Rendering stuck at 99%

Question: When I render an animation it gets to the final frame of it but then freezes, I cannot save it or do anything with and when I come out of the rendering tab and back onto the blender layout the rendering bar underneath the keyframes menu is stuck on 99%. I am using the EEVEE rendering because I don't know if I can handle cycles but I have tried it and I get the exact same problem, can someone please suggest something that I can do.
Comment: I guess it's caused by the encoding of the actual animation. I'd suggest render to an image sequence and encode afterwards using ffmpeg or davinci resolve.
Answer: Render your animation to png, not as FFMPEG. So you will have your single frame pictures on your hard disc. You can then make a movie out of it with video editing from Blender. If you are just missing one frame of your animation, you still have a 99% of a movie - instead of nothing.
If you want more help you should provide us your .blend file.
Reason for being stuck can be a lot. From you machine has to low memory until it is not stuck, but just calculating ...
Comment: Never ever render to png, recommend render to OpenEXR: https://blender.stackexchange.com/a/106671/31447
Comment: Thank you for the responses I will try both of them out and I made a compromise of using a .avi file. Also I was saving them as PNG's but I forgot where I'd saved them so I didn't think they had been saved. Thanks for the responses.
Comment: also whats in your compositing section, it has to do some calculations if theres lots of nodes there
Answer: I have been having the same problem, both Eevee and Cycles are freezing during render, whether rendering image sequence or ffmpeg. One solution I started was to render the 15 to 20 frames or so before the freeze, force quit blender, then restart blender and start rendering from the point it froze. This worked - it was rendering the frames correctly, but just kept freezing. However, using blender headless mode (command prompt) I was able to render the entire animation without issue. https://docs.blender.org/manual/en/latest/advanced/command_line/arguments.html
Comment: Why force quit blender? As long as it's not frozen you can stop rendering by hitting ESC or the X next to the render status bar... or if your animation goes from frame 1 to 100, set the end frame to 90 and render the last frames afterwards. You can do that by setting start to 91 and end to 100 or disable _Overwrite_ in the output settings, than Blender automatically begins rendering at 91 even if start is set to 1.
Comment: Because Blender WAS frozen. That's why the render was not progressing. The only solution was to force quit blender since it was pressing escape or clicking the X did nothing.
Comment: Ah okay... I understood the part with rendering the 15 to 20 frames before the freeze as if you were rendering the problematic range and force quit even before Blender was freezing. I got that wrong... Whenever I had this problem I rendered until shortly _before_ it usually froze, stopped rendering, restarted Blender and then continued with a "fresh" and empty memory so the load wasn't that heavy on the GPU's RAM. That helped with cumulating memory load. If the single frames themselves needed too much graphics memory I switched to CPU for the last frames.

Rendering stuck at 99%


Output resistors and GPIO

Question: I am planning to control a IC (CD74HCT299E). I have currently GPIO-pins directly hooked up to the IC. My Question is, does the Raspberry pi have resistors before the GPIO-pin, or do I have to or should I add my own resistor between the chip and the GPIO-pin.
(If anyone is interested, I'm using this programm to try to read the chip: Github CD74HCT299)
Answer: The HCT variants are 4.5-6V.  They may not be controllable from the Pi's 3V3 GPIO.
You don't need in-line resistors between the chip pins and the Pi pins.
However if the chip is being driven from more than 3V3 you will need to construct a voltage divider between the chip's output pin and the corresponding Pi input GPIO (to drop the voltage to a Pi safe 3V3).
Comment: In the Documentation of that chip is stated, that a pin is considered high, if V>2. So 3V3 shouldn't be a problem, right?
Answer: Your question is a bit unclear as you don't say whether you're using the GPIO as 1) input, 2) output, or 3) both. Your options will depend upon your usage - i.e. 1), 2) or 3).
First Recommendation:
Replace the CD74HCT299E with a CD74HC299E (note the missing T). The CD74HC299E has a Supply Voltage Range (VCC) from 2V to 6V. Therefore it will interface directly with the RPi GPIO pins at 3.3V without need for voltage dividers or level shifters. See this data sheet for further details on your *299 shift register.
This recommendation will cover all cases: 1), 2) & 3).
Other Recommendations:
If for some reason you are wedded to the 4.5V-5.5V part - CD74HCT299E, and your usage case is 1) ONLY (GPIO as input), then a resistive voltage divider should work. Note this IS NOT a single series resistor as implied in your question, but a voltage divider.
If your usage case is 2) ONLY (GPIO as output), you should add a level shifter (some examples sourced by Adafruit and TI) to get the GPIO outputs up to 4.5V.
The T in the part number indicates this part was built (and presumably guaranteed) to meet TTL levels which would probably cover the RPi's GPIO specs for high and low. However, the RPi is not a TTL device, and I believe a level shifter will improve the reliability across this interface.
Note also that in general level shifters may be uni-directional or bi-directional. Using a bi-directional shifter will cover use cases 1) AND 2).
If you need help sizing the resistors for the voltage divider, please let us know.
Comment: There is a Line in the Documentation for the HCT variation saying: V_IH = 2V
Comment: Whelp, just build a couple level uni-directional level shifters, and everything is working as expected. Thanks
Comment: @C0D3M4513R: Re V_IH - I stand corrected! I'll edit my answer. But I'll stick by my recommendation. The `T` in the part number was used for an entire class of CMOS devices that were developed to be compatible with [TTL logic](https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor_logic). Happy to hear you got it working.

Output resistors and GPIO


Is [SDL] only for SDL 1.x?

Question: There're sdl and sdl-2. SDL 1.x and SDL 2.x are different APIs. Should a question that asks something about SDL2 include sdl too, or only the sdl-2?
Answer: That reminds me of yii, and the drama there:
User constantly adds the wrong tag
Series of edits removing [yii] tag from [yii2] questions
The conclusion was, either it's a generic tag for all version, or the tag-name is wrong and one should start a meta-post to convince people the mods should retag them all to a version-tag and kill the non-versioned one because the differences are too great, probably including blacklisting.
For some reason, that never happened there, and I don't expect that to happen here.

Is [SDL] only for SDL 1.x?


Animal Kingdom before Sin Came into The Garden

Question: Were animals back then dangerous to each others, such as predators stalking and killing their prey? And were they dangerous to people like they so often are today?
Comment: When we are young and innocent (as Adam and Eve were in Eden), we believe that the world is so as well. As we grow up and expand our knowledge (as Adam and Eve have, after tasting from the fruit of the Tree of Knowledge), we understand that it never was.
Answer: According to Genesis there were no carnivores in God's original creation.

Genesis 1:29 and 30  And God said, Behold, I have given you every herb bearing seed, which is upon the face of all the earth, and every tree, in the which is the fruit of a tree yielding seed; to you it shall be for meat. * And to every beast of the earth, and to every fowl of the air, and to every thing that creepeth upon the earth, wherein there is life, I have given every green herb for meat: and it was so*.

God even told Adam that he would till the Earth in order to eat.

Genesis 3:17 through 19  And unto Adam he said, Because thou hast hearkened unto the voice of thy wife, and hast eaten of the tree, of which I commanded thee, saying, Thou shalt not eat of it: cursed is the ground for thy sake; in sorrow shalt thou eat of it all the days of thy life; Thorns also and thistles shall it bring forth to thee; and thou shalt eat the herb of the field; In the sweat of thy face shalt thou eat bread, till thou return unto the ground; for out of it wast thou taken: for dust thou art, and unto dust shalt thou return.

Since there were no meat eaters there would have been no reason for animals to fear either man or other beasts. God changed things with the birth of Noah.

Genesis 5:28 and 29  And Lamech lived an hundred eighty and two years, and begat a son: And he called his name Noah, saying, This same shall comfort us concerning our work and toil of our hands, because of the ground which the LORD hath cursed.

But God did not cause that prophesy to come to fruition until he had purified the Earth through the Flood.

Genesis 9:1 through3  And God blessed Noah and his sons, and said unto them, Be fruitful, and multiply, and replenish the earth. And the fear of you and the dread of you shall be upon every beast of the earth, and upon every fowl of the air, upon all that moveth upon the earth, and upon all the fishes of the sea; into your hand are they delivered. Every moving thing that liveth shall be meat for you; even as the green herb have I given you all things.

Although it does not say that he gave certain of the animals the same ability to eat meat it must be assumed that that was so.
Hope this helps you to understand the fear of animals for man and other animals.


How to Grant A User Under A Sql Domain Account To Insert and Update Records

Question: I have a sql domain account in sql server like DOMAIN\GroupName. There are many user accounts under that account like DOMAIN\user.name. I want to give insert and update permission only to a user under that domain account. How can i do it for only one user?
Comment: Please read [Overlapping User and Group Permissions](https://learn.microsoft.com/en-us/sql/master-data-services/overlapping-user-and-group-permissions-master-data-services?view=sql-server-ver15) which should help you with what you need.
Answer: Sounds like DOMAIN\GroupName is a group and DOMAIN\user.name is a member of that group. This means that DOMAIN\user.name  has access to SQL Server through that group. You have 2 options:

Create another group, let's say DOMAIN\NewGroupName and grant that group INSERT and UPDATE, then make DOMAIN\user.name a member of that group.
This is not the fastest solution, but it's a clean solution and it will make your life easy long term if you will get more and more users asking for the same rights as DOMAIN\user.name. You will need rights on AD (I assume DOMAIN\NewGroupName is an AD group.)
Just create an individual login for DOMAIN\user.name and grant him access + UPDATE and INSERT to that DB. You find documentation on how to create the login here. After you have created the login, just right click on it and go to properties --> user mapping --> select the desired database --> select db_datawriter --> click ok. You find more about database roles and access here. If you need that user to have access to all DBs on that server, you can look at server roles (listed on the properties page right above user mapping) and you have some nice documentation about that here.


Galois Group of $x^3-2$ over $\mathbb{Q}$

Question: I have a question regarding the computation of the Galois Group of $x^3-2$ over $\mathbb{Q}$. I am reading the example given in section 14.1 of Dummit and Foote. We have that the splitting field of $x^3-2$ over $\mathbb{Q}$ is $\mathbb{Q}(\sqrt[3]{2},\rho)$, where $\rho$ is a primitive cube root of unity. Then any automorphism $\sigma$ maps $\sqrt[3]{2}$ to one of $\sqrt[3]{2}, \rho\sqrt[3]{2},\rho^2\sqrt[3]{2}$. Now, the book says that $\sigma$ maps $\rho$ to either itself or $\rho^2$. My question is why can't $\rho$ be mapped to any of the other roots? Doesn't $\sigma$ map roots of $x^3-2$ to other roots of $x^2-2$?
Comment: Remember: the cube roots of unity aren't roots of $x^3-2$.
Comment: Ah, yes. So then since the minimal polynomial of $\rho$ over $\mathbb{Q}$ is the cyclotomic polynomial $x^2+x+1$, $\rho$ would have to be mapped to other roots of $x^2+x+1$, namely either itself or $\rho^2$.
Comment: The extension $K = \Bbb Q(\sqrt[3]{2}, \rho)$ has a basis as a $\Bbb Q$-vector space and any automorphism of $K$ is uniquely determined by how $G = \operatorname{Gal}(K/\Bbb Q)$ acts on these basis elements. Also, knowing how $G$ acts on these basis elements makes it much easier to determine fixed fields of subgroups of $G$.
Answer: $\rho$ itself is not a root of $x^3-2$. It is a cube root of unity, and its minimal polynomial is the cyclotomic polynomial $\Phi(x)=x^2+x+1$. Thus, $\sigma$ must map $\rho$ to another root of $\Phi$, either itself or $\rho^2$.
Comment: You should go on further and compute explicitly the Galois group $G$ of $X^3-2$ . Even better, show that $G \cong$ the dihedral group $D_6 \cong $ the symmetric group $S_3$ .


Playing mp3 with delphi

Question: Which component to use to play mp3 files from streams/files and also to know the lenght in seconds of that mp3 stream?
Answer: You could use the Bass audio library.
http://www.un4seen.com/
Search for "MP3" on the 3D Buzz site.  They have a series of video tutorials that walk you through the creation of your own MP3 player in Delphi using this library.  Free membership required.
http://www.3dbuzz.com
Answer: try DSPack which are set of Components to write Multimedia Applications.
Answer: You can also use the components at www.mitov.com which has an Audio suite that can handle this type of file.
Answer: I use NewAc components for audio conversion and filtering, it can play MP3 and several others formats.

Playing mp3 with delphi


USB and Bitlocker

Question: Is it possible to change my Bitlocker from USB encryption to password protected without the USB? The USB stick has to be installed.  I am finding that the USB is getting left in the computer so it doesn't really matter if I have Bitlocker on the computer.  This is a computer that is being used in a Dr. office so it would be much better to use a password encryption then the USB. I have turned off bitlocker and tried changing the settings but when I turn it back on it still prompts me for a USB.
Answer: The exact procedure depends of the version of windows and whether you have a TPM chip in your system but it's doable by following the documentation.
There are better ways, however, to deal with this issue.
Bruce Schneier once suggested linking hardware tokens with something that users take with them (he suggested to use them as key to the coffee machine). For instance, if your USB token is (physically) linked to your car keys, or with the badge used to unlock the door, then you're pretty sure it will be taken home when the user isn't present.
Another possible solution is to use network automatic unlock: the machine will pull the bitlocker key directly from your domain info at boot (you should still be able to use the recovery key if needed). Couple that with a sensible desktop session lock policy and you'll have a pretty robust system (I suggest you consider the use of a bluetooth proximity desktop locker tool which are, in some environment, an excellent compromise between security and ergonomic).
Edit: I realized I didn't mention the most important part: when you enable bitlocker, you don't do that for the kicks. You do that to mitigate a specific risk. What that risk is is entirely dependent on your situation, of course but when I wrote my suggestion, I was assuming that you were thinking of the typical risk mitigated by full disk encryption. physical theft of the hard drive or machine. If that is not what you had in mind, please edit your question (or better yet, ask a new, more specific one. Please don't forget to explain what environment you're running as well).

USB and Bitlocker


Difference of two-sided and oriented

Question: I always encounter two definitions: two-sided and oriented (hypersurface or submanifold). What is the difference of them? Which one is stronger?
Comment: I for one never encountered a definition of "two-sided". Could you provide me with a reference?
Comment: Many of us can justify the "*two-sided*" notion as it was done in the past. I'd think that *two-sideness* is a theorem that follows from the definition of orientedness for codimension 1 surfaces.
Comment: These notions are virtually equivalent (for codim 1) -- one is external while the other one is internal. The equivalence shows the invariance of the first one.
Comment: (It's hard to formulate an MO-answer because this material is about as old as the whole combinatorial/algebraic topology).
Answer: If the submanifold $M$ of a manifold $N$ is co-dimension one, being two-sided typically means it has a trivial normal bundle, i.e. $M$ splits the normal bundle into two path components. These are the two sides.
Technically, being two-sided is unrelated to being oriented, but there are cases where they are related.
For example, take the central circle in the Moebius band.  The circle is orientable, the Moebius band is not, the normal-bundle is not trivial.  This is in the one-sided case.
Or take the Moebius band as the 0-section in the 1-dimensional bundle (with orientable total space) that contains it.  The Moebius band is not orientable.  The total space of the 1-dimensional bundle over the Moebius band is orientable.  This is again a 1-sided case.
If the ambient manifold is orientable (or really, just the total space of the tubular neighbourhood), then the triviality of the normal bundle is equivalent to the orientability of the co-dimension one submanifold.
Comment: Ryan Budney, Thank you very much. I can understand two-sidedness now. When we say oriented sounds like we measure from internal. We need to use coordinate charts or homology to define it. For co-dimension 1, the two definition are equivalent in orientable ambient manifold.

Difference of two-sided and oriented


Nominatim: osm2pgsql path specification problem

Question: The Problem:
I've installed Nominatim on CentOS 7, but I'm running into an import error when I try to load the data. Here is the error:
Import
Please download and build osm2pgsql.
If it is already installed, check the path in your local settings  (settings/local.php) file.
ERROR: osm2pgsql not found in '/opt/Nominatim/osm2pgsql/osm2pgsql'
osm2pgsql not found in '/opt/Nominatim/osm2pgsql/osm2pgsql'

Osm2pgsql is already installed and here are the following paths after I run some find commands:
/usr/local/bin/osm2pgsql
/usr/local/share/osm2pgsql

I've tried specifying these paths in the local.php file like this:
@define('CONST_Osm2pgsql', '/usr/local/bin/osm2pgsql');
@define('CONST_Osm2pgsql', '/usr/local/share/osm2pgsql');

Unfortunately, I still get the same problem, so I must not be specifying the paths right. Does anyone know the syntax of local.php? There aren't any guides I could find online beyond basic postgresql and postgis configurations.
Answer: Use the which command to verify the correct path of the osm2pgsql binary:
which osm2pgsql

And try to use @define('CONST_Osm2pgsql_Binary', '/usr/local/bin/osm2pgsql');  instead of @define('CONST_Osm2pgsql', '/usr/local/bin/osm2pgsql');


How come my code works when I use a MessageBox.Show() in between, and does not work without it?

Question: I embedded .NET's WebBrowser into a form that has some other buttons.
The application that I'm developing does not use a keyboard, but uses a touchscreen. So it actually uses the mouse only. To scroll the webbrowser down, I made two custom buttons. When I click those buttons, it should send a "PageDown" key stroke to the browser, and the browser should scroll down.
So the code on the click event is as follows:
<code>        theForm.Activate();
        Application.DoEvents();
        theBrowser.Focus();
        Application.DoEvents();
        SendKeys.Send(key);
</code>
Where 'theForm' is the form and 'theBrowser' is the browser instance.
So when I click the button, nothing happens. When I first click on the browser, and then click the button, it DOES work. But im giving it focus right? And i gave the application enough space to set the focus?
But now what I think is strange. When I put a MessageBox.Show("HELLO"); in the code, like this:
<code>    theForm.Activate();
    Application.DoEvents();
    theBrowser.Focus();
    MessageBox.Show("HELLO");
    Application.DoEvents();
    SendKeys.Send(key);
</code>
...it does work immediatly when I click the button.

So the question is: Why does this code not work when i leave the MessageBox.Show() out, but does when I do use the MessageBox.Show()?
Hope you can help, thanks in advance...
Comment: Even if I let a page fully load, the same happens...
Answer: Without getting into whether your approach is correct. (and I suspect it is not).
I would gamble that You have a race condition.
Which mean that the browser control needs more time to load and respond to events than you are letting it.
So when you do Message.Show, suddenly the thread that you send the events is blocked and it is letting the browser control complete intializing or something else.
It is hard to know from your question whether you are running on Mobile, or regular desktop because there are better approaches to deal with touch. Look at Window7 Api for multi Touch or WPF 4.0 (which is shared by Surface Touch SDK aswell).
Hope that helps.
Ariel
Answer: To me this looks like the wrong way to be going about this.
Try something along the lines of this C++ sample or this C# sample.
At least be explicit about the HWND you are sending the message to if you are going to be simulating key presses.
Comment: That c# sample really helped a lot! Thank you!
Comment: The C# sample link appears to be broken now.
Answer: It may be that the browser control is still loading a document and the message box gives it enough time to finish. If so, wait until the browser's IsBusy property is false or use the DocumentCompleted event.
Answer: I do not know, but in general in my experience it is a bad idea to try to change the focus programmatically like this, you always end up on a bug hunt. There are lots of ways to get windows to scroll though, so maybe you should try something else? For example JavaScript in the web browser can scroll the window effectively.
Answer: I suspect that you have a race here what gets done first. Focusing the control might not be instantaneous and the keystroke you send went elsewhere, whereas after closing the message box the browser control is already focused and gets its keystroke.
Also, to quote a note from MSDN about Control.Focus():

Focus is a low-level method intended primarily for custom control authors. Instead, application programmers should use the Select method or the ActiveControl property for child controls, or the Activate method for forms.

So using one of those might be better than using Focus().
Comment: Shouldnt the Application.DoEvents() take care of that? I mean, i got that in between so it got time to actually focus on the control...


Downloading from web versus installation

Question: I have just downloaded a computer game which is around 2GB. My download speed was pretty fast, almost 30mbps. But when it comes to install the game on my computer, why is it that slow? I mean, I don't understand the downloading process because the required folders were downloaded in the blink of an eye, but the installation was not even like 10mbps. What should i know about what is happening on the memory? Where are the files being written on the memory, or are they even? Doesn't installation process have to be as fast as downloading? Thank you for answers.
Comment: the game is likely compressed, which means it must be decompressed, which requires the data to be run through the processor, cached in ram, and then put back to disk over the same IO and system buses that are still reading data in for decompression. a download only uses part of the system, optimized by IO DMA between the nic and the disk, whereas decompression uses the whole system, and does a lot more work than just copying bytes off the bus into a file on your disk.
Comment: In order to answer this question we would need to know specifics about the hdd in question.  Its also possible there was more data downloaded while the game was installed.  Specifics would be required.
Answer: Many games are downloaded over the Internet as a compressed archive, such as a ZIP for or an ISO file (I'm guessing this applies even for game distribution services such as Steam). This process is efficient, because only 1 HTTP request is sent over the network, which means the overhead of transferring the game archive to your computer is very low. Most of the time, the downloaded archive is not stored in memory, but stored in a temporary location on disk.
However, installation is a different story altogether. Installation typically requires the decompression of the archive. There are two factors at play here:

The speed at which your CPU can decompress the archive
The speed at which your hard disk can store the decompressed files

The first factor is typically less time consuming than the second. Most modern CPUs should be able to decompress archives at the highest compression ratio at more than 20 MB/s. However, it still occupies quite a large chunk of time, especially if your CPU is slow.
The second factor is even more significant. Most games contain many small files. For instance, texture and audio data may be stored as individual files. There are also many configuration files. Traditional hard disks are very slow at random writes - at times, disk utilization can be 100% but the throughput is only hundreds of KB/s. The amount of data written to disk can actually be significantly higher than the amount downloaded. If your temporary location is on the same disk as the installation location, you do not only have to consider the cost of writing the files, but also reading the archive, and this impacts throughput significantly.
Note that this may not be as significant in the case of Solid State Drives (SSDs).
Answer: You are talking about two different things: Installation and Downloading.
Downloading is a process of transferring data from one computer to another over the network. What defines how fast download will happen is performance of the network:

How fast is connection of both computers and all network via points.
How busy are network channels currently.
Overall performance of your system also plays its role in how fast download will happen.

Downloading mostly involves activity of network card and storage devices.
Installation is a process of setting up a piece of software in the way that system can use it properly. This process mostly involves processing and storage device activity. What defines how fast it will happen:

CPU performance.
Storage devices performance.
Amount of RAM can play vital role as well.

In most cases installation of big program will take longer because installation process involves unpacking of install package, copying its content to destination folders, performing necessary system changes (creating registry entries on Windows OS, etc).
So main point is - installation process deals with bigger amount of files than downloading does.
It is easier to download one file (even if it is several GB size) than unpack and copy hundreds of files.

What should i know about what is happening on the memory?

Memory (RAM) is being used as a temporary storage for data which can be accessed faster than data on hard drives. So while installation process is happening most likely operating system will put different parts of the program being installed to RAM.

Where are the files being written on the memory, or are they even?

Such term as Memory is very broad. Memory could be referenced to RAM modules, fast internal CPU cache, swap file, virtual memory. There is difference of how fast different parts of memory can be accessed and how much data can they store. Operating system will do it's best effort in order to utilize memory in best way.

Doesn't installation process have to be as fast as downloading?

If we talk about program with 500kb size install file - most likely install process will happen as fast as download.
If we talk about big program - it is hard to give an answer, because with 56 kb/s network connection it will take a couple of days to download a program and 10 minutes to install it.
Look at this example.

Someone is buying a book from local book store. He get in the car
with this book and in 5 minutes he is at home. (This is download
process - involved operation with one particle - book).
He starts to read the book. Based on his reading abilities it took 3
weeks to accomplish reading (this is installation process - involved
operation with many particles - all the pages).

Or it can be like that.

Someone bought a book and had to walk home all across the city. It
took 7 hours to get home from book store. (This is download process -
involved operation with one particle - book).
Book was just 10 pages long so it took 20 minutes to read it. (This
is installation process - involved operation with many particles -
all the pages).

So it can be seen that these two things are pretty independent (though they still have same thing they depend on).
Comment: such an awesome answer.. thank you for all of your effort!


Is there a way to tell what model iOS device is connected using Game Center?

Question: Programmed in Objective C, my application is able to use GameKit to connect two iPhone 5(S) Devices and pass data between them. Problems, however, have started to occur now that I'm porting the game to work on devices of a different screen sizes (most notably, the 3.5 inch iPhone 4S). While/After creating a real-time match between the devices, is there a way to detect the Opposing Device's Screen Size. If not, is there a way to detect the opposing device's model.
All help is appreciated.
Comment: Why not exchange that info from one device to other.
Answer: You can add a piece of code into your application that detects the screen size:
<code>[ [ UIScreen mainScreen ] bounds ].size.height
</code>
Each group of devices has a different height (4 vs. 5). You can make it so that only devices with a certain height match with a device of the same height (different methods to do the same task).
See this link for more information on determining between different devices.


How can I drive the vector input of a texture in geometry nodes?

Question: So I'd like to remap the texture generated by a noise texture node in geometry nodes, similar to how I'd do that in shader nodes by plugging texture coordinate+mapping into the vector input of the noise texture node. What would be the correct way to achieve that?
Answer: You have to use a Position node, then do some vector math on that (I added an Add node after the Position node, and added the position data from an Object Info node to it, so the position of that other object modifies the position of my texture).


Does the Pauli Exclusion Principle still apply if $c=\infty$?

Question: The Pauli Exclusion Principle comes from the fact that the wave functions of particles with half integer spin are antisymmetric under particle exchange.  From how I understand it, this relationship arises from combining relativity with quantum mechanics.  Does the Pauli Exclusion Principle still hold if $c=\infty$ or does it require a finite value for $c$?
Comment: *"The Pauli Exclusion Principle comes from the fact that the wave functions of particles with half integer spin tend to produce destructive interference."* I'm not at all sure that this is a good way to approach the matter: bosons interfere exactly as well as fermions, only they are not subject to exclusion. [Count_to_10's answer](http://physics.stackexchange.com/a/272657/520) below covers the proper difference.
Comment: The existing answer misses the point of the question. This question is basically asking whether half-integer spin obey Fermi-Dirac statistics without SR. In relativistic QFT, this is a consequence of the spin-statistics theorem, and SR plays a crucial role. To say that "spin [...] has nothing to do with special relativity" in this matter is extremely misleading. I'm not sure if the spin-statistics theorem still works for Galilean relativity.
Comment: @knzhou  I read the question and because of it's remarks regarding c = infinity,  and c being involved in the PEP, at my  (admittedly lower) knowledge level, these seemed incorrect. I would be delighted, as I would learn something and the OP would receive an alternative, more advanced answer, if you would write an answer, that would explain to me  how the points raised in the answer have a more advanced interpretation. Thanks very much.
Comment: @count_to_10 I don't know though, this is beyond my knowledge level! [This resource](http://isites.harvard.edu/fs/docs/icb.topic1146664.files/II-5-SpinStatistics.pdf) seems to say that spin-statistics still holds as long as you make reasonable other assumptions, like stability (the Hamiltonian being bounded below). But I'm not confident enough to write an answer here.
Comment: @knzhou thanks for coming back. That's the trouble with posts, I have to guess the level and whether I know enough to answer. I did post on meta asking for level of knowledge to be indicated on the post but got nowhere. Anyway, I learned something writing it. Regards.
Answer:
Spin comes from combining relativity with quantum mechanics.

I can't stress enough that this is the wrong idea about spin. Spin is an intrinsic property of the particles that have it, and has nothing to do with special relativity in any way.
You might be confused because  the Dirac Equation incorporates  quantum mechanics with special relatively and the spin of an electron can be derived from it, but a particle at rest (which is not really possible)  has the same spin as an identical particle travelling at 99.9999% c.
Spin Wikipedia

In quantum mechanics and particle physics, spin is an intrinsic form of angular momentum carried by elementary particles, composite particles (hadrons), and atomic nuclei.
Spin is one of two types of angular momentum in quantum mechanics, the other being orbital angular momentum. The orbital angular momentum operator is the quantum-mechanical counterpart to the classical angular momentum of orbital revolution: it arises when a particle executes a rotating or twisting trajectory (such as when an electron orbits a nucleus). The existence of spin angular momentum is inferred from experiments, such as the Stern–Gerlach experiment, in which particles are observed to possess angular momentum that cannot be accounted for by orbital angular momentum alone.[5]
In some ways, spin is like a vector quantity; it has a definite magnitude, and it has a "direction" (but quantization makes this "direction" different from the direction of an ordinary vector). All elementary particles of a given kind have the same magnitude of spin angular momentum, which is indicated by assigning the particle a spin quantum number.

One way of looking at the Pauli exclusion principle is to think of it in terms of wavefunctions: half-integer spin particles must be described by antisymmetric wavefunctions, and particles of integer spin are required to have symmetric wavefunctions. The minus sign in the equation below  implies the wavefunction must  vanish identically if both states are "a" or "b", leading to the PEP,  the law of nature that states  that it is impossible for both electrons to occupy the same state in a bound system, that is, they cannot have the same 4 quantum numbers.

Does the Pauli Exclusion Principle still apply if  c= ∞ or does it require a finite value for c?

The speed of light is not infinity, it is 299 792 458 m/s and it does not have any connection with the form of the wavefunction that describes the PEP.
Comment: I interpret the question as asking whether the spin-statistics theorem can be proven in non-relativistic QM, and your answer simply asserts the connection between spin and statistics.


What's my solutions if i brick my android phone?

Question: Are there any tricks (general or not) that I can use if I brick my Android phone? e.g.: when updating android..
Comment: This can vary a lot depending on what kind of phone you have.
Comment: This pretty subjective.  It usually depends on what you did to "brick" it and also varies by phone. For instance, there would be a difference in perma-bricking the device by flashing the wrong radio, vs flashing a rom and getting stuck in a boot loop or having issues flashing a recovery, etc.
Answer: As you haven't mentioned your phone related information, I can share my view.
When your phone is not responding or bricked then you can use your phone PC Compassion or PC suite or whatever depends on what your phone model gave you.
I own Sony Ericsson Xperia Mini Pro. Sometime back while installing another ROM the phone bricked. I googled and read lots of articles to unbrick the phone.
Especially XDA Forum helped me in unbricking the phone. Sony Ericsson has SEUS(Sony Ericsson Update Service).  Using this we can unbrick the Sony Ericsson phones. I am guessing the similar kind of set up is there in all the other phones also.
Comment: For samsung phones, Kies is the software for Unbricking
Answer: I Hard Bricked my phone yesterday when I went to flash a custom ROM. I think I was trying to flash a ROM for the wrong model or something, not sure. Whatever, totally bricked. I had two options as I saw it:
Option 1
Go to AT&T, play dumb, and see if they would give me a new phone. (it worked) Since it was hard bricked, they could not even turn it on, they simply gave me a new one. My default 1-year warranty covered it.
Option 2
Send my phone into the Mobile Techs. They came highly recommended and said they could unbrick a hard bricked Galaxy s3 (my specific model).


Prevent display of "shared on Google+" in YouTube

Question: When I share some video from YouTube on Google+, on YouYube, under this video, appears a comment that I've shared it on Google+. Is it possible not to display those comments on YouTube? How can I turn it off?
Comment: Can you disable comments entirely on the video?
Answer: That is the exact same problem I have. There is no solution, but I have an workaround:

My G+ profile is +MoviesVladan
I have a page built on that profile: +VladanmoviesBlogspotccc
My Youtube channel is www.youtube.com/user/vladanmovies
Youtube channel is linked to PAGE. NOT to profile!
Comments settings for channel and clips are "Only approved"
(5a. For a while I kept my "profile" banned from my channel, which prevents comments
from showing on YT, but can not prevent "profile" from sharing and commenting.)

If I share as "profile", they are all held for approval and I never approve them.
If I share from page, they do show as comments under the clip, but those I manually remove, from the clip page on YT. That way shares stay on G+, but comments are not visible on YT.


Where can I download the Windows Phone Developer tools?

Question: I found the web downloader but they never seem to work for me, how can I download the latest release in an ISO format or a full installer? I cannot use the web downloader. Thanks!
Comment: possible duplicate of [Developing apps for Windows Phone 7](http://stackoverflow.com/questions/2839120/developing-apps-for-windows-phone-7)
Comment: Not a duplicate because this question is asking specifically for an offline installer.
Answer: Try this: http://go.microsoft.com/fwlink/?LinkId=201927
(I found this link here: http://www.windowsvalley.com/windows-phone-developer-tools-final-rtw-offline-iso-image-and-training-kit-download-now/)
Answer: In the official download page http://www.microsoft.com/downloads/en/details.aspx?FamilyID=04704acf-a63a-4f97-952c-8b51b34b00ce there is a tiny iso link that point here http://go.microsoft.com/fwlink/?LinkId=201927 (yep, they should make it more discoverable).


ESP-12e - RX/TX pins flickering on boot when used as GPIO pins

Question: I am using ESP-12e as a controller for my garden lights. I am using pins 1 (TX), 3 (RX) and 5 as an analog output (PWM signal with mosfets) for three separate light sets. ESP is powered on when wall switch is turned on (wall switch turns on power adapter). When I turn the switch on, for short period of time lights connected to pin 1 and 3 work at full power and after that they are set according to PWM signal. Lights on pin 5 works just as expected. I am not using Serial communication, just elegantOTA library for OTA updates and async web server. Is it possible to somehow disable RX/TX functionality at all/before they are set to high, or I am forced to solder lights on pins 1 and 3 to another ones? I tried some software tricks I found online, but without success.
Answer: According to this reference, GPIOs 1 and 3 have dedicated behaviour during boot (debug output or pulled high) which can not be disabled in your sketch.
You have to either choose different pins or implement an additional circuitry.
Comment: Thanks. I was hoping I could solve this problem only with software because of difficult access to esp-12. I did not give enough time to the selection of pins, but at least, I learned something new.
Answer:
I am not using Serial communication,

You might not be, but the bootloader sure is.

Is it possible to somehow disable RX/TX functionality at all/before they are set to high

No. It's hard coded in ROM. There's nothing you can do.

or I am forced to solder lights on pins 1 and 3 to another ones?

You could use one IO pin to control a buffer the other IO pins. Something like an AND gate (74HC08) would do the job:

simulate this circuit – Schematic created using CircuitLab
Only when CTL is HIGH will the L0-L2 signals be mirrored on the outputs to the LEDs. That way you ignore whatever is going on with those pins until you actively drive the CTL signal high. Choose one pin that has no boot noise for CTL and the other pins then don't matter.
For more detail on what pins do what at boot time read this.
Comment: Thanks. I was hoping I could solve this problem only with software because of difficult access to esp-12. I understand the way with AND gate, but probably simpler way for me is to cut off cables from RX/TX and solder to more appropriate pins.
Comment: After some digging I realized, that esp-12 has only two pins (4 and 5) which are perfectly suitable for my job (no high state on boot), so as I need three pins, your AND buffer technique is  best option.
Comment: This is why most WiFi lights that use the ESP8266 (or ESP8285 most commonly) use a PWM LED driver chip, like the MY9231. Offload the LED control to something else and don't worry about what happens at boot on the ESP8266.


How to identify the 4-part chorale?

Question: All I know so far is how to identify triad. However, in this asisgnment, there are 4 notes for each part. So how should I identify each chord, as the  question requires? Thanks in advance!
Comment: These are just triads with one part doubled, which doesn't change the naming. If you can identify triads you can identify these.
Answer: These four-part chorales are still triad chords. The only difference is that:

Like @replete said, one of the notes (usually the root of the chord) is doubled--For example, in the first chord, there is an F in the bass clef and another F an octave above in the treble clef.

The notes are broken into two different clefs. Unlike a triad in just treble clef, the chord's notes are divided, with two in the bass clef and two in the treble clef. This is like this probably to help you learn to read notes in both bass and treble clef.

Just like this first chord in the sequence, you can find the missing chords by figuring out the notes and then finding out what triads contain these notes in the sequence. Using the picture again, the first chord is F Major. How? The notes F, C, and A are the notes that form the triad for F Major. The remaining note is just another F, so the chord is F Major. Again, as @replete said, the doubled part doesn't change the name of the chord.
Hope this helps!

How to identify the 4-part chorale?


How many different 7-place license plates are possible when 3 of the entries are letters and 4 are digits?

Question: Can somebody please explain why don't we count the arrangements of $7$ (digits and letters) as $7!$? In my understanding, it will be $7!\cdot 26^3 \cdot 10^4$ I know it's wrong and the solution tells us $35$ possible letters arrangements and not $7!$ but I can't understand why.
Comment: 1. You choose the positions where letters will be ${7\choose 3}$ 2. You choose the letters (as you didn't count positions order, you choose left to right) $26^3$ 3. And then digits $10^4$. Is that it?
Comment: Because after you placed letters, the positions of both numbers and letters are defined (i.e. you do not have a choice where to place numbers)
Comment: Compare this to the problem of finding how many different $7$-place license plates are possible when all seven of the entries are very specifically the digit $1$.  You should be able to immediately tell that there is one and only one possibility: `1111111`.  Your erroneous approach would have you think it was $7!\cdot 1^7$ possibilities.
Comment: The $26^3$ and $10^4$ ALREADY order the $3$ letters and order the $4$ digits. All that's left is to specify which of the $7$ positions hold the $3$ letters (and then the other $4$ automatically get the digits). That's $C(7,3)=35$.
Answer: Let's assume the license plate has the 3 letters on the left hand side in a row, and the four letters on the right hand side in a row, like this:
$$\mathrm{AAA}1234$$
We have have 26 possible letters to choose from, and we make this choice three times. So this gives us $26^3$ possible letter combinations. Next, we have 10 single-digit numbers to choose from, and we make this choice 4 times. This gives us $10^4$ possible number combinations. Multiplying these gives us $26^{3}\times 10^4$ possible plates.
On the other hand, if there is no restriction on the placement of letters and numbers, we could have something like this: $$\mathrm{A1A2A34B}$$ But we can still only have 3 letters and 4 numbers.
So, to start out let's decide where to put our three letters. We need to pick 3 places out of 7, so thats $7 \choose 3$ possibilities. Now that we have decided where to put our three letters, the other four spots must be numbers. At this point we have returned to our original problem where we know the positions of the letters and numbers. So the final answer should be $${7 \choose3} \times 26^3 \times 10^4$$
I'm not sure where the $7!$ comes from in your solution, but if you add in an explanation for how you came up with that, I'll be sure to explain why it doesn't work.
Comment: Thank you so much for a brilliant explanation, I finally got it.
7! got stuck in my mind from a previous exercise when I had to calculate # of 7 different books arrangements and I forgot about the repetitive orders.
Comment: Glad I could help.


Covering up a non-essential part of a license plate

Question: I was given a license plate with "In God we Trust" above the numbers. Later I learned that this was supposed to be a choice, and I was given none. Am I permitted to place a sticker over this slogan? I would not be covering up anything else.
Answer: In Florida, FS 320.061 says

A person may not apply or attach a substance, reflective matter,
  illuminated device, spray, coating, covering, or other material onto
  or around any license plate which interferes with the legibility,
  angular visibility, or detectability of any feature or detail on the
  license plate or interferes with the ability to record any feature or
  detail on the license plate

Delaware Code 2126(c)(1) semi-similarly says

No number plate, or any portion thereof, shall be covered with any
  tinted material, nor shall any other material be placed on or around a
  number plate which would conceal and/or obscure any information
  contained thereon, including the registration expiration sticker.

The first part of this, on a plain reading say "No, no portion", but the second part speaks of obscuring "information" – arguably (but this is not specified in the statute) a slogan is not "information".
Iowa Code 321.37 more narrowly restricts frames:

It is unlawful for the owner of a vehicle to place any frame around or
  over the registration plate which does not permit full view of all
  numerals and letters printed on the registration plate.

This suggests that it would be okay to cover artwork (but not a slogan, which is letters): but also it states the restriction in terms of frames, so one might assume it's legal to put tape over your license number (clearly not, and presumably the courts don't interpret the law that literally, still it's an interesting case).
Virginia Code 46.2-716(B) says

No colored glass, colored plastic, bracket, holder, mounting, frame,
  or any other type of covering shall be placed, mounted, or installed
  on, around, or over any license plate if such glass, plastic, bracket,
  holder, mounting, frame, or other type of covering in any way alters
  or obscures (i) the alpha-numeric information, (ii) the color of the
  license plate, (iii) the name or abbreviated name of the state wherein
  the vehicle is registered, or (iv) any character or characters, decal,
  stamp, or other device indicating the month or year in which the
  vehicle's registration expires.

Because of the specificity of the Virginia code, the courts are more likely to take the wording seriously, so that you could obscure the plate partially, as long as you don't obscure the tabs, "information", or color of the plate.
The Texas case of State v. Johnson is interesting in terms of how such restrictions are interpreted. In one version of the law (section 502.409(a)(5)), the restriction was

A person commits an offense if the person attaches to or displays on a
  motor vehicle a number plate or registration insignia that...:
(5) has letters, numbers, or other identification marks that because
  of blurring matter are not plainly visible at all times during
  daylight;
(6) is a sticker, decal, or other insignia that is not authorized by
  law and that interferes with the readability of the letters or numbers
  on the plate;  or
(7) has a coating, covering, or protective material that distorts
  angular visibility or detectability.

An earlier court (US v. Granado, cited in Johnson)

held that a license plate frame that partially obscures the name of
  the issuing state-but does not otherwise obscure the letters or
  numbers on the plate-does not violate section 502.409(a)(5)

Subsequently, the Texas Legislature amended the law to:

A person commits an offense if the person attaches to or displays on a
  motor vehicle a number plate or registration insignia that:
(5) has letters, numbers, or other identification marks that because
  of blurring or reflective matter are not plainly visible at all times
  during daylight;
(6) is a has an attached illuminated device or sticker, decal, emblem,
  or other insignia that is not authorized by law and that interferes
  with the readability of the letters or numbers on the plate or the
  name of the state in which the vehicle is registered;  or
(7) has a coating, covering, or protective material that:
(A) distorts angular visibility or detectability;  or
(B) alters or obscures the letters or numbers on the plate, the color
  of the plate, or another original design feature of the plate.

and in the case of Johnson, defendant had partially obscured artwork, which

alters or obscures the letters or numbers on the plate, the color of
  the plate, or another original design feature of the plate

and thus the court upheld the conviction, based on the revised wording of the law (even though the obscured material was not "vital information").
So: it matters exactly what the wording of the statute is in your state.
In Kentucky, the restriction is stated as

No rim, frame, or other covering around the plate shall in any way
  obscure  or  cover  any  lettering  or  decal  on  the  plate

but this continues

except that, any  owner  who  objects  to  the display of a trademark
  of a private corporation which appears on the registration  plate
  shall be entitled to receive a set of decals from the county clerk in
  his county of residence to cover the trademark of the private corporation

(for a cost of $3). On the face of it, nothing can be obscured on the plate, except via the official decal provision which is limited to private corporation trademark displays. It's not clear what such a thing could be, unless it's possible under the special license statute. At any rate, the exception allowing a covering decal is very narrow, and requires a special government decal.
Comment: My favorite case was the US Supreme Court ruling in Wooley v. Maynard, 430 U.S. 705 (1977), finding that the State of NH could not Constitutionally fine or imprison drivers who, for ideological reasons, obscured the display of the state motto "Live Free or Die" on their license plates. The irony was palpable.
Comment: The car is registered in Kentucky.
Comment: @Kiwiyert "In God We Trust" is not a private corporation trademark. It is one of the mottos used by the United States of America's federal government which does not claim intellectual property rights for itself as a general matter.
Comment: Thank you. I wondered if "In God we Trust" would be considered a private corporation trademark or not.
Comment: Not pertinent to Kentucky, but in PA, we had a ruling last September that [*any* obscuring of the license plate is cause to pull you over](https://www.wgal.com/article/frame-around-license-plate-could-get-you-pulled-over-in-pennsylvania/40994053). It resulted from a case where an officer pulled someone over for having the "VisitPA.com" part covered. [Relevant law](https://www.legis.state.pa.us/cfdocs/legis/LI/consCheck.cfm?txtType=HTM&ttl=75÷=0&chpt=13&sctn=32&subsctn=0)


What is the rhythmic notation for 5/8 the duration of a whole note?

Question: Assume that the whole note time equals 8.
Then a note which time equals 3 will be written as 1/4 note and dot.
How you write down a note that time is equal 5/8 of a whole note?
Comment: Hi Édouard. Thanks for correcting this. as I'm completely beginner I still struggle even with basic terminology etc
Answer: As you have said, you have to use a tie for this.  You can tie any combination of notes that make up 5/8ths.
However, it's also true that you can (and should) give a visual indicator of how you want the notes grouped metrically by which ties you use for the longer values.  For example, if you accent the first and third 8th notes (very common in 5/8 time), use a quarter tied to a dotted quarter.  If you accent the first and fourth 8th notes, use a dotted quarter tied to a quarter.  And so on.
Answer: I think I've figured this out
So to write such a note one would have to use a tie
Write a 1/2 note and 1/8 note and tie them together
Comment: This is correct, but understand that this would only be true for a duration starting at the _beginning_ of a measure of 4/4 time. In other time signatures or positions in the measure, the same duration of 5 eighth notes may be notated differently.
Comment: Thanks Yes I think I'm starting to understand this better now. Reading more about ties and what to do if a note last longer then a measure. Also looking at Michael Scott Cuthbert suggestion about tuplets
Comment: @NReilingh in fact this is not correct.  The components of the tied note should reflect the meter, so it should either be a dotted quarter tied to a quarter or vice versa, depending on how the meter is organized.
Comment: @phoog q.-q and q-q. are not the only options here, and depending on where in the measure the figure starts the specific rhythm could be completely different. h-e is perfectly acceptable at the beginning of a 4/4, as I said in my comment.
Comment: @NReilingh you're right, there will be cases where q.-q and q-q. are maybe even not the best options.  (Nice notation, by the way!)  But for a whole bar in 5/8 meter, as in the example here, it's unlikely that h-e would be preferable.
Answer: You were on the right track, but because 5/8 is an asymmetrical meter, you have to group the tie by smaller groups of the meter. In an asymmetrical meter the notes in a measure are grouped in smaller groups of two or three. The possible grouping for 5/8 are 2 eighth notes + 3 eighth notes and 3 eighth notes + 2 eighth notes. When you tie notes together, you have to abide by the groupings so the tie would be expressed as a quarter note tied to a dotted quarter note or a dotted quarter note tied to a quarter note depending on how the song groups the eighth notes.
Comment: The author isn't talking about 5/8 meter, he is just talking about 5 eigth notes, i.e. "5/8ths of a whole note." Though I totally agree that the rhythm should fit the metrical beats.
Comment: @awelotta but the author answered the question with an example in 5/8.
Answer: There's no standard way to notate this duration without ties (as OP suggests).  George Crumb uses the notation of a half note with a dot on both sides of the note for the duration (see:  ).
You could also of course write a whole note with the tuplet [8:5] above it (any rational number duration can be written as a single note with the appropriate tuplet).
It is possible to write with standard notation a rest worth 5/8ths of a whole note: just write a whole rest in a measure of 5/8.  :-)
Comment: Crumb wanted to innovate on notation and believed (so I gather) that by making a new note value that he hoped would become standard, more people would begin to use quintuple meter and consider it as fundamental to music as duple and triple meter.  His notation wasn't a success, but music history is filled with similar examples, some of which worked and we now consider obvious (stem direction according to height), some were standard but disappeared later (custodes telling you the first note of the next line) and many failed.
Comment: There is also a notation by Ian Ring (if I recall correctly) that uses a five pointed star where the dot to notate the duration of 5 eighth notes.
Comment: Also, it's not terribly confusing, in my opinion. If the rhythm is very prominent, and it only takes the "invention" of one symbol, then the composer could just define it in the performance notes / directions, or at the top of the score.
Comment: I can't imagine why GC would choose to write a mystifying and nonstandard notatation when tied half+eighth is immediately obvious to all genres of music.
Answer: Without ties a 5/8 note or rest is a double dotted triplet half note.
Comment: A triplet half note is 4/12 of a whole note. Double-dotting it gives you 7/12 of a whole note, which is not the same as 5/8.
Comment: Moreover, a "triplet note" works only if there is a whole tripleted group. Which might not be true in the situation the OP was thinking of.
Comment: @PiedPiper but a _triply_ dotted triplet half note is 15/24 of a whole note, which _is_ 5/8 of a whole note: https://music.stackexchange.com/a/135265/2257


Why didn't Zoidberg know that Leela wasn't an alien?

Question: In "The Tip of The Zoidberg" both the Professor and Mom claim that Zoidberg is an excellent doctor for aliens. But if that is true why didn't he know that Leela wasn't an alien before she found her parents and learned she was a mutant?
Comment: Note that "alien" means "anyone but another Decapodian"
Answer: Zoidberg is known for:

Having excellent medical knowledge of aliens, considered by Mom

"to be the best in the business, for his price level."

Claims to have little to no experience with human anatomy often appearing to not be able to tell male from female.
Despite this handicap, has manage to perform successful transplants of limbs and even heads on occasion.
Overall, Zoidberg's ability with humans (and thus mutants, such as Leela) to vary significantly in quality and is generally untrustworthy as a resource on the subject, despite his bizarre string of successes from time to time.
Comment: I always wondered if Mom's comment was more about the "for his price level" than "best in the business"..
Comment: You know Mom. She was always one for compliments. But it does seem like she could have had two meanings.
Comment: Yep. [At one point](http://www.gotfuturama.com/Multimedia/EpisodeSounds/1ACV13/) he couldn't even tell humans and robots apart, so his knowledge is fragmented, to say the least.
Comment: He seems to be a great surgeon, transplanting heads and so on, but hardly the most knowledgable. "Oh right, the bones. Always forget about the bones."
Comment: Zoidberg's an idiot?
Answer: There are plenty of planets in the galaxy, and an infinite number in the universe. Zoidberg might have simply not known what species Leela was and been good at treating several alien species, but not humans or Leela's then-unknown species.
Comment: @Yasskier Two *parallel* universes. But an awful lot of perpendicular ones
Comment: No, there are no infinite number of universes. Just two :)


Downloading IBM J9 JDK

Question: I have the following questions on IBM J9 JDK/JRE.

Does any one know the location where I can download the latest J9 JDK? I googed it and couldn't find the location.
What is the relation between IBM J9 JDK and Apache Harmony project?

Thank you.
Comment: You can get IBM JDKs for Linux, AIX and z/OS (OS/390) here: https://www.ibm.com/developerworks/java/jdk/ IBM JVMs generally aren't free to download & distribute (though check the T&Cs for any products you have purchased).
Answer: As McDowell suggested in his comment. You can get the J9 JDK from this link: https://developer.ibm.com/javasdk/downloads/. Specifically..
Linux - https://www.ibm.com/developerworks/java/jdk/linux/download.html
Windows - To get the JDK for windows is a tricky one. You have to download IBM Development Package for Eclipse. This will give you a eclipse Europa (3.3) version, along with J9 JDK version 1.6.
Previously J9 was the recommended VM for running the harmony class files, as their own version of JVM was incomplete. Have a look at this wiki page.
http://en.wikipedia.org/wiki/Apache_Harmony

In the end of November, 2006, the
  language support provided by these
  virtual machine was still incomplete,
  and the build instructions recommended
  to use IBM's proprietary J9 instead to
  run the class library test suite.
  However, this is not necessary anymore
  (as of July 2007). The DRLVM virtual
  machine is currently (as of July 2006)
  under heavy development, so a fast
  improvement of its features can be
  expected
Answer: 1: http://wiki.eclipse.org/J9? - try this
Comment: J9 is more than jusT the ME edition
Answer: Official J9 docker images are also available from: https://hub.docker.com/_/ibmjava/

Downloading IBM J9 JDK


Does mass have an effect on Centripetal Acceleration?

Question: I am using an online simulation for a lab concerning Centripetal Acceleration. When I change the mass the graph indicates that the magnitude of the acceleration is constant. According to the Centripetal Acceleration formula: $a=v^2/r$, this is true because no mass is present in the relationship. However, when I use Newton's Second Law of Motion, $a=f/m$, I can see that the mass and the acceleration are inversely proportional. Both of these ideas are found when I look them up online, now I am a bit confused on which one might be more valid.
Comment: Related question: [How is centripetal force related to radius?](https://physics.stackexchange.com/q/136994/179151)
Comment: And centripetal force $f$ is equal to $\frac{mv^2}{r}$
Answer: It depends on what you are looking at.
If you are applying a constant centripetal force to objects of different masses, then they will each experience a different centripetal acceleration.
If a bunch of different masses are under going circular motion around a circle of radius $r$ with speed $v$, then they will all be experiencing the same centripetal acceleration (but different centripetal forces).
So "does mass effect centripetal acceleration?" is not specific enough to have an answer. You need to add in what else you are considering, i.e. what you are holding constant and what you are allowing to change as you change the mass.
Answer: If you change the mass, then either the acceleration or the centripetal force must change as well (or both). That is what we see from Newton's 2nd law.
The simulator you are using seems to adjust the force. That's why you see no acceleration change. That is just a choice by the software developers or possibly something you can adjust for in the simulation settings. Whether that is a reasonable approach depends on the physical scenario.

In scenarios such as celestial orbits, it is reasonable since the gravitational force increases proportionally with mass.

In scenarios such as a game of tetherball, it might not be reasonable since the string force might be limited or constant regardless of mass.

Note that the expression $a=v^2/r$ isn't needed for this analysis.
Comment: I'm not sure why $v^2/r$ is irrelevant. In your tetherball example if the ball was moving faster it would experience a larger centripetal acceleration.
Comment: @BioPhysicist Yes, but that doesn't help explaining anything related to increased mass. If the mass increases, then the acceleration *might* change depending on scenario. *If* it changes, then this expression helps us translate that change into a new speed e.g. Otherwise it doesn't help with anything.
Answer: The first formula "hides" the mass, because it assumes a fixed $v$, which implies that for whatever $m$ you're working with, you're already supplying the required $f$ to bring its velocity up to $v$.
So when the mass changes, it is assumed that the used force also changes, in a way that $v$ is kept the same. And when $v$ is the same (and $r$, which we never changed), then $a=v^2/r$ will always yield the same result.
So, if you are working in a system where the force supplied is fixed, then changing the mass will change the acceleration. This is no different from how a little outboard motor is able to move a small boat better than an ocean liner. Same force, different mass, different acceleration.
However, if you are working in a system where the velocity $v$ is fixed, then changing the mass doesn't matter, because you're already accounting for any changes in mass by also changing the force required to move said mass.

Maybe it helps to use a different example.

A BMI of over 30 is unhealthy.

Ignoring that BMI is an outdated measure of bodily health, let's take this as a fact.
Also, your BMI is calculated based on your height and weight. So, here's the analogous question as you asked:

Does a change in height have an effect on what BMI values are considered healthy/unhealthy?

And the answer is no. No matter what your height/weight is, whether you're 5ft or 6ft tall, doesn't matter. As long as the ratio between your height/weight is the same (= your BMI), then the healthy/unhealthy label is also the same.
However, now consider this question:

Does a change in my weight have an effect on me being healthy/unhealthy?

And now the answer is yes, because we implicitly assume that when you gain/lose weight, you don't also gain/lose height. Therefore, the ratio between them changes, which means your BMI changes, which means that your bodily health status (healthy/unhealthy) might also change.
Answer: In many cases, a change in mass means that acceleration becomes more or less. If the mass of a car is changed, its acceleration will be less. If a ball becomes heavier it will have less speed (and thus acceleration) when thrown. If the mass of an elementary particle is smaller it's easier accelerated (that is, the acceleration increases). A small kid is easier lifted from the ground. A change in mass is normally associated with a change in acceleration.
As far as the force of gravity is concerned, all masses fall down with the same acceleration. There is no one who thinks that if a mass increases it will be harder for the mass to accelerate downwards.
The upward direction though is different. A rocket will accelerate less if it's heavier (compare this to a fire arrow). The reason is that in many cases the force we can apply is limited and the mass varies over a wide range.
So it is expected that if the mass in a circular motion becomes bigger the acceleration becomes less. It is expected that the mass will move slower.
Obviously, this will not happen because if we increase the mass then to move in the same circle with the same velocity, more force is needed. But it feels like that if we increase the mass the object will move slower. If we envision an increasing mass we associate it with smaller velocity. How in the world can the object stay moving with the same velocity if we increase its mass? Doesn't this contradict conservation of energy? Obviously not if we give it the same velocity as a smaller mass object by applying more force for linear acceleration.
That's the point. Circular acceleration doesn't give an object an increase in speed, while linear acceleration does. Circular acceleration only changes the direction of the object's velocity. If we don't apply a force to change the object's linear speed it has to move with a smaller velocity on the circle. This means that the centripetal force will stay the same. if the object maintains the same speed the centripetal acceleration will be the same but a bigger force was needed to give it linear speed.
Answer: Here's a more math-y restatement of the same general answer :)
Just from your question, we see that $v^2/r = a = f/m$.
If the simulation keeps $v^2/r$ constant ($a_1$ = $a_2$), then when $m$ changes, $f$ should change. Depending how sophisticated the simulation is, it may or may not report the value of $f$.
If you solve for $m$, the result is something like $m=\frac{fr}{v^2}$. From this you can see that when $m$ changes, at least one of the other terms will change. Maybe they all do; maybe it's just $f$.


Does different voltage jump starter make a difference?

Question: I want to get a jump starter power-bank for my car.
There are two types, one with 15v and the other with 12v both 10000mAh.
Does the difference of voltage make difference?
Comment: Shopping assistance is off-topic, so I reworded your title and removed the off-topic part of your question.
Comment: Hmm... I'm not familiar with 15 volt chargers.  Do you have a model number handy?
Answer: You should use a 12V power-bank as the electrical system on your vehicle is 12v.
Do not use a supply which provides 15v as this could harm other components in the electrical system such as various sensors or control modules.
The important thing to look for is not the capacity of the battery (10,000mah) but the CCA value. the Cold Cranking Amps is a measure of the number of amps the battery can deliver in 30s without the voltage falling below a certain threshold. this is important because the starter motor consumes a lot of amps very quickly to turn over the engine. If the power-bank cannot supply enough amps @ 12v the motor will not turn over no matter how large the capacity of the power-bank.
Answer: This more sounds like cluelessness of the seller. They sometimes just don't know anything about what they are selling and copy/paste numbers.
15v is probably the input voltage (from the charger of jump starter) to the jump starter. Because many 12v jump starters need a 15v charger. While I have seen many jump starters without any output voltage ratings, they are designed for 12v systems so they will work the correct voltages.
In either case, even if it was 15v, it wouldn't have been too high. Normally the car alternator can charge the battery up to 14.7v and many unregulated cheap chargers can go over 15v when charging the battery.
Answer: Yes, some are 14.8 volts. They do this by adding one more Li-ion cell to the bank (4x3.6v)  When fully charged to 4.2v the reading will be 16.8 which is too high to run 12 accessories.  When you connect it to a dead battery the extra voltage helps to charge the battery but the vehicle system never goes much above 12 because of the dead battery.  Most of the chargers use 3 cells which only charge up to a max of 12.8v.  Its hard to tell which ones are which.  if the nominal voltage listed on the pack is 11.1 then its a  three cell.