• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.1
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• pp.7-11
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• 2010

The reduction of optical losses in mono-crystalline silicon solar cell by surface texturing is a critical step to improve the overall cell efficiency. In this study, we have changed the sub-micrometer structure on the micrometer pyramidal structure by 2-step texturing. The Ag particles were coated on the micrometer pyramid surface in $AgNO_3$ solution, and then the etching with hydrogen fluoride and hydrogen peroxide created even smaller nano-pyramids in these pyramids. As a result, we observed that the changes of size and thickness of nano structure on pyramidal surface were determined by $AgNO_3$ concentration and etching time. Using 2-step texturing, the surface of wafers is etched to resemble the rough surface of a lotus leaf. Lotus surface can reduce average reflectance from 10% to below 3%. This reflectance is less than conventional textured wafer including anti-reflection coating.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.1
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• pp.17-30
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• 2016

In this paper, we propose an efficient public key trace and revoke scheme. An trace and revoke scheme is a broadcast encryption scheme which has a tracing and revocation algorithm. It would maintain security of the scheme to revoke pirate keys which are colluded by malicious users. In addition, property of revocation can be applied to various circumstances because it can help cipher text delivered to certain users who are supposed to. In this paper, we would change the scheme[Augmented broadcast encryption scheme] based on the bilinear groups of the composite order into that of prime order and we can improve the size of public key, secret key, ciphertext considerably. Furthermore, we define property of revocation precisely, so we can obtain the result that the scheme with limited revocation can be expanded to have a full revocation. This paper can be easily applied to the organization such as government, military, which has a hierarchical structure.

• Journal of Broadcast Engineering
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• v.4 no.2
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• pp.144-154
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• 1999

The binomial sequences are family of orthogonal sequences that can be generated with remarkable simplicity-no multiplications are necessary. This paper introduces a class of non-recursive multidimensional filters for frequency-selective image processing without multiplication operations. The magnitude responses are narrow-band. approximately gaussian-shaped with center frequencies which can be positioned to yield low-pass. band-pass. or high-pass filtering. Algorithms for the efficient implementation of these filters in software or in hardware are described. Also. we show that the binomial QMFs are the maximally flat magnitude square Perfect Reconstruction paraunitary filters with good compression capability and these are shown to be wavelet filters as well. In wavelet transform the original image is decomposed at different scales using a pyramidal algorithm architecture. The decomposition is along the vertical and horizontal direction and maintains constant the number of pixels required to describe the images. An efficient perfect reconstruction binomial QMF-Wavelet signal decomposition structure is proposed. The technique provides a set of filter solutions with very good amplitude responses and band split. The proposed binomial QMF-filter structure is efficient, simple to implement on VLSl. and suitable for multi-resolution signal decomposition and coding applications.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.51-59
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• 1991

Early stage of GaAs nucleation on Si substrate was theoretically studied by computer simulation. Compared to the constant ledge interaction energy in conventional nucleation theory, functional behavior of ledge-ledge interaction resulted in small size clusters depending on the cluster size and shape. Among various kinds of clusters, the multilayer pyramidal shape GaAs cluster requires smallest excess free energy due to the formation of Ga(111) facet planes. There this result suggests that the defects involved in GaAs/Si are originated from the early stage nucleation.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1996.06a
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• pp.169-174
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• 1996

객체 인식은 대용량의 영상 데이터를 분석, 탐색하고 재구성하기 위한 내용기반 영상 검색의 매우 중요한 분야이며, 특히 인간의 얼굴은 검색 영상 내에서 대부분 주요한 장면에 위치하고 있기 때문에 그 비중이 매우 크다. 본 논문에서는 내용기반 영상 검색을 위한 실시간 얼굴 영역 추출 방법을 제안한다. 제안된 방법에서는 다층 피라미드 구조와 간단한 형태의 머리 형판을 사용하여 얼굴의 후보 영역을 추출한 후, 보다 정확한 얼굴 영역을 추출하기 위하여 후보 영역 내에서 눈의 위치를 탐색하고, 두 눈의 위치를 기준으로 최종적인 얼굴 영역을 추출하였다. 얼굴 후보 영역 추출 단계에서는 얼굴의 형태 정보를 포함하고 있는 모자이크 형판을 사용하여 머리와 턱을 포함한 얼굴 영역을 추출하였으며, 눈 위치 추출 단계에서는 눈의 위치 정보를 사용하여 눈의 탐색 영역을 결정하고, 탐색 영역 내에서 이진 영상 형판을 사용하여 눈의 위치를 추출한 후, 눈 영역의 무게 중심을 눈의 중심 위치로 설정하였다. 마지막 얼굴 영역 추출단계에서는 두 눈의 위치를 기준으로 사각형의 영역을 얼굴 영역으로 추출하였다. 제안된 방법의 성능을 검증하기 위하여 1700장의 다양한 영상에 대하여 실험하였으며, 실험 결과 한 장의 영상에서 얼굴 영역을 추출하는데 있어서, Pentium 166Mz의 PC상에서 평균 3.2초의 처리 속도와 91.7%의 추출률을 보임으로써, 실시간 얼굴 영역 추출에 매우 효과적임을 알 수 있었다.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.33-37
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• 1998

The effects of initial pH on the synthesis of new microporus zeolitic materials, ETS-4 and ETS-10 were investigated with the initial pH from 10.4 to 11.5. The results showed that initial pH significantly affect the type of ETS-series materials to be crystallized ; that is, pure ETS-10 at 10.4 of pH, mixture of ETS-10 and ETS-4 at intermediate pH, and pure ETS-4 at pH. Micrographs show that the morphology of final solid product changes from the shape contacting the bottom sides of two truncated pyramids to the plane-like shape as initial pH increases.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.1
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• pp.13-19
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• 2016

This study is on the optimal rise depth of embossed panel for the ESS water tank. The thickness of panel is reduced at pressing operation, it could be calculated by volume conservation condition. The analysis of panel using STS304 material conducted by FEM. As a result of structural analysis, it was found that the optimal rise depth of arch embossed panel is recommended to be 70~90mm and the optimal rise depth of pyramid embossed panel is recommended to be 150~200mm. The proposed value of optimal rise depth could be a useful to the economic design of ESS water tank panel.

• The Korean Journal of Nuclear Medicine
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• v.27 no.2
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• pp.277-284
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• 1993

$^{99m}Tc$-MAG3는 세뇨관 배설을 하는 신장 기능 영상용 방사성의 약품으로서, 가운데 $^{99m}Tc$이 있고 1개의 유황과 3개의 질소가 아래쪽 면에 정사각형으로 배치되고 정점에 산소가 위치한 4각 피라미드형을 하고 있다. 그러나 시판되는 신장 영상용 MAG3는 반응성이 강한 -SH기에 의한 부산물 생성을 방지하기 위해 benzoyl기로 보호되어 있으므로 보통 조건으로는 잘 표지되지 않고 10분 정도 끓여주어야 한다. 본 실험에서는 실온에서도 benzoyl기를 잘 끊어지게 하는 이미다졸, 아고마틴, 괴리딘등과 같은 염기성 촉매제를 가하고 여러가지 PH에서 실온에서 반응시켜 본 결과, benzoyl기가 끊어지면서 $^{99m}Tc$과 -SH기가 반응하는 첫번째 반응이 일어난 후에도 산성에서 약알칼리성 범위에서는 중간체가 상당량 생성되고 알칼리성 (pH 10.5)이 되어야 최종 산물로 재빨리 넘어가는 것을 발견하였다. 또한 glucarate, medronate, phthalate, acetate 등 여러가지 다른 transchelating agent를 사용하여 같은 반응을 시킨 후에도 생성된 중간체의 HPLC 피크가 같은 retention time (Rt)을 보이는 것으로 보아 이 중간체의 화학구조내에는 transchelating agent를 포함하지 않는 것으로 보인다. 최종 생성물과 중간체의 ImM 시트테인 용액 중에서의 안정도 시험을 하여 본 결과 최종 생성물은 매우 안정하나 중간체는 불안정한 것을 발견하였다.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.10
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• pp.80-87
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• 2006

Metallic sandwich plate with a truss core has metallic inner structures which have low relative density between a pair of metal skin sheets or face sheets. In this work, low impact tests have been carried out to examine the behavior of sandwich plates with a pyramidal truss core. For the low velocity impact, the impact apparatus of drop weight type has been fabricated. From the results of the experiments, maximum energy absorption is found to happen when the upper sheet fails. The sandwich plate loses its absorption ability as soon as the inner structures have been crashed completely and optimal core thickness has existed to maximize energy absorption. Comparing the metallic sandwich plate with the monocoque plate, the absorbed energy has been improved up to 160 % and the deflection decreased by up to 76%. As a result, the metallic sandwich plate with a truss core is shown to have good material for impact resistance and energy absorption.

• Current Photovoltaic Research
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• v.5 no.2
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• pp.59-62
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• 2017

Surface texturing is affected the uniformity and size of pyramid with saw mark defect density. To analysis the influence of the saw mark defect density, we textured various si wafer. When the texturing process proceeds without the saw mark removal, silicon wafer of low-saw mark defect density showed small pyramid size of $3.5{\mu}m$ with the lowest average value of the reflectance of 10.6%. When texturing carried out after removal of the saw mark using the TMAH solution, we obtained a reflectance of about 11% and the large pyramid size of $5{\mu}m$. As a result, saw mark wafers showed a better pyramid structure than saw mark-free wafer. This result showed that saw mark can take place more smooth etching by the KOH solution and saw mark-free wafer is determined to be a factor that have a higher reflectance and a large pyramid.