I have a Noctua NF-F12 computer fan (specs: ). I also have a Samsung USB Wall Adapter (Originally for charging my tablet). The USB Wall Adapter says it can output 5V 2.0A.  My computer fan, according to the specs, runs at 12V 0.05A. How do I go about powering this? Some have said to purchase a 5V to 12V step up module with a USB connection, then solder the fan wires onto that, and plug the USB end into the wall adapter or would it work if I plugged it into a computer's USB port?   I've also seen DC wall adapters for sale. I saw a 12V DC Wall Adapter, and it says it can output 12V 100mA. However, most of them supply 500 mA, 1A, or 2A. My fan says it only needs 50 mA (0.05A). What happens if I solder the fan wires to this DC Wall Adapter? It is 12V but isn't it too much current? Will this burn out the fan?  Edit: With all that said, is it best to just purchase a DC power supply and splice the fan wires, or can I go with a 5V to 12V step-up module with a USB connection and use any of my USB wall chargers instead?  Thank you in advance.
Power supplies are available in a wide range of voltage and current ratings.  If I have a device that has specific voltage and current ratings, how do those relate to the power ratings I need to specify?  What if I don't know the device's specs, but am replacing a previous power supply with particular ratings?  Is it OK to go lower voltage, or should it always be higher?  What about current?  I don't want a 10 A supply to damage my 1 A device.
How to install Windows on GPT disk without UEFI BIOS? How can I show or hide boot messages when Ubuntu starts? Is there a way to easily turn on/off showing the boot messages (loading the services) when Ubuntu starts? Is it something in Grub2?  I am running 10.04. Multivariable limit proof: $\lim\limits_{(x,y)\rightarrow (0,0)}\frac{\left|x\right|^a\left|y\right|^b}{\left|x\right|^c + \left|y\right|^d} = 0$ I have some trouble with this: Show that if $a, b \ge 0$, $c, d &gt; 0$ and $\frac{a}{c} + \frac{b}{d} &gt; 1$ then   $$\lim_{(x,y)\rightarrow (0,0)}\frac{\left|x\right|^a\left|y\right|^b}{\left|x\right|^c + \left|y\right|^d} = 0$$  we were not really shown how to evaluate multivariable limits other than trying different paths, which wouldn't work when the limit exists, or by applying the squeeze theorem which is my initial plan. Unfortunately I cannot find a proper bound for the denominator and so I am quite lost right now. Any help would be appreciated. equivalent date from GNU to solaris Find $P(12)$ when $P(x)={1\over(x+1)}$, for $x=0,1,2,......11$ let $P(x)$ be a polynomial of degree $11$ such that  $P(x)={1\over(x+1)}$, for $x=0,1,2,......11$  then find value of $P(12)$ Confused By Copyright Rules Can't connect to wireless 13.10 I have ubuntu installed as the sole OS on a T420. Before this I had installed the #! distro (and Xubuntu before that) and wireless worked seamlessly on either. My home hotspot shows up but when I click on it tries for a while before disconnecting.  Before going into the problem further, I wanted to double check that I entered the wifi password for my home network correctly. I went to Edit Connections >> Wi-Fi Security and changed the key, but it is still not able to connect. So I think the password is definitely correct. I don't understand why it can't connect now. Is the uncertainty principle a property of elementary particles or a result of our measurement tools? In many physics divulgation books I've read, this seems to be a commonly accepted point of view (I'm making this quote up, as I don't remember the exact words, but this should give you an idea):      is not a result of our lack of proper measurement tools. The fact that we can't precisely know both the position and momentum of an elementary particle is, indeed, a property of the particle itself. It is an intrinsic property of the Universe we live in.   Then this video came out:  (skip to , if you're already familiar with the uncertainty principle).  So, correct me if I'm wrong, what we may claim according to the video is:     the only way to measure an elementary particle is to make it interact with another elementary particle: it is therefore incorrect to say that an elementary particle doesn't have a well defined momentum/position before we make our measurement. We cannot access this data (momentum/position) without changing it, therefore it is correct to say that our ignorance about this data is not an intrinsic property of the Universe (but, rather, an important limit of how we can measure it).   Please tell me how can both of the highlighted paragraphs be true or how they should be corrected. Centering in the \align* environment Why was the previous Code of Conduct FAQ (and all answers) removed? I noticed that the  was deleted.   When the  came out, I tried to look for my old answer as well as others for comparison.  Why not just mark the old one superseded by [insert link]?  Note: I don't care about lost rep. There were a lot of useful links in answers and comments there (and some less-than-useful ones too).     Old CoC FAQ may be available  and . Source: (, ). I would like to filter the markers on my (geojson) layer according to two features: year and type of event, ideally using both filters (year and eventType) as check-boxes without using layerGroup at all. I would like to be able to click on a checkbox and update dynamically the markers by filtering them according to feature.properties.eventType too, in addition to the year displayed, something like    &lt;input type="checkbox" id="all" name="all" value="all"&gt;   &lt;label for="all"&gt;All&lt;/label&gt;   &lt;input type="checkbox" id="funfair" name="funfair" value="newsletter"&gt;   &lt;label for="funfair"&gt;Funfair&lt;/label&gt;   &lt;input type="checkbox" id="trade" name="trade" value="trade"&gt;   &lt;label for="trade"&gt;Trade&lt;/label&gt;   &lt;input type="checkbox" id="exhibition" name="exhibition" value="exhibition"&gt;   &lt;label for="exhibition"&gt;Paid exhibition&lt;/label&gt;   etc... which would trigger a  filter: function(feature, layer) {   return feature.properties.eventType == value-of-checkbox; }   I have five types of eventType. So, for instance, if 1890 is checked, the map is showing all 1890 events, no matter what kind of event it is (because by default it would show all events). If the user checks the 'funfair' and the 'trade' checkbox, though, I want the map to show only the 1890 events of the funfair and trade kind, and not other kind of events.  This is my complete script, which so far is working fine with filtering by year.  var oldmap = L.tileLayer('address', {   maxZoom: 12 }),  var modernmap = L.tileLayer('https://api.tiles.mapbox.com/v4/{id}/{z}/{x}/{y}.png?access_token={accessToken}', {   maxZoom: 12,   id: 'mapbox.streets',   accessToken: 'mytoken' });  var map = L.map('map', {   center: [40.1857864,-4.5536861],   zoom: 7,   layers: [oldmap, modernmap] });  var baseMaps = {   "Old map": oldmap,   "Modern map": modernmap };  var jsontest = {"type": "FeatureCollection",   "features": [     {       "type": "Feature",       "geometry": {         "type": "Point",         "coordinates":  [ -16.5471268,28.4136726 ]       },       "properties": {         "Name":"Point1",         "year":'1892',         "eventType":"funfair",         "notes":""       }     },     {       "type": "Feature",       "geometry": {         "type": "Point",         "coordinates":  [ 2.1753895,41.3767925 ]       },       "properties": {         "Name":"Point2",         "year":'1890',         "eventType":"trade demonstration",         "notes":""       }     }   ]};  var mapLayerGroupsYear = [];  function onEachFeature(feature, layer) {   var year = mapLayerGroupsYear[feature.properties.year];   if (year === undefined) {     year = new L.layerGroup();      //add the layer to the map     year.addTo(map);      //store layer     mapLayerGroupsYear[feature.properties.year] = year;   }    //add the feature to the layer   year.addLayer(layer);    }   var myLayer = L.geoJSON(jsontest, {   onEachFeature: onEachFeature })  L.control.layers(baseMaps, mapLayerGroupsYear).addTo(map);   I am a beginner with leaflet so please forgive the dumb question, in case it is. Simple prime number generator in Python Could someone please tell me what I'm doing wrong with this code? It is just printing 'count' anyway.  I just want a very simple prime generator (nothing fancy).   import math  def main():     count = 3     one = 1     while one == 1:         for x in range(2, int(math.sqrt(count) + 1)):             if count % x == 0:                  continue             if count % x != 0:                 print count          count += 1 How to find all subgroups of a direct product? I am wondering how do we find all subgroups of a direct product? Is there a method to find it?  For example, how can we find all the subgroups of $\mathbb{Z}_2\times\mathbb{Z}_2$?  There is the answer: $\{(0, 0), (1, 0)\}, \{(0, 0), (0, 1)\}, \{(0, 0), (1, 1)\}$, and the improper and trivial subgroup. But I do not know the method how to find it.   All I can think about is the following: since the order of $\mathbb{Z}_2\times\mathbb{Z}_2$ is $4$, the order of a subgroup of it can be $1,2$ or $4$.   If order is $1$, then it is trivial, and if order is $4$, it is proper. Then, the order of a subgroup is $2$. We know all the elements of   $\mathbb{Z}_2\times\mathbb{Z}_2$, so we try all the pairs.   Is that the method?   But what if we are given a bigger order product, such as $\mathbb{Z}_2\times\mathbb{Z}_8\times\mathbb{Z}_3\times\mathbb{Z}_9$? It looks very long to try all possibilities.   Can anyone help?  Thanks Convergence of $\sqrt{n}x_{n}$ where $x_{n+1} = \sin(x_{n})$ Razr Maxx HD, How to wipe data with broken screen My screen is totally destroyed, it's black and unresponsive. The phone turns on just fine, though. I just got my new phone and I have to send this one back now.  I want to wipe the phone before I send it back, but I'm not sure how. I don't care too much about sending back a rooted phone, it seems Asurion doesn't really care about that from what I've read, but I don't want my personal data on the phone when I send it in.  What are my options to wipe the phone without a screen? I've already read a lot of threads on other forums and here on the subject, but everyone seems to say to wipe through ADB shell. Well, I can see the phone in ADB, but I am unable to enter SU through ADB shell. I assume it's because the screen is locked, and I have no way to unlock it. Others have also said to wipe through fastboot in ADB, but I am seeing conflicting recommendations and I'm not sure how to proceed. I'm not that proficient with ABD, so I want to make sure I don't mess this up.  Any advice would be greatly appreciated. I've seen some of the other threads on using strings as x axis labels, but nothing that fits my situation.  I'm trying to create a bar chart from a CSV file. I can do it so long as everything in the data is numeric. However, in my actual data table, the first row is multi-word string descriptions. I need these descriptions to be the x axis labels for each bar.  I've tried symbolic x coords, but I get the "could not parse input as a floating point number" error. I've also tried adding an ID column and using that as the x values, and assigning xtick labels as the string descriptors. I get the same issue that way.  Here's an attempt at an MWE:  \documentclass{article}  \usepackage{lmodern} \usepackage{tikz} \usepackage{pgfplots} \usepackage{pgfplotstable}  \begin{document}  \pgfplotstabletypeset[columns/category/.style={string type},col sep=comma]{Book3.csv} \vspace{1cm}  \begin{tikzpicture} \begin{axis}[ ybar, xlabel=Xstuff, ylabel=Value, symbolic x coords={cat a,cat b,cat c,cat d,cat e,cat f,cat g}, %xtick labels={cat a,cat b,cat c,cat d,cat e,cat f,cat g},% this is from when i tried the xtick label method xtick=data, nodes near coords, nodes near coords align={vertical}] \addplot table[x=category,y=value]{Book3.csv}; %\addplot table[x=category,y=value]{Book3.csv};&amp; again, from trying the xtick label method  \end{axis}  \end{tikzpicture} \end{document}   Since I suspect this might get answered quickly by you chart gurus, I have a follow-up question:  I have to do a bunch of these charts, and I would like to automate the symbolic x coords process. Is there a way to populate the dictionary of accepted x coords by reading a column of the data? (something like symbolic x coords={columns/category/{Book3.csv}} )?  Book3.csv looks like this (ignore the ID column if using the xtick label method):  ID, category, value, value 2 1,  cat a,    1,     7 2,  cat b,    2,     6 3,  cat c,    3,     5 4,  cat d,    4,     4 5,  cat e,    5,     3 6,  cat f,    6,     2 7,  cat g,    7,     1 How to prove $\,x^a-1 \mid x^b-1 \iff a\mid b$ How to prove $x^a-1\mid x^b-1 \iff a \mid b$, where $x \ge 2$ and $a,b,x \in \Bbb Z$.  I've tried the following in attempting to solve this:  $$a\mid b \Rightarrow aq=b \Rightarrow x^{aq}=x^b \Rightarrow x^ax^q=x^b$$  Because $x^q \in \Bbb Z$, it follows that $x^a\mid x^b$.  This is as far as I have gotten; any help getting further is appreciated.  Note: It may be that this identity is not true at all? How do I run an executable file with a double click? I'm trying to run an executable (testdisk) but double click doesn't work. The only way is to run:  sudo ./testdisk   from terminal. But I'd like to open executables with double click in future. How can I do this? Solve $x^{5} \equiv 2$ mod $221\ $ [Taking modular $k$'th roots if unique] An infinite subset of a countable set is countable In my book, it proves that an infinite subset of a coutnable set is countable. But not all the details are filled in, and I've tried to fill in all the details below. Could someone tell me if what I wrote below is valid?  Let $S$ be an infinite subset of a countable set $T$. Since $T$ is countable, there exists a bijection $f: \mathbb{N} \rightarrow T$. And $S \subseteq T = \{ f(n) \ | \ n \in \mathbb{N} \}$. Let $n_{1}$ be the smallest positive integer such that $f(n_{1}) \in S$. And continue where $n_{k}$ is the smallest positive integer greater than $n_{k-1}$ such that $f(n_{k}) \in S$. And because $S$ is infinite, we continue forever. Now consider the function $\beta : \mathbb{N} \rightarrow S$ which sends $k \rightarrow f(n_{k})$.   So in order for $S$ to be countable, $\beta$ would have to be a bijection. $\beta$ is injective since if $f(n_{k}) = f(n_{j})$, then $n_{k} = n_{j}$ because $f$ is injective. We also can conclude $k = j$ because the various $n_{i}$ chosen were strictly increasing.   Edit: $\beta$ also needs to be surjective. So for every $r \in S$ there exists a $q \in \mathbb{N}$ such that $\beta(q) = f(n_{q}) = r$. We know that $f^{-1}(r) \in \{n_{1}, n_{2}, ..., n_{k} ... \}$, so we can let $f^{-1}(r) = n_{d}$. Thus $\beta(d) = f(n_{d}) = r$.