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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

An experimental and numerical study of an automotive cooling module

Rynell, Anders January 2017 (has links)
Heavy vehicles are major emitters of noise. Especially at idle or low vehicle speeds a large portion of the noise emanates from the fan that forces the flow through the cooling module. The aim of this work is to investigate and reveal aerodynamic and acoustic installation effects linked to the cooling package. This introduces a multidisciplinary approach involving examination of the flow field, sound generation and sound propagation. The work includes two main parts: an experimental and a numerical part. The cooling module used throughout this work, named reduced cooling module, primarily includes a radiator, a shroud, a fan and a hydraulic engine to simplify the aeroacoustics analysis. The experimental part comprises measurements of the sound emanated from the cooling package. A new approach to the spectral decomposition method is developed yielding the fan sound power or spectrum to be formulated as a product of a source part and a system part scaling with the Strouhal number and the Helmholtz number. Also, a separate determination of the transmission loss of the radiator is performed. The impact of the radiator on the transmitted noise was found to be negligible. The numerical part incorporates comparisons from two aeroacoustics studies; a configuration where the fan is forced to operate at a fixed operation point and measured flow and turbulence statistics are available and the reduced cooling module. A hybrid turbulence modeling technique, IDDES, is adopted for the flow simulations. The sound propagation is calculated by the Ffowcs-Williams and Hawkings acoustic analogy when assuming a free-field sound propagation and by a finite element solver in the frequency domain to capture the installation effects. The simulated SPL conforms to the measured SPL and the blade response to the turbulent inflow and to the tip resolution, respectively, produce noise which spectral shape distribution is modified in accordance with earlier experimental findings published. Furthermore, the influence of an upstream radiator in close contact with the fan on the flow and sound fields is investigated. Here, the simulated aeroacoustic characteristics were found to change similarly to the acoustic measurements with and without radiator.
32

Fanfikce a intertextualita / Fanfiction and Intertextuality

Abbasová, Veronika January 2013 (has links)
Summary: The aim of this thesis was to classify the intertextual relationship entered by fan fictions. A fan fiction is a modern literary form, which developed mainly in the second half of the 20th century and has been experiencing real boom since the beginning of the Internet era. Intertextuality is a basic condition for the existence of fan fictions, as these are derivatives of other texts (usually certain popular culture products). Fan fiction is created in fandom as a product of fan activity. These texts are unauthorized, they don't bring profit to their creators and can have a subversive character. Besides the basic intertextual relation to canon, fan fictions enter into a variety of other intertextual relationships. Among these are relationships to the cultural canon similar to those formed by traditional literature. Fan fiction borrows motives and plotlines from fairytales, myths, the Bible, poetry and songs, fiction and movies. On the other hand, fan fiction also enters into such intertextual relationships that are specific for this literary genre. These are so-called crossovers - mixing of several fictional worlds, and relationships to other works of fan fiction - parodies, continuing other authors' stories, replies to so-called challenges and prompts (ideas for stories).
33

Analýza práce s fanoušky HC Pardubice / Work with fans of HC Pardubice

Ľuptovský, Vít January 2009 (has links)
Main goal of this thesis is to describe and analyze factors that influence attendance of sport events (matches) of HC Pardubice with the focus on the work with fans as one of the assumed factors of attendance rate. The theory part si focused on theories which refer to this problem. These are: demand for sport and its determinants, theory of sport product and fan definition. At the beginning of practice part, the thesis describes characteristics of the hockey club. Next chapter deals with factors which influence the attendance rate with the goal to determine the significance of particular factors. Subsequently the thesis analyzes the work with fans with special attention to sport product of the club, its price, sales promotion and other elements of club's marketing. Individual chapters are supplemented by the results of the research of HC Pardubice supporters sample that refer to the content of each chapter. In conclusion, the work with spectators is evaluated and possibilities of spectator care development are propounded.
34

Anime Music Videos and Storytelling: Performing Channels of Communication

Harris, Sabra 27 October 2016 (has links)
Anime Music Videos (AMVs) are transformative works that provide channels of communication between the viewer and the viewed. The editors who make AMVs have distinct communities built on the evolution of anime conventions in the United States but have prospered and transformed globally. In the performance of technology, AMV editors find ways of using mass-mediated texts to express themselves, to convey emotions, and to communicate social messages. They make new associations by combining materials and display these associations in sophisticated ways on social forums like the Internet and anime conventions. The associations are interpretive and articulate how storytelling, rather than a fixed and linear one-way flow, is nonlinear, a negotiation between the storytelling performer and audience.
35

Effects of distortion on modern turbofan tonal noise

Daroukh, Majd 06 July 2017 (has links) (PDF)
Fuel consumption and noise reduction trigger the evolution of aircraft engines towards Ultra High Bypass Ratio (UHBR) architectures. Their short air inlet design and the reduction of their interstage length lead to an increased circumferential inhomogeneity of the flow close to the fan. This inhomogeneity, called distortion, may have an impact on the tonal noise radiated from the fan module. Usually, such a noise source is supposed to be dominated by the interaction of fan-blade wakes with Outlet Guide Vanes (OGVs). At transonic tip speeds, the noise generated by the shocks and the steady loading on the blades also appears to be significant. The increased distortion may be responsible for new acoustic sources while interacting with the fan blades and the present work aims at evaluating their contribution. The effects of distortion on the other noise mechanisms are also investigated. The work is based on full-annulus simulations of the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. A whole fan module including the inlet duct, the fan and the Inlet and Outlet Guide Vanes (IGVs/OGVs) is studied. The OGV row is typical of current engine architecture with an integrated pylon and two different air inlet ducts are compared in order to isolate the effects of inlet distortion. The first one is axisymmetric and does not produce any distortion while the other one is asymmetric and produces a level of distortion typical of the ones expected in UHBR engines. A description and a quantification of the distortion that is caused by both the potential effect of the OGVs and the inlet asymmetry are proposed. The effects of the distortion on aerodynamics are highlighted with significant modifications of the fanblade wakes, the shocks and the unsteady loading on the blades and on the vanes. Both direct and hybrid acoustic predictions are provided and highlight the contribution of the fan-blade sources to the upstream noise. The downstream noise is still dominated by the OGV sources but it is shown to be significantly impacted by the inlet distortion via the modification of the impinging wakes.
36

Experimental analysis of fan noise and performance at the EESC-USP Fan Rig Workbench / Análise experimental de ruído e performance de fan na bancada EESC-USP Fan Rig Workbench

Rocamora Junior, Bernardo Martínez 08 February 2019 (has links)
The study of turbofan aeroacoustics has become important in academia and industry as noise from other aircraft sources, as jet noise, have been reduced. The EESC-USP Fan Rig is a long-duct low-speed fan experimental setup recently built at the Department of Aeronautical Engineering of the University of São Paulo. The objective is to provide a facility for studying fan aeroacoustics with a flexible configuration that allows changes in operational conditions and geometry of the rig so that each of the noise sources can be treated separately. In this work, three experimental campaign were taken aiming to extend the knowledge of this workbench capabilities and to observe the effect that some parameters can have on noise generation. A performance campaign was carried out to characterise the effects of controllable parameters on the aerodynamic characteristics of the flow. Starting from unrestricted flow to 70% area constraint, and a range of fan speeds, several flow measurements that could be translated into performance quantities were taken: volume flow rate, fan total and static pressures, compression ratio, total and net power, and efficiency. The measured compression ratio ranged from 1.00 to 1.02, with maximum axial Mach of 0.13 and maximum total efficiency of 65%. The surge effect, an unstable configuration characterised by rotor blades stall was also observed. Significant differences in fan performance due to the installation of an Inlet Control Device (ICD) and the rotor-stator spacing were not found, except under surge conditions. A parametric campaign was carried out exploring the effects of fan rotational speed, fan loading and rotor-stator spacing. Acoustic measurements were taken using an array of 77 wall-mounted microphones to provide a baseline data set for future comparisons. Hereby, data was processed to obtain the modal decomposition and power spectrum for each configuration. The last proved useful to compare tonal and broadband noise for each configuration. Experimental results indicate that changes in fan rotational speed scale noise generation mechanisms proportionally, do not affect noise spectral shape, and in consequence, are not useful to distinguish noise mechanisms. Although throttling does not seem to exhibit a clear effect on fan noise, it turns out that it is a good approach for cross-comparisons of other parameters\' effect on fan noise, because of its direct modification on the flow structure within the duct. Results also showed that increasing rotor-stator spacing reduces both blade passing frequencies tone levels and the acoustic power of the interaction modes, which are in agreement with results obtained by similar test facilities. In this work a instrumented stator vane was designed using recently available technologies, as 3D printing and the use of MEMS microphones, to measure this pressure fluctuations. Phase-averaging and the signal from a hall sensor were used to separate broadband content in time series. Broadband level distribution were analysed for two span lines of the instrumented stator vane and for a reference microphone located in the inlet antenna. Broadband levels increased with the increase in fan speed and its distribution over these span lines maintained its shape for different speeds. Cross-correlation of the microphones were calculated and showed decay of zero-delay cross-correlation with increase in distance between microphones over the vane. And, finally, the integral length scale, obtained by the integration of zero-delay cross-correlation curve, showed decay with increase in fan speed. The data generated by this work showed good agreements with what was expected from the literature and will help as input data to the semi-analytical and semi-empirical models that are being developed in parallel by the research group. / O estudo da aeroacústica de fan tornou-se importante na academia e na indústria à medida que o ruído de outras fontes nas aeronaves, como o ruído de jato, foram reduzidas. O EESCUSP Fan Rig é um túnel de vento aeroacústico voltado para fans de baixa velocidade, que foi construído recentemente no Departamento de Engenharia Aeronáutica da Universidade de São Paulo. Seu objetivo é prover uma bancada experimental para o estudo dos mecanismos de geração de ruído de fan com uma configuração flexível que permita mudanças nas condições operacionais e geométricas de forma a isolar tanto quanto possível cada uma das fontes. Neste trabalho foram realizadas três campanhas experimentais visando aprofundar os conhecimentos sobre as capacidades da bancada e observar os efeitos no ruído que algumas variações paramétricas podem gerar. Uma campanha de performance de fan foi realizada para quantificar os efeitos dos parâmetros controláveis sobre o as características aerodinâmicas do escoamento. Partindo de escoamento sem restrição até restrição de área de 70%, e para diversas velocidades de rotação do fan, diversas medidas do escoamento foram feitas para que se pudesse calcular as métricas de performance: vazão volumétrica, pressão total e estática do fan, taxa de compressão, potência útil, potência elétrica de entrada e eficiência. Os resultados apontaram para uma taxa de compressão entre 1.0 e 1.02, com Mach axial máximo de 0.13 e eficiência máxima de 65%. Os efeitos de \"surge\", uma configuração instável caracterizada pelo estol das pás do rotor também foi observado. Diferenças significativas na performance do fan devido à instalação de uma Inlet Control Device (ICD) e pelo espaçamento entre rotor e estator não foram encontradas, com exceção em condições de \"surge\". Uma campanha paramétrica para estudo de ruído foi realizada explorando os efeitos da velocidade de rotação e carregamento no fan, espaçamento entre rotor-estator e condição de entrada do escoamento no duto. Os resultados mostraram que o aumento do espaçamento do rotor-estator reduz os níveis tonais nas frequências de passagem das pás (BPFs) a uma taxa de aproximadamente 4dB quanto o espaçamento é duplicado. Os resultados experimentais indicam que as mudanças nos mecanismos de geração de ruído com a velocidade rotacional do fan escalam-se proporcionalmente, não afetam a forma espectral do ruído e, por consequência, não são úteis para distinguir os mecanismos de ruído. Embora a variação no carregamento não pareça exibir um efeito claro no ruído do fan, verifica-se que é uma boa abordagem para comparações cruzadas, em conjunto com a velocidade de rotação, do efeito de outros parâmetros no ruído do fan, já que, desta forma, é possível fazer uma modificação direta na estrutura do escoamento dentro do duto. Os modos Tyler-Sofrin, esperados pela contagem de pás e aletas usadas no conjunto rotor-estator, foram identificados e a potência acústica desses modos de interação acompanham a potências dos respectivos tons no espectro, levando à conclusão que a maior contribuição para o ruído tonal é, de fato, a interação rotor-estator. Também neste trabalho, também foi projetada uma aleta de estator instrumentada, usando tecnologias recentemente disponíveis, como a impressão 3D e o uso de microfones MEMS, para realizar medições de flutuação de pressão na superfície superior da aleta. Um método de processamento de sinal foi desenvolvido, usando a técnica de \"phase averaging\" combinada com o sinal de um sensor Hall para separar o conteúdo de banda larga em séries temporais. A distribuição do nível de ruido banda larga foi analisado para duas linhas na envergadura da aleta instrumentada e em um microfone de referência localizado na antena de microfones. Os níveis de banda larga aumentaram com o aumento da velocidade do fan e a sua distribuição ao longo destas linhas de alcance manteve a sua forma para diferentes velocidades. As correlações cruzadas dos microfones foram calculadas e mostraram o decaimento da correlação cruzada de zero-atraso com o aumento da distância entre os microfones sobre a aleta. Finalmente, a integral do comprimento de escala, obtida pela integração da curva de correlação cruzada de zero-atraso, apresentou decaimento com aumento na velocidade do fan. Os dados gerados por esse trabalho se mostraram de acordo com o esperado na literatura da área e servem de dados de entrada para modelos semi-empíricos e semi-analíticos que vem sendo desenvolvidos paralelamente pelo grupo de pesquisa.
37

Intersection Algebras and Pointed Rational Cones

Malec, Sara 13 August 2013 (has links)
In this dissertation we study the algebraic properties of the intersection algebra of two ideals I and J in a Noetherian ring R. A major part of the dissertation is devoted to the finite generation of these algebras and developing methods of obtaining their generators when the algebra is finitely generated. We prove that the intersection algebra is a finitely generated R-algebra when R is a Unique Factorization Domain and the two ideals are principal, and use fans of cones to find the algebra generators. This is done in Chapter 2, which concludes with introducing a new class of algebras called fan algebras. Chapter 3 deals with the intersection algebra of principal monomial ideals in a polynomial ring, where the theory of semigroup rings and toric ideals can be used. A detailed investigation of the intersection algebra of the polynomial ring in one variable is obtained. The intersection algebra in this case is connected to semigroup rings associated to systems of linear diophantine equations with integer coefficients, introduced by Stanley. In Chapter 4, we present a method for obtaining the generators of the intersection algebra for arbitrary monomial ideals in the polynomial ring.
38

Paper dimensional stability in sheet-fed offset printing : Papperets dimensionsstabilitet i en arkoffsetpress

Strömberg, Malin January 2005 (has links)
In offset printing, dampening solution is used to create a good balance in the process. If too much water is transferred to the paper, the sheet can change its size between the printing units, due to water absorption, and cause a problem with the colour register. This phenomenon is usually referred to as fanout. In this degree project, an investigation was made to see if the paper dimensions changed through its way in the sheet-fed printing process. The instrument Luchs Register Measuring Systems (Lynx) was used, and a method for measuring if the paper changed its dimensions with this instrument, was developed. Paper qualities with three different grammages were used, 90, 130 and 250 gsm. This investigation showed that all paper qualities changed their size with widening in the gripper edge in the range of 10 - 70 µm and in the trailing edge the increase was 10 - 130 µm. The elongations of the papers were in the range of 10- 300 µm. The papers with lowest grammage changed more than the heavier. To see if the print had been affected of the widening and elongation, print quality parameters like relative contrast, dot gain and mottle were correlated with the Lynx data from the sheets. The group of papers that gave correlations were in 130 gsm. The sheets had visual doubling and the combined standard deviation from the Lynx marks K3, K5 and K21 correlated with dot gain. When the variations increased so did the dot gain and this indicates that the doubling was due to the widening. There was also a correlation between the standard deviation from K3 and Mottle. The sheets widened with an average of 30 µm in the gripper edge and since there probably were doubling due to widening it also affected the Mottle values. What the widening depends on is hard to tell. Since widening was so small, it could be due to water absorption, papers being ironed out or maybe the sheets have been flattened out. It probably needs a more detailed investigation to find out what causes the widening. Further investigations about how print quality is affected by the register accuracy of a printing machine should include a print form with measuring areas close to the Lynx marks. The measuring areas should contain fine hairlines, negative text printed with at least two colours and some pictures to evaluate together with standard measuring should give a good knowledge about the subject.
39

Performance of ECM controlled VAV fan powered terminal units

Cramlet, Andrew Charles 15 May 2009 (has links)
Empirical performance models of fan airflow, primary airflow and power consumption were developed for series and parallel variable air volume fan powered terminal units. An experimental setup and test procedure were created to test the terminal units at typical design pressures and airflows. Each terminal unit observed in this study used an 8 in (20.3 cm) primary air inlet. Two fan motor control methods were considered. The primary control of interest was the electronically commutated motor (ECM) controller. Data collected were compared with previous research regarding silicon rectified control (SCR) units. Generalized models were developed for both series and parallel terminal units. Coefficients for performance models were then compared with comparable SCR controlled units. Non-linear statistical modeling was performed using SPSS software (2008). In addition to airflow and power consumption modeling, power quality was also quantified. Relationships between real power (watts) and apparent power (VA) were presented as well as harmonic frequencies and total harmonic distortion. Power quality was recorded for each ECM controlled terminal unit tested. Additional tests were also made to SCR controlled terminal units used in previous research (Furr 2006). The airflow and power consumption performance models had an R2 equal to 0.990 or greater for every terminal unit tested. An air leakage model was employed to account for leakage in the parallel designed VAV terminal units when the internal fan was turned off. For the leakage model, both ECM and SCR controlled units achieved an R2 greater than or equal to 0.918.
40

Modeling of Electronically Commutated Motor Controlled Fan-powered Terminal Units

Edmondson, Jacob Lee 2009 December 1900 (has links)
Empirical models of airflow and power consumption were developed for series and parallel variable air volume fan powered terminal units (FPTUs). An experimental setup and test procedure were developed to test the terminal units over typical operating ranges. The terminal units in this study used either an 8 in. (20.32 cm) or a 12 in. (30.48 cm) primary air inlet. All terminal units utilized electronically commutated motor (ECM) controllers. Data collected were compared against previous data collected for silicon controlled rectifier (SCR) units. Generalized models were developed for both series and parallel units, and compared against models developed for SCR units. In addition to the performance modeling, power factor and power quality data were also collected for each terminal unit. The power quality analysis included recording and analyzing harmonic distortion for current, voltage, and power up to the 25th harmonic. The total harmonic distortion (THD) was also recorded and presented. For the series terminal units, models were developed for fan airflow, fan power, and primary airflow. The models for fan airflow all had R2 values above 0.987. The models for fan power all had R2 values above 0.968. The models for primary airflow all had R2 values above 0.895. For the parallel terminal units, models were developed for leakage, fan airflow, fan power, and primary airflow. All of the leakage models had R2 values above 0.826. All of the fan airflow models had R2 values above 0.955. All of the fan power models had R2 values above 0.922. All of the primary airflow models had R2 values above 0.872. The real power THD was below 1.5 percent for both series and parallel FPTUs. The current THD ranged from 84 percent to 172 percent for series FPTUs and from 83 percent to 183 percent for parallel FPTUs. The voltage THD was below 1.4 percent for both series and parallel FPTUs. The performance models developed will help improve the accuracy of building energy simulation programs for heating, ventilation, and air conditioning (HVAC) systems utilizing ECM controlled FPTUs. Increasing the accuracy of these simulations will allow HVAC system designers to better optimize their designs for specific building types in a wide variety of climates.

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