To satisfy the growing demands of the mobile and personal broadband communications, recently, many innovative technologies have been devised and extensively used for wireless transmission and reception. In the wireless communication systems, even though the performance would be degraded due to channel characteristics, such as multipath fading and background noise, those impacts can be eliminated dramatically through the utilization of diversity and combining. However, some different kinds of interfering sources, including the significant structure interference due to their operation as multiple access in the cellular communication systems, referred to as the multiple access interference (MAI), and inevitable jammers appeared in the overlapped frequency band for common utility, are still existing and now become the main difficulties to collapse the reception performance and system capacity. To suppress the interferences, some advanced signal processing methods, e.g., smart antenna (SA), multiuser detection, interference cancellation, adaptive optimization, and frequency/ frame synchronization, have been suggested to not only alleviate the effects fundamentally but also enhance the signal quality. Orthogonal frequency division multiplexing (OFDM) is a significant multicarrier (MC) technology, and has been widely employed in some commercial communications, such as digital broadcasting and wireless local area network (WLAN). It is considered to be the one of the most promising techniques to combat multipath fading and MAI for the downlinks transmission of the broadband systems. Moreover, spatial processing exploits the diversity provided by SA or intelligent antenna arrays, in which the adaptive beamformer is utilized, and it is an alternative approach to increase the efficiency of wireless system capacity and performance without allocating additional frequency spectrum. It allows the system to make full use of spatial diversity due to multiple antennas. In this dissertation, the wireless communications based on the OFDM technique and the applications of SA are considered. Also, an adaptive linearly constrained (LC) approach via inverse QR-decomposition (IQRD) recursive least-squares (RLS) algorithm is emphasized. The proposed LC-IQRD-RLS algorithm has the merits, such as numerical stability, fast convergence rate, and implementation efficiency, over the conventional adaptive algorithms. Furthermore, by incorporating with derivative constraint, the narrowband array could improve the robustness against to the wideband and coherent jammers. Here, the iterative quadratic maximum likelihood (IQML) algorithm with norm constraint set is utilized to estimate the jammer subspace. Computer simulations verify that the use of narrowband beamformer with an appropriate algorithm, e.g., LC-IQRD-RLS or IQML, could achieve the desired performance for jammer suppression. Next, their applications to the MC-CDMA system with frequency combining process will be fully addressed. In fact, the frequency diversity is achieved through the optimization approach, based on constrained minimum output energy (CMOE) criterion. Unfortunately, it is very sensitive to the signal mismatch due to channel estimation error. To deal with the mismatch problem, the invariant-property provided by constant modulus (CM) criterion along with the LC-IQRD-RLS algorithm is developed. Simulation results show that the frequency combiner with the robust LCCM IQRD-RLS algorithm could be used to recover the transmitted signal without channel mismatch or distortion, and mitigate the MAI efficiently even in the significant near-far effect environment. To further enhance the detection performance and increase system capacity, the space-time MC-CDMA receiver is proposed by combining the advantages of SA and multicarrier transmission technique. This direct fully space-time MC-CDMA receiver can be implemented via a mathematical operator, i.e., kronecker product. For further investigation, a theoretical analysis could be evaluated under certain assumptions to obtain a closed-form expression of bit error rate (BER). This will help us look more inside the impacts due to the numbers of subcarriers and array sensors. In the last chapter, the familiar problem of carrier frequency offset (CFO) is investigated following the standard of IEEE 802.11 a/g OFDM-based WLAN. The overall frequency synchronization scheme consists of three parts, viz., the coarse and fine automatic frequency control (AFC) circuits, and phase locked loop (PLL). With the proposed frequency synchronization scheme, it reserves 2dB power consumption compared with the current specification even some timing issues presented.

There are many novel techniques have been invented to provide high-data rate with high quality communication services for future wireless communications systems. Recently, a novel digital modulation technology for multiple accesses, referred to as the Multi-Carrier Code Division Multiple Access (MC-CDMA), has been proposed to support high data rate transmission; it is based on the combination of CDMA and orthogonal frequency division multiplexing (OFDM). The MC-CDMA has been shown to be an effective technique for combating multipath fading. With MC-CDMA system, a user¡¦s spreading code can be modulated on separate subcarriers, undergo frequency-flat fading channel and offers frequency diversity advantage. But in a multi-user environment, othogonality among spreading codes is severely distorted due to multipath delay spread, such that the system capacity will be limited by the multiple access interferences (MAI). Similar situations exist due to possible narrowband interference (NBI) from other systems. Effective interference reduction will render system capacity to increase, which means interference suppression techniques are vital in improving overall system performance. In this thesis, we propose a new linearly constrained recursive least square algorithm, with diagonal loading approach, referred to as the DL-LC RLS algorithms, to further improve the system performance. The proposed diagonal loading RLS algorithm is different from conventional diagonal loading RLS algorithm, in which the diagonal loading was used to improve the robustness to pointing errors in beamforming problem. However, in this thesis, the diagonal loading approach could be used to alleviate the effect due to multiple access interference (MAI), such that under certain circumstances, better performance could be achieved. Basically, in the proposed algorithm, the power of interference plus noise of received signal will be estimated and subtracted from the diagonal terms of the autocorrelation matrix of received signal. After that instead of using the original autocorrelation matrix, the new correlation matrix, with subtracting power related to the interference plus noise, will be involved during the adaptation processes for updating the weights of the multi-user detector. Finally, computer simulation results, in terms of bit error rate, are used to demonstrate the merits of the proposed scheme compared with the conventional RLS algorithm approach without using the diagonal approaches.

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Capacity of CDMA system is limited to interference due to other users. System performance is degraded by near-far problem when undesired users are closer to base station. Beside, the channel parameters could not be estimated perfectly at receiver, refer to as mismatch problem, which would also degrade the system performance. We would like to consider the MAI and near-far interference cancellation by adaptive linear constraint algorithms to implement linear constraint minimum variance (LCMV) approach. To exploit the linearly constrained filtering, the structure of the generalized side-lobe canceller (GSC) has been employed, where the constrained problem is converted into an unconstrained form with fewer parameters. GSC structure is an indirect but simpler implementation of LCMV algorithm. Moreover, it is also known that the constant modulus (CM) criteria has advantage to combat the channel mismatch, and the performance of the adaptive constraint algorithm based on CM criteria will be investigate. In this thesis, we will derive a new GSC-IQRD-RLS algorithm to combat MAI and near-far problems by combining LC-IQRD-RLS algorithm [1][5] and GSC structure [17]; and prove that the GSC and LC structures based IQRD-RLS algorithms are equivalent, which means that the good performance of LC-IQRD-RLS algorithm can be achieved by a simpler GSC structure algorithm. We will also derive a new GSC-CM-IQRD-RLS algorithm to improve the system performance under mismatch problem by combining CM criteria [20] and GSC-IQRD-RLS algorithm.

Between 1985 and 1997 a hip hop culture emerged in Halifax, Nova Scotia through rap music artists' live performances at various venues, and by releasing original music on commercial and non-commercial cassette tapes and compact discs. This thesis examines the evolution of this grassroots musical culture through the lenses of Halifax's geography, innovative musical and technological trends, ever-present racial politics, and a strong "do-it-yourself" ethic. This thesis argues that hip hop in Halifax during these years can be divided into two eras distinguished by dynamic racial and stylistic changes. While the 1980s saw a predominantly Black hip hop community take root around Uniacke Square and Gottingen Street, the 1990s saw a geographic and demographic shift as the rap music scene expanded and competed with the mainstream music scene of the city. In doing so, the integrated downtown hip hop community produced a significant amount of work, overcoming institutional opposition

Chemical Vapour Deposition (CVD) diamond detectors were modelled for dosimetry of radiotherapy beams. This was achieved by employing the EGSnrc Monte Carlo (MC) method to investigate certain properties of the detector, such as size, shape and electrode materials. Simulations were carried out for a broad 6 MV photon beam, and water phantoms with both uniform and non-uniform voxel dimensions. A number of critical MC parameters were investigated for the development of a model that can simulate very small voxels. For a given number of histories (100 million), combinations of the following parameters were analyzed: cross section data, boundary crossing algorithm and the HOWFARLESS option, with the rest of the transport parameters being kept at default values. The MC model obtained with the optimized parameters was successfully validated against published data for a 1.25 MeV photon beam and CVD diamond detector with silver/carbon/silver structure with thicknesses of 0.07/0.2/0.07 cm for the electrode/detector/electrode, respectively. The interface phenomena were investigated for a 6 MV beam by simulating different electrode materials: aluminium, silver, copper and gold for perpendicular and parallel detector orientation with regards to the beam. The smallest interface phenomena were observed for parallel detector orientation with electrodes made of the lowest atomic number material, which was aluminium. The simulated percentage depth dose and beam profiles were compared with experimental data. The best agreement between simulation and measurement was achieved for the detector in parallel orientation and aluminium electrodes, with differences of approximately 1%. In summary, investigations related to the CVD diamond detector modelling revealed that the EGSnrc MC code is suitable for simulation of small size detectors. The simulation results are in good agreement with experimental data and the model can now be used to assist with the design and construction of prototype diamond detectors for clinical dosimetry. Future work will include investigating the detector response for different energies, small field sizes, different orientations other than perpendicular and parallel to the beam, and the influence of each electrode on the absorbed dose.

Studiens syfte var att undersöka olika projekt som specifikt arbetar med individer vilka önskar lämna en destruktiv subkultur och miljö. Frågeställningarna berörde vilka faktorer som yrkesutövarna upplever viktiga för individens in- och utträde i/ur en destruktv subkultur, hur det kliniska arbetet kan se ut i dessa projekt samt hur yrkesutövare förhåller sig till de olika faser individen genomgår i processen. Vi har gjort en intervjustudie och analyserat resultatet utefter två teorietiska utgångspunkter, vilka var exit-processen och push- och pullfaktorer. Studiens slutsatser är att individanpassade insatser ihop med relationens betydelse och individens motivation är avgörande för utfallet. Vi kan även dra slutsatsen att individens egenskaper och resurser när det gäller motivation, socialt nätverk och social situation underlättar processen till att lämna en destruktiv subkultur och miljö.

Chemical Vapour Deposition (CVD) diamond detectors were modelled for dosimetry of radiotherapy beams. This was achieved by employing the EGSnrc Monte Carlo (MC) method to investigate certain properties of the detector, such as size, shape and electrode materials. Simulations were carried out for a broad 6 MV photon beam, and water phantoms with both uniform and non-uniform voxel dimensions. A number of critical MC parameters were investigated for the development of a model that can simulate very small voxels. For a given number of histories (100 million), combinations of the following parameters were analyzed: cross section data, boundary crossing algorithm and the HOWFARLESS option, with the rest of the transport parameters being kept at default values. The MC model obtained with the optimized parameters was successfully validated against published data for a 1.25 MeV photon beam and CVD diamond detector with silver/carbon/silver structure with thicknesses of 0.07/0.2/0.07 cm for the electrode/detector/electrode, respectively. The interface phenomena were investigated for a 6 MV beam by simulating different electrode materials: aluminium, silver, copper and gold for perpendicular and parallel detector orientation with regards to the beam. The smallest interface phenomena were observed for parallel detector orientation with electrodes made of the lowest atomic number material, which was aluminium. The simulated percentage depth dose and beam profiles were compared with experimental data. The best agreement between simulation and measurement was achieved for the detector in parallel orientation and aluminium electrodes, with differences of approximately 1%. In summary, investigations related to the CVD diamond detector modelling revealed that the EGSnrc MC code is suitable for simulation of small size detectors. The simulation results are in good agreement with experimental data and the model can now be used to assist with the design and construction of prototype diamond detectors for clinical dosimetry. Future work will include investigating the detector response for different energies, small field sizes, different orientations other than perpendicular and parallel to the beam, and the influence of each electrode on the absorbed dose.

abstract: Applications of non-traditional stable isotope variations are moving beyond geosciences to biomedicine, made possible by advances in multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS) technology. Mass-dependent isotope variation can provide information about the sources of elements and the chemical reactions that they undergo. Iron and calcium isotope systematics in biomedicine are relatively unexplored but have great potential scientific interest due to their essential nature in metabolism. Iron, a crucial element in biology, fractionates during biochemically relevant reactions. To test the extent of this fractionation in an important reaction process, equilibrium iron isotope fractionation during organic ligand exchange was determined. The results show that iron fractionates during organic ligand exchange, and that isotope enrichment increases as a function of the difference in binding constants between ligands. Additionally, to create a mass balance model for iron in a whole organism, iron isotope compositions in a whole mouse and in individual mouse organs were measured. The results indicate that fractionation occurs during transfer between individual organs, and that the whole organism was isotopically light compared with food. These two experiments advance our ability to interpret stable iron isotopes in biomedicine. Previous research demonstrated that calcium isotope variations in urine can be used as an indicator of changes in net bone mineral balance. In order to measure calcium isotopes by MC-ICP-MS, a chemical purification method was developed to quantitatively separate calcium from other elements in a biological matrix. Subsequently, this method was used to evaluate if calcium isotopes respond when organisms are subjected to conditions known to induce bone loss: 1) Rhesus monkeys were given an estrogen-suppressing drug; 2) Human patients underwent extended bed rest. In both studies, there were rapid, detectable changes in calcium isotope compositions from baseline - verifying that calcium isotopes can be used to rapidly detect changes in bone mineral balance. By characterizing iron isotope fractionation in biologically relevant processes and by demonstrating that calcium isotopes vary rapidly in response to bone loss, this thesis represents an important step in utilizing these isotope systems as a diagnostic and mechanistic tool to study the metabolism of these elements in vivo. / Dissertation/Thesis / Ph.D. Chemistry 2011