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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Antenna reduction techniques in MIMO systems and ad-hoc networks

Spyridakis, Georgios George January 2013 (has links)
In this thesis, an antenna reduction technique in Multiple Input Multiple Output (MIMO) systems, which is called Code Shift Keying (CSK) Modulation, is introduced. With the use of Walsh Hadamard orthogonal spreading codes, we overcome the biggest drawback of conventional Spatial Modulation (SM) which is the antenna index estimation errors due to channel correlation. Also SM fails to perform in non normalised channel conditions. The combination of orthogonal spreading codes and antenna devices, as a means to convey information at the receiver, results in a remarkable performance improvement at the receiver.Moreover, an improved scheme that uses half the amount of spreading codes so as to represent the total number of information bits has been introduced leading to an important reduction in bandwidth usage. By maintaining the net spreading levels of the system we attain remarkable performance improvements.A technique called Polarisation Assisted Space Shift Keying Modulation (PASSK) has also been proposed which manages to exploit the polarisation domain and it is able to outperform the conventional SM technique as well as the Maximal Ratio Receiver Combine (MRRC) and Vertical-Bell Laboratories Layered Space-Time (V-BLAST) schemes. A new precoding scheme that manages to either eliminate or exploit the cross polarisation effects has also been proposed as a complementary study of the PASSK scheme.As modern and future communications show a rising demand for higher data transmission rates, network coding is increasingly incorporated in wireless communication standards. In harmonisation with this trend, this thesis discusses the main state-of-art network coding schemes. The contribution here includes a number of innovative schemes that are able to further increase throughput. Finally, the employment of network coding is discussed in conjunction with CSK Modulation resulting to further improvement in terms of throughput as well as Bit Error Rate (BER) performance at the cost of increased bandwidth usage.
2

Investigation of the tumour necrosis factor-stimulated gene-6 (TSG-6) interactome : use and development of surface sensitive techniques

Birchenough, Holly January 2014 (has links)
Tumour necrosis factor-stimulated gene-6 (TSG-6) is a protein expressed in a wide range of cell types and tissues, predominantly in response to inflammatory stimuli. The expression of TSG-6 is believed to be associated with the protection of tissues from the damaging effects of inflammation. In animal models treatment with TSG-6 protein has been found to reduce inflammatory damage in myocardial infarction, corneal injury and arthritis. Endogenous TSG-6 production has been suggested to play a protective role in inflammatory arthritis and has been implicated in bone homeostasis. The expression of TSG-6 is also essential in the process of cumulus matrix formation that occurs around the oocyte in the periovulatory period and is necessary for successful ovulation and fertilisation. In many cases the mechanism underlying a particular TSG-6 function is not fully understood. TSG-6 has numerous binding partners including the serum glycoprotein inter-alpha-inhibitor (IαI), the growth factor bone morphogenetic protein-2 (BMP-2) and the extracellular matrix protein fibronectin, as well as glycosaminoglycans (GAGs) such as hyaluronan and heparan sulphate (HS). The TSG-6 protein is mostly composed of contiguous Link and CUB domains, with the majority of ligand binding sites identified within the Link module. The CUB domain of TSG-6 has been less extensively studied. Here biophysical techniques have been used to investigate the TSG-6 interactome including both the Link module and CUB domain. Intrinsic fluorescence spectroscopy was used to establish the metal-ion binding properties of the CUB domain, which was established to have a high affinity Ca2+-binding site. Using surface plasmon resonance (SPR), a novel metal-ion dependent interaction was found for the CUB domain of TSG-6 and the heavy chains (HCs) of IαI. Investigation using mutants of both the CUB domain of TSG-6 and HC of IαI established that the metal-ion binding sites within each protein are involved in the interaction. SPR analysis was also used to define the affinities and binding sites for TSG-6 interactions with fibronectin and BMP-2. High affinity interactions between TSG-6 ligands were also revealed (e.g. BMP-2 and HC, fibronectin and HC) and their binding sites defined. The discovery of the novel interactions between these TSG-6 ligands suggests crosstalk within the TSG-6 interactome, with the potential for ternary complex formation or indeed hierarchical orders of binding. Thus work was undertaken to develop a passivated lipid bilayer platform for use with surface sensitive techniques. This platform was used to investigate the hierarchy of protein and GAG interactions using quartz crystal microbalance with dissipation monitoring (QCM-D) and dual polarisation interferometry (DPI). The investigation revealed a novel role for the Link module of TSG-6 in heparin condensation, potentially via protein dimerisation and/or oligomerisation which could affect heparin/HS functions within the extracellular matrix (ECM). Thus the biophysical analysis of TSG-6 presented here has identified novel interactions and functions of TSG-6 which may provide mechanisms for the protective functioning of TSG-6 in inflammation and its ECM structuring role in ovulation.
3

Dual-Polarized Highly Folded Bowtie Antenna with Slotted Self-Grounded Structure for Sub-6 GHz 5G Applications

Alibakhshikenari, M., Virdee, B.S., See, C.H., Shukla, P., Moghaddam, S.M., Zaman, A.U., Shafqaat, S., Akinsolu, M.O., Liu, B., Yang, J., Abd-Alhameed, Raed, Falcone, F., Limiti, E. 26 September 2021 (has links)
Yes / In this paper, a novel dual-polarized highly-folded self-grounded Bowtie antenna that is excited through I-shaped slots is proposed for applications in sub-6GHz 5G multiple-input-multiple-output (MIMO) antenna systems. The antenna consists of two pairs of folded radiation petals whose base is embedded in a double layer of FR-4 substrate with a common ground-plane which is sandwiched between the two substrate layers. The ground-plane is defected with two I-shaped slots located under the radiation elements. Each pair of radiation elements are excited through a microstrip line on the top layer with RF signal that is 180° out of phase with respect to each other. The RF signal is coupled to the pair of feedlines on the top layer through the I-shaped slots from the two microstrip feedlines on the underside of the second substrate. The proposed feed mechanism gets rid of the otherwise bulky balun. The Bowtie antenna is a compact solution with dimensions of 32×32×33.8 mm3. Measured results have verified that the antenna operates over a frequency range of 3.1–5 GHz and exhibits an average gain and antenna efficiency in the vertical and horizontal polarizations of 7.5 dBi and 82.6%, respectively.

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