• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.862-865
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• 2004

The system air conditioner has an outdoor unit and a number of indoor units, which connected by several long pipes. In comparison with building HAVC system, the system air conditioner doesn't need lots of facilities, such as control of room, cooling tower, etc. At the beginning stage for the market of the system air conditioner, its main application was a school which size is small to use the building HAVC and large to use home air conditioning system, such as PAC (package air conditioner), RAC (room air conditioner). Therefore, because of the advantages of the system air conditioner mentioned above, the market is expanded rapidly. Since it is difficult to evaluate the noise caused by the system air conditioner because it has to be implemented before the finish of construction, the prediction or estimation of the noise by using CAE technology should be very important. In this research, using a commercial code, RAYNOISE, the noise is estimated to improve the design of building.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.439-442
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• 2005

Generally, noise from a home appliance has been measured by overall sound pressure level or sound power level, dB. Customers evaluation, however, of this noise should be depend on the only overall level but also the sensory feeling, annoyance, unpleasure and so on. Moreover, in this sensory evaluation, irregular, time-varying and uneven sounds which are difficult to describe itself by overall level are more affectable. Unfortunately however the formal evaluation method for this kinds of noise is not determined yet. In this research, the evaluation method for harmonic noise, which is a major noise from home appliance and one of the unmeasurable sounds by overall level, is proposed to evaluate its acceptability based on the consumer's sense of hearing. The proposed approach could be applied to the other sound, which acoustical characteristics are similar to the tonal noise.

• Journal of the Korean institute of surface engineering
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• v.52 no.2
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• pp.96-102
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• 2019

Magnesium and its alloys are prone to be corroded, thus surface treatments improving corrosion resistance are always required for practical applications. As a surface treatment of magnesium alloys, plasma electrolytic oxidation (PEO), creating porous stable oxide layer by a high voltage discharge in electrolyte, enhances the corrosion resistance. However, due to superhydrophilicity of the porous oxide layer, which easily allow the penetration of corrosive media toward magnesium alloys substrate, post-treatments inhibiting the transfer of corrosive media in porous oxide layer are required. In this work, we employed a hydrophobizing method to enhance the corrosion resistance of PEO treated Mg alloy. Three types of hydrophobizing techniques were used for PEO layer. Thin Teflon coating with solvent evaporation, self-assembled monolayer (SAM) coating of octadecyltrichlorosilane (OTS) based on solution method and SAM coating of perfluorodecyltrichlorosilane (FDTS) based on vacuum method significantly enhances corrosion resistance of PEO treated Mg alloy with reducing the contact of water on the surface. In particular, the vacuum based FDTS coating on PEO layer shows the most effective hydrophobicity with the highest corrosion resistance.

• Journal of Korea Society of Digital Industry and Information Management
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• v.19 no.1
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• pp.43-55
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• 2023

The purpose of this study is to examine the effects of authentic leadership on employee job satisfaction as well as the mediating role of motivation in the relationship between these two variables. Prior literature on authentic leadership have repeatedly argued that authentic leadership is not simply the ethically "right" thing to do, but also can effectively boost firm performance by increasing employees' job satisfaction and motivation. This study investigates whether the proposition is supported by empirical evidence in the context of Korean companies. Survey data were collected from 230 employees from several companies in South Korea. The results show that authentic leadership has a positive effect on employees' job satisfaction. As to the effects of authentic leadership and work motivation, authentic leadership turns out to have a positive effect on both extrinsic and intrinsic work motivation. The study also confirmed partial mediating effect of job satisfaction in the relationship between authentic leadership and job satisfaction.

• Journal of Environmental Health Sciences
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• v.48 no.3
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• pp.167-175
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• 2022

Background: Disinfection is essential to provide drinking water from a water source. The disinfection process mainly consists of the use of chlorine and ozone, but when chlorine is used as a disinfectant, the problem of disinfection by-products arises. In order to resolve the issue of disinfection by-products, electro-chlorination technology that produces chlorine-based disinfectants from salt water through electrochemical principles should be applied. Objectives: This study surveys the possibility of optimally producing active chlorine from synthetic NaCl solutions using an electro-chlorination system through RSM. Methods: Response surface methodology (RSM) has been used for modeling and optimizing a variety of water and wastewater treatment processes. This study surveys the possibility of optimally producing active chlorine from synthetic saline solutions using electrolysis through RSM. Various operating parameters, such as distance of electrodes, sodium chloride concentration, electrical potential, and electrolysis time were evaluated. Results: Various operating parameters, such as distance of electrodes, sodium chloride concentration, electrical potential, and electrolysis time were evaluated. A central composite design (CCD) was applied to determine the optimal experimental factors for chlorine production. Conclusions: The concentration of the synthetic NaCl solution and the distance between electrodes had the greatest influence on the generation of hypochlorite disinfectant. The closer the distance between the electrodes and the higher the concentration of the synthetic NaCl solution, the more hypochlorous acid disinfectant was produced.

• Korean Journal of Ecology and Environment
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• v.56 no.4
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• pp.414-419
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• 2023

Aquatic ecosystem is composed of various organic and inorganic matters. Its health is essential for sustaining its members such as vegetations, mammals, birds, fishes and invertebrates. Samcheonpo stream is one of candidate streams in Sacheon area of ecological restoration. For this reason, this study conducted to build up a data base for future comparison. The results shows that biodiversity of Epilithic Diatoms and Invertebrates is below average which means that human impacts such as artificial structures and activities have been negatively related to stream health. Consequently, we suggest several key factors when ecological restoration is performed in the stream.

• Journal of Practical Agriculture & Fisheries Research
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• v.21 no.1
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• pp.81-87
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• 2019

The investigation of mycelial growth for artificial cultivation in T. albuminosus determined that within PDA, YM, MEA medium, both KNCAF 9001 and 9002 strains showed the highest mycelial growth in MEA media with 89, 81 mm, respectively, followed by YM, PDA in respected order. Furthermore, optimal mycelial growth of 89 and 77 mm in 9001 and 9002, respectively, at 25 ℃. Mycelial growth rapidly decreased at 30 ℃, but it was confirmed that it survived at 40 ℃. At pH 6, mycelial growth was fast with growth of 89 and 88 mm for both 9001 and 9002, respectively. In the case of 9001, the addition of with cotton seed hull(80%) and rice bran (20%) each other resulted in maximum productivity of 99 mm/10 days. The result differed in order of corn cob(97 mm), oak sawdust(96 mm) and poplar sawdust(93 mm). Ultimately, the result confirmed that addition of rice bran in comparison to bran resulted in higher yield. Even with identical medium component, 9002 showed the same tendency as 9001 but its growth was relatively slower than 9001. The effect of mycelial growth on the moisture content of the medium was best at 101. 94 mm/10 days when the moisture content of 9001 and 9002 was 65%. Mycelial growth rate tended to be slower when the moisture content was higher or lower than 65%.

• International Journal of Highway Engineering
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• v.6 no.3 s.21
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• pp.1-7
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• 2004

Roads, like bikeways, parkways and walks, are to be just capable of supporting light traffic and traveling public, but they are required to be human friendly and environmental-oriented. Lately soil-solidifier mixture, a kind of soil-cement, has developed and has been applied to the recycling and environment-oriented pavement as the surfacing material. Soil-solidifier pavement structure has been designed by only experience. To design this pavement mechanically, it is necessary to find out basic engineering properties of soil-solidifier mixture. This study focuses on finding out mechanical characteristics of the mixture according to mixture proportions and aging. Test molds with various mixture proportions are made, and then unconfined strength tests are performed for test molds with aging of the mixture. As the result of this study, it is found that the strength of the mixture increases with amount of cement and that maximum strength is achieved at 6%$\sim$8% of the ratio of solidifier and water. The strength increase rapidly until 14 days, after then slowly. After 28 days the strength of the mixture approaches to the constant value. The heat of hydration during curing of the mixture is measured no significantly. It also shows that temperature characteristics of the mixture is similar to that of soil. Since this mixture is mixed with soil and is able to improve engineering problems in pavement due to temperature, this mixture is expected to use effectively in the environment-oriented pavement for light traffic.

• Ecology and Resilient Infrastructure
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• v.8 no.1
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• pp.32-43
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• 2021

Multichannel automated chamber systems (MCACs) were developed for the continuous monitoring of soil CO2 efflux in forest ecosystems. The MCACs mainly consisted of four modules: eight soil chambers with lids that automatically open and close, an infrared CO2 analyzer equipped with eight multichannel gas samplers, an electronic controller with time-relay circuits, and a programmable logic datalogger. To examine the stability and reliability of the developed MCACs in the field during all seasons with a high temporal resolution, as well as the effects of temperature and soil water content on soil CO2 efflux rates, we continuously measured the soil CO2 efflux rates and micrometeorological factors at the Nam-san experimental site in a Quercus mongolica forest floor using the MCACs from January to December 2010. The diurnal and seasonal variations in soil CO2 efflux rates markedly followed the patterns of changes in temperature factors. During the entire experimental period, the soil CO2 efflux rates were strongly correlated with the temperature at a soil depth of 5 cm (r2 = 0.92) but were weakly correlated with the soil water content (r2 = 0.27). The annual sensitivity of soil CO2 efflux to temperature (Q10) in this forest ranged from 2.23 to 3.0, which was in agreement with other studies on temperate deciduous forests. The annual mean soil CO2 efflux measured by the MCACs was approximately 11.1 g CO2 m-2 day-1. These results indicate that the MCACs can be used for the continuous long-term measurements of soil CO2 efflux in the field and for simultaneously determining the impacts of micrometeorological factors.

• Journal of Mushroom
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• v.12 no.1
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• pp.17-23
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• 2014

pH of oriental medicine sludge was 5.3, which was similar to 5.2 of the main ingredient, corncob. Its sugar content, however, was 4.8 mg/g, which was 2.5 times higher than concorb's 1.9 mg/g. According to the addition content analysis of oriental medicine sludge by using blood agar plate, the experimental group showed much more robust growth than the control group. 10% of oriental medicine sludge was added to corncob and pine tree sawdust for test-tube culture. Then they were cultivated at $25^{\circ}C$ for 6 days after inoculating Flammulina velutipes liquid spawn. The control group and experimental group showed 2.2~3.4 and 5.8~6.4 cm hypae growths respectively. At the field test for 10% herbal medicine refuse, mushroom yield dropped by 5% compared to the control group. However, it had distinctively lower number of deformity and the 2nd grade products. An economic analysis was conducted based on the cultivation facility that produces 160,000 mushrooms per day. The analysis demonstrated that the facility can save 50,000,000 won in the starting year and 130,000,000 won in the following years from the unit cost of production excluding labour and operation cost.