Answer:
a) D = 4.88 * 10^(-14) m^2 / s
b) <em>t </em>= 1.1 hr
Solution:
a) Magnesium in Aluminum diffusion:
D = Do * exp(-Qd / RT)
= (1.2 * 10^(-4) m^2 / s) * exp ( - 130,000 / 8.31 * 723.15)
= 4.88 * 10^(-14) m^2 / s
D = 4.88 * 10^(-14) m^2 / s
b) The composition remains same at say the distance Xo:
(Cx - Co) / (Cs - Co) = Constant
Xo^2 / D_{550} * <em>t </em>= Xo^2 / D_{450} * 15
D_{550} * <em>t </em>= D_{450} * 15
(1.2 * 10^(-4) m^2 / s) * exp ( - 130,000 / 8.31 * 723.15) * <em>t</em>
(4.88 * 10^(-14) m^2 / s) * 15
by, solving for <em>t </em>we get:
<em>t </em>= 1.1 hr
So, the time required is 1.1 hr.
Depending on the data all answers can be used to make it easier to read. Without more info I would go with Borders (D) since they are the best way to group the data when printed, especially if the print is in color.
Alignment would be the correct answer only if the data goes out of cell boundaries. Font Color usually makes it harder to read because of bad contrast and finally changing the Font Style has a minimal effect since the default one is already pretty readable.
Normal or random variations that are considered part of operating the system at its current capability are <u> c. common cause variations.</u>
Explanation:
Common cause variation is fluctuation caused by unknown factors resulting in a steady but random distribution of output around the average of the data.
Common-cause variation is the natural or expected variation in a process.
Common-cause variation is characterised by:
- Phenomena constantly active within the system
- Variation predictable probabilistically
- Irregular variation within a historical experience base
It is a measure of the process potential, or how well the process can perform when special cause variation removed.
Common cause variation arises from external sources that are not inherent in the process and is where statistical quality control methods are most useful.
Statistical process control charts are used when trying to monitor and control 5- and 6-sigma quality levels.
The answer is C.wind machines only generate electricity when wind is blowing
