| 1. |
- Lundgren, Marcus Olof, et al.
(författare)
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Effects of Post-Injections Strategies on UHC and CO at Gasoline PPC Conditions in a Heavy-Duty Optical Engine
- 2017
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2017:March
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Tidskriftsartikel (refereegranskat)abstract
- Gasoline partially premixed combustion (PPC) has shown potential in terms of high efficiency with low emissions of oxides of nitrogen (NOx) and soot. Despite these benefits, emissions of unburned hydrocarbons (UHC) and carbon monoxide (CO) are the main shortcomings of the concept. These are caused, among other things, by overlean zones near the injector tip and injector dribble. Previous diesel low temperature combustion (LTC) research has demonstrated post injections to be an effective strategy to mitigate these emissions. The main objective of this work is to investigate the impact of post injections on CO and UHC emissions in a quiescent (non-swirling) combustion system. A blend of primary reference fuels, PRF87, having properties similar to US pump gasoline was used at PPC conditions in a heavy duty optical engine. The start of the main injection was maintained constant. Dwell and mass repartition between the main and post injections were varied to evaluate their effect. All points were run at 7 bar IMEPg. High-speed imaging of the natural combustion luminescence was performed together with measurements of performance and engine out emissions. Results show reduction in both CO and UHC with close coupled injections. A large close coupled post injection show the largest reduction in UHC. Analysis show that a post injection prior to combustion reduces the dribble and increases the recirculation in the downstream region of the fuel jet, hence reaching more of the UHC in the area near the injector. General observations show that the partition of fuel between the injections have the largest impact on the CO while the dwell time affects UHC emissions. Injector dribble seems to be a significant contributor to the UHC emissions.
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| 2. |
- Lundgren, Marcus, et al.
(författare)
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Optical study on combustion transition from HCCI to PPC with gasoline compression ignition in a HD engine
- 2016. - April
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Ingår i: SAE 2016 World Congress and Exhibition. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. ; 2016-April
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Konferensbidrag (refereegranskat)abstract
- The partially premixed combustion (PPC) concept has shown high efficiency with low soot emissions. However, the in-cylinder phenomena are still to be explained and evaluated for further progress in the research. This work studies the start of combustion process during a transition from homogenous charge compression ignition (HCCI) to PPC. The process is visualized using a heavy-duty, non-swirling engine modified for optical access. High speed video was used to capture the natural luminosity of the combustion. The fuel used was PRF87. Single and double injection strategies were used at a load kept to the moderate level of 7.5 bar IMEPg. Single injections were swept from early HCCI to retarded PPC conditions whilst running a cycle to cycle temperature sweep, to capture the effect of injection timing and temperature differences simultaneously. Results show that retarded injections show less cycle-to-cycle variation due to temperature variations. Advanced in-bowl injections show a stochastic behavior in the location of the first combustion, due to large variations in local fuel rich zones. For the double injection case the main injection cools the bulk temperature and hence delays the start of combustion before igniting in the fuel rich zones.
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| 3. |
- Wang, Zhenkan, et al.
(författare)
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Simultaneous 36 kHz PLIF/chemiluminescence imaging of fuel, CH2O and combustion in a PPC engine
- 2019
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 37:4, s. 4751-4758
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Tidskriftsartikel (refereegranskat)abstract
- The requirements on high efficiency and low emissions of internal combustion engines (ICEs) raise the research focus on advanced combustion concepts, e.g., premixed-charge compression ignition (PCCI), partially premixed compression ignition (PPCI), reactivity controlled compression ignition (RCCI), partially premixed combustion (PPC), gasoline compression ignition (GCI) etc. In the present study, an optically accessible engine is operated in PPC mode, featuring compression ignition of a diluted, stratified charge of gasoline-like fuel injected directly into the cylinder. A high-speed, high-power burst-mode laser system in combination with a high-speed CMOS camera is employed for diagnostics of the autoignition process which is critical for the combustion phasing and efficiency of the engine. To the authors' best knowledge, this work demonstrates for the first time the application of the burst-system for simultaneous fuel tracer planar laser induced fluorescence (PLIF) and chemiluminescence imaging in an optical engine, at 36 kHz repetition rate. In addition, high-speed formaldehyde PLIF and chemiluminescence imaging are employed for investigation of autoignition events with a high temporal resolution (5 frames/CAD). The development of autoignition together with fuel or CH2O distribution are simultaneously visualized using a large number of consecutive images. Prior to the onset of combustion the majority of both fuel and CH2O are located in the recirculation zone, where the first autoignition also occurs. The ability to record, in excess of 100 PLIF images, in a single cycle brings unique possibilities to follow the in-cylinder processes without the averaging effects caused by cycle-to-cycle variations.
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| 4. |
- Wang, Zhenkan, et al.
(författare)
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Ultra-High Speed Fuel Tracer PLIF Imaging in a Heavy-Duty Optical PPC Engine
- 2018
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2018-April
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Tidskriftsartikel (refereegranskat)abstract
- In order to meet the requirements in the stringent emission regulations, more and more research work has been focused on homogeneous charge compression ignition (HCCI) and partially premixed combustion (PPC) or partially premixed compression ignition (PCCI) as they have the potential to produce low NOx and soot emissions without adverse effects on engine efficiency. The mixture formation and charge stratification influence the combustion behavior and emissions for PPC/PCCI, significantly. An ultra-high speed burst-mode laser is used to capture the mixture formation process from the start of injection until several CADs after the start of combustion in a single cycle. To the authors' best knowledge, this is the first time that such a high temporal resolution, i.e. 0.2 CAD, PLIF could be accomplished for imaging of the in-cylinder mixing process. The capability of resolving single cycles allows for the influence of cycle-to-cycle variations to be eliminated. This ability to study individual cycles aids the understanding of the mixture formation process as well as the cycle-to-cycle variations. Strong air entrainment at the boundary layer can be clearly observed and followed as the mixing process progresses. The formation of eddies created by the shear force and their rotational motion can be continuously observed during the mixing process. The interaction between two adjacent spray plumes in the recirculation zone is well captured and studied. In addition, the mixing process resulting in the stratified fuel charge being located in the recirculation zone before the SOC while the areas along the original spray axis are leaned out after the end of injection, can be followed in one time sequence. Moreover, the auto-ignition position and early flame development can be studied, from the high-speed chemiluminescence imaging, together with the fuel distribution in the combustion chamber.
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| 5. |
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| 6. |
- Andersson, Marcus, 1975, et al.
(författare)
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Quartz crystal microbalance-with dissipation monitoring (QCM-D) for real time measurements of blood coagulation density and immune complement activation on artificial surfaces
- 2005
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Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 0956-5663. ; 21:1, s. 79-86
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Tidskriftsartikel (refereegranskat)abstract
- A recently developed variant of quartz crystal microbalance (QCM) called QCM-with dissipation monitoring (QCM-D) allows simultaneous and simple measurements of changes in adsorbed mass as well as the viscoelastic property (D-factor) of deposited protein layers on the sensor surface. We have taken the QCM-D technology a step further and demonstrated its advantages in the study of protein assembly as a consequence of surface induced immune complement activation, or contact activated blood coagulation. In the present study we have continued our QCM-D investigations of surface assembly of fibrin clot formation and complement activation and incubated differently modified quartz sensor surfaces in blood plasma and sera. Polymer surfaces used were spin-coated polyethylene, poly(ethylene terephtalate), poly(methylmetacrylate) and poly(dimethylsiloxane). Also used were sputtered titanium and heparin grafted surfaces. In this investigation we found that we could describe the surface induced coagulation with four independent parameters: (1) Time of onset of coagulation, (2) fibrin deposition rate, (3) total frequency shift at stable plateau, and (4) fibrin clot density. The most important finding was that the blood plasma clot density can be assessed with the use of D determinations and that the clot density varied significantly with the chemical composition of the surface. However, the D-factor did not give any new analytical information about the possible complement activation mechanisms. Nevertheless, the QCM-D was found to be a reliable tool for the analysis of surface induced complement activation. We also compared the QCM-D technique with traditional enzyme immuno assay (EIA) measurements of soluble products from the surface activation of the complement and coagulation systems. We found that the results from EIA and QCM-D measurements corresponded well for the complement activation but not for the coagulation, probably due to the biological complexity of the coagulation system.
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| 7. |
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| 8. |
- Berman, Anne H, et al.
(författare)
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Teaching digital mental health treatment in theory and practice : a proof-of-concept pilot and feasibility study
- 2023
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Ingår i: International Journal of Behavioral Medicine. ; , s. 66-66, s. 6-7
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Konferensbidrag (refereegranskat)abstract
- Objective: The labor market for mental health professionals increasingly requires competency in digital mental health treatment (DMHT). This presentation targets DMHT practitioners as course developers and teachers, describing proof-of-concept findings based on a) development of a remotely delivered DMHT course; and b) results from a qualitative evaluation of students’ experiences from the first course round.Methods: The course syllabus was developed through two structured workshops, attended by 11 stakeholders with DMHT experience. For the qualitative evaluation, interviews with seven women participants in the first course round were analyzed according to an inductive, phenomenographic approach.Results: The course development process established a 12-week syllabus covering historical development and evidence for DMHT and an 8-week DMHT clinical practicum treating students with common mental health problems. Examination was formulated as individual case reports encompassing reflections on a) the therapist and client roles; b) ethical aspects of DMHT; and c) future innovations for DMHT. The course is offered via a standard learning management system, with the practicum completed on a separate DMHT platform. The qualitative analysis of the first pilot course round, where students role-played therapists and clients, yielded six themes: overall course experience, treatment program and platform, therapist role, client role, supervision and the alliance.Conclusions: This proof-of-concept procedure led to course establishment in two formats: as an ordinary elective course for advanced clinical psychology students, and as a stand-alone national course for health professionals with basic psychotherapy training. Following local adaptation, the course could be replicated at additional universities globally.
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| 9. |
- Berman, Anne H., et al.
(författare)
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Teaching digital mental health treatment in theory and practice : A proof-of-concept pilot and feasibility study
- 2023
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Ingår i: International Journal of Behavioral Medicine. - : Springer. - 1070-5503 .- 1532-7558. ; 30, s. S67-S67
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Background: Improving relationship dynamics positively impacts both partners’ health among couples. However, few studies have investigated sexual and gender minority (SGM) couples’ relationship goals and their experiences toward achieving them.Purpose: The present study investigated SGM couples’ experiences that centered on them working toward or maintaining their relationship goals over time.Method: From a cohort study with SGM couples, a purposive sample of 40 couples was selected and interviewed over Zoom. Interviews were individual-level, semi-structured, and recorded. Thematic analysis was used to analyze the transcripts.Results: Approximately half of the 40 couples identified as gay male couples, a third as lesbian couples, and about one-fifth as queer or gender minority couples. Top three reported relationship goals were 1) improving communication, 2) working on finances, and 3) enhancing intimacy. Feeling emotionally connected, career-related decisions, and improving sexual satisfaction were other commonly reported goals. Overall, most partners felt they made progress toward at least 1 of their 3 relationship goals within the prior 6 months. However, perceived relationship goal progress varied extensively between partners across couple groups. Facilitator-related themes about relationship goal progress included dyadic efforts, having a support system including professional help, and planning. Barrier-related themes included nonexistent or minimal effort, different communication styles, employment and economical struggles, and competing life and health priorities.Conclusion(s): Dyadic efforts and support systems were key toward someone working toward or maintaining their relationships goals. Findings suggest key relationship functioning areas to target in a future multiple health behavior change intervention for SGM couples.
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| 10. |
- Berman, Anne H., Professor, et al.
(författare)
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Transdiagnostic and tailored internet intervention to improve mental health among university students : Research protocol for a randomized controlled trial
- 2024
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Ingår i: Trials. - : Springer Nature. - 1745-6215. ; 25:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Emerging adulthood is often associated with mental health problems. About one in three university students report symptoms of depression and anxiety that can negatively affect their developmental trajectory concerning work, intimate relationships, and health. This can interfere with academic performance, as mood and anxiety disorders are key predictors of dropout from higher education. A treatment gap exists, where a considerable proportion of students do not seek help for mood and anxiety symptoms. Offering internet interventions to students with mental health problems could reduce the treatment gap, increase mental health, and improve academic performance. A meta-analysis on internet interventions for university students showed small effects for depression and none for anxiety. Larger trials are recommended to further explore effects of guidance, transdiagnostic approaches, and individual treatment components.Methods: This study will offer 1200 university students in Sweden participation in a three-armed randomized controlled trial (RCT) evaluating a guided or unguided transdiagnostic internet intervention for mild to moderate depression and anxiety, where the waitlist control group accesses the intervention at 6-month follow-up. Students reporting suicidal ideation/behaviors will be excluded and referred to treatment within the existing healthcare system. An embedded study within the trial (SWAT) will assess at week 3 of 8 whether participants in the guided and unguided groups are at higher risk of failing to benefit from treatment. Those at risk will be randomized to an adaptive treatment strategy, or to continue the treatment as originally randomized. Primary outcomes are symptoms of depression and anxiety. Follow-ups will occur at post-treatment and at 6-, 12-, and 24-month post-randomization. Between-group outcome analyses will be reported, and qualitative interviews about treatment experiences are planned.Discussion: This study investigates the effects of a transdiagnostic internet intervention among university students in Sweden, with an adaptive treatment strategy employed during the course of treatment to minimize the risk of treatment failure. The study will contribute knowledge about longitudinal trajectories of mental health and well-being following treatment, taking into account possible gender differences in responsiveness to treatment. With time, effective internet interventions could make treatment for mental health issues more widely accessible to the student group.
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