• Journal of Korean Society of Water and Wastewater
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• v.25 no.4
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• pp.489-495
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• 2011

Silt Density Index (SDI) has been used as a fouling index for reverse osmosis (RO) processes for decades. In order to decrease RO fouling, feed water should meet SDI standard, which was used to select a proper pretreatment system for RO processes. However, SDI is supposed to be sensitive only to particles larger than 0.45 ${\mu}m$ in terms of diameters while nanoparticles and dissolved organic matter can be potent foulants for RO processes. Our study started from the suspected performance of SDI as a RO fouling index. SDI data from pilot plants located world wide including South Korea were collected and analyzed. Suspended partcle concentration (i.e., turbidity and particle counts), and dissolved organic matter concentration (i.e., dissolved orgnaic carbon (DOC) concentration) data were also collected and compared to SDI values of same water samples. We found that SDI values were not only affected by suspended particle concentration but also by dissolved organic matter concentration. Therefore SDI can be used as a reasonable fouling index for RO feed water because the main foulants for RO processes are suspended particle and dissolved organic matter.

• Journal of Astronomy and Space Sciences
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• v.9 no.1
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• pp.69-88
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• 1992

The effects of the ionosphere on the radio wave propagation are scattering of radio waves, attenuation, angle error, ranging error, and time delay. If ionospheric conditions are suitable, the charged particles can remove energy from radio waves and thus attenuate the signal. Also, a radio wave traveling a path along which the electron density is not constant undergoes changes in direction, positon and time of propagation. The present study is based on Korean ionospheric data obtained at the AnYang Radio Research Institute from Jan. 1985 through Oct. 1989. The data are used to simulate the Korean ionosphere following the Chapman law. The effects of the model ionosphere on the radio wave propagation, such as the angle, position error, time delay, and the attenuation, are studied for the various cases of the wave frequency and the altitude.

• Journal of the Korean Society of Food Science and Nutrition
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• v.20 no.6
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• pp.603-608
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• 1991

To improve the utilization of red pepper, the extracting conditions of oleoresin, such as kind of solvents, particle sizes of a sample, sample to solvent ratios, extraction temperatures and times, were studied. Among eight solvents used for oleoresin extraction from red pepper, the optimal solvent was acetone. The most appropriate particle size of red pepper powder, extracting temperature and mixing ratio of red pepper to acetone were 100 mesh, $25^{\circ}C$ and 1 to 3(w/w), respectively. The basis of yield in oleoresin extraction, optimum extracting time was about 5 hours. The yield of oleoresin under the above-mentioned conditions was 18.7%.

• Journal of Environmental Science International
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• v.11 no.10
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• pp.1081-1087
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• 2002

This study was performed to research the characteristics of suspended particulate for Yellow Sand of January, 1999 in Busan. Yellow Sand frequency during 13 years(1988~2000) in Busan showed maximum in April(57%), next to March(21%), May(16%). According to result of 850hPa weather map and backward isentropic trajectory, this event originated from the Gobi Desert and the Loess Plateau of China. And three mode was found in time series of TSP and PM10 concentration, primary peak showed the maximum hourly concentration at ali station. Gamjeondong as industrial site showed the highest TSP concentration and also had the longest high concentration($geq700\mu\textrm{g}/m^3$). In PM10, concentration of primary peak showed maximum value at Yeonsandong, maximum concentration of secondary and third peak was Deokcheondong. Lasted time from primary peak to secondary peak was about 30 hours, between secondary peak and third peak was 18 hours in Busan, The traveling time between occurrence of Yellow Sand the finding of it was 8~9 hours in Busan and 4~5 hours in central area.

• Journal of Environmental Science International
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• v.11 no.7
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• pp.705-711
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• 2002

In order to determine the factors causing Microcystis spp. bloom in the lower Nakdong River (Mulgum), we prepared wide ranges of pH, nutrient(N, P) concentration and the light through an enclosure experiment far 10days (pH gradient. 6.5, 7.5, 8.5, 9.5; gradient of N, P: ${\frac{1}{2}}DW+{\frac{1}{2}}River$ Water (RW), RW only; four different levels of nutrient addition/day; light: 100, 85, 60, 30, 15% of full sun light). From three days, the difference of Microcystis density in each enclosures was observed. The high density of Microcystis was maintained in the treatments over pH 9.5 and 85% of full sun light. However, in all nutrient treatments, relatively lower cell density than that of pH and light treatments was observed. These results suggested that pH and light input may play more important roles than nutrients in the early development of Microcystis bloom in the eutrophic lower Nakdong River.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.6
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• pp.905-910
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• 2006

In order to evaluate the optimum operation condition of ozonation to minimize bromate formation, based on the NOM characteristics of raw waters, the pathway of bromate formation by ozonation in domestic raw waters was investigated. Considering the bromate formation reactions, the fractions of bromate formation from bromide by OH radical and molecular ozone were calculated with measured values of ozone decay rate ($k_c$) and Rct. The results showed that molecular ozone is more important role in the formation of bromate in domestic raw waters than OH radical. The ratio of bromide oxidation reaction by molecular ozone ranged 73~88%. Fractions of $HOBr/OBr^-$ reaction with both molecular ozone and OH radical were also determined. OH radical reaction with $HOBr/OBr^-$ was dominant. The differential equations based on the stoichiometry of bromate formation were established to predict the formation rate of bromate by ozonation. The results shows good correlation with experimental results.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.3
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• pp.44-51
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• 2021

PIP is an abbreviation of 'Performance Improvement Package', which is a package that can improve performance by applying some design changes to existing aircraft. Boeing provides PIP applicable to B777-200, and Airbus provides PIP applicable to A350-900 as standard. PIP provided by Boeing and Airbus is a separate task, but it is expected to reduce fuel consumption by reducing drag through aerodynamic improvements. The PIP applied to the A350-900 includes work such as increasing Winglet Height and re-twisting Outboard Wing. This study is to verify the effect of PIP application of the A350-900 aircraft and use it as basic data for economic analysis. The aerodynamic improvement studies and expected effects of the PIP application were examined, and the actual flight data of the PIP-applied and the non-applied aircraft were compared to confirm the PIP application effect. This paper provides empirical results for the aviation industry on the PIP application efficiency as a method of improving fuel efficiency and reducing carbon emission.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.2
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• pp.14-24
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• 2021

This study aims to examine probable human errors when landing an airplane by the use of SHERPA(systematic human error reduction and prediction approach) and propose methods for preventing the predictive human errors. It has been reported that human errors are concerned with a lot of accidents or incidents of an airplane. It is significant to predict presumable human errors, particularly in the operation mode of human-automation interaction, and attempt to reduce the likelihood of predicted human error. By referring to task procedures and interviewing domain experts, we analyzed airplane landing task by using HTA(hierarchical task analysis) method. In total, 6 sub-tasks and 19 operations were identified from the task analysis. SHERPA method was used for predicting probable human error types for each task. As a result, we identified 31 human errors and predicted their occurrence probability and criticality. Based on them, we suggested a set of methods for minimizing the probability of the predicted human errors. From this study, it can be said that SHERPA can be effectively used for predicting probable human error types in the context of human-automation interaction needed for navigating an airplane.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.2
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• pp.34-43
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• 2022

In Efforts to prevent CFIT accidents so far, have been emphasizing various education measures to minimize the occurrence of human errors, as well as enforcement measures. However, current engineering measures remain in a system (TAWS) that gives warnings before colliding with ground or obstacles, and even actual automatic avoidance maneuvers are not implemented, which has limitations that cannot prevent accidents caused by human error. Currently, various attempts are being made to apply machine learning-based artificial intelligence agent technologies to the aviation safety field. In this paper, we propose a deep reinforcement learning-based artificial intelligence agent that can recognize CFIT situations and control aircraft to avoid them in the simulation environment. It also describes the composition of the learning environment, process, and results, and finally the experimental results using the learned agent. In the future, if the results of this study are expanded to learn the horizontal and vertical terrain radar detection information and camera image information of radar in addition to the terrain database, it is expected that it will become an agent capable of performing more robust CFIT autonomous avoidance.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.05a
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• pp.91-94
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• 2020

본 연구에서는 4차 산업혁명의 핵심 분야인 가상현실을 헬스 엔터테인먼트 서비스에 응용하는 시스템을 개발하였다. 스마트폰에 내장된 GPS와 GYRO센서를 활용하여 로잉머신의 동작 상태를 이중 데이터로 측정하고, 분석한 값을 활용해서 Unity를 사용하여 AR 어플리케이션을 설계, 구현하였다. 어플리케이션을 AR 글라스를 통해 실행한 결과, 생동감 넘치는 운동 환경을 사용자에게 제공한다. 그러나 사용자의 시각적 부담 과다로 인하여 로잉머신 운동효과 경험에 부분적 장애를 유발할 수 있어 2차적 개선으로 VR 콘텐츠로 전환을 적용하여 안전한 운동효과를 검증하였다. 본 연구의 VR 콘텐츠 개선기술을 적용하면 사용자 안전에 우선하는 헬스 엔터테인먼트 시장의 활성화가 기대된다.