How to use the A* path finding algorithm on a grid less 2D plane?

Question: How can I implement the A* algorithm on a gridless 2D plane with no nodes or cells? I need the object to maneuver around a relatively high number of static and moving obstacles in the way of the goal.
My current implementation is to create eight points around the object and treat them as the centers of imaginary adjacent squares that might be a potential position for the object. Then I calculate the heuristic function for each and select the best. The distances between the starting point and the movement point, and between the movement point and the goal I calculate the normal way with the Pythagorean theorem. The problem is that this way the object often ignores all obstacle and even more often gets stuck moving back and forth between two positions.
I realize how silly mu question might seem, but any help is appreciated.
Answer: Create an imaginary grid at whatever resolution is suitable for your problem:  As coarse grained as possible for good performance but fine-grained enough to find (desirable) gaps between obstacles.  Your grid might relate to a quadtree with your obstacle objects as well.
Execute A* over the grid.  The grid may even be pre-populated with useful information like proximity to static obstacles.  Once you have a path along the grid squares, post-process that path into a sequence of waypoints wherever there's an inflection in the path.  Then travel along the lines between the waypoints.
By the way, you do not need the actual distance (c.f. your mention of Pythagorean theorem):  A* works fine with an estimate of the distance.  Manhattan distance is a popular choice: |dx| + |dy|.  If your grid game allows diagonal movement (or the grid is "fake"), simply max(|dx|, |dy|) is probably sufficient.
Comment: My grid allows diagonal movement, but strangely enough the Manhattan method worked much better for calculating distance than the Math.max(|dx|, |dy|). Thanks for that tip.
Answer: Uh. The first thing that come to my mind is, that at each point you need to calculate the gradient or vector to find out the direction to go in the next step. Then you move by a small epsilon and redo.
This basically creates a grid for you, you could vary the cell size by choosing a small epsilon. By doing this instead of using a fixed grid you should be able to calculate even with small degrees in each step -- smaller then 45° from your 8-point example.
Theoretically you might be able to solve the formulas symbolically (eps against 0), which could lead to on optimal solution... just a thought.
Answer: How are the obstacles represented? Are they polygons? You can then use the polygon vertices as nodes. If the obstacles are not represented as polygons, you could generate some sort of convex hull around them, and use its vertices for navigation. EDIT: I just realized, you mentioned that you have to navigate around a relatively high number of obstacles. Using the obstacle vertices might be infeasible with to many obstacles.
I do not know about moving obstacles, I believe A* doesn't find an optimal path with moving obstacles.
You mention that your object moves back and fourth - A* should not do this. A* visits each movement point only once. This could be an artifact of generating movement points on the fly, or from the moving obstacles.
Answer: I remember encountering this problem in college, but we didn't use an A* search. I can't remember the exact details of the math but I can give you the basic idea. Maybe someone else can be more detailed.
We're going to create a potential field out of your playing area that an object can follow.

Take your playing field and tilt or warp it so that the start point is at the highest point, and the goal is at the lowest point.
Poke a potential well down into the goal, to reinforce that it's a destination.
For every obstacle, create a potential hill. For non-point obstacles, which yours are, the potential field can increase asymptotically at the edges of the obstacle.

Now imagine your object as a marble. If you placed it at the starting point, it should roll down the playing field, around obstacles, and fall into the goal.
The hard part, the math I don't remember, is the equations that represent each of these bumps and wells. If you figure that out, add them together to get your final field, then do some vector calculus to find the gradient (just like towi said) and that's the direction you want to go at any step. Hopefully this method is fast enough that you can recalculate it at every step, since your obstacles move.
Answer: Sounds like you're implementing The Wumpus game based on Norvig and Russel's discussion of A* in Artifical Intelligence: A Modern Approach, or something very similar.
If so, you'll probably need to incorporate obstacle detection as part of your heuristic function (hence you'll need to have sensors that alert your agent to the signs of obstacles, as seen here).
To solve the back and forth issue, you may need to store the traveled path so you can tell if you've already been to a location and have the heurisitic function examine the past N number of moves (say 4) and use that as a tie-breaker (i.e. if I can go north and east from here, and my last 4 moves have been east, west, east, west, go north this time)


Can single phase AC produce a continuous electric arc?

Question: Constant DC supply and 3 phase AC (in mercury rectifier) can produce a continuous arc. But can single phase AC also produce a continuous arc? Because it is written on the web that arc extinguishes at zero crossing. Also high voltage is needed to initiate arc. But what is needed to maintain the arc (high voltage or high current)?
Comment: "high", "big", "little", "low" are all subjective terms.  Your "high voltage" may be my "piddly low" voltage.  Typical small-shop arc welders operate at a strike voltage of around 60V, and currents up to 200A whether they're AC or DC.  The actual arc voltage is lower once you get it going.
Comment: Why mercury? Does it behave differently if you rectify it with selenium or silicon?
Comment: Mercury is (well, was) used in HV rectifiers. Since supplanted by solid-state types.
Answer: tl; dr version: With AC the arc current does drop to zero, but the plasma hangs around, so the visual arcing effect is continuous even if the arc current is not.
When the arc fires up it makes a plasma cloud - a region of ionized gases with lower resistance than air. This plasma persists for a time even during the AC zero-cross interval, allowing the arc jump once more at a lower strike voltage than it would in normal air. So the zero-current time is lessened in the presence of plasma for a given gap - so much so that your eye can hardly see it.
This plasma is why a 'Jacob's Ladder' can work with ever-widening electrodes, even on single-phase AC: the heated plasma travels upward, making a lowest-impedance path for the arc to strike.
Here's a slow-motion video showing an AC-arc Jacob's ladder which clearly shows the arc extinguishing and relighting between cycles. Notice that the arc alternates sides as it re-strikes, while following the rising plasma cloud. https://www.youtube.com/watch?v=4zxGK0hoqIc
The mercury-vapor lamp uses a plasma arc to generate light, and they're almost always powered by single-phase AC. The lamp's arc absolutely fluctuates, but like the Jacob's ladder this isn't visible due to the human eye persistence of vision, plus the glowing of the still-excited plasma, and not the least of which the lowered strike voltage of the activated plasma. So we don't see flickering on this kind of lamp either, though its variation is measureable.
Unrectified 3-phase AC arcing behavior is the same as single-phase. Each phase has single-phase AC potential to neutral, ground, or either of two phases. So arcs phase-to-phase or phase-to-ground (or neutral, if used) will also have intervals of zero-current and cross-plasma re-strike. Likewise, so would a discharge lamp powered by two legs of a 3-phase feed.
Comment: Minor nit -- Wye configured 3-phase has a phase-to-ground. Delta configured 3-phase is only phase-to-phase. Otherwise, nice answer!
Answer: When an electric arc first starts it ionized the air and reduces the resistance of the air. This causes the arc to be maintained easier. The arc will usually last until the metal causing the arc burns away or the electricity source is turned off. The sine wave crossing the zero axis will not extinguish the arc. Voltage is what is required to establish and maintain the arc. Current will exist but it's the difference in potential that causes the arc.


Is there any way to draw power from a cellphone?

Question: If so how would you do this? I know you can get a little power from the headphone jack, but is there any other way? is it possible to draw power from the charging port? Or is this charging port just and input source only? How much power would be available and under what conditions?
Answer: Charging USB jack on most phones is input-only.  However, some modern smartphones and tablets have a function known as USB OTG which is USB On The Go.  This allows the USB jack to supply 5Vdc at enough current to operate a USB thumb drive.
This mode is triggered when pin pin 4 of the micro-USB plug is jumpered to ground (pin 5).
There can also be other functions associated with that pin 4 on the connector - one of those functions allows the smartphone or tablet to be charged at the same time that the data lines are being used as the USB host.  These functions are triggered when a specific resistor value is used between pin 4 and ground.
There is much information available via your favourite search engine.  One graphic diagram is USB OTG connection diagram
Comment: I have a similar question, if you would like to have a look: [link-here](http://electronics.stackexchange.com/questions/270337/draw-power-from-a-portable-mobile-charger-to-power-circuits)
Answer: If the phone has USB on-the-go you can draw power from the USB port, if it doesn't have OTG the port will probabaly not be able to provide power.
That leaves only the few milliwatts available o the microphone contact of the audio socket, or the audio signals on the headphone contacts.
Or if it has a powerful LED on the back you could use that to operate a photocell :)


Getting an Easy Card in TPE airport?

Question: Can I buy an Easy Card in TPE (and load it with money)? Can I use a credit card for that, or do I need to have NTD in cash to do that?
Answer: Yes you can, either from a convenience store within the airport (7Eleven, Family Mart, etc) or from the information desk at the Airport MRT station. The card itself costs NT$100 but comes with no balance, however the cashier can apply balance there and then once the card is purchased.
From memory, credit card wouldn't be an option from the MRT station as you'd need to purchase it from the information desk (they're cash only as far as I remember), but it should be an option from the convenience stores. There's a number of ATMs located around the airport should you need to take cash out.
There's some more information about where you can purchase an Easy Card at the Easy Card website

These standard fare cards cost NT$100 each, exclusive of a deposit and balance.
Four major convenience stores (7-Eleven, FamilyMart, Hi-Life, OK Mart), information centers at Taipei/Taoyuan/Kaohsiung Metro stations, and the EasyCard Corporation Customer Service Center
Comment: The standard fare between the airport and Taipei Main is NT$160 [according to this fare map](https://www.tymetro.com.tw/tymetro-new/en/_images/document/travel-guide/price.pdf), and there doesn't seem to be any distinction between Easy Card users and single journey token users, unlike the Taipei Metro. NT$160 is roughly $5.20 US, so your other method would appear to be slightly cheaper, though I've never heard of Klook before.
Comment: There is a 20% discount for using an Easy Card instead of a single-journey token. If you visit [this page](https://web.metro.taipei/e/TicketALLresult.asp) and select your starting station, it will list the fares to all other stations on the network. For example, a journey from Tamsui (R28) to Taipei Main Station (R10) would cost NT$50 for a single journey token but only NT$40 if you were to use your Easy Card.
Comment: Do you happen to know the fare of the ride from TPE to Taipei Main Station if I pay by an EasyCard? There is a single ride ticket for 4.75 USD available through Klook, and I'm trying to figure out whether it's cheaper than using an EasyCard.
Comment: Thank you. Sorry to bother you again, but would you mind pointing out where I can find the comparison of fares for the Taipei metro when paid by EasyCard vs. by one-time passes? I wasn't able to find that on the EasyCard website.
Comment: Also worth noting that there's a minimum fare of NT$16, even if you tap into and out of the same station. I found that out when I needed to visit the toilet, but the closest one was inside an MRT station!

Getting an Easy Card in TPE airport?


In terraria mobile, how do you farm the slime staff?

Question: I heard that the slime staff is the rarest item in terraria. And I wanted it so bad that I decided to farm it but I don't exactly know how to farm it.
Answer: The Terraria wiki's Slime Staff page states:

An easy way to get this staff is to use Slime Statues, with a thin
  layer of lava.

The Slime Staff is only dropped by Slimes and Slimed Zombies, with a low 0.01% drop rate.
With this in mind, it may take time, but the Staff should eventually be found by using the aforementioned Statue method.
Comment: Ok I'll do that.
Comment: Or is you haven't found a Slime Statue, you can Try to farm the Slime Rain event when it starts, or just go outside during the event with a Water Candle on a Crafting Bench or Table with a Battle Potion.


Obtaining 1899 birth certificate of ancestor born in Turkey to Turkish parents?

Question: How do I reach the birth certificate of my grandfather who was born in Istanbul, turkey in 1899?
Comment: Duplicate of https://genealogy.stackexchange.com/questions/13343/obtaining-1899-birth-certificate-of-ancestor-born-in-turkey-to-turkish-parents ?
Answer: A good starting point is often the FamilySearch Research Wiki page for the place you are interested in.
Unfortunately, in this case, the page about civil registration for Turkey genealogy just states that civil registration in Turkey began in 1884 and doesn't provide any useful contact addresses.
This may be because, as it states on the main page, genealogy records are often kept on the local level in Turkey (Turkey is divided into 81 provinces). Perhaps not surprisingly, Istanbul is in Istanbul province (No. 34 on the map).
The website of the US Embassy in Ankarra advises that

You can obtain a family registry (nüfus kayıt örneği) from the Family Registry Office (Nüfus Müdürlüğü).

Following a brief Internet search, I think that the email address in Istanbul is:
<code>Istanbul Governorship Additional Service Building 2
Hırka-i Şerif Neighborhood Adnan Menderes Bulvarı No: 64 Pk: 34093
(Provincial Directorate of Security) Fatih / İSTANBUL
</code>
(subject to the vagaries of Google translate!)
and their email address is: firstname.lastname@example.com  (I would try this first).


Amount of energy of the Big Bang

Question: What is the currently accepted estimated range of the amount of energy of the Big Bang event?
In joules at some estimated size, so a temperature may be calculated.

For context, I wonder if the temperature of the Big Bang would make its heat radiation wavelength shorter than the Planck length.
Answer: Let's start by making some points clear:
1. We don't know what the Big Bang was.
Rather, we know that the Universe is expanding. If you extrapolate backwards, you'd expect the Universe to be denser and denser. More specifically, we talk about this as a change in the scale factor $a$, and this gets smaller and smaller as we look further back in time. According to general relativity (our modern theory of gravity), 13.8 billion years ago, $a$ should have been $0$; however, you can't have a metric with $a = 0$.
Thus, we know that general relativity is necessarily incomplete. It breaks down at the conditions of the early universe, so we currently have no physical model to explain that time. Rather, we know that the early universe expanded, and the Big Bang is the time that perplexes cosmologists. Some theories, like quantum gravity, have emerged in an effort to explain the Big Bang; however, we currently have little understanding of what it actually was.
So no, we can't tell you what the energy output of the event was, since we don't know what actually happened.
2. The temperature of the early Universe was high
Our theories break down at the Planck epoch of the Universe. The Planck epoch was the earliest epoch of the Universe and lasted until $10^{-42}$ seconds after the Big Bang — that's 200 Planck times, which are the shortest meaningful measurement of time.
During this epoch, the entire Universe was at $1.417×10^{32} \; \mathrm{K}$, which is the Planck temperature. This is the hottest possible temperature; an object at this temperature will emit photons with wavelengths of a Planck length (you can read more about this in my answer here). The point is that there is no meaningful distance smaller than a Planck length, so the Universe couldn't be hotter than the Planck temperature.
Comment: +1 for answering the question, but don't forget that theories break down, and they are only theories. We don't actually know that the temperature of the very early universe was high.
Comment: @JohnDuffield The WMAP observations provide strong evidence that the temperature of the early universe was high, ruling out a [cold Big Bang](https://en.wikipedia.org/wiki/Cold_Big_Bang). See [Komatsu et al. (2010)](https://arxiv.org/abs/1001.4538).
Comment: @JohnDuffield Well, we don't really know what the Big Bang was, so I'm a bit confused as to how you derived that.
Comment: @SirCumference total size of the universe would be *something like* the mass of the matter plus the energy, though I am sure there are better ways to say that. I did not suggest you would equate as you've stated, but I think it's reasonable to expect a larger universe to have a larger energy big bang, no? I still think you need a 3rd uncertainty item for the size of the universe, of which we have no upper limit.
Comment: @uhoh If we're talking about total energy of the universe, then yes. But the energy density of our universe *at the Big Bang* rises to infinity for any size of the universe.
Comment: I'm sure we'd all agree that the temperature of the early universe was high. But I said _don't forget that theories break down_ and said the   _very_ early universe. In fact, I'll go so far as to say this: IMHO the temperature before the big bang was absolute zero.
Comment: It's to do with [what Hawking said](http://news.bbc.co.uk/1/hi/sci/tech/4249192.stm): the universe is like a black hole in reverse.
Comment: PS: I'm not a fan of Hawking, or of Hawking radiation. But I think he was broadly correct when he said the universe is like a black hole in reverse. IMHO pulling away from a black hole through space is something like the universe expanding over time.
Comment: Even if 1. and 2. were known, does not knowing *how big* the universe is (total mass or energy) add a third and independent uncertainty?
Comment: @uhoh Well, that's if we simply equate "energy of the BB" with "energy of the universe"; the former isn't really well defined. As for the latter, you're right that not knowing the universe would prevent us from finding the total energy. An infinitely large universe would have infinite energy (assuming the cosmological principle), whereas determining the energy density of a closed universe goes hand in hand with determining its radius of curvature, allowing us to get the total energy.
Comment: @uhoh Well, "Big Bang" more or less refers to a point in time rather than an event, specifically where we get gravitational and temperature singularities. Now that I think about it, I'd expect the energy of the universe would also approach infinity as we get closer to this time. Whereas cosmological redshift decreases the energy of photons, if we went back in time we'd see the energy being higher than today. At the Big Bang (when the scale factor goes to zero), the wavelength of a photon would go to zero as well, so the energy would be infinite.
Comment: Still, wouldn't a larger universe be a "larger infinite" energy? I can never remember, but are there some flavors of infinity that can be larger than others?
Comment: @uhoh If you say "infinity" in math, it has (roughly) two distinct meanings based on the context. In set theory, it refers to a quantity of objects, specifically one that's at least as big as the number of integers (there are bigger infinities in that context, which you mentioned). In analysis on the other hand, we mainly just use it to refer to a limit (a sort of unrigorous way of saying the limit diverges). Here we're just considering how energy rises as we consider more and more matter in our universe, so when saying "infinite energy" I mean energy diverges if we make our universe infinite.
Comment: @SirCumference okay well I still think that a 3rd source of uncertainty related to the unknown size of the universe is needed, but that's just me.

Amount of energy of the Big Bang


Air distiller - attempting to turn bottled wine into spirits

Question: Using an air distiller top table system.
I would like no ferment mash and just distill wine off the grocery store shelf.
But I need help,  with knowing how to make it happen.  There's two videos that are available and both are not good.
Answer: I assume you're referring to the Still Spirits Air Still. It's rubbish and will produce a fairly terrible brandy.
However, don't let that dissuade you from giving distillation a go. For the Air Still in particular, fill it up with wine and operate it according to the instruction booklet. You could try to make cuts but it will be very difficult due to the tiny size of the air still and the amount of smearing.
The instructions will probably tell you to carbon filter it - ignore this. The Still Spirits system is designed to make neutral spirits that are flavoured with essences from their Essence range, but for a brandy you want to retain the flavours from the original wine.
Here are some great YouTube channels on home distillation:

Still It
Barley and Hops


not able to conect nodes in the compositor

Question: I'm having a weird problem, I've had it before but at the moment I'm using the compositor so much that it's getting really annoying...
at the moment I'm working in 2.82a but I've had this problem in al the versions before that one.
I'm unable to connect nodes by hand (see gif)

I am however able to do it with noderangler, but when I do that the connection starts at another point (see give)

it's also just really hard to select nodes (with a mouse and with my Wacom), sometimes when I click on the nodes or use box select I select the node next to it or just nothing at all. (see gif)

this also makes me unable to use frames because I'm probably dragging nodes "next" to them instead of on top of them...
This all points to the nodes actually being in a different place than they are being shown to me. Do you guys have any ideas on how to fix this?
As is sat I've tried different versions, restarting the program and my laptop and I don't have any other ideas.
thanks in advance
Answer: I had the same problem. It looks like having two areas of the interface displaying nodes is causing this bug.
Just close the other nodes area(s) and it should be back to normal. It worked for me !


Spring mvc -Properties file encoding

Question: I have a problem reading some character in a property file in Spring MVC.
I know properties file are encoded in ISO-8859-1 so I set my messageSource bean to set the default encode to UTF-8
@Bean
    public MessageSource messageSource() {
        ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();
        messageSource.setBasename("messages");
        messageSource.setDefaultEncoding("UTF-8");
        return messageSource;
    }

Before this modification, for example I saw the à character as �, after the à became ?
I've also tried to use ReloadedResourceBundleMessageSource with no effect
How can I display just à?
Answer: the javadoc states the following:

Characters that cannot be directly represented in this encoding can be
  written using Unicode escapes as defined in section 3.3 of The Java™
  Language Specification; only a single 'u' character is allowed in an
  escape sequence. The native2ascii tool can be used to convert property
  files to and from other character encodings.
  Source here

I been using that approach when I work with the ISO-8859-1 encoding (For example: number=N\u00famero) for a while but now I use the ReloadedResourceBundleMessageSource like you describe and it works flawlessly, as far I can know your properties file should be encoded using UTF-8 as well, you could try to encode your file using native2ascii like this example:
native2ascii -encoding UTF-8 file1.properties file2.properties

Spring mvc -Properties file encoding


Saving page preference in site navigation using SiteMapPath control

Question: I have created site navigation in my ASP.net application using SiteMapPath control and its working fine. Now my requirement is that, there is open page in my application which has Radio buttons and based on their selection datagrid is populated from database. I want to save the radio  button selection in navigation url so that when I click on that page through navigation url then page will display the data from my selected options.
Any help would be highly appriciated.
Thanks,
Yogesh
Answer: I'm not sure that I understand. I propose some other solution (using Session). Add event to radioButton onSelectionChange. When selection change, remember this in Session
 Session["name_param"] = some_params;

And in form with dataGrid get event PageLoad with code:
 if ( Session["name_param"] != null ) {
       var param = Session["name_param"];
      // using param to load data to grid
 } else {
      // something else, maybe default chance for data to grid
 }


Firing missilein animation many times

Question: I have some objects (lamps, meshes) parented to an empty. I want to fire them from a specific location as a missile. (make a copy of them there.) In bge, this is pretty simple with the 'Add Object' actuator, but I want to do it in animation. Is there a clever way, using animation nodes and/or direct python, or should I manually keyframe the missile to appear in the right frame, depart, appear in the next firing frame... I have tried 'instancer node', but it added all the copies at the frame, when it was first executed, add didn't copy the parented objects, just the empty.
Answer: to instance a full hierarchy of objects the easiest way is to group them, add as a dupligroup on some layer and use this object as the AN instancer object -need to activate 'copy full object'-
you can animate the number of instances, so new objects appear on new frames, or you can have all there at the first frame and animate them scaling from zero...
to add more animation the easiest way would be generate it from AN, something simple and parametric, or have some cyclic animation in the objects... if you need to sync it to start time for each object it can be done also, but it's more complex
here's a test scene (AN 1.6) with some simple objects, made 100 instances of a dupligroup, then use a loop and a couple of delay nodes to first scale them, and then animate in random directions, the trick is to use instance index as seed and delay factor -the usual procedure with loops-
https://dl.dropboxusercontent.com/u/16486113/Blender/archivos/temp/AN/AN%20cohetes.blend
https://dl.dropboxusercontent.com/u/16486113/Blender/archivos/temp/AN/AN%20cohetes.png
Comment: please use http://blend-exchange.giantcowfilms.com/ to host .blend files used in questions and answers for this site. If the links to your dropbox disappear then the answer wil not be as useful.

Firing missilein animation many times


How do I make gelatin gummies without adding sugar and still have it survive out of the fridge?

Question: I am on a no-sugar diet due to food insensitivity. I crave gummies and would like to make some without adding sugar (say with coconut water) and have them survive (stay firm and not grow mold) out of the fridge for my upcoming travels. How do I do it?
Comment: There might be some gelatin/agar mix that will hold, yet not crumble like pure agar candies. You'll have to experiment. Another possibility is Tapioca/rice gummies: https://www.youtube.com/watch?v=YQ2DweIAGtk
Answer: If eating fruit is ok for you, you could boil fruits rich in pectin (without adding water) to a very thick jam, then spread it out thinly onto a sheet of baking paper and let it dry. If your climate doesn't allow the jam to dry in a day or two, put it into an oven on the lowest temperature and leave the oven door slightly ajar. Adding citric acid to the jam improves durability.
Cut the jam into gummy-sized strips before it's completely dry. Dust it with a little corn starch to prevent the strips sticking together. Store them in a container that keeps moisture out.
Apples are well suited for this procedure, that was used in medieval Europe to process left-over apples before they spoiled. Unfortunately, the finished product has a brown color that is not very appetizing.
I think a similar result can be obtained by preparing gelatine with only a quarter of the prescribed quantity of water / juice.


UV mapping and removing hidden faces?

Question:

So, I made a geometric realistic house Buuuttttt, I didn't know importing to a game was going to be a NIGHTMARE! I have spots that appear to be missing, that is "invisible", and when I try to UV-map them automatically I get very bad results. How can I quickly remove the interior faces "that will never be seen by the player" and then UV-map this thing so I can go into Mudbox and make this puppy super texture realistic THEN import it into UDK without a hitch? In the future I might just make simple rooms and wood blocks that are pre UV mapped and then build the house from assets in UDK. But, so i don't feel this entire house project was a waste of 3 days of off-and-on work, how do I go about the easiest possible way of getting this bad boy ready for my game engine?
Comment: What do you mean by interior faces? You're probably going to have to delete them by hand.
Comment: I want it to be a solid mesh cause when you do UV mapping you have to select edges and every single part of the roofing is separate pieces like how real wood planks are used to make them.
Answer: If you're looking for a quick way to delete faces that will never ever be visible from the outside, you're in luck. If you're trying to do something more complex, you're going to be stuck with manual work.
To delete these inside faces, select everything using A. Then switch into face mode Ctrl-Tab>Face. Set your camera to orthographic Numpad-5. Finally enter each one of the side/top views, use Box select with MMB to de-select all the visible faces. You will need to do this for all 6 views: The short cuts are 1,3 and 7 for front, right and top (respectively) To get back left and bottom, combine  1,3 and 7 with Ctrl to get back, left and bottom (respectively). The selected faces you will now have are the inside faces. Delete them.
Answer: First, Keola, welcome to the site. Second, congratulations on your house.
GCF has given you one way to identify interior faces, but I think there are others. One of these is to have the object in wireframe view, as your first image, and rotate your mesh so that you are looking at the object through the floor. In face select mode, the faces comprising the interior walls can be more easily seen through the floor, and deleted. Note though, that the interior faces may not save you all that much, considering the method you used in building the roof. If you're attempting to model a typical "liveable" house, (by which I mean one that is well maintained) you may be able to save considerable geometry by making the roof with a large, flat, sloped plane, rather than constructing it as you have done with rafters and what seems to be individual boards in the surface. Constructing the roof as you have done in the screen shot, you have considerably more geometry in the roof sections than you have in the walls, where you have not shown the interior studs of the walls. [Note that if you are modeling a derelict house, where part of the roofing materials are missing, you may want to have the rafters and individual boards of the roof.]
As to the "invisible" faces, this sounds to me to be most likely caused by "flipped normals". There are to ways I correct these, both ways being done in edit mode, and textured shading. Textured shading is selected in the drop down menu of the shading icon just to the right of the interaction button (where you choose whether to use "edit view" or "object view". "Textured shading" is selected by selecting "texture", the option indicated by the red-and-white circle icon. If there are only a couple of instances of flipped normals, I simply select the faces, and flip the normals. If there are a larger number of faces, I use the A key once or twice to select all of the faces, and choose the option to recalculate normals. For more information on Normals, see the Wikipedia pages http://en.wikipedia.org/wiki/Normal_%28geometry%29 and http://en.wikipedia.org/wiki/Vertex_normal.
The exact location in the User interface where one would find the options to flip normals changed in more recent versions. It has always been in the tool shelf in edit mode, and in more recent versions is under the "Shading/UV" tab.
Your idea of implementing reusable components like walls and rooms is a good one, but I suspect you will find that it is difficult to have these components UV-mapped in advance. One of the reasons for this is that many game engines prefer the number of textures to be minimized, so you will likely find it expedient to make your mesh, then prepare a single texture in an image processing package [I use GIMP; cf. http://www.GIMP.org] as a collage containing all of the bits of the  building, and map the various surfaces of the mesh to the appropriate locations on the texture.
For myself, I find that I can usually make a wall (or even a simple building) quickly enough from scratch that I'd have it constructed before I remembered which ~.blend file contained the various components of the vuilding, and finding the right component in the ~.blend file, though I do make use of the technique of re-using blender components for more complex meshes.
Comment: yeah I'm trying to get ride of enough geometry and merge the roofs into one "object" I suppose so i can really easily UV map it. i suppose. idk If I'm saying it right. I'm new to this stuff so IDK if I am using the right terminology..

UV mapping and removing hidden faces?


Orbits of the action of $A_6$ on $\mathbb{P}_2$

Question: By a paper of Scott Crass  http://xxx.lanl.gov/pdf/math/9903111v1.pdf
we know that $A_6$ (Permutation on 6 elements) is an automorphism group of $\mathbb{P}_2$ which fix a sextic. What is the geometry of this action i.e., what are the orbits of this action explicitly.
Comment: You mean "Yes. Alternating."  ("Symmetric" would be $S_6$, not $A_6$.)
This group has a nontrivial triple cover $3.A_6$, with a faithful
$3$-dimensional representation that projectivizes to an action of
$A_6$ on ${\bf P}^2$.  There's some information and reference in the
Wikipedia page on the "Valentiner group":
http://en.wikipedia.org/wiki/Valentiner_group
$\phantom\infty$ It's known that $A_6$ and $A_7$ are the only simple alternating groups
whose Schur multiplier is cyclic of order $6$; the others have
Schur multiplier ${\bf Z}/2{\bf Z}$.
Comment: Is $A_6$ the symmetric group? That type of notation is usually reserved for the alternating group, i.e., the subgroup of even symmetries.
Comment: I mean the simple group with 360 elements. Yes. Symmetric.
Answer: As noted in the comments, this is a classical object, credited to
[Valentiner 1889]; the paper
by Robert Crass that you cite refers to that paper and also to work of
Wiman [1895] and Fricke [1926] that should contain the answer to your
question, and Crass himself collects those answers starting on page 13.
The generic point of course has trivial stabilizer.  For each of the $45$
involutions $i \in A_6$ there's a fixed line $l_i$, and most points on each
$l_i$ are stabilized by just $i$, and thus have an orbit of size $180$.
[The normalizer $N_i$ is an $8$-element dihedral group, and $N_i/\{1,i\}$
is a Klein four-group acting on $l_i$; the orbit of the generic point on $l_i$
consists of its four images under that four-group, and four further images
on each of the other $44$ lines, for a total of $4 \cdot 45 = 180$.]
There are two special orbits of size $60$, and one each of size $45$ and $36$,
with dihedral stabilizers of size $6$, $8$, $10$ [NB there are two
conjugacy classes of $S_3$'s in $A_6$, related by an outer automorphism
of $S_6$]; when the stabilizer is dihedral of size $2n$, the point
is at the intersection of $n$ lines $l_i$ corresponding to the $n$
non-central involutions in the group.  There is also a $90$-point orbit
with cyclic stabilizer of order $4$.
You asked for "the orbits of this action explicitly"; if you want
explicit coordinates, you must specify coordinates for ${\bf P}^2$
and matrices for (generators of) the projective action of $A_6$.
Fortunately Crass gives these coordinates and generators on pages 4ff. $-$
actually two choices ("octahedral cordinates" and "icosahedral coordinates",
citing and slightly modifying Fricke [1926]).
Alternatively you could go to the ATLAS [1985] entry for $A_6$,
and go to the "$2 \times 3 . A_6$" paragraph of the Constructions section.
This gives coordinates for the $45$-point orbit on the
lift of the Valentiner group to a complex reflection group of
$3 \times 3$ matrices (#27 in the list of Shephard and Todd [1954]).
Regarding them as dual coordinates for $45$ lines $l_i$, you should be
able to compute all the intersections that give orbits shorter than $180$,
and also to find explicit matrices for the involutions $i$ that
generate the group (and thus in particular the $4$-cycles that
stabilize the $90$-point orbit).
References (mostly from Crass):
[ATLAS 1985] John H[orton]. Conway et al.:
ATLAS of Finite Groups:
Maximal Subgroups and Ordinary Characters for Simple Groups.
Oxford: Clarendon Press, 1985.
[Fricke 1926] Robert Fricke: Lehrbuch der Algebra 2.  Vieweg, 1926.
[Shephard and Todd 1954] G.C. Shephard and T.A. Todd:
Finite Unitary Reflection Groups,
Canadian Journal of Mathematics 6 (1954), 274$-$304.
[Valentiner 1889] H. Valentiner:
De endelige Transformations-Gruppers Theori,
Videnskabernes Selskabs Skrifter, Sjette Raekke, Naturvidenskabelig og
Mathematisk Afdeling 2.  Bianco Lunos, 1889.
[Wiman 1895] Anders Wiman:
Ueber eine einfache Gruppe von 360 ebenen Collineationen,
Mathematische Annalen 45 (1895), 531$-$556.


QGIS v3.10 GRASS plugin on MacOS for hydrology

Question: Installed QGIS 3.4 and then 3.10, both gave errors "Grass was not found in /usr/local/opt/osgeo-grass/grass-base" In both cases the directory /usr/local/opt/osgeo-grass/ did not actually exist. I tried manually installing grass both with brew install and Grass 7.7 from grass-7.7dev.dmg.zip from the website. I tried setting the path for grass in QGIS to /Applications/GRASS-7.7.app and a few other locations that I forgot now.
All I need to do is create a flow accumulation raster from a DEM I have. I tried using the SAGA plugin in QGIS and that failed, wasn't able to generate a raster. I feel like my plugins have not been compiled correctly. However the base QGIS raster analysis works: I could create slope, aspect rasters sucessfully. The contents of my /usr/local/opt are currently
ant            lcms2           osgeo-libgeotiff
email@example.com        libcryptopp     osgeo-libkml
armadillo       libdap          osgeo-libspatialite
arpack          libev           osgeo-netcdf
boost           libevent        osgeo-postgresql
email@example.com      libffi          osgeo-proj
brotli          libiconv        pcre
c-ares          libidn          pcre1
cfitsio         libidn2         perl
cgal            libjpeg         firstname.lastname@example.com
cryptopp        libjpeg-turbo       pkg-config
curl-openssl        libjpg          pkgconfig
eigen           libkml-dev      popt
epsilon         libmetalink     python
expat           libmpc          python2
fftw            libpng          python3
freexl          libpq           python@2
gcc         libssh2         python@3
gcc@9           libtiff         pzstd
gdal2           libtool         qhull
gdbm            libunistring        readline
geos            libxml2         rtmpdump
gettext         libzip          sfcgal
giflib          little-cms2     sqlite
glib            mdbtools        sqlite3
gmp         mpfr            swig
hdf4            nghttp2         swig@4
hdf5            numpy           firstname.lastname@example.com
firstname.lastname@example.com       email@example.com      szip
hwloc           open-mpi        tcl-tk
icu4c           openblas        unixodbc
isl         openjpeg        webp
jansson         openldap        wget
jasper          openmpi         xerces-c
jemalloc        openssl         xz
jpeg            email@example.com     zlib
jpeg-turbo      firstname.lastname@example.com     zstd
json-c          osgeo-gdal
krb5            osgeo-hdf4
Answer: I set the path to /Applications/GRASS-7.7.app/Contents/Resources and it seems to work
Comment: Didn't work unfortunately, still got the error ```"Grass was not found in /usr/local/opt/osgeo-grass/grass-base"```


Publishing app on Japanese AppExchange

Question: I want to publish an app on the Japanese appexchange. Could someone guide what would be the steps required for it?
Answer: I think the same way that publishing an application at English. The only difference is "market place".
http://www.slideshare.net/partnerforce/publish-your-first-app-on-the-appexchange/61
Other references.
How to Transform Your Idea into an App on AppExchange
ISVforce Guide
ISVforce ガイド
アプリを開発・公開する

Publishing app on Japanese AppExchange


Is there a way for pre-setting proxy addresses for specific networks?

Question: I'm tired of commenting in and out different proxy acquire lines which located in /etc/apt/apt.conf.d/10proxy as I change networks. Is there a way for binding the settings for networks? Iphones have an option like that, but I wonder if I can do it with my computer without writing a script for doing that for me. I've made a little search and checked man proxy & man 10proxy but they don't exist and couldn't find anything useful.
Answer: I suggest pacproxy if you are familier with Ruby.
After installation, you can use like as follows.
$ bundle exec pacproxy -P ~/proxy.pac -p 3128

$ export $PROXY=localhost:3128

Answer: Whenever a network interface goes up or down, scripts in /etc/network/*.d are executed.
So for example you could make /etc/apt/apt.conf.d/10proxy a symbolic link whose target gets changed by a script in /etc/network/if-up.d. These scripts get a few environment variables, in particular IFACE with the interface name; you can use ifconfig, route, ip, etc. to obtain information about the network that's being joined. The interfaces(5) man page documents this facility.


2D Dirac delta function: how to prove $\delta(ax, by) = \frac{1}{|ab|} \delta(x,y)$?

Question: Let $\delta(x)$ be a Dirac-delta function. I am wondering how to prove the following:
\begin{align}
\delta(ax, by) = \frac{1}{|ab|} \delta(x,y)
\end{align}
Because of the definition (if I understand it correctly),
\begin{align}
\delta(ax, by) = \begin{cases}
\infty & \text{if $ax = 0,\ by=0,$}\\
0 & \text{otherwise.}
\end{cases}
\end{align}
If this is true, the scale of the argument should not influence the value of the delta function itself? Correct me if I'm wrong.
Comment: That is not a good definition of $\delta.$ A close to correct definition is that
$$\iint_{\mathbb{R}^2}\delta(x,y)\,\phi(x,y)\,dx\,dy=\phi(0,0)$$
for all smooth functions $\phi: \mathbb{R}^2\to\mathbb{R}.$
Comment: And to follow that up, consider the change of variables $t = ax$ and $s=by$, which gives $dx = dt/a$ and $dy=ds/b$.
Comment: The best way to think about the Dirac delta is not to think of it as a function on numbers,  but to think of it as a functional taking in functions in a function space with an integral norm and outputting the value of that function at 0
Answer: Note that the dirac delta satisfies:

case $ℝ→ℝ:\quad$ ${\displaystyle \delta (g(x))=\sum _{i}{\frac {\delta (x-x_{i})}{|g'(x_{i})|}}}$
case $ℝ^n→ℝ:\quad$ ${\displaystyle \int _{\mathbf {R} ^{n}}f(\mathbf {x} )\,\delta (g(\mathbf {x} ))\,d\mathbf {x} =\int _{g^{-1}(0)}{\frac {f(\mathbf {x} )}{|\mathbf {\nabla } g|}}\,d\sigma (\mathbf {x} )}$
case $ℝ^n→ℝ^n:\quad$ ${\displaystyle \int _{\mathbf {R} ^{n}}\delta (g(\mathbf {x} ))\,f(g(\mathbf {x} ))\left|\det g'(\mathbf {x} )\right|\,d\mathbf {x} =\int _{g(\mathbf {R} ^{n})}\delta (\mathbf {u} )f(\mathbf {u} )\,d\mathbf {u} }$

In Question Expression for Dirac delta $\delta(xy)$, we had an instance of case (2). Your question is an instance of case (3), with $g(\begin{smallmatrix}x\\ y\end{smallmatrix}) = (\begin{smallmatrix}ax\\ by\end{smallmatrix})$:
$$\begin{aligned}
&& δ(g(x, y))|\det g'(x)| &= \delta(x, y)
\\&⟹& δ(ax, by) \Big|\det \pmatrix{a & 0 \\0 & b}\Big| &= \delta(x, y)
\\&⟹&δ(ax, by)|ab| &=  \delta(x, y)
\\&⟹&δ(ax, by) &= \frac{1}{|ab|}\delta(x, y)
\end{aligned}$$
For a proof of the theorem, see for example Rigorous proof of the change of coordinates formula for Dirac's delta..
Answer: Simple answer: this is a simple change of variable. Heuristically, since the Dirac delta $\delta$ is defined by its action on smooth functions $\varphi$ by
$$
\langle\delta,\varphi\rangle = \iint_{\Bbb R^2} \varphi(x,y)\,\delta(x,y)\,\mathrm d x\,\mathrm d y = \varphi(0,0),
$$
it follows by the change of variable $x'=a\,x$ and $y'=b\,y$ that
$$
\iint_{\Bbb R^2} \varphi(x,y)\,\delta(ax,by)\,\mathrm d x\,\mathrm d y = \frac{1}{|ab|}\iint_{\Bbb R^2} \varphi(\tfrac{x'}{a},\tfrac{y'}{a})\,\delta(x',y')\,\mathrm d x'\,\mathrm d y' = \frac{1}{|ab|} \,\varphi(0,0),
$$
or in other words $\langle\delta(ax,ay),\varphi\rangle = \frac{1}{|ab|}\langle\delta(x,y),\varphi\rangle$ for any $\varphi$, which implies $\delta(ax,ay) = \frac{1}{|ab|}\,\delta(x,y)$

Digging a bit more, now why can we do this change of variable in the integral? Actually this is because the composition of distributions is defined so that the change of variable formula works as if everything was done with classical integrals.


2005 sebring overheating

Question: My 2005 sebring is over heating , there is no sign of water in oil,but a little milky film in the coolant reservoir . What are the possible causes. we let the car run at idle about 15 min to get the cooling fans to kick on , the engine is one of the quietest I've heard
Answer: The milky film is likely to be oil in the water. I'd say Head Gasket - a recognized problem on Sebrings, usually at around the 100,000 mile mark. On a Sebring, that's quite an expensive little job unless you can do the work yourself.
Comment: Head gasket blows after 100k without being overheated? Wow, these engines are garbage.
Comment: @IhavenoideawhatI'mdoing Chrysler motors in general suffer from bad engineering.
Comment: This one is overheating, but yes - Repairpal.com has reports of it. To the OP - I'd spend a little money at a garage confirming that it's the head gasket, as it can be a $2K job at a garage to fix. Or, you could use the  liquid sealers that they sell in the car stores, and change a 'head gasket replacement' into a 'head gasket replacement, radiator replacement, heater core replacement, and thorough flush'.

2005 sebring overheating


Macerators and Pulverizers vs Factorization Grinders?

Question: Macerators and pulverizers are pretty easy to use, doubling ore output. Grinders from Factorization seem to produce more, but need a bigger factory setup. At the end of the day, which one produces the most using the least?
Comment: Define "better". Output? Total resources used? Amount of resources input before you break even on the investment? Less fussy to use long-term?
Comment: @SevenSidedDie Just in general.
Comment: That's not really specific enough to be an answerable question and avoid "not a real question" close votes. "Better" depends on what you want from it, and the answer will be different depending on what you're looking for—or put another way, there *is* no "better", just trade-offs.
Comment: @SevenSidedDie That better?
Comment: Much better, yes.
Answer: Grinders will give you a 3:1 ratio of output metals to input ores, while macerators will give you 2:1. A grinder takes more in resources and infrastructure to get up and running – however, the more resources you process, the smaller the initial cost of setup becomes as a percentage of output. Therefore the longer you run a grinder setup, the more it pays for its original cost, and before too long the grinder becomes strictly better in terms of ratio of output to setup costs.
Comment: It's probably worth noting that pulverizers give you slightly more output than macerators, since you sometimes get bonus dusts of different materials from them.  (Of course, you can't overclock them...)
Comment: @Shinrai If it was a three-way versus question, yes, but it would only be a tangent to what the question is actually about: the easier 2:1 processors vs the annoying-to-craft Grinder.
Comment: "At the end of the day, which one produces the most using the least" - the answer is grinders, but if that's too much work the answer is pulverizers.  I upvoted your answer for being good, I just felt like it was worth noting that macerators and pulverizers are not identical in output like the question frames them.. :)
Answer: Think of them as tiers.

The Pulverizer is a T1 tech; easy to get, easy to power, but kind of self upgrades to T2 as your powerflow/system grows (it works faster when has more energy)
The Macerator is also a T1 tech, but self upgrades to T2 when you get overclockers and the like (T3 would be the rotary Macerator)
The Grinder is a T3 tech. It's expensive to make. It is quite powerful, however, and has many more uses than a Pulverizer or a Macerator.

I haven't messed with it much, so I'm not sure if this is true or not, but the Grinder doesn't use any source of power. Factorization power generation and use is still very much a WiP.
At the end of the day, you will probably already have a competent Macerator/Pulverizer setup that you don't even have a need for a Grinder by the time you can achieve it.


Is digging a "cold hole" really effective when sheltering in a snowed area?

Question: One recommendation I got in case of emergency or intentional sheltering in a snowy location is to dig a lower hole, so that the cold air can move there, while one can sleep higher up where the heat stays. I understand the physics involved, but I am not aware of how much difference it can do in practice. How many degrees are we talking here ? Is it really recommended, or does it just waste energy ?
Comment: This also referred to as a "cold air sump".
Answer: Doing it correctly can ensure the temperature of the snow cave maintains around 32°F (0°C) or higher.
Its not just about digging the extra hole but how the entire cave is constructed that can make the difference between life and death.
Here's the general idea.

Of course doing this won't guarantee your safety, but it sure helps.
To answer your question directly, it makes a huge difference and is absolutely recommended.
EDIT
As pointed out in the comments, we should always give credit to those from whom we get information from.
Source: Mike Clelland
Comment: Can we credit the authors on this use of their work please! It's a great book and I think many people would like to read it... [Allen and Mike's Really Cool Backcountry Ski Book](http://www.amazon.com/Allen-Really-Backcountry-Revised-Better/dp/0762745851) They are two NOLS instructors who have done a great job getting information out there to the masses. Bios - (http://www.linkedin.com/in/alleno), (http://littleboingmarks.blogspot.com/)
Comment: 32 degrees???? That would melt all immediatelly... Aaaah, you must mean 32 degrees Fahrenheit, not Celsius! Right?
Comment: Good use of a Mike Clelland drawing :)
Comment: You are right, I should have. I pulled it from google images without looking for where it came from.
Comment: I have recently created a Wikipedia article on this topic: [Cold hole](https://en.wikipedia.org/wiki/Cold_hole). We're talking 2016, so either people just don't know about this practice (and I mean Wikipedia, duh!) – or I'm using my words wrong, and the article already exists under a different title. I'm no hiking enthusiast (let alone mountaineer or climber), but I love the physics rationale – so I need help here from someone with an actual drive to set things right. Long story short: help! :)


Phonegap twitter plugin for Android

Question: I want to integrate twitter having compose tweet feature in my application using Phonegap.I am following https://github.com/ObjetDirect/phonegap-plugins/blob/master/Android/Twitter/www. Now   in readme file they have given the instructions, for compose tweet how can I modify my index.html page? Please help me..
Answer: Please take a look at this example of how to retrieve messages, photos, names... from twitter using javascript.
I've made it and with the help of CSS was fantastic!
http://wiki.phonegap.com/w/page/42450600/PhoneGap%20Ajax%20Sample
Comment: Thanks for your reply. But I want compose tweet feature in my app.
Answer: I think my tutorial describes what you want to do. See TMT5P1.
Requires Child Browser plugin (no Twitter plugin needed) to do OAuth 1.0a Twitter login. Video demo on PhoneGap / Android plugins.
In TMT5P1 user logs in to their twitter account from your phonegap app, gives permission to the app to access their twitter account, after which all Twitter APIs are available via javascript in your app. Includes composing and sending a tweet.
Answer: You can implement it using the concept of childbrowser. I have done this. Use the link: https://github.com/phonegap/phonegap-plugins/tree/master/Android/ChildBrowser.

Phonegap twitter plugin for Android


Remove seen notifications from Notification Centre

Question: I am using MacOS Monterrey, and whenever I get notification from say, Slack, I get a temporary banner on my screen, which then hides in the notification tray. Then I open Slack (without using the Notification Centre), check the new message, but the notification stays in the Notification Centre as if I had never opened it. This is very annoying as at the end of the day my notification centre is full of banners about events I have already checked.
Is there a way to automatically remove notifications from the Notification Centre when I have already checked them in the app? This is standard behaviour in things like Android.
Thanks!
(PS I am very new to MacOS)
Answer: I don't think there's a way to do this in Mac OS X.


Transferring docs to records library

Question: I apoligize in advance if my title to this is way off base but there could be several different possible names and I can't figure out which one works best.
My issue...
I have three document libraries on Site 1 that I am trying to transfer to three different document libraries for retention in my records center.  I have three sendto connections to the Records center that all test out and I created a retention policies in each of the libraries within the Information management policy settings in the Document content type.  I have each of the document libraries transferring to its respective document library in the records center but they all keep going into the same document library and I cannot figure out how to separate them.
I hope this does not completely confuse anyone trying to help me out.  It seems pretty straight forward to me.. but I guess not.
Site 1:  Drop off Library for Bank statements  transfers to Bank statements on the Records library
Site 1:  Drop off Library for historical transfers to historical in the Records Library.
Site 1: Drop off Library for Investment files transfers to Investment files in the records library.
For some reason all my files keep going to the Historical library in the records library.  I'm kind of lost...
Hope someone can help!
thanks,
Scott
Answer: After reading some of the related links on this site I realized I forgot to go into the content organizer rules to set up the path to the library I want the doc to go to.  IMO to many steps for something you think should be "simple".

Transferring docs to records library


Looking for a particular illustrated book of Arthurian Tales

Question: There is a book of Arthurian Tales done in large slim paperback, maybe 60 odd A4 pages in all with greyscale pencil illustrations, aimed at a late primary early secondary school audience. It's what I think of as "middling abridged", having the basic stories of the Green Knight and Mordred and most of the others but not covering the full myth cycle nor being done in a traditional saga style. I love the art and have been trying to find it for years, I remember that Mordred is pictured in a smooth faced helm in the final battle scenes and the Green Knight carries a Butterfly Axe but not much else about it.
Answer: It's 330 pages instead of 60, and the illustrations don't look like pencil to me, but your description instantly reminded me of Roger Lancelyn Green's King Arthur and His Knights of the Round Table.  Portions of the book can be read on Google Books; does this look like the kind of illustrations you remember?
Comment: No not this edition of _King Arthur and His Knights of the Round Table_ unfortunately, I've got this one as well it turns out, but there are far more detailed illustrations and less words only pages in the one I'm looking for, and less written story content in general.


Move qcow2 image to physical hard drive

Question: I have a qcow2 image that I use to boot an installation of linux using QEMU; I would like to place the contents of that image directly onto a physical hard drive so that I can boot to that linux installation directly from my desktop. I would like to do something like dd if=my-qcow2.img of=/dev/sdb. However, this will clearly not work since qcow2 does not store the contents of the virtual disk in logical order within the qcow2 file. Any suggestions?
Answer: QEMU comes with the qemu-img program to convert between image formats.
qemu-img convert -f qcow2 -O raw my-qcow2.img /dev/sdb

Comment: Old question, but: qemu-img nowadays features the `dd` subcommand, which I found slightly easier to understand. For example: `qemu-img dd -f qcow2 -O raw bs=4M if=/vm-images/image.qcow2 of=/dev/sdd1`. It works just like the usual standalone `dd` program.
Comment: Pay attention that the QCOW2 format is Compressed!  That means a 200GB QCOW2 image can convert into a 500GB hard drive...  That may cause the "device is too small" error you are receiving imho
Comment: @recolic That means that the destination disk is smaller than the uncompressed image.
Comment: It's failing with `error while converting raw: Cannot grow device files` error.

Move qcow2 image to physical hard drive


Goldstone modes $\hat a^\dagger(k) \left|0\right>$ for small $k$ or $\hat a^\dagger(0) \left|0\right>$

Question: Consider the Hamiltonian:
$$H=\sum_{\vec k} \varepsilon (\vec k)a_{\vec k}^\dagger a_{\vec k}$$
with $\varepsilon(\vec k) \rightarrow 0$ as $|\vec k|\rightarrow 0$. I know that this has gapless excitations and therefore Goldstone modes but I am confused about the actual definition of what counts as a Goldstone mode. Do the refer to the states $\hat a^\dagger(k) \left|0\right>$ for small/infinitesimal $k$ which do still have some energy or to the ground states $\hat a^\dagger(0) \left|0\right>$ which have no energy.
Answer: The massless field is called the Goldstone 'mode'. The term 'mode' does indeed make one think of a particular momentum mode and in that it is a misnomer. For simplicity lets take the $U(1)$ case with $\phi=|\phi| e^{i\theta}$. After symmetry breaking the Goldstone part of the Lagrangian is
$$
\mathcal L = \frac{1}{2} \phi_0^2  (\partial \theta)^2
$$
with $\theta \in [0, 2 \pi)$ and for some non-zero value of $\phi_0$ corresponding to the minimum of the potential. Symmetry breaking chooses one value of $\theta=\theta_0$ arbitrarily. Linearized excitations can be quantized and they change the value of $\theta$. However, strictly speaking $a^\dagger_0 |\theta_0 \rangle$ is not defined as it is not normalizable by itself and you cannot put it in a wavepacket while keeping the nerdy zero. This is related to the fact that one cannot change the vacuum of this system if the volume is infinite and it is really only in that limit that the symmetry is spontaneously broken as for finite volume one can take linear superpositions of different $\theta$ much like one can form a superposition of position for a particle living on a circle.


How do Bombers work in BF4

Question: I get a notice that a friendly/enemy bomber has been deployed.  How do I get into it, and what level of controllability is there?
Comment: Basically you have to sit around a trailer and fight off the other people in line.
Answer: The China Rising Bomber is deployed from one of the control points that is held by your team on Conquest mode. The trailer you need to enter is a yellow "portable" box with a radar disk on the side. Once you enter it, the system connects you to an inbound bomber which flys fairly quickly across the map. The bomber can drop 4 JDAM bombs and a cruise missile during each "load" and if you're quick you can get two loads per run.
You can click on the ground where the bombs are to be deployed to, however with a 5-6 second flight time they are not suited to moving targets, more likely meant for stationary infantry and vehicles. You cannot control the speed or direction of the plane, but you can deploy a bank of 30 flares to avoid any missiles fired at it.
Once you get a kill you unlock the SUAV for the recon kit, a small, battery powered, remote-controllable plane that can spot enemies, lase targets, and (currently) roadkill as many people as you can hit before the battery runs out.
Once the plane has finished it's run and you exit the command unit, there is a cooldown timer before it can be used again.
Comment: As for actually how you switch between JDAM and cruise missile munitions...I haven't worked that out yet.
Comment: @tombull89: I'd imagine that first you'd have to unlock cruise missile through the "Mother of All Bombs" assignment (15 bomber kills + destroy enemy bomber).
Comment: Can't wait to play around with this! +1
Comment: One thing to mention is that when the bomber is available, you will see a grey bomber icon overlaid on top of the bomber command box (trailer with the dish).  At that point, you can go up to the door and press E to communicate with it and drop ordinance.

How do Bombers work in BF4


Is there any way to use mods in Minecraft demo version?

Question: How can I use mods in Minecraft demo version? Can NTBExplorer do what I am talking about?
Before that when I didn't know that mods don't run in demo version, I wasted a lot of time trying to use mods but nothing useful.
Comment: I don"t think so, but not entirely sure.
Answer: That depends on the mod. Usually they are not made to be run in demo mode and that's usually not considered when developing them. It might work, it might fail.
When you install Forge, it puts a modified game in the folder that the launcher accesses. The launcher still passes the information that you don't have an account on to it. Forge could ignore that and just let you play the full version, but I don't think it does. Also a mod could do that, but I don't know any that do it.
I have two pieces of advice for you:

If you are experienced enough in the game that you already want to play with mods, I would recommend just buying the full game. The demo mode is intended to just let you try it out for one hour.
Just try it! I'm 99.9% sure that your PC won't catch fire. ;)
Comment: The 00.1% is more dangerous than you think!
Answer: if you don't want to install forge make a demo world and  cleck esc when entered world then open to lan and enable cheats plus set gamemode to creative then go back to world go to chat and type <code>/GameMode 1</code> to give you creative and if you want unlimited time just watch this

otherwise, if you want all that plus mods and shaders install forge then install optifine, then click the windows start button and are at the same time and type in the box that comes up type %appdata%, and file explorer will pop up then click on .minecraft and make a folder called mods if there isnt one already and put optifine in it plus whatever mods you like. if you want shaders download a shader then click windows start and r at same time, then go to .minecraft then make a folder called shaderpacks (all lower caps) and put the shader in it then after your done with all that restart your computer and voila it works like the real version except multplayer (it works on lan just not out of your wifi connection)
Comment: Please put some effort into spelling, grammar, and paragraphs.  As it stands, this is a large mess that will take a ton of effort to untangle.


Can Na2CO3 remove temporary hardness of water?

Question: This was asked in my test and I remembered that all compounds that can remove permanent hardness of water can remove temporary hardness of water also. But my teacher marked it wrong and I cannot find the answer anywhere.
Comment: I guess you are right..
Comment: You teacher apparently has no clue of basic chemistry. You are right. Sodium carbonate is added in most laundry detergents to soften it.
Comment: $$\ce{Ca(HCO3)2_{(aq)} + Na2CO3_{(aq)}   -> CaCO3_{(S)} +2NaHCO3}_{(aq)} $$

$$\ce{Ca(Cl)2_{(aq)} + Na2CO3_{(aq)}   -> CaCO3_{(S)} +2NaCl}_{(aq)} $$
Answer: Definition of hardness per a source:

The simple definition of water hardness is the amount of dissolved calcium and magnesium in the water. Hard water is high in dissolved minerals, largely calcium and magnesium. You may have felt the effects of hard water, literally, the last time you washed your hands.

Adding $\ce{Na2CO3}$ introduces the carbonate ions:
$$\ce{Ca++/Mg++ + CO3(2-) -> CaCO3/MgCO3 (s) }$$
which results in a precipitate of insoluble carbonates.
So, yes it is a temporary solution to address water hardness.
[EDIT] I recommend relatedly to hard water treatment with Washing Soda, a very interesting experiment of adding Na2CO3 (aq) to MgSO4(aq) as the entire solution, at times (it depends on respective concentrations),
can convert to a wet hydrate creating so-called Magnesium alba. Cited reaction per Wikipedia:

If magnesium chloride (or sulfate) is treated with aqueous sodium carbonate, a precipitate of basic magnesium carbonate—a hydrated complex of magnesium carbonate and magnesium hydroxide—rather than magnesium carbonate itself is formed:
$\ce{5 MgCl2(aq) + 5 Na2CO3(aq) + 5 H2O(l) → Mg(OH)2·3MgCO3·3H2O(s) + Mg(HCO3)2(aq) + 10 NaCl(aq) }$

where the magnesium mix oxide/carbonate is known, but not uniquely in name or precisely in chemical composition, as Magnesium alba. Now, MgSO4 aqueous per a source:

Magnesium sulfate salts can form hydrated compounds with up to seven ... Magnesium sulfate hexahydrate is formed by coordinating 6 water molecules to Mg2+ ...

So, Magnesium sulfate forms $\ce{MgSO4(H2O)6.H2O}$ with six coordinating water molecules (which could be created upon concentration of the aqueous MgSO4 solution, further extracting water from the mix). Further, if Magnesium alba similarly also extracts water, with excess MgSO4, it may be understandable as to why the entire solution can apparently turn into a voluminous wet precipitate, somewhat surprisingly.
Comment: Having prepared Mg(HCO3)2, I can share that over a course of days in a closed container, a precipitate of MgCO3 develops, so the cited reaction may be technically correct, but in time, it should not be a substantial source of ones hard water (more like problematic deposits).
Comment: As my answer was, yet again, baselessly down-voted (Maurice?), I might as well add some interesting chemistry.
Comment: according to this equation : $$\ce{5 MgCl2(aq) + 5 Na2CO3(aq) + 5 H2O(l) → Mg(OH)2·3MgCO3·3H2O(s) + Mg(HCO3)2(aq) + 10 NaCl(aq) }$$,the water still hard
Answer: Yes, you can add sodium carbonate to remove temporary hardness of water. Temporary hardness is caused due to presence of calcium/magnesium bicarbonate. Treating them with sodium carbonate also known as washing soda helps precipitation of insoluble calcium/magnesium carbonate ultimately softening of water. Overall reaction is:
$$\ce{M(HCO3)2 + Na2CO3 -> MCO3  + 2NaHCO3 ~~~~~ M = Ca,Mg}$$
Comment: The above reaction is not accurate with all magnesium ions in the presence of Na2CO3. See my expanded answer with references. I also recommend a very interesting chemistry experiment.


Writing an information security policy

Question: We are required to write an "information security policy" for our company, and I want to know how much should we cover, and if there are any template or examples that would help.
Comment: This is quite broad. Even without a password policy or BC, are you talking about what resources can use and how? How sensitive data must be handled, and what constitutes sensitive data? There's just so much here that can be (and should be) covered in an Information Security policy.
Comment: Who are "they", and what is the context in which they are asking to see your Information Security policy?
Comment: Note that they don't want us to write specific policies such as Password policy or business continuity Policy
Comment: we already have a BC and Password policy, but they are asking for another document "information security policy" and we don't know what is the coverage of this document
Answer: Refer to the CISSP manual about security policies, also refer to all the security domains they cover as they should be part of your policy (at a high level). There are also resources like SANS which can provide you with some guidance. Also check this document of GIAC which covers what a good security policy covers.
The document you will write will be the governing policy, it means it will cover a high level of requirements per security domain. Each domain should then implement the security in a technology agnostic standard (which covers specific details about the domain) and then a technology specific baseline. E.g. a network standard is implemented in a baseline for Cisco IOS Routing, Cisco IOS Switching, Juniper Routers, ...
Answer: I'd imagine that what you're thinking of here is there are several compliance standards which specifically mention the existence of an "information security policy". This is typically a high-level document covering principles of information security to which the organisation subscribes and is signed off by the board/CEO to indicate their commitment to addressing Information Security issues.  It's also used to form the basis of lower level policies which should implement specifics of the principles laid out in the top-level document.
In terms of getting some samples for this kind of thing, I'd recommend looking at the ISO27000 series of documents and people offering services around that as typically the Infosec policy will be a part of any ISO27001 documentation set.
Something like this shows the kind of content you would typically see in that kind of document, although the specifics would depend on your organisation/industry etc.
Answer: http://www.sans.org/security-resources/policies/
Sans has a good set of templates.
As far as what/how much to cover. For the first version stick to something very basic. Getting something that can be followed is more important than 100% coverage. Remember that this document is living and updatable.
Start with the 5 Ws like reporters do: Who, What, Where, When, Why.
Who does this policy apply to? (Employees, contractors, guests, etc...)
What does this policy apply to? (desktops, servers, services, byod, etc...)
Where is this policy enforced? (What location do you do business including DR sites, hosting facilities, etc...)
When is this policy enforced? (is the a time window, is it enforced for employees from start till they leave employment, if they have byod devices what polices extend after hours, etc...)
Why does this policy exist? (This should be first but lay out the reason for the policy, a revision process for the policy, who owns it, and a mandatory review period. I suggest every year unless needed sooner).

Writing an information security policy


Is it possible to use macOS 'Keychain' + 'TouchID' for pinentry-program?

Question: Is there some way of configuring pinentry-mac, which I currently use to enter the passphrase for my OpenPGP card (a Yubikey), or a different program that'll store the passphrase in the macOS 'Keychain', so that I just have to use 'TouchID' rather than type it out?
Comment: See the article [Set up Keybase.io, GPG & Git to sign commits on GitHub](https://github.com/pstadler/keybase-gpg-github) and especially the section "Optional: In case you're prompted to enter the password every time" which describes using gpg-agent with pinentry-mac.
Comment: Post seems to be dead.
Answer: I was looking into something similar (minus the Yubikey) and found out that pinentry-mac does not support Touch ID (not yet at least). I ended up writing pinentry-touchid a "wrapper"/integration around pinentry-mac that asks confirmation (via Touch ID) when retrieving the password from the macOS Keychain.
I do not currently have a Yubikey, but pinentry-touchid speaks the assuan IPC protocol to communicate with the gpg-agent. I'm guessing that it should work in this case as well. If something doesn't work, feel free to open an issue.
Comment: Nice! (9 ch to go)


Is the Mandelbrot set path-connected?

Question: The Mandelbrot set is known to be connected but whether it is path-connected is an open question. But what is the general consensus/belief among mathematicians? I am unable to convince myself either way because I am rather new to topology and don't yet have a good intuition about connectedness and path-connectedness.
Comment: According to [Wikipedia](https://en.wikipedia.org/wiki/Mandelbrot_set#Image_gallery_of_a_zoom_sequence), the Mandelbrot set is simply connected, which implies that it is path-connected. I suppose the author of that article was mistaken.
Answer: I cannot speak about the whole of the complex dynamics community of course.
If you are new to the notions of path-connectedness and local connectedness the Mandelbrot set might not be the best topic to gain intuition, since as you said those are current research areas and therefore well beyond the scope of a first course in topology.
That said, there are results (mainly due to JC. Yoccoz, a Fields medallist) proving that the Mandelbrot set is locally connected at every point except possibly some special points (called infinitely renormalizable parameters; roughly speaking they are those points that are in infinitely many nested small copies of the Mandelbrot set). That seems like a good step towards proving the conjecture.
Note that experts are not so much interested in this question by itself (local connectedness of the Mandelbrot set) but rather are interested in a conjecture called genericity of hyperbolicity, which is known to be true IF the Mandelbrot set is locally connected.
Oh and by the way I don't think there is an easy way to convince yourself one way or another (short of reading several research papers on the subject).
For the sake of completeness, here is an argument against the conjecture: it is known that the analogue of the Mandelbrot set for cubic polynomials (the connectedness locus of the Julia set) is NOT locally connected.
Comment: The question is whether the Mandelbrot set is path-connected, not whether it is locally connected. Are those questions known to be equivalent?
Comment: There are arguments for and against local connectivity; the reality is that nobody knows.
Comment: certainly. I would say that there are reasons to hope that it is.
Comment: Yes, indeed....

Is the Mandelbrot set path-connected?


Jiles-Atherton model of hysteresis

Question: In my quest for finding a good algorithm to draw hysteresis curve,I have found Jiles-Atherton model which seems to be a rather new model. But I have trouble understanding some of the variables/constants that are used in the formulation.There seems to be a rather similar question here. What I have trouble understanding is that what are Mirr and Man? And how is it possible that M is defined using Mirr and Man, and yet in the definition of Man we use M ?
Comment: Related post by OP: http://physics.stackexchange.com/q/110236/2451
Answer: I have updated my answer to the question you referenced; maybe the nature of the various components will now be clearer.
The model equations are indeed challenging.  One can substitute for $M$ in the equation for $M_{an}$, leaving a pair of simultaneous equations, one transcendental (for $M_{an}$) and one differential (for $M_{irr}$).
$$ M_{an} = M_s \left[\coth\left(\frac{H+ \alpha (cM_{an}+(1-c)M_{irr})}{A}- \frac{A}{H+\alpha (cM_{an}+(1-c)M_{irr})} \right)  \right] $$
$$ \frac{dM_{irr}}{dH} = \frac{M_{an} - M_{irr}}{k \delta - \alpha (M_{an}- M_{irr})} $$
After solving for $M_{an}$ and $M_{irr}$, $M=cM_{an}+(1-c)M_{irr}$ can be determined.
As far as I know, numerical methods are required.

Jiles-Atherton model of hysteresis


Different row tpl for every row in a view?

Question: Can I create a different row template for every row in a view? Something like views-view-fields--foobar--0.tpl.php, views-view-fields--foobar--1.tpl.php and so on?
My goal is to create a slideshow width different template for every frame.
Answer: Out of the box with views? No. The row templates apply to all the rows in a given view.
You could do something like this with a custom module though...
You can use hook_views_pre_render to step through your view, like so:
function mymod_views_pre_render(&$view){
    if($view->name == "yourviewname"){
      $count = 0;
      foreach($view->result as &$row){
          $row->template = dostuffhere($row, $count);
          $count ++;
      }
    }
}

In this example, you would step through each of the result rows and and create printable content. The dostuffhere() function would be a routing function that would load in the appropriate template files, which you could define using hook_theme (example on how to call with a template file is in the comments). The custom .tpl.php files from hook_theme could be called like with the theme() function.
The routing function would then look something like this:
function dostuffhere($data, $row){
switch ($row) {
    case 0:
        return theme('mymodule_template1', array('$row'=>data));
        break;
    case 1:
        return theme('mymodule_template2', array('$row'=>data));
        break;
    //etc...
}

Because, in this example, we're using reference variables in hook_views_pre_render, the "template" variable will become available in the row output for the view. So all you really need to do in your row view is to just print out the $template var.
Comment: Thanks for the reply, but I don't know hot to access to the data passed to the template. My theme hook return this array:
    'slideshow_1' => array('variables' =>  'row' => NULL), 'template' => 'views-view-fields--slideshow'))
But I can't find any $row variable in the template.
Answer: you can able to create a different template foe the fields which are present in the view, you can find the field template reference in , go to advanced tab in the you can able to find Theme:Information by clicking the Information Text you can able to find the template for every fields that are available in the view....


Deploying optimization model to production environment

Question: I have developed an inventory optimization model for my warehouse and I want to know, how to validate this model, perform User acceptance testing and deploy it to production environment?
Comment: Welcome to OR.SE. It would be also great if you could show your model. It gives you more chances to view and get feedback to make your model tighter.
Answer: To validate your model, you need to make sure it captures the dynamics of your system correctly. To do so, you can constrain the model with your historical data (e.g. one month, or one year depending on the nature of your model), and check that it outputs what actually happened in the "real world". You can check aggregated values of variables (such as monthly flows), KPIs (costs), and more detailed values (inventory level of given product at given hour). Determining how close the details have to be to reality is an empirical question. Aiming for 100% accuracy is neither necessary nor a good idea, as you do not want to replicate noise, data errors, etc.
This way you have a baseline or a reference model, on top of which you can safely optimize by removing baseline constraints, or perhaps adding new variables to expand the search space.
This will help validate that your model is indeed correct, and make comparisons between optimizations sensible.
For user acceptance, I think you need to show them that whatever optimization you are performing are useful. So show them that for example new KPIs with respect to baseline are better.
Comment: Yes. And your model needs *integration* with the real data sources, middleware and/or application UI. And whatever you do: don't just _throw it over the wall to sysops_. That's when projects fail. Talk to them, regularly, as your model goes into production.


How does Adobe Stratus work?

Question: I want to know How does Adobe Stratus work? to get an idea of how to do something like it on my own. So what net hack Stratus uses to work like it works?
Answer: A common hack used by P2P software is a method called holepunching. This is used to bypass NAT.
When a network uses NAT, you are unable to connect to a computer within the network, from outside of the network, thus making it impossible to make P2P connections.
Say you have two computers, A and B, located in different parts of the world, both behind NAT.
To establish a P2P connection A and B will connect to a Stratus server. This connection will open a port in A and B's routers. The stratus server will know these port numbers and will share this information with A and B. A and B can then make a connection to each others open ports thus establishing the P2P connection.
Answer: Adobe calls Stratus a "rendezvous" service.  The story goes like this, Version 10 onwards Flash player instances can directly connect to each other (peer-to-peer) using a proprietary protocol called RTMFP.
However for one flash app instance to connect to another, it needs the address of the flash app instance. Every flash app instance can get its own address / fingerprint / nearId by connecting to Adobe stratus. Once a client gets its own nearId, it needs to share it with other clients. Once a flash app instance has another flash app instance's nearId, it can connect and listen in to the other flash app instance stream.
Answer: I'm not familiar with adobe stratus, but as far as I can tell this is very equivalent to the way normal NAT traversal works in for instance SIP. You can have a look at the STUN article on wikipedia to get started. In short, you set up one naming server and use keepalive client-initiated connections to a mediating server or UnPnP to open up ports for the clients. Situations where both clients are NAT:ed are tricky, although UnPNP would work for these situations.
EDIT: A description of the Skype protocol is available here
Comment: You could also read up on how P2P apps like Skype do this, they usually use an array of hacks to get around NAT.
Comment: what array of hacks for example?
Comment: added a link to an analysis of the Skype protocol. It suggests that they use a modified version of STUN and some sort of TURN.

How does Adobe Stratus work?


Is there any way to change the currency?

Question: I am trying to make JPY (Japanese Yen) my main currency, since my business is in Japan.
Comment: JPY is now supported!
Answer: I am a developer for Cognito Forms.
We are actively developing support for selecting the Country, Language and Currency for each form.  You can track the progress of this feature at https://trello.com/c/yd97bUeA.  We anticipate releasing this support in late December to early January, as we are entering testing now.
We will support Japan-specific date and number formatting, Japanese prompts on forms, and Japanese Yen with this release.  Our Stripe integration will support payment forms in Yen as well, but at present Stripe does not support Japanese bank accounts.  However, if you have an account in one of the Stripe supported countries you will be able to process payments as well.
Comment: Our international release is now live, supporting most countries and currencies and 14 languages.


How to store photos only in SD card

Question: I store some photos on albums that is stored in SD card, however when I take new photos the photos are stored on a new album that has both SD card and camera symbols. I guess it is stored on both device and SD card. How can I ensure that newly taken photos are stored only on the SD card on an album without the camera symbol?
Answer: Your guess is erroneous. Camera symbol means that it's an album of pictures made with phone camera (and not screenshots or downloaded pictures or pictures of some other app). SD-Card symbol means the pictures are stored on the sd-card.
You can always see where a picture is stored in picture details/properties.

How to store photos only in SD card


What series to watch if I want to get the whole Bat family experience?

Question: I've been trying to find out what series to watch if I want to get the whole Bat family experience like the whole story from Robin/Nightwing's side, the whole thing about Jason Todd, Tim Drake, Batgirl and later Damian Wayne.
Comment: Watch or read? A lot of the back-story is comic based...
Comment: "the whole Bat family experience?" — I don't think that's an actual thing.
Answer: First, realize there have been many different Batman animated series over the years, some going back to the 1960s and 1970s. I'll focus on the ones from the 1990s on, as they're the ones with the greatest sense of continuity/history (internally, at least).
Even then, there have been 4 distinct series (one of which has had at least 3 names); and, each of the four has its own continuity, distinct from the others. Most use some of the same characters, whose origins are usually at least based on some version of the origins in the comic books - but the underlying source material is sometimes the only common denominator.

Batman: The Animated Series (including The Adventures of Batman and Robin; both from the mid 1990s) covers the first appearances of Batgirl (not particularly similar to the comics' original version of her origin). The New Batman Adventures, (a continuation of the original series produced in the late 1990s, around the time Superman: The Animated Series was in production) gives the series' version of Disk Grayson's transition to Nightwing, introduces Tim Drake as Robin, and has much more frequent appearances by Batgirl.
Note: It's safe to assume that this series shares a continuity (for the most part) with the televised series Superman: the Animated Series, Justice League, Justice League Unlimited, and (to a lesser extent) Batman Beyond and its spinoff, The Zeta Project.
Robin (Dick Grayson) and Batgirl both appear in The Batman (2004-2008); due in part to Robin's role in the Teen Titans show, their stories and relationship to Batman is notably different than in the comics. Batgirl shows up starting in season 3, Robin in season 4.
Dick Grayson appears in a couple of episodes of Batman: The Brave and the Bold, but is not even one of the more common guest-stars.
None of these characters appear in Beware the Batman (the most recent TV series, from 2013). Barbara Gordon appears, but does not take on the Batgirl identity.

None of the actual televised animated series cover Jason Todd or Damian Wayne in a significant way.
However, in addition to the various televised series, DC has been producing direct-to-DVD animated movies as well, for quite a while now. some of these have continuity that lines up with some of the other movies; however, those are the exception rather than the rule, I believe.
Jason Todd's story is covered in the (direct-to-DVD) animated movie Batman: Under the Red Hood; this is an adaptation of this storyline from the comics.
Damian Wayne appears in the (direct-to-DVD) animated movies Son of Batman, Batman vs. Robin, and Batman: Bad Blood (which share the same continuity).
Answer: Within the DC Animated Universe, you need to watch five series and a movie to get the full story on the Bat family.
Aside from covering Batman, Batman The Animated Series covers Dick Grayson's time as Robin, as well as a smattering of Batgirl.
The next link in the chain is The New Batman Adventures. This covers more Batgirl, Dick Grayson post-Robin, and Tim Drake. You will note here that Jason Todd isn't included -- because he doesn't exist in this universe.
After this, The Justice League is the go-to series for hints at what's happening with the Bat family.  It covers the general happenings leading up to the creation of a larger Justice League organization, in which the Bat family occasionally shows up.
For the purpose of setting up the bomb, Batman Beyond is next.  It covers the early career of Terry McGinnis (He's not on your list by name. Spoilers.), the late career of Bruce Wayne, and covers Barbara Gordon's post-Batgirl career. It touches on Dick Grayson and Tim Drake's futures, as well.
Before starting up Justice League: Unlimited, watch the Batman Beyond movie: Return of the Joker.  This wraps up Tim Drake's story.
Finally, tune in to Justice League: Unlimited, which continues the story of the larger Justice League organization and caps off with the completion of the stories of Bruce Wayne and Terry McGinnis.
Answer: There is no single animated/film/tv series that uses all of those characters.
The DC Animated Universe (DCAU) pretty well covers Robin and Batgirl through Batman: The Animated Series. Later, The New Batman Adventures covers Tim Drake, and Nightwing. Damian Wayne and Jason Todd were never part of the DCAU.
Son of Batman tells the basic story of Damian Wayne, it is continued by Batman vs. Robin and Batman: Bad Blood.
Batman: Under the Red Hood features Jason Todd, with flashbacks to him as Robin, and his subsequent death at the hands of Joker.


Synthesizing guitar sounds given a frequency

Question: I'm trying to build a web app which plays a sequence of notes. The notes should have a timbre of different instruments. For now I only concentrate on a guitar synthesis. I'm using Web Audio API for this task, since I want to do it in a browser.
I have all of the notes beforehand, so translating that into a standalone frequency is not a problem, I then generate samples as a sine wave for that frequency, add N number of harmonics to it and add LFM for a little bit of "wavy" effect to the amplitude of the sound.
The filters I've tried to add to make the sound more "natural" are: ADSR, a little compression and a low pass filter, but the sound does not resemble any instrument, it still sounds like a cheap synthesizer from 20-30 years back and it sounds very "plastic".
I do not need the sound to be exactly as the real guitar, that's probably not possible anyway.
What steps would you suggest to take in order to get close to a real guitar sound given only the duration of the specific fundamental frequency?
Would it be easier to start from FFT components rather than samples, for example somehow generating real and imaginary numbers, apply some function to it and then reverse them back to samples to play them?
Answer: In essence you are trying to build an audio synthesizer that creates sounds with a given pitch. Over the last 50 years there have been dozens of technologies developed to do this: you can start here with an overviews: https://en.wikipedia.org/wiki/Synthesizer
To get reasonably natural sounding instrument sound, your best bet is probably to build a sample player. These are based on sampling the actual instrument (typically at a few different pitches and/or play modes) and then creating the notes by pitch shifting, looping and dynamic filtering, etc. of the samples.
Comment: looks like Karplus-Strong synthesis is what I am looking for, I've found an implementation of it in JS as well https://github.com/mrahtz/javascript-karplus-strong , I'll try it out and maybe apply some wave shapers for effects like distortion, thanks. If you edit you answer to include references to physical modelling synthesis and Karplus–Strong string synthesis I'll mark this answer as the accepted one.
Comment: you might get a *"plucked string"* sound with Karplus-Strong, but i wouldn't necessarily call it a *"guitar"*.  now, like sampling keyboards have done since the 1980s, you can also record guitar notes at different pitches and, for each recorded note, define loop points and from that get a sampled guitar sound.  it will still sound like a keyboard, not guitar, when it is played.
Comment: @robertbristow-johnson, as I mentioned, I do not need an "ideal" guitar sound, plucked string will suffice. As for recording, I would like to stick to pure synthesis, due to a couple of reasons: it's fun, it's unexplored (there's a lot of sites which use presampled sounds), downloading samples from the network is slower than generating them on a client size (the browser) + I plan to expand it by adding other instruments, which I do not physically possess.
Comment: Whatever works for you. It's certainly NOT unexplored, people have tried for the last 40 years , it's just difficult and doesn't sound particularly good unless you put a lot of work into it.
Comment: Okay @IO, the two things you need to cook up will be a good random number generator to fill the delay buffer with, and then you need to understand how to use a first-order APF to realize a fractional delay.  Also you need to account for the delay of your feedback LPF (which will cause the higher harmonics to decay at a faster rate than the lower harmonics).  The entire loop delay is the reciprocal of your fundamental frequency.
Comment: @robertbristow-johnson why would I need some random numbers for the delay buffer if I already have some samples prepared? [wiki](https://en.wikipedia.org/wiki/Karplus%E2%80%93Strong_string_synthesis) says it can be either of those. Also, does it really make a difference whether I have a buffer with samples of a complex signal (a whole chord, the sine waves for each separate note are simply added) or do I ultimately need to start off with a single sine wave for each note played at a given time?
Comment: Well the K-S had traditionally filled the buffer with random numbers to start with.  But you could fill it with a sampled  initial attack.


Public API for sunrise/sunset data

Question: Is there a public API to access sunrise/sunset data? As far as the sunrise time and sunset time for any and all future calendar days?
Answer: Since the sunrise and sunset times are determined by 3 factors, position on the earth in Lat/Long & Altitude, date plus possibly obscuring items like mountains and most services leave out the mountains you rarely need a public API rather than using an Ephemeris library.
Depending on which language you are using you will find libraries available for most of them.  You will then need to specify the location and also the are a number of definitions for Sunrise/Sunset - Astronomical, Civil, Nautical and the old favorite "When you can tell a black thread from a white one". Factors such as temperature can also affect the apparent time of sunrise/set by changing the atmospheric refraction.
The good news is that once you have your ephemeris you can calculate rising and setting times for other bodies such as the moon for any date and without internet connectivity.
Some popular libraries:

Python: PyEphem
Java: jparseclibrary
C/C++ ephemeris are mostly based on parsing the JPL data.

If you don't need other bodies then the Sunrise Equation will give you a good enough value resonably simply.
It is also worth taking a look at the excellent Photographers Ephemeris.
Comment: It seems that jparseclibrary no longer exists and the project hosting website seems to be down as well...
Comment: Not just the 3 factors you mention, but also what definition of sunset?  Astronomical is different from nautical/aviation, is different from most religion or common civilian use of the term.
Comment: @ivanivan - I do mention Astronomical, Nautical, Civil & "tell black thread from white" _which is one of the religious ones_ in para 2.
Answer: http://sunrise-sunset.org/api
It's free to use. Just needs a credit link back to the website.
Answer: I know more APIs for Java programming language. Here a list (in alphabetical order):

Caarmen/SunriseSunset (based on formula given on Wikipedia)
mikereedell/sunrisesunsetlib-java (based on a simple algorithm by Ed Williams)
My library Time4J which offers an API for calculating sunrise/sunset/moonrise/moonset and solstices/equinoxes and sun positions as well as moon positions and moon phases. Calculations are mainly based on the book "Astronomical Algorithms" by Jean Meeus, but also use some NOAA-algorithms. A sister project named Time4A exists for the Android platform.

The first two libraries use old standard date/time-API in Java (java.util.Calendar and java.util.Date) while Time4J uses its own types which can easily be converted to new java.time-API (but also to old java-API).
Answer: This gets to be very complex - you have multiple definitions of the term sunset (and sunrise) - astronomical, nautical, and civilian - and then you have the latitude/longitude issue.  Don't forget that in some parts of the world, the sun does not set for weeks at a time, and in 6 months, it won't be rising for weeks at a time, so there are some edge cases where FALSE should be returned.
PHP has a nice date_sunrise and date_sunset function defined - I'd either set up something to call via HTTP(S) or look at the actual source behind the latest version of PHP.
http://php.net/manual/en/function.date-sunrise.php
http://php.net/manual/en/function.date-sunset.php
Civil twilight 96 degrees - Conventionally used to signify twilight
Nautical twilight 102 degrees - the point at which the horizon stops being visible at sea.
Astronical twilight at 108 degrees - the point when Sun stops being a source of any illumination.

Public API for sunrise/sunset data