Brightness and lightness of achromatic surface colors were evaluated under various illuminance conditions in order to make a brightness scale that can be applied for all adaptation levels. A pair of gray scales made up of six gray color chips were presented in a test field and a reference field. Brightness as well as subjective lightness of the six test colors were evaluated using a gray scale in the reference field. Not only haploscopic and also binocular viewing conditions were employed. Furthermore, two comparison techniques-a conventional direct comparison method and a newly developed cascade comparison method-Were used in the case of brightness criterion. Experimental results show that the perceived contrast decreased with decreasing illuminance for the brightness criteria.The contrast compression for a cascade comparison was larger than that for a direct comparison. No contrast compression was obtained for the criterion of subjective lightness.
Heating characteristics of water containing flat substance with an underlayer plate heated by long-wave infraredradiation and/or hot-air convection are analyzed on a simulated electrical resistance-capacitance network that is equivalentto a given thermal system. In the previous paper we presented analytical results for the case without underlayer plate S and, instead, with the rearsurface of heated substance W thermally insulated. The present analysis assumes as before that only the surface of W isheated and that the substance is heated only by thermal conduction. It also assumes that the irradiated heat flow input, apartfrom the hot-air input, is constant and that W behaves like pure water. In addition to the general analysis, two representative cases W=1mm thick water, and S=10mm thick wood plate or 1mmthick steel plate are considered. Numerical calculations show that the temperature rises of W during a constant dryingperiod are little affected compared with the previous insulated case, though temperature rises are greatly delayeddue to thermal capacitance and resistance of S and accordingly much more so for the wood plate case. The theory and the analytical results were checked against published experimental numerical data. In the previous paper, we defined and introduced evaporation resistor γv. Here, for the heating characteristics of W, theimportance of the parameter, ratio of γvto convection heat transfer resistor γh is explained. Taking advantage of theparameter, guide lines for designing an infrared system heating water containg substance W are added and fullyexplained.
We found an effective method to restrain flicker appearing in a fluorescent lamp filled with heavy rare gas when the lamp is operated at low ambient temperature by “applying a transverse magnetic field on almost the whole positive column”.Investigating other potential effects of this method, we found that applying a magnetic field is effective at improving the efficiency, restraining flicker in the dimmed condition, and restraining end flicker of fluorescent lamps.