1,720,958 research outputs found
Improved Flat Frequency Response of Conical Shellular Metamaterial-Enabled Flat Panel Loudspeaker
No full textA piezoelectric flat panel loudspeaker operates by utilizing a piezoelectric film actuator to vibrate a diaphragm, offering advantages in miniaturization, embedding, and spatial efficiency. However, achieving high sound pressure levels (SPL) at low frequencies and maintaining a flat frequency response remains challenging. This study presents a Conical Shellular Sandwich Diaphragm (CSSD), derived from conical shellular metamaterials, which combines lightweight properties with high stiffness. The CSSD enhances low-frequency SPL and improves frequency response flatness through structural optimization, eliminating the need for complex systems. Finite element analysis identifies optimal geometric parameters for the CSSD unit cell, resulting in an 11.5 dB increase in low-frequency SPL and a 53% reduction in peak-dip deviation across the 200 Hz-20 kHz range, compared to a conventional Flat Panel Diaphragm (FPD). These enhancements stem from a reduction in the CSSD's effective mass (meff) to one-hundredth of an equivalent-volume FPD and an increase in effective bulk modulus (keff) relative to structures with the same mass. Experimental tests of 3D-printed CSSD and FPD prototypes integrated with piezoelectric actuators match the simulation results. This study demonstrates the potential of mechanical metamaterials to address design limitations in flat panel loudspeakers, enabling improved sound quality and simpler configurations for commercial use.
Zero Poisson's ratio metamaterial and meander-inspired diaphragms for enhancing low-frequency performance in flat-panel loudspeaker
No full textFlat-panel loudspeakers, designed with a planar configuration, provide space-efficient audio solutions; however, they frequently exhibit limitations in low-frequency performance due to constrained diaphragm displacement. This study addresses the challenge of enhancing low-frequency sound pressure levels in flat-panel loudspeakers while preserving their slim profiles. We demonstrate that integrating metamaterial-inspired Zero Poisson's Ratio Diaphragms (ZPD) and Edge-Patterned Diaphragms (EPD) significantly improves low-frequency sound pressure levels in piezoelectric flat-panel loudspeakers. The selection of ZPD and EPD designs leverages the unique monoclastic behavior of zero Poisson's ratio structures and the high displacement characteristics of meanderspring patterns, respectively, which results in increased diaphragm flexibility and displacement. Our finite element analysis, supported by experimental results, shows that both ZPD and EPD designs enhance sound pressure levels below 200 Hz compared to a conventional bare diaphragm, achieving maximum enhancements of 11.6 dB and 20.0 dB, respectively. These findings advance the field by introducing diaphragm designs that exploit zero Poisson's ratio principles and structural patterns to improve acoustic performance without increasing overall thickness. The proposed metamaterials and structural designs demonstrate considerable potential for acoustic applications across multimedia systems, portable devices, and automotive audio, where superior low-frequency response in slim-profile loudspeakers is highly beneficial.
All-Polarized Elastic Wave Attenuation and Harvesting via Chiral Mechanical Metamaterials
No full textManipulating elastic waves of all polarizations is highly challenging due to the complex behavior of elastic waves. To achieve simultaneous broadband vibration attenuation and energy harvesting across all polarizations of elastic waves at low-frequency ranges, a chiral mechanical metamaterial-based energy harvester is proposed in this study. The systematic development of a complete bandgap and defect structure is achieved through theoretical eigenfrequency analysis and numerical simulations. The defect structure is incorporated to induce defect modes for all wave polarizations within the complete bandgap region, ensuring their compatibility with the overall shape of the structure. The proposed chiral mechanical metamaterial with defect (CMMD) demonstrated significant performance improvements, achieving electrical output power enhancements that are 20.5 times for flexural waves and 511.4 times for longitudinal-torsional waves compared to the defectless chiral mechanical metamaterial. This study accentuates the thoughtful design and multifaceted utility of chiral mechanical metamaterials, paving the way for their application not only in energy harvesting but also in wave attenuation for various polarizations. A chiral mechanical metamaterial with broken periodicity is developed to manipulate elastic waves across all polarizations. This innovative structure possesses the remarkable ability to simultaneously attenuate vibrations and harvest energy from elastic waves, irrespective of their polarization, even at low frequencies. By harnessing this unique design, the metamaterial achieves unparalleled improvements in energy harvesting performance, significantly outperforming conventional metamaterials. image
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
