Since a , I see more than I should:    I see no reason to see 134 posts are awaiting review, when there is literally nothing I can do about them. I think it is a bug, because notification is meant as something that will make me act. When I know I usually can't, obviously I will start to ignore it.  If it's not a bug, please remove bug tag and explain how it is supposed to be useful, or how can I switch to only seeing notifications about things I can act on.  Note that apaprently there are no flags for me, neither. I see only stats, migrated, close, delete, there, as if there was no flags waiting:    If you expect us to click on it every few minutes  just to see personalized numbers next to queues, why don't you simply query for personalized numbers every few minutes and cache them for us? It should cost you similar, in database usage, and will save us a lot of clicking and frustration.  If all this number means is "there might be reviews, or not" or "for sure there are none"  it would be simpler just to hide "review" link in the second case. We don't need two links with the same function next to each other, thank you, one is enough, and meaningless numbers are only irritating.

I am under the impression that increased participation in the review queue is, on the whole a good thing.  It encourages people to feel an ownership in the community and partially responsible for the site as a whole.  On Programmers.SE, I've seen what I believe to be an uptick in flagging to close (non-audits with no votes in the close queue).  I believe that to be a good thing as it indicates to me that there are at least a few on P.SE who may some day become more active participants in the site.  On the other hand, I don't often see too many new names in the "recent reviews" page.  There are often new names scattered about on close votes of recent questions which suggests to me there is a population of 3+k users who don't review, but do close recent questions.  While the close queue at P.SE is completely different than the one at SO (we start wondering about it in chat when it hits 20 and occasionally motivate people to help smash the queue back to 0), I was wondering if there wasn't something that could be done to help direct everyone possible to review (or at least be aware of it - there was a comment at one point of a 10k user who wasn't aware of anything in the /review link after clicking it as a new user and not seeing anything in it that could be done by him).  The suggestion  Next to the review link display the number of reviews that user is capable of doing at this time, akin to the way the 10k banner looks when there are flags or edits outstanding.  Many people perceive numbers as "there is something here that needs my attention".  Inbox size, alerts on mobile device apps, notifications, etc...  Using this it would be possible to point people to the review part of the application and help them become a more active participant in the site and the community as a whole.  This number would be:  min(first post queue size, first post audits doable) + min(late answer queue size, late answer audits doable) + ...    There seems to be some confusion about what this would be and what the numbers on it would be.  I have used my considerable art skills (sorry, no pie) to make a mockup of what this would look like based on the current snapshot of what I see on P.SE    "Wait," you say... "why is that a 20?  Shouldn't it be 24?"  Nope.  Because on P.SE I can only do 20 close vote reviews a day (smaller queue or something of that nature).  If you hit it with someone who hasn't reviewed most of the queue, you'll actually see that its 60.  And still the answer should be 20.  And so, min(60,20) + min(0,20) + min(0,20) + min(0,20) + min(0,20) (those are the other queues there too) is 20.  And that's the number that should be shown.  This should be something that you can get to 0 every day.  Making it something that is an unmanageable number makes it something people will ignore, and that's not what this is suggesting.


I was asked in an interview why String is immutable  I answered like this:     When we create a string in java like String s1="hello"; then an   object will be created in string pool(hello) and s1 will be   pointing to hello.Now if again we do String s2="hello"; then   another object will not be created but s2 will point to hello   because JVM will first check if the same object is present in   string pool or not.If not present then only a new one is created else not.   Now if suppose java allows string mutable then if we change s1 to hello world then s2 value will also be hello world so java String is immutable.  Can any body please tell me if my answer is right or wrong?

Does string immutability work by statement, or by strings within a statement?   For example, I understand that the following code will allocate two strings on the heap.  string s = "hello "; s += "world!";   "hello" will remain on the heap until garbage collected; and s now references "hello world!" on the heap. However, how many strings does the following line allocate on the heap...1 or 2? Also, is there a tool/way to verify the results?  string s = "goodbye " + "cruel world!";


Prove that if A is a square matrix then A and A transpose have same Eigen values.  Kindly help me how to prove this by generally not considering matrix by ourselves.

Let $ \sigma(A)$ be the set of all eigenvalues of $A$. Show that $ \sigma(A) = \sigma\left(A^T\right)$ where $A^T$ is the transpose matrix of $A$.


I would like to thank you for taking the time to read this.  My problem: I tried to install Ubuntu 12.04.4 LTS on a system in my Lab but after the installation when I restarted the system it booted straight to Windows. I restarted it many times but I did not get a boot option to load Ubuntu. During the installation I do remember the installer showing that it was installing GRUB so I want to know how I can boot to Ubuntu.  The system I used has Windows 7 Enterprise edition. I created 100 GB partition (/dev/sda6) and a 5GB swap partition (/dev/sda7) before installing Ubuntu in the 100 GB partition. I chose /dev/sda for boot loader installation. Before installation I noticed that there already was a 26 GB ext4 partition so I am guessing that someone had previously tried installing Linux on this system. Anyway I needed more space so I carried out my installation in the 100GB partition.  I have tried all different boot orders possible in the BIOS, I have tried re-formatting and re-installing Ubuntu but it still boots into Windows directly. In windows, System and security → System → Advanced system settings → Advanced → Startup & Recovery → Settings:  lists Windows 7 as the default OS and doesn't give me a choice to select Ubuntu in the drop down menu.  I have tried the recommended repair in boot-repair but it gives me an error:  Boot repair: Please open a terminal and type this: sudo chroot "/mnt/boot-sav/sda6" dpkg --configure -a sudo chroot "/mnt/boot-sav/sda6" apt-get install -fy sudo chroot "/mnt/boot-sav/sda6" apt-get purge -y --force-yes grub* shim-signed   I type them but nothing seems to happen. Then when I click the forward button I get this message:     GRUB is still present. Please try again.   I have used Boot-repair to make a    Please tell me how to proceed.   Thanks.

I am a new user of Ubuntu 12.04.   I installed Ubuntu and Windows XP, and I want to use both operating systems. When I restart or boot my PC the GRUB menu does not appear.  How can I solve this problem?


Hi, does anybody can help to recognize the font of this file. Please pay attention to "g"s. If it is typewritten, which font is nowadays similar to that in Office word? Thanks.

Is it possible to identify the font used in a specific document/picture?  Answers to this question should identify:   Possible methods to do this (perhaps one answer per method) and adequately describe how to use it (as opposed to merely stating it); Ways of finding the identified fonts, if possible (free or not); and Any prerequisites associated with the method used, if required (for example, "In order to use method X, your document has to be in format Y").   This question is meant as an FAQ, based on an . Its aim is to facilitate the community with the general procedures involved in font identification. Similar cases are solved on a per-usage basis on 's  tag.


Let $a,b,c$ be three positive real numbers such that $a+b+c = 6$. Prove that $a^2+b^2+c^2 \geq 12$.  I tried using the AM-GM inequality to solve the same, however I wasn't able to make any considerable progress.

Knowing that for any set of real numbers $x,y,z$, such that $x+y+z = 1$ the inequality $x^2+y^2+z^2 \ge \frac{1}{3}$ holds.   I spent a lot of time trying to solve this and, having consulted some books, I came to this:  $$2x^2+2y^2+2z^2 \ge 2xy + 2xz + 2yz$$ $$2xy+2yz+2xz = 1-(x^2+y^2+z^2) $$ $$2x^2+2y^2+2z^2 \ge 1 - x^2 -y^2 - z^2 $$ $$x^2+y^2+z^2 \ge \frac{1}{3}$$ But this method is very unintuitive to me and I don't think this is the best way to solve this. Any remarks and hints will be most appreciated.


By mistake and lack of knowledge I tried to change the current user to root privilege by typing the command I useradd -m -G root user3 Now I am  neither able to access this user as a root user nor a sudo user. When I type sudo apt-get update, I get the response user is not in the sudoers file. and when I try to run apt-get update , I get a permission denied response P.S: I am running my ubuntu in a mac mini

I clean-installed Ubuntu 11.10 today, and then installed VirtualBox.  This required me to add myself to the vboxusers group, and since 11.10 seems to no longer have a graphical app to add users to a group, I ran the following command:  sudo usermod -G vboxusers stephane   This is a problem.  I now see what I should have run instead is:  sudo usermod -aG vboxusers stephane   The end result is I'm no longer in the groups I should be in.  Including whatever group is required to run "sudo".  When I run any command as sudo now, I get the following:  $ sudo ls [sudo] password for stephane:  stephane is not in the sudoers file.  This incident will be reported.   Is there a way to fix this, or do I need to re-install from scratch again?


The wifi stopped working, so I plugged in a ethernet cable, and lshw -C network shows both adapters as unclaimed. I have tried a few things suggestions found google that didn't work, before trying to reinstall Ubuntu 20.04.2.0 LTS. I'm writing this from the same computer now logged into windows, so there's nothing wrong with the hardware, both wifi and ethernet are shown in windows. The clean install still did not have any network connection on the first boot (or during install). I'm on the 2nd boot attempt and I now HAVE wifi, but the ethernet is still unclaimed. I have an Asus TUF 550 motherboard with wifi. It seems a few people have had this . This has happened a few times to me since installing Ubuntu 20.04 on this desktop, but not with my dell inspiron 2016. sudo lshw -C network [sudo] password for bryan:    *-network                         description: Wireless interface        product: Wi-Fi 6 AX200        vendor: Intel Corporation        physical id: 0        bus info: pci@0000:05:00.0        logical name: wlp5s0        version: 1a        serial: 14:f6:d8:7f:b8:45        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress msix bus_master cap_list ethernet physical wireless        configuration: broadcast=yes driver=iwlwifi driverversion=5.8.0-43-generic firmware=55.d9698065.0 cc-a0-55.ucode latency=0 link=no multicast=yes wireless=IEEE 802.11        resources: irq:34 memory:fc600000-fc603fff   *-network UNCLAIMED        description: Ethernet controller        product: RTL8125 2.5GbE Controller        vendor: Realtek Semiconductor Co., Ltd.        physical id: 0        bus info: pci@0000:06:00.0        version: 04        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress msix vpd cap_list        configuration: latency=0        resources: ioport:f000(size=256) memory:fc500000-fc50ffff memory:fc510000-fc513fff

So I did a fresh install of Ubuntu 20.04 on a computer with the new RTL8125B Realtek network card and I cannot get the network to work. I was very suprised since this is supposed to be the new feature of the 5.4 kernel (I have 5.4.0-26-generic installed). Does anyone have any idea on how to get it working? Thank you. $ lspci -knn | grep Eth -A3 06:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 04) Subsystem: ASUSTeK Computer Inc. RTL8125 2.5GbE Controller [1043:87d7] Kernel modules: r8169 07:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Ellesmere [Radeon RX 470/480/570/570X/580/580X/590] [1002:67df] (rev e7)  $ dmesg | grep -i r8169 [    0.911236] r8169 0000:06:00.0: unknown chip XID 641


I have 3 conference papers which were published around 7 years ago. However, the conference proceedings are not well indexed. If I upload a 7 year old published work on arXiv to increase the audiences, will the research community take this action positively or negatively?

In my field (I am a condensed-matter theoretical physicist) it is such a normal thing to put papers on the arXiv, that people sometimes look at other people's arXiv list of papers instead of their publication record to get to know what they do, etc.  It just so happens that a few years ago I did a PhD with a supervisor that does not like the arXiv that much (he apparently had some conflict with some authors of a paper that was very similar to one of his papers, but one was already published while the other was just an arXiv preprint -or something like that). As a result, from my list of less than 20 publications, there are four of them from my PhD that are missing on the arXiv.  I was thinking of submitting the latest versions I have of them as arXiv preprints now, four years after their publication. For this I already have the agreement of all co-authors (including my supervisor), and all the journals involved seem to allow to put preprints of the material they publish. Do you see any problem with this? I fear that some people might take it as a way to advertise as new something that was already published a long time ago (though I would of course give the full reference to the published version). There may be other issues I am not aware of. The reason why I would like to do this is that I am applying for fellowships, positions, etc. and I am afraid some of my (best) publications may go unnoticed if somebody looks me up on the arXiv.  Thank you, Stephen


Find an explicit formula for the number of partitions of a positive integer $k$ into parts no larger than $2$?    I was thinking about it and worked on it, I've come up with $1^k+2^k= 3^n$.

Since last week I have been working on a way, how to sum $1$ and $2$ to have $133$.  So for instance we can have $133$ $1s$ or $61$ $s$2 and one and so on. Looking back to the example: if we sum: $1 + 1... + 1 = 133$ there is only one way. But for the second one there will be $131$ possible ways. And I have to do this for every possible combination. I am stuck with it and I have no idea whatsoever on how to begin.  Any ideas or methods I could use guys?


I'm trying to make a raster from an LAS dataset. I want to only use points classified as ground, but I can't figure out how to do this. What I've tried is:   Create LAS dataset from 2 .las files.  Filter dataset on ground using LAS Dataset to raster tool.  Pick the dataset and use linear interpolation on average cell assignment type.   The result is a raster with all points including non-ground points.  When I'm in the LAS Dataset to raster tool I'm choosing an external file that doesn't get affected from what I've done in the LAS Dataset toolbar. How do I make the filter affect the dataset before turning it into a raster?

I am trying to create a Digital Earth Model (DEM) using ArcPy under ArcGIS Pro 2, but I am running into some problems.   I can generate a DEM within ArcGIS Pro by selecting only the ground points under LAS files in the LAS dataset properties, but when I try to run the same code within ArcPy, it generates a DEM using all the points.   Any ideas how you select the return point type in ArcPy?   Here is the code that I have used.  arcpy.conversion.LasDatasetToRaster(lasd, "Test_arcpy_dem", "ELEVATION", "BINNING AVERAGE LINEAR", "FLOAT", "CELLSIZE", 10, 1)   As I said, this generates two different outputs, depending if I am in ArcGIS Pro or not.


I went there in order to meet her VS. I went there to meet her.  Could be any difference? I think my question should be more specific. 'in' is a preposition and 'order' is a noun. I know 'in' but 'order' has many meanings. What does the 'order' here mean as a noun? I see some people explain on this site 'in the intention to to do something', then the 'order's meaning is 'intention' but I couldn't find the meaning in any ordinary dictionaries.

Is it always possible to just use 'to' instead of 'in order to'?  What is actually the additional information provided by 'in order to'?  I understand in order to as meaning that the aforementioned action comes first (in order) and thus enables the subsequently mentioned action.  So we have the order: 1st action allows 2nd action.  But isn't this always the case, even when using 'to' in order to describe a following action that requires the aforementioned action?  I find it quite difficult to explain what I mean, particularly because I do not know what clauses that begin with 'in order to' are called. Cause/reason clauses, or something like that?


I can see/predict some developer-oriented sites starting to use StackOverflow as their forum, instead of maintaining their own forum. I think it would be beneficial to both parties.  They can integrate Stack Overflow content in their site with tag-specific RSS feeds, and direct people to SO to ask questions.  To link people to ask questions, they can just link to stackoverflow.com/questions/ask. But it would be even more beneficial if they could prefill tags with their site moniker, e.g stackoverflow.com/questions/ask?tags=php,mysql,mysite.com.  Is this something worth considering? (both the feature of prefilling tags, and the wider context of use as a plugin to another site) Has there been previous discussion about this? Would SO find this beneficial? Or is it a bad idea and SO is mostly interested in "direct" traffic and not serving third-party sites?

We'd like to encourage people to ask questions on Stack Overflow. For this, we'd like to have on our site a link to the Stack Overflow , but we'd like to have the "tag" field pre-filled with a tag that would then help us find the questions. Is this possible?  Use case:   I work on an open source web forms product (Orbeon Forms), which implements the W3C XForms technology. On the web site for Orbeon Forms, we'd like to encourage people to ask XForms questions on Stack Overflow. As suggested by others here, this could be done by having somewhere on our site some HTML as follows: Have questions about XForms? Ask them on Stack Overflow.


Let $(u_n)$ be a sequence of positive harmonic functions on a region $\Omega$. If $u_n(z_0)\to 0$ for some $z_0\in\Omega$, then how does the sequence $(u_n)$ behave on all of $\Omega$? My guess is that the sequence uniformly converges to zero on compact subsets of the region but I am not sure how to work this out. Any help will be appreciated.

Let $D \subset \mathbb{C}$ be an open, connected set and let $\{ u_n \}$ be a sequence of harmonic functions with $u_n: D \longrightarrow (0, \infty)$. Show that if $u_n(z_0) \rightarrow 0$ for some $z_0 \in D$, then $u_n \rightarrow 0$ uniformly on compact subsets of $D$.  If you could offer a hint or a helpful question to get me started I'd appreciate it.   Progress: I now see why showing it for the unit disk suffices (any compact subset in $D$ can be covered by finitely many disks each which is contained in $D$).


Background: A close acquaintance of mine is a tenured faculty member at a minor US college, having worked there for several decades. They are very well respected for their contributions to the college, students, and community, but they really haven't played a research role. This individual isn't the best when it comes to navigating the perils of the Internet, which brings us to the scenario and question...  Scenario: For both fiscal and, I suppose, for personal reasons, they want to submit a paper to the  conference. I think that submitting a few papers may change their title and pay grade, which would help them before moving towards retirement within the next decade, as their family has some financial issues.  Question: Is this a legitimate conference, and what risks of participating? It appears on librarian  of potentially predatory conferences. However, from my inspection, it seems to be established, but perhaps low quality. I cross-referenced a couple of their past speakers and the talks do indeed appear on actual people's CV's.  So, to reiterate, my acquaintance is not a researcher, per se, nor desires to be known as one. With that in mind, what are the pros and cons of submitting a paper and giving a talk? I mainly want to protect my friend from harm.

I recently received an invitation to a conference and I'm trying to determine how reputable it is. Is there a good way to go about this?


I'm looking to download "Android 5 Lollipop" for my Samsung Galaxy S4 i9505. I want the official "thing". My questions are...   Where can I download this? Any methods of installation? Do I need to erase ALL data from my phone? Any other things i should know?

Android 5.0 (Lollipop) was officially announced on October 15th, 2014.  You can review the high-level changes at the  and the announcement on the official .  Of course, not all devices will get this update right away and others won't get it at all. Each manufacturer and carrier often choose to add their custom modifications which tend to delay the official release.  When will each device get Android 5.0, either officially or unofficially, if ever?  See also:


While just playing around with Windows’ features, I did the following:  Right clicked on an image. Clicked on "Open with…" Chose Notepad  And the following appeared:  I did this with many programs and documents, and for all of them, this weird language appeared. And in fact, for all programs and documents which are not Notepad docs, this language appears. What is this? Is it just random or there is something in it? Is there a name of this language and if it is a sort of programming language, can a human understand this? I am almost sure that this isn't coded by the Microsoft programmers.

Why don't you see binary code when you open a binary file with text editor? For example, when I open an image with text editor, I see some weird characters and also some human readable characters; but the image should be encoded in binary.


a little background as it might be the cause to the problem. I'm running Armbian legacy Jessie on a Orange Pi Zero. It does not include an desktop so I've installed X, lightdm and xfce. I havn't managed to start X on boot so I have a @reboot line in crontab that executes a script that includes this:  #!/bin/bash while ! ping -c 1 -W 1 192.168.1.100; do     sleep 1 done /usr/bin/startx   everything works perfectly (I have autologin enabled and it starts the Mumble client on 1:0). I then have a python script that monitors my GPIO (a push to talk button) and send "CTRL + 1" if the button is pressed. Mumble is listening to that combination and starts broadcasting when it is pressed.  I must run run my python script as root to be able to access the GPIO so I have added these lines to /etc/profile (so that root can access X):  export DISPLAY=:1.0 export XAUTHORITY=/home/icuser/.Xauthority   As said this works perfectly when executed with sudo:  sudo python /home/icuser/sendptt_zero.py   but when I execute my script with (@reboot in crontab):  sudo /usr/bin/python /home/icuser/sendptt_zero.py >> /home/hallgren/ic.log 2>&1 &   I get this in my ic.log file (when I press the gpio button that starts the emulate keybord key function in python (I'm using )):  No protocol specified Could not open main display   My python script also has this line (won't work without it):  os.environ['DISPLAY'] = ':1.0'   Any ideas on how to get it to start X automatically and why it works from command line with sudo but not when started from crontab?

Once upon a time,  DISPLAY=:0.0 totem /path/to/movie.avi   after ssh 'ing into my desktop from my laptop would cause totem to play movie.avi on my desktop.  Now it gives the error:   No protocol specified Cannot open display:    I reinstalled Debian squeeze when it went stable on both computers, and I guess I broke the config.   I've googled on this, and cannot for the life of me figure out what I'm supposed to be doing.   (VLC has an HTTP interface that works, but it isn't as convenient as ssh.)  The same problem arises when I try to run this from a cron job.


got me curious:  Like you start with 500 stars. The first one leaves you with 499, the second with 497, the third with 494...  Is this already in place? Does it mean I can use only 500 stars then can't star anymore? If the above isn't true, what are the limits? Thank, and happying starring!

I noticed that I can only perform certain actions such as commenting a finite number of times in a given period of time. Obviously, rate limiting is in place to prevent accidental misuse or intentional abuse of certain features.  Where else is rate limiting applied on Stack Exchange sites, and what are the limits?


May be this is a wrong place to question this. But, please allow me to ask at least. We have some photography event in our office. So, we have mentioned the rule of date capture (like photo must be captured in between start and end date of event). But, I have seen people trying to cheat like downloading it from Internet and saving back in their Smartphones or Photoshop/Edit their details.   So, is there any way I can tell whether the image is original, or if any type of editing has been done via any image processing tools or techniques?

How can I tell if a photo has been edited or manipulated? Are there techniques for distinguishing real photos from fakes?  Are there software tools that can help? Are there things I can do in Photoshop or other imaging software which will help reveal the truth?


I would like to understand the need for ServerName in apache.  Lets say that I have a web site with IP 12.13.14.15.  In DNS zone I call it example.com and refer the Ip to it with an A record.  Why isn't this enough? It tells the www that whenever anyone writes example.com, it needs to go to 12.13.14.15 ip.  So why do I need to set it also in apache with NameServer attribute?

It's the following part of a virtual host config that I need further clarification on:  <VirtualHost *:80>   # Admin email, Server Name (domain name), and any aliases   ServerAdmin example@example.com   ServerName  141.29.495.999   ServerAlias example.com ...   This is and example config, similar to what I currently have (I don't have a domain name at the moment).  <VirtualHost *:80> - Allow the following settings for all HTTP requests made on port 80 to IPs that this server can be contacted on. For instance, if the server could be accessed on more than one IP, you could restrict this directive to just one instead of both.  ServerName - If the host part of the HTTP request matches this name, then allow the request. Normally this would be a domain name that maps to an IP, but in this case the HTTP request host must match this IP.  ServerAlias - Alternate names accepted by the server.  The confusing part for me is, in the above scenario, if I set ServerAlias mytestname.com and then made an HTTP request to mytestname.com, there would have to be a DNS record pointing to the server's IP for this to work? In which case, is ServerAlias just basically EXTRA ServerName entries?  Say I had a DNS entry such that foobar.com = 141.29.495.999 but then I had ServerName = 141.29.495.999 and ServerAlias was empty, would that mean that although foobar.com gets resolved to the right IP, because there is no reference to accept foobar.com in ServerName or ServerAlias?  Or something. Man I'm confused.


How to go to another page using only html and css. I have tried with  window.location.href="admin.html";   This statement not working.  <input type="text" value="Username" name="username" />
 <input type="text" value="Password" name="password" />
 <input type="button" value="Password" name="password" value="Log In" onClick="login()" />

How can I redirect the user from one page to another using jQuery or pure JavaScript?


Recently I've been seeing the following error while trying to send emails to some domains:  Final-Recipient: name@example.com Original-Recipient: name@example.com Action: failed Status: 5.0.0 Remote-MTA: dns; mail.example.com Diagnostic-Code: smtp; 550 "The mail server detected your message as spam and     has prevented delivery."   Neither my IP address nor my domain is blacklisted. The email is a simple test email without attachments or links.  What can I do or where can I get more information about this issue?  Thank you

This is a  about avoiding outgoing mail being classified as spam.   Also related:                    I'm wondering how to prevent my emails from my site being marked as spam? I'm using sendmail.  I'm trying to send emails through my ruby-on-rails application. The mails are all written in swedish (if that does make a difference?). I don't know why they keep getting marked as spam.  Are there any things that I can do to minimize the risk?


I'm trying to understand the behavior of $\sum_{n=1}^\infty \frac{1}{n} z^{n!}$ on the unit circle.  Since for each $m$th root of unity $\zeta_m$ $$\sum_{n=1}^\infty \frac{1}{n} \zeta_m^{n!} = C + \sum_{n=m}^\infty \frac{1}{n} = \infty$$ holds for some $C \in \mathbb{C}$, the series diverges for all $e^{\varphi \pi i}$ with $\varphi \in \mathbb{Q}$.  But what happens for $\varphi \in \mathbb{R} \setminus \mathbb{Q}$?   Does the series diverge everywhere, or are there points where it is convergent?

I recall from complex analysis a while ago that the series $$\sum_{n=1}^\infty \frac{z^{n!}}{n}$$ has radius of convergence 1, diverges on roots of unity, and converges elsewhere on the circle. It's simple enough to see that it has to diverge on roots of unity: consider $z$ such that $z^k = 1$ for some $k \in \mathbb{N}.$ Plug this into the series and you see that past the $k$'th term, $z^{n!} = (z^k)^m = 1$ for some $m \in \mathbb{N}$; hence, the series becomes harmonic and must diverge.  But I don't recall how to show that the series converges for other values on the circle. If this is simple I'd like just a hint, if it is involved I would prefer a sparse outline of the proof. Thank you!


Free Vectors graphics are really popular these days... the thing is that there are a bunch of site with lot of graphics which you don't know if you can trust. I've seen a lot of stolen and pirate stuff from paid microstock in those free sites. My question is which are the most trusted/reliable sites out there.  Thanks a lot!

Is there a free library of vector graphics for commercial use?


I am plotting a simple linear function. The plot looks fine, but I want to extend the function up to x=7. Anyone knows, please how to do that?  My code is the following:  \usepackage{tikz} %for drawings \usetikzlibrary{shapes} \usetikzlibrary{arrows} \usetikzlibrary{calc} \usepackage{pgfplots} \usepackage{tkz-fct} %for functions   \begin{figure}%[H] \centering                                              \begin{tikzpicture}     \begin{axis}[width=400pt,axis x line=center, axis y line=center, ylabel={$n$},xlabel={$x$},xmin=-2,xmax=8,ymin=-2,ymax=8]         \addplot+[mark=yes] (\x,{5-0.8*\x});         \end{axis} \end{tikzpicture} \caption{Effect of the parameter $n$ on the particle nodes scaling} \label{fn1} \end{figure}

Why does pgfplots plot functions only until x = 5 and y = 5, but not any further?    \documentclass{article}  \usepackage{tikz} \usepackage{pgfplots}  %%%< \usepackage[active,tightpage]{preview} \PreviewEnvironment{tikzpicture} \setlength\PreviewBorder{5pt} %%%>  \begin{document} \begin{tikzpicture} \begin{axis}[samples=100,ymin=0,ymax=10,xmin=0,xmax=20]  \addplot [thick] plot  (\x,  {1/(1 + exp(-0.6*(\x - 12)))}); \addplot plot (\x, {\x});  \end{axis} \end{tikzpicture} \end{document}


I want to find count of elements in an array which have the following two conditions:   1 <= i < j <= n a[i] > a[j]   Im using the following code but i need a faster one any advice?  for(int i=0; i<n; i++){     for (int j=i+1; j<n; ++j){         if (a[j] < a[i])             ans++;     } }

I'm designing an algorithm to do the following: Given array A[1... n], for every i < j, find all inversion pairs such that A[i] > A[j]. I'm using merge sort and copying array A to array B and then comparing the two arrays, but I'm having a difficult time seeing how I can use this to find the number of inversions. Any hints or help would be greatly appreciated.


I'm reading Dummit's book. (Abstract Algebra, 3ed, p224) Now I want to prove the following. Suppose $R$ is a ring with 1. Then, $|R|=1$($R$ is a trivial ring, [or the zero ring in the book]) if and only if $1=0$. $(\Rightarrow)$ : Since $0\in R$, $1\in R$ and $|R|=1$, it is immediate that $1=0$. $(\Leftarrow)$ : Suppose that $a\in R$. Then $a=a\cdot1=a\cdot0\stackrel{(*)}=0$. Thus $R=\{0\}$. But how can I justify $(*)$? Does that follow immediately from the definition of a ring with unity? Or, is there another proof for $(\Leftarrow)$?

In a ring, I was trying to prove that for all $a$, $a0 = 0$.  But I found that this depended on a lemma, that is, for all $a$ and $b$, $a(-b) = -ab = (-a)b$.  I am wondering how to prove these directly from the definition of a ring.  Many thanks!


I've been writing a simple JFrame program to solve basic math equations, the program takes 5 values, up to two of which may be null, identifies the correct equation and calculates the null values. This section of code below takes the 5 values in a hashmap, identified by a string (V,U,S,A,T), identifies which ones are null and adds them to a seperate array  (nullvalues), which is then iterated through (nullValueLoop) to identify a suitable equation and solve the unknown.  The problem arises in nullValueLoop, it only appears to iterate once, stopping abruptly after the first iteration.   I've added a lot of system.out's while trying to debug this, and have included the console output to hopefully show whats going on. The exception called is from another class (as the program continues) attempting to call the second null value and finding it to be null.  Hopefully i've explained this well, any help is much appreciated.      public void calculate() {      // Stores the keys to reference the null values in HashMap<Double> values;     ArrayList<String> nullvalues = new ArrayList<String>();       for(String tempKey : values.keySet()){         if(values.get(tempKey)==null){             nullvalues.add(tempKey);             System.out.print("Found null value " + tempKey + ", adding to array. \n");         }     }      System.out.print("Beginning loop of nullvalues, of size " + nullvalues.size() + "\n");      nullValueLoop:     for(String nullvalue : nullvalues){            System.out.print("Starting outerloop, iterating nullvalue " + nullvalue + "\n");          EquationLoop:         for(Equation e : registeredEquations){              // Flag to keep ` of if we have any unknowns yet             boolean foundUnknown = false;              // Iterate through the values required             // If the loop does not exit, the equation only requires one of our null values and the program continues.             for(String s : e.getRequiredChars()){                  // If we have a null value and havent yet had one, all is good                 if(nullvalues.contains(s) && foundUnknown == false){                     foundUnknown = true;                  // We have more than one null value, abort                 } else if(foundUnknown == true && nullvalues.contains(s)){                     continue EquationLoop;                 }             }               System.out.print("Using equation " + e.getIdentifier() + "\n");              System.out.print("Found suitable equation.\n");              Double returnValue = e.calculate(values, nullvalue);              System.out.print("Calculated return value.\n");              values.put(nullvalue, returnValue);              nullvalues.remove(nullvalue);              System.out.print("Added new value to values array\n");             System.out.print("Calculated value  " + nullvalue + " to " + values.get(nullvalue) + "\n");             break EquationLoop;         }         System.out.print("Ending outerloop iteration \n");     }     mainWindow.updateTextBoxes();  }   Console output:  Couldn't load value T | Assigning to null  Couldn't load value A | Assigning to null  Found null value T, adding to array.  Found null value A, adding to array.  Beginning loop of nullvalues, of size 2 Starting outerloop, iterating nullvalue T Using equation 3 Found suitable equation. Calculated return value. Added new value to values array Calculated value  T to 10.0 Ending outerloop iteration  Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at uk.co.ElliotPurvis.MainWindow.updateTextBoxes(MainWindow.java:143) at uk.co.ElliotPurvis.Main.calculate(Main.java:136) at uk.co.ElliotPurvis.MainWindow.actionPerformed(MainWindow.java:118) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018) Process finished with exit code 0

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 function that looks like this:  def test(in1):    if in2 = 151:     print('error')     if in2 == 1:     in1 = 14     print(in1)   The function currently takes in a string value,   I was thinking:  if in2 == 'one':    in2 = 14   But that doesn't work for some reason  Thanks

I need to convert one into 1, two into 2 and so on.  Is there a way to do this with a library or a class or anything?


For deuterium, both the proton and neutron preferentially occupy $1s_{1/2}$ orbitals which have orbital angular momentum $l=0$ and spin $s=1/2$. By coupling their orbital and spin angular momenta for a new conserved quantum value $j$, one gets a spin of $1/2$ for each particle. j-j coupling then leads to either a $I=1$ or $I=0$ total nuclear spin corresponding to symmetric and anti-symmetric spin states respectively. Since the the spatial wavefunctions for the s orbitals are each of even parity, their coupled wavefunctions would be expected to be of even parity as well. So, exchanging each of the nucleons would spatially symmetric. It is theorized that deuterium represents an anti-isymmetric isospin state. Thus the total wavefunction would be anti-symmetric in the spin one state which apparently is the only bound state for deuterium. The total wavefunction being symmetric in the spin 0 state would violate spin-statistics theorem.  It is also known that even-even nuclei have protons that pair with protons and neutrons that pair with neutrons. These pairings involve identical particles and coupling their identical spatial wavefunctions would lead to even parity and hence be spatially symmetric under exchange. Isospin being symmetric, their combined spins would need to be anti-symmetric to avoid violating spin statistics. Which is why these nuclei have total spin $I=0$.  If one were to set aside isospin considerations, the proton and neutron in the deuterium are distinct particles (their masses are not the same), so their angular momentum can be coupled to a spin one or a spin zero state without violating spin-statistics. It appears that the spin one (parallel spins) state is energetically more favorable and in fact is the only bound state, with singlet state unbounded and dissociated. However, with even-even nuclei, the pairings involve identical particles so the energetically more favorable spin one state is blocked by the Pauli exclusion principle.  So my question is there a way to explain without invoking the concept of isospin, why neutron-neutron and proton-proton pairings in even-even nuclei have anti-symmetric spins whereas the deuterium nucleons pair up with symmetric spins.

A deuterium nucleus is composed of a proton and a neutron. Both have spin $\tfrac12$ so I would expect the deuterium to have two possible spins: $1$ for the triplet and $0$ for the singlet. But apparently deuterium always has spin $1$ and the spin $0$ state doesn't exist. Why?


Assuming, below is the input list which has exp_date and qty field as blank/spaces/null. input_lst = [ {  "id": "123456",  "product": "XYZ",  "exp_date": "",  "amount": "30.5",  "qty": "1" }, {  "id": "789012",  "product": "ABC",  "exp_date": "04/15/2020",  "amount": "22.57",  "qty": "3" }, {  "id": "56789",  "product": "AAA",  "exp_date": "03/29/2020",  "amount": "2",  "qty": " " } ]  Can we write if/then/else like below - what is the correct/appropriate syntax ? output_lst = []  for dct in input_lst:     tmp_dct = dct.copy()     try:     #replace/default any blank/null/space values and convert to datetime         tmp_dct['exp_date'] = datetime.strptime(if dct['exp_date'] == "" then '01/01/1900' else dct['exp_date'], '%m/%d/%Y')     except:         pass     #replace/default any blank/null/space values and convert to int     try:         tmp_dct['qty'] = int(if dct['qty'] == '' then '1' else dct['qty'])     except:     output_lst.append(tmp_dct) print(output_lst)  Thanks!

If Python does not have a ternary conditional operator, is it possible to simulate one using other language constructs?


GCC 4.8 can't compile following code:  struct A {   struct Impl;   void f(); };  struct A::Impl {   static int stat; };  void A::f(){   A::Impl::stat=1; }  int main(int argc, char** argv) { return 0; }   and raise error:     cppbug.cpp:(.text+0xa): undefined reference to `A::Impl::stat'   collect2: error: ld returned 1 exit status   but similar inline declaraton compiled as well:  struct A {   struct Impl {     static int stat;   };    void f(){     A::Impl::stat=1;   } };  int main(int argc, char** argv) { return 0; }

Can anyone explain why following code won't compile? At least on g++ 4.2.4.  And more interesting, why it will compile when I cast MEMBER to int?  #include <vector>  class Foo {   public:       static const int MEMBER = 1;   };  int main(){       vector<int> v;       v.push_back( Foo::MEMBER );       // undefined reference to `Foo::MEMBER'     v.push_back( (int) Foo::MEMBER ); // OK       return 0; }


I have met a question when using cd command in a script. here is the test below, so, could anyone help to tell the reason?  why does not "/bin/sh  cd /root/eos/" work ,but "/bin/sh -c ls &&  cd /root/eos/" works well in centos thanks.   [root@izbp16eo65uiwii1mfm63tz eos]# pwd /root/testeosnode/CryptoKylin-Testnet/docker/eos [root@izbp16eo65uiwii1mfm63tz eos]# /bin/sh  cd /root/eos/ [root@izbp16eo65uiwii1mfm63tz eos]# pwd /root/testeosnode/CryptoKylin-Testnet/docker/eos [root@izbp16eo65uiwii1mfm63tz eos]# /bin/sh -c ls &&  cd /root/eos/ build.log  build.sh  Dockerfile  eos [root@izbp16eo65uiwii1mfm63tz eos]# pwd /root/eos    env CentOS Linux release 7.5.1804 (Core) [root@izbp16eo65uiwii1mfm63tz eos]# ls -l /bin/sh lrwxrwxrwx 1 root root 4 10oct  9 18:00 /bin/sh -> bash

I'm trying to write a shell script that, when run, will set some environment variables that will stay set in the caller's shell.  setenv FOO foo   in csh/tcsh, or  export FOO=foo   in sh/bash only set it during the script's execution.  I already know that   source myscript   will run the commands of the script rather than launching a new shell, and that can result in setting the "caller's" environment.  But here's the rub:  I want this script to be callable from either bash or csh.  In other words, I want users of either shell to be able to run my script and have their shell's environment changed.  So 'source' won't work for me, since a user running csh can't source a bash script, and a user running bash can't source a csh script.  Is there any reasonable solution that doesn't involve having to write and maintain TWO versions on the script?


Suppose we consider the space of $\lbrace 0,1 \rbrace^{256}$ as the domain and SHA-256 as our hash function.  Does SHA-256 become a one way permutation?    Has anyone tried to prove this? Or can it be shown that SHA-256 has more than one cycle under the given constraints?

It's been said that .  It the corresponding statement true for typical cryptographic hashes, like MD5, SHA-1, SHA-2 or SHA-3?  For example, would SHA-512 be bijective when hashing a single 512 bit block?


I have an older trek 8500 aluminum bike with rigid forks and I would like to change them to be suspension forks. Is this possible? Btw the tire size is 26".

I have a ~1993 Giant mountain bike.  It's not great, but I am a very new and casual rider.    The bike has a solid fork and it makes for the predictable rough trail ride.  The trails are generally fairly modest (I live in North Texas, a 100' change in altitude makes our ears pop here) and the surface is generally dirt (very few rocky areas).  So, I am thinking that it would be very nice to have a suspension bike.  And seeing that a modest fork can be purchased for a modest price, I am wondering if it makes sense to add a fork to this bike.   asked about going the other direction, and there were some cautionary words about changing steering geometry.  So, on balance, is this something that I would be best off to avoid?  I suspect that if I have to replace a bunch of steering parts, the cost will quickly approach that of a new low end bike.


How do I remove punctuation from a string in python? I followed the approach that someone posted on Stackoverflow, but it is not working.   punctuation = ['(', ')', '?', ':', ':', ',', '.', '!', '/', '"', "'"]  str = input("Hi, my name is Yael Shapiro!")  for i in punctuation:     str = str.replace(i,"")  print(str)

It seems like there should be a simpler way than:  import string s = "string. With. Punctuation?" # Sample string  out = s.translate(string.maketrans("",""), string.punctuation)   Is there?


I have a problem with my bitnami wordpress hosted on Google cloud. I have both the www and the non-www version running in parallel. I want to have all the non-www traffic 301 to the www version.  I added these lines into the conf file:      RewriteEngine On     RewriteCond %{HTTPS} !=on     RewriteRule ^/(.*) https://example.com/$1 [L,R=301]   But it does not fix the issue. Anyone has a solution?

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


I have a number of small icons all of which fit into a 32x32 pixel png with transparent backgrounds.   I wish to create a single large png which contains each of these icons in a 10x10 grid. I create a new image in PS which is 320x320px, and set a grid with 32px spacing, then turn on snap to grid.  I then open one of my icon files, select all, copy, then paste into the large image. The problem is that when PS snaps the image to the grid, it snaps the non-transparent pixels and ignores the transparent pixels around the edge of the icon.   Is there a way to paste the icons in so that PS will snap the 32x32 icon into the 32x32 grid instead of snapping the non-transparent pixels?

TLDR: When I use the marquee tool to select a box around layer and then move it with the move tool, the selection box shrinks to surround the populated region of the layer. Is there a way to keep the selection box's dimensions, instead of it shrinking on move?  Here's my situation: I have a uniform spritesheet made up of 30+ layers. I need to adjust different sprites in the sheet to different areas, but because the movement isn't uniform I need to do it sprite-by-sprite, layer-by-layer. I would save hours if I could just select a region and move the objects inside the region layer-by-layer, but because moving a selection with transparency shrinks the selection region to the populated areas, I have to reselect every time I switch layers. Any way to avoid the selection box shrinkage?


Can having too many noindex pages hurt ranking?  Eg: 50,000 low quality noindex forum posts with 1,000 indexed quality posts.   Can those 50,000 low quality noindex forum posts affect for 1,000 indexed quality postsranking?

Some SEO Gurus assured me that noindex attributes are good to devalue the unimportant pages.   When I asked in the moz Q and A, they're quite sure that having noindex on the bulk of the articles on the website can harm overall SEO ranking.   Which is true?


So I just got into Linux (or more specifically into Ubuntu) last week. I really like the ability to customize everything, so I got ahead and started to mod my OS a bit. I really wanted a terminal built in my nautilus file explorer. The only option that really worked was from launchpad.  Only each time I try sudo apt update I get this error message:  E: Failed to fetch http://ppa.launchpad.net/flozz/flozz/ubuntu/dists/eoan/main/binary-amd64/Packages  404  Not Found [IP: 2001:67c:1560:8008::15 80] E: Failed to fetch http://ppa.launchpad.net/flozz/nautilus-terminal/ubuntu/dists/eoan/main/binary-i386/Packages  404  Not Found [IP: 2001:67c:1560:8008::15 80] W: Some index files failed to download. They have been ignored, or old ones used instead.   I tried to add a [trusted=yes] in the /etc/apt/sources.list.d files belonging to the packages which cause the problem.  I tried uninstalling the nautilus terminal, and reinstalled it according to the instructions on git-hub but it did not resolve the issue.  What shall I do?

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?


I am stuck with the following problem :     If $a,b,c$ are positive and not all equal then prove that    $$\,\,(a+\frac1a)^2+(b+\frac1b)^2+(c+\frac1c)^2 \geq 33\frac13,$$ when $a+b+c=1$.   Try: $\,\,(a+\frac1a)^2+(b+\frac1b)^2+(c+\frac1c)^2  \implies a^2+b^2+c^2+\dfrac{1}{ a^2}+\dfrac{1}{ b^2}+\dfrac{1}{ c^2}+6$ and then I did few more steps but could not come up with the result.  I will be grateful if someone explains it. Thanks in advance for your time.


I heard that every SSD have a lifespan, so considering Flash Storage on Macbook devices is actually a SSD that is integrated with the logicboard, does it mean when my MBP flash drive reaches its lifespan, my mac will completely unusable? Unless I'm willing to spend a lot of money to buy a logic board replacement?

Like all tools, an SSD will wear out from use and eventually fail. Are there data on roughly how long the SSD's that Apple ships in it's portable line last?   From my research, it seems that the  that comes on Apple MacBook Pros is much slower than the others on the market, but might this have an advantage in terms of longevity?  Basically, is Apple SSD durability longer than third party drives like Crucial, OWC, or others?


I have a VPS hosting with public IP and custom domain. I am sending email from the server, but the email is recognized as spam by google. I want to add and SPF domain record. I could follow the documentation, but I could restrict it a bit more.  I use only one email address noreply@example.com. Should I add SPF record for that only one address? Or the entire domain?

This is a  about setting up .     I have an office with many computers that share a single external ip (I'm unsure if the address is static or dynamic). Each computer connects to our mail server via IMAP using outlook. Email is sent and received by those computers, and some users send and receive email on their mobile phones as well.  I am using  to generate an SPF record and I'm unsure about some of the fields in the wizard, specifically:   Enter any other domains who may send or relay mail for this domain Enter any IP addresses in CIDR format for netblocks that originate or relay mail for this domain Enter any other hosts which can send or relay mail for this domain How stringent should SPF-aware MTA's treat this?   the first few questions i'm fairly certain about... hope i have given enough info.


For some time now when I click Open with from Windows Explorer's context menu I'm getting this error     This file does not have a program   associated with it to perform this   action. Create an association in the   Set Associations control panel.   instead of the standard Choose Default Program dialog. I'm getting this error no matter what the extension of the selected file is (as long as there's Open with option for given extension; some extensions do not show this option). How can I fix this?

//As a comment, I want to say that I can actually open the context, but it does not work .  I right click on a file and hover the mouse on Open With option, then in the Open With context Menu, I want to choose default program for that file, it shows me an error saying:  This file does not have a program associated with it for performing this action, please install a program or if, one is already installed create an association in the Default programs control panel.  But I don't want to create an association in control panel every time i want to change the default program, I just want to do it by right-clicking on a file and fr


While working in command prompt, I accidentally typed following command:  sudo apt-get install python3-   and ubuntu started removing python3 and everything that depends on it (including Firefox and much more). Fortunately I closed that terminal immediately and reverted everything by checking dpkg log file, but I was wondering why an install command should act like remove?   Is it a bug?   Consider the situation that you are looking for a package name (pressing Tab twice) and going through possibilities by pressing Enter key and those Enter keys remain in the keyboard buffer and.... youhaaaa... apt-get is removing the entire installation in front of your eyes.

I was looking for some package (nautilus-terminal), and accidentally did this:  $ sudo apt-get install nautilus- Reading package lists... Done                                                                                Building dependency tree                                                                                Reading state information... Done                                                                                The following packages were automatically installed and are no longer required:                                                                                apturl apturl-common libgail-3-0 linux-headers-4.4.0-57 linux-headers-4.4.0-57-generic linux-image-4.4.0-57-generic linux-image-extra-4.4.0-57-generic                                                                       Use 'sudo apt autoremove' to remove them.                                                                                The following packages will be REMOVED:                                                                                gnome-session-flashback nautilus nautilus-sendto nautilus-share ubuntu-desktop                                                                                0 upgraded, 0 newly installed, 5 to remove and 69 not upgraded.                                                                                After this operation, 2 031 kB disk space will be freed.                                                                                Do you want to continue? [Y/n] ^[[^C                                                                                That's quite dangerous because remove is much harder to mistype than a simple dash from a failed autocompletion.     Is that an equivalent of apt-get remove? I couldn't find any documentation for that. Edit: except for overlooking the man page...


I am very new to python language a day old in python. I have to add append two jason string comma separated  {'10.10.10.1': {'msg1': 'hello1'} & {'10.10.10.2': {'msg2': 'hello2'} as {'10.10.10.1': {'msg1': 'hello1'},{'10.10.10.2': {'msg2': 'hello2'}  I know it's really very bad to ask such question.

I have two Python dictionaries, and I want to write a single expression that returns these two dictionaries, merged (i.e. taking the union).  The update() method would be what I need, if it returned its result instead of modifying a dictionary in-place. >>> x = {'a': 1, 'b': 2} >>> y = {'b': 10, 'c': 11} >>> z = x.update(y) >>> print(z) None >>> x {'a': 1, 'b': 10, 'c': 11}  How can I get that final merged dictionary in z, not x? (To be extra-clear, the last-one-wins conflict-handling of dict.update() is what I'm looking for as well.)


I have two program as shown below.  When i run both these program both working fine.  But the  the first code have a two string when I compare it gives result "ok".  the second code also have two string but this gives result "no".Why?  class Stringimp {        public static void main(String[] args) {        String str = "ali";       String s1="ali";       if (str == s1) {         System.out.println("ok");       } else {       System.out.println("no");     }  }   }   class Stringimp {         public static void main(String[] args) {         String str = "ali";        String s1="ALI";        s1=s1.toLowerCase();        if (str == s1) {            System.out.println("ok");        } else {            System.out.println("no");        }   }   }

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


I understand the binomial, geometric, Poisson, and normal distributions. However, I don't understand the usefulness or difference between the following: Gamma, exponential, and chi-squared. So far, it seems that certain populations just inherently have different properties and thus different distributions are used to deal with them. Given a new population how and why would one decide to use the Gamma, exponential, or chi-squared distributions? (I'm a beginner in statistics and am trying to wrap my head around the application of distributions)

As statisticians, we come across many distributions under the banners "discrete" or "continuous", and "univariate" or "multivariate". But can anyone provide a good reason behind the existence and motivation for so many distributions? How do we get them? And what can a layman understand from it?  What is the logic behind the existence of distributions?


What is the value of the series  $$\sum_{n=1}^{\infty} \frac{n}{2^{n}}?$$  It is neither geometric nor a telescopic series. How do we approach such kind of series, given that we know that they converge?

How can I evaluate $$\sum_{n=1}^\infty\frac{2n}{3^{n+1}}$$? I know the answer thanks to , but I'm more concerned with how I can derive that answer. It cites tests to prove that it is convergent, but my class has never learned these before. So I feel that there must be a simpler method.  In general, how can I evaluate $$\sum_{n=0}^\infty (n+1)x^n?$$


I have a layer of Brandenburg (Germany) in EPSG 25833 which I want to tranfrom to EPSG 4326. Similar to  to , I set the CRS to EPSG 4326 and go to export / save as to save this layer in 4326.  Now once I try to overlay this layer with a point shapefile of hospitals in Brandenburg taken from OSM (which is in EPSG 4326 by default) they do not match at all.  What am I missing?

I received several shapefiles from an colleague that he told me is in WGS:84. If I look at the metadata in Qgis it tells me the following:  In layer spatial reference system units xMin,yMin 3572722.82,5453423.31 : xMax,yMax 3582448.25,5462926.22 Layer Spatial Reference System +proj=longlat +datum=WGS84 +no_defs   Now when I try to save it in another projection say WGS:84 Pseudo Mercator (EPSG: 3857) it gives me the following:   Export to vector file failed.     Error: Failed to transform a point while drawing a feature with ID '1'. Writing stopped. (Exception: forward transform of     (62425.896446, 95242.109906)     PROJ.4: +proj=longlat +datum=WGS84 +no_defs +to +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs     Error: latitude or longitude exceeded limits)   A similar message is returned in R with the rgdal package. I suspect that the initial projection is somehow wrong.   Is it truly WGS84?   The problem occurs with all shapefiles.  ogrinfo -so    tells me:  INFO: Open of `XXX.shp'       using driver `ESRI Shapefile' successful. 1: XXXABC (Polygon)


I have a 4.2.1 android version phone. In internal storage there is 114 MB free space but I cannot download or update any app because I get an error saying "insufficient memory in internal storage". I tried all the first aid listed in this site but no gain :( .

Currently, my internal storage is running low on space.    What can I do besides moving applications to the external memory, as to free up more space, but preserve my current applications and avoid uninstalling?  (Some of them won't be moved)


For any real matrix $M$, let $\lambda^{+}(M)$ be the number of positive eigenvalues of $M$ counting multiplicities. Let $A$ be an $n\times n$ real symmetric matrix and $Q$ be an $n\times n$ real invertible matrix . Then which of the followings are correct?   (1) $rank(A)=rank(Q^{T}AQ)$  (2) $rank(A)=rank(Q^{-1}AQ)$  (3) $\lambda^{+}(A)=\lambda^{+}(Q^{T}AQ)$  (4) $\lambda^{+}(A)=\lambda^{+}(Q^{-1}AQ)$

For any real square matrix $M$ let $\lambda^+(M)$ be the number of positive eigenvalues of $M$ counting multiplicity. Let $A$ be an $n\times n$ real symmetric matrix and $Q$ be an $n\times n$ real invertible matrix. Then which are correct?   Rank $(A)$ = Rank $Q^TAQ$ Rank $(A)$ = Rank $Q^{-1}AQ$ $\lambda^+(A)$ = $\lambda^+(Q^TAQ)$ $\lambda^+(A)$ = $\lambda^+(Q^{-1}AQ)$   I can see 2 is correct but what about the rest?


$ ls 1.txt   2.txt   3.txt $ ls | wc        3       3      18   All three files has only 1 line, but ls|wc outputs '3'.

What does the command :  ls | wc -l   do? I know     wc <filename>   gives lines, words, and characters, and   wc -l <filename>    print the line count. But how it is being used with ls` is not clear. What does it do?


I have an ajax call to a vb function. The vb function fails because the dataTable the query alludes to TABLE_ONE does not exist in the database. I want the error message from the catch in vb to be returned to the 'error' of the ajax so that I can display that error to the user. The reason being that the error message in VB states precisely that the table does not exist in the database, whereas the error that is actually displayed to the user from here error: function (a, b, c) {             alert("Ajax call to multiAjax failed: " + a);         }  does not tell the user the error is due to a table that doesn't exist. The ajax error message is useless. How can I display the error message from the vb catch to the user? Thanks ajax: function multiAjax(funcName, queryName, onSuccess) {     var result = null;     $.ajax({         type: "POST",         url: "WebService1.asmx/" + funcName,         contentType: "application/json; charset=utf-8",         dataType: "json",         success: function (Response) {             onSuccess(Response)         },         data: JSON.stringify({ "queryName": queryName }),         error: function (a, b, c) {             alert("Ajax call to multiAjax failed: " + a);         }     }); }  VB <WebMethod(EnableSession:=True)>     Public Function getQueryNo()         Try             Dim queryNumberSql As String             Dim queryNo As Integer              Using dr As New DataReader(dif)                 queryNumberSql =                 "SELECT min(unused) AS unused             FROM (                  SELECT MIN(t1.QUERY_NUMBER)+1 as unused                  FROM TABLE_ONE AS t1                  WHERE NOT EXISTS (SELECT * FROM TABLE_ONE AS t2 WHERE t2.QUERY_NUMBER = t1.QUERY_NUMBER+1)                  UNION                  -- Special case for missing the first row                  SELECT 1                  FROM TABLE_ONE AS t1                  WHERE NOT EXISTS (SELECT * FROM TABLE_ONE WHERE QUERY_NUMBER = 1)             ) AS subquery"                  dr.ExecuteReader(queryNumberSql)                 While dr.Read()                     queryNo = Integer.Parse(dr("unused"))                 End While                  Return queryNo             End Using         Catch ex As Exception             Console.WriteLine($"Error trying to set query number: {ex}")             Return ex         End Try     End Function

Is there some way I can show custom exception messages as an alert in my jQuery AJAX error message?  For example, if I want to throw an exception on the server side via  by throw new ApplicationException("User name already exists");, I want to catch this message ('user name already exists') in the jQuery AJAX error message.  jQuery("#save").click(function () {   if (jQuery('#form').jVal()) {     jQuery.ajax({       type: "POST",       url: "saveuser.do",       dataType: "html",       data: "userId=" + encodeURIComponent(trim(document.forms[0].userId.value)),       success: function (response) {         jQuery("#usergrid").trigger("reloadGrid");         clear();         alert("Details saved successfully!!!");       },       error: function (xhr, ajaxOptions, thrownError) {         alert(xhr.status);         alert(thrownError);       }     });   } });   On the second alert, where I alert the thrown error, I am getting undefined and the status code is 500.  I am not sure where I am going wrong. What can I do to fix this problem?


Total noob here. I a trying to create a glossy screen print effect on a bottle I am designing. I am using principled BDSF for the bottle material, and I have a label texture bringing in a transparent PSD as the "label" that would be screen printed on. I would like the type in the label to be glossy, while the bottle texture (in blue) remains matte. Attaching my nodes setup here. I see a lot of content around how to do this with the Glass BDSF material in 2.8, but none for 2.9. Any ideas here would help. Thank you!

So I came across some difficulties with the "Mix shader" node in cycles. I have 3 textures on a label: gold, paper and rough black letters.  How can I mix these effects? I can make 2 textures work together, but not the 3rd one. Here's the node graph.  Here's the reference.


Let $(V, \| \ \|)$ be a Banach algebra. Given two elements $x,y\in V$ satisfying $xy=yx$, prove that $$ \lim_{n\to\infty}\|(x+y)^n\|^{1/n}\le\lim_{n\to\infty}\|x^n\|^{1/n}+\lim_{n\to\infty}\|y^n\|^{1/n} $$ I just do not know where to start. I want to use this inequality to prove a relationship between the spectrum of $x+y, x, y$.

I'm reading a book functional analysis, and reading and have seen an example of somebody please help me if you can. The example that I've seen is the following:   If $A$ is a normed algebra and $a,b\in A$ so that $ab=ba$, then $$v(a+b)\leq v(a)+v(b),$$ and $$v(ab)\leq v(a)v(b).$$  Remarks: Let $A$ is a normed algebra whith unit. For $x\in A$ number $$v(x)=\inf{\{\vert x^n \vert}^{1/n}: n\in\mathbb{N}\}$$ is spectral radius of element $x$.  Please help me. Thanks for your attention.


At work we have a GIS solution platform with 50+ GB of data in a Postgres cluster. Almost all tables have spatial columns. We have several clients consuming this information for different needs.   I'm looking for the best mobile solution for field data collection and visualization.  There is an old question about this, but since it is 4 years old, probably a lot of things had changed.   To summarize, the main requirements are: - Mobile app (Android mandatory, iOS non-mandatory) - Base maps (OSM, Google, Bing, etc) - View OGC mapping data (WMS, WFS, etc) - View forms with specific information of every layer  - Capable of adding new geometries (point, polygon, polyline) to a layer, and adding specific alphanumeric data using an associated dynamic form. This data can hit an WFS-T service - Work offline. That includes basemaps (like a local tile cache), and vector data - If some data was collected offline, it need to sync that data with the service/database  And in top of that, some clients have very specific requirements for their mobile apps. For instance, to some of them, the normal data collection app is enough, but maybe another client have a procedure in the field that requires special features. So, the possibility of development is really welcome, may be via an SDK or something similar.   What are the actual alternatives to accomplish this?

From my reading of the  the Collector for ArcGIS is tightly tied to that platform.  I would be delighted to learn that I am wrong about this.  I have a strong interest in generic mobile data collection apps for iOS and Android devices with GPSs.  Particularly ones that can collect data while out of coverage, and then sync when they get back in to coverage.  Ideally, they would also be able to cache portions of the data locally for use when off line.  What I envision is a web based application that allows one to specify your data layout, constraints, etc. and which will then generate the the backend database and allow access via a restful API.  What I need to do is enter data from a form on an mobile device, preferably both iOS and android, which will update tables in a backend database, potentially something with GIS extensions such as PostGIS.  That would enable me to easily incorporate the data into QGIS.  It must be able to work offline and many of the areas we work have not 3G coverage.  Ideally you would be able to also cache selected data on the device for offline use.  Map integrations is not important.  I have found some good cloud based solutions but I really want something where I have control of the back end data collection as some of the data is potentially sensitive.  e.g. reporting sighting of rare reptiles which are a smuggling threat.   What alternatives are the for mobile apps to get data into QGIS.


I need to show proof that r^2 is equal to R^2 given the defined r is the sample correlation between two vectors x and y.

It is often stated that the square of the sample correlation $r^2$ is equivalent to the $R^2$ coefficient of determination for simple linear regression. I have been unable to demonstrate this myself and would appreciate a full proof of this fact.


EDIT: I was offline for the last few hours, so I couldn't look at the other question of which this one here was a duplicate.  It is not a duplicate, because the linked question mentions Stack Exchange links explicitly. The problem I face has to do with the fact, that links in Stack Exchange mailings are not exactly what the Stack Exchange app would expect an Stack Exchange link to look like. I would not even call this a Stack Exchange link, since it doesn't lead to a site within the Stack Exchange network you would normally link to.  I guess they are some sort of click-tracker link, or something like that, but that's not the important part, here. Here's what one of the links looks like:  http://sg-links.stackoverflow.email/wf/click?upn=pDzA4vSaPmKy14MynsLvnZrGP7ewVN5UzFsPjLNsxf37lv5vH-2FL7YDbAQsAtLugYNp-2BJiZcu65iHCdCmWwcPykni0h3G-2BW3a5DJQvmvpqO5YYk0exrZkOZd357pJfsQtX23gZixSuNBvjUBdJW0S-2FYJxGOjASUTK1FgJWcFKhWk-3D_AOPg-2F-2BQL2BN1Z1adM2aHoJZemfJJPhUU1r33PmBub3XkdttNEsj9eAI3iXegmVDgNR1kPnNqBKQmCk2dsyn9uQ5g2T8fxWFcEgLgWVEljU9HeN8V3E9CiWFKeHBN3AsBll3Ol5ooWPcw1zAzDtJBxhi9y23WRvLODAGnxo8GjN2JvPOgbDchbKP4fGLU5bdnPtYYvcBBziE3leh3q-2FXLhm6oVzcczCqFM3tXWWWXJuY-3D   If this question is not attracting any more attention and doesn't loose the dupe tag, I guess I will have waited too long with my edit. In this case, I will delete it and submit a "new" question.    Yeah, so, the title says it. Because the links in the emails are not specifically from Stack Exchange, the app doesn't recognize it as something it's supposed to want to open and each link I tap in an email just opens my mobile browser.   App Version: 1.0.95 Device Manufacturer: Samsung Device Model: SM-A520F   OS Version: 8.0.0 (A520FXXU8CSC1)

I clicked on  to a comment in my email and it prompted a list of apps to open link. All browsers (Chrome, Firefox and etc) are in the list, but not SE app.  Most apps that can open site specific links get prompted for that app to open  the link, but not Stack Exchange links for some reason.    App Version: 1.0.95 Device Manufacturer: Asus Device Model: ASUS_Z010D   OS Version: 6.0.1 (WW_Phone-13.8.26.76-20161230)


On MacOS, El Capitan, any file I delete from Finder does not go to the Trash, it is deleted completely.  When I delete a file the warning message says "you are about to permanently delete the file".  So it seems as though, the Trash has been disabled - how do I renable it?  The Mac is a Mac Mini, Core i5, 8GB RAM and 500GB SSD.

When I want to delete a file in Finder or in the Desktop a popup appears and it says it will be deleted immediately, and I need to confirm.  The trash is always empty, and I can't use it anymore.   What's going on with Snow Leopard and not having a working trash can?


If I know that a hard disk has bad sectors, how can I "mark" them so that Windows 7 doesn't write to them when I copy files and stuff?

My SATA HDD (Hitachi DeskStar 7K160) seems to have 1 bad sector. Is it possible to try to fix it? I checked Hitachi's drive tools and all of them are diagnostic tools, so I don't know how much help they will be.  I can buy a new drive but first I really want to try to fix it since I don't want the hassle to setup Windows 7 & Ubuntu again (both are on this disk).


I am sure this is a common question, but to find it easily, what is significant about 1/125 and 1/30? My teacher asked us and I have no idea. I can not find it anywhere. Why are these shutter speeds so important?

Here are some common shutter speeds you will find on most DSLR cameras:   1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000   As you move from left to right, or as you increase the shutter speed, you are halving the amount of light that hits the sensor. In other words, you are decreasing the amount of light by one stop for each step. So 1/30 is half of 1/15, and 1/60 is half of 1/30. But then you come to 1/125, which is not half of 1/60. Half of 1/60 is 1/120. This is basic math.  So you break the sequence or pattern. But as you continue, it starts to make sense again. So 1/250 is in fact half of 1/125, and 1/500 is in fact half of 1/250, and 1/1000 is in fact half of 1/500, so on and so forth.  So there appear to be two distinct sequences here.   1/15, 1/30, 1/60 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000   Is there a sane reason for this?  I know that people sometimes talk about half stops or even thirds of a full stop. But then what is 1/125 the half stop, or third stop of? If you increase 1/60 by a third you get 1/180. This setting does not exist in the standard sequence. The closest you will get is 1/160. If you increase 1/60 by a half, you get 1/120 and it doesn't exist either.  Is this all arbitrarily set by the camera manufacturers, or is there perhaps some reason and history behind this?


I installed Lubuntu 16.04 by default because my computer system is old. I also want to try out unity in it. How should I do it? Thank you for helping me out.

I'm using Lubuntu for a while now, but found a couple of details that I wanted to view with Unity (that's another story).  Ok, the thing is: I've tried on a VM with Lubuntu to install Unity (sudo apt-get install unity) When the installation is over. I selected in the Lubuntu login Unity/Unity2D but did not work.  Right now I'm installing ubuntu-desktop, I am presuming that will work, but also it will change my login for example.  Is there a way to do a "clean" installation of Unity but not make major changes on my Lubuntu?  I would prefer Gnome-Shell instead of Unity.


I was trying to install Ubuntu 14.04 (dual boot with windows 7). But the installation failed due to a hard drive problem. Now in Windows disk manager there are three primary partitions. C belongs to Windows 7 and last 2 created during installation process. I want to delete the last 2 partitions. I want to know, if I delete them, will it affect the Windows boot loader?

I am dual-booting Windows 7 and Ubuntu, both installed on separate partitions. I don't need Ubuntu anymore. How can I remove the Ubuntu partition(s) and add the reclaimed space to my Windows 7 partition for saving files in Windows?


Every time i install Ubuntu either 12.10 or any version of Linux mint it install well but i cannot be able to see anything on the screen on when i use a DESKTOP screen by connecting on a VGA that time i see from a different screen.

I am trying to boot Ubuntu on my computer.  When I boot Ubuntu, it boots to a black screen.  How can I fix this? Table of Contents:


I know that in general for any function $f:V \longrightarrow W $ from a normed vector space $V$ to a second normed vector space $W$, being a Lipschitz function implies being continuous, is the second implication on my question the one I'm having troubles to understand.

I am studying a theorem about linear maps on normed vector spaces. The theorem states the equivalence of the following statements:     $T$ is a linear map on a normed vector space $X$ that maps to a normed vector space $Y$.         $T$ is continuous   $T$ is continuous at zero.   $T$ is bounded.      Clearly, 1 $\implies$ 2 is immediate. And 3 $\implies$ 1 is not so complicated either: suppose $\|Tx\| \le C\|x\|$, so $\|Tx-Ty\| = \|T(x-y)\| \le C\|x-y\|$, so take $\delta = \frac{\epsilon}{C}$, and $\|x-y\| < \delta \implies \|Tx-Ty\| < \epsilon$.  However, I am having some difficulty following a proof of 2 $\implies$ 3. The author makes the following claim:     If $T$ is continuous at $0 \in X$, there is a neighborhood $U$ of $0$ such that $T(U) \subset \{y \in Y : \|y\| = 1\}$, and $U$ must contain a ball $B = \{x \in X : \|x\| \le \delta\}$ about 0; thus $\|Tx\| \le 1$ when $\|x\|\le \delta$.   This is clear; it is just a restatement of the Weierstass criterion for continuity. He proceeds:     Since $T$ commutes with scalar multiplication, it follows that $\|Tx\| \le a\delta^{-1}\|$ whenever $\|x\| \le a$, that is, $\|Tx\| \le \delta^{-1}\|x\|$.   This I do not follow. What is happening here? Is this just a rescaling $x \mapsto \frac{a}{\delta} x$? I cannot replicate this conclusion.


Is there a way to have Ubuntu automatically open the windows (in the file manager) which were open when it was shut down?  I am using the Cinnamon desktop environment with Nemo as file manager.

Is it possible to preserve my open tabs between closing and opening of Nautilus file manager?  Preferably even across different logouts and restarts.


I filled all the details(fields) in my profile and got "Autobiographer badge". But if I  undo the changes the badge is still part of my profile. Below is the link   Is this a bug and if it is, can it be solved?

What are badges? How do users get badges? How can users get tag badges? Can badges be lost/revoked/taken away after they are awarded? If so, how and when? How can I suggest a new badge?   For more information, see "" and the  in the .


We have our existing website and from time to time we get leads from it, people say they reached us from Google.  Now, we are building a new website with a different wordpress template and we also   refreshed the content.  How can we check if we lose something on the way? What actions do we need to take or tools we need to use in order to make sure we don't lose value?  Thank you

I was wondering if you have any tips on the following situation.  I'm going to move a large website to a new Content Management System (CMS), here are some details on the site:   online news magazine with roughly 3,000 articles domain age: 10 years online in the current form since May 2010 indexed pages: ~10.000 percent of search engine traffic: under 10%    Unfortunately a custom-tailored CMS was used for the site. The performance, reliability and SEO capabilites have been really bad, so we are moving to a new and proven open source CMS.  All the articles will be kept as they are, but the URL structure as well as the structure of the HTML templates will be changed.  What I wanted to do now is to actually create 301 redirects for all articles from the old to the new schema, i.e:   Old: www.example.com/en/html/news/detail/title-of-the-article/ New: www.example.com/category/title-of-article.html   Is this a proven way to do something like this? If not, can you recommend a way that has worked for you?


Whenever I build something out of expensive blocks (like emerald blocks), a silly Enderman walks past and steal a block. Is there any way to prevent this, without ruining the creation (putting water around it, and spamming torches everywhere)?

Since Endermen are capable of picking up blocks, they can pick up your blocks from your house.   What's the best way to prevent Endermen from stealing your blocks?


i have the following problem about connectedness, prove that in the Euclidean plane  A={$(x,y):x \in \mathbb{I}\,$ or$ \, y \in \mathbb{I}$} is connected  (This is my interpretation of the exercise, since the statement says: “show that the set of points on the plane with at least one irrational coordinate is a connected set in the usual metric.”)  I have tried in several ways, but it causes me a problem, that some of the coordinates have to be irrational

If I want to prove that $\mathbb{R} \setminus \mathbb{Q}$ is disconnected, does it suffice to say that there are two open disjoint sets that cover $\mathbb{R}\setminus\mathbb{Q}$, namely:  $$(- \infty, 0), (0, \infty)\text{ ?}$$  Along the same lines, I want to prove or disprove that $S = \mathbb{R}^2 \setminus \mathbb{Q}^2$ (points $(x, y) \in S$ that have at least one irrationais connected. I feel that it is also disconnected; does it suffice to say that there are two open disjoint sets that cover $S = \mathbb{R}^2 \setminus \mathbb{Q}^2$, namely $((- \infty, - \infty), (0, 0))$ and $((0, 0), (\infty, \infty))$? (Very iffy on my assertion and my notation, sorry.)  Thanks!


Show that the sequence $$\sqrt{2},\sqrt{2\sqrt{2}},\sqrt{2\sqrt{2\sqrt{2}}},...$$ converges and find its limit. I put the sequence in this form , $(x_n)$ where $$\large x_n=2^{\Large\sum_{k=1}^{n}\left(\frac{1}{2^k}\right)}$$ I want to use Monotonic Convergence Theorem to show. But I stuck at proving the sequence is bounded above by 2. I manage to prove the sequence is an increasing sequence. Anyone can guide me ? I try to use induction to prove but i stuck at inductive step.

(Fitzpatrick Advanced Calculus 2e, Sec. 2.4 #12)  For $c \gt 0$, consider the quadratic equation $x^2 - x - c = 0, x > 0$.  Define the sequence $\{x_n\}$ recursively by fixing $|x_1| \lt c$ and then, if $n$ is an index for which $x_n$ has been defined, defining  $$x_{n+1} = \sqrt{c+x_n}$$  Prove that the sequence $\{x_n\}$ converges monotonically to the solution of the above equation.  Note: The answers below might assume $x_1 \gt 0$, but they still work, as we have $x_3 \gt 0$.    This is being repurposed in an effort to cut down on duplicates, see here: .  and here: .


I am a beginner in cryptography. I studied many time pad attack and now I want to solve a popular exercise, It consists 11 ciphertexts (s1,s2,...,s11), that encrypted by a same key and I want to find plaintext(p11) of s11. I know:  p10 ⊕ k = s10 p11 ⊕ k = s11 p10 ⊕ p11 = s10 ⊕ s11   Now, what should I do for getting p11? If assume k = s10 ⊕ s11, so:     s11 ⊕ k = p11   s11 ⊕ (s10 ⊕ s11) = p11   . Is it correct?

My question might appear the same as the question , but actually I did read all the answers and none of them helped me with the details I need.  I am new to cryptography and my problem is with two time pad attacks on OTP. The problem I had in my course was that I have 10 ciphertexts encrypted with the same key $K$. I am then given another ciphertext that I should decrypt.  I know that XOR-ing two ciphers gives me the XOR of their original messages.  My question is what is the correct thing to do after that?  I tried to take 3 ciphertexts $C_1, C_2$ and $C_3$.  Then get $S_1 = C_1 \oplus C_2  \oplus $' ', also get $S_2 = C_1 \oplus C_3 \oplus$ ' '.  After that I compared all corresponding characters in $S_1$ and $S_2$,  and if $S_1[i] = S_2[i]$ then I calculate $S_1[i] \oplus C_2[i]$ to get $K[i]$.  I tried this on paper before coding and it worked, but I might be missing something.  Is this the right approach? Why does it work?


That happened to me for the second or the third time now. When I am checking new questions, I saw a question (generally trying to login to a website, browser manipulation questions etc.) which contains some login data. I warned the OP about the situation.  If the OP recognizes it in time, he may have a chance to edit the question and remove it. Otherwise, login info can be viewable in the question edit history if the edit is done after the 5 minutes grace period.  Flagging the question for mod attention is right thing to do if OP edited the question after the grace period and login data still can be reachable from edit history? Can mods do anything about that? By basic logic tells me that a mod can not do anything to change a record in that style.  There was a flag about a  similar situation that I raised 18 days ago and it still is in active state.  Note: Users sharing their login data are generally new users and probably do not know that their edit history is kept.

I've observed several incidents where users inadvertently posted detailed, sensitive information. For example, a Server Fault user who posted a question with working login credentials to his actual production server, or the Stack Overflow user who posted actual medical records as example data for his question.   What should be the procedure for handling such cases?


I tried apt-get update and upgrade together and this is what I got.  E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied) E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?   What should I do?

I get this error whenever I try to install programs using the terminal:  home@ubuntu:~$ apt-get install myunity E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied) E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?   Also I'm unable to install updates using the terminal.


I want to "draw[]" a color line starting in green, ending in blue and a transition between green and blue in a smooth continuous fashion. For example in tikz/pgf plots we can use a command such as:  \shade[bottom color=gray, top color=green] (D)--(O)--(B);   to color a triangle with gray and green with a smooth (gradient) transition.  A more specific example is shown in this figure generated with gnuplot, but I do not want to plot a function, and I do not want axes. I just want to draw[] a line or an arc. In other words, I want to "shade[]" a curve in a rainbow coloring.    This is not a repeated question: I have seen these posts with similar questions:   and also:   That is not what I want.   Is there a function in TikZ or PGS (no pstricks or metapost please) that do this?  Thanks.    Update:  Here is my poor man solution:  \documentclass[12pt]{article} \usepackage{pgfplots} \usepackage{tikz} \pgfplotsset{compat=1.11}       \begin{document}       \begin{tikzpicture}       \coordinate (O) at (0,0);       \foreach \t in {0.,0.01,...,1}       {       \coordinate (A) at (\t, \t);       \def\scl{20}       \pgfmathsetmacro\s{\scl*\t}       \draw[color=blue!\s!green]  (A) circle (0.1mm);        }      \end{tikzpicture}      \end{document}   and here the plot:    The main problem here is that the curve is  hard coded. So, for another curve, I would need a new code.  I will work on creating a macro for a general path. Any ideas? Thanks.

How can I get a path following color gradient in TikZ? Here a quick example of the idea. On the left the result I'm looking for and on the right an example of a non path following gradient applied on a path.    It looks like the TikZ shading library isn't covering this.  Related questions:    .


I have a beamer presentation where I cite books and papers using alphanumeric keys (as provided by the style = alphabetic flag). The whole thing looks as follows:    In the bibliography on the last page however I do not have the alphanumeric keys:    I wonder whether I could also have the alphanumeric keys be displayed in the bibliography instead of just the reference and the icon.  My biblatex configuration currently looks as follows:  \usepackage[ backend=biber, style=alphabetic, sorting=ynt, maxbibnames=99 ]{biblatex}   I have tried a lot of things and failed but I assume there is probably an easy way to fix this.

Instead of the default icons or the text option, I would like to have numbered entries in my bibliography.  I added the line:  \setbeamertemplate{bibliography item}{}  to get rid of the icons, but can't figure out how to get numbers to display in their place. The references in the content slides are numbered, but without the corresponding number in the bibliography it's not very helpful.  MWE:  \documentclass[t]{beamer}  \setbeamertemplate{navigation symbols}{} \setbeamertemplate{bibliography item}{} \setbeamertemplate{frametitle continuation}[from second]  \setbeamertemplate{footline}{     \hspace*{0.1cm}     \text{short title}     \hspace{1cm}     \insertshortauthor     \hspace{3.5cm}     \insertsectionhead     \hfill     \insertframenumber     /     \inserttotalframenumber     \hspace{0.1cm} }  \title{a title} \author[me]{my full name} \institute{where I work} \date{today}  \begin{document}  \begin{frame}     \titlepage \end{frame}  \begin{frame}     \frametitle{1st slide}     Some text. \cite{ref_1} More interesting text. \cite{ref_2} Some even more interesting stuff. \cite{ref_3}  \end{frame}  \begin{frame}[allowframebreaks] \frametitle{References}     \tiny{\bibliographystyle{abbrv} }     \bibliography{refs} \end{frame}  \end{document}   Bib file:  @inproceedings{ref_1,   title={title 1},   author={A. Author},   booktitle={book title},   year={2010} } @article{ref_2,   title={title 2},   author={B. Author},   journal={Journal},   volume={35},   number={10},   pages={1217--1256},   year={2010},   publisher={Publisher} } @incollection{ref_3,   title={title 3},   author={C. Author},   booktitle={book title},   pages={595--606},   year={2012},   publisher={publisher} }   Resulting bibliography:


I was using Ubuntu 16.04 on a dual-boot computer, fortunately.   I attempted to upgrade from 16.04 to 18.04. Now my computer freezes during the boot-up procedure. There screen fills up with lines of code, then stops. I can't get it to do anything else. Therefore I have to boot to Windows 10.  It appears I will have to replace the entire Ubuntu partition. The question is how to do that without losing all my files and pictures.   Anyone have any ideas?

I have Ubuntu 15.10 and Windows 10 dual-booted, but I want to reinstall Ubuntu in the same partition without making any changes or causing problems in the dual boot option and without removing Windows.  Is it possible? Any guide on how to do it?


For some network reasons, my previous SSH sessions to server have disconnected. When I create a new session, I find the previous session still exist:    [root@localhost ~]# who root     pts/0        2015-03-25 21:35 (10.1.1.1) root     pts/1        2015-03-25 21:36 (10.1.1.1) root     pts/2        2015-03-26 01:44 (10.1.1.1)   The pts/0 and pts/1 are previous session terminals. And there are still some progresses running on them, such as vim:    root      2953  2906  0 Mar25 pts/0    00:00:01 vim getpasswd.sh   I want to re-login pts/0 to continue running vim progress, Is it possible? How can I do it?

I have a virtual instance of redhat running that I can ssh to from any host on the corporate network.  My ssh session was dropped while running some scripts that may or not have caused me to disconnect.  The who command locally still lists the dropped connection. Reconnecting with ssh starts a whole new session.  Is there a way to connect to the original session?  If not can I kill it?  I have root and physical access.  I was not using screen in the original session.


Issue  I have this cronjob.  5 12 * * * find /var/www/html -name "*.php" -o -name "*.htm*" -o -name "*.css" | tar -cf /var/www/export/$(date +"%m-%d-%Y")-backup-fs.tar.gz -T -   But it is not working, even no errors came to configured email.  When I run this command manually, it works.  I tried set up the rights to 777.  Where is the catch?  Thanks.

The following crontab does not work:  # TEST LINE DOES DOT RUN */1 * * * * /bin/echo 'test '`/bin/date +%Y-%m-%d` >> /tmp/test   I also tried starting it with:  SHELL=/bin/bash   Update: I thought the backtick characters ` were the villains, but as the answer below clarifies the percentage % was the culprit!


What method would you use to create new edges around this doorway maintaining it's shape? (desired outcome in red)

What is the easiest way to add/extrude an edge loop around the hole in the first image to make it like the second image?


I hope this question is in the spirit of Q&A.  I have to develop a module that manages complex datasets in Drupal and I have to decide if it is better to use Nodes or Entities to manage all the necessary stuff (there are pros and cons for any case).  I undestand the different concepts behind (what an entity is, and the relation between the concepts of node and entities), so my question is: when is better to use the former or the latter?  I don't know what: there is a guide, an intereseting experience, a checklist, or something else to allow developers to perform the rigth choice when starting the development? What a Node can do that is impossible to have with an Entity (and in the case is necessary to re-develop in the case)?  Thank you

What is the benefit to creating new entity types over just building a new content type?    It seems a bit overkill to do all of the custom coding that is required to create a new entity when you have all of the CRUD and Views functionality already built into content types.


I'd like to create a Windows Explorer context menu action for multiple selected files. I created a key HKEY_CLASSES_ROOT\*\shell\MyAction\command with a string value C:\python37\python.exe "c:\test\test.py" "%1"  This script only displays the command-line arguments for now (for debugging purpose): import sys; print(sys.argv); input() When I select two files a.txt, b.txt in the Explorer, and right click on "MyAction", then:  I'd like to have this script called once, and the command-line arguments passed to Python should be ["c:\test\test.py", "c:\a.txt", "c:\b.txt"]   instead I get this script called twice (once independently for each file), and the command-line arguments passed are: ["c:\test\test.py", "c:\a.txt"] ["c:\test\test.py", "c:\b.txt"]    How to make a context menu action call the command only once when 2 files are selected, with the 2 files as command-line arguments?  TL;DR I would like this to be launched: C:\python37\python.exe "c:\test\test.py" "a.txt" "b.raw" "file_with_noext"  and not: C:\python37\python.exe "c:\test\test.py" "a.txt" C:\python37\python.exe "c:\test\test.py" "b.raw" C:\python37\python.exe "c:\test\test.py" "file_with_noext"  when using the context menu action on multiple files.  Note:  and its answers don't solve it; I tried with HKEY_CLASSES_ROOT\SystemFileAssociations\*\shell\MyAction\command but this menu item doesn't appear when I select multiple files (let's say a.txt, b.raw, file_with_noext, and testdir\).

I need to be able to open about 16 JPGs in Chrome all at once, without having to select each one and do Open With. When I select multiple files, the Open With option disappears. How do I make it available with multiple files selected?  Several answers so far have provided decent workarounds, but they're not very flexible when I work on a large variety of files where Open With would be useful. Is there a way to actually do Open With on multiple files?  For anyone coming here in the future, I don't believe there's any proper workaround. If this matters a lot to you, I've created a  in the Feedback Hub that you can upvote.


Alright, so I have this webpage page that gets its data using AJAX requests (in javascript using JQuery). Once the data has been loaded on to the users browser I want to let them download said data without having to request it from the server again.  To do this, I found this little bit of code (in Javascript):  window.location = 'data:text/csv;charset=utf8,' + encodeURIComponent(someCSVtext);   This does what I want it to do, but it always names the file "download.csv"  Is there a way I can preset the filename assuming the user has an "always download file" option set in their browser (thus don't get a chance to rename the file)?

If for example you follow the link:  data:application/octet-stream;base64,SGVsbG8=  The browser will prompt you to download a file consisting of the data held as base64 in the hyperlink itself.  Is there any way of suggesting a default name in the markup?  If not, is there a JavaScript solution?