【单选题】The purpose of the ashing step in graphite-furnace atomic-absorption spec-troscopy is to()
A.
Vaporize metal atoms to be analyzed
B.
Cause the metal species to form carbides which are more volatile
C.
Convert the graphite furnace to ash to avoid carbide formation
D.
Burn off organic species that would interfere with the elemental analysis
【简答题】纺织纤维如何分类?各有哪些主要的性能特点?
【简答题】Atomic Emission Spectroscopy
【单选题】Which of the following is the function of the atomizer in the emission system of Atomic Absorption Spectroscopy?
A.
To split the beam into two
B.
To break the steady light into pulsating light
C.
To break large mass of liquid into small drops
D.
To reduce the sample into atomic state
【单选题】Which electronic transition in atomic hydrogen corresponds to the emission of visible light?
【单选题】下列有关组合的说法,正确的是()。
B.
组合后的图形对象不能重新分解为独立的图形对象
【多选题】下列有关投资组合的说法正确的有( )。
A.
在一个投资组合中减少风险的办法就是加入另一项新的资产或证券,扩大“组合'规模,但这种风险分散效应,随着加入资产数目的增多,呈递减趋势
C.
在投资组合中,两种资产的协方差为负,表明两种资产的收益成反方向变动
D.
如果两种资产收益率的相关系数等于+1,表明两种资产收益率的变动方向相同
E.
当投资组合中包含的资产数目达到非常大时,单项资产的方差对投资组合总体方差形成的影响几乎可以忽略不计