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## engineering – 1D Wave Equation: Vertical Rod and Displacement vs. Textbook Solution

I am trying to setup Mathematica to analyze a vertical round rod under its own weight, fixed on one end free on the other. I have the 1D wave equation and a distributed load to represent the self weight of the round rod.

The problem is when I compare the Mathematica solution to the textbook solution the two do not agree.

Sample problem is given below.

``````Y = 199*^9; (*Young's modulus in Pa *)
(Rho) = 7860; (* Steel density in kg/m^3*)
dia = 1/39.37; (* 1" dia converted to meters*)
c = Sqrt(Y/(Rho));
len = 1000; (*length in meters*)
tmax = 5; (* Max time for analysis*)
area = (Pi)*dia^2/4; (*Round rod cross sectional area*)
wtfactor = (Rho)*9.81*area/len;

frwt(x_) := (Rho)*
area*9.81*(1 -
x/len); (*Rod Self weight imposed as a distributed load*)
nsol6 = NDSolve({!(
*SubscriptBox(((PartialD)), ({t, 2}))(z(x, t))) == c^2*!(
*SubscriptBox(((PartialD)), ({x, 2}))(z(x, t))) + frwt(x) +
NeumannValue(0, x == len),
z(0, t) == 0}, z(x, t), {x, 0, len}, {t, 0, tmax},
Method -> {"FiniteElement",
"MeshOptions" -> {"MaxCellMeasure" -> 10}}
)
fnnsol6(x_, t_) = nsol6((1, 1, 2))
Plot3D(fnnsol6(x, t), {x, 0, len}, {t, 0, tmax},
PlotLabels -> Automatic, AxesLabel -> Automatic)

deltaL = (((Rho)*9.81*len^2)/(
Y*2)) (*Textbook elongation for a vertical rod under self weight*)
calcdeltaL =
fnnsol6(len,
5) (*Calculated delta Length from PDE solution.  Should match
textbook*)

deltaLfunc(x_, l_) := (Rho)*9.81*
x*(2*len - x)/(2*Y) (*Verified Correct*)
deltaLfunc(x, 1) /. {x -> Range(0, 1000, 100)}});
xydata2 =
Reverse(a)}); (*Same answer different calc format for debugging*)
Show(Plot(fnnsol6(x, 0), {x, 0, len}, PlotLabels -> {"PDE Val"},
PlotRange -> All
),
ListLinePlot(xydata2, PlotStyle -> Green, PlotLabels -> {"Correct"}))
``````

If you’ve read this far, thank you.

In summary my question is: Is this a Mathematica issue or a PDE setup problem? The PDE is right out of a textbook so I don’t think that’s the problem but Mathematica gives no errors and I am out of troubleshooting ideas so looking for some help.

Thank You

## Developer Documentation Builder – Software Engineering Stack Exchange

I am trying to build a developer documentation for my web app in the style of this: https://firebase.google.com/docs/firestore/query-data/get-data

The features I am looking for is that it has a left vertical navigation bar, and the documentation text is on the right, along with code sections. Instead of me creating everything from HTML/CSS from scratch, I am wondering if there is a website builder that I can use to drag and drop the features I want such as the vertical navigation bar, and code blocks, etc, or any other methods to create such documentation?

## usability engineering – A / B testing: is this how you calculate the average number of "Clicks to content" for participants?

I am currently calculating using Excel some collected quantitative data that I have from the participants. So far I have reached this score%:

Note: I know the metrics for Task completion time it is calculated as follows:

``````(max_score - participant_score)/(max_score - minimum_score)
``````

My main question:
Is there a similar equation / formula for "number of participant clicks" on a specific page?

## Usability Engineering – A / B Testing: Completion of Tasks% Score

I am currently calculating using Excel some collected quantitative data that I have from the participants. So far I have reached this score%:

Now I'm kind of stuck. Since I'm not sure, I will take the next step and average everything, especially since I can't find any details in the books related to "doing UX studies", therefore I am curious if anyone knows what it is like this done correctly

Task completion rate percentage but based on the number of mouse clicks, then should you basically calculate the average?

## Social engineering: Is it a good idea to use a non-ASCII name in the United States?

There are even Chinese in the United States. They name their children 李某. Would that be a problem? No. Some systems support these names, some use versions converted to ASCII through romanization. The only non-ascii character in `X Æ A-12`, Æ, p is used. in Danish names like Ægidius, converted to ascii Aegidius.

A good example of such a conversion is machine-readable passports: the last two lines of each passport contain only the characters A – Z, 0–9 and the padding character <. For passports, all the names in the world are converted to ascii.

Sometimes using simple ascii can be more problematic than non-ascii characters that are easily encoded in UTF-8: Coffee tables Bobby It has a name as unique as the little baby musk. This Robert does not have a social security number since he is a fictional character, but for real people the name is not an obstacle.

## Social engineering: Is it a good idea to use non-ascii names in the United States?

Grimes and Elon Musk called their baby: `X Æ A-12`. How bad a idea is to use non-ascii names? For example, would the COBOL unemployment platform support your name? Would it be possible to get a social security number for the baby?

I think it exposes your baby to being an easier target to pose as unicode hacking attacks

## usability engineering: UX A / B Testing, Click% Score to achieve your goal

I am currently calculating using Excel some collected quantitative data that I have from the participants. So far I have reached this score%:

Now I'm kind of stuck. Since I'm not sure, I will take the next step and average everything, especially since I can't find any details in the books related to "doing UX studies", therefore I am curious if anyone knows what it is like this done correctly

## usability engineering – UX Click% Score to achieve your goal

I am currently calculating using Excel some collected quantitative data that I have from the participants. So far I have reached this score%:

Now I'm kind of stuck. Since I'm not sure, I will take the next step and average everything, especially since I can't find any details in the books related to "doing UX studies", therefore I am curious if anyone knows what it is like this done correctly

## Self Improvement – Online Course for Backend Engineering with Java / Kotlin Knowledge

I'm not sure if that question belongs to this community, but I couldn't find anything better.

I have been developing Android apps professionally with Java / Kotlin for several years and now I would like to start learning modern backend development in JVM.

I asked and heard good feedback about Udacity's Java Backend Developer course: https://www.udacity.com/course/java-developer-nanodegree–nd035. Unfortunately, it is under reconstruction at the moment and I cannot start.

Can you recommend any other similar online courses?