| 1. |
- Milberg, Per, et al.
(author)
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A burning desire for smoke? Sampling insects favoured by forestfire in the absence of fire
- 2015
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In: Journal of Insect Conservation. - : Springer. - 1366-638X .- 1572-9753. ; 19:1, s. 55-65
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Journal article (peer-reviewed)abstract
- Fire-favoured insects are difficult to sampleexcept opportunistically after forest fires. Here, we tested ifsmoke from a small fire could be an efficient way to samplesuch insects. Insects were sampled over ca. 10 h hours, byhand-picking and netting on screens put up around the fire.Two specimens of the rare and redlisted Hormopeza spp.(Diptera, Empididae) were caught. Large numbers([20,000) of Microsania spp. (Diptera, Platypezidae) werecaught, but none in the absence of smoke. The numbers ofMicrosania spp. clearly peaked in late afternoon, and ashort sampling period would be sufficient if targeting onlythis taxon. Of the almost 200 species of Coleoptera, 17 %were considered as fire-favoured, contributing 9 % of thespecimens, suggesting low efficiency of the method for thisgroup. Using 23 sites differing in fire history, catches ofMicrosania spp. were unaffected by numbers and area offorest fire (preceding 5 years and within 10 km radius overthe sampling sites). In contrast, there was a weak trend forthe proportion of fire-favoured Coleoptera to increase withincreasing number of fires. To conclude, smoke as producedin our study can clearly attract fire-favoured Diptera,but smoke had only a weak effect on fire-favoured Coleopterain the study area. It is still likely that selectivelypicking specimens of species attracted to smoke is a morecost-efficient method than using, e.g., Malaise traps thatcatch indiscriminately.
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| 2. |
- Spohr, Reimar
(author)
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Ion Tracks for Micro- and Nanofabrication : From Single Channels to Superhydrophobic Surfaces
- 2010
-
Doctoral thesis (other academic/artistic)abstract
- A method is described for preset-count irradiations between 1 and 100 ions singling-out individual ions from an ion beam with more than a billion ions arriving per second. The ion tracks are etched in a conductometric system with real-time evaluation of the acquired data. The etch process can be interrupted when reaching a preset channel diameter. Cylindrical channels are obtained by adding surfactants to the etch solution forming a self-assembled barrier between etching medium and polymer. Asymmetric etching of single ion tracks leads to pH sensitive conical pores with diode-like properties. Using etched channels as template, homogeneous and multilayer magnetic single-wires are electrodeposited. The magnetoresistivity of the wires is studied. Single-track applications comprise critical apertures (cylindric, conic, necked), asymmetric pores (pH sensitive, biospecific), Giant Magneto Resistance sensors, and spintronic devices. On the basis of studies with individual ion tracks we tackled tilted multiporous systems such as ion beam lithography with a masked ion beam leading to micro-structures with inclined walls and anisotropic superhydrophobic ion track textures, analogous to biological shingle structures on butterfly wings. We demonstrated qualitatively, that the asymmetry of the texture translates into motion under ultrasonic agitation. This could lead to the development of rotary drives.
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| 3. |
- Westerberg, J, et al.
(author)
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Ten-year myringoplasty series: does the cause of perforation affect the success rate?
- 2011
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In: JOURNAL OF LARYNGOLOGY AND OTOLOGY. - : Cambridge University Press. - 0022-2151 .- 1748-5460. ; 125:2, s. 126-132
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Journal article (peer-reviewed)abstract
- Objective: To present the results of primary myringoplasty procedures together with the perforation cause, perforation size and site, surgeons experience, and surgical method, and to investigate how these factors relate to graft take rates. Study design: Retrospective chart review of 243 consecutive patients undergoing primary myringoplasty with temporalis fascia underlay over a 10-year period from 1994 to 2004. Results: The overall graft take rate was 95 per cent. The retroauricular approach resulted in a 97 per cent graft take rate, whereas a significantly lower rate (77 per cent) was seen for surgery conducted via the endaural approach, or via an ear speculum. There was no relationship between other factors and tympanic membrane healing. Conclusion: No association was found between perforation cause and graft take rate. The underlay technique is safe and reliable, and the retroauricular approach is preferable as it enables good surgical access and has better results.
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| 4. |
- Baart, Pieter, et al.
(author)
-
Contaminant particle migration in a double restriction seal
- 2013
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In: Proceedings of the STLE Annual Meeting and Exhibition 2013, Detroit MI, USA.. - : STLE. ; , s. 125-
-
Conference paper (peer-reviewed)abstract
- Microparticle image velocimetry (μPIV) is used to measure the grease velocity profile in small seal-like geometries and the radial migration of contaminant particles is predicted. In the first part, the influence of shaft speed, grease type, and temperatures on the flow of lubricating greases in a narrow double restriction sealing pocket is evaluated. Such geometries can be found in, for example, labyrinth-type seals. In a wide pocket the velocity profile is one-dimensional and the Herschel-Bulkley model is used. In a narrow pocket, it is shown by the experimental results that the side walls have a significant influence on the grease flow, implying that the grease velocity profile is two-dimensional. In this area, a single empirical grease parameter for the rheology is sufficient to describe the velocity profile.In the second part, the radial migration of contaminant particles through the grease is evaluated. Centrifugal forces acting on a solid spherical particle are calculated from the grease velocity profile. Consequently, particles migrate to a larger radius and finally settle when the grease viscosity becomes large due to the low shear rate. This behavior is important for the sealing function of the grease in the pocket and relubrication
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| 5. |
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| 6. |
- Baart, Pieter, et al.
(author)
-
The influence of speed, grease type, and temperature on radial contaminant particle migration in a double restriction seal
- 2011
-
In: Tribology Transactions. - : Informa UK Limited. - 1040-2004 .- 1547-397X. ; 54:6, s. 867-877
-
Journal article (peer-reviewed)abstract
- Microparticle image velocimetry (μPIV) is used to measure the grease velocity profile in small seal-like geometries and the radial migration of contaminant particles is predicted. In the first part, the influence of shaft speed, grease type, and temperatures on the flow of lubricating greases in a narrow double restriction sealing pocket is evaluated. Such geometries can be found in, for example, labyrinth-type seals. In a wide pocket the velocity profile is one-dimensional and the Herschel-Bulkley model is used. In a narrow pocket, it is shown by the experimental results that the side walls have a significant influence on the grease flow, implying that the grease velocity profile is two-dimensional. In this area, a single empirical grease parameter for the rheology is sufficient to describe the velocity profile. In the second part, the radial migration of contaminant particles through the grease is evaluated. Centrifugal forces acting on a solid spherical particle are calculated from the grease velocity profile. Consequently, particles migrate to a larger radius and finally settle when the grease viscosity becomes large due to the low shear rate. This behavior is important for the sealing function of the grease in the pocket and relubrication.
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| 7. |
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| 8. |
- Bellander, M, et al.
(author)
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Preliminary evidence that allelic variation in the LMX1A gene influences training-related working memory improvement
- 2011
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In: NEUROPSYCHOLOGIA. - : Elsevier BV. - 0028-3932 .- 1873-3514. ; 49:7, s. 1938-1942
-
Journal article (peer-reviewed)abstract
- LMX1A is a transcription factor involved in the development of dopamine (DA)-producing neurons in midbrain. Previous research has shown that allelic variations in three LMX1A single nucleotide polymorphisms (SNPs) were related to risk of Parkinson's disease (PD), suggesting that these SNPs may influence the number of mesencephalic DA neurons. Prompted by the established link between striatal DA functions and working memory (WM) performance, we examined two of these SNPs in relation to the ability to benefit from 4 weeks of WM training. One SNP (rs4657412) was strongly associated with the magnitude of training-related gains in verbal WM. The allele linked to larger gains has previously been suggested to be associated with higher dopaminergic nerve cell density. No differential gains of either SNP were observed for spatial WM, and the genotype groups were also indistinguishable in tests of attention, interference control, episodic memory, perceptual speed, and reasoning for both SNPs. This pattern of data is in agreement with previous findings from our group, suggesting that cognitive effects of DA-related genes may be more easily detected in a training context than for single-assessment performance scores.
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| 9. |
- Bergman, Karl-Olof, et al.
(author)
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Butterflies in Swedish grasslands benefit from forest and respond to landscape composition at different spatial scales
- 2018
-
In: Landscape Ecology. - : SPRINGER. - 0921-2973 .- 1572-9761. ; 33:12, s. 2189-2204
-
Journal article (peer-reviewed)abstract
- ContextLoss and fragmentation of semi-natural grasslands has critically affected many butterfly species in Europe. Habitat area and isolation can have strong effects on the local biodiversity but species may also be strongly affected by the surrounding matrix.ObjectivesWe explored how different land cover types in the landscape explained the occurrence of butterfly species in semi-natural grasslands.MethodsUsing data from 476 semi-natural grasslands in Sweden, we analysed the effect of matrix composition on species richness and occurrence. Additionally, we analysed at which spatial scales butterflies responded to matrix types (forests, semi-natural grasslands, arable land and water).ResultsForest cover showed the strongest positive effect on species richness, followed by semi-natural grasslands. Forest also had a positive effect on red-listed species at local scales. Responses to matrix composition were highly species-specific. The majority of the 30most common species showed strong positive responses to the amount of forest cover within 200-500m. There was a smaller group of species showing a positive response to arable land cover within 500-2000m. Thirteen species showed positive responses to the amount of semi-natural grasslands, generally at larger scales (10-30km).ConclusionsOur study showed that surrounding forest is beneficial for many grassland butterfly species and that forests might mitigate the negative effects of habitat loss caused by agricultural intensification. Also, semi-natural grasslands were an important factor for species richness at larger spatial scales, indicating that a landscape consisting mainly of supporting habitats (i.e. forests) are insufficient to sustain a rich butterfly fauna.
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| 10. |
- Bergner, Adam, et al.
(author)
-
Influences of forest type and habitat structure on bird assemblagesof oak (Quercus spp.) and pine (Pinus spp.) stands in southwesternTurkey
- 2015
-
In: Forest Ecology and Management. - : Elsevier. - 0378-1127 .- 1872-7042. ; 336, s. 137-147
-
Journal article (peer-reviewed)abstract
- The Mediterranean basin exhibits a multitude of forest habitats affected by former and current exploitation and management. Recent afforestation programs have resulted in an increase in the proportion of coniferous trees, while oak stands, formerly utilized for coppicing and grazing, are abandoned or converted into coniferous plantations. The loss of oak stands might negatively affect birds dependent upon broadleaved forests. Studies confirming or rejecting that statement are scarce, particularly in the eastern part of the region. Using a study area in southwestern Turkey we applied a guild-based approach to investigate how pine and oak stands across a chronosequence differ in their capacity to support forest bird assemblages. Variables describing the vegetation were sampled to characterize the stands and relate bird assemblages to stand structure. Bird abundance and species richness was positively associated with age for both stand types. Richness and diversity was highest in oak stands, while there were no differences in bird abundance between the two forest types. Pine stands supported a different bird species composition compared to oak stands of the same age. Stand age and structure, rather than forest type, held the highest explanatory powers for bird assembly structure. Primary cavity-nesters and ground-nesters were more abundant in oak stands, possibly reflecting differences in stand structure and resource distribution. To support these birds with suitable habitats, oaks stands need conservation. Management practices in pine stands should strive for increasing the amount of old trees and retain vegetation in the understory to benefit breeding birds.
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| 11. |
- Blixt, Torbjörn, et al.
(author)
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Clear-cuts in production forests: From matrix to neo-habitat forbutterflies
- 2015
-
In: Acta Oecologica. - : Elsevier. - 1146-609X .- 1873-6238. ; 69, s. 71-77
-
Journal article (peer-reviewed)abstract
- Butterfly conservation in Europe is mainly focused on well-defined grassland habitat patches. Such anapproach ignores the impact of the surrounding landscape, which may contain complementary resourcesand facilitate dispersal. Here, we investigated butterfly species richness and abundance in a habitatnormally regarded as unsuitable matrix: production forestry clear-cuts. Butterflies were recorded in 48clear-cuts in southern Sweden differing with regards to the time since clear-cutting and land-use history(meadow or forest based on historical maps from the 1870s). All clear-cuts had been managed as productionforests for at least 80e120 years. A total of 39 species were found in clear-cuts of both land-usehistories, but clear-cuts with a history as meadow had on average 34% higher species richness and 19%higher abundance than did clear-cuts with a history as forest. No effect of the time since clear-cuttingwas found, irrespective of land-use history, which was likely due to the narrow timespan sampled (<8years). The absence of temporal effect suggests that clear-cuts may provide butterflies with valuableresources for 10e15 years. Assuming a 100 year forest rotational cycle, this means that 10e15% of thetotal forested area are made up by clear-cuts valuable to butterflies, which corresponds to an area aboutfour times as large as that of species-rich semi-natural grasslands. The study illustrates the importance ofconsidering land-use legacies in ecological research and question the landscape-ecological view thatclear-cuts make up an unsuitable matrix for butterflies. Moreover, forest conservation management withspecial attention to land-use history may increase the quality of the landscape, thus facilitating butterflymetapopulation persistence. Given their large area and assets of nectar and host plant resources, clearcutsmust be considered as a butterfly habitat in its own right. Being a man-made environment withshort history, we might call it a neo-habitat.
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| 12. |
- Brauner, Susanna, et al.
(author)
-
H1N1 vaccination in Sjogren's syndrome triggers polyclonal B cell activation and promotes autoantibody production
- 2017
-
In: Annals of the Rheumatic Diseases. - : BMJ. - 0003-4967 .- 1468-2060. ; 76:10, s. 1755-1763
-
Journal article (peer-reviewed)abstract
- ObjectivesVaccination of patients with rheumatic disease has been reported to result in lower antibody titres than in healthy individuals. However, studies primarily include patients on immunosuppressive therapy. Here, we investigated the immune response of treatment-naive patients diagnosed with primary Sjogren's syndrome (pSS) to an H1N1 influenza vaccine.Methods Patients with Sjogren's syndrome without immunomodulatory treatment and age-matched and gender-matched healthy controls were immunised with an H1N1 influenza vaccine and monitored for serological and cellular immune responses. Clinical symptoms were monitored with a standardised form. IgG class switch and plasma cell differentiation were induced in vitro in purified naive B cells of untreated and hydroxychloroquine-treated patients and healthy controls. Gene expression was assessed by NanoString technology.ResultsSurprisingly, treatment-naive patients with Sjogren's syndrome developed higher H1N1 IgG titres of greater avidity than healthy controls on vaccination. Notably, off-target B cells were also triggered resulting in increased anti-EBV and autoantibody titres. Endosomal toll-like receptor activation of naive B cells in vitro revealed a greater propensity of patient-derived cells to differentiate into plasmablasts and higher production of class switched IgG. The amplified plasma cell differentiation and class switch could be induced in cells from healthy donors by preincubation with type 1 interferon, but was abolished in hydroxychloroquine-treated patients and after in vitro exposure of naive B cells to chloroquine.ConclusionsThis comprehensive analysis of the immune response in autoimmune patients to exogenous stimulation identifies a mechanistic basis for the B cell hyperactivity in Sjogren's syndrome, and suggests that caution is warranted when considering vaccination in non-treated autoimmune patients.
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| 13. |
- Brehmer, Yvonne, et al.
(author)
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Neural correlates of training-related working-memory gains in old age
- 2011
-
In: NeuroImage. - : Elsevier BV. - 1053-8119 .- 1095-9572. ; 58:4, s. 1110-1120
-
Journal article (peer-reviewed)abstract
- Working memory (WM) functioning declines in old age. Due to its impact on many higher-order cognitive functions, investigating whether training can modify WM performance has recently been of great interest. We examined the relationship between behavioral performance and neural activity following five weeks of intensive WM training in 23 healthy older adults (M = 63.7 years). 12 participants received adaptive training (i.e. individually adjusted task difficulty to bring individuals to their performance maximum), whereas the others served as active controls (i.e. fixed low-level practice). Brain activity was measured before and after training, using fMRI, while subjects performed a WM task under two difficulty conditions. Although there were no training-related changes in WM during scanning, neocortical brain activity decreased post training and these decreases were larger in the adaptive training group than in the controls under high WM load. This pattern suggests intervention-related increases in neural efficiency. Further, there were disproportionate gains in the adaptive training group in trained as well as in non-trained (i.e. attention, episodic memory) tasks assessed outside the scanner, indicating the efficacy of the training regimen. Critically, the degree of training-related changes in brain activity (i.e. neocortical decreases and subcortical increases) was related to the maximum gain score achieved during the intervention period. This relationship suggests that the decreased activity, but also specific activity increases, observed were functionally relevant.
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| 14. |
- Brehmer, Yvonne, et al.
(author)
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Working-memory training in younger and older adults : training gains, transfer, and maintenance
- 2012
-
In: Frontiers in Human Neuroscience. - : Frontiers Media SA. - 1662-5161. ; 6:63, s. 1-7
-
Journal article (peer-reviewed)abstract
- Working memory (WM), a key determinant of many higher-order cognitive functions, declines in old age. Current research attempts to develop process-specific WM training procedures, which may lead to general cognitive improvement. Adaptivity of the training as well as the comparison of training gains to performance changes of an active control group are key factors in evaluating the effectiveness of a specific training program. In the present study, 55 younger adults (20–30 years of age) and 45 older adults (60–70 years of age) received 5 weeks of computerized training on various spatial and verbal WM tasks. Half of the sample received adaptive training (i.e., individually adjusted task difficulty), whereas the other half-worked on the same task material but on a low task difficulty level (active controls). Performance was assessed using criterion, near-transfer, and far-transfer tasks before training, after 5 weeks of intervention, as well as after a 3-month follow-up interval. Results indicate that (a) adaptive training generally led to larger training gains than low-level practice, (b) training and transfer gains were somewhat greater for younger than for older adults in some tasks, but comparable across age groups in other tasks, (c) far-transfer was observed to a test on sustained attention and for a self-rating scale on cognitive functioning in daily life for both young and old, and (d) training gains and transfer effects were maintained across the 3-month follow-up interval across age.
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| 15. |
- Brown, Ian, et al.
(author)
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L-Band Polarimetric Target Decomposition of Mangroves of the Rufiji Delta, Tanzania
- 2016
-
In: Remote Sensing. - : MDPI AG. - 2072-4292. ; 8:2
-
Journal article (peer-reviewed)abstract
- The mangroves of the Rufiji Delta are an important habitat and resource. The mangrove forest reserve is home to an indigenous population and has been under pressure from an influx of migrants from the landward side of the delta. Timely and effective forest management is needed to preserve the delta and mangrove forest. Here, we investigate the potential of polarimetric target decomposition for mangrove forest monitoring and analysis. Using three ALOS PALSAR images, we show that L-band polarimetry is capable of mapping mangrove dynamics and is sensitive to stand structure and the hydro-geomorphology of stands. Entropy-alpha-anisotropy and incoherent target decompositions provided valuable measures of scattering behavior related to forest structure. Little difference was found between Yamaguchi and Arii decompositions, despite the conceptual differences between these models. Using these models, we were able to differentiate the scattering behavior of the four main species found in the delta, though classification was impractical due to the lack of pure stands. Scattering differences related to season were attributed primarily to differences in ground moisture or inundation. This is the first time mangrove species have been identified by their scattering behavior in L-band polarimetric data. These results suggest higher resolution L-band quad-polarized imagery, such as from PALSAR-2, may be a powerful tool for mangrove species mapping.
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| 16. |
- Burman, Joseph, et al.
(author)
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Revealing hidden species distribution with pheromones: the caseof Synanthedon vespiformis (Lepidoptera: Sesiidae) in Sweden
- 2016
-
In: Journal of Insect Conservation. - : Springer Science and Business Media LLC. - 1366-638X .- 1572-9753. ; 20:1, s. 11-21
-
Journal article (peer-reviewed)abstract
- Synanthedon vespiformis L. (Lepidoptera:Sesiidae) is considered a rare insect in Sweden, discoveredin 1860, with only a few observations recorded until a sexpheromone attractant became available recently. This studydetails a national survey conducted using pheromones as asampling method for this species. Through pheromonetrapping we captured 439 specimens in Southern Sweden at77 sites, almost tripling the number of previously reportedrecords for this species. The results suggest that S. vespiformisis truly a rare species with a genuinely scattereddistribution, but can be locally abundant. Habitat analyseswere conducted in order to test the relationship betweenhabitat quality and the number of individuals caught. InSweden, S. vespiformis is thought to be associated with oakhosts, but our attempts to predict its occurrence by theabundance of oaks yielded no significant relationships. Wetherefore suggest that sampling bias and limited knowledgeon distribution may have led to the assumption that thisspecies is primarily reliant on oaks in the northern part ofits range, whereas it may in fact be polyphagous, similar toS. vespiformis found as an agricultural pest in Central andSouthern Europe. We conclude that pheromones canmassively enhance sampling potential for this and otherrare lepidopteran species. Large-scale pheromone-basedsurveys provide a snapshot of true presences and absencesacross a considerable part of a species national distributionrange, and thus for the first time provide a viable means ofsystematically assessing changes in distribution over timewith high spatiotemporal resolution.
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| 17. |
- Caretta, Martina Angela, et al.
(author)
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Labour, climate perceptions and soils in the irrigation systems in Sibou, Kenya & Engaruka, Tanzania
- 2014
-
Reports (other academic/artistic)abstract
- This booklet presents the results of a 4 years project (2011-2015) by four geographers from the university of Stockholm. This research took place in two small villages: Sibou, Kenya and Engaruka, Tanzania. The overall project looks at three variables: soil, climate and labor. These aspects can give an indication of the type of changes that happened in these irrigation systems and what have been the triggers behind them. In this booklet results are presented according to location and focus on: agricultural practices, women´s and men´s labor tasks, soil and water characteristics, adaptation weather variability and how all of these aspects have changed over time.
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| 18. |
- Caretta, Martina Angela, et al.
(author)
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Soil management and soil properties in a Kenyan smallholder irrigation system on naturally low-fertile soils
- 2018
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In: Applied Geography. - : Elsevier BV. - 0143-6228 .- 1873-7730. ; 90, s. 248-256
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Journal article (peer-reviewed)abstract
- In this study we examine the impact of soil management practices on soil properties in a landscape with naturally relatively poor soils on and below the dry slopes of a Rift Valley escarpment in Kenya that have been dominated by extensive smallholder investments in canal irrigation over the last 300 years. We show that farmers in the area have been able to keep up agricultural production in the face of growing population. The actual practices of soil management at one moment in time appear to be of minor importance to soil improvement, as indicated by the low correlation between Soil Management Index (SMI) and soil chemical data. However, cultivation triggers a process of slow soil improvement manifested by a positive correlation between nutrient levels and duration of irrigated cultivation and soil management, which likely explains farmers' confidence in soil productivity. However, we also identify sodicity as a risk connected to intensified irrigation in the area. Finally, we stress the need for further studies integrating investigations of local irrigation and soil management with soil and water quality analyses. These will be crucial to shape sustainable place-based and farmer-led solutions for African agricultural growth.
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| 19. |
- Chowdhury, Sohini Roy, et al.
(author)
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Automated Augmentation with Reinforcement Learning and GANs for Robust Identification of Traffic Signs using Front Camera Images
- 2019
-
In: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. - 9781728143002 ; 2019-November, s. 79-83
-
Conference paper (peer-reviewed)abstract
- Traffic sign identification using camera images from vehicles plays a critical role in autonomous driving and path planning. However, the front camera images can be distorted due to blurriness, lighting variations and vandalism which can lead to degradation of detection performances. As a solution, machine learning models must be trained with data from multiple domains, and collecting and labeling more data in each new domain is time consuming and expensive. In this work, we present an end-to-end framework to augment traffic sign training data using optimal reinforcement learning policies and a variety of Generative Adversarial Network (GAN) models, that can then be used to train traffic sign detector modules. Our automated augmenter enables learning from transformed nightime, poor lighting, and varying degrees of occlusions using the LISA Traffic Sign and BDD-Nexar dataset. The proposed method enables mapping training data from one domain to another, thereby improving traffic sign detection precision/recall from 0.70/0.66 to 0.83/0.71 for nighttime images.
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| 20. |
- Dahlin, Sandra, et al.
(author)
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Chemical aging of Cu-SSZ-13 SCR catalysts for heavy-duty vehicles –Influence of sulfur dioxide
- 2018
-
In: Catalysis Today. - Amsterdam : Elsevier. - 0920-5861 .- 1873-4308. ; 320, s. 72-83
-
Journal article (peer-reviewed)abstract
- Selective catalytic reduction of nitrogen oxides is an efficient technique for emission abatement in heavy-dutyvehicles. Cu-SSZ-13 SCR catalysts are more active than vanadium-based catalysts at low temperatures, but aremore sensitive to deactivation by sulfur. Consequently, there is a need to study poisoning by sulfur for thiscatalyst material. This experimental investigation focuses on the effect of sulfur on the low-temperature per-formance of Cu-SSZ-13 SCR catalysts. The effect of sulfur exposure temperature, and the influence of the NO 2 /NO x ratio, are considered and two different regeneration temperatures are compared. In addition, catalystsamples from an engine-aged catalyst are evaluated. The SO 2 exposure temperature is shown to have an im-portant impact on the deactivation of the Cu-SSZ-13 catalyst. The lowest sulfur exposure temperature (220 °C)results in the most severe deactivation, while the highest temperature during sulfur exposure (400 °C) results inthe lowest degree of deactivation. This was found to be related to the amount of sulfur on the catalyst.Additionally, SO 2 exposure was shown to decrease the N 2 O selectivity. The engine-aged catalyst has a decreasedperformance in terms of both decreased activity and increased N 2 O selectivity. For this catalyst, impurities fromfuel and engine-oil can play a role in the deactivation. Different deactivation mechanisms are seen for the lab-and engine-aged catalysts.
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| 21. |
- Duenas Dobrowolski, Jan, et al.
(author)
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Experimental Study of Lubricating Grease Flow inside the Gap of a Labyrinth Seal Using Microparticle Image Velocimetry
- 2018
-
In: Tribology Transactions. - : Taylor & Francis. - 1040-2004 .- 1547-397X. ; 61:1, s. 31-40
-
Journal article (peer-reviewed)abstract
- In this study, the flow of lubricating greases in a labyrinth seal geometry is studied using microparticle image velocimetry (µPIV). The aim is to evaluate the grease velocity distribution inside the gap of a labyrinth seal and to find a relationship between the grease consistency and the transferred speed from the rotating ring in order to choose the correct grease as a sealing medium. In addition, the grease flow characteristics are important for the understanding of fracture due to grease layer displacement. For these purposes, four greases with different rheological properties were used in µPIV experiments. It was found that the grease consistency plays a crucial role in speed development as well as the grease composition and presence of a slip effect at the grease–rotating wall interface.
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| 22. |
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| 23. |
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| 24. |
- Farré-Lladós, Josep, et al.
(author)
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New method for lubricating wind turbine pitch gears using embedded micro-nozzles
- 2017
-
In: Journal of Mechanical Science and Technology. - : Springer. - 1738-494X .- 1976-3824. ; 31:2, s. 797-806
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Journal article (peer-reviewed)abstract
- The increase of power generated by wind turbines has increased the stresses applied in all of its components, thereby causing premature failures. Particularly, pitch and yaw gears suffer from excessive wear mainly caused by inappropriate lubrication. This paper presents a novel method to automatically lubricate the wind turbine pitch gear during operation. A micro-nozzle to inject fresh grease continuously between the teeth in contact was designed, manufactured, and installed in a test bench of a 2 MW wind turbine pitch system. The test bench was used to characterize the fatigue behavior of the gear surface using conventional wind turbine greases under real cyclic loads. Measurements of wear evolution in a pitch gear with and without micro-nozzle show a decrease of 70 % of the wear coefficient after 2×104 cycles.
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| 25. |
- Farré-Lladós, Josep, et al.
(author)
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New solution to preent excessive wear in wind turbine gears
- 2014
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In: Society of Tribologists and Lubrication Engineers Annual Meeting and Exhibition 2014. - : Society of Tribologists and Lubrication Engineers. - 9781634391351 ; , s. 548-550
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Conference paper (peer-reviewed)
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| 26. |
- Farré-Lladós, Josep, et al.
(author)
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The use of Rapid Prototyping techniques (RPT) to manufacture micro channels suitable for high operation pressures and µPIV
- 2016
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In: Rapid prototyping journal. - 1355-2546 .- 1758-7670. ; 22:1, s. 67-76
-
Journal article (peer-reviewed)abstract
- Purpose– This paper aims to present a new methodology to manufacture micro-channels suitable for high operating pressures and micro particle image velocimetry (μPIV) measurements using a rapid-prototyping high-resolution 3D printer. This methodology can fabricate channels down to 250 μm and withstand pressures of up to 5 ± 0.2 MPa. The manufacturing times are much shorter than in soft lithography processes. Design/methodology/approach– The novel manufacturing method developed takes advantage of the recently improved resolution in 3D printers to manufacture an rapid prototyping technique part that contains the hose connections and a micro-channel useful for microfluidics. A method to assemble one wall of the micro-channel using UV curable glue with a glass slide is presented – an operation required to prepare the channel for μPIV measurements. Once built, the micro-channel has been evaluated when working under pressure and the grease flow behavior in it has been measured using μPIV. Furthermore, the minimum achievable channels have been defined using a confocal microscopy study. Findings– This technique is much faster than previous micro-manufacturing techniques where different steps were needed to obtain the micro-machined parts. However, due to current 3D printers ' resolutions (around 50 μm) and according to the experimental results, channels smaller than 250-μm2 cross-section should not be used to characterize fluid flow behaviors, as inaccuracies in the channel boundaries can deeply affect the fluid flow behavior. Practical implications– The present methodology is developed due to the need to validate micro-channels using μPIV to lubricate critical components (bearings and gears) in wind turbines. Originality/value– This novel micro-manufacturing technique overcomes current techniques, as it requires less manufacturing steps and therefore it is faster and with less associated costs to manufacture micro-channels down to 250-μm2 cross-section that can withstand pressures higher than 5 MPa that can be used to characterize microfluidic flow behavior using μPIV.
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| 27. |
- Green, Torbjörn M., et al.
(author)
-
A new method to visualize grease flow in a double restriction seal using microparticle image velocimetry
- 2011
-
In: Tribology Transactions. - : Informa UK Limited. - 1040-2004 .- 1547-397X. ; 54, s. 784-792
-
Journal article (peer-reviewed)abstract
- A new method to visualize and quantify grease flow in between two sealing lips or, in general, a double restriction seal is presented. Two setups were designed to mimic different types of seals; that is, a radial and an axial shaft seal. The flow of the grease inside and in between the sealing restrictions was measured using microparticle image velocimetry. The results show that grease flow due to a pressure difference mainly takes place close to the rotating shaft surface with an exponentially decaying velocity profile in the radial direction. Consequently, contaminants may be captured in the stationary grease at the outer radius, which explains the sealing function of the grease.
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| 28. |
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| 29. |
- Guerrero, José-Luis, 1977-, et al.
(author)
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Exploring the hydrological robustness of model-parameter values with alpha shapes
- 2013
-
In: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 49:10, s. 6700-6715
-
Journal article (peer-reviewed)abstract
- Estimation of parameter values in hydrological models has gradually moved from subjective, trial-and-error methods into objective estimation methods. Translation of nature's complexity to bit operations is an uncertain process as a result of data errors, epistemic gaps, computational deficiencies, and other limitations, and relies on calibration to fit model output to observed data. The robustness of the calibrated parameter values to these types of uncertainties is therefore an important concern. In this study, we investigated how the hydrological robustness of the model-parameter values varied within the geometric structure of the behavioral (well-performing) parameter space with a depth function based on α shapes and an in-depth posterior performance analysis of the simulations in relation to the observed discharge uncertainty. The α shape depth is a nonconvex measure that may provide an accurate and tight delimitation of the geometric structure of the behavioral space for both unimodal and multimodal parameter-value distributions. WASMOD, a parsimonious rainfall-runoff model, was applied to six Honduran and one UK catchment, with differing data quality and hydrological characteristics. Model evaluation was done with two performance measures, the Nash-Sutcliffe efficiency and one based on flow-duration curves. Deep parameter vectors were in general found to be more hydrologically robust than shallow ones in the analyses we performed; model-performance values increased with depth, deviations to the observed data for the high-flow aspects of the hydrograph generally decreased with increasing depth, deep parameter vectors generally transferred in time with maintained high performance values, and the model had a low sensitivity to small changes in the parameter values. The tight delimitation of the behavioral space provided by the α shapes depth function showed a potential to improve the efficiency of calibration techniques that require further exploration. For computational reasons only a three-parameter model could be used, which limited the applicability of this depth measure and the conclusions drawn in this paper, especially concerning hydrological robustness at low flows.
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| 30. |
- Guerrero, Jose-Luis, et al.
(author)
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Temporal variability in stage-discharge relationships
- 2012
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In: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 446, s. 90-102
-
Journal article (peer-reviewed)abstract
- Although discharge estimations are central for water management and hydropower, there are few studies on the variability and uncertainty of their basis; deriving discharge from stage heights through the use of a rating curve that depends on riverbed geometry. A large fraction of the world's river-discharge stations are presumably located in alluvial channels where riverbed characteristics may change over time because of erosion and sedimentation. This study was conducted to analyse and quantify the dynamic relationship between stage and discharge and to determine to what degree currently used methods are able to account for such variability. The study was carried out for six hydrometric stations in the upper Choluteca River basin, Honduras, where a set of unusually frequent stage-discharge data are available. The temporal variability and the uncertainty of the rating curve and its parameters were analysed through a Monte Carlo (MC) analysis on a moving window of data using the Generalised Likelihood Uncertainty Estimation (GLUE) methodology. Acceptable ranges for the values of the rating-curve parameters were determined from riverbed surveys at the six stations, and the sampling space was constrained according to those ranges, using three-dimensional alpha shapes. Temporal variability was analysed in three ways: (i) with annually updated rating curves (simulating Honduran practices), (ii) a rating curve for each time window, and (iii) a smoothed, continuous dynamic rating curve derived from the MC analysis. The temporal variability of the rating parameters translated into a high rating-curve variability. The variability could turn out as increasing or decreasing trends and/or cyclic behaviour. There was a tendency at all stations to a seasonal variability. The discharge at a given stage could vary by a factor of two or more. The quotient in discharge volumes estimated from dynamic and static rating curves varied between 0.5 and 1.5. The difference between discharge volumes derived from static and dynamic curves was largest for sub-daily ratings but stayed large also for monthly and yearly totals. The relative uncertainty was largest for low flows but it was considerable also for intermediate and large flows. The standard procedure of adjusting rating curves when calculated and observed discharge differ by more than 5% would have required continuously updated rating curves at the studied locations. We believe that these findings can be applicable to many other discharge stations around the globe.
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| 31. |
- Hai, Ling
(author)
-
Hydrodynamic Modelling of Wave Power using Electrical Equivalent Circuit Theory
- 2014
-
Licentiate thesis (other academic/artistic)abstract
- Ocean wave energy can be harnessed and converted into electric energy nowadays. This provides a possibility for populations that live on islands or along coastlines to utilize the renewable and safe power produced by ocean waves. Point absorbing wave energy converter (WEC) is one example of such devices for electrical power production from ocean waves. It is composed of a floating buoy on the water surface, and a linear generator that sits on seabed and is connected with the buoy via a line. Electricity is generated when the buoy moves up and down in the waves.The geometry and dimensions of the floating buoy have dominant influences on the energy absorption. This thesis introduces an equivalent electric circuit for modelling the hydrodynamic interaction between the wave and a cylindrical buoy. The model allows a rapid assessment of the velocity, force in the connection line and output power, by which the system design and optimization can be performed faster and easier.The electric circuit model is based on the WEC's dynamic force analysis, and the electric components' parameters are determined from analytical approximations of the hydrodynamic coefficients. The simulation results of the equivalent circuit for one typical wave climate in Lysekil has been presented, and the results indicate a good fitting with former experimental results.The thesis also includes a hydrodynamic study for a torus shaped buoy, which aims at applying a theoretical background for a force measurement experiment. A comparison has been conducted between the torus buoy and two similar cylindrical buoys. Preliminary WAMIT simulation results demonstrate that the force in the connection line will be 5% bigger by using the torus buoy. It is also found that the torus buoy is advantageous for its larger excitation force and smaller added mass. A brief introduction of the 500kN force measurement system and the communication test have been introduced as well.
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| 32. |
- Hamedi, Naser, et al.
(author)
-
Modelling of Flexible Fibres in Viscous Fluid Flow
- 2019
-
Conference paper (peer-reviewed)abstract
- The current study relates to the development of a multiphase model of flexible fibre suspensions. An understanding of the rheology and dynamics of the deformation of such suspension is desirable in order to be able to fully disclose the flow behaviour from very low to very high shear rates. We present an approach for numerically simulating the dynamics of flexible fibres employing a particle-level method. This is performed by investigating the fibre dynamics against several orbit classes - i.e. rigid, springy, flexible and complex rotation of the fibres [1-3] enabling the model to have all degrees of freedom (translation, rotation, bending and twisting). The three-dimensional Navier-Stokes equations which describes the fluid motion are employed while the fibrous phase of the fluid is modeled as chains of fiber segments interacting with the fluid through viscous- and drag forces. The simulations are performed using OpenFOAM and the numerical outcomes are validated against experimental data.The purpose of the modelling framework applied in this work is to enable the numerical model to be extended to a 4-way coupling model, capturing shear thinning, shear thickening and the yield stress properties of a fibrous fluid suspension.
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| 33. |
- Hamedi, Naser, et al.
(author)
-
On the deformation of fibrous suspensions
- 2019
-
Conference paper (peer-reviewed)abstract
- An understanding of the rheology and dynamics of the deformation of fibrous suspension as a multiphase fluid is important in order to be able to fully disclose the flow behaviour from very low to very high shear rates. In this study, a flexible fibre model has been implemented in an open source Computational Fluid Dynamics code. The three-dimensional Navier-Stokes equations which describe the fluid motion are employed while the fibrous phase of the fluid is modeled as chains of fiber segments interacting with the fluid through viscous- and drag forces. The aim of this study is to investigate the fibre dynamics against several orbit classes - i.e. rigid, springy, flexible and complex rotation of the fibres1-3 enabling the model to have all degrees of freedom - translation, rotation, bending and twisting. The simulations are performed using the OpenFOAM open source software.
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| 34. |
- Hamedi, Naser, et al.
(author)
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On the Interaction of Side-By-Side Circular Cylinders in Viscoplastic Fluids
- 2019
-
In: Fluids. - : MDPI. - 2311-5521. ; 4:2
-
Journal article (peer-reviewed)abstract
- In this paper, the static interaction of a train of three cylinders in a Bingham fluid is studiednumerically using Computational Fluid Dynamics. The variation of drag forces for the cylinders inseveral configurations is investigated. Positions of the particles in relation to the reference particleare recognized by the separation distance between the cylinders. A steady state field is considered,with Bingham numbers between 5 and 150. Several separation distances (d) were considered, such that2.0D d 6.0D where D is the cylinder diameter. The Reynolds number was chosen in the range of5 Re 40. In particular, the eect of the separation distance, Reynolds number and Bingham numberon the shape and size of the unyielded regions was investigated. The functional dependence of thisregion and the drag coecient is explored. The present results reveal the significant influence of thegap between the cylinders on the drag force and the shape of the unyielded regions surrounding thecylinders. It was found that there are several configurations in which the drag forces over the first andthe third cylinders are almost equal depending on variation of the Bi, Re and the separation distance.
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| 35. |
- Higgins, Lindsey, 1985-
(author)
-
Linking lake variability, climate, and human activity in Basotu, Tanzania
- 2017
-
Doctoral thesis (other academic/artistic)abstract
- Paleoenvironmental investigations establish important baseline knowledge of the natural variability of lake systems, to better understand human impacts on the landscape, and the effects of climate change on water resources. By combining long-term environmental history with investigations into modern land use patterns and climatological events, a wider perspective can be reached that has practical applications in water governance. This thesis presents a case study of Lake Basotu (4.37°S, 35.07°E), a crater lake in the Hanang district of north-central Tanzania, which acts as an important source of freshwater for local people. A three-meter long sediment core from an interior crater of Lake Basotu was investigated using proxy records (diatoms, magnetic parameters, and carbon content) and radiometric dating (14C and 210Pb). The Lake Basotu record was then compared to other sediment-based reconstructions from East Africa and records of historical famines to better place it into the timeline and understanding of regional climate dynamics. This work was extended into modern times (1973–2015) by examining lake extent variations in the Landsat satellite archive. Shoreline boundaries for dry-season images were delineated and lake extent was calculated using GIS techniques. This remote sensing record was compared to climatological patterns, meteorological records, and the history of land-use changes in the surrounding district. As a whole, the Lake Basotu record indicates that major fluctuations in lake level are not abnormal; however, human influence has likely increased the lake’s sensitivity to climatic fluctuations. The timing of historical famines in East Africa were linked to periods of shallow lake conditions in Basotu, and the duration of the most extreme lake level changes correlate to a reversal in the 14C age-depth model. Recent variations in lake extent are likely connected to a mechanized wheat farming program implemented in the district as a foreign aid project in the early 1960s. To support the work done in Basotu, a preliminary investigation of sediment from the nearby Lake Babati was undertaken. Sediment from the two lakes indicates that their geographical location may be in a transition zone towards dryer conditions to the south during the Little Ice Age in East Africa. The results of this thesis support that Lake Basotu is an important location for understanding the potential impacts of climate change and human activity on water resources in this region.
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| 36. |
- Higgins, Lindsey, et al.
(author)
-
Surface Area Variability of a North-Central Tanzanian Crater Lake
- 2016
-
In: Geosciences. - : MDPI AG. - 2076-3263. ; 6:2
-
Journal article (peer-reviewed)abstract
- A history of modern (1973–2015) surface area variability for Lake Basotu in north-central Tanzania has been reconstructed using archived Landsat images from the dry season between June and October. This record was compared to local weather data as well as larger scale weather patterns. The lake has been in a state of decline interrupted by major flood events since the beginning of the satellite record. From 1973 to 1997, the lake area was between 0.97 km2 and 4.28 km2. Lake extent abruptly increased to 13.86 km2 in 1998, when a co-occurrence of El Niño and a positive Indian Ocean Dipole led to extensive flooding. It is hypothesized that local agricultural practices leading to soil erosion and subsequent basin sedimentation have most likely increased the sensitivity of Lake Basotuto climatic fluctuations.
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| 37. |
- Jacobsson, Lars, et al.
(author)
-
Health-related quality-of-life and life satisfaction 6-15 years after traumatic brain injuries in northern Sweden
- 2010
-
In: Brain Injury. - : Informa UK Limited. - 1362-301X .- 0269-9052. ; 24:9, s. 1075-1086
-
Journal article (peer-reviewed)abstract
- Objective: To describe health-related quality-of-life (HRQoL) and life satisfaction many years after a traumatic brain injury (TBI) and assess possible associations with variables related to the time of injury and follow-up and the individuals' self-appraisal of the impact of the TBI. Method: Sixty-seven individuals (18-65 years), on average 10 years post-injury, were interviewed. Data on HRQoL, using the SF-36 questionnaire, were compared with a Swedish age-and sex-matched reference sample, and life satisfaction, using the Satisfaction With Life Scale (SWLS), were compared with a nationwide Swedish sample of students. The participant's self-appraisal of the TBI was assessed with two supplementary questions. Data were analysed with hierarchical multiple regression analyses. Results: HRQoL as well as life satisfaction were lower compared with the reference samples. From the regression analyses, the individuals' own appraisal of the impact of the TBI and whether they were vocationally productive or not were strongly associated with their current physical health and life satisfaction. Conclusion: These results confirm the importance of TBI as a cause of long-term disability and the impact of the injury on the individuals' self-perceived values of health, quality-of-life and life satisfaction.
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| 38. |
- Jacobsson, Lars, et al.
(author)
-
Sense of coherence and disability and the relationship with life satisfaction 6-15 years after traumatic brain injury in northern Sweden
- 2011
-
In: Neuropsychological Rehabilitation. - : Informa UK Limited. - 0960-2011 .- 1464-0694. ; 21:3, s. 383-400
-
Journal article (peer-reviewed)abstract
- The objective of the study was to assess sense of coherence (SOC) many years after traumatic brain injury (TBI) and explore the relationship between SOC and self-rated life satisfaction (LS) as well as measures of functioning and disability, sex, age at injury, injury severity and time post-injury. Sixty-six individuals (aged 18-65 years) who were 6-15 years post-injury were interviewed. Data on SOC (SOC-13 item scale), measures of functioning and disability (Mayo-Portland Adaptability Inventory, MPAI-4), LS (Satisfaction with Life Scale, SWLS), and sex, age at injury, injury severity and time post-injury were analysed with hierarchical multiple regression analyses. The results showed that SOC in the study group did not differ from the general population and was strongly associated with LS. Regression analyses revealed that emotional factors, social participation, SOC, and time since injury, were more influential than sex, age at injury, and injury severity in explaining LS. It was concluded that SOC in this group of individuals with TBI who were many years post-injury was similar to nondisabled individuals. SOC, together with emotional factors, social participation and injury-related factors, were determinants of LS. These results confirm that LS after TBI is a complex phenomenon dependent on several factors that are important targets for rehabilitation professionals.
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| 39. |
- Johansson, Simon, et al.
(author)
-
Characteristics of flow and temperature distribution in a Ruthner process
- 2010
-
In: Proceedings of Modeling for Material Processing, 6th International Scientific Colloquium. - : University of Latvia Press. ; , s. 317-322
-
Conference paper (peer-reviewed)abstract
- This study is devoted to CFD modelling of the gas flow and particle dynamics inside the reactor of a furnace used for regeneration of hydrochloric acid from iron chloride - a rest product from the pickling process in the steel industry. The understanding of the dynamics inside the reactor has shown to be of great importance in order to optimize the process. So far the process has been a black box, where only the inflow conditions are known together with the quality of the final product. In this work the gas flow is resolved together with the thermal distribution and the particle trajectory for the injected acid molecules.
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| 40. |
- Johansson, Simon, et al.
(author)
-
Gas and particle flow in a spray roaster
- 2014
-
In: Journal of Applied Fluid Mechanics. - 1735-3572 .- 1735-3645. ; 7:2, s. 187-196
-
Journal article (peer-reviewed)abstract
- In the steel industry, waste hydrochloric acid is produced through the process to pickle steel slabs for removal of corrosion. Regenerated hydrochloric acid is obtained by separating the chloride gas from the waste product through spray roasting. This process also produces a by-product in the form of iron oxide which is sold to different industries. The present study is a continuation of a study arising from the need to better understand the dynamics inside the regeneration reactor, which in turn will improve possibilities to optimize the regeneration process, which to date has been manually adjusted by trial and error. In this study the velocity and temperature distribution inside the reactor is numerically modelled together with the droplet motion through the reactor. The main objective is to investigate the influence of a changed spray nozzle position on the flow characteristics of the continuous and dispersed phase, and the relation between temperature and energy efficiency and the regeneration process. Numerical models of the type of flow present in the regeneration reactor are not represented to any major extent in the literature, making the present study relevant to the engineers and researchers active in the steel industry and the application in question.
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| 41. |
- Johansson, Simon, et al.
(author)
-
Simuleringar av dyspositionens inverkan på flöde och temperturdistribution i en ruthner process
- 2011
-
Conference paper (other academic/artistic)abstract
- Saltsyra (HCl) används inom stålindustrin för att beta järnoxider (Fe2O3) efter varmvalsning av plåt innan den förädlas i produktionslinan. Stora mängder HCl förbrukas, vilket både är kostsamt och miljöfarlig om den inte återvinns. Återvinningen sker oftast på stålverken med en metod som kallas Ruthner process. Den kan illustreras av en cylindrisk ugn med konisk nedre del, där det strax ovanför den koniska delen sitter naturgasbrännare tangentiellt till ugnen. Den förbrukade saltsyran, som består av vatten (H2O) och järnklorid (FeCl2), tillförs genom en till fyra dysor i toppen av ugnen. Återvinningen sker - något förenklat - genom att H2O först förångas från dropparna, därefter reagerar FeCl2 med syre (O2) och H2O och bildar HCl och Fe2O3. HCl återförs till betningsprocessen och Fe2O3 kan exempelvis säljas till elektronikindustrin.Denna studie syftar till att öka förståelsen av processen så att det i framtiden är möjligt att säkerställa god kvalité av restprodukten Fe2O3. Simuleringar görs i Ansys CFX med en tvåvägskopplad Euler/Lagrange-ansats där Eulerfasen består av gas och dropparna av förbrukad HCl är på Lagrangeform. Produkten från naturgasbrännarna ges som randvillkor till inloppet. I modellen är det första steget i återvinningsprocessen då droppar förångas implementerad. Även lyftkraft p.g.a. olika gastemperaturer, energiförluster genom väggar, och dragkraft på partiklar är implementerade i modellen. Som turbulensmodell används k-ε.Ur Figur 2 ses att både temperaturfördelning och hastighetsprofil förändras med olika dyspositioner. En korrelation mellan bilderna finns; i områden med låg temperatur är hastigheten riktad nedåt. Med dysan placerad 3,5 m från centrum förskjuts dock området för negativ vertikal hastighet bort från väggen. Detta beroende på att den varma gasen från brännare stiger längs väggen. De stora skillnaderna i temperaturfördelning är att dysposition 0.5 m från centrum ger en hög utloppstemperatur samt att dysposition 0.5 m och 3.5 m ger en högre temperatur i botten. Tendensen i hastighetsprofilen är lika för de tre fallen med dysan närmast väggen. När dysan placeras i mitten blir det ett kallras i centrum. För att få en klarare bild av processen krävs det även att partiklar analyseras samt att i framtiden även implementera kemiska reaktioner.
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| 42. |
- Jonason, Dennis, et al.
(author)
-
Land-use history exerts long-term effects on the clear-cut flora in boreonemoral Sweden
- 2016
-
In: Applied Vegetation Science. - : WILEY-BLACKWELL. - 1402-2001 .- 1654-109X. ; 19:4, s. 634-643
-
Journal article (peer-reviewed)abstract
- QuestionsCan signs of 19th century grassland management, which can be observed in the flora immediately (2-4yrs) after clear-cutting in boreonemoral Sweden, still remain 4yrs later? Do the effects from the time since clear-cutting differ between forest and grassland plant species? LocationProvince of ostergotland, southern Sweden. MethodsTwelve contemporary clear-cut areas that were once meadows and 12 that were once forests were selected using land-use maps from the 1870s. Grasses and herbaceous plants were surveyed twice, once in 2009 and once in 2013 (2-4 and 6-8yrs after clear-cutting, respectively). Plant presence was recorded within 100 circular sample plots (radius 1m) placed evenly throughout each respective clear-cut area along transects spaced 25-m apart. The number of sample plots in which a species was present was taken as a measure of that species frequency. Random effects meta-analysis, odds ratios and ANCOVA were used to analyse species responses to clear-cutting over time. ResultsA total of 170 plant species were found in the study, of which 33 were classified as grassland indicator species and 31 as plants primarily confined to forests. Clear-cut areas with a history as meadowland had, on average, up to 64% higher total species richness and 110% more grassland indicator species than did clear-cut areas with a history as forest. The time since clear-cutting had no effect on total species richness. However, the odds of finding a grassland indicator species decreased with the time since clear-cutting, whereas the odds of finding a forest species increased. ConclusionsWe concluded that land-use history plays an important role in explaining the flora found in Swedish clear-cuts, and that its effects on species richness remain for a minimum of 8yrs after harvest (conservative estimate). This phenomenon highlights the importance of acknowledging land-use legacies in ecological research and conservation. Future studies should investigate various options for the promotion of grassland plants in clear-cuts with a history of grassland management while also acknowledging the potential conflicts between conservation and production. The results may pertain to other countries with similar land-use histories.
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| 43. |
- Jonason, Dennis, et al.
(author)
-
Vegetation in clear-cuts depends on previous land use : a century-old grassland legacy
- 2014
-
In: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 4:22, s. 4287-4295
-
Journal article (peer-reviewed)abstract
- Plant species richness in central and northern European seminatural grasslandsis often more closely linked to past than present habitat configuration, which isindicative of an extinction debt. In this study, we investigate whether signs ofhistorical grassland management can be found in clear-cuts after at least80 years as coniferous production forest by comparing floras between clear-cutswith a history as meadow and as forest in the 1870s in Sweden. Study sites wereselected using old land-use maps and data on present-day clear-cuts. Speciestraits reflecting high capacities for dispersal and persistence were used toexplain any possible links between the plants and the historical land use. Clearcutsthat were formerly meadow had, on average, 36% higher species richnessand 35% higher richness of grassland indicator species, as well as a larger overallseed mass and lower anemochory, compared to clear-cuts with history asforest. We suggest that the plants in former meadows never disappeared afterafforestation but survived as remnant populations. Many contemporary forestsin Sweden were managed as grasslands in the 1800s. As conservation of remaininggrassland fragments will not be enough to reduce the existing extinctiondebts of the flora, these young forests offer opportunities for grassland restorationat large scales. Our study supports the concept of remnant populationsand highlights the importance of considering historical land use for understandingthe distribution of grassland plant species in fragmented landscapes, aswell as for policy-making and conservation.
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| 44. |
- Karami, Fatemeh, et al.
(author)
-
Nano-fluid flow in a catheterized tapered artery : Consistent couple stress-theory and wall slip
- 2019
-
In: Journal of thermal analysis and calorimetry (Print). - : Springer. - 1388-6150 .- 1588-2926. ; 137:1, s. 327-342
-
Journal article (peer-reviewed)abstract
- This study was conducted with the aim of investigating the Newtonian nanofluid flow in a catheterized tapered artery through using a completely consistent couple stress theory. In the process of carrying out this study, the slip condition at the arterial wall and the catheter, as well as, the permeability was taken into account. Further, the velocity, temperature, and concentration profiles were analytically modeled and the effect of the length scale on these profiles was well presented through the way it influences small-scale flows. The effect of the slip condition at the artery and catheter walls on the velocity was also investigated and revealed that any increase in the velocity leads to an increase in the slip velocity. Furthermore, the effect of other parameters such as the catheter diameter, shape, and height of the stenosis on these profiles was explored for all three artery geometries, i.e., diverging tapered artery, converging tapered artery, and non-tapered artery, respectively. The findings suggested that any increase in the catheter diameter and stenosis height can decrease the velocity and nanoparticle concentration profiles, while the temperature profile increases. It was also found that by increasing the stenosis shape parameter the velocity and concentration profiles increase and temperature decreases.
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| 45. |
- Karlsson, Tommy, et al.
(author)
-
Biogeografisk uppföljning av kärrtrollsländor och dykarskalbaggar – habitatvalsanalys, stickprovsdesign, inventeringsmetodik och inventering 2016
- 2017
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Reports (other academic/artistic)abstract
- För arter som ingår i EUs habitatdirektiv ska bevarandestatus rapporteras till EU vart 6:e år. För att en tillförlitlig och effektiv rapportering ska kunna göras bedriver Naturvårdsverket s.k. biogeografisk uppföljning. Syftet är att på nationell nivå samla in tillräckligt med data för att kunna uppskatta populationsstorlek, utbredningsområde och status för de ingående arterna. Denna rapport syftar till att fungera som underlag för biogeografisk uppföljning av fem arter i delsystemet trollsländor och dykarskalbaggar: pudrad kärrtrollslända Leucorrhinia albifrons, bred kärrtrollslända Leucorrhinia caudalis, citronfläckad kärrtrollslända Leucorrhinia pectoralis, bredkantad dykare Dytiscus latissimus och bred paljettdykare Graphoderus bilineatus. Rapporten redovisar följande förstudier:•Analys av arternas habitatval.•Utformning och dimensionering av stickprov.•Genomgång och utvärdering av inventeringsmetoder.•Inventering/metodiktest under 2016.Analysen av habitatval (undersökta parameterar: vattenareal, fiskförekomst, pH/alkalinitet, omgivande naturtyp och vattnets näringstyp) visar att arterna kan förekomma många olika typer av vatten, även om studien indikerar vissa preferenser hos arterna. Detta innebär att det är svårt att göra riktade eftersök av dem, särskilt då planerat upplägg inom biogeografisk uppföljning är att inventera arterna gemensamt. I princip alla slags stillastående vatten utgör potentiella habitat för åtminstone någon av arterna, men de tycks i mycket liten grad förekomma i rinnande vatten. Eftersom arterna kan påträffas i många olika typer av vatten och är utbredda över en stor del av landet föreslås att biogeografisk uppföljning av dem genomförs i ett slumpvist urval av alla 1x1 km-rutor med minst 100 meter strandlinje i södra Sverige och längs med Norrlandskusten. Med nuvarande ekonomiska resurser bedöms ca 220 rutor kunna inventeras under varje sexårsperiod. Det kommer att ta lång tid att upptäcka trender hos arterna med detta upplägg, men det kommer snabbt att ge oss värdefull information om arternas utbredning och frekvens i Sverige. Under 2016 genomfördes en första inventeringsinsats av de aktuella arterna inom den biogeografiska uppföljningen. Syftet med inventeringen var att testa stickprovsupplägg och inventeringsmetodik, och att få bättre grepp om kostnader, tidsåtgång m.m. Om allt föll väl ut avsågs också undersökningen kunna fungera som ett första provtillfälle inom uppföljningen. 47 1x1 km-rutor inventerades i västra Skåne, nordöstra Götaland, i Mälardalen och vid Norrlandskusten under juni-juli. Dykarna inventerades genom fällor och trollsländorna främst genom sök av vuxna trollsländor. Vattenhåvning efter både dykare och trollsländelarver, samt sök av larvskinn testades också, men i mindre omfattning. I 30 % av rutorna påträffades någon av arterna. Vanligast var citronfläckad kärrtrollslända och bred gulbrämad dykare som påträffades i över 10 % av rutorna. Utifrån de frekvenser av arterna påträffades i under inventeringen gjordes en första uppskattning av antalet 1x1 km-rutor som arterna förekommer i totalt i landet. Vartefter flera och flera rutor inventeras kommer sedan denna siffra bli mer och mer tillförlitlig. Utifrån den utvärdering av inventeringsmetoder som presenteras i rapporten och inventeringen under 2016 bedöms sök av vuxna trollsländor och flaskfällor för dykare som de lämpligaste inventeringsmetoderna för biogeografisk uppföljning av arterna i Sverige. Inventeringen bör utföras i juni efter att trollsländorna har kläckts. Flaskfällorna bör vittjas och tas upp efter 2-3 dagar. Trollsländorna eftersöks vid soligt och varmt väder, antingen då fällorna sätts ut eller när de tas upp. Om det inte möjligt att göra åtminstone ett av besöken vid soligt och varmt väder, kan sök av trollsländornas larvskinn användas som alternativ metod.
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| 46. |
- Kluge, Jimmy Nils Erik, et al.
(author)
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Modelling heat transfer inside an autoclave: Effect of radiation
- 2016
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In: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 35:14, s. 1126-1142
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Journal article (peer-reviewed)abstract
- In this work, computational fluid dynamics simulations are performed to predict the temperature distribution on a part during an autoclave run. Data from an experimental study are used as input to the simulations and also for comparison with the numerical results. A conjugate heat transfer approach was used for the simulations, where best agreement with experiments was obtained from the simulation that included thermal radiation and utilized an experimentally obtained velocity profile as inlet velocity. A yet more detailed inlet velocity profile and more advanced turbulent model could result in an even better agreement.
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| 47. |
- Kluge, N. E. Jimmy, et al.
(author)
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An Experimental Study of Temperature Distribution in an Autoclave
- 2016
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In: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 35:7, s. 566-578
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Journal article (peer-reviewed)abstract
- In this work, the temperature distribution on an industrial mold tool is monitored during autoclave runs with three settings. In one of the settings, the temperature and pressure follow a scheme used in real moldings, while in the other two cases, the temperature is increased as fast as possible with and without an applied pressure. The temperature difference over the tool is relatively large and varies between 29℃ and 76℃ validating a detailed investigation of the temperature at different points. Two results of this are that positions on the up-stream side of the tool are heated faster than positions down-stream and the heating over the tool is symmetric while that within is asymmetric. Roughly estimated heat transfer coefficients reveal that the temperature ramping has no significant effect on the local heat transfer coefficients while the applied pressure more than doubled them. In addition flow field measurements with particle image velocimetry are performed, revealing a very slow flow near the roof of the autoclave and a velocity peak near the floor of it, indicating that the flow profile within the autoclave and variation in heat transfer coefficients should be considered in autoclave simulations.
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| 48. |
- Kluge, NE Jimmy, et al.
(author)
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Compression moulding of sheet moulding compound : Modelling with computational fluid dynamics and validation
- 2015
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In: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 34:6, s. 479-492
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Journal article (peer-reviewed)abstract
- Compression moulding experiments of sheet moulding compound, visual observations of a vacuum test with prepregs and numerical models with two main approaches for computational fluid dynamics simulations of the mould filling phase are presen ed. One assumes that there are layers near the mould surfaces with much less viscosity and the other only use one viscosity model. The numerical experiments showed that the pressure could be accurately predicted with both approaches. The property ne essary to predict correct pressure with altered mould closing velocities was that the bulk material had to obey shear-thinni g effects. Preheating effects before compression were neglected, but altering the heating time until the prepreg was assumed to start flow had a significant effect. The experiments confirmed that the pressure is predominantly affected by the mould c osing velocity. Regardless of the considered process settings, a first pressure top always appeared approximately at the logarithmic strain 0.25. A second top was associated with a slowdown of the press. The location of this was affected by the velocity and the vacuum, the latter indicating that vacuum assistance prevents a build-up of back pressure. Furthermore, heated prepreg above a critical temperature is observed to swell immediately as vacuum assistance is applied.
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| 49. |
- Li, Jinxia, et al.
(author)
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Design of test rig for visualizations of cylindrical shear and pressure driven Couette flow using μPIV
- 2014
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Conference paper (peer-reviewed)abstract
- Couette flow is often encountered in concentric cylinder application such as rheometers etc. Being able to visualize such flows is of interest both from a fundamental point of view to understand the dynamics of complex fluids, but also in specific applications such as lubricants flowing through seal geometries. In this study a concentric cylinder test rig has been designed to visualize Couette flow in both radial and axial direction using micro Particle Image Velocimetry. The rig allows for control of the flow motion; the rotating inner cylinder creates a peripheral flow and an applied pressure in the axial direction creates a pressure driven flow. Thus, a single flow direction or a combination of directions can be analyzed. To demonstrate the technique a flow of a non-Newtonian shear thinning fluid in the form of lubricating grease was investigated and discussed. It is found that it is possible to capture the yield behavior of the grease, with regions of fully and partially yielded flow visible. The influence of temperature creep flow is also presented. Grease with both high and low yield stress are measured and compared could be measured and compared in a pocket with variable size. Furthermore, non-homogeneous effects such as shear banding and wall slip can be visualized. The test rig has thus a high potential to investigate the influence of wall material and wettability between fluids and the housing on the flow and wall slip behavior as long as the fluid is optically transparent.
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| 50. |
- Li, Jinxia, et al.
(author)
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Experimental study of free surface grease flow subjected to centrifugal forces
- 2014
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Conference paper (peer-reviewed)abstract
- In order to improve the understanding of grease flow in various applications such as gears, seals and rolling bearings, the free surface flow of different greases under different running conditions has been investigated. A rotating disc has been used to study grease flow as the grease was subjected to a centrifugal force. The grease flow and mass loss was measured for greases with different rheology on different surfaces and with surface textures. It is shown that the speed at which grease starts to move is mostly determined by grease type and yield stress, while the impact of the surface material and roughness is less pronounced. The mass loss is shown to be influenced both by the rheology of the grease and the surface material
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