I read a novel from the mid to late 80's where a class was transported for a survival weekend but the transporter malfunctioned and the group wound up on an unknown planet. I believe the kids were stuck there for a couple before being found. At the end of the book one of survivors journeyed back to the new planet with a type of wagon train of pioneers. Anyone know this book and if so its name?
I would love to identify a sci-fi novel I read in the late 60s or 70s.  It followed a group of young space cadets through their training in the Space Academy.  The training culminated in small groups of cadets being sent through a gateway in the space station, into different worlds where they had to survive whatever conditions they met beyond the gateway, as part of their training.  One such trip went wrong and the group ended up stranded in a hostile world for days, hoping to be rescued by their trainers.  I can't remember much about the story or protagonists so this may be too vague, but I remember descriptions of a vast space station hall and these young cadets bringing whatever kit they hoped they might need - some brought breathing apparatus and full survival gear, but others came with very little as they believed they would not be sent into conditions where they could die without the right equipment.  They hadn't bargained for the power surge or whatever it was that misdirected them as they passed through the gateway!  I also remember rivalry between the cadets - I think the hero was male and quietly heading for top cadet of the year award... and I think at least one of the group died in the unknown planet before they were rescued.  Does this ring a bell with anyone?  I remember the mood and tension more than the details but it was a long time ago!  I have a 10-year old son who I think would love this kind of story.  If anyone can help you have my thanks!
How to show that $\lim\limits_{x \to \infty} f'(x) = 0$ implies $\lim\limits_{x \to \infty} \frac{f(x)}{x} = 0$? Gravatar profile image not showing sometimes It seems that with some profiles the Gravatar image is broken. I am not sure if this is an issue with SE or Gravatar, or both, so posting here.  As an example,  shows an error on , which shows a HTTP 500 on Gravatar.  Profile image on SO:        Image on Gravatar:        Switching to the MSE profile of the user, the image is working (but has a different hash).  Is this a bug on the SE side? Can anything be done to make Gravatar fix this?    Update 2016-10-04:  It happened to me again two times today. The last user profile was . Calling the service two or three times fixes the issue. Install macOS Sierra on VirtualBox? I’m trying to install macOS Sierra on VirtualBox, but can’t seem to make it work. For reference, here are the steps I took.   Downloaded the Install macOS Sierra app from the App Store. Used the inbuilt media creation executable, CreateInstallMedia on a disk image. Created a new VM with the default settings for an OS X El Capitan, plus 128 VRAM. Since VirtualBox refused to accept the DMG, I tried splicing out the InstallESD. VirtualBox now accepted it, but wouldn’t boot. I tried to boot through rEFInd, but still no luck. I tried to patch it both ways (base system and ESD) with iesd. No luck. When booting to GParted LiveCD, it flat-out refused to discover any of the installer CDs.   How can I patch the installer to work with VirtualBox? I don’t want to use pre-patched versions of either the installer or an existing installation, as though to avoid piracy. Let $M$ be an A-module and $f \in \text{End}(M)$ an idempotent endomorphism. Show that $M = \ker(f) \oplus \ker (f-\text{id}_M)$. I don't know how to approach this exercise, using only properties of modules and direct sums, without projections. Can you help me? Thanks in advance. I have a third party php library which I would like to use in a module. How do I do that in Drupal 8? In drupal 7, I have done things like the following code, but libraries_get_path() doesn't exist in Drupal 8, and I'm not exactly sure how things change, not that we use namespaces (of which I am a beginner).  require(libraries_get_path('twitter-api-php') . '/TwitterAPIExchange.php');   And, where should I place my library? Should I create a new libraries directory and put it in the root, just like modules and themes are now in the root? I am trying to understand Maximum likelihood estimation but it looks like I am missing something rather elementary.          suppose we have an iid random sample $X_1, X_2,..., X_n$ for which the probability density function of each $X_i$ is $f(x_i; \theta)$ where $\theta$ is an unknown parameter. Then, the joint probability density function of $X_1, X_2,..., X_n$ is given by:          $f(X_1=x_1,X_2=x_2,\cdots,X_n=x_n)=\prod_{i=1}^{n} f(x_i, \theta)$      In Maximum Likelihood estimation, we try to maximize $f$ as a function of $\theta$.  Question: Why do we maximize probability density instead of probability? In what way does it make sense?  Edit: As explained in the answers, the probability of choosing a finite number of sample points from a continuous probability distribution is zero, so maximizing probability doesn't make sense, but how does maximizing probability density make sense? Not that it's a very good idea to change it, but for fun. According to  post, there are still some problems even after changing entries in /etc/passwd, /etc/shadow, and /etc/sudoers. Any suggestions? How to understand Cauchy's proof of AM-GM inequality(the last step) The AM-GM inequality: $$a_1a_2\cdots a_n\leq\left(\frac{a_1+\cdots + a_n}{n}\right)^n$$  the trivial case: $a_1a_2 \leq \left(\frac{a_1+a_2}{2}\right)^2 $ is self-evident.  then cauchy use this fact repeatedly. He get: $$a_1a_2\cdots a_{2^m} \leq \left(\frac{a_1+a_2+\cdots +a_{2^m}}{2^m}\right)^{2^m}.\tag{$\ast$}$$  This is easy to understand, and natural, but next step:  he let  $$b_1 = a_1,\ b_2=a_2,\ \ldots,\  b_n=a_n,\  b_{n+1}=\cdots=b_{2^m}=\frac{a_1+a_2+\cdots a_n}{n}$$  replace $a_1, a_2,\ldots ,a_{2^m}$ with $b_1, b_2, \ldots b_{2^m}$ in $(\ast)$ and simplified both left and right. He get the answer. I can repeat his proof, but I don't know why Cauchy can got this idea. How does he got it? I am currently writing my bachelor thesis and I am using LyX as my standard writing program (because I am not familiar with LaTeX at all).  For my bibliographystyle I use JabRef and the citation style needs to be Journal of Finance.  Now, I found this .bst file for the Journal of Finance style online () which is actually really good. But the problem is, that I need it in German. There must be an "und" instead of "and" and all the umlauts don't work as well. Basically I need everything in German.  Do you know a website with a German .bst file? Or can I change something in the settings in LyX or JabRef and everything would be fixed? error: Unable to find vcvarsall.bat Are recommendation questions an acceptable kind of list-type question or should they be closed? Recommendations are a recurring topic on multiple Stack Exchange (SE) sites. Some sites allow recommendations (ex: ), some do not (ex: ). There are many reasons for that and I can still remember animated discussions on this subject on the Gaming meta. Then there is that existential problem with Sci-Fi SE, &quot;What problems does answering a question on this site solve?&quot;  The only common problem I can think of is What to read/watch next?, which obviously led to a big number of recommendation questions, later slightly disguised as list question. And the main trouble with these questions isn't objectivity at all, some of them aren't even subjective. It's the fact that they don't have an answer - they are open ended. -  Those questions are monstrously popular because:  There's an actual problem to be solved,  or  This problem is quite common.  In view of the  blog post, a recommendation question fails the &quot;real questions have answers, not items or ideas or opinions.&quot; criteria. But it's still a &quot;practical, answerable questions based on actual problems that you face. &quot; and it requires expertise to answer. The problem is that there are multiple acceptable answers, and the asker is not the best person to evaluate the best answer because he doesn't know which one is the best compared to the others, and he cannot test it in short term. Even the need to accept an answer is questionable. So, is a recommendation question an acceptable kind of list-type question or should it be closed just like any other list-type questions? Fatal error: Call to undefined function add_action() - an untouched problem The question was asked many times in many ways, but unfortunately is not covered well in most of the answers. I'm having the same issue doing things using include-files.  In my TwentyFourteen child theme's functions.php I used:  require_once get_stylesheet_directory_uri() .'/admin-panel/theme-options.php';   And I'm using . I've used it in many of my projects, the same way mentioned here, without having the error. But recently I'm having the issue in several of my projects. If I take the code to functions.php then everything's fine. But it's occurring only when I'm trying to include/require external file.  I'm having the error:     Fatal error: Call to undefined function add_action() in C:\xampp\htdocs\project\wp-content\themes\my-theme\admin-panel\theme-options.php on line 2   In this case I'm having the error using a child theme (of T14). But even in one of my parent theme I'm facing the issue. But in the same environment my other projects are running well with all the includes and/or requires (where several add_action()s are defined). I'm having issues in ALL the add_action() calls, like CPT assigning, Custom Taxonomy assigning etc. But I'm successfully developing another two projects including external files from inc/ folder where all my CPTs are assigned and their meta boxes too.  I tried reinstalling WordPress, deactivating all my plugins, tried from Child Theme, tried only the same thing by modifying TwentyFifteen (applying default theme), tried require(), require_once(), include(), include, require_once, and require one after another with failure. And I'm using WP 4.1.1 in all the good and problematic installs.  Majority of the previous questions are answered with a simple line:     As the message says, you haven defined the function add_action() and yet you're trying to use it.   But,   how come (isn't it already defined by WordPress)? and why it's differing project to project in the same environment (How come it's out of the scope now only in particular project[s])? In the beginning of the series, it's mentioned that Muggle-born wizards/witches are identified due to inadvertent spell-casting. However, it seems like later in the book, disarmed wizards/witches are completely helpless.   What is the explanation for why some spells can be cast without a wand and is there an in-universe explanation for why this isn't done? Also, are there spells that can be cast non-verbally (with/without a wand)? I'm trying to find a post I made on my timeline (aka wall) several months (or even years) ago, but can't find a way to search for it. I , but that's very heavy.   Currently, I open the activity log (e.g., https://www.facebook.com/username/allactivity) and start scrolling down to get some info on the page. Then I use my browser to search for the text. But this is slow and, depending on how far back I want to go, tedious. Clicking on the earliest month/year in the filter only loads those periods specifically.    Anyone know of a better way that will find the search words anywhere on your activity log quickly?    Edit: There's a  (not really a bug, but lack of a feature) related to this on Facebook's developers forum. Editing PostGIS/GeoServer data via web? I've got PostGIS installed and would like to create a web application to do some simple edits:   Draw manually (over a Basemap) points, lines and polylines, using snapping  points (points, end of lines, intersections, center of circles)  Delete points, lines and polylines  Rotate a line or group of lines around a point  Move a line or group of lines with a base point  Move polylines and points (manually and to a point given by the coordinates) Edit position of vertices of polylines and lines (manually and to a point given by the coordinates)  Create buffers around points, lines and polylines    Which is the best way to do this via web? Is there any already-built JavaScript library? Story about last 2 men on Earth. One very evil, and the other very ethical I've been told that when "the" is proceeded by a vowel sound, like "apple" or "hour", it's pronounced as "thee" and not as "thu".  But after listening to a couple of songs, I noticed that sometimes this "rule" is not followed. Take for example the two Katy Perry's songs, "Roar" and "The one that got away". In the first she sings "I got thee eye of thu tiger", but in the second she sings "Thu one that got away".  I don't know if it was sang this way to better suit the song melody (I understand nothing about those techniques), but I got confused. What's the correct pronunciation?  Thanks in advance. The question is if you have a situation where one of the singular values is equal to 0 in a singular value decomposition of a matrix, how to do you procede to find the column vector of U corresponding to this singular value?   Usually I found the columns of U with this relation, so let's say that we refer to $\vec{u_2}$ as the U column vector corresponding to singular value equal to 0:  $\vec{u_2} = (1/s_2)Av_2$  Now the as we can see the 0 is in an illegal place, since you can't divide by zero. But if you move it to the left side, I still can't quite see how to find the column of U corresponding to it. Any suggestions?  Here is an example of a matrix that provided this specific challenge  $ A = \left(\begin{array}{rrr} -3 &amp; 1 \\ 6 &amp; -2 \\ 6 &amp; -2 \end{array}\right). $  $ \lambda{_1} = 90$,  $\lambda{_2} = 0$,  $s_1 = 3 \sqrt{10}$,  $s_2 = 0$,  How can one find $\vec{v_2}$ when $\lambda{_2} = 0$? In this case, you know that the eigenvectors of $A^{t} A$ are orthogonal, solve for $\lambda{_2}$ and find the eigenvector if it's orthogonal to the eigenvector corresponding to the first eigenvalue you have your solution.  So we end up with the following normalized column vectors for V, which we can see are orthogonal:  $ \vec{v_1} = \left(\begin{array}{rrr} -3/\sqrt{10} \\ 1/\sqrt{10} \\ \end{array}\right). $  $ \vec{v_2} = \left(\begin{array}{rrr} 1/\sqrt{10} \\ 3/\sqrt{10} \\ \end{array}\right). $ How do you photograph rain? What are recommended settings for my Nikon Coolpix P1 to best portray rain?  Here's what I got. No retouching was applied.   The picture I took when the rain was heavy with the automatic settings:  The picture I took with the "Sports" program; by then, however, the rain was not as hard. Ugh, ugly gray strip at the bottom, that was the flat surface I put my camera on to get a stable picture.   My main problem is that the actual rain and hailstorm is very hard to see in the picture. The overall effect is, instead, of fog.    Follow-up from the thread, courtesy of more rain, now with less hailstorm and more thunder.  The feedback amounted to flash and faster shutter. I took a few photos and I'm having some trouble to reconstruct what I did to get each result. Two representative results:   Fast shutter, with some guest starring:I'm talking about that horrible building obviously. Faster shutter and flash:Kinda difficult to say those pictures were taken sixty seconds of each other. :)   I'm not sure, however, that either of this is really an improvement of the original results. Rewrite Sharepoint URL (Sharepoint 2013) I'd like to rewrite all my site urls in the way the the user can't figure out the exact name of the the page his viewing. let's say that my site is "www.justarandomsite.com"  and may page is "page.aspx" I' like to have instead of "www.justarandomsite.com/pages/page.aspx" sothing like this: "www.justarandomsite.com/skdhfjksdgfjksdgfjdsgvdjhsgfjdsdsjfgkdsjgfkdsgfjdsgfjkdsg"