Dissertations / Theses on the topic 'FIR Filter Structure'

State of the art filter bank structures achieve practically perfect reconstruction with very high computational efficiency. However, the increase in computational requirements due to the need to process increasingly wider band signals is paramount. New filter bank structures that provide extra information about a signal while achieving the same level of required efficiency, and perfect reconstruction properties, need to be developed. In this work a new filter bank structure, the interpolated FIR (IFIR) filter bank is developed. Such a structure combines the concepts of filter banks, and interpolated FIR filters. The filter design procedures for the IFIR filter bank are developed and explained. The resulting structure was compared with the non-maximally-decimated filter bank (NMDFB), achieving the same performance in terms of the number of multiplications required per sample and the overall distortion introduced by the system, when operating with Nyquist prototype filters. In addition, the IFIR filter is tested in both simulated and real communication environments. Performance, in terms of bit-error-rate, was found to not be degraded significantly when using the IFIR filter bank system for transmission and reception of QPSK symbols.
Master of Science

The master thesis is based upon a new type of linear-phase Nyquist finitie impulse responseinterpolator and decimator implemented using a tree-structure. The tree-structure decreasesthe complexity, considerably, compared to the ordinary single-stage interpolator structure.The computational complexity is comparable to a multi-stage Nyquist interpolator structure,but the proposed tree-structure has slightly higher delay. The tree-structure should still beconsidered since it can interpolate with an arbitrary number and all subfilters operate at thebase rate which is not the case for multi-stage Nyquist interpolators.

The diploma thesis is focused on design and optimalization of digital octave and fraction-octave band filters. This thesis describe the behavior of filters in systems with fixed point arithmetics and investigate the impact of quantization coefficients for frequency response of filter. Filters, whitch has been designed, are implemented into simple software in C. Designed filters are in accordance with standard IEC 61260.

This thesis explores the possibilities of the design and realization of compact conventional and substrate integrated waveguide structures with improved performance taking advantage of recent cross-coupled resonator filters theory achievements such as the modular filter design approach using non-resonating nodes and inline extracted pole filters. Therefore, the core of the thesis presents the following stages of work: -- Solution of electromagnetic problem for wave propagation in rectangular waveguide structures; overview of substrate integrated waveguides. -- Review of available design procedures for cross-coupled resonator filters; realization of coupling matrix synthesis methods by optimization. -- Investigation of the possibility to implement filtering modules using E-plane metallo-dielectric inserts in conventional rectangular waveguides. Application of the modules in configurations of bandpass and dual-band filters. Experimental verification of the filters. -- Implementation of inline extracted pole filters using E-plane inserts in rectangular waveguides. Use of generalized coupling coefficients concept for individual or coupled extracted pole sections. Development of new extracted pole sections. Application of the sections in the design of compact cross-coupled filters with improved stopband performance. -- Application of the techniques developed for conventional rectangular waveguides to substrate integrated technology. Development of a new negative coupling structure for folded substrate integrated resonators. Design of improved modular and extracted pole filters using substrate integrated waveguides.

It has been aimed to investigate the complexity of discrete-coefficient FIR filters when they are implemented in transposed form and the coefficient redundancy is removed by the n-Dimensional Reduced Adder Graph (RAG-n) approach. Filters with coefficients represented by different quantization schemes have been designed or selected from the literture
their transposed form implemetations after RAG-n process have been compared in terms of complexity. A Genetic Algorithm (GA) based design algorithm has been implemented and used for the design of integer coefficient filters. Algorithms for the realization of filter coefficients in Canonic Signed Digit (CSD) form and realization of n-Dimensional Reduced Adder Graph (RAG-n) have also been implemented. Filter performance is measured as Normalized Peak Ripple Magnitude and implementation complexity as the number of adders used to implement filter coefficients. Number of adders used to implement filter coefficients is calculated by using two different methods: CSD and RAG-n. RAG-n method has been applied to FIR digital filter design methods that don&rsquo
t consider reduction of implementation complexity via RAG-n with transposed direct form filter structure. For implementation complexity, it is concluded that &ldquo
RAG-n algorithm with transposed direct form filter structure&rdquo
provides better results over the &ldquo
CSD, SPT coefficient design followed by transposed direct form filter structure&rdquo
in terms of number of adders used in the implementation.

Concrete filled steel hollow structural (CFS) sections are increasingly used to support large compressive loads in buildings, with the concrete infill and the steel tube working together to yield several benefits both at ambient temperature and during a fire. These members are now widely applied in the design of highly optimized multi-storey and high rise buildings where fire resistance ratings of two or more hours may be required. Whilst the response and design of these sections at ambient temperatures is reasonably well understood, their response in fire, and thus their fire resistance design, is less well established. Structural fire resistance design guidance is available but has been developed based on tests of predominantly short, concentrically-loaded, small-diameter columns in braced frames using normal strength concrete. The current prescriptive guidance is limited and the design of CFS columns is thus often based on a detailed performance based approach, which can be time consuming and expensive and which is generally not well supported by a deep understanding of CFS columns’ behaviour in real fires. This thesis aims to understand the fundamental thermal and mechanical factors at play within these sections so as to provide guidance on how to improve their design for fire resistance when applied either as unprotected or protected sections. A meta-analysis of available furnace test data is used to demonstrate that current guidance fails to capture the relevant mechanics and thus poorly predicts fire resistance. It is also demonstrated that the predictive abilities of the available design standards vary with physical characteristics of the CFS section such as shape and size. A factor which has been observed in furnace tests on CFS sections but which is not accounted for in available guidance is the formation of an air gap between the steel tube and the concrete core due to differential expansion; this affects their structural response in fire. The insulating effect of air gap formation has not previously been addressed in literature and an experimental program is presented to systematically assess the effects of a gap on the heat transfer through the section; showing that the presence of even a 1 mm gap is important. To explicitly assess the heat transfer response within both unprotected and fire protected (i.e. insulated) CFS sections, 34 large scale standard furnace tests were performed in partnership with an industry sponsor. Fourteen tests on large scale unloaded unprotected CFS sections are presented to assess current capability to predict the thermal response and to assess the effects of different sectional and material parameters on heating. New best practice thermal modelling guidance is suggested based on comparison between the models and observed temperatures from the tests. Twenty CFS specimens of varying size and shape, protected with different types and thicknesses of intumescent paint fire insulation, were also tested unloaded in a furnace to understand the thermal evolution within protected CFS sections and to develop design guidance to support application of intumescent coatings in performance based fire resistance design of CFS sections. These tests demonstrate that the intumescent coatings were far more effective than expected when applied to CFS sections, and that current methods of designing the coatings’ thickness are overly conservative. The reason for this appears to be that the calculation of effective section factor which is used in the prescription of intumescent coating thicknesses is based on the thermal response of unprotected CFS sections which display fundamentally different heating characteristics from protected sections due to the development of a thermal gradient in the concrete core. It is also demonstrated (by calculation supported by the testing presented herein) that the steel failure temperature (i.e. limiting temperature) of an unprotected CFS column in fire is significantly higher than one which is protected; procedures to determine the limiting temperature of protected sections are suggested. Finally, the residual strength of fire-exposed CFS columns is examined through structural testing of 19 of the 34 fire tested columns along with unheated control specimens. The results provide insights into the residual response of unprotected and protected CFS section exposed to fire, and demonstrate a reasonable ability to calculate their residual structural capacity. The work presented in this thesis has shed light on the ability of available guidance to rationally predict the thermal and structural response to fire of CFS columns, has improved the understanding of the thermal evolution within protected and unprotected CFS sections in fire, has provided best-practice guidance and material input parameters for both thermal and structural modelling of CFS sections, and has improved understanding of the residual capacity of CFS sections after a fire.

In the thesis presented, three novel uni-planar left handed transmission lines based on Complementary Split Ring Resonators (CSRR) and Complementary Spiral Resonator (CSR) metamaterial particles are proposed for the first time and successfully applied for the performance enhancement of conventional coupled line filters and the design of a full scan leaky wave antenna. Based on the implementation of Complementary Split Ring Resonators (CSRR) a fully planar Composite Right left handed transmission line (CRLH-TL) plus a Dual Composite Right Left Handed transmission line (D-CRLH-TL) are proposed, designed and studied. The CRLH transmission line is realized loading a microstrip host line with CSRR metamaterial particles and capacitive gaps on the conductor strip of the line, while the D-CRLH transmission line is built bridging the capacitive gaps between the CSRR's with inductive connections to induce dual propagation properties in the structure. A further performance enhancement is achieved by a second proposal based on the implementation of Complementary Spiral Resonators (CSRs). The studies applied to the structure reveal that conditions for D-CRLH propagation are created in a transmission line composed only by CSR metamaterial resonant particles as the result of the unique electromagnetic properties acquired by the CSRs etched on the conductor line of a microstrip waveguide. The CSRR/CSR based D-CRLH transmission lines proposed are applied in the design of two enhanced coupled line filters. The implementation is possible for the first time in this work as result of the highly versatile layout features of the left handed transmission lines proposed which among other important geometrical features, allows couplings in both sides of the structure. Enhanced filtering features are reached by the metamaterial based coupled line filters proposed in terms of selectivity and size reduction in comparison with conventional coupled line filters. In the case of the CSRR loaded metamaterial coupled line filter a size reduction of 49% is achieved compared with a filter of similar performance. A further enhancement is reached by the second coupled filter proposed based on CSR metamaterial resonant particles. The CSR coupled filter proposed reach a roll off rate improvement of 8 dB/GHz and size reduction of 43% in comparison with a conventional coupled line filter of the same order. When this is compared against a conventional coupled line filter of similar performance but higher order, a remarkable size reduction of 77% is achieved by the proposed CSR coupled line filter. Finally, the CSR loaded D-CRLH transmission line is applied in the design of a fully planar leaky wave antenna. Using the CSR structures etched on the conductor line of a microstrip as part of the radiation mechanism altogether with the D-CRLH propagation features of the structure. A full scan radiation pattern is created with backward, forward and broadside radiation as result of the left handed propagation band, right handed propagation band and the balanced transition between them. Two leaky wave antennas are designed to operate at the centre frequencies of 12.5GHz and 6.0GHz. In order to corroborate the performance the CSR D-CRLH leaky wave antenna operating at 6.0GHz is fabricated and measured showing a scanning range of 30 deg with a maximum gain of 13.2 dBi.

188 p.
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A petroquímica é um dos segmentos mais expressivos de qualquer economia industrial, produzindo insumos para diversos bens de consumo. A partir da década de 1970, com os dois choques do petróleo, essa indústria passou por intensa reestruturação em todo o mundo, aprofundada na década de 1990. A racionalização dos negócios petroquímicos promoveu uma intensa onda de fusões, aquisições, joint ventures e spin-offs, refletindo as estratégias adotadas pelas empresas líderes, de integração vertical e focalização em core business. As grandes petrolíferas moveram-se downstream, beneficiando-se de vantagens de custo e acesso a matérias-primas. Os anos 2000 foram marcados pela emergência da Ásia como centro produtor, adicionando-se novas capacidades no Oriente Médio, e consumidor, com destaque para a China, apontando que o acesso às matérias-primas e aos mercados com elevado potencial de crescimento são as variáveis com maior capacidade de desencadear movimentos de reestruturação nessa indústria. No Brasil, a petroquímica foi implantada seguindo um modelo tripartite, com importante participação do Estado, via Petroquisa, que acabou por resultar em uma estrutura industrial fragmentada, de empresas monoprodutoras, diversa do padrão mundial do setor. Na década de 1990, a abertura da economia e a privatização, com redução expressiva da participação da Petroquisa, tornou manifesta a vulnerabilidade das empresas nacionais e a necessidade de reestruturação. A formação da Braskem e o retorno da Petrobras deram início ao processo de reorganização da petroquímica nacional. O objetivo do presente trabalho é analisar se o processo ocorrido no Brasil guarda semelhança com aqueles ocorridos em nível mundial, bem como identificar, utilizando-se de modelo das decisões de investimento nessa indústria baseado em determinadas driving forces, as principais estratégias da Braskem, maior player nacional, e da Petrobras, além dos desafios competitivos enfrentados pela petroquímica brasileira, associados à disponibilidade de matérias-primas, escoamento da oferta, mudanças tecnológicas, crescimento da demanda e políticas governamentais. Os resultados encontrados sugerem que a reestruturação ocorrida, além de fortalecer a petroquímica brasileira, equacionou parte de suas fragilidades competitivas, adequando-a ao padrão mundial do setor. Seu crescimento está bastante vinculado ao mercado interno brasileiro e uma maior inserção no âmbito internacional demonstra hoje boas perspectivas de se concretizar, especialmente no continente americano, tanto pela via das exportações, quanto pela internacionalização das empresas nacionais, in casu, a Braskem. Apesar dos desafios que se apresentam, majorados pela crise financeira de 2008, essa indústria conseguiu alcançar melhores condições competitivas para seguir uma trajetória sustentada de crescimento.
Salvador

Due to its nature, imaging is dependent on data visualization. More specifically, when dealing with optical microscopy imaging, diffraction limited spatial resolution and the presence of out-of-focus contributions are two of the key elements for the generation of 4D (x,y,z,t) data sets oriented to study molecular processes at the nanoscale. Within the medical nanotechnology scenario, optical fluorescence techniques have a pivotal role thanks to their non invasive capability to address biological questions in three dimensions with a remarkable capability to distinguish fine details, tremendously improved up to the nanoscale level in the last decade. Within this scenario, this Thesis concerns the study and the development of advanced fluorescence optical methods for the improvement of the imaging capability and a better exploitation of its potentialities. Two approaches have been followed in fluorescence microscopy to gather information, namely: a direct diffraction-limited observation of the sample allowed by the optical architecture and the analysis of those fluorescence signals particularly sensitive to the environmental condition. Consequently, two strategies have been pursued to improve such capabilities. They are related to the design of novel optical arrangements utilizing light interferences pathways to improve the diffraction resolution limit and to the study of novel fluorescent molecules and/or fluorescent techniques which allows the investigations of subresolved molecular interactions. In particular, following a fluorescent probe approach, a nanostructured polyelectrolyte system has been designed to study the fluorescence quenching effect induced by specific quencher molecules on the fluorescence emission process. The realized system allows entrapping the fluorescent molecules and monitoring fluorescence signal variations to probe quencher metal ions at microrange concentrations, significantly higher with respect to the current fluorescent quenching based technologies. As well, following an optical approach, the interferences effect induced by structuring the illumination light with different masks have been studied, in order to improve some features of the imaging capability of the fluorescence microscope. In the Two-Photon Excitation (2PE) and in the Confocal Single Photon Laser Scanning Microscope, the insertion of a ring shaped mask in the illumination pathway is proposed to enhance the signal to noise ratio of the optical system at the high spatial frequencies. Since in these optical systems the transmission of the high spatial frequencies is particularly weak, such features allow to improve the overall practical capability of the confocal and 2PE system to distinguish fine details of the image. In the widefield microscope, the insertion of a periodic grid to structure the light has been investigated in order to confer a 3D optical sectioning capability comparable to that of the confocal microscope, with major advantages in terms of the efficient use of the light, simplicity of construction, speed of imaging acquisition, versatility, and low cost. The proposed scheme allows to quickly collect a pure sectioned image without any computational demodulation thanks to a novel optical architecture where both the illumination and the detection light is structured by a spinning grid.

Le travail présenté ici s'inscrit dans la perspective du développement de modules électroniques à très faible coût et à très faible consommation pour les réseaux de capteurs sans fils (WSN). Il traite de la conception et du test d'une chaîne de réception RF compatible avec la norme IEEE 802.15.4 pour la bande ISM 2.4GHz. L'interface RF objet de notre étude inclue toutes les fonctions depuis l'antenne jusqu'au 1er étage du filtre analogique en bande de base, à partir duquel le gain devient suffisant pour masquer le bruit introduit par le reste de la chaîne de réception. Ce mémoire articulé autour de quatre chapitres, décrit toutes les étapes depuis la définition des spécifications de la chaîne de réception jusqu'à la présentation de ses performances, en passant par l'étude de son architecture et la conception de ses différents étages. Suite à l'étude de l'impact des interféreurs IEEE 802.15.4 et IEEE 802.11b présents dans la bande ISM 2.4GHz, une architecture utilisant une fréquence intermédiaire de 6MHz a été retenue. En outre, pour pouvoir répondre aux spécifications fixées, cette architecture est composée de plusieurs étages innovants ou originaux tels qu'un balun intégré trois accès, un amplificateur faible bruit sans inductance, un mélangeur passif piloté par un signal local (OL) à très faible rapport cyclique ainsi qu'un filtre bande de base optimisé en bruit et en linéarité. Intégré dans une technologie CMOS 90nm, ce récepteur occupe une surface de 0.07mm², ou 0.23mm² en incluant le balun intégré, qui représente une réduction de 70% par rapport à l'état de l'art des puces compatibles avec le standard IEEE 802.15.4. En prenant en compte la consommation dynamique de toute la chaîne de mise en forme du signal OL, la tête de réception précédemment décrite consomme seulement 4mA sous une tension d'alimentation de 1.35V. Enfin, en incluant le balun intégré, le gain est de 35dBv/dBm, le facteur de bruit de 7.5dB, l'IIP3 de -10dBm et la réjection d'image supérie ure à 32dB. Ces performances placent ce récepteur parmi les récepteurs RF les plus performants pour cette application. Les nombreux principes mis en Suvre sont par ailleurs transposables à d'autres bandes de fréquences et à d'autres standards de communication.

碩士
國立高雄大學
電機工程學系碩士班
100
The conversion between different periodic sampling standards is an important problem, especially for the conversion between quincunx and rectangular structures in television image processing and HDTV applications. For rcconstructing the original picture accurately, minimizing a quadratic measure of the error in the passband and stopband, a two-dimensional diamond-shaped FIR eigenfilter is designed for sampling-structure conversion. Time- and frequency-domain constraints are easily incorporated into this method, such that the design difficulty inherent to sampling-conversion filters can be effectivly solved. Finally this thesis concludes with design of filter banks. It is well known that the multirate systems can be used in many fields, such as video encoding, audio processing and video compression. In this thesis, two- and three-dimensional digital filters are designed by using the weighted least-squares (WLS) approach. The method can be generalized such that multidimensional QMF banks can be designed by the proposed to further reduce the peak error of overall magnitude response. Comparing with the existing works concern the design of perfect-reconstuction QMF bank, only of the filters is needed to be designed under the cost of magnitude distortion, but the system complexity can be reduced drastically. Several examples, including design of 2-D and 3-D QMF bank, will be presented to demonstrate the effectiveness of the proposed method. Keywords: FIR Filter、Weighted Least-Squares Approach、Two-Dimensional Digital Filter、Three-Dimensional Digital Filter、Multirate System、Filter Banks、Sampling Structure Conversion.

Multirate systems, including M th-band filters and filter banks, have greatly facilitated the analysis, understanding and compression of signals. Polyphase structure plays an important role in the study of multirate systems due to the fact that it provides a parallel and very efficient implementation architecture. In this dissertation, some polyphase structure-based approaches for the design and implementation of M th-band filters as well as filter banks are presented. The emphasis is placed on the development of new structures that satisfy certain constraints and having low computational complexity. A design algorithm for M th-band filters is first presented based on the generalized polyphase (GP) structure. Both the interpolation and linear-phase conditions are incorporated in the proposed GP realization of M th-band filters. By deriving a closed-form frequency response specification for each of the constituent filters in the GP structure, the design of the original large-tap FIR filter is simplified to the design of short-length constituent filters to reduce the overall design complexity. The GP-based approach is then extended for the design of M th-band filters meeting certain regularity requirements. To show the wide applicability of the proposed method, the design of 2-D M th-band filters via the GP structure is also considered. It is shown that by applying the singular-value decomposition (SVD) to each 2-D subfilter in the GP structure, the implementation complexity of the overall 2-D filter can be significantly reduced without introducing a large error. The second part of the dissertation is concerned with the development of new lattice structures for perfect reconstruction filter banks (PRFBs) with certain constraints, such as the linear-phase (LP) and the minor-image symmetry (MIS). The innovative work is based on the polyphase matrix representation of the analysis and synthesis filters, and a key idea of devising basic building blocks that are capable of propagating the desirable symmetry properties while being cascaded to generate the required lattice structures. Due to the added constraints, the resulting lattice structures have fewer parameters, leading to a speedy optimization design and a reduction in the heavy implementation burden. It is proved that there exists a complete and minimal lattice structure for MIS-PRFBs. It is shown that a class of well-known filter banks, namely, the cosine-modulated filter banks (CMFBs), is a subclass of MIS-PRFBs, whose non-singular matrices are of sparse coefficients. By introducing more prototype filters, in conjunction with a proper modulation, new CMFBs with more parameters are generated. Combining the linear-phase and mirror-image symmetries, a lattice structure with further reduced number of parameters is also developed for MIS-LPPRFB. The designed MIS-LPPRFB is then utilized as a block transform for image compression coding. Simulation results show that the MIS-LPPRFB, despite its reduced number of parameters, offers a competitive performance in terms of both the visual quality and the peak signal-to-noise ratio for various images under a wide range of compression ratios

碩士
華梵大學
機電工程學系博碩專班
96
ABSTRACT A fuzzy-base coefficient update method is proposed for dual FIR structure echo canceller. The fuzzification interface maps the echo suppress performance to three fuzzy sets: fine, fair, and poor. For fine echo suppress performance the aggressive strategy for coefficient update is selected. On the other hand, the conservative strategy for coefficient update is selected for poor echo suppress performance. Otherwise, an averaged strategy is employed. The coefficients of one FIR filter will be copied to the other FIR filter when the ESP difference is greater than the margin. Aggressive strategy means a small margin is used, and conservative strategy means a large margin is used. The experiment results show that the proposed fuzzy-base coefficient update method effectively discriminating echo path change from double talk, and there is no threshold constants are required for real-time applications. Keywords: echo cancellation, fuzzy logic, double talk, echo path change

博士
國立交通大學
電信工程研究所
106
In this dissertation, novel structures of types I, II, III, and IV linear-phase FIR filters, whose frequency responses satisfy given derivative constraints imposed upon an arbitrary frequency, are proposed. It is comprised of a linear combination of parallelly connected sub-filters, called the cardinal filters, with weighted coefficients being the successive derivatives of the desired frequency response at the constrained frequency. Since the cardinal filters can be synthesized via recursive closed-form expressions, regardless of the desired system amplitude response, the proposed structure provides a universal design for arbitrary derivative-constrained linear-phase FIR filters. The key to derive the coefficients of cardinal filters is the determination of the power series expansion of certain trigonometric-related functions. By showing the elaborately chosen trigonometric-related functions satisfy specific differential equations, recursive formulas for the coefficients of cardinal filters are subsequently established, which make stable their computations. At last, a simple enhancement of the cardinal filters design by incorporating the mean square error (MSE) minimization is presented through examples.

碩士
大同工學院
電機工程研究所
81
Recently, a multipath digital filter scheme has been presented to increase the throughput rate by a speed up factor of N; however, as compared to conventional realization of digital, it require N and N*N times hardware elements for FIR and IIR filter structure. In this thesis, based on the fast FIR filtering algorithm, some efficient implementaion structures of one dimensional and two dimensional filter are proposed. By means of polynomial transformation, one dimensional and two dimensional IIR filter structures are also developed. All the proposed structures not only reduce the arithemetic complexity but also maintain the same high throughput rate as delayed multipath structure. The effects of productquantization errirs in one and two dimensional filters are finally analysised.

碩士
國立彰化師範大學
機電工程學系
97
In this thesis, the physical dimensions and characteristics of the new fin-shaped coplanar-waveguide defected-ground-structure band-pass filters are discussed and investigated. In the thesis, the circuit characteristics of the basic coplanar-waveguide defected-ground-structure are analyzed. Then, I tried to change the physical dimension in order to analysis the change of the circuit characteristics. Due from the reason that the circuit of the fin-shaped structure obtains the characteristic of dual pass bands; we can improve the frequency and the loss of the signal by changing the physical dimension and the fins.

碩士
大同工學院
資訊工程研究所
82
The conversion between different periodic sampling structures is an important problem, especially for the conversion between quincunx and rectangular structures in television image processing and HDTV applications. To avoid aliasing error and remove redundant images, appropriate decimation filters and interpolation filters must be used. The one-dimensional Lagrange multiplier approach is extended for the design of two-dimensional FIR digital filters with magnitude or derivative constraints. The method is based on minimizing the integrated square error for the frequency response over the passband and stopband while imposing magnitude or derivative constraints. The technique is used to design the infinite precision interpolation and decimation filters for the sampling structure conversion first. For designing discrete coefficient FIR digital filters, the iterative Lagrange multiplier approach is proposed. The new method associates the conventional Lagrange multiplier approach and a hybrid tree search algorithm. The closed-form solutions for the elements of all matrices are obtained, and numerical design examples are presented to demonstrate the usefulness and effectiveness of the approach.

This thesis proposes a metallic hole array of a rectangular converging-diverging channel (RCDC) shape with extraordinary transmission. We use a three-dimensional (3D) finite element method to analyze the transmission characteristics of two-dimensional metallic hole arrays (2D-MHA) with RCDC. For a straight channel MHA, when the aperture size is reduced, the transmission peaks have a blue-shift. The same result is observed for a smaller gap throat for the RCDC structure. For the rectangular holes with a high length-width ratio, a similar blue-shift in the transmission peaks as well as a narrower full width at half maximum (FWHM) are observed. The asymmetry from the rectangular shape gives this structure high selectivity for light with different polarizations. Furthermore, the RCDC shape gives extra degrees of geometrical variables to 2D-MHA for tuning the location of the transmission peak and FWHM. The tunable transmission property of this structure shows promise for applications in tunable filters, photonic circuits, and biosensors.
text

Concrete-filled steel tubular (CFST) columns, composed of core concrete and outer tubes, have been extensively used as main structural elements in high-rise buildings to carry loads. Due to the composite action between the steel and core concrete, this type of composite construction has been reported to have many constructional and structural benefits, such as easy construction from the omission of formwork, restraint to local buckling of the steel tube provided by the core concrete, high strength, stiffness and ductility. Recently, there is increased interest in adopting CFST columns in composite frame systems. In recent years, fire disasters have frequently been reported worldwide, and seriously threatened personal and public safety. Exposure of concrete and steel to fire will lead to serious structural deterioration and possible failure of columns, thus resulting in local or global collapse of a building. However, in most cases, unprotected CFST columns are not able to maintain structural integrity for sufficient time under fire conditions. External insulating coating or internal reinforcing steel are required to improve the fire resistance of CFST columns, but these two methods tremendously increase the cost of CFST columns and the difficulty of construction. Although ordinary Portland cement (OPC) concrete is classified as a fire-resistant construction material, during fire exposure severe spalling may occur, as well as significant deterioration of strength and stiffness. Therefore, there is a need to find alternative materials to replace OPC to further improve the fire resistance of concrete. Geopolymer is aluminosilicate synthesised from a material of geological origin or industry by-products (e.g. fly ash) with alkaline solutions. In Australia, fly ash is abundantly available from numerous thermal power plants. The use of fly ash to manufacture construction materials can promote the better utilisation of this industry by-product, avoiding disposal into landfill. Previous studies have demonstrated that geopolymer can be successfully used as a binder to make geopolymer concrete. The absence of OPC in geopolymer concrete (GPC) can significantly reduce CO2 emissions for the construction industry. Recent research has proved that GPC has substantially better fire performance than OPC concrete. Therefore, GPC has the potential to be used in CFST columns to improve their fire performance. So far, very little research has been conducted to investigate the behaviour of geopolymer concrete-filled steel tubular (GCFST) columns, and this research aims to address this knowledge gap. In this thesis, salient parameter analysis of GPC mix was conducted based on the Taguchi method, and three optimised GPC mix designs were proposed. Material properties such as slump, density, Young’s modulus, compressive strength, flexural strength and splitting tensile strength were experimentally studied. The measured values of Young’s modulus, flexural strength and splitting tensile strength of GPC are compared favourably to the predictions of existing standards. The measured hot strength and displacement of GPC under combined loading and elevated temperature were reported. Full-range stress-strain curves of GPC and reference OPC after exposed to elevated temperatures were evaluated. The results further confirm that GPC has the potential to improve the fire performance of CFST columns. A total of 15 tests were carried out on GCFST columns and conventional CFST columns to compare their behaviours. The main experimental parameters included: (1) Concrete type (geopolymer concrete and OPC concrete); (2) Curing procedure of GPC (ambient curing and elevated temperature curing); (3) Strength of geopolymer concrete (37.4, 58.6 and 68.4 MPa); (4) Test method (tested at ambient temperature, in fire, or after fire exposure). The axial load, axial strain and lateral strain were measured for ambient temperature tests and residual property tests. The axial displacement versus the temperature curves were recorded for the specimens tested under combined load and temperature increase. The results were compared to predictions of numerical models developed with ABAQUS, and the agreement between them is reasonable. This research confirms that the behaviour of GPC at an ambient temperature is comparable to that of OPC concrete at an ambient temperature. However, GPC has better fire performance and a higher post-fire residual strength than OPC concrete. This study has proved the potential of using GPC as fire-resistant concrete in CFST columns. Thus, the use of external insulating coating or internal reinforcing steel could be potentially eliminated for CFST columns.