| 1. |
- Andersson, Tommy, 1970-, et al.
(författare)
-
Gender-related differences in risk of cardiovascular morbidity and all-cause mortality in patients hospitalized with incident atrial fibrillation without concomitant diseases: A nationwide cohort study of 9519 patients
- 2014
-
Ingår i: International Journal of Cardiology. - : Elsevier BV. - 0167-5273 .- 1874-1754. ; 177:1, s. 91-99
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Previous studies of patients with "lone" and "idiopathic" atrial fibrillation (AF) have provided conflicting evidence concerning the development, management and prognosis of this condition. Methods: In this nation-wide, retrospective, cohort study, we studied patients diagnosed with incidental AF recorded in national Swedish registries between 1995 and 2008. Controls were matched for age, sex and calendar year of the diagnosis of AF in patients. All subjects were free of any in-hospital diagnosis from 1987 and until patients were diagnosed with AF and also free of any diagnosis within one year from the time of inclusion. Follow-up continued until 2009. We identified 9519 patients (31% women) and 12,468 matched controls. Results: Relative risks (RR) versus controls for stroke or transient ischemic attack (TIA) in women were 19.6, 4.4, 3.4 and 2.5 in the age categories <55, 55-64, 65-74 and 75-85, years respectively. Corresponding figures for men were 3.4, 2.5, 1.7 and 1.9. RR for heart failure were 6.6, 6.6, 6.3 and 3.8 in women and 7.8, 4.6, 4.9 and 2.9 in men. All RR were statistically significant with p < 0.01. RR for myocardial infarction and all-cause mortality were statistically significantly increased only in the two oldest age categories in women and 65-74 years in men. Conclusions: Patients with AF and no co-morbidities at inclusion had at least a doubled risk of stroke or TIA and a tripled risk of heart failure, through all age categories, as compared to controls. Women were at higher RR of stroke or TIA than men. (C) 2014 The Authors. Published by Elsevier Ireland Ltd. This is an open access article under the CC BY-NC-SA license (http://creativecommons.org/licenses/by-nc-sa/3.0/).
|
|
| 2. |
- Andersson, Tommy, 1970-, et al.
(författare)
-
Patients with atrial fibrillation and outcomes of cerebral infarction in those with treatment of warfarin versus no warfarin with references to CHA(2)DS(2)-VASc score, age and sex - A Swedish nationwide observational study with 48 433 patients
- 2017
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:5
-
Tidskriftsartikel (refereegranskat)abstract
- Aims There is controversy in the guidelines as to whether patients with atrial fibrillation and a low risk of stroke should be treated with anticoagulation, especially those with a CHA(2)DS(2)-VASc score of 1 point. In a retrospective, nationwide cohort study, we used the Swedish National Patient Registry, the National Prescribed Drugs Registry, the Swedish Registry of Education and the Population and Housing Census Registry. 48 433 patients were identified between 1 January 2006 and 31 December 2008 with incident atrial fibrillation who were divided in age categories, sex and a CHA(2)DS(2)-VASc score of 0, 1, 2 and >= 3 and they were included in a time-varying analysis of warfarin treatment versus no treatment. The primary end-point was cerebral infarction and stroke, and patients were followed until 31 December 2009. Patients with 1 point from the CHA(2)DS(2)-VASc score showed the following adjusted hazard ratios (HR) with a 95% confidence interval: men 65-74 years 0.46 (0.25-0.83), men < 65 years 1.11 (0.56-2.23) and women < 65 years 2.13 (0.94-4.82), where HR < 1 indicates protection with warfarin. In patients < 65 years and 2 points, HR in men was 0.35 (0.18-0.69) and in women 1.84 (0.86-3.94) while, in women with at least 3 points, HR was 0.31 (0.16-0.59). In patients 65-74 years and 2 points, HR in men was 0.37 (0.23-0.59) and in women 0.39 ( 0.21-0.73). Categories including age >= 65 years or >= 3 points showed a statistically significant protection from warfarin. Our results support that treatment with anticoagulation may be considered in all patients with an incident atrial fibrillation diagnosis and an age of 65 years and older, i.e. also when the CHA(2)DS(2)-VASc score is 1.
|
|
| 3. |
- Aula, M., et al.
(författare)
-
Arc plasma emerging from foaming slag - Plasma diagnostics and visual observations
- 2018
-
Ingår i: ICS 2018 - 7th International Congress on Science and Technology of Steelmaking. - : Associazione Italiana di Metallurgia.
-
Konferensbidrag (refereegranskat)abstract
- Slag is foamed in electric arc furnace during steelmaking to reduce the amount of energy emitted to the furnace walls. The behavior of the electric arc plasma during slag foaming is not very well understood, since it is very hard to obtain empirical data about arc plasma from industrial furnaces. In this work the effect of foaming on the arc plasma is studied by generating electric arc plasma over a foaming slag in laboratory scale. The arc was generated on top of the slag with a system modified from a welding power supply and the foaming of slag was induced by blowing oxygen gas into the slag. The electric arcs were monitored with two cameras filtered to measure different wavelengths and three spectrometers measuring different spectral regions with varying spectral resolution. The first camera was able to detect only the light emitted directly from the arc plasma while the second can detect the high temperature slag surrounding the submerged arc. By comparing the two images, it was possible to differentiate between arc burning inside the foaming slag and free burning arc. The use of plasma diagnostics with optical emission spectrometry provided information about electron temperature and density of the arc plasma. The plasma diagnostics and camera pixel intensities indicate that the arc burning inside foaming slag is constricted and has high plasma temperature. Comparing the free-burning arc on top of the foaming slag and non-foaming slag show that the CO bubbles cause the plasma temperature to fluctuate significantly.
|
|
| 4. |
- Bölke, Kristofer, et al.
(författare)
-
Experimental Determinations of Mixing Times in the IronArc Pilot Plant Process
- 2019
-
Ingår i: Metals. - : MDPI. - 2075-4701. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- IronArc is a newly developed technology and an emerging future process for pig iron production. The long-term goal with this technology is to reduce the CO2 emissions and energy consumption compared to existing technologies. The production rate of this process is dependent on the stirring, which was investigated in the pilot plant process by measuring the mixing time in the slag bath. Moreover, slag investigations were done both based on light optical microscope studies as well as by Thermo-Calc calculations in order to determine the phases of the slag during operation. This was done because the viscosity (which is another important parameter) is dependent on the liquid and solid fractions of the slag. The overall results show that it was possible to determine the mixing time by means of the addition of a tracer (MnO2 powder) to the slag. The mixing time for the trials showed that the slag was homogenized after seconds. For two of the trials, homogenization had already been reached in the second sample after tracer addition, which means <= 8 s. The phase analysis from the slag indicated that the slag is in a liquid state during the operation of the process.
|
|
| 5. |
- Frisk, Robin, et al.
(författare)
-
Cast Structure in Alloy A286, an Iron-Nickel Based Superalloy
- 2019
-
Ingår i: Metals. - : MDPI. - 2075-4701. ; 9:6
-
Tidskriftsartikel (refereegranskat)abstract
- The structure and segregation of a continuously cast iron-nickel based superalloy were investigated. Cross-sectional samples were prepared from the central section of a 150 x 150 mm square billet. The microporosity was measured from the surface to the center and theoretical conditions for pore formation were investigated. A central porosity, up to 10 mm in width, was present in the center of the billet. The measured secondary arm spacing was correlated with a calculated cooling rate and a mathematical model was obtained. Spinel particles were found in the structure, which acted as inoculation points for primary austenite and promoted the formation of the central equiaxed zone. Titanium segregated severely in the interdendritic areas and an increase of Ti most likely lead to a significant decrease in the hot ductility. Precipitates were detected in an area fraction of approximately 0.55% across the billet, which were identified as Ti(CN), TiN, eta -Ni3Ti, and a phosphide phase.
|
|
| 6. |
- Gauffin, Alicia, et al.
(författare)
-
The Global Societal Steel Scrap Reserves and Amounts of Losses
- 2016
-
Ingår i: Resources. - : MDPI AG. - 2079-9276. ; 5:3
-
Tidskriftsartikel (refereegranskat)abstract
- In this study a newly developed method called the Progressing and Backcasting models were used to evaluate the annual resource utilizations of steel scrap in Sweden and globally. The model results show that it is possible to assess the amounts of steel scrap available for steelmaking at a given point in time, based on statistical dynamic material flow models. By a better mapping of the available amounts of steel scrap reserves on a country basis, it is possible to ease the trade of scrap across country boarders. This in turn can optimize the supply of recyclable metals as a raw material used in the industry. The results for Swedish steel consumption show that export bans used to secure the domestic market of steel scrap do damage the internal market due to increased amounts of losses. This suggests that export bans should be lifted to optimize recycling in countries. The model results also show that the global losses of steel are higher than for an industrialized country such as Sweden. Furthermore, the results show that the Backcasting and Progressing models can be used to calculate robust forecasts on the long term availability of steel scrap assets. This information could be used for future structural plans of scrap consuming steelmaking mills and waste management facilities. Hence, it is possible to contribute to a sustainable industrial development and a circular economy.
|
|
| 7. |
- Ghadamgahi, Mersedeh, et al.
(författare)
-
Numerical Study on the Effect of Lambda Value (Oxygen/Fuel Ratio) on Temperature Distribution and Efficiency of a Flameless Oxyfuel Combustion System
- 2017
-
Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 10:3
-
Tidskriftsartikel (refereegranskat)abstract
- The flameless oxyfuel combustion technology has been proven to be a promising new method to reduce the fuel consumption and pollutants in industrial applications. Although this technology is widely used in industrial furnaces, a lack of understanding exists about the effect of the controlling parameters on the final operational conditions is tangible. In this study, a validated computational fluid dynamics (CFD) model is used to simulate six cases of flameless oxyfuel combustion burners with different lambda values (ratio of oxygen/fuel mass flow rates). The CFD model uses the steady laminar flamelet model (SLFM) to solve the probability density function (PDF) for combustion, the discreet ordinates (DO) radiation model with the weighted sum of the gray gases model (WSGGM) to solve radiation, and the realizable k-epsilon to model the turbulence. It is seen that an increased oxygen injection velocity due to an increased lambda value increases the exhaust losses, but produces a larger volumetric flame. This leads to a more uniform temperature distribution. The total temperature difference in a case with a value of 1.02 is reported to be 272 (14.9%), while the amount for a case with a value of 1.2 is 67 (4.7%). This effect is further explained by introducing a new definition value for the furnace efficiency that includes both the thermal and production losses.
|
|
| 8. |
- Liu, Yu, et al.
(författare)
-
Decarburization in an Electric Arc Furnace using Coupled Fluid dynamics and Thermodynamics
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A coupled method of Fluid dynamics and Thermodynamics, named as Multi-zone Reaction Model, was established to simulate the flow pattern with bottom oxygen injection in a 145t electric arc furnace. The simulated maximum hot spot temperature and decarburization rate in the refining phase were compared against the data measured in the industrial operation. Moreover, the physical modeling was carried out to study the effect of nozzle size on the flow characteristics in the reaction zone. The results show, under high flow rates, the effect of nozzle size on the flow field in the reaction zone of the plume area can be neglected. The decarburization rate and hot spot temperature predicted by the modeling are consistent with the industrial measurements. The maximum hot spot temperature gradually decreases during the refining phase. The oxygen flow rate has a significant influence on the decarburization rate, hot spot temperature and average steel temperature. In terms of combined injection of O2 and inert argon gas, for a certain O2 flow rate, the decarburization rate increases due to the efficient mass transfer of carbon in the molten steel. Furthermore, for the replacement of argon using CO2, it is demonstrated that as the ratio of CO2 mass fraction increases from 0% to 40%, the maximum hot spot temperature decrease with the value of 570K, and the increment rate of average steel temperature, and the decarburization rate in the molten steel decrease with the ratio of 68%, and 81%, respectively. The endothermic reaction of CO2 with the molten steel results in a temperature drop in the plume above the hot spot zone.
|
|
| 9. |
- Pirouznia, Pouyan, et al.
(författare)
-
An investigation of the temperature distribution of a thin steel strip during the quenching step of a hardening process
- 2019
-
Ingår i: Metals. - : MDPI. - 2075-4701. ; 9:6, s. 1-14
-
Tidskriftsartikel (refereegranskat)abstract
- The dimension quality of the strip within the hardening process is an essential parameter, which great attention needs to be paid. The flatness of the final product is influenced by the temperature distribution of the strip, specifically across the width direction. Therefore, based on physical theories, a numerical model was established. The temperature of the strip for the section before the martensitic transformation was objected in the predicted model by using a steady state approach. In addition an infrared thermal imaging camera was applied in the real process in order to validate the results and to improve the boundary conditions of the numerical model. The results revealed that the temperature of strip decreased up to 250 degrees C within the area between the furnace and the quenching bath. This, in turn, resulted in significant temperature difference across the width of the strip. This difference can be up to 69 degrees C and 41 degrees C according to the numerical results and thermal imaging data, respectively. Overall, this study gave a better insight into the cooling step in the hardening process. In addition, this investigation can be used to improve the hardening process as well as an input for future thermal stress investigations.
|
|
| 10. |
- Pirouznia, Pouyan, et al.
(författare)
-
The Impact of the Gas Inlet Position, Flow Rate, and Strip Velocity on the Temperature Distribution of a Stainless-Steel Strips during the Hardening Process
- 2019
-
Ingår i: Metals. - : MDPI. - 2075-4701. ; 9:9
-
Tidskriftsartikel (refereegranskat)abstract
- A non-uniform temperature across the width of martensitic stainless-steel strips is considered to be one of the main reasons why the strip exhibits un-flatness defects during the hardening process. Therefore, the effect of the gas inlet position in this process, on the temperature distribution of the steel strip was investigated numerically. Furthermore, an infrared thermal imaging camera was used to compare the model predictions and the actual process data. The results showed that the temperature difference across the width of the strip decreased by 9% and 14% relative to the calculated temperature and measured values, respectively, when the gas inlet position was changed. This temperature investigation was performed at a position about 63 mm from the bath interface. Moreover, a more symmetrical temperature distribution was observed across the width of the strip. In addition, this study showed that by increasing the amount of the hydrogen flow rate by 2 Nm(3)/h, a 20% reduction of temperature difference across the width of strip was predicted. Meanwhile, the results show that the effect of the strip velocity on the strip temperature is very small.
|
|
| 11. |
- Schmidt, Christoffer, et al.
(författare)
-
Estimation of the molten state of scrap in an electric arc furnace by vibration measurements
- 2015
-
Ingår i: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015. - : Chinese Society for Metals. ; , s. 279-282
-
Konferensbidrag (refereegranskat)abstract
- Knowing molten state of the scrap in the electric arc furnace is very important for process control. Because of the harsh environment of the furnace new measurement techniques must be developed to measure the molten state. This paper looks at vibrations emitted from the furnace with the use of accelerometers, looking for correlations with the molten state. It was found that 87% of the heats have increasing vibrations with the respect to time. Also, 47% of the heats have a coefficient of determination (R2) of more than 0.5 between vibrations and time. Further evaluation must be conducted to see if this can be related to the scrap content in the furnace.
|
|
| 12. |
- Schmidt, Christoffer, et al.
(författare)
-
Measurement techniques for meltdown control in a stainless steel AC electric arc furnace
- 2017
-
Ingår i: ESSC and DUPLEX 2017 - 9th European Stainless Steel Conference - Science and Market and 5th European Duplex Stainless Steel Conference and Exhibition. - : Associazione Italiana di Metallurgia. - 9788898990122
-
Konferensbidrag (refereegranskat)abstract
- A method for vibrational evaluations of spectrogram data from pilot plant measurements was established for obtaining a consistent analysis of the molten scrap state. Not knowing the meltdown progress inside the furnace results in an inefficient power scheduling, which affects refractory life, process time and energy losses. Hence, there exists potential to control the furnace power so that it is kept high while there is sufficient amounts of scrap inside furnace to absorb the input energy. Thus, harmonic distortions of the electric current and measurements of the sound and vibrations emitted from the furnace were correlated to the molten state of the scrap. By using this method, a reduction in melting time in the order of minutes per heat can be obtained. The method was found to give stable signals and it was judged to be a good candidate for implementation in industry. Furthermore, the developed method is universal and may be applied for other types of signals and combined into intelligent soft sensor systems.
|
|
| 13. |
- Ternstedt, Patrik, 1979-, et al.
(författare)
-
Methods to Determine Characteristics of AOD-Converter Decarburization-Slags
- 2020
-
Ingår i: Metals. - : MDPI. - 2075-4701. ; 10:3
-
Tidskriftsartikel (refereegranskat)abstract
- Argon Oxygen Decarburization (AOD) converter slags are known to consist of both liquid and solid phases, but limited information on the slag characteristics has been published in the open literature. Therefore, a new methodology to study the characteristics of slag samples taken from the AOD converter process during production was developed based on petrography. The results show that the preparations of the slag samples using the borax method are suitable to use when determining the chemical composition of AOD slag samples using the X-ray fluorescence (XRF) method. The results also showed that both the light optical microscopy (LOM) method and a method combining scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) can be used to characterize the slag samples and that the correlation between the methods was found to be good. This means that it is possible to use the faster LOM method instead of the more complicated SEM-EDS method to characterize AOD slag samples. Finally, the results show that the difference between calculated values based on stoichiometry and measured data for Ca and Cr in AOD slags are 11.7 mass% and 11.3 mass%, respectively. This is considered to be a good agreement for industrial samples.
|
|
| 14. |
- Yin, Jun, et al.
(författare)
-
Experimental and Numerical Study of the Gas Entrainment During the Initial Mold Filling in an Uphill Teeming Ingot Casting Process
- 2021
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The gas entrainment can influence surface disturbances during the filling in the uphill ingot teeming process. Surface disturbances can result in mold flux entrapments, leading to the generation of non-metallic inclusions which are detrimental to the final steel quality. A three-dimension simulation was conducted to study the gas entrainment during the filling process. Furthermore, a water model experiment was also carried out to validate the results from the numerical simulations. The results showed a good agreement between the numerical and physical models. Moreover, the formation of a big bubble can be observed at the bend between the trumpet and the horizontal runner, and between the horizontal runner and the vertical runner. The sizes of the big bubble fluctuate during the teeming process. The current study gives a specific overview of the gas entrainment phenomenon during the initial filling of the uphill teeming process.
|
|
| 15. |
- Yin, Jun, et al.
(författare)
-
Numerical study on the influence of the filling angle on the fluid flow during the ingot side teeming process
- 2021
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 92:10
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- High turbulence at the liquid steel-mold flux interface can result in mold flux entrapments, which can generate non-metallic inclusions during the ingot casting process. Those non-metallic inclusions are detrimental to the final steel quality. The teeming process during ingot casting is typically carried out using the uphill teeming method. The authors propose a novel alternative method using a side teeming process, which decreases turbulence at the free surface. In order to define the optimum operational conditions, a 3-D mathematical model was developed to investigate the effect of the filling angle on the motion of the free surface and the resulting shear stresses during the teeming process. The investigated filling angles were: 0, 30, 45, 60 and 90 degrees. The present findings suggest that using the filling angle of 90 degrees between the mold and the runner would be an effective way of reducing the number of inclusions due to mold flux entrapments and refractory wear.
|
|
