As part of the processing of tracking targets, surveillance radars detect the presence of targets and estimate their locations. This dissertation re-examines some of the often ignored practical considerations of radar tracking. With the advent of digital computers, modern radars now use sampled versions of received signals for processing. Sampling rates used in practice result in the bin-straddling phenomenon, which is often treated as an undesired loss in signal power. Here, a signal model that explicitly models the sampling process is used in the derivation of the average loglikelihood ratio test (ALLRT), and its detection performance is shown to defeat the bin-straddling losses seen in traditional radar detectors. In monopulse systems, data samples are taken from the sum and difference channels, by which a target direction-of-arrival (DOA) estimate can be formed. Using the same signal model, we derive new estimators for target range, strength, and DOA and show performance benefits over traditional monopulse techniques that are predominant in practice. Since tracking algorithms require an error variance report on target parameter estimates, we propose using the generalized Cramer-Rao lower bound (GCRLB), which is the CRLB evaluated at estimates rather than true values, as an error variance report. We demonstrate the statistical efficiency and variance consistency of the new estimators. With several parameter estimates collected over time, tracking algorithms are used to compute track state estimates and predict future locations. Using agile- beam surveillance radars with programmable energy waveforms, optimal scheduling of radar resources is a topic of interest. In this dissertation, we focus on the energy management considerations of tracking highly maneuverable aircraft. A comparison between two competing interacting multiple model (IMM) filter configurations is made, and a recently proposed unbiased mixing procedure is extended to the case of three modes. Finally, we introduce the radar management operating curve (RMOC), which shows the fundamental tradeoff in radar time and energy, to aid radar designers in the selection of an overall operating signal-to-noise level.

Interactions are crucial for galaxy formation and profoundly affect their evolution. However, our understanding of the impact of interactions on star formation and activity of the central supermassive black hole remains incomplete. In the canonical picture of the interaction process, these processes are expected to undergo a strong enhancement, but some recent studies have not found this prediction to be true in a statistically meaningful sense. This thesis uses a sample of local interactions observed from the ultraviolet to the far-infrared and a suite of N-body hydrodynamic simulations of interactions to examine the evolution of star formation, stellar mass, dust properties, and spectral energy distributions (SEDs) over the interaction sequence. / Astronomy

Flat cosmology with collisionless cold dark matter (CDM) and cosmological constant ([Lambda]CDM cosmology) may have some problems on small scales, even though it has been very successful on large scales. We study the effect of Self-Interacting Dark Matter (SIDM) hypothesis on the density profiles of halos. Collisionless CDM predicts cuspy density profiles toward the center, while observations of low mass galaxies prefer cored profiles. SIDM was proposed by Spergel & Steinhardt [161] as a possible solution to this cuspy profile problem on low-mass scales. On the other hand, observations and collisionless CDM agree on mass scales of galaxy clusters. It is also known that the SIDM hypothesis would contradict with X-ray and gravitational lensing observations of cluster of galaxies, if the cross section were too large. Our final goal is to find the range of SIDM scattering cross section models that are consistent with those astrophysical observations in two different mass scales. There are two theoretical approaches to compute the effect of self-interacting scattering -- Gravitational N-body simulation with Monte Carlo scattering and conducting fluid model; those two approaches, however, had not been confirmed to agree with each other. We first show that two methods are in reasonable agreement with each other for both isolated halos and for halos with realistic mass assembly history in an expanding [Lambda]CDM universe; the value of cross section necessary to have a maximally relaxed low-density core in [Lambda]CDM is in mutual agreement. We then develop a semianalytic model that predicts the time evolution of SIDM halo. Our semianalytic relaxation model enables us to understand how a SIDM halo would relax to a cored profile, and obtain an ensemble of SIDM halos from collisionless simulations with reasonable computational resources. We apply the semianalytic relaxation model to CDM halos, and compare the resulting statistical distribution of SIDM halos with astrophysical observations. We show that there exists a range of scattering cross sections that simultaneously solve the cuspy core problem on low-mass scales and satisfy the galaxy cluster observations. We also present that other potential conflicts between [Lambda]CDM and observations could be resolved in Part II and III. / text

Thesis (M.SC.) - Carleton University, 2007. / Includes bibliographical references (p. 103-107). Also available in electronic format on the Internet.

Efficiency of internal combustion engines (ICEs) is far from optimal. Due to the continuously increasing demands on CO2 regulations, automobile industries are forced to improve such efficiency. A crankshaft roller bearing (CSRB) can lead to significant improvements in engine efficiency. However, before this can be implemented into an actual engine, several challenges have to be addressed. One such challenge is the satisfactory performance of CSRB. The current crankshaft limits the service life since it must act as a roller bearing raceway. Therefore, better material properties are required for the use of CSRB in crankshaft applications. In order to select suitable material for the CSRB, development of several characterization methods is required. These methods are based on failure modes that are expected to occur in the actual application. Surface initiated fatigue was shown to be the main failure mode that could lead to complete failure of such a component. The following three characterizations needs are identified: material characterization, lubricant characterization and surface roughness characterization. Two of these methods are partially part of this thesis. Material characterization is required to select the optimal steel candidate for the CSRB component. A method was developed to assess the damage modes on a reference 100Cr6 steel pair under conditions prevalent to CSRB application. However, fully formulated oil was excluded from this investigation and only low-additive oil was employed. Micro-pitting and wear damage modes were identified and were later assessed. Different surface roughness combinations were tested, from where micro-pitting regions were identified. In addition, the effects of surface hardness and sliding on micro-pitting and wear were investigated. It was found that hard steel contacts are more prone to micro-pitting damage compared to soft ones, but less susceptible to mild wear. In addition, higher sliding increases the degree of micro-pitting and wear. Lubricant characterization was performed to optimize the engine oil formulation for rolling contacts. A method to assess different engine oils in terms of micro-pitting and wear damages of rolling contacts was employed. The effect of viscosity, additive chemistry and different mixtures of base oils on aforementioned performance were presented and discussed. In addition, lubricant characterization will provide in-depth knowledge for engine oils’ manufacturers to improve engine oil formulations for satisfactory performances of CSRB design.

The advent of next generation sequencing technologies has had a major impact on inference methods for population genetics. For example, community ecology studies can now assess species interactions using population history parameters estimated from genomic scale data. Figs and their pollinating fig wasps are obligate mutualists thought to have coevolved for some 75 million years. This relationship, along with additional interactions with many species of non-pollinating fig wasps (NPFW), makes this system an excellent model for studying multi-trophic community interactions. A common way of investigating the population histories of a community's component species is to use genetic markers to estimate demographic parameters such as divergence times and effective population sizes. The extent to which histories are congruent gives insights into the way in which the community has assembled. Because of coalescent variance, using thousands of loci from the genomes of a small number of individuals gives more statistical power and more realistic estimates of population parameters than previous methods using just a handful of loci from many individuals. In this thesis, I use genomic data from eleven fig wasp species, which are associated with three fig species located along the east coast of Australia, to characterise community assembly in this system. The first results chapter describes the laboratory and bioinformatic protocols required to generate genomic data from individual wasps, and assesses the level of genetic variation present across populations using simple summaries. The second results chapter presents a detailed demographic analysis of the pollinating fig wasp, Pleistodontes nigriventris. The inferences were made using a likelihood modelling framework and the pairwise sequentially Markovian coalescent (PSMC) method. The final results chapter characterises community assembly by assessing congruence between the population histories inferred for eight fig wasp species. The population histories were inferred using a new composite likelihood modelling framework. I conclude by discussing the implications of the results presented along with potential future directions for the research carried out in this thesis.

No description available.

Metal thin films deposited on weakly-interacting substrates constitute an essential element of numerous microelectronic, catalytic, and optical devices. However, the natural tendency of metal atoms to agglomerate, upon condensation on a weakly-interacting surface, in dispersed three-dimensional (3D) islands affects negatively the performance of the above-mentioned devices. The aim of this thesis is to investigate one of the mechanisms governing silver (Ag) 3D island growth on weakly-interacting substrates, i.e. the nucleation of a new layer on the island top. Kinetic Monte Carlo (KMC) simulations are employed to calculate the top island-layer critical radius Rc required for nucleating a new layer in the out-of-plane direction. Single-island simulations are performed for growth temperatures T in the range 250 to 500 K and ratios of the pairwise adatom/substrate atom bond strength EB,sub to the corresponding adatom/adatom value EB,film in the range 0.5 to 0.75. We find that for T values below 250 K the islands exhibit a 2D morphology for all EB,sub/EB,film ratios. In contrast, for T values above 300 K there exists a range of relatively small EB,sub/EB,film values, where 2D morphology dominates. To calculate Rc for each island layer as the island shape evolves, a subroutine is developed and implemented in an existing KMC algorithm. Rc values are computed for 3D island growth at EB,sub/EB,film = 0.5 in the T range 300−500 K and the results show that Rc decreases monotonously from 17.3 to 6.0 Å and saturates approximately at 375 K. This trend is opposite to the typical behavior of islands grown under homoepitaxial conditions, for which the enhancement of downward inter-layer diffusion caused by an increase of T leads to lower atomic densities on the top, i.e. to a lower nucleation probability, and thus to an increase of Rc. This work contributes to the understanding of the physical processes that control thin-film morphological evolution; which is paramount for controlling and manipulating film growth for specific applications.

No description available.

abstract: In the past three decades with the deployment of space-based from x-rays to infrared telescopes and operation of 8-10 m class ground based telescopes, a hand-full of regions of the sky have emerged that probe the distant universe over relatively wide fields with the aim of understanding the assembly of apparently faint galaxies. To explore this new frontier, observations were made with the Large Binocular Cameras (LBCs) on the Large Binocular Telescope (LBT) of a well-studied deep field, GOODS-North, which has been observed by a wide range of telescopes from the radio to x-ray. I present a study of the trade-off between depth and resolution using a large number of LBT/LBC U-band and R-band imaging observations in the GOODS-N field. Having acquired over 30 hours of data (315 images with 5-6 minute exposures) for U-band and 27 hours for R-band (828 images with 2 minute exposures), multiple mosaics were generated, starting with images taken under the best atmospheric conditions (FWHM <0.8"). For subsequent mosaics, data with coarser seeing values were added in until the final, deepest mosaic included all images with FWHM <1.8". For each mosaic, object catalogs were made to compare the optimal-resolution, yet shallower image to the low-resolution but deeper image. For the brightest galaxies within the GOODS-N field, structure and clumpy features within the galaxies are more prominent in the optimal-resolution image compared to the deeper mosaics. I conclude that for studies of brighter galaxies and features within them, the optimal-resolution image should be used. However, to fully explore and understand the faintest objects, the deeper imaging with lower resolution are also required. For the 220 and 360 brightest galaxies in the U-band and R-band images respectively, there is only a marginal difference between the optimal-resolution and lower-resolution light-profiles and their integrated total fluxes. This helps constrain how much flux can be missed in galaxy outskirts, which is important for studies of Extragalactic Background Light. Finally, I also comment on a collection of galaxies in the field with tidal tails and streams, diffuse plumes, and bridges. / Dissertation/Thesis / Doctoral Dissertation Astrophysics and Astronomy 2018