• 제목/요약/키워드: photo-accelerator

검색결과 12건 처리시간 0.02초

아크릴계 고분자 치아수복재의 치과적 물성에 미치는 광증감제 효과 (Effect of Photo-accelerator on the Dental Properties of Acryl-based Polymeric Dental Restorative Composites)

  • 김오영
    • 공업화학
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    • 제16권1호
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    • pp.117-122
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    • 2005
  • 가시광선 중합형의 치아수복용 고분자 복합체(polymeric dental restorative composites, PDRC)에 있어서 여러 종류의 3급 아민계 광증감제가 PDRC의 치과적 물성에 미치는 영향을 기계적 물성과 심미적 특성을 분석한 후 고찰하였다. PDRC 제조에 사용한 barium silicate 필러는 아크릴계 resin matrix와의 혼화성 증가를 위해 표면을 소수성으로 처리하여 사용하였다. 광중합에 필요한 광개시제로는 resin matrix를 기준으로 camphorquinone을 0.5 wt%로 하여 사용하였다. 그 결과, 제조된 PDRC의 기계적 물성과 심미적 특성은 사용한 광증감제의 함량보다는 화학적 구조에의 의존성이 더 큼을 알 수 있었다.

PHOTO-NEUTRON SOURCE USING 2 GEV ELECTRON LINAC FOR RADIATION SHIELDING RESEARCH

  • Lee, Hee-Seock;Bak, Joo-Shik;Chung, Chin-Wha;Ban, Syuichi;Shin, Kazuo;Sato, Tatsuhiko
    • Journal of Radiation Protection and Research
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    • 제26권3호
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    • pp.333-335
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    • 2001
  • The 2 GeV electron linac, the injector of the Pohang Light Source, was used as a photo-neutron source for radiation shielding research. The operational beam parameters are the nominal electron intensity of $0.5\;{\sim}5\;nC/sec$, the repetition rate of 10 Hz, and the beam pulse length of 1.0 nsec. One electron beam line was modified in order to install the target systems for producing pulsed photo-neutrons. The neutron spectrum and intensity were investigated by the time-of-flight technique. The reliable maximum energy of the measured neutrons was about 500 MeV. The number of neutrons above 20 MeV produced by one 1 GeV electron in a thick Pb target was about $6.45{\times}10^{-4}/sr$ at 90 degrees to the beam axis. The status of the photo-neutron source and the application research are presented.

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방사선치료실 내의 광중성자 에너지 분포 평가 (Evaluation of Photoneutron Energy Distribution in the Radiotherapy Room)

  • 박은태;고성진;김정훈;강세식
    • 대한방사선기술학회지:방사선기술과학
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    • 제37권3호
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    • pp.223-231
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    • 2014
  • 의료용의 선형가속장치는 방사선치료에 있어서 그 활용도가 가장 높으며, 최근에는 10MV 이상의 고에너지 광자선을 이용한 치료가 보편화되고 있다. 그러나 광핵반응에 의한 광중성자가 생성됨으로써 방사선 방호측면에서 많은 문제를 야기 시키고 있다. 이에 본 연구는 MCNPX 프로그램을 이용하여 치료실 내의 위치별 중성자의 특성을 분석하였다. 그 결과, 광중성자의 생성 개수도 선원 중심점을 기준으로 거리가 멀어질수록 감소됨을 알 수 있었다. 그리고 10MV에서 20MV로 에너지가 높아짐에 따른 열중성자와 속중성자의 비율은 큰 차이가 없었지만, 선원 중심점으로부터 거리가 이격될수록 열중성자의 비율이 높아지는 현상을 확인할 수 있었다.

Photo-induced chemical change of di-fluoride in the CYTOP doped graphene

  • Yang, Mi-Hyun;Manoj, Sharma;Ihm, Kyuwook;Ahn, Joung Real
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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    • pp.115-115
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    • 2015
  • Many efforts have been devoted on chemical modification of graphene layer to modulate its electrical properties. In the previous report, laser irradiation on the CYTOP (Amorphous Fluoropolymer) covered graphene layer induces chemical modification wherein carbon fluoride is formed on the graphene surface. This results in the insulating I-V characteristics, which have been attracting much research interests on it. However, the direct analytical evidence of the fluoride formation on graphene surface is not yet studied. In this work we investigated what happened on the CYTOP/graphene interface during photon irradiation using spatially resolved photoemission spectroscopy method. It is found that the soft x-ray (614 eV) induces desorption of fluoride atoms from the CYTOP and change di-fluoride form to mono-fluoride. As the photo-induced fluorine desorption is continue strong dipole field generated by initial di-fluoride forms is gradually decreased, resulting in the overall binding energy shift of the C 1s core levels. Both photo-modified CYTOP and CYTOP starts to desorb above $286^{\circ}C$ (~ 0.047 eV), which means that no strong chemical interaction between CYTOP and graphene is established.

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The Alignment of Liquid Crystals on the Film Surfaces of Soluble Aromatic Polyimides Bearing t-Butylphenyl and Trimethylsilylphenyl Side Groups

  • Hahm, Suk-Gyu;Jin, Kyeong-Sik;Park, Sam-Dae;Ree, Moon-Hor;Kim, Hyung-Sun;Kwon, Soon-Ki;Kim, Yun-Hi
    • Macromolecular Research
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    • 제17권12호
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    • pp.976-986
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    • 2009
  • With the study goal of firstly elucidating the anisotropic interactions between oriented polymer chain segments and liquid crystal (LC) molecules, and secondly of determining the contributions of the chemical components of the polymer segments to the film surface topography, LC alignment, pretilt, and anchoring energy, we synthesized three dianhydrides, 1,4-bis(4'-t-butylphenyl)pyromellitic dianhydride (BBPD), 1,4-bis(4'-trimethylsilylphenyl)pyromellitic dianhydride(BTPD), and 2,2'-bis(4"-tert-butylphenyl)-4,4',5,5'-biphenyltetracarboxylic dianhydride (BBBPAn), and a series of their organosoluble polyirnides, BBPD-ODA, BBPD-MDA, BBPD-FDA, BTPD-FDA, and BBBPAn-FDA, which contain the diamines 4,4'-oxydianiline (ODA), 4,4'-methylenediamine (MDA), and 4,4'-(hexafluoroisopropylidene)dianiline (FDA). All the polyimides were determined to be positive birefringent polymers, regardless of the chemical components. Although all the rubbed polyimide films exhibited microgrooves which were created by rubbing process, the film surface topography varied depending on the polyimides. In all the rubbed films, the polymer chains were unidirectionally oriented along the rubbing direction. However, the degree of in-plane birefringence in the rubbed film varied depending on the polyimides. The rubbing-aligned polymer chains in the polyimide films effectively induced the alignment of nematic LCs along their orientation directors by anisotropic interactions between the preferentially oriented polymer chain segments and the LCs. The azimuthal and polar anchoring energies of the LCs ranged from $0.45{\times}10^{-4}\;-\;1.37{\times}10^{-4}\;J/m^2$ and from $0.86{\times}10^{-5}\;-\;4.26{\times}10^{-5}\;J/m^2$, respectively, depending on the polyimides. The pretilt angles of the LCs were in the range $0.10-0.62^{\circ}$. In summary, the soluble aromatic polyimides reported here are promising LC alignment layer candidates for the production of advanced LC display devices.

Direct Writing Lithography Technique for Semiconductor Fabrication Process Using Proton Beam

  • Kim, Kwan Do
    • 반도체디스플레이기술학회지
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    • 제18권1호
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    • pp.38-41
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    • 2019
  • Proton beam writing is a direct writing lithography technique for semiconductor fabrication process. The advantage of this technique is that the proton beam does not scatter as they travel through the matter and therefore maintain a straight path as they penetrate into the resist. The experiment has been carried out at Accelerator Mass Spectrometry facility. The focused proton beam with the fluence of $100nC/mm^2$ was exposed on the PMMA coated silicon sample to make a pattern on a photo resist. The results show the potential of proton beam writing as an effective way to produce semiconductor fabrication process.

MCNPX를 이용한 방사선 치료실의 광중성자 선량 평가 (Evaluation of Photoneutron Dose in Radiotherapy Room Using MCNPX)

  • 박은태
    • 한국콘텐츠학회논문지
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    • 제15권6호
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    • pp.283-289
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    • 2015
  • 현재 방사선치료는 치료효과를 높이기 위해 고에너지 광자선의 사용이 증가하고 있는 추세이다. 일반적으로 6~8 MeV 이상의 고에너지 광자선을 사용하는 경우에는, 광핵반응에 의한 광중성자가 발생됨으로써 방사선 방호의 측면에서 많은 문제를 야기 시킬 수 있다. 이에 본 연구는 MCNPX를 이용하여 방사선 치료실의 광중성자 선량분포를 분석하였다. 그 결과 10 MV와 12 MV 구간에서 급격한 흡수선량의 증가를 보였다. 이를 통해 10 MV를 시작으로 광중성자 플루언스의 급격한 증가가 흡수선량으로 연계됨을 알 수 있었다. 또한 산출된 흡수선량을 바탕으로 등가선량을 환산한 결과는 ICRP 103 권고안의 경우, 낮은 에너지 범위에서 인체의 흡수선량에 대한 2차 광자의 기여를 반영함으로써 ICRP 60 권고안에 비해 낮은 등가선량을 나타냈다.

광중합형의 치아수복용 고분자 나노복합체의 심미 특성 (Esthetic Properties of Photoinitiated Polymeric Dental Restorative Nanocomposites)

  • 김오영;한상혁;김창근
    • 폴리머
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    • 제29권1호
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    • pp.102-105
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    • 2005
  • 다양한 치아 수복이 가능한 광중합형의 치아수복용 고분자 나노복합체(polymeric dental restorative nanocomposites, PDRNC)를 제조하고 이들의 심미적 물성을 고찰하였다. PDRNC 제조에 사용한 충전제는 평균 입경이 1${\mu}m$인 바륨실리케이트와 40 nm 및 7 nm 크기의 나노실리카를 혼성화시켜 사용하였는데 bisphenol A glycerolate methacrylate와 triethyleneglycol dimethacrylate (60/40 wt%)으로 구성되는 기재와의 혼화성 증가를 위해 실란으로 표면을 소수성으로 처리하였다. 가시광선을 이용한 PDRNC의 광중합에 필요한 광개시제는 camphorquinone을, 광증감제는 2-(dimethylamino)ethyl methacrylate을 사용하였다. 제조된 PDRNC의 심미적 물성을 Hunter L, a, b 값으로 평가한 결과, 7nm 크기의 나노 충전제가 첨가될수록 PDRNC의 투명성이 증가되어 심미적 특성이 향상됨을 알 수 있었다.

Measurements of Photoabsorption Cross Sections of Nitric Oxide by Using Double-Ionization Chamber

  • Chung, Yang-Soo;Kim, Hyun;Chung, Young-Min
    • Journal of the Optical Society of Korea
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    • 제10권4호
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    • pp.157-161
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    • 2006
  • A synchrotron light source is useful in the vacuum ultraviolet (VUV) regime for olecular spectroscopy, such as photo absorption, photoionization, and dissociative hotoionization. In this research, we used a double-ion chamber (DIC) to measure hotoabsorption cross sections of a NO molecule in the wavelength range from 90 to 135 nm of 3B1 beam-line of the Pohang synchrotron light source with the resolution of the onochromator being 0.06 nm. The appearance wavelength for ionization was measured to be $134.19{\pm}0.09nm$ that is placed in the middle of the reported values though they don't agree with each other within the relative error limits. The auxiliary experimental works ave been done to test if there are any systematic error sources. The resultant ross-sections agree with previous results in general.