Water containing polyvinyl nitrate was experimentally assessed on the basis of organoleptic, general sanitary and toxicological indicators of harmfulness. It was established that that the compound did not change water organoleptic properties but produced a negative impact on viability of saprophytic microflora , nitrification processes and biochemical oxygen demand. Besides, in tests on animals. the substance caused acute, sub-acute and chronic toxicity. Based on those signs of harmfulness, threshold levels of exposure were established. Data obtained were taken into account for substantiation of MAC (Maximum allowable concentration) of polyvinyl nitrate in water bodies.
Assuming that scenes would be visually scanned by chunking information, we partitioned fixation sequences of web page viewers into chunks using isolate gaze point(s) as the delimiter. Fixations were coded in terms of the segments in a5×5mesh imposed on the screen. The identified chunks were mostly short, consisting of one or two fixations. These were analyzed with respect to the within- and between-chunk distances in the overall records and the patterns (i.e., subsequences) frequently shared among the records. Although the two types of distances were both dominated by zero- and one-block shifts, the primacy of the modal shifts was less prominent between chunks than within them. The lower primacy was compensated by the longer shifts. The patterns frequently extracted at three threshold levels were mostly simple, consisting of one or two chunks. The patterns revealed interesting properties as to segment differentiation and the directionality of the attentional shifts.
Relation of threshold levels fatigue crack development in low-alloy steel under harmonic and operational loading
