• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.56-61
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• 2009

Paradigm depending only on fossil fuel for building heat source is rapidly changing. Accelerating the change, as it has been known, is obligation for reducing green house gas coming from use of fossil fuel, i.e. reaction to United Nations Framework Convention on Climate Change. In addition, factors such as high oil price, unstable supply, weapon of petroleum and oil peak, by replacing fossil fuel, contributes to advance of environmental friendly renewable energy which can be continuously reusable. Therefore, current new energy policies, beyond enhancing effectiveness of heat using equipments, are to make best efforts for national competitiveness. Our country supports 11 areas for new renewable energy including sun light, solar heat and wind power. Among those areas, ocean thermal energy specifies tidal power generation using tide of sea, wave and temperature differences, wave power generation and thermal power generation. But heat use of heat source from sea water itself has been excluded as non-utilized energy. In the future, sea water heat source which has not been used so far will be required to be specified as new renewable energy. This research is to survey local heating system in Europe using sea water, central solar heating plants, seasonal thermal energy store and to analyze large scale central solar heating plants in German. Seasonal thermal energy store necessarily need to be equipped with large scale thermal energy store. Currently operating central solar heating system is a effective method which significantly enhances sharing rate of solar heat in a way that stores excessive heat generating in summer and then replenish insufficient heat for winter. Construction cost for this system is primarily dependent on large scale seasonal heat store and this high priced heat store merely plays its role once per year. Since our country is faced with 3 directional sea, active research and development for using sea water heat as cooling and heating heat source is required for seashore villages and building units. This research suggests how to utilize new energy in a way that stores cooling heat of sea water into seasonal thermal energy store when temperature of sea water is its lowest temperature in February based on West Sea and then uses it as cooling heat source when cooling is necessary. Since this method utilizes seasonal thermal energy store from existing central solar heating plant for heating and cooling purpose respectively twice per year maximizing energy efficiency by achieving 2 seasonal thermal energy store, active research and development is necessarily required for the future.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.721-730
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• 2021

Maritime air pollutants around port cities have gained a great deal of attention due to their direct impacts on regional air quality. This study aims to determine the geographical properties of sea/land breezes in different areas to discover overall ranges of maritime emission dispersion. The HOTMAC-RAPTAD modeling program was used to simulate regional-scale air dispersion considering non-linear and unsteady states during the general summer period for the target areas of the Yellow Sea (Incheon Port and Pyeongtaek·Dangjin Ports), archipelago region (Mokpo Port), South and East Sea (Busan and Masan Ports) and East Sea with mountainous area (Donghae·Mukho Ports). The resulting dispersion lengths of vessel emissions into the onshore regions around the target ports shed light on portal air quality management, because vessel emissions from the Incheon, Mokpo, Busan, and Donghae·Mukho ports were transported 27-31km (Western Seoul), 21-24km (Southern Muan), 20-26km (Gimhae and Yangsan), and 22-25km (Taebeak Mountains), respectively. Therefore, the results of this study provide useful data for regional air quality management and marine air pollution mitigation to improve the sustainability of port cities.

• Journal of Digital Convergence
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• v.18 no.12
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• pp.425-434
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• 2020

Background: Viral infection outbreaks are emerging public health concerns. They often exhibit seasonal patterns that could be predicted by the application of big data and bioinformatic analyses. Purpose: The purpose of this study was to identify trends in diarrhea-causing viruses such as rotavirus (Gr.A), norovirus G-I, and norovirus G-II in Cheonan, Korea. The identified related factors of diarrhea-causing viruses may be used to predict their trend and prevent their infections. Method: A retrospective analysis of 4,009 fecal samples from June 2010 to December 2019 was carried out at Dankook University Hospital in Cheonan. Reverse transcription-PCR (RT-PCR) was employed to identify virus strains. Information about seasonal patterns of infection was extracted and compared with local weather data. Results: Out of the 4,009 fecal samples tested using multiplex RT-PCR (mRT-PCR), 985 were positive for infection with Gr.A, G-I, and G-II. Out of these 985 cases, 95.3% (n = 939) were under 10 years of age. Gr.A, G-I, and G-II showed high infection rates in patients under 10 years of age. Student's t-test showed a significant correlation between the detection rate of Gr.A and the relative humidity. The detection rate of G-II significantly correlated with wind-chill temperature. Conclusion: Climate factors differentially modulate rotavirus and norovirus infection patterns. These observations provide novel insights into the seasonal impact on the pathogenesis of Gr.A, G-I, and G-II.

• The Korean Journal of Applied Statistics
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• v.35 no.4
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• pp.543-552
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• 2022

When frost occurs, crops are directly damaged. When crops come into contact with low temperatures, tissues freeze, which hardens and destroys the cell membranes or chloroplasts, or dry cells to death. In July 2020, a sudden sub-zero weather and frost hit the Minas Gerais state of Brazil, the world's largest coffee producer, damaging about 30% of local coffee trees. As a result, coffee prices have risen significantly due to the damage, and farmers with severe damage can produce coffee only after three years for crops to recover, which is expected to cause long-term damage. In this paper, we tried to predict frost using frost generation data and weather observation data provided by the Korea Meteorological Administration to prevent severe frost. A model was constructed by reflecting weather factors such as wind speed, temperature, humidity, precipitation, and cloudiness. Using XGB(eXtreme Gradient Boosting), SVM(Support Vector Machine), Random Forest, and MLP(Multi Layer perceptron) models, various hyper parameters were applied as training data to select the best model for each model. Finally, the results were evaluated as accuracy(acc) and CSI(Critical Success Index) in test data. XGB was the best model compared to other models with 90.4% ac and 64.4% CSI, followed by SVM with 89.7% ac and 61.2% CSI. Random Forest and MLP showed similar performance with about 89% ac and about 60% CSI.

• Korean Journal of Remote Sensing
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• v.38 no.5_3
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• pp.851-861
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• 2022

In this study, we analyzed the effects of trees planted in urban areas on PM_2.5 reduction using a computational fluid dynamics (CFD) model. For realistic numerical simulations, the meteorological components(e.g., wind velocity components and air temperatures) predicted by the local data assimilation and prediction system (LDAPS), an operational model of the Korea Meteorological Administration, were used as the initial and boundary conditions of the CFD model. The CFD model was validated against, the PM_2.5 concentrations measured by the sensor networks. To investigate the effects of trees on the PM_2.5 reduction, we conducted the numerical simulations for three configurations of the buildings and trees: i) no tree (NT), ii) trees with only drag effect (TD), and iii) trees with the drag and dry-deposition effects (DD). The results showed that the trees in the target area significantly reduced the PM_2.5 concentrations via the dry-deposition process. The PM_2.5 concentration averaged over the domain in DD was reduced by 5.7 ㎍ m^-3 compared to that in TD.

• Wind and Structures
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• v.35 no.1
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• pp.1-20
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• 2022

This research work presents an experimental study's outcomes to reveal the impact of an O-ring on the flow control over a sphere placed in a turbulent boundary layer. The investigation is performed quantitatively and qualitatively using particle image velocimetry (PIV) and dye visualization. The sphere model having a diamater of 42.5 mm is located in a turbulent boundary layer flow over a smooth plate for gap ratios of 0≤G/D≤1.5 at Reynolds number of 5 × 10³. Flow characteristics, including patterns of instantaneous vorticity, streaklines, time-averaged streamlines, velocity vectors, velocity fluctuations, Reynolds stress correlations, and turbulence kinetic energy (), are compared and discussed for a naked sphere and spheres having O-rings. The boundary layer velocity gradient and proximity of the sphere to the flat plate profoundly influence the flow dynamics. At proximity ratios of G/D=0.1 and 0.25, a wall jet is formed between lower side of the sphere and flat plate, and velocity fluctuations increase in regions close to the wall. At G/D=0.25, the jet flow also induces local flow separations on the flat plate. At higher proximity ratios, the velocity gradient of the boundary layer causes asymmetries in the mean flow characteristics and turbulence values in the wake region. It is observed that the O-ring with various placement angles (𝜃) on the sphere has a considerable alteration in the flow structure and turbulence statistics on the wake. At lower placement angles, where the O-ring is closer to the forward stagnation point of the sphere, the flow control performance of the O-ring is limited; however, its impact on the flow separation becomes pronounced as it is moved away from the forward stagnation point. At G/D=1.50 for O-ring diameters of 4.7 (2 mm) and 7 (3 mm) percent of the sphere diameter, the -ring exhibits remarkable flow control at 𝜃=50° and 𝜃=55° before laminar flow separation occurrence on the sphere surface, respectively. This conclusion is yielded from narrowed wakes and reductions in turbulence statistics compared to the naked sphere model. The O-ring with a diameter of 3 mm and placement angle of 50° exhibits the most effective flow control. It decreases, in sequence, streamwise velocity fluctuations and length of wake recovery region by 45% and 40%, respectively, which can be evaluated as source of decrement in drag force.

• Journal of Aerospace System Engineering
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• v.16 no.6
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• pp.54-63
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• 2022

Recently, electric propulsion aircraft with various propeller mounting positions have been under construction. The position of the propeller relative to the wing can significantly affect the aerodynamic performance of the aircraft. Placing the propeller in front of the wing produces a complex swirl flow behind or around the propeller. The up/downwash induced by the swirl flow can alter the wing's local effective angle of attack, causing a change in the aerodynamic load distribution across the wing's spanwise direction. This study investigated the influence of the distance between a propeller and a wing on the aerodynamic loads on the wing. The swirl flow generated by the propeller was modelled using an actuator disk theory, and the wing's aerodynamics were analysed with the VSPAERO tool. Results of the study were compared to wind tunnel test data and established that both axial and spanwise distance between the propeller and the wing positively affect the wing's lift-to-drag ratio. Specifically, it was observed that the lift-to-drag ratio increases when the propeller is positioned higher than the wing.

• Journal of the Korean earth science society
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• v.44 no.3
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• pp.196-209
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• 2023

The Nishinoshima volcano, located 940 km south of Tokyo, experienced an eruption from June to August 2020. The volcanic gas and ash from the eruption of Nishinoshima that occurred at the end of July 2020 was reported to have the potential to affect the Korean Peninsula. In this study, we used Ash3D, a numerical simulation program for volcanic ash dispersion, to investigate the eruption that occurred at 0:00 local time on July 28, 2020, with a volcanic explosivity index of three. The results showed that the volcanic ash cloud reached Okinawa on the morning of July 30, carried by an east wind. It then moved northward and reached Jeju Island on August 1, eventually circulating in a clockwise direction and reaching southern part of the Korean Peninsula on August 2. The concentration of Particulate Matter 10 (PM₁₀), measured at the Jeju Gosan Meteorological Observatory in Jeju Island, increase from August 1. A similar increase in PM₁₀ concentration was observed at the Gudeok Mountain Weather Station in Busan from August 2. These findings suggested that eruption of the Nishinoshima volcano had an impact on the fine dust concentrations at Jeju Island and southern part of the Korean Peninsula.

• Journal of Ginseng Culture
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• v.6
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• pp.105-115
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• 2024

Wild ginseng, grown in undisturbed forest environments, has been maintained for centuriesthrough human intervention and knowledge, leading to the development of current ginseng agriculture. The practice of ginseng farming has long been established in various regions of Korea. However, the ginseng farming specifically in Geumsan was recognized as a Globally Important Agricultural Heritage System (GIAHS) by the Food and Agriculture Organization of the United Nations (FAO) in 2018. This designation was granted after a thorough evaluation, which confirmed that Geumsan's ginseng farming met the necessary criteria, including historical importance, traditional knowledge system, agrobiodiversity, and agricultural landscape. Traditional ginseng farming in Geumsan practices the 'rotating agriculture system', a sustainable land use approach that has been developed over several cycles of long duration (10-15 years). It contains the knowledge to choose locations for cultivation that prioritize the direction of sunlight and wind circulation. Furthermore, it received significant recognition for its agricultural heritage value based on its maintenance of several traditional knowledge systems, including ancestral wisdom and knowledge regarding pre-planting field management techniques. As of December 2023, there are currently 86 locations in 26 nations that have been designated as GIAHS. Among these sites, Geumsan stands out as the first and only site in the world specifically recognized for the cultivation of ginseng crops. This historical record serves as a significant reminder of Korea's prominent position as a major producer of ginseng on a global level. This article first provides an overview of the concept of agricultural heritage, the designation criteria, and the status of the designation. It then identifies, among the GIAHS designation criteria, the agricultural heritage value of traditional ginseng farming in the Geumsan region from the perspective of local traditional knowledge systems.

• Korean Journal of Soil Science and Fertilizer
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• v.6 no.2
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• pp.115-127
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• 1973

Leaf discoloration of IR667 lines (tropical) and leading locals (temperate) in fields was classified according to the probable causes and nutritional disorder due to soil reduction in 1972 was investigated. 1. The causes of leaf discoloration in IR667 were low air temperature, soil reduction, seed born, insect bite, nitrogen depression, overdose pesticide, strong wind, early senescence and unknown one. 2. Leaf discoloration due to soil reduction which has been called Sageumbyeong by famers, was caused by the heavy application of $Ca(OH)_2$, compost and poor drainage followed by Zn and K deficiency and Fe toxicity. 3. About 30 days after transplanting deficiency concentration of K and Zn in leaf blade appears to be less than 2.0% and 20ppm respectively, and greater than 200ppm, 500ppm, and 1.0% respectively for toxicity or excess of Fe, Mn and Ca. and in the shoot 2.4% for K, 30ppm for Zn and 800ppm for Fe. The value of K/Ca should be greaterthan 2.0 for health. 4. When plants were damaged by soil reduction the contents of N, P, Ca, Mg, Fe, Mn, Na in shoot were increased and those of K, Zn, Si were decreased. 5. IR667 lines show in shoot higher content of N, P, Ca, Mg, Si, Na, and lower content K, Zn, Fe, Mn and lower root activity than local leading varietles in either healthy or disieased case, indicating IR667 lines are likely more suseptible to soil reduction damage. 6. Normal soil was less than 6.5 of pH and greater than -50 mv of Eh, but pH of problem soil was ranged from 6.7 to 7.4 and Eh from -100 to -190. 7. The root activity (${\alpha}$-naphthylamine oxidation) decreased at early stage of soil redudtion damage, then increased with severity and at the end it decreased again, but IR667 lines showed always lower root activity than local ones.