# 4.6 Java1490-2d fourier transforms using java, part 1  (Page 10/15)

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## Two full peaks but at different locations

If you consider the peaks at the ends of the wavenumber response for the leftmost and center images in Figure 3 to each represent only half a peak (with the other half being off the scale to the left and the right) , all three scenarios have two complete peaks in their wavenumber responses.

(You could think in terms of printing the wavenumber response on a piece of paper, cutting it out, and taping the two ends together to form acontinuous ring. As you made a complete traversal of the ring, you would encounter two peaks.)

However, the locations of the two peaks for the rightmost array are at completely different wavenumber values than are the peaks for the other twoarrays. The two peaks exhibited by the rightmost array are in the locations of the two nulls for the center array. Similarly, the null points for the rightmostarray are in the same locations as the two peaks for the center array.

## What can we learn from these scenarios?

We learn that we can have a significant impact on the wavenumber response of an array by increasing the number of elements in the array. We can also have asignificant impact on the wavenumber response by applying weights, (including sign changes) , to the electrical signals produced by the array elements before adding them together.

## Extending into two dimensions

Now let's complicate things a bit by extending our array analysis into two dimensions. Up to this point, we have assumed that our sensors were attached toa wire that was free to move up and down only. As such, waves impinging on the array were constrained to approach the array from one end or the other. In thiscase the wavenumber was completely determined by the wavelength of the wave.

(For our purposes, the wavelength is given by the ratio of propagation speed in meters per second to frequency in cycles per second.Canceling out the units leaves us with wavelength in meters per cycle.)

## Move the array to a table top

Let's move our array of sensors from the wire to a large sheet of metal on the top of a table. For the time being, we will still place the elements in aline with uniform spacing. However, we will now assume that a wave can impinge on the array from any direction along the surface of the sheet of metal.

(For simplicity, we will assume that there is some sort of insulation between the sheet of metal and the table top to prevent waves from impinging on the array from below.)

## What does a wave look like in this scenario?

Imagine a piece of corrugated sheet metal or fiber glass. (Material like this is sometimes used to build a roof on a patio.) When you look at it from one end, it looks something like the sine wave in Figure 1 . However, if you keep it at eye level and slowly turn it in the horizontal plane, the distance between the peaks willappear to become shorter and shorter until finally you don't see any peaks at all. What you see at that point is something that appears to have the samethickness from one end to the other. This is the view that one of our sensors sees as the wavefront of an impinging wave.

anyone know any internet site where one can find nanotechnology papers?
research.net
kanaga
Introduction about quantum dots in nanotechnology
what does nano mean?
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?
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
it is a goid question and i want to know the answer as well
Maciej
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
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
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
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 ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
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
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
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.
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