The main questions today concerning thermal systems are their economical and environmental impacts. These entities are generally, at present, assessed on the basis of operation performances of newly installed/designed systems, during an assumed lifetime period. While this is the common way of perceiving thermal systems, performance-over-time will change as an effect of degradation, and not solely of different operation scenarios. How and to what extent is the question that needs assessing in order to evaluate if these changes will jeopardise the intended system performance requirement, hence service life (SL). The lack of knowledge/approaches and tools for assessing durability and performance-over-time of thermal systems complicates the task of incorporating these aspects in engineering. In turn, this pro-active assessment and analysis is in line with today’s performance based directives, laws and regulations; of which the working life is an essential part. The durability of materials, components and systems is not a topic that is an end in itself, but becomes a vital part in a comprehensive perspective as sustainability. The lifetime performance assessment of thermal systems, as presented in this thesis, shows that it is a vital part of the R&D in the quest of sustainable energy/thermal systems and energy use. This thesis gives knowledge to the thermal (energy) system/technology R&D and engineering sector, regarding durability and lifetime performance assessment methodologies; but also to the durability of construction works sector, regarding the needs for assessing lifetime performance of materials and components in relation to system performance. It also presents descriptions of requirements on construction works. Specifically, the studies presented in the thesis show how durability and lifetime performance assessment of thermal systems may be sought, with knowledge on: methodologies, exposure test set-ups, modelling and the attainment and use of adequate tools. The main focus is on performance-over-time modelling, tying material/component degradation to altered thermal performance, thereby attaining performance-over-time assessment tools to be used in order to incorporate these aspects when engineering thermal systems; hence enabling the forecasting of SL. The presented work was predominantly done in association to the EU project ENDOHOUSING. The project developed a solar-assisted heat pump system solution, with heat storage, to provide the thermal energy to meet space heating, cooling and hot water requirements for domestic houses in different regions of the EU. The project constituted the platform for the work presented in this thesis, thereby outlining the main context with studies on durability and lifetime performance of: flat plate solar collectors ground heat sources/storages and interaction with a heat pump system evaluation of the ENDOHOUSING solar-assisted heat pump system The thesis also presents a study of SL prediction and estimation of district heating distribution networks (an additional thermal system application). In this particular context, the Factor Method is proposed as a methodology. The main issue of lifetime performance of thermal systems is how and to what extent performance reduction in individual materials or components influence the overall system performance, as the essence of energy/thermal system sustainability is system performance. / QC 20100810

The purpose of this thesis was to investigate potential links between trunk stiffness, vibration transmission and whole-body vibration (WBV) injuries. The investigation was comprised of field and laboratory studies. Tri-planar trunk postures, operator injury histories and 6-degree-of-freedom (DOF) vibration exposure data were collected from eight forestry skidders during normal field operations in Northern Ontario. Using this skidder posture and vibration exposure data, the laboratory investigation examined interactions between WBV exposure levels and spectra, seated trunk postures, trunk muscle activity, and trunk stiffness on the transmission of 6-DOF vibration from the seat to several levels of the spine. The field study revealed that when driving, skidder operators were exposed to vibrations with higher accelerations and lower frequency exposures while adopting the most neutral postures. When dropping-off (DOAL), picking-up (PUAL) or ploughing a load, operators were exposed to vibrations with lower accelerations and higher frequency exposures while adopting the postures furthest away from neutral. Furthermore, operators who adopted the greatest lateral trunk bending and forward flexion for the greatest percentage of time reported low-back and neck pain, however, interestingly were not exposed to the greatest exposure accelerations. Operators who complained of neck pain as a result of twisting to see the rear of the vehicle while DOAL and PAUL experienced some of the highest translational and rotational vibration exposures during those operating conditions. This suggests that WBV exposures and postures may interact to produce operator injuries. The laboratory study revealed a number of interactions between vibration exposure (magnitude, spectra and axis), posture, muscle activity, trunk stiffness, vibration transmissibility, dominant transmission frequency and spinal level. In general, experiment conditions expected to increase trunk muscle activity and stiffness typically did. In contrast, the expected increase in vibration transmissibility and dominant transmission frequency with increased muscle activity and trunk stiffness was not present under many of the simulated field conditions. Trunk muscle activity patterns necessary to maintain required trunk postures were often out of phase with input accelerations, reducing trunk stiffness and increasing transmissibility. These results are contrary to findings from previous studies thus bringing into question the appropriateness of literature based vibration exposure guidelines.

Research on 6G telecommunication networks has been initiated. Among all potential technology components, the distributed multi-input multioutput (D-MIMO) technology is one of the promising enablers. Due to the new technology solutions, additional methodologies for assessment of electromagnetic field (EMF) exposure need to be developed. This study provides methodologies and results for EMF exposure from D-MIMO operating at 3.5 GHz in an indoor industrial environment using CST Studio Suite®. The D-MIMO access points (APs) are mounted on the 7 m ceiling. The EMF exposure is statistically evaluated in a subvolume that extends up to 2.5 m above the floor, using receiving antennas that are pseudorandomly distributed over space. The resulting EMF exposure levels of DMIMO were compared to those of a ceiling-mounted reference massive MIMO array, considering different receiving antenna orientations and AP densities. The results from zero forcing (ZF) precoding were compared to those based on maximum ratio transmission (MRT) precoding. For a total radiated power of 1 W, the 99th-percentile power density values in the D-MIMO deployment are found to be 2.9 mW/m2 or lower, in all studied cases using the MRT-based precoding. This is about 0.03 % of the EMF exposure limits for the general public specified in international guidelines. The corresponding results from the reference massive MIMO array are found to be 7.7 mW/m2 or lower. In the ZF precoding case, the total radiated power and the EMF exposure levels are reduced and the reduction in the D-MIMO deployment is found greater than the reduction in the massive MIMO array. At the 99th-percentile, the power density value is found to be 0.090 mW/m2 in one of the cases of D-MIMO deployment and 5.1 mW/m2 in the corresponding case with the massive MIMO array. The effects of receiving antenna orientations and AP density on the EMF exposure levels are found to be small. This work benefits further studies by providing estimates of realistic EMF exposure and by demonstrating a simulation method for EMF exposure assessment for D-MIMO. / Forskning inom 6G har påbörjats. Bland de möjliga teknologierna för 6G är distribuerad multi-input multi-output (D-MIMO) ett lovande koncept som möjliggör 6G. På grund av den nya teknologin förväntas nya metoder behövas för bedömning av exponering för elektromagnetiska fält. I denna studie utvecklades och användes metoder för simulering av elektromagnetisk exponering från D-MIMO på frekvensen 3.5 GHz i en industriell inomhusmiljö i CST Studio Suite®. En statistisk behandling av exponeringsnivåer utfördes för pseudoslumpmässiga fördelningar av mottagarantenner. Antennerna i nätverket var placerade intill taket på 7 meters höjd och exponeringsnivån mättes i en delvolym som sträcker sig från golvet till 2.5 m höjd. Jämförelser gjordes med massiv MIMO som referens, och mellan olika vinklar hos mottagarantenner och tätheter av uppkopplingspunkter i nätverket. Antennloberna riktades med zero forcing (ZF) och en metod baserad på maximum ratio transmission (MRT). Med MRT och en total utsänd effekt på 1 W, var 99th-percentilen för elektromagnetisk fältintensitet från D-MIMO 2.9 mW/m2 eller lägre i alla studerade fall, vilket är 0.03 % av den internationella referensnivån för elektromagnetisk exponering. Motsvarande nivå för massiv MIMO var 7.7 mW/m2 eller lägre. Med ZF reducerades den totala utsända effekten och reduktionen i exponeringsnivån var större för D-MIMO än för massiv MIMO. I ett av de studerade fallen var 99th-percentilen från D-MIMO 0.090 mW/m2 , och motsvarande nivå för massivt MIMO var 5.1 mW/m2 eller lägre, Effekterna av vinklar hos mottagarantenner och tätheter av uppkopplingspunkter var liten. Detta arbete bidrar till framtida studier inom ämnet genom att ange uppskattningar av realistiska exponeringsnivåer och genom att demonstrera en metod för simulering av exponeringsnivåer för D-MIMO.