Evidences of evanescent Bloch waves in Phononic Crystals

We show both experimentally and theoretically the evanescent behaviour of modes in the Band Gap (BG) of finite Phononic Crystal (PC). Based on experimental and numerical data we obtain the imaginary part of the wave vector in good agreement with the complex band structures obtained by the Extended Plane Wave Expansion (EPWE). The calculated and measured acoustic field of a localized mode out of the point defect inside the PC presents also evanescent behaviour. The correct understanding of evanescent modes is fundamental for designing narrow filters and wave guides based on Phononic Crystals with defects.Comment: 8 pages, 3 figure

Detección de delaminaciones y otros defectos de unión en productos de acero multicapa Al/Al-Sn/Al llevando a cabo la monitorización con ondas guiadas EMAT

Rayleigh-Lamb, ultrasonic, guided wave modes were used to detect delamination, embedded steel debris and a brittle intermetallic Al-Fe diffusion bond layer at the interface between clad Al and steel, which were bonded together in a cold roll bonding (CRB) process. Multi-layered samples were produced, with artificially implanted defects of different sizes between the clad Al and steel layer to determine the sensitivity of the guided wave modes to qualitatively indicate the occurrence of defects based on signal attenuation caused by defects. Electromagnetic acoustic transducers (EMATs) were used to generate and detect the guided waves in the pitch and catch technique. Signals were measured in the as rolled and post rolling annealed state to determine the influence of the altered material properties on attenuation and Signal-to-Noise Ratio (SNR). Results show very good sensitivity of the S0 wave mode for delamination and embedded steel debris detection and a relation between attenuation, defect type, size and annealing state. However, detection of the presence of a brittle intermetallic Al-Fe diffusion layer was not possible due to the strong sensitivity to the material properties and thicknesses of the clad Al and steel materials. Micro sections of all samples were examined to explain the observations. The results suggest a promising use of Rayleigh-Lamb guided wave modes for online detection of bond defects in serial production of Al-Sn alloy/steel bimetal strips

Evanescent modes in Sonic Crystals: Complex relation dispersion and supercell approximation

Evanescent modes in complete sonic crystals (SC) and SC with point defects are reported both theoretically and experimentally in this paper. Plane wave expansion (PWE) and, in general, $\omega(k)$ methods have been used to calculate band structures showing gaps that have been interpreted as ranges of frequencies where no real $k$ exists. In this work, we extend PWE to solve the complex $k(\omega)$ problem applied to SC, introducing the supercell approximation for studying one vacancy. Explicit matrix formulation of the equations is given. This $k(\omega)$ method enables the calculation of complex band structures, as well as enabling an analysis of the propagating modes related with real values of the function $k(\omega)$, and the evanescent modes related with imaginary values of $k(\omega)$. This paper shows theoretical results and experimental evidences of the evanescent behavior of modes inside the SC band gap. Experimental data and numerical results using the finite elements method are in very good agreement with the predictions obtained using the $k(\omega)$ method.Comment: 15 pages, 3 figure

Prevalence and predictors of inadequate patient medication knowledge

© 2016 John Wiley & Sons, Ltd. Objectives: To assess medication knowledge in adult patients and to explore its determinants. Method: Cross-sectional study. Medication knowledge was the primary outcome and was assessed using a previously validated questionnaire. A multivariate logistic regression analysis was performed to explore the association between medication knowledge and the factors included in the model. Results: Seven thousand two hundred seventy-eight patients participated in the study. 71.9% (n = 5234) (95% CI: 70.9%–73.0%) of the surveyed patients had an inadequate knowledge of the medication they were taking. The dimensions obtaining the highest level of knowledge were the ‘medication use process’ and ‘therapeutic objective of medication’. The items ‘frequency’ (75.4%), ‘dosage’ (74.5%) and ‘indication’ (70.5%) had the highest percentage of knowledge. Conversely, ‘medication safety’ represented the dimension with the lowest scores, ranging from 12.6% in the item “contraindications” to 15.3% in the item ‘side effects’. The odds ratio (OR) of having an inadequate medication knowledge increased for unskilled workers (OR: 1.33; 85% CI:1.00–1.78; P = 0.050), caregivers (OR:1.46; 95% CI:1.18–1.81; P < 0.001), patients using more than one medication (OR: 1.14; 95% CI: 1.00–1.31; P = 0.050) and patients who did not know the name of the medication they were taking (OR: 2.14, 95% CI: 1.71–2.68 P < 0.001). Conclusion: Nearly three quarters of the analysed patients had inadequate knowledge regarding the medicines they were taking. Unskilled workers and caregivers were at a higher risk of lacking of medication knowledge. Other factors that correlated with inadequate medication knowledge were the use of more than one drug and not knowing the name of the medication dispensed

Designing personal informatics for self-reflection and self-awareness: the case of children with attention deficit hyperactivity disorder

A main challenge in designing for children with Attention Deficit Hyperactivity Disorder (ADHD) is to support the learning process of supressing undesired behaviour on daily routines by means of positive feedback and rewards. Personal Informatics (PI) is a model that supports capturing and integration of personal data to facilitate reflection and action that is used as a design platform to support behavioral learning. This paper presents a designdriven research study that illustrates the potential of PI to support selfawareness and self-reflection of ADHD children. Two design approaches are described which aim to support self-behavioral inhibition learning: (a) KITA, a Kinesiofeedback Toy for ADHD, being a Tangible User Interface that measures and assesses children’s activity and provides them with feedback as to whether or not behavior is within appropriate limits; and (b) WRISTWIT, a Wearable device presenting information on attention and time for ADHD to increase ontask behavior. KITA and WRISTWIT were tested in the field with children as design means to implement PI to positively modify children behavior during daily school routines

Perfect and broadband acoustic absorption by critically coupled sub-wavelength resonators

International audiencePerfect absorption is an interdisciplinary topic with a large number of applications, the challenge of which consists of broadening its inherently narrow frequency-band performance. We experimentally and analytically report perfect and broadband absorption for audible sound, by the mechanism of critical coupling, with a sub-wavelength multi-resonant scatterer (SMRS) made of a plate-resonator/ closed waveguide structure. In order to introduce the role of the key parameters, we first present the case of a single resonant scatterer (SRS) made of a Helmholtz resonator/closed waveguide structure. In both cases the controlled balance between the energy leakage of the several resonances and the inherent losses of the system leads to perfect absorption peaks. In the case of the SMRS we show that systems with large inherent losses can be critically coupled using resonances with large leakage. In particular, we show that in the SMRS system, with a thickness of λ/12 and diameter of λ/7, several perfect absorption peaks overlap to produce absorption bigger than 93% for frequencies that extend over a factor of 2 in audible frequencies. The reported concepts and methodology provide guidelines for the design of broadband perfect absorbers which could contribute to solve the major issue of noise reduction

Obtenció dels modes de resonancia a una geometria complexa: proposta didàctica de modelització amb elements finits

[EN] Finite Elements Method is a well established mathematical technique for solving Partial Derivative Differential Equations. In this article we present an example of application of Finite Elements Method: the harmonic resonance modes of a guitar obtained from the resolution of the eigenvalues equation via the Finite Elements Method. Graphical output and direct comparison with experiments facilitates the understanding of the method and an extra motivation, establishing a link between Mathematics and the resolution of real engineering problems than is specially necessary in the teaching of Mathematics in the engineering schools.[CA] Els elements finits actualment constitueixen una eina fonamental per a resolució d’equacions diferencials en contextos reals. En aquest article presentem un bon exemple per al mètode: l’obtenció dels modes de ressonància sobre la tapa harmònica d’una guitarra, a partir de la resolució d’una equació d’autovalors amb el mètode dels elements finits. Per la facilitat de interpretació i contrastació experimental dels resultats obtinguts, pot oferir a mès una gratificació i motivació addicional, molt necessària en tot procès d’aprenentatge.Fuster-Garcia, E.; Garcia Raffi, L.; Romero-Garcia, V. (2009). Obtenció dels modes de resonancia a una geometria complexa: proposta didàctica de modelització amb elements finits. Modelling in Science Education and Learning. 2:57-65. doi:10.4995/msel.2009.3123SWORD57652Zienkiewicz, Olgierd Cecil. The fi element method. Oxford: Butterworth-Heinemann, 2000, 5th ed