放射性衰变

Also it can be used in the nuclear science and engineering research for absolute measurement of nuclear decay rate.

它可供计量实验室建立放射性活度基准设备用，也可用于核科学研究和工程中核衰变率的绝对测量。

Ca is widely abundant in nature and its rodioisotope 41 Ca is a cosmogenic nuclide with a half\|life of 10 5 years. However, the 41 Ca/ 40 Ca ratio in natural samples is very low and can only be measure d by accelerator mass spectrometry. The application of 41 Ca is ve ry i mportant not only in the life science but also in geological dating, global envi ronment change studies and astrophysics.

1 引言Ca在自然界中广泛存在，它不仅是人体中含量最丰富的元素之一[1] ，也是众多其他物质的组成部分。41Ca(半衰期为 1.0 3× 10 5a)属于Ca的放射性同位素中的一种，其衰变方式为轨道电子俘获，只发射3.3keV的X射线，天然样品中41Ca 40 Ca的值很小。

He is proverbially known for his swift chariot driving.

以快速驾驶战车而闻名产生这种电子的放射性变化，称为β衰变。

The activation calculations of C276 were carried out with the FISPACT-2007 code at the same time. The activity, afterheat and contact dose rate during different cooling time after shutdown were described in detail.

同时使用FISPACT-2007程序进行活化计算，对放射性活度、衰变余热及接触剂量率等参数进行了详细分析。

This is because radioactive nuclear elements are formed in the giant outbursts of energy, and some of these decay by releasing positrons.

这是因为放射性核素在这巨大的爆炸能量中形成，其中一些放射出正电子而衰变。

According to the clear water experiment, aeration performance of the new equipment is good with high total oxygen transfer coefficient and oxygen utilization ratio.

曝气设备的动力效率在叶轮转速为120rpm～150rpm时取得最大值，此时氧利用率和充氧能力也具有较高值。

The environmental stability of that world - including its crushing pressures and icy darkness - means that some of its most famous inhabitants have survived for eons as evolutionary throwbacks, their bodies undergoing little change.

稳定的海底环境─包括能把人压扁的压力和冰冷的黑暗─意谓海底某些最知名的栖居生物已以演化返祖的样态活了万世，形体几无变化。