Why is it possible to drive a nail into a piece of wood with a hammer, but it is not possible to push a nail in by hand?

Question: It is possible to drive a nail into a piece of wood with a hammer, but it is not possible to push a nail in by hand.  Why is this so?
Answer: There's many different things at work here.
First, there's the issue of acceleration. Hammers are very hard and solid, so when you hit the nail head with the hammer, the energy and force of the blow is delivered at almost an instant. Hands, on the other hand, are rather soft, and will spread out the same amount of energy and acceleration over a longer time period, resulting in a lower force applied on the piece of wood. Different woods have different resistance to pressure, so it's still rather easy to push a nail through a sheet of balsa wood, for example, while it's much harder to push it through a sheet of oak.
Second, the hammerhead actually accumulates a lot of energy in the duration of the swing, stored as kinetic energy in the head. That's why hammerheads are heavy (and the higher force you need, the heavier the head) - it allows you to store more kinetic energy with the same velocity of the head. The maximum velocity your muscles are capable of is a lot more limited than the amount of energy they can deliver, when considering something as tiny as a nail.
Third, hammers work as an additional lever, allowing you to deliver more force as a trade-off with time. This works in tandem with the second point - a longer swing can give you more impact force. This also helps the hammerhead reach higher speeds than you would have while holding the head directly, as opposed to holding the shaft.
Fourth, you're simply not going to hit as hard with your bare fist. Your body has built-in safety mechanisms that try rather hard to prevent injury, and you can hurt yourself quite a bit by hitting a nail head-on. Note that it's quite easy to drive nails just by using a wooden board pressed straight against your hand and hitting the nail - this spreads out the force of the blow over your hand, preventing pain and injury and allowing you to hit harder.
Finally, raw force is probably the dominant factor here. Pushing allows you to use the full strength of your muscle, which is probably somewhere around your weight (with a rather large spread). On the other hand, hitting allows you to accumulate the strength of your muscles over the duration of the swing, allowing you to impart much bigger forces than would be possible with just pushing. Try driving nails just by pushing the hammer, and you'll see the difference rather easily - the only benefit you'll get from using a hammer is that you're not going to feel as much pain as when pushing against the much smaller nail head.
Comment: I think your last paragraph really hits the nail on the head (haha). The weight and length of the hammer lets the human store up energy to all be released in a very short amount of time, much like an axe. The other advantage hammers have over hands is a hard, flat surface, like the axe that has an advantage over hands in having a hard, sharp surface.
Comment: Also consider the force per unit area at the point of the nail.  While it's far from easy to push a nail into wood by hand, almost anyone can push a thumbtack (sharper point, broad head) into at least softwoods.
Comment: Could we push it by a constant applied force i.e. using a press? Is there a difference in applying impacts vs. a constant pressure on the nail?
Comment: @NothingsImpossible Yes on both. In the end, the "hit" is just a constant applied force - it's just a lot of force in a relatively short time. If you can replicate the force of the hit, the nail is going to go through the wood just fine. The difference between "impact" and "constant pressure" exists mainly because of complexity of the materials involved - as you keep pressure on the nail, some of the parts of the wood will flex and bend and accumulate damage (and/or energy). Hitting the nail may take multiple impacts to drive it all the way, while the same constant pressure will do it in one.
Comment: @NothingsImpossible In the end, the difference isn't really all that big though, as long as the speed at which the projectile impacts the target is smaller than the speed of sound of the target. There's some ways in which an impactor is limited while penetrating the target (this goes all the way back to Newton), but they don't apply quite as much in the hammer-and-nail scenario, since you need to count the nail *and* the hammer as the impactors, while you only want to drive the nail in, not the hammer. And the hammer is usually much heavier than the nail.
Answer: It is just because when you hammer a nail, you apply a force to the nail by changing the momentum of the hammer $F=\dot p$ This force helps in overcoming friction and thus pushing the nail inside. This isn't the case with your hand. Moreover, if you try to develop the same amount of force with your hand, you will get hurt because of the pressure applied to your hand by the head of the nail. Increased impact may also lead to the nail penetrating your hand, so be careful ;)
Comment: @TylerH Probably, it also means a better transmission of momentum to the nail due to the bone being harder. But pretty much anything is a better hammer than parts of your body. Tools were invented for a reason.
Comment: It's not just friction but simply the cohesive forces holding the wood together. One tries to drive a wedge into the wood, if applying the force by hand, one could end up driving the blunt end of the nail into the hand instead.
Comment: @MatthewChristopherBartsh It's been years, but I *think* I was speaking from the perspective of effectively driving a nail into wood, not from the perspective of your body or its health/state of being after trying to do so. I guess I should be explicit: I don't recommend punching a nail with your fist, either via making contact via knuckle or soft, fleshy muscle.
Comment: @Chieron and T.Deepak theoretically it would be "safer" that way to strike with a knuckle, then? It would likely be much more painful, and you're liable to crack your bone, but it would mitigate much of the risk of puncture, no?
Comment: @Chieron Oh, for sure. I was just musing out loud, mostly.
Comment: @TylerH and Chieron: Striking the nail head with a knuckle would normally be *less* safe, not more, than using the heel of your palm, say. I don't think a skin puncture is as bad as a damaged joint. Besides bone, there is also tendon and ligament, and when damaged, the latter often do not heal completely, even with medical care. On the other hand, if the nail head is contaminated with bacteria, and you have no access to medical care, then it could be argued that a skin puncture is more dangerous. But you could still get a skin puncture when striking with a knuckle. I advise readers against it.
Comment: Great answer. I have thought about this a lot, and understood it thoroughly using F = ma. But I think F = p dot is probably even better, because without the momentum there would be no acceleration. In fact, you have given me a new appreciation for momentum, and a greater interest in how in physics momentum is such a fundamental concept. I knew that conservation of momentum is more fundamental than action and reaction, and that momentum is in some situations used instead of mass (e.g. a photon is said to have momentum but not mass, although I can't fathom that. BTW, can you fathom that?)
Answer: Your hands are soft whereas the hammer head is very hard. Therefore your hand will come to rest upon striking a nail in a much greater time as compared to hammer.
Now, force is the rate of change of momentum. The hammer is heavier so momentum is more initially even if hand and hammer hit at same velocity. As well as the time taken for the momentum to change to zero is less in case of the hammer. Both these factors increases the force exerted by the hammer considerably. Hence, it is able to drive a nail inside a wall.
Answer: This is in fact possible, as evidenced by the number of videos online of someone hammering a nail in with their bare hands.
More to the point, the human hand is plenty hard enough to hammer in a nail into some pretty hard if it is swung fast enough. It's just that the damage to the hand would be rather devastating, and so our pesky brains keep us from hitting a nail as hard as we can.
Answer: You can!  But first, some precautions:

Your hand is squishier than the wood (generally, for wood of a condition to have new nails driven into it and hands prepared to do some hammering).  This means that it will take less pressure for the nail to damage your hand than for the nail to enter the wood.  The pointy bit at the front of the nail and the broad head at the end you are holding will help a lot.  However, it could be a good idea to spread the force around a bit more at the end you are going to be pressing on.  One way to do this is to glue a larger flat surface onto the head of the nail for you to press on.  I have these spare bricks...
But all this gluing and drying takes too long.  Instead, let's just pick up a small block of waste wood, a 4" (10 cm) length of 2"-by-4" (5cm by 10cm) would be adequate.  Hold that mostly flat between your hand and the head of the nail and push.  See it works.  Only a couple thousand more to go until you're done building this house...
Hmm...  Maybe this is still taking too long.  I know:  let's speed things up a bit.  Instead of just pushing against the nail, why not get a good run-up.  Raise the piece of waste wood up and lower it quickly onto the head of the nail.  (You'll probably have to hold the shaft of the nail in place with your other hand.  Warning:  you are about to swing a block of wood at your holding hand, so you might want to be ready to move it out of the way as soon as the block hits the head of the nail.  Some yelling may occur if you are not fast/careful enough.)  That's going much faster...
But, unfortunately, even though the block of wood is spreading the force around on your hand, it's still receiving higher pressures during striking from the head of the nail.  This dents and scores the surface of the block.  I suppose we need to use something a bit tougher.  I happen to have this steel doorstop on me.  Try that.  Yup.  It's still spreading the pressure on your hand.  But rather than whacking with the flat part, it mugh be easire to get a good grip around the long axis and use it that way.  (This is because, the doorstop is so much thinner than the block that your fingers actually curl around to cover a little bit of the flat side we're hitting the nails with.  To prevent the occasional clipping and snipping of finger tips by imminently smacked nailheads, we might want to find a way to hold the doorstop that doesn't have our fingers on the striking face.)
You know.  Holding that that way...  You could probably lift it above your head and swing it down onto the head of the nail and get a lot more momentum transferred to the nail.  Try it.  Yup.  That worked much better.
Oops.  Now the wedge you're holding tries to pry your fingers apart on every hit.  It's also pretty good at transferring a jarring whack to your fingers on every hit which is making them numb.  Sure is inconvenient to have the same momentum dumped back into your fingers as you are putting into the nail.  What can we do?  I'll think on that.  Keep up with the framing and I'll go rummage around in my junk box and see if anything comes to mind.
I had a great idea.  I've go this old, unused axe handle.  Notice that you're pretty much holding an axe.  This'll be great:  we attach the doorstop to the end of the handle and then you swing the contraption, kind of like an axe, to kit the heads of the nails with the small flat face of the doorstop.  This should really lower the pressure on your hand, since some of it will be appear as torque, and also the miniscule flex of the handle will spread the momentum transfer out a little bit in time and you won't be holding a wedge trying to drive your fingers apart.  This'll be great, I promise.

So, yeah, while you can drive a nail with your bare hand.  It's a much better idea to use a hammer.
Answer: TL;DR:
In order for the nail to be driven into the wood, you need to apply sufficient force to split apart the wood fibers ("make a hole") and overcome the force of friction between nail and wood.
The hammer can apply a much greater (instantaneous) force than the hand, because it is much harder (has a greater Young's modulus).

If you assume a mass $m$ is hitting a stationary object with velocity $v$, and there is a small spring between them with spring constant $k$, then we calculate the compression of the spring $\Delta x$ with a simple energy argument:
$$ E = \frac12 m v^2 = \frac12 k \Delta x^2$$
The maximum force $F = k\Delta x$ then follows:
$$F = \sqrt{m k} v$$
We see that the force goes up with velocity, and with the square root of either the mass $M$ or the spring constant $k$. In other words, a harder object (like a hammer) has a higher "spring constant" $k$, and because it decelerates over a shorter distance it will apply a greater force. And it's force we need to drive the nail.
Another way to think about this is in terms of conservation of momentum. If we need to lose momentum $Mv$, we can do this by applying a force $F$ for a time $\Delta t$. The shorter $\Delta t$, the greater $F$. Again, a "squishy hand" will spread the impact time further, and reduce the peak force.
There are secondary things at play here - for example, if you put your hammer at the end of a long stick (sledge hammer), you will be able to make it swing faster: and the force goes linearly with velocity, but only with the square root of the mass. Of course it's harder to hit accurately with a long-handled hammer: but it will deliver a bigger punch than a short, heavy one.
Answer: If you're strong enough, you can push the nail in by hand. You only need protection against the "equal and opposite reaction" of the nail against your soft hands. The nail can penetrate the wood because it is sharp, applying high pressure to the surface area it contacts. The nail's head is relatively much wider, so it will not penetrate your hand as easily as the sharp end, but it is clearly not engineered to be pushed in by hand. It's still too small a surface area for you to apply heavy pressure against your weak human skin.
To push the nail in by hand, you need some kind of defense against that pressure.

You could wear an iron gauntlet, like a medieval knight. It will not be pierced and will distribute the pressure across a larger
surface area on your hand, preventing injury.
You could place a large, at least hand-sized, metal disk atop the nail, essentially creating a nail with very large head. That's
    what a nail would look like if it were engineered for
    hand-force-touching. Of course, if you jumped on the disk you would
    probab

ly drive the nail in much faster than by just pushing on it.
Answer: Basics, Newton law and acceleration integration:
sum(F) = m.a
v = a.t

The force exerted by the hammer is dissipated in about no time, because the hammer is very though. The acceleration is therefore great.
Now, considering that your hammer is .2kg, going at 10m.s^-1, and hitting the nail during 1ms, it is pushing by (0.2kg*10m/s)/0.001s = 2000N
That's the amount of thrust required to lift 200kg.
In comparison, when you lift that much, assuming you are very strong, you rely on you whole hands. But with only one hand, most people will generate less than 500N, and without hurting themselves, with a singe finger, maybe less than a 100.
Now, the reason why pushing slowly on the nail does not work is the friction of the wood.
Answer: Because your hand is softer than a hammer, absorving most of the impact power over the nail, reducing overall power needed to penetrate wood. To compensate this, is necessary to apply too much more power that your hand will simply be injuried by nail. If the resistence of your hand skin is lower than resistence of wood, only your hand will be perfured, even considering the flat nail head format. However, if you got a nail with a ruge head, like it was a giant pin, you could tap with open hand and so got success. The bigest problem here, in truth, is the pression. The Hammer metal head can suport the nail little head size pression, your hand no. How smaller the surface area with same force, greater the relative pression. Then pression is the true force here, not exactly the hammer push strengh.


Would Tabata be any good on a stationary bike?

Question: I cycle most evenings when I get home from work.
I read about Tabata on here and wondered if it would be any good for me?
Maybe cut my total time down to 30 minutes, 5 mins warm up, 2 mins Tabata, 5 mins cool-down?
I'm trying to lose fat, at a decent rate. I eat well, just want to lose it quicker!
Answer: It's fine to use a stationary bike for Tabata-style interval training. Much of Tabata's research was on stationary bikes.
The protocol prescribes 4 minutes total of intense intervals:

The whole session last 14 minutes and comprises of a 5 minute warm up, 4 minutes of intense exercise and a 5 minute cool down. The 4 minutes of intense exercise comprises of 8 repeats of 20 seconds of maximum effort work of your selected exercise followed by a recovery of 10 seconds.

If you're reasonably fit already, doing absolutely all-out effort for twenty seconds eight times should be exhausting.
Comment: Bad typing on my count there, I meant 2 minutes as I'm not the fittest yet.
But I'm thinking go for the 4 minutes anyway now, never gonna get there otherwise!
Thanks Dave.
Comment: @Saveyourself91 I started my Tabata with 6 rounds of effort (3 mins), but progressed within a couple of weeks to the full 8. You are correct, your last few rounds will probably be very bad but you can't improve if you don't do 'em.
Comment: Thanks VPeric. I'm going to shoot the full 8 from the off. If I can't do it I'll take it down to 6 for a week then tr again.
Comment: I'm looking to start tabata on a stationary bike also. What sort of gear should I be looking at starting on? Is the idea to have the bike on an 'easier' gear so that during the high-output 20 seconds I should be peddling very quickly or should I be looking to use a difficult gear on which during the 20 seconds I am struggling to turn the wheels?
Comment: @Phizzy You should post that as its own question! :D I'd say it should be somewhere in the middle. Experiment to find which setting makes it possible to exert the most energy as fast as possible.


What is the common reading of the word 外海?

Question: 外海 has two readings がいかい and そとうみ. What is the difference of the two? Personally, I am under the impression that がいかい is the common reading because of its similarity to the word 外国【がいこく】. However, I have encountered situations (some songs) where そとうみ has been used instead.
Comment: Poetry (like song lyrics) tends to bend linguistic rules in name of artistic freedom. So I wouldn't trust it as example of common language.
Comment: https://jisho.org/search/そとうみ listed as another reading of かいがい
Comment: @JACK I also first was confused between  海外 and 外海 (like Shanghai and Kaijo....). Anyway, considering 瀬戸内海 I think that even if it is read with naikai, I think it would at least be intuitive to use sotoumi for a "sea area distant from any islands" as contrast to naikai.
Comment: がいかい is correct, I mistakenly pronounced.
Comment: @JACK OK. And, I realize my logic in my comment also didn't make much sense, so, I will up-vote the question and wait and hope that someone will answer.... ;-)
Answer: The NHK Accent dictionary and the 大辞林 include both がいかい and そとうみ readings as valid for this term.
The デジタル大辞泉 lists the first definition of kaigai and sotoumi as synonyms for a sea that is not bound by the continent, or to the open sea that is not close to the continent.
However, the second definition of kaigai, which is more metaphorical, means foreign lands, and I couldn´t find this connotation in the definitions of sotoumi. Here are the definitions for がいかい
and そとうみ.
Additionally, there is the Buddhist term
げかい that uses the same kanji.
Also, there is at least one person name with these kanji
(とのがい).
Comment: そとうみ is not the most used, but when used furigana comes along side most of the time (which is what furigana.info suggests). 海外 is read かいがい 99.9% of the time.
Comment: You´ve got a point, I will edit the answer.


How do you create a colorbox popup on the frontpage of D7?

Question: I'm using Colorbox and Drupal 7. I'm trying to create a Colorbox of an Image on the front page in a POP-UP. The problem is I can't figure out how to get it to show up on page load. How can I achieve this without adding an additional elements showing on the frontpage?
Comment: This is a similar question http://stackoverflow.com/questions/5969741/open-colorbox-on-page-load
Answer: The module: Splashify did the job.
Answer: You could use Views:

create a view with a block display
add the field with the image and set the output to colorbox
add this block to the homepage with Context or block management
Comment: I dont want to display the block other than the colorbox.
Comment: I didn't understand: what should appears in your homepage?
Comment: My homepage will appear as normal. But initial pageload, it will display a colorbox with an image of my choice.
Comment: But i dont want to add a block on the homepage just to display my colorbox.. unless i'm understanding your explanation wrong.
Comment: Ok, is more clear. You want a "popup", with colorbox, when homepage is loaded, is it right. If is this I can't help you, sorry.
Comment: This is correct.
Answer: This module is an option: Popup On Load

The module allows to display a popup after a certain delay on a page
  load. This fills a gap in popup modules family (Popups, Popup), which
  are designed to show popups only after a click on an HTML element, or
  to implement a complex behavior like modal dialog forms.


Do I need to create a new account for all stackexchange sites?

Question: I want to post some questions to stackexchange/webapps. I was requested to create a new account, which I did with the same email address I use for blender stack exchange. Do I need to create a new account for each StackExchange site? Seems a little bit cumbersome to me.
Answer: No need to create a new account. While logged in, go to the site you want to join, and click Join This Community . You will also receive an association bonus of 101 reputation points.
Comment: Ok but i was requested to set a new password and i could choose a different user name. But it's definitely the same email address. I dont get it…


How does sync.com provide zero knowledge for secure links?

Question: I tried to use sync.com for it's advertised zero knowledge. But I'm skeptical. If I create a link without a password and share it with a text message, my friend who gets this link is able to download the document and view the content. However my friend doesn't know my password. Therefore, i conclude that once i create a link, it means sync.com creates an unencrypted copy of my document on their cloud (COMPLETELY UNENCRYPTED). Therefore creating links (without passwords) essentially defeats the purpose of zero knowledge. Is this correct? So sync.com cannot claim zero knowledge for links and should explicitly state so
Comment: Related question [here](https://security.stackexchange.com/q/229477/3365)
Answer: I've only looked at this briefly, but a sync link looks like this:
<code>https://ln2.sync.com/dl/84d6f6440#4m2d2kjd-5gvmbx6i-zb4ersxn-d585kpiw
                                 ^
</code>
The characters after the hash (the fragment) are not sent to the server. I expect the server uses the ID in the path to fetch the encrypted file, and the fragment is used as a key for client-side decryption.
Comment: @sitaram - "fragment" - that was the word I couldn't remember!
Comment: I don't know about sync.com, but I am pretty sure Firefox Send (send.firefox.com) works this way, so it certainly sounds plausible.  In fact until I read about the innards of Firefox Send it never occurred to me that the browser does not (need to) send the anchor (fragment?) string to the server.


In the Star Wars Universe, is the Mandalorian race considered a real race or just an offshoot of the human one?

Question: I have no idea what the human race is called in the "Galaxy far, far away..." but if I'm not mistaken Mandalorians are just like the human race. I want to know if the Mandalorian race is an offshoot of the human race or actually a unique race with some sort of adaption or something.
Comment: By the way, Humans in the Stars Wars Universe are just Humans.
Comment: Wow... I thought this was about the series I am currently watching The Mandalorian and this is 9 years before it. Sorry wrong place...
Answer: Originally, the Mandalorians were the Taung species. They named the first planet they conquered Mandalore, in honor of their leader Mand'alor.
They led several expansion campaigns, and with time other species joined them in their conquests. Eventually the term "Mandalorians" came to describe their war-like culture more than the Taung species.
Later the Taung became extinct around the time of Mandalorian wars.
Wookieepedia has this to say:

Much like the Sith species which gave
  rise to the Sith Order, the name
  "Mandalorian" became associated with a
  multi-species culture of warrior
  clans, who, regardless of species,
  adhered to the tenets of the
  Mandalorians. These Mandalorians, who
  were mostly baseline Humans, held the
  legacy of the Taungs in high regard.
Comment: So the answer is no the Mandaolrians are not a race but the culture of the Mandalorains grew from a race. Giving the cultured, group of clans, the name "Mandalorians" or "The Mandalorian Race". Thanks!
Comment: @Justin Click the link in his answer. (i.e. the text "Taung species")
Comment: See the Appearances section at the bottom of that page.  Since Boba Fett's so popular, many authors have chosen to write about the source of his armor.  So there's quite a few books, graphic novels, and games that references Mandalorians.
Comment: What does a Taung or the Taungs look like?
Comment: Yep, already found out what they look like. Now I'm curious... how can their be so much information on the Mandalorian race...? But I bet its the Wiki thing all over again. I just wish they had a better ending than just dieing off. Sad :( I'm read (some) of this http://starwars.wikia.com/wiki/Mandalorian
Comment: @Keen will do! Seems like a lot happened to the race in general, it's a pitty that hey no longer continue as a civilization or culture. Maybe one of the authors should write them back in...
Comment: @Justin Mandalore had a couple of appearances in the on going The Clone Wars series.  I highly recommend watching those eps.  You'll probably dig watching a bunch of guys in Mandalorian armor going toe to toe with Jedi. :)
Answer: The Mandalorians started as the Taung species, hailing from Coruscant. When they finally found the planet Mandalore, their leader (himself named Mandalore) they took it and named that and Concord.
However, nowadays, the Mandalore name implies more of the culture and society than anything else.

The Resol'nare, or Six Actions when translated from Mando'a into Galactic Basic Standard, were the central tenets of Mandalorian life. They consisted of wearing armor, speaking the language, defending oneself and family, raising your children as Mandalorians, contributing to the clan's welfare, and when called upon by the Mand'alor, rallying to their cause.
Tradition dictated that anyone who wished to be considered Mandalorian were to abide by these guidelines and live these actions daily. Mandalorians whom did not follow the Resol'nare were considered to be dar'manda—someone who was ignorant of their Mandalorian heritage and bereft of their Mandalorian soul. The status of dar'manda was widely feared within Mandalorian society due to the belief it meant they were soulless and had no place in the Manda, the Mandalorian afterlife. Before and during the Mandalorian Wars, any and all non-Mandalorians were considered dar'manda and soulless from birth, until they joined the Mandalorians and lived by the Resol'nare. Groups of captured individuals would often be forcibly inducted into Mandalorian culture, and made to swear by the Resol'nare with or without their consent under the threat of death. Such zealotry faded over time as the Mandalorians became a less religious and more secular society.
Young Mandalorian children were taught a rhyme to help them learn the tenets of the Resol'nare, and their parents would explain the cultural significance of each tenet as they grew.
Wookieepedia page for Resol'nare

True, Wookieepedia is not necessarily considered 'canon' but it's as close as we can get here.
If you need further clarification, you can always email Karen Traviss, who wrote and basically created the majority of Mandalorian lore for Star Wars.
Answer: Canon
The answer to your question will depend on exactly what you mean by "Mandalorian." The term could accurately be used to refer to members of a planet, a system, or a culture.
Their homeworld was known as Mandalore and was overwhelmingly human. A sourcebook claims that 19% of the population is non-human but all on-screen sources depict them as essentially all human.

More broadly, the Mandalorian government also had a presence on various other planets and moons. The planet Mandalore was in the center of the Mandalore sector, comprised of nearly 1,000 planets. Non-human species such as the Phindians were from here.

The Mandalorian culture includes a concept where encountered children of any species in need of assistance are adopted, or at least fostered, as "foundlings."

By creed, until it is of age or reunited with its own kind, you are as its father. - The Armorer, The Mandalorian

These foundlings had Mandalorian affiliation and had the choice to fully join upon adulthood.
Grogu was the most prominent non-human foundling. However, there is no indication given that he was uniquely non-human.

In conclusion, many, if not most, Mandalorians of all definitions were human. There is no evidence that they are genetically unique from any other humans. However, 19% of the planet Mandalore's population, a sizable part of the Mandalorian sector's population, and a non-0% of the Mandalorian culture's population were non-human.


Why many abstract nouns get an indefinite article while it's taught that abstract nouns shouldn't get it?

Question: I was told that abstract nouns don't get articles. (You can see here for example). But I found many abstract nouns that get indefinite articles, such as: "of a truth", "of a size", "of a lifetime", "of a certain age", "a love", "a wish", "a difference", "a power" and more. What is the explanation for that?
Comment: Related: [The truth (definite article)](https://ell.stackexchange.com/q/102365/) and [Why "the" should be used before 'truth'](https://ell.stackexchange.com/q/150746/)
Comment: The short answer is that whoever told you that  "abstract nouns don't get articles" was simply wrong.  It just isn't true.  Sometimes they do, sometimes they don't - just like concrete nouns.
Comment: Those examples are not fully disclosed: the "chance **of a lifetime"**, "women **of a certain age**"; "the clarity **of a truth"** [countable nouns], So, all those require a noun preceding them. Abstract nouns do not take articles, that's right. [take articles not get articles]
Answer: I think you might be getting stuck on the idea that a noun is either abstract or not abstract (i.e., concrete). This is not quite correct. The same noun is sometimes abstract and sometimes not, depending on how you use it.
Let's use water as an example, because while it isn't an abstract noun, it works the same way and may be easier to visualize.

Water is necessary for life.

Here, we are talking about water in an abstract sense: water as a concept, any and all water. So, we don't use an article.
But once we start talking about a specific instance (in Andrew's terms, a "concrete example") of water, the noun is no longer being used in an abstract sense.

The water from the spring down the road tastes wonderful.

Now, we are referring to some specific water, some water that actually exists in the world. Once we do that, we have to use the article.
So it is with abstract nouns. Andrew's example with size and weight is an excellent one. In the first example, the officer needs to think about size and weight while loading and unloading cargo. In this case, size and weight are ideas, so they are abstract.
But when you associate the concepts of size and weight with a concrete object, such as a container, they stop being abstract. Now, they are characteristics or properties of an existing object, and therefore a specific instance of the two ideas: the size and the weight of the container.
You can perhaps use water again to help with this. Water means all water. As soon as you qualify water, it becomes the water: it is now only that subset of all water that fits the qualification. So, the water in my swimming pool, the water in the sink, the water in my glass, the water in Lake Superior, the water in the Atlantic Ocean, and so on.
So, it might help you to think of weight as all weight, weight not applied to anything concrete. But as soon as you qualify it, it becomes the weight: the weight of a bowling ball, the weight of a feather, the weight of a car, and so on.
Perhaps that helps.
Comment: @Manifestation_Peculiarity Yes, I noticed you mentioned the indefinite article, but the concept is the same. The definite article is just more common, so there are more examples to draw from. *He is carrying a weight on his shoulders* is an example with the indefinite article. It's a specific instance of weight. If using *fish* helps, then here are two sentences: *Fish breathe through their gills. I caught a fish.* The idea is exactly the same.
Comment: I think it is my failure that I didn't mention clearly which article I'm talking about. I'm talking especially about the indefinite article as it can be understood from all of the examples that I mentioned.
Comment: water is a **mass** noun, not an abstract noun. water, money, hay, coffee, are examples of mass nouns. truth, wealth and happiness are examples of mass nouns. So your answer is entirely misleading.
Comment: @Lambie Perhaps you will reread my post, and point out exactly where I said that water was an abstract noun? I can't seem to find it.
Answer: The fact that "truth" can sometimes take an article tells you that you can have both abstract truth and specific truths.

Truth is hard to come by, but should always be sought. (abstract)
We may never know the truth about what happened to the family that fateful night. (specific)

In the same way, you can omit the article when talking about a general, abstract concept:

When loading and unloading a container ship, the deck officer must take into account both size and weight, so as not to unbalance the cargo.

If specific, then use the article:

When loading and unloading a container ship, the deck officer must take into account both the size and the weight of the containers, so as not to unbalance the cargo.

It's more of a philosophical question than an English question whether there is any real difference between an abstract concept (like Truth or Love or Beauty or Innocence, or ...) and a concrete example of that concept, but English allows for this by choosing whether or not to use the article.  If you use the article, you must be talking specifically about some example of that concept, even if you just imply the context:

The truth will topple a king.

I could have said "Truth will topple a king" but in this case I imply that there is some specific truth about the king that will lead to his undoing.
Comment: @Manifestation_Peculiarity  that's more a philosophical question than an English question, but simply: If you talk about a specific instance of some philosophical concept, you will explain the context of that instance, and use the article.  *"Theirs was **a love that would start a war**"*.  *"**The truth (about the king)** will topple a king"*.  In other words, if I use the article, I must be talking about something specific.
Comment: @Manifestation_Peculiarity  I expect you were taught that rule to make things easier, but unfortunately they didn't explain that abstract nouns are not *always* abstract.  Please see my edited answer.
Comment: Thank you. But honestly I didn't understand the answer. We are taught that abstract nouns don't get articles, and you explain that they do? How can you explain "a truth", "a love"? it seems that this rule ("abstract noun doesn't get an article) doesn't always work. Now the question is when it's relevant and when it is not.
Comment: @MaulikV  It doesn't matter.  "**A** truth", "**the truth**", either is a *specific* truth not the abstract, nebulous concept of "Truth".  To reiterate the first sentence of my answer:  The fact that an article is used before "truth" (and other abstract nouns) tells you that, conceptually, there is abstract *Truth*, and there are also concrete *truths* that apply to a more specific context.  It's not much different from the abstract concept of "air" and the specific concept of *"the air that I'm breathing"*.
Comment: I appreciate your patience but honestly I still don't understand the answer (and I was reading it many times). Sorry.
Comment: The question is about *indefinite article!* Definite article has more flexibility in that case...
Comment: @MaulikV  In fact, *any* article does this:  *his* truth, *Bob's* truth, *that* truth, *any* truth, *some* truth, etc.  All imply that you've moved from the abstract to the concrete *application* of truth.
Answer:
I was told that abstract nouns don't get articles.

Incorrect!
So, you need to delearn this rule.
Abstract nouns, as English text books in primary schools show, are the things that you can't touch, feel, or fit into a box! But, as we grow, we learn more that abstract nouns have two types: countable and uncountable. So, this is pretty much similar to a normal noun.
Check the reference here on the Cambridge dictionary. It says:

The uncountable use has a more general meaning. The countable use has a more particular meaning.

And, this solves your question. The countable use has a more particular meaning.
One of the examples that you quoted:

Love is like a physical pain for some people (love in general/all love)

but...

I've always had a love of poetry, ever since I was a child (a specific liking for something).

Read the entire table on the dictionary. It's really helpful. Hope this solves it.

Does it give us a hint? If you want to make a general noun unique/specific, you put the definite article, and if it's an abstract noun, the uniqueness is brought by placing an indefinite article? ~ Well, I'm not sure, but from examples in Cambridge, it looks like.
Comment: unlearn, not delearn
Answer: The very site you have provided a link to mentions 'abstract noun' only once:

We do not use articles before uncountable and abstract nouns used in a general sense.

Where the boldfaced phrase clearly modifies "uncountable abstract nouns".
That is, it's not just before any abstract nouns that "we do not use articles", but it's before abstract nouns used in a general sense.
So I suggest you go back to the site and re-read the whole thing, which I'm sure will answer your question.
Answer: Question:
I was told that abstract nouns don't get articles. (You can see here for example). But I found many abstract nouns that get indefinite articles, such as: "of a truth", "of a size", "of a lifetime", "of a certain age", "a love", "a wish", "a difference", "a power" and more. What is the explanation for that?
Abstract nouns do not take articles.

Beauty is a wondrous thing. [abstract noun]
Wealth is not the same for all rich people. [abstract noun]

Do not confuse **mass nouns with abstract nouns.**
One answer here has done that: water, money, coffee, hay are examples of mass nouns.
The examples given above such as "of a lifetime" presuppose a noun preceding them:

the chance of a lifetime [lifetime is not an abstract noun]
the impact of a truth [truth there is not an abstract noun]
**the impact of these truths [plural use of non-abstract noun]
**the impact of truth [abstract noun]

VERSUS

the value of truth [that is an abstract noun]
the power of truth [that is an abstract noun]

Here is truth that is not an abstract noun:
The truths contained in the Bible are complicated. [countable noun]
There are words that can be countable nouns or abstract nouns:

The power of truth is amazing. [abstract]
The powers of the committee were very broad. [countable noun]

SUMMARY: mass nouns, abstract nouns and countable nouns behave in different ways. Some mass nouns and some abstract nouns have countable versions. So, context is everything and each case needs to be looked at individually.

Let's have a coffee. [coffee served in cups: countable]
There were two types of coffee used for the breakfast. [mass noun, uncountable]
Coffees from Africa are best. [countable, varieties of coffee]

Please note: you have to decide based on your context whether a word like power is being used countably or abstractly.


Is there a maximum or minimum temperature for take-off and landing?

Question: Is there a maximum or minimum temperature that a plane can take off or land at?
Comment: Be aware there's not just a max air temperature for some aircraft, but there are sometimes max temperature limits for the fuel. For example the 747-100/200 limit was, as I remember 54.5C (130F). Same for the -400. See http://b747400.com/pdf/limits.pdf. Back in the 1990s in the Arabian Gulf countries during summer, this was sometimes a problem.
Comment: I used to work as a load planner for UPS, and often aircraft was grounded well before approaching any max limit, because in order to fly a large aircraft like a 747 (for profit) you would have to de-fuel or unload much of the cargo, so we would just hold the plane until air temperatures cooled so we could fly it fully loaded, and take the hit on the delay.  I was also, once bumped from a flight from PHX to HNL due to density altitude issue because of the heat.
Answer: There is a maximum temp but that varies by airport altitude, runway length, aircraft and payload. You can find an answer to that question here.
There is not really a minimum temperature but it needs to be warm enough out to run the engines. Again this varies by aircraft and a preheat can usually solve this problem but there are places on earth where it be comes practically to cold to operate some aircraft. On a similar note if icing conditions prevail you are not really going anywhere but those can occur at lots of altitudes and temperatures. If the given airplane is stored outside and the airport lacks proper de-ice equipment you may be grounded.
Answer: Maximum and minimum temperatures are governed by two factors.
First, there is the limitations imposed by the manufacturer.  For example, recently the media has been reporting that some regional jets have max temps for operations, and they have been unable to operate in the southwest US.  Some manufacturers also limit low temperature operations, and may require different lubricants, fuel, etc.
Second, aside from manufacturer (or company) limitations, there are practical limitations. Engines can be hard to start at -40.  Fuel can gel. Batteries can render insufficient power to perform normal starts.  These limitations are normally determined by practicality, experience or other sources of information by the crew.
In my experience, dealing with hot soaked planes is normally easier than dealing with cold soaked planes.  Other issues like density altitude (DENALT) are operational issues, that while normally are considerations, are usually not hard limitations. For example, departing a 1200 foot strip in South American mountains on 35C days has been a limitation with a turboprop aircraft, for me, but the number of times I have had those operational considerations limit flight can probably be counted on my fingers and toes.
So in general, there are two limitations: Those imposed by the manufacturer and the aircraft certification, and those imposed by practicality (which includes best practices).
Comment: Perhaps this should be a new question, but I've read two things regarding the regional jets in Phoenix. I've heard "they can't take off because the runway isn't long enough", but I've also read "the POH (or something similar) tables don't give data above a certain temperature, therefore they can't fly (even if the runway would be long enough for the conditions), and updating the tables with new information would allow flight". Any idea which it is, or both?
Comment: I know that some of the flights are impacted by a max operating temperature. I don't have an authority on the details, but I think it is something like a 119F ambient.
Comment: The runways are about 10,000' long.  It is possible that the runways aren't long enough to satisfy the runway length requirements (significantly more runway is required than is actually needed to take off) but it is more likely that the performance charts don't have performance numbers above a certain temp.  It got up to 121°F/49.5°C in certain parts of Phoenix on 6/20 so it is very possible that crews simply could not calculate performance which means they were not legal to fly.
Answer: Yes, there are some temperature limitations, but these are typically aircraft specific.
For example, the Beechcraft King Air B200 has the following limitation:

Max Outside Air Temperature Limitations
Sea Level to 25,000 FT pressure altitude:     ISA + 37° C

These limitations are given in the AFM, and compliance is required.
Practically speaking, this limits aircraft operation of any kind—including takeoff and landing. Takeoff would not be authorized at sea level above 52°C, or at 5000 ft pressure altitude above 42°C.
For a minimum temperature, the engines have a starting limitation of at or above -40°C.
Answer: It depends on the model of the plane, particularly its engines, the length of runway available, and surface wind conditions. The aircraft's Pilot Operating Handbook will include a set of performance charts. To determine whether you can safely takeoff or land, you would plot the values (including temperature) into the chart.
This related question discusses some of the precautionary steps one should take when operating in very cold or hot weather.
In general, aircraft performance will be the limiting factor in hot weather, and in cold weather the challenge is to get things started and stop things from freezing.
There is no absolute temperature regulation-wise. Practically you can argue that the minimum temperature is when the fuel freezes and the maximum temperature is when the tire melts, but you will likely run into other troubles before this extreme is reached.
Comment: There are regulatoty limits. Air carriers must adhere to performance charts. Charts only go to 48°c? No flying at 49°c.


What type of stone is this?

Question: I have this around my yard between larger concrete stepping stones and in more open locations. It is a rough rock with hints of different colors. My guess is some sort of gravel - I'm hoping for something more specific to purchase more.
Comment: Asking a local, or giving approximate location would be helpful. I see what might be granite or quartz, and blue-grey pieces of something else (basalt?).
Comment: Located in Southern California. Thanks for the tip on asking local - will reach out to a few places selling landscaping materials.
Answer: White color makes it very likely to be mostly lime stone. The size looks like limestone "screenings" . When limestone is crushed certain size ranges are used for concrete ; so sizes are separated by screens . The angular shape also indicates a crushed material.  This is size is too small for concrete and is essentially a by-product. Smaller "dust" size particles have been washed away. If you only want a few pounds , you can get a similar ( but expensive) product at pet shops as "crushed coral" or aragonite . Aragonite is one of the crystal forms of calcium carbonate.
Comment: If limestone, should "fizz" when acid added. try vinegar etc.

What type of stone is this?


From symbol rate to sample rate fractional ratio

Question: My design has symbol rate and sample rate to DAC fixed but the ratio is not an integer.
For example assume my symbol rate is 3 Mbps but the sample rate to DAC is 20 Mbps. So i am having 3 MHZ and 20Mhz clock. Do I have to use a polyphase resampler in the Tx path to bring 3 Mbps to 4 Mbps and interpolate 5 times to 20 Mbps by RRC and then send it to DAC? Similarly on the receive side? or is there any better method?
Answer: The symbol rate is independent of the sampling rate. You can sample the symbols at any desired rate that is greater than twice the bandwidth of the symbol, where higher rates would simplify the required analog filtering after the DAC (so higher sampling is better in this regard and the initial ratios the OP is using are reasonable).
The bandwidth of each symbol is driven by the pulse shaping that may be used. With typical pulse shaping such as Raised Cosine, two samples per symbol would be a reasonable minimum sampling rate to use but would also require tighter analog filtering.
To see this, consider each "symbol" as it would appear as an analog waveform and observe how you can sample that any any rate as long as you observe Nyquist's criteria to sample greater than twice the highest bandwidth of interest in the signal. Going from digital to analog with a DAC is this same process in reverse, in that how many samples do you need to properly reconstruct the desired waveform.
Assuming this design starts with symbols sampled at one sample per symbol at a 3 MHz symbol rate, typically this would be interpolated (upsampled by inserting zeroes and then filtered) where the filter would be the pulse shaping filter defined by the waveform transmitter specifications (often a root-raised cosine filter but must be defined).  This upsampling could be matched to the transmitter sampling DAC frequency using polyphase resampling or done in stages.  If in stages resampling to only 4 MBps would not be sufficient for pulse shaping given the explanation above, but it would be reasonable to resample to 10 MHz for pulse sampling and followed by 2x interpolation for the final DAC sampling.
Comment: @ Dan I understood your explanation but the issue is symbol rate and sample rate are not integer ratios. My symbol rate is 3 Mhz and DAC sample rate is 20 Mhz. Should I  just register the 3 Mhz at 20 Mhz and send it to DAC ? No need to use a polyphase resampler? I have only 3 MHz and 20 Mhz clocks? So i cant derive any higher clocks either
Comment: @Mark there is no integer relationship required between the symbol rate and sampling rate. Are you saying that you just need to change sampling rates to match the rate of the DAC? You would need to upsample in order to pulse shape your symbols and that would also be done before the DAC - can you give more details on what you are doing about that?
Comment: Assuming my symbol rate is 3 MHz . If i am using RRC with upsampling by 4 the sample rate becomes 12 MHZ but my DAC sample rate is 20 MHz. So should i interpolate 12 Mhz 10 times to 120 Mhz and decimate by 6 to 20 Mhz and send to DAC? but i dont have these higher clocks?
Comment: @mark I see your question/issue and added another paragraph. Your prime factors are interpolate by 5x2x2 decimate by 3, so to allow BW for pulse shaping you could interpolate by 10 decimate by 3 interpolate by 2. Polyphase resampling is a good approach as you won't actually require the highest clock rate.   You can do the pulse shaping after the 10/3 rate conversion or at the final 20 MHz output rate since you would need an interpolation filter there anyway.
Comment: @mark See with the 10/3 polyphase resampler for example how you never run at 30 MHz rate: You would have 10 polyphase filters with each filter output providing you what the sample would be if you were running at 30 MHz, but because of the subsequent decimation you only select every third output for each new output sample which would be at the 10 MHz rate.
Comment: ok. So with resampler I just need 3 mhz and 10 mhz clock . I don't have to derive any other higher clocks. So I can probably do rrc after resampling. Does this have any other implications/ drawbacks?.I will try to simulate and check. Thanks Dan.  - Mark
Comment: @mark yes correct and do rrc after resampling and no drawbacks or other implications. Given you don't actually need precise timing of the 3MHz you can do it all essentially from your 20 MHz master clock.
Answer: Not to dissuade you from using integer ratios when you can (and you certainly can here), but to let people know that there is nothing mandatory about using integer ratios, despite the approach being the staple of DSP textbooks throughout decades—there is no actual requirement for integer ratios. Consider that resampling is conceptually equivalent to playing audio out a DAC at one rate, and resampling it by an ADC running at another rate. The lowpass filter of the DAC essentially calculates the continuous between-sample points, to be resampled by the ADC. There is no reason you can't calculate the new-rate sample points from a software lowpass filter directly.
One method for implementing the lowpass filter is a windowed sinc function. The only requirement is that it's a lowpass filter, but we generally want to preserve phase linearity and have a flat passband. I'll use windowed sinc as an example because it's popular, easy to compute, and has desirable qualities, but my main focus is the non-integer ratio aspect.
The advantage of integer-ratio conversion is that output samples are evenly spaced relative to the input samples. This means we can pre-compute a windowed sinc table with just the values we need. For a factor of four conversion, the table would have four sets of values corresponding to each step forward starting from one sample, before the next.
That is, for a factor of four, output sample #1 would correspond to the position of the first input sample, #2 with one-quarter way between the first two input samples, #3 half-way, #4 three-quarters way, and the cycle repeats—#5 coincident with the second input sample, and so on. So, 0, 0.25, 0.5, 0.75, step to next sample and repeat 1, 1.25, 1.5, 1.75, then 2, 2.25…always the same four positions between samples for the sinc table to be aligned to (and thus a simple application of a polyphase filter).
If you were to do this for an arbitrary ratio conversion, you would not have this simple repeating pattern. Let's say the conversion factor is 3.9. Output sample #1 would be coincident with the first input sample, as before, but the following output samples would be spaced about 0.2564 from there. This means that there would be no output sample coincident with the second input sample, and the output samples between the second and third input samples wouldn't be at the same fractional offsets as between the first and second input. 0, 0.2564, 0.5128, 0.7969, 1.0256, 1.2821, 1.5385, 1.7949, 2.0513…there is no simple repeating alignment of the table.
That's the problem with the table approach—it works well work integer ratio conversions, but isn't suitable for non-integer ratios. Why do we use a table at all? Because it's faster to look up the needed values from a pre-computed table that it is to calculate them on the fly, and each output sample requires many windowed-since evaluations.
One solution is to calculate an oversampled windowed sinc table, and interpolate arbitrary values between table values as needed. The accuracy is determined by the degree of oversampling of the windowed sinc table, and the quality of the interpolation. Windowed sinc is a relatively smooth function, so linear interpolation can be acceptable given a table with sufficient oversampling and dependent on your requirements.
Another reason you might not want to stick with integer ratios is when the sample rate might need small adjustments, such as locking to a physical clock source. A similar approach would be to upsample at a high integer rate then use a simpler interpolation between resulting intermediate output samples (note that you don't necessarily need to actually produce ever sample at the higher rate, just the ones you need for further interpolation).
I hope this helps, conceptually if nothing else!


Buildrowset ampscript with descending order for single attribute in XML feed

Question: Is it possible to use the BuildRowset function and have a descending order for a single attribute in the feed? If we get 4 records with 4 different time stamps for each, we'd like to sort them by earliest to latest.
Answer: Sorting XML with an XPATH is easier to do with XPATH 2.0, but SFMC only supports XPATH 1.0.
This may be an option for you: Have SFMC Support enable Script Activities for Automation Studio.  Write a script that retrieves your XML and writes it to a Data Extension.  In your email, use the LookupOrderedRows() function to retrieve the data in the desired order.


VMWare ESX image to run on VMWare workstation

Question: I've an linux image(debian) running on VMWare ESX 3.1.
Is it possible to copy that image and run it locally on my local VMWare workstation?
how?
Answer: Just open up the VI client, shut down the VM, browse to the datastore and then download the image. Pretty straightforward really, I do it from ESXi 3.5 -> Workstation 6.5 all the time.
Answer: I believe that while ESX (commercial) is reverse-compatible to Server (free), Server is NOT forward-compatible to ESX.
Therefore, you can import Server images to ESX, but not the other way around.
You may be able to go from an ESX host to an ESXi (free) host, however.
Answer: As far as I remember that was exactly what I did a few weeks ago. I exported the image (export facility is included in the ESX, but you'll have to power off the image while you export it). Once the image was exported I ran it through the VMware converter (free tool) and converted it to run on a workstationr/player.
However my laptop always crashes when I install VMWorkstation so I run it om a VMPlayer.
Answer: We also have such an environment and are working on it since past 5 years.  We have ESXi 3.5 virtualized environment running Centos OS virtual machines amongst others.  To use the virtual machine from ESXi on our local machine, we have installed VMWare Workstation (also VMWare Player).  We take a complete mondo backup using mondoarchive.  We then transfer these images on our local machine.  From these images, we restore the ESXi based virtual machine in our local VMWare Workstation environment.  It has been a great success for last five years and we have never faced any problem with it.
Answer: Kasper, what version of ESX are you running? Trying to export an image from our ESX server always ends in a I/O error (don't have access to the server right now so I cannot remember the exact error message).
Would love to get this feature working but I not found anything on the web that might help with this specific error.
Answer: You can also user Vizioncore vConverter or FastSCP for your migration.
Answer: This is a nice article describes how to convert different images: Please go throught it.
http://www.dedoimedo.com/computers/vmware-converter.html


Why do or don't neutrinos have antiparticles?

Question: This was inspired by this question. According to Wikipedia, a Majorana neutrino must be its own antiparticle, while a Dirac neutrino cannot be its own antiparticle. Why is this true?
Answer: Because the spinor of the Majorana neutrino is an eigenstate of the charge conjugation operator. This is different from the case of a Dirac spinor that will change under the effect of the same operator.
Comment: But why can't a Dirac spinor be an eigenstate of the charge conjugation operator? This is only a partial answer.
Comment: This depends on the way the Dirac equation is formulated. In order to produce a Majorana spinor, you need to perform an unitary transformation on the $\gamma$s matrices of the Dirac equation. This will change the behavior of your solution under charge conjugation, that is given by the $\gamma_2$ matrix.
Answer: It's often stated that if neutrinos are Dirac fermions then they're distinct from their antiparticles, and if they're Majorana fermions then they're the same as their antiparticles. Whether or not this is true depends on how do you define both "Dirac and Majorana fermions" and also "antiparticle", but in my opinion the statement is misleading according to its most natural interpretation.
When people talk about neutrinos being Dirac or Majorana fermions, they can mean at least three different incompatible things:

A fermion bispinor field configuration $\Psi(x)$ is sometimes defined to be a "Majorana field" if it is required to be left invariant by (not just to be an eigenstate of) the charge conjugation operator. In this case the field only has one independent Weyl field and two independent spin indices. $\Psi(x)$ is a "Dirac field" if it is not required to be invariant under charge conjugation, so that it has four independent spin components. Note that this is solely a statement about the field configuration, not about any Lagrangian that might describe the field's dynamics. Whether a bispinor field is Dirac or Majorana is a mathematically well-defined question but has no physical content, because quantum fields are not directly observable. When we talk about antiparticles in this context, we really mean the charge conjugation operator, and whether or not it leaves the quantum field invariant.
A particular formulation of a quantum field theory (i.e. a choice of field content and Lagrangian) is a formulation in terms of Dirac or Majorana fermions if the matter fields are expressed in terms of Dirac or Majorana bispinor fields, respectively. This distinction also has no physical content; indeed any theory of spin-1/2 fermions can be equivalently formulated in terms of either Dirac or Majorana bispinor fields, and either choice can be more convenient in different circumstances.
A quantum field theory is sometimes described as a theory of "Dirac fermions" if its action has a continuous gauge or global symmetry that ensures the conservation of lepton number, and a theory of "Majorana fermions" if not. Unlike the first two pairs of definitions, this one has physically distinct consequences (e.g. the absence or presence of neutrinoless double beta decay). However, it's only loosely connected to the first two. (The loose connection is that it's mathematically simpler to formulate such a symmetry in terms of a Dirac bispinor field.)

The third definition is the most common, but it's important to note that in the simplest formulation of "Majorana neutrinos" in beyond-Standard-Model physics, the neutrino fields are not Majorana bispinor fields, but instead are Dirac bispinor fields with mass terms that violate conservation of lepton number. So in my opinion, it's misleading to say that "Majorana neutrinos are their own antiparticles," since charge conjugation takes a Majorana neutrino field to a distinct field.
The motivation for that terminology is that operationally/experimentally, particles and antiparticles are characterized by the conservation of charge or ((particle number) - (antiparticle number)). Without such a conservation law, particles and antiparticles are difficult to distinguish in practice.
Nevertheless, I personally would say that it's correct to say that "there is no physical distinction between Majorana fermion particles and antiparticles," but it's incorrect to say that "a Majorana fermion is its own antiparticle." The distinction is subtle but important: the latter claim gives the misleading impression that Majorana fermion particles and antiparticles are both well-defined concepts that happen to
coincide, while the former claim conveys that it just doesn't really make sense to talk about antiparticles at all in the context of Majorana fermions.
Comment: +1, sorry I never got around to replying to your comment on my related answer, but I think this perfectly sums it up!
Answer: In crude terms I think it amounts to the following:
Consider, for instance, a (Dirac) fermion creation operator: $c_j^\dagger$. A Majorana fermion is somehow the "real" Part of a Dirac fermion:
$m_j = c_j + c_j^\dagger$
(conventions on normalization differs). Hence a Majorana fermion transforms into itself under charge conjugation.
Comment: This is not good as an answer either, because you can then take a pair of Majorana spinors and make a Dirac spinor out of them, and the charge conjugation eigenstates are combinations of the two. There are many different charge conjugations possible in noninteracting theories, the interesting restrictions come when when you make particles charged (hence the name "charge conjugation"). I have a hard time answering this question, because I find the idea of Dirac neutrinos laughably absurd, it is so obvious that neutrinos are Majorana. Also in (3+1)d, Majorana equals Weyl.
Comment: @Ron yes but as you said you need *two* Majorana fermions to make a Dirac one
Answer: here is how I understood the answer. Imagine that we look at the electron in our reference frame, and find that it travels in z direction and has spin projection +1/2. This one we call right-handed electron. Since it is massive, there exist reference frames in which observers see it as left-handed electron. For example those observers that travel faster than the electron in the z-direction. Its charge is Lorentz invariant quantity, so everyone agrees that this is electron and not positron. Massive electron is then described by four degrees of freedom (4 basic spinors), left and right handed electron and left and right-handed positron; it is Dirac field.
Imagine now that we have left handed neutrino in our reference frame. Since we have lot of evidence that neutrino is massive, we can see that there are reference frames in which right handed neutrino is seen. The right handed neutrino is not observed in any experiment so far, and their mass could be very high. We only observed left handed neutrino and right handed antineutrino. So we can consistently demand that the observer in the other reference frame actually sees right handed antineutrino, without introducing right handed neutrino and left handed antineutrino. For charged particle this would not work. So we can describe neutrino by only two degrees of freedom; it is then Majorana neutrino. But the neutrinos are charged under lepton number symmetry which is global symmetry of the Standard Model. Being global means that it does not create dynamics, and there is no fundamental reason why it cannot be broken. If (local) gauge symmetry is explicitly broken then it leads to inconsistency of the theory, meaning that non-physical degrees of freedom could arise.
So Majorana particles are their own antiparticles only if we do not take into account lepton number symmetry.
Answer: Neutrino definitely have anti-particles. Another question  whether an anti-particle differs from its "particle" or not. The charge conjugation operator may generally change a given "neutrino state" because a neutrino solution is not completely determined with just Dirac's equation.


Original purpose of the Rich Header in PE files

Question: The Rich Header was presumably introduced by Microsoft in a previous version of Visual Studio. What was its original purpose and how does it achieve this? Is DanS the designer, similar to MZ?
Comment: Quite interesting topic, but isn't that header still part of today's build chain and wouldn't it thus serve still the same purpose (of identifying components used) as when invented?
Comment: @Raffzahn agree, I did not know this previously. Potentially the Rich header has remained unchanged since its inception.
Answer: The Rich header is described in detail in this article by Daniel Pistelli. It contains identifiers for all the (Microsoft) compilers and related tools used to build the object files which end up in the executable, with a count of object files for each. It goes at least as far back as Visual C++ 6 (1998) and is placed in executables (including DLLs) by the Microsoft linker.
Its purpose isn't documented; presumably it was introduced so that an object file's producer could be determined after the fact, e.g. to debug build problems which aren't immediately apparent, or track changes in object output back to their origin.
DanS might be the designer; a candidate is Dan Ruder, who wrote an article on dynamic linking published in the 1993 MSDN Library, but others disagree, suggesting instead Richard Shupak and Dan Spalding.
See also the Rich Header Research repository.
Comment: Great links. In the Daniel Pistelli article do you know what advantages a kernel debugger would give over a user mode one when it was used on LINK.exe? In the same article Riched32.lib was looked at, which seems to be a library for Rich Edit Controls, part of Windows Controls. The reason for choosing this library was probably the "Rich" part of the name and is unrelated to the name "Rich header" (fairly obvious but took two readings to understand this!), other libraries could have been chosen.


What should be used to store data in GAE?

Question: My web application will have ~150 fields and when value is changed in any field (at least one), I should save changed value.
How should I store such values with GAE? Should I save them directly in datastore? Should I use memcache temporarily and then save all values at once in datastore? Or, some other approach should be followed?
Answer: The datastore is your database. Memcache is to store data that's fetched from the datastore and kept temporarily in memory to avoid too many calls back to the database. You should first design your app around the datastore and then use memcache to improve performance.
Depending on your programming language of choice (java, python, go) there are many tools out there to help you map objects in your app to the datastore and to use memcache effectively.
Answer: I'd suggest you split your entities in a root entity and a couple linked ones holding each some of the 150 attributes - this way, when you update one attribute, you only need to save one (or two, if the update reflects on the root entity) smaller entities to the datastore instead of a huge one.
Use memcache to prevent reads, not to store data that's going to the datastore. Memcache can be flushed and the data there can be destroyed before it hits permanent storage.
Going one step further, the grouping of attributes could reflect data that's updated together - say, if you always update street and zipcode together, it makes sense to keep them together in a single structure.
Answer: First of all you should find out how you are going to use your data. Which queries are you planning to make? What is the size of your entities?
Datastore is very different from relational databases. That is It doesn't really matter how many properties are changed, because there is no way to update a property on its own. You can only save entity as a whole. I don't know about your use case, but there should probably be a better approach for structuring your data, than having ~150 properties for a single entity. What is your use case?
Also having too much properties for an entity may lead to index explosion, or to slow down datastore writes.
Comment: Thanks, Maxim. More details about my case can be found there - http://stackoverflow.com/questions/9232438/how-to-protect-gae-server-side-calculation-logic


Wave Analytics -- containerId/versionId of a dataset

Question: How to get containerId/versionId of a dataset ? Previously we used to get this by turning on the SAQL mode, but after Summer 17 release it's only showing the dataset name, not the containerId/versionId names. Please let me know if we anyone has any idea how to get it.
Answer: It is still shown in the logs:

Open the Javascript console in the browser.
Enable logs:

edge.log.enabled = true;
    edge.log.query = true

Open the dataset
Change it. For example, set a "Group by" parameter.

You will see the query in the Javascript console, which includes the identifiers you are looking for.
Answer: Open workbench select the REST-api using the following route:

/services/data/v37.0/wave/datasets/"your datasetId"

Select GET as method and the response will contain the version url along with other information. The click version url and the GET method you will return the version id.
Comment: how can I do this in apex?


What tests are done on aircraft wings for testing the effects of lightning?

Question: During the testing phase of aircraft wings, there are lot of testing like temperature, pressure, humidity, vibration and load/stress. Apart from these, does any one have idea which other tests are done on them for complete qualifications like like lightning?
Comment: Your question is more applicable nowadays. 20 years ago, the airplane were enterely made of aluminium and were design to actually be a easy path for lightings as they were made of metal, the lighting was passing by. However, with the increasing composite composition of an airplane your question becomes really sensible where the lighting path goes though a composite not prepare for electricity (there are some tricks here...)
Comment: There is a difference between the title (only lightning tests) and the body (which *other* tests, like lightning). So are you interested only in lightning tests or any certification tests?
Comment: I have edited the question as other commented said apart from what all the categories I have said, only lightning is left. But if you know of any other tests, and if you explain them, that will be beneficial for everyone.
Answer: Almost all the tests done on aircraft wings can easily be categorized in one of the areas you mentioned.
The only remaining thing I can think is bending an aircraft's wing. It is stated on BBC as:

Many modern passenger jets can flex their wings nearly 90 degrees in a test rig.

For B787, it is reported:

During the test, the wings on the 787 were flexed upward
  "approximately 25 feet" which equates to 150 percent of the most
  extreme forces the airplane is ever expected to encounter during
  normal operation. The test is used to demonstrate a safety margin for
  the design and is part of the certification process to show the
  airplane can withstand extreme forces.

This video shows (also this one) how much force a wing can take before breaking.
OP asked about tests for lightning effects. Lightning commonly strikes the nose, wingtips, engine cowlings, and tip of the vertical tail. Hence, wings are not the only parts of an airplane which needs to be protected against lightning.
To avoid reinventing the wheel, please see the following questions:

How is an on ground lightning strike test conducted?
What happens when an airplane gets struck by lightning?
Comment: I would consider that part of the load and stress testing.
Comment: @NitinG If you're really asking about light(n)ing testing, then it would be best to edit your question and add that. It would make the question much more specific and therefore it would be easier to get a good answer.
Comment: I am wondering what tests are done to check if lighting will affect the wings ?
Comment: @NitinG If you are talking about lighting on wings, please look at [this question](http://aviation.stackexchange.com/q/64/65). However, I suspect you are [talking about lightning](http://libroediting.com/2012/12/07/lightning-lightening-or-lighting/).
Comment: @NitinG that's a good question. I believe those tests are done on the components and not the whole wing.
Comment: Question edited but lightning is only one thing, any other tests are still done on them apart from what I have mentioned.


What is the mass in $\vec{\nabla}\cdot \vec{B}_g=\text{something}$ called if it could be non-zero?

Question:
Maxwell's equation for gravity has
$$\vec{\nabla}\cdot \vec{B}_g~=~0,$$
see Gravitoelectromagnetism in analogy with the electrodynamics.
What is the mass called that needs to make these equations symmetric in $\vec{\nabla}\cdot \vec{B}_g=\text{something}$?
There are no magnetic monopoles so far but the electric charge is quantized anyway.
My other question is: What is preventing the quantization of mass or is it considered quantized as built from elementary particles?
Comment: More on [gravitoelectromagnetism](https://physics.stackexchange.com/search?tab=votes&q=url%3a%22*.wikipedia.org%2fwiki%2fGravitoelectromagnetism%22).
Answer: The last part of the question (v4) is a duplicate of this and this Phys.SE questions and links therein. Here we will only address the first part of the question (v4).
The formalism of gravitoelectromagnetism (GEM) is traditionally$^1$ derived from a weak field limit
$$\tag{1} g_{\mu\nu}~=~\eta_{\mu\nu}+h_{\mu\nu}, \qquad h_{\mu\nu}~\ll~ 1,$$
of General Relativity (GR), where $\eta_{\mu\nu}$ is a fixed background reference metric, usually taken to be the flat space Minkowski metric. Here the first row/column
$$\tag{2} h_{0\mu}~=~h_{\mu 0}~=~A_{\mu}$$
of the $h_{\mu\nu}$ tensor is identified with the GEM gauge $4$-potential $A_{\mu}$, see e.g. Ref. 1. The main point is that the GEM electric field $\vec{E}$, and the GEM magnetic field$\vec{B}$, i.e. the electric-magnetic field-strength $F_{\mu\nu}$, are defined from $A_{\mu}$ by standard formulas for EM in a fixed curved space, which implement the GEM no-magnetic monopole Maxwell equation
$$\tag{3} \vec{\nabla}\cdot \vec{B}~=~0 $$
manifestly via a Bianchi identity a la this Phys.SE answer. Here we have implicitly assumed that the background metric $\eta_{\mu\nu}$ doesn't have singularities. In other words, a GEM magnetic monopole in a regular spacetime point of the background metric $\eta_{\mu\nu}$ would violate the weak field framework that GEM traditionally is derived from. On the other hand, it seems that GEM magnetic monopoles may be associated with e.g. NUT-type singularities in $\eta_{\mu\nu}$, see Ref. 3.
References:

B. Mashhoon, Gravitoelectromagnetism: A Brief Review, arXiv:gr-qc/0311030.
R. Maartens and B.A. Bassett, Gravito-electromagnetism, arXiv:gr-qc/9704059.
D. Momeni, M. Nouri-Zonoz, and R. Ramazani-Arani, Morgan-Morgan-NUT disk space via the Ehlers transformation, arXiv:gr-qc/0508036.

--
$^1$ Ref. 2 claims to have developed a fully covariant GEM formalism with magnetic monopoles (hat tip: Michael Brown).
Comment: There is a [fully covariant (and as far as I can tell fully non-linear) version of GEM](http://arxiv.org/abs/gr-qc/9704059), but what bearing this has on the question I don't know...
Comment: I updated the answer.


NMOS amplifier simple question?

Question: While studying the NMOS amplifiers in my book I came across operations with differential output voltages and this circuit specifically.I want to understand what are the drain voltages and what is the Vdd voltage in this case?
Answer: No way on knowing given the circuit shown. normally there is some load connected to the drains of Q1 and Q2 that help set the operating point. The only thing you know about this circuit is that Id1 + Id2 = I.
Answer: This circuit has a current output at the drain. It means that the voltage and not the current is defined at the drains. The voltage depends on the loads connected to the outputs and the supply, but it is not included in the picture above.

NMOS amplifier simple question?


SQL server agent SSIS error

Question: I get the following error when I execute my package as a SQL server agent job.
It is an SSIS 2008 package running on a SQL Server 2008 instance. My package security is DontSaveSensitive.
I don't even know how to begin fixing this error.
Where should I check first?
Date        a value of time
Log     Job History (MyJob)

Step ID     1
Server      PCTSQL004
Job Name        MyJob
Step Name       Job_1
Duration        00:00:00
Sql Severity        0
Sql Message ID      0
Operator Emailed
Operator Net sent
Operator Paged
Retries Attempted       0

Message
Executed as user: CS\DmcSysManager. The process could not be created for step 1 of job 0x63BB5A86DB23F947866D2A806BE4CC6B (reason: A required privilege is not held by the client).  The step failed.

Comment: Has it ever run successfully?
Comment: What privileges does CS\DmxSysManager have?
Comment: @ShawnMelton - the job - no, never. ssis package inside visual studio - yes.
Comment: @mrdenny - I am not sure how I can find out the privileges of CS\DmcSysManager has. Can you tell me how to get them ? I can tell you once i know.
Comment: Within the Windows OS there are groups which can be used to assign privileges to accounts.  What groups is that account a member of?  What fixed server roles in SQL Server is it a member of?
Answer:
It is an SSIS 2008 package running on a SQL Server 2008 instance. My package security is DontSaveSensitive.

You have to save the package with EncryptAllWithPassword using a password.

Then schedule it using SQL Agent Job as below :
"DriveLetter\Program Files\Microsoft SQL Server\110\DTS\Binn\DTExec.exe" /FILE "SSIS_Package_Location\bin\Package.dtsx" /DECRYPT "PasswordStrong007" /CONFIGFILE "Location_to_Config_file_If_any\Config.dtsConfig" /CHECKPOINTING OFF /REPORTING E

Now the user account that you use should have permissions on the database server instance.
You can check the permissions using below T-SQL :
SELECT [Login Type] = CASE sp.type
        WHEN 'u'
            THEN 'WINDOWS Login'
        WHEN 's'
            THEN 'SQL Login'
        WHEN 'g'
            THEN 'GRP'
        END
    ,convert(CHAR(45), sp.NAME) AS srvLogin
    ,convert(CHAR(45), sp2.NAME) AS srvRole
    ,convert(CHAR(25), dbp.NAME) AS dbUser
    ,convert(CHAR(25), dbp2.NAME) AS dbRole
FROM sys.server_principals AS sp
JOIN sys.database_principals AS dbp ON sp.sid = dbp.sid
JOIN sys.database_role_members AS dbrm ON dbp.principal_Id = dbrm.member_principal_Id
JOIN sys.database_principals AS dbp2 ON dbrm.role_principal_id = dbp2.principal_id
LEFT JOIN sys.server_role_members AS srm ON sp.principal_id = srm.member_principal_id
LEFT JOIN sys.server_principals AS sp2 ON srm.role_principal_id = sp2.principal_id

Answer: There are a set of 'special' privileges listed under the Security role of SSMS.  One of those is BulkAdmin.  While I don't root around in this kind of stuff much, the error above hints that the user account the SSIS package is running under needs either dbo privilege or membership in one of these roles.  What database roles are assigned to CS\DmcSysManager?
Comment: How do i find out what roles are assigned to database roles are assigned to CS\DmcSysManager ?

SQL server agent SSIS error


Sharepoint online site not opening in SharePoint designer

Question: Im using SharePoint designer and when i try to open my online site in designer im getting the below error message, should i enable any settings?
Answer: You note that you are using SharePoint Online, if so the follow possibilities may be blocking SharePoint Designer access:

If you are attempting to open the root site collection (e.g. https://yourtenant.sharepoint.com/), the root site collection in SharePoint Online does not allow SharePoint Designer access.
If you are attempting to open one of the other site collections (e.g. https://yourtenant.sharepoint.com/sites/someothersite), Go to that site's "Site Settings" Page (e.g. https://yourtenant.sharepoint.com/sites/someothersite/_layouts/15/settings.aspx), and under the subheading "Site Collection Administration", click "SharePoint Designer Settings", and verify that SharePoint Designer access is allowed on this site.
Note that if this is a Modern-mode site, the "SharePoint Designer Settings" will not be available, but Designer access is NOT blocked on Modern sites.
Comment: Thanks this helped me a lot, not able to upvote your answer because of less reputations.
Answer: Your site does not open in SharePoint designer. The error is as above.
One possible reason is that this site has Designer disabled (http://support.microsoft.com/kb/940958)
Another cause (less likely to guess) is that this site was created using a template saved from a site where Designer was disabled.
RESOLUTION:

One straight forward way of doing it is from the UI (Which did not work in my case though :(  )

Right-click the ONET.XML file ( at \Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\TEMPLATE\SiteTemplates\\xml) for the site definition and open it with Notepad
If you see "DisableWebDesignFeatures=wdfopensite" section in the one.xml that means your site has been configured to disallow SharePoint designer.
You can remove this section from the file and should be able to access the site in designer now
If you are unable to get rid of "DisableWebDesignFeatures=wdfopensite" or find the correct onet.xml corresponding to your site definition, here is a simple script I put together to see if Designer is disabled on the site using the property vti_disablewebdesignfeatures2 and update it as required.

for information refer this link,
https://docs.microsoft.com/en-us/archive/blogs/namkh/the-web-site-has-been-configured-to-disallow-editing-with-sharepoint-designer
Comment: His question was tagged as #sharepoint-online.  What you propose is only possible in an on-prem environment.


How to find non-heap space memory leak in java?

Question: We have a java webserver that is using eclipse-jetty version 8.1.6. Recently we started noticing Out of memory error.
We had few profiling on the number of threads active. This seems to be reasonable around 100. The process has 5GB max heap memory and 4GB initial heap memory.
Process Details
Environment: Docker(kubernetes)
java.version="1.8.0_91"
java.vm.info="mixed mode"
java.vm.name="Java HotSpot(TM) 64-Bit Server VM"
thread size = 1024K
ulimit is unlimited for max process per user.
Container(Pod) Max memory is allocated to be 8GB

The webserver receives on a average of 350 request per minute. Also we run many such instances behind ELB(kubernetes service). After running for few hours we notice this OOM. The issue is random and it occurs on stress test.
OOM StackTrace:
java.lang.OutOfMemoryError: unable to create new native thread
   at java.lang.Thread.start0(Native Method) [na:1.8.0_91]
   at java.lang.Thread.start(Thread.java:714) [na:1.8.0_91]
   at org.eclipse.jetty.util.thread.QueuedThreadPool.startThread(QueuedThreadPool.java:441) [jetty-util-8.1.16.v20140903.jar:8.1.16.v20140903]
   at org.eclipse.jetty.util.thread.QueuedThreadPool.dispatch(QueuedThreadPool.java:366) [jetty-util-8.1.16.v20140903.jar:8.1.16.v20140903]

Since the number of thread count is reasonable. I suspect some memory leak. But I am not able to find the off heap memory size on a docker container.
Is there a way to find it ?
After searching for a while ,I found this bug below in jetty.
How to verify that if the bug is due to below issue without upgrading jetty ?
Related Bug Id: https://bugs.eclipse.org/bugs/show_bug.cgi?id=477817
Answer: You could  try to add -XX:-HeapDumpOnOutOfMemoryError into your java start parameters and to look into the dump.


How do I create an email trigger/workflow from SP list?

Question: I need to have an email sent to users based upon not completing an action in a sharePoint list. For instance if a task status was blank or incomplete, it would notify the user to provide the update. this could be based on due date approaching or missed (due date is a column within list), to remind the user to provide an update within the status column. Is this possible with some style of workflow?
Answer: One way to do this would be to run the Pause Until action and set the date you'd like to send the email.
You might want to create a workflow parameter and calculate, for example, due date minus 2 days.
I'm assuming by the way you have worded the question that you are comfortable creating the email actions within designer through custom actions.
Answer: Pause until action would make the workflow sleep and in case the date is changed it will not take updated date but wait for original date to come.
Another solution could be - you can navigate to list settings --> "Information Management Policy Settings" --> Item / or custom content type that you are using --> Check "Enable Retention" --> Add retention stage --> Delete the due date and number of days before which the reminder mail should be sent -->  Action : Select start workflow --> Select the workflow
This could be the solution for the requirement.


Read all of Lucifer's story from his spin off on Sandman?

Question: I would like to read Lucifer's story from the very beginning which I know started in a Sandman comic book issue. Which are the Sandman comics that involve Lucifer and after that do I read the books?? A little guidance would be helpful
Comment: There are many mentions of Lucifer in Sandman. However, his origin story is only told briefly.
Comment: I just noticed there are additional Lucifer comics. I'll read them and update my answer.
Comment: I simply want to have the whole story from its beginning before the solo Lucifer series and I am kinda confused, can you send me links for those volumes you mentioned as to where I can buy them ? and thanks for all he info
Comment: Updated my answer with the list of works. Ideally, you should read them in this order, but I doubt you'll get spoilers or confusions if you read them in other order. As to where you can buy them, I'd recommend the usual: comic shops, Amazon, DC's own website, etc. Since those are older comics, you'll probably find it easier to purchase them online in digital form.
Comment: There is a list of collected editions [here](https://en.wikipedia.org/wiki/Lucifer_(DC_Comics)), but it doesn't include Lucifer's appearances in *Sandman*.
Answer: TL;DR: Read Sandman volume 1, 3, 9; Sandman Presents: Lucifer #1-#3, Lucifer: Nirvana (one-shot) and the Lucifer series by Mike Carey (75 issues) - preferably in this order.
The Sandman volumes are important because they show how Lucifer abandoned Hell and moved to LA to run a nightclub called Lux (which is shown in latest Lucifer television series). The rest of Lucifer's solo career takes place after these events.


Is there anyone making actual physical badges?

Question: Does anybody know of a company or person making physical badges? Like an embroidered patch or something? Sure, it's kind of old school, but some people like to attach pieces of flair to backpacks or whatever.
Comment: Badges!?  *BADGES?!* **WE DON'T NEED NO STEENKIN' BADGES!!!**
Comment: @Pollyanna: http://en.wikipedia.org/wiki/Stinking_badges ... personally i've always preferred the *UHF* rendition: "Badgers?  Badgers?! [...]"
Answer: Making badges is easy. The hard part is implementing badge rights management (BRM) that prevents malicious users from duplicating badges that they haven't earned.
Badge piracy is a serious issue. For every legitimate, physical badge made by hard-working badge manufacturers and developers, there are sixteen (16) illegally created badges in the world.
Fraudulent badges can be identified from their frayed edges, cheap colours that wash out in the rain and increased likelihood of being infused with narcotics and/or bloody pieces of glass. While these badges may be cheaper and easier to find than authentic badges, their quality is nowhere near the same level of standards as the real deal.
So please, if you find a badge that doesn't have the BRM seal on it, please report it to the Badge Manufacturers Association of America (BMAA).
Comment: I hate those posers who wear frayed badges that you *just know* are brand new, like they've been a fan of the site for years.  If it's not Beta or Yearling, it shouldn't be frayed, hipster!
Comment: I didn't think about that. Maybe we need badges that connect to the internet and authenticate themselves every 5 minutes.
Comment: I love your answers and comments... I just do
Comment: There must be a [defective-by-design] joke somewhere in here
Comment: This sounds exactly like what a member of BMAA's propaganda machine would say. What Mr. Posse - if that is his real name -
fails to mention is that there is a plentitude of alternative Badge Making associations - the Association of Caribbean Badge Makers,
the west indies badge manufacturers conglomerate, and the North American Badge Manufacturers' organization (NABMO), to list just a few - united in the struggle against the corporate monster that is the BMAA.
Comment: For years, BMAA has been dominating the badge market using unscrupulous business practices, extortion, extremely high membership fees, and lobbyism in both Washington and Brussels. The BRM seal is only the latest ploy in the BMAA's efforts to achieve total market domination. Their lobbyists are currently trying to pressure democratic lawmakers into introducing legislation making the BRM seal mandatory for *any badge sold in the U.S.*.
Answer: I'm thinking that keeping my SO reputation up to date on a physical badge attached to my backpack is NP-hard.
Comment: Actually, a little LCD with wifi-enabled embedded Linux would probably work on campus, hmmm.... Download the config via USB key.  Maybe it's not so hard after all.   :-)
Comment: badges != flair
Comment: @fretje -- since he referenced flair in the question.  I assumed he meant "blog badges".
Comment: I meant flair in the more general sense, as in a small ornament attached to an object to show one's preference or support for something. Physical badges be flair in this case. I was referring to the "Guru" badge or the "Supporter" badge, not to the blog "flair" that you can put on your website.
Comment: @Bearddo -- ah, I see now. Make sure you put your "Supporter" badge far away from your "Athletic" badge.
Comment: With as much time as I spend in front of a computer I won't be getting any sort of "Athletic" badge anytime soon.


My computer boots to a black screen without press Tab? what can I do to fix it?

Question: My ubuntu is 18.04, and if I boot my computer with the press of the Tab(It just show the purple screen, then display the login screen) and it will boot normally.
But if without press the Tab(This time it just black, and nothing else), my computer will always be a black screen.
I can't figure out what problem is it. Can someone help me?
If you need some more other information, Please let me know?
Comment: Welcome to [ubuntu.se]! Please [edit] your question to specify _when_ you press Tab and what happens. Is it displaying the GRUB menu, for example? Do you then keep the default option in GRUB? Adding some screenshots could help. What's your hardware specification? (I guess it might be related to graphics.)
Answer: I had the same issue.
When your computer starts press
ESC key and it'll take you to the system setup settings with BIOS and everything.
Then select System Recovery ,in mine I had to press F11 for System Recovery it might be different in yours.
You'll then be directed to the Ubuntu advanced settings screen where you can run Ubuntu in recovery mode .
After you run it in recovery , select
Update or remove broken dpkg in grub

Then you'll be get a screen with multiple options select the first option that is install new software and press y for everything.


Whats the purpose of preheating a coffee roaster?

Question: I own a Gene Cafe and was wondering why many across the internet recommend that the roaster is preheated before the roasting takes place, in comparison to the manufacture which claims that one should just add the beans and start the roasting straight away while everything is cold.
Answer: Preheating your Gene Cafe lets you choose between life cycle of the roaster and roasting consistency.  By preheating your roaster, you should be able to get more consistent roast times.  In my case my garage is sometimes 50F and sometimes 80F, so a preheat cycle would certainly probably help.  I don't do it though.  Any machine has a finite number of cycles, and you are shorting that window by preheating your machine.
I roast one and a half pounds a week (a half pound for work, and one pound for home).  The half pound is always done by itself from a cold start.  When I do the pound for home, I do two half pound batches, the first is from a cold start and the second is done immediately following on a "preheated" machine.  I try to aim for the same roast level on each of the batches and the second one consistently needs less time to reach the same level.  I generally set a timer and come back 14 minutes after the start.  This allows me to fine tune the last portion of the batch, on cold batches I generally add a bit of time, and on the preheated ones I end up subtracting a bit (to get the same roast).  I am fine with this as it saves me a cycle and will prolong the life of my roaster.  However, I can see that some folks would want the roast length of two such batches to be much closer to the same at the cost of that extra cycle.  For them it may make sense.
Answer: To keep the temperature consistent probably.
Some energy would be spent on preheating the roaster, and temperature will raise at the beginning from room temperature to roasting temperature. If you preheat the roaster it will be consistent all the time. I'm not sure it will affect the result much though.