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| 3. |
- Flys, Olena, 1971-, et al.
(författare)
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Piston ring topography variation and robust characterization
- 2014
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Konferensbidrag (refereegranskat)abstract
- It is a constant challenge for the automotive industry to reduce friction losses and oil consumption in automobile engine. The piston ring friction accounts for approximately 20% of the total mechanical energy losses in a modern engine. Oil control rings limit and control the oil consumption of the engine as well. They scrape off excess lubricating oil from the cylinder walls and return it to the crank case. Piston rings are designed to distribute the thin oil film evenly to ensure piston and ring lubrication. The surface topography of a piston ring is an efficient variable in the control of the oil consumption and friction losses. In places where the interacting surfaces come in contact, the oil film thickness is extremely thin and the surface asperities may deform because of the high pressures. There are different types of oil control rings.The most common one is the twin land oil control ring, which consists of two narrow lands that scrape off the oil on the liner and a spring on the back that exerts the load. In this paper, the surfaces of the two lands were investigated, since they play the key role in its function. The goal is to map the variation in surface roughness of piston rings that appear at different scales from form and waviness to micro and nano roughness. Areal topography measurements were made by white light interferometer designed at the Halmstad University able to measure and scan the total functional area of a piston ring. An significant amount of oil control piston rings of heavy duty truck engines were examined and 24 measurements were made in circumferential direction and on each ring land. The results show both the variation and uncertainty of the ring topography and discuss the instrument and measuring methodology uncertainty. The most stable parameters were found and recommended for an effective quality control. Comparisons between established coherence scanning interferometer and the instrument built in Halmstad were made. To ensure a good quality, the measurements were made both on calibration standards and on piston ring surfaces. Finally the influence on function and energy losses in the final engine assembly is discussed to indicate future design and metrology improvements.
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| 5. |
- Hansson, Karna, et al.
(författare)
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Carbon and nitrogen pools and fluxes above and below ground in spruce, pine and birch stands in southern Sweden
- 2013
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 309, s. 28-35
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Tidskriftsartikel (refereegranskat)abstract
- We synthesised results on soil carbon (C) and nitrogen (N) fluxes and the accumulation of soil organic C and N under adjacent 50-year-old Norway spruce, Scots pine and silver birch stands growing on similar soils and evaluated the different processes involved. C and N budgets were calculated. Spruce stands had larger stocks of C and N in biomass and soil than birch stands, with pine intermediate. The differences in soil stocks were mainly found in the organic layer, whereas differences in the mineral soil were small. The study showed that there is no simple answer to what is causing the differences in soil C and N stocks, because several processes are interacting. Spruce and pine trees had higher biomass and litter production than birch trees, but total litter inputs showed no significant difference between stands, because the rich ground vegetation under pine and birch contributed with substantial litter inputs, in contrast to the poor ground vegetation under spruce. Decomposition rate (per g of C) was markedly higher under birch than under spruce and pine resulting in lower C and N stocks in the organic layer. This effect was amplified by higher abundance and biomass of earthworms, favoured by higher pH and palatable litter under birch. Earthworm bioturbation probably both increased decomposition rate and damaged the ectomycorrhizal network with negative consequences for the formation of mycorrhizal litter and C storage. In conclusion, the direct effects of spruce, pine and birch litter on C and N pools and fluxes were modified by indirect effects of understorey structure, pH and earthworm responses. (C) 2013 Elsevier B.V. All rights reserved.
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| 6. |
- Hansson, Karna, et al.
(författare)
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Differences in soil properties in adjacent stands of Scots pine, Norway spruce and silver birch in SW Sweden
- 2011
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 262, s. 522-530
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Tidskriftsartikel (refereegranskat)abstract
- Soil properties were compared in adjacent 50-year-old Norway spruce, Scots pine and silver birch stands 26 growing on similar soils in south-west Sweden. The effects of tree species were most apparent in the 27 humus layer and decreased with soil depth. At 20–30 cm depth in the mineral soil, species differences 28 in soil properties were small and mostly not significant. Soil C, N, K, Ca, Mg, and Na content, pH, base sat- 29 uration and fine root biomass all significantly differed between humus layers of different species. Since 30 the climate, parent material, land use history and soil type were similar, the differences can be ascribed to 31 tree species. Spruce stands had the largest amounts of carbon stored down to 30 cm depth in mineral soil 32 (7.3 kg C m??2), whereas birch stands, with the lowest production, smallest amount of litterfall and lowest 33 C:N ratio in litter and humus, had the smallest carbon pool (4.1 kg C m??2), with pine intermediate 34 (4.9 kg C m??2). Similarly, soil nitrogen pools amounted to 349, 269, and 240 g N m??2 for spruce, pine, 35 and birch stands, respectively. The humus layer in birch stands was thin and mixed with mineral soil, 36 and soil pH was highest in the birch stands. Spruce had the thickest humus layer with the lowest pH
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| 7. |
- Ager, Bengt
(författare)
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Skogsarbetets humanisering och rationalisering från 1900 och framåt
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Rapporten belyser skogsarbetets förändring i storskogsbruket under perioden 1900 – 2013 under inflytande av rationalisering och humanisering som förändringsprocesser. Utgångsläget var ett ytterst slitsamt, riskabelt och lågbetalt säsongsarbete i kyla och snö, med bortaliggning i undermåliga kojor.I periodens början fullbordades en spontan rationalisering som inletts i slutet av 1800-talet och som bestod av att effektivare handredskap – olika typer av sågar, barkspadar och hanteringsdon - ersatte yxan som universalredskap. Organiserad rationalisering av skogsarbetet kom igång först i slutet på 30-talet. Den hämtade då sin inspiration från industrin som vid det laget hade anpassat amerikanen F W Taylors rationaliseringskoncept till den svenska arbetsmarknaden och kulturen. Arbetsstudier blev grund för effektivisering av det manuella skogsarbetet och för en rättvisare lön. Men skogsbruket kom sedan att finna egna vägar, som ledde till en världsunik teknisk och organisatorisk utveckling med början på 1950-talet och kulmen kring 1990. Under de senaste två årtiondena har rationaliseringen i skogsbruket anslutit sig till ”mainstream” i näringslivets utveckling, som styrs allt mera av dels den globaliserade marknadens mekanismer samt dels ”Lean”, ett hopkok av amerikanska och japanska organisationskoncept, och med ”outsourcing” som främsta verktyg. Under perioden 1940-2005 utvecklades produktiviteten kraftigt, med särskilt stora språng 1960-75 och 1990-2005. Efter 2005 skedde en stagnation.Humaniseringen av skogsarbetet inleddes med provinsialläkaren Hasslers larm 1907. Starten blev trög men skogsarbetarnas boende och mathållning kom att förbättras på många håll fram till 1930-talets slut. Då blev humanisering en integrerad del av den systematiska rationaliseringen, vilket innebar radikala förbättringar av det manuella skogsarbetet. När mekaniseringen tog fart under 50- och 60-talet kom människan i produktionssystemet bort ett tag, vilket ledde till omtag på humaniseringsprocessen. Ergonomin utvecklades som redskap och som vetenskap. Från slutet av 70-talet till slutet av 90-talet blev humaniseringen, stödd av flera aktörer, åter en integrerad del av rationaliseringen, nu underbyggd av det ”sociotekniska” organisationskoncept som utvecklats av engelska och norska arbetsforskare. Arbetets organisation kom i fokus. Den totala humankvaliteten kulminerade åren kring 1990. Skogsarbetet nådde då en höjdpunkt vad gäller mångsidighet, kontaktrikedom, variation, självbestämmande, ansvar och uppmärksamhet. Sedan inleddes en viss avhumanisering. Humaniseringsaktörerna försvagades eller försvann. Marknadens ”osynliga hand” tog alltmera över utvecklingen. Humankvaliteten försämrades på en rad punkter som i huvudsak kan hänföras till organisationsmiljön – färre personliga kontakter, längre arbetsresor, sämre skiftformer, kortare framförhållning och sämre kvalitet i planeringen samt sänkt relativ lönenivå. Försämringarna kompenseras delvis av att maskinernas förarmiljö och driftssäkerhet förbättrats avsevärt, men generellt har skogsarbetet förlorat i attraktivitet. Historiken summeras utförligt i kapitel 11.I kapitlet 12 om framtidens arbetsliv nationellt och i skogsbruket hävdar författaren att det behövs ett tidsanpassat humaniseringskoncept av samma dignitet som det på 60-talet lanserade sociotekniska konceptet. En skiss på ett sådant ”socioekonomiskt” koncept presenteras, inklusive en begreppsapparat som gör anspråk på att vara innovativ, samt en rad åtgärdsförslag. Därvid beaktas lärdomar från det förgångna.
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| 8. |
- Ahlgren, Benjamin, et al.
(författare)
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A simplified model for linear correlation between annual yield and DNI for parabolic trough collectors
- 2018
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Ingår i: Energy Conversion and Management. - : Elsevier. - 0196-8904 .- 1879-2227. ; 174, s. 295-308
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a simple method for estimating annual thermal performance of parabolic trough collectors (PTCs) based on a linear relation with annual DNI for a certain latitude. A case study with simulations for a novel concentrating solar collector in 316 locations for three operating temperature scenarios worldwide was carried out and showed promising results for the latitudes and continents investigated. For a certain latitude and mean operating temperature, the annual yield of a PTC was found to be linearly proportional to yearly DNI. The proposed method will serve as a simplified alternative to the steady-state and quasi-dynamic methods already used. Estimating performance based on yearly DNI can be used by design engineers to do quick preliminary planning of solar plants. Customers can also use this method to evaluate existing solar collector installations. A TRNSYS/TRNSED tool that uses a steady-state model has been developed to carry out the simulations and it has been validated against a PTC array at Technical University of Denmark (DTU). The results show that the simplified method can give reliable estimates of long-term performance of parabolic trough collectors.
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| 9. |
- Akselsson, Cecilia, et al.
(författare)
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Weathering rates in Swedish forest soils
- 2019
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 16:22, s. 4429-4450
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Forskningsöversikt (refereegranskat)abstract
- Soil and water acidification was internationally recognised as a severe environmental problem in the late 1960s. The interest in establishing “critical loads” led to a peak in weathering research in the 1980s and 1990s, since base cation weathering is the long-term counterbalance to acidification pressure. Assessments of weathering rates and associated uncertainties have recently become an area of renewed research interest, this time due to demand for forest residues to provide renewable bioenergy. Increased demand for forest fuels increases the risk of depleting the soils of base cations produced in situ by weathering. This is the background to the research programme Quantifying Weathering Rates for Sustainable Forestry (QWARTS), which ran from 2012 to 2019. The programme involved research groups working at different scales, from laboratory experiments to modelling. The aims of this study were to (1) investigate the variation in published weathering rates of base cations from different approaches in Sweden, with consideration of the key uncertainties for each method; (2) assess the robustness of the results in relation to sustainable forestry; and (3) discuss the results in relation to new insights from the QWARTS programme and propose ways to further reduce uncertainties. In the study we found that the variation in estimated weathering rates at single-site level was large, but still most sites could be placed reliably in broader classes of weathering rates. At the regional level, the results from the different approaches were in general agreement. Comparisons with base cation losses after stem-only and whole-tree harvesting showed sites where whole-tree harvesting was clearly not sustainable and other sites where variation in weathering rates from different approaches obscured the overall balance. Clear imbalances appeared mainly after whole-tree harvesting in spruce forests in southern and central Sweden. Based on the research findings in the QWARTS programme, it was concluded that the PROFILE/ForSAFE family of models provides the most important fundamental understanding of the contribution of weathering to long-term availability of base cations to support forest growth. However, these approaches should be continually assessed against other approaches. Uncertainties in the model approaches can be further reduced, mainly by finding ways to reduce uncertainties in input data on soil texture and associated hydrological parameters but also by developing the models, e.g. to better represent biological feedbacks under the influence of climate change.
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| 10. |
- Alevronta, Eleftheria, et al.
(författare)
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Dose-response relationships for an atomized symptom of fecal incontinence after gynecological radiotherapy.
- 2013
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Ingår i: Acta oncologica (Stockholm, Sweden). - : Taylor & Francis. - 1651-226X .- 0284-186X. ; 52:4, s. 719-26
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Tidskriftsartikel (refereegranskat)abstract
- Purpose. The aim of this study was to investigate what bowel organ and delivered dose levels are most relevant for the development of 'emptying of all stools into clothing without forewarning' so that the related dose-responses could be derived as an aid in avoiding this distressing symptom in the future. Material and methods. Of the 77 gynecological cancer survivors treated with radiotherapy (RT) for gynecological cancer, 13 developed the symptom. The survivors were treated between 1991 and 2003. The anal-sphincter region, the rectum, the sigmoid and the small intestines were all delineated and the dose-volume histograms were exported for each patient. The dose-volume parameters were estimated fitting the data to the Relative Seriality (RS), the Lyman and the generalized Equivalent Uniform Dose (gEUD) model. Results. The dose-response parameters for all three models and four organs at risk (OARs) were estimated. The data from the sigmoid fits the studied models best: D50 was 58.8 and 59.5 Gy (RS, Lyman), γ50 was 1.60 and 1.57 (RS, Lyman), s was 0.32, n was 0.13 and a was 7.7 (RS, Lyman, gEUD). The estimated volume parameters indicate that the investigated OARs behave serially for this endpoint. Our results for the three models studied indicate that they have the same predictive power (similar LL values) for the symptom as a function of the dose for all investigated OARs. Conclusions. In our study, the anal-sphincter region and sigmoid fit our data best, but all OARs were found to have steep dose-responses for 'emptying of all stools into clothing without forewarning' and thus, the outcome can be predicted with an NTCP model. In addition, the dose to the four studied OARs may be considered when minimizing the risk of the symptom.
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