Academics in control: supporting personal performance for teaching-related activities

Academics are under pressure because of entrepreneurial constraints, such as budgets and cost-oriented objectives, and educational demands, such as for more flexibility and for offering courses online or with online components. Based on the results of a series of studies of desired and actual performance, and evaluations of responses to a set of prototypes of a Personal Performance Support Tool, a final prototype version of the tool was developed to research the effects the tool can have on the performance and job satisfaction of academics, especially for their teaching-related activities

Does the fluid elasticity influence the dispersion in packed beds?

Reasons are given why the axial dispersion in a gas flowing through a packed bed may be influenced by the elasticity - or compressibility - of the fluid. To support this hypothesis, experiments have been done in a packed column at pressures from 0.13 to 2.0 MPa. The elasticity E of a gas is proportional to the pressure P and the compressibility to 1/P. The axial dispersion coefficients as determined were found to be a function of the pressure in the packed bed in the turbulent flow region of 3 < Rep < 150 if the Bodenstein number is plotted as a function of the particle Reynolds number. This is shown to be an artifact. The pressure influence is eliminated, if Bom, ax is plotted versus the ratio of the kinetic forces over the elastic forces u2/E. Regrettably, Bom, ax seems to be independent of u2/E. For the moment we only can conclude that Bom, ax in the turbulent region is a unique function of the velocity of the gas which flows through the packed bed. Although the fact that a constant Bo value is obtained when plotted against u2/E, the experimental results are so intriguing we wanted to make them public already now. The experimental work proceeds

A novel numerical mechanical model for the stress–strain distribution in superconducting cable-in-conduit conductors \ud

Besides the temperature and magnetic field, the strain and stress state of the superconducting Nb3Sn wires in multi-stage twisted cable-in-conduit conductors (CICCs), as applied in ITER or high field magnets, strongly influence their transport properties. For an accurate quantitative prediction of the performance and a proper understanding of the underlying phenomena, a detailed analysis of the strain distribution along all individual wires is required. For this, the thermal contraction of the different components and the huge electromagnetic forces imposing bending and contact deformation must be taken into account, following the complex strand pattern and mutual interaction by contacts from surrounding strands. In this paper, we describe a numerical model for a superconducting cable, which can simulate the strain and stress states of all single wires including interstrand contact force and associated deformation. The strands in the cable can be all similar (Nb3Sn/Cu) or with the inclusion of different strand materials for protection (Cu, Glidcop).\ud \ud The simulation results are essential for the analysis and conductor design optimization from cabling to final magnet operation conditions. Comparisons are presented concerning the influence of the sequential cable twist pitches and the inclusion of copper strands on the mechanical properties and thus on the eventual strain distribution in the Nb3Sn filaments when subjected to electromagnetic forces, axial force and twist moment. Recommendations are given for conductor design improvements. \ud \ud \u

Optimisation of ITER Nb3Sn CICCs for coupling loss, transverse electromagnetic load and axial thermal contraction

The ITER cable-in-conduit conductors (CICCs) are built up from sub-cable bundles, wound in different stages, which are twisted to counter coupling loss caused by time-changing external magnet fields. The selection of the twist pitch lengths has major implications for the performance of the cable in the case of strain sensitive superconductors, i.e. Nb3Sn, as the electromagnetic and thermal contraction loads are large but also for the heat load from the AC coupling loss. Reduction of the transverse load and warm-up cool-down degradation can be reached by applying longer twist pitches in a particular sequence for the sub-stages, offering a large cable transverse stiffness, adequate axial flexibility and maximum allowed lateral strand support. Analysis of short sample (TF conductor) data reveals that increasing the twist pitch can lead to a gain of the effective axial compressive strain of more than 0.3 % with practically no degradation from bending. For reduction of the coupling loss, specific choices of the cabling twist sequence are needed with the aim to minimize the area of linked strands and bundles that are coupled and form loops with the applied changing magnetic field, instead of simply avoiding longer pitches. In addition we recommend increasing the wrap coverage of the CS conductor from 50 % to at least 70 %. The models predict significant improvement against strain sensitivity and substantial decrease of the AC coupling loss in Nb3Sn CICCs, but also for NbTi CICCs minimization of the coupling loss can be achieved. Although the success of long pitches to transverse load degradation was already demonstrated, the prediction of the combination with low coupling loss needs to be validated by a short sample test.Comment: to be published in Supercond Sci Techno

Infrared study of the selective oxidation of toluene and o-xylene on vanadium oxide/TiO2

Infrared spectroscopy was used to obtain information on the mechanism of the selective oxidation of toluene and o-xylene over vanadium oxide catalysts. The interaction of these aromatic hydrocarbons and the products benzaldehyde and o-tolualdehyde with the surface of a V2O5/TiO2 monolayer catalyst was investigated at different temperatures under conditions comparable to those of the catalytic reaction. The infrared results obtained for each of these compounds showed a great resemblance, indicating that their oxidation proceeds along the same reaction path. Coordinatively adsorbed aldehydes, carboxylate-like structures, and benzoate species could be identified as intermediates on the surface of the catalysts. On the basis of the spectroscopic observations a possible reaction mechanism has been proposed

Topographic hub maps of the human structural neocortical network

Hubs within the neocortical structural network determined by graph theoretical analysis play a crucial role in brain function. We mapped neocortical hubs topographically, using a sample population of 63 young adults. Subjects were imaged with high resolution structural and diffusion weighted magnetic resonance imaging techniques. Multiple network configurations were then constructed per subject, using random parcellations to define the nodes and using fibre tractography to determine the connectivity between the nodes. The networks were analysed with graph theoretical measures. Our results give reference maps of hub distribution measured with betweenness centrality and node degree. The loci of the hubs correspond with key areas from known overlapping cognitive networks. Several hubs were asymmetrically organized across hemispheres. Furthermore, females have hubs with higher betweenness centrality and males have hubs with higher node degree. Female networks have higher small-world indices

Analysis of mass transfer with chemical reaction in finite gas-liquid systems

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Validation of a strand-level CICC-joint coupling loss model

Calculating the coupling losses in cable-in-conduit conductor (CICC) joints requires a large amount of numerical effort, which is why the numerical system is often reduced by grouping strands together. However, to better understand the loss behaviour, and eventually the stability mechanism in such joints, a full-sized model working on the level of individual strands is more desirable. For this reason, the numerical cable model JackPot-AC has been expanded to also simulate the coupling losses in a CICC joint. This model has been verified with AC loss measurements on a mock-up joint, which was subjected to an applied harmonic field at different angles. The mock-up joint consisted of two sub-sized CICCs connected by a copper sole. For additional verification the AC loss of one of these conductors and the copper sole was also measured separately. The results of the simulation agree with the measurements, and the model therefore proves to be a useful analytical tool for examining the coupling loss in CICC joint

CORD, a novel numerical mechanical model for Nb3Sn CICCs

The strain state of the superconducting Nb3Sn strands in multi-stage twisted ITER Cable-In-Conduit Conductors (CICCs) strongly determines the transport properties. For an accurate prediction of the performance and a proper understanding of the underlying phenomena, a detailed analysis of the stress and strain distribution along all individual strands is imperative. Also during the cabling process, the axial stress of the individual strands must be well controlled to avoid kinks, in particular when mixing different strands, e.g., Nb3Sn and copper strands. A mechanical model for a superconducting cable (CORD) was developed, which can predict the strain and stress states of all single strands including interstrand contact force and the associated deformation. The simulation results are not only important for analysis but can be used for optimization of cable manufacturing and conductor design optimization. We discuss the influence of the sequential cable twist pitches and the inclusion of copper strands on the mechanical properties