| 1. |
- Berezovskaya, Yulia
(författare)
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Simulation-based development of distributed control systems in energy-efficient data centres
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main focus of this thesis is on the area of integrated automated control systems inmodern data centres. The data centres are mission-critical facilities since they provide services for transporting, storing and processing vast amounts of data, which can be considered the ”new oil” of the Industry 4.0 era. Reliability of data centres is crucial for providing their availability to customers; thus, they require the detecting and predicting faults and properly recovering from them on time or mitigating their effects. The sustainability of data centres is in reducing energy consumption and mitigating the negative impact on the environment. So the data centres require flexible management of IT- and cooling workload to save energy, as well as they are oriented on the use of renewable energy generation techniques and free cooling methods. Thus, the integrated automated control in modern data centres is expected to achieve sustainability and energy efficiency while maintaining reliability and availability. The thesis addresses the reliability and sustainability issues in modern data centres. The handling of such issues requires the development and validation of control strategies as well as the construction of comprehensive control and automation systems based on these strategies. Modern data centres have the modular architecture by providing clear and unified procedures for data centre components installation and replacement. Because of the modular structure of data centres, it is unreasonable for their control systems to remain centralised, static and rigid. Thus the thesis focuses on developing modular and flexible automation systems for data centres. Modular and flexible control assumes that controllers make their decisions autonomously based on their objectives and interact with each other to achieve some common goals for the holistic control system. Thus, the thesis’s first contribution is the proposition of a multi-agent control (MAC) as a distributed approach to implementing the required control functions by communication and interaction of controllers. This work suggests the general design of the multi-agent control, which focuses on base agents playing as individual controllers and interactions between the agents. The process of the automation system engineering requires progressive and continuous validation. The closed-loop approach, allowing the validation of the control system, uses a plant model as an essential part. The second contribution is a modular toolbox that enables building models of data centres of any scale and configuration with relative ease. The toolbox comprises Simulink blocks which model individual components of a regular data centre. Each block is a complete model of the corresponding component encapsulating all parameters and equations describing its behaviour. The system is extendable by adding new modifications to the existing blocks as well as by developing new blocks. Thus the constructed model is capable of substituting for the real data centre at examining the performance of different control strategies in a dynamic mode. And the third contribution, in addition to the modelling toolbox, the thesis also suggests a control toolbox, a set of Simulink blocks implementing the individual controllers, which utilise reinforcement learning algorithms. The control toolbox is capable of examining the different reinforcement learning algorithms and reward functions to select the most relevant ones to certain controllers. Thus the main outcome of the thesis is a collection of methods, algorithms and models enabling creation of the platform, which supports the development and validation of the distributed automated control systems for data centres. The platform is a modular toolbox aimed at constructing the data centre models and developing the control system in the data centre as a set of interacting autonomous agents. As well as the platform utilises the multi-agent approach as a promising approach in organising the agents’ interactions in both traditional methods, such as a voting procedure or an auction, and the multi-agent reinforcement learning approach.
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| 2. |
- Chen, Ming Wei
(författare)
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Structural studies of enzymes regulating bacterial life style and cell wall biogenesis
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bacteria can adapt to different biotic and abiotic environments by changing their life style, switching between sessile or motile, free-living or community-bound, virulent or dormant states. Each bacterium also faces the challenges of maintaining a protective barrier while growing, replicating and responding to environmental changes. Governing these processes are enzymes involved in signalling and cell-wall biogenesis, which are the subjects of this thesis. The second messenger cyclic di-GMP (c-di-GMP) regulates a vast array of processes such as motility, biofilm formation, virulence and cell cycle progression on transcriptional, post-transcriptional and post-translational levels. RocR from Pseudomonas aeruginosa is a response regulator protein containing an active EAL domain that breaks down c-di-GMP. The crystal structure of RocR was determined to 2.5 Å resolution, revealing a compact tetrameric structure with the subunits displaying two conformational states. The unique architecture allows two phospho-receiver domains to be adjacent to the EAL active sites while being exposed and available for phosphorylation events. Also, solution studies using SAXS and biochemical analyses suggest that the protein does not require large conformational changes to alter its phosphodiesterase activity, leading to a mechanistic model of signal propagation from the phosphorylation site to the EAL active site based on secondary structural changes. Tbd1265 from Thiobacillus denitrificans is a transmembrane protein containing a GGDEF-EAL tandem domain that can both synthesise and hydrolyse c-di-GMP. Functional studies confirmed the bifunctionality of this tandem domain and further suggested that a predicted coiled-coil region preceding the GGDEF domain is required for activity. The crystal structure of a construct comprising these two domains of Tbd1265 was determined to 3.4 Å, revealing a conformation of the GGDEF domains in the dimeric molecule that is not compatible with product-inhibition or catalysis. We propose a regulatory mechanism where Tbd1265 can adopt at least three conformations (resting, active and inhibited) based on signals from the periplasmic binding protein (PBP) domain. MurB is an essential oxidoreductase that produces UDP-N-acetylmuramic acid, a precursor for peptidoglycan synthesis. The crystal structure of the ternary complex of P. aeruginosa MurB with NADP+ and FAD revealed that the substrate channel can accommodate two distinct substrate molecules. The study also revealed a potassium ion in the active site that directly binds the substrates and can stabilise the transition state of the reaction, thus explaining the activating effect of potassium ions on MurB catalysis. The structure of the MurB ternary complex provides a useful template for the design of novel enzyme inhibitors that might be developed into promising drug candidates.
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| 3. |
- Chen, Song
(författare)
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Glass Ionomer Cements with Improved Bioactive and Antibacterial Properties
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dental restorative cements are placed in a harsh oral environment where they are subjected to thermal shock, chemical degradation, and repeating masticatory force. The ideal restorative dental cements should have superior mechanical properties, chemical stability, aesthetic, good handling properties, biocompatibility, antibacterial properties, and preferably bioactivity. This thesis presents research on dental restorative cements with enhanced properties. The overall aim was to increase the bioactivity and antibacterial properties of dental restorative cements without affecting their other properties.The effect from adding calcium silicate to glass ionomer cement (GIC) was investigated. The results showed that calcium silicate could increase the bioactivity and reduce the cytotoxicity of conventional glass ionomer cement without compromising its setting and mechanical properties.Hydroxyapatite (HA) with a high aspect ratio and thin nacreous-layered monetite sheets were also synthesized. Nano HA particles with an aspect ratio of 50 can be synthesized by both precipitation and hydrothermal methods. The aspect ratio was controlled via the pH of reaction medium. Thin nacreous-layered monetite sheets were synthesized through a self-assembly process in the presence of an amine based cationic quaternary surfactant. Temperature, pH, and presence of surfactant played essential roles in forming the nacreous-layered monetite sheets. Then the effect from adding silver doped HA and monetite particles was investigated. The results showed that the antibacterial properties of GIC could be increased by incorporating silver doped HA and monetite particles. Further examination showed that the pH change, F- ion release, and concentration of released Ag+ ions were not responsible for the improved antibacterial properties.The quasi-static strengths and compressive fatigue limits of four types of the most commonly used dental restorations were evaluated. In our study, resin modified GIC and resin-based composite showed superior static compressive strength and fatigue limits compared to conventional GIC. The static compressive strength of dental cements increased with the aging time. However, aging had no effect on the compressive fatigue limit of resin modified GIC and resin-based composite. The compressive fatigue limit of conventional GIC even showed a drastic decrease after aging.
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| 4. |
- Dersjö, Tomas, 1981-
(författare)
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Methods for reliability based design optimization of structural components
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cost and quality are key properties of a product, possibly even the two most important. Onedefinition of quality is fitness for purpose. Load-bearing products, i.e. structural components,loose their fitness for purpose if they fail. Thus, the ability to withstand failure is a fundamentalmeasure of quality for structural components. Reliability based design optimization(RBDO) is an approach for development of structural components which aims to minimizethe cost while constraining the probability of failure. However, the computational effort ofan RBDO applied to large-scale engineering problems has prohibited it from employment inindustrial applications. This thesis presents methods for computationally efficient RBDO.A review of the work presented on RBDO algorithms reveals that three constituentsof an RBDO algorithm has rendered significant attention; i ) the solution strategy for andnumerical treatment of the probabilistic constraints, ii ) the surrogate model, and iii) theexperiment design. A surrogate model is ”a model of a model”, i.e. a computationally cheapapproximation of a physics-based but computationally expensive computer model. It is fittedto responses from the physics-motivated model obtained via a thought-through combinationof experiments called an experiment design.In Paper A, the general algorithm for RBDO employed in this work, including the sequentialapproximation procedure used to treat the probabilistic constraints, is laid out. A singleconstraint approximation point (CAP) is used to save computational effort with acceptablelosses in accuracy. The approach is used to optimize a truck component and incorporatesthe effect that production related design variables like machining and shot peening have onfatigue life.The focus in Paper B is on experiment design. An algorithm employed to construct anovel experiment design for problems with multiple constraints is presented. It is based onan initial screening and uses the specific problem structure to combine one-factor-at-a-timeexperiments to a several-factors-at-a-time experiment design which reduces computationaleffort.In Paper C, a surrogate model tailored for RBDO is introduced. It is motivated by appliedsolid mechanics considerations and the use of the first order reliability method to evaluate theprobabilistic constraint. An optimal CAP is furthermore deduced from the surrogate model.In Paper D, the paradigm to use sets of experiments rather than one experiment at atime is challenged. A new procedure called experiments on demand (EoD) is presented. TheEoD procedure utilizes the core of RBDO to quantify the demand for new experiments andaugments it by a D-optimality criterion for added robustness and numerical stability.
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| 5. |
- Galkin, Nikolai, 1992-
(författare)
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Model-Integrated Engineering of Smart Energy Distribution Systems
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Model-Based Systems Engineering (MBSE) is a method that is used to support analysis, design, independent verification, and validation inherent in the development of software and hardware systems. MBSE applications are present in many areas of our daily lives, including manufacturing, robotics, healthcare, automation, etc. However, despite their rapid and sustainable growth during the last few years, the MBSE methods themselves are quite far from perfect. There are some current problems, which resist more rapid penetration of MBSE systems in their development. One of them is the issue of interoperability between different MBSE tools since most of them are vendor-specific. Although vendor dependency has been a problem well before the conceptualization of MBSE this problem is especially actual for the MBSE due to the heterogeneity of the concepts (model, systems thinking, and systems engineering) that it is based on. Furthermore, there is currently a gap between the development of a simulation model and the development of a control system for that model. Currently, this problem is usually solved by involving two or more groups of engineers, where each of these groups works on their problems. All this costs companies additional engineering time and, as a result, development costs. Therefore, new, and more sophisticated approaches for the generation of MBSEs are needed to overcome the challenges highlighted aboveTo narrow the field of study and better focus on specific problems, smart power distribution systems have been chosen as the main research object for this dissertation. Furthermore, the author uses the term Digital Twin to refer to the multilayered structure of the complex distributed automation system consisting of three layers, that is:– the static machine-readable information about the infrastructure of the smart energy system,– the simulation model layer,– the distributed control layer for the investigated smart energy system.In particular, the semi-automated approach is presented in Article C of this thesis. The proposed approach is semi-automated because it generates the MATLAB script of the simulation model rather than the model itself. To generate the model, the user needs to automatically generate it in MATLAB (a link to a detailed video describing this process is provided in Article C). IEC 61850 specification files, written in substation configuration language, are used as a starting point for further conversions.The IEC 61850 standard is a key component of the current dissertation. IEC 61850 is an international standard that covers different sides of smart energy distribution systems, including communication protocols for diverse equipment in a substation, including protection, control, and measurement equipment, as well as intelligent electronic devices(IEDs).The dissertation consists of five papers, each of which aims at a specific goal, namely:– Paper A touches upon interoperability problems between information architecture of different communication protocols (IEC61850/GOOSE - transformer substations, OpenADR - smart buildings, OCPP - electric vehicles), and proposes a concept for solving that problem.– Paper B describes the design challenges of the SIMULINK model, which is considered the modeling layer of the multi-layer structure of the Digital Twin. As an example, a model of a datacenter is evaluated, designed, and validated against real data.– In Paper C, an approach for information model automatic transformation from IEC61850 to OCPP is proposed. A test programming application was built, based on the proposed approach, and the generated OCPP information model was tested with the help of third-party programming tools.– Paper D presents a performance analysis of the BeagleBone Black as an IEC61850Merging Unit simulator. The goal is to determine how well BeagleBone Black’shardware and software performance meets the IEC61850 Merging Unit requirements.– Paper E reveals an approach for converting a MATLAB/SIMULINK model to an FPGA-in-Loop system. The goal is to make a step towards automation of the digital twin design process and discuss the various barriers to achieving it.Thus, the work presented in this dissertation raises questions about compatibility between different standards, the problems of converting the IEC 61850 information model to MBSE, the verification of the generated MBSE against the original IEC 61850 information model, the problems of hardware incompatibility with the target programming application, and the problems designing a Digital Twin model from SIMULINK (as an example in this thesis).
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| 6. |
- Wei, Chen, 1960
(författare)
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Metal Speciation and Toxicity in Urban River Sediments
- 1993
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Metal transport, speciation and toxicity were studied in urban runoff and receiving urban river systems. Sediments were recognised as an important environmental compartment for metals. An assessment of the accuracy and precision of sampling and analysis demonstrated the reliability of the chemical (metal analysis) and ecotoxicological (dehydrogenase activity, Microtox) procedures selected for studying urban river sediments. Significant variations in sediment sampling were found and this problem was partly overcome by mixing discrete samples at each urban river sampling site. Platinum concentrations in road sediments were shown to have increased since the introduction of catalytic converters to automobiles. Platinum concentrations in the
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| 7. |
- Yang, Chen-Wei, 1987-
(författare)
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Cyber-Physical Engineering of Distributed Automation Systems in Energy Domain
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main focus of this thesis is in the domain of Energy Systems, specifically in the engi-neering of modern Smart Grid (SG) automation systems. The SG has been categorizedas a Cyber-Physical System (CPS), a complex system which exhibits tight integration between the cyber and the physical processes and their interactions in a networked envi-ronment. The complexity and the computation of the automation system are expectedto increase with the promise of a ”smart” electric grid which is capable of self-healing, self-reconfiguration and become more resilient against cyber-attacks. These automation software systems require control strategies which are distributed in execution and requirevery tight integrations and interactions between various modular software and hardware components. As the automation system becomes more software intensive, we hypothesizethat existing design practices of developing the substation automation software system would struggle to cope with the distributed design challenges of the Smart Grid and they could be substantially enhanced by the application of model-driven design, distributed software architectures and semantic models.Model-driven engineering (MDE) is a software design paradigm that leverages the use of abstraction models at different stages of the design process for engineering complex software systems. MDE is widely used in the software engineering domain and it has proven to be effective when designing and maintaining large-scale software applications.One of the core tenants of MDE is model transformation and it is considered the heartand soul of MDE. The standard modelling language that is used for MDE in software engineering is the Unified Modelling Language (UML), which is a visual language with awide array of tool support. Despite its popularity in the software domain, UML models still have its limitations. In particular, the lack of uniformed semantics between its 13different visual diagrams and the lack of formal notations. In this thesis, we proposethe Cyber-Physical Engineering (CPE) framework, an MDE framework which combines semantic models and MDE based automatic model transformation in order to auto-generate both the automation control system and the simulation plant model from thephysical and functional specifications of CPS systems.All the scientific papers included in this thesis contributes towards the proposed Cyber-Physical Engineering methodology which includes MDE using semantic models, formal modelling of functional requirements and co-simulation testing of CPS systems.The contribution of the thesis is fivefold. Firstly, the thesis proposes the CPE frame-work, which is based on the use of semantic web modelling language where logical rea-soning can be applied to the models. The modelling language that is used is the Web Ontology Language (OWL), which is a declarative language with a strong formal foun-dation based on description logic. Secondly, the extended Semantic Web Rule Language(eSWRL) is introduced which defines the constructors that are necessary for model trans-forming OWL ontology models. The eSWRL transformation language is proposed to bean extension to the widely used ontology reasoning language Semantic Web Rule Lan-guage (SWRL) in order to address the limitations of monotonicity which restricts SWRLfrom transforming ontological models. Thirdly, the implementation of the underlying transformation engine of eSWRL in SWI Prolog. Fourthly, the formal modelling of func-tional requirements in ontology is proposed which investigates the viability of using nat-ural language based functional requirements to add control flow to the auto-generated automation control system. Lastly, an automated script based co-simulation environ-ment is shown to demonstrate how black-box validation can be performed to test theauto-generated automation control system.Finally, the thesis presents the resultant CPE framework for the modelling and genera-tion of distributed CPS automation software that leverages the use of semantic web OWL models. It is aimed to provide a top-down design approach of developing distributed con-trol software for CPS systems along with the simulation model of the physical plant. Inthis thesis, we demonstrate the development process of the CPE framework and throughcase study applications, how a semi-complete distributed automation software system in IEC 61499 can be automatically generated from substation specifications in IEC 61850 and natural language based functional requirements which provide the structure and thecontrol flow of the distributed automation software respectively. An eSWRL toolchainhas been developed to facilitate the various model transformation process of the CPE framework.
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