Solar panel, estimate power in various illuminating conditions I'm trying to estimate available power from a solar cell like this one PRT-13781    Includes:  1x Solar Panel - 2W 1x Barrel Plug Adapter - 3.5mm to 5.5mm   Features:  Monocrystalline cells - 19% efficient Open Circuit Voltage: 7.0V Peak Voltage: 6.0V Peak Current: 378mA Peak Power: 2.27 Watts Four screws on back corners of panel allow multiple mounting options Waterproof Urethane Coating UV Resistant   Obviously, the 2W will be obtained in ideal conditions, clear sky, sunny, etc and at MPPT point.  How can I estimate available power for cloudy days, (variation with temperature will be also nice to know) etc. I cannot find relevant documents to start with, however, I will do at some point some measurements.   Until then, I am looking to best effort estimate just to have a start point in choosing the DC/DC MPPT charger, discharging the battery in my actual load conditions, etc.  For example this post question almost the same    but no relevant calculation based on illumination (lux) or percent of rated illumination vs. generated power.  EDITED We can close this question, I finally found a very well documented answer here    Thanks user @Russell McMahon
How do I define solar irradiance in the context of a solar cell? This is homework. I've tried my best to find the best answer that I could understand and could be accepted by my lecturer.   I've searched my lecture notes, wiki and google to find some good explanation defining solar irradiance. But somehow I still don't understand how I should 'define solar irradiance'. Can someone give me a few good sentences explaining solar irradiance. What are the changes, if any, in a photovoltaic cell (in terms of short-circuit current and open-circuit voltage) if the irradiance is reduced by 50%?
With Unix script, I'd like to add values in column 1 if text in column 2 is the same and print the sum.  I have a file that is:    7 GeneA 2 GeneB 6 GeneC 2 GeneB 9 GeneA   I want the output to look like:   16 GeneA 4  GeneB 6  GeneC   Thanks Proving the general limit $\lim_{n\to\infty} \frac{an+c}{bn+d} = \frac{a}{b}$ factorization of a^n+1? So a couple of weeks ago my network manager icon stopped appearing; I still get automatically connected to my saved networks and the internet works fine, etc. If I go into System Settings and look at the Network settings I can still see all the networks, only the icon that's normal in the top bar is missing.  I have no idea what caused this, I don't remember installing anything. I think it just happened after a regular update.  I tried these commands to make sure I was properly up-to-date, (which I found on another forum post):  sudo apt-get -f install sudo apt-get update sudo apt-get upgrade   That didn't do it so I found this post:  and I followed the instructions in those answers:  sudo apt-get purge network-manager-gnome &amp;&amp; \ sudo apt-get install network-manager-gnome   And, quoted from an answer there:     Add nm-applet to the Startup Applications (which may be found by   entering "Startup Applications" in the Dash).   I restarted and then saw no Unity interface at all! So I tried those 3 commands above to update again and thankfully that fixed Unity but I still don't have my network manager.  If I try the command nm-applet in a terminal it says:  nm-applet-Message: using fallback from indicator to GtkStatusIcon   So.... I'm pretty much stumped. Any help would be appreciated. So I have an old unlocked phone and I'd like to load up my own OS.  I've seen some mods out there.  CyanogenMod seems to be the most popular.  However, I was curious if I could just install a pure untouched version of the OS -- as distributed by Google. I seem to remember being able to download a clean compiled version of the Android OS.    Does Google distribute any binaries like this, and if not, is there someone out there that does?    Additionally, is this even worth trying?  These days is it necessary for Android to be packaged with special drivers and such for all of the different hardware out there? How can I modify the size of swap with LVM partitions? I'm trying to add/modify a swap partition on my LVM-formatted hard disk by using GParted from a LiveCD.  I only see one big partition taking up the whole disk.    Is there a hidden swap?    Does an LVM-formatted system even need a swap?  I'm using Ubuntu 12.10. Can I use Beetel 450TC1 as wireless router? I bought a Minecraft account for my little brother for Christmas, and I'd like to play with him on my server every now and then. If I log in while he's on, however, it kicks him off since we have the same username. Is there any way to change my username so that I can play with him, or anything I can do so that we can both play together using this account on my server?  I'm open to anything that could let us play, whether it be username changes, server property changes, etc. What is the difference between a "proof by contradiction" and "proving the contrapositive"? Intuitive, it feels like doing the exact same thing. And when I compare an exercise, one person proves by contradiction, and the other proves the contrapositive, the proofs look almost exactly the same.  For example, say I want to prove: $P \implies Q$ When I want to prove by contradiction, I would say assume this is not true. Assume $Q$ is not true, and $P$ is true. Blabla, but this implies $P$ is not true, which is a contradiction.  When I want to prove the contrapositive, I say. Assume $Q$ is not true. Blabla, this implies $P$ is not true.  The only difference in the proof is that I assume $P$ is true in the beginning, when I want to prove by contradiction. But this feels almost redundant, as in the end I always get that this is not true. The only other way that I could get a contradiction is by proving that $Q$ is true. But this would be the exact same things as a direct proof.   Can somebody enlighten me a little bit here ? For example: Are there proofs that can be proven by contradiction but not proven by proving the contrapositve? Infinite series $\sum _{n=2}^{\infty } \frac{1}{n \log (n)}$ in elisp's let, how do you reference a variable bound in the same let while binding another variable? Show that the function $g(x) = x^2 \sin(\frac{1}{x}) ,(g(0) = 0)$ is everywhere differentiable and that $g′(0) = 0$ I'm Egyptian and flying to Cairo from Tbilisi, via Istanbul. The first flight Tbilisi-Istanbul is on Atlasjet, then from Istanbul to Cairo I am flying on Egyptair. For that, I have to recheck in at Istanbul to my Egyptair flight  Will I need to pass passport control at Istanbul airport to collect my bags and check in on Egyptair? Will I need a transit visa for that? Or it can be all done through neutral zone? I want to create a circuit that can detect audio frequencies and flash RGB LEDs different colors depending on the detected frequency. The frequency range will be from 20 Hz to 12 kHz, after looking at the chart below.   (source: )    So my question is: what circuit design should I choose to make a good frequency detector? I suppose I would need    Preamp for the microphone (is it necessary for the ADC?) Band pass filters (active or passive?) A microcontroller with an onboard ADC that has a sampling rate of at least 24 kHz.   Before I get too excited, are there any circuits out there that already do this? Derivation of Kepler's laws I was surfing the internet the other day when I found this phrase: Instead your precious time and attention is wasted. To my ears, it sounds wrong. But I'm not a native English speaker, so I consulted with a number of them, and some of them said that it was "is" because the adjective modifies only the noun "time" and not "attention". Others said it "is" because that's just how it is. But I still believe it should be "are". Any help is appreciated. I have a computer (Asus T200TA) with 2G RAM and 32-bit UEFI [Yep, what a wonderful idea to put 32-bit UEFI!]. I have two options:   Install a 64-bit system, boot manually and install grub-efi-ia32. Drawback: 2G is not much, systems with such low RAM are said to run better on 32-bit systems. Install a 32-bit version. (but from my state of knowledge it's not trivial to boot)   Which option would be better? I never liked that SO/SE relied on the external gravatar service, so I was glad to . However, it turns out that one cannot use as profile picture a PNG file with transparent background (something that is supported by gravatar):    Above is a screen capture of my profile page, with a profile picture that has a transparent background. That background is turned into black, which I suppose is a bug.  The method of upload doesn't change anything (I uploaded it manually to imgur, but the same black background is observed). See the difference between the two following URLs:  http://i.stack.imgur.com/Da3ex.png?s=128&amp;g=1   and  http://i.stack.imgur.com/Da3ex.png   The problem is thus in the resizing code from imgur. Proof of Divergence for a Sequence How do you maximize the cycle count of your battery?  There seems to be a debate between:   Leave plugged in 24/7 but do a full cycle once a month Charge to ~100%, drain to ~10%, repeat.   NOTE: Taking your   Which method is better and why? How much of a difference does it really make?  Here are some of the better sources I've found about battery behavior so far. Even still I feel they don't conclusively answer the question above. See my elaborations below:           Elaborating on Option 1  Now IF Apple engineers were smart and optimized for AC draw when plugged in to not use up your charge cycles, then it seem logical to assume that you are using effectively none of your 1000 charge cycles while plugged in. If that's the case, it would seem that the LiPo drop from holding at 100% would be vastly outweighed by the fact you're not using any charge cycles.  However, this is a purely speculative assumption and I could find no evidence to either confirm or deny.  If this is NOT true, and the AC adapter only goes to charging the battery, then there would be no difference. Your battery would drain to 99%, then back up to 100%, then back down to 99%, etc. Those micro-charge cycles would add up at the same rate as 100% -> 0% -> 100%, and you would get no gain. In this case the negative effect of holding LiPo batteries at 100% would outweigh everything else.  Elaborating on Option 2  There are lots of good reasons why Option 2 is the way it is:   Because of known LiPo chemistry issues, holding a 100% charge for a long time causes the battery to degrade Apple specifically recommends not to leave it plugged in all the time  Draining a battery all the way to zero all the time is bad for the cell (Which is why ~10% is used) Heat is a killer, and when plugged in AND charging, you get extra heat that causes damage.   There are a couple reasons why I'm challenging Option 2:   It seems silly that the most intuitive use case for thousands of people that use their macs as primary computers is wrong. If the hypothesis in option 1 is true, you're just burning unnecessarily through your finite charge cycles. It's a pain to have to remember to keep plugging in and plugging out and be worried about whether or not your device is plugged in.