Transient electromagnetic scattering on anisotropic media

This dissertation treats the problem of transient scattering of obliquely incident electromagnetic plane waves on a stratified anisotropic dielectric slab. Scattering operators are derived for the reflective response of the medium. The internal fields are calculated. Wave splitting and invariant imbedding techniques are used. These techniques are first presented for fields normally incident on a stratified, isotropic dielectric medium. The techniques of wave splitting and invariant imbedding are applied to normally incident plane waves on an anisotropic medium. An integro-differential equation is derived for the reflective response and the direct and inverse scattering problems are discussed. These techniques are applied to the case of obliquely incident plane waves. The reflective response is derived and the direct and inverse problems discussed and compared to those for the normal incidence case. The internal fields are investigated for the oblique incidence via a Green\u27s function approach. A numerical scheme is presented to calculate the Green\u27s function. Finally, symmetry relations of the reflective response are discussed

X-Ray Scattering Studies of Charge and Orbital Ordering in Transition Metal Oxides

This thesis focusses on the phenomena of charge ordering and orbital ordering in transition metal oxides, using the technique of resonant x-ray diffraction (RXD). The technique is suited to such studies, as it provides an elemental and band specific probe of long range electronic correlations. Here, we present hard and soft x-ray diffraction results on iron and manganese compounds, and demonstrate the utility of resonant x-ray diffraction in revealing their electronic properties. By performing comprehensive hard x-ray RXD studies on the complex charge ordered structures of magnetite and iron oxyborate, we demonstrate that both systems possess non-integer charge order by using the FDMNES simulation code. We find certain reflections have anisotropic polarisation dependencies, due entirely to the crystal structure, with no need to invoke orbital order to explain the observations. In both materials we demonstrate that the anomalous scattering components can result in a surprising conversion from linearly to non-linearly polarised light, through two subtly different interference processes. This is the first report of such mechanisms. By performing soft x-ray scattering on Pr(Sr$_{0.1}$Ca$_{0.9}$)$_2$Mn$_2$O$_7$, we have provided the first direct observation of the orbital rotation within this compound. We have found that there is no apparent change in the orbital occupation during the stripe rotation, but an increase in the charge disproportionation upon cooling. We have used soft x-ray RXD on lutetium ferrate to discover an anisotropic contribution to the scattering at the charge order wavevector. This is not apparent when probing the crystal structure directly using hard x-rays. We attribute such a signal to charge-orbital order within the system, in contrast to previous claims that the system is an orbital glass

Wave propagators for transient waves in periodic media

One-dimensional propagation of transient EM-waves in periodic media is studied. The media are periodic in the direction of propagation and can be of finite or infinite length. Wave propagators, that map a transient field from one point in the medium to another, are introduced. A number of useful relations for the propagators are presented. Some of these relations are used in the determination of explicit expressions for the short time behavior of a transient wave as it propagates in a periodic medium. The theory is exemplified by several numerical examples

NDBC Ocean Wave Observation System Update

The U.S. National Oceanic and Atmospheric Administration’s (NOAA) National Data Buoy Center (NDBC) is modifying its ocean wave observation system due to parts obsolescence. The modified system is named Ocean Wave Linux (OWL). OWL will replace the NDBC’s older and now obsolete Digital Directional Wave Module (DDWM). Once OWL completes operational verification, the DDWM will be phased out of the NDBC’s operational weather buoy network

Transient wave propagation in composite media: A Green functions approach

A generalized Green functions technique for wave propagation of transient fields in one-dimensional media is developed. The medium is partitioned into an arbitrary number of subslabs for which Green operators, that map the incident field to the internal fields, are defined. Relations between the Green operators for the entire medium and the Green operators for the subslabs are derived. The technique leads to fast numerical algorithms which are especially efficient for dispersive media. The numerical examples focus on the comparison between wave propagation in dispersive and non-dispersive media

Evolutionary Model of e-Procurement Adoption: A Case of the Vietnam Construction Industry

In order to propose more effective solutions to improve the diffusion of e-procurement technologies in the construction sector, it is very important to get a better understanding on the practical evolutionary process of e-procurement adoption at the enterprise level. This cases-study seeks to investigate the strategic evolution of e-procurement adoption in construction companies. Data collected from in-depth semi-structured interviews was analyzed by within-case and cross-case analyses to understand well the similarities and differences between the company cases regarding the way e-procurement technologies have been adopting and implementing. The present study found out a six-stage evolutionary model of e-procurement implementation specific for the context of Vietnamese construction industry. Further, it also proposed the best practical solutions for the cases studied as well as for the general context toward more collaborative e-procurement environment. Although this study is based on the experience of the construction section in a specific country, it is believed its results may be applicable to other developing countries. Using the evolutionary model developed, construction companies are able to self-assess and locate their e-procurement adoption level, and so that establish appropriate practical solutions to move forward a higher level of e-procurement applicability

Development Of An Autonomous And Intelligent System For Residential Water End Use Classification

Urban water supplies need to be ingeniously managed as a result of urbanisation and diminishing dam yield reliability. The advanced management of urban water consumption is deemed essential to maintain a sustainable water future. Understanding how, when and why water is used is vital for managing demand in cost-effective and equitable ways. Detailed knowledge on the quantities of water used in different circumstances gives critical knowledge for forecasting water and planning for water security (Stewart et al., 2010; 2011). Current intelligent water metering systems allow for the high resolution time series reading of water consumption (Beal et al. 2011). Such a high resolution of data is necessary to classify flow patterns into each and every water end-use event in the household in a particular recording period (i.e. tap, clothes washer, shower, etc.). However, the present water end-use classification techniques require extensive use of human resource to collect a combination of water use behaviours and appliance/fixture stock inventory data through a household audit followed by 2-3 hours of analyst time for each home (Stewart et al., 2010). The aim of the project is to develop an autonomous and intelligent system for residential water end-use classification, customer feedback and enhanced urban water management, which could interface with customers and water business managers via a web-portal to computer or mobile phone applications

Age of intelligent metering and big data - Hydroinformatics challenges and opportunities

We are at the dawn of a new era of widespread intelligent water metering delivering live consumption data to utilities and consumers in developed nations. As with most new technologies, intelligent metering will follow a type of hype cycle, where initial excitement and great expectation on its benefits is weighed down by disappointment and disillusionment from early adoptions and then strategic enlightenment will prevail and ultimately productive strategic implementation. Fortunately, the conservative nature of the water industry and the challenges of intelligent metering implementation have meant that the excitement never reached fever pitch and the sensible path to strategic enlightenment is being progressed, albeit very slowly. While the large multi-national metering and software companies have created a range of products and software systems for utilities to automatically collect, store and present reports on customer and citywide water consumption data, a plethora of informatics challenges urgently need to be addressed by researchers, engineers, planners and computer scientists to yield the numerous claimed urban water planning, engineering and management opportunities that can be extracted from this big data revolution. If the call to arms to address such challenges can be realised, significant opportunities will surface including water loss reductions, real-time design optimisation of water networks, live online water use tracking and billing, heightened customer satisfaction with the water utility sector, to name a few.Faculty of Science, Environment, Engineering and TechnologyFull Tex

An Investigation of the Drag Characteristics of a Tailless Delta-Wing Airplane in Flight, Including Comparison with Wind-Tunnel Data

A series of flight tests were conducted to determine the lift and drag characteristics of an F4D-1 airplane over a Mach number range of 0.80 to 1.10 at an altitude of 40,000 feet. Apparently satisfactory agreement was obtained between the flight data and results from wind-tunnel tests of an 0.055-scale model of the airplane. Further tests show the apparent agreement was a consequence of the altitude at which the first tests were made

Preparing the next Generation of Civil Engineering Graduates: Identifying and Combating the Digital Skills Gap

With the rapidly developing role of digital technology, industries have placed significant weight on individuals' level of 'digital literacy', that is, their ability to complete tasks in a digital environment. The construction industry is no exception. It must be viewed as a high-tech industry, necessitating innovation and improvement to remain competitive within today's digital economy. Digital tools offer the construction industry many potentials. However, to realise these benefits, the construction industry needs a different attitude towards the challenges posed not only by the new technology but also by the human component. For the future generation of engineers in the construction industry to be competitive and capable, it is critical in their preparation that they develop skills in the use of digital technologies. The overarching goal of this study was to determine the required skill set of the future 'digital site engineer'. With this research goal, the study sought to achieve the following objectives: (i) to understand the importance of digital technologies in the future of construction; (ii) to identify deficiencies in the current skills of site engineers; (iii) to identify opportunities to use digital technologies to enhance site operations and productivity; (iv) to determine the benefits of digital technologies in future construction projects; and (v) to determine if universities provide engineering graduates with the necessary digital skills to meet future demands. The study discussed the current deficiencies in digital skills, essential digital skills future site engineers would need, and made recommendations on strategies to provide these new skills in a continuously changing field