To extend the analysis period, he said, sometimes a double dose of tracer material is used to distribute detectable concentrations for up to a year.

他说，为了延长分析周期，我们有时会用双倍剂量的示踪剂材料来增加示踪剂分散后的可测浓度，并且可使其使用周期长达一年之久。

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To extend the analysis period, he said, sometimes a double dose of tracer material is used to distribute detectable concentrations for up to a year.

他说，为了延长分析周期，我们有时会用双倍剂量的示踪剂材料来增加示踪剂分散后的可测浓度，并且可使其使用周期长达一年之久。

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