what the difference between remount to umount/mount?

Question: When we perform this (on linux redhat 7.x)
umount /grop/sdc
umount: /grop/sdc: target is busy.
    (In some cases useful info about processes that use
     the device is found by lsof(8) or fuser(1))

We can see that mount failed on busy.
But when we do remount then ...
remount is success as the following:
mount -o rw,remount /grop/sdc
echo $?
0

So very interesting.
Does remount use the option like ( umount -l ) ? what the different between remount to umount/mount ?
Answer: man mount :

remount
Attempt to remount an already-mounted filesystem. This is commonly used to change the mount flags for a filesystem, especially to make a readonly filesystem writeable. It does not change device or mount point.
  The remount functionality follows the standard way how the mount command works with options from fstab. It means the mount command doesn't read fstab (or mtab) only when a device and dir are fully specified.

The remount option is used when the file system isn't currently in use to modify the mount option from ro to rw.

target is busy.

If the file system is already in use you can't umount it properly , you need to find the process which accessed your files (fuser -mu /path/ ) , killing the running process then unmounting the file.
Comment: so the remount dose like - umount -l & mount ?
Answer: GAD3R's reference to the man page answers your question:

This is commonly used to change the mount flags for a filesystem,

No where in the that explanation does it say the remount  calls a umount function.
Perhaps you can find your answers in these manpages
man 2 mount:

A  call to mount() performs one of a number of general types of operation, depending on the bits specified in mountflags.  The choice of which operation to perform is determined by testing the bits set in mountflags, with the tests being conducted in the order listed here:

Remount an existing mount: mountflags includes MS_REMOUNT.

Remounting an existing mount
An  existing  mount  may  be  remounted by specifying MS_REMOUNT in mountflags.  This allows you to change the mountflags and data of an existing mount without having to unmount and remount the filesystem.  target should be the same value specified in the  initial  mount() call.
Comment: Please include a relevant quote from those man pages ...


How do I force pulseaudio to use stereo instead of surround sound?

Question: I have the Audient iD14 audio interface. There are four input channels on it, and because of this pulseaudio thinks it's a 4.0 surround sound system when it's not. When playing audio, it is very unbalanced to the right. Bringing the balance slider to the left helps, but I think there's still phasing issues going on. Also, the balance is off again when I use Jack. Is there anyway I can fix this? I tried setting "enable-remixing = no" inside of "/etc/pulse/daemon.conf" and uncommented it, but that didn't work.
Answer: Just had this sort of problem as well (I'm on 16.04 by the way): Pulseaudio did an unwanted upmix on me and /etc/pulse/daemon.conf was ignored. However, it seems that the configuration file in the user's home directory is not ignored. After adding "enable-remixing = no" to ~/.pulse/daemon.conf and restarting pulseaudio, I got the stereo output I was actually playing back.
Answer: Use pavucontrol to change the type of the output device.


What is the folder where the images need to be for mass importing products?

Question: What is the folder where the images need to be for mass importing products ?
I seen there in import admin panel that is var/import/images/products_images but no is not working
Answer: Default location is
var/import/images
and do not include the path before the filename in the CSV data.

Starting with the Magento 2.3.2 release, the path specified in the
  Images File Directory concatenates for import to the images base
  directory - /var/import/images. For earlier
  Magento releases, you can use a different folder on the Magento
  server, as long as the path to the folder is specified during the
  import process.

Ref:
https://docs.magento.com/m2/ce/user_guide/system/data-import-product-images.html
Comment: why it writes /var/import/images/products_images ?
Comment: Just try to import one with magento/var/import/images/ Test and play with one.
Comment: i see the directory don't exist should i create it ? # cd import
-bash: cd: import: No such file or directory
and if yes what permissions should i give to it ? chmod 777 ?
Comment: Yes you can, remember var in Magento directory


Hilbert manifold embedding in a Hilbert space

Question: I've been working with Hilbert manifolds lately, and stumbled on the theorem which says that every smooth Hilbert manifold can be embedded in its model space.
My question is if there is a way to explicitly give this embedding.
The case I'm interested in is that of the loopspace of a manifold M.
Comment: It's still unclear to me. However, if you are given an embedding $M\to R^n$, then the loop space $L(M)$ is a submanifold in the pre-Hilbert space $C(S^1, R^n)$ (with the $L_2$-norm); then take the completion of the latter.
Comment: What do you mean by "explicitly"? This would depend on "how explicitly" your manifold is given to you.
Comment: Well i mean explicity in the case of the loopspace of a manifold. does a formula for the embedding exist?
Comment: well lets make it a little more precise. If $M = S^1$ then the theorem says that their exists an embedding $i:H^{r}(S^1,S^1) \rightarrow H^{r}(S^1,\mathbb{R} )$. So my question was more how does this embedding look like and how does it look for a general manifold
Answer: As you are interested in the Sobolev completion $L(S^1)=C^\infty(S^1, S^1)\subset H^r(S^1, S^1)$, the solution is to observe that
$$
H^r(S^1, R^2)\cong H^r(S^1, R)\oplus H^r(S^1, R)\cong H^r(S^1, R).
$$
Hence, we obtain an embedding
$$L(S^1)\to H^r(S^1, R).$$
One noncanonical thing about this embedding is an isomorphism
$$
\phi: H^r(S^1, R)\oplus H^r(S^1, R)\cong H^r(S^1, R)
$$
for which there are infinitely many choices. You may choose your favorite orthonormal basis $\{e_i\}$ in $L^2(S^1)$ and then obtain an orthogonal  isomorphism $\phi$ induced by your favorite bijection
$$
\psi: {\mathbb Z}^2\to {\mathbb Z},
$$
$$
(e_i, e_j)\mapsto e_{\psi(i,j)}.
$$
If this is not explicit enough, you have to state your notion of "explicit" in much greater detail than "a formula".


"have you ever gone to" to ask past experience

Question: is it correct to ask:
Have you ever gone to Spain?
if i want to know whether or not he had visited Spain in his life (experience)?
Answer: I don't know what you mean by "is it correct to ask", but a more idiomatic as well as more conventional way to ask someone if they have visited a particular place at least once in their live would be:

Have you ever been to Spain?
Have you ever been to London?

You would use been in this situation rather than gone.


Where can I find the error logs of nginx, using FastCGI and Django?

Question: I'm using Django with FastCGI + nginx. Where are the logs (errors) stored in this case?
Answer: Errors are stored in the nginx log file. You can specify it in the root of the nginx configuration file:
error_log  /var/log/nginx/nginx_error.log  warn;

On Mac OS X with Homebrew, the log file was found by default at the following location:
/usr/local/var/log/nginx

Comment: on Mac OS X with homebrew: /usr/local/var/log/nginx. see lfender's [answer](http://stackoverflow.com/a/27402568/576767)
Comment: On ubuntu I have it in `/var/log/nginx/error.log`. It is best to check the `nginx.conf` file and find the `error_log` setting.
Comment: That's maybe version dependent but my log is inside: `/opt/nginx/logs/error.log`
Comment: Found mine at /opt/homebrew/var/log/nginx/error.log lol. Currently on macOS 13 (Ventura). Also seems you could run `nginx -h` to view the default log output directory.
Answer: I was looking for a different solution.
Error logs, by default, before any configuration is set, on my system (x86 Arch Linux), was found in:
/var/log/nginx/error.log

Comment: Apparently this is configureable only at compile time with the `--error-log-path` compile option http://trac.nginx.org/nginx/ticket/147
Comment: on raspberry pi3 its the location
Answer: You can use lsof (list of open files) in most cases to find open log files without knowing the configuration.
Example:
Find the PID of httpd (the same concept applies for nginx and other programs):
$ ps aux | grep httpd
...
root     17970  0.0  0.3 495964 64388 ?        Ssl  Oct29   3:45 /usr/sbin/httpd
...

Then search for open log files using lsof with the PID:
$ lsof -p 17970 | grep log
httpd   17970 root    2w   REG             253,15     2278      6723 /var/log/httpd/error_log
httpd   17970 root   12w   REG             253,15        0      1387 /var/log/httpd/access_log

If lsof prints nothing, even though you expected the log files to be found, issue the same command using sudo.
You can read a little more here.
Comment: this taught me how to fish; wish I could upvote more
Comment: it's a nice trick to remember.. no guessing any more where the log files could be
Comment: +1 For an answer on how to look. I was looking for logs from a different installation of nginx and it wasn't in the top answer.
Comment: you can poke at similar data on linux in the `/proc` filesystem. `/proc/${pid}/fd` has symlinks to the open files, pipes, devices, etc
Comment: while using [$ ps aux | grep httpd] I got =auto httpd (in red). do you know what it means please?
Answer: Run this command, to check error logs:
tail -f /var/log/nginx/error.log

Answer: My ngninx logs are located here:
/usr/local/var/log/nginx/*

You can also check your nginx.conf to see if you have any directives dumping to custom log.
run nginx -t to locate your nginx.conf.
# in ngingx.conf
error_log  /usr/local/var/log/nginx/error.log;
error_log  /usr/local/var/log/nginx/error.log  notice;
error_log  /usr/local/var/log/nginx/error.log  info;

Nginx is usually set up in /usr/local or /etc/. The server could be configured to dump logs to /var/log as well.
If you have an alternate location for your nginx install and all else fails, you could use the find command to locate your file of choice.
find /usr/ -path "*/nginx/*" -type f -name '*.log', where /usr/ is the folder you wish to start searching from.
Comment: The logs will be here if you installed Nginx with Homebrew.
Answer: Logs location on Linux servers:
Apache – /var/log/httpd/

IIS – C:\inetpub\wwwroot\

Node.js – /var/log/nodejs/

nginx – /var/log/nginx/

Passenger – /var/app/support/logs/

Puma – /var/log/puma/

Python – /opt/python/log/

Tomcat – /var/log/tomcat8

Answer: For Mac OS users, you can type nginx -help in your terminal.
nginx version: nginx/1.21.0
Usage: nginx [-?hvVtTq] [-s signal] [-p prefix]
             [-e filename] [-c filename] [-g directives]

Options:
  -?,-h         : this help
  -v            : show version and exit
  -V            : show version and configure options then exit
  -t            : test configuration and exit
  -T            : test configuration, dump it and exit
  -q            : suppress non-error messages during configuration testing
  -s signal     : send signal to a master process: stop, quit, reopen, reload
  -p prefix     : set prefix path (default: /opt/homebrew/Cellar/nginx/1.21.0/)
  -e filename   : set error log file (default: /opt/homebrew/var/log/nginx/error.log)
  -c filename   : set configuration file (default: /opt/homebrew/etc/nginx/nginx.conf)
  -g directives : set global directives out of configuration file

Then, you could find some default path for configuration and log files, in this case:
/opt/homebrew/log/nginx/error.log

Comment: why is this different for different users? For me it is in ```opt/homebrew/var/log/nginx/error.log```. Doesnt make any sense
Answer: Type this command in the terminal:
sudo cat /var/log/nginx/error.log

Comment: That is not an answer and should be a comment instead. Once you have sufficient reputation you will be able to comment.
Answer: cd /var/log/nginx/
cat error.log

Answer: It is a good practice to set where the access log should be in nginx configuring file . Using acces_log /path/ Like this.
keyval $remote_addr:$http_user_agent $seen zone=clients;

server { listen 443 ssl;

ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_ciphers   HIGH:!aNULL:!MD5;

if ($seen = "") {
    set $seen  1;
    set $logme 1;
}
access_log  /tmp/sslparams.log sslparams if=$logme;
error_log  /pathtolog/error.log;
# ...
}


Covergence of discretizations to the distribution

Question: Let $\mu$ be some probability distribution on $\Bbb R$ with a continuous density function $f$. Let $X = (x_i)$ be a finite subset of $\Bbb R$ and define a discrete distribution $\mu_X$ that gives to $x_i$ probability of $$\frac{f(x_i)}{\sum_j f(x_j)}$$ Are there any conditions on the choice of $X$ to make sure that $\mu_X$ weakly converges to $\mu$ if I add more and more points to $X$?
Comment: $\sum_j f(x_j)$ might be zero. Also, which weakly convergence do you mean? In case of the weakly $L^p$ convergences this question makes no sense, because $\mu_x$ and $\mu$ have a different domain of definition.
Comment: @Adam: we can assume $f$ is positive everywhere. By weak convergence I mean $\int fd\mu_n \to \int f d\mu$ for all bounded continuous $f$.
Answer: If you allow that the $(x_i)$ are random variables distributed according to $\mu$ and independent, then it follows for every $g \in L^1(\mu)$ that
$$ \frac{1}{N} \sum_{i=1}^N g(x_i) \to \int g \mu $$
converges in probability. For details, see Law of large numbers.
Edit: Maybe if you take more and more rational points from $\mathbb{Q}$ you might get convergence for bounded, continuous functions.
Edit2: How is this related to your question?
You want to know if $\int g d\mu_n \to \int g d \mu $ for all bounded continues g. In your case we have
$$ \int g d\mu_n  = \sum_{i=1}^n g(x_i) \frac{f(x_i)}{\sum_{j=1}^n f(x_j)}.$$
So your question is what restriction on the sequence $(x_i)$ is necessary so that for every continuous bounded function g we get
$$  \sum_{i=1}^n g(x_i) \frac{f(x_i)}{\sum_{j=1}^n f(x_j)} \to \int g \mu .$$
In the case where $\mu$ is simply the Lebesgue Measue, we have $f=1$ and thus $$\int g d\mu_n = \frac{1}{N} \sum_{i=1}^N g(x_i) .$$
In the case where $\mu$ is arbitrary, notice that  if you pick the points $(x_i)$ all over $\mathbb{R}$, and the points $(y_i)$ distributed according to $\mu$, then you have
$$ \sum_{i=1}^n g(x_i) \frac{f(x_i)}{\sum_j f(x_j)} \approx \frac{1}{n} \sum_{i=1}^n g(y_i).$$
Comment: Thanks, but how is that relevant for my question? There I ask about the convergence of distributions, whereas you talk about the convergence of reals.
Comment: @Ulysses I added a short section to explain the relation to your question.


Applying Gift Cards on the PS4

Question: I got a gift card for the PS4.
I was wondering, when I use the code for one account, if it would also be available to other accounts on my PS4?
Answer: If by Gift Card you are referring to Prepaid cards to top up your wallet, then unless the other accounts can buy though another account, the answer is generally no.
Prepaid cards add funds to a PlayStation Network Account which is actually independent from any console as you can access your PlayStation Network account though the browser and buy stuff that way.
When you say,

other accounts on my ps4

I am assuming that you are referring to the associated PlayStation Network Accounts which would have their own Wallets with their own funds and generally are independent from each other.

An exception to this is using Family Accounts where the Child Family Member Accounts can spend money from the Family Manager account.

Children and teenagers can spend funds from the family manager's wallet within a spending limit set by the family manager, but only when enough funds are available.

However, once these accounts are detected to have turned 18, they graduate to Adult Family Members and are then unable to spend funds from the wallet of the Family Manager. This trade off is probably due to the fact that Child Family Member Accounts cannot add funds to their wallets whereas Adult Family Member accounts can and can also leave the Family Account (although they lose access to shared content).

Any family members over the age of 18 have full unrestricted access to PlayStation Network on their account, as well as their own wallet for purchases from PlayStation Store. However, they can't add members to the family or set parental controls for children if they haven't been made a parent or guardian by the family manager. An adult user can choose to leave the family at any time, but this will affect any content shared within the family.

If however, this gift card is part of a free game giveaway, then even if an account isn't part of the Family, it can still access the game on any that it shares with that account.

Applying Gift Cards on the PS4


Burning house as an active adjective

Question: "Burning house" is an active adjective. But i cant figure out how is that -ing form in burning house make the word as an active adj. How can we differ burning house and burnt house..
Comment: Both are particoples, Present Participle and Past Participle
Comment: "Ing" tells us about something in progress whereas "burnt " means a completed action "nothing left"
Answer: We can speak about participles here. There are different forms but we meet only two of them in your question. They are "burning " which is Present Participle and "burnt " which is called Past Participle.
Present Participles express actions in progress. "Burning " actually means "on fire".
Past Participles have passive meaning and that of a finished action. "Burnt " means that the process was completed and the house doesn't exist any more.
Comment: I just want to add that just because something is burnt doesn't mean it doesn't exist. Consider a burnt piece of toast. The toast is still there, just blackened. The same could apply to a house. In contrast a "burnt down" house would no longer exist.
Comment: Thanks, it was just a vivid expression, you are quite right.
Answer: Burning and burnt are both adjectives used in front of the noun house. You can say that the former is active, but the latter is not.
When you use the phrase "a burning house", it means a house that's still burning or on fire, whereas a burnt house is a house that's already damaged by burning.

Burning house as an active adjective


Highest Card Draw Problem

Question: Suppose there is a game where you and two people you don't know each other pay $\$10$ each, and then you get a random number between $0$ and $1$. Whoever has the largest random number among the three of you can get $\$30$. At this time, the game has a privilege, that is, you can see what the random number is, but you can't see the numbers of the other two people, for only $\$3$. If you are not satisfied with your numbers, you can opt out of this game and your $\$10$ can be returned to you. So, is this privilege worth buying?
Comment: Please don't unwind my edits.  You can't use dollar signs the way you are trying to; it confuses the formatting system.
Comment: As to the question itself, what have you tried?  What's the expected maximum of the two values you don't see?
Comment: If you click on edit now, you can see the syntax I used to get your dollar signs in,  Modify it from here if you like, but I suggest keeping that core syntax intact.
Comment: Thanks sorry about that.
Comment: Wait, are there 3 people or 4 including you?  You say two things in the problem that seem to conflict.
Comment: Updated. There are only 3 people.
Comment: Surely whether it's worth buying depends on what your number is. If you have 0.9999 you're going to win, paying $\$3$ extra to drop out would be silly. Otoh if your number is 0.001 then getting your $\$10$ for $\$3$ is a bargain.
Comment: Thanks David. I'm trying to wrap my head around if there is a way to answer this problem mathematically, I am only able to understand this through logic.
Answer: Let us assume that after looking at the number you cancel playing and lose 3 if the number less than some threshold $t$. Otherwise you continue to play and either win 20 or lose 10. Then the expected gain is:
$$G(t)=-3+\int_t^1 [20x^2-10 (1-x^2)]dx=-3+10t-10t^3.
$$
This curve has a maximum at $t=\frac1 {\sqrt3}\approx0.577$ which corresponds to the expected gain of $G\approx0.849$. The gain is positive, so the option worth buying (with a correctly chosen threshold) since the expected gain is $0$ in the standard game. It is possible that there exist even better strategies to increase the gain.
Answer: EDIT: Warning, my answer is apparently incorrect. end EDIT
In order to use the information, you must decide whether to withdraw.  If you get a high value, you'll want to continue, and if you get a low value, you'll want to withdraw.  So you have to decide upon a cutoff $c$.
Suppose your number is $x$.  If $x < c$, you withdraw and have a value of $-3$.  This occurs with probability $c$.  Otherwise, $x > c$ and you continue.  At this point, you either win or lose.
$P(x$ is the largest of the three$) = x^2$ and the payoff is $17$.
$P($lose$) = 1-x^2$ and the payoff is $-13$.
So the expected value of this game is $$c\cdot (-3) + (1-c)x^2\cdot 17 + (1-c)(1-x^2)(-13)$$ given knowledge of $x$.
The question is, can you choose a value of $c$ such that the expected value without knowing $x$ in advance is higher than the default value of $0$?
It seems you want to integrate over the possible values of $x$.  If I integrate $$\int_{0}^1 -3c + 17(1-c)x^2-13(1-c)(1-x^2) dx$$ I get $$ -10.5 + 7.5c$$ which is strictly worse than the ignorant bet for all values of $c$.
EDIT: Apparently my answer is wrong.  I thought there might be something fishy about conditional probabilities in there but couldn't nail it down.  I don't actually follow the other answers, and they match each other, so I will concede to them.
Comment: Isn't the default value 0?
Comment: You have to pay $3$ for the knowledge.
Comment: Ah, I see what you mean now.  I had to keep going through my work changing 4 to 3 and forgot that one.  Thanks for the catch.  Fixed.
Comment: Very interesting outcome took me a while to absorb.. so from a mathematical standpoint it is better off to make an ignorant bet
Comment: Apparently not, I made a mistake somewhere.  Although, if the price of information were high enough, it would become not worthwhile, I assume.
Comment: You should rewrite your expectation expression explicitly. Once you condition on the event x > c (i.e. continuing the game or not), the probabilities change. (They become uniform from c to 1 as opposed to 0 to 1).
Answer: $Game 1 =\begin{cases}20 & \text{if win}\\-10&\text{if lose}\end{cases}$
$Game 2 =\begin{cases}17 & \text{if win}\\-3&\text{if withdraw}\\-13&\text{if lose}\end{cases}$
The assumption is that expected earnings go up in second game. Expected earnings in first game is clearly 0. Let us consider the second game. We need a strategy as well as calculation of probabilities given the strategy.
Strategy: Exists a threshold number $r^*$, above which i'll play, else i'll withdraw. Given I play, I can win or lose, with certain probabilities. Given I don't play, which happens for all $r<r^*$, I walk out with $-\$3$. Let $r_o$ indicate the maximum of the others. The distribution of the max of 2 Uniform variables has pdf $f_X(x) = 2x$
Given this strategy, the expected earnings is
\begin{align*}
\mathbb E[earnings]&=-3(r^*)+\int\limits_{r=r^*}^1 \left[17\int\limits_{r_{0}=0}^r 2r_0dr_odr -13\int\limits_{r_{0}=r}^1 2r_0dr_odr\right]\\
&=-3(r^*)+\int\limits_{r=r^*}^1 \left[17r^2dr -13(1-r^2)dr\right]\\
&=-3(r^*)+\int\limits_{r=r^*}^1 \left[-13dr+30r^2dr\right]\\
&=-3(r^*)-13(1-r^*) +10(1-(r^*)^3)\\
&=-10(r^*)^3+10(r^*)-3\\
\end{align*}
We can optimize for the above, by setting the derivative to 0.
\begin{align*}
\frac{d}{dr^*}\mathbb E[earnings]&=0\\
\frac{d}{dr^*} -10(r^*)^3+10(r^*)-3&=0\\
-30(r^*)^2+10&=0\\
r^*&=\sqrt{\frac{1}{3}}\tag{0.57735}
\end{align*}
What is our expected earning?
\begin{align*}
\mathbb E[earnings]&=-10\left(\sqrt{\frac{1}{3}}\right)^3+10\left(\sqrt{\frac{1}{3}}\right)-3\\
&=-10(1/3)^{1.5}-10(1/3)^{0.5}-3\\
&= 0.8490
\end{align*}
Therefore it is worth taking the option.
See here for distribution of max of 2 uniform random variables:maximum of two uniform distributions
Comment: It would be useful to know why this answer was downvoted.
Answer: While some other answers here do a fine job of going through the computations, I thought I would add one more rigourously explaining this problem in the language of probability theory.

Consider the probability space $([0,1]^3,\mathcal{F},P)$, where $\mathcal{F}$ is the Borel $\sigma$-algebra, and $P$ is the Lebesgue measure. Let $(x,y,z)\in[0,1]^3$ denote the numbers each player receives, and let $\xi$ be a random variable equal to your winnings, given by
$$\xi = 20\:\!\mathbb{1}_{\{x>y\vee z\}} - 10\:\!\mathbb{1}_{\{x\le y\vee z\}}$$
Buying the privilege gives us access to the value of $x$, which we can model by letting $\mathcal{G}=\mathcal{B}([0,1])\times[0,1]^2\subset\mathcal{F}$ be the Borel $\sigma$-algebra of the set of $x$-values $[0,1]$ times $[0,1]^2$, i.e. slices of the cube $[0,1]^3$ that are parallel to the $yz$-plane. From this, we can use the conditional expectation of $\xi$ given $\mathcal{G}$, which is given by
$$\mathbb{E}(\xi|\mathcal{G}) = 20x^2 - 10(1-x^2) = 30x^2 - 10$$
This tells us the expected value of your winnings for your value of $x$. Since this is monotone in $x$, we choose to play the game only if $x>k$ for some fixed $k$ to be determined later. Therefore, your new winnings are given by the random variable $\eta$, which is given by
$$\eta = \xi\mathbb{1}_{\{x>k\}} - 3$$
where the indicator function $\mathbb{1}_{\{x>k\}}$ represents the fact that you only play if $x>k$. Since $\mathbb{1}_{\{x>k\}}$ is $\mathcal{G}$-measurable, your expected winnings as a function of $x$ are given by
$$\mathbb{E}(\eta|\mathcal{G}) = \mathbb{E}(\xi|\mathcal{G})\mathbb{1}_{\{x>k\}} - 3$$
In order to determine whether buying the privilege is advantageous, we compute the expectation of $\eta$ as follows:
\begin{align}
\mathbb{E}\eta &= \mathbb{E}(\mathbb{E}(\eta|\mathcal{G}))\\
&= \mathbb{E}(\mathbb{E}(\xi|\mathcal{G})\mathbb{1}_{\{x>k\}} - 3)\\
&= \int_k^1(30x^2 - 10)\,\mathrm{d}x\, - 3\\
&= 10(k-k^3) - 3
\end{align}
At $k=\frac{1}{\sqrt{3}}$, this reaches a maximum of $\mathbb{E}\eta\approx0.849$. Since $\mathbb{E}\xi=0$, we conclude that it is advantageous to buy the privilege and only play the game when your number is at least $\frac{1}{\sqrt{3}}$.
Answer: A simple proof that it is worth paying to find your number is to display a strategy where it gains.  We are not asked to find the optimum strategy.  If we don't pay to find our number the game is fair and our expected result is $0$.  My strategy is to pay to find the number, then drop out if it is less than $\frac 12$.  I then lose $3$ when the number is less than $\frac 12$, win $30$ when it is greater than $\frac 12$ and I have the highest number, and lose $13$ when my number is greater than $\frac 12$ but I lose.  If I keep my number $x$ I win with probability $x^2$ because both other players have to have a lower number, which they do with probability $x$.  My expected value is then
$$\frac 12(-3)+\int_{\frac 12}^130x^2dx-\int_{\frac 12}^1(-13)(1-x^2)dx\\
=-\frac 32+\left.(10x^3-13x+\frac{13}3x^3)\right|_{\frac 12}^1\\
=-\frac 32+\frac {43}3\cdot \frac 78-\frac {13}2\cdot \frac 12\\
=\frac{-36+301-78}{24}\\
=\frac{187}{24}$$
As this strategy shows a gain over doing nothing, it is worth paying the $\$3$ to find our number.  There may be (and another answer shows there is) a better threshold for dropping out, but that can only improve the result further.  I chose $\frac 12$ as a guess that seemed reasonable and easy to calculate with.

Highest Card Draw Problem


Can I use horizontal 90 degree elbows to run a p trap along a wall?

Question: Off center vent stack (see picture). Can I use a 90 degree elbow out of the vent stack, run drain pipe along the wall, and then another 90 degree elbow so that the p track will point directly backwards (towards the wall)? The drain pipe and 90 degree elbows will be 100% level. Will this siphon the trap? Please post any problems with this idea.
Answer: The specifics of this largely depend on your local plumbing code, and so what is acceptable during an inspection depends on that. Your inspector will be able to tell you for sure.
Elbows
My reading of Ontario build code section 220.127.116.11 says this would not be allowed:

(c) the trap arm does not have a cumulative change in direction of more than 135°.

90+90 = 180°, so that's too much.
Trap Arm Length
The other factor is trap arm length, and that depends on pipe size. Since this is a vanity I'll assume 1 1/4". To make that work, you need:

1.5m (5 ft) maximum length
1:50 slope (eg, 1/4" drop for every 1')

Fix
One option, if there's space, is to use a 90+45 (135° total) to route the pipe out:

Or you could also do it the other way around, though that would require opening the wall and cutting into the vent stack:

And if you're going to cut into the wall anyway, another option is re-route the pipe to use a single 90:

Which one makes more sense is going to depend on space available and where the studs are.
Comment: If the drawer is short enough you could just point the drap straight at the vent, with no elbows ... or if that won't work perhaps 45 degree elbows will avoid the drawer and give you 90 degree total turn.  Or even a single 45 degree elbow off the trap, THEN pointed straight at the vent will avoid the drawer.
Comment: Could also go directly to the drain location just behind the drawer box, and maintain 2% slope.
Comment: @jay613 Excellent point. Added a picture of that. It would still will require cutting a hole in the wall and cutting into the stack pipe, but definitely could be easier if it also avoids having to route the pipe through a stud.
Answer: The proposed layout would likely work just fine for the sink in a vanity where generally you are just draining water or soapy water. It would be wise however if you could raise the level of the P-trap just a little closer up toward the sink drain so that the horizontal run along the wall has a small bit of slope to it. This will help to ensure that water does not stay lingering in that section of the pipe.
To raise the P-trap some it may be necessary to shorten the tail piece coming straight down from the sink drain.


cannot get like box to appear on website

Question: I have gone through the process of building a like box for my facebook page to link to my website. I have acquired the code however whenever I go to paste the code the placeholder that appears is a tiny square. I am using Xara Web designer to build my website. I have tried everything. I have managed to get a like button to work I think but cannot get the like box to appear on my site.any help greatly appreciated
Answer: If you cannot see the like box plugin, you're probably logged into Facebook as a page account and not a user account.  Have a friends try it out for you too.
Another idea is something on your web page is keeping the like box from being rendered.  Strip down your page to bare bones and see if the like box plugin renders.


Best way to extrude Isosceles triangle from edge

Question: So I'm trying to figure out how to replicate this (picture attached). It seems pretty simple in concept, but I can't figure out how they did it. I have assumed it is based on some sort on extrusion from edge to tri, but I haven't figured out how that works. Does anyone have a clue?
Comment: It would be a better question if you created a simplified (minified) example, e.g. where you want to create/extrude (whatever you want to do) 3 triangles or so.
Answer: For 1 edge
Since you're asking about a single triangle… Select the edge, Create a custom orientation from it:

now E to extrude, ⬆ ShiftY to lock $y$ axis (defined a moment ago by using the edge), M to merge and either A or B:

For multiple edges
You could use Goemetry Nodes to find a perpendicular vector, then maybe rotate randomly and finally merge by distance:


MySQL 5.5 to 5.6 Upgrade. Will data remain the same?

Question: We are considering to upgrade to MySQL 5.6 this summer. I would like to know if our data will be changed in any way once we perform the upgrade?
I've been reading and I found that mysql_upgrade upgrades the system tables only. I tested it and it seems to be true. But I just want to make sure that our data will remain the same after the upgrade. I don't want to have problems with our apps after we do the upgrade. Thanks!
Answer: As noted, mysql_upgrade will change the system tables to include any new columns required.
MySQL 5.6 includes support for microseconds in DATETIME and TIMESTAMP, and as such uses a different format on disk for storage.  Conversion to the new format does not happen as part of mysql_upgrade, but will happen on  ALTER TABLE or OPTIMIZE TABLE and in which case you will not be able to start MySQL 5.5 and use this data directory.
Answer: Mysql version upgrade will not make any changes to your stored data from your database!
But as a best practice make sure you make a full backup for your database(dump + cold bkp) before you start the upgrade process.
Always have rollback plan
Comment: True, except for the system tables, where there are structural changes, but there should be no data loss.  Also, read the [upgrade guide](https://dev.mysql.com/doc/refman/5.6/en/upgrading-from-previous-series.html) and all of the [release notes](http://dev.mysql.com/doc/relnotes/mysql/5.6/en/) for every release of MySQL 5.6 to verify that there are no incompatible changes that may cause issues if your application is relying on some behaviors of older versions that could have changed.
Comment: +1 for "always have a rollback plan"


Android app kills on kindle fire when losing focus

Question: An app that I have made works great on any regular android device, but when the app loses focus on the Kindle Fire it kills. Does anyone have any idea as to why?
Thanks in advance.
Answer: Once your app is no longer in the foreground, its process can be terminated at any time by the OS to free up memory for other processes. This happens on every Android device. It is possible that some versions of the Kindle Fire may be more aggressive about it, but having your process be terminated is standard behavior and something your app needs to account for.
Answer: I agree with CommonsWare just to add to that point please check if in onPause ur manually finishing your activity or not sometimes that can be reason ,I know it sounds silly but people make silly mistakes sometimes :)


Tensorflow Object Detection API - showing loss for training and validation on one graph

Question: I am playing with Tensorflow Object Detection API and training the Faster R-CNN network on my own dataset. I am checking the progress of learning at Tensorbord. All metrics are there, but is there a way to have both loss plots, for training and validation data, on one graph? Or do I have to dive into TOD Api code and modify it? I would like to avoid the second because during every update of the API I will have to keep in mind that some of the code is changed locally.
Answer: The underlying data for the plots is saved under different tag names (loss vs loss_1). I believe TensorBoard does not natively support displaying different tags in one plot. There might be third-party extensions to do this.
If different models used the same tag, the graphs would be combined by default (see: Plot multiple graphs in one plot using Tensorboard).


How to create web store on localhost in wamp with database

Question: How can i create a web store in Magento 2 with database? I install Magento, i made a database which is now, after installation, full with all tables that are needed, but i have to do new database for my final work on university and there is the problem. I don't know how to join that. I read something about doing models with databases, is that it? Please, help me. I don't need to do some extra web shop, database and its functionality are important.
Comment: How to install Magento2 in your localhost? is this what you are trying to do and what your question is about?
Comment: No, my question is how to create a simple web shop/store with database and how it works, that database and Magento 2. And do i need to do anything more to create store by myself. I see how to do page and clicking and stuff, but i have to know more about db. Maybe about some files, which are important?
Answer: You can use Magento to create your store.
Once you installed it you are ready to use it.
This is an example of what you get once you install Magento2 (using sample products)
http://magento2-demo.nexcess.net/
Magento use a database to store and retrieve data (products, orders, customers, etc.)
Magento can easily reach 13.000 files/folders so it is difficult to say which one is important (I guess all of them).
Comment: Thank you very much! And just one question, is there something more i have to do with database? I know that i can change and add tables, but do i have to do anything else to create store?
Comment: To create a Magento2 store you only need to create an empty database and tell Magento the details of your database. After that Magento takes care of everything else.
Comment: Happy to help, and welcome to Magento Stack Exchange. Remember that If this answer or any other helped to solve your issue, it would be nice from you to mark it as accepted.


How to publish list of executable packages in ccnet without zipping it

Question: I have ccnet and project configured on it which generates around 7-8 big packages i.e exe which is around 1GB space. I want to list down them on ccnet dashboard. I find this http://www.cruisecontrolnet.org/projects/ccnet/wiki/Package_Publisher on ccnet website but problem is it creates zip file of all which is what i dont need as I already have installer and that is not what our customer need. Any help in this regard? Earlier I though to let it be zipped and unzip on target server but that takes lot of time as files are huge and I just want to lost on dashboard and let it be just copied without zipping.
Answer: To just copy files somewhere else you can use the build publisher. See: http://www.cruisecontrolnet.org/projects/ccnet/wiki/Build_Publisher


iCloud Keychain not syncing to Mac

Question: I've been using iCloud for many services such as Notes, Reminders, iCloud Drive and Keychain for a long time withh my Mac, iPhone and iPad.
A few weeks ago, I've noticed that new passwords have not been syncing to my Mac if I've registered somewhere on my iPhone.
I'v disabled iCloud Keychain, restarted, re-enabled it from here:

I've waited for hours on Wifi, plugged in etc, no avail.
Then I've tried logging out of iCloud on my Mac completely and logging in back again. I've got a confirmation on my iPhone for 6-digit number, took a few minutes to re-enable it, entered my passwords etc. In a few minutes everything including my iCloud Drive files, Notes, Reminders were back on my Mac, but my keychain is still not here. It's again been hours (plugged in, connected to Wifi) but here is my keychain on my Mac:

All the contents of my iCloud Keychain is available on my iPhone, and it has iCloud Keychain enabled too:

I've left both my Mac and iPhone plugged in, fully charged, connected to Wifi for hours, but I'm still not getting anything on my Mac.
How do I get my keychain back on my Mac (without resetting, of course)?
Answer: I solved the problem by deleting the keychain folder which is localised under <code>~/Library/Keychains</code>
After deleting it, restart a device and enable iCloud keychain.

iCloud Keychain not syncing to Mac


Do any passenger-carrying freighters connect Norway to North America through the Arctic?

Question: There are plenty of Trans-Atlantic freighters that carry passengers; perhaps it's the most popular crossing for freighter travel.  Some are listed at freightercruises.com or freighter-travel.com.  I've also found some north-west passage freighters, but they connect only Greenland and North-America.  Are there any passenger-carrying freighters that connect northern Norway with North-America (preferably a place in North America with onward public transportation) through the Arctic or the high north in general, rather than going south to France/UK/Ireland before crossing the Atlantic?
Comment: That would be amazing, I'd totally want to do that trip. Travel.SE meetup!
Answer: I found an interesting site that lists a lot of companies and sites that allows you to become a passenger on a freighter.  The thing is that there are no direct routes from Norway that I can find to anywhere in North America.
The best I was I able find was routes operated Hamburg Sud from Rotterdam to multiple ports in Norway and from Rotterdam to multiple places in the US.  There is also a different German Company Rickmers-Linie which operates through Hamburg and will let you again change ships to Scandinavia (Sweden and Finland) and that's about it.
Comment: Peculiar how the photo on the site shows a ship in a frozen sea.  Presumably between Sweden and Finland then.
Comment: Looks like it.  Ice is not that thick...


Can anyone tell me anything about what's being said in the inscriptions and seals on this painting?

Question: **This is a color and ink painting measuring approx. 15 x 19 inches. I think the script could be referring to the "Tian Shan" mountains but I'm not sure and I think the seal in the lower left starts out with the character for "Qing" but not sure. Any help would be deeply appreciated.enter image description here
Comment: The paining is titled "桂林山水甲天下" (the mountains and waters in Guilin are the best of the world). It's painted (写, short for 写意, which is a type of Chinese painting)in 庚午 year. Depending on it age, it could be year 1990, 1930, ...
Comment: Are you saying that the seal in the lower left does not include the artist signature?
Comment: No, I can't read the seal script. I only commented on the title on the upper-right corner.
Comment: That's okay.  Thanks for your interest and your input.  Let me know if you come up with anything on the seal script.
Comment: The left seal on the top right looks like "张". I have no idea what others are about.
Answer: This is a gift that a person receives when he reaches his birthday. Usually it is received when a person reaches 60, 79, 80, 90, 100.. such a full ten lifespan. Because the black character on the far left is a traditional Chinese character "寿".

The person giving the gift was from Guilin City, Guangxi Province, or the person who has reached the birthday was located in Guilin City, Guangxi Province. Because on the far right of the picture is written "桂林山水甲天下", which means that the scenery of Guilin is the most beautiful in the world. The scenery of Guilin is very beautiful, even US President Bill Clinton has visited it. In the picture, the sails on the boat are full of wind, which wishes this  man smooth sailing.
On the other boat, a fishman was fishing, and there were four cormorants (a kind of bird) on his clothes. This is just the scenery of Guilin. Chinese people generally believe that even numbers are auspicious and odd numbers are unlucky. So there are two boats and four cormorants. The lower right corner is bamboo, which means that this person has a good character and is respected by others.
This is a birthday painting, expressing blessings. The painting was supposed to be given away in 1990. Because of a cycle of 60 years, the year of Gengwu belongs to the horse, which is 1930, 1990, 2050... . This painting is obviously painted in modern times, that is, in 1990, on a certain person's birthday, the other three people gave him this painting together, because there are three red stamps. One of them is surnamed Zhang(张), because there is a red badge that is Zhang.


Problem with registration page

Question: I am sorry if this is a very trivial question, but I am very new to wordpress and this is the first time I use wp.
I am trying to set a website with wordpress and buddypress. I followed all the steps and the website is up and running in my localhost. Now I would like that a new members can register in the website. When I try to go to registration page server tell me that the page does not exist. I googled for a while, but I did not found any basic tutorial. Then I believe that this is a very trivial question, so I am wondering if something goes wrong during the installation. Who can help me or give me a resource to fix this problem?
Comment: Please write your solution into the answer field, and accept that answer then. Do not put the solution into the question, and do not use some arbitrary to indicate a solution. Thanks.
Answer: The problem was the mod_rewrite of Apache. I went in  /etc/apache2/sites-available/000-default  and I changed
Options Indexes FollowSymLinks MultiViews
AllowOverride None
Order allow,deny
allow from all

to
Options Indexes FollowSymLinks MultiViews
AllowOverride all
Order allow,deny
allow from all

the I restarted the apache server and all gone fine.

Problem with registration page


If the population size was large enough that the sample size required to represent it is too large to be practical, what should be done?

Question: i just started working as a quality control engineer at a poultry company, one of my first duties is to design a mechanism to ensure the quality of the end product (the Chick) and processes leading up to it (incubation...etc...etc), so naturally i suggested that a sample of the eggs going from a process to the next is taken for quality checks, the problem is the sample size, there are around 200000 eggs going through the production process and only one veterinarian, a sample size of 100000 or 50000 or even 500 is way too much to be examined. what should be done in this situation?
Comment: There are so many issues to address here that you will not be well served by any single answer, no matter how lucid or correct.  You really need to study statistical quality control or retain the services of someone who knows it.
Comment: It doesn't seem to me that the population size is relevant. What are you trying to find out about the process. Is it a matter of detecting when a change in performance occurs or are just trying to the total proportion of failures? If you sample randomly you can approximately estimate the proportion of failure using the binomial distribution since the population size is so large that it can be treated as infinite.
Answer: One of the lovely things about sampling theory is that it demonstrates that you can make good inferences from sampling, even with a very large population and a correspondingly small proportion of sampled items.  (Hell, you can even get good inferences with an infinitely large population!)  It also demonstrates that it is incorrect to assume that you will require some minimal proportion of the population to obtain reasonable inferences.  For example, if you have a population of $N$ units, and you take a sample of $n \leqslant N$ units, then a standard confidence interval (at confidence level $1-\alpha$) to infer the population mean would be:
$$\text{CI}(1-\alpha) = \left[ \bar{x}_n \pm \underset{\text{pop corr.}}{\sqrt{\frac{N-n}{N}}} \cdot \underset{\text{sampling}}{\frac{t_{n-1, \alpha/2}}{\sqrt{n}}} \cdot s_n \right] .$$
(In this equation $\bar{x}_n$ and $s_n$ are the sample mean and sample standard deviation, and $t_{n-1, \alpha/2}$ is the critical point of the Student's t-distribution with $n-1$ degrees-of-freedom and tail area $\alpha/2$.)  As you can see, the width of this confidence interval (and thus, the accuracy of the inference) is determined by a product of terms; one of these is affected by the population size $N$ but the others are not.  In the case where $N$ is large, the "population correction" term approaches one, and is therefore removed from the equation.
There are two aspects to the information taken from a sample of a finite population.  One source of information is the direct information about the sampled units, which form part of the population.  This source of information occurs in proportion to the amount of the population you have sampled.  It is reflected in the above formula by population correction term, which goes to zero as $n \rightarrow N$.  The other source of information is the indirect inferential information that the sampled units give about the non-sampled units.  This source of information is determined by the raw size of the sample, and occurs independently of the size of the population.  It is reflected in the "sampling" term, which decreases as $n$ gets larger.
Even if $N = \infty$ it is possible to reduce the width of this confidence interval (and thus increase the accuracy of the inference) as narrowly as you want by taking sufficiently large $n$.  It is possible to obtain a very narrow confidence interval (i.e., a very accurate inference) with a sample that is only a tiny proportion of the full population (or even zero proportion of an infinite population).  In sampling problems where you have a large (or even infinite) population, it is possible to get good inferences with samples that are large in raw size, but small as a proportion of the population (even infinitesimally small).  In such cases there is little to no direct information from the sample, but a large amount of indirect inferential information.
This is really the core lesson of sampling theory, so if you are unfamiliar with it, you should try taking a basic course on sampling the mean of a population.  The belief that a particular proportion of the population is required to obtain a good inference is a common sampling fallacy; it is based on ignoring the inferential information provided by the sample.


old home. no ground wire

Question: I'm in the process of making my home a "smart" home. The new outlets are not a problem as they merely plug into existing outlets. The switches, however are something different. They require a ground wire. My home was built in the early 50s and has only 2 wires (white, and black). My question is this, the wires are run in romex, and I've read from other posts that conduit can act as a ground. Is it the same with Romex as it is metal too.
Comment: @JPhi1618 - It wouldn't surprise me if there's some neutral/ground bootlegging going on here and that it actually requires a neutral, but someone (maybe even the 'official' installation instructions) suggest using ground instead.
Comment: I've seen many smart switches that require a white neutral connection, but do they _require_ a ground as well?
Answer: No. "Romex" is a trade name and is actually a brand of non-metallic cable or NM cable. Article 334 of the National Electrical Code.
If your house was wired with NM cable in the 50's or before, it most likely has no ground wire.
Smart switches require either an equipment ground or a neutral wire to power the smart switch while it is waiting to turn on the lights. You should not depend on visualizing wires in the boxes. You should test your system to determine if there is an equipment ground available at these locations. There was a method in the 50's of taking the equipment ground and wrapping it around the cable and then clamping it into the box. So, you boxes may be grounded after all.
If you don't have an equipment ground, all is not lost. You can run separate equipment ground wires to any of the boxes where you need one. It will be a hassle but the switches will not work without it.
Good luck!
Comment: Neutral is not ground.  Smart switches shouldn't "not work" if there's no ground, that would mean they are bootlegging ground as a current return (what neutral is for).
Comment: @Harper some smart switches use the neutral and some use the ground.

old home. no ground wire


Could a tipbot be construed as a money service business?

Question: In the United States this would impose obligations on the owner of the bot to log info and request KYC info from users to comply with the Bank Secrecy Act I believe. I'm not sure where tippero lives, but I imagine there are similar regulations in other countries. Does anyone have any insight into what levels of money would make a bot or other service fall into this category in any jurisdiction?
Comment: It does charge withdrawal fees and has house odds on dice.
Comment: Does tippero charge a fee? If not, is it a business?
Answer: Gov'ts seem to like making rules and seem to think that numbers (aka Mathematics, aka. crypto currencies) must be regulated by them.
Check your gov't, but assume the answer is yes.
Answer: It depends if the tipbot is operating as a business. The term "business" has been defined as that which occupies the time, attention, and labor of men for the purpose of livelihood or profit. The activity (hosting and maintaining the tipbot) must be continuous and there must be an intent to profit, see Commissioner v. Groetzinger.
If the withdrawal fees and house odds are motivating factors for running the service, then yes, the tipbot might be considered a money service business in light of the FinCEN's guidance on the Regulations to Certain Business Models Involving Convertible Virtual Currencies given that the tipbot operates as a hosted wallet service. Hosted wallet providers receive, store, and transmit cryptocurrency on behalf of accountholders. Accountholders do not have exclusive possession and control over their respective wallets' mnemonic seed and interact directly with the tipbot instead of the cryptocurrency core software (see FinCEN Guidance, pp. 15-16). As such, a tipbot operator must have an anti-money laundering program and follow the procedures for identifying, verifying, and monitoring both the user's identity and risk profile. In addition, the Funds Travel Rule would apply if transfer amounts are equal to or greater than 3,000 USD. Although, I'm not sure how this rule could be practically followed in the context of Monero.
Answer: I would imagine the amounts would be too small for any regulator to care. Its not like people are going to be tipping 5000 bucks or something (maybe you'd have to put a cap on amount one can tip).


Why do water drops form spheres in space?

Question: When water is poured out in space, why does it always take a spherical ball-like shape?
Answer: No, it's not because of gravity. You need to take quite a lot of water in order for gravitational effects to become significant.
It's because of surface tension. Sphere is a shape which minimizes the surface for a given volume. The surface-tension-related potential energy of the water is proportional to the surface, so spherical shape minimizes the potential energy.
Comment: Fun fact: this is the same reason that bubbles are round!
Comment: What is your "No" in reponse to? There's nothing in the question that mentions gravity.
Comment: @Barmar Originally there was (the only) tag "gravity".
Comment: Ahh, didn't notice that edit. But I suspect they were thinking about the lack of gravity in space, not gravity holding the water globule together.
Answer: Minimizing energy.  If there is a small amount of water, then surface tension wants to try and minimize the surface area of it, and the minimum surface area for a given volume material is a sphere.  For really large volumes of water (if you, for instance, sucked all the water out of the oceans and placed it somewhere far away in space in the standard mad-scientist way), then you also get a sphere, but for a different reason: the mass of water wants to minimize its (self-)gravitational potential energy and this is also done when it is spherical.  If such a volume is in the presence of external gravitational field (for instance if it was orbiting the Earth) then it would not be completely spherical: this is one of the reasons the Moon has a slightly odd shape, for instance.
In between these two regimes -- if you had a few thousand gallons of water for instance, then although it would eventually end up spherical in the absence of other influences, this would take a very long time.

Quantifying the effects
It is interesting to try to quantify the differences between the effects.  One way to do this is to consider a spherical ball of water (or anything else, but I'll stick to water because numbers are easy to come by) and consider what force you would need to bisect the sphere and move the two halves apart.  Then we can compute the force that would be needed to break the surface tension, and that needed to overcome the gravitational attraction of the two halves.
Surface tension
Let the radius of the ball be $R$, and surface tension be $T$: $T$ has units of force per length.  So the total force we need to exert when splitting the sphere is simply the total force exerted by surface tension around a circumference of the sphere, and we can see immediately that this goes like $R$.
$$F_T = 2\pi R T\tag{T}$$
For water, $T = 7.3\times 10^{-2}\,\mathrm{N/m}$ approximately.
Gravity
This is more complicated.  First of all we can say something about the behaviour of the force: the masses of the two hemispheres go like $R^3$, and the separation like $R$, so it's immediately obvious that the force is going to go like $R^3\times R^3 / R^2$: like $R^4$ in other words.  Gravity is going to win as $R$ gets big!
But we can actually get a number, even though the hemispheres are not, well, spheres, and thus hard to treat gravitationally: if you think about the surface which cuts the the ball into two hemispheres, then what is preventing the ball collapsing inwards across this surface is pressure.  So the gravitational force between the two halves of the ball, when they are touching, must be equal to the integral of the pressure over that surface (it took me ages to realise this trick!).
Let's assume the density is uniform, which it won't be for really large objects but it will be for reasonably small ones.  Call the density $\rho$. Then we can work out the gravitational acceleration at radius $r$ from the centre, relying on the shell theorem and knowing the mass inside $r$ is $m(r) = 4/3 \pi r^3$.
$$g(r) = \frac{4\pi}{3}G\rho r$$
And this gives us the pressure at $r$, just by integrating $g$ from $r$ to $R$:
$$
\begin{align}
 p(r_0) &= \int\limits_{r_0}^R \rho g(r)\,dr\\
        &= \frac{4\pi}{3} G \rho^2 \int_{r_0}^R r\,dr\\
        &= \frac{2\pi}{3} G \rho^2 \left[R^2 - r_0^2\right]
\end{align}
$$
or
$$p(r) = \frac{2\pi}{3} G \rho^2 \left[R^2 - r^2\right]$$
And finally we can integrate this over the surface to get the total force:
$$
\begin{align}
 F_G &= \int\limits_0^R 2\pi r p(r) \,dr\\
     &= \frac{4\pi^2}{3}G\rho^2 \int\limits_0^R R^2r - r^3 \,dr\\
 F_G &= \frac{\pi^2}{3} G \rho^2 R^4\tag{G}
\end{align}
$$
(I hope this is right: it is dimensionally OK but I might have missed factors somewhere.)
Compared
So, then, given $\rho = 10^3\,\mathrm{kg/m^3}$, $G = 6.7\times 10^{-11}\,\mathrm{m^3/(kg s^2)}$, we can solve for the radius $R$ where $F_T$ = $F_G$, and the answer is about $12.8\,\mathrm{m}$.  I was surprised how small this is (and I am worried I have made a mistake therefore).
So if this is right, it means that gravity starts beating surface tension for a ball of water which is about $13\,\mathrm{m}$ in radius, and beyond that it wins rather rapidly due to the dependence on $R^4$.  What this does not tell you is anything about how long it takes something to become spherical: I think that would be a bunch harder to work out.
Comment: @fishinear Being in presence of Earth's gravity is also enough to have an elongated shape: there is a gradient of gravitational potential. That's the same reason why we have tides on Earth: the water mass is slightly stretched by the Sun and the Moon.
Comment: Could you quantify the relative strength of surface tension vs. gravity, depending on amount of water? And wouldn't the "very long time" in all cases (i.e. also when it is not so long) depend on how "excess energy" is gotten rid of?
Comment: "If such a volume is in the presence of external gravitational field (for instance if it was orbiting the Earth) then it would not be completely spherical". To be precise: it has to be orbiting for it to be non-spherical. Just being in the presence is not enough.
Comment: @jjmontes My mistake, you are correct. It's because the gravitational field is non-uniform
Comment: @HagenvonEitzen: that's an interesting question: I can't, off the top of my head.  I think I can give a dimensional argument as to why gravity wins, which I'll try to do.
Comment: @HagenvonEitzen: I've added a calculation comparing the effects.  It may be wrong, but it's plausible I think.
Answer: I'm sure that a chemist could give a deeper answer. Or from Wikipedia we get, the surface tension occurs because water has hydrogen bonding.

Because of its polarity, a molecule of water in the liquid or solid state can form up to four hydrogen bonds with neighboring molecules. These bonds are the cause of water's high surface tension and capillary forces.

The key are the 4 possible hydrogen bonds to other water molecules of liquid water. The water molecules are bonded to each other like a free dimensional mesh.
Heating water, the water could be sprayed out in space to small pieces of course. The hydrogen bonds are weak (compared to metallic bonds) and under the influence of heat transfer the kinetic energy of the water molecules increases and the hydrogen bonds get broken.
Comment: Surface tension is not particular to water: all liquids will form a sphere in outer space. Even magma will do that, which is why planets are spherical.
Comment: Fuel oil also forms droplets and it hasnt hydrogen bonds


Wallpaper that I download

Question: How can I save a downloaded image to the folder called pictures that I see in System Preferences/Desktop & Screen Saver/Desktop?
I'm assuming that this is a good place to store images that I download for wallpaper.
Thanks
Gary
Answer: Push the <code>+</code> at the bottom of the list:

Then select a folder or create a new one in your home folder, perhaps inside your Pictures folder.
There may be a way to put a picture inside the Apple desktop pictures folders, but this is the more standard way to go about it.

Wallpaper that I download


In Recurrent NN, what's the reason for adding instead of multiplying the input term and the state term in the hidden units?

Question: As we know, the hidden layer unit has the following activation:
$$h_t=tanh(UX_t+Wh_{t-1})$$
So there is the interaction between the input and the previous state: $UX_t+Wh_{t-1}$. My question is why it is an addition? What is the reason for not using $UX_t * Wh_{t-1}$?
Answer: The suggestion you state for multiplication would also be a viable approach. This does however have some downsides, since now there is a stronger interaction between the variables (think of positive and negative when multiplying). I suspect that the optimization is easier to perform for the most used approach due to simpler gradients and less interaction of weights.
Answer: Let's look at the problem in 1D
$\frac{\partial}{\partial x} g(f(x) + y) = g'(x + y) f'(x)$
Whereas
$\frac{\partial}{\partial x} g(f(x) y) = g'(f(x)y) f'(x)y$
As you see, the differential of this function does not only depend on value of $f(x)y$, it also depends on $y$ multiplicatively. Combined with the fact that in RNNs this rule is used many times this makes problems with exploding/vanishing gradient even worse if $y$ is not very close to 1.


Some sites require that you accept cookies in order to use them. Does this mean that they can read/track my real IP?

Question: The site I want to use says that it stores permanent cookies on my computer to track various things, for instance if I have two accounts with them. It says "Please note
that if you set your browser to disable cookies, you may not be able to access certain parts of the Site for example applying for a job or posting a job. Other parts of the Site may also not work properly." Can I use it with TOR and will it get my real IP because of these persistent cookies?
Comment: The moment you open any website they already got your:
------------------------------------------------------ - IP Browser name and OS (If it is sent in your headers) - Previous website visited (If referral headers are accepted) - Request type (GET, POST, DELETE, etc) ---------- 126.96.36.199 - - [21/Jan/2015:23:04:14 +0200] "GET /robots.txt HTTP/1.1" 200 865 "-" "Mozilla/5.0 (compatible; YandexBot/3.0; http://yandex.com/bots)" So, basically, the moment you open any website even if you BLOCK all cookies, your IP is still being revealed.
Comment: Thank you, I understand there are a lot of ways for them to get info about me; but for the specific problem I described in my first comment to Mark's post, what would be the best solution? I really need your help as this is a source of income for me and I did not do anything wrong to get blocked.
Comment: Unfortunately, nobody can tell you how to deal with this specific site without knowing how their mechanism works, which is why guidance on breaking specific systems is off topic here.  Tor may or may not help.  They may block it, flag it, or identify you using other means.  Unless you know for sure, you can only a) try different access methods to see if they work or b) play by their rules, whatever rules those may be.
Comment: Thanks, I thought I did play by their rules, in fact I still don't know why I was blocked, by I have a strong suspicion it's because both myself and my husband have separate freelancing accounts and for some reason they don't like to see two account from the same IP. Perhaps they think I am trying to log in under a different name. If I could talk to them I would explain, but they're unresponsive so far.
Comment: From what i understand all you want to do is be able to create news accounts and avoid banning for using same ip for two accounts? If yes i can tell you how , i do not think you have to "play by the rules" its your PC and persistent cookies are invasive unethical and the choice for anything should always belong to YOU. Just clarifies to me what you want and i can write an answer
Comment: Also providing the link to the specific site can helps too
Answer: Not inherently, no.
Cookies and IP addresses are independent.  However, if you use the same browser for Tor and non-Tor access to the site, the same cookies will be sent both times, negating any benefit you would otherwise gain from using Tor.
Tor is not a cure-all for anonymity issues, it's merely one tool to use.  There are many ways you can be tracked other than through your IP address, both technical (eg. logging in to an account known to belong to you) and social (eg. personality traits known to be associated with you).  Gaining anonymity with Tor requires understanding these methods and how to counter them.  See, for example, the Tails warning page.
Comment: Thank you. I am not a programmer and what I am trying to do is offer services on a freelancing site. They have suspended my account because (I suspect) both myself and my husband have accounts and it detected two different logins from the same computer. The block was automatic. There is no way to discuss this with them as they don't really get back to you other than say "We'll look into it." From other users' experience the block disappeared in two months - too long for me. I need a way to create a new account with them so that their system can't connect my new account with the blocked one.
Comment: Someone suggested using Firefox Portabe, because "It is totally self contained and does not write anything to your registry or use your existing profile" (so it won't copy zombie cookies). If I install TOR, then Firefox Portable, and only use that browser to access the freelancing site, will that solve my problem?
Comment: It sounds like it may take care of the technical aspects, but not the social ones.  Further, most websites consider block evasion to be a worse offense than whatever the original block was for -- by evading a two-month block, you risk the block becoming permanent if you're caught.
Answer: If you were to use the TOR Browser Bundle, you would be using a browser that starts fresh every time that it runs with a new IP. It will also block plugins to prevent your real IP from being discovered through them. However, you could get banned for using TOR to have an account, because someone else may log in with the same IP address or they could just block TOR exit nodes to prevent abuse.
Answer: The internet works in a set of layers. Each one supposedly independent of one another. Up at the top, where the session layer sits, the cookies are meant to maintain the identity of the web user. Since IP addresses can shift and change, what people are really interested in is the identity associated with the cookie itself, which is why you see so much effort in creating and maintaining persistent cookies - these are the tokens that enable everything on the interactive web to work.
The use of the tor networks do not provide full anonymity. They provide good enough security but are not completely anonymous.
Answer: Yes, they can see your IP address and even more but that's not because of their cookies but rather other avenues (e.g, your headers sent from browser).
However the words "persistent or permanent" + cookies add a deeper cause of concern, because this means that even if you set your browser to delete cookies after each close or manually tell it to delete cookies, the cookie will regenerate itself again even without visiting the website again (I could give you a deep technically explanation for this but I won't - if you want to know more about this read about on Wikipedia).
No, using TOR will not add any benefit but rather call more attention to you and as Wikipedia states "In 2013, a top-secret NSA document was leaked by Edward Snowden 3 citing Evercookie as a method of tracking Tor users." If you log on your account via TOR they'll know it is you...
But don't give up on your privacy yet! There are some things you can do to delete these nasty cookies.
Unfortunately I'm too tired to write a tutorial for Firefox and Chrome now so I'll add links where you can see step by step what you can do and anyone feel free to edit my answer and add it if want.
For Firefox on Chrome you can't do that automatically (I think Google does not really want to fix this since its a old problem) so you will have to manually clear folders  see here.
I have found an interesting open-source software that claims to combat evercookies automatically on many browsers github download and the claims.


How to place same canvas on multiple cameras in Unity?

Question: I know how to do It on one, but I don't know how to do it using multiple cameras, 3 of them are important, i want to show the whole UI except for the minimap. I need to change the camera angle on some spots, while keeping the same canvas for displaying the number of coins XP and the current level.
Comment: Set the cameras as the main-camera when changing into them, through script?
Answer: Option 1:
Set the canvas to be a Screen Space - Overlay
This mode means that the canvas renders last directly to the screen (in screen space), regardless of which cameras are active and how they're displaying what they display.
Option 2:
Set the canvas to be a Screen Space - Camera and change which camera it renders on when appropriate.
This mode means that the canvas is the last thing rendered by the indicated camera and will only render on that camera's view (and if another camera renders afterwards, it will render over the canvas). By changing which camera is active you also change which camera the canvas renders to, you maintain the visibility of the canvas.
Option 1 is likely the preferred solution, but depending on your exact needs and camera setup, Option 2 might be what you're looking for.
Comment: Not actually how SSC works, at least not in current version Unity. It actually puts the canvas on a plane in front of the camera, which can in case environment clipping. It is possible to configure to only exist epsilon away from the ncp, but artifacts can persist; especially with very fast-moving or erratic cameras.
Answer: Here is a simple solution: duplicate another canvas then set this canvas to new camera.
You could use this simple script to read the raw_image texture from the target canvas:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class CameraTexture : MonoBehaviour
{
    public RawImage camera_texture;
    private RawImage rawImage;
    // Start is called before the first frame update
    void Start()
    {
        rawImage = GetComponent<RawImage>();
    }

    // Update is called once per frame
    void Update()
    {
        rawImage.texture = camera_texture.texture;
    }
}


Dissmiss alertview created by LMAlertView on outside tap

Question: I used LMAlertView to custom the AlertView which shown in GIF http://imgur.com/a/Bu8PR
Q: How to dismiss this alertview on outside tap?
I tried some solution shown in Dismiss modal view form sheet controller on outside tap.
The AlertView dismissed with code but the view also lost control and get the error message below
Unbalanced calls to begin/end appearance transitions for <LMEmbeddedViewController: 0x12fd03bf0>.

For the above error i tried to set [self dismissViewControllerAnimated:YES completion:nil]; animated form YES to NO or use dispatch_async(dispatch_get_main_queue(), ^{ to contain [self dismissViewControllerAnimated:YES completion:nil];, but still didn't work.
Solution:
[[self presentingViewController] dismissViewControllerAnimated:YES completion:nil];

Answer: Solution:
[[self presentingViewController] dismissViewControllerAnimated:YES
completion:nil];


Avoid re-enabling patches between reruns in Ollydbg

Question: In Ollydbg 1.1, when I create on the fly patches, they're automatically disabled when I restart the application (the debugged one, not Olly) and I have to enable them manually again.
Is there a menu option I missed, or a script that can keep those enabled between restarts ?
Comment: This post is more appropriate as a comment vs an answer. Last time I had a similar hassle where I wanted keep on the fly changes in olly, I just wrote up a dll patch and after injecting attached olly. But there was a significant number of patches so it was worth the effort.
Answer: Fly patches are what they are : fly patches. So it is the normal behavior that they don't load whenever you restart the program.
If you want to keep your patches between two executions, you've got two solutions :

Patch definitely your binary, so you won't have to do the patches again :
After you make a change to the code, highlight the changes, right click on it, choose 'Copy To Executable'. You can choose the current selection of what you just changed, or, you can choose to copy all changes to the executable.
When you select one, it will popup a new window which is the new file, right click in the new window that popped up, and choose 'Save file' and it will save the changes to the given file that you choose.
Step by step animation : http://i.imgur.com/G1J7EVP.gif
Use a plugin such as Multiline Ultimate Assembler so you can write your patches, save them and load them whenever you want during execution time.
Answer: ctrl+p -> space keep it pressed for multiple activation
source code for enable patch plugin (to automate  the keystrokes posted above)
#include <windows.h>
#include "plugin.h"
#pragma comment(lib,"user32.lib")
#pragma comment(lib,"odbgvc10.lib")
/*
compiled and linked with
@call "C:\Program Files\Microsoft Visual Studio 10.0\VC\vcvarsall.bat" x86
cl /nologo /Zi /Zp1 /W4 /EHsc /O1 /J /FD /c /analyze /TP /WX patcha.cpp
link /nologo /dll  /RELEASE /incremental:no /debug patcha.obj
*/
int Enablepatch() { //use once to activate use again to deactivate all patches
  Createpatchwindow();
  t_table *patch = (t_table *)Plugingetvalue(VAL_PATCHES);
  int patches = patch->data.n;
  Selectandscroll(patch,0,2);
  for(int i=0;i<patches;i++) {
    SendMessage(patch->hw,WM_KEYDOWN,VK_SPACE,MapVirtualKey(VK_SPACE,0));
  }
  return 0;
};

BOOL WINAPI DllMain( HINSTANCE , DWORD , LPVOID ) { return 1; }

extc int _export _cdecl ODBG_Plugindata( char shortname[32] ) {
  strcpy_s( shortname,30, "patcha" );
  return PLUGIN_VERSION;
};

extc int _export _cdecl ODBG_Plugininit( int ollydbgversion, HWND , PULONG ){
  if (ollydbgversion<PLUGIN_VERSION) { return -1; }
  Addtolist( 0, 1, "patcha Plugin by blabb" );
  return 0;
};

extc int _export _cdecl ODBG_Pluginmenu( int origin, char data[4096], PVOID ) {
  switch (origin) {
  case PM_MAIN:
    strcpy_s( data, 4000, "0 &patcha" );
    return 1;
  default: break;
  };
  return 0;
};

extc void _export _cdecl ODBG_Pluginaction( int origin, int action, PVOID ) {
  if (origin==PM_MAIN) {
    switch (action) {
    case 0:
      Enablepatch();
      break;
    default:
      break;
    };
  };
};

                   .


What's the difference between using RDFS/OWL versus XML?

Question: I was wondering what advantages the ontology languages of RDFS/OWL has over using a tagging/markup system (such as http://www.schema.org/) for managing and creating metadata?
Comment: The inference engine, that's what. Which surprisingly none of the answers below talk about. Engines such as Jena can infer new data and make use of transitive properties.
Comment: @AndrewFinnell post a more detailed explanation as an answer please
Comment: Andrew, I agree and would vote up your answer. The currently existing answers below are uninformed and of low quality.
Comment: @AndrewFinnell, I also would like you to post your own answer, also I wonder if inference is beyond the scope of the OP or not. *(I originally thought so, but then maybe it isn't)*
Answer: Your question makes little sense as is. RDFS is a very basic schema language to express RDF constraints. OWL is more advanced schema to express a complicated ontology. They have absolutely nothing in common with XML except that they can be expressed in XML.
Answer: Couldn't diagree more with ZJR's answer. It is utterly uninformed.

How do you parse Microdata? What does it parse too? RDFa parses to RDF, a common data model that is the thing the Semantic Web has been crying out for. Microdata basically came about because Hickie couldn't be bothered to read the RDF and RDFa specs. It might be easier for a developer, but it's not better for the web (i.e lazy)
For a listing of common OWL vocabularies see below:

http://vocab.org/, http://open.vocab.org/
http://schemapedia.com/
http://prefix.cc/
http://rdfs.org/ns/
http://www.sindice.com/
http://watson.kmi.open.ac.uk/
http://rdfdata.org/
http://esw.w3.org/VocabularyMarket
http://www.umbel.org/lod_constellation.html
http://www.schemaweb.info/
http://swoogle.umbc.edu/
http://schemacache.com/

The next release of RDF is imminent, including new serialisation formats such as Turtle and RDFj
SPARQL 1.1 is also dues imminently. Query federation, property path expression, SPARQL Update and much much more.
The BBC is built on RDF. The Facebook graph API provides RDF (thats right, you can deference a graph URI using the text/turtle Accepts header and get back RDF) and many other big corporations.

So in summary Semantic Web, RDF, RDFS, OWL, SPARQL and all the Semantic Web standards are very much alive and kicking. If you don't believe me, have a look at all the activity on http://www.semanticoverflow.com
Comment: The BBC is built on RDF using BigOWLIM, not microdata. Mircodata is not a canonical data format. It is an addition to HTML. The new Olympic platform is built entirely on RDF, as mentioned in press releases and presentations at their Academy.
Comment: the BBC is build on RDF, though it maps to microdata, so? They rebuilt the site in the 2000-2010 decade at a time when W3C was promising wonderful magical tools to come for RDF, those tools didn't really materialize, RDF is legacy, in there. Solid organizational structure, but awful to share, microdata covers the last mile. (and save the day)
Comment: and then some: a useful SPARQL is been imminent since forever, the wording of the RDF spec used to suck big time and scared most potential implementors away for years. (dunno if they fixed that, did they fix that? *imho, too late, anyway*) and then, the `RDF` nomenclature generates confusions and quarrels all the time.
Answer: RDF/OWL vs XML is false alternative. In fact one of popular serialization is using XML.
Also RDF/OWL vs microformats is false alternative. In fact there are standards that allow using RDF as an microformat, eRDF and W3C's official RDFa with standardized way of embedding it in HTML5.
So truly the question is what the advantage of using standard, W3C approved formats. Reasons are:

there are multiple ontologies already out there including most widely used ones as Dublin Core and FOAF.
multiple triple-stores compatible with RDF/OWL for most any programming language.
various of above mentioned triple-stores feature inference engines with SPARQL interface.

Overall, I don't see any reason why should you go for non-standard, non-W3C microformat.
Answer: RDF and OWL are established standards for encoding semantic data and their schema, on a much deeper and generic level than an ad-hoc markup.
For example, with OWL, you can define new Schema, which will be at least partially understood by other tools (because you can mix different OWL/RDF schema together). This way, you can export from one dataset different "views" of it and have everyone cooperate. Also, you can just "explore" links between objects and their properties.
With microdata, it's basically an ad-hoc, accepted set of things you can apply, not a general semantic platform.
Comment: I'm still confused about how RDF differs from RDFS differs from OWL.... Can those terms be used interchangeably...?
Comment: @WebsterThesaurus RDF is a rather simple language to describe concepts based on triples of Subject-Verb-Object. RDFS is RDF Schema, basically a predefined set of terms to make it easier define what the relations mean.

OWL is an ontology description system, much more powerful than RDFS, but harder to implement
Answer: I would like to start by noting that this answer is not written by an expert in the field. Although I'm a proponent of semantic distributed systems, I think the applications of OWL are currently limited. Although describing precisely the niche in which OWL can be applied would be beyond the scope of this answer, I might be able to bring to light some pro's and con's.
OWL is basically a language which allows the expression of semantic constructs using classification, not unlike the classes you known from OOP and constraints between classes and their instances. One could see it as a more formal and higher-order way to describe relationships you know from a relational database.
To describe and communicate this language, it needs to be serialized to a certain format. There are several formats, of which RDF is just one.
There are three different levels of OWL, allowing for increasing expressiveness, but limiting computability (eg. whether you can find a possible solution to the questions you ask the knowledgebase described by an OWL definition). These are OWL Lite, DL and Full.
The most important advantage of using OWL/RDF is the exchange of knowledge between different knowledge bases (or classification hierarchies) and creating useful inferences without having to engineer all these bases beforehand to allow them to communicate. This is done in part by defining equivalence classes. Using namespaces allows the engineer to ascertain uniqueness; a useful paradigm.
Another advantage is the ever increasing amount of inference engines and query languages. In our networked world, there is a demand for distributed knowledge exchange.
Perhaps an important disadvantage is the relative high complexity of ascertaining the computability of inferences and their space and time constraints. Eg. in OWL full you might be able to ask for inferences which cannot be proven to terminate. Thus, there is certainly a limit to the power of OWL.
OWL knowledge is discrete... there are no half-truths or believe systems. Having these would most likely make the solutions way too complex.
But the most important disadvantage to my taste is that one simply cannot find many good engineers in the field. You'll need a knowledge engineer, one or two computer scientists and a small development team to build even a small knowledge base. Therefor, it is often much cheaper and effective to just use descriptive languages such as XML schema and describe the needed semantics in a human-readable document.
Answer: RDFS is about describing structured data. It would be a lot more useful if it would include methods or functions, so we could describe interfaces with it. Currently you need an extra vocab to do so for example WSDL or Hydra by webservices. I guess there is a vocab for OOP too, I just don't know many vocabs.
OWL is something like XSD, it is about validating your data, for example if you expect a string with at most 20 chars, you use OWL to describe that rule and generate a validator. In theory you could do the same with RDFS and XSD, I have no idea why people had to invent OWL instead of just using XSD. Maybe it is because XSD is not based on RDFS, so for example XSD string is not a descendant of RDFS Literal.
Schema.org describes common classes like Person for example. They create their own RDFS like vocab, which includes Thing instead of rdfs:Class, domainIncludes instead of rdfs:domain, rangeIncludes instead of rdfs:range, and so on instead of using RDFS. Their restricted types are ad-hoc too, they use Text and Number without defining them or connecting them at least to rdfs:Literal or XSD primitives. They don't use XSD or OWL to define restricted types as far as I can tell. I am not sure if there are any restrictions in their vocab, but if so I guess they mention it in the human readable descriptions, so you won't be able to generate a proper validator against schema.org, which you could do if they would use XSD/OWL and RDFS.
So I think the advantage of using standards like RDFS, XSD, OWL that you can write libraries which you can reuse by each document.
Answer: For the purpose of developing future products, RDFS/OWL XML files are to be considered pretty much dead and gone.
They require too much work to express concepts that a custom built solution based on custom text formats would express better, while keeping the data more readable and editable to humans and machines alike. They add no real value and only make life a little more miserable for everybody that stumbles on them. (and has to deal with their namespace nomenclature)
There are gigantic document handling solutions based on them, though, and they were recently developed, deployed, and are in current service. They threaten to linger around for a very long time. Many programmers in the future will undoubtedly suffer from many RDF-and-OWL-inducted WTFs.
Microdata systems, (the validator-friendly version of microformats) like those described in schema.org, present instead a lot of advantages for developers, editors, and readers, alike; both human and mechanical.
RDF concepts (those worth saving) can be mapped (and are actually being explicitly mapped) over microdata representations painlessly.
Microdata items allow authors and document handling systems to enrich communication in a way that's pretty easy (as easy as CSS or DOM) to handle and customize for the reader.
Comment: Uninformative opinionated answer. Please show references to back-up these claims.
Comment: Wait, I don't understand... so how is Microdata any different from XML/HTML? The plan described in schema.org specifically says they use tags inside their webpages... isn't that what XML and HTML do as well?
Comment: And if Microdata is so much better, why is the W3C pushing for RDFS/OWL and not Microdata itself?
Comment: I think that answer is rather misleading, as RDF != XML.
The XML encoding of RDF is just one of many, and was designed with the purpose of being mixed into existing XML Applications.

Moreover, going back to custom systems (yes, including microdata) means going back to "write custom parser for f*cking everything" instead of being able to use generic vocabulary. With RDF/OWL I can mix different applications each working on a subset of data involved, as well as write flexible code that has automatic reflection - good example is Xanasys LinkExplorer.
Comment: @Dibbeke My original guess was that the OP was looking for pragmatic metadatas. RDF in that case is overkill.

The opininated part is relative to *my belief in RDF being always an overkill*.
Comment: @ZJR Perhaps in saying "for the purpose of developing future products", you assumed the OP was an illiterate and incompetent engineer, unable to even think of systems of a higher degree of complexity. When does metadata become "pragmatic"?


Should I use all past tense in this case?

Question: If talking about the ex experience , the verb and be-verb of the context should always be past tense ?
For ex.  If I  am talking about my ex experience of meeting an exchange student with my friend . In my conversation : I met an exchange student when I was in university and we became friends . (1)She "was "  Japanese . (2)She really "liked" Snoopy , so before she came back to Japan , I bought a Snoopy doll as gift to her.
 I used ".    "  because I was not I should use past tense or present tense there .
What confuse me is if I use "was" in sentence (1) , dose it mean she is not Japanese now ?  And for sentence (2), if I use "liked " , does it mean I thought she may not like Snoopy now ?(But I am quite sure she still like Snoopy now)
Comment: Note that we do not use *ex* to mean "former" or "past" in this sort of context. *Ex* designates a former role which has **ended**--ex-president, ex-boyfriend--but an "experience" is permanent, and it is not a role.
Comment: I'd say "past experience", to distinguish it from something which you are "experiencing" now. An experience is an event, located at a specific time, but it results in an "experienced" state which is permanent. :)
Comment: Hi , StoneyB , thank you for noticing it. So can I say " former experience " ? Or just "experience " is ok?
Answer: The use of the past tense in those examples, to me as a native speaker, implies that your interactions with that person have now ended.
If, however, you used the present tense, then that implies that you still talk to/see that person. For example:

I met an exchange student in university. She really likes Snoopy.

The act of meeting the person obviously happened in the past, and needs the past tense, but she still likes Snoopy.

I met an exchange student in university. She really liked Snoopy.

This version with the past tense would be used if either she no longer likes Snoopy, or you do not know if she still likes Snoopy for some reason, such as you no longer talk.

I met an exchange student in university. She was Japanese.

Here, a person's nationality isn't (normally) going to change, so the past tense implies that you don't talk to this person any more.
Comment: I think this is right. Using the past tense does create ambiguity with *"used to like snoopy"*. Despite this, I think we still like to use past tense here because [it's best practice to continue in the past tense when reporting speech](https://www.theguardian.com/guardian-observer-style-guide-r). I suspect that "She was Japanese" feels more distant is because it's in the style of "She stated that she was Japanese.", which (as you point out) doesn't suggest a continuing relationship.
Comment: @ChengShihMing Correct, yes.
Comment: Hi , Dan , thank you so much  for your explanation, . It really helps a lot . So if I still keep in touch with her , then I should use She "is " Japanese , right ?
Comment: I wouldn't automatically infer that they don't talk anymore. I would only infer that she's not physically around anymore.
Comment: Meanwhile, I would definitely agree with @NathanCooper here re: continuing in the past tense in cases of reported speech.


Displaying urls with case sensitivity

Question: I just bought the domain name http://www.startupsandfinance.com/. During the registration process I tried to buy it like http://www.StartupsandFinance.com/ but could not do that because they ignored it. Is there any way that the website can show up in the search results as http://www.StartupsandFinance.com/ as it looks more readable.
Answer: No, the domain name system is case insensitive.

Intercapping is often used to emphasize the meaning of a domain name.
  However, DNS names are case-insensitive, and some names may be
  misinterpreted in certain uses of capitalization, creating slurls. For
  example: Who Represents, a database of artists and agents, chose
  whorepresents.com, which can be misread as whore presents. Similarly,
  a therapists' network is named therapistfinder.com. In such
  situations, the proper meaning may be clarified by use of hyphens in
  the domain name. For instance, Experts Exchange, a programmers'
  discussion site, for a long time used expertsexchange.com, but
  ultimately changed the name to experts-exchange.com.
Intellectual property entrepreneur Leo Stoller threatened to sue the
  owners of StealThisEmail.com on the basis that, when read as
  stealthisemail.com, it infringed on claimed (but invalid) trademark
  rights to the word "stealth".
Comment: I once bought a domain name, named `TECHNOLOGY ARENA.com`. In Google search results, it was the only domain who used to be displayed in all caps.
Comment: @www.AppTec.net Let me be clear, not only does Google not display URLs with case, the DNS system itself is *case insensitive*. The registrar didn't ignore your attempt register a domain with caps in it, it's that it simply isn't possible.
Comment: Experts Exchange never used that domain name. It did own it for quite a while, but it lapse several years ago. However, you're more than welcome to perpetuate the myth. Eric Peterson / Netminder Senior Administrator, Experts Exchange
Comment: Hello. Just read it on [Wikipedia](http://en.wikipedia.org/wiki/Experts-Exchange#Trivia).
Comment: Funny that you don't know the history of your own site. Here's a link to the way back machine history of your site http://web.archive.org/web/20000622011822/http://expertsexchange.com/
Comment: It appears you were using it between 1999 and 2004
Comment: And here's the snopes entry http://www.snopes.com/business/names/domains.asp

Displaying urls with case sensitivity


What caused Oxnard to have such an amazing punk scene?

Question: Why and how did bands like RKL, Ill Repute, Agression, Stalag 13, and Dr. Know come up and be so freaking awesome?
Answer: Big generalisation: great music tends to come out of two sorts of places. Either places where music is accepted, and thrives, and the place encourages it : Austin, Nashville, wherever. Or the opposite, where the edginess or boredom of the place drive people to make great music as a way out : Woking, UK,  subject of the Jam's "Town called Malice", Coventry, UK subject of the Specials' "Ghost Town". Looked at that way, Oxnard seems to be the second kind of place.
But also where a cluster of bands come out of the same place at the same time, there has to have been someone to come first, and make some music that caught how people were feeling at the time. Without that, nothing would ever happen. Not sure who came first, with Oxnard or even if it's possible to pin that down. And someone to encourage that - Mystic Records, I guess.  I'm basing that part of my answer on independent record labels like Factory records or Rough Trade records, and the various bands and musical scenes they encouraged.
This answer is a view from a distance. An insider's view would also put it down to quirkier local things, I'm sure.


Need help on architecting a multistep wizard using visual force

Question: We are building a 5 to 6 step wizard in visual force where the user is expected to fill up a form on each step of the page.  We plan to use one controller for navigation and 5 visual force pages to handle the input and output fields .Here are things i would need some help.
1. A user can fill the form say 3 steps and abandon and come again later and fill up the form. Has any body done this and if so can you share code snippets or best approach?
2. If a user comes directly and lands on say pag3 of page5, we want the page to check if the form is completed and populate all pages with the data he has filled in. How do we do this?
Any code reference or articles with real examples would really help in this regard?
Thanks
Buyan
Comment: Have you thought up any framework for this yourself? If you have any idea how to do it, add it to your original question and that will give people a better guide on how to help you advance. It will be very difficult to write a guide on creating a multi-step wizard with these specific requirements without something to start with.
Comment: Have you looked at Visual Workflow? http://login.salesforce.com/help/doc/en/salesforce_vpm_implementation_guide.pdf
Answer: The force.com cookbook has a great example to get your feet wet creating Visualforce page wizards.
http://developer.force.com/cookbook/recipe/creating-a-wizard-with-visualforce-pages
In order to support partial completion of wizards, you'll need to maintain the state of each record as steps are completed.  You can provide your end users a link to the partially completed record if they want to complete the process later they can copy or save the link.  Alternatively, you could look up partially completed records related to running user, and the next time they access your wizard display this list.
Hope this helps.
Comment: Thanks for your comments. My approach has been storing each step in a custom object with an unique id. If the user has an incomplete form, provide him an url to complete the data. How do we store sessionid in a custom object?