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Crystal Growth and Scintillation Properties of <tex> ${\hbox {Rb}}_{2} {\hbox {CeBr}} _{5}$</tex>
Sunghwan Kim,Joon Il Lee,Sih-Hong Doh,Hong Joo Kim,Hwanbae Park,Heedong Kang,Dosung Kim,Hong U IEEE 2009 IEEE transactions on nuclear science Vol.56 No.3
<P>In this paper, crystal growth and scintillation properties of Rb2CeBr5 crystal are presented. The crystal was grown with the Bridgman method using a two zone transparent furnace. The investigation of scintillation properties of the crystal were performed under the excitation by X-ray and gamma;-ray at room temperature. The emission spectrum of the Rb2CeBr5 was observed in the range of 360 similar to 440 mn, peaking at 390.5 run, which is due to the 5d -> 4f transitions of the Ce3+. The decay time of the Ce3+ emission was composed two components. The fast component was 56.1 ns (98.8%), and the slow component was 329.9 ns (1.2%). The energy resolution of the crystal was obtained to be 6.9% for the Cs-137 662 keV gamma-ray. The absolute light yield of the Rb2CeBr5 crystal is about 34,000 phs/MeV, and the non-proportionality of the crystal was also measured.</P>
Heedong Hwang,Jaeyong Lee,So Yeong Park,Yeseong Seo,Yong Min Kim,Jin Kon Kim,Hong Chul Moon 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.88 No.-
We synthesized 6-arm star-shaped polystyrene-ran-poly(methyl methacrylate) copolymers ((S-r-M)6) for mechanically robust and thermally stable ion gels containing an ionic liquid of 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide ([EMI][TFSI]). The (S-r-M)6-based gels exhibited higher elastic modulus (E ∼ 1.67 × 105 Pa), which is more than five-times that (∼0.29 × 105 Pa) of linear PS-r-PMMA-based ion gels at the same Sty content (∼29 mol%), irrespective of applied mechanical strains (stretching and compression). In addition, they showed outstanding thermal stability. For example, the gel-sol transition temperature (Tgel) of (S-r-M)6 gels was ∼72 °C, compared with that (∼56 °C) of linear PS-r-PMMA-based ion gels. These physical properties of gels were further improved by increasing total molecular weight and the fraction of styrene, giving E of ∼3.8 × 105 Pa and Tgel of ∼163 °C. The resulting gels were functionalized by introducing electrochemiluminescence luminophores (tris(2,2′-bipyridyl)ruthenium(II) hexafluorophosphate). By utilizing the mechanical robustness of the (S-r-M)6 gels, we fabricated emissive electrochemical displays through ‘cut-and-stick’ process. Moreover, the thermally stable (S-r-M)6 gels indicated good dimensional stability, offering a chance to demonstrate ECL devices that operate even at high temperatures.
Hwang, Heedong,Park, So Yeong,Kim, Jin Kon,Kim, Yong Min,Moon, Hong Chul American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.4
<P>Ion gels composed of copolymers and ionic liquids (ILs) have attracted great interest as polymer gel electrolytes for various electrochemical applications. Here, we present highly robust ion gels based on a six-arm star-shaped block copolymer of (poly(methyl methacrylate)-<I>b</I>-polystyrene)<SUB>6</SUB> ((MS)<SUB>6</SUB>) and an ionic liquid of 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide ([EMI][TFSI]). Compared to typical ion gels based on linear polystyrene-<I>b</I>-poly(methyl methacrylate)-<I>b</I>-polystyrene (SMS), the (MS)<SUB>6</SUB>-based gels show mechanical moduli of more than twice under various strains (e.g., stretching, compression, and shear). In addition, the outstanding mechanical property is maintained even up to 180 °C without a gel-sol transition. To demonstrate that (MS)<SUB>6</SUB>-based ion gels can serve as effective gel electrolytes for electrochemical applications, tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)<SUB>3</SUB><SUP>2+</SUP>), a representative electrochemiluminescent (ECL) luminophore, is incorporated into the gels. In particular, flexible ECL devices based on (MS)<SUB>6</SUB> gels exhibit high durability against bending deformation compared to devices with gels based on linear SMS having a similar molecular weight and a composition. This result implies that star-shaped block copolymers are effective gelators for achieving flexible/wearable electrochemical electronics.</P> [FIG OMISSION]</BR>
고객 욕구 기반 성공적인 교육 플랫폼 비즈니스 모델 구축 방안에 관한 연구 : 비즈니스 모델 캔버스 중심으로
홍희동,Heedong Hong 국제문화기술진흥원 2024 The Journal of the Convergence on Culture Technolo Vol.10 No.3
최근 온라인 교육서비스 시장의 규모는 성장하고 있으나 기업이 주도하여 콘텐츠를 생성하고 소비자가 콘텐츠를 소비하는 B2C 형태의 플랫폼 교육서비스 시장이 보편화 되어 있다. 이는 콘텐츠 생성이 경직적이며 다양한 수준별 콘텐츠를 생성되는데 한계점을 가질 수 있다. 본 연구는 고객 욕구 및 혁신, 플랫폼 비즈니스의 개념과 유형을 새롭게 정립하고 플랫폼 비즈니스 창업 전 분야별 창업 성공요인과 플랫폼 창업 성공가능성 표준 진단프로세스를 새롭게 제시한다. 제시된 프로세스과정을 통해 고객, 핵심활동 및 가치제안 요인을 도출할 수 있으며 이를 기반으로 초.중.고 교육 C2C 플랫폼 창업을 위한 비즈니스 모델을 비즈니스 모델 캔버스를 중심으로 구축한다. Recently, the size of the online education service market has been growing, but the B2C platform education service market, where companies take the lead in creating content and consumers consume the content, has become widespread. This makes content creation rigid and may have limitations in creating at various levels. This Study newly establishes the concept and type of customer needs, wants, innovation, and platform business, and presents new start-up success factors in all fields of platform business start-up and a standard diagnostic process for the possibility of platform start-up success. Through the presented process, customers, core activities, and value proposition factors can be derived. Finally, a business model for starting a C2C platform for elementary, middle, and high school education is built centered on the business model canvas.
전류 흐름 개선 플레이트를 적용한 리튬이온 배터리 성능 실험
홍석진(Seokjin Hong),한상현(Sanghyeon Han),태희동(Heedong Tae),최웅철(Woongchul Choi) 한국자동차공학회 2018 한국자동차공학회 학술대회 및 전시회 Vol.2018 No.11
To reduce emissions of exhaust gases known as the main cause of global warming, governments around the world are limiting the use of internal combustion engines and strengthening environmental regulations. Which lead to the research on eco-friendly automobiles to actively proceed. Among eco-friendly cars, electric vehicles, which use electricity as their main power source, are highly dependent on batteries. Therefore, the research on batteries is very important. Although the increase of supplement by the government subsidy policies from all around world, electric vehicles are difficult to operate over long distances because the mileage per charge is shorter than that of internal combustion engines. It also suffers from insufficient Charging Infrastructure and long charging times. The batteries of electric vehicle use electric energy to run electric motors and are highly dependent on batteries. It is important to ensure reliability of battery performance in order to ensure similar driving performance to the internal combustion engine. This paper aims to verify the feasibility of current improvement plate through Li-Ion Battery discharge experiment. The measured voltage data was collected during the Li-Ion Battery discharge experiment using LabVIEW of National Instrument.
The Growth and Scintillation Characteristics of CsI:CO<tex> $_{3}$</tex> Single Crystals
Ha, S.J.,Heedong Kang,Park, H.,Kim, H.J.,Sunghwan Kim,Sih-Hong Doh,Sang Jun Kang IEEE 2009 IEEE transactions on nuclear science Vol.56 No.3
<P>We present the luminescent and scintillation characteristics of CsI:CO<SUB>3</SUB> single crystals. The CsI:CO<SUB>3</SUB> single crystals were grown by using Czochralski method for different concentrations of CO<SUB>3</SUB> from 0.007 to 0.1 mole%. The crystals were cut into a size of 10 mm times 10 mm times 5 mm. The luminescent characteristics were measured with X-rays to study the emission spectra of the CsI:CO<SUB>3</SUB> crystals. The scintillation properties of the CsI:CO<SUB>3</SUB> crystals such as fluorescence decay time, energy resolution, pulse height spectra, proportionality, and relative light output were studied by using various gamma-ray sources with a photomultiplier tube (PMT) at room temperature. The absolute light outputs of the crystals were also measured with an avalanche photo-diode (APD).</P>
Scintillation Properties of SrCl2(Eu) Crystals
Jinho Moon,김홍주,김도성,박환배,Heedong Kang,Sih-Hong Doh,김성환,Wan Kim 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.2I
The scintillation properties of SrCl2(Eu) single crystals with Eu2+ concentrations between 0.1 and 1.0 mol% are presented. These crystals were grown by using the Czochralski method. The emission spectrum of the SrCl2(Eu) crystal was observed in the range of 390 450 nm, which matches with a bialkali PMT. The scintillation properties were studied using various gamma ray sources and an alpha source. The decay time of the pure SrCl2 crystal was about 1 μs and increased with the Eu2+ concentration. The number of photoelectrons for SrCl2(Eu:0.5 %) is 1.7 times higher than that for CsI(T`) even with a green-extended PMT being used for light collection. The details of the crystal growth, the scintillator properties, and the variations of those properties with different Eu2+ concentrations are also presented.