• 한국농공학회논문집
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• 제56권1호
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• pp.41-49
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• 2014

Pig chronic wasting disease, including porcine reproductive and respiratory syndrome (PRRS) and postweaning multisystemic wasting syndrome (PMWS), have made a continuous economic damage in pig farms. Airborne spread of livestock viruses are an important spread factor which is difficult to analyze due to invisible airflow and limitation of measurement. The objective of this study is to analyze airborne disease spread between buildings in the experimental pig farm by means of field experiment and computational fluid dynamics (CFD). The field experiments were conducted to capture airborne virus using air sampler and teflon filter along multi points in the experimental pig farm. The samples were tested in terms of virus detection resulting in positive reaction for PRRS and PCV-2 viruses, which can be a firm evidence of airborne virus spread. The CFD simulation model was developed by considering complex topography, wind conditions, building arrangement, and ventilation systems and was used to analyze airborne virus spread according to different wind conditions. The CFD computed result showed a possibility of airborne virus spread via livestock aerosol from infected pig house to neighboring pig houses according to wind directions. The CFD simulation technique is expected to provide significant data for estimating and making a counterplan against airborne disease spread.

• Journal of Korean Society for Atmospheric Environment
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• 제21권E3호
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• pp.107-113
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• 2005

Using a sampling device of our own making, airborne pollen has been monitored in Kyoto, Japan from the middle of February to the end of May 2004. From the morphological analysis of pollen grains by Scanning Electron Microscope (SEM), it was possible to identify some pollen types like Cryptomeria, Pine, Alder, Cyclobalanopsis, Chamaecyparis, and Equisetum. Daily average airborne pollen counts show strong variations from the day to day which makes the appropriate daily forecasts that could be of practical use for patients difficult. Diurnal variation of airborne pollen grains at our local sampling site is very irregular and shows no similarity between pollen types. The highest concentrations of Cryptomeria and Alder pollens in the south -west wind directions might be attributed to the airborne pollen transport, while the increase in Pine pollen grain in the southern wind direction was probably due to the local spread. Prevailing wind direction (SW) during the pollinating periods of Cryptomeria and Alder pollens could suggest a long-distance transport from a distant mountain.

• 한국정밀공학회지
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• 제28권2호
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• pp.226-232
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• 2011

In this study, an optimized design of a triaxial load cell has been developed by the use of finite element analysis, design of experiment and response surface method. The developed optimal design was further validated by both stress-strain analysis and natural vibration analysis under an applied load of 30 kgf. When vertical, horizontal, and axial loads of 30 kgf were applied to the load cell with the optimal design, the calculated strains were satisfied with the required strain range of $500{\times}10^{-6}{\pm}10%$. The natural vibration analysis exhibited that the fundamental natural frequency of the optimally designed load cell was 5.56 kHz and higher enough than a maximum frequency of 0.17 kHz which can be applied to the load cell for wind-tunnel tests. The satisfactory sensitivity in all triaxial directions also suggests that the currently proposed design of the triaxial load cell enables accurate measurements of the multi-axial forces in wind-tunnel tests.

• Wind and Structures
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• 제6권5호
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• pp.325-346
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• 2003

High-sided road vehicles are susceptible to a sharp-edged crosswind gust, which may cause vehicle accidents such as overturning, excessive sideslip, or exaggerated rotation. This paper thus investigates the dynamic behaviour and possible accidents of high-sided road vehicles entering a sharp-edged crosswind gust with road surface roughness and vehicle suspension included. The high-sided road vehicle is modelled as a combination of several rigid bodies connected by a series of springs and dampers in both vertical and lateral directions. The random roughness of road surface is generated from power spectral density functions for various road conditions. The empirical formulae derived from wind tunnel test results are employed to determine aerodynamic forces and moments acting on the vehicle. After the governing equations of motion are established, an extensive computation work is performed to examine the effects of road surface roughness and vehicle suspension on the dynamic behaviour and vehicle accidents. It is demonstrated that for the high-sided road vehicle and wind forces specified in the computation, the accident vehicle speed of the road vehicle running on the road of average condition is relatively smaller than that running on the road of very good condition for a given crosswind gust. The vehicle suspension system should be taken into consideration, and the accident vehicle speed becomes smaller if the vehicle suspension system has softer springs and lighter dampers.

• 천문학회보
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• 제43권1호
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• pp.63.4-64
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• 2018

High resolution spectroscopy of the yellow symbiotic star AG Draconis is performed with the Canada-France-Hawaii Telescope to analyse the line profiles of Raman scattered O VI broad emission features at $6825{\AA}$ and $7082{\AA}$ with a view to investigating the wind accretion process from the mass losing giant to the white dwarf. These two spectral features are formed through inelastic scattering of O $VI{\lambda}{\lambda}32$ and 1038 with atomic hydrogen. We find that these features exhibit double-component profiles with red parts stronger than blue ones with the velocity separation of ~ 60 km s-1 in the O VI velocity space. Monte Carlo simulations for O VI line radiative transfer are performed by assuming that the O VI emission region constitutes a part of the accretion flow around the white dwarf and that Raman O VI features are formed in the neutral part of the slow stellar wind from the giant companion. The overall Raman O VI profiles are reasonably fit with an azimuthally asymmetric accretion flow and the mass loss rate ~ 4 ${\times}$ 10^{-7} M_sun yr^{-1}. We also find that additional bipolar neutral regions moving away with a speed ~ 70 km s^{-1} in the directions perpendicular to the orbital plane provide considerably improved fit to the red wing parts of Raman features.

• 한국대기환경학회지
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• 제10권4호
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• pp.260-280
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• 1994

The STEM II(Sulfur Transport Eulerian Model II) was adapted to simulate transport/ chemistry/deposition of air Pollutants in the Eastern China and Korea. A 32 hour model simulation starting from 9 A.M. of 1989 November 25 during which no preciptation was observed. The Prevailing wind direction is from west to east. The MM4(Meteorological Model Version 4) was used to generate meteorological data such as temperatures, horizontal wind velocities and directions, humidities, air densities. Eddy diffusivities, dry deposition velocities and vertical wind velocities were calculated from the meteorological data. The initial condition and the emission data base were constructed from the measurements and governmental reports respectively. The model predictions of NO, NO$_2$, SO$_2$, $O_3$ at Seoul, Inchon and Pusan agree reasonably well with measurements. The model's predictability for the primary air pollutants is improved considerably as the time passes. Thus, it is concluded that the model's predictability can be significantly enhanced by reducing the uncertainties of initial conditions.

• 한국해양공학회지
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• 제38권2호
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• pp.74-85
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• 2024

Offshore wind turbines are supported by various foundations, each with its considerations in design and construction. Gravity, monopile, and suction bucket foundations encounter geotechnical issues, while jacket and tripod foundations face fatigue problems. Considering this, a gravity foundation based on a steel skirt was developed, and a monopile foundation was analyzed for Pile-Soil Interaction using the p-y curve and 3D finite element method (3D FEM). In addition, for suction bucket foundations, the effects of lateral and vertical loads were analyzed using 3D FEM and centrifuge tests. Fatigue analysis for jacket and tripod foundations was conducted using a hotspot stress approach. Some hybrid foundations and shape optimization techniques that change the shape to complement the problems of each foundation described above were assessed. Hybrid foundations could increase lateral resistance compared to existing foundations because of the combined appendages, and optimization techniques could reduce costs by maximizing the efficiency of the structure or by reducing costs and weight. This paper presents the characteristics and research directions of the foundation through various studies on the foundation. In addition, the optimal design method is presented by explaining the problems of the foundation and suggesting ways to supplement them.

• 한국환경과학회지
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• 제23권2호
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• pp.207-218
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• 2014

A ventilation model was developed for predicting the air change per hour(ACH) in buildings and the airflow rates between zones of a multi-room building. In this model, the important parameters used in the calculation of airflow are wind velocity, wind direction, terrain effect, shielding effect by surrounding buildings, the effect of the window type and insect screening, etc. Also, the resulting set of mass balance equations required for the process of calculation of airflow rates are solved using a Conte-De Boor method. When this model was applied to the building which had been tested by Chandra et al.(1983), the comparison of predicted results by this study with measured results by Chandra et al. indicated that their variations were within -10%~+12%. Also, this model was applied to a building with five zones. As a result, when the wind velocity and direction did not change, terrain characteristics influenced the largest and window types influenced the least on building ventilation among terrain characteristics, local shieldings, and window types. Except for easterly and westerly winds, the ACH increased depending on wind velocity. The wind direction had influence on the airflow rates and directions through openings in building. Thus, this model can be available for predicting the airflow rates within buildings, and the results of this study can be useful for the quantification of airflow that is essential to the research of indoor air quality(temperature, humidity, or contaminant concentration) as well as to the design of building with high energy efficiency.

• 한국대기환경학회지
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• 제18권2호
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• pp.95-112
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• 2002

A precision analysis was conducted for the quantification of trace metal levels in airborne particulates using ICP-MS. According to our study the quantitative analysis using Whatman grade 41 filters produces more precise and representative values of metal concentrations than that using EPM 2000 filters. The mean concentration of PM 10 analyzed during 1998 ~ 2000 was 82 $\mu$g/m$^3$. The concentrations of human carcinogens such as As and Cr were 8.65 and 25.87 ng/m$^3$, respectively, while those of probable human carcinogens such as Cd and Pb were 3.13 and 219.46 ng/m$^3$, respectively. Time-weighted mean concentration, calculated using surface wind speed and direction, indicated that there were differences between metals of crustal origin and metals of anthropogenic origin. The rectorial concentrations of anthropogenic metals and PM 10 were higher for north -west sector with calm or low wind speed conditions than for any other sector with high wind speed conditions. On the contrary, the rectorial concentrations of crustal metals were high with high wind speed. In addition, the sectorial concentrations of crustal metals were more affected by south-west wind directions, which were compared with those of anthropogenic metals. The enrichment factor (EF) values of many anthropogenic metals were higher than 50, while those of crustal metals were lower than 3, respectively. The concentrations of Cr and Ni in Daejeon industrial complex area were 11 times higher than those in the background site of Kuopio in Finland, while that of Pb in the complex area was 22 times higher, respectively.

• 대기
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• 제26권3호
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• pp.423-433
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• 2016

In this study, performance of a computational fluid dynamics (CFD) model is assessed from analysis on air flow pattern which is observed in the artificial street canyon. Field observations focusing on flows were conducted at an artificial street canyon in Magok region. For the observation of three-dimensional airflow structures, twelve three-dimensional wind anemometers (hereafter, CSAT3) were installed inside the street canyon. The street canyon was composed of two rectangular buildings with 35-m length, 4-m width, and 7-m height. The street width (distance between the buildings) is 7 m, making the street aspect ratio (defined by the ratio of building height to street width) of 1. For the observation of above-building wind, a CSAT3 was installed above the northwest-side building. Southwesterly, westerly and northwesterly were dominant in the street canyon during the observations. Because wind direction is parallel to the street canyon in the southwesterly case, westerly and northwesterly were selected as inflow directions in numerical simulations using a computational fluid dynamics model developed through the collaborative research project between National Institute of Meteorological Sciences and Seoul National University (CFD_NIMR_SNU). The observations showed that a well-structured vortex flow (skimming flow) and an evidence of a small eddy at the corner of the downwind building and ground appeared. The CFD_NIMR_SNU reproduced both the observed flow patterns reasonably well, although wind speeds inside the street canyon were underestimated.