• Journal of the Korean Solar Energy Society
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• v.25 no.4
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• pp.133-139
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• 2005

In this paper, the ventilation performance of suspended particulates in indoor side was investigated by step-down method. Experiments were performed in function of mechanical ventilation types and locations of supply and extract air. The type 2 ventilation system shows the highest removal characteristics rather than other 2 types. It means that the displacement ventilation has also good decay rates of concentration compared to mixing ventilation.

• Asian-Australasian Journal of Animal Sciences
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• v.33 no.9
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• pp.1455-1462
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• 2020

Objective: The purpose of this study was to investigate whether goose growth and feather characteristics are influenced by their line and feeding surroundings, inclusive of floor materials and types, since there are no reports regarding these factors. Methods: The 240 White Roman geese which were hatched and sex identified came from 3 commercial goose farms. They were randomly distributed to 24 pens depending on a completely random design. The study continued for 13 weeks and included 3 lines of commercial geese and 2 floor types (cement strip floor [CSF] or cement floor [CF]). Results: The day one gosling weight from A farm was lower than other two farms (96 g vs 107 and 115 g; p<0.001). Afterwards, the body weight, back length, keel length, chest girth and main wing feather length among 3 farms showed no significance difference prior to 12 weeks. The CF group showed heavier body weight, shorter back length, longer keel length, shorter chest girth and shorter main wing feather length than the CSF group prior to 12 weeks. The down weight in the CF was heavier than the CSF group (57.1 g vs 41.8 g; p<0.01) prior to 13 weeks. Conclusion: The body weight showed the positive relations for dry feather weight (r = 0.59), down weight (r = 0.69), percent of the down weight of live body weight prior to 13 weeks (r = 0.61).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.9
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• pp.789-798
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• 2005

This paper is a numerical study concerning how the interactions between a pair of the vortices effect flow field and heat transfer. The flow field (common flow down) behind a vortex generator is modeled by the information that is available from studies on a half-delta winglet. Also, the energy equation and the Reynolds-averaged Wavier-Stokes equation for three-dimensional turbulent flows, together with a two-layer turbulence model to resolve the near-wall flow, are solved by the method of AF-ADI. The present results predict that the boundary layer is thinned in the regions where the secondary flow is directed toward the wall and thickened where it Is directed away from the wall. Although some discrepancies are observed near the center of the vortex core, the overall performance of the computational model is found to be satisfactory.

• Proceedings of the IEEK Conference
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• 2000.06e
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• pp.85-88
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• 2000

This paper describes a Band-Selective Charge-Pump PLL(CPPLL) for clock recovery and clock generator. The proposed PLL satisfies fast acquisition time and low jitter characteristics simultaneously by reducing initial frequency error. The acquisition time of the designed Band-Selective CPPLL can be decreased down to 55% of a conventional CPPLL.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.101-104
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• 2004

CFD simulation is peformed for 2D and 3D frisbees flying at 10m/s. For convenience of simulation, rotation of 3D model is not considered. CFD results show that pitching moment makes the nose down and holes at the leading and trailing edges improve the lift characteristics of the frisbee.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.10
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• pp.28-37
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• 2011

Though Korea has introduced CBP(Cost Based pool) power trading system since 2001, long-term Generation system planning has been executed by government for Cost minimization every 2 years. Until currently the model which is used for Generation system planning and best-mix only considers cost minimization and total yearly or quarterly electricity demand every year. In a view point of one day power supply operation, technical characteristics, like the ramp up/down rate of total generation system, minimum up/down time and GFRQ(Governor Free Response Quantity), are very important. this paper analyzes Optimal Fuel-Mix for 2022 Korea generation system satisfying these constraints of each fuel type and considering pump storage plants, construction cost and $CO_2$ emission charge Using MILP(Mixed Integer Linear Programming) method. Also the sensitivity analysis which follows in future power industry environmental change accomplished.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.6
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• pp.1-7
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• 2003

The experimental research was conducted to find an end mill with an ideal helix angle, which has a superior anti-vibration effect and a low machining tolerance. A conventional endmill which all low blades are $30^{\circ}$ helix angles and a different helix angle endmill which the opposite two blades are $30^{\circ}$ and the other opposites are different helix angles were studied. The cutting farce, machining tolerance and surface roughness were obtained. The AE signals appeared to have low values in up-milling rather than in down-milling. These are also appeared to have low values at low spindle revolutions rates. The cutting force values of Fxy and Fxyz were found to be increased according to the value of helix angle. In up-milling, it was difficult to find a definite tendency in machining tolerance, but in down-milling machining tolerance of the different helix angle end mill was found to be lower than that of the convention end mill. There is a definite tendency that the surface roughness gets better as the RPM increases. In down-milling, Type A($25^{\circ}$＋$30^{\circ}$) appeared to bring the most satisfactory result.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.196-201
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• 2003

The experimental research was conducted to find an end mill with an ideal helix angle, which has a superior anti-vibration effect and a low machining-tolerance. A conventional endmill which all four blades are $30^\circ$ helix angles and a different helix angle endmill which the opposite two blades are $30^\circ$ and the other opposites are different helix angles were studied. The cutting force, machining tolerance and surface roughness were obtained. The AE signals appeared to have low values in up-milling rather than in down-milling. These are also appeared to have low values at low spindle revolutions rates. The cutting force values of Fxy and Fxyz were found to be increased according to the value of helix angle. In up-milling, it was difficult to find a definite tendency in machining tolerance, but in down-milling, machining tolerance of the different helix angle end mill was found to be lower than that of the convention end mill. There is a definite tendency that the surface roughness gets better as the RPM increases. In down-milling, Type $A(25^\circ+30^\circ)$ appeared to bring the most satisfactory result.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.3
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• pp.243-253
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• 1997

In land mobile communications, incident waves to mobile antenna com mostly from directions having low elevation angles about $60^{\circ}$ down from the vertical plane. In order to receive this waves effectively, planar type antenna was fabricated and its characteristics were analyzed. This type of antenna is achieved using superstrate effect criteria which are derived for a nonzero radiation field extending down to the substrate layer surface plan. A small planar type microstrip antenna which can receive incident waves having low elevation angle was fabricated. Experimental results show that the band width of the fabricated antenna is 70 MHz at 1.2 GHz and have nonzero field down to the layer surface.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.8
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• pp.764-768
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• 2002

In this paper, a double balanced gilbert cell MMIC mixer was realized in Tachyonics SiGe HBT technology. The fabricated mixer has 17 dB conversion gain, 9.8 dB noise figure, -4.2 dBm output 1 dB compression point, -27 dBc RF to IF isolation, and the good input, output matching characteristics. It draws 10 mA from a 3 V supply. The simulation and the measured results are closer to each other, which confirms accuracy of the model library and reliability of the process.