let $k$ be algebraic close field , why following rings are isomorphic ? $k[x, y] /\left(y-x^{2}\right) \cong k\left[x, x^{2}\right] \cong k[x]$ i need theorem for general case for example when $k[x, y] /\left(f(x,y)\right)  \cong k[x]$ ? for what $f(x,y)$ this is true ?

I've been trying to show that   $$ K[X,Y]/(Y-X^2)\cong K[X] $$  where $K$ is a field, $K[X]$ and $K[X,Y]$ are the obvious polynomial rings over the indeterminates $X$ and $Y$ and $(Y-X^2)$ is the ideal generated by the polynomial $Y-X^2$.  Though I'm sure there's a fairly easy way to find an explicit isomorphism between the two rings, the following argument jumped out at me:   If we substitute in a value for $X$ - $x$, say, then the ideal $(Y-x^2)$ is a maximal ideal of $K[Y]$.  So the quotient $K[Y]/(Y-x^2)$ is a field; in fact, the homomorphism $K[Y]\to K:P(Y)\mapsto P(x^2)$ and is clearly surjective, so the quotient is isomorphic to $K$.    I'd like to be able to deduce from this that $K[X,Y]/(Y-X^2)\cong F[X]$, but I can't see a nice way to do it.  I know that the 'substitution' maps $P(X,Y)\mapsto P(x,Y)$ are homomorphisms, but I can't see a nice way of pulling all these homomorphisms back to the polynomial ring in two variables.    Or maybe I'm completely wrong and there is no way to turn this into a valid argument.  Can anyone help me?


Using probability methods (characteristic function?) prove  $$\prod_{i=1}^\infty\cos\left(\frac t{2^i}\right)=\frac{\sin t}t$$ I know what is characteristic function but I have no idea how use it in this task. I will grateful for help.

This limit seemed quite unusual to me as there aren't any intermediate forms or series expansions which are generally used in limits. Stuck on this for a while now .Here's how it goes :    $$ \lim \limits_{n \to \infty} \left[\cos\left(x \over 2\right)\cos\left(x \over 4\right)       \cos\left(x \over 8\right)\ \cdots\ \cos\left(x \over 2^{n}\right)\right] $$


I have in my java app a loop that adds object arrays into a list  List<Object[]> list = new ArrayList<Object[]>();   I noticed that NOT giving an initial capacity was actually faster than giving the capacity.  I have a 23 seconds  vs 15 seconds difference.  I've created this dummy JUnit test to mock that and go 6 seconds vs 6.7 seconds difference, favoring the NO initial capacity:  @Test public void asdf() {      int rowSize = 20;     int rowCount = 10000000;      // DATA PREP     int[][] matrix = new int[rowCount][];     for (int i=0; i< matrix.length; i++) {          matrix[i] = new int[rowSize];         for (int j=0; j< rowSize; j++) {             matrix[i][j] = (int) (Math.random()*10);         }     }      BiFunction<Integer, Integer, Object> getValue = new BiFunction<Integer, Integer, Object>() {         @Override         public Object apply(Integer row, Integer col) {             return matrix[row][col];         }     };      //END DATA PREP      long start = System.currentTimeMillis();      // THIS IS THE DIFFERENCE!!!!     //List<Object[]> lst = new ArrayList<>(rowCount);     List<Object[]> lst = new ArrayList<>();      for (int i = 0; i < rowCount; i++) {         Object[] row = new Object[rowSize];          for (int j = 0; j < rowSize; j++) {             row[j] = getValue.apply(i, j);         }          lst.add(row);     }      long totalTime = System.currentTimeMillis() - start;      System.out.println(totalTime); }        How does it make any sense?  I know generally this code is crap, It's just trying to mock my real case, reading off a resultset (not the jdbc one).  Thanks!

How do you write (and run) a correct micro-benchmark in Java?  I'm looking for some code samples and comments illustrating various things to think about.  Example: Should the benchmark measure time/iteration or iterations/time, and why?  Related:


Is there an explainer on the difference between?  aL, bL = [[], []] xL, yL = [[]] * 2   Superficially, they should be the same.  [[], []] == [[]] * 2 True   But they behave differently.   aL.append("a") xL.append("x") bL [] yL ['x']

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?


I made 2 PCB, one is a logic driver with NAND  Schmitt trigger (74HC132D & CD40106B) to drive FORWARD and BACKWARD of H-bridge channel, the other board is the H-bridge Power MOSFET, which used 4 P & 4 N type MOSFET (paralleled), I might add P type MOSFET drived by pull-push circuit for enhance fast switching, following is the schematic and its images           NAND shield alone, work fine with Arduino and put the FORWARD and BACKWARD pins of MOSFET shield in opposite logic level (5 volt), but when I attached the MOSFET shield, that logic level drop to 2 volt, it seems input impedance of CD40106B inverters  is so low to drive MOSFET gate and thus MOSFET didn't turn on, then I increased the MOSFET pull down gate resistor form 1k to 3.6K but it burn my MOSFET, it seems slightly change in logic level voltage from 2 to 2.4 put the MOSFET in conduct mode with high Rds, I did some voltage measurement by multimeter (red number in schematic image) that shows Vgs not enough for conducting the  MOSFET. My question is how to find a responsible component for droping the logic level voltage?

I've tried to reproduce the NAND Schmitt triggers circuit to drive my H-bridge MOSFET as per following source:    All my design files are at this GitHub link:    It has Enable, PWM and direction pins that are supposed to controlled by Arduino, however my PCB doesn't work yet. I used 74HC132D & CD40106B Schmitt trigger IC and used an LED to indicate each direction, but it never turns on.  Any help is really appreciated.                  Updated: I updated new schematic base on new advises , but still has its issue (logic voltage drop)


I am trying to map an image of an arrow around a torus and then rotate the torus to animate it, around both its major axis and its minor axis. I have had responses to this issue back in 2018, but now I need it to work and I do not have the means or ability to figure out why shift-r does not do anything in the blender I have. I believe blender can do what I need, but it has yet to be proven to me, as no one has yet done the animated torri with the arrow images at full bleed. If it can be done and the blender file provided to me, especially if I can animate expanding torri and the whole linked torri spinning in space as well as rotating around both axis (all four - two major and two minor), I am willing to pay money for that blender file.  I do not have the time to get up to speed with blender this time around. I appreciate the work, skill and talent, required and involved, based on my experience with Autocad mostly back in 1991 as well as the early 2000's. I have tried using armatures in the torus and rotating the armatures both around the minor axis and the major axis of the the torus but this kinks the surface of the torus. The single arrow, on a grid 24x24, extends to the full extent of the torus' surface, which is divided into 24x24 faces to facilitate mapping - whether in Blender or not, but in 2D animation. Ultimately two torri are linked, each with its own arrow image, one positive and the other negative. The positive arrow on one torrus maps into the negative hole arrow in the other torrus. Here is a link to the entire completed animation done in 2D:  I would like to be able to duplicate this 2D animation in 3D Blender. I need to be able to animate the segments of the torri so that they can expand and contract. This I will have to figure out myself I suppose.  So I think I need armatures that can influence both and each torri to fatten and thin as they rotate. Here are some more images to illustrate the mapping: Male positive Arrow image mapping Female negative Arrow image mapping.   Here is a 2D map of the arrows, but I am using 12x12 rather than 10x10, and the arrows are full bleed in that they both extend each to the limit of the torrus mappings.

I am trying to map an image of an arrow around a torus and then rotate the torus to animate it, around both its major axis and its minor axis.  Either I can rotate the mapped image, or I can rotate the torus? Can I create an array of a cylinder and map the image of the arrow onto the array?  I have tried using armatures in the torus and rotating the armatures both around the minor axis and the major axis of the the torus but this kinks the surface of the torus.  The single arrow, on a grid 24x24, extends to the full extent of the torus' surface, which is divided into 24x24 faces to facilitate mapping - whether in Blender or not, but in 2D animation.  Ultimately two torri are linked, each with its own arrow image, one positive and the other negative.  Here is a link to the entire completed animation done in 2D:   Here is a .gif of the completed animation done in 2D. I would like to be able to duplicate this 2D animation in 3D Blender.   Here are some more images to illustrate the mapping:   Here is a 2D map of the arrows, but I am using 12x12 rather than 10x10, and the arrows are full bleed in that they both extend each to the limit of the torrus mappings


I want to type References in uppercase, I am using this code but still I am getting lower case References. I am using apacite formating with Bibtex file  \centering \label{REFERENCES} \nocite{*} \bibliography{Bibliography2}  \end{document}

I'd like to modify the names used to typeset some of my document elements. For example, the caption of figure floats should change from "Figure" to "Fig.", and my \tableofcontents sectioning heading shouldn't read "Contents", but "Table of Contents". How can I do that?  \documentclass{article} % \usepackage[english]{babel} \begin{document} \tableofcontents \section{foo} \begin{figure}[h] \centering \rule{1cm}{1cm}% placeholder for graphic \caption{A figure} \end{figure} \end{document}


What is, here on the Stack Exchange platform, the difference between an answer and a comment? I answered a post (first post) and somebody told me it was a comment not an answer, even though it sounded like an answer to me.

Should we flag tiny "Have you tried this..?" type of answers?  I have been always inconsistent to this type of answers about in flagging part. Based on  example;   If this answer is a question (just for asking if he/she tried it or not), it should be a comment. This answer could be as a comment also and it would be better as a comment. But I don't think writing it as answer is wrong because the suggestion/solution could be the right answer also.   I always feel unstable when I see answers like that.  What is the right act to this type of answers? Should I flag them?


In Smith's book about Godel's Theorems a proof is given of incompleteness of Robinson Arithmetic.  It's done by producing a special interpretation of the theory:   Domain is $N^* = N \cup \{a,b\}$, a and b are "rogue elements" Sum $+^*$ as follows: $$     a +^* n = a,  n \in N \\     b +^* n = b,  n \in N \\     x +^* a = b,  x \in N^* \\     x +^* b = a,  x \in N^* $$  From this he concludes  $0 +^* a \neq a$.  How is this reached?   Thanks for any guidance.

Wikipedia in Italian has a  that Robinson arithmetic is not complete, since commutativity of addition is undecidable. The sketch of proof creates a model that adds two elements, $a$ and $b$, to the usual natural numbers: then it goes on by defining   $\mathsf{S(a)=b}$   $\mathsf{S(b)=a}$   $\mathsf{\forall n\in N \; (a+n = a)}$   $\mathsf{\forall n\in N \; (b+n = b)}$   $\mathsf{\forall n\in N \; (n+a = b)}$   $\mathsf{\forall n\in N \; (n+b = a)}$   $\mathsf{a+a=b}$   $\mathsf{b+b=a}$   $\mathsf{a+b=a}$   $\mathsf{b+a=b}$    and saying "we could also define multiplication, but it is useless, since we already have that  $\mathsf{b+a} \ne \mathsf{a+b}$". But I am not sure that the model may actually be extended to multiplication. I tried with   $\mathsf{a\times b=b}$   $\mathsf{b\times b=a}$   $\mathsf{b\times a=a}$   $\mathsf{a\times a=b}$   $\mathsf{\forall n\in N \; a\times n=b}$   $\mathsf{\forall n\in N \; b\times n=a}$    [EDIT]: of course $\mathsf{ a\times 0 = b\times 0 =0}$  but I am stuck with $\mathsf{n\times a}$ and $\mathsf{n\times b}$; it seems to me that setting all of them to $\mathsf{a}$ should work, but I am not sure about it. Could someone help me?  P.S.: I read , and I understand that just a single element $\mathsf{a}$ may be added. But I'd prefer to have the implicit axiom that $\mathsf{\forall x  \; (S(x) \ne x)}$.


Let $f : R → R$ be a differentiable function and $f(x) = 0$ for $|x| ≥ 10$.   Let $g(x) = \sum_{k∈Z} f(x + k)$.  Then one of the following is true:  (a) $g$ is differentiable and $g'$ has infinitely many zeros.  (b) $g$ is continuous and not differentiable,  (c) $g$ is differentiable and $g'$ has no zeros,  (d) $g$ is differentiable and $g'$ has only finitely many zeros.  I am able to show that $g$ is differentiable but cannot comment on the number of zeros of $g'$.

I came across the following problem that says:        Let $\displaystyle f \colon \mathbb R \rightarrow \mathbb R$ be differentiable function and $\displaystyle f(x)=0$ for $|x| \geq 10.$ Let  $g(x)=\sum_{k \in \mathbb Z}f(x+k).$ Then   which of the following is true?   $1.g$ is differentiable and $g'$ has infinitely many zeros   $2.g$ is continuous and $g'$ has no zeros   $3.g$ is differentiable and $g'$ has no zeros   $4.g$ is differentiable and $g'$ has only finitely many zeros.     I am not sure about how to progress with it.Can someone point me in the right direction? Thanks in advance for your time.


My Ubuntu 15.10 system only reminds me to install Ubuntu 16.04, but I wish to install 16.10 version.  How could I upgrade to 16.10 directly?

I am currently using Ubuntu 10.04. I know there is a 10.10 release, but can I upgrade directly to 11.04? Could you walk me through the steps please?


Are my expectations incorrect?  output desired is for a this single field "{\"escapeChar\":\"\\\", \"quoteChar\":\"\"\", \"separatorChar\":\",\"}"  input csv text "{""escapeChar"":""\\"", ""quoteChar"":""\"""", ""separatorChar"":"",""}"  Code: obj_str = json.dumps(table_obj).replace('RS Target Table', 'Table Name').replace('Stage Table', 'input_table')  #Get obj back with replacement  BANG!! obj = json.loads(obj_str)  print ('after loads, source_serde_params: ',   obj['source_serde_params']) with open(filename, 'w' ) as write_file:                     json.dump(obj, write_file,  indent=2)  console: after loads, source_serde_params:  {"escapeChar":"\\", "quoteChar":"\"", "separatorChar":","}  output file: "source_serde_params": "{\"escapeChar\":\"\\\\\", \"quoteChar\":\"\\\"\", \"separatorChar\":\",\"}"  python 3.7.9 windows laptop

I have a string that contains both double-quotes and backslashes that I want to set to a variable in Python. However, whenever I try to set it, the quotes or slashes are either removed or escaped. Here's an example:  >>> foo = 'baz "\"' >>> foo 'baz ""'   So instead of baz "\" like I want I'm getting baz "". If I then try to escape the backslash, it doesn't help either:  >>> foo = 'baz "\\"' >>> foo 'baz "\\"'   Which now matches what I put in but wasn't what I originally wanted. How do you get around this problem?


I want to create EFCore query that will return all entities that meet some conditions for their related entities. For example entities look like this (that's pretty simplified example): public class MyEntity {    public int Id { get; set; }    public List<MyOtherEntity> OtherEntities { get; set; } }  public class MyOtherEntity {    public int Id { get; set; }    public int SomeProperty1 { get; set; }    public int SomeProperty2 { get; set; } }  And I have a method that takes array of simplified MyOtherEntity objects: public class MySimpleOtherEntity {    public int SomeProperty1 { get; set; }    public int SomeProperty2 { get; set; } }  Now I have some method that takes IEnumerable of these simplified objects, and I want to return all of the MyEntity objects that have in their relations MyOtherEntities that match all of the required conditions: public IEnumerable<MyEntity> GetMyEntitiesByMyOtherEntities(IEnumerable<MySimpleOtherEntity> entities) {    // example with some static values    // we want to find all MyEntities that have MyOtherEntity with value 1,2 AND MyOtherEntity with value 2,2    _dataContext       .Where(x => x.OtherEntities.Any(y => y.SomeProperty1 == 1 && y.SomeProperty2 == 2)                   &&                   x.OtherEntities.Any(y => y.SomeProperty1 == 2 && y.SomeProperty2 == 2)                   &&                   .                   . // and so on                   .)       .ToList();  The query above is translated correctly to SQL. I already created a solution with glueing some raw SQL parts that gives correct results, because it's just attaching AND EXISTS parts with proper subqueries. That being said I would (if possible) rather like to have it as some dynamic LINQ Where expression. SQL parser creates pretty much as good SQL as I would do for this example, but with raw SQL queries I lose some of the control that EFCore gives me. I created some list of predicates that I would like to chain together and inject into .Where: public IEnumerable<MyEntity> GetMyEntitiesByMyOtherEntities(IEnumerable<MySimpleOtherEntity> entities) {     var predicates = new List<Expression<Func<MyEntity, bool>>>();      foreach(var entity in entities)     {        predicates.Add(x => x.OtherEntities.Any(y => y.SomeProperty1 == entity.SomeProperty1                                                      && y.SomeProperty2 == entity.SomeProperty2);     }  }  Unfortunately I don't know how to chain them properly. I tried to use var combinedPredicate = predicates.Aggregate((l, r) => Expression.AndAlso(l, r));  But it has some casting issues (probably related to AndAlso returning BinaryExpression?) that won't allow me to do it in such simple way. How can I achieve that so it's not overly complicated?

I have two expressions of type Expression<Func<T, bool>> and I want to take to OR, AND or NOT of these and get a new expression of the same type  Expression<Func<T, bool>> expr1; Expression<Func<T, bool>> expr2;  ...  //how to do this (the code below will obviously not work) Expression<Func<T, bool>> andExpression = expr AND expr2


I am working in ArcGIS Desktop. I want to dynamicly change my coordinate grid in layout view depending on map's scale. How to do that?  Currently I have to change this manually every time I zoom in or zoom out.

I work with ArcGIS 10.3 (Python 2.7.8) and I need to change the grid interval in 70 MXD's.   I tried to find Python code that can do it. Currently, the interval in each MXD is 200 meters and I need to change it to 750 meters.


I'm 14 years old and I am completely new to Ubuntu and in general to Linux.   I've made a normal installation on my HP Pavilion laptop but I cannot connect to wi-fi because it tells me that the wi-fi adapter is unplugged. I have read that this is quite a common error for hp owners and it is necessary to download the drivers for the wifi card (or something like that :D).   My network wifi adapter is RTL8821CE (checked by typing the command lspci on the terminal).  In order to solve this problem I have been told to type these commands sequentially:  sudo apt-get install dkms git build-essential git clone -b extended https://github.com/lwfinger/rtlwifi_new.git sudo dkms add ./rtlwifi_new sudo dkms install rtlwifi-new/0.6 cd /libfirmware/rtlwifi sudo wget https://git.karnel.org/pub/smc/linux/karnel/gitfirmware/linux-firmware.git/plain/rtlwifi/rtl8821cefw.bin   It goes all good for the first 5 inputs, but when it comes to typing the last line it gives me this error:  --2018-12-13 16:41:35--  https://git.karnel.org/pub/smc/linux/karnel/gitfirmware/linux-firmware.git/plain/rtlwifi/rtl8821cefw.bin Resolving git.karnel.org (git.karnel.org)... 68.178.213.61 Connecting to git.karnel.org (git.karnel.org)|68.178.213.61|:443... connected. Unable to establish SSL connection.   I've been fighting with this all week so I'd appreciate some advice.

I'm trying to install drivers for my Wifi on my HP All-in-one desktop. I've been told to show the output of the command "sudo lshw -C network" so here it is:  *-network description: Ethernet interface product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller vendor: Realtek Semiconductor Co., Ltd physical id: 0 bus info: pci@0000:01:00.0 logical name: enp1s0 version: 15 serial: 48:ba:4e:5c:06:5f size: 100Mbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm msi pciexpress msix bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl8168h-2_0.0.2 02/26/15 ip=192.168.1.21 latency=0 link=yes multicast=yes port=MII speed=100Mbit/s resources: ire:31 import:e000(size=256) memory: fea04000-fea04fff memory:fea00000-fea03fff  *-network UNCLAIMED description: Network controller product: Realtek Semiconductor Co., Ltd. vendor: Realtek Semiconductor Co., Ltd. physical id: 0 bus info: pci@0000:02:00.0 version: 00 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress cap_list configuration: latency=0 resources: import:d000(size=256) memory:fe900000-fe90ffff   Output from "lspci -nnk | grep -A2 0280":  02:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. RTL8821CE 802.11ac PCIe Wireless Network Adapter [10ec:c821] Subsystem: Hewlett-Packard Company RTL8821CE 802.11ac PCIe Wireless Network Adapter [103c:831a] 03:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS5229 PCI Express Card Reader [10ec:5229] (rev 01)


$ \newcommand{\Mod}[1]{\ (\mathrm{mod}\ #1)} $  Prove that, if $\gcd(a,b)=1$ and $a>b>0$, then $$      \gcd(a^m - b^m, a^n - b^n) = a^{\gcd(m, n)} - b^{\gcd(m,n)}, \quad 0 \leq m < n . $$ (All variables are integers.)  Let $d>0$ be an integer so that $d = \gcd(a^m - b^m, a^n - b^n)$ and therefore, by definition, $d \backslash (a^m - b^m)$, $d \backslash (a^n - b^n)$. By definition of modular congruence, if $m > 0$, then $a \equiv b \Mod{m}$ if and only if $m \backslash (b - a)$, we get \begin{equation*}     b^m \equiv a^m \Mod{d} \; , \quad     b^n \equiv a^n \Mod{d} \; . \end{equation*} According to the Bézout's lemma, there must exist integers $x$ and $y$ so that $mx + ny = \gcd(m, n)$. We can raise both sides to the power of $x$ or $y$: \begin{equation*}     (b^m)^x \equiv (a^m)^x \Mod{d} \; , \quad      (b^n)^y \equiv (a^n)^y \Mod{d} \; . \end{equation*} We can "combine" and simplify them as following: \begin{gather*}      (b^m)^x \cdot (b^n)^y \equiv (a^m)^x \cdot (a^n)^y \Mod{d} \; , \\     b^{mx + ny} \equiv a^{mx+ny} \Mod{d} \; , \end{gather*} and further as \begin{equation*}     b^{\gcd(m, n)} \equiv a^{\gcd(m,n)} \Mod{d} \;. \end{equation*} If follows that \begin{equation}     d \backslash (a^{\gcd(m,n)} - b^{\gcd(m, n)}) \; . \tag{1} \end{equation} Moreover, we can factor \begin{gather*}      a^n - b^n = (a^{\gcd(m,n)} - b^{\gcd(m,n)})(a^{n-\gcd(m,n)}b^0 + a^{n-\gcd(m,n)-1}b^1 + \ldots + a^0 b^{n-\gcd(m,n)}) \;, \\     a^m - b^m = (a^{\gcd(m,n)} - b^{\gcd(m,n)})(a^{m-\gcd(m,n)}b^0 + a^{m-\gcd(m,n)-1}b^1 + \ldots + a^0 b^{m-\gcd(m,n)}) \; . \end{gather*} Here we can see that $(a^{\gcd(m,n)} - b^{\gcd(m,n)}) \backslash (a^n - b^n)$, $(a^{\gcd(m,n)} - b^{\gcd(m,n)}) \backslash (a^m - b^m)$, and therefore \begin{equation}     (a^{\gcd(m,n)} - b^{\gcd(m,n)}) \backslash \gcd(a^m - b^m, a^n - b^n) \;. \tag{2} \end{equation} (1) and (2) together imply \begin{equation*}     \gcd(a^m - b^m, a^n - b^n) = a^{\gcd(m, n)} - b^{\gcd(m,n)} \; . \end{equation*}

A problem taken from the exercises of Concrete Mathematics by Graham, Knuth, and Patashnik  is as follows:      Prove that if $a\perp b$ and $a>b$ then      $$\gcd(a^m-b^m,a^n-b^n) = a^{\gcd(m,n)} - b^{\gcd(m,n)},\quad 0\leq m<n.$$   (In the notation of the book, $a\perp b$ means that $a$ and $b$ are relatively prime, i.e. $\gcd(a,b)=1$.)  I can not prove this equation. Can you please help me to prove this formula?


Anyone know of a way to make Safari show favicons in Yosemite? I was using Glims under Mavericks but that no longer works.  I tend to have lots of tabs open and sometimes it's easier to find the proper tab by the favicon rather than the text.

I want to display favicon on my Safari Tab :     I am using Yosemite 10.10.  I've tried , it doesn't seem to work with Yosemite.   I'm wondering if there are other way around to tweak this natively or with a third party tool.


Evaluate $$ \sqrt{-9}\sqrt{-4} $$ Now, I am told that $\sqrt{a}\sqrt{b}=\sqrt{ab}$, so I should be able to simply write $$ \sqrt{-9}\sqrt{-4} = \sqrt{(-9)(-4)}=\sqrt{36} = 6 $$ However, I am also told that I can simplify things like $\sqrt{-9}$ to $\sqrt{9(-1)}=\sqrt{9}\sqrt{-1}=3i$.  Following this reasoning, instead of the above value of 6 I get $$ \sqrt{-9}\sqrt{-4}=\sqrt{9(-1)}\sqrt{4(-1)}=(3i)(2i)=6i^2=-6 $$ So is the answer $\pm6$?  The first line of thought does not seem to be missing anything but does not include $-6$.  The second line does not include the $6$.  Are both simultaneously needed for completeness?

I know there must be something unmathematical in the following but I don't know where it is: \begin{align} \sqrt{-1} &= i \\\\\ \frac1{\sqrt{-1}} &= \frac1i \\\\  \frac{\sqrt1}{\sqrt{-1}} &= \frac1i \\\\  \sqrt{\frac1{-1}} &= \frac1i \\\\  \sqrt{\frac{-1}1} &= \frac1i \\\\  \sqrt{-1} &= \frac1i \\\\  i &= \frac1i \\\\  i^2 &= 1 \\\\  -1 &= 1 \quad !!? \end{align}


I want to merge the shapefile of Nigeria and Cameroon admin level 1. I downloaded the files from gadm but I cannot merge the files with QGIS or find a shapefile of Africa having countries at states level. Could anybody help me with this?

I've imported several shapefiles which where exported from a Mapinfo .tab. Several  .tab-files are imported resulting in 20+ layers. Afterwards I want to export it to GeoJSON; but I'm reluctant to select each layer and export it manually. Is there a way to merge all the layers into one using QGIS?


Suppose we have three complex numbers $a_1,a_2,a_3$ which are non-collinear. What is the best way to find the center of the circle that contains these three points ?

Get the equation of a circle through the points $(1,1), (2,4), (5,3) $.  I can solve this by simply drawing it, but is there a way of solving it (easily) without having to draw?


Is there any difference between:  public class user {            public string Name { get; set; }   }   And:  public class user {            public string Name;   }   ??? Thank you

In C#, what makes a field different from a property, and when should a field be used instead of a property?


How do I go about solving this problem, and similar ones where I have to find the number of values that satisfy this phi function?   Thanks!

So, clearly, 101 is a solution.  But $n=125$ is also a solution, so is 250.  How would one come to that solution without knowing these values beforehand?


I need to prove inequality $$(1+x+y)(1+y+z)(1+z+x) \ge 9(xy+xz+yz)$$ for nonnegative $x,y,z \ge 0$  I can do it with partitional derivates $$f(x,y,z)=((1+x+y)(1+y+z)(1+z+x)-9(xy+xz+yz))$$ and find $$ \frac{\partial f}{\partial x}=2xy + 2xz + 2yz + z^2 + y^2 + 2x - 6y - 6z + 2$$ $$ \frac{\partial f}{\partial y}=2xy + 2xz + 2yz + x^2 + z^2 + 2y - 6c - 6x + 2$$ $$ \frac{\partial f}{\partial c}=2xy + 2xz + 2yz + x^2 + y^2 + 2z - 6x - 6y + 2$$ minimum value of function $f$ is $f(1,1,1)=0$ that's why $(1+x+y)(1+y+z)(1+z+x) \ge 9(xy+xz+yz)$.  But I need the prove without partitional derivates.  Any standart inequality (Inequality of arithmetic and geometric means, Cauchy–Schwarz inequality) don't help me.

How one can prove the following.  Let $a$, $b$ and $c$ be non-negative real numbers. Then the inequality holds:  $(1+a+b)(1+b+c)(1+c+a)\ge9(ab+bc+ca).$  WLOG one can assume that $0\le a\le b\le c$.  It is not difficult to prove the statement when $0\le a\le b\le c\le 1$ or $1\le a\le b\le c$.


When a wizard dies in the Harry Potter series, do all of their spells die with them?  When I say die, I mean get lifted.   For example, in Half-Blood Prince, after Dumbledore's death, this happens:  Harry heard Hagrid’s moan of pain and shock, but he did not stop; he walked slowly forward until he reached the place where Dumbledore lay and crouched down beside him. He had known there was no hope from the moment that the full Body-Bind Curse Dumbledore had placed upon him lifted, known that it could have happened only because its caster was dead, but there was still no preparation for seeing him here, spread-eagled, broken: the greatest wizard Harry had ever, or would ever, meet.  As a counterargument, we have the ancient but powerful protective enchantments placed around Hogwarts (probably cast by the founders of the school which were Godric Gryffindor, Salazar Slytherin, Rowena Ravenclaw, and Helga Hufflepuff). We also have the enchantments on the Chamber of Secrets, which were cast by Salazar Slytherin, and by the year 1992 (the 2nd year of Harry Potter whose book name is also The Chamber of Secrets), must have been at least 1,000 years old, but still effectively working. These 4 have been dead for hundreds of years, but their magic still exist in the modern Harry Potter world.

Looking at the questions and answer to these two questions.  &  and neither mentions the longevity of magic. I recall several instances of magic failing to last; the money that was spread at the  and the broken  on.  If I recall correctly when Voldemort died, the curses on several people were lifted.  I don't recall if any other spells fell apart with his death.  Is there any canon evidence on the the length of time a spell will live?


In scikit-learn implementation of AdaBoost you can choose a learning rate.  The documentation about AdaBoost says:  "Learning rate shrinks the contribution of each classifier by learning_rate".  This learning rate is not mentioned anywhere else on AdaBoost tutorials and explanations (for example the official one here )  I don't understand this concept of shrinkage of extra trees.  Is the learning rate a shrinkage factor, such as 2 means each trees importance is divided by 2? That would be strange as the AdaBoost models learns the importance of each estimator and sample itself.  Thanks for your help!

I'm unclear how the shrinkage parameter works in Adaboost.  I understand the concept of shrinkage in the theoretical sense related to ordinary least squares, but I'm not sure how to interpret this parameter in relation to Adaboost.


I have seen many zero ohm resistors which says that maximum resistance is say 50 mOhm. But, the maximum current rating will be only 1 amps. 0603 package. Power rating they mention as 1/8 watt. Can anybody comment on this differing I^2 * R and power rating?  Edit: My purpose of question is to clarify doubt in a datasheet which has both current rating and power dissipation. Which one should i consider?

According to Ohm's Law, if the resistance is zero, the power dissipated by a resistor is unmeaning.  $$P_d = R \times I^2$$  $$I = \sqrt{ \frac {P_d}{R} }$$  Can one calculate the resistance given that power is defined? Only by knowing power, how can one calculate the maximum current of a zero-Ohm resistor?   I'm a bit confused as I've seen there is zero-Ohm resistors with specified power in the market.


I feel like I can't be barefoot around him because every time I'm in the same room as him without my shoes on, he'll find some excuse to sit next to me and he'll start to tickle my feet. He isn't disobedient, so I can tell him to stop and he stops but the very next day he tries to tickle me again. Just last summer we were at the pool and I noticed he sat next to me while I was dangling my bare feet in the water and he began to tickle my feet while I was talking with my friend! Also, every time i sit in the recliner with my feet up, he will come and grab my ankle and tickle my foot for a long time until I can get it loose. I'm very ticklish, and this is inappropriate. How can I tell my son not to tickle my feet without upsetting or otherwise embarrassing him?

I don't know where to begin with this question. It's awkward and to be honest, it makes me feel rather uncomfortable. Simply put, I'm led to believe that my four year old daughter is obsessed with my belly button. It all started one day during the summer when she was three. I decided to take my family to the pool, and I guess I didn't see my daughter follow me into the changing room. Mind you, she's still at the age where it's appropriate to see her parents naked, so I wasn't surprised when, after I finished changing into my bikini, I turned around to see her staring at me.  I followed her gaze and saw her looking directly at my belly button. I asked her what she was looking at and she screamed "mommy, I can see your belly button!" which made me giggle. I picked her up and kissed her forehead, telling her that everyone has a belly button.  I think I might have accidentally given her a green light, because over the next year she constantly asks me if she can stick her finger in my belly button, and if I don't let her, she begins to scream.  For her fourth birthday, she requested that I wear nothing but a sports bra and underwear (in toddler speak. It sounded like "mommy, show your belly button for my birthday!" I could have simply worn a crop top but i didn't want to risk her throwing a temper tantrum)  My husband obviously doesn't mind, because he gets to look at my belly button all the time but it really upsets me that my daughter's finger is constantly in my belly button.  Tomorrow is her fifth birthday and I want to discuss with her that it's not appropriate to always be poking my belly button. Any ideas on how i can talk to her without her throwing a screaming fit?


If I paste a dataset including times in mm:ss format into excel, how can I prevent it from interpreting them as hh:mm?  Changing the number format before or after pasting doesn't help, Excel still sees them as hours and minutes rather than minutes and seconds.

I want to enter time data into excel sheet in mm:ss format. The problem is - that although the cell format is mm:ss, if I enter the data like this:  12:33 the actual value stored is 12 hours and 33 min.  if I want 12 min and 33 sec, I need to enter 0:12:33  Is there a way to make the cell accept 12:33 as mm:ss ?


I read that you can assign multiple bounties to a question, but I fail to see a way to do this. My question:

I have this question here:  I chose 500 then before accepting decided that was too much and halfed it, but now I just want the answer so I'd like to raise it to 500 but I can't find how to it. Also it's just such an irritating problem that I'd give all my rep away if I could to the clever person who has the answer. It would be nice to have a few minutes after creating the bounty to be able to raise it. But for now could a mod or something please raise it for me to 500.


Can I draw something like this programmatically with LaTeX?    I drew these with Adobe Illustrator, but it gets pretty time-consuming. Even with relatively few nodes. What it attempts to demonstrate is the number of "symmetric" cryptographic keys required for secure communication between n parties - for which the formula is n(n-1)/2 (I tried to render that with LaTeX/MathJax, but it won't let me for some reason).    And it's hard to get it perfect. It's always off by a small amount, as you can see here. It might not seem like much but with a lot of nodes, it can add up and skew the output, and cause problems when trying to get everything to fit properly.    I wanted to draw a big one with up up to 100 nodes, so it would be best if I could do it programmatically, rather than having to type up several hundred lines of code manually. Is that kind of thing possible with LaTeX? I heard someone say TeX is a full Turing complete programming language. If that's true, I'm not sure, but it would probably make it pretty useful for generating diagrams with this kind of data, kinda like .  As you can see, by the time you get to 10 or 11 vertices, it can be pretty unruly:

I feel intimidated in learning TikZ. I was wondering if there are some nice materials (or just your replies) at different level:   for providing big picture, which is important to beginners to not lose direction during learning. for comprehensive reference.   Examples are important, but only examples are not always clear for understanding the big picture and organization.


Posting a bounty for  was my first activity on the StackExchange site 'Ask Different', and apparently I didn't get any reputation bonus for joining that site (as usually seems to happen) because my reputation there shows as 1. As a result, I can't comment to answers (or the question itself) on the question I posted the bounty for.   Is it a bug that I didn't get the reputation bonus when I joined a site in this way? Because there's what appears to be a +100 message stuck in my StacExchange inbox--it has a completely blank subject--and nothing happens when I click on it.  Regardless of that, if you think about it logically, shouldn't sponsoring bounty on an affiliated site trigger a special case that ensures you can at least comment in the thread?    [edit:] As I explain in an answer below, I mistakenly thought that a person's reputation was fluid across all StackExchange network sites. In fact, it's tabulated separately, and reputation from one site cannot be used at another.]

I think it would be very useful.  I have a question that I have an open bounty on. Putting up said bounty brought my reputation below the point where I am allowed to comment on other peoples' posts. It's so frustrating not to be able to comment and give feedback on the answers given!  Especially since it would be helpful, for them, me, and the readers, to know particularly what is good and isn't good about their answer, and therefore give some better guidelines to future answerers on how they can win the bounty.


Does anybody know how to solve the following differential equation?  $$w^2\cdot r+\frac{dw}{dt}\cdot r+\frac{dr}{dt}\cdot w=3g$$  where w and r are a function of time so $w(t)$ and $r(t)$. $g$ is a constant  This equation came from a thought problem of mine which I will now explain since I still do not know how to approach the problem.  Basically I want to design a spiral track in which a vehicle will accelerate. However the total acceleration needs to be constant.   The vehicle will have 2 acceleration components, a radial component ($a_r$) and a change in speed component ($a_s$). Since we want constant acceleration: $a_r + a_s = constant$  From circular motion we know that $a_r = \omega ^2 r$ where $r$ is the radius, and $\omega$    Further we know that $v=\omega*r$, therefore: $$a_s=\frac{d}{dt}(\omega r)$$  For constant acceleration $a_{total} = a_r + a_s = \omega ^2 r + \frac{d}{dt}(\omega r) =constant$  Further usefull information: Length of the track covered at a certain time $$l=v\cdot t=\omega r t$$  With all this the radius will be a function of time, $r(t)$ and the angular velocity will be a function of time, $\omega (t)$  Boundary conditions: $$r(0)  = 0$$  $$\omega (0) = 0$$  Now I would like to find a possible set of solutions to create a track by implementing end boundary conditions that i choose e.g. $v(t_{end})=100 [m/s]$ and $l(t_{end})=5000 [m]$  Here is a diagram for clarity:

Does anybody know how to solve the following differntial equation?  $$w^2\cdot r+\frac{dw}{dt}\cdot r+\frac{dr}{dt}\cdot w=3g$$  where w and r are a function of time so $w(t)$ and $r(t)$. $g$ is a constant  EDIT: This equation came from a thought problem of mine which I will now explain since I still do not know how to approach the problem.  Basically I want to design a spiral track in which a vehicle will accelerate. However the total acceleration needs to be constant.   The vehicle will have 2 acceleration components, a radial component ($a_r$) and a change in speed component ($a_s$). Since we want constant acceleration: $a_r + a_s = constant$  From circular motion we know that $a_r = \omega ^2 r$ where $r$ is the radius, and $\omega$    Further we know that $v=\omega*r$, therefore: $a_s=\frac{d}{dt}(\omega r)$  For constant acceleration $a_{total} = a_r + a_s = \omega ^2 r + \frac{d}{dt}(\omega r) =constant$  Further usefull information: Length of the track covered at a certain time $l=v*t=\omega r t$  With all this the radius will be a function of time, $r(t)$ and the angular velocity will be a function of time, $\omega (t)$  Boundary conditions: $r(0)  = 0$ $\omega (0) = 0$  Now I would like to find a possible set of solutions to create a track by implementing end boundary conditions that i choose e.g. $v(t_{end})=100 [m/s]$ and $l(t_{end})=5000 [m]$  Here is a diagram for clarity:


I'd like to see how long it takes to optimize a query. Does PostgreSQL support this feature?

Just like the MEMO structure in SQL Server which is kind of a "paper trail" of steps the optimizer takes in optimizing the query. Does PostgreSQL have the similar structure which records steps the optimizer takes?


I were stumbling through a question that was marked as a duplicate when I saw this warning and though it did not make much sense:     This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.   It did not explain the person had to explain why none of the answers in the duplicated questions could address the reason. Also it simply incited the 2nd person to make another duplicate!  It should instead be changed to:     This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question that describes why the duplicated questions does not solve the issue (or, if the reason isn't clear, just the fact).

The new closed-as-duplicate banner says:     This question has been asked before and already has an answer. If those answers do not fully address your question, please .   I think it should instead say     This question has been asked before and already has an answer. If answers there do not fully address your question, please  or  to the pre-existing one.   — to discourage re-re-asking the same question. (I also changed "those answers", which has no plural , to "answers there", which doesn't need one.)    As of September 19, 2013, the original text quoted above has returned here.


$$s=\sum_{n=2}^\infty \frac{1}{n (\ln n)^2}.$$   So I use the integral test and when I do so the integrand is $$\int\frac{1}{x\;(\ln x)^2}dx =\frac{-1}{\ln x}$$ which converges to $\dfrac{1}{\ln2}$ therefore the series is also convergent.  And I need to find an integer such that $$\left\lvert s-\sum_{n=2}^\infty \frac{1}{n\;(\ln n)^2}\right\rvert < 10^{-3}.$$  How do I set this up? Is taking the integral of a series the same as summing it?

I am attempting to prove if the below expression converges or diverges:  $$\sum_{n=2}^{\infty} \frac{1}{n (\ln n)^2}$$  I decided to try using the . So then, I set $f(n) = \frac{1}{n (\ln n)^2}$ and $g(n) = \frac{1}{n}$ and did the following:  $$ \lim_{n \to \infty} \frac{f'(n)}{g'(n)} =  \lim_{n \to \infty} \frac{-\frac{\ln(n) + 2}{n^2 (\ln n)^3}}{-\frac{1}{n^2}} =  \lim_{n \to \infty} \frac{\ln(n) + 2}{n^2 (\ln n)^3} \cdot n^2 =  \lim_{n \to \infty} \frac{1}{(\ln n)^2} + \frac{2}{(\ln n)^3} = 0 $$  I know that $\sum \frac{1}{n}$ diverges due to properties of harmonic series, and so concluded that my first expression $\frac{1}{n (\ln n)^2}$ also must diverge.  However, according to , and as suggested by , the expression actually converges.  What did I do wrong?


What are Customs rules regarding bringing vacuum cleaner from abroad to India ?

I am planning to travel to India (COK airport, Kerala) from United States. I want to take my laptop as well as my tablet (iPad). Am I allowed to take both in my backpack with my documents related my work. I think I am allowed to take only one computer as per the rule. Will the customs consider my iPad as a computer?  What all I can take?   One of my friends took 2 laptops (1 work and 1 personal) and had trouble at the airport.  Also I am planning to take some wristwatches (7 of them, each avg price is 45 $). I read in a website that I can take stuff up to max 35000 INR. Is that true? In that case, how will I manage my stuff?


I have Ubuntu 16.04 LTS on Lenovo z5170. I want to have a program (no matter what programming language) that notifies me that i'm running low on battery by a beep. I assume that the program should be sleeping until the moment that i'm out of battery(10% energy) but all I can think of is a while loop which eats up the whole processor and keeps everything else from running.  1- How should I implement such program ?  2- Which are the ways to notify users on specific event ?

I use Unity in 16.04. For some reason, I am not getting popup notifications for low battery. I have to rely on battery icon in top panel to see if battery is on the " low battery " side. Is the default behaviour in 16.04 ? Or I am not getting pop ups for low battery ?


I  need a regular expression for phone numbers. The phone numbers may contain special characters like +, ., /, -, space, (, ), [, ].  Some Examples:  (+91) 9864081806 (+91)9864081806 (+91)(98640)81806 +91.98640.81806 [+91]09864081806 +91.986.408.1806 +91-986-408-1806 Maximum numbers = 15   The special characters can exists anywhere in the code. An opening bracket should have a closing one.  I have created this pattern but it does not work:  preg_match('/^[\[\(\0-9\s.\_\-\+\/\)\]]{3,15}$/', $phone_no)

I'm trying to put together a comprehensive regex to validate phone numbers. Ideally it would handle international formats, but it must handle US formats, including the following:   1-234-567-8901 1-234-567-8901 x1234 1-234-567-8901 ext1234 1 (234) 567-8901 1.234.567.8901 1/234/567/8901 12345678901   I'll answer with my current attempt, but I'm hoping somebody has something better and/or more elegant.


I'm using Windows 10 1511.   I can't find anywhere in the new Windows Update UI to get a list of the updates available, and allow me to select which updates to install like...    It only seems to want to inform me when it wants to install updates, not the actual updates its installing.  Almost every time I install updates, after a few hours it wants to install more, yet when I view the update history, it tells me the last update installed was KB890830 on the 11th January 2017. I've run windows updates probably about 10-20 times since 11th Jan 2017.    So in summary it's repeatedly asking me to install updates, I don't know what its trying to install, none of what its installing gets listed in the update history, and there's nothing apparent to indicate there were any issues with the installation.  EDIT: I'm using Windows 10 Enterprise

We've upgraded some machines to Windows 10 and realized there were some updates which updated as required. However, I realized there was no option available to stop the download similar to that on Windows 7 and 8.1. The only way I could stop the download was to stop the Windows Update service.  My question is does anyone know of a way to stop auto updates or is stopping the service is the only solution?


I was trying to install opencv. And I followed the steps given in . But, after cloning the directories opencv.git and opencv_contrib.git and running the command:  cmake -D BUILD_TIFF=ON -D WITH_CUDA=OFF -D ENABLE_AVX=OFF -D WITH_OPENGL=OFF -D WITH_OPENCL=OFF -D WITH_IPP=OFF -D WITH_TBB=ON -D BUILD_TBB=ON -D WITH_EIGEN=OFF -D WITH_V4L=OFF -D WITH_VTK=OFF -D BUILD_TESTS=OFF -D BUILD_PERF_TESTS=OFF -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -D OPENCV_EXTRA_MODULES_PATH=/opt/opencv_contrib/modules /opt/opencv/   I  get the above error CMakeLists.txt does not appear to exist. What is the solution to this?  Added:I created a new opt folder in home directory which should have been in the root... there was where I made the mistake maybe.

I've downloaded opencv but unfortunately I've got no idea how to install it. All the pages I found online were only telling me how to download and install it directly from the console, not what to do when you already have it downloaded. Could anybody tell me what to do?


I have matrix $ A\in \mathbb{C}^{n x n}$ and $A$ is invertible.  How can I show that coefficients $c_0,...,c_{n-1}$ exist :  $A^{-1} = c_0I+c_1A+...+c_{n-1}A^{n-1}$  I tried to solve it first by multiplying the equation above with $A$ which gives:  $I = c_0A + c_1A^2 + ... +c_{n-1}A^n$  And I continued then by knowing that every square matrix can be written with Jordan canonical form ($A = VJ_aV^-1$):  $I = c_0VJ_aV^{-1} + c_1VJ_a^2V^{-1}+...+c_{n-1}VJ_a^nV^{-1}$  Which can be written in form:  $I = V(c_0J_a+c_1J_a^2+....+c_{n-1}J_a^n)V^{-1}$  After this point my task is to show that the identity matrix can be presented with sum of coefficients and Jordan canonical forms, but I don't have any idea how to do that or even if my approach to this problem is right.

Let $A$ be an $n \times n$ matrix. Prove that if A is invertible, then there exists a polynomial $p$, such that $A^{-1}=p(A)$  Thus far:  Let $W$ denote the $k$ dimensional A-cyclic subspace spanned by a vector $v$.  Then, $I_n=\sum_{i=0}^{k} a_{i}A^i$ for some scalar $a_i$.  What I want to do is multiply both sides by $A^{-1}$, so that way it just falls into my hands, but Im not sure that is 'legal'.


After running the command sudo apt-get update  I got the following error:  W: GPG error: https://deb.nodesource.com/node_7.x xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 1655A0AB68576280 W: The repository 'https://deb.nodesource.com/node_7.x xenial InRelease' is not signed. N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. N: See apt-secure(8) manpage for repository creation and user configuration details. W: The repository 'http://ppa.launchpad.net/chris-lea/node.js/ubuntu xenial Release' does not have a Release file. N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. N: See apt-secure(8) manpage for repository creation and user configuration details. E: Failed to fetch http://ppa.launchpad.net/chris-lea/node.js/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 can I fix this?

I added some extra repositories with the Software Sources program. But when I reload the package database, I get an error like the following:     W: GPG error:  trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8BAF9A6F   I know I can fix it using apt-key in a terminal, according to the official Ubuntu documentation. But I would have liked to do it graphically. Is there a way to do this without using a terminal?


I would like to call a  python function through  a c++ script. I know how to call a c++ function in a python code but no the other way. for example, I would like to use the return value of this python function in a c++ script like this:   import pandas as pd def concat(x1,x2): a = pd.DataFrame(pd.concat([pd.DataFrame(x1), pd.DataFrame(x2)], axis=1)) return a   #  void Foot::update(){ ccerr << "Merge " << PLate->me->vertIncl << endl; con[a] = concat(model->getA(),model->getB())}   Is it possible?

I would like to call python script files from my c++ program.   I am not sure that the people I will distribute to will have python installed.  Basically I'm looking for a .lib file that I can use that has an Apache like distribution license.


so when I try to convert my end direction (ex. N, S, E, W) into a positive or negative 1.0 to multiply to the eventual degrees/minutes'seconds" calculation, my double sign  always returns as 0.0. I've tried testing each letter in separate if statements and have tried putting the calculations into the if statements. I've been testing with the following coordinates: 40°35'6.9288"N public static double convertDegreesToDecimals(String strValue) {    double decimal = 0;    double sign = 1.0;     String degree = strValue.substring(0, strValue.indexOf(DEGREE));    double deg = Double.parseDouble(degree);    String minute = strValue.substring(strValue.indexOf(DEGREE)+1,strValue.indexOf(MINUTE));    double min = Double.parseDouble(minute);    String second = strValue.substring(strValue.indexOf(MINUTE)+1,strValue.indexOf(SECOND));    double sec = Double.parseDouble(second);    String direction = strValue.substring(strValue.indexOf(SECOND)+1,strValue.length());    System.out.println(direction);   //prints N, S, or whatever the direction is correctly       if(direction=="S" || direction=="E"){       double sign = -1.0;    }else if(direction=="N" || direction=="W"){       double sign = 1.0;    }       decimal = ( (deg + (min / 60.0) + (sec / 3600.0) ) * sign);    return decimal; }  I expect for the double sign to equal -1.0 when the direction is S or W, and to equal 1.0 when the direction is N or E. My calculations for degrees/minutes'seconds" are correct except for the sign, and String direction always returns the expected result(N,S,E,W). When I put println statements in the if statements, they did not execute which led me to think that something must be wrong with the if statements.

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


What is the word to describe an explanatory person who likes to explain everything even though they were asked a question that could be answered simply with "Yes" or "No"?

Usage in sentence:  Person A: Ooh - look at that crow!  Person B: Well, actually, as someone who is a scientist who studies crows, I am telling you, specifically, in science, no one calls jackdaws crows. They're not the same thing. If you're saying "crow family" you're referring to the taxonomic grouping of Corvidae, which includes things from nutcrackers to blue jays to ravens. It's not one or the other, that's not how taxonomy works.  Person A: Are you always such an XXX?   "Pedant" is close, but not quite.  It would be a mix of "know-it-all", "condescending" and "arrogant".


In a DND 5E game, my character has the staff of healing. Does this count as a staff/quarter staff for melee purposes? If so, does it get +1 to attack and damage rolls for for being magical?    The spell Magic Weapon reads     You touch a nonmagical weapon. Until the spell ends, that weapon becomes a magic weapon with a +1 bonus to Attack rolls and Damage Rolls."   This would imply that all weapons that are magical in some way would have a natural +1 to attack and damage rolls (unless stated otherwise or of a higher value)  So does the staff of healing get +1 to attack and damage rolls?

Many creatures have resistance to weapons that aren't "magic weapons".  A Magic Staff can be used as a quarterstaff, but (usually) doesn't have a bonus to hit (a "plus").  Is it considered a Magic Weapon for the purpose of damage resistance?


I know, that in Starbound you can set a "Home Planet", so when you go with the spaceship, you can always return to your home planet easyly.  But my question is about when you are in the planet.   Supose, whe you warp from the spaceship to the planet, you "land" on the coordinate X = 0.  then, you move, for example, to X = (+/-)1000. And you build a House, with your bed, and different stuff. Ok, you warp, to the Ship, and you come back, but you spawn again in X = 0.   So, the now that the "scenario" is explained, the question:  Exist any form to set you house as "warp point" when you come from the spaceship?

Is it possible to change the location you beam to on a planet? I've been to a couple of planets that have no usable resources near the spawn point and everything is a good distance East or West. It would be nice to be able to always beam down to there instead.


I'm creating a child form inside a parent form, and it gives the error(Error creating window handle). But if it's not a child form inside a parent form it Works.  I've tried more code options for creating child form, but non of them worked  private void ClanoviToolStripMenuItem_Click(object sender, EventArgs e)     {         Clanovi NewMDIChild = new Clanovi()         {             MdiParent = this         };         NewMDIChild.Show();     }

We are seeing this error in a Winform application.  Can anyone help on why you would see this error, and more importantly how to fix it or avoid it from happening.   System.ComponentModel.Win32Exception: Error creating window handle.    at System.Windows.Forms.NativeWindow.CreateHandle(CreateParams cp)    at System.Windows.Forms.Control.CreateHandle()    at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)    at System.Windows.Forms.Control.CreateControl()    at System.Windows.Forms.Control.OnVisibleChanged(EventArgs e)    at System.Windows.Forms.ButtonBase.OnVisibleChanged(EventArgs e)


Let $a_n$ be the Fibonacci sequence defined by   $$a_{n+1} = a_n + a_{n-1} \ \ \text{with} \ \  a_0 = a_1 = 1 $$  Let $$r_n = \frac{a_n}{a_{n+1}}$$  I have already found two subsequences which are $\{r_{2k-1}\}$ bounded above by $2$ and  increasing (thus is convergent), and $\{r_{2k}\}$, bounded below by $1$ and decreasing (thus is convergent,too)  Besides, $$ \lim_{k \to \infty} r_{2k-1} = \ell_1 $$ I found that $l_1^2 - l_1 - 1 = 0$ from above equation.  However, i cannot find $l_2$ where $ \lim\limits_{k \to \infty} r_{2k} = \ell_2.$

We define the $n^{th}$ Fibonacci number as $a_1 = a_2 = 1$ and $a_n = a_{n-1} + a_{n-2}$ for $n \geq 3$. Consider  $$ \lim_{n \to \infty} \frac{a_{n+1}}{a_n}. $$  I wrote a script and found that this limit converges to the golden ratio $\phi \approx 1.61803$. However, I'm having trouble giving a rigorous proof for this. Here's what I have so far:  $$ \lim_{n \to \infty} \frac{a_{n+1}}{a_n} = \lim_{n \to \infty} \frac{a_n + a_{n-1}}{a_n} = \lim_{n \to \infty} \left( 1 + \frac{a_{n-1}}{a_n} \right). $$  I'm unsure of how to proceed after this. I know that expressing the limit as a certain continued fraction would imply that it converges to $\phi$ but I'm unsure of how to get there. Any ideas?


I have downloaded ubuntu 14.04 and trying to install it on my laptop, but after installation completed, I seen that ubuntu deleted my windows 7. i never permitted to do so. then why it happens. I want my windows 7 as its back. reply with any possible options. ASAP.

I have a Toshiba satellite A-200 laptop with a Vista OS on it with 4 NTFS partitions  (C:) Vista  (D:) Entertainment  (E:) Work  (F:) Sources   and I wanted to start using Ubuntu instead. So I tried it first from the live CD and everything was OK and all the partitions were shown and working and so I decided to install Ubuntu to replace Vista on the (C:) drive. After I did that I can no longer find my folders and files on the (D:), (E:), (F:) partitions and the only file system that is shown is one 198 GB although my HDD is 320 GB.  I can't access the lost data on the remaining 120 GB which I hope is still there and not totally lost  I am now working from the live CD but I am unable to install testdisk. Can I recover the Vista partitions by the product recovery CD to get my laptop back to the factory settings? Can I recover the NTFS partitions using a recovery program for Windows or will that make the problem worse?   I need these data badly as I don't have a backup for them.


My auto update of Clam Defs doesn't seem to be working and when I do  sudo freshclam   I get  ERROR: /var/log/clamav/freshclam.log is locked by another process ERROR: Problem with internal logger (UpdateLogFile = /var/log/clamav/freshclam.log).   I've tried reinstalling Clam.. Same problem.  How can I solve it?  I tried the command from the linked question   $ sudo lsof /var/log/clamav/freshclam.log  lsof: WARNING: can't stat() fuse.gvfsd-fuse file system /run/user/1000/gvfs       Output information may be incomplete. COMMAND     PID   USER   FD   TYPE DEVICE SIZE/OFF     NODE NAME freshclam 21238 clamav    3wW  REG  253,1     3587 29757231 /var/log/clamav/freshclam.log   This seems wrong? Should I be worried? And how should I proceed?

I have installed clamav and I want to to update the files that it uses to identify viruses:  $ sudo freshclam  ERROR: /var/log/clamav/freshclam.log is locked by another process ERROR: Problem with internal logger (UpdateLogFile = /var/log/clamav/freshclam.log).   What should I do with this error?  EDIT:  $ sudo lsof /var/log/clamav/freshclam.log  COMMAND   PID   USER   FD   TYPE DEVICE SIZE/OFF     NODE NAME freshclam 866 clamav    3wW  REG  259,1   100134 10486045 /var/log/clamav/freshclam.log


I'm an American living in the UK with my European-national spouse, and we recently entered the Schengen zone to visit family for Christmas. As I've been living here in Europe for 7 years and travelling, mainly to see family, frequently I have quite a few entry and exit stamps, with some even having been done erroneously.  Well, the border control agent said he would normally have to send me back (to the UK) because the Schengen tourist visa requires there to be 2 blank pages in one's passport (he actually said 3, but I looked it up later on europa.eu and found it's actually 2), but that he would be lenient since it's Christmas.  There are about 10 spots for stamps left in my passport, which would be 2.5 pages if they were all together at the end, but they're not… because border control agents seem to put stamps in haphazardly with no consideration for keeping it tidy or leaving pages! Also, as mentioned above, some have wasted space by putting stamps in erroneously when they weren't actually needed.  So what are travellers supposed to do? How are we supposed to ensure that we maintain two pages free when agents ruin our passports? Are we just supposed to bend over and get new passports years before they expire, spending money unnecessarily?

I'm running low on blank passport pages which are sometimes needed for full page visas such as those issued by Armenia, India, and Vietnam.  When I crossed the border into Turkey the other day I got my visa-on-arrival and stamp, but instead of putting it on a partly used page, which I have many, the guy at customs and immigration put them on a previously blank page. Now I have one fewer!  What can I do to prevent or at least reduce the chances of this happening?  It's worth remembering that there's likely to be a language barrier and it's always best to be ultra-nice to these border officials.  Has anybody heard of any trick such as sticking bit of paper in your passport, either blank, or looking a bit like visas? I have noticed that nobody ever stamps a page that has a remnant of something once stapled in there in Japan. There is a kind of stub that had its major part torn off along a perforation. Might I be able to emulate this somehow or would that even be worse making the blank pages invalid for full page visas due to having holes from staples? I know some things can get very picky when it comes to customs and immigration.


How is it possible to define a variable type as an interface :  List<BigDecimal> filter = new ArrayList<BigDecimal>();   Shouldn't we define a variable by class or primitive data types and not an interface as follows :  ArrayList<BigDecimal> filter = new ArrayList<BigDecimal>();   How is it accepting interface variable definition?

I have seen this mentioned a few times and I am not clear on what it means. When and why would you do this?   I know what interfaces do, but the fact I am not clear on this makes me think I am missing out on using them correctly.   Is it just so if you were to do:  IInterface classRef = new ObjectWhatever()   You could use any class that implements IInterface? When would you need to do that? The only thing I can think of is if you have a method and you are unsure of what object will be passed except for it implementing IInterface. I cannot think how often you would need to do that.   Also, how could you write a method that takes in an object that implements an interface? Is that possible?


Solve the equation $$x^2+4\left(\frac{x}{x-2}\right)^2=45$$   My attempt,  I decided to use completing the square method, so I change it to $$x^2+\left(\frac{2x}{x-2}\right)^2=45$$  But I never encounter this before. Normally, for example $x^2+4x=5$, we can change it to $x^2+4x+(\frac{4}{2})^2=45+(\frac{4}{2})^2$. But in this question is different. Could someone give me some hints for it? Thanks in advance.

Problem Statement:- Solve the equation $$x^2+\dfrac{9x^2}{(x+3)^2}=27$$   I have tried to turn it into a quadratic equation so as to be saved from solving a quartic equation, but have not been able to come up with anything of much value. These are the things that I have tried to turn the given equation into a quadratic equation. $$x^2+\dfrac{9x^2}{(x+3)^2}=27\implies 1+\dfrac{1}{\left(\dfrac{x}{3}+1\right)^2}=3\left(\dfrac{3}{x}\right)^2$$ $$\text{OR}$$ $$x^2+\dfrac{9x^2}{(x+3)^2}=27\implies 1+\dfrac{\left(\dfrac{3}{x}\right)^2}{\left(1+\dfrac{3}{x}\right)^2}=3\left(\dfrac{3}{x}\right)^2$$


I have an HP Compaq 800 Elite CMT Business PC. Will it be able to handle a Nvidia GeForce GTX 750 Ti?  My PC specs are:   4 GB of DDR3 RAM 1333MHz Intel Core 2 DUO E8400 3.0 GHz 300W PSU 250 GB HDD  No graphics card

I've got a 320W PSU as far as I know and it's a Chinese PSU because I've seen the Chinese letters on it. I just had a question if I can upgrade my pc to Asus GTX 750Ti 2 GB OC.  My pc specs are:   4GB DDR3 RAM Intel Core 2 Duo E8400 3.0 GHZ 250GB HDD Onboard graphics card


When selecting my account on the login screen I do see the gear icon in the bottom right-hand corner. My options are "Ubuntu" and "Plasma." I can't find "Ubuntu with Wayland" anywhere. $ grep Wayland /etc/gdm3/custom.conf #WaylandEnable=false  I've also tried deleting my .config, .local, and .cache directories but the option still doesn't show up. After installing LightDM, I see the option. Although when I select it and try to log in, it just flickers and shows the login page again. I have a suspicion that this might be because I have the closed-source nvidia drivers installed.

I don't see the gear button next to the Sign in button at the login screen. I have Nvidia drivers installed (for Nvidia 730 GT card). Ubuntu boots into Xorg as seen from the terminal with echo $XDG_SESSION_TYPE which outputs x11.  How do I switch to Wayland?


I need to either prove the following or find a counterexample. I really hope you can help, I cannot figure it out.     Let $(a_n)$ be a positive sequence.   $$\sum_{n=1}^\infty \frac{a_n}{1+a_n}$$   converges, then   $$\sum_{n=1}^\infty a_n$$   converges

Let $\sum\limits_{n\geq1}a_n$ be a positive series, and $\sum\limits_{n\geq1}a_n=+\infty$, prove that: $$\sum_{n\geq1}\frac{a_n}{1+a_n}=+\infty.$$


I am trying to make this program work. It checks if a string of text entered by the user is equal to one of three. Here is my code:  boolean acceptableanswer; if(choice == choice1){     acceptableanswer=true;     return choice1; }else if(choice == choice2){     acceptableanswer=true;     return choice2; }else if(choice == choice3){     acceptableanswer=true;     return choice3; }else{     acceptableanswer=false;     return null; }   The problem is, it automatically goes to "null".

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


I am asked to either prove or disprove the following statement. $\cap_{\textrm{x} \in (1, \infty)}$ (-x, x+1] = $\left[-1,2\right]$ I attempted to show that each side was a subset of each other however, I am stuck trying to show that the right side of the equation is a subset of the left side. Can anyone assist?

I have been stuck on the following problem for some time.  I know to prove two things are equal, you use the proof where you show they are both subsets. I think I was able to show that the set on the left, (which I called A) is a subset of the interval through simple logic, but to show the converse I am having some issues. I attached my working thus far for anyone to look at it, but please note that after the line " $ \Leftrightarrow \alpha \geq -1 = \alpha + 1 \geq 0 and  \alpha \leq -2 ....$" the rest is tata (lol- but an attempt to work towards what I know would be the end of the proof, showing that a belongs also to A) I have tried using the hint, but then I end up with something along the lines of '$n > \alpha + 1$ so  $n + 1 > \alpha$', which does not bring me closer to either -x, or x+1 of the interval on the left. Any help or suggestions would be greatly appreciated. Thanks in advance.


I have an assembly which is not strong-named. I have no source code for it.  I now need it to be signed. Is there a way to do this?

I've added a weakly named assembly to my  project (which is strongly named). I'm now getting the error:  "Referenced assembly 'xxxxxxxx' does not have a strong name"  Do I need to sign this third-party assembly?


I have two-step verification (via Google Authenticator) enabled for almost all of my accounts on the Internet. I somehow feel safe with that.  I have enabled two-step verification for almost all my accounts since I have read these news:      I want hate remembering passwords, allow me to use 12345 (just kidding) everywhere and let two-step authentication take care of security for me. I wish to enable two-step authentication for all my Stack Exchange sites. How would I do that?  I Googled, but I couldn't find a way to enable it. So, may be it's a feature request (correct me if I am wrong).

Is there any possibility of setting up two factor authentication (2FA) for Stack Exchange OpenID authentication?  I could just use my (already 2FA-enabled) Google account for Stack Exchange, but I would prefer to continue use Stack Exchange OpenID.  After  (which, I appreciate, didn't affect Stack Exchange, as you use IIS and Schannel, not OpenSSL), there have been a lot of recommendations to change passwords and to enable 2FA where possible.  So, what are the chances of a text-messaging-based or Google-Authenticator-based 2FA for Stack Exchange?


Why we used " see a movie theater " instead of " watch a movie theater " ? 2 . And which one of this are right " I want to see a film on TV everyday " or " I want to watch a film on TV everyday " ?

Which of the following verbs is most commonly used with movie? Or are they both used, but the connotations are different?  I watched a good movie yesterday. I saw a good movie yesterday.


I have tried to split 25.15 into 25 and 15 but it won't work.`  double a=n.nextDouble(); int k=(int)(Math.floor(a)); int g=(int)((Math.floor((a-k)*100)));

How do I get whole and fractional parts from double in JSP/Java ? If the value is 3.25 then I want to get fractional =.25, whole = 3  How can we do this in Java?


Imagine that I'm writing the Jordan form of a matrix and I know that the eigenvalue needs to appear 4 times in the diagonal (algebraic multiplicity is 4) and we need 2 Jordan blocks (geometric multiplicity is 2). Now how do I know the size of the blocks? It could be a 1x1 and 3x3 block ou two 2x2 blocks, right? Also in the first case how do I know which block comes first in the diagonal?


Consider the ODE $$f''(x)+bf'(x)+cf(x)=0.$$  So, we are looking for solution of the form $f(x)=e^{\lambda x}$. If we replace this in the ODE, we get $$\lambda ^2+b\lambda +c=0.$$ Suppose this equation has a double root, i.e. $\lambda ^2+b\lambda +c=(\lambda -r)^2.$  Now, we know that solution are of the form $$f(x)=(A+Bx)e^{rx}.$$    How did we have the idea to consider $xe^x$ ? (because in the case where $\Delta =b^2-4c\neq 0$, i.e. $\lambda ^2+b\lambda +x=(\lambda -r_1)(\lambda -r_2)$, then solution are naturally of the form $$Ae^{r_1x}+Be^{r_2x},$$ where $r_i$ are real or complex depending on the context). So, indeed, if it has a double root, then $$Ae^{rx}+Be^{rx}=De^{rx},$$ and since the set of solution is a vector space of dimension $2$, then we must have an other linearly independent solution. So, how did we think to $xe^{rx}$ ? This comes a bit from nowhere for me. Any idea ?

When solving the differential equation $y'' + ay' + by = 0$ (with constant, real coefficients $a$ and $b$, although they could be complex if you like), you do it by setting up the characteristic equation $r^2 + ar + b = 0$, finding its solutions $r_1, r_2$, and then the general solution to this equation is $Ce^{r_1x} + De^{r_2x}$. This works both when the solutions are real and when they are complex.  However, when we have a double root $r_1 = r_2$, we get a different general solution, namely $Ce^{r_1x} + Dxe^{r_1x}$. I have no trouble seing that this is indeed a solution, and intuitive reasoning on degrees of freedom dictates that we must have a linear combination of two terms in our general solution, while $e^{r_1x}$ and $e^{r_2x}$ are the same. So the fact that there is a second term of some other form is not surprising.  I have, however, yet to see a "natural" explanation of this $xe^{r_1x}$ term. If one were developing the theory from scratch, how would one find this solution (other than blind luck)? If I wanted to teach ODE's to a class of students "the right way", i.e. with good explanations and motivations for everything (as opposed to just pulling out ready-made solutions like what was done to me when I was learning this exact thing), how would I motivate even considering a term like $xe^{r_1x}$ (other than "Well, exponentials aren't quite cutting it, but this is kindof like an exponential, right? Let's try it.")? And is there a way of solving the general differential equation that does not involve splitting into cases depending on whether the characteristic polynomial is a square?


Currently we have a tenancy we use in the university where both staff and students reside. Currently when a staff member searches on SharePoint in the search results it brings back OneDrive results is there a way of stopping OneDrive results from appearing in the results.

Hello I would like to know how I can remove student onedrive Results appearing in search . I am using SharePoint 2013 Online with O365. Staff and Student share same tenancy. Is there way to block students one drive appearing in SharePoint search.


I can't get return in function's aaa parameters a and b like:  public static void aaa( boolean a , Integer b) {     a=true;     b =2; } public static void main(String[] args) {      boolean a=false;     int b=1;     aaa(a,b);     lg.info("{} {}",a,b ); }   I will get same false 1 in output.  Each time when I need to have more than one return in function I must create class-holder:  public static class BoolAndIntHolder {     boolean a ;      Integer b ; }   public static void aa(BoolAndIntHolder s) {     s.a =true;     s.b =2; }  public static void main(String[] args) {     BoolAndIntHolder s= new BoolAndIntHolder();     s.a = false;     s.b=1;     aa(s);     lg.info("{} {}",s.a,s.b ); }   This gives true 2 in output as wanted.  But this looks so horrible each time to create different class holders. Is here any hacks how to write code in such situation in less dramatic way?   UPD  Looks like I must use data class'es in order to return several values since it is less complicated way. Solution bellow looks ugly for me. Is it possible to solve task in more elegant way?  enum TRUE_FALSE_ERR {TRUE,FALSE,ERR};  static TRUE_FALSE_ERR aaa() {     if (isConnected())     {         if getResult() return TRUE_FALSE_ERR.TRUE else              return TRUE_FALSE_ERR.FALSE;     } else     return TRUE_FALSE_ERR.ERR; }   public static void main(String[] args) {     switch (aaa()) {     case ERR:         lg.info("ERR");         break;     case TRUE:         lg.info("TRUE");         break;     case FALSE:         lg.info("FALSE");         break;     default : lg.info("default");      } }

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


We are currently hosting about 10 of our own various websites on a virtualised host. Each website is hosted by its own virtual machine with its own apache. Some of the sites connect to a shared database (MySQL) some use a different locally hosted database (again MySQL).  We're starting to run out of resources to allocate to virtual machines as there are now quite a few separate VMs. There are clearly some websites that are busier than others.  I've been considering combining a few websites onto a single host to reduce the total number of VMs to say 4.  The upshot of doing this would be to reduce the overhead required for each website but of course with that comes reduced stability; if Apache/MySQL/PHP fails for whatever reason (or needs restarting) a cluster of websites goes down rather than just one.  My question is: at what point does a website deserve its own dedicated VM?

This is a  about capacity planning for web sites. Related:      What are some recommended tools and methods of capacity planning for web sites and web-applications? Please feel free to describe different tools and techniques for different web-servers, frameworks, etc., as well as best-practices that apply to web servers in general.


I'm working through some basic algebra. I'm struggling with the following question:     Suppose $\beta$ is transcendental over $K$. Prove that $K(\beta)$ is not algebraically closed.   I thought that the Tower law might help, and seek a contraction based on the fact that if transcendental, degree is infinite.

I saw an exercise like this:     Let $K$ be a algebraically closed field. Show that $K(X)$ is not algebraically closed.   I was trying to prove that $T^2-X$ has not root in $K(X)$. How do I show it? Does it really use the hypothesis about $K$?  Thank you!


im extremely new to ubuntu, and since yesterday i've been unable to update directly from the software center. i open terminal and try sudo apt-get update, but i get the error "  E: Malformed entry 52 in list file /etc/apt/sources.list (Component) E: The list of sources could not be read. E: Malformed entry 52 in list file /etc/apt/sources.list (Component) E: The list of sources could not be read   Contents of sources.list:  deb cdrom:[Ubuntu 18.04.1 LTS _Bionic Beaver_ - Release amd64 (20180725)]/ bionic main restricted  # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to # newer versions of the distribution. deb http://us.archive.ubuntu.com/ubuntu/ bionic main restricted # deb-src http://us.archive.ubuntu.com/ubuntu/ bionic main restricted  ## Major bug fix updates produced after the final release of the ## distribution. deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates main restricted # deb-src http://us.archive.ubuntu.com/ubuntu/ bionic-updates main restricted  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu ## team. Also, please note that software in universe WILL NOT receive any ## review or updates from the Ubuntu security team. deb http://us.archive.ubuntu.com/ubuntu/ bionic universe # deb-src http://us.archive.ubuntu.com/ubuntu/ bionic universe deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates universe # deb-src http://us.archive.ubuntu.com/ubuntu/ bionic-updates universe  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu  ## team, and may not be under a free licence. Please satisfy yourself as to  ## your rights to use the software. Also, please note that software in  ## multiverse WILL NOT receive any review or updates from the Ubuntu ## security team. deb http://us.archive.ubuntu.com/ubuntu/ bionic multiverse # deb-src http://us.archive.ubuntu.com/ubuntu/ bionic multiverse deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates multiverse # deb-src http://us.archive.ubuntu.com/ubuntu/ bionic-updates multiverse  ## N.B. software from this repository may not have been tested as ## extensively as that contained in the main release, although it includes ## newer versions of some applications which may provide useful features. ## Also, please note that software in backports WILL NOT receive any review ## or updates from the Ubuntu security team. deb http://us.archive.ubuntu.com/ubuntu/ bionic-backports main restricted universe multiverse # deb-src http://us.archive.ubuntu.com/ubuntu/ bionic-backports main restricted universe multiverse  ## Uncomment the following two lines to add software from Canonical's ## 'partner' repository. ## This software is not part of Ubuntu, but is offered by Canonical and the :    on  was my saving grace.

I have unistalled and reinstalled the Ubuntu Software Center as per info I found in a similar thread and I got the same response about line 91 or something like that.  I just tried to upload a screen shot but since I'm new it won't allow me to.  I also can not figure out how to cut and paste anything so I have to hand type what the error screen says, both when I attempt to open the software center and nothing happens, when I try to enter commands into the terminal to uninstall, reinstall, whatever I get the same following:  COULD NOT INTITIALIZE THE PACKAGE INFORMATION An unresolvable problem occured while initializing the package information Please report t:his bug against the 'update-manager' package and include the following error message: 'E: Malformed line 91 in source list/etc/apt/sources.list (dist parse)  E: The list of sources could not be read.,  E: The package list of status file could not be parsed or opened.   How do I report bugs?  What can be done about this.  I have searched and everything everyone says to do leads me back to the same line error message.  So, I don't know how to get to line 91 in the source list; to tell you what it says. Sorry, I'm really new to this. That is what I need is to find out how to get there and fix what it says. I would really like to NOT have to re partition my hard drive and start from scratch, so I'm really looking forward to getting this problem solved. I need to be able to install new software.


I was wondering if it was possible to change the font of one letter in my Latex document ?  I have an equation where I want one of the letters in that to be Arial instead of Times New Roman, which is my main font.  So, is it possible ?

I'm a little confused on the purposes of each kind of text in LaTeX. I know the function of some of them, but sometimes people use each for different reasons. For example:   \texttt is for code (no discussion right?). \emph is to make emphasis. \textsc is used for names, right? \textbf when should I use it? \textmd When should I use it?   And something more: If I write for example "HI-TECH C PIC Compiler" in between a paragraph, the capital words doesn't look very good. Is it convenient to use \textsf?  Can normal text be mixed with different types? Under which circumstances?  P.S: I'm using the article class with the normal font.


I would like to search wildcard query in my php.model file.  I tried to apply these code but always get empty result.  public function get_web_search($data) {        $sql = "select p.name,c.name AS category_name,p.product_id AS item_id ,'Product' AS category_group from  product p left join category c on p.category_id = c.category_id  WHERE p.name LIKE '%?%' UNION select m.merchant_name,c.name AS category_name,m.merchant_id AS id,'Merchant'  AS category_group  from  merchant m left join category c on m.category_id = c.category_id WHERE m.merchant_name LIKE '%?%'";        $result = $this->db->query($sql, array($data['id'],$data['id']));        $records = $result->result_array();        return $records;    }   May I know how to set proper select statement in  p.name LIKE '%?%' ?  Please help. Thank you.

Anyone know how to combine PHP prepared statements with LIKE? i.e.   "SELECT * FROM table WHERE name LIKE %?%";


I have been given this version of the 'Monty Hall' Problem and am having some issues:  On this version of the show, you are, as usual, shown 3 face down cards, one of which is the Q♥ and the other two of which are black spot cards. Your objective is to select the Q♥, which wins $1,000.  As usual, you have to select a face-down card, and then the host turns over one of the other two cards. The twist this time is that the host himself does not know where the Q♥ is, and so may reveal the winning card. In this case you would win immediately!  The answer is that it doesn't matter you switch or not, but I am having trouble understanding why. If anybody could help me out using the law of total probability, that would be great. I understand 'regular' iterations of the Monty Hall but not this specific version where the host doesn't know where the card is.

Many of us know the   But the other day I was asked a variation of this riddle.  The answer of the original question is, of course, $ 66\% $ in favor of changing doors, but this is based on the fact that the game show host knows where the prize is.  Suppose he does not know where the prize is, and after you make your pick, he opens one of the other two doors and it happens to be a goat. Is it still better to change doors when he asks?   I believe it is. (After all it still leaves us with two chances instead of one.) But some of my friends think otherwise. We are not mathematicians, just a couple of riddle-likers, so we are not sure of the correct answer. So I thought to post it here.  Edit :   I read this on wikipedia and if I understand it correctly it seems to support my answer:  Morgan et al. (1991) and Gillman (1992) both show a more general solution where the car is (uniformly) randomly placed but the host is not constrained to pick uniformly randomly if the player has initially selected the car, which is how they both interpret the well known statement of the problem in Parade despite the author's disclaimers. Both changed the wording of the Parade version to emphasize that point when they restated the problem. They consider a scenario where the host chooses between revealing two goats with a preference expressed as a probability q, having a value between 0 and 1. If the host picks randomly q would be 1/2 and switching wins with probability 2/3 regardless of which door the host opens. If the player picks Door 1 and the host's preference for Door 3 is q, then in the case where the host opens Door 3 switching wins with probability 1/3 if the car is behind Door 2 and loses with probability (1/3)q if the car is behind Door 1. The conditional probability of winning by switching given the host opens Door 3 is therefore (1/3)/(1/3 + (1/3)q) which simplifies to 1/(1+q). Since q can vary between 0 and 1 this conditional probability can vary between 1/2 and 1. This means even without constraining the host to pick randomly if the player initially selects the car, the player is never worse off switching. However, it is important to note that neither source suggests the player knows what the value of q is, so the player cannot attribute a probability other than the 2/3 that vos Savant assumed was implicit.  What are your thoughts?


I recently updated my system with Pacman and am getting a could not start kdeinit5 error message.  After some Googling. It seems I simply need to update Pacman.  However, as I am on Wifi and have no means of connecting via Ethernet. I need to connect to my WPA2-PSK protected network before Pacman will function.  I'm a new Manjaro user. How can I connect to my network?

I would like to switch from gnome to awesome and I would like to connect my wifi network in command line (instead of using gnome tools).  So, I searched on the internet and found approximatively the same methods :  ifconfig wlan0 up iwconfig wlan0 essid "MyNetwork" key THEHEXAKEY dhclient wlan0   When I run awesome alone and execute those commands, I'm tucked at the 3rd one. It looks like DHCP cannot be resolve (the command continue running endlessly).  But when I run awesome in Xephyr and execute the same commands, dhclient wlan0 works well.  So I suppose Gnome do something that I don"t but I can't find what.  Could someone help me ?


I am trying to prove  $$\sum_{n\geq1}\frac1{n^2+1}=\frac{\pi\coth\pi-1}2$$ Letting $$S=\sum_{n\geq1}\frac1{n^2+1}$$ we recall the Fourier series for the exponential function $$e^x=\frac{\sinh\pi}\pi+\frac{2\sinh\pi}\pi\sum_{n\geq1}\frac{(-1)^n}{n^2+1}(\cos nx-n\sin nx)$$ Plugging in $x=\pi$ $$e^\pi=\frac{\sinh\pi}\pi+\frac{2\sinh\pi}\pi\sum_{n\geq1}\frac{(-1)^n}{n^2+1}(\cos n\pi-n\sin n\pi)$$ $$e^\pi=\frac{\sinh\pi}\pi+\frac{2\sinh\pi}\pi\sum_{n\geq1}\frac{(-1)^n}{n^2+1}((-1)^n-n\cdot0)$$ $$e^\pi=\frac{\sinh\pi}\pi+\frac{2\sinh\pi}\pi S$$ $$S=\frac{\pi e^\pi}{2\sinh\pi}-\frac12$$ But that is nowhere near to correct. What did I do wrong, and how do can I prove the identity? Thanks.

How to show the following equality? $$\sum_{n=0}^\infty\frac{1}{a^2+n^2}=\frac{1+a\pi\coth a\pi}{2a^2}$$


Is it:     I would like to know who is that person he is speaking to.   or:     I would like to know who that person he is speaking to is.   I am confused as to which sentence structure is grammatically accurate. Or are both sentences correct?

Which of the following is a correct sentence:   Does anyone know where's Linda?  Does anyone know where Linda is?    Does anyone know why and how to use above usage if #2 is correct. Also please let me know this kind of specific structures.


I have short question because I can't understand my mistake.  I have a collections:        List<ManagedFilesAuthorityDTO> managedFilesAuthorityDTOs = filesAuthorityRepository.findAll().stream()         .map(ManagedFilesAuthorityDTO::new)         .collect(Collectors.toList());   then I'm creating new list   List<ManagedFilesAuthorityDTO> outputFileList = null;   and I would like to iterate for managedFilesAuthorityDTOs and assign some object to outputFileList.  Here's my loop:   for (ManagedFilesAuthorityDTO dto : managedFilesAuthorityDTOs) {         outputFileList.add(dto);     }   And I still getting NullPointerException because my outputFileList is equals null. What I am doing wrong that I can't create new List?

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 was transferring some large files from my SSD to HDD, and looked at the Task Manager to see the usage of the drives. Here is a screenshot:   What this appears to show is my SSD working 95-100% all the time, and my HDD fluctuating between 50 and 100, which may mean that it is waiting on the SSD for the files to be read. Additionally, starting any programs on my SSD became very slow when the files were being moved. Is it possible that my SSD is actually slower then my HDD?  EDIT: I don't find the question that has been marked as duplicated from to be at all relevant. He is asking for a benchmarking tool, which I'm pretty sure goes under the "Opinion based" category anyway, and is completely different from my question which asks for reasons behind a bottleneck.As can be seen below it has attracted a completely different answer, to which I found to be useful.

I have just ordered my first SSD, and I want to run some tests on my current HDD now, and then run the same tests again once I get my SSD up and running in a couple of days, so I can see in detail how faster the new SSD is.  Can you recommend a (or a number of) good hard drive benchmarking tools for this sort of task?  Thanks


Say that someone has a French visa for study purposes. If he wants to travel to Germany by train for instance, can he go there freely without a passport or visa check?

I’m going to Germany for a semester exchange and I have a long-stay visa from Germany. Can I travel to the other Schengen states during this period with this visa or do I have to apply for a separate short stay Schengen visa?  My visa is German national visa type D. It is for a duration of 4 months, i.e., longer than 90 days. It says on the visa that the long stay visa is valid in Deutschland, which is different from my earlier visa, which I had when I visited Germany earlier; that one was a short stay visa and said it was valid in Schengen Staten.  Perhaps my current visa means that I can stay in Germany for a period of longer that 90 days can visit the other Schengen states if I don’t exceed the 90 day period.


How can i disable the visual volume overlay which appears at the top left on windows 10? It is very annoying if I change the volume then I have to wait 3-4 seconds till it dissapears, and I can't click anything which lays behind it during this time.  Is there a registry entry or something which I can set to false?

When adjusting the volume in Windows 8.1, a box appears at the top left corner of the screen. This box sticks around for ~13 seconds before it fades away. If you attempt to dismiss it by click on it, it switches to the music app.  How do you disable or dismiss this annoying box? At the very least, can the time visible be adjusted? More times than not, it's in the way.


I recently installed ubuntu(<12 hours) and I was able to mount my ntfs partitioned drives (orginally from Win 10)in ubuntu using this command  sudo mount -t ntfs-3g -o ro /dev/sda3 /media/win   When I try the same command with read permissions   sudo mount -t ntfs-3g -o rw /dev/sda3 /media/win   I get the following error     The disk contains an unclean file system (0, 0). Metadata kept in   Windows cache, refused to mount. Failed to mount '/dev/sda3':   Operation not permitted The NTFS partition is in an unsafe state.   Please resume and shutdown Windows fully (no hibernation or fast   restarting), or mount the volume read-only with the 'ro' mount option.   but I have shut down Windows 10 the normal way. What is the reason for this error and how can I solve it?  Part 2:  When mounting the drives in read only mode, I had to do that everytime I booted into the OS. Is there any way I can automate that(like create a shell script that will do the mounting for me and runs everytime the OS is booted).

Whenever I boot Ubuntu, I get a message that it cannot mount my windows partition, and I can choose to either wait, skip or manually mount.  When I try to enter my Windows partition through Nautilus I get a message saying that this partition is hibernated and that I need to enter the file system and properly close it, something I have done with no problem so I don't know why this happens.    Here's my partition table, if any more data is needed please let me know.     Device Boot      Start         End      Blocks   Id  System /dev/sda1            2048    20000767     9999360   83  Linux /dev/sda2        20002814   478001151   228999169    5  Extended /dev/sda3   *   478001152   622532607    72265728    7  HPFS/NTFS/exFAT /dev/sda4       622532608   625141759     1304576   82  Linux swap / Solaris /dev/sda5        20002816   478001151   228999168   83  Linux


We know that Gravitational Force that is applied by the sun on the moon is greater than that by the earth on the moon.  My Question is then why does not the moon escape from the earth and go towards sun?

The sun pulls on the moon with a force that is more than twice the magnitude of the force with which the earth attracts the moon. Why, then, doesn’t the sun take the moon away from the earth?


Is there a Stack Exchange site for question about  (the statistics software) only?

I've been using SO for a little over a year now, and recently I've noticed a shift of users between SO and stats.stackexchange.com.   I'm wondering if there has been any discussion on where questions about R, a statistical environment, best fits. Would you say it's better to ask R questions on SO or would it be better to ask over at stats.stackexchange.com? What, if any, determinants would you use to decide to post between the two? What about cross posting?


how can I stop the OSX Mail app from opening periodically? I am not talking about startup, I mean when the system is running. If I do not quit the mail app it will be coming to front on a regular basis. It sometimes even opens when I have another program/app in full screen mode and divides the screen to also open in fullscreen...  How do I run the mail app minimised without itself opening all the time?

When I am doing some work on my macbook pro, Mail app's main window keeps popping up in the background, it even pops up when I watch movies by interrupting full screen. This is so frustrating, I can't find out solution to this, googled and went to many discussion forums, no luck, suggestions that I found are very old and outdated. Has anyone faced similar issues or does anyone knows solution to this?


I have two materials here and i want to mix them to have a smooth border between them.(but not just put them one after another like layers). Explain me please how to do it.

I need to make the transition smoother between the 2 different colored objects in my scene, somehow like one of the colors fades into the other one, while still keeping the line between them.


Let $M$ be a finitely generated projective module over a commutative ring $R$ with finitely maximal ideals. Also assume that $M$ has constant rank i.e. rank of $M_P$ as $R_P$-module remains constant as $P$ varies over all prime ideals of $R$.  How to show that $M$ is free ?   I'm allowed to assume that finitely generated projective modules over local rings are free.   My try: Let $J$ be the Jacobson radical of $R$. Then $R/J$ is a finite direct product of fields. Now $M/JM$ is a projective $R/J$-module. Now I'll be done if I can show $M/JM$ is free over $R/J$. Unfortunately I'm unable to show this last part.   Please help.

Let $R$ be a commutative ring with finitely many maximal ideals $\mathfrak m_1,\ldots,\mathfrak m_n$. Let $M$ be a finitely generated module. Then there exists an element $x\in M$ such that $\frac{x}{1}\not\in\mathfrak m_iM_{{\mathfrak m}_i}$ for every $i=1,\dots,n$.    I cannot prove that such an element there exists. I was trying to prove it by induction on $n$. If $n=1$ it is true by Nakayama, so suppose it is true for $n-1$. Then for every $i$ I can find an $x_i\in M$ such that $\frac{x_i}{1}\not\in \mathfrak m_jM_{\mathfrak m_j}$ for every $j\neq i$. If $\frac{x_i}{1}\not\in \mathfrak m_iM_{\mathfrak m_i}$ for some $i$ we are done, so suppose $\frac{x_i}{1}\in\ m_iM_{m_i}$ for every $i$. I don't know how to go on, could you help me?