What does 'A' stand for in A, AA & AAA accessibility conformance levels

Question: I have been going through WCAG 2.0 guidelines and I couldnt find any reference to the letter 'A' in Conformance levels of A, AA & AAA standards. What does letter 'A' stand for ? Is it an abbreviation for accessibility ?
Comment: Perhaps these are variations on an 'A' grade? So when A, B, C grades denote best, good, medium, A, AA and AAA denote best, bester, bestest? (tongue in cheek...)
Comment: I'm voting to close this question as off-topic because is not important info.
Comment: Most likely it is for accessibility. Hence the levels for accessibility.
Comment: Similar to @Hans-MartinMosner's comment, possibly (but with no references) something I've just called _preemptive grade saturation_. E.g. in Europe, "white goods" were originally graded **G** (poor) to **A** (good). With better manufacturing (and more stringent limits), there is now **A**, **A+** through to **A+++** (and, generally, I believe, new machines can only be "A-something"). They could have chosen C, B, A for A, AA, AAA, but then what do they use for "better than A". With the current scheme, they can add AAAA if needed.
Comment: As the first letter in the english alphabet, 'A' is just used to denote first or best, and since there's no more letters before it to denote something even better, extra A's or +'s or `*`'s (UK school exam grades now include A`*` as a higher rank than A) are used. One exception is UK road numbering, initially A roads were the highest quality, followed by B roads, followed by C (usually unsigned). When motorways were introduced they labelled them M rather than A+ :-)
Answer: WCAG 1.0, published in 1999, assigned priorities to checkpoints and defined three conformance levels: Level "A", Level "Double-A" and Level "Triple-A".
Early drafts of WCAG 2.0 did not assign priorities to "checkpoints", as they were still known, but planned this for later. See "Priorities and Techniques" in the August 2001 working draft. By April 2003, the conformance levels were named "Minimum Level", "Level 2" and "Level 3", and each of the  checkpoints had "levels of implementation listed for it". In the June 2003 working draft, the conformance levels had been renamed to "WCAG 2.0 Core", "WCAG 2.0 Core+" (i.e. for site meeting "Core" and some of the "Extended checkpoints") and "WCAG 2.0 Extended" (for sites meeting all checkpoints). By that time, it was clear that the term "priorities" when referring to WCAG 1.0 checkpoints.
By November 2004 checkpoints had been renamed to "success criteria", which were categorised into three levels: "Level 1", "Level 2" and "Level 3". Conformance levels were called "level A", "level Double-A" and "level Triple-A" (see WCAG 1.0, above). The April 2006 draft was the last one that used numbered levels for success criteria (Level 1, 2, 3) and the letter scheme for conformance levels; the May 2017 draft used A, AA and AAA for both conformance levels and success criteria.
What can be seen from the above comparisons is that two things happened:

WCAG 2.0 got rid of the term "priority" (from WCAG 1.0).
WCAG 2.0 rejected alternatives such as "Minimum Level", "Core" versus "Extended", and numbered-based level identifiers. (A number of other schemes were discussed internally but never made it into a public working draft, e.g. "Gold", "Silver", "Bronze".)

The main rationale was that disability groups are not equally represented in the success criteria at each level (especially those with cognitive impairments or learning disabilities) and the WCAG working group wanted to avoid making the impression that any disability group is less important than other disability groups (i.e. by being less well represented at level A or AA). This meant that a naming scheme that suggested that the "higher" conformance levels encompassed the "lower" levels (like matryoshka dolls) was fine, but anything that suggested priority or higher importance of certain disability groups had to be avoided. The naming scheme "Level A", "Level AAA", "Level AAA" achieves this. As far as I know, the "A" is not intended as an abbreviation of anything: the oldest mention I found on the working group's mailing list dates from March 1999, when Daniel Dardaillier wrote:

For what it's worth, at the time this conformance schema was discussed, I suggested A, AA and AAA.

This suggestion reminded some people of the grading system used in North America (see Eric Hansen's response from the same day), rather than seeing the "A" as an abbrevation for accessibility. In addition, when I was a member of the WCAG working group (especially 2005-2008), "A" was never discussed as an abbreviation of anything.
Comment: Just the last paragraph would have been sufficient...
Answer: Not sure what it stands for but it was decided back in the first version.

Conformance Level "A": all Priority 1 checkpoints are satisfied;
Conformance Level "Double-A": all Priority 1 and 2 checkpoints are satisfied;
Conformance Level "Triple-A": all Priority 1, 2, and 3 checkpoints are satisfied;
Comment: This describes what they are used for, but not why 'A' was used in the first place.
Comment: Exactly. I couldn't find any reference in WCAG website for the reason for using letter 'A'


My mist browser Win64 0.6.2 doesn't show up

Question: I was downloading the blocks in the test-network and when I noticed it stopped downloading. I decided to restart the app. resulting into this:

This is what I see for a brief second before showing the first picture, what can I do. The wallet is still on the test-network. I don't know how to put it back to the main net.
Redownloaded, restarted my pc didn't fix the problem either.
Answer: Solved it myself by downloading a previous version.


Are there any real world examples of encoding data in EM polarization?

Question: Data can be encoded by modulating the frequency, amplitude and phase. But I can't find any references for encoding data in the polarization of EM waves (either analog or digital). This is probably for a good reason which I do not understand. Are there any examples of such schemes?
Comment: In the optical realm, a projector is used with varying circular polarization to produce the [RealD 3D](https://en.wikipedia.org/wiki/RealD_3D) effect.
Answer: A receiver connected to a simple receiving antenna cannot distinguish between a plain carrier of polarization A and the same carrier transmitted with a different polarization and amplitude - they could look the same to the receiver.
If there was something that could re-polarize the transmission as a means of modulating the carrier, the receiver would just detect it as amplitude modulation.
Simple transmit antennas (and probably some quite complex ones too) can't be electrically made to change their polarization.
Signal reflections from objects can reorient polarization and this could muddle things up.
Comment: @SteveSh theoretically it's zero but in practice not.
Comment: Could you have two antennas one for vertical and one for horizontal polarization and switch transmission between the two?
Comment: @Artium sure you can.
Comment: The effect of receiving a signal polarized in one direction (say X) with an antenna or antenna element designed for the orthogonal pol (Y in this case) is a large reduction in the coupled/received signal strength, maybe 20-25 dB difference.  Once past the element stage, the signals look the same, except for the differences in amplitude.
Answer: It certainly can be done, it just isn't very useful, except in certain situations.
For example, ham radio operators sometimes like to do experiments with reflecting signals off the moon (EME, or earth-moon-earth, a.k.a. "moonbounce"). It's useful to transmit with circular polarization, because the reflection comes back with the opposite polarization, which means that the receiving antenna is better at rejecting unwanted terrestrial reflections.
However, in the general case, different polarizations have different propagation characteristics, which makes it difficult to maintain coherency in terms of demodulating a useful payload at the receiving end.


How to move a Daily Partition to a Monthly Partitioned Table

Question: I would like to switch out a partition from a daily partitioned table and merge it into monthly partitioned table.  I am unsure as to how to go about it.  Here's what I have so far.
I have two tables, Event_Daily and Event_Archive_Monthly.  Both tables are partitioned on CreatedDate datetime with Event_Daily being partitioned by Day and Event_Archive_Monthly being partitioned by Month.
Event_Archive_Monthly has the following file groups:

Archive_Monthly_2018_05_01_FG
Archive_Monthly_2018_06_01_FG
Archive_Monthly_2018_07_01_FG

Event_Daily has the following file groups:

Daily_L_NULL_FG
Daily_2018_06_18_FG
Daily_2018_06_19_FG

I have 9 records in Event_Daily in the 2018_06_18 file group and no data on the other partitions.  I have created a SwitchOut table on Daily_2018_06_18_FG  and have issued these commands to switch out the data and merge the boundary point:
PRINT 'switching out previous days data'

ALTER TABLE [dbo].[Event_Daily]
SWITCH PARTITION 2 TO dbo.Event_Daily_SwitchOut;
GO

PRINT 'merging boundary point'

ALTER PARTITION FUNCTION Daily_PF ()
    MERGE RANGE ( '2018-06-18' )
GO

At this point I am unsure as to how to get this data into the archive table.  Ideally, after everything is said and done the file group Daily_2018_06_18_FG is gone.  One option I know I have is to just insert the data and then drop the SwitchOut table and drop the file group.
Is there a way, using the Partitioned Table, to merge the SwitchOut table that is on the filegroup Daily_2018_06_18_FG into the partition on Archive_Monthly_2018_06_01_FG?
Answer: Community wiki answer:

Is there a way, using the Partitioned Table, to merge the SwitchOut table that is on the filegroup Daily_2018_06_18_FG into the partition on Archive_Monthly_2018_06_01_FG?

No, you'll need to use INSERT...SELECT for row processing. MERGE/SPLIT/SWITCH DDL are partition level.


Does Google reprocesses submitted sitemaps from time to time?

Question: Assuming one submits a sitemap for a website in Google Webmaster, does Google reprocess it from time to time? If yes, at which rate?
Answer: Edit: Google will recrawl it (see comment by John Mueller from Google below).
However, if you want your sitemap reprocessed more quickly by Google, the recommended practice is to resubmit it.
You can resubmit using Webmaster Tools or using an HTTP request.
Using Webmaster Tools:

On the Webmaster Tools Home page, click the site you want.
Under Optimization, click Sitemaps.
Select the Sitemap(s) you want to resubmit, and then click the Resubmit Sitemap button.

Source: http://support.google.com/webmasters/bin/answer.py?hl=en&answer=183669
The linked source also describes the slightly more complex alternative method where you use an HTTP request.
Comment: We recrawl Sitemaps files regularly, for most sites that's usually every couple of days. It's faster to ping if you know that something changed though (usually we recrawl them right away when they're pinged).


How did people travel to remote islands like Easter Island?

Question: Easter Island is extremely remote, being thousands of kilometers from its nearest neighbor. How did people get there safely, and how did they even know it was there?
Answer: As to how they made it safely, don't be fooled by the fact that they only had 'canoes';  double-hulled ships are far more seaworthy than single hulls of a similar size.
That's not to say it wasn't risky or difficult, but modern people have successfully followed the paths of early Polynesian migrations using traditionally designed boats and (more impressively, imho) traditional navigation techniques.  Ben Finney wrote a book about his experiences in Hokule'a, a double-hulled canoe which later (in 1999) made the voyage to Easter Island.
How they decided to make that first trip, without knowing for sure that an island was there, is a more interesting question.  Rapa Nui (Easter Island) tradition says that a king dreamt of the island's existence and ordered an expedition to find it.  You don't have to be woo to believe that something like that might have actually happened - after centuries of sailing eastward and settling new islands, the idea of trying it again wouldn't have seemed all that outrageous.  Anything from overpopulation to a ruler showing off for a girl could have led to such an order being given.
Obviously no one knows for sure what happened, but I found an article in which Finney explains the difficulties the first expedition would have faced, not least of which is the primarily easterly winds in that part of the Pacific.  A sailing vessel can actually sail against the wind by zigzagging, but it's difficult and greatly increases the distance of the journey. Therefore, Finney says:

The key to reaching Rapa Nui would be to get enough days of favorable westerly winds ... to come close enough to the island to see it, or detect it indirectly by telltale cloud formations, by the appearance of terns or other 'land finding' birds, or by other signs by which island navigators use to recognize when land is near.

He speculates that perhaps

some especially adventurous voyagers [went] down to around 35° South to try to run before westerlies there, and that after a week or two the cold wind and rough seas forced them to angle north to seek the warmth of the tropics. If so, they might have stumbled across Rapa Nui in their flight from the cold.

Another possibility is that

Marquesans sailing to the Tuamotus could have been driven far to the east by sudden westerly gales, and then have elected to keep heading in that direction in hope of finding land sooner than it would take them to work their way back to the west. Similarly, people making a crossing from Mangareva to Pitcairn, or between islands in the Austral group might have been driven far past their target by strong westerlies and then opted to keep pressing eastward.

The article goes into a lot more detail, and also has links to diaries of the Hokule'a expedition to Easter Island.
Comment: Seems to me the most logical explanation is somebody got lost.
Comment: @Dunk - It would have to have been someone who happened to have a viable amount of people of both genders with them, along with chickens and the other polynesian food crops found there.
Comment: @FelixGoldberg Wrong link. Right link = http://en.wikipedia.org/wiki/Kon-Tiki / http://en.wikipedia.org/wiki/Thor_Heyerdahl
Comment: To your very good answer one simply must add a mention of the original boat expedition - the Kon-Tiki (http://en.wikipedia.org/wiki/The_New_Turkey).
Answer: Polynesians discovered and colonized pretty much the entire Pacific this way. Easter Island is one of their more impressive discoveries, but it isn't even the most impressive. That title has to go to Madagascar, which was settled from Borneo (about 5,000 miles away!).
How did they do this? Well, the Polynesians were the ancient world's best navigators, and had developed all kinds of techniques. One thing not many of us land-lubbers think about is migratory birds. They can't fly forever, so islands they can stop and rest at are important to them. They don't just flap around the ocean aimlessly looking for islands when they get tired; they fly straight from island to island. Therefore an ancient navigator knows he must eventually find land if he just follows the trail of migratory birds.
One other thing to note. Sweet Potatoes were domesticated in (mainland) South America. However, they somehow appeared in New Guinea (and got added to the standard diet) about 1200 years ago. That's 8,000 miles away. How did this happen? There are some wacky one-in-a-million theories running around, but the most likely explanation is that there was some small amount of interaction (perhaps even trade) going on between Polynesians and South Americans as far back as 800 CE.
Comment: Reminds me of the Raven technique used by the ancient vikings.  When sailing and searching for land they released ravens from their ships.  The birds would hover straight up and if they could see land they'd fly towards it and the vikings would follow in the same direction.  If on the other hand the birds couldn't see land they'd settle on the ship again.
Comment: Read up on the long - very, very long - [non-stop migratory flights of the bar-tailed godwit](https://www.mnn.com/earth-matters/animals/photos/9-birds-that-set-records-for-their-amazing-flights/longest-non-stop). Much to my surprise when reading this, migratory birds generally ***do not*** stop *en route*, regardless the length of the flight, but fly non-stop. This actually *reduces* the net danger, from the elimination of predators and parasites.
Comment: @Karlth - Polynesians used the [frigatebird](https://en.wikipedia.org/wiki/Frigatebird#Cultural_significance) for exactly that purpose.
Answer: According to this page, Rapa Nui's latitude is -28, almost -30. That is a border between zones of prevailing eastern winds (to the North from -30) and prevailing western winds (to the South), according to the map.
Another point is that the navigation of the Polinesians was a right-angle one. They sailed first along the meridian (by polar star or Southern cross or Sun (by measuring 90 degrees from the sunrise point with correction for the latitude), up to the known parallel. Afterwards they sailed along parallel (by measuring the height of the Polar star or the Sun.) Alternatively, they sailed first along the known parallel up to the known island and after that along the meridian. So they solved the problem of longitude measurements, even though they never measured it.
Such navigation was possible for them, because when the wind was not in their back, they simply rowed and didn't change their course due to the wind. They didn't change their course because of the style of their navigation, not because they were not able to change the course. Obviously, they strongly preferred the wind to their back.
So, if somebody wanted to return back from the islands to America and was to the South of the Equator, he should go down to -30. This would be out of the zone of eastern winds, to its border, where the sailing to the East became easier and could easily go along the parallel. Of course, according to the season, it could be parallel a pair of degrees to the North or to the South of -30. So, finding Rapa-Nui, which was so close to the "magical" wind border, was inevitable.
If somebody, as in the legend that Rose mentioned, wanted to find some new country, sailing from America, where would he sail? Of course, along the southern edge of the area of eastern winds, because all areas to the North were already checked. Also, the desert -25-30 parallels were the best candidates for such a search. Again, the find was very probable.
So, it seems that finding Rapa Nui was much less random than the finding of most other islands in the Pacific.
One more possibility is that they voluntary checked all parallels with some methodic process, going further and further to the south. This would explain the find of New Zealand, too.
Comment: @Gangnus - Sail is the generic technical term for voyaging by watercraft, whether that craft be powered by paddle, oar, steam engine or nuclear reactor. "Swum" in english means they actually traveled without a boat... so you either meant sail in the generic, or paddled in the specific. Cite: http://www.thefreedictionary.com/sail
Comment: @RI Swamp Yankee they did not use sail all of the time. On the contrary.
Comment: What does that mean? Are you saying that they swam all ~3500kms?
Answer: I don't know how Easter Island was first discovered, but returning to it after discovery was done by celestial navigation. For each latitude on Earth their are certain key stars that pass directly overhead at that latitude. Thus, knowing the celestial latitude of key stars meant that one could find his own latitude. The navigators would sail due North / South (also by way of celestial navigation, though this is more difficult in the southern hemisphere due to the lack of a pole star) to the desired latitude, then turn west or east to get to the island in question.
Lots of good info on Wikipedia's celestial navigation page and on the page of Arcturus, zenith star of the Hawaiian Islands.
Answer: The idea that reaching distant islands would be difficult or impossible for "primitive" peoples is something commonly believed by city dwellers inexperienced with ocean sailing. If you go to Bath or Newport and start hanging out with the old timers there, they can quickly disabuse you of the notion that sailing to Rapa Nui is impossible. In fact, if you watch Robert Redford's recent movie "All is Lost" you can see him sailing thousands of miles completely alone in a relatively small vessel, and then doing hundreds more in a life raft. Vikings routinely rowed and sailed thousands of miles in the treacherous North Sea, loaded down with weapons no less.
After World War II, a Scandinavian adventurer named Thor Heyerdahl specifically set out to show a few men with only the most primitive of equipment could explore the breadth of the oceans. In 1947, he captured the public imagination with his Kon Tiki expedition, going from South America to the Polynesian islands in an oversized raft. He wrote a series a books on his findings. If you read these books, it should resolve any questions you may have about the abilities of ancient mariners.

Kon Tiki vessel in 1947.
Answer: OK, extremely crazy theory here, but is it possible that they just walked? If you take a look at this satellite view it looks as if Easter Island was the highest peak of a mountain range that is no longer above the sea level. However, in order for that to have occured, this "peak path" should either be extremely shallow (no way to easily verify right now), or that happened many thousands of years ago (at least if we take into account the evolution of the sea level over time).
Comment: Those sea mounts are being raised from the ocean bottom by volcanic action.  The sea floor has never been exposed for billions of years.


Question about reading addresses/offsets in C++ within a hooked function

Question: I'm a beginner at this and I'm following tutorials but I am kind of stuck.
I found a function that accesses all characters X position in game. I found this using Cheat Engine and here's how it looks:
All these addresses are X positions of characters in game.
I looked up this function in IDA and the functions looks like this:
double __thiscall sub_427380(int this)
{
  return *(float *)(this + 80);
}

So I managed to hook this function and read the values in C++.
Here's the code:
double hookedFunction(int i)
{
    float f = *(float *)(i + 80);
    return originalFunction(i);
}

This works but when I try to read values from other offsets that I found using the "Dissect Data/Structures" function in Cheat Engine I'm stuck.
Here's the structure from one of the addresses I found in Cheat Engine:

When I subtract 80 from the address and I create a new data structure in Cheat Engine it looks like this:
So here's where I need help. How do I read the string at offset 0040 and the 4 bytes at offset 003C in my hooked function.
I tried doing stuff like:
DWORD d = *(DWORD *)(i + 0x3C);

But whatever I try I can't get the right values.
Answer: This is more of a C development question, however the answer is offset 0x40 has a pointer to an array of chars.
Code should be the following:
char* charname = *(char **)(i + 0x40);


Unsure if Bell Pepper plant or not

Question: This summer I planted pepper plants and noticed that these other plants have popped up after it has reached the end of its season. I think they are bell pepper plants but am unsure if they are since the original bell pepper plant died at the start of fall. Would appreciate some thoughts on if it is a bell pepper plant or not.
Answer: It's definitely a different kind of plant. Peppers have significant stems/branches and leaf stems. The leaves usually are not just growing all from one spot without branches (I mean, they don't grow like comfrey plants; they're more like trees in shape, even when young). They're usually (not always) a darker green color, too. I've never seen a bell type that wasn't a darker green color, actually, but it should easily be possible to breed one with light green foliage. Lower light and nutrient deficiencies could lighten the foliage, too.
You can see a bell pepper plant at this link, but if it happens to be broken some day, or if they remove the image, just do an image search for pepper foliage.
The plant does remind me of calendula (Bamboo mentioned that as a possibility in the comments already), and weeds I've seen before, but I don't know what it is.
Comment: Nor Calendula - the leaves are neither hairy nor does the shape fit.

Unsure if Bell Pepper plant or not


How to convert a genus name to a noun or adjective

Question: Consider the crayfish family Cambaridae.  As I understand it, this familial name can be turned into an English noun or adjective by changing the first letter to lower case and dropping the "ae." An example use is "Responses of cambarid crayfish to predator odor" (adjective). Similar conversions from generic names are widely used as well.  For example, for the crayfish genus Procambarus, the english conversion "procambarid" is widely used, primarily as an adjective, but also as a noun. A google scholar search for this word turns up hundreds of uses.  A search for "id" conversions for other generics names for hermit crabs, and snake genera turn up uses of them as well. I cannot find any information that actually describes this conversion and it's rules.  Can someone point me to a reference, or otherwise help clarify the issue?
Comment: some resources note the capitalization but not the rules themselves: https://scientistseessquirrel.wordpress.com/2020/10/13/why-dont-we-capitalize-taxonomic-names-used-as-adjectives/ (i left a comment there asking)
Answer: I think that it boils down to taking a Latin name and removing the case ending to get an acceptable English adjective. Given that it might be a purely linguistic situation, it's possible another SE site would be better (English language?), but this topic is definitely relevant to biologists, as they're probably the ones who run into it most frequently.
We can look at IAPT article 60.10 and it suggests a systematic way to do this, albeit for an unrelated reason. I don't see that they directly address the anglicized Latin adjective form:

A noun or adjective in a non-final position appears as a compounding form generally obtained by
(a) removing the case ending of the genitive singular (Latin ‑ae, ‑i, ‑us, ‑is; transcribed Greek ‑ou, ‑os, ‑es, ‑as, ‑ous and its equivalent ‑eos) and
(b) before a consonant, adding a connecting vowel (‑i- for Latin elements, ‑o- for Greek elements).

I think that we want to apply step (A) but not step (B) here, as their goal is the formation of compound names, and step A alone will get us -id, which is an anglicized adjectival ending (-idus --> -id).
Taking your examples:

Cambaridae --> remove Latin genitive suffix -ae --> cambarid.
Procambarus --> make Latin noun into the adjective procambaridus --> remove suffix -us --> procambarid.

Unfortunately, it looks like there are a ton of possible Latin adjectival endings- the -id examples seem pretty straightforward because you can get an English adjectival ending directly, but other taxonomic names don't resolve so neatly. For example, if I want to use "Lachnospiraceae" as an adjective, I could imagine the following (applying only step A above doesn't seem to work well: "lachnospirace"):

lachnospiraceid
lachnospiraceal
lachnospiraceous

and I don't really know how to pick among them!
I have left a comment on a blog post from Stephen Heard on a related subject (comment above), perhaps he'll see fit to weigh in here.


Frame-challenge – guidelines proposal

Question: Update: The FAQ is now live. Please do not make changes or discuss them here anymore.

This is a follow up to the idea collection, please see that post as to what this is about.
First of all, thanks to everybody who participated in the idea collection.
I tried to distill the results into a coherent set of guidelines, filling some apparent gaps here and there.
The result can be found below.
In general, we will continue to give wide latitude to askers, answerers, and commenters; this is not an attempt to introduce many new, confusing rules. However, introducing these guidelines will be helpful in order to mediate disputes or other cases where moderation action becomes necessary.
Please review the guidelines and do the following:

Feel free to edit minor issues directly. This is a community wiki.
Post an answer if you disagree with a point, want to propose an addendum, or similar. However, please refrain from simply re-iterating suggestions that were already rejected by votes in the idea collection.

How to deal with a question that contains a false premise?
Somebody posted a question that makes an assumption I disagree with or think might be wrong.
How do I best inform the asker of this?
Do I post a comment or an answer, or should I vote to close the question or do nothing at all?

What you want do is called a frame challenge:
You claim or suggest that the question is based on a misconception, wrong assessment of a situation, or similar.
The frame set by the asker is challenged by the answer or comment you want to post.
The following is mostly a set of guidelines that should give you an idea of best practices and avoid unnecessary confrontation.
There often is a lot of leeway, but drastic deviations will be moderated.
We primarily distinguish frame challenges by what they are about, with some general rules of thumb at the end:
Misconceptions about academic procedures, norms, or similar
These misconceptions concern the very topic of this site. For example:

Assertion: You must have a PhD to submit a paper to a journal.

These are mostly free game for frame challenges.
However, before challenging such an assumption, please consider that you may be wrong because academic customs vary a lot between fields, countries, etc..
Misconceptions about off-topic aspects
Typically this is about the content of academic research or teaching, but it may also be other off-topic things. For example:

Assertion: My newly developed method that makes a very good guess whether a number is prime topples modern cryptography.

Whether such statements are correct is off-topic here.
If you want to discuss this off-topic material, do it in chat; discussion in the comments or answers will likely be deleted.
If such an off-topic aspect is central to a question, the question should likely be closed or migrated.
Wrong goal (XY problem)
The asker wants to achieve X and thinks doing Y helps them to do this, so they ask how to do Y. However, Y is not a good way to achieve X.
Most often, we can only suspect an XY problem, since the asker doesn't talk about X, but only about their outlandish goal Y.
In this case, we can only tactfully inquire what the asker wants:

Can you please elaborate why you want to do this, so we can provide better answers? I may be wrong, but this feels like an XY problem.

If X is detailed, you can suggest alternative ways to achieve it, as long as the focus is helping the asker.
Wrong assessments of individual experiences
Here the asker potentially wrongly assessed something that happened to them – as opposed to general facts.
For example:

Assertion: The student I supervise does not take my criticism seriously.
Assertion:  My paper was cited for some claim it did not make.

In these cases, we almost always lack all the relevant information (or it would be off-topic) and cannot make a judgement.
The asker should know better than we do, and they are responsible to ensure that such an assertion is correct.
Therefore frame challenges about such situations are usually not appropriate.
However, there are some exceptions, where a short and tactful caveat is appropriate:

The misconception is common and applies to many people in a similar situation, e.g.:

Assertion: The referee did not thoroughly review my paper, as they misunderstood the key concept.
Caveat: Before proceeding please consider that you are very familiar with your work and thus may not have noticed shortcomings in your explanations.

The asker describes in detail how they arrived at an assertion and this makes it seem unlikely that they are correct.
For example:

Assertion: My professor is not satisfied with my work, because X, Y, and Z.
Caveat: What you describe are normal activities for a supervisor.
Just by your report I would not assume that your professor is dissatisfied.

If the asker's judgement should be incorrect, it may have severe consequences:

Assertion: My professor asked me to fudge some data by applying X.
Caveat: Please be aware that this is a serious accusation. I am not saying you are wrong, but before escalating this, please consider consulting with an expert whether applying X is really inappropriate in this situation.

In all such cases, such a caveat should not be much longer than the asker's description of the assertion and respect the asker's assessment instead of directly denying it.
Mind that this does not apply to questions asking us to evaluate a situation, e.g.:

My professor does X, Y, and Z. Is this normal? Does this mean that she is not satisfied with my work?

Sexism, racism, discrimination, and other traumatic events
A relevant subcategory is when the asker experienced sexism, racism, discrimination, or similar behaviour, usually towards themselves.
Such events are often traumatic and denying what happened may easily add to the trauma.
Moreover, we almost certainly don't know all the details (context, tone, gestures) and thus cannot judge the situation.
In this case, the above exceptions do not apply:
We can assume that the asker has already considered alternative interpretations of events and is aware of the severity of the respective accusations.
At best, you may very tactfully ask for further details or assess the details if relevant for the question, e.g.:

I am sorry for your experience. To better answer your question, can you please [edit] your question to tell us whether you have any evidence of this? I understand if you do not want to go into the details; it suffices to know how much evidence you roughly have.

General rules of thumb
Before you write a frame challenge, see whether you can answer all of the following with yes:

Is the misconception central to the question? If the question can be asked as well without the misconception, it's better to edit it out or only address it briefly. If on-topic, you can ask or suggest a separate question about it.

Would you write a frame challenge if the question provided fewer details?

Are you confident that the asker did not already consider your frame challenge?

Does your frame challenge actually help the asker?

Does your frame challenge respect the asker, in particular their expertise, privacy, and problems?
Comment: @AnonymousPhysicist: Why? The idea is that answers criticise individual aspects of the proposal and not that they compete with it.
Comment: I didn't realize there was going to be another question
Comment: I'd recommend editing this so the question has the "General rules of thumb" and a TOC which links to to the more detailed points in the answers.
Comment: @AzorAhai-him-: I can make a separate answer for each section with a TOC in the final question, but I wouldn't put the general rules of thumb in the question in that case, since I expect this to be confusing. Of course, if this is the answer people tend to upvote the most, it will come first.
Comment: @AzorAhai-him-: At least there will be if this one gets any effective answers to separate the guide and the discussion about it. If everybody is more or less happy with this version, I might as well edit this question.
Comment: @Wrzlprmft This should have been posted as an answer, not a question.
Answer:
I tried to distill the results into a coherent set of guidelines, filling some apparent gaps here and there.

This has been unsuccessful.  Your post does not accurately reflect the idea collection.  It is also too long and disorganised.  Further, it is redundant.
Comment: Can you make any specific suggestions how to improve things?
Comment: @Wrzlprmft I think we should stick to the existing rules, or make them simpler.  I consider the entire discussion of "frame challenges" to be redundant, not just this post.

Frame-challenge – guidelines proposal


App Develompment with Minimum salesforce edition

Question: I have to give suggestions to my clients about the Minimum Salesforce Edition require to build an app for AppExchange. I had gone through all the editions and had a detailed overview of all of them. I am now stuck between professional and Enterprise edition. I want to know any major kind of differences between them.
And Also I want to know about the future of Group edition or any possibility to develop app on it.
Answer: The edition they choose does not matter for purposes of development; your application will be created in a Developer Edition org, which is like an Enterprise Edition org but with limited storage space. They should choose whichever edition suits their business practices. For differences, see the marketing material. Enterprise has a lot to do with automation, such as workflow rules, API access, etc.
If they just need to get started, Professional Edition should be sufficient for their purposes. They can always choose to upgrade later. Group Edition has been replaced with Essentials Edition. It is typically not suited for anything more than the smallest of businesses. Again, this has nothing to do with development, so they should make their purchase decision based on their business needs.
Comment: If you look in the screenshot, it is saying that lightning platform is not included. I didn't understand this point.
https://pasteboard.co/I0a4V14.png
Comment: @Soul_In_Code That's not relevant to if they can do development, though, as the package will be in a Developer Edition org. It has to do with being able to use App Builder, apparently, but that only applies to the ISV's org, not to what they can create.
Comment: let say I am developing an App from the Developer Edition and having some functionalities which are using some automation features of the lightning platform. So what will happen if I will install the app into professional? (As it is metioned that Lightning Platform customize and Automate process are not available)
Comment: @Soul_In_Code that's a completely different issue, and one I'm not actually sure about. I suggest asking a new question to address that specifically. Again, their choice of which edition is used to run their ISV business is completely unrelated to the capabilities of the application being developed.


How should I go about straightening up my baby trees?

Question: We just had a house built, and in the front and back yards are baby trees. The trees are supported by a large, narrow piece of wood fastened to the tree trunk. A few weeks ago we had a terrible windstorm and now both baby trees are pointed at 45 degree angles. Should I bother digging a small hole and re-fastening the supporting wood to the baby trees or is there a more efficient way to fix them?
Comment: Were the root balls shifted in the ground, or are the trunks just leaning? Look at the base of the tree - does it come out of the ground vertically, or is it at an angle? If it's angled, I suspect you need to dig out around the root ball and straighten them back up. Otherwise, I'd just re-tie them to the support.
Comment: How big are the trees?  I'm not picturing the support - how is it attached to the tree, what is the other end attached to, and how long is it?  What kind of trees?
Comment: Trees are about 8 feet tall, trunks are about 2" wide. A 6 foot tall piece of wood about the same width of the trunk is fastened to the trunk with green elastic tape. It used to be just buried a few inches in the ground until it was pulled out.
Answer: That piece of wood is not really providing any support to the tree and was probably encouraging poor growth. Most trees do not need staking and if they did it should be removed after a year. See this excellent post for more than you ever wanted to know about staking.
Most trees will live fifty to seventy five years outside of a forest so it is worth investing an hour of your time to straighten them now so you don't have to look at a crooked tree.
Depending on how securely they are rooted and the soil dig on the side they are leaning away from and the side they are leaning towards. Cut and fill as required.
This is also a good time to check for damage to the trunk.  A healthy eight foot tree should not need staking unless it was recently planted.  If you see breaks in the bark or long vertical wounds such as in this picture on the trunk consider cutting your losses and planting a new tree.


How can I disassemble and install an old Schlage door knob?

Question: I have an old brass Schlage unkeyed door knob/latch set. I would like to install it in a door, but can't figure out how to take it apart. The rosettes thread on, but I can't figure out how to get a knob off. There are 2 small holes on both knob shafts. I have already tried pushing something into the holes and pulling/turning the knobs.
Comment: 2 small holes in the shaft?  or one small hole in the shaft?
Comment: I added a bit more info for you.
Answer: A pin in the small hole starts it. Pull on the handle as you push the pin in the hole. An ice pick or small nail will be strong enough to do what you need. After the knob is off, you may be able to remove the rosettes as you suggest, but a lot of the rosettes are removed by prying of the rosette by setting a flat screwdriver tip in the slot that is visible at the edge of the rosette where it meets the door. This is usually located on the low side of the rosette. After that is off, the 2 screws that hold the rest of the knob is visible.

This is for the other hole, this is just for the idea, the pin on this one is too big to fit in the hole of the rosette.

It takes a little finess to remove, first be certain you are able to depress the release. On practically every schlage I worked on, only one side will release. Once you know you have something depressed, lightly push and pull on the knob, you should be able to observe the slight movement of the knob at the hole were the pin is inserted, the hole will move one way then another to touch the pin. Once that is confirmed, pull the knob and release the pin after a firm pull is made. If it does not work on that side, try the other side. It will work.
Comment: I have already tried pushing something in the hole and pulling on the knob. This doesn't do anything.
Comment: You may not be applying enough force to release the spring retainer.
Comment: I added a bit more info for you.
Comment: Thanks so much for all the info, still nothin tho. A 2 mm allen wrench fits in the hole, and it's clearly the hole that's been used in the past is it's obviously enlarged as compared with the others (this is the hole near the bottom of the photo). I've also tried all manner of smaller things, picks and nails and pins.
Comment: Does the knob have any slop in it like I mentioned above around the hole where the Allen wrench goes in at? This is the way the knob comes off and they have froze in place somehow. Have you tried the exact same thing on the other side at the other hole that mimics the one you worked with already?
Comment: The Schlage 021415 spanner might be the correct special tool.  It has a knob-release poker and a pin spanner for rotating the coverplate.
Answer: So I have the same lock, I bend a fork to use as the push pin, wiggle it with some force and got it to come off.
Comment: I really like the old fork idea.  You could also bend part of a cheap fork into a spanner-like hook to do the rotating of the face cover.  I'm going to remember that hack for use on other hook-spanner type nuts.
Answer: You have to turn the inner handle until you see a small depression of metal. That is what you push into and pull the handle.
Comment: Welcome! I think your're on the right track - this is an important piece of information that was missing from Jack's answer. When there's an existing answer that does a pretty good job, especially if you don't feel like writing a comprehensive answer of your own, you could consider attaching your clarification as a comment to that existing answer.


Does Stack Overflow encourage one comprehensive answer or many "incomplete" ones?

Question: Let's say someone asks a question that requires multiple "parts" to an answer (for example, an advantages/disadvantages question). Now let's assume someone answers this question and touches on most points, but is missing a point or two (and let's say his/her answer was picked by the OP as the correct answer). Would it be better to add that additional information as your own answer, or suggest it to the author of the correct answer in a comment? Also, if the answer is a community wiki, is it good etiquette to edit another person's answer and add more info?
Answer: If you have information that further answers the original question, I would submit the information as another answer (instead of adding a comment). That way it comes under the scrutiny of the voting system and allows users to comment directly to your answer.
Also, the general etiquette of editing posts seems to lean more towards copy editing; making the post more clear and concise. Correcting grammatical problems or spelling errors is okay. Adding to or changing its meaning is not.
Comment: I disagree strongly with that last sentence... I don't think i've ever run into trouble adding to or correcting problems with an answer, provided i was respectful of the original author (adding alternate solutions vs. editing out controversial assertions). You could argue that the rep system encourages posting new answers over editing existing ones though.
Comment: Heh... I suspect i probably behave fairly close to what you describe. If an answer is completely worthless, unhelpful, flat-out wrong, etc... Then i'll probably post a different one rather than edit. If it's decent, i will edit to expand on it.
Comment: Heheh... You know, that post reminds me of something else (tangentially-related): examples. I've seen answers that do a good job of describing the solution, but don't put it all together in an example code listing... and end up confusing the person asking the question (who's new to the language or API). I'd just as soon edit in an example to an already-good answer than add a duplicate answer just to provide semi-redundant code.
Comment: I shouldn't say that "changing meaning is not [okay]" as a policy that everyone has to follow. It's just my personal behavior/opinion. If a user is saying something they believe but is blatantly wrong, I wouldn't go in and change it all up to make it true. I would just leave a comment pointing out the error. I *would* fix a statement (or code) if I felt that it was a typo or if something simple was omitted, though. That's just where *I* draw the line.
Comment: See, now I was coming around to your way of thinking after this: http://stackoverflow.com/questions/1196840/simple-sequence-generation/1196859#1196859. I pointed out an error in the sample code. The problem is now the code works as written but the implementation was changed (and is now *completely* wrong). And I would be a jerk for putting it back the other way (with my corrections). I should have just fixed the original code outright.
Comment: There ya go. You got me rethinking my assertions and I learned something new today.
Answer: Robert Cartaino's answer is somewhat ambiguous to me. I agree that if you have additional information that significantly answers the question you should add another answer, but I also think that you should include all of the other information so that your answer is comprehensive.
Every answer should stand alone. They might cite other answers, but they should answer the question as completely as possible.
The only general exception to comprehensiveness should be in cases where there are actually multiple independent answers. Tho, even then, the best answer would be one that exhaustively and definitively includes all possible answers (and any important info about the differences thereof).


Will an upside down or mirrored image of trademarked logo infringe on the original trademark?

Question: If someone creates a logo of 100% mirrored logo (180 degress) or upside down version (180 degrees) of an existing trademark, is it illegal? is that infringing any copyright or trademark laws? or that new logo cannot be protected by copyright law or any trademark law? I want to know this just for educational purposes.
Comment: Trademark or not.. it would be copyright infringement.
Answer: If it is likely to be confused with the original trade mark it is infringing if it is used to promote trade. A flipped logo? Definitely likely to be confused.
Comment: Oh my goodness! You changed your... your... picture! I don't know what to to think of you now!
Answer: In the U.S. the purpose of trademarks is to avoid confusion. You can use another's trademark as long as you are not doing so in a manner that will confuse. You can use someone else's trademark to refer to their product as long as you do not do so in a manner that is confusing (e.g., falsely suggesting an endorsement of your product).
The question you need to ask is whether you are doing something that would cause confusion?


Animation with non-uniform frame sizes

Question: How do you know when to draw the next frame if its bounding box is larger/smaller than the current? For example, in KOF, some characters have elastic arms and things of the like..How are these handled in a game?
Comment: There are special tools for having 'elastic arms', like *Flash Bone Tool*, but final quality of animations using these tools are never as good as animations based on manually drawn frames or on a 2D/3D character using a skeleton.
Comment: @MarkusvonBroady Is it possible to incorporate skeleton animation in a 2D game?
Comment: That's exactly what Jari Komppa suggested. In Flash you would simply create a "backbone" Movieclip, and place two arm-bones and two leg-bones there. All bones except backbone would have their registration point (x:0, y:0) set on one side, and another bone(s) added on another side. Now, if you rotate arm-bone, all bones belonging to it will move together with it.
Comment: My suggestion doesn't require rotation of limbs as such; each frame of the animation of each limb just needs offsets to be in the correct position.. but yes, naturally rotation and even scaling would work with the pivot points.
Answer: You know those paper dolls with moving arms? The arms are attached to the doll using tacks or something similar. What you're looking for is basically the virtual counterpart to this.

To have complete freedom between the sprite frames and their sizes, each part has to have a reference points (both from and to).
Comment: Can you elaborate please? A link to an existing implementation if one exists would be awesome :=)
Comment: No ready code, but basically, for each piece you need offsets per frame. These probably need to be set by the artist. Most probably the easiest way would be to write a tool for this. If this starts to sound like too much effort for the end result, you may want to reconsider the way you design your animation system =)
Answer: You would want to set up a definition of a Frame class which describes the position and dimensions of a single frame (independent of an actual image), a FrameSet class which has a name and a series of Frames to iterate over (again, independent of an catual image), and a Animation class that has a name, a FrameSet, the ability to iterate through the FrameSets, and a target spritesheet. When an Animation is called by name it blits from the spritesheet at the location described by the current frame in the current frameset with dimensions equal to the current frame.
Comment: Thanks! Who gets to specify where to draw the individual frames? Is it the graphics artist?
Comment: @saadtaame The frames on the sheet are designated by the artist, who then tells you their pixel locations and dimensions. The target where to draw the result is determined by the graphics library and the logic used in your game.
Answer: Lets take Dhalsim for example, classic and answers your category of stretchy limbs.
This is how it is done:
http://sfgalleries.wikia.com/wiki/Sprite_Sheets#Dhalsim
The artists, draws the sprite frames and places them on a sheet with enough room so that each frame has it's own rectangle. In another layer, the artist marks the center of mass of the character in each frame (so that the frames are in-synch during animation)
Another person, usually not an artist, uses a tool to save the positions of these rectangles mentioned above and their width and height.
If you require more detail on how to implement the tool that helps extract the rectangles and save them to xml or text format ask and I could elaborate.
How to write a tool to collect data for a sprite sheet:

Display the sprite-sheet(I assume you have that covered)
Allow moving(arrow keys or wasd) the image on (x,y) while retaining the offset -> offset.x, offset.y (the offset is the (x,y) of top left corner pixel currently displayed)
Allow zooming in and out (+, -) 2x / 4x / 8x/ with two keys -> zoom

point is (x,y)
rect is (x,y,width,height,label,index);
pseudo code main loop:
If(userClickedMouse()) {
    if(point1 == null)
        point1 = new Point();
        point1.x = offset.x + mouse.x/zoom;
        point1.y = offset.y + mouse.y/zoom;
    else
    {
        point2 = new Point();
        point2.x = offset.x + mouse.x/zoom;
        point2.y = offset.y + mouse.y/zoom;
        //prompt user to enter frame label and number//
        rects.push( Math.min(point1.x, point2.x),
                    Math.min(point1.y, point2.y),
                    Math.abs(point1.x - point2.x),
                    Math.abs(point1.y - point2.y)
                    label, index));
        //The rect is just an array a struct (x,y,width,height) values over and over - you can also use a struct (but I would just use integers)
        point1 = null;
        point2 = null;
    }
}

if (point1 != null) //display a rectangle describing the currently selected area.

If this makes sense let me know or please feel welcome to ask for elaboration.
To pick the frames 'character centering point' use a similar loop, that only asks the user to input one point.
Alternative:
Have the artist add this one pixel points in a new layer in Gimp/Photoshop and write a tool that opens the point layer and extracts their coordinates by iterating on all pixels and saves the results into your the format your prefer.
If you do it that way, you could easily calculate which point belongs in each rectangle and then pair them automatically.
Comment: Pseudo code is enough. I use C/SDL but don't want to take much of your time.
Comment: Would psuedo code be fine, or do you need a specific language?

Animation with non-uniform frame sizes


running a script just by clicking it

Question: I'm running Kubuntu 12.04 and have a script written to log into my EC2 server. I would like to automatically have this run in the terminal just by clicking on it. Is this possible to do? I have tried making the default "open with" file the konsole with the run in terminal option selected, but that has not worked yet.
Comment: Dolphin seems to have a bug where it sometimes doesn't respect your "open with" settings.
Answer: You can't really do this. You'll need to make a .desktop shortcut to it and then modify its properties to run in a terminal. Or you could convert the script to not require a terminal.

running a script just by clicking it


Help me with my panic attack during meditation

Question: Today when i was doing "space between breathing" meditation i experienced something strange which caused me to panic.
When i got deep enough in meditation, gradually space between my breaths expanded and my breaths became very shallow. I could no longer feel my breathing. Also i lost sensation of my body and awareness of environment. I entered a silent dark space which was very tight.
I felt like a vibrating round mass. The vibration gradually increased and also i felt a really hot sensation in my body. As heat increased i felt as if the space became tighter. Then i had the panic attack. My heart start beating very forcefully and fast. I couldn't feel and move my body. I couldn't find my breathing. It took me so long to find my breath and get back to awareness. I am so scared i cannot meditatie again.
I was wondering what was this sensation. is this feeling  normal. How can i avoide the panic i experienced
Answer: I would recommend learning & practising meditation in a group, that has a competent teacher or monk, so you can learn to become fluent in the basics of meditation.
As for your panic attack, it sounds like your mind was focusing more & more on the space, thus lengthening the gap of the space & shorting the duration of the breathing.
Therefore, not only did your mind lose a soothing, comforting & calming sense object (the breathing) but also found itself in a state of 'emptiness' ('diminishing ego') that it could not cope with; thus fear or panic arose; which is similar to a fear of 'death' people commonly feel.
Ultimately, correctly practised Buddhism meditation should 1st develop a strong foundation of calm, which gives the mind refuge & strength to develop more profound insights.
Where as "space between breathing" (emptiness) meditation is taught by ambitious teachers who foolishly believe they will enlighten students more quickly.
The real Buddhist meditation path is something gradual & natural and based on giving up desire (craving) & positive & negative judgments (rather than based on exercises designed to eliminate the 'ego' or 'self' prematurely; when the mind is not yet ready or spiritually mature enough).
Comment: Thank you. Most of us started with "mindfulness with breathing" meditation called 'anapanasati' because it makes the mind calm.
Comment: Thank you for your response. So you believe i shouldn't practice this kind of meditation so early in my practice? What can i do instead of this?
Answer: It sounds like you may have had a very deep meditative practice. It is possible that your body may have fallen asleep while you were still awake. It's not very common but pro-meditators (like the 9 hour guys) may experience it more often than others.

Did your limbs randomly move or shift without your effort? This is usually one of the first signs that your body falling asleep. Your brain is now trying to wake up different parts of the body.
Did you lose your ability to move while sitting in meditation posture? At this point your body released a hormone which paralyzes the body not to move. If you can't move your arm or finger than your paralyzed. It's not permanent but it can be scary.
The mental realm became more solid. Your body is beginning to shut down and the brain starts activating the areas of the brain associated with sleep. The dream state you experience in the morning starts to become active in your sitting.
Sense organs officially start shutting down. You can no longer hear, smell, taste, touch, or see the room you previously were in. Your body has officially fallen asleep while your brain still remains partially active/asleep. You are officially conscious of the subconscious realm.

Of course this is not recommended for most meditators, and it shouldn't be practiced without having a trained teacher. But this does sound like your body was beginning to fall asleep. Tips on how to handle the anxiety?

Move your attention onto Metta meditation.
Move your attention onto the breath.
Move onto walking meditation.
Move your attention into the anxiety and notice how it's just energy.
Keep your awareness center and let the anxiety be itself.
Encase the anxiety in a space bubble and let it slowly disappear overtime.
Place your hand on your chest and let love flow into your body.
etc....
Comment: Yes as you said i lost ability to move my body, i couldn't even hear the loud ticking sound of my room's clock. It was exactly like the sleep paralysis i sometimes experience in my sleeps. So do you think this meditation is harmful for me right now?  What can i do to prepare my self?
Comment: I recommend on finding a teacher such as a Tibetan Lama for meditations such as these. They have certain protocols  to protect you while in such deep states of mind. They will also tell you if your practice is moving forward or not. Sometimes the deep experiences can be the worst hindrances for our practice.


I can't find my edited Lightroom photos or catalog after Lightroom crashed. What are my options?

Question: Lightroom crashed after I exported pictures. I had to shutdown the computer. When I turned it back on and opened Lightroom, my pictures were gone.  I have tried to find a backup file and I can't. I have gone through all of the online options I could find, and nothing has worked.  Any ideas would be appreciated.
Answer: Lightroom is a non-destructive photo editor (see Are RAW files safe from changes?). It means that it never touches your original files (unless you ask it too). So regardless of Lightroom state (the software itself or its catalog), you will find your original images where you put them (or where you told Lightroom to import them).
Concerning your editions, they are indeed in the LR catalog and could possibly be stored in sidecar files (see Where does Lightroom keep changes? and Why employ the xmp sidecar file in Lightroom?). If your catalog has been corrupted, you should be able to retrieve a backup copy. To know where your catalog and its backups are, in LR go to Edit > Catalog Settings.
As a last option, you can also try to re-import images using LR and selecting your hard drives but it may discard your edits. It may help to locate the images you are looking for. You can also try to search for them in a files explorer.
This answer is valid only if your images are locally stored (no online hosting service involved).
Comment: If Windows - search of whole disk. Useful - from cmd prompt: dir \*.xxx /s > c:\ALLFILES. | Come back in morning. ALLFILES  will contain a text listing of files of type *.xxx.


Sort by one criteria and have another to fall back on

Question: I'm trying to configure a view (using the Views module) that sorts the content by content weight, then by total content views (loading a max of 6 items).
For a quick explanation, this is to list the most popular 'resources' on the resources page (PDFs). I'd like the list to be sorted by total views, which I've already achieved. However, I want to be able to give a weight to specific resources (resource is a content type, I've created a weight field using a simple list(integer) field that goes from -3 to 3) which the 'Popular Resources' view sorts by first before loading by total views.
I've tried giving the view 2 sort criteria, which are:

Content: Most Popular Resources Block Weight (asc)
Content statistics: Total views (desc)

I have 1 resource with a popular resource block weight set (the rest don't have a weight set), but the view isn't showing this resource as it has a lower number of total views than the others being loaded.
If possible I'd like the view to sort by resources that have a weight set, then when it runs out of blocks that have a weight, use total views to load and sort the rest of the resources. I've tried looking for a way to do this but haven't found anything yet.
Any assistance would be greatly appreciated.
Answer: Managed to find the issue. The resources that didn't have a weight set were treated as having a lower weight than ones that did. I changed the weighting to sort by descending, which is the opposite of how weight should work, but seems to be the only solution.


Fully detail authentic way to read Salat

Question: I spent a lot of time on the internet looking for how to pray in the right way the way Muhammad swa prayed. One question that comes to my mind again and again is that we now have a collection of all the hadiths, so why no one is compiling the detailed instructions on prayers from these books of hadith so that we can benefit.
so can anybody help me out by providing all the detail explanation of prayer which may be in form of articles or books, whatever you recommend which is authentic would appreciable??
Comment: I've came across of sheikh al-albani's book but I've found various instructions missing on that for instance in the tashahud when/where to move your index finger or just erect it while supplicating because here in muslim (https://sunnah.com/muslim:746a) a hadith split the tashahud in three parts -last one is dua' and we know that prophet swa move his index finger while supplicating! But vast majority of scholars including al-albani said we should move it throughout the tashahud????  And who knows how many things like this are missing!!
Answer: First of all, the way Muslims pray in general is based on fiqh perspectives and views based on authentic ahadith. Authentic ahadith here must be clarified a bit more: authentic based on the qualification of the faqih himself.
So whether you pray the way described by hanafi, maliki, shafi'i or hanbali etc. fiqh books with the intention to follow the sunnah of the prophet () your prayer will be fine.
Why?
Because all of them tried to follow the sunnah as they witnessed it in their society and heard it via hadith and reports of the sahabah and tabi'yn.
Now you may ask why is there a deviation?
Simply speaking because the prophet() didn't stick on one way:

he taught his sahabah different versions of how to start the prayer: different wordings of the so called du'a al-Istiftah (see for example in Is it proven to say this du'a before niyyah of salah?) and he might also start reading al-Fatihah right after the first takbeer to start the prayer.
He taught different words for the du'a of ruku', standing after ruku', sujud, sitting between two sajdah and the tashahud (see for example in Is there a sect-neutral tashahhud?)
He taught or showed or approved or remained silent upon different positions and movements of the hands and fingers etc. during some acts of the prayer.

So scholars of madhhabs have made a choice of the versions that seemed the most correct, accurate and authentic to them. In most if not almost all cases they have chosen authentic ahadith agreed upon ahadith in very few cases they were wrong. (See also Why do people pray salah differently?)
Having that said: You may find what you want in all fiqh books that contain hadith references (I'd assume especially the shafi'i and hanbali school of fiqh might offer more choices here) and one of the most prominent books today is the book of sheikh al-Albani on the prayer of the prophet (). But be aware that none of these sources claims to be complete.
The best way to pray however is to pray intending to follow the sunnah of the prophet () and trying to vary as much as you can of the wordings etc.. As this is a kind of reviving the sunnah of the prophet ().
See also:
Why are there so many uncertainties and differences in the performance of Salah?
Answer: Actually, there are quite a lot of books that discuss the way of The Prophets prayer ﷺ in a very detailed manner based on authentic Hadiths and sources. Of these books are: Shama'il Muhammadiyah and The description of the Prophet's prayer from Takbeer to Tasleem as if you see it by the Scholar Muhammad Nasiruddin al-Albani.


How to politely remind somebody of a meeting we had a few days ago?

Question: The person in question is a superior and I was wondering how to start the email I am writing to this person with a reminder of that meeting.
Comment: Hi, and welcome to Writers. This is a "what to write" question, which is off-topic for us. Please take our tour and see our help center http://writers.stackexchange.com/help/on-topic to see what kinds of questions we can answer.
Comment: I am sorry about that, can you please tell me where this would be an appropriate question?
Comment: You could try [The Workplace](http://workplace.stackexchange.com/). I'm sure they have their own requirements, but this seems like an issue they'd handle. Alternately, if this is an issue with English as a second language, you could try [English Language Learners](http://ell.stackexchange.com/).
Comment: Thanks @NeilFein, should I delete the question here?
Answer: (I am assuming you actually had the meeting - and want to refer to it, in the email)
[Boss]
Thanks for meeting with me on Wednesday. Recall that I was the [engineer] who had many questions about [issue].
You asked me to send a summary email with the questions, so you could more easily address them. Here they are:

...
...
...

Thanks in advance for giving this some attention. It will really help me to [complete my job better or more quickly] - and will go a long way towards [resolving a specific issue or improving a specific situation - name it here]
[employee]
Comment: I think my question was not clear, the meeting was the first time I met the person, so I have to remind him of me too.
Answer: Business correspondence is just one of the subjects discussed at The Workspace, a Stack Exchange forum for career and work related subjects.
Specific to your question...
Do you have a real-business reason to contact this superior or are you just trying to demonstrate that your willing to waste both of your work time, in the hopes of improving your visibility (and therefore your career) within the company?
When dealing with people who have authority, always demonstrate professionalism until they invite you into a more relaxed correspondense.  There doesn't have to be a critical business emergency to justify every short note, but there should at least be a reason for your writing.  If you received any take-away assignments from that previous meeting then informing your superior that those tasks are complete is an excellent excuse to write.
Once you have a reason for writing, it is good practice to remind the receiver of who you are, especially if this is your first time writing to them.  So right after you tell them the purpose of the correspondense, thank them for something they said directly to you during the previous meeting.  If no such statement is available, then mention the date, time and subject of the meeting and move on to your reason for writing.  Then next time you are in a meeting with the recipient, make sure to say something memorable so that you can use it in your next correspondense.
Comment: Nope, he wanted me to mail him about the questions I asked him when we met. Thank you for your response.
Comment: @PriyathamKattakinda, "Mail me about the questions which you asked" is both a take-away assignment and a slight invitation to a more open dialogue.  I had imagined your scenario very differently from what it now seems to have been.  I imagined that you and several dozen other co-workers were invited to a meeting with someone who is several levels higher than you in the corporate heirachy.  In such a case, continuing correspondence would be acceptable only under the conditions I described above.  In any Stack Exchange forum, it is good practice to provide relevent details in your questions.


GNS3 - configure two DHCP servers within one VLAN

Question: I have the following configuration:

I would like to provide every host from VLAN_101 with DHCP-provided IP addresses. There are two DHCP servers running - one grants adresses for every host below switch LAN_1 and the other one - below LAN_2.
What can I do, except from turning one DHCP server off, to make hosts in VLAN_101 be in a single subnet?
Is this manner correct? If not, what should I change to make it genuine? Any advices are welcome.
Comment: You can make another VLAN, e.g. 102, and put LAN_2 hosts in this VLAN. And then reconfigure your DHCP for new VLAN.
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 provide and accept your own answer.
Answer: In your topology the host in VLAN 101 connected to switch LAN_2 are in a separate network that those connected to switch LAN_1. This is because you have a router between them.
So you have 2 distinct VLAN 101, which could be very confusing.
I strongly suggest you change the VLAN name for one of them.
Apart this, you have nothing special to do to provide different DHCP on those networks, since they are totally independent.
Answer: You can use one DHCP server for both LANs, but you need to put in a DHCP relay in the router. For Cisco devices, that is the ip helper-address command. You place it on the interface of the LAN without the DHCP server, and you configure scopes for both LANs on the one DHCP server.
Assume that the DHCP server is on LAN_1 at 192.168.3.254 and that LAN_2 is connected to the router on interface FastEthernet0/2. Your DHCP relay would look something like this on R1:
interface FastEthernet0/2
  ip helper-address 192.168.3.254
!


I need to change the chainset on my carrera vengance 27.5 frame and wheels

Question: What chainset would you recommend for my bike I'm new to cycling and pretty well I'm a virgin tbh,,,it's 24 speed carrera vengeance the one I have now well it looks like it's warped when peddling,It also slips whenever I put real pressure on it I smashed my knee last time on it...it also makes the chain hit the gear selector for the big cogs.thanks...
Comment: You should have some knowledgeable person look at it.  It could be a loose chainring or a loose bearing.  Even if the chainring is bent, it's often possible to straighten it with the application of a "monkey" wrench.
Comment: When you say "gear selector" is it the front or rear derailleur mechanism?
Comment: When you say "chainset" do you mean the entire chain transmission, or the front chainring?   Sound sto me like you have bent/buckled your big chainring from an impact, and the chain isn't running on it smoothly.  Please edit a clear and well lit photo into your question to help with identifying the issues.
Comment: It's the front 3 cogs the centre cog seems to be buckled I don't know how I haven't come off or no impact to it
Answer: Have someone look at the crank. As mentioned in comments the whole crank may not need to be replaced.
If the crank does not replacement: The Halfords web page for the current Vengance model shows the bike has a mix of Shimano Altus and Tourney components, a Suntour XCE crank and a square taper cartridge bottom bracket.
Assuming your bike is the same, you can actually replace the crank with any square taper, triple ring crank designed for 8 rear gears, with the same chainring sizes (42/34/24 for the current model, but check what you have).
There are a number of manufacturers that make inexpensive cranks, a replacement Suntour or Shimano Altus crank are safe bets.
The Suntour XCE crank appears to have removable chainrings so if your big ring is damaged you will be able to replace it. Many inexpensive cranks are riveted together and the chainrings are not removable.
Comment: OK many thanks exactly the info I was after.


Violation of Newton's third law in case of fluids

Question: If a steel ball hits an iron surface it bounces back due to the Newton's third law of motion. Then why does'nt it bounce back when it hits a water surface? or for that matter even air?  The molecules of water / air should apply the force of equal magnitude on the ball as the ball applies to the water molecules. Can anyone please explain this?
Comment: Two comments. One: you have misunderstood what Newton's 3rd Law requires in the case of a solid, liquid impact. Two: ever skipped a stone?
Comment: Have a look https://www.youtube.com/watch?v=NF8aQHwcKN0
Comment: Possible duplicate of [If Newton's third law is true, why can we sink in sand?](https://physics.stackexchange.com/questions/409109/if-newtons-third-law-is-true-why-can-we-sink-in-sand)
Answer: The third law of motion:

When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.

Edit after revisit:

The molecules of water / air should apply the force of equal magnitude on the ball as the ball applies to the water molecules.

The basic misunderstanding here is in the notion of force. Acceleration for impacts will define the force, and it is best to think of the dp/dt definition of force. An incoming ball does not have 10 Newton's force , it has a constant velocity, so no force . Force is generated on impact by dp/dt.
Impacts with solids distribute momentum and energy on the whole solid due to the cohesiveness of the electromagnetic interactions, and the total momentum energy balance can be calculated with the impact point , and dp/dt calculated to give the force of impact.
Impact on air is coming in tiny scatters and tiny dp/dt. Impact on water is similar if the ball has enough energy, molecules bounce left and right with a small dp/dt slowly dissipating the energy and dispersing the momentum.
end edit
You ask :

Then why does'nt it bounce back when it hits a water surface ?

Bouncing back depends on elasticity of surfaces deformations and dissipative motions of the surfaces which absorb the energy and momentum of impact , and have to be estimated for each individual case.
Have you estimated the force that the steel ball exerts on the water molecules? dp/dt   will transfer momentum to all the column of water it penetrates  and dissipate the energy until it hits the bottom. At the surface little except ripples because the liquid is displace-able with little energy/momentum needs . Look at the video for a drop falling, which has the same density as the water and small energy/momentum to transfer to see how the third law is obeyed by dissipating the impulse and still a small drop bounces back.
Air is a non thinker: individual molecules have very small mass with respect to the ball and pick up the tiniest fraction from the impact diminishing the motion of the ball very slightly at best.
One has to do the calculations  to see that the third law is OK ? It is called a law because innumerable people have done the calculations and found that the law is validly describing data.
Comment: Thanks for your efforts, but things are not yet clear. Force = mass * acceleration. So when i throw a ball with a force of suppose 10 Newtons it would hit any surface (correct me if i am wrong) with 10 N ignoring air resistance. so if ball applies 10 N on a brick wall, the wall should apply 10 N on ball and so ball should then bounce back with same velocity, since the mass is constant. Same thing applies to the water surface. Then why doesn't the water apply 10 N of force on ball ?
Answer:
If a steel ball hits an iron surface it bounces back due to the Newton's third law of motion. Then why does'nt it bounce back when it hits a water surface ? or for that matter even air ? The molecules of water / air should apply the force of equal magnitude on the ball as the ball applies to the water molecules. Can anyone please explain this?

A simple explanation:
The forces that appear when a 100 kg iron sphere traveling at 100 km/h comes in contact with a motionless 0.1 kg plastic sphere are the same on both spheres. This is Newton's third law.
However, this does not mean the 100 kg ball has to bounce back.
Answer: force exerted by the heavy steal ball on air partical is very very small. If a ball moves with even as much as 1000kmps may exert a very small force of 0.000001N on a body.
Force exerted on a air particles by steel ball is very small although it has great speed. Force is rate of change of momentum . A very small particle of air cannot reduce its momentum to a larger extent. Instead the rate of change of momentum brought by it is very small. so, force due to momentum change by iron ball on air is very small, in return force on ball by air is also very small and ball experiences a very small drag which reduces speed of iron ball after sometime ( say 10-20 mins).
Although very small force it is, but on air it causes much greater acceleration and greater effect.
Whereas since ball is very heavy deacceration is very small.
Answer: After reading your comment on Anna V 's  answer , I think I have got your doubt.
When you throw a ball with a force of 10 N , you have applied the force and you are not continuously applying the force after the ball has left your hands. What I mean to say is that all the force that you applied on the ball (10N) has been applied by the time the ball leaves your hand. That force (10N ) = rate of change of momentum of the ball ... ie 10N=( mv-m.0)/t (where u=0) . Obviously t will be very small. Take m out and you get 10=ma. The point is that you have applied all the force and if there is no gravity (to avoid projectile motion) , the ball moves with a constant velocity which aboviously depends on a (and a obviously depends on t). So now the ball moves with a constant velocity. As it hits the wall it's velocity and hence it's momentum is changed. The rate of change in momentum (which is also the force by the wall on the ball and by the ball on the wall) is (mv2-mv1)/t (where v2 is the velocity of the ball after the collision and v1 is the velocity of the ball that it had gained after you had applied the 10 N force ) . Now as the others have said v2 depends on the material of the ball and the wall (coefficient of restitution) . Hence v2 will be different for a steel wall , a brick wall and a water wall. Since v2 will be different for different types of walls , the force on ball by the wall will be different and hence the acceleration of the ball would be different. Obviously for a water surface wall elastic properties will also matter and the ball will penetrate into the water surface.
So you were getting wrong the fact that the wall also applies a force on the ball  which is equal to the force you had initially applied (it may be equal but that depends on the collision )
I hope you got it useful !


what is the difference between 现场 and 地点?

Question: Do both of them mean "location" or "site", or is there something that sets them apart? Thank you in advance!
Comment: iciba
现场 释义相关词条
locale scene theater  。。。
地点 释义相关词条
locus place site situs spot 。。。
also many examples showing difference, also quotes 百科 for both
Comment: Ah, I'll remember to check out iciba next time. Thanks!
Answer: 地点 = location, while 现场 = being present at a location
地点 normally describes a precise location.
现场 describes the fact that some one is in a place. That place can be a precise location or an area.
For example
请告诉我地点。
Please tell me the location.
我在现场,请告诉我具体地点。
I am here, please tell me the exact location.
Comment: 现场 = scene?  Being present at a location sounds more like 现在的位置, thou it basically means the same
Comment: This response was great, thank you very much!
Answer: 现场 scene eg. crime scene 犯罪现场
地点 location or address
Comment: Could you add some more examples, besides crime scene?
Answer: 现场 is a 地点, more specifically, it's a specific 地点. You can understand it in this way: think 地点 as the word "location" or "site" or "scene", in English, you normally wouldn't just say "site" or "location", you have to define it with an article, so it would be come "the location/site" or "a location/site". Now, you could think 现场 as "the site/scene". See the transition here?
That's way you can use 地点 in a unspecific context, but you can only use 现场 in a more specific context. For example 犯罪现场, means "crime scene", not necessarily "THE crime scene", but still you need to define 现场 with crime. Or the specification may be implicit in the context. For example "I arrived at 现场(the site)" here 现场 is specific to whatever place the speaker is talking about.
All this is because of the character 现 which means present, now, current, which are little bit similar to the function of "the".
Answer: 地点 is a place where something is or could be located.
现场 is the place where an action or event occurs.
Comment: This is the right distinction.
Answer: If you're wanting to use the two, others' explanations are correct, and here are some tips to add to the picture. 地點 is a somewhat formal word that is used nearly interchangeably with most other words for "place," though it is rarely used in casual conversation. You'll typically encounter it in literature and news, that is, written mediums. It sounds very "dictionary" in tone: "某個地點" is a common example you'll see. Encyclopedic, scientific sounding writing will prefer 地點 over some of the "place" alternatives for its formality.
現場 is not very related in meaning as others have made clear. It requires some context around it usually, as you'll see an example given was not just any scene but a "crime scene." Using 現場 without some matching context that specifies the "scene" it's referring to is uncommon. A great word to know for 現場 is 現場直播. Literally has a "live stream/on the air" kind of meaning but also is used as slang for PDA (public display of affection). I find this makes this word hard to forget.


MS Reporting Services

Question: We are setting up a two MS 2008 servers to handle our web application.  On server A, we are running MS SQL 2008 Web Edition with our database.  On server B, we are running IIS, MS SQL 2008 Web Edition with just MS Reporting Services.  When I trying to make the Reporting service connection from Server B to Server A, I got "The feature: "Remote access to report data sources and/or the report server database" is not supported in this edition of Reporting Services."  Does anyone know which version of MS SQL will make this work?
Answer: Standard or higher. Or Developer (for testing); see this.

MS Reporting Services


In Attack on Titan, what differs royal blooded people from Subjects of Ymir?

Question: Subjects of Ymir are all descendants of Ymir. What differs the so called royal bloodline from the rest?
Answer: That's actually a really good question. I suppose you are talking about how only the royal bloodline can use the full potential of the Founding Titan. My theories as a somewhat mediocre fan to solve this apparent plot hole are as follows:

 It actually doesn't matter from what we have seen in the manga. Eren was able to seize control of the Founding Titan by convincing Ymir, the First Titan, to make her own choice as she was a slave to the will of the royal bloodline since the days of the founding king, Fritz. Hence the royal bloodline wasn't really special. They just had the advantage of manipulating a nigh-omnipotent girl to do their bidding.

The first theory can be shot down when you consider the fact that Zeke's spinal fluid can be used to turn Eldians into pure Titans. Thus perhaps the royal bloodline is special.
I'm no geneticist, just a hyperactive high schooler, so what I'm about to propose may be scientifically preposterous. I think because since the royal family is directly descended from Maria, Rose, and Sina, the first humans to eat Titan blood raw I might add, it's possible that there's a higher concentration of the original power in the royal bloodline hence their abilities. How you might ask? They may have taken a page from the Targaryens.

I hope this answer is ok. If I'm wrong somewhere, please correct me.
Comment: Yeah, that's theories, but it's not explained, right?
Answer: We don't have an answer for that so far, even with the ending of the manga, it was never explicit why there is the difference in the royal blood, but I saw a theory that I think it makes sense (it isn't cannon, merely theory).
Basically, we know that Ymir got eaten by her children after her death, and the theory supports that 1 of those 3 children, ate the neck part (the most important human's body part when it comes to titans), and with that, she gained the original power, getting the power of The Founder Titan.
Once again, it's not confirmed but for me, it gives a reasonable explanation about it!
Answer: Plain and Simple,
What we know is that in the Beginning there were Many tribes and Eldia was the dominant one and it was lead by Master Fritz (A power hungry man). So, one day he hunted one of his Servants Ymir, for letting of a pig, who ran to the forest and receives the Titan powers from a Spine like Creature. Seeing that Ymir would be useful, Fritz made her do all the work of his nation, like creating Bridges and fighting wars and made her his Concubine and had three Children. They were Rose, Maria, and Shina (Whose names are the Three walls), So when Ymir was killed, sacrificing herself for Fritz. Fritz made his three children eat Ymir dead remains, and kept the Power of Ymir's Titans. Eventually Eldia Multiplied and prospered with the Help of their Titans and captured many other countries like Marley, bringing hate on them in the Future.
So in one sentence the Royal Bloodline are the Children of Ymir and Fritz and the normal
eldians are the ones that were Kings Fritz' subjects and Servants and other children.
If you think there is something Wrong or if you have other Theories and aswers please correct me.
Thanks
Comment: Only Subjects of Ymir in general can become Titans. Technically all Eldians must be royal blooded. This is wrong.


Which module in python will help me write a program that can run in the background?

Question: I have written a python code that will copy a file from its source directory, paste it into a new directory and parse it into an XML file. I got to know certain modules in python such as subprocess, multiprocess, threading, etc. which will help me frequently perform the aforementioned tasks in the background. But I don't know which is the appropriate one. Please help!
Answer: My go-to solution for this is this amazing article: in short, it uses some permission management to allow you/the computer to use the Python interpreter as a command, which can then be executed by nohup, which is the command which executes what you are looking for.
If you would like a solution based in Python (meaning no OS dependancy), use the subprocess module. It is the easiest way to do it in my opinion, especially if you are loading large amounts of data into RAM or, as in your case, you are opening files, in which case multiprocessing/threading can get cumbersome and risk corrupting your files. Essentially, as explained here in the Python docs, you can control the input/output method of your program, allowing you to, in a way, emulate your own shell. Note that will need to momentarily run the command to call this, but if you set it up right you can emulate the nohup command, provided the code you already have is being called from a separate file.
Comment: I will try this for sure. Thank you for such detailed answer! I'll let you know for sure if it works.


Sent Stellar to the same wallet address

Question: I have sent Stellar to the same Wallet address! will this go back into my Wallet account after some time. Or is there something I can do to retrieve it back?
Answer: I tested a transaction on testnet using the stellar laboratory and it seems that if you send lumens to the same account it only deducts a fee - assuming the source account of the txn envelope is the same account on both sides of the payment operation. I actually expected the txn would fail but it did not. The lumens balance did not change except for the small amount for the fee.
Given this behavior, if your stellar balance decreased by more than the fee amount, you may have sent it to another address. Double check the transaction hash and make sure.
Answer: You don't need to worry about that much. You will just get charged for very small amount fee of XLM (depending on the number of XLM you sent, but it's generally very low), and that's it.
Comment: I don't see what this adds to the existing answer.
Comment: @Chenmunka sorry about that.

Sent Stellar to the same wallet address


What happens to a Demon's Cover when the mortal providing part of that Cover dies?

Question: Demon Dora buys from mortal Fred his childhood experiences in Townsville in return for fortune and fame.   Fred uses the money to buy a car, crashes, and dies.  Does anything happen to the Cover Dora crafted from those experiences?
Answer: The pact ends with Fred's death, but the Cover remains.
From the section on Pact Duration, p. 193:
"Pacts are usually permanent, lasting for as long as the contract exists and both parties live. They can be nullified, typically by destroying the contract, but otherwise continue to have their effects."
The wording here is important (go figure for contract law). There is a difference between a Pact ending and being nullified.
So unless some special circumstance causes the Pact to be nullified at the time the pact ends, the effects continue. Fred's heirs get the wealth. Dora keeps the cover.
If, for some special reason, the Pact nullifies, then Dora is in for a loss of a dot of Cover rating and has to check for a glitch. See the section on contract destruction for more info.
Also, Fred must have a pretty boring childhood in Townsville for this to be a valid contract. Even if he had only one close childhood friend, that relationship alone would be worth a 3 point (the maximum) cover benefit for a Pact.


which is the best circuit simulator for my purpose?

Question: hi all i want to know the the limit of my circuit,upto which it can withstand,so that i can select or change the components accordingly.When i tried simulation in NI MltiSIM, it works fine,but the issue is when you apply 50A directly to an LED, it'll still work fine,I am wondered how is that possible??I would like to know which other simulators can show "when my circuit will get fried?"
Comment: Also, circuit simulators are pretty universally mediocre at best. They generally only produce results as good as your understanding of the circuit.
Comment: NI Multisim is pretty niche. Give it time.
Comment: this is the first time i've seen(on stack exchange community sites) no response even after an hour...
Answer: The problem is that you are expecting a model to have more functionality than it has. Most models are simply parameters in an equation. They are designed to approximate the actual device behavior within specific operating conditions. For example, a diode is modeled using the following equation:
\$\Large I_f = I_S(e^{\frac{Vf}{NV_t}} - 1)\$
Where Vf is the applied voltage and If is the forward current. Notice that there's nothing stopping me from putting 50V as the applied forward voltage, and I will definitely get an answer from the simulator. It will be completely nonsense, but the model is assuming that the behavior of the diode is always described by that equation.
I have seen device models with voltage breakdowns and melting currents, but typically those are in "high end" models used for IC design. It is specifically coded into the models. I'm using Spectre and HSPICE, but I don't think that's going to help you much. If you MUST use a simulator to identify if a part is going to fail, then you need to understand when the part is going to fail and watch the simulation results for those conditions.
Relying on a simulator to guarantee whether or not a part works is asking for disaster. Simulators model everything as "ideal" - and that is making a LOT of assumptions. Keep in mind that a simulator considers everything perfect unless told otherwise. Doing conceptual design with a simulator is dangerous.
Answer: Some simulators will issue a warning when an excessive current is detected in a circuit. These warnings are typically triggered when a current exceeds 100 or 1000 Amps, for example. The purpose of the warning is not to tell you when the failure limit of a part is reached but only to let you know you might have set up a circuit incorrectly or with unrealistic parameters.
In fact, the device models themselves don't even include the self heating behavior that, in the extreme, leads to damage. Even if they did, your circuit drawing would then have to include information about heat-sinking and air-flow in order to produce accurate results.
What you have to do is run the circuit simulation to find out what currents will be produced if the device continues to operate nominally, and then compare that result to the datasheet limits for each part.
Comment: so we can not simulate for the same purpose?is actual implementation the only way out?
Comment: You can simulate to see if you exceed the parts limits, to a certain extent. But you will have to check the currents against the datasheet yourself -- the simulator won't do it for you. And you will need to leave some design margin because the simulator won't include self-heating effects. Also, you'll need to consider that your simulator model for a given component represents a "typical" part -- real parts vary from the nominal, and you also need to consider whether a worst-case part (say highest or lowest gain, highest or lowest resistance, etc) will function in the design.
Answer: I accept with The Photon. It may not possible to detect accurately without giving too much parameters like heat-sinking, air-flow and such.
And I haven't seen any simulator to do the job of warning you before or at the frying point.
But I would like to say that you should not trust the SPICE. That is because

Analog guru Bob Pease says so :)
It is not 100% true all the time, it may lead to production mistakes that cost you much.
If you base your circuit design on SPICE with trial and error, then you will not improve your circuit design skills and practice your theory.
If you do not practice your circuits in real world, you will never get the experience of the real world and will not be able to design circuits for real world, because you won't know much about the real world. ( That is lots of real world! )

These are the things I've learned and still learning.