Radar network system to observe & analyze Tokyo Bay vessel traffic

A complete grasp of the actual vessel traffic flow by accurate observation is essential to carry out vessel traffic management, design of vessel traffic route, plan of port construction, etc. Up to now, the observation of vessel traffic has needed many efforts such as the use of a special ship or car equipped with radar observation systems and the observation staff preparation for a considerably long period. In order to perform accurate observation of vessel traffic without such efforts, the authors have developed a completely automated radar network system covering the main traffic route of Tokyo Bay. In August 2003, as the second remote radar station attaching AIS equipment was set at East Ogishima (the first was installed at the National Defense Academy in 2002), the observing range could be enlarged and cover most traffic routes in Tokyo Bay. These two radars can observe the vessel traffic in Tokyo Bay simultaneously so as to know the traffic flow accurately on the basis of analyzing the integrated radar data. In addition to the development of a radar network system, the software to analyze observed vessel traffic flow has been developed. This software has various functions such as tracking of ship's position, automatic determination of ship's size, animation of ship's movements, superposition of successive radar images, display of ship's tracks, calculation of ship's speed distribution, extraction of dangerous ship encounters using subjective judgment value and bumper model, etc. Some analyzed results on vessel traffic flow observed by the remote radars in January and September 2003 are shown in this paper.     

Progress of super-pressure balloon development: A new “tawara” concept with improved stability

The super-pressure balloon (SPB) has been expected to be a flight vehicle that can provide a long flight duration to science. Since 1997, we have developed the SPB. Now we are at the phase of developing an SPB of a practical size. In 2009, we carried out a test flight of a pumpkin-shaped SPB with a 60,000 m³ volume. The undesirable result of this flight aroused us to resolve the deployment instability of the pumpkin-shaped SPB, which has been known as one of the most challenging issues confronting SPB development. To explore this deployment issue, in 2010, we carried out a series of ground tests. From results of these tests, we found that an SPB design modified from pumpkin, named “tawara”, can be a good candidate to greatly improve the deployment stability of the lobed SPB.     

Telescience testbed for biomedical experiments in space morphological and physiological experiments of rat musculoskeletal system.

As the second telescience testbed experiment we were examined sophisticated processes of biomedical experiment, such as an implantation of a transmitter into the hamster's abdominal cavity, non-stressful blood sampling, large amount of blood collection, muscle extirpation and biopsy from the hamsters on February 6-8, 1990. To make clear the differences between successful results obtained by an experienced hand and by a non-experienced one, three operators were selected for three successive experimental days; an engineer who had never experienced any biological experiment, a non-biology student, who experienced on biological experiments, and a veterinary surgeon. Surgical procedures need much experiences on maneuvering and understanding of theory to shorten the elapse time. Especially for a non-experienced hand, graphic instructions were much helpful to understand and to maneuver the procedures. Continuous recordings of ECG from a operator and PIs were of an advantage to grasp an extent of the mental strain, which was compared with their reports requested after end of each experimental day. The mental strain was not related to degrees of scientific achievement, but showed faithfully difficulty of each experimental procedure. Training effects on PIs in successive experimental days were found in their instructions for the operator to let understand the procedures.     

An experimental study on carbon nanotube cathodes for electrodynamic tether propulsion

Research and development of an electrodynamic tether propulsion system for space debris removal has been started in the Institute of Space Technology and Aeronautics, Japan Aerospace Exploration Agency (JAXA). An experimental investigation of a carbon-nanotube field-emission cathode (FEC), which is suitable as an electron emitter in this propulsion system, was conducted in this study. One of the important issues in the design of a FEC is to suppress an electron flow to a gate electrode to avoid thermal deformation of the electrode and to reduce power loss. For meeting this requirement, we designed an FEC device having a masking plate on a cathode surface. A numerical simulation indicated that presence of the masking plate distorts the electric field adjacent to the cathode surface and a converged electron beam that does not impinge on the gate electrode is formed. Several FEC devices were fabricated based on the simulation results, and they were tested experimentally. Results showed that no electron current flowed to the gate electrode when all the electrodes were assembled and aligned correctly.     

Attempt to study Marangoni flow of low-Pr-number fluids using a liquid bridge of silver

In order to experimentally investigate the Marangoni flow of low-Prandtl-number fluids in a liquid bridge geometry under the condition of small Marangoni numbers close to the critical Marangoni numbers Ma_c1 and Ma_c2, the formation of a liquid bridge of silver was attempted. The available temperature difference between the upper and lower rods to obtain a small Marangoni number, such as Ma = 50, was calculated for a 5 mm high liquid bridge for several molten metals. For molten silver, the possible temperature difference was estimated to be 16 K, whereas, for molten silicon, this was 0.38 K, which is unrealistic for the purposes of experiments. For silver, a free surface can be obtained in the wide range of oxygen partial pressures, whereas, for molten silicon, the available oxygen partial pressure range is very small; equilibrium oxygen partial pressure for SiO₂ formation is as low as 1.1 × 10⁻¹⁴ Pa. A liquid bridge of molten silver was successfully prepared and temperature oscillation was observed; the estimated Marangoni number was 160 and oscillation frequency was 0.26 Hz.