• Journal of Korean Society of Water and Wastewater
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• v.18 no.3
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• pp.357-365
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• 2004

Effect of artificial circulation on amelioration of water quality in Yeoncho Lake was analyzed using summer data between 1991-2002. Two sites, intake tower area where aeration systems are concentrated in and near the inlet of reservoir were selected for comparison in this study. Summer averages between may and september Showed that aeration system might be beneficial in the improvement of water quality of BOD5, COD, and TN while Chl-a concentration and transparency did show opposite pattems. Wilcoxon's singed rank test for matched pair indicated slight increase of BOD5 and COD concentrations in the vicinity of intake tower while other variables did not show any significant differences from data of inlet of reservoir. During the study, it was found that the following subjects need to be investigated for more detailed analysis. 1) Dynamic pollutant loading from outside and inside the lake, 2) Biological, Chemical and Physical lake data when aeration systems are in and not in operation and 3) Radius of influence of aeration system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1282-1289
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• 2003

Transport of a scalar quantity, such as chemical concentration or temperature, is important in many engineering applications and environmental flows. Here we report on results obtained from the large eddy simulations of flow and concentration fields inside the tank performed using a spectral multi-domain technique. The computations were driven by specifying the impeller-induced flow at the blade tip radius (Yoon et al.). This study focused on the concentration development at different molecular diffusivities in a stirred tank operated under turbulent conditions. The main objective of the work presented here is to study the large-scale mixing structure at different molecular diffusivities in a stirred tank by using the large eddy simulation. The time sequence of concentration and flow fields shows the flow dependency of the concentration development. The presence of spatial inhomogenieties is detailed by observing the time variation oflocal concentration at different positions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1290-1298
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• 2003

The stirred tank reactor is one of the most commonly used devices in industry for achieving mixing and reaction. Here we report on results obtained from the large eddy simulations of flow inside the tank performed using a spectral multi-domain technique. The computations were driven by specifying the impeller-induced flow at the blade tip radius. Stereoscopic PlY measurements (Hill et al. $^{(1)}$) along with the theoretical model of the impeller-induced flow (Yoon et al. $^{(2)}$) were used in defining the impeller-induced flow as superposition of circumferential, jet and tip vortex pair components. Large eddy simulation of flow in a stirred tank was carried out for the three different Reynolds numbers of 4000, 16000 and 64000. The effect of different Reynolds numbers is well observed in both instantaneous and time averaged flow fields. The instantaneous and mean vortex structures are identified by plotting an isosurfaces of swirling strength for all Reynolds numbers. The Reynolds number dependency of the non-dimensional eddy viscosity, resolved scale and subgrid scale dissipations is clearly shown in this study.

• International Journal of Fluid Machinery and Systems
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• v.10 no.1
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• pp.76-85
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• 2017

Wall pressure measurements and flow visualization were conducted for a 90 degree elbow with an axis curvature radius the same as its inner diameter (125 mm). Reynolds numbers 320,000 and 500,000, based on the inner diameter and bulk velocity, were examined. A deflected inflow, having an almost constant velocity slope and a faster velocity at the inside, was introduced. Ensemble averaged pressure distributions showed that no difference of normalized pressure could be found in both the Reynolds number cases. Power spectral density functions of pressures exhibited that the fluctuation having the Strouhal number (based on the inner diameter and bulk velocity) of 0.6 existed in the downstream region of the elbow, which was 0.1 larger than that of the uniform inflow case [1]. Results of numerical calculations qualitatively coincided with the experimental ones.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.478-485
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• 2003

Today, although there have been high technical developments of a compressor in the respect of its capacity, it has been so hard to develop in the respect of vibration and noise because mechanical structure of it has originally numerous vibration and noise. However, if we can grasp the point of systematic phenomena of vibration and noise through the understanding of dynamic characteristics in mechanical equipment, it may be possible to consider countermeasures. In this study about a reciprocal compressor, the part of its machinery is modeled as rigid body, and the part of its spring is modeled as flexible body, and then they are analyzed by DADS. Each rigid body and spring are connected with joint torque of a motor is applied to shaft, and pressure is applied to a piston so that a compressor can be revolved. Based on this modeling, influence of a compressor's vibration is analyzed through changes of offset, connecting rod and crank radius In the case of weight balance, it I produced after re-design, and then changes of vibration of a compressor's inside are checked through experiments. These analysis data may help set measures of reducing vibration of a reciprocal compressor.

• Magazine of the Korean Society of Agricultural Engineers
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• v.31 no.1
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• pp.58-70
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• 1989

The paper compared the Bishop methed to the Fellenius method in the analysis of slope stability. Laboratory model test was carried out in the case of seepage flow considered. The results obtained from this study were summarized as follows; 1. The slice pieces of 10 were enough to analysis the slope stability. 2. The safety factor. by the Fellenius method was lower than the Bishop method by the 96 to 97% in the case of no seepage flow and by the 95 to 96% in the case of seepage flow considered. 3. Besides the parameter of soil and slope, the safety factor of slope was influenced by the height of slope. This phenomena was distinct in the height of height less than 10 meters. 4. In the case of clay, there was no difference in the safety factor of slope between Fellenius and Bishop rnethod. The safety factors of slope with the seepage flow considered were lower than those with no see-page flow. 5. The influence of cohesion on the safety factor was more significant in the Bishop method than in the Fellenius method. 6. The slope failure of model test of A and B soil samples with high permeability coefficient was taken place slightly in vicinity of toe by the concentration of stress and gradually increased 7. Under condition of same slope height, the shapper the slope, the shorter the radius and the center of critical circle appered downward and finally failure of slope occured inside the slope.

• Journal of The Korean Astronomical Society
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• v.40 no.1
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• pp.9-16
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• 2007

We examine the morphology and luminosity distribution of a strongly warped spiral galaxy PGC 20348 by conducting a detailed BVI CCD surface photometry using BOAO 1.8m telescope. The radial surface brightness shows a break at warp radius $(r_{\omega})$ with a shallow gradient in the inner disk and a steeper gradient in the outer disk. The luminosity of east side of the disk is ${\sim}0.5$ mag fainter than the west side at r > $r_{\omega}$. The reason for the asymmetric luminosity distribution is thought to be the asymmetric flarings that result in the formation of a large diffuse region at the edge of the east disk and a smaller diffuse region at the west disk. The vertical luminosity profiles show a thick disk component whose scale heights increase with increasing galactocentric distances. The warp of PGC 20348 seems to be made by the tidal interactions with the two massive companion galaxies since the flarings and radial increase of disk scale heights are thought to be general properties of tidally perturbed disks. According to the colors of the two clumps inside the diffuse region at the edge of the east disk, they seem to be sites of active star formation triggered by tidal forces from the companion galaxies.

• Journal of The Korean Digital Architecture Interior Association
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• v.10 no.1
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• pp.15-22
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• 2010

As for structural system, which constitutes his construction, there are column inside dimension and span which constitutes plane, and as for constructions for section, there are C.H and slab, and as for constructive factors for envelope, there are window and closing panel of outer wall, and as for opening, there are punching window and wave window. With these constructive parts and opening of envelope, his construction composes volume and mass. The relation of structure and modulor which are shown in his later construction can be divided in two cases that modulor is directly and indirectly adapted for rate and measure calculation of the constructive body. As for indirectly adapted case, we can find it form most of his later construction, it is living place in which human beings life is, and it is adapted mainly for small space. In his construction, he tried to tell human scale and sense of musical rhythm through modulor. In other words, he played sense of space and musical scale by adapting regular and repetitive modulor of opening, and in small space for daily life, he made the size of space into the space which human can perceive. And, if we interpret mudulor in modern meaning, it is an establishment of radius of human act. And, we can make organic and harmonic design of space if we use modulor as origin of human centered measurement calculation, and if we adapt space after dividing by use.

• Korean Journal of Optics and Photonics
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• v.12 no.4
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• pp.289-293
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• 2001

A metal capillary splice fiber-optic sensor was fabricated for use as an intensity-based macro-bending sensor. As the radius of curvature due to the macro-bending decreases, the angular misalignment of the fiber ends inside the metal capillary increases, i.e., the coupling efficiency of the fiber splice is reduced. Thus, macro-bending can be detected by the measurement of the reduction of transmitted power. The detectable range of macro-bending. was measured approximately from 20 mm to 85 mm. The center wavelengths of the fiber Bragg gratings are 1543.3 nm and 1549.5 nm, respectively. The maximum bending loss of this sensor was measured about -11.92 dB. Using this metal capillary spliced fiber sensor and fiber Bragg gratings, macro-bending detection has been demonstrated, and it is shown to have potential for multi-point macro-bending sensors. nsors.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.11a
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• pp.267-270
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• 2017

As IT technology developed, storage media also developed. Among them, USB, which is a removable storage medium, is used not only to have several per person but also to work in various companies. Users store valuable and confidential data within USB. As time went on, the need for security increased. In order to solve this security problem, USB has been introduced to allow users to access internal files by inputting ID and password by embedding a security program in USB. However, the method of storing ID and Password inside is low confidentiality and high risk of information leakage. To solve these problems, we propose a 2 factor authentication system using Radius server in addition to login authentication. The proposed system not only improves the authenticity of the device, but also reduces the risk of infringement of personal information when lost. It also encrypts internal files to increase the confidentiality of internal information.