The bistable spherical compliant mechanism (BSCM) is a novel device capable of large, repeatable, out-of-plane motion, characteristics that are somewhat difficult to achieve with surface micromachined microelectromechanical systems. An improved pseudo-rigid-body model (PRBM) to predict the behavior of the BSCM is presented. The new model was used to analyze seven different versions of the device, each with a different compliant joint length. The new model, which adds torsion, is compared with a finite element analysis (FEA) beam model. The new model more closely approximates the results yielded by FEA than previous models used to analyze the BSCM. Future work is needed to quantify stress-stiffening interactions between bending and torsion. Both FEA and the current models show that increasing the length of the compliant segment decreases the amount of force required to actuate the device.

Cilia are small microtubule based protrusions found on most cells of the vertebrate body. In humans, defects in the structure or function of cilia results in a large class of developmental and homeostatic diseases known collectively as the ciliopathies. Ciliogenesis is accomplished by the concerted action of a number of molecular pathways including the intraflagellar transport (IFT) system. IFT is a group of ~20 highly conserved proteins that assemble into large macromolecular complexes known as trains. These trains act to carry cargo bi-directionally between the cell body and ciliary tip, via interaction with the microtubule motors kinesin and dynein. IFT train dynamics are required for both cilia structure and function, however the controls on these dynamics are still incompletely understood. Here, I present the first platform for study of IFT dynamics within vertebrate multiciliated cells, an understudied population with critical functions in development and homeostasis. Using this platform, I demonstrate that the planar cell polarity effector protein Fuz is required for IFT dynamics via its control of the cytoplasmic localization of a subset of IFT proteins. Subsequently, I find that a Fuz binding partner, the putative small GTPase Rsg1, is also required for IFT protein localization and dynamics. Additionally, I describe a role for Rsg1 in basal body docking, one of the earliest events of ciliogenesis. Finally, I show that the poorly studied protein TTC29 is required for a specific subset of IFT dynamic behaviors. These data reveal novel regulatory motifs for ciliogenesis and demonstrate, specifically, the complexities of IFT regulation in the cytoplasm and within the cilium itself. Finally, they suggest that multiciliated cells provide a tractable platform for generating robust datasets for the investigation ciliary dynamics. Such studies are critical for informing our understanding of the molecular etiology of human ciliopathic diseases. / text

A new technique is developed that uses planar laser-induced fluorescence (PLIF) imaging of sublimated naphthalene to image the transport of ablation products in a hypersonic boundary layer. The primary motivation for this work is to understand scalar transport in hypersonic boundary layers and to develop a database for validation of computational models. The naphthalene is molded into a rectangular insert that is mounted flush with the floor of a Mach 5 wind tunnel. The distribution of naphthalene in the boundary layer is imaged by using PLIF, where the laser excitation is at 266 nm and the fluorescence is collected in the range of 320 to 380 nm. To investigate the use of naphthalene PLIF as a quantitative diagnostic technique, a series of experiments is conducted to determine the linearity of the fluorescence signal with laser fluence, as well as the temperature and pressure dependencies of the signal. The naphthalene fluorescence at 297 K is determined to be linear for laser fluence that is less than about 200 J/m². The temperature dependence of the naphthalene fluorescence signal is found at atmospheric pressure over the temperature range of 297K to 525K. A monotonic increase in the fluorescence is observed with increasing temperature. Naphthalene fluorescence lifetime measurements were also made in pure-air and nitrogen environments at 300 K over the range 1 kPa to 40 kPa. The results in air show the expected Stern-Volmer behavior with decreasing lifetimes at increasing pressure, whereas nitrogen exhibits the opposite trend. Preliminary PLIF images of the sublimated naphthalene are acquired in a Mach 5 turbulent boundary layer. Relatively low signal-to-noise-ratio images were obtained at a stagnation temperature of 345 K, but much higher quality images were obtained at a stagnation temperature of 380 K. The initial results indicate that PLIF of sublimating naphthalene may be an effective tool for studying scalar transport in hypersonic flows. / text

We study the maximum differential coloring problem, where an n-vertex graph must be colored with colors numbered 1, 2...n such that the minimal difference between the two colors of any edge is maximized. This problem is motivated by coloring maps in which not all countries are contiguous. Since it is known that this problem is NP-hard for general graphs; we consider planar graphs and subclasses thereof. In Chapter 1 we introduce the topic of this thesis and in Chapter 2 we review relevant definitions and basic results. In Chapter 3 we prove that the maximum differential coloring problem remains NP-hard even for planar graphs. Then, we present tight bounds for regular caterpillars and spider graphs and close-to-optimal differential coloring algorithms for general caterpillars and biconnected triangle-free outer-planar graphs. In Chapter 4 we introduce the (d, kn)-differential coloring problem. While it was known that the problem of determining whether a general graph is (2, n)-differential colorable is NP-complete, in this chapter we provide a complete characterization of bipartite, planar and outerplanar graphs that admit (2, n)-differential colorings. We show that it is NP-complete to determine whether a graph admits a (3, 2n)-differential coloring. The same negative result holds for the ([2n/3], 2n)-differential coloring problem, even when input graph is planar. In Chapter 5 we experimentally evaluate and compare several algorithms for coloring a map. Motivated by different application scenarios, we classify our approaches into two categories, depending on the dimensionality of the underlying color space. To cope with the one dimensional color space (e.g., gray-scale colors), we employ the (d, kn)-differential coloring. In Chapter 6 we describe a practical approach for visualizing multiple relationships defined on the same dataset using a geographic map metaphor, where clusters of nodes form countries and neighboring countries correspond to nearby clusters. The aim is to provide a visualization that allows us to compare two or more such maps. In the case where we are considering multiple relationships we also provide an interactive tool to visually explore the effect of combining two or more such relationships. Our method ensures good readability and mental map preservation, based on dynamic node placement with node stability, dynamic clustering with cluster stability, and dynamic coloring with color stability. Finally in Chapter 7 we discuss future work and open problems.

In this thesis, a low-profile, high-gain, ultra-wideband (UWB) planar dipole antenna is presented for radar imaging applications. The antenna is loaded with open complementary double concentric split-hexagonal-ring resonators (LC tank) and chip resistors, and backed with a novel double-layer FSS reflector for gain enhancement. A broadband microstrip to parallel-plate transformer is designed as the feeding structure of the antenna to provide impedance matching and balanced-to-unbalanced transition. The measurement results show the proposed antenna operates over the frequency bandwidth of 0.65-3.8 GHz with S11< -10 dB (VSWR) and smooth gains in the range of 6.2-9 dBi.

Milimetrinių bangų sritis yra perspektyvi daugelyje sričių, nuo kasdienio vartojimo įtaisų tokių, kaip telekomunikacijų tinklų įranga iki specifinių taikymų kariuomenėje, bei diagnostinėje medicinoje. Milimetrinių bangų imtuvuose dažniausiai naudojamas netiesinis elementas yra Šotkio (Schottky) diodas. Nors jo veikimo dažnių ruožas yra iki terahercų srities, tokie trūkumai kaip jautrio priklausomybė nuo temperatūros, neatsparumas elektrinėms perkrovoms, bei jo parametrų blogėjimas laikui bėgant verčia ieškoti naujų alternatyvų. Disertacijoje pristatomi dviejų tipų mikrobangų diodai, pagaminti naudojant įvairiatarpius GaAs/AlGaAs darinius. Puslaidininkinių darinių sluoksnių kokybė buvo eksperimentiškai įvertinta naudojant nuostoviosios fotoliuminescencijos ir laike koreliuoto fotonų skaičiavimo metodus. Aprašytas mikrobangų diodų gamybos procesas. Elektrinės savybės buvo įvertintos išmatavus mikrobangų diodų voltamperines charakteristikas, o detekcinės jų savybės ištirtos plačiame dažnių ruože. / Spectrum region of millimeter wave is extensively used in various areas: from consumer devices in telecommunication networks, to specific applications in military and diagnostic medicine. Schottky diode is the most commonly used two terminal device in microwave receivers. Although the operational frequency of Schottky diode is reaching the terahertz frequency range it has several drawbacks such as sensitivity dependence on temperature, long-term instability and sensitivity to overloads. These drawbacks impelled one to search new type of devices. Two types of microwave diodes fabricated using GaAs/AlGaAs heterostructures are presented in the thesis. The quality of semiconductor epitaxial layers was experimentally estimated using photoluminescence and time correlated single photon counting techniques. The process of microwave diode fabrication is described. Electrical properties of microwave diodes were estimated from current-voltage characteristics and properties of microwaves detection were investigated in wide frequency range.

Spectrum region of millimeter wave is extensively used in various areas: from consumer devices in telecommunication networks, to specific applications in military and diagnostic medicine. Schottky diode is the most commonly used two terminal device in microwave receivers. Although the operational frequency of Schottky diode is reaching the terahertz frequency range it has several drawbacks such as sensitivity dependence on temperature, long-term instability and sensitivity to overloads. These drawbacks impelled one to search new type of devices. Two types of microwave diodes fabricated using GaAs/AlGaAs heterostructures are presented in the thesis. The quality of semiconductor epitaxial layers was experimentally estimated using photoluminescence and time correlated single photon counting techniques. The process of microwave diode fabrication is described. Electrical properties of microwave diodes were estimated from current-voltage characteristics and properties of microwaves detection were investigated in wide frequency range. / Milimetrinių bangų sritis yra perspektyvi daugelyje sričių, nuo kasdienio vartojimo įtaisų tokių, kaip telekomunikacijų tinklų įranga iki specifinių taikymų kariuomenėje, bei diagnostinėje medicinoje. Milimetrinių bangų imtuvuose dažniausiai naudojamas netiesinis elementas yra Šotkio (Schottky) diodas. Nors jo veikimo dažnių ruožas yra iki terahercų srities, tokie trūkumai kaip jautrio priklausomybė nuo temperatūros, neatsparumas elektrinėms perkrovoms, bei jo parametrų blogėjimas laikui bėgant verčia ieškoti naujų alternatyvų. Disertacijoje pristatomi dviejų tipų mikrobangų diodai, pagaminti naudojant įvairiatarpius GaAs/AlGaAs darinius. Puslaidininkinių darinių sluoksnių kokybė buvo eksperimentiškai įvertinta naudojant nuostoviosios fotoliuminescencijos ir laike koreliuoto fotonų skaičiavimo metodus. Aprašytas mikrobangų diodų gamybos procesas. Elektrinės savybės buvo įvertintos išmatavus mikrobangų diodų voltamperines charakteristikas, o detekcinės jų savybės ištirtos plačiame dažnių ruože.

No description available.

Persistent organic pollutants (POPs) are a threat to the environment and human health because they are ubiquitous, resistant to degradation, can bio-accumulate in organisms and bio-magnify in food chains. They have a detrimental effect on the reproductive, nervous and immunity systems of vertebrates. An international treaty, the Stockholm Convention on POPs, came into force in 2004 and aims to limit and eventually prohibit any use and unintentional production of POPs. South Africa ratified the Convention in 2002. Those compounds currently listed by the Stockholm Convention as POPs include chlorinated pesticides such as dichlorodiphenyltrichlorethane (DDT), chlordane and dieldrin, and industry-related compounds such as polychlorinated biphenyls (PCBs) and hexachlorobenzene. Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are also regarded as POPs but - together with some PCBs - they are the unintentional result of anthropogenic activity. This study focussed on the PCDDs, PCDFs and dioxin-like PCBs in the aquatic environment of South Africa particularly because the water resources in this country are under pressure. Despite the fact that South Africa has the sources of these compounds, little is known about the levels of these three groups of compounds. The concentration of twelve dioxin-like PCBs, seven PCDDs and ten PCDFs were determined for 22 sites selected on the grounds of their proximity to possible pollution sources. Analytical determinations included gas chromatography/mass spectrometry and a cell-based bio-assay, the H4IIE-/17C reporter gene assay. Possible sources of the observed pollution were inferred using the following statistical investigative methods: principal component and hierarchical cluster analysis. Seven of the sites had levels higher than the threshold effect concentration of Canada's sediment quality guidelines of 0.85 ngTEQ kg'1 (Toxic Equivalency Quotient). The other sites had lower levels. The highest concentration, 17.8 ng TEQ kg"1, was measured at a site in the southern Gauteng Province. Most of the PCDD/F pollution seemed to have come from combustion sources related to human activity, rather than industrial combustion. Most of the dioxin-like PCB pollution seemed to have been from commercial PCB preparations. Future research would require better characterisation of the sources in order to reduce the formation of these compounds, but also to better understand the exposure and risk scenarios, if humans are to be in close contact with these sources. / Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2008.

This study is focused on designing conformal antennas to be deployed with the inflatable wings for unmanned aerial vehicles (UAV). The main emphasis is on utilizing the structure of the wing to develop antennas for various frequency bands, while maintaining the wing’s aerodynamic performance. An antenna modeler and optimizer software called 4NEC2 and a program called WIRECODE were used to design and determine the characteristics of the antennas. The effect of flexibility of the inflatable wing on the antenna characteristics during flight is also evaluated.