Eccentric lunar frozen orbits are analyzed in this study in relation to lunar navigation and communications missions, particularly the proposed Magnolia-1 mission. An overview of the Earth/Moon system, frozen orbits, and the Magnolia-1 mission is provided. A review of existing literature is presented, and potential limitations are discussed. Both preliminary and numerical perturbation analyses are presented, and a general set of perturbations for further analysis of high-altitude lunar orbits is identified. Analysis of potential orbits for the Magnolia-1 mission is performed through calculation of a maximum deviation metric and through visualization as a function of initial orbital elements. Trends are identified within a closed search space by varying elements individually and in combination. Potential orbit designs for the Magnolia-1 mission are selected and compared to established alternatives. A method of orbit refinement is used to improve behavior, and coverage and eclipse analyses are performed to establish suitability. Conclusions are made involving general trends related to eccentric lunar frozen orbits and the specific designs proposed for the Magnolia-1 mission, and a method for the design of similar orbits is suggested. Ideas for further study are also presented.

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<p>This thesis is centered around three infinite dimensional diffusion processes:</p> <p>(i). the infinitely-many-neutral-alleles diffusion model [Ethier and Kurtz, 1981],</p> <p>(ii). the two-parameter infinite dimensional diffusion model [Petrov, 2009] and [Feng and Sun, 2010],</p> <p>(iii). the infinitely-many-alleles diffusion with symmetric dominance [Ethier and Kurtz, 1998].</p> <p>The partition structures, the ergodic inequalities and the asymptotic theory of these three models are discussed. In particular, the asymptotic theory turns out to be the major contribution of this thesis.</p> <p>In Chapter 2, a slightly altered version of Kingman's one-to-one correspondence theorem on partition structures is provided, which in turn becomes a handy tool for obtaining the asymptotic result on the partition structures associated with models (i) and (ii).</p> <p>In Chapter 3, the three diffusion models are briefly introduced. New representations of the transition densities of models (i) and (ii) are obtained simply by rearranging the previous representations obtained in [Ethier, 1992] and [Feng et al., 2011] respectively. These two new representations have their own advantages, by making use of which the corresponding ergodic inequalities easily follow. Furthermore, thanks to the functional inequalities in [Feng et al., 2011], the ergodic inequality for model (iii) becomes available as well.</p> <p>In Chapter 4, the asymptotic properties of models (i) and (ii) are thoroughly studied. Various asymptotic results are obtained, such as the weak limits of models (i) and (ii) at different time scales when the mutation rate approaches infinity, and the large deviation principle for models (i) and (ii) at a fixed time, and that of the transient partition structures of models (i) and (ii). Of all these results, the weak limit and the large deviation principle of the transient partition structures are of particular interest.</p> <p>In Chapter 5, the asymptotic results on the stationary distribution and the transient distribution of model (iii) are both obtained. The weak limit of the infinitely-many- alleles diffusion with symmetric overdominance at fixed time t serves as an alternative answer to Gillespie's conjecture [Gillespie, 1999]. The weak limit of the stationary distribution of the infinitely-many-alleles diffusion with symmetric overdominance provides a complete solution to the remaining problem in [Feng, 2009].</p> / Doctor of Philosophy (PhD)

No / This paper investigates the effect of channel bandwidth on the accuracy of AOA estimation algorithms based on the detection of the direct path. The accurate detection of the Line of Sight (LOS) signal in a multipath environment is crucial for reliable direction finding. In this work, the estimation algorithms are applied to the LOS component in the time domain channel impulse response which is acquired by applying the inverse Fourier transform to the simulated channel transfer function in the desired bandwidth. Different channel bandwidths as well as two AOA estimation methods have been considered in the modelling to investigate the performance of the standard deviation of angle estimation error. It has been shown that increasing the bandwidth in all simulated channel scenarios improves the estimation accuracy. / Seven Technologies Group, KTP project grant No. 008734.

The background for the study is to investigate the reporting and handling of break deviations from an ambulance department under the Clinic for Prehospital Services in Vestre Viken HF. Deviation management is an important function in organisations that contributes to improving the working environment in organisations, and this applies to the organisation studied. It is therefore important that deviation management takes place in an effective way so that the organisation has the opportunity to look for and implement improvements.  The study has focused on helping the organisation improve their current practices for reporting and handling break deviations reported from the ambulance. Starting with perceptions of this phenomenon and then analysing it to find opportunities for improvement.  Through a qualitative analysis of collected empirical data and theory on quality, deviation management, continuous improvement and more, seven areas for improvement in reporting and handling of break deviations have been identified these are: accessibility, reporting format, feedback, training, data foundation, procedure design, motivation. All improvement areas are based on identified challenges in the reporting and handling of break deviations, of which the study provides suggestions for how the organisation can meet these seven areas. By focusing on the identified areas for improvement, the organisation has the opportunity to improve its practices in the reporting and handling of break deviations and, in the long run, this may help to improve break deviation. / Bakgrunden till studien är att undersöka rapportering och hantering av pausavvikelser från en ambulansavdelning under Kliniken för Prehospitala Tjänster i Vestre Viken HF. Avvikelsehantering är en viktig funktion i organisationer som bidrar till att förbättra arbetsmiljön i organisationer, och detta gäller även för den studerade organisationen. Det är därför viktigt att avvikelsehanteringen sker på ett effektivt sätt så att organisationen har möjlighet att söka efter och genomföra förbättringar. Studien har fokuserat på att hjälpa organisationen att förbättra sina nuvarande rutiner för rapportering och hantering av pausavvikelser som rapporteras från ambulansen. Genom en kvalitativ analys av insamlad empiri och teori om kvalitet, avvikelsehantering, ständiga förbättringar med mera har sju förbättringsområden för rapportering och hantering av pausavvikelser identifierats, nämligen: tillgänglighet, rapporteringsformat, återkoppling, utbildning, datagrund, utformning av rutiner, motivation. Samtliga förbättringsområden baseras på identifierade utmaningar i rapporteringen och hanteringen av rastavvikelser, varav studien ger förslag på hur organisationen kan möta dessa sju områden. Genom att fokusera på de identifierade förbättringsområdena har organisationen möjlighet att förbättra sina rutiner för rapportering och hantering av rastavvikelser, vilket i förlängningen kan bidra till att förbättra rastavvikelserna.

The ionosphere is the conducting part of the upper atmosphere that plays a significant role in trans-ionospheric high frequency (HF, 3-30 MHz) radiowave propagation. Solar activities, such as solar flares, radiation storms, coronal mass ejections (CMEs), alter the state of the ionosphere, a phenomenon known as Sudden Ionospheric Disturbance (SID), that can severely disrupt HF radio communication links by enhancing radiowave absorption and altering signal frequency and phase. The Super Dual Auroral Radar Network (SuperDARN) is an international network of low-power HF coherent scatter radars distributed across the globe to probe the ionosphere and its relation to solar activities. In this study, we used SuperDARN HF radar measurements with coordinated spacecraft and riometer observations to investigate statistical characteristics and the driving mechanisms of various manifestations of solar flare-driven SIDs in HF observations. We begin in Chapter 2 with a statistical characterization of various effects of solar flares on SuperDARN observations. Simultaneous observations from GOES spacecraft and SuperDARN radars confirmed flare-driven HF absorption depends on solar zenith angle, operating frequency, and intensity of the solar flare. The study found flare-driven SID also affects the SuperDARN backscatter signal frequency, which produces a sudden rise in Doppler velocity observation, referred to as the ``Doppler flash'', which occurs before the HF absorption effect. In Chapter 3, we further investigate the HF absorption effect during successive solar flares and those co-occurring with other geomagnetic disturbances during the 2017 solar storm. We found successive solar flares can extend the ionospheric relaxation time and the variation of HF absorption with latitude is different depending on the type of disturbance. In Chapter 4, we looked into an inertial property of the ionosphere, sluggishness, its variations with solar flare intensity, and made some inferences about D-region ion-chemistry using a simulation study. Specifically, we found solar flares alter the D-region chemistry by enhancing the electron detachment rate due to a sudden rise in molecular vibrational and rotational energy under the influence of enhanced solar radiation. In Chapter 5, we describe a model framework that reproduces HF absorption observed by riometers. This chapter compares different model formulations for estimating HF absorption and discusses different driving influences of HF absorption. In Chapter 6, we have investigated different driving mechanisms of the Doppler flash observed by SuperDARN radars. We note two particular findings: (i) the Doppler flash is predominantly driven by a change in the F-region refractive index and (ii) a combination of solar flare-driven enhancement in photoionization, and changes in the zonal electric field and(or) ionospheric conductivity reduces upward ion-drift, which produces a lowering effect in the F-region HF radiowave reflection height. Collectively, these research findings provide a statistical characterization of various solar flare effects on the ionosphere seen in the HF observations, and insights into their driving mechanisms and impacts on ionospheric dynamics. / Doctor of Philosophy / The Earth's ionosphere, extending from about 60 km to 1000 km in altitude, is an electrically charged region of the upper atmosphere that exists primarily due to ionization by solar X-ray and extreme ultraviolet radiation. The ionosphere is an effective barrier to energetic electromagnetic (EM) radiation and charged particles originating from the Sun or any other extraterrestrial sources and protect us against harmful space radiation. High frequency (HF, 3-30 MHz) radio communication, broadly used for real-time medium and long-range communication, is strongly dependent on the state of the ionosphere, which is susceptible to solar activities, such as solar flares, solar energetic particles (SEPs), and coronal mass ejections (CMEs). Specifically, we are interested in the impacts of solar flares. In this study, we use Super Dual Auroral Radar Network (SuperDARN) HF radars, ground-based riometers, and coordinated spacecraft observations to investigate the driving mechanisms of various space weather impacts on the ionosphere and radiowave propagation following solar flares. We begin in Chapter 2 with a characterization of various kinds of ionospheric disturbances manifested in SuperDARN backscattered signal following solar flares. Specifically, we characterized HF absorption effects and frequency anomalies experienced by traveling radiowaves, also known as Shortwave Fadeout (SWF) and Sudden Frequency Deviations (SFDs), respectively. In SuperDARN HF radar observations, SFDs are recorded as a sudden enhancement in Doppler velocity, which is referred to as the ``Doppler flash''. In Chapter 3, we investigate a special event study that elucidates the nonlinear physics behind HF absorption caused by multiple simultaneous solar flares and flares co-occurring with SEPs and CMEs. In Chapter 4, we explore an inertial property of the ionosphere, known as sluggishness, and its dependence on solar flares can provide important information about the chemical proprieties of the ionosphere. We found that the enhanced solar radiation during a solar flare increases the molecular vibrational and rotational energy that in turn enhances the electron detachment rate and reduces ionospheric sluggishness. In Chapter 5, we describe a framework to estimate HF absorption observed by riometers following solar flares. We analyze the influence of different physical parameters, such as collision frequency and electron temperature, on HF absorption. In Chapter 6, we delved into the physical processes that drive the Doppler flash in SuperDARN observations following solar flares. We find, (i) the Doppler flash is predominately driven by change in the F-region refractive index and (ii) a combination of solar flare-driven enhancement in photoionization, and change in zonal electric field and(or) ionospheric conductivity reduces upward ion-drift, which produces a lowering effect in the F-region HF radiowave reflection height. Taken together, these research findings provide new insights into solar flare impacts on the ionosphere and could be used to improve forecasting of ionospheric space weather disturbances following solar flares.

Implementing Lean in the United States transportation equipment manufacturing industry holds the promise for improvements in, among other things, productivity, quality, and innovation, resulting in more competitive success and profits. Although Lean has been applied throughout the industry with noted success, there have been some difficulties in demonstrating the financial benefits derived from Lean initiatives. Most of the evidence supporting a positive relationship between Lean implementation and improved financial performance is anecdotal. As companies have become more proficient in carrying out Lean initiatives in manufacturing, they have extended Lean ideas to other parts of their organization and throughout the entire supply chain. Nowadays, it is widely recognized that a holistic, enterprise-wide view is critical to obtain the potential benefits of a Lean transformation. However, Lean transformations are often undertaken without consideration of supporting functions such as accounting and finance. Lean transformation in accounting and finance should be run in the same way as it is in the manufacturing environment by decreasing reporting cycle time, improving transaction processing accuracy, eliminating unnecessary transaction processing, changing product costing procedures, and financial reporting among many other things, but there is limited empirical evidence of that happening. To address these shortcomings, this research focuses on three areas. First, this study aims to evaluate transportation equipment manufacturing facilities in respect to their operational and financial performance. Second, this study aims to investigate the extent of Lean implementation of a given operation in respect to leadership, manufacturing, accounting and finance, and supplier and customer relationship and correlate these results to their performance. Finally, this study aims to further examine the contextual characteristics of companies that successfully aligned their systems with Lean. A mixed-mode survey, addressed to a subset of the United States transportation equipment manufacturing industry, asked questions pertinent to companies' Lean transformation efforts, performance, and general characteristics. During the four months long survey period, a total of 69 valid responses were received, for a response rate of 3.78 percent. From the 69 valid responses, 8 responses were eliminated due to containing more than 20 percent missing values. Multiple imputation procedure was applied to handle remaining missing values in the dataset. Before testing study hypotheses, scale reliability and construct validity tests were run to decide whether a particular survey item should be retained in further analysis. Study hypotheses were then tested using profile deviation analysis, multiple regression analysis, and hierarchical regression analysis. When the level of Lean implementation and performance relationship was investigated using a multiple regression analysis, results did not show any evidence that the higher level of Lean implementation along four business dimensions (leadership, manufacturing, accounting and finance, and supplier and customer relationship) of transportation equipment manufacturing facilities positively influences their operational and financial performance. However, it was revealed that the higher level of Lean implementation in transportation equipment manufacturing facilities' manufacturing dimension resulted in better quality performance as measured by first-time through, inbound quality, and outbound quality. When the same relationship was investigated using a profile deviation analysis, results were identical. When the level of Lean implementation in accounting and finance and its relationship with performance was investigated using a single regression analysis, results showed that the higher level of Lean implementation in transportation equipment manufacturing facilities' accounting and finance dimension has a positive effect on accounting performance and on operational performance (e.g., on time-based performance and delivery-based performance), but no effect on financial performance. When the same relationship was investigated using a profile deviation analysis, results were different by showing no relationship between the level of Lean implementation in transportation equipment manufacturing facilities' accounting and finance dimension and accounting, operational, and financial performance. Lastly, the effect of contextual variables (e.g., industry segment, location, annual sales volume, and unionization) on performance, the level of Lean implementation, and the performance -- Lean implementation relationship was investigated using hierarchical regression. Results showed that transportation equipment manufacturing facilities' performance is influenced by annual sales volume. Their level of Lean implementation in the accounting and finance dimension is influenced by location, while their performance -- Lean implementation in the accounting and finance dimension relationship is influenced by industry segment. / Ph. D.

Yes / This paper examines how deviation from firms’ target leverage influences their decisions on undertaking foreign acquisitions. Using a sample of 5,746 completed bids by UK acquirers from 1987 to 2012, we observe that over-deviated firms are more likely to acquire foreign targets. Consistent with co-insurance theory, we find that over-deviated firms engage in foreign acquisition deals to relieve their financial constraints and to mitigate their financial distress risk. We also note that foreign acquisitions enhance over-deviated firms’ value and performance, measured by Tobin’s q and return on assets (ROA) respectively. These findings support the view that over-deviated firms pursue the most value-enhancing acquisitions. Overall, this paper suggests that co-insurance effects, value creation and performance improvements are the main incentives for over-deviated firms’ involvement in foreign acquisitions.

No / In normal vision, detecting a kink (a change in orientation) in a line is scale invariant: it depends solely on the length/width ratio of the line (D. Whitaker, D. M. Levi, & G. J. Kennedy, 2008). Here we measure detection of a change in the orientation of lines of different length and blur and show that strabismic amblyopia is qualitatively different from normal foveal vision, in that: 1) stimulus blur has little effect on performance in the amblyopic eye, and 2) integration of orientation information follows a different rule. In normal foveal vision, performance improves in proportion to the square root of the ratio of line length to blur (L: B). In strabismic amblyopia improvement is proportional to line length. Our results are consistent with a substantial degree of internal neural blur in first-order cortical filters. This internal blur results in a loss of scale invariance in the amblyopic visual system. Peripheral vision also shows much less effect of stimulus blur and a failure of scale invariance, similar to the central vision of strabismic amblyopes. Our results suggest that both peripheral vision and strabismic amblyopia share a common bottleneck in having a truncated range of spatial mechanisms-a range that becomes more restricted with increasing eccentricity and depth of amblyopia. / Leverhulme Trust, Wellcome Trust, NIH