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Influence of salt quality in the spreading process

Section 1: Data collection

1. Introduction

Salt is spread on the roads every year to combat the winter effects of ice and snow which make

the roads dangerous for driving (Figure 1). Basically, salt works by lowering the freezing point

of water. The most common system to spread the salt is the spinning disk. Its popularity is

motivated by its low production costs, its large spreading width, its small size and its simple

construction (Aphale et. al, 2003).

Figure 1. Spreading salt on icy road (BREDAL A/S 2014)

The centrifugal spreader consists of a rotating disk with blades fixed to the surface. The salt is

poured onto the spreader disk colliding with the rotating blades, accelerating outwards, before

it eventually leaves the spreader.

The process of salt spreading starts in the tank where the salt is stored and thanks to the feeder

mechanism it is supplied to the spreader disk where it is distributed into the air. Eventually,

after being airborne it ends up jumping or sliding at the road surface.

The salt spreading process is still

NOT under control and too often we

come across inadequate spreading

patterns when testing units indoor

(Figure 2). As it is seen in the figure,

around 25% of the salt was spread

directly outside the road in this

particular test set.

This inability to ensure an even

distribution is even bigger when the

test is done outdoor, closer to the

unit´s real working conditions.

Figure 2. Full scale test done at Engineering Center Bygholm

Influence of salt quality in the spreading pattern

2

A vast variety of salt features can be related to the quality of the salt. In this first approach salt

quality is only regarded to size distribution and only rock salt was tested. As seen in Figure 3,

the size and shape of the salt particles in a truck´s tank may show a large variation.

Figure 3. Rock salt particles (Takai, 2013b)

Table 1. Salt particle classification

< 1 mm Small particles

1 - 2,8 mm Medium particles

2,8 - 5,6 mm Big particles

1.1. State of the art

The performance of spinning spreader disks has been widely investigated (Patterson & Reece,

1962; Hao, Jianqun & Hong, 2013; Macías, 2014). Abundant are the papers which analyse

fertilizer spread and less are the ones with salt as object of the investigation. Nevertheless, the

physics behind the movement of both materials on the spreader disk is comparable. Therefore,

research on salt spread on roads as well as fertilizer distribution with agricultural purpose have

been studied.

The object of the studies has been quite varied, including some authors focusing their research

on identifying which factors influence the spread pattern. A multitude factors have been

identified as influencing the spreader pattern from a spinner disk dedicated to distribute

fertilizer or salt. These can be divided in three main groups: the environment where the

spreading takes place, the machine used and the material spread´s characteristics.

The last group is composed of authors who focused their investigations on identifying which

fertilizer characteristics change spread patterns. For this purpose, (Hofstee & Huisman, 1990)

investigated the influence of some factors on particle motion on and off the disk. That included

fertilizer characteristics such as particle size distribution, coefficient of friction, coefficient of

restitution, particle strength and aerodynamic resistance. The effect on the spread pattern from

the particle size distribution has been studied by (Yule, 2011). This study included an analysis

of 1700 tray samples which revealed the effect small particles have on the spreading pattern.

As the proportion of small particles increases it was observed that the peak value around the

centre line also increased. Nevertheless, the author claims that if the proportion remains below

15%, of particles smaller than 0.4 mm the coefficient of variation of spread is not disturbed

more than a 5%. (Takai, 2013b) observed that small particles land close to the disk and large

particles land further from the disk.

In this study, the maximum size allowed was 5,6

mm and as seen in table 1, the salt particles were

divided into small, medium and big depending on

their size.


3

2. Method

2.1. Spreader disk features

The spreader disk used for the experiments is flat and has a diameter of 0.7 m (Figure 4). It was

equipped with three straight blades since in this first approach the purpose was to study a simple

geometry. In general, conventional blades on the industrial market have non-straight

geometries. However, if the salt quality has a significant influence for the chosen simple

geometry then probably it also has it for more complex geometries.

Figure 5. Straight blade geometry

The blade was 0.29 m long and 0.05 m high (Figure 5).

The feeding point is situated 0.15m from the centre of the disk and the rotational speed used in

the tests was 150 rpm.

2.2. Salt quality tested

During the summer of 2015 several spreader units came to Test Center Bygholm to be tested.

One of the trials done was a sieve analysis of the salt they were spreading (Table 2).

Table 2. Results of sieve analysis from rock salt samples presented as percentages in mass, Bygholm 2015

K38-S1 K40-S1 K56-S1 K41-S2 K38-S2 K59-S1 K39-S1 Average

<1mm 22 16 26 21 23 21 21 22

1 - 2,8mm 56 57 64 53 55 67 57 58

2,8 - 5,6mm 22 27 11 25 21 12 22 20

The average of these sieve analysis is considered sample 3 in this study. From this sample 3 the

rest of the samples (1, 2, 4 and 5) are established by the following procedure.

200 grams of salt with sample 3 size distribution was prepared, properly mixed and deposited

in a plastic recipient. This container was manually shaken for a couple of minutes, as a simple

simulation of the movement of the truck spreading salt, causing the flow of the small particles

to the bottom. The size distribution of samples 1, 2, 4 and 5 was obtained by analyzing the

content of the 2 top and 2 bottom fractions of salt in the new disposition after the shaken

operation. A diagram of the whole process can be seen in Figure 6.

0.05m 0.7m

Figure 4. Flat disk dimensions

0.2m


4

To summarize, the size distribution of the 5 different samples tested during this study can be

seen in the following figure:

Figure 7. Size distribution of the samples

In order to distinguish the 3 different size fractions on each sample, the salt particles have been

colored depending on their size using food coloring (Figure 8). Thus, the small particles are

black, the medium blue and the big ones are pink.

Figure 8. Coloured salt particles

During shaking the

small particles tend to

flow to the bottom of the

container

Samples are

taken from the top

and from the

bottom

SAMPLE 5

SAMPLE 4

SAMPLE 2

SAMPLE 1

Initially the

particles are

homogeneously

distributed

independently

of their size

SAMPLE 3

Figure 6. Overall view of the test samples determination


5

These colors were chosen for their different grey intensity levels when seen through the high

speed camera used in the experiments. A MATLAB® script was developed to enhance the

images obtained using grey-level transformations and to segment these images highlighting this

way the black, blue and pink salt particles as can be seen in section 6.4.

2.3. Data adquisition

In order to observe the influence of the salt quality in the salt spreading process several

approaches were taken at the same time. From simple observation of the spreading pattern to

the analysis of high speed movies going through the measure of the angles of the salt particles

leaving the disk (Figure 9).

Figure 9. Overall view of the study

2.3.1. From spreading plates

In order to get an idea of the influence of the salt quality on the spreading pattern, 3 plates were

strategically placed to collect salt portions during every test when using the coloured salt

(Figure 10). The standard plates in use had a dimension of 2,5 x 1 m and are the same type often

used in full scale tests at the Engineering Center Bygholm.

High speed movies


6

Figure 10. Plates and high speed camera disposition during the test

The position of the plates during the tests is specified in the following figures and also their

numbering for the result analysis (Figure 11 and Figure 12).

Figure 11. Plan view of plate disposition

sssassa

s

sssas

sas

sss

assas

High speed camera AOS S-PRI plus 2124

Spreader disk Straight blades

Spreading plates 1m x 2,5m

Plate 3

Plate 2

Plate 1


7

Figure 12. Elevation view of plate disposition

The 5 samples were tested, repeating the test for samples 1 and 5. It was no possible to repeat

the test with every sample due to the time consuming preparation of each one.

2.3.2. From motion-blurred images

To measure horizontal outlet angles, a simple imaging system was developed to capture the

trajectories followed by the salt particles in the vicinity of the spreader disk (Figure 13).

Figure 13. Motion-blurred imaging arrangement

The camera was placed approximately 1 meter

above the spreader disk. During all the

experiments the camera axis was set parallel to

the spreader disk. The camera exposure was set

in 1/25 seconds, long enough so that salt

particles appear as stripes on the pictures

captured (Figure 14).

Figure 14. Example of motion-blurred image

Every sample was tested following this procedure similar to the one used in (Villete et al.,

2008). Due to the time consuming sample preparation only samples 1, 3 and 5 were tested twice.

A summary of the results obtained is presented in section 3.2 and some of the images captured

in section 6.2.

sss

assas sss

assas

sss

assas

Camera Canon EOS 1100D

Spreader disk Straight blades

Trajectory

Disk and blade

tangential direction

Outlet angle

Salt particle trajectories

Spreading disk

Plate

Background Black plates


8

2.3.3. From high speed videos

In order to observe the flow of rock salt particles on the spreader disk, two series of videos were

recorded using a modular and compact high speed camera. A first series using the conveyor

belt mechanism to provide a constant feed of salt to the spreader disk once the disk has already

reached the 150 rpm mentioned speed. And a second series without the feeder mechanism

starting with the disk completely still with the samples to test set in a pre-established position

on the disk, 0,15 m from the centre of the disk. The disk accelerates until reaching 150 rpm.

For the first series the camera was placed focusing on the disk with some angle of inclination.

Throughout filming, the spreader unit was static and the only movement came from the salt

spreader disk. In total, 10 kilograms of sample were spread every time with a constant mass

flow of 0,9 kg/s.

Limitations in the lighting equipment available forced the shoots to be taken outdoors in

daytime. Therefore, the sun has been the main and unique light source. A different setting was

used for practically every shooting made because of the changing nature of the weather.

Moreover, the lighting condition in every filming session highly influenced the quality of the

images obtained.

In Figure 10, it was shown one example of layouts used to take the shoots outdoors and the

equipment needed.

For the second series, the camera was placed approximately 1´5 meter above the spreader disk

with the axis set parallel to the spreader disk and the videos were recorded inside a greenhouse

(Figure 15).

Figure 15. General layout for the second series

First, 20 grams of sample 1, of sample 3 and of sample 5 were spread at once. Second, 5 grams

of big salt particles, of medium salt particles and of small salt particles were spread at the same

time (Figure 16). In every case, a portion of sample collected already by the blade and another

not.


9

Figure 16. Second series

A summary of the results obtained in both series is presented in section 3.3 and the Matlab code

used to analyzed the frames extracted from the high speed videos is shown in section 6.4.

Sample 3 20g/each Sample 5

20g/each

Sample 1 20g/each

Medium 5g/each

Small 5g/each Big

5g/each


10

3. Results

3.1. From spreading plates

In this first approach, with limited time available, results have been obtained by simple

observation of the plates. In agreement with Takai, 2013b, it was observed that small particles

land closer to the disk and large particles land further from the disk.

When sample 3 (“average” size distribution) was spread, a significant amount of salt particles

landed in the plate referred as 1. The amount of salt particles resulting in plates 2 and 3 seemed

similar to each other.

However every time the extreme sample 1 or sample 5 have been spread the results have been

way different from those experienced with sample 3. Practically no salt particles have landed

in plate referred as 1 and there is a big difference between the content of plates 2 and 3,

containing a larger amount of salt particles after the test the last one.

Following it is shown a comparison of the salt present in plate 1 after spreading sample 1,

sample 3 and sample 5 (Figure 17).

As it has already been mentioned, when spreading sample 1 (above) and sample 5 (beneath)

very few particles land in plate 1. However, when spreading sample 3 (above) a significant

amount of particles land in plate 1.

Sam

ple

1

Sam

ple

3

1 2

1

2

1

2

1 2

PLATE 1

PLATE 1


11

Figure 17. Comparison particles landing in plate 1

Another observation was the variation in the distance flown by the particles before landing on

the plates depending on the sample being tested. The size distribution of the salt spread seems

to have a big influence in the spreading pattern.

Following it is shown a comparison of the salt present in plate 3 after spreading sample 3 and

sample 5 (Figure 18).

As shown above, medium particles (blue ones) fly further from the disk when spreading

sample 5 (landing mainly between sections 5 and 8) than when spreading sample 3 (landing

mainly between sections 4 and 7).

9

8

7 6

4 3 8

6

4 3

3

5

2

7 9

5

1 2

3 2

3

Sam

ple

3

Sam

ple

3

Sam

ple

5

Sam

ple

5

0,25 m

0,25 m

Sam

ple

5

PLATE 1

PLATE 3

PLATE 3

PLATE 3

PLATE 3


12

When spreading sample 3, from the first landing section of the plate it is already seen a

significant amount of small particles and some big particles. However, when spreading

sample 5, just few small particles land in the first section of the plate and no big particles at

all are present. Figure 18. Salt particles landing sections

In general, all sizes of salt particles fly further from the disk when spreading sample 5 than

when spreading sample 3.

A selection of images collected during the experiments is presented in section 6.1. later in this

report.

3.2. From motion-blurred images

In order to present the results of the spreading

angles in a comprehensive way, 12 sections of the

spreading disk (covering 18 degrees each), have

been highlighted in Figure 19 and the results will

be referred to them. In the adjacent figure it is also

pointed the direction of rotation of the disk and

the driving direction.

A schematic view of the results is presented in

tables 3, 4 and 5.

A selection of images captured during the

experiments is presented in section 6.2.

Figure 19. Sections of the spreader disk

The 12 sections defined above are divided in 3 groups since the way the salt particles leave the

disk differs depending on where in the disk they are when they initiate the flight. The 3 areas

are highlighted in Figure 20.

Figure 20. Areas of spreading

Area 2

Area 1

Area 3


13

Area 1 – Sliding/rotation of the particles towards the edge of the disk due to its rotation

Outlet angles for Section 1:

Table 3. Outlet angles Area 1

SAMPLE 1 Section

SAMPLE 3 Section

SAMPLE 5 Section

1 1 1

Range 46-60 Range 49-61 Range 46-59

Average 51,6 Average 53,7 Average 52,3

# data 18 # data 40 # data 24

Area 2 - Superposition of particles leaving due to the rotation of the disk and particles leaving

being pushed by the blade

Outlet angles for Sections [2-6]:


SAMPLE 1 Section

2 3 4 5 6

Range 45-59 43-54 47-51 43-54 46-49

Average 51,6 47,9 49 50,4 47,4

# data 13 14 7 14 9

SAMPLE 3 Section

2 3 4 5 6

Range 44-59 47-62 45-64 39-59 36-51

Average 53,2 54,4 55 49,6 43,5

# data 22 21 17 21 14

SAMPLE 5 Section

2 3 4 5 6

Range 46-61 45-60 44-54 40-53 39-57

Average 55,4 51,1 49,9 46,2 45,1

# data 22 7 15 14 15

Area 3 - Particles leaving the disk after touching the blade

Outlet angles for Sections [7-11]:


SAMPLE 1 Section

7 8 9 10 11

Range 34-46 27-30 25-29 25-30 26-27

Average 41,2 28,3 27,3 27,3 26,6

# data 5 3 6 6 7


14

SAMPLE 3 Section

7 8 9 10 11

Range 31-42 27-28 26-28 27-28 28-31

Average 35,5 27,5 27,25 27,5 29

# data 8 2 4 2 5

SAMPLE 5 Section

7 8 9 10 11

Range 30-33 27-32 28-32 26-30 26-29

Average 31,3 29,4 29,5 28,4 27,7

# data 3 13 12 5 3

The results obtained in section 3.1. show the biggest differences in plate 1 which is influenced

by sections 1, 2 and 3 of the spreading disk. Following in Figure 21 is represented the range of

spreading angles in these 3 mentioned sections and also the average of the angles obtained in

each case.

Figure 21. Spreading angles over plate 1

Plate 1

Plate 2

Average

Sample 1

Sample 3

Sample 5

Average

Average


15

3.3. From high speed videos

3.3.1. First series

Videos from every sample have been recorded but only 3 of them are going to be analysed in

detail, the corresponding to the samples studied in sections 3.1. and 3.2. (samples 1, 3 and 5).

First, an overall view of all the samples is shown in Figures 22 to 26:

SAMPLE 1

Figure 22. Movement of sample 1 on the disk

SAMPLE 2



16

SAMPLE 3


SAMPLE 4



17

SAMPLE 5


From the sequences above, it can be appreciated how it takes longer for the small particles to

leave the disk. In the following images, the small particles have been highlighted by means of

the Matlab code presented in section 6.4.

The same line of dark particles (small particles) is seen when spreading the 5 different samples.

Figures 27 to 29 illustrate this line of dark particles for the samples containing the largest

proportion of small particles where it is easier to appreciate it.

SAMPLE 1

Figure 27. Small particles highlighted on the disk in sample 1

Line of small particles


18

SAMPLE 2


SAMPLE 3


3.3.2. Second series

A selection of images extracted from the videos is shown below in Figure 30 to provide an

overall view of the behaviour of the different sizes subjected to the same rotational velocity of

the disk.




19

Figure 30. Movement of 5g-clusters of small, medium and big particles on the disk

The small particles are the first ones in start leaving the disk and they also stay the longest on

the disk (in agreement with the previous results exposed in section 3.3.1.).

Moreover, the big particles are the fastest on the disk.

Big Big

Big

Big Big Big

Small

Small Small

Small

Small

Small

Medium

Medium

Medium

Medium

Medium

Medium


20

A new selection of images extracted from high speed videos is shown below in Figure 31 to

analyse the respond of samples 1, 3 and 5 subjected to the same rotational speed of the disk.

Figure 31. Movement of 20g-clusters of samples 1, 3 and 5 on the disk

Samples 1 and 3 are the first ones in start leaving the disk, however, sample 5 is the first to have

completely left the disk.

5

3 1

5

3 1 1

5 3

5

3 1

5

3

1 5

3

1


21

4. Discussion

During the data collection it was observed that salt particles are cast in sub-clusters, as it had

previously been pointed out in (Takai, 2013a). These sub-clusters disintegrate on the way to the

floor. This process causes separation of particles according to their size. In general, small

particles land the closest to the disk and big particles the furthest.

This study used 5 salt samples with different size distributions and was divided in 3 parts:

behaviour of the rock salt particles on the disk, angle of the salt particles leaving the disk and

resulting spreading pattern.

These tasks, in this first approach, were developed by simple visual observations. One drawback

is that these observations require a large number of high speed videos that are expensive and

quite time consuming. A deeper study in the area would require the development of a

mathematical model of the behaviour of the sub-cluster depending on its size distribution.

During the study it was clear that the salt quality being spread has an important meaning in the

resulting spreading pattern. The pictures taken after spreading the different samples differ

significantly from each other.

An explanation for the results mentioned before may have been the change of angles of the

particles leaving the disk when spreading different samples. However, as it was shown in

section 3.2., the angles of the rock salt particles leaving the disk do not differ much between

different samples. Another possible explanation for these spreading pattern may be the amount

of salt leaving the disk on each section of the disk depending on which sample is being spread.

With the setup used during these tests it was impossible to get information about this topic.

Therefore, a future experimental setup might be designed to collect the salt in baskets around

the disk in order to obtain data about the amount of salt leaving the disk at each section of the

disk, similar to the one in use in (Reumers et al., 2003).

Several high speed videos were recorded for the analysis of the behaviour of the different

samples on the disk. The high speed camera needs plenty of light to get good images.

Limitations in the lighting equipment available forced us to record the movies outside, which

means that the wind also became a source for noise in the data collection.

The monochrome high speed camera used in the experiments made it difficult to distinguished

the different salt particles sizes/colours in the videos. Moreover, the changing nature of the light

source added shadows and light reflection which complicated even more the image

segmentation tasks.

Overall, the data collected along this study support the hypothesis that the salt quality has a

significant impact in the salt spreading process.


22

5. Conclusion

This work intended to shed some light on the spreading process with respect to the influence of

the size particle distribution and the spreading pattern. This study used 5 salt samples with

different size distributions and was divided in 3 parts: behaviour of the rock salt particles on

the disk, angle of the salt particles leaving the disk and resulting spreading pattern.

This piloting study is based on a simplified design with straight blades. In general, conventional

blades on the industrial market have non-straight geometries. However, if the particle size

distribution of the salt has a big influence on the spreading pattern then probably the same

would happen when using more complex geometries.

The results of this study show that salt quality, considered as size distribution in this first

approach, matters. The spreading patterns further from expected experienced by users and

manufactures could be caused by spreading salt of a different quality that the one assumed.

In agreement with (Takai, 2013b), it was observed that small particles land closer to the disk

and large particles land further from the disk.

However every time the extreme sample 1 or sample 5 have been spread the results have been

way different from those experienced with sample 3. Practically no salt particles have landed

in plate referred as 1 and there is a big difference between the content of plates 2 and 3,

containing a larger amount of salt particles after the test the last one.

In general, all sizes of salt particles fly further from the disk when spreading sample 5 than

when spreading sample 3.

The way the salt particles leave the disk differs depending on where in the disk they first land

from the tank. Therefore, we distinguished 3 areas: an area 1 where the particles slide and rotate

towards the edge of the disk due to the rotation of the disk, an area 2 where there is a

superposition of particles leaving due to the rotation of the disk and particles leaving being

pushed by the blade and an area 3 where the particles leave the disk after being in contact with

the blade. The angles of the rock salt particles leaving the disk do not differ much between

different samples in either of the mentioned areas.

A closest look to the behavior of the different samples on the disk showed that the velocity

needed to move small particles is less than the one needed to move big particles. However, once

in movement, the big particles travel faster than the small ones for the same rotational speed of

the disk. The small particles are the first ones in start leaving the disk and they also stay the

longest on the disk. Hereby the reason of being samples 1 and 3 the first ones in start leaving

the disk and sample 5 the first to have completely left the disk.

These promising results encourage extending studies including pre-wetted salt and the

development of a mathematical model to avoid as far as possible the expensive and time

consuming full scale tests.


23

6. Annexes

6.1. From spreading plates

Link to picture selection:

https://www.dropbox.com/sh/h7bxpl6ij8mmorn/AAAhWwPjgyEiqIsa30DBqBsBa?dl=0

6.2. From motion-blurred images

Link to picture selection:

https://www.dropbox.com/sh/w8dad1oa9d04q6m/AABYfZJzKxHPwfVhiRiYqTUGa?dl=0

6.3. From high speed videos

Link to video selection from the first series:

https://www.dropbox.com/sh/kubbvoad5f1h7bf/AACdZkcmTQXO6LWlW-xAKLbia?dl=0

Link to video selection from the second series:

https://www.dropbox.com/sh/lyw3b68uh3mnry3/AAAucCFK1CntGMzAV1kL-41-a?dl=0

6.4. MATLAB® script %For a 2D greyscale image this function improves it and then segments it

ima=imread('SAMPLE 2-RR.png'); %sample image

im=rgb2gray(ima);

%Improve a 2D image

%OptionA:

A=imadjust(im);

%OptionB:

h=fspecial('unsharp');

B=imfilter(im,h);

%OptionC:

C=imsharpen(im);

%OptionD:

D = histeq(im);

%OptionE:

E = imadjust(im,stretchlim(im),[]);

% Visualize the image improvements

figure('color','w')

subplot(2,3,1), imshow(im)

set(get(gca,'Title'),'String','Original')

subplot(2,3,2), imshow(A)

set(get(gca,'Title'),'String','Option A - Adjust image intensity')

subplot(2,3,3), imshow(B)

set(get(gca,'Title'),'String','Option B - Unsharp filter')

subplot(2,3,4), imshow(C)

set(get(gca,'Title'),'String','Option C - Unsharp masking')

https://www.dropbox.com/sh/h7bxpl6ij8mmorn/AAAhWwPjgyEiqIsa30DBqBsBa?dl=0

https://www.dropbox.com/sh/w8dad1oa9d04q6m/AABYfZJzKxHPwfVhiRiYqTUGa?dl=0

https://www.dropbox.com/sh/kubbvoad5f1h7bf/AACdZkcmTQXO6LWlW-xAKLbia?dl=0

https://www.dropbox.com/sh/lyw3b68uh3mnry3/AAAucCFK1CntGMzAV1kL-41-a?dl=0


24

subplot(2,3,5), imshow(D)

set(get(gca,'Title'),'String','Option D - Contrast enhancement')

subplot(2,3,6), imshow(E)

set(get(gca,'Title'),'String','Option E - Contrast adjustment')

choice=menu('Select the option you wish to proceed with','Option A','Option B','Option

C','Option D','Option E','Original');

switch choice

case {1}

image=A;

case {2}

image=B;

case {3}

image=C;

case {4}

image=D;

case {5}

image=E;

case {6}

image=im;

otherwise

image=im;

end

%----------------------------------------------------------------------------------

imput_img=ima;

imput_img2=ima;

imput_img3=ima;

%Change the limits of Bl, Bk and Pk depending on the image on use

Bl=image(:,:)>=(99)&image(:,:)<=(218); %logical 1 if grey intensity belongs to blue salt,

otherwise logical 0

Bk=image(:,:)>=(0)&image(:,:)<=(54);

Pk=image(:,:)>=(219)&image(:,:)<=(255);

%Find the rows and column with 1

[row,col]=find(Bl);

[row2,col2]=find(Bk);

[row3,col3]=find(Pk);

%In the original image, change the positions found before by black, blue or pink

for i=1:size(row) %BLUE

imput_img(row(i),col(i),1)=0;



end

for i=1:size(row2) %BLACK

imput_img2(row2(i),col2(i),1)=0;



end

for i=1:size(row3) %PINK


25




end

subplot(2,2,1)

imshow(image)

title('Original Image');

subplot(2,2,2)

imshow(imput_img)

title('Medium size');

subplot(2,2,3)

imshow(imput_img2)

title('Small size');

subplot(2,2,4)

imshow(imput_img3)

title('Big size');


26

References

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Dynamics on and off a Spinner Spreader. Biosystems Engineering, 85 (3), pp. 319-329.

BREDAL A/S, 2016. Products. [Online] Available at: http://www.bredal.com/ [Accessed 05 May 2016]

Hao, L., Jianqun, Y. & Hong, F., 2013. Simulation of the operation of a fertilizer spreader based on an outer

groove wheel using a discrete element method. Mathematical and Computer Modelling, 58(3-4),

pp. 842-851.

Hofstee, J.W. & Huisman, W., 1990. Handling and spreading of fertilizers part 1: Physical properties of

fertilizer in relation to particle motion. Journal of Agricultural Engineering Research, 47, pp. 213-234.

Macías, P., 2014. Standardization of test method for salt spreader: Air flow experiment. Report 12: Flow of

salt particles in a spinning spreader disk. Aarhus University, Engineering Centre Bygholm, Test and

Development.

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