I have a JPG with a black background, and I want to remove the background without losing the transparency of the image. This is the image:

This fire image:    As you can see, it has a black background, which I can't delete (because it would probably destroy the smooth-looking fire effect). I want to place some fire in a photo.  However, I remember it was possible to take such images and do something in photoshop so that when you place them over a photo, the black is gone and the fire is perfectly blended there. But I can't remember what feature or option was it. Any ideas?  Photoshop CS5.


If my list is at the middle of sentence:     3 proteins: albumin (ALB), catalase (CAT), and epidermal growth factor (EGF)*** were digested with enzymes and mixed with ...   , what should I use at ***?

The whole department: John, Jeff, Jean, and the accountant [?] were thrown into jail.


So I was thinking about what's more efficient, making a number by directly adding them as a string to each other, or string.Formatting them.  So I made a little code piece:      private static void measuringStuff()     {         Stopwatch stw = new Stopwatch();         Random random = new Random();         string a;          stw.Start();         for (int i = 0; i < 10000000; i++)         {             a = random.Next(10) + "" + random.Next(10);         }         stw.Stop();         Console.WriteLine("#+\"\"+#: " + stw.ElapsedMilliseconds);          stw.Reset();         stw.Start();         for (int i = 0; i < 10000000; i++)         {             a = string.Format("{0}{1}", random.Next(10), random.Next(10));         }         stw.Stop();         Console.WriteLine("string.Format: " + stw.ElapsedMilliseconds);     }   And it turns out:  # + "" + #: 1928 string.Format: 2667   Why?

I've got a small piece of code that is parsing an index value to determine a cell input into Excel.  It's got me thinking...  What's the difference between   xlsSheet.Write("C" + rowIndex.ToString(), null, title);   and  xlsSheet.Write(string.Format("C{0}", rowIndex), null, title);   Is one "better" than the other? And why?


What is the code for the symbol used to represent the tangential part of a vector? For the normal part, one can use $v^{\perp}$, but how about the tangent part?

I know what my symbol or character looks like, but I don't know what the command is or which math alphabet it came from. How do I go about finding this out?


Depending on the word, using an before a consonant is not right.  What about in this phrase, "David has just gotten an SX250". To me, it does sound a lot better than "David has just gotten a SX250".   I saw a similar phrase in a book the other day, and it did not sound/look right at all!  Don't know if I'm going crazy or what..

Possible Duplicates:             Since SSD (solid-state drive) is pronounced es-es-dee, I'm wondering whether one should write "an SSD" or "a SSD". Saying "a SSD" out loud feels a bit off...


Votes to close are known to expire, for the reasons explained eg in answers to this question:   Does something like this happen to flags to close cast by users lacking ?  Side note - related question makes one feel that it's unlikely the case:     I ask because per  flags like that are no longer targeted to moderators only, but instead, go to same  as votes to close. This makes one wonder if the reasoning for votes expiration can now be applied to flags.

Here is the close queue:        Here is an active flag I have:        I currently have 5 flags pending in the close queue. Some, like this one, are months old. This doesn't feel right and may discourage newer users from flagging things that need attention with the assumption that a flag may be ignored for 4 months, so why bother?  Here are some possibilities:   Bump flags that have been languishing for more than 30 days to the front of the close queue (or weight questions with said flags a bit higher). Won't solve the issue, but will make it less egregious Punishing a misbehaving mod by forcing them to go through every sub-3000 user's flagged close votes in the queue and free them from flag limbo , "a new 10K flag list for "stuck" flags, which would be any close flag that is unhandled within 30 days."   This question has been heavily edited under the assumption that flags didn't get refreshed every day. Apparently they do, thanks to Bill and Asheesh, so sorry about the misdirection. Languishing flags still an issue though!


So, I was reading some book and it had source code with a single cpp file, no classes and a bunch of static functions.  After some searches, I mostly see material about static member functions, which I know what they do and doesn't provide me any answer.  I also found something about anonymous namespaces vs static functions, but didn't quite understand the point.  So, can anybody out there provide me some insights on what are static non member functions, what's their uses or why to use them?

The question was about plain  functions, not  static methods, as clarified in comments.  I understand what a static variable is, but what is a static function?  And why is it that if I declare a function, let's say void print_matrix, in let's say a.c (WITHOUT a.h) and include "a.c" -  I get "print_matrix@@....) already defined in a.obj", BUT if I declare it as static void print_matrix then it compiles?  UPDATE Just to clear things up - I know that including .c is bad, as many of you pointed out. I just do it to temporarily clear space in main.c until I have a better idea of how to group all those functions into proper .h and .c files. Just a temporary, quick solution.


Today’s hair care products, typically shampoos, usually incorporate  natural oil for better smoothness.  Today’s hair care products, typically shampoos, usually incorporate  natural oils for better smoothness.    What's the proper form of oil, singular or plural? I need some explanation for this specific case.

How do you I refer to different kind of an uncountable noun? For example, this is a part of my writing:     Using oil (coconut oil, olive oil) to moisturize your skin after bath. Those oil...   I want to explicitly refer to two kinds of oil to avoid other oil like engine oil mistakenly. Does those suit here? Are they countable? I think it's yes (look, I use they and them to refer to them in this sentence and the previous one). However, isn't that after using those, we should use the plural form of the noun? In that case, oils, not oil, should be use, right? And in that case, is oil a countable noun now?


I wrote a custom validator for jquery validator plugin .  Problem is, the custom validator I wrote is throwing error for anything I input. If I input plain text, it will still show error message.

How do you create a simple, custom rule using the jQuery Validate plugin (using ) that doesn't use a regex?  For example, what function would create a rule that validates only if at least one of a group of checkboxes is checked?


how can I solve this?  $$\lim_{n\to \infty } \left(\frac{1}{1+n} + \frac{1}{2+n} + ... + \frac{1}{2n}  \right) $$  but the limit of this?  $$(x_n) = \frac{1}{\ln(n^2)} + \frac{1}{\ln(n^3)} + ... + \frac{1}{\ln(n^n)} $$  At the second sequence I tried  this:  $$ (x_n) = \frac{1}{\ln(n)}\Bigl(\frac{1}{2} + \frac{1}{3} + ... + \frac{1}{n}\Bigr)$$ That is indetermination $ 0\cdot \infty$ since the sum diverges, but I don't know how to continue.

What is the sum of the 'second half' of the harmonic series?  $$\lim_{k\to\infty}\sum\limits_{n=k+1}^{2k}{\frac{1}{n}} =~ ?$$  More precisely, what is the limit of the above sequence of partial sums?


I have been working on a GUI code in wxpython that more or less repeats the same information 4 times. There are a lot of buttons on the screen that I have had to bind events to, and I'm finding that I have a lot of on_button_click definitions that look almost identical. So, I was wondering if there was a way to just pass through a parameter when binding the button to an event and cutting out 3 of the definitions. Here is an example:  self.VDBenchSlot1 = wx.Button(self, -1, "Slot 1 VDBench") sizer.Add(self.VDBenchSlot1,(1, 5), (1, 5), wx.EXPAND) self.VDBenchSlot1.Bind(wx.EVT_BUTTON, self.VDBenchSlot1_clicked)  self.VDBenchSlot2 = wx.Button(self, -1, "Slot 2 VDBench") sizer.Add(self.VDBenchSlot2,(1, 5), (1, 5), wx.EXPAND) self.VDBenchSlot2.Bind(wx.EVT_BUTTON, self.VDBenchSlot2_clicked)  self.VDBenchSlot3 = wx.Button(self, -1, "Slot 3 VDBench") sizer.Add(self.VDBenchSlot3,(1, 5), (1, 5), wx.EXPAND) self.VDBenchSlot3.Bind(wx.EVT_BUTTON, self.VDBenchSlot3_clicked)  self.VDBenchSlot4 = wx.Button(self, -1, "Slot 4 VDBench") sizer.Add(self.VDBenchSlot4,(1, 5), (1, 5), wx.EXPAND) self.VDBenchSlot4.Bind(wx.EVT_BUTTON, self.VDBenchSlot4_clicked)  def VDBenchSlot1_clicked(self, event):            global diskchange     if diskchange[1] == 'No Disk':         self.TextSlot1.AppendText("No Disk is currently in the slot so you cannot run this! \n")     else:           # Open the file startDisk#VD.sh that has the setup to start running VDBench         os.system("echo pcieRocks | sudo -S gnome-terminal --profile=VDbench --working-directory=/home/pciedev3ubuntu/Documents -e './vdbench -f disk%dVDscript.txt -vr' &" %diskchange[1])  def VDBenchSlot2_clicked(self, event):     global diskchange      if diskchange[2] == 'No Disk':         self.TextSlot2.AppendText("No Disk is currently in the slot so you cannot run this! \n")     else:            # Open the file startDisk#VD.sh that has the setup to start running VDBench         os.system("echo pcieRocks | sudo -S gnome-terminal --profile=VDbench --working-directory=/home/pciedev3ubuntu/Documents -e './vdbench -f disk%dVDscript.txt -vr' &" %diskchange[2])  def VDBenchSlot3_clicked(self, event):     global diskchange      if diskchange[3] == 'No Disk':         self.TextSlot3.AppendText("No Disk is currently in the slot so you cannot run this! \n")      else:            # Open the file startDisk#VD.sh that has the setup to start running VDBench         os.system("echo pcieRocks | sudo -S gnome-terminal --profile=VDbench --working-directory=/home/pciedev3ubuntu/Documents -e './vdbench -f disk%dVDscript.txt -vr' &" %diskchange[3])  def VDBenchSlot4_clicked(self, event):     global diskchange      if diskchange[4] == 'No Disk':         self.TextSlot4.AppendText("No Disk is currently in the slot so you cannot run this! \n")     else:            # Open the file startDisk#VD.sh that has the setup to start running VDBench         os.system("echo pcieRocks | sudo -S gnome-terminal --profile=VDbench --working-directory=/home/pciedev3ubuntu/Documents -e './vdbench -f disk%dVDscript.txt -vr' &" %diskchange[4])   I've tried changing VDBenchslotx_clicked to VDBenchslotx_clicked() and passing parameters to it, but one of two things happen; it tells me that the parameters entered do not match the parameters of the def, or it lets my program run but it automatically executes the def at program startup and not when the button is pressed, and the button then does not function properly.

I haven't found an answer elsewhere and this doesn't appear to have been asked yet on SO.  When creating an event binding in wxPython, is it possible to pass additional arguments to the event? For example, this is the normal way:  b = wx.Button(self, 10, "Default Button", (20, 20))         self.Bind(wx.EVT_BUTTON, self.OnClick, b) def OnClick(self, event):         self.log.write("Click! (%d)\n" % event.GetId())   But is it possible to have another argument passed to the method? Such that the method can tell if more than one widget is calling it but still return the same value?   It would greatly reduce copy & pasting the same code but with different callers.


I am having some problems when I type     sudo apt-get update   Error occurs saying the following      E: The repository ' bionic Release' does not have a Release file.   N: Updating from such a repository can't be done securely, and is therefore disabled by default.   N: See apt-secure(8) manpage for repository creation and user configuration details.   Please help.

When updating, I get the following error message:   W: The repository 'http://ppa.launchpad.net/mc3man/trusty-media/ubuntu xenial Release' does not have a Release file.   Here, I find another statement on this error:   This recommends removing certain PPAs; and, I'm not sure if I should do that since it might mean not getting the updates that I need.    Is this what I should do?


I created a form using the module "Webform". Now I want to add an #ajax item to the submit button.  Here's what I already did:  use \Drupal\Core\Form\FormStateInterface;  function mytheme_form_alter(&$form, FormStateInterface $form_state, $form_id) {   $form['#submit']['#ajax'] = array(     'callback' => '\Drupal\mymodule\Controller\DefaultController::process_form_submission'   ); }   The '#submit' field of the form now looks like this:  '#submit' => array(2)     '0' => string(12) "::submitForm"     '#ajax' => array(1)         'callback' => string(72) "\Drupal\mymodule\Controller\DefaultController::process_form_submission"   But the process_form_submission function is not called. Instead the page reloads on submit as before.

I'm using the Webform module for Drupal 8. The module confirmation settings for a form are the following:   Page (redirects to new page and displays the confirmation message) Inline (reloads the current page and replaces the webform with the confirmation message.) Message (reloads the current page/form and displays the confirmation message at the top of the page.) URL (redirects to a custom path or URL) URL with message (redirects to a custom path or URL and displays the confirmation message at the top of the page.)   But how am I able to submit a form via AJAX so that the page doesn't reload on submit, but a confirmation message still replaces the form? What did I do wrong?    EDIT:  Here is the solution which works:  First you have to hook the form alter function and set an AJAX callback (as in ):  use \Drupal\Core\Form\FormStateInterface;  function MYTHEME_form_alter(&$form, FormStateInterface $form_state, $form_id) {   if ( isset($form['#webform_id']) && $form['#webform_id'] == 'MYWEBFORM' )   {     // add an AJAX callback to the form submission     $form['actions']['submit']['#ajax'] = array(       'callback' => '\Drupal\MYMODULE\Controller\DefaultController::processFormSubmission',       'event' => 'click',     );   } }   Then in the processFormSubmission function you can process the form (put use \Drupal\Core\Form\FormStateInterface; at the top of your file) like:  // Instantiate an AjaxResponse Object to return. $ajax_response = new \Drupal\Core\Ajax\AjaxResponse();  /* do sth */  // in the DOM: replace the form with the text 'form submitted' $ajax_response->addCommand(new \Drupal\Core\Ajax\HtmlCommand('#MYFORM', 'form submitted'));  return $ajax_response;


I answered  and noticed in  23 distinct entries  of Became Hot Network Question. The first 20 timestamps show 2020-06-20 01:55:14Z and the last three show 2020-06-20 01:55:17Z.   Is this a bug?

The Boardgames Stack Exchange question  became a Hot Network Question three times, according to its :  All three events have the exact timestamp (19:14:39 UTC - shown when you click the 'toggle format' link or upon hovering) so it's probably a race condition or something. It's not a unique case;  finds instances on a single site, and  lists all occurrences in the network (currently 448). The current record holders, with 44 HNQ entry events, are   on Retrocomputing  on Worldbuilding


I know what "wrapped around her little finger" means, but I cant get straight on where it originates. Thanks

I just had occasion to write she's got him wrapped around her finger (under complete control).  I'd never really thought about this one before, but my guess would have been the idiom had some connection to wedding rings. On the other hand, intuition (and a Google Books search) tell me that the expression usually involves a little finger - not normally associated with wedding rings.  Does anyone know when/why the idiomatic usage arose? I can't find anything in OED or a cursory search online.


I want to create a watershed shapefile with areas, streams and pour points in it.  Is there a way to merge the areas (polygons) with streams (polylines) and pourpoints (points)?

Since a shapefile can only contain a single geometry type (e.g. point, polygon, etc), how could I persist both?   If I must create a shapefile for each geometry type, how can I pass them to a colleague to load?  In kml I can just pass the single kml to load.  Is there a shapefile manifest equivalent that I am missing?


As the title says: I want t prove or disprove the irreducibility of $X^4+1$ in $\frac{\mathbb{Z}}{p\mathbb{Z}}[X]$, $ p$ prime.  I have already proven that $X^4+1$ can't have linear factors in $\frac{\mathbb{Z}}{p\mathbb{Z}}[X]$, since it doesn't have roots in $\mathbb{Z}.$ By contradiction, such a root $k$ with $k^4=-1$ would have order $8$ which can't be since $8 \not| p$.   But that still leaves the possibility of a nontrivial decomposition with quadratic factors. So say $X^4+1 = (a_1x^2+q_1)(a_2X^2+q_2) \implies a_1a_2 = 1, a_1q_2+a_2q_1 = 0, q_1q_2 =0$. My hunch is that there is a contradiction somewhere in this equations, but I can't find it. Maybe there is none?

I have proven that in $\mathbb F_{p^2}^*$ exists an element $\alpha$ with $\alpha^8 = 1$.      Let $f(X) := X^4+1 \in \mathbb F_p[X]$. How can I prove that $f$ is reducible over $\mathbb F_p$?    Has $f$ a zero in $\mathbb F_p$ ?


I have converted .xls file to .ods by using below command in terminal  COMMAND : soffice --headless --convert-to ods abcd.xls   After conversion I am not able to read fileName.ods using SpreadSheet API of jOpenDocument1.3.jar. When ever I try to read .ods file it will throw NullPointer Exception .  I am working in Ubuntu platform, if I convert .xls file to .ods using LibreOffice then it is working fine but if I convert it using soffice terminal then it is throwing exception!.   Is there any way to convert file(s) using command line, so that Java code able to read it properly.    I am using below code to read converted fileName.ods file .  File file = new File(path); String sheetName = "SheetName"; // spread Sheet Name Sheet sheet = SpreadSheet.createFromFile(file).getSheet(sheetName);   "createFromFile" is giving NullPointer Exception  ava.lang.NullPointerException     at org.jopendocument.dom.ODPackage.getODDocument(Unknown Source)     at org.jopendocument.dom.ODPackage.getSpreadSheet(Unknown Source)     at org.jopendocument.dom.spreadsheet.SpreadSheet.createFromFile(Unknown Source)     at com.thales.dbtool.controller.DBManageController.getUiParamsFromExcel(DBManageController.java:1316)     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)     at java.lang.reflect.Method.invoke(Method.java:498)     at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)     at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)     at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandl   Any help will be appreciated.

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?


the steam guard email isn't going to any of the emails that I have and I don't know what email address it is going to

I cannot access the email that is linked to my Steam account and need to change it. However, Steam Guard sends a verification code to that email address.  Is there any way around this?


I have a layer that is defined by a complex SQL query.   It works fine but I would like to move that complexity out of QGIS and into the data base so I can access it from elsewhere (GeoServer).  I have tried creating a postgres view which represents the layer by using the database manager in QGIS (save as view) and by creating the view from the database itself but when I try and load the layer it is marked with a '!' and I can not select it.  Yes this is a duplicate question (sorry I don't know how to insert a reference to it) but the answers to that question don't work with current (2.18) versions of QGIS.  In particular they do not include the step to click on the schema button which is what I was missing.  I suspect that needing to do this is a bug but I will check this in QGIS 3 before reporting it as such.  The process of adding views is rather unintuitive and 'Get Spatial's explanation is clearer than any of the answers to the original question.  If we dump my question (feel free :) then please ensure that this answer gets added to the original one.  I note that several people besides me have up voted that answer.

In PostGIS 2.0, I am seeking an efficient way to create a spatially enabled view that is viewable in QGIS.    I followed the context of Part 2 of @Mike Toews answer to , and the view shows up as a point layer (in my case) in the "Add PostGIS Layers" dialog.  But after creating the view and spatially enabling it, I received the following error when trying to add the view to QGIS:     You must select a table in order to add a layer   Can someone explain why the spatial view will not load into QGIS, and what I need to do in order to make it loadable as a layer in QGIS?  I'm currently using QGIS v1.8 from the OSGEO installer  I view is built from the geonames database, loaded into PostGIS.  The geoname table/spatial data can be selected/viewed in QGIS just fine.  When I try to select the "mt_view", QGIS sees the view in the dialog, but won't let me select it.  It gives a dotted box around the area, but does not highlight and select the view.      I just noticed that when I run my first query:  CREATE OR REPLACE VIEW data.test AS SELECT * FROM data.geoname WHERE admin1='MT'   the view shows up in the QGIS Add Layer Dialog, but is unselectable.  Then when I run:  SELECT Populate_Geometry_Columns('data.test'::regclass);   I get the result of "0", where according to the , I think it should be returning "1".


My problem is when in an open javafx project and try to run it without editing it, an error appear like this, and everything install for java FX.


I need to replace a string where it follows a specific string and some varying data. I need to keep the beginning and the middle and just replace the end. When I tried the code below, it replaces only the last occurance. I have tried switching to a non greedy match but then it doesn't find it. The middle could contain new lines as well spaces, letters and numbers.  String s = "Beginning of story. Keep this sentence. Old ending.\n"; s += s; s += s; s1 = Regex.Replace(s, @"Beginning of story. ([\s\S]*) Old ending.", "Beginning of story. " + @"$1" + " New ending.", RegexOptions.Multiline | RegexOptions.IgnoreCase);  The result is this: Beginning of story. Keep this sentence. Old ending. Beginning of story. Keep this sentence. Old ending. Beginning of story. Keep this sentence. Old ending. Beginning of story. Keep this sentence. New ending.   How do I replace every occurance of "Old ending."

I have this gigantic ugly string: J0000000: Transaction A0001401 started on 8/22/2008 9:49:29 AM J0000010: Project name: E:\foo.pf J0000011: Job name: MBiek Direct Mail Test J0000020: Document 1 - Completed successfully  I'm trying to extract pieces from it using regex. In this case, I want to grab everything after Project Name up to the part where it says J0000011: (the 11 is going to be a different number every time). Here's the regex I've been playing with: Project name:\s+(.*)\s+J[0-9]{7}:  The problem is that it doesn't stop until it hits the J0000020: at the end. How do I make the regex stop at the first occurrence of J[0-9]{7}?


We know that $$\sum _{k=1}^{\infty } \frac{H_k}{k^3} = \frac{\pi^4}{72}.$$ Is there a closed form for the sum $$S=\sum _{k=1}^{\infty } \frac{(-1)^k H_k}{k^3}?$$ Mathematica doesn't give anything resembling a closed form and I have no idea if one exists.

How to analytically prove   $$\sum_{k\geq 1}\frac{(-1)^k}{k^3}H_k=-\frac{11\pi^4}{360}+\frac{\ln^42-\pi^2\ln^22}{12}+2\mathrm{Li}_4\left(\frac12\right)+\frac{7\ln 2}{4}\zeta(3) $$  As O.L answer   where  $$H_k = \sum_{n\geq 1}^{k}\frac{1}{n}.$$  Addition   So far I developed the following   $$\sum_{k\geq 1} \frac{H_k}{k^2} \, x^{k}  = \text{Li}_3(x)-\, \text{Li}_3(1-x)+\, \log(1-x) \text{Li}_2(1-x) +\frac{1}{2}\log(x) \log^2(1-x)+\zeta(3)$$  where $\text{Li}_3(x)$ is the trilogarithm .  For the derivation see   Update  A frined on another site gave the following


When I used to type sudo apt-get update it says error 404  Not Found [IP: 91.189.95.83 80] on 12 hits.

When updating, I get the following error message:   W: The repository 'http://ppa.launchpad.net/mc3man/trusty-media/ubuntu xenial Release' does not have a Release file.   Here, I find another statement on this error:   This recommends removing certain PPAs; and, I'm not sure if I should do that since it might mean not getting the updates that I need.    Is this what I should do?


I'm trying to prove that a function $ f \in C^{\infty}(\mathbb{R}, \mathbb{R})$ that is strictly positive on $]-1,1[$ and equals $0$ everywhere else verifies the following statement : there exists $ m \in \mathbb{N}^*$ such that $f^{(m)} $ has strictly more than $m$ zeros in $]-1,1[$.  I tried some things that doesn't give me much information, for instance I know that there is a decreasing sequence $(x_p)_{p\geq2} \in ]-1,1[^{\mathbb{N}}$ so that $x_p \longrightarrow_{p \rightarrow \infty} x \in ]-1,1[$ and $\forall p \geq 2, f^{(p)}(x_p) = 0$.  Thanks for help.

Let $f\in C^{\infty}(\mathbb{R},\mathbb{R})$ such that $f(x)=0$ on $\mathbb{R}$\ $(-1,1)$. Prove that there exists $n\in\mathbb{N}$ such that $f^{(n)}$ has at least n+1 zeros on $(-1,1)$  My attempt :   Assume $f$ is strictly positive  (if not n=0 works). Let $Z(f^{(n)})$ the number of zeros of $f^{(n)}$ on $(-1,1)$. Then we have: $$ \forall n\in\mathbb{N}:\;f^{(n)}(-1)=f^{(n)}(1)=0 $$ so that iterating the Rolle theorem to the successive derivatives of f we have  $$  \;Z(f^{(k+1)}) \geq Z(f^{(k)}) +1 $$ thus, by induction : $$ \forall n\in\mathbb{N}: \;Z(f^{(n+1)}) \geq Z(f^{(n)}) +1 $$ Therefore, $$ Z(f^{(n)}) \geq n $$ How can I find an another zero ?   I'm still looking for an another proof which does not use the lemma ..,  Thank you in advance.


I am trying to pull words and integers from a text file and have them all print on the same line using if statements. Would I need to continue with the for loop to achieve the outputs to be printed on the same line? I am trying to get it print frame #, type:0x0800 with open('wireShark.txt', 'rt') as file_content: for line in file_content:     if 'Frame' in line:         i=line.find(':')          idnum = line[0:i]          print(idnum)      if 'Type' in line:         i=line.find(':')         idnum4 = line[4:9]         print (idnum4)      if '0x0800' in line:         i=line.find(')')         idnum5 = line[16:i]         print (idnum5)

I'd like to do it in Python. What I'd like to do in this example in C: #include <stdio.h>  int main() {     int i;     for (i=0; i<10; i++) printf(".");     return 0; }  Output: ..........  In Python: >>> for i in range(10): print('.') . . . . . . . . . . >>> print('.', '.', '.', '.', '.', '.', '.', '.', '.', '.') . . . . . . . . . .  In Python print will add a \n or space, how can I avoid that? Now, it's just an example, don't tell me I can first build a string then print it. I'd like to know how to "append" strings to stdout.


I got an external drive that may need to be repaired.  When I try to mount it, I get the following error:  wrong fs type, bad option, bad superblock on /dev/sda1, missing codepage or helper program, or other error.   I have issues to repair the disk. I wanted to make a image copy of the disk before attempting any fsck repair. However making a image clone with dd takes 111 days for 300GB, and this is not an option:  dd if=/dev/input/DEVICE-HERE of=/dev/OUTPUT/DEVICE-HERE bs=64K conv=noerror,sync   This is the output from the dd command, and it is warning me that there is an error in the drive:  42598400 bytes (43 MB, 41 MiB) copied, 2035.41 s, 20.9 kB/s 42663936 bytes (43 MB, 41 MiB) copied, 2039 s, 20.9 kB/s dd: error reading '/dev/sda1': Input/output error 437+214 records in 651+0 records out 42663936 bytes (43 MB, 41 MiB) copied, 2042.48 s, 20.9 kB/s 42991616 bytes (43 MB, 41 MiB) copied, 2048 s, 21.0 kB/s dd: error reading '/dev/sda1': Input/output error 441+215 records in 656+0 records out 42991616 bytes (43 MB, 41 MiB) copied, 2051.39 s, 21.0 kB/s 43253760 bytes (43 MB, 41 MiB) copied, 2055 s, 21.0 kB/s dd: error reading '/dev/sda1': Input/output error 444+216 records in 660+0 records out 43253760 bytes (43 MB, 41 MiB) copied, 2058.75 s, 21.0 kB/s 43581440 bytes (44 MB, 42 MiB) copied, 2062 s, 21.1 kB/s   Any suggestions?

I want to clone a whole disk bytewise, something like  dd if=/dev/$SRC of=/dev/$DST bs=65536 count=$count   There are better tools for the job, which understand the file system (Windows) and work faster (I don't care), but they fail because of unreadable sectors on the old source disk.  There's actually a single invalid block I have to skip. So I thought about using dd multiple times like  dd if=/dev/$SRC of=/dev/$DST bs=65536 count=... dd if=/dev/zero of=/dev/$DST bs=65536 count=... skip=... seek=... dd if=/dev/$SRC of=/dev/$DST bs=65536 count=... skip=... seek=...   with replacing the broken sector data by zeros. Is this a valid approach? I found this  which confuses me.


I'm very helpless at the moment. I have a error while running this program:  import java.awt.*; import javax.swing.*;  public class Puzzle extends JFrame {     static Puzzle m_fenster;     private JPanel ahead, center, buttom;     private JButton ol, om, or, ml, mm, mr, ul, um, ur;     Puzzle(String titel)     {         super(titel);         setLayout(new FlowLayout());         ahead = new JPanel();         center = new JPanel();         buttom = new JPanel();          ol = new JButton();         om = new JButton();         ol = new JButton();         ml = new JButton();         mm = new JButton();         mr = new JButton();         ul = new JButton();         um = new JButton();         ur = new JButton();          ol.setIcon(new ImageIcon("aheadLeft.png"));         om.setIcon(new ImageIcon("aheadCenter.png"));         or.setIcon(new ImageIcon("aheadRight.png"));         ml.setIcon(new ImageIcon("centerLeft.png"));         mm.setIcon(new ImageIcon("centerCenter.png"));         mr.setIcon(new ImageIcon("centerRight.png"));         ul.setIcon(new ImageIcon("bottomLeft.png"));         um.setIcon(new ImageIcon("bottomCenter.png"));         ur.setIcon(new ImageIcon("bottomRight.png"));          ahead.add(ol);         ahead.add(om);         ahead.add(or);         add(ahead);          center.add(ml);         center.add(mm);         center.add(mr);         add(center);          bottom.add(ul);         bottom.add(um);         bottom.add(ur);         add(bottom);      }     public static void main(String[] args) {         m_window = new Puzzle("Puzzle");         m_window.setSize(800,700);         m_window.pack();         m_window.setVisible(true);     }  }   I'm sure the files exist in the folder. The code can be compiled without problems, but when running the error  Exception in thread "main" java.lang.NullPointerException at Puzzle.<init>(Puzzle.java:30) at Puzzle.main(Puzzle.java:55)   It's possible it's a very simple error. Any idea?

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 mean to write a templated function, which should be available for a somewhat large number of typenames. So, I mean to avoid needing explicit instantiation.  In this case, is it mandatory to write the definition of the function in the header?  Is there any other way? (It would be used in several places, so the definition cannot be written in any single source file).  PS:   refers to templated classes. Even though it may be reasonable to think that the same applies to functions, perhaps sometimes, it may not be the case. Thus, the link does not answer this specific question.

Quote from :     The only portable way of using templates at the moment is to implement them in header files by using inline functions.   Why is this?  (Clarification: header files are not the only portable solution. But they are the most convenient portable solution.)


I opened my laptop after a month of inactivity (Dell, running 14.04). It was in the suspended state during this time, and upon reopening it, the laptop functioned perfectly. After this initial use, I shut down the laptop. When I booted it the next time, the launcher bar had disappeared along with the top bar, leaving me a blank desktop (only the default ubuntu background remained).  I was able to create a new folder and navigate myself through to the Chromium application. I have made multiple attempts to try and fix this problem with the responses already existing on askubuntu. But my problem remains. I've tried to mess around with ccsm, and tweaking unity, but to no avail.  I have little experience with ubuntu, but I will follow whatever instructions you provide. Please help!  UPDATE I know this question has been marked as a duplicate, but I've honestly tried the solutions on that page. Since the original post, Ive moved to a different wifi zone, and as such am unable to connect to wifi from the computer. I'm posting this update from my phone. I request that those who marked it as a duplicate undo that action because it may prevent my question from being answered.

When I login, nothing happens.   I am presented with my desktop wallpaper.    No Dash, no Launcher, nothing.


I'm receiving some JSON from an API. I created a Wrapper like this: public class Wrapper{      public class cA{          List<cB> recordsB;          public class cB{             cC recordC;              public class cC{                 String _some_id; // <--- Here I'm getting the error             }         }     } }  So, when I call it to my HTTP future class, I try to parse it with: Wrapper.cA dataResponse = (Wrapper.cA)JSON.deserialize(input, Wrapper.cA.class); And I get the error  "Invalid character in identifier".  Thing is that I cannot change the name of the comming field _some_id. Can anybody tell me how could I parse this child class in order to receive the name as it is? Thanks a lot in advance!

This is a canonical question and answer developed by the community to help address common questions. If you've been directed here, or your question has been closed as a duplicate, please look through the resources here and use them to shape more specific questions. To browse all canonical questions and answers, navigate to the  tag.  This question and answer is owned by the community! If you can improve it and make it more useful, you're welcome to edit it.  I have a specific JSON structure in mind. I need to either deserialize this structure that's coming in from a web service, or I need to serialize data into this structure to transmit it to another system. How should I get started on this project in Apex?


MD5 has a digest size of 128 bits but has long been discouraged.  Is there an alternative algorithm with 128 bit digest size which is still considered secure?

Since MD5 is broken for purposes of security, what hash should I be using now for secure applications?


Lets imagine i have made a square of sides 1 unit*1 unit and now i make a pentagon in it with all sides equal and now i keep adding sides with condition that length of all sides be same. So now lets say number of sides is close to infinity so would it become a circle at one point and how can we differentiate it from other inscribed polygon with MANY SIDES (NOT INFINITY)?

My son is in 2nd grade.  His math teacher gave the class a quiz, and one question was this:     If a triangle has 3 sides, and a rectangle has 4 sides,    how many sides does a circle have?   My first reaction was "0" or "undefined".  But my son wrote "$\infty$" which I think is a reasonable answer.  However, it was marked wrong with the comment, "the answer is 1".  Is there an accepted correct answer in geometry?  edit: I ran into this teacher recently and mentioned this quiz problem.  She said she thought my son had written "8." She didn't know that a sideways "8" means infinity.


Trying out a few examples, let (i) $a=3, n=1, m=2, 3^2+1=10, 3^4-1=80, 10\mid 80$, (ii) $a=3, n=2, m=3, 3^4+1=82, 3^8-1=6560, \frac{6560}{82}= 80$.  To derive a proof, should derive $a^{2^n} +1$ as a factor of $a^{2^m} -1$, & as $m\gt n$, so $a^{2^m}=a^{2^n}.a^{2^{(n-m)}}$, so  $a^{2^m}-1=a^{2^n}.a^{2^{(n-m)}}-1$.  It is possible to state the next step, based on something like $a^2-1=(a-1)(a+1)$, but lack familiarity with such type of polynomial (if chosen the correct word) division.  Also, would request a generalized answer, for different bases for powers of $n,m$.

I've been struggling with this all day today. I imagine it's not very hard, but my algebra skills are terrible. So, how can I show that if $m>n$ and $a$ is a positive integer, then $$a^{2^n}+1 \mid a^{2^m}-1.$$ I just can't get a coherent picture of what I'm supposed to do. If this too (see yesterday's question) boils down to the Unique Factorization Theorem, I would be very grateful for any intuition on how to think about this!


If B and C are both inverses of the matrix A,then B=C.   Can't i prove it in following way ?  Proof:   AB=BA=I and AC=CA=I,then BA=CA=I  By postmultiplication $\Rightarrow (BA)(A^{-1})=(CA)(A^{-1})=(I)(A^{-1})\Rightarrow B=C=A^{-1}$,   or by premultiplication $AB=AC=I\Rightarrow (A^{-1})(AB)=(A^{-1})(AC)=(A^{-1})(I)\Rightarrow B=C=A^{-1}$.

From my textbook     ... if a 2×2 matrix $A$ is invertible then its inverse is unique.   I wonder, how can one prove this? Also can one extend this proof to larger square matrices of order $n$? Thanks


I am trying to run the following model:             I(week^2):mutation_status +             (week + I(week^2) | subject_id) ,            data = sim_dat)  This is the output I get from this model. There is one random slope that is rather high (-0.95) and I was curious to know how I can change my data simulation code to lower that value.  I am also having issues with convergence and would love to get thoughts on how to avoid issues regarding convergence. Thank you! Linear mixed model fit by REML. t-tests use Satterthwaite's method [lmerModLmerTest]  Formula: fetal_weight ~ week + mutation_status + week:mutation_status + I(week^2) +  I(week^2):mutation_status + (week + I(week^2) | subject_id) Data: sim_dat  REML criterion at convergence: 114  Scaled residuals:      Min      1Q  Median      3Q     Max  -1.9343 -0.3980 -0.0075  0.4168  1.9928   Random effects:  Groups     Name        Variance  Std.Dev. Corr         subject_id (Intercept)   1.51524  1.2309                          week         61.01832  7.8114   0.16                   I(week^2)   496.20236 22.2756  -0.19 -0.95  Residual                 0.05892  0.2427              Number of obs: 100, groups:  subject_id, 20  Fixed effects:                            Estimate Std. Error       df t value       Pr(>|t|)     (Intercept)                  3.1331     0.4226  17.9961   7.413 0.000000713699 *** week                        -1.2465     3.5210  18.0053  -0.354          0.727     mutation_statusY             0.5061     0.5977  17.9961   0.847          0.408     I(week^2)                   34.5706    10.8146  18.0084   3.197          0.005 **  week:mutation_statusY       -1.0697     4.9795  18.0053  -0.215          0.832     mutation_statusY:I(week^2) 202.5521    15.2942  18.0084  13.244 0.000000000101 *** --- Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1  Correlation of Fixed Effects:             (Intr) week   mttn_Y I(w^2) wk:m_Y week        -0.160                             muttn_sttsY -0.707  0.113                      I(week^2)    0.145 -0.966 -0.103               wk:mttn_stY  0.113 -0.707 -0.160  0.683        mtt_Y:I(^2) -0.103  0.683  0.145 -0.707 -0.966  Code for data simulation: set.seed(123)  # set the seed J <- 20  # number of individuals (clusters) cs <- 5  # number of time points (cluster size) gam <- c(0, 0.75, 1.34)  # fixed effects G <- matrix(c(1.75, 0, 0,               0, 0.0125, 0,               0,0,0.0625),              nrow = 3)  # random effect variances (G-matrix) sigma2 <- 0.08  mutation_status <- rep(0:1, each = 5) mutation_status <- rep(mutation_status, times = 10)  X <- cbind(1, seq_len(cs),             (seq_len(cs))^2)  # for each individual X <- X[rep(seq_len(cs), J), ]  X <- X[rep(seq_len(cs), J), ]  X[,2] <- X[,2]*0.05 X[,3] <- X[,3]*0.05  # repeat each row cs times pid <- seq_len(J)  # individual id pid <- rep(pid, each = cs)   # Generate person-level (lv-2) random effects uj <- lmf::rmnorm(J, mean = rep(0, 2), varcov = G)  # Generate repeated-measure-level (lv-1) error term eij <- rnorm(J * cs, sd = sqrt(sigma2))  # Compute beta_j's betaj <- matrix(gam, nrow = J, ncol = 3, byrow = TRUE) + uj  # Compute outcome: y <- rowSums(X * betaj[pid, ]) + eij + mutation_status*X[ , 3]*10 + 3  # Form a data frame sim_dat <- tibble(y, time = X[ , 2], pid, mutation_status) sim_dat <- sim_dat[,c(3,2,4,1)] colnames(sim_dat) <- c("subject_id", "week", "mutation_status", "fetal_weight") sim_dat$week_2 <-sim_dat$week*5 + 15  sim_dat$mutation_status <- as.factor(ifelse(sim_dat$mutation_status == 0, "N", "Y")) sim_dat$subject_id <- as.factor(sim_dat$subject_id ) #Model Building

I am trying to run the following model:         I(week^2):mutation_status +         (week + I(week^2) | subject_id) ,          data = sim_dat)  This is the output I get from this model. The correlation between week and I(week)^2 is rather high (-0.95) and I was curious to know how I can change my data simulation code to lower that value. I am also having issues with convergence and would love to get thoughts on how to avoid issues regarding convergence. Thank you! Linear mixed model fit by REML. t-tests use Satterthwaite's method [lmerModLmerTest]  Formula: fetal_weight ~ week + mutation_status + week:mutation_status + I(week^2) +  I(week^2):mutation_status + (week + I(week^2) | subject_id) Data: sim_dat  REML criterion at convergence: 114  Scaled residuals:      Min      1Q  Median      3Q     Max  -1.9343 -0.3980 -0.0075  0.4168  1.9928   Random effects:  Groups     Name        Variance  Std.Dev. Corr         subject_id (Intercept)   1.51524  1.2309                          week         61.01832  7.8114   0.16                   I(week^2)   496.20236 22.2756  -0.19 -0.95  Residual                 0.05892  0.2427              Number of obs: 100, groups:  subject_id, 20  Fixed effects:                            Estimate Std. Error       df t value       Pr(>|t|)     (Intercept)                  3.1331     0.4226  17.9961   7.413 0.000000713699 *** week                        -1.2465     3.5210  18.0053  -0.354          0.727     mutation_statusY             0.5061     0.5977  17.9961   0.847          0.408     I(week^2)                   34.5706    10.8146  18.0084   3.197          0.005 **  week:mutation_statusY       -1.0697     4.9795  18.0053  -0.215          0.832     mutation_statusY:I(week^2) 202.5521    15.2942  18.0084  13.244 0.000000000101 *** --- Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1  Correlation of Fixed Effects:             (Intr) week   mttn_Y I(w^2) wk:m_Y week        -0.160                             muttn_sttsY -0.707  0.113                      I(week^2)    0.145 -0.966 -0.103               wk:mttn_stY  0.113 -0.707 -0.160  0.683        mtt_Y:I(^2) -0.103  0.683  0.145 -0.707 -0.966  Code for data simulation: set.seed(123)  # set the seed J <- 20  # number of individuals (clusters) cs <- 5  # number of time points (cluster size) gam <- c(0, 0.75, 1.34)  # fixed effects G <- matrix(c(1.75, 0, 0,               0, 0.0125, 0,               0,0,0.0625),              nrow = 3)  # random effect variances (G-matrix) sigma2 <- 0.08  mutation_status <- rep(0:1, each = 5) mutation_status <- rep(mutation_status, times = 10)  X <- cbind(1, seq_len(cs),             (seq_len(cs))^2)  # for each individual X <- X[rep(seq_len(cs), J), ]  X <- X[rep(seq_len(cs), J), ]  X[,2] <- X[,2]*0.05 X[,3] <- X[,3]*0.05  # repeat each row cs times pid <- seq_len(J)  # individual id pid <- rep(pid, each = cs)   # Generate person-level (lv-2) random effects uj <- lmf::rmnorm(J, mean = rep(0, 2), varcov = G)  # Generate repeated-measure-level (lv-1) error term eij <- rnorm(J * cs, sd = sqrt(sigma2))  # Compute beta_j's betaj <- matrix(gam, nrow = J, ncol = 3, byrow = TRUE) + uj  # Compute outcome: y <- rowSums(X * betaj[pid, ]) + eij + mutation_status*X[ , 3]*10 + 3  # Form a data frame sim_dat <- tibble(y, time = X[ , 2], pid, mutation_status) sim_dat <- sim_dat[,c(3,2,4,1)] colnames(sim_dat) <- c("subject_id", "week", "mutation_status", "fetal_weight") sim_dat$week_2 <-sim_dat$week*5 + 15  sim_dat$mutation_status <- as.factor(ifelse(sim_dat$mutation_status == 0, "N", "Y")) sim_dat$subject_id <- as.factor(sim_dat$subject_id ) #Model Building


When we open a form in a new window, we would like to click a button to close the window without alert box.  Is it possible?  Any help is appreciated.  Thanks alot

How can I close a browser window without receiving the Do you want to close this window prompt?  The prompt occurs when I use the window.close(); function.


I am following a code academy tutorial and i am finding this difficult.  The assignment is the following:     Use a for-in loop to print out all the properties of nyc.   var nyc = {     fullName: "New York City",     mayor: "Michael Bloomberg",     population: 8000000,     boroughs: 5 };  // write your for-in loop here for (var  in nyc){     console.log(population); }

How do I enumerate the properties of a JavaScript object?  I actually want to list all the defined variables and their values, but I've learned that defining a variable actually creates a property of the window object.


I am aware that the neurtal wire provides a return path for the current to the power source. But that neutral wire too, is connected to the ground at somewhere between the load and the source. My question is: Why use three wires Live, Neutral and Ground? Instead we can use two wires Live and Ground which does the same work, as Neutral and Ground are joined. Another question: Does two grounds of different localities have same potential? If they have different potentials, is this the reason why we use neutral as the common reference for both the load and the supply?

Current flows through a conductor connecting points at different potentials.  Leaving aside multi-phase details, common/conventional AC systems use a 3-wire setup:   Wire-1: a line/live/hot/phase wire presenting a point that oscillates between 2 potentials. Wire-2: a neutral wire presenting a point of unknown/unspecified and varying potential, that nevertheless presents some fixed/specified potential difference to Wire-1 at least some of the time. Wire-3: a ground/earth wire presenting a point at 0V potential difference to its immediate physical surroundings.   Wire-1 and Wire-2, in addition to some device that is to be powered, are used to construct a closed electrical circuit. Wire-3, leaving aside EMI/shielding concerns, is used to ensure that current will flow through it, rather than the device's user, if there ever occur any faults and the device's user comes in contact with Wire-1 or Wire-2.  Additionally to this however, Wire-2 and Wire-3 are at some point connected. This is done to ensure that Wire-2's potential remains close to that of Wire-3 .. which seems to be important for some reason.  Now the part I don't understand is why there needs to be a distinction between Wire-2 and Wire-3 at the power socket, if there is none a few meters further down the line.  I have tried to look this up, but all answers I could find so far seem incomplete. The answers depend on how the question is phrased:   If the question is phrased as "Why do we need Wire-3 in addition to Wire-2" the answer is because "Wire-2 may be at a substantial potential difference to its surroundings/user and thus endanger him/her if he/she ever comes in contact with it or Wire-1". If the question is phrased as "Why do we need Wire-2 in addition to Wire-3" the answer is because "Wire-2 is needed to form a closed electrical circuit" or phrased somewhat differently "Wire-2 is needed to create a potential difference to Wire-1 and thus for current to flow" .. with the argument further being that when taking practical considerations into account Wire-3 can't provide a reliable/stable potential difference to Wire-1 like Wire-2 can.   This doesn't really answer why there's a need to differentiate between Wire-2/Wire-3 though, considering how    Wire-3 remains Wire-3 and maintains 0V potential difference to its surroundings/user, regardless of whatever else happens around it .. since that is what it's supposed to do, or phrased differently, since that is the reason for Wire-3 being useful in the first place .. right?   and   Wire-2 is connected to Wire-3   What am I missing here?    Why is it safe to touch Wire-3 but not Wire-2, or why can Wire-3 provide a level of protection that Wire-2 can't?  Why differentiate between Wire-2 and Wire-3 at the power socket but then connect them further down the line?


I'm trying to replace an apostroph ( ' ) with acute ( ´ ) from a string after entered into a form and submitted it.  <?= str_replace("'","´",$_POST['string']) ?>   string for example is: "Jan's Motel" > should become "Jan´s Motel"  This works good when using charset iso-8859-1, but I need my website to be in utf-8.  I utf-8 the result string is "JanÂ´s Motel"  I don't understand why it becomes " Â´ " instead of " ´ "  Here ist my example code:  <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml">   <head>     <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />     <title>notitle</title>   </head>    <body>     <form action="?" method="post">       <input type="text" name="string" value="<?= str_replace("'","´",$_POST['name']) ?>" />     </form>   </body> </html>   Can anyone please help?

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


I am a first year graduate student, and I am looking for a good numerical analysis book to self-study. Ideally, I am looking for a book that introduces the basics of floating point arithmetic, interpolation, solutions to non-linear equations, and numerical methods in ODE's and PDE's. More importantly, I would like a book that has good exercises as well. I will most likely be taking a course on numerical PDE next term so I am looking for a book that would help me brush up on numerical analysis.

I'm in a numerical analysis course right now and it's pretty rigorous but I'm enjoying it a lot. I took a lower level course before that was more oriented towards implementation of numerical methods, so it's not my first time with the material.  Anyway, my professor wrote his own course notes and they're fantastic but I wanted some reference material since I'm currently outlining my own notes. Just wondering what the big ones out there are  edit: I would say I'm at an advanced undergraduate level


I want to have a norm symbol with three line in my equation such as |||x||| but with equal distances.

I would like to create a norm-like operator with 3 verticals bars instead of two. It has to look like $|||\cdot|||$. I would like to know how to decrease the spacing between the vertical bars such that it has the same spacing as the $\lVert .. \rVert$ command.  There is a command available in the stmaryrd package called \biginterleave, but this command has to much spacing between the vertical bars, especially in display math mode.  Is there some work-around to adjust the spacing between to vertical bars?


Suppose there is an assassin at each end of the train, and they each use their own laser guns to assassinate a passenger $A$ located in the center of the train. At the same time, $A$ will die, otherwise $A$ will survive.  They fired on $A$ at the same time, and Observer $A$ on the train saw himself dead.  However, due to the movement of the train, the observer $B$ on the platform saw that $A$ was not dead because the laser gun did not hit $A$ at the same time.  So is $A$ dead or not?    There are three points on the platform, $A1$, $B$ and $A2$. The distance between $A1$ and $A2$ is $H$, and the distance between $A1$ and $B$ is $H / 2$.  On the train, the distance between assassins is $H$, and the distance between $A$ and any assassin is $H / 2$. The train is moving. When one assassin reaches $A1$, the other assassin reaches $A2$. Two assassins fired at the same time, and $A$ died. On the platform, $B$ saw that two assassins fired at points $A1$ and $A2$, so $B$ thought $A$ would die. But according to Einstein's theory, $A$ won't die because two assassins didn't fire at $A1$ and $A2$ at the same time. So is $A$ dead or not?

I have currently been introduced to relativity of simultaneity with the following thought experiment:  Consider a train in which there are two presidents, one sitting at the front and the other at the back of the train. The two presidents must sign an agreement simultaneously for everyone to be happy. The way that they are going to carry this out is by having a laser shoot a light beam simultaneously towards each of the presidents and when the light beam gets to each president they will sign the agreement. Now consider this train moving from left to right and we will analyse this situation from the two inertial reference frames "train frame" and "platform frame". It then follows that from the "platform frame" the two presidents have not signed the agreement simultaneously while regarding this situation from the "train frame" the presidents did sign the agreement simultaneity. Until this point I understand everything  Q: Now consider that there is a bomb in the middle of the train and that bomb would blow up if the two presidents don't sign the agreement simultaneously and won't blow up if they do (this can be achieved via sensors added at the back and front of the train). Now this experiment is carried and from " platform frame" train blew up while in "train frame" train didn't blow up. Now this poses a paradox as the train can't blow up and not blow up in the same time even if its a matter of reference frames, since reality is connected. How can this paradox be resolved?   Moreover from this paradox I get the feeling that, even though observers in different inertial reference frames don't agree on simultaneity, they must agree on something, maybe cause of their action on nature around them? I don't know how to call this agreement. Because if they wouldn't agree on this (idk how to put it into words) then we would get paradoxes as the one above. Thank you for any help  ps: The though experiment with the presidents was presented by Brian Greene in his course on special relativity


After installing Ubuntu 13.04 the display brightness of my laptop has reduced. Increasing the brightness in system settings makes no change. Can you help me tackle this problem?

To work around  (changing LCD brightness via hotkeys impossible), I'd like to have one command line query for increasing and one for reducing the brightness of my LCD. I could then map a hotkey to each one of this queries.  The problem is: I don't know how to increase and reduce the LCD brightness on the command line. Do you?


This is not a question about how to insert images at the top, but rather asking whether or not this is common practice.  The template I've received from my university automatically inserts figures at the top of a page if no other flags are given using \begin{figure}[t] as default.  Personally, I find it a bit awkward to be introduced to a certain image before reading about the respective explanation within the text. But I got a feeling that top-positioned images are the way one usually writes LaTeX documents.  At the end of the day, it's a question about preference, but I really want to know which of the two following is "the way to go": Left or right?

When you turn in a manuscript to an academic publisher, they may insist (referring to their style guide and publication process) that all figures are placed on top/bottom of the manuscript's pages rather than exactly where you need them (e.g., in the middle on one page and on top on another page). Why? Assuming single-column layout and that no huge line stretching, no huge vertical gaps, and no vertical overflows occur, what good reasons could exist nowadays for figures to be moved out of the very place where you need them?  An example could be the figures in the : they are placed typically where the reader needs them rather than always at the top/bottom of the pages.


\documentclass[11pt]{article} \usepackage[utf8]{inputenc} \usepackage{listings} \usepackage{amsmath} \usepackage{amssymb} \begin{document} Similarly, the state-space averaging is used to described the AC small signal dynamics: \begin{multline} \begin{bmatrix} L_1 & 0 & 0 & 0\\ 0 & L_2 & 0 & 0\\ 0 & 0 & C_1 & 0\\ 0 & 0 & 0 & C_2 \end{bmatrix} \frac{d}{dt} \begin{bmatrix} i_{L1}(t)\\ i_{L2}(t)\\ v_{C1}(t)\\ v_{C2}(t) \end{bmatrix} =\\ \begin{bmatrix} 0 & 0 & D & -D'\\ 0 & 0 & -D' & D\\ -D & D' & -\frac{D'}{R_l} & -\frac{D'}{R_l}\\ D' & -D & -\frac{D'}{R_l} & -\frac{D'}{R_l} \end{bmatrix} \cdot \begin{bmatrix} i_{L1}(t)\\ i_{L2}(t)\\ v_{C1}(t)\\ v_{C2}(t) \end{bmatrix} + \begin{bmatrix} D'\\ D'\\ \frac{D'}{R_l}\\ \frac{D'}{R_l} \end{bmatrix} \cdot \hat{v}_g(t) + \\ \begin{bmatrix} V_{C1} + V_{C2} -(V_g - V_D)\\ V_{C1} + V_{C2} -(V_g - V_D)\\ -I_{L1} -I_{L2} + \frac{V_{C1}}{R_l} + \frac{V_{C2}}{R_l} - \frac{V_g - V_D}{R_l}\\ -I_{L1} -I_{L2} + \frac{V_{C1}}{R_l} + \frac{V_{C2}}{R_l} - \frac{V_g - V_D}{R_l} \end{bmatrix} \cdot \hat{d}(t) \end{multline} Also, $\hat{v}_{C1}(t) = \hat{v}_{C2}(t) = \hat{v}_C(t) \ and \ \hat{i}_{L1}(t) = \hat{i}_{L2}(t) = \hat{i}_L(t)$. While DC state equations are: \begin{equation} \begin{bmatrix} 0\\ 0\\ 0\\ 0 \end{bmatrix} = \begin{bmatrix} 0 & 0 & D & -D'\\ 0 & 0 & -D' & D\\ -D & D' & -\displaystyle\frac{D'}{R_l} & -\displaystyle\frac{D'}{R_l}\\ D' & -D' & -\displaystyle\frac{D'}{R_lZ_l} & -\displaystyle\frac{D'}{R_l} \end{bmatrix}\cdot \begin{bmatrix} I_{L1}\\ I_{L2}\\ V_{C1}\\ V_{C2} \end{bmatrix} + \begin{bmatrix} D'\\ D'\\ \displaystyle\frac{D'}{R_l}\\ \displaystyle\frac{D'}{R_l} \end{bmatrix} \cdot (V_g - V_D) \end{equation} The state space equations hence become, \begin{multline} sL\cdot \hat{i}_L(s) = (D - D')\cdot \hat{v}_C(s) + D'\cdot \hat{v}_g(s) + (2V_C-V_g+V_D)\cdot \hat{d}(s) \\ sC\cdot \hat{v}_C(s) = (D'-D)\cdot \hat{i}_L(s) - \displaystyle\frac{2D'}{R_l} \hat{v}_C(s) + \displaystyle\frac{D'}{R_l} \hat{v}+g(s) + (-2I_L + 2\displaystyle\frac{2V_C}{r_l} - \displaystyle\frac{V_g-V_D}{R_l})\cdot \hat{d}(s) \end{multline} Steady state values are: \begin{equation} V_C = \displaystyle\frac{1-D}{1-2D} \cdot (V_g-V_D) \end{equation} and \\ \begin{equation} I_L=\displaystyle\frac{1-D}{(1-2D)^2} \cdot \displaystyle\frac{V_g}{R_l} \end{equation} \end{document}   Warning: Overfull and Underfull.

\documentclass[11pt]{article}  \begin{document}   The above equations on application of Laplace Transform become:  $$sL_1\hat{i}_{L1}(s) = D\cdot \hat{v}_{C1}(s) + D\cdot \hat{v}_{C2}(s) - D\prime \cdot \hat{v}_g(s) + (C_{C1} + V_{C2} - V_g + V_D)\cdot \hat{d}(s)$$ $$sL_2\hat{i}_{L2}(s) = -D\prime \cdot \hat{v}_{C1}(s) + D\cdot \hat{v}+{C2}(s) + D\prime \cdot \hat{v}_g(s) + (C_{C1} + V_{C2} - V_g + V_D)\cdot \hat{d}(s)$$ $$sC_1\hat{v}_{C1}(s) = -D\cdot \hat{i}_{L1}(s)+ D\prime \cdot \hat{i}_{L2}(s) + (-I_{L1} -I_{L2} - I_1)\cdot \hat{d}(s) -D\prime \cdot \hat{i}_l(s)$$ $$sC_1\hat{v}_{C1}(s) = D\prime \cdot \hat{i}_{L1}(s)- D\cdot \hat{i}_{L2}(s) + (-I_{L1} -I_{L2} - I_1)\cdot \hat{d}(s) -D\prime \cdot \hat{i}_l(s)$$ $$sL_l\hat{i}_l(s) = D\prime \cdot \hat{c}_{C1}(s) + D\prime \cot \hat{v}_{C2}(s) - D\prime \cdot \hat{v}_g(s) +(V_g - V_D - V_{C1} - V_{C2})\cdot \hat{d}(s) - R_l \cdot \hat{i}_l(s)$$  \end{document}   Error:   181 Underfull \hbox (badness 10000) in paragraph at lines 181--181 181 Overfull \hbox (22.63293pt too wide) detected at line 181


I'm running Thunderbird 24.3 on Debian 7 and sometimes when I click on 'Write' and it opens up a new window it's not in focus and my keystrokes are sent to the main Thunderbird screen not the new Write screen. The Windows Manager I'm using is XFCE4.   It's happening for other users of the same system and I have yet to find a pattern to reproduce this.  I've also had this happen with firefox 27.0.0 and with Thunderbird whilst using thunderbird inline conversations plugin on one of the machines which doesn't start a new window.  What I've tried and I still have the problem   clicking on title bar Check error console Start a fresh profile (Move the .thunderbird directory and start completely fresh)   Update  Tried the thunderbird 24.4.0 and still have the problem.  Noticed that if I quickly hit Ctrl+n about 10 times I can re-enact the problem.

I'm using Thunderbird 2.0.22, the version that comes with Ubuntu Intrepid 8.10.  When I hit "Reply" or "Write", a new email window pops up, but it ends up being under the main Thunderbird Window, and doesn't have focus. Thunderbird is the only application that exhibits this weird behaviour, and it just started happening one day, whereas it worked fine before.  I've seen this problem years ago as well, and wasn't sure how I fixed it.


What I mean by notifications are reputation changes, I don't get that at all, as for notifications of new comments and the like, I get them in my inbox but no notification about that, I mean I have to open the inbox and if there is a notification from area51 then I see it there? is this a bug or status-by-design?

The new Top-Bar does not show reputation changes from Area 51.


When using hamachi do both users have to have hamachi? and also should this strategy work on macs? I've already tried making a server and i didn't work so this is my last option to play with my friends. Looking forward to reply


I want to simulate a TCP handshake with Python. For example, I want to establish a connection from 192.168.0.101:1234 to 192.168.1.102:80. I followed  and wrote a similar program sending an SYN packet to the server. The server responds an SYN+ACK packet to me, but my operating system sends an RST packet immediately, interrupting the communication.   Thus, I hope to let the client listen to the 1234 port and do no respond automatically. However, after I bind the address with socket.socket(socket.AF_INET, socket.SOCK_STREAM), the Python module sends the RST packets, instead of the system.   How can I achieve such goal? I think I should control the Inernet Layer, but I have no idea how to do that.   Thank you.

Ok, I realize this situation is somewhat unusual, but I need to establish a TCP connection (the 3-way handshake) using only raw sockets (in C, in linux) -- i.e. I need to construct the IP headers and TCP headers myself.  I'm writing a server (so I have to first respond to the incoming SYN packet), and for whatever reason I can't seem to get it right.  Yes, I realize that a SOCK_STREAM will handle this for me, but for reasons I don't want to go into that isn't an option.  The tutorials I've found online on using raw sockets all describe how to build a SYN flooder, but this is somewhat easier than actually establishing a TCP connection, since you don't have to construct a response based on the original packet.  I've gotten the SYN flooder examples working, and I can read the incoming SYN packet just fine from the raw socket, but I'm still having trouble creating a valid SYN/ACK response to an incoming SYN from the client.  So, does anyone know a good tutorial on using raw sockets that goes beyond creating a SYN flooder, or does anyone have some code that could do this (using SOCK_RAW, and not SOCK_STREAM)?  I would be very grateful.    MarkR is absolutely right -- the problem is that the kernel is sending reset packets in response to the initial packet because it thinks the port is closed.  The kernel is beating me to the response and the connection dies.  I was using tcpdump to monitor the connection already -- I should have been more observant and noticed that there were TWO replies one of which was a reset that was screwing things up, as well as the response my program created. D'OH!  The solution that seems to work best is to use an iptables rule, as suggested by MarkR, to block the outbound packets.  However, there's an easier way to do it than using the mark option, as suggested.  I just match whether the reset TCP flag is set.  During the course of a normal connection this is unlikely to be needed, and it doesn't really matter to my application if I block all outbound reset packets from the port being used.  This effectively blocks the kernel's unwanted response, but not my own packets.  If the port my program is listening on is 9999 then the iptables rule looks like this:  iptables -t filter -I OUTPUT -p tcp --sport 9999 --tcp-flags RST RST -j DROP


There is Graph which is connected with Submultiples. (I am sorry but I don't know what this is called.)  For example,  10-node Graph has 10 nodes, 18 edges. node 1 connect all the other nodes. node 2 connect node number 2,4,6,8,10. node 3 connect 3,6,9. node 4 connect 4,8. etc.  This is Planar graph of 10-node graph.    Question 1.  It is easy to check if 11-node graph is planar or not. (Just put the node no.11 and connect with no.1) But, Is 12-node Submultiple graph planar? And how can I prove it? (I saw  But I cannot find the graph of $K_{3,3}$ If there is, please show me with picture.  Question 2.  If 12-node Submultiple graph is possible, How many node are possible? (I mean, 14 or 15 nodes graph is planar? or not?)

A recently-deleted question asked to show that if $G(n)$ is the graph on $[n]=\{1,\dots,n\}$ where $x$ and $y$ are adjacent if $x|y$ or $y|x$, then $G(n)$ is planar.  This is false if $n\geq150$, for the subgraph induced by $\{2,3,5,90,120,150\}$ is isomorphic to $K_{3,3}$.  My question is, what is the largest value of $n$ such that $G(n)$ is planar?  Of course, various software packages would make short work of this, but I'd be interested in a verbal argument, if someone can give one.


I'm having difficulty in assess this problem in a method without relying too much in too many trial and error. I have noticed there is a similar puzzle but in such it includes the value of one of the digits, but how do you solve this without knowing any other information?. The problem is as follows:  Using the expression from below: $$\frac{\overline{ASIR}}{\overline{RISA}}=4$$ Find $\overline{RI}-\overline{SA}$  The alternatives given in my book are as follows: $\begin{array}{ll} 1.&\textrm{75}\\ 2.&\textrm{-75}\\ 3.&\textrm{57}\\ 4.&\textrm{-57}\\ 5.&\textrm{-48}\\ \end{array}$ How exactly should this problem be assesed without just guessing?. Can someone help me with this?. So far the only thing which I could come up with was with the following: $\overline{ASIR}=4\overline{RISA}$ $1000A+100S+10I+R=4000R+400I+40S+4A$ From this it can be obtained: $996A+60S=3996R+390I$ But that's it. That's the place where I came stuck. From then on I think its just trial and error, but on looking on the equation all letters with the exception of R and A can take values between 1 to 9. So how to constrain those or to solve this thing in a more orderly manner?. Can someone help me with a step-by-step approach and the most detailed as possible?.

This is question 26 from Australian Maths Competition 2013.  $pqrs $ is a 4-digit number and has the property that $pqrs \cdot 4 = srqp$.If p=2,what's the value if the 3-digit number qrs?  Here's what I tried.  $(2000 + 100q+10r+s)(4)=1000s+100r+10q+2$  So,  $ \frac {1000s+100r+10q+2}{4} $= some integer.  $250s+25r+ \frac {5q}{2} + \frac 12 =2000+100q+10r+s$  $ \frac {5q}{2} $ should be an fraction so that when it adds up with half, it will be an integer. So,$q$ must be an odd number.  $pqrs \cdot 4 =srqp $,where $p=2$  $4s= 10j +2$, where j is some integer  $250s=625j + 125$  And then I'm lost.


so I am having a problem with null pointer exceptions and can't figure out what is wrong: so our homework task was to implement our own version of a stack by extending vector. This is what I got: import java.util.Vector; class Stack<T> extends Vector<T> {     private Vector<T> stack;       // returns false or true, given the stack is empty or not.     public boolean isEmpty() {         return stack.size() == 0;     }      //returns the top element of the stack without removing it.     public T peek() {         return stack.get(stack.size()-1);     }      //puts a new element to the top of the stack     public void push(T element) {         stack.add(element);     }      //returns and removes the top element of the stack     public T pop() {         return stack.remove(stack.size()-1);     } }  Then our second task was to find a way to implement a calculator that uses this stack. Here, I got this: public class CalculatorImpl {     //creating a new Integer Stack called calc     private Stack<Integer> calc;      //create a new calculator (Stack)     CalculatorImpl(){         calc = new Stack<>();     }      //sets the given integer     public void set(int num){         calc.push(num);     }      // adds the given integer     public void add(int num){         calc.push(num);     }      //subtracts the given integer.     public void subtract(int num){         calc.push(-num);     }      //multiplies by the given integer     public void multiply(int num){         int prev = calc.pop();         calc.push(prev*num);     }      //clears what is entered previously     public void clear(){         calc.pop();     }      //divides by the given integer (integer division!)     public void divide(int num){         int prev = calc.pop();         calc.push(prev/num);     }      //computes and returns the result of the expression.     public int compute(){         int out = 0;         while (!calc.isEmpty()){             out += calc.pop();         }         return out;      }  }  It looks fine so far but as soon as I try to run the main method, a null pointer exception is thrown and I dont know why. This is the main method:  class CalculatorApplication {         public static void main(String[] args) {             CalculatorImpl calculator = new CalculatorImpl();             calculator.set(4);             calculator.add(2);             calculator.multiply(4);             // 4 + 2 * 4 = 12             System.out.println(calculator.compute());                  calculator.set(2);             calculator.subtract(6);             calculator.add(7);             calculator.multiply(3);             calculator.divide(2);             calculator.add(5);             // 2 - 6 + 7 * 3 / 2 + 5 = 11             System.out.println(calculator.compute());              }     }  The error message is: Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.util.Vector.add(Object)" because "this.stack" is null     at Stack.push(Stack.java:20)     at CalculatorImpl.set(CalculatorImpl.java:12)     at CalculatorApplication.main(Calculator.java:4)  Does anybody have an idea what I am doing wrong? Thanks for your tips!

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?


On OS X 10.11 El Capitan, I am trying to add a word to the Kotoeri lookup dictionary. It is a name that does not come up when you type the Hiragana. The way to do it pre-10.10 no longer works. How can I add the word?

I am trying to figure out how to add new words to the Japanese dictionary.   Specifically, my problem is, name of one of my friends is Manaka, spelled  愛可 (yes, that's 可愛い in reverse).  Problem is, if I type in まなか and try find an appropriate kanji substitute, the only one that I find is 愛花 (and yes, I've tried looking at the general kanji selection, by the reading, by radical,  names, etc).  Currently I type her name in by typing in あいか, which is annoying.  Is there a way to teach the hiragana input, that when I type in まなか I want to see 愛可 as one of the options presented to me?  MacOS X 10.7, MBP 13", English UI with Hiragana input added.


I tried to use vertical align in another div. I know that if you want to vertical align you must at least have an image and span in one div. but what if I want to use it when my image and h4 in a different div? Is there any way to use it like that?  this is my example code (I'm using bootstrap for row and col):

             “Education is the most powerful weapon which you can use to change             the world.”

             Nelson Mandela

             Ex president of south africa

    this is my css code:  #paham-quotes{     font-family: 'Nunito', sans-serif;     max-width: 1200px;     margin: 0% auto;     border: none; }  #paham-quotes .quotes-img > img{     text-align: center;     width: 250px;     height: auto; }  #paham-quotes .quotes-caption{     color: #1D3962;     text-align: left;     display: inline-block;     vertical-align: middle;     padding-right: 100px; }  #paham-quotes .quotes-caption h4{     font-size: 1.4em;     font-style: italic; }    can someone help me solved this? Some of topic that I read is pointing in the same div like this:

I have a div with two images and an h1. All of them need to be vertically aligned within the div, next to each other. One of the images needs to be absolute positioned within the div. What is the CSS needed for this to work on all common browsers?

testing...


X and Y are random variables. So $E[X|Y]$ is conditioned on a random variable.  Do we always have:    $$E[E[X|Y]^2] = E[X|Y]^2.$$   I have the doubt because I know that $E[X|Y]$ is a random variable and not a number in this case.  Thanks in advance

I am trying to simplify $E[YE[Y|X]|X]$ can I use this property:   $$E[E[Y|X]|X]= E[Y|X]$$  If yes I have never seen a Proof of this property (that seems very reasonable), could I have a reference? If I am right the correct result would be $$E[YE[Y|X]|X] = E[(Y|X)]^2$$


I use nginx as proxy-server apache2 and I have a problem with netstat output:  $ netstat -ntu | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n    5 109.195.36.169   6 109.195.33.205   8 194.190.59.4  14 83.246.143.75  19 109.195.33.201 725 127.0.0.1   Part of output: netstat -nt   tcp        0      0 127.0.0.1:59703         127.0.0.1:8080          TIME_WAIT tcp        0      0 127.0.0.1:11211         127.0.0.1:45684         ESTABLISHED tcp        0      0 127.0.0.1:45848         127.0.0.1:11211         ESTABLISHED tcp        1      0 127.0.0.1:8080          127.0.0.1:59867         CLOSE_WAIT   How to remove these localhost connections? Or this is normal behavior? I suspect that my site have DDOS-atack.

This is a  about Server Security - Responding to Breach Events (Hacking)   See Also:                  Canonical Version I suspect that one or more of my servers is compromised by a hacker, virus, or other mechanism:   What are my first steps? When I arrive on site should I disconnect the server, preserve "evidence", are there other initial considerations? How do I go about getting services back online? How do I prevent the same thing from happening immediately again? Are there best practices or methodologies for learning from this incident? If I wanted to put a Incident Response Plan together, where would I start? Should this be part of my Disaster Recovery or Business Continuity Planning?   Original Version       2011.01.02 - I'm on my way into work at 9.30 p.m. on a Sunday because our server has been compromised somehow and was resulting in a    attack on our provider. The servers access to the Internet   has been shut down which means over 5-600 of our clients sites are now   down. Now this could be an FTP hack, or some weakness in code   somewhere. I'm not sure till I get there.      How can I track this down quickly? We're in for a whole lot of   litigation if I don't get the server back up ASAP. Any help is   appreciated. We are running Open SUSE 11.0.            2011.01.03 - Thanks to everyone for your help. Luckily I WASN'T the only person responsible for this server, just the nearest. We managed   to resolve this problem, although it may not apply to many others in a   different situation. I'll detail what we did.      We unplugged the server from the net. It was performing (attempting to   perform) a Denial Of Service attack on another server in Indonesia,   and the guilty party was also based there.      We firstly tried to identify where on the server this was coming from,   considering we have over 500 sites on the server, we expected to be   moonlighting for some time. However, with SSH access still, we ran a   command to find all files edited or created in the time the attacks   started. Luckily, the offending file was created over the winter   holidays which meant that not many other files were created on the   server at that time.      We were then able to identify the offending file which was inside the   uploaded images folder within a  website.      After a short cigarette break we concluded that, due to the files   location, it must have been uploaded via a file upload facility that   was inadequetly secured. After some googling, we found that there was   a security vulnerability that allowed files to be uploaded, within the   ZenCart admin panel, for a picture for a record company. (The section   that it never really even used), posting this form just uploaded any   file, it did not check the extension of the file, and didn't even   check to see if the user was logged in.      This meant that any files could be uploaded, including a PHP file for   the attack. We secured the vulnerability with ZenCart on the infected   site, and removed the offending files.      The job was done, and I was home for 2 a.m.            The Moral   - Always apply security patches for ZenCart, or any other CMS system for that matter. As when security updates are released, the whole   world is made aware of the vulnerability.   - Always do backups, and backup your backups.   - Employ or arrange for someone that will be there in times like these. To prevent anyone from relying on a panicy post on Server   Fault.


I am learning Java internals and this can be a naive question. I understood the concept of garbage collection in Java that JVM decides when to perform garbage collection but we can only REQUEST JVM by using System.gc() . So my question is that if System.gc() does not force the garbage collection then what is the importance of the command? What exactly we can achieve by this call? What are the considerations while supporting System.gc() call? Essentially the question is why Java provide System.gc() call?

I know that garbage collection is automated in Java. But I understood that if you call System.gc() in your code that the JVM may or may not decide to perform garbage collection at that point. How does this work precisely? On what basis/parameters exactly does the JVM decide to do (or not do) a GC when it sees System.gc()?  Are there any examples in which case it's a good idea to put this in your code?


If I wanted to know the opinions of people about the quality of service in the context of  hotels/banks/restaurants, what should I use: "think of" or "think about"?  According to my Google search:     What do you think about the service?   is more common than:     What do you think of the service?   At first I thought "think of" is more fitting because that is how I used to ask about people's opinions, but now I am not sure anymore!  Does it matter when you ask people about the service in general, and when you ask them about an instance of the service, I mean, a particular occasion?   Have a look at "" from Cambridge's Dictionary   to have a good opinion of someone or something:      She thinks very highly of her boss.   This one is related too

Could someone help me to understand when I should use think of and when think about in sentences?  What is the difference between using one or the other?


Is it possible to keep putty 'alive' while im rebooting my remote computer? Of course with logging in again.  Means: I'm connected to my remote host via putty. I reboot the remote host via commandline and now I usually have to start putty again.   I've already ticked 'Enable TCP keepalives' and set 'Sending of null packets' to 600.

After a small hiccup in internet connection, any open PuTTY windows throw up a message box saying there was a connection error.  Is there a way to automate retry attempts?  Or better yet, tell it to watch the status of the network and reconnect when internet access is reestablished?  I know there's the "stackoverflow" solution of writing a program that invokes PuTTY using its command line interface using -load and -pw.  But I'm looking for a "superuser" solution because that seems like less work.  Should I look into Tunnelier instead?  Background: I'm using an SSH tunnel with port forwarding to get remote access to a database on BlueHost.


I'm  trying to disable the validation of a method of one class. I've seen the annotation @SkipValidation but it doesn't work.  I tried to put the following interceptor-ref to my action but it doesn't work either. <interceptor-ref name="validation">     <param name="excludeMethods">ricerca,execute</param> </interceptor-ref>  I need to remove the validation of a Date field of this class.

I'm developing web project in struts2 and I want validation in my own customized validation by disabling the struts2 validation, because if one field is being sent back it will check all fields but I want to check only at the time of submit.


Can anybody explain why the 'clock rule' has been designed the way it is?  I mean, why is it that the polarity is North pole, if current flows in the anticlockwise sense as viewed from above and vice-versa.   What is the reason behind assigning the different fingers in Fleming's left or right hand rule? Why do we assign the thumb to the motion of conductor, the finger for the magnetic field and the middle finger for current?

How do you derive ? What is the theoretical explanation for the directions of the magnetic field, current and the force on the current for being oriented in that way relative to one another?


When referring to the regions in England, do we refer to them as the "South of England" or the "south of England"? Same with "South" and "south" - is it capital (or not capital) when using this noun to refer to the regions in the UK? Regions meaning: London, South West and South East etc. Also, for the "North-South" divide, is that also capitalised or not? Thanks.

Should cardinal points be capitalised? Please give a reason why they should or should not.


I used the following template for my CV :. I can build it on Overleaf, but not with Textworks. I've specified to use Xelatex as compiler.  This is the output that I get with Textworks:  ! LaTeX3 Error: Command '\FA' already defined!  For immediate help type H <return>.       ...                                                    l.166 \newfontfamily                         \headerfont[     ? H      You have used \NewDocumentCommand with a command that already has a     definition.      The existing definition of '\FA' will not be altered.      ?    And here is the log file : . Can someone help me? Thanks for the help,  Warok

I am trying to use the AwesomeCV template () for creating a CV using TexMaker 5.0.3 with XeLaTex. However, I am not able to get this to work as I get the following error messages:    Does anyone know what the source of problem might be and how to solve it?  Thanks a lot in advance,  Cheers


I know how to check if a package is installed and if its available for install but I cannot find any list of packages that are installed with a release from Ubuntu.  Sometimes I am trying to answer something and I cannot remember if the tool I will refer was installed by default of if I installed in a later point and cant remember. What if its something I have and a user using another desktop environment does not?  I know I can recommend to install the package prior to asking him to use it but I would like to know if its installed by default or not.  Is there such list? Where can I find it?

I am developing an offline installer for all versions of Ubuntu, and I need Ubuntu's default installed packages list. Is there a way to get this information from any server (web server)? Any script to fetch any Ubuntu version's default installed packages list.  I will give the Ubuntu version, and the script will fetch the packages list.  Note: I need at least a server address. I can write a script for this.


I have an array of arrays, something like this:  Array ( [0] => Array     (         [0] => DC1F180E-FE57-622C-28AE-8194843B4D84         [1] => First Choice         [2] => 1     )  [1] => Array     (         [0] => EB877F3C-7A3B-98A7-9240-580FB797030A         [1] => Second Choice         [2] => 0     )  [2] => Array     (         [0] => D3C0EA56-73D2-C7E3-8236-EEA2400DFA9C         [1] => Third Choice         [2] => 0     )  )   How do I can rename all the keys in "nested" arrays to get something like this in all "nested" arrays:  ... [1] => Array     (         [id] => EB877F3C-7A3B-98A7-9240-580FB797030A         [name] => Second Choice         [status] => 0     ) ...

Is there a way to change all the numeric keys to "Name" without looping through the array (so a php function)? [     0 => 'blabla',     1 => 'blabla',     2 => 'blblll',     // etc ... ]


The context would be in a romantic pursuit or a job opportunity - you've applied for the job and are waiting to hear back from them - you're constantly checking your emails, you're calling the receptionist to ask why they haven't got back to you (way to spoil your chances), etc.   Is there a word or phrase to describe this state.   Example usage might be a friend saying:      I think you're [over focusing] on this opportunity here. Maybe it'll all work out well - but in the meantime you should divert your attention somewhere else.

I want to describe a situation in which someone gets interested in something/someone to such extent that he forgets other activities and normal life, and just cares and thinks about the beloved activity/person. This is the sentence in which I want to use this word:     I devoted myself to this/her/him so (the word) that ... .   One word that comes to my mind is to use the adjective form of ascetic. But I'm not sure it's the best or even a correct choice.


Difference between connection.close and connection.dispose using Asp.net Connection String ? for ex:  Globals.dr.Dispose();  Globals.dr.Close();

Having read the threads  and  I am wondering for classes such as SqlConnection or one of the several classes inheriting from the Stream class does it matter if I close Dispose rather than Close?


Let $h, k, l$ be three co-prime integers. Can we always find a set of integers $n_1, n_2, n_3$ such that $n_1 h + n_2 k + n_3 l = 1$ ?  Thanks.

Given $a_1, a_2, a_3, \ldots , a_n$ not all zero, show $\gcd(a_1, a_2, a_3, \ldots , a_n)$ is the least positive integer that can be expressed in the form $a_1x_1+a_2x_2+ \ldots +a_nx_n$. Also deduce $a_1x_1+a_2x_2+ \ldots +a_nx_n = b$ has solutions $\iff \gcd(a_1, a_2, a_3, \ldots , a_n)|b$.   I know that $ax+by=n$ has integer solutions $\iff \gcd(a,b)|n$. I'll need to use induction to show $a_1x_1+a_2x_2+ \ldots +a_nx_n = \gcd(a_1, a_2, a_3, \ldots , a_n)$ has solutions, and then I will be able to say that as $\gcd(a_1, a_2, a_3, \ldots , a_n) | a_1x_1+a_2x_2+ \ldots +a_nx_n $ for any $x_1,x_2, x_3 \ldots x_n$ then $c \leq \gcd(a_1, a_2, a_3, \ldots , a_n)$ and $c \geq \gcd(a_1, a_2, a_3, \ldots , a_n)$, and thus $c=\gcd(a_1, a_2, a_3, \ldots , a_n)$.


I want to use the coreference resolution from Stanford NLP. I have downloaded the latest version 3.6.But when I run the following code, I am getting NullPointerException. I looked up in net, and few people seem to have to experienced the same problem, but no solution is mentioned. Any help would be appreciated.  public static void main(String[] args) {   Properties props = new Properties();   props.put("annotators", "tokenize, ssplit, pos, lemma, ner, parse, dcoref");   props.put("dcoref.score", true);   StanfordCoreNLP pipeline = new StanfordCoreNLP(props);   String sentence="Stanford University is located in California. It is a great university, founded in 1891.";   Annotation document = new Annotation(sentence);    pipeline.annotate(document);   System.out.println(document);   Map<Integer, CorefChain> graph = document.get(CorefChainAnnotation.class);   Set<Integer> set=graph.keySet();   Iterator <Integer> it=set.iterator();   while(it.hasNext()) {     CorefChain c=graph.get(it.next());     System.out.println("CorefChain: "+c);   } }

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


I have a strange behaviour I cannot explain: the scrollbar for my page is not around the tag "main" as expected when I put the line <!DOCTYPE html> at the beginning of my code. If I remove this first line, I have the expected behavior. Why is that? What is my mistake here?    <!DOCTYPE html>          <meta charset="UTF-8">     <meta name="viewport" content="initial-scale=1.0">     <title>Off Track</title>                             bla bla
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                         NB : I also have the expected behavior if I replace height:calc(100% - 70px) by height:calc(100vh - 70px), but I want to avoid using vh.

As the title describes, what are the different doctypes available and what do they mean? I notice that the layout looks a little different in IE7 when I switch from   <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >   to  <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">   Are there any others and what are the effects or ramifications?  Thanks!


I have an 64bits windows 8.1 pc with UEFI and I am not able to dual boot the latest version of Ubuntu 64 bits on it, it says that it doesn't support EFI. Need help pls, and I don't want to change UEFI for traditional bios

I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu?


I'm having trouble proving that  is non planar, I think that I have to look for a subdivision of the graph $K_{3,3}$ using Kuratowski's theorem, can someone give me any tips to find this?

I've been trying to find out if this graph is planar or not for a while and have really been coming up short when it comes to creating a planar drawing of the graph. My intuition is telling me that it's non-planar, but I cannot find any subgraph of the graph homeomorphic to K3, 3 (by Kuratowski's Theorem). Any help would be greatly appreciated. The graph can be seen below:


After a longer period of time, I went to visit one of my sites, tasmamiandevilz and a security alert popped up. Never happened to me before, so I did some Googling.. and apparently the sso.anbtr.com is quite common.  The issue is, that all the information I was able to find was on how to remove it from my PC.  The issue is, I am pretty sure it's not a problem of my PC, but rather the website itself. This is the only website where I get the error and I don't seem to have any other symptoms.   Is it possible that the malware would be directly on my site ? How can I get rid of it ?  Thanks.

My website is under attack by malware. How can I remove it and prevent its recurrence?


I wanted to make sweet potato fries but it was very disappointing and not crunchy at all. I put the first batch in a medium-heat oil and left them for a while, they got out all soggy. I turned up the heat for the second batch, it got a bit better but still way below my crunch expectations. I even tried to put the first batch back in the hot oil, remembering that good Belgian potato fries should go in the oil twice, but I just managed to burn them. Do you know what I did wrong? Is it because of an excess of humidity? They were pretty dry already when I put them in the oil. I've read that they should be coated in flour before, does that work? I don't see how it would stick well to the sweet potatoes, aren't them too dry for that?

I bought a roto deep fryer recently. But everytime I make yam fries, they end up being soggy.   My process: I cut the sweet potato fries to about 1/4 inch. I follow deep fryer instructions of preheating to 370'F before dropping the basket. From there, I fry a full basket for about 12-14 minutes.  The yam fries always come out soggy.  Any suggestions to improve the process?


<div>  <lightning-button-icon icon-name="utility:attach" type="file"></lightning-button-icon>    <lightning-input  onchange={insertFiles} type="file"></lightning-input>  </div>     How do I replace the upload files in the image with attach utility icon,which invokes the same JavaScript function?

How can I change the colors of lightning-button?  I tried doing this in my css:  .my-button {     background-color: #14a6bc;     color: #ffffff; }   and applying that class to my <lightning-button> and removing the variant but I still get the base colors? I am trying to use these examples:


Again, I am using Ubuntu 13.10  These are the index files that failed to download:   W: Failed to fetch http://ppa.launchpad.net/ubuntu-x-swat/x-updates/ubuntu/dists/saucy/main/binary-amd64/Packages  404  Not Found  W: Failed to fetch http://ppa.launchpad.net/ubuntu-x-swat/x-updates/ubuntu/dists/saucy/main/binary-i386/Packages  404  Not Found  E: Some index files failed to download. They have been ignored, or old ones used instead.   How can this be fixed?

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


Installing ubuntu on my windows 10 laptop, do my files and programs stay, or do I need to reinstall all my programs


I am using the new Photos App (Yosemite). Everything is synchronised (iCloud) but the faces.  Is this a feature or a bug?

The new Photos updates for iOS 10 and MacOS Sierra includes a much more powerful and integrated approach to organizing photos by who's in them.  It's built around powerful, on-device facial recognition.  But once it does its automated thing (finding the faces it thinks are the same person), there's still a lot of manual merging and labeling to be done if you have a lot of photos and are as obsessive about organization as I am.  For example, if you have, say... three thousand photos of your daughter, Photos will find almost all of them, but may guess they're 5 or 6 different people.  So you have to merge the buckets that all are one person, assign them a name (so you can search by it), etc.  But unlike other changes (edits, deletions, organization into albums, etc.), manual changes to "people" data don't seem to sync at all by default.      Is there really no way to do this?  It seems bizarre that one of the flagship features Apple's touting in this Photos update doesn't play at all with what was Photos primary selling point over iPhoto - everything synced on all your devices.


I am experiencing 502 Bad Gateway errors after deploying a python flask application using dokku on digital ocean. I followed  to deploy my app on digital ocean using dokku.  2018/10/23 07:40:59 [error] 28652#28652: *1 connect() failed (111: Connection refused) while connecting to upstream, client: xxx.xxx.xxx.xx, server: api.domain.com, request: "GET / HTTP/1.1", upstream: "http://172.17.0.3:5000/", host: "api.domain.com"   Here is proof that the app is up and listening for requests:  2018-10-23T07:37:30.165794640Z app[web.1]: [2018-10-23 07:37:30 +0000] [9] [INFO] Listening at: http://127.0.0.1:8000 (9)   My question is how configure proxy_pass in a python flask dokku application.

This is a  about Connection Refused    We see a lot of questions to the effect      When I try to connect to a system I get a message      Connection refused      Why is this ?


I have a doubt about the difference between those two questions.  Could you guys give me an appropriate examples and explanation?  Thanks in advance!

Non-native speakers often get confused about what the various tenses  and aspects mean in English. With input from some of the folk here I've put together a diagram that I hope will provide some clarity on the matter.  I offer it as the first answer to this question. Consider it a living document. Input is welcome, and good suggestions will be  incorporated into the diagram.    Nota bene: What this is not is a discussion of whether there are  more than two tenses in English. , to which this question is not intended to supply arguments one way or the other.  Here, the aim is to provide an overview of what constructions English-speaking people use for conveying information about actions referring to past, present, and future, and to provide it first and foremost to precisely the people who are likely to use "tense" as a catch-all term in their search, rather than to linguists who know better.  Breaking News There is now an excellent ELU blog article titled  . It is highly recommended reading.