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  • Carlsson, Oscar (författare)
  • Engineering of IoT Automation Systems
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Major societal challenges such as environmental sustainability, availability of energy and raw materials, and globalisation are creating new requirements for many actors in society. These new requirements relate to efficiency, flexibility, sustainability, and competitiveness. While these aspects have all been around for some time, and many systems have been locally optimised with regards to one or a few of these requirements, recent advances in communication and processing capabilities promise increased possibilities for connecting different parts of society, allowing optimal operation on a much larger scale.While industrial production systems have been controlled electronically for decades, the digitisation of market channels and consumer systems, together with the possibility to interconnect different production facilities, now allow for automated interaction along the whole supply chain from raw materials to end users.Simultaneously, increased demand for efficiency forces increased specialisation among actors, which with increased possibilities of interconnectivity, creates large enterprises of cooperating, specialised stakeholders.One of the major remaining obstacles for a widespread adaptation of more intelligent, more connected systems, able to deliver these envisioned results, is a coherent approach to the engineering and management of Systems-of-Systems involving very large numbers of devices and operating across several automation domains.For traditional automation systems there are established engineering procedures and numerous standards for engineering data, although most are focused on the static processes that have traditionally been the norm. For full integration with a digital society many of the existing automation systems will need significant modifications and as many automation systems are ageing and in need of replacement, a suitable solution to this may be a large scale migration to new automation solutions.The work presented in this thesis includes some new approaches and methodologies to utilise the existing engineering procedures and standards, while introducing some of the flexibility proposed by the emerging technologies. The major technical solutions presented consist of a structure way to organise connected systems and how they are related, regardless of engineering standards used to design their interactions, and an approach to allow configuration of heterogeneous systems through service interactions.Further contributions include an approach for migrating certain categories of existing industrial control systems to a service oriented architecture, as a basic outline for adaption of the next generation of automation systems in industry.Certain remaining challenges have been identified, which have to be addressed for a successful launch of widespread interconnected automation systems based on Internet of Things and associated technologies.
  • Carvalho, Lara, 1978- (författare)
  • Opportunities to broaden biomass feedstocks in thermochemical conversion technologies
  • 2018
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Global environmental concerns are motivating a growing interest in broadening the biomass feedstock base in several energy sectors, including (i) the domestic heating sector, presently dominated by stem wood combustion, and (ii) biofuel production, presently dominated by edible crops. The objective of this thesis is to investigate new opportunities to broaden the biomass feedstock in thermochemical conversion technologies. The performance of different feedstocks was therefore investigated for (i) heat production in small-scale combustion systems and (ii) biofuel production in large-scale gasification-based plants. The selected feedstocks were agricultural residues, forest wood, pyrolysis liquid and industrial by-products, such as lignin, black liquor, crude glycerol and fermentation residues.The alkali metals content in biomass has an important role in combustion and gasification. Alkali metals can cause ash-related problems in small-scale combustion systems, while they can catalyse gasification reactions thus increasing conversion efficiency. Keeping this effect in mind, the present investigation was based on combustion tests with pelletised agricultural residues (non-woody feedstocks with ash contents of 3-8 wt% on a dry basis) to evaluate their combustion feasibility in several small-scale appliances. Moreover, the potential techno-economic benefits of alkali addition in gasification-based biofuel plants were investigated in two different systems: (i) stand-alone biofuel plant operated with wet-alkali-impregnated forest residues and alkali-rich lignin as well as (ii) biofuel plant integrated with a Kraft pulp mill operated with black liquor (an inherently alkali-rich feedstock) mixed with different blend ratios of pyrolysis liquid, crude glycerol or fermentation residues (co-gasification concept). The techno-economic analysis in large-scale entrained-flow-gasification-based biofuel plants was made with the help of simulation tools.The combustion tests have shown that high alkali feedstocks lead to problems with ash accumulation and slag formation in small-scale appliances. The results indicated that non-woody feedstocks can only be burned in appliances adapted to manage high ash content feedstocks. Effective ash cleaning and enhanced combustion controlling mechanisms are relevant characteristics to have in appliances when using these feedstocks. It has been shown that four out of the seven selected feedstocks can be burned in small-scale appliances, while fulfilling the legal European requirements (EN 303-5:2012) in terms of combustion efficiency and emissions. The nitrogen content and ash composition were shown to be important parameters to evaluate whether a feedstock can be utilised in small-scale combustion appliances.The techno-economic investigations of the gasification-based biofuel plants have shown that alkali impregnation is an attractive option to increase energy performance and downstream biofuel production. The economic assessment has indicated that alkali impregnation does not significantly increase biofuel production costs, while it allows the application of a new syngas cleaning system that can significantly reduce biofuel production costs. The present study has shown that the vi co-gasification concept has also techno-economic benefits as a result of the (i) alkali content in black liquor and (ii) economy-of-scale effects. These benefits can be enhanced by choosing energy-rich and low-cost blend-in feedstocks. The gasification-based biofuel production routes hereby investigated exhibit a good economic performance since biofuel required selling prices were economically competitive with other biofuel production routes as well as with taxed gasoline.
  • Cassar, Mario (författare)
  • Investigating the persuasive impact of online textual content : A narrative theory approach
  • 2019
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Higher levels of competition in online channels and the resulting information overload among customers is becoming an issue of increasing concern among marketers who seek to provide persuasive content. Past research has revealed that storytelling is an effective tool to achieve persuasion. Research has also suggested that consumers are essentially storytellers who narrate their experiences in the form of stories. Several researchers have looked at consumers’ stories and investigated the effect that these stories have on their receivers. In the last decade the research about storytelling has shifted to the online world. There is a board agreement amongst researchers that this is indeed very persuasive when compared to other forms of promotional online content. Although online content can possess various characteristics, textual content is the dominant type of content employed by both consumers and sellers/producers. This thesis asks: What effect do characteristics of online textual content have on persuading consumers? This research question is grounded in Narrative Paradigm Theory that is used to present a conceptual model that allows for the development of more specific research questions dealing with characteristics of online textual content. To do this, a distinction is first drawn between user generated content (UGC) and producer generated content (PGC). In both cases, textual content can be story- or argument-based and can possess various other characteristics, that can be basic (valence and word count), stylistic (story-/ argument-based) and semantic (use of meaning in words). The thesis seeks to investigate what effect these characteristics have on the persuasion process of customers viewing online textual content. It seeks to understand what characteristics make textual content, (whether UGC or PGC) believable and influential and whether the knowledge learnt from UGC can be used by marketers to create persuasive content. A further aim of the research, is to identify an analytical tool that can help content creators identify the persuasive potential of any given text.The main research question and model gave rise to the following five sub-research questions:RQ1: What are the themes and concepts used by reviewers expressing differing customer satisfaction when posting UGC?RQ 2: Does the narrative force resulting from reviews posted as UGC differ by declared customer satisfaction ratings?RQ3: What is the impact of different content type and length of online textual reviews on narrative believability and purchase intention?RQ4: Does objective knowledge effect the impact of different content type of online textual reviews on narrative believability and purchase intention?RQ5: Does story-based textual PGC improve website stickiness? To answer these research questions, four empirical studies are undertaken. Study one analyses the first two research questions whilst the remaining three studies each analyse a further research question. Different research methods for collecting and analysing data were used to address the research questions. Using different research methods is regarded advantageous because it allows for methodological rigorousness. The first study employs the qualitative analytical tools using the Diction and Leximancer software while the three other studies make us of an experimental approach. Experimental designs are preferred when the goal of the research is theory application. This doctoral thesis is presented in a monograph format comprising five chapters: Introduction, Literature review, Methodology, Empirical studies, and Conclusion. The latter indicates how the research contributes to the body of knowledge by providing multiple theoretical and managerial implications.
  • Cenamor, Javier (författare)
  • Managing Platform-Mediated Ecosystems : Investigating ecosystem interdependencies and strategic choices
  • 2015
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • The rapid and ubiquitous spread of information technologies (IT) is creating unprecedented effects that challenge traditional fundamentals of the business world. Platform-mediated ecosystems are increasingly attracting the attention of practitioners from diverse industries, from telecommunications to video consoles, as well as academics from different fields ranging from management to economics, and information systems (IS) and innovation management. A platform-mediated ecosystem can be defined broadly as an industrial architecture with an infrastructure in the center that facilitates value co-creation among different agents (platform owners, and providers and users of complementary products) and a set of rules governing their interdependencies. The speed and the magnitude at which platforms diffuse are inspiring numerous analyses from diverse perspectives, mainly focused on drivers of success and ecosystem interdependencies in different contexts. This thesis highlights the importance of detangling the different interdependencies within platform-mediated ecosystems, while building a comprehensive approach based on the ecosystem as a whole. The wide range of platform types and their rapid evolution makes it difficult to establish a consensual categorization of platforms. A common aspect among most of them is that platform-mediated ecosystems usually present network effects that is the value of products depend on the number of peers within the ecosystem. In this sense, the number of adopters, known also as the size of the installed base, in a market has traditionally had a central importance in the literature. The platform-mediated ecosystems, however, are becoming more and more complex due to rising competition. Thus, there is a need for advancing understanding of the fundamentals of platform-mediated ecosystems and the management alternatives inherent in designing such systems which would enable a comprehensive platform approach to be built. Consequently, the main purpose of this thesis is to advance the understanding of the strategic management of platform-mediated ecosystems. Specifically, this thesis aims to unravel the ecosystem interdependencies and to identify strategic choices as a source of competitive advantage. To achieve this aim, different methodologies are applied in this thesis. Specifically, Paper I was based on a structured literature review of relevant papers in platform-mediated ecosystems for the period 2000 through 2014. The empirical analyses conducted in Papers II, III, and IV use different secondary samples from the video console ecosystem. Finally, the results in Paper V were based on a qualitative, multiple case study of global manufacturing firms implementing product-service systems (PSS) through a platform architecture. Overall, the findings within this thesis present the following main theoretical contributions. First, the thesis presents a comprehensive approach toward platform mediated ecosystems covering new ways of value creation and value capture, new governance regimes, and new agents making interdependent choices. Precisely, platform ecosystems offer unprecedented efficiencies and innovation enhancements, and the possibility of establishing rules for new role participation and interaction. Thus, the findings shed light on the fundamentals and future trends in the platform approach. Second, different ecosystem interdependencies may increase the platform adoption and performance. Specifically, the thesis highlights the importance of the positive effects from different agents in the complementary product markets. Accordingly, the findings contribute on unraveling the interdependencies within platform ecosystems. Third, platform performance can be enhanced by exploiting complementarities among strategies and regions. Precisely, the findings show significant complementarities from the joint management of different activities related to the complementary products and the platform, and from the presence in several countries. Consequently, the findings provide strategic choices as a source of competitive advantage. Finally, transformation toward global PSS may be guided by a platform approach, which may be helpful to explain the origins in building a platform ecosystem. In this respect, the findings shed light on how platform-mediated ecosystems are created. In sum, these findings have important implications for researchers in strategic management, economics, and information systems as well as managers from highly innovative industries and traditional sectors under structural transformation. This thesis concludes with the limitations that should be considered when interpreting the findings and some suggestions for future researchers.
  • Chabuk, Ali (författare)
  • Solid Waste Landfills in an Arid Environment : Site Selection and Design
  • 2019
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Selecting landfill sites is considered a complicated task because its whole process is based upon several factors and restrictions. This study shows the present status of solid waste management, sources, collection personnel, machinery and equipment that are involved in the waste collection process, financing and financial management for the major cities of the Babylon Governorate in Iraq (Al-Hillah, Al-Qasim, Al-Mahawil, Al-Hashimiyah and Al-Musayiab). The management of waste collection and disposal in the Babylon Governorate and its districts is through open waste dumps, so the quality of the collection and disposal process is poor, and these sites do not conform to the scientific and environmental criteria usually applied in the selection of landfill sites.In the first part of the current study, three methods were used to calculate the solid waste quantity for each specific year up to the year 2030 as well as the cumulative quantity of solid waste for the period (2020-2030) for Babylon Governorate. The results show the cumulative quantity of solid waste resulting from (method 3) receives a high value compared to other methods, and so it is used as a maximum value to estimate the required area for candidate sites for landfills in each district. The generation rate in 2030 will be (0.97, 0.69, 0.48, 0.62 and 0.91) (kg/capita/day) in (Al-Hillah, Al-Qasim, Al-Mahawil, Al-Hashimiyah and Al-Musayiab), respectively, based on method 3, where the estimated annual incremental generation rate is 1 %. The second part of this study aims to find the best sites for landfills in the arid areas that are distinguished by a shallow depth of groundwater. The Babylon Governorate was selected as a case study because it is located in an arid area, and the depths beneath the ground surface to the groundwater level are shallow.   For this purpose, 15 important criteria were adopted as follows: groundwater depth, rivers, soil types, agricultural land use, land use, elevation, slope, gas pipelines, oil pipelines, power lines, roads, railways, urban centers, villages and archaeological sites. These criteria were then entered into the geographic information system (GIS). The GIS software has a large capacity to manage and analyze various input data using special analysis tools. In addition, Multi-Criteria Decision Making (MCDM) methods were used to derive the relative weightings for each criterion in different styles. These methods are (Analytical Hierarchy Process (AHP), Simple Additive Weighting (SAW), Ratio Scale Weighting (RSW) and Straight Rank Sum (SRS)).Raster maps of the selected criteria were prepared and analyzed within the GIS software. The final map for candidate landfill sites was obtained through combining the GIS software and (MCDM) methods. Subsequently, comparison methods (Change Detection, Combination, Kappa and Overall Assessment) for each pair of raster maps that result from using the two different methods of multi-criteria decision making were implemented to determine the pixel percentage of matching and non-matching as well as to determine and check the suitability of the selected sites for landfills on both resulting maps using two methods.  Two suitable candidate sites for landfills were determined to fulfill the scientific and environmental requirements in each major city. These areas are (6.768 and 8.204) km2 in Al-Hillah, (2.766 and 2.055) km2 in Al-Qasim, (1.288 and 1.374) km2 in Al-Hashimiyah, (2.950 and 2.218) km2 in Al-Mahawil, and (7.965 and 5.952) km2 in Al-Musayiab. The required area of the selected sites can accommodate solid waste from 2020 until 2030 based on the required areas according to the third method.The third part of this study includes soil investigations for the selected landfill sites. The suggested design should ensure that there is no groundwater pollution by leachate from these sites because the groundwater depth is very shallow in the Babylon Governorate. To avoid this problem, soil investigation was conducted at these sites so that the most suitable landfill design could be established. Each site was subjected to field soil tests to find the composition of the soil strata at each site to a depth of 10 m, and these results were compared with the soil properties adopted for final site selection. The Iraqi Ministry of Housing & Construction, National Centre for Construction Laboratories and Research Babylon, Iraq, carried out the analytical work on the soil in 2016. The results of the soil investigation at these sites include the soil profile, groundwater depth, chemical properties, allowable bearing capacity, atterberg limits test results and material characteristics of the soil strata. According to the results of these tests, the best design is the one that puts the compacted waste at the surface.The fourth part of this study covers the selection of a suitable proposed design in the arid areas (Babylon Governorate, Iraq) for the selected landfill siting. In the current study, the design of this landfill includes the suggested soil layers for the liner system and final cover system.  For the base liner system (from the bottom toward the top), the composite bottom barrier layer consists of highly compacted sandy clay. The thickness of the bottom barrier layer is 60 cm, and its saturated hydraulic conductivity is 1.0E-7cm/s. The 1.5 mm thick geomembrane (HDPE), with hydraulic conductivity of 2.0E-13 cm/s, is placed over the composite bottom barrier layer. The leachate collection system consists of drainage layer (gravel) with a thickness of 30 cm and a hydraulic conductivity of 3.0E-1 cm/s. The diameter of the main drainpipes is between 15 and 20 cm. The protection layer consists of sand material, and its hydraulic conductivity is 5.0E-3 cm/s. The thickness of the protection layer is 30 cm.The compacted solid waste is placed upon the surface to a height of 2 m because of the shallow groundwater depth and to avoid groundwater contamination by leachate from the landfill site. The density of the compacted waste is 700 kg/m3, and its saturated hydraulic conductivity is 1.0E-5 cm/s.Three scenarios were used for the suggested designs for the final cover system of the landfills in arid areas. The first scenario was “evapotranspiration soil cover (ET) (capillary barriers type)”, the second scenario was a modified cover design of "RCRA Subtitle D", and the third scenario was the “Recommended design”. In this study, “Recommended design”, the third scenario for the final cover system, was adopted in the arid area (Babylon governorate, Iraq) based on combining certain layers from the first and second scenarios. For the three scenarios, the soil components in these designs used was based on available local materials in the study area. The layers of the base liner system were adopted in all scenarios.The third scenario for the final cover system, “Recommended design”, was implemented based on weather parameters in the arid areas. The water infiltrated from the surface of landfill is stored within upper layers that have fine particles. This allows the stored water to evaporate from the soil surface of the landfill or transpire through vegetation due to the high temperature during most months in the study area. The water that enters from the surface of the landfill should be contained above the geomembrane liner and top barrier layer without leakage into the waste body, thereby preventing leachate generation.For the layers of the final cover system (from the bottom to the top), the intermediate cover is used to cover the waste body, and this layer consists of moderate compacted silty clayey loam (native soil). The thickness of the intermediate cover is 30 cm, and its saturated hydraulic conductivity is1.0E-6 cm/s. The foundation layer consists of coarse sand material with a thickness of 30 cm and a saturated hydraulic conductivity of 1.0E-2 cm/s. This layer acts as a cushion for the layers of the final cover system. The gas collection system can be installed within the foundation layer.  The top barrier layer is placed over the foundation layer. This layer consists of highly compacted sandy clay of (45 - 60 cm) thickness with compacted lifts (each lift is 15 cm). The saturated hydraulic conductivity of the barrier layer is 1.0E-7 cm/s. The geomembrane liner, (HDPE) of 0.5 cm thickness and a saturated hydraulic conductivity of 2.0E-13 cm/s, is put on top of the barrier layer. The upper layers of the final cover system are the support vegetation layer and the topsoil layer. The composition of the support vegetation layer is moderate compacted loam. This layer is placed directly on the geomembrane liner. The saturated hydraulic conductivity of the support layer is1.0E-5 cm/s, and its thickness is 45 cm. The topsoil layer consists of silty clayey loam, and it is placed over the support vegetation layer with a slope of 3%. The thickness of the topsoil layer is 15 cm, and its hydraulic conductivity is 4.0E-5 cm/s.  The Hydrologic Evaluation of a Landfill Performance (HELP 3.95 D) model was applied to the selected landfill sites in the governorate to check if there could be any infiltration of the leachate that will result from the waste in the landfills in the selected sites in the future. The HELP model, which utilizes both weather and soil data, is the most commonly used model for landfill design, and it is employed to evaluate the quantity of water inflow through soil layers for the designed landfill. This suggested landfill is designed using the weather parameters (rainfall, temperature, solar, and the required date to calculate evapotranspiration) for the 12 consecutive years from 2005 to 2016, as well the required data for soil design.In the HELP model, the result for the suggested landfill design for both the recommended design (third scenario) and the second scenario was a modified cover design of "RCRA Subtitle D", which showed there was no leachate through the soil sub-layers, including the bottom barrier layer. The proposed design for the final cover system showed a reduction in the surface runoff and an increase in actual evapotranspiration. In the first scenario “evapotranspiration soil cover (ET) (capillary barriers type)”, there was no leachate percolation through the bottom barrier layer during the study years, apart from in 2013 and 2014. In these years, water percolation figures were 1.4E-5 and 4.0E-6 mm, respectively. These values are considered small, and they resulted from the high rate of rainfall during these years. Although, these values were small, they should still be taken into consideration when adopting this design in the study area.In the HELP model, the average annual and peak daily results for all scenarios showed that there was no water percolation through the bottom barrier layer during the years from 2005 to 2016.
  • Chapman, David, 1972- (författare)
  • Urban design of winter cities : Winter season connectivity for soft mobility
  • 2018
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • All across the world the form of the built environment is playing a crucial role as enabler or inhibitor for urban outdoor activity such as soft mobility. Urban form can make it more attractive for people to be mobile outdoors and playing a role in the public life, or it can put people off venturing outside. For winter cities, a question for urban design is how we can design environments that are attractive for outdoor activity in the winter season as well as summer and additionally how will climate change influence these aspects.The reason for studying this is the importance of understanding how, in relation to urban form, weather, seasonal variations, and climate change influences human outdoor activity. In this study the focus on outdoor activity is problematised around the concern that people spend a low percentage of their time outdoors in winter conditions. For society, the problem is that this trend and the related low levels of physical activity are associated with a range of health issues.To study this the main question for this research is what attracts and hinders soft mobility during the winter season and how can this knowledge underpin new considerations about urban design for connectivity in winter cities? To address this, the research methods focused on document studies, surveys, mental mapping, photo elicitation and semi-structured discussions.The study works at three scientific levels. Firstly, it seeks to understand the interrelationship between the built environment and people’s outdoor activity in winter. Secondly, it attempts to understand how connectivity for soft mobility in winter is being affected by weather and climate change. Thirdly, it seeks new ways of thinking about how the urban form can be designed to increase outdoor soft mobility in winter.The discussion and conclusions focused on the argument that in winter settlements, the winter season can alter spatial patterns and settlement organisation. Here it was argued that in these settlements the winter season can be an aspect of urban morphology and can be part of the process of shaping the public realm and its connectivity for soft mobility in winter.
  • Chibba, Aron (författare)
  • Supply Chain Quality Management : Exploring performance of manufacturing organizations
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • This thesis addresses the issue of quality performance in supply chains in the manufacturers’context. Research shows that the management and performance of supply chains play a major rolein gaining competitive advantage, especially in times of decreasing international trade barriers andquickly evolving information technology. Some researchers claim that it is the supply chain itselfthat competes on a market and not merely the organisations with their specific strategies andgoals. Supply chain performance has been widely discussed in the research literature in recentyears. However, this research points out that supply chain quality management (SCQM) and itsimpact on firm performance (both inter-organisational and intra-organisational) have not beensufficiently understood. Further studies are needed to identify the direct and indirect impact ofSCQM practices on firm performance at multiple levels.A problem that many organisations face is the lack of resources and knowledge on how to managesupply chain quality performance (i.e., which performance to measure, how to controlperformance, and how to improve performance). Studies show that often even large companiesmeasure effectiveness using key performance indicators (KPI) and that these indicators often donot depict key characteristics critical to organisational performance or customer behaviour.Therefore, such indicators might be inadequate for fully capturing the performance of supplychains. As quality management standards evolve, managers need to adapt to changingrequirements. To fulfil the new version of ISO 9001, organisations are required to determinecriteria and apply methods to ensure effective operation and control of their processes (both intraorganisationaland inter-organisational performance). This includes monitoring and measuringperformance indicators. The quality performance of a supply chain is dependent on its ability toimprove and thereby enable organisations to stay competitive over time. Good measurements ofsupply chain quality performance must reflect this ability. To do so, organisations need to knowwhich measures and metrics to use and how to analyse performance of their supply chains.From the seven studies presented in this thesis we are able to draw a number of more generalconclusions that bear on the main research question: What improves quality performance of supplychains that include manufacturing? At the process level, it has been found that manufacturersshould focus on the quality and delivery performance of each process within the organisation. Atthe internal, integrated supply chain level, a manufacturing organisation should focus on quality(conformance), delivery performance (on-time delivery), and cost cutting in the internal supplychain. Collaboration using cross-functional teams seems most appropriate when working withproduct development. The use of a process-oriented mapping tool was found to facilitatedescription of information flows and physical material flows and also to identify disturbances thatcould be improved and rationalized to generate a better flow in the total supply chain. At both theupstream and downstream sides of the supply chain, one-sided measures that depict performanceover organisational boundaries were found to be the most common. At the downstream side of asupply chain, suppliers could be chosen based on cost, conformance, speed, and flexibility. At theupstream side, procedures that handle changing requirements and information about delays orincorrectness of materials were found to influence flow. The results from these seven studies arethe basis for the development of a supply chain quality improvement model. In the literature,supply chain performance is often discussed on a strategic level with measures for quality,flexibility and delivery. Managers also need metrics that can be followed up on at a detailed level(e.g., capacity load, breakdown rates, claims, cost of poor quality, and lead-times). To bridge thisgap, a Key Performance Indicators Matrix of supply chain quality performance indicators formanufacturers is proposed.
  • Conrad, Sarah (författare)
  • Iron isotopes in aquatic systems
  • 2019
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • The cycling of iron (Fe) is a key component for understanding water quality and biogeochemical processes. It serves as mediator during biotic and abiotic processes, as electron acceptor during the degradation of organic matter, as surface for trace element and organic matter adsorption, and is necessary for primary production processes. Since the beginning of Fe isotope studies, researchers focussed on the ratios in soils, rivers and oceans in various environments. The aim of this study was to characterize the Fe isotope ratios from the source (e.g. soils), along the river course, through the estuaries and into the adjacent sea within the boreal landscape. Therefore, seasonal sampling of water from Swedish headwater streams (2016/2017), rivers (2016), estuaries (2013/2014) and the Baltic Sea (2013/2014) were conducted, with the purpose to better understand the role and fate of riverine Fe export. Fe is transported in two main phases from the headwater streams into the oceans: organic Fe complexes and Fe(oxy)hydroxide. It has been proposed that these Fe phases varies in response to seasonal differences in hydrology.                      This thesis includes the first Fe isotope dataset describing seasonal variations of headwater streams on a regional scale. In the headwater streams positive and negative Fe isotopes ratios can be used to distinguish between different Fe phases. Furthermore, Fe isotope ratios in headwater streams could verify regional drought periods and the subsequent rewetting of the subsurface soils.Within the rivers and estuaries, we found positive Fe isotopes in the dissolved phase (< 0.22µm) and negative Fe isotopes (> 0.22µm) in the particulate phase during high discharge. The correlation between different chemical parameters, Fe and DOC showed that the Fe isotope composition during spring flood is evolving in the upper soil layers of headwater streams. Therefore, the lighter Fe isotope signal is correlated to the organic-rich soil layers of the riparian zones in forested catchments. During baseflow, particulate Fe has a positive Fe isotope signal. This shows that the Fe has different origin throughout the season within one catchment.Salt-induced flocculation in the estuaries and under experimental conditions, is removing about 80 % of the dissolved and particulate Fe. Newly formed colloids and particles aggregate and sediment due to small changes in salinity. This major flocculation at low salinities might cause an underestimation of riverine Fe flux. Interestingly, salinity-induced aggregation experiments revealed that Fe(oxy)hydroxide, which dominated aggregates, displayed lower Fe isotope ratios than in the river samples Fe, while organic Fe complexes in the suspension had higher Fe isotope values. The seasonal variability in Fe isotope values could not be simply linked to Fe phases but was probably also influenced by variation in source areas of Fe and processes along the flow-path that alter both Fe phases and isotopic composition.Within the estuarine mixing zone, no Fe isotope fractionation was observed. The Fe isotope signal is constant over time and space, which excludes fractionation processes for example by oxidation. The Fe isotope signal within the Bothnian Bay was positive showing that different surface properties of Fe-OC and Fe(oxy)hydroxide aggregates lead to the flocculation of negative Fe aggregates.
  • Couceiro, José, 1983- (författare)
  • X-ray computed tomography to study moisture distribution in wood
  • 2019
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • X-ray computed tomography (CT) has been used as an analysing tool for different features in wood research since the beginning of the1980s, but it can also be used to study wood-water interactions in different ways, such as by determining wood moisture content (MC). The determination of wood MC with CT requires two CT images: one at the unknown moisture distribution and a second one at a known reference MC level, usually at oven-dry condition. The two scans are then compared, and the MC is calculated based on the differences between the images. If the goal is to determine the MC in local regions within the wood volume, e.g. when studying moisture gradients in wood drying, wood shrinkage must be taken into account during the data processing of the images. The anisotropy of wood shrinkage creates an obstacle, however, since the shrinkage is not uniform throughout the wood specimen. The technique is thus limited in two ways: it cannot measure MC in local regions and it cannot do it in real time.The objective of this thesis was to study methods to overcome these two limitations. The work explores up to three different methods to estimate local MC from CT images in real time. The first method determines shrinkage for each pixel using digital image correlation (DIC) and is embedded in a broader method to estimate the MC, which verified against a reference. It involves several steps in different pieces of software, making it time-consuming and creating many sources of possible experimental errors. The determination of shrinkage within this method is further explored to enable the implementation of all steps in a unique piece of software. It is shown that it is possible to calculate MC through this method with a root mean square error of prediction of 1.4 percentage points for MC between 6 and 25%.The second method studied succeeds in determining the MC distribution in research applied to wood drying, but the calculation of shrinkage differs from the previous method: instead of calculating shrinkage in the radial and tangential directions, it does so by using the displacement information generated from the spatial alignment of the CT images. Results show that the algorithm can provide consistent data of internal MC distribution of wood at the pixel level that entail continuing researching wood drying processes with an improvement in the accuracy of the MC determination. It represents an improvement regarding the first method because the calculation is fast and highly automatized in a single piece of software.The third method studied is the application of dual energy CT (DECT) to moisture. DECT would provide means for MC calculation at the pixel level and, potentially, in real time, which would mean an important breakthrough in wood drying research. Previous research shows promising results, but its implementation in medical CT, the tool used throughout this work, has shown poor predicting ability. Nevertheless, further research is encouraged.The work done in this thesis proves that it is possible to measure local distribution of MC in wood using CT with accuracy and precision. It also shows that further research could potentially provide a means for MC estimation in real time.
  • Cristescu, Carmen (författare)
  • Self-bonding of beech veneers
  • 2015
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • This thesis presents studies on the self-bonding of veneers, and investigations into the properties of boards obtained by hot-pressing beech veneers without adhesives. The raw material is pressed at temperatures from 200 to 250ºC, at pressures from 4 to 6 MPa and pressing times from 240 to 360 s. The hot-pressing of five layers of veneers results in a self-bonded, compressed, densified board, darker than the raw material. The manufacturing process was optimised using a statistical analysis, the response surface experimental design method. The input factors were the pressing parameters and the output factors were characteristics of the product, the raw material properties being kept constant. The results showed correlations between the pressing parameters, especially temperature, as input data and the physical and mechanical properties as responses. Resistance to water absorption and swelling as well as shear strength, bending strength, and hardness were all enhanced by more severe pressing conditions. All the samples pressed at 250ºC became water-resistant while samples pressed at 200ºC delaminated rapidly in water. It was found that the colour of the edges can be used as an indication of the hardness. Chemical investigations were performed on samples taken from veneers (raw material), bond-lines and inner parts of pressed veneer. A High-Performance Liquid Chromatography (HPLC) analysis was used to detect and compare the levels of water-soluble monosaccharides (glucose and fructose) in the veneer before pressing and the levels of 5-hydroxymethyl-furfural (HMF) and furfural in boards. From the results obtained in this thesis it is suggested, that besides other degraded compounds of hemicelluloses, the monosaccharides were transformed into hydroxymethyl-furfural during hot-pressing that could further participate in forming new browning compounds that are related to the bonding phenomenon. The UV spectroscopic analysis to evaluate the content of water-soluble phenols showed that the bond-line had a higher amount of conjugated phenols than the inner veneer suggesting a migration of degraded lignin towards the veneer surfaces during pressing. A CP/MAS 13C NMR study on the solid material showed that the presence of β-ether structures and methoxyl groups in lignin was higher in the bond-line, supporting the hypothesis of a migration of lignin and possibly a condensation reaction occurring at higher temperatures, explaining the water-resistance property acquired by the boards.In a comparative study, oxidative activation with hydrogen peroxide and ferrous sulfate as a catalyst was performed before pressing. Boards made from beech veneer subjected to the pre-treatment step showed a greater mass loss, a lower thickness swelling but also a somewhat lower shear strength. For beech veneers such an oxidative pre-treatment step could be used to gain water-resistant boards pressed at lower pressing temperatures or shorter times than those needed to bond untreated veneers. Scots pine veneers were found to be less suitable for self-bonding than beech veneers. Boards of Scots pine hot-pressed without the oxidative pre-treatment delaminated in water, whereas, under the same pressing conditions, boards made from pre-treated veneers showed a water-resistant bond-line.
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