Wood torrefaction is a mild pyrolysis process that improves the fuel properties of wood. At temperatures between 230 and 300
°C, the hemicellulose fraction of the wood decomposes, so that torrefied ...wood and volatiles are formed. Mass and energy balances for torrefaction experiments at 250 and 300
°C are presented. Advantages of torrefaction as a pre-treatment prior to gasification are demonstrated. Three concepts are compared: air-blown gasification of wood, air-blown gasification of torrefied wood (both at a temperature of 950
°C in a circulating fluidized bed) and oxygen-blown gasification of torrefied wood (at a temperature of 1200
°C in an entrained flow gasifier), all at atmospheric pressure. The overall exergetic efficiency of air-blown gasification of torrefied wood was found to be lower than that of wood, because the volatiles produced in the torrefaction step are not utilized. For the entrained flow gasifier, the volatiles can be introduced into the hot product gas stream as a ‘chemical quench’. The overall efficiency of such a process scheme is comparable to direct gasification of wood, but more exergy is conserved in as chemical exergy in the product gas (72.6% versus 68.6%). This novel method to improve the efficiency of biomass gasification is promising; therefore, practical demonstration is recommended.
This review provides an overview of the existing literature on school-aged children’s and youth’s (i.e. 6- to 18-year-olds) personal and social development within the context of physical education ...and sports. A total of 4359 non-duplicate articles were retrieved from six databases. After the title, abstract and full text screening, 88 articles met the inclusion criteria and were included for further analysis. Articles had to be published in a peer-reviewed journal between 1 January 2008 and 6 December 2017. The 88 studies used several study designs, methods and instruments to investigate a variety of concepts related to personal and social development. Concepts were grouped into the following 11 themes: work ethic; control and management; goal-setting; decision-making; problem-solving; responsibility; leadership; cooperation; meeting people and making friends; communication; and prosocial behaviour. The main findings for each of the 11 themes are reported, and limitations and implications are provided to guide researchers and practitioners in their future work.
The effect of fuel composition on the thermodynamic efficiency of gasifiers and gasification systems is studied. A chemical equilibrium model is used to describe the gasifier. It is shown that the ...equilibrium model presents the highest gasification efficiency that can be possibly attained for a given fuel. Gasification of fuels with varying composition of organic matter, in terms of O/C and H/C ratio as illustrated in a Van Krevelen diagram, is compared. It was found that exergy losses in gasifying wood (O/C ratio around 0.6) are larger than those for coal (O/C ratio around 0.2). At a gasification temperature of 927
°C, a fuel with O/C ratio below 0.4 is recommended, which corresponds to a lower heating value above 23
MJ/kg. For gasification at 1227
°C, a fuel with O/C ratio below 0.3 and lower heating value above 26
MJ/kg is preferred. It could thus be attractive to modify the properties of highly oxygenated biofuels prior to gasification, e.g. by separation of wood into its components and gasification of the lignin component, thermal pre-treatment, and/or mixing with coal in order to enhance the heating value of the gasifier fuel.
Islet cell transplantation can cure type 1 diabetes (T1D), but only a minority of recipients remains insulin-independent in the following years. We tested the hypothesis that allograft rejection and ...recurrent autoimmunity contribute to this progressive loss of islet allograft function.
Twenty-one T1D patients received cultured islet cell grafts prepared from multiple donors and transplanted under anti-thymocyte globulin (ATG) induction and tacrolimus plus mycophenolate mofetil (MMF) maintenance immunosuppression. Immunity against auto- and alloantigens was measured before and during one year after transplantation. Cellular auto- and alloreactivity was assessed by lymphocyte stimulation tests against autoantigens and cytotoxic T lymphocyte precursor assays, respectively. Humoral reactivity was measured by auto- and alloantibodies. Clinical outcome parameters--including time until insulin independence, insulin independence at one year, and C-peptide levels over one year--remained blinded until their correlation with immunological parameters. All patients showed significant improvement of metabolic control and 13 out of 21 became insulin-independent. Multivariate analyses showed that presence of cellular autoimmunity before and after transplantation is associated with delayed insulin-independence (p = 0.001 and p = 0.01, respectively) and lower circulating C-peptide levels during the first year after transplantation (p = 0.002 and p = 0.02, respectively). Seven out of eight patients without pre-existent T-cell autoreactivity became insulin-independent, versus none of the four patients reactive to both islet autoantigens GAD and IA-2 before transplantation. Autoantibody levels and cellular alloreactivity had no significant association with outcome.
In this cohort study, cellular islet-specific autoimmunity associates with clinical outcome of islet cell transplantation under ATG-tacrolimus-MMF immunosuppression. Tailored immunotherapy targeting cellular islet autoreactivity may be required. Monitoring cellular immune reactivity can be useful to identify factors influencing graft survival and to assess efficacy of immunosuppression.
Clinicaltrials.gov NCT00623610.
This study investigated the effects of a peer feedback tool and a reflection tool on social and cognitive performance during computer supported collaborative learning (CSCL). A CSCL-environment was ...augmented with a peer feedback tool (Radar) and a reflection tool (Reflector) in order to make group members aware of both their individual and their group behavior. Radar visualizes how group members perceive their own social and cognitive performance and that of their peers during collaboration along five dimensions. Reflector stimulates group members to reflect upon their own performance and the performance of the group. A 2
×
2 factorial between-subjects design was used to examine whether Radar and Reflector would lead to better team development, more group satisfaction, lower levels of group conflict, more positive attitudes toward problem-based collaboration, and a better group product. Results show that groups with Radar perceived their team as being better developed, experienced lower conflict levels, and had a more positive attitude towards collaborative problem solving than groups without Radar. The quality of group products, however, did not differ. The results demonstrate that peer feedback on the social performance of individual group members can enhance the performance and attitudes of a CSCL-group.
A peer feedback tool (Radar) and a reflection tool (Reflector) were used to enhance group performance in a computer-supported collaborative learning environment. Radar allows group members to assess ...themselves and their fellow group members on six traits related to social and cognitive behavior. Reflector stimulates group members to reflect on their past, present and future group functioning, stimulating them to set goals and formulate plans to improve their social and cognitive performance. The underlying assumption was that group performance would be positively influenced by making group members aware of how they, their peers and the whole group perceive their social and cognitive behavior in the group. Participants were 108 fourth-year high school students working in dyads, triads and groups of four on a collaborative writing task, with or without the tools. Results demonstrate that awareness stimulated by the peer feedback and reflection tools enhances group-process satisfaction and social performance of CSCL-groups.
Content analysis: What are they talking about? Strijbos, Jan-Willem; Martens, Rob L.; Prins, Frans J. ...
Computers and education,
2006, 2006-01-00, 2006-1-00, 20060101, Volume:
46, Issue:
1
Journal Article
Peer reviewed
Open access
Quantitative content analysis is increasingly used to surpass surface level analyses in computer-supported collaborative learning (e.g., counting messages), but critical reflection on accepted ...practice has generally not been reported. A review of CSCL conference proceedings revealed a general vagueness in definitions of units of analysis. In general, arguments for choosing a unit were lacking and decisions made while developing the content analysis procedures were not made explicit. In this article, it will be illustrated that the currently accepted practices concerning the ‘unit of meaning’ are not generally applicable to quantitative content analysis of electronic communication. Such analysis is affected by ‘unit boundary overlap’ and contextual constraints having to do with the technology used. The analysis of e-mail communication required a different unit of analysis and segmentation procedure. This procedure proved to be reliable, and the subsequent coding of these units for quantitative analysis yielded satisfactory reliabilities. These findings have implications and recommendations for current content analysis practice in CSCL research.
This study investigated the effects of feedback providing improvement strategies and a reflection assignment on students’ writing motivation, process, and performance. Students in the experimental ...feedback condition (n=41) received feedback including improvement strategies, whereas students in the control feedback condition (n=41) received feedback without improvement strategies. Within each feedback condition, half of the students received a reflection assignment on feedback use and the revision (experimental reflection condition), while the other half received a reflection assignment on feedback perception (control reflection condition). Results indicated that in the experimental feedback condition writing performance gained from the control reflection assignment, while in the control feedback condition it gained from the experimental reflection assignment. Improvement strategies negatively predicted self-efficacy beliefs, especially when initial self-efficacy beliefs were low, and positively predicted planning/revising. Reflections on feedback use and the revision positively predicted mastery goal when mastery goal initially was low or moderate.
► Feedback providing strategies together with reflection on use of feedback harms performance. ► Feedback providing strategies reduces students’ self-efficacy beliefs. ► Students’ feedback perception explains negative effects on self-efficacy beliefs. ► Feedback providing strategies contributes to students’ planning/revising.
Purpose
This study aims to report the design, development and evaluation of a digital quality assurance application aimed at improving and ensuring the quality of assessment programmes in higher ...education.
Design/methodology/approach
The application was developed using a design-based research (DBR) methodology. The application’s design was informed by a literature search and needs assessment of quality assurance stakeholders to ensure compliance with daily practices and accreditation requirements. Stakeholders from three study programmes evaluated the application.
Findings
As part of the development of the application, module- and programme-level dashboards were created to provide an overview of the programme’s outcomes, assessment methods, assessment metrics, self-evaluated quality indicators and assessment documents. The application was evaluated by stakeholders at the module and programme levels. Overall, the results indicated that the dashboards aided them in gaining insight into the assessment programme and its alignment with underlying assessments.
Practical implications
Visualisation of the assessment programme’s structure and content identifies gaps and opportunities for improvement, which can be used to initiate a dialogue and further actions to improve assessment quality.
Originality/value
The application developed facilitates a cyclical and transparent assessment quality assurance procedure that is continuously available to various stakeholders in quality assurance.
Students' use of a rubric for research theses Prins, Frans J.; de Kleijn, Renske; Tartwijk, Jan van
Assessment and evaluation in higher education,
01/2017, Volume:
42, Issue:
1
Journal Article
Peer reviewed
A rubric for research theses was developed, based on the manual of the American Psychological Association, to be used as an assessment tool for teachers and students. The aim was to make students ...aware of what is expected, get familiar with criteria, and interpret teacher and peer feedback. In two studies, it was examined whether students use and value these functions. In the first study, a rubric was provided to 105 Educational Sciences students working on their bachelor's thesis. Questionnaire data indicated that students did value the rubric for the intended functions, although rubric use was not related to ability. In a panel interview, teachers stated that the number of proficiency levels should be increased to be able to distinguish between good and excellent students adequately, and that a criterion concerning student's role during supervision should be added. Therefore, in the second study, 11 teachers were interviewed about their motives to give high grades and about the supervision process. This lead to an extra criterion concerning student's role during supervision and an additional proficiency level to assess excellent performance. It is argued that an adequate course organisation is conditional for the rubric's effectiveness.
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