The purpose of this study is to confirm objectively by an instrumental measurement if there is less eye fatigue in VDT work when using a wood rim covered display than when using a plastic housing display. The subjects were 26 graduate and undergraduate university students. Each subject did the same 60-min VDT activity with both a plastic housing and wood-covered display. Before and after VDT activity, each subject's near-point accommodation distance was measured by a near-point ruler. As a result, it was confirmed that variation rate of the near-point accommodation distance by the VDT work with the wood-covered display was smaller than with the plastic housing display. From sensory tests, progression of subjective symptoms such as eye pain and headache was less with the wood-covered display than with the plastic housing display.
The purpose of this study was to measure each color of three sections of wood with instruments, and to examine whether there were differences between each color of three sections. The total number of tree species measured was 60, with the same number of conifers and broadleaf trees. A test piece, which was a cube with one side of 34 mm, was prepared for each tree species. End grain, edge grain, bark side and pith side of each test piece were flattened by a hand planer. Then, lightness L* and hue/saturation (a*, b*) in the L*a*b* color space were measured with a spectrophotometer. The results showed that the end grain had a lower L* compared to the other planes. The end grain was reddish and yellowish because it had a large a* and small b*. When chroma C* and hue angle h in the L*C*h color space were calculated from a* and b*, the end grain had a small dullness with less vividness because C* was smaller than the other planes. L*, a*, b*, C* and h on the other planes excluding the end grain were almost equal for each plane. Furthermore, it was found that the plane whose lightness L* had the strongest correlation with the density of the test piece was the end grain. Therefore, the correlation diagrams between the density, average of annual ring width, and L*of the end grain of each test piece were shown.
To clarify if eye fatigue is lessened when looking at wood, we carried out objective examinations using a near-point ruler and also performed sensory evaluations. Visual contact target materials were a white plastic panel, a black plastic panel or a wood panel which had Japanese ash flat grain surface. Each size of the materials was 140 9 280 mm. Test subjects were 30 undergraduate and graduate students. Each subject's visual distance to a panel was 40-50 cm. The results showed that subjects suffered from more eye fatigue when looking at white and black plastic panels compared to looking at the wood panel in objective examinations. In sensory evaluations, almost all subjective symptom items for eyes and head progressed when subjects looked at white plastic panel or black plastic panel. However, almost no progression of subjective symptoms was noted when subjects looked at the wood panel. In both objective examinations and sensory evaluations, eye fatigue was most highly associated with the black plastic panel, followed by the white plastic panel and, finally, the wood panel.
To clarify the inducing mechanism of kerf deviation caused by unsymmetrical set of the handsaw, we hypothesized that the moment on the bottom edge of the saw blade, which is generated by the unsymmetrical set on handsaw teeth, bends the saw blade and this deformation mechanisms originated from unsymmetrical set on the saw teeth.
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