# 4.10 Frequency domain problems  (Page 4/6)

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## Circuits filter!

A unit-amplitude pulse with duration of one second serves as the input to an RC-circuit having transfer function $H(f)=\frac{i\times 2\pi f}{4+i\times 2\pi f}$

1. How would you categorize this transfer function: lowpass, highpass, bandpass, other?
2. Find a circuit that corresponds to this transfer function.
3. Find an expression for the filter's output.

## Reverberation

Reverberation corresponds to adding to a signal its delayed version.

1. Assuming $\tau$ represents the delay, what is the input-output relation for a reverberation system? Is the systemlinear and time-invariant? If so, find the transfer function; if not, what linearity or time-invariancecriterion does reverberation violate.
2. A music group known as the ROwls is having trouble selling its recordings. The record company'sengineer gets the idea of applying different delay to the low and high frequencies and adding theresult to create a new musical effect. Thus, the ROwls' audio would be separated into two parts (oneless than the frequency ${f}_{0}$ , the other greater than ${f}_{0}$ ), these would be delayed by ${\tau }_{l}$ and ${\tau }_{h}$ respectively, and the resulting signals added. Drawa block diagram for this new audio processing system, showing its various components.
3. How does the magnitude of the system's transfer function depend on the two delays?

## Echoes in telephone systems

A frequently encountered problem in telephones is echo. Here, because of acoustic coupling between the ear pieceand microphone in the handset, what you hear is also sent to the person talking. That person thus not onlyhears you, but also hears her own speech delayed (because of propagation delay over the telephonenetwork) and attenuated (the acoustic coupling gain is less than one). Furthermore, the same problem appliesto you as well: The acoustic coupling occurs in her handset as well as yours.

1. Develop a block diagram that describes this situation.
2. Find the transfer function between your voice and what the listener hears.
3. Each telephone contains a system for reducing echoes using electrical means. What simple system couldnull the echoes?

## Effective drug delivery

In most patients, it takes time for the concentration of an administered drug to achieve a constant level in the blood stream. Typically, if the drug concentration in the patient's intravenous line is ${C}_{d}u(t)$ , the concentration in the patient's blood stream is ${C}_{p}(1-e^{-(at)})u(t)$ .

1. Assuming the relationship between drug concentration in the patient's drug and the delivered concentration can be described as a linear, time-invariant system, what is the transfer function?
2. Sometimes, the drug delivery system goes awry and delivers drugs with little control. What would the patient's drug concentration be if the delivered concentration were a ramp?More precisely, if it were ${C}_{d}tu(t)$ ?
3. A clever doctor wants to have the flexibility to slow down or speed up the patient's drug concentration. In other words, the concentration is to be ${C}_{p}(1-e^{-(bt)})u(t)$ , with $b$ bigger or smaller than $a$ . How should the delivered drug concentration signal be changed to achieve this concentration profile?

can someone help me with some logarithmic and exponential equations.
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
Commplementary angles
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
a perfect square v²+2v+_
kkk nice
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
rolling four fair dice and getting an even number an all four dice
Kristine 2*2*2=8
Differences Between Laspeyres and Paasche Indices
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
is it 3×y ?
J, combine like terms 7x-4y
im not good at math so would this help me
yes
Asali
I'm not good at math so would you help me
Samantha
what is the problem that i will help you to self with?
Asali
how do you translate this in Algebraic Expressions
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
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
what is nanomaterials​ and their applications of sensors.
what is nano technology
what is system testing?
preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
what is system testing
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
can nanotechnology change the direction of the face of the world
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
how did you get the value of 2000N.What calculations are needed to arrive at it
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