Experimental Evidence of Non-Linear Dissipation Using Acoustic Micro-Lapses

Non-linear material behaviour is observed experimentally in a laboratory using a new method called Acoustic Micro-Lapses (AML). In this approach, the shooting of two waves is synchronised in a way that the second wave (TW) is to sense the fluctuations in material stiffness induced by the first (PW). The tests include four samples; twenty trials are performed for each sample by increasing time-delays between the waves. The recorded waves are decoupled and compared to determine spectral differences by computing a quantity proportional to the energy difference as function of the increasing time delay (). For a tight sandstone and aluminium samples, the random behaviour of implies that TW finds the same equilibrium conditions as PW. The Lucite and the Berea sandstone depict distinct maxima, implying that TW sensed the transitory perturbations induced by PW. Therefore, it is inferred that PW and TW must propagate with different phase speeds. To assess the previous results, quasi-static modelling is performed using two time delayed step functions. The corresponding creep compliance shows a strong discontinuity when the second step is applied, implying the existence of two unrelaxed moduli. This supports the lab data in that the two waves must have different dispersion relations such that they propagate with different speeds

Effect of structural relaxation on the electronic structure of graphene on hexagonal boron nitride

We performed calculations of electronic, optical and transport properties of graphene on hBN with realistic moir\'e patterns. The latter are produced by structural relaxation using a fully atomistic model. This relaxation turns out to be crucially important for electronic properties. We describe experimentally observed features such as additional Dirac points and the "Hofstadter butterfly" structure of energy levels in a magnetic field. We find that the electronic structure is sensitive to many-body renormalization of the local energy gap.Comment: 5 pages, 6 figures. Supplementary material is available at http://www.theorphys.science.ru.nl/people/yuan/attachments/sm_hbn.pd

Investigation of the influence of wall stiffness on the stress ratio in mammoth silos

To calculate the stresses on the walls of silos, it is necessary to have a good estimate of the ratio of horizontal to vertical stress. This ratio however is not known precisely, especially in cases of static stress as found in a mammoth silo. In this paper the influence of the wall stiffness on the ratio of horizontal to vertical stresses in situations with limit strain is investigated. A new test method is developed, with which the ratio can directly be measured. A key feature of this method is the comparability with the practice. The method uses reinforced rubber membranes which have the same order of radial stiffness as mammoth silos. Another objective was to determine the extent to which the ratio of horizontal to vertical stresses with limit strain is dependent on the internal angle of friction, ¿i. Special attention was paid to Jaky's formula, which is often used to calculate the neutral stress ratio

Effect of structural relaxation on the electronic structure of graphene on hexagonal boron nitride

We performed calculations of electronic, optical and transport properties of graphene on hBN with realistic moir\'e patterns. The latter are produced by structural relaxation using a fully atomistic model. This relaxation turns out to be crucially important for electronic properties. We describe experimentally observed features such as additional Dirac points and the "Hofstadter butterfly" structure of energy levels in a magnetic field. We find that the electronic structure is sensitive to many-body renormalization of the local energy gap.Comment: 5 pages, 6 figures. Supplementary material is available at http://www.theorphys.science.ru.nl/people/yuan/attachments/sm_hbn.pd

Synthesis and Experiments of Inherently Balanced Umbrella Canopy Designs

This paper shows how umbrella canopies and umbrella canopy-like mechanisms can be designed inherently balanced. Inherently balanced means that the center of mass of the moving parts remains stationary at a single point for any position of the mechanism simply because of the specific design of the mechanism where no countermasses or springs are needed. The advantages of a balanced canopy are that it can be opened and closed easily with minimal effort even if it has large dimensions and that it is inherently safe since the canvas cannot collapse or fall down. Also a shaking ground or floor does not affect an inherently balanced canopy. This is due to its dynamic force balance, allowing the canopy to be perfectly suitable as a retractable roof on for instance a truck on a bumpy road. In this study, three inherently balanced umbrella canopy designs are synthesized from principal vector linkages and their balance conditions are derived. Also a prototype was built and tested to show the feasibility of the design in practice

Artificial neural networks for 3D cell shape recognition from confocal images

We present a dual-stage neural network architecture for analyzing fine shape details from microscopy recordings in 3D. The system, tested on red blood cells, uses training data from both healthy donors and patients with a congenital blood disease. Characteristic shape features are revealed from the spherical harmonics spectrum of each cell and are automatically processed to create a reproducible and unbiased shape recognition and classification for diagnostic and theragnostic use.Comment: 17 pages, 8 figure

Claiming and Reclaiming Settings, Objects, and Situations: A Microethnographic Study of the Sociomaterial Practices of Everyday Life at Swedish Youth Homes

The aim of this study is to explore social interactions in the spatial and material environment within everyday life at special youth homes in Sweden, where youths with psychosocial problems, or criminal behavior are cared for involuntary. A microethnographic approach was chosen, and data was collected through participant observation. A theory integrating analysis, using Burke’s (1969) dramatistic pentad as a tool for structuring the data and Goffman’s (1956; 1961) dramaturgical perspective was undertaken. The findings demonstrate that the staff’s control over settings and objects also means control over the definition of what kind of place the special youth home is, and what takes place there. This is shown through a decorous behavior of sociomaterial control practices, rather than care practices, by the staff. This study contributes to knowledge on spaces and objects as crucial parts of care practices highlighting the intentions inscribed in institutional design and objects

Be prepared and do the best you can: a focus group study with staff on the care environment at Swedish secure youth homes

PURPOSE: This study examined staff members\u27 experiences of the institutional care environment within secure youth homes. METHODS: Data were collected through three focus group discussions with 17 staff members at two secure youth homes. Subsequently, a thematic analysis was conducted. RESULTS: The analysis indicated two main themes: risk management and damage control in a restricted environment and compensating and reconstructing ordinariness-trying to make the best of it; each theme had three subthemes. The care environment seems to be experienced by staff as characterized by conflicting demands, thus constituting a gap between needs and what is possible to achieve-a balancing act that constitutes a constant struggle. CONCLUSIONS: The staff members\u27 constant struggle could be interpreted as conflicting moral and instrumental demands; they know what the youths need, but the environment of the secure youth homes demands the decorous behaviour of sociomaterial control practices-rather than care practices