• Journal of the Korean Association of Geographic Information Studies
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• v.18 no.3
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• pp.1-10
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• 2015

Rapid urban expansion and densification of the various industrial facilities affect the changes of topography and building in urban areas. Even if buildings proceed with high rise, they get mixed with low-rise buildings such as houses and industrial parks that have existed in the area. This may confuse the designer in estimating a surface roughness, an important factor in calculating the design wind velocity of building. This study analyzed the surface roughness by using a geographic information. Referring to the criteria of each country's building code, this study proposed a method to distinguish the surface roughness depending on the height of the surrounding buildings where the design building is located and calculated the surface roughness using 1:5000 topographic map and GIS. It is expected to solve problems that an existing designer calculates the surface roughness in a subjective manner and to help to design more rational buildings resistant to wind.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.1 s.12
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• pp.15-24
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• 2004

Generally, a ${\pi}$-type girder composed of two I-type girders is known to have a significant disadvantage in wind resistance design because of aerodynamic instability. A representative bridge for this girder was Tacoma Narrows Bridge. Since Tacoma Narrows Bridge had very low stiffness of the bridge structure and its cross-section shape had aerodynamic instability, the bridge collapsed after severe torsion and vibration events in 19m/s wind speed. Aerodynamic vibration can be avoided by enhancing structural stiffness and damping factor and conducting a study of cross-section shapes. This study shows the angle of attack for the four-span cable stayed bridge having ${\pi}$-type cross-section and describes the aerodynamic characteristics of the changed cross-section with aerodynamic vibration damping additions, by carrying out two-dimension vibration tests. As a result of uniform flow and turbulent flow, the study shows that because the basic ${\pi}$-type cross-section alone can have efficient wind resistant stability, there is no need to have additional aerodynamic damping equipment. Since this four 230m-main-span bridge has a large frequency and also has a big stiffness compared to other bridges containing a similar cross-section, it has aerodynamic stability under the design wind speed.

• Journal of the Korea Convergence Society
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• v.11 no.9
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• pp.175-180
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• 2020

In this study, the freight vehicles were modelled and the flow analysis on the existence or non-existence of a cargo container and the wind deflector were carried out. Based on the driving speed of 100 km/hr, at all models A, B and C, the highest flow rate was shown between 58 m/s and 59 m/s at the top of the model shape. All models A, B and C showed the highest pressure of air resistance between 652Pa and 671Pa at the front of the model geometry. The maximum pressure of model A is considered to be the smallest, with the least flow resistance to speed compared to models B and C. Therefore, it can be seen that model A has an advantageous condition for air resistance in terms of fuel costs. Unlike model B which causes the rapid flow resistance at the cargo compartment, model C can be found to flow a little more smoothly on the streamlined wind deflector. So, the flow air at a streamlined shape is considered to be more advantageous in terms of air resistance than at angular shape. By applying the research analysis result on the air flow in driving according to a cargo container and the wind deflector, it is seen that this study is adequate at the practical efficient design and aesthetic convergence.

• Korean Journal of Plant Resources
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• v.27 no.5
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• pp.546-555
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• 2014

The final aim of this study is to develop a biofiltration system integrated with plant vegetation for improving indoor air quality effectively depending on indoor space and characteristics. However, to approach this final goal, several requirements such as constant pressure drops (PDs) and soil moisture contents (SMCs), which influence the capacity design for a proper ventilation rate of biofiltration system, should be satisfied. Thus, this fundamental experiment was carried out to adjust a proper wind speed and to ensure a stabilization of initial SMCs within biofilter for uniform distribution of SMCs and PDs, and for normal plant growth, especially avoiding root stress by wind. Therefore, we designed horizontal biofliter models and manufactured them, and then calculated the ventilation rate, air residence time, and air-liquid ration based on the biofilter depending on three levels of wind speed (1, 2, and $3cm{\cdot}s^{-1}$). The relative humidity (RH) and PD of the humidified air coming out through the soil within the biofilter, and SMC of the soil and plant growth parameters of lettuce and duffy fern grown within biofilter were measured depending on the three levels of wind speed. As a result of wind speed test, $3{\cdot}sec^{-1}$ was suitable to keep up a proper RH, SMC, and plant growth. Thus, the next experiment was set up to be two levels of initial SMCs (low and high initial SMC, 18.5 and 28.7%) within each biofilter operated and a non-biofiltered control (initial SMC, 29.7%) on the same wind speed ($3cm{\cdot}sec^{-1}$), and measured on the RH and PD of the air coming out through the soil within the biofilter, and SMC of the soil and plant growth parameters of Humata tyermani grown within biofilter. This result was similar to the first results on RHs, SMCs, and PDs keeping up with constant levels, and three SMCs did not show any significant difference on plant growth parameters. However, two biofiltered SMCs enhanced dry weights of the plants slightly than non-biofiltered SMC. Thus, the stability of this biofiler system keeping up major physical factors (SMC and PD) deserved to be adopted for designing an advanced integrated biofilter model in the near future.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.3
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• pp.77-86
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• 2010

In this study, the model of the indirect wind suction waste sorting machine for characteristics of the screening of waste was studied using computational fluid dynamics and the drag coefficient for the model and the suction wind speed were obtained. The wind separator are developing by installing a cyclone air outlet to the suction blower impeller waste is selective in a way that does not pass the features and characteristics of the inlet pipe of the pressure loss and separation efficiency can have a significant impact on. Using Wind separator for selection of waste in the waste prior research on the aerodynamic properties are essential. For plastic cases, it is reasonable to take the drag coefficient between 0.8 and 1.0, and for cans, compression depending on whether the cans, the drag coefficient is in the range from 0.2 to 0.7. The separation efficiency of waste as change suction speed was the highest efficiency when the suction speed was 25~26 m/s. Shape of the inlet, depending on how the transfer pipe of the duct pressure loss occurs because the inlet velocity changes through the appropriate design standards to allow for continued research is needed.

• Journal of Navigation and Port Research
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• v.36 no.10
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• pp.839-844
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• 2012

Anemometer is a meteorological instrument that measures wind direction and wind speed in real time, and is mounted to the cranes that are used at ports, shipbuilding yards, off-shore structure, or construction sites that are influenced by wind, and it is used in conjunction with the safety system. Load cell-type anemometer measures the wind direction through the ratio of load between 4 positions by mounting the thin plate to 4 load cells, and measures wind velocity through the summation of loads. According to previous research, the load ratio between two adjacent windswept with respect to the wind direction has unstable value due to vortex around windswept. This causes the result that increases an error on the wind direction. In this study we compared and analyzed the difference between the load ratio with respect to three type windswept shapes in order to suggest the proper windswept shape to reduce this error. The computational fluid flow analysis is carried out with ANSYS CFX to analyze the load ratio between three windswept shapes. Wind direction was adopted as the design variable, and selected 9 wind direction conditions from $0^{\circ}{\sim}90^{\circ}$ with $11.25^{\circ}$ interval for computational fluid flow analysis.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.4
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• pp.309-316
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• 2020

Waterway design should prioritize appropriate channel width to ensure preferential safe passage for the arrival and departure of vessels. To calculate the minimum channel width required for safe passage a comprehensive review of several factors is required. These factors include vessel maneuverability, determined by vessel size, type and speed; environmental factors such as wind, tide, and wave action; human factors, including personal experience and operator judgment as well as marine traffic and navigation support facilities for decision making. However, the Korean channel width design standard is based only on vessel length, and requires improvement when compared with the standards of PIANC, USA, and Japan. This study aims to estimate the appropriate channel width required for one-way traffic in a straight channel, considering various vessel and environmental factors, using Fast Time Simulation (FTS). When the wind speed is 25 knots, with a current speed of 2 knots and a normal vessel speed of 10 knots FTS shows that a 150K GT Cruise Ship requires a minimum channel width of 0.67-0.91 the vessel length (L), whereas a 120K TEU Container Ship and a 300K DWT VLCC require 0.79-1.17 and 1.02-1.59, respectively. Such results can be used to calculate the minimum channel width required for safe passage as an improved Korean design standard.

• Journal of the Korea Fashion and Costume Design Association
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• v.16 no.1
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• pp.117-123
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• 2014

This paper examined dyeing using sulfur dye with nylon and the characteristics of high gauge knitting for generating high functionality including light weight, wind resistance and elasticity using fine nylon threads. Yarn tension, stitch field and knitting speed of high and fine gauge knitting were measured. The influence of reducing agents on sulfur dye, optimum dyeing conditions and fastness features in nylon dyeing were analyzed. The analysis results are presented below. When nylon (Hyoseong, 40d/34f) and spandex (Hyoseong, 20d) for use as hosiery yarn were used to knit high gauge and flat weave, 44 gauge, the effective knitting conditions were a stitch field over 8.2cm in 1 course length, yarn tension of less than 5g and knitting speed below 18rpm. Nylon dyeing using sulfur dye showed effective results when a rongalite reducing agent was used at more than 10% o.w.f. and dyeing was maintained at $98^{\circ}C$ for 30 minutes. For dyeing nylon and spandex composite using sulfur dye, color fastness in washing, water, daylight and friction were higher than Class 4 or 5, which indicated a superior property. The analysis results verified that the existing problems in nylon dyeing could be solved by using sulfur dyes that don't use heavy metals due to superior fastness and therefore quality, high gauge nylon knit products could be produced.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.1
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• pp.1-9
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• 2014

Structural loading on a wind turbine is due to cyclic loads acting on the blades under turbulence and periodic wind field. The structural loading generates fatigue damage and fatigue failure of the wind turbine. The individual pitch control(IPC) is an efficient control method for reducing structural loading. In this paper, we present an IPC design method using Decentralized LQR(DLQR) and Disturbance accommodating control(DAC). DLQR is used for regulating rotor speed and DAC is used for canceling out disturbances. The performance of the proposed IPC is compared with CPC, which was designed with a gain-scheduled PI controller. We confirm the effect of fatigue load reduction with the use of damage equivalent load(DEL).

• International Journal of Railway
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• v.4 no.4
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• pp.109-115
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• 2011

An analysis and design method for reducing aerodynamic noise in high-speed trains based on biomimetics of noiseless flight of owl is proposed. Five factors related to the morphology of the flight feather have been selected, and the candidate optimal shape of the flight feather is determined. The turbulent flow field analysis demonstrates that the optimal shape leads to diminished vortex formation by causing separation of the flow as well as allowing the fluid to climb up along the surface of the flight feather. To determine the effect of scaling of the owl's flight feather on the noise reduction, a two-fold and a four-fold scaled up model of the feather are constructed, and the numerical simulations are carried out to obtain the aerodynamic noise levels for each scale. Original model is found to reduce the noise level by 10 dBA, while two-fold increase in length dimensions reduces the noise by 12 dBA. Validation of numerical solution using wind tunnel experimental measurements is presented as well.