Is there a pen-and-paper way to securely share a secret via public key encryption?

We have several questions tagged  talking about encryption, hashing, signing, etc. but no question asks about exchanging a secret via public key encryption in a secure way.  Does any solution exist, which would allow us to exchange a secret via a public channel (think: key exchange) using nothing but pen-and-paper and which can be handled by people who are not (what one might call) “math wizards” (read: people who can calculate whole algorithms using nothing but their brain) but who do know their way around maths and who do understand crypto?  As far as I’m aware there isn’t any such solution in classic (pre-computer) cryptography. But that doesn’t automatically mean it can’t be done.  Of course, potential solutions won’t offer the security we get and expect from computer-based solutions like RSA or elliptic curve cryptography. Yet, to keep it simple let’s assume we’re not trying to protect ourselves against nation-state adversaries here. Nevertheless, suggestions should provide a usable security margin.  What would be a not so neck-breaking way to exchange a secret over a public channel using nothing but pen-and-paper means? Is it even possible to do so in a somewhat secure way without using computers, mobile phones, or other, even more rudimentary tools — like mechanical machines — that aren't always available? (Hence the tag .)  To clarify: I am not looking for  made for the purpose of “demonstrating to a 12-year-old how encryption works” and/or to be used in a “fantasy story”. My question asks for an actually usable and secure solution (as mentioned above).


This is one of those cases where I would google if I could, but I don't know what to search for.  I've come across this symbol a few times, but I have no clue what it means or what it is called.  $$\prod$$  Furthermore, what are the $\coprod$ and $\amalg$ symbols for?  I could not list all the places I found it, but the one that sparked it was a discussion on solving the Diophantine equation, $\frac{1}{x} + \frac{1}{y} = \frac{1}{n}$.


I'm using a very simple tool on Windows called  which allows me to set screen regions and maximizes to that region. Is there similar software on OS X? The one's I've found only allows you to split 50/50 and requires you to press a special key.  Thanks, Dennis


MacBook Pro won't recognize my analog audio jack headphones. Help?

Periodically, my MacBook Pro 17" stops recognizing my headphones. No amount of unplugging and replugging seems to help. The sound settings never show headphones as an output device. How can I fix this? The only thing I can find elsewhere on the Internet are people saying, "Reboot!" This works, but is impractical and annoying.


Git sparse checkout without leading directories

I understand how to configure a sparse checkout in Git, but I was wondering if it's possible to eliminate the leading directories. For example, say I have a Git repository with a folder structure like so:   folder1/foo folder2/foo/bar/stuff folder3/another/foo/bar/stuff2   And I only want the contents inside stuff2. For sparse checkout of those directories, the .git/info/spare-checkout file would look like this:  folder3/another/foo/bar/stuff2/   My problem is after I'm finished with the sparse checkout, I don't see stuff2 or the contents of stuff2 inside the root of my directory; I see folder3 and then all of the subdirectories leading up to stuff2.  I'm guessing the answer to this question is that it's not possible with Git, but I just wanted to make sure. This is one (and only) behavior of SVN that I miss; the ability to run svn co https://url.com/myrepo/folder3/another/foo/bar/stuff2 . and have the contents dumped into the current directory.


How is Software updater installing updates without my password?

I've noticed  Software updater in 12.10 installs updates without asking for my password the way it used to.  My question is, how is it doing this and what is to prevent a malicious script/program using the same technique executing privileged commands without my password or in fact without me even knowing?


Bibliography on different systems is empty

I have a problem. I'm working on my document on MacOS using prepared template. The problem i to generate bibliography. During compilation error occur - Bibliography empty. Here is my configuration:  \usepackage[ style=numeric, sorting=none, language=autobib, autolang=other, urldate=iso8601, backref=false, isbn=true, url=false, maxbibnames=3, backend=bibtex]{biblatex}  \addbibresource{mybib.bib}   I tryied backend as biber and mpm --install and --update both biber and bibtex does not working. Can anyone help ? Thanks


Using the PROC GENMOD of SAS, in "Criteria For Assessing Goodness Of Fit", I got :  Deviance = 0.6841  Scaled Deviance = 1.1002   I know that a model with too large a deviance doesn’t fit the data well, but I dont know which deviance should I take  Some help would be appreciated


I'm new to Ubuntu and Linux in general and coming from Windows I was wondering how to upgrade Ubuntu from one version to another. A new version is released each six months, right? So let's say I'm now running 13.04. When 13.10 will be released in october, how will I upgrade my system?  Will I have to reinstall my whole Linux, loosing all my programs or is there a way to simply replace 13.04 by 13.10?


What criteria does Hearthstone use to determine which minions get summoned by N'Zoth?

The Elder God N'Zoth's battlecry says:      "summon your deathrattle minions that died this game"   If this summons more minions than will fit on your side of the board, how does the game decide which minions will be summoned and which will not?


What is the justification for "Hot Network Questions" on the professional-leaning sites?

After searching for how to turn off 'Hot Network Questions' I see that debate over this topic has been raging for years. Threads have repeated and on-going replies with users posting their frustrations at looking to remove it.  It is extremely surprising that there is still no option to do so. Why is this?  Like many others, I find Stack Overflow a useful resource for professional programming and statistical issues, but this time is much less productive than it should be because of this section, and frequently turns me off Stack Overflow and makes me look for other sources first, where I won't be distracted by, for example, philosophical debate (from the interesting to the ludicrous, they're still a distraction and often not appropriate for work) or this week's Game of Thrones spoilers.  I realise this is a repeat topic, but there seems to be a large body of users who are against the Hot Network Questions sidebar, at least in its current implementation, and there does not seem to be a clear justification for why it remains like this.   Edited to clarify distinction from previous question 'what is the goal of "Hot Network Questions?" (although this also seems unresolved); I think the specific issue that I and a lot of other users have is that they are an unwanted and inappropriate distraction when trying to use Stack Exchange for work purposes.


Is there a way for Lazarus Free Pascal to check if a XML Code is well formed without using a DTD? A DTD is really specific but i just want to check if the Syntax is right.


How many naked-eye stars have 'died' since they emitted the light we are seeing?

This question is sort of in the spirit of :        The light we get from stars was emitted many years in the past, but the distances to stars which are bright enough to be visible to the naked eye are not that great, so the light we received likely wasn't emitted long enough ago that the stars would have undertaken significant changes.  On the other hand, some bright stars are red giants, which are very bright, very far away, and pretty close to the end of their lives, so there is a higher chance that they have collapsed in the meantime.  So: what numerical fraction of stars which are visible by naked eye are likely to have undertaken significant steps in their stellar evolution? Here I'm interested both in main-sequence stars evolving into red giants, giants undergoing collapse, and similar events. Similarly, how does this answer change if you increase the range to stars that are visible using a reasonable pair of binoculars?  In case special relativistic effects are important, for the purposes of this thread, both the current frame of reference of the solar system and the rest frame of the galaxy are interesting.


I don't quite understand pipes in Linux command line.  I noticed that:  ll - R | grep *.pdf   will list files ending with  .pdf  But   locate *.pdf | du -h   will not calculate the size of files ending with .pdf. Rather it will list the size of files in the current directory.  What is going wrong here?   What I have in mind is the output of the first command is the input of the next.


Show by induction: $(1+\frac{1}{n})^{n}<n$

Show by induction that for all natural numbers n>3  $(1+\frac{1}{n})^n<n$  Let $(1+\frac{1}{n})^n<n$ be true !   We show that $(1+\frac{1}{n+1})^{n+1})<n+1$  $(1+\frac{1}{n})^n(1+\frac{1}{n})<n(1+\frac{1}{n})$   $(1+\frac{1}{n})^{n+1}<n+1$  So now we just need to show that   $(1+\frac{1}{n+1})^{n+1}<(1+\frac{1}{n})^{n+1}$  So here , If I show that :   $(1+\frac{1}{n+1})<(1+\frac{1}{n})$   Does that mean im done with exercise ?


What is the difference between the Bash operators [[ vs [ vs ( vs ((?

I am a little bit confused on what do these operators do differently when used in bash (brackets, double brackets, parenthesis and double parenthesis).  [[ , [ , ( , ((   I have seen people use them on if statements like this :  if [[condition]]  if [condition]  if ((condition))  if (condition)


I am using version 2.9 I have looked at several videos and posts, but do not see this problem. I lose the menu when using the xyz math functions. see:  Thanks for any help.


In polar coordinates $(r, \theta)$, the equation $$r = \sin\left(a \theta\right)$$ gives a rose with $a$ petals if $a$ is odd, or $2a$ petals if $a$ is even.  Thus, the number of petals generated for some values of $a$ are     a   | petals =======+========    1   |   1    2   |   4    3   |   3    4   |   8    5   |   5    6   |   12    7   |   7   Conspicuously missing from this table are roses with $4n+2$ petals. How can you generate a rose of the same "shape" with $2, 6, 10, \ldots$ petals? If you can't, why (intuitively) is it impossible?


Did making Nagini a horcrux made it immortal?

So, Voldemort thought it was a good idea to make Nagini one of the horcruxes.   Did making Nagini ( or any other living creature, generally speaking ) a horcrux also make it immortal ?   Because snakes have a limited life-span, and his ambitions to live and rule forever would not seem very secure, if part of his soul lied in a mortal being.


Why do we use "./" (dot slash) to execute a file in Linux/UNIX?

Why do we use ./filename to execute a file in linux?  Why not just enter it like other commands gcc, ls etc...


From what I understand, entropy is a concept defined by the experimentalist due to his ignorance of the exact microstate of a system. To say the number of accessible microstates $W$ of the universe is constantly increasing is nothing more than saying 'ignorance begets ignorance'.  I have often encountered the argument of ever increasing entropy for the presence of an inherent time asymmetry, most prominently in the works of Penrose. It just doesn't seem to make sense.  Let us imagine alien beings who are experiencing time in reverse. For them, increasing ignorance is in the direction of our decreasing ignorance. So how can perpetual increase in entropy indicate an 'arrow of time'?  One possible explanation (I thought of) for this argument was the fact that there may never be a mechanism to reduce ignorance. I will pose this as a question:  An observer determines the number of possible microstates of system+observer to be $W_0$ at time $t_0$. After improving his measurements, can he (at a later time) measure $W'$ (where $W_0>W'$) as the number of possible microstates? Assume that all the microstates are equally probable in this case.  Unless the above in false in general, how else can anyone claim that entropy reveals an arrow of time?  EDIT: I am performing this discussion for isolated systems (the universe or it's parts if relevant). The means I propose to reduce entropy in the present, is by redefinition of macroscopic variables and of microscopic models used to count the number of distinguishable micro-states (that obviously yield the same macro-state). This is essentially an argument against the robustness of entropy via redefinition.


Can I use the same instance in multiple threads running in parallel?

Is it fine/safe if I have multiple threads running in parallel and each thread uses the same HashMap instance? The HashMap object will only be used to read data. There will be no writing data to the HashMap in any of the threads.  To be clear, the HashMap instance is a member of a base class and I will be calling the background threads in its subclasses. Those threads will then refer to the HashMap object.


ImportError: No module named datetime upgrade to Ubuntu 16.04 LTS AWS CLI

I can't get the AWS CLI using python2.7 to work after upgrading to Ubuntu 16.04LTS.  I've tried the suggestions from  with no luck.  I also uninstalled and reinstalled python2.7.  The error I get is ImportError: No module named datetime


Possible Duplicate:          I'm looking for a good book on commutative algebra covering most of (but not limited to) :   Basic Galois theory and Module algebra Primary decomposition of ideals Zariski topology Nullstellensatz, Hauptidealsatz Noether's normalization Ring extensions "Going up" and "Going down"   The emphasis is on the approach, as I would like a book giving a good geometric intuition of ring theory that I could use as a solid basis to start learning algebraic geometry.  All in all, do you remember a book that gave you a deeper geometric insight of commutative algebra ?


Is there a standard naming convention for XML elements?

Is there any standard, de facto or otherwise, for XML documents? For example which is the "best" way to write a tag?  <MyTag /> <myTag /> <mytag /> <my-tag /> <my_tag />   Likewise if I have an enumerated value for an attribute which is better  <myTag attribute="value one"/> <myTag attribute="ValueOne"/> <myTag attribute="value-one"/>


There's currently an outstanding need:  when a question needs clarification, and I'm discussing this with the OP, I receive notifications of their comments, but not edits.   And this is despite the fact that edits are the recommended way to reply to clarification requests! This has led some OPs to employ a kludge: in addition to editing the post, do a comment like "see the update".   Related:    - talks about answers, too. This one is only interested in the question  - same on the purpose but it's completely blank what the OP wants to see as a result. In the end, they - and the answer - go off on a tangent about "commenting and not showing up" and some extravagant mechanisms. This one proposes a straightforward and simple solution: notify on edits as well as comments.  - focuses on distinguishing between "major" and "minor" edits instead which is a lost cause


What is the difference between ++i and i++?

In C, what is the difference between using ++i and i++, and which should be used in the incrementation block of a for loop?


How to create a new partition on an already encrypted hard drive?

I have already encrypted my hard drive and while installing Ubuntu 17.10 on my Lenovo Ideapad. Now I wish to create a new partition on it but Gparted is not allowing me to do so. Is there any way to create a new partition without reinstalling the OS.


Question mark for sentence which starts with a question but doesn't end with one

I'm basically looking at sentences which start with a question, and end with an explanation to it. But there may be more instances of a similar structure. Sample sentence :      Can you book a room in advance, because otherwise we'd be in trouble   Should this sentence end with a period or a question mark?  PS: I read the apparently similar question  but the sentence structure there is different from what I'm looking for.  Edit: I just discovered that this question is a duplicate. A resolved question already  exists:   But i do like the explanations here better.


Ubuntu 19.10 Slow response when run programs

I have installed yesterday Ubuntu 19.10 and some programs need about 30 seconds or 1 minute to start. E.g WPS Office latest version when I click on Icon I need to wait about 30 to 60 seconds to open program. In meantime nothing happening and just pop up like normal start. Also VLC player (Latest version also), when I open video nothing happens and then after some time it's just start. I have used before Fedora and Manjaro and I didn't have any similar problems.  Here is my Laptop Specs:  System:   Host: nenad-HP Kernel: 5.3.0-24-generic x86_64 bits: 64    Desktop: Gnome 3.34.1 Distro: Ubuntu 19.10 (Eoan Ermine)  Machine:   Type: Laptop System: Hewlett-Packard product: HP ProBook 640 G1    v: A3009DD10303 serial: <root required>    Mobo: Hewlett-Packard model: 1993 v: KBC Version 16.39    serial: <root required> UEFI: Hewlett-Packard v: L77 Ver. 01.21    date: 09/03/2014  Battery:   ID-1: BAT0 charge: 46.2 Wh condition: 48.4/48.4 Wh (100%)  CPU:   Topology: Dual Core model: Intel Core i3-4000M bits: 64 type: MT MCP    L2 cache: 3072 KiB    Speed: 798 MHz min/max: 800/2400 MHz Core speeds (MHz): 1: 798 2: 798    3: 798 4: 798  Graphics:   Device-1: Intel 4th Gen Core Processor Integrated Graphics driver: i915    v: kernel    Display: x11 server: X.Org 1.20.5 driver: i915 resolution: 1600x900~60Hz    OpenGL: renderer: Mesa DRI Intel Haswell Mobile v: 4.5 Mesa 19.2.1  Audio:   Device-1: Intel Xeon E3-1200 v3/4th Gen Core Processor HD Audio    driver: snd_hda_intel    Device-2: Intel 8 Series/C220 Series High Definition Audio    driver: snd_hda_intel    Sound Server: ALSA v: k5.3.0-24-generic  Network:   Device-1: Intel Ethernet I217-V driver: e1000e    IF: enp0s25 state: down mac: 38:63:bb:b9:11:74    Device-2: Intel Wireless 7260 driver: iwlwifi    IF: wlo1 state: up mac: 80:19:34:86:21:c6  Drives:   Local Storage: total: 223.57 GiB used: 23.78 GiB (10.6%)    ID-1: /dev/sda vendor: Patriot model: Burst size: 223.57 GiB  Partition:   ID-1: / size: 218.57 GiB used: 23.77 GiB (10.9%) fs: ext4 dev: /dev/sda2  Sensors:   System Temperatures: cpu: 44.0 C mobo: 0.0 C    Fan Speeds (RPM): N/A  Info:   Processes: 263 Uptime: 7h 54m Memory: 7.69 GiB used: 2.39 GiB (31.0%)    Shell: bash inxi: 3.0.36


$$ \frac{\sum_{r=0}^{24}\binom{100}{4r}\binom{100}{4r+2}}{\sum_{r=1}^{25}\binom{200}{8r-6}} $$  I tried this problem using Complex number approach and arrived at the solution. When I tried the numerical 'normally' by summing up the binomial coefficients using various properties I was encountering some difficulty in simplifying it.  Can anybody give an alternate approach to this problem?


Is the lay explanation of the equivalence principle wrong?

The common explanation/trope for the equivalence principle always has something to do with you being inside an elevator or spaceship, and your supposed inability to differentiate, say, gravity from a rocket, or free-fall from being motionless in empty space. For example, Wikipedia  "being at rest on the surface of the Earth is equivalent to being inside a spaceship (far from any sources of gravity) that is being accelerated by its engines." Many other sources say similar things, often making broad, sweeping generalizations like "there is no measurement you can make to distinguish the two scenarios."  Isn't that just plainly wrong? Gravitational fields aren't homogeneous. Here on the Earth, a clock on the floor runs more slowly than a clock on the table, and we have clocks precise enough to measure such small differences due to the gravitational gradient. But doesn't a clock in an accelerating spaceship run at the same rate no matter where in the ship you put it?  I searched the top 50 or so questions about the equivalence principle and found  that talks about tidal effects in gravitational fields, but the explanation is very confusing. As far as I can tell, it seems to be saying the "attraction" between the particles that arises as a result of slightly different gravity vectors is somehow equivalent to the actual mutual gravitational attraction the particles should have absent the external gravitation field. I don't see how that could possibly be the case.  Also in that answer is a link to  of tidal forces and the equivalence principle, which seems to be saying the opposite: that tidal forces are, in fact, a distinguishing characteristic between gravitational acceleration and rocket acceleration, and that the equivalence principle only exactly applies to small enough points in space over a small enough duration, where tidal effects are negligible.  I know what seems most correct to me, but as I'm not an expert in this field, would an actual expert please shed some light on these varying views of the equivalence principle?


For Switching Applications - BJT or MOSFET

I am trying to read and understand on what device would be a better switching element - BJT or MOSFET. From what I have read and my understanding is that: If the application requires faster switching, we need to go for the BJT because, the capacitance between the base and emitter is very less when compared to the capacitance between the gate and the source of the MOSFET. Since, charging the capacitance takes some time, and this capacitance in a MOSFET is higher, it is slower to switch than a transistor. Am I correct? And my other conclusion is that, the MOSFET has Rds(on) parameter. So, when in full conduction, there is an inherent power loss due to this internal resistance. Whereas in a transistor, there is no resistor. So, there is no big power loss. I am not sure about the cost part of the device. Which would cost us more? Is my understanding correct? Please let me know if my understanding is correct and if there are other critical parameters I have missed?


Install Windows 10 on a partition with ubuntu 16 already installed

I want to start by saying that I know this question has been asked a lot, but the 10~15 articles and posts I've read all assume that the reader is knowledgeable on the subject, and I'm not.   So, I currently have ubuntu 16 installed on a dell latitude 6430u (if that matters). Basically what I've gathered is that I would want to install some windows 10 software on a flash drive and create a new partition on my SSD so that I could dual boot into windows 10 (switching by pressing f12 on start up to get into the bios). Now, I can't fully understand how I'm supposed to do most of that. I'm seeing a lot of installing/using grub but I'm not sure what it's saying. Any way I could get some pointers?  Some places are saying it's easier to whipe ubuntu and install windows 10, then reinstall ubuntu, but I would prefer to avoid that. Thanks  Edit: I think my question is different than the given duplicate because they're talking about windows 7. Also using cd drives, which I don't have.


Am I going to have trouble flying without my full name on the ticket?

In my passport, my name is Firstname middlename1 middlename2 lastname, and in the ticket is LASTNAME/FIRSTNAME MR.  Will be a problem? I'll travel from Brazil to Bali, Indonesia and according to the agency I bought the ticket from, there's no problem and it's common.  The airline is Qatar Airlines and I have looked , which says that the passenger name can't be changed after the booking has finished.  But I don't know if it is a problem.


what does f 22 do if lens only shuts down to 6.3

what happens when I dial in an f stop of 22 on my old canon xti using a 200mm telephoto 3.5 - 6.3?


Is it grammatically correct to change tense in a sentence?

When writing a sentence, can I change from past-tense to present-tense in the middle of it? For example,     Joey realized that the ball is green.   or     Joey realized that the ball was green.   I am talking about a ball which is always green. The second example implies that the ball was green and that it may or may not still be green. However, Joey realizes it in the past. Is the first sentence grammatically correct?


She has five kids. I can imagine how busy she would be.   Is the use of would be right in this sentence? What about      She has five kids. I can imagine how busy she is.   Are both correct? Do they mean different things?


Howdy guys,  so i am trying to use Case operation on a String ,is Case operators only works with Integers ? Because the compiling error :  switch quantity not an integer   And i have this code as an example :  #include <iostream> using namespace std;   int main(){ string type; cout<<"Please enter your computer type (PC ,Laptop, Smartphone) : "<<endl; getline(cin, type);   switch(type){  case "PC":  cout<<"Ok so you'vr got a "<<type;  break;  case "Laptop":  cout<<"Aha ,u got a "<<type;  break;  case "Smartphone":  cout<<"That s not bad ,u ve got :"<<type;  break; }   return 0; }   I know that i can use other logical operators like IF ; but i am stydying the Case operators so i am curious can i work with Strings or not.


Why can even cycles be bipartite? Are all even cycles bipartite?

I'm drawing it and I'm having trouble finding the two sets. Could someone give me a drawing with colorings of a cycle with even length such that it is bipartite? Also, could someone provide a proof of whether every even cycle is bipartite? I already know that a bipartite graph has no odd cycles.   EDIT: I just figured it out with $C_4$. Could someone still provide a proof whether all $C_n$ is bipartite?


SQL - Multiple Values comma separated when using GROUP BY

I have data that looks like   CUSTOMER,  CUSTOMER_ID, PRODUCT ABC INC    1            XYX ABC INC    1            ZZZ DEF CO     2            XYX DEF CO     2            ZZZ DEF CO     2            WWW GHI LLC    3            ZYX    I'd like to write a query that'd make the data look like this:   CUSTOMER, CUSTOMER_ID, PRODUCTS ABC INC   1            XYX, ZZZ DEF CO    2            XYX, ZZZ, WWW GHI LLC   3            ZYX    Using Oracle 10g if helps.  I saw something that would work using MYSQL, but I need a plain SQL or ORACLE equivalent.   I've also seen examples of stored procs that could be made, however, I cannot use a stored proc with the product i'm using.  Here's how'd it work in MySQL if I were using it  SELECT CUSTOMER,         CUSTOMER_ID,         GROUP_CONCAT( PRODUCT )  FROM MAGIC_TABLE  GROUP BY CUSTOMER, CUSTOMER_ID   Thank you.


Fan control on Lenovo Thinkpad Edge S430 and Ubuntu 13.04

I'm trying to make my thinkpad's fan run on higher speeds because of overheating. I've enabled fan_control in thinkpad-acpi module, at least I think so:  $ cat /sys/module/thinkpad_acpi/parameters/fan_control  Y   However, it does not seem to respond to changes:  $ echo 'level 7' > /proc/acpi/ibm/fan   No error, but no reaction either. Any advice on how to proceed? Does it mean my Thinkpad does not support fan control?  Note that this question is NOT the same as  - my fan_control is apparently on, and I do not get any invalid argument error when I'm trying to echo new level.


"variance matrix is nonsymmetric or highly singular" in Stata; no SEs in table

I get the above warning in Stata when I run a (clustered-panel pseudo-Poisson ML gravity-) regression.   Observations are pairs of countries and the regression includes dummies for each combination of country and year (2005-2012) as well as a lagged variable of one continuous independent variable.  If I drop either the set of dummies or the lagged variable, it works fine. But of course I'd like the dummies AND the lag to be in that regression...  Can anyone tell me what causes that warning and how I can work around it?  Results can be found here:  (note: I am aware that the dependent should not be logged)


My recipe calls for a small tin of tomatoes plus another tin of tomatoes. Is a small tin of tomatoes equal to a 14 1/2 oz size can of tomatoes and the tin of tomatoes equal to the 28 oz size can or is the tin of tomatoes equal to a 14 1/2 oz can size and the small tin equal to something along the size of a tomato sauce can?


This question's my profesors. I know $x^n$ is a pointwise convergent sequence. But I don't know how can I show that this limit. Can you show me solution of this question. $f:[0, 1]\rightarrow \mathbb{R}$ continuous function. $$\lim_{n\rightarrow \infty }\int_0^{1}x^nf(x) \, dx$$ Find the limit.


Which are the safety recommendations for soldering?

I was reading about tin alloys for electronics soldering and found it it has about 40% of lead in composition. Lead, everyone knows, it's very dangerous to breathe due to being a heavy metal. Also, I found some recommendations using the combination of an exhauster and a respirator when working with soldering. Is there any international regularization of which respirator type should I use? If not, which type do you recommend? Beyond this, is there any additional safety equipment recommended?  For economics reasons and for better soldering resistance, I've already discarded Pb free solder reflow.


How can we address the relative imbalance in the review queue lengths?

In an effort to unashamedly pursue cool looking hats   improve the quality of the glorious SO forums, it seems that whereas the Close Votes queue looks my work inbox after spending so much time on SO during Winterbash rather overwhelming, all the other queues seem like my bank balance after Xmas rather anemic.  As a result, I rather feel like any new posts which do make it into queues like First Posts, Late Answers et al get gobbled up like a lone steak tossed to a pack of wolves processed rather quickly, to the point where the post has already been stolen by cretinous fellow hat snatchers actioned by other esteemed members.  Would SE be open to any ideas on how to improve the Queue status quo, e.g. by deviously closing a few Close Vote posts and reflagging these as Vote to Reopen instead, raising the bar on the Close Vote queue, whilst lowering the requisite counts on the less bloated queues?  Merry Winterbash!


How to set all pixels with value <= 0 to "nodata" in DEM raster?

I have a DEM raster with pixel values between about 3000 and -0.0003. I need to set all pixel with a value of 0 and smaler (<=0) to "nodata" (for later raster calculations and to reduce the filesize).  It seems for me that this is a task for the raster calculator (set value of  pixels <=0 to "nodata") or a reclassification (set value of  pixels <=0 to "nodata" and keep all other values) but I dont know how.


Underfull \hbox (or \vbox) and Overfull \hbox (or \vbox)

I'm currently using the  with strong requirements on text with and text heigth. After compilation of my latex file I got a lot of warnings of the following kinds   Underfull \hbox (badness 10000) or Overfull \hbox (3.7778pt too wide)   for instance. As a consequence some black boxes appear at the end of some lines or in some diagrams of the generated pdf file.  How can I take care of these warnings ?  To be more specific, please find below a few lines of code that causes a warning "Overfull \hbox (3.778 too wide)":  $$\xymatrix{\underset{~}{Z}\ar[rr]^t \ar@{ >->}[dd]_*[@]{\hbox to 4pt{$\sim$}}_-{h\quad}&&X\ar[dd]^f\\&\circlearrowright&\\Z'\ar[rr]_u &&X'}$$ one has $$\xymatrix{\underset{~}{Z}\ar[rr]^t \ar@{ >->}[dd]_*[@]{\hbox to 4pt{$\sim$}}_-{h\quad}&&X\ar[rr]^r \ar[dd]^f&&Y\ar@{->>}[dd]^g\\&\circlearrowright&&\circlearrowright&\\Z'\ar[rr]_u&&X'\ar[rr]_{r'}&&Y'}$$   If I change the 4pt{$\sim$} by 8pt{$\sim$} then the warning disappears and the small undesired black box in the pdf file does too. However by incrementing to 8pt the \sim symbol is a bit too far above the arrow for my taste but it's not a big problem.  Do you have a better solution ? Especially for avoiding to make this change by hand in every single diagram where the problem occurs ?   Thanks


Error message "E: unable to locate package firmware-b43-installer"

I am using an Acer Aspire 5002WLMi laptop and set up a dual boot with Windows XP and Ubuntu 12.04. Wi-Fi is working well in Windows XP, but when I start Ubuntu I will get the below error.  [ 95.514855] b43-phy0 ERROR: You must go to http://wireless.kernel.org/en/users/Drivers/b43#devicefirmware and download the correct firmware for this driver version. Please carefully read all the instruction on this website.   Then I followed the instructions from the below link.  file:///C:/Documents%20and%20Settings/MGL/Desktop/how%20to%20install%20ubuntu/Ubuntu%2012.04%20Splash%20Screen%20Lockup%20with%20LiveCD%20_%20Ben%20Rousch%27s%20Cluster%20of%20Bleep.htm  But I am stuck in installing the Broadcom Wi-Fi firmware in Terminal, and it is showing this error:      E: unable to locate package firmware-b43-installer   How can I proceed?


The Ellipse Problem - finding an ellipse inside a triangle

The problem statement is as follows:  A triangle is dissected into six smaller triangles by its angle bisectors. Prove that the intersections of the angle bisectors of each of these smaller triangles lie on an ellipse.  Could anybody here solve it?


Most of the people seem pretty much content with classical electromagnetic theory .And most of the applications use classical EM theory .However, in such situations I would like to know what was the necessity of Quantum Electrodynamics. Is it an advanced version of classical EMT ? Does it remove any flaws in classical EMT ? Are there any practical applications of QED ?


Pork sausage patties in a crockpot overnight

Is it safe to store a crockpot full of freshly cooked pork sausage breakfast patties overnight?  set on Warm. ? Also do you think this will make them "dry" to eat in the morning?  If it's safe, do you know any tips for making them keep their taste/texture ?


What is a good way to sync two MySQL databases?   I would like to sync the data in my production website's database to my local development database. Right now, I am just using the PHPMyAdmin interface to export it from one, and then I import it into the other.  These would be user-initiated sync's, not necessarily periodic or automated (something like a one-click sync).


Temperature of room for open door of refrigerator

Will the temperature of the room increase or decrease when the refrigerator door is kept open for a while ?  My book says that , the room temperature increases . But I don’t understand its reasoning.   I want to understand the role of compressor here along with the roles of evaporation and condensation tubes...How do the refrigerants warm up the room ?


What is the meaning of the ending of Goodfellas?

Henry looks into the camera and "gets shot" by Joe Pesci.  Why does he look to into the camera and "gets shot" by Joe Pesci?   I understand how meaningful the name of the song is but I don't understand the rest. I have heard it's related to The Great Train Robbery. Is this true?


I installed Ubuntu 16.04 on my new Asus A540LJ Laptop. The touchpad works but multitouch isn't. Please help me.  I really love Ubuntu,but I need multitouch on it.  Here's the output of xinput  $ xinput ⎡ Virtual core pointer                      id=2    [master pointer  (3)] ⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)] ⎜   ↳ FTE1001:00 0B05:0101                      id=11   [slave  pointer  (2)] ⎣ Virtual core keyboard                     id=3    [master keyboard (2)]     ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]     ↳ Power Button                              id=6    [slave  keyboard (3)]     ↳ Video Bus                                 id=7    [slave  keyboard (3)]     ↳ Video Bus                                 id=8    [slave  keyboard (3)]     ↳ Sleep Button                              id=9    [slave  keyboard (3)]     ↳ USB2.0 VGA UVC WebCam                     id=10   [slave  keyboard (3)]     ↳ Asus WMI hotkeys                          id=12   [slave  keyboard (3)]     ↳ AT Translated Set 2 keyboard              id=13   [slave  keyboard (3)]


Show that there is no rational number such that $x^2=3$

i've juste asked myself if it is possible to proof that there is no rational number such that $x^2=3$ using rational sequence. I know that there is a more direct maneer to proof this assertion but i'd like to know if it is possible to show with sequences. I was thinking to try to proof by absurd and show then that the left and right limit are not equal. Thanks in advance!


Law of cosines in Time dilation formula derivation

In my book, Bob takes off on a spaceship with a light clock so that the direction of motion of his spaceship is perpendicular to the direction of motion of light in the light clock.  As a result, Alice (on Earth) sees the distance traveled by light to be $\sqrt{L^2+(vt)^2}$, (given by Pythagoras theorem) which leads to the usual time dilation formula.  But if Bob's spaceship doesn't travel perpendicular to the light, then the distance observed by Alice would be given by law of cosines. This will lead to a different formula for time dilation  Why is the second formula not valid?


Raspbian: Lock (but not logout) of Command-line-only system so that background processes can continue

I have a Raspberry pi running full Buster but only boots to command line interface (CLI).  Currently, I can only login or log out.  I want to be able to stay logged in so my background processes can keep running, but lock the system so that someone can't walk up and accidentally mess with it.  I would also like to enable auto-login so certain scripts requiring a logged in user can run, but still have the security of a lock. This question has nothing to do with SSH anymore and thus the 10 year old SSH thread a moderator recommended is neither partially or wholly duplicative.


Proving the Exchange Principle in model theory

Let $\mathscr{M}$ be an $\mathscr{L}$-structure; we say that a definable $\mathit{X}\subseteq\mathit{M^n}$ is strongly minimal if $\mathit{X}$ is defined by an $\mathscr{L}_\mathit{M}$-formula $\phi(v)$ and for any $\mathscr{M} \prec \mathscr{N}$, if $\mathit{X}^\mathscr{M}$ is the subset of $\mathscr{N^n}$, then any definable subset of $\mathit{X}^\mathscr{N}$ is finite or cofinite.  Suppose $\mathit{X}\subseteq\mathit{M^n}$ is strongly minimal, and let $\mathit{acl^X} = \mathit{X} \cap \mathit{acl(A)}$ for $\mathit{A} \subseteq \mathit{M}$. Show that if $\mathit{x} \in \mathit{acl^X(A \cup \{b\})}$ and $\mathit{x} \notin \mathit{acl^X(A)}$ then $\mathit{b} \in \mathit{acl^X(A \cup \{x\})}$.  I've wrestled with this problem for a little while now and I'm honestly not quite sure what to even do here, at this point I'm really just looking for a nudge in the right direction--whether that be a little perspective or a question to make me think about this differently. This problem comes from David Marker's Model Theory: An Introduction page 106, problem 3.4.15 part (a).  Here is what little I've got so far: if $\mathit{x} \in acl^X(A \cup \{b\})$ then $\mathit{x}$ is algebraic over $\mathit{A \cup \{b\}}$, so there is some formula $\psi(v, \bar{w})$ and $\bar{a} \in \mathit{A \cup \{b\}}$ for which $\mathscr{M} \models \psi(x, \bar{a})$ and the set $\mathit{\{x_0 \in M:\mathscr{M} \models \psi(x_0, \bar{a})}\}$ is finite. Because of the definition of of $\mathit{acl^X}$, anything in it is also in $\mathit{X}$, which would allow me to make use of its strong minimality, though I'm unsure of where that comes in. Also, since $\mathit{x \notin acl^X(A)}$ doesn't that force the $\mathit{\bar{a}}$ parameter for $\psi$ to be precisely $\mathit{b}$ ?


Who is the single most powerful entity in the marvel universe?

Okay, I know this might be a really stupid question to ask, but I have always been on the look out for the being to whole the title "most powerful" and when I was watching  I got curious as to who would fit the bill in the Marvel universe.  I have looked into characters such as , , , , , , and , all of which listed some way that they could be destroyed.  So, my question is two-fold. Who, in the Marvel Multi-verse, A) has the greatest power and B) the smallest (preferably non-existent) weakness?


Titles should be stand-alone summaries of questions *without* depending on tags

Titles should be completely independent of tags.  A good title tells an expert whether they want to read the full question all by itself. I know this has come up multiple times before, before, but in each case, the discussion has seemed to have turned into a different question.  For example,   really asks, "Don't we need tags in titles to help with SEO"? So, "no, we don't, because we add the top tag (or two, in some cases) to the crawler results," is correct, but it appears that people are interpreting that to mean that people generally can (or should) omit key terms from their titles if they exist in the tags.  To be clear:  I agree that we should never force a tag into a title if it's not helpful;  should NOT have "[Baking]:" jammed into the title, because it adds nothing to a reader's understanding of what it's about, BUT...  Nothing should be left out of a title just because it exists in the tags.   Trilogy examples:   , ,   examples: , , , The problem with all of these is that without a language, OS, or game title, they fail to convey whether you care to read the question, because you need to read the tags to even figure out if you work with the language or own the game in question. A term being in a tag in no way reduces the need for it in the title.  Tags are great for filtering, but a title is supposed to function like a headline. This is a good headline:  This is not very good headline:  Titles, like headlines, are BIG AND BOLD on the front and other pages.  So you can browse and stuff.  Tags are small, and kind of low contrast.  So they don't, you know, distract you from the headlines. Bear in mind that on non-technical sites, new visitors, even new experts, don't necessarily even know what tags are. The title test:  If you assume the reader can't even see the tags, is your title a good, stand-alone summary of the question for an expert on that topic?  I'm sticking with gaming examples because they're more broadly accessible than some topics:   does not need, "in Starcraft" added, because it's impossible to be interested in the answer and not know that a zergling question relates to Starcraft.  but...  , absolutely needs "...in Starcraft 2" added to it, because without the tags, it's currently useless as a way to decide if you want to read it.  This is really no change from :  In the wake of that comment, people seemed to mostly hear:  "stop forcing a word you don't need in just cuz it's a tag"  ... which is right, but what it really says is,  "most of the time, some tags will naturally belong in a title that effectively summarizes the question".  EDIT: Some folks felt this was (an unduly public) way to call out gaming specifically. It's not - I think this is a problem to varying degrees on a number of sites, but used examples from gaming because they're easy for most readers to follow. Sincere apologies to anyone in the Arqade community who felt I was using a network-wide forum to criticize a gaming practice - I wanted to clarify the best practice for all the sites that encounter this at least sometimes, including SO, where you still see people stripping languages from titles in edits sometimes.


Some Old Arxiv.org papers PdfLatex Problem

Some 90's papers in arvix.org do not produce proper PDF. When the PDF is generated, some texts are cut off from the bottom of every single page. Here is a link to a paper in the arxiv which demonstrates the problem:   There are a lot of important old papers in the arxiv which have this issues. I tried downloading the Latex source file first and then compile it, but it doesn't run, shows a lot of errors.  Is there a direct way to solve this problem? There is of course always a brute force method: First download the paper latex source file from the arxiv, then change the document class to something like `amsart' and then change all of the other codes in the file to the to appropriate amsart document class codes.  This process becomes practically impossible for a long paper.   It would be a big help if there were some direct ways to solve this problem.


Looking for more occupational records of Walter Cowin

Looking for occupational records of a Walter Cowin, born circa 1910. He can be found on the 1939 register living at 6 Mill Street Chester, as a "public works labourer".   He was between the age of 18 and 41, and I don't see that as a reserved occupation so I assume he was conscripted into the army. Where can I look for more records about his occupation? I've tried British Newspaper Archive but it costs money to use.


Let $R$ be a Artinian commutative ring with $1 \neq 0$. If $I$ is prime, then $I$ is maximal.

Prove: Let $R$ a Artinian commutative ring with $1 \neq 0$. If $I$ is prime, then $I$ is maximal.     I got stuck on this. I understand that every ideal is generated by finitely many elements. Here is my approach:  It's enough to prove the following implication: $$ R/I \ \text{is a domain} \quad \Rightarrow \quad R/I \ \text{is a field}$$ Then only finding an inverse is left. So let $x \in R$ in arbitrary. We have to find an inverse element of $x+I \in R/I$, that as an element y so that $x \cdot y \in I+1$. We denote $I = (x_1, x_2, \cdots, x_n)$.  Now I have to find y so that $xy -1 = r_1 x_1+ r_2 x_2 + \cdots + r_n x_n$. This is where I no more knew what to do.   Your advise will be appreciated.


Return Code Best Practices in Windows apps

A windows application requires to return different error codes when there has been a problem while being called from Command Line. I am trying to find an appropiate way to define the error codes. So far I have only found standards related to Operative Systems or HTTP.  For example in Windows:


Internet bandwidth consumption monitor process wise monitoring?

I had some three or four askubuntu pages open in my firefox's tabs, and the pages suddenly started responding extremely slow. I checkd the system monitor, and it showed huge amounts of data being downloaded and it was continuous at the highest bandwidth my DSL connection can offer with some notches at intervals. I couldn't figure out the reason why it happened, couldn't draw any conclusions from the monitors process information. Then I closed the browser, and the download graph went down too.  I need help with some command tool/script (preferable) that would instantly display an ordered list of the processes consuming my bandwidth. (some packet tracing utility? bandwidth consumption monitor?) And please summarize how to get it done.  Update 1: I tried nethogs and made some test download with web broswer and other tools. nethogs did show what programs were consuming the bandwidth, (please note that previously in my problem I too guessed it was firefox, but the actual problem was what in firefox is devouring my bandwidth? It's not auto-update! I don't think I've configured anything for autoupdates in my system.) I want the suggested tools to show me what things are being downloaded and not just the client; for example the tool should say "it's chromium-browser downloading file1.something and file2.somethingelse".


Unable to change execute permissions of .sh file

I'm out with a new problem. I've downloaded a jdk7.sh file. Now I'm unable to change the permission of the file to allow executing the file as a program. I mark the check box and again it disappears.


How to get data from “dead” hard disk drive?

I went through few questions (see the list below) but haven’t found the answer to my question...          The question is what software can I use to analyze to find out if I can get any data from my Seagate ST300003U2 External USB hard disk drive.  It was lying in a drawer for few months unused and few weeks later I wanted to access my backed up pictures there and Windows now will not recognize it properly after plugging it in and Ubuntu will not detect it at all.  I went to the professionals and they quickly tried by connecting to a Win machine and told me that if I left the drive with them there they “might” recover something. I asked how they would do it and the I was told that they got some tool to run it against. I want to try them by myself if there is any free version. Of course they did not tell me name of the tools.  Any idea what free/opensource software on Windows or Linux or self bootable solution I can use to analyze such a hard disk drive?   UPDATE  I get this message on Win7. So there is no issue with cables or so in my eyes. I wonder why Ubuntu gives me no message.    I got this from Device Manager: Windows has stopped this device because it has reported problems. (Code 43)


In category theory, a monomorphism is a situation where     $g: A \rightarrow B \;\;$ , $\;\;h: A \rightarrow B\;\;$ and $\;\;f:B  \rightarrow C$      $f \circ g = f \circ h \;\text{ imples in } \; g = h$   I heard recently something about monomorphism to be an injective homomorphism , but it didn't make sense to me and I still couldn't prove it.   How can I prove that monomorphism is an injective homomorphism (at least for monoids)?


I have a list in SharePoint 2010 that contains Active Directory users in one column and their birthday in a second column.  Early in the morning of their birthday I want SharePoint to automatically send an email with predefined text.  I have created a workflow with the predefined text and the condition to send an email to the user if the birthday is equal to today, but I can't get it to work.  Help!!


I have a new client whose site I will be re-building. I noticed on his site he has a badge from McAfee saying the site is secure. Below is an example:     I have seen similar type badges by other companies as well on other sites.   My question is this:   Do these types of services increase conversion and trust for a site? In other words, these services claim that it will increase the trust for the consumer thus increase sales and interactions on your website.  I am looking for studies that provide proof or results than just an opinion as an answer, preferably by a third party who does not offer the service.  Edit   is essentially the same but the answer there provide opinions vs documented studies (other than the ones the companies provide). I am looking for documented studies as an answer.


Let f be an entire function. Suppose $\exists$ $M>0$ such that   $\mid$$f(z)$$\mid$ $\leq$ $M$$\mid$$z$$\mid$ $\forall$   $z$$\in$$\Bbb{C}$. Show that $\exists$$\lambda$$\in$$\Bbb{C}$ such   that f(z)=$\lambda$$z$ $\forall$ $z$$\in$$\Bbb{C}$.   This problem is related to Liouville's theorem (which is a corollary of the cauchy inequalities) and someone told me use function g(z)=f(z)/z. But since g(z) is not 'entire' function, I don't really know how to use this function to solve this problem. How can I solve this matter?


Cropping videos in Windows Live Movie Maker

I want to crop (as in, take a subset of each frame, like when you crop a photo) a video in Windows Live Movie maker. Is there a way to do this, and failing that is there another free tool i can use to do that?


I am using a 2 column document and have a 2 column figure placed at the top of the page. The problem is that the figure is showing up on page 3 instead of page 2. It is the first figure in my document.  \begin{figure*}[t!]\         \centering         \includegraphics[width=\textwidth]{results}\\         \caption{Recall vs. IOU for class \textit{car} with an average of 500 proposals. Best viewed in colour.}         \label{fig:results}     \end{figure*}


Use a polygon for a reverse cookie cutter

Is there a way using c# or arcpy to use a polygon to cut a  hole in a database through lines, points, and polygons, like a reverse cookie cutter?  This is without having to import and export the whole database. Just cut the hole in place in the database.


What does the phrase "all but" signify in following text?

What does the phrase "all but" mean in this sentence?     Interpol has all but ruled out terrorism.


Interpreting coefficient in a linear regression model with categorical variables

I will give my examples with R calls. First a simple example of a linear regression with a dependent variable 'lifespan', and two continuous explanatory variables.  data.frame(height=runif(4000,160,200))->human.life human.life$weight=runif(4000,50,120) human.life$lifespan=sample(45:90,4000,replace=TRUE) summary(lm(lifespan~1+height+weight,data=human.life))  Call: lm(formula = lifespan ~ 1 + height + weight, data = human.life)  Residuals: Min       1Q   Median       3Q      Max  -23.0257 -11.9124  -0.0565  11.3755  23.8591   Coefficients:              Estimate Std. Error t value Pr(>|t|)     (Intercept) 63.635709   3.486426  18.252   <2e-16 *** height       0.007485   0.018665   0.401   0.6884     weight       0.024544   0.010428   2.354   0.0186 *   --- Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1   Residual standard error: 13.41 on 3997 degrees of freedom Multiple R-squared: 0.001425,   Adjusted R-squared: 0.0009257  F-statistic: 2.853 on 2 and 3997 DF,  p-value: 0.05781   In order to find the estimate of 'lifespan' when the value of 'weight' is 1, I add (Intercept)+height=63.64319  Now what if I have a similar data frame, but one where one of the explanatory variables is categorical?  data.frame(animal=rep(c("dog","fox","pig","wolf"),1000))->animal.life animal.life$weight=runif(4000,8,50) animal.life$lifespan=sample(1:10,replace=TRUE) summary(lm(lifespan~1+animal+weight,data=animal.life))  Call: lm(formula = lifespan ~ 1 + animal + weight, data = animal.life)  Residuals: Min      1Q  Median      3Q     Max  -4.7677 -2.7796 -0.1025  3.1972  4.3691   Coefficients:             Estimate Std. Error t value Pr(>|t|)     (Intercept) 5.565556   0.145851  38.159  < 2e-16 *** animalfox   0.806634   0.131198   6.148  8.6e-10 *** animalpig   0.010635   0.131259   0.081   0.9354     animalwolf  0.806650   0.131198   6.148  8.6e-10 *** weight      0.007946   0.003815   2.083   0.0373 *   --- Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1   Residual standard error: 2.933 on 3995 degrees of freedom Multiple R-squared: 0.01933,    Adjusted R-squared: 0.01835  F-statistic: 19.69 on 4 and 3995 DF,  p-value: 4.625e-16   In this case, to find the estimate of 'lifespan' when the value of 'weight' is 1, should I add each of the coefficients for 'animal' to the intercept: (Intercept)+animalfox+animalpig+animalwolf? Or what is the proper way to do this?  Thanks Sverre


How does TD Ameritrade calculate the overall volatility for each expiration?

The image below shows option chains in thinkorswim. Note the percentages on the right hand side:  The percentage on the right hand side is the overall volatility for options in each expiration (while the number in parenthesis is the expected move based on the volatility) (). I can't seem to figure out how they're determining the volatility. It's not available in the API. Is this some sort of average of all the underlying strikes?


“Was” or “were” in sentence where no noun subject exists

I can't figure out if the below sentence should use “was” or “were”, since I'm not sure what the subject of the sentence is. Is the sentence incomplete? How do I handle this kind of sentence, where no nouns or pronouns are present?     Knowing how to jump and being able to run was / were crucial during my high jump career.


There do not exist $m\times n$ and $n\times m$ rectangular matrices $A$ and $B$ . t. $AB=I_m$ (The $m\times m$ Identity matrix)

Let $m,n\in\Bbb N$ be positive with $m>n$. Prove that $\nexists A\in M_{mn}\ \&\ B\in M_{nm},\ AB=I_m$ (The $m\times m$   Identity matrix)   I have noticed that this is not true if the matrices are multiplied the other way. That is, say $B=\begin{bmatrix} 1 &0  &0 \\   0&  1& 0 \end{bmatrix}$ and $A=\begin{bmatrix} 1 &0 \\ 0&1 \\ 0&0 \end{bmatrix}$ Then the product $BA$ yields $I_2$, But not the other way. Here this does not contradict with the statement in the question because of the order of the matrix mentioned in the question (that is the one with a higher number of rows should be multiplied first). So, a proof for the given question is highly appreciated


Android app development issue - Where to ask?

I need advice on how I can design an Android browser with an on-the-fly HEVC conversion capability to reduce the file size of media files.   Is there a Stack Exchange site appropriate for this question?


Altera DE2 interfacing with analog sensor

Can Altera GPIO pins read the analog output of a light sensor? The light sensor output is analog and I want the Altera to turn an LED on whenever the signal of the sensor is greater than some specific value.   Can I do that directly, or do I have to connect the output of the sensor to an ADC? How would I go about that?


How can I upgrade from 5.1.1 to 6.x in order to utilize  storage?


Is there an alternative to using enums in PHP? I only ask because in C# I have methods that return an emum, but in PHP nothing similar exists. Here are some possible return types from a fictitious method:  function login() {     // logged in     // log in failed verify account     // log in failed account suspended     // log in failed account banned  }   What's the best way to do something like this in PHP?


How can I download the installer for macOS Sierra 10.12?

I have a MacBook Pro running El Capitan that I need to upgrade to Sierra 10.12 (not High Sierra) for development reasons.  I have previously upgraded my personal computer as follows: El Capitan -> Sierra -> High Sierra.  Knowing that, I should be able to see the previous version in the App Store as outlined in .  However, I don't see Sierra in my Purchased tab in the App Store:    Was Sierra 10.12 completely removed from the store (including previous purchases)?


SSH gateway with all config on the gateway?

I have a ubuntu server running some LXD containers - none of these have public IP's, but are exposed to the web by a reverse proxy for HTTP.   These containers belong to different individuals and I would like to be able to allow them to login to the container via SSH. I don't want to allow users to be able to try passwords on containers other than their own one, And I don't want users to have to configure the SSH tunnel / gateway themselves.   So I'm wonderig if there's a way that I can set up an SSH gateway such that, based on the users key or username, the proxying is automated for them through the gateway.  This old article -  - seems to imply that something like this is possible: "The SSH gateway works by forcing a ssh to another host as a particular username, based on the ssh key."   However I can't find any other reading about it ... Is this something that can be done?


This script counts the days between two dates and shows the result on a span element:     But instead I want to show the result as value of an input element:  <input name="name" type="text" id="name" value="i want count days here " />   How can I do this?  This is the complete code:  <!DOCTYPE html>               <meta charset="utf-8" />         <title>jQuery UI Datepicker - Default functionality</title>         <link rel="stylesheet" href="http://code.jquery.com/ui/1.10.2/themes/smoothness/jquery-ui.css" />                           <link rel="stylesheet" href="/resources/demos/style.css" />                                     <form class="formwhite">

From:	<input type="text" id="from" onKeyUp="calculate();" />&nbsp;

To:	<input type="text" id="to" onKeyUp="calculate();" />

         </form>


Is there any non-human organic life still alive by the time of the events of 'The Matrix'?

We are told in The Matrix by Morpheus that humanity had blocked sunlight in the hope that it would prevent the Machines from recharging.  At the same time though, almost all life depends on sunlight, either directly or indirectly.  Therefore, by blocking sunlight, it would severely hinder the capability of organisms to survive.  My question is then, by the time of the events of The Matrix when Neo is freed from The Matrix, is there any non-human organic life?


I bought a laptop that came with Windows 8 installed. There were problems with my laptop and I couldn’t even use the Windows 8 refresh or restart, so I installed Ubuntu. I now have only Ubuntu on my laptop and was wondering if there was any way I could go back to Windows 8 without paying. In my BIOS, it says my factory installed OS is Windows 8, and I have the sticker on my laptop to prove it in case I have to send it in.  EDIT 1:  I called them and they said it would cost $30 to get another cd.  My sticker looks like the one on the left.    EDIT 2:   My laptop is an HP Pavilion g6 I have wiped the partition and there is only one with Ubuntu on it. I think I have my win 8 serial written somewhere Nowhere on the PC does it have any key. I have a legal Win XP SP2 cd (with key) if that helps.


using jQuery to add element in DOM after page content has fully loaded

It is easy to add text in page after loading thanks to javascript but I would like to add a link with a link  and be able to catch the click event without reloading page  $("#div").html("new link");   // not work, because no  $("#new").click(function(e) {     e.preventDefault();     alert('click'); });   Do you know if there is a way ?


I'm on Ubuntu 12.04 and I was wondering if is there any way to sort the indicators like this(Image):    The bottom bar is the default one and the upper bar is how I'd like to sort 'em.   dbus-send --type=method_call --print-reply --dest=com.canonical.indicator.application /com/canonical/indicator/application/service com.canonical.indicator.application.service.GetApplications | grep "object path"   returns this:  object path "/org/ayatana/NotificationItem/lang_indicator/Menu" object path "/org/ayatana/NotificationItem/My_Weather_Indicator/Menu" object path "/org/ayatana/NotificationItem/transmission/Menu" object path "/org/ayatana/NotificationItem/bluetooth_manager/Menu" object path "/org/ayatana/NotificationItem/indicator_sysmonitor/Menu" object path "/org/ayatana/NotificationItem/nm_applet/Menu"   How I have to edit the "~/.local/share/indicators/application/ordering-override.keyfile" to do this?


Ordinary generating function for $\binom{3n}{n}$

The ordinary generating function for the central binomial coefficients, that is, $$\displaystyle \sum_{n=0}^{\infty} \binom{2n}{n} x^{n} = \frac{1}{\sqrt{1-4x}} \, , \quad |x| < \frac{1}{4},$$ can be derived by using the duplication formula for the gamma function and the generalized binomial theorem. But what about the ordinary generating function for $ \displaystyle  \binom{3n}{n}$? According to Wolfram Alpha,   $$ \sum_{n=0}^{\infty} \binom{3n}{n} x^{n} = \frac{2\cos \left(\frac{1}{3} \arcsin \left(\frac{3 \sqrt{3x}}{2} \right)\right)}{\sqrt{4-27x}} \, , \quad |x| < \frac{4}{27}. $$ Any suggestions on how to prove this? EDIT: Approaching this problem using the fact that $$ \text{Res} \Big[ \frac{(1+z)^{3n}}{z^{n+1}},0 \Big] = \binom{3n}{n},$$ I get $$ \sum_{n=0}^{\infty} \binom{3n}{n} x^{n} = -\frac{1}{2 \pi i x} \int_{C} \frac{dz}{z^{3}+3z^{2}+3z - \frac{z}{x}+1},$$ where $C$ is a circle centered at $z=0$ such that every point on the circle satisfies $ \displaystyle\Big|\frac{x(1+z)^{3}}{z} \Big| < 1$. Evaluating that contour integral would appear to be quite difficult.


can't get HTML to display in Apple Mail signature

I'm stumped.  I cannot get the HTML I wrote to display!  I followed all the steps properly with creating a webarchive file, renaming so that it shows up in Apple Mail. But then when I go back in and see the signature, it's there but it doesn't display the HTML ... it just displays the code!  I've tested the HTML code on a webpage, and it works just fine.  I have my message format as Rich Text.  The code is:


How to Zip and Unzip a directory and its files in Linux

I am a newbie in Linux.Whats is the complete process to zip and unzip a directory and its files.Please mention if any installation has to be done.


"him arriving and me finishing the wine"

I copied the below sentence from one of the answers to another question:  This means that he arrived and I quickly finished the last of the wine. The two events (him arriving and me finishing the wine) happened at roughly the same time- both in the past.  Shouldn't we use "his arriving" instead of "him arriving" and "my finishing the wine" instead of "me finishing the wine"


Do I use "is" or "are" in this sentence?

What strategies is your school using to the reduce summer melt? OR What strategies are your school using to the reduce summer melt?


The periodic orbits in $3x+1$ conjecture on $\mathbb {Z}$

The $3x+1$ conjecture is defined on $\mathbb{N}$ as  $$ f(x) = (3x+1)/2 $$ if $x$ is odd and $$f(x)=x/2$$ if $x$ is even.  As far as I know the only periodic orbit is the trivial  $$1\to 2 \to 1\to 2....$$  If we extend the domain to include the integers, then I found nontrivial periodic orbits such as $$-5\to -7\to -10\to -5\to -7\to -10.....$$  and $$-1\to -1\to -1\to -1....$$  and $$ -91\to -136\to -68\to -34\to -17\to -25 \to -37 \to -55 \to -82 \to-41\to -61\to -91 .....$$  My first question is " Are these the only periodic orbits in the extended $3x+1$ conjecture ?"  The other question is "Are all orbits in the extended $3x+1$ conjecture  eventually periodic?"


Reputation shows twice for one post (before and after editing)

Using the iOS app, I was checking my achievements, and it showed the reputation from the same  twice. Once before the edit of the parent post's title, and the other text from after. See the screenshot. I (of course) was awarded just the 50 rep from the 5 upvotes.    Having no issues using the website.


I have the following environment to display a sidebar:  \newcommand{\dummy}{}  \newenvironment*{lsidebar}[2][0.5] {     \renewcommand{\dummy}{#1}      \wrapfigure{l}{#1\textwidth}         \rule{#1\textwidth}{1pt}          \rule{#1\textwidth}{18pt}          \vspace{-18pt}         \centerline{\textcolor{white}{#2}}          \vspace{5pt}         \footnotesize         \leftskip=5pt         \rightskip=5pt         \setlength{\parskip}{0.2cm}         \setlength{\parindent}{0pt}  } {         \leftskip=0pt         \rightskip=0pt         \setlength{\parindent}{0pt}         \rule{\dummy\textwidth}{1pt}         \rule[.19in]{\dummy\textwidth}{2.5pt}     \endwrapfigure }   I use the environment like this:  \begin{lsidebar}{Example Sidebar}     \label{sb:Example}      An example sidebar. \end{lsidebar}  Refer to sidebar \nameref*{sb:Example}.   It renders how I want it to. However, the label does not resolve as expected when using \nameref*{sb:Example}. Instead of displaying the sidebar's title, it displays the chapter title:    Here is a complete repro:  \documentclass{book}  \usepackage{graphicx} \usepackage{wrapfig} \usepackage{hyperref} \usepackage{color}  \newcommand{\dummy}{}  \newenvironment*{lsidebar}[2][0.5] {     \renewcommand{\dummy}{#1}      \wrapfigure{l}{#1\textwidth}         \rule{#1\textwidth}{1pt}          \rule{#1\textwidth}{18pt}          \vspace{-18pt}         \centerline{\textcolor{white}{#2}}          \vspace{5pt}         \footnotesize         \leftskip=5pt         \rightskip=5pt         \setlength{\parskip}{0.2cm}         \setlength{\parindent}{0pt}  } {         \leftskip=0pt         \rightskip=0pt         \setlength{\parindent}{0pt}         \rule{\dummy\textwidth}{1pt}         \rule[.19in]{\dummy\textwidth}{2.5pt}     \endwrapfigure }  \begin{document}  \chapter{First} \label{ch:First}  \begin{lsidebar}{Example Sidebar}     \label{sb:Example}      An example sidebar. \end{lsidebar}  Refer to sidebar \nameref*{sb:Example}.  \end{document}   Can anyone tell me how to resolve the name/title of the sidebar instead of the chapter?


Prove that if $I-BA$ is invertible then $I-AB$ is invertible.   Though I have found this question already posted and  also it has some answers like   Use:$(I−BA)(I+B(I−AB)^{−1}A)=I(I−BA)(I+B(I−AB)^{−1}A)=I $  I have done it like this.  $I-BA$ is invertible $\implies 0$ is not an eigen value of $I-BA\implies 1$  is not an eigen value of $BA\implies 1$ is not an eigen value of $AB\implies 0$ is not an eigen value of $I-AB\implies I-AB$ is invertible.  I have used the facts the    $AB,BA$ have same non-zero eigen values    Proof:Let $c\neq 0$ be a eigen value of $AB$ corresponding to eigen vector $\alpha$.Then $A(B\alpha)=c\alpha$  Now $(BA)(B\alpha)=B(AB\alpha)=c(B\alpha)\implies c$ is an eigen vector of $BA$ corresponding to $B\alpha$.Also $B\alpha\neq 0$ otherwise $c=0$ .  Similarly every eigen value of $BA$ is an eigen value of $AB$.  How to show that they have same eigen values for if $A,B$ are $n\times n$ matrices?  and    If $c$ is an eigen value of a matrix $M$, then $1-c$ is an eigen value of $I-M$.   Please check whether my answer is correct/not.


We have recently launched our web page but cannot find it on Google.if we type in our name nothing comes through but if we include.com then the site comes up on google. We used many key words thinking this would help customers locate our site, but type these key words in and still we are not listed. Can you advise if we are doing something wrong Thank you


An analytic function having no element of negative x-axis in its range

Let $f$ be an analytic function defined on open unit disc such that range of f is contained in $\Bbb{C}\setminus(-\infty,0]$. Then I need to tell whether $f$ must be a constant function. I was thinking of discarding this by an example. But I am not able to find one. Please help.


Persists the "Awaken"-Spell through Polymorph

DND 5e Question: What would happen, if you Polymorph a Zombie or another low Int Creature to a Plant or lower Int Beast like a Wolf, Awaken it and then let the Polymorph run out?(This would need two Casters, one to start the Awaken Cast and one to Polymorph the target before Awaken is actually casted) Would the target stay an Awakened Plant. Would the Zombie be Awakened after returning to it's previous form? As it would return to it's original Stat-block, it would probably lose it's newfound Intelligence and it's newly gained Language(Speaking, but not sure about understanding)


I'm having some issues with my VPS Ve, right now I have two sites running with PHP (one of them with Wordpress), a few days ago the RAM usage rose above 100%, strange thing is I made no changes.  RAM memory is increasing progressively in the MediaTemple statics panel, what I don't understand is why do I have so much difference between the data I get from the console.  My Setup:         nginx   php-fpm   apc   mysql   Ubuntu 10.04   4GB RAM (VPS)      htop:    Free -m:  total      used    free  shared buffers  cached Mem:       6348    2854    3494    0       0       2403 -/+ buffers/cache:   450       5897 Swap:    0     0       0   Could you guide me so I may know what is it that is using up memory?  Thanks!


Minimum reputation for answering your own question should be higher than what is needed to ask

If we're implementing , why don't we also require that users have at least 1.5 times the amount of reputation needed to ask their current question in order to answer their current question?  I believe this would really reduce the amount of non-answers that should have been edits to the original question, or perhaps a comment under another answer.  Edit  Inspired by marcog's excellent suggestion , perhaps it would make more sense to set a minimum amount of time that must pass before you can answer your own question. New users would need to wait in the neighborhood of six hours, while users with more reputation could answer their own question within minutes if they discovered the solution on their own.  This would get in the way of the behavior that we don't want, which is people posting answers that should have been edits while not annoying most.


Differentiate "it is said" from "it has been said"

It has been said that everyone lives by selling something.  Can I substitute the bold part with "it is said"? I think since it is kinda like a saying, using present simple is more appropriate. But I also feel "it is said" can also mean this sentence was said before, and the impact on the present is that now people generally accept that. And present perfect I think carry the implication that people now may or may not say this anymore.


Solving for $x$ after simplifying, please check my work!


I have two cpp files and two header file, they are a.cpp, b.cpp, a.h and b.h respectively. I have a method defined in the a.cpp file and I would like to call the method in the b.cpp file. How do i go about doing it? Please advice Thank you.  Can i make use of the friend function to do so?


Publishing my first application on PPA (Launchpad)

Let's say that I have a little script that outputs "Hello world!" in terminal:  echo "Hello World!"   How can I publish it to Launchpad PPA so I can type:  sudo add-apt-repository ppa:myusername/hello-world && sudo apt-get update sudo apt-get install hello-world   Then running hello-world in terminal the application will output "Hello World!".  I read the instructions from , but the image is blurry for me...


How can I convert a live USB to Linux on USB on 18.04?

I have a single USB drive and Ubuntu 18.04 has been installed on it. I want to convert this drive to Linux on USB, meaning that Ubuntu gets installed on the USB drive as a standard installation that is writable and whatnot. How can this be done? When I try to format the USB drive (which has Ubuntu running live from RAM) using GNOME Disks, I get the following message:  Error unmounting filesystem Error unmounting /dev/sdb: target is busy (udisks-error-quark, 14)   This appears to be because it is not obvious how to unmount the root partition. How should I approach this problem?


Show that $\exists c \in \mathbb{R} : f(c) = 0$

Let $f : \mathbb{R} \longrightarrow \mathbb{R}$ be a differentiable function such as $\forall x \in \mathbb{R}, f'(x) > 2$. What could I do to show that $\exists c \in \mathbb{R} : f(c) = 0$ ? At first I thought I could use the mean value theorem but it did not help me. In fact, I don't really understand why $f(x)$ couldn't be strictly positive $\forall x \in \mathbb{R}$. Would you know how to proceed ? Thanks for your help.


HOW TO: ralink 148f:7601 wifi adaptor installation

I am a new Ubuntu user and doing my first steps slowly... I have a wireless usb like in this issue with the same problem.    After read it, I tried to follow the steps but i had problems...   I downloaded driver and patch on downloads and moved to /tmp I went to terminal then typed...  sudo apt-get install --reinstall linux-headers-generic build-essential cd /tmp tar xjf DPO_MT7601U_LinuxSTA_3.0.0.4_20130913.tar.bz2 cd DPO_MT7601U_LinuxSTA_3.0.0.4_20130913/    but in this step I don't know what to do. I have to change ~/(ADD THE PATH) for anything?  patch -p0 < ~/(ADD THE PATH)/rt2870-mt7601Usta-kuid_t-kgid_t.patch


I have a need have my entire page's HTML passed into a PHP variable, but I have no idea if this is even possible or if it will accomplish what I'm trying to do.   The idea is that the user would click a button (PRINT) and the script would gather the entire HTML of the page and POST it to a PHP file. The PHP file is generating a PDF using a third party service (DocRaptor).  Any thoughts on the best way to do this? Would it even work?  EDIT Some code since you asked. This is as far as I get. This works and I get a PDF of the text submitted in the text input box. But that's obviously not what I need. I'm just not sure how to POST something that not the text input, but rather the entire current HTML of the page. It doesn't have to be a form obviously, a button (Print Page) would be ideal.  HTML:  <form method="POST" action="print_submit.php">  Innovation Name<input type="text" name="this_data">      <input type="submit" value="Sumbit my choice"/>  </form>   PHP (print_submit.php):  <?php $api_key = "XXXXXX"; $url = "https://docraptor.com/docs?user_credentials=$api_key";  $content = $_POST['this_data']; $name = 'docraptor_sample.pdf'; $post_array = array(   'doc[name]' => $name,   'doc[document_type]' => 'pdf',   'doc[test]' => 'true',   'doc[document_content]' => $content  );   $postdata = http_build_query($post_array);   $opts = array('http' =>   array(       'method'  => 'POST',       'header'  => 'Content-type: application/x-www-form-urlencoded',       'content' => $postdata   )  );   $context = stream_context_create($opts);   $doc = file_get_contents($url, false, $context);   file_put_contents($name, $doc);  ?>  Here is a link to your pdf: <a href="<?=$name ?>"><?=$name ?>


I know this is so common question & there are so many answers for this, but my problem is different, I want to accept the URL with all below formats:  http://www.sample.com https://www.sample.com http://www.sample.com/xyz www.sample.com www.sample.com/xyz/#/xyz sample.com  // & much more ...   So here idea is, I am allowing the user to enter there website & another user can just click on the saved website & go to users website. So here it's not a good idea to restrict the user to input proper URL, they can enter any of the above formats. Here is the regex I am using right now, but that only checks if URL starts from proper protocol:  ^(ftp|http|https):\/\/[^ "]+$


I replace my windows 7(was not booting) to ubuntu, but now ubuntu will not start withou the usb have tried many approaches without luck, have tried reinstalling grub but still not luck boot-repair gives me a message to GPart, i am new user to ubuntu love the new system but want it to be my permanant os on my laptop.


Why does Ubuntu require restart to complete updates?

I have heard that Linux machines can run for months without restarting. Why then does Ubuntu say "Restart required to complete updates..." after installing updates?     Linux and UNIX users brag about how they haven't restarted their systems since George Bush Sr. was president.


I'm confident that there are already quite a lot of answers to this topic. However, it is always important how the particular setup is configured. I'm new to Linux and would not like to execute commands which I do not understand and which are not tailored for my case. So I would be grateful if somebody would post instructions. My setup:  sda: contains Ubuntu 20.04 partitions and an ntfs partition which I intend to use for data exchange  for Windows and Linux sdb: Windows 10  I installed Ubuntu manually, so Grub loader should be (hopefully) installed on the sda only.  My aim is to extend the space on root as originally I didn't know that programs are installed there. I have backup of my disks by Acronis True Image 2020 (run from Windows). As you see I already could free up some space taken from home (boot from live USB). Resizing of / dind't work straight forward. As I read so far I should move some partitions and (most likely) do something with Grub loader. That's are the two things where I am not sure what to do in my case.


How can I see how many edits left for Archaeologist badge?

For  badge, users need     Edited 100 posts that were inactive for 6 months.   I can see my all  but, Is there any way to see how many edits of mine fits for Archaeologist badge?


Interpretation of measurements and Eigenstates for continuous variables

I find myself (probably like many others) somewhat unclear on the implications of the postulate of quantum mechanics that "measurements of a value leave the system in an eigenstate". The interpretation of this is clear (if philisophically muddled) for measurements of discrete values such as the energy of an harmonic oscillator in a superposition of energy eigenstates: a single eigenvalue is obtained, and the system is left in the eigenstate corresponding to that eigenvalue, with the probabilities determined by the mod-squared amplitudes of the superposed eigenstates. I find myself unclear, though, on the interpretation of this for the measurement of a continuous value such as position. Clearly, the system cannot be left after measurement in an eigenstate of the position operator, both on the grounds that this would leave it in a complete superpostion of momentum states (which appears to me completely unphysical and not observed in experiment), and that a dirac delta function, while useful conceptually, is not a well behaved and well defined mathematical function that could serve as the physical distribution of some form of real matter. It seems apparent to me that some part of my reasoning here is flawed - either the understanding that measurment leaves a system in an egienstate, or in my understanding of what it would physically mean for a particle to be in an eigenstate of a continuous variable. Help finding the hole would be appreciated!


Proof that the intersection of any finite number of convex sets is a convex set

How to prove that the intersection of any finite number of convex sets is a convex set?  I have no idea.


Terraria: Witch Doctor not spawning despite me killing the Queen Bee (in a friend's duplicate server of my world)

I'm pretty new to Multiplayer Terraria. My friend recently got my world files and we played together. We decided to hunt the Queen Bee as I wanted to get the Witch Doctor to join my city. I asked him whether it would work if we'd fight the Queen Bee in that particular server, would the Witch Doctor appear in my village, and responded 'Yes'. So we destroyed Queen Bee and I went back to my ordinary server. This is the part I don't understand:  The path we dug through the underground jungle into the hive was clearly shown on my mini-map, although the path we dug through was untouched.  I've been waiting with a valid jungle house, (following what was said throughout the wikis and guides) however, the Witch Doctor has not shown up for the past 2 game days.  I'm planning to repeat the same procedure in Single Player (as the larvae has only been destroyed in the duplicate world [like all the other blocks we destroyed along our path]) and hopefully, he would come. Before I do this tomorrow, could it be some other reason the Witch Doctor is not spawning?


How to make option selected in jquery by Name

How can i make the option selected in jquery by Name  Here is the   Here is the script  <select name="zoom_cat[]" style="margin-left:15px;" id="contact_country">     <option value=""  selected="selected">Nothing</option>    <option value="0">Singam</option>   <option value="1">Karadi</option>   <option value="2">Poonai</option>   <option value="3">Yaanai</option> </select>   And here is the script   var myText = "Singam";         $("#contact_country option:text=" + myText +"").prop("selected", "selected");


How do i count total number of distinct elements in a column of MySQL table?

i have  a table named city in my database and  I have tried using theselect  distinct count(*) from city but it's not returning the answer that is required


Bounty Notices disappear on loading edits

While browsing a question with a bounty, I started typing an answer. During that time, another answer was edited. On loading the edits for that answer, the bounty notice disappeared. I found this pretty confusing.  The notice appeared again only after I refreshed the page.  How about a fix?


What changes occur while an atom approches the speed of light?

My knowledge of atomic dynamics is a little superficial. But to my understanding an electron travels an orbital path around a nucleus of an atom. "correct?" So let's say that if a hydrogen atom were to travel "extremely close to" the speed of light (relative to some laboratory system). With the electron circling the proton approximately already traveling "extremely close to" the speed of light, how is it that the electron can circle the proton without exceeding light speed? (or does it continue to orbit at all?)


I need to wrap a tasks environment inside a custom \NewEnviron. Apparently, tasks chokes on code besides its \task or \item due to the , presumably causing it to do so on \BODY. Any way to get around this? Exact error given is "Something's wrong--perhaps a missing \item", as per:  \documentclass[a4paper]{book} \usepackage{environ} \usepackage[more]{tasks}  \NewTasks[style=enumerate,counter-format=tsk[1]),label-width=2ex]{mytaskenum}[\item](3) \NewEnviron{mytaskenv}[1][Exercises]{   % Misc. stuff to precede the tasks env here   \begin{mytaskenum}   \BODY   \end{mytaskenum}   % Misc. stuff to follow }{}  \begin{document}  \begin{mytaskenv}   \item item 1   \item item 2   \item item 3 \end{mytaskenv}  \end{document}


Do effects with the duration of one minute end at the beginning or the end of your turn?

The Rage class feature of the Barbarian allows you to rage for one minute given you either took damage or attacked every round. A round is defined as a 6-second interval. So the rage can last up to 10 rounds. Now my question is, does it end at the end of your 10th round or at the beginning of your 11th round? There are other effects like that, also concentration spells with the duration of 1 or 10 minutes. Sometimes those are activated before combat starts and end during combat. In general: Does an effect/concentration end at the end of your last turn during the timespan or at the beginning of your first turn after the timespan?


Does a "dupe" on another (non-SE/SO) site warrant a vote to close?

On Stack Overflow a user asked the following question:   As noted by user , this exact question has been asked on Nvidia's forums as well:    He goes on to state "Vote to close". Not taking into account the quality of this particular question, I would say that this is a bit much. The OP is, in my opinion, fully within his right to ask the same question on a different Q&A-site or forum if he wishes to do so.   So my question is: If the question asked on SO is a duplicate of a question asked on a different (non-SE/SO) site, does that warrant a vote to close (as duplicate)?  I would say it does not, but would like to hear your thoughts on this.


Traveling through Heathrow on separate tickets

I will be travelling from IAD (Washington DC) to VIE (Vienna) on two separate tickets, first one being on Virgin Atlantic (redeeming miles from IAD to LHR) and second one being on British Airways from LHR to VIE. I am planning to have a layover of about 5 hrs 20 min between both the flights (both arriving and departing from terminal 3 at LHR)  I have an Indian passport with a valid US visa. I have following questions:   Is there even a slight chance that my luggage will be checked through? Does anyone have any experience here? This will help me avoid the UK border and immigration check. I checked with Virgin Atlantic and they said baggage cannot be tagged through to VIE since I have separate tickets. Still I was hoping that things may change at the gate while boarding at IAD. On checking  I see that I will not need a visa for passing UK Border and Immigration. However, the results on this website say "You might be eligible for ‘transit without visa’" if you are arriving from USA and have an onward flight leaving on same or next day. The words 'might be eligible' concern me. Again anyone with experience here? There's an earlier BA flight available (leaving me with a layover of 2 hours between arriving and departing flights from the same terminal 3). Will this be sufficient? Or should I stick to the later flight giving me 5 hrs and 20 min in transit?   Many thanks for your replies.


I debated with my peers that we can use the word emails when referring to more than one and it would be grammatically right.     But most of them said since we don't say we received mails today, similarly we won't say we received emails .   Quick advice please.


Is the integral of $\frac{1}{x}$ equal to $\ln(x)$ or $\ln(|x|)$?

The inconsistency I see between mathematical subjects is really confusing me. I understand that it isn't possible for $e^x$ to be less than zero for real $x$, which is probably why they say that the integral is $\ln(|x|)$.  Before I ramble on too much, I just want to ask: Is there a set of guidelines to follow to help me choose whether to let the integral of $\frac{1}{x}$ equal to $\ln(x)$ or $\ln(|x|)$?  Thanks, Aralox


Why does the wildcard work differently when placed at the start or at the end of a grep phrase?

For example, I wanted to count how many files in my current directory have a certain extension.  I used:  ls | grep ".txt" | wc -l   This works and so does:  ls | grep ".txt*" | wc -l   But why does this not work either?  ls | grep "*.txt" | wc -l   Why does the wildcard seem to not work in the grep expression when I use it before the extension and why does it have no effect at the end (all txt files simply end with .txt so I am guessing it does not work if it was something like .txt.zip)?


New user with root access in Linux Debian

I've created a new user by using "User Accounts" in "System Settings". How do I grant rights so that this new user can have the same level of access as root?


Is there a way to create a command which is like a \pagebreak (in that it suggests that it might be a good place to break a page, but certainly doesn't enforce it) but which inserts 'PTO' ("please turn over") near the bottom of the first page?   [The context is that I have computer-generated material in which there are, roughly speaking, many pairs of 'headers' and associated 'pictures'. Sometimes the pictures are so large that they have to go on a page of their own. The PTO would indicate that this has happened, and so one could distinguish a header-with-picture from a header-without-picture (which occasionally occurs).]


How do we know that radioactive decay rates are constant over billions of years?

A friend and I recently discussed the idea that radioactive decay rates are constant over geological times, something upon which dating methods are based.  A large number of experiments seem to have shown that decay rate is largely uninfluenced by the environment (temperature, solar activity, etc.). But how do we know that decay rates are constant over billions of years? What if some property of the universe has remained the same over the one hundred years since radioactivity was discovered and measured, but was different one billion years ago?  An unsourced statement on the Wikipedia page on radioactive decay reads:     [A]strophysical observations of the luminosity decays of distant   supernovae (which occurred far away so the light has taken a great   deal of time to reach us) strongly indicate that   unperturbed decay rates have been constant.   Is this true?  I'm interested in verifying constancy of decay rates over very long periods of time (millions and billions of years). Specifically, I'm not interested in radiocarbon dating or other methods for dating things in the thousands-of-years range. Radiocarbon dates, used for dating organic material younger than 50,000 years, are  and crossed-checked with non-radioactive data  of millennial trees and similarly countable yearly deposits in marine , a method of verification that I find convincing and that I am here not challenging.


Should i spend on upgrading my Beginner Camera or go for a new Lens instead?

I have a top of the Line (from bottom) Canon 1200D camera, 18-55 stock and 50mm 1.8. I want to spend on a Sigma 18-35 f/1.8 but some of my friends are suggesting to upgrade the camera first instead of going for this lens. Is it worth upgrading my camera first, or just go for a new Sigma ? I can spend upto $700.   I have gone through some questions too like  and  but i have a different camera model and I mostly shoot in low light, mostly random shots including portraits and landscapes. (Learning Phase). Thats why i was thinking to go for sigma 18-35 lens but on the other hand better camera body will have higher ISO noise reduction and higher dynamic range.


Does Tolkien ever speak of himself still living in Middle-Earth?

It has been noted in other questions and answers on this site that Tolkien's conception of Middle-Earth has an imaginative relation to Earth history. Some salient sections of Tolkien quotes from answers to  are worth repeating here for background:                    Then a final one from an answer on :        So the question is does Tolkien ever express in his own words that he himself is still living in "Middle-earth"—in an imaginative sense, I would suspect, but one in which Tolkien's time (A.D. 1892-1973) and place (Britain/Europe) he refers to as Middle-earth, rather than Earth or Europe, etc.?   Another way to state this is if Tolkien conceives the identity of what he calls "Middle-earth" as passed away, and what remains during his time is no longer Middle-earth, but simply Earth—or does he view "Middle-earth" as still continuing in his day.  Some might ask why this matters. It matters in determining the "voice" Tolkien might use in his narration of events, specifically in a fundamental difference between what is plausible for how Tolkien would voice a narrative aside in his writing, which is the basis for  (and a difference in view on his voice as ). So an answer here could resolve the validity of that answer to my question.  Clarifying How this is a Distinct Question  This question has been closed as a duplicate to one that it had linked to as background. But that other question is a very distinct question from this one.   is asking about whether Tolkien conceived of Middle-earth being a part of "our Universe." It was a question about where Tolkien imagined the stories of Middle-earth taking place. Fundamentally, it was a question about how he conceived his world of Middle-earth.  This question is asking how Tolkien conceived of himself in relation to his world. That is, did he perceive Middle-earth to be continuing as Middle-earth during his own time period, such that he was himself still living in Middle-earth.


Is this how to "Implement IDisposable correctly"?

I ran Code Analysis on one of my projects, and it gave me two finger wags, namely:  CA1063 Implement IDisposable correctly Provide an overridable implementation of Dispose(bool) on 'UserStore' or mark the type as sealed. A call to Dispose(false) should only clean up native resources. A call to Dispose(true) should clean up both managed and native resources.  ...on this line of  code:  public class UserStore : IUserStore<User>, IUserPasswordStore<User>,  IUserClaimStore<User>   ...and this:  CA1063 Implement IDisposable correctly Modify 'UserStore.Dispose()' so that it calls Dispose(true), then calls GC.SuppressFinalize on the current object instance ('this' or 'Me' in Visual Basic), and then returns.  ...on my empty Dispose:  public void Dispose() {     // }   Can I assassinate two avians with one petrified dirtclod by doing this:  public override void Dispose() {     Dispose(true);     GC.SuppressFinalize(this); }   ? Is that what it's suggesting?  UPDATE  To answer my question (sort of), apparently not - I figured I'd just add the code and see if the Code Analysis would then feed back the yearned-for "'NRBQ.API.UserStore.Dispose()': no suitable method found to override"


What effect does 1x1 convolution has on quality of feature being learnt?

I was learning about inception module from deeplearning.ai by Andrew Ng, wherein we use 1x1 convolution to reduce computational cost. for example, if we directly apply 5x5 convolution we need to multiply for about 120M times whereas by introducing 1x1 convolution we reduce it by the factor of 10.  My question what effect does this have on the feature maps that are being learned or will the quality of feature maps differ if we had not used 1x1 convolution.  below is the screenshot of how we reduce multiplications from 120M to about 12M:


Is there a roadmap for https support for ppas?

I'm fairly new to Ubuntu, and just realised that all my ppa's I've been adding are http only  Are there plans for https support in the future?


Why we usually do not exceed ARMA(5,5) models in practice? Is there any mathematical justification for this?


divide the list into rows (create a nested list from a list)

this probably has a super-easy solution, but I cannot get it right.  I have a list of 400 integers. Now. I want to divide this list so that the first 20 go in one list, the second 20 in another, etc. In the end I want to have a 20x20 nested list.  Any ideas? Thanks!


Why isn't my rendered image appearing right?

I don't understand why I get this image result when i render through the render tab. It takes around 1 min to render and I get this image. Image of render wanted (shot through the quick render):  Image of what image I got when i press F12 to render  My render tab settings (Only shows edited ones, all the rest settings are on default)  My Output tab settings (Intentionally left metadata cause its not necessary)  File:  I'd appreciate it if you could help.


Calculating noise voltage of a thermopile for NEP

I am trying to calculate the noise voltage Vn of a thermopile sensor for NEP. As according to formula NEP = Vn/R Can someone elaborate how would i do that if my thermopile is connected to AD360 amplifier ?


In edit mode, there is an origin located off the side of it's face. It ends up clumping everything together when subdivided. How do I fix this please?

The meshes clump together when subdivided:    The origin is off of the face:


Did regular Americans speak the way actors in the 30s and 1940s did?

I watch a lot of old movies, and I've noticed that American actors of the 1930s and 1940s often spoke in a quasi-generic-posh-British accent.  Katherine Hepburn's accent would be the perfect example. It seems exaggerated, and I imagine it was not common off the stage and screen. What was that? Was it just an accent or was it a dialect? Did real people actually speak that way?


How to make Files use file-roller again?

How can I get more options (in addition to zip, tar.xz and 7z) and the option to add password when making archive files in file-roller in Gnome 3.22? Thanks!  Screen-shot of new create archive in Files (nautilus) 3.26.0   Archive Manager (file-roller)


Where does new blood comes from when penis get erected?

In Humans, During sexual arousal in males, his penis will get erected with blood.  Where does this new blood coming to fill his penis which is required for erection ?


The function $f (n) = (1 + 1 / n) ^ {n+1}$ is decreasing

I cannot prove that the function $$f (n) = \left(1 + \frac1n\right) ^ {n + 1},$$ defined for every positive integer $n$, is strictly decreasing in $n$. I already tried to prove by induction and also tried to prove by calculating the difference between $f (n + 1)$ and $f (n)$. I need help.