[en] The Gd_1.9-xLi_0.1Eu_xO₃ (x=0.02, 0.05, 0.08, and 0.12) powders (=1 μm) synthesized by sol-gel method, whose surfaces are modified in a colloidal silica suspension (size of SiO₂ particles: ∼30 nm), have been fabricated to highly stable and effective luminescent films on the glass substrates. Thanks to the fused SiO₂ nano particles in the vicinity of the glass softening temperature (at around 700 .deg. C), Gd_1.9-xLi_0.1Eu_xO₃ powders are strongly attached onto the surface of glass substrate (>9H, pencil hardness tester). This simple and low-cost method to get Gd_1.9-xLi_0.1Eu_xO₃ phosphor films without any loss of luminescence brightness would promise for applications to display devices

[en] The SrRu_1-xFe_xO₃ films (x=0.0, 0.1, 0.3, 0.5) were successfully fabricated using the powders coated with SiO₂ nano-particles (∼30 nm). The SrRu_1-xFe_xO₃ powders (∼500 nm) were synthesized by a conventional solid-state reaction. Thanks to the fused SiO₂ nano-particles in the vicinity of the glass softening temperature at approximately 700 deg. C, the SrRu_1-xFe_xO₃ powders are strongly attached onto the surface of the glass substrate. The various techniques were performed to characterize the films, such as X-ray photoelectron spectroscopy, field emission-scanning electron microscopy, Moessbauer spectroscopy and resistivity measurements. This simple and low-cost method to get the SrRu_1-xFe_xO₃ films (x=0.0, 0.1, 0.3, 0.5) may promise for applications to microelectronics field, such as dynamic random access memory or ferro-electric random access memory

[en] The guided wave mode conversion phenomena were investigated for the NDE of a plate-like structure with thickness variation. The ratios of reflection and transmission (R/T) were measured via the self-calibrating procedure which allows us to obtain experimental guided wave data in a more reliable way regardless of the coupling uncertainty between transducer and specimen. The results on R/T could be used to determine the thickness reduction of the structure. It was shown that not only the incident modes but also the converted ones need to be considered in the self-calibrating guided wave inspection to extract a reasonable correlation between experimental data and the thickness variation. Through this study, the potential of guided wave inspection as a quantitative NDE technique was explored based on the combined concept of self-calibration and multi-mode conversion in guided wave scattering problems.

[en] The modal characteristics of guided waves were investigated for the NDE of a plate with thickness variation. Using the hybrid boundary element method, the reflection and transmission factors were numerically calculated for various guided wave modes and compared to experimental data. It was shown that the reflection factors and transmission factors of each mode are greatly influenced by plate thickness variation. The presented results could be used to enhance penetration ability and sensitivity of plate waves in nondestructive evaluation of jointed plates, tapered plates and corrosion wastage, which represent thickness variation along the waveguide.

[en] The study on the cylindrical guided wave was carried out to investigate its feasibility for nondestructive evaluation of tubular structures such as heat exchanger tubings of power industries and various pipings of chemical plants. The concept of wedge design and incident angle selection to optimize guided wave generation is presented based on the dispersion theory and the snell's law for the cylindrical guided wave. The brass tubes with artificial defects in the circumferential or axial direction were used for detect defection experiments. It was found that guided wave sensitivity for detecting an axial defect can be remarkably improved by using non-axisymmetrically launched guided waves. Through this study, it is expected that the guided wave can be successfully applied to tubular structure inspections as an more advanced and efficient NDE technique than a conventional point-by-point technique.

[en] The guided wave mode conversion phenomena were investigated for the NDE of a plate-like structure with thickness variation. The ratios of reflection and transmission (R/T) were measured via the self-calibrating procedure which allows us to obtain experimental guided wave data in a more reliable way regardless of the coupling uncertainty between transducer and specimen. The results on R/T could be used to determine the thickness reduction of the structure. It was shown that not only the incident modes but also the converted ones need to be considered in the self-calibrating guided wave inspection to extract a reasonable correlation between experimental data and the thickness variation. Through this study, the potential of guided wave inspection as a quantitative NDE technique was explored based on the combined concept of self-calibration and multi-mode conversion in guided wave scattering problems

[en] We have synthesized Mn-doped Zn_2SiO_4 phosphors by solgel method using colloidal silica. The adsorption characteristics of the citric acid molecules onto the silica surfaces enables us to use colloidal silica as a Si-source instead of TEOS which is generally utilized for the fine particle synthesis of the silicate based compounds. At a very low temperature (800 .deg. C), we could obtain the single phase of Zn_2SiO_4, which is remarkable compared to that of the solid state reaction (about 1300 .deg. C). The mean size of particles prepared at 800 .deg. C, 900 .deg. C, and 1000 .deg. C is 100 nm, 200 nm, and 400 nm, respectively. The PL intensity of Zn_1_._9_2Mn_0_._0_8SiO_4 prepared at different temperature between 800 .deg. C and 1200 .deg. C, increases as the synthetic temperature rises up. Moreover, the PL intensity of Zn_1_._9_2Mn_0_._0_8SiO_4 prepared at 1200 .deg. C is remarkable compared to that of the commercial Zn_2SiO_4 : Mn (Kasei company, Japan). The PL intensity for Zn_1_._9_2Mn_0_._0_8SiO_4 as a function of colloidal silica content, do not induces a considerable change in PL intensity, but a considerable modification in the morphology of particles. It might be said that colloidal silica is a promising chemical as a Si-source for the synthesis of fine particle of silicate compounds, instead of TEOS. The Mn"2"+-doped Zn_2SiO_4 phosphor has been used as a luminescent material for lamp and plasma panel display because of its high-luminescent efficiency and chemical stability. The emission of the Zn_2_-_xMn_xSiO_4 at 520 nm is attributed to d-level spin-forbidden transition for Mn(II). According to the earlier literatures, the photoluminescence (PL) process of Zn_2_-_xMn_xSiO_4 phosphors has been characterized by the transition of 3d"5 electrons in the manganese ion acting as an activation center in the willemite structure. In particular, the transition from the lowest excited state to the ground state, i. e. "4T_1("4G) → "6A_1("6S) transition, is directly responsible for the green light emission

[en] Tetragonal K₂N_iF₄-type La_22xSr_2xCu_1xFe_xO_4y solid-solution have been synthesized by citrate based sol-gel method. The valence state of iron was determined by Mossbauer spectroscopy and subsequent iodometric titration clearly showed that the copper ions in this solid-solution are in the mixed valence state Cu(II/III). When x ≤ 0.3, Fe(III) is competing with the mixture of Cu(II) and Cu(III) and La_22xSr_2xCu_1xFe_xO_4y exhibits a metallic character. No evidence for Cu(II)-O-Fe(IV) ↔ Cu(III)-O-Fe(III) valence degeneracy was observed. In contrast, a small amount of Fe(IV) is observed with increasing x (x = 0.4 and 0.5), revealing a semiconducting behavior. These results suggest that the electronic interaction of Cu(III)-O-Fe(III) contributes greatly to the metallic character, while the electronic interaction of Cu(II)-O-Fe(IV) deteriorates the metallic character of La_22xSr_2xCu_1xFe_xO_4y

[en] The results of this study categorized into two parts. The first part is the guidelines for EID designs. The procedure to observe for EID design is composed of 6 steps; 1) to define a target system, 2) to make an abstraction hierarchy model, 3) to check the link structure among each components included in the layers of abstraction hierarchy model, 4) to transform information requirements to variables, 5) to make the graphs related to each variables, 6) to check the graphs by visual display design principles and heuristic rules. The second part is an EID design alternative for nuclear power plant. The EID for high level function represents the energy balance and energy flow in each loop of nuclear power plant. The EID for middle level function represents the performance indicators of each equipment involved in the all processes of changing from coolants to steam. The EID for low level function represents the values measured in each equipment such as temperature, pressure, water level and so on

[en] Y_1.9-xLi_0.1Eu_xO₃ (x=0.02, 0.05, 0.08, and 0.12) films were fabricated by spin-coating method. A colloidal silica suspension with Y_1.9-xLi_0.1Eu_xO₃ phosphor powder was exploited to obtain the highly stable and effective luminescent films onto the glass substrate. After heating as-prepared Y_1.9-xLi_0.1Eu_xO₃ films at 700 ^oC for 1 h, the phosphor films exhibit a high luminescent brightness as well as a strong adhesiveness on the glass substrate. The emission spectra of spin-coated and pulse-laser deposited Y_1.82Li_0.1Eu_0.08O₃ films were compared. The cathodoluminescence of the phosphor films was carried out at the anode voltage 1 kV.