Multivariate Estimation of Poisson Parameters

This paper is devoted to the multivariate estimation of a vector of Poisson means. A novel loss function that penalises bad estimates of each of the parameters and the sum (or equivalently the mean) of the parameters is introduced. Under this loss function, a class of minimax estimators that uniformly dominate the maximum likelihood estimator is derived. Crucially, these methods have the property that for estimating a given component parameter, the full data vector is utilised. Estimators in this class can be fine-tuned to limit shrinkage away from the maximum likelihood estimator, thereby avoiding implausible estimates of the sum of the parameters. Further light is shed on this new class of estimators by showing that it can be derived by Bayesian and empirical Bayesian methods. In particular, we exhibit a generalisation of the Clevenson-Zidek estimator, and prove its admissibility. Moreover, a class of prior distributions for which the Bayes estimators uniformly dominate the maximum likelihood estimator under the new loss function is derived. A section is included involving weighted loss functions, notably also leading to a procedure improving uniformly on the maximum likelihood method in an infinite-dimensional setup. Importantly, some of our methods lead to constructions of new multivariate models for both rate parameters and count observations. Finally, estimators that shrink the usual estimators towards a data based point in the parameter space are derived and compared

Molecular mechanisms of crystal nucleation and growth at ferritin/oxide Interfaces : a theoretical investigation

The biomimetic production of micro- and nanostructures from magnetic materials is a suitable way to replace conventional methods with an environmentally friendly and sustainable solution. Biomineralization is nature's way of synthesizing inorganic materials through living organisms. One of the best-known representatives is the protein ferritin, which is found in many organisms and serves as an iron store. Ferritin consists of a total of 24 subunits, which are arranged in the form of a hollow sphere in which iron is biomineralized in the form of iron oxide hydroxide. These subunits were used in this theoretical work and supporting experiments to allow magnetic layers of iron oxide hydroxide to grow without spatial limitations. In this work the different substrate/protein/mineral interfaces, the crystal growth process as well as structure and composition of the resulting mineral phase are analyzed by classical Molecular Dynamic (MD) simulations and quantum mechanical (QM) modelling

Filtration of Cellulosic material - the impact of ionic strength and electric field

It is crucial that dewatering technology is considered if an economically feasible production of cellulosic materials is to be achieved. Cellulosic materials are often produced in dilute streams and therefore require great amounts of water to be removed to allow for reasonable transportation costs and/or further modifications. Although various types of drying techniques are suitable for this purpose, they are rather energy intensive. One way of reducing the total energy demand is to add an efficient mechanical dewatering step prior to the drying step: filtration is the technique most commonly used. However, micro/nano cellulosic materials have large surface areas, resulting in an extensive filtration resistance and thus requiring large filters. It therefore becomes important to evaluate the impact of external factors, and ionic strength in particular, as this is known to affect electrostatic interactions between cellulose particles and may thereby impact the filtration behaviour. Another alternative is to use an electro-assisted method where an electric field, applied across the filter chamber, introduces several electrokinetic phenomena that can be beneficial to dewatering. The work presented in this thesis examines the filtration of cellulosic material in the form of microcrystalline cellulose (MCC) and microfibrillated cellulose (MFC). The influence of ionic strength on the dead-end filtration of MCC was investigated by the addition of NaCl in the range of 0-1 g/L. It was concluded that increasing the ionic strength improved the filtration rate: the surface charges of the MCC particles were shielded which, in turn, promoted agglomeration and reduced the total surface area subjected to the liquid flow. This confirms the importance of electrostatic interactions between MCC particles during dead-end filtration.The MFC was produced via 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation and an electro-assisted filtration technique was employed to dewater the suspension. Compared to conventional dead-end filtration, electro-assisted filtration significantly improved the dewatering rate due to the electrokinetic phenomena it introduced. Three different levels of electric field were used, and it was observed that the dewatering rate increased proportionally to the strength of the electric field. In addition, molecular dynamic (MD) simulations were performed to obtain an understanding of the dewatering mechanism on a molecular level

Development of a non-destructive field testing method for thermal assessment of district heating pipes

The thermal state of a district heating (DH) network governs the heat losses. It is a parameter considered if a change is to be made in the network. Heat losses are costly and economic aspects are important when planning for the maintenance or replacement of DH pipes. In addition, knowledge of the DH network, and of the parts of the network that may contribute to high heat losses, is important for system control. Pre-insulated DH pipes have been in use for over 40 years. The thermal performance of these pipes decreases over time as a result of thermal aging, leading to higher heat losses. Present methods cannot assess these heat losses with high accuracy. This thesis proposes a developed non-destructive cooling method, the main purpose of which is to perform a temporary shutdown of a selected part of a network, and where temperature measurements are performed during the cooling phase.This thesis presents the development process and the final method to use for thermally assessing pre-insulated DH pipes with high accuracy. The main research questions of this work were linked to the accessibility and measurability of the buried pipe or its connected parts. The methodology for developing the method is based on laboratory tests, field tests with several measurement points, and mathematical models of DH pipes and connected valves.The work resulted in a method and a user guide that can be used by network owners to assess parts of a DH network. A method that by a shorter shutdown, in the range of a few hours, can be used to capture the temperature decline in a DH pipe. Results indicate that drainage valves, which are directly connected to the underlying DH network, were suitable measurement points where the temperature-decline phase of the DH pipe could be captured. The method allowed a prediction of the thermal conductivity of a buried DH pipe in operation with 2% deviation from the reference value

Hva kan man oppnå gjennom universell utforming? En undersøkelse av ulike sider ved begrepet

Strategien universell utforming står for noe nytt, fordi vekten legges på inkludering og likestilling. Fra å tilrettelegge for funksjonshemmede, skal planleggingen ta utgangspunkt i variasjoner i funksjonsevne og et stort menneskelig mangfold. Målet er å hindre diskriminering på grunn av nedsatt funksjonsevne. Begrepet universell utforming drøftes med utgangspunkt i offentlige dokumenter og ny norsk lovgivning, som lovfester nedbygging av funksjonshemmende barrierer. Funksjonshemming forstås i dag som en relasjon mellom individ og omgivelser. Universell utforming kan bidra til å skape inkluderende omgivelser med god tilgjengelighet, og dermed legge til rette for samfunnsdeltakelse. Artikkelen peker på behov for en innholdsbestemmelse som muliggjør evaluering av konkrete løsninger. Det er også nødvendig med mer teoretisk arbeid, og en kritisk tilnærming til hva det er mulig å opp-nå gjennom universell utforming

Development of a non-destructive testing method for thermal assessment of a district heating network

This thesis presents the development of a non-destructive testing (NDT)method for thermal assessment of pre-insulated district heating (DH) pipes with high accuracy, in which the development process from literature review to its present stage is presented and discussed. Pre-insulated DH pipes have been in use for more than 40 years. The thermal performance of these pipes decreases over time as a result of thermal aging, which leads to higher heat\ua0 losses. Present methods are unable to assess these heat losses with a high accuracy.The main idea with the method is to perform a temporary shutdown of a selected part of a network for less than two hours, which enables temperature measurements during the cooling phase. Measured temperatures are then used for analyzing the thermal performance of the pipes. The accessibility for temperature measurements on the pipes depend on the conditions in field. Thus, the methodology for the development of this cooling method involves different measuring points during different conditions in field. This thesis covers three conducted field tests during maintenance, which allowed for temperature measurements on the service pipe, the casing pipe, and connected valves. Furthermore, the method utilizes the copper wire, which is already embedded in the polyurethane insulation for detection of water leakage, as a sensor for measuring the mean temperature at copper wire position along the pipe under assessment. This thesis presents the possibilities and uncertainties with the cooling method at its present stage. The method shows good potential to meet the aim as an NDT method with high accuracy, and to be a future tool for the network owners

On Falsification of Large-Scale Cyber-Physical Systems

In the development of modern Cyber-Physical Systems, Model-Based Testingof the closed-loop system is an approach for finding potential faults andincreasing quality of developed products. Testing is done on many differentabstraction levels, and for large-scale industrial systems, there are severalchallenges. Executing tests on the systems can be time-consuming and largenumbers of complex specifications need to be thoroughly tested, while manyof the popular academic benchmarks do not necessarily reflect on this complexity.This thesis proposes new methods for analyzing and generating test casesas a means for being more certain that proper testing has been performed onthe system under test. For analysis, the proposed approach can automaticallyfind out how much of the physical parts of the system that the test suite hasexecuted.For test case generation, an approach to find errors is optimization-basedfalsification. This thesis attempts to close the gap between academia and industryby applying falsification techniques to real-world models from VolvoCar Corporation and adapting the falsification procedure where it has shortcomingsfor certain classes of systems. Specifically, the main contributionsof this thesis are (i) a method for automatically transforming a signal-basedspecification into a formal specification allowing an optimization-based falsificationapproach, (ii) a new collection of specifications inspired by large-scalespecifications from industry, (iii) an algorithm to perform optimization-basedfalsification for such a large set of specifications, and (iv) a new type of coveragecriterion for Cyber-Physical Systems that can help to assess when testingcan be concluded.The proposed methods have been evaluated for both academic benchmarkexamples and real-world industrial models. One of the main conclusions isthat the proposed additions and changes to the analysis and generation oftests can be useful, given that one has enough information about the systemunder test. The methods presented in this thesis have been applied to realworldmodels in a way that allows for higher-quality products by finding morefaults in early phases of development