What's the relationship between bandwidth and symbol rate for a modulated signal?

Question: I was hoping somebody could help me with understanding the relationship between the bandwidth of a modulated carrier signal (say using QPSK) and the symbol rate(s) you can transmit across a channel. If anyone knows links to helpful visual representations please link them here. Thanks in advance.
Comment: \$\pi /2 ~~ QPSK  \$ is even better with Trellis and FEC
Answer: Bandwidth is defined by the pulse shape. (Full stop!)
If scaling the symbol rate that you use with a feasible pulse shape impulse response, you'll necessarily have to scale that impulse response, too, thus making bandwidth for a fixed pulse shape proportional to symbol rate.
Answer: The possible data bandwidth is determined more by the worst case signal-to-noise ratio over the channel than by the symbol rate or channel bandwidth.
(e.g. as an extreme case, in zero noise you can theoretically use an approaching infinite number of voltage level to encode lots of bits per symbol).
The spectral bandwidth is determined to some degree by the edge rate of the pulse or symbol transitions.


Can a new platform / cryptocurrency be built on top of Monero?

Question: Can we build a new platform / cryptocurrency on top of Monero like Counterparty / Factom is built on top of Bitcoin?
Answer: The Monero blockchain can be used to send any information, as long as it's part of a transaction.  There is a field (tx_extra) where you can effectively put whatever you want in there.  It's really a matter of size as the limiting factor.  As with the bitcoin blockchain, tx fees need to be paid (based on the size of the transaction).  So, yeah, it would work in sort of the same way.
Comment: That is nice to hear, i think soon we will see new altcoins built on top of Monero block chain.
Comment: Indeed.  And I'm hoping you'll get a slightly more technical answer than mine, to provide some more insight into this arena.


Is it better to survey the entire population if it is feasible?

Question: I'm researching behavior of a certain group of people through a survey. I have access to the entire population which is 8000 and plan to email a survey, and collected data through Qualtrics, an online survey website. Is there a downside to surveying the entire population or should I do formal calculations given a 95% confidence interval and an anticipated response rate of say 20%, which will require me to send out the survey to about 2000. But, as all the data is electronic and therefore all the statistics will be done by a compute, isn't it ideal to survey the entire population?
Comment: Technically it's not called a "survey" at that point, it's a "census".
Comment: Is there any way you can make them all answer the questions? Because if not, you will still only sample the part of the population which is willing to cooperate.
Comment: It kind of matters what you call it, a survey is something specific and many of the assumptions behind survey methods do not hold anymore (actually they start being problematic earlier, for example if you sample, say, half of the population). It's not necessarily bad but you need to adjust your computations accordingly. I won't be able to provide much details but it might be worth asking about this on the stats SE website. Also, is this "entire population" the only thing you are interested in or can you think of a theoretical population that's larger (e.g. future members of the group, etc.)?
Comment: Call it what you want; does the name actually invalidate my question?
Answer: Usually the size of the survey is governed by a cost-benefit analysis. With interviews, for example, the cost scales linearly with the number of participants, so you want to survey only as many as needed to get the confidence you want. With an online survey, your marginal cost may be zero or close to it, so if the additional information is of use, go for it. Of course, only a (possibly nonrepresentative) fraction of the population will respond.
Answer: If the cost and time are not problems for your study, use all of the population.
Based on the complete population, you have less error than the sampling based ones.
Also, you can compute your error (technically your standard error) and report the confidence interval based on the population.
For further details you can see the following textbooks,
Cochran book, sampling wiley.
Answer: If you cannot count or measure the whole population, be certain that you take a random sample.  And, if your sample size, n,  is greater than or equal to 10% of the population, use a finite population adjustment of the standard deviation of the mean (the standard error). That is multiply it by
sqrt{(N-n)/(N-1},
where the size of your entire population is N.
As pointed out by Brick,  you will get some non-responses in either case.
In either case your population is not what you seek, but rather the population of ,,, which responded. That will have to be made clear in your report. And, if you attempt to get samples from the entire population, you  do not need to make a finite correction because the non-responders constitute another population.
Comment: Valuable point about the responding subpopulation not necessarily representing the whole.
Answer: If Qualtrics will charge you the same amount to send out 2,000 or 8,000 surveys, you may as well send it to everyone. But be aware that if you have data for the whole population, it will change the interpretation of statistical test results somewhat. With full-population data you are no longer generalizing results to the population from a sample but instead describing that population precisely. This may or may not matter for your purposes in this case, but is worth being aware of.
Also, as a general piece of advice, terminology matters in technical fields like statistics. Using the wrong term doesn't necessarily invalidate a question but can make it much harder to understand, let alone answer in a way that is helpful to you. Corrections and requests for clarification shouldn't prompt a harsh response.
Answer: If you can survey the entire population, you should do it. If you have data from everyone in the population, statistics will become much and much simpler. There is no such thing as confidence interval. You will just need to compute the population mean, population variance etc.
However, you'll most likely get missing data (not everybody will respond to you).


Diagnostic plots with residuals and fitted values for Poisson regression

Question: I want to get a bit familiar with diagnostic plots for count data. I generated these two plots but I don't understand what they should tell me.
Maybe someone can sum up few important things?
Comment: I think it would be more common to put the fitted values on the x-axis for your 2nd plot.
Comment: Related: [Diagnostic plots for count regression](https://stats.stackexchange.com/q/70558/).
Comment: What are "breaks in data"?
Comment: sry , breaks is the count variable in the data set. It is the response variable, nummber of breaks.
Comment: i allready read the thread but it doesnt rly helped me , because he only says : ,,Here we see some very large residuals and a substantial deviance of the deviance residuals from the normal''. ( for plot deviance residuval vs fitted values)
Answer: Deviance residual (DR) plot:

Are the DRs about mean centered?
Is the variance about the same across the range of fitted values?
Is the net spread of the DRs about distributed according to a standard normal distribution (if they are spread otherwise, there may be over/under dispersion)
Is there heaping of 0-inflated at the lowest DR (you may need to use "jitter" to assess that one in a scatter plot).

Predicted vs observed plot:

Does a logarithmic curve seem to interpolate the mean of the values at each level?
Is the variance of the spread about the mean equal to that mean? (As @gung noted, you have transposed the plot from the typical way we usually inspect it).

Most of the inspections are assessing the same essential qualities of the model, the DR is most precise in terms of how to organize such results, but the predicted vs. observed can tell you more about how those values (say, outliers or heteroscedasticity) affect the model. Most of these "checks" seem to hold with the plots you generated by my eye. When these hold, a Poisson distribution shares many characteristics with the data you are modeling, so inference, predictions, and simulations based on that probability model should be reasonable.
Comment: Hmm..  how you can see all this things from the plot ?
Comment: @DimaKu as I mentioned it is in the training of the eye. You can use graphical methods in R or actually print the plot out and draw lines. It is subjective. Diagnostics *benefit* from impreciseness because mild/non-noticeable departures from model assumptions result in mild/inconsequential problems with inference, and the tendency for computational tests of assumptions is to be too precise.


Which source code to make "checksum bits appended"

Question: Can anyone tell me the specified source code to make "checksum bits appended", before doing Base58 conversion? Thanks very much!!!!
Answer: See src/base58.cpp Line 124:
std::string EncodeBase58Check(const std::vector<unsigned char>& vchIn)
{
    // add 4-byte hash check to the end
    std::vector<unsigned char> vch(vchIn);
    uint256 hash = Hash(vch.begin(), vch.end());
    vch.insert(vch.end(), (unsigned char*)&hash, (unsigned char*)&hash + 4);
    return EncodeBase58(vch);
}

As you can see, the data vch is hashed, then the first 4 bytes of the hash are appended to the end of vch before base58 encoding.
Comment: Thank you so much for your answer. Stupid me, I ask the wrong question, what I want ask is the source code to attach the prefix not checksum. would you please tell me which source to attach the prefix before do Base58?
Comment: I think you may be looking for these lines: https://github.com/bitcoin/bitcoin/blob/v0.16.2/src/base58.cpp#L226. Note this has changed in the latest 0.17 release candidate to https://github.com/bitcoin/bitcoin/blob/v0.17.0rc3/src/key_io.cpp#L29


i want to print c# windows form by windows printer

Question: I want to print c# windows form by printer.when i click print button in form, a print dialog should open just like when  we give any notepad or doc file to print.and i should be able to print the report or invoice.how to do it?
Answer: Use PrintDocument
http://msdn.microsoft.com/en-us/library/system.drawing.printing.printdocument(v=VS.100).aspx
Hope this helps.
Edit:
Also see http://msdn.microsoft.com/en-us/library/system.windows.forms.printdialog.aspx if you are interested in dialog options.
Answer: check out http://msdn.microsoft.com/en-us/library/system.drawing.printing.aspx I think you will find what you need there
Answer: You can use reporting services to generate a report based on whatever values are on the screen and then use the ReportViewer control to display and print the file.
I can't give you much guidance on how to do that off the top of my head but you could google winforms reporting services print and see what comes up...


Do humans have a loud sound avoidance reflex?

Question: I accidentally played music wearing earphones at top volume, and felt maybe half a second of pain before I seemingly involuntarily swatted the earphones to the ground. I don't remember even having time to think about the loud noise before the earphones were on the ground, and it left me thinking, do humans have a reflex to "swat" away loud noises from the ears?
Comment: https://en.wikipedia.org/wiki/Sonic_weapon
Answer: What you are describing sounds like a startle response. The startle response, along with the vestibular-occular reflex and acoustic reflex, and are often thought of as reflexes, despite not involving a reflex arc where a sensory neuron synapses with the spinal cord allowing for motor responses to occur without the signal reaching the brain. The startle response involves a number of brain structures and therefore, even though it is an unconscious response, in the strictest sense, it is not a reflex.
Comment: There's a subsection on that startle response wiki about the "acoustic startle response," which seems almost similar to what I'm looking for


Compute $ \sqrt{n^2 +3} - \sqrt{n^2 +2} $.

Question: I have a question concerning determining a basic limit of $ \sqrt{n^2 +3} - \sqrt{n^2 +2} $ as $n \rightarrow \infty $. Upon using the difference of squares, this yields: $ \frac{1}{\sqrt{n^2 +3} + \sqrt{n^2 +2}} $Now the limit seems intuitive, but I cant find a formal way of determining it. Any hints about what the next step should be would be appreciated.
Comment: $\frac{a}{\infty}=0$
Answer: Note that for any given $\epsilon>0$, we have
$$\begin{align}
\left|\sqrt{n^2+3}-\sqrt{n^2+2}\right|&=\left|\frac{1}{\sqrt{n^2+3}+\sqrt{n^2+2}}\right|\\\\
&\le \frac{1}{2n}\\\\
&<\epsilon
\end{align}$$
whenever $n>N=1+\lfloor \frac2\epsilon\rfloor$.
Answer: Hint :
Use Squeeze Principle.
$0 \le \dfrac{1}{\sqrt{n^2 +3} + \sqrt{n^2 +2}} \le \dfrac{1}{2n}$.
Comment: @RuslanMushkaev Note that $n^2+2>n^2$ and $n^2+3>n^2$.  So, $\sqrt{n^2+2}+\sqrt{n^2+3}>2n$.  Finally, $$\frac{1}{\sqrt{n^2+2}+\sqrt{n^2+3}}<\frac1{2n}$$which is the same inequality that I used in the $\delta-\epsilon$ proof I posted herein.  -Mark
Comment: Thanks. I knew I could use it, its just I couldn't really come up with anything. In this case, how did you come up with $1/2n$? Do you simply know this from before or is there some inequality that I am not aware of?
Comment: You're welcome. @Ruslan Mushkaev. To use squeeze principle, it is a standard trick - Put away all constants aside. And make the expression constant-free. You can do this by decreasing denominator and increasing numerator.
Answer: Let $f(x) = \sqrt{1+3x} -\sqrt{1+2x}$.
Then $f(0) = 0$ and $f'(0) = {1 \over 2}$, hence for $x$ sufficiently
small, we have $|f(x)| \le |x|$.
Hence for $n$ sufficiently large, we have
$|\sqrt{n^2+3} -\sqrt{n^2+2} | = n |f({1 \over n^2})| \le {1 \over n}$,
from which the limit follows.


How to check for normal distribution using Excel for performing a t-test?

Question: I want to know how to check a data set for normality in Excel, just to verify that the requirements for using a t-test are being met.
For the right tail, is it appropriate to just calculate a mean and standard deviation, add 1, 2 & 3 standard deviations from the mean to create a range then compare that to the normal 68/95/99.7 for the standard normal distribution after using the norm.dist function in excel to test each standard deviation value.
Or is there a better way to test for normality?
Comment: https://en.wikipedia.org/wiki/Q%E2%80%93Q_plot
Answer: You have the right idea.  This can be done systematically, comprehensively, and with relatively simple calculations.  A graph of the results is called a normal probability plot (or sometimes a P-P plot).  From it you can see much more detail than appears in other graphical representations, especially histograms, and with a little practice you can even learn to determine ways to re-express your data to make them closer to Normal in situations where that is warranted.
Here is an example:

Data are in column A (and named Data).  The rest is all calculation, although you can control the "hinge rank" value used to fit a reference line to the plot.
This plot is a scatterplot comparing the data to values that would be attained by numbers drawn independently from a standard Normal distribution.  When the points line up along the diagonal, they are close to Normal; horizontal departures (along the data axis) indicate departures from normality.  In this example the points are remarkably close to the reference line; the largest departure occurs at the highest value, which is about $1.5$ units to the left of the line.  Thus we see at a glance that these data are very close to Normally distributed but perhaps have a slightly "light" right tail.  This is perfectly fine for applying a t-test.
The comparison values on the vertical axis are computed in two steps.  First each data value is ranked from $1$ through $n$, the amount of data (shown in the Count field in cell F2).  These are proportionally converted to values in the range $0$ to $1$.  A good formula to use is $\left(\text{rank}-1/6\right)/\left(n+2/3\right).$  (See http://www.quantdec.com/envstats/notes/class_02/characterizing_distributions.htm for where that comes from.)  Then these are converted to standard Normal values via the NormSInv function.  These values appear in the Normal score column.  The plot at the right is an XY scatterplot of Normal Score against the data.  (In some references you will see the transpose of this plot, which perhaps is more natural, but Excel prefers to place the leftmost column on the horizontal axis and the rightmost column on the vertical axis, so I have let it do what it prefers.)

(As you can see, I simulated these data with independent random draws from a Normal distribution with mean $5$ and standard deviation $2$.  It is therefore no surprise that the probability plot looks so nice.)  There really are only two formulas to type in, which you propagate downward to match the data: they appear in cells B2:C2 and rely on the Count value computed in cell F2.  That's really all there is to it, apart from the plotting.
The rest of this sheet is not necessary but it's helpful for judging the plot: it provides a robust estimate of a reference line.  This is done by picking two points equally far in from the left and right of the plot and connecting them with a line.  In the example these points are the third lowest and third highest, as determined by the $3$ in the Hinge Rank cell, F3.  As a bonus, its slope and intercept are robust estimates of the standard deviation and mean of the data, respectively.
To plot the reference line, two extreme points are computed and added to the plot: their calculation occurs in columns I:J, labeled X and Y.
Comment: For the formulas in Col B, would you explain the reason to add 1 and divide by 6 and 3 ("+ 1/6" and the "+ 1/3")? Also is there a reason you chose to divide by 6 in the Hinge Rank Cell?
Comment: @Michael Good questions. $1/6$ is one simple, well-known way to establish [probability plotting points.](http://www.itl.nist.gov/div898/handbook/apr/section2/apr221.htm) I recall John Tukey recommending this in his book, *EDA*. The hinge rank formula is mysterious: I should have explained that I am picking two points equally far in from the ends at the $100\times 1/6$ and $100\times 5/6$ percentiles. Any multiplier substantially greater than $0$ and less than $1/2$ would work. $1/4$ is  popular: it corresponds to the quartiles. So is $0.16$, corresponding to 1 SD for a Normal distribution.
Comment: The formula (rank + 1/6) / (n+1/3) doesn't seem to be symmetric as we might anticipate. e.g. with the middle observation of 3 the rank is 2 and this would suggest a corresponding percentile of 0.65 rather than what would seem to be natural to take for the middle observation (0.5). Did I miss something obvious?  [ I've seen Tukey use a few different formulas in different places, including (i-1/3)/(n+1/3).  The formula at your link fits into the common (i-a)/(n+1-2a) scheme but the formula you give in your answer doesn't]
Comment: @Glen_b Thank you for catching that.  I had misquoted the formula.  My source is (my own page!) at http://www.quantdec.com/envstats/notes/class_02/characterizing_distributions.htm, where the correct formula is given and justified: generally one uses $$\frac{r-a}{n+1-2a}$$ where $r$ is the rank (from $1$ through $n$) and $a$ typically is a number between $0$ and $1$, often $1/6$.  That yields $(r-1/6)/(n+2/3)$ as the desired formula.  ($a=1/3$ gives the Tukey formula you quote.) I have fixed the formula and the Excel illustration.
Answer: You could plot a histogram using the data analysis toolpack in Excel. Graphical approaches are more likely to communicate the degree of non-normality, which is typically more relevant for assumption testing (see this discussion of normality).
The data analysis toolpack in Excel will also give you skewness and kurtosis if you ask for descriptive statistics and choose the "summary statistics" option. You might for example consider values of skewness above plus or minus one be a form of substantive non-normality.
That said, the assumption with t-tests is that the residuals are normally distributed and not the variable. Furthermore, they also quite robust such that even with fairly large amounts of non-normality, p-values are still fairly valid.
Answer: This question borders on statistics theory too - testing for normality with limited data may be questionable (although we all have done this from time to time).
As an alternative, you can look at kurtosis and skewness coefficients.  From Hahn and Shapiro: Statistical Models in Engineering some background is provided on the properties Beta1 and Beta2 (pages 42 to 49) and the Fig 6-1 of Page 197.  Additional theory behind this can be found on Wikipedia (see Pearson Distribution).
Basically you need to calculate the so-called properties Beta1 and Beta2.  A Beta1 = 0 and Beta2 = 3 suggests that the data set approaches normality.  This is a rough test but with limited data it could be argued that any test could be considered a rough one.
Beta1 is related to the moments 2 and 3, or variance and skewness, respectively.  In Excel, these are VAR and SKEW.  Where ... is your data array, the formula is:
Beta1 = SKEW(...)^2/VAR(...)^3

Beta2 is related to the moments 2 and 4, or the variance and kurtosis, respectively.  In Excel, these are VAR and KURT.  Where ... is your data array, the formula is:
Beta2 = KURT(...)/VAR(...)^2

Then you can check these against the values of 0 and 3, respectively.  This has the advantage of potentially identifying other distributions (including Pearson Distributions I, I(U), I(J), II, II(U), III, IV, V, VI, VII).  For example, many of the commonly used distributions such as Uniform, Normal, Student's t, Beta, Gamma, Exponential, and Log-Normal can be indicated from these properties:
Where:   0 <= Beta1 <= 4
         1 <= Beta2 <= 10

Uniform:        [0,1.8]                                 [point]
Exponential:    [4,9]                                   [point]
Normal:         [0,3]                                   [point]
Students-t:     (0,3) to [0,10]                         [line]
Lognormal:      (0,3) to [3.6,10]                       [line]
Gamma:          (0,3) to (4,9)                          [line]
Beta:           (0,3) to (4,9), (0,1.8) to (4,9)        [area]
Beta J:         (0,1.8) to (4,9), (0,1.8) to [4,6*]     [area]
Beta U:         (0,1.8) to (4,6), [0,1] to [4.5)        [area]
Impossible:     (0,1) to (4.5), (0,1) to (4,1]          [area]
Undefined:      (0,3) to (3.6,10), (0,10) to (3.6,10)   [area]

Values of Beta1, Beta2 where brackets mean:

[ ] : includes (closed)
( ) : approaches but does not include (open)
 *  : approximate

These are illustrated in Hahn and Shapiro Fig 6-1.
Granted this is a very rough test (with some issues) but you may want to consider it as a preliminary check before going to a more rigorous method.
There are also adjustment mechanisms to the calculation of Beta1 and Beta2 where data is limited - but that is beyond this post.
Comment: Perhaps it is best to qualify the method further: Hahn and Shapiro (as referenced above) advise that caution should be exercised, especially when the sample size is less than 200 - and recommend that this be followed by further verification, such as a frequency table that compares the fitted distribution with the actual data.  But in my view it is a useful method that *can suggest* where the data might lay within a spectrum of possibilities.  I have used it on data sets not smaller than roughly 3000 and have built it into computer simulation software where it has proved useful.
Comment: That's right. All I am saying is that if it is dangerous to try, from a small sample, to test whether the population is Gaussian, then it must be at least as dangerous to use the skewness and kurtosis to identify what the underlying distribution might be! In fact, it seems like such an attempt would actually be worse because it relies on unstable statistics like the kurtosis. Although Pearson's system can be a powerful guide to help people identify possible distributions, it provides less insight than even limited graphical displays like histograms.
Comment: A lot of this material can work well for large datasets and I agree with your initial assessment that normality testing can be limited or questionable with small datasets. But given the *huge* variability of skewness and kurtosis, it would seem that any effort to identify the type of underlying distribution based on these statistics would be even more questionable and less certain.  Consequently, wouldn't this approach be (at best) misleading even as a preliminary check?
Comment: I can see your method giving useful information with datasets of 3000 or greater. However, then there is no need to perform distributional testing to assess the applicability of a t-test of the mean.
Comment: Whether one views this as a useful technique, as I do, or otherwise, as appears to be your view, it nonetheless is a quick and long-established (by Pearson) alternative to testing for normality (and Students-t application) in the context of this thread.  Please don't get me wrong, I acknowledge and do agree with your concerns.  But we would both agree, would we not, that without prior information, trying to establish whether an entire population can be modelled on a Gaussian from a very small data sample is a shot in the dark at best with any method, and at worst is dangerous.
Comment: It can be argued that the Student's-t should not be applied unless there is prior information that the population is in fact Gaussian, as it is designed for less than 30 samples anyway.  The Students-t is in essence a way to 'narrow the spread' of a predicted population as a small number of samples is increased, but the assumption is that the population must be Gaussian to start with.
Comment: That argument continues to take place.  Going back at least to Box 50 years ago, many have pointed out that the t-test actually is an approximation to a non-parametric (permutation) test: it does not require Normality of the population, but only approximate Normality of the *sampling distribution* of the mean. Simulations (and some theory) indicate the t-test may break down with skewed distributions, but even then it can be surprisingly robust.
Comment: @whuber, I surrender.  You've just exceeded my depth of knowledge on this subject ;-}


Using xml workspace to overwrite geodatabase in ArcGIS Server 10 with ArcSDE for SQL Server?

Question: I want to transfer a geodatabase from my development server to my client's production server. We are using SQL Server, but in different versions. Hence I cannot use Backup/restore or detach/attach. The servers don't have direct connection, so that I cannot copy the database. I used Moving a geodatabase using an XML document to export the database and then Import it to the destination. The export is done successfully, but since there are existing feature classes on the target database, I cannot import the data to the destination. I have to delete the existing features or overwrite the imported xml, but I don't know how.
Comment: I'm not sure if it is the right way or not, but I just deleted all the features when the connection was open, and then imported the XML workspace. I really appreciate if anybody can shed some light on it.
Answer: You might consider exporting your development database to a file geodatabase first (XML workspace export/import would work fine). Then if you have a connection to your production SQL Server database from the ArcGIS Desktop, you could set a Python script or a model with ModelBuilder that would truncate all the rows (in 10.0, the tool is Delete Rows) in all of the feature classes and tables you have in your client's production database. Then you could just run the Append tool for each element in your file geodatabase in order to "merge" the empty feature elements in the production database with the data you have in your development database.
This is much better than deleting database elements because when appending the data you don't have to delete any element and thus all the behaviours you set up (relationships, domains, etc.) will be preserved.


Is there a way to change the parse order of snippets or plugins?

Question: Is there a way to force snippets or plugins to be parsed late or at least after advanced conditionals are parsed?
Comment: You can add parse="inward" to a plugin to parse the contents first. See: http://ellislab.com/expressionengine/user-guide/templates/plugins.html
Comment: Can you explain what you want to achieve? the current question is very broad. In general, no, snippets are like "copy-paste" data that are replaced very early on in the template. If what you want to do is more clear, there might be other solutions.
Comment: @GDmac Basically, my problem is that some tags in the snippets are not parsed because they or parse order problems. This causes problems where the actual tag string literal i.e. '{foo}' is being passed.
Comment: which tags are not parsed inside your snippets?
Answer: There are plenty of plugins to mess with the parse order, but I usually try to avoid installing plugins if I can help it.
The simplest solution, which works in 99% of cases, is to just use an embed. Embeds are parsed after everything else, so whenever you have an early parsing issue, just throw the problem code into an embed.
It's true that embeds have slightly worse performance, but most people worry about this way too soon. Don't optimize for performance until performance is a problem. YAGNI.
Before:
{exp:channel:entries}
    {exp:annoying_plugin parameter="{entry_id}"}
{/exp:channel:entries}

After:
{exp:channel:entries}
    {embed="partials/.my_embed" entry_id="{entry_id}"}
{/exp:channel:entries}

Inside partials/.my_embed:
{exp:annoying_plugin entry_id="{embed:entry_id}"}

Answer: You can use Stash to delay the parsing of an arbitrary group of tags until after template parsing has completed:
{exp:stash:parse process="end"}
   {exp:channel:entries}
       ...
   {/exp:channel:entries}
{/exp:stash:parse}

However, parse order issues generally arise when you need to pass values generated by one tag to another tag or position somewhere else in your template. Adopting the template partials pattern can help you avoid these parse order problems in the first place.


Why is my Galaxy S stuck on downloading 'do not turn off target'?

Question: I was updating the firmware on kies for my galaxy s and it got half way through and then said error and is no frozen on the downloading 'do not turn off' screen, I have taken out the battery and put it back in, and tried the hard reset, which leads me to a phone symbol, a computer symbol and an error symbol in the middle, help plzzzzzz
Answer: I had the same problem (except I didn't use Kies, I had the problem after the first OTA Update)
Here are the steps I did to get my device back in a usable state:
Keep in mind, this will revert your phone to a rather old (android 2.1) version of TouchWiz. You may want to see if there are newer ODIN files available.
You will probably need different files anyhow, as the ones I have below are for the Galaxy S Vibrant.
Also, I take no responsibility if this does not work for you, or your phone explodes in the process. These are the steps I took, and they worked for me. Good Luck.

Download ODIN3 1.0

Download 512 PIT

Download JFD tar

Note that all 3 of those are from the same thread. It also wouldn't hurt for your to read that post too.

Open Odin, plug in your phone, then put it into download mode.

To expand on this because a lot of people were asking "how to put in download mode". The easiest way I found to actually do it, if you can can connect via ADB is to do the following:

<code># reboot download</code>
If you can't get that to work, try how i mention below (phone off, battery out, hold vol+ & vol-), or try searching these forums for "vibrant download mode" you will find other things that "work" for people

load the PIT file in appropriate area.

load the .tar file in the PDA area.

DO NOT check 're-partition'.

Click start, let it finish.

At this point ODIN failed on me. and I got the "mobile-!-pc" image.

Now, pull your battery and unplug USB

I also took out the SIM and sdcard at this point.

bring the phone to download mode again

plug the USB back in (the phone should be off)
Hold down vol+ & vol-
Put battery back in
press power

re-run ODIN as mentioned above

Don't give up if this doesn't work. If you get the device to boot, even if it is to the "Error Screen", there is a possibility of recovering.
Answer: You should experiment with rebooting via the various key combinations / battery pulls / USB plugged-in-ness below first.  Sometimes the phone can be jolted out of the bad mode it's in by doing that.  If the firmware was partially written though, you'll have to do Odin as Ryan suggests.

I basically agree with Ryan's answer, but I'd use at least Odin 1.5.  Here's Odin 1.7, it includes the 512 PIT file.
For the GT-i9000 (international Galaxy S), get firmware from this XDA thread.  You probably want the newest for your region (excluding Gingerbread, since it hasn't been officially released).
I also recommend checking re-partition in Odin.  This will wipe 100% of your data, however.
I think the easiest way to get into Download Mode is through key combinations.  For the i9000, just hold Power + VolDown + Home until the phone reboots, then let go of Power only; after a second you'll get to a yellow triangle with an Android in it.  For the Vibrant, remove the battery, plug into USB, hold VolDown + VolUp, and insert the battery.
Comment: Yep, I upvoted your answer ... I just had too much to put in comments (and didn't want to take over your answer through edits).  I've spent way too much time playing with Odin :P
Comment: Yes, finding the latest ODIN is a good idea. I really just posted the exact steps and tools I used when I had this problem.


Does wardrobe/closet need doors?

Question: I was always told to let the wardrobe doors open sometimes, so "let the air circulate". And I wonder, does the wardrobe actually need to have doors? What would be the problems (other them visual) of let it always open?
Comment: Hey Tom, is there any information you are looking for specifically beyond what has already been answered?
Answer: The main reason for having doors that I can think of is that UV light will fade clothes and degrade some materials over time. As a commenter said, this might more of a problem depending on what direction the rooms window faces.
Having doors also will help to some degree with smells from cooking or smoking.
Comment: Note: UV in this way can come from direct sunlight, to a much lesser extent reflected sunlight (off a mirror, or even wall), and from some florescent bulbs. In other words, this consideration is much more important in a closet that gets direct sunlight during the day and not all that important in a dark-painted room with a north-facing window and incandescent lighting.  +1 though, I can't think of any other non-aesthetic reason for closet doors.
Comment: I doubt doors are much protection from smoke or odors. When the doors are opened then closed (presumably daily), the odors in the room at that moment are shut into the closet, even if the room is then aired. Your wardrobe interiors likely smell like your bedroom, in the end, regardless of doors. The only way to keep odors out of clothes is to seal in plastic clothes bags immediately after washing or dry-cleaning...or masking the odors by lining your wardrobe interior with bare cedar.
Comment: You can tell if UV is a problem if the exterior edge/side of clothes that you habitually hang in one direction ever seem faded relative to the shadowed interior side. Likewise for furniture or carpeting in the room. Otherwise, any uniform fading you're noticing is simply due to outdoor wear, where you get much greater exposure to UV.
Answer: For someone that has toddlers, doors to any room are requirements.
Answer: Tom,
I have 6 bedrooms with 7 closets, 4 of which are open. My experience says that the open closets get used more efficiently.
In our open closets:

We can see everything so everything gets worn. Nothing gets hidden in the back corner.
We end up organizing much better. We were not very organized before removing the doors. Now we have to be organized as everything is on display.
One room with on open closet is a guest room, and the closet is kept completely empty for the guests. The guests really like the empty closet because when they stay with friends they usually have to live out of their suitcases due to no available closet space. None have ever mentioned having an issue with the open closet.
We ended up getting a lot of new hangers. Because everything is on display it looked better if everything is on matching hangers.
In our case we don't have an issue with UV light fading the clothes.
One of the closed closets does not contain clothes, and it is jammed full. We have to open the door carefully. That is not really possible with the open closets.

We took the sliding doors off of our closets during a remodel. They never got reinstalled. We don't miss them at all.
Answer: In addition to the points already raised... your clothes are going to get eaten more easily by clothes moths if you don't store them in a closed cabinet.
Comment: Do doors really discourage moths? Don't moths like crawling into dark places to lay eggs?
Comment: @hobs - They're going to spread more easily without doors.
Answer: Aesthetics.
Open doorways and large cabinets or closets without doors make a space seem public. They're an invitation for browsing (or toddling as someone else mentioned). If the stuff inside the open space isn't selected and organized artistically, it will look unattractive. Museums and libraries have shelves and display cases without doors or with windows. Bedroooms have cabinets with opaque, translucent (think rice paper), or slatted doors--for looks. The slatted or louvered designs clearly rule out the design intent of protection from moths or blocking clothes from exposure to air and odors. Though dust is effectively reduced by louvers.
Recently my wife and I "discussed" open bedside table furniture designs (tables without drawers or doors) and she helped me appreciate what doors and drawers are for.

Does wardrobe/closet need doors?


Using Ryanair online check-in, how to print boarding pass for the return flight?

Question: I am flying with Ryanair and have managed to print my outgoing boarding pass, but it says you can't print a return until 8 days before departure. What do you do then?
Comment: Next time fly with a company who isn't trying to rob you using nonsense clauses of doubtful legal standing.
Comment: http://www.theguardian.com/money/2014/may/19/ryanair-hidden-charges-booking-online-check-in *sigh*.
Answer: You print your boarding pass while at your destination. Make sure you don't forget, otherwise you'd be hit with a €55/£55 fine. Your hotel/hostel should be able to print it out for you. If not, visit the nearest internet cafe.
Also note that Ryanair rarely enforces their rule on non-EU passengers having to print and confirm their boarding pass, so you could also use a mobile boarding pass instead and most likely you'd be fine.
Answer: Just use the mobile boarding pass.
I stopped printing boarding passes for ryanair a couple of years ago.
(if you really want the paper one, your hotel will probably be able to print one copy for you)


how do you easily turn a flash light into a lamp

Question: Is there any way to easily take a flash light and make it spread its light out more like a lamp instead of just a straight beam?
Answer: Take a bottle filled with water. Make sure that the bottle is not colored. Now switch off the lights and focus your light source at the neck of the bottle, pointing it to the bottom of it.
Answer: A white, plastic shopping bag. Even when this bag is not completely white, it will still work! Basically, this is a combination of all answers mentioned before :)
Answer: The simplest method would be to use a Convex Mirror. A convex mirror reflects the light to all directions. This can be used to illuminate a small room, provided the torch is a strong enough. This is by far the easiest hack you can use. It is very economical, and efficient.
Comment: Because *everyone* has a convex mirror lying around...  Yes, this works well, but you'll get a harsh light that casts strong shadows, and are unlikely to have the required equipment.
Answer: Stand the flashlight with the lens up and put a frosted plastic medicine cup (the kind that comes with cough syrup) on the lens.  The cup will diffuse the light with little loss (less than a paper cone or cup) and no color shift.  The small cups in which single serving preserved fruit are sold will work for larger flashlights.
Answer: Depends on the flashlight. On some flashlights (e.g. Maglite) you can screw the mirror and lens assembly off, leaving the bare lamp in place. This will spread the light out more.
Answer: Pointing the light at any white surface will diffuse the light.  This is easy to do in a room with a white ceiling.
If your light has a pocket clip, you can also clip an index card on it as shown:

Unfortunately the card blows easily in wind, so it's not quite as slick as it looks.  A sturdier piece of cardboard from a white box will work better if there is a draft.
Answer: I would get a piece of paper and roll it into a cone with a base the size of your lens. Stand the lamp on its base and pointing upwards. Balance the cone on the lens. The paper will diffuse the light around the room.


Appropriate AccessDataSource Delete command or tweaking?

Question: Using AccessDataSource and ListView when I hit del in browser following error is shown

OleDbException (0x80004005)
        : The record cannot be deleted or changed because table 'tblOrders' includes related records.

I am trying to solve the problem through a couple of ways which are as follows
DeleteCommand="DELETE FROM [tblCustomers] , [tblOrders] WHERE [pkeyCustomerID] = ? "

The Default command generated by ASP is
DeleteCommand="DELETE FROM [tblCustomers] WHERE (([pkeyCustomerID] = ?) OR ([pkeyCustomerID] IS NULL AND ? IS NULL)) "

Or
I removed <asp:Parameter Name="pkeyCustomerID" Type="String" /> from <DeleteParameters>
and replace it with the parameters of selected table
so the foreign key issue isnt affected
tag now there are no errors but the record isnt deleted either
How do i get around this?
Answer: Your first query:
DELETE FROM [tblCustomers] , [tblOrders] WHERE [pkeyCustomerID] = ?

Is not valid syntax, you cannot delete from two tables simulatenously, you would need something like
DELETE FROM [tblOrders] WHERE [pkeyCustomerID] = ?;
DELETE FROM [tblCustomers] WHERE [pkeyCustomerID] = ?;

However I don't think Access supports multiple statements. The best solution would be to edit this relationship to use the cascade delete referential action trigger.
To do this go into the relationships in Access:

Then double click on the relationship between tblOrders and tblCustomers which will bring up the properties. Then either uncheck "Enforce Referential Integrity", or ensure that the cascade referential action options are checked (ignore the field names, it was the first relation I came across in a test database I have):

This will ensure that when you delete a customer, you delete all related orders too.


Is there a common method to password protect registration pages?

Question: The site I am working on requires that affiliates register on the site. I've created a profile type for affiliates with corresponding permissions and a registration page. I'd like to give access to this and the site's main registration pages without having to deal with all the spam account registration attempts. Is there a standard way of allowing only users that you want to register to have access to registration pages?
Answer: Well, till they register/login, you can't actually say who they are.
I will suggest a CAPTCHA in the registration form. If you want to restrict it more, then you can search for email white listing modules. https://drupal.org/sandbox/amrit_b/1768342 This is something I wrote few months back. This is still in dev. In case you don't find anything else, you can try this one.


Flat tires every morning

Question: I just bought a new bike. I ride about 3 times a week. The last 2 times I've taken my bike out the front tire has been completely flat. I put air in it the first time it happened and went for a 10mi ride and the tire was still fine. Then next morning it was flat again (same thing the 2nd time).. I recently got into riding and I have no clue about the maintenance and fixing my bike. Any help would be greatly appreciated.
Comment: If you haven't been changing the tubes (sounds like you haven't), I'm going to go with leaky/stuck valve as my first guess and tiny puncture in the tube as my second guess.
Comment: Gidday and welcome to SE Bicycles.  Punctures and leaks are probably the single most common issue on a bike.  Please use the site's search functionality to find existing questions where someone has asked the same or similar things before.
Comment: You might try removing the tube, put a little air in it, and then hold it completely underwater, pools work good for this, a sink or bucket will also do fine, you will see bubbles being formed where your air is escaping.
Comment: I should mention that there are a few exotic brands of "racing" tubes which are ultra-thin and leak down in about 24 hours.  You normally wouldn't have these unless you'd intentionally installed them (though perhaps without knowing the problems they'd cause), but it's vaguely possible that the bike shop sold you a "racer's upgrade" or some such that includes them.  (But the simple "slow leak" problem described by others is far more likely.)
Answer: It sounds like you have a slow leak, either from the valve or from a tiny puncture in the tube, like Batman mentioned in the comments.
An easy way to fix this is by simply changing the tube in the front tire. If you've never done this before, this video may help or you can take your bike into your local bike shop and have someone fix it for you. If you choose the latter of the two, ask if they can teach you how to change out the tube, since this is an invaluable skill to have.
Comment: OP - If you do switch the tube, be sure to drag your hand around the inside of the tire to check for thorns and debris, it will save you ruining a new tube, i have found micro thorns that were nearly to small to see this way. They get stuck in the rubber and penetrate just deep enough to poke the tube creating a slow leak.

Flat tires every morning


Logon Windows XP with smartcard

Question: Suppose that I had an SDK to develop an application on smartcard to store my password and acts as an Authentication server toward Windows XP. That is, when an user wants to log on Windows XP with a certain username and password, Windows XP will send this account's information to smartcard and wait for a response. If smartcard says YES, user will be granted to log in.
This is my idea but I don't know how to implement it with Windows XP. I have designed an interface between smartcard and Windows XP but I don't know where to begin? I must write my logon application (prefered in C#.NET) to replace the actual standard logon process of Windows XP? How can I intervene in the Windows XP process?
I highly appreciate your helps
Best regards,
Hai-Binh LE
Answer: Smart Card Authentication is worth a read.
Answer: Write custom GINA:
http://en.wikipedia.org/wiki/Graphical_identification_and_authentication
and
http://msdn.microsoft.com/en-us/magazine/cc163803.aspx
and
http://msdn.microsoft.com/en-us/magazine/cc163786.aspx
But it is not trivial task.

Logon Windows XP with smartcard


Deorbit first stage?

Question: I have read the answers about deorbiting second/upper stage. But since the lastest launch of Long March 5B raised concern about its uncontrolled reentry (yeah, too big).
Unlike SpaceX's Falcon, other rockets are not designed for reuse, do people still care about intentionally deorbiting the first stage, and how?
Comment: First stages do not reach orbit, they are suborbital and fly on ballistic trajectories. So the question doesn't arise. That said there is concern about where first stages land both from the point of view of reuse as well as safety.
Comment: I think there is some confusion in the comments: the  Long March 5B stage has most certainly reached orbit. It launched on April 30 and has been orbiting Earth since... It is sometimes referred to as a "core stage" rather than first stage since it uses four strap-on boosters. Not sure what the correct technical terminology is. But the point of the question is, that these types of launches seem to lead to the large core stage de-orbiting uncontrolled (same happened with the first Long March 5B: launch May 5, 2020 core came down uncontrolled over May 11 in Côte d'Ivoire).
Comment: @Slarty That would make a perfectly good answer.
Comment: @Slarty The question is not wrong- on China's most recently developed launch vehicle, the hydrogen/lox first stage coasts all the way to leo, which is the rocket the question is referring to. It forgoes a second stage unlike most launch vehicles, presumably for simplicity.
Comment: Related question about terminology of "first stage" versus "core stage". https://space.stackexchange.com/questions/35310/what-does-the-core-stage-of-a-launch-vehicle-mean
Comment: @Reuben Farley-Hall I suspect you are confusing entry into space with entry into orbit which are very different things. Getting into orbit requires far greater amounts of velocity ~ x10 and energy ~x50 than getting into space. No launch vehicle has accomplished a single stage to orbit. https://en.wikipedia.org/wiki/Single-stage-to-orbit Wikipedia is not always correct but in this instance I believe it is. If you have some examples of any single stage to orbit vehicles I would be very interested to read some references to them.
Answer:
I have read the answers about deorbiting second/upper stage
[…]
do people still care about intentionally deorbiting the first stage

It doesn't matter whether it is a first stage, second stage, third stage, fourth stage, kick stage, space tug, satellite dispenser, satellite, space station, tank, or something else entirely.
It is not a good idea to have anything hit the ground uncontrolled.
In fact, it also doesn't matter whether it reaches orbit or not. Debris falling uncontrollably is bad, period. Regardless of whether it came from a first or second stage, and regardless of whether it reached orbit or not.
That's why there are Flight Termination Systems, for example, or why there are Launch Corridors.
The reason why we typically do not hear much about specifically deorbiting specifically the first stage is simply the fact that normally, first stages usually do not reach orbit. So, for almost all launch systems, the question is moot.
The Chang Zheng 5B is a special case.
But launch providers most certainly do care about where our first stages end up. For example, the Space Shuttle deliberately did not achieve orbit using the Space Shuttle Main Engines to make sure that it could drop the External Tank on a sub-orbital trajectory, then used the Orbital Maneuvering System thrusters to boost the Orbiter into orbit. It would have been simpler and more efficient to skip the OMS burn and use the SSMEs to go all the way to orbit, but that would have left the ET in an uncontrolled orbit.
Note: technically, this is not 100% answering your question, because in this case, we deliberately prevented a big hunk of metal from reaching orbit in the first place, rather than intentionally deorbiting it after reaching orbit. I would still argue that the intention behind the decision is the same, though.
As a rule-of-thumb, it is considered to be irresponsible to let anything above 10t reenter uncontrolled. This is just a rule-of-thumb, of course, since e.g. a 10t modular space station, and a 10t titanium cannonball would behave very differently because of their different ballistic coefficients: the modular space station with its oddly-shaped modules, solar panels, and radiators would probably be ripped into multiple smaller pieces which are more likely to completely burn up in the atmosphere.
Note that some debris from the last Chang Zheng 5B mission's first stage did fall on a village in Côte d'Ivoire in Africa. Miraculously, nobody was hurt. But the ground track also passed over densely populated areas of the United States, for example, so if the stage had reentered just a bit earlier or later, the results may very well have been very different.
I am not just talking about the potential loss of life and property damage caused by the immediate event, but also the potential political fallout from Chinese military hardware raining hell on the US during the very strained relationship of the Trump Presidency.
Comment: The Shuttle main engines weren't restartable.  The only way it would be possible to reach orbit on them is if you could time your burn to circularize during your launch burn--and for any given rocket & payload the altitude to do this will be fixed.  Also, not taking the tank to orbit means a bit less weight--I haven't done the math but my gut says it's roughly equal between using the main engines vs the orbital engines, the lower weight approximately offsetting the lower ISP of the orbital engines.
Comment: "the fact that normally, first stages usually do not reach orbit" Is there any first stage that did reach orbit?  So  simply remove the words normally and usually : "the fact that all first stages do not reach orbit"
Comment: @Uwe: "Is there any first stage that did reach orbit?" – Yes, there is. The very first stage that this question is about.
Answer: The premise of this question is flawed First stages do not reach orbit, they are suborbital and fly on ballistic trajectories. So the question has never arisen at least up until now. It is theoretically possible to build a single stage to orbit vehicle and the Lockheed X33 experimental vehicle almost made it but was cancelled prior to being tested.
https://www.thespacereview.com/article/3815/1
That said there is usually concern about where sub orbital first stages land both from the point of view of reuse as well as safety. However the Chinese seem to be particularly willing to accept risks far in excess of what would be acceptable in the West. Presumably due to the fact that it is an authoritarian state. There are many instances of rocket debris falling near human habitation in china.
https://spaceflight101.com/chinese-villagers-capture-falling-long-march-rocket-booster-on-video/
https://www.reddit.com/r/China/comments/7x41q9/rocket_booster_debris_falls_in_guangxi_village/

Deorbit first stage?


How to identify which region the LWC component is locating in App Page or Record Page?

Question: I have an lwc component that is enable in App Page and Record Page. Whenever using this component, I want this component can identify which page is using it and which region on that page is it being located (For Example: Right/Left Side Bar, or Subheader, etc). Is there any possible solution to achieve this requirement? Please help. Thanks!
Comment: Never done it, but I would start here: https://www.salesforceben.com/lightning-web-components-enhancements/ or https://www.apexhours.com/composition-shadow-dom-and-query-selectors-in-lightning-web-components/. Add the component to an app and record page. Inspect the DOM for both to see how the DOM got generated.. They may have something unique about them :). Then you could use that to help you identify its location based on the "parent" within the DOM. In case other logic is needed, you can also utilize the available lifecycle hooks.. Let me know if that works :) !!!!
Comment: Why? Feels like an [XY Problem](https://xyproblem.info/). Identifying the page should be possible via the URL, but determining where in the page - forget it. You could have a property the admin sets when dropping the component into the page in the Lightning App Builder (but they probably won't bother to be accurate unless this actually helps them somehow). If to select a different presentation style, let the admin choose that...
Answer: You cannot know where is the sidebar, left or right, but you can know whether a component is in a sidebar or in the header or in the main body exposing a @api flexipageRegionWidth property.
It will hold the following values:

SMALL - if the width is less than 50% - I.E. Left or Right sidebar region (region 3 of the screenshot)
MEDIUM - if the width greater or equal 50% and less than 100% - I.E. the body of Header and Left/Right Sidebar (region 2 of the screenshot) or both regions of Header and Two Equal Regions.
LARGE - if the width is 100% - I.E. any region of Header and One Region and One Region template or header region of Header and Left/Right Sidebar (region 1 of the screenshot).

You could have few getters to show/hide part of the component.
JS
@api flexipageRegionWidth;

get isSmallRegion() {
    return 'SMALL' === this.flexipageRegionWidth;
}

get isMediumRegion() {
    return 'MEDIUM' === this.flexipageRegionWidth;
}

HTML
<template lwc:if={isSmallRegion}>

I'm in a sidebar

</template>
<template lwc:elseif={isMediumRegion}>

I'm in a medium region, maybe there is a sidebar

</template>
<template lwc:else>

I'm in a large region

</template>

By the way, there is an undocumented value:

XLARGE - Header region Header and Two Equal Regions

To know whether the LWC is in a Record Page or in an App Page, you could rely on URL:

/lightning/n/ means that it's in an App Page
/lightning/r/ means that it's in a Record Page

Again you could define few getters:
get isAppPage() {
    return location.pathname.startsWith('/lightning/n/');
}

get isRecordPage() {
    return location.pathname.startsWith('/lightning/r/');
}

Then use them in the template:
<template lwc:if={isAppPage}>

This is an App Page

</template>
<template lwc:elseif={isRecordPage}>

This is a Record Page

</template>

Comment: Thanks @RubenDG, it's really what i need


Are all diatonic chords in the diminished scale diminished?

Question: I think there's some confusion about the definition of the word 'diatonic'. I'm not using it here to refer to the the prominent primal pattern of the heptatonic scale that has a group of two and three whole steps separated by half steps, but rather as an adjective to describe a note, chord, etc. as being 'of the scale'. In the major scale, I know the diatonic chords to include a major 1, 4, & 5, a minor 2, 3, & 6, and a diminished 7.
I'm trying to find out what the diatonic chords would be in a diminished scale. I've done some work down below, and think I've arrived at the conclusion that all eight chords will be diatonic if they are diminished, whether in the half-whole or whole-half dim scale. Is this a correct conclusion? I'm also open to any insight about chord progressions in a diminished key.
Note - For the purpose of this question, I'm not concerned with extended chords like 7ths, etc. Only triads with a tonic, third interval, and fifth interval.
Comment: @EthanRichardson, I _really_ hope you restore your question, because it is a good one. In my answer I tried to explain about the scale spellings which was the point of one of the comments about the source you used. Keep in mind you got 2 up votes on your question. That indicates the community believes it a good question!!!
Comment: I'm confused about your destructive edit: it seems that you have some good comments and answers here, and I don't see any snide comments....
Comment: So would you consider C-E-G to be "of the C half-whole diminished scale"?
Comment: I don't believe there's a 'diminished key'. Certainly diminished scales, but that doesn't mean there will be a 'key'. There's the 'whole tone scale', but no 'whole tone key'.
Comment: Several of the note names should be spelled enharmonically.
Comment: Your title doesn't seem to reflect that you want "Only triads with a tonic, third interval, and fifth interval": it implies that you want to evaluate all chords made with notes in the diminished scales. If we're evaluating all chords, then the answer to your title question is a big fat no: a "diatonic" non-triadic chord that can be created with the C Half-Whole Diminished Scale is the C minor chord.
Comment: This source is completely incorrect. There is no diminishing here, only augmentation. It should be C Db Eb Fb Gb Abb Bb and so on. First chord should be C Eb Gb ...
Comment: @user207421, I think you meant to end that sequence as `Bbb Cbb`? With a `Bb` the first chord would be a half diminished seventh chord.
Comment: @EthanRichardson, if you want snide remarks, you should visit StackOverflow instead ;) The people in this community are nothing but helpful, and even when they downvote or question the wording of your question, it is out of a desire to help and make the question a viable one for future people in need. I have a very positive experience with Music.StackExchange, and I would certainly encourage you to not turn away from this community either. There are a lot of great and knowledgeable people here.
Answer: If you consider every chord made up of notes from a diminished scale to be "of the scale", then a diminished scale contains not just diminished triads. The diminished scale is highly symmetrical, so to find triads in a diminished scale you only have to consider a small number of candidates, which you can then transpose to get the full list.
Let's look at the C half-whole diminished scale:

C  C# D  Eb E  F  F# G  Ab A  Bb B
*  *     *  *     *  *     *  *

We'll only look at triads starting on C or C#:

C  C# D  Eb E  F  F# G  Ab A  Bb B
*        *        *       (*)       Cdim
*        *           *              Cm
*           *        *              C
   *        *        *       (*)    C#dim

To get the full list of triads, we transpose these four chords in steps of three half-tones:

Cdim    Ebdim    F#dim    Adim
Cm      Ebm      F#m      Am
C       Eb       F#       A
C#dim   Edim     Gdim     Bbdim

This is the list of 16 triads for C half-whole diminished, but also for:

C  half-whole diminished
Eb half-whole diminished
F# half-whole diminished
A  half-whole diminished
C# whole-half diminished
E  whole-half diminished
G  whole-half diminished
Bb whole-half diminished

because these eight diminished scales are enharmonic, they are made up of the same notes. There are two further "families" of diminished scales: the scales above transposed 1 half-tone step up, and the scales above transposed 1 half-tone step down.
To find the 16 triads for a diminished scale from one of the other two "families", check whether it is a scale in the list transposed a half-tone up or down, and then transpose the 16 triads a half-tone up or down.
You will notice that the list of 16 triads for one "family" of enharmonic diminished scales contains 4 major triads, 4 minor triads, and 8 diminished triads. This means that two non-enharmonic diminished scales share 4 diminished triads, but no major or minor triads. E.g. the C half-whole diminished scale and the C# half-whole diminished scale share these triads:

C#dim   Edim     Gdim     Bbdim

while the C half-whole diminished scale and the B half-whole diminished scale share these triads:

Cdim    Ebdim    F#dim    Adim
Comment: That first scale, should that be "C-Db-Eb" instead of "C-C#-Eb"? Personally, I find this question based on extending all sorts of concepts well outside their area of applicability. You can try to make sense of it, but why should one?
Answer: Yes.
The diminished scale is symmetrical: every third is the same distance as all the other thirds.  Since all the thirds are minor thirds, all the chords that naturally occur in the scale will be m3+m3 = a diminished triad.
The same will be true of the whole tone scale: every third is a major third, so every triad will be augmented.
Answer: The other answers provide a lot of information and go into a lot of technical detail. I could list all the nuts and bolts as well, but it seems like you are just discovering music and want a simpler algorithm to memorise, perhaps.
There are 2 diminished scales, each has 8 notes per octave. You can think of those notes as being odd or even in number (for the C half-whole diminished scale, note 1 would be C, the root, and note 2 would be C#).
In terms of chords, both half-whole and whole-half diminished scales follow a very predictable pattern:

The half-whole diminished scale
Every odd note produces a major triad[1], a minor triad[2] and a diminished chord[3]. Every even note produces just the diminished triad.

The whole-half diminished scale
The pattern gets reversed: now every odd note produces just the dimished triad, and every even note produces a major triad, a minor triad and a diminished chord.

It's that simple!

1 The formula for the major triad is 0-4-7 (where 0 is the root, and every other number denotes how many semitones away from the root the next note is) or R-W+W-W+H (where W is a whole tone and H is a semitone).
2 The formula for the minor triad is 0-3-7 or R-W+H-W+W.
3 The formula for the diminished triad is 0-3-6 or R-W+H-W+H.
Answer: This question seems to hinge on how things are spelled - including enharmonic spellings - and the effect of spelling on interval names.
If the diminished scales are spelled as two superimposed diminished seventh chords, we get...

|C  |Eb  |Gb  |Bbb  |
|  D|   F|  Ab|   Cb|

...or...

|C  |Eb  |Gb  |Bbb  |
| Db|  Fb| Abb|  Cbb|

Let's use the second scale for examples. We can make a chord C Fb Abb and enharmonically re-spell it to C E G. The first chord C Fb Abb is a diminished fourth and a minor third. The other spelling is a major third and a minor third.
We could re-spell the scale so that the two superimposed diminished seventh chords structure is obscured:

|C  |Eb |F# |A  |
| Db|  E|  G| Bb|

With that spelling we can make C E G without any enharmonic re-spellings.
Of course the issue here is the gamut (the seven letters) are for a heptatonic diatonic scale, but the diminished scales are octatonic, and the naming of intervals is first based on the position in the letter sequence and then qualified by the size in semi-tones.
When tertian chords are built the spelling details matter. C E G is two stacked thirds where the specific qualities are major third and minor third. C Fb Abb is NOT two stacked thirds. It is a diminished fourth and a minor third. If our "diatonic" chords are to be tertian triads in root position, then C Fb Abb is not a diatonic chord, but C Eb Gb or Db Fb Abb would be diatonic chords.
For what it's worth, when the second scale of superimposed diminished seventh chords is used and we have chord like Abb Cbb Db it's is enharmonically equivalent to a diminished triad, but as spelled it is an inverted diminished seventh chord with the third tone omitted.

Are all diatonic [of the scale] chords in the diminished scale diminished?

I think "yes" provided that the chords are tertian and the scale is spelled as two superimposed seventh chords.

EDIT
Part of the discussion with this question is about the possibility to  construct a major triad in the diminished scale and should that be considered diatonic.
In my initial answer where the diminished scales were constructed from superimposed diminished seventh chords I said "no" because the chord spelling used a diminished fourth.
However, you could construct the diminished scale using superimposed major triads and get different spellings...

scale degree: 1  2  3  4  5  6  7  8  1  2  3  4
              C  Db Eb E  Gb G  A  Bb C  Db Eb E
              | (C#)|  |  |  |  |  |    (C#)   |
              ----------------  |  |     |     |
                    |     |  |  |  |     |     |
                    ----------------     |     |
                          |     |  |     |     |
                          ----------------     |
                                |        |     |
                                ----------------

The three chords are C, Eb, Gb, and A all major triads in a sequence of chromatic mediants. The A chord needs an enharmonic respelling of Db to C#.
You could then harmonize the scale with a series of alternating root and first inversion triads:
C A6/3 Eb C6/3 Gb Eb6/3 A Gb6/3 | C
Now you could say all the 'diatonic' chords of the diminished scale are major triads.
Comment: I think of chords that come from enharmonic spellings of scales as potential scale applications, but might say in a sloppy moment that those chords are in the scale. In practice, these enharmonic applications make melodic minor, harmonic minor, and pentatonic scales (to name the most common) very flexible.
Comment: When I asked "would you consider C-E-G to be of the C half-whole diminished scale?" the OP said "yes, I would consider the notes and the C major chord they form as being of the diminished scale". This (and his anger about terminology nitpicking in the comments) led me to believe that his question was quite practical, and not concerned with the subtleties of whether C-E-G and C-Fb-Abb are the same.
Comment: "potential scale applications..." sure. I don't mean to say `C E G` or other enharmonic spellings could not be used. But I don't think that is the main point of the question. It seems to be about unpacking the meaning of _diatonic_ when switching from heptatonic to octatonic.
Comment: I don't think I would call anything 'practical' when working with an octatonic scale! I only wanted to point out that the spelling of the scale can make a difference deciding what "diatonic" should mean in an octatonic system.
Answer: The diminished scale is often used with the 7b9 family of chords. C half-whole diminished is associated with the C7b9 chord:
C E G Bb Db
(the whole scale is C Db D# E F# G A Bb... notice that you have a major 3rd between C and E thanks to skipping over both Db and D#)
Edim7 is the same chord as C7b9 without C in the bass, so they're often completely interchangeable.
You can create very nice extended chords by adding-in other notes from the C diminished scale:

C E G Bb Db A (C13b9)
C E G Bb Dd F# (C7b9#11)
C E G Bb Db D# (C7b9#9)
Answer: In jazz we derive major triads from dim scale all the time. Also dominant, minor 7 etc.


How to derive a nonparametric minimum volume tolerance region from a random sample?

Question: Given only a sample of IID variables with unknown density $f$, is there a way to derive a nonparametric tolerance region $T$ that contains at least a specified proportion $p$ of the population with at least a specified confidence $c$ and with minimum volume? Such a region would prioritize points of high density and not be one contiguous region in space:
$c\leq Pr(p\leq\int_Tf(x)dx:f(x:x\in T)\geq f(x:x\notin T))$
Comment: Two questions: (1) How strict is the requirement that $T$ have minimal volume? That is, could you live with a region $T$ that satisfied the proportion and confidence requirements but didn't necessarily have the smallest volume possible? (2) Have you looked into kernel density estimation so far as a general strategy for getting at $f$?
Comment: (1) Ideally asymptotically minimal volume with increasing sample size. (2) I have come across Chatterjee and Patra's approach (1980), but as di Bucchianico et al. (2001) noted, the approach is overly conservative (ironically, Li and Liu (2008) would find that di Bucchianico's approach OVERestimates the tolerance coverage denoted by 'p' in my post). Li and Liu's data depth approach is close to what I want, but it inherently disallows disjoint regions.
Comment: Right now I'm down this rabbit hole of univariate sample spacings (the differences between adjacent order statistics). I figure that at least for the univariate case, the sample spacings be ordered, and a tolerance region could be constructed from a union of the smaller sample spacings. No idea what the distribution of the ordered sample spacings would be, though, nor even if it could be independent of the sample variables' distribution.
Answer: I took a quick look at the papers of di Bucchianico et al., and of Li and Liu. (I couldn't get my hands on Chatterjee and Patra.) I see what you're saying about the data depth approach disallowing disjoint regions.
A quick idea that would build on the depth approach while allowing multiple, disconnected regions is the following:
(1) Use an unsupervised machine learning method like $K$-means clustering to partition the observed data into $K$ groups.
(2) For each group, use the depth approach to define a tolerance region.
(3) Take the union of the $K$ individual tolerance regions.
I'm finessing on details here: how to choose the number of groups $K$, and how to set $p$ and $c$ values for each group. These are definitely nontrivial. For choosing the number of groups, you could take a look at different ideas here. The dispersion within each group and the group size seem like important considerations for setting the individual $p$ values, so maybe you could use the covariance matrices of the groups to develop some criterion.
All that said, getting an asymptotically minimal volume would be a big question mark. I don't have enough expertise, nor is the method fleshed out enough.
Comment: So I got the paper, and it claims in part to have derived a way to compute a tolerance region that is a union of a specified number of shortest inter-order statistic intervals. When I got to the specifics though, what they have done is derived the mean and variance of the tolerance. In my own simulation from a univariate Gaussian mixture, it turns out their formulas are correct only if you sort by interval coverage, not length; in their proofs they noted that the two sorts were identical in the uniform case and claimed it extended to any continuous distribution.
Comment: I finally tracked down a paper (Frey, 2009, Data-driven nonparametric tolerance sets) whose abstract claims to have developed a method to do what I want, if only for univariate data. Problem is the full text isn't available online, but I've put a request for it through ResearchGate. Hopefully they respond to my normie ass.


Why will connecting batteries in series only generate large current flow between the two batteries if one is less charged than the other?

Question: If you connect an uncharged battery to a charged battery in series (+ to - and - to +) there will be a large current flow between the batteries and it will heat up as if it's being short circuited, but if you do this with two charged batteries it will just double the voltage that the system has. Why? It seems that the electrons would flow from the negative of one to the positive of the other for each battery if they were connected in series bringing both of them to 0 volts, but why does this not happen?
Comment: please draw for us the circuits you describe. Include the load resistances in each case.
Comment: @nielsnielsen the circuit I am thinking of is just two batteries connected to each other, positive of one connected to negative of the other and vice versa.
Answer: What you have described is what I would call shorting two batteries out. In both cases you will get a very high current that is only restricted by the internal resistance of the two batteries (and the wires you used). A dead battery will have a much higher resistance than a changed battery. Thus, contrary to what your question stipulates, the circuit with the two good batteries will have a much higher current than a circuit with one good and one dead battery. A circuit with two dead batteries will have an even lower current.
The correct way to describe the circuit is $I = V_{total}/R_{total}$, where $R_{total}$ is the sum of the internal resistances of the two batteries + the total resistance of the wires. $V_{total}$ is the sum of the voltages of the two batteries with no load—i.e. as measured by a high-impedance voltmeter while not connected to any load (this is just what we normally call voltage).


Are there any measurements of other galaxies indicating the existence of exoplanets?

Question: Of course scientists assume there would also be exoplanets in other galaxies besides our own Milkyway.
Is it true that our telescopes are not good enough to see planets in other galaxies, nor by brightness changes of the stars nor by inclination changes of stars. If so could the total mass of those galaxies be an indication of the presence of exoplanets, or is dark matter a problem for that?
Comment: I think it might be theoretically possible to detect a planet in the Magellanic Clouds, because [pulsars have been detected there](https://arxiv.org/abs/1304.6412), and careful observation of pulsar timing has led to the detection of [planets](https://en.wikipedia.org/wiki/PSR_B1257%2B12).
Answer: Yes, it is true that our telescopes are not big/strong enough to detect planets in other galaxies. All we know at the moment are some few planets (not even complete systems!) around some of the stars in our closest galactic neighbourhood.
But let me explain why this is so.
Far away objects are very faint and thus send out few light-particles our way. To compensate this, we must build bigger and bigger telescopes to catch more light-particles from those faint objects. And at the moment we are limited until the 30-40metre class telescopes become active in ~2025.
However there is a class of 'cosmic accidents' that allow telescopes to catch more light-particles. We call those accidents micro-lensing events, as they briefly concentrate the light of a background star around a planet's gravitational sphere of influence.
The result is a spike of light in our telescopes. The shape of this spike informs us about the characteristics of the lensing star and planet.
To put this into context with your question about other galaxies, I've plotted for you how far away we have discovered planets so far:

Here we have on the x-axis the distance to the planet-hosting star, and on the y-axis the declination (one of the celestial coordinates or directions).
In red I've painted the planets that we have discovered with microlensing, in blue are all other methods.
The microlensing discoveries lie all on one line around dec = -30°, because this is the direction of the galactic center, where the polish OGLE project is looking.
The famous US-satellite Kepler that uses the transit method has it's field of view around dec = +45°, and this is also the biggest blue bunch of discoveries.
The small bump in between is the fov of the french CoRoT-satellite that also did some transit-discoveries and pioneered the transit searches from space.
So what do we learn from this graph?
We see that we can discover planets on a massive scale up to ~2000pc away.
Further away it's only possible with luck (while OGLE also looks at quite an impressive number of stars at any given time) and lensing. Now to put this into context, our milky way galaxy has a diameter of ~40.000parsec, and the next galaxy, the Andromeda galaxy is 1 million parsec away.
So that's gonna be hard, even with microlensing, and even harder with the other techniques you've mentioned.
Although there is one event from 2009 claiming to have found something that looks like a planet in their lensing-curve, I don't think this technique is mature enough to announce that extra-galactic planet searches.
Comment: Is this sentence: " All we know at the moment are some few planets (not even complete systems!) around some of the stars in our closest galactic neighbourhood." based on this sentence: "Although there is one event from 2009 claiming to have found something that looks like a planet in their lensing-curve"? Or is your first sentence pointing at something else?
Comment: @Marijn: No, they're unrelated. The first sentence shall mean that we only have a small sample of incomplete systems. And those orbit only the small part of the galaxy that is our galactic neighbourhood. I wanted to emphasize how incomplete our information about exo-systems is. And the second sentence closes the paragraph with finally answering what you've asked for: Are there any detected exoplanets in other galaxies?
Comment: I don't know if this answer really gets to the core of the problem. It isn't so much that distant galaxies/stars don't produce enough light. It's that individual stars are not resolvable. Distant galaxies appear to us as diffuse, "clouds" of light where we cannot pick out a single star out of the group to analyze. The only exception is the closest galaxy, Andromeda where we have been able to observe individual stars, but only with extreme effort (e.g., the PHAT survey).
Answer: All discovered planets are in our Galaxy. The signature of a planet is too weak to be detected around the faint and unresolvable stars in even the nearest other galaxies. New telescopes like the Large Synoptic Survey Telescope will be capable of detecting transiting planets, and also microlensing events by planets, in the Magellanic clouds (e.g. see Mroz & Poleski 2017).
The fraction of galactic mass that is tied up in exoplanets should be a tiny fraction of the total mass. If you add up the mass of all the planets in the solar system you end up with around 1% of a solar mass (mostly Jupiter).
There is no indication that other stars have many more planets than the solar system, or that the mass of the solar system planets are at all unusual.
The fraction of planets that end up not attached to stars is also likely to be quite small. Essentially some fraction of planets might be stripped away from their parents during the earliest phases of stellar evolution in a dense cluster (where the minority of stars are formed actually). So free-floating planets are unlikely to contribute much and indeed this has been confirmed by experiments a decade and more ago to detect "massive compact halo" objects in our own galaxy, which were unable to attribute much of the dark, baryonic matter to planets or the like.
Finally, the dark matter problem is not just that there is matter that cannot be seen - it is that the majority of the matter in the universe is non-baryonic - that is, it is not made of the normal stuff that makes up stars and planets. So lots and lots of planets could not explain away most of the dark matter problem in any case.
Comment: ITS not possible seem planets in another galaxies. Not yet with actual tech.


How do i dual boot kde neon and ubuntu

Question: Hi I would like to know how hard it is to dual boot kde neon and ubuntu. I have kde neon on one hard drive and I would like to use another hard drive for ubuntu. (Ubuntu and kde neon will be on different hard drives)
and for those who need more info I'll be getting the new ubuntu 19.10
So can you tell me if this is possible and how
I hope this won't be hard. BTW
And I have a t430s laptop with kde on it and I'm replacing my broken optical drive for a 2nd hdd caddy that will fit in there.
Comment: In my experience easy.  My desktop contains Ubuntu 18.04 LTS & Ubuntu 19.10 in a dual-boot setup.  I did nothing except partition the system as I want it (I only have a single drive; your dual drive should be easier), and install; the second installed version took ownership of the MBR (master boot record; or first 512 bytes of my HDD) (you can post-install change this easily).  You should still backup, and I always use 'something-else' & partition myself. but it's your choice.  *I have another machine with 3 hdds & 7 OS (debian & ubuntu) systems installed*
Answer: You seem quite well prepared -- only one big thing missing: the BIOS mode in which you want to start your system.
Your model seems a bit aged, and I could not find uefi mentioned. This is no problem. That would mean you just stay on "legacy" (or MBR, your only) BIOS boot mode.
I have listed some boot scenarios in a similar situation:
grub2-unable-to-detect-a-fresh-...-intstallation
Have a look. The problem is often that the user does not know about the whole thing and the installing program tries to guess, and grub also has to be told where to put which kind of boot loader.
If you are lucky, then ubuntu's installing programm will guide you and everything should work. Get some specific info from ubuntu's wiki etc. after you read this. But before you install ;)
In your two-drive-dual-boot I see two methods for selecting at startup:

go to BIOS for each change of boot order (just like you are able to select the CD-ROM drive for booting).
boot as now into first grub. grub can then find the second kernel and initrd and load them with the second root= argument. OR chain load the second grub - like you have to on MBR and (old?) lilo.

Grub or Uefi BIOS are the glue between the computer's legacy firmware and the kernel at startup (system boot): Has to be at the right spot, nut just "there".
Check out grub or uefi in wikipedia to get another view of these interesting but tricky problems when you boot an OS.
Any OS. BIOS and also grub are exactly made for running any OS, and for choosing which one at startup. Linux, BSD, etc, Windows: any OS running on amd64/intel aka x86.
And always make sure you know how to use your rescue system from an external storage device (USB "pen") in case you break something - adding a second internal drive (SSD or HDD) to boot from with MBR is quite some step.

How do i dual boot kde neon and ubuntu


Change the channel color in Dopesheet/Graph Editor

Question: I am trying to change the color of the channels in the DopeSheet, Graph Editor and Timeline.
Can somebody tell me where to change the yellow-ish color so I can actually read the channel names?
I tried finding it in Preferences-Theme-Graph Editor, but it isn't there.
I'm using the dark Theme in Blender 2.90 on Ubuntu20.04
Answer: It's probably because you've assigned colors to your bones in Pose mode:

You can disable it in the Graph Editor > header menu > View > Show Group Colors (I don't know why it is not available in the Dope Sheet though):
Answer: To change the actual text colour from grey, Edit > Themes> Dope Sheet > Theme Space List and click on the current grey colour. I've changed mine to black under 2.8.

I've not looked at the settings for the other editors but I guess they'll be the same.


Is Whonix 100% Anonymous?

Question: I have imported and run Whonix - Anonymous Operating System appliance in my VirtualBox. I am seriously excited about anonymity that given by this OS. How can I trust and verify the anonymous state of this OS?
Comment: Nothing is 100% anonymous.
Comment: using it on a VM defeats some anonymity
Comment: Please explain a bit.
Answer: No, but it helps a lot.
Your usage habits themselves, what time you use a computer, common sites you visit, even the speed at which you type certain phrases, and the phrases you use all help to paint a digital fingerprint which can be used to identify you as a user.
This may not happen in real-time as some correlation is involved but if you frequent a site like Stack Exchange and always create new accounts at a certain time, post a three sentence question to security, then view tor.stackexchange.com, bricks.stackexchange.com, and then finally blender.stackexchange.com in a fairly repeatable pattern. An organization may be able to correlate your current activity with your past activity before you were using Whonix or even when you did the same pattern from your cell phone on vacation. These human patterns are not really as anonymous as you would think.
Similar things happen to different types of users. For an attacker, they may always do a specific type of recon first or check for new exploits before working. A journalist may read a news website or two before communicating with a whistle-blower. Basically, the things you do, even with Whonix and Tor eventually reveal some things about you. So no it's not perfect anonymity.
This said, the more you know about this tool the better you will be at using it. If you are just looking to avoid your local ISP from recording your traffic this will probably work great.
Comment: Thanks a lot. So, it is impossible to make someone's identity 100% anonymous.
Comment: @Anuruddha your ISP can see to who you're connecting, it might be a VPN, but then the one holding the VPN can see, and so on
Comment: Got the point.Always there is someone, in the top, looking at connections coming from bottom.
Comment: It is possible to have anonymous communications but it takes a lot of work and you really need to understand where and what is being recorded. In most cases, people don't need perfect anonymity so much as they need it to be good enough to accomplish a certain goal for a certain time period. If you understand what can be done in the context of your goals you can often come up with a solution that is good enough for your needs even if it is not "perfect".
Answer: Anonymity is like security on one point: perfection exists in neither, except on a non connected system in a secure building. As soon as you exchange information, you give something and receive something other. So you should be aware of:

what contains what you send outside, and what is the risk at that level
what channel(s) you are using, and what is the risk at that level
what do you get in return and how does it change your platform (cookies at first sight, but more importantly trojans or other malware)
most importantly: what do you want to protect, and from whom

In short, if you cannot understand what a system adds to your privacy, you cannot trust it. Simply because you could inadvertantly break a rule and expose something you do not want.

Is Whonix 100% Anonymous?


Straight line as circle in Euclidean geometry

Question: In Euclidean geometry ,is it possible to have two concentric circles of infinite radius?
Comment: What is a circle of infinite radius?
Comment: There's no such thing as "circle of infinite radius" in Euclidean geometry.
Answer: A circle of infinite radius doesn't exist.
If, instead, you meant generalised circle, then two concentric "generalised-circles-that-turn-out-to-be-lines" are parallel.
Comment: Thanks.Please suggest some reference so that I can develop a better understanding of the concept of concentric circles becoming parallel lines.
Comment: Take two concentric circles of radius $1$ and $2$, centered at the origin. Then two concentric circles of radius $2$ and $3$ centered at $(1,0)$. Then two concentric circles of radius $11$ and $12$ centered at $(10,0)$. Keep going like this, having circles centered at $(r,0)$ with raduis $r+1$ and $r+2$, and see that the two generalised circles you eventually get are the two lines $x = -1$ and $x = -2$.
Comment: Thanks.
Please consider my doubt given below.
In the limit as radius tends to infinity,considering the fact that (infinity minus infinity = infinity),will it be contradictory that the difference in radii in this case is one unit(a finite number).
I don't know clearly about what infinity is,but I have seen that "infinity-infinity=infinity".
Comment: I never said anything about $\infty-\infty$. I said "large number minus almost the same number", and see what happens as the large number gets larger and larger, beyond all bounds. This is often _called_ "$\infty-\infty$", but it's not what it is. There are many things that is called $\infty-\infty$, some of them finite, some of them infinite, some of them negative infinite, this is just one of them.
Comment: Thanks for the clarification.
Answer: The answer to the exact question you're asking is "no" but there are contexts where you want to think of a straight line as a "circle of infinite radius".
One is when you're looking at a pencil of circles. In this picture from wikipedia you can imagine a vertical blue line that is the limit of the blue circles of increasing radius:

The idea is useful when you think about what happens to circles on a sphere  when you represent the surface by stereographic projection onto a plane. Some circles become lines:
Answer: This is a model of geometry, which yields all three (spheric, euclidean, hyperbolic), from the notion of homogenious isotropic Gauss-Riemann curvature.  It is the closest model to the one you use when you don't know if the universe is closed or not.  But i use it to find tilings in hyperbolic geometry.
There is a general catergory of 'isocurves', or curves of constant isotropic curvature.  Curves, horocycles, and bollocycles (pseudocycles) are the main examples.
In a given geometry, a curve is 'straight' if it has the same curvature as the space it is in.  So great circles are straight lines in the sphere they fall on, but not in lesser ones.
Curvature roughly corresponds to $\frac 1{r^2}$.
Parallel lines are a sub-class of isocurves sharing two parameters.  Lines crossing at a point, or circles passing through two points, are other examples.  Parallels are of three types of crossing, positive, negative, and zero.  They create orthogonals that are of the opposite type.
You can have parallel horocycles both in euclidean and hyperbolic geometries, these are orthogonals to rays emerging from the same point or direction in infinity.
It is of course, possible to have two circles of infinite radius, they can be concentric, or cross each other.  In hyperbolic geometry, it is possible that they cross in a circle.
Comment: Thanks for the detailed explanation.


Microcontrollers: Can I perform floating point operations in a Microblaze controller?

Question: I wonder if I could perform floating point operations in a Microblaze controller?
Thank you to all posible answers with direct references to documentation or articles.
Answer: Floating-point operations are available, see this document. Try the Xilinx forums for support.
That document, in the FPU section on page 78, says that the processor supports:

The FPU implements the following floating point operations:
  • addition, fadd
  • subtraction, fsub
  • multiplication, fmul
  • division, fdiv
  • square root, fsqrt (available if C_USE_FPU = 2)
  Comparison
  • compare less-than, fcmp.lt
  • compare equal, fcmp.eq
  • compare less-or-equal, fcmp.le
  • compare greater-than, fcmp.gt
  • compare not-equal, fcmp.ne
  • compare greater-or-equal, fcmp.ge
  • compare unordered, fcmp.un (used for NaN)
  Conversion
  The FPU implements the following conversions (available if C_USE_FPU = 2):
  • convert from signed integer to floating point, flt
  • convert from floating point to signed integer, fint
Answer: Any microcontroller can implement floating point, it is just that those with hardware can do it much much faster. The compiler can do the required work to get options like floating point division, it can just take 1000s of clock cycles.
Comment: Yes, but any microcontroller has direct instrucctions that manage directly the floating point arithmetic? For Instance: plus,3.678,2.45
Comment: A xilinx microblaze controller has a latency of 30. (See the page 136 of this document http://www.xilinx.com/support/documentation/sw_manuals/mb_ref_guide.pdf )
Comment: @Peterstone, you can code in assembly, but if you are using C the compiler will handle it for you. I was making this point so that people do not make microcontroller decisions based on a floating point operation they must compute every 3 days.
Answer: It's been a couple of years, but I believe that one can build a MicroBlaze with or without hardware floating point.  If I remember correctly, without took 3 DSP48x blocks  and with took 6 DSP48x blocks.    I think when you build it, it sets the switches so that the compiler knows what it has.
Part of the decision process in design was how many BRAM blocks to use as well and whether to put these on local bus to the MicroBlaze or on AXI.  I think that it is possible to use dual port BRAM and use one port as local bus (1 cycle faster) and the other side as AXI. Something like that.


Why do MakerDAO auction keepers overpay for ETH?

Question: Looking at a recent closed auction (https://defiexplore.com/liquidation/ETH/4876), I see that the auction keeper overpaid for too little ETH. Why?
Answer: They didn't overpay, they paid 207.97 DAI for 1.12 ETH, which is 185.6875 DAI per ETH. Around ~$5 profit per ETH. Not much, but it likely covered the gas costs + a little real profit