Workshop "Netz- und Service-Infrastrukturen" vom 19.-22. April 2004 in Löbsal (bei Meißen)

This dissertation details an algorithm to solve the Intratheater Airlift Operations Problem (IAOP) using advanced tabu search. A solution to the IAOP determines the routes and assignment of customer requests to a fleet of aircraft over a given time horizon. This problem and other variants comprise an ongoing challenge for United States Air Force (USAF) planners who manage detailed logistics throughout many theaters of operations. Attributes of the IAOP include cargo time windows, multiple cargo types, multiple vehicle cargo bay configurations, vehicle capacity, route duration limits, and port capacities. The IAOP multi-criteria objective embraces several components with the primary goal of satisfying as much of the demand as possible while minimizing cost. The algorithm is extended to allow split load deliveries of customer requests, allowing a shipment to be split into two or more sub-loads which are delivered separately to the customer. The split load relaxation, while significantly increasing the complexity of the problem, allows for possible improvement in the solution. The necessary changes to the model and algorithm are detailed, providing a foundation to extend any local search algorithm solving a vehicle routing problem to allow split loading. Results allowing split loading are presented and compared with results without split loading. The algorithm is also extended to include a rolling time horizon. Starting from a solution found at a previous time step, the algorithm is limited on how the solution can be modified. This reflects the reality of operations in which near-term plans are locked as they approach and enter execution while longer-term plans are continually updated as new information arrives. / text

The Vehicle Routing Problem (VRP) is a classical problem in logistics that has been well studied by the operations research and transportation science communities. VRPs are defined as follows. Given a transportation network with a depot, a set of pickup or delivery locations, and a set of vehicles to service these locations: find a collection of routes starting and ending at the depot, such that (i) the customer's demand at a node is satisfied by exactly one vehicle, (ii) the total demand satisfied by a vehicle does not exceed its capacity, and (iii) the total distance traveled by the vehicles is minimized. This problem is especially hard to solve because of the presence of sub--tours, which can be exponential in number. In this dissertation, a special case of the VRP is considered -- where the underlying network has a tree structure (TVRP). Such tree structures are found in rural areas, river networks, assembly lines of manufacturing systems, and in networks where the customer service locations are all located off a main highway. Solution techniques for TVRPs that explicitly consider their tree structure are discussed in this dissertation. For example, TVRPs do not contain any sub-tours, thereby making it possible to develop faster solution methods. The variants that are studied in this dissertation include TVRPs with Backhauls, TVRPs with Heterogeneous Fleets, TVRPs with Duration Constraints, and TVRPs with Time Windows. Various properties and observations that hold true at optimality for these problems are discussed. Integer programming formulations and solution techniques are proposed. Additionally, heuristic methods and conditions for lower bounds are also detailed. Based on the proposed methodology, extensive computational analysis are conducted on networks of different sizes and demand distributions. / text

We propose using overlapping, tapered windows to process seismic data in parallel. This method consists of numerically tight linear operators and adjoints that are suitable for use in iterative algorithms. This method is also highly scalable and makes parallel processing of large seismic data sets feasible. We use this scheme to define the Parallel Windowed Fast Discrete Curvelet Transform (PWFDCT), which we apply to a seismic data interpolation algorithm. The successful performance of our parallel processing scheme and algorithm on a two-dimensional synthetic data is shown.

Making an application user-friendly is a key goal when it comes to the experience it intends to deliver. There are numerous factors that have to be taken into account when a design is developed. One of those is simplicity. The application has to be simple enough to ensure the expected user experience. This is often solved by applying instructions. To what extent does the application have to mediate instructions of functionality to the user? That question is the underlying purpose of this thesis. The thesis studies three common ways of presenting instructions to arrive at a concluding result: the use of a popup window, an added information button to the design or relying on the design to present itself. The gathered results show a need for instructions to ensure a user-friendly environment. A further analysis of the results concludes that presenting instructions using an information button is the most prominent option.

X windows is a graphic display management system. It is designed to work on a variety of machines and display adapters, however it is not designed for terminals with local graphics capabilities. X windows can be made to work on this type of terminal, although in a slower and restricted form. The problem with designing a variation of X for these terminals is the translation from X requests to native graphics commands, and the mapping of terminal input into X events. These implementation issues are discussed and example code is provided. / Department of Computer Science

This thesis examines exact and heuristic approaches to solve the Ship Routing and Scheduling Problem (SRSP). The method was developed to address the problem of loading cargos for many customers using heterogeneous vessels. Constraints relate to delivery time windows imposed by customers, the time horizon by which all deliveries must be made and vessel capacities. The objective is to minimise the overall operation cost, where all customers are satisfied. Two types of routing and scheduling are considered, one called single-cargo problem, where only one cargo can be loaded into a ship, and the second type called multi-cargo problem, where multiple products can be carried on a ship to be delivered to different customers. The exact approach comprises two stages. In the first stage, a number of candidate feasible schedules is generated for each ship in the fleet. The second stage is to model the problem as a set partitioning problem (SPP) where the columns are the candidate feasible schedules obtained in the first stage. The heuristic approach uses Tabu Search (TS). Most of the TS operations, such as insert and swap moves, tenure, tabu list, intensification, and diversification are used. The results of a computational investigation are presented. Solution quality and execution time are explored with respect to problem size and parameters controlling the tabu search such as tenure and neighbourhood size. The results showed that the average of the solution gap between TS solution and SPP solution is up to 28% (for small problems) and up to 18% for large problems. However, obtaining an optimal solution requires a large amount of computer time to produce the solution compared to obtaining approximate solutions using the TS approach. The use of Tabu Search for SRSP is novel and the results indicate that it is viable approach for large problems.

In this thesis the capacitated vehicle routing problem with time windows (VRPTW) is studied, where the objective is to serve a set of geographically dispersed customers with known demands and predefined time windows at the minimum cost. It is hard to find an optimal solution for the VRPTW even if the problem size is small. Therefore, many heuristic methods are developed to obtain near optimal solutions. In this study a local search algorithm is proposed for solving the VRPTW, which consist of route construction and route improvement phases. Computational experiments are conducted with Solomon (1987)&rsquo / s and Homberger and Gehring (1999)&rsquo / s problem sets in order to test the performance of the proposed algorithm. From the computational results encouraging results are obtained in terms of solution quality.

This thesis explores the relationship between information literacy and learning. In formal education, students are frequently required to independently find and use information to learn about a topic, and information literacy is often claimed to be a generic skill and graduate attribute. However, to date; the experienced relationship between information literacy and learning has not been investigated. In order to investigate this experience, I have based this research on interviews with 19 students enrolled in third year music composition courses, and 18 students enrolled in a third year tax law course at an Australian university. My primary research question was 'What is the experienced relationship between information literacy and learning?' The secondary research question was "What are the generic and situated aspects of information literacy?' In this study, I have used phenomenography to describe the qualitatively different ways that students in two distinct disciplines experience the relationship between information literacy and learning. I have suggested curriculum implications of this description based on a relational approach to learning and teaching. The outcomes of the study include two related sets of categories which map the experience of students in music composition and tax law, and the theoretical GeST windows model for information literacy which is based upon literacy models and theories. The key findings of this study include: * A description of the nature of the experienced relationship between information literacy and learning in music composition and tax law as 1) Applying, 2) Discovering and 3) Expressing (music) or Understanding (tax law); * the theoretical GeST windows model and alignment of the model with the empirical study; * the presentation of curriculum implications in music and tax law, and * an exploration of the nature of information as-it-is-experienced. The findings may be used by teachers, students, librarians, academic skills advisors, academic developers and policy makers in higher education.

Thesis (M.Sc.). / Written for the Dept. of Atmospheric and Oceanic Sciences. Title from title page of PDF (viewed 2008/12/08). Includes bibliographical references.