[en] High construction technologies enable huge underground structures and a number of new structures are constructed underground over the limit. Construction of underground structures increases available surface space and resolves many specially-considered problems of onground structures, which increases safety and reliability of structures. Since a slight accident of a nuclear plant can bring a catastrophe, however, application of new construction technologies is required to be careful. In this study, strengths and weakness of underground nuclear plants are examined and compared with those of on-ground nuclear plants. Three fundamental concepts of seismic deformation method, response acceleration method, and dynamic analysis method for seismic response analysis of underground structures are reviewed. Korean seismic design code for underground cavity is summarized. The underground nuclear plants have strengths such as upgrade of containment, improvement of seismic safety, economic benefits, and ease of decommission. However, a few studies have been performed about the underground nuclear plants. They are not studied in Korea. Since importance of the underground space is increasing in Korea which has limited surface space and underground nuclear plants will be constructed in the near future, strong theoretical and technical foundations has to be provided through detailed studies on the underground nuclear plants

[en] The consistent transmitting boundaries, boundary element methods, and infinite elements are numerical approaches which are frequently employed for the energy radiation into infinity. Since nonlinearities in a system can influence significantly its dynamic behaviors, the necessity for nonlinear soil-structure interaction analysis is increasing recently. Nonlinear behaviors in a mechanical system can be best represented by nonlinear finite elements in the time domain. In this study, a “practical” numerical approach for nonlinear soil-structure interaction analysis of a NPP containment building installed in poroelastic soil is proposed. The proposed approach is based on mid-point integrated finite elements and viscous boundary. In this study, a “practical” numerical approach for nonlinear soil-structure interaction of a NPP containment building installed in a poroelastic soil was proposed. In order to represent the energy radiation through soil, its far-field region is represented by midpoint integrated finite elements and viscous boundary. The mid-point integrated finite elements can be expressed in the same way as the conventional finite elements. The viscous boundary can be represented by a simple mechanical damper. Therefore, nonlinear soilstructure interaction problems can be solved with existing numerical codes modified slightly in order to implement the mid-point integrated finite elements and viscous boundary.

[en] With the introduction of performance based design, it is recommended that deign ground motions be consistent with uniform hazard response spectra (UHRS) with annual probability of exceedance of 10-5. Recently, it is proposed that design ground motions be consistent with uniform risk response spectra (URRS) rather than the UHRS. Thus, the conversion of UHRS to URRS has been studied. Earthquake responses of nuclear power plants are greatly affected by soil-structure interaction. Therefore, it has been studied how to obtain UHRS/URRS at soil sites from those at the bedrock level considering soilamplification effects. In this study, seismic hazard curves at soil sites will be computed from those at the bedrock level and the effects of soil amplification will be investigated. In this study, seismic hazard curves at soil sites were computed from those at the bedrock level. It was observed that the slopes in the log-log plot of the curves can be varying.

[en] An attempt is made to see numerically the effect on the solidification of cooling during filling and the residual flow after finishing filling process in a casting process. Emphasis is given to simultaneous analysis of fluid flow and heat transfer in the whole casting process from filling to the end of solidification. To treat the free surface, MAC method is employed in the SIMPLER algorithm of the finite volume approach. Thermal stresses during solidification is calculated based on temperature distributions through the finite element analysis. Results show the distinct difference between the present analysis and the conventional analysis, which just deals with solidification process only

[en] The temperature uniformity on a wafer during Post-Exposure Bake (PEB) process in photolithography has been an important factor to Critical Dimension (CD) uniformity as the feature size of semiconductors decreases. To design the bake system which has enhanced temperature uniformity for the PEB process, the heat distribution of the system was analyzed numerically. Among many reasons of temperature non-uniformity, the effect of wafer warpage was investigated first. And as the results of this analysis implies, the numerical analysis for designing the resistive heater pattern of a multi-zone hot plate in the bake system was conducted. By the numerical analysis with Fluent 6.2, the need of the multi-zone hot plate and the possibility of the temperature non-uniformity on the multi-zone hot plate can be explained

[en] Highlights: • Oxyfluoride glass–ceramics containing CaF_2 nanocrystals doped with Er"3"+ and Yb"3"+ ions were formed on the glass surface by CO_2 laser and a heat gun exposure. • Most of Er and Yb ions were distributed inside CaF_2 nanocrystals and fluorine loss was observed in the EDS element maps. • IR-to-VIS upconversion emission efficiency of laser annealed glass ceramics was much increased and compared with that of the furnace-annealed glass ceramics. • Distributed volume of the glass ceramics were estimated by a confocal fluorescence microscope imaging. - Abstract: We report the glass–ceramic precipitation on the oxyfluoride glass surface by spatially selective annealing with a CO_2 laser and a heat gun exposure. X-ray diffraction analysis showed the formation of major CaF_2 and miner Ca_2SiO_4 nanoparticles. We observed ∼100 nm nanoparticle aggregation by tunneling electron microscopy and element distribution in glass and crystal phases. Spatial distribution of glass ceramics near the glass surface was probed by confocal fluorescence microscope by using much enhanced emission from the Er ions in the laser-treated area. Strong emissions at 365 nm excitation and visible up-conversion emissions at 980 nm excitation also indicated well incorporation of Er and Yb ions into a crystalline environment

[en] Highlights: • Oxyfluoride glass–ceramics containing CaF₂ nanocrystals doped with Er³⁺ and Yb³⁺ ions were formed on the glass surface by CO₂ laser and a heat gun exposure. • Most of Er and Yb ions were distributed inside CaF₂ nanocrystals and fluorine loss was observed in the EDS element maps. • IR-to-VIS upconversion emission efficiency of laser annealed glass ceramics was much increased and compared with that of the furnace-annealed glass ceramics. • Distributed volume of the glass ceramics were estimated by a confocal fluorescence microscope imaging. - Abstract: We report the glass–ceramic precipitation on the oxyfluoride glass surface by spatially selective annealing with a CO₂ laser and a heat gun exposure. X-ray diffraction analysis showed the formation of major CaF₂ and miner Ca₂SiO₄ nanoparticles. We observed ∼100 nm nanoparticle aggregation by tunneling electron microscopy and element distribution in glass and crystal phases. Spatial distribution of glass ceramics near the glass surface was probed by confocal fluorescence microscope by using much enhanced emission from the Er ions in the laser-treated area. Strong emissions at 365 nm excitation and visible up-conversion emissions at 980 nm excitation also indicated well incorporation of Er and Yb ions into a crystalline environment

[en] The fluorescence detector (FD) of the Telescope Array Low-Energy Extension (TALE) has been designed with different structures comprised of various materials. However, the cycle of expansion and contraction in these materials in response to thermal effects results in structural deformation. Furthermore, because the TALE-FD is exposed to high-temperature environments, significant light dispersion occurs as a result of the substantial deformation of the mirror (due to thermal expansion mismatch); this is considered to be an important issue that must be addressed in order to enhance the array performance and productivity. As the optical surface accuracy may be influenced by the structural deformation, an assessment of any significant structural deformations of the component materials is necessary to increase confidence in the array’s operation. The primary purpose of this paper is to identify the relationship between temperature increases and changes in the surface accuracy of the TALE-FD large mirror. For this purpose, Cherenkov light emission and the fluorescence processes of ultra-high-energy cosmic rays (UHECRs) are emulated in order to assess the optical performance of the TALE-FD in practical situations. Additionally, the detection sensitivity of the TALE-FD large mirror is experimentally identified by measuring the distribution of the focused spot produced by incident light over the surface of a photomultiplier tube (PMT) sensor array.

[en] It is possible for us to perform the dynamic analysis of the structures, such as normal mode analysis and transient response analysis, having very large amount of finite elements in CAE fields utilizing finite element method. But the dynamic analysis of large system is still very time-consuming even though the great improvement of computing power because we need the finer finite element model to get more accurate results. Therefore, model reduction method still has much advantage when it comes to the computational efficiency. In this paper, the model order reduction(MOR) method based on moment matching is introduced and its application to the normal mode analysis is represented to show the efficiency and accuracy of the MOR method

[en] Experimental investigation is made to study the dependence of performance characteristics of heat pipe on the types of wick shapes. Types of wick shapes adoped are open groove wick, screen wick, closed groove wick and no wick.(thermo-syphone). The dependence of heat pipe performance on the wick shape is turned out in the following order ; open groove wick, closed groove wick, screen wick and no wick. This shows that the heat transfer efficiency of heat pipe depends more upon the returning capacity of liquid from condenser to evaporator, implying that the wick which has low capillary pressure but good permeability is better than those which has higher capillary pressure. (Author)