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In a scrap based stainless steel plant the dominant process for carbon reduction is the Argon oxygen decarburisation process (AOD). The process goes through three steps: decarburisation, reduction and desulphurisation where the main challenge is to oxidise carbon to CO without oxidising the expensive chromium. The general practical approach is to inject a mixture of oxygen and an inert gas, like argon or nitrogen, through tuyeres at the converter side starting with a high amount of oxygen gas which followingly is reduced as the inert gas is increased during the decarburisation steps. This allows for a decrease in partial pressure for the CO bubbles which is thermodynamically favourable for carbon oxidation. Recent studies have shown that an aged AOD converter with a worn lining can decarburise the melt faster than a fresh vessel due to favourable thermodynamic conditions occurring since the bath height is lower in the aged converter. The studies show 8-10% savings of oxygen gas which have led to an interest to study the matter. One of two approaches are taken in the present work with the focus to develop a numerical model that simulates a downscaled AOD converter with applied inclinations that is to be validated through physical modelling. A 75-ton industrial converter was downscaled for water-air experiments where three inclination angles namely 0, 5.5 and 14° were studied with focus on mixing time and penetration length. The physical model was replicated for computational fluid dynamics (CFD) modelling using the Euler-Euler approach in ANSYS Fluent. The models show rather good similarities when comparing gas penetration length, flow structure and mixing time however needs some complementary work and final adjustments before upscaling as well as coupling with thermodynamic modelling can be done. / Den dominerande processen för kolfärskning vid skrot baserad rostfri ståltillverkning är AOD- processen (Argon Oxygen Decarburisation). Processen går igenom tre steg, kolfärskning, reducering av krom och svavelrening där de största utmaningarna ligger i att oxidera kol utan att oxidera krom. I praktiken gör detta genom att injicera en blandning av argon och syrgas från sidan av AOD-konvertern för att sänka partial trycket av den kolmonoxid som bildas när kol oxideras. Syftet är att göra det mer termodynamiskt fördelaktigt att oxidera kol i systemet. Den injicerade blandgasen har olika förhållanden under kolfärskning med en hög andel syrgas i början som sedan sänks genom processen tills bara argon injiceras. Tidigare studier har visat att kolfärskningen är en funktion av konverterns ålder där ju äldre en konverter är desto snabbare går kolfärskning. Enligt studierna har det visats att 8-10% mindre syrgas eller användning av reducerings medel kan uppnås i en gammal konverter vilket har väckt ett intresse för vidare studier. I detta arbete har en av två metoder prövats för att undersöka om man kan applicera det som sker i en gammal konverter till en ny. En numerisk modell av en nerskalad AOD-konverter har utvecklats och validerats mot en vattenmodell då konvertern vinklas. En 75-tons konverter nerskalades till en vattenmodell där vinklarna 0, 5.5 och 14° studerades med fokus på blandningstid och penetrations djup. Vattenmodellen gjordes om till en numerisk modell som använde Euler-Euler metoden i ANSYS Fluent. Modellerna visade likheter gällande penetrationsdjup, flödes struktur och blandnings tid men kräver en del justeringar innan en uppskalning samt koppling till termodynamisk modellering kan ske.

<p>The focus of this thesis is on groundwater vulnerability assessment by process-based simulation models and data acquisition for these assessments. A modelling system for intrinsic groundwater vulnerability assessment in water supply areas was developed, consisting of flow- and transport models for the unsaturated zone and the groundwater zone, coupled to a geographical informa-tion system. The system was applied to a water supply area located close to a major road south of Stockholm. Chloride was used as an indicator in determining the vulnerability for groundwater contamination from the road. The approach was useful to illustrate the dynamic change of chlo-ride concentrations both during the stage of continuous application and after the applications was terminated. A structure and content of a database for flow and transport modelling, based on hydrogeological environments, was outlined. An existing hydrogeological parameter database, HPAR at the Geological Survey of Sweden (SGU), was examined as a potential source of data for the new database. Values for some important parameters needed for groundwater modelling, such as hydraulic conductivity and effective porosity, were lacking in the three municipal HPAR databases that were studied. It was suggested that these data should be added, together with information on the hydrogeological environments, for all geographical positions of interest. Without such minimum information, the efficient use of modelling tools could not be expected.</p><p>Typical profiles of three common Swedish hydrogeological environments (sand deposits, glacial till and clay covered areas) were used to represent generic input data to model simulations in the unsaturated zone so that the importance of soil, vegetation type and groundwater levels on turn-over times of conservative contaminants transported by natural recharge could be examined. The same profiles were used to predict the penetration depth of accidental liquid spills that occur at the land surface level. In the case of contaminant transport by natural recharge, water storage in the soil profile and vegetation type played an important role for turnover times. For liquid spills, the hydraulic con-ductivity was found to be of major importance, while the water retention properties were of less importance. Modelling, together with available data sources, were successfully used to demon-strate the vulnerability of different environmental conditions.</p>

The focus of this thesis is on groundwater vulnerability assessment by process-based simulation models and data acquisition for these assessments. A modelling system for intrinsic groundwater vulnerability assessment in water supply areas was developed, consisting of flow- and transport models for the unsaturated zone and the groundwater zone, coupled to a geographical informa-tion system. The system was applied to a water supply area located close to a major road south of Stockholm. Chloride was used as an indicator in determining the vulnerability for groundwater contamination from the road. The approach was useful to illustrate the dynamic change of chlo-ride concentrations both during the stage of continuous application and after the applications was terminated. A structure and content of a database for flow and transport modelling, based on hydrogeological environments, was outlined. An existing hydrogeological parameter database, HPAR at the Geological Survey of Sweden (SGU), was examined as a potential source of data for the new database. Values for some important parameters needed for groundwater modelling, such as hydraulic conductivity and effective porosity, were lacking in the three municipal HPAR databases that were studied. It was suggested that these data should be added, together with information on the hydrogeological environments, for all geographical positions of interest. Without such minimum information, the efficient use of modelling tools could not be expected. Typical profiles of three common Swedish hydrogeological environments (sand deposits, glacial till and clay covered areas) were used to represent generic input data to model simulations in the unsaturated zone so that the importance of soil, vegetation type and groundwater levels on turn-over times of conservative contaminants transported by natural recharge could be examined. The same profiles were used to predict the penetration depth of accidental liquid spills that occur at the land surface level. In the case of contaminant transport by natural recharge, water storage in the soil profile and vegetation type played an important role for turnover times. For liquid spills, the hydraulic con-ductivity was found to be of major importance, while the water retention properties were of less importance. Modelling, together with available data sources, were successfully used to demon-strate the vulnerability of different environmental conditions. / QC 20101020

The overall purpose of this research is to develop a real-time ultrasound based system for controlling robotic weld quality by monitoring the weld pool. The concept of real-time weld quality control is quite broad, and this work focuses on weld penetration depth monitoring and control with laser ultrasonics. The weld penetration depth is one of the most important geometric parameters that define the weld quality, hence remains a key control quantity. This research focuses on the implementation and optimization of the laser phased array generation unit and the development of signal analysis algorithms to extract the weld penetration depth information from the received ultrasonic signals. The system developed is based on using the phased array technique to generate ultrasound, and an Electro-Magnetic Acoustic Transducer (EMAT) as a receiver. The generated ultrasound propagates through the weld pool and is picked up by the EMAT. A transient FE model is built to predict the temperature distribution during welding. An analytical model is developed to understand the propagation of ultrasound during real-time welding and the curved rays are numerically traced. The cross-correlation technique has been applied to estimate the Time-of-Flight (ToF) of the ultrasound. The ToF is then correlated to the measured weld penetration depth. The analytical relationship between the ToF and penetration depth, obtained by a ray-tracing algorithm and geometric analysis, matches the experimental results. The real-time weld sensing technique developed is efficient and can readily be deployed for commercial applications. The successful completion of this research will remove the major obstacle to a fully automated robotic welding process. An on-line welding monitoring and control system will facilitate mass production characterized by consistency, high quality, and low costs. Such a system will increase the precision of the welding process, resulting in quality control of the weld beads. Moreover, in-process control will relieve human operators of tedious, repetitive, and hazardous welding tasks, thus reducing welding-related injures.

The offshore oilfield industry is continuously developing unique and break-through technologies and systems to extract hydrocarbons from ever increasing ocean depths. Due to the extreme depths being explored presently, large anchors are being utilized to secure temporary and permanent facilities over their respective drilling/production site. A vertically loaded, torpedo-style, deepwater mooring anchor developed by Delmar Systems, Inc. is one of these anchors. The OMNI-Max anchor is an efficient, cost-effective alternative for use as a mooring system anchor intended for floating facilities. The OMNI-Max is designed to free-fall towards the ocean bottom and uses its kinetic energy for self-embedment into the soil, providing a mooring system anchor point. Values such as drag coefficient and terminal velocity are vital in predicting embedment depth to obtain the mooring capacity required by the floating facility. Two scaled models of the Mark I OMNI-Max anchor were subjected to a series of tests in the Haynes Coastal Engineering Laboratory at Texas A & M University to evaluate the overall drag coefficient and penetration depth. The 1/24 scale model was tested by measuring the amount of penetration into an artificial mud mixture. The 1/15 scale model was attached to a tow carriage and towed through a water-filled tank to measure the drag forces and evaluate the drag coefficient. The anchor terminal velocity was measured using underwater cameras to track the free fall of the model anchor through 15 ft of water inside the tow tank. The 1/24 scale model penetrated the mud an average of 22 inches from the leading tip of the anchor to the mud surface, approximately 1.5 anchor lengths. The penetration depth increased as impact velocity increased, while the penetration depth decreased as the fins were retracted. The 1/15 scale anchor was towed at 6 different velocities producing a varied total drag coefficient between 0.70 and 1.12 for Reynolds number flows between 3.08E 05 and 1.17E 06. The drag coefficient increased as the fins were retracted and when the mooring rope was attached. The 1/15 scale anchor was allowed to free-fall in the tow tank and obtained an average terminal velocity of and 14.6 feet per second. The drag coefficients ranged from 0.46 to 0.83, which increased as the fins were retracted. When using the results to estimate prototype sized anchor drag coefficient, the average value was estimated to be 0.75.

No description available.

Vid röjning av RSV-ammunition saknas idag adekvat beslutstöd för att dimensionera skadebegränsande åtgärder mot jetstrålens verkan. I uppsatsen vidareutvecklas en beräkningsmodell som författaren tidigare föreslagit. Syftet är att skapa ett verktyg som kan införas i ammunitionsröjningsverksamheten. Fullskaliga skjutförsök har genomförts för att klarlägga inverkan av förhållanden som är typiska vid ammunitionsröjning; en skyddskonstruktion byggd av sandsäckar och med ett långt detonationsavstånd till röjningsobjektet. Försöksresultatet visar att den grundläggande hydrodynamiska penetrationsteorin inte är användbar för dessa förhållanden. Vidare ger sandsäckskonstruktionen signifikant bättre skydd mot jetstrålen än en homogen grusbädd. Genom störningsanalys har känsligheten hos de enskilda parametrarna i beräkningsmodellen för verksamhetstypiska fel utretts. Härefter har Monte Carlo-simulering använts för att analysera den sammanlagda inverkan som dessa fel kan ge. Resultatet har legat till grund för att bestämma modellens säkerhetsmarginal. Militär nytta innebär att modellen skall kunna tillämpas fältmässigt, med korta tidsförhållanden och utan tillgång till avancerade beräkningshjälpmedel. Detta har lett fram till att ett enkelt diagram inkluderats i det kompletta dimensioneringsverktyget. Verktyget föreslås införas i regelverk och utbildningssystem för att avhjälpa den brist som råder idag. / During the clearance of shaped charge ammunition, explosive ordnance disposal (EOD) personnel lack adequate means for the design of protective measures against the jet. In this thesis a calculation model, previously suggested by the author, is developed further. The aim is to create a tool that can be applied to EOD operations. Full-scale experiments have been conducted to clarify the effects of conditions that are typical for EOD operations: protective measures built from sandbags with a long standoff distance to the ordnance. The results indicate that the hydrodynamic penetration theory is not suitable for these conditions. Furthermore, a sandbag construction provides significantly better protection against the jet than a homogeneous gravel construction. By disturbance analysis, the sensitivity of the individual parameters in the model is studied for typical errors. Subsequently, Monte Carlo simulation has been used to analyse the effect these errors can cause. The simulation results have then been the used to determine the model´s margin of safety. Military utility implies that it should be possible to use the model under field conditions, with limited time frames and without access to advanced calculating means. This has resulted in a simple diagram included in the comprehensive design tool. It is proposed that the tool is implemented in regulations and curricula in order to remedy today’s lack of decision support.

Abstract After the discovery of topological insulators (TIs), it has come to be widely recognized that topological states of matter can actually be widespread. In this sense, TIs have established a new paradigm about topological materials. Recent years have seen a surge of interest in topological semimetals, which embody two different ways of generalizing the effectively massless electrons to bulk materials. Dirac and, particularly, Weyl semimetals should support several transport and optical phenomena that are still being sought in experiments. A number of promising experimental results indicate superconductivity in members of half-Hesuler semimetals which realize the mixing singlet and triplet pairing symmetry. We now turn to results we got through the work on topological semimetals. This work presents quantum high field transports on Dirac and Weyl topological semimetals including Sr1-yMn1-zSb2 (y, z < 0.1), YbMnBi2 and TaP. In case of Sr1-yMn1-zSb2 (y, z < 0.1), massless relativistic fermion was reported with m* = 0.04-0.05m0. This material presented a ferromagnetic order for in 304 K < T < 565 K, but a canted antiferromagnetic order with a net ferromagnetic component for T < 304 K. These are considered striking features of Dirac fermions For YbMnBi2, we reported the unusual interlayer quantum transport behavior in magnetoresistivity, resulting from the zeroth LL mode observed in this time reversal symmetry breaking type II Weyl semimetal. Also, for Weyl semimetal TaP the measurements probed multiple Fermi pockets, from which nontrivial π Berry phase and Zeeman splitting were extracted. Our ultra-low penetration depth measurements on half-Heuslers YPdBi and TbPdBi revealed a power- law behavior with n= 2.76 ± 0.04 for YPdBi samples and n=2.6 ± 0.3 for TbPdBi sample. We may conclude the exponent n > 2 implies nodless superconducting gap in our samples. Also, we found that despite the increase in magnetic correlations from YPdBi to TbPdBi, superconductivity remains robust in both systems which indicates that AF fluctuations do not play a major role in superconducting mechanism.

By allowing to measure the magnetic field distribution inside a material, muon spin rotation experiments have the potential to provide valuable information about microscopic properties of high-temperature superconductors. Nevertheless, information about the intrinsic superconducting properties of the material is masked by random thermal and static fluctuations of the magnetic field which penetrates the material in the form of vortices of quantized magnetic flux. A good understanding of the fluctuations of those vortices is needed for the correct determination of intrinsic properties, notably the coherence length &xi;, and the field penetration depth &lambda;. We develop a simulation based on the Metropolis algorithm in order to understand the effect, on the magnetic field distribution, of disorder- and thermally-induced fluctuations of the vortex lattice inside a layered superconductor. <br /><br /> Our model correctly predicts the melting temperatures of the YBa₂Cu₃O_{6. 95} (YBCO) superconductor but largely underestimates the observed entropy jump. Also we failed to simulate the high field disordered phase, possibly because of a finite size limitation. In addition, we found our model unable to describe the first-order transition observed in the highly anisotropic Bi₂Sr₂CaCu₂O_8+<em>y</em>. <br /><br /> Our model predicts that for YBCO, the effect of thermal fluctuations on the field distribution is indistinguishable from a change in &xi;. It also confirms the usual assumption that the effect of static fluctuations at low temperature can be efficiently modeled by convolution of the field distribution with a Gaussian function. However the extraction of &xi; at low fields requires a very high resolution of the field distribution because of the low vortex density.