Artículos de revistas: "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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5

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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7

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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10

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.

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11

Comber, David B., E. Bryn Pitt, Hunter B. Gilbert, Matthew W. Powelson, Emily Matijevich, Joseph S. Neimat, Robert J. Webster y Eric J. Barth. "Optimization of Curvilinear Needle Trajectories for Transforamenal Hippocampotomy". Operative Neurosurgery 13, n.º 1 (25 de julio de 2016): 15–22. http://dx.doi.org/10.1227/neu.0000000000001361.

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Abstract BACKGROUND: The recently developed magnetic resonance imaging–guided laser-induced thermal therapy offers a minimally invasive alternative to craniotomies performed for tumor resection or for amygdalohippocampectomy to control seizure disorders. Current laser-induced thermal therapies rely on linear stereotactic trajectories that mandate twist-drill entry into the skull and potentially long approaches traversing healthy brain. The use of robotically driven, telescoping, curved needles has the potential to reduce procedure invasiveness by tailoring trajectories to the curved shape of the ablated structure and by enabling access through natural orifices. OBJECTIVE: To investigate the feasibility of using a concentric tube robot to access the hippocampus through the foramen ovale to deliver thermal therapy and thereby provide a percutaneous treatment for epilepsy without drilling the skull. METHODS: The skull and both hippocampi were segmented from dual computed tomography/magnetic resonance image volumes for 10 patients. For each of the 20 hippocampi, a concentric tube robot was designed and optimized to traverse a trajectory from the foramen ovale to and through the hippocampus from head to tail. RESULTS: Across all 20 cases, the mean distances (errors) between the hippocampus medial axis and backbone of the needle were 0.55, 1.11, and 1.66 mm for the best, mean, and worst case, respectively. CONCLUSION: These curvilinear trajectories would provide accurate transforamenal delivery of an ablation probe to typical hippocampus volumes. This strategy has the potential both to decrease the invasiveness of the procedure and to increase the completeness of hippocampal ablation.

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12

Torres, A., A. Medina, F. J. Higuera y P. D. Weidman. "On super free fall". Journal of Fluid Mechanics 723 (16 de abril de 2013): 653–64. http://dx.doi.org/10.1017/jfm.2013.144.

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AbstractVillermaux & Pomeau (J. Fluid Mech., vol. 642, 2010, p. 147) analysed the motion of the interface of an inviscid liquid column released from rest in a vertical tube whose area expands gradually downwards, with application to an inverted conical container for which experimental measurements were carried out. An error in the analysis is found and corrected in the present investigation, which provides the new governing equation for the super-accelerated interface motion down gradually varying tubes in general, and integrated results for interface trajectories, velocities and accelerations down a conical tube in particular. Interestingly, the error does not affect any of the conclusions given in the 2010 paper. Further new results are reported here such as the equation governing the centre of mass and proof that the end point acceleration is exactly that of gravity.

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13

Feng, Huicheng y Teck Neng Wong. "Electrophoresis of a Cylinder in a Cylindrical Tube". Communications in Computational Physics 22, n.º 4 (28 de julio de 2017): 1101–22. http://dx.doi.org/10.4208/cicp.oa-2017-0011.

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AbstractElectrophoresis of a cylinder suspended in a cylindrical tube is analytically studied in the limit of thin electric double layer approximation. The electric and fluid flow fields within the annulus, and the cylinder velocities are analytically obtained in bipolar coordinates. The results are analyzed with various values of dimensionless parameters: eccentricity, cylinder-to-tube radius ratio and tube-to-cylinder zeta potential ratio (i.e., tube-to-cylinder velocity scale ratio). The analysis shows that microvortices are generated within the annulus. By changing the parameters, different flow patterns can be created, which shows potential for mixing enhancement in micro/nanofluidics. Moreover, the cylinder not only translates but also rotates when the cylinder and tube are eccentric. The cylinder rotation might be utilized as a micromotor or an electric field detector. The cylinder trajectories show that the cylinder may approach the tube wall or rest within the tube depending on the zeta potential ratio.

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Behnia, Masud, L. A. Amoroso y R. A. Platfoot. "VISUALIZATION OF FLY ASH PARTICLE TRAJECTORIES WITHIN A BOILER TUBE BANK MODEL". Journal of Flow Visualization and Image Processing 3, n.º 1 (1996): 91–107. http://dx.doi.org/10.1615/jflowvisimageproc.v3.i1.70.

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15

Lin, Weiyao, Yang Zhou, Hongteng Xu, Junchi Yan, Mingliang Xu, Jianxin Wu y Zicheng Liu. "A Tube-and-Droplet-Based Approach for Representing and Analyzing Motion Trajectories". IEEE Transactions on Pattern Analysis and Machine Intelligence 39, n.º 8 (1 de agosto de 2017): 1489–503. http://dx.doi.org/10.1109/tpami.2016.2608884.

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16

Krueger, Paul S. "Circulation and trajectories of vortex rings formed from tube and orifice openings". Physica D: Nonlinear Phenomena 237, n.º 14-17 (agosto de 2008): 2218–22. http://dx.doi.org/10.1016/j.physd.2008.01.004.

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17

Forney, L. J., Z. Feng y X. Wang. "Jet Trajectories of Transverse Mixers at Arbitrary Angle in Turbulent Tube Flow". Chemical Engineering Research and Design 77, n.º 8 (noviembre de 1999): 754–58. http://dx.doi.org/10.1205/026387699526737.

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18

Ivchenko, Anastasia Yurievna, Alexey Alexeevich Kislitsyn y Yurii Nikolaevich Orlov. "SIR distribution for dynamical system trajectories on the example of underground tube". Keldysh Institute Preprints, n.º 155 (2018): 1–21. http://dx.doi.org/10.20948/prepr-2018-155.

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19

Ait Oucheggou, Ouardia, Véronique Pointeau, Guillaume Ricciardi, Élisabeth Guazzelli y Laurence Bergougnoux. "Particle-laden flow around an obstacle in a square pipe: experiments and modeling". Mechanics & Industry 21, n.º 5 (2020): 517. http://dx.doi.org/10.1051/meca/2020063.

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Particle trapping and deposition around an obstacle occur in many natural and industrial situations and in particular in the nuclear industry. In the steam generator of a nuclear power plant, the progressive obstruction of the flow due to particle deposition reduces the efficiency and can induce tube cracking leading to breaking and damage. The steam generator then loses its role as a safety barrier of the nuclear power plant. From a fundamental standpoint, dilute and concentrated particulate flows have received a growing attention in the last decade. In this study, we investigate the transport of solid particles around obstacles in a confined flow. Experiments were performed in a simplified configuration by considering a laminar flow in a vertical tube. An obstacle was inserted at the middle height of the tube and neutrally-buoyant particles were injected at different locations along the tube. We have investigated first the trajectories of individual particles using particle tracking (PT). Then, the particle trajectories were modeled by using the Boussinesq-Basset-Oseen equation with a flow velocity field either measured using particle image velocimetry (PIV) or calculated by the Code_Saturne software in order to account for the three-dimensional (3D) character of the obstacle wake. This paper presents a comparison between the experimental observations and the predictions of the modeling for an obstacle consisting of a rectangular step at a Reynolds number of ≈100 and evidences the importance of accounting for the 3D complex nature of the flow.

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Leão, Gonçalo, Carlos M. Costa, Armando Sousa y Germano Veiga. "Detecting and Solving Tube Entanglement in Bin Picking Operations". Applied Sciences 10, n.º 7 (26 de marzo de 2020): 2264. http://dx.doi.org/10.3390/app10072264.

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Manufacturing and production industries are increasingly turning to robots to carry out repetitive picking operations in an efficient manner. This paper focuses on tackling the novel challenge of automating the bin picking process for entangled objects, for which there is very little research. The chosen case study are sets of freely curved tubes, which are prone to occlusions and entanglement. The proposed algorithm builds a representation of the tubes as an ordered list of cylinders and joints using a point cloud acquired by a 3D scanner. This representation enables the detection of occlusions in the tubes. The solution also performs grasp planning and motion planning, by evaluating post-grasp trajectories via simulation using Gazebo and the ODE physics engine. A force/torque sensor is used to determine how many items were picked by a robot gripper and in which direction it should rotate to solve cases of entanglement. Real-life experiments with sets of PVC tubes and rubber radiator hoses showed that the robot was able to pick a single tube on the first try with success rates of 99% and 93%, respectively. This study indicates that using simulation for motion planning is a promising solution to deal with entangled objects.

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Ganesh, C. L., K. Santosh, Mallanna Renuka y Karthik Shastry. "Design Of An Electrostatic Ion Trap And Time-of-Flight Tube Using SIMION Software". ECS Transactions 107, n.º 1 (24 de abril de 2022): 18859–66. http://dx.doi.org/10.1149/10701.18859ecst.

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Electrostatic traps are a class of ion traps that rely on electric fields to confine charged particles in a region of space. It uses an electric field to trap the incoming ions from an ion source, confine them for a certain period of time, and then release them either as a continuous or pulsed ion beam. Ions once released from the trap are made to fly through a Time of Flight (ToF) tube for segregation based on their energies and mass. The time taken to travel the length of the ToF tube is equated to the mass of the ion, which can further be used to calculate the energy and mass of the ions. SIMION software simulates the trajectories of charged particles through electric and magnetic fields of different geometries. In this proposed paper, we will be presenting simulations of an (a) electrostatic ion trap and (b) Time of Flight tube using SIMION software. Experimental data of confinement time of ions in the trap and the time of flight of the ions in a 1m and 2m long ToF tube are simulated and tabled. The results from the simulations reported in this paper can be used as a template to design and develop custom electrostatic traps in conjunction with ToF tubes for specific instruments like spectrometers, medical devices, etc.

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22

Lin, Y. T., M. Choi y R. Greif. "A Three-Dimensional Analysis of the Flow and Heat Transfer for the Modified Chemical Vapor Deposition Process Including Buoyancy, Variable Properties, and Tube Rotation". Journal of Heat Transfer 113, n.º 2 (1 de mayo de 1991): 400–406. http://dx.doi.org/10.1115/1.2910575.

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A study has been made of the heat transfer, flow, and particle deposition relative to the modified chemical vapor deposition (MCVD) process. The effects of variable properties, buoyancy, and tube rotation have been included in the study. The resulting three-dimensional temperature and velocity fields have been obtained for a range of conditions. The effects of buoyancy result in asymmetric temperature and axial velocity profiles with respect to the tube axis. Variable properties cause significant variations in the axial velocity along the tube and in the secondary flow in the region near the torch. Particle trajectories are shown to be strongly dependent on the tube rotation and are helices for large rotational speeds. The component of secondary flow in the radial direction is compared to the thermophoretic velocity, which is the primary cause of particle deposition in the MCVD process. Over the central portion of the tube the radial component of the secondary flow is most important in determining the motion of the particles.

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Sivathanu, Y. R. y J. P. Gore. "Effects of Surface Properties on Radiative Transfer in a Cylindrical Tube With a Nonparticipating Medium". Journal of Heat Transfer 119, n.º 3 (1 de agosto de 1997): 495–501. http://dx.doi.org/10.1115/1.2824123.

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Radiative heat transfer inside a cylindrical tube is modeled using a statistical method called the discrete probability function (DPF) method. The DPF method involves solution of the equation of radiative heat transfer using Lagrangian simulations of representative photon trajectories on a discrete spatial grid. The DPF method is different from the Markov Chain method in terms of associating a probability with each state of the photon rather than a transition from one state to another. The advantages and disadvantages of the DPF method in comparison to the Markov Chain method are demonstrated in this paper using two practical applications of the cylindrical tube radiative heat transfer problem. The cylindrical tube has a hot source at one end and a detector at the other end. The cylindrical wall absorbs and reflects (both diffusely and specularly) the radiation incident on it. The present calculations have applications in: (1) intrusive pyrometry with collimating light guides, and (2) measurement of the spectral absorption and reflection coefficients of coatings using two, coated cylindrical tubes as specimen. The results show that: (1) the effect of light guide surface properties on errors in pyrometry must be carefully assessed, and (2) the method can be used for a convenient evaluation of radiative properties of coatings.

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Sakamoto, Hitoshi, Yuji Takakuwa, Toyokazu Hori, Yoshiharu Enta, Hiroo Kato y Nobuo Miyamoto. "Development of a three-electrode-lens drift tube for time-of-flight mass spectrometry". Journal of Synchrotron Radiation 5, n.º 3 (1 de mayo de 1998): 612–14. http://dx.doi.org/10.1107/s0909049597019390.

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A three-electrode-lens drift tube for time-of-flight mass spectrometry (TOF-MS) has been developed for utilizing a detector to observe photon-stimulated desorption (PSD). In spite of a small detection area, the detector has a high detection efficiency and durability to reactive gas atmosphere at high pressure. The TOF-MS performance of the drift tube was examined for PSD using single-bunch-mode synchrotron radiation on a dichlorosilane (SiH2Cl2)-saturated Si(001) surface. The measured acceleration and focusing-voltage dependences of the time of flight, intensity and full width at half-maximum for the peak of H+ and Cl+ PSD ions are discussed in terms of the numerical calculations of ion trajectories and focusing characteristic of the drift tube.

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Snyder, J. M. y J. F. Wilson. "Dynamics of the Elastica With End Mass and Follower Loading". Journal of Applied Mechanics 57, n.º 1 (1 de marzo de 1990): 203–8. http://dx.doi.org/10.1115/1.2888305.

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Orthotropic, polymeric tubes subjected to internal pressure may undergo large deformations while maintaining linear moment-curvature behavior. Such tubes are modeled herein as inertialess, elastic cantilever beams (the elastica) with a payload mass at the tip and with internal pressure as the eccentric tip follower loading that drives the configurations through large deformations. From the nonlinear equations of motion, dynamic beam trajectories are calculated over a range of system parameters for the special case of a point mass at the tip and a terminated ramp pressure loading. The dynamic responses, which are unique because the loading history and the range of motion are fully defined, are presented in nondimensional form and are compared to static responses presented in a companion study. These results are applicable to the dynamic design of high flexure, tube-type, robotic manipulator arms.

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Kulesa, P., M. Bronner-Fraser y S. Fraser. "In ovo time-lapse analysis after dorsal neural tube ablation shows rerouting of chick hindbrain neural crest". Development 127, n.º 13 (1 de julio de 2000): 2843–52. http://dx.doi.org/10.1242/dev.127.13.2843.

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Previous analyses of single neural crest cell trajectories have suggested important roles for interactions between neural crest cells and the environment, and amongst neural crest cells. To test the relative contribution of intrinsic versus extrinsic information in guiding cells to their appropriate sites, we ablated subpopulations of premigratory chick hindbrain neural crest and followed the remaining neural crest cells over time using a new in ovo imaging technique. Neural crest cell migratory behaviors are dramatically different in ablated compared with unoperated embryos. Deviations from normal migration appear either shortly after cells emerge from the neural tube or en route to the branchial arches, areas where cell-cell interactions typically occur between neural crest cells in normal embryos. Unlike the persistent, directed trajectories in normal embryos, neural crest cells frequently change direction and move somewhat chaotically after ablation. In addition, the migration of neural crest cells in collective chains, commonly observed in normal embryos, was severely disrupted. Hindbrain neural crest cells have the capacity to reroute their migratory pathways and thus compensate for missing neural crest cells after ablation of neighboring populations. Because the alterations in neural crest cell migration are most dramatic in regions that would normally foster cell-cell interactions, the trajectories reported here argue that cell-cell interactions have a key role in the shaping of the neural crest migration.

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27

Jiang, W. "A New Constitutive Model in the Theory of Plasticity—Part II: Examples". Journal of Pressure Vessel Technology 117, n.º 4 (1 de noviembre de 1995): 371–77. http://dx.doi.org/10.1115/1.2842138.

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This part of the paper presents several examples to further demonstrate the hardening model proposed in the first part of the paper. Closed-form solutions are achieved for a thin-walled tube subjected to linear, rectangular, and circular loading paths, and the corresponding yield center loci and plastic strain trajectories are illustrated. The features of this model are further discussed.

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Zhu, L., E. Lauga y L. Brandt. "Low-Reynolds-number swimming in a capillary tube". Journal of Fluid Mechanics 726 (31 de mayo de 2013): 285–311. http://dx.doi.org/10.1017/jfm.2013.225.

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AbstractWe use the boundary element method to study the low-Reynolds-number locomotion of a spherical model microorganism in a circular tube. The swimmer propels itself by tangential or normal surface motion in a tube whose radius is of the order of the swimmer size. Hydrodynamic interactions with the tube walls significantly affect the average swimming speed and power consumption of the model microorganism. In the case of swimming parallel to the tube axis, the locomotion speed is always reduced (respectively, increased) for swimmers with tangential (respectively, normal) deformation. In all cases, the rate of work necessary for swimming is increased by confinement. Swimmers with no force dipoles in the far field generally follow helical trajectories, solely induced by hydrodynamic interactions with the tube walls, and in qualitative agreement with recent experimental observations for Paramecium. Swimmers of the puller type always display stable locomotion at a location which depends on the strength of their force dipoles: swimmers with weak dipoles (small $\alpha $) swim in the centre of the tube while those with strong dipoles (large $\alpha $) swim near the walls. In contrast, pusher swimmers and those employing normal deformation are unstable and end up crashing into the walls of the tube. Similar dynamics is observed for swimming into a curved tube. These results could be relevant for the future design of artificial microswimmers in confined geometries.

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Fitzsimmons, Eric J., Reginald R. Souleyrette y Shashi S. Nambisan. "Measuring Horizontal Curve Vehicle Trajectories and Speed Profiles: Pneumatic Road Tube and Video Methods". Journal of Transportation Engineering 139, n.º 3 (marzo de 2013): 255–65. http://dx.doi.org/10.1061/(asce)te.1943-5436.0000501.

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30

Beavers, J., K. Huddleston, N. Hines y W. McNeil. "Modeling electron transport and multiplication in photomultiplier tubes using COMSOL Multiphysics^®". Journal of Instrumentation 17, n.º 12 (1 de diciembre de 2022): P12015. http://dx.doi.org/10.1088/1748-0221/17/12/p12015.

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Abstract Combining stochastic and finite element methods, a modeling approach was executed that will inform new photomultiplier tube and scintillation detector designs. Time-dependent signal formation within a commercially available photomultiplier tube was modeled including the release and transport of electrons from the photocathode through the dynode stages. An ET Enterprises 9214B photomultiplier tube was digitally reproduced using Computed Tomography, X-ray radiography, and SolidWorks solid-modeling software. Simulations were executed with COMSOL Multiphysics® finite element solving package. Stochastic models of electron emission from the photocathode and dynodes were integrated within the COMSOL framework. Photoelectron emission energy was modeled by combining NaI(Tl) spectral emission characteristics and K2CsSb photocathode quantum efficiency. Secondary electron emission yields were produced to follow nominal photomultiplier gain, while secondary electron energies were sampled from the Chung-Everhart distribution. Electron emission trajectories were sampled according to Lambert's cosine law. Coupling stochastic and finite element models, simulation reproduced signal formation for the commercial photomultiplier tube including timing characteristics within 9.5% and gain within 3% over a voltage range of 900–1250 V.

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31

Morse, T. F., C. Y. Wang y J. W. Cipolla. "Laser-Induced Thermophoresis and Particulate Deposition Efficiency". Journal of Heat Transfer 107, n.º 1 (1 de febrero de 1985): 155–60. http://dx.doi.org/10.1115/1.3247372.

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The interaction of laser radiation and an absorbing aerosol in a tube flow has been considered. The aerosol is produced by external heating of reactants as in the MCVD (Modified Chemical Vapor Deposition) process to produce submicron size particles in the manufacture of optical fiber preforms. These particles are deposited by thermophoretic forces on the inner wall of the tube as they are convected by a Poiseuille velocity profile. Axial laser radiation in the tube interacts with the absorbing particles, and the laser heating of the gas induces additional thermophoretic forces that markedly increase the efficiency of particulate deposition. A particle concentration dependent absorption coefficient that appears in the energy equation couples the energy equation to the equation of particle conservation, so that a nonlinear set of coupled partial integro-differential equations must be solved. Numerical solutions for aerosol particle trajectories, and thus deposition efficiencies, have been obtained. It is shown that laser enhanced thermophoresis markedly improves the deposition efficiency.

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32

Vyskrebtsov, V. G. "Possibility for finding of a common solution for Navier-Stokes equations". Izvestiya MGTU MAMI 6, n.º 2-2 (20 de marzo de 2012): 270–77. http://dx.doi.org/10.17816/2074-0530-68538.

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The paper considers equations of a particle of a Newtonian fluid motion (equations of Navier-Stokes) in a vector form. The equality to zero of a rotor of the gradient is used, so it allows to move to one vector equation only by the speed and rotor speed. This equation contains the linear and quadratic terms. On the basis of the observations of the trajectories of the liquids flow in leakage from the tank through a tube, the trajectories of the flow does not change when fluid consumption changes, the conclusion is that with a change in flow velocity the equality of quadratic and linear parts of the motion equations can only be stored in that case, if these parts are equal to zero. This allows you to move to a more simple system of equations than the Navier-Stokes equations.

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33

Davison, James, Melissa Pritchard, Emma Footitt, Paul Gissen, Mildrid Yeo y Maureen Cleary. "Mucolipidosis type II growth trajectories and requirement for enteral tube feeding: A single centre review". Molecular Genetics and Metabolism 135, n.º 2 (febrero de 2022): S35. http://dx.doi.org/10.1016/j.ymgme.2021.11.077.

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34

Wen, Zhifei, Rebecca Fahrig, Steven Conolly y Norbert J. Pelc. "Investigation of electron trajectories of an x-ray tube in magnetic fields of MR scanners". Medical Physics 34, n.º 6Part1 (15 de mayo de 2007): 2048–58. http://dx.doi.org/10.1118/1.2733798.

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35

CHANDRA, A., A. BHATTACHARYA y B. CHAKRABARTI. "HEAVY PENTAQUARKS AND DOUBLY HEAVY BARYONS IN QUASIPARTICLE APPROACH". Modern Physics Letters A 27, n.º 01 (10 de enero de 2012): 1250006. http://dx.doi.org/10.1142/s021773231250006x.

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In the framework of the quasiparticle approach, the ground state mass of heavy pentaquarks have been investigated in diquark–diquark–antiquark picture and the higher states are investigated in the mass loaded flux tube model where two light diquarks are supposed to be linked by a flux tube to the heavy quark. The Regge trajectories for heavy pentaquarks have been studied. The Regge slope (α) of these particles have been obtained as ≈1 GeV2 which indicates that the Regge trajectory follows the linearity conditions with universal value of α (~ 1 GeV2). The ground state mass of doubly charm and doubly bottom baryons like [Formula: see text] have also been investigated in quasiparticle approach. The results are found to be in reasonably good agreement with the experimental and other theoretical estimates.

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36

Kohutova, P., E. Verwichte y C. Froment. "First direct observation of a torsional Alfvén oscillation at coronal heights". Astronomy & Astrophysics 633 (enero de 2020): L6. http://dx.doi.org/10.1051/0004-6361/201937144.

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Context. Torsional Alfvén waves are promising candidates for the transport of energy across different layers of the solar atmosphere. They have been predicted theoretically for decades. Previous detections of Alfvén waves so far have however mostly relied on indirect signatures. Aims. We present the first direct observational evidence of a fully resolved torsional Alfvén oscillation of a large-scale structure occurring at coronal heights. Methods. We analysed IRIS imaging and spectral observation of a surge resulting from magnetic reconnection between active region prominence threads and surrounding magnetic field lines. Results. The IRIS spectral data provide clear evidence of an oscillation in the line-of-sight velocity with a 180° phase difference between the oscillation signatures at opposite edges of the surge flux tube. This together with an alternating tilt in the Si IV and Mg II k spectra across the flux tube and the trajectories traced by the individual threads of the surge material provide clear evidence of torsional oscillation of the flux tube. Conclusions. Our observation shows that magnetic reconnection leads to the generation of large-scale torsional Alfvén waves.

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37

Eckert, Mark A., Shawn Pan, Kyle M. Hernandez, Rachel M. Loth, Jorge Andrade, Samuel L. Volchenboum, Pieter Faber et al. "Genomics of Ovarian Cancer Progression Reveals Diverse Metastatic Trajectories Including Intraepithelial Metastasis to the Fallopian Tube". Cancer Discovery 6, n.º 12 (7 de octubre de 2016): 1342–51. http://dx.doi.org/10.1158/2159-8290.cd-16-0607.

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38

Sugihara-Seki, Masako. "The motion of an ellipsoid in tube flow at low Reynolds numbers". Journal of Fluid Mechanics 324 (10 de octubre de 1996): 287–308. http://dx.doi.org/10.1017/s0022112096007926.

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The motion of a rigid ellipsoidal particle freely suspended in a Poiseuille flow of an incompressible Newtonian fluid through a narrow tube is studied numerically in the zero-Reynolds-number limit. It is assumed that the effect of inertia forces on the motion of the particle and the fluid can be neglected and that no forces or torques act on the particle. The Stokes equation is solved by a finite element method for various positions and orientations of the particle to yield the instantaneous velocity of the particle as well as the flow field around it, and the particle trajectories are determined for different initial configurations. A prolate spheroid is found to either tumble or oscillate in rotation, depending on the particle–tube size ratio, the axis ratio of the particle, and the initial conditions. A large oblate spheroid may approach asymptotically a steady, stable configuration, at which it is located close to the tube centreline, with its major axis slightly tilted from the undisturbed flow direction. The motion of non-axisymmetric ellipsoids is also illustrated and discussed with emphasis on the effect of the particle shape and size.

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39

Jabari, Mohammad, Manizhe Zakeri, Farrokh Janabi-Sharifi y Somayeh Norouzi-Ghazbi. "Inverse Kinematics of Concentric Tube Robots in the Presence of Environmental Constraints". Applied Bionics and Biomechanics 2021 (14 de agosto de 2021): 1–12. http://dx.doi.org/10.1155/2021/4107732.

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Inverse kinematics (IK) of concentric tube continuum robots (CTRs) is associated with two main problems. First, the robot model (e.g., the relationship between the configuration space parameters and the robot end-effector) is not linear. Second, multiple solutions for the IK are available. This paper presents a general approach to solve the IK of CTRs in the presence of constrained environments. It is assumed that the distal tube of the CTR is inserted into a cavity while its proximal end is placed inside a tube resembling the vessel enabling the entry to the organ cavity. The robot-tissue interaction at the beginning of the organ-cavity imposed displacement and force constraints to the IK problem to secure a safe interaction between the robot and tissue. The IK in CTRs has been carried out by treating the problem as an optimization problem. To find the optimized IK of the CTR, the cost function is defined to be the minimization of input force into the body cavity and the occupied area by the robot shaft body. The optimization results show that CTRs can keep the safe force range in interaction with tissue for the specified trajectories of the distal tube. Various simulation scenarios are conducted to validate the approach. Using the IK obtained from the presented approach, the tracking accuracy is achieved as 0.01 mm which is acceptable for the application.

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40

Jun, Yong-Du y Widen Tabakoff. "Numerical Simulation of a Dilute Particulate Flow (Laminar) Over Tube Banks". Journal of Fluids Engineering 116, n.º 4 (1 de diciembre de 1994): 770–77. http://dx.doi.org/10.1115/1.2911848.

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This paper presents an investigation of numerical simulation for a dilute particle laden flow (laminar) over in-line tube banks. Particles behavior of two different sizes and density (100 μm sand and 40 μm fly ash) is demonstrated through the present study for a fixed geometry and flow condition, that is, a square in-line tube bank of two rows deep with pitch-to-diameter ratio of two at Reynolds number 400. Dilute particulate flow assumption is used and the drag force is considered as the only external force term that affects the particles behavior in the flow. Experimental rebounding data and semiempirical equation for the erosion estimation are used. It was found through the present simulation that the particles behavior of the different sizes and density in tube bank system is quite different in their trajectories, impact and the erosion pattern. The protective role of the first row of cylinders could be supported with respect to the particles collision on the cylinder but not necessarily to the erosion point of view. Also the information at impact such as the impact velocity and the impact angle which affect the erosion (Tabakoff et al., 1988) can be estimated by using the numerical simulation shown in the present study.

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41

Demiray, Hilmi. "Interactions of Nonlinear Waves in Fluid-Filled Elastic Tubes". Zeitschrift für Naturforschung A 62, n.º 1-2 (1 de febrero de 2007): 21–28. http://dx.doi.org/10.1515/zna-2007-1-204.

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In this work, treating an artery as a prestressed thin-walled elastic tube and the blood as an inviscid fluid, the interactions of two nonlinear waves propagating in opposite directions are studied in the longwave approximation by use of the extended PLK (Poincaré-Lighthill-Kuo) perturbation method. The results show that up to O(k3), where k is the wave number, the head-on collision of two solitary waves is elastic and the solitary waves preserve their original properties after the interaction. The leading-order analytical phase shifts and the trajectories of two solitons after the collision are derived explicitly.

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42

SONG, YI, STEPHEN P. BANKS y DAVID DIAZ. "DYNAMICAL SYSTEMS ON THREE MANIFOLDS PART I: KNOTS, LINKS AND CHAOS". International Journal of Bifurcation and Chaos 17, n.º 06 (junio de 2007): 2073–84. http://dx.doi.org/10.1142/s0218127407018221.

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In this paper, we give an explicit construction of dynamical systems (defined within a solid torus) containing any knot (or link) and arbitrarily knotted chaos. The first is achieved by expressing the knots in terms of braids, defining a system containing the braids and extending periodically to obtain a system naturally defined on a torus and which contains the given knotted trajectories. To get explicit differential equations for dynamical systems containing the braids, we will use a certain function to define a tube neighborhood of the braid. The second one, generating chaotic systems, is realized by modeling the Smale horseshoe.

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43

Grevcev A. S., Zolotukhin P. A., Il’ichev E. A., Petrukhin G. N., Popov A. V. y Rychkov G. S. "An investigation of reading thermal images processes by a thermal image receiver made in the image intensifier tube architecture". Technical Physics 92, n.º 5 (2022): 545. http://dx.doi.org/10.21883/tp.2022.05.53669.338-21.

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The results of calculations of electric fields, potentials, and trajectories of photoelectrons calculations of single-channel dual-spectral thermal imager, implemented in the IIT architecture are presented. The values of the optimal potentials on the control electrodes (microchannel plate, reading electrode, and photocathode) that form a picture of the images of objects and ensure the correct reading of the potential relief from the surface of the sensor-converter pyroelectric film of the image thermal receiver under discussion are determined. Keywords: image intensifier tube, spontaneous polarization, a pyroelectric sensor, photocathode, photoelectronic emission, thermal object image receiver, secondary electron emission.

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44

WATANABE, Keizo y Jie ZHANG. "Characteristics of Gas-Liquid Flow in a Spiral Tube. Numerical Simulation for Trajectories of a Single Bubble." Transactions of the Japan Society of Mechanical Engineers Series B 64, n.º 627 (1998): 3597–602. http://dx.doi.org/10.1299/kikaib.64.3597.

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45

Wang, Lipo y Norbert Peters. "A new view of flow topology and conditional statistics in turbulence". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, n.º 1982 (13 de enero de 2013): 20120169. http://dx.doi.org/10.1098/rsta.2012.0169.

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By partitioning a turbulent flow field into relative simple units, the original complex system may be better understood from studying decomposed structures. In this paper, some general principles for identifying geometrical decomposition are discussed. Logically, to make analysis more objective and quantitative, the decomposed units need to be non-arbitrarily defined and space filling. Following this vein, we introduced two topological approaches satisfying these prerequisites and the relevant work is reviewed. For a given scalar variable, dissipation elements are defined as the spatial regions that the gradient trajectories of this scalar can share the same pair of scalar extremums (one maximum and one minimum), whereas for the general vector variables, vector tube segments are the part of vector tubes bounded by adjacent extremums of the magnitude of the given vector. Both structures can be characterized by representative shape parameters: the length scale and the extremum difference. On the basis of direct numerical simulation data, the statistics of the shape parameters have been studied. Physically, those structures reveal the ‘nature’ topology of turbulence, and thus their characteristic parameters reflect the flow properties. For instance, when the vector tube segment approach is applied to the velocity case, the negative skewness of the velocity derivative can be explained by the asymmetry of the joint probability density function of the shape parameters of streamtube segments. Conditional statistics based on these newly defined structures identify finer flow physics and are believed helpful for modelling improvement. Application examples illustrate that, in principle, these methods can generally be applied to different flow cases under different situations.

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46

Demiray, Hilmi. "Nonlinear Wave Modulation in a Fluid-Filled Elastic Tube with Stenosis". Zeitschrift für Naturforschung A 63, n.º 1-2 (1 de febrero de 2008): 24–34. http://dx.doi.org/10.1515/zna-2008-1-205.

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In the present work, treating the arteries as a thin-walled and prestressed elastic tube with a stenosis and the blood as a Newtonian fluid with negligible viscosity, we have studied the amplitude modulation of nonlinear waves in such a composite system by use of the reductive perturbation method. The governing evolution equation was obtained as the variable coefficient nonlinear Schr¨odinger (NLS) equation. By setting the stenosis function equal to zero, we observed that this variable coefficient NLS equation reduces to the conventional NLS equation. After introducing a new dependent variable and a set of new independent coordinates, we reduced the evolution equation to the conventional NLS equation. By seeking a progressive wave type of solution to this evolution equation we observed, that the wave trajectories are not straight lines anymore; they are rather some curves in the (ξ ,τ ) plane. It was further observed that the wave speeds for both enveloping and harmonic waves are variable, and the speed of the enveloping wave increases with increasing axial distance, whereas the speed of the harmonic wave decreases with increasing axial coordinates. The numerical calculations indicated that the speed of the harmonic wave decreases with increasing time parameter, but the sensitivity of wave speed to this parameter is quite weak.

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47

Izadi, Hojjat A., Brandon W. Gordon y Youmin Zhang. "Decentralized Model Predictive Control for Cooperative Multiple Vehicles Subject to Communication Loss". International Journal of Aerospace Engineering 2011 (2011): 1–13. http://dx.doi.org/10.1155/2011/198308.

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The decentralized model predictive control (DMPC) of multiple cooperative vehicles with the possibility of communication loss/delay is investigated. The neighboring vehicles exchange their predicted trajectories at every sample time to maintain the cooperation objectives. In the event of a communication loss (packet dropout), the most recent available information, which is potentially delayed, is used. Then the communication loss problem changes to a cooperative problem when random large communication delays are present. Such large communication delays can lead to poor cooperation performance and unsafe behaviors such as collisions. A new DMPC approach is developed to improve the cooperation performance and achieve safety in the presence of the large communication delays. The proposed DMPC architecture estimates the tail of neighbor's trajectory which is not available due to the large communication delays for improving the performance. The concept of the tube MPC is also employed to provide the safety of the fleet against collisions, in the presence of large intervehicle communication delays. In this approach, a tube shaped trajectory set is assumed around the trajectory of the neighboring vehicles whose trajectory is delayed/lost. The radius of tube is a function of the communication delay and vehicle's maneuverability (in the absence of model uncertainty). The simulation of formation problem of multiple vehicles is employed to illustrate the effectiveness of the proposed approach.

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48

Tsuda, A., J. P. Butler y J. J. Fredberg. "Effects of alveolated duct structure on aerosol kinetics. I. Diffusional deposition in the absence of gravity". Journal of Applied Physiology 76, n.º 6 (1 de junio de 1994): 2497–509. http://dx.doi.org/10.1152/jappl.1994.76.6.2497.

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We examined the effects of alveolar duct structure on particle deposition in the pulmonary acinus. The low Reynolds number velocity field of carrier gas in a geometric model of the alveolated duct was solved numerically. Particle trajectories were computed from the Langevin equation. Conditional probabilities of the trajectories were calculated with an eigenfunction expansion technique in the absence of gravity. For submicron particles, Brownian motion dominated the process; the deposition rate dramatically decreased with boundary layer growth. For fine particles, fully developed boundary layer profiles determined the deposition over most of the acinar length. The assumption of a uniform radial profile results in a substantial overestimation of the local deposition rate. The deposition rate in an alveolated duct was always smaller than that in an equivalent straight tube of the same volume. Within the alveolus the deposition pattern was markedly nonuniform, with higher deposition near the alveolar entrance ring; this finding is consistent with experimental observations in animals (e.g., see Zeltner et al. J. Appl. Physiol. 70: 1137–1145, 1991). We conclude that the structure of the alveolar duct has an important influence on aerosol particle deposition in the lung acinus.

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49

Yetendje, Alain, Maria Seron y José De Doná. "Robust multisensor fault tolerant model-following MPC design for constrained systems". International Journal of Applied Mathematics and Computer Science 22, n.º 1 (1 de marzo de 2012): 211–23. http://dx.doi.org/10.2478/v10006-012-0016-7.

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Robust multisensor fault tolerant model-following MPC design for constrained systemsIn this paper, a robust fault-tolerant control strategy for constrained multisensor linear systems, subject to sensor faults and in the presence of bounded state and output disturbances, is proposed. The scheme verifies that, for each sensors-estimator combination, suitable residual variables lie inside pre-computed sets and selects a more appropriate combination based on a chosen criterion. An active fault tolerant output feedback controller yields an MPC-based control law and, by means of the notion of a "tube" of trajectories, we ensure robust closed-loop exponential stability and good performance in the fault-free case and under the occurrence of abrupt sensor faults.

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50

Choi, M., Y. T. Lin y R. Greif. "Analysis of Buoyancy and Tube Rotation Relative to the Modified Chemical Vapor Deposition Process". Journal of Heat Transfer 112, n.º 4 (1 de noviembre de 1990): 1063–69. http://dx.doi.org/10.1115/1.2910479.

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The secondary flows resulting from buoyancy effects in respect to the MCVD process have been studied in a rotating horizontal tube using a perturbation analysis. The three-dimensional secondary flow fields have been determined at several axial locations in a tube whose temperature varies in both the axial and circumferential directions for different rotational speeds. For small rotational speeds, buoyancy and axial convection are dominant and the secondary flow patterns are different in the regions near and far from the torch. For moderate rotational speeds, the effects of buoyancy, axial and angular convection are all important in the region far from the torch where there is a spiraling secondary flow. For large rotational speeds, only buoyancy and angular convection effects are important and no spiraling secondary motion occurs far downstream. Compared with thermophoresis, the important role of buoyancy in determining particle trajectories in MCVD is presented. As the rotational speed increases, the importance of the secondary flow decreases and the thermophoretic contribution becomes more important. It is noted that thermophoresis is considered to be the main cause of particle deposition in the MCVD process.

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