What is Rebbi Yehuda's source for allowing a succah to be above 20 amos?

Question: Some say that R' Yehuda held that there is no Biblical source for the 20 amos limit and therefore ruled that a succah could be higher than 20 amos. But that would seem to go against the Gemara that says סוכה דאורייתא תני פסולה מבוי דרבנן תני תקנתא. And if he held there is no source, why did R' Yehuda rule that a מבוי which is דרבנן does not need to be lowered. This suggests that he did have a Biblical source for allowing a higher than 20 amos succah.
Comment: https://judaism.meta.stackexchange.com/q/1081/759
Comment: Vote to close. You could pose the question and then answer it, but this is not currently in line with the site's standards.
Comment: Learning...  I answered in my first post. comments were to clarify my answer. I will post a second post with answer separated.  thank you
Comment: Welcome to MiYodeya 613JLM. Since MY is different from other sites you might be used to, see [here](https://judaism.meta.stackexchange.com/a/3887/11501) for a guide which might help understand the site. Great to have you learn with us!
Comment: In line with SethJ's comment I'm going to edit out the bit where you answer your question so that this remains open. You're welcome. If you insist on having that link in there, feel free to roll back, but at least include a summary of the contents of the link, just in case something happens to that webpage.
Answer: I think you are misunderstanding the line of דאורייתא תני פסולה מבוי דרבנן תני תקנתא.
Here is the passage in context:
Succah 2a

תנן התם מבוי שהוא גבוה מעשרים אמה ימעט רבי יהודה אומר אינו צריך מאי
  שנא גבי סוכה דתני פסולה ומאי שנא גבי מבוי דתני תקנתא סוכה דאורייתא תני
  פסולה מבוי דרבנן תני תקנתא ואיבעית אימא בדאורייתא נמי תני תקנתא מיהו
  סוכה (דנפישי מילתה) פסיק ותני פסולה מבוי דלא נפיש מיליה תני תקנתא
We have learnt elsewhere : If the [cross-beam above an] alley-entry is
  more than twenty cubits high, it must be lowered. R. Judah says this
  is unnecessary. Now wherein lies the difference [between the two cases
  that] with regard to the Sukkah it is declared NOT VALID, while with
  regard to [the cross-beam over] the alley-entry, a remedy is
  indicated? — With regard to the Sukkah, since it is a Pentateuchal
  ordinance, it [was proper categorically to] state, NOT VALID; with
  regard to [the cross-beam over] an alley-entry, however, since the
  injunction is only Rabbinical, a remedy is given. And, if you wish,
  you may say that even with a Pentateuchal command a remedy may be
  given, but with regard to the Sukkah, as the ordinances relating
  thereto are many it was briefly stated, NOT VALID [while in the case
  of a cross-beam over] an alley-entry, since the regulations thereof
  are not many, a remedy is indicated.(Soncino translation)

It does not mean that the Torah says that a succah cannot exceed 20 amos in height, as that would, of course, refute the opinion of R. Yehuda. What it means is that the Sages used the term "invalid" because (according to their view) the invalidity of such a succah is already established by the Torah, so they can refer to such a succah as invalid. As opposed to a mavuy where the cross-beam is not discussed in the Torah, so saying that it is invalid if higher than 20 amos is meaningless because prior to the Mishnah there is nothing that makes it invalid. Thus, the Sages instead say that it must be lowered.
R. Yehuda disagrees in both cases. He does not agree that the Torah stipulates that a succah must not exceed 20 amos. Once the Sages declared it invalid, R. Yehuda responds that it is valid. By the mavuy, once the Sages said that it must be lowered, R. Yehuda says that it need not be lowered.
This is essentially Rashi's explanation:

סוכה מדאורייתא. דעשרים אמה דילה ילפינן מדאורייתא וקודם שנשנית המשנה
  נאמרה שיעורה מסיני: תני פסולה. שייך למיתני בה לשון פסול כלומר לא נעשית
  כתורה וכהלכה: מבוי. דכוליה מדרבנן דמדאורייתא סגי ליה בשלש מחיצות ואינו
  צריך לקורה זו אלא מדרבנן: תני תקנתא. דלא שייך למתני בה לשון פסול דמאן
  פסלה קודם שנשנית משנה זו הרי היא תחלת הוראתו ומצותו

R. Yehuda's source for his view (as explained by Rambam in his commentary to the Mishnah) is that he disagrees with the premise that a succah is meant to be a "temporary dwelling".

Additionally, regarding the basis of R. Yehuda's position, Rashi states that the disagreement will be explained in the Gemara. The Penei Yehoshua points out though that the Gemara never explains R. Yehuda's position. He first suggests that when the Gemara offers three explanations of the Sages' position, and asks a question on each one, we simply assume that R. Yehuda agrees with the questions. However, he then argues that for the first explanation that can't be true (based on a later Gemara), so he then suggests that Rashi was only referring to the reason according to the explanation of Rava which is the explanation accepted l'halacha. As that explanation is that a succah must be a "temporary dwelling", it is understood that R. Yehuda does not require a temporary dwelling.
Comment: @613JLM I'm not sure I see your point.
Comment: "R. Yehuda's source for his view (as explained by Rambam in his commentary to the Mishnah) is that he disagrees with the premise that a Succah is meant to be a "temporary dwelling"."
Comment: @613JLM Is there an issue with that sentence?
Comment: meant to add... Daf 7b notes that 8 Tannaim required one particular aspect of a succah to be fixed without which a succah is invalid.  If it is as you say than R' Yehuda would have to be interpreted as requiring a succah to be above 20 amos, without which it is invalid.  It must mean that he requires that a succah be built in a permanent space as well as a temporary space.
Comment: @613JLM Not what "fixed" means. You remember Rava from 2a that the Chachamim require a Sukkah to be less than 20 Amos so that it's a temporary dwelling? So these Tannaim disagree with that and require it to be a permanent one.
Comment: @DonielF https://www.dropbox.com/s/yd84ka1btshtbej/Temporary%20vs.%20Permanent%20.png?dl=0
Answer: R' Yehuda holds that a succah had to be both Temporary and Fixed from the verse:  בסוכות תשבו שבעת ימים אמרה תורה כל שבעת הימים. Temporary from the word "שבעת" as you see from Rava's explanation and his rationale of why a perfect succah above 20 amos is פסולה. It has nothing to do with the materials used, as the Gemara states: למעלה מכ' אמה דאדם עושה דירתו דירת קבע כי עביד ליה דירת עראי נמי לא נפיק but instead the space in which it is built.  And he holds Fixed from the word "תשבו" as you see from Daf 28b כל שבעת הימים אדם עושה סוכתו קבע וביתו עראי. As the Gemara states: "מה"מ דת"ר "תשבו.
Hence the Mishna states Daf 28b: כל שבעת הימים אדם עושה סוכתו קבע וביתו עראי
Therefore, the Rabbis who disputed R' Yehuda taught in a Barasisa: כיצד היו לו כלים נאים מעלן לסוכה מצעות נאות מעלן לסוכה אוכל ושותה ומטייל בסוכה
And R' Yehuda taught: עושה סוכתו קבע וביתו עראי means to build a succah in the 3-denominational space where a house would be temporary (less than 4X4) and where your succah would be permanent like a house (above twenty amos). Or, if your succah is built greater than 4X4 amos your succah would necessarily be permanent like a house (greater than 4x4 amos) and like a house built temporary similar to a succah (less than 20 amos).
The final result being that the words בית and סוכה in the Torah are stripped of any material relevance in terms of קבע and עראי and comes to represent abstract measurements that equate to the mental state of a person perceiving this world as their permanent or temporary dwelling.
It is significant that the Torah represents a בית as the two dimensions of length and width (area) to further illustrate that man naturally stands on the earth and horizontally sees what is in front of him and at his side and begins to think that this world and all that he sees with his physical eyes is the point to life. And, he directs his thoughts and heart after it, while neglecting his spiritual obligations. The remedy provided by the Torah is the mitzvah to dwell in a succah which has the power to bring the spiritual dimension of height (succah) down into our two dimensional lives (House) where we can all declare together: קָדושׁ קָדושׁ קָדושׁ ה' צְבָאות מְלא כָל הָאָרֶץ כְּבודו
כְּבודו מָלֵא עולָם
It would seem that Mescestes Sukkah is an instruction manual on how to build our minds into a Beis Hamikdash from which we can connect to and properly serve Hashem.
https://www.dropbox.com/s/evgbjju4wpmvybs/We%20are%20the%20Succah.png?dl=0
https://www.dropbox.com/s/yd84ka1btshtbej/Temporary%20vs.%20Permanent%20.png?dl=0


Oracle vs Google: Can Oracle sue any company who is using Java and making profit?

Question: Lot of companies in the world use Java including the company I work for. AFAIK there is no licensing deal and we use most of the Java packages for which Oracle sued Google. So can Oracle sue any company which is using Java and making profit? If not, then why only Google is being targeted?
Comment: Usage of java is allowed. Re-implementing java based on the api docs isn't (according to Oracle).
Comment: If you're using Oracle's Java (as opposed to OpenJDK) commercially, you need to negotiate a paid license with Oracle.  Java isn't free for commercial use (and hasn't been since around 1.2 or 1.3).
Comment: what do you mean by using Oracle's Java?  The JVM is free, as in beer, to download.  As is the JDK.  There are terms and conditions...but you can certainly use it.
Answer: The issue is not the use (calling) the Java API. The issue was copying portions of it and re-releasing it within the Android SDK.
Simple use of Oracle's Java SDK is not what they are suing over.
Answer:
So can Oracle sue any company which is using Java and making profit?

Yes. In fact, it is not necessary for them to be making a profit, just that there is not a fair use defence.

why only Google is being targeted?

You sue people with money, preferably lots of money. There is no reason to sue someone if they are unable to pay the judgement.
Answer: In the javadoc api license there is the following clause:

License for Evaluation Purposes. Oracle hereby grants you a fully-paid, non-exclusive, non-transferable, worldwide, limited
  license (without the right to sublicense), under Oracle's applicable
  intellectual property rights to view, download, use and reproduce the
  Specification only for the purpose of internal evaluation. This
  includes (i) developing applications intended to run on an
  implementation of the Specification, provided that such applications
  do not themselves implement any portion(s) of the Specification, and
  (ii) discussing the Specification with any third party; and (iii)
  excerpting brief portions of the Specification in oral or written
  communications which discuss the Specification provided that such
  excerpts do not in the aggregate constitute a significant portion of
  the Specification.

Clause 2 has language that requires distributed implementations to be fully compliant to the docs (and require passing the Technology Compatibility Kit).
Similar language has been there since java 5.
This means that Google is not allowed to re-implement just parts of the java standard library described in the javadoc. Which they did for android.


what is the difference between //span and //*?

Question: I am learning selenium Xpath. what are the different ways of Xpath ? what is the difference between //span and//*?
Comment: What rrsearch have you done so far? What google says?
Answer: The difference is that //* selects any element and //span select elements that are within a span tag
Answer: // means that you look for the elements wherever they are ander the current node of xml tree. In your case you start from // which means that the "current node" is the root node.
Then you specify which element you would like to search. span is just a concrete node name while * is a mask accepting any node name. So in your case //span means "take all nodes with name span wherever they are in document hierarchy. //* means take all nodes of the document.
Answer:
Open any website and click f12, and click the elements tab:

Now click ctrl+F, you can see a text field where you can search the element using XPath,text or CSS

Now click on some element and then give then type the locators //span, and //* in the text field, see what's happening
Answer:

'//' means that look for the element from 'Current node'
//span looks for elements with tag 'span', so on searching you will find only elements with tag name span'
//* looks for elements with any tag, so it will literally find all the tags in the webpage

Note:
Searching "//span" might find the non-span tag in the chrome inspect element, this is because the search field also supports normal text search in the DOM. But in selenium, it will find only tags with name 'Span'


What dangers present themselves when someone uses the grounding system as a neutral?

Question: What dangers present themselves when someone uses the grounding system as a neutral?  I'm just looking for insight into the theories.
Comment: Electrocution would be top of the list.
Comment: Possible duplicate of [Can I connect ground to neutral in a 3 wire outlet?](https://diy.stackexchange.com/questions/9256/can-i-connect-ground-to-neutral-in-a-3-wire-outlet)
Answer: Unlike the European   double-insulated 2-wire single-phase distribution system, the American single-phase system implements safety by using a 3-wire system consisting of a 'hot', a 'return' and a 'ground' wire. It takes just 4   milliamperes of current to flow from the 'hot' to the 'ground' to activate the ground-fault circuit interruption of a well configure 120 VAC power distribution circuit. Any more than 4 milliamperes results in sufficient current to cause cardiac arrest in large people.
If you are using the ground wire (green) as a neutral, not only do you have an unsafely configured AC power distribution circuit.  But also, you do not know what "else" is between the green wire at the point you tap it and the point where the green wire is bonded to the return (usually at the panel).  Almost all electrocutions that occur with swimmers swimming close to marinas occur because some electricity is returning via the green wire (faulty boat or marina circuit).  DO NOT DO IT YOU COULD KILL SOMEONE IN YOUR HOME!!!
Comment: I swam near marinas my whole childhood, I had no idea this was a danger.
Answer: Neutrals come loose. Happens all the time.
Imagine a situation where a neutral wire fails to conduct well, due to looseness, wire damage or overload.   What happens?  The loads pull neutral "up" away from 0 volts.  That's because the loads are "in series" with the weakness in the neutral wire.  Draw it out in an electrical diagram, it will make sense.
If the neutral is cut, then the neutral will float up to 120V because it is connected to 120V through the load.
Now, if you have combined neutral and ground in some way, you are now putting 120V on every surface that's supposed to be grounded - including wall switch cover screws, appliance chassis, and even the service panel itself.  So when you open the service panel door to check the breakers, ka-pow!
It doesn't really matter how you combine neutral and ground - whether you have ground and bootleg neutral, or have neutral and bootleg ground. Same issue either way.
Answer: The neutral carries the unbalanced current.  Depending on how the circuit is configured this unbalanced current can get very high.  Plus years of electrical modifications to a homes wiring where things are added and tampered with adds to the neutral carrying more unbalanced current.  So, what happens when someone haphazardly uses a ground as a neutral is they put all that hazardous current on potentially all the conductive metal items throughout the home, potentially creating dangerous shock hazards.
Comment: In residential the neutral is the return path not unbalanced, in a pure 240v circuit the neutral is not used, in a 240 with 120 loads 4 wire circuit the neutral is the return path for 120v loads again.
Comment: Leniar or non leniar there are only 2 wires in a residential 120v circuit the hot supplying the circuit and the neutral returning back to the source. The ground is not a current carrying conductor unless the circuit is faulted.
Comment: @Ed Beal 1.While it is true a 120v branch circuits should have equal "balanced" loads, MWBC's behave differently. The sum of both branches, as you know, will cancel out the return load with only the differential "unbalanced" portion remaning.  In my answer, the expression of "unbalanced current" takes the latter into consideration while emphasizing that modifications to existing wiring may without care add to the unbalanced.  Hope that helps clarify things.


Impatriate Tax Regime

Question: I will be moving to Luxembourg soon and just got to know about this tax regime for expatriates in Luxembourg. I think I am qualified for this regime because I will be getting a European Blue Card once I land in Luxembourg. The Blue Card, as we all know, is reserved for highly skilled workers. So my question is how can I get aboard this tax regime? Is it on the mercy of my employer to give it to me or is it my right as a highly-skilled worker to demand it? The astonishing thing is that my employer's tax advisor (PwC) never told me about this. Which makes me wonder if my employer wants me to benefit from this regime. What should I do?
Comment: It's your employers tax adviser, not yours. They are paid to look after the employers best interests, not yours, just keep that in mind.
Comment: They might or might not, but it's a conflict of interest for them. They aren't going to give you advice that costs their customer more to have you, no matter how much it benefits you. The best thing to do would be to find an impartial (or partial to you) tax expert with experience in this kind of situation to advise you on your best strategy.
Comment: So now I do know about this, do you think they would help me? I don't have the slightest idea who should I contact regarding this. If they refuse, what options do I have?
Answer: It's not obvious to me that merely being a blue card holder necessarily means you qualify as highly skilled for the purpose of this tax regime (although the criteria actually seem laxer than for the blue card). Also, the list of expenses you can declare is quite limited and very specific, it's not a straightforward discount like some other similar schemes (e.g. the Dutch 30% ruling).
But most importantly, as explained in the second paragraph,

A specific tax regime exists for the costs incurred in moving highly qualified workers and borne by the employer.

So the employer has to pay for these costs, submit these as operating expenses and send a list of employees benefiting from this regime to the tax office. In other words, it's not something you can apply or benefit from, your employer does. It also doesn't matter if you are incurring some of these costs (e.g. moving costs), the regime only applies if your employer paid for them.
The goal is to help Luxembourg-based employers be more attractive by offering e.g. tax-free relocation packages to highly qualified hires. But if you have already agreed to come without these benefits, your employer has little incentive to give you an additional benefit that was not part of the original negotiation. That's what you would need for this regime to apply.
Comment: @ChiragArora That's more or less what is explained on the website and in my answer. If you want them to pay for flight tickets (or whatever), you need to negotiate that with them. The tax regime doesn't really matter to you, really.
Comment: Aah, so basically this tax incentive is only for employers. Which means they can write-off the perks given to employees to attract talent. I did think earlier this may be the case but the following line: "The employee may request a contribution from their employer for the following moving costs and expenses, as long as the expenses incurred do not exceed a reasonable amount:"; made things somewhat confusing.
Comment: @ChiragArora I think it's a little more complicated than that, in that my understanding is that these payments also do not count towards your personal income tax. But the first hurdle is convincing your employer to pay a relocation package covering all or some of the expenses listed. If you don't have such a package, then the tax regime is moot. If you do, let your employer deal with it, whether they save on taxes is more important to them than to you. Either way, you would not be requesting to benefit from the tax regime, that's a secondary consideration.
Comment: My employer is giving me a relocation lump-sum, but nothing from the 'recurring costs' such as the house rent and yearly flight tickets back to home.
Comment: I contacted PwC and this is what they said: "Please kindly note that unfortunately, you cannot decide to benefit from the expatriate regime by on your own. It is the company who decided which employees are entitled to benefit from it and communicate the list of employees to the government. In general, when you receive the offer from the employer they inform you about this option - if it is available for you, also could happen that they indicate it in the employment contract."

Impatriate Tax Regime


Canon 5D photos look terrible, possible Focus Screen issues?

Question: I have an original Canon 5D. I cannot get good, sharp, clear photos no matter how much I try. They will look clear at one area, and distorted looking in another area. Not Bokeh or bad focus, but just distorted looking. This happens indoors or out. I shoot in RAW, but it has also happened in Auto, and Program modes when I've checked different settings with the same results. I have a couple of fast lenses 50mm 1.4, 24-70mm 2.8, and a 35mm f2. I bought the camera used and was told that the Focus Screen had been replaced in it at one time. Could I possibly have the wrong FS in it and need to replace it to accommodate my faster lenses? Any help or advice is greatly appreciated. TIA
Comment: Can you provide test shots of your distortion?
Comment: There's a custom functions setting to tell the cam which focus screen you have in it. You might check that. You can always send the camera in to Canon for diagnosis.
Comment: Try manual focusing to see if something is wrong with autofocus.
Answer: The focusing screen has nothing to do with:

Autofocus performance. There is a separate optical path to the PDAF sensor that does not pass through the focusing screen.
The actual image recorded by the camera when the shutter is open and the photo is exposed. The focusing screen is not in the optical path at the time the image is recorded.

The focusing screen does affect:

What you see when looking through the viewfinder. If the view is distorted or out of focus only in the viewfinder but not in the resulting photos then the issue could be with the focusing screen. If you are manually focusing then a misadjusted focusing screen could make subjects that look focused in the viewfinder appear blurry in the resulting images.
What the camera's light meter measures. The focusing screen is in the optical path between the lens and the light meter located in the prism housing. If an optional focusing screen has replaced the original Ee-A focusing screen, it could affect the amount of light allowed to pass through prior to being measured by the light meter. If the replacement focusing screen is the Ee-D (precision matte grid lines) or Ee-S (Super precision matte for lenses faster than f/2.8) then the camera's menu will allow you to specify such in the settings. The camera will then compensate for the slightly different amount of light allowed to pass through the focusing screen that reaches the light meter. But a slight inaccuracy in metering should not cause your photos to be distorted or blurry unless they are overexposed enough to cause pixel blooming.

Without seeing some example images it is hard to guess what is going on with your camera. It may be that the lens mounting flange is no longer square with the imaging sensor or vice-versa. This could lead to images that look like they were taken with a tilt lens or with a lens with misaligned elements. If the reflex mirror is slightly misaligned it would affect both what you see through the viewfinder and the accuracy of the PDAF system, but wouldn't have any effect on the resulting images (other than an incorrect point of focus - but something that is either closer or further than the intended subject should be in focus).
Comment: I will see if I can dig up a sample of what I am talking about. If I've even kept them. Stay tuned please.....
Answer: just stating the obvious

lens

did you try different lenses? you mentioned you have several lenses but did not precise if you tried changing them. if not, you may have a bad lens.

mirror

some early models of the 5D had faulty mirror mechanisms. sometimes they would fall or drop and distort the image....also since the focus screen was changed it may not be fixed properly...
but you would see that on the viewfinder before taking the pic....unless you do see it...
if that´s so, you can easily reposition the fs yourself or send it to be adjusted.


Creating a real photo album - need a recommendation for an app to create family photo albums

Question: I have been creating my last two family photo albums in a crappy album creator application (tied to the print house).
I really need to switch to something easier. My requirements are not that high. In terms of quality, it has to be good (not marriage album level) and to be able to order the result on thick pages. But I want the user experience to be excellent - Saving arrangement templates, auto placement of pictures.
And I want to be able to send the result for printing.
I want to to learn about your experience with creating family albums software.
Thanks.
Comment: What operating system should it run on?
Comment: And should it be free, or do you have a budegt in mind?
Answer: For a family vacation in 2003, I used my usual thumnail and image file management program (ThumbsPlus, if you care, but I'm not here to recommend a product but describe an approach to this problem) to print all the pictures, 4-up on a page, with ID numbers.  The quarter-page was just a little smaller than the normal print, and I could take care of a small number of featured photos separately.
It automatically and trivially generated album pages, which I then put in plastic page protectors in a 3-ring binder.
That's as easy as it gets! Uniform filled pages, not faux-scrapbook. There's a button for that.
Answer: Just to let you know I am just starting to use Light Room 5 to create a photo book. If I remember correctly, the photo book creation was added to Light Room starting with version 4, so if you have Light Room software, it has to version 4 or 5.
It has really good options and lets you upload to Blub.com for printing - this is what I've read in the help file, I have not yet uploaded as I am still working on my book - and it also allows you to save as a .pdf or .jpg; again, from the help file.


Does aging in oak barrels add the same compounds to beer as it does to wine?

Question: If I remember correctly, aging wine in barrels is known to promote aeration and add phenols from the wood into the mix.
Does the wood react any differently to produce any flavors unique to beer?  Is the aeration beneficial for flavor?
Answer: You remember correctly.
(http://indianapublicmedia.org/amomentofscience/age-wine-wooden-barrels/)

(Tannic acid, a tannin found in oak)
Tannins, the chemicals that are transferred from the oak barrels to the wine, are extremely good at forming hydrogen bonds (just look at the structure!), which makes them very soluble in water. Considering that both beer and wine have no shortage of water in them, these molecules are quite willing to join either substance.
As for the aeration, I believe that may actually be an undesirable consequence of using the barrels for beer. However I can't imagine the effects being very profound unless you were aging the beer like you would with wine (months or years versus weeks).
Answer: Beer barrel-aging is a complex topic, and there's more than one reason for doing it.
It has become a common practice in the american industry to age strong beers in barrels (mostly ex-bourbon oak barrels, but no only), to mellow it and add another layer of flavors (almost the same thing that happens with whisky). It's very common with Imperial Stouts, for example, which is one of the styles that goes best with this kind of practice. Generally, boozy and dark beers are more suitable for this, but not only (people age belgian tripels, for example, which, while being sometimes boozy, aren't roasty at all).
So, talking about oak, you get that vanilla, coconut, sherry flavors, sometimes some smoke from the barrel's inside toast, and things like that. Boozines is softened as well (mellowed). Off course, inside the barrel, a lot of complex reactions occurs, and I don't know how it can be compared with wine chemically, but, along with other compounds, tannins are incorporated to the beer, altough it doesn't always appear so much in the final product like in wines. It all depends on a series of factors, including the amount of time the liquid spends in the barrel.
Besides it, some aeration and in consequence oxidation does occur, but that's not the main purpose in that "type" of aging. Flavors of the original barrel's content may be picked as well, in higher or lower levels.
Another main use of barrels in the beer industry is for production of wild/sour beers, in that case, the micro-aeration being a main desired factor. When people want to sour their beers and/or develop wild characteristics in it, they use different organisms after the primary fermentation. In order to sour it they use bacteria and for the rustic (wild) flavors they use another kind of yeast called brettanomyces in a further step of fermentation/maturation, in which oxygen presence is fundamental, but a slow pace is mandatory as well to avoid an overgrowth of the organisms and a possible "spoilage" of the beer. So, the barrel is a perfect place for this process to take place, because wood allows the oxygen to get in very slowly. Besides it, the barrel itself becomes a colony house for all those bugs (as brewers call those wild microorganisms), so you may not even need to pitch any yeast/bacteria after some time anymore. Off course, the wood alone impairs some flavors to the beer as well. You end up with a very, very complex product.
These days, people are doing all kinds of crazy experiments you can think of, and there's no mandatory rule when using barrels. It all depends on what result you want to achieve and real-world experience as well. There's a lot of methods, and every one is still figuring it out.


Sending a full Transcript, or only a part?

Question: I have a quick question. I have to send in official transcripts to some graduate schools. I am trying to apply for Mathematics. However, since i am also doing a B.A in Philosophy and Economics, the last semester has no mathematics classes as I have some classes I have to take. I have the option to not disclose that in my official transcript and "cut off" the future semester. Would that be seen as disingenuous? I don't want the admissions to think I am "avoiding" mathematics, there is sim ply no math courses my school offers that I would like to take and I need some courses for my other majors.
Comment: Send in the full transcript. Just because there's a semester of no math doesn't mean they'll look down on it.
Answer: I have just one advise: Be honest. Changing an official transcript to make you look better is not honest, and could get you into trouble.
Moreover, a semester without math does not necessarily look bad.
Answer: Perhaps the lack of more advanced courses in your undergraduate program could be a point of discussion in your letter or essay? I agree with Sean Roberson -- send the entire transcript. If you were judged alongside another applicant and you each have equivalent maths coursework, the advanced courses in Philosophy or Economics may make you more appealing/interesting.
Have you reached out to the administrators and/or faculty in some of the departments to which you are applying? You can ask them their opinion on this, and other things. You could remain anonymous, or not. There's not much to lose and potentially a lot to gain by asking them these questions. Good luck!


Workflow if-Else help

Question: I have a workflow and the ending is not working for me no matter what I try. The point is that in Collect 6 the person says YES or NO to a question. If they say NO, it goes to Collet 7 and thats it. ( This works perfect) BUT if they say yes it should go to collect 8, then collect 9 skipping collect 7. BUT it is going to 7,8,9. Can anyone see what I am doing wrong for this second part. TIA!
http://postimg.org/image/ooeibgkn1/
Answer: You have accidentally nested The if's. Move the second if down until it is outside of the first if and you should be fine.
Comment: Thank you! helped but still did not quite work.
Answer: You have messed up your if statements. See the image below and change your if blocks accordingly.
This image is not taken from the designer. I have edited your image to show the correct sequence.

Workflow if-Else help


How do you deal with time estimates?

Question: If given too little time, quality suffers. If given too much time, developers will find a way to use all alloted time, no matter what. What would be a good way with dealing with estimates? Are they a necessary evil?
Comment: In the words of the late great Douglas Adams "I love deadlines. I like the whooshing sound they make as they fly by."
Comment: I think your assumption that "developers will find a way to use all alloted time, no matter what" quite misguided.  I've finished a lot of projects early and don't randomly use up alloted time.  Perhaps rewording your question could eliminate your undocumented assumption.
Comment: @Walter - not so fast. This phenomenon is well established and is not specific to developers. For example, how often in college did you have your term paper written and ready to turn in a week before the due date?
Comment: @Walter - man, I must be working in the wrong place. That's how it is here at least, maybe we are really dysfunctional.
Comment: @PeterAllenWebb - It doesn't make them lazy if they find a way to fill up the available time. There are always ways to improve on a software project (more testing, tweaking the UI, adding better error handling, general refactoring). I'm not suggesting they are wasting the extra time, just that they will fill the time available delivering the best product available given the time constraints. Also, my comment said specifically that this is true of everyone, not just developers.
Comment: "If given too much time, developers will find a way to use all alloted time, no matter what." I agree with Walter. This is a false statement. Why are developers the lazy ones? Why are their managers magically able to summon resolve to get a project done in a reasonable amount of time, but not developers?
Comment: @JohnFx - All I'm asking for is documentation that all developers will use up all the time available to them, "no matter what".  Otherwise its an unsupported assumption.  PS.  I finished many projects in school prrior to the deadline.
Comment: @JohnFx They shouldn't just fill up time. Not if they realize that an early delivery would be better than an on-time one, which would generally be the case. I beat estimates routinely. That doesn't mean that I sit around thinking of ways to gild my code and documentation. In the same way, I don't declare project failure or start working 18-hour days the instant I slip past an estimated completion time. It was an estimate. It would be much more shocking if it were correct than incorrect.
Comment: Please follow this proposal for that kind of question: [Organization aspects](http://area51.stackexchange.com/proposals/25661/organizations-aspects?referrer=VWCGRjdShg3eJFzjytmq4Q2)
Comment: possible duplicate of [How to respond when you are asked for an estimate?](http://programmers.stackexchange.com/questions/648/how-to-respond-when-you-are-asked-for-an-estimate) and of [How possible is it to estimate time for programming projects?](http://programmers.stackexchange.com/questions/39468/how-possible-is-it-to-estimate-time-for-programming-projects)
Answer: Of course they're necessary but they're not intrinsically evil, they're just done badly.
The basics of a good estimate:
1) Developers, ideally the ones who will do the work, have to be involved in generating them.
2) An estimate is a range (usually best case, worst case, most likely case), not a single value.  You may use the range to approximate a single value ((best case + 4* most likely case + 2 * worst case) / 7 being a fair formula for doing so) but never forget that that's all it is - an approximation.
3) In my experience the most common reason for bad estimates is wishful thinking, either on the part of the developer (who is optimistic it will all go fine) or the manager (who is desparate for it all to go quickly).  This needs to be fought - any estimate based on everything going well is pretty much a cert to be massively under.  Most likely case should probably assume that a certain amount of stuff isn't going to go the way you want it to.
4) In my experience the second most common reason for bad estimates is not thinking through everything that has to be done.  It's not just the coding, it's the unit testing, the admin, the user guide, the back end maintenance screens relating to the functionality.  Break down the task into individual components each taking between quarter of a day and five days - that sort of size can be estimated with a reasonable level of accuracy.
5) Measure the actual time things took and review afterwards and use that to improve estimates.  Refer to actuals for similar previous tasks as a bench mark and to justify why things are higher than might be expected.
6) Estimate both at the micro level (each individual task) and the macro level (gut feel on how long the whole thing should take).  Usually the macro level estimate will be lower - this is an indication that you might want to review (but not necessarily change) the micro level estimates.  The sweet spot in my experience is when they either agree or, more likely, the macro level estimate is still lower but no one is willing to change any of the individual task estimates.  At that point you use the individual task estimates.
7) Don't confuse the estimate and the commercial aspects.  If you estimate 100 days and the usual charge out rate is $1,000 per day that should obviously be $100,000.  If they say they can't charge that and win the business that's fine but (unless the scope changes) the estimate doesn't change, the charge out rate does.
8) Developers should be challenged on their estimates (as in asked to explain why something takes that long) but not pressured to lower them.  Certainly not just because the numbers aren't what someone wants in any case - if they can't justify them then they usually need to be pushed for a better breakdown and potentially a second set of eyes but in a non-confrontational manner - remind the PM (or if you are the PM remember) that they're going to look bad if the project isn't delivered on time too so they should be keen that the estimates are solid.
9) Contingency should be added both shit happens contingency (usually 10 - 20%) and to cover specific risks.  Contingency should be planned in but is "owned" by the project manager - that is if a developer needs to go into it he has to speak to the PM and say why he's over run his estimate.  This usually helps stop the just filling time and keeps contingency for genuine stuff.  If anyone objects to your shit happens contingency budget then explain it's just the reality of IT projects - stuff happens you can't predict.  If they still don't like it then remember to hide it inside the estimates next time.
10) (Edit) Don't confuse effort and elapsed time.  Effort is the total time that will need to be spent doing something, elapsed is the difference between when it starts and when it ends.  They're normally different - admin, support, mentoring and life mean that the chances are that you won't get 5 days effort completed in a working week.  Take 4 as a rough guide but adjust according to the company and the other commitments of the team members.
11) (Edit - from Martin Wickman) Other work you've done or are planning can be a valuable source of information when estimating.  In the comments below Martin refers to Relative Estimating which involves comparing like tasks with each other to ensure that the estimates assigned seem in proportion given the work involved.  It's surprising how often you'll happily assign 1 week to one task and 1 week to another but when you look at the two things one is clearly more complex than the other - that's a good indication that one (or both) figures are wrong.  Taking this further you get into evidence based scheduling which uses completed tasks and projects as a key input into estimates for future work - at a very basic level "how long did it take last time we did something like this?"
Steve McConnell wrote about all of this in Software Estimation.  It's a bit dry but it's very thorough on the subject.
Comment: One I'd like to add to your list, that Mr. McConnell really harps on in his book: an *estimate* is not a *commitment* is not a *plan to meet a target.* Always clarify what you're being asked for. People will often ask for an estimate when what they really want is a commitment or a plan to meet a target.
Comment: +1 Personally I find point 7) is usually the definer, particularly in small businesses.  Downward pressure from sales/marketing people corrupting time estimates to meet client cost or timeframe demands.
Comment: +1 Hell of an answer. What has personally been a game-changer for me, is my company now gives me one day every sprint (two weeks) to come up with estimates. When you spend 10% of your time going through code, you have a very clear idea of what needs to be changed before you dig in. This is time that is usually spent anyway (but on the wrong side of the estimate-giving).
Comment: @Jon @noone. While Jons answer is classic and exhaustive, I think it is missing (what I consider) the most powerful way to estimate: *relative estimation*. This means you don't estimate in time, but compare task sizes against each other, and uses completed tasks as a way to know how much work you can handle each iteration.
Comment: @Martin - it's a good point.  I'll make some tweaks to it to incorporate this.
Answer: Estimates are not a necessary evil.  If they're evil, you should question if they're necessary.
One of significant recent trends in software engineering is the proliferation of Lean software development philosophies, particularly Kanban.  And - don't shoot the messenger -- the proponents of Lean and Kanban put it bluntly: "Estimation is waste."  What do you do with waste?  "Eliminate it."
(Henrik Kniberg, the famous author of Scrum and XP from the Trenches, has gotten into Kanban.  His latest book, Lean from the Trenches is coming out soon.  In the book, he contends that story-point, relative size estimation is a waste of time.)
What they do instead of estimation is a huge, separate topic, but the gist of it is: they embrace variability, optimize the flow of valuable features to the users, measure the lead time and optimize the whole system for lead time or throughput -- instead of controlling the time it takes to execute individual tasks.
If you visualize the journey of a user requirement from the point when it's identified to when it's delivered to the user, you can see how little of it actually involves typing code.  Even in the development phase, lots of time can be lost while in-progress work items are:

in blocked state (how effective is
your escalation process?)
waiting for non-instantly available resources
getting thorough other bottlenecks
reworked

A less-than-superefficient software development team can easily waste (as far as the customer is concerned, that's all waste) several days on any of the above causes, which brings into question whether a precise estimate that it would take 5 days instead of 2 to code some feature adds any value.  Remember the customer doesn't care how many of 45 days from the feature request to delivery was spent on coding or something else and in what order.
To use an analogy, an Amazing Race contestant adds value by getting to the finish first.  Estimating how long it would take him to eat 1 kilogram of local food is not a value-adding activity.
I don't know whether you can implement any of this thinking at your workplace, I contend this is a useful perspective.
Comment: I find that any estimate with accuracy below weeks is not suitable for anything other than elementary projects that are particularly well understood.  Obviously this low accuracy magnitude has to scale with project size.  If someone says *"can you build me Facebook"*, then the minimum accuracy should probably be years.
Comment: Days? I've known teams to get blocked for months, particularly on the old 'waiting for resources' issue.  Clients can be a primary bottleneck.
Comment: @Orbling: I used "days" instead of "months" mostly to soften the shock. ("Estimation is waste" is a shocking statement to many.) There are so many managers and developers fixated on finessing estimates in the 4-to-12-hour range, completely oblivious to the fact that their lead times are measured in months (at least).
Answer: The phenomenon you are referring to is known as Parkinson's Law, which states "Work expands to fill the available time for its completion."
That is, people have a tendency to pace themselves to finish things just in time for the deadline. I don't think it is a result of laziness, but more a consequence that there is always more to do than time to do it, so you prioritize things according to when you have to deliver them.
The best solution to the deadline dilemma, in my experience, is an iterative process that breaks the project into small frequent deliverables. This keeps the sense of urgency up and also helps to keep the estimates realistic as it is much easier to estimate a small task than a larger one. Be careful though to give the developers a lot of input and control over the deadlines. A manager who dictates a million tiny deadlines = a micromanager.
In any case, deadlines should be set by real business constraints. Creating deadlines based on estimates of how long it will take to do the work is somewhat akin to using a ruler to measure itself.
Comment: Oh boy I so have a micromanager here... Thanks, John!
Comment: +1 For staged deadlines, this is general theory for deadlines, software or not.  People work to the deadline as a rule.  Or in a lot of cases, some way after it...
Comment: +1 For iterative and frequent releases. This (and relative estimation) is the key to good estimation.
Answer: Delevopers should be the ones producing estimates for their own work, not you. (Or, rephrased, you should only be estimating your own work.)
Time and experience will allow you to estimate more accurately, especially if you track your own estimates.
The real problem with programming is that for a particular language, on a particular project, you might be able to give highly accurate estimates to routine feature requests. But a lot of the time you have to give an estimate on something that you haven't done before (and possibly in a language you don't know, and/or with a framework you don't know). In which case your estimate is, in some form, a guess. Try guess anyway, keep track of your estimates, and reflect.
Comment: Thanks Frank. Do you see benefits on using methods such as function points?
Comment: I think it's more important to have a pretty good idea of the requirements you're implementing, and not get too hung up on estimates. They are just estimates. It's only when you actually implement something that you get to truly understand how complex the thing you're making actually is.
Comment: +1 For the exceptionally important point, that for completely unploughed furrows, development mirrors research rather than construction and time estimates are then a guess.
Answer: The simple answer: use relative estimates and ship frequently. This is basically the approach used in the Extreme Programming method. The basic steps:

The team creates a list of every useful step forward, generally written from the user's perspective. (E.g., "Customer adds item to cart".)
The product manager sorts the list by priority, inserting release markers. (E.g., "first internal alpha", "first public beta".)
The developers pick out the smallest non-trivial item. They call that 1 point.
The developers estimate everything else in terms of that. Anything too large (e.g., 8 points) gets broken down into smaller pieces.
The developers start in building things one feature at a time, making a working system (that is, something you could release if somebody put a gun to your head) at least once a week.
Each week, the team counts up the points they completed. Next week, they try to take on about the same amount. If they complete all that early, they can opt to do more.
If the product manager wants an estimate for some particular release, they can look at the weekly velocity, count up the points in the release, and do the math.

This may sound too simple, but it has worked very well for me, and plenty of other teams. In particular, because the product manager has full control over the schedule through arranging the upcoming work, schedule pressure is no longer a problem for developers. Business people get to argue with one another about priorities and schedules as much as they want, and I get to keep coding.
Comment: I should add that I think one a team gets good at this small-unit style of working, they can drop estimates altogether and just use a Kanban approach unless businesspeople have a particular need for numerical estimates or the ability to compare different paths.
Comment: +100 Relative estimation is awesome, and imo the only truthful way to estimate. Why? Because you don't need any padding or "multiply with pi" to get it to work.
Answer:
Break down the task into subtask that takes maximum time t to deliver. (For exampe t=1day)
Do historical analysis to get a picture on how good your team estimated the time and try to improve.
Answer: Developers or tech leads estimate the time for a project, depending on the features to be added. If this time is much more then you will have to discuss with them for reducing the feature/functionality. The estimates will also change depending on the developer to developer. A fresher can not complete the job in same time as an experience developer can complete. So such things should be taken into consideration. And developers do take all the time probably because there requirements are kept changing.
Comment: +1 For an important point managers fail to take in to account often.  Estimates must be for the people who will do the project.  A lot of estimates are made by senior experienced developers, and then the work is given to juniors who take four times as long.  In coding, experience is nine-tenths of skill.
Answer: You really need to read and understand JP Lewis' "Large Limits to Software Estimation"
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.28.4205
http://scribblethink.org/Work/kcsest.pdf
http://scribblethink.org/Work/Softestim/softestim.html
Rather like the fact that you can't in general read a program's code and decide if it halts or not, in general, you can't read requirements and decide how long it will take to implement them.  I don't believe this is arguable.
Answer: I'm surprised there's no mention of agile paradigm.  We've used agile on projects to break up the work into small manageable chunks.  Each chunk is somewhat easy to estimate and usually shouldnt be more than a week's worth of work.  Daily scrum's allow mgmt and other devs to know when something is starting to exceed the timeframe.  Analyze your project daily so you always know where you are in the overall "race" to finish the total project.  If something hold's you back, management doesn't find out days before the total deadline, you see it coming.
Answer: A completed project is not a set of code.  A completed project is a set of code at a specific point in time.  If your customers/users don't care about when they get the code, then it's probably not very important.

How do you deal with time estimates?


Confusion in PID loop for the case of zero error?

Question:
I am already studying PID control and some how to some extent I have understood it except one main confusion. When the difference between reference input \$r(t)\$ and current output value \$y(t)\$ is zero, \$e(t)\$ will be zero and hence \$u(t)\$ will also be zero, so how will then the plant act or work when its input \$u(t)\$ is zero?
Comment: No error, so no need to correct or adjust control.
Comment: The output of an integrator is not necessarily zero even if the input is zero.
Comment: @KevinWhite Yes.  The output setting (whatever it is) stays as it is because it is at the set point, or no error, so no need to correct or adjust control.
Comment: The whole point of the integrator is that it provides a constant output when its input is zero. That constant output need not (and usually is not) equal to zero. An integrator in the forward path, whether it's in the plant or the controller, ensures that the steady state error will be zero in response to a step input.
Comment: @StainlessSteelRat - not true, the output needs to be maintained. For example a heater still needs to be driven when the target temperature is reached.
Answer: No, e(t) being zero does not imply that u(t) is also zero. It only implies that the output of the "P" process is zero.
Remember, the "I" and "D" processes have memory — they depend on the past behavior of e(t). u(t) is zero only if the sum of all three processes is zero.
Comment: @Graham: I think "Damping" is an even better term (which coincidentally starts with "d").  The term "friction" is often used to describe resistance which is independent of velocity, but "damping" implies velocity-sensitive resistance.
Comment: As far as "I" process concerned,it can have memory since it integrates past values but how "D" process can have memory of past when it is used for future??
Comment: @engr: The D term is used to "predict the future" in a sense, but it is calculated entirely on past values -- in particular, the difference between the present value and previous value(s).
Comment: @engr The D term is simply the velocity with a gain on it.  It should be clear (I hope) that you can be in some position with zero velocity, or you can cross zero position with a large velocity.
Comment: @engr BTW, the classical PID description of the D term "predicting the future" (as Dave says), whilst true, doesn't always help.  A better description IMO is that the D term is friction.  We all understand friction, right?  Like physical friction, the faster the system moves, the more the D term pushes back to try to slow you down.
Comment: I think thinking of D as the derivative (its literal definition) makes more sense than any of these proposed analogies/simplifications. The term is large when the input to the block, e(t), is changing quickly. That's it. Whether it actually acts as damping or friction, or as a prediction of the future, depends on the system itself and the coefficient chosen.
Answer: There can be a couple of scenarios.
Consider a system \$\frac{1}{s (s+1)}\$. A PI controller is \$\frac{0.9 s+0.27}{s}\$. In steady state after the controller has made \$y=r\$, the error \$e\$ and its integral are both  zero. In this case when \$e=0\$ then \$u=0\$. If there is a nonzero input going to this system, the output will keep on increasing.
For a system such as\$\frac{1}{s+1}\$ and PI controller \$\frac{1. s+2.0006}{s}\$, the error goes to zero in steady state, but the integral of the error does not. This gets multiplied by 2.0006 and is the control input that maintains the output at the reference value.
The computations below are done in Mathematica. The plots below show the error signals. Both go to zero. However the integral of the one on the left is also zero. The integral of the one on the right is not zero but around 0.5
Answer: Take a motor control PID for example.  The motor (once running) will have small load perturbations that will cause it to overshoot or undershoot the zero error case, so then the system will react and cause the motor to slightly overshoot in the opposite direction.
If you were to zoom in on a graph of the error, it would be little zig zags across the zero error line.  Assuming that it's been tuned properly.
Also u(t) doesn't go to zero when the error is near zero.  u(t) goes to the value that makes the error near zero.


MTG Lifelink Before Death?

Question: I'm the farthest thing from a magic know it all, so I have a question for you. If my opponent has a 40/40 with trample and I have a 20/20 with lifelink that is blocking it. and I have 20 life left. Do I gain life from lifelink at the same time the damage is dealt to me? Thanks for taking the time to answer!
Comment: You do but still end up at 0 life ;)
Comment: @Stephane no you don't. Your 20/20 blocks the 40/40, soaking up 20 of the damage, the other 20 goes to your life. Your 20/20 gives you 20 life for the damage it dealt, which in effect cancels out the rest of the damage, so you end up at 20 life since 20-(40-20)+20=20
Comment: My bad. You're right.
Answer: Yes, lifelink is not a triggered ability like you might expect but a static replacement effect that replaces damage being dealt with the damage being dealt and you gaining that much life:

119.3f Damage dealt by a source with lifelink causes that source's controller to gain that much life, in addition to the damage's other results.
702.15a Lifelink is a static ability.

Note that this is not the case with cards that say "Whenever this card deals damage, you gain that much life"; that would be a triggered ability, and you would lose before it could resolve.
Comment: While the conclusion is correct, I'm pretty sure Lifelink is not a replacement ability. It modifies the normal result of damage being dealt in the same way infect does.

MTG Lifelink Before Death?


How to delete a particular variable from a configuration created by a custom module

Question: I have created a custom module and a configuration say 'abc_settings'. This configuration creates a variable for each vocabulary present on the site like vocab1_options, vocab2_options, vocab3_options etc.
I want to delete 'vocab1_options' when vocabulary 1 (vocab1) will be deleted. How to achieve this ?
Answer: Deleting a config key:
Updating per Berdirs comment, deleting/clearing a key within a config object, not deleting the entire config object:
Drupal::configFactory()->getEditable('abc_settings')->clear($entity->id() . '_options')->save();

Deleting config objects:
I did this within TVI module, anytime a term or vocab is deleted:
/**
 * Implements hook_ENTITY_TYPE_delete().
 * Remove TVI settings when vocabularies are deleted.
 * @param EntityInterface $entity
 */
function tvi_taxonomy_vocabulary_delete(EntityInterface $entity) {
  Drupal::configFactory()->getEditable('tvi.taxonomy_vocabulary.' . $entity->id())->delete();
}

/**
 * Implements hook_taxonomy_term_delete().
 * Remove TVI settings when terms are deleted.
 * @param EntityInterface $entity
 */
function tvi_taxonomy_term_delete(EntityInterface $entity) {
  Drupal::configFactory()->getEditable('tvi.taxonomy_term.' . $entity->id())->delete();
}

Of course, you would pass your own config name to getEditable(), and the hook names need to have your module name and not tvi.
This will delete any config matching that name when a term or vocab is deleted.
I haven't taken the step yet in my own code, but you could go further and implement a method that before a vocabularly entity is deleted, get all of its children, loop and delete config, then delete the vocab and its config.
Example:
Drupal::configFactory()->getEditable($entity->id() . '_options')->delete();

Comment: Is that really what was asked? This deletes whole configuration objects, I understood the question as deleting keys in a configuration object. For that, you can use ->clear('some_key')->save().
Comment: From the names I inferred them as a config object per vocab. I see now..


1970s(?) science fiction movie - Mad scientist transplants brains from his victims into monstrous creatures

Question: I saw this movie on TV back in the 80's. I believe, however that it was made most likely in the 70's based on it's film style.  The movie was in color.  The only parts I can really remember was at the end our heroes confronted there enemy (a mad scientist type) in his lair.  I believe his lair was in a volcano or perhaps a cave.  The "mad scientist" used his technology to either transplant brains from his victims into other creatures or perhaps just there consciousness. I can't remember.  At the end though one of his creations (if memory serves it was a woman who had been implanted into a gryphon like creature) attacks him allowing our heroes to escape.  Does this information sound familiar to anyone?
Comment: Well it sounds like one of a million TV takes on *The Island of Doctor Moreau*. It was frequently ripped off in 80s TV and film - is there anything else you can remember?
Comment: Wish I could remember more.  You never think of those things at the time. :)  Really the biggest plot element I can remember was woman being turned into the gryphon like creature.  I've wracked my brain but that's it.
Answer: Could this be The Twilight People from 1972?
This is the only "Island of Dr. Moreau" rip-off/tribute I can think of that had any flying type creature in it. It also has a scientist who is experimenting with animal/human hybrids, he has a lab in a mountain? or volcano and it takes place on an island.
Comment: Wow this did fit many of my criteria LOL but alas it is not the one.  I distinctly remember the woman into gryphon part.  I get the impression (from old memory anyway) that the movie I'm looking for is more scifi ish and less like Island of Dr. Moreau.  Man I wish I could remember more, but it was so long ago. Thanks for trying though.
Comment: Wow. I really want to know what this is now! The only '70s movie with a gryphon I can think of is "The Golden Voyage of Sinbad".
Answer: Could this be "Latitude Zero" (1969)?
The plot involves people being rescued and brought to a base in a mountain on an island by a submarine. Here is part of the plot synopsis from Wikipedia that describes the gryphon type creature and the brain transplants.

Latitude Zero is a paradise hidden fifteen miles below the surface at
  the intersection of the Equator and the International Date Line. Gold
  is plentiful there and is used for protective clothing by the island's
  newcomers, while those who arrived in the 19th century prefer to dress
  as they are accustomed, as no one ages or dies. Diamonds are very
  common and used only in industrial use.
Dr. Malic, however, wishes to destroy the paradise of Latitude Zero,
  and uses giant rats and anthropomorphic bats in addition to James
  Bond-style devices against the undersea kingdom. Worst of all, after a
  cruel experiment grafting the wings of an eagle to a lion, he removes
  the brain of the unsuccessful Kuroi and places her brain in the
  creature. This proves to be his undoing when, at a critical moment,
  Kuroi turns against Malic as he prepares to fire an energy cannon at
  the escaping visitors, causing their destruction.

You can see the 'gryphon' at 1:17 in the trailer and the part where he takes out the brain of the woman to put into the gryphon at 1:38. You also get glimpses of animal/human hybrids and the volcano.
Comment: Oh yes this is it LOL.  Wow this came out the year I was born LOL. Thanks tons.  Now I can scratch this title off my bucket list LOL.
Comment: Thanks much MrInfinity, this was driving me crazy too! It came out 1 year before I was born. It's actually like Island of Dr. Moreau and 20,000 Leagues Under the Sea combined.


What are the Benefits and Limitations of Pair Testing?

Question: Can you give me a brief overview of what pair testing is, along with some of its pros and cons over single person testing.
Comment: What do you think the answer is? What research have you done? Have you listed out the benefits and drawbacks of pair testing? /
Answer: Pair Testing :
Pair testing is a collaborative effort, versus a single-person testing effort.  Typically, one of the team members is a tester and the other is either a developer or a business analyst.  Please refer this below link.                   (https://blog.testlodge.com/what-is-pair-testing/)
Advantages:

Pair testing helps in indentifying the negative flow in the functionality.
It helps to improve better communication with the peers
Pair testing helps to save time while testing.
It is very helpful to train the peers who are working in the project.
Pair Testing can not be done only by testers. It can also be done by Business analysts, Project Managers and Developers also can do.

When to do pair Testing?

When we working on an agile environment with 2 or 3 weeks sprint then pair testing will be really helpful to improve the quality of the application.
When there is a addition of new resources in the team then when doing pair testing helps to train the new comer
Comment: Please reference your quotes - I found the definition of pair testing you used above on several sites.
Answer: What is Pair testing?
Answer:
Pairwise testing is a practice where two team members are sitting together to test the software application on the same machine. The team members for pair testing can be a tester- developer, tester-tester, tester-business analyst.
The Outcome of Pair testing

Test documentation
Defect reports
Session reports
Shared knowledge

We can do pair testing with colleagues from my Scrum team on a regular basis. Some sessions are short, minutes to an hour, and some are longer, up to a day. Sometimes it is planned, and sometimes it's spontaneous.
Why Pair testing?
Answer:

A tester working alone may jump to incorrect conclusions
Reduces the number of tests to be performed
To test a specific area of functionality

Benefits of pair testing

Combine testers from different technical backgrounds and hence being
able to provide different perspectives and approaches to the test.
Combine testers of different levels of experience
More interactions with developers and management teams
Faster bug identification and prevention
Better feature usability can be achieved.

For more details about pair testing, you can check out
Pair Testing
How to perform Pair Testing


Contractibility of curves and embedding into projective space

Question: Let $f:X \to Y$ be a proper surjective morphism of projective surfaces such that there exists a curve $C \subset X$ for which $f|_{X\backslash C}$ is an isomorphism and $f(C)$ is a set of points. Suppose $X$ is a closed subscheme of $\mathbb{P}^n$ for some integer $n$ and $C$ contracts to a rational singularity i.e., $f(C)$ are rational singularities on $Y$. Does there exist a closed immersion of $Y$ into $\mathbb{P}^n$ for the same integer $n$?
Answer: No. Take a smooth cubic surface $S\subset \mathbb{P}^3$, and a line $E\subset S$. Then $E$ can be contracted to give a smooth Del Pezzo surface of degree 4 (a complete intersection of two quadrics in $\mathbb{P}^4$), which cannot be embedded in $\mathbb{P}^3$.
Answer: Let $X\subset \mathbb P^3$ be an arbitrary smooth projective surface of degree $d>2$ and assume that $X$ contains a line $\ell\simeq \mathbb P^1$ If $d=4$, assume in addition that $X$ is general among such surfaces. This implies that its Picard number is $2$. A simple adjunction computation shows that $\ell^2=2-d<0$ ($l^2$ computed on $X$). This implies that $\ell\subset X$ is contractible, so we have a morphism $f:X\to Y$ as requested.
Claim. $Y$ cannot be embedded into $\mathbb P^3$. If $d>4$, then $Y$ cannot be embedded into any smooth $3$-fold.
Proof:

If $d=3$ (case abx): Since $X$ is rational, so is $Y$, so if it could be embedded to $\mathbb P^3$, its degree would have to be $1,2$ or $3$. Its easy to see using adjunction and that fact that $f$ is the  blow up a smooth point that none of these is possible.
If $d=4$ (case Olivier): The Kodaira dimension of $X$ is $0$, so if $Y$ were embeddable, it would have to have degree $4$. In this case adjunction does not help, because $0=K_X=f^*K_Y$. However, if $H'\subset Y$ is the hyperplane section of $Y\subset \mathbb P^3$, then $f^*H'\cdot\ell =0$ and since the Picard number of $X$ is $2$, we can compute that in this case $f^*H'=2mH+m\ell$ for some $m\in \mathbb N_+$. But then $H'^2=18m^2\neq 4$, so this leads to a contradiction and hence $Y$ cannot be embedded into $\mathbb P^3$.
If $d>4$ (case new):This is actually the easiest. If $Y$ embeds into any smooth $3$-fold, then it is Gorenstein and $K_Y$ is a Cartier divisor. Then we have $K_X=f^*K_Y+ a\ell$ for some $a\in \mathbb Z$. Using adjunction for $\ell$ and our earlier computation tells us that $$2-d=\ell ^2=\frac {-2}{a+1}$$ which means that $$2=(d-2)\cdot(a+1),$$ that is, $d-2$ divides $2$ so $d>4$ is out of the question. This completes the proof.
Comment: @Kovacs: Thank you for the very detailed and exhaustive answer.
Answer: Let $X$ be a projective complex K3 surface whose Néron-Severi-group is generated by two classes $h$ and $l$ such that $h^2=4$, $hl=1$ and $l^2=-2$ and $h$ is ample. One sees that such a surface exists using the surjectivity of the period map for K3 surfaces. General theorems about linear systems on K3 surfaces imply that $h$ is very ample and embeds $X$ in $\mathbb{P}^3$.
Since $l^2=-2$, $l$ or $-l$ is effective. Since $hl=1$, it is $l$ that is effective, and it has to be the class of a line in $\mathbb{P}^3$. This line is a $-2$-curve and may be contracted to a node. Let $f:X\to Y$ be this contraction map.
Since $Y$ is a singular K3 surface, if it were possible to embed it in $\mathbb{P}^3$, the degree of the embedding would necessarily be $4$, but this is impossible as no line bundle on $Y$ has this degree.
Comment: @Benoist: Could you say why $Y$ has no line bundle of degree $4$?
Comment: @user43198: Its pull-back to $X$ would be a degree $4$ line bundle on $X$ that is orthogonal to $l$ (because the line that is a section of $l$ is contracted by $f$). But line bundles on $X$ that are orthogonal to $l$ are proportional to $2h+l$ and $(2h+l)^2=18$.


How do I get rid of hum in mixing desk when guitar plugged in?

Question: I have an rcf f6x mixing desk, whenever I plug in an acoustic guitar I get a weird hum through the speakers, it seems to dissapear when I kill the bass on the guitar eq and the mixer but obviously this then sounds like you know what. Also I've noticed a slight static shock from my mic, I've noticed this in the past when I played in venues which I assumed had dodgy wiring but never with this hum noise.
Interestingly using a cheap electric guitar tele style doesn't make any hum. I've tried 2 acoustics so it's not the guitar as far as I can tell.
The power block has a changeable plug for eu and uk sockets and I'm using the uk one -though the prong is plastic so I don't know if it's doing anything to ground the desk. Anyone know of a quick or long term fix for this?
Answer: Looking at the pictures at Thomann, that looks like a cheap switch-mode PSU. They are notorious for a slight 'tingle' when you touch anything connected to them. You can't 'fix' them in any meaningful way except by swapping to an expensive 'traditional' wound transformer.
The hum is not insurmountable, though there's no single perfect fix.
You should grab a bag of ferrite beads, few quid on eBay - example. Put one on the 'input' end of every cable. They're not miracle cures but they can help a little bit with high end whine. They're cheap as chips, so you can afford a bag.
Also, a bit of DIY electricals. Grab a spare UK plug & a length of wire - mains preferably, but you're not using this for "earthing" you're going to use it for "grounding" (the US doesn't differentiate, but usefully the UK does.)
Using the screw on the back of the desk…

Take this out, scrape some of the paint from around it so it makes good contact, then wrap one end of your wire round it & tighten it back in.  The other end goes into the earth pin on your plug; then plug it into a regular earthed socket. This is not dangerous so long as you can wire a plug. You might need to add a bit of cable sheath around the single wire so the cord grip holds properly.
This will properly ground the equipment.
There is still potential for ground loops, but if you plug all your gear into the same ring main, this should be minimised.
You can extend this by strapping the frames of all audio gear together in a chain.
You still might have to touch metalwork on a guitar to fully close this circuit - or like we used to do with especially errant guitars in the studio, use one of those computer grounding wrist straps round the guitarist's wrist & clipped to some part of the guitar's metalwork.
If all that doesn't work, look for a new desk… or some expensive isolating mains 1:1 transformers ;)
Comment: A locking washer might help to grip that earthing cable too.
Answer: It sounds like you are using an unbalanced connection from the guitar to the desk by way of a regular guitar lead yes? This would be a cable with only 2 conductors instead of 3 like a mic cable, for a mono signal.
I checked on the RCF site and:
The mono jacks for channel 1/2 is balanced input (3 conductor).
The mono/stereo jacks for chan 3/4 is unbalanced input.

Have you tried using a DI box? This almost certainly will fix it.
Have you tried using chan 1/2 using a "TRS jack to XLR" cable? This maybe will work. If the gat has balanced out, a "stereo jack" cable may work.
Tetsujin's fix appears to fix the instance of "stray capacitance" buildup in the chassis leaking to audio path. This is nice, but try a DI box first! Easier and likely better. The chassis sound enters the path as you plug the lead into the guitar (try plugging halfway in guitar)
Does it have piezo or magnetic pickups? Piezo requires 10 megaohm preamp. If you buy one, ensure it has balanced XLR output.
Only XLR to XLR guarantees balanced pathway blindly. I checked and your desk has balanced TRS on 1/2.
I've heard that power isolators (1:1) can help with noise floor issues; I've not tried that. All DI boxes use 1:1 transformers and should provide that same "ground lift" but to your audio path not power. Good audio gear uses linear power supplies (AC normally). Low grade gear sometimes/always uses switching power supplies (DC). It maybe not trivial, but if you could get a linear power supply that outputs DC that mite work.

The simple use of a good quality DI box - one with a ground lift switch - is highly likely to take the hum to negative infinity, and let you output to balanced equipment no matter what harsh RF interference maybe about, and also over long cable runs no problem. Running that cable over power supplies should produce no hum believe it or not; a regular unbalanced should pickup some 50 / 60 hertz when laid over a lot of power cables etc.
Since it is unlikely your guitar would make use of a TRS jack, using a TRS jack to XLR mite not work if the desk (or the guitar) bridges cold to earth. A regular guitar lead bridges cold to earth because it only have 2 conductors, and the cold conductor on the bigger part of the plug is shorting to where the earth "band" would appear (on a quarter inch gat jack lead). The short happens inside the guitars female jack.
Rather than replace your guitars jack, you can use a DI box to interrupt this bridging in the jack, because the DI box isolates the guitar from the desk via a transformer. The earth on guitar is now no longer connected to the desk chassis (it's the balanced earth that touches it). The ground lift will then have next to no effect because it refers to the balanced connection (XLR pin 1) not cold, between the DI box and the desk not the guitar, and with balanced signals it is the differential inversion that kills all interference not the shield. Linking the shield to ground helps by way of the Faraday cage effect, especially if it has phantom power (a Faraday cage requires a little DC current to also flow through the cage, it's not important).
Finally, some low current 48v DC phantom power runs from hot to earth. While it can not flow through pickups / line-outs, because those circuits return via cold, it may begin to flow when you plug a 2 or 3 conductor cable like I said (TRS jack to XLR) straight from desk to guitar. Notice how just using a DI box fixes everything.
If you do not use phantom power at home you may only notice this at gigs, where phantom power runs certain condensor mics and usually all the DI boxes. I would assume your shocks come plugging guitar directly into the desk then. Again, a DI box blocks that lip tangling badness!
Comment: Thank you both for your replies, I lost my login details so couldn't reply.
One thing I discovered is when I plug the mixer into my bose s1 the hum disappears when I use the kettle lead to power it, so basically I now have to bring my speaker with me to every gig and use it as a monitor, which is a pain but I think it may be safer than wiring the screw to ground as I'm not confident enough to do this. Also to reply to the second poster, I use a boss ve8 pedal, so run a guitar lead in and an xlr out of the unit into the mixer but I will consider a DI box. I've also bought ferrite beads so will
Comment: I love to use XLR and balanced anywhere that it seems possible... but if you don't have one, you may find great utility in getting a proper DI box still (transformer based, with earth lift switch).


Waveshare AD/DA espansione board setting sampling frequency

Question: In order to acquire 3 analog signals with Raspberry pi 4 I want to use ADS1256 Waveshare's AD expansion board ( 8 channels single-ended, 24 bit). I was wandering if there's a way to set a different sampling frequency to each channel. ADS1256's datasheet states that the maximum fs is 30kSPS. Since I need to acquire 3 signals and one of them need to be sampled at 10kHz, I want to know if there's a way to set a specific fs to each channel. In this way I could sample correctly the audio signal (10kHz) and not oversample the other ones. So far, I've just downloaded the source code ( Python) provided by Waveshare https://www.waveshare.com/wiki/File:High-Precision-AD-DA-Board-Code.7z but I don't understand if there's a way to change it to do what I want. Thanks
Comment: Ah, let me see.  ADS1256 can convert in either "continuous mode" or "single shot mode". In single shot mode you can decide the sampling speed. Let us take Channel 1 for example, if you take one one-shot conversion each second, then sampling rate is just 1 sps. if you take one one-shot conversion each half second, then the sample rate is 2 sps.  If you are converting 2 channels, each second you take Channel One 100 one one-shot conversions, and in the same second you take Channel Two 1,000 conversions (evenly or not evenly spread out), then you have Channel One 100sps,  Channel Two 1000 sps.
Comment: #Dmitry Grigoryev's 3 signals at 10 kHz is for continuous conversions, for continuous wave. The one shot mode is for the case that you only need to take random number of samples for a randomly long time for one or two, up to 8 channels.
Answer: 3 signals at 10 kHz is exactly 30 kSPS, so you should be able to sample all three channels at the same rate, then throw away unneeded samples on slow channels.
Sampling different channels at different rates is difficult to implement correctly. Naive implementations result in jitter, because two consecutive samples of a fast channel will have a shorter sampling time than the same two samples with a sample of a slow channel in between.


How can I create custom contribution page (CiviCRM 4.7.25 on Wordpress 4.8?)

Question: I want to create custom contribution page but I don't know how?
for creating custom pages is needed any extensions or plugins?
the below page is one of the pages that I created I want to delete yellow section and also the membership
Answer: Can you please edit your question to add your CMS and CiviCRM version. Depending on your CMS there may be other options for customization.
The yellow section only appears when a user is logged in to the site. It is designed to prevent a user from overwriting their information with another if they are entering a contribution on another person's behalf. I would recommend leaving it there to avoid accidental data changes. You could add some custom CSS to change the look.
As for the form itself and the pricing section you may want to review the information here which is an overview of the contribution pages: https://docs.civicrm.org/user/en/latest/contributions/online-contributions/
Also reviewing the following two sections on profiles & price sets can be helpful.
Profiles: https://docs.civicrm.org/user/en/latest/organising-your-data/profiles/
Price Sets: https://docs.civicrm.org/user/en/latest/events/complex-event-fees/#price-sets
Hope this helps.
Answer: Apart from all the usefull advice from KiakwaBT I would like to add that if you want to start customizing CiviCRM and/or adding to CiviCRM I would certainly recommend you to study the developer guide at https://docs.civicrm.org/dev/en/latest/


Is programming in quantum computer same as programming in quantum simulator in classical computer?

Question: I just started programming in Q# and I wonder if the coding for Q# in classical computer would be the same as coding in a quantum computer. Obviously, these 2 kinds of computers work differently, so I guess the language must be working differently as well. Does this affect the coding part in any way (syntax, dealing with operations and variables etc.)?
Answer: Running programs on a quantum computer will indeed require some routines which are not required for running them on a classical simulation. Two easiest examples are error correction (a classical simulation is perfect but a quantum device will be noisy and will require error correction to produce useful results) and translating logical qubits and gates to physical ones (in a simulation you can do any gate on any pair of qubits, but a physical device will be limited to certain set of primitive gates and a certain connectivity scheme).
However, the person writing high-level quantum code is likely uninterested in such low-level routines (unless they are researching them specifically), same as a person writing this answer doesn't really want to care about the addresses of the bytes storing it on their computer. High-level programming languages (in particular Q#, since you asked about it) aim to provide a high-level abstraction for the programmer and delegate low-level routines to the compiler. This also allows to run the same code on the simulators (for debugging and resource estimation purposes) and then to take it to a quantum device without modifications.
Answer: As far as working is concerned, you are right. A quantum computer works entirely differently than a classical simulator for the same.
Whether there will be any difference in the "coding part" depends on the specific cases. While you cannot get a real quantum computer yet, a lot of online tools are available for cloud Quantum Computation. IBM's Qiskit, for instance, would have no difference in the coding part in the cloud quantum and the classical simulation. All you change is you import another library for the API usage. You can check the same for Rigetti's pyQuil.


Could a large plateau surrounded by continuous waterfalls form?

Question: Could a structure similar to that shown in the image below inspired by Roger Dean's "Close to the edge" actually exist in nature? If not could it be constructed artificially and if so how? Assume the two bodies of water obscured by the mountain on the right terminate in waterfalls and that the waterfalls run constantly at high volume.
Answer: Yes, this is strictly a matter of size. You need a massive influx of water from rain, which is proportional to the surface (goes roughly with the radius squared), while the waterfalls outflux is proportional to the circumference of the plateau.
When the radius is large enough, you can get enough water to feed all the waterfalls. In nature however you'll get some waterfalls to erode faster than the others, lowering the water level, so that you don't really get a continuous range of waterfalls; given long enough, "there will be only one".
So you need a maintenance mechanism that counteracts the erosive effect (which for waterfalls is huge - I heard that the Garganta del Diablo falls back half a meter every year, or something like that).
You could posit some kind of reef coral able to grow and counteract the erosion; the coral cannot live outside the water, and it thrives at the brim due to the influx of oxygen and food particles, so it only reaches up to the brim, reinforcing it. Also possibly imperceptibly raising it over the centuries, so that the plateau slowly becomes a "cup". The effect is self-limiting, because if the coral grows too much, the waterfall slows down, oxygen and food become scarcer, the coral begins to die and the "waterfall-less" area crumbles, restoring the waterfall at that point.
Taking a rain check
We cannot have too large a plateau because we need to get humid winds all over it, and there are no plausible mechanisms that allow this on a Earth-sized planet, constantly and for very long distances.
Also, as @Braydon correctly pointed out, if we have a moon, or the same strong winds that feed rain to the plateau, they'll start interacting with the water surface and disrupt the waterfalls.
So let's try to come up with a size estimate for the plateau.
It needs a lot of rain. On Earth a plausible "lot of rain" (monsonic rain) is around 120mm/die in multiple daily or nightly showers (I witnessed a 250mm/hour downpour and was quite shocked, but survived).
A waterfall rate like Niagara is 2500 cubic meters per second over 1200 meters of aperture. Let's approximate it to F = 2 cubic meter per second per meter of aperture.
The available water daily rate is 12cm, approximated in P = 1/8 cubic meter per square meter. Every eight square meters of surface we have, give us one cubic meter each day and no more.
One day contains 86400 seconds, so every meter of the circumference requires F*86400 m3 of water, which means we need F/P*86400 m2 of surface to sustain each meter of circumference.
So it must be true that (imagining the plateau as circular) surface $\pi r^2$ is F/P*86400 times the circumference $2\pi r$. With F=2 and P=1/8, F/P is 16.
$\pi r^2 = F/P*2*86400\pi r$ means a minimum radius of r = 2764800 m, or 2800 km, and a surface of 24 million square kilometers - more than three times the size of Australia.
In short, $r = 17280*F/P$ with r in kilometers, F in cubic meters per meter of aperture, and P as centimeters of rain per day.
By reducing F or increasing P, the surface can be reduced. For example halving the flow to half of that of Niagara, F = 1 m3/s per meter, the surface is reduced by a factor 4.
A still respectable waterfall is about 0.3 m3 per meter, and this would allow us to reduce the radius by a factor of six (the surface by about forty times), to "only" 470 km.
Remaining with the original figure of 2800 km, there would be another thing that's not really going to fly - where is the rain coming from? That precipitation rate is an average, but it's not likely that in the center of the plateau, 2800 km from the border, there's a significant inflow of humid air; all rain brought by the wind ought to have fallen in the first 2800 km, and actually one has to wonder what the clouds and the winds at the border must look like.
Actually, it stands to reason that if the wind need to arrive 2800 km inland in one day, it has to travel at almost hurricane speed, always.
So we're talking about a planetary-sized permanent hurricane - something like the Great Red Spot on Jupiter.
The same formulas work if we suppose that there's constant heavy rainfall near the border and more bearable weather further inland, provided the average rate stays the same. Which means, the drier the center, the more abysmal the conditions on the boundary.
Comment: Coral idea is great. Self correcting feedback mechanism!
Comment: It would also be possible by artificial means without rain if water from a higher level plateau elsewhere could be piped down - along and up under the area in the photo. Water would then flow in by gravity.
Comment: @LSerni It is also worth noting that if this area becomes massive enough it will be significantly influenced by tides, causing waterfalls to stop on either end at low tide, as the water is pulled away. Winds fast enough can also throw off the balance.
Comment: Yes, but that leaves the question of how the higher plateau gets its water. I think it would simply move the problem farther.
Comment: @Slarty That would require the higher plateau be as massive as mentioned by LSerni. Realistically if this were to be done artificially it would require a massive pump connected to the same water source the falls go into. Then the water can be circulated infinitely in a fountain system.
Comment: Very good observation @Braydon - editing answer
Comment: @ LSerni I think the calculations you made show that it's effectively impossible by rainfall especially given the scale. The road and the house on one of the islands suggest probably less than a mile across. That said it should be possible artificially by pipe from a higher reservoir that was large enough to collect sufficient rain to feed the smaller one.
Comment: @ LSerni Using 0.3 m3 per meter of waterfall and a 1 mile diameter gives a circumference of 3.14 miles or 1609*3.142 metres = 5055 metres of waterfall each with 0.3 m3 /s gives 5055*0.3 = 1517 m3 /s total flow rate required which is much less than Niagara so if the other reservoir was the size of Niagara's water catchment area it should work. That's big, but not impossible on a planetary scale and it could be smaller with heavy rains.
Answer: This is very similar to the OPs other question
How to form a world with steep sided very high plateaus and very deep depressions
except not exactly the same.  So I suppose it should remain different so someone does not say OP is asking too much at once.
The answer again is yes; tepuis.  Angel Falls is the highest waterfall in the world and comes off of one of the high tepuis.

There is not a spring up there.  The tops of tepuis get a lot of rain.  If you had a really big one it could be enough rain to get a near circumferential waterfall.  I suspect over time though the water would find the path of least resistance and you would wind up with one big waterfall.  Although waterfalls can be very wide.  This Chutes Wagenia (not on a tepui!) is 4500 feet across; well over a mile.
Comment: How to form a world with steep sided very high plateaus and very deep depressions is a similar question in some respects but the other question does not require water, so is a distinct question from this one which obviously does require water in very large quantities.
Answer: As mentioned by slarty in the comments of another answer, this could be managed through siphoning from a higher reservoir. This was mentioned as an artificial method, but siphons are also expected to form naturally. Although it would take some stretches for a large enough one to both form naturally and be made of hard enough rock to not be very quickly eroded by such a high flow rate.
Possibly a tuya would provide a good solution. Solid igneous rock would resist erosion and may justifiably have a series of lava tubes for the siphon. Glaciation would also lead to deep valleys which might justifiably be dammed up naturally, leading to the required high reservoir for input. This natural damming could also justify this waterfall being geologically recent so the erosion is not as much of an issue.
Answer: No, it can't appear in nature because there is no addition of new water, and as the water falls off at the water falls, it is not replenished. The only way to achieve this would be with a colossal pump under the lake pushing up massive quantities of water, basically making it a colossal fountain.
If you want something naturally occurring and similar, the most similar scenario would be that it has a higher cliff face on one edge from which more water pours down, replenishing the waterfalls. You would also likely need to town back the water falls.
Comment: What? Does it not ever rain where you're from?
Comment: @Shalvenay Hardly ever. Anyway that aside, it doesn't rain enough to maintain the seen in the picture anywhere on earth. Almost as soon as the rain stopped the waterfalls would stop. Others have brought up the fact that it could get enough rain if it was large enough, yes, if it is the size of a continent, but plateaus that large don't exist.