• 한국전기전자재료학회논문지
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• 제30권3호
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• pp.175-179
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• 2017

In this study, we investigate the $SiO_2$ current blocking layer (CBL) to improve light output power efficiency in nonpolar a-plane (11-20) GaN LEDs on a r-plane sapphire substrate. The $SiO_2$ CBL was produced under the p-pad layer using plasma enhanced chemical vapor deposition (PECVD). The results show that nonpolar GaN LED light output power with the $SiO_2$ CBL is considerably enhanced compared without the $SiO_2$ CBL. This can be attributed to reduced light absorption at the p-pad due to current blocking to the active layer by the $SiO_2$ CBL.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.821-824
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• 2009

LFG-MGT CHP system development project with $CO_2$ enrichment in greenhouses was introduced. LFG is produced from the anaerobic digestion of landfilled waste and it has been utilized for power/heat generation since it contains around 50% of $CH_4$. Utilization of LFG from small scale landfill is also needed as well as large scale landfill. However, due to economy of scale, it is very difficult to develop business model. In this context, combining CHP system with greenhouses is considered as feasible option for LFG utilization. LFG-MGT CHP system with $CO_2$ fixation in greenhouses has been derived as an active greenhouse gas reduction strategy, The focus of the system is beyond carbon neutral LFG utilization to neutral carbon absorption. The system is feasible in terms of direct and indirect $CO_2$ emission reduction with more economical way.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.687-692
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• 2007

Vacuum cleaner, one of those household articles, have easily used in our life. Recently vacuum cleaner tends to be compact and portably with high suction power and low noise. As increasing this suction power, the vibration and noise of vacuum cleaner become important problem. To reduce noise efficiently, it is important to identify the noise and the vibration. This pater is to characterize the noise and vibration of a vacuum cleaner.

• 한국연소학회지
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• 제19권2호
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• pp.28-36
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• 2014

Bio fuel oil combustion experiments were successfully demonstrated at the 75 MWe oil-fired power plant without major equipment retrofit and 100% bio-fuel oil combustion was possible without big problems. The experimental data error correction was conducted and numerical model-based analysis technique was applied for the evaluation of the results. Incase of bio fuel oil combustion, heat absorption of radiative heat transfer section was reduced while convection section has opposite trend. The furnace exit gas temperature tends to rise slightly. Environment emissions such as NOx and SOx concentrations showed a tendency to decrease during the bio fuel oil combustion period. On the other hand, boiler efficiency was slightly underestimated.

• 한국연소학회지
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• 제16권1호
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• pp.1-7
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• 2011

340 MWe circulating fluidized bed (CFB) boiler in Yeosu power station is under construction. The circulating fluidized bed boiler in the Yeosu power plant has a number of differences from other domestic boilers in terms of scale and design. Evaluation of design parameters of the Yeosu CFB boiler should be required because the direct application of existing technology is limited. In this study, design characteristics of the Yeosu CFB boiler was summarized. And thermogravimetric analysis was conducted with comparing other rank coals. Watersteam side heat absorption, flue gas temperature and heat transfer coefficient were calculated by heat and mass balance. Design parameters for the Yeosu CFB boiler were discussed along with typical value in the CFB design range.

• 한국광학회:학술대회논문집
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• 한국광학회 2005년도 제16회 정기총회 및 동계학술발표회
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• pp.292-295
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• 2005

Variable optical attenuators (VOA) made of low-loss fluorinated polymers are demonstrated which shows a low operating power less than 30 mW due to the superior thermo-optic effect of polymer material and a low insertion loss less than 1.0 dB by incorporating highly fluorinated polymers to reduce the absorption loss at 1550 nm. An attenuator-integrated low-crosstalk polymeric digital optical switch (DOS) is also demonstrated. The switch and attenuator shares a single connected electrode which is controlled by a single current source. Due to the simple structure of the integrated attenuator, the device length is reduced to 1 cm so as to provide low insertion loss of 0.8 and 1.1 dB for 1300 and 1550 nm, respectively. The attenuator radiates remained optical signal on the switch-off branch in order to decrease the switching crosstalk to be less than -70 dB with an applied electrical power of 200 mW.

• 천문학논총
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• 제15권spc1호
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• pp.73-83
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• 2000

X-ray astronomy deals with measurements of the electromagnetic radiation in the energy range of $E\~0.1-100 keV (\lambda\~0.12-120{\AA})$. The wavelength of X-ray is comparable to the size of atoms, so that the photons in the X-ray range are usually produced and absorbed by the atomic processes. Since the launch of the first X-ray astronomy satellite 'Uhuru' in 1970, technological advances in a launch capability and a detection capability make X-ray astronomy one of the most rapidly evolving fields of astronomical research. Particularly, a spectral resolving power $E/{\Delta}E$ has been increased by an order of 2 - 3 (in the energy range of 0.1 - 10 keV) during the past 30years. In this paper, I briefly review a developing process of the resolving power and spectroscopic techniques. Then I describe important emission/absorption lines in X-ray astronomy, as well as diagnostics of gas property with line parameters.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 추계학술발표회논문집(1)
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• pp.15-20
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• 1996

We present the result of physical studies for three integral-type burnable absorbers of gadolinia, erbia and IFBA, in the hexagonal fuel assembly. The analysis of nuclear characteristics for gadolinia and IFBA cases shows that the spectrum hardening of hexagonal fuel assembly compared to rectangular one leads to smaller reactivity hold-down worth(RHW) and less change of MTC in the negative direction per insertion of one burnable absorber rod. Erbia case, on the other hand, exhibits reversed trend in RHW and MTC due to the enhanced absorption of large resonance of Erbium at 0.5 eV It turns out to be that Erbia performs best in terms of minimizing the peak pin power and maintaining as more negative MTC as practically attainable during the entire operational phase, and IFBA provides the least residual reactivity penalty at EOC. Therefore, we take Erbium as the suitable burnable absorber and provide optimal designs of 60, 120, 180, 240 and 300 erbia-shimmed hexagonal fuel assemblies with regard to minimizing the peak pin power.

• 한국유체기계학회 논문집
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• 제17권1호
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• pp.47-53
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• 2014

This paper aims to present the design and performance evaluation of a counter-rotating tidal turbine using CFD and to compare its performance with single rotor. The device scale is 10kW and the rotating part consists of two rotors which rotate in opposite direction. Compared with conventional single rotor, the counter-rotating system shows higher power efficiency at high stream velocity but lower efficiency at low stream velocity. The added counter-rotated rotor together helps improve the energy absorption capacity but has influence on the upstream rotor that reduces its performance. In terms of power capture, the designed counter-rotating tidal turbine is more advantageous in high speed tidal condition.

• 전기학회논문지
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• 제57권12호
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• pp.2249-2254
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• 2008

A non-thermal micron size plasma needle is applicable for medical treatment because it includes radicals, charged particles, ultraviolet emission, and strong electric fields. The electric fields around the plasma needle device driven by a radio frequency wave are investigated in order to calculate the power delivered to the cell. A commercial multi-physics code, CFD-ACE, was utilized for the calculation of electric fields for the optimization of the needle structure. The electric field and energy absorption profiles are presented with the variation of the device structure and the distance between the needle and tissues. The living tissues effectively absorb the radio frequency power from the plasma needle device with the covered pyrex structure.