Overheating and more

Question: Hi I have a 2000 Buick park ave v6 3800 series and the problem started as a small leak in the radiator from the little drain plug so I righted that and the leak moved to the whole opposite side of the radiator then I put stop leak in it (Polly my first n worst mistake) and it ran fine for like two hours then overheated and started making noise as if there was no oil in it and shut off while drivimg on freeway so i I checked oil let it cool down. Oil was low,  I put some in then started driving home which was only like 4 miles and as I got about 300 yards from my driveway it stop as engine light came on and now it Bailey wants to run as over flow bottle boils with engine light on and slowly  but surely gets hot. Can u help and please diagnose this problem and give me a rough estimate of labor costs and labor it will take to fix am I better off replacing motor as this one has 265,000 miles or should I buy new car. Thanks  '
Comment: Sounds to me like you have a tired, worn out engine in your Park Ave. The 3800 is a good motor, but they only last so long. If you have the mad skills, I'd suggest buying a replacement motor and replace it. If the vehicle is worn out (most are at 260k+), you may just want to consider replacing the whole thing. Just my opinion, so leaving it as a comment.
Answer: This is a bit difficult to diagnose over the internet, but it sounds like you have a coolant circulation problem as well as a pretty bad oil leak. I would take it to GMC or Chevrolet and pay them to diagnose it. It only costs $100.00. A skilled tech can tell you exactly whats wrong with it and how to go about fixing it. If it's a head gasket (Which it sounds like it might be), get rid of it and buy a new car. There are many things that can cause a car to overheat and leak oil. The 3800 in that car is very resilient, however one of the most common problems with them is head-gasket failure. I've changed many in my career, and it costs a lot of money for the costumer.
I would still take it to someone to be looked at professionally. It could be as simple as a coolant leak, and your oil was conveniently low at the same time. I hope you get it figured out!
Comment: I forgot to mention the only leak of the oil was coming from a couple spark plugs dripping on to the exhaust thanks for taking the time to answer my question.
Comment: On your valve cover you should have spark plug seals. When they "Dry Rot", they will leak oil through cracks in the rubber. If you replace those it should fix the oil leaking issue as long as there are no other leaks. It's not uncommon for those to leak.
Comment: @BobbyDall do you mean the valve cover gasket? i thought on the 3.8 the plugs were on the side of the head.
Comment: They are. Forgive me for the typo. I meant to say valve cover gaskets. Once you replace those you should remedy the oil problem.
Answer: A couple of tests you can do to help determine what is happening.
Head gasket:
Compression test.  minimum 120 psi, should all be within ~10%
Oil and coolant are mixed.  Check oil and coolant.
Exhaust smells like coolant or burning oil.  Might smoke excessively
Bubbling in the radiator while running.
Check plugs for oil/coolant.
Cooling System:
First, fix all leaks.  it will never be right if there is a visible leak
Radiator pressure test to determine if the system can hold pressure.  If not, should help to point out the leak.
Alternately, let the engine get hot and feel the upper radiator hose, it should be stiff with pressure.
Cold spots on the radiator - the 'stop leak' could had caused a clog
Stuck thermostat - heat, radiator hoses cold
Bad water pump - no heat, radiator hoses cold.
For a clogged rad, or stuck thermostat, running the heat full blast should help keep the engine cool.
I'm sure there are a few things I missed, but that should give you a good idea.  At least look into it a bit before you trash it.  No sense buying a new car/engine if you can fix what you have for cheaper/less work.

Overheating and more


Spam users and rules

Question: I'm getting swamped by spam users.  Can I use rules to automatically delete users that 1) don't have content/comments, 2) have never activated in a few weeks, and 3) have only activated the same day they created their account, but haven't posted content/comments?
Comment: In addition tio the suggestions by Triskelion, check out the answers to these questions: http://drupal.stackexchange.com/questions/72765/change-waiting-time-for-new-user,
http://drupal.stackexchange.com/questions/54512/how-to-deal-with-unverified-users-in-drupal
Answer: To get rid of inactive users, have a look at the Inactive User module.
User Stats will keep track of the IP's used by the various users.
The Spambot module is quite effective at blocking bots which create the inactive accounts. If you can take the time, it will let you report and delete spam postings to help block future attempts.
However nothing will stop them. One of my sites just came under attack over the weekend. Over 600 new user registrations in less than 12 hours (at times 3 per minute). I checked the IP's and found that I had multiple accounts created from a few IP's (between 15 and 45 users from the same IP). Manually blocking the IP's involved at /admin/config/people/ip-blocking and deleting the accounts was the only way to stop the attack.
Good luck.
Answer: Install honeypot module and also create a rules which banned the IP when it fails on honeypot.
Honeypot have a rules integration, just create a rules and action to banned the IP when it fails on honeypot.
On honeypot, create a meaningful field name like "country" or "city"
I combat the spam bot for a week, and finally found this method to block them.  My banned list was growing larger and larger in the database and then I analyze the banned IP addresses and create IP ranges banned in .htaccess file.
This way, you have multiple layer of security.
Good luck

Spam users and rules


How can I make a custom IK arm rig on an already made Auto Rig Pro rig

Question: I rigged my character with auto rig pro but a disadvantage of Auto Rig Pro that I've experienced is that the arm moves as an FK rig (As opposed to Rigify with its IK arm rig). I've tried to customize an IK of the arm movement by applying an IK constraint to ARP's hidden bone layers. But I cant manage to do it without messing up with the rig. Can anyone help me?
Answer: I guess you already found your answer but maybe other peoples will need this too.
Here is one way to do :
Once you have your rig, go into pose mode and select the rectangle part of the hand.
Then on the panel on the upper right of the screen go to "tool"

Under Rig Main Properties you have "IK-FK Switch". 1 = FK ; 0 = IK
So if you want IK, switch it to O. I hope this will help.


What is the best runs strategy to burn fat

Question: i want to burn some extra fat on my body and im a bit confused should i do jogging for long distance or do multiple sprints as more as i can ?
Comment: We've had several topics about burning fat in the past, the bottom line is that consuming less energy than you expend will result in weight loss (which includes fat).
Answer: Calories burnt during exercise:

Running 7 mph (11.2 km/h) for an hour (a 155 lbs or 70 kg person): 809 Calories (Wisconsin.gov)
Sprinting for 10 minutes (no more details revealed): 800 Calories (EurekAlert)

Anyway, the simplest tactic to lose excessive body fat is to consume less calories than you spend. This can help you decrease appetite:

Avoid carbohydrates that are quickly absorbed: sugary foods (cola, fruit juices, sweets, deserts) and foods with plain starch (potatoes, white rice, white pasta)
Avoid foods made mainly from fat + carbs (chocolate, chips)
Eat foods high in fiber, such as whole grain bread or other cereals and low-calorie vegetables
Comment: Thanks,  so i guess sprinting is more effective
Comment: 10 minutes of sprinting would require 20 sprints x 30 seconds, for example, with some rest in between. So, it's up to you what you find more convenient. It doesn't seem to be easier to me than running for an hour at 11 km/h.
Answer: it depends upon your current physical condition.  If you are at the verge of obese, your heart is the first muscle you should begin conditioning! lots of interval marching. The same is true if your a sedentary with some fat beginning to develop.    if you are active, and have a few thick spots, progressive plyometrics can ramp off fat fairly quickly.    yes, sprints.     Jogging, is a test for, or the maintenance of, a healthy heart. Goal of to feel capable of a short marathon.


What are the best swords?

Question: What are the best steel and silver swords in the game? I have a 300 damage silver sword and 260 damage steel one. If you know of any better swords, what level do you have to be and where are they found?
Comment: This is really going to depend on what stats you value, unless you mean "What are the highest-damage swords in the game?". I am also unsure how much RNG goes into drops.
Comment: the best that I have come across so far are the fully upgraded Witcher school weapons, I am at level 36 and there are not a great deal of high levels quests that I have not completed, however as @Jeeva mentions there may be some better RNG gear available.
Comment: Yeah, the various bits of upgradable Witcher gear are generally held to be the best by a fair amount of damage. But, rng...
Answer: Dunno...for the most part, the various witcher school gear is amongst the best you can craft. They are typically over-spec'd as it is, probably usable well into your 40's. However, if you venture about and do monster contracts and explore ruins/ tunnels etc. you'll find higher level gear than even that of your master crafted witcher school gear.
I can't remember the name, but I found one such sword in a vampire's crypt, I think. Far south of Midscope, in an abandoned village overrun by ghouls. Do the monster contract and there and you should get this sword as a drop and/ or in the nearby chest. It's one of those relic sword designs that has an "S" shape running the whole length of the blade, like waves...looks cool. Kind of like a Celtic design. It's a level 37 steel relic sword and does more base damage than my master craft witcher cat school steel sword, although, my Cat School has the best attributes. What I wonder, though, is if your level determines your loot. I have run through this game 3 times(story) and the last two times I was getting a pretty sweet looking level 27 relic sword that had knuckle guards and a serrated blade, from near the lighthouse that is south of Novigrad, on an island and in a serpent's nest. This last time through, I was very low level and didn't get that same sword and instead, got some other level 17 relic sword. So you might not get the sword I got from that crypt, until you are around 30.

What are the best swords?


How to go about learning perl

Question: I am a bioinformatics student and am in the process of learning perl.  I don't have a strong programming background but would like for that to change.
Right now I am in the process of reading/following and coding from this book
I want to know is this the best way to go about learning perl?  Should I be experimenting with regular expressions more?  Should I keep trying writing sample perl scripts?
Related: what are good books for learning perl
Answer: The definitive learning Perl book is aptly called "Learning Perl". Get it.
I cannot recommend writing sample scripts. Try to write something that you need. It doesn't have to be a big endeavor; everyone needs a little tool now and then. Writing sample scripts is boring; always was, always will be.
Comment: agreed. write something that makes sense to you and is usefull
Comment: and refactor it often as you learn more about the language.
Comment: You may also hear this book referred to as "the camel book."
Comment: @R. Bemrose: "Learning Perl" is the Llama book, "Programming Perl" is the Camel.
Answer: This seems like a potential duplicate as here are some related questions:

What are the best resources to starting learning Perl?
What's the best online source to learn Perl?
Answer: Like most other answers on this post I can't disagree with the choice of "Learning Perl" as your first Perl text. Keep a copy of the perldoc documentation available for quick reference(I prefer using the html/pdf format which is available as a download from the main page).
In order to keep things from getting boring, especially in the initial stages I started converting my shell scripts to Perl, hacking away at it until I had three or more different versions of the same program with decreasing file size(not great for maintenance though). But then you know what they say - TMTOWTDI. Now I don't bother with shell scripts any more, writing it in Perl results in smaller turnaround times and the code can be easily reused and enhanced.
Once you are familiar with the more advanced concepts and are approaching a level of comfortability with using it for your day-to-day work or just simple one-liners you might want to have a look at Mark Jason Dominus' Higher-Order Perl which, according to me, takes the language and the reader's understanding of it to an entirely new level. The chapter on "Recursion and Callbacks" was a real eye-opener and changed my style completely from that of writing C-programs in Perl to actually writing "Perl" programs in Perl.
Answer: I use the online book "Learning Perl the Hard Way" to teach my coworkers about Perl.
Don't be intimidated by the title, it's just that it's directed at programmers who are already fluent in another language and therefore it doesn't focus on the programming part, but mostly on the Perl part, so it may apply better to your case (or not).
Answer: You really can't go wrong with the Lama book
Learning Perl
There's quite a library of O'Reilly books on Perl.  Programming Perl is also excellent and probably worth having to complement the Lama book - I have both on my shelves and although I haven't needed to code in Perl for quite some time I found these books together a solid enough combination.  The Perl Cookbook came in useful too (yes, this is one of those areas that O'Reilly has pretty much sew up :-).
As to practical exercises, Perl does have something of a reputation as a 'Write Only' language, so look for clear examples and if you are confused by anything don't necessarily assume that the problem is you - there's always more than one way to do it.
Answer: You also might want to look for examples of good code to study.
Answer: My experience is that there's nothing better for learning than doing.  But you need someone to provide feedback, especially when you hit roadblocks that you can't get past.  Stackoverflow is good for that, but, IME, Perlmonks is better in that there is a chatterbox for immediate feedback, as well as their question-and-answer posts for longer questions, combined with a more specialised environment.  (And Larry Wall has been rumoured to hang out there, too, as well as a number of the authors of the above-referred-to books.)
Answer: Learn by doing.  Get the books mentioned by others, but the real way to learn is to start a simple project.  Mine was a Gtk based SQL editor.  If you run into problems ask questions here and on the Perl Beginners list.
Answer: The choice of book is can be vary from person to person. So, as bioinformatics student who use perl, don't get any book that called "(X Programming language) for bioinformatics". Usually this kind of book is either.

They only give very basic of that programming language. You gonna to miss all the power from that language.
Wasting its space on how to use API, which you can find information easily via google.

How to go about learning perl


How to reset the channels and get back to the stable release

Question: I am unable to update, and add repos. I upgraded to Ubuntu 13.10, but it now says I am using the developmental trusty channels, and I need some advice on how to reset the channels and get back to the stable release.
Answer: This is not possible. There isn't a "safe" way to downgrade packages between releases. The only way is a total reinstall of the system.


How to unlock an LG mp260?

Question: How do I unlock and root an LG MP260? My LG v30 was stolen and I am trying to use an older phone from Metro PCS on my T-Mobile account until I can replace it.
Answer: When I moved my phone from MetroPCS to T-Mobile, I did not need to unlock it. Since MetroPCS is now a T-Mobile brand, it should be easy.

How to unlock an LG mp260?


Which comic first shows how Superman built his "Fortress of Solitude"?

Question: Can anyone tell me which classic Superman comic (from the 60s & 70s) was the very first time that showed how Superman built the Fortress of Solitude?
Answer: Based on your description, that would be Superman #176 from 1964 in which we see Superman constructing his "Fortress of Solitude" with his bare hands from the side of a mountain on the outskirts of Metropolis.

Note that before this one, he'd already had several other hideaways including an Arctic Citadel, a meteor base and an undersea fortress which we see him constructing in Action Comic #144 from 1958.
Comment: Interesting. The "Artic Citadel" sounds more like the Fortress of Solitude we all know and love. I'll have to look that one up.


Web.config was wiped out by Visual Studio

Question: Upon trying to edit our web.config file on our SharePoint 2010 Enterprise server via "wss\VirtualDirectories\80", Visual Studio started up to load the file for editing and then threw an error, something like an "unknown exception", and then refused to load the config file. Subsequently, the \80 folder shows that the web.config file no longer exists there! It's not in the recycle bin and is not found in any of the sub-folders under \80. Obviously this breaks the entire SharePoint farm connection. Is there any way to recover the web.config file?
Answer: First thing, You should always keep a backup of web.config and shouldn't touch it unless you know what you are doing.
If your web application isn't customized then just create another web application in CA which will create a new web in IIS too a and virtual directory for it. You can copy newly created Web application's web.config to create a web.config for your old web application. It happened to me so many times.
Web.Config is just xml document with elements that you can use for web application's configuration for example if you want to see full trace errors, so building a new one from scratch shouldn't be rocket science until you know what exactly you want.
This file also contains safe controls entries which you will need to add if there's any control that needs to in it. I have seen IIS manager making backup copies of web.config on my development server and web application's virtual directory if you could find it.
Comment: See, the thing is that there were backups and those were wiped out as well. I knew exactly what I wanted to change in the file (set executionTimeout in httpHandlers tag), so it wasn't an issue of me changing the wrong thing in the file. It seems to be an inexplicable glitch with VisualStudio not allowing the file to be edited in the first place. Strangely, trying to replace the config file from another server's web.config results in a 403 Not Logged In error. I'll try your suggestion but in the future I will back up the file in a non-\80 folder as well as  try with a different editor!
Comment: Oh yeah getting file from another WFE would be a good idea too, but right now I am not 100% sure as what things one should be looking at to change, I will check it on my environment in morning time and will let you know then. for the error, do you want to try this, http://serverfault.com/questions/272474/anonymous-authentication-anonymousauthentication-403-forbidden-access-is
Comment: I'll have to see what the exact error was, but thank you very much for the suggestions. Currently trying to restore the config file from a server backup image.


Weakly compact operators between Banach spaces

Question: Let $X$ and $Y$ be complex Banach spaces and $B(X,Y)$ be the Banach space
of all bounded operators. An operator $T\in B(X,Y)$ is weakly compact if
$T(\{ x\in X;\; \| x\| \leq 1\})$ is relatively compact in the weak topology
of $Y$. If $X$ or $Y$ is reflexive, then every operator in $B(X,Y)$ is weakly
compact. I guess that the converse holds as well: if every operator in $B(X,Y)$
is weakly compact then either $X$ or $Y$ has to be reflexive. But I cannot
find a satisfactory argument for this. I know about some characterizations of weakly
compact operators: factorization through a reflexive Banach space or continuity with
respect to the right topology in $X$. However it seems to me that there must be a
simple argument which forces that either $X$ or $Y$ is reflexive if every operator
in $B(X,Y)$ is weakly compact. I am asking if someone knows this simple argument
or if there is a paper with an answer to my question.
Answer: The fact that each $T\in B(X,Y)$ is weakly compact does not imply $X$ or $Y$ reflexive. For example, every non-weakly compact operator $T:\ell_\infty\to Y$ is an isomorphism on a subspace isomorphic to $\ell_\infty$ (See Prop. 2.f.4 in Classical Banach spaces I, by Lindenstrauss ans Tzafriri).
Thus if $Y$ is a non-reflexive space containing no copy of $\ell_\infty$ (e.g. $\ell_1$, or a separable non-reflexive space) then every $T\in B(\ell_\infty,Y)$ is weakly compact.
Comment: I do not know a general answer; only special cases. Denoting $W(X,Y)$ the weakly compact operators, if $X$ is separable and $L(X,C[0,1])=W(X,C[0,1])$ or $L(X,\ell_\infty)=W(X,\ell_\infty)$, then $X$ is reflexive. If $X$ contains no copies of $\ell_1$ and weakly convergent sequences in $Y$ are norm convergent (like in $\ell_1$) then $B(X,Y)=W(X,Y)$.
Comment: Thank you for the answer! My intuition was wrong. Now I see,
why I couldn't find an answer to my question in books and papers.
However, is there a known general result which says what type of
spaces have to be $X$ and $Y$ if every operator in $B(X,Y)$ is weakly compact?
Comment: Thank you once more for your answer and useful information.
Answer: I don't know if the following helps:
Let $B(X,Y) = W(X,Y)$. Then the following hold.
(i) If there exists a surjection $T\in B(X,Y)$ then $Y$ is reflexive.
(ii) If there exists an injection $T\in B(X,Y)$ with closed range then $X$ is reflexive.
Indeed, denote by $B_r$ and $K_r$ the open and closed ball around $0$, respectively. By the open mapping theorem, $TB_1$ is open. Thus, there exists $r > 0$ such that $K_r\subset TB_1\subset TK_1$, i.e., $K_r$ is weakly compact in $Y$, meaning that $Y$ is reflexive. If $T$ is an injection with closed range then a similar argument as above shows that $\operatorname{ran} T$ is reflexive. But as $T : X\to\operatorname{ran} T$ admits a bounded inverse, $X$ is reflexive.
Comment: Thank you for those results. Any new information about weakly compact operators is welcome. Although that I am not studying these operators somehow they have appeared in my research work. I am especially interested in the question when $B(X,Y)=W(X,Y)$. It seems that there is no complete answer to this question in literature.


Cross-platform alternative for MS Reader?

Question: Is there an alternative tool similar to MS Reader that allows one to both publish and view ebooks in Linux, Mac and Win?
Answer: Perhaps Calibre will do the trick for your needs. It's a rather comprehensive eBook manager/reader/converter.
Answer: That entirely depends on the format you prefer, if you want to open Microsoft's proprietary LIT format and various platform, then Calibre (as per Mavrik's suggestion) is your best bet.
If you're willing to settle for .txt, .doc, .html, .fb2 or .rtf formats then i suggest Cool Reader. Version 3 is a cross-platform (Linux, Mac and Windows) open source E-Book viewer.

Cool Reader 2 is my personal favorite, but version 2 only works for the Windows platform, unlike version 3 it supports skinning, text-to-speech and MP3 export.

Cool Reader 2 is closed source, but free and portable.
Don't mind the Russian screen shots, despite its origin, the software is all in English. :)
Answer: Just save your files as PDF. That's the most cross-platform you'll get (all OS + all phones, handhelds and web)


direction of Pockels Effect. Refractive index eigendirections

Question: There is a linear electro-optic effect called Pockels Effect
The brief is that refractive index changes due to electric field.
If there is an anisotropy (like birefringence) and electric field is in perpendicular to optical axis then refractive index changes for different polarization of ordinary rays.
It gets eigendirections 45 degrees to electric field.
Why so? Why it gets min 45 degrees but not exactly towards direction of E?
Answer: Pavel, I think an excellent and concise description of the Pockels effect is provided here: http://www.rp-photonics.com/pockels_effect.html. If you need some more information, please provide an illustration to your question, it will help to understand it.


Adobe Flash plugin: no full screen

Question: in my Lubuntu 13.04 (with Gnome Shell 3.8), Flash videos won't go to full screen in certain Flash players (i.e. on certain sites).
- Actually in most players, that means it doesn't work at all. Upon left-click on the fullscreen-button, I see a flicker as if it did got to full-screen, but then it stays standard size, kinda like a pop-up ad being killed by ad-block.
- Some players have a "toggle fullscreen" option available on right-click menu, this is the only option that works for me now. In this case, I have to press and hold the right mouse button and release it over the "fullscreen" menu entry. The menu disappears when releasing the mouse button.
- Only exception I found so far: Youtube, which works normally with left click on the fullscreen-button.
My current Flash-plugin version is 22.214.171.1245ubuntu0.13.04.1.
I wonder if Gnome Shell might be messing with Flash?
Is anyone else experiencing this problem?
Edit: this problem is present in Firefox, Opera and Chromium browsers.
The graphics card I'm using (as reported in Gnome settings > details) is GeForce 8100/nForce720a/integrated/SSE2
Answer: I found the following solution which worked perfectly for me:
Workaround fo this:

Install devilspie (via Terminal:)
sudo apt-get install devilspie

Write config for firefox (via Terminal:)
mkdir ~/.devilspie
nano ~/.devilspie/flash-fullscreen-firefox.ds

(if
(is (application_name) "plugin-container")
(begin
(focus)
)
)

Make devilspie autostart

Done.
Solution from:
https://plus.google.com/100368718538258540940/posts/eJWwPj8B4dX (last post)
Comment: here's how I made the autostart work: in Gnome dash, search for "Startprogramme" (means autostart applications - my UI is in German!). In terminal, type: which devilspie , output: /usr/bin/devilspie . In "Startprogramme", click "add" and insert this output in the "command" field. Fullscreen Flash is now working again.
Comment: I'm stuck at step 3. How do you make a command line appplication autostart? Remember I'm on Lubuntu 13.04 with Gnome Shell.
Answer: I created a devilspie script to make flash play videos full screen in Chromium and Firefox.
Save the following snippet to a file, make it executable and run it.
(Tested on Fedora Linux 19 using yum instead of apt-get)
#!/bin/bash

set -e

sudo yum install devilspie

mkdir -p ~/.devilspie

echo '(if
(or
    (is (application_name) "plugin-container")
    (and
        (contains application_name) "chromium-browser")
        (contains application_name) "flash-plugin")
    )
)
(begin
(focus)
)
)' > ~/.devilspie/flash_fullscreen.ds

echo '#!/bin/bash

echo "running" > /home/maarten/devilspie.log

while [ true ]; do
  /usr/bin/devilspie;
done' > ~/.devilspie/devilspie_daemon.sh

chmod a+x ~/.devilspie/devilspie_daemon.sh

mkdir -p ~/.config/autostart

echo '[Desktop Entry]
Type=Application
Exec=/home/maarten/.devilspie/devilspie_daemon.sh
Hidden=false
X-GNOME-Autostart-enabled=true
Name[en_US]=Devilspie Daemon
Name=Devilspie Daemon
Comment[en_US]=Script will continuously restart devilspie if stopped
Comment=Script will continuously restart devilspie if stopped
' > ~/.config/autostart/devilspie_daemon.desktop

Adobe Flash plugin: no full screen


Render times changing over course of render

Question: I started rendering an animation in cycles in the late after noon than went to bed with it rendering rendering at around 25 sec per frame (when tested at what should of been the most labor intensive frame) and it had 1718 frames. When you do the math this should take around 12 hours to render. When I got up in the morning 16 hours had passed and it was rendering at around 30 sec a frame. At 30 sec a frame it should only take around 14 hours but it was at 16 and was still not done (it was really close though). I'm freaking out thinking my pc over heated or something especially bc it felt slightly warm to the touch over the tempered glass closest to the cpu. Please help!
Comment: Hello, computation times can depend on the complexity of the materials lighting and the scene. For example, via a sheepit farm, I lost a lot of points because I had badly made the materials (I had trapped a light in a semi-transparent material, and I had left the bounces of light)
Your computer can also lose computing power depending on its temperature (lowering the cpu frequency to limit heat emission). The estimated time for a sequence of images is rarely accurate.
Answer: Render times are different for each frame, depending on the complexity of the content.
Any change inside the scene and within the image has to be computed separately.
Estimated rendering times are never accurate for the same reason, you can have a relatively simple scene to render at the beginning of the shot, and then have an explosion with particles and all kinds of complications or motion blur, those will take longer (sometimes much, much longer) to render.
3D Rendering is quite demanding in terms of resources and will push any computer. When computers get hot they go into a slower speed in order to protect the hardware. If the hardware reaches a critical temperature it will fail and shut down. If you experience abnormal heat and the computer is "throttling"  you need to invest in some kind of cooling system.
Answer: I often had this same difficulty with animations. My camera was following a path and while the first frames render fast (10s) the later frames would take much longer (2min). The shown time of render is calculated only for the currently rendered frame, but when the complexity of the scene varies greatly over the animation also the rendertime will vary. The easiest way i know for making estimates of the total rendertime is to render every 100th frame or so and then multiply the time by 100


How to denote physical (not logical) impossibility in modal logic?

Question: Say I want to note that in this world, it's physically impossible to jump over the Eiffel Tower. I can just write ¬◇x, but this seems to say that in all possible worlds x is impossible, and I want to specify THIS world.
Answer:
Say I want to note that in this world, it's physically impossible to jump over the Eiffel Tower. I can just write ¬◇x, but this seems to say that in all possible worlds x is impossible, and I want to specify THIS world.

Well, in the rather popular Kripke semantics, ¬◇x means there are no accessible worlds where x is true.  Now, depending on your accessibility relation, this might not prohibit x from being true in the current world (by default the "actual world").
So, if x is the predicate "One can jump over the Eiffel Tower," then just write ¬x , or to be clear that you specifically mean the actual world, w*, use the forcing operator. (aka the validation operator, or satisfaction operator).
<code> w* ╟─ ¬x
</code>
Answer: ¬◇x actually says more or less what you want. It doesn't explicitly specify THIS world, but at least it doesn't say that in all possible worlds x is impossible. Instead, it says something about an arbitrary but fixed world. It need not be completely arbitrary, the meta-context may have restricted it a bit, for example to a world reachable from another previously given arbitrary world, or to an arbitrary world with some additional properties (like being a transitive model of ZFC). In theory, the meta-context may even say that it is actually THIS world, but I am not aware that this is actually done in practice.
You may wonder why those additional properties of the arbitrary world are not also written down in modal logic, but only specified at the meta-context. Some of those properties (like being reachable from another previously given arbitrary world) could be expressed in modal logic, for some it is unclear whether they could even be expressed (like being a transitive model of ZFC), and some (maybe meaningless) properties (like actually being THIS world) can definitely only be stated as meta-context. But you basically always need the meta-level, even for those properties of the arbitrary world which can be expressed in modal logic. This can be hard to accept, even for experienced logicians, at least when it comes to free variables. (See http://math.andrej.com/2012/12/25/free-variables-are-not-implicitly-universally-quantified/, or perhaps rather https://chat.stackexchange.com/transcript/message/29883983#29883983 to see the reaction if the experienced logician is not talking to somebody famous like Andrej Bauer, but to a "student" having some perceived misconceptions.) You may look at the worlds in modal logic as similar to free variables in predicate logic. They somehow seem to be universally quantified, while they are actually just (more or less) arbitrary but fixed.
Comment: It actually does not. Negation of a weak operator or quantifier makes it a strong operator or quantifier. For instance, just like ¬∃xP(x) is equivalent to ∀x ¬P(x). ¬◇x is equivalent to □¬x. Which, in essence, translates in the semantics of possible world: x is false in every possible world.
Comment: @BertrandWittgenstein'sGhost Maybe it gets clearer if we give the name w to the world under discussion. Then the translation becomes "x is false in every possible world which is reachable from world w". What I try to make clear with my answer is that even so w is basically arbitrary, it is not necessary to assume an implicit universal quantification over w. (The case with the free variables is easier, since there the name of the free variables at least occurs in the formula under discussion.)
Comment: I see what you are saying, but the problem is not semantical. That is, it is not because of how we define our worlds it is syntactical. Regardless of how you define it, negation of a weak operator will give you a strong operator which will necessarily have to be instantiated in every subcontext accessible to the main context.
Comment: Also, keep in mind in quantified modal logic there can not be a free variable. It must be bound in order for the formalism to make sense. "Modal Logic for Philosophers"/systems of Quantified Modal Logic.
Answer: Let P: jump over the Eiffel Tower. Then, ¬◇P implies ¬∃$w_k$, k∈[1,n) such that P is true in it. So, in essence, when you negate a weak modal operator, you get a strong operator just like it is the case for Universal and Existential. For example, ¬∃xQ(x)≡∀x¬Q(x).  Keeping that in mind, we can not speak of contingent impossibilities within possible-world or Kripkean semantics.
We can only speak of possibilities and necessities such that they hold in all possible worlds, or in all worlds accessible to the actual world.
That said, once you start quantifying over possible worlds then you can meaning full speak of contingent impossibilities. There are system which do that.
Answer: The Eiffel example doesn't quite fit the idea of "physical impossibility". It may be biology, not physics, that prevents the jump, and with different physical laws one would have to ensure the Eiffel Tower can still exist and not collapse due to stronger gravity etc. But let's grant for the sake of argument that jumping over the Eiffel tower is logically but not physically possible.
Let the accessibility relation between possible worlds x and y be

y is physically possible relative to x

In other words, x and y obey the same physical laws (so this will be an S5 modal logic).
Then "Nobody jumps over the Eiffel Tower" is not logically valid, because there are some worlds with different physical laws where somebody does jump over the Eiffel Tower. But it necessarily true, at our current world.


What, if any, are the differences between materialism and empiricism?

Question: Are the differences, if they exist merely semantic ("First World War" vs "World War One") or are they more substantial; for example one's a historical trend and the other's a broader philosophical system? Speaking only as philosophical amateur I suspect Materialism is an outlook and Empiricism is a methodology but I could be wrong.
Comment: I'm asking a question though
What is the relationship between materialism and empiricism?
Are there any similarities amongst the two?
Answer: Philosophically, materialism and empiricism are quite different, so much so that it would not even be useful to speak of their differences. We're not merely talking apples and oranges here, we're talking apples and Lamborghini Gallardo's. Let me show you where each concept resides in philosophy:
Note: While there are no "official" categories, people typically use at least 4 major top-level categories when sorting theories in philosophy: Metaphysics (what is out there? what is it like?), Epistemology (what is the source and scope of knowledge?), Ethics (what is right and wrong?), and Logic (study of reason and inferences).

Materialism is the theory that all that exists is material (physical); it clearly falls under metaphysics because it tries to assert what things are (made of). (Specifically, it falls under philosophy of mind which itself falls under metaphysics.) As a theory regarding the ontological makeup of the universe, and it is often contrasted with dualism and idealism.
Empiricism is a theory of knowledge which asserts that knowledge can only (primarily) come from sensory experience, which places it clearly within the realm of epistemology because it tries to assert how we can know things. It is often contrasted with rationalism or idealism.
I hope that clears things up.
Comment: Excellent answer.  Concise, clear and accurate. (I disagree about the "4 major top-level categories", but that's a subject for another day.)
Comment: So aesthetics isn't philosophy now?
Comment: Good answer -- since you emphasize how different the two positions are, it may be worth clarifying how idealism could be a contrary position to both
Comment: @Joseph: Meh, it's outside the scope of the question. Feel free to edit it in though :P
Comment: It would seem that you've quite successfully described their differences, despite your protestations. ;-)
Comment: @Neil: Haha, well, *categorical* differences—rather than qualitative differences between the concepts—is what I was referring to in that statement. :P
Comment: i voted down because that's not really all these terms ever mean
Answer: Materialism is a global assumption while Empiricism is often a method or practice. Stoicfury is right in placing Materialism as metaphysics.
However, John Locke is the founder of British Empiricism. Yet Locke found God a sensible concept, despite how un-empirical God remains. Bishop Berkeley followed Locke, and is almost an idealist in his disbelief of the necessity of matter through an analysis of the empirical facts as "impressions". David Hume followed after Locke and Berkeley and set yet a different tone, altogether.
Locke is closest to an empiricist, Berkeley is practically an idealist, and Hume, practically a materialist. What is primary for Empiricism is the sufficiency of the brain to process sensory stimuli, regardless of the sufficiency of the mechanics of matter to enable such processes.
Empiricism too strictly defined actually strays from empirical practice as a gathering of knowledge as it presents itself, and a confidence that the most reliable, universal, or repeatable experiences are the most fruitful for establishing understanding.
What is the empirical experience of empiricism absent Locke, Berkeley, and Hume?
Empiricism can best be described as a practice or method(-ology, if you must).
Comment: "[Empiricism](https://en.wikipedia.org/wiki/Empiricism)" used in this philosophical context is _not_ a method or practice ... those who are empiricists (again, in this context!) think the only way to gain knowledge is through sense perception (as opposed to examining one's conscience, for example).
Answer: Aristotle is probably the greatest empiricist to date.  In practically all of his philosophy, including his ethics, he thought the correct place to start was with observations of the world.  This is the crux of empiricism; we apply reason to our experiences of the external in order to do philosophy.  You will note that Aristotle was by no means a materialist; he believed in a great number of immaterial things.  Aristotle did not find materialism tenable given his experience of the world, so he rejected it.
Empiricism can be contrasted with idealism, such as that of Aristotle's teacher, Plato.
Both empiricism and idealism are advocated by a significant number of present day philosophers of widely varying qualifications and backgrounds.
Materialism has not (yet?) had any particularly notable proponents in the same way empiricism has.  Materialism is a particular metaphysics which holds that matter is the fundamental substance in nature, and that all phenomena, including mental phenomena, spiritual phenomena, and consciousness, are the result of material interactions.  It has largely been replaced by philosophical physicalism, which states that all that is is physical in some sense, and is, in general, a much easier position to hold.
You can read more about Materialism here
Answer: To supplement the other answers here, I thought to quote from PhilosophyForums.com, but I modify the writing and omit blockquotes for easier reading.
Source: Posted Oct 31, 2009 by user 'Hamandcheese'
As a materialist I think every thing is made of matter, akin to naturalism. If someone claims, say, that a statue of Mary cried a tear, the materialist would point out: the substance that the rock is made out of, is all it is, and is no different than the rock before it was extracted from the earth, only that it has been shaped. Thus materialism is an important premise for my deductive and inductive reasoning.
Empiricism is the statement that everything that we know, we know through our direct senses, or some other aided observation (an empiricist would be fine with a microscope). Traditionally empiricists reject the idea of innate ideas, being entirely skeptical that intuitions and instinct could reliably inform our knowledge.
So the difference is pretty substantial. There are plenty of materialists who are not strict empiricists: that is, they think that only matter exists, but that some truth is innate in our brain and certain facts can be determined through intuitive reasoning. Empiricists, on the other hand, don't necessarily have to believe that all that exists is matter. Indeed, George Berkeley is famous for being both a strong empiricist and 'immaterialist'.
Source: Posted Nov 1, 2009 by user 'mrnormal5150'
empiricism tends to be an epistemological position while materialism is a metaphysical one. Sometimes one entails the other, but not always.


Is it true that Durga had problems with a demon that only created clones? What is this story?

Question: Someone said that in a YouTube Comments that Devi Durga had problems with a demon that only created clones. I don't know if this is true. What is the story related to it?
Comment: Also since you're new, when you're satisfied by the answer you can accept it by clicking the tick (✔) below the voting arrows. It shows everyone that's the correct answer. Also if you like an answer you can contribute an upvote by pressing the up arrow
Comment: This forum is not a forum to verify youtube videos. Please direct youtube inquiries in the future to the youtube author.
Comment: I'm voting to close this question because this forum is not a forum to verify youtube videos. Please direct youtube inquiries in the future to the youtube author.
Comment: The purpose of my question is to check if such a story exists, not to verify if what a youtube video says is true or not also I never mentioned the youtube videos mentioned the youtube comments two different things. What you say does not make any sense (No offense). Pd: the video where I found the comment that mentions the story is not about such a thing (durga's story) it is literally a video of an anime.
Comment: And the reason why I wanted to confirm such a thing was so that I could read the story and know if it was the same as what the guy who mentioned it said (he was mocking and minimizing Durga)..
Comment: @Mikael777 a reference to youtube video and screenshot of the comment which inspired your question would certainly be helpful :-)
Answer: Devi Mahatmyam, which is a part of Markandeya Purana doesn't tell that Devi had any problem killing the Ratkabija. You can read the full story in this chapter. Actually the Gods (devas) were greatly afraid seeing the alarming increase in the number (clones) of Raktabija:

व्याप्तमासीत्ततो देवा भयमाजग्मुरुत्तमम्॥८८.५१
Asura's blood pervaded the whole world; thereat the gods fell into the utmost terror

Seeing this fear of Gods, Sri Chandika just laughs and tells Goddess Kali the way to end that demon:

तान् विषण्णान् सुरान् दृष्ट्वा चण्डिका प्राह सत्वरा ।
उवाच कालीं चामुण्डे विस्तीर्णं वदनं कुरु॥८८.५२॥
मच्छस्त्रपातसम्भूतान् रक्तबिन्दून् महासुरान् ।
रक्तबिन्दोः प्रतीच्छ त्वं वक्त्रेणानेन वेगिना॥८८.५३॥
भक्षयन्ती चर रणे तदुत्पन्नान् महासुरान् ।
एवमेष क्षयं दैत्यः क्षीणरक्तो गमिष्यति ।
भक्ष्यमाणास्त्वया चोग्रा न चोत्पत्स्यन्ति चापरे॥८८.५४॥
Seeing the gods dejected, Chaṇḍika laughed and said to Kali, "O Chamuṇḍa! stretch out your mouth wide; with this mouth do you quickly take in the great Asuras, which are the drops of blood, that have come into being out of Raktavija at the descent of my weapon on him. Roam about in the battle, devouring the great Asuras who sprang from him; so shall this Daitya with his blood ebbing away meet destruction. These fierce demons are being devoured by thee and at the same time no others will be produced.

Then this is how he met with his end:

इत्युक्त्वा तां ततो देवी शूलेनाभिजघान तम् ।
मुखेन काली जगृहे रक्तबीजस्य सोणितम्॥८८.५५॥
ततोऽसावाजघानाथ गदया तत्र चण्डिकाम् ।
न चास्या वेदनां चक्रे गदापातोऽल्पिकामपि॥८८.५६॥
तस्याहतस्य देहात्तु बहु सुस्त्राव शोणितम् ।
यतस्ततः स्ववक्त्रेण वामुण्डा सम्प्रतीच्छति॥८८.५७॥
मुखे समुद्गता येऽस्या रक्तपातान्महासुराः ।
तांश्चखादाथ चामुण्डा पपौ तस्य च शोणितम्॥८८.५८॥
देवी शूलेन चक्रेण बाणैरसिभिरृष्टिभिः ।
जघान रक्तबीजं तं चामुण्डापीतशोणितम्॥८८.५९॥
स पपात महीपृष्ठे शस्त्रसंहतितो हतः ।
नीरक्तश्च महीपाल रक्तबीजो महासुरः॥८८.६०॥
ततस्ते हर्षमतुलमवापुस्त्रिदशा नृप ।
तेषां मातृगणो जातो ननर्तासृङ्मदोद्धतः॥८८.६१॥
Having enjoined her thus, the goddess next smote him with her dart. Kali swallowed Raktavjja's blood with her mouth. Then he struck Chaṇḍika with his club there; and the blow of his club caused her no pain, even the slightest, but from his stricken body blood flowed copiously, and from whatever direction it came, Chamuṇḍā takes it then with her mouth. The great Asuras, who sprang up from the flow of blood in her mouth, Chamunda both devoured them and quaffed his blood. The goddess smote Raktavija with her dart, her thunder-bolt, arrows, swords and spears, when Chamuṇḍā drank up his blood. Stricken with that multitude of weapons, he fell on the earth's surface, and the great Asura Raktavija became blood-less, O king. Thereat the thirty gods gained joy unparalleled, O king. The band of Mothers which sprang from them broke into a dance, being intoxicated with blood.

Previously here is how he has creating havoc in the Universe:

पलायनपरान् दृष्ट्वा दैत्यान् मातृगणार्दितान् ।
योद्धुमभ्याययौ क्रुद्धो रक्तबीजो महासुरः॥८८.३९॥
रक्तबिन्दुर्यदा भूमौ पतत्यस्य शरीरतः ।
समुत्पतति मेदिन्यां तत्प्रमाणो महासुरः॥८८.४०॥
युयुधे स गदापाणिपरिन्द्रशक्त्या महासुरः ।
ततश्चैन्द्री स्ववज्रेण रक्तबीजमताडयत्॥८८.४१॥
कुलिशेनाहतस्याशु बहु सुस्त्राव शोणितम् ।
समुत्तस्थुस्ततो योधास्तद्रूपास्तत्पराक्रमाः॥८८.४२॥
यावन्तः पतितास्तस्य शरीराद्रक्तबिन्दवः ।
तावन्तः पुरुषा जातास्तद्वीर्यबलविक्रमाः॥८८.४३॥
ते चापि युयुधुस्तत्र पुरुषा रक्तसम्भवाः ।
समं मातृबिरत्युग्रशस्त्रपातातिभीषणम्॥८८.४४॥
पुनश्च वज्रपातेन क्षतमस्य शिरो यदा ।
ववाह रक्तं पुरुषास्ततो जाताः सहस्रशः॥८८.४५॥
वैष्णवी समरे चैनं चक्रेणाभिजघान ह ।
गदया दाडयामास ऐन्द्री तमसुरेश्वरम्॥८८.४६॥
वेष्णावीचक्रभिन्नस्य रुधिरस्त्रावसम्भवैः ।
सहस्रशौ जगद्व्याप्तं तत्प्रमाणैर्महासुरैः॥८८.४७॥
शक्त्या जघान कौमारो वाराही च तथासिना ।
माहेश्वरी त्रिशूलेन रक्तबीजं महासुरम्॥८८.४८॥
स चापि गदया दैत्यः सर्वा एवाहनत् पृथक् ।
मातः कोपसमाविष्टो रक्तबीजो महासुरः॥८८.४९॥
तस्याहतस्य बहुधा शक्तिशूलादिभिर्बुवि ।
पपात यो वै रक्तौघस्तेनासञ्छतशोऽसुराः॥८८.५०॥
तैश्चासुरासृक्सम्भूतैरसुरैः सकलं जगत् ।
Seeing the asuras harassed by the band of Matrs and fleeing, the great asura Raktabija strode forward to fight in wrath. Whenever from his body there fell to the ground a drop of blood, at that moment rose up from the earth asura of his stature. The great asura fought with Indra's shakti with club in his hand; then Aindri also struck Ranktabija with her thunderbolt. Blood flowed quickly and profusely from him who was wounded by the thunderbolt. From the blood rose up (fresh) combatants of his form and valour. As many drops of blood fell from his body, so may persons came into being, with his courage, strength and valour. And those persons also sprung up from his blood fought there with the Matrs in a more dreadful manner hurling the very formidable weapons. And again when his head was wounded by the fall of her thunder-bolt, his blood flowed and there from were born persons in thousands. Vaisnavi struck him with her discus in the battle, Aindri beat that lord of asuras with her club. The world was pervaded by thousands of great asuras who were of his stature and who rose up from the blood that flowed from him when cloven by the discus of Vaisnavi. Kaumari struck the great asura Raktabija with her spear, Varahi with her sword, and Mahesvari with her trident. And Raktabija, that great asura also, filled with wrath, struck everyone of the Matrs severally with his club. From the stream of blood which fell on the earth from him when he received multiple wounds by the spears, darts and other weapons, hundreds of asuras came into being. And those asuras that were born from the blood of Raktabija pervaded the whole world; the devas got intensely alarmed at this.
Comment: Thank you so much
Comment: @Mikael please press green tick button
Answer: Well the story you are talking about is the story of a demon named Raktabīja, he came to known by this name after he was blessed with a unique boon by Lord Brahma. As per this boon, if a drop of blood from his body would fall on the ground, clones would be formed out of that drop. The story goes as follows:

Raktabīja was an asura (loosely translated as demon) who fought with
Shumbha and Nishumbha against Goddess Parvati and Goddess Kali or
Goddess Chamunda. Raktabīja had a boon that whenever a drop of his
blood fell on the ground, a duplicate Raktabīja would be born at that
spot (rakta = blood, bīja = seed; "he for whom each drop of blood is a
seed"). According to some sources, Raktabīja was, in his previous
birth, Rambha (asura), king of demons and the father of Mahishasura.
The eighth chapter of the Devi Mahatmya, raktabIja-vadh, focuses on
Ambika's battle with Raktabīja as part of her battle against the
asuras Shumbha and Nishumbha, who had disenfranchised the gods from
heaven. Raktabīja was wounded, but drops of blood falling on the
ground created innumerable other Raktabījas, and Ambika and the
Matrikas were in difficulty. At this point, the Goddess Kali joined
the battle, who collected blood pouring from Raktabīja's body in a
bowl while other goddesses wounded him. Kali devoured his duplicates
into her gaping mouth. This form who drank the demon's blood is also
called Raktheshwari.
Ultimately, Raktabīja was annihilated.
Comment: Thank you so much


If we stood on the surface of a Jovian moon, Saturn would appear as a dot. Why doesn't Saturn appear like this in a telescope?

Question: Images from the conjunction like these show Saturn just a bit smaller than Jupiter. However, if you were in the vicinity of Jupiter, Saturn would still appear as a dot to the naked eye, wouldn't it? If so, why is Saturn recognizable as a planet through a telescope in which Jupiter is also seen as a planet? As if they were actually very close to each other, at about the same distance from the Sun. I mean, if you recognize Jupiter in a telescope, shouldn't Saturn behind it look like a dot, unless you have a much, much larger zoom in which Jupiter would appear too close to match into the whole image while being too unsharp anyway?
Answer: Telescopes magnify, they don't bring you closer.
So if from Earth Jupiter has an apparent radius of 0.01 degrees (measured as an angle because it is the apparent size)
And if Saturn has an apparent angle of 0.005 degrees, then if you magnify 100x then Jupiter will have an apparent size of 1 degree, and Saturn would have a size of 0.5 degrees.  Magnification just increases the angular size in proportion
But if You go to Jupiter you have travelled less than half the distance to Saturn.
So saturn is still small. Travelling closer does not make everything increase in size in proportion.
You can see this simply:  Stand where you can see something 20 metres of so away, and where you can see into the hills (etc) in the background.  Walk towards the thing.  Note that the thing appears to get bigger as you approach, but the distant hills don't change size.  Travelling closer does not magnify everything in proportion.
Telescopes don't "bring things closer" they "magnify".
Comment: Wouldn't the hills look about the same both in binoculars and with the naked eye closer? Whatever, why does Saturn have half the apparent radius than Jupiter in the first place even though it's so much farther? If Uranus and Neptune were close to them, would they appear of similar size too, would we see four planets then? Sorry if my questions sound very greenhornish.
Comment: As @James K pointed out, Saturn is more than twice the distance of Jupiter. Place one of your fingers twice as far from your eye as another finger, and it will look half the size of the closest fingers. So, Saturn looks about half the angular size of Jupiter. QED. Uranus and Neptune are slightly less than the physical diameter of Jupiter and Saturn, but they're respectively about 4 and about 8 times further from Jupiter, so they look quite small—about 3.5 and about 2.25 arcseconds, respectively, against Jupiter's 40 arcsecs and Saturn's 17 arcsecs (all on average).
Comment: No.  If you have a ball 20 meters away and you have binoculars that magnify x2.  You look at the hills in the binoculars and they are x2.  You look at the ball and it is x2.  Now you walk 10 meters towards the ball.  The ball is now x2 without binoculars.  But the hills are not.  This is such a common notion that you can easily confirm. Telescopes don't bring you closer. The magnify it is different.
Comment: Thank you, now I see.
Answer: Saturn has a diameter of about 116,000 km and is about 1.4 billion km from Earth. For Jupiter, the corresponding numbers are 140,000 and about 800 million km (the distances vary somewhat as the planets move around the Sun. The size of the images of the planets is determined by the ratios of these, so Saturn is about $$\frac{116000}{1400000000} = 0.00008$$ radians and Jupiter about $$\frac{140000}{800000000}
= 0.000175$$ radians as seen from Earth. Both are too small to show a disk to the naked eye, but a  suitable telescope will show you two disks, one about twice the size of the other.
Seen from, say, Callisto (one of the moons Jupiter), Jupiter is about 1.8 million km away, and Saturn, at its closest, about 600 million kilometers. So, we can do the same calculations. Saturn subtends an angle of $$\frac{116000}{600000000} = 0.000193$$ a little bigger than Jupiter seen from Earth, but still star-like. Jupiter occupies about $$\frac{140000}{1800000} = 0.077$$ radians -- about 10 times as big as a full moon.
Comment: But the distance from Jupiter to Saturn is the same, so why do you see Saturn in a telescope planet-like at the same zoom as when you would see Jupiter from Callisto? And at these vast distances it's better to use AU I suggest.
Comment: Moving closer is not the same as zooming. AU is ood for the distances, but not the diameters.


How to find number of borrowed bits in subnetting

Question: I am an Electrical Engineer learning about computer Networks, So this question might be childish and easy for most of you. Please answer it briefly.
I am performing subnetting where I have this address 184.108.40.206. In this worksheet, I can understand all the data except a number of borrowed bits which are 4. Please tell me How and from where this 4 came from?

I have downloaded different worksheets and docs but was not able to understand this.
Comment: See the excellent answer to [this question](https://networkengineering.stackexchange.com/q/7106/8499).
Comment: Could you explain me where is borrow part in the question you are linking to OR you are just a fan of marking duplicates?
Comment: There is a section called **Calculating subnets** that explains this. Also, understand that network classes are dead, killed in 1993 by RFCs 1518 and 1519, which defined CIDR (_Classless_ Inter-Domain Routing). Modern networking does not use network classes. Please let them rest in peace. Also, all "_education, certification, or homework_" questions are explicitly off-topic here.
Answer: The borrowed bits are the host bits in the default subnet mask that are used for network in the custom subnet mask.
In your example:
Last byte of the default subnet mask:
Binary      Decimal
00000000 -> 0

Last byte of the custom subnet mask:
Binary      Decimal
11110000 -> 240

The first four (4) bits go from host to network, they are borrowed bits.
It can be understood easily using CIDR notation:
Netmask           CIDR Notation
255.255.255.255   32

Netmask           CIDR Notation
255.255.255.0     24

Netmask           CIDR Notation
255.255.255.240   28


Vim freezes in insert mode when .vimrc contains set tags=tags;

Question: I am using vim-gtk on Ubuntu 16.04 and use exuberant-ctags to generate a tags file in the root directory of my project. My instance of vim would randomly freeze in insert mode, usually after inserting a full stop (.) and the only thing I could do is close that terminal and open a new instance of vim in a new terminal. I was able to narrow the problem down to something with ctags by removing things from my .vimrc file. When I remove set tags=tags;, vim works fine and never freezes. I have also noticed that if I remove the tags file in my root directory, it no longer freezes even though set tags=tags; is in the vimrc.
Things I have tried:

other questions mentioned Ctrl+S and Ctrl+Q. When it freezes in insert mode Ctrl+Q has no effect and I am sure I am not accidentally typing Ctrl+S since I have tried pressing it intentionally and then Ctrl+Q does work.
Uninstalling and reinstalling vim, vim-gnome, vim-gtk, etc...
Uninstalling and reinstalling exuberant-ctags

Neither of these fix the problem.
Has anyone encountered this problem before?
If there is no obvious fix, can anyone recommend an alternative to exuberant-ctags that can be used with vim without making it freeze on my machine?
Answer: Vim was freezing because my tags file was too large. I added several directories and filetypes to .agignore and then reran ctags using ctags -R --exclude=@.agignore which resulted in a much smaller tags file (19MB instead of 2GB) and now vim no longer freezes


Does rooting (but no custom roms) trigger knox's void warranty

Question: Does it make Knox's "void warranty" = 0x1
Answer: There are two events that will trigger the Knox flag to change from 0x0 to 0x1.

Unsigned recovery (recovery.img) is flashed
Unsigned kernel (boot.img) is flashed

It's not the actual custom rom that trips Knox when you get to flashing. It's the step before that, getting a custom recovery loaded in order to flash the rom itself.
This is also why the de-la-vega root method works, because it flashes a prerooted stock system image to your device without touching the two partitions that DO trip Knox of modified.
Answer: Lucky boy! When I did the root procedure on my Galaxy S4, I did not figure out that I was going to lost my warranty increasing the Knox counter... Infact almost any root procedure will do this.
But, as I told you before, you are lucky because there is some new root-procedure that will not increase the Knox counter. You can read further on this: http://www.theandroidsoul.com/universal-root-de-la-vega-script/
Hope I've helped you!
Luca
Comment: Have you actually tried this?
Comment: The linls are dead on that site and in the comments people were having a lot of trouble
Comment: I did not tried it by myself cause I already did the "classic" root procedure with the Chainfire CF-AutoRoot. I'm sorry but I can't help you more :(


Connecting to internet raspberry pi 3 model B built in Wi-Fi

Question: I am having trouble connecting to my Wi-Fi. I have looked all around, but they are all about pi2 or model 1 or 2. When I try using the built in Wi-Fi, I enter my pre-shared key and then it says it is invalid. I have tried messing with the code of numerous files, but much to my dismay I have broken my os (Raspbian), which I have then had to reinstall. What I have found odd is that my /etc/network/interfaces is only 1 line long. Any suggestions? Remember I am running Raspbian version March 2018, Release date 2018-03-13, and Kernel version 4.9 on a raspberry pi 3 model B revision 1.2. Thanks!
Comment: Please add details to your question, such as the contents of /etc/network/interfaces and any file it calls up.  Obscure anything sensitive with stars or similar.
Comment: what are you using to login to your wifi? the button on the desktop? `raspi-config`?
Comment: "I have looked all around, but they are all about pi2 or model 1 or 2." - then you obviously haven't even searched this site.
Answer: It's all here, dude - a complete walk-through for setting up WiFI on your Pi - and it works for Pi3. Work through this, and come back with specific questions.
Answer: Do not make any changes to /etc/network/interfaces
Your solution is not in there.  That file is completely ignored by the version of the OS that you specify.


Is there any augmentation tool for images and bounding boxes?

Question: I don't have a lot of training data and I'm looking for some tools in python or executable program like labelimg that do some heavy augmentation on images, even better if they also change bounding boxes coordinate accordingly. Any help will be appreciated!
Answer: I think you should look into imgaug. It supports most image augmentation and does have support for bounding boxes.
Docs: https://imgaug.readthedocs.io/en/latest/
Answer: Other widely used Python libraries for data augmentation include:

OpenCV: has functions/methods for bounding boxes, changing color space, scaling, cropping, translation, rotation, filters, blur, thresholding, etc.
Scikit-image: also has features allowing converting from another color space to another, resizing/rescaling/rotating, erosion/dilation, filters, etc.
Pillow: also has features for color space conversion, resizing/rotation/cropping, filters, pixel-level transformations, etc.
Answer: There is also bbaug which implements Google's bounding box augmentation policies.
Answer: Albumentations can do that augmentation. It supports multiple formats of bounding boxes annotations.  From the docs:

Albumentations is a Python library for fast and flexible image augmentations. Albumentations efficiently implements a rich variety of image transform operations that are optimized for performance, and does so while providing a concise, yet powerful image augmentation interface for different computer vision tasks, including object classification, segmentation, and detection.


Disequilibrium during infinitesimal steps of a thermodynamic reversible process & cause of maximum work to be achieved during reversible process?

Question: In almost every sites and even in my book,it is written that "Reversible process is the process which is carried out infinitesimally slowly so that in each step thermodynamic equilibrium is maintained and any infinitesimal change in the condition can reverse the process to restore both system & the surroundings to their initial states" . Now 'a process is done infinitesimally slowly' means the process is done in infinitesimal steps . But during each step ,as beautifully examplified in the accepted answer of my another question by @André Neves, there is disequilibrium . At the end of the step,can only the equilibrium be reached . So, doesn't it bother the definition? But this is not the point. I want to know only by performing a process infinitesimally slowly using innumerable steps can make it reversible,while if I do the same process with a rapid change,it becomes irreversible. Is it so? Why? I know here comes one key that is relaxation time ie. during the irreversible process,the system does not get sufficient time during the process to attain equilibrium . But how can I avoid the fact that while doing a process infinitesimally slowly i.e. by performing innumerable steps to make the process reversible,disequilibrium exists during each step? Is not it contradictory to the definition which says that at all stage there is equilibrium? Do they don't care about the disequilibrium at each step? It is quite confusing to me; perform a process using infinitesimal steps during which disequilibrium exists and then write a definition which says at all the time equilibrium is maintained? Why? Another question which arises in my mind that how by performing reversible process ie. infinitesimally slowly to reach a certain state,maximum work is obtained and while doing the same process irreversibly ie. rapidly,least work is obtained. Why? Is work proportional to time? I will be very grateful if anyone answer these two questions. Plz help.
Answer: I think André Neves' answer to your other question says the opposite of what you think it says. But let me try to make it a little bit clearer for you, if I can.
In André Neves' answer, he talks about a gas in a piston that's weighed down by 1000 pieces of lead shot, each weighing a small amount $m$. After each lead shot is removed, there is indeed a period of disequilibrium before the system goes back to equilibrium at a different state. As a result of this disequilibrium, a little bit of heat $q$ is generated (mostly by friction as the piston oscillates up and down before it comes to rest) and transferred to the environment.
But these pieces of lead shot are not infinitesimal, they are merely quite small. Let's try to get a bit closer to the infinitesimal case, and consider 100,000 grains of sand, each weighing $m/100$. Now when you remove a grain of sand there's still a period of disequilibrium, but there's much less equilibrium at each step than there was with the lead shot, and (it turns out, once you do the math) that the amount of heat that's generated is much less than $q/100$. (If I'm not mistaken, it should be approximately $q/100^2$.) This means that after you've removed all those tiny grains of sand one at a time, the total amount of heat generated through friction will be much less than it was when you did it with lead shot.
Now, a quasi-static (or "reversible") process is an idealisation. You can't really remove an infinitesimal piece of weight from the piston, since the smallest thing you can remove is an atom, and in theory you'd have to wait an infinite time for the system to go to equilibrium after each step. (Well, ok, there are smaller things. But they're still bigger than infinitesimal no matter what you do you.) In reality there is no such thing as a quasi-static process, but because some things behave like them to a good approximation, people find it a useful thing to think about.
So what you have to imagine is that you keep doing this with smaller and smaller grains of sand, and that you keep going for ever, until they're basically zero mass, and there's an infinite number of them. It turns out, once you do the maths, that as the grains get smaller, the total heat that gets generated also gets smaller, and by the time you get to zero-size grains the total heat produced by friction will also be zero. This is what we call a reversible process, and as I said it doesn't really exist - but the point is, if you do this experiment with lead shot it will be a pretty good approximation, and the frictional heating will already be so small that you can basically ignore it.
Now, your second question was how the same process can be irreversible if done quickly but reversible if done infinitely slowly. I hope now the answer is clearer: when you do it quickly, it produces heat (often through friction as in the example above). But if you do it slowly it produces less heat, and if you're careful you can channel that same energy into useful work instead. So the system ends up in the same state after the irreversible and reversible versions of the same process, but its environment can be in a different state, containing more heat after the irreversible version than it does after the reversible one.
Answer: I will come up with an explanation that has to do with information.
One possible interpretation of the second principle of thermodynamics is that, during an irreversible process, there is a loss of information about the state of the system that can never be recovered (this interpretation is mostly due to Jaynes).
Now, when you perform (for instance) a transformation very very fast, the only thermodynamical states that are well defined are the initial and the final ones. The thermodynamic path in between these two states is unknown (and not even defined) because of the speed of the process and a lot of information is being lost then. Ultimately, you could even find a final state that has nothing to do with the initial state (because the final state is essentially set by the final constraints only).
A contrario, if you perform a very very slow transformation on a system, you can keep track of the state of the system at almost every time during the process and you minimize (in the infinitely slow process limit) the amount of information that is lost during the transformation; the process is therefore said to be reversible.
To make my point even clearer, in an infinitely slow process, you have a one-to-one correspondence between the initial state and any state along the thermodynamic path that leads to the final state; therefore you cannot have any loss of information. In a very fast irreversible process, that is not the case: you can have multiple initial states that will reach the same final state with the same protocol.
Comment: Sir, I know nothing about information theory. But what you wrote is crystal-clear to me. Can you suggest me any book or site for studying information theory for beginner like me?
Comment: Sir,can you tell why is maximum work received only from reversible process?
Comment: You can have a look at the [wiki page](http://en.wikipedia.org/wiki/Entropy_in_thermodynamics_and_information_theory) which is quite concise and simple and the references therein. Regarding the maximum work statement, I am not sure it is even true so won't try to discuss it here.


How can i wrap the earth image around a 3D Sphere using OpenGL, GLFW, GLAD, GLM?

Question: Please help me out with this thing and currently i am a little more than a beginner so please tell me in that context. i don't need any obsolete methods for creating this like using GLUT or GLEW.can you just tell me its algorithm to create the outline of it(like using icosphere or triangles) and how and where in the whole program do i implement this algorithm. currently i am referring the "learnopengl.com" tutorials.i know how to create triangles and 3d rotational cube.
Answer: I'm not going to post proper working code here just giving you a guideline. There might be an easier way but what I did back in my days was to create a sphere using Triangle Strips. There is an icosahedron approach as well but I haven't looked into that.
So first of all look up on GL_TRIANGLE_STRIPS and how they work. Secondly you need to look up on Spherical coordinates and how to convert them to Cartesian Coordinates.
A brief overview is that Spherical coordinates have parameters (radius, zenith, azimuth). Radius is pretty much self explanatory. Zenith angle is the inclination angle from the pole of the sphere (lines of longitude) While the Azimuth angle runs along the latitude. Zenith runs from 0-PI (assuming 0 starts from 1 pole and PI is the second pole) or -PI/2 - PI/2 (assuming the extreme at both poles and 0 is the center) and Azimuth from 0-2PI (all the way around the sphere).
Now after that you can think of the sphere forming up from concentric Rings. At each fraction of the Zenith angle there is ring that runs around the sphere (the latitude lines). Then you create triangle strips between those rings to fill the sphere up.
So basically you want something like,
zenith = azimuth = 0
ring_increment = PI/num_rings;
sector_inrement = 2PI/num_sectors;

for(i=0; i < PI; i+= ring_increment)
{
    for(j=0; j < 2PI; j+= sector_increment)
    {
        vertex_list.add(convertToCartesianCoord(radius, zenith, azimuth))
        zenith += ring_increment
        vertex_list.add(convertToCartesianCoord(radius, zenith, azimuth))
        zenith -= ring_increment
    }
}

The more the number of rings and the number of sectors the smoother the sphere will be.
Answer: Build a hexahedron from 6 triangles(!), setting its 2 vertices at the poles of the sphere, and the other 3 vertices equally around the equator. Then iteratively or recursively subdivide all triangles, projecting the new vertices at the sphere surface (!). Triangle subdivision can be done by replacing an original triangle by 4 new ones, adding new vertices in the middle of all 3 edges and in the middle of the original triangle.


Adding standard deviation bars in Excel 2007

Question: In Excel 2007 I am using a double bar graph (like a regular bar graph, but with two columns under one x-axis value) as my chart. I have 8 x-axis values, making a total of 16 actual bars.
I need to add a different value of standard deviation for each bar (meaning 16 different values of standard deviation).

How can I do this?
How do I add the standard deviation for each bar if each standard deviation is different / unique for each bar?
Answer: What you need is Error Bars


A text-to-speech software for French

Question: I have some french text, would like convert them to MP3 files to listen. Any text-to-speech software to recommend? I hope it's free and for Windows. Note: not necessarily to MP3, as long as it could convert to audio files, e.g. .wav, it's ok.
Comment: (1) Natural reader – free trial, various voices, limited to ½ hour for free version. Unlimited for paid version. (2) Dragon.  Note, both have lots of voices in various languages including French. (3) Foxit is a free pdf reader and can do also text-to-speech (in the View menu). However, you will need to find a French voice. RealSpeak Sophie (French) used to be free, but now I can't find it. You might also want to consider a browser plugin.
Comment: @aparente001 seems none is free on converting to mp3? e.g. natural reader trial version could read, but to convert to mp3 need upgrade...
Comment: You might be able to record to Audacity (free) through some sort of streaming.
Answer: I am the author of Intelligent Speaker - extension for browser, we use the best available speech engine - Polly from Amazon.

You can get your podcast feed and grab m4a files (better than mp3 - better quality for smaller filesize).
Answer: You can e.g. use the free Balabolka which can save as MP3. It's free and runs on Windows. It will detect the installed voices.

You'll need a French voice so that the text sounds proper. Using e.g. Microsoft Anna will not give good results. Nuance has French voices for ~ 40 €.

A text-to-speech software for French


An argument that everything is possible

Question: I have an argument that claims everything is possible. For, if something is impossible, it is not a thing at all. "Going faster than the speed of light" is merely a statement, not a thing at all. It does not describe an actual state of the universe. So, is this argument a good argument? And have any philosophers advanced this argument?
Comment: How is this not a definition (for all X if X is a thing then X is possible) instead of an argument?
Comment: Yes, if a "thing" exists, then its existence is possible.
Comment: So, when you speak of "everything" there is an ambiguity between existing objects and "concepts" like *unicorn*. Unicorns do not exist: are they possible? Maybe. Square circles do not exist? Are they possible: no.
Answer: If you just restrain the "things" category to what is possible, then "everything is possible" is a mere tautology that says nothing more than "every possible occurence is possible".
But it is not what people who say "some things are not possible" mean by "thing", obviously because they include "going faster than C" into the "thing" category. What they mean in fact, if we use your vocabulary, is "some statements are not possible", which at least says something of some interest.
It is the goal of analytic philosophy to criticize language and identify the faulty reasoning it's ambiguity can provoke.
I also must note that you are ignoring the case of states of the universe whose possibility is nor established nor disproven. Are they thing?
Answer: We can put forward ideas that do not or can not take on a physical form.  If we are to say that these are not a thing then it behoves us to say how we are to describe these ideas, since the fact that we can formulate these ideas can not be denied.
Answer: The first legitimate question here is:

What does it mean "possible" ?

Possible for whom and for what.
Parmenides says:

... you will not find thinking apart from what is

If we are talking about the possibility like a way of thinking about something then of course all things which are though exist and which aren't - don't.
But again, turning to your question.
Is it really possible for you to fly without planes and things like that?
The fact that you could fly is a thing, but you cannot.
Answer: a) "Going" is not even a thing.
b) Your "argument" is tautological (also, logically circular) to the definition: if possibility is necessary for a thing to be, therefore things are only what is possible.

So, is this argument a good argument?

As good as "I am very intelligent because I am not very stupid".

An argument that everything is possible


Switching multiple objects to sculpt mode easily

Question: Is there any way to quickly move all my selected objects into sculpt mode? The reason being, I'd like to navigate between them by Alt-clicking them while sculpting. If I select multiple objects, then go to the sculpting tab on the top, it only changes one of the objects into sculpt mode. The only way I found to work around this is one by one selecting the objects and changing them from object mode to sculpt mode. Then if I want to let's say go back to the modeling tab and do some modifications in Edit or Object mode, the objects remain in sculpt mode, so I have to change them back again one by one. Is there any way to work around this?
Answer: Select all of the objects you want to move into sculpt mode, and press CtrlJ to join them into a single object. With this "multi-object" selected, sculpt it as you normally would. After you are done, press Tab to go into Edit Mode. Press P and select "by loose parts" to split them into individual objects again.


Google Custom Search Engine tracking

Question: I am having this problem for quite some time now: I have a WordPress website that is using Google's Custom Search Engine. I want to track what people/visitors are searching on in that Google CSE. Is that possible and how?
Answer: I want to track what people/visitors are searching on in that Google CSE. Is that possible and how?
Yes, it is possible using Site Search reports in Google Analytics:

The Site Search reports in Google Analytics provide data and metrics on how people use search on your site. If you already have a
  Google Analytics account (using the same Google Account you use for
  your search engine), we recommend that you configure these reports
  directly from the Custom Search control panel. The Site Search reports
  provide the following data:

Search usage: What did users search for on your site? Did they refine their searches? Where did they go after searching?
Trending terms: What are people searching for?
Pages: Which pages on your site have the most search usage?

Follow the instructions here to Configure Google Analytics Site Search. For the "query parameters" in step number 6 there, see the last step here: Install Google Analytics Site Search In 5 Steps
Alternatively, using a front-end search form as covered in this question, you could develop custom tracking suited to your specific needs.
Comment: Thanks for this! by the way what is google query parameter? because this is required when I am doing the setup.
Comment: You're welcome! See step number 5 [here](http://www.portent.com/blog/analytics/install_google_analytics_site.htm)
Comment: Hi. I'll check step 5. Accept means checking it right? sorry I am fairly new to this system.
Comment: Yes, no worries. Thanks for feedback - I've updated the answer so others will know what to use for query parameters too. Welcome to the site by the way :-)

Google Custom Search Engine tracking


Lightweight primality certificates for untrusted DH parameters

Question: Are there any light-weight techniques to generate primality certificates for custom Diffie–Hellman parameters that could be sent to the client to allow it to verify primality without needing to run its own expensive rounds of primality testing? By lightweight, I mean not significantly harder than the recommended number of Miller–Rabin rounds on the generation side, and significantly less intensive during verification (after all, there's no point if it doesn't make life easier for the client).
Comment: I'm not qualified to answer. I'm guessing your choice to use custom parameters is to prevent attacks involving precomputation. I suspect the implementation might be too risky or inconvenient. Choosing large enough key spaces, I think, makes the DH precomputation attack I recall infeasible. I don't think the same attack works for ECC either. There are some positives to using fixed parameters. It's possible to optimize code better and may be less work to check for correctness. Your security level to resource consumption ratio can possibly be better with say curve25519.
Comment: @FutureSecurity Security from DH does not come from the keyspace, but you are right that the difficulty of precomputation. However, if a technique is found that can break 2048-bit DH in, say, a year for $100 million, generating custom parameters is the difference between one broken key exchange and an unlimited number of broken exchanges.
Comment: @forest Use X25519, and batch attacks don't scale like that.  Plus you'll get faster cheaper safer smaller implementations.
Comment: @SqueamishOssifrage I know that ECC can be better, but I'm not wondering what the best key exchange technique is (otherwise I would just use an x25519-NewHope hybrid handshake and call it a day).
Answer: Well, one possibility to generate a moderately lightweight certificate would be to use this theorem:
If we have values $p, q, g$ such that:

$1 < g < p$
$q > \sqrt{p}$
$q \mid p-1$
$g^q \equiv 1 \pmod p$
$q$ is prime

Then $p$ is prime.
So, for a certificate, we would have a list of $(p_i, g_i)$ values such that $p_{i-1}, p_i, g_i$ meet the above conditions (as $p, q, g$), with $p_0$ is the value $p$ we're actually interested in proving, and the final $p_n$ value is a prime small enough to make primality proving trivial (e.g. it may less than 16 bits long).  Each line in the certificate (almost) halves the value of $p_i$, and so the total number of lines is managable.
As for verifying the certificate, it should be fairly obvious, for each line in the certificate, we would check the first four conditions directly, and then step to the next line to verify the last condition; as the last step, you'd do a quick check that $p_n$ is prime.  The expensive part is the $g^q \equiv 1$ condition; if you total it, it's a bit less than a single Miller-Rabin computation (but has the advantage that it is deterministic; if it validates, there is no need to do a second iteration).  Whether this counts as 'significantly less' is something you'll need to decide.
As for generating the certificate, you can't select a random $p$ and try to generate the certificate.  Instead, you would create the certificate (and the prime) from the bottom-up; select a $p_n$, and then at each step, given $p_i$, you would search for a prime value $p_{i-1}$ (and $g_i$, but that's easy), eventually ending up with a $p_0$ value of the desired size.  The FIPS 186-4 Shawe-Taylor algorithm does exactly this (you'll just need to record the intermediate $p_i, g_i$ values).
As a side effect, $g_1$ is an appropriate generator for the DH group (as it generates a large prime-sized subgroup).
On the other hand, I would second Future Security's suggestion to the ECDH instead; that uses less resources, and doesn't have any known 'solve this problem and break the entire group' attacks
Comment: Is this a more efficient technique than, say, ECPP certificates for larger primes?
Comment: @forest: yes, both for generation, and (to a lesser extent) for verification.  On the other hand, ECPP certificates can be generated for any prime; for the above procedure to work, you need to generate the prime and the certificate at the same time.


Apple "option" keyboard shortcuts and touch typing

Question: Apple keyboards can have shortcuts using alt/option to type non-standard characters. For example, I can type the Swedish å by using alt+k and then typing a, and the Portuguese ç by using alt+c and then typing c. Now, from a touch typing perspective, how should I use these shortcuts? I mean, with which finger should I type them? I reckon that these resemble all the shift+key combinations, which I strike with the pinky of each hand, but the apple keyboard has only one alt key on the left side.
Answer: I had a similar issue but solved it in a different way.
I simply "modified" the keyboard layout to the level it suits my needs and uses.
If you press and hold a certain key example "a" a pop up will show me all options for it.

Here is how it works.
Find a file in /System/Library/Input Methods/PressAndHold.app/Contents/Resources   that is your keyboard Keyboard-??.plist (in my case it is called Keyboard-de.plist (German keyboard)
Copy that file to your Desktop (to modify it) since you can not modify the original file.
Open it (it will open in Text mode)
Find for example the "c" it looks like this (and I added the Portuguese ç)
<key>Roman-Accent-C</key>
    <dict>
        <key>Direction</key>
        <string>left</string>
        <key>Keycaps</key>
        <string>C Č č Ç</string>
        <key>Strings</key>
        <string>C Č č ç</string>
    </dict>

now add any "c" accents you like to use (Open the Character Viewer and find it) and just drag it over to the text file.
Once done replace the original keyboard-??.plist file with yours.
Now you have a highly customized keyboard specific to your uses, and no need to remember some finger breaking key combination to get it.
Comment: I up voted your answer and found it very useful. However, I will wait for a while before accepting it, just in case someone has an answer more focused on the actual typing technique or on changes in layout (perhaps assigning another option key to the right side of the keyboard, for example).


Is the force between solitons with same charge always repulsive?

Question: I know the one-dimensional case in which the force is proportional to $e^{-R}$ and the force is attractive for solitons with opposite charge and repulsive for solitons with same charge. I was calculating in an approximated model in 3+1 dimensions the force between solitons and I obtain repulsive for different charge and attractive for same charge. This result seems strange. Is there some law or theorem that doesnt allow this? Do you know any model where this happens?
Answer: Skyrme model leads to an attractive interaction for two several separated solitons of topological charge Q=1. See Manton, topological solitons, section 9.8.


What does poorest country by population mean?

Question: I understand poorest countries based on GDP but what does poorest countries by population mean? Below is the link to the information I was looking at.
http://worldpopulationreview.com/countries/poorest-countries-in-africa/
Comment: The measure used seems to be GDP divided by population (i.e. per capita)
Answer: "Poorest country by population" doesn't really mean anything: I think this is just sloppy writing by the website. The table on the website is actually ranking countries by
$$\text{GDP Per Capita}=\frac{\text{GDP}}{\text{population}}.$$
This is a measure of the value of goods or services that the average person in a country produces.


Chrysler Sebring won't start

Question: IT'S about 32 degrees out, not sure if that matters. When I went to start my 2007 Chrysler Sebring it just clicked a few times, but wouldn't start
 What could be the problem?
Answer: In general, car batteries don't like cold weather
Especially if they are weak/considerably discharged. The colder the outside temperature is, the lesser the amperage the battery will be able to deliver. This results in slower turning speeds, which if severe enough, will result in the audible clicking that indicates the starter motor is unable to turn the engine.
Answer: Clicking usually suggests the battery doesn't have enough power to turn over the starter motor. Check the battery voltage, or try getting a jump from another vehicle.
Answer: My main commuter car is a Chrysler Sebring 2001.  I have heard that "clicking" sound enough times over the years.  The problem is very likely a weakly charged battery.  Get a cheap portable jumper for the immediate problem.  Best thing in the long run is to get a $20 to $30 "Battery Tender Jr." which is a block that trickle charges your car's lead acid battery from your home's AC power.  It has firmware that specifically conditions the lead acid battery as well helping to extend the lead acid battery's life.  Lead acid batteries do not like to be fully discharged and actually be chemically damaged shortening their life.

Chrysler Sebring won't start


I have a Russian Tortoise. Should I let him hibernate from fall till spring without feeding him? Or should I wake him up?

Question: I have an estimated 15 year old Russian tortoise who I've had for 5 years. I typically leave his lights off throughout fall. This year he's gone through winter, too. Should I be doing this or is it healthier to keep his lights on year round and feed him every day?
Comment: I cannot give you a definite answer, but for the most common pet tortoises like Red Eared Slider it's adviced to let them hibernate in a cold and dark place like the fridge. Lights alone don't start or end hibernation, the temperature is crucial. If you keep your tortoise too warm without foot it will starve.
Comment: @Elmy RES turtle live in the water, while tortoises are living most times at land. Because of this I am carfull with conclusions from one to the other. In general the animal needs to have enough weight before starting the hibernation (look for weight-tables for the single species). And it should have visited a vet before to exclude health issues during hibernation.
Answer: I would say dont wake him up. If you want to give him food, then stick it in the hole/next to his shell and he will eat when he wants to. However waking him up may scare him or make him mentally ill.
Comment: Because, If you wake him up suddently, he might go into shock. "To wake your tortoise up you should place your tortoise in a warm room for a few hours. And gradually it will start to wake up. After emerging from hibernation, your tortoise will be dehydrated, so it is very important to provide your tortoise with a shallow bath each day at this stage." According to https://www.exoticdirect.co.uk/news/how-care-tortoise-after-hibernation
Comment: Yes, thanks for that source, but that still doesn't explain a turtle suddenly becoming mentally ill.
Comment: Going into shock can be considered mentally ill in a way
Comment: Kind of. Not 100%, but I see your reasoning.
Comment: Thank you my good sir.


Calculate apsides without knowing eccentricity

Question: How would one go about determining the apsides of an orbit, knowing only the current distance between the 2 bodies, the orbital velocity, and the period? Every formula I've seen requires eccentricity, but conveniently, every formula for eccentricity requires the apsides. Surely there must be some way to find one without knowing the other?
Comment: Do you have measures of the distance as a function of time perhaps? Or are the bodies co-orbital? In latter case, there simply isn't enough information to infer their orbit, unless you also have ratios (in which case it might be possible, but tricky).
Comment: @TildalWave I do not have a formula like that, else I would be able to find the apsides just by minimizing and maximizing the function. I have the relative velocity, relative position, and semi-major axis, as well as the gravitational parameters of the planet and the vessel in orbit.
Answer: You mention this is a system in which a vessel is orbiting a planet. In that case it's fair to assume the mass of the vessel is negligible compared with the planet mass and
the planet will sit in one of the focal points of the ellipse.
You can then use Kepler's second law to find the semi-minor axis as
$$ \frac{1}{2} r v = \frac{\pi a b}{P} $$
where $r$ the current distance and $v$ the current velocity, $P$ is the period and $a$ and $b$ give the respective semi-major and semi-minor axes.
From $b$ you find the eccentricity as
$$ b=a \sqrt{1-e^2} $$
And the apsides follow as
$$ \mathrm{periapsis} = a ( 1 - e ) $$
$$ \mathrm{apoapsis}  = a ( 1 + e ) $$
Comment: This formula  is incorrect. By the vis-viva equation, for all orbits with the same semimajor axis around the same body, the scalar velocity is the same for all radial distances they share. The substitution done to get v assumes that the velocity vector is perpendicular to the distance vector r, in which case the magnitude of r is already the periapsis or the apoapsis.


How is option margin determined by my broker

Question: How does my broker determine how much option margin they can or will allow me? For example if I have $1,000,000 in cash or stocks how do they determine how much option margin I may use?
Answer: Many brokers will apply the exchange margin calculation rule. For example if you buy a "SPY" option listed on the CBOE, the rules are detailed at the bottom of this page:

Margin: Uncovered writers must deposit 100% of the options proceeds plus 15% or 20% of the aggregate contract value (current ETP price multiplied by $100) minus the amount by which the option is out-of-the-money, if any. Minimum margin is 100% of the option proceeds plus 10% of the aggregate contract value. Long puts or calls must be paid in full.

However some brokers may require more than that minimum margin amount and some may require less if they take hedging positions into account. The exact policy being broker dependent it is generally detailed on the broker's website or contract. For example interactive broker's policy is an example of the latter and as you can see the calculation can be fairly complex.


Rounded corners and shading issues

Question: Here's what i am trying to do: a beveled cube, inside of it a rectangular hole with rounded corners. First i made a cube with the hole, then added a plane with beveled vertices for the rounded corners; merged both and bridged the edge loops and added a edge split modifier. It worked, but there are still shading issues from certain angles. Is there a better way to do this?

Edit: .blend-file:
Comment: Please upload your blend file to: http://blend-exchange.giantcowfilms.com/ and I will make an answer.
Comment: Great thanks, tell me also what is the purpose of this mesh? Is this gonna be game asset, realistic rendering or something else?
Comment: possibly some kind of vending machine, low-poly asset for game-engine use
Answer: One method:
Add a Plane and scale on the "X" axis to form your rectangle.

TAB into Edit Mode and add four Loop Cuts (CTRL + R) positioned where you want your hole to be.

Select all by pressing "A". Extrude by pressing "E" + "Z" to constrain on the z axis.

Scale in by pressing "S" + SHIFT "Z" to constrain to the x and y axis.
Select the inner top face and press "X" and "Only Faces" from the drop down menu to delete it.

Add a Subdivision Surface Modifier (View and Render set to two.

Tab into Object Mode and set shading to Smooth. Tab back into Edit Mode and add Loop cuts to tighten up you corners.

Repeat for all your corners.
Comment: thanks, the shading is much better that way. The only downside is, that the subsurf modifier requires way more extra geometry (edge loops) to refine the corners.

Rounded corners and shading issues