Is there any law against bribing an elector?

Question: Is there any law against bribing an elector of the US Electoral College or against an elector accepting a bribe (other than the laws against violating their pledge)?
Comment: I don't have any citations for you, but its illegal to bribe state and federal officials, and electoral are defined by a mixture of state and federal laws, so it would almost certainly fall into existing state/federal bribery laws.
Answer: Found a reference elsewhere which led me to 52 USC 10307:

(c) False information in registering or voting; penalties Whoever
  knowingly or willfully gives false information as to his name, address
  or period of residence in the voting district for the purpose of
  establishing his eligibility to register or vote, or conspires with
  another individual for the purpose of encouraging his false
  registration to vote or illegal voting, or pays or offers to pay or
  accepts payment either for registration to vote or for voting shall be
  fined not more than $10,000 or imprisoned not more than five years, or
  both: Provided, however, That this provision shall be applicable only
  to general, special, or primary elections held solely or in part for
  the purpose of selecting or electing any candidate for the office of
  President, Vice President, presidential elector, Member of the United
  States Senate, Member of the United States House of Representatives,
  Delegate from the District of Columbia, Guam, or the Virgin Islands,
  or Resident Commissioner of the Commonwealth of Puerto Rico.

Note that selecting a presidential elector is listed separately, so "electing any candidate for office of President" refers to the actual election of the President, that is, the vote of the Electoral College.


can you set permissions with HooKan Permissions Manager

Question: can you set permissions with HooKan Permissions Manager, or does it just display them? I see this plugin is for setting permissions and I didn't know if I needed to get both, http://devot-ee.com/add-ons/entry-permissions
Answer: You can set permissions with HooKan. The HooKan CP will display permission statuses as you set/unset them. The interface is ajax, so you see status as you make changes.


is it possible to interact with entities that are in unloaded areas or chunks?

Question: I was thinking of shooting a sheep faraway from one end of the world to another. Though arrows can go that far, what if they do? And if they do, will they be able to hit the sheep that's standing in the unloaded area or chunk? Well, the real question is, is it possible to do any interactions to entities in unloaded chunks?
Answer: Nope.
Unloaded chunks are, rather unsurprisingly, not loaded.  This means they only exist on disk, not in memory.  In order to do anything with them, they would first have to be loaded into memory, at which point you could no longer call them "unloaded chunks."  So by definition, nothing interesting ever happens in an unloaded chunk.
(You probably could point an NBT editor at the unloaded chunks, but I wouldn't risk it.  Shut down Minecraft before you try to edit its files, since it might decide to load chunks when you aren't expecting it.)
Comment: On a side note spreadplayeres do load chunks when it spreads the player/entity.
Answer: There is a way to shoot the faraway sheep. If the sheep is within a spawn chunk it will never be unloaded. Then you can go as far as you like and take your shot!
Comment: Arrows are themselves entities.  If OP's arrow enters an unloaded chunk on the way to the spawn chunk, it may stop.


Registry Expiry Date

Question: I'm fairly new to dealing with domain names and I have a question that's been puzzling me. Upon checking the WHOIS information for my domain, I came across two distinct expiration dates:

Registry Expiry Date: 2023-06-25
Registrar Registration Expiration Date: 2023-10-31

I'm finding it hard to determine when my domain will actually expire and subsequently go offline. Is it on the earlier date of 2023-06-25, or will it be later on 2023-10-31? My concern has grown because the first date is just around the corner, and, unfortunately, I won't be able to reach out to my hosting provider over the weekend. I only became aware of this today, so I realize I'm cutting it very close, but I'd really appreciate some clarity on this matter.
Comment: What is the TLD of this domain? Are you seeing these two dates in the same whois lookup? I would expect either one or the other (depending on the WHOIS server), and they _should_ be the "same" in my experience? Since the first date has now past what have you found out?
Answer: Are you looking in https://lookup.icann.org/en/lookup, the official ICANN lookup site?
If I look there it only has the Registry expiry date which is what I would trust.

Registry Expiry Date


How do I remove Selfmite worm?

Question: In June this year I experienced what I've found to be called the "Selfmite" worm on my Nexus 5 smartphone.
On 24.06 and 29.06 it sent the message "Dear [contact name], Look The Self-time, http://goo.gl/[...]" to 13 of my contacts, chosen in what seems to be a random order.
Once I realised this had happened, I looked the issue up on Google through the phrase used in the message and found that this worm should actually install itself as an app called "The self-timer" that you should be able to uninstall, but I could not find this after looking through all of the installed apps listed in the settings page.
At the time I had enabled the security option within Android that allows the installastion of apps from unknown sources and I realized my mistake then, though I do not know how the worm actually reached my phone since I had never clicked any dodgy links in messages or the internet.
After this I disabled the installation of apps outside of the Play Store, and installed the avast! Mobile Security app for whatever help it may be in the future.
It wasn't until this Saturday, on 23.08, that the messages were sent again to the same contacts. I had not touched any security settings, nor had I accessed any sketchy sites, and once more I have found no unusual app to have installed itself.
My question now is, does anyone know of a way to prevent another occurence of this without actually wiping my phone clean? Though I wouldn't know if this would even help as I don't understand how the worm exists in the phone in the first place.
Would activating Avast's firewall within their app be of use? Rather, I'm asking if going through the hassle of rooting the phone is worth the trouble.
Thank you in advance to anyone who has advice or opinions to offer.
Answer: Wipe your phone, and reinstall the OS following the official instructions. Make sure to download the ROM images on a computer that isn't backdoored, and verify the checksums before you install.
That's the only way you'll be able to trust this device with private data again. Since you don't know how this malware was installed, you also don't know what other malware might already be on your phone.

How do I remove Selfmite worm?


Are there any drawbacks to using all-lowercase file names in an ASP.NET Core project?

Question: I'm about to port my web site, which currently uses all-lowercase file names for everything, to ASP.NET Core.  When I look at example code and open source projects, I see that everything seems to use mixed case (e.g. MyClass.cs rather than myclass.cs).  The latter seems like it could have some benefits.  For example, considering that client-side JavaScript code generally uses all-lowercase and certain files such as project.json do by convention, it would eliminate confusion as to what capitalization to use for what file, especially if the project were ever to be browsed on a case-sensitive file system.  Are there any drawbacks to this approach, any reason why it doesn't ever seem to be done?
Comment: I generally have script files all lower case, code that is going to be compiled should stay camel case.  It's only the devs who are gonna see the source anyway.
Comment: Also, default view name is based on related controller name so for some file the capitalization would be important. **For consistency and to allows automatic renaming of a class when file is renamed from `Solution Explorer`, it is usually recommended to use file name that is the same as the class name.** A good habit is to usually have one file per class.
Answer: Regarding referenced files in the solution should not matter.
C# however can have some case sensitive parts to it so you might want to have a read of this Why is C# Case Sensitive? just to be sure no other issues are there from lowercase variables etc.


Xbox live gamertag recovery

Question: How do recover a gamertag, on Xbox live? But I know longer know the email address or the password associated with the account
Answer: You will need to personally contact Microsoft's Xbox Support. they give you a couple of options, from email contact to phone support.
The more proof you have that you are the original owner of the account, the better. Here are some things you can have at the ready to give them more confidence, and hopefully sort your problem out quicker:

Any personal details you signed up to the account with (an old address, phone number or email address)
Any credit card you have linked to the account (they will only need the last four numbers, in effort to keep your cards secure)
Any key you redeemed (eg. games you purchased as an Xbox key, DLC redemption codes you might have received with physical games)
A rough history of your account use (anybody can check if an account has played a copy of Batman: Arkham Asylum, for example, but the owner is more likely to be the only one that knows the game was played for a couple of months half a year after its release, and never again, since.)
Answer: You are going to need to talk to Microsoft Support for XBox Live.. That is pretty much your only option at this point in time.

Xbox live gamertag recovery


Repairing cracks in sneaker treads

Question: I have a pair of Jordan 1 low and today I found out that the midsole of the shoe start having cracks. I am thinking if I can use any rubber mould to cover those crack or if there are any other ways to help to cover the cracks on the midsole. If you could help, that will mean the world to me. Because that Jordan is my favourite shoe. It has been with me for 10 years, so please help.
Comment: If you can get the gel version of superglue, that will work - but not for long, in my experience, unfortunately, Otherwise, take 'em to a shoe repairer, see if they've got a solution.
Answer: Styrene-butadiene rubber cements (glues), that is, styrene-butadiene copolymer dissolved in an organic solvent, such as Shoe Goo, is effective.
Clean and wire-brush the sole before applying, force the goo into the cracks, and try to shape it to the tread pattern with a popsicle stick.
In my experience, it adheres fairly well, but eventually wears a bit faster than the original rubber sole.
N.B. If the sole has started to crack, then you'll find many more forming, though.

Repairing cracks in sneaker treads


Who reviews the postdoc file applications? (UK)

Question: I was informally invited to apply for a postdoc position at a university in the UK. The professor will be the PI of that project and said I can use the resume and the covering letter I had once for a postdoc. The problem is that the advertised position asks for certain skills that I didn't  highlight in the cover letter. So, I'm not sure if I should use trust the PI and use the original documents or I need to customize the files a bit more. Is the PI is the only person who reads the application documents? Or the files get analyzed first by the HR team and then they're sent to the PI?
Comment: I don't know how it works in the UK, but in the US context I would be very wary of generalizing any answer from one university to the next or even between different departments at the same university.
Comment: @AlexanderWoo Things are more universalised over here, because HR and management have a tighter stranglehold
Comment: Actually this potential PI told me to use the same documents I used in a different university. But this documents are already 80% close to the person specification, it's just this postdoc have extra skills (mostly soft skills).
Answer: Similarly to the answer of @YemonChoi above, the way recruitment is supposed to work at the place I have experience (n=2, higher than @Yemon, but not massively) is that HR passes the documents, mostly without reading them, to a recruitment pannel chaired by the PI who holds the grant.
The panel independently score the applicants on a predetermined scoring scheme matched the person specification drawn up for the position (and normally advertised with it) and the applicants with the highest scores are invited to interview. For any internal redeployment or disabled candidates that are not invited to interview, there most be an explicit reason why not.
Interviews are conducted using predetermined questions/activities and the panel score the interviewees independently. After the interviews, the panel confer, but ideally, the best performing candidate is offered the job first.
Thats the theory.
In practice, the PI generally decides who they want to interview, and checks that the rest of the panel agrees.
At interview, most panel members don't bother to score on the predetermined criteria. After the interview, they have a conversation, but in the end the PI makes the decision. Scores are then created to justify the decision made.
What this means for the OP is that if the PI wants you, the rest of the panel will not get much say. That said, it probably can't hurt to make some optimizations to your materials, unless that will be very time consuming and you worry about a soft or hard deadline, or creating a poor impression to the PI for being slow.
Comment: Thank you for your answer Ian, I took the safe road and customized the application a little bit. For my case, the PI is interested in my application and encouraged me to apply, and warned me that the competition is going to be tough, so I want to avoid creating a poor first impression.
Answer: Caveat: I only have direct experience with one place in the UK (my current employers).
Based on this experience:

The files pass to central HR first who are then meant to pass them onto a panel which will include the PI and selected colleagues. I am not sure if they undergo any screening beyond "were the right documents supplied".

It is the panel's responsibility to make a shortlist, during which they will give applications a score based on certain tick-boxes. For instance, some of the criteria mentioned in the job advertisement might say

"Essential: experience with MATLAB or similar software"

and then the panel might give the application a score such as "3: exceeded" or "2: met" or "1: partially met" or "0: not met".

The panel should have access to all submitted documents, not just the cover letter. However they are NOT meant to make use of external private knowledge, to avoid prejudicing the decision. E.g if the PI knows that you have done X, Y and Z but you don't include this in any of the documents, then strictly speaking they are not meant to use this when making their evaluation and rankings.

My observations are based on recent experience of being on such a panel, but not being the PI.
Depending on the institution and the discipline, the panel might include people from outside the specialist area but with some general experience in related project management; it could potentially include cross-faculty members depending on the nature of the project.
Usually the PI is the chair of the panel and hence informally gets "final say" in edge cases. Nevertheless, my recommendation would be to play safe and customize the documents a bit more -- it just makes it easier for supportive panel members to tick the appropriate boxes.
Comment: Thank you for your answer. I was just worried that documents will have an initial screeining by someone else before sending them to the PIs. But I think I'll play it safe!
Comment: My experience (of two places, rather than one) is that what is described here is what is supposed to happen, but in reality, the PI asks a couple of their friends to be on the panel, will let them know ahead of time what his preferences are on the candidates. The PI will definately make the decision on who to short list. After interviews the PI will ask for the panels opinion, but in the end will make the decision themselves more or less independently. Any documentation will be written afterwards to fit the decision.
Comment: @IanSudbery Sure, but I thought that I would give the author of the original question the "safe" advice rather than saying "hey the PI says you're in, so no need to sweat". I can only say that the description above is what happened for the panel that I was on, but perhaps that was due to a conscientious PI and colleague with whom I am on good terms.
Comment: @IanSudbery You're welcome to write an answer setting out your experiences. (I mean this sincerely and without snark, since one point of SE platforms is that contrasting answers can be left!)


Views - user/role has access to edit node

Question: I'm trying to set a view that shows only the nodes that current user or role has access to edit. I've tried with contextual filters and relationships but with no luck. Anyone know how to restrict it?
Answer: Views accessed can be controlled by Views Access configuration, check the screen shots if it helps.
Step 1: Find the Views Access Configuration

Step 2 : Opt the permissions, which suit your needs

Step 3 : Configure the permissions
Comment: This is pretty much spot on! And also a recommended way instead of using the views_php module.
Answer: It can be done with Views PHP, but I don't think it can be done just within normal Views configuration - would be delighted to be contradicted.
If you're OK to use Views PHP the steps are:

Add Content: Nid as a Field in your view and exclude it from display.
Add a Global: PHP filter and include the following snippet:
return !node_access('update', node_load($row->nid));

PHP explanation (for non-seasoned PHPers) - the PHP snippet get the node object by using the node id that is made available by virtue of adding the Content: Nid field. With the first parameter of node_access set as 'update' the function will check whether the the node is editable. You can also check for 'view', 'delete' or 'create' powers. If no third parameter is specified, the function checks the powers of the current user. The function will return true if the user can edit it, but the Global: PHP filter needs a return value of false in order to show the row, so the ! flips the true/false value returned by the function.
Answer: In Drupal 7 with Views 3 and Views PHP it can be done in one step. Create a Global PHP Filter and in the Filter code add:
return !node_access('update', node_load($data->nid));

Comment: No offence, but this is a pretty terrible idea all around. Using php.module or anything that leverages it is a bad idea in general, but you're also performing a `node_load()` on *every* row/node that the view displays - which is a REALLY expensive way of doing things.


Using an air pump for an pneumatic forearm trainer

Question: I am attempting to create a forearm training device which  looks like this (I don't know what it's called). Can I use this air pump motor with an arduino? It can provide pressure up to 100 kpa, but I don't understand how much that is physically. Are there any other alternatives I can/should use?
Answer: First of all you need to share more plans for this design, this is more elaborate thing than you have cared to share. Secondly if you want to copy the design shown in posted picture, you will need to create a vacuum in the connectors which run across the fingers so that fingers can work against the vacuum. In that case this air pump wont do the job. Simpler approach would be to use this pump to blow up a rubber ball to a certain pressure controlled by Arduino (you will need a pressure sensor too). User can then control the pressure in the ball according to their workout needs. Needless to say there might be out of the box solutions for doing just that, like simpler finger trainers or hand grips for similar exercises.


Possible bug in Postsharp ReturnValue Location aspects

Question: I've been working with PostSharp for a year now and recently moved to version 3, I've had a great deal of success with it. I'm attempting to widen it's adoption in our company and the killer feature for adoption will be multicasted contract attributes.
I've been looking into PostSharp.Patterns.Contracts and written MulticastAttributes for them but there are several things that cause friction when applying these aspects  to our legacy code, such as ArgumentNullException instead of ArgumentExceptions in some string validations but the most significant is that ReturnValues cannot use these attributes.
I have to double the number of aspects - one set for Parameters and one set with the same validations, albeit different exceptions, for ReturnValues using OnMethodBoundaryAspect - which is not acceptable to our developers, so I have been trying to develop a set of contracts that can be applied to both Parameters and Return Values.
I note that a LocationContractAttribute is derived directly from MulticastAttribute and only contains code to support various exceptions and their messages so it looks like a simple task to write my own but the following simple aspect gives an exception when Postsharp kicks in after compilation:
[AttributeUsage(AttributeTargets.ReturnValue),
    AspectConfiguration(SerializerType = typeof(MsilAspectSerializer)),
    MulticastAttributeUsage(
        MulticastTargets.ReturnValue
        , TargetMemberAttributes = MulticastAttributes.NonAbstract
        , Inheritance = MulticastInheritance.Multicast
        , PersistMetaData = true
    )]
public class SimpleReturnValueAttribute: MulticastAttribute,
    ILocationValidationAspect<string>
{
    public Exception ValidateValue(string value, string locationName, LocationKind locationKind)
    {
        return null;
    }
}

to the class:
public class AspectTarget
{
        [return: SimpleReturnValue]
        public string ReturnEmptyString2()
        {
            return null;
        }
}

gives the exception:
Error   1   Unhandled exception (188.8.131.52, 32 bit, CLR 4.5, Release): System.NullReferenceException: Object reference not set to an instance of an object.
   at PostSharp.Sdk.CodeModel.MethodDefDeclaration.^bvoT7mPt9PXI(Int32 _0)
   at PostSharp.Sdk.AspectInfrastructure.CanonicalMethodMapping.^X0NY.EmitLoadArgument(Int32 _0, InstructionWriter _1)
   at ^670BgLZZ9jB2.^X5f4d1Yo.Implement(MethodBodyTransformationContext _0)
   at ^EbCRMdujK27A.^LuETqvLKzZPB(MetadataDeclaration _0, MetadataDeclaration _1, MethodSemantics _2, InstructionBlock _3, Object[] _4, CanonicalMethodMapping _5, LocalVariableSymbol _6, InstructionSequence _7, TypeDefDeclaration _8, PipelineTransversalState _9)
   at ^PE9ycIe2cLwm.^HvVDHXOj(MetadataDeclaration _0, IDependencyTransformationInstance[] _1, PipelineTransversalState _2, MethodSemantics _3)
   at PostSharp.Sdk.AspectInfrastructure.AspectInfrastructureTask.^jwku0geZ(MetadataDeclaration _0, PipelineTransversalState _1, MethodSemantics _2, Boolean _3)
   at PostSharp.Sdk.AspectInfrastructure.AspectInfrastructureTask.^MwzbegST(IMetadataDeclaration _0)
   at PostSharp.Sdk.AspectInfrastructure.StructuredDeclarationDictionary`1.^d+wOzSPF(IMetadataDeclaration _0, Func`2 _1)
   at PostSharp.Sdk.AspectInfrastructure.StructuredDeclarationDictionary`1.^+g+TCqVg(TypeDefDeclaration _0, Func`2 _1, Set`1 _2)
   at PostSharp.Sdk.AspectInfrastructure.StructuredDeclarationDictionary`1.^fJqG(Func`2 _0)
   at PostSharp.Sdk.AspectInfrastructure.AspectInfrastructureTask.Execute()
   at PostSharp.Sdk.Extensibility.Project.ExecutePhase(String phase)
   at PostSharp.Sdk.Extensibility.Project.Execute()
   at PostSharp.Hosting.PostSharpObject.ExecuteProjects()
   at PostSharp.Hosting.PostSharpObject.InvokeProject(ProjectInvocation projectInvocation)

Deriving the aspect from LocationLevelAspect gives the same error. I've also tried various values AspectConfiguration and PersistMetaData or omitting them altogether but I get the same exception.
Could do with some assistance.
Cheers.
Answer: The root cause is that ILocationValidationAspect cannot be applied to return values. This scenario is not supported, but instead of getting a nice error message, you get an exception.
Currently, return values must be validated using an OnMethodBoundary aspect (OnSuccess advise).
If you want to provide developers with a single custom attribute instead of two, you can have this single custom attribute implementing IAspectProvider, and have this aspect provide one of the two implementations.
Please use https://postsharp.uservoice.com/ to request this feature (ILocationValidationAspect should support return values).
Thanks.


How many primary cluster and secondary Cluster is supported by Global Database Network(GDN) in Alibaba Cloud?

Question: Recently I find an option named as GDN   in Alibaba Cloud Polar DB, Now before creating GDN network I have to know about what is GDN and how many primary and secondary(read-only) cluster is supported by Global Database Network(GDN)
Answer: What is GDN?
Global database network (GDN) is the distributed of Apsara PolarDB clusters in different global regions where all are synchronized across the network.
Why do you need GDN?
When your business operates in multiple regions, you'd have applications deployed in multiple regions as well, but accessing your primary region database could create performance issues due to network latency. That's where GDN comes in. It synchronizes your primary cluster and secondary clusters with reduced latency.
You can have one primary cluster and up to 4 secondary clusters, but don't be confused with multiple zones cluster, which is the clustering between zones (high availability) in the same region, while GDN is for across regions.
You can read more about GDN here.
Answer: The GDN (Global Database Network) is a feature for Alibaba Cloud cloud-native database PolarDB, it can be used to deploy databases across multiple sites While managing the data synchronization between or among multiple database instances.
Currently, by default, it supports  1 primary PolarDB cluster and up to 4 secondary (read-only) clusters (if you need more secondary clusters, please submit a ticket) into a single PolarDB GDN.


What are the main differences between the "unitary coupled cluster" and the "hardware efficient" ansatzes in VQE?

Question: There are two popular initial states, in general, for VQEs: the unitary coupled cluster ansatz and the hardware efficient ansatz (for details, see here: https://quantaggle.com/algorithms/ansatz/). Intuitively, what are the main differences between these two and when do we prefer one to the other?
Answer: The original proposal to do calculate the molecular ground state energy was to use quantum simulation and quantum phase estimation, like what proposed  through this paper: Simulated Quantum Computation of Molecular Energies and Simulation of Electronic Structure Hamiltonians Using Quantum Computers. Unfortunately, even though efficient, it still is very expensive for current hardware. Current hardware are noisy and don't have too many qubits, hence the name Noisy Intermediate-Scale Quantum (NISQ). So quantum simulation and phase estimation is not achievable.
This is when the Variational Quantum Eigensolver (VQE) came out. It tries to mitigate the some of this circuit depth issue to the number of circuits one would need to perform... through the use of variational principle.

Notice that calculate $\langle \psi(\theta) | H| \psi (\theta) \rangle$ you have to use many quantum circuits as $H = \sum_{i}^{poly(N)} \alpha_i P_i$ and so  $\langle H\rangle_{\psi(\theta)} = \sum_{i}^{poly(N)} \alpha_i \langle P_i \rangle$ but we can only measure in the computational basis so many circuits will be needed to do this calculation. Note that the decomposition of the Hamiltonian $H$ to Pauli strings is only in $O(poly(N))$ for the certain problems (like the molecular electronic Hamiltonian). But for a general Hamiltonian, you would need $4^N$ terms.
In any case, the question now is, what is the implementation of $U(\theta)$? The space of unitary matrices is huge (there are uncountable many unitary matrices)... but motivated by classical methods, the original paper of VQE proposed to implement $U(\theta)$ through the use of UCCSD, which is chemically motivated. Furthermore. this can be implement efficiently on a quantum computer. This is great, but it is still way too expensive for current quantum hardware! To see why, let's look at the UCCSD circuit for the $LiH$ problem that being used as an example in the Qiskit tutorial.

There is no way any current quantum hardware will be able to do something like that. So this is where the Heuristic Ansatze idea came about. People tried and still trying (like here or here or here and many more) to find ways to design quantum circuit( $U(\theta)$ ) that is very short-depth but still able to achieve an energy that is within the ground state energy within chemical precision. Because it is a heuristic ansatze, we don't usually know if we will be able to achieve an energy within chemical accuracy, opposed to the UCCSD ansatze. However, heuristic ansatze allows us to design quantum circuit that matches the hardware layout. This way, you can save a lot of the swapping overhead that you would encounter otherwise.


Is Bitcoin's mining difficulty adjusted if it fails to solve a block

Question: If the current Bitcoin miners lose 99.99% of their hash rate, mining the next block would take a lot more than the average set of 6 per hour (10 minutes). Is the mining difficulty somehow readjusted in order to face this potential problem?
Answer: No,
According to the Bitcoin Wiki, the difficulty is only adjusted every 2016 blocks.

The difficulty of the mathematical problem is automatically adjusted by the network, such that it targets a goal of solving an average of 6 blocks per hour. Every 2016 blocks (solved in about two weeks), all Bitcoin clients compare the actual number created with this goal and modify the target by the percentage that it varied. The network comes to a consensus and automatically increases (or decreases) the difficulty of generating blocks.

However, Bitcoin Cash has a solution to the problem.
If less than 6 blocks have been mined in the past 12 hours. It becomes 20% easier to mine blocks.
Comment: To clarify a little, in Bitcoin cash, difficulty is not adjusted at the 12th hour, but at the 6th block after 12 hours.
Comment: The only reason that BCH needed the faster difficulty adjustment was to ensure survival when nobody knew how many miners would switch to BCH at the time of the fork. A fast difficulty adjustment is not needed for a healthy network, it's not a "problem" that needs solving.
Comment: Can we expect BCH to drop the feature?
Comment: No, because that would be another hard fork. The feature pretty much has to be there forever, unless you can get *all* BCH users to agree to drop it.


Malbim's grammatical argument in Parashat Tzav

Question: Can someone help me to understand the grammatical/ interpretive point that the Malbim is making in his commentary to Leviticus 6:21 (the entries numbered 67 and 68 on Sefaria)?
Answer: In 67 he is making the point that when someone mentions the parts comprising a category, it would not do to leave out any parts of the category. But sometimes the individual parts can be grouped into mini-categories that contain all the parts. For example, all colors could be grouped under darks or lights, as we do with laundry. So too in the passuk, bronze includes all metals which are similar to bronze, and pottery includes all similar materials.
However, this only applies when you can see that the Torah is using categories. In a case where the Torah just says use a certain material, you have to assume it means that material specifically.
Comment: Thank you! Your second paragraph was the hard part for me. Why does the word "kli", according to the Malbim, clue us in that we are using categories?
Comment: Keli is what the Malbim calls שם הסוג, or the word for the category as a whole. We don't necessarily focus  on this in English, but in Biblical Hebrew, saying a vessel of copper is more inclusive than plain copper. But only if you see the verse is using categories. If the verse says vessel of something without using categories, it is specific.

Malbim’s grammatical argument in Parashat Tzav


Does Google Assistant listen to everything?

Question: I just upgraded to Google Assistant on my phone, and it overheard me ask a colleague a question. It then searched it to try and find the answer. Does Google Assistant listen to everything? I definitely did not say "ok google". Even with a keyword, doesn't that mean it's listening to everything until you say the phrase "ok google" and that triggers the search? Is there any way to control when it listens or executes a search?
Comment: Your question is off-topic, but the short answer is it can. Just like W10's 'reports'.
Answer: Yes, it does listen to everything but only activates and streams to Google on keyword activation. It has to listen all the time to trigger itself.
Once you say the keyword it will stream a few seconds before you said 'Ok Google' listen to your question then send the data to Google for an answer.
All this data is logged as well, here is a guide to find and delete voice recordings: https://qz.com/526545/googles-been-quietly-recording-your-voice-heres-how-to-listen-to-and-delete-the-archive/
Answer: I recommend you to not use Google Assistance since exists vulnerabilities or security problems.Google Assistance is recording your calls and can use google search engine to detected you.
Example: Talking to my wife about "dogs" and Google Assistance was recording me. After the call ended I opened the browser and i have in google box the word "dogs".
https://www.howtogeek.com/319490/how-to-disable-google-assistant-or-at-least-take-its-shortcut-back/
Comment: "since exists vulnerabilities" Are you saying there are known vulnerabilities in Google Assistant? You might want to cite your sources on that.


Using BRAM instead of SRAM in Virtex-5 FPGA

Question: I am working on a project where we are capturing signals from an ADC using a Virtex-5 FPGA and the samples are being stored on a 128K x 256 SRAM from where the data samples are acquired by a PC. I believe the Virtex-5 provides an option for a BRAM and while I understand that the depth is nowhere close to what the SRAM provides, I'd like to make use of the BRAM option in the Virtex-5 as a buffer to hold the samples temporarily until they are acquired by the PC. How difficult would this be to implement ?
Comment: You can easily use the memory generator to create a memory buffer for your design, but having a 256 bits wide data makes it pretty slow. the best way is to create a 256 bits FiFo between your ADC and your PC interface, the size can be less than 128k if you design your interface right or if you need to capture a frame that is 128k large, you should create it in HDL and let the synthesis tool map it for you.
Answer: Good news. This is a really common application for ADC interfaces. It's actually very easy to set up the block RAM in Xilinx devices.
You will want to run the "Block Memory Generator" Coregen by Xilinx, which will generate basically a black-box VHDL module that you can instantiate in your top level VHDL module. In the coregen, you can customize your block RAM so that it "looks" just like your existing external SRAM. The only difference will be that you will be connecting signals in your top-level module to the new black-box module that you've instantiated instead of to your external pins.
I'm not sure that you can get a data width of 256 (did you really mean 8?), but I think that you could get a depth of 128K on most Virtex-5 devices. The datasheet showing the Virtex-5 resources table (how much BRAM is available) is available here.
The datasheet that explains Block Memory Generator is here. It can explain the settings, etc.
To launch the block memory generator in ISE 14, right click in the project heirarchy and select "new source". Then select source type as "IP (Core...". Then select Block Memory Generator as the IP type as shown below.

Once the "Block Memory Generator" opens, select whichever options you want, then click configure. It will add the black-box core to your project. You will have to instantiate it in your top level module. You can usually see the "instantiation template" by clicking the core in the project heirarchy and selecting the "View HDL Instantiation Template" in the processes window.
Comment: The way the current setup is the SRAM is 32M and which is structured in a 256 x 128k format. Each 256 length word consists of 16, 16-bit samples which are sent to the SRAM from the FPGA after the data is received from the ADC. When the user wants to acquire the data through the PC, it uses a microcontroller to access the SRAM through the FPGA registers. I don't need the depth to be 128k since I would only need to use it as a buffer, but I believe the 256 width is necessary.
Comment: I see. You aren't going to get 32M in your Virtex FPGA, but it sounds like you don't need it anyway. I just looked at the tool and it looks like you can indeed set it up to take a 256 bit width (at least on the Spartan 6 target that I'm using right now).
Comment: Yeah, I don't need the 32 MB. Just enough to hold the buffer before transferring it to the PC.
Answer: Block RAMs are very easy to get the tools to produce from HDL code - no need to mess  with Coregen.
The advantages of doing it without coregen are:

No extra tools in the flow
you can use constants and generics (or their Verilog equivalents) from the rest of your design to configure the memory depth and width
coregen can add several minutes onto a compilation run when you've changed something, whereas a quick tweak to an HDL file doesn't change the compilation time by a noticeable amount in my experience.  I have no idea what Coregen is doing all that time!

Check your synthesiser manual for how to write code that will infer block ram, and there are some examples in the answers to this question


How do I exchange my follower for another one?

Question: I have the Vampire Serana following me and I don't want to sacrifice her for the Bohethia Calling quest. When I try to hire someone else e.g. from pubs in cities, they say "it looks like you already have someone" even if I ask Serana to wait at my house. Can anyone help?
Answer: Don't tell your follower to "wait" tell them to "part ways". They will then return to a predetermined location (usually where you found them) where they can be picked up later (many followers tell you where).
Comment: Serana in particular will generally return to either Castle Volkihar or the Dawnguard fort (whatever it's called).  Since she's essential, I doubt she *can* be sacrificed in any event.
Answer: Talk to her and choose "part ways" option. After that, you can hire other followers for sacrifice (I choose Stenvar from Candle Hearth Windhelm for this). After you are done with Boethiah Quest, then you can invite Serana in Fort Dawnguard. Good luck


How to smoothly join two cubes and then subdivision without "pinching" at the joints?

Question: I am trying to make simple easy 3D "cartoon" body shapes with noodle arms and legs similar to the style of Adventure Time or old Popeye cartoons:

The idea is to have simple elemental forms for the body/torso/head and then even thickness noodle arms/legs that connect smoothly to the body.
The way I would like to do this, especially when prototyping proportions etc, is to use very basic elemental types like cubes and smoothly connect them.
For example, I can take a cube for a body, a mirrored cube for an arm, and with a boolean to join them and then a subsurface modifier, I can get arms and a torso:

This captures the aesthetic I'm trying to create very quickly and it's very easy to adjust and prototype designs and shapes (vs. creating something entirely top to bottom via extrusion and manual mesh editing).
The problem with this approach is it is pinching inwards at the joints rather than smoothly blending and expanding from the limbs into the body. From top view:

This is obviously not favorable and ruining what would otherwise be a very easy way to design and build.
I have spent hours experimenting to find some way to make this work. I can't find a way to not make it pinch. You can see I even flared out the arm cubes towards the body in the hopes it would help but it does not.
Is there any way in a procedural fashion to get a smooth connection like I'm seeking without the pinching effect?
Alternatively is there some other method you would do this by?
I also tried building the 3D cartoon prototypes using the Skin modifier and Mirror with Subsurface but it really misbehaves any time you try to create a sharp change between something very thick/round (like a cartoon body) and something much narrower (like a noodle arm/leg). It only works well if everything is close in diameter.
I also tried using a cylinder for the arms/legs, beveling/subsurfing the body first, and then attaching the cylinder edge via a cylinder vertex group and shrinkwrap to the body but this then creates a sharp joint rather than a smooth one.
I presume there must be some way to this. I just can't figure it out.  Any thoughts or ideas?
Thanks for any help.
Answer: Boolean operations almost always produce topology that is not suitable for subdivision smoothing. If you want to model using booleans and get smooth transitions between parts, you can subdivide each object before the boolean, then use a remesh modifier after any booleans in order to smooth the intersections.

Otherwise, you will need to use another method such as sculpting or traditional poly modeling with extrusions.


"World Master" Title in Korean TKD

Question: Is it traditional in Korean Tae Kwon Do 8th Dan to be given the title of 'World' Master if the person is established in Aust and NZ?
Answer: There is no such thing as a "World Master" rank in any of the official Taekwondo federations that I'm aware of.
However, there is the WTF, the World Taekwondo Federation. A master rank in the WTF might be misinterpreted as "World Master". Maybe that's what you're seeing?
Also, I just did a Google search on the term, and I found out there quite a lot of places that sound similar: "World Taekwondo Masters Union", "World Taekwondo Masters Association", "World Class Taekwondo", etc. The term "World" is used quite a lot with Taekwondo organizations.
ITF Taekwondo has a rank structure that places 1st dan through 6th dan as "instructor" ranks, and 7th dan through 9th dan as "master" ranks. The interesting thing is that its 1st through 3rd dan are called "national instructor" ranks, while its 4th through 6th dan are called "international instructor" ranks. However, a similar "international" rank does not exist in the master ranks. The 7th dan is a "junior master", 8th dan is a "senior master", and 9th dan is a "grand master". The 10th dan is mostly honorary, awarded to only a handful of people, and is referred to as a "supreme grand master".
So, my best guess is that someone got confused and called their 8th dan a "world master" instead of a "senior master". It's a minor issue, because 8th dan is 8th dan no matter what you call it in English.
Hope that helps.
Answer: No.
An 8th Dan is a Master(Sahyun-nim). Not a 'World Master'.
However it could be a title within the person's own federation/association in Aust and NZ (and many other parts of the world). He can be a 'World Master', or 'Senior GrandMaster', or 'Supreme Grandmaster' or 'Senior Master', but traditionally an 8th Dan is called a Master.
A Master title is given to those who have attained 7th Dan and 8th Dan. Upon attaining 9th degree the person is deemed a Grandmaster. No more ranks above 9th Dan, although there are federations going beyond that.
Comment: We have patterns up to 6th Dan only, because advancement from 7th Dan to 8th Dan (and 8th to 9th) is based on merit. The candidate has to have largely contributed to the Taekwon-do community. I suppose it is in the same vein as an honorific one.
Comment: Usually there are some honorific 10th dan.
Comment: 10th Dan is never given by ITF. Like I said, anything above 10th Dan is given and recognized within one's own federation/association only.
Comment: Oops, seems like you're right! Anyway, as I said, the 10th dan (in other federation, like WTF) is honorific. It's a "gift" for those who contributed to the success/development of the art more than a consideration of any skills/experience.
Comment: It's also somewhat system dependent. I believe WTF awards Master title at 4th degree, ATA starts with Master at 6th, then Senior Master (7th) and Chief Master (8th).
Comment: I agree it's system dependent. Well, it is just a number anyway. A rank certificate does not keep you safe, only skills and fitness do.

"World Master" Title in Korean TKD


Is there a setting in FireFox to allow the parent document access to the DOM of an IFRAME on another domain?

Question: Notice how Firebug can access the DOM of cross domain iframes and even allow you to modify them? I'm wondering if there is an firefox addon extension or a config setting that will allow a page on our intranet to do this.
Longer explanation:
I have a two "kiosks" in our reception area that the public can use. As we're running in kiosk mode (fullscreen, no chrome), I have created a small web application consisting of a menu and an IFRAME. The menu allows users to browse to approved sites and also perform actions like printing. It also gloms onto requests for popup windows and instead overlays them in a modal iframe rather than allowing the browser and OS chrome to be exposed - breaking the "kiosk" experience.
Obviously, this works perfectly on anything internal because it's all on the same domain. It gets trickier when browsing external sites because the XSS protection kicks in and you can't see the DOM inside the IFRAME.
I have also tried using a web-based proxy server on the same domain (PHProxy for example), which works okay, but there are horrible edge cases where it doesn't work - a big one is the CAPTCHA on our website forms. So that's pretty much not an option for me.

Basically I think the only solution that will work for me is to modify the browser in some way using a security setting or an addon. Any ideas?
Thanks guys very much for you time and consideration. It is VERY much appreciated.
--Iain
Answer: There is a way for unpriviledged JavaScript code (loaded from a web page) to request more privileges in Firefox. This is an old, non standard API that prompts the user for permission and if accepted allows the JavaScript to do things normal JavaScript cannot. One of these things is to bypass Same Origin Policy.
Sample code:
<code>try {
    // ask user for permission
    netscape.security.PrivilegeManager.enablePrivilege('UniversalBrowserRead');
  } catch (e) {
    // user refused permission
    alert('Permission "UniversalBrowserRead" was denied.');
  }
  //Should now be capable of bypassing same origin policy if user accepted
</code>
Since the kiosk browser does not restart (I suppose) very often, the dialog just has to be accepted once. Not sure this is the most elegant solution but might work, at least for now (the API is old and might disappear).
Here is a link for more details: http://www.mozilla.org/projects/security/components/signed-scripts.html#privs-list
While looking for the exact privilege name I found this page about Security Policies in Firefox. This would be a much nicer solution. I have never used it, so I cannot give more info, but here is the link, might be a good place to start looking:
http://www.mozilla.org/projects/security/components/ConfigPolicy.html
Hope this helps!
Comment: This would only work if you have a very old (< v15.0) version of Firefox - using such an old Firefox would introduce other security vulnerabilities.
Answer: I found an addon called CrossDomain. The addon hasn't yet been updated for newer versions of Firefox. In the end, I solved this whole problem by writing an HTA and using the internet explorer rendering engine - which made my IT manager happy :). Here is the link to CrossDomain in case this helps someone one day. Thank you everyone for your submissions.
https://addons.mozilla.org/en-US/firefox/addon/13004/
Answer: Why not use Greasemonkey, it will allow you to run your script on any page.


How did Gandalf come to possess one of the Elf rings?

Question: Gandalf wasn't an elf, but rather he was one of a few wizards sent to help Middle Earth. So, how did he end up with one of the Elf Rings? And, why did Frodo not notice it, when he easily noticed Galadriel's ring?
Comment: those damn wizards have sticky fingers ;P
Comment: 'Never play Sabacc with an old bloke in a big grey hat'
Comment: 'Do not meddle in the affairs of wizards, for they are subtle and quick to anger.'
Answer: Gandalf was given Narya by Círdan the Shipwright because he believed that Gandalf had the highest inner greatness of all the Istari (Wizards).  The scene is described in The Silmarillion:

Take now this Ring, for thy labours and thy cares will be heavy, but in all it will support thee and defend thee from weariness. For this is the Ring of Fire, and herewith, maybe, thou shalt rekindle hearts to the valour of old in a world that grows chill.

There's more about this in Unfinished Tales, such as Saruman's knowledge of Gandalf's possession of the ring:

And the Grey Messenger [Gandalf] took the Ring, and kept it ever secret; yet the White Messenger [Saruman] (who was skilled to uncover all secrets) after a time became aware of this gift, and begrudged it, and it was the beginning of the hidden ill-will that he bore to the Grey, which afterwards became manifest.

Gandalf hid the fact that he had the ring, unlike Galadriel or Elrond, and so it was assumed that Círdan was the holder of the third Elven ring (until the ring bearers left Middle-earth).  At the end of Return of the King, we are told:

As he turned and came towards them Frodo saw that Gandalf now wore openly upon his hand the Third Ring, Narya the Great, and the stone upon it was red as fire.

We aren't told exactly how Gandalf concealed the ring; presumably some sort of magic is involved.
The ring's bearer between its creation and Círdan passing it to Gandalf is not clear: Unfinished Tales says that Círdan received the ring from Gil-galad, who received it from Celebrimbor, but The Lord of the Rings says that Círdan received the ring directly from Celebrimbor, at the same time that Galadriel received her ring.
Comment: This does happen in the books, but it's not red light: "*One wheeled towards him; but it seemed to Pippin that he raised his hand, and from it a shaft of **white light** stabbed upwards*".  This may be the same kind of light as is seen from afar during Gandalf's battle with the Nazgul on Weathertop and his battle with the Balrog on Celebdil.
Comment: "Gandalf hid the fact that he had the ring, unlike Galadriel or Elrond, and so it was assumed that Círdan was the holder of the third Elven ring" Galadriel and Elrond also hid that they were Ringbearers.  At the Council Elrond refused to name the bearers of the Elven Rings and the only reason Galadriel was revealed earlier was Frodo could see Nenya after having the One Ring as long as he did.
Comment: I thought that Gandalf revealed that he had Narya once, when he was the "White Rider", maybe at the end of Two Towers or beginning of ROTK? The Nazgul were closing in (on Minas Tirith?) and Gandalf comes riding along and stops a Nazgul (not the Witch-King, one of the other two with him), with a beam of red light. I'm sorry, I should give you a page number. Could that be an instance of Gandalf using the power bequeathed by Narya?
Comment: @FeralOink In the (Jackson) films Gandalf drives off the Nagzûl with a light from his staff.  I'm fairly certain this doesn't happen in the books.
Comment: Okay, that seems more familiar, that the light emanated from Gandalf's staff, not his ring. Thank you!
Answer: Of course, Tony Meyer's answer answers where Gandalf got the Ring. Why did Frodo never notice it? He didn't yet have the ability.
In Fellowship of the Ring, in The Mirror of Galadriel:

Frodo gazed at the ring with awe; for suddenly it seemed to him that he understood.
'Yes,' she said, divining his thought, 'it is not permitted to speak of it, and Elrond could not do so. But it cannot be hidden from the Ring-bearer, and one who has seen the Eye. Verily it is in the land of Lorien upon the finger of Galadriel that one of the Three remains. This is Nenya, the Ring of Adamant, and I am its keeper.

Emphasis added
Before that point, Frodo had been the Ring-bearer, but had not yet seen the Eye. It isn't clear why this allows him to see the Rings of Power, but it must be magic.


Vielen Dank allen oder euch allen?

Question: From what I understood Vielen Dank is the somewhat more formal version of thank you. I've seen Vielen Dank euch allen a couple of times before, but I don't understand what the euch is adding, instead of just saying Vielen Dank allen to say thank you everybody for exemple?
Answer: In

Vielen Dank euch allen.

euch is the dative form of the personal pronoun 2nd person plural. The expression means "Thanks a lot to you all".
Your suggestion

Vielen Dank allen.

is not idiomatic in German.
Comment: However you could say _Ich danke allen_, which uses the verb _danken_.
Comment: I'd also add *Vielen Dank an alle.*
Comment: @Spencer: Where do you draw the line between "ungrammatical" and "unidiomatic"?
Comment: Is "Vielen Dank allen" even grammatical?
Comment: In case it's not obvious, you'd only use *euch* if it's people you're on *du* terms with, otherwise *Ihnen*.
Comment: But it is for instance correct to say "Vielen Dank allen, die mir geholfen haben."
Answer: First off: "Vielen Dank allen." is indeed correct.
It is an ellipse of an old construct:

Dank sei + Dativ

For instance Dank sei dem Herrn ....
@Spencer, @Sonyfreak:

Vielen Dank allen, die geholfen haben.

Is indeed correct. "Dank" is not a verb here but - see above - a noun and the complete (today not used any more) phrase would be:

Vielen Dank sei allen, ...

Vielen Dank allen oder euch allen?


What really is the difference between these two types of electric current conduction?

Question:
Current passes from $L_2$ to $L_3$ which have no physical contact (except air) between them.

The current still transported through air but unlike previous picture the process is obviously different. Now I know previous image is representing electromagnetic induction and later one electrostatic discharge. But apart from the definition what exactly is happening here internally causing such difference? I am somehow familiar with Maxwell's equations I can handle a little technical answer. Thanks in advance.
Comment: In the first case, $no$ current passes between the left hand and right hand circuits.
Comment: One anonymous flagger writes:   This question is badly formatted , the images are non in imgur, and the link of the first one gives "The owner of www.rroij.com has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website." in firefox, so I cannot repair the question by editing.
Answer: The first diagram represents induction, not conduction. The circuit on the left is an LCR oscillator, with $L_2$ and $L_3$ being inductors (basically just loops of wire). Now, as the current through $L_2$ varies, so does the magnetic field around it. This varying magnetic field induces an alternating current in $L_3$ (as stated by Faraday's Law of Induction), which in turn drives the circuit on the left, without direct contact.
In the second picture, current passes directly through air through a phenomenon is called dielectric breakdown. Normally air is an insulator, but given a high enough electric field (about $2MV/m$ for air), gas molecules get ionised and start conducting. Electrons in the conducting gas constantly leave and recombine with gas molecules, leading to the emission of light. Hence, the path of the current appears as a blue arc.


How powerful must a gravitational wave be, to be audible to a human?

Question: Sufficiently powerful gravitational waves can excite an eardrum and be heard. How powerful would the waves have to be for a human to actually hear them, and what would be the side-effects of that intensity of gravitational radiation?
Comment: Does this answer your question? [Would you hear a gravitational wave, if its amplitude and frequency were suitable?](https://physics.stackexchange.com/q/237306/)
Comment: Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/109711/discussion-on-question-by-benrw-could-a-human-even-in-principle-hear-a-gravita).
Answer: No, not really. There are a number of factors for why you can't:

As duly pointed in the comments, you 'hear' something when the eardrum moves with respect to i.e. differently from your body. If you are in the middle of a wave, then you body is deformed in the same way as your eardrum. Also, there is the fact that the disturbance caused by the waves themselves are in the order of magnitudes of the size of an atomic nucleus. There is no way our eardrums can detected that (more on that in point 2). So, you can't hear the wave itself.
Gravitational waves tend to have very low frequencies (corresponds to long wavelengths). According to an answer here, the maximum frequency of a gravity wave is proportional to $\sqrt{G\rho}$, where $\rho$ is the density of whatever object released the waves. Waves which have longer wavelengths just pass through an object smaller than it's wavelength (Though it has been pointed out in the comments below, that we can hear sounds of wavelength $17$m). Keeping in mind the usual wavelengths of gravity waves, (and the size of the ears), to hear a gravity wave would require a ridiculously large amount of energy. The disturbance caused by any regular gravity waves is in the order of magnitudes of an atomic nucleus. Our eardrums are not built to be that sharp. So, if the gravity wave has to 'disturb' our eardrum, it needs humungous amounts of energy.  And that energy has to be produced by something having $\rho$ more than anything we have ever detected or hypothesised. (And such an event of high energy, may as well destroy Earth itself; not by gravity waves, but by other forms of radiation or free energy)
The most important point: gravity waves don't work that way. The eardrum vibrates when any sound wave applies pressure on it. Gravity waves are not like conventional waves: they don't apply a pressure on anything. In fact, they just stretch and compress space itself, and that does not inflict any pressure on an object. If your ear is anywhere near a gravity wave, the eardrum would be squished and squashed, which is not the equivalent of a vibration caused by a sound wave. If you want to know more about how the gravity wave stretches and compresses space, take a look at my answer here: How can we imagine gravitational waves?

So, that is why you could not 'hear' gravitational waves.
Comment: This answer is wrong.  Humans can hear sounds with a frequency as low as 20 Hz, which corresponds to a wavelength of about 17 m – much larger than a human body.  Also, if you think gravitational waves cannot apply pressure to an object, how do you think LIGO is able to detect them?  "Squishing and squashing" an eardrum does create vibrations that can be detected by the cochlea.
Comment: You have misunderstood how LIGO works. The lasers there are not directly influenced by gravitational wave pressure and deflected by them. Instead the squishing and squashing causes a delay in the arrival of the lasers. It is sort of 'not okay' that you are just commenting and/or downvoting based on wrong opinions. Your second point may  hold but there is the point that the ear cannot detect such small changes . Still, it is just incorrect to say that the answer is wrong and imply that you _can_ hear gravity waves.
Comment: LIGO's arms actually change length under the influence of gravitational waves.  That is, the mirrors move closer together and then farther away.  As the [LIGO website](https://www.ligo.caltech.edu/page/vibration-isolation) says, "gravitational waves make themselves known through vibrations in LIGO's mirrors."  This is obviously a simplification for a general audience, but it's not wrong.
Comment: As for your second point, you're right that the ear cannot detect gravitational waves as small as the ones LIGO measures, but that wasn't the question.  A sufficiently powerful gravitational wave would absolutely be audible to a human ear, which is why your answer is factually incorrect.
Comment: Yes, the arms of LIGO do change length, but its not because the waves themselves are applying pressure to compress them. It's because the space itself contracts along with everything in that space. I am not saying anything about simplification or complex reality, I am saying that _pressure_ is different from _space contraction_. Also, refer to my edited answer for your second query.


Gas densities and the atmosphere

Question: The density of nitrogen is greater than the density of oxygen, hence the denser nitrogen would be present in the lower atmosphere. If so it would be deprived of oxygen as it would be pushed to the higher atmosphere due to its low density. But we live due to the intake of oxygen from the lower atmosphere. How is this possible?
Comment: Related: [Why ozone being heavier than air does not settle down?](http://chemistry.stackexchange.com/q/43498/7951), [Ozone is above, nitrogen is below](http://chemistry.stackexchange.com/q/41261/7951), and [Chlorofluorocarbons rising](http://chemistry.stackexchange.com/q/41338/7951)
Comment: You have it backwards. Oxygen gas is more dense than nitrogen gas.
Answer: Gas molecules in the air continuously collide with each, shoot off in different directions etc. This constant motion is like stirring a fluid. You wouldn't observe perfect density separation in a container with oil and water in it if you keep shaking/stirring it. The situation is similar here, the atmosphere is a fluid that is continuously being agitated. I believe this to be the reason, at least off the top of my head.
Answer: Although you mixed up the densities of $\ce{N2}$ and $\ce{O2}$, $\ce{O2}$ being more dense than $\ce{N2}$ rather than the other way around, the meaning of you question is still clear and valid.  To paraphrase: "Why  aren't the Earth's gases separated based on density, such that the most dense lie at the bottom of the atmosphere and the less dense gases rise to the top?"
According to this Wikipedia article:

The homosphere and heterosphere are defined by whether the atmospheric
  gases are well mixed. The surface-based homosphere includes the
  troposphere, stratosphere, mesosphere, and the lowest part of the
  thermosphere, where the chemical composition of the atmosphere does
  not depend on molecular weight because the gases are mixed by
  turbulence.

A more thorough discussion of the nature of the homosphere and heterosphere with respect to you question can be found in my answer here.
Answer: The density of oxygen is greater than that of nitrogen. At a certain set temperature and pressure, all gases occupy the same volume. Since oxygen has a higher molar mass, it is denser.

Gas densities and the atmosphere


what is the maximum life-time for Let's Encrypt certificates

Question: Let's Encrypt is one of the most popular TLS Certificate Authorities. I have conflicting information about its certificates life-time. In this link it says 90-days. In one research paper I read 1 month. Can you please inform me what is the correct maximum life-time for Let's Encrypt issues certificates?
Comment: Perhaps the paper was suggesting to renew it every month rather than it expires every month?
Comment: I wonder if the research paper confused how long before expiry renewals happen with valudity of the cert. Cert validity is definately 90 days.
Comment: Can you give the references of that research paper?
Answer:
What is the lifetime for Let's Encrypt certificates? For how long are they valid?
Our certificates are valid for 90 days. You can read about why here.
There is no way to adjust this, there are no exceptions. We recommend automatically renewing your certificates every 60 days.

Reading the FAQ should be the first thing you do when you have questions about a product or a service.
Comment: There is no reason to believe the FAQ to be outdated. They explicitly mention 90 days, and that 60 days is recommended renewal time. You can also check their own certificate, for letsencrypt.org, which is issued by themselves, and is indeed 90 days validity.
Comment: Thanks. I did read this. But as I said, I found another research paper saying it is one month. I thought the FAQ can be outdated.


Suhosin changes

Question: I've recently purchased a virtual server in order to use it as a stage development for my site which is based on a forum script (ipb).
Problem is that before the installation and after it, ipb shows me some messages about suhostin limits. For example
<code>'suhosin.post.max_vars' is 1000 and has to be changed to 4096
'suhosin.request.max_vars' is 1000 and has to be changed to 4096
</code>
For both occasions, it says that these settings are on my php.ini. After looking up, couldn't find any mention of suhosin there. But I found them at /etc/php5/conf.d/suhosin.ini and I proceed and changed them with the correct values.
Problem is that I keep gettin the error messages and when I load phpinfo, I see that the old values are still there. I restarted apache, I even restarted the server but suhosin still has the old values even if I edit the suhosin.ini file and see my edits are there.
Could anyone explain what I'm doing wrong ? I even added the lines to php.ini but still nothing changed.
Thanks
Answer: You need to make a file called "php.ini" in your admin directory (you find this through the root where you have your forums) and put the following in. Change the values as needed.
<code>suhosin.request.max_varname_length = 400
suhosin.get.max_value_length = 2000
suhosin.request.max_vars = 4100
suhosin.post.max_vars = 4100
</code>

Suhosin changes


How to restart/delete game data on iPhone 6 IOS 11?

Question: I want to restart Clash of Clans from the beginning, but each time I delete the app and re-download it I pick up from where I left off. I tried going into settings into the game center section and couldn't find anything useful. I did the same with iCloud and had the same result. Any suggestions?
Answer: You cannot restart clash of clans even if you delete the app, the only way to restart it is to both delete the app and also log out of gamecenter and sign into gamecenter with a different Apple ID.


Fix the Lightning component on app page

Question: I need to fix the position of 1st component on top & 2nd component at the bottom of page.Both shouldn't be scrollable (As i want them as buttons). If any other component is in between that should only scroll.
Answer: I don't believe that you can get this out of the box. Try looking at Flexbox, a lot of people have implemented this kind of layout over the years. Example: https://stackoverflow.com/questions/47659664/flexbox-with-fixed-header-and-footer-and-scrollable-content/47661523

Fix the Lightning component on app page


Can the Thai government legally ban Thai citizens from entering Thailand?

Question: I read on https://bangkokpost.com/thailand/general/1891790/govt-temporarily-blocks-all-travel that the Thai government will temporarily block all inbound travel. Can the Thai government legally ban Thais from entering Thailand?
Answer: The Section 34 of Constitution of the Kingdom of Thailand says (highlight mine):

[…] No  person  of  Thai  nationality  shall  be  deported  or  prohibited  from  entering the Kingdom.

The referenced document points to the most recent 2017 Constitution.
So the naive answer is No, however some legal gap may be found by the Constitutional Court (Section 27).
More specifically, it would depend on the legal equivalence of terms "Thai citizens" and "person of Thai nationality".
Comment: There may also be, as in most countries, the possibility that a temporary prohibition for reasons of public health might somehow be permissible in the face of the constitutional provision against such a prohibition.  I doubt that there's any line of reasoning in which "person of Thai nationality" would not include Thai citizens.
Comment: I agree with @phoog that "person of Thai nationality" is either equivalent to or broader than the term "Thai citizen". Often constitutional provisions that are facially absolute are subject to implied exceptions, however.
Comment: There's a difference between 'Denying Entry' and 'Delaying Entry'. In a quarantine period, you'll be *eventually* admitted.


Skip WooCommerce 4.5.x onboarding with WP-CLI

Question: I have a bash (.sh) script that I use to install WordPress and install/activate various plugins through WP-CLI commands. Now I want to extend that by installing/activating WooCommerce and setting various wp_options through wp option set command.
I want to enter basic stuff (address etc) that is asked in the WooCommerce onboarding setup steps, but in bash. I don't want to deal with the actual onboarding steps in wp-admin.
Already tried:
wp option set woocommerce_onboarding_opt_in "yes"
wp option set woocommerce_onboarding_profile "" // aleady tried setting it to serialized data as well
wp option set woocommerce_store_address "street address number"
wp option set woocommerce_store_address_2 ""
wp option set woocommerce_store_city "Mycity"
wp option set woocommerce_store_postcode "1234"
wp option set woocommerce_default_country "BE"

But that doesn't seem to be enough. Anyone an idea on how to properly install and configure WooCommerce with WP-CLI without having to deal with the onboarding afterwards in wp-admin?
Answer: Not very sure, but maybe you need to install WooCommerce pages?
wp option set woocommerce_onboarding_opt_in "yes"
wp option set woocommerce_onboarding_profile ""
wp option set woocommerce_store_address "street address number"
wp option set woocommerce_store_address_2 ""
wp option set woocommerce_store_city "Mycity"
wp option set woocommerce_store_postcode "1234"
wp option set woocommerce_default_country "BE"

wp wc --user=admin tool run install_pages


My teen wets the bed. He is in diapers just at night but he says it's hard to sleep because "the diaper feels weird"

Question: My teen has been wearing a brand called Depends. It's supposed to be a light and nonbulky diaper. I don't understand, please help.
Comment: Is this a recent change? What is the reason he wets the bed?
Comment: Have you seen a doctor about this?
Answer: Bed Wetting for teens is not uncommon. Other than diapers a good option is to monitor water consumption and urination before bed. And a mid-night alarm to get up and urinate would help getting rid of this.
Answer: Not sure diaper is a good idea. It can  hurt his self esteem, making him feel helpless.
Unless this is some known medical condition and doctor advised to use a diaper, I'd have him just sleep normally, and if he wakes up wet during the night, help him change sheets, and get back to sleep on clean sheets again.
This way he should feel both more comfortable, and more in control over his actions.
If you prefer a diaper anyway (e.g. what I said before, medical condition) then I'd suggest a different brand that can be more comfortable on the skin, and absorb the urine better. From quick search I've made, a brand that got good reviews is this: (note: link might be blocked by adblockers)

Surely there are others, you can try few different brands and see which feels best for your teen son. Good luck!
Comment: A teen can change his own sheets.  No need for the parents to be involved.  He can also do the laundry.
Comment: @swbarnes2 ideally, sure. But not all teens are so independent. Sure, it can be part of education, but that's out of scope here. I just know for sure that there are teens who don't change their own sheets and don't do laundry.
Comment: @swbarnes2 It's possible that this particular teen is low functioning. OP didn't give enough information for us to tell if said teen would be able to change his own sheets.
Answer: I grew up wearing diapers to bed. Positive family attitude made all the difference. 4 boys and I was the only bedwetter. I also struggled during the day and had way too many daytime accidental wetting issues. I usually wore layers of briefs with plastic pants during the day. I rarely had any teasing from brothers. I decided I would stop the diapers when I entered high school. After a couple months of nightly floods I put myself back in diapers. Later urodynamic testing showed I had a neurogenic bladder and from my history the dr. Said likely since birth. I was also told it was not a curable condition. I guess the trick is attitude.
Answer: I have just noticed the question mention usage of Depends, so I have possible explanation to the "weird feeling" for the person in question.
Depends isn't really a diaper but rather an absorbent, disposable underwear. This means it can absorb only limited amount of urine, and if there is more, it becomes heavy and even start to leak. This can explain the issue.
Solution is simply to use "real" diaper, that can absorb more urine without becoming "heavy" or leaking. (See my other answer to get an example of such diaper.)

My teen wets the bed. He is in diapers just at night but he says it’s hard to sleep because "the diaper feels weird”


Fatal error: Unknown: Failed opening required '/app/magento-vars.php

Question: I am trying to configure Magento 2 CE on a localhost using Docker.  I am getting these errors when I visit localhost:
<code>Warning: Unknown: failed to open stream: No such file or directory in Unknown on line 0

Fatal error: Unknown: Failed opening required '/app/magento-vars.php' (include_path='.:/usr/local/lib/php') in Unknown on line 0
</code>
Have googled for this and not seeing any recommendations,
Answer: I also faced the same problem,just create app directory in the root folder of your magento container and place the magento-vars.php file there.
Clear the cache and run.
Hope it works!


Managing DUKPT keys in AWS cloud

Question: I work on a payments system.  So DUKPT keys are a must-have requirement.  In most cases PIN and Card data are encrypted using DUKPT keys.  However, every time we have checked with AWS, we have found that none of the HSMs available on their cloud are DUKPT capable.  That is obviously a non-starter for us.  Can some experts here shed some light on this?  Have you run into this problem on AWS?  How have you worked around this AWS limitation (short of moving away from AWS)?
Answer: DUKPT is required for payment processing because PIN pads are comparatively weak HSMs running on low horsepower devices that are at high risk of being stolen and attacked. DUKPT exists to meet several security requirements, including the protection of past keys, the efficient production of future keys, and to ensure datagrams are always different.
AWS HSMs aren't subject to the same limits or risks, and since their capabilities include cryptographically secure pseudo random number generation, DUKPT doesn't make sense on that platform.
Instead of asking AWS to meet DUKPT requirements, ask your payment provider for alternatives that work in AWS.
Comment: Acquirers use DUKPT keys due to reasons you have explained.  We have projects on the roadmap that require those keys to be put in our gateway's HSM, instead of having them injected in the terminal.  It will be an uphill task to get the acquirers to change their key management scheme for us.

Managing DUKPT keys in AWS cloud


Laptop is unable to load webpages in Chrome or IE, over WiFi or Ethernet. Can ping servers through Command Prompt, but only reliably by IP address

Question: Yesterday, while at school, I downloaded and installed WAMP on my laptop, and this seems to have caused my computer to be unable to load any webpages.
Before I knew about WAMP, I was partway through setting up Windows IIS (I think), and I had enabled it in the "Turn Windows Features On or Off" menu. After installing WAMP, I fiddled a bit with the stuff in the toolbar menu, like starting/stopping services, installing Apache through the menu, etc. to get the icon to go green. Once it did I went to "localhost" in Chrome and was brought to some Microsoft welcome page that seemed to be related to their IIS service. Thinking this was not the page I should be seeing, I disabled IIS in the Windows Features menu, and restarted my computer. Upon trying to reopen the Chrome tabs I had, nothing loaded. The only thing that showed up was a page that said "This webpage is not available" with a message below in smaller text that said "ERR_NAME_RESOLUTION_FAILED".
I was able to ping servers (tried 18.104.22.168 and 22.214.171.124) through command prompt's "ping" command at multiple times yesterday. At one point while I was home, I power-cycled my modem. After this I was able to ping websites by name, such as google.com and facebook.com, and I was also able to load facebook's website in Chrome. I didn't try loading Google. This only lasted for about a minute, and the same ping command returned "Ping request could not find host xyz". Refreshing facebook at this point gave me the familiar "This webpage is not available" page.
Things I've tried so far:

Turning IIS back on. Just did this now and for ~30 seconds I was able to load Facebook a couple times, and Reddit a couple times. Refreshed both pages again and got essentially text-only versions of each site with very little formatting and graphics, but as far as I could tell both pages still had the same content. Another refresh a minute or two later and it's back to the same error page.
Windows Network Diagnostics troubleshooter. When I ran it yesterday, I got an error along the lines of "Your DNS server might be unavailable.", and when I run it now I get "Your broadband modem is experiencing connectivity issues". I'm able to load webpages just fine over WiFi on both my phone and my brother's laptop, so I'm skeptical that the modem could be the issue. This is compounded by the fact that I had the same issues on my school's internet yesterday.
Manually assigning IPV4 to DNS servers 188.8.131.52 and 126.96.36.199. Did this yesterday in response to the first troubleshooter error message and nothing changed. Currently, I've set IPV4 back to automatically retrieving the DNS server address.
Some commands in Admin Command Prompt, that didn't solve the problem:

ipconfig/renew, release
something winsock reset
flushdns

Uninstalling WAMP through the Windows "Uninstall a Program" page. Again no change.

System Specs:
Laptop: Samsung ATIV Book 8, NP880Z5E-X01U8
OS: Windows 8.1, 64-bit
WiFi Adapter: Intel Centrino Advanced-N 6235
Internet Provider: Verizon FiOS
I'd be happy to provide any more relevant specs upon request.
Answer: You could try clearing the computers cache by opening the Command Prompt and entering:
<code>ipconfig /flushdns
</code>
More information on this command is listed here:
https://technet.microsoft.com/en-us/library/cc781949%28v=ws.10%29.aspx
Comment: Forgot to mention, I actually did this as well. Thanks for your suggestion.


Seeking Papers with Significant Associations in Univariate but not in Multivariable Analysis Due to Sample Size

Question: I am looking for example scientific papers in which association works (p-value < 0.05) in a univariate setting but is not significant in multivariable analysis due to low sample size (p-value > 0.05). Moreover, the researchers should have (for example) a biological explanation of why they think it would be independently associated with a greater sample size.
Comment: It looks like this could reasonably be made community wiki.
Answer: You are comparing two different things: Univariate analysis assesses marginal distribution, whereas multivariate analysis assesses conditional distribution. They answer different questions. Both analyses only give association estimates and do not necessarily reveal causal relationship. To understand common techniques in causal inference, see my answer to
Seeking Assistance in Evaluating My Research Plan for Regression Analysis. For best practice related to p value, see my answer to Justification for reporting non-significant effect sizes.
The p value is the conditional probability of observing more extreme outcomes conditional on that the null hypothesis (e.g., coefficient is zero) is true. This condition or hypothesis is different in univariate (direct effects of other covariates are not separated) and multivariate (direct effects of other covariates are controlled for) analyses. The size of a p value is affected by several factors, and sample size is only one of them. For specific p values in different models, it is impossible to tell apart if the significance disparity is due to the sample size or something else (e.g. effect size, power of a statistical test, conditions, model specification, etc.). If the sample size keeps increasing, any given magnitude of difference or association can eventually become significant. Therefore, in a well-designed experiment, increasing the planned sample size may undermine the study by reducing the p value and inflating the Type-I error. There is also a matter of multiple testing when many variables are tested one after another.
I disagree with the statement that Mikolaj Buchwald gave.

Usually in practical settings, the more variables you have the more probable it is that you will find the relationship between observed change and (quasi)experimental intervention

It is possible to observe nonsignificant relationship in univariate analysis but significant ones in multivariate analysis, as they answer different questions. Therefore, controlling more covariates may not reduce the p value of the treatment indicator. There are some covariates that should not be controlled given an experimental design. In practice, picking between univariate and multivariate analysis is in essence variable selection and model selection. For confirmatory studies, theory and biological mechanisms should guide this process. For exploratory studies, many techniques are useful.
More materials than listed in my other to answers:

Academy, E. (2019, November 15). Chasing the p-value: Statistical significance and the perils of p-hacking. Enago Academy. https://www.enago.com/academy/chasing-the-p-value-statistical-significance-and-the-perils-of-p-hacking/
Benjamini, Y., & Hochberg, Y. (1995). Controlling the false discovery rate: A practical and powerful approach to multiple testing. Journal of the Royal Statistical Society: Series B (Methodological), 57(1), 289–300. https://doi.org/10.1111/j.2517-6161.1995.tb02031.x
Elliott, G., Kudrin, N., & Wüthrich, K. (2022). Detecting p-Hacking. Econometrica, 90(2), 887–906. https://doi.org/10.3982/ECTA18583
Wasserstein, R. L., & Lazar, N. A. (2016). The ASA statement on p-values: Context, process, and purpose. The American Statistician, 70(2), 129–133. https://doi.org/10.1080/00031305.2016.1154108
Wasserstein, R. L., Schirm, A. L., & Lazar, N. A. (2019). Moving to a world beyond "p < 0.05." The American Statistician, 73(sup1), 1–19. https://doi.org/10.1080/00031305.2019.1583913
Comment: In general, and especially with regression models that are not regular linear models, only one of uni variable and multivariable analyses can be correct.  The study design will dictate which one should be used (it's usually the multivariable one).  Comparisons of the two are less useful than they seem.
Answer: It would be interesting to see a simulation meeting your criteria. Usually in practical settings, the more variables you have the more probable it is that you will find the relationship between observed change and (quasi)experimental intervention -- it is due to the fact that in biology (and in the physical world in general) usually the observed (and measured) phenomenon is influenced by multiple factors, not a single one. (I mean: weakly/moderately by multiple factors, not strongly by a single one.)
There are some reports in which for univariate analysis more variables turned out to be statistically significant than in the multivariate analysis:
https://onlinelibrary.wiley.com/doi/abs/10.1002/jso.2930510208
https://www.sciencedirect.com/science/article/pii/S0302283802004931
https://www.sciencedirect.com/science/article/abs/pii/S0959804905802928
However, you would have to check if in any of these papers this effect was attributed to the insufficient sample size for the multivariate analysis. In other words, what would happen with the significance of the univariate outcomes if the sample size was bigger? Would it not increase too? As I was saying, in my area of research usually even for the smaller sample sizes multivariate analysis just works better.


How can CoffeeScript be written in CoffeeScript?

Question: How is it possible that written a programming language like CoffeeScript in  itself like CoffeeScript? Firstly CoffeeScript doesn't exist that read CoffeeScript scripts and interpret them?
Answer:
First you design a language A on paper and white board.
Then you write an implementation of a language A (compiler, vm, interpreter, runtime depending on a scope of language) in language B.
Once you have stable environment for language A, you can start writing version of environment for language A in language A.

I would say, that unless language is slow or not turing complete, it's tools should always be implemented in it. That makes it's much easier for developers to work with it.
Comment: I have to disagree with your last statement, or specifically with its absoluteness ("always"). Some languages are good for writing compilers in, some aren't. You have to weigh the benefits of writing a compiler in the language it compiles and thus increasing the amount of people able to work with it (because they only need to understand one language, not two) against the increase in complexity caused by using a language that might not be up to the task. I personally would much rather maintain a SQL compiler written in Scala than one written in SQL.
Comment: Wrong. Language traits that are required for writing compilers (pattern matching, ADTs, compile-time metaprogramming, etc.) are not necessarily the traits you want in your target language. And, by the way, you don't need a Turing-complete language to write a compiler.
Comment: @JörgWMittag I'm sorry, I meant turing complete languages, I've edited my post.
Comment: @SK-logic last paragraph is my opinion. And I didn't say that you need turing complete languages to write compiler, you don't need languages with fast environments to write compiler either. That is my preference and my opinion. In the end, if I'm a full time _LanguageA_ programmer, I will understand _LanguageA_ better than other languages, even if we suppose that there is _LanguageB_ that's the best language to write compilers.
Answer: Think of a subset of language to build another language. Don't watch it as building A with A but instead building A with B where B is a small language.
Think of it in this way:
You build a simple interpreter with JavaScript and name it CoffeeScript, later on as your project goes bigger and bigger you start writing parts of your code with your new functions/construcs or in short - your own language like CoffeeScript.
Comment: The first compiler was written in Ruby, not JavaScript, but yeah, that's basically how it works.


Windows 7 Search automatically searching federated search

Question: I have a a federated search that searches SharePoint. When I press the windows and begin typing I want it to search my machine and the federated search. Is this possible?
Answer: It doesn't appear to be possible. You can add links to do the federated search on your query as described here, but it still has to be launched separately.


In a general physical sense, is the position of a particle really a vector?

Question: Is it consistent to define the position of a particle in some frame as a vector or is just an informal representation? Velocity and acceleration can be added up and multiplied by real numbers and still have physical meaning (they live in tangent spaces). But what is the physical meaning of adding a position to another or, in relativity's domain, does adding two events have any sense? If this has no sense, then defining the position of a particle as a "vector living in a vector space" is surely wrong?
Comment: Closely related/possible duplicate: https://physics.stackexchange.com/a/192887/226902 "Does spacetime position not form a four-vector?", see also: https://physics.stackexchange.com/q/156395/226902. Regarding affine Minkowski space: https://physics.stackexchange.com/a/279215/226902 "Four-vector addition in Minkowski space".
Answer: It depends on context:

In the context of affine spaces (such as, Newtonian mechanics or SR), positions are strictly speaking not vectors, but position differences/displacements are vectors, i.e. positions measured relative to some chosen origin/fiducial point are vectors.
In the context of manifolds (such as, GR or Newton-Cartan theory), positions are generally not vectors.
Comment: Really cool answer. Equivalently, we may say that in SR the displacement is a vector because it belongs to the local tangent space to the "origin/fiducial point", which can be easily seen as a vector space (while the origin/fiducial point is a point of the manifold in GR).
Comment: Hi@Quillo. Thanks.
Answer: No, positions are not really vectors in a vector space. They are points in an affine space https://en.m.wikipedia.org/wiki/Affine_space . An affine space comes with a vector space though and you can use the vector space to parametrize the affine space nicely. This, is of course, the classical (and in fact, special relativistic I.e. no general relativity) description.
Answer:
Historically, vectors were introduced in geometry and physics (typically in mechanics)

Geometry means three dimensional space

A Euclidean vector, is thus an entity endowed with a magnitude (the length of the line segment (A, B)) and a direction (the direction from A to B). In physics, Euclidean vectors are used to represent physical quantities that have both magnitude and direction, but are not located at a specific place, in contrast to scalars, which have no direction. For example, velocity, forces and acceleration are represented by vectors.

This includes defining the location of a particle in three dimensional space.
Actually the question should be :

In a general physical sense, can the th position of a particle really a vector?

as assigning numbers to particles is the process of modeling with algebra and mathematics.
Comment: So define position as Vector makes sense only in a euclidian space, but not in more general spaces, like manifolds?
Comment: Of course, as long as the "vectors" obey vector algebra, and form vector spaces. The question discusses position, which is either 3 vectors, or four vectors for relativity and general relativity
Comment: Position is not a vector in GR though. Strictly speaking it's not a vector in SR either. Rather, you specify a *displacement* vector from an arbitrary point you call "the origin".
Comment: @user76284 three vectors are part of four vectors , so a four vector defines also the position in a given inertial frame, No?


Why is aluminium(III) considered a hard acid if it forms covalently bonded compounds like aluminium oxide?

Question: If something is a hard acid, it tends to form ionic bonds as it is polarizing. So why is the aluminium ion a hard acid when it forms bonds with covalent character. A similar argument follows for why carbon dioxide is considered a hard acid?
Comment: The hydrogen proton is the hardest acid, yet I can't think of any ionic compounds with the hydrogen proton as a component. Perhaps you may need to reexamine your rule of thumb.
Comment: what is the rule of thumb then?
Answer: Short summary - HSAB theory has it's limits of applicability, and this is a good example.
More recent discussion of acid-base theory center on the frontier orbital concept, e.g. W. B. Jensen, The Lewis Acid-Base Concepts (1980) pp. 112-155.
In this concept, an "acid-base" reaction creates new HOMO-LUMO orbitals of the product. So it's about energy matching between the acid (empty LUMO) and base (filled HOMO) (and also symmetry and orbital overlap). It's still very much a Lewis picture, since you have the electron pair on the base and an electron acceptor on the acid.
For example, if we react $\ce{NH3 + H+ -> NH4+}$ we combine the HOMO of $\ce{NH3}$ (i.e., a lone pair) with an empty LUMO on $\ce{H+}$ to create the adduct.
IMHO, this is a nice concept, since the orbital energy match between Al and O is good, you get covalent character to the resulting product. (Now you also get ionic character, but that's a different question.)
Answer: The Orbital Molecular Theory explains it very well; the symmetry and orbital overlap defined by the wave functions gives a complete approach. I add some thoughts to the question qualitatively:
The concept of covalent and ionic bonds must be taken carefully when talking of acidity, a property normally refereed to aqueous solution where other interactions (hydration enthalpy) take place.
The $\ce{Al^3+}$ ion is very polarizing, and has a high charge and low ionic radius leading to high effective nuclear charge. In solution the cation must have many shells of hydration, coordinating or polarizing water molecules and attaching $\ce{OH-}$ groups in order to compensate the positive charge, thus increasing the net amount of available $\ce{H+}$.
Similarly, carbon dioxide is a gas and it can be seen as a separated phase on a soda drink (bubbles); so first it must be dissolved in water. The dissolution of a $\ce{CO2 (g)}$ molecule in water increases the acidity, $\ce{[H+]}$, as can be tasted when leaving a glass of soda open in equilibrium with air for a while. I copy here the equations found at this link which explains why carbon dioxide is acidic. If you follow the link, it has a brief explanation:
$\ce{CO2 (g) <=> CO2 (aq)}$
$\ce{CO2 (aq) + H2O (l) <=> H2CO3 (aq)}$
$\ce{H2CO3 (aq) <=> HCO3- (aq) + H+ (aq)}$
$\ce{HCO3- (aq) <=> CO3^2- (aq) + H+ (aq)}$


Exclude user from OOM killer in unix

Question: Is there anyway to exclude some users from the out-of- memory killer in Unix? On the other way, can I set priority for user?
Answer: There is no way to instruct OOM to ignore specific user processes. Though you can instruct it to ignore a specific process and based on that you can construct a loop which will check all processes for specific user and update it via cron or whatever way you like. Cycle itself will look something like that:
while read r_pid ; do
    echo -16 | sudo tee /proc/$r_pid/oom_adj ;
done < <(pgrep -U Yoki)

you can wrap it in script and schedule to be run once per minute or any interval you like.
or you can completely disable OOM with
sysctl vm.overcommit_memory=2
echo "vm.overcommit_memory=2" >> /etc/sysctl.conf

though it is not recommended way at all, as it might lead to unexpected behaviour such as kernel panics or system hang.
Comment: Change -17 to something like -16 and the user's processes will be picked before other "critical" system processes.
Comment: Good point. Updated. Thx.
Comment: There's nothing wrong with setting `overcommit_memory=2`, it's just that certain applications (java, browsers) try to gobble up more virtual memory than is available, so they fail.  You might actually run out of memory, so monitor swap with a monitoring program, and if swap usage begins to climb, it might be a problem.

Exclude user from OOM killer in unix


How to discuss about time in an entirely empty space?

Question: Assuming that there is a volume in universe where light havent reached yet from the beginning of the universe and every matter(or anything) is so far away from that it so no field from that even reached there yet so if we have to discuss about the presence of time there how can we say that time is also there yet...means how we can relate time to pure space(entirely empty space)? How to prove that time is there?
Comment: Hi Mohammad, I would vote to close this question as it is based more on philosophy than physics, imo. If it does get closed , or if TBBT's answer is insufficient for you, could I suggest moving it to PhilosophySE?
Comment: I'm voting to close this question as off-topic because it is based on a philosophical question rather than a physically verifiable one.
Answer: The perception of the passage of time is the increasing in entropy of the system. If your "supposedly volume of the universe does not change as it reaches maximum entropy, then there is no way to measure the passage of time. Therefore, time stands still.