• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.399-400
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• 2007

In this work, we have investigated the characteristics of the phosphorescent OLED and flexible OLED fabricated on IZTO/glass and IZTO/PET anode film grown by magnetron sputtering, respectively. Electrical and optical characteristics of amorphous IZTO/glass anode exhibited similar to commercial ITO anode even though it was deposited at room temperature. In addition, the amorphous IZTO anode showed higher work function than that of the commercial ITO anode after ozone treatment for 10 minutes. Furthermore, a phosphorescent OLED fabricated on amorphous IZTO anode film showed improved current-voltage-luminance characteristics, external quantum efficiency and power efficiency in contrast with phosphorescent OLED fabricated on commercial ITO anode film. This indicates that IZTO anode is promising alternative anode materials for anode in OLEDs and flexible OLEDs.

• Membrane Journal
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• v.32 no.6
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• pp.427-441
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• 2022

Polymer electrolyte membrane (PEM) serving as a separator that can prevent the permeation of unreacted fuels as well as an electrolyte that selectively transports protons from the anode to the cathode has been considered a key component of polymer electrolyte membrane fuel cell (PEMFC). The perfluorinated sulfonic acid-based PEMs, represented by Nafion®, have been commercialized in PEMFC systems due to their high proton conductivity and chemical stability. Nevertheless, these PEMs have several inherent drawbacks including high manufacturing costs by the complex synthetic processes and environmental problems caused by producing the toxic gases. Although numerous studies are underway to address these drawbacks including the development of sulfonated hydrocarbon polymer-based PEMs (SHP-PEMs), which can easily control the polymer structures, further improvement of PEM performances and durability is necessary for practical PEMFC applications. Therefore, this study focused on the various strategies for the development of SHP-PEMs with outstanding performance and durability by 1) introducing cross-linked structures, 2) incorporating organic/inorganic composites, and 3) fabricating reinforced-composite membranes using porous substrates.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.4
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• pp.414-420
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• 2011

Thermal stress analysis of a planar anode-supported SOFC considering electrochemical reactions has been performed under operating conditions where average current density varies from 0 to 2000 $A/m^2$. For the case of the 2000 $A/m^2$ operating condition, Structural stress analysis based on the temperature distributions obtained from the CFD analysis of the unit cell has also been done. From this one way Fluid-Structure Interaction(FSI) analysis, Maximum Von-Mises stress under negligible temperature gradient fields occurs when cell components are perfectly bonded. The maximum stress of the electrolyte, cathode and anode in a unit cell SOFC is 262.58MPa, 28.55MPa and 15.1MPa respectively. The maximum thermal stress is critically dependent on static friction coefficient.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.467-467
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• 2008

전계 방출 디스플레이는 CRT와 FPD(평판디스플레이)의 장점을 모두 갖춘 디스플레이로서 주목을 받고 있으며, 여러 국가와 많은 연구자들이 연구개발을 활발히 진행하고 있는 차세대 디스플레이 중 하나이다. 본 연구에서는 최근 차세대 디스플레이로서 연구가 활발히 진행되고 관심이 높아지고 있는 전계 방출 디스플레이의 특허 동항에 대하여 살펴보았다. 전계 방출 디스플레이 분야의 특허는 1994년과 1995년을 전후하여 출원이 급격하게 증가하고 있고, 최근에도 출원량이 증가하는 것으로 나타났다. 국가별 분포에서는 한국이 37%로 가장 높게 나타났고, 미국이 32%, 일본이 27%, 유럽이 4%의 순으로 나타났다. 특히 한국은 최근에도 다른 나라에 비해 특허 출원량이 가장 많은 것으로 분석되었다. 이는 최근 한국이 디스플레이 전체에 대해 세계적으로 주도하고 있는 경향을 반영하고 있다. 각 기술별 출원 동향을 보면, 캐소드가 주요 출원국가 전체에서 가장 높은 비율을 차지하고 있고, 진공실장, 구동회로, 애노드의 순서로 분석되었다. 전계 방출 디스플레이 분야의 주요 출원인을 살펴보면 삼성SDI가 압도적으로 많은 비율을 차지하였고, 그 뒤를 LG전자 및 Canon, 오리온전자, 마이크론 등이 주요 출원인으로 분석되었다. 국가별 분석 결과에서와 같이, 주요 출원인에서도 디스플레이 시장을 선도하는 삼성SDI, LG전자, Canon 등이 가장 많은 출원 비율을 차지하는 것을 알 수 있었다. 국가별 주요 출원인으로, 한국에서는 삼성SDI, LG전자, 오리온전자, 일본에서는 Canon, Sony, Toshiba였고, 미국에서는 마이크론과 ITRI, 유럽에서는 삼성SDI와 Sony로 분석되었다. 따라서, 전계 방출 디스플레이를 연구 하고자 하는 연구소나 기업에는 삼성SDI, LG전자, Canon, Sony 등의 연구 개발 상황 또는 특허 출원 상태를 면밀하게 분석할 필요가 있다. 캐소드의 전자방출원의 형성 형태로는 팁형이 가장 많고, CNT형, 평면형의 순서로 나타났다. 그러나, 한국에서는 전자방출원으로 CNT헝이 가장 많게 나타나므로서 다른 나라들과는 연구 개발 형태가 조금 다른 것으로 분석되었다. 전계 방출 디스플레이의 특허 동향을 분석한 결과, 한국이 일본, 미국, 유럽보다 더 활발하게 특허 출원하고 있는 것으로 분석되었고, 최근에도 다른 나라에 비해 활발하게 특허를 출원하고 있어 향후에도 디스플레이 시장은 한국에서 주도해 나갈 것으로 판단되었다. 주요 출원인으로는 삼성SDI, LG전자, Canon, Sony로 분석되었으며, 위와 같은 선진 기업 및 주요 출원인은 연구개발 및 특허 출원 상황을 면밀하게 검토할 필요가 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.4B
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• pp.200-207
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• 2007

Many P2P systems which are designed to implement large-scale data sharing have been introduced in internet recently. They exhibit interesting features like sell-configuration, sell-healing and complete decentralization, which make them appealing for deployment in ad hoc environments as well. This paper proposes an Gnutella-based P2P system that can operate efficiently in ad hoc networks. The objectives of this paper are to extend the overall system lifetime, to reduce overheads, and to provide enhanced performance. The proposed system uses an ultrapeer election scheme based on metric values and proactive distribution of ultrapeer information. According to the simulation results, the proposed system can provide better performance than Gnutella in terms of query success rate, query response time, overhead and residual battery power by utilizing network resources efficiently.

• Journal of KIISE:Databases
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• v.34 no.3
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• pp.206-216
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• 2007

With respect to the Semantic Web proposed to overcome the limitation of the Web, OWL has been recommended as the ontology language used to give a well-defined meaning to diverse data. OWL is the representative ontology language suggested by W3C. An efficient retrieval of OWL data requires a well-constructed storage schema. In this paper, we propose a storage schema construction technique which supports more efficient query processing. A retrieval technique corresponding to the proposed storage schema is also introduced. OWL data includes inheritance information of classes and properties. When OWL data is extracted, hierarchy information should be considered. For this reason, an additional XML document is created to preserve hierarchy information and stored in an XML database system. An existing numbering scheme is utilized to extract ancestor/descendent relationships, and order information of nodes is added as attribute values of elements in an XML document. Thus, it is possible to retrieve subclasses and subproperties fast and easily. The improved query performance from experiments shows the effectiveness of the proposed storage schema construction and retrieval method.

• Applied Chemistry for Engineering
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• v.34 no.6
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• pp.567-575
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• 2023

Water electrolysis is undergoing active research as one of the promising technologies for producing effective green hydrogen. Using seawater directly as a raw material for a water electrolysis system can solve the problem of the limitations of existing freshwater raw materials, as seawater accounts for approximately 97% of the water on Earth. At the same time, abundant by-product materials can be obtained, representative examples of which are Cl₂, ClO^-, Br₂, and Mg(OH)₂ produced during electrolysis, depending on their composition and pH environment. In order to develop a successful seawater electrolysis system and oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalysts, it is necessary to understand the causes and consequences of reactions that occur in the seawater environment. Therefore, in this paper, we will investigate the reaction mechanism and characteristics of the seawater electrolysis system as well as the research and development trends of electrochemical catalysts used in anode and cathode electrodes.

• Journal of Broadcast Engineering
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• v.11 no.3 s.32
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• pp.263-275
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• 2006

This paper introduces an interactive contents authoring system which can easily and conveniently produce interactive contents for the Terrestrial Digital Multimedia Broadcasting (T-DMB). For interactive broadcasting service, T-DMB adopted MPEG-4 BIFS technology. In order to the interactive service becomes flourishing on the market, various types of interactive contents should be well provided prior to the service. In MPEG-4 BIFS, broadcasting contents are described by the combination of a large number of nodes, routes and descriptors. In order to provide interactive data services through the T-DMB network, it is essential to have an interactive contents authoring system which allows contents authors to compose interactive contents easily and conveniently even if they lack any background on MPEG-4 BIFS technology. The introduced authoring system provides powerful graphical user Interface and produces interactive broadcasting contents in the forms of binary and textual format. Therefore, the BIFS contents authoring system presented in this paper would vastly contribute to the flourishing interactive service.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7B
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• pp.605-619
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• 2003

The main memory DBMS(MMDBMS) efficiently supports various database applications that require high performance since it employs main memory rather than disk as a primary storage. In this paper, we discuss the index manager of the Tachyon, a next-generation MMDBMS. Recently, the gap between the CPU processing and main memory access times is becoming much wider due to rapid advance of CPU technology. By devising data structures and algorithms that utilize the behavior of the cache in CPU, we are able to enhance the overall performance of MMDBMSs considerably. In this paper, we address the practical implementation issues and our solutions for them obtained in developing the cache-conscious index manager of the Tachyon. The main issues touched are (1) consideration of the cache behavior, (2) compact representation of the index entry and the index node, (3) support of variable-length keys, (4) support of multiple-attribute keys, (5) support of duplicated keys, (6) definition of the system catalog for indexes, (7) definition of external APIs, (8) concurrency control, and (9) backup and recovery. We also show the effectiveness of our approach through extensive experiments.

• Applied Chemistry for Engineering
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• v.30 no.1
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• pp.74-80
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• 2019

$Nafion/TiO_2$ composite membranes were prepared via an in-situ sol-gel process with different immersing periods from 1 day to 7 days for the low humidifying proton exchange membrane fuel cell. As the immersing time increased, the $TiO_2$ content within the Nafion membrane increased. The contact angle decreased with the increased $TiO_2$ content in the composite membrane due to the increased hydrophilicity. The water uptake and proton conductivity reached to the highest level for 4 day immersing period, then decreased as the immersing period increased. A 7 days of immersing time was shown to be too long because too much $TiO_2$ aggregates were formed on the membrane surface as well as interior of the membrane, interfering the proton transfer from anode to cathode. Cell performance results were in good agreement with those of the water uptake and proton conductivity; current densities under a relative humidity (RH) of 40% were 0.54, 0.6, $0.63A/cm^2$ and $0.49A/cm^2$ for the immersing time of 1, 3, 4 and 7 days, respectively at a 0.6 V. The composite membrane prepared via the in-situ sol-gel process exhibited the enhancement in the cell performance under of RH 40% by a maximum of about 66% compared to those of using the recasting composite membrane and Nafion 115.