1,720,997 research outputs found
Extreme resilience and dissipation in heterogeneous elasto-plastomeric crystals
No full textWe present a microstructure-topology-based approach for designing macroscopic, heterogeneous soft materials that exhibit outstanding mechanical resilience and energy dissipation. We investigate a variety of geometric configurations of resilient yet dissipative heterogeneous elasto-plastomeric materials that possess long-range order whose microstructural features are inspired by crystalline metals and block copolymers. We combine experiments and numerical simulations on 3D-printed prototypes to study the extreme mechanics of these heterogeneous soft materials under cyclic deformation conditions up to an extreme strain of >200% with strain rates ranging from quasi-static (5.0 × 10−3 s−1) to high levels of >6.0 × 101 s−1. Moreover, we investigate the complexity of elastic and inelastic “unloading” mechanisms crucial for the understanding of shape recovery and energy dissipation in extreme loading situations. Furthermore, we propose a simple but physically intuitive approach for designing microstructures that exhibit a nearly isotropic behavior in both elasticity and inelasticity across different crystallographic orientations from small to large strains. Overall, our study sets a significant step toward the development of sustainable, heterogeneous soft material architectures at macroscopic scales that can withstand harsh mechanical environments.peer-reviewed2024-11-0
Transforming Wave Propagation in Layered Media via Instability-Induced Interfacial Wrinkling
No full textThe ability to control wave propagation in highly deformable layered media with elastic instability-induced wrinkling of interfacial layers is presented. The onset of a wrinkling instability in initially straight interfacial layers occurs when a critical compressive strain is achieved. Further compression beyond the critical strain leads to an increase in the wrinkle amplitude of the interfacial layer. This, in turn, gives rise to the formation of a system of periodic scatterers, which reflect and interfere with wave propagation. We demonstrate that the topology of wrinkling interfacial layers can be controlled by deformation and used to produce band gaps in wave propagation and, hence, to selectively filter frequencies. Remarkably, the mechanism of frequency filtering is effective even for composites with similar or identical densities, such as polymer-polymer composites. Since the microstructure change is reversible, the mechanism can be used for tuning and controlling wave propagation by deformation.Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies (Contract W911NF-13-D-0001
Magneto-viscoelastic laminates in finite shear
No full textThis paper presents a comprehensive theoretical framework for modeling magneto-viscoelastic laminates (MVLs) under both finite and infinitesimal strains. The laminate-based approach preserves explicit information about the material's internal structure through the orientation of layers, providing a direct link between microstructural architecture and macroscopic properties. By explicitly considering two distinct viscoelastic phases within the laminate, each with its own internal variable and relaxation time, our model captures the complex dynamic behavior observed in experimental studies. The governing equations are first derived for homogeneous strains, and then specialized to both finite and infinitesimal shearing deformation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Strategies to Control Performance of 3D-Printed, Cable-Driven Soft Polymer Actuators: From Simple Architectures to Gripper Prototype
No full textThe following is a study of the performance of soft cable-driven polymer actuators produced by multimaterial 3D printing. We demonstrate that the mechanical response of the polymer actuator with an embedded cable can be flexibly tuned through the targeted selection of actuator architecture. Various strategies, such as the addition of discrete or periodic stiff inserts, the sectioning of the actuator, or the shifting of the cable channel are employed to demonstrate ways to achieve more controllable deformed shape during weight lifting or reduce the required actuation force. To illustrate these concepts, we design and manufacture a prototype of the soft polymer gripper, which is capable of manipulating small, delicate objects. The explored strategies can be utilized in other types of soft actuators, employing, for instance, actuation by means of electroactive polymers.Israel Science Foundation (projects 1550/15)Israel Science Foundation (projects 1973/15
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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