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열형광 CaSO₄:Dy 소자의 최적 제조조건에 관한 연구
김장렬,남영미,장시영,김두영,양정선,박재우 제주대학교 산업기술연구소 2000 尖端技術硏究所論文集 Vol.11 No.1
An experimental investigation has been performed to determine optimal conditions for preparing the thermoluminescent CaSO4:Dy pellets which have been widely used as personal radiation dosimeter material. Our investigation has shown that an optimal weight concentration of the dopant Dy in the bulk CaSO4:Dy is 0.1 mol%, and an optimal temperature of adding Dy in the preparing process is 320 ℃. An optimal time and temperature for sintering the CaSO4:Dy crystal produced from the chemical process are found to be 2 hours and 800 ℃, respectively. The maximum thermoluminescent sensitivity was observed when the CaSO4:Dy crystal was pulverized to grain sizes of 63 - 200 ㎛ in diameter before being fabricated into pellets. The commercial Teflon was selected as an adhesive for the fabrication of the CaSO4:Dy pellets with an optimal mixing ratio of the Teflon and CaSO4:Dy being 70 to 30 in weight.
열형광 CaSO₄ : Dy 소자의 최적 제조조건에 관한 연구
양정선,장시영,김장렬,김두영,남영미,박재우 濟州大學校 産業技術硏究所 2000 산업기술연구소논문집 Vol.11 No.1
An experimental investigation has been performed to determine optimal conditions for preparing the thermoluminescent CaSO_(4):Dy pellets which have been widely used as personal radiation dosimeter material. Our investigation has shown that an optimal weight concentration of the dopant Dy in the bulk CaS0_(4):Dy is 0.1 mol%. and an optimal temperature of adding Dy in the preparing process is 320℃. An optimal time and temperature for sintering the CaSO_(4):Dy crystal produced from the chemical process are found to be 2 hours and 800℃. respectively. The maximum thermoluminescent sensitivity was observed when the CaSO_(4):Dy crystal was pulverized to grain sizes of 63 - 200 m in diameter before being fabricated into pellets. The commercial Teflon was selected as an adhesive for the fabrication of the CaSO_(4):Dy pellets with an optimal mixing ratio of the Teflon and CaSO_(4):Dy being 70 to 30 in weight.
Li 화합물을 첨가한 CaSO₄:Dy 열중성자 측정용 TLD 소자 개발
양정선,김두영,박재우,김장렬,장시영 제주대학교 방사능이용연구소 2003 연구보고 Vol.17 No.-
Personal neutron dosimetry is quite a difficult area because a neutron is always accompanied with gamma radiation, which is required of a capability for mixed field dosimetry. CaSO₄:Dy phosphor is known to have a very high sensitivity to gamma, but the neutron capture cross section of the constituents of CaSO₄:Dy are so small that the interactions between the thermal neutron and the phosphor are rare. One method to improve the neutron interaction is by introducing an impurity ion with a large thermal neutron captures cross section into the phosphor to act as a neutron target centre such as 6Li. In neutron-gamma mixed radiation fields, if two detectors for the 6Li-7Li compounds embedded CaSO₄:Dy TL pellets are used, a 6Li-compound embedded pellet can detect the neutron and gamma radiation together, and the other pellet can only detect the gamma radiation. Recently Korea Atomic Energy Research Institute (KEARI) has developed a new type of CaSO₄:Dy TL materials embedded with phosphorous (KCT-300) to detect beta and gamma radiation with a very high sensitivity[1]. This paper presents the development of CaSO₄:Dy TL pellets embedded with 6Li compound for a thermal neutron measurement, and the detection method of the neutron and gamma dose in mixed fields with CaSO₄:Dy TL pellets embedded with a 6Li compound(KCT-306) and CaSO₄:Dy TL pellets embedded with a 7Li compound(KCT-307) is introduced. The net neutron sensitivity of CaSO₄:Dy TL pellets embedded with 6Li compound developed in this study is higher than that of the TLD-600 (Harshaw Co.) dosimeter which is available in the open market.
양정선,박재우,김두영,김장렬,장시영 제주대학교 방사능이용연구소 2002 연구보고 Vol.16 No.-
CaSO_4 : Dy series TL material is widely used as a personal dosimeter because of its high sensitivity to radiation. KAERI(Korea Atomic Energy Research Institute) has been produced CaSO_4 TL powder activated by Dy(rare earth elements) for several years and continually tried to improve its sensitivity having more than that of commercialized Teledyne CaSO_4 : Dy TL powders(USA). The TL powder is prepared by adding 0.1mol% Dy as an activator and by the acid evaporation method at first. And new step of washing this powder by distil-water is appended to separate non-crystalized powder in the initial crystal of CaSO_4 : Dy powder. CaSO_4 : Dy crystal TL powder which is produced by applying this new method has higer sensitivity than before washing step, and it has also higher sensitivity than that of Teledyne CaSO_4 : Dy TL powder. This CaSO_4 : Dy TL powder shows good TL characteristics such as dose response, energy response and fading. It is not possible to make solid detectors of only CaSO_4 : Dy TL phosphor without any binding material. Until now widely used sintered pellets. which were made from a mixture of CaSO_4 : Dy TL phosphor and Teflon. But, due to reduction in content of CaSO_4 : Dy TL phosphor in pellets(15∼20wt%) the TL sensitivity of pellets was reduced correspondingly. To variously use the CaSO_4 : Dy TL phosphor, research for preparing detectors by mixing CaSO_4 : Dy TL phosphor with different binding substances has been conductedThis paper described development of a new type of CaSO_4 : Dy pellets by using P-compounds as a bonding material(KCT-300), and compared the TL sensitivity with that of the commercialized Teledyne CaSO_4 : Dy pellets. Sensitivity of a new developed KCT-300 shows about 6 times than Teledyne ones, and can be used to measure very low radiation dose.
Jang, Chang-Doo,Leem, Hyo-Kwan,Choi, Yeoung-Dal,Bang, Jun-Kee,So, Ha-Young The Society of Naval Architects of Korea 2007 Journal of ship and ocean technology Vol.11 No.2
For the assessment of the retardation of fatigue crack propagation behavior due to overload, new FE analysis algorithms considering compressive residual stress redistribution near crack tip was proposed in this paper. The size of plastic zone near crack tip was obtained by elasto-plastic analysis and it was compared with Irwin's equation. The amount of residual stress redistribution was assessed by subsequent elasto-plastic analysis, and the difference of residual stress distributions between constant amplitude load and overload was obtained. In the analysis of fatigue crack propagation, the applied SIF range was evaluated by ASTM E647, and the effect of residual stresses on crack propagation was considered using the effective SIF concept. The test results of crack propagations were compared with the predicted data obtained by the analysis.
저속 충격을 받는 복합 재료 적층판의 층간 분리 성장에 관한 연구
장창두(CHANG-DOO JANG),송하철(HA-CHEOL SONG),김호경(HO-KYUNG KIM),허기선(KI-SUN HUR),정종진(JONG-JIN JEONG) 한국해양공학회 2002 韓國海洋工學會誌 Vol.16 No.6
Delamination means that cracking occurs on the interface layer between composite laminates. In this paper, to predict the delamination growth in composite laminates subjected to low-velocity impact, the unit load method was introduced, and an eighteen-node 3-D finite element analysis, based on assumed strain mixed formulation, was conducted. Strain energy release rate, necessary to determine the delamination growth, was calculated by using the virtual crack closure technique. The unit load method saves the computation time more than the re-meshing method. The virtual crack closure technique enables the strain energy release rate to be easily calculated, because information of the singular stress field near the crack tip is not required. Hence, the delamination growth in composite laminates that are subjected to low-velocity impact can be efficiently predicted using the above-mentioned methods.