Size of object from its image
Can I calculate the size of a real object by just looking at the picture taken by a Camera?
How do we "restore" notepad after crash? I was running NotePad and Chrome when my computer suddenly shuts down.  After reboot, chrome was able to "restore" itself such that I didn't lose any data.  However, how do we "restore" notepad.exe? How to debug "Cross-thread operation not valid" error in C#? How can i check if $remote_addr IP is NOT in CIDR range in nginx? I am using nginx latest web server. How can i check if the $remote_addr ip is NOT in specified CIDR range and return appropriate error code.  i would like to return specific error codes if IP is NOT in specific CIDR IP ranges.  how can i do this for CIDR IP range ?  e.g.    If remote_addr is not in 123.123.123.123/24 then return 444 code . Why is the network configuration I set in /etc/network/interfaces ignored on Ubuntu 17.10? Dimensions with Rank-Nullity question $f:V \rightarrow V$, $\dim(V) = n$  a) If $n$ is odd, prove that there does not exist a linear transformation with $\operatorname{im}(f) = \ker(f)$  b) Is it false to affirm the previous statement if $n$ is even?  My answer: $$ i = \dim(\operatorname{im}(f))\\ k = \dim(\ker(f)) \begin{cases} n=2i                           &amp; \text {if $i=k$} \\ n=i+k   &amp; \text{if $n\neq k$} \\ \end{cases}  $$  b) Yes.  Is that a valid proof? What is wrong with \ifnum#1=0.09\relax? The following code does not compile with the following error message     Missing = inserted for \ifnum   \documentclass[pstricks,border=4pt]{standalone} \usepackage{multido}  \psset{linewidth=.5\pslinewidth} \psset{xunit=2cm}  \newcommand\FixedScale[1]{%     \multips(0,0)(.1,0){\the\numexpr10*#1+1\relax}{\psline(0,0)(0,-3pt)}     \multips(0,0)(.5,0){\the\numexpr2*#1+1\relax}{\psline(0,0)(0,-6pt)}     \multips(0,0)(1,0){\the\numexpr#1+1\relax}{\psline(0,0)(0,-9pt)}     \multido{\i=0+1}{\the\numexpr#1+1\relax}{\uput[-90](\i,-5pt){$\i$}} }  \newcommand\VernierScale[2][0.09]{%     \rput(#2,0){%     \psset{xunit=#1,linecolor=red}%     \multips(0,0)(1,0){11}{\psline(0,0)(0,3pt)}%     \multips(5,0)(5,0){1}{\psline(0,0)(0,6pt)}%     \multips(0,0)(10,0){2}{\psline(0,0)(0,9pt)}%     \ifnum#1=0.11\relax         \multido{\i=0+5}{3}{\uput[90](\i,8pt){\tiny$\the\numexpr10-\i\relax$}}     \else         \multido{\i=0+5}{3}{\uput[90](\i,8pt){\tiny$\i$}}     \fi     } }  \begin{document} \multido{\n=0.00+0.01}{21}{% \begin{pspicture}(0,-.5)(2,.55) \FixedScale{2} \VernierScale[0.09]{\n} \end{pspicture}} \end{document}   What is wrong with \ifnum#1=0.09\relax? I want to change my thesis topic (to the extent that the ethos is still in tact) but my advisor does not agree. What can I do? I am doing a phd where my aim is to solve a problem A which is very interesting. My supervisor has got a lot of connections in a technology B and he claims to be an expert in B. I came to this group because of these accomplishments. But soon I realized that B is not really a great technology for A.   So in my phd proposal I proposed a method which encompasses B but is more general (say R). Now I realize that I do not want to use B at all because my preliminary results are not encouraging. In fact, I am inclined to use E as a base technique which does not have any impact on R.  But my supervisor, who is interested in only publishing in B  and frowns upon everything else (it was a nightmare to convince him to let me work on R) is dead against it. He says that he is an expert in B and his vision of the group is not inclined with me trying other things.  There are other professors in my university who have worked in E and could collaborate but my supervisor won't collaborate with people from outside his kingdom. I also know professors from outside my university who could help me if needed. I could knock the doors of school committee in order to  help me but that would create a lot of problems as my supervisor wields a lot of power and influence everywhere.    Another query is, is it ethical to collaborate with people outside the university (of course after letting my supervisor know) for my PhD work. My Masters supervisor would be happy to help me out.  Edit: After looking at comments, I am thinking that after all, it is MY PhD. Yes, I have spent 1.5 years, but 1.5 years is left. Why should I spend any moment of my life on something I find to be not exciting, particularly less exciting because it is forced on me. And in those 1.5 years I learnt to write well and also learnt 'A' which is important. Its not total waste. My supervisor has his agenda, and why should I give up mine to make him happy? His vision is fine, but he does not have the right to force his vision on me. How can the backtick character ` be included in code? I tried before to post a shell script that contained a ` character as an answer on Stack Overflow. The parser insisted on treating the backtick as formatting instead of part of code.  How can I include it? Old title - "change resolution to 1280x1024 using xrandr gives: X Error of failed request: BadValue (integer parameter out of range for operation)"  I have installed a fresh Ubuntu 17.10 and have a monitor with 5:4 resolution. settings has no resolution higher than 1024x768. But I need the resolution 1280x1024 (5:4).  I use the default motherboard graphics card:  # lspci|grep VGA 00:02.0 VGA compatible controller: Intel Corporation 4 Series Chipset Integrated Graphics Controller (rev 03)   Also xrandr gives the following:  $ xrandr Screen 0: minimum 320 x 200, current 1024 x 768, maximum 8192 x 8192 XWAYLAND0 connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm    1024x768      59.92*+   I tried to add the 1280x1024 resolution using xrandr. so first created the resolution information using gtf:  $ gtf 1280 1024 60    # 1280x1024 @ 60.00 Hz (GTF) hsync: 63.60 kHz; pclk: 108.88 MHz   Modeline "1280x1024_60.00"  108.88  1280 1360 1496 1712  1024 1025 1028 1060  -HSync +Vsync   Then added to resolutions:  xrandr --newmode "1280x1024_60.00"  108.88  1280 1360 1496 1712  1024 1025 1028 1060  -HSync +Vsync   then again did the command: xrandr --addmode XWAYLAND0 1280x1024_60.00  Then nothing changed. When I tried to change it using xrandr --output XWAYLAND0 --mode 1280x1024_60.00 --rate 60 But an error occurred:  $ xrandr --output XWAYLAND0 --mode 1280x1024  --rate 60 X Error of failed request:  BadValue (integer parameter out of range for operation)   Major opcode of failed request:  140 (RANDR)   Minor opcode of failed request:  7 (RRSetScreenSize)   Value in failed request:  0x0   Serial number of failed request:  21   Current serial number in output stream:  22   I don't know what did I do wrong. Or how to change resolution to the correct one: 1280x1024 What is the rule to convert the 'mm' notation to the 'optical zoom' notation? I searched a bit and found this one:  optical zoom = maximum focal length / minimum focal length   For example a 18-55mm lens would have a 3x optical zoom, and a 18-200mm lens would have a 11x optical zoom. Is that right? For $f$ continuous, show $\lim_{n\to\infty} n\int_0^1 f(x)x^n\,dx = f(1).$ How to derive variance-covariance matrix of coefficients in linear regression I am reading a book on linear regression and have some trouble understanding the variance-covariance matrix of $\mathbf{b}$:    The diagonal items are easy enough, but the off-diagonal ones are a bit more difficult, what puzzles me is that  $$ \sigma(b_0, b_1) = E(b_0 b_1) - E(b_0)E(b_1) = E(b_0 b_1) - \beta_0 \beta_1 $$  but there is no trace of $\beta_0$ and $\beta_1$ here. At what pressure will be particles in a medium be unable to form a sound wave when disturbed? How can this pressure be described mathematically?  My guess is that this would correspond to the point at which the restoring force due to pressure is unable to create a transverse wave and the disturbed particles travel infinitely far away before the hypothetical wave reaches it's amplitude. But I have no idea how you would even begin to start finding a quantitative value for this point. Convergence of the $\sum_{n=1}^{\infty}n^3b_n^3$ where $b_n=\int_{-\pi}^{\pi}f(t)\sin (nt)\ dt$. I am aware of what hyperfocal distance is and the general principles behind it. However, most of the tutorials I have seen and read regarding it make use of lenses with focus distance indicators. Unfortunately, neither of my lenses (Nikkor 18-55mm &amp; 35mm f1.8) have indicators.  I have read that you can 'cheat' and simply focus a third of the way into the shot (which I have done previously simply by spot-focusing on the lowest focus point in my VF). I also assume you could pace out the distance and note an object to focus on when you get back to the camera (though that might be easier said than done).  Does anyone have any suggestions on how to achieve maximum sharpness from front to back without focus distance markers. A new lens is not an option; global economic crisis and all that! Questions about a commutative ring with exactly three ideals Let $R$ be a commutative ring with identity. Assume that $R$ has exactly three distinct ideals: $\{0\},I, R.$      1) Show that if $a \in R-I$, then $a$ is a unit in $R$.      2) Let $a,b\ne0$ in $I$. Show that $ab=0$. Fitting unbreakable large equation on one line in a twocolumn layout My competitor is using Alexa to see what I am doing. I need to get stop Alexa from including my sites in their rankings. How can I do so?   Is it possible to deny access to any visitor with the Alexa toolbar and deny access to Alexa bot requests? Let $\mathbb{F}_3$ be the field with three elements. Let $n\geq 1$. How many elements do the following groups have?   $\text{GL}_n(\mathbb{F}_3)$ $\text{SL}_n(\mathbb{F}_3)$   Here GL is the , the group of invertible n×n matrices, and SL is the , the group of n×n matrices with determinant 1. How do I make Thunderbird open links in Chromium? I want to be able to click links in Thunderbird emails and have them open in Chromium (package name chromium-browser). Instead, they open in Firefox.  I have tried the following:   xfce preferred applications (Chromium is not listed, so I had to hunt down the executable) -- next time I run chromium, it complains that it is no longer the default browser. Telling Chromium to set itself as the default browser. Thunderbird opens links in Firefox. update-alternatives. It's already listed as an alternative at the same priority as Firefox. The "open web browser" app menu item opens Chromium. Thunderbird opens links in Firefox.   I have looked through the entire preferences gui in Thunderbird (but not the advanced config editor yet) and seen nothing that mentions what browser to open links in.  Please note that this is not Google Chrome.