Fraunhofer Chalmers Research Centre for Industrial Mathematics
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Evaluation and Characterization of Polyurethane Foam from Naturally and Artificially Aged District Heating Pipes
No full textMicroscopic modeling of exciton diffusion and pump-probe spectroscopy in atomically thin materials
No full textDue to the reduced dielectric screening in two-dimensional materials, transition
metal dichalcogenides (TMDs) exhibit a strong Coulomb interaction that leads
to the formation of excitons (bound electron-hole pairs) with binding energies in
the order of hundreds of meV. Therefore, excitonic eects dominate the physical
properties of these materials even at room temperature. Due to their impressive
properties, TMDs are suitable candidates for novel optoelectronic devices. For
a better understanding of these materials it is necessary to investigate the microscopic
mechanisms behind basic phenomena such as optical excitation, energy
relaxation, and transport. To this end, a fully quantum-mechanical theoretical
framework based on density matrix theory is presented in this thesis in order to
address two fundamental questions: (1) the eect of excitation density on the excitonic
and optical properties of TMDs, and (2) exciton spatial diusion and the
appearance of excitonic halos under strong excitation.
To nd the eect of carrier density on the coherent excitonic states and the
optical properties of the material, semiconductor Bloch equations are combined
with the Wannier equation. Using this approach, it is found that exciton properties
are signicantly altered and even suppressed at high carrier densities due to
dielectric many-particle screening and Pauli blocking. In the rst part of this thesis,
pump-probe experiments are modeled to provide a microscopic understanding
of experimental observations of these phenomena.
Moreover, the Wigner representation is introduced to study the spatio-temporal
dynamics of incoherent exciton populations and, specically, the eect of excitation
density on exciton diusion. While under a weak excitation exciton diusion
follows the conventional Fick law, the results presented in this thesis show that
under strong excitation a signicant temperature gradient is created in the excitonic
system, leading to the formation of spatial excitonic halos. This work unveils
the microscopic mechanisms responsible for this unconventional phenomenon that
was experimentally observed very recently
Micropatterned Heater for Multiplexed Nanoplasmonic Sensing
No full textIn order to utilise nanoplasmonic sensing for air quality measurements, the temperature
of the sensing layer must be controlled. This is possible through the use of a
microheater localised on the sensor, which trough Joule heating can make it possible
to manage the sensor’s temperature with high accuracy. However, the microheater’s
design can determine both energy efficiency and the sensing properties of the sensor,
hence careful design and characterisation of the micropatterned heater must take
place in order to optimise it. Further more, for multiplexed sensing where several air
pollutants are measured simultaneously, the microheater must be able to maintain
several distinct temperatures on the same sensor.
In this thesis, several sensors with new geometries have been modelled and fabricated,
both for the purpose of multiplexing and to yield lower power consumption.
By using thermoresistive measurements on the microheaters, it was determined that
it was possible to decrease the power consumption up to 51% by lowering the sensor
thickness and decreasing the size of the heated region. Through the use of thermal
imaging, it was also confirmed that the temperature uniformity of the heated region
could be increased by introducing a laser cut groove or gap around it. For the
multiplexing sensors, which were designed to be able to sense at least four different
gases, heating one distinct region to 120 C resulted in the remaining sensing areas
to reach temperatures of 30-43 C
Nurses’ Psychosocial Work Environment A case study in a large Swedish hospital
No full textDuring the last couple of years, the turnover rate of nurses leaving Swedish hospitals has increased.
This in combination with the fact that before 2026, 38 900 new nurses need to be employed in
order to handle Sweden’s population that only gets older and older creates a difficult situation. The
healthcare also struggles with many of their nurses ending up on sick leave due to a poor
psychosocial work environment. Hence, the psychosocial work environment needs to be improved
to lower the turnover of nurses and reduce the sick leave in order for Swedish healthcare to reach
Sveriges Kommuner och Landsting’s goal.
The empirical findings of this study consist of interviews with nurses at one healthcare department
and leaders at seven different departments at Sahlgrenska University Hospital in Gothenburg,
Sweden. Furthermore, data was also collected from survey answers provided from the HRstrategy-department at Sahlgrenska University Hospital. The findings include an understanding of
how organisational structure and social support impact nurses’ psychosocial health at a healthcare
department. Additionally, these findings were analysed with the help of an analysis model which
was constructed from combining Self-Determination Theory with Rubenowitz’s job satisfaction
model.
The result of the study showed an issue in terms of an organisational structure since there are no
natural development paths in the profession. This generates a low feeling of work satisfaction and
may lead to that the nurses have to leave the department in order to develop in their profession.
Another identified problematic aspect is the nurses’ feeling of the leaders not always listening to
them, which might depend on leaders’ high workload. This may occur due to the fact that the
leaders are responsible for a large number of employees. Moreover, the leaders seem to aim to be
transformational leaders. However, the hospital environment seems to make it difficult to act as a
transformational leader and, instead, the leaders act towards a transactional leadership style. In
addition, the nurses have a strong feeling of relatedness among themselves. However, it may occur
because many parts of the psychosocial environment are lacking, and the nurses feel the need to
compensate for this and perceive this feeling as stronger. To conclude, the recommendations for
future improvements are: (1) create opportunities for development and growth, (2) ensure feedback
from leaders and (3) standardise routines for suggestions of improvements, (4) clarify how the
nurses are expected to prioritise, (5) clarify how the leaders are expected to prioritise, (6) clarify
what is expected from the nurses, (7) clarify what is expected from the leaders and (8) create room
in the lead role to be a present leader
Mathematical representation for the rule of the production rule system Drools
No full textComputational science is a source of many technological paradigms as declarative programming. Declarative programming is used in industries that want to reach optimal processing. Drools is a rule engine allowing this declarative programming.
For classical programs (imperative programming), many verifying programs exist tocheckthebehavioroftheseprograms,dependingonlyonthecode. Foraprogram based on declarative programming, the technics of verification are not common.
This thesis purposes a mathematical representation for the rule of the business rule management system: Drools. This representation is used to define two main errors for a set of rules: overlap and subsumption. Then, a presentation of the program developed is done
Expandergrafer Spektral grafteori och felr¨attande koder
No full textF¨orst bevisas existensen av expandergrafer med Margulis konstruktion och de spektrala egenskaperna hos Markovoperatorn. D¨arefter visas att egenrummen till Markovoperatorn definierad p˚a en Cayleygraf av SL(2,Fp) har stor dimension, vilket anv¨ands f¨or att bevisa Gowers sats f¨ or SL(2,Fp). Slutligen studeras bipartita expandergrafer i samband med felr¨attande koder, och de visas ge upphov till avkodningsalgoritmer med linj¨ar tidskomplexitet