963 resultados para Automobiles, Racing -- Aerodynamics


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Automotive catalysts are the most effective short-term answer to air pollution from automobiles. Since strict control of exhaust emissions is, or will be,covered by legislation in most developed countries in the world, catalytic devices will be increasingly fitted to cars. There is consequently an urgent need for the development of catalysts that will not compete for scarce precious metal resources. A number of problems have already been identified in connection with base metal catalysts but quantitative investigations are lacking. The base metal reduction catalysts developed by Imperial Chemical Industries Limited, catalysts and Chemical Group, in collaboration with the Air Pollution Control Laboratory, B L Cars Limited for automotive emission control, are susceptible to de-activation by three major mechanisms. These are: physical loss of the wash-coat (a high surface area coating which supports the active species), aggregation of the active species and poisoning by fuel and engine oil additives. This thesis is especially concerned with the first two of these and attempts to indicate the relative magnitude .of their effect on the activity of. the catalysts. Aggregation of the active species or sintering, as it is loosely called, was studied by using impregnated granules to overcome effects due to the loss of the wash-coat. Samples were aged in a synthetic exhaust gas, free from poisons, and metal crystallite sizes were measured by scanning-electron microscopy. The increase in particle size was correlated with the loss in catalytic activity. In order to maintain a link with the real conditions of service a number of monolithic catalysts were tested in an engine-dynamometer and several previously tested endurance catalysts were examined. A mechanism is proposed for the break-up and subsequent 10s.5 of the wash-coat and suggestions for improved resistance to loss of the' coating and active species are proposed.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Wireless sensor networks have been identified as one of the key technologies for the 21st century. In order to overcome their limitations such as fault tolerance and conservation of energy, we propose a middleware solution, In-Motes. In-Motes stands as a fault tolerant platform for deploying and monitoring applications in real time offers a number of possibilities for the end user giving him in parallel the freedom to experiment with various parameters, in an effort the deployed applications to run in an energy efficient manner inside the network. The proposed scheme is evaluated through the In-Motes EYE application, aiming to test its merits under real time conditions. In-Motes EYE application which is an agent based real time In-Motes application developed for sensing acceleration variations in an environment. The application was tested in a prototype area, road alike, for a period of four months.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

How motorsport companies harness network diversity for discontinuous innovation.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The motorsport industry is a significant part of the UK economy. According to industry estimates approximately 4,500 companies are involved in the UK Motorsport and Performance Engineering Industry and its wide-ranging support activities. The industry has an annual turnover of £6.0 billion, and contributes £3.6 billion worth of exports. The Motorsport Industry Association estimates that the support side of the sector alone "involving events management, public relations, marketing, sponsorship and a host of other support functions" accounts for approximately £1.7 billion of the yearly industry total. And in terms of employment, UK Motorsport supports 38,500 full and part-time jobs, including 25,000 engineers.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

General note: Title and date provided by Bettye Lane.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

General note: Title and date provided by Bettye Lane.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

A novel surrogate model is proposed in lieu of Computational Fluid Dynamics (CFD) solvers, for fast nonlinear aerodynamic and aeroelastic modeling. A nonlinear function is identified on selected interpolation points by<br/>a discrete empirical interpolation method (DEIM). The flow field is then reconstructed using a least square approximation of the flow modes extracted<br/>by proper orthogonal decomposition (POD). The aeroelastic reduce order<br/>model (ROM) is completed by introducing a nonlinear mapping function<br/>between displacements and the DEIM points. The proposed model is investigated to predict the aerodynamic forces due to forced motions using<br/>a N ACA 0012 airfoil undergoing a prescribed pitching oscillation. To investigate aeroelastic problems at transonic conditions, a pitch/plunge airfoil<br/>and a cropped delta wing aeroelastic models are built using linear structural models. The presence of shock-waves triggers the appearance of limit<br/>cycle oscillations (LCO), which the model is able to predict. For all cases<br/>tested, the new ROM shows the ability to replicate the nonlinear aerodynamic forces, structural displacements and reconstruct the complete flow<br/>field with sufficient accuracy at a fraction of the cost of full order CFD<br/>model.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Cette thèse tente de comprendre lâimpact des restructurations des entreprises multinationales sur les stratégies syndicales. Les acteurs syndicaux locaux sont-ils déterminés par lâappartenance à des régimes nationaux et à des contingences organisationnelles ou peuvent-ils influencer des décisions objectives comme les restructurations ? Cette recherche sâinsère dans une problématique large qui fait la jonction entre la mondialisation économique sur une base continentale, la réorganisation productive des entreprises multinationales et lâaction syndicale. Au plan théorique, nous confrontons trois grandes approches analytiques, à savoir : le néo-institutionnalisme et les structures dâopportunités ; lâéconomie politique critique et la question du pouvoir syndical ; la géographie économique critique mettant de lâavant les contingences, lâencastrement et lâespace concurrentiel. Sur la base de ces trois familles, nous présentons un modèle dâanalyse multidisciplinaire. Au plan méthodologique, cette thèse est structurée autour de quatre études de cas locales qui ont subi des menaces de restructurations. Cette collecte a été effectuée dans deux pays (la France et le Canada) et dans un secteur particulier (les équipementiers automobiles). Trois sources qualitatives forment le cÅur empirique de cette thèse : des statistiques descriptives, des documents de sources secondaires et des entretiens semi-dirigés (44), principalement avec des acteurs syndicaux. Lâanalyse intra et inter régime national éclaire plusieurs aspects de la question des stratégies syndicales en contexte de restructurations. Les principales contributions de cette thèse touchent : 1. lâimpact des facteurs relationnels et des ressources de pouvoir développées par les syndicats locaux sur les structures dâopportunités institutionnelles; 2. lâimportance des aspects « cognitifs » et dâenvisager le pouvoir de manière multi-niveaux; 3. lâimportance de lâencastrement social et des dynamiques relationnelles entre syndicats et patronats; 4. lâinfluence de la concurrence internationale/nationale/régionale/locale dans le secteur des équipementiers automobiles; et 5. lâimportance des arbitrages et des relations entre les acteurs de lâentreprise par rapport à la théorie de la contingence pour comprendre les marges structurelles des syndicats locaux. Notre recherche invite les acteurs sociaux à repenser leur action dans le cadre des restructurations. En particulier, les syndicats locaux se doivent dâexplorer de nouveaux répertoires stratégiques pour répondre aux nombreux défis que posent le changement économique et les restructurations.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Cette thèse tente de comprendre lâimpact des restructurations des entreprises multinationales sur les stratégies syndicales. Les acteurs syndicaux locaux sont-ils déterminés par lâappartenance à des régimes nationaux et à des contingences organisationnelles ou peuvent-ils influencer des décisions objectives comme les restructurations ? Cette recherche sâinsère dans une problématique large qui fait la jonction entre la mondialisation économique sur une base continentale, la réorganisation productive des entreprises multinationales et lâaction syndicale. Au plan théorique, nous confrontons trois grandes approches analytiques, à savoir : le néo-institutionnalisme et les structures dâopportunités ; lâéconomie politique critique et la question du pouvoir syndical ; la géographie économique critique mettant de lâavant les contingences, lâencastrement et lâespace concurrentiel. Sur la base de ces trois familles, nous présentons un modèle dâanalyse multidisciplinaire. Au plan méthodologique, cette thèse est structurée autour de quatre études de cas locales qui ont subi des menaces de restructurations. Cette collecte a été effectuée dans deux pays (la France et le Canada) et dans un secteur particulier (les équipementiers automobiles). Trois sources qualitatives forment le cÅur empirique de cette thèse : des statistiques descriptives, des documents de sources secondaires et des entretiens semi-dirigés (44), principalement avec des acteurs syndicaux. Lâanalyse intra et inter régime national éclaire plusieurs aspects de la question des stratégies syndicales en contexte de restructurations. Les principales contributions de cette thèse touchent : 1. lâimpact des facteurs relationnels et des ressources de pouvoir développées par les syndicats locaux sur les structures dâopportunités institutionnelles; 2. lâimportance des aspects « cognitifs » et dâenvisager le pouvoir de manière multi-niveaux; 3. lâimportance de lâencastrement social et des dynamiques relationnelles entre syndicats et patronats; 4. lâinfluence de la concurrence internationale/nationale/régionale/locale dans le secteur des équipementiers automobiles; et 5. lâimportance des arbitrages et des relations entre les acteurs de lâentreprise par rapport à la théorie de la contingence pour comprendre les marges structurelles des syndicats locaux. Notre recherche invite les acteurs sociaux à repenser leur action dans le cadre des restructurations. En particulier, les syndicats locaux se doivent dâexplorer de nouveaux répertoires stratégiques pour répondre aux nombreux défis que posent le changement économique et les restructurations.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The focus of the current dissertation is to study qualitatively the underlying physics of vortex-shedding and wake dynamics in long aspect-ratio aerodynamics in incompressible viscous flow through the use of the KLE method. We carried out a long series of numerical experiments in the cases of flow around the cylinder at low Reynolds numbers. The study of flow at low Reynolds numbers provides an insight in the fluid physics and also plays a critical role when applying to stalled turbine rotors. Many of the conclusions about the qualitative nature of the physical mechanisms characterizing vortex formation, shedding and further interaction analyzed here at low Re could be extended to other Re regimes and help to understand the separation of the boundary layers in airfoils and other aerodynamic surfaces. In the long run, it aims to provide a better understanding of the complex multi-physics problems involving fluid-structure-control interaction through improved mathematical computational models of the multi-physics process. Besides the scientific conclusions produced, the research work on streamlined and bluff-body condition will also serve as a valuable guide for the future design of blade aerodynamics and the placement of wind turbines and hydrakinetic turbines, increasing the efficiency in the use of expensive workforce, supplies, and infrastructure. After the introductory section describing the main fields of application of wind power and hydrokinetic turbines, we describe the main features and theoretical background of the numerical method used here. Then, we present the analysis of the numerical experimentation results for the oscillatory regime right before the onset of vortex shedding for circular cylinders. We verified the wake length of the closed near-wake behind the cylinder and analysed the decay of the wake at the wake formation region, and then studied the St-Re relationship at the Reynolds numbers before the wake sheds compared to the experimental data. We found a theoretical model that describes the time evolution of the amplitude of fluctuations in the vorticity field on the twin vortex wake, which accurately matches the numerical results in terms of the frequency of the oscillation and rate of decay. We also proposed a model based on an analog circuit that is able to interpret the concerning flow by reducing the number of degrees of freedom. It follows the idea of the non-linear oscillator and resembles the dynamics mechanism of the closed near-wake with a common configured sine wave oscillator. This low-dimensional circuital model may also help to understand the underlying physical mechanisms, related to vorticity transport, that give origin to those oscillations.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Different selection objectives within the Quarter Horse breed led to the formation of groups with distinct skills, including the racing and cutting lines. With a smaller population size in Brazil, but of great economic representativeness, the racing line is characterized by animals that can reach high speeds over short distances and within a short period of time. The cutting line is destined for functional tests, exploring skills such as agility and obedience. Although the athletic performance of horses is likely to be influenced by a large number of genes, few genetic variants have so far been related to this trait and this was done exclusively in Thoroughbreds, including the g.38973231G>A singlenucleotide polymorphism in the PDK4 gene and the g.22684390C>T single-nucleotide polymorphism in the COX4I2 gene. The results of the present study demonstrate the presence of polymorphic PDK4 and COX4I2 genes in Quarter Horses. The analysis of 296 racing animals and 68 cutting animals revealed significant differences in allele and genotype frequencies between the two lines. The same was not observed when these frequencies were compared between extreme racing performance phenotypes. There were also no significant associations between alleles of the two polymorphisms and the speed index. These results suggest that the alleles of the PDK4 and COX4I2 genes, which are related to better racecourse performance in Thoroughbreds, are probably associated with beneficial adaptations in aerobic metabolism and therefore play secondary roles in sprint racing performance in Quarter Horses, which is mainly anaerobic.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Racing motorcycles are prone to an unstable oscillatory motion of the swingarm and rear wheel, commonly known as â˜chatterâ. This vibration mode typically has a frequency of 17 Hz to 22 Hz and typically occurs during heavy braking manoeuvres. The appearance of chatter can cause reduced rider confidence, and therefore lead to longer lap times during races and the increased risk of crashing. This thesis looks to further the understanding of this mode. It includes the development of a simplified model to explore the effects roll angle and lateral dynamics have on the chatter mode using linear analysis. The mechanisms of instability and parameter sensitivities are also examined. The effects of the nonlinearities present in the minimal model equations of motion are examined, including the identification of limit cycles and their stability, inspecting individual nonlinear terms and their effects, and introducing tyre relaxation and determining the effect it has on the dynamics. Finally, an exploratory study of the mid-corner region of a typical racing manoeuvre is performed in hopes to better understand if any high frequency tyre induced instabilities like chatter can occur.