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  • (2010) Cole, Fletcher; Cox, Shane; Frances, Maude
    Conference Paper
    An opportunity to explore the topic of data usages is presented by the collaborative research being undertaken by a federation of applied science research units affiliated with a number of different Australian research organizations (the Cluster). The research aims to investigate how members of the collaboration understand and work with data in their day-to-day practice.

  • (2019) Zhang, Weizheng
    Wireless communication has been developed rapidly in recent years with the utilization of multiple-input multiple-output (MIMO) systems. One promising technique to support ultra-high data rate communication is massive MIMO, or large MIMO, where the number of antennas goes to tens or hundreds. Unmanned Aerial Vehicles (UAVs) have the advantages of high mobility and flexibility that can be used as aerial nodes to provide communication to ground users or base stations. In this thesis, the optimization of pilot based channel estimation with limited pilot length is studied for a massive MIMO system. The pilot length is optimized to maximize the system spectral efficiency. Then, the optimal pilot design is discussed under the constraint of finite pilot length. The performance of uplink signal-to-interference-plus-noise ratio (SINR) and the effect of feedback error are also analyzed in time division duplex (TDD) and frequency division duplex (FDD), respectively. Then, a large MIMO system is utilized for UAV communication. In order to provide directional beamforming, the channel estimation in UAV millimeter wave (mmWave) system is studied. A beam training and tracking method is proposed with user mobility. For beam training, a training codebook is designed based on user location distribution. For beam tracking, two tracking methods are proposed based on different types of user mobility to reduce the training overhead. The proposed beam training codebook provides larger average downlink capacity than the conventional codebook. The proposed beam tracking design is also shown to outperform the existing methods. Lastly, a multiple UAV system in mmWave band is considered and studied. Hybrid beamforming is designed for both fully connected antenna array and partially connected subarray structures. Furthermore, a simultaneous beam tracking scheme for multiple UAV users is proposed based on subarray structure, where both UAV mobility and instability effects are taken into consideration. Simulation results show that with the proposed method, the average downlink sum capacity is improved.

  • (2018) Khaled, Mohammad
    The characteristic length of the thin film systems used nowadays in nanoscale thermoelectric and microelectric devices are comparable to the mean free path and wavelength of energy carriers. As a result, the application of classical theorise to characterise thermal transport at the nanoscale is questionable. However, it is essential to understand the underlying physics of heat propagation in thin film systems to control, manipulate, and manage thermal properties in micro and nanodevices. Understanding thermal properties by experiment are challenging, especially for materials with low thermal conductivity and small mean free path (MFP). On the other hand, molecular dynamics (MD) allows investigation of sophisticated crystalline, bulk, interface and surface effects of thermal conduction problem with accuracy, fidelity, and reliability. Nevertheless, the computational results of MD can suffer from the wrong choice of critical parameters, unfit empirical potentials for thermal application and provide unreliable thermal conductivity. Moreover, the dependence of the thermal boundary resistance (TBR) on temperature, thin film's dimension, and defects are not systematically assessed for the important thin films in the thermal application. To solve this problem, a systematic equilibrium molecular dynamics (EMD), addressing the critical issues in thermal conduction characterisation is proposed at the classical temperature range, where thermal conduction is dominated by phonons. The model has been validated by investigating the thermal conduction of Si and dielectrics used in thin film systems. The issue with empirical potential is addressed by critically assessing the performance of a potential on the basis of thermal conductivity, atomic energy and phonon density of state prediction. Later, thin film systems are studied to understand relative phonon propagation at the interface and quantify TBR's dependence on interface area, interfacial distance as well as temperature. Finally, the thermal resistance of thin film systems with defects is characterised to understand realistic phonon propagation scenario in the thermal application of thin film systems.