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Sökning: L4X0:1402 1544 > (2015-2019) > (2016)

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31.
  • Hu, Xianfeng (författare)
  • Studies on Carbothermic Reduction of Chromite in the Presence of FeOx
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Direct chromium alloying by chromite ore is a promising technology for producing Crcontainingsteels, as the ferrochrome production process and the chromium alloying processare integrated into a single step, which has the potential of saving energy and raw materials.In this work Thermogravimetric Analysis experiments and induction furnace experiments (upto 80-kg scale) have been carried out to investigate the carbothermic reduction process ofchromite in the presence of FeOx (iron, mill scale or magnetite). The aims are to investigatethe effect of FeOx on the carbothermic reduction of chromite and to explore the potential ofdirectly alloying steel with chromium by the designed alloying precursor ‘chromite ore +FeOx + carbonaceous material’.The results from the Thermogravimetric Analysis experiments show that FeOx can enhancethe carbothermic reduction of chromite and the enhancing effect increases when increasedamounts of FeOx are added to the chromite. The enhancing effect is attributed to the presenceof added metallic iron or the metallic iron reduced from mill scale or magnetite, which candecrease the activity of chromium by having chromium dissolve in the iron in situ. The resultsfrom the induction furnace experiments show that the steel can be directly alloyed withchromium by using the designed alloying precursor ‘chromite ore + mill scale + petroleumcoke’ and the chromium yield from chromite ore increases when increased amounts of millscale are added to the alloying precursor.The designed alloying precursor, on one hand, can be potentially used to directly alloy steelwith chromium in the Electric Arc Furnace steelmaking process and, on the other hand, can bepotentially used to produce Cr pre-alloyed iron powder or Cr pre-alloyed Direct Reduced Ironby the solid-state reduction process. The proposed applications have the potential to improvethe raw materials efficiency and energy efficiency.
32.
  • Iqbal, Naveed (författare)
  • Analysis of Catenary Effect in Steel Beams and Trusses Exposed to Fire
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • The goals of structural design are fundamentally different when designing structures at normal temperature or when designing them in a fire situation. While structures are primarily designed for normal temperature situations considering the different design limit states, in the fire design situation, however, the already designed structure is assessed for its resistance in the fire design limit state. The assessment of the structure in the fire limit state may lead to either active or passive fire protection measures. The assessment of the structure in fire may be done in several different domains such as its structural resistance, integrity of structural components to prevent spread of fire and insulation properties of materials. The focus of the thesis presented here is on the structural resistance of steel structural members particularly steel beams and trusses in fire situations.The Eurocodes permit designers to use either a simple prescriptive design procedure or a more complex performance based procedure for design of structures in fire. The prescriptive design is a simple choice regarding design of steel structures in fire due to their use of simple analytical equations; but through several studies it has been established that this approach might be conservative and in some situations it might not reflect the complexity of interaction between the heated structural members and its surrounding colder parts of the structure. The performance based approach has therefore been increasingly adopted in structural fire design, which, although more complex than the prescriptive approach, is closer to the real structural behaviour.Through a performance based approach, this thesis aims to establish that steel structural members are able to offer structural resistance in fire situations that are much higher than would be expected from a prescriptive approach. Two different types of structural members such as steel beams in multi-storey buildings and trusses in single storey buildings were considered here. It has been shown through extensive finite element analysis in both cases that actual resistance of these structural members in fire situations can exceed their primary resistance mechanism through flexure. Alternative load transfer mechanism through catenary action offers the added resistance at much higher temperatures than the conventional critical temperatures from prescriptive design. The thesis also proposes simplified calculation procedures that can be used to reasonably predict the structural resistance at elevated temperatures considering the catenary action.
33.
  • Iqbal, Sarfraz (författare)
  • Ensemble View on Designing Pedagogical Online Information Security Laboratories
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Distance education and e-learning in the field of information security is gaining popularity. An online information security programme is supposed to include plenty of hands-on exercises, but in most cases the lab experiments are unavailable to distance students that represent a challenge in online education. In information security education, virtual labs facilitate hands-on learning in distance education. An online information security lab is an artefact which involves a collection of systems and software used for teaching information security, and which is accessible through the Internet. However, the design, development and implementation of an online InfoSec lab has many challenges. This research is motivated from an on-going information security lab development initiative at Luleå University of Technology (LTU).Thus, the researcher focused on the question of how we can design a pedagogical online InfoSec lab which is flexible, usable and adapts to different educational contexts. The current literature about online InfoSec labs still lacks well-specified pedagogical approaches and concrete design principles. This hinders the accumulation of technical and pedagogical knowledge for the implementation and use of online educational InfoSec labs. Moreover, the literature focuses mainly on details of technical lab implementations, whereas the pedagogical elements of the curriculum and the rationale behind them were ignored. This leads to inadequate guidance about how the instructor and the learner can make use of the lab to pedagogically align the course objectives, teaching / learning activities and assessment methods. In order to design an online InfoSec lab to improve flexible hands-on education and security skills development the Action design research (ADR) approach was chosen. The ultimate goal is to design an ensemble IT artefact as a result of emerging design, use, and refinement in context through continuous interaction between technology and organization during the design process. Following the IT-dominant BIE process of ADR approach made it possible not only to develop the lab and instantiate it in different courses but also to formulate design principles and abstract the findings to a generalizable level. Furthermore, a framework for evaluation in design science research (FEDS) was adopted for evaluation purposes. The framework was used to conduct formative and summative evaluations. Feedback from all the stakeholders including teachers and students showed that the online InfoSec lab is a usable learning media for hands-on education from a distance.This research contributes by showing the design, development and implementation of an online InfoSec lab aimed at the improvement of hands-on education and evaluation of its use in context. Following technology as a development project perspective of an ensemble view, my research work at its current status contributes by serving two major purposes. First, this study proposed a conceptual design model of an online InfoSec lab comprising important building blocks or entities. The study conceptualizes the online InfoSec lab as an ensemble artefact. This study unfolded the black-box tools view of the lab so as to understand and explain the important building blocks (entities of the lab), and the interrelationships of the entities. This study provides conceptual clarity given the existing literature on online InfoSec labs, by recognizing the stakeholders and explaining their roles for each entity in the proposed conceptual model of an online InfoSec lab; this is a view which has not been recognized or discussed in similar earlier works. Second, the study suggests design principles for implementing a conceptual model of an online InfoSec lab in different educational contexts. The emerging design principles were shaped during this research work together with the other stakeholders. The design principles such as Contextualization based on programme goals, Contextualization based on course goals, Pedagogical alignment of lab activities, Flexible learning, Collaboration among lab stakeholders, Scalability, User friendly interface with properly arranged resources and targets and Isolate the InfoSec lab incorporate the socio-technical perspective, which ensures that the resulting artefact developed using these principles should be an ensemble artefact. The design principles can provide support to practically construct, implement and test the online InfoSec lab. The study introduced a productive learning media (InfoSec lab) that is designed to meet the active learning preferences of distance learners of information security, such as support for flexible and individualized hands-on learning. Practitioners wishing to include lab activities in their courses and programmes can utilize this knowledge to understand fully how much human and technical resources are needed to design the lab and conduct exercises.
34.
  • Karim, Zoheb (författare)
  • Nanocellulose based affinity membranes for water purification: Processing technologies for optimal adsorption of dyes and metal ions
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • The aim of current study was to fabricate high flux affinity membrane with mechanical stability, porosity and high functionality for capturing of contaminants (dyes and metal ions) from water. Cellulose nanocrystals (CNCSL) and cellulose nanofibers (CNFSL) as well as a special grade of cellulose nanocrystals (CNCBE) isolated following bioethanol pilot scale process were used for the membrane fabrication. To improve the functionality and adsorption capacity of the membranes, enzymatic phosphorylated CNCSL (PCNCSL) and in situ TEMPO functionalized CNCBE (TEMPO-CNCBE) membranes were adopted. The removal of water contaminants via adsorption on carboxyl, sulphonic and phosphoryl functional groups on nanocellulose based membranes was evaluated. Freeze-drying was used as one approach to fabricate CNCSL based hybrid membranes. In spite of high percentage removal of positively charges dyes, low water flux and mechanical stability was recorded. Very fast and effective process, viz. vacuum-filtration was further used to fabricate layered membranes with improved mechanical properties. CNFSL based support layer was coated with more functional nanomaterials (CNCSL and CNCBE) via dipping. The study showed that it was possible to tailor the specific surface area, pore sizes, water flux and wet strength of the membranes based on drying conditions (105 °C at a load of 100kN and 28 oC at ≈20N) and acetone treatment. This study was further extended to fabricate high flux bi-layered membrane having support layer of micro-sized cellulose sludge and top layer of CNCSL, CNCBE and PCNCSL within gelatin matrix for adsorption. The aim of this approach was to provide mechanical stability without decreasing the water flux significantly. In the final study, to increase the adsorption capacity of CNCBE layered membranes; in situ functionalization (TEMPO oxidation) of top layer was performed. Furthermore, CNFSL was introduced in support layer to understand the structural and functional behavior of CNFSL. All membranes were subjected to pollutants removal [dyes and Ag(I), Cu(II), Fe(II)/Fe(III) metal ions]. Remarkable increase in adsorption capacity towards metal ions was recorded after modification of nanocellulose (phosphorylation and in situ functionalization). The outstanding performance of nanocellulose reveals the possibility of next generation affinity membranes for water purification.
35.
  • Kassaeyan, Kasra (författare)
  • Factors Affecting Upvoting Intention On Social Bookmarking Sites
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Technological developments of last decade have changed how people communicate and how companies operate. With the emergence of the Internet, and specifically of the interactive web or Web 2.0, traditional word of mouth evolved to a new, more collaborative form where users can easily obtain, share and compare information about products or services with each other. This phenomenon, referred to as electronic Word of Mouth (eWoM), is at the heart of this dissertation. People share, like, bookmark or recommend content and resources to each other on a variety of platforms, including so-called social bookmarking sites. Their collective opinions can have asignificant impact on brands, and the shared electronic word of mouth can present a boon to firms when consumers praise and promote their services and products through votes etc. In order to maximize positive eWoM, managers require a clear understanding of when and why users decide tovote on social bookmarking sites. Despite the significant promises, this research topic of “voting intentionality” is little understood. Thus, this study concentrates on understanding “upvoting” (positive eWoM) intentionality on social bookmarking sites. In order to explore this phenomenon, the Theory of Planned Behavior (TPB) and Social Cognitive Theory (SCT) are combined to form a conceptual framework and research hypotheses. In terms of the empirical context, data were collected from Reddit, currently the biggest (in terms of members) and most active social bookmarking sites (in terms of content posted and upvotes casted). Upvoting data were collectedthrough voluntary participation in a web survey. To analyze the 342 usable sample cases and to test the model, structural equation modeling SEM statistical techniques were employed, using SPSS and AMOS software packages. The structural model testing results indicate that a series of factors (e.g., perceived behavioral control and attitude toward voting for posts) significant influence upvoting intention among members of Reddit. The framework developed here contributes to our conceptualization of the dissemination of electronic word of mouth, and the findings help marketingpractitioners integrate social bookmarking sites into their social marketing campaigns to boost and improve the overall marketing performance.
36.
  • Källander, Björn (författare)
  • Drying and thermal modification of wood - studies on influence of sample size, batch size, and climate on wood response
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Research on wood drying and wood modification is primarily done in laboratories, using clear wood specimens treated under well-defined conditions in laboratory cabinets. Laboratory tests differ from industrial treatment both regarding the size and homogeneity of the material treated, and the size of the batch and kiln used.Knowledge about how the size of the material treated and the size of the batch or kiln influence the results is limited, which makes it difficult to utilize results from laboratory research in development of industrial processes. A better understanding of the influence of size can also improve the possibilities to design laboratory studies so that the results are easier to implement industrially.The studies presented in this thesis focus on how the size of the batches treated and the size of the individual wood samples treated influence the process and resulting properties of the wood. The aim of the studies, the so called researchquestion in the context of a PhD-thesis, is to help transfer knowledge gained from testing small wooden samples in laboratories to industrial treatment of full size timber.This thesis describes studies on vacuum drying, high temperature (HT) drying, and thermal modification of wood according to the Thermowood© process. Drying and thermal modification of wood have been studied under industrial andlaboratory conditions. Kiln climates and wood response have been determined during vacuum drying, conventional drying, high temperature drying, and thermal modification.The results show that both the size of the material treated and the size of the kiln or batch strongly influence the processes and the resulting wood properties.The results show that the sample size influences different material properties in different ways. Equilibrium moisture content is reduced less during thermal treatment of small clear wood specimens than during treatment of dimensionaltimber. Mass loss on the other hand is higher in small samples. Reduction in impact bending strength, mass loss, and reduction in EMC after thermal treatment of dimensional timber do not seem to be correlated.Laboratory treatment of small clear wood specimens show considerably stronger influence on the wood properties than treatment of similar samples together with industrial production.
37.
  • Lanke, Amol, 1982- (författare)
  • Mine Production Assurance Program- Development and Application
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • ssuring production forms a crucial part of mining business profitability. Factors related to various mine operations, activities and business processes can threaten required/planned mine production.   To address problems and ensure production level in mining, it is necessary to implement a mine production assurance program (MPA). In order to propose a guideline and its component, this study started by reviewing four such techniques used in process industries. Comparing the tools, techniques   and focus with mining productivity and production factors, it was observed that applicability of these methods for mining is limited due to lack of focus on equipment focus, cost focus and other parameters. Similarity of objectives and requirements of equipment focus lead to conclusion that PAP from oil and gas industry seems to be method which can guide MPA.\parAs a basis of MPA, an index is required to create a clear relationship between different situations which can occur in mining operation and production loss. A literature review on mining productivity improvement methods shows availability, utilisation and production performance of equipment are the key factors in determining overall production. A single index applicable for chain operation in mining is needed. A Mine Production index (MPi) is thus proposed. This index involves all three parameters for equipment productivity mentioned above.  Weights associated with MPi calculation for bottleneck equipment can point out critical factors in equipment operation. Once bottleneck equipment and relevant critical factors are known, further analysis can be carried out to determine the possible causes of production loss. By using MPi for machine operations, it is possible to rank machines in terms of production effectiveness. When the study applied MPi to chain operations in a mining case study, a crusher was determined as bottleneck equipment.\parMining operation is heavily influenced by internal and external uncertainties. Operational uncertainties related to equipment includes its key factors leading to production i.e. availability, utilisation and performance. These factors are in turn dependent upon downtime, idle time, rated capacities. External parameters related to weather are based upon location of mining operation. Influence of these factors on production volume, could be used for better decision making during mining operations optimization. To effectively propose a method for correlating internal and external parameters with production volume, case studies in an open pit mine were conducted. During these case studies a multi-regression modelling methodology is used. It was found that at system level availability is important criteria for increasing production. At level of shovel and truck fleet, availability and utilisation are most important characteristics to be focused for reduction in production uncertainty. Environmental factors are although correlate to less variation in production volume compared to operational factors.  Amongst considered environmental factors snowfall is highly influencing followed by rainfall.  At system level  use of maximum capacities of equipment and availability are key point for increasing production. Based on analysis of internal operational factors, it was concluded that capacity of shovel and trucks is underutilised. For shovels availability and idle time are influential factors. For trucks utilisation is highly correlated to production volume generated.  Analysis of environmental factors concluded that, period of zero snowfall and rainfall are perfect condition for equipment production increase. Period when either snowfall or rainfall stabilisation are also equivalent to achieve higher production. Although these production levels are significantly less than period without snow and rain
38.
  • Larsson, Johan (författare)
  • Managing radical innovation in the Swedish infrastructure sector A study of industrialized construction
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Industrialized construction has been a key enabler for managing increasing customer demands and addressing low productivity problems in the house building industry. It has also been proposed as a solution for low productivity in the infrastructure construction sector, but diffusion has been slow. The focus in industrialized construction is on maximizing the efficiency of the whole production system by implementing both novel products and processes in a traditionally project-based industry. Hence, industrialized construction should be considered and managed as a radical innovation involving multiple stakeholders throughout the supply-chain. Thus, the purpose of the research underlying this thesis was to increase understanding of the management of radical innovation in the infrastructure sector, as exemplified by industrialized construction.To increase knowledge of the whole innovation process, an exploratory approach including both case studies and surveys was applied. A contractor perspective was adopted in an initial study, focusing on the development phase of industrialized construction. It revealed that industrialized construction is a comprehensive and multi-faceted activity that must be managed strategically rather than at a project level. However, early studies also revealed major challenges in the diffusion of the concept. Consequently, the research underpinning this thesis has also addressed the diffusion phase, which occurs in the Swedish infrastructure sector mostly in construction projects managed by a public client (often the Swedish Transport Administration, STA). Five studies were conducted during the course of the research, which have contributed insights into different aspects of the challenging management of radical innovation in the mature Swedish infrastructure sector.The findings reveal that the radical innovation process involves a clear separation between the development and diffusion phases, but these are strongly intertwined. They also show that the major role of public clients (especially STA) in management of the diffusion of innovations developed by contractors exacerbates difficulties of diffusing industrialized construction in the infrastructure sector. Both the client and contractor need to acknowledge the nature of industrialized construction as a radical innovation with two separate phases. The contractor, who drives the development phase of a radical innovation, must apply an appropriate process that addresses needs of stakeholders (both internal and external) who may affect the diffusion phase, while the client must act as a problem owner and facilitate diffusion, due to the strength of the client’s position. The findings further reveal major shortcomings in the current diffusion phase and show that procedures in Swedish infrastructure projects must be modified to facilitate increased diffusion of radical innovations such as industrialized construction. The STA has recognized the need to increase rates of innovation, both by initiating an innovation program and by increasing the rate of design-build contracts, to resolve the issue of low productivity. Diffusion of industrialized construction has been slow. However, the insights regarding management of the radical innovation process presented in this thesis could be beneficial for industry representatives seeking to raise rates of the implementation of such innovation. The thesis addresses various aspects of the radical innovation process and emphasizes the difficulty of diffusing innovations in the current industry climate. The more comprehensive understanding of the system thereby provided may increase the ability of stakeholders, especially the STA, to make appropriate long-term decisions to facilitate increases in productivity.
39.
  • Larsson, Richard (författare)
  • Modeling the Zeeman Effect in Planetary Radiative Transfer and Applications
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Remote sensing is about retrieving distant physical properties from locally observed radiation. The first step to remote sensing is to describe, or model, the radiative transfer. Without locating the origin of the observed radiation, and without proper interpretation of what it represents, understanding and utilizing instrumental results are nearly impossible. The focus of my thesis is on how radiation interacts with a weakly magnetized medium by means of the Zeeman effect. One molecule of particular interest affected by the Zeeman effect is the oxygen molecule. The thesis work started by an implementation of a module for the Zeeman effect in an existingradiative transfer model. Later works has applied this module to Earth and Mars radiative transfer.The high relative concentration of the oxygen molecule in Earth’s atmosphere, and the fact that the molecule interacts with sub-millimeter radiation, has made it a prime target for temperature retrievals using both ground- and satellite-based radiometers. The Zeeman effect is important for molecular oxygen at mesospheric altitudes on Earth, where the geometry of the magnetic field and of the observation influence the polarized absorption of radiation. Simulations of ground-based measurements by a radiometer in Bern, Switzerland, have the Zeeman module reproduce the dependency on observational geometry for the local magnetic field, partly validating the module. Simulations of satellite measurements comparing the Zeeman module to a fast, parameterized, implementation of the Zeeman effect for numerical weather predictions also indicates that the module works. There are small discrepancies between the two models but both are close to the satellite measurements given the noise of these measurements. Work to move beyond simulation space and analyze these satellite measurements to find the atmospheric temperatures at high altitudes also show promising results.Besides Earth applications, the module has been used for Mars conditions, where only trace amounts of molecular oxygen is available. Mars does not have a global magnetic field but instead have several magnetic sources scattered throughout its crust. This gives a magnetic field that is significantly weaker than on Earth and with much more structures. It is possible to utilize the Zeeman effect on molecular oxygen to measure the magnetic field of Mars. The last part of this thesis work suggests a measurement scheme for a satellite capable of retrieving the horizontal components of the Martian crustal magnetic field. It shows the expected errors associated with such a measurement scheme.
40.
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