Wing-Chung Chan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 81-85). / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Multiresolution Signal Decomposition --- p.5 / Chapter 2.1 --- Introduction --- p.5 / Chapter 2.2 --- Laplacian Pyramid --- p.6 / Chapter 2.2.1 --- Gaussian Pyramid Generation --- p.7 / Chapter 2.2.2 --- Laplacian Pyramid Generation --- p.7 / Chapter 2.2.3 --- Decoding --- p.8 / Chapter 2.2.4 --- Limitation --- p.9 / Chapter 2.3 --- Multiresolution Transform --- p.9 / Chapter 2.3.1 --- Multiresolution Approximation of L2(R) --- p.9 / Chapter 2.3.2 --- Implementation of a Multiresolution Transform --- p.12 / Chapter 2.3.3 --- Orthogonal Wavelet Representation --- p.16 / Chapter 2.3.4 --- Implementation of an Orthogonal Wavelet Representation --- p.18 / Chapter 2.3.5 --- Signal Reconstruction --- p.21 / Chapter 3 --- Multiresolution Learning Method --- p.23 / Chapter 3.1 --- Introduction --- p.23 / Chapter 3.2 --- Input Vector Representation --- p.24 / Chapter 3.2.1 --- Representation at the resolution 1 --- p.24 / Chapter 3.2.2 --- Representation at the resolution 2j --- p.25 / Chapter 3.2.3 --- Border Problem --- p.26 / Chapter 3.3 --- Back-Propagation Network Architecture --- p.26 / Chapter 3.4 --- Training Procedure Strategy --- p.27 / Chapter 3.4.1 --- Sum Squared Error (SSE) --- p.28 / Chapter 3.4.2 --- Intermediate Stopping Criteria --- p.30 / Chapter 3.5 --- Connection Weight Transformation --- p.31 / Chapter 3.5.1 --- Weights between the Input and Hidden Layers --- p.31 / Chapter 3.5.2 --- Weights between the Hidden and Output Layers --- p.33 / Chapter 4 --- Simulations --- p.36 / Chapter 4.1 --- Introduction --- p.36 / Chapter 4.2 --- Choices of the Impulse Response h(n) --- p.36 / Chapter 4.3 --- XOR Problem --- p.39 / Chapter 4.3.1 --- Setting of Experiments --- p.39 / Chapter 4.3.2 --- Experimental Results --- p.41 / Chapter 4.4 --- Numeric Recognition Problem --- p.50 / Chapter 4.4.1 --- Setting of Experiments --- p.50 / Chapter 4.4.2 --- Experimental Results --- p.52 / Chapter 4.5 --- Discussions --- p.72 / Chapter 5 --- Conclusions --- p.75 / Chapter A --- Proof of Equation (4.9) --- p.77 / Chapter B --- Proof of Equation (4.11) --- p.79 / Bibliography --- p.81

The introduction of software radio has meant that standards for radio communication can evolve in a much more natural way, changing only a little at a time without making all of the hardware obsolete. It has become apparent that these changes may affect some systems more favourably than others so allowing the software radio to decide how to adapt can actually improve the link quality. This development is known as cognitive radio and can improve the performance of a single radio link. As an extension of this progress is being made on designing cognitive networks where the software radios which make up the network not only optimise their own link but share information about their goals and situation with other nodes in the network, using all of this data together can optimise overall end-to-end performance of the network. These advances in network design and optimisation come at a time where many parts of the world are re-structuring the television broadcast bands. These have been allocated for a long time and are a generous allocation of a valuable resource. With the power of a cognitive network it is possible to design equipment that can automatically avoid the licensed TV transmitters which only take a fraction of the total bandwidth in any one area. This allows many smaller cells to be fitted between the main transmitters. Assessing the availability of bandwidth and generating maps of available spectrum for these new cognitive networks requires a new approach to radio propagation modelling in the TV bands. Previous models use a worst case scenario to make sure that there is at least enough signal to receive the public service broadcasts in the majority of homes. Predicting where the limits of reception are and where it would be safe to broadcast on these channels requires a better, terrain dependent transmission model. In this thesis the Parabolic Equation Model is applied to the problem of predicting TV band occupancy and the results of this modelling is compared to field measurement to get an idea of how accurate the model is in practice.

"In modern wireless communication systems, intersymbol interference (ISI) introduced by frequency selective fading is one of the major impairments to reliable data communication. In ISI channels, the receiver observes the superposition of multiple delayed reflections of the transmitted signal, which will result errors in the decision device. As the data rate increases, the effect of ISI becomes severe. To combat ISI, equalization is usually required for symbol detectors. The optimal maximum-likelihood sequence estimation (MLSE) based on the Viterbi algorithm (VA) may be used to estimate the transmitted sequence in the presence of the ISI. However, the computational complexity of the MLSE increases exponentially with the length of the channel impulse response (CIR). Even in channels which do not exhibit significant time dispersion, the length of the CIR will effectively increase as the sampling rate goes higher. Thus the optimal MLSE is impractical to implement in the majority of practical wireless applications. This dissertation is devoted to exploring practically implementable symbol detectors with near-optimal performance in wireless ISI channels. Particularly, we focus on the design and implementation of an iterative detector based on the belief propagation (BP) algorithm. The advantage of the BP detector is that its complexity is solely dependent on the number of nonzero coefficients in the CIR, instead of the length of the CIR. We also extend the work of BP detector design for various wireless applications. Firstly, we present a partial response BP (PRBP) symbol detector with near-optimal performance for channels which have long spanning durations but sparse multipath structure. We implement the architecture by cascading an adaptive linear equalizer (LE) with a BP detector. The channel is first partially equalized by the LE to a target impulse response (TIR) with only a few nonzero coefficients remaining. The residual ISI is then canceled by a more sophisticated BP detector. With the cascaded LE-BP structure, the symbol detector is capable to achieve a near-optimal error rate performance with acceptable implementation complexity. Moreover, we present a pipeline high-throughput implementation of the detector for channel length 30 with quadrature phase-shift keying (QPSK) modulation. The detector can achieve a maximum throughput of 206 Mb/s with an estimated core area of 3.162 mm^{2} using 90-nm technology node. At a target frequency of 515 MHz, the dynamic power is about 1.096 W. Secondly, we investigate the performance of aforementioned PRBP detector under a more generic 3G channel rather than the sparse channel. Another suboptimal partial response maximum-likelihood (PRML) detector is considered for comparison. Similar to the PRBP detector, the PRML detector also employs a hybrid two-stage scheme, in order to allow a tradeoff between performance and complexity. In simulations, we consider a slow fading environment and use the ITU-R 3G channel models. From the numerical results, it is shown that in frequency-selective fading wireless channels, the PRBP detector provides superior performance over both the traditional minimum mean squared error linear equalizer (MMSE-LE) and the PRML detector. Due to the effect of colored noise, the PRML detector in fading wireless channels is not as effective as it is in magnetic recording applications. Thirdly, we extend our work to accommodate the application of Advanced Television Systems Committee (ATSC) digital television (DTV) systems. In order to reduce error propagation caused by the traditional decision feedback equalizer (DFE) in DTV receiver, we present an adaptive decision feedback sparsening filter BP (DFSF-BP) detector, which is another form of PRBP detector. Different from the aforementioned LE-BP structure, in the DFSF-BP scheme, the BP detector is followed by a nonlinear filter called DFSF as the partial response equalizer. In the first stage, the DFSF employs a modified feedback filter which leaves the strongest post-cursor ISI taps uncorrected. As a result, a long ISI channel is equalized to a sparse channel having only a small number of nonzero taps. In the second stage, the BP detector is applied to mitigate the residual ISI. Since the channel is typically time-varying and suffers from Doppler fading, the DFSF is adapted using the least mean square (LMS) algorithm, such that the amplitude and the locations of the nonzero taps of the equalized sparse channel appear to be fixed. As such, the channel appears to be static during the second stage of equalization which consists of the BP detector. Simulation results demonstrate that the proposed scheme outperforms the traditional DFE in symbol error rate, under both static channels and dynamic ATSC channels. Finally, we study the symbol detector design for cooperative communications, which have attracted a lot of attention recently for its ability to exploit increased spatial diversity available at distributed antennas on other nodes. A system framework employing non-orthogonal amplify-and-forward half-duplex relays through ISI channels is developed. Based on the system model, we first design and implement an optimal maximum-likelihood detector based on the Viterbi algorithm. As the relay period increases, the effective CIR between the source and the destination becomes long and sparse, which makes the optimal detector impractical to implement. In order to achieve a balance between the computational complexity and performance, several sub-optimal detectors are proposed. We first present a multitrellis Viterbi algorithm (MVA) based detector which decomposes the original trellis into multiple parallel irregular sub-trellises by investigating the dependencies between the received symbols. Although MVA provides near-optimal performance, it is not straightforward to decompose the trellis for arbitrary ISI channels. Next, the decision feedback sequence estimation (DFSE) based detector and BP-based detector are proposed for cooperative ISI channels. Traditionally these two detectors are used with fixed, static channels. In our model, however, the effective channel is periodically time-varying, even when the component channels themselves are static. Consequently, we modify these two detector to account for cooperative ISI channels. Through simulations in frequency selective fading channels, we demonstrate the uncoded performance of the DFSE detector and the BP detector when compared to the optimal MLSE detector. In addition to quantifying the performance of these detectors, we also include an analysis of the implementation complexity as well as a discussion on complexity/performance tradeoffs."

"A comprehensive analysis of a novel detection scheme for SISO wireless transmission scenarios is presented in this dissertation. The scheme, which is based on Belief-Propagation (BP) detectors, is evaluated in both a computer simulation environment and a custom-built software-defined radio test-bed. In this dissertation, we address the design aspects of BP-based receivers, including several approaches to minimize the bit error rate of MAP detectors. We also present the development of an interface framework for a software defined radio platform that aims to implement complex communication transceivers capable of prototyping the hybrid structure with a pre-filter filter and BP detector. Numerical simulations compared the proposed schemes with an existing approaches and showed significant performance gains without requiring great computational cost at the receiver. Furthermore, experiments using GNU Radio Companion and the FMCOMMS software defined radio hardware platform confirm the correct functionality of the proposed interface, and stress tests are conducted to assess the functionality of the interface and how it deteriorates across a range of operating conditions. Finally, we present several experiments using the FMCOMMS software defined radio platform that implement the proposed BP-based receiver scheme and discuss its capabilities and limitations."

Localization inside the human body using radio frequency (RF) transmission is gaining importance in a number of applications such as Wireless Video Capsule Endoscopy. The accuracy of RF localization depends on the technology adopted for this purpose. The two most common RF localization technologies use received signal strength (RSS) and time-of-arrival (TOA). This research presents a comparison of the accuracy of TOA and RSS based localization inside human tissue using computational techniques for simulation of radio propagation inside human tissues. Computer simulation of the propagation of radio waves inside the human body is extremely challenging and computationally intensive. We designed a basic, MATLAB coded, finite difference time-domain (FDTD) for the radio propagation in and around the human body and compared the results obtained from this software with the commonly used and commercially available Finite Element Method (FEM) modeling in ANSYS HFSS. We first show that the FDTD analysis yields comparable results. Then we use the software to simulate the RSS and TOA of the wideband signals propagated inside the human body for RF localization to compare the accuracies of the two methods. We then develop a statistical TOA model using empirical data gathered from these simulations; and, in conjunction with pre-established mathematical models for RSS, we compare the accuracy of each technique with the Cramer-Rao Lower Bound (CRLB) commonly used for calculation of bounds for the performance of localization techniques and the effects of human body movements.

Fraturas são descontinuidades físicas, presentes em diversos materiais utilizados na engenharia, e são responsáveis pela redução da resistência e da rigidez global dos materiais. Tratando-se de fraturas de pequena dimensão, é possível definir a existência de duas escalas: a escala microscópica, onde as fraturas são visíveis, e a escala macroscópica, onde o material fraturado é homogêneo. Maghous et al. (2010) utilizaram a micromecânica para expor o tensor de rigidez homogeneizado para materiais elásticos fraturados, fazendo a ressalva de que fraturas transmitem esforços por suas faces. Utilizando os conceitos formulados por Maghous, Lorenci (2013) ampliou sua aplicação, estendendo à distribuição aleatória das fraturas. Utilizando o mesmo procedimento realizado por Lorenci, determinou-se os tensores de rigidez homogeneizados para materiais elásticos fraturados, os quais foram empregados para formular as condições de propagação de fraturas para materiais elásticos. Conceitualmente, a condição de propagação de fraturas em meios elásticos é formulada com base em conceitos clássicos da termodinâmica, baseados na dissipação de energia. Tratando-se de meios viscoelásticos, a dissipação de energia adquire um novo termo denominado de dissipação viscosa. Nguyen (2010) estabeleceu uma condição de propagação de fissuras em meios viscoelásticos, entretanto, as fissuras admitidas por Nguyen não são responsáveis pela transferência de esforços. Para estender a análise de Nguyen ao caso de fraturas, foi necessário determinar os tensores de relaxação do material viscoelástico fraturado, estes tensores foram obtidos combinando-se os tensores elásticos homogeneizados com os conceitos da transformada de Carson-Laplace, admitindo que as fraturas não se propagam ao longo do tempo. Com base no tensor de relaxação isótropo homogeneizado, determinou-se um modelo reológico equivalente que represente o material viscoelástico fraturado assumindo diferentes modelos reológicos para a matriz e para fraturas. Por fim, analisou-se as condições de propagação de fraturas em meios viscoelásticos de duas formas: de forma aproximada (apurando os estudos realizados por Nguyen) e de forma homogeneizada (admitindo que a propagação de fraturas se dá na escala macroscópica). / responsible for reducing the overall strength and stiffness of the material. In the case of small fractures, is possible set two scales: a microscopic scale, where fractures are visible, and the macroscopic scale, where the fractured material is homogeneous. Maghous et al. (2010) used the micromechanics to expose the homogenized stiffness tensor for fractured elastic materials, making the observation that fractures transmit efforts by their faces. Using the concepts formulated by Maghous, Lorenci (2013) expanded its application, extending to a random distribution of fractures. Using the same procedure performed by Lorenci, the homogenized stiffness tensor was determined for fractured elastic materials, which were employed to formulate the fracture propagation conditions for elastic materials. Conceptually, the fracture propagation conditions for elastic means is made based on classical concepts of thermodynamics, based on the energy dissipation. In the case of viscoelastic means, the energy dissipation acquires a new term called viscous dissipation. Nguyen (2010) established a condition of crack propagation in viscoelastic means, however, the Nguyen’s cracks are not responsible for the transfer of efforts. To extend Nguyen analysis to the case of fractures, was necessary to determine the relaxation tensor for viscoelastic fractured materials, these tensors are obtained by combining the homogenized elastic tensor to the concepts of the Carson- Laplace transform, assuming that the fractures are not propagate over time. Based on the isotropic homogenized relaxation tensors, was determined an equivalent rheological model representing the fractured viscoelastic material assuming different rheological models for matrix and fractures. Finally, was analyzed the fracture propagation conditions in viscoelastic means in two ways: in an approximate way (improving the studies conducted by Nguyen) and homogenized form (assuming that the propagation of fractures occurs at the macroscopic scale).

This study reports a novel and simple technique for successfully coating multi-walled carbon nanotubes (MWCNTs) on to the surface of carbon fibre (CF) fabric for the production of multi-scale CF-epoxy composites. Initially, epoxy composites with multi-scale reinforcement were produced by resin infusion (RI) using woven CF fabric coated with a dispersion of 1 wt. % MWCNTs in an epoxy binder of low molar mass. The effects of this reinforcement on the CF-epoxy interface with MWCNTs was studied in mode I and mode II interlaminar fracture toughness (ILFT) using double-cantilever beam (DCB) and 4 point end-notch flexure (4ENF) tests, respectively. Relative to an equivalent composite reinforced with non-coated CF reinforcement, the binder/MWCNTs coating increased significantly the ILFT of the CF-epoxy composite; in mode I by 105% and in mode II by 50%. This increase in ILFT was attributed to two main effects: Firstly, the binder alone (without MWCNTs), which has a much lower glass transition temperature (Tg) than that the matrix (45 vs. 140 °C), hindered crack propagation and increased the ILFT of the epoxy matrix by 25% for mode I and 15% for mode II; Secondly, the energy absorbing mechanisms of MWCNTs during fracture particularly pull-out and crack bridging. However the Tg of the matrix epoxy of the multi-scale composites was reduced to 118 °C compared to 140 °C, for the unmodified composite, due to phase mixing with the low Tg binder. For RI processing, the CF volume fraction of the composites prepared using coated CF was ≈50% compare to at ≈55% for the composite with non-coated CF. Curing agents were added to the binder, which not only increased the Tg from ≈50 °C to ≈100 °C, but also increased the Tg of the matrix epoxy of the multi-scale composites to 154 °C. Relative to an equivalent composite reinforced with non-coated CF reinforcement, the curable-binder/MWCNTs coating increased the ILFT of the CF-epoxy composite; in mode I by 120% and in mode II by 90%. A hybrid RI-hot press (HP) process was used to prepare CF-epoxy composites from coated fabrics with CF volume fractions of ≈55%. The damping curves for the HP-composites consisted of a β-peak, due to the formation of a third mixed phase, in addition to a γ-peak (assigned to the Tg of the binder) and an α-peak (assigned to the Tg of matrix epoxy). The β-peak, and the uniformly distributed nodular particles observed on the fracture surface of the matrix, by SEM, for HP-composites, are indicative of the formation of mixed-phase particles due to reaction induced phase separation (RIPS). Relative to an equivalent RI-composite, the curable-binder/MWCNTs treatment increased the ILFT of the CF-epoxy multi-scale composite; in mode I by 134% and in mode II by 15% for HP-composites. Impact test results showed that HP-composites absorbed more energy, due to CF fracture, compared to equivalent RI composites, which showed larger delamination areas after 5 J and 10 J impact. The out-of-plane electrical conductivity and thermal conductivity of the HP-composite with CF coated with curable-binder/MWCNTs was increased by ≈38% and ≈50%, respectively, compared to the composite with non-coated CF, indicating formation of MWCNTs networks in the matrix rich areas of the multi-scale composite.

Para otimizar o processo de plantio mecanizado, faz-se necessário o uso de toletes menores, que possibilitem a adaptação dos mesmos às máquinas agrícolas. O objetivo do estudo foi avaliar a influência do tamanho e da posição do propágulo no colmo da cana-de-açúcar e da aplicação de biorreguladores (ethephon) e bioativadores (cianamida hidrogenada) no desenvolvimento inicial da planta. Foram realizados 8 experimentos no Departamento de Produção Vegetal da Escola Superior de Agricultura \"Luiz de Queiroz\" - ESALQ/USP, município de Piracicaba - SP. Quatro dos experimentos foram realizados em ambiente aberto, em área experimental, e outros quatro em ambiente protegido, casa de vegetação. Foram utilizadas duas variedades nos experimentos, RB966928 e CTC15. Os propágulos foram seccionados de acordo a sua posição no colmo da cana-de-açúcar, apical, mediana e basal. Seu tamanho foi variável devido à diferença de nós e entrenós ao longo de um mesmo colmo. Foram realizadas avaliações semanais das plantas, sendo coletados dados de altura, diâmetro, e número de brotos. O delineamento utilizado foi o de blocos ao acaso, com 4 repetições por tratamento, distribuídas em 4 blocos, sendo que cada sulco correspondeu a um bloco. Os dados numéricos obtidos de número de brotos, altura e diâmetro de plantas foram submetidos à análise de variância e, quando o F foi significativo à 5%, as médias foram submetidas ao Teste de Tukey. As análises estatísticas foram realizadas com o software SAS. Verificou-se que a posição dos propágulos no colmo de cana-de-açúcar influencia a brotação; os propágulos da posição apical são superiores em brotação aos da posição basal; a aplicação do biorregulador ethephon em propágulos de cana-de-açúcar estimula a brotação e prejudica o desenvolvimento inicial em altura dos brotos; a aplicação do bioestimulante cianamida hidrogenada não influencia a brotação de propágulos de cana-de-açúcar; os propágulos com duas gemas apresentam melhor desempenho em brotação e desenvolvimento inicial dos brotos do que propágulos com apenas uma gema. / To achieve improves on sugarcane mechanical plantation, the use of smaller stem pieces becomes necessary, which enables their adaptation to agricultural machinery. The aim of this study was to evalue the influence of size and position of stem on sugarcane stalk and the application of ethephon and hydrogen cyanamide on plant initial development. There were performed eight experiments in Department of Vegetal Production from Escola Superior de Agricultura \"Luiz de Queiroz\" - ESALQ/USP, Piracicaba, São Paulo. Four experiments were performed on field, in experimental area, and four other were performed in greenhouse. There were utilized two cultivars, RB966928 and CTC15. The stems were cut according their position in sugarcane stalk, apical, mean and basal. Their size were variable, due the difference of node and internode along a same stalk. There were performed weekly evaluation of the plants, of which was collected height, diameter and shoots number. The statistical design was randomized blocks, with four replicates by treatment, in four blocks, wherein each planting furrow corresponding to a block. Numerical data obtained by shooting, plant height and diameter were submitted by analysis of variance by F test and compared by Tukey test at 5% of probability, using SAS software. There were verified that stem position influences sprouting; apical stem have a superior number of shoots than basal stem; ethephon application in sugarcane stems stimulates sprouting and damages initial development in height of plants; hydrogen cyanamide application does not influences stem shooting; stems with two buds present better performance in sprouting and initial development of shoots than stems with one bud.

The time-dependent elastic wave equation is the foundation of seismology. It is very useful in studying the wave propagation in elastic solids. Simulation of Rayleigh waves, which is governed by the equation, requires high accuracy solutions. Finite difference method have been widely used for the simulation of Rayleigh waves. However, it is not obvious how to effectively impose the free surface boundary condition on a curved surface. On the other hand, discontinuous Galerkin methods are more flexible in handling complex geometries. / In this thesis, we develop a class of discontinuous Galerkin methods for time-dependentelastic wave equation in isotropic homogeneous medium. This method is explicit, locally and globally energy conserving. Also, the L² convergence of this method is optimal and the convergence in energy norm is independent of Poisson's ratio. / Besides, we apply our method to simulate Rayleigh waves on curved free surfaces. We also impose a perfectly matched layer to absorb the outward waves. Numerical examples show that our method can accurately capture features of Rayleigh waves even in a domain with high Poisson's ratio. / 時間依賴型彈性波動方程」是地震學的基礎。這組方程對於波在彈性固體中傳播的研究非常有用。雷利波是由這個方程所控制。模擬雷利波須要有非常準確的解。有限差分法廣泛地應用在雷利波的模擬上，可是如何有效地施加自由表面邊界條件於曲面上的方法並不明顯。另一方面，間斷伽遼金方法能更靈活地處理複雜的幾何形狀。 / 在這篇論文中，我們發展了一類間斷伽遼金方法去求「在均勻各向同性的介質上的時間依賴型彈性波動方程」的解。我們將表明，這種方法是顯式的，局部及全域能量守恆的，而它的收斂是最優的和獨立於泊松比的。 / 除此之外，我們運用這個方法來模擬雷利波在具有起伏的自由表面的半空間模型的傳播。我們會使用完美匹配層去吸收朝外的波動。數值算例反映，即使在高柏松比的介質中，這個方法也可以準確地捕捉雷利波的特徵。 / Lam, Chi Yeung. / Thesis M.Phil. Chinese University of Hong Kong 2014. / Includes bibliographical references (leaves 44-47). / Abstracts also in Chinese. / Title from PDF title page (viewed on 06, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

Particle Image Velocimetry (PIV) based pressure field calculation is becoming increasingly popular in experimental fluid dynamics due to its non-intrusive nature. Errors propagated from PIV results to pressure field calculations are unavoidable, and in most cases, non-negligible. However, the specific dynamics of this error propagation process have not been unveiled. This dissertation examines both why and how errors in the experimental data are propagated to the pressure field by direct analysis of the pressure Poisson equation. Error in the pressure calculations are bounded with the error level of the experimental data. The error bounds quantitatively explain why and how many factors (i.e., geometry and length scale of the flow domain, type of boundary conditions) determine the resulting error propagation. The reason that the type of flow and profile of the error matter to the error propagation is also qualitatively illustrated. Numerical and experimental validations are conducted to verify these results. The results and framework introduced in this research can be used to guide the optimization of the experimental design, and potentially estimate the error in the reconstructed pressure field before performing PIV experiments.