaluation of the altitudinal distribution of Ephemera in Korea. These results will be used in a further research study on altitudinal shift of the species of Ephemera under climate change.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.2
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• pp.234-240
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• 2010

Gas flow uniformity is an important factor to guarantee particle removal performance of electrostatic precipitators (EP), and the gas flow uniformity is evaluated by a fraction of standard deviation to the mean of gas flow distribution (%RMS) or a technical standard, ICAC EP-7, provided by The Institute of Clean Air Companies. In this study, relationship between the ICAC EP-7 and %RMS in evaluation of gas flow uniformity was investigated in terms of flow velocity. The maximum values of %RMS for gas velocity distribution of normal distribution has been obtained, and the maximum values of %RMS with gas velocity distribution satisfying ICAC EP-7 standards were also evaluated. With gas flow distribution obtained from CFD analysis and physical model test of real EP, %RMS values were calculated and it was tested if those gas flow distribution satisfy the criteria specified in ICAC EP-7. The %RMS values satisfying criteria of ICAC have been appeared to have similar values with %RMS values calculated with normal distribution of gas velocities.