## Can a malicious optical disc infect Ubuntu without user action?

Assuming that a malign user has unlimited resources at his/her disposal to infect a computer running Ubuntu, but he/she is only limited in transferring the malware through an optical disc (CD, DVD, BD etc.). The computer is assumed to be malware free at any level of software and hardware, most importantly the optical disc drive firmware is not altered. If the computer user inserts the malicious disc in his optical drive, can the malware automatically activate without the user’s interference?

P.S: In Windows, such infection methods are possible through Autorun, but in Ubuntu, even if auto-running software is enabled, the user gets prompted to execute it.

## Changing optical drive of virtualbox with ubuntu 16.04

I am using a virtualbox having ubuntu 16.04 on a ubuntu 16.04 laptop. I had mounted a 32 bit image of ubuntu in the virtual machine, but now i want to change the optical drive to a 64 bit image, but doing so gives me a error.

How can I change the optical drive image?

## How to set the boundary conditions for Eigensystem for optical waveguide using FEM?

I have been working on waveguide mode analysis using FEM in Mathematica for a week, but I haven’t succeeded until now.

The optical fiber-like waveguide is featured with different refractive index in core and in clad, and the interface between the core and the clad should have the boundary condition of Dz (the normal component of D) and En (the tangential component of E) are continuous. But I don’t know how to express this kind of boundary condition in Mma. I think this is of course different in Neumann, Dirichlet and Robin conditions.

Here is my unsuccessful try.( Mma 12.0, Win 10)

``<< NDSolve`FEM`  r = 0.8; outerCirclePoints =    With[{r = 2.},     Table[{r Cos[θ], r Sin[θ]}, {θ,       Range[0, 2 π, 0.05 π] // Most}]]; innerCirclePoints =    With[{r = r},     Table[{r Cos[θ], r Sin[θ]}, {θ,       Range[0, 2 π, 0.08 π] // Most}]];  bmesh = ToBoundaryMesh[    "Coordinates" -> Join[outerCirclePoints, innerCirclePoints],     "BoundaryElements" -> {LineElement[       Riffle[Range[Length@outerCirclePoints],          RotateLeft[Range[Length@outerCirclePoints], 1]] //         Partition[#, 2] &],       LineElement[       Riffle[Range[Length@outerCirclePoints + 1,           Length@Join[outerCirclePoints, innerCirclePoints]],          RotateLeft[          Range[Length@outerCirclePoints + 1,            Length@Join[outerCirclePoints, innerCirclePoints]], 1]] //         Partition[#, 2] &]}];  mesh = ToElementMesh[bmesh]; {bmesh["Wireframe"], mesh["Wireframe"]}  glass = 1.45; air = 1.; k0 = (2 π)/1.55; n[x_, y_] := If[x^2 + y^2 <= r^2, glass, air]  helm = \!\( \*SubsuperscriptBox[\(∇\), \({x, y}\), \(2\)]\(u[x, y]\)\) +     n[x, y]^2*k0^2*u[x, y]; boundary = DirichletCondition[u[x, y] == 0., True];  (*region=ImplicitRegion[x^2+y^2≤2.^2,{x,y}];*)  {vals, funs} =    NDEigensystem[{helm, boundary}, u[x, y], {x, y} ∈ mesh, 1,     Method -> {"Eigensystem" -> {"FEAST",         "Interval" -> {k0^2, glass^2 k0^2}}}]; vals   Table[Plot3D[funs[[i]], {x, y} ∈ mesh, PlotRange -> All,    PlotLabel -> vals[[i]]], {i, Length[vals]}] ``

## Ive seen many conflicting answers online: For Optical storage, does a pit represent a ‘1’ bit or does a land represent a ‘1’ bit?

Ive seen many conflicting answers online so:

Which one of these is true:

A ‘pit’ represents 1 and A ‘land’ represents 0

or

A ‘pit’ represents 0 and A ‘land’ represents 1

## Ubuntu 18.10 – Sound changes from Optical Audio (On Motherboard) to HDMI (Onboard Graphics – Intel) at random

I’ve been running Ubuntu 18.10 on my media center since January. It’s been working fine until recently where it keeps changing the audio device from the Optical/SPDIF Output (to my sound bar) to the HDMI audio from the onboard graphics. I have no idea why, and changing it back within the settings menu works fine.

I’ve tried using pavucontrol to force using the correct audio device, and it seemed to work for a couple hours. But it switched back again.

I’m completely at a loss, I haven’t had this happen before. Any help would be appreciated.

## Are there some software for Optical Mark Recognition (OMR), like Remark Office OMR, in UBUNTU?

I need a software that reconignizes a printed form like Remark Office OMR. I need to correct tests from my students in school. Are some free software to do this?

## High resolution photography with C API and optical zoom

I am currently looking for solutions to take high resolution photos of objects via a dedicated software. (The software will be developed by myself.) Therefore I am looking for ideas for cameras, where:

• The camera has a full API (settings, focus, exposure, etc…) available in C/C++. (Similar to the Canon EOS-SDK)
• The camera supports an optical zoom via the API. (The objects vary between 3m and 0.5m in size, I would like to zoom in for the smaller objects to capture them with max resolution)

As far as I know the Canon cameras (EOS) do not support optical zoom via their API, all I would be able to do is to crop the image in the SW hence simulating a digital zoom.

Do you have any suggestions, which products I should look at closely? (I am not much of a photography expert)

TeBe

## Why is the depth-of-field preview in the optical viewfinder of my Canon 500D inaccurate?

I have noticed that in my Canon 500D, the depth-of-field preview in the optical viewfinder is inaccurate with large aperture settings.

If I press the DoF preview button, there is very little difference between, say, f/1.8 and f/3.5. In particular, pressing the DoF preview button with f/1.8 vs. f/2.8 seems to make no difference at all.

Obviously, there is a huge difference in the photo, and certainly I can also see the same difference if I use live view (LCD screen) and the DoF preview button. And even with the optical viewfinder, the DoF preview button seems to work as expected with smaller apertures (say, the difference between f/4.0 and f/8.0 is clear and what I see in the viewfinder matches what I see in the photos).

What is going on? Exactly what limits the performance of the DoF preview button with the optical viewfinder, and what is the largest aperture with which it still produces “correct” results? Are there differences between different camera models regarding this aspect?

After a lot of googling, I was able to find this page which suggests that the focusing screen in the optical viewfinder might be the limiting factor:

“Oddly, these modern screens get no brighter when you’re using a lens faster than f/2.8. Try it: put on an f/1.8 or other fast fixed lens and flick the depth of field button. You’ll see no change in anything until you stop down to about f/2.5!”

Sounds familiar – but the above quotation is about Canon 5D, which is obviously a very different thing from my 500D.