89,001 research outputs found
Fixed and reconfigurable multiband antennas
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel UniversityWith the current scenario of development of antennas in the wireless communication field, the need of compact multiband, multifunctional and cost effective antenna is on the rise. The objective of this thesis is to present fixed and reconfigurable techniques and methods for small and slim multiband antennas, which are applicable to serve modern small and slime wireless, mobile and cognitive radio applications. In the fixed designs, independent control of the operating frequencies is investigated to enhance the antennas capabilities and to give the designer an additional level of freedom to design the antenna for other bands easily without altering the shape or the size of the antenna. In addition, for mobile phone antenna, the effect of user’s hand and mobile phone housing are studied to be with minimum effect. Although fixed multiband antennas can widely be used in many different systems or devices, they lack flexibility to accommodate new services compared with reconfigurable antennas. A reconfigurable antenna can be considered as one of the key advances for future wireless communication transceivers. The advantage of using a reconfigurable antenna is to operate in multiband where the total antenna volume can be reused and therefore the overall size can be reduced. Moreover, the future of cell phones and other personal mobile devices require compact multiband antennas and smart antennas with reconfigurable features. Two different types of frequency reconfigurability are investigated in this thesis: switchable and tunable. In the switchable reconfigurability, PIN diodes have been used so the antenna’s operating frequencies can hop between different services whereas varactor diode with variable capacitance allow the antenna’s operating frequencies to be fine-tuned over the operating bands. With this in mind, firstly, a switchable compact and slim antenna with two patch elements is presented for cognitive radio applications where the antenna is capable of operating in wideband and narrow bands depending on the states of the switches. In addition to this, a switchable design is proposed to switch between single, dual and tri bands applications (using a single varactor diode to act as a switch at lower capacitance values) with some fine tuning capabilities for the first and third bands when the capacitance of the diode is further increased. Secondly, the earlier designed fixed antennas are modified to be reconfigurable with fine-tuning so that they can be used for more applications in both wireless and mobile applications with the ability to control the bands simultaneously or independently over a wide range. Both analytical and numerical methods are used to implement a realistic and functional design. Parametric analyses using simulation tools are performed to study critical parameters that may affect the designs. Finally, the simulated designs are fabricated, and measured results are presented that validate the design approaches
Dual-band slim inverted-F antenna with enhanced operational bandwidth
No full textIn this article, the design of a dual-band slim inverted-F antenna with an enhanced operational bandwidth is presented. Initially, a slim inverted-F antenna for operation in 850 and 1900 MHz bands supported by a large ground plane of 120 × 40 mm is introduced. This antenna offers dual band operation but with narrow bandwidth around each desired frequency. To reduce its ground plane length to 90 mm as well as to improve its operational bandwidth, a ground slot and a strip are introduced. By the proper placing of the slot and the strip, the lower frequency bandwidth is improved, while the good performance at the upper band is maintained. The designed antenna is fabricated and experimentally tested showing operational bandwidths covering GSM850 and PCS1900, with reference to the 6 dB return loss (VSWR 3:1). Its radiation patterns are omnidirectional at the lower band and become directional at higher frequencies, with the gain varying between −1 and 3 dBi
Electrophysiological effects of slim straight intracochlear electrode position - CORRIGENDUM
No full textOrdonez F, Sudhoff H, Todt I. Electrophysiological effects of slim straight intracochlear electrode position - CORRIGENDUM. Journal of Laryngology and Otology. 2022
Distribution of GO-slim functional classification.
No full text<p>(A) (D) and (G) represent the GO-slim classification of <i>G</i><i>. arboreum</i>; (B), (E) and (H) represent <i>G</i><i>. australe</i> and (C), (F) and (I) represent the combined assembly (<i>G</i><i>. arboreum</i> & <i>G</i><i>. australe</i>). (A) (B) and (C) are the distribution of the level 2 Biological Process within GO-slim classification; (D), (E) and (F) are the level 2 Cellular Component distribution and (G), (H) and (I) are the level 2 Molecular Function distribution. The pie charts corresponding to the detailed GO-slim classification are arranged clockwise.</p
Sir William Slim
No full textSir William Slim laying the foundation stone of the United Church, corner of Smith and Peel Streets, Darwin. Reverend N. Pearce on the left and Reverend Stuart Lang on the right.Cheater, F. and Cheater, K.Date:195
Slim wrapped inverted-F antenna for GSM/DCS/PCS operation
No full textIn this letter, the design of a super slim multiband wrapped inverted-F antenna that covers the frequency bands allocated for GSM, DCS, and PCS wireless services is described. In the first step, the quarter-wavelength (at 850 MHz) open-end arm of an inverted-F radiator is folded and meandered. Then, the antenna is wrapped using a fourth-order folding technique to reduce its projection area to only 40 mm × 10 mm × 3 mm. Full wave electromagnetic (EM) simulations show that the antenna excites a lower mode resonance at ∼850 MHz and a higher one at about 1900 MHz. Its radiation pattern is nearly omni-directional with a gain of about 2.5 dBi at the lower band and 4.6 dBi at the upper band. A prototype of the proposed antenna is fabricated and tested. A close agreement between the simulated and measured results is achieved. The measured 6-dB return loss or voltage standing wave ratio (VSWR) 3:1 bandwidths for the lower and upper resonances is 200 MHz (770–970 MHz) and 280 MHz (1710–1990 MHz), respectively. These bandwidths are sufficient to cover GSM 850/900/1800/1900 MHz, DCS 1800 MHz, and PCS 1900 MHz bands. Because of its small volume, the proposed antenna is a very attractive candidate for modern slim portable transceivers
Finite element modelling for structural performance of slim floors in fire and influence of protection materials
No full textSlim floor systems are very common nowadays and various types are currently being used for the construction of high-rise buildings and car parks. Concrete in slim floor beams encases the steel beam section which helps to improve their fire resistance. Despite their higher fire resistance, several fire protection materials like intumescent coatings are often used to achieve a higher fire resistance where desired. The thermal properties and behaviour of various intumescent coating materials were previously studied through experimental investigations. This paper presents finite element analyses to simulate the response of unprotected and protected slim floor beams in fire using different simulation tools. For this purpose, fire tests conducted on unprotected slim floor beams and intumescent coating materials are modelled using research and commercial software. Results from the analyses are compared and verified with the available test data. These validated models are later combined to study the behaviour of protected slim floor beams in fire. Results from the study show that the research and the commercial software replicate the behaviour of slim floor beams and protection materials with good accuracy. Due to the presence of the intumescent coating, the protected slim floor beams displayed a better fire resistance as the temperature of the steel part remained below 400 °C even after 60-min of standard heating. The protected slim floor beams continued to support the external loads even after 120 min of heating
Electrophysiological effects of slim straight intracochlear electrode position
No full textOrdonez F, Sudhoff H, Todt I. Electrophysiological effects of slim straight intracochlear electrode position. The Journal of Laryngology & Otology. 2020;134(12):1077-1080.#### Objective
The electrical current distribution of a cochlear implant electrode within the cochlea is essential for post-operative hearing performance. The slim straight electrode is designed to enable the placement of contacts in a lateral or medial direction to the modiolus. The electrophysiological effect of this different contact direction is so far unknown. The aim of this study was to determine the influence of intracochlear laterally or medially directed electrode contacts on electrophysiological behaviour.
#### Method
A slim straight electrode was inserted into the cochleae of five patients, and the neural response threshold was measured in a laterally and medially directed contact position. The cochleae in five temporal bone specimens were de-capped allowing an insertional observation of the contact position (lateral versus medial) of the electrode.
#### Results
There was no difference in neural response threshold between a lateral and a medial position of the contacts. Temporal bone study indicated no intracochlear torsion of the electrode.
#### Conclusion
Our study provides evidence that the intracochlear position of slim straight electrode contacts does not affect the neural response threshold
Representation of slim algebraic regular cozero maps
No full textClick on the link to view the abstractKeywords: Frame, bounded f-module, closed l-ideals, maximal spectrum, slim algebraic regular cozero map, natural uniformly continuous cozero transformationQuaestiones Mathematicae 29(2006), 383–39
- …
