How to inform former intern boss that I'm re-applying to their company

Question: I interned at company X a couple years ago. At the end of the summer, one of my supervisors told me, "Let me know if you'd like to work here after you graduate" (would be happy to have me back, etc.). I recently applied to a position at company X and was notified that I'm in the final stages of the process. I completely forgot to notify him earlier, but feel like I should because a) he told me to and b) perhaps it could help with my application. We were on pretty good terms during the internship, haven't talked to him for a while though. Is there a way of writing this email that doesn't come off in a totally opportunistic way, i.e. only getting back in touch because I need something?
Comment: *"but feel like I should because a) he told me to"* - Actually, you indicated that this person said "let me know if you would like to work here after you graduate", not "let me know if you apply here after you graduate"... I see no "obligation" to tell this person that you are applying
Answer:
Is there a way of writing this email that doesn't come off in a totally opportunistic way, i.e. only getting back in touch because I need something?

To be honest, I see no convincing reason nor need to write this email.
You already at the final stages of the application process, so chances are you will most likely land it. Writing an email to this person may or may not increase your chances further, but it will surely seem a bit opportunistic.
You say you feel compelled to write because "he told you so", however in no way you are forced to write to him.
In fact, the "Let me know if you'd like to work here after you graduate" was a suggestion if you ever wanted to return, but given the fact that you have already applied seems that you missed the timing for that invitation (i.e.: you should have done it before applying by your own means).
Bottom line: I suggest you don't write such email and continue your process naturally. If you land the job you can then go greet your former manager in person. If you don't, you can then decide if it's worth to use your contact to see if you can land it that way.
Answer: Since you already had a good relationship, feel free to shoot him an email along the lines of
"Hey , how are things going at  I have good news; I applied for a job there and am now in the final stages of the interview. I enjoyed my internship so I'm looking forward to the opportunity to work with  again. I was wondering if you had any advice for me going forward. Thanks, and I hope to see you again soon"
As for not sounding opportunistic, I wouldn't worry about it if I were you. This sort of thing happens all the time in the professional world. But, if you are genuinely interested in catching up, you can invite him to catch up over lunch. He would probably enjoy seeing you again if you had a good relationship before.


What does a lens hood do?

Question: Pretty straight forward question.  What does a lens hood do?
Comment: See http://photo.stackexchange.com/questions/399/why-are-some-lens-hoods-petal-shaped-and-others-not - some good answers there
Answer: A lens hood has two purposes - one is to shield the lens elements from stray light - either directly from the sun, from passing cars, from a flash, etc.  This stray light can cause lens flare and reduced contrast, so it is best to limit it.
Its also useful for avoiding bumps to your lens or filter.  I use mine a lot in the car, because my lens is always very close to the window.
(It can also make that huge telephoto look that much more impressive)
Comment: Impressive-looking telephotos are very important in situations where you have to look like serious photographer, for example if you're trying to get past security into press sections on a show or sports event.
Comment: It also helps to keep rain off the front of the lens.
Comment: Another advantage when shooting close to a window is that you can press the lens hood up against the glass, and block out any light from the camera side of the window and reduce reflections.
Comment: Do I need hood in conical petal form to make product photography in white shooting tent outside when sun is shining? Now same question except that do I still need to have hood on when making same photography indoors with limited lighting source? I have Panasonic G5 with 14-42mm lens kit.

What does a lens hood do?


Basil plants turned completely woody and brown

Question: I grew basil in 2 different containers. I had a huge spider mite problem after I purched Miracle Gro soil in one container. Earlier this year, I harvested all the leaves off completely and leaves grew back. The spider mite problem somehow transferred to the other pot and I did the same, harvested all the leaves and that worked fine but it's been really cold lately in TX, I am not sure if it is bc the basil has flowered before but it's turned woody, completely, as stated in the title. I'm not sure if it's diseased and if I should get start a new batch of seeds now or if there's an oz of home for these growing twigs? It sucks because it was my favorite container of basil too. They were extremely bushy.
Answer: On the assumption you were growing outdoors, Basil (Ocimum basilicum) is only perennial in very warm regions; it's a tender annual plant in colder areas. Now that it's cold, it's unlikely to grow again. You've not said precisely which USDA zone you're in, but if you expect even colder weather during winter, then its definitely not going to grow again, so you might as well dispose of the woody brown one. You've not said what condition the other basil plant is in, in the other container, but if your temperatures are either 60 deg F or likely to get lower, then you will lose that one as well.
You can grow it from seed indoors, but as it grows, it will require as much sun as you can give it, see here for more  information on Basil growing generally
https://www.thespruce.com/how-to-grow-basil-plants-1402624
Comment: Austin, TX. The other basils are fine. They're in large laundry container with a tomato that I started this summer. I've had to bring the plants in from the cold. This sucks, I'll have to wait til spring to start some seeds up again.
Comment: You're lucky you rescued the other basils in time - your usda zone is 8b, which means temperatures down to 15-20 deg F
Comment: I'm inspecting the other ones now and parts of them are trying to turn woody, yay, But thank you for clarifying! I've had this issue another year and I kept watering those stems for no reason before I gave up. Thought I'd ask before I kept watering them again hahaha.
Comment: If you can keep it alive inside until the weather warms up, it might spring back to life.  The trouble is keeping on top of mites while it's inside.


What are the differences between single and double annular combustion chambers?

Question: The combustion chamber of a jet engine may be can type or annular type. Annular type combustion chamber can be SAC (single annular combustion chamber) or DAC (double annular combustion chamber). What are the major changes between these  two types of combustion chamber? Is the CFM56-7B26 a SAC or DAC engine?
Answer: See this answer for the difference between a SAC and DAC combustor. The EASA type certificate for the CFM56-7 also identifies which engines have the DAC and which have the SAC. The answer depends on exactly which -7B26 version you are referring to.


Multi-currency wallet api

Question: I need a api or an application that can generate and handle (send/receive and so on...) multi currency wallet.
For an example: It can generate dogecoin address, bitcoin address, litecoin address, peercoin address and so on... and handle them. Like send/receive/check balance.
Comment: Please read why you shouldn't thank users for reading your question (and reverting edits towards that direction): http://meta.stackexchange.com/questions/2950/should-hi-thanks-taglines-and-salutations-be-removed-from-posts
Comment: The RPC API is identical for almost every client...
Answer: I am developing an open source wallet that handles multiple currencies and stores the keys in a deterministic key chain (BIP44).
It is currently on Android but it is written in am modular way so that the core library could be used in any java application. The library is based on a slightly modified Bitcoinj and for the blockchain queries it uses Electrum servers. It supports BTC, LTC, DOGE and in beta PPC, DRK, RDD and I am adding now NuBits.
Check out the repo from here: https://github.com/Coinomi/coinomi-android. At some point I will separate the core lib from the android app.
enjoy
Comment: @john-l-jegutanis great work you did there, by the way. we are all using your wallet!
Answer: There are a few API providers that do multi-currency / wallet integration. The first that comes to mind is https://www.block.io/ they support LiteCoin/DogeCoin and Bitcoin. There may be others that have even wider digital currency support.
The way that most people do this is by running separate instances for each client blockchain and then using the RPC interface. There are similarities between most of the coins that forked Bitcoin. So although more resource intensive you could run each client you were interested in and use the native interface to communicate with them individually.
Comment: Hmm... I dont really want to run all client program for each currency becuase to generate a address...
Comment: Its easier to use an external API, mostly because you don't have to manage the underlying infrastructure. But the address generation is the same, you run the getnewaddress rpc call on the node for the type of address you want.

Multi-currency wallet api


People involved in your job application

Question: I have been in a few interviews and at the end of the interview, the interviewer will mention that he will check with his colleague and get back to me if I make it to the second round.  My question is this, the job interviewer's colleague was not present in the job interview so why does he have a say if I make it to the second round?
Answer: There may be other interviews being done by other staff, so they need time to collaborate their results.  Sometimes its a polite way of saying "we've got a lot to think about"  or "we have more interviews to do with other people"
Interviews are important, but some companies will have one person interviewing and picking their top two or three, and another person choosing two or three based purely on the CV.   Knowledge of the candidate in the interview may skew the purely-academic selection.
Personally I've never been offered a position straight from the interview; that would be particularly rare.
Comment: also quite often the interviewer doesn't have the authority to do more than make a recommendation
Comment: Typically for technical positions in my country they do a HR and a technical interview separate, precedence is up to the company and position. In the team I work we also accepted applications, but can't all the 8 of us come to the interview for quite a lot of reasons, but we discuss applicants to make sure we are all positive that s/he will be worthful as a member and we commonly agree with the decision. In this case 2 of us go to the interview, and later we evaluate the results, so Jeffrey would face somewhat same situation.
Answer: I've never been told straight out that that I made it to the second round while at the interview. Not a single time. I've had it alluded to and hinted at but even in cases where there were strong suggestions that they wanted me, I've gotten as many negative results as positives.
There are many reasons why an interviewer may tell you they want to ask a colleague.

It may be a group decision or at least one where group input is necessary
There may be thoughts and impressions the interviewer wants to discuss with someone else to see if they share that opinion.
They may not want to tell you face to face that you're not what they want, to avoid a discussion or attempt to have their mind changed.
Colleague could also mean "person actually doing the hiring" and telling him/her "you're going to interview with Jeffrey next week" might not be appropriate.

This list goes on and on. Don't focus on what they say as much as what they do. If you get a call, great. You shouldn't stop looking though. You've done your best now it's time to get another interview elsewhere. Keep looking until you get an actual offer.
Answer: Usually interviewers don't like to give the feedback straight away. Especially as they need to consider their answer. You're the one on test and under pressure. They already got the job so got the time to answer to you.
My opinion is just an excuse not to answer face to face, but it doesn't mean it's a negative things.
I got jobs in the past and they didn't tell me straight away I got it.

People involved in your job application


What mean philosophy?

Question: My question is clear: what is philosophy and why it is exist and why people still care about philosophy when we have science?
Comment: Because science can not give answers to ultimate questions that people have.
Comment: Science can only deal with natural phenomena. But many people believe in a bigger and broader reality that exist outside the natural realm. People have the tendacy to believe and imagine things that aren't always true, that do not really exist. Perhaps this was an advantage for the first members of our species.
Comment: Science is logical modeling of phenomena, and possibly the best thing philosophy has produced yet.
Answer: Historical note: Only a few centuries ago no distinction was being made between philosophy and science. Physics at the time of Newton, for example, was referred to as "natural philosophy".
Science is a particular method of acquiring knowledge: observe nature -> form a hypothesis -> make a prediction -> conduct multiple experiments -> confirm or reject. Scientific knowledge is one of the most reliable kinds we have, second only to mathematical knowledge.
Philosophy, on the other hand, encompasses any "knowledge" that could be obtained through questioning, speculation, discussion, reasoning, and not necessarily including observation.
In that sense, science is a very narrow part of philosophy. It is not concerned with (among other things):

the unobservable, e.g. claims of the existence of a god who never interferes with the universe
the unobjective, e.g. ethical question, which are very much dependent on the cultural background of who's asking them
the untestable, e.g. string theory is sometimes criticised as "unscientific" for beautifully explaining nature but not making any testable predictions about it
the unrepeatable, e.g. claims of miracles - one-time violations of the known laws of physics

Philosophy (apart from science) exists because of the human desire to pursue knowledge, even at the cost of its quality.

What mean philosophy?


static big files and a way to serve them securely (central authentication CDN)

Question: I need to serve few static big files(about 4GB each) to several users, using 5 servers that are in different geographical regions.
The idea is that nobody else gets the content as there's information in those files that is not meant for general public.
The task is to serve those files using a web server and some authentication mechanism or rewrite URLs or something that expires in a timely manner.
For this I could do a web app that would serve the clients the links and/or the credentials needed to access the files.
I have seen, for instance, that nginx could check if a cookie is set in the browser and could do a URL rewrite based on this fact but this might not be enough as I can't seem to find a way to validate the cookie contents.
I also saw the nginx http_auth works for authentication on a reverse proxy for emails. This might be a good idea, but again, static big files and a way to serve them securely.
Any ideas?
Answer: you can try using s3 form amazon. it`s easy to use, secure and serves your requests.


Can I call Jesus "Rasool Allah"?

Question: As Salam Aleikhum can I call Isha Rashool Allah or YA Rashool Allah as Muhammad Rashool Allah.because Isha is also my prophet as Muhammed is my prophet can I give same reference to Isha.
Answer: Jesus was a Prophet and a Messenger just like Moses and Muhammad, so yes you can call him رسول الله  and this is proven in the Quran:

المسيح عيسى ابن مريم رسول الله وكلمته القاها الى مريم وروح منه
Al-Masihu `Isa Abnu Maryama Rasulu Allahi Wa Kalimatuhu 'Alqaha 'Ila Maryama Wa Ruhun Minhu
The Messiah, Jesus, the son of Mary, was a messenger of Allah and His word which He directed to Mary and a soul from Him.
 Quran 4:171
واذ قال عيسى ابن مريم يا بني اسراييل اني رسول الله اليكم مصدقا لما بين يدي من التوراة ومبشرا برسول ياتي من بعدي اسمه احمد
Wa Idh Qala Isa Abnu Maryama Ya Bani Isra'ila Inni Rasulu Allahi 'Ilaykum Musaddiqaan Lima Bayna Yadayya Mina At-Tawraati Wa Mubashiraan Birasulin Ya'ti Min Ba`di Asmuhu 'Ahmad
And [mention] when Jesus, the son of Mary, said, "O children of Israel, indeed I am the messenger of Allah to you confirming what came before me of the Torah and bringing good tidings of a messenger to come after me, whose name is Ahmad."
 Quran 61:6

I'm not sure if you'd say "ya rasul-allah" unless you were talking to him.
Answer: You could but in general we really refer to him as Isa (AS)
It's fine so... I guess yes you could do that
But Isa (as) is not in front of us so it's better not so say YA rasool Allah
Answer: I think you can.
We Muslim are certain about that the result of our every actions depends on our Mind(Niyaat).
So if u call him "Rasool Allah" with the proper & accurate status & position that we find by the Quranic Verses & authentic Hadiths,that is pretty well.
We Muslims are of wide minded and try to follow the teachings of every prophet & messenger of Allah besides Muhammad(Pubh).
Obviously,our main core beleif is Quran what Muhammad (Pubh) got from Allah(SAW) .And as a direction of Quran we try to follow various teachings from our Prophhets.
Likely,Patience from Noh,Ayub.
Sacrifice from Ibrahim and so on.
Answer: No.  Reason is we were send a rasuul (Mohammad ibn Abdullah ibn Abdulmutalib ibn Hashim ) SAW.  He is representative for Isa ibn Maryama AS.  Isa was not sent for all creation. Therefore his message/mission was not completed. Until new prophet to complete the cycle and Isa to return to only confirm that he is Muslim.  So Rasuul lulaah is only applicable to the latest 1 which is the 1 you follow.

Can I call Jesus "Rasool Allah"?


sharing pledges between contacts

Question: In the user workflow I currently have, parents sign up for tuition payment plans for the program their children are attending. These are processed as pledges with varying numbers of installments, attached to the parent contact. Is there any way for me to assign those pledges to multiple people? For example in a two parent household, I would like both to get reminder emails. I feel like this is somewhat similar to giving soft credits to household members for contributions, but I'm not sure how to do it for pledges as well. Ideas?
Answer: Unfortunately there is not a way to assign a pledge to multiple contacts.
In the CiviCRM database, the pledge is assigned to a contact, but the individual pledge payment/installment is related to the pledge and not the contact.
Without a customization, this would not be possible.  Sorry
Comment: Bummer! Thanks for answering my question though. I will look into customization, though it may be above my skill level to do that.

sharing pledges between contacts


Capture the Flag: FAQ on Flagging

Question: What is flagging for moderator attention? How does the flagging process work? What are the different flags, and what are they useful for?
Comment: **Note** This post was sparked (I believe) by an email I sent to Asaf proposing the creation of a FAQ on flagging, after realizing from recent events that many flagging issues are not clear to many users. I was hoping to solicit input from many folks (including past and current mods) before posting a first draft, but now that Asaf has already done so, perhaps discussion can occur here. In particular, I think it would be helpful to attempt to devise *recommended* policies on flagging, and for this it is essential for experienced users to share their insights on what works best.
Comment: Also, it would be helpful to mention precisely what powers mods have to act on various flags (e.g. see Arturo's [recent question](http://meta.math.stackexchange.com/q/4319/242) about this), and how dispute resolution works, etc.
Comment: Indeed the email sparked this post. I figured that first we need to iron out *what* is flagging and what is the extent of the power of this system. Then we can iron out policies.
Answer: Flagging in general is a process in which a normal users requests the moderators to attend to a specific post. The flagging itself requires the user to have 15 points of reputation.
Some of the flags appear in the Moderator Tools page which is accessible to users whose reputation is at least 10,000. Users can then review the flagged post and give their opinion by agreeing with the flag (or flagging for a different reason) or by invalidating the flag.
Flags stay visible in a moderator's tools as long as they are not voted on (see below the cut). If you vote to support the flag, invalidate it, etc. it will disappear from your moderator tools but appear on others, that is until the question is closed/deleted or the flag is cleared by a moderator.
Repeated flags are allowed, meaning one can flag a single post several times. This can be done only after the first flag has been cleared, though. Otherwise a message appears reminding you that you already flagged the post.
It is therefore important not to act on flags that you are not certain about. Every action increases the bias of other users which may follow your footsteps.
Users have ten flags to use every day. This number increases with the reputation and with the number of helpful flags raised and can reach 100.
There are essentially three different forms of flags:

Automatic flags, these are raised by the software to alert the moderators that something may need intervening. There are three flags of this sort:

Low-quality post, this flag is raised when the software considers a post to be of low quality. On our site, due to short-but-TeXy answers the flag may be raised on answers which are actually very good answers.
Multiple deletions, this flag appears less often than the others, when a user removes a series of posts quickly. Often it is raised when someone deletes unattended posts (without answers/votes/comments). However it may actually be vandalism.
More than 20 comments, a flag raised automatically when a discussion occurs in the comments.

In a recent request, one of the moderators discussed the input the community should give to automatic flags: http://meta.math.stackexchange.com/q/4056/622.
Free form flags, these flags appear only for moderators. Users may employ these to address the moderators with a short text. Some possible uses for this form of flags are:

Requesting that a post be made Community Wiki.
Pointing out that a user has a duplicate account that needs to be merged.
Sending a request for re-opening or deleting a closed post.
Any other request which might be accompanied by an explanation or an otherwise non-standard flag.

It is important to stress that these flags appear only for moderators. If the actual content of the flag is pointing out that something is off topic, or that an answer is actually a comment it is better to use the standard flags, as these flags can be supported or invalidated by other users as well (which may also vote to close, delete, etc. bad posts).
Standard flags which are predetermined requests for a specific attention. These flags are divided to three groups:

Offensive and spam flags should be used only when something is truly offensive or contains spam. After three such flags a post is removed from the front page, and after six flags it is deleted automatically, along with a 100 reputation points loss to the poster.
Closure flags are for questions only and can be used for low-reputation users to point out that a question is off topic (and possibly suggest a migration target) or that the question is a duplicate of another post. Note that users with sufficient reputation to cast closure votes do not see this dialog and have the standard closing votes dialog instead.
Not an answer, this flag is for answers only. It can be used to point out that something is not an answer to the question. There are three major reasons for raising this flag:

Users without sufficient reputation for commenting try to post comments as an answer. In which case a moderator can convert the answer to a comment on the appropriate post.
Users which come from outside the site and do not know how the site works post a new question as an answer to an old question.
The original poster uses an answer to address others or suggest edits. Sometimes the user is unregistered and simply cannot comment or edit because the account had split. (In such case a free form flag suggesting an account merge is also appropriate.)

Low quality is the last flag, and the least useful too. The purpose of this flag is to point out a very low quality post. The moderators, however, do not intervene with the content of the posts and therefore usually have nothing to do about this sort of flag.
Not all is bad with this flag, though. Sometimes low quality posts are  posts which should be flagged for other reasons. In such cases the flag is helpful, although it is best to use the appropriate flag instead.

So what happens after you flagged?
Some of the flags will appear in the Moderator Tools page and be viewable by users with 10K reputation. And all of the flags will be shown to the analogous page for the Moderators. The flags will stay on the pages until either (a) a moderator clears the flag (and it disappears from the page for all users) or (b) the user votes support or disputes the flag (in which case it will disappear from your own queue).
Flagging a post, and supporting or disputing a flag, are relatively straight forward. User with over 10K reputation should however read the following two Meta Items

http://meta.math.stackexchange.com/questions/3127/what-are-those-flags-in-the-mod-tools-good-for-when-and-how-should-i-act-on-th
http://meta.math.stackexchange.com/questions/4056/about-the-more-than-20-comments-posted-system-flag

But when the flag lands on a Moderator's plate, that's where things can get tricky. Here are an interesting fact about the Moderator tool panel:

For each group of flags on a post (which basically means that all flags, supporting votes, and disputing votes by 10K users *since the last time the flags were cleared on that post) the Moderator can choose one and only one action. The entire group can be marked either helpful or we can mark to decline the flag.

For a single flag (or flag with supporting votes) this is fairly straight forward. A moderator looks at the flag, decides

Some action is required:

Sometimes off-topic or spam posts needs to be closed or deleted; "comments as an answer" will need to be migrated to the correct threads. When moderators close or delete a post, the flags are automatically considered helpful. The user who flagged will see that also as their feedback.
Sometimes other type of action is required: the OP needs to be contacted, accounts need to be merged. In those cases after performing said action the moderator will manually mark the flag as helpful.
One interesting case where action by moderator will automatically decline a flag is when a post is flagged Low Quality. The flag is intended to signal posts which are so bad that they cannot be conceivably salvaged. If the moderator proceeds to edit that post, the system interprets it to mean that the post is in fact salvageable and automatically declines the flag.

Some action is not required:

Sometimes flags are purely informational and does not need to be acted upon. In those cases the moderators often leave the flags open for a while so that other moderators also have a chance to see them, and afterward mark the flag as helpful but with no action required.
Sometimes moderators materially disagree with the flag, in which case the flag will be declined with either a standard reason such as "A moderator has reviewed your flag and found no evidence to support it" or "A flag should only be used to indicate something that requires moderator intervention", or a free-form reason which the moderator will provide. The reason for the declined flag will be displayed to the original flagging user.

In the case where there are multiple (possibly mutually conflicting) flags and/or supporting votes and/or disputing votes, the situation becomes more complicated.

In the case that there are disputing votes (where a 10K user marks a flag invalid), the only feedback returned to all users from moderator action is Disputed (note, not declined nor helpful; always disputed). If the moderator marks the group of flags as helpful, that would be the only feedback to the users. If the moderator declines the group of flags, in addition to seeing the word "disputed", the users will all see the reason for declining the flag. This is a known bug.
To emphasize: if you are a 10K user and you see your dispute vote return a feedback of "Disputed - a moderator reviewed your flag and found no evidence to support it", most likely this means that the Moderator actually agrees with you and declined the original flag. Conversely, if you flag a post and see a feedback of only "Disputed" with no further reason, it means that other users do not agree with your flag, and that the moderators either agree with the flag or acknowledges the fact that there is a disagreement about the flag.
For more information about this one may wish to read

Am I using the "Invalid Flag" flag wrongly?
What is a disputed flag?

In the case that there are not disputing votes, again recall that a moderator can only mark as helpful or decline an entire group of flags at a time. So if you and some other user both flagged the same post but for drastically different reasons, you may see your flag declined for strange reasons. A moderator may or may not contact you specifically about this; feel free, however, to e-mail the moderators when there is some doubt to why your flag was declined.
Comment: I stopped now because an hour was enough to make me a bit dizzy. I may edit and give it a final touch later on. I also left out comment flags completely because I never really used those.
Comment: @Willie: I don't know about closure flags; but if I flag something and then it gets community-deleted it is marked as helpful too.
Comment: Cool! Can I shamelessly steal this later? I'll give attribution, of course!
Comment: @Alenanno: No problem, but please wait another few days. I might improve this a bit.
Comment: Sure! Thank you. :) Just ping me here.
Comment: But if you flag something and someone disputes it and it gets community-deleted, I think it will get marked as "Disputed".
Comment: I don't know about that. We can either run an experiment or ask the StackOverlords.
Comment: Thanks for this.  I stopped flagging duplicates, because my most recent flag (for a duplicate) was declined, with the reason being given as "declined - flags should only be used to make moderators aware of content that requires their intervention".  I don't think I have any other way of drawing attention to duplicates (other than in comments), but I supposed that flagging must not considered the appropriate way to do this (even though it's specifically one of the flag options).  From what you've written, it looks like it might just be a case of the flag being declined 'for strange reasons'.
Comment: @Tara: actually, in that case a moderator did decline your flag (being the only one on that question). I, however, have no idea why he chose to do so.
Comment: @Tara: There was some incoherence after the elections and some moderators invalidated flags without fully understanding the flagging system. It should not stop you from flagging the future, and in case you feel that you are flagging and you think a flag was wrongfully declined (e.g. as in the situation you describe) you can start a thread [like I did here](http://meta.math.stackexchange.com/questions/4315/wrongfully-declined-flag) to get a better understand why the flag was declined, and help prevent future cases like this.

Capture the Flag: FAQ on Flagging


Brakes spongy after pad change

Question: I changed the brake pads on a Hilux and after doing so, the pedal has gone very spongy. The brake fluid also seems to have risen above max. When I start the car, the first press of the brake pedal seems normal but after that it's very spongy.
Comment: this is not uncommon after changing brake pads,it should get better after some use.
Comment: Did you release the bleed nipples when you pushed the brake pistons in?
Answer: Do a preliminary check of the hydraulics and vacuum booster by holding down the brake pedal and feel if there is continuous release of pressure.  Pulse the brake pedal repeatedly and continue pulsing while your turn off the engine.  The pedal should get harder and harder to push and eventually settle to a consistent pressure on your foot with no 'lag' and additional slow downward movement.
If the 'sponginess' is only when you are trying to stop the moving car you may have oil or contaminants on the rotors or may need to break in the pads.
Best to refresh the system by doing a hydraulic bleed if possible.  As a stopgap measure keep a continuous check on the fluid reservoir and keep a periodic visual leak check on each caliper piston and hoses.
Again you may just have oil on the rotor.
Answer: You need to bleed the brake lines, as it means there is an air bubble trapped in the line raising the fluid level.
Comment: Welcome to M.SE, Frank. You need to proof-read before submitting your answer. Site policy is "Write to the best of your ability
We don't expect every answer to be perfect, but answers with correct spelling, punctuation, and grammar are easier to read. They also tend to get upvoted more frequently. Remember, you can always go back at any time and edit your answer to improve it." See [How to answer](https://mechanics.stackexchange.com/help/how-to-answer)..
Answer: If you did only change the brake pads and pushed the caliper pistons back the brake fluid level will go up.
You should not need to bleed the calipers after this,it is not unusual that the brake pedal feels a little spongy after changing brake pads but it should get back to normal in a short time after some driving.
If the pedal still feels spongy after a week of normal use of your car you need to have it looked at.

Brakes spongy after pad change


Way to enable vertical two-finger scrolling, but not horizontal?

Question: I like vertical two-finger scrolling and enabled it. However, I keep accidentally swiping left and right with two fingers and going back and forward in Chrome, as well as doing weird stuff in other apps. Is there a way to keep vertical two-finger scrolling, but disable to horizontal scrolling?
Answer: This answer applies only to Loki
Okay, so I might have just proven myself wrong.  I did:
sudo apt-get remove xserver-xorg-input-libinput libinput-tools

This removes libinput touchpad driver.  Then install synaptics:
sudo apt-get install xserver-xorg-input-all xserver-xorg-input-evdev xserver-xorg-input-synaptics

Then restart.  In terminal type:
synclient HorizTwoFingerScroll=0

This disables two finger horizontal scroll.  Can also add:
synclient PalmDetect=1

for palm detection.  Changes do not seem to persist across reboots so you might have to create a custom command on startup for each of these.
I have not tested this extensively, but seems to work so far, use at your own risk.  You could always remove the synaptics packages and reinstall the libinput ones if needed.
Jay
Comment: Thank you. I'd add that `sudo apt-get install --reinstall ` might be a good idea.
Answer: This answer applies only to Loki
I don't think it is possible.  It appears that the touchpad driver used is now libinput and according to this post:
https://wayland.freedesktop.org/libinput/doc/latest/scrolling.html
It does not differentiate between horizontal and vertical scrolling.  Someone can chime in and correct me if i'm wrong.  I'd love to have a way to disable it too.
Also mentioned in this post regarding Ubuntu with Gnome:
https://ubuntuforums.org/showthread.php?t=2321626
Jay


Why does BGP RR only reflect the best path?

Question: Can anyone answer why does BGP RR only reflect the best path?
Comment: Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can post and accept your own answer.
Answer: To conserve memory at destination, it was not important to micro-optimize forwarding path in the past. This is quote from RFC4456:

One of the key component of the route reflection approach in
addressing the scaling issue is that the RR summarizes routing
information and only reflects its best path.

While scaling is always important, clearly there are today scenarios where we'll rather spend RIB memory than choose suboptimal path.
To address this issue there is BGP AddPath and BGP optimal reflection. AddPath is available from both Cisco and Juniper, while optimal reflection currently is not implemented by major vendors.
AddPath allows BGP to send more than single best path. Optimal reflection will use SPF (ISIS, OSPF) to reflect best route from POV of receiver, not from route reflectors own point of view.
Answer: Bear in mind that the idea with iBGP and route reflection has been to distribute path information with the idea that specific routing/forwarding decisions would be accommodated by the underlying IGP (particularly including multipathing, internal failover, etc).  As such, a pointer to what ought to be fairly static next-hops can be kept in table while avoiding the churn associated with localized network information.
Scalability and stability were (and arguably should be) the primary objectives of BGP - even at the price of suboptimal path choice and fast convergence.  The traditional implementation of the RR epitomizes this.  Ideally the information on RR's should be as static as possible and timers should be kept on the long side.
BTW - There are circumstances in which an RR might send multiple paths to the same v4/v6 destination - both the AddPath feature mentioned above as well as in the MPLS VPN case where a given prefix is associated with the RD's of multiple PE's.
Comment: Not sure I'd lump RR in with the original iBGP design goals (which you're totally right about, especially regarding scalability and stability); RR was proposed in a separate RFC to alleviate the scaling issues someone would run into with iBGP full mesh and the desire to have synchronization disabled. Otherwise a great answer, and upvoted as such.
Comment: I'd like to point out that prefix with different RD is _unique prefix_, reflector has no idea it it'll be non-unique at receiver PE at receiver VRF. This is exactly the function of RD, without it, you couldn't have overlapping prefixes in VRFs.
Answer: To add to the previous answers, you have a new feature called BGP path diverse to allow the RR to advertise a diverse path. For more detail, please check RFC6774 or Cisco implementation at http://www.cisco.com/en/US/docs/ios/ios_xe/iproute_bgp/configuration/guide/irg_diverse_path_xe.html


Can a girl & a boy be friends

Question: I didn't use to have much boys as friends but with time I made several boy friends from which some were really close. I want to know what has Lord Buddha chanted about a girl & a boy being friends?  Will it be something bad when I get married?
Comment: Yes, I'm married and celibate. No problem, if you have the right partner.
Answer: If you are not married, the Buddha said to look at opposite sex friends like brother & sister:

'Come now, monks: with regard to women who are old enough to be your
  mother, establish the attitude you would have toward your mother. With
  regard to women who are old enough to be your sister, establish the
  attitude you'd have toward a sister. With regard to women who are
  young enough to be your daughter, establish the attitude you'd have
  toward a daughter.'
SN 35.127

If a person wishes to get married, the Buddha taught a suitable partner has the same life goals & attitudes; particularly living according the five precepts:

Householders, if both husband and wife wish to see one another not only in this present time but also in the future, they should have
  the same faith, the same virtuous behavior, the same generosity and
  the same wisdom. Then they will see one another not only in this
  present time but also in the future.
AN 4.55

Householders, there are these four ways of living together. What four? A male wretch lives together with a female wretch; a male wretch lives together with a female goddess; a male god lives together with a female wretch; a male god lives together with a female goddess.
AN 4.53

When both husband and wife are endowed with faith, charitable and self-controlled, living their lives righteously, addressing each other
  with pleasant words, Then many benefits accrue to them and they dwell
  at ease.
AN 4.53 & AN 4.55

If one or both people had many sexual partners before they get married and do not respect the precept of sexual fidelity then, as the Buddha taught above in AN 4.53 & AN 4.55, their marriage will most likely (but not always) have problems. The Buddha particularly emphasised sexual misconduct should be avoided by and towards women, as follows:

242. Unchastity is the taint in a woman.
242. In a woman, misconduct is an impurity.
Dhammapada
Comment: Thanks a lot. This answer helped me a lot. No, I didn't mean any sort of a sexual-relationship but a general friendship in which we share many things. The thing is, being a girl from an Asian country, not all boys understand to be just friends with a girl. Some understand the whole thing in a wrong way when I try to maintain a good friendship with them.
Comment: OK. Thank you also. You are welcome. With metta
Answer: According to Bodhisattva, if you are unmarried then treat every boy and girl like your sibling. So, your question can be boiled down to, "Can siblings be friends?" to which I will answer, "Siblings are almost always friends!" The Buddha never spoke explicitly about this, though he mentioned that adultery is a sin and a hindrance to Nirvana- and anybody who commits his mind to such thoughts is also as much at fault as the one who actually commits the sin. There is no place for lust in friendship, so I think, yes. Boys and girls can be friends.
Answer: For the monastic, celibacy is a precept. For the lay follower planning to get married and become a householder, the consideration is much gentler, with a clear prohibition against illicit sexual conduct.

And what is the treasure of virtue? There is the case where a disciple of the noble ones abstains from taking life, abstains from stealing, abstains from illicit sexual conduct, abstains from lying, abstains from taking intoxicants that cause heedlessness. This, monks, is called the treasure of virtue (AN7.6 Thanissaro)

Notably, the lay path will be difficult:

"… the sentient beings who refrain from sexual misconduct are few, while those who don't refrain are many. …"

Can a girl & a boy be friends


SpaceX: Recovery/reuse of upper stages - where would they land?

Question: I know all about the plans for reusing the 1st stage, ocean landing vs. fly back, etc. But, Musk wants to make stages 2 and 3 reusable as well. Surely they would have far too much velocity and height to turn around and come back? Or, would they just go for a long ballistic arc to somewhere in Africa on the 2nd, and circumnavigating the planet with the 3rd, to return to the launch site?
Answer: Elon Musk has said that they have basically given up on Falcon 9 upper stage recovery, focusing on first stage recovery for Falcon 9, and whatever you want to call Falcon Heavy's side boosters and center core.  The center core is not quite a second stage, but is kind of sort of a second stage.  Stage 1.5?
For the upper stages on a LEO mission, it is basically in orbit.  On a GEO/GTO mission it is in a pretty high orbit.
Getting that back is basically the same problem as a Dragon recovery, which is probably going to add a major payload hit.
For upper stage recovery they have decided that BFR (Big F***ing Rocket) they plan for Mars missions, using the a cluster of Raptor (million lb thrust LOX/CH4 engine) will be reusable on first stage and second stage.
There has been some confusion and suggestions that in fact, the second stage of the BFR will be the MCT (Mars Colonial Transport).  That is, the first stage delivers the second stage which proceeds to orbit.  Possibly is refueled by other BFR launches, and finally departs for Mars.
In that case, many BFR/MCT launches will likely be needed to refuel the first MCT waiting to go to Mars. So upper stage reuse of the MCT will be critical.
So to the actual question, where would they land?
Well they will basically be in orbit once they are ready to land, so going once around and aiming for the launch site is likely possible, assuming their orbital inclination did not move them too far away from the launch site. If they have sufficient aerodynamic control they can likely make it back to the launch site.
Smartest place to land is wherever they intend to refurb them for reuse.  Likely the launch site, but that is unclear.
Comment: "Big F***ing Rocket". That is: Big Falcon Rocket.
Comment: @LocalFluff It if BFR like the B-52 is a BUFF.  Big Ugly Friendly Fellow if you want to be polite. But that is not what the first F really stands for. Trying to be polite.


How can I avoid wearing out flash memory by frequently changing symlinks?

Question: I have a circular buffer of files in ram disk. A new file is created every second. I want to always refer to the latest file using the same file name for access by a browser and apache. So, each time I update the file, I update a symlink from FIXED_FILE_NAME to VARIABLE_FILE_NAME. My concern is that such a frequent update of the file system wears out the flash memory that stores the system. How can I avoid this wear ? Thank you in advance for your help.
Comment: Can't the symlink be on the RAM disk as well?
Answer: You can't, but it does not matter because it will take more than a decade to wear a card out that way.  I've pointed out previously that there is much paranoia about this amongst pi users, perhaps because of reports of filesystem corruption which litter the internet, although these have nothing to do with wearing out cards.  I don't think there is the same degree of hysteria amongst camera and smartphone users.
Anyway, let's unsuperstitiously go through the math.  Say you have a cheap 4 GB card.  It doesn't matter whether you allocate the whole thing or not, because SD cards use virtual addressing and  wear leveling.  Physically, the whole card is in play no matter what, even if you are only using a 1 GB filesystem.
Let's also say that cheap card has a very crappy lifespan -- 1000 write cycles.  Then let's say it only takes half that time before enough failed blocks have been excluded by the card's built-in controller to make using it silly and splurging another $10, as painful as it seems, becomes worthwhile.
So in total, you can write 2 terabytes to the card.  Now let's say that changing an inode is 1 kB.  It certainly won't really be that much from a filesystem perspective, but we might as well increase it to 4 kB in case there's something about the SD card which requires changing entire blocks of a certain minimal size, such as 4 kB (this is probably the case).  If all you use the SD card for is small writes, this means you could do this on average:
2000000000000 / 4000 = 500000000

500 million times.  There are 86400 seconds in a day; at 365 days per year that's
500000000 / 31536000 seconds = 15 years

But of course that's not all that is going on with the card.  Add on average another 100 MB per day writing to the card.  Spread out, that's another ~1157 bytes per second; we don't need to compensate for the minimal block size here presuming the average write is more than 4 kB.  Now we have:
2000000000000 / 5117 / 31536000 = 12 years

To be on the safe side, I suggest you replace the card every 2-3 years if you can afford the expense.  If you are really strapped, try pushing it to 5-6.  You should keep a backup of the system and, if it is crucial, have a spare card at hand anyway.
There is an additional factor in your favour, which is that the OS uses a page cache in free memory.  Frequent changes will not all take place on disk, they will take place in the page cache and occasionally get synced to disk -- this is one reason filesystem corruption is possible in the first place, because if you suddenly kill the power when the system is busy, the cache is not completely synced with the disk at that moment (however, the risk of this really causing a problem is low).  See also man sync.
Of course, if you reduce the amount of free memory by using a giant ram disk, you reduce the efficacy of the page cache.  That may or may not be wise depending on context, but it likely it is not.  Try to leave at least 50-100 MB free unless you do not care about the overall performance of the system.1
Note that the pi, or some pis, seem to be prone to causing corruption even when using a read-only filesystem -- at least, we've had a few separate reports of that here.  You cannot guard against this unknown problem, which may have to do with an old kernel bug (if you have a kernel built in the past year, don't worry), or it may be an electrical flaw in some pis.

1. Note there are two metrics common in reporting memory usage, the total amount of RAM used by userspace processes, and the total amount of RAM used.  The difference between the two is mostly because of the page cache; if you look at the output of free, this is indicated on the second line, +/- buffers/cache.  If the system has been running for long enough, particularly on a relatively low memory device like the pi, chances are the kernel will have filled all free RAM (as in, not used by userspace processes) with the page cache.  This is why the metric that's relevant for most purposes is the first one, i.e., the memory used by userspace process, because the amount of "free" memory available for use by userspace processes (that is, all the programs you run) is the total amount minus the amount they are already using, and not including the page cache. Remember, stuff in the page cache isn't really in use, it's stuff that was in use and is cached in RAM in case something wants to use it again.  If instead something needs more memory for some other purpose, chunks of the page cache are discarded to provide it (possibly being synced to disk first).
So for user purposes, you can consider the page cache free RAM.  Hence the second line of free.  Here's a headless B+ that's been up for a few days:
>free
             total       used       free     shared    buffers     cached
Mem:        448376     278064     170312       8416      45968     194780
-/+ buffers/cache:      37316     411060

On the first line, it looks like I've used 278 MB.  But that includes the page cache.  If I added up all the memory used by all my running processes, it wouldn't be anywhere near that amount.  That's the number on the second line -- I've really only used 37.3 MB.  However, some tools, including top, only report the number from the first line (however, top does report numbers for buffers and cached, which you can subtract from that).
Comment: Based on your reply, I am concerned about three things: (1) does wear leveling work as well as you say on micro-SD cards and USB flash drives, (2) do 2-bits/cell and 3-bits/cell flash drives have as many write cycles as you estimate, and (3) how do I maintain at least 50 to 100 MB of free memory ? I usually see only about 15 to 20 MB of free memory in 'top' and most of the memory usages reported by 'top' are 0% so the memory usage numbers don't add up and I don't know what functions to massage to free up more memory.
Comment: I've added a lengthy footnote that may explain what you are seeing in `top`.  Looks like Ronny Nilsson has a clever solution to your symlink question, although I still feel tackling this as an [XY problem](http://meta.stackexchange.com/questions/66377/what-is-the-xy-problem/66378#66378) was the way to go.  WRT wear leveling and various things, you'd have to do your own research, but I believe pretty much all the flash memory in consumer storage devices use it..
Comment: ..My general point is there's no point in bending over backward this way.   Say the card only lasts 18 months?  So what?  It is easy to keep a backup of and restore a 4 GB file filesystem; not doing so is just lazy and that's what you should put an effort into.  Why not find out for yourself here -- if the card fails in a year, then maybe you want to take some kind of action.   But right now you have no good reason to believe that will happen.
Answer: Create symlinks in two levels. When creating a new file, also create a symlink to it and put that symlink in the same directory as the temp file. Then create a second symlink for the webserver which points to the first symlink. The second symlink should never have to be rewritten, only recreate the first symlink.
Comment: This is interesting. Does this mean the file system is clever enough not to update inode tables in flash memory about ANY files or folders that are stored in ram disk, which has been defined in /etc/fstab ?
Comment: @NewtownGuy A [symlink](https://en.wikipedia.org/wiki/Symbolic_link) does't point to an inode; it contains an actual path.  So if you link `/ramdisk/whatever` to `/ramdisk/foo`, and `/ramdisk/foo` to `/fs/foo`, you can change the target of `/ramdisk/foo` as much as you like; even when its own inode changes, as long as its path remains the same, it can be accessed via `/fs/foo`, and nothing about `/fs/foo` needs to change.
Comment: It's correct as goldilocks say. Something like this should solve the problem:
ln -sf /ramdisk/one_tempfile /ramdisk/latest_tempfile.
ln -s /ramdisk/lastes_tempfile /fs/www/tempfile.txt.
Comment: I had a problem linking a filesystem file to a tempfilesystem file because the tempfilesystem file does not exist at boot time because tempfilesystem is flushed at boot. So if the system is up and running, and I made a symlink from filesystem to tempfilesystem, that link disappears when the system reboots. I had to put startup code in /etc/rc.local and make sure the file exists, so I had to wait for my application to start, before I make the symlink again. Am I doing something wrong ?
Comment: I appreciate that I need to add a link to a link. My concern is that when I tried to make a static link to a temp file, that link disappeared at boot because the file did not exist yet. Won't I have the same problem trying to make a permanent link to a temp link ?


What are good substrates for parrot cages?

Question: I'm looking for a substrate to use in a parrot cage. It needs to be safe (firstly), but then also not to bad looking and easy to clean.
Answer: Looking at the opinions of other keepers and internet consultants the safest and most recommended/used substrate for parrot cages is paper. Newspaper and white or brown butcher paper are mentioned on ALL personal sites.
Comment: I cannot find any authoritative sources for substrates, so I would like to call for known reliable sources for this answer please.
Comment: What would you consider an authoritative source? I highly doubt there's been an academic study on parrot substrates. Paper is cheap, easy to change, and easy to examine droppings if necessary. Unless you are wanting a substrate that can be left in a cage without changing for an extended period of time, I can't think of anything with a benefit over paper.
Comment: @Jestep. Yes. I got hold of A New Owner's Guide to African Grey Parrots by Nikki Moustaki. 2004. T.F.H Publications, which for example does not even mention substrates. She does however encourage cages with a grating or grill at the bottom for greys not to get in contact with whatever substrate you're using. I don't think all keepers will have access to such a luxury though. I was looking for safe options on this topic.
Answer:
I have two budgies, one male, one female. Each bird has its own cage because the female tends to bully the male so I give him his own cage.
See photo. I use Hagen Vision cages for my budgies. The design has a plastic base which is about 10 cm (4") deep. I fill this base to  depth of about 8 cm (3") with clean shredded waste paper i.e. junk mail etc that has been passed through a shredder with a cross-cut function so the paper is cut into strips about 0.5 cm wide x 2.0 cm long.
This homemade litter is free, clean, low-dust, non-toxic and my budgies (especially my female) like playing with the pieces of paper so it is an extra toy.
I work from home so I can let my birds spend all day outside their cages and return only to sleep. Each morning I release the birds and then clean the cages. Under the sleeping perch there is a small heap of night-time droppings. I lift this out with a handful of shredded paper and smooth over the gap. I then clean out the water and food bowls. It takes about five minutes to make each cage perfectly clean and ready to be used again that night.
At the end of the week the litter is emptied into a compost bin to be recycled and I clean and disinfect the cages and add new shredded paper. It takes about 20 minutes to wash each cage.
Shredded litter means effortless petcare which is 'green', ethical, and very efficient. I recommend it!
Answer: Normally newspaper is what people would use but you can actually buy sandpaper like sheets from the pet store for use with parrot and small parakeet cages.  They are brown and about the size of a piece of writing paper (8x11").


No Sound on Ubuntu 12.04

Question: After I installed Ubuntu 12.04, there are no sound at all on my headphone (rear jack panel).
On Sound settings > playback, it seemed that the sounds were detected after I choose 'play sound'.
Anybody can fix this issue??
Thanks.
Answer: https://help.ubuntu.com/community/SoundTroubleshootingProcedure
I just did Step 1 and then reboot my laptop and the sound works.
If you are using Ubuntu 12.04 or later, then execute this command and reboot:

Carefully read and understand what these commands do. For instance, the  sudo apt-get install
  command includes the entire Ubuntu desktop. This will likely create
  problems for users of the other flavors of Ubuntu -- a Kubuntu user
  would not want the Unity interface installed. While the outcome of
  running the suggested command string below may indeed fix certain
  sound problems, be aware that it is a very blunt approach and could
  result in unintended consequences.

sudo add-apt-repository ppa:ubuntu-audio-dev/ppa;              \
sudo apt-get update;                                           \
sudo apt-get dist-upgrade;                                     \
sudo apt-get install linux-sound-base alsa-base alsa-utils gdm \
     ubuntu-desktop  linux-image-`uname -r` libasound2;        \
sudo apt-get -y --reinstall install linux-sound-base alsa-base \
     alsa-utils gdm ubuntu-desktop  linux-image-`uname -r`     \
     libasound2;                                               \
killall pulseaudio;                                            \
rm -r ~/.pulse*;                                               \
sudo                                                           \
    usermod -aG $(                                             \
          cat /etc/group |                                     \
          grep -e '^pulse:' -e '^audio:' -e '^pulse-access:'   \
          -e '^pulse-rt:' -e '^video:' |                       \
          awk -F: '{print $1}' |                               \
          tr '\n' ',' |                                        \
          sed 's:,$::g'                                        \
    ) $(whoami)

Paste the whole code block into your terminal with CTRL-SHIFT-V, then press enter.
Comment: thank you so much. This problem take me a long time to find solutions.
Comment: Another answerer to this question was burned by this command because they were not running default Ubuntu Unity. I've edited this post to prevent this sort of thing in the future.
Answer: Try this:
sudo killall pulseaudio
sudo alsa force-reload

Answer: Whatever you do don't enter the huge code on the first answer! It completely ruined my login screen.
Just use killall pulseaudio in the terminal.
Answer: Have you been muted? For pulseaudio, try pavucontrol, and check if the mute button is on in the Output Devices tab:
Comment: its a little wierd but i just canged the port (on the picture) and it worked!
hope it helps :)
Answer: I had the same issue, I ended up plugging my speakers into the rear audio out and it worked. On the sound test under "stereo mode" the front left/right works, but when I put it in 5.1, my speakers are converted to the rear channels like they are supposed to be. So I just leave it in stereo (that's what they are anyways).
Although, if you have a laptop or "non-HD audio" hardware (only a line in, line out, mic), this won't be possible.
Also, the strange thing was my front panel audio works fine, must be something goofy with the Realtek HD audio drivers...
Answer: I was having the same issue as the OP for a little while and I finally figured it out.
Check your BIOS and make sure that your onboard audio is set to Enabled. Not Auto or Disabled. Mine was on auto and nothing would make 12.04 see the device.
Answer: This is what fixed it for me.
Open terminal
sudo gedit /etc/modprobe.d/modprobe.conf

A new file will be opened, write a line below then save.
options snd_hda_intel model=mb5

Close file Reboot the computer.
Thanks to No sound on an iMac
Answer: In a terminal, I ran gstreamer-properties, forced both input and output to ALSA Advanced Linux Sound Architecture, and rebooted. Then it worked fine!
Answer: This did not work for my case Ubuntu AMD 64 12.04 with HP quad core PC 5GB ram.
Other issues existed and sound disappeared after updates and other software install.
May have had a script bug as well?
Located odd files and delited from home page.
found that Kubuntu driver for the PC using the DVD ISO was NVidea MCP61
used sudo apt-get install Nvidea MCP61
Located synaptic files that were broken and tried to fix them.
Un installed or removed one, installed another, updated the third file.
Turned of PC and restarted after waiting for updates and upgrades to install.
The next day the sound setting are back to normal and the Dummy output setting is gone.
Comment: This doesn't really answer the question as you don't say anything specific to guide the OP.
Answer: Try to read this: Skype FAQ - sound system change
Answer: Okey. I see your problem. I had it too. Try this. It's safe and worked for me.
Open the terminal and type

alsamixer

Press S and select the HD-Audio Generic option.
Scroll to automute and disable it
now turn up all the volume options
Press Esc to exit
Done!
Now try and play something
Best of luck ;) :D

No Sound on Ubuntu 12.04


How were long-running talmudic discussions actually conducted?

Question: Eiruvin 13b records two years-long disputes between Beit Hillel and Beit Shammai, and surely these are not the only long-running debates.  How did that work in practice?  Did they really have a single discussion that lasted 2.5 (in one case) or 3 (in another) years, straight through?  Or was it something they came back to every now and then, in between other discussions?  If the latter, how did they track progress/context (or did they rehash a lot)?  Was it normal to have several different "threads" of discourse going at any given time?
Comment: I'm not sure I understand the question. I'm fairly certain they did not engage in daily debate on a single topic, filibuster-style, for 2.5 years. Is that what your first thought is?
Comment: @SethJ, that's what I meant with the first option, yes (though with more discourse and less "I'm going to hold the floor until you give up" like in a fillibuster).  Was there a single discussion going at a time and it went until resolved and then move on to the next topic, or was it multi-threaded, or what?  And if the latter, how did they keep track of the arguments over such a long period (or didn't they)?
Answer: First considering that Gemarra was codified traditionally in 450 more likely in 960 in either case centuries after many of these debates occured, so precise details in how they occurred were not recorded by any person with living memory of them.
However, there is no reason to believe that they occurred any differently than debates amongst Rabbanim(and more likely their students) occur today, just with less speed and no internet coverage.  Especially once the Jewish people were divided between the various academies in Eretz Yisrael and Babylonia you would need runners(people who would actually go back and forth and say what was being taught in each) or letters or other correspondence to be sent.
Three debates that I can think of in recent times that took place over a protracted period of time are:
Rav Moshe Feinstein and Rav Shlomo Zalman Auerbach over whether chicken bones were muktze(forbidden to be handled on shabbat, unless necessary).  That one actually played out between their talmidim for quite some time until the two men wrote to one another and accepted each other's positions for their respective locations(in the US people don't eat chicken bones, and in Israel at the time they did).
Rav Ovadia Yosef and Rav Eliashiv over whether conversions that took place in the army were valid.  They eventually reached a sort of compromise.
Rav Hershcel Shachter vs a whole slew of internet bloggers who are students of big people that have not yet weighed in themselves on the issues regarding agunah/get meusah.  This one is still ongoing and getting quite nasty to be honest.


What does linking mean in the context of compilers?

Question: I'm learning more about compilers. While trying to understand this Wikipedia article on LLVM I ran across the term "linking". I've seen this term before but don't truly understand it. In the context of compilers what does linking mean?
Comment: From the beginning of the exact link you posted, see [here](http://en.wikipedia.org/wiki/Link-time)
Answer: Linking is the process of connecting all the compiled objects to each other to form the final executable. When you call a function in one piece of code, it's the job of the linker to hook the code that calls the function to the code that implements the function.
Answer: Source: here
"Linking refers to the creation of a single executable file from multiple object files. In this step, it is common that the linker will complain about undefined functions (commonly, main itself). During compilation, if the compiler could not find the definition for a particular function, it would just assume that the function was defined in another file. If this isn't the case, there's no way the compiler would know -- it doesn't look at the contents of more than one file at a time. The linker, on the other hand, may look at multiple files and try to find references for the functions that weren't mentioned."
In other words: Linking connects together all your compiled libraries/binaries that depend on each-other so that execution of your program will be possible.


How to distinguish power chords from single notes?

Question: I have been learning guitar by ear for the past few years. I was listening to a song I've been trying to learn for a while, and realized numerous notes I had thought were single notes were actually power chords. As a result, I would like to know how to distinguish power chords from single notes on songs which involve the guitar.
Comment: This is a very legit question, single notes doubled an octave lower by the bass, with extremely high gain amplice and multiple overdubs can easily sound like power chords. Unfortunately, I think the only reasonable answer is: *they don't sound exactly the same, practice until you can tell them apart*.
Answer: What you can do is to learn what they sound like on their own, and then practice them in context of the song. With practice, you will be able to isolate the guitar parts and figure out if they're power chords or not.
You can do this by playing the power chord parts alongside a drum track, or with minimal accompaniment from the other instruments so they don't make your own guitar sound hard to distinguish from them.
This website has drum tracks for different types of beats at different BPMs, as well as "jam tracks" for improvisation practice: http://www.guitarlessons.com/jam-tracks/
I suggest using a drum track close to the BPM of the song you're playing.
If you are not able to distinguish power chords from single notes yet, it also helps to look up the tabs or notation of the song, instead of, or in addition to learning the song by ear.


Why do we have exit codes in Java?

Question: In Java, we use System.exit(int) to exit the program.
The reason for an "exit value" in C was that the exit value was used to check for errors in a program. But in Java, errors are reflected by an Exception being thrown, thus they can be handled easily. So why do we have exit values in Java at all?
Comment: The exit value is specified for the operating system.
Comment: possiblity duplicate http://stackoverflow.com/q/457338/668970
Comment: @developer I was asking why we have exit codes in Java at all. The question you linked to talks about the argument 0 in System.exit(0)
Comment: check the documentation which is provided in that post. Is given the explanation of System.exit also
Answer: exit values are returned to the calling program e.g. the shell. An Exception cannot be caught by an external program.
BTW When you throw an Exception it is caught by that thread or that thread dies, the finally blocks are still called for that thread.  When you call System.exit(), all threads stop immediately and finally blocks are not called.
Answer: For the same reason.
Exit codes are exclusively used by parties and applications outside of the program for debugging and handling purposes.  A super-application can definitely handle a return code better than trying to parse a stack trace.
Also, if you are creating an application for an end-user, you would much rather exit gracefully from your app than post a bunch of stack trace information, for a couple of reasons: one, you will just be scaring them with lots of crazy-looking techno-gibberish, and two, stack traces often reveal sensitive and confidential information about the way the program is structured fundamentally (giving a potential attacker more knowledge about the system).
For a real-world example, I was working on a Java Batch program which used exit codes for its jobs.  A user could see whether the job executed successfully or not based on whether the exit code was "0".  If it was anything else, they could contact technical support, armed with the additional information of the exit code, and the help desk would have all the necessary information based on that exit code to help them out.  It works much nicer than trying to ask a non-technical end-user, "Okay, so what Exception are you getting?"
Answer: exit values are returned to the callers to signal the successful or insuccessful completion of the program. The caller may not be able to catch the exception and handle it accordingly.
For eg. 0 exit value means successful completion whereas non-zero return value means some error in execution.
Also, System.exit() will make all the threads in the application to stop at that point itself.
Answer: Long story short, Exit codes are simplified signals to the user who encounters an exception while running a Java program. Since we assume that most of the users do not understand stack trace data of an exception, these simple non zero custom code will tell them that something is wrong and this should be reported to the vendor. So the vendor gets the code and he knows the stack trace associated with that code and tries to repair the system. This is an abstraction provided by the programmers so that users don't have to read and report voluminous stack traces. A very good analogy here is the getErrorCode() method in SQLException class. This method also closes the current JVM that is running on the client machine. This implies that this terminates all the threads that are in the JVM. This method calls the exit method in the class Java.lang.Runtime. If you go to the documentation of this method, you will understand how virtual machine is shut down.
This is the link
http://docs.oracle.com/javase/6/docs/api/java/lang/Runtime.html#exit%28int%29

Why do we have exit codes in Java?


Significance of the word Cloverfield

Question: In the Cloverfield franchise every film have Cloverfield in the title but what is the significance of "Cloverfield", In 10 Cloverfield Lane it was the address of that area but in first film I can't understand its significance. Am I missing something? Does this word have some significance for the franchise?
Answer: In and Out of Universe Answers:
It's the name or codename of the Government's case and the out of universe answer is that it's road/exit JJ Abrams takes to work at the Santa Monica office.

Title
The film was initially named Cloverfield. This changed several times
  throughout production before it was decided that the original title
  would be used. Matt Reeves explained that the title was changed
  frequently due to the hype caused by the teaser trailer. "That
  excitement spread to such a degree that we suddenly couldn't use the
  name anymore. So we started using all these names like Slusho and
  Cheese. And people always found out what we were doing!" The
  director said that "Cloverfield" was the government's case designation
  for the events caused by the monster, comparing the titling to that of
  the Manhattan Project. "And it's not a project per se. It's the way
  that this case has been designated. That's why that is on the trailer,
  and it becomes clearer in the film. It's how they refer to this
  phenomenon [or] this case", said the director. The film's
  final title, Cloverfield, is the name of the exit Abrams takes to his
  Santa Monica office. In turn, the road used to lead to the
  Santa Monica Airport, which originally bore the name Clover
  Field.[citation needed]
One final title, Greyshot, was proposed before the movie was
  officially titled Cloverfield. The name Greyshot is taken from the
  archway that the two survivors take shelter under at the end of the
  movie. Director Reeves said that it was decided not to change the
  title to Greyshot because the film was already so well known as
  Cloverfield.
The film received a subtitle in Japan, where it was released as
  Cloverfield/Hakaisha (クローバーフィールド/HAKAISHA Kurōbāfīrudo/HAKAISHA). The
  subtitle "Destroyer" was chosen by Abrams and was translated into
  Japanese as Hakaisha (破壊者 lit. "Destroyer") by Paramount Japan at his
  request. The subtitle Kishin (鬼神 lit. "Demon[ic] God") was chosen for
  the manga spin-off, Cloverfield/Kishin, released exclusively in
  Japan. https://en.wikipedia.org/wiki/Cloverfield
Comment: For a while the original film was promoted as "Monstrous": http://www.cloverfieldnews.com/2007/07/25/clear-image-of-the-monstrous-cloverfield-poster/ I picked up a copy of the poster at San Diego Comic-Con and have it hanging in my hallway at home.

Santa Monica Airport was originally named Clover Field in 1923 for a local fighter pilot who died in France during WWI, Greayer Clover: https://en.wikipedia.org/wiki/Greayer_Clover
Comment: Cool! Thanks @jeffronicus ! I love extra trivia!!! :)

I kind of wonder if the history of the fighter pilot influenced or inspired Forever Young?? Abrams wrote the script and the short story it's based on...
Answer: In the first Cloverfield movie, it was the government/military code name for the "incident" involving other-dimensional aliens. Neutral-sounding code names are used by the military in real life.  Examples: "Fat Man", "Little Boy", and "Tuskegee Experiment".
However, that doesn't explain why that specific name was chosen.
Comment: I think you're conflating "Tuskegee" and "Tunguska", which are very different spots.
Comment: Well, certainly Cloverfield was "the biggest interdimensional cross rip since the Tunguska Blast of 1909." - Ray Stantz, Ghostbusters
Comment: @JesseC.Slicer Nice reference!

Significance of the word Cloverfield


Do universe 6 saiyans transform more easily than universe 7 saiyans?

Question: So far we've seen 3 saiyans from universe 6 with an important role in Dragon Ball Super. In a short period of time, less than 48 hours for Kale and Caulifla if I recall correctly, and less than a year for Kyabe, they've mastered more than one transformation. Kale mastered super saiyan berserker and super saiyan green, Caulifla mastered super saiyan , ultra super saiyan (not sure if this is a state or transformation) which chances to master super saiyan 3 in the tournament according to Goku, and Kyabe mastered super saiyan and super saiyan . Why is so? Do universe 6 saiyans transform naturaly more easily than universe 7 saiyans or is there another reason?
Comment: Ooooh I'm starring this. I really need to start watching super again. Because it seems like power spikes are flying all over place again. I'm feeling all nostalgic. Like Ascended saiyans vs super saiyan 2 debates back in the middleschool lunchroom.
Comment: watching dragon ball is like reading fanfic with lots of OP character come out of nowhere
Answer: Officially the original super saiyan transformation was triggered by pure anger and enough raw power to transform. The only possible explanation this is that U6 saiyan have the power but they are not that interested in fighting so they never really explored their power.
One more thing that you can't expect a story to be perfect and with no plot armor because the mangaka has to make the story interesting.
Answer: The answer to this is more complicated than it seems. Because the answer is yes and no at the same time. Due to proper guidance they were able to achieve higher forms easier but they simply "unlocked" it they didn't master it. As shown in episode 114 Goku has mastered the movements and can withstand 2 saiyans on his own in a lower form if he wants. They are able to have a higher power output but in terms of effieciency they lack a lot.
Unlocking the Saiyan state(s) require strong emotions and pushing yourself to the utter limit. Kyabe's anger unlocked ssj1, his desire to show his master around on his planet in his universe unlocked ssj2. Due to the high stress levels caused by the punishment for losing the tournament their emotions are affected majorily resulting in an easier way to unlock states if used properly.
The girls had similar experiences, one desire strength and power while the other desires to protect her sister and to fight beside her.
Goku unlocked his states when he was pushed to his limits with the desire of becoming stronger. Gohan had the desire for justice and Vegeta the desire as his duty as the Saiyan prince and ofcourse his jealousy towards Kakarot.
But I only want to emphasize on the difference between unlocking a new saiyan state AND mastering a new saiyan state. SSJ2 has more raw power than SSJ1. A mastered SSJ1 is stronger than SSJ2 due to knowing the limits and how to use his body with the stamina output etc.
I hope this answers your question. Feel free to comment if you would like to know more.
PS: if I dive into it I can provide all episodes to back up my statements but that would require a lot time. If you wish I can provide a list of episodes but I don't think it is needed for this question.


Fruit color change

Question: Just recently I have made 6 batches of Mango Jam.  All turned very dark brown while cooking and are almost black when jarred but they taste great. What is the reason for the color change?
Comment: Hello, and welcome to Stack Exchange. Has this happened before?
Comment: I have a whole lot of cut mango in my freezer which I was planning to turn into jam once the weather cooled off.  Now I am not so sure I want to have 10 or 12 jars of black jam to try to give away. Does anyone know if this mango behavior is common?  Or just a freaky anomaly?
Answer: I reckon it could be due to oxidation of fruits.
It's very common once you leave fruits that are cooked/uncooked in the open air. It probably helps if you could add a little salt in there ( even though it may seems weird, but it definitely works).
The reason why factory made jam does not turn dark at all is because of all the additional food addictive and preservative that is inside the food. I honestly, do not recommend keeping fresh mango jam for too long because it does go bad very quickly.
It happens to a lot of other food stuffs like potato etc.
Comment: One of the common additives used to prevent browning is vitamin C, and it's often sold with canning supplies for that purpose.
Comment: "additional food addictive" - I hope not!! :P
Comment: It's the fact. It's called addictive or preservative. They are all the same. I guess everyone do realize why certain food can be kept so long for ages, like literally years but doesn't spoil? When you look behind like (E254), blah blah, all these is the one that kept your food for ages and they also all food addictive.
Comment: @TeoChuenWeiBryan Additive, my friend, as in something that's added. Addictive means you'd get addicted to it, like alcohol, or cocaine. I was just making a joke, it's a simple mistake :) (Of course, people may add addictive substances to their products, but we would hope that this is not common practice!)
Comment: of course we hope it's not, unfortunately it is :( i miss those days where food addictive ain't a common thing you know.
Answer: It could be oxidation as Teo Chuen Wei Bryan has already said in their answer. It might also matter what sort of pot you cooked the jam in - metal pots other than stainless steel sometimes react chemically with the food and that could lead to darkening.

Fruit color change


How to increase the bandwidth of half-wave dipole antenna?

Question: I have designed a half-wave dipole antenna for frequency range of 150 to 200 MHz. Due to resonant frequency of 175 MHz, Its dimensions are:
L=817.44 mm, R=1.71 mm. Impedance is also equal to 73 ohms.
After simulating in CST MWS, the bandwidth was about 18.64 MHz. How I can increase the bandwidth? I want to use this antenna for frequencies of 150 to 200 MHz. What's the method?
Comment: With a folded dipole I've managed 136-174 MHz, under 1.5:1. But you should explain what is the real problem you're trying to solve? Is this homework (so use a fat bicone, a thick cylinder, a matching network?) or a product design?
Comment: Hello Mohammadsadeq, and welcome to ham.stackexchange.com!
Answer: Marcus and Richard have answered the question that you asked, how to triple the bandwidth of a dipole, with the correct answer that it can't be done.  I suggest that you edit your question to give us more information about the problem that you're trying to solve and its constraints, and then we can offer more targeted suggestions.  In the meantime, here are some generic suggestions of ways to increase bandwidth of an antenna system:

Use a log-periodic antenna.  There are many existing commercial antenna models that use a log-periodic for the 174–216 MHz VHF television band.

Use a discone antenna.

Redesign the radio to tolerate a larger impedance mismatch.  This would not be easy for a high-powered transmitter.

Use an automatic antenna tuner.
Answer: You might experiment with increasing the diameter of the conductors of the dipole to improve its SWR bandwidth, along with optimizing the physical lengths of those conductors (equally) to center the low-SWR bandwidth of the dipole in your r-f spectrum of interest.
Author edit of 14 Aug 2020:
Below for "calibration" is a comparison of a case where the radius of the conductors stated in the OP was increased by a factor of 5:
Comment: discone? i.e., variable diameter...
Comment: Yep, diameter variation is a usual technique, but I doubt he can triple the bandwidth that way.
Comment: Thank you so much. The bandwidth increased to about 27 MHz by 8.55mm radius.
Answer: You can increase the bandwidth of a dipole by adding capacitive hats (you may have to shorten the dipole to maintain a given resonant frequency).  Conical hats, hemispherical hats, or hats with a circular rim will work better than short 90 degree radial spikes at the ends, or an H shaped dipole.
Small capacitive hats might even raise the radiation resistance, as well as broadening the dipole's bandwidth. Maybe 10% or less in size compared to the long dimension of the dipole (which, again, will have to be resized to re-center the resonance frequency to the desired value.)
You also can increase the bandwidth by adding wires spread apart a little, and turning your dipole into either a cage dipole or a fan dipole.  A fan dipole with each fan element a slightly different length will also broaden the bandwidth.
At the limit you can turn these (fan or cage) wires into conical sheets centered at the feed, and end up with a discone or biconical dipole, which have much wider bandwidths than a wire dipole (but are still 2-element dipoles of a sort).
Comment: Thank you kindly. Does capacitive hat increase the bandwidth by a factor of 3? and Can I implement capacitive hat in CST MWS?
Answer:
After simulating in CST MWS, the bandwidth was about 18.64 MHz.

According to which definition of bandwidth?
I'm asking this because every antenna is a tradeoff. The easiest way, probably, to deal with this is to simply reduce your requirements for what "bandwidth" is.

How I can increase the bandwidth?

You're using a dipole, but you want a bandwidth of more than a fourth of the center frequency.
That's usually not going to work; you need a different design if you need to use a bandwidth that large relative to your center frequency, or relax your definition of "bandwidth".
You can of course help the situation by doing as Richard recommends: a larger-diameter conductor usually helps a bit with bandwidth, but I don't think you'll increase your bandwidth by a factor of 3 that way.
Comment: 18.64 MHz is according to Return loss plot, using -10 dB levels. Our goal is to obtain desired bandwidth in the base of a dipole antenna; May I use LPDA structure or there is a better method?
Comment: either you build a dipole, or a LPDA, those are two different antennas


How can we know that we experience sensations as a series of discrete sensations?

Question: I'm currently reading the book "Mastering the Core Teachings of the Buddha" by Daniel Ingram, and he insists over and over that the continuity of sensations is an illusion, and that sensations actually come to us in a sort of flickering.  I've done some meditation and have started to feel what he is talking about.  But if we can detect the gaps in between the sensations, isn't the detection of the gaps itself a sensation?  How do we know that the experience of flickering isn't the illusion, and that the reality is a continuous stream of sensations?
Comment: See also [Awareness of two things](https://buddhism.stackexchange.com/q/10716/254)
Comment: Daniel posts here: https://www.dharmaoverground.org/
Answer: There is obviously not a continuous stream of sensations otherwise the mind could remember every sensation, similar to how every frame in reel of movie film can be viewed. In other words, the sensation experienced one second ago has disappeared, forever. To believe there is a continuous stream of sensation is to only observe arising & to not observe passing/disappearance. Its like a person given a box of delicious chocolates that hungrily can only see the next chocolate to be eaten, never realising each chocolate is disappearing & soon there will be no chocolates left, which eventually brings despair when the chocolates (similar to life) run out
Regardless, what Daniel is writing about, such as observing 40 sensations per second, is not found in the reported teachings of the Buddha, although it may possibly be found in later philosophy called Abhidhamma. To me, what Daniel is writing about is unimportant for clear insight, because objects must be very discrete to experience abrupt disappearance (rather than a blur of oscillating sensations the mind becomes infatuated with; like becoming infatuated with the oscillations or vibrations of a girl dancing on a cliff; rather than watching the girl fall off the cliff, to her death).
The Buddhist scriptures refer to observing the coming-to-be & then disappearance of a single in-breath, then an out-breath (MN 118) then, on a more advanced level, the arising, persisting & disappearing of a feeling, perception or thought (AN 4.41). This is more than enough for the purpose of vipassana. For example, merely observing a single breath, until it disappears; then observing the next breath, until it disappears, is enough to get started on seeing the true nature of life phenomena.

We are typically quite sloppy about what are physical sensations and what are mental sensations (memories, mental images, and mental
  impressions of other sensations). These two kinds of sensations
  actually oscillate back and forth, a back and forth interplay, one
  arising and passing and then the other arising and passing, in a
  somewhat quick but quite penetrable fashion. Being clear about exactly
  when the physical sensations are there will begin to clarify their
  slippery counterpart that helps create the illusion of continuity or
  solidity: flickering mental impressions.
If you can perceive one sensation per second, try for two. If you can perceive two unique sensations per second, try to perceive four. Keep
  increasing your perceptual threshold in this way until the illusion of
  continuity that binds you on the wheel of suffering shatters. In
  short, when doing insight practices, constantly work to perceive
  sensations arise and pass as quickly and accurately as you possibly
  can
How fast are things vibrating? How many sensations arise and
  vanish each second? This is exactly what you are trying to experience,
  but some very general guidelines can provide faith that it can be done
  and perhaps point the way as well. Begin by assuming that we are talking
  about one to ten times per second in the beginning. This is not actually
  that fast. Try tapping five to ten times per second on a table or
  something. It might take two hands, but it's manageable, isn't it? You
  could obviously experience that, couldn't you? That's the spirit!
  There are faster and slower vibrations that may show up, some very
  fast (maybe up to forty times per second) and some very slow (that are
  actually made up of faster vibrations), but let's just say that one to ten
  times per second can sometimes be a useful guideline in the beginning.
Page 20
Since I just used this dangerous phrase "the mind," I should quickly mention that it cannot be found. I'm certainly not talking about the
  brain, which we have never experienced, as the standard for insight
  practices is what we can directly experience. As an old Zen monk once
  said to us in his extremely thick Japanese accent, "Some people say
  there is mind. I say there is no mind, but never mind. Heh, heh,
  heh!"
Answer: You could try to understand this by your own meditation experience, or you could trust science (for now).
From this April 2016 article in Quartz based on this research paper:

First, the authors argue, we unconsciously process visual stimuli
  continuously, and are oblivious to this stage. We only then become
  consciously aware of the information once it has been transferred to
  conscious perception, which happens in discrete moments, or "time
  slices."
Michael Herzog, a professor at the École polytechnique fédérale de
  Lausanne's Brain Mind Institute in Switzerland, and Frank Scharnowski,
  a cognitive neuroscientist at the University of Zurich, argue that
  we're unaware of the gaps in our consciousness. They say there can be
  a 400-milisecond lag between unconsciously receiving stimuli and
  transferring it to conscious perception.
"We perceive time as continuous just as we perceive a line as
  continuous even though its ink is of discrete atomic nature," the
  authors write in their paper.
But our perception of conscious does not align with reality.
  "According to our model, the output of unconscious processing is
  discrete, meaningful, and rendered conscious at once. Large parts of
  unconscious processing will never reach consciousness," the
  researchers say.
The authors note that the debate over how consciousness works has a
  long history. In the third century BC, the Abhidharma Buddhist school
  put forward the theory that consciousness is made up of discrete
  moments. There are numerous more recent papers arguing for just such a
  conclusion. Meanwhile, experiments show that when two stimuli are
  presented in rapid succession, they're perceived simultaneously, while
  discrete perception is thought to explain various visual tricks, such
  as the optical illusion that often makes spoked wheels look as though
  they're moving in reverse, and flash lag illusion, where a flash that
  occurs in the same place as a moving object is perceived to be in a
  different location.

This April 2016 Science Alert article adds:

In other words, while we're taking the world in, we're not actually
  consciously perceiving it. Instead, we're just mutely using our senses
  to record data for up to 400 ms at a time. Then, in what could be
  called a moment of clarity, we consciously perceive the stimuli that
  our senses have detected.
The team thinks this presentation of information to our consciousness
  lasts for about 50 milliseconds, during which we also stop taking new
  sensory information in. And then repeat.
Our senses start taking new information in from whatever stimuli are
  around us, before handing it off to our consciousness to perceive and
  enjoy – back and forth, and so on, and so on.
The team says each window of recording and playback would last for a
  different amount of time, depending on the kind of information being
  processed.
While the constant to-and-fro suggests consciousness is anything but a
  seamless experience, if the researchers are correct, our brains
  somehow manage to stitch everything together so it feels like a
  continuous flow of events with no interruptions.
Answer: You have to do this by stages while practicing Satipathana.
Just practice breath meditation first.
Then practice some walking meditation.
It is gradual training.


Gimp batch process for 'tiling' images

Question: I have a directory containing several images size 640*480px and I'd like an automated procedure using Gimp to pick these up and 'tile' the images beside each other with no overlap, to make a new large image a bit like a proof sheet.  For example, the output image could be four source images wide by ten deep, for a 2560*4800 resulting image.
Answer: Why use Gimp for this. Use ImageMagick's montage command.
Answer: Use ImageMagick instead
Whenever you need to do a bulk image operation and you are reaching for GIMP stop and try ImageMagick first. 99% of the time, it's the right tool for the job.
In this case, the Imagemagick montage command is just what you need.
montage -geometry +0+0 *.png montage.png

This will result in a tile sheet named "montage.png" that contains all PNG files in the current directly, with no border and no resizing. Imagemagick will count the number of images and determine the appropriate number of tiles per row (which you can manually override with the -tile argument).
The montage command has lots of options to tweak if you need something more specific.
"But I asked for GIMP..."
If you are hellbent on doing this in GIMP, I'm not sure how. A quick google search reveals lots of plugins and techniques for manipulating a tileset (like you'd see in an old-but-still-awesome 8-bit RPG), but I didn't find an easy way to stitch together a bunch of images except doing it by hand.

Gimp batch process for 'tiling' images