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Yang, Hyeeun,Yu, Jung-Hoon,Seo, Hyeon Jin,Jeong, Rak Hyun,Boo, Jin-Hyo Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.461 No.-
<P><B>Abstract</B></P> <P>Nanoporous NiO thin films were fabricated on indium tin oxide glass by simple chemical bath deposition (CBD). Dense porous structure was formed by NiO flakes with thickness controlled by aluminum through CBD. Nanoporous NiO thin films with high porosity showed excellent electrochromic properties, with transmittance change of 77% at 550 nm and coloration efficiency of 99.5 cm<SUP>2</SUP>/C. Electrochemical properties of these thin films were studied in a 0.1 M KOH electrolyte by cyclic voltammetry and chronoamperometry measurements. These nanoporous NiO thin films showed high porosity structure with excellent electro-reversibility. They are also very stable with long cyclic durability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> NiO, one of the electrochromic materials, was synthesized by chemical bath deposition. </LI> <LI> Aluminum was added at atomic percent to control the thickness of the thin film very thinly. </LI> <LI> The nanoporous NiO was fabricated with the thickness controlled film. </LI> <LI> The increased interconnect membrane increases the contact force with the substrate and the contact area with the electrolyte. </LI> <LI> The nanoporous NiO enhanced the overall electrochromic properties and the coloration efficiency was as high as 99.51 cm<SUP>2</SUP>/C. </LI> </UL> </P>
Yang, Hyeeun,Yu, Jung-Hoon,Jeong, Rak Hyun,Boo, Jin-Hyo Elsevier 2018 THIN SOLID FILMS - Vol.660 No.-
<P><B>Abstract</B></P> <P>Tungsten trioxide (WO<SUB>3</SUB>) is a typical electrochromic material that exhibits reversible optical property changes depending on the applied voltage. Previously, studies for its application in smart windows and various technologies have been made. However, improvements to the WO<SUB>3</SUB>-specific low color change rate are needed. The above problem can be solved by fabricating a color change layer with a large specific surface area through physical/chemical modification of the WO<SUB>3</SUB> layer and structural control for smooth electrolyte injection. In this study, three dimensional porous WO<SUB>3</SUB> nanostructures were prepared using polystyrene nanospheres. Inverse opal structured WO<SUB>3</SUB> thin films with high porosity showed excellent electrochromic properties. The change in transmittance was 86% at a wavelength of 700 nm; the response time was 5.55 s; and the coloration efficiency was calculated at 154.94 cm<SUP>2</SUP>/C. The response time was about 3 times faster and the coloration efficiency was about 2 times higher than that of the flat thin film. As a result, the WO<SUB>3</SUB> thin film with an inverted opal structure exhibited excellent electro reversibility and enhanced properties.</P> <P><B>Highlights</B></P> <P> <UL> <LI> WO<SUB>3,</SUB> one of electrochromic materials, was synthesized into a needle-shaped colloidal ink. </LI> <LI> The polystyrene beads were used as a template to fabricate an inverse opal structure. </LI> <LI> As the layer increases, the contact area with the electrolyte increases. </LI> <LI> Increasing the area of WO<SUB>3</SUB> in contact with the electrolyte improves ion transport. </LI> <LI> That is, the porous WO<SUB>3</SUB> film improves the overall electrochromic characteristics. </LI> </UL> </P>
Linda Hyeeun Yang,전지현(Jeon, Jihyeon) 한국비서학회 2014 비서·사무경영연구 Vol.23 No.1
영어능력이 개인의 역량 중 중요한 지표가 되면서, 구직 시나 취업 이후에도 영어학습의 열풍이 이어지고 있다. 많은 연구자가 학습동기가 영어학습의 성공에 중요하다고 밝히고 있지만, 한국인 성인 학습자의 영어 학습동기에 대한 연구는 상대적으로 부족하며, 특히 동기저하에 대한 연구는 국내에서 찾아보기 힘들다. 본 연구는 서비스 분야에 종사하는 성인 학습자의 영어학습 과정 중 1) 동기저하 경험 2) 동기저하를 극복하는 데 성공하는 요인 3) 동기저하를 극복하는 데 실패하는 요인을 살펴보는 것을 목적으로 수행되었다. 중요사건기법을 활용한 설문에 서울소재 호텔종사자들 중 133명이 응답하였고, 응답결과는 내용분석(content analysis)되었다. 분석결과, 응답자의 65%가 영어학습 중 동기저하를 적어도 한 번은 겪은 것으로 나타났다. 동기저하에 영향을 준 요인은 심리적인 이유, 학습자체의 어려움, 그리고 부적절한 교수/학습 방법인 것으로 나타났다. 동기저하를 경험한 학습자의 69%는 심리적인 회복 또는 이전과는 다른 학습 방법의 시도를 통하여 동기저하를 극복하고 있었다. 그러나, 안타깝게도 동기저하를 경험한 학습자의 21%는 관심과 노력의 부족으로 영어 학습동기를 다시 회복하지 못하는 것으로 나타났다. 연구결과를 토대로 성인학습자의 영어학습 동기부여 방안을 논의한다. The English language is becoming more and more important as countries globalize. In studying language learning, many researchers have focused on motivation as an important factor that determines success. However, research related to demotivation or overcominng demotivation is relatively insufficient. This research examined 1) adult learners" experiences of demotivation; 2) success factors for overcoming demotivation; and 3) failure factors for overcoming demotivation in studying English language within the service industry. The study conducted surveys on employees of hotels located in Seoul. One hundred and thirty three questionnaires were collected via Critical Incident Survey. Data were then analyzed by content analysis using Excel. The results show that 65% of participants experienced demotivation which means these learners lost motivation in learning the English language at least once. Factors causing demotivation were psychological reasons, learning difficulties, and inappropriate teaching/learning methods. Among learners who experienced demotivation in learning English language, 69% of learners were able to recover their motivation by psychological recovery as well as different learning methods. Unfortunately, however, 21% of students who experienced demotivation were not able to overcome their psychological problems, learning difficulties, or inappropriate learning methods mainly due to insufficient effort and concerns by the learner. Methods for motivating adult learners are discussed based on the results.
Hierarchical NiO/TiO<sub>2</sub> composite structures for enhanced electrochromic durability
Yu, Jung-Hoon,Yang, Hyeeun,Jung, Rak Hyun,Lee, Ji Won,Boo, Jin-Hyo Elsevier 2018 THIN SOLID FILMS - Vol.664 No.-
<P><B>Abstract</B></P> <P>This study presents the fabrication of nickel oxide (NiO) thin films with enhanced electrochromic durability by combining titanium dioxide (TiO<SUB>2</SUB>) honeycomb structure. The final structure possesses an hierarchical architecture with a substructure of honeycomb structured TiO<SUB>2</SUB> prepared by liquid phase deposition through polystyrene sphere monolayer template with diameter of 800 nm and a superstructure of porous NiO nanoflake array prepared by chemical bath deposition. Compared to the pure NiO nanoflake film, the composite NiO/TiO<SUB>2</SUB> films exhibits noticeable electrochromic cycling durability (only 25% decrease after 5000 cycles) at 550 nm and fast coloration and bleaching response rate (13.4 and 6.7 s). This improvement in electrochromic properties is due to the rapid dissociation of electrons and photons through the composite structure of the n-type TiO<SUB>2</SUB> core/p-type NiO shell and rapid electrolyte penetration through ordered array geometry with increased surface area.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hierarchical NiO/TiO<SUB>2</SUB> composite films were achieved by chemical bath deposition. </LI> <LI> The NiO/TiO<SUB>2</SUB> composite films exhibits shorten coloring and bleaching response time. </LI> <LI> Noticeable improvement of durability for the NiO/TiO<SUB>2</SUB> composite was observed over 5000 cycles. </LI> <LI> These P/N composite can enhance the separation of electron and proton by the electric junction field. </LI> </UL> </P>