• Solar Energy
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• v.19 no.2
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• pp.9-19
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• 1999

For determining solar benefit hour are two different methods required as a direct calculation which is more accurate but too slow, and a computer graphic protration which is less accurate but too fast. To have the later accurate, the hour to hour interpolation is used to provide less visual deviation. With directly pointing the solar location into the screen coordinate the waldram projection and stereographic projection which needs the number of fast algorithms to calculate the coordinates of the sun path and building configuration casting to the space are applied.

• Nuclear Engineering and Technology
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• v.33 no.3
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• pp.327-338
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• 2001

A computational fluid dynamics (CFD) analysis was performed to propose the optimum design of flow mixing vane on the space grid in a PWR fuel assembly. The flow mixing vanes considered in this study for optimum design are swirl-vane and twisted-vane. A single subchannel of one grid span was modeled using flow symmetry to minimize the computational effort. The CFD predictions are in good agreement with the experimental results for the split- vane, which shows the applicability of the CFD method. The mixing effect by swirling flow and crossflow, and the pressure drop were estimated and compared for the various vane angles. The optimum vane angle is proposed to be 40。 and 35。 from the direction of axial flow for the swirl-vane and the twisted-vane, respectively.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2009.04a
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• pp.129-133
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• 2009

country for green growth under minimizing boils to do change in climate under confronting boil the use of petrifaction resources energy and in change. Reduces the greenhouse gas and a environmental contamination, continuity for the growth which is possible demobilizes the greens and ecosystem, with alternative the roof which is an idle space from the construction water and the greens and uses creates in compliance with the effect which is various an energy economy and applies. Roof telerecording the synergy effect which follows with the effect which is various is not the energy saving which leads one effect which is simple in harmony and this lives together the environment which leads and possibility means that becomes the environmental element which hits.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.271-272
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• 1996

Assuming that particles can be accelerated to high energies via diffusive shock acceleration process at the accretion shocks formed by the infalling flow toward the clusters of galaxies, we have calculated the expected spectrum of high-energy protons from the cosmological ensemble of the cluster accretion shocks. The model with Jokipii diffusion limit could explain the observed cosmic ray spectrum near $10^{19}eV$ with reasonable parameters and models if about $10^{-4}$ of the infalling kinetic energy can be injected into the intergalactic space as the high energy particles.

• Solar Energy
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• v.9 no.1
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• pp.36-42
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• 1989

Following the oil crisis in 1979, there have been surge of movements by the government in Korea to conserve petroleum-based energy in every sector of society. One of these movements was the application of passive solar technologies into the construction of school buildings. Various passive designs are developed paying special regard to architectural and climatic factors. This paper is related to the application of the passive solar technology to elementary school buildings. It is proposed to place the hallway on the south side of the building to improve the thermal performance as well as indoor lighting effects. The cases have been compared with those of the existing school buildings where substantial improvements are noted. Finally, standard drawings are prepared in detail to promote the application of this passive solar technology in practical school building.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.6
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• pp.330-335
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• 1999

This paper proposed the p-q-r coordinate system where the instantaneous active power p, and the two instantaneous reactive powers qq, qr were defined. The three power components are linearly independent, so the compensation for the two instantaneous reactive powers leads to control the two components of the current space vector. With the theory, the neutral current of a three-phase four-wire system can be eliminated by only compensating the instantaneous reactive power using no energy storge element.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.11 s.242
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• pp.1248-1256
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• 2005

This study was undertaken to investigate the flow characteristics of emulsified fuel with the ultrasonic energy-adding system by using the chaotic method. Efffcts of water contents within emulsified fuel, flow rate and tube length with 5m in diameter from an emulsified chamber has been discussed on the strange attractor and power spectral density function. Five probe sensors were set up from 0.5 to 2.5m by length in 0.5m increments in the tube. In particular, the chaotic features of this system have been practically characterized in terms of chaotic statistics such as the power spectral density function and phase space portraits by resorting to the somewhat noble deterministic chaos theory. In the tube, the dominant frequency increased with increasing water contents and flow rate, but decreased a little with an increase in the length from the emulsified chamber.

• Proceedings of the KIEE Conference
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• 2003.11b
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• pp.279-282
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• 2003

This paper proposes a medium-access control(MAC) protocol designed for wireless multi-hop sensor networks which is used for connecting physical world and cyber computing space. Wireless multi-hop sensor networks use battery-operated computing and sensing device. We expect sensor networks to be deployed in an ad hoc fashion, with nodes remaining inactive for long time, but becoming suddenly active when specific event is detected. These characteristics of multi-hop sensor networks and applications motivate a MAC that is different from traditional wireless MACs about power conservation scheme, such as IEEE 802.11. Proposed MAC uses a few techniques to reduce energy consumption. Result show that proposed MAC obtains more energy sayings.

• Solar Energy
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• v.18 no.3
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• pp.137-146
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• 1998

In this paper, the current status of manufacturing technologies for GaAs/Si solar cell were revived and provied new MOCVD. In the manufacturing process of GaAs/Si solar cells and an experiment to get the high efficiency GaAs solar cells, we must investigate the optimum growth conditions to get high quality GaAs films on Si substrates by MOCVD. The GaAs on Si substrates has been recognized as a lightweight alternative to pure substrate for space applicaton. Because its density is less the half of GaAs or Ge.So GaAs/Si has twofold weight advantage to GaAs monolithic cell. The theoretical conversion efficiecy limit of tandem GaAs/Si solar cell is 32% under AM 0 and $25^{\circ}C$ condition. It was concluded that the development of cost effective MOCVD technologies shoud be ahead GaAs solar cells for achived move high efficiency III-V solar cells involving tandem structure.

• Nuclear Engineering and Technology
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• v.34 no.3
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• pp.211-217
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• 2002

A 1-MW vacuum feedthrough for the KSTAR ICRF antenna is fabricated and high power RF test is performed. It is designed to have two alumina $(Al_2O_3)$ ceramic cylinders and O-ring seal instead of a brazed seal for good mechanical and thermal strength, which is important in long pulse or steady state operation. For cooling of the ceramics, dry air is circulated in a space between the two cylinders and the outer conductor. Independent cooling water channels are installed to cool the inner conductor of the feedthrough. RF high voltage test is performed using two kinds of ceramics with the purities of 99.7% and 97%. Stable operation is possible with the RF voltage of 30 kVp at long pulse of 300 sec without any severe damage.