Is it possible to have a true conditional statement with a false converse? If there is does anyone have an example of one? or why doesn't one exist?

I found this proposition and don't see exactly as to why it is true and even more so, why the converse is false:  Proposition 1. The equivalence between the proposition $z \in D$ and the proposition $(\exists x \in D)x = z$ is provable from the definitory equations of the existential quantifier and of the equality relation. If $D = \{t_{1},t_{2},...t_{n}\}$, the sequent $z = t_{1} \vee z = t_{2} \vee z \vee ... z = t_{n}  \vdash z \in D$ is provable from the definition of the additive disjunction $\vee$.  The converse sequent $z \in D \vdash z = t_{1} \vee z = t_{2} \vee ... z = t_{n}$ is not provable.  The author goes on to say:  "We adopt the intuitionistic interpretation of disjunction. With respect to it, one can characterize a particular class of finite sets"  On the first part of the proposition, well I am not sure what the point is as if we take an element z in D, then we could just call this element x and hence this x = z.  Is there something more to this?  On the second part of Proposition 1 since $z = \text{ some } t \in D$ since t is in the set of axioms and $t = z$, then $t \vdash z$ as z is derivable from t.  For the converse if $z \in D$ then why wouldn't z = some $t \in D$?  Is this because of the Incompleteness theorem?  That perhaps there D as a set of axioms has some consequence which can not be proven by the set of axioms in D?  Or perhaps I am way off here.  Any ideas?  Thanks,  Brian


${x_{n}}$ is a sequence in $\mathbb{R}$ where $n\geq 1$ such that all $x_{n} >0$. If  $(\limsup_{n\to\infty} x_{n})\cdot(\limsup_{n\to\infty} 1/x_{n})=1$, how can I show that ${x_n}$ converges? I am thinking about using the contrapositive  of the statement but I'm not sure if that's the best way. Thank you.

Let $a_n$ be a sequence such that $\forall n\in \mathbb n: 0<a\le a_n\le b <\infty.$      Prove:          $\displaystyle\limsup_{n\to\infty}\frac 1 {a_n}=\frac 1 {\displaystyle\liminf_{n\to\infty}a_n}$   $\displaystyle\limsup_{n\to\infty}a_n\cdot \limsup_{n\to\infty}\frac 1 {a_n} \ge 1$ and there's an equality iff $a_n$ is converging.       Suppose there are two subsequences: $a_{n_l}, \ a_{n_k}$ such that $\lim a_{n_k} = k, \ \lim a_{n_l}=l$ and suppose $l\le k$, so $\lim \frac 1 {a_{n_k}}=\frac 1 k , \ \lim \frac 1 {a_{n_l}}=\frac 1 l$ so clearly: $\frac 1 k\le \frac 1 l\le l\le k$ so it's easy to see once the largest limit (supermum) is 'inverted' it has to become the smallest limit (infimum).   I realize this doesn't show equality, I don't know how to do the other way and I'm not even sure if what I did is good. If $a_n$ converges, suppose to $L$ as its limit then we have: $L\cdot \frac 1 L=1$.  If it does not converge then $a_n$ may tend to infinity or won't have a limit. From 1 we can change it to $\displaystyle\limsup_{n\to\infty}a_n\cdot \frac 1 {\displaystyle\liminf_{n\to\infty}a_n} \ge 1$ and from BW, every sequence has a converging subsequence, and since for converging subsequences: $\liminf a_n\le \limsup a_n$ we have $\frac {\limsup a_n} {\liminf a_n}=\limsup a_n\cdot \limsup\frac 1 {a_n} \ge 1$.   This should probably be in absolute value since one of those subsequnce limits can be negative, but it isn't in absolute value in the question.


Let $a>0$ and $b>0$. Prove that $n- \sqrt{n+a} \sqrt{n+b}$ converges to $-\frac{a+b}{2}$. I need some help!

I need to evaluate the limit $$\lim_{n\rightarrow \infty}(n-\sqrt{n+\alpha}\sqrt{n+\beta})$$  My work: $$(n-\sqrt{n+\alpha}\sqrt{n+\beta})=n-\sqrt{n^2+\alpha n+\beta n+\alpha\beta}$$ I understand that both $\alpha$ and $\beta$ are just constants. But, now how should I factor this? I understand the calculus behind limits, but the algebra troubles me.


I have a script that I can run like this: bash myscript.sh -ram 4096M -jar something.jar -dir /home/something I would like to be able to access the variable ram, jar, and dir from within the script. How do I do this?

myscript [-a a-arg] [-c c-arg] [-b] [-e] somedirectory   Given that I want my shell script be invoked at the command line using the above parameters - where [these brackets] denote that they are optional - what is the best method to parse them?


I’ve been having trouble getting WiFi to work reliably on my laptop with Ubuntu 16.04.3 and MATE 1.12.1. I can connect to the network, but Firefox and the terminal both time out whenever I try to do anything, despite System Moniter showing that I am transmitting and receiving (tiny) amounts of data. Occasionally itll suddenly start working again for a minute or two before stopping again. I don’t think it’s my router, as my phone works fine, but Ethernet works fine. Does anyone know what this is and how to fix it?

My wifi connection doesnt work properly; it stays connected only for around 5 minutes after I turn on the PC. I'm using Ubuntu 16.04.  I've tried   sudo service network-manager restart   which makes no difference  Same with   killall nm-applet && nm-applet &   After that I tried   sudo gedit /etc/pm/config.d/config   where I insert this string  SUSPEND_MODULES = "drivername logicalchipname"   But since I don't have permission to modify that file I tried to use chmod on it, which led to  but left me still in the same situation.  $ lspci -knn | grep Net -A3; rfkill list 03:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. RTL8821AE 802.11ac PCIe Wireless Network Adapter [10ec:8821] Subsystem: XAVi Technologies Corp. RTL8821AE 802.11ac PCIe Wireless Network Adapter [1b9a:2482]  Kernel driver in use: rtl8821ae  Kernel modules: rtl8821ae  0: hci0: Bluetooth  Soft blocked: yes   Hard blocked: no 1: phy0: Wireless LAN   Soft blocked: no    Hard blocked: no   What do you suggest I do?


Everything we learn about colour in relation to matter is based on "normal" matter that has electrons around it. Absorption and emission of electromagnetic radiation is explained in terms of electrons transitioning between quantum levels with different colours being caused by the energy difference between transitions. In this thought experiment I have a piece of neutronium at room temperature. As there are no electrons to interact with light of any wavelength, what colour would it be? (You need to do the measurement quickly in the few attoseconds before it explodes). I can only make 3 guesses but I can't think of any way of deciding which one is the least unlikely. 1 - Transparent. 2 - Perfect mirror 3 - Perfectly black. My limited physics suggests #1 as being plausible as there are no electrons, no orbitals and therefore no interactions with light. However, a totally non-scientific gut feeling says that transparent is ridiculous. How can something with such insane density have no interaction with light and look like it's essentially invisible? Surely it has to either reflect light perfectly, or absorb it perfectly? Then again, perhaps there would be the neutron matter equivalent of an absorption spectrum. That at relatively low photon energies (visible light), neutronium would be transparent, but at stupidly high energies (cosmic rays from matter falling into black holes,) it would absorb photons. There's no great reason for asking, just intellectual curiosity. A mental itch that needs scratching.

Neutron matter is matter comprised entirely of neutrons, as it exists in .  Most optical phenomena encountered in everyday life, such as light reflection and spectral absorption (i.e. color appearance) are the result of mechanisms involving electrons.  My simple question: How would a macroscopic sample of matter consisting entirely of neutrons (without electrons) appear to the naked eye?  Assume the matter is  and stable.  Let me add here that I'm not specifically asking about the appearance of a neutron star, as Wikipedia states that it would radiate so much that it appears white.


Let $f: [0, 1]\rightarrow R$ be continuous and suppose that $f(0) = f(1)$. Prove that for each positive integer $n$ there is an $x$ in $[0, 1 - \frac{1}{n}]$ such that $f(x) = f(x + \frac{1}{n}$). Without loss of generality, take $f(0)=f(1)=0$. I have been able to show that if $f(x)\ge 0$ or $f(x)\le 0$ the statement is true. It actually isn't that difficult to show. The trick is to define $g_n(x) = f(x+\frac{1}{n})-f(x)$, on $[0,1-\frac{1}{n}]$ then notice that $g(0)=f(\frac{1}{n})$ and $g(1-\frac{1}{n}) = -f(1-\frac{1}{n})$. We want to exclude the cases where $f(\frac{1}{n})=0$ and $f(1-\frac{1}{n})=0$ since that will immediately prove our statement. Using our condition $f(x)\ge 0$ and $f(x)\le 0$ and applying intermediate value theorem, we deduce that there's some $c$ such that $g_n(c)=0$. When we don't have the condition $f(x)\ge 0$ and $f(x)\le 0$, we could have continuous function such that $f(\frac{1}{n})\cdot f(1-\frac{1}{n}) = -|f(\frac{1}{n})\cdot f(1-\frac{1}{n})|$ (this is a long way of saying they have different sign). Notice that the method I described in the paragraph above can be extended to any interval $[a,b]$ if $b-a\ge \dfrac{1}{n}$. The main obstacle I face right now is that $f$ could have at least $n$ zeros such that the distance between any consecutive zeros the distance is at most $\frac{1}{n}$. However, I have struggled with this problem for a while now and I have made little progress. I would appreciate some hints, but please don't post complete solutions.

Let $f \in C[0,1]$ and $f(0)=f(1)$.   How do we prove $\exists a \in [0,1/2]$ such that $f(a)=f(a+1/2)$?  In fact, for every positive integer $n$, there is some $a$, such that $f(a) = f(a+\frac{1}{n})$.  For any other non-zero real $r$ (i.e not of the form $\frac{1}{n}$), there is a continuous function $f \in C[0,1]$, such that $f(0) = f(1)$ and $f(a) \neq f(a+r)$ for any $a$.  This is called the Universal Chord Theorem and is due to Paul Levy.  Note: the accepted answer answers only the first question, so please read the other answers too, and also this answer by Arturo to a different question:     This is being repurposed in an effort to cut down on duplicates, see here: .  and here: .


I am new to Ubuntu.  As for Windows, can I copy or clone an entire drive,  including the operating system, when using Ubuntu 18.04?   Regards,   Jerin

I'm a new Linux user. I've reinstalled my Wubi from scratch at least ten times the last few weeks because while getting the system up and running (drivers, , etc.) I've broken something (X, grub, unknowns) and I can't get it back to work. Especially for a newbie like me, it's easier (and much faster) to just reinstall the whole shebang than try to troubleshoot several layers of failed "fixing" attempts. Coming from Windows, I expect that there is some "disk image" utility that I can run to make a snapshot of my Linux install (and of the boot partition!!) before I meddle with stuff. Then, after I've foobar'ed my machine, I would somehow restore my machine back to that working snapshot. What's the Linux equivalent of Windows disk imagers like  or ?  Note: I found a similar question:


I have problem. It look piece of cake. But i already works on it almost 3 hours and I don't know what happen. No error but it don't show even alert.  Below is jquery script. The 1st function works successfully. But the 2nd is not.  $("#btnKeyword").on("click",function(){      var param = document.getElementById('inputKeyword').value;      $.ajax({         //type: "POST",         url: "http://10.1.17.20:8040/services/search/"+param,         success: function (data) {              var data=data.result;             console.log(data);              alert("Length: "+data.length);              if($(".row-parent").length){                 $('.row-parent').remove();             }                for(var i=0; i<data.length; i++){                  var no = i+1;                  $table ="
";                 $table += ""+no+ "	";                 $table += ""+data[i].link+ "	";                 $table += ""+data[i].shared_link+ "	";                 $table += ""+data[i].message_header+ "	";                 $table +="
";                  $("#tableParent").append($table);             }               load = function() {                 window.tp = new Pagination('#tablePaging', {                     itemsCount: data.length,                     onPageSizeChange: function (ps) {                         console.log('changed to ' + ps);                     },                     onPageChange: function (paging) {                         //custom paging logic here                         console.log(paging);                         var start = paging.pageSize * (paging.currentPage - 1),                             end = start + paging.pageSize,                             $rows = $('#tableParent').find('.row-parent');                          $rows.hide();                          for (var i = start; i < end; i++) {                             $rows.eq(i).show();                         }                     }                 });             }              load();          },error: function (xhr, ajaxOptions, thrownError) {alert("ERROR:" + xhr.responseText+" - "+thrownError);}     }); });  //Display clicking row parent     $(".row-parent").on("click",function(){     alert($('.row-parent').index(data)); });   Hopefully anyone can help me..  Thank is advance:

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


I need to show that if R is an integral domain and it has unity then the only elements of R which are inverse to itself are 1 and -1 (with respect to multiplication). But I don't know where to start. Can anyone help? Thanks..

I like to be thorough, but if you feel confident you can skip the first paragraph.  Review: A ring is a set $R$ endowed with two operations of + and $\cdot$ such that $(G,+)$ is an additive abelian group, multiplication is associative, $R$ contains the multiplicative identity (denoted with 1), and the distributive law holds.  If multiplication is also commutative, we say $R$ is a commutative ring. A ring that has no zero divisors (non-zero elements whose product is zero) is called an integral domain, or just a domain.  We want to show that for a domain, the equation $x^2 = 1$ has at most 2 solutions in $R$ (one of which is the trivial solution 1).    Here's what I did:   For simplicity let $1,a,b$ and $c$ be distinct non-zero elements in $R$.  Assume $a^2 = 1$.  We want to show that letting $b^2 = 1$ as well will lead to a contradiction.  So suppose $b^2 = 1$, then it follows that $a^2b^2 = (ab)^2 = 1$, so $ab$ is a solution as well, but is it a new solution?  If $ab = 1$, then $abb = 1b \Rightarrow a = b$ which is a contradiction.  If $ab = a$, then $aab = aa \Rightarrow b = 1$ which is also a contradiction.  Similarly, $ab = b$ won't work either.  So it must be that $ab = c$.  So by "admitting" $b$ as a solution, we're forced to admit $c$ as well.  So far we have $a^2 = b^2 = c^2 = 1$ and $ab = c$.  We can procede as before as say that $(abc)^2 = 1$, so $abc$ is a solution, but once again we should check if it is a new solution.  From $ab = c$, we get $a = cb$ and $b = ac$, so $abc = (cb)(ac)(ab) = (abc)^2 = 1$.  So $abc$ is not a new solution; it's just one.  At this point I'm stuck.  I've shown that it is in fact possible to have a ring with 4 distinct elements, namely $1,a,b$ and $c$ such that each satisfies the equation $x^2 = 1$ and $abc = 1$.  What am I missing?


I am reading this blog post , where the author uses the command mv !(old-project) old-project.  What does it do ?  My guess is that it copies all contents of old-project to the old-project subfolder except the old-project subfolder itself. How does it do that though ?

Say I want to copy the contents of a directory excluding files and folders whose names contain the word 'Music'.  cp [exclude-matches] *Music* /target_directory   What should go in place of [exclude-matches] to accomplish this?


From this exercise:     If $s_1 = \sqrt{2}$, and $$s_{n+1} = \sqrt{2+\sqrt{s_n}} \quad (n = 1,2,3,\dots),$$ prove that $\{s_n\}$ converges, and that  $s_n< 2$ for $n = 1,2,3,\dots$.   in the book Principles of Mathematical Analysis, I find this book very obscure about many concepts, so I really need some help. Can someone help me with proving the convergence of a sequence written in this form?

Problem  The sequence $(a_n)_{n=1}^\infty$ is given by recurrence relation:   $a_1=\sqrt2$, $a_{n+1}=\sqrt{2+a_n}$.   Evaluate the limit $\lim_{n\to\infty} a_n$.  Solution   Show that the sequence $(a_n)_{n=1}^\infty$ is monotonic. The statement $$V(n): a_n < a_{n+1}$$ holds for $n = 1$, that is $\sqrt2 < \sqrt{2+\sqrt2}$. Let us assume the statement holds for $n$ and show that $V(n) \implies V(n+1)$. We have that $$a_n < a_{n+1}.$$ Adding 2 to both sides and taking square roots, we have that $$\sqrt{2+a_n} < \sqrt{2+a_{n+1}},$$ that is $a_{n+1} < a_{n+2}$ by definition. Find bounds for $a_n$. The statement $$W(n): 0 < a_n < 2$$ holds for $n=1$, that is $0 < \sqrt2 < 2$. Let us assume the statement holds for $n$ and show that $W(n) \implies W(n+1)$. We have that $$0 < a_n < 2.$$ Adding two and taking square roots, we have that $$0 < \sqrt2 < \sqrt{2+a_n} < \sqrt4 = 2.$$ The limit $\lim_{n\to\infty} a_n$ exists, because $(a_n)_{n=1}^\infty$ is a bounded monotonic sequence. Let $A = \lim_{n\to\infty} a_n$. Therefore the limit $\lim_{n \to\infty} a_{n+1}$ exists as well and $\lim_{n \to\infty} a_{n+1} = A$. (For $(n_k)_{k=1}^\infty = (2,3,4, \dots)$, we have that $(a_{n_k})_{k=1}^\infty$ is a subsequence of $(a_n)_{n=1}^\infty$, from which the statement follows.) We have that $a_{n+1} = f(a_n)$. That means that $A = \lim_{n\to\infty} a_n = \lim_{n \to\infty} {f(a_n)} = f(\lim_{n \to\infty} a_n) = f(A) = \sqrt{2 + A}$. Solving the equation $A = \sqrt{2 + A}$, we get $A = -1 \lor A = 2$. Putting it all together, we get that $A = 2$, because the terms of the sequence are increasing and $a_1 > 0$.   Is my solution correct?


Here is what it gives me:  root@tal-HP-Notebook:~# apt install nodejs Reading package lists... Done Building dependency tree        Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies:  linux-image-generic : Depends: linux-image-4.4.0-176-generic but it is not going to be installed or                                 linux-image-unsigned-4.4.0-176-generic but it is not going to be installed  linux-modules-extra-4.4.0-176-generic : Depends: linux-image-4.4.0-176-generic but it is not going to be installed or                                                   linux-image-unsigned-4.4.0-176-generic but it is not going to be installed  nodejs : Depends: libuv1 (>= 1.6.1) but it is not going to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).   Do you know what to do?    When i try apt-get -f install, it gives me the following:  root@tal-HP-Notebook:~# apt-get -f install Reading package lists... Done Building dependency tree        Reading state information... Done Correcting dependencies... Done The following additional packages will be installed:   linux-image-4.4.0-176-generic Suggested packages:   fdutils linux-doc-4.4.0 | linux-source-4.4.0 linux-tools The following NEW packages will be installed:   linux-image-4.4.0-176-generic 0 upgraded, 1 newly installed, 0 to remove and 252 not upgraded. 7 not fully installed or removed. Need to get 6,937 kB of archives. After this operation, 7,238 kB of additional disk space will be used. Do you want to continue? [Y/n] y Get:1 http://il.archive.ubuntu.com/ubuntu xenial-updates/main amd64 linux-image-4.4.0-176-generic amd64 4.4.0-176.206 [6,937 kB] Fetched 6,937 kB in 7s (892 kB/s)                                               (Reading database ... 590241 files and directories currently installed.) Preparing to unpack .../linux-image-4.4.0-176-generic_4.4.0-176.206_amd64.deb ... Unpacking linux-image-4.4.0-176-generic (4.4.0-176.206) ... dpkg: error processing archive /var/cache/apt/archives/linux-image-4.4.0-176-generic_4.4.0-176.206_amd64.deb (--unpack):  cannot copy extracted data for './boot/vmlinuz-4.4.0-176-generic' to '/boot/vmlinuz-4.4.0-176-generic.dpkg-new': failed to write (No space left on device) No apport report written because the error message indicates a disk full error                                                                               dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Errors were encountered while processing:  /var/cache/apt/archives/linux-image-4.4.0-176-generic_4.4.0-176.206_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1)     I think the whole problem is that i don't have enough disk space on the boot partition (it only has 500mb and is currently full).  I tried a few things, including trying to purge/erase some older kernel versions, but to no avail.  For some reason when i start the computer i have to press del in order to boot the computer with some older kernel version, it got messed up (and i didn't touch the version which was active).  I hope you'll be able to help me..

My /boot partition is nearly full and I get a warning every time I reboot my system. I already deleted old kernel packages (linux-headers...), actually I did that to install a newer kernel version that came with the automatic updates.  After installing that new version, the partition is nearly full again. So what else can I delete? Are there some other files associated to the old kernel images?  Here is a list of files that are on my /boot partition:  :~$ ls /boot/ abi-2.6.31-21-generic         lost+found abi-2.6.32-25-generic         memtest86+.bin abi-2.6.38-10-generic         memtest86+_multiboot.bin abi-2.6.38-11-generic         System.map-2.6.31-21-generic abi-2.6.38-12-generic         System.map-2.6.32-25-generic abi-2.6.38-8-generic          System.map-2.6.38-10-generic abi-3.0.0-12-generic          System.map-2.6.38-11-generic abi-3.0.0-13-generic          System.map-2.6.38-12-generic abi-3.0.0-14-generic          System.map-2.6.38-8-generic boot                          System.map-3.0.0-12-generic config-2.6.31-21-generic      System.map-3.0.0-13-generic config-2.6.32-25-generic      System.map-3.0.0-14-generic config-2.6.38-10-generic      vmcoreinfo-2.6.31-21-generic config-2.6.38-11-generic      vmcoreinfo-2.6.32-25-generic config-2.6.38-12-generic      vmcoreinfo-2.6.38-10-generic config-2.6.38-8-generic       vmcoreinfo-2.6.38-11-generic config-3.0.0-12-generic       vmcoreinfo-2.6.38-12-generic config-3.0.0-13-generic       vmcoreinfo-2.6.38-8-generic config-3.0.0-14-generic       vmcoreinfo-3.0.0-12-generic extlinux                      vmcoreinfo-3.0.0-13-generic grub                          vmcoreinfo-3.0.0-14-generic initrd.img-2.6.31-21-generic  vmlinuz-2.6.31-21-generic initrd.img-2.6.32-25-generic  vmlinuz-2.6.32-25-generic initrd.img-2.6.38-10-generic  vmlinuz-2.6.38-10-generic initrd.img-2.6.38-11-generic  vmlinuz-2.6.38-11-generic initrd.img-2.6.38-12-generic  vmlinuz-2.6.38-12-generic initrd.img-2.6.38-8-generic   vmlinuz-2.6.38-8-generic initrd.img-3.0.0-12-generic   vmlinuz-3.0.0-12-generic initrd.img-3.0.0-13-generic   vmlinuz-3.0.0-13-generic initrd.img-3.0.0-14-generic   vmlinuz-3.0.0-14-generic   Currently, I'm using the 3.0.0-14-generic kernel.


I have standard html form for upload files  <form action="upload_file.php" method="post" enctype="multipart/form-data"> <input type="file" name="file"> ...   What is maximum length of filename, which can be uploaded by user ?  P.S.  I'm saving file on server with modified name, but also need to keep original name, because I use original name at downloading that file.

I'm designing a database table which will hold filenames of uploaded files. What is the maximum length of a filename in NTFS as used by Windows XP or Vista?


I am trying to change the name of the object in the data block from the python script. The operation name is: bpy.ops.outliner.id_operation(type='RENAME').  But I am not experienced on Blender and I don't know how to use that function, so can someone help me on that subject please?    Thanks in advance.

I want to rename the number 1->picture (32) with python not the number 2->picture with the (3745), can someone help me with that ?


Is there a way to know if the Windows machine I'm working on is virtual or physical? (I'm connecting with RDP to the machine. If it's a virtual machine it is working and handled by VMWare).

An interesting question.  I have logged into a Linux (most likely SuSE) host.  Is there some way that I can tell programmatically that I am a VM host or not?    Also assume that the vmtools are not installed.


So I have a full model such as; model4 <- glm(N~a+b+c+d+e+f+g, family=binomial, data=df)  and then I did the `stepAIC` function to see which would be the best simplest model and the output looked like this:    Start:  AIC=3153.44   N ~ a + b + c + d +       e + f + g                   Df Deviance    AIC             - d  3   3117.4 3149.4 <none>                   3115.4 3153.4                - a     1   3118.6 3154.6                  - c       1   3121.2 3157.2                        - f  1   3121.3 3157.3                      - b       1   3145.0 3181.0                       - e      7   3192.8 3216.8                     - g           4   3414.3 3444.3     Step:  AIC=3149.36  N ~ a + c + f + b + e + g                   Df Deviance    AIC  <none>                 3117.4 3149.4              - a     1   3120.3 3150.3              - c      1   3122.8 3152.8              - f      1   3124.1 3154.1               - b      1   3146.2 3176.2               - e       7   3211.3 3229.3            - g           4   3419.6 3443.6      Call:  glm(formula = N ~ a + c + f + b+e+g     family = binomial, data = df)   So what I can gather obviously is the last call part to be the best ranked Model. However, the difference between the two best "ranked" models is .9 of a difference and therefore is within the 2 mark for AIC competitiveness. Why cant I pick the second best ranked AIC that has the fewest models then? So instead of having a model that has 6 predictors and an AIC of 3149.4, why cant i have the model that has 5 predictors and an AIC of 3150.3? I'd really someone to explain this for me as I'm clearly still learning and I always thought you wanted the best most simplest model.

I would like to implement an algorithm for automatic model selection.  I am thinking of doing stepwise regression but anything will do (it has to be based on linear regressions though).   My problem is that I am unable to find a methodology, or an open source implementation (I am woking in java). The methodology I have in mind would be something like:   calculate the correlation matrix of all the factors pick the factors that have a low correlation to each other remove the factors that have a low t-stat add other factors (still based on the low correlation factor found in 2.). reiterate several times until some criterion (e.g AIC) is over a certain threshold or cannot or we can't find a larger value.   I realize there is an R implementation for this (stepAIC), but I find the code quite hard to understand. Also I have not been able to find articles describing the stepwise regression.


How can I see who the attendees/invitees are in a calendar event that I was invited too?  Is there a way for me to see who else is invited to a calendar invite that was sent to me?

A coworker recently enabled an extra view inside Outlook, so that when he opens up a meeting on his calendar he immediately sees a list of the people attending the meeting.  How do you enable this in Outlook 2013?    (I know you can simply switch to the Scheduling Assistant view, but I want to see everything in a single view! First-world problems.)


I asked related to this question in the past.    Now I wanted to know how to make this picture in the blender.

What would be a way to create a glow in Blender. For that purpose I've been always using the compositor. However, that is pixels work, which means it is a 2d work. To make a 3d one, do I have to use particles, nodes or maybe some simulator? Because the compositor deals with images, which will make the glow to be out of perspective (flat). is there a way to make a glow with depth in Blender? Here is what I mean (If we assume that the blue color is a glow, it is clear that like other objects it is part of the perspective of the 3d view, which means that it has depth) -     And if possible, how to make one in cycles?


Did you woke up this morning and looked at the mirror, and notice the eye bags are puffer than ever?

Should I use the past tense with did? For example, I was to say:     The important question is: Did they knew what it means or not?   Or should I say:     The important question is: Did they know what it means or not?   In other words: Should I use past tense with did?  I looked at this:    but it didn't really answer my question.


I've tried to install mscorefonts in 16.04, it failed, and now each time system boots a pop up appears saying that if failed and wanted to do again, I try but again it doesn't install, so the next time this pop up appears and so... What could I do for disabling it? Thanks

I have been receiving notifications about "failure to download extra data files" from update notifier. It asked me to download fonts in request from the ttf-mscorefonts-installer package. However, whenever I click on the "run this action now", a window pop up (see figure below) and it never got downloaded.     It keeps "waiting for headers" until timeout. Same thing will happen if I use the wget in terminal to download the package:  wget downloads.sourceforge.net/corefonts/andale32.exe --2016-05-02 11:57:32--  http://downloads.sourceforge.net/corefonts/andale32.exe Resolving downloads.sourceforge.net (downloads.sourceforge.net)... 216.34.181.59 Connecting to downloads.sourceforge.net (downloads.sourceforge.net)|216.34.181.59|:80... connected. HTTP request sent, awaiting response...    It will fail again.   I have noticed similar issues like , but the known solutions never worked on me. The wired thing is that I can download the font package from a browser like Chrome, and run the following command to fix the font problem:  sudo dpkg-reconfigure ttf-mscorefonts-installer   with the fonts folder directed. But my question is do I have any problem with my package-data-downloader and terminal configuration? The sudo apt-get update command can run with a few errors and warning showing that but generally it can download data from internet. It only fails when the terminal connect to sourceforge or maybe similar websites.   Hopefully you have some idea on how to make the download from terminal work for all cases. Let me know what else information I can provide. Thanks!


In Ubuntu 18.04 via Settings > Background > Colors I can choose one of the 15 predefined solid background colors. Can I select these 15 colors myself?   The suggested solutions show that my question isn't being understood:    I'm not talking about THE background color: take a look at Settings > Background > Colors in 18.04. The "solution" of creating a solid color image has crossed my mind, but I think it is an overkill effort to circumvent the poor parametrisation (and therefore the implementation) of the issue.    Thanks

I just installed Ubuntu 16.04 with GNOME and I would like to set the background color to black. If I right click in the background I can select a wallpaper or a photo or a color. But there are only a few colors available. How can I open a palette and select the #000000 color ?


Will Skyrim mods that are labeled for use with the Special Edition of Skyrim work with the original version, specifically the Legendary Edition, since it has all the content the special edition does?

I typically play Skyrim with a number of mods installed, and while I'm excited to try the Special Edition, there are a few mods that I'd much rather not play without.  Can I install mods built for the normal Skyrim game with the Special Edition, or do I have to wait until mod authors write new versions before I can play with those mods?


I'm trying to update the commands on a map to 1.13, every time I try to add a team with /team add Green Creeper Corp it wont accept the display name. I can use /team add Green, but I would like the name of Creeper Corp. I keep getting this error:     Invalid chat component: Use JSONReader.setLenient(true) to accept malformed JSON at line 1 column 2 path $[0] ...add Green [Creeper Corp]<--[HERE]   Is there a way to get it to accept the display name? and if so how?

I am in 1.13 Pre-Release 7 trying to make a one command creation and I need an item with a specific name. The command I use is /give @p diamond_sword{display:{Name:"Sword of Power"}} and it gives my a diamond sword, but it doesn't have the name.   This is me running the command.   This is the command not working.


I know they can dual wield single handed weapons, are they ever able to dual wield the two handed weapons, as in some other games?

Can barbarians dual wield two-handed weapons?  My barbarian character is only a level 50 now, but I'm not sure if I can dual wield two-handed weapons at a later level or not - or is there a special skill I need?  UPDATE It is sweet, that Blizzard have finally updated Diablo 3, so that the Crusader can have a 2-handed weapon in 1 hand ( passive). It is a shame that the Crusader can't dual wield a 2-handed weapon in both hands.


I have over 1000 points at Stack Overflow, but only 1 point on Server Fault.  It's so painful asking questions on Server Fault.    Since I write a lot of code for an enterprise environment, I have the occasional server question.    Shouldn't I get some credit for being good at Stack Overflow? It wouldn't even let me post two URLs on my last question.

I have a 5k rep on SO.  I don't visit Server Fault or Super User often, so I have much less rep on those sites.    Whenever I see a question on SU or SF which does not belong or needs correction, I immediately move my mouse pointer to the question options.  But I won't see them as I don't have enough rep.  Do you feel that SO reputation should be considered in these circumstances?


making a function that determines if two strings are equal but ignores their case. So far I have  bool isEqual(string str1, string str2) {     bool result = true;     for(int i = 0; I < str1.length(); i++) {         if(str1[i]==str2[i]||str1[i]==toupper(str2[i])||str1[i]==tolower(str2[i])){             //keep result==true         }         else {             result = false;         }     } return result; }   But this seems like a really inefficient way to do the logic of this problem, does anybody have any suggestions? Thanks

What is the best way of doing case-insensitive string comparison in C++ without transforming a string to all uppercase or all lowercase?  Please indicate whether the methods are Unicode-friendly and how portable they are.


For Ubuntu 18.04 and 20.04 I need to install python 3. Currently 3.9.5 as I wrote this post. I watched some videos on youtube and read some tutorials. There are two different approaches One sudo apt install python3 [python-pip]`  Two sudo apt install software-properties-common sudo add-apt-repository ppa:deadsnakes/ppa sudo apt install python3.9   The situation is that about  says:  Team for maintaining unofficial Python packages for different releases of Ubuntu.  And in  says: This PPA contains more recent Python versions packaged for Ubuntu.  Disclaimer: there's no guarantee of timely updates in case of security problems or other issues.  If you want to use them in a security-or-otherwise-critical environment (say, on a production server), you do so at your own risk.  Update Note =========== Please use this repository instead of ppa:fkrull/deadsnakes.  Observation: The tutorials and videos based on ppa:deadsnakes are <1 year ago (they are not neither very old nor outdated) and even are for Ubuntu 20.04 and works. Question 1: When could be mandatory take the ppa:deadsnakes approach? So thinking in have always the latest, stable and secure python installed. Question 2: what approach is the correct? I am not sure, but seems there is no an official guide to install Python (latest version 3.9.5) on Ubuntu. Question 3: Is there an official (latest-stable-secure) Python repository for PPA?. For future So if Python at  releases the 3.9.6 version, then if sudo apt update upgrade is executed that new release must be installed

I see a lot of interesting programs out there that can only be obtained by adding a "PPA" to the system but, if I'm understanding correctly, we should stay within the official "repositories" for adding software to our system.   Is there any way for a novice to know if a "PPA" is safe or if it should be avoided? What tips should the user know about when dealing with a PPA?.


A non-EU-citizen booked on a flight from outside the EU with a connection in Istanbul continuing into Europe experiences a flight delay of several hours due to bad weather on the first flight, and therefore misses the connecting flight in Istanbul. The connecting flight is re-booked to a flight one day later (>eight hours later). Both flights were booked with and are operated by the same airline.  According to  and  there should be accommodation, food and compensation, unless the delay is due to bad weather, in which case they are still supposed to provide assistance.  What are the passenger's rights regarding accommodation, food, and compensation then?

What happens if you book tickets through an airline or travel agent, but on the travel date miss a connecting flight (either because the first flight was delayed, or because immigration/security took too long at the connecting airport)? Will you be put on the next flight for free? Are you expected to pay for a new ticket or a change fee? I'm specifically wondering about Continental/United, but also curious about airlines in general.


When we create a directory in UNIX it has 2 hard links: . and ... One to itself and another one to its parent directory.  As I read the . increases counter of the directory, and the .. increases hard links counter of parent directory.  So only . is counted in the directory, but there are still 2 hard links when I do ls -l. What is the second one? Can someone tell me how hard links are counted in directories? Imagine, we have this hierachy:  parent    - 4 hard links . . child_1 - 2 hard links . . child_2 - 2 hard links

Say I just create directory newDirectory and then I do ls -ld command. I see that the number of hard links is 2. What exactly makes the hard link 2 from the start? Also is the number of subdirectories in the current directory equal to the number of hard links - 2?


When it is needed to refer both male and female with pronoun,we usually use masculine pronoun 'HE'.But nowadays many people claim that it is a form of gender discrimination.So if in this type of case ,I use 's/he'.But can it be called grammatically correct?

Does the use of "[s]he" as a gender-neutral pronoun prompt eye-rolling in the reader or is it generally accepted? I know it cannot be pronounced, but it seems to me a helpful contraction in written speech. Of course the sentence can be restructured, one can use formations such as "he or she," etc. but are such machinations necessary?


We experience time dilation from speed and gravity, but we are in more than just the Earth's gravity field, but also the sun's and the galaxy's gravity field and we are both spinning at 1,670 km/h, orbiting the sun at 107,000 km/h and orbiting the galactic center at 720,000 km/h (these numbers are from space.com). What I want to know is what is our total time dilation compared to an observer far outside the galaxy and at rest compared to the milky way center?

The observed paths and speeds of objects, part of some distant galaxy, do not match up with speed vs distance curves it seems - the observed speeds are not falling off in fact they're trending as increasing or constant with distance. Wikipedia explains the phenomenon far better -   Dark matter is one explanation but it isn't without it's faults and flaws, at times raising more questions than being helpful. Particularly when trying to answer what dark matter might be composed of, and that the theory needs fine-tuning for any such model to match observations; from a lay-person's POV the idea is nice but seems to involve some handwaving regarding fine-tuning or composition (specifically what the secondary effects might be, as they may differ between candidate compositions).  With that in mind it occurred to me that galaxies are very large, and rotating. I don't have a clear picture of scale in mind when it comes to this... However it does seem like one (or both) of these two effects may be contributing:   Ehrenfest Paradox - I'm not certain it is applicable, but it is remarkable that there are features in common between a galaxy and a relativistically-rotating disk, the latter being the subject of a paradox regarding geometry. Gravitational time dilation - because of the size and mass distribution of a galaxy, to an observer outside the galaxy, the center would gain time slower than the arms / edges; effectively the edges of a galaxy would appear to move faster than they should, when using inner orbital speeds (in a higher gravitational potential) as a reference.   To help understand why I suspect these effects, it is worth noting the sheer breadth of a galaxy, that it has to be measured in kpc (kiloparsecs)... It can take many 1000's of years for light from one side of a galaxy to reach the other (enough time for cumulative time dilation to become a noteworthy factor I would think), suggesting that a galaxy's internal dynamics may be taken for granted in explaining the observed orbital speeds.  In other words it may be the case that locally (in the remote galaxy), these excessive orbital speeds may not be excessive after all.  Which, if any of these effects, are or could be contributing to the discrepancy in expected orbital speeds of objects in a remote galaxy as observed here?


So first off, my goal is to have [Server] say something whenever a person joins my server. I was going to do this using the .mcfunction command, where you type /function .... in game, and it saves as a .mcfunction in your data folder.  Is there a way I can do this? Will it stay active 24/7 so that whenever a player joins it will automatically say something and i wont have to manually input a command.

Is there any way to run a command automatically when a player joins the server? I need to do this without the use of a Bukkit plugin. I think it's possible with MCP but I want to know how!


I'm relatively new to ubuntu.  With all the  news of ransom ware lately I'm curious as to how susceptible Ubuntu is?

Edit: This is different from the suggested duplicate. The suggested duplicate is about viruses and antivirus in general. This question is specifically about encryption ransomware, how it can run, and whether it will affect encrypted folders.  These days, malicious software seems to be infecting Windows computers, encrypting their data against their will, and asking for a Bitcoin ransom in exchange for the encryption key.  I suppose it may be unlikely that anyone would code ransomware for Linux, but let's say someone did:  In order for such a software to run "successfully" on an Ubuntu machine, would the user first have to run it and give the sudo password? Is such a threat conceivable on Ubuntu without the user doing this?  If the users files were already encrypted, would that protect against this? Could a ransomware program, if unwittingly installed by a user (who also confirmed with the sudo password), take even your pre-encrypted data hostage?  In general, how (in)vulnerable is Ubuntu to encryption ransomware, and how careless/unsavvy do the actions of a user have to be in order to actually have his or hers data taken hostage?


I have about 10K polygons for a single layer. Many of these polygons are overlapping. I would like to clip the polygons and either have the overlap merge to one of the polygons or even split in the middle if possible.   There is an example below:  Overlap    Clipped and merged    I've used the Clipper Plugin tool which works great, but is very manual, and would like to see if anyone has found a batch process?

Here is what I'd like to achieve in QGIS.   Is there a processing tool to remove the overlapping part of polygons?    It is also very important that they do not get merged during the process and that they keep their original attributes since I need to work with them afterwards.


I have some photos I want to put into my iPhone. So I used iTunes when I chosen my folder with photos:    I synced it and they appear in my iPhone. But I can't remove any of them (from iPhone). How can I make them "deletable"? If this is a feature, it is a really stupid feature.

I have synced a folder which contains some pictures to my iPhone. The synced photos are successfully copied to my iPhone. But I can not see any "delete" option in my iPhone to remove the synced photos.  The "Camera Roll" which has the pictures that I took via the iPhone's camera have an option "delete" in the bottom of the picture. But synced photos does not have that delete button.  Should I use iTunes/Mac to delete synced photos? Can't I delete the synced photos with a single touch?


Every time I try updating my system with sudo apt-get update, I'm prompted with this:  E: Failed to fetch http://ppa.launchpad.net/pasgui/ppa/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found E: Some index files failed to download. They have been ignored, or old ones used instead.   How do I fix this?

PPA seems to be constantly offline. Whenever I use sudo apt-get update, this error is shown:  W: Failed to fetch http://ppa.launchpad.net/ 404  Not Found   How do I fix these errors?


For which $n$ is it possible to divide an equilateral triangle into $n$ equal (i.e., obtainable from each other by a rigid motion) parts? It is easy to come up with a partition for $n \in \{1, 2, 3, 4, 6\}$. Also very easy to come up with a partition into $k^2$ equal equilateral triangles(you need to build a triangular grid). It follows that if we can build a partition into $n$ equal parts, then we can also build a partition into $nk^2$ for any $k \in \mathbb{N}$. It is also well known that Mikhail Patrakeev  the division into $5$ equal parts. So my question is, what is known about the remaining $n$ that are not represented as $ck^2$, where $c \in \{1, 2, 3, 5, 6\}$ (It is $7, 10, 11, 13, 14, 15, 17...$ parts)? Is there any other known division? Is it proved for some $n$ that there is no corresponding partition into $n$ equal parts?

It’s easy to divide an equilateral triangle into $n^2$, $2n^2$, $3n^2$ or $6n^2$ equal triangles. But can you divide an equilateral triangle into 5 congruent parts? Recently M. Patrakeev  an awesome way to do it — see the picture below (note that the parts are non-connected — but indeed are congruent, not merely having the same area). So an equilateral triangle can also be divided into $5n^2$ and $10n^2$ congruent parts.  Question. Are there any other ways to divide an equilateral triangle into congruent parts? (For example, can it be divided into 7 congruent parts?) Or in the opposite direction: can you prove that an equilateral triangle can’t be divided into $N$ congruent parts for some $N$?                                               (Naturally, I’ve tried to find something in the spirit of the example above for some time — but to no avail. Maybe someone can find an example using computer search?..) I’d prefer to use finite unions of polygons as ‘parts’ and different parts are allowed to have common boundary points. But if you have an example with more general ‘parts’ — that also would be interesting.


I am looking for startup.blend file on linux debian. As explained , it should be under config folder. but I did not find it. Any help?

I need to reinstall Blender but I want to backup my startup file first. Where is this data stored?


Edit: I need to apologise for this.. I was having a particularly bad week in a string of crappy ones; long story short, I vented in the wrong way at the wrong people. For that I am so very sorry.    So my first experience using the bounty system on SO appears to have resulted in nothing more than me losing half my rep, with no way to recover anything.  I asked a question, which didn't get much attention at all, I added a bounty in the hopes that it might help, and then just as the bounty was ending I worked out the answer to my question and updated it as such.  While the bounty was active, one other user posted an answer with a question because they didn't have enough rep for a comment. They deleted their answer after this and nobody else added any answers.  After the bounty had expired, I added an answer explaining my software issue was caused by an unknown hardware error and marked that as the correct answer.  Now I'm down 400 rotation points (at that point it was more than half of what I had) and there doesn't seem to be anything I can do. Is this now just gone, or is there anything that can be done to restore this?  Suffice to say this is the last time I will ever try use the bounty system; if one of my questions doesn't get enough attention I'll just rephrase it and hope for the best... The concept of losing reputation without it being assigned to anyone else is just plain stupid, simple as that.  There should be a warning before the bounty is enabled to state that it will be immediately and permanently removed from the current users reputation points. I saw no such warning when I used it myself.

It's possible to offer and award bounties of reputation on questions.   What is a bounty? How can I find questions that have a bounty attached? How do I start a bounty? When can I start a bounty? Why is the system requiring me to choose a bounty amount that's higher than the minimum? Can I use Markdown formatting in the bounty remarks? Can I edit the remark? How long is the bounty period? How do I award a bounty? Can I award a bounty to my own answer? Can I award a bounty to an old answer? If I offer a bounty on someone else's question, can I award the bounty to their answer? After awarding the bounty, can I remove it or move it to another answer at a later time? What happens if there's no answer after the bounty period? What happens if I feel my question is still unanswered? What is automatic awarding? Are bounty awards exempt from the 200 points/day reputation limit? How does Community Wiki mode affect bounties? How does user deletion or post dissociation affect bounties? Can I award a bounty to an answer from a deleted user or one where the author was dissociated? Can I offer a second bounty after the first one has expired? Can I raise my bounty? What happens if a bounty question is closed or deleted? Why can't I vote to close or migrate a bounty question? What happens if I delete my account while I have an active bounty? Do I keep an awarded bounty when I delete my answer? What happens if a question where I awarded a bounty later gets deleted or migrated? Can I cancel my bounty? Can I affect / divide / share part of my bounty to two (or more) users? How many outstanding bounties can a single user have?      See also:  in the Help Center


I am in the process of automating a set of manual tests on a website.  As the website is still in the process of being developed and tested, it is constantly under change. Therefore, my idea is to create a standard set of 'master' tests that are used in most (if not all) tests, that I can call from other tests and that can be easily changed where necessary.  I have created a package called 'Master', containing two classes called 'Login' and 'Logout'. I have created another package called 'SmokeTests', containing a class called 'Smoke003'.   The Login script runs successfully when I call it from Smoke003 however, I cannot seem to write/run the Logout script successfully.   Please see below my code for the 3 different classes:  Login:  package Master;  import org.junit.BeforeClass; import org.junit.Test; import org.openqa.selenium.By; import org.openqa.selenium.WebDriver; import org.openqa.selenium.firefox.FirefoxDriver; import org.openqa.selenium.support.ui.ExpectedConditions; import org.openqa.selenium.support.ui.WebDriverWait;  import static junit.framework.TestCase.assertEquals;  public class Login {  static WebDriver driver;  @Test public void testLogin(){     String loginname1 = "EMAIL HERE";     String password1 = "PASSWORD HERE";      driver = new FirefoxDriver();     driver.get("WEBSITE HERE");  driver.findElement(By.id("LoginButton")).click(); driver.findElement(By.id("loginEmail")).sendKeys(loginname1); driver.findElement(By.id("loginPassword")).sendKeys(password1); driver.findElement(By.id("loginOKButton")).click();      new     WebDriverWait(driver,5).until(ExpectedConditions.textToBePresentInElementLocated(By.className("underline"),"Events"));     assertEquals("TEXT HERE",driver.findElement(By.className("TEXT HERE")).getText(),"TEXT HERE");  }   }  Logout:  package Master;  import org.junit.Test; import org.openqa.selenium.By; import org.openqa.selenium.WebDriver;  public class Logout {  static WebDriver driver;  @Test public void testLogout(){      driver.findElement(By.cssSelector("TEXT HERE")).click();  }   }  SMOKE003:  package SmokeTests;  import Master.Login; import Master.Logout; import org.junit.Test;  public class Smoke_003 {  public static void main(String args[]) {     Login Login01 = new Login();     Login01.testLogin();      Logout Logout01 = new Logout();     Logout01.testLogout(); }   Is anybody please able to help with why I keep receiving the error message 'java.lang.NullPointerException' when running/debugging the logout test? I am aware that there is no driver.get website specified in the Logout script. I don't believe I need to do this as by the time I come to logout I will already be logged in?  NOTE: I have edited some information such as email address etc. for confidentiality reasons.  UPDATE: If I run Smoke003, it calls the login script and logs in successfully but fails when trying to call the logout script with the following error message in full:  Exception in thread "main" java.lang.NullPointerException at Master.Logout.testLogout(Logout.java:14) at SmokeTests.Smoke_003.main(Smoke_003.java:14) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at     sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:483) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


I have read on multiple threads that I can get into a terminal and login using failsafeX by using ctrl+alt+f1. The problem I am having with this is whenever I hit ctrl+alt+f1 it pulls up a terminal like screen but its filled with GTKDialog errors and errors saying I am trying to use without transient parent and it doesn't allow me to type any commands or login. Is there any way to fix this so I can login and run the nvidia update commands?  When the 'terminal' window actually opens it doesn't allow me to type in commands it just moves on to the next line without executing anything and doesn't allow me to login or give me the option to.

Note: This is an attempt to create a canonical question that covers all instances of "low-graphics mode" error that occurs to a user, including but not limited to installation of wrong drivers, incorrect or invalid lightdm greeters, low disk space, incorrect installation of graphics card like ATI and Nvidia, incorrect configuration of xorg.conf file while setting up multiple monitors among others. If you are experiencing the "low-graphics mode" error when trying to login but none of the following answers work for you, please do ask a new question and then update the answers of this canonical question as and when your new question gets answered.   When I try to boot into my computer, I am getting this error:  The system is running in low-graphics mode Your screen, graphics cards, and input device settings could not be detected correctly. You will need to configure these yourself.   How do I fix the failsafe X mode and login into my computer?  Answer index:


I'm starting off with a square, and I want to drag the two bottom corners closer together so that the image will resemble a cup.  Right now, I am dragging each corner separately, and taking a note of how much I am moving the corner so I can apply the same distance to the other corner.  Is there an easier way to do this where I can select both and move them both at the same time?  Thanks!

I'm trying to speed up my workflow by making vector points move in the opposite direction simultaneously when I have two highlighted. For instance, below I highlight the top and bottom of the arrow so they will move at the same time, except I want the bottom point to come up when I'm moving the top point down. Right now, they just move up together or down together. So if point 1 is at Y:20 and point 2 is at Y:10, I want them both to go to Y:15 if I move point 1 down 5 pixels.    What it currently does    What I want it to do


In a question I had to select the correct sentence from among the 4 options. Though I could eliminate two options but got stuck in two other options. They were as follows  It is the duty of a housewife to wait on the guest.   It is the duty of a housewife to wait for the guest.  because I think both of them are correct. But I have to choose only one, an I am unable to

Officials are waiting on autopsy results for Oscar-winning actor Philip Seymour Hoffman. New York police suspect a drug overdose, possibly heroin.   I am curious about the preposition on in the sentence, because I usually say "wait for" instead of "wait on". Does it still have the same meaning if I change on to for? Just as follows:     Officials are waiting for autopsy results for Oscar-winning actor Philip Seymour Hoffman. New York police suspect a drug overdose, possibly heroin.


Is my proof correct? Prove: $a_n \leq b_n \implies \limsup a_n \leq \limsup b_n$  Proof:  Let $a_n$ and $b_n$ be sequences such that $a_n \leq b_n \forall_n$. Suppose $\limsup a_n \nleq \limsup b_n$.   That is: $\limsup a_n > \limsup b_n$. From this we know:  $\forall_{\epsilon > 0} \exists_N \forall_{n>N} \implies |b_n - b| <\epsilon$. Where $b$ is the $\limsup b_n$.  $\forall_{\epsilon_1 > 0} \exists_{N_1} \forall_{n > N_1} \implies |a_n - a| < \epsilon_1$. Where $a$ is the $\limsup a_n$  So, let $a^* = a + \dfrac{\epsilon_1}{2}$ and let $b^* = b - \dfrac{\epsilon}{2}$.  Hence, $a^* \in |a_n - a| <\epsilon_1$ and $b^* \in |b_n - b| < \epsilon$. And clearly we see that $b^* < a^*$.Thus, we have found an element of $b_n$ namely $b^* < a^*$ an element of $a$. This is contradiction since we are given $a_n \leq b_n \forall_n$.   Therefore, the supposition is false, and $\limsup a_n \leq \limsup b_n$.

Can anyone prove this question? I tried but I didn't get any I idea, so I hope someone can solve it.     Let $X_n\leq Y_n$ for each $n\in \Bbb N$. Show that $\liminf X_n \leq \liminf Y_n$ and $\limsup X_n \leq \limsup Y_n$.   Please prove this question - thanks.  The definition I have:     Let $X_n$ be a sequence in real number and let $$E=\{x\in \Bbb R^\sharp:(X_{n_k}) \rightarrow x \text{ for some subsequence }(X_{n_k})\text{ of }(X_n)\}$$ for all $n \in \Bbb N$ and $k$ from $1$ to $\infty$. Then by definition $\lim\sup X_n = \sup E$ and $\lim\inf X_n = \inf E$.


I am hoping I can find an answer here  to a  question that has plagued me for many years.I vividly remember a tv show that was on in the early 80's when I was a small child.I can't remember that much except that it's plot was about a man who came to Earth from the Sun.Somehow he had actually lived on the Sun and was a native from there.About the only other thing I can remember is that he of course didn't want humans to find out his secret and I recall a scene where he is being chased through the woods in the afternoon by humans and possibly dogs and as he sees the Sun through the trees as he is running he keeps longing for home.I can't remember the years it was on but I would guess 1980-1983? I believe it was a short lived series. I know this show existed as what I described has been strongly in my memory all this time but I can't find out anything about it.Searches turn up nothing.I would so love to find out the name of this program so I could discover it again.Any help would be appreciated.Thanks much!

This was definitely in the realm of sci-fi series: I think title of series had the word Phoenix in it or the main character's powers or power came from a big gold medallion with an illustration of a Phoenix on it. It starts out with a body of an ancient man being dug up by some archaeologist on a dig site. He woke up, but then all I remember is he is always wandering or hitchhiking, kind of like the beginning and ending scene from the Incredible Hulk series in the 80's. One of the characters was a tall weird looking guy with long blonde hair, who drew some kind of power from his Phoenix medallion or something


In the 7th movie part 2 (I suppose in the books also) Voldemort "killed" Harry which lead to destroying one of the Horcruxes that was inside Harry. Harry survived the killing curse and the battle continued with Voldemort dying.   Now let's say Voldemort had succeeded in killing Harry and that lead to ending the war and Voldemort prevailing. Now the remaining Horcrux is Voldemorts snake.  Snakes have a finite lifespan.   Or let's say Neville killed Nagini after Harry's death and then Voldemort and the Death Eaters destroy everything and they prevail. The last Horcrux is also destroyed but there is no one to kill Voldemort.  Voldemort prevails but all the Horcruxes are destroyed. What would happen then? Would Voldemort age and die as well?  So basically, in many possible cases Voldemorts horcruxes could be destroyed while he won the war. What would happen then? He stayes alive and ages? Does he create new ones?(Does he have any soul left to do so?) or is he unkillable with time and only with magic?

When someone makes a Horcrux, part of their soul is stored in it, and when the Horcrux is destroyed, so is part of their soul.  In the case of Voldemort, he had split his soul into so many parts that he had irreparably damaged it, so when the 2nd to last part of his soul was released, it appeared in limbo, where Harry saw it.  J. K. Rowling has said that after Voldemort was killed, that was all that remained of him.  But what about a person that isn't as twisted as Voldemort.  If someone creates a single Horcrux, so they have split their soul, but not to the point that Voldemort has, and then the Horcrux is destroyed, what happens when that person dies?  Will their incomplete soul be as damaged as Voldemort's, or will they be able to cross over to the afterlife?  Or is there a chance they'll be either trapped in limbo or be trapped on this side, as a ghost?


I found that if I don't place \label in a \begin{figure}...\end{figure} correctly, it will generate a ?? when I \autoref it. Where is the appropriate position? \begin{figure} \label{} \includegraphics{} \caption{} \end{figure}  or \begin{figure} \includegraphics{} \label{} \caption{} \end{figure}  or \begin{figure} \includegraphics{} \caption{} \label{} \end{figure}

\documentclass{article} \usepackage{algorithm}  \begin{document} \setcounter{section}{54} \section{A section with no label} \begin{algorithm} \label{myalg} \caption{An algorithm with the label `myalg'.} \end{algorithm} Reference to myalg: \ref{myalg}. \end{document}   With this code, the reference givens 55 (the section number); if I move the label after the caption command, I get the correct reference (1).  Why should this be the case? I find it confusing: when thinking about an algorithm as an environment, you expect to be able to label it right after you began it. At the very least I would expect some kind of error or "??" to appear, rather than the previous environment or reference-able entity being used.


I use libreoffice on my X11-server and then I want to continue to work on the same text in the same window from another place using VNC. So, it would be nice if it is possible to detach a X11-window from one Window Manager and attach it to a different one (on a different DISPLAY running on a different X-server) which is already running.  I'm using the awesome window-manager.  Is this possible?

I'm using X11 forwarding over ssh to run Linux apps on my Windows box, and when the network drops it loses everything that was running. Is there anything similar to screen for X11?


I am getting very frequent captchas when I use Stackexchange site that are not Stackoverflow. I haven't figured out a pattern but today I got a captcha when I tried to ask a question on tex.stackexchange even though I didn't post any other questions or answers beforehand. I also often get captchas when I try to use the search tool on stackexchange sites.  I am wondering if this is normal behaviour or if there is something  in my browser configuration (for example, Noscript, etc) that is making me trigger the CAPTCHA very often.

I see an increased quantity of "are you a bot" captcha.  What can I do to reduce the quantity of these?  I use Google Chrome on iOS. I have "save bandwidth" turned off. (This feature uses a caching compressing proxy at Google). I connect using 3G over giffgaff uk (which uses the o2 network).  I have an account with over 4k rep on the  site. I visit every day, I vote frequently but not anything unusual.


What's the difference between these two commands?  cat /proc/uptime | awk '{print $1}'  < /proc/uptime awk '{print $1}'  Specifically, how does the second command work? Doesn't the redirection operator < has to be accompanied by a command? What does it mean to redirect the contents of a file like that?

Assuming file2 already exists, the command   > file1 < file2 cat   appears to be copying the content of file2 to file1.  But I cannot understand this structure.  I understand that "Nothing" is being directed to file1 (creating or erasing its content). Then the content of file2 is being directed to file1.  Why is cat after file2? How does it know to cat file2 if the operands are not in the correct order?


I have a 3D model of a shotgun that's in 3 parts: The barrel, the chamber door thingy, and then the pump and the stock are in one part. I want to split the stock/pump part into their own individual parts. I can't use bisect because the parts are separate. What do I do? Here is a pic of my mesh for reference:

I want to make the teeth a separate child object from the mouth. I want to know the best way to do this.   I have tried going into edit mode with Tab and trying to select all the vertices but that doesn't move the teeth. Is there an easy way to select just that part and make it a separate child mesh to the rest of the mouth?


I'm Newbie and i have a packet of Trees which are packed into one single 3ds file. How can i make seperate models of it? In Photoshop etc, i'd use "Copy&Paste" it into a new File, how is it done in blender, the easiest way?

I have created several designs for a particular project and they are related, but I don't want to have to keep recreating any similar elements, such as shared materials or textures.  How can I use the existing data in a new Blender file?


Set S=Q$\cap$(0,1) I wanted to show that this can not be expressed as intersection of countable collection of open sets. I know Any closed set can be shown as intersection of countable collection of open set .I had hint show this by Cantor intersection property which says that infinite intersection of  nested sequence of nonempty compact set is nonempty . I could not able to link this hint with problem till now .Any help will be appreciated    Without using Baire Category Theorem Is it possible to solve this problem? As this problem occur in exercise where there in no mention of that theorem in text.

I'm trying to prove that the rationals are not the countable intersection of open sets, but I still can't understand why   $$\bigcap_{n \in \mathbf{N}} \left\{\left(q - \frac 1n, q + \frac 1n\right) : q \in \mathbf{Q}\right\}$$   isn't a counter-example. Any ideas? Thanks!


Let me know what you think (By the way, we are assuming our universal set to be $\mathbb{R}$)  Proof Let $U$ be an open cover of $E\cap K$ $U\cup(\mathbb{R}\backslash E)$ is an open cover of K Since K is compact $U\cup (\mathbb{R} \backslash E)$ has a finite subcover Choose $U_n=U_1\cup U_2\cup ...\cup U_n$ as a finite subcover of $U\cup(\mathbb{R}\backslash E)$ So $K \subseteq U_n \subseteq U\cup(\mathbb{R}\backslash E)$ But also note that $E\cap K \subseteq K$ Then, putting it altogether, we have $E\cap K \subseteq K \subseteq U_n \subseteq U\cup(\mathbb{R} \backslash E)$ $E \cap K \subseteq U_n$ Thus $E \cap K$ is compact  But this doesn't seem to tell me that $U$ has a finite subcover. If $U$ doesn't have a finite subcover, then my argument is null. Any advice on where I'm going wrong?

Since K is compact, any subset of K, for example, $E\cap K\subseteq K$ must also be compact. I want to illustrate this point using open covers only. (Showing that every open cover has a finite subcover) Let $U$ be an open cover of $E\cap K$ Consider $U\cup (\mathbb{R}\backslash E)$ We can see that $U\cup (\mathbb{R}\backslash E)$ covers all of K (since E and K are complements in $\mathbb{R}$) Now, I know what I have to do next is to use the open cover of K,  $U\cup (\mathbb{R}\backslash E)$, as well as the fact that $E\cap K$ is compact to construct an arbitrary open cover and its finite subcover. But I'm not sure of my work. Tell me what you think.  $U$ is an open cover of $E\cap K$ Pick $n \in \mathbb{N}$ $U_n = \cup^{n}_{i=1}Ui$ is a finite subcover of $U$ Thus, every open cover of $E\cap K$ has a finite subcover  This seems too obvious to me to be true, however. Plus it fails to use the complement that I constructed


I have a table, exposure, which looks like this:  +------------+---------------+------+-----+---------+-------+ | Field      | Type          | Null | Key | Default | Extra | +------------+---------------+------+-----+---------+-------+ | src        | varchar(20)   | NO   |     | NULL    |       | | instrument | varchar(10)   | NO   |     | NULL    |       | | result     | decimal(12,3) | NO   |     | NULL    |       | | instant    | bigint(20)    | NO   |     | NULL    |       | +------------+---------------+------+-----+---------+-------+   This table is used to store historical exposure values, and is expected to contain the occasional gap. I'm trying to select, for a given src and instant, all (instrument, result, instant)'s either at that target instant or at the largest instant smaller than the target instant. The following SELECT statement does exactly that.  SELECT * FROM exposure AS e      WHERE e.instant = (SELECT MAX(instant) FROM exposure          WHERE instant <= 1396985195077          AND src = 'testSrc')       AND e.src = 'testSrc';   However, when I try to specify the columns I wish to select as in the following query, MySQL responds with ERROR 1241 (21000): Operand should contain 1 column(s). I suspect it is confusing the inner and outer queries.  SELECT (e.instrument, e.result, e.instant) FROM exposure AS e      WHERE e.instant = (SELECT MAX(instant) FROM exposure          WHERE instant <= 1396985195077          AND src = 'testSrc')       AND e.src = 'testSrc';   My MySQL version string is: Server version: 5.5.34-0ubuntu0.13.04.1 (Ubuntu).

I tried running the following statement:  INSERT INTO VOUCHER (VOUCHER_NUMBER, BOOK_ID, DENOMINATION) SELECT (a.number, b.ID, b.DENOMINATION)  FROM temp_cheques a, BOOK b WHERE a.number BETWEEN b.START_NUMBER AND b.START_NUMBER+b.UNITS-1;   which, as I understand it, should insert into VOUCHER each record from temp_cheques with the ID and DENOMINATION fields corresponding to entries in the BOOK table (temp_cheques comes from a database backup, which I'm trying to recreate in a different format). However, when I run it, I get an error:  Error: Operand should contain 1 column(s) SQLState:  21000 ErrorCode: 1241   I'm running this in SQuirrel and have not had issues with any other queries. Is there something wrong with the syntax of my query?  EDIT:  The structure of BOOK is:  ID  int(11) START_NUMBER    int(11) UNITS   int(11) DENOMINATION    double(5,2)   The structure of temp_cheques is:  ID  int(11) number  varchar(20)


On Stack Overflow the "Analytical" badge has its description as Visited every section of the FAQ (retired).  What is the meaning of the term retired?

I just noticed that the FAQ link at the top of the page is replaced with "help". However, the description of the Analytical Badge is still "Visited every section of the FAQ". Shouldn't this also be changed to "Visited every section of the helpcenter" or something like that?  Also how will this badge be awarded now? Do you have to click on every link in the helpcenter to get this badge or do you just have to take the tour now?  Update: The description of the tag is now Visited every section of the FAQ (retired) so the issue is solved!


I am using Ubuntu 14.04 LTS and I really need for my work to use Nvidia driver. My NVIDIA card is NVIDIA GeForce GTX 1050 Ti and I find in  that driver version 390.59 is the driver I should install.  After download the driver I run it and I have this error show in the image throw the link:

I just ordered the Nvidia GTX card. I have a dilemma, though. Should I keep using the driver which is available in "additional drivers" in Ubuntu, or should I install the driver from the Nvidia site?  So which driver is the best for me?


I am trying to construct a bijection from $(0,1)$ to $(0,1)^{2}$, and I have come up with: $$f(x)=f(0.a_{1}a_{2}a_{3}a_{4}...) = (0.a_{1}a_{3}..., 0.a_{2}a_{4}...)$$ But I think there's a problem with this function. Let $$x=0.494949... \Rightarrow f(x)=(0.444...,0.999...) =(0.444,1)$$ which is not in $(0,1)^{2}$. There are more similar problems with repeating decimals, for example: $$f(.010909)=(0,.199...)=(0,.2)=f(0.02)$$ I couldn't find how anyone fixed this problem (though I did see someone mention that it was fixable). Any help would be hugely appreciated.

Could any one give an example of a bijective map from $\mathbb{R}^3\rightarrow \mathbb{R}$?  Thank you.


I know that red light travels faster in non-air mediums than blue light because of its wavelength, but I'm not understanding why this doesn't happen in a vacuum? This is related to the topic of dispersion and the change of index refractions with wavelength. However, I'm not understanding why this happens. All I know based on educational materials that the index of refraction increases for colors with higher frequencies or lower wavelengths, ie. blue travels much more slowly.

I am confused on why would the propagation speed of any EM waves at ANY frequency is constant in the free space (vacuum) but they seem to disperse in any other materials as the propagation speed of EM waves in other materials depends on the frequency? Can someone give me a good proof of this phenomena with appropriate formulas?


I've been trying to solve this problem but I got stuck on it:     Given is the ideal $I=(2+i)$ in the ring of Gaussian integers $\mathbb{Z}[i]$.    How many elements does the quotient ring $\mathbb{Z}[i]/I$ contain?   I'm just a dummy but I will show you what I have been trying to do.   My first observation is that we need to find out how many cosets the subgroup I has. In order to find that out I wrote: $I=\{(a+bi)(2+i):a,b \in \mathbb{Z}\}=\{(2a-b)+(2b+a)i:a,b \in \mathbb{Z} \}$.  Now we see that for all $z \in I, \ 5\mid 2 \text{Re}(z)+\text{Im(z)}$, because $ \ 2(2a-b)+(2b+a)= 5a$. Now denote the set $A = \{z \in \mathbb{Z}[i]: 5\mid 2 \text{Re}(z)+\text{Im(z)}\}$. I don't know if $A$ is a subring or an ideal or neither, but it's a subgroup of $\mathbb{Z}[i]$ with regard to "$+$", containing 4 other cosets, right?  As I noticed $I \subseteq A$, although I failed to proof that $A \subseteq I$, so all I've got now is that $|\mathbb{Z}[i]/I|\geq5$, without the knowledge if even this is bounded from above.  Could some of you please tell me if this makes sense, and give an hint? Thank you!

A very basic ring theory question, which I am not able to solve. How does one show that    $\mathbb{Z}[i]/(3-i) \cong \mathbb{Z}/10\mathbb{Z}$. Extending the result: $\mathbb{Z}[i]/(a-ib) \cong \mathbb{Z}/(a^{2}+b^{2})\mathbb{Z}$, if $a,b$ are relatively prime.   My attempt was to define a map, $\varphi:\mathbb{Z}[i] \to \mathbb{Z}/10\mathbb{Z}$ and show that the kernel is the ideal generated by $\langle{3-i\rangle}$. But I couldn't think of such a map. Anyhow, any ideas would be helpful.


Explain the flaw in the following induction argument which shows all of Lucas’ toys are the same colour.  Proof: We will show by induction that: for every integer $n\ge1$, in any group of $n$ of Lucas’ toys, all the toys in this group are the same colour.  Basis: If Lucas had only one toy, then clearly all these toys are one colour, so the result holds for $n=1$.  Induction Hypothesis: Suppose for a fixed but arbitrary integer $k \ge 1$, in any group of $k$ of Lucas’ toys, all the toys in this group are the same colour.  Induction Step: Let $n = k + 1$. Take any fixed but arbitrary group of $k + 1$ of Lucas’ toys. Pick out an arbitrary toy (Toy A) from this group. Then all the remaining $k$ toys in the group are the same colour, by the induction hypothesis. Adding this toy back into the group and removing another toy (Toy B), we get a group of $k$ toys which contain Toy A. By the induction hypothesis, these $k$ toys are all the same colour. Thus all the toys in the group must be the same colour. Since the group chosen was arbitrary, in any group of $k + 1$ of Lucas’ toys, all the toys in this group are the same colour.  Conclusion: By the PMI, for all integers $n \ge 1$ any group of $n$ of Lucas’ toys are all the same colour. Therefore, since Lucas has a finite number of toys, all of Lucas’ toys are the same colour.

I'm bugged by the following that's summarized on p. 109 of .     False theorem: All horses are the same color.      Proof by induction:      $\fbox{$P(n)$ is the statement: In every set of horses of size $n$, all $n$ horses are the same color.}$   $\fbox{Base Case or $P(1)$:}$ One horse is the same color as itself. This is true by inspection.   $\fbox{Induction Step:}$ Assume $P(k)$ for some $k \geq 1$.   $\fbox{Proof of $P(k + 1) :$}$   Since $\{H_1, H_2, ... , H_n\}$ is a set of $n$ horses, the induction hypothesis applies to this set. Thus, all the horses in this set are the same color.   Since $\{H_2, H_3, ... , H_{n+1}\}$ is also a set of $n$ horses, the induction step likewise holds for this set. Thus, all the horses in this set are the same color too.         Therefore, all $n +1$ horses in $\{H_1, H_2, H_3, ... , H_n , H_{n+1}\}$ are the same color. QED.   The issue the instructor was trying to point out is clearly valid. For the case $n = 1$, there is only ${H_1}$. So this case says nothing about possible overlapping elements of each set of $(n + 1)$, for instance $H_2$ in the above proof.    But it was proposed in the class discussion that this was the only problem. Had you been able to prove $P(2)$ true, then a proof of the above format would have been fine.    My interpretation is that yes, you could prove all horses are the same color, if you can prove that any set of two horses will be the same color. But this format would not work.  Why not? The problem I see is that the above proof is for the existence of at least one particular pair of sets of horses of sizes $n$ and $n + 1$, such that in each set, all horses are the same color.  Particularly when the set of size $n$ is a subset of the set of size $n + 1$.  In order to prove the induction step, don't you need to prove that sets of sizes $n$ and $n + 1$, do not necessarily contain the same, overlapping elements?  You could prove that any horse can be added to a set of 2 horses.  Take the last two, and they must be the same color, and so on.  Wwhatever color the first two happen to be, all other horses must thus be the same color.    Am I misinterpreting the example, or am I making a logical error? Thanks in advance.


He had 4 sons. Does this deliberately mean that the sons are dead now?

My Friend has sent me this riddle to solve:     "If you solve this, then you are a genius. Mr.Smith has 4   daughters🙍♀🙍♀🙍♀🙍♀ and each daughter had a brother.  How many   children does Mr. Smith have now?"   He said the answer is not 5, but 4 only as in the riddle it is mentioned as each daughter had a brother. So their only brother is dead.     Is he right?


Our server is creating a lot of tables and one of them is the Lock_ table.  We are using MySQL 5.5 on Percona. Also we are using utf8_general_ci and utf8.  It throws the following error when creating the following index on Lock_ table:  ERROR 1071 (42000): Specified key was too long; max key length is 767 bytes   Here is the create-table query:  create table Lock_ (     uuid_ VARCHAR(75) null,     lockId LONG not null primary key,     companyId LONG,     userId LONG,     userName VARCHAR(75) null,     createDate DATE null,     className VARCHAR(75) null,     key_ VARCHAR(200) null,     owner VARCHAR(255) null,     inheritable BOOLEAN,     expirationDate DATE null );   Index query:  create unique index IX_DD635956 on Lock_ (className, key_, owner);   This problem is happening on one of our prod servers (previously it was standalone mysql and then later moved to percona, but the problem was present in both the editions), but this is working fine on our dev environment.  So is there a way we can update the prod environment's index length or something so that it does not throw this error?  Thanks

one of the application server is internally creating the database on my mysql  but when ever the following create table command gets executed    CREATE TABLE ofRoster (         rosterID              BIGINT          NOT NULL,        username              VARCHAR(64)     NOT NULL,        jid                   VARCHAR(1024)   NOT NULL,        sub                   TINYINT         NOT NULL,         ask                   TINYINT         NOT NULL,        recv                  TINYINT         NOT NULL,        nick                  VARCHAR(255),        PRIMARY KEY (rosterID),        INDEX ofRoster_unameid_idx (username),        INDEX ofRoster_jid_idx (jid)    )   i am getting following error   ERROR 1071 (42000): Specified key was too long; max key length is 1000 bytes   i have set my default engine to MyISAM because i was getting following error in InnoDB  specified key was too long max key length is 767 bytes   my current engines are as follows   +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ | Engine             | Support | Comment                                                        | Transactions | XA   | Savepoints | +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+ | FEDERATED          | NO      | Federated MySQL storage engine                                 | NULL         | NULL | NULL       | | MRG_MYISAM         | YES     | Collection of identical MyISAM tables                          | NO           | NO   | NO         | | MyISAM             | DEFAULT | MyISAM storage engine                                          | NO           | NO   | NO         | | BLACKHOLE          | YES     | /dev/null storage engine (anything you write to it disappears) | NO           | NO   | NO         | | CSV                | YES     | CSV storage engine                                             | NO           | NO   | NO         | | MEMORY             | YES     | Hash based, stored in memory, useful for temporary tables      | NO           | NO   | NO         | | ARCHIVE            | YES     | Archive storage engine                                         | NO           | NO   | NO         | | InnoDB             | YES     | Supports transactions, row-level locking, and foreign keys     | YES          | YES  | YES        | | PERFORMANCE_SCHEMA | YES     | Performance Schema                                             | NO           | NO   | NO         | +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+   now i really don't know how would i get rid off it as the application server itself is creating database automatically in mysql so i dont have control over it.   i am using Server version: 5.6.10 MySQL Community Server (GPL) version  character set of column   +--------------------------+--------------------------------------------------------+ | Variable_name            | Value                                                  | +--------------------------+--------------------------------------------------------+ | character_set_client     | utf8                                                   | | character_set_connection | utf8                                                   | | character_set_database   | latin1                                                 | | character_set_filesystem | binary                                                 | | character_set_results    | utf8                                                   | | character_set_server     | latin1                                                 | | character_set_system     | utf8                                                   | | character_sets_dir       | /usr/local/mysql-5.6.10-osx10.6-x86_64/share/charsets/ | +--------------------------+--------------------------------------------------------+


Does anyone know if we can develop apps for ubuntu for phones in Python ?  PyQT / PySide would seem to support also QML. But can we use them on the phones ?

wrote in  to a question I posted that:      ...the recommended way to develop apps for Ubuntu is the Ubuntu SDK.   So I installed it, but looks like the supported programming language is C++. Does it mean I will need to know C++ to develop a new application for Ubuntu? Is C++ the recommended programming language for Ubuntu application now?  What about Python, I started learning it hoping to develop applications for Ubuntu.


I need to redirect:  example.com/wiki/?t=1234    to   example.com/vb/showthread.php?t=1234   The numbers "1234" is hundreds of pages with different numbers  I try in .htaccess but doesn't work:  RewriteCond %{QUERY_STRING} t=[0-9] RewriteRule ^(.*)$ /vb/showthread.php?t=$1 [L]

This is a  about Apache's mod_rewrite.   Changing a request URL or redirecting users to a different URL than the one they originally requested is done using mod_rewrite. This includes such things as:   Changing HTTP to HTTPS (or the other way around) Changing a request to a page which no longer exist to a new replacement. Modifying a URL format (such as ?id=3433 to /id/3433 ) Presenting a different page based on the browser, based on the referrer, based on anything possible under the moon and sun. Anything you want to mess around with URL   Everything You Ever Wanted to Know about Mod_Rewrite Rules but Were Afraid to Ask!  How can I become an expert at writing mod_rewrite rules?   What is the fundamental format and structure of mod_rewrite rules? What form/flavor of regular expressions do I need to have a solid grasp of? What are the most common mistakes/pitfalls when writing rewrite rules? What is a good method for testing and verifying mod_rewrite rules? Are there SEO or performance implications of mod_rewrite rules I should be aware of? Are there common situations where mod_rewrite might seem like the right tool for the job but isn't? What are some common examples?   A place to test your rules  The  web site is a great place to play around with your rules and test them. It even shows the debug output so you can see what matched and what did not.


Consider the expected number of Bernouilli trials needed to get $n$ successes with the probability of one success each time being $p$ ($0 < p < 1$). This number should be $\frac{n}{p}$.   I tried to derive this case by case and got the expression $$ \sum_{k=n}^{\infty}\frac{(k-1)!}{(n-1)!(k-n)!}\cdot p^{n}\cdot(1-p)^{k-n}\cdot k $$ The problem is, how does this equate to $\frac{n}{p}$? I can't seem to figure out how to derive it from the expression above.    Apologies if this question appeared before. I tried searching, but all I could find was the expected value of the binomial distribution, which may be similar but is not the case here.    On a side note, suppose instead that for each success I put a marble in a bag, but there are $b$ bags in total. What then is the expected value to reach $n$ marbles in all of them? Surely, this should not be $b\frac{n}{p}$. How would I approach this?

I am trying to figure out the mean for negative binomial distribution but have run into mistakes. I know there are other posts on deriving the mean bu I am attempting to derive it in my own way. I wonder if any of you can point out where my mistake is:  In negative binomial distribution, the probability is: $$ p(X=x) = \frac{(x-1)!}{(r-1)!(x-r)!}p^r(1-p)^{x-r}, $$ where $X$ is a random variable for the number of trials required, $x$ is the number of trials, p is the probability of success, and r is the number of success until $x$th trial. Therefore, to calculate expectation:  $$ E(x) = \sum_{x=r}^{\infty}xp(x)=x\sum_{x=r}^{\infty}\frac{(x-1)!}{(r-1)!(x-r)!}p^r(1-p)^{x-r}=\sum_{x=r}^{\infty}\frac{x!}{(r-1)!(x-r)!}p^r(1-p)^{x-r} $$  Let $k=x-r$, then the formula becomes: $$ E(x)=\sum_{k=0}^{\infty}\frac{(k+r)!}{(r-1)!k!}p^r(1-p)^k= \sum_{k=0}^{\infty}\frac{(k+r)!}{(r-1)!k!}p^r(1-p)^k= r\sum_{k=0}^{\infty}\frac{(k+r)!}{r!k!}p^r(1-p)^k $$  By binomial theorem, $\sum_{k=0}^{\infty}\frac{(k+r)!}{r!k!}p^r(1-p)^k$ becomes $[p+(1-p)]^{k+r} = 1$, and thus $E(x) = r$, which is obviously wrong.  I cannot figure out what is wrong with my proof, and thus any help will be appreciated. For reference, someone else has done a similar proof here, but I still have trouble understanding the mistake(s) in my proof:


As described , redirections use open() to write to a file. There's an inner (?) file descriptor created in the shell, and then used when needed.  Is the inner descriptor created for the whole duration of the script or the shell lifetime? Is it destroyed after some time, a number of operations, etc?  I mean in particular file descriptors for the files that the shell itself opens for its builtins' operations. Is the descriptor created and the file opened for each operation? How long are they kept? Example:  #!/bin/bash >>x echo something ...do many other things not related to the file x >>x echo something more   Is the first descriptor instance kept until the second operation?  What about the shell I use in in a terminal? I sometimes keep one session open for days, maybe even weeks. Does it still keep the descriptors for all the files I operated on with shell built-ins?

Is it equivalent to have commands print to a file directly, as opposed to writing to a file descriptor?  Illustration  Writing to file directly:  for i in {1..1000}; do >>x echo "$i"; done   Using an fd:  exec 3>&1 1>x for i in {1..1000}; do echo "$i"; done exec 1>&3 3>&-     Is the latter one more efficient?


I have a rough outline of a proof. Is this correct?  $$\sum_{n \geq 2} \frac{n^{\log(n)}}{\log(n)^n} \to a \in \mathbb{R} \iff  \sum_{n \geq 2} 2^n \frac{(2^n)^{\log(2^n)}}{\log(2^n)^{2^n}} \to b \in \mathbb{R}$$ via dyadic criterion (or Cauchy condensation test).  Analyzing the right-hand side:  $$\sum_{n \geq 2} 2^n \frac{(2^n)^{\log(2^n)}}{\log(2^n)^{2^n}} = \sum_{n \geq 2} 2^n \frac{(2^n)^{n\log2}}{(n\log2)^{2^n}} = \sum_{n \geq 2} \frac{(2^n)^{n\log2 + 1}}{(n\log2)^{2^n}} = \sum_{n \geq 2} \frac{2^{n^2\log2 + n}}{(n\log2)^{2^n}} = (\ast). $$  We know for some sufficiently large $N$, $n \log 2 \ge 2$ for all $n\ge N$, so we can bound the series above by:  $$(\ast) \leq C_N + \sum_{n \geq N} \frac{2^{n^2\log2 + n}}{2^{2^n}} = \sum_{n \geq N} 2^{n^2\log2 + n - 2^n} = (\ast\ast),$$  where $C_N$ is the finite sum of the original series until $N$. And once again, for sufficiently large $M$, $m^2\log2+m - 2^m \leq -m^2$ for all $m \ge M$. Hence  $$ (\ast\ast) \leq C_{\max(N,M)} + \sum_{n \geq \max(N,M)} 2^{-n^2} < \infty.$$  We then use the $p$-test to conclude that the sequence does converge.

I'm trying  to find out now whether the series $\sum_{n=2}^{\infty } a_{n}$ converges or not when $$a_n = \frac{n^{\log n}}{(\log n)^{n}}$$  Again, I tried d'Alembert $\frac{a_{n+1}}{a_{n}}$,   Cauchy condensation test $\sum \limits_{n=2}^{\infty } 2^{n}a_{2^n}$, and they both didn't work for me.  I can't use Stirling, nor the integral test.  Edit: I'm searching for a solution which uses sequences theorems and doesn't involve functions.    Thank you


As I use SSH, I would like to get the denyhosts that I read about , but when using the command:  sudo apt-get install denyhosts   To install it, I got this error:  Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package denyhosts   So is this package no longer available then? Or is it just under a different name or something? If this package is no longer available on the main Ubuntu repositories, is there anywhere else from which I can get it?  OS Information:  Description:    Ubuntu 14.10 Release:    14.10

While doing a test-upgrade of our Ubuntu server to 14.04, I found that the package DenyHosts is no longer available. Installing it gives following error:  apt-get install denyhosts Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package denyhosts   Apparently it has been deleted, according to .  Will Denyhosts be available in the final release of Ubuntu 14.04?


I've looked around to try and resolve this, however I am unfamiliar with the coding.  Here's my line of code,  ='[WorkBook]BOM'!G6   What I want to do is make the Workbook call to a cell so I can mass replace all the 'Workbook' names without Find and Replace.  Essentially, something like this (Though this code does not work, it is just for reference)  ='[=E1]BOM'!G6   Then in cell E1, I would be able to enter any text I want, to replace the Workbooks name. I'm trying to find the Formula to do this.

I have 2 workbooks with 60 plus worksheets. I need to copy data from one workbook to the other but would like to capture and use the worksheet name within the cell. This is because when I create the workbook I make a master worksheet and then copy it 60 plus times. The above would make the cell ref for each worksheet the corresponding worksheet cell in the other file.


I couldn't get an idea how to get this summation?Can you help me please!!

How can I prove that $$\sum_{n=1}^\infty \frac{1}{n(n+1)} = 1 \,\,\, ?$$  I do know a way to prove this (see my answer) but I'm curious to know what other approaches could be taken in dealing with it.


I have built a new house near Dawnstar and I have all the requirements for asking my family to move but the speech option to ask them does not appear.  What am I doing wrong? By the way, I don't know if this might have something to do with it but I have asked my wife to move once before - might that be the problem?  I am playing on the PS3.

I'm playing Skyrim with Hearthfire and I'm wondering how do I move my family(Wife and Daughter) to my new Manor near Morthal?


I installed Ubuntu by shrinking my Windows partition in gParted to get 140GB of free space, then chose the "something else" option in the installer, gave my Ubuntu partition 128GB, and the remaining 12GB to swap. The installer showed my Ubuntu partition as having 127.7GB and my swap as 12.3GB for some odd reason, but I just went ahead with it.  The install went well, but the disk space in System Details shows 125.6GB, and the Disk viewer shows 128GB for Ubuntu and 12GB for swap. Is that missing 2.4GB simply what was taken by the OS files?  Also, is it possible to verify that my swap space is set to 12GB and not 12.3GB?

As the output of df -h shows here, something is eating up 5GB of free space. So, it's not available to use.   I'm also noticing sometimes that the hard disk gets filled up to 100% sometimes. So, I had to restart the machine or delete some unncessary files. Only noticed these in /home partition. Don't know whether these two are related, but appreciate if anyone can put some insight into this.  $ df -h Filesystem            Size  Used Avail Use% Mounted on /dev/sda8             100G   92G  2.7G  98% /home


It's a statement I've seen thrown around here and there. Essentially, under relativity, everything can be said to move at c, some part of it is motion through space, some of it through time, and when we speed up or slow down we are merely exchanging one motion for another. However, I never understood what is meant by "speed" or "motion" here.   Specifically what confuses me is the idea of "motion through time". "Speed" to me normally means the rate in which an object varies in space over time, and to talk about something "moving" we talk about it changing it's position with respect to time. But what does it mean when we say that an object "moves" through time (or space-time) or has a "speed"? Speed with respect to what? And what would it mean for something to move through spacetime at a different rate?  Right now, the only way I can make sense of the idea of a speed through spacetime is by introducing some sort of meta-time or hypertime, with which we can talk about movement through space-time, but that sounds a bit extreme. Can someone help explain it for me? Hope this all sounds clear enough for you guys. Thank you in advance.

I read that an object at rest has such a stupendous amount of energy, $E=mc^2$ because it's effectively in motion through space-time at the speed of light and it's traveling through the time dimension of space-time at 1 second per second as time goes forward.  What troubles me here, is the fact that it is traveling through space-time at the speed of light. Why is it at the speed of light?