Literatura académica sobre el tema "Tube of trajectories"
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Artículos de revistas sobre el tema "Tube of trajectories"
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YAZGI, Arzu, Vedat DEMİR y Adnan DEĞİRMENCİOĞLU. "Comparison of computational fluid dynamics-based simulations and visualized seed trajectories in different seed tubes". TURKISH JOURNAL OF AGRICULTURE AND FORESTRY 44, n.º 6 (8 de diciembre de 2020): 599–611. http://dx.doi.org/10.3906/tar-1910-15.
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The objective of this study was to compare computational fluid dynamics (CFD)-based simulations and visualized seed trajectories in different seed tubes that can provide seed incorporation into the soil with enhanced seed spacing. The other objective was to determine the relation between the seed trajectories and peripheral speed of the vacuum disk. In order to meet the first objective, 2 different seeds (corn and cotton) and artificial spherical material (Ø10 mm) were tested under laboratory conditions. The seeds and artificial material were released by free fall into the semitransparent seed tubes (seed tubes A and B) from different release points, and their trajectories were recorded using a video camera. For the second objective, corn seeds were used and released from a vacuum-type metering unit equipped with a semitransparent seed tube (seed tube A) at 3 different peripheral speeds of the vacuum disk, as a function of 3 forward speeds of the seeder. For both objectives, the seed tubes were modeled and release of the seeds into the seed tubes was simulated and analyzed using ANSYS Fluent for CFD. The results obtained from the captured video and simulations were compared. As a result of the comparisons, it was found that the seed release point was an effective parameter on both the seed trajectory and seed spacing, since seed bouncing and skating in the seed tube, based on the release point, may occur. The results also showed that the lab tests and simulations were found to be very similar in terms of the seed trajectories and seed spacings. It is believed that this study, using CFD, will be an example and enable the development and design of new seed tubes in order to obtain better seed distribution uniformity.
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Garriga-Casanovas, Arnau y Ferdinando Rodriguez y Baena. "Complete follow-the-leader kinematics using concentric tube robots". International Journal of Robotics Research 37, n.º 1 (28 de diciembre de 2017): 197–222. http://dx.doi.org/10.1177/0278364917746222.
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Concentric tube robots offer the capability of follow-the-leader motion, which is desirable when navigating in cluttered environments, such as in minimally invasive surgery or in-situ inspections. The follow-the-leader capabilities identified in the existing literature, however, are limited to trajectories with piecewise constant-curvature segments or piecewise helical segments. A complete study of follow-the-leader kinematics is, therefore, relevant to determine the full potential of these robots, and clarify an open question. In this paper, a general analysis of follow-the-leader motion is presented, and a closed-form solution to the complete set of trajectories where follow-the-leader is possible under the assumption of no axial torsion of the tubes composing the robot is derived. For designs with constant-stiffness tubes, the precurvatures required are found to be either circumference arcs, helices, or deformed helices with exponentially varying curvature magnitude. The analysis developed also elucidates additional motions of interest, such as the combination of follow-the-leader motion in a robot segment with general maneuvers in another part. To determine the applicability of the assumption regarding the tubes’ torsion, the general equilibrium of the robot designs of interest is considered, and a closed-form solution to torsion in two-tube robots with helical precurvatures is derived. Criteria to select a desired torsional behavior are then extracted. This enables one to identify stable trajectories where follow-the-leader is possible, for potential application to minimally invasive surgery. An illustrative case study involving simulation and experiment is conceived using one of these trajectories, and the results are reported, showcasing the research.
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Wacławiak, Krzysztof y Sylwester Kalisz. "Influence of Selected Parameters on Ash Particle Trajectories When Modelling Deposition on Superheater Tubes in Pulverised Coal Boilers Using Fluent Code". Chemical and Process Engineering 35, n.º 3 (1 de septiembre de 2014): 305–16. http://dx.doi.org/10.2478/cpe-2014-0023.
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Abstract Widely used CFD codes enable modelling of PC boilers operation. One of the areas where these numerical simulations are especially promising is predicting deposition on heat transfer surfaces, mostly superheaters. The basic goal of all simulations is to determine trajectories of ash particles in the vicinity of superheater tubes. It results in finding where on the surface the tube will be hit by particles, and what diameter and mass flow of the particles are. This paper presents results of CFD simulations for a single tube and a bundle of in-line tubes as well. It has been shown that available parameters like ash particle density, shape factor, reflection coefficients affect the trajectories in a different way. All the simulations were carried out with Fluent code of Ansys software.
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ISHII, Takahiro y Junta DOI. "Tube Representation of Trajectories Using Spline Functions". Journal of the Visualization Society of Japan 11, Supplement2 (1991): 101–4. http://dx.doi.org/10.3154/jvs.11.supplement2_101.
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Gabor, Grzegorz. "Periodic solutions for nonautonomous differential equations and inclusions in tubes". Abstract and Applied Analysis 2004, n.º 12 (2004): 1057–79. http://dx.doi.org/10.1155/s1085337504403042.
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We study the existence of periodic trajectories for nonautonomous differential equations and inclusions remaining in a prescribed compact subset of an extended phase space. These sets of constraints are nonconvex right-continuous tubes not satisfying the viability tangential condition on the whole boundary. We find sufficient conditions for existence of viable periodic trajectories studying properties of the exit subset of the tube. A new approximation approach for continuous multivalued maps is presented.
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Nandan, Hemwati y Akhilesh Ranjan. "Regge trajectories of exotic hadrons in the flux tube model". International Journal of Modern Physics A 31, n.º 04n05 (3 de febrero de 2016): 1650007. http://dx.doi.org/10.1142/s0217751x1650007x.
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We have investigated the Regge trajectories of exotic hadrons by considering different possible pentaquark configurations with finite quark mass in the flux tube model. Significant deviation is observed in the linear behavior of the Regge trajectories for pentaquark systems in view of the universal value of the Regge slope parameter for hadrons. The modified Regge trajectories are also compared with the available experimental and lattice data. It is observed that the nonlinear Regge trajectories of such pentaquark systems can be well described by the relativistic corrections in view of the current quark masses and the high rotational speed of the quarks at the end of flux tube structure.
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Choi, M., R. Greif y H. R. Baum. "A Study of Heat Transfer and Particle Motion Relative to the Modified Chemical Vapor Deposition Process". Journal of Heat Transfer 111, n.º 4 (1 de noviembre de 1989): 1031–37. http://dx.doi.org/10.1115/1.3250764.
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Heat transfer and particle motion relative to the modified chemical vapor deposition process have been studied for general values of the torch speed. Three-dimensional temperature fields have been obtained over the entire cross section of the tube and the effects of tube rotation and localized torch heating in the axial and circumferential directions have been studied. The particle trajectories have been calculated from a formulation that includes the contributions from forced flow, i.e, Poiseuille flow in the axial direction, rigid body rotation about the tube axis, and thermophoretic contributions in the axial, radial, and angular directions. The particle trajectories are helices and are shown to be strongly dependent on the tube rotation.
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Bourgois, Auguste, Simon Rohou, Luc Jaulin y Andreas Rauh. "Proving Feasibility of a Docking Mission: A Contractor Programming Approach". Mathematics 10, n.º 7 (1 de abril de 2022): 1130. http://dx.doi.org/10.3390/math10071130.
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Recent advances in computational power, algorithms, and sensors allow robots to perform complex and dangerous tasks, such as autonomous missions in space or underwater. Given the high operational costs, simulations are run beforehand to predict the possible outcomes of a mission. However, this approach is limited as it is based on parameter space discretization and therefore cannot be considered a proof of feasibility. To overcome this limitation, set-membership methods based on interval analysis, guaranteed integration, and contractor programming have proven their efficiency. Guaranteed integration algorithms can predict the possible trajectories of a system initialized in a given set in the form of tubes of trajectories. The contractor programming consists in removing the trajectories violating predefined constraints from a system’s tube of possible trajectories. Our contribution consists in merging both approaches to allow for the usage of differential constraints in a contractor programming framework. We illustrate our method through examples related to robotics. We also released an open-source implementation of our algorithm in a unified library for tubes, allowing one to combine it with other constraints and increase the number of possible applications.
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Dumbrajs, Olgerts. "ELECTRON TRAJECTORIES IN A REALISTIC GYROTRON RESONATOR". Mathematical Modelling and Analysis 3, n.º 1 (15 de diciembre de 1998): 74–80. http://dx.doi.org/10.3846/13926292.1998.9637088.
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Gyrotron is a special tube generating powerful radiowaves in the millimeter wave range. Gyrotrons are mainly used to heat nuclear fusion plasma, in order to induce controlled thermonuclear reactions on earth. In addition, they have found a wide utility in radars and the high‐temperature processing of materials. Differential equations describing gyrotron operation are analyzed from the mathematical point of view. Phase portraits of electron trajectories in realistic resonators are determined.
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Ren, Dong-Jie, Shui-Long Shen, Arul Arulrajah y Huai-Na Wu. "Evaluation of ground loss ratio with moving trajectories induced in double-O-tube (DOT) tunnelling". Canadian Geotechnical Journal 55, n.º 6 (junio de 2018): 894–902. http://dx.doi.org/10.1139/cgj-2017-0355.
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This paper investigates the influence of moving trajectories on ground loss ratio (GRL) due to the double-O-tube (DOT) tunnelling method. DOT tunnelling has three moving trajectories: pitching, yawing, and rolling, which have different behaviours during tunnel construction compared with those from single circular shield tunnelling. These moving trajectories cause overexcavation during tunnelling. The calculation method of gap area between the DOT shield machine and linings is evaluated in this research. Based on the superposition concept, the modification equation of GLR is proposed, which takes both moving trajectory and grouting volume into consideration. A field DOT tunnelling case is analysed to determine the correlation between moving trajectories and ground settlement. The influence of tail grouting is discussed by adjusting the grouting volume in different periods. The finite element method is also employed by setting the modified ground loss ratio (GLR′) as the contraction increment of linings. Results from both the measured and simulated settlements verify the reasonability of the proposed equation and the effect of moving trajectories on ground loss.
Tesis sobre el tema "Tube of trajectories"
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Oke, Isdin. "Concentric Tube Robotics: Non-Linear Trajectories for Epilepsy Surgery". Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:27007762.
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Recurrent and unprovoked epilepsy seizures affect more than 50 million people worldwide. Despite advances in antiepileptic drugs, more than 30% of patients continue to demonstrate abnormal neuronal activity; at present, this is primarily treated with surgical intervention1,2. In 80% of patients with medically intractable seizures, the epileptic focus is located in the medial temporal lobe and neurosurgical treatment of these foci requires large skin incisions, extensive bone removal, and potentially harmful excision of brain tissue, several times the size of the epileptic focus3.
Minimally invasive approaches rely on straight endoscopic cannula to either deliver depth electrodes to further refine the target area or lasers to ablate the epileptogenic tissue. However, straight cannulas struggle to properly access non-linear targets such as the amydalo-hippocampal region often implicated in medial temporal lobe epilepsy. Furthermore, the cannulas must be positioned to avoid critical structures such as blood vessels and cerebrospinal fluid filled ventricles. We propose to overcome the limitations of straight cannulas by introducing curved concentric tubes to perform non-linear 3D minimally invasive trajectories.
Concentric tube robots are composed of multiple superelastic Nitinol tubes arranged telescopically4. Each segment can be independently translated and rotated giving rise to two degrees of freedom that can be modeled computationally. Parameterization of the robot characteristics in conjunction with a global pattern search optimization method can determine the optimal trajectory to achieve the greatest coverage of a target volume5. Semi-automatic segmentation of MRI images can generate surface models of target structures as well as obtain coordinates for entry points and boundary constraints. In addition, we can incorporate weighted constraints for surgically critical structures such as ventricular spaces and blood vessels.
We demonstrate that a multi-segmented concentric tube trajectory can consistently achieve a greater percent coverage of a target hippocampus than a manually defined linear trajectory. We also demonstrate that the total skull surface area from which the target can be approached increases as a function of trajectory complexity. Most interestingly, the magnitude of benefit for each additional segment was found to decay such that the greatest increase in target coverage occurs between N = 1 and N = 2 with very gradual improvement for N > 3. Results suggest that the addition of a single curved segment to a linear laser probe will dramatically increase both the target coverage and potential entry positions. Ultimately, the optimized parameters generated will serve as guidelines to fabricate a prototype concentric tube navigation system. As a novel non-linear surgical platform, concentric tube robotics promises an exciting advance in laser ablation neurosurgery.
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Pena, Luciana Prado Mouta. "Análise de um método para equação de convecção formulado à luz da mecânica dos meios contínuos a advecção de anomalias oceânicas e meteorológicas". Universidade do Estado do Rio de Janeiro, 2006. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=872.
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No presente trabalho estudamos e analisamos o método do Tubo de Trajetórias, um algoritmo conservativo, explícito, simples, fisicamente intuitivo, semi-Lagrangiano para equação de convecção. Mostramos que o método é incondicionalmente estável, essencialmente não-dispersivo, convergente e acurado de ordem 2 no tempo e no espaço. Soluções numéricas de sistemas e equações diferenciais ordinárias são testadas no contexto do método do Tubo de Trajetórias, com difíceis problemas clássicos. Aplicações são consideradas no âmbito do transporte oceânico e na advecção de frentes atmosféricas. A fim de testar as propriedades conservativas do método estudado, uma estimativa do erro de balanço de massa é usado aqui. Comparações com outras metodologias mostram a superioridade do método do Tubo de Trajetórias.In the present work we studied and analyzed the Trajectories Tube method, a conservative, explicit, simple, physically intuitive, semi-Lagrangian algorithm for the convection equation. Kinematical aspects of the mechanics of continuous media are essentially the tools used for formulation and feasibility analysis. We showed that this method is unconditionally stable, essentially nondispersive, convergent and accurate of order two in time and space. Computational experiments with non-isochoric and isochoric motions show that the studied method can be used in compressible and incompressible flow. Numerical solutions of systems of ordinary differential equations (necessary conditions for acomplishment of the scheme) are tested in the Trajectories Tube method context, with classical difficult examples. Applications are considered in the ambit of oceanic transport and advection of atmospheric fronts, including the tracer problem within a Stommel gyre and the computation of the Dowell frontogenesis. Comparisions with other methodologies show the superiority of the Trajectories Tube method.
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Wu, Chun-Kuan y 吳俊寬. "The Simulation and Analysis of Electron Trajectories in the X-Ray Tube". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/74033078924688824967.
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Jacquier, Vanessa. "Metastability for serial and parallel dynamics". Doctoral thesis, 2022. http://hdl.handle.net/2158/1274534.
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Metastability is an ubiquitous phenomenon in nature. It appears in a plethora of diverse fields including physics, chemistry, biology, computer science, climatology and economics. Metastability is best described as a dynamical phenomenon that occurs when a system is close to a first order phase transition. After changing some thermodynamic parameters, the system remains for a considerable (random) time in the old phase, the metastable state, before suddenly making a transition to the new phase, the stable state. In other words, on a short time scale, the system behaves as if it was in equilibrium, while, on a long time scale, it moves between different regions of the state space. At low temperature, this motion is preceded by the appearance of a critical mesoscopic configuration of the system via a spontaneous fluctuation or some external perturbation. Thus, when the system is initiated in the metastable phase, it starts its long transition towards the stable phase. In particular, it must overcome an energy barrier to reach the stable state starting from the metastable state. Formally, an Hamiltonian or energy function and the associated dynamics characterized the detailed evolution of the system. Moreover, it is possible to define an equilibrium measure based on the Hamiltonian, for example the Gibbs measure. If the dynamics satisfies the detailed balance condition, then it is reversible with respect to this equilibrium measure.
There are three interesting questions that are typically investigated in metastability. The first is the study of the transition time from the set of metastable states to the set of the stable states, i.e., the time necessary to arrive at the equilibrium phase. The second issue is the identification of the so-called critical configurations that the system creates in order to reach equilibrium. The third question concerns the study of the typical paths that the system follows with high probability during the transition from the metastable state to the stable state.
The thesis is organized in five chapters. In the first two chapters, we present the different approaches and results on asynchronous (serial) and synchronous (parallel) dynamics, in Chapters 2 and 3 respectively. In particular, at the end of the third chapter, we present one of the novelties of this work: an estimate of the mixing time and of the spectral gap, and the computation of the prefactor for the mean transition time also in the case of a series of degenerate metastable states. Next, we study three models evolving under different dynamics. In Chapter 4, we examine the Ising model on the hexagonal lattice with a serial non-conservative dynamics, Glauber dynamics. In particular, we prove some model-dependent results that together with the results of Chapter 2 yield the desired metastability theorems. Indeed, we identify the metastable states proving the recurrence property and computing the maximal stability level. In addition to this, we give a geometrical description of the critical configurations and we show how these are related to polyiamonds. The characterization of the shape of the critical configurations allows us to estimate the mean transition time via potential-theoretic approach. In Chapter 5.1, we describe a particular Probabilistic Cellular Automata model to represent the metastable
behavior of a system subject to parallel dynamics. In particular, using our model-independent results at the end of Chapter 3, we show the behavior of the mixing time and the spectral gap, and we find a rigorous estimate of the expected hitting time. In addition, we identify the metastable states proving recurrence property and classifying the configurations according their stability level. Finally, in Chapter 6, we study the Blume-Capel model evolving under a serial conservative dynamics, the Kawasaki dynamics. These results are still quite heuristic since this is an ongoing project. We present an heuristic study of the phase-diagram and we explain the behavior of the system showing which should be the stable and the metastable states. We suggest an idea based on the crucial role of the boundary to estimate the stability level, to prove the recurrence property and to show the asymptotic behavior of transition time.
Libros sobre el tema "Tube of trajectories"
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Sulmasy, Daniel. The Ethics of Medically Assisted Nutrition and Hydration at the End of Life. Editado por Stuart J. Youngner y Robert M. Arnold. Oxford University Press, 2016. http://dx.doi.org/10.1093/oxfordhb/9780199974412.013.14.
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This chapter examines the ethics of medically supplying nutrition and hydration to dying patients. It first considers the available treatment modalities for patients who are unable to eat or drink, including nasogastric tube feeding, percutaneous endoscopic gastrostomy tube feeding, surgical gastrostomy or jejunostomy tube feeding, proctoclysis, intravenous hydration and nutrition, total or partial parenteral nutrition, and hypodermoclysis. Before discussing the ethics of their use in palliative medicine, the medical aspects of these techniques as well as their risks and benefits are outlined. The author then proposes a classification of four critical decisional junctures along the trajectory of disease progression and highlights a number of disabling, chronic, progressive, and eventually fatal diagnoses with differing trajectories toward death. Finally, it looks at a number of ethical controversies surrounding medically assisted nutrition and hydration, including the issue of religion and the moral and psychological aspects of stopping and starting nutritional therapy.
Capítulos de libros sobre el tema "Tube of trajectories"
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Niyaz, Sherdil, Alan Kuntz, Oren Salzman, Ron Alterovitz y Siddhartha Srinivasa. "Following Surgical Trajectories with Concentric Tube Robots via Nearest-Neighbor Graphs". En Springer Proceedings in Advanced Robotics, 3–13. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-33950-0_1.
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Szabo, Victor. "Coda: Ambient Music in the 21st Century". En Turn On, Tune In, Drift Off, 315—C5.F2. Oxford University PressNew York, 2022. http://dx.doi.org/10.1093/oso/9780190699307.003.0006.
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Abstract A coda to the book considers how today’s ambient music is transforming, and how it may continue to transform, into a more inclusive, aesthetically dynamic, and socially enriching genre culture. Through a series of audio spotlights, it offers some insights into the many promising directions ambient artists have explored since the turn of the twenty-first century. After taking stock of the book’s history of ambient music’s psychedelic past and analysis of ambient’s formation as a popular genre, the coda proposes these recent works as trajectories from which to imagine a more expansive place and meaningful social role for ambient music and its genre culture today.
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Lancaster, Lynne C. "Two Terracotta Vaulting Elements". En Building the Classical World, 134–51. Oxford University Press, 2022. http://dx.doi.org/10.1093/oso/9780190690526.003.0009.
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Imperial Rome had some of the most innovative vaulted architecture from the ancient world, but even before the Imperial period, builders were experimenting by creating new ways of using terracotta vaulting elements, usually in the context of bath buildings. This chapter examines the origins of two of them: vaulting tubes and armchair voussoirs. The initial uses of both techniques developed in response to the need for creating fire- and moisture-proof ceilings over the hot rooms of bath buildings at a time before concrete technology had developed. The roots of both techniques go back to the 3rd century BCE. The chapter traces their subsequent morphological development and geographical dissemination and suggests that the differing trajectories for each can be understood in relation to changing economic factors in different regions that affected the scale of terracotta production.
Actas de conferencias sobre el tema "Tube of trajectories"
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Puscas, Mihai Marian, Enver Sangineto, Dubravko Culibrk y Nicu Sebe. "Unsupervised Tube Extraction Using Transductive Learning and Dense Trajectories". En 2015 IEEE International Conference on Computer Vision (ICCV). IEEE, 2015. http://dx.doi.org/10.1109/iccv.2015.193.
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Li, Linlin, Guoying Gu y Li-Min Zhu. "Motion Control of the Piezoelectric Tube Scanner for Lissajous Trajectories with Modified Repetitive Control". En 2018 International Conference on Manipulation, Automation and Robotics at Small Scales (MARSS). IEEE, 2018. http://dx.doi.org/10.1109/marss.2018.8481174.
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Thanganadar, Dhinesh, Nigel Simms, Kumar Patchigolla, Stefano Mori y Anand Kulkarni. "A Detailed Modelling of Deposition on Superheater Tubes to Enhance Boiler Flexibility". En ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-82282.
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Abstract Biomass cofiring in coal-fired power plants is a promising way to reduce CO2 emissions from existing coal plants. However, the changes in the fuel composition influence the ash deposition mechanisms on superheater tubes, therefore negatively impacting the boiler efficiency, as well as promoting corrosion which compromises the life of the boiler tubes. The continuous fluid flow combined with the ash particle trajectories has been simulated using a Eulerian-Lagrangian model. A novel alkali vapour condensation model has been added to the previous in-house powdery dry deposition model. This paper describes the modelling methodology applied and the in-house user-defined functions. This work analyses the deposition flux, and deposit profiles around the superheater tubes for the changes in four different boundary conditions namely 1) flue gas temperature, 2) tube metal surface temperature, 3) flue gas inlet velocity, and 4) alkali vapour concentration from the flue gas by performing a series of sensitivity studies., revealing that flue gas temperature variation primarily influences the mean ash deposition flux. The tube-tube interactions were analysed in detail by simulating three rows of tube banks containing a total of six tubes arranged in a staggered manner, and results show that row 2 encounters the highest ash deposition flux.
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Fournier, Guillaume J. J., Felicitas Schaefer, Matthias Haeringer, Camilo F. Silva y Wolfgang Polifke. "Interplay of Clusters of Acoustic and Intrinsic Thermoacoustic Modes in Can-Annular Combustors". En ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-80785.
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Abstract Thermoacoustic systems can exhibit self-excited instabilities of two nature, namely cavity modes or intrinsic thermoacoustic (ITA) modes. In heavy-duty land-based gas turbines with canannular combustors, the cross-talk between cans causes the cavity modes of various azimuthal order to create clusters, i.e. ensembles of modes with close frequencies. Similarly, in systems exhibiting rotational symmetry, ITA modes also have the peculiar behavior of forming clusters. In the present study, we investigate how such clusters interplay when they are located in the same frequency range. We first consider a simple Rijke tube configuration and derive a general analytical low-order network model using only dimensionless numbers. We investigate the trajectories of the eigenmodes when changing the downstream length and the flame position. In particular, we show that ITA and acoustic modes can switch nature and their trajectories are strongly influenced by the presence of exceptional points. We then study a generic can-annular combustor. We show that such configuration can be approximated by an equivalent Rijke tube. We demonstrate that, in the absence of mean flow, the eigenvalues of the system necessarily lie on specific trajectories imposed by the upstream conditions.
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Vardelle, M., A. Vardelle, B. Dussoubs, P. Fauchais, T. J. Roemer, R. A. Neiser y M. F. Smith. "Influence of Injector Geometry on Particle Trajectories: Analysis of Particle Dynamics in the Injector and Plasma Jet". En ITSC 1998, editado por Christian Coddet. ASM International, 1998. http://dx.doi.org/10.31399/asm.cp.itsc1998p0887.
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Abstract The conditions of particle injection into the side of plasma jets play an important role in determining the microstructure and properties of sprayed deposits. However, few investigations have been carried out on this topic. The current work presents the results of an experimental and computational study of the influence of injector geometry and gas mass flow rate on particle dynamics at injector exit and in the plasma jet. Two injector geometries were tested: a straight tube and a curved tube with various radii of curvature. Zirconia powders with different particle size range and morphology were used. A possible size segregation effect in the injector was analyzed from the space distribution of particles collected on a stick tape. The spray pattern in the plasma jet was monitored from the thermal radiation emitted by particles. An analysis of the particle behavior in the injector and mixing of the carrier-gas flow with the plasma jet was carried out using a 3-D computational fluids dynamics code.
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Epelbaum, Greg. "Corrosion Study and Modification of Superheater Tubes in a Large Mass Burn WTE Boiler (Abstract)". En 13th Annual North American Waste-to-Energy Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/nawtec13-3143.
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Essex County Resource Recovery Facility (one of American Ref-Fuel Company’s six operating plants) has processing MSW capacity of approximately 2700 TPD and about 60% of this waste comes from NY City. Therefore, availability of the Essex plant boilers is very important not only for the company’s financial performance, it is also critical for the overall garbage disposal situation in the NYC Metropolitan area. One of the main factors affecting plant availability is boiler unscheduled downtime. The most recent data show that approximately 85% of Essex boilers unscheduled downtime is caused by tube failures, the majority of which occur in the superheater tubes. These tube failures are almost exclusively caused by fireside tube metal wastage driven by complicated mechanisms of corrosion in combination with local erosion. The corrosion is caused by chloride salts in the slag that deposits on the boiler tubes, coupled with high temperatures of flue gas going through the boiler. Corrosion rates are known to be very sensitive to flue gas temperature, tube metal temperature, heat flux, flow distribution. Erosion is typically caused by high velocities and flyash particle loading and trajectories. Extensive research revealed that in addition to this typical to WTE boiler corrosion/erosion mechanism, Essex boiler superheater tubes experienced a unique problem, resulting in tube overheating, accelerated wastage, and ultimate failure. In order to address this problem a modification plan was developed, which comprised several redesign options. A specially developed Three-dimensional Computational Fluid Dynamics (3-D CFD) model was utilized for comprehensive technical evaluation of the considered design options and for predicted performance simulations of the selected design at different operating conditions. The economical analysis, conducted in conjunction with the superheater redesign, provided financial justification for this project. The project has been recently executed, and field data collection is still in progress. Some preliminary data analyses have been performed. They have shown that the boiler performance after superheater modification is very close to the predicted target simulated by the CFD model. The plant and the company are already measuring financial benefits as a result of this project, the initial phase of which is presented in this paper.
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Luxat, J. C. "Dynamic Sensitivity Analysis of Thermal-Mechanical Deformation of a CANDU Fuel Channel". En 16th International Conference on Nuclear Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/icone16-48656.
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In a limiting critical break loss of coolant accident in a CANDU reactor significant degradation of heat transfer from the fuel can occur. As a result of the subsequent increase in fuel temperature it is possible that the pressure tube undergoes heat up at intermediate pressure during blowdown. This can result in ballooning deformation of the pressure tube into contact with its calandria tube. It is required that fuel channels not fail as a consequence of the thermal mechanical deformation of the pressure tube and calandria tube in such events. Dynamic sensitivity functions are derived as analytical partial differential equations derived from the equations used to model the time-dependent behavior of physical systems. The dynamic sensitivity functions can be used to propagate uncertainties using a time-dependent perturbation approach in which the variations in a set of output variables, with respect to perturbations of the input parameters, are evaluated about reference response trajectories of the input parameters and associated output variables. The dynamic sensitivity method is described in this paper and results are presented for the pressure tube heatup phase of a LOCA. These results show the importance of all key parameters with respect to specified safety evaluation criteria. The dynamic sensitivity method is applied in a probabilistic uncertainty analysis to evaluate the probability of a pressure tube experiencing creep strain deformation to contact its calandria tube during the early stages of a LOCA.
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Chen, Yue, Megan E. Poorman, David B. Comber, E. Bryn Pitt, Cindy Liu, Isuru S. Godage, Hong Yu, William A. Grissom, Eric J. Barth y Robert J. Webster. "Treating Epilepsy via Thermal Ablation: Initial Experiments With an MRI-Guided Concentric Tube Robot". En 2017 Design of Medical Devices Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/dmd2017-3408.
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Epilepsy is a prevalent neurological disorder affecting 65 million people globally [1]. Anti-epileptic medications fail to provide effective seizure control for 30% of patients, placing them at a 7–17% risk of Sudden Unexplained Death in Epilepsy and recurrent seizures. Surgical resection of the seizure focus is a potentially curative treatment for patients with seizures that electrophysiologically correlate to a focal lesion. For these patients, focal surgical resection can result in 60–70% seizure-freedom rates [2]. However, open resection carries the risk of cognitive impairment or focal neurologic deficit [3]. Recent innovations in MRI enable high resolution soft tissue visualization, and real-time temperature monitoring, making MR-guided ablation therapy a promising minimally invasive technique to restrict the tissue destruction to just the seizure focus. Commercial products (e.g., Visualase, Medtronic Inc.; ClearPoint, MRI Interventions Inc.; NeuroBlate, Monteris Inc.) have recently been introduced for MR-guided laser-based thermal ablation. These products require the physician drill a hole into the skull for ablation probe placement, and may not always be able to ablate the entire seizure focus when the structure has a curved shape (such as the hippocampus) [4]. Incomplete ablation of the seizure focus would lead to seizure recurrence. We have recently proposed concentric-tube steerable needles as a means to address these challenges [4–7]. They enable nonlinear trajectories and offer the potential to enter the brain through the patient’s cheek via a natural opening in the skull base (i.e. the foramen ovale). We have designed and fabricated an MR-compatible robotic system to provide high resolution actuation for helical needle deployment [5]. We have shown in simulation that the curved medial axis of hippocampus can be accessed via a helical needle that delivers the ablation probe into the brain [4]. These preliminary results suggest that MR-guided robotic transforamenal thermal therapy could potentially provide a less invasive approach for potentially curative epilepsy treatment. In this paper we present our first results delivering heat along curved paths in brain phantoms and imaging the resulting treatment zones using MRI.
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Nikbakht, Abbas, Omid Abouali y Goodarz Ahmadi. "3-D Modelling of Brownian Motion of Nano-Particles in Aerodynamic Lenses". En ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98488.
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A computer code for analyzing nano-particle motions in an aerodynamic particle beam focusing system was developed. The effectiveness of the focusing system consisting of several lenses, nozzle and downstream tube of the nozzle was analyzed. The code included an accurate 3-dimensional model for the Brownian diffusion of nano-particles in sharply varying pressure field in the aerodynamic lens system. Lagrangian particle Trajectory analysis was performed assuming a one-way coupling model. The particle equation of motion used included drag and Brownian forces. Trajectories of different size nano-particles in an aerodynamic lens were analyzed, and the particle beam focusing process was studied. The numerical results of 3-D model for particle beam diameter, penetration efficiency and beam divergence angle were compared with axisymmetric model and discussed. The importance of the accuracy of the computational model for the simulation of the Brownian diffusion for predicting the focusing performance of the aerodynamic lenses was discussed. The simulation results showed that for particle diameters less than 50 nm in helium, the Brownian force could significantly affect the beam focusing and particle collection efficiency. Furthermore, the nano-particle trajectories in this range are three-dimensional and an axisymmetric model may not correctly capture the features of particle motions in aerodynamic lenses.
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Ghenaiet, A. y S. C. Tan. "Numerical Study of an Inlet Particle Separator". En ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-54168.
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Helicopters operating in a desert region are often subjected to the environmental effects of sand ingestion that can erode gas turbine engines and block the cooling passages. Traditional method of removing sand particles include barrier filters that employed vortex tube and impact filter designs, and inertial particle separator (IPS). Barrier filters are normally quite heavy and require constant servicing or replacement. IPS relies on contoured surfaces to direct particulates to a scavenge area through the actions of the viscous forces and bounce characteristics of the sand particles. The geometrical design of an IPS plays an important role in determining the sand separation efficiency. This paper presents a numerical study of the RTM322 IPS, which includes the effects of changing the hub, splitter and scavenge duct geometries on the sand separation efficiency. The flow field calculation in the IPS was performed with the commercial CFD software package called TASCflow. The particle trajectories were computed using an in-house developed trajectory code, which was based on the lagrangian method. The effects of flow turbulence on the trajectory were simulated using the eddy lifetime concept. Several design geometrical modifications were investigated such as the shape of the hub and splitter and their relative locations. Particle trajectories and separation efficiency were performed for a range of sand particle sizes, inlet mass flow rates and scavenge ratios.
Informes sobre el tema "Tube of trajectories"
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Weiland, Mark A., Robert P. Mueller, Thomas J. Carlson, Zhiquan Deng y Craig A. McKinstry. Characterization of Bead Trajectories Through the Draft Tube of a Turbine Physical Model. Office of Scientific and Technical Information (OSTI), febrero de 2005. http://dx.doi.org/10.2172/15011275.
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Weiland, M. A., R. P. Mueller, T. J. Carlson, Z. D. Deng y C. A. McKinstry. Characterization of bead trajectories through the draft tube of a turbine physical model. Office of Scientific and Technical Information (OSTI), febrero de 2005. http://dx.doi.org/10.2172/1218122.
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