I'm a beginner at circuits (I'm a high school student interested in electronics), and I'm currently working on a school project about a Magnetostriction Oscillator. The circuit construction is as follows, and I need some help understanding certain aspects of the same.  So from my understanding, the circuit working is as follows:  When the battery is attached a voltage V is supplied to the LC oscillator. Which induces an oscillating flux in the rod: A question I had is that since its a DC supply, won't the capacitor saturate after the time constant is completed, making the induced magnetic field constant (all current directed through L1) The apparently oscillating magnetic field in the rod induces an EMF in L2 - which gets amplified through the BJT and gets fed back into the parallel LC oscillator (is this why it acts as an AC voltage allowing the parallel LC to oscillate??): I get the induced EMF (provided magnetic field is oscillating) - but don't get the amplification. Won't the induced emf/current get amplified and move towards the reference ground node instead of the LC oscillator?? If it does could you please explain why? Any additional help on understanding how the LC circuit oscillates and how the transistor plays a role in the same would be much appreciated!  Thanks a lot!!
Could someone please explain the role of the transistor in this circuit? I have a feeling it has to do with the LC circuit but I'm not sure and don't understand completely. The following is an image of the circuit (the transistor is n-type. It is used in lots of sensors to detect and generate ultrasonic waves.
My phone was stolen last night. I made sure it was in Lost Mode in iCloud and it was immediately in Offline status when I open iCloud. I am positive the thief switched it off. Now I am 100% certain the Find my iPhone option was turned on on my iPhone, but will the "Lost Mode" be of any help if it was not turned on on the iPhone? Would it be showing "Offline" if I did not turn on the option? bi-directional sync with rsync Suppose we have a situation like      A ball of some mass $m$ with some velocity collides with rod hinged at point $A$. Is momentum conserved in this situation? I know that hinge will give impulsive force on rod but that is internal force when we take ball and rod together as a system so that shouldn't stop us using conservation of momentum equation How does ServerName and ServerAlias work? Allow an edit to notify downvoters: "I think I've fixed the issue now - please check" To me, a downvote usually indicates a problem with an answer. When I downvote it's to mark the answer as having a problem, not the person. If the answer is fixed, I want to remove that downvote - but it's tricky to keep track of all the questions I've looked at over the last few hours.  I don't actually downvote very much, but it's very easy to forget what's going on.  It would be nice to have some way of indicating in an edit that you (the editor/answerer) believe the reason for the downvote has now been resolved, so that the downvoters could come and undo their downvotes or explain why it's still not fixed.  (Note: this isn't about rep-recovery, but quality control. I would feel a lot better about downvoting on "iffy" answers if I felt it was likely that the answer would be fixed and I could undo the vote. Whether or not I'd get back the cost of the downvote is somewhat immaterial.) Idea behind proof that $\frac{21n+4}{14n+3}$ is irreducible for all $n$ I have a proof of $\frac{21n+4}{14n+3}$ being an irreducible fraction for any positive integer $n$. The proof starts with the following: Indeed, from the equality: $$2(21n+4)-3(14n+3)=-1$$ and so on..But how does this equality follow from the fraction? $\mathbb{Z}[X]/(X^2-1)$ is not isomorphic with $\mathbb{Z}\times \mathbb{Z}$ I have to show that the ring $\mathbb{Z}[X]/(X^2-1)$ is not isomorphic with $\mathbb{Z}\times \mathbb{Z}$.    I know that $(\mathbb{Z}\times\mathbb{Z})^*=\{(\pm1,\pm1)\}$, so I thought I should be looking for elements which have inverses in $\mathbb{Z}[X]/(X^2-1)$ and hopefully find more or less than 4. But I didnt succeed, so I need hints. Thanks. Recently I had a bunch of my own scripts for the thumbnails in Nautilus: , , office documents and so on.  Seems like either I’m doing something wrong (thumbnail generation behavior changed), or custom thumbnailes don’t work in latest GNOME at all, even my previous scripts, which worked smoothly on previous versions of Ubuntu.  I’ve done some research, tried to run a simple script (see below) and it didn’t work out.  My test thumbnailer in /usr/share/thumbnailers/z.thumbnailer:  [Thumbnailer Entry] Exec=/home/maximal/thumb.sh %s %i %u %o MimeType=image/webp;image/x-webp   Where /home/maximal/thumb.sh is:  #!/bin/bash echo $0 &gt;&gt; /home/maximal/thumb.log echo $1 &gt;&gt; /home/maximal/thumb.log echo $2 &gt;&gt; /home/maximal/thumb.log echo $3 &gt;&gt; /home/maximal/thumb.log echo $4 &gt;&gt; /home/maximal/thumb.log   Then, when I remove thumbnail cache rm -rf ~/.cache/thumbnails and restart Nautilus nautilus -q, my log file doesn’t contain anything and ~/.cache/thumbnails/fail/gnome-thumbnail-factory contains all the failed thumbs (looks like corrupted/empty PNGs):    So, apparently, Nautilus even didn’t try to execute my thumbnailer script. When I try to run thumb command itself, it works perfectly. For example convert through cwebp|dwebp package:  convert -thumbnail 256x256 file.webp png:file.webp.png   When I wrap this command to a thumbnailer, it looks like it wasn’t even requested to run by Nautilus.  [Thumbnailer Entry] Exec=convert -thumbnail %sx%s %i png:%o MimeType=image/webp;image/x-webp;   Exactly the same situation occurs with other my thumbnailers: audio waveforms, office documents, photoshop files and so on.  Could anyone help? I frequently need to do the following things in MySQL:   Create a non-root user Set that user's password Grant that user all privileges Make a database with the same name as the new user Allow usage only for users from the localhost.   Previously I did this using PHPmyadmin, but I would prefer doing it directly from BASH. Is there a CLI way to execute these steps? Banner ads should not be shown on the right-hand ad slot How do I prevent object distortion when applying a curve modifier? I've been working on some animations recently, and I've noticed that I'm having poor luck with certain things, namely the fact that I don't really use Blender's graph editor very well.  One of the major issues that I have is pretty widespread among 3D graphics programs; when I create an animated object, it defaults to using a curved graph instead of a linear graph, which means that the most movement is at the middle of the animation, and stuff just practically stops near the beginning or the end. While this helps with organic camera movements or such, it's also not what I usually want. Can I set animation curves to default to linear? The  lists various combinatorial objects that are described by them. I posit that there might be bijections between these various combinatorial objects. For some of them (like Dyck paths, correctly matched parentheses and paths from the bottom left to top right of a $2n \times 2n$ grid) they are quite obvious.   I was then trying to find a bijection between the number of Dyck words and the number of ways of associating $n$ applications of a binary operator to $n+1$ items (third one on the list). I attempted to do this for a simple case ($n=3$ which is the example provided in the Wikipedia article). However, couldn't find one after multiple hours. Is it reasonable to expect such a bijection will exist? If so, how do we go about finding it?    EDIT: In addition to the very nice answer by @Marc, the following page also helped me see the bijection:   "Let $P$ be the Dyck path and $f(P)$ be the binary tree. If you go up in the Dyck path, create a left child. Otherwise, go up one vertex until creating a new right child is possible and create one."    Here is one of my attempts:   Number of Dyck words with length $2 \times 3$ is $\frac{6 \choose 3}{4} = 5$. They are:  hhhttt; hhthtt; hhttht; hthhtt; hththt  And the number of applications of a binary operator among $3+1=4$ factors is:  ((ab)c)d;     (a(bc))d;     (ab)(cd);     a((bc)d);     a(b(cd))  Both combinatorial objects have been arranged in a way that there is some kind of ordering between them. For the Dyck words for example, if h equals +1 and t equals -1, then the order is lexicographical from the left to the right of the cumulative score along the sequence.   Now, the first and last characters of the Dyck words are always h and t respectively. So, we can ignore them. We are left with:  hhtt; htht; htth; thht; thth  I tried to start from the left of the sequence abcd and if I see 'h', merge the character with the one to its right. This approach didn't produce a valid mapping from the third Dyck word to the third binary operator precedence order. Can an inanimate thing lift Mjolnir? Can an inanimate thing can lift Mjolnir without the help of a living being (unworthy)  Scenario 1  Mjolnir in a very light car with a sail attached to it, then a very strong wind blew and moved the car uphill.  It is possible or not?  Scenario 2  Can upward wind alone lift the Mjolnir? I've just returned from several unusual countries in Asia, and annoyingly despite being told I'd have no problem, I'm unable to find anyone in London to change back to pounds.  I've tried Travelex in Heathrow, a currency exchange place, and the post office.  The currencies include cash from: Mongolia, Kyrgyzstan, Kazakhstan and Uzbekistan.  Most of the responses when shown the money is to the tone of "What the hell currency is this?" which doesn't fill me with confidence.  Any suggestions welcomed for places that may change this. Otherwise I may need to go back next year ;) Are there any differences between Skyrim & Skyrim: Special Edition? How can I fuse a lot of cubes? So, I made a mesh with a lot of cubes ( I've created a cube, and copied it, pasted it to make figures ), And, when I've done it, I tried to smooth it, but it looks wierd because it's made with a lot of cubes, so a lot of faces, I already tried Ctrl + J, but faces remain, Is there anyway to fuse those lot of faces in one? dpkg exit with error parsing file `/var/lib/dpkg/status`, what to do? When I try to install any software, I encounter this error, and therefore I cannot update.  Preconfiguring packages ... dpkg: error: parsing file '/var/lib/dpkg/status' near line 51245 package 'oracle-xe':  mixed non-coinstallable and coinstallable package instances present N: Ignoring file 'gcl' in directory '/etc/apt/sources.list.d/' as it has no filename extension N: Ignoring file 'gcl' in directory '/etc/apt/sources.list.d/' as it has no filename extension E: Sub-process /usr/bin/dpkg returned an error code (2) Infinite algebraic extensions of $\mathbb{Q}$ I need help to solve the following exercise:   If $K$ is an algebraic extension of $\mathbb{Q}$ (finite or infinite), then we let $O_{K}$ denote the ring of algebraic integers in $K.$ If $\frak{P}$ is a prime ideal of $O_{K}$ then $\frak{P}∩\mathbb{Z}$ is a prime ideal of $\mathbb{Z}.$ Moreover, if $\frak{P}$ is non-zero, then so is $\frak{P}∩\mathbb{Z}$ . Thus $\frak{P}∩\mathbb{Z}=$$ p\mathbb{Z}$ for some prime $p.$ Show that $O_{K}/\frak{P}$  is a field, and is an algebraic extension of $\mathbb{F}_{p}$; then show that it is Galois over $\mathbb{F}_{p}$ with abelian Galois group.  Now suppose that $K/F$ is a (finite or infinite) Galois extension. Let $\frak{P},$  $O_{K}$ be as before and put $\frak{p}=\frak{P} \cap $$O_{F}$, a prime ideal of $O_{F}.$  Show that $\mathrm{Gal}(K/F)$ acts transitively on the set of prime ideals of $O_{K}$ above $\frak{p}.$   Thanks in advance I accidentally installed some USB drivers to my Windows 7 system, they were the wrong ones and now my keyboard and mouse won't work. A system restore would get rid of them, but obviously I can't control my computer to make that happen.  Keyboard and mouse still work before windows has loaded, in the BIOS and boot system, so can I do anything from there? I've already tried booting into another OS, accessing my windows filesystem and deleting the Program Files entry, but it didnt work so they must go deeper than that. Or could i launch it from a remote machine? I've got some VNC server insalled so if i could get that running that could work.