| 11. |
- Du, Chengjun, 1985, et al.
(författare)
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Ignition Delay, Lift-off and Soot Luminescence in Diesel-Ethanol Spray Combustion
- 2015
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Ingår i: Lecture Notes in Mobility. - Cham : Springer International Publishing. - 2196-5544 .- 2196-5552. ; , s. 85-91
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- To investigate the influence of ethanol blending in Diesel fuel on the spray combustion characteristics, experiments were carried out in an optically accessed high-pressure/high-temperature spray chamber. Three different fuels were investigated: (1) Diesel, based on the European EN590 standard; (2) E10 with 10 % ethanol and (3) E20 with 20 % ethanol. Gas conditions were kept at a constant gas density of 24.3 kg/m3 at a lower combusting temperature (550 °C, 57.3 bar) and a higher combusting temperature (600 °C, 60 bar). The experimental results showed that ignition delay and delay time of soot formation were increased as ethanol was blended in Diesel fuel. Less soot luminescence was observed and longer lift-off length was measured in Diesel-ethanol blends compared to pure Diesel.
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| 12. |
- Du, Chengjun, 1985, et al.
(författare)
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The effect of cavitation on the estimation of fuel injection rates based on momentum flux measurements
- 2019
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 238, s. 354-362
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Tidskriftsartikel (refereegranskat)abstract
- A study was conducted to determine how geometry-induced cavitation affects the reliability of injection rate estimates based on momentum flux measurements. Experiments were performed with two hydro-grinding diesel injector nozzles (Do = 190 µm), one having a cylindrical nozzle orifice that has a strong tendency to induce cavitation, and the other having a convergent nozzle orifice that tends to suppress cavitation. In addition, near-field microscopic images were captured to investigate the influence of cavitation on the liquid jet at the nozzle exit. The momentum flux measurements and near-field imaging were conducted at ambient pressure, using injection pressures of up to 2500 bar. When estimating the injection rate based on momentum flux measurements, failure to account for cavitation caused the integrated injection rate to be overestimated around 9% for the cavitating (cylindrical) nozzle but not for the non-cavitating (convergent) nozzle. We therefore recommend that cavitation should be accounted for when estimating injection rates for cavitating nozzles but not for non-cavitating nozzles. Further, we show that the tendency of a given nozzle orifice to induce cavitation can be evaluated by measuring the nozzle's momentum flux under the assumption of zero cavitation and then comparing the estimated mass of injected fuel to the weighed mass.
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| 13. |
- Du, Chengjun, 1985, et al.
(författare)
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The Influence of Ethanol Blending in Diesel fuel on the Spray and Spray Combustion Characteristics
- 2014
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Ingår i: SAE International Journal of Fuels and Lubricants. - : SAE International. - 1946-3952 .- 1946-3960. ; 7(3):November 2014, s. 823-832
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Tidskriftsartikel (refereegranskat)abstract
- The influence of ethanol blending in Diesel fuel on the spray and spray combustion characteristics was investigated by performing experiments in an optically accessible high-pressure / high-temperature spray chamber under non-evaporating, evaporating and combusting conditions. Three fuels were investigated: (1) Diesel - a European Diesel based on the EN590 standard; (2) E10 - a blend of Diesel containing 10% ethanol and 2% emulsion additive; and (3) E20 - a blend of Diesel containing 20% ethanol and 2% emulsion additive. A constant gas density of 24.3 kg/m3 was maintained under non-evaporating (30 °C, 21.1 bar), evaporating (350 °C, 43.4 bar), low combustion temperature (550 °C, 57.3 bar) and high combustion temperature (600 °C, 60 bar) conditions. A single-hole injector with a nozzle diameter of 0.14 mm was used and injection pressure was held constant at 1350 bar. Various optical methods were used to characterize the non-combusting and combusting sprays.Despite the differences in the fuels' compositions, they did not differ significantly with respect to their liquid phase spray penetrations or cone angles under non-evaporating or evaporating conditions. However, under combusting conditions, reducing the ambient temperature increased the ignition delay and delayed the onset of soot formation for all fuels. Under equivalent combustion conditions, E10 and E20 had longer ignition and soot formation delays than Diesel. As the ethanol content of the fuel was increased from 0% to 20%, the lift-off length increased and the detectable soot luminescence decreased.
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| 14. |
- Du, Chengjun, 1985, et al.
(författare)
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Time-Resolved Liquid and Vapor Phase Distribution Measurement in Diesel Sprays Using a Light Absorption Scattering Technique
- 2016
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Ingår i: ILASS – Europe 2016, 27th Annual Conference on Liquid Atomization and Spray Systems, 4-7 September 2016, Brighton, UK.
-
Konferensbidrag (refereegranskat)abstract
- The laser absorption scattering (LAS) technique [Suzuki, et al., 1993, SAE Technical Paper, 930863] is a line-of-sight extinction technique that has several advantages such as high signal-to-noise ratio, low ambient temperature dependence and no fluorescence quenching. However, the LAS technique has been limited to single-shot measurements, which means only one spray image could be captured in one injection event. In order to record the whole vapor phase distribution development in one injection event, a new approach was developed using high-speed video cameras, and n-dodecane with 2% and 10% 1-methylnaphthalene was used as model fuels. Spray imaging was carried out in a spray chamber with temperature varied in the range 423 – 653 K, the ambient pressure was kept constant at 58 bar, and a fuel injection pressure of 800 –1200 bars was applied. It was shown that using UV light and visible light, the detailed liquid and vapor phase distribution development was captured clearly for both 2% 1-MN and 10% 1-MN fuel. Extinction tends to be saturated in UV images with 10% 1-MN fuel at various ambient temperatures. However, with 2% 1-MN fuel, there is no saturation at the applied conditions.
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| 15. |
- Du, Chengjun, 1985, et al.
(författare)
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Two-dimensional measurements of soot in a turbulent diffusion diesel flame: the effects of injection pressure, nozzle orifice diameter, and gas density
- 2018
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Ingår i: Combustion Science and Technology. - : Informa UK Limited. - 0010-2202 .- 1563-521X. ; 190:9, s. 1659-1688
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Tidskriftsartikel (refereegranskat)abstract
- © 2018, Published with license by Taylor & Francis Group, LLC © 2018 [Chengjun Du, Sven Andersson, Mats Andersson]. Two-dimensional light extinction, flame luminosity, and OH* chemiluminescence images were captured at a constant ambient temperature of 823 K and two gas densities (20 and 26 kg/m3), with injection pressures of 800–2500 bar using nozzle orifices with diameters of 0.19 and 0.10 mm. Soot volume fraction and OH distribution images were obtained using the Abel inversion method, and the local equivalence ratio in the lift-off length region was predicted. The results show that the equivalence ratio along the jet’s center at the lift-off length (ϕCL) was found to play a critical role in soot formation. Reductions in ϕCLthickened the OH zone in the upstream region of the jet, reducing the volume corresponding to the maximum soot volume fraction. The expansion of the OH zone also helped reduce the sooting zone’s width. Under high sooting conditions (e.g., ϕCL>3.5), the sooting zone width in the downstream jet was independent of ϕCL.
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| 16. |
- Hibar, Derrek P., et al.
(författare)
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Novel genetic loci associated with hippocampal volume
- 2017
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (r(g) = -0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness.
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| 17. |
- Kagwesage, Anne Marie
(författare)
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Coping with Learning through a Foreign Language in Higher Education in Rwanda
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overarching aims of this thesis are to investigate how students in higher education in Rwanda experience learning through the medium of a foreign language, mainly English, and the strategies they employ in order to successfully complete their university studies during a period of both language and educational change. Taking a sociocultural perspective, the thesis subscribes to a qualitative research design. Interviews were used in order to gain in-depth understanding of how higher education students reflect on, handle and cope with learning through a foreign language. Video and audio recorded interactions of students’ formal and informal group discussions were used to capture some of the seen but unnoticed linguistic and communicative details that might be of interest in shedding light on aspects related to learning in a foreign language. Four empirical studies show that students face different challenges in using the newly adopted language of learning and teaching. They are, however, aware of the fact that the globalisation process and dissolution of national boundaries may create new opportunities and are therefore willing to upgrade their English in order to cope with the new academic situation. Findings show that active use of multiple languages, although time consuming, has great potential to facilitate learning, thus emphasizing the complementarities rather than the exclusion of languages used in Rwanda. Also, teacher and student initiated group discussions have the potential to promote knowledge construction in content subjects as students afford a context for confident participation. Although the mother tongue is not officially recognised as language of instruction in higher education, it plays a mediating role for the negotiation of meaning of domain specific content through responsible code switching and translanguaging.
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| 18. |
- Lannemyr, Lukas, 1974, et al.
(författare)
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Differential Effects of Levosimendan and Dobutamine on Glomerular Filtration Rate in Patients With Heart Failure and Renal Impairment:ARandomized Double-Blind Controlled Trial.
- 2018
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Ingår i: Journal of the American Heart Association. - 2047-9980. ; 7:16
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Tidskriftsartikel (refereegranskat)abstract
- Background The management of the cardiorenal syndrome in advanced heart failure is challenging, and the role of inotropic drugs has not been fully defined. Our aim was to compare the renal effects of levosimendan versus dobutamine in patients with heart failure and renal impairment. Methods and Results In a randomized double-blind study, we assigned patients with chronic heart failure (left ventricular ejection fraction <40%) and impaired renal function (glomerular filtration rate <80mL/min per 1.73m2) to receive either levosimendan (loading dose 12μg/kg+0.1μg/kg per minute) or dobutamine (7.5 μg/kg per minute) for 75minutes. A pulmonary artery catheter was used for measurements of systemic hemodynamics, and a renal vein catheter was used to measure renal plasma flow by the infusion clearance technique for PAH (para-aminohippurate) corrected by renal extraction of PAH . Filtration fraction was measured by renal extraction of chromium ethylenediamine tetraacetic acid. A total of 32 patients completed the study. Following treatment, the levosimendan and dobutamine groups displayed similar increases in renal blood flow (22% and 26%, respectively) with no significant differences between groups. Glomerular filtration rate increased by 22% in the levosimendan group but remained unchanged in the dobutamine group ( P=0.012). Filtration fraction was not affected by levosimendan but decreased by 17% with dobutamine ( P=0.045). Conclusions In patients with chronic heart failure and renal impairment, levosimendan increases glomerular filtration rate to a greater extent than dobutamine and thus may be the preferred inotropic agent for treating patients with the cardiorenal syndrome. Clinical Trial Registration URL: https://www.clinicaltrials.gov . Unique identifier: NCT 02133105.
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| 19. |
- Rusanganwa, Joseph
(författare)
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Enhancing Physics Learning through Instruction, Technical Vocabulary and ICT : A Case of Higher Education in Rwanda
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overarching aim of this thesis is to explore how teaching and learning in tertiary education is performed in times of change both in language policy and learning approaches. The study takes social constructivist and socio-cultural theories as its major points of departure. These theories are combined with cognitive theory of learning with multimedia.The four studies comprising this thesis are born out of a new situation demanding the mastery of a scientific language in English and new ways of teaching and learning backed with ICT. The studies set out to investigate (i) how students and teachers adapt to a change of medium of instruction (ii) what teachers and students of physics learn when constructing a multimedia vocabulary learning instrument (iii) the impact of two methods of teaching vocabulary on students’ test performance and (iv) how teachers reflect on the use of ICT in Physics teaching.To attain these targets, the study employed a blend of qualitative and quantitative designs to gather relevant data. In three studies, data were gathered from classroom practices in tertiary education. The fourth study included teacher interviews on their experiences with ICT. Findings indicate that the understanding of physics was facilitated by a variation in language use in different classroom spaces, students and teachers’ collaborative selection of technical vocabulary and a multimedia tool of technical vocabulary software constructed by two teachers and the researcher. According to the teachers, the quality of physics teaching would be enhanced further by adopting learner-centred teaching methods and the integration of more advanced ICT. The studies show that teachers and students are on their way to develop ICT tools for teaching and learning. Given adequate support, this can pave the way for transforming teaching and allowing for further quality development in innovative and creative ways of learning with ICT.
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| 20. |
- Satizabal, Claudia L., et al.
(författare)
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Genetic architecture of subcortical brain structures in 38,851 individuals
- 2019
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Ingår i: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 51:11, s. 1624-
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Tidskriftsartikel (refereegranskat)abstract
- Subcortical brain structures are integral to motion, consciousness, emotions and learning. We identified common genetic variation related to the volumes of the nucleus accumbens, amygdala, brainstem, caudate nucleus, globus pallidus, putamen and thalamus, using genome-wide association analyses in almost 40,000 individuals from CHARGE, ENIGMA and UK Biobank. We show that variability in subcortical volumes is heritable, and identify 48 significantly associated loci (40 novel at the time of analysis). Annotation of these loci by utilizing gene expression, methylation and neuropathological data identified 199 genes putatively implicated in neurodevelopment, synaptic signaling, axonal transport, apoptosis, inflammation/infection and susceptibility to neurological disorders. This set of genes is significantly enriched for Drosophila orthologs associated with neurodevelopmental phenotypes, suggesting evolutionarily conserved mechanisms. Our findings uncover novel biology and potential drug targets underlying brain development and disease.
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