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A White-Light-Emitting Molecule: Frustrated Energy Transfer between Constituent Emitting Centers
Park, Sanghyuk,Kwon, Ji Eon,Kim, Se Hun,Seo, Jangwon,Chung, Kyeongwoon,Park, Sun-Young,Jang, Du-Jeon,Medina, Begoñ,a Miliá,n,Gierschner, Johannes,Park, Soo Young American Chemical Society 2009 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.131 No.39
<P>White-light-emitting single molecules are promising materials for use in a new generation of displays and light sources because they offer the possibility of simple fabrication with perfect color reproducibility and stability. To realize white-light emission at the molecular scale, thereby eliminating the detrimental concentration- or environment-dependent energy transfer problem in conventional fluorescent or phosphorescent systems, energy transfer between a larger band-gap donor and a smaller band-gap acceptor must be fundamentally blocked. Here, we present the first example of a concentration-independent ultimate white-light-emitting molecule based on excited-state intramolecular proton transfer materials. Our molecule is composed of covalently linked blue- and orange-light-emitting moieties between which energy transfer is entirely frustrated, leading to the production of reproducible, stable white photo- and electroluminescence.</P>
Park, Sanghyuk,Seo, Jangwon,Kim, Se Hun,Park, Soo Young WILEY-VCH Verlag 2008 Advanced Functional Materials Vol.18 No.5
<P>Aiming for highly efficient blue electroluminescence, we have designed and synthesized a novel class of tetraphenylimidazole- based excited-state intramolecular proton-transfer (ESIPT) molecules with covalently linked charge-transporting functional groups (carbazole- and oxadiazole-functionalized hydroxyl-substituted tetraphenylimidazole (HPI), i.e., HPI-Cbz and HPI-Oxd, respectively). High T<SUB>g</SUB> (ca. 130 °C) amorphous films of HPI-Cbz and HPI-Oxd showed intense and ideal blue-light emission (λ<SUB>max</SUB> = 462 and 468 nm, Φ<SUB>PL</SUB> = 0.44 and 0.38) with a large Stokes shift of over 160 nm and a narrow full width at half-maximum of less than 65 nm. Organic light-emitting devices using HPI-Cbz and HPI-Oxd as the emitting layer generated an efficient blue electroluminescence (EL) emission peaking at around 460 nm with excellent CIE coordinates of (x, y) = (0.15, 0.11). A maximum external quantum efficiency of 2.94%, and a maximum brightness of 1 229 cd m<SUP>−2</SUP> at 100 mA cm<SUP>−2</SUP>, as well as a low turn-on voltage of 4.8 V were achieved in this work.</P> <B>Graphic Abstract</B> <P>Novel hydroxyl-substituted tetraphenylimidazole derivatives promise efficient bright-blue electroluminescence as shown in the figure. Devices based on these structures attained current densities of 1.96 cd A<SUP>−1</SUP> and quantum efficiencies of up to 2.94%. The devices also showed much improved morphological and thermal stability. <img src='wiley_img/1616301X-2008-18-5-ADFM200700827-content.gif' alt='wiley_img/1616301X-2008-18-5-ADFM200700827-content'> </P>
Microstructural evolution of chemically vapor-deposited tantalum carbide at elevated temperatu
Jangwon Han,SangMin Jeong,Ji Yeon Park,Hyun-Geun Lee,Weon-Ju Kim,Chan Park,Daejong Kim 한양대학교 청정에너지연구소 2022 Journal of Ceramic Processing Research Vol.23 No.6
Tantalum carbide (TaC), one of the ultra-high temperature ceramics, was chemically vapor-deposited at 1100 - 1300 oC in a TaCl5-C3H6-H2 system. Microstructural evolution of TaC was evaluated after heat treatment at 1850 oC for 4 hours. Various tantalum carbides with different orientation and microstructure were obtained depending on the deposition temperature andthe position. Crystallophic preferred orientation of the TaC changed from highly oriented (111) and (200), to random texture, as deposition temperatures increase. The continuous feed of TaCl4 powders using screw-driven feeder led to the fluctuation of TaCl4 partial pressure during the deposition process, resulted in a low crystallinity and formation of micropores. A dense TaC was only obtained at the high partial pressure of TaCl5. Heat treatment dramatically enhanced crystallinity but micropores were coalesced into large pores along grain boundaries. The influence of crystallophic orientation and microstructure on microstructural evolution and hardness during heat treatment were investigated.
VL-ECC: Variable Data-Length Error Correction Code for Embedded Memory in DSP Applications
Jangwon Park,Jongsun Park,Bhunia, Swarup IEEE 2014 IEEE Transactions on Circuits and Systems II: Expr Vol. No.
<P>Increasing process variations coupled with aggressive scaling of cell area and operating voltage in the quest of higher density and lower power have greatly affected the reliability of on-chip memory. Error correction code (ECC) has been traditionally used inside memory to provide uniform protection to all bits in a code word. They suffer from either adequate protection against multibit failures or large overhead due to encoding/decoding logic and parity bits. To address this issue, we present a variable data-length ECC (VL-ECC) for the embedded memory devices of digital signal processors, in which the data length of ECC can be dynamically reconfigured to preferentially protect the relatively more important bits. In the proposed VL-ECC, when the number of failures exceeds the error correction capability, the data length of ECC is reduced to focus on the relatively more important higher order data bit parts, thereby minimizing system quality degradation due to bit failures. When the proposed VL-ECC is applied to the embedded memory devices of an H.264 processor, average peak signal-to-noise-ratio improvements of up to 5.12 dB are achieved compared with the conventional ECC under supply voltage of 800 mV or lower. With the fast Fourier transform processor, signal-to-quantization noise ratio is improved by up to 5.2 dB.</P>
박장원(Jangwon Park),이오영(Ohyoung Lee),임종빈(Jongbin Im),이수용(Soo-Yong Lee),박정선(Jungsun Park) 한국항공우주학회 2008 韓國航空宇宙學會誌 Vol.36 No.5
본 논문에서는 이동최소자승법을 이용한 근사모델을 사용하여 신뢰성 최적설계를 수행하였다. 신뢰성 최적설계의 수행을 위한 반응표면 생성에는 RSM 과 Kriging이 사용될 수 있다. RSM은 계산시간은 빠르나 비선형성이 강한 문제에 약하며 Kriging은 비선형성이 강한 문제에 적용할 수 있으나 계산시간이 오래 걸리는 단점이 있다. 이 두 방법을 보완한 방법인 이동최소자승법(MLSM)을 이용하여 신뢰성 최적설계를 위한 반응표면을 생성하였다. 이동최소자승법을 이용한 신뢰성 최적설계기법은 Rosenbrock function 과 six-hump carmel back function으로 검증하였고 다른 기법과 비교하였다. 이동최소자승법을 이용하여 무인항공기 배기 덕트의 신뢰성 최적설계를 수행하였고 이는 항공우주구조물의 최적설계 에 유용할 것으로 보여 진다. This study is focused on reliability based design optimization (RBDO) using moving least squares. A response surface is used to derive a limit-state equation for reliability based design optimization. Response surface method (RSM) with least square method (LSM) or Kriging will be used as a response surface. RSM is fast to make the response surface. On the other hand, RSM has disadvantage to make the response surface of nonlinear equation. Kriging can make the response surface in nonlinear equation precisely but needs considerable amount of computations. The moving least square method (MLSM) is made of both methods (RSM with LSM+Kriging). Numerical results by MLSM are compared with those by LMS in Rosenbrock function and six-hump carmel back function. The RBDO of engine duct of smart UAV is pursued in this paper. It is proved that RBDO is useful tool for aerospace structural optimal design problems.
Seo, Jangwon,Kim, Sehoon,Gihm, Se Hoon,Park, Chong Rae,Park, Soo Young Royal Society of Chemistry 2007 Journal of materials chemistry Vol.17 No.48
<P>We have synthesized a novel class of excited-state intramolecular proton transfer-active molecule (DOXG) forming columnar liquid crystals with enhanced fluorescence emission. The intramolecularly H-bonded core of DOXG produced columnar hexagonal and rectangular phases during cooling as a result of strong core-to-core interactions. In its mesophase, DOXG produced tilted stacking (J-type) in the inner column due to the elliptical molecular shape, bringing about a strong (quantum yield of 34%) and large Stokes' shifted (∼173 nm) fluorescence emission.</P> <P>Graphic Abstract</P><P>We report a fluorescent columnar liquid crystal consisting of an ESIPT core of elliptical molecular shape that plays a key role in establishing a tilted columnar stacking and enhanced fluorescence emission. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b711883j'> </P>
Multi-Channel PCNN 모델을 활용한 약물-약물 상호작용 관계 추출
박찬희(Chanhee Park),조민수(Minsoo Cho),박장원(Jangwon Park),박상현(Sanghyun Park) 한국컴퓨터정보학회 2019 한국컴퓨터정보학회 학술발표논문집 Vol.27 No.1
DDI 추출은 생물 의학 문헌으로부터 약물-약물 상호작용(Drug-Drug Interaction) 관계를 추출하는 작업으로, 기존에 알려지지 않은 인체 내 약물 간의 효과 또는 부작용 정보를 제공하는데 중요한 역할을 한다. 본 연구에서는 PCNN 모델을 활용하여 특징추출 과정을 자동화하고 약물 개체 간의 구조 정보를 포착해 개체 간 관계를 효율적으로 추출하였으며, 생물 의학 문헌에서 쓰이는 생소한 용어를 보다 풍부하게 표현하기 위해 5가지 버전의 단어 임베딩을 PCNN의 채널로 사용하였다. 본 연구에서 제안하는 MC-PCNN 모델의 성능 평가를 위해 DDI’13 Corpus 데이터를 사용하여 비교 실험을 진행하였으며, 그 결과 기존 연구 보다 F1 점수 기준 최대 2.05%p 향상된 성능을 보이며 DDI 관계 추출에서 효과적인 방법론임을 확인하였다.
First record of the genus Daiconotrechus (Coleoptera: Carabidae) in Korea
Jangwon Seo,Jong-seok Park 한국응용곤충학회 2023 한국응용곤충학회 학술대회논문집 Vol.2023 No.10
The genus Daiconotrechus Ueno, 1971 is endemic genus of Japan with two subgenera, Daiconotrechus Ueno, 1971 and Tsuiblemus Ueno, 2007. Adults of all species in this genus are eyeless with depigmented and elongated body. These morphological features are typical characters of adaptation to subterranean environments. Distribution of all species of the subgenus Tsuiblemus is restricts to Tsushima Island, Japan. In this study, we report the genus Daiconotrechus for the first time in Korea, with a new species in the subgenus Tsuiblemus. Illustrations of morphological characters and habitus are also provided.