Yes / In this paper, a pyramidal horn antenna loaded with unit cell of metamaterial is proposed, designed and realized for L-band that including terrestrial digital audio broadcasting TDAB, GPS and GSM. The proposed antenna operates in the frequency range from 1.722 GHz to 1.931 GHz. The metamaterial is fabricated on a printed circuit board as Capacitive Loaded Loop (CLL). The work aims to exhibit the advantage of metamaterial loaded inside the horn antenna in terms of the gain enhancement of the radiation pattern and the resonant frequency shift towards lower frequency. The retrieval technique used show that the constitutive parameters of the unit cell as CLL have a zero index metamaterial (ZIM) from 1.34 GHz to 1.49 GHz and a near zero index of refraction from 1.495 GHz to 2 GHz, which is within the operating frequency of the horn antenna. The achieved results show that the total gain is improved over the frequency range. The simulation and the measurement are in good agreement.

The goal of this project was to design a lens utilisinga glide symmetric periodic structure. A Lüneburg lens forantennas with a center frequency of 8 GHz has been designed.The structure was constructed using a unit cell in the shape ofan angular Bowen knot. This unit cell was then etched on themetallic surface of a parallel plate waveguide. Two symmetrycases for the unit cell were studied, the mirror symmetry andthe glide symmetry. Mirror symmetry is when the unit cell wasmirrored on the opposite metallic sheet, and glide symmetrywhen the cell was mirrored and shifted half a period. Theglide symmetric case was found to be less dispersive and moreisotropic. Further, we study the influence on the refractive indexwhen changing the geometry of the unit cell. A sufficient rangeof refractive index for realising the lens was found. These resultswere used to construct a full lens. Simulation of the complete lensshows the desired point to planar wave behavior of a Lüneburglens. In conclusion, the angular Bowen knot with glide symmetryhas the potential to construct a functioning Lüneburg lens. / Målet för detta projekt var att konstrueraen lins med glidsymmetriska periodiska strukturer. En Lüneburg-lins för antenner med en centerfrekvens på 8 GHz har de-signats. Strukturen byggdes med en enhetscell i formen avett sankthanskors etsat på en metallisk plattkondensator fylldmed ett dielektriskt substrat. Två symmetrifall betraktades,spegelsymmetri, då enhetscellen speglades på motstående me-tallskikt, och glidsymmetri där den även var förskjuten en halvperiod. Glidsymmetrin fanns ha mindre spridning och störreisotropi. Därtill undersöktes förändringarna i brytningsindex dåenhetscellens geometri förändrades. En tillräcklig räckvidd avbrytningsindex kunde uppnås. Dessa resultat användes för attkonstruera en fullständig lins. Simulering av den kompletta linsenvisade det önskade punkt till planvågbeteendet hos en Lüneburglins. Slutsatsen är att enhetsceller i formen av ett sankthanskorsmed glidsymmetri har potentialen att konstruera fungerandeLüneburg-linser. / Kandidatexjobb i elektroteknik 2020, KTH, Stockholm

Feldspars are one of the archetypical families of framework silicates. They not only comprise around 60% volumetrically of the Earth's crust, but are among some of the most structurally complicated minerals. Investigation into the structural behavior of various intermediate plagioclases at pressure has been undertaken with the intent of categorizing the elastic behavior with pressure across the solid solution series and establishing a conceptual model to characterize feldspar compression. Complex behavior has been observed in the Equation of State for plagioclase feldspars in excess of 3 GPa, including an anomalous softening of ordered albite in excess of 8.4 GPa (Benusa et al 2005: Am Min 90:1115-1120). This softening was not observed in the EoS for the more intermediate plagioclase compositions containing between 20 and 40 mol% of end-member anorthite. The calculated elastic compliance tensor sums at room pressure show a general stiffening with increasing anorthite component, small elastic changes at the C-1 to I-1 transition, and a dominantly first-order response at the P-1 to I-1 transition near end-member anorthite. The crystal structure of An37 plagioclase was determined by single-crystal X-ray diffraction. The compression mechanisms in An37 are similar to those in albite at lower pressures. The softening in albite at higher pressures is therefore attributed to the structural shearing in albite that is absent in An37 plagioclase up to 9.5 GPa. / Master of Science

Cellular structures are present from the atomic level all the way up to patterns found in human skeleton. They are prevailing structures in the nature and known for their excellent mechanical, thermal, and acoustic properties. Two typical types of cellular structures, lightweight structures and compliant mechanisms, are investigated. Lightweight structures are rigid and designed to reduce weight, while increasing strength and stiffness. Compliant mechanisms are designed to transform motions and forces. Most available artificial lightweight structures are patterns of primitives. However, the performance of lightweight structures can be enhanced by using adaptive cellular structures with conformal strut orientations and sizes, like the trabeculae in femoral bone. Bending, torsion, and nonlinear behaviors of compliant mechanisms have not been sufficiently studied. In order to design adaptive cellular structures, a new unit cell, the unit truss is proposed. The unit truss approach facilitates the design of adaptive cellular structures for enhanced mechanical properties via geometric modeling, finite element analysis, shape optimization, and additive fabrication. Four research questions, which address representation, structural analysis, design synthesis, and manufacturing respectively, are raised and answered. Unit truss enables representation and mechanics analysis for adaptive cellular structures. A synthesis method using engineering optimization algorithms is developed to systematically design adaptive cellular structure. Two examples, graded cellular structure for prosthesis and compliant mechanism for morphing wings, are studied to test the unit truss approach.

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No description available.

Phased arrays are electromagnetic antenna systems comprised of many radiating elements and processing electronics. Radiating elements are typically positioned in an orderly grid within the antenna aperture. In the receive mode of operation, radiating elements capture some of the signal energy from incoming radiation and guide these signals to processing electronics. Signals are filtered and amplified to maintain the desired sensitivity and complexly weighted using circuits with reconfigurable amplification gain and phase delay. Finally, all signals are combined. The summation of these complexly weighted spatial samples forms a spatial filter in the same way complexly weighted temporal samples establish a temporal filter in a finite impulse response discrete-time filter. Therefore, a phased array behaves like a spatial filter that strongly favors signals arriving from a specific direction. This favored direction represents the look angle of its beam, and the shape of the beam directly relates to the complex weights applied to the signals in the array. Analogous to the flexibility offered by digital filters, phased arrays enable agile beam steering, sidelobe control, and multiple independent beams. These capabilities have revolutionized radar, radioastronomy, and communication systems. Phased arrays have increasingly employed printed circuit board (PCB) fabrication techniques and processes to maximize array channel density, achieve lower profile, and minimize component integration cost. A few applications which leverage these qualities include low-cost radar, mobile satellite communication (SATCOM), and intelligence, surveillance, and reconnaissance (ISR). Further, PCB-based arrays readily accommodate advancements in highly integrated beamforming radio frequency integrated circuits (RFICs), multi-chip modules, and RF micro-electro-mechanical system (MEMS) device technologies. On a prior effort, an integrated unit cell design was developed for a PCB-based SATCOM array application. However, the design failed to meet the requirements. The primary objective of this work is to demonstrate an improved design using systematic microwave design techniques and modern analysis tools to meet the requirements for the same application. The proposed design must improve gain, bandwidth, size, and manufacturability over the prior design. Additionally, the design must be generally extensible to phased array implementations across the SHF band (3-30 GHz). This work discusses the advantages of phased arrays over continuous apertures (e.g. reflectors), reviews phased array theory, and proposes an improved unit cell design. The proposed design is 35% smaller than a dime and consists of an orthogonally-fed, slot-coupled stacked patch antenna and dual-stage branchline coupler implemented in a multilayer PCB. Within the operating band from 10.7 to 14.5 GHz, the design achieves an average return loss of 15 dB, a uniform radiation pattern with peak realized gain of 4.8 to 7.0 dBic, cross-polarization level below -17 dB, and stable performance in a closely-spaced array. When configured in an array, the design supports X/Ku-band SATCOM in full-duplex operation, electronically rotatable polarization, and a 47.5˚ grating lobe free conical scan range. Further, a Monte Carlo analysis proves the design accommodates tolerances of material properties and manufacturing processes, overcoming a major challenge in PCB-based high frequency antenna design.

The aim of this project is to design a cost-effective planar Maxwell fish-eye lens in PCB technology operating at the center frequency 5 GHz with a bandwidth of 20 %. An approach to design a cost-effective lens is to use a metasurface, which is commonly realized as a periodic structure of unit cells. In this project, a study was made by comparing different unit cells and considering the effect of applying glide symmetry to the unit cells. Comparing different unit cells withand without glide symmetry demonstrates that glide symmetry is necessary to achieve a 20 % bandwidth. Introducing glide symmetry showed a reduction in dispersive behavior, an increaseof isotropy and effective refractive index. Simulations of the full lens show a functioning lens with a power transfer of 67 % at 5.46 GHz. In conclusion, glide symmetry will improve the performance of the lens and is necessary to fulfill the requirement of a 20 % bandwidth.

Thesis (MScEng)--University of Stellenbosch, 2002 / ENGLISH ABSTRACT: A Representative Unit Cell (RUC) model for flow through two-dimensional porous media is presented and applied to two industrial related problems. The first application is to that of cross-flow in tube banks. Both staggered and square (inline) configurations are investigated and the model results are compared to experimental data. The second application is to flow through a stack in a timber-drying kiln. The RUC model is applied to the anisotropic timber stack ends and the centre part is modelled with a standard duct flow solution. The results of the models applied to a timber stack are compared to experimental data obtained from model tests undertaken in a wind tunnel. The results of the RUC and duct flow models are found to be in excellent agreement with the data of the experimental models. These models may be used to optimize kiln designs. / AFRIKAANSE OPSOMMING: 'n Verteenwoordigende Eenheid Sel (VES) model vir vloei deur twee-dimensionele poreuse media word weergegee en toegepas op twee industriële toepassings. Die eerste toepassing is op dwarsvloei deur banke van buise. Beide gestapelde en inlyn konfigurasies word ondersoek waarvan die model resulte met eksperimentele data vergelyk word. Die tweede toepassing is op vloei deur 'n stapel in 'n hout-droogoond. Die VES model word toegepas op die anisotropiese ente van houtstapels en die middelste seksie word gemodelleer deur 'n standaard kanaalvloei oplossing. Die resultate van die modelle toegepas op n 'houtstapel word vergelyk met eksperimentele data verkry uit model toetse wat in 'n wind-tonnel uitgevoer is. Die VES en kanaalvloei modelle se resultate stem uitstekend ooreen met die data van die eksperimentele modelle. Hierdie modelle kan gebruik word om die ontwerp van droogoonde te optimeer.

Thesis (MScEng (Mathematical Sciences. Applied Mathematics))--University of Stellenbosch, 2006. / When considering flow through porous media, different flow regimes may be identified. At very small Reynolds numbers the relation between the pressure gradient and the velocity of the fluid is linear. This flow regime ...