# 4.6 Java1490-2d fourier transforms using java, part 1  (Page 6/15)

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## How can we compute the array response?

This is where Fourier transforms come into play. We could compute the response of our one-dimensional array for waves propagating along the length ofthe wire by treating the elements of the array as samples in space and performing a one-dimensional Fourier transform on the elements of the array.

## A sampled space series

In this case, we would consider the array elements to constitute samples taken in space in the same way that we consider a sampled time series toconstitute samples taken in time. In other words, the array elements constitute a sampled space series. The Fourier transform of a sampled time series is thefrequency spectrum of the time series. The Fourier transform of a sampled space series is the wavenumber spectrum of the space series.

## Three example wavenumber spectra

To set the stage for what we will be seeing later, Figure 2 depicts three different two-element arrays with different spacing in the three (black and white) images across the top of the figure. The wavenumber response for each of the three arrays is shown inthe three images in the bottom row of images in Figure 2 .

(In Figure 2 , the array elements are represented by the white dots on the black background.)
Figure 2. Three example wavenumber spectra.

## Plots of 3D surfaces

The images shown in Figure 2 were produced using the class named ImgMod29 , which I explained earlier in the module titled Plotting 3D Surfaces using Java . You can refer back to that module for a detailed explanation of the display format. Briefly, each of the sixindividual images in Figure 2 is a plot of a 3D surface, with the elevation of the surface at any particular point being indicated by the color at that pointbased on the colors on the calibration scale below each plot.

(The calibration scale is the strip that changes color in a smooth gradient from black through blue, cyan, green, yellow, red, and white with black at the leftend and white at the right end.

The three images in the top row of Figure 2 with the white dots on the black background represent the arrayelements for each of the three arrays. The three images in the bottom row of Figure 2 represent the wavenumber response of the corresponding arrays in the top row.)

## Black, white, and the colors in between

The lowest (algebraic) elevation in the plot is colored black. Hence the backgrounds are black in the top three plots. The highest elevation is colored white. Thearray elements are white in the top three plots.

Between black and white, the elevation is given by the color scale below the plot with the lowest elevation on the left of the scale and the highestelevation on the right. Thus, a green elevation is about half way between the lowest and highest elevations. Blue elevations are near the low end. Redelevations are near the high end. Cyan and yellow elevations fall in between as shown by the calibration scale.

## The maximum array output

All three wavenumber plots have a maximum response at the center, which is the zero wavenumber origin. In effect, this corresponds to infinite wavelength.If the wavelength is infinite, it doesn't matter what the separation between the elements is, they will all move up and down in unison and their electricaloutputs will add constructively to produce a maximum output.

what is the stm
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
research.net
kanaga
sciencedirect big data base
Ernesto
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
How can I make nanorobot?
Lily
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
how can I make nanorobot?
Lily
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
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