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시각 특성을 고려한 스케일러블 비디오의 패킷 손실 최적화 기법
이현호(Lee, Hyunho),이광현 (Lee, Kwanghyun),이상훈(Lee, Sanghoon) 한국방송·미디어공학회 2011 한국방송공학회 학술발표대회 논문집 Vol.2011 No.7
본 논문에서 우리는 unequal loss protection(ULP) 알고리즘을 기반으로 패킷이 손실될 수 있는 망 환경에서 인지적으로 재구성된 영상의 왜곡을 최소화하는 방법을 제안한다. 알고리즘에는 2가지의 주요 요인이 있다. 첫째, 인간 시각 체계의 균일하지 않은 분포의 함수로 압축된 영상에 가중치를 준다. 둘째, 패킷은 오류 전파가 일어나지 않도록 하면서 각각의 group of picture(GOP)내에서 시간적인 중요성이 할당된다. 프레임의 인지적인 중요성과 GOP의 계층적인 중요성을 동시에 고려하여, 제안하는 ULP알고리즘은 인간 시각적으로 가장 중요한 지역의 크기를 식별하여 효율적인 forword error correction(FEC) 알고리즘을 수행한다.
Graphene Quantum Dot Layers with Energy-Down-Shift Effect on Crystalline-Silicon Solar Cells
Lee, Kyung D.,Park, Myung J.,Kim, Do-Yeon,Kim, Soo M.,Kang, Byungjun,Kim, Seongtak,Kim, Hyunho,Lee, Hae-Seok,Kang, Yoonmook,Yoon, Sam S.,Hong, Byung H.,Kim, Donghwan American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.34
<P>Graphene quantum dot (GQD) layers were deposited as an energy-down-shift layer on crystalline-silicon solar cell surfaces by kinetic spraying of GQD suspensions. A supersonic air jet was used to accelerate the GQDs onto the surfaces. Here, we report the coating results on a silicon substrate and the GQDs’ application as an energy-down-shift layer in crystalline-silicon solar cells, which enhanced the power conversion efficiency (PCE). GQD layers deposited at nozzle scan speeds of 40, 30, 20, and 10 mm/s were evaluated after they were used to fabricate crystalline-silicon solar cells; the results indicate that GQDs play an important role in increasing the optical absorptivity of the cells. The short-circuit current density was enhanced by about 2.94% (0.9 mA/cm<SUP>2</SUP>) at 30 mm/s. Compared to a reference device without a GQD energy-down-shift layer, the PCE of p-type silicon solar cells was improved by 2.7% (0.4 percentage points).</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-34/acsami.5b03672/production/images/medium/am-2015-03672b_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b03672'>ACS Electronic Supporting Info</A></P>
Lee, Hyunho,Tyagi, Priyanka,Rhee, Seunghyun,Park, Myeongjin,Song, Jiyun,Kim, Jaehoon,Lee, Changhee IEEE 2017 IEEE journal of photovoltaics Vol.7 No.6
<P>We present the analysis of photovoltaic properties in perovskite solar cells to explore the impact of excitonic features, disorder, recombination, and space charge effects using temperature and photo-intensity dependence. Photo-intensity dependence reveals an enhancement of classical Einstein relation due to the presence of traps and formation of space charge effects resulting in reduced conductivity. Exciton versus free charge density upon photo-excitation is analyzed from temperature dependence of photocurrent. Temperature dependence of V-OC is excellently explained by considering a combined energetic disorder in a solar cell, and a moderately high value of variance similar to 125 meV is obtained.</P>