508 resultados para ALE


Relevância:

20.00% 20.00%

Publicador:

Resumo:

By employing a research approach, known as subjective personal introspection - the critical "I" - four co-researchers wrote extensive autobiographical essays on their responses to an advertisement for Caffrey's Irish Ale. By delving in the shamelessly subjective this paper draws out the main themes by comparing, contrasting and critiquing the introspective insights of these four critical "I's". In doing so, it demonstrates that there can be no grounded interpretations of an advertising text, that the critical "I" can yield uniquely illuminating insights, and that its chief power, as a research method, lies in its capacity for creativity, imagination and discovery.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This paper presents a comparative study on the response of a buried tunnel to surface blast using the arbitrary Lagrangian-Eulerian (ALE) and smooth particle hydrodynamics (SPH) techniques. Since explosive tests with real physical models are extremely risky and expensive, the results of a centrifuge test were used to validate the numerical techniques. The numerical study shows that the ALE predictions were faster and closer to the experimental results than those from the SPH simulations which over predicted the strains. The findings of this research demonstrate the superiority of the ALE modelling techniques for the present study. They also provide a comprehensive understanding of the preferred ALE modelling techniques which can be used to investigate the surface blast response of underground tunnels.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Rolling Element Bearings (REBs) are vital components in rotating machineries for providing rotating motion. In slow speed rotating machines, bearings are normally subjected to heavy static loads and a catastrophic failure can cause enormous disruption to production and human safety. Due to its low operating speed the impact energy generated by the rotating elements on the defective components is not sufficient to produce a detectable vibration response. This is further aggravated by the inability of general measuring instruments to detect and process the weak signals at the initiation of the defect accurately. Furthermore, the weak signals are often corrupted by background noise. This is a serious problem faced by maintenance engineers today and the inability to detect an incipient failure of the machine can significantly increases the risk of functional failure and costly downtime. This paper presents the application of noise removal techniques for enhancing the detection capability for slow speed REB condition monitoring. Blind deconvolution (BD) and adaptive line enhancer (ALE) are compared to evaluate their performance in enhancing the source signal with consequential removal of background noise. In the experimental study, incipient defects were seeded on a number of roller bearings and the signals were acquired using acoustic emission (AE) sensor. Kurtosis and modified peak ratio (mPR) were used to determine the detectability of signal corrupted by noise.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Increasing threat of terrorism highlights the importance of enhancing the resilience of underground tunnels to all hazards. This paper develops, applies and compares the Arbitrary Lagrangian Eulerian (ALE) and Smooth Particle Hydrodynamics (SPH) techniques to treat the response of buried tunnels to surface explosions. The results and outcomes of the two techniques were compared, along with results from existing test data. The comparison shows that the ALE technique is a better method for describing the tunnel response for above ground explosion with regards to modeling accuracy and computational efficiency. The ALE technique was then applied to treat the blast response of different types of segmented bored tunnels buried in dry sand. Results indicate that the most used modern ring type segmented tunnels were more flexible for in-plane response, however, they suffered permanent drifts between the rings. Hexagonal segmented tunnels responded with negligible drifts in the longitudinal direction, but the magnitudes of in-plane drifts were large and hence hazardous for the tunnel. Interlocking segmented tunnels suffered from permanent drifts in both the longitudinal and transverse directions. Multi-surface radial joints in both the hexagonal and interlocking segments affected the flexibility of the tunnel in the transverse direction. The findings offer significant new information in the behavior of segmented bored tunnels to guide their future implementation in civil engineering applications.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

It has been well accepted that over 50% of cerebral ischemic events are the result of rupture of vulnerable carotid atheroma and subsequent thrombosis. Such strokes are potentially preventable by carotid interventions. Selection of patients for intervention is currently based on the severity of carotid luminal stenosis. It has been, however, widely accepted that luminal stenosis alone may not be an adequate predictor of risk. To evaluate the effects of degree of luminal stenosis and plaque morphology on plaque stability, we used a coupled nonlinear time-dependent model with flow-plaque interaction simulation to perform flow and stress/strain analysis for stenotic artery with a plaque. The Navier-Stokes equations in the Arbitrary Lagrangian-Eulerian (ALE) formulation were used as the governing equations for the fluid. The Ogden strain energy function was used for both the fibrous cap and the lipid pool. The plaque Principal stresses and flow conditions were calculated for every case when varying the fibrous cap thickness from 0.1 to 2mm and the degree of luminal stenosis from 10% to 90%. Severe stenosis led to high flow velocities and high shear stresses, but a low or even negative pressure at the throat of the stenosis. Higher degree of stenosis and thinner fibrous cap led to larger plaque stresses, and a 50% decrease of fibrous cap thickness resulted in a 200% increase of maximum stress. This model suggests that fibrous cap thickness is critically related to plaque vulnerability and that, even within presence of moderate stenosis, may play an important role in the future risk stratification of those patients when identified in vivo using high resolution MR imaging.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Underground tunnels are vulnerable to terrorist attacks which can cause collapse of the tunnel structures or at least extensive damage, requiring lengthy repairs. This paper treats the blast impact on a reinforced concrete segmental tunnel buried in soil under a number of parametric conditions; soil properties, soil cover, distance of explosive from the tunnel centreline and explosive weight and analyses the possible failure patterns. A fully coupled Fluid Structure Interaction (FSI) technique incorporating the Arbitrary Lagrangian-Eulerian (ALE) method is used in this study. Results indicate that the tunnel in saturated soil is more vulnerable to severe damage than that buried in either partially saturated soil or dry soil. The tunnel is also more vulnerable to surface explosions which occur directly above the centre of the tunnel than those that occur at any equivalent distances in the ground away from the tunnel centre. The research findings provide useful information on modeling, analysis, overall tunnel response and failure patterns of segmented tunnels subjected to blast loads. This information will guide future development and application of research in this field.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Pro gradu -työssä tarkastelen tšekin ja suomen kielessä esiintyviä eläinten nimityksistä johdettuja fraseologisia ilmauksia ja sanontoja. Eläinfraseologia muodostaa kielessä keskeisen osan, jolle ovat tyypillisiä voimakas tunnelataus, rajoittunut, sovinnainen käyttö ja puhekielenomaisuus. Tarkastelen eläinilmauksia morfologisesti ja semanttis-leksikaalisesti, mutta muitakin piirteitä esiintyy. Vertailen kumpaakin kieltä ja selvitän kielten fraasien, idiomien ja muiden sanontojen yhtäläisyyksiä ja eroja. Sanonnat (ynnä johdokset ja sanaparit) jaan neljään eri ryhmään seuraavasti: 1. kummassakin kielessä olevat samanlaiset ilmaukset, 2. kummassakin kielessä olevat osittain samanlaiset ilmaukset, 3. tsekkiläiset ilmaukset ja 4. suomalaiset ilmaukset. Työni materiaali on peräisin tsekkiläisistä, suomalaisista ja muunkielisistä sanakirjoista (lähinnä fraseologisista). Selvittelen erityisesti keskeisimpien kotieläinten nimistä (koira, kissa, hevonen, lehmä, lammas, sika, kana), joidenkin muiden eläinten nimistä (karhu, susi, karppi, käärme) ja joidenkin ulkomaisten eläinten nimistä (leijona, elefantti, apina) johdettuja fraseologisia ilmauksia. Materiaali käsittää yhteensä 145 eri eläintä, 163 eläimen nimitystä ja 585 eläinilmausta. Aineistoni pohjalta voi todeta, että tšekin ja suomen kielessä on yllättävän paljon samantyyppisiä eläinilmauksia, vaikka kielet poikkeavat huomattavasti toisistaan. Korpuksessani olevista ilmauksista on täysin symmetrisiä 119/20,3 %, osittain samanlaisia (epäsymmetrisiä) 127/21,7 %, pelkästään tsekkiläisiä 161/27,5 % ja pelkästään suomalaisia 146/25,0 %. Sanaparit ja sananlaskut, joita käsittelin erillisenä ryhmänä (32 kpl) muodostivat aineistosta 5,5 % (niistäkin löytyi yhtäläisyyksiä). Yleisimmin esiintyvät eläimet ovat koira ja kissa. Koira on kuitenkin tšekin fraseologiassa yleisempi eläin kuin suomessa, jossa taas kissa on yleisimmin esiintyvä eläimen nimi. Yleisiä ovat myös mm. hevonen, sika, lintu, kala ja kana. Karitsa, hanhi ja vuohi esiintyvät paljon useammin tšekin fraseologiassa, suomessa esiintyy taas usein sika silloin, kun tšekissä on porsas. Joillakin eläinten nimillä on selvästi negatiivisempi tunnelataus (susi, käärme) kuin toisilla (koira, kissa). Toisin kuin suomessa, kissa on tšekissä valheellinen, vuohi herkuttelee, pöllö ja apina edustavat viisautta ja oppivaisuutta ja kovakuoriainen hellyttää. Yhteisiä eläinten nimityksiä kummassakin kielessä on aineistossani 106/163 (65,03 %). Tšekin fraseologiassa on lähes kaksi kertaa enemmän (37/163 = 22,7 %) sellaisia eläinten nimiä, joita ei esiinny suomen fraseologiassa verrattuna pelkästään suomen fraseologiassa esiintyviin eläinten nimiin (20/163 = 12,27 %). Pelkästään tšekissä esiintyviä eläimiä ovat mm. lumikko, majava, murmeli, mäyrä, näätä ja riikinkukko; pelkästään suomen fraseologiassa esiintyvät puolestaan mm. kiiski, muikku, peippo, poro, sopuli ja telkkä. Vertauskuvat ovat kummassakin kielessä erittäin tyypillisiä. Eläinten nimet viittaavat useimmiten ihmisen kielteisiin luonteenpiirteisiin tai ominaisuuksiin (mazaný jako liška ja viekas kuin kettu). Aineistoni pohjalta vaikuttaa siltä, että tšekissä on enemmän vaihtoehtoisia ja eri eläinten lajeista muodostettuja ilmauksia (mm. lintu- ja kalalajeista). Kummassakin kielessä on myös huudahduslauseita (Ty jsi ale liška pod itá! ja Senkin vanha kettu!), kansainvälisiä ilmauksia (jádro pudla ja villakoiran ydin) ja ns. petollisia ystäviä toisiaan erehdyttävästi muistuttavia, mutta eri asiaa merkitseviä sanontoja (tsekin kočičí život kissanelämä tarkoittaa ´sitkeähenkisyyttä´ − ei suomen kissanpäiviä). Kansallisista erityispiirteistä ovat esimerkkeinä mm. tšekin ilmaus mít se jako husa o Martině "voida kuin hanhi Martinpäivänä" (suomeksi ´voida kurjasti´; viittaus Martinpäivän hanhensyömisperinteeseen) tai suomen ilmaukset kuin hyttysen liraus Itämereen ja sopulilauma.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Accurate numerical solutions to the problems in fluid-structure (aeroelasticity) interaction are becoming increasingly important in recent years. The methods based on FCD (Fixed Computational Domain) and ALE (Alternate Lagrangian Eulerian) to solve such problems suffer from numerical instability and loss of accuracy. They are not general and can not be extended to the flowsolvers on unstructured meshes. Also, global upwind schemes can not be used in ALE formulation thus leads to the development of flow solvers on moving grids. The KFVS method has been shown to be easily amenable on moving grids required in unsteady aerodynamics. The ability of KFMG (Kinetic Flux vector splitting on Moving Grid) Euler solver in capturing shocks, expansion waves with small and very large pressure ratios and contact discontinuities has been demonstrated.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This study aims to determine optimal locations of dual trailing-edge flaps and blade stiffness to achieve minimum hub vibration levels in a helicopter, with low penalty in terms of required trailing-edge flap control power. An aeroelastic analysis based on finite elements in space and time is used in conjunction with an optimal control algorithm to determine the flap time history for vibration minimization. Using the aeroelastic analysis, it is found that the objective functions are highly nonlinear and polynomial response surface approximations cannot describe the objectives adequately. A neural network is then used for approximating the objective functions for optimization. Pareto-optimal points minimizing both helicopter vibration and flap power ale obtained using the response surface and neural network metamodels. The two metamodels give useful improved designs resulting in about 27% reduction in hub vibration and about 45% reduction in flap power. However, the design obtained using response surface is less sensitive to small perturbations in the design variables.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The heat transfer from a solid phase to an impinging non-isothermal liquid droplet is studied numerically. A new approach based on an arbitrary Lagrangian-Eulerian (ALE) finite element method for solving the incompressible Navier Stokes equations in the liquid and the energy equation within the solid and the liquid is presented. The novelty of the method consists in using the ALE-formulation also in the solid phase to guarantee matching grids along the liquid solid interface. Moreover, a new technique is developed to compute the heat flux without differentiating the numerical solution. The free surface and the liquid solid interface of the droplet are represented by a moving mesh which can handle jumps in the material parameter and a temperature dependent surface tension. Further, the application of the Laplace-Beltrami operator technique for the curvature approximation allows a natural inclusion of the contact angle. Numerical simulation for varying Reynold, Weber, Peclet and Biot numbers are performed to demonstrate the capabilities of the new approach. (C) 2014 Elsevier Ltd. All rights reserved.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

An arbitrary Lagrangian-Eulerian (ALE) finite element scheme for computations of soluble surfactant droplet impingement on a horizontal surface is presented. The numerical scheme solves the time-dependent Navier-Stokes equations for the fluid flow, scalar convection-diffusion equation for the surfactant transport in the bulk phase, and simultaneously, surface evolution equations for the surfactants on the free surface and on the liquid-solid interface. The effects of surfactants on the flow dynamics are included into the model through the surface tension and surfactant-dependent dynamic contact angle. In particular, the dynamic contact angle (theta(d)) of the droplet is defined as a function of the surfactant concentration at the contact line and the equilibrium contact angle (theta(0)(e)) of the clean surface using the nonlinear equation of state for surface tension. Further, the surface forces are included into the model as surface divergence of the surface stress tensor that allows to incorporate the Marangoni effects without calculating the surface gradient of the surfactant concentration on the free surface. In addition to a mesh convergence study and validation of the numerical results with experiments, the effects of adsorption and desorption surfactant coefficients on the flow dynamics in wetting, partially wetting and non-wetting droplets are studied in detail. It is observed that the effects of surfactants are more in wetting droplets than in the non-wetting droplets. Further, the presence of surfactants at the contact line reduces the equilibrium contact angle further when theta(0)(e) is less than 90 degrees, and increases it further when theta(0)(e) is greater than 90 degrees. Nevertheless, the presence of surfactants has no effect on the contact angle when theta(0)(e) = 90 degrees. The numerical study clearly demonstrates that the surfactant-dependent contact angle has to be considered, in addition to the Marangoni effect, in order to study the flow dynamics and the equilibrium states of surfactant droplet impingement accurately. The proposed numerical scheme guarantees the conservation of fluid mass and of the surfactant mass accurately. (C) 2015 Elsevier Inc. All rights reserved.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A comprehensive numerical investigation on the impingement and spreading of a non-isothermal liquid droplet on a solid substrate with heterogeneous wettability is presented in this work. The time-dependent incompressible Navier-Stokes equations are used to describe the fluid flow in the liquid droplet, whereas the heat transfer in the moving droplet and in the solid substrate is described by the energy equation. The arbitrary Lagrangian-Eulerian (ALE) formulation with finite elements is used to solve the time-dependent incompressible Navier-Stokes equation and the energy equation in the time-dependent moving domain. Moreover, the Marangoni convection is included in the variational form of the Navier-Stokes equations without calculating the partial derivatives of the temperature on the free surface. The heterogeneous wettability is incorporated into the numerical model by defining a space-dependent contact angle. An array of simulations for droplet impingement on a heated solid substrate with circular patterned heterogeneous wettability are presented. The numerical study includes the influence of wettability contrast, pattern diameter, Reynolds number and Weber number on the confinement of the spreading droplet within the inner region, which is more wettable than the outer region. Also, the influence of these parameters on the total heat transfer from the solid substrate to the liquid droplet is examined. We observe that the equilibrium position depends on the wettability contrast and the diameter of the inner surface. Consequently. the heat transfer is more when the wettability contrast is small and/or the diameter of inner region is large. The influence of the Weber number on the total heat transfer is more compared to the Reynolds number, and the total heat transfer increases when the Weber number increases. (C) 2015 Elsevier Ltd. All rights reserved.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Aborda o comportamento e as capacitações desejáveis ao profissional de Secretariado Executivo na Câmara dos Deputados. Analisa o grau de competências por intermédio de conhecimentos, habilidades e atitudes necessárias para a obtenção de resultados efetivos junto à Câmara dos Deputados. Define o perfil desejável para a função de secretária executiva na Câmara dos Deputados. Indica fatores que podem contribuir para o aperfeiçoamento profissional e desenvolvimento pessoal dos indivíduos que exerçam a atividade.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

导弹潜射是集高速流动、冲击、结构响应于一体的流体—固体—气体三态非线性耦合复杂过程,是决定潜射导弹发射成败的关键环节。本文应用LS-DYNA显式程序建立了三种包含水体、空气、导弹、发射井和筒盖的多物质耦合ALE网格模型,使用罚函数流体—固体耦合方法对导弹水下无攻角潜射过程进行了数值模拟,给出了弹体质心的轴向加速度、轴向流体阻力及阻力系数、空泡区压力分布。仿真结果表明,模型2的仿真过程与实际导弹潜射过程最为相符。同时总结介绍了LS-DYNA程序中流体—固体耦合计算的相关设定原则和方法。本文可为潜射导弹的水动力载荷设计和数值仿真提供有益的参考。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

导弹潜射过程是流-固-气三态耦合的非定常复杂过程,更是决定导弹发射成败的关键.本研究运用ANSYS/LS-DYNA显式程序对导弹的水下发射过程进行了模拟,以期为导弹设计提供有益的技术参考.文中流体模型采用多物质ALE单元,使用罚函数流-固耦合方法进行导弹潜射过程仿真,流体初始静水压力应用动力学平衡方法进行初始化,最终仿真得到导弹的流体阻力及压力分布时程曲线.基于仿真所得数据,对导弹流体阻力系数进行了计算和讨论,为导弹的流体阻力系数提供了一种全新的校核方法.