The repository may no longer be available or could not be contacted because of network problems. If available an older version of the failed index will be used. Otherwise the repository will be ignored. Check your network connection and ensure the repository address in the preferences is correct.  GPG error:  xenial/mongodb-org/3.4 Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY BC711F9BA15703C6The repository ' xenial/mongodb-org/3.4 Release' is not signed.Updating from such a repository can't be done securely, and is therefore disabled by default.See apt-secure(8) manpage for repository creation and user configuration details.The repository ' bionic Release' does not have a Release file.Updating from such a repository can't be done securely, and is therefore disabled by default.See apt-secure(8) manpage for repository creation and user configuration details.Problem executing scripts APT::Update::Post-Invoke-Success 'if /usr/bin/test -w /var/lib/command-not-found/ -a -e /usr/lib/cnf-update-db; then /usr/lib/cnf-update-db > /dev/null; fi'Sub-process returned an error code
I added some extra repositories with the Software Sources program. But when I reload the package database, I get an error like the following:     W: GPG error:  trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8BAF9A6F   I know I can fix it using apt-key in a terminal, according to the official Ubuntu documentation. But I would have liked to do it graphically. Is there a way to do this without using a terminal?
How do I use/change Animation Extrapolation? (Can't find F-Curves / Animation Modifiers in 2.8(1)) Suppose I have a question in my mind that I think is answerable but because I don't already know the answer, I'm not sure how to express in a way that makes it clear and definitively answerable. I suspect that someone more knowledgable than me would understand what I'm trying to get at though and could help me word the question properly.  Is there a good place to find this sort of help? Assume $\{a_n\}$is a sequence which  satisfies the following recursion formula: $$a_{n+1}=a_n+\frac{2a_{n-1}}{n+1}~(n\geqslant 1).$$ and $a_0=\pi,a_1=\pi^2 $. How to compute $\displaystyle\lim_{n\to \infty}\frac{a_n}{n^2}$? I want to show that the two annuli $$A=\{r&lt;|z-z_0|&lt;R\} $$ $$A'=\{r'&lt;|z-z_0'|&lt;R'\} $$ are conformally equivalent (i.e. there exists a biholomorphic map between the two) iff $$\frac{R}{r}=\frac{R'}{r'}. $$  Sufficiency:  Suppose the ratios of the radii are the same. A suitable scaling (by $\frac{r'}{r}$) will make $A$ congruent to $A'$, and a translation will map the scaled $A$ onto $A'$. This is clearly a conformal homeomorphism.  Necessity:  The annulus $A$ has the following set of periods $$\left\{ \pm \frac{2 \pi}{\log (R/r)} \right\} $$ (this step required some computations which I will omit)  Similarly $A'$ has   $$\left\{ \pm \frac{2 \pi}{ \log(R'/r')} \right\}$$ as its set of periods. Since the set of periods is a conformal invariant. The ratios of the radii must indeed by the same.  Is this proof correct?   Thanks! How to obtain $f(x)$, if it is known that $f(f(x))=x^2+x$? QGIS - export a project with dependencies I recently wanted to add some RAM to my old computer, but unfortunately I mixed together "good" RAM with chips that I extracted from a computer that failed after getting too much voltage. I know it sounds like a bad idea to just plug it into a motherboard, so I figured I'd ask first - is there usually any protection in the motherboards against this kind of faulty chips? Also, how likely is that RAM got damaged when computer got his deadly current or failed for internal reasons (something shorted because of dust, failed components etc.)? I am able to locate files in a folder containing a specific text string using this command:  grep -lir 'string' ~/directory/*   How do I move the files that appear in the above result to another location? Show that the equation, $x^3+10x^2-100x+1729=0$ has at least one complex root $z$ such that $|z|>12.$ Why is it necessary to sample from the posterior distribution if we already KNOW the posterior distribution? My understanding is that when using a Bayesian approach to estimate parameter values:   The posterior distribution is the combination of the prior distribution and the likelihood distribution. We simulate this by generating a sample from the posterior distribution (e.g., using a Metropolis-Hasting algorithm to generate values, and accept them if they are above a certain threshold of probability to belong to the posterior distribution). Once we have generated this sample, we use it to approximate the posterior distribution, and things like its mean.   But, I feel like I must be misunderstanding something. It sounds like we have a posterior distribution and then sample from it, and then use that sample as an approximation of the posterior distribution. But if we have the posterior distribution to begin with why do we need to sample from it to approximate it? How can I understand and prove the "sum and difference formulas" in trigonometry? Calculating values of field based on two others using Field Calculator in ArcGIS Desktop? I need to combine two fields in an attribute table.  I want to do this using the field calculator.  What is the proper script to write to combine a field called "name" and "type", so that it produces one field with "name type"?  I'm using ArcGIS Desktop 10.0. Say I have the titanic kaggle competition, but I'm not interested in the competition for predicting survival for each individual. Instead I want the most accurate estimate of total survivors on the titanic. Would this be achieved by using a probabilistic model, then adding the probabilities for each individual? For example, if I have 3 people and 1 survived, but my model produced 0.4, 0.4, and 0.4 probabilities for each person to survive, I calculate 0 survived. But if I add 0.4 for each person, I get 1.2, which is closer to the actual. Does this make sense? What is the meaning of “runneth”? What is the meaning of “runneth” in ? Is there a goto or any equivalent in Python to be able to jump to a specific line of code? su options - running command as another user I was wondering how to run a command as another user from a script.  I have the script's owner set as root. I also have the following command being run within the script to run the command as the hudson user:  su -c command hudson   Is this the correct syntax? Objects, shadows and reflections not rendering in EEVEE I started to work with EEVEE short time ago and I was amazed by the capabilities of this engine. However, I noticed something strange when I was rendering some tests. Some objects/reflections/shadows dissapear when they're off canvas. I imagine that maybe this is for save memory data, but it can be not suitable to some projects. To make my point graphical, I made a simple scene with simple objects. The main object is the sphere with a mirror-like shader. Out of focus there are different objects with different shaders. A yellow cone, a blue cylinder and a white cube light. But surprisingly, those objects dissapear when the composition is rendered. See the rendered animation below:  Notice that the blue cylinder is not even showing at all in the final render. And the blooming effect from the light cube also dies. I would like to improve this bahaviour and render the objects that are still out of canvas using EEVEE. Do I missing something like memory configuration or reflection/shadow tweaks? Is this caused by the EEVEE engine or by my GPU config (GTX1060)? Thank you in advance! Why does std::getline() skip input after a formatted extraction? A word or short phrase for 'better in every way'? When we're comparing two or more things, there are times when we have to weigh the advantages or disadvantages of each one.  There are other times when one of the things is better for every way in which it's being judged, and the final decision is not based upon trade-offs.  I know that I've heard a phrase for this (I want to say it was two words), but I've had no luck in remembering it.    I don't think 'clearly superior' or 'clear winner' quite fit the bill, as that might still suggest that the disadvantages are significantly outweighed by the advantages.  Is there such a phrase, or even a single word, that would convey this meaning without using idioms? Notification for reviews shows way too many Since a , I see more than I should:    I see no reason to see 134 posts are awaiting review, when there is literally nothing I can do about them. I think it is a bug, because notification is meant as something that will make me act. When I know I usually can't, obviously I will start to ignore it.  If it's not a bug, please remove bug tag and explain how it is supposed to be useful, or how can I switch to only seeing notifications about things I can act on.  Note that apaprently there are no flags for me, neither. I see only stats, migrated, close, delete, there, as if there was no flags waiting:    If you expect us to click on it every few minutes  just to see personalized numbers next to queues, why don't you simply query for personalized numbers every few minutes and cache them for us? It should cost you similar, in database usage, and will save us a lot of clicking and frustration.  If all this number means is "there might be reviews, or not" or "for sure there are none"  it would be simpler just to hide "review" link in the second case. We don't need two links with the same function next to each other, thank you, one is enough, and meaningless numbers are only irritating.