[en] In many cases oxide films formed on metals in atmosphere or aqueous solution are chemically inactive, especially it is the case with aluminum. In this study, anodic dissolution of aluminum was done using various electrolyte and cathode, mechanism of which was examined. As a consequence, oxide film on aluminum surface was dissolved together with the dissolution reaction of metal by the anodic current. It was shown that the dissolution reaction due to the contact between electrolyte and metal happened in the same time

[en] We have studied the escape rate crossover between pure quantum and thermally assisted tunneling in Mn₁₂-acetate molecular magnet with an external field applied perpendicular to the easy axis. Unlike previous model we include fourth-order anisotropy terms due to the tetragonal symmetry in the spin Hamiltonian. We find higher crossover temperature (∼1.0-∼1.2 K) that agrees with experimental observation [12]. We also obtain a phase diagram for the crossover types, from which the first-order region is observed to be enlarged. More interestingly, when the field is applied along the hard axis there exist several small second-order regions inside the first-order region

No abstract available

[en] The geoscientific study on geological disposal for radioactive wastes has established the stepwise site characterization program, methods and investigation technology. However the intrinsic properties of geological material such as heterogeneity and scale dependent properties make difficulty on satisfactory understanding of geological conditions. To avoid unnecessary time delay and unexpected extra-cost for site investigation, the accurate and complete site investigation program should be established in a stepwise manner and the QC programs for investigation methods and procedures. Moreover, the technical requirements and preferences for a repository should be distinguished and be assessed at the end of each investigation step

[en] We present a search for a non-Standard-Model invisible particle X⁰ in the mass range 0.1-1.8GeV/c² in B⁺→e⁺X⁰ and B⁺→μ+X⁰ decays. The results are obtained from a 711 fb^-1 data sample that corresponds to 772×10⁶BB pairs, collected at the Υ(4S) resonance with the Belle detector at the KEKB e⁺e^- collider. One B meson is fully reconstructed in a hadronic mode to determine the momentum of the lepton of the signal decay in the rest frame of the recoiling partner B meson. We find no evidence of a signal and set upper limits on the order of 10^-6.

[en] It has not been performed to inspect the underclad cracking of nuclear pressure vessel in Korea since there is no code requirements for inspection. However, underclad cracks in nuclear pressure vessels have been reported since the early 1970s. The aim of this experiment is to find the suitable ultrasonic inspection techniques for underclad cracking. The various transducers, for example ⁷⁰[ backprime?] refracted longitudinal wave, 50/70 multibeam, SLIC-40, SLIC-50, are used in this investigation. Experiments on prescreening blocks and a demonstration block under the same condition as in the nuclear power pressure vessels show that the ⁷⁰[ backprime?] refracted longitudinal wave method is the best one for the length evaluation and also gives a good signal pattern for detection of the crack, while the 50/70 multibeam transducer is more effective for the detection of underclad cracking. On the other hand, the SLIC-50 transducer using M-SPOT(Satellite Pulse Observation Technique) and M-PET (Peak-Echo Technique) methods is the most effective one for the depth of underclad crack estimation

[en] The efficiencies of single escape and double peaks were calculated by using Monte Carlo method, and compared with the measured efficiency. The efficiencies of the escape peaks were obtained by using the measured full absorption energy peak efficiencies and the area ration to escape peak. For the escape peaks interfered with another λ-ray peak, the pure area were obtained by correction. The GEANT code developed by CERN was used as Monte Carlo code. The calculated efficiencies of escape peaks almost agreed to the measurement within 12%

[en] The single mode gamma-ray spectrometer of the PGAA(Prompt Gamma Activation Analysis) facility constructed at HANARO of the Korea Atomic Energy Research Institute was updated to the multi-mode gamma-ray spectrometer including the single mode, Compton suppression mode and pair mode, and its performances were tested. The timing parameters were tuned for the optimized spectroscopic condition and Compton Suppression Factor(CSF) and Reduction Factor(RF) were measured by using the standard sources and the detection efficiency and the count rates of background peaks were also measured and compared with those before the installation of the new spectrometer

[en] In the study of the focal trough of panoramic radiograph, using the Moritta company Panex EC a series of 48 exposures were taken with the 6-18 brass pins placed in the holes of the plastic model plate, then evaluated by 4 observers. The author analyzed the focal trough defined by the sharpness criteria and calculated the vertical and horizontal magnification range in the corrected focal trough. The results were as follows; 1. Continuous focal trough was not defined in the anterior region using a very high degree of sharpness. 2. As degree of sharpness used in the analysis became less, focal trough was continuous in the anterior and posterior regions, symmetrized bilaterally, and the widths of the focal trough increased more in the posterior region. 3. As sharpness criteria were reduced, the percentage range of image magnification increased in both vertical and horizontal magnification, and especially the percentage range of horizontal magnification was greater than that of vertical magnification.

[en] As a new device of stress monitoring method, ultrasonic backscattering method has been used to aluminium samples with various grain sizes at rayleigh critical angle in order to observe the relationships between applied stress and ultrasonic backscattered energy. It was found that the ultrasonic backscattered energy was observed to decrease as the grain size increased at the given applied stress. At the same grain size, the ultrasonic backscattered energy increased with increasing the applies stress. Through this study, we provided some possibility to evaluate stresses in materials under loads nondestructively, and this method is expected to be used as a new stress monitoring device