Does this system of simultaneous Pell-like equations have any non-trivial positive integer solutions?

Question: Let $a,b,c$ be positive integers satisfying
\begin{align}
2a^2-1 &= b^2,  \\
2a^2+1 &= 3c^2.
\end{align}
The trivial solution is $(a,b,c)=(1,1,1)$. Are there others?
Comment: Continuing @barto's comment, one needs to show that $(2+\sqrt{3})^n + (2-\sqrt{3})^n = \lceil (2+\sqrt{3})^n\rceil$ is not a square. Since the residues are cyclic, and $4$ is already there, any modular attempts will fail. An interesting question, would be nice to see a solution.
Comment: @Supersingularity, good find. And the [answer](http://math.stackexchange.com/a/1690596/269624) there actually treats the problem like it's trivial, whithout solving it
Comment: Indeed that is frustrating. Here is something else someone might be able to do better with: we have $b+a\sqrt{2}$ is a unit in $\mathbb{Z}[\sqrt{2}]$, so it looks like $\pm (1+\sqrt{2})^n$ for some $n$ (really more $\pm$'s but I'm just simplifying. Hence $b = \sum_{k=0}^{n/2} \binom{n}{2k} 2^k$ for some $n$. On the other hand, because $b + c\sqrt{3}$ lies over 2 in $\mathbb{Z}[\sqrt{3}]$, we should have $b+c\sqrt{3} = (\sqrt{3}+1)(2+\sqrt{3})^n$ (something like this). Expanding again, we get another binomial type expression for $b$. Maybe comparing them would force $n$ to give $a=b=c= \pm 1$.
Comment: $2a^2+1 = 3c^2$ is not a Pell equation!
Comment: It is equivalent to $(2a^2-1)(2a^2+1)=3d^2$, that is, $(2a^2)^2-3d^2=1$. By Pell-theory, $2a^2+d\sqrt3=(2+\sqrt3)^n$ for some $n>0$ but I'm not sure how to proceed from here. Certainly $n$ is odd by inspection mod $3$.
Comment: Let $T_k = k(k+1)/2$ denote the $k$th triangular number. Then the system implies there exist integers $\alpha, \beta, \delta$ such that $T_\alpha = 2T_\beta = 3T_\delta,$ _i.e._, there is a triangular number which is simultaneously twice and three times a[nother] triangular number. To prove: $\alpha=\beta=\delta=0$.
Comment: I was trying to prove this on one piece of paper and arrived at the conclusion that the only solution in positive integers for only the first equation is $(1,1)$ but it could be that I am wrong. Do you know for any other solution of only the first equation other than $(1,1)$?
Comment: @Farewell: There are an infinite number, starting with $a=1,5,29,169,985,5741\dots$.
Comment: Right, now I checked my attempt and there was $-$ where it should be $+$. I will keep trying to find an elementary solution to your problem.
Comment: For $a,b,c \leq 1000$ the only solution is $1,1,1$
Comment: @KierenMacMillan are you suggesting $a\in$ [A001653](https://oeis.org/A001653)?
Comment: @AnthonyHernandez: Yes, $a \in$ https://oeis.org/A001653, and also $a \in$ https://oeis.org/A054320. The conjecture that there are no non-trivial solutions is, I suppose, equivalent to the conjecture that https://oeis.org/A054320 $\cap$  https://oeis.org/A001653 $=\{1\}$.
Comment: My old "answer" was incorrect, but I found the same question asked here which may be useful: https://math.stackexchange.com/questions/1690550/solutions-to-simultaneous-diophantine-equations-2y2-3x2-1-and-z2-2y2-1?rq=1. I'll try to think if I can rework the algebraic number theory method.
Comment: @Piquito: Fixed (I think?).
Comment: @KierenMacMillan: That's right. Regards.
Answer: ${\bf Summary:}$ We prove that for any positive integer solution $a$, $b$ and $c$ to the given equations there exist $x,y\in \Bbb{Z}$ such that
$$
4a=x^2+3y^2,\quad b=\frac{|x^2-3y^2|}{2}\quad\text{and}\quad c=|xy|.
$$
We insert these values into the second equation and obtain
$(3(x^2-y^2))^2=8(x^4-1)$ which implies $x^2=y^2=1$, hence $a=b=c=1$.
${\bf Edit:}$ Thanks to a hint of Zhoraster to the rational slope method, the first part has been simplified.
Assume $a$, $b$ and $c$ are an integer solution to the given equations. Adding the two equations we obtain:
$$
4a^2=b^2+3c^2\quad\Rightarrow\quad 1=\left(\frac{b}{2a}\right)^2+3\left(\frac{c}{2a}\right)^2.
$$
So $\left(\frac{b}{2a},\frac c{2a}\right)$ is a rational point of the ellipse
$$
1=u^2+3v^2.
$$
If $u,v\in\Bbb{Q}$, then the slope of the line through $(u,v)$ and $(1,0)$ is rational, i.e., there exists $t\in\Bbb{Q}$ with $t(u-1)=v$.
But then, if $(u,v)$ is on the ellipse,
$$
1=u^2+3(t(u-1))^2\quad \Rightarrow\quad (u-1)(3t^2(u-1)+u+1)=0.
$$
If $u\ne 1$, we obtain
$$
u=\frac{3t^2-1}{3t^2+1}\quad\text{and}\quad v=t(u-1)=-\frac{2t}{3t^2+1},
$$
so all rational points of the ellipse different from $(1,0)$ are parametrized by $t\in \Bbb{Q}$. Write $t=\frac yx$ for some coprime integers $x,y$,
then
$$
u=\frac{3y^2-x^2}{3y^2+x^2}\quad\text{and}\quad v=t(u-1)=-\frac{2xy}{3y^2+x^2}.
$$
In particular, for $(u,v)=\left(\frac{b}{2a},\frac c{2a}\right)\ne (1,0)$ there exist $x,y$ coprime integers, such that
$$
\frac{b}{2a}=\frac{3y^2-x^2}{3y^2+x^2}\quad\text{and}\quad \frac{c}{2a}=-\frac{2xy}{3y^2+x^2}.
$$
Now $x,y$ cannot be both even, since they are coprime, and if one is even and the other is odd, then $3y^2-x^2$ and $3y^2+x^2$ are both odd, which
contradicts $\frac{b}{2a}=\frac{3y^2-x^2}{3y^2+x^2}$, since $2\not|b$. So $x$ and $y$ are both odd. Moreover, if $3|x$, then we can set
$x_1=y$, $y_1=\frac x3$, and then $x_1, y_1$ are coprime, $3\not| x_1$ and
$$
\frac{b}{2a}=\frac{x_1^2-3y_1^2}{3y_1^2+x_1^2}\quad\text{and}\quad \frac{c}{2a}=-\frac{2x_1y_1}{3y_1^2+x_1^2}.
$$
So, we have achieved the following result: If $a$, $b$ and $c$ are integer solutions to the given equations, there exists $x,y$ coprime odd integers,
such that $3\not| x$ and such that
$$
\frac{b}{2a}=\pm\frac{3y^2-x^2}{3y^2+x^2}\quad\text{and}\quad \frac{c}{2a}=-\frac{2xy}{3y^2+x^2}.
$$
Since $gcd((3y^2+x^2)/2,xy)=1=gcd(c,2a)$, we have
$$
c=\pm xy, \quad \pm 4a=3y^2+x^2\quad\text{and}\quad b=\pm\frac{3y^2-x^2}2.
$$
Now we insert these values into the second equation $2a^2+1=3c^2$ (or in the equivalent equation $16a^2+8=24 c^2$) and obtain
$$
(x^2+3y^2)^2+8=24x^2y^2\quad \Leftrightarrow \quad (3(x^2-y^2))^2=8(x^4-1).
$$
By the Lemma below, in $\Bbb{Z}$ the solutions of this equation satisfy $x^2=1$ and $x^2=y^2$,
hence $(a,b,c)=(1,1,1)$ is the only positive integer solution.
${\bf Lemma:}$ The only two integer solutions of $R^2=8(x^4-1)$ satisfy $R=0$ and $x^2=1$.
${\bf Proof:}$ Evidently $R=0$ and $x^2=1$ give solutions. Assume by contradiction that $x\ne \pm 1$. We also can assume that $x>0$. We have
$$
R^2=2^3(x^2+1)(x+1)(x-1),
$$
and clearly $x$ is odd (else $2^3$ would be a square).
Since
$$
gcd(x^2+1,x+1)=gcd(x^2+1,x-1)=gcd(x+1,x-1)=2,
$$
any prime $p>2$ which divides $x^2+1$ cannot divide $x+1$ or $x-1$, hence $x^2+1=2^i r^2$ for some $i,r\ge 1$, with $r$ odd.
Similarly $x+1=2^js^2$ and $x-1=2^k t^2$ for some $j,k,s,t\ge 1$, with $s,t$ odd.
Moreover, since $2^{i+j+k+3}$ is a square, necessarily $i+j+k$ is odd. But, if $i$ is even, then $x^2+1=(2^{i/2}r)^2$, which is impossible,
since $x\ne 0$. So $i$ is odd and $j+k$ is even.
We have
$$
2=x+1-(x-1)=2^j s^2-2^k t^2\quad \Rightarrow\quad 1=2^{j-1} s^2-2^{k-1} t^2,
$$
and so $j=1$ or $k=1$, hence both $j$ and $k$ are odd.
But then $1=(2^{(j-1)/2}s)^2-(2^{(k-1)/2}t)^2$, which is impossible, since $t>0$.
This contradiction concludes the proof. $\Box$
Comment: In fact, the part until the last lemma is proved easier. One may add the equations, yielding $4a^2 = b^2 + 3c^2$. The last equation is solved in a standard way by considering rational secants of $x^2 + 3y^2 = 4$, yielding exactly your first claim.
Comment: @san, http://math.rice.edu/~evanmb/math499spring10/vigrenotes3.pdf.
Comment: @zhoraster: Well, with that parameterization, plus san's last lemma, there's the elementary proof I wanted.
Comment: Seems nice! I'm going to let it sit for a day or two while I (and others) look it over, and then accept if no flags are raised.
Comment: Would still be nice to find an elementary solution, of course — but that won't stop me from accepting this answer.
Comment: @zhoraster: I'm no longer confident it can be fixed. Award the full bounty to san when you're ready.
Answer:
NOTE: As pointed out by Erick Wong, there was a flaw in the original proof. It may be fixable, though I haven't found a fix yet; leaving here for history (and just in case anyone else can take this method to the goal line).

Theorem. The Diophantine system of equations
\begin{align}
2a^2-1 &= b^2, \\
2a^2+1 &= 3c^2
\end{align}
has only the trivial solution $\lvert a\rvert = \lvert b \rvert = \lvert c \rvert = 1$.
Proof. Evidently, $\lvert a\rvert = \lvert b \rvert = \lvert c \rvert = 1$ is a solution. We also see that $\lvert c \rvert = 1$ forces $\lvert a\rvert = \lvert b \rvert = \lvert c \rvert = 1$. We now assume, contrary to the theorem, that there is a solution with $bc > 1$ [positivity assumed without loss of generality].
Multiplying the two original equations yields
\begin{align}
  (2a^2-1)(2a^2+1) &= (b^2)(3c^2)  \\
  (2a^2)^2 - 1 &= 3(bc)^2.
\end{align}
Evidently $bc$ is odd, say $bc=2u+1$ for an integer $u \ge 1$ [because $bc > 1$]. There are exactly two cases to consider.
Case 1: $a \equiv 1\!\pmod{3}$. Say $a=3v+1$ for an integer $v \ge 1$ [because $a > 1$]. Substituting, expanding, and simplifying yields
\begin{align}
  \bigl(2(3v+1)^2\bigr)^2 - 1 &= 3(2u+1)^2  \\
  324v^4 + 432v^3 + 216v^2 + 48v + 3 &= 12u^2+12u+3  \\
  v(3v+2)(9v^2+6v+2) &= u(u+1).
\end{align}
Since all the factors are positive [by hypothesis], the Fundamental Theorem of Arithmetic implies there exist positive integers $p,q,r,s$ such that
\begin{align}  \tag{1}
v(3v+2) &= pq, &
u &= pr, \\
9v^2+6v+2 &= rs, &
u+1 &= qs.
\end{align}
The left-hand pair of relations implies $rs-3pq=2$, and the right-hand pair implies $qs-pr=1$. Solving these two equations for $q$ and $r$ in terms of $s$ and $p$ yields
\begin{align} \tag{2}
q &= \frac{s+2p}{s^2-3p^2}, &
r &= \frac{2s+3p}{s^2-3p^2}.
\end{align}
Since $q$ and $r$ are both integers [by hypothesis], it must be that $s^2-3p^2$ divides both $s+2p$ and $2s+3p = 2(s+2p)-p$, and so it must divide $p$. But $qs-pr=1$ implies $\gcd(p,s)=1$, and hence $\gcd(s^2-3p^2,p)=1$. Therefore we conclude $s^2-3p^2 = \pm 1$; since $s^2-3p^2=-1$ has no integer solutions, we have $s^2-3p^2=1$. Substituting this into (2) gives $q=s+2p$ and $r=2s+3p$.
[PROOF INCORRECT AFTER THIS POINT]
NOTE: One can quickly deduce that $(s,p)$ and $(r,q)$ are consecutive solutions to $U^2-3V^2=1$, with $r>s$ and $q>p$. Since $(2a^2,bc)$ is also a solution, we can let $(s,p)$ be the $n$th solution, so that $(r,q)$ is the $(n+1)$th, and $(2a^2,bc)$ is the $(2n+1)$th. One can then show [using standard elementary Pell theory] that $(b,c)=(q+p,s+p)$, so that $b-c=2p$. From that point, I can't get any more useful information with this method.
Comment: Sorry, there's a typo in the line where $r-q$ is first calculated: $r-q = s+p$, not $s-p$.  This seems to eliminate the contradiction of $(s-p)^2 = s^2 - p^2$.
Comment: From  the last system I only obtain $(3p^2-s^2)(3q^2-r^2)=1$. How you obtain $qs=1$?


Very slow 3G internet connection on Ubuntu 11.10

Question: I installed Ubuntu 11.10 on Dell laptop. I connected a phone with 3G connection to the laptop using bluetooth for internet. The net is very slow...How can I fix this?? It was pretty fast on windows
Comment: wait... what you stated in here is 3G tethering, not Dialup.  Which is it?  (Dialup is where you have to have your computer dial a phone number in order to connect to an internet server, and has been pretty sparsely seen in the USA since about 2000 :/)
Answer: the problem is the bluetooth, data transfer via bluetooth is very slow. If the function is available, use USB or better still if your phone is a smartphone, set up a portable wi-fi hotspot. I hope this helps.


Archipack in Blender3.0

Question: B"H  Archipack worked in Blender2.93  After upgrading to 3.0, archipack is no longer in Preferences.  How to reinstall?  Thank you.
Answer: Hi I was wondering the same thing (11 months later). Archipack was removed from Blender 3.x releases. You can download the original free version that shipped with blender, aka the 'community edition' for a donation or the full (paid) version.
All details are here: https://github.com/s-leger/archipack/wiki

Archipack in Blender3.0


Why does adding a new external function increase gas for calls to all other functions?

Question: I have added a new external function to my Solidity smart contract.
When checking the gas usage for calls to other already existing external functions, I see the gas usage has increased slightly. Does anyone know why this is? and if the gas increase can be avoided?
Answer: As you have not provided any code, I am writing down a possible reason for this.
It's not because of the external visibility. It's because EVM calls the function on a sorting basis.
Let's say you have 3 functions
function green() public pure returns (string memory) {
    return "green";
      //costs 750 gas
}

function blue() public pure returns (string memory) {
    return "blue";
    //costs 728 gas

}

function red() public pure returns (string memory) {
    return "red";
    //costs 706 gas
}

These functions have their own signatures like this:
"ed18f0a7": "blue()",
"f2f1e132": "green()",
"2930cf24": "red()"

When we call a function, the EVM iterates through this object and matches the function signature that we provided. And that iteration costs gas.
This iteration happens in ascending order, for example in the above function signatures, if we try to call any of the three functions, the EVM will first check the red(2930cf24) function, if it doesn't match the one we called then it will check the blue(ed18f0a7) one, and at last the green(f2f1e132) function.
With this logic, you can see the gas difference while calling the above functions.
If we remove the blue and red function from the above code, then the green function will cost exactly 706 gas which is equal to what red cost before. Because this time EVM didn't have to iterate through 2 more function signatures.
Let me know if this was clear, also share the code and gas differences in case there's any other reason for this.


On Lutris, Epic Store games running on Integrated Graphics despite Epic Store launcher itself running on Dedicated GPU

Question: My laptop has an AMD Hainan Dedicated GPU and Intel Integrated Graphics 520. I installed Epic Games Launcher from the install script provided on the Lutris' website. I ran Lutris with DRI_PRIME=1 and then, ran Epic Store Launcher. I monitored my dGPU usage through radeontop. My laptop is perfectly using my dGPU when running Epic Games launcher, but switching back to Intel Integrated Graphics when running GTA V through it. Please suggest me how to run GTA V from Epic Store on my dedicated AMD GPU.
Comment: Kubuntu 20.04 LTS
Comment: If you can disable the iGPU that would be a an assured solution. Other than that you need to find a way to prime select the actual game directly instead of the store. Lutris is NOT Steam.
Comment: I don't think I will be able to disable iGPU as my laptop display is directly connected to it and dGPU rendered frames has to pass through it to reach my display. I also made 'DRI_PRIME=1' as global environment parameter in my OS to render every possible thing through my dGPU. But still facing the same problem.
Comment: No, it works on both or just the dGPU, I never seen a hybrid graphics laptop requiring the iGPU for external connections. The reason being if you're using a monitor then you're near an electric outlet so the reduced battery life due to using the dGPU is moot.
Comment: Are you talking about an external monitor connected to my laptop? I was talking about my laptop display. I do not use an external monitor. If you are talking about my laptop display, then please tell me how to diable iGPU completely. I made 'DRI_PRIME=1' as global environment parameter. Still, my problem persisted.
Answer: After searching on internet for solutions, I came to know that it is the problem of my radeon GPU driver. Apparently there is some issue of Vulkan support with this driver(Reference Article Here). My GPU is also supported by amdgpu driver. It was also present in my laptop, but my Linux distro selected radeon by default.
I followed this article and switched my driver from radeon to amdgpu
and now, nearly everything runs on my dedicated GPU. The problem with my Epic Store games is now solved and few Steam games, which were earlier not detecting my dGPU are now running on it. There are a few performance issues though. I am working on it.
Though I have little qualification to comment on this, but I recommend that the distros should be configured to select the latest drivers for the hardware wherever possible. This could minimise the compatibility issues to a great extent. I have seen on the internet that many gamers are facing this driver issue(especially the ones which have slightly older hardware), which is an unnecessary hassle. Lesser issues will attaract more gamers to Linux.


how to debug RMI/IIOP through internet?

Question: I have a client/server applciation that communicates through JNDI/RMI/IIOP using, on client side, some Glassfish client code (NOT packaged as a Glassfish client) and on server side a Glassfish instance.
I have some Glassfish multimode scripts that I use to make sure the domains I create on any machines are totally identical and correctly configured.
Using that script on local network, I have already made sure I could access a remote Glassfish server instance from client code on my machine (that was quite a reasonable guess, however I tend to test all things I'm not totally sure of).
Next step is to have that client/server application working over (I should instead say "through") internet : with my client code in my company LAN (in other words on my machine) and my server code on an Amazon VM running my Glassfish server. For some reasons, the remote Glassfish is running on a Windows VM.
Obviously (as I ask that question, you can safely guess the through internet test is NOT working. And you're right.
So, to have more guesses, I started SmartSniffer both on my machine and on server.
On my machine, I can only see one TCP packet going to that server instance (and nothing coming back).
On server instance, I can see one packet entering (the client query) and one packet exiting (the server answer). That server answer looks like this :

[4/4/2012 11:47:13 AM:917]
  GIOP.......(................NameService....._is_a...................NEO................ª.......(IDL:omg.org/SendingContext/CodeBase:1.0............n........172.27.63.145.Ô2....¯«Ë........e...........................
  ...................
  ...   ...........&...............(IDL:omg.org/CosNaming/NamingContext:1.0.

That 172.27.63.145 address is my IP in local network.

[4/4/2012 11:47:13 AM:917]
  GIOP.......2............NEO................0.......(IDL:omg.org/SendingContext/CodeBase:1.0............ô........46.137.114.###.'5....¯«Ë........d...........................
  ...................
  ...   ...........&...........!...|...............$...
  ...f............10.241.42.###.'6.@........g..............g........default...................g...............+IDL:omg.org/CosNaming/NamingContextExt:1.0.............¢........10.241.42.208.'5...M¯«Ë....
  ...d...   S1AS-ORB............RootPOA....
  TNameService............................... ...................
  ...   ...........&......

That 46.137.114.### is external one of my Amazon VM, and 10.241.42.### is its internal IP in amazon magical virtual server.
So it seems server is answering, no ?
But that answer never finds its way to my machine in my network.
So ... how can I check where it get lost ? Seems likepacket sniffer has done its job, but what can I do now ?
NOTE This question is a clarification of "How to Connect a glassfish client to glassfish server over NATs?"
Answer: Perhaps stupid question, but is your Amazon EC2 instance is configured with all required ports   open for your communication protocol to work? You could see configured open ports in security group your instance assigned to in AWS console, under EC2->Security Groups.

how to debug RMI/IIOP through internet?


Working configuration for transparent FTP caching proxy with Squid3 and IPTABLES

Question: Does anyone have Squid3 working to successfully cache FTP requests coming in transparently?
Should the proxy still listen on 3128, and I redirect incoming reuests on 21 to 3128?
Answer: Squid doesn't support FTP transparanet proxying. Squid is an HTTP proxy and only supports HTTP connection in its listening port. SO HTTP tranparent proxy only works for Squid. If you really need a transparent FTP proxy, use Frox
Squid support FTP proxying when you configure it manually in the browsers because browser request FTP object using HTTP messages in that case.
Comment: More specifically, Squid can passthrough FTP traffic (or any TCP traffic actually) via `CONNECT` requests. However it only passes through whatever data there is and can't cache nor interpret that traffic.
Answer: As far as I know there is no Proxy that will support FTP transparently.
This is partly because FTP in some ways is a more complex protocol the HTTP.  HTTP uses a single TCP connection for everything.  FTP uses a separate TCP connection for the control channel, and for data transfers.  The additional connection details for the additional TCP connections are negotiated between the client and server within the control channel.
An ftp transparent proxy would be far more complicated for FTP then HTTP.
Comment: Squid doesn't support transparent FTP proxying, but Frox yes.


variable-watches stopped working in vs2010 / C# debugging

Question: I've got a major problem here.
Whenever I debug a C#-solution, set a breakpoint and try to inspect a variable-content nothing happens. I can't see it when I drag it into a watch-window ("unable to evaluate the expression.") - the Autos and Locals windows are just empty, Immediate Window just tells me "Unable to evaluate the expression") and even the memory-windows just give me "Unable to evaluate the expression.".
When I switch to F# everything works just fine - VB.net is gone too.
I guess this has something to do with the Async CTP I tried to install.
What I tried so far:
- Deinstalled the CTP
- Tried to repair the VS2010 installation
- Uninstalled/Reinstalled VS2010
Not working - after reinstall VS is starting as ever (with the problems and all settings/installed plugins)
So what? Wipe the system? I hope not.
Answer: Async CTP causes this problem. Try to install SP1 Beta. This solved the problem.


'Only X left Threshold' for each product (not globally)

Question: I would like to show 'Low Stock Notification' on my website.
I have set 'Only X left Threshold' globally.
Is there any possibility to set this for each product individually?
Answer: In terms of concept, I would...

Create a module that generates a product attribute for low stock threshold (integer of course). Ensure the attribute can be set at the appropriate levels (global,  website,  store)
Extend the low threshold core model to include this attribute in the threshold check logic.

Keep in mind that the threshold is used in a few places - the low inventory RSS feed for example.
Answer: Best way, go for @iUseMagentoNow solution. A quick and temporally solution would be to create an attribute temp_qty_left and use a conditional at the frontend
<code>$qtyLeft = $_product->getData('temp_qty_left');
if($_product->getQty() < $qtyLeft) {
    echo 'Only' . $qtyLeft . ' left';
}
</code>


How to import an Axis2 sample project into eclipse?

Question: How to import an Apache Axis2 sample project into eclipse ? I tried to import the project named pojo, but no success.. What folder to import??? It seems that normal importing method doesn't work here.
Answer: Create a new dynamic web project in Eclipse (You need to have Eclipse J2EE version)

Copy the sample pojo source code from the AXIS2_HOME\sample directory to the dynamic web project source code directory

Create a new Webservice from Eclipse

Select Bottom Up and Select the AddressBookService in the package sample.addressbook.service
Make sure you select Axis, and the Project name. Also check the Client options as below,

Click Finish

Move the client code to the client project PojoClient (AddressBookADBClient in package sample.addressbook.adbclient

Refactor the package name and methods to fit the stub automatically generated
I have made 3 changes
Modified the package name to match the stubs
1) //import sample.addressbook.stub.AddressBookServiceStub;
import sample.addressbook.service.AddressBookServiceStub;

Modified the method name to match the stubs
2)//addEntry.setArgs0(entry);
   addEntry.setEntry(entry);

Modified the method name to match the stubs
3) //findEntry.setArgs0("Abby Cadabby");
    findEntry.setName("Abby Cadabby");

One final change in the service, since i was not able to get the test it.
I made the entries variable to static
 private static HashMap entries = new HashMap();

All Set response from SOAP UI

Response from Client Java Code


Is there a Pathfinder first edition Druid archetype that enhances Wild shape generically?

Question: I would like to know about wild shape in Pathfinder first edition. The Shifter class in that system seems restrictive and not nearly as flexible at run-time as Dungeons & Dragons third edition's Shifter prestige class or version 3.5's Master of Many Forms prestige class. I found Ancient Guardian and Feral Shifter which appear to enhance wild shape, but do not allow additional forms to turn into. Is there an archetype that increases the available form options for wild shape?
Answer: One archetype published by Paizo, technically: the Naga Aspirant, which requires being a Nagaji, adds the ability to become a naga without otherwise affecting wild shape.
And, one 3rd party archetype I've found: the Ossuarite, which has an explicit and strong connection to undeath.
Beyond that, I can't find any and don't know of any.
The PFSRD has a list of all of the archetypes that Paizo published along with a fair number published by 3rd party publishers. Where it shines is that each archetype in the list shows what's changed (or removed), so it's a fairly straightforward job to go though those that change some of the Wild Shape entries, at least for a first pass.
Draconic Druid doesn't strictly increase the available forms, instead granting uses of a draconic version of themselves or becoming a medium/large dragon per form of the dragon 1 or 2.
The Kraken Caller similarly restricts the list of target creatures (to "animals with the aquatic or water subtype or that have the amphibious special quality") while allowing the druid to instead grow tentacles that can be used to attack or climb, swim, or perform dirty tricks or combat maneuvers.
The Toxicologist can change into vermin instead of elementals or plants.
The Cave Druid trades being able to take plant form for being able to take the form of an ooze. Their wild shape is also delayed 2 levels.
The Desert Druid trades plants for vermin and has their wild shape delayed 2 levels.
The Mountain Druid trades plants for giant forms (as giant form 1 and 2) and have wild shape delayed 2 levels.
The Treesinger Druid, which requires being an elf, trades being able to become an animal or elemental for enhanced plant options.


Are the Venusian "continents" likely to have existed before the global resurfacing event?

Question: A topographic map of the surface of Venus shows the large highland areas Ishtar Terra, Aphrodite Terra and Lada Terra that have occasionally been described as "continents", plus various other smaller regions such as Beta Regio. Are these "continents" likely to have existed before the global resurfacing event, or is the topography of the planet likely to have been completely altered?
Answer: Ishtar Terra belongs to the tessera type of terrain, "one of the most tectonically deformed types of terrain on Venus", representing ~7.3 % of Venus' surface (Ivanov & Head 2011, Global geological map of Venus). Tessera are "dated" (relatively, from stratigraphic relationships) from the Fortunian, the oldest period:

The most important features of the Fortunian are large tessera-bearing
crustal plateaus (e.g., Fortuna, Ovda, etc.) that form a specific
class of first-order (a few thousands of kilometers across) highs on
Venus [...] The lowest stratigraphic position of tessera and its
relative abundance show that this unit is of extreme importance as a
probable 'window' into the geological past of Venus.

Stratigraphy of defined and mapped geologic units on Venus. The
visible geologic history of Venus consists of the Fortunian,
Guineverian, and Atlian Periods. The major portion of the surface of
Venus (about 70%) was resurfaced during the Guineverian Period. See
text for discussion. T is the mean model absolute age of the surface

Further works by Ivanov & Head detail the history of volcanism (2013) and tectonism (2015) on Venus. They consider tessera themselves as a resurfacing process:

The globally observed stratigraphic relationships among the tectonic and volcanic units that make up the absolute majority (~96%) of the surface of Venus divide the observable portion of its geologic history into three different episodes, each with a specific style of resurfacing. These are as follows: (1) Global tectonic regime, when tectonic resurfacing dominated. Exposed occurrences of these units comprise about 20% of the surface of Venus. (2) Global volcanic regime, when volcanism was the most important process of resurfacing and resurfaced about 60% of Venus. (3) Network rifting-volcanism regime, when both tectonic and volcanic activities were about equally important. During this regime, about 14% of the surface of Venus was modified.

So, to summarize, "continent-like" (tessera) terrains like Ishtar Terra have existed for a long (yet unknown) time, and have survived the resurfacing from volcanism that covers most of the surface today. But they are themselves considered to represent a (tectonic) resurfacing process that has affected older (and unknown) pre-Fortunian terrains.

A global correlation chart that shows the three major regimes of
resurfacing on Venus: global tectonic regime, global volcanic regime,
and Network-rifting-volcanism regime.
Comment: I had no idea that Venusian stratigraphy was so detailed, thanks for all the references!
Answer: Wiki describes the global resurfacing event as follows :-

NASA's Magellan spacecraft mission discovered that Venus has a geologically young surface with a relatively uniform age of 500±200 Ma (million years). The age of Venus was revealed by the observation of over 900 impact craters on the surface of the planet. These impact craters are nearly uniformly distributed over the surface of Venus and less than 10% have been modified by plains of volcanism or deformation. These observations indicate that a catastrophic resurfacing event took place on Venus around 500 Ma, and was followed by a dramatic decline in resurfacing rate.

In the same paragraph :-

Based on its surface features, it appears that Venus is tectonically and convectively alive but has a lithosphere that is static.

(Some emphasis on 'lithosphere is static')
The above paragraph makes it less likely that the Venusian 'Continents' could have existed before the resurfacing event, but we cannot be sure that the same rules applied before the event.
I also found this website that says that doesn't really say anything about 'continent'-like things before the resurfacing event, but it says that the event might have :

"turned off" any plate tectonics on the planet, completely solidifying the crust into a single surface.

This means that any further resurfacing events would be unlikely.
Couldn't find any papers on the same though.


Adenium Boehmianum branches

Question: Is there a trick to get my Adenium Boehmianum to sprout new branches?  It has never grown any more branches than when I bought it more than 5 years ago.  I just repotted it in proper soil with lots of drainage holes in the pot.  I am in AZ and it has just started sprouting leaves.  It goes into the garage when temperature drops below 45 degrees.  I must admit I have not been good about fertilizing.
Comment: A picture really helps!
Comment: Very poisonous...they use the sap to dip arrowheads in for better killing...if you have just re-potted this plant, leave it alone for now.  Re-potting is stressful.  Don't overwater and let us know what you have done already for type of soil (hopefully a sterilized potting soil purchased in a bag), last time you fertilized, what you added, where you are keeping this guy.
Answer: So, I knew nothing of this plant before today but I read a really interesting paper put out by the University of Florida that provided the advice below.
There's a few different types of adenium boehmianum, and some are naturally bushy while others tend to have just a few stems until they mature fully.
If your Adenium Boehmianum is getting leggy and you need to encourage branching, pinch back or remove a few inches of stem. Prune just above the leaves and it will be more likely to result in multiple branches than if you prune further down on the plant on bare stem. You can do this once a year, preferably from February to September. Trying to do this during winter often fails to generate healthy branching. If you do any of this be VERY careful. The sap, I'm sure you know, is highly poisonous.
If you provide pictures of your plant, someone may be able to help you further.
Comment: That all said, reading more on the subject I'd advise that unless the plant is stressed by not having enough branches, or is becoming dangerously top heavy, you consider letting it just be. It should branch out eventually if given proper growing conditions.
Comment: Thanks!  I'm guessing mine may be of the needing to mature type as the leaves are on the ends of all stems and there would be no place to trim unless I trimmed off the leaves.  I'm thinking I will leave it be and concentrate on better fertilizing for a couple of years.  Maybe the new space in the new pot will help.

Adenium Boehmianum branches


Detect bot on AWS

Question: We use angular for our front end, our compiled dist folder is uploaded to an S3 bucket which is connected to a load balancer. In order for our site to be rendered correctly for search engine bots we implemented Angular Universal which is running on an ec2-instance. The question is among all AWS service which one can we use to detect bot(or even allow a script that does) and redirect to the ec2-instance. Or is there any alternative approach this can take?
I am currently looking into cloudfront and lamba.
Comment: It is not different content, bot can't crawl pure angular code, this is not cheating it is done by all this situation.
Answer: One solution is to segregate users by JavaScript support.
Looking at duckduckgo.com?q=example one can observe the following;
<code><noscript>
    <meta http-equiv="refresh" content="0;URL=/html?q=example">
</noscript>
</code>
Checking the user agent is another solution (example).

Detect bot on AWS


Are there are alternatives to gradient update rule?

Question: Most optimization techniques (that I'm aware of) for non-linear cost functions that are commonly implemented rely on linearly updating a variable iteratively until a minimum is reached or a condition is met. The update is itself a function of the gradient. Are there any alternative methods to this, say those that rely on a product update, for example? Is there any result of 'optimality' of the gradient descent, say that it is the best way to get to the optimum?
Answer:
Are there any alternative methods to this, say those that rely on a product update, for example?

There are a number of alternatives to gradient descent.

Problems such as OLS are minimizing quadratics, so you can solve them directly. Do we need gradient descent to find the coefficients of a linear regression model?
Newton's method is a second-order optimization method. See Why is Newton's method not widely used in machine learning?
Halley's method is a third-order optimization method. See Why not use the third derivative for numerical optimization?
Non-convex problems have their own elaborate methods which deviate from the pattern of gradient descent. If we think of gradient descent a iterative, sequential updates within some neighborhood, non-convex optimization will tend to bounce around, either randomly (random search) or in an attempt to make educated guesses. See Optimization when Cost Function Slow to Evaluate and related posts for more discussion.

Is there any result of 'optimality' of the gradient descent, say that it is the best way to get to the optimum?

"Best" how? A very general theme in numerical optimization is that different methods have different cost-benefit relationships, so choosing the "best" method is about selecting an acceptable trade-off in terms of accuracy/optimality of the result, the amount of time spent to compute the solution, memory consumption, etc.
If your problem is small and the objective is quadratic, gradient descent can be pointlessly slow and inaccurate because you can solve the problem directly.
If your problem is huge, gradient descent might be nice because it doesn't require factorizations of large matrices (QR decomposition) or solving large linear systems (Newton's method). Comparatively, gradient descent is cheap. This is a large part of the motivation for using gradient descent for training neural-networks.
As a matter of pedagogy, gradient descent is easy to explain and understand and is very general. As a matter of practice, gradient descent is really cheap. But depending on the problem you're trying to solve, "better" solutions can exist, where "better" can be taken to mean "less computation time" or "more precise result" etc.


Out of power after one hour of canning

Question: I was canning hot packed chicken for 1:15 minutes and the power went off after one hour. I left everything there and I could hear the boiling in the canner for the remainder of the 15 minutes. The power came back on after 25 minutes so I set it for the remaining 15 minutes. Is that ok?
Comment: Does this answer your question? [I put canned meat back in the pressure canner to process longer- is that ok?](https://cooking.stackexchange.com/questions/122200/i-put-canned-meat-back-in-the-pressure-canner-to-process-longer-is-that-ok)
Comment: Not really a duplicate. In that question, broth was processed an appropriate time, and then processed more time. Here, the power went off interrupting the processing time before it was complete.
Answer: Barring the somewhat unlikely case that the pot was boiling with pressure maintained for 15 minutes with the power off, official advice is that the timer restarts from zero after an interruption (so it should have been processed for an additional 1:15, not 0:15.)
I'll have a look around for some of that official advice to link. I've seen it in print enough to know it.

IMPORTANT: If at any time pressure goes below the recommended amount, bring the canner back to pressure and begin the timing of the process over, from the beginning (using the total original process time). This is important for the safety of the food.

Quote source: https://nchfp.uga.edu/publications/uga/using_press_canners.html#gsc.tab=0
However, this answer suggests an officially sanctioned approach from Germany/Austria (double-processing in boiling water) that might allow recovery rather than discarding the food. https://cooking.stackexchange.com/a/103220/34242 You could, of course, use the pressure canner rather than just boiling water for the second go-round.
Comment: It's actually not unlikely that it would maintain pressure for 15 minutes after all contents have reached 120°C. Water has a huge specific heat, and as long as the canner stays closed there's no evaporation that would quickly lower the temperature. Whether it would indeed stay hot enough to continue destroying the spores depends on how well the canner is insulated.

Out of power after one hour of canning


Tagging for questions determining site scope

Question: We have questions here in meta tagged as [on-topic-definition] as well as ones tagged [allowed-topics]. Let's pick one, any preference?
Answer: Since the FAQ will link to all these discussions, we'll need a single tag for all of them, whether they're on- or off-topic. (We could link to more than one tag, but presenting users with a single tag they can page through seems to be simpler.)
Bicycles.se uses the tag [on-off-topic] for this, English Language and Usage uses [on-topic-off-topic], for example. I propose using [on-topic-definition], since a lot of questions use it already. (We can add [on-topic] and [off-topic] as well if people think it's important to identify these questions as on-or off-topic.)
Comment: I used the [on-topic-definition] tag in my questions because I saw it commonly used on some other meta sites.
Answer: [on-topic-definition] would be the tag I'd use for when the question is about what is generally allowed.
I'd use [off-topic] when it is about what is not allowed.
Comment: We need a tag that covers both, so we can link to it from the FAQ.
Comment: At the core these are the same topic.  "Is this allowed or not?"


"Buy me a coffee" as in-app purchase?

Question: Does Apple tolerate a "buy me a coffee" feature as In-App purchase ?
Answer: Yes. This kind of 'donation' IAP is fine and approved by Apple.
This has always been possible, but Apple also clarified this with an update to the App Store Guidelines in February 2021:

3.1.1: Clarified how apps can enable customers to "tip" developers: "Apps may use in-app purchase currencies to enable customers to "tip" the developer or digital content providers in the app."

For an example of an app which uses this, see Pedometer++ (an app promoted by Apple on numerous occasions) which uses three donation IAPs of different values to allow users more control over the quantity of their donation—also allowed.

Comment: Thanks for this answer. Any thoughts on this sort of things as a auto-renewing subscription? My app is a service that provides ongoing value to the user.

"Buy me a coffee" as in-app purchase?


Add "email" to /admin/people overlay view

Question: I have been browsing around trying to find the answer to this but I am not having any luck. I want to add the users email to the table so that we can identify them easier. I have tried to create a new page and use "/admin/people" as the path but I get the error that it can not be overridden. I am relatively new to Drupal so if it sounds like a noob question that is why.
Comment: Hi and welcome to Drupal Answers. It seems a bit unclear what exactly you are trying to accomplish. Which table are you referring to?
Answer: Have you tried using Views for this? This will work well if you want to make a new page that lists all of the users. It won't work out of the box if you want to add the email information to the existing admin/people overlay.

To use Views, enable the module and go to admin/structure/views/add
Give the View a name, and then for the 'Show:' option from the
dropdown select 'Users'
To create a new page, leave the 'create a new page' item checked, give the new page a title and path, and under Display Format select 'Fields' Hit Continue and Edit
On the next screen under Fields hit the Add button, and select User:email

There are tons of options to configure with Views - check out the Views Documentation for more information if you're new to Views.
Comment: I have the view created like you said and it will take me to a page and display what I want but I would like it to display like the people as an overlay, I do not see an option for that, also the table matches the existing people table style in the view editor but on the new page itself it is different colors.
Comment: I got it figured out
Answer: Similiar to @kbrinner answers, I recommend installing the Admin Views module.
This module:

Replaces administrative overview/listing pages with actual views for
  superior usability.

By doing this you can then edit the People view and add the email column for all users.


Does relativistic mass have weight?

Question: If an object was sliding on an infinitely long friction-less floor on Earth with relativistic speeds (ignoring air resistance), would it exert more vertical weight force on the floor than when it's at rest?
Comment: I am not a relativist and I hesitate to write an "answer", but my understanding is something like *The "relativistic mass" is energy and all energy couples to gravity, so the short answer is "yes", but there are some caveats because it also shows up in other elements of the stress-energy tensor generating contributions with the opposite sign so that you can not, say, accelerate a body until it forms a black hole.* Not sure what the final effect is.
Comment: The question has to make explicit how the answer is supposed to treat the effect of the curvature of earth's surface.
Comment: @Johannes Or we could just assume a hypothetical universe in order to answer the spirit of the question
Comment: Interesting question
Comment: The answer is just yes.
Answer: First off, your question is phrased in terms of relativistic mass, which is an obsolete concept. But anyway, that's a side issue.
The question can be posed in terms of either the earth's force on the puck or the puck's force on the earth. We expect these to be equal because of conservation of momentum.
In general relativity, the source of gravitational fields is not the mass or the mass-energy but the stress-energy tensor, which includes pieces representing pressure, for example. The puck has some stress-energy tensor, and this stress-energy tensor is changed a lot by the puck's highly relativistic motion. Therefore the puck's own gravitational field is definitely changed by the fact of its motion. However, the change is not simply a scaling up of its normal gravitational field. The field will also be distorted rather than spherically symmetric. Yes, the effect is probably to increase its force on the earth. The earth therefore makes an increased force on the puck.
Here is a similar example that shows that you can't just naively use $E=mc^2$ to calculate gravitational forces. Two beams of light moving parallel to each other experience no gravitational interaction, while antiparallel beams do. See Tolman, R.C., Ehrenfest, P., and Podolsky, B. Phys. Rev. (1931) 37, 602, http://authors.library.caltech.edu/1544/
Comment: "Two beams of light moving parallel to each other experience no gravitational interaction, while antiparallel beams do."

Ahhhh... This general relativity thing is still too difficult for me...
Comment: I wonder how close the anti-parallel beams have to be in order to orbit each other.
Answer: My previous answer proved to be wrong. Energy density ("relativistic mass") does contribute to gravity - and the fact that the object is moving at relativistic speeds does affect the space-time around it.
There is an interesting document that explains the problem in further context.
Besides, when we think about it, if energy density didn't contribute to the force of gravity, photons, mass of which consists of their energy density, would not be affected by gravity. But we have provided many times, that the lightwaves - thus photons - are affected by gravity.
Comment: *Gravity does not couple to the rest mass.*  - That would mean that still objects are not affected by the gravity - wouldn't it? After reading a few documents, I'm quite concerned that gravity is affected by the total $m$ which equals to: $\frac{m_0}{\sqrt{1-v^2/c^2}}$ so the rest (or *invariant*) mass affects gravity too. I might be confused by the terminology though.
Comment: It's okay to say that the object's rest mass remains the same and *classically* gravity depends on rest mass. But, don't we consider mass-energy? (which increases exponentially with velocity). I think it still affects the stress-energy tensor.
Comment: I'm just reading some works that actually prove that my answer is wrong. I'll edit it.
Comment: Gravity does not couple to the rest mass.
Comment: What I mean is that gravity couples to energy and momentum (and their fluxes) and not to rest mass (which your earlier answer stated).
Comment: Ok, following the edit your answer is less problematic.
Answer: "Does gravity depend on relativistic mass or rest mass?" is a rather interesting question -- Einstein's initial approach was to say "the relativistic mass", and this was the pre-general relativistic answer, but this is not satisfactory, since the relativistic mass is only one component of the energy-momentum vector (and it would actually sound more reasonable to say it depends on the rest mass).
This is the theoretical motivation for general relativity, in which gravity depends on the stress-energy-momentum tensor, and only the time-time component of gravity, $\Gamma^i{}_{00}$, depends on the relativistic mass, whose density is also the time-time component of the stress-energy tensor, and the other components depend on on the other components of the stress-energy tensor by the Einstein field equations.
Comment: Minor quibble: Any reason to avoid refer to GR as level 3 approximation? If level infinity is taken, where does that leave a future QG theory?
Comment: The actual level 2 approximation does not change r in a straightforward way, it has an attraction given by the product of the energies (relativistic masses) but with a peculiar radial dependence given by the gravitomagnetic contribution, which is best to work out by boosting to the rest frame of one of the objects, where the gravitational field is known.
Answer: Assuming the frictionless floor is locally horizontal, orthogonal to the radial direction and ignoring the effects of the spinning earth, the force on the floor would actually be zero when you reach the velocity of $v=\sqrt{GM/r}$ where r is the radial distance to the center of the earth. This is because the sliding object would now be in orbit.
I suspect the force on the sliding floor generally could be written as:
$$F=-\frac{mGM}{r^2}\hat{r}+m\frac{v^2}{r}\hat{r}$$
If you have pure non-radial motion. This would become zero long before relativistic effects become noticable. I guess a totally correct answer depends a bit on if the floor "bends with the Earth" so it is always orthogonal to the radial direction. The answer here is correct if the floor "bends with the Earth".

Does relativistic mass have weight?


Morphology - Detailed description

Question: The adjective "happy" is a free morpheme. And at the same time, it is an adjective which is one of the lexical morphemes. So, can I say that "happy" is (a lexical free morpheme)?
In the same way, can I say for example that the word "the" is (a functional free morpheme) or that the suffix "-ed" is (an inflectional bound morpheme)?
Comment: @bytebuster "Language-specific grammar and usage questions are off-topic *unless primarily concerned with linguistics rather than usage*." The question is clearly more about linguistic analysis than usage, especially in being extendable to any language, which is why I vote to leave it here.
Comment: This is a very basic question - was there anything in particular which made you think that you couldn't say happy is a free lexical morpheme?
Comment: Welcome to Linguistics. Since this question is English-specific, you may probably find a better audience for it at English.SE or English Language Learners.SE
Answer: I can't really imagine a context where such a description would be useful, since normally you talk either about combinatorial behaviour (free vs bound vs something else) or semantic properties (lexical vs functional vs ...), and now you're kind of jumbling these two parameters up.1
But it's not wrong either, so I guess it would be okay to say.

1 It's also partially redundant because e.g. derivational morphemes are always bound (except there are some very weird language where this isn't the case; in this case feel free to correct me).
Maybe it would sound better if you switched the order and said "bound inflectional morpheme", because the latter implies the former and putting the more specific thing first and as a second description what is already implied anyway (like "inflectional bound") sounds a bit clumsy to my ears. But that's just hair-splitting.
Answer: I agree with lemontree that it's mixing up formal and functional properties (which may not always be useful), and that usually, it's probably better to put it in the sequence lemontree mentioned. With that said, I think there is one context where one could possibly say 'free lexical morpheme': To contrast them with bound lexical morphemes, which are present in modern Mandarin as well as other varieties to a lesser extent. For example, the Chinese word for 'happy' contains a free lexical morpheme kuai4 ('fast') and a bound lexical morpheme le4 ('happy').
Also, you should be very careful when calling 'the' a free morpheme. 'The' can only appear with an NP after it, and never in isolation. It is also phonologically unstressed and dependent on the NP. Though it appears to be free in our conservative writing system, in practice it's more like a clitic, and many modern writers prefer to call a spade a spade and refer to it as one.

Morphology - Detailed description


Can we integrate WhatsApp From Marketing Cloud?

Question: I want to Integrate WhatsApp From Marketing Cloud . Can we do it ?
Answer: It is not possible within the standard features of Marketing Cloud. There might be 3rd party solutions allowing you to do so, but I don't have adequate knowledge of these to recommend one over the other.
You should also observe the limits WhatsApp has on the number of messages you can send during a 24 hour period.
Answer: As of now, I fear there are no out-of-the-box functionalities to accomplish this task.
Perhaps your team can take advantage of the Journey Builder custom activities. Yet this requires a solid background in development.
Build Custom Activities and Events
https://developer.salesforce.com/docs/atlas.en-us.noversion.mc-app-development.meta/mc-app-development/creating-activities.htm
As you can see below there have been ideas from other customers related to Whatsapp.
Integration With WhatsApp
https://success.salesforce.com/ideaView?id=0873A000000PZZ7QAO
SALESFORCE CRM INTEGRATION WITH WHATSAPP
https://success.salesforce.com/ideaView?id=0873A000000TtbxQAC
Digital Engagement WhatsApp Business Messaging FAQs
https://help.salesforce.com/HTViewSolution?id=000352588
Comment: is there any other way ?
Comment: Not in my knowledge.
Answer: GroupConnect only supports LINE and Facebook Messenger at this time, however, Direct Messenger is a third-party Custom Activity that enables you to send WhatsApp messages to Contacts in a Journey.
Comment: You might want to be a little more specific in your question then...
Comment: i want to send that link it in email


IndustrialCraft machines not receiving power

Question: I have a nuclear reactor hooked up to an MFSU, which then goes through MV and LV transformers to reach machines like compressors and macerators. It all worked fine up until I placed a mass fabricator on the output wire of the MFSU. Suddenly, all my machines stopped getting power, even when I removed the mass fabricator. I checked all the connections, but it should all be working fine. My quarry (which is connected to the HV output of the MFSU) is still getting power and working normally. I have roughly 5000000 EU in the MFSU, and even if I switch on my nuke it still does not power the machines. How do I fix this problem?
Comment: Did you checked the output/input side on the transformers? Maybe they are facing the wrong way.
Comment: @Balen nope, like i said, the machines worked fine until the mass fabricator was added - the transformers did not change
Comment: I have sometimes noticed that for whatever reason the connector blocks (conduit conductive pipe, what have you..) "die" for lack of a better term. So I would have to break and replace. Sometimes one block. Others the whole line. Hope that's the issue. As it's a simple enough fix, heh heh.
Comment: @Bob I tried breaking/replacing all my glass fibre cable and something really weird has started happening. The machines get a tiny amount of power when i connect them again, and if i send s redstone pulse to my centrifuge extractor it starts to work for a very short period of time. They all then lost all their power. And I still have 5000000 EU in my MFSU, and i even tried disconnecting my quarry thinking it might be eating all my power, but to no avail
Comment: I have noticed that sometimes glass Fibre can be finicky.  I would suggest trouble shooting the line. Go two blocks of Fibre away from the mfsu. Then put something that should be able to accept power. What I suspect is happening is that some little short is occurring somewhere. Which would be a bug. As I assume glass Fibre should function like conduit.  Also it seems like there might be a problem with the transformers. As it is outputting power.   Still curious as to why it happened only after having the mass fabricator added.
Comment: ...my last suggestion. Perhaps the mass fab is just too efficient at taking and using power. I barely use that mod set. But is there a way for you to throttle the power being sent to the fabricator. The way you can set the output on Redstone cells? As that could provide a choke. Allowing power to the other machines.
Comment: @Bob I removed the fabricator and it's still bugged. Also I'm in tekkit classic so there's no redstone conduits
Answer: After starting a brand new world, a total fluke left me with the solution. In my new world, I had placed a lever next to a redstone engine, but on top of an LV transformer. As it turns out, when you apply a redstone current to a transformer, it prevents the flow of electricity. Sure enough, when I loaded my old world, I found a lever on a centrifuge extractor (which was on top of the LV transformer) and was therefore preventing the flow of electricity.


Finishing challenges: prestige first?

Question: I'm currently just trying to finish out off the challenges available pre-prestige, but am wondering if anyone out there has any experience doing this after prestiging, and whether it seems earier to do while going through the weapons-unlocking again.
Comment: Please put the reference to the game in the name of the question.
As for the question you will lose the progress of all challenges except some Prestige challenges. But this will not matter if you are pre-prestige.
Comment: Why reference the game in the question? That's what the tags are for!
Answer: You don't gain a real advantage after prestiging that would make challenges easier, so I don't think it would matter when you choose to do them (Aside from losing progress, but if you haven't gotten that far, it shouldn't matter).
Personally, I do the challenges after prestiging (if I even choose to), because unlocking the same weapons over again is boring to me and the challenges keep it fun.
Answer: I'm on 8th prestige at the moment, and here are some thoughts:
It's tough to lose all your weapons and perks (losing Ninja Pro is painful)! IMO it's always tough to get all your stuff back and finish off challenges after entering prestige, because you'll always think to yourself: "Hey, I've done this before! Why did it just said... Oh! That's because I've entered prestige..."
Having said that, there are certain challenges that are easy to get (they tend to be the ones that are available from the get-go) and some that are the complete opposite (such as dropping a crate to an enemy)! But, when you do prestige, at least you'll have some idea how to do those challenges.
Answer: I'd do the challenges after prestiging once, as that unlocks even more challenges to complete
Answer: Well, one thing is that after completing 70 levels you've got the experience to make it that much easier to go through again.  You don't have to relearn the maps, you know strategies / campout locations, etc.
One good about prestiging is the extra class you get.  While not all that useful immediately it is nice when you re-unlock One Man Army.
On the flip side (in my own personal opinion) I'm reluctant to prestige as I prefer the sniper rifles.  You just don't get the kills while sniping that you do in close combat.  Takes longer to progress.  Could be that I just suck, though :)
Comment: Before I hit 70, I tended to sniper -- but, since I started really going for the challenges, I've been going through the other weapons quite rapidly.
Answer: As squillman mentioned, you receive an extra class every odd level prestige.  Also, there are extra challenges available for each type of weapon and kill streaks once you prestige for the first time.
I am currently fifth prestige, and I usually completed one type of master challenge per weapon type (SMG, Assault rifle, sniper rifle and LMG).  So at one time, I had a class dedicated to a SMG, Assault rifle and LMG.  I have completed all of the SMG master challenges.  I only need to complete the M240 master challenge for the LMGs.  The f2000 and AK47 master challenge for assault rifle challenges.  The WA2000 and M21 EBR for sniper rifle challenges.

Finishing challenges: prestige first?


Are there smaller packages for Standard rcl (resistor, inductance, capacitor) than 0402mm

Question: I need to miniaturize a PCB as much as possible. Are there packages available on mouser for standard components like resistors (100k) or inductance (Up to 30nH) or Cap (Up to 100pF)?
Comment: I know there's 01005 packages, which probably correspond to metric 0201. No clue what component values are available in them, but I suspect you won't get a 30 nH inductor in that form factor.
Comment: You might be better to use the smallest parts you can get easily and using more PCB layers, buried & blind vias, and tighter spacing (subject to your PCBA house capabilities) to get higher densities. I'm not sure many places can actually mount 008004 parts reliably. HDI PCBs, on the other hand, are easily available, if a bit expensive.
Answer: Your best bet is going to stick to 01005 available from common distributors like Digikey.
Note the caveats with the size:

01005 resistors can only handle ~1/32 W power. Sizes below 01005 are not commercially common -- digikey sells only one resistor with a smaller size, with a resistance of 0.02 ohms, and a minimum order quantity of 40000.
01005 capacitors can easily range well past 100 pF but may have lower voltage tolerance, tempco, etc. Below that, you have a tiny selection of specialty caps.
01005 inductors are available; the largest I saw was 56 nH. Current handling is relatively limited. Below 01005/0402 metric, none are commercially listed.

Past 01005 there are very few options available. There are rare 008004 packages, as well as custom ones, but if you really need the miniaturization, you may need to consider integration on an IC (of course, scaling your design and passives to values achievable on a process that you can afford).
Comment: That's a surprisingly high inductance in such a small package. I bet the saturation current is tiny.
Comment: @nanofarad I was looking for a package that is even smaller than 0204 metric which is equivalent to 01005
Comment: @MarcoBobinger Beyond 0204 is a rarity -- you can see that [very few options are available](https://www.digikey.com/en/products/filter/ceramic-capacitors/60?s=N4IgjCBcoCwGxVAYygMwIYBsDOBTANCAPZQDaI8cChlA7CDbTAKwMVP00ActnFPXEAF1CABwAuUEAGVxAJwCWAOwDmIAL6EAtACZEIFJHkBXAsTIhWIkBKkb16oA). Of course, it's possible to get custom parts, with the right budget and volume.
Comment: @nanofarad the link is broken, could you eventually provide a new link please?
Comment: @MarcoBobinger The link works for me on Chrome, including in an incognito window. It's nothing more than a digikey search for ceramic caps in every size smaller than 0.4mm*0.2mm. This [digikey short link](https://www.digikey.com/short/5q8mt0zw) might work, but if not, it shouldn't be too hard to manually enter the same search criteria.


Upper limit on BTC PoW hash rate?

Question: Is there an upper limit on the amount of hash rate for Bitcoin's Proof of Work? Is there a big difference security-wise going from 175 EH to 275 EH?
Answer: AFAIK there's no limit set by the Bitcoin network protocol. It obviously affects the network difficulty / target but I believe the upper bound of difficulty represents an extraordinarily high hashrate.
https://en.bitcoin.it/wiki/Difficulty#What_is_the_maximum_difficulty.3F says

What is the maximum difficulty?
There is no minimum target. The maximum difficulty is roughly: maximum_target / 1 (since 0 would result in infinity), which is a ridiculously huge number (about 2^224).
The actual maximum difficulty is when current_target=0, but we would not be able to calculate the difficulty if that happened. (fortunately it never will, so we're ok.)

That link also shows you how to convert that maximum non-infinite difficulty number to a hashrate. I think that gives you around 5 x 10141 (an exahash is a tiny 1018)
The difference in security between 175 and 275 EH/s really depends on the available amount of unused hashpower as much as on the deployed hashpower.
Note that hash rate is measured in EH/s not EH.

Upper limit on BTC PoW hash rate?


how to delete a particular line from random access file

Question: I am using a random access file in which i want to delete a line which satisfies some condition like if i have records
MCA 30
MBA 20
BCA 10
now my requirement is if i enter MBA then second line is to be deleted.
Comment: Are the lines always the same length?
Answer: Generally, removing an item from the middle of the file means rewriting all entries after the entry so as to use the space the item occupied.
Some things instead mark items that are deleted with some invalid value so as to spot that the slot is unused.  Typically they don't even reuse deleted slots, as this is rather more management than you might imagine, and is basically implementing a heap-like architecture in a file.  They need a separate 'compacting' step to remove this dead space later.  Microsoft Jet (as in Access) worked like this.
There's a very cool optimisation that's applicable in some cases:
If the rows are unordered, and equal length, you can overwrite the entry you want to 'delete' with the last entry, and truncate the file.
If the rows are unordered but not fixed length, you can use a more complicated variant of this approach where you move some entry from near the end that is the same length as the item being removed, so as only to need to shuffle up as few entries as possible.
Answer: If it is a simple text file than you'll have to copy everything except the MBA line(s) to a new file. Random Access files don't really support delete or insert.
Optimization: move everything after the MBA line up (in the same file)
Alternative: use something more structured like a database.
Answer: It sounds to me like you're looking for a 'grep' like implementation. There's a Java implementation of GNU grep, you can find the documentation here,
and download from a link in this page.


Is it possible to use mixed 110V / 208V power on a single server with dual power supplies?

Question: Is it possible to run a dual power supply server with one PS plugged into 110V, and the other power supply plugged into 208V? We've asked the vendors and they say they've never tested it or some other "i dunno" type of answer. The power supplies both work at 110 and 208 without any issue, it's the 'mixed' operation that is in question.
Comment: This has been discussed a few times previously. It will *probably* work. You will *probably* be fine. If your case falls outside the "probably" envelope (and there's no real way of knowing) **VERY BAD THINGS** could happen.  Procedure is not recommended.
Comment: No (in my test). I just tried something similar with HP server with 2 different PSUs - a 240VAC PSU and a 48VDC PSU - it complained on boot and I had to take one out..
Comment: I'm voting to close this question as off-topic because without knowing which model of power supply and mother board, it is impossible to answer. And it is probably best to trust what the vendor says.
Answer: It almost certain will actually work yes, doesn't mean it's a smart idea however - do don't do this please.
Answer: Thats up to the server vendor. If you don't even tell us, which servertype you use, nobody could you answer this.
It should work, as the supplies will output the prober voltage anyway. But maybe the server's monitoring chipset don't likes that.
EDIT
As you really need the mixed-operation you should test it with an old/broken system first. If there is no trouble, you have a great chance the other systems will stay alive.
Keep the mixed-operation as short as possible, but long enough to allow the supplies to make a failover.
Comment: When playing with voltages like that, and given that vendors don't know the effect of doing it, I'd highly recommend not doing it if for no other reason than we're talking about servers, not fireworks.
Comment: Currently moving a datacenter from 110V to 208V... being able to hot move the servers without outages would be nice to be able to do. Mostly a mix of Dell poweredge and Cisco Nexus 22xx/50xx equipment, with a small number of HP servers as well.
Answer: Obviously, I have to disclaim any liability for if something happens.
That being said, running them on two different voltages is no different than running them on two different 120v circuits. The power supplies transform the power to uniform outputs, so the only issues that you could run across are things like differing ground references, power factor differences, etc.--the same types of problems that can come up with from different circuits of the same voltage.
Although this is possible, it's not necessarily helpful; with 208, you are using two hot legs of a three-phase, 120v system. In other words, you are doubling your risk exposure versus using only one: if either hot leg fails on the 208, you're down. If your building also had a 277/480 service, that would provide a higher level of reliability, since they are different services (different transformer, feeders, and gear/switching).
Comment: It's to allow us to move to 208V without taking outage on the server, though obviously, you're right on the exposure, though from what I understand, with the loading we have, if we lost a leg, we're pretty much SOL regardless.
Answer: Yes.  You can power the PSU modules at any voltage that module supports.
Comment: I would recommend including a link with official information from the vendor backing up that statement.
Comment: Let's see your official vendor information rebutting that statement.


Restrict DHCP server to listen only to AP?

Question: I configured a DHCP server on my Ubuntu 12.04 using the isc-dhcp-server package. But I want my DHCP server to serve requests which are received from my Wireless Access Point and not to/from any other machine. How do I go about configuring this?
Answer: Disable any other DHCP servers on the LAN and configure your Wireless Access Point (WAP) as a wireless switch by connecting it to your existing LAN (containing your DHCP server) via the LAN ports of the WAP.
Answer: You can't practically do what you are attempting in the general case as an Access Point is a layer 2 device and will appear to the DHCP server to be no different to an ethernet device.   Thus as @packets suggested you should move everything onto 1 DHCP server.
In a specific case you could set up your DHCP server to only answer for specific mac addresses - those of devices (wireless interfaces), by hard-coding each mac address into the configuration file, and not handing out IP addresses for other machines.
Alternatively you could add an interface on your DHCP server and connect the access point to that.  You would then (probably/practically)need to use routing in your network, but you could select to only bind DHCP to the interface connected to the wireless access point.
[I note that as a purely intellectual excersize it is probably possible to bridge the Interfaces and do some ebtables filtering to prevent requests leaving the non Wireless AP interface instead of doing routing, but this would be a bit of a hack and quite complex to set up - and even more complex to debug. ]


Two player mahjong?

Question: My understanding of Mahjong is that you need four players. Is that right? Or is it possible to play with 2 or 3?
If so, can anyone assist with a link to the rules.
Comment: Not just 2 & 4  I've played it under house rules for 5 players.
Answer: These rules have 2 and 3 person variant rules.
So yes you can play with 2 or 3 people as well.
Here's the relevant rule changes:

Two-Player Mah Jong
This is good practice for beginners although not quite such a good game as the more typical version with 4 players. One player plays East, the other West. The preliminaries are conducted in the same way as for the 4 player game, 4 walls are built and the game starts with East's discard. The game continues as with the standard game but with the following differences:
No chows are allowed and therefore before either player can go Mah Jong, the player must gather four doubles or be entitled to the limit or half-limit score.
  When scoring, East Wind neither pays nor receives double.
  When scoring, the player going Mah Jong has a lower score than the player's opponent, the player with the Mah Jong receives the normal total score plus the difference between the scores.
Three-Player Mah Jong
There are two main ways to play three-player Mah Jong. One common way to play is with four walls but to have the North wind position as a 'dummy'. The alternative is to play with 3 walls in a triangle. The 'dummy' method results in a satisfactory game but there are a number of special rules that are required and Masters Traditional Games believes that the triangular game for three players is simpler and more elegant and so that is our recommendation.
In South East Asia, Triangular Mah Jong is so popular that there are companies who make special triangular Mah Jong tables.
Triangular Mah Jong for 3 players eliminates the North position completely and the 4 North wind tiles are removed from the set before starting so that a set of 132 tiles are used.
The walls therefore consist of 22 stacks (44 tiles) in a triangle shape and there are 3 hands in each round and 3 or 4 rounds as agreed. Other than that, the game is played in the same way as for 4 player Mah Jong.
If flowers and seasons are included, one season and one flower is removed, usually Winter and Bamboo tiles so that 138 tiles are used and each wall consists of 23 stacks (46 tiles).
Answer: We have a mahjong set and regularly play with only three people but using the same rules as the four-player game. The only difference is that it is often slightly easier for someone to win with three players. That said, we still goulash every so often. The two player game is also possible using different rules, usually with making all pairs in a hand, however I find this method a bit boring so we still play normal rules with two players. That way someone always wins a hand, just more quickly.
One piece of advice I have is to treat the game as fun! I have met many people who are so serious about what is or isnt 'allowed' in playing mahjong that it can be a bit off putting. Why not try the usual play with fewer people--it's just as much fun even if you aren't changing the rules to suit fewer than four...
Answer: I don't know much about two-player mahjong, but three-player riichi mahjong is extremely popular online (about as popular as four-player mahjong, at least on some sites). It's often known by its Japanese name, sanma. It usually has the following rule adjustments:

The 2 through 8 of characters are removed. This increases the frequency of pairs, triplets, and honor tiles, makes tan'yao (a.k.a. All Simples) harder to get, and generally increases the pace of play.
Players cannot call "chi" (a.k.a. "chow").
Rounds are 3 hands (plus any repeats) instead of 4, since there's one fewer player. So a South game might be as short as six hands even if nobody gets eliminated.
Since North will never be a valid round wind or seat wind, it can act rather like flower tiles in other forms of mahjong: you call "Pei!" (or "Kita!"), set it aside face-up, and draw a replacement tile. Each pei call adds 1 han to your hand.

Pei calls are considered a form of dora and don't count as a yaku for the scoring minimum. You don't have to call pei, though; you can still use your north as ordinary tiles to complete your hand. You can also discard them if you need a safe tile late in the hand.
If north is a dora tile as shown by the dora indicator and you call pei, it counts double: 1 han from the pei call and 1 han from the dora indicator. (A previous version of this post incorrectly claimed that pei tiles only count for 1 han when called whether they're dora or not. Oops!)
Finally, it is possible to call ron on another player's pei, similar to robbing a kan, though you don't gain any han for it. But you do get 1 han if you tsumo immediately after a pei call, just as you would after making a kan.
Also be aware that you get fewer points for tsumo than for ron, because the payouts are the same as for 4-player mahjong but there is one fewer player to collect points from.

Two player mahjong?


Interaction between metalic nanoparticles and aggregation

Question: I can't find any publication to deal with aggregation of colloidal metalic nanoparticles. What type of interaction(s) is/are there between aqeous metalic nanoparticles which give(s) rise to aggregation?
Answer: Metallic nanoparticles, considered as colloids, are attracted to each other by van der Waals forces. To prevent their aggregation, we normally use dispersant using electrostatic repulsion or steric hindrance to stabilize the colloids.


Why is the $B$-Field an axial Vector?

Question: in trying to understand the Wu-Experiment I wonder why the $B$-Field is an axial vector. I know that $\vec{B} = \vec{\nabla} \times \vec{A}$. Under Parity transformation I'd expect $\vec{A} \rightarrow -\vec{A}$, however I don't know whether $\vec{\nabla} \rightarrow -\vec{\nabla}$.
Comment: Short answer: the cross product changes sign. The right hand rule becomes the left hand rule under parity.
Comment: NB This question/answer is older than the duplicate, but for whatever reason the newer version received more attention.
Answer: Maybe the best way is to think about $\vec{B}$ in terms of the Biot-Savart law.
Imagine a loop carrying a current $I$ in a plane that is perpendicular to a mirror. The Biot-Savart law says that the B-field at position $\vec{r}$ is given by
$$\vec{B}(\vec{r}) = \frac{\mu_0}{4\pi}\, \oint \frac{I\, d\vec{l} \times \vec{r'}}{|\vec{r'}|^2}\ dl, $$
where $\vec{r'} = \vec{r}-\vec{l}$ is the displacement from an element on the loop to where the field is calculated.
This is an axial vector because if we look at this situation in a mirror, the current would appear to flow in the opposite sense, $\vec{l}$ is reversed and the $\vec{B}$ field should actually be in the opposite direction to its mirror image. i.e. An actual mirror image would look like it was obeying a left-hand rule, rather than a right-hand rule.
This is actually exactly the example used on the wikipedia page on pseudovectors, which is another name for an axial vector.
In this example, both $\vec{l}$ and $\vec{r}$ are displacements and are true vectors. Their vector product must be an axial vector.
You are asking about a parity transformation, but as far as I am aware $\vec{B}$ is unchanged by a parity inversion. Axial vectors do not change signs under parity inversions. Angular momentum is another example of an axial vector that does not change under a parity inversion. $\vec{A}$ on the other hand is a true vector and has its sign flipped by a parity inversion. The curl of a true vector is an axial vector  and the curl of an axial vector is a true vector. So $\nabla$ is behaving as a true vector in this regard where $\nabla \rightarrow -\nabla$ is odd under a parity inversion (because $\partial/\partial x \rightarrow -\partial/\partial x$ etc.)
Comment: As parity is an inversion and not a mirror image, we'd still have to rotate the right image, correct? If so, this would make sense to me.
Comment: @infinitezero Yes. The current loop is invariant under parity (you move each current element to its diametrical opposite, and you flip the current direction), as is the magnetic field it produces. You can see the right-hand image as a mirror version or as a rotation - those two pathways differ by a parity inversion, and are therefore equivalent.
Answer: (Within Netwonian mechanics) You can start with Lorentz Force law $$\vec{F}=q\vec{E}+q\vec{v}\times\vec{B}$$We know that $\vec{F}$ is a physical vector(From Newton's law). We also know that $\vec{v}$ is a physical vector. Therefore $\vec{B}$ must be an axial vector.
Comment: I like this argument.

Why is the $B$-Field an axial Vector?


Concept of Hopfield Networks

Question: Just want to double check my understanding of comcept of Hopfield networks. would a trained hopfield network have an energy function that has local minimas equal to the number of the training patterns?
Comment: What do you mean when you say "training patterns"?
Answer: Basically yes, but Hopfield net of a given size can have only so much local minima and if you try to train it with  larger number of training patterns then it fails and two patterns can become merged.

Concept of Hopfield Networks


How to enable USB OTG in Walton Primo F4?

Question: I have a Walton Primo F4, running Android 4.2.2. How can I enable USB OTG in my device?
Answer: Head into settings, about device, then tap the build number 7 times. From there, head back and you will see a menu called developer options. Tap it,  and tap enable USB debugging. Accept the warning,  and you are done.
Comment: What does USB debugging have anything to do with USB OTG?
Comment: @Firelord Honestly?  No idea.  A small glitch to my device involves me randomly needing USB debugging for OTG,  so.....
Comment: @Firelord Besides, it seems to have worked...


The 'law' is a tag of off-topic-osity

Question: The law tag is nearly completely off-topic. I've taken a swat with my available vote inventory; would anyone else care to join in?
Comment: And wow, you can really tell the EU Cookie law .. well .. happened.
Comment: I haven't seen any evidence @Tim. Absolutely no one has come to give me cookies... Do you know where they are?
Comment: I think we need a place to send the valid ones first. The ones with up-votes about the EU cookie law all seem to be valid. They just don't need the tag.
Comment: I've gone through all the open ones and voted to close all save 2. They were on-topic just mistagged. One point people closing: Not all are off-topic, some are just old not constructive etc...
Comment: I went through a bunch of them too. Note, some of the questions revolving around an OSI approved license are in the on topic realm, e.g. 'can I mix this code with this code' and the like. I _think_ I caught the rest that were just tagged incorrectly.
Answer: Why not setting it as a synonym of legal?
Comment: I'd be all for burninating that one too. Anyone who takes legal advice from anonymous strangers on the internet is a fool, and we shouldn't be encouraging them to ask.
Comment: Right. There're stuff about software licensing and a lot of off-topic as well. Perhaps it opens a door to non constructive, debate-like questions. But for those who don't ("how will my program's license interact with this or that"), what should OP use?

The 'law' is a tag of off-topic-osity


How do I install Chocolatey in a different location than standard, say, even on a different partition?

Question: I would like to install Chocolatey on a separate partition. Is this possible, or do I have to take the default C:\?
I currently have E:\ partition where I install all my software. I would like all my cinst packages to go there.
Is this just a function of changing the PATH variable, after installing Chocolatey, or do I have to do something more substantial?
Answer: You can install Chocolatey exactly where you would like, and to make that easier, there's even some information written up on the wiki for Chocolatey about that!

Create a user environment variable named ChocolateyInstall and set it to the folder you want chocolatey to install to prior to installation.
Create the folder manually.
Install Chocolatey.

The simple and "automated" way
If you'd like to keep it simple, simply open upen an administrative session of PowerShell (if you need so), and run the following snippet. It'll do the steps above.
Set-Variable -Name "ChocolateyInstall" -Value (Read-Host -Prompt "Install location")
New-Item $ChocolateyInstall -Type Directory -Force
[Environment]::SetEnvironmentVariable("ChocolateyInstall", $ChocolateyInstall, "User")
iex ((new-object net.webclient).DownloadString('https://chocolatey.org/install.ps1'))

Always be careful, and read snippets of code before executing it.
Comment: Seems the chocolatey docs not really helpfull. Chocolatey install guide should be arranged like this answer.
Comment: Ah. Thank you. I read and misunderstood that to mean the variable had to be in 'system partition'. Apologies.
Comment: @runtime_error Stuff happens! I added a complete/simple way to do it.


Do I have a chance at an academic career in North America or Europe?

Question: I have two masters, topped both of them, and published articles that have been widely cited, though they date before 2013. I am struggling with my PhD because of a lack of support from the faculty and funds. I have been too busy surviving after that. What can I do to maximize my chances of an academic career in Europe or North America? Is my age a crucial factor?
Comment: There's a chance this will be closed as opinion-based. Could you rephrase so that the question focuses on something more operational and/or narrow? E.g. how can I maximize my chances for program X with my particular resumé? How important is age or time-to-submission? How important is a gap in publications? etc. (Some of these questions already have answers on this site.)
Answer: My answer to this question of yours Does the time taken to do a PhD affect post doctoral applications? does also apply here: There is a chance, yes. How high that chance is depends on many factors. Your age, your publications, etc. are some of them, but others are for example the quality of your work, the availability of the position you are looking for, the energy you put into applying (e.g. do you contact every last university in all of North America and Europe?), what you want as a "career"  - e.g. are you happy with a postdoc position that is not limited, or do you want to get to dean of the department before you hit 60 - etc.
So yes, there is a chance and yes, it is somewhat lowered by the points you gave. If you want to take it or not is your choice, no one else can make it for you.


Example of a symbolic or a discrete dynamical system where $NW(f) \not\subset \overline{R(f)}$?

Question: In this question there is an example of a continuous dynamical system with $NW(f) \not\subset \overline{R(f)}$. The definitions I am working with are exactly same as that question. I want to find a symbolic or a discrete dynamical system with the mentioned property. I would really appreciate a not-so-involved example, so that I can gain an intuition to distinguish non-wandering points from points in the closure of the set of all recurrent points.
Answer: One example is the orbit closure of ${}^\infty 0 1 0 1 0 0 1 0 0 0 1 \cdots 1 0^n 1 0^{n+1} 1 \cdots$ with respect to the shift map. The left tail is just repeating 0s, and on the right are 1s with increasing gaps. The only recurrent point is the all-0 configuration, but ${}^\infty 0 1 0^\infty$ is nonwandering.
Comment: There is no other element in the orbit closure than $\infty 010\infty$ and all-$0$ which is not in the orbit, right? Btw, thank you very much, I think this example fits perfectly to what I was searching.
Comment: @テレビ スクリーン Correct. The shift space contains the point I defined, the point ${}^\infty 010^\infty$, the all-0 point and their shifts, nothing more.


If someone is on my "Close friends" list on Facebook, will I get notified when they post on a non-friend's wall?

Question: If a "close friend" posts on someone's wall (that isn't my friend) will I still get a notification?
Comment: No, but it may appear in wall
Answer: You will only be notified when a close friend interacts with their own timeline in the following ways:

They posting a status update
Post a photo
Checkin
Update their profile picture

You can turn on/off these notifications via the instructions here
Answer: No, you get notifications only when a close friend posts on their own wall.


PayPal Express checkout - review page doubling total amount

Question: Everything is OK in the Cart and on the PayPal site. However, when returned to the Review page - the Total prices are doubled. I tried looking at frontend/base/default/template/paypal/express/review/details.phtml but it seems fine - I don't see where it's doubling. Where can I find this? Here is a screenshot.
Answer: The problem is most likely that collectTotals is called within the theme somewhere.  When helping someone else with this issue who was utilizing a third-party theme (Galabigshop), we found that our Grand Total was being tripled.  Sure enough, we found the following code in the theme's sidebar twice:
if (!(Mage::app()->getRequest()->getControllerName()=='onepage') && !(Mage::app()->getRequest()->getControllerName()=='cart')) {
$quote = Mage::getModel('checkout/cart')->getQuote();
$quote->collectTotals();
$quote->getShippingAddress()->collectTotals();
}

Without going into excessive detail, each time $quote->getShippingAddress()->collectTotals(); the total of the order is added again to the total.
The major problem with the code above is that the conditional does not account for the express controller (i.e. express), only onepage and cart. As a result, collect totals is run on the order review page (controller name express) and the total is erroneous.
To confirm that this is the issue, try utilizing the default magento theme, clearing your cache, and seeing if it resolves.


Can I use Microsoft SharePoint 2013 to be my ASP.NET application portal?

Question: I'm not an expert in SharePoint but what I know that SharePoint 2013 Foundation Edition is free, and I'm developing ASP.NET applcation which will have a portal. I'm wondering Can I user SharePoint 2013 Foundation as my application portal?
I'll use this portal to show visual reports (SSRS reports) in webparts, like in Microsoft Dynamics AX it use SharePoint as its portal and call it Enterprise Portal.
Answer: Yep, SharePoint can do what you ask for there, except if you have as you say another ASP.NET application, Microsofts general recommendation is to host stuff like that on a server that isn't running SharePoint. You can use still use client side APIs to talk to SharePoint from your other app, and if your app has any APIs you can probably call it from client side code within SharePoint pages.
Comment: Yes you can use SSRS to get data out of your other databases and show it in reports, and then surface those reports within SharePoint. This is a fairly easy task, the biggest tripping point is to make sure you set up an Execution Account in SSRS, and that that Execution Account has access to your other database.
Comment: Good answer, Thanks but basically SharePoint will be portal to show information and webparts reports, but Can I show data from other Database than SharePoint Database or it's better to replicate the data?


Can an Orthodox doctor ask a not-yet-religious Jewish doctor to take his shabbos rounds?

Question: Can an Orthodox doctor ask a not-yet-religious Jewish colleague to exchange Shabbos hospital rotations?
Comment: Is a not-yet-religious Jew less bound by the laws (or less able to save someone's life)?
Comment: Ooh. I remember a machlokes amongst the Israeli Rabbis if you should rather use an irreligious  car service to take you to the hospital. One said yes. And one said no as the allowance of chilul shabbos for pikuach nefesh etc is only for one who actually keeps Shabbos, not for one who brazenly desecrates it. I think the question was regarding driving a woman in labor to the hospital, if that matters.
Comment: Machloket Rav moshe feinstein and Rav Shlomo zalman aurbach
Comment: See nishmat Abraham....
Comment: Isn't this a bit like asking if a law abiding citizen can ask a criminal to commit a crime for him?
Answer: Shemiras Shabbos 40:27 says that the orthodox doctor should not exchange with the non-religious doctor as the latter may come to transgress shabbos.
Comment: I suspect you mean "in ways unnecessary to save lives", but if so, you should add that.
Comment: I was aware of this when I wrote my answer. Pekuach nefesh docheh shabbos is a given and applies to everyone in all cases so why would one assume otherwise in this specific case?
Comment: Rav Feinstein disagree.


getting java.net.UnknownHostException while running GOCD docker container in QNAP

Question: I am trying to run gocd docker container (https://hub.docker.com/r/gocd/gocd-server/) on QNAP (TS-451 x86 based, firmware 4.2.0) in container station.
container doesn't' start and bombs out with java.net.UnknownHostException:
May 21 20:21:28 gocd-server-1 syslog-ng[16]: syslog-ng starting up; version='3.5.3'
using default settings from /etc/default/go-server
ERROR: Failed to start Go server. Please check the logs.
java.lang.RuntimeException: gocd-server-1: gocd-server-1
        at com.thoughtworks.go.util.ExceptionUtils.bomb(ExceptionUtils.java:36)
        at com.thoughtworks.go.server.util.GoSslSocketConnector.getHostname(GoSslSocketConnector.java:102)
        at com.thoughtworks.go.server.util.GoSslSocketConnector.storeX509Certificate(GoSslSocketConnector.java:92)
        at com.thoughtworks.go.server.util.GoSslSocketConnector.sslConnector(GoSslSocketConnector.java:56)
        at com.thoughtworks.go.server.util.GoSslSocketConnector.<init>(GoSslSocketConnector.java:51)
        at com.thoughtworks.go.server.Jetty9Server.sslConnector(Jetty9Server.java:133)
        at com.thoughtworks.go.server.Jetty9Server.configure(Jetty9Server.java:76)
        at com.thoughtworks.go.server.GoServer.configureServer(GoServer.java:84)
        at com.thoughtworks.go.server.GoServer.startServer(GoServer.java:70)
        at com.thoughtworks.go.server.GoServer.go(GoServer.java:63)
        at com.thoughtworks.go.server.util.GoLauncher.main(GoLauncher.java:31)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:606)
        at com.simontuffs.onejar.Boot.run(Boot.java:306)
        at com.simontuffs.onejar.Boot.main(Boot.java:159)
Caused by: java.net.UnknownHostException: gocd-server-1: gocd-server-1
        at java.net.InetAddress.getLocalHost(InetAddress.java:1496)
        at com.thoughtworks.go.server.util.GoSslSocketConnector.getHostname(GoSslSocketConnector.java:100)
        ... 15 more
Caused by: java.net.UnknownHostException: gocd-server-1
        at java.net.Inet4AddressImpl.lookupAllHostAddr(Native Method)

I checked /etc/hosts inside the container - it includes correct host mapping : 10.0.3.2 gocd-server-1
127.0.0.1       localhost
::1     localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
10.0.3.2 gocd-server-1

hostname resovles correctly:
root@gocd-server-1:/tmp# hostname
gocd-server-1

the container image is fine - I have run exactly the same gocd docker container on vagrant Ubuntu vm without any issues
so the issue is somehow related to QNAP Linux (which seems to be Ubuntu 4.1.2)
[~] # cat /proc/version
Linux version 3.12.6 (root@NasX86-12) (gcc version 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)) #1 SMP Fri Mar 11 02:20:16 CST 2016)
any ideas how to get around java.net.UnknownHostException exception?
Answer: To close this thread: though I still don't understand why this exception happens I think I found the workaround. So if you are the owner of QNAP and want to run GOCD server using ContainerStation the following steps might be useful:
1. Create a new container, using travix/gocd-server:lastest image (https://hub.docker.com/r/travix/gocd-server/). This container uses JDK8 (instead of JDK7 as official gocd container) plus it includes more options to configure (if you go to advanced settings while creating a container in ContainerStation).
2. Start the container - you will get the exception -  Caused by: java.net.UnknownHostException.
Why? no idea, I am pretty sure my /etc/hosts settings are correct. In fact I know they are correct.

next step - keep the container running but ssh to your QNAP:
ssh email@example.com (in my case - change ip of the box to yours)
// check what images are running:
docker ps -a

dde6ce028868        travix/gocd-server:latest   "/docker-entrypoint.s"   21 hours ago        Up 21 hours                 0.0.0.0:32793->8153/tcp, 0.0.0.0:32792->8154/tcp   gocd
// ssh into the container
docker exec -it dde6ce028868 bash

// run go-server start script
/usr/share/go-server/server.sh

let it run, in my case it successfully started gocd.

clean up work dir
rm -rf /var/lib/go-server/work/
and now restart the container from ContainerStation

in my case it starts up correctly without unknown host exceptions
any theories why? (DNS caching, permissions, some initialisations which silently fail?)
Answer: it turned out the issue is related to ACL which gives read access to /etc/hosts and /etc/resolv.conf only to root. So java application running inside the container under a different user, can't access these files.
pls. see this discussion for more information:.
why am I getting permission denied on file with read permissions inside Docker container?
if you want to use GOCD with QNAP - you might try to use this container https://hub.docker.com/r/rshestakov/docker-gocd-server/
which includes the following fix:
# modify ACL so go user would have read access
# to /etc/hosts and /etc/resolv.conf
# this is to avoid HostUnknown exception which happends
# when the gocd container is used on QNAP with ContainerStation
setfacl -m user:${USER_ID}:r /etc/resolv.conf
setfacl -m user:${USER_ID}:r /etc/hosts