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A poly vinyl chloride (PVC) gel actuator shows great potential for use as an artificial muscle because of such positive characteristics as movement in the air, large deformation, and being lightweight. A bending type actuator using PVC gel was studied previously [4]-[6]. We have proposed the structure of a contraction type actuator to construct an artificial muscle, and we have conducted some experiments using the single-layer PVC gel actuator [8]. In this paper, we investigate the characteristics of the multi-layer PVC gel actuator experimentally and evaluate its specifications in terms of the composition of PVC gel and the structure of the mesh electrode. The experimental results showed that the contraction rate of the actuator was about 14%, the response rate was 7Hz, and the output force was 4kPa. Also, we found that the stiffness of the actuator increased as the applied dc field increased like human muscle. The characteristics of the PVC gel actuator are shown to be very effective for constructing an artificial muscle.

In 1995 the great Hanshin-Awaji earthquake disaster occurred in the Japanese city of Kobe and its vicinity, and more than 6000 people were killed as a result of the collapse of buildings. This was a clear demonstration of how very strong ground motion in the area near a seismic fault can cause severe structural damage beyond that which is usually estimated. It also emphasized the importance of earthquake engineering research in solving such problems as why and how structures collapse in real conditions. In response to this disaster, the National Research Institute for Earth Science and Disaster Prevention (NIED) and the Science and Technology Agency of the Japanese Government (STA) planned to build a three-dimensional, full-scale, earthquake-testing facility as one of the core research facilities for earthquake disaster prevention. It is hoped to be able to carry large-scale structures and to simulate the process of dynamic collapse using three-dimensional, strong earthquake motion. For this purpose, the NIED and the STA began to develop large actuators and related components in 1995 and completed them in 1998. Through this development and testing, the design and manufacturing techniques of a large actuator system were successfully achieved. After that, the NIED and the STA began the design and construction of the new facility in the scal year of 1998. The construction work is now in progress in Miki City, near Kobe, Japan. It is scheduled to be completed by the beginning of 2005. In this paper, we summarize the performance and features of this new facility and the results of the technical developments.

The thoracic musculature of the insect order Psocodea has been examined in only a few species of a single suborder to date. In the present study, we examined the thoracic musculature of species selected from all three suborders of Psocodea to elucidate the ground plan of the order and to examine the phylogenetic utility of the character system. The sister‐group relationship between the suborders Troctomorpha and Psocomorpha received support from two novel nonhomoplasious synapomorphies, although the support from other morphological characters for this relationship is ambiguous. The sister‐group relationship between the infraorders Epipsocetae and Psocetae also received support from one nonhomoplasious synapomorphy, although no other morphological characters supporting this relationship have been identified to date. The present examination revealed the potential of thoracic muscle characters for estimating deep phylogeny, possibly including interordinal relationships.

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