A new active-passive approach for the control of noise radiated from a small axial fan was investigated. The approach involved the installation of an axial fan into a short duct with both passive and active noise control functions. First, a systematic methodology for the analytical modeling of finite-length ducts with multiple discontinuities was formulated. The procedure involved the modeling of a duct as a collection of simple duct sections, which were interconnected at multiple junctions. Analytical studies have shown that a short lined duct provides passive noise reduction effects through the mass-loading effect of the duct air volume at low frequencies and the sound absorption by a passive liner at high frequencies. It was also shown that active control can provide further noise attenuations at low-to-mid frequencies, thereby enhancing the overall noise control performance. Two alternate designs of active-passive noise control fan duct were considered. One was a simple non- segmented duct with a 2x2 active control and the other was an internally segmented duct with an 8x8 active control. It was indicated that the latter design possesses a significantly higher global noise control potential than the former with respect to both bandwidth and attenuation level. This was attributed to the reduction of the unwanted pressure contributions from the duct cross modes through the high frequency shifting of the associated cut-on frequencies. The experimental validation of the noise control approach was also carried out. An active-passive noise control fan duct incorporating the segmented duct design with 8x8 active control was constructed in conjunction with a hybrid feedforward-feedback control system. Experimental results have shown significant reductions in the total fan noise power associated with the first four BPF tones by the feedforward control and the broadband fan noise power by the feedback control. The overall active-passive noise control characteristics were observed to be in accordance with the analytical results. / Ph. D.

Unmanned aerial vehicles (UAVs) are increasingly being used for both military and commercial applications to replace more costly and dangerous manned operations. Vehicles with vertical take-off and landing (VTOL) and hovering capabilities are of interest for functions such as surveillance and inspection where the ability to hold the position of the vehicle is desired. Ducted fan vehicles are of particular interest because of their high efficiency per unit diameter when compared to the more commonly seen multirotor vehicles. This makes ducted fan UAVs very well suited for size-constrained missions such as indoor inspection or urban reconnaissance. However, the advantages of ducted fans come at the cost of complex nonlinear dynamics which present challenging modeling and control problems. This thesis provides a detailed discussion of the instrumentation, modeling, and control of a ducted fan UAV. The dynamic model of the UAV is computed from a simplified parametric model. Unknown parameters of the model are found from system identification based on flight data. Synthesis of a linear state feedback controller based on this model is discussed, and it is demonstrated in hardware that this controller can effectively stabilize the vehicle. / Master of Science

This thesis creates an improved fan experience creating the heart of a city through a design that the community can call home throughout the year. It extends the design of sports stadiums to include the fan experiences throughout the interior and the community experiences throughout the exterior to merge. By combining the stadium and city into experiential layering, the architectural decisions to form pedestrian streets and programmatic features can enhance the fan experiences and community experiences to merge through materials, structures, and spaces. The thesis creates an iconic entertainment hub that allows these experiences to expand into the city of Chicago, Illinois, USA. / Master of Architecture

An innovative implementation of the Herschel-Quincke tubes concept for the reduction of noise from turbofan engines is proposed here. The approach consists of installing circumferential arrays of Herschel-Quincke (HQ) tubes or waveguides in the inlet of the turbofan engine. An analytical technique was developed to predict the effects of HQ tubes applied to circular inlets. The modeling technique involves modeling the tubes-inlet interfaces as finite piston sources that couple the acoustic field inside the inlet with the acoustic field within the HQ tubes. An optimization technique based on genetic algorithms was also developed to be able to design and optimize the system parameters. The accuracy of the model was validated with experimental data obtained from two types of turbofan engines. Analytical predictions are shown to correlate well with experimental data. The analytical model is then used to provide insight into the noise control mechanisms involved in the system. It is shown that the energy in an incident mode is in part reflected back to the fan and that some energy is also scattered into other higher-order modes. Thus, the suppression of a particular mode is due to the combination of the scattered contributions from the various incident modes. The effects of the system parameters were analyzed and parametric studies were conducted. Different configurations for the arrays of HQ tubes such as helical patterns or tubes at an angle with respect to the inlet axis were also investigated. The results show the great potential of the HQ tubes system to reduce noise from turbofan engines. / Master of Science

Alluvial fan surfaces in the Atacama Desert of northern Chile preserve evidence of recent, precipitation-driven, surface flows. Determining the hydrologic characteristics of these flows is important for understanding the effects of rare yet significant storms in the region. Flow reconstruction, runoff analysis, and comparison with climatological data yield surface activation recurrence intervals of ~1-20 years for three small fans and associated catchments proximal to Iquique and Antofagasta. Relatively short-lived and intense precipitation events (1-3 hour, > 4 mm/hr) are required to mobilize and transport the largest surface grains. Modeled discharges provide minimum constraints on the rates of precipitation that yield surface-forming flows in the hyper-arid region. The results of this study aid in understanding the evolution of various surfaces in the region. In particular, results provide a clear indication of the ability of a particular storm event --i.e., precipitation rate to activate a surface. / Master of Science

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Large air‐cooled heat exchangers and condensers make use of fan arrays to provide cooling. The performance of the fan arrays are however negatively affected by distorted inlet conditions. Given the size of these fans, quantifying exactly what the detrimental effects are is practically impossible. This serves as motivation for developing a scaled multi‐fan testing platform that is able to mimic the behaviour of a full‐scale array but at a more measureable and manageable scale. This investigation was conducted in two parts. A Reynolds number investigation was conducted to determine what effect incorporating Reynolds number effects will have on the scaled fan performance. Computational fluid dynamics (CFD) was used to determine where turbulent transition onset occurs on the full‐scale fan blades and trip wires were then sized and positioned appropriately to recreate the same transition effect. From this initial investigation it was found that the trip wires have an allround negative impact on fan performance but when compensated for by increasing the blade angle, the tripped fan static pressure rise performance is comparable with the non‐tripped fan performance. This suggests that the Reynolds number effects may be ignored for this scaled fan testing investigation. Scaled equivalents of the fans in cooling arrays were tested in a three row multi‐fan array which, using symmetry, represents a typical bay in a full‐scale installation. Various platform heights were simulated and the corresponding decrease in system performance was compared to a model formulated to predict how fan volumetric effectiveness decreases with platform height. The model deviated from the test data at very low platforms heights. A replacement fan for the scaled equivalent fan was tested while installed as the edge fan of a multi‐fan array, the fan worst affected by any inlet disturbance, and was found to perform similarly to the scaled equivalent fan for most platform heights but exceeded the scaled equivalent fan’s performance for the lowest platform height and the most adverse conditions. This proves the effectiveness of the replacement fan as an edge fan. / AFRIKAANSE OPSOMMING: Groot lugverkoelde warmteruilers maak gebruik van waaier matrikse om verkoeling te voorsien. Die verrigting van die waaieropstelling word egter negatief beïnvloed deur versteurde inlaattoestande. Gegewe die grootte van hierdie waaiers is daar geen praktiese metode om die nadelige invloed van die versteurde inlaattoestande te kwantifiseer nie. Hierdie dien as motivering vir die ontwikkeling van ‘n multi‐waaier toetsplatform wat daartoe in staat is om die gedrag van die volskaal opstelling na te boots maar op ‘n baie meer meetbare en hanteerbare skaal. Hierdie ondersoek was uitgevoer in twee dele. ‘n Reynoldsgetal ondersoek was uitgevoer om te bepaal watter impak dit sal hê op die skaalwaaier verrigting indien die Reynolds getaleffekte ingesluit word in die toetswerk. Berekende vloeidinamka (BVD) was gebruik om te bepaal waar turbulente oorgang voorkom op die volskaal waaierlemme en pooitjiedrade was geselekteer en geposisioneer hiervolgens om dieselfde oorgang te herskep. Vanuit hierdie aanvanklike ondersoek was dit gevind dat die pooitjiedrade ‘n algehele afname in verrigting tot gevolg het, maar wanneer dit oorkom word deur die lemhoek op te stel, die gedrag en verrigting van die gepooitjiede waaier soortgelyk is aan die van die nie‐gepooitjiede waaier. Hierdie gedrag stel voor dat die Reynoldsgetalle maar geïgnoreer kan word vir hierdie skaalwaaier toetswerk. Gelykwaardige skaalwaaiers van die wat in bedryf is in volskaal opstellings was getoets in ‘n drie ry multi‐waaier opstelling wat, deur simmetrie, verteenwordigend is van ‘n tipiese straat in ‘n volskaal opstelling. Verskeie platformhoogtes was gesimuleer en die ooreenstemmende afname in stelsel verrigting was vergelyk met ‘n model wat geformuleer is juis om te voorspel hoe die volumetriese effektiwiteit afneem met platformhoogte. Die model wyk af van die toetsdata by baie lae platform hoogtes. ‘n Vervangingswaaier vir die aanvanklike geskalleerde waaier was getoets as ‘n randwaaier, die waaier wat die ergste benadeel word deur versteurde inlaattoetstande, in die multi‐waaier opstelling. Die vervangingswaaier het soortgelyk aan die aanvanklike waaier verrig vir meeste platformhoogtes, maar oortref die aanvanklike waaier se werksverrigting by die laagste platformhoogte en mees ongunstige toestande. Hierdie bewys die vermoëns van die vervangingswaaier as ‘n randwaaier.

The topic of my thesis is conning in the Czech Republic. Conning stands for actions, which take place at conventions of fans of the fantasy genre called cons. Ethnographic study consist of two circuits. The first one focuses on cons, and their different aspects of realization, as well as services, including mechandising. The second on is dedicated to participants of this kind of event. The research focuses not only on their activity at conventions, but also reflects the consumption of the genre and partecipation of related activities. The theoretical part was based on the specialist literature. Theoretical bases served to define research questions. Methods used for data collection include participant observation, semi-structured ethnographic interviews, analysis of documents, informal and unstructured ethnographic interviews and questionnaires. Timeframe for data collection is the period from June 2015 to April 2016. For analysis were used the grounded theory principles, namely open and axial coding. The output is an paradigmatic model. Research identifies characteristic elements of conning in the Czech Republic, differences between domestic and foreign cons and experience of the participants. Also illustrates the role of a fantasy genre fiction in the life of participants, and their perception of...

The popularity of wearing costumes and masks has a long tradition. The phenomenon called cosplay began to be discussed for the first time in the 1980s. Cosplayers are fans of media content that not only wear costumes, but they also try to imitate the character's character on festivals. Some individuals, thanks to their activity, become celebrities themselves within the community. Fans may not always be just a passive group of recipients of media content. This thesis focuses on how these positions can be achieved and how the hierarchy is shaped in the Czech cosplay community. The theoretical framework is based on findings of fan studies. Methods used for data collection include participant observation and semi-structured interviews. The timeframe for data collection is the period from May 2018 to October 2018. For analysis were used the grounded theory principles, namely open and axial coding. The output is a paradigmatic model. This research has brought new information related to the topic of hierarchy in fan communities. Not only has the high activity of the individuals but also the social ties had an influence on hierarchy formation. This work also reflected the Czech cosplay community.

The present study examined how a fan's desire to participate in superstitious behaviors depends on team identification, team location, and game outcome. The study is a 2 (team identification: high vs. low) x 2 (game outcome: close game vs. blowout) x 2 (location of team: local vs. distant) between subjects factorial design. Participants for the current study included 234 students, recruited from undergraduate psychology classes at Western Kentucky University. Participants completed the Sport Spectator Identification Scale, read a randomly assigned vignette differing in team location and game outcome, and filled out the Superstition Questionnaire to measure their desire to complete superstitious behaviors based on the vignette. They also filled out the Desirability of Control Scale, and the Depression Anxiety Stress Scales to account for the possible covariates of desirability of control and anxiety level. An analysis of the covariates showed that there were no significant correlations between desirability of control or anxiety level and the desire to complete superstitious behaviors. Results indicated that highly identified fans reported wanting to perform more superstitious behaviors than low identified fans. However, no main effect was found for game outcome or team location, and there were no interactions. This finding reiterated the importance of team identification and its effects on the fan. The study also brought new variables to the table, game type and team type, that could be used in future research.

Zugl.: Hildesheim, Univ., Diss., 2006