Doctor of Philosophy / Department of Hospitality Management and Dietetics / Deborah D. Canter / Despite the enormous amount of research about job satisfaction and intent to leave, few studies have focused on Registered Dietitians (RDs) with management responsibilities. Even less is known about the level of career satisfaction or intent to leave the dietetics profession. This study examined job and career satisfaction among members of four dietetic practice groups (DPGs). An online questionnaire included 36 items of the Job Satisfaction Survey (JSS), career satisfaction and intent to leave measures. Data were analyzed from 966 dietitians in management and clinical practice using traditional statistical procedures. Management dietitians had significantly higher composite scores for six out of nine facets of job satisfaction than dietitians in non-managerial positions. Overall satisfaction scores for management dietitians (M = 153.75 ± 26.68) were also significantly higher compared to non-management dietitians (M = 140.79 ± 30.26, t = 4.368, p < 0.001). Overall satisfaction scores also differed significantly across seven groups of management dietitians, F (6, 844) = 4.41, p < 0.001. The majority of dietitians in this study did not intend to seek other jobs or leave their current jobs. Overall, management dietitians were satisfied with their careers (19.82 ± 3.73). In contrast, non-management dietitians were closer to neutral and significantly less satisfied with their careers (16.44 ± 5.06, t = 6.907, p < 0.001). Career satisfaction scores also differed significantly across seven job titles of managers, F (6, 839) = 5.69, p < 0.001. Intent to leave the profession was not observed for the majority of dietitians in this study. Additional results, implications for the dietetics profession and recommendations for future research are discussed.

Doctor of Philosophy / Department of Hospitality Management and Dietetics / Carol W. Shanklin / The purpose of this study was to survey country club professionals’ importance perceptions of food defense and the frequency with which preventive practices were implemented in their clubs to prevent bioterrorism. Gaps between importance perceptions and practice frequency were compared with concern of food terrorism and practice frequency implementation. Perceived self-efficacy measures and perceived barriers were compared with motivations to develop a food defense management plan and practice frequency implementation. Importance perceptions and practice frequencies were studied to ascertain if there were differences among operational factors. Club professionals with smaller gaps implemented preventive practices more frequently. Club professionals with higher self-efficacy levels were more motivated to develop food defense management plans and implemented preventive practices more frequently. Club professionals with higher barriers were less motivated to develop food defense management plans and implemented preventive practices less frequently. The field study component investigated food security practices in private country clubs. Club manager interviews and observations of operational practices were conducted. Most club managers stated that they did not think their clubs were at risk of a bioterrorist attack. Cost and lack of need were identified as barriers towards implementing a food defense management plan. Club employees were perceived to be more likely to initiate a bioterrorism attack than non-employees. Background checks and good employment practices were perceived as effective in increasing food security in clubs. Most clubs did not monitor arrivals and over half did not secure their chemicals. Based on the results of the field study, the researcher recommended several actions that could improve food security in country clubs including installing video surveillance and developing disaster management plans that include food defense. Recommendations for future research included continued examination of club managers’ self-efficacy perceptions towards biosecurity and identifying barriers to food defense implementation in other retail foodservice segments.

Master of Science / Department of Industrial & Manufacturing Systems Engineering / Todd W. Easton / Westside High School (WHS) of Omaha, Nebraska utilizes a novel scheduling system called Modular scheduling. This system offers numerous advantages over the standard school day in terms of student learning and faculty development. Modular Scheduling allows teachers to design the structure of their own classes by adjusting the frequency, duration and location of each of their daily lessons. Additionally, teachers are able combine their classes with those of other teachers and team-teach. Modular scheduling also allows for open periods in both students’ and teachers’ schedules. During this time, students are able to complete school work or seek supplemental instruction with a teacher who is also free. Teachers are able to use their open mods to plan, meet in teams and help students who have fallen behind. Currently, a semester’s class schedules are constructed over the course of a seven week period by a full-time employee using a computer program developed in FORTRAN®. The process is extremely tedious and labor intensive which has led to considerable wasted time, cost and frustration. This thesis presents a novel scheduling program called the SMART Scheduler that is able to do in seconds what previously took weeks to accomplish. Once parameters have been input, The SMART Scheduler is able to create cohesive class schedules within a modular environment in less than 6 seconds. The research presented describes the steps that were taken in developing the SMART Scheduler as well as computational results of its implementation using actual data provided by WHS. The goal of this research is to enable WHS and other schools to efficiently and effectively utilize modular scheduling to positively affect student learning.

Master of Science / Department of Industrial and Manufacturing Systems Engineering / Todd Easton / Integer programs (IPs) are mathematical models that can provide an optimal solution to a variety of different problems. They have the ability to maximize profitability and decrease wasteful spending, but IPs are NP-complete resulting in many IPs that cannot be solved in reasonable periods of time. Cutting planes or valid inequalities have been used to decrease the time required to solve IPs. These valid inequalities are commonly created using a procedure called lifting. Lifting is a technique that strengthens existing valid inequalities without cutting off feasible solutions. Lifting inequalities can result in facet defining inequalities, the theoretically strongest valid inequalities. Because of these properties, lifting procedures are used in software to reduce the time required to solve an IP. This thesis introduces a new algorithm for synchronized simultaneous approximate lifting for multiple knapsack problems. Synchronized Simultaneous Approximate Lifting (SSAL) requires O(|E1|SLP_|E1|+|E2|,m + |E1|2) effort, where |E1| and |E2| are the sizes of sets used in the algorithm and SLP is the time to solve a linear program. It approximately uplifts two sets simultaneously to creates multiple inequalities of a particular form. These new valid inequalities generated by SSAL can be facet defining. A small computational study shows that SSAL is quick to execute, requiring fractions of a second. Additionally, applying SSAL inequalities to large knapsack problem enabled commercial software to solve faster and also eliminate off the initial linear relaxation point.

Master of Science / Department of Industrial & Manufacturing Systems Engineering / Todd W. Easton / Integer programs (IPs) are a commonly researched class of decision problems. These problems are used in various applications to help companies, governments, or individuals make better decisions by determining optimal resource allocations. While IPs are practical tools, they require an exponential amount of effort to solve, unless P = NP. This fact has led to much research focused on reducing the time required to solve IPs. Cutting planes are a commonly used tool for reducing IP solving time. Lifting, a process of changing the coefficients in an inequality, is often employed to strengthen cutting planes. When lifting, the goal is often to create a facet defining inequality, which is theoretically the strongest cutting plane. This thesis introduces two new lifting procedures for the Node Packing problem. The Node Packing problem seeks to select the maximum number of nodes in a graph such that no two nodes are adjacent. The first lifting method, the Simultaneous Lifting Expansion, takes two inequalities and combines them to make a stronger cut. It works for any two general classes of inequalities, as long as the requisite graph structures are met. The second method, the Cliques On Odd-holes Lifting (COOL) procedure, lifts from an odd-hole inequality to a facet defining inequality. COOL makes use of the Odd Gap Lifting procedure, an efficient method for finding lifting coefficients on odd holes. A computational study shows COOL to be effective in creating cuts in graphs with low edge densities.

Master of Science / Department of Industrial & Manufacturing Systems Engineering / Todd W. Easton / Integer programs (IPs) are mathematical models that can provide organizations with the ability to optimally obtain their goals through appropriate utilization and allocation of available resources. Unfortunately, IPs are NP-complete in the strong sense, and many integer programs cannot be solved. Introduced by Gomory, lifting is a technique that takes a valid inequality and strengthens it. Lifting can result in facet defining inequalities, which are the theoretically strongest inequalities; because of this, lifting techniques are commonly used in commercial IP software to reduce the time required to solve an IP. This thesis introduces two new algorithms for exact simultaneous up lifting multiple sets into binary knapsack problems and introduces sequential simultaneous lifting. The Dynamic Programming Multiple Lifting Set Algorithm (DPMLSA) is a pseudopolynomial time algorithm bounded by O(nb) effort that can exactly uplift an arbitrary number of sets. The Three Set Simultaneous Lifting Algorithm (TSSLA) is a polynomial time algorithm bounded by O(n2) and can exact simultaneously up lift three sets. The simultaneously lifted inequalities generated by the DPMLSA and the TSSLA can be facet defining, and neither algorithm requires starting with a minimal cover. A brief computational study shows that the DPMLSA is fast and required an average of only 0.070 seconds. The computational study also shows these sequential simultaneously lifted inequalities are useful, as the solution time decreased by an overall average of 18.4%. Therefore, implementing the DPMLSA should be beneficial for large IPs.

Master of Science / Department of Industrial & Manufacturing Systems Engineering / Todd W. Easton / Epidemics have been modeled mathematically as a way to safely understand them. For many of these mathematical models, the underlying assumptions they make provide excellent mathematical results, but are unrealistic for practical use. This research branches out from previous work by providing a model of the spread of infectious diseases and a model of quarantining this disease without the limiting assumptions of previous research. One of the main results of this thesis was the development of a core simulation that rapidly simulates the spread of an epidemic on a contact network. This simulation can be easily adapted to any disease through the adjustment of many parameters. This research provides the first definition for a quarantine cut and an ellipsoidal geographic network. This thesis uses the ellipsoidal geographic network to determine what is, and what is not, a feasible quarantine region. The quarantine cut is a new approach to partitioning quarantined and saved individuals in an optimized way. To achieve an optimal quarantine cut, an integer program was developed. Although this integer program runs in polynomial time, the preparation required to execute this algorithm is unrealistic in a disease outbreak scenario. To provide implementable results, a heuristic and some general theory are provided. In a study, the heuristic performed within 10% of the optimal quarantine cut, which shows that the theory developed in this thesis can be successfully used in a disease outbreak scenario.

Master of Science / Department of Industrial & Manufacturing Systems Engineering / Todd W. Easton / Integer programming (IP) is a powerful technique used by many companies and organizations to determine optimal strategies for making decisions and managing resources to achieve their goals. One class of IP problems is the multiple knapsack (MK) problem. However, MK and other IP problems, are extremely complicated since they are ${\cal NP}$-hard problems. Furthermore, there exist numerous instances that can not be solved. One technique commonly used to reduce the solution time for IP problems is lifting. This method, introduced by Gomory, takes an existing valid inequality and strengthens it. Lifting has the potential to form facet defining inequalities, which are the strongest inequalities to solve an IP problem. As a result, lifting is frequently used in integer programming applications. This research takes a broad approach to simultaneous lifting and provides its theoretical background for. The underlying hypergraphic structure for simultaneous lifting in an MK problem is identified and called a constellation. A constellation contains two hypercliques and multiple hyperstars from various conflict hypergraphs. Theoretical results demonstrate that a constellation induces valid inequalities that could be obtained by simultaneous lifting. Moreover, these constellation inequalities can be facet defining. The primary advancements, constellations and the associated valid inequalities, of this thesis are theoretical in nature. By providing the theory behind simultaneous lifting, researchers should be able to apply this knowledge to develop new algorithms that enable simultaneous lifting to be performed faster and over more complex integer programs.

Master of Agribusiness / Department of Agricultural Economics / Jason Bergtold / ABSTRACT Grands Moulins d'Abidjan (GMA) is a flour milling company operating in Côte d'Ivoire. It wishes to determine the optimal blend of wheat and additives that minimizes its costs of production while meeting its quality specifications. Currently, the chief miller selects the mix of ingredients. The management of the company would like to dispose of a scientific tool that challenges the decisions of the chief miller. The thesis is about building and testing this tool, an optimization model. GMA blends up to six ingredients into flour: soft wheat, hard wheat, gluten, ascorbic acid and two types of enzyme mixes. Quality specifications are summarized into four flour characteristics: protein content, falling number, Alveograph W and specific volume of a baguette after four hours of fermentation. GMA blending problem is transformed into a set of equations. The relationships between ingredients and quality parameters are determined with reference to grains science and with the help of linear regression. The optimization model is implemented in Microsoft Office Excel 2010, in two versions. In the first one (LP for Linear Programming model), it is assumed that weights of additives can take any value. In the second one (ILP for Integer Linear Programming model), some technical constraints restrain the set of values that weights of additives can take. The two models are tested with Premium Solver V11.5 from Frontline Systems Inc., against four situations that actually occurred at GMA in 2011 and 2012,. The solutions provided by the model are sensible. They challenge the ones that were actually implemented. They may have helped GMA save money. The optimization model can nevertheless be improved. The choice of relevant quality parameters can be questioned. Equations that link ingredients and quality parameters, and particularly those determined with the help of linear regression, should be further researched. The optimization model should also take into account some hidden constraints such as logistics that actually influence the decision of GMA chief miller. Finally, sensitivity analyses may also be used to provide alternative solutions.

Master of Science / Department of Industrial and Manufacturing Systems Engineering / Jessica L. Heier Stamm / Gifts-in-kind (GIK) donations negatively affect the humanitarian supply chain at the point of receipt near the disaster site. In any disaster, as much as 50 percent of GIK donations are irrelevant to the relief efforts. This proves to be a significant issue to humanitarian organizations because the quantity and type of future GIK are uncertain, making it difficult to account for GIK donations at the strategic planning level. The result is GIK consuming critical warehouse space and manpower. Additionally, improper treatment of GIK can result in ill-favor of donors and loss of donations (both cash and GIK) and support for the humanitarian organization. This thesis proposes a robust facility location approach that mitigates the impact of GIK by providing storage space for GIK and pre-positions supplies to meet initial demand. The setting of the problem is strategic planning for hurricane relief along the Gulf and Atlantic Coasts of the United States. The approach uses a robust scenario-based method to account for uncertainty in both demand and GIK donations. The model determines the location and number of warehouses in the network, the amount of pre-positioned supplies to meet demand, and the amount of space in each warehouse to alleviate the impact of GIK. The basis of the model is a variant of the covering facility location model that must satisfy all demand and GIK space requirements. A computational study with multiple cost minimizing objective functions illustrates how the model performs with realistic data. The results show that strategic planning in the preparedness phases of the disaster management cycle will significantly mitigate the impact of GIK.