Analytical and experimental study of two concentric cylinders coupled by a fluid gap

From a structural point of view a liquid coolant type nuclear reactor consists of a heavy steel vessel containing the core and related mechanical components and filled with a hot fluid. This vessel is protected from the severe environment of the core by a shielding structure, the thermal liner, which is usually a relatively thin steel cylinder concentric with the reactor vessel and separated from it by a gap filled with the coolant fluid. This arrangement leads to a potential vibration problem if the fundamental frequency, or one of the higher natural vibration frequencies, of this liner system is close to the frequency of some vibration source present in the reactor vessel. The shell rigidly clamped at its base and free at the top was investigated since it is a better description of the conditions encountered in typical reactor designs

Dynamics of composite Haldane spin chains in IPA-CuCl3

Magnetic excitations in the quasi-one-dimensional antiferromagnet IPA-CuCl3 are studied by cold neutron inelastic scattering. Strongly dispersive gap excitations are observed. Contrary to previously proposed models, the system is best described as an asymmetric quantum spin ladder. The observed spectrum is interpreted in terms of ``composite'' Haldane spin chains. The key difference from actual S=1 chains is a sharp cutoff of the single-magnon spectrum at a certain critical wave vector.Comment: 4 pages 4 figure

Nonlinear Dynamic Analysis of Cracked Beam on Elastic Foundation Subjected to Moving Mass

This paper presents a finite element algorithm for nonlinear dynamic analysis of cracked beams on an elastic foundation subjected to moving mass. Quantity surveying with parameters of varied cracks, foundation and loads shows their influence levels on the nonlinear dynamic response of the beams. The findings of the paper are the basis for the analysis, evaluation, and diagnosis of damages of beam structures on the elastic foundation subjected to moving loads, in which the common defects of the beams such as cracks are considered in order to improve the system's operational efficiency in a wide range of engineering applications

Shortcuts in a Nonlinear Dynamical Braneworld in Six Dimensions

We consider a dynamical brane world in a six-dimensional spacetime containing a singularity. Using the Israel conditions we study the motion of a 4-brane embedded in this setup. We analyse the brane behaviour when its position is perturbed about a fixed point and solve the full nonlinear dynamics in the several possible scenarios. We also investigate the possible gravitational shortcuts and calculate the delay between graviton and photon signals and the ratio of the corresponding subtended horizons.Comment: 26 pages, 9 figures. References and discussion added. Title changed to match the version accepted in Class. and Quant. Gra

Large-scale radio continuum properties of 19 Virgo cluster galaxies The influence of tidal interactions, ram pressure stripping, and accreting gas envelopes

Deep scaled array VLA 20 and 6cm observations including polarization of 19 Virgo spirals are presented. This sample contains 6 galaxies with a global minimum of 20cm polarized emission at the receding side of the galactic disk and quadrupolar type large-scale magnetic fields. In the new sample no additional case of a ram-pressure stripped spiral galaxy with an asymmetric ridge of polarized radio continuum emission was found. In the absence of a close companion, a truncated HI disk, together with a ridge of polarized radio continuum emission at the outer edge of the HI disk, is a signpost of ram pressure stripping. 6 out of the 19 observed galaxies display asymmetric 6cm polarized emission distributions. Three galaxies belong to tidally interacting pairs, two galaxies host huge accreting HI envelopes, and one galaxy had a recent minor merger. Tidal interactions and accreting gas envelopes can lead to compression and shear motions which enhance the polarized radio continuum emission. In addition, galaxies with low average star formation rate per unit area have a low average degree of polarization. Shear or compression motions can enhance the degree of polarization. The average degree of polarization of tidally interacting galaxies is generally lower than expected for a given rotation velocity and star formation activity. This low average degree of polarization is at least partly due to the absence of polarized emission from the thin disk. Ram pressure stripping can decrease whereas tidal interactions most frequently decreases the average degree of polarization of Virgo spiral galaxies. We found that moderate active ram pressure stripping has no influence on the spectral index, but enhances the global radio continuum emission with respect to the FIR emission, while an accreting gas envelope can but not necessarily enhances the radio continuum emission with respect to the FIR emission.Comment: 37 pages, 26 figures, accepted for publication in A&

A process for developing and validating performance assessment rubrics for laboratory techniques

PROBLEM Achieving competence in technical skills is a key learning objective in the laboratory programs of our institution’s Pharmaceutical Science course. However, their assessment is often achieved through indirect outcome indicators since performance assessment through direct observation is time-consuming and there is a lack of validated, efficient and scalable methods. PLAN We report on our approach towards the development, validation and optimisation of a set of rubrics for the formative and summative assessment of common chemistry laboratory techniques. Efficiency and user-friendliness are key criteria in the rubric development.  Drawing on recent work by Seery et al. (2017) and Chen et al. (2013), we propose a four-stage process: Rubric design based on practitioner input, literature sources and lab observations Testing involving student self-assessment, peer evaluation and instructor assessment Optimisation and validation based on assessment data, student and instructor feedback Developing supporting procedures (e.g., instructor training). ACTION AND EVALUATION We have started implementation in two synthetic chemistry subjects, initially targeting rubrics for four techniques (reflux setup, thin-layer chromatography, vacuum filtration and recrystallisation). Rubric evaluation will involve both quantitative (assessment data) and qualitative methods (surveys/focus groups with instructors and students, human ethics application in progress). REFERENCES Chen, H. J., She, J. L., Chou, C. C., Tsai, Y. M., & Chiu, M. H. (2013). Development and application of a scoring rubric for evaluating students’ experimental skills in organic chemistry: An instructional guide for teaching assistants. Journal of Chemical Education, 90(10), 1296–1302. https://doi.org/10.1021/ed101111g Seery, M. K., Agustian, H. Y., Doidge, E. D., Kucharski, M. M., O’Connor, H. M., & Price, A. (2017). Developing laboratory skills by incorporating peer-review and digital badges. Chemistry Education Research and Practice, 18(3), 403–419. https://doi.org/10.1039/C7RP00003