CsPbX3/SiOx (X = Cl, Br, I) monoliths prepared via a novel sol-gel route starting from Cs4PbX6 nanocrystals

Park, Sungwook,An, Mai Ngoc,Almeida, Guilherme,Palazon, Francisco,Spirito, Davide,Krahne, Roman,Dang, Zhiya,De Trizio, Luca,Manna, Liberato The Royal Society of Chemistry 2019 Nanoscale Vol.11 No.40

<P>We developed a facile synthesis of nanocomposite powders of CsPbX3 nanocrystals (NCs) embedded in silica. The synthesis starts from colloidal Cs4PbX6 NCs that are mixed with tetraethyl orthosilicate in the presence of nitric acid, which triggers the sol-gel reaction yielding the formation of SiOx and the conversion of starting NCs into CsPbX3 ones. The overall reaction delivers CsPbX3 NCs encased in a silica matrix. The resulting CsPbX3/SiOx nano-composite powders exhibited enhanced moisture and thermal stability in air. Also, when mixing different CsPbX3/SiOx samples having diverse anion compositions, no interparticle anion exchange processes were observed, which is a further indication that the silica matrix acts as a robust barrier surrounding the NCs. Finallly, we used these composites as down-converter phosphors on top of a blue light-emitting diode (LED), delivering nearly ideal white light emission with the Commission Internationale de l'Eclairage (CIE) color coordinates (0.32, 0.33).</P>

Demolding temperature in thermal nanoimprint lithography

Park, Sunggook,Song, Zhichao,Brumfield, Lance,Amirsadeghi, Alborz,Lee, Jaejong Springer-Verlag 2009 APPLIED PHYSICS A MATERIALS SCIENCE AND PROCESSING Vol.97 No.2

Detection of Avian Influenza Virus from Cloacal Swabs Using a Disposable Well Gate FET Sensor

Park, Sungwook,Choi, Jaebin,Jeun, Minhong,Kim, Yongdeok,Yuk, Seong-Su,Kim, Sang Kyung,Song, Chang-Seon,Lee, Seok,Lee, Kwan Hyi Wiley (John WileySons) 2017 Advanced Healthcare Materials Vol.6 No.13

Prediction of wall impingement in a direct injection spark ignition engine by analyzing spray images for high-pressure injection up to 50 MPa

Park, Junkyu,Kim, Taehoon,Kim, Donghwan,Park, Sungwook Elsevier 2018 Fuel processing technology Vol.179 No.-

<P><B>Abstract</B></P> <P>This study was performed to analyze the wall impingement and fuel film formation in a DISI engine with injection strategies using image-based analysis and CFD. The direct injection engine uses a high-pressure injection strategy to improve the homogeneity of the air-fuel mixture, so the spray behavior was analyzed by spray visualization for various injection pressures, and the wall impingement was predicted for various engine operating conditions based on the acquired images. The mass distribution of the injected fuel was calculated using the injection profiles and the spray image, and the amount of fuel that impinges on the piston and wall (i.e., the geometric boundaries of the cylinder) was calculated using data from the spray behavior for various engine operation conditions such as load and engine speed. The image-based analysis was limited to understanding the influence of the injection strategy on the droplet behavior after wall impingement of the fuel spray. Therefore, CFD using KIVA 3 V code was additionally conducted to analyze the effects of the injection strategies on wall film formation and droplet rebounding reflecting in-cylinder conditions. In the early- and late-injection conditions, the initial piston position is high, and most of the injected fuel impinges on the piston. As the injection pressure increases, the injection timing at which wall impingement occurs is advanced because of the rapid spray development. The results of the 3D analysis for the temperature and the intake flow in the engine cylinder showed that both the wall impingement and the fuel film were reduced as the injection pressure increased because the fuel evaporation increased due to improved atomization.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A prediction method of wall impingement in DISI engines is introduced. </LI> <LI> Effects of injection pressure and injection timing on spray wall impingement are analyzed using image-based method. </LI> <LI> 3D CFD are used to analyze effects of the engine conditions on formation of fuel film. </LI> <LI> Higher injection pressure conditions can reduce formation of fuel film due to superior vaporization characteristics. </LI> </UL> </P>

Spontaneous reduction of Cr(VI) using InSnS₂ under dark condition

Park, Sungmook,Kim, Woolcheol,Selvaraj, Rengaraj,Kim, Younghun Elsevier 2017 Chemical engineering journal Vol.321 No.-

<P><B>Abstract</B></P> <P>The flower-like In<SUP>3+</SUP>-doped SnS<SUB>2</SUB> (InSnS<SUB>2</SUB>) was synthesized by microwave-assisted method for the photoreduction of toxic Cr(VI) to less-toxic Cr(III). InSnS<SUB>2</SUB> showed a narrow bandgap (2.0eV) and a broad spectrum response (400–800nm), suitable to apply the photocatalytic reduction of Cr(VI) under visible-light irradiation. In our latest report, we found that the enhanced photocatalytic activity was caused by the indium doping and the formic acid, which acted as the inhibitor to hole–electron recombination and hole scavenger, respectively. Herein, as a further study, the contact time of Cr(VI) with InSnS<SUB>2</SUB> in the dark condition was adjusted to ensure the adsorption–desorption equilibrium, and its effect on the reduction activity was evaluated. The results show that spontaneous reduction of Cr(VI) was observed in the initial adsorption process in the dark condition via the synergistic effect of In<SUP>3+</SUP> release and HCOOH, and at later the reduction of Cr(VI) only occurred by the photocatalytic reaction under visible-light irradiation. Finally, the adsorption of Cr(VI) on photocatalyst before light irradiation was found as an important factor to enhance the photoreduction of Cr(VI).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Microwave-assisted synthesis of In<SUP>3+</SUP> doped SnS<SUB>2</SUB> as visible-light-driven photocatalyst. </LI> <LI> Spontaneous reduction of Cr(VI) in dark condition via the synergistic effect of In<SUP>3+</SUP> and HCOOH. </LI> <LI> Indium-doping and formic acid acted as inhibitor of hole–electron recombination and hole scavenger. </LI> <LI> Adsorption before light irradiation on photocatalyst was important factor. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Reusing the Optimized Code for JavaScript Ahead-of-Time Compilation

Park, Hyukwoo,Kim, Sungkook,Park, Jung-Geun,Moon, Soo-Mook Association for Computing Machinery 2018 ACM transactions on architecture and code optimiza Vol.15 No.4

Simultaneous reduction in the exhaust emissions by a high exhaust gas recirculation ratio in a dimethyl-ether-fuelled diesel engine at a low-load operating condition

Park, Su Han,Cha, Junepyo,Park, Sungwook,Lee, Chang Sik SAGE Publications 2012 Proceedings of the Institution of Mechanical Engin Vol.226 No.8

<P>The purpose of this study was to investigate the effect of the exhaust gas recirculation rate on the combustion and exhaust emission reduction characteristics of dimethyl ether fuel in a single-cylinder diesel engine. To investigate the effects on emission reduction, the test set-up was composed of a dimethyl ether supply system, a spray visualization system, an engine combustion system and an emissions analysis system. In this work, the spray visualization and exhaust emissions were measured using a high-speed camera with a metal halide lamp, a smoke meter and an emission gas analyser. The spray tip penetration and tip velocity of dimethyl ether fuel were lower than those of conventional diesel fuel. The reduction slope of the spray cone angle for dimethyl ether was less than that for diesel fuel owing to its low density and superior evaporation characteristics. The increase in the exhaust gas recirculation rate caused an extension of the ignition delay for dimethyl ether. During the extended ignition delay, the improved mixing characteristics influenced the slight decrease in the combustion period. An increase in the exhaust gas recirculation rate caused a significant reduction in the emission of nitrogen oxides. In addition, the soot emission was very low owing to the intrinsic characteristics of dimethyl ether (no direct carbon-carbon bonds). At the given equivalence ratio condition, the indicated specific hydrocarbon and indicated specific carbon monoxide emissions for dimethyl ether were extremely low when dimethyl ether spray was injected into the piston bowl (from 25 degrees before top dead centre to top dead centre). Also, in this case, a change in the exhaust gas recirculation rate for dimethyl ether combustion had minimal effects on the indicated specific hydrocarbon and indicated specific carbon monoxide emissions. These results suggest that the use of high exhaust gas recirculation with dimethyl ether fuel can achieve near-zero exhaust emissions (nitrogen oxides, soot, hydrocarbons and carbon monoxide).</P>

Mission at the Roundtable of diversity in God’s Mission

PARK SungKook 성공회대학교 신학연구소 2013 Madang: Journal of Contextual Theology Vol.19 No.-

“Asia” has been known as the icon and expression of “Variety”, “Diversity” and “Cultural richness”. Asia – as a continent – forms the largest piece of soil on earth and is home to almost 4 billion people. Economically, Asia is a continent that reflects the most paradox phenomena: While certain countries are regarded as the most affluent ones in the world, the Asian continent also shows in some of its parts, the lowest income and hence, the poorest among the poor. Following their economical standards the gap between different technically equipped and non- or less equipped is evident: While some of the countries in Asia are praised to be equipped with one of the most sophisticated technical achievements in the human history, some regions in Asia show serious ‘underdevelopment’ in these respective terms. And historically, Asia is a wound-driven continent where most of the countries in Asia bear dark memories of being exploited in the past, and still many are still getting exploited. The term “cultural richness”, expresses itself in a huge variety of diverse forms of cultures; different languages (probably the most languages in numbers in the world) and different religions and religious practices. We may witness the oldest forms of human settlements (or civilization) up to the youngest developed industrial powers in Asia. In Asia we witness a wide spectrum from politically stable democratic countries to unstable, almost fragile countries; peaceful regions but also frequently or even constantly conflict driven places; regions that never have been affected by calamities or disasters, but also regions where calamities or disasters are almost like on the ‘daily agenda’.

읽기장애아동과 일반아동의 통사적 다양성에 따른 운율 특성 비교

박성숙(Sungsook Park),성철재(Cheoljae Seong) 한국음성학회 2021 말소리와 음성과학 Vol.13 No.4

읽기와 관련된 운율은 내용의 전체적인 맥락에 연결되어 독자가 전달하고자 하는 의미를 자연스럽게 표현할 수 있도록 음도, 강도, 발화속도 등의 변화로 나타난다. 읽기장애아동은 자연스러운 운율을 사용한 읽기에 어려움이 있어 표현력 있게 정보를 전달하지 못하는 경향이 있다. 이와 관련하여 본 연구는 문장 유형에 따른 읽기 과제를 통하여 읽기장애아동 집단과 일반아동 집단 간의 운율 특성 차이를 규명하였다. 초등학교 3-6학년 읽기장애아동 15명, 일반아동 15명을 대상으로 통사적으로 다양한 문장 유형(단문, 의도, 가정/조건, 관형절 내포문)에 따른 읽기 과제를 실시하였다. 읽기장애아동은 일반아동에 비해 음도 범위가 넓었으며 읽기 속도와 조음 속도가 느렸다. 또한 휴지 빈도가 높았으며 전체 휴지 지속시간도 길었다. 읽기장애아동은 문미 억양구와 문장 내 어절 단위 음도 기울기에서 일반아동에 비해 기울기 값이 컸으며 이상의 내용은 모두 통계적으로 유의하였다. 결과적으로 문장 유형에 따른 읽기 과제에서 읽기장애아동은 일반아동에 비해 자연스럽고 표현력 있는 읽기에 어려움을 보였다. 본 연구를 통해 읽기장애아동의 운율 특성을 파악하였고, 효과적인 중재를 위한 접근 방법의 필요성을 제시했다. Proper prosody in reading allows the reader to naturally convey the meaning, which manifests as changes in pitch, loudness, and speech rate. Children with reading disability face difficulty in delivering information due to poor prosody. This study identified the difference in prosodic features between children with reading disabilities and nondisabled children through means of reading tasks. Reading tasks, according to sentence types (short sentences, assumptions/conditions, intentions, relative-clause), were recorded by 15 children studying in the 3rd to 6th grade in elementary school. Children with reading disability had a statistically significant wider range of pitch, slower speech rate, more frequent usage of pauses, longer total pause duration, and steeper pitch slope than nondisabled one in sentence-final and -medial words. Children with reading disability, therefore, exhibited a less natural and expressive reading than nondisabled children. Through this study, the characteristics of prosody observed in children with reading disability were identified and the need for an approach for effective intervention was also suggested.

전기자동차 배터리 성능저하 관리 제도

박성욱(Sungwook Park) 한국자동차공학회 2023 오토저널 Vol.45 No.7