• Journal of Advanced Navigation Technology
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• v.22 no.6
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• pp.551-556
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• 2018

In recent years, drones have been used to measure aircraft flights data and weather information. Related applications include the measure for low-altitude atmospheric data, the measure for atmospheric fine dust, and the measure for air pollution. However, the mounting position of the atmospheric measurement sensor should be mounted by considering the effects of propeller flow, the EMI effects, and the changes in the weight of the drone. Among these, the upper flow of the propeller affects the wind speed and direction, so the optimal position should be selected. This study deals with the proper height of the atmospheric data measurement sensor. Through the flow analysis, we study the flow characteristics of around a drone and suggest the proper sensor mounting height.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.9
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• pp.207-214
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• 2019

Natural ventilation through openings such as windows in school buildings is an efficient resource for natural cooling during the intermediate season of the year. Because the natural ventilation uses the wind outside the building, the amount of ventilation will depend not only on the wind speed and wind direction but also on the window layout and open window ratio. Therefore, in this study, the natural ventilation plans of school classroom windows are divided into 4 types and 8 cases as shown in Table 1. The characteristics of cooling effect by natural ventilation are simulated by applying Energyplus's Airflow Network Model and the comfort of the occupants is evaluated by the number of hours included in the 80% acceptability range of the ASHRAE Standard 55-2010 adaptive comfort model for the weekdays (Monday-Friday) and the class hours (08: 00-19: 00). Based on the analysis results of the above, this study presents basic data related to classroom cooling plan using intermediate season natural ventilation.

• Korean Journal of Remote Sensing
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• v.31 no.2
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• pp.65-75
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• 2015

In this study, the observation environment of surface wind at an automatic weather station (AWS 288) located at Naei-dong, Mirang-si was analyzed using a computational fluid dynamics (CFD) model and geographic information system (GIS). The 16 cases with different inflow directions were considered before and after construction of an apartment complex around the AWS 288. For three inflow directions (south-south-westerly, south-south-easterly, and north-north-westerly), flow characteristics around the AWS 288 were investigated in detail, focusing on the changes in wind speed and direction at the AWS location. There was marked difference in wind speed between before and after construction of the apartment complex in the south-south-westerly case. In the south-south-easterly and north-north-westerly cases which were frequently observed at the AWS 288, the construction of the apartment complex had no marked influence on the observation of surface wind.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.245-251
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• 2005

When we design coastal and harbol facilities deepwater design wave and wind speed are the important design parameters. Especially, the analysis of these informations is a vital step for the point of disaster prevention. In this study, we made and an extreme value analysis using a series of deep water significant wave data arranged in the 16 direction and supplied by KORDI real-time wave information system ,and the wind data gained from Wan-Do whether Station 1978-2003. The probability distributions considered in this characteristic analysis were the Weibull, the Gumbel, the Log-Pearson Type III, the Normal, the Lognormal, and the Gamma distribution. The parameter for each distribution was estimated by three methods, i.e. the method of moments, the maximum likelihood, and the method of probability weight moments. Furthermore, probability distributions for the extreme data had been selected by using Chi-square and Kolmogorov-Smirnov test within significant level of 5%, i,e. 95% reliance level. From this study we found that Gumbel distribution is the most proper model for the deep water design wave height off the southwest coast of Korea. However the result shows that the proper distribution made for the selected site is varied in each extreme data set.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.20 no.1
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• pp.117-129
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• 2017

This research was conducted to construct a tree belt around Saemangeum reclaimed land using various planting methods and to analyze initial growth amount, to provide practical data to construct tree belt of various purposes. Tree species used in tree belt construction were Pinus thunbergii and Quercus serrata, and the main planting treatment methods used were categorized by existence of windy fence, mixed planting, and un-mixed planting. Growth amount analysis was conducted using ANOVA to compare growth amounts in different experimental groups and Duncan's multiple range test. Growth amount analysis results of tree belt by planting method showed that it is most statistically plausible to install 50% porous windy fence from the direction of wind and frost, followed by planting P. thunbergii and Q. serrata in areas that require mixed tree species tree belt around Saemangeum reclaimed land. In areas where un-mixed planting tree belt is required, it was appropriate to use P. thunbergii alone without a windy fence. Lastly, if the purpose of the tree belt is limited to rapid growth, it was most ideal to plant P. thunbergii alone (without windy fence) or install 50% porous windy fence from the direction of wind and frost, followed by planting P. thunbergii and Q. serrata. This research is based on initial growth amount of tree belt and there is a need for a long-term monitoring of tree belt growth to increase tree-planting success rate in establishing tree belt according to Saemangeum internal development.

• Journal of Astronomy and Space Sciences
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• v.31 no.2
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• pp.149-157
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• 2014

As the prediction of geomagnetic storms is becoming an important and practical problem, conditions in the Earth's magnetosphere have been studied rigorously in terms of those in the interplanetary space. Another approach to space weather forecast is to deal with it as a probabilistic geomagnetic storm forecasting problem. In this study, we carry out detailed statistical analysis of solar wind parameters and geomagnetic indices examining the dependence of the distribution on the solar cycle and annual variations. Our main findings are as follows: (1) The distribution of parameters obtained via the superimposed epoch method follows the Gaussian distribution. (2) When solar activity is at its maximum the mean value of the distribution is shifted to the direction indicating the intense environment. Furthermore, the width of the distribution becomes wider at its maximum than at its minimum so that more extreme case can be expected. (3) The distribution of some certain heliospheric parameters is less sensitive to the phase of the solar cycle and annual variations. (4) The distribution of the eastward component of the interplanetary electric field BV and the solar wind driving function BV2, however, appears to be all dependent on the solar maximum/minimum, the descending/ascending phases of the solar cycle and the equinoxes/solstices. (5) The distribution of the AE index and the Dst index shares statistical features closely with BV and $BV^2$ compared with other heliospheric parameters. In this sense, BV and $BV^2$ are more robust proxies of the geomagnetic storm. We conclude by pointing out that our results allow us to step forward in providing the occurrence probability of geomagnetic storms for space weather and physical modeling.

• Journal of Environmental Science International
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• v.16 no.5
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• pp.583-591
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• 2007

In this study, meteorological characteristics concerning the occurrence of fog are analyzed using 4-years (2000-2003) data at Chuncheon. From the analysis of meteorological characteristics, the fog at Chuncheon occurred before sunrise time and disappeared after that time and lasted for 2-4 hours. When fog occurred, on the whole, wind direction was blew the northerly and wind speed was below 2.1 m/s. Especially, about 42 % of foggy day fell on the calm($0{\sim}0.2m/s$) conditions. The difference between air temperature and dew point temperature near the surface were mainly less than $2^{\circ}C$. For the lack of water surface temperature, the water sur-face temperature was calculated by using Water Quality River Reservoir System (WQRRS). In Chuncheon, there is close correlation between the frequency of fog day and outflow from Soyang reservoir and high frequency of occurrence due to the difference between air and cold outlet water temperature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1281-1289
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• 2011

This paper deals with several statistical distribution functions for the analysis of fatigue life data of composite laminates for small wind-turbine blades. A series of tensile tests was performed on triaxial glass/epoxy laminates for loading directions of $0^{\circ}$, $45^{\circ}$, and $90^{\circ}$. Then, fatigue tests were carried out to determine the fatigue life at the aforementioned loading directions and the fatigue stresses at four levels. Two-parameter Weibull, three-parameter Weibull, normal, and log-normal distributions were used to fit the fatigue life data of the triaxial composite laminates. The three-parameter Weibull distribution most accurately described the fatigue life data measured experimentally for all the cases considered. Furthermore, the variation of fatigue life was simultaneously affected by the loading direction and fatigue stress level.

• Atmosphere
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• v.25 no.4
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• pp.707-718
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• 2015

This study investigates the characteristics of turbulent fluxes observed at Ieodo Ocean Research Station (IORS) in autumn 2014. The 10 Hz IORS data is quality controlled and calculated to be the 30 minutes turbulent fluxes. The quality control consists of five steps: a weather check, Vickers and Mahrt (VM) sequential check, VM parallel check, flag check, and direction check. Since the IORS is an open-sea station with no orographic influence, there are no significant diurnal variations for the turbulent fluxes and 10 m wind speed. According to stabilities, the unstable and semi-unstable states appear more than 28% and 70% in autumn, respectively and they have strong winds of over $10m\;s^{-1}$. In addition, the turbulent fluxes increase with increasing wind speed. In particular, the latent heat flux and its deviations are clearly shown because the latent heat flux is influenced by the change of both the sea surface roughness and wave height induced by the wind. To demonstrate the changes of the turbulent fluxes before and after typhoon, Vongpong (1419), which is the most intense typhoon affecting the Korean Peninsula in 2014, is considered. The turbulent flux fluctuates in accordance with the location of Vongpong. The turbulent fluxes have a large (small) variation when Vongpong approaches (retreats) at the IORS. The overall results represent that the IORS data helps us understand physical processes related to air-sea interaction by providing the valuable and reliable observed data.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.2
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• pp.265-278
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• 2022

The global energy paradigm is rapidly changing by centering on carbon neutrality, and wind energy is positioning itself as a leader in renewable energy-based power sources. The success of onshore and offshore wind energy projects focuses on securing the economic feasibility of the project, which depends on securing high-quality wind resources and optimal arrangement of wind turbines. In the process of constructing the wind farm, the optimal arrangement method of wind turbines considering the main wind direction is important, and this is related to minimizing the wake effect caused by the fluid passing through the structure located on the windward side. The accuracy of the predictability of the wake effect is determined by the wake model and modeling technique that can properly simulate it. Therefore, in this paper, using WindSim, a commercial CFD model, the wake diffusion pattern is analyzed through the sensitivity study of each wake model of the proposed onshore wind farm located in the mountainous complex terrain in South Korea, and it is intended to be used as basic research data for wind energy projects in complex terrain in the future.