24 resultados para Unipotent Transformations


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Poster at Open Repositories 2014, Helsinki, Finland, June 9-13, 2014

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Nowadays, computer-based systems tend to become more complex and control increasingly critical functions affecting different areas of human activities. Failures of such systems might result in loss of human lives as well as significant damage to the environment. Therefore, their safety needs to be ensured. However, the development of safety-critical systems is not a trivial exercise. Hence, to preclude design faults and guarantee the desired behaviour, different industrial standards prescribe the use of rigorous techniques for development and verification of such systems. The more critical the system is, the more rigorous approach should be undertaken. To ensure safety of a critical computer-based system, satisfaction of the safety requirements imposed on this system should be demonstrated. This task involves a number of activities. In particular, a set of the safety requirements is usually derived by conducting various safety analysis techniques. Strong assurance that the system satisfies the safety requirements can be provided by formal methods, i.e., mathematically-based techniques. At the same time, the evidence that the system under consideration meets the imposed safety requirements might be demonstrated by constructing safety cases. However, the overall safety assurance process of critical computerbased systems remains insufficiently defined due to the following reasons. Firstly, there are semantic differences between safety requirements and formal models. Informally represented safety requirements should be translated into the underlying formal language to enable further veri cation. Secondly, the development of formal models of complex systems can be labour-intensive and time consuming. Thirdly, there are only a few well-defined methods for integration of formal verification results into safety cases. This thesis proposes an integrated approach to the rigorous development and verification of safety-critical systems that (1) facilitates elicitation of safety requirements and their incorporation into formal models, (2) simplifies formal modelling and verification by proposing specification and refinement patterns, and (3) assists in the construction of safety cases from the artefacts generated by formal reasoning. Our chosen formal framework is Event-B. It allows us to tackle the complexity of safety-critical systems as well as to structure safety requirements by applying abstraction and stepwise refinement. The Rodin platform, a tool supporting Event-B, assists in automatic model transformations and proof-based verification of the desired system properties. The proposed approach has been validated by several case studies from different application domains.

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Nowadays, the re-refining of the used lube oils has gained worldwide a lot of attention due to the necessity for added environmental protection and increasingly stringent environmental legislation. One of the parameters determining the quality of the produced base oils is the composition of feedstock. Estimation of the chemical composition of the used oil collected from several European locations showed that the hydrocarbon structure of the motor oil is changed insignificantly during its operation and the major part of the changes is accounted for with depleted oil additives. In the lube oil re-refining industry silicon, coming mainly from antifoaming agents, is recognized to be a contaminant generating undesired solid deposits in various locations in the re-refining units. In this thesis, a particular attention was paid to the mechanism of solid product formation during the alkali treatment process of silicon-containing used lube oils. The transformations of a model siloxane, tetramethyldisiloxane (TMDS), were studied in a batch reactor at industrially relevant alkali treatment conditions (low temperature, short reaction time) using different alkali agents. The reaction mechanism involving solid alkali metal silanolates was proposed. The experimental data obtained demonstrated that the solids were dominant products at low temperature and short reaction time. The liquid products in the low temperature reactions were represented mainly by linear siloxanes. The prolongation of reaction time resulted in reduction of solids, whereas both temperature and time increase led to dominance of cyclic products in the reaction mixture. Experiments with the varied reaction time demonstrated that the concentration of cyclic trimer being the dominant in the beginning of the reaction diminished with time, whereas the cyclic tetramer tended to increase. Experiments with lower sodium hydroxide concentration showed the same effect. In addition, a decrease of alkali agent concentration in the initial reaction mixture accelerated TMDS transformation reactions resulting in solely liquid cyclic siloxanes yields. Comparison of sodium and potassium hydroxides applied as an alkali agent demonstrated that potassium hydroxide was more efficient, since the activation energy in KOH presence was almost 2-fold lower than that for sodium hydroxide containing reaction mixture. Application of potassium hydroxide for TMDS transformation at 100° C with 3 hours reaction time resulted in 20 % decrease of solid yields compared to NaOH-containing mixture. Moreover, TMDS transformations in the presence of sodium silanolate applied as an alkali agent led to formation of only liquid products without formation of the undesired solids. On the basis of experimental data and the proposed reaction mechanism, a kinetic model was developed, which provided a satisfactory description of the experimental results. Suitability of the selected siloxane as a relevant model of industrial silicon-containing compounds was verified by investigation of the commercially available antifoam agent in base-catalyzed conditions.

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Carbon dioxide is regarded, nowadays, as a primary anthropogenic greenhouse gas leading to global warming. Hence, chemical fixation of CO2 has attracted much attention as a possible way to manufacture useful chemicals. One of the most interesting approaches of CO2 transformations is the synthesis of organic carbonates. Since conventional production technologies of these compounds involve poisonous phosgene and carbon monoxide, there is a need to develop novel synthetic methods that would better match the principles of "Green Chemistry" towards protection of the environment and human health. Over the years, synthesis of dimethyl carbonate was under intensive investigation in the academia and industry. Therefore, this study was entirely directed towards equally important homologue of carbonic esters family namely diethyl carbonate (DEC). Novel synthesis method of DEC starting from ethanol and CO2 over heterogeneous catalysts based on ceria (CeO2) was studied in the batch reactor. However, the plausible drawback of the reaction is thermodynamic limitations. The calculated values revealed that the reaction is exothermic (ΔrHØ298K = ─ 16.6 J/ ) and does not occur spontaneously at rooms temperature (ΔrGØ 298K = 35.85 kJ/mol). Moreover, co-produced water easily shifts the reaction equilibrium towards reactants excluding achievement of high yields of the carbonate. Therefore, in-situ dehydration has been applied using butylene oxide as a chemical water trap. A 9-fold enhancement in the amount of DEC was observed upon introduction of butylene oxide to the reaction media in comparison to the synthetic method without any water removal. This result confirms that reaction equilibrium was shifted in favour of the desired product and thermodynamic boundaries of the reaction were suppressed by using butylene oxide as a water scavenger. In order to obtain insight into the reaction network, the kinetic experiments were performed over commercial cerium oxide. On the basis of the selectivity/conversion profile it could be concluded that the one-pot synthesis of diethyl carbonate from ethanol, CO2 and butylene oxide occurs via a consecutive route involving cyclic carbonate as an intermediate. Since commercial cerium oxide suffers from the deactivation problems already after first reaction cycle, in-house CeO2 was prepared applying room temperature precipitation technique. Variation of the synthesis parameters such as synthesis time, calcination temperature and pH of the reaction solution turned to have considerable influence on the physico-chemical and catalytic properties of CeO2. The increase of the synthesis time resulted in high specific surface area of cerium oxide and catalyst prepared within 50 h exhibited the highest amount of basic sites on its surface. Furthermore, synthesis under pH 11 yielded cerium oxide with the highest specific surface area, 139 m2/g, among all prepared catalysts. Moreover, CeO2─pH11 catalyst demonstrated the best catalytic activity and 2 mmol of DEC was produced at 180 oC and 9 MPa of the final reaction pressure. In addition, ceria-supported onto high specific surface area silicas MCM-41, SBA-15 and silica gel were synthesized and tested for the first time as catalysts in the synthesis of DEC. Deposition of cerium oxide on MCM-41 and SiO2 supports resulted in a substantial increase of the alkalinity of the carrier materials. Hexagonal SBA-15 modified with 20 wt % of ceria exhibited the second highest basicity in the series of supported catalysts. Evaluation of the catalytic activity of ceria-supported catalysts showed that reaction carried out over 20 wt % CeO2-SBA-15 generated the highest amount of DEC.

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Iron is one of the most common elements in the earth’s crust and thus its availability and economic viability far exceed that of metals commonly used in catalysis. Also the toxicity of iron is miniscule, compared to the likes of platinum and nickel, making it very desirable as a catalyst. Despite this, prior to the 21st century, the applicability of iron in catalysis was not thoroughly investigated, as it was considered to be inefficient and unselective in desired transformations. In this doctoral thesis, the application of iron catalysis in combination with organosilicon reagents for transformations of carbonyl compounds has been investigated together with insights into iron catalyzed chlorination of silanes and silanols. In the first part of the thesis, the synthetic application of iron(III)-catalyzed chlorination of silanes (Si-H) and the monochlorination of silanes (SiH2) using acetyl chloride as the chlorine source is described. The reactions proceed under ambient conditions, although some compounds need to be protected from excess moisture. In addition, the mechanism and kinetics of the chlorination reaction are briefly adressed. In the second part of this thesis a versatile methodology for transformation of carbonyl compounds into three different compound classes by changing the conditions and amounts of reagents is discussed. One pot reductive benzylation, reductive halogenation and reductive etherification of ketones and aldehydes using silanes as the reducing agent, halide source or cocatalyst, were investigated. Also the reaction kinetics and mechanism of the reductive halogenation of acetophenone are briefly discussed.

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The need for industries to remain competitive in the welding business, has created necessity to develop innovative processes that can exceed customer’s demand. Significant development in improving weld efficiency, during the past decades, still have their drawbacks, specifically in the weld strength properties. The recent innovative technologies have created smallest possible solid material known as nanomaterial and their introduction in welding production has improved the weld strength properties and to overcome unstable microstructures in the weld. This study utilizes a qualitative research method, to elaborate the methods of introducing nanomaterial to the weldments and the characteristic of the welds produced by different welding processes. The study mainly focuses on changes in the microstructural formation and strength properties on the welded joint and also discusses those factors influencing such improvements, due to the addition of nanomaterials. The effect of nanomaterial addition in welding process modifies the physics of joining region, thereby, resulting in significant improvement in the strength properties, with stable microstructure in the weld. The addition of nanomaterials in the welding processes are, through coating on base metal, addition in filler metal and utilizing nanostructured base metal. However, due to its insignificant size, the addition of nanomaterials directly to the weld, would poses complications. The factors having major influence on the joint integrity are dispersion of nanomaterials, characteristics of the nanomaterials, quantity of nanomaterials and selection of nanomaterials. The addition of nanomaterials does not affect the fundamental properties and characteristics of base metals and the filler metal. However, in some cases, the addition of nanomaterials lead to the deterioration of the joint properties by unstable microstructural formations. Still research are ongoing to achieve high joint integrity, in various materials through different welding processes and also on other factors that influence the joint strength.

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Technological innovations and the advent of digitalization have led retail business into one of its biggest transformations of all time. Consumer behaviour has changed rapidly and the customers are ever more powerful, demanding, tech-savvy and moving on various plat-forms. These attributes will continue to drive the development and robustly restructure the architecture of value creation in the retail business. The largest retail category, grocery yet awaits for a real disruption, but the signals for major change are already on the horizon. The first wave of online grocery retail was introduced in the mid 1990’s and it throve until millennium. Many overreactions, heavy investments and the burst IT-bubble almost stag-nated the whole industry for a long period of time. The second wave started with a venge-ance around 2010. Some research was carried out during the first wave from a single-viewpoint of online grocery retail, but without a comprehensive approach to online-offline business model integration. Now the accelerating growth of e-business has initiated an increased interest to examine the transformation from traditional business models towards e-business models and their integration on the companies’ traditional business models. This research strove to examine how can we recognize and analyze how digitalization and online channels are affecting the business models of grocery retail, by using business mod-el canvas as an analysis tool. Furthermore business model innovation and omnichannel retail were presented and suggested as potential solutions for these changes. 21 experts in online grocery industry were being interviewed. The thoughts of the informants were being qualitatively analysed by using an analysis tool called the business model canvas. The aim of this research was to portray a holistic view on the Omnichannel grocery retail business model, and the value chain, in which the case company Arina along with its partners are operating. The key conclusions exhibited that online grocery retail business model is not an alterna-tive model nor a substitute for the traditional grocery retail business model, though all of the business model elements are to some extent affected by it, but rather a complementary business model that should be integrated into the prevailing, conventional grocery retail business model. A set of business model elements, such as value proposition and distribu-tion channels were recognized as the most important ones and sources of innovation within these components were being illustrated. Segments for online grocery retail were empiri-cally established as polarized niche markets in contrast of the segmented mass-market of the conventional grocery retail. Business model innovation was proven to be a considera-ble method and a conceptual framework, by which to come across with new value proposi-tions that create competitive advantage for the company in the contemporary, changing business environment. Arina as a retailer can be considered as a industry model innovator, since it has initiated an entire industry in its market area, where other players have later on embarked on, and in which the contributors of the value chain, such as Posti depend on it to a great extent. Consumer behaviour clearly affects and appears everywhere in the digi-talized grocery trade and it drives customers to multiple platforms where retailers need to be present. Omnichannel retail business model was suggested to be the solution, in which the new technologies are being utilized, contemporary consumer behaviour is embedded in decision-making and all of the segments and their value propositions are being served seamlessly across the channels.

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This thesis is done as a part of the NEOCARBON project. The aim of NEOCARBON project is to study a fully renewable energy system utilizing Power-to-Gas or Power-to-Liquid technology for energy storage. Power-to-Gas consists of two main operations: Hydrogen production via electrolysis and methane production via methanation. Methanation requires carbon dioxide and hydrogen as a raw material. This thesis studies the potential carbon dioxide sources within Finland. The different sources are ranked using the cost and energy penalty of the carbon capture, carbon biogenity and compatibility with Power-to-Gas. It can be concluded that in Finland there exists enough CO2 point sources to provide national PtG system with sufficient amounts of carbon. Pulp and paper industry is single largest producer of biogenic CO2 in Finland. It is possible to obtain single unit capable of grid balancing operations and energy transformations via Power-to-Gas and Gas-to-Power by coupling biogas plants with biomethanation and CHP units.

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In the globalising business environment ever fewer market areas remain unknown. Mongolia is yet only considered as an isolated strip between two power states. The purpose of this study is to put Mongolia on the map of academic business research. This is done by describing the transforming network of a foreign company operating in Mongolia. The objective of the study is approached through a case study, which presents the transformation of a Finnish company operating in Mongolia. This study aims at providing understanding on how the foreign case company observes the transformations of its network. The transformation within the case company is reflected to the transformations that occur in the Mongolian business environment. This study was conducted through a qualitative, intrinsic case study approach. The empirical data was gathered by using the method of network pictures. The network pictures were completed with the assistance of themed interviews. In order to be able to analyse the transformation within a network, three different time periods were observed: the past period around 2000, the present around 2014, and the estimated future around 2020. The data was collected from four executives positioned either in Finland, Russia or Mongolia. The respondents have a long experience within the case company, they hold managerial position, and therefore were able to offer valuable data for this study. The analytical framework used to analyse the collected data was built on the industrial network model, the ARA (actors-resources-activities)-model. The study shows that the changing business environment of Mongolia was utilised by the case company. In order to better meet the transforming customer wishes, the case company transformed from being a retailer to being a manufacturer. The case company was able to become a pioneer in the market. Thus, the case company has undergone similar kind of rapid transformation as the economy of Mongolia in entirety. This study shows that the general nature of the ARA-model makes it usable for new research contexts. The initial ARA-model offers a way to identify the dimensions of a network and a mean to understand these dimensions. The ARA-model can be applied to different contexts and to all time dimensions, past, present and future. The managerial recommendations offered in this study are directed towards the managers that plan to start operations in Mongolia. While this study is the first of its kind, it offers a good starting point for the future research on the change of Mongolian business networks. Valuable information could, for example, be obtained from a comparative study between the case company of this study and a multinational mining company operating in Mongolia.