• Journal of Industrial Technology
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• v.44 no.1
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• pp.51-61
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• 2024

The purpose of this study is to analyze the effects of external inflow and meteorological factors on PM₁₀ and PM_2.5 concentrations in Chuncheon area for a long time. In Korea, various policies have been implemented to reduce air pollution, but the improvement in the concentration of air pollutants (O₃, SO₂, PM₁₀, PM_2.5, NO₂) in particular, O₃,, PM₁₀, PM_2.5, remained insignificant, and the concentration of ultrafine dust (PM_2.5) is still the highest among OECD member countries. In this situation, it is a very important task to accurately identify the cause of pollutant generation and increase in concentration. In this study, concentration analysis was conducted considering the effects of external inflow and weather, assuming that the causes of occurrence and increase of PM₁₀ and PM_2.5 in Chuncheon area were influenced by external inflow and weather. The effects of external inflow were evaluated using reverse trajectory analysis modeling, and the correlation between pollutant concentration and meteorological variables was presented for meteorological factors through statistical analysis. Through this, we tried to find out how much the concentration of air pollutants in Chuncheon in Korea is affected by external inflow and meteorological factors. Most of the reverse trajectory clusters at high concentrations were introduced from the west. In view of this, the high concentration of air pollutants in Chuncheon was mainly affected by the airflow introduced from the west. In the relationship between meteorological factors and concentration, wind speed showed a weak negative correlation with PM₁₀ and PM_2.5 concentration, and PM_2.5 was somewhat more strongly affected by wind speed. Humidity showed a weak negative correlation with PM₁₀, but a weak positive correlation with PM_2.5. Compared to Seoul, Chuncheon had a larger correlation, but it was confirmed that there was little effect of wind speed and wind direction on the concentration because it was weak or insignificant.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.437-437
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• 2022

The prediction of dam inflow rate is crucial for the management of the largest multi-purpose dam in South Korea, the Soyang Dam. The main issue associated with the management of water resources is the stochastic nature of the reservoir inflow leading to an increase in uncertainty associated with the inflow prediction. The Autoregressive (AR) model is commonly used to provide the simulation and forecast of hydrometeorological data. However, because its estimation is based solely on the time-series data, it has the disadvantage of being unable to account for external variables such as climate information. This study proposes the use of the Autoregressive Exogenous Stochastic Volatility (ARXSV) model within a Bayesian modeling framework for increased predictability of the monthly dam inflow by addressing the exogenous and stochastic factors. This study analyzes 45 years of hydrological input data of the Soyang Dam from the year 1974 to 2019. The result of this study will be beneficial to strengthen the potential use of data-driven models for accurate inflow predictions and better reservoir management.

• The Journal of the Acoustical Society of Korea
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• v.41 no.6
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• pp.698-704
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• 2022

In this paper, the radiated aerodynamic noise generated from sound sources of a nozzle inflow is quantitatively investigated and compared with experimental results of externally radiated noise. A high-resolution unsteady compressible Large Eddy Simulation (LES) technique is used to accurately predict the internal and external flow of three types of nozzle shape. Through using the vortex sound source for sound sources, the geometry of nozzle neck is identified as most significant aerodynamic noise sources. For validation of quantitative analysis, the vortex sound source intensity of internal nozzle flow is compared with results of external radiated noise of calculation and experiment.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.2
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• pp.68-76
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• 2018

A vortex tube is a simple energy separating device that splits a compressed air stream into a cold and hot stream without any external energy supply or chemical reactions. The efforts of many researchers and designers have been focused on improvement of vortex tube efficiency by changing the parameters affecting vortex tube operation. The effective parameters are nozzle specifications and inflow pressure conditions. Effects of different nozzle cross-sectional area and number of nozzles are evaluated by computational fluid dynamics (CFD) analysis. In this study, CFD analysis of 3-D steady state and turbulent flow through a vortex tube was performed. We investigated the cold air mass flow rate, the cold air temperature, and the cold air heat transfer rate behavior of a vortex tube by utilizing seven straight nozzles and four inflow pressure conditions.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.607-612
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• 2006

A pressure-type rapid automatic filter of 2000mm diameter and 170 ton/h filtering capacity was fabricated. In case of no external impurity inflow, the turbidity removal efficiency on raw water was experimented and the numbers of impurities of each sizes were analyzed by particle counter. As the result of circulated filtering, the raw water of 40 NTU was filtered to 0.44 NTU and the numbers of impurities above $1{\mu}m$ were removed by approximately 95%. With the filtering efficiency experimented and the mathematical method, the turbidity change of circulation water were calculated according to the inflow rate of external impurity and water treatment method of blow-down or filtering. The cost of blow-down water was calculated from above results. And simple payback period for this filter is calculated as about one year. Nowadays, as the cost of water is continuously increasing and environment regulations will be more strict, the water quality control using this filter will be expected to satisfy the user requirement.

• Journal of the Korea Organic Resources Recycling Association
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• v.13 no.4
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• pp.128-135
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• 2005

This study was done to improve the effectiveness of nitrification and denitrification using the aeration-anoxic combination method using CFSTR(continuous-flow stirred-tank reactor) attached with an anoxic reactor filled with a media. In order to calculate the concentration of nitric acid within the aeration tank proportional to the anoxic rate within the reactor, supernatant within the inflow and precipitation tanks were influxed into the anoxic reactor. The rate of nitrogen removal was calculated using the concentration of inflow and flow of returned supernatant. From the results of this experiment, the carbon source needed in the anoxic reactor came from the inflow so that anoxification was achieved completely using the inflow source without the introduction of an external carbon source. However, as the ratio of nitric acid becomes large in inflow and nitric acid flow, the carbon source within the input source decreases so that the concentration of carbon source is important.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.1
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• pp.41-51
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• 2018

Downwash from helicopter rotor blades and external winds from various maneuvering make an unguided rocket change its trajectory and range. For the prediction of the trajectory and range, it is essential to consider the downwash effect. In this study, an algorithm was developed to calculate 6-Degree-Of-Freedom(6 DOF) forces and moments exerting on the rocket, and total flight trajectory of a 2.75-inch unguided rocket in a helicopter downwash flow field. Using Actuator Disk Model(ADM) analysis result, the algorithm could analyze the entire trajectory in various initial launch condition such as launch angle, launch velocity, and external wind. The algorithm that considered the interference between a fuselage and external winds could predict the trajectory change more precisely than inflow model analysis. Using the developed algorithm, the attitude and trajectory change mechanism by the downwash effect were investigated analyzing the effective angle of attack change and characteristics of pitching stability of the unguided rocket. Also, the trajectory and range changes were analyzed by considering the downwash effect with external winds. As a result, it was concluded that the key factors of the rocket range change were downwash area and magnitude which effect on the rocket, and the secondary factors were the dynamic pressure of the rocket and the interference between a fuselage and external winds. In tailwind case which was much influential on the range characteristics than other wind cases, the range of the rocket rose as increasing the tailwind velocity. However, there was a limit that the range of the rocket did not increase more than the specific tailwind velocity.

• Journal of the Korean Regional Science Association
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• v.13 no.2
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• pp.25-43
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• 1997

This paper empirically estimates gains from capital inflow to a regional ecomomy. It will be a usefulc for indicator for a local government to build a policy for attracting capital. We estimate the respective Cobb-Douglas production function for 11 provinces of Korea, derive its marginal productivity of capital, and then calculate the amount of capital moved between two provinces and gains from the capital movement. With no barriers to capital movement, there would be a strong motive for capital inflow to Seoul, Pusan, and Kyungki, whereas capital outflow would be expected in Chonnam, Chungbuk, Chungnam, and Kyungbuk. The ratio of gains from capital movement to the regional domestic from capital movement to the regional domestic product(RDP) is high in Cheju, Kangwon, Chungbuk, and so on. It turns out that capital flows from an area with lower productivity of capital to one with hihger productivity. This implies that if the local government of an underdeveloped region wants to lure capital investment from outside, it needs to provide it with strong incentives of eax reduction and special loans.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.39 no.2
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• pp.149-158
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• 2013

L-ascorbic acid, the representative antioxidants, has a great effect on skin whitening, collagen synthesis, and anti-aging, but has low oxidative stability during storage. Therefore, in this study, thermal and oxidation properties of L-ascorbic acid under various storage conditions (powder, aqueous phase, changes of temperature, UV-irradiation, and inflow of external air etc.) were investigated. And the storage stability of ingredient was validated in the double-spaced pouch by analysing oxidation properties under each storage conditions (powder phase and blended with essence). In oder to analyze the thermal properties, TGA, DSC, and FT-IR analysis were carried out and UV-visible spectrophotometer & redox titration were used in parallel for oxidation property analyses. From the result of experiment, L-ascorbic acid was oxidized fast when it contained lots of metallic ion, hydroxy ion in aqueous solution under high temperature, UV-irradiation & inflow external air, whereas it was not oxidized for a long time when it was stored as pure powder although it has same condition as heating up, UV-irradiation & inflow external air. Based on this result, retention period of cosmetics which is using L-ascorbic acid, less stable material in oxidation can be innovatively increased when using double-spaced pouch that is designed and produced for separating storage of active ingredients.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.409-415
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• 2017

This study examines the effect of pay dispersion on labor productivity by focusing on the inflow of newcomers into the tournament and the outflow of stayers from the tournament. According to tournament theory, the expansion of pay dispersion within the organization contributes to enhanced organizational performance by attracting high performers externally and by removing low performers internally within the organization. However, previous studies regarding tournament theory have overlooked the participant aspects. Therefore, this study explores how external hiring and involuntary turnover influence the effect of pay dispersion on labor productivity. This paper hypothesizes that pay dispersion will have a positive effect on labor productivity. Moreover, this paper predicts that the inflow of new competitors will strengthen the positive effects of pay dispersion on labor productivity, whereas the outflow of incumbents will weaken this relationship. Empirical results showed that pay dispersion increased labor productivity and the inflow of newcomers strengthened this positive relationship. However, contrary to our prediction, the outflow of incumbents weakened the positive effect between pay dispersion and labor productivity. These theoretical arguments and empirical findings highlight the proper conditions should be equipped to practically achieve the positive effect of pay dispersion on labor productivity.