question: Some soil contains 3ppb(parts per billion by weight) U-238. Calculate the specific activity of the soil?? t(1/2)=half life = 4.468*10^9(y) mass M=238 the activity of 1g U-238: A= (6.02*10^23)*ln(2)/[t(1/2)]*M = (6.02*10^23)*0.693/(4.468*10^9)*238 = 12445Bq/g 3ppb=3/10^9(g) Finally, A = [3/10^9(g)]* (12445Bq/g)=3.6735/10^5Bq/g=9.93/10^13Ci/g Is it right? Thanks for help!!
g*u
8 楼
有意思。
c*7
9 楼
那个A给钱更多么?
b*y
10 楼
You can do sitemap xml file. Directories used to be very good ways to get links, but not anymore. You can do blog commenting as a way to get back links. Guest blogging is even better. You have to have killer feature on your site, or, you can have good content. Best way is to let users/customers find you, so that means you need to have killer feature or good content. Social media is good if you can do it. 另外可以参考这些关于流量的文章: http://www.jiansnet.com/search?q=%E6%B5%81%E9%87%8F
【在 b******y 的大作中提到】 : : You can do sitemap xml file. : Directories used to be very good ways to get links, but not anymore. : You can do blog commenting as a way to get back links. Guest blogging is : even better. : You have to have killer feature on your site, or, you can have good content. : Best way is to let users/customers find you, so that means you need to have : killer feature or good content. : Social media is good if you can do it. : 另外可以参考这些关于流量的文章: