• Environmental and Resource Economics Review
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• v.13 no.1
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• pp.83-117
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• 2004

This study investigates the spatial distributions of the ambient levels of air pollutants ($SO_2$, $NO_2$, $O_3$, CO, and PM) in Seoul metropolitan area using the data obtained by the air pollution observation stations. This study estimated a non-parametric kernel density function and two types of inequality indices, Gini and Entropy. Our estimation results show that the degree of inequality in spatial distribution of air pollution, in general, tends to be stable or slightly decreasing for the period of 1990~2001. In addition, we found that there are significant dynamics of air pollution levels in terms of spatial ranking.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10c
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• pp.480-484
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• 2007

일반적으로 x선 CT는 물체 투과율이 짧기 때문에 대형 산업공정 내부의 영상진단 시 대상체는 금속으로 구성되어 있으며 내부는 액체, 고체, 기체 등 고밀도 물질이 포함되어 있어 계측이 어렵다. 따라서 본 논문에서는 물체 투과율이 x선에 비해 긴 감마선을 사용하였다. 대형 산업공정 내부의 단면영상을 재구성하기 위하여 반복적인 영상재구성 방법의 가중치 함수를 비교하였다. 실험 결과를 통하여 감마 CT 영상에서 빔 통과 여부에 따른 가중치 함수보다 빔 길이나 면적에 의한 가중치 함수로 복원할 경우, 원 영상과 유사함을 확인하였다.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.10a
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• pp.1-4
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• 2006

공초점 자가 간섭 현미경은 측정 광학계에 복굴절 물질을 사용하여 반사된 빛에 대해 간섭 현상을 일으키는 것을 특징으로 한다. 이 간섭을 자가 간섭이라고 부르는데, 이는 시편의 한 점에서 반사되어 나온 빛이 간섭을 일으키기 때문에 붙여진 이름이다. 공초점 자가 간섭 현미경의 점 확산 함수는 종래의 공초점 현미경의 점 확산 함수와 자가 간섭의 곱으로 나타나며, 자가 간섭의 주기가 종래의 공초점 현미경의 점 확산 함수의 중심폭보다 작은 경우 점 확산 함수의 중심폭이 작아져서 수평 방향으로의 분해능이 향상되게 된다. 이러한 분해능 향상 정도를 측정하기 위하여 지름이 100nm 인 금으로 된 비드를 사용하였다. 측정된 결과는 전산모사한 결과와 잘 일치하며 공초점 자가 간섭 현미경에서 2배의 분해능 향상을 보여준다.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.217-223
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• 1996

혼합증기(수증기/공기)의 막응축 열전달 계수를 수직한 벽면에서 측정하고 상관식을 개발하였다. 열전달 상관식은 액막측과 증기측으로 구분하여 만들었고, 액막측 전열계수의 상관식은 액막의 Reynolds수와 Prandtl수의 함수로 나타냈으며, 증기측 전열계수의 상관식은 증기의 Reynolds수, Prandtl수, Schmidt수 및 공기의 질량분율, 액막 Reynolds수의 함수로 제안하였다. 응축 액막의 두께와 확산층의 순간온도 측정결과로부터 액막의 파형 계면이 확산층에서의 열 및 물질전달에 큰 영향을 끼치고 있음을 확인하였고, 증기측 전열계수의 상관식에 포함된 액막 Reynolds수가 파형 계면의 영향을 반영하고 있다.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.104-107
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• 2004

지반오염을 조사하기 위해서는 시추작업을 통하여 시료를 채취하는 방법이 일반적이지만, 실시간으로 원위치에서 다양한 오염물질들의 오염도 변화를 체계적으로 모니터링하는 것은 대단히 어렵다. 본 연구에서는 Frequency Domain Reflectometry(FDR) 장비를 고안하여 지반의 유류오염을 파악하기 위한 유전율 측정법의 실험적 접근을 시도하였다. 구체적으로 포화 및 불포화 매질에 대한 오염도의 측정 및 오염도와 체적함수비의 관계를 측정하여 유전율 반응으로부터 매질의 물성치를 파악할 수 있는 것을 확인하였다.

• Journal of the Korean Society of Radiology
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• v.15 no.2
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• pp.173-179
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• 2021

Scattered x-ray generated by digital radiography systems also have the advantage of increasing signals, but ultimately detectability is reduced by decreasing resolution and increasing noise of x-ray images transmitted objects. An indirect method of measuring scattered x-ray in a modulation-transfer function (MTF) for evaluating resolution in a spatial-frequency domain can be considered as a drop in the MTF value corresponding to zero-frequency. In this study, polymethyl methacrylate (PMMA) was used as a patient tissue equivalent, and MTFs were obtained for various thicknesses to quantify the effect of scattered x-ray on resolution. X-ray image signals were observed to decrease by 35 ~ 83% with PMMA thickness increasing, which is determined by the absorption or scattering of x-rays in PMMA, resulting in reduced MTF and increased scatter fraction. The method to compensate for MTF degradation by PMMA resulted in the MTF inflation without considering the optical spreading generated by the indirect-conversion type detector. Data fitting or zero-padding are needed to compensate for MTF more reasonably on edge-spread function or line-spread function.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.41-46
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• 2011

The tire damage classification method is researched by periodicity detection of ultrasonic envelope signals to occur at the driving vehicle tire. Because periodic signals is generated by rotations of the damaged tire, it should convert to pulse for using the density function. After time intervals of pulses are represented by the density function, the dominant periodicity is detected. The threshold to make a pulse is calculated by moving average of envelope signals. The result of time density function in case of one damage material, the first peak's time is equals to tire's rotation period, 162ms and 102ms, about the speed of 50km/h and 80km/h. In case of more than one damage material, the sum of each peak's time is equals to tire's rotation period about the speed.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.11
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• pp.803-808
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• 2013

The purpose of this study was performed to investigate the optimum conditions of pH, concrete sludge, seed dosage, mixing intensity, operation time in treating fluoride-containing wastewater as $CaF_2$ using the ready-mixed concrete sludge. Considering fluoride removal, water content, that pH 6, concrete sludge dosage of 10 g/L, Seed dosage ($CaF_2$) of 2 g/L, mixing intensity of 100 rpm and operation time of 60 min were found to be optimum. Correspondingly, removal of fluoride and water content was about 85% and 64%, respectively. Increase in amount of seed dosage did not affect fluoride removal efficiency. but the result that the water content is decreased was shown up in occuring the solid-liquid separation well.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.6
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• pp.291-296
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• 2015

The tire damage classification method is researched on the periodicity detection of ramdomness ultrasonic signals to occur at the driving vehicle tire. Setting method of adaptive threshold is proposed in order to valid pulse detection by tire damage in ultrasonic noise on the road and used low pass filter for decrease signal ramdomness as preprocessing. Time interval of detected pulse is setted the density function depend on the vehicle's speed and the method of tire damage detection is proposed that measuring the first peak's time of time density function.The result of time density function in case of one damage material, the first peak's time is measured within the error limit of tire's rotation period, 169.8ms and 97.9ms and 81.8ms, about the speed of 50km/h and 80km/h and 100km/h. In case of more than one damage material, the sum of each peak's time is measured within the error limit of tire's rotation period about the speed.

• Journal of the Korean Geotechnical Society
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• v.28 no.9
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• pp.69-83
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• 2012

A study on strength decrease due to water contents through infiltration has been conducted with 9 rocks of high frequency in Korea. It has been proved that a strength decrease through infiltration has high dependence on rock strengths ranges while the species of rock have no impact. It has been found that the weaker the rocks are, the more sensitive the strength decreases are, and that water content of 0.5% corresponds to strength decrease of almost 50%. Another finding is that most rocks have a failure when water content is about one quarter~one half of its saturation. It has been shown that the weakening of rock strength due to water content results from leaching and the weakening of bonding strength of cementation materials.