# 4.3 Java1484-spectrum analysis using java, complex spectrum and  (Page 9/14)

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(By now, you may be suspecting that I have a particular affinity for a data length of 400 samples. If so, you are correct. This is not a technicalaffinity. Rather, it is a visual one. These figures are formatted such that the plotted data occupies an area of the screen containing approximately 400pixels. By matching the plotted points to the positions of the pixels, it is possible to avoid, or at least minimize, the distortion that can occur whenattempting to map from sample points to pixel locations when there is a mismatch between the two.

To see the result of such mapping problems, repeat the experiment shown in Figure 2 and use your mouse to stretch the Frame horizontally by a very small amount. Depending on how much you stretch the Frame, you should seevertical lines disappear, vertical lines that are too close together, or a combination of the two. This is another manifestation of the impact ofsampling that I don't have the time to get into at this point.)

## The length of the pulse

As you can see in Figure 4 , the length of the pulse for this experiment was 11 samples, all but one of which had a value of zero.

(In this case, I could have made the pulse length 1 but for simplicity, I will keep it at 11 for several different experiments.)

## Defining the origin of time

As you may have discovered by playing video games, we can do things with a computer that we can't do in the real world. For example, the Fourier transformprogram allows me to specify which sample I regard as representing zero time. Samples to the left of that sample represent negative time (history) and samples to the right of that one represent positive time (the future) .

In this case, I specified that the first sample (sample number 0) represents zero time. As you will see later, this has a significant impact on thedistribution of energy between the real and imaginary parts of the transform results, and as such, has a significant impact on the phase angle.

## Computational frequency range

Because I am using a DFT algorithm (instead of an FFT algorithm) I can compute the Fourier transform across a range of frequencies of my choosing. Asshown in Figure 4 , I chose to compute the transform across the range of frequencies from zero to one-half the sampling frequency, known as the Nyquistfolding frequency. Thus, the spectral analysis was performed at 400 individual frequencies between these two limits.

## The values that make up the pulse

The computational frequency range is followed in Figure 4 by the values of the samples that make up the pulse. Note that the first sample has a value of 180 while the other ten samplesall have a value of 0.

## Results of spectral analysis on an impulse

I used the program named Graph03 to plot the output from this program, and the results are shown in Figure 5 .

(Note that rather than plotting each sample value as a vertical bar, Graph03 plots each sample as a dot and connects the dots with straight line segments.)

Figure 5. Spectral analysis of an impulse at zero time.

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
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
how did you get the value of 2000N.What calculations are needed to arrive at it
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