We propose a compact conformal wearable antenna that operates in the 2.36-2.4 GHz medical body-area network band. The antenna is enabled by placing a highly truncated metasurface, consisting of only ...a two by two array of I-shaped elements, underneath a planar monopole. In contrast to previously reported artificial magnetic conducting ground plane backed antenna designs, here the metasurface acts not only as a ground plane for isolation, but also as the main radiator. An antenna prototype was fabricated and tested, showing a strong agreement between simulation and measurement. Comparing to previously proposed wearable antennas, the demonstrated antenna has a compact form factor of 0.5 λ 0 ×0.3 λ 0 ×0.028 λ 0 , all while achieving a 5.5% impedance bandwidth, a gain of 6.2 dBi, and a front-to-back ratio higher than 23 dB. Further numerical and experimental investigations reveal that the performance of the antenna is extraordinarily robust to both structural deformation and human body loading, far superior to both planar monopoles and microstrip patch antennas. Additionally, the introduced metal backed metasurface enables a 95.3% reduction in the specific absorption rate, making such an antenna a prime candidate for incorporation into various wearable devices.
The concept of invisibility has garnered long‐standing interest throughout human history but has only been realized experimentally within the past decade, albeit over a limited bandwidth. While the ...physical wave phenomenon of a reduced scattering signature has been demonstrated with different cloaking methods such as transformation optics and scattering cancellation, such technology has yet to be incorporated into any practical real‐world devices. Through the use of quasi‐2D functional metasurfaces, the long‐standing issue of simultaneous mutual coupling and radiation blockage is addressed that occurs when two or more electromagnetic radiators are placed in close proximity to one another. The proposed compact and ultralightweight metasurfaces, comprising arrays of subwavelength electric and magnetic resonators with tailored dispersive properties, are capable of fully restoring the intrinsic properties of real‐world electromagnetic radiators when placed in a multiradiator environment. This work introduces a general design approach to bridge the gap between the theory and practice for cloaks, which is applicable to microwave, terahertz, and optical radiators, as well as acoustic and thermal sources. Moreover, this technology provides an unprecedented opportunity for enabling high‐density deployment of radiating systems with low interference and undistorted signal wave fronts.
Integrated ultralightweight metasurface cloaking coatings are demonstrated for restoring intrinsic properties of electromagnetic radiators. By tailoring the dispersive properties of the metasurfaces, the mutual coupling and mutual blockage between multiple radiators can be simultaneously reduced. The general concept and design approach pave the way for dense deployment of terahertz/optical antennas as well as radiators in other realms of physics.
A low-profile high-gain unidirectional antenna is proposed and demonstrated using both metamaterial (MM) and substrate-integrated waveguide (SIW) technologies. First, the leaky modes supported by a ...grounded anisotropic slab are studied. These investigations reveal that a grounded slab consisting of an anisotropic zero/low index material can provide an extremely low value for the real part of the propagation constant of the leaky mode, thereby facilitating stable unidirectional broadside radiation over a wide frequency range. The truncation effect of the slab is then investigated through full-wave simulations, which is found to be beneficial for a practical implementation of dispersive metamaterials. Finally, to validate the proposed concept, a subwavelength end-loaded dipole array is designed to realize the required anisotropic zero-index property and is applied to a SIW fed longitudinal slot antenna for the 5.8 GHz wireless local area network (WLAN) band. Measurements of the fabricated antenna prototype are shown to be in strong agreement with simulation results, thus confirming the proposed antenna design. The resulting antenna is only 0.12 λ thick, all while accomplishing a broadside gain of more than 10 dBi and a front-to-back ratio larger than 26 dB, which is ~ 7 dB and ~ 10 dB higher than that of the SIW fed slot alone, respectively. The -10 dB impedance bandwidth is more than 9% both with and without the presence of the MM coating. The proposed technique offers a means for realizing low-cost and low-profile unidirectional antennas with moderate bandwidth.
Wie weit zeigen sich in aktuellen (schulischen) Texten gegenüber früher veränderte Schreibmuster? Hat sich im Schreiben junger Menschen ein neuer Schreibstil zu etablieren begonnen, und wenn ja: Was ...können die Gründe dafür sein? Auf solche Fragen werden hier Antworten entwickelt und zu begründen versucht. Ausgangspunkt sind Analyseergebnisse von Untersuchungen aktueller (schulischer) Texte von jungen Erwachsenen, die in ihrer Textstruktur eine Nähe zu (konzeptioneller) Mündlichkeit zeigen. Zur Kennzeichnung dieser Phänomene wird der aus der Musikwissenschaft entlehnte Begriff Parlando für die Linguistik übernommen. Ziel ist eine genauere Bestimmung der Parlando -Phänomene sowie deren Erklärung. Empirische Basis dafür bildet einerseits eine Sammlung von aktuellen Abituriententexten, die im Rahmen des Zürcher 'Sprachfähigkeiten-Projekts' erstellt worden ist. Zum anderen konnte ein historisches Textkorpus von Abiturarbeiten aus dem Zeitraum von 1881-1991 zusammengestellt und untersucht werden, um möglichen Sprachwandelphänomenen auf die Spur zu kommen. In einem ersten Teil wird das Merkmalsbündel dokumentiert und gedeutet, das mit dem Begriff Parlando gefaßt wird. Das führt zum Ergebnis, in den Parlando -Phänomenen ein Indiz zu sehen für eine Veränderung kommunikativer Grundmuster in der Schriftlichkeit. Der zweite Teil will Erklärungen für die beschriebenen Sprachwandelphänomene im Bereich der Schriftlichkeit beibringen. Dafür werden über die textlinguistischen Überlegungen des ersten Teils hinaus sprachtheoretische und sprachgeschichtliche, aber ebenso sozialwissenschaftliche und bildungstheoretische Perspektiven entfaltet. Als Ergebnis wird am Textmuster Parlando ein soziokommunikativer Sprachwandel sichtbar, der seine Ursachen in verändertem Kommunikationsbedarf sowie in gewandelten Kommunikationsbedingungen und -bedürfnissen hat.
Anlagenbetreiber stehen vor vielfältigen Herausforderungen wie Fachkräftemangel, Internationalisierung, Betriebserlaubnis und Druck zur Produktivitäts‐ und Effizienzsteigerung. Ein neuer und ...ganzheitlicher Ansatz zur Digitalisierung des Sicherheitslebenszyklus eröffnet jetzt neue Potenziale und hilft dabei, die Herausforderungen zu meistern.
Sichere, flexible und anwendungsspezifische Programmierlösungen für die Funktionale Sicherheit einer Prozessanlage können zu langen Entwicklungszykluszeit führen, wenn beispielsweise langwierige ...Prüfprozesse den Anlagenbau ausbremsen. Ein modularer Ansatz kann diesen Prozess beschleunigen. Hier zeigt sich der Nutzen der Digitalisierung.
Several approaches in the literature have been attempted for reducing the radar cross-section (RCS) of antennas, specifically for planar patch antennas. Ideally, the antenna should function unimpeded ...at the communication frequency, but should have a minimal radar signature at all other frequencies of interest. Here, absorbing frequency selective surfaces (FSSs) are used as the ground plane of a planar antenna in order to reduce the RCS at higher frequencies. This technique offers many advantages over existing published approaches in the literature that generally show limited RCS reduction or poor antenna performance.
Wie hat sich die Diskussion um die Didaktik des Schreibens in den letzten Jahrzehnten im deutschsprachigen Raum entwickelt? Wichtige Entwicklungslinien werden mit einem spezifischen Augenmerk auf die ...Diskussionen und Beiträge aus der Deutschschweiz nachgezeichnet. In der produktiven Kooperation von Schreibforschung und Schreibdidaktik ist eine empirische Fundierung der Schreibdidaktik möglich geworden. Dabei hat der Blick auf den Schreibprozess in den vergangenen Jahren einen zentralen Stellenwert erhalten. Eine "prozessorientierte Schreibdidaktik" entwickelte auf diesen Grundlagen eine Vielzahl von Anregungen für einen erfolgreichen Schreibunterricht. In jüngster Zeit werden - auch im Licht der öffentlichen Thematisierung von schulischen Leistungen - die erzielten Effekte stärker wahrgenommen und diskutiert: Mit der Notwendigkeit einer breiten Literalitätsförderung wird der Aufbau von Textkompetenz zu einem zentralen Untersuchungsgegenstand. (DIPF/Orig.).
How did the discussion about the teaching and learning of writing evolve in the German speaking area during the last decades? This paper reconstructs important lines of development, paying special attention to discussions and contributions from German-speaking Switzerland. An empirical foundation for teaching and learning of writing has been built up through a productive cooperation between research on writing, and writing didactics. Within this cooperation, the view on the process of writing has become a central issue. Based on this foundation, process-oriented writing didactics have brought forth a number of suggestions for successful writing didactics. Recently - in part due to a higher public interest in school achievement -, more attention has been paid to the effects of this teaching, leading to more frequent discussions. As the promotion of literacy has become a societal necessity, the issue of text competence is an increasingly important topic of research. (DIPF/Orig.).
Background
The transfemoral approach is an extensile surgical approach that is performed routinely to facilitate cement and implant removal and improve exposure for revision stem implantation. ...Previous studies have looked at clinical results of small patient groups. The factors associated with fixation failure of cementless revision stems when using this approach have not been examined.
Questions/purposes
We determined (1) the clinical results and (2) complications of the transfemoral approach and (3) factors associated with fixation failure of revision stems when using the transfemoral approach.
Patients and Methods
We retrospectively examined all our patients in whom femoral stem revision was performed through a transfemoral approach between December 1998 and April 2004 and for whom a minimal followup of 2 years was available. One hundred patients were available for this study. The mean (± SD) postoperative followup was 5 years (± 1.64 years).
Results
The average Harris hip score improved from 45.2 (± 14.02) preoperatively to 83.4 (± 11.86) at final followup. Complete radiographic bony consolidation of the osteotomy site was observed in 95% of patients. Dislocations occurred in 9% of patients. Four revision stem fixation failures were observed, all occurring in patients with primary three-point fixation. Three-point fixation was associated with short osteotomy flaps and long revision stems.
Conclusions
The transfemoral approach is associated with a high rate of osteotomy flap bony healing and good clinical results. When using the transfemoral approach, a long osteotomy flap should be performed and the shortest possible revision stem should be implanted.
Level of Evidence
Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
For more than a decade, metamaterials have generated significant interest due to their theoretical and later experimentally demonstrated properties that are not observed in nature; yet, many of these ...designs are plagued by very limited bandwidth and/or high losses due to the dispersion characteristics of metamaterials. While many applications exist where a narrow band response is acceptable, examples of dual-band and multi-band responses within a communication bandwidth are limited. Furthermore, the ability to implement reconfigurability becomes complicated due to the lack of high performance switch technologies. In this dissertation, a new technique for constructing and synthesizing broadband metasurfaces is presented. A synthesis technique using Bézier surfaces is subsequently shown to not only outperform known optimization techniques but to produce results with bandwidths far exceeding those found in the literature. Additionally, a composite metamaterial geometry is introduced that facilitates a dual band response with a tunable frequency ratio within usable bands. The design also facilitates reconfigurablity. To mitigate the loss and bandwidth concerns of existing RF switch technologies a new technology is introduced and characterized - a chalcogenide glass phase change material enabled bistable switch. The superior efficiency and bandwidth are subsequently demonstrated by a novel quad state frequency selective surface, which once again boasts multiband reconfigurability within a communication band.
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