• Journal of Electrochemical Science and Technology
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• 제10권4호
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• pp.402-407
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• 2019

Water electrolysis is known as the most sustainable and clean technology to produce hydrogen gas, however, a serious drawback to commercialize this technology is due to the slow kinetics in oxygen evolution reaction (OER). Thus, we report on the nanoporous IrNi thin film that reveals a markedly enhanced OER activity, which is attained through a selective etching of Os from the IrNiOs alloy thin film. Interestingly, electrochemical selective etching of Os leads to the formation of 3-dimensionally interconnected nanoporous structure providing a high electrochemical surface area (ECSA, 80.8 ㎠), which is 90 fold higher than a bulk Ir surface (0.9 ㎠). The overpotential at the nanoporous IrNi electrode is markedly lowered to be 289 mV at 10 mA cm^-2, compared with bulk Ir (375 mV at 10 mA cm^-2). The nanoporous IrNi prepared through the selective de-alloying of Os is promising as the anode material for a water electrolyzer.

• Journal of information and communication convergence engineering
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• 제8권5호
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• pp.595-601
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• 2010

The strategy through visual sense is one of the ways that subject builds the outside world and communicates. The visual sense seems higher level of dependence than the other senses and contributes to intercommunication. For this reason, the desire of image dates back to primitive art and visual image(visual media and visual culture) has dialectically developed in the history of mankind. Visual subject, based on perspective of Renaissance, was moved from God to human beings. Andre Bazin's 'la genese automatique' through technical art has epochally changed the paradigm of visual art and visual culture. From primitive art to photo and film, the image, based on visual sense, has reflected human wish, appealed visual desire and led to evolution of image. In the late 20 century, without dialectical evolution of technology and culture, rapidly progressive digital image has changed social and cultural implication over rational strategy of production and distribution and it strengthened authority of image through visual approach of endless desire. The goal of this study is to analyze the value change of digital image developing a new Renaissance through production, reading, communication, and implication of evolution due to digitalized image, which has evolved as object and tool of desire.

• 한국통신학회논문지
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• 제38A권8호
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• pp.712-723
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• 2013

근래 전 세계적으로 스마트 폰의 수요가 급증하면서 기존의 3G 표준에 비해 높은 데이터 전송률을 제공하는 long term evolution (LTE) 서비스가 활발히 보급되고 있다. 특히, 이동통신 강국인 우리나라는 LTE의 최신 릴리즈인 LTE-Advanced (LTE-A) 서비스를 최근 시작하였다. 높은 데이터 전송률을 얻기 위한 LTE와 LTE-A 시스템의 핵심기술로 다중입출력 안테나 (multiple-input-multiple-output; MIMO)기술을 들 수 있다. MIMO 기술은 주파수와 전력의 증가 없이 안테나 수에 비례하는 채널용량을 얻을 수 있는 장점으로 큰 주목을 받아왔으며 다양한 측면에서 진화 발전이 이루어지고 있다. 본 논문에서는 단일사용자 MIMO에서 다중사용자 MIMO, 그리고 최근 주목받고 있는 대용량 MIMO까지 MIMO기술의 이론적 배경 및 시스템을 구현하기 위해 필요한 고려사항들을 살펴본다.

• 한국전기전자재료학회논문지
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• 제31권1호
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• pp.11-18
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• 2018

Two-dimensional (2D) materials such as transition metal dichalcogenides have attracted tremendous scientific interests owing to their potential of solving the zero band-gap issue of graphene. In this work, the research areas and technology evolutionary dynamics of the 2D materials were identified using the scientometric method focusing on keyword mapping and clustering. The time-series analysis showed that the technological progress of 2D material is in the early growth period. The overlay mapping analysis were carried out to investigate the technology evolution of 2D materials with time. The strategic diagram of co-word analysis classifying the topological positions of keyword was derived to support the analysis results. It is conjectured that extensive research will be conducted widely on the application of 2D materials not only in electronic and optoelectronic devices, but also in various other fields such as biomedical applications, and that their development will be more rapid based on accumulated results of extant graphene research.

• 디지털콘텐츠학회 논문지
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• 제18권7호
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• pp.1281-1291
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• 2017

본 연구는 e-커머스의 진화 과정을 정리하면서 초기의 사업모델부터 최근 페이스북을 중심으로 나타나고 있는 새로운 형태의 커머스인 스마트 커머스의 출현까지 지난 20여 년 동안 국내 전자상거래 산업이 어떻게 진화되어 왔는지를 단계별로 고찰하였다. 연구자들은 단계별 진화 과정을 나선형 진화 이론을 적용, 비즈니스 모델의 진화, 플랫폼의 진화, 고객 서비스 가치의 진화, 분석과 평가 등 네 가지 진화 요인을 중심으로 설명하였고, 또 단계별 진화 과정에서 축적된 기술과 경험의 축을 중심으로 사업자의 관점과 사용자의 관점에서 탐색과 활용 이론을 적용, 혁신적인 기술과 고객의 피드백을 분석, 혁신적인 비즈니스 모델을 제시하였다. 연구자들은 산업의 진화 연구를 통해 미래를 예측할 수 있다는 측면에서 본 연구가 e-커머스 산업과 정책에 대한 이론적, 실무적 공헌 점이 있을 것으로 기대한다.

• Journal of Astronomy and Space Sciences
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• 제8권1호
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• pp.11-23
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• 1991

The dynamical evolution of globular clusters is studied using the orbit-averaged multicomponent Fokker-Planck equation. The original code developed by Cohn(1980) is modi-fied to include the effect of stellar evolutions. Plommer's model is chosen as the initial density distribution with the initial mass function index $\alpha$=0.25, 0.65, 1.35, 2.35, and 3.35. The mass loss rate adopted in this work follows that of Fusi-Pecci and Renzini(1976). The stellar mass loss acts as the energy source, and thus affects the dynamical evolution of globular clusters by slowing down the evolution rate and extending the core collapse time Tcc. And the dynamical length scale $$R_c, $$R_h is also extended. This represents the expansion of cluster due to the stellar mass loss.

• 경영과학
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• 제29권3호
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• pp.169-182
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• 2012

This study examines the co-evolutionary process between open innovation and firms' absorptive capacity. The effects of open innovation can be maximized through the capacity to absorb the knowledge from the external sources such as universities, government-support research institute, and private R&D centers. This study used data of STEPI technology innovation survey conducted at 2002, 2005, and 2008 (3 points measures). The data were analyzed through a structural equation model. Results suggest that open innovation at t0 point influences positively the absorptive capacity at t1 point, which subsequently enhances the intention of open innovation at t2 point. This result suggests the existence of co-evolutionary process between open innovation and firms' absorptive capacity. When knowledge comes from universities, the co-evolution has sustained; whereas when knowledge comes from private firms' R&D centers, the co-evolution has not effected. Theoretical and practical implications are discussed.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.205-210
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• 2002

This article presents an integrated modeling approach for coupled analysis of heat transfer and microstructure evolution in welding carbon steel. The modeling procedure utilizes commercial [mite element code ABAQUS/Standard as the platform for solving the equation of heat conduction. User subroutines that implement computational thermodynamics and kinetics models are integrated with the FEA code to compute the transient microstructure evolution. In this study, the integrated models are applied to simulate the hot-tap repair welding of carbon steel pipeline. Microstructural components are treated as user output variables. Based on the predicted microstructure and cooling rates, hardness distributions in the welds were also predicted. The predicted microstructure and hardness distribution were found in good agreement with metallographic examinations and hardness measurements. This study demonstrates the applicability of computational models for the development of welding procedure for in-service pipeline repair.

• Animal cells and systems
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• 제11권2호
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• pp.93-98
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• 2007

Gonadotropin-releasing hormone (GnRH), synthesized in the hypothalamus, plays a pivotal role in the regulation of vertebrate reproduction. Since molecular isoforms of GnRH and their receptors (GnRHR) have been isolated in a broad range of vertebrate species, GnRH and GnRHR provide an excellent model for understanding the molecular co-evolution of a peptide ligand-receptor pair. Vertebrate species possess multiple forms of GnRH, which have been created through evolutionary mechanisms such as gene/chromosome duplication, gene deletion and modification. Similar to GnRHs, GnRH receptors (GnRHR) have also been diversified evolutionarily. Comparative ligand-receptor interaction studies for non-mammalian and mammalian GnRHRs combined with mutational mapping studies of GnRHRs have aided the identification of domains or motifs responsible for ligand binding and receptor activation. Here we discuss the molecular basis of GnRH-GnRHR co-evolution, particularly the structure-function relationship regarding ligand selectivity and signal transduction of mammalian and non-mammalian GnRHRs.

• 한국결정성장학회지
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• 제14권2호
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• pp.58-62
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• 2004

The shape evolution of the interface void of copper metallization for intergrated circuits under electromigration stress is modeled. A 2-dimensional finite-difference numerical method is employed for computing time evolution of the void shape driven by surface diffusion, and the electrostatic problem is solved by boundary element method. When the diffusion coefficient is isotropic, the numerical results agree well with the known case of wedge-shape void evolution. The numerical results for the anisotropic diffusion coefficient show that the initially circular void evolves to become a fatal slitlike shape when the electron wind force is large, while the shape becomes non-fatal and circular as the electron wind force decreases. The results indicate that the open circuit failure caused by slit-like void shape is far less probable to be observed for copper metallization under a normal electromigration stress condition.