10,212 research outputs found
RFID Antennas for Difficult Environments
No full textThe research work explored the fundamental ideas and techniques required to design an antenna placed on different common target objects for radio frequency identification. This was achieved by studying the effect of antenna conductivity in a wide range and the substrate relative permittivity from 1 to 10. The effect on wire meander antenna properties are different to that for a straight linear dipole antenna; the increase in wire radius of the meander antenna increases the resonant frequency but increases in wire radius of a straight dipole antenna decreases the resonant frequency. This study concluded that the approximate antenna bandwidth needed for common target object materials is 28.5%. A genetic algorithm GA code was written to optimize the meander antenna structure to obtain a larger bandwidth. The GA optimized each vertical element and horizontal element for radius and length. The optimized antenna has 14.5% bandwidth which covers the entire UHF RFID frequency.
As conductivity is not changed further, the properties of antennas on ungrounded substrates with different permittivity and thickness were investigated. The solution for this problem involved transforming a circular cross section wire antenna structure to a planar strip antenna structure. A number of theoretical approaches were assessed to solve for the effective permittivity when the substrate material is thin. Surface impedance and slab waveguide propagation techniques were compared to a capacitive solution and an insulated wire antenna. The insulated wire method gives most accurate results (< 3.5% error) and was verified using numerical modelling and experimental work. Measurements on a planar straight dipole on FR4 (fc = 1.50GHz) compare favourably with the antenna modelled without the substrate and scaled using the insulated wire technique at (fc = 1.49GHz).Thesis (PhD Doctorate)Doctor of Philosophy (PhD)Griffith School of EngineeringScience, Environment, Engineering and TechnologyFull Tex
Wells Griffith of Caldwell County, Kentucky : his family and some of his descendants /
No full textMode of access: Internet
Low-energy photodetachment of Ga- and elastic electron scattering from neutral Ga
No full textWe present a comprehensive study of the photodetachment of the negative gallium ion and elastic electron scattering from neutral Ga for photon and electron energies ranging from threshold to 12 eV. The calculations are carried out with the B-spline R-matrix method. A multiconfiguration Hartree-Fock method with nonorthogonal term-dependent orbitals is employed to generate accurate initial- and final-state wave functions. The close-coupling expansions include the 4s24pnl(kl) bound and continuum states of Ga and the 4s-excited autoionizing states 4s4p2. The calculated photodetachment and elastic cross sections exhibit prominent resonance features. In order to clarify the origin of these resonances, the contributions of the major ionization channels to the partial cross sections are analyzed in detail.Full Tex
Modelling the Hydraulic Characteristics of Artificial Wetlands
No full textGriffith Sciences, Griffith School of EngineeringFull Tex
Using continuous simulation to assess the impacts of inundation on emergent vegetation in stormwater wetlands
No full textGriffith Sciences, Griffith School of EngineeringFull Tex
Salinity intrusion in coastal drains and creeks
No full textGriffith Sciences, Griffith School of EnvironmentNo Full Tex
Conductivity and resistivity tensor rotation for surface impedance modeling of an anisotropic half-space
No full textGriffith Sciences, Griffith School of EngineeringNo Full Tex
Investigation of continuing loss estimation for medium sized tropical catchments
No full textGriffith Sciences, Griffith School of EnvironmentNo Full Tex
Dynamical Near Optimal Training for Interval Type-2 Fuzzy Neural Network (T2FNN) with Genetic Algorithm
No full textType-2 fuzzy logic system (FLS) cascaded with neural network, called type-2 fuzzy neural network (T2FNN), is presented in this paper to handle uncertainty with dynamical optimal learning. A T2FNN consists of type-2 fuzzy linguistic process as the antecedent part and the two-layer interval neural network as the consequent part. A general T2FNN is computational intensive due to the complexity of type 2 to type 1 reduction. Therefore the interval T2FNN is adopted in this paper to simplify the computational process. The dynamical optimal training algorithm for the two-layer consequent part of interval T2FNN is first developed. The stable and optimal left and right learning rates for the interval neural network, in the sense of maximum error reduction, can be derived for each iteration in the training process (back propagation). It can also be shown both learning rates can not be both negative. Further, due to variation of the initial MF parameters, i.e. the spread level of uncertain means or deviations of interval Gaussian MFs, the performance of back propagation training process may be affected. To achieve better total performance, a genetic algorithm (GA) is designed to search better-fit spread rate for uncertain means and near optimal learnings for the antecedent part. Several examples are fully illustrated. Excellent results are obtained for the truck backing-up control and the identification of nonlinear system, which yield more improved performance than those using type-1 FNN.Thesis (Masters)Master of Philosophy (MPhil)School of Microelectronic EngineeringFull Tex
Development of keratin-coated titanium as an aid to osseointegration
No full textThe development of bioactive materials that can mimic bone tissue has been an area of active research to try and improve the process of implant integration. Wool-derived keratin, a readily available natural polymer, has been shown in vivo to enhance bone
healing and as such may be a novel material for use in the development of biomimetic devices. Coating titanium with keratin, therefore, may be a promising approach to achieve this, but effective bonding between keratin and titanium and the molecular response of osteoblasts to keratin has not been fully delineated. Using aminosilane (APTES) and glutaraldehyde (GA) to prepare the titanium surface, two coating strategies were employed in the present study i.e., solvent casting and molecular grafting, to try and improve the coating's chemical and mechanical properties and improve the interaction between keratin and adherent osteoblastic cells. This thesis had three main goals. First, to characterize the physiochemical and mechanical properties of the keratin coating using various analytical techniques. Second, to evaluate the cytocompatibility of the keratin coating with osteoblastic MG-63 cells in vitro. Finally, to investigate the bone healing response to keratin-coated titanium in vivo using a rat calvarial defect model. [...]Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of Medicine & DentistryGriffith HealthFull Tex
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