57,394 research outputs found
Using performance assessment in secondary school mathematics: an empirical study in a Singapore classroom
No full textThis article reports an exploratory study on using performance assessment in mathematics instruction in a high-performing secondary school in Singapore. An intact mathematics class participated in the study, and received chapter-based performance tasks as intervention during regular mathematics lessons for about one and a half school years. The performance tasks used included authentic and/or open-ended tasks. The students’ academic achievements and attitudes in mathematics were compared with a comparison class that did not receive the intervention. Both quantitative and qualitative data were collected, mainly through questionnaire surveys, performance task tests, conventional school exams, and interviews with students and teachers. The results suggest that the students receiving the intervention performed significantly better than their counterparts in solving conventional exam problems, and in general they also showed more positive changes in attitudes towards mathematics and mathematics learning. The students from the experimental class also expressed positive views about the benefits of using performance tasks in promoting their ability in higher order thinking, though no statistically significant difference was detected between the two classes of students in solving unconventional tasks before and after intervention. Overall, the results appear to support teachers’ using contextualised problems in real life situations and open-ended investigations in students’ learning of mathematic
Richardson, Barbauld, and the construction of an early modern fan club
No full textMPhilMuch has been written about the life and long works of the eighteenth century epistolary novelist, Samuel Richardson, but the prospect of his position as the first celebrity novelist – responsible for courting his own fame as well as initiating his own fan club – has largely been ignored. The body of manuscripts housed at the National Art Library in the Victoria and Albert Museum in London provides the modern scholar with evidence of the skeletal beginnings of an early fan club. This thesis aims to show how these manuscripts were turned into a saleable commodity by the publisher and entrepreneur Richard Phillips, while under the guiding hand of another, slightly later, literary celebrity, Anna Laetitia Barbauld. In order to restore Richardson’s reputation amongst a new nineteenth century audience, Barbauld was required to construct her own idea of him as an eighteenth century celebrity author, and in doing so the insecurities of a self-professed, apparently diffident man, are revealed. Barbauld’s capacious, but heavily edited selection of letters is analyzed in this thesis, providing ample evidence that Richardson’s correspondents were more than just eager letter writers. By using Barbauld’s biography of Richardson this thesis aims to show how she manipulates the genre of life writing in her construction of him.
This thesis offers an alternative reading of how the Richardson manuscripts are viewed, redefining them as not simply a collection of letters, but as a collective entity, deliberately selected and archived as evidence of an early modern fan club, and its celebrity managing director
Development of a rotor model for the numerical simulation of helicopter exterior flow-fields
No full textIncludes bibliographical references (leaves 84-85).A numerical methodology is developed to model the effect of a rotor on the surrounding flow-field. The model calculates the time-averaged aerodynamic forces exerted on the air by the fan blades within the blade-swept region, and permits the user to specify blade properties such as cross-sectional profile and orientation at a particular radial and azimuthal location. The calculated forces are included as source terms within the Reynolds-averaged Navier-Stokes equations for an incompressible fluid, which are solved by the commercial CFD solver, FLUENT. The effects of turbulence are incorporated through the use of Launder and Spalding's k-g turbulence model. This method is selected as being the most efficient use of the resources available, giving the economic advantages of a steady simulation, while allowing radial and azimuthal variations of rotor characteristics. In order to validate the accuracy of the numerical model for both aligned and non-aligned inflow conditions, results are compared with experimental data reported for an axial flow fan. Agreement between experimental and numerical results is excellent to good. Fan static pressure rise is closely predicted by the numerical solution, while fan power consumption and fan static efficiency are under and over-predicted respectively. This error may be attributed to frictional losses not accounted for in the numerical model. These include physical rotational instabilities, leading to increased mechanical losses, and tip effects due to the clearance between the fan blade tips and the fan casing. Trends are nevertheless consistently predicted by the numerical model for inflow angles up to 45°, and for the range of blade pitch settings used. The adverse effect of off-axis inflow on the fan static pressure rise is numerically predicted, while fan power consumption is found to remain independent of inflow angle, as had been experimentally observed. The rotor model is finally integrated with the fuselage of the CIRSTEL (Combined Infra-Red Suppression and Tail rotor Elimination) prototype in an analysis of the helicopter exterior flow-field. No experimental data for this configuration was available for validation purposes. However, the model is used in the simulation of several common helicopter flight conditions. Results are presented graphically, and generally indicate good agreement with physically observed phenomena
Experimental study of blade thickness effects on the global and local performances of a Controlled Vortex Designed axial-flow fan
No full textThe purpose of this work is to study the effects of blade thickness on the performances of an axial-flow fan. Two fans that differ only in the thickness of their blades were studied. The first fan was designed to be part of the cooling system of an automotive vehicle power unit and has very thin blades. The second fan has much thicker blades compatible with the rotomoulding conception process. The global performances of the fans were measured in a test bench designed according to the ISO-5801 standard. The curve of aerodynamics characteristics (pressure head versus ow-rate) is slightly steeper for the fan with thick blades, and the nominal point is shifted towards lower flow-rates. The efficiency of the thick blades fan is lower than the efficiency of the fan with thin blades but remains high on a wider flow-rate range. The mean velocity field downstream of the rotors are very similar at nominal points with less centrifugation for the thick blades fan. The thick blades fan moreover maintains an axial exit-flow on a wider range of flow-rates. The main dierences concern local properties of the flow: Phase-averaged velocities and wall pressure fluctuations strongly differ at the nominal flow-rates. The total level of fluctuations is lower for the thick blades fan that for the thin blades fan and the spectral decomposition of the wall fluctuations and velocity signals reveal more harmonics for the thick blades fan, with less correlation between the different signals. For this kind of turbomachinery, the use of thick blades could lead to a good compromise between aerodynamic and acoustic performances, on a wider operating range
Are Bayesian Fan Charts Useful for Central Banks? Uncertainty, Forecasting, and Financial Stability Stress Tests
No full textThis paper shows how fan charts generated from Bayesian vector autoregression (BVAR) models can be useful for assessing 1) the forecasting accuracy of central banks’ prediction models and 2) the credibility of stress tests carried out to evaluate financial stability. Using unique data from the Czech National Bank (CNB), we compare our BVAR fan charts for inflation, GDP growth, interest rate and the exchange rate to those of the CNB, which are based on past forecasting errors. Our results suggest that in terms of the Kullback-Leibler Information Criterion, BVAR fan charts typically do not outperform those of the CNB, providing a useful cross-check of their accuracy. However, we show how BVAR fan charts can rigorously deal with the non-negativity constraint on the nominal interest rate and usefully complement the official fan charts. Finally, we put forward how BVAR fan charts can be useful for assessing financial stability and propose a simple method for evaluating whether the assumptions of banks’ stress tests about the macroeconomic outlook are sufficiently adverse.Bayesian vector autoregression, fan chart, inflation targeting, stress tests, uncertainty.
Use of fan rig data for the understanding and prediction of fan broadband noise and noise changes due to a variable area nozzle
No full textThis thesis presents the results of the research component of this EngD, entitledUse of fan rig data for the understanding and prediction of fan broadband noise and noisechanges due to a variable area nozzleAs suggested by the title, fan rig noise measurements form an integral part of this thesis. Theanalysis of a database of rig noise measurements forms the first section of this thesis, in twoparts. The first part describes the analysis of a set of fan rig noise measurements, including thevariation of fan broadband and tone noise in forward and rearward arcs. The second partexamines a large database of fan rig noise measurements, and attempts to derive correlationsof fan broadband noise and fan performance parameters. Cluster Analysis, PrincipleComponent Analysis, and Regression Analysis are used to understand and describe theunderlying physics of broadband noise generation and the relationships between thesepredictors.The second section of this thesis uses a cascade broadband noise model to investigate rotorstatorbroadband noise. Predictions of the broadband noise from this noise model arecompared to rig measurements, showing good accuracy. The underlying physics of rotorstatorbroadband noise generation is investigated by performing two parametric studies usingthe broadband noise model. The first parametric study investigates the effect on broadbandnoise of simple flow and geometric parameters, namely number of vanes, vane chord, vanestagger angle, and rotor wake turbulence intensity, turbulent length scale, and flow Machnumber onto the cascade. These results are used to derive scaling power laws for theprediction of changes in broadband noise due to changes in these parameters. The secondparametric study expands upon this by investigating the effect on broadband noise of the fandesign parameters shaft speed, pressure ratio, and efficiency, at approach, cutback and cruiseconditions. The variation in broadband noise due to these design parameters is explained byconsidering the underlying flow and geometric parameters such as number of vanes and Machnumber, and the scaling power laws based on these simple parameters are used to predict thechange in broadband noise between different performance points.The final section of this thesis investigates the effect of varying exhaust nozzle area on totalengine noise. A new method is presented that allows the transfer of changes in fan rig noise toEugene P. Deane EngD Thesis September 2009 2engine noise predictions, to estimate the change in fan noise due to the pressure ratio changesbrought about by a variable area nozzle. Changes in engine noise are investigated forapproach, cutback, and sideline conditions, and the application of the new method assessed.As the research displayed in this thesis is closely linked to industry, the foundation of workpresented in several chapters is dependent on data or figures that are commercially sensitive.It has therefore been necessary to create a confidential appendix (Appendix X) to includethese commercially sensitive items. These additional results and figures in Appendix X aresupplementary in nature, and sufficient results are presented in the public thesis to illustratethe results of the various chapters. Where supplementary information and results are available,this is clearly indicated at the pertinent point in the published thesis, along with the section ofAppendix X where the information can be found
Development of a Method for Enhanced Fan Representation in Gas Turbine Modeling
No full textA challenge in civil aviation future propulsion systems is expected to be the integration with the airframe, coming as a result of increasing bypass ratio or above wing installations for noise mitigation. The resulting highly distorted inlet flows to the engine, make a clear demand for advanced gas turbine performance prediction models. Since the dawn of jet engine several models have been proposed and the present work comes to add a model that combines two well established compressor performance methods in order to create a quasi three dimensional representation of the fan of a modern turbofan. A streamline curvature model is coupled to a parallel compressor method, covering radial and circumferential directions respectively. Model testing has shown a close agreement to experimental data, making it a good candidate for assessing the loss of surge margin on a high bypass ratio turbofan, semi-embedded on the upper surface of a broad wing airframe
Measurements of K S 0 - K L 0 asymmetries in the decays Λ c + → p K L , S 0 , p K L , S 0 π + π − and p K L , S 0 π 0
No full textAbstract Using e + e − annihilation data sets corresponding to an integrated luminosity of 4.5 fb −1, collected with the BESIII detector at center-of-mass energies between 4.600 and 4.699 GeV, we report the first measurements of the absolute branching fractions B Λ c + → p K L 0 = (1.67 ± 0.06 ± 0.04)%, B Λ c + → p K L 0 π + π − = (1.69 ± 0.10 ± 0.05)%, and B Λ c + → p K L 0 π 0 = (2.02 ± 0.13 ± 0.05)%, where the first uncertainties are statistical and the second systematic. Combining with the known branching fractions of Λ c + → p K S 0 , Λ c + → p K S 0 π + π − , and Λ c + → p K S 0 π 0 , we present the first measurements of the K S 0 - K L 0 asymmetries R Λ c + K S , L 0 X = B Λ c + → K S 0 X − B Λ c + → K L 0 X B Λ c + → K S 0 X + B Λ c + → K L 0 X in charmed baryon decays: R Λ c + p K S , L 0 = − 0.025 ± 0.031 , R Λ c + p K S , L 0 π + π − = − 0.027 ± 0.048 and R Λ c + p K S , L 0 π 0 = − 0.015 ± 0.046 . No significant asymmetries with statistical significance are observed
Analysing International Sports Fan Motivations and Constraints: The Case of Japanese International Sports Fan Tourists and Rugby World Cup Fan Tourists
No full textThe scale of professional sports leagues and mega sports events has expanded recently. Many sports fans travel to foreign countries to watch international events featuring the world’s top athletes or players. The number of international sports fan tourists has increased, and understanding their behaviour is very important for stakeholders and those involved in marketing, such as sports organisations, travel companies, and government tourist organisations.
This study examines the motivations and constraints of Japanese international sports fan tourists and Japanese Rugby World Cup fan tourists. Sports fan tourists are tourists as well as sports fans. Many researchers have examined motivation either from a sports fan’s perspective or a tourist perspective. However, a motivation scale for international sports fan tourists (combining both sports fan and tourist motivations) has been not developed as there has been a lack of research into the behaviour of the international sports fan tourist.
The main research aim of this study is to analyse the motivation and constraint factors of both Japanese international sports fan tourists and Japanese Rugby World Cup tourists. The methodology aims to:
1.profile Japanese international sports fan tourists and Japanese Rugby World Cup tourists;
2.develop a motivational scale for actual sports fan tourists and a constraints scale for potential sports fan tourists (those who considered going but did not go);
3.analyse these factors according to demographics;
4.examine factors related to motivations and constraints on fans’ satisfaction, or their intention to attend future events.
A quantitative approach was employed. The main data collection methods were three email surveys:
1.Study 1 collected data about actual international sports fan tourists (N=338) and potential sports fan tourists (N=292).
2.Study 2 collected data about actual Rugby World Cup 1987-2007 tourists (N=101) and potential tourists (N=297).
3.Study 3 collected data about actual Rugby World Cup 2011 tourists (N=84) and potential tourists (N=115).
In previous studies, the sample was collected either from actual fans or potential fans separately; however, in this study, samples were collected not only from actual sports fan tourists but also from potential sports fan tourists from the same database.
The data analysis predominantly used explanatory factor analysis (EFA), confirmatory factor analysis (CFA), independent t-test, ANOVA, regression analysis, and structure equation modelling (SEM) including interaction effects analysis.
The results of this study were analysed using four steps:
1.Showing the demographic profiles and behavioural patterns of Japanese international sports fan tourists and Japanese Rugby World Cup fan tourists.
2.Developing motivation and constraints scales:
• an International Sports Fan Motivation Scale
• an International Sports Fan Tourist Motivation Scale
• an International Sports Fan Constraints Scale
• a Rugby World Cup Sports Fan Motivation Scale
• a Rugby World Cup Fan Tourist Motivation Scale
• a Rugby World Cup Fan Constraints Scale.
3.Comparing the mean scores of extracted factors by demographics such as gender, age, sports experiences etc.
4.Analysing the impact on satisfaction or future intention using interaction effect methods.
The results showed some interesting academic and practical implications. This study has thus made a significant and unique contribution to the knowledge of international sports fan behaviour by researching the combined sports fan motivation factors and tourist motivation factors of actual sports fans, and the constraints of potential sports fan tourists. The study has also provided an academic contribution to the sports and tourism fields, and has provided a practical contribution to the areas of sports fan behaviour, tourism, leisure constraints, and sports events management
FAN 2002: um modelo neuro-fuzzy para reconhecimento de padrões
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia de Produção.Nesta tese é apresentado FAN 2002 - free associtive neurons - como uma abordagem neuro-fuzzy para reconhecimento supervisionado de padrões. Aspectos foram modificados desde a sua publicação inicial, em 1997: a criação de células para a combinação de características é substituida pela inclusão de uma característica extra que representa a combinação das demais; a forma de realizar a penalização em caso de erro é modificada; a inicialização dos neurônios é realizada com valores aleatórios; um hedge é usado no teste de um padrão. Os resultados em aplicações são mostrados: no problema de classificação de cromossomos, a comparação com os resultados o obtidos por outros métodos apresentados ilustra o desenvolvimento do modelo desde as suas primeiras implementações; A aplicação do modelo em jogos de empresas na construção de um agente; Os conceitos de FAN na construção dos Mapas FAN e a solução do problema do XOR. A apresentação de FAN 2002 visa proporcionar aos interessados na aplicação de soluções em reconhecimento de padrões uma ferramenta útil e de uso geral.A conclusão do trabalho mostra o resumo dos avanços obtidos no desenvolvimento de FAN e aponta para o futuro do método uma possibilidade interdisciplinar de subsidiar pesquisadores de outras áreas a resolverem os seus próprios problemas de classificação e reconhecimento
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