I tried to make a 14.04 live USB with Universal USB Installer. I get to the screen where it says Try Ubuntu, Install Ubuntu, etc. but no matter what I select, it eventually ends in this error;  end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)  Does anyone know how to fix this? The computer that this is on is a Dell Inspiron 1545. I've seen a few cases around where you had to format the flash drive as FAT32, but I tried that and it still displayed the same message.  Sorry if this is a duplicate. Any help is appreciated!
I am a new user for Ubuntu. I downloaded 13.10 yesterday and made a bootable USB with universal USB installer on my Lenovo IdeaPad Z580 laptop which is now using UEFI; everything appeared OK.  When I booted from the LiveUSB I got the choices of trying or installing Ubuntu but both of them keep giving me these error:  [ 1.929082] kernel panic-not syncing vfs unable to mount root fs on unknown-block (0.0)   Please tell me what is going wrong?
show elements of order 15 in $S_8$ satisfy a relation Let $G$ be a group.  Define a relation $\sim$ on $G$ by $a \sim b$ if there exists $g \in G$ such that $a = gbg^{-1}$.  Prove that all elements of order 15 in $S_8$ are related by $\sim$.  I noticed that in order to have order $15$ in $S_8$. We need a $5$ cycle and a $3$ cycle. Then, I am stuck. Can anyone give me some ideas about what to do? Thank you in advance. Modular exponentiation by hand ($a^b\bmod c$) Short story: people rediscover how to do math and want to put people in bombs Many years ago I remember reading a short story about an advanced civilization at war that rediscovers how to do math mentally. The reason I remember it is the guy tells it to government officials who are delighted because it means they can put people inside bombs or missiles instead of computers, which were thought to be more valuable.  I believe this is one of those stories I read in a science fiction anthology my father brought home on one of his business trips in the sixties or seventies. Prove by induction that for all $n \ge 0$:  $${n \choose 0} + {n \choose 1} + ... + {n \choose n} = 2^n.$$  In the inductive step, use Pascal’s identity, which is:  $${n+1 \choose k} = {n \choose k-1} + {n \choose k}.$$  I can only prove it using the binomial theorem, not induction. Why is there a difference between urls submitted to a sitemap and urls in the google index? Divisibility by 7 rule, and Congruence Arithmetic Laws How do you access the Shrine of Winter? In Dark Souls 2 there is a 'Shrine of Winter' near Sinners Rise. When you approach the shrine it will not let you open the door and a message pops up that says      Seek Mightier Souls   What does this mean and how do you open this shrine? There has been quite a few times that I wished I could send a message to another user on SO - not ask a question for everyone to see, but just a short message informing them of something or requesting them to do something.  Are there any plans to allow this to happen in the future?  Related: Noticing that Newtonian gravity and electrostatics are equivalent, is there also a relationship between the general relativity and electrodynamics? Python ( or general programming ). Why use  instead of != and are there risks? I tried using integration by parts twice, the same way we do for  $\int \sin {(\sqrt{x})}$ but in the second integral, I'm not getting an expression that is equal to  $\int x\sin {(\sqrt{x})}$.  I let $\sqrt x = t$ thus, $$\int t^2 \cdot \sin({t})\cdot 2t dt =  2\int t^3\sin(t)dt = 2[(-\cos(t)\cdot t^3 + \int 3t^2\cos(t))] = 2[-\cos(t)\cdot t^3+(\sin(t)\cdot 3t^3 - \int 6t \cdot \sin(t))]]$$  which I can't find useful. Consider the curve $\frac{1}{x}$  where $x \geq 1$. Rotate this curve around the x-axis.   One Dimension - Clearly this structure is infinitely long.  Two Dimensions - Surface Area = $2\pi\int_∞^1\frac{1}{x}dx = 2\pi(\ln ∞ - \ln 1) = ∞$   Three Dimensions -  Volume = $\pi\int_∞^1{x}^{-2}dx = \pi(-\frac{1}{∞} + \frac{1}{1}) = \pi$   So this structure has infinite length and infinite surface area. However it has finite volume, which just does not make sense.  Even more interesting, the "walls" of this structure are infinitely thin. Since the volume is finite, we could fill this structure with a finite amount of paint. To fill the structure the paint would need to cover the complete surface area of the inside of this structure. Since the "walls" are infinitely thin, why would a finite amount of paint not be able to cover the outside of the "walls" too?  Please help me make sense of this whole thing. Did Snape ever commit murder? It's well known that Severus Snape was, in one way or another, a Death Eater since he was at Hogwarts. He hung out with the likes of Avery and Mulciber who became well known Death Eaters, he joined Voldemort right after he left Hogwarts, and he basically became Voldemort's right hand man until the very end.   However, in his time as a Death Eater did he ever kill anyone? We know that he was a Death Eater for around 3 years before Voldemort fell; Lily and James died at 21 and they were the same age as Snape, so it would have been 3 years since they left Hogwarts. Then after Voldemort came back in book 4, Snape would have been a Death Eater again for around 3 years. That's a total of around 6 years of Death Eaterhood with Voldemort.  So, in either of these periods, did Snape commit murder as part of his job as Death Eater? I'm not counting a certain death at the end of book 6 for reasons which are obvious if you've read book 7.   Clearly it's much more likely he killed before Voldemort fell since that roughly correlated with the period when he pledged allegiance only to Voldemort, before he became a teacher at Hogwarts. But did he ever do it? Call to a member function on a non-object So I'm refactoring my code to implement more OOP.  I set up a class to hold page attributes.  class PageAtrributes  {   private $db_connection;   private $page_title;      public function __construct($db_connection)      {         $this-&gt;db_connection = $db_connection;         $this-&gt;page_title = '';     }      public function get_page_title()     {         return $this-&gt;page_title;     }      public function set_page_title($page_title)     {         $this-&gt;page_title = $page_title;     } }   Later on I call the set_page_title() function like so  function page_properties($objPortal) {         $objPage-&gt;set_page_title($myrow['title']); }   When I do I receive the error message:     Call to a member function set_page_title() on a non-object   So what am I missing? I am in the process of creating a LaTeX template for a conference submission, and up until now I've been working only with the anonymous submissions. Now I need to create the "camera-ready" version, which means I need to add authors to the document.   The template is based on article.cls, with some tweaks to meet the font and formatting specifications. The following image contains the examples from the Word template for the conference:    Basically, I need to be able to bold the author's name (which could I suppose be done manually in the document rather than in the template) and more importantly: divide the authors into two columns, with an optional centered last column with an odd number of authors. The font size of the author block corresponds to my \LARGE defined in the class file.  Are there any packages that facilitate this type of conditional formatting, either in a document, or in a .cls file? How can I use those packages to achieve the formatting I require? Why and how is the speed of light in vacuum constant, i.e., independent of reference frame? Who made the decision for Gandalf's promotion from 'grey' to 'white'? In the first book of the LoTR, after his fight with the Balrog of Moria, Gandalf the Grey changed to .   My question is, who made the decision to 'promote' him from grey to white? Was it ? Or was it the ? Or was it the ? Why can't you use the keyword 'this' in a static method in .Net? I'm trying to use the this keyword in a static method, but the compiler won't allow me to use it.  Why not? Let $G$ be abelian, $H$ and $K$ subgroups of orders $n$, $m$. Then G has subgroup of order $\operatorname{lcm}(n,m)$. Let $G$ be abelian, $H$ and $K$ subgroups of orders $n$, $m$. Then G   has subgroup of order $\operatorname{lcm}(n,m)$.   This is a statement that my lecturer mentioned in my (beginners') Abstract Algebra class. I'm not sure I understand why it's true.  What I have so far: Use the abelian group structure theorem on $\langle H, K\rangle$ (finite group generated by $H$ and $K$). Then $\langle H,K\rangle=C_{a_1}C_{a_2}\dotsm$ and $n, m |\langle H,K\rangle$. Which means it's also true that $\operatorname{lcm}(n,m)|\langle H,K\rangle$. Can I leverage this to say there's a subgroup of order $\operatorname{lcm}(n,m)$? Logistic regression cost surface not convex I am building a simple logistic regression model on 2D data. Here is the input I use.    I built a logistic regression model using this data and it successfully is able to find the discriminating line between these two classes. Here is the separating line found by my program:    Also, just for debugging, I plotted number of iterations vs J(theta), which also looks fine:    Now, confusing part comes into play. I am investigating the cost surface of this model that the logistic regressions is doing the gradient descent on. I am considering three different loss functions. Sum-of-squared loss, hinge-loss, log-loss.  Hinge loss:    Log-loss:    Sum-of-squared loss:    As far as I know, both hinge loss, sum-of-squared loss and log-loss should produce a convex surface. When I look at my surfaces, however, sum-of-squared surface does not look convex to me. Why is that the case?  For convenience, here is the two critical functions from my code:  function retval = J(X, y, theta)     M = size(y, 1);     % sum of squared error     retval = (1/(2*M)) * sum((h(X, theta) - y).^2);  endfunction  function retval = h (X, theta)     % logistic     retval =  1 ./ (1+ exp(-1 * (X * theta))); endfunction