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1381.
  • Ökvist, Lena Sundqvist (författare)
  • Co-injection of basic fluxes or BF flue dust with PC into a BF charged with 100% pellets effects on slag formation and coal combustion
  • 2004
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Based on 100% pellets operation at BF No. 3 at SSAB Tunnplåt in Luleå a new pellet with CaO/SiO2=1 was developed during early nineties. The pellet showed good results in metallurgical laboratory test but caused slag formation problems in the bosh. A high basicity slag was formed during interaction with basic fluxes and its melting point was increased when the slag was finally reduced. By injection of basic fluxes, the slag formation problems in the bosh can be avoided. Without a sinter plant, dusts have to be recycled in a cold bonded briquette. Injection of some of BF flue dust would improve the properties of the briquette and may be beneficial for the BF process. Based on top charging or tuyere-injection of basic fluxes and the injection of BF flue dust studies have been done. The studies carried out will clarify some phenomena of slag formation and the effect of co- injection on coal combustion in the blast furnace, including the effect of: 1) basic fluxes on slag formation in the blast furnace, if they are top- charged; 2) basic fluxes on slag formation in the blast furnace, if they are tuyere injected; 3) chemical composition and metallurgical properties of pellet and fluxes on slag formation; 4) reduction conditions on (reduction temperature, reducing gas composition) on bosh slag formation; 5 co- injection of BOF slag or BF flue dust on coal combustion efficiency and BF performance. From the results, it can be concluded that the interaction between pellets and fluxes starts when softening and melting starts in the cohesive layer. By choosing fluxes of a high melting point the dissolution of them in the bosh slag can be delayed and the excessive basicity of the bosh slag can be limited. A basic flux with a low melting point will easily dissolve into the bosh slag causing its basicity to increase, which is beneficial to S refining when acid pellets are used. The formation of a bosh slag of excessive basicity (which causes BF operation disturbances, because its high melting point, increases further during reduction) can be avoided by tuyere injection of basic fluxes with the coal. The positive effect is greatest when a fluxed pellet of basicity B21 and with a high Fe content is used as ferrous burden. In this case, the slag amount can be significantly decreased. BOF slag has suitable high-temperature properties for use as a basic flux in combination with e.g., olivine pellets. It has a low softening and melting temperature, does not shrink, is slowly reduced in the BF shaft and its properties are almost unaffected by the partial reduction occurring in the shaft of the BF. BOF slag absorbs a low content of alkalies, which causes volume increase at elevated temperatures, when the basicity is still high. The results indicate that co-injection of BOF slag or BF flue dust with PC has positive effects on the BF operation. The injection of BOF slag decreases the Si content in HM by an increased basicity of the slag formed during combustion leading to a decreased activity of SiO2 in the slag and by an increased FeO content in the tuyere slag that will be reduced by SiFe in the metal at the tuyere level, if the SiFe is initially high. The consumption of reducing agents can be reduced because of a decreased Si content in HM and a decreased slag amount. The permeability is improved by prohibiting the formation of a shell at the raceway end because of improved melting properties of tuyere slag caused by an increased basicity and FeO content, consumption of coal and coke fines by FeO and improved radial transport of tuyere slag. The injection of BOF slag improves the bosh slag because an excessive basicity caused by top-charged fluxes added for neutralisation of coal and coke ashes and non-uniform slag formation caused by uneven distribution of top-charged fluxes are avoided. The productivity increases because of the possibility to decrease the slag amount. The injection of BOF slag can be done without negative effects on combustion efficiency by using very finely ground BOF slag and because of improved total consumption of coal and coke fines by direct reduction in the coke bed. The injection of BF flue dust decreases the Si content in HM by an increased FeO content of the tuyere slag that will be reduced by SiFe in the metal at the tuyere level, if the SiFe is initially high. The consumption of coal and coke is decreased because of a high of C content in BF flue dust and the decreased Si content in HM. The permeability is improved by prohibiting the formation of a shell at the raceway end because of consumption of coal and coke fines by FeO and improved melting properties of tuyere slag promoting the radial transport of the tuyere slag. The injection of BF flue dust can be done without negative effects on the total consumption of coal and coke fines by direct reduction in the coke bed. Injected BF flue dust supplies oxygen for combustion, but because of endothermic reactions as reduction of hematite and calcination of limestone occurring in the BF flue dust at the same temperatures as release and disintegration of VM, it will have a negative effect on the combustion of HV coal. SSAB Luleå and SSAB Oxelösund have started up projects aiming to make tuyere- injection of BF flue dust part of the standard BF operation.
1382.
  • Öqvist, Anna (författare)
  • Skolvardagens genusdramaturgi en studie av hur femininiteter och maskuliniteter görs i år 5 med ett särskilt fokus på benämningar som hora och kärring
  • 2009
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Syftet med studien är att beskriva och analysera hur femininiteter och maskuliniteter görs i skolvardagen. Ett särskilt fokus riktas mot hur benämningar som hora och kärring används men även till viss del hur flickor genom andra språkliga och kroppsliga handlingar gör femininiteter i relation till varandra. En teoretisk utgångspunkt för studien är det social konstruktionistiska perspektivet där kön ses som någonting som görs och där individer är aktiva agenter i denna process. Raewyn Connells teoretiska ramverk har använts. Connell argumenterar där för att skolan är både en institutionell agent som bidrar till att skapa genus och som en arena där unga iscensätter, förstärker eller omförhandlar femininitet och maskulinitet. En viktig utgångspunkt i teorin är att det existerar multipla femininiteter och maskuliniteter som konstrueras både inom och mellan könen i en hierarkisk ordning. På lokal nivå kan detta studeras i form av genusregimer. Connell menar att dessa genusregimer oftast varierar och ser olika ut på lokal nivå mellan till exempel olika skolor, men kan både överensstämma med och avvika från samhällets övergripande genusordning.Det empiriska materialet som avhandlingen bygger på baseras på en etnografisk metod där fältanteckningar och deltagande observation använts som datainsamlingsmetod i tre år fem klasser på tre olika skolor i en medelstor svensk kommun. Åldern på eleverna var mellan 11-12 år. De tre skolorna ligger i skilda bostadsområden inom tätorten. En skola ligger i ett bostadsområde som i hög utsträckning bebos av arbetarfamiljer och de två andra skolorna ligger i medelklassområden. Studiens huvudsakliga resultat visar att kön, femininiteter och maskuliniteter kontinuerligt görs i skolvardagen. Platsen, kamratgruppen och aktiviteten har stor betydelse för hur benämningarna används. I denna process är makt och hierarki centrala komponenter både mellan som inom könen. Till skillnad från Connell, som menar att genusregimer oftast varierar lokalt, visar den här studien likheter snarare än skillnader mellan de tre skolorna.
1383.
  • Öqvist, Rikard, 1982- (författare)
  • Measurement and perception of sound insulation from 20 Hz between dwellings
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Population growth and urbanization are projected by the United Nations to add 2,5 billionpeople to the world’s urban population by 2050. We need to construct buildings in anunprecedented scale to meet global housing demand. Sustainable development is critical.Compared to traditional heavy constructions, lightweight wooden constructions are moreenvironmentally friendly and will play a key role in meeting future demands. However, thereare two major problems with lightweight constructions that need to be addressed: 1) Limitedlow frequency sound insulation and 2) Variations in sound insulation.Annoyance from walking sound tend to be higher in lightweight than in heavy constructionseven with the same measured sound insulation. The Swedish research program AkuLiteindicated that the correlation between measured sound insulation and annoyance wassignificantly improved by extending current evaluation methods from 50 Hz down to 20 Hz.Secondly, large variations in sound insulation between nominally identical lightweightconstructions are common, which leads to larger safety margins. By identifying and quantifyingunderlying causes, production costs can be minimized and the performance can be improved.The aim of the thesis is to develop a new evaluation method for impact sound insulation thatbetter correspond to rated annoyance, and to identify and control underlying causes forvariations in sound insulation. The thesis contains six papers.In Paper I and II, sound insulation measurements were carried out in a large number ofnominally identical rooms of two different industrially prefabricated lightweight woodenconstructions. The purpose was to assess and quantify the variations in impact and airbornesound insulation. In Paper I, 30 nominally identical apartments of a volume based system wasevaluated. The apartments on the highest floor achieved significantly better sound insulationdue to the extra weight on lower floors affecting the elastic connections between stories. InPaper II, 18 rooms of a cross-laminated timber system of plate elements were evaluated.Additionally, several potential parameters related to measurement uncertainty wereinvestigated.Paper III deals with measurement uncertainty. An empirical study of reverberation timemeasurements showed that current methods need to be improved, if sound insulationrequirements are to be extended to 20 Hz.Paper IV and V verified that the frequency range 20-50 Hz is important for walking soundannoyance, and that alternative frequency adaptation terms can improve the correlation betweenmeasured impact sound insulation and annoyance ratings. In Paper IV, the methodology was toperform extensive field measurements in apartment buildings of various construction types andto perform questionnaire surveys among the residents. In Paper V, the methodology was toevaluate annoyance based on binaural recordings of walking sound in a two-part listening test.In Paper VI, 70 measurements in a lightweight wooden system were evaluated to quantify thetotal variations in impact and airborne sound insulation from 20 and 50 Hz, respectively. It wasconcluded that the proposed metrics of impact sound insulation were primarily determined bythe impact sound level 20-40 Hz and that the measurement methods must be evaluatedthoroughly to avoid excessive safety margins.A new evaluation method for impact sound insulation from 25 Hz, that correspond to the ratedannoyance for both heavy and lightweight constructions is proposed. By using the proposedmethod and attending the specific causes for variations, the lightweight industry will be able todevelop improved multi-story dwellings with higher perceived acoustic quality.
1384.
  • Örtqvist, Daniel (författare)
  • Entrepreneur role stress essays on the travails of the entrepreneur
  • 2007
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • This thesis aims to contribute to a better understanding of the social situation of the entrepreneur and the travails of entrepreneurship. More specifically, it examines the role of the entrepreneur by acknowledging that the role is influenced by expectations and proscriptions of stakeholders, scripts for social conducts, and norms. This influence opens up situations demarcated by demanding expectations and resource inadequacies-in terms of role stress-which complicate entrepreneurs' role fulfillment. The detrimental consequences of role stress have been widely acknowledged in professions outside the entrepreneurship setting. Recognizing that role stress is a well-established field of research, the role of the entrepreneur is related to some unique characteristics but with limited prior focus earned. This study therefore aims at contributing to a better understanding of entrepreneurs' role stress, traces possible antecedents, and maps some potential consequences. The thesis is based on a selection of seven academic papers. A meta- analytic review of prominent role stress consequences, together with a narrative literature review of role stress antecedents, lays the foundation for a conceptual analysis of how role stress can be used in entrepreneurship research. A subsequent theoretical analysis of this material implied and strengthened the thesis that the inclusion of role stress is valuable in the study of entrepreneurs. Empirical examinations in different scholarly papers support the role of the entrepreneur and reveal that role stress is an important and prominent phenomenon among entrepreneurs. Role stress is found both to influence the likelihood of inclination for new venture termination and to reduce performance and satisfaction. In a two-year longitudinal data set, role stressors are shown to transform to a proclivity for venture withdrawal through feelings of burnout and dissatisfaction, which sustains over time once triggered. The effect of burnout feelings is direct but not sustained, while the effects from dissatisfaction are lagged. Examining the origin and consequences of entrepreneurs' role stress reveals the lack of fit between entrepreneurs' personality traits and environmental characteristics to develop role stress, and that invested personal resources aiming to resolve role stress can increase venture performance at the cost of exhaustion and reduced self-satisfaction. Further examinations reveal that role stress experiences transform into functional outcomes depending on the coping strategies employed and the levels of role stress experienced. Results moreover reveal that negotiating expectations and/or working harder to meet expectations positively affect venture performance, whereas suppressing perceived expectations negatively influences venture performance.
1385.
  • Österlund, Helene (författare)
  • Further characterisation and applications of the diffusive gradients in thin films technique In situ measurements of anions and cations in environmental waters
  • 2011
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • As both the toxicity and the mobility of trace elements are related to chemical forms present, robust methods for element speciation analysis are of great interest. During the last 15 years, hundreds of scientific articles have been published on the development and applications of the diffusive gradients in thin films (DGT) passive sampling technique. The aim of this thesis was to explore new application areas as well as carry out further characterisation of DGT-adsorbents already on the market. The commercially available DGT containing ferrihydrite adsorbent, currently in use for the determination of phosphate and inorganic arsenic, was characterised with respect to anionic arsenate, molybdate, antimonate, vanadate and tungstate determination. Tests were performed in the laboratory as well as in the field. Diffusion coefficients were determined for the anions using two different methods with good agreement. Simultaneous measurements of arsenate were conducted as quality control to facilitate comparison of the performance with previous work. The ferrihydrite-backed DGT was concluded useful for application over the pH-range 4 to 10 for vanadate and tungstate, and 4 to <8 for molybdate and antimonate. At pH values ≥8, deteriorating adsorption was observed. Further investigations of the ferrihydrite-DGT device were done with respect to organic arsenic species. From previous research it is understood that the two most prevalent forms of organic arsenic in natural waters, monomethylarsinate (MMA) and dimethylarsonate (DMA), adsorb to ferrihydrite. It was concluded that MMA and under some conditions DMA are accumulated and might therefore be included in total arsenic measurements. A method for speciation of inorganic As, DMA and MMA was described. DGT sampling was applied at three stations, with different salinities, in the brackish Baltic Sea. Time series as well as vertical profiles were taken and complementary membrane- (<0.22 μm) and ultrafiltrations (<1 kDa) were conducted on discrete samples collected at 5 m depth. A combination of a restricted pore (RP) version of DGT and the normal open pore (OP) DGT, both loaded with Chelex cation exchanger, was used for speciation of copper and nickel. Due to minimal differences in results between the OP- and RP-DGTs it was suggested that the complexes were smaller than the pore size of the RP gel (~1 nm) resulting in both DGTs accumulating essentially the same fraction. Furthermore, there seemed to be a trend in copper speciation indicating a higher degree of strong complexation with increasing salinity. The low salinity stations are more impacted by fluvial inputs which will likely affect the nature and composition of the organic ligands present. Assuming that copper forms more stable complexes with ligands of marine rather than terrestrial origin would be sufficient to explain the observed trend. Additionally, uranium results from the same sampling tours were used to evaluate OP-DGT for in situ uranium measurements. Previous research has focused on laboratory studies for characterisation of a range of suitable uranium adsorbents, including Chelex. From the Baltic Sea study, a strong correlation between DGT-labile uranium and pH was revealed. The correlation could not be associated to organic complexation, since the ultrafiltration results implicated that uranium was truly dissolved. Instead it must be attributed to the formation of stable inorganic anionic uranyl-carbonate complexes, the stability of which increases with increasing numbers of carbonates and pH. Transplanted aquatic moss has commonly been used to monitor bioavailable trace metal contaminations in freshwater. Like the DGT technique the method has the advantage of generating time-weighted averaged concentrations. The DGT technique has in several previous studies been suggested to mimic biological uptake of trace metals. Four speciation/fractionation techniques – DGT, transplanted aquatic moss, ultrafiltration (1 kDa) and membrane filtration (0.22 μm) – were used in parallel for measurements of Al, Cd, Co, Cu, Fe, Mn, Ni and Zn in a contaminated freshwater stream in northern Sweden. Differences and similarities between the methods were investigated and how these depend on geochemical water quality. Strong correlations between DGT-results and the concentrations in the filtrate (<0.22 μm) and ultrafiltration permeate for Al, Cu, Cd, Co and Zn were detected and, generally, elevated trace metal concentrations were found in the transplanted moss, compared to moss from the non-polluted reference stream. However, no correlation between moss and DGT-labile concentrations could be discerned.
1386.
  • Östlund, Rickard (författare)
  • Microstructure based modelling of ductile fracture in quench-hardenable boron steel
  • 2015
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Reduction of fuel consumption and emissions by vehicle weight minimization constitute a major driving force for the development of new materials and manufacturing processes in the automotive industry. Simultaneously formed and quenched boron steel components have higher strength to weight ratio than conventional mild steel components. Additionally, hot formed components can be tailored to have regions with lower strength and higher ductility, improving their crash performance. This is often realized via dierential in-die cooling rates, thus yielding a variable microstructure compositiongiving rise to distributed mechanical properties. Predicting the performance envelopes of these types of components poses some challenges in terms of constitutive modelling, due to the dierential material composition and mechanical properties. Moreover, fractureinitiation is often a limiting design factor. This thesis aims to contribute to the constitutive and ductile fracture modelling of quench-hardenable boron steels, with reference to microstructure composition and hence process history. Modelling techniques which in an approximate manner can estimate the eective material properties based on the properties of the constituents in combination with ductile fracture models are presented.Computational issues concerning numerical nite element modelling of material instabilities are also addressed, essentially via two dierent methods. Introducing a discretization dependent parameter in the constitutive description, or by kinematic enhancements with respect to the localization problem. Both aim to reduce mesh sensitivity and provide improved predictions of post-instability response with industrially relevant mesh sizes.Additionally, an experimental investigation on the ow and fracture properties of boron steel, with a comprehensive range of dierent microstructure compositions, is presented. A full-eld measurement technique enabled the direct evaluation of mechanical properties and fracture relevant data from tensile tests. These results have supported the establishment of models and enabled their calibration, and they provide further insight to the inuence of microstructure and processing conditions on the ductile fracture properties. Comparisons between simulations and experiments indicate that useful predictions of the overall hardening behaviour and fracture elongations can be obtained by the suggested microstructure based modelling approach.
1387.
  • Östmark, Åke (författare)
  • An infrastructure for service-oriented embedded internet systems
  • 2006
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Embedded systems are in general designed to do some specific task, rather than be a general-purpose computer for multiple tasks. Common for embedded systems is that processing devices, sensors, transceivers, actuators, networks, and software are built into a system, encapsulated by the device it controls. Often, the development of various applications requires an embedded system that is small and lightweight, both in terms of hardware and software. Technology advances in ASIC design have enabled digital and analog components on a single chip by integrating e.g. processing, storage, and Micro-Electro-Mechanical System. The vision due to the improved miniaturization is to have self-configured, low-power, and small form-factor platforms that share resources, have access to the environment, and are deployed in an ad hoc fashion. This, together with wireless communication standards, enables ubiquitous access to information anywhere and anytime. Feeding the digital world with information, as measurements of physical phenomenon, is done by the use of sensors. Extending the control from the digital world to the physical world can be achieved by actuators. Combining those sensors and actuators with wireless networking capabilities enables a new paradigm for e.g. scientists, medical personnel, and engineers to observe physical phenomena. The world of networking sensor and actuator devices is vast and covers aspects such as energy-efficient hardware design principles, medium access protocols, routing and transport protocols, embedded operating systems, security, low-power operations, localization, data storage, mobility, and network management etc. All these areas are important for embedded systems targeting the interconnection of small devices. In the scope of this thesis, the embedded system is realized in the form of a small sensor and actuator node, a device with interfaces to measure physical phenomenon and/or affect the surrounding environment. Our primary hypothesis is that standards-based protocols and de facto standards can be utilized as the fundamental operational infrastructure of the sensor and actuator nodes. Using a universal widespread standard protocol can be advantageous in respective to a custom made solution when developing and deploying networking nodes. Today, TCP/IP is the most widespread networking protocol suite in computer communication in use. As a consequence, we show how the readily available TCP/IP protocol suite can be used as a foundation for intra/internetworking even for resource constrained sensor and actuator nodes. A platform that is intelligent and accessible over the Internet opens new possibilities for control, maintenance, and remote monitoring. In this thesis commercial off-the-shelf hardware components are used in combination with software based on standard protocols as a basis for the platform architecture. First, a small wireless networking node accessible from devices in close proximity is presented. The generic architecture enables the rapid development of various applications, adaptable to different usage scenarios. Second, it is shown that a small spontaneous network of mobile nodes can be established, even though the resources on the nodes are very limited. Third, many applications require a large number of small and lightweight nodes to cooperate. However, one of the challenges with networking sensor and actuator nodes is the distributed functionality without central control. The approach taken in this thesis was to leverage emerging technologies to model the functionality of the nodes, thus nodes are provided with the capability and mechanisms to present themselves and to discover peer nodes. Consequently, application-level interoperability is enabled by introducing service discovery techniques which have the potential to automate the discovery of nodes and required services.
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