Hermitian adjoint of 4-gradient in Dirac equation

Question: I'm having issues deriving the Dirac adjoint equation, $$\overline{\psi}(i\gamma^{\mu}\partial_{\mu}+m)=0.\tag{1}$$
I started by taking the Hermitian adjoint of all components of the original Dirac equation, giving me
$$\psi^{\dagger}(-i\gamma^{\mu\dagger}\partial_{\mu}^{\dagger}-m)=0.\tag{2}$$ The adjoint of the gamma matrices is defined to be $\gamma^{\mu\dagger}=\gamma^0\gamma^{\mu}\gamma^0$, so no issues there. Now intuitively, I would think that the adjoint of the 4-gradient would be $\partial_{\mu}^{\dagger}=-\partial_{\mu}$. In non-relativistic quantum mechanics, it can be shown that first derivative operators are anti-Hermitian, so for example, $\frac{d}{dx}^{\dagger}=-\frac{d}{dx}$. So I would think this would the same case for the 4-gradient, but apparently it isn't. Among the many derivations I've gone over, for example, on page 77 here, it claims that the 4-gradient is self-adjoint. Could someone please explain why my intuition is incorrect?
Comment: Depends on the space. If you're taking adjoints in $L^2$, then yes, it's anti-Hermitian. But here you're taking adjoints in spinor space (that is, transposing and conjugating spinors and matrices), so the derivative is unaffected.
Comment: @Javier Could you explain why exactly the derivative is unaffected? I'm not very familiar with spinor space. Thanks.
Answer: Expanding on my comment.
The basic idea is that what you mean by adjoint depends on the vector space being considered. For example, we might have $\mathbb{C}^n$ as our space, with the usual inner product; in that case, the adjoint of a vector or matrix is the transpose conjugate. Note that technically, taking adjoint of a vector doesn't return a vector, because row vectors and column vectors belong to different spaces.
We could also use $L^2(\mathbb{R}^n)$ as our vector space. Its elements are functions, and the inner product is defined by
$$(f,g) = \int d^n x\ f^* g$$
You can take adjoints here too, using the inner product defined above. It can be shown that the derivative operator, which is a linear transformation on $L^2$, is anti-Hermitian.
Now to the Dirac equation. The vector space (that is, spinor space) being considered here is $\mathbb{C}^4$, not $L^2$. That is, $\psi$ is a vector because it has four components, not because it's a function. The fact that its components are functions is irrelevant here. When we take adjoints, we transpose and conjugate vectors and matrices. The derivative is an operator if you think about what it does to functions, but it is not a $4\times4$ matrix; it does nothing to spinors. Therefore, the particular adjoint we're doing here doesn't affect it.
Comment: What will be the hermitian conjugate of 4-Gradient in interacting scalar theory? The space is real vector space.
Comment: @sawankt Integrating by parts with appropriate boundary conditions, $\int f \partial_\mu g = - \int (\partial_\mu f) g$, so the adjoint is $-\partial_\mu$. The theory being interacting is irrelevant.
Answer: My answer is pretty much similar to what others have written here, but maybe in a slightly different fashion.
So let's first motivate the definitions of :-
Hermitian Conjugate of an Operator - VS - Hermitian Conjugate of a Vector
Hermitian Conjugate (Adjoint) of "Operator" :-
A Hermitian Conjugate (technically known as Adjoint ) of an operator $\hat{\mathrm A}$ is defined via the rule
$\langle\phi|\hat{\mathrm A}|\psi\rangle\ =\langle\hat{\mathrm A}^\dagger\phi|\psi\rangle$, where $\ \hat{\mathrm A}^\dagger$ denotes the Adjoint of the operator $\mathrm{\hat{A}}$.
CONCLUSION 1 :- In order to find the Adjoint of an "Operator", one needs to consider the expectation value of the operator, that is, to evaluate an Integral over all Space-Time Coordinates.
$\langle\phi|\hat{\mathrm A}|\psi\rangle\ =\displaystyle \int_{Entire\\ Domain}  \phi^*(t,\mathbf{r})\ \hat{\mathrm A}\ \psi(t,\mathbf{r})\ dt\ d^3\mathbf{r}\ $

SIDE NOTE:- For Operators that can be written as Finite Dimensional Matrices such as \begin{bmatrix} f(x) & g(x) \\ h(x) & k(x) \end{bmatrix} where $x \in (-\infty,\infty)$, we can find the Adjoint as $$\langle\phi|\hat{\mathrm A}|\psi\rangle = \displaystyle \int_{-\infty}^\infty \begin{bmatrix} a^*(x) & b^*(x) \end{bmatrix} \begin{bmatrix} f(x) & g(x) \\ h(x) & k(x) \end{bmatrix} \begin{bmatrix} c(x) \\ d(x)\end{bmatrix}\ dx$$
$$ = \displaystyle \int_{-\infty}^\infty \left(\begin{bmatrix} f^*(x) & h^*(x) \\ g^*(x) & k^*(x) \end{bmatrix} \begin{bmatrix} a(x) \\ b(x) \end{bmatrix}\right)^\dagger \begin{bmatrix} c(x) \\ d(x)\end{bmatrix}\ dx = \langle{\hat{\mathrm A}^\dagger}\phi|\psi\rangle $$
Implying $\hat{\mathrm A}^\dagger = \begin{bmatrix} f^*(x) & h^*(x) \\ g^*(x) & k^*(x) \end{bmatrix}$.
Therefore, one can easily find the Adjoint simply by taking the Complex
Conjugate Tranpose of the Operator represented as a matrix. This technique
however does NOT apply to Operators that CAN NOT be represented as Finite
Dimensional Matrices. Keep that in mind for it is important.

Hermitian Conjugate of a Vector :-
If $\ |\psi\rangle$ is a state vector, then the Hermitian Conjugate is defined as $\ |\psi\rangle^\dagger\ =\langle\psi|$.
A finite dimensional vector helps us to visualise this better.
Take for example, $|\psi\rangle = \begin{pmatrix} a\\ b\\ c \end{pmatrix}$
Then, $\langle\psi| = \begin{pmatrix} a^* & b^* & c^* \end{pmatrix}$
CONCLUSION 2 :- In order to find the Hermitian Conjugate of a "Vector", one needs to consider only the complex conjugate transpose of the vector, and NOT any Integral over Space-Time Coordinates.
Now, lets examine a difference between the two Hermitian Conjugates :-
The statements written in Conclusion 1 and 2 are very important. Why?
Consider the vectors
$|\chi_1\rangle = \begin{pmatrix} e^{-\frac{x^2}{2}} \\ \frac{1}{x^2+1} \end{pmatrix}$; $\quad$
$|\chi_2\rangle = \begin{pmatrix} x^2e^{-\frac{x^2}{2}} \\ \frac{1}{x^2+4} \end{pmatrix}$
Task 1:- To find the "Hermitian Conjugate Vector" of $\frac{\mathrm d}{\mathrm {dx}}|\chi_1\rangle$, where $x \in (-\infty,\infty)$
$\frac{\mathrm d}{\mathrm {dx}}|\chi_1\rangle = \begin{pmatrix} \frac{\mathrm d}{\mathrm {dx}}\left(e^{-\frac{x^2}{2}}\right) \\ \frac{\mathrm d}{\mathrm {dx}}\left(\frac{1}{x^2+1}\right) \end{pmatrix} = \begin{pmatrix} xe^{-\frac{x^2}{2}} \\ -\frac{2x}{(x^2+1)^2}\end{pmatrix}$
$\left(\frac{\mathrm d}{\mathrm {dx}}|\chi_1\rangle\right)^\dagger = \begin{pmatrix} xe^{-\frac{x^2}{2}} & -\frac{2x}{(x^2+1)^2}\end{pmatrix} = \begin{pmatrix} \frac{\mathrm d}{\mathrm {dx}}\left(e^{-\frac{x^2}{2}}\right) & \frac{\mathrm d}{\mathrm {dx}}\left(\frac{1}{x^2+1}\right) \end{pmatrix} = \frac{\mathrm d}{\mathrm{dx}} \begin{pmatrix} e^{-\frac{x^2}{2}} \\ \frac{1}{x^2+1} \end{pmatrix}^\dagger = \frac{\mathrm d}{\mathrm {dx}} \left(|\chi_1\rangle^\dagger\right)$
$\boxed{\left(\frac{\mathrm d}{\mathrm {dx}}|\chi_1\rangle\right)^\dagger = \frac{\mathrm d}{\mathrm {dx}} \left(|\chi_1\rangle^\dagger\right)}$
CONCLUSION 3 :- The Hermitian Conjugate ($\dagger$) did nothing to $\frac{\mathrm d}{\mathrm {dx}}$ simply because we are NOT computing any Integral over the spatial(and/or temporal) coordinates at all. $\frac{\mathrm d}{\mathrm {dx}}|\chi_1\rangle$ simply yields another "Vector" whose complex conjugate transpose is being calculated here. That's all. Nothing more.
Task 2:- To find the "Hermitian Conjugate Operator" of $\frac{\mathrm d}{\mathrm {dx}}$, where $x \in (-\infty,\infty)$
$\langle\chi_2|\frac{\mathrm d}{\mathrm {dx}}|\chi_1\rangle\ =\displaystyle \int_{-\infty}^\infty \begin{pmatrix} x^2e^{-\frac{x^2}{2}} & \frac{1}{x^2+4} \end{pmatrix} \begin{pmatrix} \frac{\mathrm d}{\mathrm {dx}}\left(e^{-\frac{x^2}{2}}\right) \\ \frac{\mathrm d}{\mathrm {dx}}\left(\frac{1}{x^2+1}\right) \end{pmatrix}\ dx$
$ = \displaystyle \int_{-\infty}^\infty x^2e^{-\frac{x^2}{2}}\frac{\mathrm d}{\mathrm {dx}}\left(e^{-\frac{x^2}{2}}\right)\ dx + \int_{-\infty}^\infty \frac{1}{x^2+4}\frac{\mathrm d}{\mathrm {dx}}\left(\frac{1}{x^2+1}\right)\ dx$
Integrating By Parts would give:-
$\left[\left(x^2e^{-\frac{x^2}{2}}\right)\left(e^{-\frac{x^2}{2}}\right)\right]_{-\infty}^\infty - \displaystyle \int_{-\infty}^\infty \frac{\mathrm d}{\mathrm {dx}}\left(x^2e^{-\frac{x^2}{2}}\right)e^{-\frac{x^2}{2}}\ dx + \left[\left(\frac{1}{x^2+4}\right)\left(\frac{1}{x^2+1}\right)\right]_{-\infty}^{\infty} - \int_{-\infty}^\infty \frac{\mathrm d}{\mathrm {dx}}\left(\frac{1}{x^2+4}\right)\frac{1}{x^2+1}\ dx$
Surely, the boundary terms are 0. This yields
$\displaystyle \int_{-\infty}^\infty \begin{pmatrix} -\frac{\mathrm d}{\mathrm {dx}}\left(x^2e^{-\frac{x^2}{2}}\right) & -\frac{\mathrm d}{\mathrm {dx}}\left(\frac{1}{x^2+4}\right) \end{pmatrix} \begin{pmatrix} e^{-\frac{x^2}{2}} \\ \frac{1}{x^2+1} \end{pmatrix}\ dx\ = \int_{-\infty}^\infty \left[-\frac{\mathrm d}{\mathrm {dx}}\begin{pmatrix} x^2e^{-\frac{x^2}{2}} & \frac{1}{x^2+4} \end{pmatrix}\right] \begin{pmatrix} e^{-\frac{x^2}{2}} \\ \frac{1}{x^2+1} \end{pmatrix}\ dx$
Thus, $\langle\chi_2|\frac{\mathrm d}{\mathrm {dx}}|\chi_1\rangle\ = \langle -\frac{\mathrm d}{\mathrm {dx}}\chi_2|\chi_1\rangle$ , yielding
$\boxed{\left(\frac{\mathrm d}{\mathrm {dx}}\right)^\dagger = -\frac{\mathrm d}{\mathrm {dx}}}$
CONCLUSION 4 :- The Hermitian Conjugate ($\dagger$) does act on $\frac{\mathrm d}{\mathrm {dx}}$ this time, simply because we are ARE computing any Integral over the spatial(and/or temporal) coordinates.
FINAL CONCLUSION :- It was just the confusion of notation that led to the trouble. While finding the Hermitian Conjugate of an Operator, it has a completely different evaluation procedure than finding the Hermitian Conjugate of a Vector. Unfortunately, the same notation ($\dagger$) is used for both, which is where potentially lies the confusion.
P.S. You may wonder how does one know which definition one should use when? Well that is simple. In the context of Dirac equation

If you are supposed to find the Adjoint of Dirac Operator $(i\hbar\gamma^{\mu}\partial_{\mu} - mc)^\dagger$, you will simply have to use the definition applicable to operators, that is the Expectation Value of this Operator.

If you are supposed to find a Dirac-like Equation that would be satisfied by Hermitian Conjugate Vector $|\psi\rangle^\dagger$, then this is even simpler, for you do not need to find any Expectation Value. Just the Complex Conjugate Transpose of the entire equation. So, ALL Space-Time dependent Operators like $\frac{\mathrm d}{\mathrm {dx}}$ will remain unaffected.
Comment: When you are writing a Lagrangian (of any field - scalar, fermion, spin 1, etc), it has to be a "Real Scalar". Lagrangian CAN NOT be an Operator. This implies that any $\partial_\mu$ you observe in a Lagrangian cannot exist independently. It must act on the field, just like in your example, you have 2 copies of $\partial_\mu \phi$, each of which is a **vector** and NOT an **operator**.
So, you need to apply the "Hermitian Conjugate of a Vector".
Hence, $(\partial_\mu \phi)^\dagger = \partial_\mu \phi^\dagger$.
Comment: Then for scalar field where $\mathcal{L} = \frac{1}{2} ( \partial_\mu \phi)^\dagger \partial^\mu \phi - \frac{1}{2} m^2( \phi^\dagger \phi)$, what will be the hermitian conjugate of $\partial_\mu$?
Answer: Perhaps the following argument is more convincing:

The Dirac equation$^1$
$$ (i\gamma^{\mu}\stackrel{\rightarrow}{\partial}_{\mu}-m)\psi~=~0 \tag{A}$$
is by the fundamental lemma of variational calculus equivalent to
$$ \forall \phi:\quad 0~=~\int d^4x~\bar{\phi}(i\gamma^{\mu}\stackrel{\rightarrow}{\partial}_{\mu}-m)\psi, \tag{B}$$
where $\phi$ is an arbitrary (off-shell) Dirac spinor.
Hermitian conjugation in Dirac spinor space leads to
$$ \forall \phi:\quad0~=~\int d^4x~\bar{\psi}(-i\stackrel{\leftarrow}{\partial}_{\!\mu}~\gamma^{\mu}-m)\phi, \tag{C}$$
which is equivalent to
$$ \bar{\psi}(i\stackrel{\leftarrow}{\partial}_{\!\mu}~\gamma^{\mu}+m)~=~0,\tag{D}$$
cf. the above comment by Javier.
On the other hand, if we also integrate (C) by parts, we get (after discarding boundary terms)
$$ \forall \phi:\quad 0~=~\int d^4x~\bar{\psi}(i\gamma^{\mu}\stackrel{\rightarrow}{\partial}_{\mu}-m)\phi, \tag{E}$$
where the derivative now acts on $\phi$.

--
$^1$ We use the following conventions:
$$ \bar{\psi} ~=~ \psi^{\dagger}\gamma^0 , \qquad\gamma^{\mu\dagger}~=~\gamma^0\gamma^{\mu}\gamma^0, \qquad (\gamma^0)^2~=~{\bf 1}_{4\times 4}. \tag{F}$$
Answer: I totally agree with the answers above, but there is a problem when you try to prove that the Hamiltonian operator is Hermitian. In fact, in the hermitian adjoint of the Dirac hamiltonian, the alpha-matrices terms will have a minus sign because of the i factor, and the space derivative will stay unaffected. So at the end we will have to say that the alpha matrices should be anti-hermitian in order for the hamiltonian to be hermitian.
Sorry for not writing the expressions. I'm new here and I don't know yet how to write equations.
Comment: You can write equations by putting the math between dollar signs. See https://math.meta.stackexchange.com/questions/5020/mathjax-basic-tutorial-and-quick-reference?rq=1 for a much more thorough explanation.
Comment: Alright, thank you!


Error trying to publish Flattened contracts on Etherscan - DeclarationError: Identifier not found or not unique

Question: I flattened my files and they compile no problem on Remix, but when I try to upload them to Etherscan, they won't accept it with the error:
 Compiler debug log:
Error! Unable to generate Contract ByteCode and ABI (General Exception, unable to get compiled [bytecode])
For troubleshooting, you can try compiling your source code with the Remix - Solidity IDE and check for exceptions

Compiler Warning(s):

DeclarationError: Identifier not found or not unique.
    --> APIConsumer.sol:1095:5:
     |
1095 |     ENSResolver_Chainlink resolver = ENSResolver_Chainlink(s_ens.resolver(linkSubnode))
     |     ^^^^^^^^^^^^^^^^^^^^^

This is the first part of my APIConsumer file before I flattened it.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

import "@chainlink/contracts/src/v0.8/ChainlinkClient.sol";

contract APIConsumer is ChainlinkClient {
    using Chainlink for Chainlink.Request;

    bytes32 public api_data;
    address private oracle;
    bytes32 private jobId;
    uint256 private fee;

After I flattened it (to which I uploaded to etherscan):
// File: @chainlink/contracts/src/v0.8/vendor/ENSResolver.sol

pragma solidity ^0.8.0;

abstract contract ENSResolver {
  function addr(bytes32 node) public view virtual returns (address);
}

And the file carries on with all the functions it inherits for another 1000 lines.
Did I do something wrong with flattening? I don't want to disturb peace and up breaking things just to publish my programs as my contracts work fine. How would I debug this problem?
EDIT: The other sighting of ENSResolver in the file:
  /**
   * @notice Sets the stored oracle and LINK token contracts with the addresses resolved by ENS
   * @dev Accounts for subnodes having different resolvers
   * @param ensAddress The address of the ENS contract
   * @param node The ENS node hash
   */
  function useChainlinkWithENS(address ensAddress, bytes32 node) internal {
    s_ens = ENSInterface(ensAddress);
    s_ensNode = node;
    bytes32 linkSubnode = keccak256(abi.encodePacked(s_ensNode, ENS_TOKEN_SUBNAME));
    ENSResolver_Chainlink resolver = ENSResolver_Chainlink(s_ens.resolver(linkSubnode));
    setChainlinkToken(resolver.addr(linkSubnode));
    updateChainlinkOracleWithENS();
  }

  /**
   * @notice Sets the stored oracle contract with the address resolved by ENS
   * @dev This may be called on its own as long as `useChainlinkWithENS` has been called previously
   */
  function updateChainlinkOracleWithENS() internal {
    bytes32 oracleSubnode = keccak256(abi.encodePacked(s_ensNode, ENS_ORACLE_SUBNAME));
    ENSResolver_Chainlink resolver = ENSResolver_Chainlink(s_ens.resolver(oracleSubnode));
    setChainlinkOracle(resolver.addr(oracleSubnode));
  }

Comment: Please inclde the part of the code where ENSResolver_Chainlink resolver = ENSResolver_Chainlink(s_ens.resolver(linkSubnode)) appears, that seems to be the actual problem
Comment: I do not know what your purpose is to use a flattened contract, but for the sake of efficiency, I use hardhat to verify my contracts through the Standard-Json-Input method. Read the docs. You only need to know like 4 commands to get started with it.
Comment: I typically use brownie to verify my contracts but it one day stopped publishing my contracts. I'll give that a shot. And thank you @JulissaDC, I ended up deleting the _Chainlink to the ENSResolver and got rid of that error... only to find several more (just warnings of unused variables and mismatches of bytecode). I'll give Gray's advice a shot. Thank you.
Answer: Looks like Remix Flattener trimmed a piece of the name of that abstract contract. This approach worked for me:

Flatten contract using Remix IDE plugin
Paste it inside the Etherscan verification field
Rename abstract contract ENSResolver to abstract contract ENSResolver_Chainlink
Hit "Verify"


MXP to Interlaken

Question: My flight lands at MXP at 10AM June 21st, 2024. It's an international flight from Canada.
I need to go to Interlaken on the same day.
Looks like the schedule is not available yet. Also looks like there will be a repair work on the Domodossola line.
When should I look into booking this? what's the best way to go there?
Comment: Sbb.ch gives several options on that day, you could book those right now.
Comment: SBB currently only shows a route that involves a detour via Lugano. This because Italian schedules for June are not on line yet.
Answer: MXP is not a convenient airport for Interlaken.
But the best route is going to be: Bus to Domodossola, then train from there. And I would expect schedules to be available May or so.
Info on the bus you will find here: https://www.comazzialibus.com/ComazziAlibus/?locale=EN
And schedules for the trains you will find on www.sbb.ch. But schedules for June are not complete yet.

MXP to Interlaken


Changing php version on OSX Server

Question: I need to get php 5.3 working on my os server (snow leopard) machine.  When I goto a php webpage on the server that is running phpinfo() it tells me that I am running php version 5.2.14, also it informs that php is installed at /private/etc/php.ini.  Strangely, when I log onto the server and execute php -v from the terminal it tells me I am running version 5.3.0 and which php tells me that is installed at /opt/local/bin/php.  I am confused that I am getting conflicting data from these two sources.  How do I make it so that the php version being used on the server is the 5.3.0 version?
Answer: You need to edit the Apache config to make it load the new php module, rather than the one that came with the OS.  First, find the module you built (not the php program, the loadable module that runs inside Apache); it's probably named something like /opt/local/apache2/modules/libphp5.so.  Then, edit /etc/apache2/httpd.conf to load it instead of the builtin one.  Find the "LoadModule php5_module" line, and replace "libexec/apache2/libphp5.so" with the path to your updated module.
Comment: Thanks for your help, I changed LoadModule php5_module to point to /opt/local/apache2/modules/libphp5.so which is the location my other php module was installed but now I cannot start by web service.  I get an error 1000002 stating that there should be details in the error log but the error logs of the server admin app have nothing about php.  Is there another place I should be looking for this error log?
Comment: Which error logs did you look in?  I'd check the apache error log (/var/log/apache2/error_log, visible in the Logs section of Web service in Server Admin) and the system log (/var/log/system.log, visible in the Logs section of the main server entry in Server Admin).

Changing php version on OSX Server


How does Location based Wi-Fi work?

Question: I have turned on Location based Wi-Fi Setting, I have followed the steps to enable this feature for a Wi-Fi Network at Home and at College,  so, whenever I am at either of these two Locations Wi-Fi automatically turns on,
But I wish to know how this happen, because the Wi-Fi automatically turns on when near the saved Wi-Fi, it happens even when Mobile Data is switched off. I want to further add that I had kept the GPS off during the entire process mentioned above. I don't understand how can it know that the device is near a Saved Wi-Fi region.
Comment: A google search got me this [Wi-Fi Positioning system](https://en.wikipedia.org/wiki/Wi-Fi_positioning_system) and a related [SU post](http://superuser.com/questions/727732/how-does-wifi-determine-a-devices-location)
Answer: Location based Wifi apps such as  Wi-Fi Matic will remember the cell tower ids of your mobile network operator and link it with the connected wifi network. The cell tower id is area dependent, and wifi network in most cases is area dependent. So, it works.
These apps or services constantly monitor the cell tower id of your phone's connected network. And if they find the matched cell tower ids, they know that phone is in/around known wifi network and turn the wifi on.
Similarly, when the cell tower id doesn't match the ones linked with remembered wifi's, it just turns off wifi.
And monitoring tower ids doesn't require data connection. There is no reverse lookup of location here. Just known cell tower ids linked to known wifi networks.
In recent versions of android, there is an option in Wifi advanced settings, called Scanning always available. If you turn on this setting, background scanning always happens even when wifi is off, knowing the access point names of detected wifi networks. Such apps can also use this data to turn on/off wifi based on saved networks.

How does Location based Wi-Fi work?


Embedded External Flash Device using NAND architecture

Question: Our SoC device supports both external NAND devices as well as Multi-IO/QSPI NOR devices.
I can use either of them.
Now, for NAND device, it will store only Program Code and Const Data.
That means SoC will never write anything back to NAND device. It will always read from the NAND device.
Do I need to implemented Wear Leveling as well as Bad Block Management support within the SoC software as NAND device is purely being used as Read-Only Mode device always?
Will there be Bit-Flipping Error possible in the NAND device in this mode of operation?
Thank you.
Regards
Pashan
Answer: Reading the device causes no damage of any type.  Writing the device is a different matter and there's a description and a band diagram that describes the electrical conditions required for injection that puts traps in the oxide.
Comment: So, as long as NAND Flash is used within the system in Read Only mode, it's reliability related behavior is comparable to NOR Flash devices.
Is that always true under temperature/voltage/process variation within the specification limit?
Thank you.
Regards
Pashan
Comment: @user3806728 This will be always true.  PVT are not really issues that you need worry yourself about if you have a discrete IC.  Most of my circuits are designed to be robust to PVT, and that is a circuit designer problem and not a user problem.


What's is a deep meaning for "You are dead to us. We hope you fail"

Question: Can you explain this phrase "You are dead to us. We hope you fail", please? It looks like sarcasm. Is it OK for colleague farewell? Is "We hope you fail" a good wish and why?
Comment: I suppose it might be used sarcastically, within a group highly prone to sarcasm, but normally it would be interpreted as an insult -- saying that all communications between parties will be cut off, and expressing a wish for bad luck.
Comment: Very different from "break a leg" that actors wish each other in good humour, because the superstition is not to say "good luck".
Comment: I've heard this only as an expression of parents who separate themselves completely from a child, when they no longer wish to be associated in any way.  Ostracism.  Expulsion from the family.
Comment: me thinks it means what is says
Answer: Are you familiar with the concept of a "roast"? I didn't know whether this was culture-specific, and I see now that, according to Wikipedia, it's an American thing. It's a tradition of insulting people or wishing them ill as a way of honoring them or wishing them good luck. The TV channel "Comedy Central" sometimes hosts a "celebrity roast" where someone from the entertainment industry is "honored" by colleague after colleague from throughout the person's career taking them microphone and saying the most horrible things about the honoree. Years ago, the entertainer Dean Martin was known for hosting these.
The implication is that the honoree knows that they are so well loved that it is safe to take the insults all in a spirit of fun and knowing that nobody means what they've said seriously.
Comment: But insults at a roast are generally not of the nature of those in the original question.
Comment: I don't know, I don't have a list of every insult ever spoken at a roast. Does it alter the general point about couching good wishes in insults being an existing phenomenon?
Comment: Insults at a roast are not generally of the "I hate you" nature, but more along the lines of implying "you're ugly", "you're stupid", "your taste in music stinks", etc.


Why do some door locks require the key to be twisted twice?

Question: This has been nagging me lately.  Why 2 twists? I mean one twist seems enough to keep the door essentially locked. If the extra twist is for strength, wouldn't it be a better idea to implement a longer travel of the locking mechanism for single twist. I have no knowledge whatsoever when it comes to houses and carpentry and the like so forgive me  if the question seems dumb.
Comment: On some locksets, the first twist locks the latchbolt (the part that springs in to latch the door). The second twist sets a separate deadbolt.
Comment: Do you have a specific lockset that you're inquiring about? Is it a Key-In-Knob lockset or a mortise lockset, for that matter? (It would not surprise me if there are locks that require a multiple movement simply to set the actuator to begin with...)
Answer: It's for security, making the lock harder to pick. About twice as hard. First you have to pick it to rotate the cylinder. Once it travels 360 back to the upright, the pins pop out from behind the rotatory sheath and must be re-picked to continue the final leg of the journey. With a key this is instant, but with a single-pin pick it doubles the (at least) the typical pick time.
Depending on the mechanism (if the key is "stuck in" when unlocked "halfway") it can prevent bumpkey attacks as well since you can't pull back the bumper once the key is affixed. Some of what isherwood notes applies as well, tangentially, because high-security locks that have such a mechanism also have thicker/longer bolts and more robust mechanisms that require additional torque, compared to a crappy kwikset or schlage a residential customer might get at a box store.
Answer: The gearing of the bolt throw mechanism needs to be appropriate so that enough force can be applied on the bolt. Since some bolts drag on the bore slightly, they need to be geared low. This allows a light force on the key to impart a stronger force on the bolt.


What should follow the word crazy, About, or Over, or both?

Question: Is going crazy about something the same as going crazy over it?
I mean.
I was crazy about/over it.
What's the difference between going crazy about something, and going crazy over it?
Answer: They're similar in usage when they mean "passionate".  Context and emphasis are very much needed to determine just how much it is "unreasonable" or "insane" vs. just "intense"... or even if it's "crazy good" or "crazy bad".
But "crazy about" is generally a clear statement of intensely liking something.   So I'm crazy about this new StackExchange site would mean you like the site a lot.  It doesn't usually mean that the interest level is actually "irrational" or "unjustified".
"crazy over" is more likely to be used with "going", and often does suggest something actually unreasonable is happening.  People are going crazy over (some toy) this Christmas--parents are getting in fistfights at the store to be first in line to buy one.
If the 'crazy' is emphasized, it might really mean crazy:

When the neighbors have parties on Fridays and play their loud music, he's *crazy* about it.  Starts yelling, beating on the walls, threatening to change into a werewolf and go eat them.  (Generally that would include get, as in "he gets crazy about it")

I was crazy about/over it.

Here specifically, you'd most likely see:

I was crazy about it. (probably means: "I really liked it.")
I went crazy over it. (probably means: "It really upset me.")

Again, there's a lot of leeway with this from context.


Why does the boolean data type need 8 bits?

Question: Boolean data type only evaluates to true or false, so it is always going to take only one bit of memory. So why is there a need of extra 7 bit of memory, isn't it a waste of memory?
Comment: It actually takes more memory than just one 8bits - JVM usually implements booleans with int values. Why this is done that way? In order to understand that better, think about a JVM which has to handle several boolean values - if a boolean value were using only one bit, your JVM would need to keep mapping `variable to value byte and bit number`. Also fetching a boolean value would require to perform AND operation (storing would require OR). So it was easier to implement booleans as full bytes (or int's)
Comment: Yes waste of memory for us, but efficient and less complex opcodes for Java people. They don't have to create specific opcodes for loading nd storing booleans from memory
Comment: Question marked as duplicate has answer in question (lack of support), but the OP here **want to know the reason**. This are diffrent questions.
Answer: I think it may need more than 8 bits. It depends on JMV." In Oracle JVM primitive boolean needs 8 bits, the reason is limited support and lack of optimization.
Read also: What is the size of a boolean variable in Java?
After The Java Tutorials - Primitive Data Types

boolean: The boolean data type has only two possible values: true and false. Use this data type for simple flags that track true/false conditions. This data type represents one bit of information, but its "size" isn't something that's precisely defined.

After The Java® Virtual Machine Specification

Although the Java Virtual Machine defines a boolean type, it only provides
  very limited support for it. There are no Java Virtual Machine instructions solely
  dedicated to operations on boolean values. Instead, expressions in the Java
  programming language that operate on boolean values are compiled to use values
  of the Java Virtual Machine int data type.
In Oracle's Java Virtual Machine implementation, boolean arrays in the Java
  programming language are encoded as Java Virtual Machine byte arrays, using 8 bits per
  boolean element.

For example Boolean type looks in memory like this
header:   8 bytes
value:    1 byte
padding:  7 bytes
------------------
sum:      16 bytes

As an alternative to boolean[] you can use for example java.util.BitSet.
Why is hard to store booleans as 1 bit? Read Vlad from Moscow answer. You cant address one bit of memory.
Comment: i think this is the answer, thank u. I will research on it
Answer: It depends of addressability of the memory. The least addressable unit is byte. You can take an address of a byte and do the address arithmetic with it. Moreover there are built-in machine commands that operate with bytes. However it is impossible to take the address of a bit and perform the address  arithmetic. In any case at first you have to calculate the address of the byte that contains the target bit and apply additional machine commands that depend of the position of the bit in the byte that to set or reset this bit.
Answer: See Oracle's Java Virtual Machine implementation:

Although the Java Virtual Machine defines a boolean type, it only
  provides very limited support for it. There are no Java Virtual
  Machine instructions solely dedicated to operations on boolean values.
  Instead, expressions in the Java programming language that operate on
  boolean values are compiled to use values of the Java Virtual Machine
  int data type.

The Java Virtual Machine encodes boolean array components using 1 to
  represent true and 0 to represent false. Where Java programming
  language boolean values are mapped by compilers to values of Java
  Virtual Machine type int, the compilers must use the same encoding.
Answer: You can see a discussion of the actual size used here:
What is the size of a boolean variable in Java?
But basically it comes down to a trade off between memory efficiency and performance - especially when you consider that every other variable in the class needs to start word-aligned anyway.
You can only gain by packing them smaller when you have multiple smaller objects to pack, and then you still need to potentially leave padding to align the next member.
Answer:
isn't it a waste of memory?

Yes it is a waste of 7 bits, but as everyone of us know a byte is the smallest unit of storage, JVM says it to be of 1 byte.
Comment: sorry, but not understood
Comment: @MariuszS right, but you can't directly address bits.  bytes are the smallest addressable unit of memory
Comment: [Byte](http://en.wikipedia.org/wiki/Byte) is not the smallest unit, you can store [bits](http://en.wikipedia.org/wiki/Bit) in memory too. You can compact your data.
Comment: yes, but this is something else than _smallest unit of storage_ ;)
Comment: Ok bits is the smallest unit. But aren't the 7 bits wasted in this case?
Comment: This depends, you can store 8 boolean in 1 byte without any waste :)
Comment: @iliketocode bitmasks FTW


Are the "Lord of the Rings" and "The Hobbit" movies connected someway?

Question: Are those two movies connected, if yes, what should be the order in which I shall watch these movies?
Comment: They are in the same universe, but they don't need really an order. The Hobbit is supposed to happen before the Lord of The Rings, and it wasn't filmed/released in that order. No issue there.
Answer: The Hobbit is the prequel to the Lord Of The Rings trilogy.  It's during his exploits chronicled in the Hobbit book (movie) that Bilbo first finds the One Ring, and the Lord Of The Rings trilogy is all about Bilbo needing to get said ring to Mordor to be destroyed.  Of course, his nephew Frodo is actually tasked with the delivery, but Bilbo does meet up with him in Rivendell.


Key Exchange using RSA public key without a certificate

Question: I want to share AES key using RSA. What is the recommended/widely used format for encrypting the AES key and its attributes with the public key? I know that PKCS#7/CMS enveloped-data allows encrypting any key with its attributes using a certificate. But how can I achieve the same thing without a certificate and only using a public key?
Comment: Leaving the certificate/process aside, how are you planning to do this key exchange? Over Email? Interaction between two cloud services, or what?
Comment: And why exactly do you want to use a public key and not a certificate?
Comment: @Limit The exchange will happen over TLS
Answer: Generally you'd just use RSA with OAEP padding if you want to encrypt a key. Your question however talks about exchange a key. That could also be performed using RSA-KEM.
Note that RSA was often used with TLS to provide key exchange using the RSA_ cipher suites. That RSA key was part of a trusted certificate, so it also performed entity authentication. Nowadays we like forward secrecy where the ephemeral key pair is only used once. The disadvantage of RSA for forward secrecy is that the key pair generation can take very long - it depends on how quick the primes are found.
Beware that you need some way to trust the public key or the key exchange and resulting secret. If that trust is not there then you might be encrypting with one provided by an adversary, and confidentiality of the AES key may be lost in a man-in-the-middle attack or a similar attack.
Generally you'd not use CMS / PKCS#7. That is usually used with certificates and it adds a lot of overhead which is usually unnecessary if you just want to encrypt a key value.
Answer: You can use OpenSSL rsautil to encrypt the AES key with RSA key. You need to change the RSA key into valid format which OpensSSL can accept. (OpenSSL also supports raw encryption without padding. Use only if you know what you are doing)
To encrypt:
openssl rsautl -encrypt -inkey pubkey.pem -pubin -in aes.key -out AES.enc.key
To decrypt:
openssl rsautl -decrypt -inkey key.pem -in aes.enc.key -out aes.key
You can also check SSH (RFC 4253) working which I think might me helpful.


Can the illusory copies from Mislead move through walls?

Question: Can the intangible illusory copies obtained by casting mislead move through walls?
If the illusory copies cannot move through walls, what would happen if an illusory copy tries to push someone else?
Answer: Mislead's invisibility ends if the push is attempted
From the rules text:

the invisibility ends if you attack or cast a spell (PHB. p. 260)

I am making an interpretation here, because the character controls what the illusion does, and "you attack" seems to fit with "the illusion attacks" depending upon whether you are moving your illusory double, or if you have switched back to your own senses.  It's unclear if the illusion can attempt an attack at all.  A push fits into the category of shove which is a special form of melee attack.  (p. 195, PHB, Shoving a Creature).

Using an attack action, you can make a special melee attack to shove a
  creature ...

Moving through walls is not addressed in the rules, so there you have to get a ruling based on either "if it doesn't say I can, I can't" or "if it doesn't say I can't, I can" which is as much a DM/table philosophy as anything else.
Since the general intent in D&D 5e is that "spells do what they say they do" it's a fair ruling to say "No, the illusion created by mislead doesn't move through walls."
Moving through walls, if allowed, would likely give away the illusion to any other observer, so as DM it would be appropriate for anyone seeing the mislead-created illusion moving through walls to have advantage on an ability check to notice that it is an illusion, or to recognize it as an illusion of your character without a roll.
(The comparison to Project Image has been removed now that the question has been updated).
Answer: Mislead tells you it can co-occupy and pass through occupied spaces in its first sentence, which reads (emphasis added):

You become invisible at the same time that an illusory double of you appears where you are standing.

It literally appears where the caster is standing on top of their (now invisible) body.
Supplementally, all spells that require sight carefully include the wording "you can see". For example, contrast the wording of the Acid Splash cantrip (emphasis added):

Choose one creature you can see within range, or choose two creatures you can see within range that are within 5 feet of each other.

with the wording of the Chill Touch cantrip:

You create a ghostly, skeletal hand in the space of a creature within range.

Note that moving the illusory double created by Mislead does not contain the "you can see" wording:

You can use your action to move your illusory double up to twice your speed and make it gesture, speak, and behave in whatever way you choose.
Answer: RAW it is allowed, but is at the DM's discretion
The description of the illusion school of magic in the PHB/basic rules says:

Illusion spells deceive the senses or minds of others. They cause people to see things that are not there, to miss things that are there, to hear phantom noises, or to remember things that never happened. Some illusions create phantom images that any creature can see, but the most insidious illusions plant an image directly in the mind of a creature.

The double being illusory as stated in the spell, it is not real. As you would expect from illusions, they don't actually interact physically with the world. In other words, it would not be blocked by a wall or even a creature for that matter. Same applies to Major Image, for example.
However, as pointed out by KorvinStarmast, witnessing it passing through objects or creatures would undoubtedly give away it's illusory nature. Shoving a creature might feel like a bump... but all the implications of a bump have no reason to physically happen.
In many illusion spells a lot is left unsaid; even more so in Mislead. This is on purpose. Jeremy explicitly said so in this Dragon Talk: Sage Advice on Illusions. The intent is to allow the DM to adjudicate the limits of illusions and encourage players to come up with creative uses. Notice that Jeremy mentioned different examples of illusions passing through barriers or objects/creatures passing through them. That is because the assumption is that unless said otherwise, illusions aren't actually physical.
Answer: Can move through walls, but that is interpretation not RAW
The question begins, "Can the intangible illusory copies obtained by casting mislead move through walls?"
The querent is assuming that mislead creates intangible illusory copies.  In fact, the spell does not say that the "illusory double" is intangible.  In contrast, the "illusory copy" of yourself created by project image is explicitly said to be intangible (and to be fair the original version of this question asked about both mislead and project image).
To be clear, I do believe that the misleading double is intangible, but it is important to distinguish between RAW and interpretation, and mislead does not actually specify whether the double is tangible or not.  Let's assume from here on that it is intangible.
Our question then becomes, "Can the illusory copies move through walls?"  And while it might seem obvious that intangible things can pass through a solid wall, that too is interpretation rather than RAW.  In fact, it is not actually clear what "intangible" means.  To be more precise, the rules do not specify how an intangible things interacts differently with the world than a tangible one.  Contrast this, for example, with incorporeal, which has a clear and consistent effect on movement and damage.
'Intangible' is used once in the Monster Manual (for the illusory self-image of an aboleth), once in the Dungeon Master's Guide (in flavor text quoting a Richard Baker story), and thrice in the Player's Handbook (in the spell descriptions of clairvoyance, imprisonment, and the aforementioned project image).  Nowhere is is defined in a game sense, and nowhere does it say that intangible things can move through solid objects.
So, rather than worrying too much about 'intangible', let's look at the nature of illusions.  Many illusion spells conclude with some variation of 'Physical interaction with the [illusion] reveals it to be an illusion, because things can pass through it' in their description.  Mislead does not use this phrase, although I believe that this was an editorial oversight.  So, as with intangible, let's proceed assuming that mislead should have this standard text about things being able to pass through it.
It seems both logical and reasonable that if solid things can pass through the illusion, then the illusion can pass through solid things - and yet in a strict RAW sense, nowhere does it ever say that.  Further, for all the illusion spells that allow one to create movable images, nowhere does it ever explicitly say they can be moved through solid objects like walls.
Many illusion spells say that their images appear at 'a spot within range'.  This is notably different from creature-summoning spells, which typically say that the creatures appear in 'unoccupied spaces that you can see'.  The fact that illusory images are not restricted to spaces that are unoccupied is another clue that they can, in fact, pass through solid things.  It could be argued that the ability to place an illusion on 'a spot within range' rather than 'a spot within range that you can see' implies that you could start your illusion on the far side of a wall or inside a solid object.  However, the counter-argument to that are the "clear path to the target" rules, which say that even if you don't need to see the point in space you are targeting, it still cannot be behind total cover to you.  Thus you could not make a silent image of an illusory ghost starting inside a wall and later have it move out.
As user2105464 points out in their answer, the description of mislead explicitly states that the double appears in an occupied space - the space that you are occupying!  This doesn't confirm that it can move through such a space, but it is pretty strong evidence that it can.
Finally, consider the description of major image.  There, the illusory image you create "appears at a spot that you can see within range".  Once you have made it, though, you can "use your action to cause the image to move to any other spot within range" without regard to whether or not you can see the spot.  This strongly implies that it would be possible to create the image on the near side of the wall, and then have it pass through to the far side.  If that is a working example of how illusions function, it seems like your misleading illusory copy can be sent through walls as well.
RAW, nothing says that the misleading copy is intangible or can move through walls, and in fact no illusions are explicitly said to be able to pass through physical objects.  However, the illusion in mislead appears in an occupied square and similar illusion spells permit physical objects to move through them, so a reasonable interpretation is that these kinds of illusion spells, mislead included, can move through walls and other solid spaces.
Can't attack, but if it could that wouldn't make you visible
It should be clear from the above that I think the misleading copy is insubstantial, and thus incapable of a physical attack.  As evidence for this, 'spells do only what they say they do', and nowhere in the spell description does it say that the illusory copy can attack.  This might appear to be special pleading since my argument here is that 'mislead doesn't say it is intangible or can be detected, but I bet it was intended to and that was left out as an editorial error.'  How can I be confident that the error was not actually in leaving out the part about using the copy to attack?
The difference for me lies in the practicality of adjudicating the flawed spell.  If we assume that the illusory copy was meant to be intangible but detectable, we can default to the 'pass through' detection rules used in so many other illusion spells.  But if we assume that the illusory copy was meant to be a creature that can attack, we still don't have a stat block for it.  If we assume the illusory copy was supposed to be an animated object, we still don't know its AC or hp.  Granting the spell the capacity to attack doesn't tell you anything about how the spell attacks, and there is no standard illusory stat block to default to.
However, suppose a DM rules that the misleading copy can attack, such as by making a Shove, and assigns it a Strength score.  Fair enough.  In such a case I would disagree with KorvinStarmast's interpretation that the attack would end the caster's invisibility.  Mislead says 'the invisibility ends if you attack or cast a spell' and your illusory copy is not you, any more than your familiar or your summoned animals are you (and you don't become visible when they attack, either).


Why bother with this board?

Question: The "privileged-bully" model you guys use really sucks for folks with useful knowledge, but who haven't spent lots of time in your little kingdom.  Seems that there are a bunch of you who do anything you want, and enjoy putting others down.
Comment: Hey, you're obviously upset about something. I'm pretty new here, and there are things I'm still figuring out, but I do think it's a  useful community. Perhaps your could be a little more specific about the problems you're having? That way you might get some explanation of the way things are, or how we could change to be more helpful.
Comment: Marko, I think I see what has irked you, and I don't understand it myself. I've started a question specifically about your question so we can get to the bottom of the situation. If you are open to hearing any suggestions, I suggest patience and check back here on the meta over the next few days and then decide how you feel about Music.SE: http://meta.music.stackexchange.com/questions/2675/why-was-this-question-deleted-instead-of-just-on-hold-closed-etc
Comment: You have three decent answers and on upvote so far here. That's pretty respectable and many people (myself included) don't start off as successful. Do you feel like you've been put down here? I didn't see any negative comments on your answers, nor down votes. The only negative response I see in your profile is down votes on this question. What specifically has caused you concern?
Comment: @SuperQueryLad "Crocker's rules encourage being tactful with anyone who hasn't specifically accepted them"...
Comment: Crockers Rules: other people are allowed to optimize their messages for information, not for being nice to you. You have accepted full responsibility for the operation of your own mind; anyone is allowed to call you a moron and claim to be doing you a favor. People using the rules should be able to communicate all relevant information in a minimum amount of time, without paraphrasing or social formatting. Note, that the rules do not mean you can insult people; it means you are responsible for insulting or being insulted. The rules are a discipline, not a privilege.
Answer: I started on Stack Overflow. They tend to be much stricter there even compared to Music Practice/Theory. If you look at my record of questions, none of them were ever really particularly well-received and I started to develop a bit of an attitude. Frankly, people can be jerks, and there's no excuse for that. However, responding to "jerky" comments with other jerky comments (as I've done here as well) hurts your credibility. Usually, I find, when I allow my feelings to get in the way of actually focusing on the site topic, I'm not actually focusing on the site topic. And I get my feelings hurt.
A few things to remember:

Most of the people on SE are working professionals and have stuff to do. Nobody's here to babysit anyone else, and that sucked for me when I aspired to be a coder on Stack Overflow.
We're all human, and sometimes people say stuff online that they wouldn't say to someone in person. If you've ever been online, you've said something you wouldn't say in person, almost as a rule. It's not good, or even excusable, but we all need to realize that in some way, shape or form, each of us is as guilty of abuse of anonymity as the next.  A little grace would go a long way, and realize that anonymity brings out the beast in all of us, even though in person we try to hide it. But grace is the important thing, because people will blow it even when they know they will ;-)
A lot of misunderstanding happens on the internet, and there's reason's why. First of all, the internet is where we go when it's the end of the day and we're tired (as it should be... The first fruits of our time ought to go to what we're being payed to do) so crabby, knee-jerk responses run rampant. Also, sometimes (a lot of times) intent is not carried through the text, so something that is meant to seem like a gentle correction comes across as a snarky, hot-headed, prideful reproof.
Stack Exchange actually really rocks. I've found that looking back on questions that I wrote which got closed or ill-received, it was because of my misunderstanding of Stack Exchange or the topic. Not the system's fault, actually, my fault. And whether or not people could be nicer to beginners is another question, and not specific to Stack Exchange (probably better here than at other places, depending on the stack)

As for privileged bullies, all of the privileges on Stack Exchange are earned, which is what makes Stack Exchange rock. Not just any morons get to moderate. Moderators are selected by a vote, and, for the most part, are there "for life" (they're volunteers, of course). A lot of privileges are available to non-moderators, like you and me. Now, sometimes, just because we're opinionated, stupid humans, wrong decisions can be made. This isn't specific to Stack Exchange. However, when you have a problem with a way a specific issue was handled, Stack Exchange has the meta for discussion. Note "specific issue." General questions (like this one) about people being mean and whatnot are generally not helpful.
In fact, if you have a complaint about a specific way a question or post was dealt with, by all means, ask away! That's why the meta exists. Most importantly, don't give up on the system too soon. Democracy ain't all that bad.
Comment: General Nuisance - My original post contained nothing 2017 considers offensive/abusive - that was not an issue. music.stackexchange.com/questions/52264/… The "privledged-bully" description is in quotes and spelled in an archaic manner to avoid offense while describing an operational setup.
Answer: If the problem is that you put a lot of effort into writing an answer to your own question and it got deleted, then I understand why you are upset.  I probably would be too. But that doesn't really excuse your commentary about privileged bullies.
You didn't do your research to find out what type of question works on Stack Exchange sites. Your question itself is just not a good question for this site - and the community down voted it and flagged for closure.
When people do put others down, we actually nip that in the bud quickly, with warnings, suspensions and deletion of posts that are abusive or offensive.  In that vein, please realise that your post here could be seen as rude and offensive...
But in summary, while I think the content of what you wrote is reasonable as a blog post, as someone else mentioned, it is not structured in an objective, specific way that works here.
Comment: Dr. Mayhem - My original post contained nothing 2017 considers offensive/abusive - that was not an issue.                  http://music.stackexchange.com/questions/52264/what-do-you-need-to-know-about-buying-a-guitar   The "privledged-bully" description is in quotes and spelled in an archaic manner to avoid offense while describing an operational setup.
Comment: And I specifically told you why it wasn't a good question- nothing to do with that comment. It just wasn't appropriate here. Putting something in quotes, though, doesn't avoid offense.
Comment: I apologize if my wording offended you.  I made good-faith efforts for it to not be read *ad hominem*, and feel badly that those were inadequate.
Comment: I waS disappointed the way this site is managed.                 My post was deleted by a moderator almost immediately (<2 hrs), while I was comprehensively re-casting it specifically to conform to the advice of the only four commenters who communicated.       There was one *conditional* "VTC" (vote to close?) by @Todd Wilcox - so it doesn't seem to me "the community down voted it and flagged for closure".           Wilcox himself has questioned the delete activity http://meta.music.stackexchange.com/questions/2675/why-was-this-question-deleted-instead-of-just-on-hold-closed-etc
Comment: Anything off topic will be rapidly handled if flagged by the community (and to be fair, you won't get to see moderator flags, I'm afraid) and often deleted really quickly. I'm popping a fuller answer over on Todd's post.
Answer: Marko - we know little about you - the profile is empty - so for me at least it's difficult to respond. When I started on this site, I was unimpressed by what I felt was, in some cases, ignorant (I use the word advisedly) comments and downvotes, and closed questions. Still unhappy about downvotes, given with no reasons, but maybe one day that'll be addressed. However, continuing for a while made me realise what a useful addition to my armoury this site is. Just about any questions will throw up decent answers, and sometimes it's good to see other people's viewpoints.
Yes, occasionally, I agree that stuff is done with seemingly little forethought, but being human is probably to blame for that! I'm sure your experiences (in music, not on this site!) will benefit us all, and you may well learn a shedload of stuff at the same time - I certainly have!
'If you can't beat them, join them' springs to mind. But, if you feel that you and the site are incompatible, so be it. We're all grown-ups!
Comment: Tim - Marko and I had a really good chat to get to the bottom of things. I understand much more about where he is coming from, and hopefully I got across some of the reasons why things are in the position they currently are: http://chat.stackexchange.com/rooms/52212/discussion-on-answer-by-dr-mayhem-why-am-i-leaving-mpt
Answer:
The "privileged-bully" model you guys use really sucks for folks with useful knowledge, but who haven't spent lots of time in your little kingdom.

I've defended music.se in my answer here, so I'll be a bit less equivocal here.
I think you're right.
I don't think the anyone here has the intention of bullying - but I also don't think we do very well at welcoming newcomers, ESL speakers, those who would like to explore alternative viewpoints, and so on. There's still a bit too much of that "oooh, lets mutter amongst ourselves, and downvote and close something - that will help the site!" and not quite enough of 'hey, this person is new and doesn't quite get how the site works - let's make a friend of this person and help them!'
(That isn't to disagree with those who've said that you could also have taken a little more time to understand the site and given it a second chance - its strengths are genuine).
Comment: Pretty much...  I spent time - and provoked responses - enough to understand how this was working.  I don't think you folks intend to be wrong-headed "rankists".  The nature of M:P&T does that for you.  As I wished you before... Good luck!
Comment: @Marko my mother often sends me random internet links. A while back I got one from her entitled *Pedants' corner*. Before I opened it, I *knew* it would be a link to a Stack Exchange site - and indeed it was. I think it was EL&U, but anyway... Stack Exchange is indeed full of actively anti-social behaviour; it's very much the nature of the beast.  M P&T.... really isn't *so* bad for an SE site. And it does have strengths that in my experience only SE sites have.
Comment: I finally got my "click and you're done" email (after four days!).  One last answer (the unanswered Sun Ra question), and I'll be leaving now.  There are nice folks here (@Dr Mayhem and @Todd WIlcox, noted).  I thought political sites were the worst.  But for useless bitchiness, it looks hard to beat SE.
Comment: @Marko look after yourself, and see you on the next site maybe (I'm the same name on most of them!)

Why bother with this board?


3 way switch confusion

Question: I've got a couple of sets of 3 way switches in my house that aren't functioning properly.  Basically, one switch has to be in the "up" position for the other switch to control the light.  In the set pictured, the metal box is the existing/untouched switch 1, the blue is a new box and relocated switch 2.  If switch 1 is down, the light is dead and switch 2 has no effect.  If switch 1 is up, switch 2 can turn the light on an off.  Aside from the taped neutrals with no wire nut and overall sloppy install of switch 1, what is wrong with the wire placement?
Comment: @isherwood - Suggesting trial and error electrical wiring is the most terrible advice you could give.
Comment: One of our resident sparkies will come along shortly and give you a spot-on answer, but you can try swapping the wires on them until it works. I've done so many times without the ability to instantly diagnose the situation like they can. Worst case scenario your breaker won't turn back on and you have to undo the last change.
Comment: I'll agree with 3-ways, worst thing is the light will turn on wacky... but you lost me at "Worst case your breaker won't turn back on".  If you're risking a bolted fault, it's time to stop experimenting. The worst case is actually that the protection will fail to work because it exposes a latent fault in the wiring.
Comment: Not with three-ways. There's not much that can go wrong if the breaker is off. Trust me, I could offer much worse advice. :D
Comment: Can you post a photo of the inside of the box for the light please?
Comment: @ThreePhaseEel the light is in a basement stairwell and not easily accessible.  I don't have a ladder tall enough to get up there.
Answer: Rather than melt your brain with white, black, red blah blah, let's call travelers yellow.    Here's how a 3-way circuit actually works.

Golly, that's simple. Align the two switches onto the same yellow wire, light lights.  Easy peasy.
But of course, they don't make cables in yellow-yellow-white.  They only make them in black-white-red; and; depending on the other needs of the circuit, the two travelers might be any combination of colors. That's what colored electrical tape is for.  $5 will get you a 5-pack of 5 colors.
Identify the travelers.  Travelers are

always in the same cable (so might the third wire, but it won't be that way on both ends).
On the brass switch screws if the circuit is wired correctly

Assuming your lower switch is untouched, black and red are your travelers in this circuit.  I would remark them with yellow on both ends.
Then, it's dog simple: yellow wires to brass screws, remaining wire to remaining screw and Bob's your uncle.
3-way switches don't take neutral wires, so the white wire in the blue box is definitely not a neutral.  It must be re-marked a color.  (any color but gray or green, but it's preferable to mark it for its function: black always-hot, red switched-hot).
Answer: If the metal box/switch in untouched, then the 2 travelers, black & red, connected to the two brass screws on that switch should go to the other switch in the blue box and be connected to the same two brass screws. They're not. You've got white and red to those two screws. Try swapping the white and black wires. If all works right tape the travelers at each location with some yellow tape or someone on this site will yell at you.
Comment: The white wire should be marked with black tape as well.
Comment: Thanks, Jack.  Makes sense.. I was nervous to try swapping things around without really knowing what I was doing.  And I obviously didn't pay attention to the orientation of the wires when I removed the old switch.  Will swap them around this evening and let the forum know how it goes.
Comment: @JPhi1618  Yep. another one of those "it's obvious"  when it really isn't.... thanks.
Answer: The blacked terminal screw denotes the common on the switch, which goes to the live feed in on one, and the live out to the light on the other. The two wires that go between the two switched terminals are called 'travelers' and since you've got a black and a red on one, those same two wires should be at the two switched terminal on the other switch.

Image from here
Comment: Rather than bringing the neutral 'forward' to the second box and the light, the switched live may be carried back to the first box by one of the wires - if it's the white it needs to be sleeved or taped to mark it as live.
Comment: There are probably about a half dozen ways to wire up 3-way switches.  The diagram above is my favorite way: Power in on one switch 14/3 to the other switch and from there to the fixture(s), no "code taping" needed. Conceptually straight forward.   But sometimes you end up with power-in & the switched wired to the fixture(s) in the same box.   Also, an older practice was to run power to the fixture box and then a switch leg to the switch, that really complicated 3 way switches and required lots of "code taping" to properly mark the wire. Best to take it all apart and sort it out properly.
Comment: The orientation of this circuit is different from the one pictured.  I wired in a new, separate 3 way switch setup last night that goes from switch to switch, then to the light (as pictured) and it works as intended.  This one, I'm not certain if the light is first or in the middle, but it is definitely not last.  It seems as though the white wire may actually be the common in switch 2?  Will try that when I get home.  Thanks

3 way switch confusion


is it possible to make a whole blockchain from scratch using javascript?

Question: I was wondering if javascript has alot of tools of doing stuff and help with hashing and helper nodejs modules that help with web3 development but my question is it possible to make something like ethereum or solana using javascript also is it hard to do and what nodes do i need know about , do they mean a dedicated AWS servers ? can someone explain how its possible to do this with JS and is there a pros and cons of coding this using JS and GO language ?
Answer: You can do everything in JavaScript, including Windows95 or MacOS.
(just like you can play Doom on pregnancy test)
Current list of clients: https://ethereum.org/en/developers/docs/nodes-and-clients/
(there is no JavaScript client that is widely used in production)

https://github.com/ethereumjs/ethereumjs-monorepo

Finally, the EthereumJS Execution Client (EthereumJS) has been in active development for some time now. It already serves a variety of purposes like testing, research (e.g. EIPs) and developer tooling to engage with the protocol.

Hope that helps.
Maybe you can edit question for clarity, what exactly are you trying to achieve.
Comment: thank u so much Mars , these resources will be helpful to understand how node and ethereum works for building a blockchain :)
Comment: will read these , i was trying to learn how to make something similar to ethereum but in JS because its a widely used framework all over the world from creating an EVM to actually working blockchain like ethereum or bsc or solana for learning purposes
Comment: You can make a blockchain on piece of paper or in Google Doc. Hash of the previous message is appended as a header to a new file. Or this: https://learnmeabitcoin.com/ or https://www.lopp.net/bitcoin-information.html - loads of educational information available... Maybe you'll find a DIY implementation of a blockchain for learning purposes.


Which symbol is best interpreted as describing a social interaction?

Question: I am working on a project of social media like website and I have to symbolize the interaction between two peers in a small space - equivalent to a standard FB profile picture for instance.
The question is simple, what is a commonly understood way to symbolize an interaction between two peers (or a relation) without using plain words to explain it?
Comment: Hi Pierre, welcome to ux.se. I'm not sure I understand exactly what the 'interaction' *is* that you are trying to symbolize. Is it a conversation (IM), or exchange of documents, or a ping or notification of some kind. If you *were* using plain words to explain it - what would those words be?
Comment: Hi Roger, thanks for the help. Th einteraction I am talking about is a real life interaction just as when two people go on holidays together or just like you helping here.
Therefore, depending on the context, the interaction can be Roger helped Pierre or Luke and Leia went on holidays together.
Once this interaction is translated into a post, one user may re-post it. Then I am looking for a general way to signify this re-post.
I hope that's descriptive enough.
Answer: If people have avatars, you could show both avatars beside each other. Nothing more. Do not try and connect the avatars as this may be confused or even misconstrued! If there are no avatars for someone then use a default head/shoulder blank avatar.
Let whitespace do the separation between the avatars and the description.
Take Trello as an example, where several users may be attached to a card. The important thing is that people are not related directly to each other - they are both only directly related to the event itself.
This example is taken from the Trello public development board

Answer: I think you have several ways people could relate:

Handshake
Synergy
Conversation
Social

Images below are illustrated below.
Note: These were are all taken from Google Images, so credit is not mine and some are stock photos. They are just examples.

Handshake

Synergy

Conversation

Social


Should an IT Security Policy allow employees use public Wi-Fi?

Question: Should an IT Security Policy allow employees use organisation-owned laptops holding potentially sensitive data access public Wi-Fi in locations like hotels and airports?
Comment: *"organisation-owned laptops"* does not describe any security measures actually employed on the systems. For example there are laptops which have separate compartments for business and private use and VPN which are specifically designed to protect the business data even when used within public Wi-Fi.
Comment: Even with a endpoint security suite and vpn this is a risky thing to do. However the question is more like, would it be feasible to forbid it? You do need to have to offer users a method to get things done.
Answer: Wi-fi traffic can be intercepted at will. It's essentially a broadcast, in the clear in open wi-fi, or encrypted with the password if one's present; most of the time, even that encryption is insecure.
Public wi-fi is generally unsecured networks or networks with a shared key. This allows an attacker unfettered access. A typical traveler won't know which of the many appropriately-named networks in the airport is official, and which is an opportunistic attacker. So it's a safe assumption that the traffic routinely sent through open wi-fi networks will at some point, in some network, eventually get intercepted.
As to whether it's a security problem, in the perfect scenario where the sensitive data just lies on the drive, preferably encrypted, the user is not an admin, they only use the wi-fi for their personal needs, never to send sensitive mail or access company data, and they use encrypt&authenticate all their traffic, it's not.
In the imperfect real-world scenario, where sensitive and personal data is mixed up, the users alternate between using their laptop like a workstation and like a public terminal (disregarding security, since they're "just checking the weather"), it is. You'd be trusting several human-dependent protections for security, the breach of even one of which will leak the data. Worst-case scenario, the user's laptop can get a RAT (remote access trojan) uploaded to it.
It's not an automatic security fail - much of the web uses SSL now, so it's not like everyone sees everything, and VPN traffic can come through encrypted as well. But it's a large attack surface for a dedicated or opportunistic attacker.
The best solution is, IMO, to ensure the laptops used for travel aren't holding sensitive information, and aren't plugged into the vulnerable parts of the intranet (assuming zero-trust is not in place). On top of that, ensure the personnel on travel follows at least a minimum of security practices, such as not using open networks and not mailing sensitive data without end-to-end encryption.
If it's absolutely necessary to transfer sensitive data beyond mail to and from laptops while traveling, it's possible to design a corporate network that's secure over insecure channels, but it takes considerably more security expertise to set up and keep secure than can be realistically covered in a SE answer. The VPN has to be secure and always up, the laptops have to reject all other connections, including for Windows update, there shouldn't be any ways around it, and so on.
Given the negligible cost of local SIM cards compared to the expense of business travel, it's best to use them in favor of public wi-fi, together with other security measures (encrypted mail, encrypted files, low privileges, compartmentalization, monitoring, VPN). Even secured wi-fi is still someone else's network, someone local that can be impersonated and that gets two-way access to your traffic.
Comment: Note that even a WPA2 network is effectively open if the key is shared, as anyone with the key can decrypt the traffic.
Comment: Yep. It's a screen door at best, unless you own the network.
Answer: I think the question has the wrong focus by asking only about public Wi-Fi. In general it is a bad idea to transmit any kind of sensitive information over untrusted networks without additional protection. Such untrusted networks can be public Wi-Fi, but also paid Wi-Fi in hotels, network access when visiting some customer or contractor, mobile networks, ... .
It is possible to use any of these untrusted networks with the proper additional protection on top, preferable a VPN into the trusted company network. Of course one need to make sure that really all traffic is passing always through the VPN, i.e. not only company specific sites, not only IPv4 and not only web traffic but also DNS and that no relevant traffic passes before the VPN is established. This is not easy and many VPN products fail to do it properly, but there are ways to do this correctly.
Apart from that the sensitive data on the laptop itself should be well protected even if the laptop is not inside some network. Laptops easily get stolen so the sensitive data need to be protected against theft, maybe combined with previous password leakage through should surfing.
Answer: As steffen mentioned, a good solution may be a company VPN. You probably want to have one anyway, so you just have to enforce all traffic through the VPN. The employees can access the internet and the data is mostly secure. All the other precautions and warnings from Theracs post still apply though, as do all best practices, for example encrypting work data  and separating them from personal data.
Comment: How does VPN help if the MITM attack occurs over insecure WiFi and targets data on the hard-drive ?
Comment: @alfasin VPN is basically an encrypted tunnel. As long as you don't accept any traffic other than the VPN connection, there is no way they can do anything using the wifi, without getting into the VPN tunnel, which with good settings should be near impossible.
Answer: As the others have touched upon, one of the greatest issues entailed with this scenario is that accessing public WiFi presents significant security challenges. This is the case due to poorly secured Wireless Access Points (WAPs). Additionally, you then face the threat of rogue access points and clone access points (utilized for Evil Twin attacks). Mitigating the threat posed by these security flaws is difficult, but if one must connect to public "hotspots," then the best approach is to utilize a VPN.
However, one could argue that a VPN is not enough in this instance. If we are discussing the prospect of utilizing a machine that contains vital information on a public network, then we must find other means of securing it. Basically, the machine should have a strong password, have anti-malware software on board, be up-to-date with common malware signatures, and potentially have an encrypted hard disk (think FDE [Full Disk Encryption]).
It is worth stating, however, that any system that contains classified/sensitive material is unlikely to be allowed to leave the premises. In removing such a device from the premises an employee usually runs the risk of violating their clearance, violating the terms of their contract, and potentially violating non-disclosure agreements (NDAs). You might also potentially risk being accused of stealing that information for some nefarious purpose.
In the post-Snowden era, you can be guaranteed that most companies that have highly sensitive information are going to ensure their employees cannot bring this information home. The only exception may be found with remote employees, of whom work from home and have different conditions applied to their access of sensitive material. Generally speaking, information security specialists (especially information assurance experts) should ensure employees follow so-called best practices and do not violate their own security and/or the company's.


What happens if I test Covid positive while staying in a German Hotel

Question: I'm due to stay in a hotel for a couple of nights in a small hotel in Cologne before flying back to the UK. I now need to get a pre-departure Covid test. What happens if I test positive? The hotel may not want us to stay, and may not have room or even room service/facilities for us to isolate properly. The German rules seem to be that you have to isolate where you are but I'm not sure how that would work in this case.
Comment: The [German Foreign Office](https://www.auswaertiges-amt.de/en/coronavirus/2317268) says "If travellers develop symptoms associated with COVID-19 ... they should get in touch by phone with a doctor or contact the hotline 116 117. Often travel guides or hotels can also help in such cases. Travellers should keep the contact details of their home country's embassy or consulate in Germany in case they need to contact them." As to how hotels react, if they can't accommodate you, then you can't stay there, and you'll have to pay additional costs - exactly where you stay will be up to the state govt.
Comment: My understanding is that you should continue to isolate where you are: https://www.zusammengegencorona.de/en/from-suspected-infection-to-isolation/

Whether or not your hotel does not have the facility to house you, I'd say you need to contact your travel insurance provider in the first instance, and the embassy/representation of your country in the second. The reason I say to contact your insurance provider first is that your travel insurance may be affected due to your infection: https://travelhealthpro.org.uk/news/499/novel-coronavirus-covid-19-general-advice-for-travellers
Answer: Last I've heard was that you will have to report to the local Health Office or "Gesundheitsamt". They will manage this but as far as I can tell there is not a whole lot of consistency or predictability in the process.


How to construct a pattern that match the multiple partial differential of any multi-variable functions?

Question: For example,I want to match a multiple partial derivative of a function $f^{(1,0,1)}[x,y,z]$ which is the same as$\frac{\partial^2{f}}{\partial{x}\partial{z}}$.The only information given is the list of the independent variables such as {x,y,z} in this example. So I try to construct a
pattern something like u_^[(n__)][independ] to match an arbitrary partial differential of an unknown function. However, it turns out to be wrong. For a simple case that has only one independent variable like $f^{(3)}[x]$ I can construct a pattern like D[u_[independ],{independ,n_}] to correctly match the partial derivative.But i don't know how to proceed to the multivariable cases. Are there some good soulutions?
Answer: Tutorial: Introduction to Patterns
"...the structure the Wolfram Language uses in pattern matching is the full form of expressions printed by FullForm."
Consider
D[foo[x, y, z], {x, 2}, {y, 3}]

See the underlying expression using FullForm:
FullForm @  %

Derivative[2, 3, 0][foo][x, y, z]

So the pattern you need is Derivative[__][_][__]:
list = {g[x], D[foo[x, y, z], {x, 2}, {y, 3}], x + 4, w''[x]};

Cases[Derivative[__][_][__]] @ list

Answer: Define some test cases, including 1 that we would like to leave unchanged
tests = Flatten[{f[u], f'[x], D[f[x, y], {{x, y}, 2}]}];

Examining the FullForm of these gives us a clue as to what we are trying to match
FullForm[tests] // OutputForm
(* List[f[u], Derivative[1][f][x], Derivative[2, 0][f][x, y], Derivative[1, 1][f][x, y],
Derivative[1, 1][f][x, y], Derivative[0, 2][f][x, y]] *)

Define a pattern to match this (and a rule, transforming the result)
pattern = Derivative[ns__][g_][xs__] -> g[xs, ns];

Demonstrate that it matches where desired
tests /. pattern
(* {f[u], f[x, 1], f[x, y, 2, 0], f[x, y, 1, 1], f[x, y, 1, 1], f[x, y, 0, 2]} *)


Commerce discount promotions as a fieldtype?

Question: I'd like to create an entry in Craft that talks about a new discount, and then choose that discount via a field (so a bit like you can choose an entry or a product). That way, should the parameters of the discount change, I'm not having to manually update the information in the entry to match any changes to the discount details. Is there a plugin for this?
Comment: ^ I guess the same could apply to commerce subscriptions as well. By the way I'm using Craft 3 and Commerce 2.
Answer: That field type doesn't currently exist, but it wouldn't be hard to create it.
Here's the relevant code you'd need if you want to take a stab at it:
use Craft;
use craft\base\ElementInterface;
use craft\commerce\models\Discount;
use craft\commerce\Plugin as Commerce;

// ...

public function normalizeValue($value, ElementInterface $element = null)
{
    if ($value !== null) {
        return Commerce::getInstance()->discounts->getDiscountById($value);
    }

    return $value;
}

public function getInputHtml($value, ElementInterface $element = null): string
{
    $options = [];
    foreach (Commerce::getInstance()->discounts->getAllDiscounts() as $discount) {
        $options[] = ['value' => $discount->id, 'label' => $discount->name];
    }

    /** @var Discount|null $value */
    return Craft::$app->view->renderTemplate('_includes/forms/select', [
        'id' => $this->handle,
        'name' => $this->handle,
        'options' => $options,
        'value' => $value->id ?? null,
    ]);
}

With that, the field type's value would always either be a Discount model or null, so in your templates you could do this:
{% if entry.myDiscountField %}
    Code: {{ entry.myDiscountField.code }}
    ...
{% endif %}

Alternatively, you could pull this off with a simple Plain Text field that stores a discount code, and then fetch the discount manually from your template.
{% if entry.myDiscountCodeField %}
    {% set discount = craft.commerce.discounts.getDiscountByCode(entry.myDiscountCodeField) %}
{% else %}
    {% set discount = null %}
{% endif %}

{% if discount %}
    Code: {{ discount.code }}
    ...
{% endif %}

Comment: I am having a problem after create the discount field. When I try to save the entry with discount field, I got the error "Discount Field should contain at most 255 characters." I checked the code in the field, and commented out "normalizeValue" function. Or instead of commenting ```public function normalizeValue($value, ElementInterface $element = null)
{
    if ($value !== null) {
        return Commerce::getInstance()->discounts->getDiscountById($value)->id;
    }

    return $value;
}``` might be right?


How do you make Empties visible in final renders

Question: I can't see the images I imported into blender in the final render.
Comment: You can't render an empty, you should have imported the image as "Images as Planes", or go into View > Viewport Render Image
Answer: If you add the image as a Reference or Background, it won't show up in the render. Instead, you should add it as a texture to a plane. There is an add-on called Import Images as Planes that simplifies this.

Once it is enabled, its operator will show up (Add > Image > Images as Planes). When you run it, it will open a file browser to allow you to select the image file you want to use. More importantly, you should tweak the operator settings. The most important are the Material Settings which will determine how the plane will behave in the render.
Comment: Thank you. That helped
Comment: You're welcome!


Problems with import photo from AD to SP 2013

Question: I have imported user's profiles from AD to SP. I got all attributes that I need except AD photo (thumbnailPhoto). I did the same steps like here, and the problem still exists. I double checked permissions of my account in "User Profile Service Application", also I checked DB permmissons of my account.
Answer: SharePoint 2013 supports two types of profile synchronization:

The classic "Synchronization Service" with ForeFront Identity Manager.
The new Feature "AD Import".

Picture-Import is only possible with the Sync-Service.
AD-Import is not able to import pictures (see here: "The AD import option does not support property mappings for complex types like pictures and special AD types.")
You can check your configuration in the UserProfile Service by clicking on "Configure Synchronization Settings"
Comment: Thank you for your answer! I did "AD Import" in sync in  UserProfile Service. Can I get some attributes by "AD Import" and get photos by another type of synchronization?
Comment: Sorry, this is not possible. You have to decide for one of them. But if you managed to get Sync-Service running, there is no big difference in SharePoint to configure the mappings. Please note that your existing Sync-Connection will get lost if you switch from AD-Import to Sync-Service. So document your changes!


How do reality and online TV shows prevent leaks regarding winner names?

Question: Big Online Reality TV Shows are able to keep the winner names a secret even after the shooting is finished. Even after searching on the Internet one is not able to find them. How do they keep such things confidential when there are huge audiences present?
Comment: FWIW, my wife and I were on a game show, and we won some money. We had to sign a contract that said (1) we would get our money when the show aired in a few months, and (2) if we told anybody we won or posted our win on Twitter or something, we would _not_ get the money.
Comment: @Vishwa I thought about it, but the OP is asking about "reality TV" shows. A game show is technically "reality", but it's very different than _Survivor_ or _The Bachelorette_.
Comment: "Big Online Reality TV Shows" - like which ones? Most reality TV shows I know of (Big Brother, Love Island...) are broadcast live.
Comment: @F1Krazy - Survivor may be one example. I seem to remember many years back when they did have a leak. Naval guy out of Seattle area or something.
Comment: I was talking in general a recent example would be Comicstaan which is Amazon Prime India's Exclusive show and uploads an episode every Friday. It ended today.
Comment: @F1Krazy I am not talking about live ones but the ones which are pre-recorded
Comment: Whilst not a game show, I went to a live recording of the comedy sci-fi Red Dwarf. We didn't have to sign anything, but beforehand the main writer and co-creator basically asked the audience nicely not to spoil anything online, and I believe it worked - certainly didn't encounter anything for that episode, or any others.
Comment: @BrettFromLA I think you should make your experience as an answer
Comment: @BrettFromLA yes exactly I was also wondering why I'm getting all my answers as game shows. I am more concerned with shows where there is competition for a whole season rather than new people in every few episodes
Comment: Related: https://movies.stackexchange.com/questions/62443/how-do-they-keep-the-identity-of-the-winner-secret
Answer: I had a friend who was on a baking competition show. He was required to sign a non-disclosure agreement saying that he would not reveal the winners or losers of the show until the episode had aired. There was some penalty if he did reveal anything, though I don't recall what it was. Surely if he had won (he didn't) they would have revoked his winnings.
On the up side, the day it aired, he baked several of the things he made on the show and we ate them while we watched the competition!
Comment: I have a friend who was on a quiz show, in addition to having to sign an NDA; if they won the episode/money this would not be paid out until the episode had aired.  So no rocking up in a brand new Mercedes saying he couldn't tell us if he'd won.


xmlsitemapprovider multiple nodes with same URL

Question: Google it around but cannot get the answer.
<code><siteMapNode url="~/BV1Menu.aspx" title="Baseline Visit 1 Menu" description="Baseline Visit 1 Menu">
    <siteMapNode url="~/Forms/RAND.aspx" title="RAND" description="RAND BV1" />
    <siteMapNode url="~/Forms/PDQ.aspx" title="PDQ 39" description="PDQ 39" />
    <siteMapNode url="~/Forms/HSU.aspx" title="Health Status Update" description="Health Status Update" />
</siteMapNode>
<siteMapNode url="~/MonthlyMenu.aspx" title="Monthly Menu" description="Monthly Menu">
      <siteMapNode url="~/Forms/HSU.aspx" title="Health Status Update 1" description="Health Status Update" />
</siteMapNode>
</code>
As you can see I have 2 "~/Forms/HSU.aspx" here, so it give me a exception said that "Multiple nodes with same URL".
I tried 2 ways to solve it but never achieve. I have a encrypted query string.

Adding "#".
When I adding "#" like this "~/Forms/HSU.aspx#?eq=123456789", not working because the eq is null.
When I adding "#" like this "~/Forms/HSU.aspx?eq=123456789#", not working because the SiteMap Control always find the first HUS.aspx as current node, and it's parent node would be BV1Menu.aspx.
Adding dummy query string.
Not working, the same situation like the 2nd above.

I know there is a URL rewriting solution, but my query string is encrypted, no way to rewrite the URL.
Please help.
Answer: Here's an example for a project that I'm working on, it's worked fine for me:
<code> <siteMapNode url="~/ExperimentsView.aspx?path=htt" title="HTT" />
 <siteMapNode url="~/ExperimentsView.aspx?path=mtt" title="MTT"/>
 <siteMapNode url="~/ExperimentsView.aspx?path=HPLC" title="HPLC"/>
 <siteMapNode url="~/ExperimentsView.aspx?path=UVSpec" title="UV-Spec"/>
</code>


Webistrano - Phusion Passenger - Could not find rake

Question: I'm having issues running deploy tasks in Webistrano.
This only when I run Webistrano from Nginx with Phusion Passenger.
When I run Webistano with the following command, everything runs fine.

ruby script/server -d -p 3000 -e production

But when running it from from Phusion Passenger (compiled with "passenger-install-nginx-module") and I want to do a deploy (the application is running) I get the following error in my log:
/usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.1.5/lib/bundler/spec_set.rb:90:in `materialize': Could not find rake-0.9.2.2 in any of the sources (Bundler::GemNotFound)
from /usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.1.5/lib/bundler/spec_set.rb:83:in `map!'
from /usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.1.5/lib/bundler/spec_set.rb:83:in `materialize'
from /usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.1.5/lib/bundler/definition.rb:127:in `specs'
from /usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.1.5/lib/bundler/definition.rb:172:in `specs_for'
from /usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.1.5/lib/bundler/definition.rb:161:in `requested_specs'
from /usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.1.5/lib/bundler/environment.rb:23:in `requested_specs'
from /usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.1.5/lib/bundler/runtime.rb:11:in `setup'
from /usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.1.5/lib/bundler.rb:107:in `setup'
from /usr/local/lib/ruby/gems/1.9.1/gems/bundler-1.1.5/lib/bundler/setup.rb:17

My bundle gemlist:
  Gems included by the bundle:
  * actionmailer (2.3.11)
  * actionpack (2.3.11)
  * activerecord (2.3.11)
  * activeresource (2.3.11)
  * activesupport (2.3.11)
  * bundler (1.1.5)
  * capistrano (2.6.0)
  * erubis (2.7.0)
  * exception_notification (22.214.171.124)
  * highline (1.6.13)
  * mocha (0.9.8)
  * mysql (2.8.1)
  * net-scp (1.0.4)
  * net-sftp (2.0.5)
  * net-ssh (2.5.2)
  * net-ssh-gateway (1.1.0)
  * open4 (0.9.3)
  * rack (1.1.3)
  * rails (2.3.11)
  * rake (0.9.2.2)
  * syntax (1.0.0)

This is in my nginx.conf :
passenger_root /usr/local/lib/ruby/gems/1.9.1/gems/passenger-3.0.15;
passenger_ruby /usr/local/bin/ruby;

And my specific server config:
passenger_enabled on;
rails_env production;

It's strange that running this with WeBrick just works as it should, but passenger via nginx isn't.
I'm not very into Ruby, and I don't really know where I should start looking.
I install ruby from the source, no rvm.
Thanks in advance!
Edit:
The error comes from this line :

ruby script/runner -e production ' deployment = Deployment.find(1085); Webistrano::Deployer.new(deployment).invoke_task! '

Works as aspected when executed from commandline, but doesn't when executed from within the app via nginx/passenger.
Answer: Maybe a bit late, but I'd guess that the error is related to the user that it's being run under.  Passenger runs under the Apache user.  There is an issue with git that is discussed on the Webistrano wiki that is similar.
https://github.com/peritor/webistrano/wiki/Installing-with-Phusion-Passenger


SSH hangs on "exec request accepted on channel 0"

Question: I have a question that appears very similar to others that have been asked but none of them have answered my problem. I'm running into an ssh error on sending a command (not loading an interactive shell).
The Scenario
My default shell at my company is csh instead of something more sane like bash. I know bash is supported since some other teammates use it as the default shell. For all of our processes, csh works fine but I would just like to use something better. I've modified my .cshrc to start up bash.
setenv SHELL /bin/bash
exec /bin/bash --login

That creates the shell just fine, sets the SHELL environment variable and starts bash on startup. The issue arises with all of the ssh (and rsh) commands that are run either through scripts or manually. I can run ssh user@host and get a shell just fine but I'm trying to run ssh -vvv user@host "echo hello"
It hangs at the end, after authenticating and sending the command, with
debug1: Sending command: echo hello
debug2: channel 0: request exec confirm 1
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel 0: rcvd adjust 2097152
debug2: channel_input_status_confirm: type 99 id 0
debug2: exec request accepted on channel 0

What I've Tried
These changes are being tested by just sshing to the localhost to keep it simple.
.bashrc and .bash_profile changes
I've played around with so many different configurations of .bashrc and .bash_profile making sure it's not related to environment variables. That doesn't really seem to be the issue since they're all the same in bash as they are in csh (which works just fine).
Adding -t
I added the -t flag to ssh to connect but that doesn't actually run the command I tell it to run but gives me a shell to use.  It also isn't necessarily a solution in and of itself since a bunch of scripts can't be modified as they're shared by everyone.
[user@host: ~/test ] $ ssh -t user@host "echo hello"
[user@host ~]$

Sanity Testing In csh
With -t:
[user@host: ~/test ] $ ssh -t user@host "echo hello"
hello
Connection to host closed.
[user@host: ~/test ] $

Without -t:
[user@host: ~/test ] $ ssh -t user@host "echo hello"
hello
[user@host: ~/test ] $

Additional Info
IT support at my company has taken a look and just said it was a problem with my bash profile and to look at my .bashrc and .bash_profile, basically telling me to figure it out myself. I'm not saying they're wrong but I am saying I've done all the debugging I can think of, which is why I'm coming here. This also pretty much means I can't change anything on the server side and have to rely on the client/user side.
Bash is definitely loaded and not running csh with my .cshrc changes, as judged by ps:
   PID TTY          TIME CMD
  6725 pts/68   00:00:00 bash
 26391 pts/68   00:00:00 ps

Conclusion
What the heck is going on? I'm pretty confused since I don't know all that much about the inner workings of ssh and I'm even less certain why csh would behave one way and bash another. Is my bash startup funky?
Answer: Answering my own question but...I tried something new that seemed to work?
I ended up moving the bash startup commands (the setenv and exec) from .cshrc to .login. I have no idea why this would change things since as far as I know, csh loads both of those things the same way and one right after another. But with that, ssh now works and all my scripts I needed runs. So...if anyone else ever has an issue like this, try this simple step.


Spacetime Mercury vs Earth

Question:
What is the time dilatation between the planets Mercury and Earth?
Can a person survive on the dark side of Mercury in the In the L2 position to Mercury and the Sun?
Comment: Not specific to your question, but Mercury has craters which never get sunlight and are actually cold like empty space.   Some of those craters even have ice in them.   It would be a workable location to set up a lander to study Mercury or possible to land some people.   The dark side of Mercury would also be explorable for months at a time too.   I wouldn't want to live there, but manned exploration of Mercury is possible.   Exploration of Venus on the surface would be much more difficult.
Answer: The time dilation on Mercury is mostly negligible.    At closest pass to the sun, 47 million KM, the gravitation field strength from the sun is less than 2% the gravitation from Mercury, so that's virtually nothing.  Even on the surface of the sun the gravitational time dilation is tiny, but at Mercury distance it's minuscule.   What has a bigger effect is the speed of Mercury's orbit, but the effect there would need to be measured in vector combination with the the speed of the Sun around the Milky way and the speed of the Milky way through the universe, so that would rise and fall depending on where Mercury was in it's orbit, and even at plus/minus 180,000 kph, the time dilation effect is very small.
Can a person survive in the L2 position in space?   That's an odd question.   People can't survive in empty space without a ship anywhere, and within a space ship, survival in space is no longer an issue, so I'm not sure what you're going for there.
Would the ship be hot that close to the sun?  Yes, it would need some cooling function, unless it was in shadow, which L2 of Mercury might be.  (I'd have to run the numbers).
In any case, All L2 orbits are unstable but the L2 of Mercury is more unstable than most due to Mercury's elliptical orbit and high orbital velocity.   Are you asking if L2 would be shaded from the sun by Mercury or did you have something else in mind?   L2 is still a good location for an orbit of sorts, as it requires much less adjustment, but it still always requires adjustment cause objects don't stay in L2.
Comment: Just look at the [MESSENGER spacecraft](https://www.nasa.gov/mission_pages/messenger/main/index.html) which orbited Mercury for ~4 years (it did its first flyby in 2008 and inserted into orbit in 2011).  They used a heat shield.

Spacetime Mercury vs Earth