I have a 12V 18Ah battery I wish to run through a boost converter at 40v and 2.5A to power a 100w led.  Could someone figure out how long my battery would power my led and show the calculatins/formulas.  Thanks
How long can I run a water pump which requires 12V and 50W from a 12V, 40Ah, 400A car battery?  Can you explain how this was calculated?
I am currently using Sheep It! to render my blend (built on v2.68c) on multiple computers, and I noticed something rather strange. According to the log on-site, the frames rendered from other people's blends were completing in 3 to 4 minutes. This was on an 4 core i5. My main rig (with an 8 core i7) was completing frames in no less than half an hour. How is this possible?  To clarify, these people's frames are very complex, often with very detailed textures. I have 2 objects in my blend. Below are the options I changed for my blend:   Aspect Ratio: 1000px x 1000px Output: PNG Clamp Indirect: 0.98 Render Sampling: 128 Min Light Bounces: 0 Max Light Bounces: 4 Cycles Render   Is there something in there that I should change to make it go faster? I can't really comprehend how it's going to quickly.  EDIT: To answer what @Duarte asked...   System Specs: i7-920, 3GB DDR3, GT 630, Windows 10 I have two circles, extended to form a sort of coin with a star on it. It is not complex at all. I have Firefox and Steam running in the background, but not actively. I've been away from the computer for 8 hours and noticed this behavior. (I am running Blender from Steam.) I made sure when I began rendering that the blend was set for CPU rendering.          And to answer what @pycoder asked, yes, I am using Cycles Render. Export data as CSV in back end with proper HTTP headers I wrote a plugin that displays all products in a woocommerce store in admin settings option, now I want to add a link to download the products as CSV file.  The problem is, when I click the link I get a permission error saying I don't have permission to view this page.  Here's my code:  function extra_tablenav($which) {     if ($which == "top") {         echo '&lt;h3 style="display:inline"&gt;'         . __('These products are currently in the database:')         . '&lt;/h3&gt;' .         '&amp;nbsp;&amp;nbsp;&amp;nbsp;' .         '&lt;a href="' . admin_url('admin.php?page=download_csv.php') . '"&gt;' . __('Export to CSV') . '&lt;/a&gt;';     } }   How can I fix those permissions? I just fit a model in lme4, and I'm wondering what the heck I fit...  I have individuals id, and each is measured pass/fail on items that can be described using two factors, f1 and f2. My theory says that id and f2 can interact. So I want to compare these models:  # f2 doesn't matter m1 &lt;- lmer(pass ~ f1 + (1|id), family="binomial")  # f2 is a fixed effect, doesn't interact with individuals m2 &lt;- lmer(pass ~ f1 + f2 + (1|id), family="binomial")  # f2 is a nested random effect, interacting with individuals m3 &lt;- lmer(pass ~ f1 + (1|f2/id), family="binomial")   First, am I right that there's a random effect of each level of f2, and each individual's level of f2 is partially pooled, depending on the number of observations for that individual?  Second, does it make sense to fit f2 as a fixed effect with random individuals nested within each level of f2? How does one write that?  Third, what's this, with f2 and id reversed in the formula? I typed it by accident, but now I want to understand it.  m3weird &lt;- lmer(pass ~ f1 + (1|id/f2), family="binomial") Zero to the zero power – is $0^0=1$? Could someone provide me with a good explanation of why $0^0=1$?  My train of thought:  $x&gt;0$  $0^x=0^{x-0}=0^x/0^0$, so  $0^0=0^x/0^x=\,?$  Possible answers:   $0^0\cdot0^x=1\cdot0^0$, so $0^0=1$ $0^0=0^x/0^x=0/0$, which is undefined   PS. I've read the  on mathforum.org, but it isn't clear to me. Possible Duplicate:          On  it's a stated fact that if $I$ and $J$ are coprime ideals of a ring $A$, then $I^k$ and $J^\ell$ are also coprime for any integers $k,\ell$.   There's no proof given. Why is this fact true? Force fsck.ext4 on reboot, but really "forceful" One of my Ubuntu 10.04 servers is giving me trouble. When I run fsck.ext4 -n /dev/sda5 it tells me there are errors in the free inode count, free block count, and more.  I have tried:  touch /forcefsck   Also tried:  shutdown -rF now   and still, after reboot, I see errors.  I also just checked on my eeePC netbook, Ubuntu 10.10, and have the same issue!  How can I force a really "forced" "forceful" "seriously fix my filesystem" fsck of the "/" filesystem on reboot?  Clarification: I run fsck.ext4 -n because it's a mounted filesystem, to check if there are errors. This tells me that there are. I thought that the automatic fsck every 30 mounts during the boot-up process is precisely to take care of errors in the root filesystem. But it doesn't do it in my case. I could reboot with a LiveCD and fix the errors, and then reboot again, but that's some serious downtime for a live server. A reboot, auto fsck, then continue booting is much more sustainable on a live server, and I believe should be the right behaviour.  Additional info: Here is the output. It looks like something that the autofsck would fix, doesn't it?  root@server:~# fsck.ext4 -n /dev/sda5 e2fsck 1.41.11 (14-Mar-2010) Warning!  /dev/sda5 is mounted. Warning: skipping journal recovery because doing a read-only filesystem check. /dev/sda5 contains a file system with errors, check forced. Pass 1: Checking inodes, blocks, and sizes Pass 2: Checking directory structure Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information Free blocks count wrong (1849368, counted=1948909). Fix? no  Free inodes count wrong (545504, counted=552134). Fix? no   /dev/sda5: ********** WARNING: Filesystem still has errors **********  /dev/sda5: 116752/662256 files (0.2% non-contiguous), 795324/2644692 blocks Where to upload too big files? I have a big HTML file that causes no errors in most of the browsers. However, when I open it with, let's say, Google Chrome, the program shuts down and I cannot trace why this is happening.   This HTML file is quite big and cannot be posted to a question in SO, but it should be ran as a whole as I cannot trace where the problem is. What is/are the most appropriate file upload website/s to upload and paste the link into the question? How does entropy depend on location and scale? How do I disable the profiles button in Chrome? Since Chrome version 38, there's a pretty ugly button in the title bar of the Chrome window that allows you to switch profiles quickly.  Since I'm the only one that uses my computer, this is not really useful to me, and I'd rather reclaim the space for more open tabs.  I've looked in the settings but don't see a way to disable it.  How can I get rid of the button? $X^n-Y^m$ is irreducible in $\Bbb{C}[X,Y]$ iff $\gcd(n,m)=1$ I am trying to show that $X^n-Y^m$ is irreducible in $\Bbb{C}[X,Y]$ iff $\gcd(n,m)=1$ where $n,m$ are positive integers.    I showed that if $\gcd(n,m)$ is not $1$, then $X^n-Y^m$ is reducible. How to show the other direction. Please help. Skip certain tables with mysqldump How to correctly add a path to PATH? I'm wondering where a new path has to be added to the PATH environment variable. I know this can be accomplished by editing .bashrc (for example), but it's not clear how to do this.  This way:  export PATH=~/opt/bin:$PATH   or this?    export PATH=$PATH:~/opt/bin My computer boots to a black screen, what options do I have to fix it? What graphics packages are there for creating graphics in LaTeX documents? What packages do you use and recommend for creating graphics in your LaTeX documents?     As this is a community wiki post, please add your package to the accepted answer (or add a comment, and someone with >100 rep will add it to the CW answer), and include a brief description of what differentiates it from others and how it can be used (GUI drawing tool which generates code, type in raw text, or generates image for inclusion in document).   We'll eventually sort these answers under headings. How to run .sh script with keybind Natural Sort Order in C# I have to give low and high bounds for the following:  $$ \sum_{n=1}^\infty \frac{1}{2^n - 3^n } $$  How do I determine an upper bound? How can I show this sum exists?  edit: removed erroneous conclusion. Do we have any other evidence other than red shift? Is anyone trying to disapprove inflation? Also, can red shift occur because of large distance, not only because two objects are going farther from each other? Deleted comments leave badge on iOS app When someone leaves a comment that involves you being notified, you get the notification both on the main toolbar on Stack Exchange and as a notification/badge on the iOS app.  If you read a comment on the website and cause the notification to be removed from the toolbar, the badge also gets removed from the iOS app.  However, when a comment that has previously caused a notification/badge to appear on iOS gets deleted, the badge remains on the iOS app while the notification gets removed from the website toolbar.  Could the badge also be removed from the iOS app in this situation? Problem installing .deb in Software Install Ubuntu 20.04