| 28671. |
- Karacic, Sabina, 1987, et al.
(författare)
-
Biodeterioration of reinforced sprayed concrete in subsea tunnels (peer-reviewed)
- 2018
-
Ingår i: Proceedings pro123-1 : Final Conference of RILEM TC 253-MCI: Microorganisms-Cementitious Materials Interactions. - 9782351582077 ; 1:PRO 123, s. 209-221
-
Konferensbidrag (refereegranskat)abstract
- Progressive microbial deterioration of steel fibre reinforced sprayed concrete for rock support has been observed in the Norwegian Oslofjord subsea tunnel due to reddish/brown and black biofilms. The concrete mix design corresponded to B45 and M45, with water/binder ratio = 0.42. Previous research on the microbial community has revealed complexity of the microbial composition involved in degradation of the cement paste matrix, material loss and steel fibre corrosion. In this study, we analysed microbial community dynamics and concrete degradation over time, biominerals and water chemistry composition to understand most important mechanisms involved in the biodeterioration process. Results showed temporal variations of microbial community and concrete degradation in association with changes in the water flow. The dataset from 2011 revealed a biofilm bacterial community dominated by Marinicella sp. (Proteobacteria) with a few ammonia oxidisers within Nitrosomonas and nitrite oxidisers within Nitrospinaceae. The data from 2015-2016 showed that the major phylum groups detected were Proteobacteria, Thaumarchaeota, Planctomycetes, Bacteroidetes, Actinobacteria, Acidobacteria, Nitrospirae, and Gemmatimonadetes with relative sequence abundance >2%.
|
|
| 28672. |
- Karacic, Sabina, 1987, et al.
(författare)
-
Microbial attack on subsea sprayed concrete
- 2016
-
Ingår i: International RILEM Conference on Microorganisms-Cementitious Materials Interactions. - 9782351581605 ; , s. 63-75
-
Konferensbidrag (refereegranskat)abstract
- A novel deterioration process has recently been discovered in several Norwegian subsea tunnels resulting in degradation of the sprayed concrete matrix and destructive corrosion of steel fibers in association with biofilms rich in Mn(IV), Fe(III) and exopolymers. Microbial processes together with abiotic attack from saline ground water, containing high concentrations of Cl−, SO42−, Mg2+ and HCO3 −, are assumed to be responsible for the degradation. In this initial study of the biofilm microbial communities, high throughput amplicon sequencing of 16S rRNA genes was used to survey the biofilm composition and diversity. Results showed a high abundance of iron oxidizing bacteria within Mariprofundus, which was in accordance with the observed accumulation of Fe(III) and exopolymers in the biofilms. Also iron and manganese reducing bacteria were detected. Surprisingly, the biofilm harbored autotrophic nitrogen converting microorganisms at high relative abundances, while no known manganese oxidizingor sulfur reducing bacteria were detected. Furthermore, a number of the numerically important contributors in the biofilm communities could not be assigned to any function. Apparently, the biofilm transformations were more complex than initially anticipated and the role of for instance the nitrogen converting- and the undetermined bacteria for the degradation processes remains unsolved.
|
|
| 28673. |
- Karacic, Sabina, 1987, et al.
(författare)
-
Subsea tunnel reinforced sprayed concrete subjected to deterioration harbours distinct microbial communities
- 2018
-
Ingår i: Biofouling. - : Informa UK Limited. - 0892-7014 .- 1029-2454. ; 34:10, s. 1161-1174
-
Tidskriftsartikel (refereegranskat)abstract
- Deterioration of concrete is a large societal cost. In the Oslofjord subsea tunnel (Norway), deterioration of sprayed concrete and corrosion of reinforcing steel fibres occur under biofilm formed at sites with intrusion of saline groundwater. In this study, the microbial community structure, in situ environmental gradients and chemical composition of the biofilms were examined at three tunnel sites. Ammonia- and nitrite-oxidising microorganisms, in particular Nitrosopumilus sp., and iron-oxidising bacteria within Mariprofundus sp., were omnipresent, together with a diversity of presumably heterotrophic bacteria. Alpha- and beta diversity measures showed significant differences in richness and community structure between the sites as well as over time and null-models suggested that deterministic factors were important for the community assembly. The superficial flow of water over the biofilm had a strong effect on oxygen penetration in the biofilm and was identified as one major environmental gradient that varied between the sites, likely being important for shaping the microbial communities. © 2019, © 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
|
|
| 28674. |
- Karacic, Sabina, 1987, et al.
(författare)
-
The effect of time and surface type on the composition of biofilm communities on concrete exposed to seawater
- 2022
-
Ingår i: International Biodeterioration and Biodegradation. - : Elsevier BV. - 0964-8305. ; 173
-
Tidskriftsartikel (refereegranskat)abstract
- Microbially induced deterioration is a threat to concrete infrastructures in marine environments. Complex microbial biofilms form on concrete surfaces exposed to sea water and cause material deterioration. However, the mechanisms determining the composition and the development of the biofilm communities are poorly understood. We designed a mesocosm experiment to determine the influence of concrete surface structure (smooth/rough) and steel fiber reinforcement (presence/absence) on biofilm development over a period of 455 days. This enabled a novel methodology to systematically assess biofilm formation of bacteria on concrete exposed to marine water. The biofilm communities were distinctly different from the planktonic communities in the systems. The alpha diversity increased with time and longer time intervals correlated with higher turnover of taxa. Several taxa within Caulobacterales and Rhodobacterales were identified as early biofilm formers, which decreased in relative abundance and were replaced by taxa within Planctomycetales as the biofilm developed. Throughout the experimental period, concrete surface type influenced the microbial community composition. Some taxa such as Magnetospiraceae, Portibacter, Rubripirellula, and Rhodopirellula, possibly involved in the oxidation and reduction of iron, were for instance more abundant in biofilms on steel-fiber containing concrete. Null models suggested that mainly deterministic factors were shaping the microbial communities with limited importance of stochasticity at shorter time intervals.
|
|
| 28675. |
- Karácsony, Máté, 1988, et al.
(författare)
-
Using fusion to enable late design decisions for pipelined computations
- 2016
-
Ingår i: FHPC 2016 - Proceedings of the 5th International Workshop on Functional High-Performance Computing, co-located with ICFP 2016. - New York, NY, USA : ACM. ; , s. 9-16
-
Konferensbidrag (refereegranskat)abstract
- We present an embedded language in Haskell for programming pipelined computations. The language is a combination of Feldspar (a functional language for array computations) and a new implementation of Ziria (a language for describing streaming computations originally designed for programming software defined radio). The resulting language makes heavy use of fusion: as in Feldspar, computations over arrays are fused to eliminate intermediate arrays, but Ziria processes can also be fused, eliminating the message passing between them, which in turn can give rise to more fusion at the Feldspar level. The result is a language in which we can first describe pipelined computations at a very fine-grained level, and only afterwards map computations onto the details of a specific parallel architecture, where the fusion helps us to generate efficient code. This flexible design method enables late design decisions cheaply, which in turn can lead to more efficient produced code. In the paper, we present two examples of pipelined computations in our language that can be run on Adapteva’s Epiphany many-core coprocessor and on other back-ends.
|
|
| 28676. |
- Karadotcheva, Elitza, et al.
(författare)
-
Structural power performance targets for future electric aircraft
- 2021
-
Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 14:19
-
Tidskriftsartikel (refereegranskat)abstract
- The development of commercial aviation is being driven by the need to improve efficiency and thereby lower emissions. All-electric aircraft present a route to eliminating direct fuel burning emissions, but their development is stifled by the limitations of current battery energy and power densities. Multifunctional structural power composites, which combine load-bearing and energy-storing functions, offer an alternative to higher-energy-density batteries and will potentially enable lighter and safer electric aircraft. This study investigated the feasibility of integrating structural power composites into future electric aircraft and assessed the impact on emissions. Using the Airbus A320 as a platform, three different electric aircraft configurations were designed conceptually, incorporating structural power composites, slender wings and distributed propulsion. The specific energy and power required for the structural power composites were estimated by determining the aircraft mission performance requirements and weight. Compared to a conventional A320, a parallel hybrid-electric A320 with structural power composites >200 Wh/kg could potentially increase fuel efficiency by 15% for a 1500 km mission. For an all-electric A320, structural power composites >400 Wh/kg could halve the specific energy or mass of batteries needed to power a 1000 km flight.
|
|
| 28677. |
- Karageorgis, Anastassia, et al.
(författare)
-
A multi-center preclinical study of gadoxetate DCE-MRI in rats as a biomarker of drug induced inhibition of liver transporter function
- 2018
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203 .- 1932-6203. ; 13:5
-
Tidskriftsartikel (refereegranskat)abstract
- Drug-induced liver injury (Dili) is a leading cause of acute liver failure and transplantation. Dili can be the result of impaired hepatobiliary transporters, with altered bile formation, flow, and subsequent cholestasis. We used gadoxetate dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), combined with pharmacokinetic modelling, to measure hepatobiliary transporter function in vivo in rats. The sensitivity and robustness of the method was tested by evaluating the effect of a clinical dose of the antibiotic rifampicin in four different preclinical imaging centers. The mean gadoxetate uptake rate constant for the vehicle groups at all centers was 39.3 +/- 3.4 s -1 (n = 23) and 11.7 +/- 1.3 s -1 (n = 20) for the rifampicin groups. The mean gadoxetate efflux rate constant for the vehicle groups was 1.53 +/- 0.08 s -1 (n = 23) and for the rifampicin treated groups was 0.94 +/- 0.08 s -1 (n = 20). Both the uptake and excretion transporters of gadoxetate were statistically significantly inhibited by the clinical dose of rifampicin at all centers and the size of this treatment group effect was consistent across the centers. Gadoxetate is a clinically approved MRI contrast agent, so this method is readily transferable to the clinic. Conclusion: Rate constants of
|
|
| 28678. |
- Karahasanovic, Adi, 1988, et al.
(författare)
-
Adapting Threat Modeling Methods for the Automotive Industry
- 2017
-
Konferensbidrag (refereegranskat)abstract
- We live in a world that is getting more interconnected by each day and we are witnessing a global change where all the devices in our surroundings are becoming “smart” and connected to the Internet. The automotive industry is also a part of this change. Today's vehicles have more than 150 small computers, embedded control units (ECUs), and multiple connection points to the Internet which makes them vulnerable to various on-line threats. Recent attacks on connected vehicles have all been results of security vulnerabilities that could have been avoided if appropriate risk assessment methods were in place during software development. In this paper we demonstrate how the threat modeling process, common for the computer industry, can be adapted and applied in the automotive industry. The overall contribution is achieved by providing two threat modeling methods that are specifically adapted for the concept of the connected car and can further be used by automotive experts. The methods were chosen after an extensive literature survey and with support of domain experts from the vehicle industry. The two methods were then successfully applied to the connected car and the underlying software architecture based on the AUTOSAR standard. We have empirically validated our results with domain experts as well as tested the found vulnerabilities in a simulated vehicle environment.
|
|
| 28679. |
- Karamchedu, Seshendra, 1987, et al.
(författare)
-
Changes in the surface chemistry of chromium-alloyed powder metallurgical steel during delubrication and their impact on sintering
- 2015
-
Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136. ; 223, s. 171-185
-
Tidskriftsartikel (refereegranskat)abstract
- Changes induced in the surface chemistry of metal powder during the delubrication stage affect the subsequent sintering process and hence the final properties of the sintered compacts. The different stages during delubrication were characterized by means of in situ visual observation of components made by compacting chromium-alloyed water-atomized steel powder with lubricant additions. A strong correlation is found between this visual observation of changes of the compact appearance during the delubrication and the component chemistry depicted via the monitoring of the exhaust gases composition (CO2, O-2 and H2O), thermogravimetric analysis, and changes in powder surface composition (X-ray photoelectron spectroscopy combined with scanning electron microscopy and energy dispersive X-ray analysis). The compacts were delubricated at different conditions and the effect of different parameters was studied, including temperature (300, 450 and 900 degrees C) and processing gas (N-2 or air). Delubricated compacts were further sintered at 1120 degrees C in N-2/3%H-2 mix to evaluate the effect of delubrication on the properties of the sintered components. The mechanical properties, chemistry and microstructure obtained after sintering show a strong relation to the surface changes induced during delubrication. The results indicate that delubrication at 450 degrees C in dry N-2 preserves the original surface condition of the powder and upon sintering the compacts exhibit optimum properties. Sintered compacts delubricated at 450 degrees C in air and at 900 degrees C in N-2 exhibited inferior properties. In the former case, this was related to the growth of Fe-oxide on the powder surfaces. In the latter case, the initial thin Fe-oxide layer, covering most of the powder surfaces, was reduced and oxygen made available was transferred into stable Cr-Mn-Si-rich oxide particles. Delubrication at 300 degrees C resulted in insufficient lubricant removal along with soot formation contributing to inferior mechanical properties after sintering as well. (C) 2015 Elsevier B.V. All rights reserved.
|
|
| 28680. |
- Karamchedu, Seshendra, 1987, et al.
(författare)
-
Effect of active constituents in the atmosphere on the sintering of chromium-alloyed PM steels
- 2016
-
Ingår i: World Powder Metallurgy 2016 Congress and Exhibition, World PM 2016; Hamburg; Germany; 9 October 2016 through 13 October 2016. - 9781899072484
-
Konferensbidrag (refereegranskat)abstract
- Sintering of chromium-alloyed PM steels in atmospheres containing hydrogen and carbon monoxide has been studied. Thermogravimetric analysis was performed on PM steel compacts in atmospheres containing the gaseous constituents individually and when present together. Oxidation/reduction and carburization/decarburization of the compacts was evaluated based on thermogravimetric analysis complemented with bulk carbon and oxygen analysis of the samples. The results suggest that hydrogen promotes the reduction of the iron oxide layer covering the powder surface below 650 °C, the effectiveness of which improves with an increase in the concentration of hydrogen in the atmosphere. When hydrogen was additionally present, an enhancement in the reduction and carburization behavior was observed in the case of carbon monoxide containing atmospheres.
|
|
