• 전기학회논문지
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• 제66권2호
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• pp.354-356
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• 2017

We focused on light management technology in amorphous silicon solar cells to suppress increase in absorber thickness for improving power conversion efficiency (PCE). $MgF_2$ and $TiO_2$ anti-reflection layers were coated on both sides of Asahi VU ($glass/SnO_2:F$) substrates, which contributed to increase in PCE from 9.16% to 9.81% at absorber thickness of only 150 nm. Also, we applied very thin $MgF_2$ as a rear reflector at n-type nanocrystalline silicon oxide/Ag interface to boost photocurrent. By reinforcing rear reflection, we could find the PCE increase from 10.08% up to 10.34% based on thin absorber about 200 nm.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.72.2-72.2
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• 2010

Nowadays, the crystalline Si Solar cell are expected for economical renewable energy source. The cost of the crystalline Si solar cell are decreasing by improvement of its efficiency and decrease of the cost of the raw Si wafers for Solar cells. This Si wafer based crystalline Si solar cell is the verified technology from several decade of its history. Now, I will introduce one method that can be upgrade the efficiency by using simple and economical method. The name of this method is Rear Side Etching(RSE). The purpose of rear side etching is the elimination of n+ layer of rear side and increase of the flatness. The effects of rear side etching are the improvement of Voc and increase of efficiency by reducement series resistance and forming of uniform BSF. The experimental procedure for rear side etching is very simple. After anti-reflection coating on solar cell wafer, Solar cell wafer is etched by the etching chemical that react with only rear side not front side. This special chemical is no harmful to anti-reflection coating layer. It can only etched rear side of solar cell wafer. We can use etching image by optical microscope, minority carrier life time by WCT 120, SiNx thickness and refractive index by ellipsometer, cell efficiency for the RSE effect measurement. The key point of rear side etching is development of etching process condition that react with only rear side. If we can control this factor, we can achieve increase of solar cell efficiency very economically without new device.

• 한국해안해양공학회:학술대회논문집
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• 한국해안해양공학회 1996년도 정기학술강연회 발표논문 초록집
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• pp.176-183
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• 1996

In order to reduce wave reflection from a breakwater, a perforated wall caisson is often used. A conventional perforated wall caisson breakwater for which the water depth inside the wave chamber is the same as that on the rubble mound berm has less weight than a vertical solid caisson with the same width and moreover the weight is concentrated on the rear side of the caisson. (omitted)

• 한국해양공학회지
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• 제27권6호
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• pp.90-94
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• 2013

This paper reports the results obtained for there flection and transmission coefficients on rubble mound breakwaters in Busan Yacht Harbor. A2D physical model test was conducted in the wave flume at the Coastal Engineering Research Laboratory at Pusan National University, Busan, South Korea. In this study, physical model tests were completed to further our understanding of the hydrodynamic processes that surround a rubble mound structure subjected to irregular waves. In particular, the reflection and transmission coefficients, as well as the spectrum transformation, were analyzed. This analysis suggests that with an increase in wave height around a rubble mound, the reflection coefficient drastically increases at each water level (HHW or MSL or LLW). Moreover, when the water level changes from HHW to LLW, the reflection coefficient is suddenly reduced. A further result of the analysis is that the transmission coefficient strongly drops away from the rear of the structure. Finally, in regard to the rubble mound breakwater in Busan Yacht Harbor, a consideration of the reflection and transmission coefficients plays an important role in the design.

• 교육시설 논문지
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• 제20권1호
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• pp.37-44
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• 2013

The present study examines the effects of periodic type diffusers for producing the preferred acoustics for speech and determines the more successful configurations of sound-absorbing and diffusing treatments for achieving good acoustics in classrooms. The measurements were carried out in a 1/10 scale model classroom systematically adding diffusers to one or more of four surfaces of the room. A total of 13 combination of diffusers with absorptive treatments were investigated. Adding diffusers on the ceiling were more effective to increasing the early-arriving reflection energy($G_{50}$) than adding absorptive materials on the entire ceiling. The late arriving reflection energy($G_{late}$) was decreased with increasing amounts of diffusing treatments of upper front or rear wall and this resulted in achieving higher early-to-late ratios($G_{50}$). Adding diffusers on the upper front wall($AC_{100}DUFW_{26}$) achieved more uniform acoustical conditions over the receiver positions than adding diffusers on the upper rear wall($AC_{100}DUFW_{26}$). Adding diffusers on the ceiling and absorptive materials on the lower front wall($AC_{75}DC_{25}ALFW_{26}$) achieved better acoustical conditions than adding the absorptive materials on the entire ceiling and lower front wall($AC_{100}ALFW_{26}$).

• 한국해양공학회지
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• 제16권3호
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• pp.1-7
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• 2002

In this paper, a numerical model to analyze the performance of a vertical slit-type wave absorber is developed under the assumption of inviscid water waves. The formulation combines the linear potential theory with a semi-empirical description of the eddy-shedding at a slit-type wave absorber. We investigated the reflection coefficients over a wide frequency range for a vertical slit-type wave absorber both with and without a solid rear wall. Model test was conducted at KRISO' s two dimensional wave tank to validate the theoretical results. It is found that the agreement between theoretical results and experimental data is surprisingly good. We found that the wave absorbing system using a vertical slit plate has sufficient potentials for breakwaters for ocean development.

• 한국광학회지
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• 제8권5호
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• pp.395-402
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• 1997

$\1.55mu\textrm{m}$ InGaAsP MQW FP 반도체 레이저 단면의 무반사 코팅 두께를 앞면에 무반사 코팅하는 동안 뒷면의 출력을 실시간으로 측정하여 결정하였다. 굴절률 1.85인 $SiO_x$ 박막의 최적 두께는 188 nm이고, 무반사 코팅 전, 후의 문턱전류비로 계산한 단면의 반사율은 약 2 $\times$ $10^{-4}$이었다. 무반사 코팅 후 주입전류 60 mA일 때 출력이 87%, 기울기 효율이 3.4배, 문턱전류가 2.64배 증가하였다. 또한 실시간으로 $Si/SiO_2$ 박막의 고반사 코팅을 뒷면에 한 후 코팅 전보다 출력이 약 160% 향상되었고, 기울기 효율이 3.8배 증가하였으며, 문턱전류는 1.07배로 코팅 전과 거의 비슷하여, 무반사 및 고반사 코팅 후 반도체 레이저의 출력특성이 크게 향상되었다.

• 한국태양에너지학회 논문집
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• 제29권4호
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• pp.28-33
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• 2009

In 2008, the global photovoltaic(PV) market reached 5.6GW and the cumulative PV power installed totalled almost 15GW compared to 9GW in 2007. Due to a favourable feed-in-tariff, Korea emerged in 2008 as the 4th largest PV market worldwide. PV power installation rose 495.5 percent to 268MW in 2008 compare to 45MW in 2007. Building integrated photovoltaic(BIPV) has the potential to become a major source of renewable energy in the urban environment. BIPV has significant influenced on the reflection by rear materials such as white back sheet and the heat transfer through the building envelope because of the change of the thermal resistance by adding or replacing the building elements. In this study, to use as suitable building materials into environmentally friendly house like green home, characteristic analysis of BIPV module according to rear materials achieved. Electrical output of PV module with white back sheet is high about 10% compared to other pv module because of 83% reflectivity of white back sheet compared to 8.4% reflectivity of other PV modules with different rear materials(black back sheet and glass). In the result of outdoor experiment during a year, electrical output of four different PV module is decreased about 3.72%.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.975-978
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• 2007

This paper investigates stage acoustics in concert halls for ensemble performance in terms of stage support parameters. A concert hall with large stage area was selected. Objective measurements were carried out according to Gade's methods for investigating stage support (ST1). The sound field on the stage was evaluated using stage and audience acoustical parameters. According to the positions at stage, different acoustical characteristics were found. Higher ST1 and lower $IACC_{E3}$ were measured near side and rear stage walls. In case of conductor/soloist vs. orchestra player, objective measurement of acoustical parameters shows that early sound fields depend on the source-receiver distance but late sound fields depend on the location of side and rear walls. In addition, in-situ evaluation of the trio instrumentalists was carried out. Results show that ensemble is favored by higher early reflection of sounds and sound diffusion affecting ‘blending’ of their performance.

• International Journal of Advanced Culture Technology
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• 제1권1호
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• pp.15-18
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• 2013

This paper describes new gestures on the Multi-touch table. The 2 new gestures with 3 fingers are used for minimizing of all windows that is already open and converting Aero mode. We also implement a FTIR (Frustrated Total Internal Reflection) Multi-touch table that consists of sheet of acrylic, infrared LEDs, camera and rear projector. The operation of proposed gestures is verified on the implemented Multi-touch table.