Wi-Fi issue on laptop (likely not driver issue)
Dell Vostro 5490 no WIFI in Ubuntu 18.04
How do I convert materials from Blender Internal to Cycles? I know this may be a tough or confusing question, but I have numerous existing materials I created and reuse for a project, which were all prepared for Blender Internal.  Now, I want to start the transition to Cycles, but I've hit a roadblock. How can I transition my materials without completely starting over? Or should I just forget it and start with fresh materials? Linearization of PDE: $0$ is an eigenvalue since all translates of travelling waves are also travelling waves Consider the following PDE: $$ u_t=u_{xx}+f(u)-w,~~~~~w_t=\varepsilon (u-\gamma w),~~~~~~~~~(1) $$ where $f(u)=u(u-a)(1-u), 0&lt;a&lt;\frac{1}{2}, \varepsilon,\gamma &gt;0, \varepsilon\ll 1,\gamma\ll 1$.  A travelling wave for (1) is a solution that is a function of the single variable $\xi=x-ct$, i.e., $(u(\xi),w(\xi))$ satisfies $$ -cu'=u''+f(u)-w,~~~~~~-cw'=\varepsilon (u-\gamma w)~~~~~~~('=d/d\xi).~~~~~~(2) $$  If (1) is recast in a moving coordinate frame, i.e., in terms of variables $\xi=x-ct$ and $t$, it becomes $$ u_t=u_{\xi\xi}+cu_{\xi}+f(u)-w,~~~~~~w_t=cw_{\xi}+\varepsilon (u-\gamma w).~~~~~~~~(3) $$  One can see by (2), that a travelling wave is an equilibrium solution of (3). So one nearby question is to ask whether a travelling wave is stable.    For a fixed $\varepsilon$, let $U_{\varepsilon}(\xi)=(u_{\varepsilon}(\xi),w_{\varepsilon}(\xi))$ be a travelling wave for (1), i.e., an equilibrium solution for (3).          A standard technique for determining stability of $U_{\varepsilon}(\xi)$ is to linearize: If the right-hand side of (3) is linearized along $U_{\varepsilon}(\xi)$, the resulting operator is     $$ L\begin{pmatrix}p\\r\end{pmatrix}=\begin{pmatrix}p_{\xi\xi}+cp_{\xi}+f'(u_{\varepsilon})p-r\\cr_{\xi}+\varepsilon (p-\gamma r)\end{pmatrix}, $$     where $\begin{pmatrix}p\\r\end{pmatrix}(\xi)\in\text{BC}(\mathbb{R},\mathbb{R}^2):=\left\{u\colon\mathbb{R}\to\mathbb{R}^2 | u\text{ is bounded and uniformly continuous}\right\}$.      (The linearized criterion for stability of the travelling wave is that the spectrum of $L$ (except for $0$) lies in a left half-plane and $0$ is a simple eigenvalue.)  Thats the background.  Now, there is a statement that I could not understand yet.          Note, that $0$ must be in the spectrum because the translate of a travelling wave is another travelling wave.      I know that a translate of a travelling wave is again a travelling wave. But why does this imply that $0$ is in the spectrum of $L$?  Edit  After some looks at definitions, I have an idea:  Consider a solution $U(\xi,t)$ that is a translate of the travelling wave $U_{\varepsilon}(\xi)=(u_{\varepsilon}(\xi),w_{\varepsilon}(\xi))$, i.e.  $$ U(\xi,t)=U_{\varepsilon}(\xi-k)=(u_{\varepsilon}(\xi-k),w_{\varepsilon}(\xi -k)) $$ for some $k$. Then $U$ is an equilibrium solution of (3), too.  If I am not totally wrong, then we have  $$ p=u_{\varepsilon}(\xi-k)-u_{\varepsilon}(\xi),~~~~r=w_{\varepsilon}(\xi-k)-w_{\varepsilon}(\xi) $$ and  $$ p_t=0,~~~w_t=0, $$ because travelling waves are equilibria for (3) and a translate of a travelling wave is a travelling wave.  Hence $$ L\begin{pmatrix}p\\r\end{pmatrix}=\begin{pmatrix}0\\0\end{pmatrix}, $$ meaning that $$ \text{ker}(L-0\text{ id })\neq\left\{\begin{pmatrix}0\\0\end{pmatrix}\right\}, $$ because for each translate of the travelling wave, $p,r\neq 0$ and  $\begin{pmatrix}p\\r\end{pmatrix}\in\text{ker}(L-0\text{ id})$.  Hence $0$ is in the spectrum (point spectrum) of $L$.  Is this what was meant? When is a clause not essential? I am having trouble figuring out when to use commas to set off &quot;nonessential&quot; information.  Sometimes it's obvious:  Bob, who is thirty years old, is an alcoholic.  But other times I'm not sure:  The day he quits drinking * he will start a llama farm He has his heart set on owning El Duderino ranch * in New Mexico.  In the first case, my ear says that there should be a comma at *, even though information before it seems essential to me.  In the second case, the stuff after * is not essential, and yet it seems a little much to use a comma. Even that last sentence I wrote confuses me.  &quot;In the second case&quot; seems essential but I used a comma.  Is this correct? Does it depend on personal style and the length of the clause?  Or perhaps I'm misinterpreting the meaning of &quot;essential&quot; in this context? Here is my question:  Is a homeomorphism, that is, a continuos function whose inverse function is also continuous, always bijective? How to use `ybar interval` without skipping the last value I have the following code  \documentclass[tikz]{standalone} \usepackage{pgfplots} \usepackage{pgfplotstable} \usepackage{filecontents}  \begin{filecontents}{testdata.dat}   -3.316988309367815e-07 0.07000000000000001   -1.948815911147526e-08 0.13   7.15864175355987e-08 0   1.799432483450127e-07 0   0.0002850606647384129 0   0.0009429559686380238 0.08999999999999997   0.00157188462064142 0   0.005259918700865051 0   0.01739392641273605 0.18   0.06208364670743995 0.55   68.69485148165926 6.970000000000001   31.217611224923 79.12   0 12.89 \end{filecontents}  \pgfplotsset{compat=newest} \pgfplotstableread{testdata.dat}\datatable  \begin{document} \begin{tikzpicture} \begin{axis}[   ybar interval,   width=10cm,   height=5cm,   enlargelimits=false,    xtick=data,   ymin=0, ymax=100,   xticklabels={0 -- 0.063,0.063 -- 0.125,0.125 -- 0.25,0.25 -- 0.5,0.5 -- 1,                1 -- 2,2 -- 4,4 -- 5.6,5.6 -- 8,                8 -- 11.2,11.2 -- 16,16 -- 22.4,22.4 -- 31.5},   x tick label style={rotate=60,anchor=east}   ]   \addplot table[x expr=\coordindex,y=0]{\datatable};   \addplot table[x expr=\coordindex,y=1]{\datatable};  \end{axis} \end{tikzpicture} \end{document}   and the output looks like this:    But the command ybar interval does skip the last value. It should look like:    I prefer to have the last value to show up in the interval 22.4 -- 31.5. How do I achieve this without inserting a row of zeros to my table? Do not show ellipsis when not needed in search results When doing a search, the results page shows an ellipsis when it is not needed. For instance:    The message of that answer is shorter than the text overflow limit, which means the ellipsis (...) should not be shown. Offset a background image from the right using CSS How to locate a font in Ubuntu? Ubuntu desktop with 12.04 is about to crash.  Installed 13.04 on a new machine, want to transfer Book Antiqua font from old machine to the new one.  How do I find it on the old machine?  My /usr directory is empty. My fonts.conf file has these lines: &lt;!-- Font directory list --&gt; &lt;dir&gt;/usr/share/fonts&lt;/dir&gt; &lt;dir&gt;/usr/x11R6/lib/X11/fonts&lt;/dir&gt;  &lt;dir&gt;/usr/local/share/fonts&lt;/dir&gt; &lt;dir&gt;~/.fonts&lt;/dir&gt;  Don't know what this means, but my /usr directory has nothing in it. The reply buttons in chat shouldn't reposition themselves on pinged messages In our 5e game, we stole a boat. And a horse carriage. And a lot of other stuff for moving things between cities.   Our DM meant for this to be a way to skip road encounters. We decided to fund a shipping company and hire managers (Knights retainers, etc.) to turn a profit. The DM ruled that these would cover lifestyle expenses, provide us with easy smuggling, etc.   However, we want to keep tabs on the treasure we're moving back and forth.   What can we use for communicating with our managers from anywhere in the world? What about from say, across the city?  We don't need to communicate often or for long - a single round will work. All we need is for the manager to say "we need you back" Show that $n$ lines separate the plane into $\frac{n^2+n+2}{2}$ regions My wireless has suddenly became disabled by hardware switch, BIOS, rfkill, fn+f8 do nothing How can I use the subdivision surface modifier to create more high poly meshes without ruining sharp edges? For example this mesh  The sphere should be subdivided but the rim of the cylinder should stay the same because it is a sharp edge. This is the result of the subdevision  How can I get sharp edges to not be affected by the sub surf mod? Any way to send a personal message to another user? dpkg:error:parsing file '/var/lib/dpkg/status' near line 1146 package 'python-minimal' Inequality $(1+\frac1k)^k \leq 3$ Why do corticosteroids harm COVID-19 patients? states that steroids could do more harm than good in treating coronavirus (COVID-19), referring to .      Understanding the evidence for harm or benefit from corticosteroids in   2019-nCoV is of immediate clinical importance.   It's unclear to me how exactly the use of corticosteroids (which is a common treatments for Asthma patients) can do harm other than the vague explanation of "steroids also impair the immune system's ability to fight viruses".   How exactly does the use of steroids harm the body in case of fighting a virus such as SARS-CoV-2 (2019-nCoV) that causes COVID-19? Please allow using nested expressions when filtering with tags Please support the use of nested expressions like  and (or ) when searching.  Looking here, on meta, at questions tagged   and at questions found with +search +tag +boolean I didn't see any information on this topic. Renaming accessor/mutator methods in Eclipse? Is there any way to automatically rename accessor/mutator when a variable they get/set gets refactored -> renamed (Eclipse 3.4)? Is energy content of a system different depending on the observer? For the sake of simplicity, let's imagine that the entire universe is empty except for a single lump of (classical) matter with mass $m$. In its center of momentum frame, it is clear that the total energy is simply $E_\text{CoM}=mc^2$. However, in a frame moving relative to it with speed $v$, we have $E_\text{moving}=\sqrt{m^2c^4+p^2c^2}&gt; mc^2$ for all nonzero $v$.  Are we to infer that the energy content of a system can be different relative to the observer? Does this not violate the first law of thermodynamics?