sump pit not filling like it used to

Question: Is it possible that work done to the basement slab can affect ground water flow to the sump pit? We recently had a toilet moved in our basement and since then our sump pit has been bone dry. The house was built in 2013 and we have lived here for two years. The reason I am concerned is that we live at the bottom of a hill and our pit usually has a constant flow (outside of winter time) of water and the pump runs every 4-8 minutes depending on rain and what not. Our neighbors along the base of the hill all have discharge from their outlets. Is this something I should be concerned with or are there other factors at play?
Comment: How's the weather been?
Comment: I feel like we got good snow through the winter although perhaps not as much spring rain as usual. It did run today as we got about 6-7 hours of rain yesterday.
Answer: If you don't have water coming inside don't sweat it! But yes a new toilet and rock packed around the line may have provided a new drain path for the water. If the basement is dry I would be happy the work helped the drainage.
Comment: Thus makes sense; the work could have changed flow under the slab or near that corner. The pump did run today as we got a good six or so hours of rain.
Answer: Weeping tile is a perforated pipe that captures groundwater from the soil around your foundation and to your sump pump. Maybe the contractor who moved your toilet broke or clogged your weeping tile.
If your pump ran every 4-8 minutes before this work was done and now it does not run at all, I would be concerned.
You can hire a plumber with a snake camera to inspect your weeping tile or you can rent a camera yourself (https://www.homedepot.com/tool-truck-rental/Drain-Camera/CGPF-ECAM-ACE/index.html). Shove this camera into the pipe within your sump pit and see if all is clear inside. It should go all-around your house without major obstruction.
Comment: I got to see the hole and what they were working on and I don't think they were anywhere near the weeping tile. Good idea about snaking it though. It'd be good to see what shape it is in given the amount of water it typically drains.

sump pit not filling like it used to


x230 tablet , realtek 8192ce connects to router but no internet

Question: The issue:
I can ping all devices on the network except the gateway (192.168.0.1) and in turn can not access outside of the network without proxying through another device.
The system:
Lenovo x230 Tablet with a Realtek wifi adapter running on Quantal:
Network controller: Realtek Semiconductor Co., Ltd. RTL8188CE 802.11b/g/n WiFi Adapter (rev 01)
The wtf:
I can obtain an IP from the router
wlan0 Link encap:Ethernet HWaddr e0:06:e6:c2:d2:e0
inet addr:192.168.0.102 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::e206:e6ff:fec2:d2e0/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:178844 errors:0 dropped:0 overruns:0 frame:0
TX packets:101517 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:121465876 (121.4 MB) TX bytes:10612848 (10.6 MB)

I can ping other devices:
➜ ~ ping 192.168.0.101
PING 192.168.0.101 (192.168.0.101) 56(84) bytes of data.
64 bytes from 192.168.0.101: icmp_req=1 ttl=64 time=3.84 ms
64 bytes from 192.168.0.101: icmp_req=2 ttl=64 time=1.32 ms

I can not ping the gateway:
➜ ~ ping 192.168.0.1
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
From 192.168.0.102 icmp_seq=1 Destination Host Unreachable
From 192.168.0.102 icmp_seq=2 Destination Host Unreachable

My resolv.conf is autogenerated with:
➜ ~ cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 127.0.1.1
search nc.rr.com

My /etc/hosts:
➜ ~ cat /etc/hosts
127.0.0.1 localhost
127.0.1.1 quantal

My routing table:
➜ ~ route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default 192.168.0.1 0.0.0.0 UG 0 0 0 wlan0
link-local * 255.255.0.0 U 1000 0 0 wlan0
192.168.0.0 * 255.255.255.0 U 9 0 0 wlan0

Lastly, my module info for device:
➜ ~ modinfo rtl8192ce
filename: /lib/modules/3.5.0-17-generic/kernel/drivers/net/wireless/rtlwifi/rtl8192ce/rtl8192ce.ko
firmware: rtlwifi/rtl8192cfw.bin
description: Realtek 8192C/8188C 802.11n PCI wireless
license: GPL
author: Larry Finger <email@example.com>
author: Realtek WlanFAE <email@example.com>
author: lizhaoming <firstname.lastname@example.com>
srcversion: DD4F3D83A75531AC98862F2
alias: pci:v000010ECd00008176sv*sd*bc*sc*i*
alias: pci:v000010ECd00008177sv*sd*bc*sc*i*
alias: pci:v000010ECd00008178sv*sd*bc*sc*i*
alias: pci:v000010ECd00008191sv*sd*bc*sc*i*
depends: rtlwifi,mac80211
vermagic: 3.5.0-17-generic SMP mod_unload modversions
parm: swlps:bool
parm: swenc:using hardware crypto (default 0 [hardware])
(bool)
parm: ips:using no link power save (default 1 is open)
(bool)
parm: fwlps:using linked fw control power save (default 1 is open)
(bool)

Things I've attempted:
Turning off fwlps, ips. Attempted to compile a driver from upstream(realtek.com) and even tried the latest daily mainline kernel for Quantal. Also tried latest compat-wireless and switching out firmware. Tested Windows 7 and verified the card worked. Tested slackware 14, Fedora, Arch and they all exhibit the same issue.
Has anyone seen this before? What really baffles me is that I can not ping the gateway. To verify I can ping the gateway from another system:
λ ~ → ping 192.168.0.1
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
64 bytes from 192.168.0.1: icmp_req=1 ttl=64 time=1.35 ms
64 bytes from 192.168.0.1: icmp_req=2 ttl=64 time=1.22 ms
64 bytes from 192.168.0.1: icmp_req=3 ttl=64 time=5.11 ms

This also doesn't happen outside of my network as I was able to use this laptop at UDS-R which kind of points to a router issue but anything without a Realtek adapter works :\
I dont know if any Realtek developers monitor this site but has anyone run into an issue like this?
Thanks
Adam
Answer: For anyone interested, the relevant bug report is:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/902557
@Adam: I have the same setup as you (an X230 with the realtek adapter) and following these instructions fixed the issue:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/902557/comments/166
I am on Ubuntu 12.04 with 3.2.0-35-generic.
Comment: No luck unfortunately. When i strace a ping it returns a MSG_NOSIGNAL even though i can ping other devices on the network.
Answer: For me changing router to form 802.11bgn to 802.11bg` solved the problem. Answer found here: https://askubuntu.com/a/483040/12325


Format zsh prompt according to the value of an environment variable

Question: I want the color of my zsh prompt to be decided based on whether I'm inside a tmux session or not. In bash, it can be done by checking the value of $TMUX, but I can't find an equivalent method in zsh. Is it possible in zsh?
Comment: The `TMUX` variable is independent of the shell you use. What is the issue you're having?
Comment: In bash I could put `${TMUX:+colorcode}` in the PS1 variable, to set the color, it doesn't work in zsh and I can't find a similar way to do it in the manual.
Comment: The `%{x.t.f%}` can only test for a predefined set of conditions.
Answer: In zsh, the prompt_subst option is off by default. If you want to use variable substitutions in your prompt, turn it on.
setopt prompt_subst
PS1='$foo'

For $TMUX, though, you don't need this. The value doesn't change during the session, so you can initialize PS1 when the shell starts.
setopt prompt_subst
if (($+TMUX)); then
  PS1='[tmux:${TMUX_PANE//\%/%%}] %# '
else
  PS1='[not tmux] %# '
fi

Note that prompt expansion happens after variable susbtitution, this is why the percent signs in the variable's value need to be protected.
Answer: When launched tmux will inherit the environment variables of the shell that launched it (like all other processes).
From that point tmux will then bestow those same environment variables onto the pseudo terminals it creates.
Except for one important environment variable
$TERM

The tmux server will hold the value give to it by the original shell.
You can query this with
<C-b>:display-message "$TERM"

on my system this gives xterm-256color.
but all pseudo terminals tmux starts will get something like
$TERM=screen

on my system I set the pseudo terminals to TERM=screen-256color so that programs (vim) running inside tmux know the color capabilities of the terminal. You can do this with this tmux command
set -g default-terminal "screen-256color"

Either way you can check for the presence of this string and set your prompt accordingly
~/.zshrc
if [[ $TERM == *screen* ]]; then
    # you're in tmux, congratulate yourself :)
    # set your tmux prompt here
else
    # you're not in tmux
    # set your fallback prompt here
fi


How to change i3 theme

Question: So I'm trying to change the theme of i3 to this:
http://lovelybacon.deviantart.com/art/i3-Finally-it-all-comes-together-563203883
and I have no clue how to do this, does anyone have a tutorial or can tell me how to do it as I quite cannot find how to do it. (I'm using arch if it matters)
Answer: To my understanding there's no "change theme and apply" utility for i3. There's lxappearance, but that just changes your GTK theme, which isn't really the deal here.
It's all about editing your i3config and i3status configuration file. i3config should be located under /etc/i3/ but I would recommend you to copy it to your /home folder.
Answer: I found lovelybacon i3 conf on the interweb ..  http://dotshare.it/dots/1022/ and http://dotshare.it/dots/1030/  I have not tried it.. But it looks like only i3 conf settings to me.. Also an other background image. I use feh to set my background image.
I don't like to link conf files links in a response. Should I copy paste the conf here?

How to change i3 theme


Is it possible to track allocation/deallocation?

Question: As far as I can tell, this is isn't possible, so I'm really just hoping for a left field undocumented allocation hook function.
I want a way to track allocations like in _CrtSetAllocHook, but for C#/.NET.
The only visibility to the garbage collector/allocation appears to be GC.CollectionCount.
Anyone have any other .NET memory mojo?
Answer: The CLR has a 'profiling API' that hooks into pretty much everything - it is what the commercial .NET memory profiling products use, I believe. Here is an MSDN link to the top level of the documentation: .NET Framework General Reference: About the Profiling API
See this MSDN magazine article for an introduction to the memory piece: Inspect and Optimize Your Program's Memory Usage with the .NET Profiler API
Answer: I would just use Red Gate's ANTS Profiler. It will tell you a lot about what's going on in memory without you having to learn the profiling API yourself.


Bias or fallacy of assuming rank when two things differ?

Question: Is there a name for the assumption that, if two options or things are different from each other, one must be necessarily better than the other?
Comment: Could you give an example? [Apples and oranges](https://en.wikipedia.org/wiki/Apples_and_oranges) come to mind, "a false analogy... such as where an apple is faulted for not being a good orange".
Comment: I've noticed in discussions of science fiction, for example, where divisions are made between "hard" and "soft" or in discussions of fantasy as "high" or "low," emotions start running high quickly because the participants assume descriptions (usually "soft" and "low") are meant as pejoratives.
Comment: Or, for another example, the idea that either an omnivore diet or a vegetarian diet must be the better one, when each is "better" along certain dimensions, or in certain situations. Or the idea one nose shape or skull shape (or other trivial physical detail) must be "better" than another. The most obvious name for this idea I could come up with is "false heirarchy" or "assuming a heirarchy," but these phrases don't seem to have been used this way before.
Comment: If I catch your drift we can add snobbery, elitism and racism to that list. But in all of these examples it is not that people mistakenly *assume* there must be a ranking between two things, they affirmatively *judge* one as "morally superior" to the other. Terms for this, like illusory superiority, are more typically applied to people than things, but can be projected to diets or fiction too, where people attach themselves to the "high" vs "low". Much is wrong with such self-serving judgments, but it is not a mistake of reasoning or fact, I think. "Moral worth" is *assigned*, not inferred.
Comment: As formulated, "better than" implies an absolutism about differences (e.g. 19 would be in all cases, even independently of human minds, better than 37). Differences are subjective (depends on the subject) and relative (depends on the object). If x=10+9, then 19 is better than 37 for x (the object) in such equation, for my goals (the subject).
Answer: This sounds like a false dichotomy.
"Better" or "more good" are very fluffy, vague terms. As you said, it may be that the options are entirely unrankable.
If someone is attempting to force ranking or choice, they are committing a false dichotomy because they are neglecting option 3; that both are equal or non comparable.


How to prevent 206 HTTP status codes

Question: I recently upgraded my website from Joomla 1.5 to Joomla 3.0 and I have been getting a crazy amount of traffic through 206 codes than previously with Joomla 1.5. I don't know where to start to go looking for the problem if it even is a problem (if it's just part of the Joomla upgrade) so can someone give some insight to what steps should I take to prevent the amount of bandwidth being used by these HTTP status codes?
Answer: I don't think it is a problem.    Your server should only respond with 206 Partial Content if the client requested only part of a document.
This might happen if the request got interrupted the first time for any reason (including the user pressing the stop button in the middle).
This may have started happening all of a sudden because your webserver now supports features that can enable it such as ETags or LastModified.
Comment: So the best thing to do would to contact the host since the amount of bandwidth has 10 folded in the last month?
Comment: 206 partial content responses should be saving you bandwidth since the users are not downloading full pages.  If bandwidth usage has increased, it doesn't seem likely to be related to 206 statuses in your log files.
Comment: 1.1 GB of bandwidth was used with the status so I am quite confused... But either way I will refer it to my host :) Thanks for the input!

How to prevent 206 HTTP status codes


How to find the last monster in Hotland/Core?

Question: I am currently doing an Undertale Genocide Route and I am in Hotland/Core, just before fighting Mettaton.
I'm trying to hard to find the final monster for me to kill but I don't know where to look.
I need help trying to figure out how to find this one last monster because I have been wondering about for hours.
Comment: @Karlyr Not sure what it was like before, but you do now. The fight with NEO Mettaton will have a different ending if you don't kill them all, saying "If you tried to be all evil, you failed."
Comment: Oh yeah right... It's just the hotlands that you can "skip"... But it's merged with core. I'm dumb.
Comment: Have you received a message saying that (No one is here) or something like that? If you got that there are no monsters for you to kill. Besides mettation... And ASGORE
Comment: Well, not to be a party pooper... but you don't need to kill any in the Hotland/Core to have the genocide ending. Unless they fixed it recently.
Answer: The problem is that the more monsters you kill, the less frequent the random encounters are. This can make the last couple very tedious. However, there is a cool hack/trick that I have found to help you get the last one.

Go to an area that monsters definitely can spawn in. They usually don't spawn in puzzle rooms, so just go somewhere that you remember having a random encounter in.
If you are in fullscreen, hit F4 to go back to windowed mode.
Hold down an arrow key. Any arrow key, doesn't really matter, but don't walk into a wall or an object.
While you are still holding down the arrow key, press alt-tab. This will cause the game to lose focus. However, Frisk will continue to walk without actually moving. The game registers this as you walking.
Watch youtube until a random encounter happens. This shouldn't take more than 2-3 minutes at most.

This doesn't make grinding very much faster, but it definitely makes it less tedious.
Comment: How do you know if you did the game un-focus correctly?
Answer: On the bridge right next to Mettaton NEO, walk towards the north part on the bridge. Once you hit the north wall, hit arrow UP and arrow DOWN and hold it. You will get the last couple encounters. Hope this helps people.
Note: DO NOT GO INTO METTATON'S FIGHT ROOM UNTIL YOU EXHAUST THE COUNT OR THE GENOCIDE ROUTE WILL BE ABORTED!
Answer: In regards to Hotland/Core, the last three monsters are actually not random encounters. The last three are in Core. I can't remember EXACTLY where it is in Core, but you will get a mini cutscene of a silhouette of the monsters and then get to fight them.
I'm not sure if there was a patch to change this, but as of April 4th, 2016, this was the way I had to kill all of the monsters in Hotland/Core
EDIT: The spot where you find the last three is the same spot as the three monsters on the bridge in the Pacifist run, which I believe is the very north part of core
EDIT 2: I just did the genocide route again last week and this was how to get the last three. So I am unsure how this could be wrong.
Comment: Not sure why the down vote. This is correct
Comment: no it's not lol
Comment: @alex I just did it.
Comment: yep. That's why your post has 2 down votes.
Comment: Because I did it and thats how I beat the genocide route?
Comment: Ugh I just can't win this argument
Comment: No, please explain how this is wrong so I may modify and/or delete it.
Comment: Well the reason you have down votes is because it doesn't have a link to where they are or around where they are.
Comment: I will try to specify
Comment: ok  then. There might be a undertale wiki link to it.


IPhone and Cocos2d Sprites/Layers

Question: I am using cocos2d-iphone to place Sprites onto a Layer to setup a game playfield.  At certain points in the game, certain Sprites need to be removed based upon game conditions.  What I would like to do is setup an array of Sprite pointers, but I have two questions:
What's the best way to place Sprite pointers in an array?
How does one remove the Sprite in cocos2d with only a pointer to the Sprite?  I know how to do it from its parent layer, but that is too runtime intensive for the main game loop.
Thanks in advance!
Comment: Please feel free to accept your own answer instead of mine. By the sound of things, you were able to get it working using your method, and I won't be offended! :)
Answer: The Sprite class inherits from CocosNode, so you should be able to call spritePointer.parent.remove(spritePointer)
Answer: I figured it out.  If anyone else is interested, the way to do it is to declare an array of Sprite pointers, such as:
Sprite * mySprites[10][10]; // assuming a 10x10 playfield where obstacles get placed

Then, when setting up your Sprites:
mySprites[0][0] = [Sprite spriteWithFile: @"obstacle.png"];
[myLayer add:mySprites[0][0]];

To remove the Sprite:
[myLayer remove:mySprites[0][0]];

Answer: There's also [mySprite removeFromParentAndCleanup:YES].

IPhone and Cocos2d Sprites/Layers


How much water do betta fish need?

Question: How much water do betta fish need?
Comment: http://bettafishawarenessday.blogspot.co.nz/2012/10/the-betta-fish-tank-debate.html?m=1  might be a good place to start. From reading it there is a lot of debate. 5 gallons seems like a good point, as you can establish a nitrogen cycle without stressing the beta with an overly large territory. There are petitions for a gallon minimum so the tank is temperature stable and there is space for a plant(hiding)
Answer: You shouldn't keep a betta in anything under about 20 litres. The shops will often tell you that 5 litres is enough but it's really not.
You'll want to have at least 20 litres for a few reasons. Firstly, as the fish is always creating waste, the more water you have per fish, the more diluted the waste is in that water. More water, less toxic ammonia (or nitrates) hanging around in the water.
Secondly, small volumes of water are notoriously difficult to keep at consistent levels (of pH, KH, temperature, etc.) Even 20 litres is still a very small amount of water. Anecdotally, I had a a 20 litre tank initially and it was far harder to keep at consistent levels than my 180 litre tank. Get the biggest one you can realistically stretch to.
Remember, getting a fish is like getting any other pet except you also have to provide the environment for it too. If this is your first fish or you don't know what the nitrogen cycle is then please do your research. This hobby can be incredibly rewarding but it can also be incredibly upsetting if you get it wrong.

Further Reading
Nitrogen Cycle
Betta Feeding
General Care
Useful DIY Fishkeeping Videos

How much water do betta fish need?


Leveling a bathroom floor - toilet in the low spot

Question: We are upgrading the bathroom and the floor (ceramic tile over installed over plywood) is out of level and the low spot is around the toilet. I had thought of using floor leveler but I now don't think that will work.  It seems like floor leveler would just run down the opening for the toilet drain pipe. Open to any suggestions.
Comment: That's pretty sizable. Is the foundation solid at the dip? Sistering would be the best overall though obviously the most work as well since you'd need to take out the tub and sink cabinet, too. If you're up to it, go for it! Did pretty much the same in my house. However, it will be an added challenge unless you also take out the drywall below for reconnecting toilet (and maybe tub) drain. Could be done if you only put in the subfloor at those locations so you can still reach in the joist bays and then finish laying the floor once the drains are connected and tested.
Comment: So you're implying that it's lower by more than the thickness of the flange which is pretty significant. I'm assuming this must be an older house so there is likely water damage that has caused the floor to sag there over time. Do you have access underneath to inspect for damage? Or are you simply mean the entire bathroom floor is flat but not level? In that case I'd be tempted to leave it unless it's obvious. How much do you think you'd need to build it up at the toilet?
Comment: Yes, this is an old house. Unfortunately (at least for this) the previous owners finished the basement so these is a drywall ceiling under the floor joists. They also put .5" plywood and ceramic tile over the old floor boards. I have removed most of the tile and there is water damage around the tub which will need to be repaired. Also, the plywood does not extend under the tub. Front wall to back is a bit over 1.5" drop and about the same from side walls to center of the back wall. The toilet sits noticeably crooked. I'm thinking my best bet might be taking up the floor and sister joisting it.
Answer: Depending on how large of an area is sunken, you could cut up the old plywood with a circular saw. Sister boards to the joists and add cross members to the cavities to raise the area to match the surrounding floor. Follow up with plywood and then cement board before tiling and you should have a solid, fairly level floor to work with. This can all be done  easily even though the basement is already finished. This seems preferential to any floor leveler, since you'd actually be addressing the problem, which is a sunken floor.
It would also be a good time to inspect the existing floor joists and see how damaged they may be. If the damage isn't extensive, doubling them up my suffice, or you may need to replace larger sections entirely.
Answer: Self leveling products should normally be no thicker than 1/4 inch.
If it is less than 1/4" difference.
Simply cover the flange hole with anything from a plastic bowl or whatever generic item you come up with.
Rub some oil (cooking oil works) around the edge of the "bowl covering the hole" so when the self leveling product dries, you will have no problem removing the "bowl".
Comment: @Karl You could use layers of 1/4" underlayment to reduce thickness of compound needed. I did that in a few sections of my house as well (up to 1.5" like your's). However, you need to verify the foundation and joists are good where the dip is first if you go that route. Plus I'm not sure how you'd set the toilet since the flange would then be 1.5" below floor level. IDK if anything exists to permanently extend the flange that far.
Comment: Thanks - good ideas, but I need much more than a .25" difference.


Install pdflatex via SSH on Amazon EC2 instance

Question: I need to install pdflatex on my Linux powered machine (Amazon EC2 instance, didn't decided yet which distribution would be the best so also feel free to give a hint) because I want to connect pdflatex & PHP to produce rendering of LaTeX code to PDF on my website (so user could type in LaTeX, click render and download a PDF, like http://www.scribtex.com). Can you give me some directions?
Comment: Did you build this system? Do you start a new pdflatex process each time you make changes?
Answer: Depending on your instance, you might already have a lot of tex tools installed. So when you get it, first check if they're there.
That being said, you can grab the pdftex source from the net using wget, and then compile it from there (assuming Amazon gives you compilers, I've never used their service). Something like this:
wget http://sarovar.org/frs/download.php/1292/pdftex-1.40.10.tar.bz2
tar xf pdftex-1.40.10.tar.bz2
cd pdftex-1.40-10
./configure
make
make install

Those commands will probably be different based on what kind of environment they give you. Just remember that you can download any file from the net using wget or curl. Once you've got that down, downloading source and packages is a breeze. Good luck!
Answer: You can install the texlive-pdftex from any repository. For instance in current Amazon Linux (based on redhat) this appears:
$ yum search pdftex
Complementos cargados:priorities, update-motd, upgrade-helper
992 packages excluded due to repository priority protections
====================== N/S matched: pdftex ======================
texlive-pdftex-bin.x86_64 : Binaries for pdftex
texlive-pdftex-def.noarch : Colour and Graphics support for PDFTeX
texlive-pdftex-doc.noarch : Documentation for pdftex
texlive-iftex.noarch : Am I running under pdfTeX, XeTeX or LuaTeX?
texlive-pdftex.noarch : A TeX extension for direct creation of PDF
texlive-thumbpdf.noarch : Thumbnails for pdfTeX and dvips/ps2pdf

Answer: This question would possibly be on-topic on TeX Stack Exchange. If you are using Linux, you probably want to use TeX Live. Specifically, two reasonable choices are:
1) Use Debian (or Ubuntu) TeX Live packaging. The Debian TeX Packaging is quite good. It is also, mostly a one man effort, unfortunately, by Norbert Preining.
2) Use upstream TeX Live. Norbert describes how do this on Debian.
Answer: The command I used recently to install pdflatex on an AWS instance for a similar application was:
sudo yum install texlive-pdftex texlive-latex-bin texlive-texconfig* texlive-latex* texlive-metafont* texlive-cmap* texlive-ec texlive-fncychap* texlive-pdftex-def texlive-fancyhdr* texlive-titlesec* texlive-multirow texlive-framed* texlive-wrapfig* texlive-parskip* texlive-caption texlive-ifluatex* texlive-collection-fontsrecommended texlive-collection-latexrecommended


Prime with digits reversed is prime?

Question: Well, just another idea came up into my mind and i have no idea how to solve it :D
Is there infinitely many prime numbers, which are not repunits and their inverse is also prime? (For example, inverse of 31 is 13 which is also prime. i didn't have any other name to describe the function!)
P.S:I now know they are called Emirps.
Comment: Do you allow palindromic primes? It is conjectured, but not proven, that there are infinitely many repunit primes (eg 11).
Comment: look at http://en.wikipedia.org/wiki/Emirp
Comment: are reverse ordered prime numbers, e.g., $31\rightarrow 13$, which are still prime, are infinitely many?
Comment: and for repunit I suggest http://en.wikipedia.org/wiki/Repunit
Comment: well i bet i should say that they are not repunits.
Comment: 13 and 31 are emirp (decimal notation).  But D and 1F are not emirp (hexadecimal notation).  It seems a strange question to me.
Answer: Actually, it has a name and it's quaintly called an "emirp". (The word "prime" in reverse.)  The link given is to the Online Encyclopaedia of Integers' list,
$13, 17, 31, 37, 71, 73, 79, 97, 107, 113, 149, 157, 167,\dots$
While there are an infinite number of primes, I believe it is an open problem if there is an infinite number of emirps.
P.S. Regarding terminology, given $x$, then its "multiplicative inverse" (or "reciprocal") is $1/x$. For functions, for ex, given $\sin(x)$, then its "inverse function" is $\arcsin(x)$.
Comment: Ah, some things get lost in translation, do they?  :)
Comment: Confusingly, in French it's the other way around; the "réciproque" of $\sin(x)$ is $\arcsin(x)$, and "l'invers" of $\sin(x)$ is $\csc(x)$.

Prime with digits reversed is prime?


Duplicate tags sql-like and like-operator

Question: Both have a description which point to the same concept.
like-operator
sql-like
Should the be merged? Synonyms?
Comment: Related: [I would like to clean up like](http://meta.stackexchange.com/q/142241/146015)
Answer: Thinking for the long term, they can't really be synonyms. Personally I don't like like-operator - while a SQL practitioner may know exactly what it is (and it is a technically correct term), there is nothing to stop facebook questions using it mistakenly. And what's to prevent LINQ questions using it? When this happens you end up in the same place as what you were with just the like tag.
There are enough different usages of like for it to be necessary to use tags like sql-like for disambiguation. In a lot of ways it is very similar to the group tag - it has a bunch of uses.
To prevent this becoming the same old mess just with a different tag, I would suggest that like-operator is synonymed to sql-like, and sql-like becomes the chosen tag to use for SQL related questions. As mentioned in my comment, having the context prepended on the front of the like tag makes it easily understandable by everybody - there are a lot of people out there who don't think too much when choosing their tags.
Comment: There are 0 questions at the cross-section of [tag:facebook] and [tag:like-operator] ([combined tags link](http://stackoverflow.com/questions/tagged/facebook+like-operator)). It's not because something can potentially be misused that it isn't the right thing to use. The swarm (a.k.a. Facebook question askers) will keep using [tag:like] until we make it something else, if we do.
Comment: As for LINQ, it's a good point, but there isn't a direct `LIKE` in LINQ, AFAIK. If I had a LINQ question regarding `LIKE`, I wouldn't find it that much of a stretch to use [tag:like-operator], if the goal is to emulate its functionality.
Comment: @MPelletier My point is that while `like-operator` is not incorrect, if this becomes the chosen one you will eventually end up in the same place: different tag, same mess. With the technology/stack/context prepended on the front **everybody** can easily understand which one to use. Overall though you have a good point, there is clean up required.


Irreversibility and increase of number of microstates

Question: We know,in an irreversible process,always entropy of an isolated system increases,from Clausius inequality.Again,entropy is the logarithm of the number of accessible microstates of a system.How can we merge these two ideas,i.e,an irreversible process always increases the number of accessible microstates of a system?
Answer: Here is a combinatorial example that demonstrates the answer to your question. Say we have two systems $A$ and $B$. $A$ is represented by a two-compartment box with one ball; $B$ us a two-compartment box that is empty.  We then combine the two systems into a single box with four compartments and one ball.

Before combining the systems we have 2 microstates in $A$ and 1 microstate in $B$. After combining we have 4 microstates in the system $A+B$. That is:
$$
   \Omega_{A+B}> \Omega_A \Omega_B \Rightarrow
   \boxed{\vphantom\int\log\Omega_{A+B} > \log\Omega_A+\log\Omega_B}
$$
This example represents irreversible expansion in an isolated system. By combining the two smaller boxes into a larger box we increase the number of possible microstates because the balls of each box can now be found in the other part as well. Generally and irreversible process takes place when a constraint is removed (here, the wall that separates the two boxes) and by doing so the system reaches more microstates that were previously unaccessible.
Answer: Let $\Omega_1$ be the set of accessible microstates at the beginning of a thermodynamic process, and let $\Omega_2$ be the set of accessible microstates at the end. Let $P$ denote the time evolution operator acting on microstates, so if we start with a microstate $\omega_1$ then at the end of the process, the resulting microstate is $P(\omega_1)$.  Note that the laws of physics are reversible on the microscopic level. What this means is that there exists a time-reversal operator $T$ acting on microstates, and a time-reversed evolution operator $P^{*}$ (itself describing a physically allowed process; for example, the time-reverse of expanding the container of a gas is contracting it) such that if $\omega_2 = P(\omega_1)$ then $T\omega_1 = P^{*}(T\omega_2)$ (where $T^2 = 1$). Note that this implies that $P$ is invertible, that is it conserves the number of microstates. (However, in general the inverse function $P^{-1}$ might not represent a physically allowed process).
If we take any accessible microstate at the beginning and then evolve it in time, at the end of the process the resulting microstate is clearly accessible. That is, $P(\Omega_1)\subseteq \Omega_2$. On the other hand, the reversibility of $P$ shows that $|P(\Omega_1)| = |\Omega_1|$ (where $|\cdot|$ is the size of a set). Therefore $|\Omega_1| \leq |\Omega_2|$ (this is the "proof" of the Second Law of Thermodynamics!)
Now any suppose that $|\Omega_1| = |\Omega_2|$. It follows that $P(\Omega_1) = \Omega_2$. I will assume that if a microstate is accessible then so is its time-reverse. Hence we see that $P^{*}(\Omega_2) = P^{*}(T \Omega_2) = T \Omega_1 = \Omega_1$. That is, the process $P^{*}$ precisely implements the reverse thermodynamic process. So processes that are thermodynamically irreversible must have $|\Omega_2| > |\Omega_1|$.
What happens for irreversible processes is that $P^{*}(\Omega_2) \supsetneq \Omega_1$. So there is some very small fraction of microstates in $\Omega_2$ which go back to the initial macrostate under $P^{*}$, but the probablity that we are in such a microstate is vanishingly small for large systems. Indeed, this probability is given by $|\Omega_1|/|\Omega_2| = e^{S_1 - S_2}$, (where we introduced the entropy $S_j = \log |\Omega_j|$), and entropy is an extensive quantity so the probability is exponentially small in system size.
Exercise for the reader: work out where the "thermodynamic arrow of time" slipped into the above argument. It's subtle!


what is memory aliasing?

Question: I was reading about ARM M series and somewhere it was written that:
 "the flash memory area is aliased from address 0x0000 0000".
what does it mean?
Comment: It means that it can be accessed using this memory address in addition to some other mapping.
Answer: A typical microprocessor system works by having a CPU send an address to the memory subsystem along with either a read request or a write request containing a piece of data to be written.  Various other devices in the system will look at the addresses sent out from the CPU, decide whether they are "interesting", and react accordingly.
A typical memory subsystem will have an address input along with some control inputs, and a data input and output.  Some interface logic will look for the CPU to generate addresses that match certain criteria and, if such addresses are observed, signal the memory that it should read or write them (the memory subsystem will receive the lower portion of the address, which it will use to select an individual byte or word).
If a system has 64KB of memory mapped from 0x08000000-0x0800FFFF and the CPU issues request to write 0x99 to 0x08001234, then the memory will process that as a request to write 0x1234.  If the memory were also wired to respond to addresses 0x00000000-0x0000FFFF (which might be accomplished by simply having its interface logic ignore bit 27 of the address), then a request by the CPU to read address 0x00001234 would be seen by the memory as a request to read 0x1234 (the location that was previously written).
In many cases, the memory itself won't know or care that the write was done at a different address from the read.  It simply sees a write to what it regards as address 0x1234, and a read from that same address.
Answer: In Cortex-M, the processor always boots by reading the stack pointer from address 0x00000000, and the vector table starts at 0x00000004. The documentation you're reading here will be referring to an implementation of the processor, since it affects the memory system (not the processor).
Depending on how the design is arranged with bootloader and main code, it might be possible to 'remap' the memory map after boot. This might, for example, give you a way to change the interrupt vectors. Typically before changing the configuration of the address decoders, you would branch to the 'new' address of your code. To make this easier, two different memory addresses can map to the same physical memory (this wastes address space, but there is 'plenty' with 1Gb of code space on these devices).

what is memory aliasing?


Using collection_select with an array

Question: I am trying to use a dropdown in my edit.html.erb that is populated with a list of icon filenames (on the server). I used an array of label/value pairs to populate the list, which works great, except I want the dropdown to be preselected with the value that is currently in the record. When using collection_select with an actual model, the current value is selected. Do I have to create a tableless model instead of the array of structs to make this work?
Answer: you can use options_for_select (API) and pass value that you want to be selected as second argument

Using collection_select with an array


gdal.rasterizeLayer in QgisPython results in Nan values

Question: I have a vector layer projected in WGS84. I would like to use gdal.rasterizeLayer() from the python console to convert it to a raster. I would like to burn values from a field. I followed the gdal cookbook and adjusted the code based on the answer to this thread.
Here is the code I used:
import math
import os
from osgeo import ogr, gdal

# 1. Define pixel_size and NoData value of new raster
NoData_value = -9999
x_res = 0.5 # assuming these are the cell sizes
y_res = 0.5 # change as appropriate
pixel_size = 1

# 2. Filenames for in- and output
_in = "D:\...\\polyTry.shp"
_out = "D:\...\\poly2.tif "

# 3. Open Shapefile
source_ds = ogr.Open(_in)
source_layer = source_ds.GetLayer()
x_min, x_max, y_min, y_max = source_layer.GetExtent()

# 4. Create Target - TIFF
cols = int(math.ceil((x_max - x_min) / x_res ))
rows = int(math.ceil((y_max - y_min) / y_res ))

_raster = gdal.GetDriverByName('GTiff').Create(_out, cols, rows, 1, gdal.GDT_Byte)
_raster.SetProjection(source_layer.GetSpatialRef().ExportToWkt())
_raster.SetGeoTransform((x_min, x_res, 0, y_max, 0, -y_res))
_band = _raster.GetRasterBand(1)
_band.SetNoDataValue(NoData_value)

# 5. Rasterize why is the burn value 0... isn't that the same as the background?
 gdal.RasterizeLayer(_raster, [1], source_layer, options = ["ALL_TOUCHED=TRUE", "ATTRIBUTE=id"])

The photo below show the output raster with the green input polygons. Note the Nan values on the left (legend). I also inspected different x, y_resolutions (0.00416, 0.0833333). Additional attempts include creating a floating point and integer raster at both 32 and 64 bit (signed, e.g. gdal.GDT_Float64). All have failed and produced Nan values.
Also note that burn_values = [1] create a raster with all values set to 0.
How can it be solved ?
Answer: Try to define:
_raster = None
..in the end to close the new raster dataset.
Comment: Welcome to GIS SE. Please, edit and expand your answer. Explain the context and behavior of the code modification proposed by you


What to do if I forget surah during salat?

Question: My Question is "What To do if I forget surah in salaah?". Should I go to ruku or should I read any other surah instead of the surah I forgot. Few days back it happened to me and I just started reading another surah. Was I right?
Comment: Happend to me too. I forgot Surah e Nas last verse.
Answer: That would be a Shaytan of the category of Khinzib (خنزب) who come and distract you in prayer, make you forget what you are reading etc.  What you do is seek refuge in Allah, then blow three times on your left side.  And when I say blow, it is between blowing and spitting, meaning you are not really bowing, and you are not really spitting, but in between that.  Not many people practice this Sunnah now days, so it may come as a surprise to them.  See the Hadith in Saheeh Muslim.
Lastly if you forget the Surah you were reading, you may change the surah or deal with the ayahs you already read, for perhaps in the second Rak'ah you may remember the rest of it, and Allah A'lam.
Answer: The ruling of the surah after Fatiha is mustahabb. There are no reports of any companions doing sajdah sahw due to forgetting a Surah. If you forget a Surah you continue. If you didn't recite 3 ayat in this rakat, then fine, because as I said, even if you recite 0 ayat it's perfectly fine.
But remember something important, if you do sajdah sahw before Salam for not reciting ayat, then unfortunately the prayer is invalid. That's why, you should do sajdah sahw in the cases narrated from our Prophet, sallAllahu 'alayhi wa sallam, or don't. (But if you wrongly do a sajdah sahw after salam, then this does not invalidate the prayer.)
So in summary: Reciting a Surah is mustahabb. Because it's mustahabb, there's no sajdah sahw for it. Hence if you do a sajdah sahw for it before Salam, you will need to make-up for the prayer even if it's a few days later that you remembered it, but if you did sajdah sahw for it after the salam, which you shouldn't have, the prayer isn't harmed.
Answer: Recite it when you are next standing.  If no more left, recite the missed sura when you are sitting after Et ta hayatu.
At the end of the salah before you salut the angels on both sides, perform 2 more sajdas for repentance for the mistake.
Comment: pardon my question, we've been taught to perform 2 sujud after the at-ta-hiyatu. then again start from the at-ta-hiyatu then the durud and dua-e masura. but what if i forget after the at-ta hiyatu and remember before the salam? if you know the correct opinion then please help with reference.


Is there a formal proof for the superposition theorem?

Question: I was just wondering whether there is a formal prove for the superposition theorem in electric circuits? I tried searching it online but couldn't find anything sufficient. Most of the sources assume it follows from the definition of linear systems, but then how do you prove linearity without using the superposition theorem? Any input will be much appreciated!
Comment: Well, [Wikipedia states](http://en.wikipedia.org/wiki/Superposition_theorem): *"The superposition theorem for electrical circuits states that for a linear system[..]"*, i.e. the fact "The circuits are linear systems" is *assumed* to prove the superposition theorem, so I do not understand the question.
Comment: R. E. Scott, *Linear Circuits*, New York: Addison-Wesley, 1960.
Comment: *"how do you prove the linearity without using superposition theorem"* - the (differential) equation(s) constraining the circuit variables are linear.
Comment: @user40908 you don't prove linearity **using superposition theorem**, you first check if your circuit is linear in the variables of interest to you. That is the same as checking if the superposition holds.
Comment: Maxwell's equations are linear. As long as the response of the circuit elements is also linear then superposition works by construction.
Answer: There are a few key  bits of physics and math to understand here, but one does need to be very careful to avoid producing a circular argument. The key, concept I think is that of a

linear circuit element, for which the output is precisely proportional to the input.

The precise meaning of 'input' and 'output' depend on the precise device, but this does not matter so much. For a linear capacitor, if you double the charge on the plates, you double the potential difference across them. For a linear resistor, the potential drop between the terminals is proportional to the current through it. For a linear inductor, it is proportional to the rate of change of current.
It is important to note that not all circuit elements are linear. A diode, for example, will respond differently if you change its polarity. A light bulb will increase its resistance as the current increases. Iron-core inductors show hysteresis, so their inductance is different depending on whether their magnetization is increasing or decreasing. In general, most circuit elements will show some nonlinearity if you drive them hard enough (even if "hard enough" is "so hard that you fry it", which is also nonlinear behaviour).
The restriction to linear circuits, then, is part definition and part physics. You are explicitly ruling out, for your circuit, those elements which behave nonlinearly. If I hand you a circuit board with a complicated circuit printed on it, and you want to decide whether it is linear or not, you need to take it apart and measure the response curves of all its components. Are they all linear? Great! your circuit is linear.
Thus, when you start off your proof with "let $C$ be a linear circuit ...", you are assuming that this step (which is where most of the physics is) has already been completed. This is therefore a safe assumption to use in a proof, and it comes at the price of restricting the validity of the result to only those circuits that have been empirically checked to be linear.
This is essentially all you need. You know the (linear!) equations which connect the (charge / current / rate of change of current) in each element with the potential difference across it, and you can use Kirchhoff's laws (which embody charge conservation at each node and energy conservation along each loop, and therefore always hold) to link them up. This will naturally result in a linear system between your sources and your output. This linear system has the mathematical property that the final solution is the sum of what you'd get if each of the sources were turned on by itself in turn, which is what the superposition theorem, as stated in Wikipedia, states. If your system has the physical property corresponding to the mathematical linearity assumption, it will also have the physical property that corresponds to the mathematical result.
Answer: Superposition is essentially a mathematical concept. Inspection of a physical phenomenon and the choice of the mathematical model to represent it, define the mathematical relations that the phenomenon is suggested to be subject to, and superposition may be one of them.
For example, when we say that a capcitor follows the mathematical rule $I = C\frac{\mathrm{d}V}{\mathrm{d}t}$, and that an RC circuit follows the ODE $\frac{\mathrm{d}}{\mathrm{d}t}V(t)+\frac{1}{RC}V(t) = \frac{1}{R}V_{\text{in}}(t)$, then "automatically" we get the superposition property for $V_{\text{in}}(t)$ thanks to the mathematical nature of ODEs.
But, if you take into account that a capacitor is not linear (i.e. doesn't follow exactly $I = C\frac{\mathrm{d}V}{\mathrm{d}t}$) but rather a more complex non linear form, then superposition of $V_{\text{in}}(t)$ would not hold.
So, the "proof of superposition" is actually within the scope of mathematics, while the choice of the mathemtical model to represent a physical phenomenon is subject to theoretical and/or experimental studies.
Answer: There are many proofs, the problem is that they become too mathematical and hence end up distracting electrical engineering students from core electrical engineering.
Very rigorous proofs involve assuming your circuits can be represented as planar graphs. Additional assumptions including no short circuits, independent current and voltage sources only. Proofs involving dependent sources become complicated.
In any case, to do the full proof, you lay down KVL and KCL (node analysis, mesh analysis) and you end up with linear system of equations needed to solve the circuit.
Of course, you can just solve the linear equation using elementary linear algebra techniques, but if you pay careful attention you see that the equations are always of the form:
linear combination of node voltages = linear combination of independent voltage sources and current sources
(OR, of course, linear combination of branch currents ) = ...
(pay attention to the fact that the coefficients for the voltage sources and current sources in the above equations are simply algebraic functions of resistors ONLY)
... from here it should be easy too see that we can solve circuits by simply flipping on one source at a time (and keeping all other sources set to zero), and then adding up the "effects"
so to sum it up: what we are doing is assuming a linear system of equations exist, that this is system has as many unknowns as there are equations (not over/under specified) -- but we are not going to write this system down and solve it, instead, we set all V's and I's to zero, and flip back one V or I at a time and solve for currents/node voltages at a time.


Facebook group members without profile link?

Question: In the members list of a Facebook group I manage, some members are listed without a link to their profile (name only). What does this mean?
Answer: They are unavailable.
If you use a computer log into your Facebook account.
Go to members on the left and click. Down the middle there should be a list of every member starting from admin/mods etc. On the right you should see a list that says unavailable. You will find there name in there. We delete the ones that we can. Some won't let you.
Comment: Did that work for you?


Can I copy xcode from my applications folder to external hard disk?

Question: I downloaded xcode from the Mac App store on my home computer and it installed to around 11 GB on my applications folder. I tried copying the xcode app from the applications folder to my external hard drive where I was stopped mid-way and the error said some items can't be moved to due permission issues (that's not exactly what the error said but something like that). Is there any solution?
Comment: "The operation can't be completed because you don't have permission to access some of the items." @patrix
Comment: The exact error message actually would help us to help you :-)
Comment: You can do it with sudo from terminal. This will move all as root. If you got anyway issues after move you just need to run as root (via sudo) chown youruser pathtoexternalxcode, or chmod 777 -R ...
Answer: Have you reviewed the helpful details in this question?
I have successfully moved Xcode to a different drive (though in my case an internal SSD), but as the answer says a simple move doesn't quite sort everything out, and you need to fix where various Command Line Tools think the install is. The problem with permissions is probably not due to it being an external drive. You need to get enough permissions to move files, which you can do at the command line ('terminal' application). If you don't know how, then look for help on moving and relinking directories in OS X and proceed carefully having practiced on tiny directories first, having taken a backup.
PS I can't comment on the question, wpbut I think your mean move not copy which makes a big difference.
Answer: There are a lot of possible solutions, including, making use of symlinks, dual booting two versions of macOS (one on external SSD), and many more.
But the best way I found was to create a new macOS user and change its home directory to external SSD (by going to advanced user settings under Users & Groups System Preferences).
The exact steps I followed:

Create a new APFS partition on external SSD with 100GB storage. (say NewVol)
Create new macOS user and change its home directory to /Volume/NewVol/user
Logged into the new user with external SSD connected, and installed xcode in ~/Application. (i.e. the local Application folder, not /Application)

Why this works best is because you don't need to manually manage symlinks, also symlinks might create problems during builds. All the required files (including builds and temporary files) are stored in user directory, so no space occupied on internal drive. Also, no hassle of installing a complete separate OS, and going through cycles of reboots to switch the OS.


$K[X]$-modules are $K$-vector spaces with a linear transformation

Question: In the Atiyah's book there is this example about $A$-modules.

Let $A=\mathbb{K}[x]$, where $\mathbb{K}$ is a field. An $A$-module is a $\mathbb{K}$-vector space with a linear transformation.

Can someone explain this claim to me?
Answer: Let $\;V\;$ be a $\;\Bbb K\,-$ vector space, and let $\;T:V\to V\;$ be any linear operator. Then, $\;V\;$ gets a structure of $\;\Bbb K[x]\,-$ module if we define
$$\forall\,v\in V\;,\;\;x\cdot v:=Tv$$
and then we extend this action in the obvious way, meaning:
$$\sum_{j=0}^m k_jx^j\cdot v:=\sum_{j=0}^mk_jT^jv\;,\;\;k_j\in\Bbb K$$
I'll leave to you to check details.
Comment: @LordShadow Yep, thanks.
Comment: "$T:A\to A$ is any linear operator$" , it think it has to be $V$ not $A$. Please correct me if I'm wrong
Answer: Say $M$ is the $k[x]$ module in question which is also a $k$ vector space by means of the inclusion $k \hookrightarrow k[x]$. The action of $x \in k[x]$ is that of a linear transformation i.e. $x(am) = a x(m)$ and $x(m+m') = x(m)+x(m')$. Conversely, given any linear $L: M \to M$ we can let $x(m) = L(m)$ to define a $k[x]$-module structure on the vector space $M$. Note this while the action of $k$ is faithful because it is a field, the action of $k[x]$ may not be. For instance the linear transformation could be nilpotent or something.
Answer: Working with $K$-vector spaces and (unital) $K$-algebras....

Every $K[x]$-module is a $K$-vector space, because $K \subseteq K[x]$.
The $K[x]$-module structures on a vector space $V$ are in bijection with $K$-algebra homomorphisms $K[x] \to \mathrm{End}(V)$.
$K$-algebra homomorphism $K[x] \to \mathrm{End}(V)$ are in bijection with elements of $\mathrm{End}(V)$.
Answer: I want to supplement DonAntonio's Answer, because his answer seems to give a converse of what OP really asked for. To make the answer whole, I prove the both direction for OP.

Fact: Let $k$ be a field, and set $A:=k[x]$. Then, an $A-$module is a $k-$vector space with a $k-$linear map $T:V\longrightarrow V$ given by $T(v):=\mu(x,v)$, where $x$ is considered as a polynomial in $k[x]$ and $\mu$ is action in the definition of modules.
Conversely, given any $k-$vector space $V$ and any $k-$linear map $T:V\longrightarrow V$, we can turn $V$ into an $A-$module using the map $\mu:A\times V\longrightarrow V$ defined by $\mu(f(x),v)=\mu(\sum_{i=0}^{n}a_{i}x^{i},v):=\sum_{i=0}^{n}a_{i}T^{i}(v)$, for any $f(x)\in k[x]$ and $v\in V$.

Proof:
Let $V$ be an $A-$module with action $\mu:A\times V\longrightarrow V$. Then, $V$ is clearly a $k-$vector space, because all the elements in $k$ can be considered as constant polynomials in $k[x]$, and thus the action of $A$ on $V$ provides the scalar multiplication of $V$ by $k$.
Moreover, the axioms of $\mu$ ensure that $T$ is linear. Indeed, for any $v,w\in V$ we have $$T(v+w):=\mu(x,v+w)=\mu(x,v)+\mu(x,w)=T(v)+T(w).$$ Further, for any $a\in k$ and $v\in V$, note that the scalar multiplication is provided by $\mu$, which means that to prove $T(av)=aT(v)$, what we actually need to show is that $T(\mu(a,v))=\mu(a,T(v))$. This is true, because $$T(\mu(a,v)):=\mu(x,\mu(a,v))=\mu(xa,v)=\mu(ax,v)=\mu(a,\mu(x,v))=\mu(a,T(v)).$$
The converse direction is a trivial check of the axioms of $\mu$. The proof is concluded.

Just a remark here that, if you are new learner of module, do not write the action map as multiplication or as a dot $\cdot$. This will confuse everything. Just be heavy in notation and write $\mu$, which will make things clear.
So the axioms of the "multiplication'' are: $\mu:A\times M\longrightarrow M$ is a mapping such that for all $a,b\in A$ and $x,y\in M$, we have
\begin{align*}
\mu(a,x+y)&=\mu(a,x)+\mu(a,y)\\
\mu(a+b,x)&=\mu(a,x)+\mu(b,x)\\
\mu(ab,x)&=\mu(a,\mu(b,x))\\
\mu(1_{A},x)&=x.
\end{align*}


I can't get Steven to show up. Am I doing something wrong?

Question: I can't get Steven to show up in Pokemon Soul Silver. Please do tell me if I am doing something wrong
Answer: You need to obtain all 16 badges, thus beating the elite four in the process. Then go and defeat Red at the top of Mt. Silver. Then Steven should appear in the Silph Co building in Saffron City. Then pick the colour of the Hoenn starter you want (Green - Treeko, Blue - Mudkip, Red - Torchic). I'm purely guessing this is what you are looking for as you haven't made it very clear where you are in the story or what you have tried.

I can’t get Steven to show up. Am I doing something wrong?


Why do internal forces support conservation of momentum but not law of conservation of energy when a shell explodes?

Question: When a shell explodes, we get several pieces with different kinetic energies but the momentum is conserved since no external force is acting. But the sum total of the kinetic energies of the pieces is more than the original kinetic energy of the shell. Now by conservation of energy, work must be done to change kinetic energy of a system. This work is done by the internal forces. But for conservation of momentum, the internal forces should add to zero. Hence there should be no net force and hence no work.Then why is the momentum conserved if the internal forces do work?
Comment: It is conversion of chemical potential energy to kinetic energy, in the case of dynamie for example that conserves energy. the total system has to be considered
Answer: The answer is straightforward. As we know that energy can neither be created nor be destroyed the total energy before and after an event must remain constant. The key word is total energy. Before the explosion the bomb (or anything you're bursting) had potential energy in the form of chemical energy.
When you ignite it you provide enough energy to break bonds, that further provide the energy for throwing the materials outwards. The kinetic energy was zero initially but as you might remember from the law of conservation of energy the total energy is conserved.
If you manage to calculate the chemical energy stored in the bond by using bond energies and compare it to the kinetic energies of shell materials you'll see that they are equal.
Think about when you throw a ball upwards. At each point in the trajectory the total energy i.e. the sum of Kinetic and potential energy was the same. At the top of the trajectory the kinetic energy is zero but we still say that energy was conserved, right? Because we're looking not just at Kinetic energy but at the total energy
Comment: Also, conservation of momentum is used to calculate velocities because it is convenient to measure the velocities of the broken pieces than measuring the potential energy of the chemicals involved.
Comment: OK @Sad_lab_rat, I got ur   point of conversion of chemical energy into kinetic energy. But when we say that " momentum is conserved if no external forces act on the system " , we assume internal forces add up to zero. But my point is that if internal forces of the system(the shell ) do work to provide kinetic energy, their sum total shouldn't be zero . In this case how is the momentum conserved ?
Comment: Imagine that you and one of your friends are pulling a rope from its end points. Both of you are applying equal force in the opposite direction. None of you is moving. so kinetic energy is zero. Now I cut the rope from middle. You both gain kinetic energy in the opposite direction and move. Now imagine that the atoms in the chemical are holding a rope. They're pulling in the opposite direction because of electrostatic repulsion. This rope is called bond that keeps them together despite the repulsion. The process of igniting the chemical is like snapping the rope.
Comment: Internal forces were "balanced". They had the capability to do work but can't because the circumstances are not right. You create the right circumstances then they'll do the work and produce the kinetic energy.
Answer: One thing is that the internal forces cancel out each other .so momentum is conserved. But this is just for understanding purpose. We are anyway talking about the whole system so we must ensure whether any impulsive force is acting or not which will bring change in momentum . If not then momentum is conserved in both directions


People left mean comments on my question, how do I resolve this?

Question: I wrote the following question, and it received a lot of bad spirited comments. How do I fix this situation? Do I need to delete the question and start over? Should it be edited? What mistake did I make in asking the question?
Comment: You are not responding to other users' requests for information. You are ignoring them. Unfortunately I'm out of votes today...
Comment: You've received 9 upvotes, and 11 downvtoes as of now.  That means you had a total positive reputation gain of 45-22=23.  I would recommend that you don't delete the question, but instead consider responding to the comments.  Showing more code, and showing the stack trace will likely lead you very quickly to the problem.
Comment: Since when does asking the "OP" or the guy/gal who posted the question to provide the code for review from people WILLING to answer your question.  Seems like a no brainer to me...
Comment: What a turn of events. It turns out that it was a bug in the .Net framework after all. Of course this couldn't be seen from the original question, so after a bit of heartache, and the OP responding with more detail, there are now some good answers.
Answer: Some of the comments are borderline, but overall the problem is that you're being told something by the community ("Hey, post the code we need to see."), but you haven't responded to them.  You haven't provided that code, and to top it off, you're jumping to the conclusion that it must be a problem in .NET.
If you'd like better comments on your posts, try the following approach:

Post all relevant code.
Assume that Select isn't broken.
Be engaged in your post, and when people come up with questions, update your post to answer those questions.
Comment: The point about being engaged is important, but it is also a natural mistake for new users to make: most help sites on the internet are *slow* by comparison.
Comment: +1 agreed.  The reason I say he isn't engaged is because he took the time to write out a meta post complaining about their behavior, but didn't take the time to address their behavior.
Comment: A fine "Moderator" worthy response...
Comment: i am sorry i realize i should not have complained here. i was frustrated with problem and comments made me worse. i had my friend write explanation better to write what i am trying to do and write comments here to provide explanation. thank you for the help
Answer: The comments seem to suggest that you haven't included enough information for someone else to reproduce the problem.  Further, others suggest that you check the stack trace to find out where the stack is overflowing.
Your lack of responses to the comments suggests that you haven't fixed the first problem (ie, give enough code to show the problem) and that you haven't followed the second recommendation.
If you aren't able to provide enough code, or follow simple debugging steps, people can't help you out much.
Comment: But where is he responding to the comments?
Comment: @Pekka - Sorry, I mis-wrote that.  Fixed.
Comment: i will consider this but i may not make recovery for bad question reps can i delete question to post better??
Comment: @Prashant - If you flag the question for moderator attention, request that it be deleted, and that your reputation be recalculated, then your reputation will go back to where it was prior to asking the question.  I suggest that you spend some time answering other people's questions before asking more of your own.  By answering other people's questions you'll get a better idea of how questions should be asked, and you'll get a better sense of the community here.
Comment: @Prashant P Your best bet is to edit the question, or have someone else edit the question. I went ahead and edited it so maybe it'll stop losing votes.
Comment: @Prashant: Currently you've gained 21 rep (+45, -24) for a very poor question. I would edit it so that it's *not* a bad question, and be done with it.
Answer: The question, and the assumption that there must be a bug in .NET, may indeed have been dumb (I can't judge it) but this looks pretty excessive both on the vote count, and in the comments, especially seeing as the OP hasn't yet responded to anything. I think the users there are being dicks, and this is not the way SO is supposed to work.
Comment: I agree with this completely, many comments were uncalled for and have been removed.
Comment: +1, I could understand a -2 or -3 just because of the possible presumptuousness but it was at -9 for a while there which is just folks piling on
Comment: The history of *"I found a bug in [the compiler|very common library]"* posts on Stack Overflow has seem a fair amount of pile on like that. Seems odd to me since *everyone* has a moment like that early on.
Answer: You are asking questions that are:

Not clear
Not the best English

To top it off you are not responding to comments where other users are clearly asking for more information so that they can help you.
Sorry, but you deserve to be down-voted when not responding to comments when your questions leave a lot to be desired.
Monitor your questions and comments and be more responsive.
Comment: You deserve nine downvotes and asshole comments if you don't respond to comments *within one hour*? I don't agree. If people obviously deliberately ignore comments (i.e. respond to some and ignore others), I'm the first to vote down. But for all we know, he just returned to his question and found it in the state it is in now.
Comment: @Pekka I certainly don't agree with asshole comments and didn't say I did, but I think if you're learning the ropes asking a poor question and then pissing off for an hour is pretty bad form too. I scanned his question history, so it wasn't an off-the-cuff remark. It's not as if you have to wait more than 1 minute for feedback on SO...
Comment: @chibacity okay, I didn't see the question history. Still, the nature of SO as almost a "live chat" is hard to grasp in the beginning, there should be *some* leeway
Comment: @Pekka Tough love is sometimes the *right* love.
Comment: @chibacity I wholeheartedly agree with that. But this is just people being dicks... Anyway, let's hope the OP learned his lessons. :)
Comment: @Pekka Agreed - Sometimes ripping someone's arm off and beating them around the head with the soggy end is the *right* thing to do ;)
Answer: I can see both sides of this - on one hand you should have posted the code and jumping to the conclusion that "it's a bug in .NET" is a bit ridiculous (yes, there are bugs in .NET but what do you think is more likely a bug in this scenario?) It's also not that clear on the language front and on the face of it could've been phrased a lot better.
That said, a vote count of -6 and below is in my mind a bit excessive, I've seen far worse questions get of much lighter and I've upvoted the question to try and balance things out a bit (not because I think it's a good question but because I don't think it deserves a score quite that low!)
So yes, in my mind people are being a tad unreasonable there. But calling people "dicks" and not updating your question to reflect the changes requested won't do you any favours.
If you want to try and redeem the situation somewhat, I'd edit the original question, post the code people want to see, phrase things much better and apologise for the poor quality of the original post. People are generally much more likely to give you a second opinion and help out if you apologise and provide the material that's needed to answer the question properly in a clear format.


iMovie 10.0.9 Won't load video

Question: I have a camcorder hooked up to my iMac running iMovie 10.0.9. When I try to import the video, I get question marks, and then the HDD Camera clicks off the menu. How can I get the video into iMovie to edit?
Answer: Try using Mac's Image Capture (in Applications folder). Then import video to iPhoto instead of iMovie. Then iMovie will automatically import your video from iPhoto.
It's the long way around, I know, but it worked for me.

Daniel
Answer: It's impossible if your trying to convert another video that's already on your computer. This is unless you get Adobe Media Encoder which costs a ton of money.

iMovie 10.0.9 Won't load video


How much space does Blender take up on a computer?

Question: I've been considering downloading Blender, but am unsure how much space it'll take up on my computer's memory.  Thanks to anyone who can help answer this question!
Comment: The installation is around 300MB
Comment: Yes, after extraction/installation a default Windows Blender installation should be anywhere between 290 and 300Mb aproximately. But then again if your hard drive is so full that 300Mb cause trouble, then you should probably be doing some cleanup maintenance to your computer in the first place anyway, and perhaps uninstall uneeded stuff and archive old documents
Comment: It depends greatly on what you're doing in Blender. As long as you have 1Gb of available memory, it should be fine for most cases.
Comment: Blender recommends minimum of 2 GB system memory. It recommends at least 8 GB of memory for average use. https://www.blender.org/download/requirements/
Answer: Taken from https://www.blender.org/download/requirements/
Blender 2.66a - Needs about 186Mb of harddrive space
Blender 2.78b - Needs about 330Mb of harddrive space
Blender 2.83< - Needs about 395Mb of harddrive space
Minimum (basic usage) hardware
32-bit dual core 2Ghz
CPU with SSE2 support.
2 GB RAM Physical Ram
24 bits 1280×768 display
Mouse or trackpad
OpenGL 2.1 compatible graphics with 512 MB RAM
Recommended hardware
64-bit quad core CPU
8 GB RAM Physical Ram
Full HD display with 24 bit color
Three button mouse
OpenGL 3.2 compatible graphics with 2 GB RAM
Optimal (production-grade) hardware
64-bit eight core CPU
16 GB RAM Physical Ram
Two full HD displays with 24 bit color
Three button mouse and graphics tablet
Dual OpenGL 3.2 compatible graphics cards with 4 GB RAM
For Your reference My Production system Built...
Windows 10 64bit
Asus COG8580 i73770K 3.5GHz 4 Core 8 Logical Processor
16GB Ram Physical Ram
2 X Eizo Screens
Basic 3 button wired Logitech mouse
Nvidia GTX970 + Nvidia GTX680 (Dual Graphics)
2 X Solid state drives 260GB + 120GB
1 X SATA 1TB drive
For learning purposes blender should run just fine with any system that isn't too old to begin with. If you are having problem I do suggest installing an earlier build since those versions are less intensive and a learning tool before investing on a more appropriate system.


ACF - Tags not showing up in Custom Post Types

Question: I have a tags taxonomy and then I've added it to my CPT, however it does not give me the option to add tags to my CPT now. How do I get it to do that?
Comment: there's no code in your question can you edit it to include the code? Also your question mentions ACF in the title but nowhere else, how is ACF related? If you're using ACF to register both your taxonomies and CPTs then you'll need to ask this in an ACF community as questions about 3rd party plugins are offtopic here
Comment: That's a big topic with so many possible factors that to try and answer it I would have to make massive guesses. Please edit your question to show your CPT code and how you added tags to it. Then someone has a chance of at least giving an answer that matches your needs.
Answer: To enable tags for your custom post type CPT using Advanced Custom Fields ACF, you need to ensure that you have properly configured the field group associated with your CPT to include a taxonomy field for tags
During registering your custom post type, make sure to include support for the tags taxonomy by setting the taxonomies parameter to array('post_tag')
register_post_type('your_custom_post_type', array(
    // Other parameters
    'taxonomies' => array('post_tag'),
));


Display Block to retrieve information from Order Item's Product Variant and display rating & review inside product page

Question: I am working on an e-commerce website development. I have the conventional Products -> Product Variants which goes through Order and payment gateway workflow. However, there is something different in this conventional scenario.
I have setup Product -> Product Variation to categorise the different type of fabrics which fall under a same style.
We have different kinds of fabric which we source from vendors in lots. It so happens that we do not get the same colour, pattern every time and so our Product and Product Variant will be obsolete once we have exhausted the stock.
For this reason, I have setup Taxonomy as per the product classification in our case and I am tagging each product variant with appropriate taxonomy.
This is my Taxonomy hierarchy for example:

And I have made provision to tag this Taxonomy to my Product Variant and this is how it looks:

Now, I would want the user to leave a rating and review for the Product variant after he/she places an order with us. I have added FiveStar rating module and jEditable modules (this is used to edit the field by user in display mode) so that user will be able to Rate and add a Review in "Order Item" as I want the user to be able to rate and review each line item which he/she buys from us. This is how it looks:

It's all fine until now. But now I want to create a Block which will be placed below the product variant selected by user and it should do the following:

Place a block below in the Product Variation Page.
Fetch all Order Items (within Orders) placed by all users for the same taxonomy which is being shown in the Product Variant Page.
Display the User Name, User profile picture, rating and review left by the user from the above fetched order item which contains the same taxonomy information.

I seem to be completely lost in this last step of fetching ratings & reviews by users on previously placed orders on the same taxonomy as the product variation which is being viewed by the user currently. I have tried to see if there is a module which I am trying to achieve but could not find any. Also tried to see how I can build blocks to achieve this but I seem to be lost. Do I need to do some custom coding to achieve this or is it possible to fetch this relationship somehow? Am I missing something?
Thanks!
Answer: This is what I would try:
Create product block view, add 5 star rating field.
Under advanced (located in the far right).
Add relationship of tax term field.
Add relationship of user.
Add contextual filter of term ID (select provide default value, tax term id from url)
Add contextual filter of user ID (select provide default value, user ID from logged in user).
Place view block, and check a product page.


Is it bad if you start all your chapters with a description of the surroundings?

Question: Is it bad if you start all your chapters with a description of the surroundings? I wrote 4 chapters and it looks terrible, because I always start in a room and I am just describing the room with the most accuracy possible, which sounds weird, what are some other ways to start a chapter? Could you provide a few examples?
Comment: How long are your opening descriptions? A short paragraph or a full page?
Comment: I don't think there's any hard and fast rule you could cite that would point you in one direction or the other on this, apart from whether what you're doing is justifiable artistically and will engage your target reader. A friend told me once that Borges loved finding ways of breaking rules artistically for the right reasons. Writing is a dance between same and different - provide enough variety it could become a masterful riff on a 'theme and variations' structural approach. Make it too samey and it will easily put people off.
Comment: "Could you provide a few examples?" Sure. Your favourite books.
Comment: I ALWAYS start out orienting my reader to the location at the start of the chapter, but it's rarely more than a paragraph, sometimes just a line or two. Add essential descriptions after in an organic (not forced) way.
Answer: There needs to be enough setting in the opening of a scene to orient your reader.  To read for six paragraphs on the assumption they are talking in the library only to discover it's in the garden can be quite a jolt.
However "most accurate" is a problem, because it takes up space.  An absolute master of style might be able to write such openings with such marvelous beauty that people would want to read them, but descriptions on the whole are dangerous because they stop the story dead.  (There is some leeway if your point-of-view character is the sort of character who notices things, but that also needs delicate handling.)
The trick is to provide enough detail to let the reader know where they are, and to be telling details that make the place vivid, as briefly as you can.  (Which takes a lot of practice.)
Comment: No writer can appeal to every reader.
Comment: I don't care how "beautifully" an author can write.  After ten pages of extraneous detail of things that don't interest me or the characters and don't move the story, I'm going to put the book down and find something better to do with my time.
Comment: Very succinct and to the point.
Comment: @JRE Beauty is in the eye of the beholder, and all that. If it bores you, it's clearly not your idea of beautiful writing.
Answer: Alright, I haven't answered a question in a long time but I guess I'm back.
So, in my opinion there isn't really anything wrong with starting off a lot of your chapters with descriptions of your surroundings, but starting off all of them that way is definitely going to get extremely repetitive and boring.
No matter how sneaky it is, your readers will eventually piece together the fact that every time they finish a chapter, they'll have to read the description of a new room, and they'll eventually subconsciously stop looking forward to the next chapter and, in turn, stop reading the book as much or at all.
Now, this obviously doesn't apply to all readers, I'm sure there's lot of people who would have a party if they got to read a book where every chapter started with a description, but the majority of people are going to get bored of it, and honestly, it's the same if you started off every chapter with a fight scene. It gets old, no one wants to read the same thing worded slightly differently every time they finish a chapter, no matter what the thing is.
This obviously doesn't mean you can't make the majority of your chapters start off with descriptions, and it definitely doesn't mean you can't make any chapters start off with descriptions at all, but if every single one is the same thing, it just won't work.
Some other good ways to start a chapter is simply wherever you left off the previous chapter. If the character was kidnapped the chapter before, instead of describing how the room he's now in looks, describe how he feels. How he didn't realize what was happening at first until he felt the sharp pain in the back of his head, which is where he was hit by the bat that the kidnapper had used to knock him out, after that you can transition into a description of how the room looks, and bam, that chapter is now entirely different from every other chapter you've written.
If nothing happened the previous chapter that requires a continuation, just time skip. For example, if the previous chapter left off with the soldier's scouts finding the enemy base, which was filled with dragons and mermaids and a bunch of other mythical creatures, start off the next chapter something like this.
It had been three days.
Cole woke up, looking out of his tent at the soldiers around him, they were already getting armed for combat, the command to move out would be given at any moment. He cursed himself for sleeping in late.
He jumped out of bed, heading for (insert whatever the hell he does next). Anyways, I think you get the point. In summary, no, I don't think it's a great idea to start off all your chapters with a description, but it's fine if you start off the majority of your chapters that way.
Answer: As a reader, I don't want a "most accurate" description of a room.  Most of the details are uninteresting (nobody cares if the ceiling is exactly 249 centimeter high instead of the standard 250 centimeters) or irrelevant (it doesn't it matter if there's a poorly painted patch on the north wall.)
Tell me the details I need.  Better yet, tell me the details that your character finds interesting or necessary.  That tells me something about the character and the setting.  Best of all is to have your character discover needed details.
Here's an example from Helen Wright's A Matter of Oaths:

Rafe  splashed  cold  water  on  his  face,  dribbled  it
over his head, temporarily driving back the
unmistakable after-pain of a sleepbeam. A
stateroom  was  the  last  place  he  had  expected  to
wake;  neither  the  provosts  nor  Security  habitually
provided such accommodation for their guests.
Which  left  a  very  large  question  to  be  answered:
whose guest was he?
Or  rather,  whose  prisoner.  When  he  tried  the
door  of  the  stateroom,  it  was  locked.  There  was  an
intercomm on the wall that might yield the
answers,  but  he  ignored it  in  favour  of  a  rapid
examination of the rest of his surroundings.
Standard model luxury stateroom, the storage units
empty  except  for  a  selection  of  clothes  that  were
suspiciously  close  to  his  size  and  had  the  look  of
new  fabric.  An  inactive  console,  hidden  behind  a
decorative  panel  of  real  wood.  A  range  of  personal
items  in  the  san,  all  new.  Nothing  that  suggested
how he had arrived here, or why.
He  remembered  being  trapped  between  Security
and  the  provost  sergeant,  catching  the  edge  of  a
sleepbeam  as  he  moved  to  avoid  it.  After  that,  his
memory  was  less  clear.  A  condition  he  should  be
accustomed  to  by  now,  he  jibed  at  himself.  There
was a vague impression of being supported by
somebody, then the deadening sensation of another
sleepbeam. Then nothing until this stateroom.

Rather than dump a detailed description of the room on the reader, Ms. Wright has the involved character explore the room and discover relevant details.
You should also assume your readers can remember where your characters were or where they were going.
If character A says they are going to the library, then there's a chapter involving character B, then the next chapter involves character A again, you should assume that your readers remember that character A was going to the library.  You can gloss over the trip to the library (if it is uneventful) and go straight to character A pulling a book from the shelf or riffling through the card catalog.  You don't have to describe the library unless the library itself is somehow interesting - or your character finds it interesting and your readers will find that knowledge about your character interesting.

Many authors seem to think cataloging all the details in a story is a good thing.  In the middle of an intense action scene, they'll have characters mentally cataloging the appearance and weaponry of each opponent.  People don't do that.  People notice what is necessary to accomplish whatever task they have in hand.  They notice things that impede them.  They notice random details that pop into view and remind them of things (though usually not while fighting for their lives.)
The author should have all of those details in mind, and judiciously share them with the reader where and when needed.  Dumping all the details into the story is usually a bad idea, though.
If a detail is there, it needs to have a purpose.  That purpose can be to move the plot along (Chekhov's gun, hanging on the wall for future use,) or it should be to give the reader some insight into the characters (the poorly painted patch of wall as an indicator of a previously well off person living in a home they can no longer afford to properly maintain, making do and trying to keep up appearances.)
You only have so much "credit" with your readers.  They'll follow your flood of details for a while, but will lose patience and skip stuff or drop your book eventually.  Spend that credit wisely and "buy" your readers' interest.  You want them to trust that your details are relevant, and that they will be rewarded with interesting things when they spend their time reading your prose.
A detailed but irrelevant description of a setting squanders that credit.  It bores your readers and makes them more likely to drop your book.  Do it once, and they might forgive you.  Do it in every chapter, and you'll be lucky if anyone ever finishes reading your story.
Comment: MINOR point: I disagree that you can assume readers remember character A was on the way to the library. A gentle reminder (possibly just a word) helps greatly. The reader may have put the book down and come back the next day between chapters. Chapter breaks are so traditionally used for location jumps that readers may expect them.
Comment: @DWKraus, indeed. I just read a scene in the first draft of my current WIP (after having put it down for three months). I have no clue where the characters are, or for that matter how they ended up "there," so now I have to figure that one out. Note to self: thank you for the headache...
Comment: "Many authors seem to think cataloging all the details in a story is a good thing." Yep - I blame 'show don't tell'...
Comment: @DM_with_secrets Show-don't-tell is a bit like medicine - you need it, but taking too much can poison you too. I had another author tell me to ignore it, and worry more about avoiding infodump. Not sure I'd go that far, but you do get more leeway in sci-fi (which is where I'm at).
Comment: @DWKraus I like that analogy - notably, you only need it when you're ill :P
Answer: You don't have to waste all that description you wrote. Just move it. Keep the first sentence like "Jane settled back into her favourite armchair" and then carry on with what you're doing. After a few sentences or paragraphs she can gaze warmly at that painting/decanter/whatever and think to herself about what she likes about it. Or she can get up and walk and her bare toes can sink into the deep luxurious carpet, or love/hate the cold slate under them, or whatever. She walks to a window maybe, and looks out at the familiar? changed? terrifying? view. If there's someone else in the room, they can discuss the view, the room, would you like a cookie, are you cold I can get you a blanket, I told you not to wear that sweater, whatever. This will probably involve references to where things are kept or the fact one character has brought a suitcase or backpack with them.
As the author, you need a detailed and accurate description of all your settings. But you don't need to share all of it with the reader, and not as the first 6 paragraphs of each chapter. It's great that you wrote it. Now take it out and put it in a settings document, and refer to it as you liven up people's walking across rooms or opening cupboards or whatever. When one character envies another, you have the details on the differences in their homes or offices already written up to use in an internal monolog or a dialog with a third person about how unfair something is.
Comment: It's always convenient when someone gives a better version of the answer I was still getting around to giving.
Answer: You could always start with surroundings because it's really never a bad place to start, however, the issue arises when you become predictable, not for a lack of skill in describing scenery, but because it really does get boring to start a chapter the same way again and again. Would you like to read an author who does that even if he or she was good? If the answer is no, then you've got work to do.
There are an infinite amount of ways to begin a chapter: dialogue, tangential thoughts, cursory thoughts or cursory scenery, and even things that have nothing to do with anything you've been writing about. Remember, you are writing on a blank page, so think of the beginning of each chapter as such. Anything can happen insofar as you have the mastermind for your story. Let loose and keep your eye on the path and surely you'll find a variety of ways to begin a chapter and keep yourself interested in it. Truth be told, if you can keep yourself psyched about what you're writing, then chances are someone else will, too.
Answer: Your chapters should behave like scene changes in film or television and have one setting that is consistent for the purposes of what that chapter serves.  As the story progresses, it might be necessary to break a scene with a chapter to run concurrently with another scene.
Consider Star Wars: Return of the Jedi, who's climax hinges on the main characters three different attacks (Luke fights Vader in the Emperor's Throne room on the Death Star, Lando leads the rebel fleet's assault on the Death Star to blow it up, Han, Leia, Chewie, R2 and C3PO lead the ground assault to disable the Death Star's shields).   If they were chapters, you would have each change of scene laid out so that each scene hinges on a cliffhanger (Chapter X opens with the Death Star firing on the Rebel fleet.  The fleet realizes it's dangerous and moves to pull back only to see the Imperial Fleet cutting their retreat.  Akbar declares "It's a Trap" [chapter X+1] Luke gives in to the Emperor's Temptation to strike down the emperor, pulls his saber, swing for the Evil Emperor... and is blocked by a red blade... he now must fight vader [chapter + 2]  New chapter opens on the Ewoks attacking the Storm Troopers at the Endor base and builds up to Han trying to break into the bunker while Leia provides cover... he accidentally closes the blast doors [chapter x+3]  Back in space, the rebel fleet is getting torn apart. Lando tells Ackbar to move the ships towards the imperial fleet as the Death Star wouldn't risk shooting their own ships and while it's very risky, they're more likely to survive the engagment with conventional forces.
If you're chapter takes place in a setting that should already be familiar to the audience, you need not say anything beyond the elements that changed.   For example, if the story takes place over a year of time, you might describe the main room of a house as various seasonal decorations are added or changed (For example, the family room has muted glow of Christmas Lights from the tree twinkling in winter, but is warm and sunny with no lit lights during summer.).
In other cases, the chapter ending might be done to build suspense for the reveal, in which case the break could signal a gap to build suspense.
Suppose that some meddling kids and a talking dog finally caught the monster in the barn woth a trap.  "Now, let's see who you really are?" Says the smart girl as she reaches for the mask and pulls up to reveal the face of... [end chapter] [New chapter begins with a cut to some other developing plot point and wraps up.[end chapter][new chapter is back in barn] "Old Man Jenkins/Rold Ran Renkins," The meddling kids and their talking dog shout in unison...
In that situation, the reveal could be built up or paused as reveal is signaled.  Often this is done to hook you into reading more or getting the urgency of the situation or for dramatic effect.  In other times, it's to cater to people who would read one chapter at a time... the cliff hanger can be used to get you to come back to read tomorrow.
Some fun techniques could be used here, like say the Monster is definitely either "Old Man Jenkins" or the meddling kid's lovable Jock's rival "Red Herring", the chapter could transition like:
"Now, let's see who you really are?" Says the smart girl as she reaches for the mask and pulls up to reveal the face of... [end chapter] [Next Chapter] Red Herring made his way to the basement of the barn house... [end chapter][Next Chapter] ""Old Man Jenkins/Rold Ran Renkins," The meddling kids and their talking dog shout in unison...
Note that in that example, the end of the first chapter and the begining of the second almost fit perfectly in a sentence (she reaches for the mask and pulls up to reveal the face of Red Herring).   But once you read the first sentence of the second chapter, we learn that Red Herring is not even in the same scene and is up to something at a different location (The heroes are in the barn, while Red is making his way to the basement of the Barn House).  When Red's chapter ends, we come back to the scene in the Barn and learn the real answer.
This not only shows multiple events at once, but also creates some dramatic tension as well as give the readers incentive to get through the non-reveal to find out who really done it.  This could also be used to change POV of the narrator (perhaps Red was sneaking up on the heroes... he might watch as the mask is pulled from afar but when Old Man Jenkins is revealed, we now see the events from his POV.  The Smart Girl explains that while the stoner dude and his talking dog were eating, the knocked off her glasses, causing her to fumble around until she found an important clue which she realizes the significance of after the fashionista girl tells them about what she saw in the cellar after she fell through the trap door.  All while Red watches from afar plotting his next move.