Modeling thin-film piezoelectric polymer ultrasonic sensors

This paper presents a model suitable to design and characterize broadband thin film sensors based on piezoelectric polymers. The aim is to describe adequately the sensor behavior, with a reasonable number of parameters and based on well-known physical equations. The mechanical variables are described by an acoustic transmission line. The electrical behavior is described by the quasi-static approximation, given the large difference between the velocities of propagation of the electrical and mechanical disturbances. The line parameters include the effects of the elastic and electrical properties of the material. The model was validated with measurements of a poly(vinylidene flouride) sensor designed for short-pulse detection. The model variables were calculated from the properties of the polymer at frequencies between 100 Hz and 30 MHz and at temperatures between 283 K and 313-K, a relevant range for applications in biology and medicine. The simulations agree very well with the experimental data, predicting satisfactorily the influence of temperature and the dielectric properties of the polymer on the behavior of the sensor. Conversely, the model allowed the calculation of the material dielectric properties from the measured response of the sensor, with good agreement with the published values.Fil: González, Martín Germán. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Sorichetti, Patricio Aníbal. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; ArgentinaFil: Cardozo Santiago, Gustavo David. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentin

Haptic Experience and the Design of Drawing Interfaces

Haptic feedback has the potential to enhance users’ sense of being engaged and creative in their artwork. Current work on providing haptic feedback in computer-based drawing applications has focused mainly on the realism of the haptic sensation rather than the users’ experience of that sensation in the context of their creative work. We present a study that focuses on user experience of three haptic drawing interfaces. These interfaces were based on two different haptic metaphors, one of which mimicked familiar drawing tools (such as pen, pencil or crayon on smooth or rough paper) and the other of which drew on abstract descriptors of haptic experience (roughness, stickiness, scratchiness and smoothness). It was found that users valued having control over the haptic sensation; that each metaphor was preferred by approximately half of the participants; and that the real world metaphor interface was considered more helpful than the abstract one, whereas the abstract interface was considered to better support creativity. This suggests that future interfaces for artistic work should have user-modifiable interaction styles for controlling the haptic sensation

Damaging and Cracks in Thin Mud Layers

We present a detailed study of a two-dimensional minimal lattice model for the description of mud cracking in the limit of extremely thin layers. In this model each bond of the lattice is assigned to a (quenched) breaking threshold. Fractures proceed through the selection of the part of the material with the smallest breaking threshold. A local damaging rule is also implemented, by using two different types of weakening of the neighboring sites, corresponding to different physical situations. Some analytical results are derived through a probabilistic approach known as Run Time Statistics. In particular, we find that the total time to break down the sample grows with the dimension $L$ of the lattice as $L^2$ even though the percolating cluster has a non trivial fractal dimension. Furthermore, a formula for the mean weakening in time of the whole sample is obtained.Comment: 10 pages, 7 figures (9 postscript files), RevTe

Summary of investigations of light scattering in highly reflecting pigmented coatings

Light scattering in highly reflecting pigmented coatings - silver bromide and particle suspensions and paint film

The Haunting of L.S. Lowry: Class, Mass Spectatorship and the Image at The Lowry, Salford, UK

In a series of momentary encounters with the surface details of The Lowry Centre, a cultural venue located in Salford, Greater Manchester, UK, this article considers the fate of the image evoked by the centre’s production and staging of cultural experience. Benjamin’s notion of ‘aura’ as inimical to transformations of art and cultural spectatorship is explored, alongside its fatal incarnation in Baudrillard’s concept of ‘simulation’. L.S. Lowry, I argue, occupies the space as a medium: both as a central figure of transmission of the centre’s narrative of inclusivity through cultural regeneration, and as one who communes with phantoms: remainders of the working-class life and culture that once occupied this locale. Through an exploration of various installations there in his name, Lowry is configured as a ‘destructive character’, who, by making possible an alternative route through its spaces, refuses to allow The Lowry Centre to insulate itself from its locale and the debt it owes to its past

A viscous paint model for interactive applications

We present a viscous paint model for use in an interactive painting system based on the well-known Stokes’ equations for viscous flow. Our method is, to our knowledge, the first unconditionally stable numerical method that treats viscous fluid with a free surface boundary. We have also developed a real-time implementation of the Kubelka-Munk reflectance model for pigment mixing, compositing and rendering entirely on graphics hardware, using programmable fragment shading capabilities. We have integrated our paint model with a prototype painting system, which demonstrates the model’s effectiveness in rendering viscous paint and capturing a thick, impasto-like style of painting. Several users have tested our prototype system and were able to start creating original art work in an intuitive manner not possible with the existing techniques in commercial systems