Fraunhofer Chalmers Research Centre for Industrial Mathematics
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Online Monitoring Of Brake Capability for Heavy Vehicles
No full textThe recent advancement in heavy vehicle brakes involves development of a novel fastacting
electronic brake system. This brake system comprises a slip controller that
aids in reducing the stopping distances and tracks longitudinal wheel slip demands
accurately during extreme braking manoeuvres. The slip controller and pressure
controller relies on the knowledge of the ‘brake gain’ to calculate the desired brake
pressures. The brake gain is defined as a relation between applied brake pressure
and received brake torque. Currently the brake gain is assumed to be known and a
constant, which is far from true.
In this master thesis an algorithm to measure and estimate the brake gain on-line
has been developed and evaluated. The developed estimator captures the variation
of the brake gain with brake fade and actuator geometry. A temperature model is
developed to estimate disc temperature based on the total braking energy at each
braking event. The predicted brake disc temperature is used to estimate the discpad
interface friction coefficient. Further this information is used to monitor the
brake capability. The developed estimator shows that the estimations converge to
the reference
Bakteriella polysackarider - enzymatisk syntes och jakt på nya nedbrytande enzymer
No full textA common problem in society today is tooth-related diseases caused by dental plaque.
Dental plaque is a microbial biofilm which works like a protecting shield for organisms
to live within, and consists of mostly water and polysaccharides. Dental plaque can
eventually lead to diseases such as caries or tooth decay, hence treating dental plaque
at an early stage is of importance. Despite preventional methods in use today, dental
plaque is still a widespread global problem suggesting that these methods are insufficient. There are a limited number of enzymes known today which can break down
mutan or alternan, which are two polysaccharides that can be found in the dental plaque
matrix. This project aimed to isolate and categorise enzymes from microorganisms
with the ability to break down mutan and alternan. A long-term goal with finding new
enzymes able to break down the polysaccharides is to incorporate these enzymes in
dental hygiene products.
Since mutan and alternan are not commercially available they were produced from the
enzymes GtfJ and GtfL, and then purified by centrifugation and filtration. To confirm
the purity, the polysaccharides were tested by reducing sugar analysis and thereafter
freeze-dried before use. The polysaccharides were then used as a carbon source in cultivation
plates and in liquid media when cultivating microorganisms. Field studies were
carried out for collection of samples in two green belts around the Gothenburg area.
The sampling included water and soil samples from different biotopes, which were introduced
to cultivation plates made up of agar and alternan or mutan. A cultivation
plate only containing agar was used as control. Growth was studied for a couple of
weeks, and some colonies which showed growth with a clearing zone were restreaked
on additional cultivation plates. Thereafter, samples were inoculated into liquid media
for faster growth and to generate a sufficient amount of DNA for sequencing. Samples
which showed growth after inoculation, and had a clearing zone when restreaked, were
analysed by 16S and ITS sequencing. Results from the sequencing showed the possible
presence of a known fungal species, Brettanomyces bruxellensis, and also the probable
presence of five fungal and bacterial species belonging to the genera Cladosporium
and Paenibacillus. Out of the six species discovered, five of them were able to break
down mutan and one of them was able to break down alternan. Due to lack of time the
purpose of isolating and characterising enzymes from said microorganisms could not
be achieved, and hence it is a possible subject for further studies. These studies may
involve enzyme efficiency and function in vivo, along with comparisons between several
dierent enzymes in order to obtain optimal enzyme characteristics
Circumstellar Envelopes of Stars on the Asymptotic Giant Branch:The determination of gas mass-loss rates, identification of molecules and detection of dust
No full textUsing data observed in Band 6 (211-275 GHz) and Band 7 (275-373 GHz) with the interferometer
ACA (part of ALMA) from the DEATHSTAR project [1] we have analysed the CSEs
of 5 AGB stars; three carbon-rich (Y Hya, U Hya and R For) and two oxygen-rich (R Hya
and R Crt). The analysis was comprised of three main areas: determining the gas mass-loss
rates, ˙M , identifying molecules and investigating the presence of dust, where the analysis of
M
was the most extensive. Using the CO lines J = 2 ! 1 and J = 3 ! 2 we determined ˙M
with an equation from Ramstedt et al. 2008 [2] based on CO radiative transfer, as well as the
expansion velocities of the CSEs. All calculated values of ˙M , ranging 2.2-22 · 10−7 Myr−1
(+79%/ − 66%), were within the equations stated error margin of a factor of three[2] and
consistently higher, compared to values in the literature obtained with CO radiative transfer
modelling[3, 4]. Due to the equation used for ˙M being based on single-dish telescopes, conversions
for our data had to be made. Therefore, a systematic error in the conversion could
account for the higher values. Furthermore, the expansion velocities were significantly higher
than those in the literature[4] for all stars except Y Hya. However, the data used by us had
a higher signal to noise ratio and overall lower uncertainty in comparison[5], indicating that
our values may be more accurate. All molecules identified from the frequency spectra in
Band 6 (215.4 - 217.4, 217.3-219.3, 230.2-231.2, 231.1-233.1 GHz) and Band 7 (330.3-331.3,
331.3-333.3, 342.5-344.5, 345.1-346.1 GHz), 15 in total with 11 in the carbon stars and 10 in
the oxygen stars, were common for the respective spectral type except the recently (2016)
discovered AlO [6], which was identified in R Crt. The spectral index, , was calculated
from the flux in continuum emission in Band 6 (224.3-241.9 GHz) and band 7 (338.2-354.0
GHz). The temperature was calculated for the stars with 2 (Y Hya and R Crt) and
agreed with the temperatures in the literature [3, 4]. For the stars with 6= 2 (U Hya, R
For and R Hya) the dust mass, MD, and the dust mass-loss rate, ˙MD, was calculated with
an assumed dust temperature of Tdust =100 K if the measured flux was 10% higher than
expected (R For and R Hya), giving the uncertain values (due to Tdust having an exponential
relation) MD = 10−5M for both stars and ˙MD = 10−8M yr−1 and ˙MD = 10−7M yr−1
for R For and R Hya respectively
Aerodynamiska effekter vid platooning: En simuleringsstudie på Windsormodellen i olika formationer
No full textPlatooning är ett koncept där fordon kör i grupp med korta avstånd sinsemellan. Idag är det
en säkerhetsrisk att ligga nära framförvarande fordon, därför sker utvecklingen parallellt med
självkörande fordon. Potentiella fördelar med platooning är bland annat att det kan leda till reducerat
luftmotstånd vilket bidrar till minskad bränsleförbrukning. Detta är också fördelaktigt
för exempelvis transportsektorn ur ett kostnads- och miljöperspektiv.
Tidigare studier är genomförda i vindtunnel med skalmodeller för att analysera flödesfenomen
vid platooning. Testerna i vindtunnel kan vara dyra och tidskrävande vilket gör att det är av
intresse att analysera platooning med Computational Fluid Dynamics (CFD) - analys. I denna
studie kommer de aerodynamiska effekterna vid platooning av en kolonn med tre fordon analyseras
med Star-CCM+. De huvudsakliga modellerna som används är Reynolds Averaged Navier
Stokes och K- turbulens. Fordonsmodellen som används i simuleringarna är en Windsormodell
med hjul. Simuleringsstudien är indelad i två testserier, den första serien med varierande avstånd
och den andra med varierande sidvind för tre olika intervall. Rådata från simuleringarna
bearbetas och analyseras för att upptäcka trender.
I studien åskådliggörs gynnsamma trender för båda dessa testserier. I simuleringarna utan sidvind
är den övergripande trenden att de två bakomvarande bilarna besitter de mest gynnsamma
placeringarna. När en sidvind appliceras observeras en motsatt trend. Där har istället den ledande
bilen den mest förmånliga placeringen. Då sidvind appliceras ökar luftmotståndet alltid för
varje placering bakåt i kolonnen. Platooning är därmed ett känsligt koncept som har potential
att ge stora förbättringar på aerodynamiken om alla omkringliggande faktorer är optimala
Improvements of Warehouse Operations to Reduce the Impact of Quality Deficiencies
No full textIn the increasingly competitive market of 3PL:s, it is important to have efficient processes
limiting non value adding time as much as possible while at the same time delivering high
quality services. There are a number of different quality deficiencies that may occur in the
warehouse operations and DB Schenker Logistics AB wants to understand their current
situation and how the impact of quality deficiencies can be reduced to make their operations
more efficient. The purpose of this thesis is therefore to increase the understanding of quality
deficiencies occurring in the warehouse operations and how the operations can be improved to
reduce the impact of the deficiencies. Three of Schenker’s larger customers were the focus for
the thesis. To be able to fulfil the purpose, five different data collection methods were used
which were interviews, observations, time studies, surveys and data from Schenker’s databases.
The results from the data collection were the identification and quantification of the time
consumption for managing a number of different quality deficiencies. Based on the
quantification, suggestions for how to reduce the impact of the deficiencies with the largest
impact were presented. The main areas which Schenker can work with and study further are
picking errors and their consequences, transportation and the education of new employees
