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Thermal Impact of a Calibrated Stereo Camera RigAndersson, Elin January 2016 (has links)
Measurements performed from stereo reconstruction can be obtained with a high accuracy with correct calibrated cameras. A stereo camera rig mounted in an outdoor environment is exposed to temperature changes, which has an impact of the calibration of the cameras. The aim of the master thesis was to investigate the thermal impact of a calibrated stereo camera rig. This was performed by placing a stereo rig in a temperature chamber and collect data of a calibration board at different temperatures. Data was collected with two different cameras and lensesand used for calibration of the stereo camera rig for different scenarios. The obtained parameters were plotted and analyzed. The result from the master thesis gives that the thermal variation has an impact of the accuracy of the calibrated stereo camera rig. A calibration obtained in one temperature can not be used for a different temperature without a degradation of the accuracy. The plotted parameters from the calibration had a high noise level due to problems with the calibration methods, and no visible trend from temperature changes could be seen.
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Applicability of Quantitative Functional MRI Techniques for Studies of Brain Function at Ultra-High Magnetic Fieldvon Smuda, Steffen 23 March 2015 (has links) (PDF)
This thesis describes the development, implementation and application of various quantitative functional magnetic resonance imaging (fMRI) approaches at ultra-high magnetic field including the assessment with regards to applicability and reproducibility.
Functional MRI (fMRI) commonly uses the blood oxygenation level dependent (BOLD) contrast to detect functionally induced changes in the oxy-deoxyhaemoglobin composition of blood which reflect cerebral neural activity. As these blood oxygenation changes do not only occur at the activation site but also downstream in the draining veins, the spatial specificity of the BOLD signal is limited. Therefore, the focus has moved towards more quantitative fMRI approaches such as arterial spin labelling (ASL), vascular space occupancy (VASO) or calibrated fMRI which measure quantifiable physiologically and physically relevant parameters such as cerebral blood flow (CBF), cerebral blood volume (CBV) or cerebral metabolic rate of oxygen (CMRO2), respectively.
In this thesis a novel MRI technique was introduced which allowed the simultaneous acquisition of multiple physiological parameters in order to beneficially utilise their spatial and temporal characteristics. The advantages of ultra-high magnetic field were utilised to achieve higher signal-to-noise and contrast-to-noise ratios compared to lower field strengths. This technique was successfully used to study the spatial and temporal characteristics of CBV, CBF and BOLD in the visual cortex. This technique is the first one that allows simultaneous acquisition of CBV, CBF and BOLD weighted fMRI signals in the human brain at 7 Tesla.
Additionally, this thesis presented a calibrated fMRI technique which allowed the quantitative estimation of changes in cerebral oxygen metabolism at ultra-high field. CMRO2 reflects the amount of thermodynamic work due to neural activity and is therefore a significant physical measure in neuroscience. The calibrated fMRI approach presented in this thesis was optimised for the use at ultra-high field by adjusting the MRI parameters as well as implementing a specifically designed radio-frequency (RF) pulse. A biophysical model was used to calibrate the fMRI data based on the simultaneous acquisition of BOLD and CBF weighted MRI signals during a gas-breathing challenge.
The reproducibility was assessed across multiple brain regions and compared to that of various physiologically relevant parameters. The results indicate that the degree of intra-subject variation for calibrated fMRI is lower than for the classic BOLD contrast or ASL. Consequently, calibrated fMRI is a viable alternative to classic fMRI contrasts with regards to spatial specificity as well as functional reproducibility. This calibrated fMRI approach was also compared to a novel direct calibration technique which relies on complete venous oxygenation saturation during the calibration scan via a gas-breathing challenge.
This thesis introduced several reliable quantitative fMRI approaches at 7 Tesla and the results presented are a step forward to the wider application of quantitative fMRI.
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Fiber optic strain gauge calibration and dynamic flexibility transfer function identification in magnetic bearingsZutavern, Zachary Scott 30 September 2004 (has links)
Historical attempts to measure forces in magnetic bearings have been unsuccessful as a result of relatively high uncertainties. Recent advances in the strain-gauge technology have provided a new method for measuring magnetic bearing forces. Fiber optic strain gauges are roughly 100 times more sensitive than conventional strain gauges and are not affected by electro-magnetic interference. At the Texas A&M Turbomachinery Laboratory, installing the fiber-optic strain gauges in magnetic bearings has produced force measurements with low uncertainties. Dynamic flexibility transfer functions exhibiting noticeable gyroscopic coupling have been identified and compared with results of a finite element model. The comparison has verified the effectiveness of using magnetic bearings as calibrated exciters in rotordynamic testing. Many applications including opportunities for testing unexplained rotordynamic phenomena are now feasible.
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Fiber optic strain gauge calibration and dynamic flexibility transfer function identification in magnetic bearingsZutavern, Zachary Scott 30 September 2004 (has links)
Historical attempts to measure forces in magnetic bearings have been unsuccessful as a result of relatively high uncertainties. Recent advances in the strain-gauge technology have provided a new method for measuring magnetic bearing forces. Fiber optic strain gauges are roughly 100 times more sensitive than conventional strain gauges and are not affected by electro-magnetic interference. At the Texas A&M Turbomachinery Laboratory, installing the fiber-optic strain gauges in magnetic bearings has produced force measurements with low uncertainties. Dynamic flexibility transfer functions exhibiting noticeable gyroscopic coupling have been identified and compared with results of a finite element model. The comparison has verified the effectiveness of using magnetic bearings as calibrated exciters in rotordynamic testing. Many applications including opportunities for testing unexplained rotordynamic phenomena are now feasible.
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Deformation theory of Cayley submanifoldsMoore, Kimberley January 2017 (has links)
Cayley submanifolds are naturally arising volume minimising submanifolds of $Spin(7)$- manifolds. In the special case that the ambient manifold is a four-dimensional Calabi--Yau manifold, a Cayley submanifold might be a complex surface, a special Lagrangian submanifold or neither. In this thesis, we study the deformation theory of Cayley submanifolds from two different perspectives.
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Uncertainty analysis of integrated powerhead demonstrator mass flowrate testing and modelingMolder, King Jeffries 06 August 2005 (has links)
A methodology has been developed to quantify the simulation uncertainty of a computational model calibrated against test data. All test data used in the study undergoes an experimental uncertainty analysis. The modeling software ROCETS is used and its structure is explained. The way the model was calibrated is presented. Next, a general simulation uncertainty analysis methodology is shown that is valid for calibrated models. Finally the ROCETS calibrated model and its simulation uncertainty are calculated using the general methodology and compared to a second set of comparison test data. The simulation uncertainty analysis methodology developed and implemented can be used for any modeling with a calibrated model. The methodology works well for a process of incremental testing and recalibration of the model whenever new test data is available.
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Thrombingenerierung und Rotationsthromboelastometrie bei gesunden Erwachsenen / Thrombin generation and Rotational Thromboelastometry in the healthy adult populationSchneider, Tobias 21 July 2016 (has links) (PDF)
Die vorliegende Arbeit untersucht in einer Population von 132 gesunden Probanden die Hämostase mittels Calibrated Automated Thrombogram (CAT) und Rotationsthromboelastometrie (ROTEM). CAT wurde im plätchenarmen Plasma mit einer tissue factor (TF) von 1 und 5 pM durchgeführt. Lag time, Thrombin peak, Time to thrombin peak und das endogene Thrombin Potential (ETP) wurden ermittelt. ROTEM wurde ohne Aktivator durchgeführt (NATEM) und die Daten für Gerinnungszeit (clotting time, CT), Gerinnselbildungszeit, Alpha Winkel und maximale Gerinnselfestigkeit (MCF) mit den Daten der Thrombingenerierung korreliert. Es zeigte sich eine positive aber nicht lineare Korrelation bezüglich Alter versus lag time und time to peak, sowie eine annähernd lineare Korrelation bezüglich Alter versus thrombin peak und ETP. Für ROTEM konnte eine positive Korrelation bezüglich Alter versus MCF und Alpha Winkel, aber eine negative Korrelation bezüglich Alter versus CT dargestellt werden. In der Gegenüberstellung beider Assays korrelierten Thrombin peak und ETP (aktiviert mit einer TF Konzentration von 5 pM) signifikant mit dem Alpha Winkel und der MCF. Alle signifikanten Korrelationen zeigten lediglich eine moderate Regressionssteigung. / Published data on thrombin generation variables and their correlation with thromboelastometry in the healthy population are scarce. This study aimed at assessing thrombin generation in adults and its correlation to classical rotational thromboelastometry (ROTEM). Methods: Thrombin generation was
measured in platelet-poor plasma from healthy volunteers using the calibrated automated thrombogram (CAT) with 1 and 5 pmol/l tissue factor final concentration. Lag time, thrombin peak, time to thrombin peak and endogenous thrombin potential (ETP) were analyzed. ROTEM was performed without activator (NATEM) and data for clotting time, alpha angle, clot formation time and maximum clot firmness were correlated with
those of thrombin generation. Results: Altogether 132 persons (72 men, 60 women; median age: 48.0 years) were included. There was a positive non-linear correlation for age versus lag time (p < 0.001) and time to peak
(p = 0.001), and almost linear correlation for age versus thrombin peak (p = 0.024) and ETP (p = 0.001), although with a moderate regression
slope. Regarding ROTEM, there was a positive correlation between age and maximum clot firmness and alpha angle (p = 0.001), but a negative correlation between age and clotting time (p = 0.039). Comparing both assays, thrombin peak and ETP measured with a final tissue factor concentration of 5 pmol/l correlated significantly with alpha angle and maximum clot firmness. Conclusion: The age-related changes in CAT and ROTEM variables among adults are not linear. There is a significant correlation, although with a moderate slope, between data from CAT measured with 5 pmol/l tissue factor and ROTEM.
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Applicability of Quantitative Functional MRI Techniques for Studies of Brain Function at Ultra-High Magnetic Fieldvon Smuda, Steffen 02 May 2015 (has links)
This thesis describes the development, implementation and application of various quantitative functional magnetic resonance imaging (fMRI) approaches at ultra-high magnetic field including the assessment with regards to applicability and reproducibility.
Functional MRI (fMRI) commonly uses the blood oxygenation level dependent (BOLD) contrast to detect functionally induced changes in the oxy-deoxyhaemoglobin composition of blood which reflect cerebral neural activity. As these blood oxygenation changes do not only occur at the activation site but also downstream in the draining veins, the spatial specificity of the BOLD signal is limited. Therefore, the focus has moved towards more quantitative fMRI approaches such as arterial spin labelling (ASL), vascular space occupancy (VASO) or calibrated fMRI which measure quantifiable physiologically and physically relevant parameters such as cerebral blood flow (CBF), cerebral blood volume (CBV) or cerebral metabolic rate of oxygen (CMRO2), respectively.
In this thesis a novel MRI technique was introduced which allowed the simultaneous acquisition of multiple physiological parameters in order to beneficially utilise their spatial and temporal characteristics. The advantages of ultra-high magnetic field were utilised to achieve higher signal-to-noise and contrast-to-noise ratios compared to lower field strengths. This technique was successfully used to study the spatial and temporal characteristics of CBV, CBF and BOLD in the visual cortex. This technique is the first one that allows simultaneous acquisition of CBV, CBF and BOLD weighted fMRI signals in the human brain at 7 Tesla.
Additionally, this thesis presented a calibrated fMRI technique which allowed the quantitative estimation of changes in cerebral oxygen metabolism at ultra-high field. CMRO2 reflects the amount of thermodynamic work due to neural activity and is therefore a significant physical measure in neuroscience. The calibrated fMRI approach presented in this thesis was optimised for the use at ultra-high field by adjusting the MRI parameters as well as implementing a specifically designed radio-frequency (RF) pulse. A biophysical model was used to calibrate the fMRI data based on the simultaneous acquisition of BOLD and CBF weighted MRI signals during a gas-breathing challenge.
The reproducibility was assessed across multiple brain regions and compared to that of various physiologically relevant parameters. The results indicate that the degree of intra-subject variation for calibrated fMRI is lower than for the classic BOLD contrast or ASL. Consequently, calibrated fMRI is a viable alternative to classic fMRI contrasts with regards to spatial specificity as well as functional reproducibility. This calibrated fMRI approach was also compared to a novel direct calibration technique which relies on complete venous oxygenation saturation during the calibration scan via a gas-breathing challenge.
This thesis introduced several reliable quantitative fMRI approaches at 7 Tesla and the results presented are a step forward to the wider application of quantitative fMRI.:1 Introduction 3
2 Background to Functional Magnetic Resonance Imaging 7
2.1 Magnetic Resonance 7
2.1.1 Quantum Mechanics 7
2.1.2 The Classical Point of View 10
2.1.3 Radio Frequency Pulses 12
2.1.4 Relaxation Effects 13
2.1.5 The Bloch Equations 15
2.2 Magnetic Resonance Imaging 16
2.2.1 Data Acquisition 16
2.2.2 Image Formation 17
2.2.2.1 Slice Selection 17
2.2.2.2 Frequency Encoding 18
2.2.2.3 Phase Encoding 19
2.2.2.4 Mathematics of Image Formation 20
2.2.2.5 Signal Formation 22
2.3 Advanced Imaging Methods 24
2.3.1 Echo-Planar Imaging (EPI) 24
2.3.2 Partial Fourier Acquisition 25
2.3.3 Generalised Autocalibrating Partially Parallel Acquisition (GRAPPA) 25
2.3.4 Inversion Recovery (IR) 26
2.3.5 Adiabatic Inversion 26
2.3.5.1 Hyperbolic Secant (HS) RF pulses 28
2.3.5.2 Time Resampled Frequency Offset Corrected Inversion (tr-FOCI) RF Pulses 28
2.4 Physiological Background 29
2.4.1 Neuronal Activity 30
2.4.2 Energy Metabolism 31
2.4.3 Physiological Changes During Brain Activation 32
2.4.4 The BOLD Contrast 34
2.4.5 Disadvantages of the BOLD Contrast 35
2.5 Arterial Spin Labelling (ASL) 35
2.5.1 Pulsed Arterial Spin Labelling 37
2.5.2 Arterial Spin Labelling at Ultra-High Field 41
2.6 Vascular Space Occupancy (VASO) 42
2.6.1 VASO at Ultra-High Field 44
2.6.2 Slice-Saturation Slab-Inversion (SS-SI) VASO 45
2.7 Calibrated Functional Magnetic Resonance Imaging 47
2.7.1 The Davis Model 47
2.7.2 The Chiarelli Model 50
2.7.3 The Generalised Calibration Model (GCM) 52
3 Materials and Methods 53
3.1 Scanner Setup 53
3.2 Gas Delivery and Physiological Monitoring System 53
3.3 MRI Sequence Developments 55
3.3.1 Tr-FOCI Adiabatic Inversion 55
3.3.2 Optimisation of the PASL FAIR QUIPSSII Sequence Parameters 60
3.3.3 Multi-TE Multi-TI EPI 64
4 Experiment I: Comparison of Direct and Modelled fMRI Calibration 68
4.1 Background Information 68
4.2 Methods 69
4.2.1 Experimental Design 69
4.2.2 Visuo-Motor Task 70
4.2.3 Gas Manipulations 71
4.2.4 Scanning Parameters 71
4.2.5 Data Analysis 72
4.2.6 M-value Modelling 72
4.2.7 Direct M-Value Estimation 73
4.3 Results 74
4.4 Discussion 79
4.4.1 M-value Estimation 79
4.4.2 BOLD Time Courses 82
4.4.3 M-Maps and Single Subject Analysis 82
4.4.4 Effects on CMRO2 Estimation 83
4.4.5 Technical Limitations and Implications for Calibrated fMRI 84
4.5 Conclusion 89
5 Experiment II: Reproducibility of BOLD, ASL and Calibrated fMRI 90
5.1 Background Information 90
5.2 Methods 91
5.2.1 Experimental Design 91
5.2.2 Data Analysis 91
5.2.3 Reproducibility 93
5.2.4 Learning and Habituation Effects 95
5.3 Results 95
5.4 Discussion 101
5.4.1 Breathing Manipulations 102
5.4.2 Functional Reproducibility 107
5.4.3 Habituation Effects on Reproducibility 109
5.4.4 Technical Considerations for Calibrated fMRI 110
5.5 Conclusion 112
6 Experiment III: Simultaneous Acquisition of BOLD, ASL and VASO Signals 113
6.1 Background Information 113
6.2 Methods 114
6.2.1 SS-SI VASO Signal Acquisition 114
6.2.2 ASL and BOLD Signal Acquisition 114
6.2.3 Experimental Design 114
6.2.4 Data Analysis 115
6.3 Results 115
6.4 Discussion 116
6.5 Conclusion 120
7 Conclusion and Outlook 121
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Thrombingenerierung und Rotationsthromboelastometrie bei gesunden Erwachsenen: Thrombin generation and Rotational Thromboelastometry in the healthy adult population: Publikationspromotion zur Erlangung des akademischen GradesDr. med.an der Medizinischen Fakultät der Universität LeipzigSchneider, Tobias 16 June 2016 (has links)
Die vorliegende Arbeit untersucht in einer Population von 132 gesunden Probanden die Hämostase mittels Calibrated Automated Thrombogram (CAT) und Rotationsthromboelastometrie (ROTEM). CAT wurde im plätchenarmen Plasma mit einer tissue factor (TF) von 1 und 5 pM durchgeführt. Lag time, Thrombin peak, Time to thrombin peak und das endogene Thrombin Potential (ETP) wurden ermittelt. ROTEM wurde ohne Aktivator durchgeführt (NATEM) und die Daten für Gerinnungszeit (clotting time, CT), Gerinnselbildungszeit, Alpha Winkel und maximale Gerinnselfestigkeit (MCF) mit den Daten der Thrombingenerierung korreliert. Es zeigte sich eine positive aber nicht lineare Korrelation bezüglich Alter versus lag time und time to peak, sowie eine annähernd lineare Korrelation bezüglich Alter versus thrombin peak und ETP. Für ROTEM konnte eine positive Korrelation bezüglich Alter versus MCF und Alpha Winkel, aber eine negative Korrelation bezüglich Alter versus CT dargestellt werden. In der Gegenüberstellung beider Assays korrelierten Thrombin peak und ETP (aktiviert mit einer TF Konzentration von 5 pM) signifikant mit dem Alpha Winkel und der MCF. Alle signifikanten Korrelationen zeigten lediglich eine moderate Regressionssteigung. / Published data on thrombin generation variables and their correlation with thromboelastometry in the healthy population are scarce. This study aimed at assessing thrombin generation in adults and its correlation to classical rotational thromboelastometry (ROTEM). Methods: Thrombin generation was
measured in platelet-poor plasma from healthy volunteers using the calibrated automated thrombogram (CAT) with 1 and 5 pmol/l tissue factor final concentration. Lag time, thrombin peak, time to thrombin peak and endogenous thrombin potential (ETP) were analyzed. ROTEM was performed without activator (NATEM) and data for clotting time, alpha angle, clot formation time and maximum clot firmness were correlated with
those of thrombin generation. Results: Altogether 132 persons (72 men, 60 women; median age: 48.0 years) were included. There was a positive non-linear correlation for age versus lag time (p < 0.001) and time to peak
(p = 0.001), and almost linear correlation for age versus thrombin peak (p = 0.024) and ETP (p = 0.001), although with a moderate regression
slope. Regarding ROTEM, there was a positive correlation between age and maximum clot firmness and alpha angle (p = 0.001), but a negative correlation between age and clotting time (p = 0.039). Comparing both assays, thrombin peak and ETP measured with a final tissue factor concentration of 5 pmol/l correlated significantly with alpha angle and maximum clot firmness. Conclusion: The age-related changes in CAT and ROTEM variables among adults are not linear. There is a significant correlation, although with a moderate slope, between data from CAT measured with 5 pmol/l tissue factor and ROTEM.
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Improved building energy simulations and verifications by regressionVesterberg, Jimmy January 2016 (has links)
It is common with significant differences between calculated and actual energy use in the building sector. These calculations are often performed with whole building energy simulation (BES) programs. In this process the analyst must make several assumptions about the studied building and its users. These calculations are often verified with measured data through the EUI benchmark indicator which is calculated by normalizing the annual energy use (from the grid) with the floor area. Due to the highly aggregated nature of the EUI indicator it is problematic to use this indicator to deduce erroneous assumptions in the calculations. Consequently, the learning process is often troublesome. Against this background, the main aim of this thesis has been to develop methods that can provide feedback (key building performance parameters) from measured data which can be used to increase simulation accuracy and verify building performance. For the latter, regression models have been widely used in the past for verifying energy use. This thesis has the focus on the use of regression analysis for accurate parameter identification to be used to increase the agreement between BES predictions and actual outcome. For this, a BES calibration method based on input from regressed parameters has been developed which has shown promising features in terms of accurate predictions and user friendliness. The calibration method is based on input from regressed estimations of air-to-air-transmission losses, including air leakage (heat loss factor) and ground heat loss. Since it is known that bias models still can give accurate predictions, these parameters have been evaluated in terms of robustness and agreement with independent calculations. In addition, a method has been developed to suppress the bias introduced in the regression due to solar gain. Finally, the importance of calibrated simulations was investigated. The regressed parameters were found to be robust with yearly variations in the heat loss factor of less than 2%. The regressed estimates of ground heat loss were also in good agreement with independent calculations. The robustness of the heat loss factor based on data from periods of substantial solar gain was also found to be high, with an average absolute deviation of 4.0%. The benefit with calibrated models was mainly found to be increased accuracy in predictions and parameters in absolute terms. With increased access to measured data and the promising results in this thesis it is believed that the presented regression models will have their place in future energy quantification methods for accessing energy performance of buildings. / Det är vanligt med betydande skillnader mellan beräknad och verklig energi användning inom byggnadssektorn. Dessa beräkningar utförs ofta med hjälp av byggnads energi simulerings (BES) program där användaren måste göra ett flertal antaganden om den aktuella byggnaden och dess brukare. Det beräknade resultatet kontrolleras ofta i ett senare skede mot byggnadens faktiska behov av energi från nätet. I denna kontroll är det dock svårt att särskilja den energimängd som byggnaden behöver och den del som är kopplad till brukaren. Detta gör att lärdomarna som kan dras i denna verifieringsprocess ofta blir begränsade. Mot denna bakgrund, har det huvudsakliga syftet med denna avhandling varit att utveckla metoder som kan användas för att extrahera information om byggnadens prestanda från mätdata. De extraherade parametrarna skall kunna användas för att öka noggrannheten i prediktioner från BES modeller och för att verifiera byggnaders prestanda. Regression analys har ofta använts i det senare fallet i avseendet att verifiera energi användning. Denna avhandling fokuserar på att utveckla regressionsmodeller som ger en hög noggrannhet i modellens parametrar som möjliggör att de bl.a. kan användas för att kalibrera BES modeller och på så sätt minska den vanligt förekommande diskrepans mellan simulerat och faktiskt utfall. En BES kalibrerings metodik har utvecklats baserat på skattning av transmissions förluster ovan mark, inklusive luftläckage (värmeförlust koefficient) samt värmeförlust till mark (G) med hjälp av regressionsanalys. Denna kalibrerings metodik uppvisar lovande egenskaper i form av noggranna prediktioner och användarvänlighet. Goda prediktioner är dock ingen garanti för att modellens ingående parametrar är fysikaliskt rimliga. Därför har regressionsmodellernas parametrar utvärderats i termer av robusthet och överensstämmelse med oberoende beräkningar. Dessutom har en metod utvecklats för att minimerar solens inverkan på regressionsskattningarna. Slutligen har vikten av kalibrerade simuleringar undersökts. Parametrarna i de framtagna regressionsmodellerna visade sig vara robusta, med årliga variationer i värmeförlust koefficient mindre än 2%. Ytterligare visade sig G var i god överensstämmelse med oberoende beräkningar. Robustheten i värmeförlustfaktorn baserad på data från perioder av betydande solstrålning konstaterades också att vara hög, med en genomsnittlig absolut avvikelse på 4.0%. Fördelen med kalibrerade modeller visade sig främst vara en ökad noggrannhet i prediktioner och modell parametrar i absoluta tal. Med ökad tillgång till mätdata och lovande resultat i denna avhandling är det författarens övertygelse att de presenterade regressionsmodellerna kommer att ha sin plats i framtida bedömnings metoder av byggnaders energiprestanda.
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