As lead and arsenic pollution element are skew distribution, statistics of a natural background value and a content of lead and arsenic are worked out using median method of skew distribution.
由手铅、砷污染元素呈偏态分布，故采用偏态分布中的中位数法作了铅、砷自然背景值及含量的统计。
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In this paper calculating method of lead angle of helical gear by measuring span length of length bar and base tangent length is put forward and lead angle calculating formula is deducel.
To lead anode plate thickness uniformity, we proposed the dynamic lost heavy method realization lead anode plate casting method. It increased the precision of casting the lead anode plate.