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Because of the shorter wavelengths involved, typical radar sensors are usually small enough that they can be physically turned and tilted. Thus, it isnot unusual to see radar sensors turning around and tilting up and down. Although I'm not personally aware of any applications that use arrays of radarsensors, my suspicion is that there probably are some being used in fixed air surveillance operations.

Petroleum exploration

A large percentage of petroleum exploration involves the insertion of a powerful surge of acoustic energy into the ground (or into the ocean) and listening for and recording the echo signals returned by the various layers ofthe earth. By moving across the earth and repeating this process, a profile of the earth's layering can be produced. An experienced exploration geophysicist can examine the profiles and reach conclusions as to the likelihoodthat a particular stratum contains petroleum.

Exploration geophysicists have been using arrays of sensors for this purpose for at least the past 55 years according to my personal knowledge, and probablyfor many years before that.

Image processing

Image processing in the wavenumber domain

While the examples described above are interesting, they are beyond the scope of anything that I can demonstrate online. However, there are severalinteresting applications using 2D Fourier transforms that I can demonstrate online. One of those applications is image processing.

Future modules will show how to use 2D Fourier transforms for such purposes as softening images, sharpening images, doing edge detection on images, etc. Forthis application, it is satisfactory to use a 2D Fourier transform program that assumes that the space domain data is purely real. Therefore, the program that Iwill present and explain in Part 2 of this module will make that assumption.

Image processing in the space domain

The 2D Fourier transform will be used in future modules to help explain how and why 2D image convolution behaves the way it does. A preview of that materialis shown in Figure 6 .

Figure 6. Image processing in the space domain.
missing image

Convolution versus multiplication

Convolution in the space domain is equivalent to multiplication in the wavenumber domain, and vice versa.

A simple space function and its wavenumber spectrum

The top left image in Figure 6 shows a simple 3D surface in space consisting of a raised square. The wavenumber spectrum of that surface is shown in thelower left image in Figure 6 . Note that the spectrum has a peak at a wavenumber value of zero with low values at the higher wave numbers near the edges. Thepeak in the center is relatively narrow with respect to the folding wave number at the edges.

A 2D convolution operator and its spectral response

The image in the upper center of Figure 6 shows a typical 2D convolution operator consisting of a value of +8 in the center surrounded by eightcoefficients each having a value of -1.

The wavenumber spectral response of that convolution operator is shown in the lower center. Note that it has peaks at the folding wavenumbers on all foursides with a low value in the center.

Questions & Answers

what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
how to synthesize TiO2 nanoparticles by chemical methods
Zubear
what's the program
Jordan
?
Jordan
what chemical
Jordan
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Digital signal processing - dsp. OpenStax CNX. Jan 06, 2016 Download for free at https://legacy.cnx.org/content/col11642/1.38
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