Dielectric resonators offer high-Q (low loss) characteristics which make them ideal for filters with narrow bandwidth and low insertion loss specifications. They are mainly used in satellite and wireless system applications. Such applications desire the highest performance filters with the lowest amount of size and mass, which has been the main motivation for size reduction techniques invented over the past three decades for these filters. In addition with the emergence of different communication system technologies, several bands are now required to be supported by a single front-end, calling for emergence and development of dual-band and multi-band filters. To date few work has been done in the area of dual-band dielectric resonator filters. Dielectric resonators filters are important components in many communication systems, when a group of such filters are brought together to perform multiplexing of RF channels. These multiplexer systems tend to be fairly complex and bulky in design, and there is strong desire to reduce their size and mass to the maximum extent possible. Novel quadruple-mode, dual-mode, and dual-band filters as well multiplexers are presented in this thesis. The first ever quadruple-mode dielectric resonator filter using the simple cylinder structure is reported in this work. A cylindrical dielectric resonator sized appropriately in terms of its diameter and height is shown to operate as a quadruple-mode resonator, which is achieved by having two mode pairs of the structure resonate at the same frequency. Single-cavity, quad-mode filters and higher order 4n-pole filters are realizable using this quad-mode cylindrical resonator, offering significant size reduction for dielectric resonator filter applications. The structure of the quad-mode cylinder is then simplified by cutting lengthwise along the central axis of the cylinder, to produce a half-cut cylinder suitable for operation in a dual-mode regime. Novel dual-mode, 2n-pole filters are realizable using this half-cut cylinder, by making the two resonances equal in frequency. The dual-mode half-cut filter is shown to be a strong contender for replacing existing dual-mode filters used in satellite and wireless applications, as it offers superior size and mass characteristics. By making the resonances unequal in frequency, novel dual-band filters and multiplexers are further realizable, by carrying separate frequency bands on different resonant modes of the structure. The first true orthogonal mode dual-band dielectric resonator is presented in this work, using the half-cut structure. Multiplexers are also derived from these dual-band resonators, which greatly reduce size and mass of many-channel multiplexers at the system level, as each two channels are overloaded in one physical branch. Full control of center frequencies of resonances, input and inter-resonator couplings are achievable, allowing realization of microwave filters with different bandwidth, frequency, and return loss specifications, as well as advanced filtering functions with prescribed transmission zeros. Spurious performance of the half-cut cylinder can also be improved by cutting one or more through-way slots between opposite surfaces of the resonator. Size and mass reduction achieved by using the full and half-cut resonators described in this thesis, provide various levels of size reduction in microwave systems, both device and system level.

Submarine slope failure releases sediments; it is an important mechanism that changes the Earth surface morphology and builds sedimentary records. I study the mechanics of submarine slope failure in sediment that dilates under shear (dilative slope failure). Dilation drops pore pressure and increases the strength of the deposit during slope failure. Dilation should be common in the clean sand and silty sand deposits on the continental shelf, making it an important mechanism in transferring sand and silt into deep sea. Flume experiments show there are two types of dilative slope failure: pure breaching and dual-mode slope failure. Pure breaching is a style of retrogressive subaqueous slope failure characterized by a relatively slow (mm/s) and steady retreat of a near vertical failure front. The retreating rate, or the erosion rate, of breaching is proportional to the coefficient of consolidation of the deposit due to an equilibrium between pore pressure drop from erosion and pore pressure dissipation. The equilibrium creates a steady state pore pressure that is less than hydrostatic and is able to keep the deposit stable during pure breaching. Dual-mode slope failure is a combination of breaching and episodic sliding; during sliding a triangular wedge of sediment falls and causes the failure front to step back at a speed much faster than that from the breaching period. The pore pressure fluctuates periodically in dual-mode slope failure. Pore pressure rises during breaching period, weakens the deposit and leads to sliding when the deposit is unstable. Sliding drops the pore pressure, stabilizes the deposit and resumes breaching. The frequency of sliding is proportional to the coefficient of consolidation of the deposit because dissipation of pore pressure causes sliding. Numerical model results show that more dilation or higher friction angle in the deposit leads to pure breaching while less dilation or lower friction angle leads to dual-mode slope failure. As a consequence, pure breaching is limited to thinner deposits and deposits have higher relative density. / text

Variable pressure electron beam etching and lithography for Teflon AF has been demonstrated. The relation between dose and etching depth is tested under high vacuum and water vapor. High resolution structures as small as 75 nm half-pitch have been resolved. Several simulation tools were tested for surface plasmon excitation. Grating based dual mode surface plasmon excitation has been shown numerically and experimentally.

Iudicet iudicarive iubeat. Reflexões sobre os origens do processo civil romano e as causas da bipartição. Depois da introdução, o segundo capítulo analisa os aspectos da história constitucional da Monarquia e início da República, sobretudo as críticas à historiografia tradicional no tocante à passagem de um regime ao outro, além de estudar a religião romana arcaica. O terceiro capítulo busca elementos da administração da justiça no direito comparado (babilônico, gregos e germânicos), enquanto que o quarto analisa o início do processo criminal romano. O quinto capítulo, por sua vez, investiga as várias teorias acerca do início do processo civil, como da arbitragem, defesa privada, Volksjustiz etc. O sexto capítulo trata das várias teorias da bipartição, procurando estabelecer se teve caráter originário no processo civil romano e suas causas. O sétimo capítulo analisa as legis actiones mais antigas (legis actio sacramento, legis actio per manus iniectionem e legis actio per iudicis arbitrive postulationem). O oitavo capítulo tenta verificar o conteúdo da iurisdictio romana e suas relações com o imperium, enquanto que o capítulo nono trata das figuras do iudex e do arbiter. O décimo capítulo apresenta as críticas às teorias expostas, formulando hipótese acerca do surgimento do processo civil romano por meio de resolução das controvérsias no âmbito da comunidade anteriormente à formação da civitas com base em cultura e religião comuns, razão por que a presente tese propõe a adoção do termo justiça comunitária pré-cívica para qualificar esse sistema, propugnando pelo abandono das expressões autotutela/justiça privada e Volksjustiz por serem ambas portadoras de equívocos. No tocante à bipartição, a presente tese considera verossímil sua consolidação na época da Lei das XII Tábuas em razão sobretudo do fenômeno da dessacralização do processo / Iudicet iudicarive iubeat. Remarks on the origins of the Roman civil procedure and the causes of its dual mode. After the introduction, the second chapter analyses some aspects of constitucional history of Monarchy and the beginning of Republic, mainly the critics against the tradicional historiography concerning the transition from the first to the latter and it also studies the ancient Roman religion. The third chapter seeks elements from the administration of justice in comparative law (Babylonic, Greeks and Germanics), while the forth one analyses the beginning of the criminal persecution in Rome. The fifth chapter investigates the theories about the beginning of civil litigation, such as arbitration, self help, Volksjustiz etc. The sixth chapter deals with the dual mode procedure theories, trying to set if is had an original character and its causes. The seventh chapter analyses the most ancient legis actiones (legis actio sacramento, legis actio per manus iniectionem e legis actio per iudicis arbitrive postulationem). The eighth chapter tries to verify the content of the Roman iurisdictio and its relationships with imperium, while the nineth chapter deals with the figures of iudex and arbiter. The last chapter presents the critics to the analysed theories and formulates a hypothesis about the beginning ot the Roman civil procedure through the disputes settlement inside the community before the creation of civitas basing on common culture and religion. Thus, the thesis proposes the adoption of the term justiça comunitária pré-cívica (precivic community justice) in order to qualify this system, refusing the expressions self help, private justice and Volksjustiz, who are dubious. Regarding the dual mode, the thesis sustains it is plausible that it had already benn consolidated by the time of the Twelve Tables Law according mainly to the dessacralization of process.

The objective of the proposed research is to develop simplified reconfigurable transmission systems with frequency multipliers for the transmission of complex modulated signals. Because they rely on nonlinear properties, frequency multiplier-based transmission systems require proper linearization techniques and accurate modeling of the signal transfer function. To accomplish these two goals, the author has developed techniques to model and linearize frequency multipliers and to digitize feedback signals for nonlinear characterization. First, adaptive predistortion techniques and zonal transfer theories have been developed for modeling and linearization. The predistortion system has been verified by applying an IS-95B signal to various frequency multipliers built by the author. Second, because the output signals at higher harmonic zones occupy wider frequency bandwidths than the signal in the fundamental zone does and thus make it harder to use traditional sampling techniques, a simplified but effective method called the sub-Nyquist sampling rate was developed and verified. Third, two methods for reconfigurable transmitters using frequency multipliers in conjunction with digital predistortion linearizers were developed. Both methods make it possible to transmit complex signals via frequency multipliers by using dual-band transmission systems that incorporate frequency multipliers that are based on linearization techniques. One of these methods uses a circuit topology that can be switched between a fundamental-mode in-phase combined amplifier and a push-push frequency doubler using input phasing. The second suggested method uses a fundamental-frequency power amplifier followed by a varactor multiplier that can be bypassed with an RF switch. This work will contribute to the development of low-cost and size-effective reconfigurable transmission systems because it requires fewer transmitting components and needs less sampling of the feedback networks.

Emerging technologies such as Bluetooth and 802.11b (Wi-Fi) have fuelled the growth of the short-range communication industry. Bluetooth, the leading WPAN (wireless personal area network) technology, was designed primarily for cable replacement applications. The first generation Bluetooth products are focused on providing low-cost radio connections among personal electronic devices. In the WLAN (wireless local area network) arena, Wi-Fi appears to be the superior product. Wi-Fi is designed for high speed internet access, with higher radio power and longer distances. Both technologies use the same 2.4GHz ISM band. The differences between Bluetooth and Wi-Fi standard features lead to a natural partitioning of applications. Nowadays, many electronics devices such as laptops and PDAs, support both Bluetooth and Wi-Fi standards to cover a wider range of applications. The cost of supporting both standards, however, is a major concern. Therefore, a dual-mode transceiver is essential to keep the size and cost of such system transceivers at a minimum. A fully integrated low-IF Bluetooth receiver is designed and implemented in a low cost, main stream 0.35um CMOS technology. The system includes the RF front end, frequency synthesizer and baseband blocks. It has -82dBm sensitivity and draws 65mA current. This project involved 6 Ph.D. students and I was in charge of the design of the channel selection complex filter is designed. In the Bluetooth transmitter, a frequency modulator with fine frequency steps is needed to generate the GFSK signal that has +/-160kHz frequency deviation. A low power ROM-less direct digital frequency synthesizer (DDFS) is designed to implement the frequency modulation. The DDFS can be used for any frequency or phase modulation communication systems that require fast frequency switching with fine frequency steps. Another contribution is the implementation of a dual-mode 802.11b/Bluetooth receiver in IBM 0.25um BiCMOS process. Direct-conversion architecture was used for both standards to achieve maximum level of integration and block sharing. I was honored to lead the efforts of 7 Ph.D. students in this project. I was responsible for system level design as well as the design of the variable gain amplifier. The receiver chip consumes 45.6/41.3mA and the sensitivity is -86/-91dBm.

In recent years, tremendous growth of the wireless market can be defined through the following words: smartphone and high-data rate wireless communication. This situation gives new challenges to RF power amplifier design, which includes high-efficiency, multi-band operation, and robustness to antenna mismatch conditions. In addition to these issues, the industry and consumers demand a low-cost small-sized wireless device. A fully integrated single-chip CMOS transceiver is the best solution in terms of cost and level of integration with other functional blocks. Therefore, the effective approaches in a CMOS process for the abovementioned hurdles are highly desirable. In this dissertation, the new challenges are overcome by introducing adaptability to a CMOS power amplifier. Meaningful achievements are summarized as follows. First, a new CMOS switched capacitor structure for high power applications is proposed. Second, a dual-mode CMOS PA with an integrated tunable matching network is proposed to extend battery lifetime. Third, a switchless dual-band matching structure is proposed, and the effectiveness of dual-band matching is demonstrated with a fully-integrated CMOS PA. Lastly, a reconfigurable CMOS PA with an automatic antenna mismatch recovery system is presented, which can maintain its original designed performance even under various antenna mismatch conditions. Conclusively, the research in this dissertation provides various solutions for new challenges of advanced mobile terminals.

Bandpass microwave filters are often modeled as a set of coupled discrete and localized resonators. This model is adequate in the narrow-band case. It, however, fails to describe accurately compact structures where stray couplings can be strong. To address this problem, a new view is proposed in this thesis. Instead of basing the model on localized discrete resonances, we start by constructing a model that is based on the global resonances of the structure. These are the resonances that the ports see and emerge when the entire structure is treated as a single unit. The resulting circuit, the transversal circuit, is universal. It is valid for any coupled resonator filter. The circuit is used in optimization of compact and ultra wideband suspended stripline filters and excellent results were obtained. In order to relate the global-eigen modes model to the conventional model, the issue of representation of microwave filters is investigated in detail. It is shown that a microwave filter can be represented by an infinite number of similar coupling matrices by using different modes as basis. According to this new view, a similarity transformation in microwave coupled resonator filters is interpreted as a change of basis. Two circuits that are related by a similarity transformation represent the same filter structure by using different sets of modes as basis. These conclusions were exploited in establishing a design theory for filters with dual-mode cavities. The new theory leads to direct and accurate design techniques that need no, or minimal, optimization. No tuning is used in the CAD steps. Tuning may only be required to account for manufacturing tolerances. A new tuning configuration is described and validated by computer simulation. A novel dual-mode filter with improved quality factor and reduced sensitivity is developed and designed within the same approach. The filter is fabricated and measured and excellent results are achieved. The same design methodology was used to introduce a new class of dual-mode dual-band microwave filters with improved sensitivity. It is also shown that canonical dual-mode filters can be designed within the same view with minimal local optimization of the input cavity. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2010-03-31 01:33:36.818

A novel localized surface plasmon resonance (LSPR) sensor that differentiates between background refractive index changes and surface-binding of a target analyte (e.g. a target molecule, protein, or bacterium) is presented. Standard, single channel LSPR sensors cannot differentiate these two effects as their design allows only one mode to be coupled. This novel technique uses two surface plasmon modes to simultaneously measure surface binding and solution refractive index changes. This increases the sensitivity of the sensor. Different channels or modes can be created in sensors with the introduction of gold nanospheres or gold nanorods that act as receptor mechanisms. Once immobilization was achieved on gold nanospheres, the technique was optimized to achieve the same immobilization for gold nanorods to get the expected dual mode spectrum. Intricate fabrication methods are illustrated with using chemically terminated self assembled monolayers. Then the fabrication process advances from chemically silanized nanoparticles, on to specific and systematic patterns generated with the use of Electron Beam Lithography. Comparisons are made within the different methods used, and guidelines are set to create possible room for improvement. Some methods implemented failed, but there was a lot to learn from these unsuccessful outcomes. Finally, the applications of the dual mode sensor are introduced, and current venues where the sensors can be used in chemical and biological settings are discussed.

Distance education as delivery mode is currently attracting more and more learners globally who want to improve their skills and qualifications. This is necessitated by especially the limited components of existing contact universities, financial expenditure and working learners. The presenting of open distance learning by existing contact universities in South Africa is relatively unknown. Consequently the aim of this study is also to investigate a model for Open Distance Learning used at the NWU, an existing contact university. In order to achieve this aim, several other aims were set as well. The most important findings of these aims are subsequently summarized. Aim one was to determine how distance education, open distance learning and e-learning have been conceptualized in the literature. It emerges clearly from the literature that various barriers and challenges accompany the implementation and delivery of distance and open distance learning program. These barriers particularly concern matters such as academic, cultural and technical aspects like the student’s experience, the position of the lecturer regarding the program, the design of the program, the fact that development in technology is constantly kept in mind and kept up with, as well as problems with financial aspects. The second aim intended to compare open distance learning in developed and developing countries as far as contact classes and e-learning are concerned, in order to establish the best practices for a suitable management model. The open distance learning models of twelve universities were examined separately and compared to one another. From these comparisons the following components of open distance learning were indentified which would be applicable to both developing and developed countries: (i) the use of traditional paper-based study material; (ii) the use of various forms of technology; (iii) the use of e-learning, and (iv) voluntary supporting contact classes. From the literature it has been shown that, despite limited infrastructure, poverty, illiteracy and geographical isolation, e-learning and m-learning are increasingly implemented as delivery modes in open distance learning programmes in developing as well as developed countries. Aim three was to establish, from within the literature, the nature of management models with specific reference to the innovations within managing business models in the context of open distance learning. Firstly variables which play a role in new business models were considered. Secondly the levels according to which the innovation of new models should take place were investigated, and also how these could possibly be implemented within the NWU, as well as the principles applicable to the innovation and implementing of a new model from an existing mother company. Factors which could play a part in the plans to present distance learning programs were also considered, whether these would imply a new distance education unit or the continued presentation of such programs. The most important aspects to consider for such a management model are addressed in aim seven. Aim four investigated the effect of attendance or non-attendance of contact classes on the academic achievement of open distance learning students within selected Advanced \certificate in Education (ACE) programs. This aim referred to an empirical investigation which comprised five phases. A consecutively progressing research design was used, consisting of both quantitative and qualitative methods, known as the multi-mode design. Phases one to three address aim four. Spearman’s rank order correlations, one-way ANOVAs (t-tests) and two-way tables (Cramer’s effect sizes) were calculated in order to identify significant correlation (effect sizes) between variables. It was found that students who attended contact classes did not achieve significantly better during examinations than students who did not attend. The average module mark in the examination of students who did not attend contact classes was 49.5%. The average mark of students who attended three or more contact classes was 52.6%. Considering the examination results, the passing rate of students who attended contact classes was 89% as opposed to 82% for those who did not attend any contact classes. Upon comparing data of students attending vacation school and those who did not, it emerged that students who attended vacation school achieved an average module mark (for all modules) of 42.4% as opposed to 52.7% of those who did not attend any vacation school. Aim five considered the open distance learning student’s opinions on and experience of attending contact classes and not attending, within selected ACE programs. Questionnaires were distributed to a number of students who attended contact classes, and to some who did not attend. The following findings emerged: reasons why students do not attend contact classes are (i) distance from tuition centre; (ii) personal reasons such as family responsibilities or funerals; (iii) because classes are not presented by full-time NWU lecturers; (iv) medium of instruction, limited time and class sizes also seemed to pose problems. Aim six investigated the readiness of the open distance learning student for e-learning within selected ACE programs. Focus group interviews regarding this aim were conducted with three groups of students. The following was found: (i) the vast majority of students (62.1%) do not have computers at home; (ii) 80.4% indicated that that they could not access the Internet, and that (iii) cell phone communication seemed to be the solution, since 93.1% of students own cell phones. Aim seven investigated the opinions of management experts at the NWU concerning the components and practice of an ODL model at the NWU. In order to comply with this aim, an intensive literature study was done on open distance learning models internationally. In the second place an empirical investigation was conducted regarding attendance of contact classes and e-learning as teaching method for the teaching and learning component of an open distance learning model. Thirdly focus group interviews were conducted with senior management of the NWU regarding challenges, risks and components of an open distance learning model. According to the data obtained from these interviews, various matrix analyses were done, which could serve as basis for a management model in open distance learning. The matrix analyses identified the following eleven components as important for a management and practice model for open distance learning: (i) Teaching and learning pertaining to development and quality of study material, effective assessment, the required program designers, training of lecturers and facilitators for presenting open distance learning programs, and efficient quality evaluation. (ii) ITC for open distance learning refers to technological support for processes such as assessment, interactive presentation of lessons, using Internet, cell phone technology and the use of the web page. (iii) Support practice for management which involves matters such as the policy of administrative processes regarding registration, cooperation with consortiums, assessment of assignments and examinations, and dealing with administrative processes different from on-campus. (iv) Finances which refer to compiling annual budgets, remuneration of facilitators, determining the profitability of programs presented, as well as financing technological development. (v) Tuition centres: coordination between the university and tuition centres is crucial as far as contact classes, interactive presentations, group discussions as well as examinations are concerned. (vi) Short courses and projects, especially as far as continuing professional development is concerned, as well as the development of a preparatory college for prospective students and cooperation with private institutions. (vii) Quality processes which include compulsory evaluation of program content and of the effect of programs as evaluated by the private sector, identifying new programs and cooperation with other faculties. (viii) Marketing which can be done by the university itself or by a consortium of collaborators. (ix) A structure for open distance learning with its own, unique and particular structure according to need. Factors which may be significant are the number of students studying through open distance learning, the nature of the programs presented and cooperation between consortiums. (x) Hierarchical structure which in the first place requires effective management of an open distance unit, and secondly also that such unit functions in cooperation with and within existing structures. Especially executive authority and lines for reporting should be outlined clearly. (xi) Research must be done in collaboration with other faculties in order to acquire a particular distance education entity. Research regarding the management of, e.g. the effect of programs, contact class attendance, readiness for e-learning and technology at tuition centres, can also be conducted. The exigency for development of an o pen distance learning unit within the NWU, together with a management model for effective management and practice of distance programs, was the main theme of this study. This study has succeeded in suggesting a management model which could be utilized profitably in endeavoring to attain the strategic aim of presenting programs by means of distance education. It also addresses the national need in South Africa of access to tertiary education for more learners. / PhD (Education Management), North-West University, Potchefstroom Campus, 2012