How to prove document ownership at a specific time

Problem Given any piece of data, I could sign it with public key and made available online. This proves I am in possession of given data, but it doesn't tell I am the creator. The only possibility (I'm aware of) to prove this, is to prove, that I was chronologically first to have it. Simple approach. Lets assume, that I wrote piece of code, and I want to generate some proof, that I am legitimate author of it. I can simply sign it's hash with e.g. RSA and put the signature along source code to some trusted site, like github. Now my commit has timestamp generated with this trusted site, and even if some Alice would sign herself the same source code, her upload to any trusted site will have newer timestamp proving she's not the legitimate author. This works as long as we'd assume data on github has undetermined life span and will be always available which is hardly true about any server out there. When that commit would be lost, my rights to the source code are lost as well: I might still have my local signed copy, but I cannot prove I've created it at given time. My understanding of the problem. I believe there is no possibility to self-authenticate, that I were in possession of given data at specific time - I could just made up arbitrary timestamp and sign it. Moreover, anyone out there could get my publicly available data, replace personal data with their, made up older timestamp and call me thief. Thus, sign from trusted server is needed. Trusted timestamp My idea of the mechanism is as follow: sign source code, optionally append personal data, generate hash and send this hash to trusted server. Then this server would have to send me back signed information, that it received hash H at time T. This way I've got publicly accepted certificate, that I've got file with hash H at time T. Even if the server had go down, I would still have the certificate. Question So is the "trusted timestamp" good solution to the legitimate author problem? Do you know of any available open source tools to achieve this goal? Maybe other techniques? Assuming, I want to public code/publication/anything else licensed for non-commercial use only, should I be concerned with such issues?


Why is not both sides of a fan equally effective?

I have a fan on my desktop. I started to wondering if it would not be just as effective if I flipped it 180 degrees. Since all the wind that comes out of the front has to be sucked in from behind, right? But it was not. It felt much less effective. I don't have any equipment to perform any actual measurements, but the cooling effect was MUCH lower. I cannot say I noticed anything. It was like having it turned off. Why is this?


Steam doesn't start - Segmentation faults

[SOLVED] I managed to fix the issue by uninstalling the proprietary AMD drivers, rebooting, starting Steam letting it update, reinstalling AMD drivers, reboot. It seems to be working and I can now play all my Steam linux games. I just installed Ubuntu 13.10 64bit on my main PC. I also installed Steam (.deb from ). The install went without errors. On running Steam, nothing happens. I run Steam from the terminal and receive two segmentation faults, always occurring on different lines of Steam.sh when I run Steam: /home/samathy/.local/share/Steam/steam.sh: line 755: 11111 Segmentation fault   /home/samathy/.local/share/Steam/steam.sh: line 755: 11239 Segmentation fault   The rest of the output on the terminal is just dump-saving text. I can't see anything about GLX issues, or locale issues (they seem to be popular issues with steam) I'm running Ubuntu 13.10 64bit with Xubuntu (installed after the Ubuntu install.) My specs are as follows: AMD FX 6350. AMD HD7870 (With AMD proprietary beta drivers) 12GB DDR3 Samsung 840 EVO 120GB. This problem is a little weird to me because Steam runs fine on my Ubuntu 13.10 + Xubuntu-desktop, Intel Atom N270 netbook without any fiddling, I can even run games. I've googled a lot and only really found solutions to other steam issues, not my own. If anyone could help, that'd be wonderful. Thanks! edit: I should mention that I've tried doing ~$steam --reset  It does not produce errors its self, but also doesnt solve the problem either. I have also tried installing Steam from Ubuntu package manage, but that results in the same errors.


Is it mathematically possible to take a SHA256 hash and turn it into a 0-99 number where each number in 0-99 range is equally likely to be picked?  As a 256 bit hash means the highest value possible is 2^256, this is not a nice or "round" number for the purposes of simplifying a hash down to ranges more natural for humans.


Brute force method of solving the cube: How many moves would it take?

Given that Rubik's cube has finitely many positions, one possible "brute force" method to solve it would be to determine once a sequence of moves which eventually reaches every possible position of the cube, and then whenever you want to solve a cube, you just mindlessly follow the sequence until you eventually reach the solved cube. This strategy is absolutely failsafe, provided you have an extraordinary memory and enough time (so, it's not a strategy for humans, but maybe for bored gods waiting for their just created universe to finally develop intelligent life ;-)).  However, the question is: How many moves does the shortest possible sequence which visits every reachable position have? Of course, it's easy to give a lower bound: At least as many moves as there are reachable positions, which according to Wikipedia is $43\,252\,003\,274\,489\,856\,000 \approx 4{.}3 \cdot 10^{19}$. However, I doubt that there's a sequence which gives a not yet visited position at every move, so the actual number of moves is likely even higher.  Is there maybe even a constructive method to create this "bored god's algorithm" (so that even gods with less than stellar memory can apply it)?


Alternatives to APFS which keeps corrupting itself?

Macos mojave locked up, forcing me to reboot. I was then presented with the prohibitory symbol indicating that the OS can no longer load. It was caused by APFS being corrupted, confirmed by disk utility in recovery mode. Disk utility did nothing to repair the problem.  I reinstalled the OS and restored everything from a backup. One day later macos locked up again, and I once again had to reboot. It now stops booting after filling the progress bar while loading the OS. APFS has once again managed to corrupt itself, evident both when staring in verbose mode and when running disk utility in recovery mode. A checksum for some object is invalid. Disk utility once again makes no attempt to actually fix anything and I have found no evidence of any other APFS tools from apple for this purpose.  I'm not resizing partitions or anything advanced when it happens, just using Firefox and getting a beach ball.  I can't think of any other solution to the situation other than to get rid of APFS:   Reinstalling the OS onto an HFS+ partition. I tried this -- the installer ignores the existing file system and created APFS anyway. Install an older version of the OS on HFS+ Use some hack to force mojave onto HFS+ Use a different OS   The SSD is a 500 GB, less than a year old Samsung 860 EVO that boots Windows 10 with seemingly no problems so the hardware does not seem to be the problem.  Are there any other obvious options that I have missed in my list? (buying new hardware because the file system is useless doesn't qualify)


Prove that the following ‘cancellation property’ holds in any group: ab = ac implies b = c, and ba = ca implies b = c.  Need help with this, don't know how to prove it for a group.


Regarding the time that must pass between posting and acceptance of an answer

Correct me if I'm wrong but AFAIK:   There is a time required to pass between an answer being posted and the questioner being able to accept it; This time is much longer (2 days!) if the answer is a self-answer; this is correct at least on Math SX, where I just self-answered this and upon trying to accept I found myself confronted with:      You can accept your own answer in 2 days.      However, I have the impression this time lapse significantly varies between sites; for example, if I remember well, I tried to self-accept my self-answer to  though convinced it would complain about this time lapse, and it got accepted, much to my surprise.   So I am asking:   How much time must there pass between when an answer is posted and when it is accepted? Is this site-specific or system-wide? Why is the time lapse for self-answers so much longer than for other answers? And above all, why exactly does this time lapse even exist? Couldn't it just be eliminated? Is there a reason for forcing an accepter to wait, potentially causing him to load other questions and forget about the answer he was going to accept? And this "potentially" part is not just a guess at a possibility, but my memory of stumbling on an old question of mine and being surprised I had not yet accepted an answer when I surely had decided to accept it ages before…


In the famous Christmas carol , presents like "geese a-laying" and "swans a-swimming" are mentioned. What does the "a" refer to in this context?


I heard on the radio that in the Super Bowl, Kansas City is considered the "home" team, despite the game being played in Tampa, where the Bucs are the real home team.  So... does Tampa get to use their "home team" locker room or do they have to give it to Kansas City?  I can't find the answer anywhere on the internet.


If the plural of "moose" is "moosen," what's the plural of "animuson"?  Skimming MSE questions on the Android app tonight revealed  that was closed by ...twice:


How to tell which device the USB drive is assigned as?

How can I tell which device the USB drive is assigned as?  Before inserting the USB drive:  $ lsblk NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT nvme0n1     259:0    0 238.5G  0 disk  ├─nvme0n1p5 259:3    0  15.9G  0 part [SWAP] ├─nvme0n1p1 259:1    0 222.6G  0 part / └─nvme0n1p2 259:2    0     1K  0 part    After:  $ lsblk NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT sda           8:0    1   1.9G  0 disk  ├─sda2        8:2    1   2.4M  0 part  └─sda1        8:1    1   1.2G  0 part  nvme0n1     259:0    0 238.5G  0 disk  ├─nvme0n1p5 259:3    0  15.9G  0 part [SWAP] ├─nvme0n1p1 259:1    0 222.6G  0 part / └─nvme0n1p2 259:2    0     1K  0 part    Is it /dev/sda??


I have an old laptop running as a server (It runs Ubuntu Natty).  When I SSH into the box, it often takes a long time to log on, if it's been a while since last time I logged on. I suspect the reason to be that the SSH daemon is put to sleep somehow, and has to be woken before I can log on. Can anyone explain why this happens?  Additional info  Besides SSHD the server runs Transmission Daemon and two Dropbox instances.  I have appended "UseDNS no" to /etc/ssh/sshd_config.  The machine is running a desktop kernel, because I use it as a backup desktop machine as well. Would it help to change it to a server kernel, or would that disable my desktop? I have read that there might be issues with nVidia drivers when running a server kernel, but don't know if this applies on Natty.


How to help so I can improve on my documentation and reapply

I am a Ghanaian male. A 3rd year non working Medical student in the carribean but a registered Pharmacist in my home country. But currently in the carribean. I was refused a standard visitors visa for which I wanted to visit the Uk for 3weeks for vacation and return to school. I would like to reapply this December for vacation. I would really appreciate any recommendations and criticisms as to what I have to do in order to increase my chances of getting the visa. Thank you.


Color mismatch between render and viewport

Initially, the colors were greyish in the viewport aswell - after changing the color management settings in the render tab, the viewport is as it should be - but when I render it out, it remains with wrong colors. What am I missing here? Thanks in advance. Edit: The slight tint of the image in general is due to f.lux. But the issue remains even if turned off. Edit 2: I already found out about color management settings that are set to filmic by default in 2.8+. In this specific case I've set it to raw as the texture input I'm rendering is in raw format, but for the albedo textures, I used standard, which still tints the render - not the viewport. The viewport was greyish before when the setting was on 'filmic' too. But changing the color management settings fixed that - but not the render. This is what I'm trying to understand here, as the color management settings are part of the render tab, and I don't understand why the render tab changes my viewport, but not the render. I found a quick fix by using "render viewport" instead of the normal render. But it's still awkward to not know what's going on.


70s(?) sci-fi story about astronauts using their knowledge of evolution to figure out they're in a space zoo

I read it back in junior high, and Google isn't helping. I would have read it about a decade ago, but I think it's from the seventies. From what I remember, a group of astronauts lands on a planet that has a bunch of animals on it. What they observe is that some of the animals have two limbs, some four, some six, some eight. What they eventually found strange was that animals seeming to be of the same level of evolutionary development would have such a disparate number of limbs. Looking at Earth, for example, what we might think of as "upper level" animals have four limbs. Then they notice other things that hint that the animals all may be from different planets. They conclude that they're in some kind of zoo or collection. I don't remember if they get off the planet or anything.


I'm using GPT as my partitioning scheme. I check the UUID's of my partitions:  # ls -l /dev/disk/by-partuuid/ total 0 lrwxrwxrwx 1 root root 10 Oct 18 22:39 0793009a-d460-4f3d-83f6-8103f8ba24e2 -> ../../sdb3 lrwxrwxrwx 1 root root 10 Oct 18 22:39 13f83c47-ad62-4932-8d52-e93626166e7f -> ../../sdc3 lrwxrwxrwx 1 root root 10 Oct 18 22:39 1b247b1f-0b7b-419e-bc3b-0f90cbadb87c -> ../../sdc2 lrwxrwxrwx 1 root root 10 Oct 18 22:39 224d5933-7a23-4833-b785-79a67c9b9306 -> ../../sda1 lrwxrwxrwx 1 root root 10 Oct 18 22:39 2ff625b2-b96b-4ce5-b752-57cdf7092258 -> ../../sda3 lrwxrwxrwx 1 root root 10 Oct 18 22:39 449956f9-7289-49ed-9a37-ed6be9264d1c -> ../../sdb1 lrwxrwxrwx 1 root root 10 Oct 18 22:39 a2a95e45-7e4c-4b20-a2bd-66d96e737590 -> ../../sdb2 lrwxrwxrwx 1 root root 10 Oct 18 22:39 a8c07f74-9d6d-4f45-9453-dd2e6998f100 -> ../../sda2 lrwxrwxrwx 1 root root 10 Oct 18 22:39 c2c9e94c-9c73-4d6e-a4ec-2229f56152e8 -> ../../sdc1   And add /dev/sdc2 using its UUID:  # mdadm /dev/md0 --add /dev/disk/by-partuuid/1b247b1f-0b7b-419e-bc3b-0f90cbadb87c mdadm: added /dev/disk/by-partuuid/1b247b1f-0b7b-419e-bc3b-0f90cbadb87c   But when I look at the details of the RAID array it reports /dev/sdc2 instead of the UUID.  # mdadm --detail /dev/md0 /dev/md0:         Version : 1.2   Creation Time : Thu Oct 18 21:52:43 2012      Raid Level : raid1      Array Size : 1048564 (1024.16 MiB 1073.73 MB)   Used Dev Size : 1048564 (1024.16 MiB 1073.73 MB)    Raid Devices : 2   Total Devices : 2     Persistence : Superblock is persistent      Update Time : Fri Oct 19 15:57:19 2012           State : clean  Active Devices : 2 Working Devices : 2  Failed Devices : 0   Spare Devices : 0             Name : cow:0  (local to host cow)            UUID : 9e691db1:f8fcc7d8:f56d9c11:1c202693          Events : 47      Number   Major   Minor   RaidDevice State        2       8       34        0      active sync   /dev/sdc2        1       8       18        1      active sync   /dev/sdb2    Is it impossible to construct a RAID array using UUID's? Or is it using the UUID but reports the normal name to increase the readability? In that case, how can I tell? I would like to use UUID's so that I may move the disks around freely in the machine without breaking anything. Doesn't that sound like a good idea?


Is there a simple way to find the conjugacy classes of $A_n$?

For the symmetric groups $S_n$ there's a quite simple way to find all the conjugacy classes. We find partitions of $n$, that is, we write  $$n = n_1+\cdots+n_k,$$  and then for each such partition there's a conjugacy class which is the set of all permutations of the form  $$\sigma=\sigma_1\cdots\sigma_k,$$  being $\sigma_i$ one $n_i$-cycle.  Now, what about $A_n$, the alternating groups? Is there any systematic way like that to find all the conjugacy classes?


Create a user solely for FTP in Windows 7

I was tasked to research and create a manual about installing an FTP server on Windows 7, and everything's fine and all until the specified user part during the creation of an FTP site. I'm told that the FTP user must be a new user. Language barrier sets back my understanding of the issue at hand (Japanese colleagues), and what required of me is to create a user that can't do anything other than serve as a login credential when connecting to ftp, or just not allow me to log in (remotely or locally) to Windows. So I was wondering how to do it. I've tried just removing the user from all groups including the Users group, and it works, but I know there must be a better way. Will removing the user from all groups (including Users) present an issue?  TLDR:  I need a way to create a user for FTP access only. User should not be able to log in Windows.  This needs to be done on IIS in Windows 7.  UPDATE:  This  about user groups doesn't provide enough information for me. If for example, I used IIS_IUSRS group (as it seems the most likely), what will I be able to do?


How to find Bounding Box given 4 Lat/Long and Bearing?

I need to find a bounding box given 4 lat/long points and a bearing (as seen in the example picture). I always know which two points are lined up by the bearing (1 and 2 in the example), so I will always know the length of the bounding box.  The width however is arbitrary, with the points being anywhere along the lines (3 and 4 in the example).    My first thought is that I'll have to calculate the angles between the points (1 & 3, 1 & 4, 2 & 3, 2 & 4) and then use a series of "law of cosine" equations to calculate the corner points.  Is there a simpler way?  Would that even work?


Optimal Number of MySQL InnoDB Buffer Pool Instances

Server Characteristics  Total system RAM: 8GB (running MySQL + other stuff than MySQL on it i.e. not dedicated to MySQL) Number of CPU Cores: 6 I have data in the db amounting to about 2GB I have InnoDB Buffer Pool Size set to 4GB  Which is better:  Innodb Buffer Pool Instances set to 1? Innodb Buffer Pool Instances set to 2 (2GB in each)? Innodb Buffer Pool Instances set to 4 (1GB in each)? Innodb Buffer Pool Instances set to 8 (the default setting)  I'm thus not sure as to how to reason when it comes to Buffer Pool Instances and also the whole "use instances or suffer OS Swap when having such large InnoDB Buffer Pool Size".


"must include one of these tags -- bug feature-request discussion support"

I just tried to post a question to Meta and received:     Oops! Your question couldn't be   submitted because:         must include one of these tags -- bug feature-request discussion support      Why are these tags required? What are the proper usages for each one? I wasn't able to find any documentation about these tags? Should this be in ?


I have a database with MongoDB 2.4.14 and I want to migrate the database to MongoDB 3.6.  Note: the file is original from the db path. Not from mongodump.  This process is messy as it requires doing so on many of our clients.  Any advice will be welcomed as I'm a bit lost in this process.


Show that if $f$ is a differentiable function whose third derivative is continuous, then there exists $c\in (0,1)$ such that $f'''(c)\geq 24$

Let $f:[0,1] \to \mathbb{R}$ be a function whose third derivative $f'''(x)$ is continuous on $[0,1]$. Suppose that $$ f(0)=f'(0)=f''(0)=f'(1)=f''(1)=0 \text{ and } f(1)=1$$ Then there exist $c\in(0,1)$ such that $f'''(c)\geq 24$  I am trying to prove the above statement via Taylor's theorem, and see if I can make use of the Darboux's theorem, but I don't know how to come up with a 24 in the last sentence of the statement. Any kind of hints are much appreciated, thank you.


How can I prove to S.S office that I returned on time without the stamp of US customs on my passport?

how can I prove to Social Sec. office that I did return to US on time without the stamp on my passport ??


Suppose  that $V$ is the bounded open subset of the plane and $f\in C(\bar V)\cap H(V)$. Show that if $M\ge 0$ and $|f(z)|\le M$ for all $z\in\partial V$ then $|f(z)|\le M$ for all $z\in V$.  I was trying to apply maximum modulus principle or open mapping theorem but the open set $V$ is not given to be connected and since then i have no idea how to do it.  Any type of help wil be appreciated. Thanks in advance.


I've just answered a question in SO where I had to post four snippets of XML (yes, it was a JavaEE question, how did you guess?)  I made an effort to keep the snippets short and meaningful, but all this code can clutter the visuals of the page, and moves attention away from the rest of the answer.  The site can already detect which parts of the question or answer are code, and paints them in a different font and background. What if it could also add a small toggle button that hides/display each snippet of code?  An example. Displayed:   Hidden:   Please acknowledge my superior Photoshop skillzs.


How can I use these both OS on my laptop, without having to reinstall one? For my personal use I always had Ubuntu installed (13.10 32bit) as my single OS. Then for my new job I needed to install Win8.1 (64bit). Now I have these both OS on a separate partition, but I can boot only to a Win8.1 OS.  Is there a way that I can restore the Grub or whatever to do, in order to have a choice to boot any of my two OS (preferably without having to reinstall one)?


Nikon D5100 - lost or missing images on memory card

After shooting all day and viewing the images on the camera, when I put the card into my PC and tried to open it, I did not have all the images from today. I did have all the old images, from yesterday and older. Is there any where for me to look for these lost images and retrieve them??


I have a Queue<T> object that I have initialised to a capacity of 2, but obviously that is just the capacity and it keeps expanding as I add items.  Is there already an object that automatically dequeues an item when the limit is reached, or is the best solution to create my own inherited class?


i have this error Exception in thread "AWT-EventQueue-0"

I am trying to insert the one column "array" in SQL. I create my database on SQL and I used Java to create the table but when I tried to insert the values in the array in the SQL, I have this error?  private class Handler_c implements ActionListener{     public void actionPerformed(ActionEvent arg0) {         try{             Class.forName("com.mysql.jdbc.Driver");             Connection conn = (Connection) DriverManager.getConnection("jdbc:mysql://localhost:3307/database_vf","root","");             conn.setAutoCommit(false);             Statement stmt1 = null;             stmt1= conn.createStatement();             String query1 ="CREATE TABLE result  (result INT)";             stmt1.execute(query1);              String query2 = "INSERT INTO result VALUES (?)";             PreparedStatement pst1 = null   ;              for(int i=0; i<array.length; i++)             { pst1.setDouble(i+1, array[i]);}             pst1 = (PreparedStatement) conn.prepareStatement(query2);             pst1.execute();              conn.commit();             pst1.close();             conn.close();             System.out.println("Success result to mysql table");          }          catch(ClassNotFoundException e){             System.out.println(e);         }catch(SQLException ex){             System.out.println(ex);         }        }   }   The error is :      Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException   at browse_gui$Handler_c.actionPerformed(browse_gui.java:191)   ,,,,,,,,,,,,,,,,,,,,,,,,,,,,   This is line 191:  for(int i=0; i<array.length; i++)


I'm trying to amass a list of physics books with open-source licenses, like Creative Commons, GPL, etc. The books can be about a particular field in physics or about physics  in general.  What are some freely available great physics books on the Internet? edit: I'm aware that there are tons of freely available lecture notes online. Still, it'd be nice to be able to know the best available free resources around.  As a starter:         Table of contents sorted by field (in alphabetical order):


So, I know that this question may be tough to answer, but I am asking this question in all seriousness, and I don't consider myself a newbie...  Lately, I am trying to find a way to "generalize" my approach classical mechanics. Specifically, I need a system that can always guarantee a solution to any problem. In a sense, just like mathematicians like to generalize stuff. For example, if you get a system of linear equations, you can always solve it by using the Gauss method of substitution...  I often have the problem of seeing why the solution provided by the textbook is right, but I don't see why my solution is wrong... I'm guessing this is the motivation behind my quest.  I know a field as big as mechanics is hard to cover with one or two principles, but I need something to always help me set the correct system up, the rest being "just math". So is there a method that yields a uniform system?  I have heard that Lagrangian mechanics can provide something like this, but I'm not sure whether to take it up... Can anyone post their experiences with that?  Lastly, I would add that I am no stranger to advanced math topics. I like linear algebra and multivariable calculus... from my experience learning new math has always enhanced and deepened my understanding of physics. Don't hesitate if you have to offer something... maybe a book or similar resource...


Measure space $(\Omega ,\mathcal F)$ and $\mathbb P:\mathcal F\to [0,1]$ that is finite additive but not $\sigma -$additive

I'm looking for a space $(\Omega ,\mathcal F)$ and a function $\mathbb P:\mathcal F\to [0,1]$ s.t. $\mathbb P(\Omega )=1$ and $\mathbb P$ is addtitive but not $\sigma -$additive.  Of course I got inspired but several post on mathstack exchange by $\Omega =\mathbb R$, $$\mathcal F=\{A\subset \mathbb R\mid A\text{ or $A^c$ is countable}\},$$ and $\mathbb P(A)=0$ if $A$ is countable an $\mathbb P(A)=1$ if $A$ is not countable. But unfortunately this is a probability measure. Any example ?    My question is not a duplicate of  (as several thought) because the answers don't provide probability spaces.


What happened to the link to the duplicate when a question is closed as a duplicate?

Possible Duplicate:          This question:      has been closed as an exact duplicate, but there is no link to the duplicate so we can neither assess whether the closure is valid nor see the explanations in the duplicate question.  It wasn't so long ago that the duplicate links were shown — is there a policy change (and if so, why?), or is it just a glitch?


What is the first movie where the audience believes a dream sequence is reality until the character wakes up?

In Spy Kids (2001), Gregorio Cortez almost think that he smash the big guy into windows at school & all kids claps for it. even audience view the scene what he think.  But in reality, he actually didn't smash the big guy.  so What is the first movie to show thinking way in such like this?


Show that if a group $G$ has odd order, any subgroup $H$ of index 3 in $G$ is normal in $G$?

Show that if a group $G$ has odd order, any subgroup $H$ of index 3 in   $G$ is normal in $G$.   I think this is equivalent to the following: Let $H$ and $K$ be subgroups of a group $G$, with $K \leq H$. We can then show that $[G:K]=[G:H] \cdot [H:K]$. However, I'm not sure what the best approach is here. What's a good way to prove this theorem?  This question is different from  because we are not assuming that $3$ divides the order of $G$.


Book on structural equation modelling/ confirmatory factor analysis

Is there any "state of the art" book on SEM/CFA that you can recommend?  I am looking for something that offers both some theory and some practice and I am using R with lavaan.  I am a psychologist and mainly interested in CFA to test questionnaire structure, etc.  Please note why your book of choice is worth reading.


Why is the computer useful if a chaotic system is sensitive to numeric error?

In every textbook on , there are a lot of numerical simulations. A typical example is the .  But why is numerical simulation still meaningful if the system is very sensitive to numerical errors?


Is there any way to call multiple @wire methods sequentially? As per the documentation, all the wire methods will run asynchronously, but what if I want to execute multiple wire methods sequentially, is there any way?


Having a Problem After Installing Mac-osx Theme and setting it up With Cairo dock

When I enter sudo apt-get upgrade, this message shows up:  dpkg: error: cannot scan updates directory `/var/lib/dpkg/updates/': No such file or directory E: Sub-process /usr/bin/dpkg returned an error code (2)   Any Help ?!


How far a villager needs to be from the village before he will try to run to it?

I have a standard 6 door village with a breeder below it, and to the side I have an auto wheat farm with a villager in it, and it's working great. However, when I tried to build the same farm a bit further, using carrots this time, the villager inside it was just stuck to the wall, in the direction of the village.  I later found out that carrots are not the same as wheat as far as villagers are concerned, and the farmer wasn't interested in harvesting the carrots. I put another villager in the farm to see if they will throw food to each other - and they did. But both of them along with the baby villager are stuck in the corner, looking towards the village.  Q: Is there any specific distance that villagers need to be from the center of the village in order to behave normally?  Thanks


Python - How to read list values from config file (INI) using python configParser

i am trying to read some header values from config file in python while creating CSV. Working Python file: headers = ['Column1','Column2','Column3'] ... writer.writerow(header) ...  Using Config: text.conf [CSV] headers = 'Column1','Column2','Column3'  Python file config = configparser.ConfigParser() config.read(text.conf) header = config['CSV'].get('headers')  But my csv file looks something like this, ',C,o,l,u,m,n,1,',",",',C,o,l,u,m,n,2,',",",',C,o,l,u,m,n,3,'  Expected: Column1,Column2,Column3


Calling stored procedure creates null reference exception

I have a simple code which calls a stored procedure:  bool connOpened = OpenConnectiontoDB(); SqlCommand cmd = new SqlCommand("spRegisterUser", cn); cmd.CommandType = CommandType.StoredProcedure;  SqlParameter userName = new SqlParameter("@UserName", username); SqlParameter pass = new SqlParameter("@Password", password); SqlParameter user_email = new SqlParameter("@Email", email);  cmd.Parameters.Add(userName); cmd.Parameters.Add(pass); cmd.Parameters.Add(user_email);  int returnCode=0;  try {     returnCode = (int)cmd.ExecuteScalar(); } catch (Exception e) {     int i = 0; }  return returnCode;   An exception is thrown at :  returnCode = (int)cmd.ExecuteScalar();       Message: "Object reference not set to an instance of an object."   I have no idea why, I checked:  cn.status it shows as open, I can run the stored procedure directly in the DB. And cmd appears to be populated so what is this error?  why you say the query returns null? It does not. It runs a stored procedure which returns an integer. And I tested the sp I only get -1 or 1.  The proposed duplicate answer does not answer this question. It only shows how to handle the error when object is null. My question was what is the cause of null.


When using my Tamron 16-300mm lens I frequently experience chromatic aberrations in my photos. how so I prevent this?


In my terminal it printed out a seemingly random number 127. I think it is printing some variable's value and to check my suspicion, I defined a new variable v=4. Running echo $? again gave me 0 as output.  I'm confused as I was expecting 4 to be the answer.


Creating your own summation-like command

Now I've asked this question here before, but since then I've lost my account, and after an hour of trying to find the answer again somewhere on this site, I thought I'd just ask it again. So it definitely is a duplicate, but I haven't a clue at how to find where this question was asked before. I apologize in advance.  The essential problem is to make your own summation command. The idea would be instead of writing \Omega_{j=1}^n which renders the j=1 to the lower right of Omega and renders the n to the upper right of Omega, I would like to have them indexed beneath and above, respectively. Exactly how the command \sum is rendered, except I don't want a capital sigma, I want a capital omega.  I can't remember how I did it before, and I recently lost the Latex files for a document I wrote using this command incessantly. I'm now in the midst of reconstructing the Latex file from the PDF and I can't for the life of me remember how I made this command.  Any help would be greatly appreciated.


Programming language books explain that value types are created on the stack, and reference types are created on the heap, without explaining what these two things are. I haven't read a clear explanation of this.  I understand what a stack is. But,    Where and what are they (physically in a real computer's memory)? To what extent are they controlled by the OS or language run-time? What is their scope? What determines the size of each of them? What makes one faster?


Email app download badges should be modernized

For the first one, the up-to-date design is available , and there also should be a newer version of Google's with a sans-serif font.


X/Ubuntu 20.10 on Asus ROG Strix G17 has no sound

Just tried Ubuntu and Xubuntu 20.10 on the laptop Asus ROG Strix G17 and it has no sound. Sound worked on a clean install of X/Ubuntu 20.04 Any suggestions?


Prove that for any connected graph, there exists a closed walk that visits every edge exactly twice.

For this to occur, every vertex has to have an even degree. Since this is a connected graph, we know that this must be true.   How do you prove that the closed walk visits every edge exactly twice? Does the existences of a closed walk mean that there is a cycle in the graph?


Error:request for member of non class type

I was just trying a simple program that calculates the volume of a cube. I have declared the object in main and when I try accessing the function of the class with user input arguments it shows an error : request for member 'volume cube' in 'vol', which is of non class type 'Vellimi()'. Why does this occur ?   #include <iostream> using namespace std;  class Vellimi { private:  double width; double height; double length;  public: Vellimi(double,double,double); double volume_cube (double width,double height,double length) {     return width*height*length; }  };   Vellimi::Vellimi(double a,double b,double c){   width=a;    height=b;    length=c; } int main() {    double x,y,z;     Vellimi vol();     cout<<"Input the width : "<<endl;    cin>>x;    cout<<"Input the height : "<<endl;    cin>>y;    cout<<"Input the length : "<<endl;    cin>>z;    cout<<"The volume is "<<vol.volume_cube(x,y,z)<<endl;    return 0;  }


xdvipdfmx:fatal: Unable to open "xxx.pdf"

I am trying to compile with pdf open in Adobe reader. Anyone knows a workaround other than close the pdf viewer every time?


How can I write e^(3j) in LaTeX?  I have tried many syntax, like $e^(3j)$ or $e^*{3j}$  Any help will be very well received.


Apostrophe s' or s's - When to use each?

In this sentence should I use Apostrophe as s's or s'? I am always confused with what exactly the rule behind s' and s's. The sentence is:     Hours later Fadnavis's resignation, the the NCP-Congress leaders combined met Governor and staked claim to form the Government.   Fadnavis is the name of the Chief Minister (for your understanding)


Higher Amperage and Higher Watt for Laptop Charger

My laptop's charger was not working anymore. So I bought a new one. However I couldn't find an exact matching charger, I bought a different one. My question is; Will there be any problems with new charger? Specifications of chargers are below;  Original charger: 65W, input: 100-240V, 1.6A, 50-60 Hz, output: 18.5V, 3.5A  The new one I bought: 90W, input: 100-240V, 1.5A, 50-60Hz, output: 19V, 4.74A


I am unable to get  to work with pdftex. Is there an alternative that will allow me to easily define a cube structure? I've looked at TikZ alternatives but they require me to define each sub cube in the structure, which is very time consuming.


Does anyone actually recognize Cersei as Queen?

In season 6 finale Cersei crowns herself queen of the Seven Kingdoms, but whom will she de facto rule over? Even if we put aside that her realm is about to be attacked by two great forces from the north and the east, there doesn’t seem to be much support for her Iron Throne in the Seven Kingdoms. The North has essentially seceded, as have the Iron Islands, while Highgarden and Dorne are plotting against her. The Vale seems to have aligned them selves with the Starks and while the situation in The Stormlands is currently unknown it is unlikely that they would support a Lannister queen. This leaves only The Westerlands (which were “hers” already), The Riverlands (which might be in disarray after Arya killed the key Freys) and The Crownlands.  I realize that this probably doesn’t even matter in the grand scheme of things with the eminent arrival of the Night’s King and Daenerys, but it just seems that she will not be ruling much, something that she is probably oblivious to in her blind quest for power.


In a templated class, how do I define a function with a different typename

EDIT: This is NOT a duplicate of the standard templating questions.  My scenario involves a templated class and a member function of that class whith one argument that is templated, but not of the same type as the class.  Even when I put the definition in the header I still can't find the correct syntax.  Can someone help me with my specific question?    My oversimplified code:  Foo.h:  template<typename T1> class Foo { public:     template<typename T2>     static void bar(vector<T1>& a, vector<T2>& b); };   Foo.cpp:  #include <Foo.h>  template<typename T1> template<typename T2> void Foo<T1>::bar(vector<T1>& a, vector<T2>& b) {     //code logic }   Goo.cpp:  #include <Foo.h>  int main(int argc, char** argv) {     vector<int> a;     vector<double> b;     Foo<int>::bar(a, b); }     My error:  undefined reference to void Foo<int>::bar<double>(std::vector<int, std::allocator<int> >&,  std::vector<double, std::allocator<double> >&)     I couldn't find the proper way to define the templates.  I also noticed that the order of the typenames will change the error (also putting the entire function in the class declaration).  What is the correct syntax?


What's the way to resolve the following error in jmeter?

Root CA certificate: apachejmetertemporaryrootCA created in JMeter bin directory You can install it following instructions in component reference documentation (see installing the jmeter CA Certificate for HTTPs recording paragraph) Please check the details below when installing the certificate in the browser CN=_DO NOT INSTALL unless this is your certificate (jmeter root CA) OU=username:XXXXXXXXX, C=US Fingerprint(SHA1):XXXXXXXXX Created:XXXXX


Why am I unable to update from Software Updater?

I am unable to update through software updater. After clicking install now, it shows "requires installation from untrusted package".   Then there is two options: Settings and OK.  I click OK but the software updater window closes and stops.


Why replace function doesn't replace all occurrences?  1) Ex that doesn't work:  //the funcion call '999.999.999,00'.replace('.', '')  //This replaces only the first match, given as result as below '999999.999,00'   2) Ex that works, but using regex:   //the funcion call '999.999.999,00'.replace(/\./g, '')  //This replaces all matches, given as result as below '999999999,00'   Is It right for Ex 1? Is It the correct behavior for replace?


How can xkb or some other tool be used to permanently bind Caps Lock to ctrl+b while in terminal?  (This is to make Caps Lock the default prefix key for tmux. It could also be mapped to a specific key if that's too difficult, e.g. a function key, which could then be made the tmux prefix instead.)


Find all triangles of which perimeter and area are numerically equal. I have got    solution for right angle triangles but not of others


int x=33333333; float y = 1.0f; System.out.println(x+y);   What I get is  3.3333332E7 but why?


How do I store 2 pounds of Grated Parmesan cheese

How do I store 2 pounds of grated Parmesan cheese? Last time I froze it and it turned to mush when I defrosted it.  I also left in original package and it developed mold.


Someone told me that the English language is special (compared to German, at least) in the way that every noun could be used as a verb. I think this phenomenon is called supine. Is this correct?  Examples:   house → to house well → to well phone → to phone table → to table lamp → to lamp   At first it seemed to me that this would work with all nouns. But then I thought of the following nouns, and I think they can't be used as a verb, am I right?   person →(?) to person human →(?) to human baker →(?) to baker computer →(?) to computer example →(?) to example   It seems that nouns describing people (person, human, baker) are exceptions? But it works for "author" ("to author"). Hmm. "Computer" seems smiliar to a person's job to me (could be a human instead of a machine that computes).  But what about "example"? I think "to example (something/someone)" is not possible, is it? What would a native speaker understand/think if someone says:      He examples.      I want to example it/him.   Which are the nouns that can't be used as a verb?


I want to create 5 second mp4 video from 1 image.  When I use below code the video is smooth. Default direction is zoom in to top left.  ffmpeg -loop 1 -i prop1.jpeg -vf "zoompan=z='min(zoom+0.0015,1.5)':d=125" -c:v libx264  -t 5 -s "800x450" fade.mp4   So, to zoom in to top right I figure it out to use the code below  ffmpeg -loop 1 -i prop1.jpeg -vf "zoompan=z='min(zoom+0.0015,1.5)':x='if(gte(zoom,1.5),x,x+1)':y='y':d=125" -c:v libx264  -t 5 -s "800x450" fade.mp4   It is zooming in to the right direction but the video become jittery.  Also got some error when converting :  [swscaler @ 0x429bda0] deprecated pixel format used, make sure you did set range correctly [swscaler @ 0x429bac0] deprecated pixel format used, make sure you did set range correctly [swscaler @ 0x429bac0] Warning: data is not aligned! This can lead to a speedloss [swscaler @ 0x429bac0] deprecated pixel format used, make sure you did set range correctly Last message repeated 97 times [output stream 0:0 @ 0x37af200] 100 buffers queued in output stream 0:0, something may be wrong. [swscaler @ 0x429bac0] deprecated pixel format used, make sure you did set range correctly Last message repeated 24 times [swscaler @ 0x42b7040] deprecated pixel format used, make sure you did set range correctly Last message repeated 1 times   What is wrong with the code?


How do I delete the center of the letter A in Adobe Illustrator CS5?

I need the center of the letter A in Illustrator to be transparent so you can see the background underneath. Same with letter D, B, O, P, R.  I imported a vector version of a word, and I am able to select the letter but if I click delete button it deletes the whole word.


Windows 10 dual boot with Ubuntu 16.04.2 - dual boot disappeared

I recently installed Ubuntu alongside Windows 10. At first it seemed to work completely fine, restarted, came up with the GRUB and I could access Ubuntu. I think I did that twice. Then I decided to boot up Windows to check that everything there was still in order, but now the GRUB menu does not appear on start up, nor does it seem to appear at all.   To check whether the install still exists, I have tried these things: bcdedit in Administrator mode, which does not come up with anything except the Windows boot. The partition which I saved Ubuntu to shows as completely empty in Disk Management in Windows. Going into BIOS settings in Boot mode to see the options and order in which they are placed. It does not appear there either.  None of them give any indication that Ubuntu is even installed. However, I want to check that I am not misunderstanding this as I am not experienced in this sort of thing and do not want to try to install something on top of what is there. Can anyone tell me if it is normal for the installation to just completely disappear or if it is likely to be able to hide it in this way?


Group theory - isomorphism and cyclic groups

Prove that:- Any group of order 4 is either cyclic or isomorphic to Z2*Z2 where Z2 is residue group of natural numbers modulo 2.


I am trying to understand an exercise in Bondy and Murty's book "Graph Theory with Applications".  The exercise is as follows: "Consider the permutation group $\Lambda$ with elements $(1)(2)(3)$, $(1,2,3)$ and $(1,3,2)$.  Show that there is no simple graph $G$ with vertex set ${1,2,3}$ such that $\Gamma(G)=\Lambda$" Here $\Gamma(G)$ means the automorphism group of $G$. I don't see how to start this proof.  Edit: It looks like this question is a duplicate of a question posted last year:


Render giving me nothing but a rough background

I'm making a little picture    And when I click (shift-Z) it gives me this  I have no idea what caused this if anyone has an idea how to fix this, that would be very much appreciated. Thanks


How to separate the object to smaller units to give different materials to the different parts?

I have been trying to create a closet in Blender 2.8 and giving materials to the frame, the doors and the handles, but whenever I try to assign a material for example to certain doors, the whole object got selected. My first idea was to use "Mark Seam" to use it as "boundary" of the different materials, but it didn't work, then I used key P to make separations in the object, but it - although separates the object by selection - still didn't work, it keeps using the whole obejct. Can anyone please help me? Thank you.


I am living in London for a few months. I have been living in London for a few months.   What is the difference?  Is number one a common error?


Latest Edit: Fixed! First Edit: Someone tried to identify this post as a . The commands that were posted there are not working for me, which I stated below. Also, I do not believe this is from Google Chrome. I don't even have Chrome installed. So, I know this has already been asked, but the commands don't seem to work for me. I don't know how to fix this error. I am on Ubuntu 20.10. The full error message is posted below. Skipping acquire of configured file 'main/binary-i386/Packages' as repository 'https://download.mono-project.com/repo/ubuntu stable-focal InRelease' doesn't support architecture 'i386'  I have already tried to use the command below to fix this, with no luck. deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main  Hopefully someone here knows how to fix this.


I'm trying to create a simple Space Invaders game in JavaFX. This is my first time so I have no idea how you properly do this. I'm trying to add collision detection, to remove a sprite if it's hit by a bullet.  All my sprites are rectangles with an imagePattern.  The enemies are 60 x 43, the bullet is 4 x 8. My idea was to just check if the bullet is within the translateX of a sprite, and if its the same Translate Y - its height. But for some reason this code doesn't work. It causes an Exception in thread "JavaFX Application Thread" java.lang.NullPointerException when a bullet hits a sprite.  if (game.lookup("#bullet") != null) {     for (Sprite sprite : enemies) {         if (game.lookup("#bullet").getTranslateX() >= sprite.getTranslateX() && game.lookup("#bullet").getTranslateX() <= sprite.getTranslateX() + 60 && game.lookup("#bullet").getTranslateY() == sprite.getTranslateY() - 43) {             System.out.println("HIT!");         }     } }   Some help would be much appreciated.  Note: I am sure this is not the most efficient way to go about it, but its the only idea I have.  The stack trace:  Exception in thread "JavaFX Application Thread" java.lang.NullPointerException at Main$1.handle(Main.java:131) at javafx.graphics/javafx.animation.AnimationTimer$AnimationTimerReceiver.lambda$handle$0(AnimationTimer.java:57) at java.base/java.security.AccessController.doPrivileged(Native Method) at javafx.graphics/javafx.animation.AnimationTimer$AnimationTimerReceiver.handle(AnimationTimer.java:56) at javafx.graphics/com.sun.scenario.animation.AbstractMasterTimer.timePulseImpl(AbstractMasterTimer.java:357) at javafx.graphics/com.sun.scenario.animation.AbstractMasterTimer$MainLoop.run(AbstractMasterTimer.java:267) at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:514) at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:498) at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulseFromQueue(QuantumToolkit.java:491) at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runToolkit$11(QuantumToolkit.java:319) at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96) at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method) at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:175) at java.base/java.lang.Thread.run(Thread.java:844)


Story with people from another world who rely on some technology/machine which feeds them with an artificial sense of reality

I read this English young adult fiction book 5-6 years ago. This has probably a been brought out after 2000.  All I remember is that the main character-a boy visits a place where people are in some kind of induced-dream state. The "dream-world" offers them things that are not achievable in the real world. The caretaker of the place tells the protagonist that people prefer to be in that world rather than the real one.  Also I remember mentions of there being more than one sun .In another book of the same series,the main character gets treated to wellness in a tribal house-a girl tends to him there.There also is a contest of some sort in one of the books,the protagonist is the youngest person in it and yet he wins(something conducted for the entertainment of some other people).


SQL Query - Concatenating Results into One String

I have a sql function that includes this code:  DECLARE @CodeNameString varchar(100)  SELECT CodeName FROM AccountCodes ORDER BY Sort   I need to concatenate all results from the select query into CodeNameString.  Obviously a FOREACH loop in C# code would do this, but how do I do it in SQL?


What is our understanding of what our (i.e. observable) universe has expanded into?

In his latest Fermilab video, Dr. Don Lincoln :     (...) even though we shrunk the visible universe down to tiny size, the number line is still infinite. That means that, even when the universe began, it might have already started out to be infinite in size. So that's kind of a mind-blower.   Consider my mind blown.  I always thought that even if beyond the observable[a] is at least 500x bigger (according to the same video), shrinking the universe as a whole would equally shrink the farthest regions to the same point[b] (the farthest out, the bigger the shrink for a given duration).  I presume it's because there's no supporting data (is that correct?), even if it is a logical deduction. But suppose the universe indeed was already infinite before/at/after the Big Bang, then what is our current understanding of what the observable universe had expanded into – space expanding into space?[c]    [a] Is there a better name for it? I couldn't find one. [b] I understand it's not a center, but anywhere can be that point. [c] If the beyond the observable didn't share that point, and it isn't known for sure, then equally it isn't known for sure there was nothing, what implications does that have or what is known about that?


What do we mean when we say 't Hooft proved that Standard Model is renormalizable?

This question is inspired from  Ron Maimon says that standard model is renormalizable, and though there seems to be conflicting (?) answers. Is this because each answer differs in what "renormalizability" means? Furthermore, what paper Ron Maimon is referencing to by saying "'t Hooft proved it"?  Also, in  it says standard model is renormalizable. So standard model is renormalizable?


How to deal with forgotten password without loosing any data from ubuntu based laptop?

When I logged in today on my laptop and tried to do something  it asked me for my password. So i typed in my password  and it keeps on saying that It's invalid.  I know for sure I didn't change it. Is there any way to change it or make it work without loosing any data from my laptop ? How do I reset a lost  password? doesn't work for me.  please any one suggest how to make it work without loosing any data because if any data are remove my research work are totally stop .


I know this problem has been addressed a few times on here.  I tried following the directions for setting proper headers, I still run into problems with my emails going into the spam filter in Gmail.   If anyone can please take a look at what I've tried, I'd really appreciate it.  The code below is without the headers added as explained here:   Thanks in advance.  define("WEBMASTER_EMAIL", 'myName@mydomain.com'); if($post) {     $name    = stripslashes($_POST['name']);     $email   = trim($_POST['email']);     $subject = trim($_POST['subject']);     $message = stripslashes($_POST['message']);      $error = '';      // Check name     if(!$name)         $error .= 'Name required! ';      // Check email     if(!$email)         $error .= 'E-mail required! ';      if($email && !ValidateEmail($email))         $error .= 'E-mail address is not valid! ';      // Check message     if(!$message)         $error .= "Please enter your message!";      if(!$error)     {          $mail = mail(WEBMASTER_EMAIL, $subject, $message,             "From: ".$name." <".$email.">\r\n"             ."Reply-To: ".$email."\r\n"             ."X-Mailer: PHP/" . phpversion());          if($mail)             echo 'OK';     }     else         echo '
'.$error.'
'; }


Keep window on top and steal focus in WinForms

I realize that this would be COMPLETELY bad practice in normal situations, but this is just for a test app that needs to be taking input from a bar code scanner (emulating a keyboard).  The problem is that I need to start up some scripts while scanning, so I need the window to regain focus directly after I click the script to run it.  I've tried using Activate(), BringToFront(), Focus() as well as some Win32 calls like SetForegroundWindow(), Setcapture() and SetActiveWindow()... however the best I can get any of them to do is to make the taskbar item start blinking to tell me that it wants to have focus, but something is stopping it.  BTW, I'm running this on XP SP2 and using .NET 2.0.  Is this possible?  Edit: To clarify, I am running the scripts by double-clicking on them in explorer.  So I need it to steal focus back from explorer and to the test app.


I recently got a message that says      Haven't heard anything from you in a while.   I always thought that the right way to say this would be to use for insdead of in. Are both versions correct? Would there be a difference in meaning?


How do I remove old kernel versions to clean up the boot menu?

Every time I install a new Linux kernel, it gets left in the grub_config, making the boot menu longer each time.    I know I can manually search through the installed packages and remove them.  Does Ubuntu provide any easier way to clean them up or keep them from showing in the boot list?


I want to make a tree which is made of segments connected via parenting, i want the children have collision with the environment, atm the children will simply pass throught them.  How can i make it.  edit: described what i want in image


Object array NullPointerException, Processing 3.3.6

I'm trying to make a simple 3d game in Processing but I've run into a problem. I tried to make an array to keep track of my environment objects and to make it easier to modify. However, when I try to run the program, it won't work.  Main code:    //arrays BoxCl[] envArr;  void setup() {   size(640, 360, P3D);    envArr[0] = new BoxCl(1,1,-1,1);              //it shows the error here   envArr[envArr.length] = new BoxCl(2,1,-1,1); }  void draw() {   background(0);   camera(mouseX, height/2, (height/2) / tan(PI/6), width/2, height/2, 0, 0, 1, 0);   Update();   Draw(); }  void Update(){  }  void Draw(){   for(BoxCl i : envArr){     i.Draw();   } }   BoxCl Class:  class BoxCl{    float x, y, z;   int s;    BoxCl(float x, float y, float z, int size){     this.x = x;     this.y = y;     this.z = z;     this.s = size;   }    void Draw(){     translate(scale*x, scale*y, scale*z);     stroke(255);     fill(255);     box(s * scale);     translate(scale*-x, scale*-y, scale*-z);   }  }   I've tried looking it up () but I think I'm too inexperienced to understand what I am supposed to do.  Please help.  edit: I am aware that a variable/array/object should be defined before being used. But how do I define the envArr in a way that it can still change? (i.e. increase or decrease in size when I have to create or delete an object)


I have a webpage where I list all my database data. I have a DELETE link in front of each record. When a user click that DELETE link, it redirect user to a page called delete.php and in this page I run the delete query. My process is  Index.php  <a href="delete.php?action=delete&id=<?php echo $ID; ?>">DELETE   delete.php  if (isset($_REQUEST["action"])) if ($_REQUEST["action"] == "delete") {     $id= $_GET['id'];     $del_query = mysql_query("DELETE FROM TABLE WHERE id= '$id'"); }   Can anyone tell me any secure method of deleting data because this process is not secure and user can directly type this in the URL delete.php?action=delete&id=3 which will delete that record.


Opportunities in quantum computing for an undergrad

I am currently an undergrad student in computer engineering in Brazil and I have taken the Quantum mechanics subject as well as I am did a  (the two jupyter notebooks, it's in portuguese though) on quantum computing with a teacher that is currently building one at my college. Apart from the chances I already have of learning about this subject are there other means or opportunities any of you recommend going after?


In Aura components, we use  to display pre-formatted HTML. As per the document, there is no corresponding LWC component. Is there any way I can display HTML content stored in a metadata field as-is?


In the Star Trek universe, how do we know that the transporter didn't kill you and create a replicant?

One of the reasons I would personally never get in a transporter is that there is no evidence that the Real Me isn't just vaporized and a Copy Me created at the other location. The Copy Me might have all my memories and be indistinguishable from the original, but it isn't the Real Me.   I know that some early characters (especially in ST:Enterprise) had problems with transporters -- but these mostly seemed to concern safety. No one discussed the metaphysics of the technology.   Was there ever proof -- or even discussion -- of the question of whether the transporter really was transporting, or just creating a heck of a good copy?  Note 1: Yes, the transporter tech in ST sends the 'atoms' as well as the 'bits' to reconstruct the atoms, so it's not quite a 23rd century fax machine. But you're still being vaporized.....   Note 2: And yes, I do wake up each morning wondering if I am the same person who went to sleep the previous night, thank you very much. Why do you ask?


The door is locked and I can't read the last book how do I get the key to the door?


How to retrieve the tile URL in OpenLayers 3?

I have a question about Openlayers3 , I have the below code that initializes my map on my small demo application:  var map = new ol.Map({     layers: [         new ol.layer.Tile({             source: new ol.source.OSM()         })     ],     target: 'map',     controls: ol.control.defaults({         attributionOptions: /** @type {olx.control.AttributionOptions} */ ({             collapsible: false         })     }),     view: view });    You can see a demo   Now my question is how do I get the Tile url , so that I can store it locally using localstorage ? how do I get the Tile url ?   I saw the  , but I am not sure how to use it ? can anybody help me understand how to get the tile url ? (can can play around in the Chrome Developer Tools for the demo that I have provided.)


Is there a built in type for a lookup/reverse lookup table?

I'm trying to implement a Baudot character encoding.  Right now, I'm using 2 dictionaries which are simply mirrors of each other:  Dictionary<char, int> Lookup = new Dictionary<char, int> {     { ' ', 0x100100 },     { '-', 0x011000 },     { '/', 0x010111 },     { '0', 0x001101 },     { '1', 0x011101 },     ... };  Dictionary<int, char> Reverse = new Dictionary<int, char> {     { 0x100100, ' ' },     { 0x011000, '-' },     { 0x010111, '/' },     { 0x001101, '0' },     { 0x011101, '1' },     ... };   Is there a built in type that handles this already?  Something like:  var lookup = new Lookup<int, char>(); lookup.GetByKey(0x100100); lookup.GetByValue('c');   I couldn't find anything when I searched for 'reverse lookup' or 'lookup table', everything seemed to be related to DNS or LinqToSql.  (I'm using  because it's necessary for some  devices)


How do you get the co-ordinates of en element from browser window top and left in javascript?

I need to get the element co-ordinates relative to browser window. How do you get that in javascript ?


Yesterday,  I installed netbeans by downloading it from website  I ran the .sh file which installed it  Now i want to remove it   It does not show in the installed panel in ubuntu software center  what should i do ?


Whats the difference between these two C++ syntax for passing by reference?

I'm learning modern C++ and sometimes I see values passed by reference written slightly differently with a space.   int &i   Is there a difference?  int& x     #include <iostream> using namespace std;  void swapnum(int &i, int &j) {   int temp = i;   i = j;   j = temp; }  void f(const int& x) {   int& y = const_cast<int&>(x);   ++y; }


Prove that $243^{2020} \equiv 1 \pmod 5$

I was supposed to use that  $a^4 \equiv 1 \pmod 5$, but that's not helping me, specifically, I don't know how to prove that $243^{505}$ is not as $5k, k \in \mathbb{Z}$.


how to combine multiple row and get a table as shown in the picture?

How can I make the following table in my latex document.  This is exactly what I want, this is what I have done so far \usepackage[utf8]{inputenc}  \PassOptionsToPackage{es-tabla,spanish,es-lcroman,es-noquoting}{babel} \usepackage{float}  \usepackage{anysize}                      \marginsize{2cm}{2cm}{2cm}{2cm}   \begin{document}    \section{Introduction}   \begin{table}[H] \begin{tabular}{l|l|l|l|} \hline \multicolumn{1}{|c|}{\textbf{Id}} & \multicolumn{1}{c|}{\textbf{Tipo de riesgo}}            & \multicolumn{1}{c|}{\textbf{Riesgos}}  & \multicolumn{1}{c|}{\textbf{Probabilidad}} \\ \hline \multicolumn{1}{|l|}{}   &  & & \\ \hline \multicolumn{1}{|l|}{}  & \multirow{5}{*}{\begin{tabular}[c]{@{}l@{}}Entorno de desarrollo \\y tecnologías\end{tabular}} & \begin{tabular}[c]{@{}l@{}}Las herramientas de desarrollo no funcionan\\  como se esperaba\end{tabular}  & Probable \\ \cline{1-1} \cline{3-4}   \multicolumn{1}{|l|}{}  & & \begin{tabular}[c]{@{}l@{}}El sistema de gestión de base de datos que se utiliza\\  no permite procesar muchas transacciones por\\  segundo como se esperaba.\end{tabular}   &  \\ \cline{1-1} \cline{3-4}  &  & \begin{tabular}[c]{@{}l@{}}Falta de dominio en las tecnologías que se utilizan\\  para la implementación del sistema\end{tabular}  &  \\ \cline{3-4}  &   &    &   \\ \cline{3-4}  &  & \begin{tabular}[c]{@{}l@{}}Las herramientas de desarrollo no se han elegido \\ bien en función de las características técnicas y no\\  proporcionan las prestaciones previstas\end{tabular} &  \\ \cline{2-4}  \end{tabular} \end{table}  \end{document}


What should I do when my Scanner is not working on my IF?

package mygame;  import java.util.Scanner;  public class Main {     public static void main(String[] args) {         Scanner scan = new Scanner(System.in);         String nome;          nome = scan.nextLine();          if(nome == "1") {             System.out.println("It worked");          }          scan.close();     } }   I'm trying to understand why my IF is not working. I'm using Scanner to get any information but no matter what my IF doesn't work.


Can we enable VF page in a lightning component?

Can we enable VF page in a lightning component. If possible provide me with suggestion how to achieve it.


Question: Let $T(n)$ be a running time that satisfies the recurrence    $$T(n) = 1 + \sum_{k=0}^{n-1} T(k) \quad \text{and}\quad T(0) = 1.$$   Show that $T(n) = 2^n.$   The recurrence above can be obtained in CLRS's Introduction to Algorithms, $3$rd edition, page $364,$ where the authors discuss rod-cutting problem using Recursive top-down implementation.   Does anyone how to obtain the solution for the recurrence of $T(n)$ above?


Linear regression what does the F statistic, R squared and residual standard error tell us?

I'm really confused about the difference in meaning regarding the context of linear regression of the following terms:   F statistic R squared Residual standard error   I found  which gave me great insight in the different terms involved in linear regression, however the terms mentioned above look a like quite a lot (as far as I understand). I will cite what I read and what confused me:      Residual Standard Error is measure of the quality of a linear   regression fit.......The Residual Standard Error is the average amount that the response (dist) will deviate from the true regression line.   1. This is thus actually the average distance of the observed values from the lm line?     The R-squared statistic provides a measure of how well the   model is fitting the actual data.   2. Now I'm getting confused because if RSE tells us how far our observed points deviate from the regression line a low RSE is actually telling us "your model is fitting well based on the observed data points" --> thus how good our models fits, so what is the difference between R squared and RSE?      F-statistic is a good indicator of whether there is a relationship   between our predictor and the response variables.   3. Is it true that we can have a F value indicating a strong relationship that is NON LINEAR so that our RSE is high and our R squared is low


I am trying to create user registration form in js which beautiful and flexible

I am using drupal 7. I am trying to create user registration form with javascript which beautiful and flexible. Something like this:    How can I achieve this?


Why does echo `ls -l` does not have newlines?

I am running WSL (Windows Subsystem for Linux) and when I use the ls -l function on the terminal, I get new lines printed i.e. each file is on a new line e.g.:  total 12K drwxrwxrwx 1 user user 4.0K Apr  4 23:28 . drwxr-xr-x 1 user user 4.0K Apr  4 23:28 .. -rw-rw-rw- 1 user user    0 Mar 28 01:03 a1.file -rw-rw-rw- 1 user user 4.5K Mar 23 16:27 books.xml -rw-rw-rw- 1 user user    0 Mar 13 00:19 file1 -rw-rw-rw- 1 user user  513 Mar 13 00:19 file2.txt -rw-rw-rw- 1 user user 2.8K Mar 13 12:42 file3.txt -rw-rw-rw- 1 user user  405 Apr  4 23:26 ls_l.txt -rw-rw-rw- 1 user user    0 Apr  4 23:28 ls_l2.txt -rw-rw-rw- 1 user user   89 Mar 13 00:18 pattern -rw-rw-rw- 1 user user   86 Mar 28 01:41 somefile.file   However, when I use echo `ls -l` > file1.txt, it has the same thing as ls -l normally but all in one line, where each line is separated by spaces and not new lines e.g.:  total 12K drwxrwxrwx 1 user user 4.0K Mar 27 22:45 . drwxr-xr-x 1 user user 4.0K Mar 27 22:45 .. -rw-rw-rw- 1 user user 4.5K Mar 23 16:27 books.xml -rw-rw-rw- 1 user user 0 Mar 13 00:19 file1 -rw-rw-rw- 1 user user 513 Mar 13 00:19 file2.txt -rw-rw-rw- 1 user user 2.8K Mar 13 12:42 file3.txt -rw-rw-rw- 1 user user 403 Mar 27 22:45 ls_l.txt -rw-rw-rw- 1 user user 89 Mar 13 00:18 pattern   Note that I have these relevant aliases:  alias l='ls -CF' alias la='ls -A' alias ll='ls -alF' alias ls='ls -lah'


Editing a VF page embedded in a Std page layout?

On my opportunity page layout, I want to embed a related record from another object  with VF. Can they edit that VF page within the parent Std page?  So more specifically  Std page = view mode, VF  = edit?  std page = edit mode, VF = edit?


I've been using it when she gets fussy and she seems to love it. Is this a bad habit to get into? I've heard there are potential dental/breastfeeding/dependency issues. Is there any truth to this?


Let's $v$ the smallest positive integer > 1 for which $2 ^ {v} - 1$ divisible by $p$. Prove that $2 ^ {m} - 1$ ($m > v$) divisible by $p$ then and only then $v$ divide $m$?  There is a hint that enough to divide $m$ into $v$ with the remainder, but it gives me nothing.


Can we find a unified theory of physics?

We now have two overarching theories to explain just about every physical phenomenon: Einstein’s theory of gravity (general relativity) and quantum mechanics. The former is good at explaining the motion of everything from golf balls to galaxies. Quantum mechanics is equally impressive in its own domain — the realm of atoms and subatomic particles. Trouble is, the two theories describe our world in very different terms. In quantum mechanics, events unfold against a fixed backdrop of spacetime — while in general relativity, spacetime itself is flexible. What would a quantum theory of curved space-time look like? “We don’t even know what it is we’re trying to quantize.” For decades now, string theory — which pictures matter as made up of tiny vibrating strings or loops of energy — has been touted as the best bet for producing a unified theory of physics. But some physicists prefer loop quantum gravity, in which space itself is imagined to be made of tiny loops. So can all of these theories be unified? If yes, then how?


Best strategy (tried and tested) for using Box2D in a real-time multiplayer game?

I am currently tackling real-time multiplayer physics updates for a game engine I am writing. My question is how best to use Box2D for networked physics. If I run the simulation on the server, should I send position, velocity etc to every client on every tick? Should I send it every few ticks? Maybe there is another way that I am missing?  How has this problem been solved using Box2D before? Anyone with some ideas would be greatly appreciated!


having trouble interpreting confint function using R (logistic regression)

I'm trying to interpret these results of using R confint function , but I can not understand. This is a logistic regression about breast cancer. how to interpret confint function. What the 2.5% and 97.5% means?  logit1 = glm(goodmodel, data=train, family=binomial(link = logit)) summary(logit1) confint(logit1)   summary(logit1)  Call: glm(formula = goodmodel, family = binomial(link = logit), data = train)  Deviance Residuals:       Min        1Q    Median        3Q       Max   -1.76595  -0.00368  -0.00011   0.00000   2.57451    Coefficients:                           Estimate Std. Error z value Pr(>|z|)   (Intercept)             -58.106512  37.736869  -1.540   0.1236   radius_mean              -4.791077   1.933346  -2.478   0.0132 * texture_mean              0.543094   0.222894   2.437   0.0148 * compactness_mean        -93.504749  52.018859  -1.798   0.0723 . `concave points_mean`   212.367971  86.957163   2.442   0.0146 * radius_se                18.268981   7.771317   2.351   0.0187 * smoothness_se           394.202770 347.004692   1.136   0.2560   concavity_se            -78.413761  64.179173  -1.222   0.2218   `concave points_se`     -26.914245 469.938101  -0.057   0.9543   radius_worst              5.978607   4.897600   1.221   0.2222   area_worst               -0.003889   0.045800  -0.085   0.9323   concavity_worst          27.647216  14.104588   1.960   0.0500 * symmetry_worst           25.702777  15.984453   1.608   0.1078   fractal_dimension_worst  10.690937  79.071866   0.135   0.8924   --- Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1  (Dispersion parameter for binomial family taken to be 1)      Null deviance: 533.015  on 397  degrees of freedom Residual deviance:  26.608  on 384  degrees of freedom AIC: 54.608  Number of Fisher Scoring iterations: 12  > confint(logit1) Waiting for profiling to be done...                                 2.5 %        97.5 % (Intercept)             -1.482910e+02    7.95727142 radius_mean             -9.791086e+00   -1.66857433 texture_mean             1.961861e-01    1.13920334 compactness_mean        -2.299043e+02   -5.16464149 `concave points_mean`    6.027894e+01  432.99676482 radius_se                6.704669e+00   39.25468272 smoothness_se           -1.961348e+02 1307.22045246 concavity_se            -3.122203e+02   25.69408799 `concave points_se`     -1.038278e+03  891.07772306 radius_worst            -2.977840e+00   17.32103028 area_worst              -9.549641e-02    0.09462597 concavity_worst          6.661555e+00   64.03373503 symmetry_worst           1.562622e+00   63.43243116 fractal_dimension_worst -1.619176e+02  168.07512057 There were 50 or more warnings (use warnings() to see the first 50) ````


Drag vertices without pulling other faces

So I have subdivided a face on a cube 9 times and I want to pull a certain area of the face backwards into the cube to make eyes. However, when I select certain vertices and bring them back, they pull the faces surrounding them back as well so they are slanted. Is there a way to only bring the faces that I selected back, so new faces are created on the side?  Thanks in advance!


When do we're say " a few" instead of few?

When do we use 'a few'instead of 'few'? For example, why is it incorrect to say "I have few dollars left" instead of "I have a few dollars left"? Most people reason it should be few dollars because "dollars" is a plural noun.


Does a bonus action end invisibility gained from the Boon of the Night Spirit?

As the title says really. The Boon of the Night Spirit says:  While completely in an area of dim light or darkness, you can become invisible as an action. You remain invisible until you take an action or a reaction. (DMG, Chapter 7, page 232)  If a character did something that they can do as a bonus action (certain spells, dash or disengage for a rogue, etc.), would the invisibility end?


Possible to keep a window in all virtual desktops?

In Ubuntu you can have virtual desktops, and toggle individual windows to exist on all of those desktops. How do I do the same in Windows 10?


I am trying to customize  document, it's a CV template for XeTeX. What I'd like to be able to do is change the main font. I belive the section of the code I need to change is this:  %FONTS \defaultfontfeatures{Mapping=tex-text} \setmainfont[SmallCapsFont = Fontin SmallCaps]{Fontin}   I downloaded and installed Fontin just to be able to see the document in its original form before trying to customize it. It works fine.  Now I need some other fonts to try, and I can't figure out how to find out the font names I could use. I tried a few well-known names like Times and Verdana, these fonts were not found. Also tried some font names I have found in different documents and webpages, eg. Cambria, TeX Gyre Bonum, Lucida Grande, which were rejected because either they were not found or their names contained an illegal character: a space. (Which pretty much stunned me since the fontspec documentation is full of multi-word font names...)  The documentation on the fontspec package (v2.1e 2010/11/17) doesn't help me much. All it says about this is "TODO: add explanation for how to find out what the font name is."  So how do I find the names of the fonts I can use?    Edit: I'm using Ubuntu 10.10 with the latest TeXlive 2010 from tug.org.


My friend who has only recently downloaded blender has come across a workspace issue. He said he accidentally pressed a button and it has entirely changed his user interface/ Workspace. He can't open, save or do anything with the change.    This is a full window image!


How to convert Ridge regression into a constraint optimization problem?

I hope this question wasn't asked before, I was looking for an answer and didn't find one. I'm trying to understand the Ridge regression problem.  If I understand correctly, Ridge regression is trying to solve the following problem:  Given $A \in \mathbb{R}^{n \times d}$, $b \in \mathbb{R}^n$ and $\lambda \in \mathbb{R}$, find $x \in \mathbb{R}^d$ that minimizes:  $(1)$ $arg\,min_{x \in \mathbb{R}^d}(||Ax-b||_2^2+\lambda^2||x||_2^2)$  I'm trying to understand the meaning of $\lambda$. I thought that the above equation is identical to the following equation:  $(2)$ $arg\,min_{x \in \mathbb{R}^d}||Ax-b||_2^2$ s.t. $||x||_2^2 \leq \lambda^2$  But after solving both problems separately in matlab, I got different solutions for $x$.  I solved problem $(1)$ by this formula: $x={(A^TA + \lambda^2 I)}^{-1}A^Tb$.  I solved problem $(2)$ by using $cvx$ library in matlab that is able to solve convex optimization problems.  As I said, in both cases I got different $x$. Are the two problems supposed to be identical? and if not, what change (if possible) should I do to problem $(2)$ so it can be identical to problem $(1)$.  Thanks  $\textbf{Edit:}$  Whoever put the link  for me. Thank you!  It indeed worked in Matlab and I got the same solution for both cases. But I did not expect to get such a strange solution.  Just to make sure I understand since it really looks strange to me.  By the answer in the link, you can actually convert the second problem to this problem:  $arg\,min_{x \in \mathbb{R}^d}||Ax-b||_2^2$ s.t. $||x||_2^2 \leq ||x'||_2^2$  where $x'={(A^TA + \lambda^2 I)}^{-1}A^Tb$ is the solution to the first problem.  It looks too trivial/strange since it means that the constraint is actually equal constraint and not 'less than or equal' constraint (the first one is a non-convex problem and the second one is a convex problem).  It also means that you need to solve the first problem and actually find $x$ from the first problem in order to find the same $x$ again in the second problem. which makes no point on solving the second problem.  Does it guarantee that it always finds  $arg\,min_{x \in \mathbb{R}^d}||Ax-b||_2^2$ s.t. $||x||_2^2 = ||x'||_2^2$ (non-convex problem)  and not  $arg\,min_{x \in \mathbb{R}^d}||Ax-b||_2^2$ s.t. $||x||_2^2 < ||x'||_2^2$ (convex problem)  Thanks!


How to refer to your blog when answering?

I know that putting a link to your blog in a signature is frowned upon and rightly so.  Is it okay to link to your blog in an answer if that blog post answers the question?  Are there other situations where it would be acceptable to promote your own web site in a question or answer?  Related:


How to Change When Battery Turns Red 15.10

I was wondering how to change the settings so it shows the battery as critical (red) at 10% instead of 30% since 30% is still over an hour of usage on my laptop. Thanks!


C skips user input from subsequent scanf statement

I have a main program that implements some functions for a stack in C. While accepting input from the user I find unusual results. Can someone point out what is a better way to accept user input in C.  int main() {     int choice;     int flag=1;     char n;     char string[100];     while(flag==1)     {         printf("\nMake a selection\n");         printf("Enter 1 to push an element in the stack\n");         printf("Enter 2 to pop an element from the stack\n");         printf("Enter 3 to print the stack elements\n");         printf("Enter 4 to display the top element of the stack\n");         printf("Enter 5 to reverse a string using stack\n");         printf("Enter 6 to verify balanced brackets in an expression\n");         printf("Enter 9 to quit\n");         scanf("%d",&choice);         printf("Entered choice %d\n",choice);         switch(choice)         {             case 1:                 printf("Enter an element to push into the stack -->  ");                 scanf("%c",&n);                 Push(n);                 break;              case 2:                 top=Pop();                 break;              case 3:                 PrintElements();                 break;              case 4:                 if(top==NULL)                     printf("Stack is empty");                 else                     printf("\nThe top element on the stack is --> %c",top->data);                 break;              case 5:                 printf("Enter a string\n");                 fgets (string,100,stdin);                 printf("\n Original string is --> %s",string);                 for(int i=0;i<100;i++)                 {                     if(string[i]=='\0')                         string[i-1]='\0';                 }                 StringReverse(string);                 printf("Modified string is --> %s",string);                 break;              case 6:                 printf("Enter a string\n");                 fgets (string,100,stdin);                 for(int i=0;i<100;i++)                 {                     if(string[i]=='\0')                         string[i-1]='\0';                 }                 CheckParanthese(string);                 break;              case 9:                 flag=0;                 break;              default:                 printf("Incorrect selection");                 break;         }       }     return 0; }   Sample Output Here when I enter 1 it automatically skips the next scanf statement which asks for user input for an element to push into stack  Make a selection Enter 1 to push an element in the stack Enter 2 to pop an element from the stack Enter 3 to print the stack elements Enter 4 to display the top element of the stack Enter 5 to reverse a string using stack Enter 6 to verify balanced brackets in an expression Enter 9 to quit 1 Entered choice 1 Enter an element to push into the stack --> Make a selection Enter 1 to push an element in the stack Enter 2 to pop an element from the stack Enter 3 to print the stack elements Enter 4 to display the top element of the stack Enter 5 to reverse a string using stack Enter 6 to verify balanced brackets in an expression Enter 9 to quit


Vader says 'Build another imperial level'. I've already built all 16. Is this a bug?

As the title says I've been working through the Vader quests and now he's asking me to 'Build another Imperial level to find out what to assemble next!'. I've already built all 16 Imperial levels. Obviously I could skip the quest but that costs 100 Bux, and I would feel exceedingly ripped off to waste 100 Bux on what feels to me like a bug which could happen again.  Have I reached the end of the quests, is that really what's happened here?


My son is 2, going on three. He's doing really well during the day for potty training. He tells me when he needs to go.   How do I do this with him at night? Diapers are too small. He's in a six for diapers at night, and pulls-ups are more expensive then diapers.   I'm a first time mother and this is all new to me. I need help, please!


Are there in-universe explanations for how some species' appearances change between series?

Through the course of the Star Trek franchise, some species have undergone significant changes in their appearance.  For example, here is a Klingon as seen in The Original Series.    And, here is one from The Next Generation.    Quite interestingly, if we go further back into Star Trek universe history, we find that Klingons from before the time of TOS looked much like they did in TNG.  Here's one from Enterprise.    Klingons weren't the only ones who went through this, and it didn't just happen in the transition from TOS to the TNG/DS9/VOY era.  Here's a Trill from an episode in TNG.    And, this is one from DS9.    I'm sure these aren't the only species to have undergone changes like this.  Have there ever been in-universe explanations for these, or others?


Why doesn't Visual Studio refresh the folders when I click the Solution Explorer refresh button?

In Visual Studio 2008, I can see all my project files in my Solution Explorer, and these files exist in an actual diectory. However, if I add a file to that directory (let's say, an test.sqlite file in the App_Data folder, or say, images created by some other program), then these files do NOT appear in my Solution explorer, even if I click the refresh button. How can I make files created by other applications appear in my Solution Explorer? (so far, I have to create them somewhere else, then copy and paste them into the solution explorer itself, but there must be an easier way).  Edit: Is there an advantage to this "fake solution view", i.e. I could have a file "test.sqlite" in my App_Data directory but in my solution, it could be appearing in my root directory. Coming from an Eclipse WYSIWYG Solution Explorer mindset, I don't see the advantage of having this extra virtual meta-information about the actual files in your directory. Is there a way you get an advantage out of this metaphor?


Fork Bomb: Why Piping Output Into Another Copy of Fork Bomb works if no Output is returned?

I understand the basic syntax of this famous fork bomb : ( ) { : | : & } ; : but I am currently struggling to understand the part of : | :, where one pipes the output of : to another :.  What I do not understand is simply that since the function :() takes no parameters and returns nothing when called, how can one pipe its output (what output is it?) to another copy of the same function? Thank you for your time and help!


GUI freezes, not access to to TTY, lost root partition

I keep going back and forth between Ubuntu and Windows 10. I want to use Ubuntu for good but I keep getting two main problems. Here's the worst one that happened yesterday.  Once in a while, Unity freezes completely. My mouse doesn't move or anything. This is on a 2 days old install. Everytime that happens, I don't even have access to a TTY. So I'm forced to turn off the computer with the power button. Yesterday though, Ubuntu didn't like it. When I started my computer, I was greated with a blinking cursor. Grub didn't start. I even tried reinstalling Grub from a live DVD but that didn't work. So I had to reinstall everything.  That being said, I'd like to get this freezing problem solved.  At first I thought it might have been Chrome using up all my 4 GB of RAM. So I installed an extension to shut off all my inactive tabs. But when it froze yesterday I had one or two tabs and Firefox opened with 3 tabs. Normally, on my Windows install, I never have any issue. Right now, I have Android Studio running and am writing this from Chrome with 10 active tabs opened. So that's not the problem.  I thought it may have something to do with my graphic card. I have some issues with it. It's an Intel. On Ubuntu but mostly on Ubuntu Gnome and LinuxMint, once in a while, the screen goes completely black for a split second, usually when I'm using the terminal. Also, my computer becomes a lot hotter on Ubuntu than on Windows when the lid is closed.  Oh and this happens with swappiness at 60, 10 or 0.  Anyone know what I can do to solve this? I my computer is a laptop, HP EliteBook 8440p with 4 gb or RAM.   Thanks!


When should one use "a" versus "an" with initialisms?

With initialisms, should one choose "a" or "an" based on the sound of the first letter of the initialism or based on what the first letter denotes?   For example, if "MOU" denotes Memorandum of Understanding, should one choose "a" or "an" based on "em" or based on "memorandum" -- a MOU or an MOU?   The choice presents an issue when the first letter of an initialism is a consonant with a vowel sound or a vowel with a consonant sound, e.g.:   FAQ – Frequently Asked Question; a FAQ or an FAQ?  LOC – Level of Concern; a LOC or an LOC?  MOU – Memorandum of Understanding; a MOU or an MOU? NPV – Net Present Value; a NPV or an NPV?  R&D project – Research and Development project; a R&D project or an R&D project? SOP – Standard Operating Procedure; a SOP or an SOP?  XRD – X-Ray Device; a XRD or an XRD? URL – Uniform Resource Locator; a URL or an URL?    Also, does the choice depend on whether the writing is formal (e.g., technical, legal, policy) or informal?


I'm trying to create a function with two inputs that can append a value into a list of choice. I'm starting of with two lists to get the code working before I build up.  a = [] b = []  def func(z,x):    if z == a:        a.append(x)    elif z == b:        b.append(x)    print(a,b)   For some reason it appends to the first list, then the second, no matter which I select. I've only just started to learn python, so I may have missed something basic.


When I try to start XAMPP with sudo /opt/lampp/lampp start command it gives me a message like this.  Starting XAMPP for Linux 1.7.7... XAMPP: Another web server daemon with SSL is already running. XAMPP: Starting MySQL... XAMPP: Couldn't start MySQL! XAMPP: XAMPP-ProFTPD is already running. XAMPP for Linux started.   What is this and how can I find what was this another web server daemon with SSL. How to stop this server ?


There is features both in windows and mac that opens a interface you can see the currently opened windows. I recently saw that feature in the GNOME workaround. Is there anything like that in the unity included in the installation itself? Or anything that can be installed through the terminal? . Reminder, i know the workspaces tool and use it frequently with pleasure. And the alt+tab is not enough.


Why use endl when I can use a newline character?

Is there a reason to use endl with cout when I can  just use \n? My C++ book says to use endl, but I don't see why. Is \n not supported as widely as endl, or am I missing something?


How should I handle sprite creation for customizable 2D characters?

I'm want to create avatar animations (sprites) for a browser-based MMORPG. The player is able to customize the character, and the content changes often (new weapons, armors, and so on). How can I structurally manage the creation and updating of all the sprite sheets?  The amount of different combinations are big enough that simply generating all permutations won't work.  This can be server- or client-based, but if it works entirely on the client, please keep it to just HTML5/CSS/Canvas/WebGL.


Unable to enter password to login in control alt f1 screen

Disclaimer: I am BRAND new to Ubuntu.  A quick background: my laptop hard drive crashed, I bought a new one, didn't want to pay for windows for an old laptop, installed ubuntu, it worked great for a week.   One day I booted up and logged in and got a black screen (no cursor showing as many have). I am able to log into guest just fine. Did my research --appears to be an issue with Nvidia drivers. There are many answers on how to deal with that (though I do not understand them yet).  Finally learned how to open the console/GUI/Ctrl+Alt+F1 (not sure technical name). I am prompted to enter a username and password. I can enter a username, but when I hit enter after entering my username, I am completely unable to enter a password. It will not let me enter a single character into the password, and after a few seconds it says the attempt fails, and loops right back to entering a username.   TL:DR I cannot enter any code to fix the NVidia drivers because I cannot get past my username and password. I know my username and password, but I am not able to enter my password.   I am fine with reinstalling the whole operating system, this computer is completely clean without any personal files, but I am unable to make any changes from the guest login because of lack of administrative permissions.   I am sorry if this is a duplicate, I have searched for a couple weeks and not found a situation exactly like mine, many similar though.


Want to link to a USB Host via my laptop

I have this device that has to be setup as a USB Host.  Normally, my laptop is a USB Host, how do I connect to such a device? When I plug the USB cable into my laptop, I don't see a tty being assigned (ttyUSB0/ttyACM0).


What do you call a person who is utterly independent and a loner?

I was just in the midst of writing a description for a story I am writing, and I'm trying to describe one of the characters, or more rather think of a word I could use to describe them.   They are independent, they do everything by themselves, they enjoy solitude, and believe that friends or socialization is unnecessary and causes nothing but issues. They are quite egotistical and quite narcissistic because of this, but I'm looking for a word that explains their need to do everything alone.   If this helps, my sentence is as follows, or something along those lines:      Marina is a proud _____, she believes that buddies are for weak people, and she could very well cope on her own.


Removing Big, old Files that do not belong in git

Long story short, there are very big files (like iso files-big) that were pushed into git. Not during my time with the group, but they've been treating the repo like an SVN-VC.   Anywho, how can i removed iso's from the repo and its history, to lighten the repo.  Or   Would it be easier to just move the code to a new repo, losing it's repo?


How much faster would a Clock without gravity run?

Pardon the misleading title.  It is to my understanding that moving/heavy clocks run slow. The Earth itself is under gravitational influence from many sources, and is moving. Is there a way to know how much 'faster' a clock would run if those influences were removed? I don't need a precise number, an order of magnitude is fine, just to get the idea.  Any insight is appreciated.


How do I install Tor Onion Browser on Ubuntu 16.04?

I followed the  and got a      SIGNATURE VERIFICATION FAILED!   error when trying to launch the program. So I re-inputted this in command line:   gpg --homedir "$HOME/.local/share/torbrowser/gnupg_homedir/" --refresh-keys --keyserver pgp.mit.edu    (I highlighted it differently this time and the terminal result came out more successfully[?]) then relaunched Tor, now it's stuck at 0% on      Downloading and installing Tor Browser for the first time.   I'm now trying to launch Tor but when I click the program nothing happens.


How can I put a permanent current into a superconducting loop?

I know that you can use induction to create a current in a superconducting loop, but this only works as long as the coil that induces the field has a current flowing through it. And obviously, this cannot work for the really big magnets that are used in MRI scanners or NMR machines.  How does it work?


If I want to solve $x^2=x$ then obviously $x(x-1)=0$ so $x=0$ or $x=1$.  But, what if I try to solve it differently:  $$x^2=x$$ $$\frac{x^2}{x}=1$$ $$x=1$$  Then for some reason the solution $x=0$ vanishes. Apparently I am missing something. Question is: what am I missing and how to also get $x=0$ as a solution in the second method?


I am struggling with a basic matrix calculus question.   Suppose you had $f(\textbf{x}) = (\textbf{a} - \textbf{Bx})^T(\textbf{a} - \textbf{Bx})$  where $\textbf{a}$ and $\textbf{B}$ are a vector and matrix of constants respectively. I am interested in finding the gradient of $f$ with respect to $\textbf{x}$. I would appreciate it if someone could write down the steps needed to compute this gradient.  I know that $d(\textbf{a} - \textbf{Bx})/d\textbf{x} = -\textbf{B}^T$, but I don't know how to apply the derivative operator to the product of $(\textbf{a} - \textbf{Bx})$ with itself.  EDIT: the gradient and the derivative are not the same thing. I am interested only in the gradient.


Set Windows 7 to use cable network instead of wireless network?

My system automatically uses wireless instead of wired. How do I set the priority in Windows 7?


like making a rule or something. I am trying to autofill a function, the first cell is (B14-B2)/B2, the second is (B26-B14)/B14, the third is (B38-B26)/B26, so I wanna to increase number by 12, however, the excel didn't get it and try to fill in (B17-B5)/B5;(B29-B17)/B17;(B41-B29)/B29; how can I let excel autofill function in the way I want it to?


How to handle a off topic or closed question?

How could one handle any closed or off topic questions?   I have googled many times, browsed through the FAQs.   But seriously I couldn't understand how to get my doubts clarified here,  I mean how to get a relevant answer, rather how to present a proper question.   In short the problems I am facing can briefly stated as:   I am not able to post a proper question.  I am not able to work on my off topic questions; actually I can't understand what the relevant sites are for my questions.   I am not asking for any question in particular.  But won't it be less troublesome for a new user to post their questions if the sites briefly mention their topics (related)?  Can't we later post these irrelevant questions in relevant sites and get an answer?  E.g. a person (new user) wants to clarify his or her doubt /problem (faced) against cellular networking and he sees a brief intro about Super User. He thought it would be a suitable site, but the site deals with software and hardware concepts. Oops! The new user's question is closed.


How to create animated GIFs of prototype mockups, like the ones on Dribbble?

I'm sure you've seen Dribbblers upload animated mockups of their designs.   Here's an example:     I can create mockups on Photoshop and even apply simple Tween Animations to them but I can never get my GIFs to look like the example here.   What are Dribbblers using to create these animations?   Notice that the animations also include touch points and perfect motion. I would like to convert my Photoshop mockups to do the same.  How can I create an animated example of my mockups, similar to the ones created by Dribbblers?