Quantification of total phosphorus (TP) loads entering a lake or reservoir is important because phosphorus is most often the limiting nutrient in terms of algae growth, thus phosphorus can control the extent of eutrophication. Four methods for assessing the annual tributary phosphorus loads to two different Virginia reservoirs were analyzed, three methods that use tributary monitoring program data and one that uses land-use and rainfall data. In this project, one tributary has been extensively monitored for many years and served as a control on which the other methods were tested. The key difference between this research and previous studies is the inclusion of flow-weighted composite storm sampling instead of simple grab sample analyses of storm flow. Three of the methods employed flow stratification, and the impact of the base flow separation point was examined. It was found that the Regression Method developed in this research was the least sensitive to the base flow separation point, which is a valuable attribute because a wrong choice will not significantly affect the estimate. The Monte Carlo Method was found to underestimate the TP loads. The amount of rainfall impacted the accuracy of the methods, with more error occurring in a year with lower precipitation. / Master of Science

As laptop mobile users expect more application features and long battery life, the processor current has to increase to response the demanding while the voltage has to decease to save the power loss. Therefore, it is necessary for a system designer to improve the efficiency of the voltage regulator converter (VRC) for the processor. Laptop processor architecture is more complicated than desktop because of different mode operations and their transitions. The laptop processor runs at different voltage levels for each operation mode to save the battery life. Therefore, the VRC needs to supply the correct and stable voltage to the processor. In this thesis, an analysis of power loss is derived to estimate the efficiency and switching frequency, three widely current sensing methods are discussed, two methods to compensate for the thermal resistance in loss less current sense methods are proposed, the tolerance of load line base on the component's tolerance in the converter is analyzed, the equation to estimate the output capacitance is derived, and the small signal analysis of multiphase synchronous buck converter with the droop current loop is derived. A hardware prototype was implemented base on 4-phase synchronous buck topology to provide high efficiency and lower cost solution. The results of load line meets the Intel specification in different modes of operation, provides the best transient responses, and meets the specification during the load transient. The control loop lab measurement is also matched with the analysis and simulation. / Master of Science

Pallets are a critical component of logistics infrastructure. Approximately 1.9 billion pallets are used each year in the United States for transportation of goods, from raw materials to finished products. Solid wood pallets represent 90% to 95% of the pallet market. To run their operations, wood pallet companies deal with suppliers, customers, and other supply chain components. Each of the steps is important to deliver the right products, with the required quality, and in a timely fashion. However, there is little research about the industry's supply chain practices. The objective of this research is to increase the understanding of the U.S. wood pallet manufacturing industry, its supply chain management practices, and factors affecting the supply chain management processes. To accomplish the research objectives, a nationwide mail survey of wood pallet manufacturers was carried out. In total 1,500 companies were sent questionnaires and the response rate was 14%. A model for supply chain success factors was developed based on previous research and was analyzed using the results from the survey. Results of the survey provide an up-to-date profile of the US wood pallet industry. It was found that pallet production per company was 727,229 units on average during 2009. Out of the 1500 respondents, 38.6% indicated they were medium-sized companies (20 to 99 employees) and 53.9% small companies (1 to 19 employees). Thirty five percentage of respondents indicated that their sales were less than one million dollars and 43% from one to five million dollars. Also, 45% of respondents were involved in pallet recycling or repair, and these companies indicated that, on average, 42% of the material in a recycled pallet is, in fact, new material. Regarding Supply Chain practices, close to three-quarters (73.1%) of respondents sold their products directly to customers and the order lead time for raw materials to shipment was 1 to 10 days for 81.9% of companies. The most important factors for purchasing decisions are availability, cost, and reliability of supplier (all rated 4.4 in an importance scale from 1 to 5, respectively). Respondents' answers suggest a preference to work with domestic materials (rated 4.3); however, respondents also indicated that there is currently a high level of competition for raw materials (rated 4.3). Results also indicated that information technology (IT) appears to receive little attention from wood pallet manufacturers, given that the importance of items in this area were rated relatively low, especially the use of internet for purchasing and training in IT (rated 2.2 and 2.1, respectively). Lastly, 86.0% of respondents did not believe that their customers would be willing to pay a premium for environmentally certified pallets, citing cost as the major barrier for a higher demand of these products. Also, a theoretical framework of supply chain management was designed, developed, and tested with factor analysis, allowing identification of seven factors in the wood pallet supply chain: (1) environmental uncertainty, (2) information technology, (3) supply chain relationships, (4) value-added process, (5) supply chain management performance, (6) business management, and (7) customer satisfaction. Relationships between factors were tested using multiple linear regression. Results show that value-added process positively affects supply chain relationships, and these in turn are positively correlated to supply chain management performance and customer satisfaction. Results from this research are useful for the industry to formulate a well-informed supply chain management strategy by understanding the connections between the different supply chain management practices and the business performance and customer satisfaction. The information presented is also useful for organizations supporting the wood pallet industry to design more effective assistance and educational programs. / Master of Science

The transient response of various plate structures subject to blast loads is analyzed. In particular, simply supported isotropic and laminated composite plates are modeled using the commercial finite element code NASTRAN and the method of modal superposition. Both analysis procedures are used to quantify the linear transient response of such plates subject to uniform and patch blast loads. Furthermore, NASTRAN is used to study the nonlinear response of plates subject to close proximity explosions. Also considered here is the case for which a blast loaded plate impacts another closely neighboring plate. The NASTRAN solution used here accounts for nonlinearities due to large plate deflections, plasticity, and plate-to-plate contact. Many studies are currently available in which the blast load is considered to be spatially uniform across the plate; with a temporal distribution described by step, N-pulse, or Friedlander equations. The novel aspect considered here is the case for which the blast pressure is due to a close proximity explosion, and it is therefore taken to be both spatially and temporally varying. A FORTRAN program is described which automates the application of an arbitrary blast load to a generic finite element mesh. The results presented here are a collection of analyses performed for a variety of parameters important to the dynamic response of blast loaded contacting plates. Conclusions are drawn concerning the influence of the various parameters on the nature of the plate response and the quality of the solution. / Master of Science

Optimization problems of location-assignment correspond to a wide range of real situations, such as factory network design. However most of the previous works seek in most cases at minimizing a cost function. Traffic incidents routinely impact the performance and the safety of the supply. These incidents can not be totally avoided and must be regarded. A way to consider these incidents is to design a network on which multiple assignments are performed. Precisely, the problem we focus on deals with power supplying that has become a more and more complex and crucial question. Many international companies have customers who are located all around the world; usually one customer per country. At the other side of the scale, power extraction or production is done in several sites that are spread on several continents and seas. A strong willing of becoming less energetically-dependent has lead many governments to increase the diversity of supply locations. For each kind of energy, many countries expect to deal ideally with 2 or 3 location sites. As a decrease in power supply can have serious consequences for the economic performance of a whole country, companies prefer to balance equally the production rate among all sites as the reliability of all the sites is considered to be very similar. Sharing equally the demand between the 2 or 3 sites assigned to a given area is the most common way. Despite the cost of the network has an importance, it is also crucial to balance the loading between the sites to guarantee that no site would take more importance than the others for a given area. In case an accident happens in a site or in case technical problems do not permit to satisfy the demand assigned to the site, the overall power supply of this site is still likely to be ensured by the one or two available remaining site(s). It is common to assign a cost per open power plant and another cost that depends on the distance between the factory or power extraction point and the customer. On the whole, such companies who are concerned in the quality service of power supply have to find a good trade-off between this factor and their overall functioning cost. This situation exists also for companies who supplies power at the national scale. The expected number of areas as well that of potential sites, can reach 100. However the targeted size of problem to be solved is 50. This thesis focuses on devising an efficient methodology to provide all the solutions of this bi-objective problem. This proposal is an investigation of close problems to delimit the most relevant approaches to this untypical problem. All this work permits us to present one exact method and an evolutionary algorithm that might provide a good answer to this problem. / Master of Science

A three-dimensional, nonlinear dynamic analysis is conducted on a fully submerged, rigid, solid cylinder to be used as a breakwater. The breakwater could potentially be used as a single cylinder to protect small structures. Alternatively, multiple cylinders could be positioned in series to protect shorelines, harbors, or moored vessels from destructive incident water waves. The cylinder is positioned with its axis horizontal and is moored to the seafloor with four symmetrically placed massless mooring lines connected at the ends of the cylinder. The mooring lines are modeled as both linearly elastic ("regular") springs and compressionless springs. All six degrees of freedom of the structure are considered. The breakwater is modeled in air with a net buoyant force acting through the cylinder's center of gravity. The six "dry" natural frequencies of the structure are computed. Both linear and nonlinear free vibrations of the structure are considered. Linear damping is used to model the fluid and mooring damping effects. Normal and oblique harmonic wave forces at various frequencies and amplitudes are applied to the cylinder. The effects of the forcing amplitude and frequency, and the coefficient of damping, on the motion of the breakwater are studied. The results show that more erratic behavior occurs for the breakwater with compressionless springs, mainly due to the development of snap loads in the mooring lines. / Master of Science

The ability to analyze a power system is essential to power system engineers and planners. The Bus program, a Microsoft Windows-based program, helps users make these analyses. Unlike other power system analysis programs, the Bus program performs three different types of analyses (short circuit, load flow, and state estimation) and offers users a graphical interface on which to enter their system and data. This thesis presents the Bus program and discusses various aspects of it, focusing on the load flow and state estimation routines, which were the main thrust of the project. Each of these routines was written by setting up a flowchart and defining the calculations to be carried out. Vehicles were then developed so that users can enter system data and view the results of the calculations. The ability to do this graphically is one of the main features of the program. Several test cases are presented to demonstrate the program's operation, and a User's Manual is included to show users how to operate the program. / Master of Science

The vertical load on a moving tire was estimated by using accelerometers attached to the inner liner of a tire. The acceleration signal was processed to obtain the contact patch length created by the tire on the road surface. Then an appropriate equation relating the patch length to the vertical load is used to calculate the load. In order to obtain the needed data, tests were performed on a flat-track test machine at the Goodyear Innovation Center in Akron, Ohio; tests were also conducted on the road using a trailer setup at the Intelligent Transportation Laboratory in Danville, Virginia. During the tests, a number of different loads were applied; the tire-wheel setup was run at different speeds with the tire inflated to two different pressures. Tests were also conducted with a camber applied to the wheel. An algorithm was developed to estimate load using the collected data. It was then shown how the estimated load could be used in a control algorithm that applies a suitable control input to maintain the yaw stability of a moving vehicle. A two degree of freedom bicycle model was used for developing the control strategy. A linear quadratic regulator (LQR) was designed for the purpose of controlling the yaw rate and maintaining vehicle stability. / Master of Science

A newly-developed technique for short-term load forecasting is generalized. The algorithm combines features from knowledge-based and statistical techniques. The technique is based on a generalized model for the weather-load relationship, which makes it site independent. Weather variables are investigated, and their relative effect on the load is reported. That effect is modeled via a set of parameters and rules that constitute the rule based technique. This technique is very close to the intuitive judgmental approach an operator would use to make his guess of the load. That is why it provides a systematic way for operator intervention if necessary. This property makes the technique especially suitable for application in conjunction with demand side management (DSM) programs. Moreover, the algorithm uses pairwise comparison to quantify the categorical variables, and then utilizes regression to obtain the least-square estimation of the load. Because it uses the pairwise comparison technique, it is fairly robust. Since the forecast does not depend on any preset model, the technique is inherently updatable. A generalized version of the technique has been tested using data from four different sites in Virginia, Massachusetts, Florida and Washington. The average absolute weekday forecast errors range from 1.30% to 3.10% over all four seasons in a year. Error distributions show that the errors are 5% or less around 91 % of the time. / Master of Science

Characterization and modeling of devices at high drive levels often requires specialized equipment and measurement techniques. Many large-signal devices will never have traditional nonlinear models because model development is expensive and time-consuming. Due to the complexity of the device or the size of the application market, nonlinear modeling efforts may not be cost effective. Scattering parameters, widely used for small-signal passive and active device characterization, have received only cursory consideration for large-signal nonlinear device characterization due to technical and theoretical issues. We review the theory of S-parameters, active device characterization, and previous efforts to use S-parameters with large-signal nonlinear devices. A robust, calibrated vector-measurement system is used to obtain device scattering parameters as a function of drive level. The unique measurement system architecture allows meaningful scattering parameter measurements of large-signal nonlinear devices, overcoming limitations reported by previous researchers. A three-port S-parameter device model, with a nonlinear reflection coefficient terminating the third port, can be extracted from scattering parameters measured as a function of drive level. This three-port model provides excellent agreement with device measurements across a wide range of drive conditions. The model is used to simulate load-pull data for various drive levels which are compared to measured data. / Master of Science