C++ Decrease memory page size from 4096 bytes

Question: Now on my system (debianx64)the page size is 4096 bytes. Is there any possibilty to decrease it? I would like to store in memory many small pieces but even for 1 byte reserved I can't use another 4095 because of thing added in 1st message here.
Is it true or am I wrong?
Is it possible to do it?
Thx for replies.
Comment: Duplicate of http://stackoverflow.com/questions/4420891/c-new-new-how-is-it-allocating-memory.
Answer: No.
4096 is the smallest page size provided by the x86 platform. This is a limitation imposed by the CPU. It offers larger sizes (up to 4MB, depending on the mode), but this is normally selected by the operating system at boot time.
What you can do is make a relatively large allocation as the backing store for an object pool. Then if you need many small objects, they can all be stored within a single page or memory region. This is a common idiom for improving performance in memory allocations.
Moreover, most sane memory allocators work this way anyway, so it's not necessary to implement an object pool unless you find in profiling that you need it.
Answer: Page size is an OS-wide item. You can't just create a new page size for your application only since the page-fault logic has to work with all other processes.
I'm not sure what exactly you're attempting to do. I will say that if you're even worried about this issue, then you need to make your software more cache-friendly by storing and accessing memory consecutively, like in an array.
Answer: Page size (which BTW can't be lowered below 4K on x86 platforms) is most likely irrelevant to your situation. If you allocate data on the heap, the question of page size will not arise in the manner you assume.


Expressing a torsion point of an elliptic curve as a combination of the generators

Question: I'm facing the following problem:
Suppose that we have a finite field $\mathbb{F}_p$ and an elliptic curve $E$ defined over it. Suppose that for $m\in \mathbb{Z}$ not multiple of the characteristic of the base field. So we have an isomorphism
$$E[m]\longleftrightarrow (\mathbb{Z}/m\mathbb{Z})^2$$
Suppose we know that
$$E[m]\subset E(\mathbb{F}_q)$$
where $q$ is a power of $p$. Suppose also that we have given generators $P,Q\in E[m]$ and a third point $R\in E[m]$. I want to find $a,b \in [0,m-1]$ for which
$$R=aP+bQ$$
What is the computational cost of this problem? The most efficient algorithm i'm thinking about consists of trying to solve a lot of ECDLP
$$R-aP=bQ$$
where $a\in [0,m-1]$. This of course has a computational cost $O(m\sqrt{m})$ since for the single ECDLP there are algorithm with computational cost $O(\sqrt{m})$.
Thanks to all for your time.
Answer: There's probably an even quicker way, but here's one idea. Compute the Weil pairings $<P,Q>$ and $<R,Q>=<P,Q>^a$ and $<P,R>=<P,Q>^b$. Then you just have to solve the DLP twice in $\mathbb F_q^*$ to find $a$ and $b$, and there are subexponential algorithms for DLP over finite fields. And the Weil pairing is polynomial (essentially linear) time.
Comment: Thank you for your answer and your time. This is very effective way to compute it. Now i have another curiosity: if the 2 points are not known to be the generators of a torsion subgroup, are there effective algorithms solving the "double discrete logarithm" problem:
$$R=aP+bQ$$
Thanks again.


Reference tuning pitch

Question: I was having problems with my bass guitars, fender JB and P bass and an epiphone viola.  After several trips to my local music store, the instruments were checked and I was told they were in tune.  They all checked out on the electronic tuning meter.  However when playing along with cd's, the instruments still didn't sound right.  After a good part of the day experienting, I changed the reference pitch to 445hz.  They all sound perfect, no problems with intonation.  Why are the guitars in tune at 445hz and not at 440hz?
Comment: Could you give some example songs that you're playing along with that sound in tune with 445?
Answer: Post-production often raises the pitch (and increases the tempo) of a recording.  Plus, there is no guarantee that the recording was made at A440 in the first place.  Further, even in classical music, pitch standards vary regionally.  So, it is not surprising that you would find yourself to be out of tune with a recording when you are playing at A440.
If A445 works well with the recordings you are using, go for it.
Answer: Consider the source of your recordings, and the process of recording them.
Maybe, after recording the backing track, the producer decided the whole thing benefited from a slight change of tempo. Changing the playback speed affected the tuning.
Maybe, for the session, the band didn't tune to a reference pitch; they just tuned to each other. I remember in some of the obituaries for Dimebag Darrell of Pantera, it was noted that he didn't use a tuner, or unison tuning; he'd turn the tuners until it sounded right to him. I'm sure plenty of musicians do the same.
Maybe the arrangement includes an instrument that can't be tuned, and which is sharp or flat compared to reference pitch.
Maybe the song contains a sample that itself isn't at standard pitch, or has been sped up or slowed down until it's at a non-standard pitch.
Maybe the basis of the song was played on an instrument with continuous pitch control (fretless bass, upright bass, violin, trombone, washtub bass, voice, etc.), and the rest of the arrangement was pitched to match.
The speed of a recording may have varied in the mastering process, either by accident (on old recordings, the speed of tapes and disk cutting platters might not be well controlled), or on purpose (Jake Riviera of Stiff Records notoriously attended mastering sessions and demanded that singles be sped up, so much so that producers began to send him slowed-down versions to compensate).
So you see, there are many, many reasons why a recording might not be tuned to a A440 standard.
Practical solutions, for playing along:

As you have done, tune your instrument to match the recording
Adjust the pitch of the recording in software, for example Audacity. Audacity has an option to adjust the pitch independent of tempo (with some quality degradation).
Answer: I heard a rumour that one's sense of pitch alters with age. And that aging conductors have over the centuries gradually raised the standard pitch to its present position (when technology intervened). Are you listening to really old guys?
Comment: One's sense of pitch alters with not just age, but also a whole host of other factors such as the state of your body at a given time. I can identify approximate frequencies, but I still need to "calibrate" myself quite often since my sense of pitch can (and does) drift off course.
Comment: Not just a rumor that sense of pitch changes with age, it's observed in people with perfect pitch that their perception of pitch shifts *sharp* - but then we'd expect them to tune flatter as they age, to compensate, not sharp.
Answer: Depends on source.. We used to drop to match the singers pitch in the studio.. Or for a tempo issue..Time constraints, etc..(analog days)..

Reference tuning pitch


Why is angular velocity the same for all points on a spinning disk, even though they are at different radii from the center?

Question: Why is angular velocity the same for all points on a spinning disk, even though they are at different radii from the center?
Comment: Question titles should be like book titles. They distinguish the book from other books, give a hint about the content, but do not tell the full story. The content then should elaborate the topic to full depth the author is able to do.
Comment: Question titles should not be like book titles. They should give as much information about the question as possible within the space limits. This title does not seem too long to me.
Comment: Because the concept of angular (versus linear) velocity was introduced in order to describe the phenomenon of a rotating rigid disk
Comment: I've removed a number of comments that were attempting to answer the question and/or responses to them. Commenters, please keep in mind that comments should be used for suggesting improvements and requesting clarification on the question, not for answering.
Answer: Because angular velocity is measured in radians per second. Every point on a spinning disk along a radial line from the centre completes one full revolution ($2\pi$ radians) in exactly the same amount of time. You are confusing tangential velocity with angular velocity, tangential velocity is different at every point along the same radial line.
Answer:
The angular velocity $\omega$ is quite literally the rate of change of the angle $\theta$:
$$\omega=\frac{\text{d}\theta}{\text{d}t}$$
Clearly it is independent of radius.
The tangential velocity of the point $P$ however is dependent on the radius:
$$v_P=\omega R(P)$$
Answer: Yes. Angular velocity is a property of the body or the reference frame and it does not depend on the location where it is measured.
Since it can be defined without any location information, the rotational velocity vector $\boldsymbol{\omega}$ is pure vector conveying only magnitude and direction.
This is to contrast with translational velocity $\boldsymbol{v}$, which must be defined at a position to have meaning. And in general translational velocity varies by location.
$$\boldsymbol{v}_A = \boldsymbol{v}_B + \boldsymbol{\omega} \times \boldsymbol{r}_{A/B} $$
The exception being a pure translation where all the points on a body have the same value. But that is just a special case.
In fact, to know where a body is rotating about (the axis of zero velocity) you need to consider both rotational and translational velocity.
$$\boldsymbol{r}_{\rm axis} = \frac{ \boldsymbol{\omega} \times \boldsymbol{v} }{ \| \boldsymbol{\omega} \|^2 } $$

Momentum $\boldsymbol{p}$ is another pure vector, where a body has momentum and there is no need for defining the location of where momentum is measured.
Angular momentum $\boldsymbol{L}$, on the other hand, needs location specification, you measure it at different points using a similar law
$$\boldsymbol{L}_A = \boldsymbol{L}_B + \boldsymbol{p} \times \boldsymbol{r}_{A/B} $$
Similarly the line of action of momentum ,where angular momentum is zero is found when considering both linear and angular vectors at the same time.
$$\boldsymbol{r}_{\rm axis} = \frac{ \boldsymbol{p} \times \boldsymbol{L}}{\| \boldsymbol{p} \|^2} $$
Answer: To understand the reason, one should be knowing that the angular velocity of a point on a rotating body is the angle swept per unit time by the straight line joining that point to the center of rotation.
It is worth noticing that the line joining each point on a spinning disk to the center of rotation/spin sweeps an equal angle in equal time interval irrespective of the radial distance of concerned point on spinning disk. Therefore the angular velocity remains constant for each and every point on a spinning disk.
Let there be a disk spinning about its center O.  Consider any two arbitrary points say A & B at radial distances $r_1 $  & $r_2$ respectively such that at start of spinning, the angle between the line OA & X-axis is $\alpha$ & angle between lines OA & OB is $\beta$. Now let the disk spin uniformly through an angle $\theta$ over time $t$ .

Then the angular velocities of points A & B are given as
$$\omega_A=\frac{\text{Angle swept by line OA}}{\text{Time taken}}=\frac{\alpha+\theta-\alpha}{t}=\frac{\theta}{t}$$
$$\omega_B=\frac{\text{Angle swept by line OB}}{\text{Time taken}}=\frac{\alpha+\beta+\theta-(\alpha+\beta)}{t}=\frac{\theta}{t}$$   Thus the angular velocities of points A & B at different radial distances are equal i.e. $\omega_A=\omega_B$
Answer: Everybody standing on a turntable will be rotating at the same rate (they will face the north wall the same number of times every second, for example) even though they are moving at different speeds.
Answer: If you also think about it intuitively, you will notice that the angle traveled for an object along a circular object is will the same no matter how far or close it is to the center. It is true that the arc length changes as the radius increases, however, that is what is known as tangential velocity. So since the radius has no play in the size of an angle, angular velocity doesn't change because of the radius.


Why do the terms "large scale" and "small scale" seem to swap meanings?

Question: Sometimes when someone says a map is "small scale", it seems to mean a map shows a small area, but the things are drawn large as a result, and other times it means the things in the map are shown much smaller, allowing for a large area to be shown.
Answer: It's the difference between scale and scope.
In cartography jargon, "scale" is the ratio between the actual size of something, and how it appears on the map.
If a road is 10 km long in real life, and is 10 cm long on the map, then the scale map is 1/100,000 times the size of the real world. The scale is 1:100,000.
If the road is 20 cm long, then it is 1/50,000 times the size of real life, and the scale is 1:50,000.
1/50,000 is a larger number than 1/100,000 (it's twice as big) and so we say it's a larger scale.
In everyday speech, however, we tend to use "scale" to refer to the scope of something.  And in this sense, a map that covers a larger area has a larger "scale".  This is where the confusion comes in.  To those unfamiliar with cartography or geometry, the "scope" meaning seems more natural but for those trained in the field, the more precise use of scale to mean the scale ratio is normal.
Cartographers do have another term, "extent" which means how big the area covered is, along with where it is.  This is closer to what non-cartographers usually mean by "scale".
Comment: Nice explanation, thanks! ....For your information, you can write a question and an answer at the same time, by clicking the "Answer your own question" box at the bottom of the "Ask Question" page. +1 +1 :)
Comment: @Shokhet Yes, that was what I'd intended but I forgot to check the box.
Comment: Yeah, I noticed the timestamps were different :) (*I've done the same myself on other SE sites*)


What is a word or expression to define that you have reached the limit of your capabilities?

Question: I am referring to the stage where someone  reaches his/her capabilities limits, especially  professional limits. I am thinking about career advancements as well as the growth in professional life. We all reach our limit in that progress and going further would be unnatural or might put us in a difficult position because we are not able to cope with a higher level of abilities or responsibilities. Is there a word or expression to define this limit in personal progress?
Answer: Medica's answer pointing to the Peter Principle is on the money, however just to add a phrase or two...
colloquially: maxed out, plateaued, sweet spot
Having "risen to his level of incompetence" refers to having gone beyond Jack's referred to territory of competence. "Out of his depths" would similarly express having risen above that territory.
Comment: +1 On the affirmative side, you could say *She's reached her pinnacle* (or *the pinnacle of her success*).
Answer: Actually, you are describing the Peter Principle to a "T".

The Peter Principle is the principle that "in a hierarchy every employee tends to rise to their level of incompetence".

Formulated by Dr. Laurence J. Peter and Raymond Hull in the late 60's,

The Peter Principle is a special case of a ubiquitous observation: anything that works will be used in progressively more challenging applications until it fails.  There is much temptation to use what has worked before, even when it may exceed its effective scope. Dr. Peter observed this about humans.
[Similarly] members of a hierarchical organization eventually are promoted to their highest level of competence, after which further promotion raises them to incompetence. That level is the employee's "level of incompetence" where the employee has no chance of further promotion, thus reaching their career's ceiling in an organization.

The Principle further states that the work of that person who has reached their level of incompetence tends to be done by those below him who are better equipped. Managing upward is the idea that a better-suited subordinate finds ways to subtly "manage" superiors in order to limit the damage that they end up doing.

The employee's incompetence is not necessarily exposed as a result of the higher-ranking position being more difficult — simply, that job is different from the job in which the employee previously excelled, and thus requires different work skills, which the employee may not possess. For example, a factory worker's excellence in their job can earn them promotion to manager, at which point the skills that earned them their promotion no longer apply to their job.

On an very public level, the disastrous response by FEMA to Hurricane Katrina was shown to be the result of FEMA Director Michael D. Brown's being a victim of a poor promotion. Brown had excelled in his previous position, and naturally was given a job with greater responsibilities by President G.W. Bush.

Brown was vilified by the media, but it's difficult not to commiserate with him. He was good at his previous job, and -- as is dictated by the American Dream -- when offered a position with more prestige, salary and potential for growth, he took it. The person who gave him the job had faith in his abilities, so why shouldn't he take the job? But Brown proves that a promotion isn't always a good thing.

This seems to match well your statement that "We all reach our limit in that progress and going further would be unnatural or might put us in a difficult position because we are not able to cope with a higher level of abilities or responsibilities.
Whether it has a more succinct or different name, I don't know. I've only ever heard this referred to as the Peter Principle.
You might describe it non-specifically: you've exhausted your potential, reached your limits of expertise, you'll be in over your head, etc.
Comment: I have to disagree. The PP is that you've been promoted _beyond_ the zone at which you're competent and can be useful, into a zone where you're out of your depth, doing more damage than good. That doesn't sound like the OP case, where it sounds like you are in a zone where you are at maximum effectiveness, and any promotion _beyond_ that would make you leave your effective zone. Anyway, the OP needs to define whether the person in question is actually still in their "effective" zone, or has been promoted beyond it into an "ineffective" zone (and the PP has come into play).
Comment: At this point the employee is "out of their depth" or "in too deep"
Comment: @PhilPerry Hmm, you're right. The OP recognized he's on the threshold of the Peter Principle.
Comment: From the OP "We all reach our limit ... going further would be unnatural or might put us in a difficult position because we are not able to cope with a higher level."
Answer: I have reached a peak in my career.
Comment: Alternately, "I've peaked".
Comment: This isn't a bad example, but could be expanded.
Comment: The question is so simple, and the answer so obvious (i.e., this answer), it's hard to see how it could be expanded.  (Perhaps just by googling for 100000 examples.)
Answer:
Fulfilled your potential

That might be the most neutral, least provocative way of expressing this idea.

maxed out and plateaued

Are good suggestions from @MarkKasson, although they may be slightly pejorative.

sweet spot

Also from @MarkKasson's answer, is not correct IMO. This expression has nothing to do with reaching a limit - it simply means you've gotten something "exactly right"; "the stars were perfectly aligned"; "everything came together".
Comment: haha I tldr'd that one, so you get the rep!
Comment: @MarkKasson _I may have to downvote myself_ - no need to go to extremes! You could edit though, if you care to. I didn't downvote you. In particular, _plateaued_ is excellent. I just upvoted you for that one.
Comment: @BigHomie _maxed out_ is not mine! It's from the first answer, as cited in my answer.
Comment: Vector, in hindsight, you're right regarding "sweet spot" when taken literally.  I was thinking of using it a bit more euphemistically (perhaps even sarcastically).  Not a proper answer for OP though.  I may have to downvote myself.
Answer: Jack,
I am thinking about career advancements as well as the growth in professional life.
The Peter Principle is way off. You are describing a situation where you want to progress, right? Also, you say that it is 'personal progress'...?
Personal Progress
If you are concerned about your own personal abilities to become a person who can learn to advance, or adapt to the demands of being more creative/organized/productive, then that is a personal development issue. You might be frazzled at your limit, and raising the bar might make you feel worse, as you would feel you couldn't perform at 100% even with your best efforts...
Professional Progress
If you are concerned about your career being stonewalled, or hitting a dead end, or any of the other terms, then it is a matter of being the kind of person that will fill any void of opportunity. That is, you will get bored/sloppy/lazy if you go to work on auto-pilot.
I see a lot of folks stay in one position forever. They have a job. Others are completely unsatisfied where they are, and are continually moving up... They have a career.
Avoiding the risk of pissing off the moderators for ending an answer with a question mark (however professional/polite it is):
Ask yourself what type of person you are, and you will know what kind of professional you are.
pat
:)
Answer: You might say that one has reached their capacity to improve.
Comment: Not a terrible answer.


Why don't gas pumps spark and explode?

Question: What Electrostatic Discharge (ESD) protections exist in the gas pumps at gas stations?  I believe that here more than ever even one spark is intolerable.  How can a it be assured that there is never any potential difference between a car and the gas pump that would cause voltage to arc from the gas tank to the pump when inserting the hose?
Comment: It helps when the pump is not located in or near a Hollywood film set.
Answer: photos here  In fact, they do spark and explode!
A sign that tells you how to to behave is the only obvious protection I can see, though maybe there's hidden stuff behind the scenes.  Personally, I think some sort of affordance that forces users to touch a grounded piece of metal before pumping would help a bunch.  In the olden days, we'd always have to flip some form of mechanical lever to enable the pump and reset the price tally from the person who pumped before us, so this is probably doable.
I think a flame detector in the pump handle that cut off the gas flow might prove useful, too.  The really bad accidents occur when the fumes flash over and somebody panics and removes the still-pumping handle.
At many of the gas stations I've used, they remove the clip that keeps the handle pressed down, so you're forced to hold on to the handle to keep pumping gas.  It puts an end to the messing around to build up static, but I don't like this approach.  Instead of making me hold down the handle, it just encourages me to use other gas stations that leave the retention clips in place.
Answer: Basically it's because everything is static dissipative.  i.e. conductive, but not highly so, but sufficient to ensure that any charge gets bled off.  Even the concrete being poured is slightly conductive.
This reminds me of a homework question in EM theory that talks about the need to have ground clamps on aircraft whilst pumping fuel because of the charge build up from fuel in the hose being ionized (from gamma rays etc.) on the way to the plane and thus pumping charge into the plane.  When the nozzle is removed you get a spark.
Answer: Not to say it doesn't happen, of course, but the problem may not be as serious as you think. An explosion only happens if the fuel/air mixture is just right, which isn't that common at gas stations, or we'd hear about a lot more explosions.
Instead of trying to ground the car, the pump, and the user without creating a spark near the pump, a better approach might be to have some sort of sensor that sounds an alarm in the presence of dangerously high concentrations of gasoline fumes in the air.
Comment: You don't need an explosion. A fire is bad enough. Gasoline vapors are very flammable.
Comment: Amusingly, since answering this question five years ago I have become a CFEI, so I can answer this a little more definitively now!

You're not going to get a fire from gasoline vapors unless the vapor concentration is in a particular range; below the lower explosive limit, there's not enough fuel to burn, and above the upper explosive limit there's not enough oxygen.  So as long as you keep the fuel/air mix below a particular range, you won't see combustion from gasoline fumes.
Answer: I am of an understanding there is a Ground wire in the delivery hose.
Much the same as the cable found in washing machine fill hoses.
A static danger does exist while filling a gasoline container,
so a warning sign is posted at the pump island,
to place the container on the cement or a specifically designed holder.
I have seen people smoking while pumping gas, to read the "No Smoking" sign.
Remove the cigarette from their mouth, and discard it in a puddle of spilled gas.

Why don't gas pumps spark and explode?


VirtualBox with existing operating system

Question: So my laptop is set up for dual-booting, Windows 7 and Ubuntu Linux 10.04. There are certain applications in which I want to access Windows from Linux. Is there a way to do this using VirtualBox? Everything I've read involves booting from an ISO or something, but is there a way to boot from an existing drive (the one that has Windows 7 installed on it)? I currently get the error message, FATAL: No bootable medium found
Answer: You need to set up a bootloader and tell it how to find that partition when running inside VirtualBox.
There is some info here.
Comment: the link is dead
Answer: I've tried to set this up a few times but I never got it to work or even (as far as I remember) found any evidence that it's been successfully done. The reason is that when you install Windows, it customizes itself to the hardware configuration of the computer you install it on. If you try to run it on completely different hardware, it won't boot up.
This is a problem because VirtualBox has its own "virtual hardware" that it uses to run the operating system - that is, when Windows (running on a VM) tries to access information about, say, the graphics card, it gets the information about the virtual graphics card provided by VirtualBox, not the real graphics card. Same with the CPU, RAM, etc. So the Windows from your hard drive won't be able to run on the different "hardware" of the virtual machine.
Windows XP had a feature which allowed it to store different hardware profiles, so that you could get it to run on multiple different computers, or on a physical computer and a VM. But that feature was removed in Vista.
Answer: If you want to be able to run Windows programs within Linux, take a look at Wine. You can use VirtualBox to do that, but Wine has less overhead because you aren't running a full virtual machine.
Answer: They call this Raw Disk Booting. This is sort of a last resort though. Before you resort to this, try finding a Linux counterpart, running wine, or even offloading its function to another device or tool.


Word to describe a character who is famous but misunderstood or taken out of context

Question: The best example I can think of at the moment is Frankenstein's monster from Mary Shelley's Frankenstein. Many people know of the existence of this character well enough to allude to it (though usually erroneously by the name of its creator) at times when they see or imagine a grotesque being. However, if one actually knew the story, they probably would see more in the character than just its grotesqueness (despite it being a major trait, even in the eyes of Frankenstein the creator), as it has a story of its own. Yet most people (who I assume haven't encountered the story in any comprehensive form) seem to remember the character only for that one trait alone, more than even its name. How do you describe a character like Frankenstein's monster that's popularly referred to but misunderstood or taken out of context? For example, "Frankenstein's monster has become something of a ________ character."
Answer: There is nothing wrong with the word "misunderstood" in your context. This website among many others uses the term "misunderstood characters". The term carries all the implications of hidden depth, better motivation, being more sympathetic than people think and so on that you want.
Answer: One word is caricature:

[Merriam-Webster]
1 : exaggeration by means of often ludicrous distortion of parts or characteristics • drew a caricature of the president
2 : a representation especially in literature or art that has the qualities of caricature • His performance in the film was a caricature of a hard-boiled detective.

So, your example sentence would look something like:

The public image of Frankenstein's monster has become something of a caricature of the actual character in the novel.

I always found it somewhat strange that while literature and art often exaggerate something from real life, in this case it's real life (and movies, another form or art) that is exaggerating something from literature itself.
Comment: You've nailed it with this one. +1
Answer: One-dimensional would work in some cases. It doesn't mean they got it wrong, just disingenuously oversimplified.

2 : lacking depth : superficial
   one-dimensional characters

"One-dimensional." Merriam-Webster.com. Merriam-Webster, n.d. Web. 2 Sept. 2018.


why does the PEWDIEPIE'S TUBE SIMULATOR didn't save the current game?

Question: When I am playing the pewdiepie's game, I already reach the level 11 of the game and suddenly I decided to restart my phone due to the laggy thing of the phone, then when I try to open it up again (the app) I didn't see the level 11 game that I played before, it starts again in the beginning. What should I do and why does this error happens?
Comment: @RudolfL.Jelínek No.  Please stop duping everything to yours.  It should all be duped to the original.
Answer: My guess is that you were logged out and the game didn't log you back in (The data is probably saved online), if you log in again you should get your data back. If you go to the "Social" tab (which is the speech bubble with a blue and pink person piece), there should be a button that says "Link accounts", I recommend trying that out. I haven't tested it myself, but that's the most probable resolution.
Answer: It depends on if you had linked the account or not. If you hadn't, then unfortunately you would be out of luck. If you had, though, then you would need to go to the Social tab (the blue one with a speech bubble) and click Link Accounts, then 'This is my new device', then Android, then yes to the prompt.


How long does Netz last?

Question: If one wants to daven Netz (at sunrise) how long of a period does one have to have caught this time? Is it only a few seconds, or longer?
Comment: Surely this depends on latitude/season
Answer: The actual length of Netz is a little more than 2 minutes.
The MB in Biur Halacha 58:1 sv Kemo indicates that the time is at the beginning of Netz. (He also discusses the shita of the Rema who says Netz is about an hour, which he finds hard to explain based on facts. The Gr"a says it's typo)
The Ish Matzliach in the middle of an extremely long Teshuva, (in the linked page, start at the bold words and go as long as you can) brings this time down, with all the different opinions if the time to start is at the beginning, in middle, or end of the Netz.
Practically speaking the Pnenei Halacha says the custom is to try to catch the beginning of Netz but not to be too overly concerned since there are plenty of opinions that give more time.
Comment: it's definitely not a typo in the rama, see darkei moshe who cites and explicitly makes fun of the girsa the gra supports; you can try to disagree with the rama but you can't pretend that opinion wasn't alive and well 500 years ago.
Comment: the gra (and most people nowadays) think like modern astronomers so they don't understand how the rishonim's words fit with the metzius and hence are too quick to reject lots of traditional sources. it's like the rishonim were speaking a different language: of course it doesn't take an hour for the disk of the sun to come over the horizon, but that's obviously not what rishonim meant by 'sunrise'.
Comment: Regardless of the time that Rema mentioned, the M"A says, and the Machtzis Hashekel and Levushei Serad explain, that the time to daven would be at the beginning of Netz and according to the other opinions it might be at the end of Netz which is only a few minutes later. So for this question, about when to daven, the hour long mentioned by Rema is irrelevant since nobody says that davening an hour after sunrise is still Netz.
Comment: Depending which opinion you're holding like of what the goal of davening netz is. We have a machloket rishonim if it's tefilla or shema that's supposed to be at netz and furthermore a machloket of if the goal is to start right away or just to have the two things on the right two sides of that line. For the one girsa the rambam is giving the longer time for his view of shema being before netz, but for the other opinions you may indeed have much longer. (like consider https://mi.yodeya.com/a/118891/759 even if shema isn't before netz it could still be worth praying the amida during netz)
Comment: Anyway the rama isn't saying an hour after what you call sunrise is still netz. That's the whole point. Your two minutes are just somewhere in his hour.

How long does Netz last?


pattern for filling uitableview from results of async nsconnection call

Question: I'm struggling to understand the correct model.
I have a uitableview full of rows of data.
The data is the result of a REST call, which depends on the result of a previous REST call.
So in my appDelegate didFinishLaunchingWithOptions: method I'm making an NSURLConnection for the first REST call and then getting the results back in didReceiveData: delegate method.
When that's finished, I need to make a second rest call - so I'm doing that in the connectionDidFinishLoading: method of the first REST call; which in itself feels wrong - but i don't know how else to only do it when the first REST call has finished (without multi-threading and synchronizing which seems overkill given how powerful this stuff is).
So then i get the xml back from the second REST call and build up my data objects ready for the UITableView:cellAtIndexPath: delegate method.
But - the UI is already drawn before the data objects are populated - so i can't figure out where to put in a spinner, and how to synchronise on the connectionDidFinishLaunching: message of the second REST call
.
does that makes sense? IT's really a pattern question, more than a code question - but i can't find a good example.
regards,
Richard
Answer: Ah.
So it's [self reloadData].
I was thinking it was going to work like Adobe Flex; where the table is bound to the dataSource - and a change in the dataSource changes what the table shows.
but no - I just need to tell the UITableView to reload its data once i've populated the array/data.
So I'll answer myself.


Does running a PID Autotune with an increased cycle count result in more accurate PID values?

Question: I'm using the mriscoc firmware for Creality Ender 3 V2. The firmware has the option to run more PID Autotune cycles. The default is 5 cycles. Does running a PID Autotune with an increased cycle count result in more accurate PID values? For example running 50 cycles instead of the default 5?
Answer: In short, yes, More PID cycles will generally yield 'better' results.
However, the PID values are being averaged over these multiple runs, and it will very quickly pass the point of diminishing returns after 5 cycles, Hence why it is the default.
By the time you reach the hypothetical 50 cycles, you have likely far exceeded the margin of error present as a result of tolerances in your setup, and are only averaging noise.
Comment: An interesting question that may arise from your answer is why better results are generated by doing more than one cycle.


Naan without tandoor?

Question: I miss Indian food and especially good naan bread. I haven't really tried it, but I wanted to test if it's possible to make naan without a tandoor? Has anyone tried this, do you have some good tips and do you manage to make it just as good as the naan you get in India?
Answer: Never having been to India, I've only had naan from Indian restaurants and frozen from the supermarket. That said, I have made it with some success before.
The best method I've used is to grill (American) it. You can do it with a gas grill (barbecue) set to high, or with the hottest of hot charcoal. It doesn't quite approach the 900 F (480 C) typical of a tandoor, but it's close, especially with charcoal. Simply oil the grill and do 2-3 minutes per side.
The next best method I've tried is using a pizza stone in a blazing hot oven. The cook times are similar.
Comment: I second the pizza stone idea; it works a treat for me.
Comment: True.  It depends on the size of the grill.
Comment: In the US, at least, the typical pizza stone would occlude at least 80% of most grills.
Comment: What about a pizza stone on the grill?
Comment: @chris: I've never tried it. However, I imagine that it would significantly restrict the airflow over the coals and thus result in a significantly lower temperature.
Comment: Chris, you can't make classic pizza's in a domestic oven due to the limit on the sheer temperature the oven can reach. Due to this lower heat, the pizza base tends to come out 'biscuity' rather than crisp on the outside and chewy on the inside. It's a heat thing, domestic ovens just don't get hot enough.
Comment: Here is a link to Kenji Alt's article on making naan at home with a grill:  http://www.seriouseats.com/2011/08/the-food-lab-how-to-sort-of-make-naan-at-home.html?ref=obinsite
Answer: If it's something you want to eat often, you could make your own tandoor, or use a large terracotta pot over your charcoal grill.
Comment: If you do decide to build a tandoor like crazy Alton Brown, _do not_ forget those gloves. Reaching over a 900 degree jet engine is not comfortable at all.
Comment: @hobodave - And burning arm hair really stinks.
Answer: Although it doesn't simulate a tandoor, I stopped my quest for making the best naan after seeing the result from a Dutch oven on max heat. Fantastic. Lid on keeps the moisture in and stops it from going too crispy or hard, it bubbles up and parts of it get that slight charring.
Use a cheap Dutch oven as the charring marked my expensive one.
Try it, you'll be surprised!
I assume you're making the dough. I had a friend who tried it and said it wasn't that great. Then they were simply reheating those cardboard pre-packaged things.
Comment: Note that in some English speaking countries such as the UK/Aus/NZ, a "Dutch oven" is called a "casserole".
Answer: Yes, you can make perfectly acceptable naan breads without the need for a tandoori oven.
The keys are very high heat, ie under a domestic grill (watch while they puff up and brown) and yoghurt. You can also make them with baking powder without the need for yeast, which produces surprisingly good results.
Answer: I've made naan on a (propane, american) grill with no problems, straight on the grate.  (maybe singed a little bit, that's what you want for naan).  Well, no problem grilling; I rolled them all out while I was still inside, and had them stacked up with dry waxed paper between them, and the weight of the stack meant that by the time I got maybe 5-6 of 'em done, the whole stack had glued itself together, which slowed me down quite a bit.
I've also done it stovetop in a cast iron pan to get a good sear, and then transfered to the oven to finish cooking while I made up the rest.  As I was rolling 'em as I went, I didn't have that sticking problem.
Comment: I do pita bread on the grill, and I also use wax paper to carry the bread outside. It helps a lot if you lightly dust each layer of wax paper with flour before slapping the pita on, and the top of the pita before the next layer of wax paper.
Answer: I have tried baking with a pizza stone and tiles in the oven, but I get the best results from frying the naan in a cast-iron pan that has been lightly greased with oil on medium-high heat.
I admit that this is very far from a tandoor, but surprisingly naan that was fried turned out way better in terms of texture, air-bubbles, and flavour.
Admittedly I have never grilled it because I only cook one or two loaves at a time (keeping the dough in the fridge until it runs out), so I can't really justify firing up a charcoal grill.
Answer: I miss my naan and gave up cooking it at home when I found I couldn't replicate it.
However, I did find roti-chapatis that you can cook in seconds on a skillet and come out very tasty and fresh, despite keeping forever in the fridge.
It's still indian bread, very tasty, and not totally disimilar. I filled my need when cooking curry at home.
Answer: We can make naan at home on tawa and get the same look and taste too.
INGREDIENTS:
Wheat flour (Maida), 1 TSP curd, water, pinch of salt, 1 TSP ghee or butter
STEPS:
1. Mix all the ingredients and make a soft dough
2. Cover it with a muslin cloth and rest for 2 hours
3. Take a piece of dough, make it round
4. Roll it like a chapati and grease some butter or ghee and make a triangle
5. Now roll the triangle chapati
6. grease water on one side of naan
7. let the tawa or flat pan become a bit hot
8. place the watered side of naan on the tawa
9. let it be for 30 seconds
10. with help of tongs reverse the side of tawa/flat pan on the flame and try to provide flame to all sides of the naan and it will come out automatically.
11. The watered naan will have the same crust which a tandoor provides.
Answer: The best way is :- once you have your rolled out naans, wet one side with water then place the watered side6on a hot cast iro or similar tawra. Wait till you see bubbles appearing then flip the pan over, the naan will stay stuck to the pan, then put the inverted pan including tge bread over the flame. Wait till you get tge desired blistering and it's done. Good luck
Answer: If you have a chapati pan and a gas grill then you can have a good go.  I think the secret to naan is that both sides have to cook at the same time, so if you get the pan very hot and then put your naan under a preheated grill, that's probably the closest you'll get without a tandoor.

Naan without tandoor?


Elementary Diophantine equation

Question: Solve $(x+y)(xy+1)=2^z$ in positive integres. My attempts is to use $x+y=2^a$, $xy=2^b-1$ and therefore $x,y$ are the roots of the quadratic equation $w^2-2^aw+2^b-1=0$. I try to analyze its dicriminant but it seems to be a dead end...
Comment: As I understand it, this question is equivalent to asking when $2^{2(a-1)} - 2^b + 1$ is a perfect square, with $a,b \in \mathbb{N}$.
Comment: Jyrki's comment under their answer has basically demonstrated the way to translate the language of abstract algebra into a purely elementary one. This bounty is rather meaningless.
Comment: @Saad : right ! and how come Jyrki's solution has never been accepted :-( ?
Answer: You have a good start in using uniqueness of factorization.
Because $xy+1\ge x+y$, we have $b\ge a$. Therefore $xy\equiv-1\pmod{2^a}$. As we also have $x\equiv-y\pmod{2^a}$, we can conclude that
$$
x^2\equiv-xy\equiv1\pmod{2^a}.
$$
Assume that $a\ge3$. Then we know that the group $\mathbb{Z}_{2^a}^{\times}$ of units of this residue class ring is isomorphic to $C_2\times C_{2^{a-2}}$. Therefore there are exactly four elements of order two in this group, and they are easily seen to be the residue classes of $\pm1$ and $\pm1+2^{a-1}$. The same reasoning applies to $y$. As we know that $0<x,y<2^a=x+y$, the remaining possibilities are $\{x,y\}=\{1,2^a-1\}$ and $\{x,y\}=\{2^{a-1}-1,2^{a-1}+1\}$.
Both of these work, the first choice leads to $b=a$ the latter to $b=2a-2$.
I leave the cases $a<3$ to you.
Comment: If you want to avoid the use of that bit of group theory, then you can simply verify that if $2^\ell$ is the highest power of two dividing either $x-1$ or $x+1$, then $2^{\ell+1}$ is the highest power of two dividing $x^2-1$.
Comment: @Douglas: To each $a$ there are two possibilities for $b$ - corresponding to the two $\{x,y\}$ pairs. I edited the answer to make this clearer.
Comment: In your hint $b$ hardly appears whereas you reduce mod $2^a$. Is $b$ uniquely determined by $a$ and the condition that $x$ and $y$ are integers?
Answer: Hint: Your idea will work. The discriminant is $2^{2a} -4(2^b-1)$. For simplicity divide by $4$. We get $2^{2c}-4\cdot 2^b+1$. Now an analysis of size will bring the problem down to small cases. A useful fact is that there is no perfect square strictly between $x^2$ and $(x+1)^2$.
Answer: ETA: Jyrki's answer and comments already says this it turns out, and so he really should get the bounty.
Let $x$ and $y$ be positive integers satisfying $x+y\ge 16$. Then $x+y$ must be a power of $2$. Write then, $x+y=2^a$ for some $a \ge 4$. Then $xy+1$ must also be a power of $2$, and as the strict inequality $xy+1 \ge x+y$ for all such $x,y$, it follows that
$$xy+1=(2^a-y)y+1 =2^b$$ $$= 2^ay -y^2+1,$$ where $b$ is an integer satisfying $b>a$. And so $2^a| (y^2-1)$. So from this it follows that $2^{a-1}$ divides one of $y+1, y-1$ [because $4$ can only divide one of $y+1,y-1$]. Likewise, $2^{a-1}$ divides one of $x-1,x+1$. So from this one can deduce WLOG that $2^{a-1}$ divides $y+1$ and $2^{a-1}$ divides $x-1$, as this is the only way $x$ and $y$ can sum to something that is $0$ mod $2^a$. As $x+y=2^a$ and both $x$ and $y$ are nonnegative integers, it follows that $x$ and $y$ must respectively satisfy either the equations $x=2^{a-1}+1$ and $y=2^{a-1}-1$, or $y=2^a-1$ and $x=1$.
However, for each positive integer $a  \ge 4$, note that if on the one hand either $x$ and $y$ satisfy the respective equations $x=2^{a-1}+1$ and $y=2^{a-1}-1$, then $(x,y,z)$, with $z=3a-2$, is a solution: $$(x+y)(xy+1)=2^a((2^{2a-2}-1)+1) = 2^{3a-2}.$$ If on the other hand $x=1$ and $y=2^a-1$ then $(x,y,z)$, with $z=2a$ is also a solution: $$(x+y)(xy+1)=(1+y)(1+y)$$ $$=2^a×2^a =2^{2a}.$$
Comment: Thanks for the not so academic solution: I will give Jyrki the bounty as you suggest. Have  a nice day
Comment: you reason for $x+y>=16$ and $a>=4$, but, does same reasoning not hold for $x+y>=8$ and $a>=3$ as well (i.e.: to find (3,5,7)) [where $x<=y$]? Finally if one considers positive to mean greater or equal to $0$ there are solutions (0,2^n,n) too. Current aswers seem to consider positive to mean strictly greater than $0$, which is fine.
Comment: @FirstNameLastName, yeah, my condition $x+y \le 16$ is not really needed, I just put it in to be safe. But yes, $(x,y)=(1,1)$ works, as does $(x,y)=(1,3)$, and $(x,y)=(1,7), (3,5)$ works.
Comment: Actually $x+y \le xy+1$ for any positive integers $x,y$. This can be readily checked; assume WLOG $x\ge y$. Then if $y=1$ then $xy+1=x+1=x+y$, and if $y\ge 2$ then $xy +1  \ge 2x +1 =x+x+1 > x+y$.
Answer: The idea of discriminant works nicely, as @Jyrki, @Andre and @Mike answered. Yet, I think of another (perhaps more "number theory"ish :) way.

First, the equation is symmetric in $x$ and $y$, hence without loss of generality, we assume $x\ge y$.

Since $xy+1$ divides $2^z$ and is not equal to $1$, then it should be even, meaning that $x$ and $y$ should both be odd. Let $x=2a+1$ and $y=2b+1$. A replacement yields
$$
4(a+b+1)(2ab+a+b+1)=2^z.
$$
Since $a+b+1$ is a power of $2$, $2ab+a+b+1$ will too be another power of $2$ only if $2ab=a+b+1$ or $2ab=0$ (a simple proof follows from assuming contrary). The latter case yields $b=0$ (or $a=0$) which means $y=1$ and $(x+1)^2=2^z$. Therefore, a set of solutions is found among $(x,y,z)=(2^u-1,1,2u)$ (and obviously $(x,y,z)=(1,2^u-1,2u)$). The former case yields
$$
{2ab=a+b+1\implies
\\(2a-1)(2b-1)=3\implies
\\(x-2)(y-2)=3\implies
\\x=5,y=3\implies z=7
\\\text{ or }
\\x=3,y=5\implies z=7
}.
$$

In conclusion, all the solutions are
$$
(x,y,z){\in
\left\{(2^u-1,1,2u):u\in\Bbb N\right\}
\\\cup
\left\{(1,2^u-1,2u):u\in\Bbb N\right\}
\\\cup
\left\{(3,5,7),(5,3,7)\right\}
}
$$
Comment: Actually : any $(x,y)=(2^n-1,2^n+1)$ gives a solution where $z=3*n+1$. Proving these are only ones for $1<x<=y$ in a simple way is the harder part.
Comment: You are right. The part saying "...only if $2ab=a+b+1$ or $2ab=0$ ..." gives a subset of solutions. I don't currently know whether or not it's possible the solve for the general case as easily, so I'll spend some time later to find it out. Anyway, thanks for the nice comment on my reply.

Elementary Diophantine equation


How can I find all of the domain names owned by a company?

Question: What tools or techniques can I use to find all of the domain names owned by a company?  A paper or guide would also be beneficial.  I don't think there is one solution to this problem,  so I'm curious as to your ideas on the topic.
Comment: Download all the whois data for all top level domains and grep for the company name. Otherwise, call whoever is responsible for domain registrations at that company and ask them.
Answer: These are more unsorted thoughts than an actual answer, but they may provide some information.

There is no official way for outsiders to find all the domains belonging to an owner, at least not for any of the big TLDs. But I think I saw a country TLD once (a very small country) that allowed searching for owner handles and domains that belonged to that person - this may be the case for a few TLDs. Most however do not allow reverse searching for owners.
There are third-party services that make a living from sifting through the web and building a backward searchable domain database. @plua links to one of them; here is a bunch of others. I know of no free service. I have seen companies that provide these services for the .com/.net/.org TLDs and for .de, not sure whether they exist for every TLD out there.
Many .com registrars offer protected registrations that are not traceable to their real owner at all. British .co.uk addresses can be completely anonymized to the public. Obviously, you will not be able to trace the real owner in these cases. Contrary to that, you have it fairly easy in Germany: The owner info is always publicly on record.
A very interesting method to find domains that belong together is reverse IP lookup, which concentrates on domains on a certain Server/IP rather than domains belonging to somebody. This can reveal the most interesting things like hitherto unrevealed connections between brands where the company was careless enough to host them on the same server or hosting package. This free service shows fairly decent results; I have little experience in the market but there are many paid services as well. The method they employ is the same as the "reverse owner lookup" services - they crawl and use search engine results to find domains that resolve to a certain IP. The quality of the data will vary and is probably higher with the paid services. Note that you can get a lot of false positives when the domain you query is running on a shared hosting package.
The greatest interface to mass query domains from a lot of TLDs is Speednames. The system is brilliant, and mysteriously, completely free.
Answer: Robtex is a useful tool when doing research about domain names. It queries  publicly available information to get interesting results. For example, there are quite a few domains owned by Apple.
Most TLDs don't connect a specific legal entity with domain registrations, and that makes it impossible to find what you're looking for. However, the <code>.ca</code> TLD is an exception, and requires registrants to identify themselves as individuals, corporations, or other legal entities. But even then, I don't think this information is freely available.
While recently working with a client, I discovered that they owned twice as many domain names as they had on record. This only became apparent when they received invoices for those domains! If even the registrants don't know what their domains are, how do you expect to find out?
Answer: You can try Reverse Whois from Domain Tools. There are other, similar companies that offer similar services. It is as far as I know always a paid service. At least to get a pretty complete picture. In case of Domain Tools, you pay depending on the number of websites that are being found. Up to 9 sites costs you $80, if there are 1000 sites it will cost you $1,000, so I hope you are not looking for all domains of a company that is too active on the internet...
Answer: http://reverseinternet.com/ does exactly that. Rather than relying on WHOIS data that is most likely shielded by privacy registration, it uses google ids, linking patterns, nameservers etc to find such websites. Give it a try.
Answer: You can't, except maybe by forcing them to reveal the information as part of a court proceeding.
Research tools may be able to find correlations in publicly- (and semi-publicly-) available information. But if the company is trying to obfuscate the information in any way, they pretty much will succeed.
Comment: You sir are mistaken.
Comment: No I'm not. Really.


AMD Catalyst Beta Open Source Drivers

Question: I'm a gamer with a pretty low-end computer, so I always update to the beta drivers to squeeze out every bit of performance I can get. I currently have 13.3 installed, but I want to install the 14.6 beta. I want to use the open source version, instead of downloading from AMD's website. How can I do that in the terminal? And please explain what the commands mean so I can do it on my own in the future. Thanks in advance!
Comment: I think you are in a bit of confusion. There is nothing like "14.6 beta open source version". The 14.6 beta driver(and all other drivers you get by using `apt-get install fglrx` or from the AMD website) are all called proprietary drivers(which means that they are released by AMD and not open source but closed source). The open source drivers are the ones installed default in Ubuntu. To use them you just have to remove all the proprietary drivers and thats all(if you haven't already purged the open source drivers).
Comment: You don't use Beta graphics drivers, ever.
Answer:
I want to install the 14.6 beta. I want to use the open source
  version, instead of downloading from AMD's website

Well, you either use the open source drivers or the latest beta drivers(Also called 'proprietary' drivers) which is not open source. For the open source drivers you can open the Dash(Press Super key aka Windows key). Then start typing 'Additional drivers'. When you open the Additional drivers window you will something similar to this :-

There(as it is seen above) select the one that says open source, tested and you will be using the open source drivers.
For the latest beta you need to take this.
Comment: Oh, I thought there was an open source equivalent for each proprietary release, thanks!

AMD Catalyst Beta Open Source Drivers


Inserting a Horizontal Space Character

Question: In Pages, is it possible to insert a tab-like character that fills the remaining space between on a line? I want to have the first few words on a line left-aligned, and the last few words on the line right-aligned. I'm working inside a table cell, if that makes any difference, but cannot make additional table cells to make this work as that would mess up the remaining text. Is there some way of inserting a horizontal space character of this kind?
Comment: Yes, that's what I mean.
Comment: You're asking about filling in the space horizontally within the same line, and not about filling space vertically between two lines, correct?
Answer: It's possible to this easily outside of a table cell. To do this,

insert a tab between the two text, and then
add a tab mark on the ruler above.
Move the tab mark to adjust the tab width.

Doing this inside a table cell is difficult because pressing the tab key automatically advance the cursor to the next table cell. What I suggest is

create the tab outside the table cell, then
paste it inside the table cell, then
adjust the tab width.

I've snapshot to illustrate what I mean. Hope it helps.

Inserting a Horizontal Space Character


Semi-Aquatic Ants

Question: Is it plausible for a species of ant that inhabits a mangrove-like marine environment to have their abdomen evolve into a tail-like appendage for swimming to move from tree to tree to forage?
Comment: Tangentially relevant XKCD: https://xkcd.com/1610/
Comment: tail like might be tricky, that would require a complete redesign of the abdomen, bristly legs that work like paddles are far far more likely, you may want to look at boatsman bugs for ideas.
Comment: How will they follow [pheromone trails](https://en.wikipedia.org/wiki/Trail_pheromone) through water?
Comment: I honestly hadn't even considered that @user535733
Answer: You want bubble bees.
There exist aquatic hymenopterans!  I had never heard of them until I read for this question so thank you!  Hymenoptera is the order to which ants as well as bees and wasps belong.
https://link.springer.com/chapter/10.1007/978-1-4020-8259-7_51

All aquatic Hymenoptera are parasitoids. Many species have relatively
  dense pubescence to trap air and elongate, tarsal claws to grip the
  substrate, when underwater. Most species are known from the Holarctic
  and Oriental regions, but this is likely an artefact caused by lack of
  knowledge of other regions of the world. Aquatic behaviour has evolved
  independently at least 50 times within the order.

Dense pubescence means they are hairy, which is the method diving spiders use to carry a bubble of air around with them.  Bees are plenty hairy already and I bet they could pull this off.  Breathing thru a tail snorkel is done by rat-tailed maggots which are fly larvae so if you really wanted to do that you could have your bees with rat tails.  But the maggots are not super mobile I do not think - mobile things like spiders, wasps, beetles and your bees will probably just surface to recharge the bubble.
I found this video of Prestwichia aquatica and I think I can see the bubbles trapped under the wing.
https://www.youtube.com/watch?v=EzMhgKp-ylY

For such a cool animal I was surprised to find nothing on the pop biology sites!  Even the Wikipedia article is translated from the Russian.  National Geographic if you are watching, aquatic wasps would be a fine topic.
Answer: No evolution needed, in the Ants View of the World an individual can be sacrificed and used as part of a bridge.  Clusters of ants bridge over or float over, get on a clump of mangrove, and strip it bare.  When no more resources on the dry, they start extending out.  Tides, winds, fish splashing, etc. break off clumps that then float a few more feet and hit another clump of mangrove, or perhaps a bridge out exploring gets lucky.  Plenty of youtube vids of clumps of ants floating, forming bridges across small spans of still water, etc.
Comment: This does not work as standard procedure, if done every day this will quickly leave you with no ants.

Semi-Aquatic Ants


What happens to your assets if Coinbase (or an equivalent site) closes down?

Question: If a bank institution closes down, there is an amount of money insured.
What happens if Coinbase or Crypto.com which are actually just websites shuts down?
Answer: There is a saying: "Not your keys, not your bitcoin".
If you don't put your own money in your own personal non-custodial wallet and look after it yourself then you are relying on the honesty and competence of a large number of other people.
You can hope that the closed business didn't close because it lacked solvency to pay its creditors (including you) or that it had some kind of insurance that will cover your loss.
Many businesses claim to be regulated but those claims are mainly to reassure customers. The truth is that in most jurisdictions, this kind of business is far less regulated than retail banks are and they are typically not required to contribute to industry compensation schemes for customers of failed businesses.
Personally I think customers of these businesses take an overly optimistic view based on almost no supporting evidence. Many such businesses have closed and their customers have often lost all or most of their money. That's just my opinion though.
Consider the fate of customers of businesses that were industry-leading and highly regarded, such as MtGox, Quadriga-Cx and many others.


Could anyone help me decipher this?

Question:
Could anyone help me "decipher" this word below the arrow? I'm guessing its Priroda ("Nature"). But would be great if someone else could have a look at it for me too.
Answer: This word is "Лирика".
And the first line is из цикла "Лирика".
Comment: Thank you, that corroborates with surrounding evidence! (This handwriting is from 1921)

Could anyone help me decipher this?


How to flip direction of dupli objects?

Question: I want to know how to get the dupli object to flip? Examlpe: I have bolts distributed on one side of the default cube. How can I get the "bolts" to point out on the other side of the cube.
I have a mesh that I'm using for the duplication (have tried with dupli faces, and verts). I have the "bolts" placed on one side of the cube no problem, but no mater how I try to rotate the faces of the duplication mesh the bolts still face the same way. I have tried adding a mirror modifier on the duplication mesh, copying and rotating the faces but to no avail.
Answer: If you scale an object by negative 1, it will reverse it on all axes.  Then you can just rotate it by 180 degrees on a single axis, and you will have essentially created an exact mirror image of an object without the hassle of a mirror modifier.
Hope this helps!
Answer: To let the bolts appear on each side you could you would need to setup the geometry for your child object like:

Let the bolts be duplicated from a smaller object so that the dups have an offset to corners of the actual object.

The result looks like:
Answer: With duplication set to verts, the objects are oriented the same as the original.

When duplication is set to faces, the objects are oriented by the face normals.

You can change the normals direction of selected faces by choosing Flip Normals under Mesh->Normals, or use the shortcuts CtrlN and ShiftCtrlN to set them to face out or in.

You can also turn on the display of the normals in edit mode under Mesh Display in the properties sidebar N.

To have the bolts displayed at the corner of the cube but still control the direction create another mesh to do the duplication with small faces in place that isn't rendered.

How to flip direction of dupli objects?


What is Sound Design in the context of synthesizers

Question: When reading opinions about various synthesizers, I very often encounter a phrase like "instrument A is better for sound design than instrument B". What does it mean in this context? Does it refer to overall flexibility of a given instrument to modify its parameters and enabling the user to create a large variety of custom sounds (as opposed to using pre-made presets), or does it refer to the ability of the instrument to produce a certain specific type of sounds?
Comment: Yea, I was afraid you were going to say something like this.  You're watching people whose expertise is in YouTube video production, not sound synthesis.  Pads are easy.  Find someone who can synthesize the sound of a trumpet being played underwater, or a convincing alien voice, or the sound of a black hole swallowing a planet while you watch.  Then you can learn something about the capabilities of a synth.
Comment: That's why I build my own in Reaktor - You can design it to do exactly what you want it to do on a fundamental-level.
Comment: Yes. It refers to both, depending on context
Comment: I don't understand the second option you've presented.  If a synth has a lot of synthesis capabilities to reach a lot of different sonic territories, it's probably useful for sound design.  More like the first option you wrote.
Comment: @DataProcessing well, my impression is that when people try to demonstrate the "sound design" capabilities of a synthesizer, the examples they show are often pad-type sound, long and rather soft sounding, though complex. I may lack a better word for it. I wonder if this results from some dominant trends and collective taste of the synth experts, or such sounds are more difficult to achieve, thus better demonstrate the capabilities than more lead type of sounds, or maybe there is something about concept of sound design in it – like creating background cinematic music?
Answer: I feel like this is like saying one guitar is better for playing the blues than another guitar. It's the player, not the guitar, that is better or worse at playing the blues.
To me when someone describes a synth as being "good for sound design", they are really saying they can see how they would design arbitrary sounds with it. Another person with a different approach may consider the same synth to be "bad for sound design" and they would prefer a different synth.
I'm thinking of all of the hardware and software synthesizers I've used (not counting keyboards that are just wavetable playback devices that are called "synths" but shouldn't be) and I can't think of one that a creative person couldn't use to design a vast variety of unique sounds.


Water pressure loss every 30 seconds

Question: My water pressure almost stops every 30 seconds (I timed it while showering). This happens throughout the house. I have a well. We just bought the house, and we're new to wells. This morning it started doing this about every 5 seconds. Please help!
Thank you!
Comment: Is it every 30 seconds or every 5 seconds? When the pressure drops, how long does it stay low? Does the water stop flowing entirely or does it just slow down? Does any air spray out of your faucets?
Comment: Pictures of your plumbing near the water inlet/pressure tank would be helpful.
Comment: maybe the pump is overheating? it is hot out right now...
Answer: Something is not right with your pressure tank/pressure switch.
The most likely (there are several less likely options) is that you may have a failed bladder, assuming the usual modern case of having a bladder type tank (where a membrane or bladder is supposed to prevent contact between the air in the pressure tank and the water in the pressure tank.)
Typically the most cost effective way to solve that is a new pressure tank.
But.
There are small odds that things are just horribly mal-adjusted. A properly installed well-pump system will have a pressure gauge you can see somewhere near the pressure tank - you should abserve that while water is running, and pay attention to where the pressure is when it switches the pump on and off.
You can check by turning off the pump and draining the water; then check the air pressure on the tank (there should be a tire valve, usually on/near the top, sometimes under a cover - use a tire gauge to read that pressure.) If it's zero ( with the water side drained & at zero), you almost certainly have a failed bladder, but try pumping it up (with a tire pump - there should be air in there) if it does not hold pressure, you definitely have a failed bladder. If it will hold pressure, it should be adjusted to about 2-3 PSI below where the pump turns on (so if the pump starts at 40 PSI, 37-38 PSI)
Depending what type of pump you have, restarting the pump may be more or less difficult - if it's in the well (submersible) it's generally no work at all - if it's a pump in the house you may need to prime it, and thus you might not even want to start the "turn things off and drain the system" checks until you have an understanding of how to prime and restart the pump, or you won't have ANY water until you do.
To help you understand the (most likely) problem, the pressure tank acts to store water under pressure by compressing an air bubble. The tank and resulting air bubble are typically supposed to be sized to allow for 1 or 2 minutes of pump operation (which results in a certain volume of water) each time the system cycles. If the air bubble is not the right size, much less water is stored, and the pump cycles more frequently. In the "properly adjusted" state, the 2-3 PSI below the pump turn-on (also known as cut-in) pressure prevents any noticeable loss of pressure (the tank is still supplying water as the pump starts to replenish it), and the pressure simply varies between 40 & 60 PSI, or 30 & 50, or 20 & 40, or possibly other values.
A "much rarer these days" case would be a non-bladder type pressure tank - those have contact between the air and water, and the air gradually dissolves into the water, so it needs to be replenished. Those systems typically have valves that are supposed to suck in air as the water is pumped, but they may malfunction, and the typical solution until they are fixed (or the whole thing is replaced with a bladder tank) is to pump air into the tank manually if a valve is provided for that, or to drain all the water out of the tank, which provides a tank-full of air when you restart the pump.
Comment: You **MAY** be able to kludge a temporary improvement by NOT draining the system and pumping air into the top of the tank (try to draw off water until "just before" the point where the pump would turn on, first.) This will not "fix" the problem, but it might make it enough better temporarily that you can take a calm and measured aproach to getting it fixed properly, which is generally less expensive than a "hurry-up and make it better, on a weekend" fix. Often *significantly* less expensive...

Water pressure loss every 30 seconds


where does electricity come from in piezoelectric?

Question: I have some questions here. BaTiO3 is a material which exhibit piezoelectric effect when we give external pressure on it. It contain Ba2+, Ti4+, and O2- ion in its crystal unit. The Ti4+ ion will move up or down, so the crystal will polarize and that it could produce electricity. But how's that possible? I mean, electricity (current) is a flow of the electrons but I still have no idea about where the electron come from? My guess is: these electron came from Ti4+ ion. Can somebody explain to me what actually going on?
Comment: Why does electricity need to be flow of electrons?
Comment: so what do you mean? as far as i know, electricity is flow of electrons or ions through conductor circuit. If my previous question was wrong, could you please explain to me what actually going on in piezoelectric material that it could produce electricity
Comment: You have physically separated charge by deforming the unit cell, which provides a potential that drives current.
Comment: Ok, I know the potential due to the polarization in piezoelectric material. So you mean that: if we attach external circuit to the piezoelectric, and because there's potential difference between the two end of the circuit, there'll be electron flow (current) in the circuit?
Comment: Correct. There is no flow in the conventional sense inside the piezo (or else you couldn't polarize it in the first place).
Answer: This is due to the molecular arrangement of the atoms in the crystal.

Basically,  a piezoelectric crystal contains molecules arranged in,  say, tetrahedral fashion.
The dipole moments of each and every atom pairs are well balanced.
When you squeeze or twist the crystal, the equilibrium gets disturbed. That is, one or the other dipoles remain only partially opposed.
This happens to many dipoles, and as a result a net dipole moment develops in the crystal.
This can  also be interpreted in terms of potential difference.
These two ends when connected to a circuit, causes a current.

Remember,  as Gede panji quoted , potential difference causes current here,  not
the reverse. I hope this clears your doubt.


How to connect GNS3 to loopback adapter on Windows 10

Question: I'm trying to have a simple topology by connecting a router (c7200) and the local machine which is windows 10. For this I use GNS3 GUI (not the VM application). I have to do that, due to the limit of the RAM I can't run GNS3 on VM, since even after setting up the topology I have to start Pycharm. I set up loopback adapter and GNS3 router configuration correctly but I couldn't connect them. I turned off the firewall and restarted the PC as well but didn't work out. It's really helpful if anyone can help me on this. GNS3 version is  2.2.15 on Windows (64-bit) with Python 3.6.8 Qt 5.12.1 and PyQt 5.12
Thanks in advance.
Comment: Not sure if I understand your question correctly - a loopback is an internal, virtual interface that you can't connect anything to.
Comment: Yeah since the GNS3 router also an internal device it should be able to connect to the loopback adapter. Matter of fact I have watched videos on it's getting done. It can be done on both GUI & VM applications of GNS3. But when I try it (I use GUI), it doesn't work.
Comment: Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can post and accept your own answer.
Answer: Step 1.On Windows 10 open the Run window and type hdwwiz and click OK. The hdwwiz command is a short way to add and Adapter
Step 2. After the hardware wizard opens, click Next to Continue.
Step 3. Continue by selecting Advanced as we will add the Loopback card manually.
Step4. In the Hardware Types window, select Network Adapters  and click the Next button.
Step 5. Select Microsoft from the manufacturer section, and then select Microsoft KM-TEST Adapter from the right pane.
Step 6. The following window provides a summary of the hardware to be installed. In this window, click Next to continue.
Step7. Adding hardware is complete and click Finish to close the window.
Step 8. You can see that the loopback card has added successfully. You can rename the loopback card to avoid confusing it with other network cards.
Step 9.Double-clck on GNS3LOOPback.
Step 10. You need to set and IP address for the GNS3Loopback network card. You can change the IP address settings here. After configuring the IP address settings. Click OK to save the settings.
Step 11. You can check the configuration by clicking the details button on the network card.
Step12. After restoring your computer, run the GNS3 program and create a new project.
Step 13. Drag and drop one Router and Cloud into the GNS3 workspace. Click Right-Click / Configure to set up Cloud1.
Step 14. IN the Cloud1 configuration window, you need to select the loopback network card you added in the Ethernet interfaces section. Once you have selected the GNS3Loopback adapter, click the Add button.
Step 15. After successfully completing the loopback network card insertion steps, click OK to save the settings.
Step 16. To cable cloud1 and Cisco Router, Chick cabling then click Could1. The Loopback network card will become selectable as you can see in the image below.
Step 17. Assign an IP address to the Cisco Router FastEthernet 0/0 interface and turn it on Then, test the connection by pinging the loopback IP address.
Cloud1 and Cisco router can communicate with each other.


Why did Mark remove the roof from the rover?

Question: I've just seen the movie and may have missed the explanation, but why did Mark remove the roof from the Rover towards the end, before he tries going to Ares 4 landing site ?
Answer: This is a vestigial element from the book.  In the books, there are 2 working rovers, and he hooks them up together.  In the second rover, which is acting as a trailer, he needs to store a bunch of large equipment from the hab that will sustain life support (specifically heat and air).  To fit the equipment in the rover, he removes a portion of a wall, and integrates the equipment into the rover and seals it up using some of the material from a pop tent (a piece of equipment in the books).
In the film, this sequence is not present.  But they include the section of him removing a chunk of the rover's wall and roof and patching it up.
From Chapter 20 of the book:

LOG ENTRY: SOL 376
I'm finally done with the rover modifications!
The tricky part was figuring out how to maintain life support. Everything else was just work. A lot of work.
I haven't been good at keeping the log up to date, so here's a recap:
First I had to finish drilling holes with the Pathfinder-murderin' drill. Then I chiseled out a billion little chunks between the holes. Okay, it was 759 but it felt like a billion.
Then I had one big hole in the trailer. I filed down the edges to keep them from being too sharp.
Remember the pop-tents? I cut the bottom out of one and the remaining canvas was the right size and shape. I used seal-strips to attach it to the inside of the trailer. After pressurizing and sealing up leaks as I found them, I had a nice big balloon bulging out of the trailer. The pressurized area is easily big enough to fit the oxygenator and atmospheric regulator.
Comment: @CBredlow Yeah, but there's no explanation for why, or what they're trying to accomplish.
Comment: They do show him and the JPL team doing the modifications such as sawing off the roof on Mars (I think he falls through the roof when trying to break it off)
Answer: In the book he removes sections of the roof to accommodate the extra equipment for the longer trip:
Log Entry: Sol 207

I stowed the panels on the roof. The trailer gives me room to store another seven (half of its roof will be missing because of the hole I'm cutting in it).
Answer: Mark was modifying the rover so that it can better handle the long distance travel.  There's a montage where he is trying to get the rover ready by putting in extra equipment for fresh water and air recycling.
Comment: Yes.  Some of the equipment he takes with him is excised from the hab and wasn't designed to be small/mobile.  And some is improvised (the water bath for heating the air).  The stuff was too large to fit in the unmodified rover - hence the hole - yet needed an atmosphere around it - hence the canvas extension.


Incorrect Parents name on ESTA

Question: My question is about the US Visa ESTA. Does anyone know if it matters if I  put my name under the section of parent on my ESTA? How do I edit it ?
Answer: The only section you can't edit is your passport data, that requires a new ESTA, everything else can be changed at https://esta.cbp.dhs.gov/esta/ (source). Changing the parent name could occur for various reasons, marriage is a common one but most countries have legal ways to change a name so this is not as big a deal as it seems.

Incorrect Parents name on ESTA


Django: Override 404 template in some views

Question: I have a custom 404 template for my whole django application but I would like to show a different one for specific views.
Is there a way to overrride the 404 template at runtime for one specific view?
Answer: I think this is what you want
def not_found404(request, exception):
        data = {}
        if request.path == "/spesific-view-path/":
            return render(request, 'your_app/different_404.html', data)
        return render(request,'your_app/404.html', data)

main urls.py
handler404 = 'your_app.views.not_found404'


Book, lecture series or course on linear models

Question: I am looking for a free book, lecture series or a course to thoroughly explain linear models concepts and the underlying math behind them, and give intuition.
I am thinking of a material that connects all the concepts together, for example, how mean square error is related to R-square? how the coefficient is related to the correlation? etc.
The books that I went through explain these concepts but they don't connect the dots.
I only get the intuition of these concepts when they are connected.
Comment: Can you give title for some of the books you tried, so we can get a better idea of what you are *not* looking for?
Comment: Linear models with R, Julian Faraway, and Basic econometrics, Damador Gujarati. I also took the regression models course by Johns Hopkins on Coursera.
Comment: There are previous threads for book requests, check them out. (See tag [tag:refrences].)
Comment: Your request is quite difficult. I think you develop understanding and intuition with practice. The textbooks normally give you the basics but they cannot cover all possible relationships between all possible concepts. What often happens is that you develop this intuition over years of work. That being said, I would love to see a textbook with as much intuition and dot-connecting as possible.
Comment: That's what I'm trying to do now, to ask specific question and try to find answers. But I have a feeling that someone thought of this before and wrote a book to satisfy this hunger.
Answer: Probably Wikipedia isn't a bad place for start, but if you're looking for something thorough and free then try some of the MOOC courses offered in www.coursera.org and www.edx.org.
For instance:
https://www.coursera.org/learn/inferential-statistics-intro
Comment: Thanks. I guess I took some of those, but I still don't feel satisfied :/
Comment: It's not free, but I found the book "Introductory Econometrics: A Modern Approach" (Jeffrey Wooldridge) to be very good for undergraduate level (comparing to Gujarati, Maddala and others). This, of course, it's subjective


Strange number of upvotes for questions

Question: Can someone look into neurofluxations recent jQuery questions. It appears there is some gaming going on as the amount of upvotes he has been receiving is way out of kilter with a standard jQuery question.
Comment: ah I see. From a comment of Will: *he's part of the dch.co.uk vote ring. Its been noted, and their fate is awaiting decision by the dark lords of SO. We are hoping they will realize its douchy to automatically upvote your friends and/or colleagues and stop doing it.*
Comment: IMHO this should be treated as a "serial upvoting" case, only manually noted in the DB rather than via the detection script -- i.e. all the members of this "vote ring" should be permanently prevented from voting on each others' posts, and all such previous votes nullified in the DB. Let their posts stand or fall on their merits, from votes from the rest of the SO community.
Comment: Well, take a look at the recent jQuery questions. You will struggle to find any with 5+ upvotes, especially in the timeframe that he received them. The last q got 8 upvotes within 4 mins.
Comment: sorting on votes shows that 9 upvotes is the maximum ammount of upvotes neurofluxations received. I don't follow jQuery questions but that doesn't strike me as strange.
Comment: For reference, here's a data dump query of posts on the jquery tag along with the number of upvotes (I ignored downvotes for simplicity): http://odata.stackexchange.com/stackoverflow/q/7413/recent-posts-in-a-given-tag-along-with-the-upvotes-on-them?TagName=jquery
Comment: It surprises me time and again how naïve I seem to be. Gaming the system like that wouldn't even have crossed my mind...
Answer: What's really off-kilter is that 3 out of the 4 questions have way more upvotes for the questions than for the answers.

Strange number of upvotes for questions


How to enable sharding for all databases/collections by default

Question: We are doing sharding process for 6 servers which includes 1 master process, 2 config process, 6 sharding processes.
We enabled the sharding by doing sh.enableSharding(database_name) and sh.shardCollection('mydb.collection_name', {_id: hashed}) It worked.
Now, if i add any other database/collection to the cluster, is there any way that, the database/collection get sharded automatically.
Answer: Answer is simple. NO!
Every DB and collection in them, must be shard individually. Just because all collections are not created as equal and _id: hashed is not best solution to everything.
Comment: thanks @JJussi. So, what is the solution regarding `_id`?
Comment: _id:hashed (or any sharding with _id) works only when (most of, not all necessary) your queries have _id field. Problem selecting sharding field is that is should be field what is included in most of queries. If sharding field is not included, you get scatter gather query (https://docs.mongodb.com/manual/core/distributed-queries/) where query is sent to all shards and not only one. Yes, _id:hashed (or any 'key' with hashed) is "easy" solution where you get absolutely equal/even distribution of data. Hopefully this ( https://www.mongodb.com/blog/post/on-selecting-a-shard-key-for-mongodb ) help.


Physical significance of product of two charges

Question: In Coulomb's Law we see the product of two charges in numerator, and I was wondering what it really signifies, because charge multiplied by charge is not a charge. So what exactly is a charge multiplied by a charge? This question could also be asked about the product of two masses in Newton's law of gravitation.
Comment: Let me ask a counter-question: Do you see this product anywhere else, without Coulomb's constant to take away its units?
Comment: sorry i couldn't understand the purpose of your question perhaps i should say  i didn't understand your question as whole .please if u can elaborate .
Comment: In some rough sense charge multiplied by charge at a point distant from the system is proportional  to the the electrostatic potential energy of the system at that point.
Answer: Charge multiplied by charge is... charge multiplied by charge. Unfortunately, we don't have a name for this quantity, nor do we have any sort of physical intuition with it, because it simply never appears in varied enough locations and situations (i.e. somewhere other than Coulomb's Law) that a name would be useful. The same can be said of squared mass. We just never have a reason to think of that quantity separately from its law.
Comment: why its appearance only in Coulomb's Law  can be a reason that we don't need to have any physical intuition and how is appearance in varied enough locations a condition to have the need for physical intuition . please if you can make it more clear
Comment: Let's try for a moment to get some physical intuition on squared charge. By rearranging Coulomb's Law we get that squared charge is proportional to force times area, or mass times volume per squared time, if you will. So we get *another* quantity that we have no intuition for! Unless you can find a way to link squared charge directly to another thing that we already have an intuition for, it seems impossible to gain any intuition from it.
Comment: Any deeper than this, and we stray into the realm of philosophy: "Why do we measure the things we do? Why do we consider basic units basic? Where does intuition on these basic things come from?" Unfortunately, not being a philosopher or a metrologist, I am not qualified in any sense to answer these questions.
Answer: Ultimately it is correct because it matches the experiments, but we can give some a posteriori justification to this.
Physicists describe electromagnetism by means of electric and magnetic field, rather than Lorentz force; the same holds for gravitational field vs. Newton's force.
The way the interaction between (two, for simplicity) particles is modelled is the following: every particle per se radiates a field that permeates spacetime. Then, if some other particle "can feel" that field, it experiences a force.
So let's for a moment focus on the fact that is some region of spacetime. The ability of a particle to feel some field is described by saying that the particle is charged with respect to that field. For EM field the charge is electric charge; for (newtonian) gravitational field the charge is mass. Therefore we have that the force experienced by the particle is proportional to electric charge or mass.Therefore we have
$$
\text{force} \propto (\text{charge}) \times (\text{field})
$$
Now let's go back to the creation of the field. For electromagnetism the property that allows a particle to create the field is electric charge; for gravitational field it is mass. Therefore the field will be dependent on the electric charge or the mass; in the simplest case it will be proportional to the electric charge and the mass, ie
$$
\text{field} \propto  (\text{charge})
$$
Therefore we have
$$
\text{force} \propto (\text{charge})^2.
$$
Note that the first relation ($\text{force} \propto (\text{charge}) \times (\text{field})$) is really the definition of field. The second relation, on the opposite side, is a very special feature of these forces. We could as well have forces for which "the generator" is different from "the probe", or for which the field is not proportional to charge. But for electromagnetism and (newtonian) gravity nature seems to be simple.


Monodevelop on Xubuntu Missing ASP.NET

Question: I am running XUbuntu 16.04 and I installed mono-complete and monodevelop. However when I run Monodevelop, I can't create a web project. It seems like ASP.NET is not installed.
How can I install ASP.NET? Thanks
Answer: I also had this issue. As an aside, MonoDevelop (with the ASP.NET add-in) still works fine in Ubuntu 14.04 and 14.10, so I am unsure what has changed to make it not work in Ubuntu 16.04.
In my case, this was enough to push me off Ubuntu and over to Fedora (with CentOS servers for my Mono/ASP.NET application). Fedora 23 runs MonoDevelop with ASP.NET and NUnit perfectly, straight out of the box.
I found a question about this on Stack Overflow a few weeks ago, and I note that it has just had a response from someone claiming that they have found a resolution: https://stackoverflow.com/questions/36101232/asp-net-template-not-found-after-installed-monodevelop-ide-on-ubuntu-16-04
UPDATE: There is a confirmed resolution to this issue at the SO link above. I have created a step by step resolution (thanks to Abu for the original post) that will guide you through it.
UPDATE 2: I have written this up as a blog post on my website, so hopefully this brings further attention to this issue, which really shouldn't be happening in an LTS. The full post is at https://brendaningram.com/article/how-to-fix-monodevelop-on-ubuntu-16-04/

This is how to resolve the issue:
Firstly, setup using the following commands, which are as per the
  official Mono installation instructions, but with the change from
  wheezy to alpha.
sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
echo "deb http://download.mono-project.com/repo/debian alpha main" | sudo tee /etc/apt/sources.list.d/mono-xamarin.list
sudo apt-get update

Then, install Mono itself:
sudo apt-get install mono-devel mono-complete ca-certificates-mono mono-xsp4

Then, to install the specific version of MonoDevelop that gives you a
  working ASP.NET add-in:
sudo apt-get install monodevelop=184.108.40.2061-0xamarin2

I am not completely happy with this solution, obviously. A mainstream
  distribution such as Ubuntu (and especially their current LTS) should
  not have these kinds of regression issues. However, we at least have a
  resolution to the issue.
Of note is that Fedora Workstation 23 has a working
  Mono/MonoDevelop/ASP.NET environment straight out of the box. While I
  have previously been a Debian/Ubuntu user, this issue was enough to
  push me across to Fedora, where I have been happily working away
  without a single bug or other issue. Will I stay with Fedora? That's
  uncertain, but it has certainly been a pleasure to find an enjoyable
  and stable alternative to Ubuntu.
Answer: The best way is to compile MonoDevelop from source, as the official 6 distro runs in the flatpak sandbox. If you're developing stuff, that must not run in a sandbox, that's bad. Here's a very good tutorial how to build from source, that works:
Here are the steps from this blog post which has the full details:
sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
echo "deb http://download.mono-project.com/repo/debian wheezy main" | sudo tee /etc/apt/sources.list.d/mono-xamarin.list

(don't worry about the repository name - the post is specific to Ubuntu 16.04 and later)
sudo apt update && sudo apt upgrade

Get the dependencies
sudo apt install -y autoconf automake cmake fsharp git gnome-sharp2 gtk-sharp2 libssh2-1-dev mono-complete referenceassemblies-pcl zlib1g-dev

Now cd to the directory where you want to install, for example, ~/Apps/MonoDevelop and clone the source into it
git clone https://github.com/mono/monodevelop.git --branch monodevelop-18.104.22.168 --depth 1 188.8.131.52

In this example, we acquire MonoDevelop 188.8.131.52, but it's possible to acquire other versions as well. The list of released versions can be found on the releases page.
The last option in the command is the name of the directory where the source code will be located. So, after running this command, a new directory named 126.96.36.199 will appear. This directory structure will allow us to use multiple MonoDevelop versions at the same time. For example:
~/Apps/MonoDevelop/18.104.22.168
~/Apps/MonoDevelop/126.96.36.1999

cd to a directory with a version of MonoDevelop that you're going to build, for example
cd ~/Apps/MonoDevelop/184.108.40.206

Configure the build
./configure --profile=stable --enable-release

Build MonoDevelop:
make

Sometimes, the build may fail because some of NuGet packages cannot be found. The error may look similar to this one:
mono .nuget/NuGet.exe restore
Unable to find version '2.8.2' of package 'NuGet.CommandLine'.
Unable to find version '2.6.4' of package 'NUnit.Runners'.
Makefile:1124: recipe for target 'restore-packages' failed

In this case restore NuGet packages:
mono main/external/nuget-binary/nuget.exe restore main/Main.sln

And try again
Assuming that the build completed successfully, we can now run MonoDevelop from the directory with
make run

See the link (or other posts here) for steps to create a .desktop file for easy launching. Sample .desktop file contents:
[Desktop Entry]
Type=Application
Terminal=false
Icon=/home/USER/Apps/MonoDevelop/184.108.40.206/main/theme-icons/GNOME/monodevelop-48.png
Name=MonoDevelop
Exec=make --directory /home/USER/Apps/MonoDevelop/22.214.171.124 run

X-Ayatana-Desktop-Shortcuts=188.8.131.52;220.127.116.119

[18.104.22.168 Shortcut Group]
Name=22.214.171.124
Exec=make --directory /home/USER/Apps/MonoDevelop/220.127.116.11 run

[18.104.22.1689 Shortcut Group]
Name=126.96.36.1999
Exec=make --directory /home/USER/Apps/MonoDevelop/126.96.36.1999 run

Comment: Welcome to Ask Ubuntu!  **;-)** Although your answer is 100% correct, it will also become 100% useless if that link is moved, archived, deleted or the site just ceases to exist!  Therefore, please copy the relevant parts from that site to your answer and leave the link at the bottom as a reference to your source.

Monodevelop on Xubuntu Missing ASP.NET


HTC Desire C stopped working after factory reset

Question: I have a HTC Desire C. I performed a reset to factory settings. It went through the whole process, was shutting down to restart but it never restarted and now I can't even turn it on. I have pulled the battery, I've pulled the SD card... doesn't matter what I do I can't get it to turn on. Any ideas???? Can't even find the software for it to reinstall it. I plug into my computer it acknowledges that it is there but do have the software....ugh.
Answer:
If your phone is not starting anyway try performing hard reset using hardware buttons

Performing a factory reset using hardware buttons

Note: All your data will be lost.

If you can't turn HTC Desire 700 on or access settings, you can still perform a factory reset by using the hardware buttons on HTC Desire 700.
Important: The Fast boot option in Settings > Power must not be selected.

Remove the battery, wait for a few seconds, then reinsert the battery.
Press and hold the VOLUME DOWN button, and then press and hold the POWER button.
Wait for the screen with the three Android images to appear, and then release the POWER and VOLUME DOWN buttons.
Press VOLUME DOWN to select FACTORY RESET, and then press the POWER button.

If doing the above doesn't help you should reach your nearest htc service center