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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Bengtsson Blücher, Daniel, 1975
(författare)
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Carbon Dioxide: The Unknown Factor in the Atmospheric Corrosion of Light Metals. A Laboratory Study
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The atmospheric corrosion of Al and Mg-Al alloys was investigated using controlled air in the laboratory. The effects of CO2, temperature, NaCl, relative humidity, SO2, NO2 and O3 on corrosion rate and corrosion product composition were examined. Initial stages of corrosion were studied in situ using Scanning Kelvin Probe Force Microscopy (SKPFM), which monitors the Volta potential and the topography at sub-micrometer resolution. The corrosion products were analyzed by techniques including IC, GI-XRD, ESEM/EDX, SKP, FIB/SEM and AES. The main finding is that ambient concentrations of CO2 (350ppm) inhibit the NaCl-induced atmospheric corrosion of Al and Mg-Al alloys. In the absence of CO2, high pH regions form in the surface electrolyte due to the cathodic reduction of oxygen. The high pH electrolyte dissolves the alumina-containing passive film, resulting in rapid corrosion. When CO2 is present, it forms carbonic acid that neutralizes the hydroxide formed in the cathodic vicinity, which slows the corrosion. On aluminum-based alloys NaCl produces general corrosion in humid air without CO2, while pitting is observed at ambient CO2 levels. The temperature-dependence of the NaCl induced atmospheric corrosion of aluminum alloys is strongly non-linear. With increasing temperature, the inhibitive effect of CO2 declines due to the decreasing solubility of CO2 in water. On Mg-Al alloys, corrosion attack is localized in the absence of CO2, while general corrosion prevails in its presence. The inhibitive effect of CO2 is relevant to occluded areas, where the supply of CO2 is limited, for example in crevice corrosion and corrosion beneath organic coatings. In humid air, SO2 accelerates the atmospheric corrosion of Al and Mg-Al alloy. The surface electrolyte is acidified by sulfuric acid formation, destabilizing the passive film. However, for aluminum alloys, SO2 inhibits the NaCl-induced pitting corrosion. The precipitation of aluminum hydroxy sulfates was believed to retard pit propagation. The deposition rate of SO2 on Al is slow and almost independent of the SO2 concentration. In contrast, SO2 deposition on Mg-Al alloys is transport limited at high humidity. In the presence of SO2, Mg-Al alloys suffer pitting corrosion that preferentially attacks the a phase.
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| 3. |
- Bengtsson-Blücher, Daniel, et al.
(författare)
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Influence of ppb levels of SO2 on the atmospheric corrosion of aluminum in the presence of NaCl
- 2005
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Ingår i: Journal of the Electrochemical Society. - 1945-7111 .- 0013-4651. ; 152(10), s. B397-B404
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Tidskriftsartikel (refereegranskat)abstract
- The effect of part per billion (ppb) levels of SO2 on the atmospheric corrosion on Al (99.999%) was investigated in the laboratory at 22 degrees C. Exposure time was 20 and 672 h. The effect of SO2 concentration (46-1300 ppb), relative humidity (70- 99% RH), and the amount of NaCl applied prior to exposure (0- 250 mu g/cm(2)) was studied. In addition, the effect of O-3 and NO2 on the SO2 deposition rate was addressed. The samples were investigated by gravimetry, grazing incidence X-ray powder diffraction, ion chromatography, optical microscopy, and environmental scanning electron microscopy equipped with energy-dispersive X-ray fluorescence. SO2 accelerates the atmospheric corrosion of Al, forming corrosion product "islands" containing aluminum hydroxy sulfate. Combining NaCl and SO2 has a synergistic effect on the average corrosion rate. In contrast, the chloride-induced pitting of aluminum is significantly reduced by SO2. The corrosivity of SO2 is attributed to the acidification of the surface electrolyte that destabilizes the alumina passive film. The suppression of pitting corrosion by SO2 is attributed to the formation of aluminum hydroxy sulfates that are less soluble than the corresponding chlorides and slows down pit propagation. At relative humidities above 70% RH, there is a measurable steady-state deposition of SO2 that corresponds to the rate of formation of sulfate. The SO2 deposition rate is not limited by the oxidation of (IV)-valent sulfur on the surface. SO2 deposition is enhanced by sodium chloride because the corrosion reactions in the NaCl(aq) electrolyte result in high pH in the cathodic regions and the formation of aluminum hydroxide. Ozone in the ppb range has only transient effects on the SO2 deposition rate, whereas ppb levels of NO2 had no effect at (c) 2005 The Electrochemical Society.
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| 4. |
- Bengtsson, Lars, 1958, et al.
(författare)
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Development of a Voice Controlled UHF Radio
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- More and more devices attempt to improve user interaction, including the use of speech recognition. The project aim was to develop an efficient system for voice control of an operative UHF radio in sporting environments. The objective was to perform a theoretical study and analysis of state of the art in voice control algorithms. In a second phase, the work was focused on developing and testing a demonstrator device with the concepts and conclusions reached in the theory study. An Android device recognizes specific voice commands and sends the orders to the UHF radio by a combination of serial and TCP/IP communications. For control with maximum accuracy and minimum power consumption, Hidden Markov Models (HMMs) and Dynamic Time Warping (DTW) algorithms for voice recognition have been studied, optimized and implemented through several applications in Java.
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| 5. |
- Esmaily, Mohsen, 1987, et al.
(författare)
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Atmospheric Corrosion of Mg Alloy AZ91D Fabricated by aSemi-Solid Casting Technique: The Influence of Microstructure
- 2015
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 162:7, s. C311-C321
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Tidskriftsartikel (refereegranskat)abstract
- The atmospheric corrosion behavior of alloy AZ91D produced by a semi-solid metal (SSM) technique and by conventional high pressure die casting (HPDC) was investigated for up to 1176 hours in the laboratory. Alloy AZ91D in the SSM state was fabricated using a rheocasting (RC) technique in which the slurry was prepared by the RheoMetal process. Exposures were performed in 95% RH air at 22 and 4 degrees C. The RC alloy AZ91D exhibited significantly better corrosion resistance than the HPDC material at two temperatures studied. The effect of casting technology on corrosion is explained in terms of the microstructural differences between the materials. For example, the larger number density of cathodic beta phase particles in the HPDC material initially causes relatively rapid corrosion compared to the RC material. During later stages of corrosion, the more network-like beta phase particles in the RC alloy act as a corrosion barrier, further improving the relative corrosion resistance of the RC material.
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| 6. |
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| 7. |
- Gunnarsson, Adrian, 1990, et al.
(författare)
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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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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 57:36, s. 12288-12295
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Tidskriftsartikel (refereegranskat)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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| 8. |
- Gunnarsson, Adrian, 1990, et al.
(författare)
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Soot Formation and Radiative Heat Transfer in Oxy-Fuel and Oxygen-Enhanced Propane Flames
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)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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| 9. |
- Högman, Ulf, 1961, et al.
(författare)
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Requirements on New Technology and the Technology Implementation Process
- 2010
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Ingår i: 8th International NordDesign Conference, NordDesign 2010; Goteborg; Sweden; 25 August 2010 through 27 August 2010. ; 2, s. 289-300
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Konferensbidrag (refereegranskat)abstract
- In literature, many authors have pointed to the importance of technology and technology development for company competitiveness. In this study we aim to study the technology in more detail and attempt to develop an understanding on the requirements and needs on “technology” from the perspective of product development. The research question which we aim to answer in this study is:“What are the requirements on maturity of technology when this technology is about to enter into the product development process?“A qualitative research strategy, based on three study cases involving 17 interviewees, has been chosen. All three cases come from one single company, Volvo Aero Corporation (VAC) in Sweden, in the context of the aero engine industry. The study contributes with a broad mapping of requirements and how they relate to different categories of technologies, showing big differences both regarding content and timing. It is concluded that attention should be payed both to how the organization builds new capabilities and to the capabilities of the technology itself. A surprisingly complicated picture on the requirements relating to the implementation of new technologies has emerged in the study. This contributes to the understanding regarding the difficulties of developing new technology and integrating it into an application.
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| 10. |
- Mahashabde, Sumedh, 1985, et al.
(författare)
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A Frequency Selective Surface based focal plane receiver for the OLIMPO balloon-borne telescope
- 2015
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 5:1, s. 145-152
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Tidskriftsartikel (refereegranskat)abstract
- We describe here a focal plane array of Cold-Electron Bolometer (CEB) detectors integrated in a Frequency Selective Surface (FSS) for the 350 GHz detection band of the OLIMPO balloon-borne telescope. In our architecture, the two terminal CEB has been integrated in the periodic unit cell of the FSS structure and is impedance matched to the embedding impedance seen by it and provides a resonant interaction with the incident sub-mm radiation. The detector array has been designed to operate in background noise limited condition for incident powers of 20 pW to 80 pW, making it possible to use the same pixel in both photometric and spectrometric configurations. We present high frequency and dc simulations of our system, together with fabrication details. The frequency response of the FSS array, optical response measurements with hot/cold load in front of optical window and with variable temperature black body source inside cryostat are presented. A comparison of the optical response to the CEB model and estimations of Noise Equivalent power (NEP) is also presented.
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