| 1. |
- Alamia, Alberto, 1984, et al.
(författare)
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Assessment of waste heat recovery for a power generation system based on Volvo dual fuel engines
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The electricity production from distributed renewable energy sources, like wind or solar PV, has considerably increased in last decade. To ensure a wide penetration of these renewable sources is necessary to integrate the fluctuation in the electricity production within the existing power network, even in network with limited transfer capacity between clusters.This work investigates possibilities to integrate the fluctuations of the renewable energy sources with production of electricity with a system based on internal combustion engines of the Dual Fuel (DF) type using synthetic natural gas (SNG), and waste heat recovery (WHR).The system retains high flexibility in the electricity output (i.e. quick regulation), and high efficiency comparable to large electricity plants.The design is based on a set of four medium size DF engines for a total power of around 2MW, and a WHR cycle operated with steam. The results showed an efficiency above 50% in a large range of operation of the engines with a peak above 52%, therefore comparable to gas turbine plants. Two designs of the WHR system were investigated (high pressure and low pressure) to improve heat recovery. The high pressure configuration is considered more suitable due to the lower complexity (single heat exchanger), which can be further exploited to expand the number of engines.The efficiency of the steam turbine/expander is the most critical parameter for the WHR system. However, the results showed that even with low efficiency of steam turbine (ηST 50% - 60%) the total efficiency can reach above 50%, when the engines are operated at high load. A high efficiency steam turbine (ηST 80% - 90%) can rise the total efficiency by 2.5 percentile units.
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| 2. |
- Alamia, Alberto, 1984, et al.
(författare)
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Fuel Quality Analysis for Biogas Utilization in Heavy Duty Dual Fuel Engines
- 2012
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Ingår i: World BioEnergy 2012 - conference in Jönköping , May 2012. ; , s. 1-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The perspective of using gas form biomass gasification as fuel for dual fuel (DF) engines, without refine it all the way to synthetic natural gas (SNG) has been investigated. The initial gas from gasification contains of a blend of various components which are not commonly present in natural gas (NG). The operability of these components in a heavy duty DF engine has been assessed and compared to those of NG. Three parameters have been used to define the quality of the fuel: Lower Heating Value (LHV), Methane Number (MN) and Lower Flammability Limit (LFL).
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| 3. |
- Alamia, Alberto, 1984, et al.
(författare)
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Fuel Quality Analysis for Biogas Utilization in Heavy Duty Dual Fuel Engines
- 2012
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Ingår i: 20th European Biomass conference & exhibition - Milan -June 2012. - 9788889407547 ; , s. 5-
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Konferensbidrag (refereegranskat)abstract
- Internal combustion engines using oil-derived fuels are dominating the heavy transportation sector today. However, the climate issue and security of supply drive the development towards new fuels and engine technologies. In the short term, Natural Gas (NG) is expected to have a dominant role, due to its high availability and a favourable H/C ratio. Thereafter, it is expect an introduction of biofuels of second and third generations. In this scenario the engine suppliers need to develop engines for various fuels of both fossil and renewable origin. One possibility is the Dual Fuel engine (DF), which uses a Diesel pilot to ignite a gas mixture and, it can be used for natural gas of various qualities as well as synthetic natural gas (SNG). To obtain significant share of second and third generation biofuels into the transportation sector a key process is gasification of the raw solid biomass to gas, as it can offer high production capacity and high efficiency. One interesting biofuel is SNG and at present there are a number of projects focusing on SNG production through gasification of biomass to be fed to the NG grid. However, this is a rather advanced and several stage process. The initial gas from the gasification before the gas is upgraded to CH4 (SNG) contains of a blend of various gas components such as H2, CO, CO2, CH4 and fractions of C2H2, C2H4, C3H6, and C3H8, as well as, longer hydrocarbons. The upgrading takes place in many process steps, where each step involves a cost and loss of energy. The question raised is if there are more efficient routs to introduce biomass derived gas than refine it all the way to SNG, from a well to wheel (WTW) perspective? The first step in such an analysis is to investigate how different gas mixtures could meet emission limits, together with the required performance of efficiency and load. This issue has been addressed in this work, where the operability in DF engines using gaseous fuels with a variation in fuel quality has been investigated. The operability has a key role in the optimization of the WTW efficiency, since it influences both the production process and the combustion in the engine. The definition of fuel quality for gaseous fuels to be used in gas engines is still not in place and proper legislation and standards are not available. Here, three parameters which are fundamental for a proper combustion in a DF engine: the Methane Number (MN), the Lower Flammability Limit (LFL) and the Lower Heating Value (LHV) have been studied. All parameters influence the combustion performance in the DF engine of the Port-injected type, which is more sensitive to the fuel quality than the Direct-injected type. The components available from biomass gasification were evaluated together with those from different NG compositions on the European market. Specific relations between the composition and fuel quality parameters have been derived, which can be used as starting point for future well to wheel analysis.
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| 4. |
- Allan, Julie, et al.
(författare)
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Etiska perspektiv på specialpedagogers yrkesroll och värdepedagogiska praktik
- 2022
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Yrkesetik handlar om att hantera motstridiga värden på ett professionellt sätt. Olika dilemman är ständigt närvarande i skolans vardag och kan handla om att minimera risken för att elever ska exkluderas eller om att säkerställa att elever får möjlighet att visa sina kunskaper på rätt sätt. I sin yrkesroll ställs specialpedagogen inför mångfacetterade arbetsuppgifter som omfattar att stödja barn och elever i svårigheter, vara en kvalificerad samtalspartner i pedagogiska frågor och samverka med andra yrkesgrupper för att utveckla skolans verksamhet. Arbetet innebär val mellan olika handlingsalternativ som kräver både kunskap och förmåga att urskilja och värdera etiska aspekter i komplexa sammanhang. I boken diskuteras både dilemman och möjligheter där etiska perspektiv spelar en viktig roll. Kapitlen tar upp frågor med praktiknära innehåll som lämpar sig för såväl individuell reflektion som kollegiala samtal med syftet att skapa ett gemensamt yrkesetiskt språk. Boken vänder sig till blivande och praktiserande specialpedagoger samt andra yrkeskategorier med arbetsuppgifter inom det specialpedagogiska området.
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| 5. |
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| 6. |
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| 7. |
- Eismark, Jan, 1962, et al.
(författare)
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Role of formation and transportation of hydroxyl radicals for enhanced late soot oxidation in a low emissions heavy-duty diesel engine.
- 2010
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Ingår i: Thiesel 2010 conference on Thermo-and fluid dynamic processes in Diesel Diesel Engines. - 9788469350096 ; , s. 173-190
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Konferensbidrag (refereegranskat)abstract
- In previous research enhancement of late soot oxidation by increased mixing rates has been identified as an important measure to decrease engine-out soot emissions. Additionally, the availability of oxidants, especially hydroxyl radicals (OH) in the mixing zones, is considered as essential for an effective fuel and soot burn-out process. The objective of this study was to combine experimental and computational methods to identify the role of OH for late soot oxidation. Experimental data from a high pressure/high temperature spray chamber and a heavy-duty single cylinder engine were analysed using combustion CFD. The formation, lifetime and transportation of OH were studied together with other important in-cylinder parameters. The soot formation and oxidation processes were analysed for a dataset of engine results with equal NOx emissions but having a large variation of engine-out soot emissions. The spray chamber experimental set-up includes a flame divider designed to enable studies of the OH history in the leading edge of the flame vortex. The engine combustion CFD results could be compared with CFD analysis of the spray chamber results regarding the behaviour of OH. From this study, it is suggested that the fluctuating interface between the soot leading edge and the important soot oxidant specie OH is influenced by interactions between local turbulent flame movements and the availability of OH. The soot and OH interface was observed to develop smoothly in a strongly re-directed side of a flame as well as on the free side of the same flame. According to experimental observations and analysis of CFD source terms of soot formation and oxidation rates, both the OH radical pool and the soot oxidation reach farther downstream in the flame than the soot formation. The study gave an increased understanding of limiting factors for enhanced late soot oxidation during diesel engine operation.
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| 8. |
- Hallberg, Gunilla
(författare)
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Effects of Endogenous and Exogenous Hormones on the Female Breast : With Special Reference to the Expression of Proteoglycans
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis aims to study the effects of endogenous and exogenous hormones and mammographic breast density (BD) on cellular markers in non-cancerous female breast tissue. Women on the waiting list for breast reduction plastic surgery were recruited (n = 79), and randomized to 2 months of hormone therapy or no therapy before surgery. The women had a mammogram and a needle biopsy 2 months before surgery and tissue samples were obtained at the operation. In premenopausal women, estrogen receptor (ER)α levels were associated with age (p = 0.0002), were similar in the follicular and luteal phases of the menstrual cycle and were higher in parous than in nulliparous women (p = 0.009). Current smokers had lower PR levels than non-smokers (p = 0.019). Women on oral contraception had lower ERα (p = 0.048) and PR (p = 0.007) levels than women in the follicular phase. The ERα levels did not differ significantly between postmenopausal estrogen and estrogen-progestogen users, but PR levels were lower among estrogen-progestogen users (p = 0.03). We found lower expression of the genes for decorin and syndecans 1 and 4 in the luteal phase than in the follicular phase, among parous women. Protein levels of the androgen receptor, syndecan-4 and decorin was lower in premenopausal women who were using oral contraceptives (OC) than in those in the follicular phase (p = 0.002 - 0.02), whereas no significant differences between OC use and the luteal phase were found. In premenopausal women, BD was negatively associated with age and body mass index but was similar for the menstrual phases. Breast density was associated with genetic expression of the androgen receptor and remained significant after adjustment for age (rs = 0.56; p = 0.04). After adjustement for age, breast density was also marginally associated with expression of the caspase 3 gene (0.55; 0.053). However, protein levels of caspase 3 was negatively associated (-0.61; 0.03).
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| 9. |
- Hallberg, Gunilla, et al.
(författare)
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Effects of pre-and postmenopausal use of exogenous hormones on receptor content in normal human breast tissue: A randomized study
- 2008
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Ingår i: Gynecological Endocrinology. - : Informa UK Limited. - 0951-3590 .- 1473-0766. ; 24:8, s. 475-480
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Tidskriftsartikel (refereegranskat)abstract
- Objective. To examine the effects of exposure to endogenous and exogenous hormones on estrogen receptor- (ER) and progesterone receptor (PR) levels in normal human breast tissue. Methods. In a randomized study of women scheduled for mammary reduction plasty (n = 81), ER and PR content in breast parenchyma was analyzed in premenopausal (n = 49) and postmenopausal (n = 16) women. Premenopausal women were randomized to surgery in the follicular or luteal phase of the menstrual cycle or after oral contraceptive treatment for 2 months. Postmenopausal women were randomized to sequential or estrogen-only therapy for 2 months prior to surgery. Results. ER content was higher in parous than in nulliparous (p = 0.009) premenopausal women and displayed a positive association with age (rs = 0.51, p = 0.0002). Compared with premenopausal women in the follicular phase, postmenopausal women had higher ER content (p = 0.040) whereas premenopausal women on oral contraception had lower ER (p = 0.048) and PR (p = 0.007) content. Smokers had lower PR content than non-smokers (p = 0.02). Conclusion. In the present study ER content was higher in parous than in non-parous women and associated with premenopausal age. Short-term oral contraceptives yielded lower ER and PR contents. Postmenopausal estrogen/progestogen combined therapy yielded lower PR content than estrogen-only therapy.
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| 10. |
- Immerstrand, Charlotte, 1974-, et al.
(författare)
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Altered impedance during pigment aggregation in Xenopus laevis melanophores
- 2003
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 41:3, s. 357-364
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Tidskriftsartikel (refereegranskat)abstract
- Melanophores are dark-brown pigment cells located in the skin of amphibia, fish and many invertebrates. The skin colour of these organisms is regulated by the translocation of pigment organelles, and the pigment distribution can be altered by external stimuli. The ability to change colour in response to stimuli makes these cells of interest for biosensing applications. It was investigated whether pigment aggregation in Xenopus laevis melanophores can be detected by impedance measurements performed in transparent microvials. The results show that cell attachment, cell spreading and pigment aggregation all resulted in impedance changes, seen particularly at the highest frequency tested (10 kHz). The mechanisms behind the impedance changes were investigated by the addition of latrunculin or melatonin, both of which cause pigment aggregation. The latrunculin-induced aggregation was associated with cell area decrease and filamentous actin (F-actin) breakdown, processes that can influence the impedance. Lack of F-actin breakdown and an increase in cell area during melatonin-induced aggregation suggest that some other intracellular process also contributes to the impedance decrease seen for melatonin. It was shown that impedance measurements reflect not only cell attachment and cell spreading, but also intracellular events.
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