1,720,985 research outputs found
A Simply Accessed Approach of 2D Shaping Liquid Metal in Microwave Device Applications
Get PDFIn this letter, a simply accessed approach of 2D shaping liquid metal (LM) is presented. This approach allows a microwave device to take advantage of LM in both stretchability and removability. This approach is achieved based on the Young-Laplace theory of liquid surface tension, as well as the surface oxidization that LM possess. An application example of this approach is demonstrated by a functional changeable microwave device. The proposed device operates in antenna mode when LM is not incorporated. Then, it can change to resonator mode after filling 2D shaped LM into fluidic channels. To our knowledge, it is the first device that is capable of changing its function using LM. The measured gain of the proposed microwave device is 7.1 dBi at 2.68 GHz when it operates in antenna mode. The measured insertion loss of the proposed microwave is 1.8 dB at 2.62 GHz when it operates in resonator mode
X-Band Reconfigurable Phase Shifters Based on SIW and Liquid Metal Technologies
No full textThis paper presents three reconfigurable phase shifters operate at X-band and designed utilizing liquid metal (LM). The phase shifters operate at 10 GHz and they have very low insertion loss performance and able to handle high levels of radio frequency (RF) power. Besides, the proposed phase shifters able to achieve a total of 360° phase shift and they are compact in size as they are designed using substrate integrated waveguides (SIW). This enable the proposed phase shifters to be integrated within SIW based feeding structures to realize complete phased array antenna systems. The phase shift is realized by inserting a series of liquid metal vias in the SIW. When a single or multiple via connection is needed, the via hole is filled with liquid metal and conversely, the liquid metal is withdrawn from the via when the connection is no longer required.</p
Circuits and Antennas Incorporating Gallium-Based Liquid Metal
Get PDFThis article reviews the application and technology advancement of gallium (Ga)-based liquid metal (LM) in high-frequency circuits and antennas. It discusses the material properties of common LMs, the fluidic channels used to contain LM and their manufacturing techniques, and the actuation techniques, which are all critical for the design and implementation of LM-based devices. LM’s fluidic and pliable nature, together with its excellent electrical, thermal, and rheological (i.e., fluid flow) properties, provides some unique and innovative solutions to flexible/wearable electronics, reconfigurable circuits, and antennas. This article provides a comprehensive review of a wide range of LM-enabled high-frequency circuits and antennas, including interconnects and transitions, reconfigurable passive circuits (such as resonators, filters, and couplers), switches, phase shifters, reconfigurable antennas, flexible and wearable antennas, and metamaterials (i.e., periodic materials with properties not found in nature). This article presents various design concepts and implementation techniques, highlights key capabilities, and discusses the challenges and opportunities with the use of Ga-based LM materials
10 GHz Low Loss Liquid Metal SIW Phase Shifter for Phased Array Antennas
Get PDFThis article presents a proof of concept demonstrator for a pair of novel phase shifters based on substrate integrated waveguide (SIW) technology. Gallium-based liquid metal (LM) is used to reconfigure each phase shifter. This article presents LM phase shifters that, for the first time, have a phase shifting range of 360°. The phase shifters have a small electrical size, and they are intended for use within phased array antenna applications. This article also presents a design procedure for the phase shifters. The procedure has been used to design two phase shifters operating at 10 GHz. The design process can be readily scaled for operation at other frequencies. The proposed phase shifters are reciprocal and bidirectional, and they have very low insertion loss (IL). A series of reconfigurable LM vias are used to achieve the phase shift. Each of LM via is activated once a drill hole is filled with LM and it is deactivated once LM is removed. Using this method, it is possible to achieve a phase shift step ranging from 1° to 100° using a single LM via. Moreover, the overall phase shift can be extended to 360° by employing several LM vias in series inside the SIW. The proposed phase shifters have an IL lower than 3 dB and provide a total phase shifting range of approximately 360° in eight steps of approximately 45° each. This enables the proposed two phase shifters to have an extraordinary figure of merit (FoM) of 131.3°/dB and 122.4°/dB
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
mm-Wave Low-Cost 3D Printed MIMO Antennas With Beam Switching Capabilities for 5G Communication Systems
Get PDFThis paper presents designs and prototypes of low cost multiple input multiple output (MIMO) antennas for 5G and millimetre-wave (mm-wave) applications. The proposed MIMOs are fabricated using 3D printing and are able deliver beams in multiple directions that provide continuous and real time coverage in the elevation of up to {\mp }30^{\circ } without using phase shifters. This equips the proposed MIMO with a superior advantage of being an attractive low cost technology for 5G and mm-wave applications. The proposed MIMO antennas operate at the 28 GHz 5G band, with wide bandwidth performance exceeds 4 GHz and with beam switching ability of up to {\mp }30^{\circ } in the elevation plane. The direction of the main beam of the single element antenna in the MIMO is steered over the entire bandwidth through introducing 3D printed walls with different heights on the side of the 3D printed radiating antenna. Unlike all other available beam steering techniques; the proposed wall is not only able to change the direction of the beam of the antenna, but also it is able to increase the overall directivity and gain of the proposed antenna and MIMO at the same time over the entire bandwidth
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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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