Recovering Deleted Photos from SD Card using PhotoRec

I recently deleted all the photos from my SD card and my attempts to find a reliable open source photo recovery software did not bear any fruit until I came across photo rec…
However, with photo rec, you dont get a direct executable program that will recover your phots at the click of a button, you need to have a basic experience of using the command line in your operating system. Even if you do not have any experience in the same, just follow the steps below,

On Ubunutu Photo Rec is available as a package called ‘testdisk’

sudo apt-get install testdisk

For Windows and Mac users you can download the respective packages from here: http://www.cgsecurity.org/wiki/TestDisk_Download

For Linux: follow the steps below

sudo photorec

It will then display a list of the available drives. In my case it was dev/sdc/.

 

Next you just have to select the partition table type, in my case it was Intel/PC – PhotoRec highlights the detected partition table type by default

After that you have to choose the partition, here I chose “Whole disk”:

After that choose the filesystem type. Once again the default is the auto-detected value. In this case Other because our card is FAT.

Next you decide where to save the files. PhotRec creates directories inside this location itself so Desktop will suffice:

Next the recovery begins…

Once complete you should find all your files in a directory named: “recup_dir.1″.

This took about 10 mins for a 2GB card on my machine and lo and behold my photos were restored.

REVEL: Bring Virtual Touch to the Real World

At the recently held SIGGRAPH 2012 conference in Los Angeles, a team of Disney Researchers have demonstrated an interactive display that would change the way ordinary objects feel using a weak electrical signal throughout the whole body. This wearable technology does not need the users to use any kind of wearable gesture interface to create a sense of touch. Now, the users can sense different surfaces like wood, furniture, metal objects, walls, etc.

REVEL Technology with a Surface Display

In these recent years, computer interface research has accelerated as the hardware has become more cheaper and the software, more sophisticated. One branch of active research is touch or haptics, although it requires the users to interact with a specialized device.

The Disney Interface exploits a a tactile effect known as ‘Reverse Electrovibration’ wherein  an imperceptible weak electric signal is created around the user’s body. When the user touches any surface which shares a common ground with the REVEL device, a unique vibrational force is generated between the user’s finger and the surface. The force can modified for different surfaces by varying the shape, amplitude and frequency of the signal providing the user with different tactile sensations.

The REVEL devices can easily communicate with any image on a large number of surfaces provided the surface has a conductive element in it. For example, the paint on a wall if includes copper-based pigments will be conductive and can communicate with the REVEL device. the users do not have to interact with the REVEL devices as these weak signal generators could be embedded easily and effectively in their shoes, chair, etc.

Possible applications for this research includes guide and augmentation for the blind. REVEL could change the way textures feel in a bespoke environment according to the story in which you are in.

However, there involves lot of scope for research to create different signal for a broad domain of surfaces. However, the most important and unique aspect of this research is that the REVEL device does not need the hardware to be changed in shape which makes it pretty cheap to implement except that it is still a decade away from commercialization.

Some of the other interesting projects revealed at SIGGRAPH were:

1. A Colloidal Display: Membrane Screen That Combines Transparency, BRDF, and 3D Volume
2. Chilly Chair: Facilitating an Emotional Feeling With Artificial Piloerection
3. Interactive Light-Field Painting
4. Turn: A Virtual Pottery by Real Spinning Wheel

Neil Harbisson: I listen to color

 

Neil is the first person in the world to wear an eyeborg and have it included in his passport photograph as well. Neil has modified the eyeborg even further so that he could perceive the color saturation as well along with the hues.

The eyeborg works with a head mounted camera that picks up the colours directly in front of a person, and converts them in real-time into sound waves.Neil memorised the frequencies related to each colour: high frequency hues are high-pitched, while low frequency hues sound bolder.

System Load Statistics on Linux vs Windows 7 Distros

 

 

I tried to see the CPU Load Statistics on my linux distro as well as Windows 7 OS installed on my laptop…

Was amazed to see such drastic difference in the cpu usage..

In each case, I had one Matlab Script running and 3 tabs opened in a web browser….

‘ BOOTMGR is Missing; Press Ctrl+Alt+del to restart’

Recently, one of my friends here at MIT had a very common error that many of you might have come across, which is the ‘BOOTMGR is missing’ error. You might even come across the ‘blue screen of death’ which begins to dump your physical memory and then when you try to reboot the computer, the DOS command line flashes ‘BOOTMGR is Missing’.

What I realized over the entire period while searching on google for different possibilities of the above mentioned problem, there was no single article which talked about the collection of all these problems and their solutions as well so that any person if landed on such a page would return back either with a solution or a better direction to search for the errors he/she comes across.

So I have attempted to include all the possibilities that we could think of in solving this problem. At the same time, I have tried to keep this post as simple as possible from the technical perspective for everyone’s use and reference.

The computer used was a Dell Inspiron 1564 Laptop Camputer.

Insert a bootable Windows/ Linux disc into the computer, if it takes you to the installation setup, it means there was some problem with the registry and you can solve that from steps 1 and 2 below.

If you get a message still saying that the boot manager is missing and asking you to reboot like the one shown below. It means that there is either a problem with one/more of your RAM chips or the Hard Disk. In such a case you may want to skip the points 1&2 and directly jump to point 3

1. Start-up Repair using Windows Install CD

You need a bootable Windows Install Disk for performing this operation. Many a times, the ‘BOOTMGR is missing’ error is mainly because of some unwanted change in the system’s registry. This is not the only reason why the ‘blue screen of death’ occurs leading to the ‘BOOTMGR is missing’ error. There are tons of errors and out of the scope of this post. You can however find them on the following article here.

In such a case you should insert your windows install disk and allow the boot operation to run until you arrive at this selection menu on your screen.

Select the ‘Startup Repair’ Option and wait for the system to update its registry to default values.

Wait for the operation to get over select finish and reboot your computer; and remember to remove your install disk before rebooting.

In case you get an error go to option 2 although 2 is just an alternative to 1.

2. Command Line using Windows Install Disk

If the startup repair does not work, this is what you should do…

Arrive at the same menu described earlier and in the image below:

Select the Command Line Option instead of Startup Repair and type in the following set of commands:

bootrec /fixboot     (This command will fix your boot options only)

If this works, you should get the following meassage displayed in the command line:

If you still get an error go to step 3

3. Now either there is a problem with your RAM in allocating or accessing the registry or the hard disk is corrupt.

Try to play around with the RAM if you have multiple RAM chips installed try using permutations and combinations to check whether any particular RAM is corrupted. If you still seem to get an error you may want to check with another Hard Disk

Before you open your computer make sure you read some manuals or search over the web for images/videos that describe how to open your particular system(especially for laptops/notebook computers).
For example, for our machine, i.e. dell inspiron 1564,. this procedure is explained on this link.

Follow the instructions carefully and replace the hard disk and check whether the system goes to the linux/windows installation after inserting the linux/windows install disk (bootable).

In our case, changing the hard drive solved the problem, but we also found one of the RAM chips to be corrupt.

References:

1. Blue Screen of Death : http://technet.microsoft.com/en-us/library/cc750081.aspx
2. Fixing ‘Bootmgr is Missing’ error : http://www.howtogeek.com/howto/windows-vista/fixing-bootmgr-is-missing-error-while-trying-to-boot-windows-vista/
3. Using the Bootrec.exe tool : http://support.microsoft.com/kb/927392
4. Fix ‘Bootmgr is Missing’ in windows 7 : http://www.techsupportalert.com/content/how-fix-bootmgr-missing-error-vista-and-windows-7.htm
5. Hard Disk Damage or Corrupt Boot Manager : http://forum.videohelp.com/threads/316097-Hard-disk-damage-or-corrupt-boot-manager-[Solved]
6. How to open dell Inspiron 1564 : http://beercafe.wordpress.com/2011/11/04/how-to-open-dell-inspiron-1564/

Interesting Way to Prove the Area of Circle…

Basic Mathematical Proof of the area of a circle
(*You may skip these steps and scroll down directly to the video…)

Here is a proof of the area of a circle to satisty the usual questions teachers get all the time when introducing the formula to find the area of a circle: A = Pi × r²

Soon or later teachers have to confront kids as they ask, ” Where did you get that from ? “
or ” Why is the area of a circle Pi times radius squared ? “

We start our proof by having you look at the following figures:

proof for circle

proof for area of circle

Did you notice that as we went from 4 sides to 8 sides, the area outside the circle, but inside the square shrank considerably? This is illustrated below in brown

Now if we keep increasing the number of sides to a very very big number ( call the resulting polygon an n-gon), this space will be so small, it will look like the circle is the same as the n-gon with a lot of sides

Keep this fact in mind since we will refer back to it later!

Now, consider the following figure. Hang on! we are halfway of completing the proof of the area of a circle :

The area of triangle AOB is 1/2 ( base × height) = 1/2 (s × r)

However, we can make 8 such triangles inside the octagon as show below:

This means that the area of the entire octagon is 8 ×( 1/2 (s × r)) = 1/2 r × 8s

Notice that 8s is equal to the perimeter of the octagon

As stated before, if we increase the number of sides to infinity or a very big number, the resulting n-gon ( The regular polygon which number of sides is a big number) will will almost look like a circle

This means that the perimeter of the octagon will almost be the same as the perimeter of the circle

As a result, the closer the perimeter of the polygon is to the circle, the closer the area of the polygon is to the area of the circle

It is reasonable then to replace 8s by 2 × pi × r, which is the perimeter of the circle, to calculate the area of the polygon or the circle when the number of sides is very big

Doing so we get:

Area of circle or polygon equal = 1/2 r × 2 × pi × r = pi × r²

If you want to avoid all the math, here is an interesting way to prove the area of circle…

The Purpose behind Undergrad Internship

My First try with trollface…

Illusion of Choice

You don’t have as much ‘choice’ as you think you do have!!

Pretty IPod Colors by using Anodisation

What do those colorful iPod Nano cases have in common with sapphires?

In both substances the color is not on the surface, but integrated in the structure of the material. Bill Hammack,  in his latest Engineer Guy episode has unveiled the interesting concepts behind coloring metal through anodization

Bill explained what is actually going on with the electrochemical process; touching on facts we already knew; like that the voltage range will affect the color of the annodized surface. But he goes on to explain why these surfaces are different colors and then outlines how anodized metals can be dyed. That’s right, those iPod cases are colored with dye that will not wash or scratch off.

Pores are opened when the aluminum goes through anodization. Those pores are filled with dye, then the metal is boiled in water which closes them, sealing in the color.  You can find the details in the video below.

Fluorescent Lamp Recycling

A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. A fluorescent lamp converts electrical power into useful light more efficiently than an incandescent lamp. Lower energy cost typically offsets the higher initial cost of the lamp. The lamp fixture is more costly because it requires a ballast to regulate the current through the lamp.

While larger fluorescent lamps have been mostly used in commercial or institutional buildings, the compact fluorescent lamp is now available in the same popular sizes as incandescents and is used as an energy-saving alternative in homes.

The United States Environmental Protection Agency classifies fluorescent lamps as hazardous waste, and recommends that they be segregated from general waste for recycling or safe disposal.

The following video explains in detail how the recycling of the florescent lamps is done: