Measuring monopole and dipole polarizability of acoustic meta-atoms

We present a method to extract monopole and dipole polarizability from experimental measurements of two-dimensional acoustic meta-atoms. In contrast to extraction from numerical results, this enables all second-order effects and uncertainties in material properties to be accounted for. We apply the technique to 3D-printed labyrinthine meta-atoms of a variety of geometries. We show that the polarizability of structures with shorter acoustic path length agrees well with numerical results. However, those with longer path lengths suffer strong additional damping, which we attribute to the strong viscous and thermal losses in narrow channels

Research and development of an air-puff excitation system for lightweight structures

© 2019 International Group of Operational Modal Analysis. Lightweight, thin-walled structures appear in numerous engineering and natural structures. Due to their sensitivity, vibration excitation by, now traditional, contacting techniques, such as modally-tuned impact hammers or electrodynamic shakers, to investigate their dynamics is challenging since it typically adds substantial mass and/or stiffness at the excitation location. The research presented in this article, therefore, is intended to yield a system for the non-contact excitation of thin-walled structures through small, controlled blasts of air. An air-puff system, consisting of two fast-acting solenoid-controlled valves, a small air outlet nozzle and bespoke control software with a programmable valve control sequence, is researched and developed. The excitation impulse characteristics are investigated experimentally and described in detail for varying input control parameters. Ultimately, suitability of the system for the excitation of thin-walled structures is explored, for both a 3D-printed micro-satellite panel and a natural bee honeycomb, with promising results when compared to that of an impact hammer

Co-registration of Laser Altimeter Tracks with Digital Terrain Models and Applications in Planetary Science

We have derived algorithms and techniques to precisely co-register laser altimeter profiles with gridded Digital Terrain Models (DTMs), typically derived from stereo images. The algorithm consists of an initial grid search followed by a least-squares matching and yields the translation parameters at sub-pixel level needed to align the DTM and the laser profiles in 3D space. This software tool was primarily developed and tested for co-registration of laser profiles from the Lunar Orbiter Laser Altimeter (LOLA) with DTMs derived from the Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) stereo images. Data sets can be co-registered with positional accuracy between 0.13 m and several meters depending on the pixel resolution and amount of laser shots, where rough surfaces typically result in more accurate co-registrations. Residual heights of the data sets are as small as 0.18 m. The software can be used to identify instrument misalignment, orbit errors, pointing jitter, or problems associated with reference frames being used. Also, assessments of DTM effective resolutions can be obtained. From the correct position between the two data sets, comparisons of surface morphology and roughness can be made at laser footprint- or DTM pixel-level. The precise co-registration allows us to carry out joint analysis of the data sets and ultimately to derive merged high-quality data products. Examples of matching other planetary data sets, like LOLA with LRO Wide Angle Camera (WAC) DTMs or Mars Orbiter Laser Altimeter (MOLA) with stereo models from the High Resolution Stereo Camera (HRSC) as well as Mercury Laser Altimeter (MLA) with Mercury Dual Imaging System (MDIS) are shown to demonstrate the broad science applications of the software tool

Explanatory debugging: Supporting end-user debugging of machine-learned programs

Many machine-learning algorithms learn rules of behavior from individual end users, such as task-oriented desktop organizers and handwriting recognizers. These rules form a “program” that tells the computer what to do when future inputs arrive. Little research has explored how an end user can debug these programs when they make mistakes. We present our progress toward enabling end users to debug these learned programs via a Natural Programming methodology. We began with a formative study exploring how users reason about and correct a text-classification program. From the results, we derived and prototyped a concept based on “explanatory debugging”, then empirically evaluated it. Our results contribute methods for exposing a learned program's logic to end users and for eliciting user corrections to improve the program's predictions

Treatment efficacy of a specialized psychotherapy program for Internet Gaming Disorder

Background and aims: Internet Gaming Disorder (IGD) has become health concern around the world, and specialized health services for the treatment of IGD are emerging. Despite the increase in such services, few studies have examined the efficacy of psychological treatments for IGD. The primary aim of this study was to assess the efficacy of a specialized psychotherapy program for adolescents with IGD [i.e., the “Programa Individualizado Psicoterapéutico para la Adicción a las Tecnologías de la Información y la Comunicación” (PIPATIC) program]. Methods: The sample comprised 31 adolescents (aged 12–18 years) from two public mental health centers who were assigned to either the (a) PIPATIC intervention experimental group or (b) standard cognitive-behavioral therapy (CBT) control group. The interventions were assessed at pre-, middle-, and post-treatment phases, as well as a 3-month assessment was carried out after completing the interventions. Results: No significant differences between either group in the pre-treatment phase were found. Relating to the different interventions examined, significant differences were found at pre-test and post-test on the following variables: comorbid disorders, intrapersonal and interpersonal abilities, family relationships, and therapists’ measures. Both groups experienced a significant reduction of IGD symptoms, although the PIPATIC group experienced higher significant improvements in the remainder of the variables examined. Discussion and conclusions: The findings suggest that PIPATIC program is effective in the treatment of IGD and its comorbid disorders/symptoms, alongside the improvement of intra- and interpersonal abilities and family relationships. However, it should also be noted that standard CBT was also effective in the treatment of IGD. Changing the focus of treatment and applying an integrative focus (including the addiction, the comorbid symptoms, intra- and interpersonal abilities, and family psychotherapy) appear to be more effective in facilitating adolescent behavior change than CBT focusing only on the IGD itself

A place to die for: apoptosis in cancer and infection, Capri 2002

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Acoustic meta-atom with experimentally verified maximum Willis coupling

© 2019, The Author(s). Acoustic metamaterials are structures with exotic acoustic properties, with promising applications in acoustic beam steering, focusing, impedance matching, absorption and isolation. Recent work has shown that the efficiency of many acoustic metamaterials can be enhanced by controlling an additional parameter known as Willis coupling, which is analogous to bianisotropy in electromagnetic metamaterials. The magnitude of Willis coupling in a passive acoustic meta-atom has been shown theoretically to have an upper limit, however the feasibility of reaching this limit has not been experimentally investigated. Here we introduce a meta-atom with Willis coupling which closely approaches this theoretical limit, that is much simpler and less prone to thermo-viscous losses than previously reported structures. We perform two-dimensional experiments to measure the strong Willis coupling, supported by numerical calculations. Our meta-atom geometry is readily modeled analytically, enabling the strength of Willis coupling and its peak frequency to be easily controlled