Thesis (Ph.D.)--University of Nebraska-Lincoln, 2007. / Title from title screen (site viewed Oct. 10, 2007). PDF text: 115 p. : ill. UMI publication number: AAT 3260512. Includes bibliographical references. Also available in microfilm and microfiche formats.

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This work focuses on simulation of core blowing into the core boxes. Mechanical production of cores is now a normal part of any foundry. But can never predict whether core can make right the first time. This situation can be used as a helper QuikCAST simulation program that is able to handle the issue and deal with and can find the optimal basis.

The stable operating range of axial compressors is limited by the onset of rotating stall and surge. Mass injection upstream of the tip of an axial compressor rotor is a stability enhancement approach which can be effective in suppressing stall in tip-critical rotors, and thus increasing the operating range of compressors. In this article, investigations on active flow control related to the rotor tip gap sensitivity are discussed. The experiments were performed in a 1.5-stage low-speed research compressor. Measurements at part speed (80 per cent) and full speed (100 per cent) with varying injection rates are discussed. These tests were performed for two rotor tip clearances of 1.3 per cent and 4.3 per cent of rotor blade tip chord. Results on the compressor map, the flow field as well as transient measurements to identify the stall inception are discussed. Supplementary, the numerical results are compared to the experiments based on the configuration with the greatest benefit in operating range enhancement.

The following essays explore ways in which the environment affects and is affected by organizations. The first essay, “Trust and the Division of Labor” considers that the trust environment of a firm helps determine its structure. Jointly with Stephan Meier and Patryk Perkowski, I show that exogenously imposed culture leads to variation in organizational form. An experiment primes trust using past performance from a pilot study and demonstrate that the level of trust within an organization affects division of labor and consequently organizational productivity. This evidence is consistent with a cross-country link between trust and the division of labor that we observe in data from the European Social Survey. A simple evolutionary game theoretic model is provided to illustrate the results. The second essay, Nobody Likes a Rat”, considers the impact of norms against certain types of behavior (in this case dishonesty) on behavior and organizational composition. Jointly with Ernesto Reuben, I investigate the intrinsic motivation of individuals to report, and thereby sanction, fellow group members who lie for personal gain. We find that when groups can select their members, individuals who report lies are generally shunned, even by groups where lying is absent. This facilitates the formation of dishonest groups where lying is prevalent and reporting is nonexistent. Finally, "NFTs, Volume, and Social Influence" observes how organizations and individuals use environmental cues like rankings and volume for sensemaking in a market with high quality uncertainty. Using observational data scraped from the top 1000 NFT collections I find a significant positive relationship between volume and price. Then, using plausibly exogneous variation in blockchain-level transaction fees, I fit an instrumental variable model which helps validate the causal interpretation that changes in volume lead to changes in price. I further add an experiment on NFTs to tease out two plausible channels through which volume could affect prices: user attention and normative social influence. The experiment finds strong evidence that being told an NFT is higher volume leads subjects to pay more attention to that NFT, whereas this has no significant effect on a subject's reported preference for the NFT. A second experimental treatment, in which subjects were told the NFTs were ordered by volume transaction costs, does observe a significant positive affect on reported preferences (as well as attention).

Food fraud can be traced back to the beginning of second century, but it was not until 2013 that the phenomenon of food fraud received the definition “intentional violation of the rules motivated by economical or financial gain” by the EU. In Sweden, the Swedish Food Agency (Livsmedelsverket) together with the municipal food inspectors work against food fraud. It is essential to detect food fraud in order to protect the Swedish consumers safety and health. The aim of this study is to assess consumers experience about food fraud and their mistrust to any food groups as well as consumers awareness about whistle blowing functions. In addition, differences between consumers and municipal food inspector’s estimation of the extent of food fraud in Sweden will be investigated. The study revealed that 51 % of the consumers have experienced food fraud and 48 % have experienced fear of being exposed to food fraud. Approximately 16 % also have a lack of trust to some food groups. The municipal food inspectors usually only control fraud when receiving tips but only a relatively small group of consumers are aware of the whistle blowing functions. An interesting pattern throughout the report is that meat and meat products scores significant high, both regarding consumers experience of fraud, avoidance of food groups and in ranking of most exposed food group. The study showed no significant difference between the consumers and the municipal food inspector’s estimation of the existent of food fraud in Sweden.

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<p> The foaming process has received increased attention by the rotational molding industry in recent years. The use of metallocene catalyzed polyethylenes for producing a cellular structure is a new development in rotational molding. The objective of this work was to investigate the effects of different chemical blowing agents, resin properties and processing conditions on the structure of foamed metallocene polyethylene and obtain a fundamental understanding of the parameters governing the foam structure and part properties.</p> <p> An experimental study was conducted to produce metallocene polyethylene foams in dry-blending-based rotational foam molding. The physical and cell structure properties of the final foamed parts were examined. The critical processing parameters that optimize the foam structure have been identified through adjustments to the molding conditions.</p> <p> The foaming performance of exothermic and endothermic chemical blowing agents were examined and it was revealed that selecting an appropriate chemical blowing agent was crucial as the foam structure depends significantly on the properties of the blowing agent. Exothermic blowing agents resulted in greater foam density reduction compared to endothermic blowing agents.</p> <p> The effect of rheological properties on the foaming process and foam properties was also examined. Rotomolding experiments were performed in monolayer and skin-foam moldings. Observations indicated that the final foam properties were profoundly influenced by the rheological properties of the polymer materials. There was a good correlation between the foam properties produced in both monolayer and two layer moldings. It was discovered that polymer materials with higher extensional viscosity could provide a promising foaming performance at different processing conditions.</p> <p> The effect of the surface tension of the polymer materials was investigated. It was found that type of reaction of the blowing agent (exothermic/endothermic) and composition of gas generated determine whether the surface tension of the resin contributes to the trend of changes in foam properties.</p> / Thesis / Master of Applied Science (MASc)

The research effort presented in this dissertation consists of employing active trailing edge blowing control to reduce the unsteady stator-rotor interaction in a turbofan simulator. Two active flow control systems with different wake sensing approaches are successfully implemented on the engine simulator. The first flow control system utilizes Pitot probes as flow sensors. Use of Pitot probes as sensors is appropriate as a first step toward a more in depth investigation of active trailing edge blowing control. An upper performance limit in terms of wake-filling can be obtained and serves as the baseline in evaluating other control systems with indirect wake sensors. The ability of the system to achieve effective wake filling when subjected to a change in inlet flow conditions demonstrates the feasibility and advantage of active flow control. Significant tonal noise reductions in the far field are also obtained. The second control system involves using microphones as indirect wake sensors. The significance of these acoustic sensing approaches is to provide a practical TEB approach for realistic engines implementations. Microphones are flush mounted on the inlet case to sense the tonal noise at the blade passing frequency. The first sensing approach only uses the tone magnitude while the second novel sensing approach utilizes both the tone magnitude and phase as error information. The convergence rate of the second sensing approach is comparable with that of the Pitot-probe based experiments. The acoustic results obtained from both sensing approaches agree well with those obtained using Pitot probes as sensors. In addition to the experimental part of this research, analytical studies are also conducted on the trailing edge blowing modeling using an aeroacoustic code. An analytical model for trailing edge blowing is first proposed. This model is then introduced into the two-dimensional aeroacoustic code to investigate effect of various trailing edge blowing managements in the tonal sound generation. / Ph. D.