• Nuclear Engineering and Technology
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• v.40 no.7
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• pp.581-592
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• 2008

In this study, a conceptual pyroprocess flowsheet has been devised by combining several dry-type unit processes; its applicability as an alternative fuel cycle technology was analyzed. A key point in the evaluation of its applicability to the fuel cycle was the recovery yield of fissile materials from spent fuels as well as the proliferation resistance of the process. The recovery yields of uranium and transuranic elements (TRU) were obtained from a material balance for every unit process composing the whole pyroprocess. The material balances for several elemental groups of interest such as uranium, TRU, rare earth, gaseous fission products, and heat generating elements were calculated on the basis of the knowledge base that is available from domestic and foreign experimental results or technical information presented in open literature. The calculated result of the material balance revealed that uranium and TRU could be recovered at 98.0% and 97.0%, respectively, from a typical PWR spent fuel. Furthermore, the anticipated TRU product was found to emit a non-negligible level of $\gamma$-ray and a significantly higher level of neutrons compared to that of a typical plutonium product obtained from the PUREX process. The results indicate that the product from this conceptual pyroprocessing should be handled in a shielded cell and that this will contribute favorably to retaining proliferation resistance.

• Journal of Powder Materials
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• v.26 no.4
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• pp.334-339
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• 2019

To meet the current demand in the fields of permanent magnets for achieving a high energy density, it is imperative to prepare nano-to-microscale rare-earth-based magnets with well-defined microstructures, controlled homogeneity, and magnetic characteristics via a bottom-up approach. Here, on the basis of a microstructural study and qualitative magnetic measurements, optimized reduction conditions for the preparation of nanostructured Sm-Co magnets are proposed, and the elucidation of the reduction-diffusion behavior in the binary phase system is clearly manifested. In addition, we have investigated the microstructural, crystallographic, and magnetic properties of the Sm-Co magnets prepared under different reduction conditions, that is, $H_2$ gas, calcium, and calcium hydride. This work provides a potential approach to prepare high-quality Sm-Co-based nanofibers, and moreover, it can be extended to the experimental design of other magnetic alloys.

• Journal of Biomedical Engineering Research
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• v.8 no.2
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• pp.171-176
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• 1987

Wiener filtering method was applied to the dual energy imaging procedure in digital radiography(D.R.). A linear scanning photodiode arrays with 1024 elements(0.6mm H 1.3mm pixel size) were used to obtain chest images in 0.7 sec. For high energy image acquisition, X-ray tube was set at 140KVp, 100mA with a rare-earth phosphor screen. Low energy image was obtained with X-ray tube setting at 70KVp, 150mA. These measured dual energy images are represented in the vector matrix notation as a linear discrete model including the additive random noise. Then, the object images are restored in the minimum mean square error sense using Wiener filtering method in the transformed domain. These restored high and low energy images are used for computation of the basis image decomposition. Then the basis images are linearly combined to produce bone or tissue selective images. Using this process, we could improve the signal to noise ratio characteristics in the material selective images.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.586-589
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• 2001

In Case of High speed PM machines with surface-mounted magnet. A rare-earth PM with high remanence flux density is used on the rotor. Therefore, It is very difficult to adhesion and assemble PM on the surface of rotor, because of very repulsive force between magnets. So, for solving this problem, rotor with surface-mounted magnet is wholly magnetized after mounting magnetic-material on the surface. In this paper, In order to Magnetize rotor with surface-mounted PM, magnetizing machine is designed, analyzed and simulated for large PM machines using the 1dimensional analytical method and 2dimensional finite element method. (20-FEM).

• Electrical & Electronic Materials
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• v.9 no.1
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• pp.93-104
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• 1996

연질자성재료는 대부분 직류 및 고주파용 변압기, inductor, 대형 motor, 자기헤드의 자심재료 및 센서등으로 사용되고, 경질자성재료는 주로 motor 및 speaker용으로 사용되며, 자기기록매체재료는 화상, 음성 및 컴퓨터 정보의 기록용으로 사용된다. 특수자성재료로는 microwave용, 전자파 흡수, 열팽창 제어, 기체밀봉등 많은 용도에 이용되고 있다. 최근 국내외에서 수요가 급증하는 첨단 전자기기용 자성재료 시장등이 내구, 내열성 뿐만 아니라 소형화, 경량화 됨에 따라 자성재료의 고성능화를 요구하고 있다. 따라서 본 고에서는 경질자성재료의 개발현황을 살펴보고 자성재료의 고성능화를 위한 연구동향을 생각해 보고자 한다.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.155-155
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• 2011

신재생에너지 수요가 확대됨에 따라 신재생에너지 관련 제품에 소요되는 물질에 대한 관심이 확대되고 있다. 이들 물질은 공급리스크가 존재하는 희유금속이 주를 이루고 있다. 본 연구에서는 신재생에너지 등의 high tech 기술 확대로 인한 희유금속의 수요 및 공급을 전망하고 있는 미국의 critical raw material 관리 전략을 살펴보고자 한다. 미국은 2010년 12월 미국 에너지성(DOE : Department of Energy)에서 위기 물질 전략(Critical Materials Strategy)에 관한 리포트를 공표하였다. 클린 에너지 기술 4개 분야(영구자석, 선진 전지, 태양전지 박막, 형광 물질)에서 핵심이 되는 물질(희유금속 등)의 수급 불균형이 일어날 가능성에 대해 조사를 실시하여 리스크 평가하여 단기, 중단기로 구분하여 위기물질을 선정하였다. 클린 에너지 기술 4개 분야에서 핵심이 되는 물질(네오디움, 디스프로슘, 코발트, 리튬, 랜턴, 세륨, 테룰, 인듐, 갈륨, 유로피움, 테르비움, 이트륨)의 12광종 수급을 2025년까지 전망한 결과 전체적으로 단기(2010년~2015년)보다 중기(2015년~2025년)에 공급 부족이 확대한다고 예측되었다. 단기적으로는 인듐이 약간 부족하는 것 외에 디스프로슘과 이트륨에 관해서도 공급 부족할 것으로 예측되었다. 중기적으로는 코발트(전지 기술에 사용)와 유로피움(고효율 조명용의 형광 물질에 사용) 외 대상이 된 다른 모든 물질은 공급 부족이 발생할 것으로 전망되었다. 이를 종합하여 단기적으로는 디스프리슘, 유로피움, 인듐, 테르븀, 네오디움, 이트륨 등이, 중기적으로는 디스프리슘, 유로피움, 테르븀, 네오디움, 이트륨 등이 위기물질(Critical Material)로 분석되었다. 에너지성은 위기물질을 공급원다각화, 대체물질개발, 리유즈, 리사이클링 등을 국제적 파트너와 함께 추진하여 리스크를 관리할 것이며, 2011년까지 최신정보를 구축하여 위기물질 전략을 재설정할 예정이다. 체계적인 위기물질 선정 및 관리전략 등을 참조하고, 신재생에너지기술 변화에 따른 원재료의 중요성 및 리스크 관리현황을 기초로 우리나라에 적합한 위기관리 물질 선정 및 관리가 필요할 것이다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12S
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• pp.1278-1285
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• 2003

This study investigated the phase transformation of the REBa$_2$Cu$_3$$O_{7-x}$ (RE=Nd, Gd, Dy) superconductor, and CCT (Continuous-Cooling-Transformation) along with the TTT (Time-Temperature-Transformation) diagrams are suggested according to the isothermal and continuous cooling heat-treatments. The peritectic temperature of the 123 phases decreased approximately 3$0^{\circ}C$ when the ionic radius of the rare-earth elements was reduced. The optimum cooling rate where BC and Cu-free phases do not exist was 0.001$^{\circ}C$/s. At this cooling late, the 123 phase grew with a c-axis Perpendicular to the surface and had a well-distributed 211 phase. When the oxygen partial pressure was reduced Outing isothermal heat-treatment, the formation temperature of the 211 phase decreased. In addition, the formation temperature of the 123 phases decreased from 100$0^{\circ}C$ (Nd-123) to 9$25^{\circ}C$ (Gd-123), and finally 875$^{\circ}C$ (Dy-123) according to the decrease in the ionic radius of the tare-earth elements. Compared to Nd-123, Gd- and Dy-123 had a better texture with a well-distributed 211 phase.e.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.8
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• pp.688-693
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• 2000

In this paper an optical voltage sensor and an optical current sensor which can be used for the measurement of impulse voltage and current are implemented. BSO single crystal is utilized as a voltage sensor(Pockels effect cell). An rare earth doped YIG is used as a current sensor(Faraday effect cell). A new signal processing technique is adopted not only to avoid the influences o external optical fiber pertubations of transmitting optical fiber but also to improves the frequency response characteristics of the fiber-optic voltage and current sensors. Experimental results show that optical voltage sensor has maximum 2.5% error within the voltage range from 0V to 500V. and optical current sensor has maximum 2.5% error within the current range and that of optical current sensor is about 1.5% within temperature range from -2$0^{\circ}C$ to 6$0^{\circ}C$. The proposed optical sensors have good frequency response characteristics within the frequency range from DC to 10MHz.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.546-546
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• 2013

Zinc silicate ($Zn_2SiO_4$) has been identified as a suitable host material for a wide variety of luminescent activators, such as transition metal and rare earth elements. In particular, manganese-activated $Zn_2SiO_4$ exhibits highly efficient photoluminescenceand cathodoluminescence, which allows this material to be used in fluorescent lamps and display applications. In this study, we investigated the green and yellow luminescence from Mn-doped $Zn_2SiO_4$ thin films that were synthesized using radio frequency magnetron sputtering followed by annealing at $600{\sim}1,200^{\circ}C$ The refractive index of the $Zn_2SiO_4$: Mn films showed normal dispersion behavior. It was found that the $Zn_2SiO_4$: Mn films annealed at $800^{\circ}C$ ossessed a mixture of alpha and beta phases. The obtained photoluminescence spectrum consisted of two emission bands centered at 525 nm in the green range and 574 nm in the yellow range. The green luminescence originates from the divalent Mn ions in alpha phase of $Zn_2SiO_4$, while the yellow luminescence comes from the divalent Mn ions in beta phase. The films annealed at and above $900^{\circ}C$ xhibited only the alpha phase. The broad PL excitation band was observed ranging from 220 to 300 nm with a maximum at around 243 nm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05a
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• pp.42-45
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• 2003

The phase transformation of $REBa_2Cu_3O_{7-x}$ (RE=Nd, Gd, Dy) was investigated using isothermal heat-treatment and continuous cooling in air. During continuous cooling, the $REBa_2Cu_3O_{7-x}$ (RE=123) superconducting phase with well-distributed $REBa_2Cu_3O_{7-x}$ (RE-211) was obtainde at a cooling rate of $0.001^{\circ}C$/s. Single phase RE-123 (Nd, Gd, Dy) was stable at $1050^{\circ}C$, $1050^{\circ}C$, and $950^{\circ}C$ during isothermal heat-treatment, respectively. Above these temperatures the RE-211 phase existed within the RE-123 grains. The RE-123, RE-211, $BaCu_2Od_2$, and CuO phases coexisted at $50^{\circ}C$ below the partial melting temperature for each respective rare-earth RE-123.