Seismic-response-controlled structure with active mass driver system. Part 1: Design

An Active Mass Driver (AMD) system is proposed to suppress actively the response of a building to irregular external excitations such as earthquakes and typhoons. This system has been introduced to an actual ten-storey office building for the first time in the world. The system controls the motions of a structure by means of an external energy supply. It consists of an auxiliary mass installed in a building and an actuator that operates the mass and produces a control force which counters disturbances to the building. The design method of the AMD system, including the location of the installation and the capacity and stability of the system, is proposed. Simplification of the control algorithm is also described.     

Significance of High-Frequency Wind Forcing in Modelling the Kuroshio

Motivated by an analysis of a satellite sea surface temperature image suggesting that a train of extra-tropical cyclones induces amplification of the Kuroshio meander, a regional Kuroshio/Oyashio general circulation model was used to investigate the impact of high-frequency wind on the Kuroshio path variations. Near Japan, the standard deviation of the wind stress curl can be 10 times larger than the monthly mean, so the synoptic variations of the wind stress curl cannot be neglected. With the bimodal Kuroshio case realized in the model, sensitivity tests were conducted using monthly and daily mean QuikSCAT-derived wind stress forcings. The comparison showed that the high-frequency local wind perturbed the Shikoku recirculation gyre (SRG) and caused a transition of the path from straight to meander. The strong anticyclonic eddy within the SRG triggered the meander in the latter case. The high-frequency wind perturbed the motion of the eddy that would have otherwise detached from the Kuroshio, migrated south and terminated the meandering state. The result reinforces the suggestion from previous studies that the anticyclonic eddy within the SRG plays an active role in controlling the Kuroshio path variations.     

Meteor Orbit Determinations with Multistatic Receivers Using the MU Radar

The MU radar of RISH (Research Institute for Sustainable Humanosphere, Kyoto University), which is a MST radar (46.5 MHz, 1 MW peak power), has been successfully applied to meteor studies by using its very high versatility. The system has recently renewed with 25 channel digital receivers which significantly improved the sensitivity and precision of interferometer used in meteor observation. The transmission is now synchronized to GPS signals, and two external receiving sites with a ranging capability has additionally been operated in order to determine the trajectories and speeds of meteoroids.