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We present optimal solutions for a point-mass electrodynamic tether (EDT) performing phasing and orbit-raising maneuvers. An EDT is a conductive tether on the order of 20 km in length and uses a Lorentz force to provide propellantless thrust. We develop the optimal equations of motion using Pontryagin's Minimum Principle. We find numerical solutions using a global, stochastic optimization method called Adaptive Simulated Annealing. The method uses Markov chains and the system's cost function to narrow down the search space. Newton's Method brings the error in the residual to below a specific tolerance. We compare the EDT solutions to similar constant-thrust solutions and investigate the patterns in the solution space. The EDT phasing maneuver has invariance properties similar to constant-thrust phasing maneuvers. Analyzing the solution space reveals that the EDT is faster at performing phasing maneuvers but slower at performing orbit-raising maneuvers than constant-thrust spacecraft. Also several bifurcation lines occur in the solution spaces for all maneuvers studied. / Master of Science

Being able to identify fuel efficient transfers between orbits is critical to planning and executing missions involving spacecraft. With a renewed focus on missions in cislunar space, identifying efficient transfers in the dynamical environment characterized by the Circular Restricted Three-Body Problem (CR3BP) will be especially important, both now and in the immediate future. The focus of this thesis is to develop a methodology that can be used to identify a valid low-cost transfer between a variety of orbits in the CR3BP. The approach consists of two distinct parts. First, tools related to dynamical systems theory and manifolds are used to create an initial set of possible transfers. An optimization scheme is then applied to the initial transfers to obtain an optimized set of transfers. Code was developed in MATLAB to implement and test this approach. The methodology and its implementation were evaluated by using the code to identify a low-cost transfer in three different transfer cases. For each transfer case, the best transfers from each set were compared, and important characteristics of the transfers in the first and final sets were examined. The results from those transfer cases were analyzed to determine the overall efficacy of the approach and effectiveness of the implementation code. In all three cases, in terms of cost and continuity characteristics, the best optimized transfers were noticeably different compared to the best manifold transfers. In terms of the transfer path identified, the best optimized and best manifold transfers were noticeably different for two of the three cases. Suggestions for improvements and other possible applications for the developed methodology were then identified and presented. / Master of Science / Being able to identify fuel efficient transfers between orbits is critical to planning and executing missions involving spacecraft. With a renewed focus on lunar missions, identifying efficient transfers between orbits in the space around the Moon will be especially important, both now and in the immediate future. The focus of this thesis is to develop a methodology that can be used to identify a valid low-cost transfer between a variety of orbits in the space around the Moon. The approach was evaluated by using the code to identify a low-cost transfer in three different transfer cases. The results from those transfer cases were analyzed to determine the overall efficacy of the approach and effectiveness of the implementation code. Suggestions for improvements and other possible applications for the developed methodology were then identified and presented.

Thesis (MBA)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The greatest potential worry that an on-line shopper has is what happens to his/her credit card details from the moment "submit" is pressed on the computer. Is it possible for someone on the Internet to intercept the message and use credit card details maliciously? Also, there is a lot of talk about personal details being encrypted, but how sure is one that this was indeed the case once "submit" has been pressed? Is there a way in which one can be sure that a transaction will occur only once? Many of the security issues are new and many experts are only learning how to deal with these now. This thesis offers suggestions and strategies a user can follow to minimize misuse and abuse of payment details. Electronic payment is the backbone of e-commerce, and the biggest threat towards widespread acceptance and usage of e-commerce is security. Many innovative solutions have been developed by vendors to address security issues. For example, the Secure Electronic Transfer (SET) protocol was developed to ensure that credit card transactions could be conducted safely and securely on the Internet. Secure Socket Layer (SSL) ensures that all communications and transactions are conducted in a tightly secure environment. This is critical for online or mobile banking and other financial activities. Others developments include payment systems that ensure that credit card details are never exposed to a merchant (e.g. SET), while some ensure that credit card numbers never enter the Internet. The five corner stones of security are confidentiality, privacy, authentication, integrity and non-repudiation. Authentication, non-repudiation and integrity can be resolved with digital certificates, digital timestamps and digital signatures. Message confidentiality, on the other hand, is ensured through the use of strong encryption. Encryption systems mutilate data or a message to such an extent that it is totally useless to someone who does not have the appropriate algorithm and key to decode it. The most widely used encryption schemes are the secret key and public key encryption systems. The public key cryptosystem generates two keys, called a public and private key. The public key can be made generally known, but the private key must be kept secret. A unique property of the scheme is that once data is encrypted with one key, only the corresponding other key of the pair can decrypt it. This makes it possible to address issues of authentication, integrity and non-repudiation. Traditional payment instruments such as cash, cheques, debit and credit card transactions are being replaced by their electronic equivalents. The driving forces behind these are transactional security, efficiency and speed. Novel payment solutions and strategies have been devised to meet the challenges of this new economy. For example, smart cards can act as an electronic purse that can hold electronic money. Other information, such as personal details, medical records, driver's licence, etc. can also be stored on the card. Whilst many security experts are in agreement that security is not a barrier anymore for wider usage of the Internet for financial transactions, many consumers are still apprehensive about how secure and safe it really is. This work aims to diminish those fears and show that the Internet is safe for business. / AFRIKAANSE OPSOMMING: Een van die grootste bekommernisse wat 'n kliënt met aankope op die Internet kan ondervind, is die onsekerheid wat presies gebeur nadat betalings aangegaan is en "Submit" is gedruk. Is dit moontlik dat iemand die boodskap kan onderskep en betaling besonderhede vir eie gebruik kan herwin? Daar is ook baie publisiteit oor kodifisering, maar hoe kan die klient verseker wees dat betalings besonderhede wel gekodifiseer is wanneer "Submit" gedruk was? Is daar 'n manier waarmee 'n mens verseker kan wees dat betaling slegs eenkeer gaan geskied? Baie van die sekuriteits lokvalle is nuut en sekuritiets kenners is tans besig om te leer hoe om die probleme te hanteer. Die werkstuk offer wenke en strategieë vir die verbruiker om die misbruik van betaling besondehede op die Internet te minimiseer. Elektronies betalings meganisme is die ruggraat van elektroniese besigheid, en die grootste struikelblok tot die grootskaalse gebruik daarvan is sekuriteit. Daar is baie innoverende oplossings om die probleme hok te slaan. By voorbeeld, die Secure Electronic Transfer (SET) protokol was ontwikkel om te verseker dat betalings met kredietkaart met hoë sekuriteit en veiligheid aangegaan kan word. Secure Socket Layers (SSL), verseker dat alle kommunikasies en transaksies in 'n sekuur en veilige omgewing plaasvind. Dit is veral krities wanneer die verbruiker gebruik maak van die Internet of vanaf selfone om transaksies aan te gaan met 'n bank. Ander ontwikkelinge sluit in betalings metodes wat verseker dat die handelaar nooit die kredietkaart besonderhede sien nie (bv. SET). Ander verseker weer dat die betalings besonderhede nooit oor die Internet hoef gestuur te word nie. Die vyf hoekstene van sekuriteit is konfidensialiteit, privaatheid, outentisiteit, integriteit en non-repudiasie. Outentisiteit, integriteit en non-repudiasie word opgelos deur die gebruik maak van digitale sertifikate, digitale tydstempels en digitale handtekeninge. Konfidensialiteit kan verseker word deur die boodskap te kodifiseer. Kodifikasie behels die verandering van data of boodskappe op so 'n wyse dat dit van geen betekenis is vir 'n persoon wat nie die korrekte algoritme en sleutel het om dit te dekodifiseer nie. Die geheime en publieke kodifiserings stelsels word die meeste gebruik om data te kodifiseer. Die publieke kodifiserings stelsel genereer twee sleutels, naamlik 'n privaat en publieke sleutel. Die publieke sleutel kan alom bekend gemaak word, maar die private sleutel moet slegs bekend wees aan sy gebruiker. 'n Unieke eienskap van die stelsel is dat indien 'n boodskap gekodifiseer is met een sleutel, slegs die ander sleutel van die paar dit sal kan dekodifiseer. Dit maak dit moontlik om outentisiteit, integriteit en non-repudiasie toe te pas. Die tradisionele metodes van betaling soos kontant, tjek en debiet of kredietkaart, gaan mettertyd vervang word deur hul elektroniese eweknie. Die dryfkrag agter die verskynsel is die hoë sekuriteit, doeltreffendheid en spoed waarmee transaksies op die manier gehanteer kan word. Vindingryke betaling metodes is ontdek om die besondere uitdagings van die nuwe ekonomie aan te speek. Byvoorbeeld, knap kaarte kan gebruik word as 'n elektroniese beursie wat elektroniese geld bêre. Ander persoonlike inligting, mediese records, bestuurlisensies, ens. kan ook op die kaart geberg word. Terwyl baie sekuriteits kenners glo dat sekuriteit nie meer 'n stuikelblok is om die Internet vir besigheids transaksies te gebruik nie, bly baie van die verbruikers skepties. Die werkstuk se doel is om daardie onsekerhede uit die weg te ruim, deur te verduidelik hoe sekuriteit toe gepas word, en om te bewys dat die Internet interdaad veilig is as a medium vir besigheids transaksies.

Thesis (D Phil (History))--University of Pretoria, 2004. / Includes bibliographical references.

Thesis (M. A.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references (leaves 123-133). Also available via the World Wide Web.

abstract: Resource transfers can confer many adaptive benefits such as specialization, helping genetically related individuals, future compensation, and risk-pooling. Need-based transfers are a risk-pooling mechanism in which partners mitigate unpredictable losses by transferring resources based on need. Need-based transfers are likely to be most useful for resources that are necessary and unpredictable because being unable to reliably obtain essential resources would be devastating. However, need-based transfers make people vulnerable to two types of exploitation: a person can be greedy by asking when not in need and a person with a surplus of resources can be stingy by not giving to someone in need. Previous research suggests that people might have cognitive mechanisms for detecting greediness and stinginess, which would serve to protect against exploitation by cheaters. This study investigated whether resources that are necessary and unpredictable are most likely to trigger greediness and stinginess detection mechanisms. Participants saw four types of rules. One rule could be violated through greedy behavior, another through stingy behavior, another by not paying a debt, and another was a descriptive rule that could be violated by not finding one type of resource near another type of resource. Then, participants saw information about events relating to one of the rules and indicated whether the rule in question could have been violated. Consistent with past research, participants were better at detecting greediness, stinginess, and debts not paid than at detecting violations of a descriptive rule. However, contrary to my predictions, the necessity and unpredictability of resources did not impact people’s ability to detect greediness and stinginess. The lack of support for my hypothesis might be because the benefits of detecting greediness and stinginess might outweigh the costs even for situations in which need-based transfer rules are unlikely to apply, because people might be able to consciously activate their greediness and stinginess mechanisms even for resources that would not naturally trigger them, or because of methodological limitations. / Dissertation/Thesis / Masters Thesis Psychology 2019

The global trade in weaponry has created an environment in which states are now utilizing arms transfer agreements to bolster their own domestic defense industry aspirations. Previous research concerning arms transfers has suggested that a state may alter its behavior depending on its level of dependency on foreign sourced weapons. However, previous scholarship primarily examined the effect from importing arms and not the effect that military industry will have upon state behavior. Since the number of states possessing domestic defense industries has risen by 250% since 1950, it is paramount that we understand the effect of a domestic military industry on state behavior. To explore this problem, this dissertation utilizes militarized interstate dispute and arms procurement data. 3 primary independence variables are created, all of which measure military independence in different ways. These variables include, military industry presence, arms supplier diversification, and foreign dependence on military goods. The dissertation hypothesizes that the level of military independence will have an effect on the probability that a state will be involved, initiate as well as decrease dispute duration.

This dissertation is composed of three essays, each examining a unique question relating to the role of intergovernmental transfers in fiscal federalism. Using a panel of the 48 contiguous U.S. states along with recent advances in nonstationary panel and spatial econometric methods this dissertation offers a number of important insights into the workings of intergovernmental transfers and therefore a clearer understanding of the interactions among the different layers of government. The third chapter examines the relationship between intergovernmental revenues from the federal government and intergovernmental expenditures to local governments. As observed by Wildasin (2010), there remains remarkable stability in the ratio of state-tolocal transfers to federal-to-state transfers despite the disparate programs being financed by each. Therefore, the purpose of this essay is to examine the extent to which states serve as a conduit for funds from the federal government to local governments. In particular, the research question asks to what degree do federal transfers stimulate transfers to local governments. The fourth chapter explores the direction of causality between tax revenues and expenditures in answering the four hypotheses set forth in the literature: tax-spend, spend-tax, fiscal synchronization, and institutional separation. Furthermore, along with exploring the role served by intergovernmental transfers within the revenue-expenditure nexus, this essay also examines differences relating to the revenue-expenditure nexus between states with relatively higher debt levels and states with low debt levels, in order to better understand the fiscal causal links favorable for debt accumulation. The purpose of the fifth chapter is to ascertain the effect interstate fiscal interactions on the stimulative effect of grants on state level expenditures. The vast literature on fiscal competition suggests that states do not make decisions in isolation, therefore, spatial econometrics are used to capture spillovers and mimicking behavior across states. Following Boarnet and Glazer (2002), the effect of informational externalities arising from grants awarded to neighboring states are examined as well as the effect of spending spillovers from neighboring states. The results show that the flypaper anomaly (i.e. the stimulative effect of grants greater than a pure income effect) can be explained by interstate fiscal interactions.

The recent advancements in healthcare is extending the lives of older people. However, such advancements come at a cost: higher medical expenses with less financial resources and limited, if not truncated, monetary assistance. The dilemma is further compounded by the unreliable quality of life produced by extending life of the chronically ill. Using the RAND data, I examine three financial transaction outcomes at different points-in-time in context of the onset of a health issue: one, the probability of a transaction occurring, two, how much is given, and three, the frequency of transactions. I also examine how a health issue impacts financial transaction choices within a given year, a year after the health issue occurs, and the longer term impacts on subsequent intergenerational financial transactions. I find no change in financial behavior of an adult child immediately after the health issue occurs and minimal over the longer period of time. However, this study does show a slight and statistically significant shift in financial transactions within the first year after a health issue occurs. Additionally, the results suggest that those who can live in assisted care and near respondent children have higher transactions between family members.