| 1. |
- Akhtar, Sultan, et al.
(author)
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Real-Space Transmission Electron Microscopy Investigations of Attachment of Functionalized Magnetic Nanoparticles to DNA-Coils Acting as a Biosensor
- 2010
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In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 114:41, s. 13255-13262
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Journal article (peer-reviewed)abstract
- The present work provides the first real-space analysis of nanobead-DNA coil interactions. Immobilization of oligonucleotide-functionalized magnetic nanobeads in rolling circle amplified DNA-coils was studied by complex magnetization measurements and transmission electron microscopy (TEM), and a statistical analysis of the number of beads hybridized to the DNA-coils was performed. The average number of beads per DNAcoil using the results from both methods was found to be around 6 and slightly above 2 for samples with 40 and 130 nm beads, respectively. The TEM analysis supported an earlier hypothesis that 40 nm beads are preferably immobilized in the interior of DNA-coils whereas 130 nm beads, to a larger extent, are immobilized closer to the exterior of the coils. The methodology demonstrated in the present work should open up new possibilities for characterization of interactions of a large variety of functionalized nanoparticles with macromolecules, useful for gaining more fundamental understanding of such interactions as well as for optimizing a number of biosensor applications.
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| 2. |
- Almqvist, Bjarne, et al.
(author)
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Magnetic characterisation of magnetite and hematite from the Blötberget apatite-iron-oxide deposits (Bergslagen), south-central Sweden
- 2019
-
In: Canadian journal of earth sciences (Print). - : Canadian Science Publishing. - 0008-4077 .- 1480-3313. ; 56:9, s. 948-957
-
Journal article (peer-reviewed)abstract
- Rock magnetic measurements were carried out on drill core material and hand specimens from the Blötberget apatite-iron oxide deposit in the Bergslagen ore province, south-central Sweden, to characterise their magnetic properties. Measurements included several kinds of magnetic susceptibility and hysteresis parameters. Petrographic and scanning electron microscopy (SEM) were used to independently identify and quantify the amount and type of magnetite and hematite. Two hematite-rich samples were studied with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to quantify the trace element chemistry in hematite and investigate the potential influence of trace elements on magnetic properties. Three aspects of this study are noteworthy. 1) Hematite-rich samples display strong anisotropy of magnetic susceptibility, which is likely to affect the appearance and modelling of magnetic anomalies. 2) The magnitude-drop in susceptibility across Curie and Néel temperature transitions show significant correlation with the respective weight percent (wt%) of magnetite and hematite. Temperature dependent magnetic susceptibility measurements can therefore be used to infer the amounts of both magnetite and hematite. 3) observations of a strongly depressed Morin transition at ca -60 to -70 C (200 to 210 K) are made during low-temperature susceptibility measurements. This anomalous Morin transition is most likely related to trace amounts of V and Ti that substitute for Fe in the hematite. When taken together, these magnetic observations improve the understanding of the magnetic anomaly signature of the Blötberget apatite-iron oxide deposits and may potentially be utilised in a broader context when assessing similar (Paleoproterozoic) apatite-iron oxide systems.
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| 3. |
- Andersson, Klas, 1977, et al.
(author)
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3D-Modelling of the Radiative Heat Transfer in Rotary Kilns with a Present Bed Material
- 2018
-
Conference paper (other academic/artistic)abstract
- This work presents a 3D-model of the radiative heat transfer in cylindrical furnaces with a present bed material. Experimental data gathered in a down-scaled version of a rotary kiln has been used as input data to the model analysis. In future work, the model is to be used to study full-scale rotary kilns used in different industries such as the iron ore industry, heating and sintering iron ore pellets.
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| 4. |
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| 5. |
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| 6. |
- Bejhed Stjernberg, Rebecca, et al.
(author)
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Magnetophoretic Transport Line System for Rapid On-Chip Attomole Protein Detection
- 2015
-
In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 31:37, s. 10296-10302
-
Journal article (peer-reviewed)abstract
- A lab-on-a-chip traveling wave magnetophoresis approach for sensitive and rapid protein detection is reported. In this method, a chip-based magnetic microarray comprising lines of micrometer-sized thin film magnetic elements was used to control the movement of magnetic beads (MBs). The MBs and the chip were functionalized, forming a sandwich-type assay. The MBs were transported across a detection area, and the presence of target molecules resulted in the immobilization of MBs within this area. Target quantification was accomplished by MB counting in the detection area using an optical microscope. In order to demonstrate the versatility of the microarray, biotinylated antiavidin was selected as the target protein. In this case, avidin-functionalized MBs and an avidin-functionalized detection area were used. With a total assay time of 1 to 1.5 h (depending on the labeling approach used), a limit of detection in the attomole range was achieved. Compared to on-chip surface plasmon resonance biodetection systems, our method has a larger dynamic range and is about a factor of 500 times more sensitive. Furthermore, our MB transportation system can operate in any chip-based biosensor platform, thereby significantly improving traditional biosensors.
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| 7. |
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| 8. |
- Bonaglia, Stefano, et al.
(author)
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Activated carbon stimulates microbial diversity and PAH biodegradation under anaerobic conditions in oil-polluted sediments
- 2020
-
In: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 248
-
Journal article (peer-reviewed)abstract
- Biodegradation by microorganisms is a useful tool that helps alleviating hydrocarbon pollution in nature. Microbes are more efficient in degradation under aerobic than anaerobic conditions, but the majority of sediment by volume is generally anoxic. Incubation experiments were conducted to study the biodegradation potential of naphthalene-a common polycyclic aromatic hydrocarbon (PAH)-and the diversity of microbial communities in presence/absence of activated carbon (AC) under aerobic/anaerobic conditions. Radio-respirometry experiments with endogenous microorganisms indicated that degradation of naphthalene was strongly stimulated (96%) by the AC addition under anaerobic conditions. In aerobic conditions, however, AC had no effects on naphthalene biodegradation. Bioaugmentation tests with cultured microbial populations grown on naphthalene showed that AC further stimulated (92%) naphthalene degradation in anoxia. Analysis of the 16S rRNA gene sequences implied that sediment amendment with AC increased microbial community diversity and changed community structure. Moreover, the relative abundance of Geobacter, Thiobacillus, Sulfuricurvum, and methanogenic archaea increased sharply after amendment with AC under anaerobic conditions. These results may be explained by the fact that AC particles promoted direct interspecies electron transfer (DIET) between microorganisms involved in PAH degradation pathways. We suggest that important ecosystem functions mediated by microbes-such as hydrocarbon degradation-can be induced and that AC enrichment strategies can be exploited for facilitating bioremediation of anoxic oil-contaminated sediments and soils.
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| 9. |
- Bäckström, Daniel, 1985, et al.
(author)
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Measurement of the size distribution, volume fraction and optical properties of soot in an 80 kW propane flame
- 2017
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In: Combustion and Flame. - : Elsevier BV. - 0010-2180 .- 1556-2921. ; 186, s. 325-334
-
Journal article (peer-reviewed)abstract
- This work presents measurements of the size distribution, volume fraction, absorption and scattering coefficients of soot in an 80 kW swirling propane-fired flame. Extractive measurements were performed in the flame using an oil-cooled particle extraction probe. The particle size distribution was measured with a Scanning Mobility Particle Sizer (SMPS) and the optical properties were measured using a Photo Acoustic Soot Spectrometer (PASS-3). A detailed radiation model was used to examine the influence of the soot volume fraction on the particle radiation intensity. The properties of the gas were calculated with a statistical narrow-band model and the particle properties were calculated using Rayleigh theory with four different complex indices of refraction for soot particles. The modelled radiation was compared with measured total radiative intensity, the latter which was measured with a narrow angle radiometer. The results show that the measured soot volume fraction yields particle radiation that corresponds well with the determined difference between gas and total radiation. This indicates that the presented methodology is capable of quantifying both the particle and gaseous radiation in a flame of technical size. (C) 2017 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 10. |
- Cedervall, Johan, et al.
(author)
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Influence of cobalt substitution on the magnetic properties of Fe5PB2
- 2018
-
In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 57:2, s. 777-784
-
Journal article (peer-reviewed)abstract
- In this study the effects of cobalt substitutions in Fe5PB2 have been studied. An increased cobalt content reduces the magnetic exchange interactions. This has been concluded from a large, linear decrease in both the Curie temperature as well as the saturated magnetic moment. At high cobalt concentrations, cobalt prefers to order at the M(2) position in the crystal structure. A tunable Curie transition like this shows some prerequisites for magnetic cooling applications.The substitutional effects of cobalt in (Fe1–xCox)5PB2 have been studied with respect to crystalline structure and chemical order with X-ray diffraction and Mössbauer spectroscopy. The magnetic properties have been determined from magnetic measurements, and density functional theory calculations have been performed for the magnetic properties of both the end compounds, as well as the chemically disordered intermediate compounds. The crystal structure of (Fe1–xCox)5PB2 is tetragonal (space group I4/mcm) with two different metal sites, with a preference for cobalt atoms in the M(2) position (4c) at higher cobalt contents. The substitution also affects the magnetic properties with a decrease of the Curie temperature (TC) with increasing cobalt content, from 622 to 152 K for Fe5PB2 and (Fe0.3Co0.7)5PB2, respectively. Thus, the Curie temperature is dependent on composition, and it is possible to tune TC to a temperature near room temperature, which is one prerequisite for magnetic cooling materials.
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| 11. |
- Cedervall, Johan, et al.
(author)
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Magnetostructural transition in Fe5SiB2 observed with neutron diffraction
- 2016
-
In: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 235, s. 113-118
-
Journal article (peer-reviewed)abstract
- The crystal and magnetic structure of Fe5SiB2 has been studied by a combination of X-ray and neutron diffraction. Also, the magnetocrystalline anisotropy energy constant has been estimated from magnetisation measurements. High quality samples have been prepared using high temperature synthesis and subsequent heat treatment protocols. The crystal structure is tetragonal within the space group I4/mcm and the compound behaves ferromagnetically with a Curie temperature of 760 K. At 172 K a spin reorientation occurs in the compound and the magnetic moments go from aligning along the c-axis (high T) down to the ab-plane (low T). The magnetocrystalline anisotropy energy constant has been estimated to 0.3 MJ/m3 at 300 K.
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| 12. |
- de la Torre, Teresa Zardan Gomez, et al.
(author)
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Molecular diagnostics using magnetic nanobeads
- 2010
-
In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6596.
-
Conference paper (peer-reviewed)abstract
- In this paper, we investigate the volume-amplified magnetic nanobead detection assay with respect to bead size, bead concentration and bead oligonucleotide surface coverage in order to improve the understanding of the underlying microscopic mechanisms. It has been shown that: (i) the immobilization efficiency of the beads depends on the surface coverage of oligonucleotides, (ii) by using lower amounts of probe-tagged beads, detection sensitivity can be improved and (iii) using small enough beads enables both turn-off and turn-on detection. Finally, biplex detection was demonstrated.
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| 13. |
- Donolato, M, et al.
(author)
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Size-dependent effects in exchange-biased planar Hall effect sensor crosses
- 2011
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 109:6, s. 064511-
-
Journal article (peer-reviewed)abstract
- Exchange-biased planar Hall effect magnetic field sensor crosses with arm width w have been studied as function of w. For large values of w, the magnetic behavior is hysteresis-free and follows the single domain Stoner-Wohlfarth model. When w is decreased, hysteresis is observed in the sensor response. For intermediate values of w, the magnetization reversal takes place in two steps, and for small values of w, the magnetization reversal takes place in a single step. Based on electrical measurements, magnetic force microscopy, and micromagnetic simulations, the observations are explained by an increasing magnetic shape anisotropy of the arms of the cross. We propose a simple analytical model that captures the essential physics of the observations and parameterizes the effects of the cross-shape on the central part of the cross.
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| 14. |
- Draper, Teri, et al.
(author)
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A comparison of industrial-scale (471 MWe) radiometer heat flux measurements between pulverized-coal and 85% coal/15% biomass co-firing combustion
- 2021
-
Conference paper (other academic/artistic)abstract
- This work evaluates and compares radiative heat transfer measurements conducted at the 471 MWe Hunter Powerplant Unit 3 utility boiler in Utah, USA, during commercial operation with coal and during tests with co-firing of coal and biomass. The coal used was a Utah sourced bituminous coal, which was mixed with 15 wt% of torrefied wood in the co-firing test. The measurements were gathered using two different narrow angle radiometers and one ellipsoidal radiometer to measure the radiative heat flux. Data were gathered at several floors through port openings in the boiler wall and the samplings were spread out over several hours. Additionally, the gas temperature was measured at positions close to the inner walls of the different floors. Overall, the measured heat fluxes decreased with increasing boiler floor level, and while the measurement data spread is rather high for each measurement, the data spreads for both fuel conditions significantly overlap each other, indicating that it is likely the heat flux profile remains unchanged when running either type of fuel.
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| 15. |
- Ehlmé, Elias, 1998, et al.
(author)
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Heat Transfer Conditions in Hydrogen-Fired Rotary Kilns for Iron Ore Processing
- 2023
-
In: Industrial & Engineering Chemistry Research. - 1520-5045 .- 0888-5885. ; 62:37, s. 15098-15108
-
Journal article (peer-reviewed)abstract
- This work analyzes the heat transfer conditions in a rotary kiln used for the heat treatment of iron ore pellets in the grate-kiln process. The analysis concerns conditions relevant to fuel switching from coal to hydrogen gas. A modeling assessment of the radiative heat transfer in the kiln is conducted including the pellet bed and inner kiln wall temperature conditions. The results show that the heat transfer rate to the iron ore pellets under conditions of a pure hydrogen flame is comparable to the conditions relevant to coal firing. However, it is higher at the kiln wall surfaces near the burner region and lower in the remaining parts of the kiln. Increasing the particle concentration in the hydrogen flame represents a practical implication of co-firing coal with hydrogen. By adding particles, the emittance of radiation from the flame is significantly influenced, leading to further increased kiln surface temperatures closer to the burner position. Increased flame length also showed enhanced heat transfer rates to the kiln wall, although further away from the burner region.
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| 16. |
- Eriksson, Klas, 1983, et al.
(author)
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Design and Characterization of H-Band (220-325 GHz) Amplifiers in a 250-nm InP DHBT Technology
- 2014
-
In: IEEE Transactions on Terahertz Science and Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 2156-342X .- 2156-3446. ; 4:1, s. 56-64
-
Journal article (peer-reviewed)abstract
- Design and characterization of InP DHBT amplifiers in common-emitter and common-base topologies are presented. Both one-stage and multistage circuits are demonstrated. For one of the amplifiers, a peak gain of 24 dB at 255 GHz is measured, which is among the highest reported gains for HBT amplifiers above 200 GHz, and more than 10 dB gain at 210-315 GHz. The noise figure of this amplifier is measured on-wafer at 240-295 GHz, and it demonstrates a minimum noise figure of 10.4 dB at 265 GHz, which is the lowest reported noise figure for HBT amplifiers above 200 GHz.
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| 17. |
- Eriksson, Klas, 1983, et al.
(author)
-
InP DHBT Amplifier Modules Operating Between 150 and 300 GHz Using Membrane Technology
- 2015
-
In: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 63:2, s. 433-440
-
Journal article (peer-reviewed)abstract
- In this paper, we present WR05 (140-220 GHz) and WR03 (220-325 GHz) five-stage amplifier modules with novel membrane microstrip-to-waveguide transitions. The modules use a 250-nm InP double heterojunction bipolar transistor (DHBT) technology and multilayer thin-film microstrip transmission lines. The waveguide transitions use E-plane probes on 3- μm-thin GaAs membrane substrate. Beam lead connectors integrated on the transition eliminate the need of highly reactive bond wires. In addition, process steps such as backside metallization, backside vias, and nonrectangular dicing of the integrated circuits (ICs) are not required. The WR05 amplifier module demonstrates a peak gain of 24 dB at 245 GHz and more than 10-dB gain from 155 to 270 GHz. The WR-03 module has 19-dB gain from 230 to 254 GHz with input and output return loss better than 10 dB from 225 to 330 GHz. The two modules were also characterized in terms of noise. The minimum noise figures were measured to 9.7 dB at 195 GHz and 10.8 dB at 240 GHz for the WR05 and WR03 modules, respectively. To the authors' best knowledge, these are the first published results on an InP DHBT amplifier modules operating at these high frequencies. It is also the first time that membrane technology is used for IC packaging, regardless of IC technology.
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| 18. |
- Eriksson, Klas, 1983, et al.
(author)
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Suppression of Parasitic Substrate Modes in Multilayer Integrated Circuits
- 2015
-
In: IEEE Transactions on Electromagnetic Compatibility. - 0018-9375 .- 1558-187X. ; 57:3, s. 591-594
-
Journal article (peer-reviewed)abstract
- Integrated circuits (ICs) with multilayer backend process and a large front-side ground plane support the propagation of parasitic substrate modes. These modes resonate at frequencies that typically are within the bandwidth of circuits operating close to and in the submillimeter-wave range, i.e., beyond 300 GHz. The resonances cause unwanted coupling and feedback, which result in circuit instability and degraded performance for circuits operating in the range of these resonances. A common method to suppress these modes from propagating is to use numerous through-wafer vias distributed over the entire circuit. In this letter, we present a study of substrate modes in multilayer ICs with thin-film microstrip interconnects at 125-330 GHz. We show that a doped Si carrier underneath the circuit effectively eliminates the effect of substrate modes on the circuit functionality. This method requires no backside processed through-wafer vias and no backside metallization.
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| 19. |
- Fang, Hailiang, et al.
(author)
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Directly obtained tau-phase MnAl, a high performance magnetic material for permanent magnets
- 2016
-
In: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 237, s. 300-306
-
Journal article (peer-reviewed)abstract
- The metastable tetragonal iota-phase has been directly obtained from casting Mn0.54Al0.46 and (Mn0.55Al0.45)(100)C-2 using the drop synthesis method. The as-casted samples were ball milled to decrease the particle size and relaxed at 500 degrees C for 1 h. The phase composition, crystallographic parameters, magnetic properties and microstructure were systematically studied. The results reveal that the iota-phase could be directly obtained from drop synthesis. The highest M-s of 117 emu/g was achieved in the (Mn0.55Al0.45)(100)C-2 where the iota-phase was stabilized by doping with carbon. Carbon doping increased the c/a ratio of the tau-phase as it occupies specific interstitial positions (1/2, 1/2, 0) in the structure. Furthermore, ball milling increases the coercivity (H-c) at the expense of a decrease in magnetic saturation (M-s). The increase in coercivity is explained by a decrease of grain size in conjunction with domain wall pinning due to defects introduced during the ball milling process.
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| 20. |
- Fang, Hailiang, et al.
(author)
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Insights into phase transitions and magnetism of MnBi crystals synthesized from self-flux
- 2019
-
In: Journal of Alloys and Compounds. - : ELSEVIER SCIENCE SA. - 0925-8388 .- 1873-4669. ; 781, s. 308-314
-
Journal article (peer-reviewed)abstract
- To effectively synthesize high purity ferromagnetic low temperature phase (LTP) MnBi with optimal microstructure is still a challenge that needs to be overcome for the system to reach its full potential. Here, the phase transitions and magnetic properties of MnBi crystals are reported. The phase transition between the low and high temperature structure of MnBi was systematically investigated at different heating/cooling rates using in situ synchrotron radiation X-ray diffraction. The material crystallizes in a layered hexagonal structure giving a platelike microstructure. The magnetic characterization of the crystals reveal that the saturation magnetization varies from 645 kA/m at 50 K to 546 kA/m at 300 K. Magnetization measurements also show that the sample upon heating becomes non-magnetic and transforms to the high temperature phase (HTP) at similar to 640 K, and that it regains ferromagnetic properties and transforms back to the LTP at similar to 610 K upon subsequent cooling.
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| 21. |
- Fang, Hailiang, et al.
(author)
-
Structural, microstructural and magnetic evolution in cryo milled carbon doped MnAl
- 2018
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
-
Journal article (peer-reviewed)abstract
- The low cost, rare earth free τ-phase of MnAl has high potential to partially replace bonded Nd2Fe14B rare earth permanent magnets. However, the τ-phase is metastable and it is experimentally difficult to obtain powders suitable for the permanent magnet alignment process, which requires the fine powders to have an appropriate microstructure and high τ-phase purity. In this work, a new method to make high purity τ-phase fne powders is presented. A high purity τ-phase Mn0.55Al0.45C0.02 alloy was synthesized by the drop synthesis method. The drop synthesized material was subjected to cryo milling and followed by a fash heating process. The crystal structure and microstructure of the drop synthesized, cryo milled and flash heated samples were studied by X-ray in situ powder diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy and electron backscatter diffraction. Magnetic properties and magnetic structure of the drop synthesized, cryo milled, flash heated samples were characterized by magnetometry and neutron powder diffraction, respectively. The results reveal that the 2 and 4hours cryo milled and flash heated samples both exhibit high τ-phase purity and micron-sized round particle shapes. Moreover, the fash heated samples display high saturation magnetization as well as increased coercivity.
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| 22. |
- Faure, B., et al.
(author)
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2D to 3D crossover of the magnetic properties in ordered arrays of iron oxide nanocrystals
- 2013
-
In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 5:3, s. 953-960
-
Journal article (peer-reviewed)abstract
- The magnetic 2D to 3D crossover behavior of well-ordered arrays of monodomain γ-Fe2O3 spherical nanoparticles with different thicknesses has been investigated by magnetometry and Monte Carlo (MC) simulations. Using the structural information of the arrays obtained from grazing incidence small-angle X-ray scattering and scanning electron microscopy together with the experimentally determined values for the saturation magnetization and magnetic anisotropy of the nanoparticles, we show that MC simulations can reproduce the thickness-dependent magnetic behavior. The magnetic dipolar particle interactions induce a ferromagnetic coupling that increases in strength with decreasing thickness of the array. The 2D to 3D transition in the magnetic properties is mainly driven by a change in the orientation of the magnetic vortex states with increasing thickness, becoming more isotropic as the thickness of the array increases. Magnetic anisotropy prevents long-range ferromagnetic order from being established at low temperature and the nanoparticle magnetic moments instead freeze along directions defined by the distribution of easy magnetization directions.
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| 23. |
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| 24. |
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| 25. |
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| 26. |
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| 27. |
- Gall, Dan, 1981, et al.
(author)
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Recirculation of NO x and SO x Scrubber Effluent to an Industrial Grate Fired MSW Boiler-Influence on Combustion Performance, Deposition Behavior, and Flue Gas Composition
- 2022
-
In: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 36:11, s. 5868-5877
-
Journal article (peer-reviewed)abstract
- The concept of scrubber effluent recirculation has recently received attention in connection to NOxemission control. Here, we present data from an industrial-scale MSW-fired plant, where effluent from a combined NOxand SOxscrubber was recirculated and injected into a grate-fired boiler. The combustion characteristics were carefully studied during the injections to observe the potential effects on burnout and flue gas composition. In addition, deposition measurements were performed to observe effects on growth rate and chemical composition of deposits, which are critical factors for any solid fuel-fired heat and power plant. The recirculation of the nitrogen-rich waste streams was performed via pre-existing liquid injection equipment, and the results show that the N-containing compounds in the scrubber effluent were efficaciously reduced to inert nitrogen gas. Furthermore, the recirculation of the scrubber effluent may reduce ammonia demand for selective non-catalytic reduction systems by inhibiting the formation of ammonium chloride. Sulfur and alkali components in the effluent increased the deposition growth rate and also changed the chemical composition of the deposits. Understanding how the local conditions at the injection point influence the distribution and speciation of the injected compounds is essential for a successful recirculation strategy.
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| 28. |
- Gavagnin, Marco, et al.
(author)
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Free-Standing Magnetic Nanopillars for 3D Nanomagnet Logic
- 2014
-
In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 6:22, s. 20254-20260
-
Journal article (peer-reviewed)abstract
- Nanomagnet logic (NML) is a relatively new computation technology that uses arrays of shape-controlled nanomagnets to enable digital processing. Currently, conventional resist-based lithographic processes limit the design of NML circuitry to planar nanostructures with homogeneous thicknesses. Here, we demonstrate the focused electron beam induced deposition of Fe-based nanomaterial for magnetic in-plane nanowires and out-of-plane nanopillars. Three-dimensional (3D) NML was achieved based on the magnetic coupling between nanowires and nanopillars in a 3D array. Additionally, the same Fe-based nanomaterial was used to produce tilt-corrected high-aspect-ratio probes for the accurate magnetic force microscopy (MFM) analysis of the fabricated 3D NML gate arrays. The interpretation of the MFM measurements was supported by magnetic simulations using the Object Oriented MicroMagnetic Framework. Introducing vertical out-of-plane nanopillars not only increases the packing density of 3D NML but also introduces an extra magnetic degree of freedom, offering a new approach to input/output and processing functionalities in nanomagnetic computing.
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| 29. |
- Gavagnin, Marco, et al.
(author)
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Magnetic force microscopy study of shape engineered FEBID iron nanostructures
- 2014
-
In: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 211:2, s. 368-374
-
Journal article (peer-reviewed)abstract
- The capability to control matter down to the nanoscale level in combination with the novel magnetic properties of nanomaterials have attracted increasing attention in the last few decades due to their applications in magnetic sensing, hard disc data storage and logic devices. Therefore, many efforts have been devoted to the implementation of both nanofabrication methods as well as characterization of magnetic nanoelements. In this study, Fe-based nanostructures have been synthesized on Si(100) by focused electron beam induced deposition (FEBID) utilizing iron pentacarbonyl as precursor. The so obtained nanostructures exhibit a remarkably high iron content (Fe>80at.%), expected to give rise to a ferromagnetic behaviour. For that reason, magnetic force microscopy (MFM) analyses were performed on the obtained FEBID Fe nanostructures. Moreover, object oriented micromagnetic framework (OOMMF) magnetic simulations have been executed to study the influence of the geometry on the magnetic properties of iron single-domain nanowires. FEBID is a mask-less nanofabrication method based on the injection of precursor gas molecules in proximity of the deposition area where their decomposition is locally induced by a focused electron beam.
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| 30. |
- Ghosh, Sourav, et al.
(author)
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Investigating the stable operating voltage for the MnFe2O4 Li-ion battery anode
- 2021
-
In: Sustainable Energy & Fuels. - : Royal Society of Chemistry. - 2398-4902. ; 5:6, s. 1904-1913
-
Journal article (peer-reviewed)abstract
- Template-free synthesis of MnFe2O4 nanopowder is carried out by co-precipitation in a basic medium, evaluating the effects of cation ratio and reaction temperature on the phase composition crystallinity of the resulting powder. Single-phase samples of the target spinel are obtained at the stoichiometric Mn : Fe = 1 : 2 ratio under reflux conditions (100 degrees C), as confirmed by X-ray diffraction (XRD) and Fourier Transformed Infrared (FTIR) spectroscopy. Transmission electron microscopy (TEM) images confirmed that nanostructured MnFe2O4 particles are obtained, which is further supported by Debye-Scherrer calculations from XRD data and by AFM measurements. The produced oxide demonstrated considerable thermal stability according to TGA data. Magnetic characteristics are strongly dependent on the content of magnetic phase and phase composition, achieving a maximum of 54 emu g(-1) for single-phase stoichiometric MnFe2O4. Further, the electrochemical stability of this material as the anode is investigated in Li-ion batteries (LIBs). When the MnFe2O4 electrode is operated in the potential window of 0.01-3.0 V, the reversible capacity is enhanced by almost 45% (802 mA h g(-1)) after the 100(th) cycle with reference to the 2(nd) cycle reversible capacity (548 mA h g(-1)). Methodically dQ/dV plots are analyzed and compared to understand processes behind the evolution of extra capacity beyond its theoretical limit. Further, the upper cut-off potential is tuned to identify a stable operating potential window for the MnFe2O4 anode in LIBs.
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| 31. |
- Gunnarsson, Adrian, 1990, et al.
(author)
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3D-modelling of the radiative heat transfer in a rotary kiln for iron ore pellets production
- 2015
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In: Nordic Flame Days, 2015.10.06-2015.10.07, Helsingör.
-
Conference paper (other academic/artistic)abstract
- This paper presents work focused on the development, evaluation and use of a 3D-model for investigation of the radiative heat transfer in rotary kilns. The model applies the discrete-ordinates method to solve the radiative transfer equation considering emission, absorption and scattering of radiation by gas species and particles. The model uses input of temperature, particle distribution and gas composition in the radial, axial and angular directions. The model is compared with literature data and a 1D-model for validation. The model is tested in its capability to model radiative intensity using experimental data from a 400 kW rotary kiln test furnace and used to calculate the radiative heat flux to the wall using different temperature and particle loads as well as different fuels and fuel combinations. The results show that the 3D-model can be used to predict trends when operating conditions are changed.
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| 32. |
- Gunnarsson, Adrian, 1990, et al.
(author)
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Discrete-Ordinates Modelling of the Radiative Heat Transfer in a Pilot-Scale Rotary Kiln
- 2020
-
In: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 13:9
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Journal article (peer-reviewed)abstract
- This paper presents work focused on the development, evaluation and use of a 3D model for investigation of the radiative heat transfer in rotary kilns. The model applies a discrete-ordinates method to solve the radiative transfer equation considering emission, absorption and scattering of radiation by gas species and particles for cylindrical and semi-cylindrical enclosures. Modelling input data on temperature, particle distribution and gas composition in the radial, axial and angular directions are experimentally gathered in a down-scaled version of a rotary kiln. The model is tested in its capability to predict the radiative intensity and heat flux to the inner wall of the furnace and good agreement was found when compared to measurements. Including the conductive heat transfer through the furnace wall, the model also satisfactorily predicts the intermediate wall temperature. The work also includes a first study on the effect of the incident radiative heat flux to the different surfaces while adding a cold bed material. With further development of the model, it can be used to study the heat transfer in full-scale rotary kilns.
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| 33. |
- Gunnarsson, Adrian, 1990, et al.
(author)
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Full-Scale 3D-Modelling of the Radiative Heat Transfer in Rotary Kilns with a Present Bed Material
- 2018
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Conference paper (other academic/artistic)abstract
- This work discusses the development and usage of a radiative heat transfer model in 3D of a rotary kiln with a present bed material. Using a discrete-ordinates method to solve the radiative heat transfer equation, radiative properties are calculated using a weighted-sum-of-grey-gases (WSGG) model for gases and Mie and Rayleigh theory for particles including fuel, ash and soot. Measurement data gathered from a pilot scale test furnace, comprising temperature, gas composition and particle concentration, is used to model a pilot-scale rotary kiln and satisfactory agreement to radiative heat flux measurement is shown. Combining measurements, from the same test furnace, with data gathered from an industrial full-scale rotary kiln used for iron ore pelletizing, a full-scale rotary kiln with a present bed material is modelled. Conductive heat transfer within, as well as between, the bed and wall material is included in the model and surface temperatures are calculated within the model. The model also includes heat losses from the outside wall of the rotary kiln due to radiation and convection and a simplified mixing model of the pellet bed. When compared to measurements for the inside and outside wall as well as the bed material, the model predicts the surface temperatures with errors less than 10%. The total heat transfer to the present bed material was also studied showing that more than 90% originated form the radiative heat transfer within the furnace.
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| 34. |
- Gunnarsson, Adrian, 1990, et al.
(author)
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Full-scale 3D-modelling of the radiative heat transfer in rotary kilns with a present bed material
- 2020
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In: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310. ; 147
-
Journal article (peer-reviewed)abstract
- This work discusses the development and use of a detailed 3D radiative heat transfer model of a rotary kiln with a present bed material, used for iron ore pelletizing. A discrete ordinates method is used to solve the radiative heat transfer equation with radiative properties calculated using a weighted-sum-of-grey-gases (WSGG) model for gases and Mie and Rayleigh theory for particles including fuel, ash and soot. Measurement data gathered from a pilot-scale test furnace, comprising temperature, gas composition and particle concentration, is used in combination with temperature data and operation parameters gathered from a conventional rotary kiln to model a full-scale rotary kiln with a present bed material. The modelled cases have a thermal input of about 37 MWth and in addition to radiative heat transfer, conductive heat transfer within, as well as between, the bed and wall material are included in the model along with convective heat transfer from the gas and heat release from exothermic reactions in the bed. The model also considers the rotational wall and includes a simplified mixing model of the bed material as well as heat losses from the outside wall of the rotary kiln due to radiation and convection. For two different flames, one coal and one oil flame, surface temperatures are calculated on the inside and outside of the rotary kiln and compared to measurements. The model appears to predict the inner wall and bed surface temperatures well with errors less than 11%. The total heat transfer to the present bed material was also studied revealing that more than 80% originated from the radiative heat transfer within the furnace.
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| 35. |
- Gunnarsson, Adrian, 1990, et al.
(author)
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Heat Transfer Conditions in a Rotary Kiln Test Furnace Using Coal, Biomass and co-firing Burners
- 2016
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In: Clearwater Clean Coal Conference, 2016.06.05-2016.06.09, Clearwater, Florida, USA.
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Conference paper (other academic/artistic)abstract
- In this work the radiative heat transfer in a 580 kWth pilot scale test furnace resembling a full scale rotary kiln used for production of iron ore pellets has been studied. The aim has been to quantify the radiative heat transfer in coal and co-firing flames in a project which examines the use of biomass in the grate-kiln process. Three cases of coal and co-firing are in this work studied and evaluated using a detailed radiation model. The model treats the furnace as an axisymmetric and infinitely long cylinder. Overall, the differences in radiative intensities and heat fluxes between the three studied fuel combinations are minor which implies that introduction of renewable fuels by co-firing in a full scale rotary kiln should be feasible with respect to heat transfer conditions. The modeling results show reasonable to good predictivity compared to the measured intensity data, which implies a satisfactory quality of the collected experimental data.
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| 36. |
- Gunnarsson, Adrian, 1990, et al.
(author)
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Heat transfer modelling of industrial rotary kilns for iron ore pelletizing
- 2019
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Conference paper (other academic/artistic)abstract
- This work discusses the development and usage of a detailed heat transfer model of a rotary kiln in 3D, applying a discrete-ordinates method to solve the radiative heat transfer equation. The model includes conductive and convective heat transfer as well as heat release due to reactions in the bed and heat losses from the outside of the kiln. The rotation of the wall is considered along with a simplified mixing model of the bed. Measurement data gathered from a test furnace, is used in combination with temperature data and operation parameters gathered from a full-scale rotary kiln to calculate surface temperatures. Compared to measurements, the model predicts the temperatures well with errors less than 10%. Different contributions of the total heat transfer to the bed was studied, revealing that more than 80% originated from radiation.
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| 37. |
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| 38. |
- Gunnarsson, Adrian, 1990, et al.
(author)
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Modelling and measurements of radiation in a 400kWth rotary kiln test furnace
- 2015
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In: Industrial Furnaces and Boilers, 2015.04.07-2015.04.10, Porto Gaia, Portugal.
-
Conference paper (other academic/artistic)abstract
- This work is focused on the radiative heat transfer in rotary kilns used for iron ore production with the aim to obtain a better understanding of the radiation and peak flame temperatures. This was done by performing measurements in a cylindrical, refractory lined, 400 kWth down scaled model of a rotary kiln and evaluating the results with a detailed radiation model. A mixture of coal and torrefied biomass was used as fuel in the experiments. Radiative intensity, gas composition, temperature and particle concentration were measured along the diameter in the flame. The radiation model treats the furnace as an axisymmetric and infinitely long cylinder. The gas properties are calculated with a statistical narrow-band model while the particle properties are calculated with Mie theory. The radiative heat transfer, peak flame temperatures and the influence from different parameters using sensitivity analyses are studied. It is shown that the total radiation is dominated by the contribution of particles, hence the total radiation is sensitive to changes in the particle concentration and size distribution. It was also possible to estimate the peak flame temperatures, and conclude that more accurate temperature and particle measurements are needed in future work.
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| 39. |
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| 40. |
- Gunnarsson, Adrian, 1990, et al.
(author)
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Radiative Heat Transfer Conditions in a Rotary Kiln Test Furnace Using Coal, Biomass, and Cofiring Burners
- 2017
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In: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 31:7, s. 7482-7492
-
Journal article (peer-reviewed)abstract
- This work studies the radiative heat transfer in a 580 kW(th) pilot scale test furnace that resembles a full-scale rotary kiln for iron ore pellet production. The aim is to quantify the radiative heat transfer in coal and cofiring flames and also to study the possibility to model the radiative heat transfer for such combustion conditions. Three combustion cases of coal and cofiring are studied, and an evaluation is made using a detailed radiation model. The test furnace is cylindrical and refractory lined but does not rotate and no iron ore pellet bed material is included. In-flame measurements of temperature, gas composition, particle concentration, radiative intensity, and radiative heat flux are conducted for the different fuels and fuel combinations. Overall, the differences in measured radiative intensities and heat fluxes among the three studied fuel cases are minor, which implies that introduction of renewable fuels by cofiring in a full-scale rotary kiln should be feasible with respect to heat transfer conditions. In the model, the furnace is treated as an axisymmetric and infinitely long cylinder, and gas properties are calculated with a statistical narrow-band model, while particle properties are calculated using Mie theory. The modeling results show reasonable to good predictivity compared to the measured intensity data. This indicates that the experimental data is of good quality but also indicates the potential use of the model in full-scale rotary kiln calculations in future work.
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| 41. |
- Gunnarsson, Adrian, 1990, et al.
(author)
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Radiative Heat Transfer Modeling and in Situ Diagnostics of Soot in an 80 kWth Propane Flame with Varying Feed-Gas Oxygen Concentration
- 2018
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In: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 57:36, s. 12288-12295
-
Journal article (peer-reviewed)abstract
- This work presents experimental measurements of various 80 kWth propane flames, using a swirl burner, and modeling of the radiative heat transfer. The combustion conditions were altered by varying the oxygen concentration in the oxidant within range of 21-32%, while keeping the thermal input and oxygen-to-fuel ratio constant. Temperature, gas composition, and radiative intensity were measured using probes, while the soot volume fraction was quantified using nonintrusive laser-induced incandescence. The radiative intensity and the soot volume fraction increased with an increased oxygen concentration in the flame. When the oxygen concentration exceeded 27% the soot volume fraction was increased more than 14-fold. The results reveal the potential of promoting radiative heat transfer by increasing the oxygen concentration; the total radiative intensity becomes dominated by the soot particle contribution. In addition, laser-induced incandescence was successfully used for instantaneous and spatially resolved soot measurements in this type of furnace being at a technical scale.
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| 42. |
- Gunnarsson, Adrian, 1990, et al.
(author)
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Soot Formation and Radiative Heat Transfer in Oxy-Fuel and Oxygen-Enhanced Propane Flames
- 2018
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Conference paper (other academic/artistic)abstract
- This work aims to determine radiation-related properties of various propane flames, where the measurements were conducted in a down-fired and cylindrical 100 kW furnace equipped with a swirl burner. The combustion conditions were varied by altering the composition of the oxidant. For six cases, oxygen-enhanced air was used, step-wise varying the oxygen concentration in the oxidant from 21% to 32%. Also for six cases, the furnace was operated in oxy-fuel mode, recirculating dry flue gas and varying the oxygen concentration from 25% to 42%. All measurements were conducted at an axial distance of 384 mm from the burner. Temperature, gas composition and radiative intensity were measured (by intrusive instruments) along the furnace diameter using probes while the soot volume fraction was quantified using non-intrusive laser induced incandescence (LII). An Nd:YAG laser at wavelength 1064 nm was used for the LII measurements, and a diode laser at wavelength 808 nm was used for extinction measurements for absolute calibration of the LII-signal. Two-dimensional images of the LII-signal were captured using an intensified CCD-camera and radial profiles of the soot volume fraction were achieved. The soot volume fraction increased with increasing oxygen concentration in the feed gas, and, when the oxygen concentration exceeded 30 and 42% for the oxygen-enriched air and oxy-fuel cases, respectively, the soot formation was substantially enhanced with volume fractions more than 10 times higher than for lower oxygen concentrations. The higher oxygen concentration required for the increased soot production in the oxy-fuel combustion cases is mainly due to the higher heat capacity of carbon dioxide that lowers the flame temperatures. The data collected from the measurements was used to model the radiative intensity using a discrete transfer model. In this model, gas properties are calculated using a statistical narrow-band model and particle properties are calculated using Rayleigh theory. Good agreement was achieved between the modeled and measured radiative intensity for most flames and the use of an LII-system to measure the soot volume fraction in this type of furnace was successful.
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| 43. |
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| 44. |
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| 45. |
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| 46. |
- Gunnarsson, Sten, 1976, et al.
(author)
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pHEMT and mHEMT Ultra Wideband Millimeterwave Balanced Resistive Mixers
- 2004
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In: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. ; 2, s. 1141-1144
-
Conference paper (other academic/artistic)abstract
- Two ultra wideband millimeterwave single balanced resistive mixers utilizing a Marchand balun for the LO-hybrid are simulated, fabricated and characterized for 30-60 GHz in both up and down conversion. Two different versions of the mixer were manufactured in a commercial pHEMT-MMIC and a mHEMT-MMIC process respectively. A measured down conversion loss of approximately 6 to 12 dB over the whole band is obtained for both versions of the mixer with external IF power combining. In spite of the balanced design, the required LO power is quite low, 2 dBm is sufficient for low conversion loss. The LO-RF isolation is excellent, often more than 30 dB for both type of mixers. Low noise figure and high IIP3 figures are obtained. It is also shown that by applying selective drain bias, up to 5 dB improvement of IIP3 can be obtained for the mHEMT mixer with small LO powers.
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| 47. |
- Gunnarsson Sarius, Niklas, 1976-
(author)
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Surface Technology for Optical and Electrical Connectors
- 2010
-
Doctoral thesis (other academic/artistic)abstract
- This thesis treats surface engineering with the purpose of improved quality of optical and electricalconnectors with a focus on electroplated and magnetron sputtered materials. In electroforming of tools formanufacturing optical connectors, the influence of ultrasonic agitation on intrinsic stresses and fillingproperties of electroplated Ni has been studied. It is established that the ultrasonic agitation at the substratesurface during deposition impacts the intrinsic stresses making it possible to increase deposition rate viacurrent density, with stress-free or low-stress levels in the Ni layers. Reduced variations of the intrinsicstress over the surface with the current density is a further important result. Filling of grooves byelectroplating of Ni using ultrasonic agitation is demonstrated. This is due to increasing mass transport ofspecies into the grooves compared to conventional pumped agitation. The enhanced filling propertiesmakes it possible to electroplate Ni in the bottom of high-aspect-ratio grooves. In order to industriallyimplement new nanocomposite coatings on electronic connectors, studies have been performed regardingthe thermal diffusion barrier properties against Cu for Ti-Si-C and Ti-Si-C-Ag nanocomposites, depositeddirectly onto Cu substrates or with sputtered Ni, Ti or electroplated Ni as an intermediate coating. Theapplication of an electroplated Ni diffusion barrier coating, hinders Cu from reaching the surface of thenanocomposites. Also, Ti-Si-C-Ag nanocomposite deposited on magnetron sputtered Ni or Ti on Cusubstrates hinder Cu from diffusing to the surface after annealing. The contact resistance of Ag-Pdtopcoated Ti-Si-C-Ag-Pd and Ti-Si-C-Ag nanocomposite coatings in contact with hard gold is shown tocompete with hard gold in contact with itself, as electrical contact coatings at contact forces around 5 N.Ag-Pd topcoated Ti-Si-C-Ag-Pd in contact with hard gold is shown to have approximately the same contactresistance as hard gold in contact with hard gold at contact forces around 0.1 N, which here is in the 10 mΩrange, while Ti-Si-C-Ag nanocomposite coatings in contact with hard gold has a contact resistance that isup to 10 times higher. The overall contribution of this thesis can be summarised as a deeper knowledge andunderstanding of techniques and coatings, that help reduce cost and increase reliability of electronics.
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| 48. |
- Hedlund, Daniel, et al.
(author)
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Magnetic properties of the Fe5SiB2−Fe5PB2 system
- 2017
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In: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 96:9
-
Journal article (peer-reviewed)abstract
- The magnetic properties of the compound Fe5Si1−xPxB2 have been studied, with a focus on the Curie temperature TC, saturation magnetization MS, and magnetocrystalline anisotropy. Field and temperature dependent magnetization measurements were used to determine TC(x) and MS(x). The saturation magnetization at 10 K (300 K) is found to monotonically decrease from 1.11MA/m (1.03MA/m) to 0.97MA/m (0.87MA/m), as x increases from 0 to 1. The Curie temperature is determined to be 810 and 615 K in Fe5SiB2 and Fe5PB2, respectively. The highest TC is observed for x=0.1, while it decreases monotonically for larger x. The Curie temperatures have also been theoretically determined to be 700 and 660 K for Fe5SiB2 and Fe5PB2, respectively, using a combination of density functional theory and Monte Carlo simulations. The magnitude of the effective magnetocrystalline anisotropy was extracted using the law of approach to saturation, revealing an increase with increasing phosphorus concentration. Low-field magnetization vs temperature results for x=0,0.1,0.2 indicate that there is a transition from easy-axis to easy-plane anisotropy with decreasing temperature.
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| 49. |
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| 50. |
- Houghton, Lara, et al.
(author)
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Measuring Radiation from High Pressure Oxy-Coal Flames
- 2018
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Conference paper (other academic/artistic)abstract
- Narrow angle radiometers are being used for forest fire and combustion applications. Generating accurate radiative flux data from these instruments is essential to build flame models and predict fire behavior. Further investigation of current radiometers has revealed a level of uncertainty in measurements that stem from design flaws, calculation error, and lack of information. Main design issues deal with the narrow probe, focusing device, field of view, and sensor. Available information on narrow angle radiometer instrumentation is highly limited. To address this issue, our group is developing a narrow angle radiometer which will be applied to high-temperature and pressure oxy-coal flames in Brigham Young Universities Pressurized Oxy-coal Combustor (POC). This presentation will provide a review of radiometer design. Data will be provided to elucidate the impact of environmental conditions on calibration repeatability. In addition an instrument model will be provided that allows the conversion between the quantity of interest (incident radiation) and the quantity measured (electrical signal).
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