頁籤選單縮合
題 名 | 現行放射率測定技術質疑=Are the Current Radioactivity Rate Measuring Techniques Adequate |
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作 者 | 汪厥明; | 書刊名 | 中華農學會報 |
卷 期 | 28 民48.12 |
頁 次 | 頁9-16 |
關鍵詞 | 放射率; 測定技術; |
語 文 | 中文(Chinese) |
英文摘要 | In 1905 E.V. SCHWEIDLER formulated a description of the process of radioactivity in terms of disintegration probabilities. He assumed that the probability p for a particular atom of a radioactive element to disintegrate in a time interval △t is independent of the past history and that it depends only on the length of the time interval △t. If we consider not one atom, but a large initial number N0 of the radioactive atoms, then the fraction remaining unchanged after time t we may take to be N/N0= e-λt, where N is the number of unchanged atoms at the moment after a t time interval of distegration and λthe proportionality constant characteristic of that species of radioactive atoms. This exponential law of decay is just that which RUTHERFORD had already found experimentally for the radioactivities. The fact that variation of the radioactivity rate per unit time obeys poisson's error law has been verified by the author's experimental determination on the radioactivity rates of background and a β-radiative source at a laboratory of Reseach Institute of Taiwan Cane Sugar Company with permission by Dr.SHIN-CHUNG WANG (王世中), the section head and assistance by Mr. TZO-CHUAN TUANG (莊作權), The current rate measuring techniques practically used by the experimentors and practitioners are one of two processes below: (1) Counting frequency of radioactivity in an interval of n minutes predetermined and dividing the frequency by n to obtain the mean rate per minute which, for statistical purposes, is also used as the rate variance of frequency distribution. (2) Repeating observations of the radioactivity rate per minute n times and calculating the average rate per minute and the rate variance (σx2) of frequency distribution by the formula below: σx2=Σ(x-χ)2/n where x is an observed rate of radioactivity per minute and χ its main. (3) An approach to the Poisson's error law by approximating it to the probability of normal variate, as illustrated by JARRETT in research report when the mean rate equals to or larger than 20. With method (1) the radioactivity rate per unit time interval is liable to be underestimated and with process (2) the poissonian behaviour of rate may not appear. The approach of Poisson's error law to normal probabilities can not be varified, as very large discrepacies between Poisson's and Normal law have been obseved when the mean rate equals to 20 and 50 respectively. Therefore, whether all the current techniques above including the attempt to approach Poisson's law to normal law are adequate is now in doubt. Until the corrected techniques come out further research need be done. |
本系統中英文摘要資訊取自各篇刊載內容。