Asymmetric Wave Propagation in Nonlinear Systems

A mechanism for asymmetric (nonreciprocal) wave transmission is presented. As a reference system, we consider a layered nonlinear, non mirror-symmetric model described by the one-dimensional Discrete Nonlinear Schreodinger equation with spatially varying coefficients embedded in an otherwise linear lattice. We construct a class of exact extended solutions such that waves with the same frequency and incident amplitude impinging from left and right directions have very different transmission coefficients. This effect arises already for the simplest case of two nonlinear layers and is associated with the shift of nonlinear resonances. Increasing the number of layers considerably increases the complexity of the family of solutions. Finally, numerical simulations of asymmetric wavepacket transmission are presented which beautifully display the rectifying effect

Conceptual design of sound, custom composition languages

Service composition, web mashups, and business process modeling are based on the composition and reuse of existing functionalities, user interfaces, or tasks. Composition tools typically come with their own, purposely built composition languages, based on composition techniques like data flow or control flow, and only with minor distinguishing features-besides the different syntax. Yet, all these composition languages are developed from scratch, without reference specifications (e.g., XML schemas), and by reasoning in terms of low-level language constructs. That is, there is neither reuse nor design support in the development of custom composition languages. We propose a conceptual design technique for the construction of custom composition languages that is based on a generic composition reference model and that fosters reuse. The approach is based on the abstraction of common composition techniques into high-level language features, a set of reference specifications for each feature, and the assembling of features into custom languages by guaranteeing their soundness. We specifically focus on mashup languages

Conceptual development of custom, domain-specific mashup platforms

Despite the common claim by mashup platforms that they enable end-users to develop their own software, in practice end-users still don't develop their own mashups, as the highly technical or inexistent user bases of today's mashup platforms testify. The key shortcoming of current platforms is their general-purpose nature, that privileges expressive power over intuitiveness. In our prior work, we have demonstrated that a domainspecific mashup approach, which privileges intuitiveness over expressive power, has much more potential to enable end-user development (EUD). The problem is that developing mashup platforms - domain-specific or not - is complex and time consuming. In addition, domain-specific mashup platforms by their very nature target only a small user basis, that is, the experts of the target domain, which makes their development not sustainable if it is not adequately supported and automated. With this article, we aim to make the development of custom, domain-specific mashup platforms costeffective. We describe a mashup tool development kit (MDK) that is able to automatically generate a mashup platform (comprising custom mashup and component description languages and design-time and runtime environments) from a conceptual design and to provision it as a service. We equip the kit with a dedicated development methodology and demonstrate the applicability and viability of the approach with the help of two case studies. © 2014 ACM

Damping behavior of 316L lattice structures produced by Selective Laser Melting

Selective Laser Melting is a powder-bed additive manufacturing technology that allows producing fully-dense metal objects with complex shapes and high mechanical properties. In this work, Selective Laser Melting was used to produce 316L specimens including lattice structures with the aim of exploring the possibility given by additive manufacturing technologies to produce parts with increased damping capacity, especially in relation to their weight. The internal friction of bulk and lattice specimens was measured in terms of delay between stress and deformation (i.e. tanδ) for different applied loads and frequencies. A finite element model was used to design the test and microstructure investigations were performed to support the results obtained by dynamo-mechanical tests. Keywords: Additive manufacturing, Selective Laser Melting, 316L, Lattice structure, Damping, Internal frictio

Modeling, enacting, and integrating custom crowdsourcing processes

Crowdsourcing (CS) is the outsourcing of a unit of work to a crowd of people via an open call for contributions. Thanks to the availability of online CS platforms, such as Amazon Mechanical Turk or CrowdFlower, the practice has experienced a tremendous growth over the past few years and demonstrated its viability in a variety of fields, such as data collection and analysis or human computation. Yet it is also increasingly struggling with the inherent limitations of these platforms: each platform has its own logic of how to crowdsource work (e.g., marketplace or contest), there is only very little support for structured work (work that requires the coordination of multiple tasks), and it is hard to integrate crowdsourced tasks into stateof-the-art business process management (BPM) or information systems. We attack these three shortcomings by (1) developing a flexible CS platform (we call it Crowd Computer, or CC) that allows one to program custom CS logics for individual and structured tasks, (2) devising a BPMN-based modeling language that allows one to program CC intuitively, (3) equipping the language with a dedicated visual editor, and (4) implementing CC on top of standard BPM technology that can easily be integrated into existing software and processes. We demonstrate the effectiveness of the approach with a case study on the crowd-based mining of mashup model patterns

Distributed orchestration of user interfaces

Workflow management systems focus on the coordination of people and work items, service composition approaches on the coordination of service invocations, and, recently, web mashups have started focusing on the integration and coordination of pieces of user interfaces (UIs), e.g., a Google map, inside simple web pages. While these three approaches have evolved in a rather isolated fashion although they can be seen as evolution of the componentization and coordination idea from people to services to UIs in this paper we describe a component-based development paradigm that conciliates the core strengths of these three approaches inside a single model and language. We call this new paradigm distributed UI orchestration, so as to reflect the mashup-like and process-based nature of our target applications. In order to aid developers in implementing UI orchestrations, we equip the described model and language with suitable design, deployment, and runtime instruments, covering the whole life cycle of distributed UI orchestrations. © 2011 Elsevier Ltd. All rights reserved

Influence of the COVID-19 Pandemic on Admissions for Retinal Detachment in a Tertiary Eye Emergency Department

Purpose: To compare the incidence and clinical characteristics of retinal detachments (RDs) diagnosed in a tertiary eye emergency department (EED) during the COVID-19 pandemic and in the corresponding period of the previous 4 years. Methods: EED consultations performed from February 21, 2020 (first national case of COVID-19 infection) to May 3, 2020 (end of lockdown imposed by national Government) and for the same date range of 2016-2019 (pre-COVID-19 period), and with a confirmed diagnosis of RD were collected and reviewed. The following demographical and clinical features have been analyzed: age, gender, etiology of RD, macular involvement, best corrected visual acuity (BCVA), and duration of experienced symptoms. Results: Eighty-two subjects (20.5\ub11.0 eyes/year) were diagnosed with RD in the pre-COVID-19 period, compared to 12 patients in the COVID-19 period (-41.5%). During the pandemic, patients complained symptoms for a median of 8.5 days (IQR, 1.7-15 days) before the EED consultation, while in the pre-COVID-19 period, they declared they had been symptomatic for 2 days (IQR, 1-4 days) (p=0.037); macula-off RD raised from 56% to 75% and no one reported trauma as a triggering event. Conclusion: During the COVID-19 pandemic, the rate of RD diagnosed in our EED decreased significantly and patients waited longer before asking for an ophthalmologic examination. These findings are probably due to the fear of contracting the COVID-19 infection attending hospital environments. Even if emergency departments are often misused by people suffering non-urgent conditions, patients complaining of sudden visual loss, visual field defects, or phosphenes should always and promptly attend an EED visit to prevent a worse prognosis