I bought a Raspberry Pi and I noticed some of the routings are not straight lines but instead they make a funny ondulatory shape (see picture at the right and bottom of the processor).  I'm not sure the reason of this shape. I have two guesses:   It makes this signals slightly delayed compared to others. It makes the the route a certain exact length which would avoid resonance frequencies.   Are my guesses correct? Or this shapes are for something else?
I've been reading an  ( eMagazine) relating to the Raspberry Pi; "An ARM GNU/Linux box for $25."  In the article, page 17 at the bottom it shows an area on the Pi where a track zigzags next to a straight one with the explanation text:     The “wiggles” in tracks, ensure signals are matched  electrically,   reducing interference and signal delay.  This is particularly   important for high speed video  data and HDMI signals.     I have very limited knowledge of electrical engineering so perhaps this is a very simple question but why would you incorporate these 'wiggles' in a PCB design?  I realise the quote gives me an answer and I sort of understand the interference point due to problems with power cables and coaxial cables running next to each other but I'd appreciate something assuming very little knowledge that explained why you would get the problems and how wiggles help. For example, why isn't the board covered in wiggles?
"All I need (is/are) cigarettes and alcohol": which one is correct? In one of Oasis's songs — Cigarettes and Alcohol — there are two sentences that make me confused:     All I found was cigarettes and alcohol   ...and...     All I need is cigarettes and alcohol   Why would is and was be correct in these sentences instead of are and were, since they're referring to more than one thing? Can we define tension in a string as the reactive force produced in a string being pulled at both ends? In my textbook, the definition of tension was given that  is the reactive force which exists when string is being stretched at its both end. After it there was a case given that to calculate acceleration and tension produced in string while it's attached with different masses at both its ends and passed over a frictionless pulley. First body is being hung and second is placed over horizontal frictionless surface with relatively smaller mass. It is given in my book that there are three forces acting on the body placed on horizontal smooth surface viz., Weight of body, the reaction force to weight and tension in string pulling body towards pulley's wheel. How can there be tension in string according to the definition given my book however there is no acting force (pulling force) on the body that pulls it away from wheel.  There are different definitions for tension. The one in our book is creating problem however second one, that is, " tension describes the pulling force exerted by each end of a string, cable, chain, or similar one-dimensional continuous object " is al right.  Since acceleration is lowered due to Tension then acceleration produced in the body must be given by, $a=\frac{Net-Force}{m}$ $=&gt;$ $a=\frac{m_1g-T}{m_1}$ since $W_1$ $&gt;$ $T$.  If tension in string is the reactive force to the weights pulling the string apart then according to Sir Isaac Newton, $W_1=W_2=T$. I am doing exercise 3.24 of Marcus which is the following.           Let $L,K$ be number fields with $L/K$ a finite extension (of degree $[L:K] = n$) with $R = \mathcal{O}_K$ and $S = \mathcal{O}_L$. A  prime $P$ of $R$ is said to be totally ramified in $L$ iff $PS = Q^n$ for some prime $Q$ of $S$.           (a) Show that if $P$ is totally ramified in $L$ then it is totally ramified in $M$ for any intermediate field $M$, $K \subseteq M \subseteq L$.          (b) If $P$ is totally ramified in $L$ and unramified in another extension $L'$ of $K$ then $L \cap L'= K$.           (c) Give a new proof that $\Bbb{Q}(w)$ where $w = e^{2\pi i/m}$ has degree $\varphi(m)$ over $\Bbb{Q}$ (First do it for $m = p^r$ by using the fact that $(p) = (1- w)^{\varphi(m)}$ and then build up to any $m$ by using (b) above.      Now I have done (a) and (b) but when I come to (c) I fail to see how the problem is essentially circular. Even in the case $m = p^r$, I would have to use the fact that the ring of integers of $\Bbb{Q}(w)$ is $\Bbb{Z}[w]$. The proof of this fact already uses knowledge of $[\Bbb{Q}(w) : \Bbb{Q}]$ being equal to $\varphi(m)$. Am I missing something here?  Thanks. How do I install Ubuntu from an USB drive / create a live USB-stick in Windows? I tried to use the usb-creator.exe from Ubuntu 10.10 desktop i386 ISO image and it does create an USB stick that doesn't boot. When I try to boot from it I get:     Operating System not found.   I try to do this from Windows 7 x64. I'm not looking to create a live Ubuntu media, only an installation USB disk.  I repeated the process several times and I even tried to reformat the USB drive (FAT32), no success yet.  The USB stick is a 8GB one. In QGIS, I have been learning a few expressions to style my trail maps but still know little and am stumped on what to use to filter my symbol data. I am showing Parking locations on my map. I use a marker symbol as a background element, so I can do callouts. I created a data field and added values to display beside this symbol a number that references a list of parking addresses in the book's text. All good except if the field has no number to display, it is NULL, it does not display my marker symbol. I need to filter this, so it does show even when there is no value in the field. How do I remove the LAMP stack so I can start over? I'd like to start over with my webserver and I'd like to reinstall all the LAMP packages, how do I do that? Optimization paramters read-only mysql 5.7 database? What's the best way to configure a MySQL database that is only read-only, and will never have any modifications made to it?  1) I have increased my innodb_buffer_pool_size to 70% of available RAM  2) Increase query cache size to 40mb  Running against a load generator, after some time the database starts bottlenecking to only 1000 statements per second.  The configuration is 2-cores, 8GB ram 50GB SSD. The database contains a single InnoDB 13 GB table with the same exact query running on two indexed columns.  We are using a vertx server to hit the database. The symptom we see is that the web service performance degrades after 15-20 minutes of heavy load.  Where can the bottleneck be? What parameters should we optimize? Installing two glibc alongside in debian/ubuntu Is it possible to install and use two different glibc versions on the same machine. Where one version is only used to run legacy software, which relies on old glibc binaries?  Is it possible to do that with the aid of the package manager (something like "install this package, and its dependencies, to /opt/old-glibc), instead of managing it dire Show that if $a^{n-1} \equiv 1 \pmod{n}$ for all $a$ such that $\gcd(n,a) = 1$, then $a^{n} \equiv a \pmod{n}$ for all $a$. In Burton's Elementary Number Theory, when introducing absolute pseudoprimes (also called Carmichael numbers), the author states that they are composite numbers $n$ such that $a^{n-1} \equiv 1 \pmod n$ for all integers $a$ with $\gcd(a,n) = 1$.   When showing that 561 is an absolute pseudoprime, he then concludes that $a^{561} \equiv a \pmod{561}$ for all $a$.   I searched a bit on the internet, and it seems that these two are actually equivalent definitions of a Carmichael number. However I have not been able to find a proof; the fact that the implication in the title of the post is stated so plainly in my textbook makes me think it is quite simple to see, but I can't seem to understand the argument. How to exit from an application which doesn’t exit on press back button? What do the subscripts in expectations mean in loss function Can someone explain me what this equation means? I read it from page 152 on . Why do some Jedi disappear when they die while others don't? Some Jedi disappear when they die:   In Star Wars Episode IV: A New Hope       At the end of his duel with Vader on the first Death Star, Obi-Wan Kenobi let down his guard and concentrated for a moment, disappearing entirely just as Vader's lightsaber passed through his empty robe.   In Star Wars Episode VI: Return of the Jedi      When Luke returned to Dagobah in the Return of the Jedi, Yoda also disappears when he peacefully dies.  In Star Wars Episode VIII: The Last Jedi      When Luke is exhausted after “being” on Crait he looks into the Horizon and disappears.    And others don't:   Star Wars Episode I: The Phantom Menace      When Qui-Gon Jinn's dies after his duel with Darth Maul, he doesn't  disappear and is cremated.  Star Wars Episode VI: Return of the Jedi      When Vader/Anakin Skywalker dies on the second Death Star, he does not disappear and he is cremated by Luke.      Also, they all became a "ghost" after their death. My C# application is returning 0xE0434352 to Windows Task Scheduler but it is not crashing how is this picture made? Good day guys, i have to something like this, any idea how is this picture made ?  so it looks like negative i did invert it in photoshop but the bright side of his face was blue, so there been negative effect and smting been used to change his face to blue before nagative or smting that changed his face to normal skin color after negative ? what can it be ? what do you guys think ? THANKS ! for help. Differences between hash- and encryption algorithms? There is a lot of confusion between hash- and encryption algorithms; I would like to understand:   When do we use a hash algorithm and when do we use an encryption algorithm (a cipher)? How difficult it is to reverse hash- and encryption algorithms? From the theoretical/mathematical perspective, what differentiates a hash- and encryption algorithm? Word for "the entire back part of the body"? When we lie down, the "back part of the body" is in contact with the bed. It includes the heels, the calves, the backside, the back, and the back of the neck, and the back of the head etc.  How do we refer to the entire "back part" of the body? In a topological space, why the intersection only has to be finite? I was wondering if there is a reason why in the definition of a topologic space, the reunion of any collection of open sets is also an open set but the intersection has to be finite to be a set.  Is there because of the definition of an open set itself ? I have always seen it as a definition, but now I want to know why.  Thanks for your help. FTP and Apache permission issues Single word for floating dust visible in sunlight Is there a single word used in English for the visibility of dust particles floating in a stream of sunlight?     shutterstock.com Cycles not rendering with background image