• Journal of the Korean Solar Energy Society
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• v.23 no.2
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• pp.21-34
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• 2003

This study aims to present the applicability of wind turbine generator system to urban buildings for the utilization of clean renewable energy. The results are as follows; According to the wind resource analysis, it has been found that small sized wind power system can be viable for buildings application due to the amplification of wind velocity around buildings or building clusters, in spite of low mean velocity of 2-3m/s in Seoul and Kyunggi urban areas. But planners must perform micrositing analysis around building so that wind turbine can be located at high velocity zones. The system must be designed to avoid obstacles preventing prevailing wind in buildings. It should be recognized that wind speeds are changing depending on the height and length from buildings. The wind power system can be used as a symbol of landmark which shows a sustainable architecture from the scenary Itself A case study for apartment building in urban showed that wind power systems can be applicable in two kinds of place, rooftops and ground levels. Especially, the wind power systems must be carefully positioned so that wind resources do not decrease when it is installed at ground levels. and according to life cycle cost analysis, adaption of new small win4 power systems to buildings were proved to produce a profit if it is considered the expense of environment improvement and the wind speed increasing according to rise of building height. This research will ultimately achieve green architecture that preserves nature and at the same time provides pleasant environment to humans, and will play a great role in establishing the environment-preserving sustainable architecture of the 21th century.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.924-932
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• 1992

This paper presents the results of an experimental study on the characteristics of the vortex- induced vibration of an elastically supported circular cylinder in the cross air flow. For a range of velocities, power spectral densities of the signals from a hot-wire anemometer placed in the wake of an oscillating circular cylinder and gap sensors placed in the both ends of a circular cylinder were obtained to determine vortex-shedding frequencies, natural frequencies and vibrating frequencies of a cylinder. The effects of slots in the test section on vortex shedding and cylinder oscillation were investigated. The present study covered the reduced velocity range 1.0 .leg. Ur .leg. 64.6. The response characteristics of the cylinder has been shown to vary extensively, depending on the slots in the test section as well as on the reduced velocity. For an elastically supported cylinder, a purely translation mode oscillation was observed at a low velocity, however a rotation mode oscillation was often superposed for higher velocities. These two oscillating frequencies were equal to their natural frequencies irrespective of the changes of free stream velocities.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.10
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• pp.1327-1333
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• 2018

Numerical analysis has the advantage that no actual flow pathways need to be formulated, making this technique especially useful for simulation analysis such as pathway design. However, it does require that the complete physical parameters of the fluid and the complete boundary conditions be known. If any of them are unknown, either the calculation will become impossible, or even if the calculation does converge, the reliability of the result will be low. Therefore, a means of more accurate acquisition of flow information is required. In this paper, we present techniques for estimating flow field from a constraint equation for image information and velocity field, based on the image intensity changes accompanying the motion of dye in waterway. In the equation, we entered a stabilizing term to suppress estimation error. We show the effectiveness of our method through experiments with generated and real images of a Karman vortex.

• Earthquakes and Structures
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• v.17 no.5
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• pp.511-519
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• 2019

The concrete gravity dam is one of the most important parts of the nation's infrastructure. Besides the benefits, the dam also has some potentially catastrophic disasters related to the life of citizens directly. During the lifetime of service, some degradations in a dam may occur as consequences of operating conditions, environmental aspects and deterioration in materials from natural causes, especially from dynamic loads. Cumulative Absolute Velocity (CAV) plays a key role to assess the operational condition of a structure under seismic hazard. In previous researches, CAV is normally used in Nuclear Power Plant (NPP) fields, but there are no particular criteria or studies that have been made on dam structure. This paper presents a method to calculate the limitation of CAV for the Bohyeonsan Dam in Korea, where the critical Peak Ground Acceleration (PGA) is estimated from twelve sets of selected earthquakes based on High Confidence of Low Probability of Failure (HCLPF). HCLPF point denotes 5% damage probability with 95% confidence level in the fragility curve, and the corresponding PGA expresses the crucial acceleration of this dam. For determining the status of the dam, a 2D finite element model is simulated by ABAQUS. At first, the dam's parameters are optimized by the Minitab tool using the method of Central Composite Design (CCD) for increasing model reliability. Then the Response Surface Methodology (RSM) is used for updating the model and the optimization is implemented from the selected model parameters. Finally, the recorded response of the concrete gravity dam is compared against the results obtained from solving the numerical model for identifying the physical condition of the structure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.5
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• pp.587-594
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• 2019

This study experimentally investigated the effects of high and low densities of vegetation patches on the flow characteristics in a stream-scale outdoor experimental channel with rooted willows. Stream-scale experiments on vegetated flows were carried out for an emergent condition of vegetation. Vegetation patches were arranged by alternate bar formation and the flows in vegetated and non-vegetated sections were compared. Three-dimensional flow structure was measured by ADV (Acoustic Doppler Velocimeter) and the vertical distributions of longitudinal velocity were mainly analyzed from the measurements at various points. Flow velocities show different patterns depending on the density of vegetation patches. The difference in flow velocity between in the vegetated and non-vegetated sections appear to large in the dense patches and the flow becomes complicated at the downstream edge of the patch. Despite the upstream flow disturbed by the first patch, the flows over the second patch show the similar pattern.

• Advances in nano research
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• v.10 no.5
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• pp.415-422
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• 2021

Silicene, a 2D allotrope of silicon, is predicted to be a potential material for future transistor that might be compatible with present silicon fabrication technology. Similar to graphene, silicene exhibits the honeycomb lattice structure. Consequently, silicene is a semimetallic material, preventing its application as a field-effect transistor. Therefore, this work proposes the uniform doping bandgap engineering technique to obtain the n-type silicene nanosheet. By applying nearest neighbour tight-binding approach and parabolic band assumption, the analytical modelling equations for band structure, density of states, electrons and holes concentrations, intrinsic electrons velocity, and ideal ballistic current transport characteristics are computed. All simulations are done by using MATLAB. The results show that a bandgap of 0.66 eV has been induced in uniformly doped silicene with phosphorus (PSi₃NW) in the zigzag direction. Moreover, the relationships between intrinsic velocity to different temperatures and carrier concentration are further studied in this paper. The results show that the ballistic carrier velocity of PSi₃NW is independent on temperature within the degenerate regime. In addition, an ideal room temperature subthreshold swing of 60 mV/dec is extracted from ballistic current-voltage transfer characteristics. In conclusion, the PSi₃NW is a potential nanomaterial for future electronics applications, particularly in the digital switching applications.

• Journal of Korean Society on Water Environment
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• v.27 no.1
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• pp.36-43
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• 2011

This study is selected two points of combined sewer that occurred Fish Kill after first flush, that analyzed generation of pollutants and stream runoff generation of combined sewer overflows (CSOs) as fine weather and rainfall. In addition, this study was to analyze the relationship between CSOs and sediments, to propose measures to reduce the sediment relevant with CSOs and rainfall runoff from entering sewage treatment plants and measures for discharged directly into streams when indicate relatively good water quality after overflow. Sediments in combined sewer system was discharged about 50~80% as overflows during rainfall and we can reduce the amount of the CSOs at least 50% or more if the sewer does not exist in the sediments because of the amount of discharge about the amount of intercept has been investigated by 3~5 times. Because of velocity at sediment interval in sewer is very low, sewage velocity of about 3~5 times as much as it can increase the amount of sediment can be reduced if the separation wall is installed. Effective control of BOD overflow load is respectively 77.5%, 75.8% at first point, second point by the separation wall is installed. Drainage area greater than area in this study or many combined sewer overflows region is increased the more effective control of separation wall. Turbidity to measure changes in water quality of overflows can be used as an factor to control the intercept flows because the intercept flows(3Q) after the first flush has lowered removal efficiency and increases the operational load of sewage treatment plants. Sewage water quality after a overflow when the reasonable turbidity was measured at this point flows to excluded intercept flow(1Q) can be discharged to stream.

• Korean Journal of Applied Biomechanics
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• v.32 no.3
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• pp.103-110
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• 2022

Objective: The aim of this study was to investigate effect of core stabilization exercises on the erector spinae contractile properties and trunk isokinetic muscle function of middle age with low physical activity and sedentary lifestyle. Method: Twenty (female: n=10, male: n=10) middle-age subjects (age: 37.25 ± 6.08 years, height: 168.01 ± 6.84 cm, weight: 71.37 ± 11.75 kg) participated in this study. Tensiomyography was measured on the erector spinae, and the isokinetic trunk muscle function test was measured at an angular velocity of 60 °/s and 90 °/s. All subjects performed the core stabilization exercises for 60 min per day, 3 times a week, for 7 weeks. A paired t-test was performed with a significance level of 0.05. Results: Tensiomyography of the erector spinae revealed a significant post-exercise increase in the maximum radial displacement (p < .05) and velocity of contraction (p < .05), however, there wasn't a significant post-exercise change in the contraction time. Additionally, the isokinetic muscle function test of the trunk revealed a significant post-exercise increase in trunk extensor relative strength (p < .05) and strength ratio (p < .05). Conclusion: Our results indicated that core stabilization exercises reduced erector spinae muscle stiffness, increased the velocity of erector spinae contraction. Additionally, data showed the improvement in the trunk extensor strength help induce a more balanced development in trunk muscle.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.45-50
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• 2023

Microfluidic preconcentration technologies, which collect or extract low-abundance analytes in a specific location, have been spotlighted in various applications such as medical and bio-engineering. Here, we conducted extensive studies on the variables to be considered when concentrating target samples based on electrophoresis in an electromembrane system utilizing an ion exchange membrane. Using negatively charged Alexa Fluor 488 and positively charged Rhodamine 6G as fluorescent dyes, we examined the effects of flow velocity of the main channel, channel electrolyte concentration, and applied voltage on sample preconcentration. As a result, it was found that the preconcentration of the target sample occurs much better when the flow velocity is slow and the concentration of the main channel containing the sample is high, given that the channel concentration ratio (main and buffer) is constant. In addition, based on the experimental data acquired in this study, the electrophoretic mobility values of Alexa Fluor 488 and Rhodamine 6G were experimentally calculated and compared.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.77.3-77.3
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• 2019

We present an analysis of the stellar population of compact elliptical galaxies (cEs) in various environments. Following conventional selection criteria of cEs, we created a list of cE candidates in the redshift range of z < 0.05 using SDSS DR12 catalog. We finally selected cEs with low-luminosity (Mg > 18.7 mag), small effective radius (Re < 600 pc), and high velocity dispersion (> 60 kms-1). We divide our cE sample into those inside and outside of the one virial radius of the bright (Mr < -21 mag) nearby host galaxy which is then defined as cEs with (cEw) and without (cEw/o) host galaxy, respectively. We investigated the stellar population properties of cEs based on the Hb, Mgb, Fe 5270, and Fe 5335 line strengths from the OSSY catalog. We found that cEw has a systematically higher metallicity than cEw/o. In the velocity dispersion-Mgb distribution, while cEw/o follows the relation of early-type galaxies, cEw are found to have a systematically higher metallicity than cEw/o at a given velocity dispersion. The different feature in the metallicity between cEw and cEw/o can suggest that two different scenarios can be provided in the formation of cEs. cEw would be the remnant cores of the massive progenitor galaxies that their outer parts have been tidally stripped by massive neighbor galaxies (i.e., nurture origin). On the other hand, cEw/o are likely to be faint-end of early-type galaxies maintaining in-situ evolution (i.e., nurture origin).