The coastline of the northern Gulf of Mexico (NGOM) represents important non-breeding habitats for 28 species of migratory shorebirds. As processes of climate change accelerate, these habitats are expected to experience dramatic land loss. In addition, the NGOM has experienced several natural and human mediated disasters over the last decade, including Hurricane Katrina and the Deepwater Horizon Oil spill (DWH). Predicting the impacts of these events requires an understanding of the interactions between shorebirds and their habitats. However, the migration ecology of shorebirds on the NGOM has not been well studied. To better understand the effects of the DWH and the importance of NGOM habitats to the migration ecology of shorebirds I carried out two related studies. First, I investigated the potential for long term, large-scale effects of oil exposure to migratory shorebirds through both a literature review, and by investigating the exposure to DWH oil in seven species of shorebirds that winter or stopover along the NGOM. I found that through migratory carry-over effects, oil spills and other environmental disasters, have the potential to impact ecosystems far from the event. Exposure results suggest as many as 1 million shorebirds were impacted by direct exposure to oil, and many more may have been negatively affected by disturbance from cleanup activities in oiled habitats. Second, I investigated the migration ecology of three near-arctic breeding species of shorebirds (Semipalmated sandpipers (Calidris semipalmatus), Western Sandpiper (C. mauri) and Dunlin (C. alpina), by measuring within- and among-species variation in habitat use, stopover duration, and refueling rates, as measured by plasma metabolites, across 3 habitat types. I found that among species, shorebirds vary in their migration ecology according to the distance to the next stopover site, suggesting NGOM habitats may be particularly important to longer-distance â"u20acœjumpâ"u20acù migrants (Dunlin). I also found that while shorebirds are found across all habitat types sampled, the back bay habitats of barrier islands provided a higher quality habitat (as evidenced by higher prey biomass, and a higher refueling rate) than traditional coastal mudflats or remnant wetlands, highlighting the importance of considering shorebird ecology in barrier island restoration plans. / 1 / Jessica Renee Henkel

Shipping industry belongs to an international business. It plays an extremely important role in the economic and trade development of a country, so it can be regarded as a symbol of extension of the national strength of a country. Besides, it earns a lot of foreign capital for the country, but never creates any negative effects to the society domestically, such as environmental protection, noise, congestion, and so on. This is something that other manufacturing industries are incomparable with. Especially that Taiwan is an island, Taiwan should be engaged in the studies of shipping business through the rich marine resources. Then, unlimited business opportunities and vitality must be brought to Taiwan, achieving the aspiration of and confidence in standing in Taiwan but looking far to the world. International marine transportation business can be divided into irregular bulk shipping and regular container shipping. Between them, irregular bulk shipping is mostly the loading of the bulk cargoes by one or two consignors in one whole vessel. It is almost a completely competitive market. In order to obtain the greatest profit through the unlimited shipping lines and cargo loading, the best business operation ways and the best vessel allocation should be selected. For regular container shipping, services are provided to a great number of consignors with fixed shipping lines, fixed anchoring harbors and fixed rate. The cost of refueling of shipping industry occupies an extremely high proportion of the variable cost of marine transportation. When the price of the international fuel rises continuously, the cost of fuel increases accordingly. Taking the international vessel-use fuel MF-180 for example, the market quotation of oil in Taiwan on Jan. 6, 1999 was US$74/MT. After that, the price rose continuously. Down to Oct. 2007, there appeared the market quotation of oil at above US$500/MT. According to the ¡§Medium Term Oil Market Report of International Energy Agency (IEA)¡¨ announced on Jul. 9, 2007, the whole world would face the shortage of oil supply in five years, and the oil price was estimated to be rising continuously. Bulk marine transportation is irregular shipping without the fixing of any regular shipping lines and cargo loading. If refueling is to be made to vessels, there should be more efficient estimation and decision on the refueling harbor, refueling volume and refueling cost so as to achieve the minimum variable cost and acquire the greatest profit. Through review of the literature about the refueling of voyages as well as the interviews with experts, the paper investigates the literature of the decision support system, and uses the prototype development method to complete the model construction and the analytical design of system, practically establish a prototype of refuel decision support system for bulk shipping, and provide the solutions of average sailing speed of voyages, refueling volume and refueling harbor. After the results are compared with those of the actual cases, the paper evaluates the effects of the decision support system. Through the users¡¦ feedback, the prototype is revised to increase the completeness of the system, which provides a reference for the bulk shipping proprietors in constructing a refueling decision support system in future.

No description available.

Master of Science / Department of Industrial and Manufacturing Systems Engineering / Todd W. Easton / Jessica L. Heier Stamm / Locomotives in the U.S. use over 3 billion gallons of fuel each year and faster refueling can increase rail network capacity without the infrastructure cost associated with new terminals or tracks. This thesis introduces the locomotive refueling system configuration problem (LRSCP), which seeks to improve efficiency in refueling yards through new technologies or policies. This research also creates two new methods to solve LRSCP. The first method uses an integer program to solve the off-line LRSCP and develop a static refueling policy. The train refueling integer program, TRIP, maximizes the weighted number of train combinations that can be refueled without delay. TRIP is optimized and its outputs are used as inputs to a simulation developed in Simio® for testing and validation. The second method creates an integrated integer program and simulation to solve the on-line LRSCP and produces a dynamic refueling policy. This tool, built in Python, incorporates a different integer program, the strike line integer program (SLIP), into the simulation. SLIP determines the optimal refueling assignment for each incoming train. The simulation incorporates SLIP’s solution for testing and validation. This tool is truly integrated and requires approximately 300 instances of SLIP to simulate a single day. Based on experimental results, solving either TRIP or SLIP and incorporating the optimal refueling policy improves railyard operations by 10 to 30%. This impact is statistically significant and increases the capacity of a railyard. Additionally, it impacts other important parameters such as time spent in the yard and the maximum queue for the railyard. Furthermore, there is a significant decrease in wasted time and an improvement to railyard efficiency. Implementing either method should increase a railyard’s capacity and significantly increase revenue opportunities.

No description available.

Several mathematical models are developed for a hose-drogue refueling system in an attempt to represent the physical system accurately and to subsequently observe the dynamic response of the system under different initial conditions. The mathematical models examined include a flexible hose model and a model which includes elastic bending effects. The equations of motion include aerodynamic, gravitational, and tensile forces, and solutions of the refueling system are found using fewer assumptions than in previous work. Once the equations of motion are developed, they are separated into equilibrium and perturbation portions. Solutions of the nonlinear equilibrium tension distribution are obtained by solving the equations in closed form using a two point boundary value problem solver program. The solution to the linear equilibrium tension distribution is found and compared to the nonlinear solutions. Results indicate that the behavior of the solutions is similar, but the linear solution gives larger values of tension near the hose attachment point. The perturbation equation is discretized using a finite difference scheme and the resulting first order differential matrix equation is integrated to calculate the dynamic response for given parameters and initial conditions with the various equilibrium tension distribution solutions. Results show negligible differences between the different tension values upon substitution and it is therefore recommended that the linear approximation to the equilibrium tension distribution be used in analysis of this hose-drogue refueling system because of the ease in obtaining solutions with this method. / M.S.

In 2004, President Bush addressed the nation and presented NASA's new vision for space exploration. This vision included the completion of the International Space Station, the retirement of the Space Shuttle, the development of a new crew exploration vehicle, and the return of humans to the moon by 2020. NASA's Exploration Systems Architecture Study (ESAS) produced a transportation architecture for returning humans to the moon affordably and safely. This architecture requires the development of two new Shuttle-derived launch vehicles, an in-space transportation vehicle, a lunar descent and landing vehicle, and a crew exploration vehicle for human transportation. The development of an in-space propellant transfer capability could greatly improve the performance, cost, mission success, and mission extensibility of the overall lunar architecture, providing a more optimal solution for future exploration missions. The work done in this thesis will analyze how this new capability could affect the current NASA lunar architecture, and will outline the value proposition of propellant refueling to NASA. A value proposition for propellant refueling will be provided to establish why an architecture that utilizes propellant refueling is better equipped to meet the goals of the Vision for Space Exploration than the current baseline design. The primary goal addressed in this research is the development of a sustainable and affordable exploration program. The value proposition will outline various refueling strategies that can be used to improve each of the architecture Figures of Merit. These include a decrease in the Life Cycle Cost of both the lunar and Mars exploration campaigns, the ability to more than double the mission payload that can be delivered to the lunar surface during cargo missions, improving the probability of successfully completing each lunar mission, decreasing the uncertainty, and therefore risk, experienced during the development process, and improving the extensibility of the exploration architecture by utilizing a greater portion of the lunar program for future crewed mission. The ability to improve these Figures of Merit provides NASA with a more valuable architecture because NASA is able to achieve a greater return on its large initial investment.

Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Panagiotis Tsiotras; Committee Member: Eric Feron; Committee Member: Joseph Saleh; Committee Member: Ryan Russell; Committee Member: William Cook

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: This thesis presents the development of a state estimation system for use in an Autonomous Airborne Refueling (AAR) operation through the simulated implementation of GPS, monocular and stereoscopic vision, inertial measurement sensors and boom parameter measurement in combination with the Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF). A set of functional criteria for the estimation system was developed through an analysis of the control system input requirements and associated constraints. The estimation system is further developed by integrating the sensor configurations into the estimation algorithm structures through the derivation of the applicable mathematical models. Final sensor configurations are set based on a sensitivity analysis in which the effect of parameters such as sensor noise, placement and quantity are related to the accuracy with which the states are estimated. Uncertainty in the process noise, which is typically approximated, is overcome by adding an adaptive element to the estimation algorithms in which the current process noise is estimated allowing compensation for unmodeled process noise uncertainty. Finally twelve practical sensor configurations are established utilising unique combinations of the five sensors. Each configuration is simulated using both estimation algorithms after which all results are evaluated with respect to one another as well as to the minimum state accuracy criteria. Conclusions are presented based on the evaluation of the results followed by recommendation for future development. / AFRIKAANSE OPSOMMINGS: Die ontwikkeling van ’n toestandafskattingstelsel, spesifiek toegepas op outonome brandstofhervulling, word voorgelê in hierdie tesis. Hierdie ontwikkeling behels die implementering van GPS, monukulêre- en stereo-visie sensors, inersiële sensor eenhede en verbindingsarmsensors wat gebruik word in ’n Uitgebruide Kalman Filter (Extended Kalman Filter) en Geurlose Kalman Filter (Unscented Kalman Filter). ’n Volledige ontleding van die beheerstelsel se toevoervereistes en geassosieerde beperkings is gebruik om ’n stel beoordelingsmaatstawwe vir die toestandafskatting-stelsel te bepaal. Die stelsel is verder ontwikkel deur verskillende sensorkonfigurasies met die afskattingsalgoritmes te kombineer deur die afleiding van toepaslike wiskundinge modelle. Hierdie konfigurasies is verfyn deur ’n sensitiwiteitsanalise, waar die verwantskap tussen die effekte van sensorruis, sensorligging, hoeveelheid sensors ondersoek is met betrekking tot afskattingsakkuraatheid. Onsekerheid in die stelsel se prosesruis is deur ’n aanpassings substelsel hanteer, wat kompensasie vir ongemodeleerde onsekerheid moontlik maak. Twaalf praktiese sensorkonfigurasies is opgestel vanuit unieke kombinasies van die vyf sensore behartig in die projek. Hierdie konfigurasies is deur beide afskattingsalgoritmes gebruik om sodoende die akkuraatheid van die konfigurasies asook die afskattingsalgoritmes te evalueer met betrekking tot mekaar en aan die hand van die beoordelingsmaatstawwe vir die beheerstelsel. Die tesis is afgesluit deur gevolgtrekkings asook aanbevelings vir toekomstige navorsing.

On-orbit servicing (OOS) of space systems provides immense benefits by extending their lifetime, by reducing overall cost of space operations, and by adding flexibility to space missions. Refueling is an important aspect of OOS operations. The problem of determining the optimal strategy of refueling multiple satellites in a constellation, by expending minimum fuel during the orbital transfers, is challenging, and requires the solution of a large-scale optimization problem. The conventional notion about a refueling mission is to have a service vehicle visit all fuel-deficient satellites one by one and deliver fuel to them. A recently emerged concept, known as the peer-to-peer (P2P) strategy, is a distributed method of replenishing satellites with fuel. P2P strategy is an integral part of a mixed refueling strategy, in which a service vehicle delivers fuel to part (perhaps half) of the satellites in the constellation, and these satellites, in turn, engage in P2P maneuvers with the remaining satellites. During a P2P maneuver between a fuel-sufficient and a fuel-deficient satellite, one of them performs an orbital transfer to rendezvous with the other, exchanges fuel, and then returns back to its original orbital position. In terms of fuel expended during the refueling process, the mixed strategy outperforms the single service vehicle strategy, particularly with increasing number of satellites in the constellation. This dissertation looks at the problem of P2P refueling problem and proposes new extensions like the Cooperative P2P and Egalitarian P2P strategies. It presents an overview of the methodologies developed to determine the optimal set of orbital transfers required for cooperative and non-cooperative P2P refueling strategies. Results demonstrate that the proposed strategies help in reducing fuel expenditure during the refueling process.