How can I deploy fields on the new ServiceAppointment or ServiceTerritory objects?

Question: Salesforce has baked some standard Field Service Lightning objects into the Winter 17 release, like "ServiceAppointment". But those do not appear to be exposed in the metadata API or in ChangeSets. How can we deploy these?
Answer: The key to being able to download and deploy these is to have the appropriate FSL permission set licenses and permissions sets on the user you're using to perform the action. In that respect, it's like CampaignInfluence and some other features that are not even accessible via the API unless the accessing user has the appropriate permission set licenses. FSL objects include:

OperatingHours
ServiceAppointment
ServiceResource
ServiceResourceSkill
ServiceTerritory
ServiceTerritoryMember

If your user account in the source org does not have FSL permissions you won't be able to see/download this metadata. If your user account in the destination org doesn't have FSL permissions you will receive an error like:

The object "ServiceAppointment" can't be updated through a flow.


According to my calculations Jupiter's moons do not follow Kepler's 3rd law - Why is that?

Question: I'm asked to collect data on the orbital properties of the four Galilean satellites of Jupiter and show that they obey the same scaling as in Kepler's 3rd law.
My approach for moon Io:
Online, I found that the distance from Io to Jupiter is 422,000km ~= 0.00282089577 AU
which is
$2.82\times10^{-3} AU$
Io's orbit around Jupiter is 1.77 Earth days; 1.77/365 ~= $ 4.85\times10^{-3}\, \mathrm{Earth\ years}$
By Kepler's 3rd law, $P^2(\mathrm{Earth\ years}) = a(AU)^3$
Thus
$(4.85\times10^{-3})^2 = (2.82\times10^{-3})^3$ which is obviously not true even just by looking at the powers of 10 after distributing the exponent on each side.
Comment: Reread the task: *that they obey **the same scaling as in** Kepler's third law*. It's to be expected the moons don't move at the same speed as the planets; that's because they orbit a different body, with a different mass. Coincidentally, you can't say anything about ratios by looking at only one moon.
Comment: I guess I don't really understand what they mean by "the same scaling". Can you please expand on that?
Comment: I also feel that because the Kepler's law that you're to be using is the "modified" or Newtonian version, $P^2=\frac{a^3}{(M+m)}$ or the full equation, $P^2=\frac{4\pi^2a^3}{G(M+m)}$. Either way I think you're simply looking for the 4-2-1 relation of the moon's orbits wrt the proportionate distances they are from Jupiter.
Comment: How can you mess up with the 3rd Kepler law in such a way? You never thought to check the correctness of the equation before to make a post here?
Comment: @LaserYeti What about Jupiter's 4th moon though? It's not included in that 4-2-1 relation/ratio.
Comment: @ribarcheto94 I understand that I only listed three within the 4-2-1, the reason is that you will not usually find other satellites listed within the Jovian set that have a "nice" resonance pattern... the reality is that the 4-2-1 is a farce, and just for the intro astronomy students, so they can wrap their heads around the idea of orbital resonance. However if you wanted to continue the pattern, it would be something like **9-4-2-1**, none of these are exact, but they are fairly close so it should still work.
Answer: Kepler's third law is that $R^3/P^2$ is a constant. However it is not a universal constant; it depends on the mass of the body that is being orbited.
$$\frac{R^3}{P^2} \simeq \frac{GM}{4\pi^2},$$
where $M$ is the mass of the orbiting body (assuming that $M\gg$ the mass of the moons).
Depending on your level of sophistication, you could try plotting $R^3$ against $P^2$, or better, $\log R$ against $\log P$, to demonstrate consistency with Kepler's third law.
Answer: One must consider the mass of the object being orbited. Kepler's third law is true for all planets orbiting the Sun, and for all moons orbiting Jupiter, but not across different gravity wells. This was not understood until Newton, and must've posed an interesting problem (I've never thought of before) already in Kepler's time since the orbital periods and relative distances of the four Galilean moons were known then. And of course the orbit and relative distance of Earth's own moon. Maybe it was even a key inspiration for Newton's thinking about gravity?
Answer: This is what they are looking for. I tried it with numbers and it worked. Thank you for your input, you put me on the right track.
M1 + M2 = A3 / P2
Consistent units must be used to make this equation work. If the data are not given in a consistent system of units, they must be converted.
The masses must be measured in solar masses, where one solar mass is 1.99 X 1033 grams, or 1.99 X 1030 kilograms.
The semi-major axis must be measured in Astronomical Units, where 1 AU is 149,600,000 kilometers, or 93,000,000 miles.
The orbital period must be measured in years, where 1 year is 365.25 days.
Comment: The correctness of Kepler's third law does not depend on what units are used.


Cosmological models other than FRW

Question: The FRW is a nice isotropic and symmetric metric but I think its assumptions are too many. I was wondering about alternative models. Specifically are there any prominent alternatives that have more fleshed out local detail? For example, are there any models that can ascribe a more local interpretation to data which was considered as crucial support for the Big Bang.
Answer: An obvious example is the Hubble bubble though this doesn't invalidate the FLRW model, it just means the homogeneity is on a larger scale than the observable universe. However I get the impression the Hubble bubble idea is not widely considered likely.
Comment: I don't know of any such theories, or at least none taken seriously by the physics community. There's a good reason the FLRW approximation has survived this long :-) I suppose the axis of evil or the CMB North-South asymmetry (http://arxiv.org/abs/0809.0934) might be candidates.
Answer: There's also the Mixmaster Universe, studied in the 1980s. I'll give a couple references:

Neil Cornish and Janna Levin, "The mixmaster universe: A chaotic Farey tale". Phys.Rev. D55 (1997) 7489–7510. Eprint arXiv:gr-qc/9612066
Charles Misner's original paper "Mixmaster Universe". Phys. Rev. Lett. 22 (1969) 1071–1074. DOI:10.1103/PhysRevLett.22.1071

Cosmological models other than FRW


Probability of picking a real number randomly

Question: If we randomly pick a real number from the number line, the probability of picking a number (say x) is 0. This is true for all real numbers x and it makes sense to me why this must be true. But seemingly there is a paradox lurking here. Suppose we pick the number y. This number also had probability 0 but was still chosen in the random process. If it was chosen, it means the probability of it being chosen was finite. Isn't this a paradox? What am I missing here?
Comment: nice question. A bit of limit based approach will help. (something like the probability tends to 0)
Comment: Also, notice that when numbers get infinite, we move on to an higher dimension. here from 1d to 2d. rather than probability of a single point on a number line, we now talk about a finite interval (line segment), whose probability can be calculated by measuring the 'length'
Answer: Infinity doesn't work like you think it does.  There are several ways to interpret probability.  One of those ways is the "frequentist" interpretation - you divide the number of outcomes you're looking for by the number of outcomes possible, and that's the probability.  The issue is that, although that's fine for finite sets of outcomes, it doesn't work when there are infinitely many outcomes (or, more accurately, it always produces zero).
In your interpretation, you are really asking "what is the probability that the number is $y$ now that I've already selected it, and the answer is 100%.  That isn't surprising - there is one outcome and you've chosen it.
However, from the frequentist perspective, what was the probability that you would select $y$ and not, say, $y + \delta$, for any real $\delta$?  Well, there are two issues:

There are infinitely many reals on any interval, so technically this is $\frac{y}{\infty}$, which is always zero

Worse, the size of the interval doesn't seem to matter.  Whether we choose some extremely small interval or an extremely large one, the size is still infinite.

It is #2 above that breaks the frequentist interpretation entirely unless the probability of a particular outcome is always zero.  Basically, the probability of a particular outcome in the frequentist interpretation must change (or stay at zero and only zero) if the set of possible outcomes expands.  Specifically it must reduce, presuming that the outcomes are independent.  You cannot have a probability less than 0, so it works out.
So instead we don't talk about probability of a given number.  We talk about the probability that the outcome will be within some interval, which does have a very well defined interpretation from the perspective of the size of the various sets.
Answer: Probability zero does not mean impossible. Just as probability 1 doesn't mean guaranteed to happen.
A different example of the same phenomenon is this: Flip a coin until you get a heads. The probability that you get a heads at some point and therefore stop is 1. But it clearly isn't completely, absolutely guaranteed to happen. The probability that you keep getting tails indefinitely and never stop is 0. But it clearly isn't impossible. (This is actually almost equivalent to picking a real number uniformly at random from the interval $[0,1)$ and asking whether the chosen number was $0$.)
Comment: Well, yes and no...in real life, the coin flip thing will never happen. But in the OP's setup, we know that _something_ with zero probability is bound to happen. I would say the resolution is that in real life, we can never pick a real number randomly.
Comment: @TonyK It will _almost surely_ never happen. That's what probability 0 implies. I see no mathematical reason why every single coin flip ever done from this moment forth can't be a tails. It is just as likely as any other particular sequence of throws.
Comment: @TonyK In addition: If we keep throwing coins indefinitely regardless of the results along the way, then the sequence we work our way towards will have a prior probability 0 of occurring. In my setup I just choose to stop when it is clear that the sequence we get isn't the sequence I guessed ahead of time, which is "just tails, from now and forever".
Comment: But Arthur, life is too short to toss an infinite number of coins. That is why I said in real life we can't pick a real number randomly.
Comment: @TonyK When has math problems ever cared about such minute details as "real life"?
Comment: @Arthur Math problems haven't. But the (philosophical) problem of the OP lives and dies with the fiction that you *can* pick a number (up to infinitely many decimal places), randomly (whatever that means).
Comment: @Arthur Very nice approach! only a little bit more explanation(which you have done in the comments) would have helped...
Comment: I somehow find it related to 0.99....99=1


Does it exist an Bayesian "version" of the Theil-Sen estimator?

Question: From what I read the Theil-Sen estimator seems to be a really cool estimator; robust and easy to understand. Would it be possible to device (or does it already exists) a Bayesian "version" of the Theil-Sen estimator so that you provide a prior for the slope and get a probability density back instead of just a point estimate? How would such an estimator look/work?
Answer: According to the Complete Class Theorem proved by Abraham Wald in his book "Statistical Decision Functions", an estimator is admissible if and only if it is Bayes for some prior. Hence, if the Theil-Sen estimator can't be obtained as a Bayes decision, it is inadimissible.
Comment: The thought is that if it's decision-theoretically 'any good' i.e. 'admissible' in the technical sense used there, then it has formulation that is Bayesian. (which doesn't, of course, imply that it is admissible, that applying decision theoretic criteria make sense anyway, or that it's otherwise sensible).
Comment: Does this mean that there is no Bayesian version of Theil-Sen? Sorry I don't really understand the answer...
Comment: Well, then my question must have been vague. Even if I asked if the could be a Bayesian "version" I was also interested in how that "version" would look, not only if it existed... Clarified my question above...
Answer: Since the Theil-Sen thingy is robust to outliers by virtue of dealing with medians, I guess the natural Bayesian regression model is one with a t-distribution with unknown degrees of freedom (or other fat tailed distribution, e.g. double exponential might be closest in spirit) replacing the normal distribution of classical regression.
In this case the prior for the slope is not so important because fatter tails for Y allow occasional outliers without affecting the slope estimate.  The degrees of freedom in the relevant t is, in a complete analysis, marginalised out of the joint posterior.
Some discussion of this class of models can be found in chapter 14 and 17 of Gelman's Bayesian Data Analysis.  A choice of distributions is explored in chapter 8 (stacks) of the BUGS Examples Volume one.
Comment: I don't think so.  Sen seems to think that it is biased and inconsistent in the present of measurement error, as one might expect.  See e.g. sentence 2 of [The Theil–Sen estimator in a measurement error perspective](http://projecteuclid.org/DPubS?service=UI&version=1.0&verb=Display&handle=euclid.imsc/1291044758) where the 'discounted parameter' that is median-unbiasedly estimated is an attenuated version of the actual slope of interest.
Comment: I was thinking about that, but then I thouht that it seemed more like a Bayesian version of [Least Absolute Deviation Regression](http://en.wikipedia.org/wiki/Least_absolute_deviations) which is robust outliers in y (if y ~ x) but not outliers in x. A nice property of the Theil-Sen is that it is both robust to outliers in x and y.


What plugins create a directory on the root directory of WordPress?

Question: How can I detect if a plugin or a program is creating a folder on the root directory of my WordPress site? How will I know if I could safely remove them?
Comment: Someone or something must be creating these backups. That's all I can tell you. I would go to my hoster asking about this. They should be able to tell you if they're always created at the same time, if they are created on the server or simply uploaded, etc.
Comment: WP doesn't create backups by default. So either some plugin or some person must have created these. You need to ask either of them what they are for, I'm sorry but we cannot help you for this.
Comment: There are no other backup plugins other than Updraft and it looks like it's being updated continuously because the new files are from today.
Answer: What I would do here is first rename the folder to something else, this way if something breaks you can just rename it back.
After a couple if days if all is well on the site just delete it.
Backup folders and files usually cause more issues  than they are worth. If you haven't needed a backup from 2018 chances are you never will.


Dash switch panel on 1995 VW Golf fan switch melted, only works on 4 high. Can this be fixed from inside the cabin?

Question: Some time ago material started blowing out of the vents, kind of looked like bits of light grey foam. The fan switch had already started having problems, only worked on 2 and 4. On 4 with the AC on the plastic on the switch got soft and slightly deformed. Now it only works on 4. The AC does not get cold, I had it checked, drained and refilled and still no cold AC. 1. Are these 2 separate problems? 2. Will I find anything to fix behind the switch panel? love my car
Answer: These are definitely two separate problems. I'll start by addressing the blower motor speed issue.
This is almost always caused by a bad blower motor resistor in a car. These directly control the speed of the blower motor fan while the hvac system in a vehicle is in use. Usually these are located underneath the dash very close to the blower motor itself. Here is a forum that discusses locating the resistor for your particular vehicle. http://forums.vwvortex.com/showthread.php?5335524-95-Golf-blower-motor-resistor-replacement
Your second problem is going to be a lot more in-depth. There are several things that can be wrong with your AC system to cause it to not blow cold air. Provided that you already drained and refilled the system means that a shortage of refrigerant can already be crossed off of the list of things to look at.
From there, there are still quite a few possibilities for the cause of your problem. Your compressor itself could be faulty, you could have an obstruction within the coolant system lines, or your blend door for the HVAC system could be stuck in a position that does not allow the cool air to circulate. Here is another resource for you to look at to help you diagnose the trouble with your AC system. http://www.aa1car.com/library/ac_no_cooling.htm
AC problems can turn into labor-intensive struggles just due to the nature of the systems, so you should get a professional's opinion at any point that you feel you're in over your head or don't know how to proceed. Best of luck!


How to create unique contribution addresses for a referral system by smartcontract

Question: I ran into some trouble with my smartcontract. I want to be able to allocate referral tokens to each person who participated in the ICO referral program. In order to do this, the smart contract must be able to distinguish contributions made and link them to a certain participant. I am looking for a way to let the smart contract create unique contribution addresses for each participant that registers for the ICO. These addresses will receive contributions and immediately transfer them to the "main" contract address, this way knowing each contribution made by each contributor seperately, even if he contributes from multiple wallets. How can i do this?
Comment: I don't get it, you just want to know WHEN a contributors contributed?
Comment: No, i want to know WHO is the contributor, even if he contributes from 3/4 different addresses. I want a way to create a unique address for each ICO participant, so i know who sends what.
Comment: You cannot assign an address from the smart contract, but you can assign them an ID.
Comment: And how does that work exactly?
Comment: So, just to be clear : A person who wants to contribute signs up on a website, and gets his dashboard. On this dashboard he will get a referral link and can see the amount of people who signed up through that link, and next he will see the total amount of all contributions made by those people. I need to know how i can distinguish these contributors, by giving  each of them a contribution address of which the smart contract will know who it is. Otherwise, there is no way of knowing who contributed what.
Answer: According to the comments in the OP:
You cannot assig na new address to a sender while in a smart contract. Moreover, inside the contract, there is new way for you to know what address belongs to you. Moreover, this is only my point of view, user send ether from where they want, usualy from only one account. Its their responsability to send from where they want, not ours.
But, even if you manage to identify users, I would create a mapping with a uint as a key and a mapping as a value. This other mapping would be the list of addresses user sent ether from. This way, you are able to identify addresses.
Comment: And what if i make receiver contracts for each participant and a seperate accumulation contract which accumulates all the amounts of the receiver contracts? How would i trigger this receiver contract to automatically send each contribution to the accumulation contract?
Comment: Contracts to handle contracts to... ? Do you have any idea how much this will cost you (or the sender)? A lot of money. In solidity, make things simple, not complicated, or you will lose a lot of money.
Comment: How would you suggest me to do it then?
Answer: You have to have two contracts: Main and Reciever. Main contract which will have a function to create an instance of a Receiver contract and register this instance in mapping to make sure we are going to receive payments only from valid Receivers.
Receiver contract will implement default payable fallback function which transfer any value to the main contract. There is only small amount of gas which can be used by default payable function when ETH is being send so you may ask your users to call special function to make their payments. I called it PayTransfer. Working code, tested on Remix is below. To test it you have to:

Create Main Contract
Call AddReceiver function in Main contract.
New Receiver address will be displayed in Event NewReceiver and also in public variable lastReceiver.
Then you have to make a payemnt to receiver contract. In remix you can attach PaymentReceiver contract to the address you got in previous step. Use At Address button.
Once payment is done you can check your Main contract balance, Receiver Balance and Receiver contribution value to the main contract using functions as follows:

MyBalance
ReceiverBalance
ReceiverContribution

In case default payable fallback function will not work ( works on Remix ) you can either ask your clients to call PayTransfer function to make their payments or modify fallback function not to transfer msg.value to Main contract and use RetrievePayment function to transfer ETH to your main contract ( you will have to pay for gas in this case ).
Hope this helps.
<code>pragma solidity ^0.4.24;

contract PaymentReceiver {

    Main public main;

    function () payable {
        main.ReceivePayment.value(msg.value)();
    }

    function PayTransfer() public payable {
    main.ReceivePayment.value(msg.value)();
    }

    function RetreivePayment() public {
        main.ReceivePayment.value(address(this).balance)();
    }
    constructor() public {
        main = Main( msg.sender);
    }
}

contract Main {

    event NewReceiver(address receiver);
    event ReceivedPayment(address receiver, uint256 value);
    mapping(address => uint256) contributions;
    mapping (address=>bool) validReceiver;
    address public lastReceiver;

    function ReceivePayment() public payable {
        require (validReceiver[msg.sender]);
        contributions[msg.sender] = contributions[msg.sender] + msg.value;
        emit ReceivedPayment(msg.sender,msg.value);

    }

    function AddReceiver() public {
        PaymentReceiver receiver = new PaymentReceiver();
        validReceiver[address(receiver)] = true;
        lastReceiver = address(receiver);
        emit NewReceiver(receiver);
    }

    function MyBalance() public view  returns (uint) {

    return address(this).balance;

    }

    function ReceiverBalance(address receiver) public view returns (uint256) {
        require(validReceiver[receiver]);
        return address(receiver).balance;
    }

    function ReceiverContribution(address receiver) public view returns (uint256) {
        return contributions[address(receiver)];
    }

}
</code>


What is XLNC an example of?

Question: XS sounds like excess, B4 sounds like before, XLNC sounds like excellency, etc.  What are these wordplays called?
Comment: You might be interested in William Steig's book *C D B?*
Answer: After some googling, I found the term grammagram referring to this type of wordplay.  While not as common/official as rebus, this term is much more specific, since a rebus is usually mostly pictures, with few letters.  It is an RL-coined (Richard Lederer) word, apparently (see this thefreelibrary entry), which, together with the comparative rarity of grammagrams themselves, would explain its uncommon status.
Personally, I'd use it, though rebus (or letter rebus) would be more widely understood.
Comment: The OED doesn't have 'grammagram', but it does have 'logogram' – 'a sign or character representing a word'. It's not clear if the definition can be extended to cover more than one sign or character, but it seems pretty close.
Answer: That sort of wordplay is called a rebus.
Comment: A rebus usually has pictures as well.
Comment: True, but pictures are not required to make it a rebus; at the wikipedia link you can see some examples which are all-letter rebuses, just as the OP's are.
Comment: I agree that *rebus* fits the bill, albeit loosely.  I suppose one could say *letter rebus* if one wanted to make it more specific.

What is XLNC an example of?


The definition of surjective multivalued

Question: I am confused  by the question of how to define surjectivity for multivalued mapping( if this definition has already existed).
Answer: We say that a function $f: A \rightarrow B$ is surjective if for all $b \in B$ you can find an $a \in A$ such that $f(a)=b$. If you are working with a multivalued mapping (i.e. if the relation $f$ is not necesarily univoque), I think that the notion of surjectivity will be the same that the one I stated above.


Configuration of Cognito Forms with MailChimp

Question: Is there any way to have the contact information to be automatically uploaded to our MailChimp account from all form submissions?
Answer: I am a developer for Cognito Forms.
Although we do not have a way to directly send over information from Cognito Forms to Mail Chimp. You can use Zapier to have each entry submitted also send information into your Mail Chimp account. You can learn more about how Zapier can help send data to Mail Chimp and other useful programs, and how to activate the Cognito Forms Zap, check out our Blog post on the topic.


Is possible get this image with tikz and random?

Question: I don't know if is possible draw a picture like the next with tikz and some random related command:
Comment: you have to do a lot of calculations because the textboxes do not intersect. tikz is not the right tool here.
Comment: A little bit related: http://tex.stackexchange.com/q/180510
Comment: Yes. It is possible. That is, it is just boxes of text in different sizes and colours at different angles. So you could, if you really wanted, recreate it. No idea why you would want to do that, but it seems a relatively harmless project as these things go.
Comment: You can also look at: http://tex.stackexchange.com/a/146178/1952
Comment: Related: [Wordle-like word clouds](http://tex.stackexchange.com/q/917/5764); [Text collage (word cloud) in LaTeX?](http://tex.stackexchange.com/q/135462/5764)
Answer: Basically, yes, you could do this. However, you could not do it automatically or randomly because it requires the programme take account of the shapes of the glyphs, which TeX knows nothing about. To TeX, everything is just a box. It neither knows or cares what is in the boxes. But this kind of word cloud requires things to be slotted together in ways which are sensitive to the shapes of the characters and not just to the size, location and rotation of the boxes containing them.
That is, it would be bonkers to try doing this in TikZ. Like trying to use a rose petal to bail out a sinking ocean liner. Best not to try.


Is there a code that cause an ereader from assuming a page-break between adjoining files

Question: I have a number of books that I am editing in Sigil in which the author chose not to have Chapters or other major sectioning -- consequently, the book consists of one single continuous page that, because of epub size limitations, is broken into many separate files.  But they need to be displayed on an ereader as a continuous page.  Is there a code that will cause the ereader to not issue a page-break when moving from one file to the next?  I have tried page-break-before:always and page-break-after:always -- but no success.  Does anyone know of a way join two separate files for display purposes?
Answer: Starting on a new page for each XHTML document is a choice made by the Reading Systems. The vast majority of ePub Reading Systems (Apple iBooks, Adobe Reader Mobile) follow this rule.
There is nothing you can do about this, as long as the majority of ereaders are based on Adobe Reader Mobile, which is the only Reading System to apply the size limitations for XHTML documents.


Which objects are displayed when i click on related lists , during ediing a page layout on any Object?

Question: Which objects are displayed when i click on related lists , during ediing a page  layout on any Object?  Some times I don't find the objects I am looking for when i click related lists when editing  a page layout of a object in Salesforce
Answer: The related lists that are available for page Layouts on Objects depends on the object.  Some lists are available to most objects like Activity History while others are specific to the object for example Account Teams list on Account object.  For custom objects if there is a master-detail relationship usually the detail object is available as a related list for the master object.
Do you have a specific object that your are looking at?
Comment: can you give me an example?
Answer: Generally speaking, any time there is a relationship field on another object that points to the object whose page layout you're editing, the object with the relationship field will be available as a related list.
For example, the Account object will have Contact, Opportunity and Case related lists available (among others), because each of those objects have a lookup or master-detail relationship field pointing to the Account object.
There are also some special related lists, like Notes & Attachments and Activity History. These appear on most standard objects that support activities, and they'll appear on custom objects if you specify when you create an object that you want to allow activities or notes/attachments.
If an object you're looking for isn't showing up,  check that it has relationship field pointing to the object you're editing.


Wi-Fi won't work on Motorola Droid

Question: I bought a Motorola Droid A855. I don't have a verizon plan, but i was going to use it on Wi-Fi only. I turned off the phone radio, I also turned the Airplane Mode on. After I turned the Wi-Fi on. It showed that I'm connected, but I can't go on the web or anything requiring Wi-Fi. I tried going into the market and it said I don't have a data connection, but I don't need one since I'm using Wi-Fi. So, if anyone has any tips pleae help.
Comment: 1st switch to airplane mode (shuts everything down), then re-enable wifi.
Answer: Many phones will show Wi-Fi as connected, but won't work unless Airplane Mode is turned off.
Answer: Wi-Fi won't work if Airplane Mode is on.
This is because Airplane Mode disables ALL wireless communications, for use on a plane.
On Stock ROM's, Airplane Mode also disables the FM Radio.
Solution:
Turn Airplane Mode off.
Comment: Funny. On my Droid2 as well as on my HTC buzz it works fine the way the OP describes it: 1) turn Airplane mode on, **then** 2) turn Wifi on. Of course it won't work the other way round, as turning Airplane mode on would include switching Wifi off. But once in Airplane mode, I can activate parts (here: Wifi) just fine, while all others stay off until explicitly activated (or Airplane mode turned off again).

Wi-Fi won't work on Motorola Droid


Workgroup DNS server can't register workgroup client

Question: I have a Windows 2008 R2 server running both DHCP and DNS roles and a client machine (Windows 7). DHCP is configured with 003, 006 and 015 options and the win7 machine is successfully configured with DHCP but the win7 machine dose not register itself in DNS. Any idea why?
Answer: If you're not using a default route (you're using DHCP) you need to include 249 Classless Static Routes.


copying preferences and add-ons from older version to a new one

Question: trying to copy preferences and more importantly, add-ons from an older version of Blender (2.75 to 2.79b) The tread that has been closed that claims to work does not work for me. Need help please. Working on MacBook Pro running High Sierra. What's with the editing to make humans sound like robots? What happened to the other Blender forum? I like that one much better.
Comment: Why did you edit out link to the related question? It helps getting the context more than "thread that claims to work". If something isn't working explain why please by posting details what you did and what did you expect to happen. This is not a forum, forum is at https://blenderartists.org/
Comment: This is not a forum. Please take the [tour] to understand how this site works.
Comment: Thanks god I found it. So long!!! I'll search for answers hear when I 'm desperate but I won't actively participate. Kinda blows....
Answer: Copying the preferences file does not copy the script files for the addons. Addons can live in a few places: the folder where blender is installed (you might need to use the show package contents for the blender.app on a mac blender.app/Contents/Resources//scripts) or on the directories listed in this link: https://docs.blender.org/manual/en/dev/getting_started/installing/configuration/directories.html#macos
Just copy the addon you nedd to the current version you need and enable it in the system preferences.


Prevent a user from deleting the folders and files in his own home

Question: How to prevent a user from deleting the folders and files on his own home directory? In my scenario user can create & modify the folders but user should not delete them. How could we achieve this?
Comment: How about telling us what you want to achieve on a higher level, rather than already suggesting an unfeasible approach to solve what you want to achieve. In other words, what is the reason why you want to prevent deletion? Do the files have to exist physically at all times for some reason? Or do you just want to prevent accidential data loss? Depending on this, there may be other solutions to your scenario than access rights.
Comment: Similar to question: [How to prevent users from deleting a directory?](http://unix.stackexchange.com/questions/55259/how-to-prevent-users-from-deleting-a-directory)
Suggestion:
[http://unix.stackexchange.com/a/286376/92974](http://unix.stackexchange.com/a/286376/92974)
Answer: Deleting a file requires write permissions to the file's parent directory. The same permissions you would need to have to be able to create files in the directory in the first place, so your requirements are conflicting: removing write permission to the user's homes to prevent deletion also prevents creation of files.
Note that file creation and file deletion are very similar: in both cases you are changing the entries in a directory, whether by adding or removing an entry.
Answer: If you really wanted to, I suppose you could manually make important existing files immutable with the following:
<code>$ chattr +i filename
</code>
This will add the i attribute to the file, which would prevent anyone from modifying or deleting it in any way. You can check if a file is immutable as such:
<code>$ lsattr filename
----i--------e-- filename
</code>
If the i tag is present, it is immutable. To remove it, use:
<code>$ chattr -i filename
</code>
NOTE: you have to be root to add or remove the immutable tag to files.
The downside to this, of course, is that you'd have to go and do this manually for all the files you want to be protected from deletion. The upside is, it does not prevent a user from creating new files.
Comment: But it prevents the user from editing the file.


Mutually Assured Destruction and Cyber Warfare

Question: During the Cold War, the U.S. and the former Soviet Union pursued a policy of mutually assured destruction (MAD).  I am wondering if it is safe to assume that organizations such as the National Security Administration and its counterparts in Russia are now pursuing a similar strategy vis-a-vis cyber warfare.  I read in the newspapers about the vulnerability of the electrical grid and the banking system.  Could it already be true that both the Russian and the U.S. governments have the capability of taking down each others' electrical grids and banking systems?
Comment: Any answer would require a lot of speculation.
Comment: Sorry, security is nowhere *near* good enough. We can only speculate on how bad it really is.
Comment: MAD doesn't really exist in the cyber realm. It is much more difficult to trace a digital attack to its origin with certainty, and there's no clear definition of what constitutes "cyber-warfare." In the physical world attacks are obvious when they occur, the damages are clear, and the origins are easy to trace. None of that is true in the digital world.
Comment: I guess I'm looking for reassurance from an expert that, no, security is good enough that not even governments will have such  capability.  Unless they get lucky, at best what they can do is fairly limited in scope...
Comment: Given the recent spate of airplane incidents, I should probably also add airplane computer systems to the question above.
Comment: @drewbenn I believe there are similar problems with isolating targets in nuclear warfare, e.g. the nuclear winter.
Comment: @ting05 In a cyber attack, I would have thought damage can be completely clear, e.g. I can't access my computer files because they are being held for ransom.  In a nuclear attack, it may not be clear where the missiles are coming from, for example if they are launched from the Chinese-Russian border and one has only 20 minutes to respond.
Answer: While, as others have said, Mutually Assured Destruction is not something that could apply to Cyber Security, it is certainly true that tit-for-tat cyber aggression has been going on for quite a while and has been pretty nasty over the last few years between the main government supported hacking groups.
Indeed, I believe that the USA did a deal with a large competitive country around 18m or maybe a bit less ago to get them to calm things down.
One of the issues with cyber warfare of course is that it is very difficult to attribute so those of us not involved with cyber military/intelligence can never be sure who is doing what.
The bottom line, though, is that security is certainly not "good enough", not in any industry sector - even a few days ago, one of the US electricity companies found some malware on an offline computer though thankfully not one (at least that they admit to) that was controlling the grid.
Anyone following the cyber security news will painfully be aware of the vulnerabilities in many industries including critical ones such as government, health, city control ("smart" cities), power, ...

However, I do not believe that the capability exists currently for one attacker to take down an entire power grid in any of the major, large, countries. In general, they are too fragmented to be brought down in a single attack.
Similarly, banking is very tightly controlled and banks are very cautious about their systems and how they are interacted with. They have numerous interlocking safety mechanisms to prevent mass fraud or other manipulations. Indeed, the biggest worry with banking is attacks undermining public confidence rather than actual failure of the systems.

UPDATE: MAD does not exist in the cyber realm because of the vast complexity involved and because the physical world is relatively unimpacted (compared to nuclear holocaust).
You can take down a network maybe, a website for a while, you can steal lots of data. But most systems have backups and are quickly restored with new patches and security added.
The worst cyber attacks so far have taken down an organisation for a few days. Sony Pictures may have been the worst admitted too, they were off for a couple of weeks I think but they had appalling security!
One of the biggest current fears in cyber security is un-noticed changes to data rather than mass encryption or theft. We've yet to see a big example of that but I know that there are lots of experts who are worried about that. But even that doesn't amount to world destruction, the worst that is likely to happen is that a government would fail - maybe some lives lost (if certain industries were impacted, like health). Understand that I'm not dismissing such impacts, they are certainly severe, but they don't rank amongst impacts like MAD.
In regard to your comment about banking. Whilst nobody in their right mind would consider banks as entirely "good" actors after the litany of bad things that have happened over the last decade. Most countries have remarkably tight rules regarding banking for this very reason. In any case, most banks carry their own liabilities - even though they may be bailed out by governments, it comes at a terrific price to the people in charge. They are so carefully inspected in the majority of countries that wrong-doings inevitably are found out in the end. There are also too many people involved inside the banks for such things to be well hidden - the well-known banking issues were mainly caused in areas where a relatively few people control everything.
Comment: I've added a comment to explain about MAD & to address your comment on banking. I'm afraid that there are far bigger things to worry about than the ones you've picked on. The risks you mention are not inconsiderate but pale into insignificance against rising nationalism, climate change and extremism. **But** both people and the world are amazingly resilient and inventive, New Year is a time to be optimistic not frightened for the future.
Comment: @drewbenn, indeed, cascades are an issue and, as I said, I don't want to imply that havoc couldn't be caused. But the question was about **destruction** which is an altogether different thing.
Comment: Can you expand on why MAD does not exist in the cyber realm?  I remain unconvinced.
Comment: One more comment: I worry that banks are not necessarily "good" actors.  It's really a separate question, but I can imagine a type of computer hacking which a bank might find to its advantage and allow to happen-- something that would simultaneously improve the state of their account books and give them plausible deniability.
Answer: I would argue that the poster stating that MAD does not apply in cyberwarfare is inaccurate, in that systems are not nearly isolated enough from one another to prevent countries from attacking and destroying a significant portion of internet and other infrastructure. One of my best examples would be to point you to the massive cyberattack in 2007 on the Estonian internet infrastructure.
If the Russians can take down a small country's infrastructure for whom they do not spend significant amounts of time devising an attack strategy, just wonder what the US and Russia could do to each other with the thirty odd years they have been preparing for war with one another.
Even more interesting is the case of military cyberattack preparation of the Chinese during Operation Titan Rain. They, I would assume, have as much capability as the Russians to create widespread disruption/destruction.
I can safely say that cyberwarfare becomes an ever more dangerous way for nation-states to attack one another, even if it does not yet reach the level of MAD.


Given proper temperature and luminosity, Is the Circumstellar Habitable Zone larger for larger stars?

Question: I was seeing a size comparison video of the size of the Sun with other stars, and I could see there are stars hundreds of times larger than the Sun. I understand the Circumstellar Habitable Zone depends on  temperature and luminosity. Given proper temperature and luminosity, Is the Circumstellar Habitable Zone larger for larger stars, or not necessarily? Do some of these giant stars have giant Circumstellar Habitable Zones?
Answer: Yes.
When our Sun expands into a humungous red giant in a few billion years, the habitable zone will indeed increase in size with it. It is expected to evolve into an AGB (asymptotic giant branch) star, which generally have a couple hundred solar radii. During this phase, it will be a cold M-Type star, but its utterly gigantic surface area will make up for its temperature, far exceeding the Sun's current energy output - even though it is a nice toasty G2V.
With that being said, colder planets like Jupiter and Saturn will heat up, theoretically becoming temperate or similar to Earth's current climate depending on how big the Sun ends up becoming. As for Earth itself, if it isn't completely engulfed, will be absolutely scorched by the now nearby surface.
Comment: Thank you for the reference. By "will no longer be suitable for life after this event", I just meant that the red giant will essentially finish sealing the planet's fate, not inherently cause it. To clarify, I will rephrase that segment to make it more concise, thanks again for the information.
Comment: Due to the Sun's gradually increasing luminosity, the Earth will be uninhabitable in a billion years or so, well before the Sun becomes a red giant.
See https://en.wikipedia.org/wiki/Timeline_of_the_far_future#Earth,_the_Solar_System_and_the_universe


Convergence in Distribution implies convergences almost surely

Question: Suppose we have a sequence of non decreasing random variables that converges to 0 in distribution. How can we prove that this sequence converges to 0 almost surely?
Answer: I will use two standard theorems :
(1) Convergence in Distribution to a constant r.v. $\Rightarrow$ Convergence in Probability
(2) If $X_n$ converges in probability to $X$ then there exists a subsequence $X_{n_k}$ such that $X_{n_k}$ converges almost surely to $X$ as $k \rightarrow \infty$.
For the given problem, $X_n(w)$ is a bounded non-decreasing sequence, therefore, $\lim_{n\rightarrow \infty}X_n(w)$ exists for all $w$. Let $n_k$ be the subsequence from (2) above. Let $T = \mathrm{P}[w : X_{n_k}(w) \rightarrow 0]$. Then $X_n(w) \rightarrow 0$ for all $w \in T$. From (2) we know $P(T) = 1$ and we are done.


XMl Data into String in blackberry

Question: Read the contents of an local XML file in an application and get the whole contents of xml file into a string for blackberry application?
Answer: To create a string from a local file see this blackberry forum entry: Open txt file from mediacard
Assuming you want to use the data within the XML, I would recommend using a XML parser rather than string manipulation. The following links should get you going with XML parsers and explain some of the trade-offs:

Blackberry How To - Use the XML Parser
Parsing XML in J2ME
Add XML parsing to your J2ME applications

If, however, you have any say about the format used JSON might be a good alternative. JSON is easy for machines to parse (thus using fewer resources) and it's human readable.
Answer: I have found using a SAXParser and subclassing DefaultHandler has worked well.  Allows to go element by element.

XMl Data into String in blackberry


Is knowledge without certainty contradictory?

Question: Is it consistent to say "I know that London is the capital of England, but I am not certain"? For I could have been lied to all my life, so I am not certain of it.
Comment: There is a difference between Psychology and Philosophy. What is a fact is not subjective.You seem to be basing much on language itself. In reality it happens to be London is the capital of England. This has nothing to do with philosophy or language. It is more to do with authority than something academic. Because you don't know something let's call x doesn't mean there is no truth about x.  X can be true or false if you knew about it or not. To say you know x with certainty means there is no possibility for error. There are slang context where it's not so serious where you will be called out.
Comment: Depends on what "certainty" means, it is a very vague predicate. Degree of certainty for knowledge is expected to be higher than for mere opinions, but absolute certainty isn't required. Presumably, one has to be certain enough to act on it, but that does not rule out doubts. There is even a term [uncertain knowledge](https://www.tandfonline.com/doi/abs/10.1080/13642529.2014.873577).
Comment: There is a case where this would be a contradiction. If we understand that knowledge is a collection of definitely true statements and that certainly is the process of verifying that these statements are definitely true, then having knowledge without certainty would be a contradiction. It would be like having the sum as the result of the process of arithmetic addition without having performing the process that results in this sum.
Comment: Parliament is sovereign, and sits in Westminster, a separate city than The City of London, which  became part of England by treaty rather than force of arms, fortified by the remains of a Roman built wall which had been restored after repeated occupation by Vikings before the Normans. There are a host of questions about exactly what capital means, and London has to be regarded as that of England only colloquially, not formally. There is no certain knowledge, outside of a specific context & definitions, which culture & language never hold unchanging over time.
Answer:
I can know that p without being certain that p if, for instance, I have evidence sufficient for knowledge that p but am uncertain whether the evidence is sufficient. No contradiction.

I can also know that p without being certain that p if, for instance, I knew that p at time t1, I remember that p at time t2 but, at t2, am uncertain whether I am veridically or falsely remembering. No contradiction.

The avowal, 'I know that p but I am not certain that p', raises different issues. In saying, 'I know that p' you imply that you have the highest degree of confidence that p. In which case how can you consistently avow also that you are not certain that p, since not being certain that p implies having less that the highest degree of confidence that p? Contradiction.
Comment: "Knowledge" without logically justified certainty is actually some degree of presumption even though the common usage of the term is not taken to mean this.


When may one do a Hechi Kedushah?

Question: May a Chazzan decide on his own to do a Hechi Kedushah, or are there rules for when it is appropriate/mandated?
Comment: Alternatively known as "Hoiche / Heiche Kedushah" or "Chatzi Kedusha." (Actually, I don't think I've ever heard it pronounced "Hechi.")
Comment: Side note: The Previous Lubavitcher Rebbe said about a personal Hechi Kedushah that its bad enough you came to shul late, but now you want to announce it to the entire congregation?
Comment: @user1292 That's a good reason for the latecomer to avoid coming late again, NOT to ignore part of Halacha.
Comment: @Dave, I'm generally pretty Makpid on spelling/transliterating Hebrew, but since I'm not even entirely sure what language it is, I spelled it the way it generally sounds to me when I hear it.
Comment: @SethJ - no prob, I just wanted to clarify for those who might not understand the title.
Comment: @SethJ - Also known as *Heicha Kedushah*?
Comment: @AdamMosheh, I think your above 2 points were already addressed earlier.
Answer: I read in The Making of a Gadol that (according to R' Yaakov Kaminetzky) in Kenesses Yisroel in Slabodka during the week they did a hoiche kedusha for mincha because the institution of chazaras hashatz was for a beis hakenneses where baal habatim davened because of the possible presence of the ignorant, not for a beis medrash of baalei torah.  Friday mincha, though, they did a full chazaras hashatz because many baalei batim came for shabbos davening. (I guess that made it into a shul?)
Comment: Wow, I really don't like the logic there, but thanks for the interesting anecdote! I'm not sure it answers the question, but since I'm not sure it doesn't, and since it's really interesting, +1 from me.
Comment: related: http://judaism.stackexchange.com/questions/16958/why-do-we-still-do-chazarat-hashatz
Comment: @YDK So all of the chachamim that davened with a normal chazaras ha'shatz before them were baalei batim? If such a reason developed so late, seems a little funny...
Comment: I have heard that this logic is what a number of _y'shivos_ rely on.
Comment: @msh210, I'm not actually criticizing the logic per se (I know, it sounded like I was); I'm criticizing questioning inquiring about the assumption that the logic is based upon, that Ḥazarath HaSha"Tz is _only_ for the ignorant and is superfluous in a B"M or Yeshivah.
Comment: @YDK - Which page in the book is it on?
Comment: I do not know.  I have since returned the book to its owner in Eretz Yisrael.
Comment: I've tried unsuccessfully to find earlier sources that make this point. Isn't it odd that such an important built-in heter to a common takana isn't mentioned prominently until the last century?
Comment: @sethJ, I also thought part of the Chazarat HaShatz was to end up with 100 berachot each day per Dovid haMelech.
Answer: The Shulchan Aruch (OC 232:1) recommends doing this when השעה דחוקה=the time is pressing, which the Rama (OC 124:2) defines as when the congregation is afraid that if they do the full repetition they won't finish by the end of the allotted time for that prayer. (See Biur Halacha OC 124 sv SheYa'avor who debates if this is Chatzot or Sof Zman Tefillah in regards to Shacharit.)
The Mishna Berurah there (sk 6) points out that if it is not a pressing time one should not do this, as the proper form of the enactment of Chazal is to have the repetition come after the silent prayer.

The Aruch HaShulchan (OC 232:7) suggests that, at a very small minyan where it is doubtful that 9 people will answer Amen (as they tend to talk, etc.), one should always do a Heichi Kedusha lest the leader's blessings during his repetition be levatala.
Comment: Our Conservative shul in Gaithersburg, Maryland, does a Heiche Kedushah for mussaf on Shabbat. We have a lot of families with young children and our Rabbi feels pressure to finish the main service in sync with the children's services, so that families are reunited before the kids "have a melt-down." We have experimented with a break-away minyan for Mussaf (both to have a full Amidah and to experiment with alternative niggunim) but it didn't seem to attract the attendance it needed.
Comment: Although it's odd, I've actually seen a Shul do it for Musaf on Shabbath. I'm pretty sure they weren't pressed for time bc of Zeman, but they might have (legitimately) felt pressure to finish by a certain time for logistical and Tzorech HaTzibur issues. Does anyone state that the ShU"'A might allow for other pressing situations?
Comment: @SethJ - I once heard of a (Conservative?) Shul that does this for both Shacharith and Musaf on Shabbath.
Comment: @AdamMosheh, Interesting. Any idea where?
Comment: It is my experience that many Conservative synagogues do a heicha kedusha for musaf.  I have also been in a Chabad that did this for the same sorts of reasons (the tzibbur will not tolerate more davening/won't pay attention anyway).
Comment: @Ze'evFelsen Probably better to cut out half of Pesukei Dizimra, all the Yekum Purkan stuff, and Anim Zemirot than to skip the repetition.
Comment: @DoubleAA, Maybe those are things they should have done.  I am merely eporting what they actually did.

When may one do a Hechi Kedushah?


Repetitive string password

Question: Salesforce users can have a repetitive string as a password. Can I as a admin do something about it? The main reason is to force the users to have secure passwords.
Answer: In Salesforce there is not a declarative setting to prevent repetetive strings in the password however by forcing users to mix numbers, uppercase, lowercase letters and special characters you can reduce the risk caused by this.
Just having repeated strings is not necessarily insecure if the password is of a reasonable length and requires mixed characters, e.g. 12 characters with mix numbers, uppercase, lowercase and special. Example P4ssP4ssP4s!
Passwords on their own are not a particularly strong security mechanism so think of using other aspects of SF platform security.
You can also use multifactor authentication to increase security, see documentation.

Repetitive string password


Show soft keyboard when Activity starts when no text field is present

Question: I want to open soft keyboard while starting an activity.
The activity contains nothing as its element. I just need to open soft keyboard on the launch.
I've tried with
<activity android:windowSoftInputMode="stateAlwaysVisible|stateVisible|adjustResize" but it didn't work.
Also tried with
getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE);

but it didn't work as well
i'm using emulator to run the code
Thanks in advance
Answer: Have you tried
<activity
android:windowSoftInputMode="stateVisible|adjustPan">

?
Answer: HI,
you could try :
 InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
imm.showSoftInput(flags, InputMethodManager.SHOW_IMPLICIT);

This will not open the keyboard if there is a physical one available and opened.(flags can be 0 if there is nothing.)
Answer: try the below code hope it helps
<activity android:windowSoftInputMode="adjustPan">

for more information regarding this Read


What is the difference between higashi (ひがし) and touyou (とうよう)?

Question: It says that higashi is translated as "East" , and touyou is translated as "the East". But since I can only find books with Japanese - English and I'm not native English speaker, I still don't understand.
Comment: I guess, this is might be a case when you can use Google Translate for good: https://translate.google.com/translate?hl=ja&sl=auto&tl=en&u=https%3A%2F%2Fja.wikipedia.org%2Fwiki%2F%25E6%259D%25B1%25E6%25B4%258B Set the translation to your native language.
Answer: [東]{ひがし} (Higashi) is a general term for the direction east. It is also used to refer to the eastern part of countries/areas, for example in:

[東日本]{ひがしにほん} (Higashi-Nihon) eastern Japan, a term often heard in weather forecasts
the country of East Timor: [東]{ひがし}ティモール.

[東洋]{とうよう} (Tōyō) refers to 'the East' as a part of the world / the eastern part of Eurasia. According to Daijirin this usually means countries like Japan, Korea, China, India, Thailand etc. This is opposed to 'the West' ([西洋]{せいよう}), which means Europe and America.
Comment: FWIW, 洋 is the Kanji for "ocean". If you think of the Pacific ocean as the boundary, 東洋 (Japan, Korea, China, India, Thailand, etc.) is the area located at the _east_ 東 of the _ocean_ 洋, whereas 西洋 (America, Europe) is the area located at the _west_ 西 of the same _ocean_ 洋.
Comment: @jarmanso7:  While 洋 may *have* the meaning of "ocean", 1) the primary kanji for ocean is 海, and 2) I've never seen it used that way (other than ocean names).  It's main usage is "west"/"western" (see 洋服、洋楽、洋裁、洋風、洋式、etc.)  So your comment may be misleading to beginners.
Comment: @istrasci, I get your point, maybe I should have said something along the lines "one of the meanings of 洋 is ocean". Anyway, can you elaborate on your claim that 海 is the _primary_ kanji for ocean rather than 洋? It seems to me that 海 is a general word that includes both the sea, ocean or waters, not particularly referring to the ocean (and only the ocean). But I'm no expert at all, so I might be completely wrong.
Comment: Also note that as a beginner myself I found this idea of 洋 ≈ ocean very useful to remember the meaning "west/western" as well, rather than confusing. In fact, this supposedly main meaning of "west" comes later from the original "ocean" meaning, by extension of the idea of "what is across the ocean", a.k.a "the west".
Comment: I agree, 洋 = ocean. I usually treat 洋 this way: if 洋 comes first in a 熟語 then it means "west"/"western"; otherwise, it's ocean.


Can i use a XT 8000 crank instead of GRX crankset

Question: I want to lower the gearing in a GRX 800 set up from a single 40 ring to a single 32 ring or use a XT M8000 crank with 32 ring.Im old and slow.Will it work
Answer: A single ring is quite easy because there is no front derailleur to worry about.
I assume you have FC-RX810-1, which has 110mm BCD, and uses the same chainrings as FC-RX600-1
Wolf Tooth go to 36t https://www.wolftoothcomponents.com/products/110-bcd-asymmetric-4-bolt-for-shimano-cranks
There are some Chinese 34t chainrings as well
https://www.aliexpress.com/item/4000620134076.html
If you want to swap a XT crank you can but you will need to remove (or replace) your BB and fit 3x 2.5mm spacers  https://si.shimano.com/api/publish/storage/pdf/en/dm/MBFC001/DM-MBFC001-01-ENG.pdf
Then your XT crankset will have slightly (0.23cm) wider chainline and substantially (2cm) wider q-factor
Comment: I think it would be feasible to offset the chainline changes by installing one of the spacers to non-drive-side instead. This would result in 0,2mm smaller chainline, which I doubt would cause any clearance issues especially with a significantly smaller chainring.
Comment: The chainring situation is a bit odd. Wolf Tooth's listing for GRX rings only goes down to 38t. I believe the outer BCD for GRX 2x cranks is also 110mm, and so the GRX 1x BCD should be the same. I'm not sure why the GRX 1x rings would have different compatibility than the road 1x rings? I'll have a link to Wolf Tooth's GRX 1x chainrings in my answer.
Comment: the bolt pattern is the same. https://www.gravelcyclist.com/bicycle-tech/q-a-with-shimano-about-gravel-cycling-and-the-all-new-grx-groupset/ It might be due to the dishing of the chainrings - GRX ring are out more (which is mostly a marketing thing IMO), however I don't know how much that is from the spider and how much from the chainring design. Both should work though.
Answer: They are not drop-in replacements for each other because M8000 is a mountain crank and GRX is road, at least in terms of the spindle length and chainline.
The non-boost M8000 cranks (FC-M8000-1) have 50.4mm chainline and the 1x 800-level GRX cranks (FC-RX810-1) have 49.7. That's close enough that you wouldn't usually find a meaningful difference, but it is within possibility with short enough chainstays.
In all cases you could get a bottom bracket to install FC-M8000-1 in place of what you have, but which bottom bracket that would be depends on your shell type. If you have BB86, I don't think there's a better solution available than to just use spindle spacers outside the bearings.
The boost variants of M8000 will push out the chainline enough to cause issues in most cases, so shouldn't be seen as compatible.
Answer: The chainline is a concern. The GRX 1x crank has a chainline of 49.7mm. The M8000 1x crankset, because it's designed for mountain bikes which use Boost spacing, has a chainline of 53.4mm. That means that the MTB crankset's chainring will be 3.7mm further outboard than on the GRX. This means that in your lower gears, you will be more cross chained. This will increase the amount of noise you produce and it will cause faster wear, plus increase the amount of drivetrain friction.
I believe you also will need spacers for your bottom bracket, as MTB BBs are more widely spaced than drop bar frames - without spacers, you would have some of the axle unsupported and there would be a lot of play in the system. Another possible concern is the Q-factor, i.e. the stance width. This doesn't apply to all riders, but if you are a roadie who prefers relatively narrow stance widths, then the MTB Q-factors are considerably wider. Nevertheless, many folks do frequently switch from road bikes to MTBs, and we don't see MTB riders getting spates of injuries from their wider cranks.
While it would only be a 2t chainring difference, Wolf Tooth makes a 38t chainring for GRX 1x systems. They are unfortunately out of stock right now, but there should be other aftermarket component manufacturers. (As per @thelawnet's answer, Wolf Tooth does list 36t 1x rings for Shimano road cranksets, and I'm not sure if there is any issue with GRX compatibility. The BCD should be identical.)
On the off chance that this is a GRX Di2 setup, I know that it is compatible with an XT MTB Di2 rear derailleur (what you can't do is mix road Di2 levers a road front derailleur with an MTB rear derailleur, both derailleurs have to be MTB or road), which would let you put an MTB cassette on there (e.g. 11-46). Or, for mechanical RDs, you can get a different Wolf Tooth product called the Tanpan, which lets you use a mechanical MTB RD with your GRX shifters. That should get you compatibility with an 11-46 cassette. Also, because Shimano's specs are conservative, you can likely use a 11-42 cassette with your existing setup; in conjunction with a slightly smaller chainring, that might provide low enough gearing.
This paragraph is more of an editorial. I believe that Shimano has admitted to being well behind SRAM in the shift to 1x drivetrains on MTBs, and I think many would agree that they are behind on gravel bikes as well. It is clear that their 1x gearing ranges are more limited than SRAM's 11s and 12s 1x groups. Unfortunately, this question does highlight some of the gearing limits with Shimano's 1x groups.
Comment: Shimano used to make a non-boost M8000 crankset. Chainline 50.4mm. Almost identical. Maybe hard to find now? But a single non-boost mtb crankset should not be hard


How do nodes verify backwards incompatible blocks?

Question: When you start the initial block download with the latest versions of Bitcoin Core, how does your node know that old blocks were valid according to different rules prior to soft forks?
Answer: Old blocks in the chain are still valid under the current consensus rules.
In a broad sense, this is because the code will be written to enact rule changes at specific block heights, and thus older blocks will not be subject to said new rules.
To put it differently: the consensus ruleset doesn't just cover what new blocks are supposed to look like, they also cover what the historical valid chain looks like!
Sometimes, specific exceptions are written in, such as is the case with BIP 30.
Comment: No it isn't, in such an example the consensus rules would be *"all blocks after x height must follow 'new rule'"*. Older blocks are thus still implicitly valid under this 'current consensus ruleset'. To put it differently: the consensus ruleset doesn't just cover what new blocks are supposed to look like, they also cover what the historical valid chain looks like!
Comment: Ah ok I see what you mean, your answer wasn't clear to me. Yeah if you include the historical consensus rules in the soft fork consensus rules then yeah old blocks are still valid because they are not being assessed by the same rules as the new blocks.
Comment: @MichaelFolkson I edited the answer to include some text from my comment, hopefully its a little more clear. Appreciate the feedback, helps to keep content on here accurate and easily digestible
Comment: This is incorrect. Old blocks aren't necessarily valid under the new consensus rules post soft fork activation. A soft fork enforces additional restrictions that old blocks aren't expected to abide by.
Answer: A soft fork is a change to the Bitcoin protocol that adds additional restrictions to the rules enforced by full nodes. However, these additional restrictions only apply to blocks from the point of activation. Blocks pre soft fork activation aren't expected to meet the new restrictions. These blocks are validated according to the old protocol rules that continue to be present in the code of a protocol implementation (e.g. Bitcoin Core).


What is the difference between -O0 ,-O1 and -g

Question: I am wondering about the use of -O0,-O1 and -g for enabling debug symbols in a lib.
Some suggest to use -O0 to enable debug symbols and some suggest to use -g.
So what is the actual difference between -g and -O0 and what is the difference between -01 and -O0 and which is best to use.
Comment: Related, but not the same: [What's the difference between a compiler's `-O0` option and `-Og` option?](https://stackoverflow.com/questions/63386189/whats-the-difference-between-a-compilers-o0-option-and-og-option/63386263)
Answer: -O0 is optimization level 0 (no optimization, same as omitting the -O argument)
-O1 is optimization level 1.
-g generates and embeds debugging symbols in the binaries.
See the gcc docs and manpages for further explanation.
For doing actual debugging, debuggers are usually not able to make sense of stuff that's been compiled with optimization, though debug symbols are useful for other things even with optimization, such as generating a stacktrace.
Answer: -OX specify the optimisation level that the compiler will perform. -g is used to generate debug symbols.
Comment: And --help gives you the same answer ;)
Comment: @Binyamin which is to use if i want debug symbols.
Comment: @MichielvanVaardegem - and the documentation will give an answer for most question in SO in general :)
Answer: From GCC manual
http://gcc.gnu.org/onlinedocs/

3.10 Options That Control Optimization`
-O
-O1
Optimize. Optimizing compilation takes somewhat more time, and a lot more memory for a large function. With -O, the compiler tries to reduce code size and execution time, without performing any optimizations that take a great deal of compilation time.`
-O2
Optimize even more. GCC performs nearly all supported optimizations that do not involve a space-speed tradeoff. As compared to -O, this option increases both compilation time and the performance of the generated code.`
-O3
Optimize yet more. -O3 turns on all optimizations specified by -O2 and also turns on the -finline-functions, -funswitch-loops, -fpredictive-commoning, -fgcse-after-reload, -ftree-vectorize and -fipa-cp-clone options.`
-O0
Reduce compilation time and make debugging produce the expected results. This is the default. `
-g
Produce debugging information in the operating system's native format (stabs, COFF, XCOFF, or DWARF 2). GDB can work with this debugging information.`
Answer: -O0 doesn't enable debug symbols, it just disables optimizations in the generated code so debugging is easier (the assembly code follows the C code more or less directly). -g tells the compiler to produce symbols for debugging.
It's possible to generate symbols for optimized code (just continue to specify -g), but trying to step through code or set breakpoints may not work as you expect because the emitted code will likely not "follow along" with the original C source closely.  So debugging in that situation can be considerably trickier.
-O1 (which is the same as -O) performs a minimal set of optimizations. -O0 essentially tells the compiler not to optimize.  There are a slew of options that allow a very fine control over how you might want the compiler to perform:  http://gcc.gnu.org/onlinedocs/gcc-4.6.3/gcc/Optimize-Options.html#Optimize-Options
Answer: As mentioned by others, -O set of options indicate the levels of optimization that must be done by the compiler whereas, the -g option adds the debugging symbols.
For a more detailed understanding, please refert to the following links
http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#Optimize-Options
http://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html#Debugging-Options


Process of getting a token on an exchange?

Question: Does anyone know what the typical process of getting a token on exchanges is?
Answer: I think it would have to be worth the effort on the part of the exchange before they would list it. (Depending on the exchange, I suppose.)
If your token isn't widely used, then the exchange isn't going to make any money from listing/trading it. There is presumably a point where the value they could make outweighs the cost of the process of adding it, at which point you might have more luck.


How do I create a Jenkins Build Pipeline?

Question: I have downloaded Jenkins' Build Pipeline Plugin.
The docs state:

Create a view of the new type Build Pipeline View.
You will then be redirected directly to the configuration page.

I just don't see the right button to create a new pipeline. What am I missing?
Answer: The Build Pipeline plugin allows you to create views of the downstream and upstream relations between your jobs (and also add manual steps in-between them). To create the pipeline you should first define these relations by using post-build triggers or the Build after other projects are built option, for example.
Then, you create the view as izzekil described in his answer and get a pipeline similar to the one below:
Answer: As per your quotation a Build Pipeline is not of a job kind: it is a view. You have to use "Create view" which is rendered as a plus sign placed in right-most tab. Or you can use direct link: http://jenkins.example.com/newView. There you will be able to select "Build Pipeline View" and proceed to its configuration page.
Comment: I only have List View and My View options. Maybe they removed it in the new version.
Answer: I have Jenkins v 1.6 and I had it under the + button here:
Answer: In addition to @izzekil's useful link above to the newView page, you might also be able to make sure of the Views tab if you have it on the Jenkins home page.


I'm trying to build mass, and I had a great upper body workout yesterday, but I only got about an hour and a half of sleep last night

Question: Does this completely negate my workout? Is there something I can do to compensate for it today? I know it was only one session, but I just absolutely hate the feeling that the entire session wasted. Was it?
Comment: I just hope you're not denying your legs...
Answer: Short answer: Don't worry about it. This is a detail.
Long answer: Restitution is very important, but as long as you don't go back to the gym and start doing another upper body workout immediately, you're still resting. You can, for instance, compensate by eating a bit more, and providing more nutrition to the muscles.
So long as this is something that happens rarely, it's not something you need to worry about. Not even the most successful strongman or bodybuilder or fitness model gets 8 hours every single night.
Answer: I often consider good workouts followed by negligible sleep to be lost workouts that need to be repeated. We don't get stronger or bigger from lifting, we get stronger or bigger from lifting then eating and resting.
One and a half hours sleep is extreme. I would consider your workout nearly wasted. Get back to a good sleep schedule, eat plenty, hydrate, get some sun, and stop worrying about it. You're doing the best you can.
Comment: @DaveLiepmann - I somewhat agree, but I think that so long as his habits are otherwise on point, and this was a one-time deal, then it's not a wasted workout. Since he's talking about this as a particular case, I'm assuming that there's nothing wrong with his sleeping schedule and dietary habits. He should be able to catch up on sleep, and still enjoy the benefits of that workout. It's not like the first sleep after a workout is necessarily the only one that counts.
Comment: what if the rest time was an hour or two less than usual? would it help to sleep those 1-2 hours during next day?
Comment: @Herokiller In my own training I've found a direct relationship between sleep quality and recovery. Naps can *help* but they aren't the same as the real thing.
Answer: Answering your question is difficult and requires a guess at best.  The ability to recover from an exercise session is a very individual thing.  There are many factors (diet, stress, age, etc.) that need to be considered, one of which, is sleep.  And, the level of intensity of your workout will also factor into your ability to recover and build mass.

Does this completely negate my workout?

I don't think so.  Building mass (naturally) is a long term process.  You shouldn't feel like it was a "wasted session".  The fact that you recognized the importance of sleep should provide an incentive in the future to follow through on it.

Is there something I can do to compensate for it today?

I would not stress about it.  And, I would not try to work harder "today" to make up for it.  You run the risk of putting your body (and CNS) in a deficit.  If you plan to train "today", I would approach the workout  as a "maintenance" session.
Answer: I know how much that sucks because it happens to me too from time to time.
I don't think it is a fully wasted workout. I am doing a linear progression. Each time when I don't get a minimum amount of sleep, I simply insert one additional rest day. When I eventually go back to the gym, I always find that it was not so terrible after all, because my linear progression has moved forward, i. e. I am still able to do some more reps, sometimes as many as I had expected, only a day or two later. So I guess that inserting one or more additional rest days sort of compensates at least partially. I believe that bad sleep slows down my progress but it does not stop it altogether.
Don't get obsessed. Just do your best to get enough sleep: avoid caffeine altogether, wake up at the same exact time every day, don't work out short before going to bed (google for "sleep hygiene" for more useful tricks) and insert rest days whenever that is not possible.
I would like to show you something that will convince you of not worrying so much about one isolated sleepless night. Since I started my training five months ago, I register my sleep times together with my weight, reps and so on. I have now enough data to start drawing some interesting conclusions:
The first graphic shows how many hours I sleep each day vs how many hours I slept the day before. This graphic really pisses me off: as you see, sleeping more than six hours for me has often bad consequences the following night, I will not be tired enough and I won't sleep much. I have accepted that and stopped trying to get as much sleep as possible every night. This has improved my quality of life. I don't sleep much, but at least I sleep regularly now.

But the most interesting graphic follows. The horizontal axis shows here the same: how many hours I sleep each day. But the vertical axis shows the average hours slept each day plus the day before (for instance, 3 hours today and 7 hours tomorrow will be 5 hours in the vertical axis):

The points here have a tendency to clutter in a central band. That shows that having a bad night is not so important in the long run, because my body will compensate the following day (assuming I allow for that). It is not perfect (the band is not horizontal, so yes, the missing slept is never 100% recovered) but it should show you that, as long as you allow your body to compensate the missing hours, a poor sleep night is diluted in just a couple of days.
Your muscles do not recover and grow during the very first post-workout night only. It takes a couple of days as anyone here will tell you. If you couple that fact with the latter graphic, you won't worry so much about missing one isolated night.
Of course, if you don't allow for recovery the next night and so you start missing one night after the other, nothing I said is valid and you will be ruining not only your workouts, but your entire health. Also, it is important to stress here that I always insert an additional rest day in my schedule for each bad sleep night.


Are the Skeleton Traps permanent?

Question: After the release of the Halloween Update for Clash of Clans, I noticed a new trap (the Skeleton Trap) had been created. The cost to upgrade them is pretty expensive (600,000 gold is insane), so is there any information regarding the duration of the Skeleton Trap?
Answer: Yeah they are permanent and will stay for ever and are not only for the halloween, also the cost to upgade is actually considerable cuz the traps act like cc troops and every upgrade brings in another added skeleton

Are the Skeleton Traps permanent?


How does blood/saliva boil in outer space?

Question: Why would the blood boil? Is it because of the temperature or pressure? Because I really can't figure it out. I thought space didn't have a temperature above freezing unless close to a star or the sun. But if it is the pressure how would that work?
Comment: Ans to heading question: very gruesomely. The hapless body the said bodily fluids belong to is warm (at least for the next few minutes), so a representative temperature to plug into e.g. the Clausius Clapeyron equation to tell whether a phase change (boiling) is likely to happen is $37^o C$, not the temperature of space. YUK!
Answer: There are lots of related questions on this site but I couldn't find one that answered your question exactly. If you're interested try searching the site for boiling vacuum or something similar.
The boiling point of a fluid depends on the external pressure. Specifically a fluid will boil when its vapour pressure is greater than or equal to the external pressure. The vapour pressure of water at body temperature is about 0.06 atmospheres, so when the external pressure has fallen below 0.06 atmospheres the water in your body will start to boil.
However as water boils it cools, because heat is carried off by the water vapour. So the boiling will cool your blood/saliva/whatever. The vapour pressure of water is temperature dependant so the cooling will reduce the rate of boiling, and of course at some point it will be cooled enough to freeze. There is some debate about how fast you would freeze because we've never done the experiment. There is some discussion of this in Direct exposure to the vacuum of space and How does space affect the human body (no space suit, no space craft).
Note that ice sublimes in a vacuum so even after freezing you would slowly lose water and dry out. However the rate of water loss gets very low at low temperatures, which is why it's possible ice can be found on the Moon.
Comment: So in short, vacuum exposure is a really horrible way to die. Always triple-check your space suit.
Comment: I don't think the blood *IN* your body would boil at all. Just because external pressure is low doesn't mean the pressure in your body goes to nothing as well. Any liquid directly exposed to the vacuum (the moisture in your eyes, saliva in your mouth, etc.) would boil, though.
Answer: In space there is no air pressure at all, and pressure is the continuous physical force exerted on or against an object by something in contact with it. Also the temperature in space can be as low as 0 Kelvin, but also as high as 2.7 Kelvin because any object in space will just radiate heat until it cools, and it will stay cool. However this is for objects that are not exposed to sunlight
Because there is no pressure in space to keep the liquids in our bodies from being a liquid state, because the boiling process would cause them to lose heat very rapidly, then the fluids would freeze before they were totally evaporated.
Your tissues i.e the skin, heart etc would expand due to the boiling fluids, but they wouldn't explode. You would also be exposed to a number of different types of radiation and would experience the absolute 0 of space
Comment: But the temperature in space is not $0K$. In fact even the coldest regions in deep space are as high as $2.7K$ because of the Cosmic Microwave Background Radiation left over from the big bang.
Comment: :) I suggest you edit your answer accordingly to make it more factually correct!
Answer: What you are looking for is called the "Armstrong limit". The lower the pressure then the easier a fluid can boil... so beyond a certain pressure, and without a pressurized suit, your blood could be capable of boiling at your normal body temperature.
http://en.wikipedia.org/wiki/Armstrong_limit


Choosing the threshold for computing the confusion matrix

Question: Is there any way of selecting the best possible threshold to minimize the number of false positives and false negatives (to get the best possible minimized combination of false +ves and -ves)?
Answer: The optimal threshold will ideally minimize the combined loss function you obtain by selecting a false positive or a false negative. If both are considered equally undesirable, you can generate a receiver-operating characteristic (ROC) curve and then determine the point which is closest in linear distance to the 100% sensitivity and specificity point.


Purpose of dual diode

Question: I'm referring the DALI 2 schematics by Mikroe.
Within the circuit what is the function of D1 in given schematics?
And why they are using a dual diode?
Comment: Well, if you need two diodes, why not use a dual diode? It's convenient.
Answer: In a DALI network, maximum system current is limited to 250 mA and a node is allowed to draw a maximum of 2 mA. This is generally the current drawn by node during receiving (receive opto's LED).
To limit the node current to somewhere around 2 mA a current sink/limiter is needed. And its formed by Q2 and its surrounding components. D1 is there to basically provide a reference voltage for the current source formed by Q2 and its surrounding components. The current limit, ILIM, will be determined by the following equation:
$$
\mathrm{2 \ V_{F(D1)} = V_{BE(Q2)}+I_{LIM}\cdot R7 \\
\Rightarrow I_{LIM}=\frac{2 \ V_{F(D1)}-V_{BE(Q2)}}{R7}}
$$
The diodes are biased with a 100k resistor, so the biasing current will be way less than 1 mA and this will make the forward drop less than 0.7V, probably somewhere around 0.5V. So the reference voltage, 2 VF(D1), can be assumed as 1V. The VBE(Q2) can be assumed as 0.5~0.6V as well due to very low base current. So this will make the current sink's limit something around 2 mA.
And, as Justme stated in their answer, two diodes in a single package saves space and cost. Because there's already a diode drop due to Q2's base, the reference should be stable and higher than a diode drop. Of course a Zener or an LED could have been used instead of D1 but they require higher current for proper biasing (in mA range), and that'd cause the limit of 2 mA to be exceeded.
Answer: Purpose of D1 is to provide a voltage drop of two diodes. And that's why it is a single component with two diodes rather than two separate diodes.
It's a reference voltage for the base of the transistor circuit used as constant current sink.
Answer: That transistor with double diodes and two resistors is a very common circuit for a current source/current sink. There are commercial LED drivers which operate using such a configuration. As others have already said, the diodes are forming a voltage reference (with the 100k bias resistor).
One benefit of the configuration which others haven't discussed is that it provides temperature compensation: as the temperature increases, the Vf of the diodes decreases, which causes a reduction in the current being sunk. This negative temperature coefficient is beneficial with LEDs, because it prevents thermal runaway (the LED Vf also decreases with increased temperature, which can cause progressively higher power draw, which causes further self-heating, etc.) Using a Zener in reverse bias alone does not provide this critical feature.
Commercial examples of this all in a single chip package are the BCR series by Infineon (e.g. BCR420, BCR421), although they are designed for 10 mA and up I believe.
https://en.wikipedia.org/wiki/Current_source#/media/File:Const_cur_src_112.svg
https://en.wikipedia.org/wiki/Current_source

Purpose of dual diode


JavaFX UI creation & Progress bar Update

Question: I have a rather tricky question here .
What I have :
I am currently making a JavaFX application that renders a graph ( with lots of nodes and edges ) on the screen . I am able to construct the graph using the Graphiz library and it shows fine on my screen . But the graph rendering can take time bex my graph can contain >1000+ nodes and I drawing them on the screen is slow . Here is my code to do that
protected synchronized void layoutWithGraphviz() {
    if (listener == null)
        listener = new LayoutResultListener();
    Utils.CreateGraphLayout(this,
            listener);
}

Now my LayoutResultListener() is a listener that ensures that the vertex on view dont overlap each other / look nice and hence I redraw the graph if they dont . This all works perfectly .
What I need :
I want a progress bar to show my overall progress . Now since I am unsure how many times my LayoutResultLisener() will be called so i am OK with an indeterminate progress bar . However the tricky part is I cant delegate the UI creation part to a background thread as JavaFX doesnt allow this . I see it documented here as well Concurrency in JavaFX
So i dont know what to do I cannot delegrate UI creation to background thread . So how do i show a progress bar ? Any idea ?
Answer: Try to wrap your UI creation code inside :
Platform.runLater(new Runnable(){
    @Override
    public void run() {
        //your JAVAFX UI codes
    }

});


How did the builders of Derinkuyu light it?

Question: I understand that the air shafts and deep streams incorporated into the underground city of Derinkuyu covered the essentials, and they doubtless harvested and stored food from surface farms, but there is one item that I haven't heard addressed:  how did they light their living quarters?  I would assume burning oil lamps and candles is going to put a ton of smoke into those caverns, especially with thousands of people doing it simultaneously, but I have seen no evidence of it in photographs and videos.  In a sci-fi setting, or a dwarven fantasy setting,I would expect some kind of luminescent crystal or bioluminescent plant
Comment: I don't know about the ancient Cappadocians, but I do know that the ancient Greeks and Romans used olive oil in their oil lamps. Olive oil lamps produce very very little smoke, almost none. You can leave one burning for years and it won't stain your ceiling.
Comment: This belongs on history.stackexchange, not here.
Comment: If you are determined enough, and you know the surroundings, you can live with _very_ little light most of the time. You don't actually need nearly as many lamps as you think. Often, you can move around in complete darkness, and you are just fine as long as clutter is kept away to avoid accidental tripping. Hearing can compensate a lot, too: you don't need to see others as they move around because you can hear their footsteps, and at close proximity you can pass each other gently.
Comment: it was originally used for storing food and temporary shelter against raiders so I don't think they would light the whole tunnel maybe parts of it, I suspect the living condition inside and the lack of threat outside eventually turn the place into a ghost city ;D
Answer: Archaeologists believe that Derinkuyu was illuminated by a combination of oil lamps and reflectors.  As it was also ventilated, and that the olive oil commonly used in such lamps burns with little smoke, smoke was unlikely to be an issue.
As for modern photos of Derinkuyu, it is currently illuminated by anachronistic modern electric lights.
Luminescent crystals or bioluminescence may prove to be more difficult than simple oil lamps.  Luminescent crystals would be very rare unless they are handwaved in, and would likely require being charged in sunlight for some time, or might be radioactive if they don't require solar charging.  Bioluminescent plants and animals are rare and tend to require conditions not compatible with human comfort.  Oil lamps have the benefit of being easily made, easily fueled, and easily maintained, and they produce more light than phosphorescent compounds or bioluminescent organisms.


How to remove old plastic pool deck sleeves

Question: How to remove old plastic pool deck sleeves. 1 1/4" hole in concrete. Sleeve is 4" deep. Broken at the top, no flange left on top.
Comment: can you post a picture?
Answer: Select (or go buy) a cheap chisel - you don't want to do this with a nice one.
Wear safety glasses, the plastic is probably brittle with age and sun exposure.
You might want ot experiment with pouring boiling water into the hole first, to see if it makes this process easier - depending on plastic type, it may.
Set the chisel on the plastic, next to the concrete, and hammer it. Repeat as needed until the plastic sleeve is reduced to either plastic slices/shards you can remove, or possibly you may be able to remove the whole thing once you get one cut through it and can lever one of the sides inward from the hole in the concrete.
Comment: Most plastics have a very high coefficient of thermal expansion, much higher than that of concrete, so boiling water will swell the plastic sleeve inside the hole & make it more difficult to remove. I could opt for using dry ice to pack the hole, though - that'll also make the plastic much more brittle & easier to shatter.
Comment: Shucks, I forgot to bring my dry ice today.


Changing ArcMap Display Order of Elements in Same Layer File?

Question: I have a bunch of polygons in a layer file and I want to reorder those polygons so one of them is "sent to back". I am using ArcMap 10.5.
Comment: The only reliable way to do this for certain is to create a second layer, with a definition queries to specfy the "back" features and "front". Due to spatial indexing and other quirks even an ORDER BY might be violated in rendering.
Answer: I would use the Advanced symbology tool Symbol Levels as discussed a bit here: [How to force polygons to the bottom, without compromizing drawing speed?
Go to Symbology tab, Advanced, Symbol Levels. Click on the use symbol levels box, then move the polygons up and down to control drawing order. However, if you have a lots of ones needing to go back because they are larger, I would do two layers based on a definition query on size (as Vince suggested).


Is it necessary to add editors in citation?

Question: I am adopting the MLA citation style. If a book is written by a principal author with an editor, is it obligatory to add an editor of the book in citation?
Comment: Perhaps specify what kind of editor. Is s/he on the cover?
Answer: Many books don't have editors (unless they are employees of the publisher). But some do, and it is possible you should add their name to the citation. For example if the book is a collection of papers by [famous author], then the editor is important, since they chose which papers to collect. Similarly the editor of a review volume is also important even if they didn't contribute any articles to the volume.
If the name of the editor appears on the front cover, I would default to 'yes'.
Answer: There are a lot of kinds of editors, but it would be very unusual if any of them contributed to the actual intellectual content of a work. In that sense, no, it isn't necessary to cite them so some would put the name of the editor, say in parentheses, with the citation: "...(edited by x.y)".
Some editors handle the publication process, some give advice on writing style, some might even rearrange things, but few would contribute to the actual ideas. There might be rare exceptions.
There is, however, another kind of editor. Some books are little more than a compendium of the work of several authors. In this case and "editor" will have done the creative work, such as it is, of collecting those papers into a single volume. Then, if you need to cite the volume itself, cite the "editor" who created it. But the papers themselves don't need the editor's name attached.
Comment: I've seen books where only the editors are displayed on the cover even e.g. https://link.springer.com/book/10.1007%2F978-3-642-37569-9
Comment: In my field the book and the editor end in the references list not the contributing authors of the chapters/sections. Usually investing time on writing a handbook chapter does not bring much citations.


The speed of light and unstable matter

Question: Mr.E is on a luxury spaceship travelling about 1/2 the speed of light and finds a cubic lump of unstable matter(attached to a bomb) in his cabin. He of course is an expert with bombs but this device is based on the unstable matter's critical mass. The lump of matter fluctuates a tiny amount constantly but if it is more than 2k.g, (say for the sake of argument) it will cause the bomb to explode. Right now it is at 1.9999k.g., if the ship accelerates making it over 2kg relative to the people anxiously monitering the ship from Earth they would think it should detonate yet relative to Mr.E and the fellow passengers its mass is still under 2kg?? Is this loose reasoning valid?
Comment: No, with the critical mass, you are thinking about something like an atomic bomb. Now, the thing is that while the mass would increase, you'd still have as many atoms in the material. And therefore not enough to get a chain reaction and thus an explosion.
Comment: If an object is accelerating towards c would any inherent radioactivity of the object increase?
Answer: Critical mass is actually more about 'the right number of nuclei in a specified space'. As we are talking about solid matter this equivalently translates to a given number of atoms (or molecules depending on your matter). And this furthermore translates to our everyday mass. But it's 'not about mass', it is just a practical way to specify the quantity.
So in your example: It doesn't matter who sees how much mass. The question is whether is has the 'critical number of nuclei' in it and that doesn't change.
Comment: critical number of nuclei within a critical volume, to be precise.  So next we could calculate the relativistic dimensions of the bomb :-) (Yes, I know that only changes for the outside observer)
Comment: This brings a new question but it's a nice game. For the outside observer, the size and shape of the lump of matter (let's assume a sphere for simplicity) will change. But so does the movement of inner particles (make them neutrons to follow the atomic bomb line). Consequently the size and shape for 'criticalness' changes as well. As a result it won't explode for the outside observer either.
Comment: I'd just like to point out that in modern relativistic theory, mass is considered constant in all inertial frames. There is no relativistic increase of mass. Of course, the predictions of the theory are no different from before, it just comes down to the definition of mass. Issues like the one in the OP's question led to the idea that mass should really be defined as a Lorentz scalar. C.f.: https://en.wikipedia.org/wiki/Mass_in_special_relativity
Answer: The bomb doesn't "care" what its mass might look like to an observer in another frame.
If you calculate critical mass you don't worry how big it might seem to observers located in billions of other possible frames of reference. Local frame of reference is the only one valid for making calculations concerning the occurence of local phenomena.

The speed of light and unstable matter