It is difficult to design the Virtual Reality (VR) Environment which controls VR sickness and promotes presence. This is because the relationship between the user's susceptibility to VR sickness and a sense of presence, determined by velocity and visual angle of the visual information, involves a trade-off between the two. Then we propose the optimal value search system which computes efficiently the velocity and visual angle which control VR sickness and do not impair presence by taking account of a subject's characteristic. Under certain experimental conditions, some subjects showed serious VR sickness whose simulator sickness questionnaire total score was more than 60 and needed more than 30 minutes to recover from VR sickness. However, on the condition of angular velocity and visual angle computed by our proposed method, all subjects felt their vection, which was our index for the sense of presence, over 70 percent of their experiment time; no subject needed more than 5 minutes to recover from VR sickness.

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Phenylacetylene is stereoselectively brominated by molecular bromine adsorbed on graphite in carbon tetrachloride, to produce E-a-P-di bromostyrene; isomerisation of the €-isomer to the Z-isomer, usually catalysed by bromine, is inhibited by graphite.

An epidemiologically investigated of invasion of Rickettsia tsutsugamushi, inhabitant of mites and serum sample from patients with Tsutsugamushi disease in Gunma prefecture from 1984 to 1994 was made. Our data clearly indicated that Rickettsia tsutsugamushi was not located but widely spreaded throughout the Prefecture. Mites on rodents, were classified into 4 genus and 12 species and about 15% of them were Leptotrombidium pallidum and Leptotrombidium scuttellare, well known virulent vectors. The highest incidence rate of this disease was observed in the northwest area of the Prefecture from October to December, while a smaller number of patients occurred in other areas and in other months. About fifty percent of the serum samples from the patients wer positive to the Karp strain. These results suggest that the major cause of this disease is the Karp strain and the disease could occur potentially in various areas of the Prefecture.

This paper analyzes the driver's collision avoidance behavior in an emergency. Experiments, in which participants drove a test vehicle at around 40 km/h and a dummy vehicle suddenly appeared from the side, were conducted on a proving ground. Two out of 56 participants did not respond to the emergency situation by applying their brakes. Most participants steered the vehicle to some extent, though it was their braking operation that was essential to avoid collisions. Driver behaviors in the emergency revealed, for example, that the average brake response time was 0.45 seconds and the average deceleration after braking was 7.0 m/s 2. These values should be considered when designing the driver support systems for emergencies.