| 1. |
- Andersson, Patrik, 1974
(författare)
-
High Frequency Tyre Vibrations
- 2002
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High frequency (above 1 kHz) noise generation from the tyre/road interaction is still not fully understood and accurately modelled.Two noise generation mechanisms previously suggested in the literature are reviewed: air pumping and noise generation cased by adhesive effects between the tyre tread and road surface. These mechanisms are located in and near the tyre/road contact zone, and a deterministic description of these mechanisms requires a tyre model that is able to describe the high frequency behaviour of the tyre, including local deformation in both the radial and tangential directions. A three-dimensional two-layer plate tyre model based on the elastic field equations is suggested as a model that would fulfil these requirements. This model was developed earlier [1], and is now extended to allow for comparison to mobility measurements on real tyres. The overall agreement between the model and measurements is surprisingly good in view of the simplicity of the model. However, some limitations of the model are also presented.The tyre model is used in two investigations focusing on the dynamic behaviour of tyres in both the radial and tangential directions in the frequency range from 50 Hz to 4 kHz; (i) investigation of the dynamic behaviour of smooth and patterned tyres at high frequencies for both radial and tangential directions, and (ii) a parameter study investigating the relation between internal tyre parameters and the response at the outermost surface. It was found that the radial point mobility is greatly influenced by properties of the local deformation at high frequencies and/or small excitation areas. The tangential point mobility is affected by local deformation in almost the whole frequency range. Hence, it is mainly the properties of the tread cap and the pattern that determine the response at high frequencies and in the tangential direction. The radial response is determined by the combined properties of the belt and the tread cap at medium frequencies, while it is the dimension and the pre-tension in the plies that determines the low frequency response.
|
|
| 2. |
- Lind, Patrik, 1976-
(författare)
-
Regionbildning : En institutionell studie av Region Skåne, Västra Götalandsregionen, och "Region Svealand"
- 2010
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Based on the concept of path-dependence, this thesis examines regional representatives’ notion of rationalizations in three Swedish regions. In the provinces of Skåne and Västra Götaland the responsibility for welfare issues like health care, regional development, communications, and culture, is appointed to the two organizations Region Skåne and Västra Götalandsregionen. Both organizations are results of merger processes between old organizations called landsting, with a smaller geographical scale and less responsibility. In Svealand three landsting formally have applied for a similar fusion like the ones in Skåne and in Västra Götaland. The idea behind these fusions is that rationalizations in the field of welfare, are achieved by changing the scale of production, from lesser to larger units. This thesis shows that the perceived effect of rationalization by fusion, can take time. Old norms, values, and cultures that emanate from the landsting are for example conceived by the regional representatives in Västra Götaland and in Svealand, to prevent what kind of rationalizations the organizations are able to accomplish. In Skåne, on the contrary, the notion that the regional organization has overcome its historically defined problems, dominate. In that sense, Västra Götalandregionen and the region-building process in Svealand are path-dependent. But Region Skåne, on the other hand, has overcome its historical institutional legacy. This thesis highlights the importance of examining organization histories to be able to understand why certain decisions are hard to make, and why institutions evolve or not. This is also important to acknowledge when the regions’ representatives try to construct regions. From this perspective, the thesis tries to clarify how people’s expectations can delay what kind of rationalizations an organization can implement and how these expectations seem to legitimize what decisions the organization are able to take. The thesis also tries to clarify one way of using the concept of “path-dependence” in academic studies by the usage of ideal types.
|
|
| 3. |
- Nilsson, Emil, 1989-
(författare)
-
Borehole Thermal Energy Storage Systems for Storage of Industrial Excess Heat : Performance Evaluation and Modelling
- 2020
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Improving industrial energy efficiency is considered an important factor in reducing carbon dioxide emissions and counteract climate change. For many industrial companies in cold climates, heat generated at the site in summer will not be needed to fulfil the site heat demand during this time, and is thus removed to the outdoor air. Although a mismatch between heat generation and heat demand primarily being seasonal, a mismatch may also exist at times in the winter, e.g. during milder winter days or high production hours. If this excess heat instead of being sent to the outdoors was stored for later use when it is needed, purchased energy for the site could be decreased. One way to do this is by the use of a borehole thermal energy storage (BTES) system.A BTES system stores energy directly in the ground by using an array of closely drilled boreholes through which a heat carrier, often water, is circulated. So far, BTES systems used for heating purposes have mainly been used for storage of solar thermal energy. The BTES system has then been part of smaller district solar heating systems to reduce the seasonal mismatch between incoming solar radiation and heat demand, thus increasing system solar fraction. For this application of BTES systems, energy for storage can be controlled by the sizing of the solar collector area. At an industrial site, however, the energy that can be stored will be limited to the excess heat at the site, and the possible presence of several time-varying processes generating heat at different temperatures gives options as to which processes to include in the heat recovery process and how to design the BTES system. Moreover, to determine the available heat for storage at an industrial site, individual measurements of the heat streams to be included are required. Thus, this must be made more site-specific as compared to that of the traditional usage of BTES systems where solar thermal energy is stored, in which case long-time historic solar radiation data to do this is readily accessible for most locations. Furthermore, for performance predictions of industrial BTES systems to be used for both seasonal and short-term storage of energy, models that can treat the short-term effects are needed, as traditional models for predicting BTES performance do not consider this.Although large-scale BTES systems have been around since the 1970’s, little data is to be found in the literature on how design parameters such as borehole spacing and borehole depth affect storage performance, especially for industrial BTES applications. Most studies that can be found with regard to the designing of ground heat exchanger systems are for traditional ground source heat pumps, working at the natural temperature of the ground and being limited to only one or a few boreholes.In this work, the performance of the first and largest industrial BTES system in Sweden was first presented and evaluated with regard to the storage’s first seven years in operation. The BTES system, which has been used for both long- and short-term storage of energy, was then modelled in the IDA ICE 4.8 environment with the aim to model actual storage performance. Finally, the model was used to conduct a parametric study on the BTES system, where e.g. the impact on storage performance from borehole spacing and characteristics of the storage supply flow at heat injection were investigated. From the performance evaluation it could be concluded that lower than estimated quantities and/or quality of the excess heat at the site, resulting in lower storage supply flow temperatures at heat injection, has hindered the storage from reaching temperatures necessary for significant amounts of energy to be extracted. Based on the repeating annual storage behavior seen for the last years of the evaluation period, a long-term annual heat extraction and ratio of energy extracted to energy injected of approximately 400 MWh/year and 20% respectively are likely.For the comparison of predicted and measured storage performance, which considered a period of three years, predicted values for total injected and extracted energy deviated from measured values by less than 1 and 3% respectively, and predicted and measured values for injected and extracted energy followed the same pattern throughout the period. Furthermore, the mean relative difference for the storage temperatures was 4%. A time-step analysis confirmed that the intermittent heat injection and extraction, occurring at intervals down to half a day, had been captured in the three-year validation. This as predictions would become erroneous when the time step exceeded the time at which these changes in storage operation occur.Main findings from the parametric study include that 1) for investigated supply flows at heat injection, a high temperature was more important than a high flow rate in order to achieve high annual heat extractions and that 2) annual heat extraction would rapidly reduce as the borehole spacing was decreased from the one yielding the highest annual heat extraction, whereas the reduction in annual heat extraction was quite slow when the spacing was increased from this point. Another conclusion that came from the performance evaluation and the parametric study, as a consequence of the Emmaboda storage being designed as a high-temperature BTES system, intended working temperatures being 40–55 °C, was that the possibility of designing the BTES system for low working temperatures should be considered in the designing of a BTES system. Lower storage operation temperatures allow for more energy to be injected and in turn for more energy to be extracted and reduces storage heat losses to the surroundings.
|
|
| 4. |
- Nygren, Patrik, 1979-
(författare)
-
De Novo Design and Characterization of Surface Binding Peptides - Steps toward Functional Surfaces
- 2006
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The ability to create surfaces with well-defined chemical properties is a major research field. One possibility to do this is to design peptides that bind with a specific secondary structure to silica nanoparticles. The peptides discussed in this thesis are constructed to be random coil in solution, but are “forced” to become helical when adsorbed to the particles. The positively charged side-chains on the peptides strongly disfavor an ordered structure in solution due to electrostatic repulsion. When the peptides are introduced to the particles these charges will strongly favor the structure because of ion pair bonding between the peptide and the negatively charged nanoparticles. The peptide-nanoparticle system has been thoroughly investigated by systematic variations of the side-chains. In order to determine which factors that contributes to the induced structure, several peptides with different amino acid sequences have been synthesized. Factors that have been investigated include 1) the positive charge density, 2) distribution of positive charges, 3) negative charge density, 4) increasing hydrophobicity, 5) peptide length, and 6) by incorporating amino acids with different helix propensities. Moreover, pH dependence and the effect of different nanoparticle curvature have also been investigated. It will also be shown that the system can be modified to incorporate a catalytic site that is only active when the helix is formed. This research will increase our understanding of peptide-surface interactions and might be of importance for both nanotechnology and medicine.
|
|
| 5. |
|
|
