This thesis identifies the potential net economic gains from substituting less costly transit for relatively costly parts inventory through pipeline reduction. The analysis considers long run steady state economic implications of adjusting the current mix of inventory investments and transportation expenses. The scope of the analysis is focused on a case study of Department of Defense (DoD) parts inventories within the US. The inventory scope is limited to high cost low priority, non-mission critical, replenishment parts (engines, electronics, assemblies and components, etc.). The study uses baseline data collected over 9 months from over 200 inventory sites on thousands of parts. Pipeline reductions are achieved by replacing the current 6 day transit time with a conservative 3 day commercial carrier (e.g., UPS, DHL, Emory Air, etc.). Warehouses in the case study automatically lower inventory levels in response to lowered transit times to prevent inventory buildup. These lower inventory levels will generate reductions in inventory investment and associated holding costs. The reductions in these inventory costs are compared to the increases in transportation expenses to generate benefit to cost ratios. / Master of Arts

Network coding is a promising technology that many researchers have advocated due to its potentially significant benefits to improve the efficiency of data transmission. In this thesis, we use simulations to evaluate the performance of different network topologies using network coding. By comparing the results with networks without network coding, we confirm that network coding can improve the network throughput. It also has a potential to decrease the end to end delay and improve the reliability. However, there are tradeoff (between delay and reliability) when network coding is used, and some limitations which we summarize. Finally, we have also implemented network coding to a three-dimensional underwater network by using parameters that truly reflect the underwater channel. Our performance evaluations show a better throughput and end-to-end delay but not the PDR (Packet Delivery Rate) in the underwater topology we used.

This dissertation provides a comprehensive analysis of the coding-spreading tradeoff problem in finite-sized synchronous DS-CDMA systems. In contrast to the large system which has a large number of users, the finite-sized system refers to a system with a small number of users. Much work has been performed in the past on the analysis of the spectral efficiency of synchronous DS-CDMA systems and the associated coding-spreading tradeoff problem. However, most of the analysis is based on the large-system assumptions. In this dissertation, we focused on finite-sized systems with the help of numerical methods and Monte-Carlo simulations.Binary-input achievable information rates for finite-sized synchronous DS-CDMA systems with different detection/decoding schemes on AWGN channel are numerically calculated for various coding/spreading apportionments. We use these results to determine the existence and value of an optimal code rate for a number of different multiuser receivers, where optimality is in the sense of minimizing the SNR required for reliable multiuser communication. Our results are consistent with the well-known fact that all coding (no spreading) is optimal for the maximum a posteriori receiver.Simulations of the LDPC-coded synchronous DS-CDMA systems with iterative multiuser detection/decoding and MMSE multiuser detection/single-user decoding are also presented to show that the binary-input capacities can be closely approached with practical schemes. The coding-spreading tradeoff is examined using these LDPC code simulation results, where agreement with the information-theoretic results is demonstrated.We extend our work to the DS-CDMA systems on two idealized Rayleigh flat-fading channels: the chip-level flat-fading (CLFF) and the (code) symbol-level flat-fading (SLFF). These models represent ideal fast fading and slow fading channels, respectively. Both information-theoretic results and LDPC code simulation results are presented to show the effects of channel fading on system performance and the coding-spreading tradeoff. It is shown that fast fading can be beneficial to system performance under the condition of perfect channel state information at receiver, but slow fading is very harmful. Slow fading also increases the importance of coding greatly, compared to the AWGN and fast fading.Finally, we present some comparisons with large-system results on AWGN and CLFF channels, which show both consistencies and discrepancies.

While there is growing evidence that shade/flood tolerance tradeoffs may be important in distributions of bottomland hardwood trees and indications that they should apply to herbs, no studies have definitively explored this possibility. Four years of field data following historic flooding were supplemented with a greenhouse experiment designed to identify interactions congruent with tradeoffs. Fifteen bottomland species were grown in two levels of water availability and three levels of shade over 10 weeks. Results indicate responses of Fimbristylis vahlii and Ammannia robusta are consistent with tradeoffs. Modification of classical allometric responses to shade by substrate saturation indicates a potential mechanism for the tradeoff in A. robusta. Responses indicating potential for increased susceptibility to physical flooding disturbance are also discussed.

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Bakgrund och problemdiskussion: Företag motiverar vanligtvis centraliserad finansiering med att det leder till värdeökande effekter, något som forskningsvärlden endast teoretiskt berört vilket ger indikationer på att en centraliserad finansiering kan utgöra en värdeökande strategi. Det föreligger därmed ett intresse att undersöka detta empiriskt. Avsaknaden av ett mått för centraliseringsgraden av finansiering medför att framställande av detta mått dock måste genomföras före teorin om värdeökning kan testas empiriskt. Syfte: Studien syftar till att 1) ta fram ett mått för centraliseringsgraden av finansiering, 2) säkerställa validiteten i detta mått och 3) genom detta mått testa centraliseringsgradens effekt på företagsvärde. Metod: Första syftet uppfylls genom en explorativ studie där närliggande teorier använts tillsammans med observationer av verkligheten. Andra syftet uppfylls genom en mindre statistisk undersökning utifrån årsredovisningar samt en enkätundersökning riktad till experter inom området. Tredje syftet uppnås genom en kvantitativ studie där formulerade hypoteser testas i en statistisk undersökning på 152 svenska börsnoterade bolag.  Resultat och slutsatser: Studien säkerställer ett approximativt mått för centraliseringsgraden av finansiering. Måttets samband med företagsvärde kan dock inte säkerställas. Centraliseringsgraden har däremot ett samband med företagsvärde under vissa förhållanden vilket innebär att ett samband inte heller kan uteslutas. Vidare finner studien empiriskt stöd för Tradeoff Theory, däremot kan ingen förklarande modell för kapitalstrukturen säkerställas och därmed inte heller centraliseringsgradens betydelse för kapitalstrukturen. Slutligen har studien även påbörjat en förklarande modell till centraliseringsgraden av finansiering i och med att geografisk spridning visar sig ha positiv påverkan på centraliseringsgraden. / Background: Firms using centralized financing function usually motivates it by it’s value adding property, something today’s research only theoretically touched which indicates that centralized financing can be a value adding strategy. Therefore it exists an interest for an empirical examination. The lack of a measurement for the degree of centralized financing implies that this measurement have to carried out before the theoretical value adding strategy can be empirical tested. Purpose: The study’s purposes is 1) bring forward a measurement for the degree of centralized financing, 2) secure the measurement’s validity and 3) through this measurement test it’s value adding effect to firm value. Method: The first purpose is achieved through an explorative research design where theories close to the subject together with observations of reality were applied. The second purpose is achieved through a smaller statistical study based on financial reports in conjunction with a survey aimed towards experts within the knowledge area. The third purpose is achieved through testing hypotheses in a statistical study on 152 Swedish listed companies. Results and conclusions: The study validates an approximate measure of the degree of centralized financing. The measurement’s connection to firm value can not be established. Although, the degree of centralization has a connection to firm value given certain circumstances which implies that the connection cannot be ruled out either. Further, the study finds empirical support for Tradeoff Theory, however, there are no empirical support for the explanatory model for the capital structure and, by extension, neither for the degree of centralization’s significance on capital structure. Finally, the study has also begun an explanatory model for the degree of centralization of financing since geographical spread has a significant positive effect on the degree of centralization.

O trabalho apresenta inicialmente a importância da tomada de decisão em uma sociedade com recursos limitados e muitos interesses antagônicos. Essas decisões com base em objetivos conflitantes, independente do seu grau de importância, geram ganhos em alguns aspectos e perdas em outros, e a isto se denomina tradeoff. Em problemas complexos, uma decisão mal tomada, ou um estudo de tradeoff mal conduzido podem afetar significativamente aspectos muito relevantes, como o dimensionamento de redes de transporte, por exemplo. Assim, a proposta deste trabalho é oferecer um procedimento para auxilio à tomada de decisão em sistemas de transporte aquaviário, baseado em análises com múltiplos critérios. Além disso, o estudo visa utilizar a técnica de simulação de eventos discretos para fornecer subsídio a estes estudos de tradeoff. É realizada também uma aplicação do método descrito juntamente com um modelo de simulação para o dimensionamento de um sistema de transporte aquaviário específico, contando com análises de sensibilidade. A aplicação realizada foi conclusiva e comprovou a eficácia do método desenvolvido para o auxílio à decisão em problemas desse porte. / This work primarily highlights the importance of decision making in a society with limited resources and several antagonistics interests. Decisions based on conflicting goals, regardless of their importance level, might generate positive gains associated to a certain number of variables and losses associated to others. This process is known as tradeoff. In complex problems, such as transportation networks planning, taking a bad decision or carrying out a bad tradeoff study, may affect matters of primary interests of the problem players. The proposal of this work is providing a procedure in order to support decision making process in water transportation systems based on multi-criteria analysis. In addition, the study aims at using the technique of discrete event simulation to provide subsidies to these trade-off studies. The work also presents an application of the proposed methodology, concomitantly with a simulation model for the planning of a specific maritime transportation system, including the respective sensitivity analyzes. The application was successful and conclusive about the effectiveness of the developed method helping the decision making for problems of this magnitude.

O trabalho apresenta inicialmente a importância da tomada de decisão em uma sociedade com recursos limitados e muitos interesses antagônicos. Essas decisões com base em objetivos conflitantes, independente do seu grau de importância, geram ganhos em alguns aspectos e perdas em outros, e a isto se denomina tradeoff. Em problemas complexos, uma decisão mal tomada, ou um estudo de tradeoff mal conduzido podem afetar significativamente aspectos muito relevantes, como o dimensionamento de redes de transporte, por exemplo. Assim, a proposta deste trabalho é oferecer um procedimento para auxilio à tomada de decisão em sistemas de transporte aquaviário, baseado em análises com múltiplos critérios. Além disso, o estudo visa utilizar a técnica de simulação de eventos discretos para fornecer subsídio a estes estudos de tradeoff. É realizada também uma aplicação do método descrito juntamente com um modelo de simulação para o dimensionamento de um sistema de transporte aquaviário específico, contando com análises de sensibilidade. A aplicação realizada foi conclusiva e comprovou a eficácia do método desenvolvido para o auxílio à decisão em problemas desse porte. / This work primarily highlights the importance of decision making in a society with limited resources and several antagonistics interests. Decisions based on conflicting goals, regardless of their importance level, might generate positive gains associated to a certain number of variables and losses associated to others. This process is known as tradeoff. In complex problems, such as transportation networks planning, taking a bad decision or carrying out a bad tradeoff study, may affect matters of primary interests of the problem players. The proposal of this work is providing a procedure in order to support decision making process in water transportation systems based on multi-criteria analysis. In addition, the study aims at using the technique of discrete event simulation to provide subsidies to these trade-off studies. The work also presents an application of the proposed methodology, concomitantly with a simulation model for the planning of a specific maritime transportation system, including the respective sensitivity analyzes. The application was successful and conclusive about the effectiveness of the developed method helping the decision making for problems of this magnitude.

Cooperative breeding is a phenomenon whereby breeding and nonbreeding individuals collectively provision young. Nonbreeding group members ("helpers'') may gain indirect and/or direct fitness benefits by breeding in a group, but there has been conflicting evidence regarding the benefits to breeders. In fact, the presence of helpers may sometimes be detrimental to aspects of breeder fitness. For example, in some species of the chiefly Australian genus Malurus, breeding males with helpers have lower within-pair paternity than do males without helpers. Additionally, indirect benefits to breeding males are often limited by low relatedness to their helpers due to high extrapair paternity rates, and helpers often appear to have minimal impact on breeder reproductive success. However, the presence of helpers may allow breeding males to shift their behaviors from guarding and provisioning young to alternative behaviors that affect other components of fitness, such as extraterritory forays (which might increase extrapair mating success) and self-maintenance (which might increase survival). We investigated these possibilities in the facultatively cooperative Red-backed Fairywren (Malurus melanocephalus). Males with helpers spent significantly less time engaging in guarding behaviors and provisioning of young than did those without helpers, but there was no difference in the frequency of extrapair forays nor the number of young sired by males with vs. without helpers. Additionally, the decreased investment in nesting behaviors did not result in consistently higher survival, but may have increased survival in some years. Overall, the results of this study did not suggest any strong direct fitness benefits to breeding males, which may indicate that the costs of retaining helpers are negligible relative to the indirect benefits of helping a potentially related male.