<p>A faithful depiction of the tropical atmosphere requires three-dimensional sets of observations. Despite the increasing amount of observations presently available, these will hardly ever encompass the entire atmosphere and, in addition, observations have errors. Additional (background) information will always be required to complete the picture. Valuable added information comes from the physical laws governing the flow, usually mediated via a numerical weather prediction (NWP) model. These models are, however, never going to be error-free, why a reliable estimate of their errors poses a real challenge since the whole truth will never be within our grasp. </p><p>The present thesis addresses the question of improving the analysis procedures for NWP in the tropics. Improvements are sought by addressing the following issues:</p><p>- the efficiency of the internal model adjustment, </p><p>- the potential of the reliable background-error information, as compared to observations,</p><p>- the impact of a new, space-borne line-of-sight wind measurements, and</p><p>- the usefulness of multivariate relationships for data assimilation in the tropics.</p><p>Most NWP assimilation schemes are effectively univariate near the equator. In this thesis, a multivariate formulation of the variational data assimilation in the tropics has been developed. The proposed background-error model supports the mass-wind coupling based on convectively-coupled equatorial waves. The resulting assimilation model produces balanced analysis increments and hereby increases the efficiency of all types of observations.</p><p>Idealized adjustment and multivariate analysis experiments highlight the importance of direct wind measurements in the tropics. In particular, the presented results confirm the superiority of wind observations compared to mass data, in spite of the exact multivariate relationships available from the background information. The internal model adjustment is also more efficient for wind observations than for mass data. </p><p>In accordance with these findings, new satellite wind observations are expected to contribute towards the improvement of NWP and climate modeling in the tropics. Although incomplete, the new wind-field information has the potential to reduce uncertainties in the tropical dynamical fields, if used together with the existing satellite mass-field measurements.</p><p>The results obtained by applying the new background-error representation to the tropical short-range forecast errors of a state-of-art NWP model suggest that achieving useful tropical multivariate relationships may be feasible within an operational NWP environment.</p>

Frequency domain models for power electronic circuits are either based on iterative techniques such as Newton's method or linearised around an operating point. Iterative frequency domain models provide great accuracy as they are capable of calculating the exact switching instants of the device. On the other hand, the accuracy of a linearised frequency domain model relies on the magnitude of input waveform to be small so that the circuit's operating point does not vary or varies very little. However, an important advantage of a linearised model is its ability to provide insight into waveform distortion interaction, more specifically, the frequency cross-coupling around a power electronic circuit. In general, a linearised model for harmonic analysis would not normally include the description of feedback control. Likewise a linearised model for control analysis would usually disregard frequency interactions above the fundamental (or the most significant component); that is assuming the cross-coupling between harmonic frequencies does not affect the dynamics of control. However, this thesis proposes that a linearised model for control analysis shall also include the complete description of frequency cross-coupling between harmonics to produce the correct dynamic response. This thesis presents a harmonic state-space (HSS) model of an HVdc converter that incorporates the full effect of varying switching instants, both through control and commutation period dynamics, while remaining within the constraints of a linear time-invariant (LTI) system. An example is given using the HSS model to explain how a close to fifth harmonic resonance contributes to the dominant system response through the frequency cross-coupling of the converter and the controller feedback loop. The response of the system is validated against a time domain model built in PSCAD/EMTDC, and more importantly, the correct response cannot be produced without including the harmonic interactions beyond the fundamental frequency component.

High resolution rotational spectra of ¹⁰BH₃CO, ¹¹BH₃CO, ¹¹BD₃CO, PH₂D and CD₃CN were studied to obtain information concerning the electronic and magnetic properties of these molecules. From the analysis of the hyperfine structure of the rotational spectra of the molecules the following constants were determined: rotational constants (B₀), nuclear quadrupole coupling constants (eOq [x], spin-spin constants D (X-Y) and spin rotation constants (C[x]). The two instruments used in these experiments were a Stark modulated microwave spectrometer and a molecular beam maser spectrometer. The J = 0 to 1, F₁ = 3 to 3 and F₁ = 3 to 4 transitions of ¹⁰BH₃CO were studied. The molecular constants in KHz which were derived from the spectral analysis were: B(,0) = 8980060.3 (+/-) 1.0, eQqₐₐ (¹⁰B) = 3463.- (+/-) 8.0, C(¹⁰B) = .2 (+/-) .2, D(¹⁰B-H) = -2.8 (+/-) .2, D(H-H) = -7.2 (+/-) .5 and C(H) = 0.0 (+/-) .7. All three of the F₁ components of the J = 0 to 1 rotational transition of ¹¹BH₃CO were observed. The molecular constants in KHz which were obtained from the data analysis were: B₀ = 8657333.8 (+/-) .6, eQqₐₐ (¹¹B) = 1661.9 (+/-) 2.3, C(¹¹B) = .7 (+/-) .3, D(¹¹B-H) = 8.3 (+/-) .4, D(H-H) = -6.8 (+/-) .2 and C(H) = .4 (+/-) .4. Only spectra of the J = 0 to 1, F₁ = 3/2 to 3/2 transition of ¹¹BD₃CO were obtained. From the analysis of the spectra the following molecular constants were derived: eQqₐₐ (D) = -48.5 (+/-) 2.3, eQq(,zz)(D) = 116.9 (+/-) 5.4, C(D) = 0.0 (+/-) .8 and D(¹¹B-H) = -1.2 (+OR-) .3. The investigation of the 4₀₄ to 4₁₄ and 1₁₁ to 1₀₁ rotational transitions of PH₂D was unsuccessful in determining any molecular parameters. The spectra of the 4₀₄ to 4₁₄ rotational transition were not amenable to analysis and no spectra were obtained for the 1₁₁ to 1₀₁ rotational transitions. The three components of the J = 0 to 1 rotational transitions of CD₃CN were studied with the maser in the two cavity configuration. The constants in KHz which were determined were: B₀ = 7857978.7 (+/-) .1, eQqₐₐ(N) = -4229.2 (+/-) .6, eQqₐₐ(D) = -55.1 (+/-) .4, eQq(,zz)(D) = 165.5 (+/-) 5.0, C(,N) = 1.7 (+/-) .1 and C(,D) = 0.0 (+/-) .03.

This research focused on the synthesis of novel ogranoboron reagents in efforts to perform a variety of synthetic transformations, and additionally, the development of new methodologies to generate drug-like scaffolds. Initially, three novel tripod ligands were synthesized, and two were effectively chelated to boron to provide the desired organoborates. Such organoborates were employed in nucleophilic additions where they were found to be ineffective, whereas some activity was observed in Suzuki-Miyaura cross-coupling reactions. An additional project on organoboron compounds was conducted and focused on the development of organoboron frustrated Lewis pairs (FLPs) to facilitate the storage and transfer of hydrogen, nucleophilic addition reactions, and Claisen rearrangements. A new method for synthesizing a pyrrolidine diol unit was accomplished, and this intermediate was utilized to synthesize two FLPs. The reactivity of the FLPs with small molecules was assessed, and the pyrrolidine diol unit was subsequently evaluated for its ability to undergo a multicomponent reaction (MCR) to yield compounds possessing beneficial biological activity. Further research in this area was conducted, and a 5-aminoimidazole scaffold was synthesized employing a new MCR which is more efficient than previously reported methodologies. 5-Aminoimidazoles are frequently found in compounds which possess desirable biological activity, and this novel method was employed to generate a library of eleven 5-aminoimidazoles. Additionally, two post condensation modification reactions were developed. During initial studies, a side product was observed which was identified as a dihydrotriazine, which is another biologically appealing chemotype. Therefore, an enhanced method of synthesizing this product was developed, and a library of eleven dihydrotriazines was produced. In summary, novel organoboron reagents were synthesized, and their activity was evaluated. The pyrrolidine diol utilized to synthesize FLPs was applied towards an MCR. Furthermore, a novel MCR was developed for the synthesis of 5-aminoimidazoles, and an enhanced protocol for the synthesis of dihydrotriazines was found.

No description available.

Software is an integral part of our everyday lives, and hence the quality of software is very important. However, improving and maintaining high software quality is a difficult task, and a significant amount of resources is spent on fixing software defects. Previous studies have studied software quality using various measurable aspects of software, such as code size and code change history. Nevertheless, these metrics do not consider all possible factors that are related to defects. For instance, while lines of code may be a good general measure for defects, a large file responsible for simple I/O tasks is likely to have fewer defects than a small file responsible for complicated compiler implementation details. In this thesis, we address this issue by considering the conceptual concerns (or features). We use a statistical topic modelling approach to approximate the conceptual concerns as topics. We then use topics to study software quality along two dimensions: code quality and code testedness. We perform our studies using three versions of four large real-world software systems: Mylyn, Eclipse, Firefox, and NetBeans. Our proposed topic metrics help improve the defect explanatory power (i.e., fitness of the regression model) of traditional static and historical metrics by 4–314%. We compare one of our metrics, which measures the cohesion of files, with other topic-based cohesion and coupling metrics in the literature and find that our metric gives the greatest improvement in explaining defects over traditional software quality metrics (i.e., lines of code) by 8–55%. We then study how we can use topics to help improve the testing processes. By training on previous releases of the subject systems, we can predict not well-tested topics that are defect prone in future releases with a precision and recall of 0.77 and 0.75, respectively. We can map these topics back to files and help allocate code inspection and testing resources. We show that our approach outperforms traditional prediction-based resource allocation approaches in terms of saving testing and code inspection efforts. The results of our studies show that topics can be used to study software quality and support traditional quality assurance approaches. / Thesis (Master, Computing) -- Queen's University, 2013-01-08 10:10:37.878

The transmitting of video content over Vehicular Ad Hoc Networks (VANETs) faces a great number of challenges caused by strict QoS (Quality of Service) requirements and highly dynamic network topology. In order to tackle these challenges, multipath forwarding schemes can be regarded as potential solutions. However, route coupling effect and the path length growth severely impair the performance of multipath schemes. In this thesis, the current research status about video streaming over VANETs as well as multipath transmissions are reviewed. With the demand to discover a more suitable solution, we propose the Location-Aware Multipath Video Streaming (LIAITHON+) protocol to address video streaming over urban VANETs. LIAITHON+ uses location information to discover relatively short paths with minimal route coupling effect. The performance results have shown it outperforms the underlying single path solution as well as the node-disjoint multipath solution. In addition, the impact of added redundancy on the multipath solution is investigated through LIAITHON+. According to the results, added redundancy has a different impact depending on the data rate.

Fiber tapers have attracted much attention and have been successfully employed in various applications, ranging from resonators, filters, interferometers to sensors. This thesis studies the properties of fiber tapers for the purpose of making tapered-based devices and sensors in aerospace related application where small size and light weight are critical. This thesis includes theoretical derivation and experimental verifications of distributed mode coupling in tapered single-mode fibers (SMFs) with high-resolution optical frequency-domain reflectometry (OFDR) technique. The studies are realized with OFDR through phase detection of a Mach-Zehnder interferometer (MZI), which measures local refractive index change relative to the reference arm. The wavelength shifts converted by the phase change give the group index differences between the fundamental mode and higher-order modes of fiber tapers. The energy re-distribution is observed in Rayleigh backscatter amplitude as a function of fiber length with a ~13µm resolution over the entire fiber taper, and group index difference between core and cladding modes is measured with a spatial resolution of ~2cm by using autocorrelation data processing. The thermal and mechanical properties of fiber tapers have also been characterized with OFDR. The cross-correlation wavelength shift is related to the refractive index change of the modes. It is shown that residual stress induced by the tapering process results in the inhomogeneous thermal property, which can be significantly reduced by an annealing treatment. A fiber taper with a waist diameter of ~6µm has a force sensitivity of ~620.83nm/N, ~500 times higher than that of SMF. Furthermore, polarization-preserving character of tapered polarization-maintaining fibers (PMFs) is evaluated by OFDR-based distributed birefringence along tapered PMFs. Three tapered-based micro-fiber devices have been used as effective mode selecting components to build narrow-linewidth tunable Erbium-doped fiber ring lasers. The fabrication is easy and at a low cost. 1) a tapered fiber tip forms multimode interference mechanism; 2) a two-taper MZI has been demonstrated by splitting/combining the fundamental mode and higher-order modes through fiber tapers and is tuned by bending one taper waist; 3) a novel tunable fiber Fabry-Perot filter, consisting of a hollow-core photonic bandgap fiber and a micro-fiber, is employed in the reflection mode.

Mobility is something able-bodied people take for granted. Approximately 132,500 people in the United Kingdom have disabilities which permanently confine them to a wheelchair; 40,000 of these require a powered wheelchair. The opportunity to lead a normal life and be accepted as an equal by the able-bodied population is limited by their reduced mobility. As much freedom of movement as possible is therefore crucial for these people. Powered wheelchair users' mobility depends upon the manoeuvrability of the chair. For optimum manoeuvrability a chair must be capable of moving in any direction. Currently no omni-directional powered wheelchairs are commercially available. This thesis describes the design and deVelopment of a powered base unit for a wheelchair, controlled to instantaneously move in any direction. The novelty is principally represented by the innovative design and configuration of four omni-directional roller wheels* (LUMAN wheels) which, when individually controlled, produce the omni-directional movement of the base unit. Further novelty within the design is a set of bi-directional angled roller couplings that simultaneously disengage the wheels from the motors, via a cable linkage mechanism, and simple control system. Mathematical data models illustrate the theoretical performance of the wheel configuration, and a prototype base unit is tested to prove these hypotheses.

Accurate coupling between the resolved scale dynamics and sub-grid scale physics is essential for accurate modelling of the atmosphere. Previous emphasis has been towards the temporal aspects of this so called physics-dynamics coupling problem, with little attention towards the spatial aspects. When designing a model for numerical weather prediction there is a choice for how to vertically arrange the required variables, namely the Lorenz and Charney-Phillips grids, and there is ongoing debate as to which is the optimal. The Charney-Phillips grid is considered good for capturing the large scale dynamics and wave propagation whereas the Lorenz grid is more suitable for conservation. However the Lorenz grid supports a computational mode. In the first half of this thesis it is argued that the Lorenz grid is preferred for modelling the stably stratified boundary layer. This presents the question: which grid will produce most accurate results when coupling the large scale dynamics to the stably stratified planetary boundary layer? The second half of this thesis addresses this question. The normal mode analysis approach, as used in previous work of a similar nature, is employed. This is an attractive methodology since it allows one to pin down exactly why a particular configuration performs well. In order to apply this method a one dimensional column model is set up, where horizontally wavelike solutions with a given wavenumber are assumed. Applying this method encounters issues when the problem is non normal, as it will be when including boundary layer terms. It is shown that when addressing the coupled problem the lack of orthogonality between eigenvectors can cause mode analysis to break down. Dynamical modes could still be interpreted and compared using the eigenvectors but boundary layer modes could not. It is argued that one can recover some of the usefulness of the methodology by examining singular vectors and singular values; these retain the appropriate physical interpretation and allow for valid comparison due to orthogonality between singular vectors. Despite the problems in using the desirable methodology some interesting results have been gained. It is shown that the Lorenz grid is favoured when the boundary layer is considered on its own; it captures the structures of the steady states and transient singular vectors more accurately than the Charney-Phillips grid. For the coupled boundary layer and dynamics the Charney-Phillips grid is found to be most accurate in terms of capturing the steady state. Dispersion properties of dynamical modes in the coupled problem depend on the choice of horizontal wavenumber. For smaller horizontal wavenumber there is little to distinguish between Lorenz and Charney-Phillips grids, both the frequency and structure of dynamical modes is captured accurately. Dynamical mode structures are found to be harder to interpret when using larger horizontal wavenumbers; for those that are examined the Charney-Phillips grid produces the most sensible and accurate results. It is found that boundary layer modes in the coupled problem cannot be concisely compared between the Lorenz and Charney-Phillips grids due to the issues that arise with the methodology. The Lorenz grid computational mode is found to be suppressed by the boundary layer, but only in the boundary layer region.