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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

On the design of implementation of turbo-coded Hybrid-ARQ

Oteng-Amoako, Kingsley, Electrical Engineering & Telecommunications, Faculty of Engineering, UNSW January 2005 (has links)
The problem of the efficient use of Hybrid Automatic-Repeat-reQuest (Hybrid-ARQ) in wireless communication has attracted a considerable amount of research. In this thesis, the use and implementation of turbo codes as the Forward Error Correction (FEC) code for Hybrid-ARQ is investigated. The major accomplishments of the research include both the analysis and implementation of turbo Hybrid-ARQ. The thesis begins by obtaining a tractable bound for the performance of turbo codes with M-ary Quadrature-Amplitude-Modulation (M-ary QAM). The research considers the design problem of turbo coded Hybrid-ARQ optimized for AWGN and fading channels. The design problem of turbo Hybrid-ARQ in wideband channels is considered and an optimization strategy is proposed based on Orthogonal-Frequency-Division- Multiplexing (OFDM). The research also presents a novel rate scalable encoder structure that optimal selects a disparate but optimal pair of component codes given the channel conditions. A second part of the thesis considers the implementation of turbo Hybrid-ARQ in Very Large Scale Integration (VLSI ) systems. A design for a single architecture for Type-I and Type-II turbo Hybrid-ARQ is suggested in addition to approaches for improving performance of the Soft-Output-Viterbi-Algorithm(SOVA) decoder core. The research also proposes a SOVA decoder architecture that exploits reliability information to select between the SOVA and bi-directional SOVA.
42

Visual writing : a critique of graphic devices in hybrid novels, from a visual communication design perspective.

Sadokierski, Zoe January 2010 (has links)
This thesis examines hybrid novels – novels in which graphic devices like photographs, drawings and experimental typography are integrated into the written text. Within hybrid novels, word and image combine to create a text that is neither purely written, nor purely visual. Although not new, hybrid novels are increasingly appearing in commercial publishing, and increasingly recognised as an insufficiently explained phenomenon by both literary critics and academics. Book reviews and essays show that readers and critics accustomed to conventional novels can find hybrid novels perplexing. They ask: What are these images? What are they doing in novels? How does one ‘read’ them? These questions point to the need for new approaches to the analysis and critique of hybrid texts, approaches that account for the interplay between words and images. This thesis proposes that Visual Communication Designers – those versed in both the verbal and the visual – offer useful analytical tools and critique for the study of hybrid texts. So the research asks: How could a designer’s particular knowledge of wordimage interplay explain the function of graphic devices in hybrid novels? A preliminary study of fifteen hybrid novels develops: criteria for identifying hybrid novels; a typology of graphic devices in hybrid novels – photographs, illustrative elements, unconventional typesetting, ephemera and diagrams; and a set of analytical tools to critique the effectiveness of the graphic devices in hybrid novels. Then, a primary study uses the analytical tools to critique the graphic devices in three exemplar hybrid novels: Jonathan Safran Foer’s Extremely Loud and Incredibly Close, Steven Hall’s The Raw Shark Texts and Dave Egger’s You Shall Know Our Velocity. This thesis is practice-led in that an issue identified through my design practice led to the research, and analytical and critical tools derived from practice are applied as research methods. The research also draws upon a theoretical framework from the emergent field of Visual Studies, where scholars call for the interdisciplinary study of hybrid texts in a critically acute and widely accessible way. Finally, this thesis is itself a hybrid text; a combination of graphic devices and writing form parts of the argument.
43

Evaluation of the heterotic potential of sorghum [Sorghum bicolor (L.) Moench] adapted to the southern Africa region

Mpofu, Leo Thokoza 25 April 2007 (has links)
Sorghum [Sorghum bicolor (L.) Moench] production in Africa is widespread with low yields due to low inputs and the lack of sorghum hybrids. This situation has forced most of these farmers to grow maize hybrids since they are readily available in the seed market. Sorghum hybrids could be used if their potential was demonstrated. The objective of this study is to document the level of heterosis in Southern Africa sorghum germplasm. The performance of 52 F1 grain sorghum hybrids and their parental lines was evaluated in four environments. Measurements for grain yield, panicle exsertion, days to mid anthesis and plant height were analyzed to obtain estimates of high parent heterosis. High parent heterosis was observed to be 37.18% for yield, 82.77% for exsertion, -0.02% for days to mid anthesis and 23.7% for height. ICSR-939 and (87EON366*90EON328)-LD30 can be used as testers to develop more female lines for further hybrid seed production in breeding programs because they had the highest general combining ability. Protein content averaged 11.69%. ATx635 had significantly higher protein content than ATx631 (13.49% compared to 9.69%, respectively) and its hybrids had more protein than ATx631 hybrids (11.6% compared to 10.67% for ATx631). Mean heterosis for protein content was negative at -12.5%. This shows that hybrids had lower protein content than their parents since protein content is negatively correlated to grain yield (-0.35**). Starch content averaged 72.13% and ATx631 hybrids had more starch than ATx635 hybrids (73.16 compared to 72.37% respectively). Two hybrids, ATx.631/(87EON366*90EON328)-LD30 and ATx631/ ((TAM428*SV1)*CE151)-LD3 had the highest yields (5.04 t/ha and 4.93 t/ha, respectively). These hybrids also had small grains with good hardness and acceptable whiteness. They had good exsertion, flowered in good time and had acceptable plant heights. These two hybrids were compared to regional check varieties Macia and Tegemeo for all traits and they were either superior or within an acceptable range. These two hybrids are therefore recommended for release in the region. There is need therefore to start working on the various components of seed systems in the region so that seed of these two hybrids is made available to farmers who need the seed.
44

Kinetics and dynamics study on the allosteric pathway of phosphofructokinase from Escherichia coli

Tie, Cuijuan 10 October 2008 (has links)
Phosphofructokinase from Escherichia coli (EcPFK) is allosterically regulated by MgADP and phosphoenolpyruvate (PEP), which act to activate or inhibit, respectively, by changing the substrate (Fru-6-P) affinity of the enzyme. Both ligands bind to the same allosteric site in EcPFK. Therefore, the questions we want to address are how these two molecules regulate EcPFK and how the allosteric signal is propagated throughout the enzyme. EcPFK has 28 potential site-site interactions. These interactions in turn derive from multiple copies of 6 potentially unique homotropic interactions and 4 potentially unique heterotropic interactions. Making hybrid tetramer of EcPFK is used to isolate a single heterotropic interaction. To improve the yield of the 1:3 hybrid, the in vivo hybrid formation method was developed. Four heterotropic interactions were isolated by this manner and re-evaluated. The same kinetics characteristics were obtained for each 1:3 hybrid from both the in vivo and in vitro method. To address the question of how the allosteric signal is transmitted throughout EcPFK, we identified residues (G184, Asp59 and S157) that are important for the allosteric regulation for both PEP inhibition and MgADP activation. The impact of each mutation on individual interaction is unique and also suggests that the structural basis for PEP inhibition is different from that for MgADP activation. Most importantly, since the sum of each heterotropic interaction with a modification in only one subunit is equal to the total heterotropic interaction with a modification in all four subunits, this result indicates that the heterotropic allosteric signal transmission is realized in a single subunit. The 23Ã heterotropic interaction, which contributes the most to the PEP inhibition, was chosen to study the dynamic properties. Fluorescence was used to study the dynamic perturbations of the 23Ã interaction upon ligand binding. Taking advantage of the hybrid formation strategy and the tryptophan-shift mutagenesis method, a tryptophan residue can be placed at different individual locations throughout the native subunit containing the 23Ã heterotropic interaction. The steady-state anisotropy and lifetime measurement at each tryptophan position indicate that the 23Ã allosteric interaction involves the perturbation of side-chain dynamics both near and quite far away from the respective ligand binding sites.
45

Hybrid air foil bearing with external pressurization

Park, Soongook 15 May 2009 (has links)
Foil bearings are widely used for oil-free micro turbomachinery. One of the critical technical issues related to reliability of the foil bearings is a coating wear on the top foil and rotor during start/stops. Bearing cooling is also mandatory for certain applications because the foil bearings can generate significant amount of heat depending on operating conditions. Usually axial flow is used through the space between the top foil and bearing sleeve. In this thesis, a hybrid air foil bearing with external pressurization is introduced. The hybrid operation eliminates the coating wear during start-up/shut down, and also reduces drag torque during starts. Furthermore, this hybrid foil bearing does not need cooling system. An experimental test with a loaded bearing under hydrostatic mode demonstrates the high potential of hybrid air foil bearings. The load capacity of the hybrid foil bearing was measured at 20,000 rpm, and compared with that of hydrodynamic foil bearing. The hybrid foil bearing has much higher load capacity than the hydrodynamic foil bearing. The starting torque was also measured and compared with hydrodynamic bearing. A simple analytical model to calculate top foil deflection under hydrostatic pressurization has been developed. Predictions via orbit simulations indicate the hybrid air foil bearings can have a much higher critical speed and onset speed of instability than the hydrodynamic counter part. Major benefits of the hybrid foil bearings also include very low starting torque, reduced wear of the top foil and rotor, and very effective cooling capability by the pressurized air itself. This new concept of hybrid air foil bearings are expected to be widely applied to the oil free turbomachinery industry, especially for heavily loaded and/or high temperature applications.
46

A Hybrid LCC-VSC HVDC Transmission System Supplying a Passive Load

Kotb, Omar January 1900 (has links)
High Voltage Direct Current (HVDC) transmission systems continue to be an excellent asset in modern power systems, mainly for their ability to overcome the problems of AC transmission, such as the interconnection of asynchronous grids, stability of long transmission lines, and use of long cables for power transmission. In the past 20 years, Voltage Source Converter (VSC)-HVDC transmission systems were developed and installed in many projects, thereby adding more operational benefits to DC transmission option, such as high controllability, ability to supply weak networks, and reduced converter reactive power demand. Nevertheless, VSC-HVDC transmission suffers from the disadvantages of high losses and cost. In this research, a hybrid HVDC employing a Line Commutated Converter (LCC) as rectifier and a VSC as inverter is used to supply a passive network through a DC cable. The hybrid system is best suited for unidirectional power transmission scenarios, such as power transmission to islands and remote load centers, where the construction of new transmission lines is prohibitively expensive. Control modes for the rectifier and inverter are selected and implemented using Proportional Integral (PI) controllers. Special control schemes are developed for abnormal operating conditions such as starting at light load and recovering from AC network faults. The system performance under steady state and transient conditions is investigated by EMTP-RV simulations. The results show the feasibility of the hybrid system. / UOIT
47

Towards a Microfluidic Toolbox for Proteomics: Novel Sample Pre-processing and Separation Techniques

Watson, Michael 15 September 2011 (has links)
Microfluidics was introduced in the early 1990’s and was posited to usher in a new age of integrated analysis systems in the form of labs-on-a-chip. To date, numerous embodiments of microfluidic technologies including fully integrated analysis systems have been described for various applications. Microfluidics can be sub-divided into two paradigms based on fluid manipulation in streams or droplets. In the former, streams of fluids flow through micron-dimension channels, and typical volumes manipulated are in the pico-liter to nano-litre range. These devices are mainly employed for rapid, high efficiency chemical separations, among other applications. In the latter, droplets are manipulated on a dielectric-coated array of microelectrodes in a process called digital microfluidics (DMF). In DMF each droplet is individually addressable, giving superior spatial control over fluid droplets with volumes in the pico-liter to micro-litre range. Independently addressable droplets make DMF amenable to carrying out sequential reactions. This thesis presents methods towards the integration of these two microfluidic paradigms into “hybrid microfluidic” platforms. Hybrid devices contain a DMF array for sample preparation and a microfluidic channel network for on-line analysis by chemical separation. Sample transfer between the platforms is made by way of a digital-channel interface, which has been fabricated in two geometries: side-on and vertical. Chemical separations on hybrid devices are performed in various open-channel and chromatographic modes. In open-channel methods analytes are separated by microchannel zone electrophoresis (MZE) or micellar electrokinetic chromatography (MEKC). In chromatographic separations porous polymer monolithic (PPM) columns were created in situ by UV-initiated polymerization of acrylate monomers. Prior to integration into hybrid microfluidic devices PPMs were optimized for use in gradient elution microchannel electrochromatography (MEC) of peptides. It is anticipated that hybrid microfluidic devices will bridge a large bottleneck for myriad analyses by combining sample preparation with on-line analysis by chemical separation.
48

Towards a Microfluidic Toolbox for Proteomics: Novel Sample Pre-processing and Separation Techniques

Watson, Michael 15 September 2011 (has links)
Microfluidics was introduced in the early 1990’s and was posited to usher in a new age of integrated analysis systems in the form of labs-on-a-chip. To date, numerous embodiments of microfluidic technologies including fully integrated analysis systems have been described for various applications. Microfluidics can be sub-divided into two paradigms based on fluid manipulation in streams or droplets. In the former, streams of fluids flow through micron-dimension channels, and typical volumes manipulated are in the pico-liter to nano-litre range. These devices are mainly employed for rapid, high efficiency chemical separations, among other applications. In the latter, droplets are manipulated on a dielectric-coated array of microelectrodes in a process called digital microfluidics (DMF). In DMF each droplet is individually addressable, giving superior spatial control over fluid droplets with volumes in the pico-liter to micro-litre range. Independently addressable droplets make DMF amenable to carrying out sequential reactions. This thesis presents methods towards the integration of these two microfluidic paradigms into “hybrid microfluidic” platforms. Hybrid devices contain a DMF array for sample preparation and a microfluidic channel network for on-line analysis by chemical separation. Sample transfer between the platforms is made by way of a digital-channel interface, which has been fabricated in two geometries: side-on and vertical. Chemical separations on hybrid devices are performed in various open-channel and chromatographic modes. In open-channel methods analytes are separated by microchannel zone electrophoresis (MZE) or micellar electrokinetic chromatography (MEKC). In chromatographic separations porous polymer monolithic (PPM) columns were created in situ by UV-initiated polymerization of acrylate monomers. Prior to integration into hybrid microfluidic devices PPMs were optimized for use in gradient elution microchannel electrochromatography (MEC) of peptides. It is anticipated that hybrid microfluidic devices will bridge a large bottleneck for myriad analyses by combining sample preparation with on-line analysis by chemical separation.
49

Fabrication and Optical Properties of ZnO Nanocrystal/GaN Quantum Well Based Hybrid Structures

Chieh-Yi, Kuo January 2012 (has links)
Optical properties of hybrid structures based on zinc oxide nanocrystals (NCs) and Gallium Nitride quantum well (QW) has been studied. The ZnO NCs thin films on the top of GaN QW structures were fabricated using spin coating. The surface morphology was characterized by scanning electron microscopy (SEM). We have performed temperature dependence time-resolved photoluminescence (TRPL) measurements of the bare AlGaN/GaN QW structures and hybrids, containing ZnO NCs. It was found that at some temperatures the QW PL decay has shorter decay time in the presence of ZnO NCs thin film compared to the bare QW. The effect was stronger for the samples with thinner cap layers. The results are discussed in terms of three models such as exciton nonradiative energy transfer (NRET), tunneling effect, and piezoelectric field influence on the QW exciton energy.
50

Advancement of cotton (Gossypium) radiation hybrid mapping tools

Todd, Steven Michael 15 May 2009 (has links)
The assembly of a robust structural genomics system requires the development and integration of multiple types of genome maps. This research focused on the development of a relatively new means of plant genome mapping, radiation hybrid mapping, for use in cotton genomics. Simple sequence repeat markers were genotyped onto an existing wide-cross whole-genome radiation hybrid panel for genome mapping of the Gossypium barbadense line ‘3-79’. A new mapping panel was created for genome mapping of the G. hirsutum line ‘TM-1’. Carthagene software was compared to RHMAP and found to be superior in most regards. A total of 92 simple sequence repeat markers were genotyped onto the mapping panel for G. barbadense. Data from 64 of the 92 markers were deemed robust and combined with pre-existing data to develop an expanded framework map, which provides partial coverage of 7 chromosomes and three unidentified linkage groups. A new mapping population was created to allow mapping of the G. hirsutum genome. The population was developed by treatment of TM-1 pollen with 8 krad of radiation, which was used to make more than 1000 controlled cross-pollinations. From these, 979 bolls were harvested and seeds were planted until a population of 115 viable plants was obtained. Of these, 92 were selected at random for inclusion in the mapping panel. Carthagene genome mapping software was evaluated and compared to the previously utilized RHMAP. Carthagene compared favorably in ease of use, calculation speed, and reliability of results. As such, it is recommended for use for the RH mapping project.

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