The purpose of this study was to investigate the relationship between the visual skill and the batting ability. The sports visions such as the kinetic visual acuity, depth perception, moment (instant) perception, eye-hand coordination, speed of eye movement, choice reaction time, visual field, and focal accommodation were measured for highschool baseball players. The batting ability of players was evaluated by the coach. In this study, the result of rating was classified into two groups (high evaluation and low evaluation groups). It was examined whether players belonging to high evaluation group had better visual abilities (sports vision) than those belonging to low evaluation group. In addition, we investigated what kind of functions of sports vision was highly related to the batting ability. As a result, we found a significant relationship between batting ability and the visual skills such as the kinetic visual acuity, eye-hand coordination, and choice reaction time. These visual skills include the function to pay attention to the visual stimuli and process them quickly in the central nervous system. On the other hand, the sport visions such as the depth perception and moment perception for the high evaluation group were differ from those for the low one. As for the visual fields, the high evaluation group tended to have wider and more recognizable visual field than the low one.

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Self-threading screws have some operational peculiarities. In spite of their economical advantage which require no prior tapping operation, one of the weaknesses of the self-threading screw tightening operation is that the screws could easily be tightened at a non-rectangular angle and thus resulting in improper tightening strength. The required criteria for evaluating such operation are identified. They are (1) Tightening torque, (2) Maximum vertical pressure and its timing of realization, (3) Driver tilt area at threading period and tightening period, and Driver tilt angle. In order to verify the criteria, an experiment was conducted taking work experience as a variable factor using 62 subjects with varying degrees of experience. As a result, the criteria were found to be effective and useful. It was revealed that the work experience had little effect on the performance which proved the effect of the peculiarity of the operation. By the use of the criteria, the workers with proper aptitude could be identified.

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This paper studies the relationship between the ride discomfort and the longitudinal acceleration of automotives. Eight subjects rated their ride discomfort caused by the maneuver of a mini-van type automobile they rode. Their rating scores were recorded together with the acceleration of the automobile. Relationship between the rating scores of ride discomfort and the longitudinal acceleration/jerk was investigated. A linear multiple regression model with the longitudinal acceleration and jerk as the explanatory variables and the subjective ratings of ride discomfort by the subjects as criterion variables was set up to model the relationship between ride discomfort and acceleration/jerk. Then the model was applied to estimate the ride discomfort induced by acceleration and deceleration of automotives. The high correlation coefficients between the estimation and the subjective rating scores verified the efficacy of the proposed model. The research is expected to be able to improve ride quality of mass transportation.

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This paper deals with the human sense of safety affected by the motion of electric ceiling-hoist. The effect of motion was examined by the subjective evaluation. Subjects were 35 handicapped persons who regularly used wheelchair and 20 persons over 60 years old. The hoist was capable of controlling the transfer speed and the acceleration. The angular acceleration of spreader bar for hanging of the human body was measured to take quantitatively the degree of body swing in the direction of hoist movement. Subjects were asked to rate the sense of safety in 5-grading scale about nine patterns of motion, compared with the typical motion of hoist on the market. The results revealed the followings. (1) The number of subjects who feel safe increases as the transfer speed and acceleration decreases. (2) 95% of subjects didn't feel danger for the transfer speed below 0.33m/s, the acceleration below 0.24m/s², and the maximum of angular acceleration below 0.59deg/s².

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