Innovative Damage Control Systems Using Replaceable Energy Dissipating Steel Fuses for Cold-formed Steel Structures

This paper describes the development of innovative seismic technologies for cold-formed steel structures; a rocking steel shear wall system with replaceable energy dissipating steel fuses for low rise housing units. In this system, the fuses are placed at the base of a folded-steel sheet wall connecting an anchor bolt and the steel sheet wall. It is designed so that most of the earthquake energy can be dissipated by plastic deformation of the fuse elements, while the shear wall remains intact and resists vertical and horizontal forces caused by large earthquakes. As expected in seismic events, the fuses at the base move cyclically into plastic regions when the wall behaves in a rocking manner. As a result, the wall system is expected to show a stable energy absorption behavior. To maximize its energy absorption capability in this research, the shape of the fuse is optimized, such that a butterfly shape is employed to have a greater yielding region. To verify the seismic performance of the proposed system, static shear wall tests and earthquake response analyses were respectively conducted. It was confirmed, with both results, that the developed fuses have high energy absorbing capacity and the rocking shear wall systems using them also have high seismic performance in comparison with conventional shear wall systems. The proposed system contributes to increased sustainability of the building systems through which damaged fuses are replaced after strong earthquakes

DECIGO pathfinder

DECIGO pathfinder (DPF) is a milestone satellite mission for DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) which is a future space gravitational wave antenna. DECIGO is expected to provide us fruitful insights into the universe, in particular about dark energy, a formation mechanism of supermassive black holes, and the inflation of the universe. Since DECIGO will be an extremely large mission which will formed by three drag-free spacecraft with 1000m separation, it is significant to gain the technical feasibility of DECIGO before its planned launch in 2024. Thus, we are planning to launch two milestone missions: DPF and pre-DECIGO. The conceptual design and current status of the first milestone mission, DPF, are reviewed in this article

The status of DECIGO

DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) is the planned Japanese space gravitational wave antenna, aiming to detect gravitational waves from astrophysically and cosmologically significant sources mainly between 0.1 Hz and 10 Hz and thus to open a new window for gravitational wave astronomy and for the universe. DECIGO will consists of three drag-free spacecraft arranged in an equilateral triangle with 1000 km arm lengths whose relative displacements are measured by a differential Fabry-Perot interferometer, and four units of triangular Fabry-Perot interferometers are arranged on heliocentric orbit around the sun. DECIGO is vary ambitious mission, we plan to launch DECIGO in era of 2030s after precursor satellite mission, B-DECIGO. B-DECIGO is essentially smaller version of DECIGO: B-DECIGO consists of three spacecraft arranged in an triangle with 100 km arm lengths orbiting 2000 km above the surface of the earth. It is hoped that the launch date will be late 2020s for the present

Control of Chemical Forms of Tritium in FLiNaK under Low Flux Neutron Irradiation

The use of the isotopic exchange between tritium produced in molten salts and hydrogen molecules in a sweep gas has been proposed as a way of recovering tritium in a self-cooled molten salt liquid blanket system [1-3]. In the present study, rate coefficients of the isotopic exchange for molten FLiNaK (LiF-NaF-KF) have been evaluated in a series of low flux neutron irradiation experiments with an AmBe neutron source at the OKTAVIAN facility of Osaka University in Japan. Approximately 300 cm3 of FLiNaK were irradiated at 773 K in an Inconel 600 crucible, and tritium released from the free surface of FLiNaK has been swept by a pure He gas or He+H2 (0.1%) gas. The change in the amounts of soluble tritium (TF, HTO) and insoluble tritium (HT) recovered by water bubblers has been evaluated in each sweep gas to evaluate the effectiveness of the tritium recovery with the isotopic exchange