In figure 12 of  EMI Design Guidelines for USB Components, I can see that VBUS and Gnd signals from the USB receptacle are bypassed with ferrite beads and then connected to their respective power and ground planes, while the USB receptable itself is tied to the ground plane at its connection points. Following this guide, my design should look like the one below:  However, after reverse engineering the PCB layout of a simple wired Razer mouse, I saw that they implemented the filtering of the ground signal slightly differently. Specifically, the ground signal from the USB cable is tied to the ground plane (no f.bead) while the USB shield* connects to the ground plane through a ferrite bead. *Noted that in this case the USB cable is not connected to the PCB via a standard micro-B USB receptable like in the first case, but instead through a permanently attatched vertical 2mm pitch 5-pin header. So when I say shield for this second case I mean the 4th pin of the Razer USB cable which is the extension of a  bundle of thin copper wires (acting as a shield) that are wrapped around the other 4 wire signals (V, D-, D+, GND). In the first case, where a USB receptable is used, the 4th pin is the ID pin meant for  , unrelated to this question. My question: Are those two methods of connecting the gnd signal to the respective ground plane similar in terms of EMC performance, or should I expect to see my board fail at the test house after following one design over the other? I would be inclined to follow the design guide had I not seen an actual product designed in a different way.
This is about the seemingly controversial shield to ground connection. The system is basically a body-worn intel-based computer, powered by a battery. Two USB 3.0 (or 3.1 Gen1) cables come out to a PCB that contains two USB 3.0 hub chips (). Two external cameras plug in to this usb hub PCB (one camera for each hub). So the usb hub PCB has 4 usb connectors (2 upstream and 2 downstream).  The question is, what to do with each of the usb connector shields? The main directive is USB connection robustness.  I have seen many recommendations. For example:  Recommendation 1  TI's TUSB8020B hub reference design  ties all shells directly to ground.    Intel's  also recommends to tie to ground (although this was written for USB 2.0).    Recommendation 2  TI's TUSB8020B EVM (and datasheet) connect shields together, and to ground using RC filter:    Microchip's  also ties shields together and uses an RC filter, but a 3 orders of magnitude smaller R:    Recommendation 3  Cypess  ties each shield independently to ground using either LC or L filter (chokes really):    The cameras themselves (off the shelf) use Cypress recommendation (LC to ground). The embedded computer seems to tie to ground from visual inspection and checking continuity to ground, but I'm not 100% sure (schematics are not available).  Now we face the shield dilemma with the hub PCB (which by the way currently does not have a metallic enclosure, it is a 3d printed plastic enclosure).   What is your say?
Save text area to file Understanding Bash's Read-a-File Command Substitution I am trying to understand how exactly Bash treats the following line:  $(&lt; "$FILE")   According to the Bash man page, this is equivalent to:  $(cat "$FILE")   and I can follow the line of reasoning for this second line. Bash performs variable expansion on $FILE, enters command substitution, passes the value of $FILE to cat, cat outputs the contents of $FILE to standard output, command substitution finishes by replacing the entire line with the standard output resulting from the command inside, and Bash attempts to execute it like a simple command.  However, for the first line I mentioned above, I understand it as: Bash performs variable substitution on $FILE, Bash opens $FILE for reading on standard input, somehow standard input is copied to standard output, command substitution finishes, and Bash attempts to execute the resulting standard output.  Can someone please explain to me how the contents of $FILE goes from stdin to stdout? How can I add a new value to a picklist using APEX? I have queries pulling all of the information correctly but what I can't seem to find was a way to add new options to a picklist using APEX.  I currently have   Package__c.Products__c.add(new Schema.PicklistEntry(products[j].Name));   Package__c is my custom object, and Products__c is the picklist. products[j] is pulling a list of products pulled from our products page.  And I've tried adding it as a select option, or even casting the variable type.  And this information has to go to the actual picklist within a custom object, and not within a visual force page or anything like that. How would I import/export Blender's preferences? I constantly stay up to date with each new release of Blender, but this means my preferences are wiped clean each time. How do I export/import these preferences to avoid loosing my carefully crafted set up each time? Where can I ask an open discussion question? Prove the existence of an analytic function Let $\Delta=\{z\in \mathbb C: |z| &lt; 1\}$. Let $f: \Delta \rightarrow \mathbb C$ be a one-to-one analytic function fixing the origin. Prove that there is a one-to-one analytic function $g: \Delta \rightarrow \mathbb C$ such that $[g(z)]^2=f(z^2)$. Further, show that such a function is odd.  The only idea which comes to my mind is the following (not sure whether it is the right direction though). Let $h: \Delta \rightarrow \Delta \rightarrow \mathbb C,\ z\mapsto z^2\mapsto f(z^2)$. Note that $h'(0)=0,\ h''(z)=2f'(z^2)+4z^3f''(z^2)$; since $f$ is one-to-one and analytic, its derivative never vanishes, so $h''(0)\ne 0$. So $h$ is an analytic function of $\Delta$ with a zero of order two at the origin. Then there is an analytic function $g$ defined in an open disc about the origin with a simple zero at the origin such that $[g(z)]^2=f(z^2)$.   This is the only thing I came up with, but it seems to be a little bit irrelevant since I don't see any way of extending this $g$ to the whole $\Delta$, and also the injectivity and oddness of such a $g$ are unclear. How to Prevent the System.QueryException I am getting "Error System.QueryException: List has no rows for assignment to SObject".   Line 1: Account ac = [select id from Account where name='testaccount' limit 1] Line 2: if(ac != null) {           //do something         }   I got the above error in line 2 if there is no record.   Any help? Why aren't people voting for questions? While at least some answers from every question seem to have been up-voted as a "helpful" answer:   about 49% of questions have score of 0 or 1. another 21% of questions have a score of 2.   Most questions seem to have an answer or two with score +5. Is it that we have a lot of fluff questions and not useful ones? Or perhaps it just seems more natural to vote for answers than questions? If we want the most useful info on Stack Overflow to filter to the top, how can this disparity be fixed?  I think this may cause real problems for people getting the badges which require +25 or +100 votes on questions.    I like a lot of the feedback I'm seeing. Two problems are highlighted:   The work flow doesn't promote voting for questions the way it promotes voting for answers. One solution: when a user answers a question, the system should invite them to vote for the question.  If someone cares enough to answer a question, then they care enough to vote for it as well. Users with less than 15 reputation cannot vote for questions or answers. Is this warranted?  Maybe these users could provisionally vote for questions and answers and those ratings would only take effect when the user reaches 15 reputation?   All I ask is this. As you browse Stack Overflow, when you see a good question: vote for it.  If everyone does, then this problem will disappear. Prove that $ n < 2^{n}$ for all natural numbers $n$. Prove that  $ n &lt; 2^{n}  $ for all natural numbers $n$.  I tried this with induction: Inequality clearly holds when $n=1$. Supposing that when $n=k$, $k&lt;2^{k}$. Considering $k+1 &lt;2^{k}+1$, but where do I go from here?  Any other methods maybe? sit on the beach vs. sit at the beach Why is the gravitational force always attractive? Is there another way to explain this without the curvature of space time?   PS: If the simple answer to this question is that mass makes space-time curve in a concave fashion, I can rephrase the question as why does mass make space-time always curve concavely? Aligning Vertices Diagonally I am designing the layout for a touchscreen for outside use, What are some good color combination to use that will be visible under the sun light for outside use? Maybe bright neon colors? Related:   This is a subtly different question because I'm not asking whether there's a historical relationship between the two lineages.  I am asking this question because answers to these questions:      are making assumptions about the appearance of Padme while pregnant, the period of gestation, and appearance of newborn babies.  All of these presuppose that the "humans" of the Star Wars Galaxy are 100% biologically equivalent to us.   In fact, as far as I know, we don't actually know any of those facts from canon.   (Do we?)   All we know is that "human" children and adults look like us.  So, do we have any canon or out-of-universe commentary that tells us that Star Wars humans and Earth humans are biologically equivalent?  Another way to put this would be  If presented with a Star Wars human and a Milky Way human, would the best doctors or the best medical droids be able to distinguish them? Texmaker generated pdf file not showing the position of cursor I am compiling LaTeX files with Texmaker on Ubuntu 12.04 system.   When I run pdflatex and then view the pdf file (internal), it does not show me the exact place where I am editing on Texmaker i.e. the generated pdf file does not show me the position of the cursor.   But some days before it was working fine. I don't know what causes this problem.  I already tried uninstalling and then reinstalling, I did update and upgrade too. But the problem still persists. Normal + Connected -> Uncountable Here's a solution (to the exercise "prove that if $X$ is a space with more than one element, and is normal and connected then $X$ is uncountable"):   by Urysohn's lemma, given $A$ and $B$, closed and disjoint in $X$, there exists a continuous function from $X$ into $[0,1]$ such that $f(A)={0}, f(B)={1}$.   If $X$ were countable, so it would be $f(X)\subset [0,1]$; choose $r\in (0,1)\setminus f(X)$, then $X=f^{-1}([0,r))\cup f^{-1}((r,1])$, so $X$ is disconnected.  But the full power of the lemma wasn't used, all that was used is that there exists a continuous function $X\longrightarrow [0,1]$, so the condition of being normal seems too much.  So my question is, what are the weakest conditions on $X$ for the existence of such continuous functions into $[0,1]$ (or $\mathbb{R}$, for that matter)? can anyone help me with this, I got stuck on it.  let $a_n$ and $b_n$ (for $n$ a non-negative integer) be two sequences of real numbers such that $\lim_{n\to \infty}a_n=a$ and $\lim_{n\to \infty}b_n=b$. prove that $\lim_{n\to \infty} \frac{a_0b_n+a_1b_{n-1}+....+a_nb_0}{n}=ab$. Eclipse not working in 16.04 latex gives me the error: Ouch---my internal constants have been clobbered As the title states, compiling with latex produces the error, right away:  Ouch---my internal constants have been clobbered!---case 14   I have no idea what this means... I use TexLive 2012. I updated my texmf.cnf and ran fmtutil-sys and texhash. I guess texhash may have messed it up?  Any ideas?  As requested a minimal working example:  \documentclass{article} \begin{document}     Any tex file. \end{document} Run a program without administrative privileges in Windows 7 My account in Windows 7 is an administrator account. When I open the Run box (WinKey + R), I am warned, "This task will be created with administrative privileges."    Is there any way to run programs as myself, but without administrative privileges when logged in as an administrator?