• Proceedings of the Korean Information Science Society Conference
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• 2002.10c
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• pp.262-264
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• 2002

데이터웨어하우스는 대용량의 데이터를 대상으로 복잡한 분석을 수행하거나 전략적 의사 결정을 위해 사용되기 때문에 신속한 질의 응답을 위한 성능 관리가 무엇보다 중요하다. 데이터웨어하우스는 일반 운영계 시스템과는 다른 목적과 특성을 가지기 때문에 그에 적합한 성능 모니터링 방법이 필요하다. 본 연구에서는 오라클 데이터베이스를 위한 OLTP(On-Line Transaction Processing)용 국산 성능 모니터링 도구인 DBMax를 데이터웨어하우스 환경에 적용할 수 있도록 기능을 확장한다. 우선 기존의 운영계 시스템과는 구분되는 데이터웨어하우스의 특성을 토대로 오라클9i에서 제공하고 있는 성능 항상 기법인 실체화된 뷰(MV: Materialized View)와 EH(Data Extraction, Transformation and Loading) 화장 기능을 모니터링하기 위한 요구사항을 분석하고 이를 지원하기 위한 DBMax 확장 방안을 설계 및 구현한다. 실체화된 뷰와 ETL 확장 기능을 위해 제공되는 오라클9i의 다양한 스키마 객체에 대한 정보 및 성능 관련 지표를 제시하여 SQL 튜닝 기능을 지원하며 사후 분석을 위한 DBMax의 로그 파일에서 의미 있는 SQL문을 추출하여 잠재적으로 유용한 실체화된 뷰를 권고할 수 있도록 기능을 확장한다.

• Journal of the Semiconductor & Display Technology
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• v.19 no.4
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• pp.94-98
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• 2020

The core/shell of nanowires (NWs) with Cu-doped CdSe quantum dots were fabricated as an electron transport layer (ETL) for perovskite solar cells, based on ZnO/TiO2 arrays. We presented CdSe with Cu2+ dopants that were synthesized by a colloidal process. An improvement of the recombination barrier, due to shell supplementation with Cu-doped CdSe quantum dots. The enhanced cell steady state was attributable to TiO2 with Cu-doped CdSe QD supplementation. The mechanism of the recombination and electron transport in the perovskite solar cells becoming the basis of ZnO/TiO2 arrays was investigated to represent the merit of core/shell as an electron transport layer in effective devices.

• International Journal of Computer Science & Network Security
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• v.21 no.6
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• pp.237-244
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• 2021

Clustering is a most powerful un-supervised machine learning techniques for division of instances into homogenous group, which is called cluster. This Clustering is mainly used for generating a good quality of cluster through which we can discover hidden patterns and knowledge from the large datasets. It has huge application in different field like in medicine field, healthcare, gene-expression, image processing, agriculture, fraud detection, profitability analysis etc. The goal of this paper is to explore both hierarchical as well as partitioning clustering and understanding their problem with various approaches for their solution. Among different clustering K-means is better than other clustering due to its linear time complexity. Further this paper also focused on data mining that dealing with high-dimensional datasets with their problems and their existing approaches for their relevancy

• Journal of Plant Biotechnology
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• v.39 no.2
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• pp.93-98
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• 2012

This study was conducted to evaluate effects of somatic embryos (SEs) induction with different kinds and concentrations of osmoticum, with gelrite and SEs germination with different abscisic acid (ABA) and embryogenic tissue lines (ETLs) in Japanese red pine (Pinus densiflora). In comparison of somatic embryos induction with different kinds and concentrations of osmoticum, the highest record (45/90 mg FW) was obtained from the treatment of 0.1 M maltose+3.75% PEG 4000. In addition, the higher one was also recorded from 0.2 M maltose (41 SEs), it turned out this treatment was also effective in induction of SEs with previous one. In effects of various gelrite concentrations for SEs production, no SEs were occurred in the treatment of 0.4 or 0.6% gelrite, however, the highest no. of SEs shown in 1.0% gellrite (41 SEs), and some comparable results were also marked with 0.8 (37.3 SEs) or 1.2% (39.7 SEs) gelrite. Therefore, SEs can be produced from above 0.8% concentration of gelrite. Finally, in comparison of SEs germination with different concentrations of ABA, ETLs, and AC, the best germination rates (45%) were obtained from the SEs derived from both concentrations of 150 and $200{\mu}M$ ABA in 06-6 ETL and when cultured on germination supplemented with 0.2% AC. When SEs were cultured on germination medium without AC, best germination rate (28.9%) came from the SEs which cultured on $250{\mu}M$ ABA in 06-6 ETL.

• Journal of Korea Spatial Information System Society
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• v.11 no.2
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• pp.143-150
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• 2009

Spatial data warehouses are a system managing manufactured data through ETL step with extracted spatial data from spatial DBMS or various data sources. In load period, duplicated spatial data in the same subject are not useful in extracted spatial data dislike aspatial data and waste the storage space by the feature of spatial data. Also, in case of extracting source data on heterogeneous system, as those have different spatial type and schema, the spatial extract method is required for them. Processing a step matching address about extracted spatial data using a standard Geocoding DB, the exiting methods load formal data set. However, the methods cause the comparison operation of extracted data with Geocoding DB, and according to integrate spatial data by subject it has problems which do not consider duplicated data among heterogeneous spatial DBMS. This paper proposes efficient extracting method to integrate update query extracted from heterogeneous source systems in data warehouse constructer. The method eliminates unnecessary extracting operation cost to choose related update queries like insertion or deletion on queries generated from loading to current point. Also, we eliminate and integrate extracted spatial data using update query in source spatial DBMS. The proposed method can reduce wasting storage space caused by duplicate storage and support rapidly analyzing spatial data by loading integrated data per loading point.

• Clean Technology
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• v.29 no.4
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• pp.244-248
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• 2023

Recently, displays play an important role in quickly delivering a lot of information. Research is underway to reproduce various colors close to natural colors. In particular, research is being conducted on the light emitting structure of displays as a method of expressing accurate and rich colors. Due to the advancement of technology and the miniaturization of devices, the need for small but high visibility displays with high efficiency in energy consumption continues to increase. Efforts are being made in various ways to improve OLED efficiency, such as improving carrier injection, structuring devices that can efficiently recombine electrons and holes in a numerical balance, and developing materials with high luminous efficiency. In this study, the electrical and optical properties of the seven-layer stacked structure rear-light emitting blue OLED device were analyzed. 4,4'-Bis(carazol-9-yl)biphenyl:Ir(difppy)2(pic), a blue light emitting material that is easy to manufacture and can be highly efficient and brightened, was used. OLED device manufacturing was performed via the in-situ method in a high vacuum state of 5×10-8 Torr or less using a Sunicel Plus 200 system. The experiment was conducted with a seven-layer structure in which an electron or hole blocking layer (EBL or HBL) was added to a five-layer structure in which an electron or hole injection layer (EIL or HIL) or an electron or hole transport layer (ETL or HTL) was added. Analysis of the electrical and optical properties showed that the device that prevented color diffusion by inserting an EBL layer and a HBL layer showed excellent color purity. The results of this study are expected to greatly contribute to the R&D foundation and practical use of blue OLED display devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.234-234
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• 2012

고효율 저전력 고휘도를 장점으로 가지고 있는 OLED의 개선을 위하여 수많은 재료와 기술이 연구되어 왔다. 전기적 손실의 방지를 위하여 다양한 재료가 연구되고 있지만 그 중에서도 가장 각광받는 것은 그래핀이다. 그래핀(graphene)은 탄소원자가 육각형 벌집 모양 배열의 격자구조를 가지는 원자 단층 두께의 물질이다. 그래핀은 에너지와 역격자의 k 벡터가 선형적으로 비례하며 전도띠(conduction band)와 가전자띠(valence band)가 한 점에서 만나는 구조를 가지는 특징으로 인해 매우 빠른 전하 이동도(Mobility)를 가지고 있다. 이와 같은 그래핀의 특성을 이용하여 전극 층으로 이용함으로써 소자 특성의 개선이 가능할 것으로 예상되었다. $1{\times}1$ inch Glass에 ITO 대신에 그래핀을 증착한 후 Spin coater를 사용하여 PEDOT을 각각 1,000 rpm, 2,000 rpm으로 도포 하였다. 그 후 HTL (Hole transport latey), ETL (Electron-transport layer), EML (Emissive layer), EIL (Electron injection layer)를 순차적으로 증착 하여 소자를 제작하였다. 발광층에는 유기물질 Alq3를 사용하여 녹색광을 방출하도록 하였다. Spin coater의 rpm에 따라 전도성 고분자의 두께가 결정이 되는데, rpm이 높을수록 두께가 얇으며, 얇을수록 소비전력 효율이 낮다. 하지만 전류밀도 특성이 균일하지 못한 것을 확인하였다. 휘도 효율 특성은 PEDOT의 두께가 얇을수록 동일한 전압에서 휘도가 낮은것을 확인 하였다. 또한 ITO를 이용한 동일 공정의 OLED와 비교하였을 때 상대적으로 낮은 휘도와 전류 효율특성을 보였지만, 전류밀도는 상대적으로 그래핀이 높은 것으로 확인되었다. 본 연구를 바탕으로 그래핀 소자의 개선이 이루어진다면 더욱 높은 효율과 휘도를 낼 수 있을 것으로 판단된다.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.151.2-151.2
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• 2016

We characterized the n-type organic field-effect transistors (OFETs) with non-conjugated polyelectrolytes (NPEs) interlayers as the electron injection layer. Novel NPEs with various ions (Cl-, Br-, I-) improved the electron mobility from $5.06{\times}10^{-3}$ to $2.10{\times}10^{-2}cm^2V^{-1}s^{-1}$ in OFETs based [6,6]-Phenyl-$C_{61}$-butyric acid methyl ester (PCBM) when $PEIEH^+I^-$ spin-cast from 0.6% solution was deposited onto the PCBM layer. Reduced electron injection barrier (${\phi}_e$) at NPE/metal electrode interface was induced by dipole formation and led to increase the electron injection and transport. These findings are important for understanding how NPEs function in devices, the improvement of device performance, and the design of new materials for use in optoelectronic devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.147-147
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• 2015

The multilayer structure of the organic light emitting diode has merits of improving interfacial characteristics and helping carriers inject into emission layer and transport easier. There are many reports to control hole injection from anode electrode by using transition metal oxide as an anode buffer layer, such as V2O5, MoO3, NiO, and Fe3O4. In this study, we apply thin films of LiF which is usually inserted as a thin buffer layer between electron transport layer(ETL) and cathode, as an anode buffer layer to reduce the hole injection barrier height from ITO. The thickness of LiF as an anode buffer layer is tested from 0 nm to 1.0 nm. As shown in the figure 1 and 2, the luminous efficiency versus current density is improved by LiF anode buffer layer, and the threshold voltage is reduced when LiF buffer layer is increased up to 0.6 nm then the device does not work when LiF thickness is close to 1.0 nm As a result, we can confirm that the thin layer of LiF, about 0.6 nm, as an anode buffer reduces the hole injection barrier height from ITO, and this results the improved luminous efficiency. This study shows that LiF can be used as an anode buffer layer for improved hole injection as well as cathode buffer layer.

• Journal of Korea Multimedia Society
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• v.19 no.5
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• pp.939-947
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• 2016

As the number of legacy database systems and the size of data to manipulate have been vastly increased, it has become more difficult and complex to analyze characteristics of data. To improve the efficiency of data analysis and help administrators to make decisions in business life, BI(Business Intelligence) system is used. To construct data warehouse and cube from legacy database systems makes it easy and fast to transform raw data into integrated and categorized meaningful information. In this paper, we built a BI system for an University administration. Several source system databases were integrated to data warehouse to build data cubes. The implemented BI system shows much faster data analysis and reporting ability than the manipulation in legacy systems. It is especially efficient in multi dimensional data analysis, nonetheless in single dimensional analysis.