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Dukhyun Nam,Geunhyeong Lee,Jooheon Kim 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.123 No.-
The development of effective, stable, and inexpensive electrocatalysts through oxygen evolution reaction(OER) is important but also very difficult. Anion defects are used to control the active sites of electrocatalysts. In this study, we persent an easy NaBH4 reduction strategy for engineering a novel Fe-doped nickelphosphide material with phosphorus vacancies, (i.e., Fe-Ni2P (PV)) for OER. Interestingly, this easy NaBH4reduction tactic can fulfill defects engineering (i.e., P vacancies). The P vacancies can adjust the electronicstructures of electrocatalyst for OER. Fe-Ni2P (PV) has outstanding OER performance, e.g., a lower overpotential(290 mV at 10 mA cm2), smaller Tafel slope (41.15 mV dec-1), and excellent durability (93.5% for12 h) under alkaline condition. This work indicates the detailed structural changes of NaBH4 reductiontreated-engineered materials and improves understanding of the structure-effect relationship of highperformance OER electrocatalyst.
Vehicle Software Validation & Testing Automation
Dukhyun (Dan) Lee 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Quality of an automobile heavily depends on reliability of the automotive system software which enables most of controllers in a vehicle to work and communicate each other. In the development of an automotive embedded system, it is important to determine if the software system meets its stated requirement, specification, and if its behavior is correct. Therefore, thorough validation of the software system is one of key factors to improve automobile quality. This paper is to address an effective automotive system software validation process not only to improve automobile quality but also to avoid high warranty cost. From the development phase to the production phase of a vehicle development, required activities from each validation phase is also discussed in detail. The automotive system software validation largely is executed in two major testing environments, system and subsystem level. Content and purpose of each testing environment is included in this paper. The software validation, however, requires experienced software test engineers and timely completion of required or planned testing. Therefore, the testing automation is a way to reduce required number of experienced test engineer and to meet a validation timing target. Two ideas of the testing automation are introduced in this paper. The first idea is to develop a modeling with MATLAB or Simulink to automatically perform testing on a system test bench or subsystem test bench. The second idea is to develop an automated testing tool within AUTOSAR (AUTomotive Open System ARchitecture) to verify automotive system software in the early phase of vehicle development life cycle.
Choi, Dukhyun,Choi, Min-Yeol,Choi, Won Mook,Shin, Hyeon-Jin,Park, Hyun-Kyu,Seo, Ju-Seok,Park, Jongbong,Yoon, Seon-Mi,Chae, Seung Jin,Lee, Young Hee,Kim, Sang-Woo,Choi, Jae-Young,Lee, Sang Yoon,Kim, Jo WILEY-VCH Verlag 2010 ADVANCED MATERIALS Vol.22 No.19
<B>Graphic Abstract</B> <P>The cover shows an image of fully rollable transparent nanogenerators synthesized using chemical vapor deposition grown large-scale graphene sheets as transparent electrodes and piezoelectric ZnO nanorod arrays. Sang-Woo Kim, Jae-Young Choi, and co-workers report on p. 2187 the electrical and structural stability of the nanogenerators, with excellent charge scavenging performance under external mechanical loads such as bending and rolling. This study shows that graphene-based nanogenerators are very promising for self-powered rollable transparent device applications. <img src='wiley_img_2010/09359648-2010-22-19-ADMA201090066-content.gif' alt='wiley_img_2010/09359648-2010-22-19-ADMA201090066-content'> </P>
Plasmonic Optical Interference
Choi, Dukhyun,Shin, Chang Kyun,Yoon, Daesung,Chung, Deuk Seok,Jin, Yong Wan,Lee, Luke P. American Chemical Society 2014 NANO LETTERS Vol.14 No.6
<P>Understanding optical interference is of great importance in fundamental and analytical optical design for next-generation personal, industrial, and military applications. So far, various researches have been performed for optical interference phenomena, but there have been no reports on plasmonic optical interference. Here, we report that optical interference could be effectively coupled with surface plasmons, resulting in enhanced optical absorption. We prepared a three-dimensional (3D) plasmonic nanostructure that consists of a plasmonic layer at the top, a nanoporous dielectric layer at the center, and a mirror layer at the bottom. The plasmonic layer mediates strong plasmonic absorption when the constructive interference pattern is matched with the plasmonic component. By tailoring the thickness of the dielectric layer, the strong plasmonic absorption can facilely be controlled and covers the full visible range. The plasmonic interference in the 3D nanostructure thus creates brilliant structural colors. We develop a design equation to determine the thickness of the dielectric layer in a 3D plasmonic nanostructure that could create the maximum absorption at a given wavelength. It is further demonstrated that the 3D plasmonic nanostructure can be realized on a flexible substrate. Our 3D plasmonic nanostructures will have a huge impact on the fields of optoelectronic systems, biochemical optical sensors, and spectral imaging.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2014/nalefd.2014.14.issue-6/nl5008823/production/images/medium/nl-2014-008823_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl5008823'>ACS Electronic Supporting Info</A></P>
Dependence of the mechanical properties of nanohoneycomb structures on porosity
Choi, Dukhyun,Lee, Sangmin,Lee, Changwoo,Lee, Pyungsoo,Lee, Junghyun,Lee, Kunhong,Park, Hyunchul,Hwang, Woonbong IOP 2007 Journal of micromechanics and microengineering Vol.17 No.3
<P>Mechanical properties of nanohoneycomb structures are measured for varying porosity (or pore diameter) of the nanohoneycomb structure. The indentation modulus and hardness in the pore direction (or thickness direction) are obtained from indentation tests using a nano-indenter. The bending modulus of the nanohoneycomb structures in the vertical direction relative to the pore (generally along the beam length) is determined from bending tests in AFM. To determine the bending modulus of the nanohoneycomb structures, the area moment of inertia of the nanohoneycomb structure is determined according to the arrangement of the pores. The indentation moduli and the hardness are found to decrease nonlinearly with increasing porosity. The bending moduli of the nanohoneycomb structures also decrease nonlinearly as a function of porosity over a large range. It is made clear that the elastic modulus of a homogenous material can be controlled by changing the pore diameter.</P>
Fully Rollable Transparent Nanogenerators Based on Graphene Electrodes
Choi, Dukhyun,Choi, Min-Yeol,Choi, Won Mook,Shin, Hyeon-Jin,Park, Hyun-Kyu,Seo, Ju-Seok,Park, Jongbong,Yoon, Seon-Mi,Chae, Seung Jin,Lee, Young Hee,Kim, Sang-Woo,Choi, Jae-Young,Lee, Sang Yoon,Kim, Jo WILEY-VCH Verlag 2010 Advanced Materials Vol.22 No.19
<B>Graphic Abstract</B> <P>Fully rollable transparent nanogenerators have been developed using chemical vapor deposition-grown large-scale graphene sheets as transparent electrodes and piezoelectric ZnO-nanorod arrays. The electrical and structural stability of the nanogenerators with excellent charge scavenging performance under external mechanical loads such as bending and rolling shows that graphene-based nanogenerators are suitable for self-powered rollable transparent device applications. <img src='wiley_img_2010/09359648-2010-22-19-ADMA200903815-content.gif' alt='wiley_img_2010/09359648-2010-22-19-ADMA200903815-content'> </P>