| 1. |
- Aasa, Ulrika
(författare)
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Ambulance Work : Relationships between occupational demands, individual characteristics and health-related outcomes
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Although musculoskeletal disorders (MSDs) and other health complaints are an occupational problem for ambulance personnel, there is a lack of knowledge regarding work-related factors associated with MSDs and other health complaints. The overall aim of this thesis was to investigate the relationships between occupational demands, individual characteristics and health-related outcomes among ambulance personnel. A random sample of 234 female and 953 male ambulance personnel participated in a national questionnaire survey on work-related factors, and musculoskeletal and other health complaints. Physical demands was associated with activity limitation due to neck-shoulder and low-back complaints among the female personnel. Among the male personnel, physical demands was associated with low-back complaints and activity limitation due to low-back complaints. Psychological demands was significantly associated with neck-shoulder complaints, sleeping problems, headache and stomach symptoms among both female and male ambulance personnel. Worry about work conditions was associated with musculoskeletal disorders and sleeping problems, headache and stomach symptoms. A local sample of 26 ambulance personnel was followed during a 24-hour work shift and for the next two work-free days. Subjective stress- and energy levels, and cortisol levels were measured at regular intervals, and heart rate was registered continuously by electrocardiogram (ECG). Autonomic reactivity to standardized tests before (pre-work) and at the end of the work shift (post-work) was also investigated. For the whole group, baseline values of heart rate were higher pre-work than post-work, but autonomic reactivity did not differ. Increased reactivity to the mental test, modest deviation in heart rate variability (HRV) pattern during the late night hours at work and higher morning cortisol values during work than during leisure time were observed in personnel with many health complaints, but not among their co-workers without or with few complaints. Ambulance personnel with many health complaints also reported higher psychological demands and tended to be more worried about work conditions. Heart rate (HR), lactate level (LL) and perceived exertion (RPE) were investigated in 17 female and 48 male ambulance personnel during a simulated standardized work task “carry a loaded stretcher”. The ambulance personnel had to carry the loaded stretcher (920 N) up and down three flights of stairs twice. The high physiological strain (HR, LL, RPE) for the male, and near or at maximal strain for the female ambulance personnel, implied the importance to identify what kind of physical capacity is most important for ambulance personnel. Therefore, the explained variance of developed fatigue by tests of cardiorespiratory capacity, muscular strength and endurance, and coordination was investigated. The results showed that VO2max and isometric back endurance were important predictors for development of fatigue when carrying a loaded stretcher. The influence of body size on the relationships between maximal strength and functional performance was investigated in a methodological study. The results confirm that the assessment of physical performance could be confounded by the body weight. Therefore, the models for explaining development of fatigue when carrying the loaded stretcher were adjusted for height and weight. Including height in the models significantly increased the explained variance of accumulated lactate among female, but not among male personnel. Lactate levels were higher among short compared to tall female personnel. Weight had no effect on any of the models. In conclusion, the national survey showed that self-reported physical demands was a risk factor of having MSDs, and that self-reported psychological demands and worry about work were important risk factors of having MSDs and other health complaints. Stress monitoring of ambulance personnel during work and leisure time showed that physiological and subjective stress markers did not show any differences between the 24-hour ambulance work shift and leisure time afterwards. However, ambulance personnel with many health complaints had certain physiological changes during the work shift in comparison with the next two work-free days. The physiological and subjective responses during carrying a loaded stretcher, especially among the female ambulance personnel, showed that female and male ambulance personnel could be exposed to internal exposures at different levels when performing the same work task. A better understanding of the relationships between occupational demands and health-related outcomes require further studies on age- and gender matched groups in long-term perspective studies.
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| 2. |
- Ahlenius, Martin
(författare)
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The impact of motivation and person-job fit on employee turnover among Swedish real estate brokers: A mixed method approach
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Residential real estate is a vital part of the economy, and homes are important for individuals for both financial and emotional reasons. Residential homes change owners for numerous reasons, and there is a need for these transactions to be secure and efficient from both the economic and individual perspective. The general idea of residential real estate brokerage is to facilitate these transactions securely and efficiently. Real estate brokerage has therefore captured both media as well as scholarly interest. Some scholars even argue that brokerage is a relevant research and literature field of its own. Like other occupations within sales, the brokerage industry suffers from problems connected to recruiting and retaining employees, as put forth by several spokespersons within the industry and scholars alike. Prior studies argue that there is a need for further studies that describe the occupational life cycle of brokers and employee turnover antecedents, such as intrinsic motivation. Hence, the overarching purpose of this thesis is to describe and analyze occupational turnover and its antecedents among Swedish real estate brokers. This thesis sprung out of a firsthand occupational experience of Swedish brokerage, curiosity, and an abductive stance toward knowledge creation. It is primarily explorative, and the embedded articles consist of different types of methodologic approaches and therefore also different ways of gathering data such as interviews, surveys, and registered data. All data solely involves Swedish real estate brokers. Results of the four articles show that the occupational life cycle of brokers is significantly longer than expected and that Swedish brokers display high levels of work-related intrinsic motivation, occasionally rooted in affective commitment towards customers and gained trust from sellers. Furthermore, being driven by gained trust and customer relations has a positive effect on person-job fit which in turn reduces turnover intentions. A majority of the results within the four articles are not in line with prior studies, which is interesting and prompts speculation. The service landscape of brokerage, and particularly Swedish brokerage due to the broker’s intermediary role and personal responsibility for the entire transaction, arguably drives intrinsic motivation and reduces turnover. This is enhanced by the high educational threshold for becoming a broker in Sweden. This thesis contributes to the literature field of brokerage by providing insights about what motivates brokers and the theoretical field of person-job fit by suggesting ways of improving the operationalization and the validity of person-job fit.
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| 3. |
- Ahmadi, Elena, 1978-
(författare)
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Managers’ Work, Working Conditions and Wellbeing in Small Companies with Profitable Growth
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background Managers’ work, working conditions and wellbeing are important determinants of occupational health in organizations. Nevertheless, little research has investigated these factors in the context of small growing businesses, which are known to contribute to employment, economic growth and social stability. The aim of this thesis was to explore managers’ work, working conditions and wellbeing in the context of small businesses with profitable growth. Methods Study I used a cross-sectional design to assess patterns in managerial work activities and leadership behaviours. Studies II–IV used qualitative interviews with managers (II–IV) and employees (II) to explore the effects of managers’ wellbeing on their leadership (II), their working conditions (III), and changes in their working conditions and wellbeing in the context of growing small businesses (IV).Results Managers worked long hours, posing risks for occupational health, but also adopted work practices that bolster occupational health. Firm size matters for managerial work. Managers’ wellbeing reflected in their mood and energy levels and influenced their leadership behaviours and performance, and the company’s work environment. Managers were more constructive when they felt well, and more passively destructive when they felt unwell. Certain factors mitigated the consequences of their negative behaviours in the organization. Five types of managers’ demands and resources (daily managerial work; achievement of results; and social; organizational; and individual factors) were identified, where the specificity of the small business context revealed unique characteristics. Company growth changed managers’ experiences of working conditions and wellbeing.Conclusions The specific context of small growing businesses shaped managers’ work, working conditions and wellbeing and the interplay between them. Dynamism in the organizational context due to growth had implications for managers’ work, working conditions and wellbeing.
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| 4. |
- Ahmadi, Zahra, 1966-
(författare)
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The role of market orientation in public housing companies: : A study of MO’s effect on construction strategies
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of public housing companies in Sweden is strongly influenced by legal, economic, and demographic changes. The companies long tradition of taking responsibility for customer welfare in living have recently been criticized for excessive dominance over price setting, which is claimed to give them competitive advantages in the housing market. New legislation in 2011 requires financial return on investment, implying increased competition with radical changes for the companies. Because of the law, they find themselves transitioning from the role of being responsible for living conditions in Sweden to having to work in a businesslike manner with increased competition.The purpose of this dissertation is to analyze how the public housing companies’ deal with market orientation constructs and what their impact is on construction strategy choices. Theoretically, the market orientation concept is seen as a tool for companies to create superior value for the customers and influence strategic performance, which is a relationship tested and analyzed in this dissertation.The research was conducted through data collection stages using qualitative and quantitative methods. In the first stage, a qualitative pilot study was conducted with interviews of 15 managers in 11 public housing companies in central Sweden. In the second stage, two quantitative comparative studies of public and private housing companies in declining markets in central Sweden were conducted, collecting data from 23 (22 survey respondents) public and 37 private housing companies (16 respondents). In the third and final stage, two quantitative studies were conducted, collecting data from all 289 public housing companies (165 respondents) in Sweden.Results of the five studies show, firstly, that economic condition in the municipality have a major impact on the housing companies’ construction strategies, causing them to act innovatively in order to create superior customer value. Secondly, market orientation efforts contribute to competitive advantages in growing markets, while weak economic conditions limit the companies’ construction strategy choices in declining markets. After analyzing the link between market orientation constructs and construction strategy in declining markets, results showed that the public housing companies demonstrate higher responsiveness to customer demands compared to the private sector, but these have no effects on construction strategy. Thirdly, the analysis of moderating (external) and mediating (corporate social responsibility) effects on the market orientation and construction strategy relationship confirms that economic conditions in society influence construction strategy planning and decisions. The results of the mediating effects of CSR indicate that environmental and social issues have a positive influence on the market orientation and construction strategy relationship.
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| 5. |
- Alizadeh, Mahmoud
(författare)
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Characterisation, Modelling and Digital Pre-DistortionTechniques for RF Transmitters in Wireless Systems
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wireless systems have become an inevitable part of modern technologies serving humankind. The rapid growth towards large dimensional systems, e.g. 5th generation (5G) technologies, incurs needs for improving the performance of the systems and considering aspects to make them as far as possible environmentally friendly in terms of power efficiency, cost, and so on. One of the key parts of every wireless communication system is the radio frequency (RF) power amplifier (PA), which consumes the largest percentage of the total energy. Hence, accurate models of RF PAs can be used to optimize their design and to compensate for signal distortions. This thesis starts with two methods for frequency-domain characterisation to analyse the dynamic behaviour of PAs in 3rd-order non-linear systems. Firstly, two-tone signals superimposed on large-signals are used to analyse the frequency-domain symmetry properties of inter-modulation (IM) distortions and Volterra kernels in different dynamic regions of RF PAs in a single-input single-output (SISO) system. Secondly, three-tone signals are used to characterise the 3rd-order self- and cross-Volterra kernels of RF PAs in a 3 × 3 multiple-input multiple-output (MIMO) system. The main block structures of the models are determined by analysing the frequency-domain symmetry properties of the Volterra kernels in different three-dimensional (3D) frequency spaces. This approach significantly simplifies the structure of the 3rd-order non-linear MIMO model.The following parts of the thesis investigate techniques for behavioural modelling and linearising RF PAs. A piece-wise modelling technique is proposed to characterise the dynamic behaviour and to mitigate the impairments of non-linear RF PAs at different operating points (regions). A set of thresholds decompose the input signal into several sub-signals that drive the RF PAs at different operating points. At each operating point, the PAs are modelled by one sub-model, and hence, the complete model consists of several sub-models. The proposed technique reduces the model errors compared to conventional piece-wise modelling techniques.A block structure modelling technique is proposed for RF PAs in a MIMO system based on the results of the three-tone characterisation technique. The main structures of the 3rd- and higher-order systems are formulated based on the frequency dependence of each block. Hence, the model can describe more relevant interconnections between the inputs and outputs than conventional polynomial-type models.This thesis studies the behavioural modelling and compensation techniques in both the time and the frequency domains for RF PAs in a 3 × 3MIMO system. The 3D time-domain technique is an extension of conventional 2D generalised memory polynomial (GMP) techniques. To reduce the computational complexity, a frequency-domain technique is proposed that is efficient and feasible for systems with long memory effects. In this technique, the parameters of the model are estimated within narrow sub-bands. Each sub-band requires only a few parameters, and hence the size of the model for each sub-band is reduced.
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| 6. |
- Amin, Hadi
(författare)
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Study on the Earth’s Surface Mass Variations using Satellite Gravimetry Observations
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Our complex planet is continuously undergoing temporal and spatial changes. In this context, ongoing processes in the Earth subsystems (geosphere, biosphere, cryosphere, hydrosphere, and atmosphere) cause changes in the gravity field of the Earth across a wide range of temporal and spatial scales. Accordingly, by both spatially and temporally tracing our planet’s ever-changing gravity field, scientists can better constrain the underlying processes contributing to such dynamic changes of mass distribution within the Earth system. Monitoring the Earth’s gravity field and its temporal variations is essential, among others, for tracking disasters and specifying land areas with a high risk of flooding, earthquakes, and droughts, movements of tectonic plates, and providing accurate positioning through satellite positioning technology. On short-term timescales, temporal variations in the Earth’s gravity field are mainly caused by the movement of water in its various forms. Accordingly, sea-level variations and ice-sheet and glacier changes, which are known as critical indicators of global warming and climate change, can be accurately monitored by tracking the Earth’s gravity field changes. Since there is a close link between water redistribution and the Earth’s energy cycle, climate system, food security, human and ecosystem health, energy generation, economic and societal development, and climate extremes (droughts and floods), it is essential to accurately monitor water mass exchange between the Earth system components. Among all observational techniques, satellite gravimetry has provided an integrated global view of ongoing processes within the Earth system. The current generation of satellite gravimetry missions (the Gravity Recovery and Climate Experiment (GRACE) mission and its successor, GRACE Follow-On) has dramatically revolutionized our understanding of dynamic processes in the Earth’s surface and, consequently, has significantly improved our understanding of the Earth’s climate system. By considering different aspects of studying the Earth’s gravity field, this thesis brings new insights to the determination and analysis of the mass change in the Earth system. First, by studying the shortcomings of the common techniques of estimating the geoid potential, a new approach is examined that simultaneously estimates the geoid potential, W0, and the geometrical parameters of the reference Mean Earth Ellipsoid (MEE). In this regard, as the geoid needs to be considered as a static equipotential surface, the sensitivity of the estimations to the time dependent Earth’s gravity field changes is studied. Secondly, relying on the GRACE monthly gravity fields and the complementary observational techniques, and by pushing the limit of GRACE, mass redistribution over land and ocean is investigated. Within the ocean, satellite altimetry and Argo products are utilized along with the GRACE monthly solutions for quantifying the global barystatic sea-level change and assessing the closure of the global mean sea level budget. Over land, a region with relatively high temporal mass change (oil and water extraction) is chosen in which by taking advantage of having in-situ observations and hydrological models, the ability of GRACE products in quantifying the changes in groundwater storage is studied. In this frame, for both the ocean and land studies, different aspects of the processing of GRACE monthly gravity fields are investigated and GRACE inherent errors are addressed appropriately to arrive at reliable and accurate estimates of the Earth’s surface mass change. As the final contribution in this thesis, a rigorous analytical model for detecting surface mass change from the time-variable gravity solutions is proposed and examined in different case studies of surface mass change. Since the launch of the GRACE twin satellites, the GRACE(-FO) time-varying gravity fields are conventionally converted into the surface mass change using a spherical analytical model that approximates the Earth by a sphere. More recently, the analytical mass change detection model has been improved by considering an ellipsoid as the shape of the Earth, which improved the previous estimations of surface mass change, especially over high latitudes with relatively large mass change signals. However, by taking into account the real shape of the Earth and considering more realistic assumptions, a new analytical solution for the problem of surface mass change detection from the time-varying gravity fields is proposed in this thesis. It is shown that the simplistic spherical and ellipsoidal geometries are no longer tenable and the new model surpasses the common spherical approach and its ellipsoidal version.
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| 7. |
- Amin, Shoaib
(författare)
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Characterization and Linearization of Multi-band Multi-channel RF Power Amplifiers
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The World today is deeply transformed by the advancement in wireless technology. The envision of a smart society where interactions between physical and virtual dimensions of life are intertwined and where human interaction is mediated by machines, e.g., smart phones, demands increasingly more data traffic. This continual increase in data traffic requires re-designing of the wireless technologies for increased system capacity and flexibility. In this thesis, aspects related to behavioral modeling, characterization, and linearization of multi-channel/band power amplifiers (PAs) are discussed.When building a model of any system, it is advantageous to take into account the knowledge of the physics of the system and include into the model. This approach could help to improve the model performance. In this context, three novel behavioral models and DPD schemes for nonlinear MIMO transmitters are proposed.To model and compensate distortions in GaN based RF PAs in presence of long-term memory effects, novel models for SISO and concurrent dual-band PAs are proposed. These models are based on a fixed pole expansion technique and have infinite impulse response. They show substantial performance improvement. A behavioral model based on the physical knowledge of the concurrent dual-band PA is derived, and its performance is investigated both for behavioral modeling and compensation of nonlinear distortions.Two-tone characterization is a fingerprint method for the characterization of memory effects in dynamic nonlinear systems. In this context, two novel techniques are proposed. The first technique is a dual two-tone characterization technique to characterize the memory effects of self- and cross-modulation products in concurrent dual-band transmitter. The second technique is for the characterization and analysis of self- and cross-Volterra kernels of nonlinear 3x3 MIMO systems using three-tone signals.
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| 8. |
- Amiri, Shahnaz, 1962-
(författare)
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Economic and Environmental Benefits of CHP-based District Heating Systems in Sweden
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Future energy systems and thus the climate are affected by many factors, such as energy resources, energy demand, energy policy and the choice of energy technologies. Energy systems of the future are facing three main challenges; the steady growth of global energy demand, the energy resource depletion, as well as the increasing emissions of carbon dioxide (CO2) and other greenhouse gases and their impact on climate change. To meet the mentioned challenges with sustainability in mind, actions that increase energy efficiency and choosing an energy-efficient energy system which is cost efficient will be essential. Combined heat and power (CHP) plants and district heating and cooling could contribute greatly to increased system efficiency by using energy otherwise wasted.The aim of this study is to increase the understanding of how CHP-based district heating and cooling systems using different primary energy sources can contribute to more cost-efficient energy systems, which reduce global CO2 emissions, and to highlight the impact of some important parameters and measures on Swedish municipal district heating systems. An important assumption in this study is the estimation of CO2 emissions from electricity production, which is based on marginal electricity perspectives. In the short term, the marginal electricity is assumed to come from coal-fired condensing power plants while in the long term it consists of electricity produced by natural gas-fired combined cycle condensing power plants. This means that the local electricity production will replace the marginal electricity production. The underlying assumption is an ideal fully deregulated European electricity market where trade barriers are removed and there are no restrictions on transfer capacity.The results show that electricity generation in CHP plants, particularly in higher efficiency combined steam and gas turbine heat and power plants using natural gas, can reduce the global environmental impact of energy usage to a great extent. The results confirm, through the scenarios presented in this study, that waste as a fuel in CHP-based district heating systems is fully utilised since it has the lowest operational costs. The results also show how implementation of a biogas-based CHP plant in a biogas system contributes to an efficient system, as well as lowering both CO2 emissions and system costs. The results show that replacing electricity-driven (e.g. compression) cooling by heat-driven cooling using district heating (e.g. absorption chillers) in a CHP system is a cost-effective and climate friendly technology as electricity consumption is reduced while at the same time the electricity generation will be increased. The results of the study also show that there is potential to expand district heating systems to areas with lower heat density, with both environmental and economic benefits for the district heating companies.The results reveal that the operation of a studied CHP-based district heating system with an imposed emission limit is very sensitive to the way CO2 emissions are accounted, i.e., local CO2 emissions or emissions from marginal electricity production. The results show how the electricity production increases in the marginal case compared with the local one in order to reduce global CO2 emissions. The results also revealed that not only electricity and fuel prices but also policy instruments are important factors in promoting CHP-based district heating and cooling systems. The use of electricity certificates has a large influence for the introduction of biogas-based cogeneration. Another conclusion from the modelling is that present Swedish policy instruments are strong incentives for cogeneration with similar impact as applying external costs.
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| 9. |
- Andersson, Harald, 1987-
(författare)
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Optimization of confluent jets ventilation with variable airflow
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, applications of confluent jets for design of ventilation supply devices have been widely studied. Similarly, numerous studies have been made on the potential and application of variable air volume (VAV) in order to reduce the energy demand of ventilation systems. This study investigates the combination of confluent jets ventilation (CJV) and VAV, both in terms of the near-field flow behavior of the device and the impact on thermal comfort, indoor air quality and energy efficiency in conference room and classroom environments when the airflow rate is varied. For the investigation of CJV with VAV in a classroom environment two experimental studies were performed. One was a field study in a school classroom with a constant supply temperature and four cases with varying heat loads and airflow rates. The other took place in a laboratory environment with five cases, all with varying heat loads, supply temperatures and airflow rates. The two experimental studies measured mean age of air, air speeds and temperatures in the occupied zone. Both studies showed that CJV had higher energy efficiency and indoor air quality than conventional mixing ventilation. The main effects of lower supply temperatures were higher velocities in the occupied zone as well as lower temperatures due to higher energy efficiency . CJV produces mixing ventilation conditions at lower airflow rates (<4.2 ACH) and non-uniform conditions at higher airflow rates. The thermal comfort was similar to that of conventional mixing ventilation and had very small temperature gradients compared to displacement ventilation. For the investigation of CJV with VAV in a conference room environment three combined experimental and numerical studies were performed. One focused on the jet velocity profiles from the CJV supply device, the results of which were used as boundary conditions for the two other studies. The second study measured the conditions in the confluent jet development area and the occupied zone experimentally for six cases with different supply temperatures, airflow rates and nozzle matrix configurations. The results were used for validating the numerical model which was used in the last paper. The final paper was a parametric numerical study which used the response surface method to investigate the impact of four design variables: heat load, number of nozzles, airflow rate and supply temperature on energy efficiency, indoor air quality and thermal comfort. The results show that indoor air quality is increased with higher airflow rates. The energy efficiency has a negative correlation to the heat load but a positive correlation to the airflow rate which results in relatively stable heat removal effectiveness of 110% as heat load is increased and the VAV system compensates with higher airflow rates. The results also show that in a VAV system which aims at providing uniform temperatures in the occupied zone, the thermal comfort is mostly dependent on a combination of the CLO value and the range of the airflow rates. At low CLO values the range of the airflow rate needs to be increased to create a satisfactory thermal climate.
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| 10. |
- Andersson, Hanna, 1991-
(författare)
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Tradeoffs between self and environment in environmental judgment and decision making
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One of the greatest challenges of today is to change our behavior to act more pro-environmentally to reduce global warming. We need to make sacrifices for the environment, e.g., use a means of transportation that take a longer time but causes less CO2 emission. The present thesis aims to study different factors (intrinsic, extrinsic motivational, and extrinsic motivational-neutral information) that influence us when making tradeoffs between self and environment. Paper I examined how an anchor (a reference price) and an ecolabel influence price judgments. It was found that both a judgment of an objective fact (product price) and a subjective preference (willingness to pay for the product) were affected by an anchor. An eco-label resulted in higher judgments of objective facts. People with higher environmental concern were more affected by an anchor when stating their willingness to pay than their low concern counterparts. In Paper II and Paper III, an interaction between a high anchor and a normative message that put the emissions into context was found when making a tradeoff between CO2 emissions and travel time for a flight (Paper II) or a car journey (Paper III). People with higher concern for the environment gave a longer travel time when they received a high anchor (Paper II and Paper III) or no anchor (Paper III). Paper IV investigated how a survey measuring environmental concern can be divided to different indices and how they predict answers in a tradeoff task. The result suggests that a two-factor structure divided into ecocentric and anthropocentric concern is a possible alternative and that people scoring higher on any of the environmental concern indices were willing to travel for a longer time. Taken together, the results show that normative messages, anchors, and concern for the environment are factors that can influence and interact when people make tradeoffs between self and environment in environmental judgment and decision making.
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