Exam Resit 2021

Question 1

Suggest a reasonable sampling frequency for a sinusoidal signal with the frequency f. [5p]

Answer 1

Shannon theorem says that a minimum sampling frequency should be 2 f, but for a good reconstruction we suggest 10 f.

Question 2

We record 3 periods of a signal that has a frequency of 10 Hz. The sampling frequency is 1000 Hz. How many samples do we eventually
obtain? [5p]

Answer 2

3 x 0.1 x 1000 = 300 samples

Question 3

Which of the following statements is correct ? [5p]

1. A too high sampling frequency has only advantages.
2. A too low sampling frequency will create aliasing.
3. A too high sampling frequency will create aliasing.

Answer 3

A too low sampling frequency will create aliasing.

Question 4

What is the principle of deliberative control? Give two types of systems where it is used. (5 points)

Question 5

For a smart home, write a controller that measures the room temperature and when this is more than 20 degrees Celsius, only a red LED
should turn on, and if the temperature is less than 15 degrees Celsius, then only a green red should turn on. When the temperature is between
15 degrees and 20 degrees, both LEDs should be turned off. (5 points)

Question 6

Regarding mean and median filters for images, which of the following statement is correct? [5p]

1. They both do the same thing.
2. Mean filter calculates the average of the colours of the neighbours including the pixel itself. Median filter is ordering all the pixels by colour and
   takes the middle value.
3. Mean filter is ordering all the pixels by colour and takes the middle value. Median filter calculates the average of the colours of the neighbours
   including the pixel itself.

Answer 6

Mean filter calculates the average of the colours of the neighbours including the pixel itself. Median filter is ordering all the pixels by colour and
takes the middle value.

Question 7

8. We record for 5 seconds a signal which is a sum of two sinusoidal signals, one with the frequency of 100 Hz and amplitude 1V, and one of frequency of 200 Hz, and amplitude 2V.
   Given the figures below, which statement is true? [5p]

A. A is the spectrogram and B is the frequency spectrum.
B. C is the spectrogram and D is the frequency spectrum.
C. C is the spectrogram and B is the frequency spectrum
D. A is the frequency spectrum and D is the spectrogram.

Answer 7

C. C is the spectrogram and B is the frequency spectrum

Question 8

we want to shift it one pixel to the left, by applying a convolution operation with a 3x3 kernel. Design a suitable kernel
that will do the job. [5p].

Answer 8

000
001
000

Question 9

10. Given the spectrograms below, label correctly the word they represent. Some words were uttered a few times. [5p]

Answer 9

1 thunder
2 mama
3 uuu-haaa [u like in hood]
4 thunder
5 mama
6 uuu-haaa [u like in hood]

Question 10

which features do you propose for classification of keys and coins? Justify your answer. [5p]

Question 11

What are Hidden Markov Models (HMM) and how do they work? [5p] Describe an experimental setup where we can use HMM to recognize
activity in a kitchen [5p].

Question 12

Imagine that you have to design a neonatal incubator, which is a rigid box-like enclosure, in which a baby can be kept in a controlled environment for observation and care. The goal is to keep temperature at 36 degrees Celsius.

Identify five stakeholders, formulate one functional requirement and one non-functional requirement. [5p]

Question 13

Imagine that you have to design a neonatal incubator, which is a rigid box-like enclosure, in which a baby can be kept in a controlled environment for observation and care. The goal is to keep temperature at 36 degrees Celsius.

Identify one accident and one hazard that could cause the accident. For this hazard, imagine a possible causal scenario and a mitigation measure to prevent it. [5 p]

Question 14

Imagine that you have to design a neonatal incubator, which is a rigid box-like enclosure, in which a baby can be kept in a controlled environment for observation and care. The goal is to keep temperature at 36 degrees Celsius.

Identify two ethical questions related to this system. [5p]

Question 15

17. Imagine that you have to design a neonatal incubator, which is a rigid box-like enclosure, in which a baby can be kept in a controlled environment for observation and care. The goal is to keep temperature at 36 degrees Celsius.

Below you see a block diagram illustrating the feedback control process. In this figure, label correctly the components. [5p]

Answer 15

1 desired temperature
2 comparator
3 controller
4 heater
5 current temperature in the incubator
6 thermometer

Question 16

1. Given this signal plotted in time domain, which statement is true? [5p]

A. These are 6 periods of a sinusoidal signal with the DC component = 0V, amplitude = 1.5V and frequency = 0.05Hz.

B. These are 3 periods of a sinusoidal signal with the DC component = 1.5 V, amplitude = 0.5V and frequency = 0.1 seconds.

C. These are 3 periods of a sinusoidal signal with the DC component = 1.5 V, amplitude = 0.5V and frequency = 10 Hz.

D. These are 3 periods of a sinusoidal signal with the DC component = 0 V, amplitude = 1.5V and frequency = 10 Hz.

Answer 16

C. These are 3 periods of a sinusoidal signal with the DC component = 1.5 V, amplitude = 0.5V and frequency = 10 Hz.