Articles de revues : « Kinematic source parameters »

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Fayjaloun, R., M. Causse, C. Cornou, C. Voisin et S. G. Song. « Sensitivity of High-Frequency Ground Motion to Kinematic Source Parameters ». Pure and Applied Geophysics 177, n^o 5 (26 avril 2019) : 1947–67. http://dx.doi.org/10.1007/s00024-019-02195-3.

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Corradini, M., I. W. McBrearty, D. T. Trugman, C. Satriano, P. A. Johnson et P. Bernard. « Investigating the influence of earthquake source complexity on back-projection images using convolutional neural networks ». Geophysical Journal International 229, n^o 3 (27 janvier 2022) : 1824–39. http://dx.doi.org/10.1093/gji/ggac026.

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SUMMARY The retrieval of earthquake finite-fault kinematic parameters after the occurrence of an earthquake is a crucial task in observational seismology. Routinely used source inversion techniques are challenged by limited data coverage and computational effort, and are subject to a variety of assumptions and constraints that restrict the range of possible solutions. Back-projection (BP) imaging techniques do not need prior knowledge of the rupture extent and propagation, and can track the high-frequency (HF) radiation emitted during the rupture process. While classic source inversion methods work at lower frequencies and return an image of the slip over the fault, the BP method highlights fault areas radiating HF seismic energy. Patterns in the HF radiation are attributable to the spatial and temporal complexity of the rupture process (e.g. slip heterogeneities, changes in rupture speed). However, the quantitative link between the BP image of an earthquake and its rupture kinematics remains unclear. Our work aims at reducing the gap between the theoretical studies on the generation of HF radiation due to earthquake complexity and the observation of HF emissions in BP images. To do so, we proceed in two stages, in each case analysing synthetic rupture scenarios where the rupture process is fully known. We first investigate the influence that spatial heterogeneities in slip and rupture velocity have on the rupture process and its radiated wave field using the BP technique. We simulate two different rupture processes using a 1-D line source model: a homogeneous process, where the kinematic parameters are constant along the line, and a heterogeneous process, where we introduce a central segment along the line that has a step change in kinematics. For each rupture model, we calculate synthetic seismograms at three teleseismic arrays and apply the BP technique to reveal how HF emissions are influenced by the three kinematic parameters controlling the synthetic model: the rise time, final slip and rupture velocity. Our results show that the HF peaks retrieved from BP analysis are better associated with space–time heterogeneities of slip acceleration. We then build on these findings by testing whether one can retrieve the kinematic rupture parameters along the fault using information from the BP image alone. We apply a machine learning, convolutional neural network (CNN) approach to the BP images of a large set of simulated 1-D rupture processes to assess the ability of the network to retrieve, from the progression of HF emissions in space and time, the kinematic parameters of the rupture. These rupture simulations include along-strike heterogeneities whose size is variable and within which the parameters of rise-time, final slip and rupture velocity change from the surrounding rupture. We show that the CNN trained on 40 000 pairs of BP images and kinematic parameters returns excellent predictions of the rise time and the rupture velocity along the fault, as well as good predictions of the central location and length of the heterogeneous segment. Our results also show that the network is insensitive towards the final slip value, as expected from theoretical results.

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Schmedes, J., Ralph J. Archuleta et Daniel Lavallée. « A kinematic rupture model generator incorporating spatial interdependency of earthquake source parameters ». Geophysical Journal International 192, n^o 3 (23 décembre 2012) : 1116–31. http://dx.doi.org/10.1093/gji/ggs021.

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Causse, M., L. A. Dalguer et P. M. Mai. « Variability of dynamic source parameters inferred from kinematic models of past earthquakes ». Geophysical Journal International 196, n^o 3 (24 décembre 2013) : 1754–69. http://dx.doi.org/10.1093/gji/ggt478.

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Farah, Edris, et Shao Gang Liu. « 3D Modeling and Closed-Form Inverse Kinematics Solution for 6dof Surgical Robot ». Applied Mechanics and Materials 455 (novembre 2013) : 533–38. http://dx.doi.org/10.4028/www.scientific.net/amm.455.533.

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Since robots began to inter the medical fields, more research efforts and more attention have been given to this kind of robots. In this paper six degrees of freedom surgical robot was studied. The Denavit-Hartenberg parameters of the robot have been computed and 3D model has been built by using open source robotics toolbox. The paper also discussed a closed form solution for the inverse kinematics problem by using inverse kinematic decoupling method.

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Rooker, Tim, Graeme Potts, Keith Worden, Nikolaos Dervilis et Jon Stammers. « Comparing approaches for multi-axis kinematic positioning in machine tools ». Proceedings of the Institution of Mechanical Engineers, Part B : Journal of Engineering Manufacture 235, n^o 10 (27 mai 2021) : 1698–711. http://dx.doi.org/10.1177/09544054211019668.

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Maintaining minimal levels of geometric error in the finished workpiece is of increasing importance in the modern production environment; there is considerable research on the identification, verification and calibration of machine tool kinematic error, and the development of Postprocessor implementations to generate NC-code optimised for machining accuracy. The choice of multi-axis positioning function at the controller, however, is an often-overlooked potential source of kinematic error which can be responsible for costly mistakes in the production environment. This paper presents an investigation into how mis-management of the positional error parameters that define the rotary-axes’ pivot point can lead to unintended variations in multi-axis positioning. Four approaches for kinematic positioning on a Fanuc-based controller are considered, which reference two separate parameter locations to define the pivot point – managing the kinematics within the Postprocessor itself, full five-axis positioning with a fixture offset, full five-axis with rotation tool centre point control and 3+2-axis with a tilted workplane. Error vectors across four sets of rotary-axis indexations are simulated based on the theoretical kinematic model, to highlight the expected differences in geometric error attributable to mismatched pivot point parameters. Finally, the simulation results are verified experimentally, demonstrating the importance of maintaining a consistent approach in both programming and operation environments.

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Cardona, Manuel, Cecilia E. García Cena, Fernando Serrano et Roque Saltaren. « ALICE : Conceptual Development of a Lower Limb Exoskeleton Robot Driven by an On-Board Musculoskeletal Simulator ». Sensors 20, n^o 3 (31 janvier 2020) : 789. http://dx.doi.org/10.3390/s20030789.

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Objective: In this article, we present the conceptual development of a robotics platform, called ALICE (Assistive Lower Limb Controlled Exoskeleton), for kinetic and kinematic gait characterization. The ALICE platform includes a robotics wearable exoskeleton and an on-board muscle driven simulator to estimate the user’s kinetic parameters. Background: Even when the kinematics patterns of the human gait are well studied and reported in the literature, there exists a considerable intra-subject variability in the kinetics of the movements. ALICE aims to be an advanced mechanical sensor that allows us to compute real-time information of both kinetic and kinematic data, opening up a new personalized rehabilitation concept. Methodology: We developed a full muscle driven simulator in an open source environment and validated it with real gait data obtained from patients diagnosed with multiple sclerosis. After that, we designed, modeled, and controlled a 6 DoF lower limb exoskeleton with inertial measurement units and a position/velocity sensor in each actuator. Significance: This novel concept aims to become a tool for improving the diagnosis of pathological gait and to design personalized robotics rehabilitation therapies. Conclusion: ALICE is the first robotics platform automatically adapted to the kinetic and kinematic gait parameters of each patient.

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Jordan, Christopher E. « Scale effects in the kinematics and dynamics of swimming leeches ». Canadian Journal of Zoology 76, n^o 10 (1 octobre 1998) : 1869–77. http://dx.doi.org/10.1139/z98-131.

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Slender-bodied organisms swimming with whole-body undulations exhibit what appears to be a high degree of kinematic parameter conservation, which is independent of body size. However, organisms of very different sizes swim in fundamentally different physical realms, owing to the relative scaling of viscous and inertial fluid stresses as a function of size and speed. In light of the size-dependent fluid forces, the kinematic constancy suggests three hypotheses: (1) swimming organisms adopt a single "ideal" swimming mode requiring the modification of muscle forces or motor patterns through ontogeny, (2) swimming kinematics are determined predominantly by the passive mechanical interaction of the body and the fluid, resulting in a single swimming mode independent of absolute body size, or (3) while undulatory swimming kinematics may be similar between organisms, there are important size-dependent kinematic differences. In this study, I address this issue by examining the swimming kinematics and dynamics of the medicinal leech Hirudo medicinalis L. as a function of body size. Over a 5-fold increase in body length, the relative amplitude of body undulations during swimming did not change; however, swimming speed, propulsive wave speed, and propulsive wave frequency all decreased, while propulsive wave number increased slightly, strongly supporting hypothesis 2. To determine the source of the observed size-dependent swimming kinematics, I manipulated the dynamic viscosity of the organism's fluid environment to alter the constraints placed on swimming behavior by the physical surroundings. In the elevated-viscosity treatment, all kinematic parameters changed in the opposite direction to that predicted by hypothesis 2, rejecting both the idea that swimming kinematics are simply determined by passive mechanical interactions and that leeches have a target swimming mode under active control.

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Yabing Song et Na He. « Evaluation of kinematic parameters and characteristics of the source zone of the debris flow in Kongniba Watershed ». World Journal of Advanced Engineering Technology and Sciences 5, n^o 2 (30 mars 2022) : 034–44. http://dx.doi.org/10.30574/wjaets.2022.5.2.0042.

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The characteristics of the source zone of the debris flow watershed is one of the most significant factors governing debris flows initiation, at the same time it also plays a crucial role for disaster risk evaluation. With the aim of obtaining the basic characteristics of the source zone and computing the kinematic parameters, field investigations were conducted comprehensively, combining with the results of remote sensing interpretation, the origin and distribution regulations can be identified, and total amount of the loose solid materials can be determined, the corresponding value is 4.91×106 m3. Using the collected data of this watershed, and with the help of previous theoretical models, the kinematic parameters under different rainfall frequencies are calculated, which including debris flow discharge, total volume of one-time debris flow and the total volume of solid materials. Such parameters are helpful and essential for debris flow disasters evaluation, prevention and designing mitigation measures.

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Causse, M., L. A. Dalguer et P. M. Mai. « Correction to : Variability of dynamic source parameters inferred from kinematic models of past earthquakes ». Geophysical Journal International 207, n^o 3 (8 octobre 2016) : 1837. http://dx.doi.org/10.1093/gji/ggw371.

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Luxford, Fay, et Tim Woollings. « A Simple Kinematic Source of Skewness in Atmospheric Flow Fields ». Journal of the Atmospheric Sciences 69, n^o 2 (1 février 2012) : 578–90. http://dx.doi.org/10.1175/jas-d-11-089.1.

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Abstract Geopotential height fields exhibit a well-known pattern of skewness, with distributions that are positively skewed on the poleward side of the midlatitude jets/storm tracks and negatively skewed on the equatorward side. This pattern has often been interpreted as a signature of nonlinear dynamical features, such as blocking highs and cutoff lows, and there is renewed interest in the higher moments of flow variables as indicators of the nature of the underlying dynamics. However, this paper suggests that skewness can arise as a simple kinematic consequence of the presence of jet streams and so may not be a reliable indicator of nonlinear dynamical behavior. In support of this, reanalysis data are analyzed to demonstrate a close link between the jet streams and the skewness patterns. Further evidence is provided by a simple stochastic kinematic model of a jet stream as a Gaussian wind profile. The parameters of this model are fitted to data from the reanalysis and also from an aquaplanet general circulation model. The skewness of the model’s geopotential height and zonal wind fields are then compared to those of the original data. This shows that a fluctuating jet stream can produce patterns of skewness that are qualitatively similar to those observed, although the magnitude of the skewness is significantly overestimated by the kinematic model. These results suggest that this simple kinematic effect does contribute to the observed patterns of skewness but that other processes (such as nonlinear dynamics) likely also play a role.

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Cao, Zelin, Xiaxin Tao, Zhengru Tao et Aiping Tang. « Kinematic Source Modeling for the Synthesis of Broadband Ground Motion Using the f‐k Approach ». Bulletin of the Seismological Society of America 109, n^o 5 (23 juillet 2019) : 1738–57. http://dx.doi.org/10.1785/0120180294.

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Abstract A procedure for building a kinematic source model is proposed in this article for the synthesis of broadband ground motion based on the frequency–wavenumber Green’s function. The spatial distribution of slip on the rupture plane is generated by combining asperity slip with random slip. A set of scaling laws recently updated for the global and local parameters of seismic sources is adopted. To characterize the temporal evolution of slip on the rupture plane, different rupture velocities, and rise times are first generated by considering the correlation with slip, and a source time function obtained by rupture dynamics is selected for each subsource. Then, the entire rupture process is set as the object to jointly determine the rise time and rupture velocity for a given slip distribution under the selection criterion that the entire rupture process should radiate the closest seismic energy to the expected energy. To reduce uncertainty, 30 spatiotemporal rupture processes for an earthquake scenario are realized to select a mean source model. To demonstrate the feasibility of the proposed source modeling approach, two California earthquakes, the Whittier Narrows earthquake and the Loma Prieta earthquake, are chosen as case studies. The performance of the obtained source models shows that our modeling approach is advantageous for estimating the size of the rupture plane, emphasizing the effect of asperity, and considering the correlation between temporal rupture parameters and slip. The bias values between the observed and synthetic pseudospectral accelerations are relatively small compared to those for the methods on the Southern California Earthquake Center broadband platform. The synthetics are further compared with the estimates from regional ground‐motion prediction equations for four scenario earthquakes with moment magnitudes of 6.0, 6.5, 7.0, and 7.5. Finally, the sensitivity of the synthetic motion to various rupture parameters is analyzed.

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Emolo, A. « Kinematic Source Parameters for the 1989 Loma Prieta Earthquake from the Nonlinear Inversion of Accelerograms ». Bulletin of the Seismological Society of America 95, n^o 3 (1 juin 2005) : 981–94. http://dx.doi.org/10.1785/0120030193.

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Cultrera, G., A. Cirella, E. Spagnuolo, A. Herrero, E. Tinti et F. Pacor. « Variability of Kinematic Source Parameters and Its Implication on the Choice of the Design Scenario ». Bulletin of the Seismological Society of America 100, n^o 3 (14 mai 2010) : 941–53. http://dx.doi.org/10.1785/0120090044.

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Kropivny, Oleksandr, Andrii Hrechka, Andrii Kyrychenko et Kyryl Shcherbyna. « Kinematic Dependencies of Two-axis Parallel Manipulator With Rotary Fastening of Hinges of Variable Length Links ». Central Ukrainian Scientific Bulletin. Technical Sciences 2, n^o 5(36) (2022) : 22–30. http://dx.doi.org/10.32515/2664-262x.2022.5(36).2.22-30.

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In the article the kinematic problem for a new two-axis parallel manipulator with rotary hinged parallelogram, the source of which is a spindle unit, is performed. The analysis of the received kinematic dependencies is carried out. The presence of special provisions of the source body of the mechanism is established. The directions of further scientific researches are outlined. The parallel manipulator structure for consideration differs from previously developed fastenings of hinges of rods of variable length on rotary levers which rotation is coordinated with rotation of an initial link with a spindle unit. On the basis of the developed scheme mathematical dependences for lengths of actuators are established. The performed mathematical transformations allowed to solve direct and inverse kinematic problems for the mechanism. Analysis of the obtained kinematic dependences showed the presence of special positions of the initial body of the mechanism in the form of kinematic parallel singularities. Their graph is given. Graphs of changes of coordinates of an output link at change of lengths of rods of the drive of giving are shown. The analysis of graphic dependences shows existence of such combinations of constructive parameters of the mechanism at which the drive of giving starts to work in a multiplicative mode. The obtained dependences will allow to ensure the functioning of the kinematic circuits of the feed drive of this mechanism. The established points of the kinematic parallel singularity of the feed drive and its operation in the multiplicative mode require further consideration taking into account the dynamic loads. By selecting the design parameters of the mechanism, it is possible to achieve close to rectilinear relationships between changes in the length of the rods and the movement of the spindle unit.

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Kruger, F., et F. Scherbaum. « The 29 September 1969, Ceres, South Africa, Earthquake : Full Waveform Moment Tensor Inversion for Point Source and Kinematic Source Parameters ». Bulletin of the Seismological Society of America 104, n^o 1 (7 janvier 2014) : 576–81. http://dx.doi.org/10.1785/0120130209.

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Xu, Dongtao. « Kinematic reliability and sensitivity analysis of the modified Delta parallel mechanism ». International Journal of Advanced Robotic Systems 15, n^o 1 (1 janvier 2018) : 172988141875910. http://dx.doi.org/10.1177/1729881418759106.

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In order to improve the kinematic reliability, it is crucial to find out the influence of each error source on the kinematic reliability of the mechanism. Reliability sensitivity analysis is used to find the changing rate in the probability of reliability in relation to the changes in distribution parameters. Based on the structural response surface function method, the functional relation between the kinematic reliability of a modified Delta parallel mechanism and the original input-error vectors is described using the quadratic function with cross terms. Moreover, the partial derivatives of the functional relation with respect to the means and variances of the original input errors are derived, which can efficiently evaluate kinematic reliability sensitivity of the mechanism. The advantages of this method are as follows: First, the response surface function, which can be easily set up by the position-error model of the mechanism, is convenient for calculating the variance, partial derivative, and reliability sensitivity. Second, in this case (unlike in the traditional error-mapping model), although the input-error values are unknown, pseudorandom variables used as random input-error sources can be generated by MATLAB software. Furthermore, the kinematic reliability of the mechanism can be assessed using the Monte Carlo method.

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Boeche, Corrado. « The RAVE harvest : from the relation between abundances and kinematic of the Milky Way stars to tools for the abundance analysis of the spectra ». Proceedings of the International Astronomical Union 9, S298 (mai 2013) : 292–97. http://dx.doi.org/10.1017/s1743921313006480.

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AbstractRAVE is a spectroscopic survey of the Milky Way which collected more than 500,000 stellar spectra of nearby stars in the Galaxy. The RAVE consortium analysed these spectra to obtain radial velocities, stellar parameters and chemical abundances. These data, together with spatial and kinematic information like positions, proper motions, and distance estimations, make the RAVE database a rich source for galactic archaeology. I present recent investigations on the chemo-kinematic relations and chemical gradients in the Milky Way disk using RAVE data and compare our results with the Besançon models. I also present the code SPACE, an evolution of the RAVE chemical pipeline, which integrates the measurements of stellar parameters and chemical abundances in one single process.

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Eva, Elena, Franco Pettenati, Stefano Solarino et Livio Sirovich. « The focal mechanism of the 7 September 1920, Mw 6.5 earthquake : insights into the seismotectonics of the Lunigiana–Garfagnana area, Tuscany, Italy ». Geophysical Journal International 228, n^o 3 (11 octobre 2021) : 1465–77. http://dx.doi.org/10.1093/gji/ggab411.

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SUMMARY To understand the seismotectonics and the seismic hazard of the study sector of the Northern Apennines (Italy), one of the most important earthquakes of magnitude Mw = 6.5 which struck the Lunigiana and Garfagnana areas (Tuscany) on 7 September 1920 should be studied. Given the early instrumental epoch of the event, neither geometric and kinematic information on the fault-source nor its fault-plane solution were available. Both areas were candidates for hosting the source fault and there was uncertainty between a normal fault with Apenninic direction or an anti-Apenninic strike-slip. We retrieved 11 focal parameters (including the fault-plane solution) of the 1920 earthquake. Only macroseismic intensity information (from 499 inhabited centres) through the KF-NGA inversion technique was used. This technique uses a Kinematic model of the earthquake source and speeds up the calculation by a Genetic Algorithm with Niching. The result is a pure dip-slip focal solution. The intrinsic ambiguities of the KF-NGA method (±180° on the rake angle; choice of the fault plane between the two nodal planes) were solved with field and seismotectonic evidence. The earthquake was generated by a normal fault (rake angle = 265° ± 8°) with an Apennine direction (114° ± 5°) and dipping 38° ± 6° towards SW. The likely candidate for hosting the source-fault in 1920 is the Compione-Comano fault that borders the NE edge of the Lunigiana graben. The KF-NGA algorithm proved to be invaluable for studying the kinematics of early instrumental earthquakes and allowed us to uniquely individuate, for the first time ever, the seismogenic source of the 1920 earthquake. Our findings have implications in hazard computation and seismotectonic contexts.

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IVANOV, OLEG. « PLANETARY SELF-ORGANIZATION ». LIFE OF THE EARTH 42, n^o 3 (26 août 2020) : 271–82. http://dx.doi.org/10.29003/m1481.0514-7468.2020_42_3/271-282.

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The general characteristics of planetary systems are described. Well-known heat sources of evolution are considered. A new type of heat source, variations of kinematic parameters in a dynamical system, is proposed. The inconsistency of the perovskite-post-perovskite heat model is proved. Calculations of inertia moments relative to the D boundary on the Earth are given. The 9 times difference allows us to claim that the sliding of the upper layers at the Earth's rotation speed variations emit heat by viscous friction.This heat is the basis of mantle convection and lithospheric plate tectonics.

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Paradisopoulou, P. M., E. E. Papadimitriou, V. G. Karakostas et A. Kilias. « Application for source parameters calculations as input for static stress changes studies ». Bulletin of the Geological Society of Greece 40, n^o 4 (1 janvier 2007) : 2008. http://dx.doi.org/10.12681/bgsg.17294.

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The study of static Coulomb Stress changes requires initially the collection of information on the major active faults in a study area concerning their geometry and kinematic properties and then a series of complex calculation for stress changes that are associated with both coseismic displacements of the stronger events and the tectonic loading on these major faults. The Coulomb Stress Application has been developed as a tool to provide a user-friendly way of entering the necessary data and an efficient way to perform the complex calculations procedure. More specifically the aim of the application is a) the collection of data (catalogues of earthquakes, fault parameters) in a relational database, b) the calculation of earthquake source parameters such as the length and the width of the causative fault, and the coseismic slip by using available scaling laws, and finally, c) the execution of all the necessary programs and scripts (e.g. dis3dop.exe, GMT package) to get a map of static stress changes for an area. Coulomb Stress application provides a way to store these data for a study area and it is a method to perform a series of calculations by plotting a series of maps and examine the results for a number of cases.

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Kaur, Barjinder, et N. S. Saini. « Dust Ion-Acoustic Shock Waves in a Multicomponent Magnetorotating Plasma ». Zeitschrift für Naturforschung A 73, n^o 3 (23 février 2018) : 215–23. http://dx.doi.org/10.1515/zna-2017-0397.

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AbstractThe nonlinear properties of dust ion-acoustic (DIA) shock waves in a magnetorotating plasma consisting of inertial ions, nonextensive electrons and positrons, and immobile negatively charged dust are examined. The effects of dust charge fluctuations are not included in the present investigation, but the ion kinematic viscosity (collisions) is a source of dissipation, leading to the formation of stable shock structures. The Zakharov–Kuznetsov–Burgers (ZKB) equation is derived using the reductive perturbation technique, and from its solution the effects of different physical parameters, i.e. nonextensivity of electrons and positrons, kinematic viscosity, rotational frequency, and positron and dust concentrations, on the characteristics of shock waves are examined. It is observed that physical parameters play a very crucial role in the formation of DIA shocks. This study could be useful in understanding the electrostatic excitations in dusty plasmas in space (e.g. interstellar medium).

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Carollo, Daniela. « CN Anomalies in the Halo System ». Proceedings of the International Astronomical Union 10, H16 (août 2012) : 282–83. http://dx.doi.org/10.1017/s1743921314005778.

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AbstractI present an evaluation of the kinematic properties of halo red giants thought to have formed in globular clusters based on the strength of their UV/blue CN and CH absorption features. The sample has been selected from the catalog of Martell et al. (2011). The orbital parameters of CN-strong halo stars are compared to those of the inner and outer halo populations, and to the orbital parameters of globular clusters with well-studied Galactic orbits. It has been found that both the clusters and the CN-strong field stars exhibit kinematic and orbital properties similar to the inner halo population, indicating that globular clusters could be a significant source of inner halo field stars, and suggesting that both globular clusters and CN-strong stars could belong primarily to the inner halo population of the Milky Way.

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Polini, Wilma, et Andrea Corrado. « A kinematic approach for error modelling in drilling ». Engineering Computations 36, n^o 4 (13 mai 2019) : 1364–83. http://dx.doi.org/10.1108/ec-11-2018-0511.

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Purpose The purpose of this paper is to model how geometric errors of a machined surface (or manufacturing errors) are related to locators’ error, workpiece form error and machine tool volumetric error. A kinematic model is presented that puts into relationship the locator error, the workpiece form deviations and the machine tool volumetric error. Design/methodology/approach The paper presents a general and systematic approach for geometric error modelling in drilling because of the geometric errors of locators positioning, of workpiece datum surface and of machine tool. The model can be implemented in four steps: (1) calculation of the deviation in the workpiece reference frame because of deviations of locator positions; (2) evaluation of the deviation in the workpiece reference frame owing to form deviations in the datum surfaces of the workpiece; (3) formulation of the volumetric error of the machine tool; and (4) combination of those three models. Findings The advantage of this approach lies in that it enables the source errors affecting the drilling accuracy to be explicitly separated, thereby providing designers and/or field engineers with an informative guideline for accuracy improvement through suitable measures, i.e. component tolerancing in design, machining and so on. Two typical drilling operations are taken as examples to illustrate the generality and effectiveness of this approach. Research limitations/implications Some source errors, such as the dynamic behaviour of the machine tool, are not taken into consideration, which will be modelled in practical applications. Practical implications The proposed kinematic model may be set by means of experimental tests, concerning the industrial specific application, to identify the values of the model parameters, such as standard deviation of the machine tool axes positioning and rotational errors. Then, it may be easily used to foresee the location deviation of a single or a pattern of holes. Originality/value The approaches present in the literature aim to model only one or at most two sources of machining error, such as fixturing, machine tool or workpiece datum. This paper goes beyond the state of the art because it considers the locator errors together with the form deviation on the datum surface into contact with the locators and, then, the volumetric error of the machine tool.

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Gopinathan, D., M. Venugopal, D. Roy, K. Rajendran, S. Guillas et F. Dias. « Uncertainties in the 2004 Sumatra–Andaman source through nonlinear stochastic inversion of tsunami waves ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 473, n^o 2205 (septembre 2017) : 20170353. http://dx.doi.org/10.1098/rspa.2017.0353.

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Numerical inversions for earthquake source parameters from tsunami wave data usually incorporate subjective elements to stabilize the search. In addition, noisy and possibly insufficient data result in instability and non-uniqueness in most deterministic inversions, which are barely acknowledged. Here, we employ the satellite altimetry data for the 2004 Sumatra–Andaman tsunami event to invert the source parameters. We also include kinematic parameters that improve the description of tsunami generation and propagation, especially near the source. Using a finite fault model that represents the extent of rupture and the geometry of the trench, we perform a new type of nonlinear joint inversion of the slips, rupture velocities and rise times with minimal a priori constraints. Despite persistently good waveform fits, large uncertainties in the joint parameter distribution constitute a remarkable feature of the inversion. These uncertainties suggest that objective inversion strategies should incorporate more sophisticated physical models of seabed deformation in order to significantly improve the performance of early warning systems.

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Vişan, Alexandra Liana, Gabriel Constantin Bogdanof, Dumitru Milea, Radu Ciupercă et Gabriel Gheorghe. « Kinematic parameters determination of the drilling equipment designed to work in slope degraded terrains ». E3S Web of Conferences 112 (2019) : 03016. http://dx.doi.org/10.1051/e3sconf/201911203016.

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This paper aims to present the cinematic parameters determination of a drilling equipment design to work in slope degraded terrains, based on field experimental data acquired in normal exploitation condition and also in heavy environmental conditions. This equipment is developed in order conduct forestation and rehabilitation works of degraded lands and to be incorporated on innovative planting technology (degraded soil processing, levelling and terrace surface modelling, planting settlement, etc). This technology answers to the need to implement measures of environmental rehabilitation and enhancement of slope-degraded forestlands, by development several performing equipments that answer to technological needs of this works (land stability, terrace dimensions, type of power source and seedlings planting variety) in order to rise to the performances and to respect the labour safety standards under difficult working conditions. Also, here in presented equipment has a great impact on forestry and pomiculture works, and also on environmental technical works meant to improve soil quality, lowering the surface and depth erosion, rainwater capitalization, lowering the dust pollution and natural calamity risk, and at last to rehabilitate the inland flora.

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Böttger, Sven, Tolga-Can Çallar, Achim Schweikard et Elmar Rückert. « Medical robotics simulation framework for application-specific optimal kinematics ». Current Directions in Biomedical Engineering 5, n^o 1 (1 septembre 2019) : 145–48. http://dx.doi.org/10.1515/cdbme-2019-0037.

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AbstractMost kinematic structures in robot architectures for medical tasks are not optimal. Further, the workspace and payloads are often oversized which results in high product prices that are not suitable for a clinical technology transfer. To investigate optimal kinematic structures and configurations, we have developed an adaptive simulation framework with an associated workflow for requirement analyses, modelling and simulation of specific robot kinematics. The framework is used to build simple and cost effective medical robot designs and was evaluated in a tool manipulation task where medical instruments had to be positioned precisely and oriented on the patient's body. The model quality is measured based on the maximum workspace coverage according to a configurable scoring metric. The metric generalizes among different human body shapes that are based on anthropometric data from UMTRI Human Shape. This dexterity measure is used to analyze different kinematic structures in simulations using the open source simulation tool V-REP. Therefor we developed simulation and visualization procedures for medical tasks based on a patchwork of size-variant anatomical target regions that can be configured and selectively activated in a motion planning controller. In our evaluations we compared the dexterity scores of a commercial lightweight robot arm with 7 joints to optimized kinematic structures with 6, 7 and 8 joints. Compared to the commercial hardware, we achieved improvements of 59% when using an optimized 6- dimensional robot arm, 64% with the 7-dimensional arm and 96% with an 8-dimensional robot arm. Our results show that simpler robot designs can outperform the typically used commercial robot arms in medical applications where the maximum workspace coverage is essential. Our framework provides the basis for a fully automatic optimization tool of the robot parameters that can be applied to a large variety of problems.

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Sinclair, Jonathan, Jack Hebron et Paul J. Taylor. « The Test-retest Reliability of Knee Joint Center Location Techniques ». Journal of Applied Biomechanics 31, n^o 2 (avril 2015) : 117–21. http://dx.doi.org/10.1123/jab.2013-0312.

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The principal source of measurement error in three-dimensional analyses is the definition of the joint center about which segmental rotations occur. The hip joint has received considerable attention in three-dimensional modeling analyses yet the reliability of the different techniques for the definition of the knee joint center has yet to be established. This study investigated the reliability of five different knee joint center estimation techniques: femoral epicondyle, femoral condyle, tibial ridge, plugin-gait, and functional. Twelve male participants walked at 1.25 m·s−1and three-dimensional kinetics/kinematics of the knee and ankle were collected. The knee joint center was defined twice using each technique (test-and-retest) and the joint kinetic/kinematic data were applied to both. Wilcoxon rank tests and intraclass correlation coefficients (ICCs) were used to compare test and retest angular parameters and kinematic waveforms. The results show significant differences in coronal and transverse planes angulation using the tibial ridge, plug-in-gait, and functional methods. The strongest test-retest ICCs were observed for the femoral epicondyle and femoral condyle configurations. The findings from the current investigation advocate that the femoral epicondyle and femoral condyle techniques for the estimation of the knee joint center are currently the most reliable techniques.

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Bollen, Dylan, Devika Kamath, Hans Van Winckel, Orsola De Marco et Mark Wardle. « Jet parameters for a diverse sample of jet-launching post-AGB binaries ». Monthly Notices of the Royal Astronomical Society 502, n^o 1 (11 janvier 2021) : 445–62. http://dx.doi.org/10.1093/mnras/stab071.

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ABSTRACT Jets are a commonly observed phenomenon in post-asymptotic giant branch (post-AGB) binaries. Due to the orbital motion of the binary, the jet causes variable absorption in the Balmer profiles. In previous work, we have developed spatio-kinematic and radiative transfer models to reproduce the observed Balmer line variability and derive the spatio-kinematic structure of the jet and its mass-loss rate. Here, we apply our jet model to five post-AGB binaries with distinct H α line variability and diverse orbital properties. Our models fit the H α line variations very well. We estimate jet mass-loss rates between $10^{-8}\,$M$_\odot \, \text{yr}^{-1}$ and $10^{-4}\,$ M$_\odot \, \text{yr}^{-1}$, from which we deduce accretion rates on to the companion between $10^{-7}\,$ M$_\odot \, \text{yr}^{-1}$ and $10^{-3}\,$ M$_\odot \, \text{yr}^{-1}$. These accretion rates are somewhat higher than can be comfortably explained with reasonable sources of accretion, but we argue that the circumbinary disc in these systems is most likely the source feeding the accretion, although accretion from the post-AGB star cannot be ruled out. The diversity of the variability in the five objects is due to their wide ejection cones combined with a range of viewing angles, rather than inherent differences between the objects. The nature of the observations does not let us easily distinguish which jet launching model (stellar jet, disc wind, or X-wind) should be favoured. In conclusion, we show that our jet model includes the physical parameters to successfully reproduce the H α line variations and retrieve the structure and mass-loss rates of the jet for all five objects that are representative of the diverse sample of Galactic post-AGB binaries.

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Li, Nannan, Hongbin Ma, Qing Fei, Hao Zhou, Shaoke Li et Sunjie Chen. « Motion Control of 6-DOF Manipulator Based on EtherCAT ». Journal of Advanced Computational Intelligence and Intelligent Informatics 22, n^o 4 (20 juillet 2018) : 415–28. http://dx.doi.org/10.20965/jaciii.2018.p0415.

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We introduce a real-time motion control system that uses the EtherCAT protocol and apply it to a manipulator with six degrees of freedom. The complexity of a multi-joint manipulator leads to higher requirements for synchronous and real-time performance. EtherCAT technology can greatly improve the performance in terms of accuracy, speed, capability, and band width in industrial control, which is crucial in our robot projects. In this paper, we discuss a servo motion control system based on EtherCAT using IgH as the open-source master station. A Linux operating system is adopted because of the advantages of open-source, high-efficiency, and high-stability operation as well as multi-platform support, which provide more flexibility, freedom, and extendability to developers. Considerable research has been conducted to explore EtherCAT technologies, completely implementing home-made codes with the aid of open-source libraries, debugging the master-slave communication process, and testing the resulting motion controller running on Linux or POSIX-compatible operating systems. To improve the real-time response of servo control, a real-time Xenomai kernel has been compiled, adopted, and tested, and it showed significant enhancement of the real time of a servo motion control system. Furthermore, we explore trajectory planning and inverse kinematic solutions. A trajectory planning method based on B-spline interpolation of three degrees, which makes each part of the trajectory planning curve have relative independence and continuity, is proposed for the kinematic trajectory planning problem in Cartesian space. A coordinate system is established using the modified D-H parameters method to obtain the inverse kinematics of the manipulator. The simulation and experimental results show that the calculation speed of inverse solutions is excellent and the motion of the manipulator is continuous and smooth.

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Alam, Md Moktadir, Soichi Ibaraki et Koki Fukuda. « Kinematic Modeling of Six-Axis Industrial Robot and its Parameter Identification : A Tutorial ». International Journal of Automation Technology 15, n^o 5 (5 septembre 2021) : 599–610. http://dx.doi.org/10.20965/ijat.2021.p0599.

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In advanced industrial applications, like machining, the absolute positioning accuracy of a six-axis robot is indispensable. To improve the absolute positioning accuracy of an industrial robot, numerical compensation based on positioning error prediction by the Denavit and Hartenberg (D-H) model has been investigated extensively. The main objective of this study is to review the kinematic modeling theory for a six-axis industrial robot. In the form of a tutorial, this paper defines a local coordinate system based on the position and orientation of the rotary axis average lines, as well as the derivation of the kinematic model based on the coordinate transformation theory. Although the present model is equivalent to the classical D-H model, this study shows that a different kinematic model can be derived using a different definition of the local coordinate systems. Subsequently, an algorithm is presented to identify the error sources included in the kinematic model based on a set of measured end-effector positions. The identification of the classical D-H parameters indicates a practical engineering application of the kinematic model for improving a robot’s positioning accuracy. Furthermore, this paper presents an extension of the present model, including the angular positioning deviation of each rotary axis. The angular positioning deviation of each rotary axis is formed as a function of the axis’ command angles and the direction of its rotation to model the effect of the rotary axis backlash. The identification of the angular positioning deviation of each rotary axis and its numerical compensation are presented, along with their experimental demonstration. This paper provides an essential theoretical basis for the error source diagnosis and error compensation of a six-axis robot.

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Reinwald, Michael, Moritz Bernauer, Heiner Igel et Stefanie Donner. « Improved finite-source inversion through joint measurements of rotational and translational ground motions : a numerical study ». Solid Earth 7, n^o 5 (21 octobre 2016) : 1467–77. http://dx.doi.org/10.5194/se-7-1467-2016.

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Abstract. With the prospects of seismic equipment being able to measure rotational ground motions in a wide frequency and amplitude range in the near future, we engage in the question of how this type of ground motion observation can be used to solve the seismic source inverse problem. In this paper, we focus on the question of whether finite-source inversion can benefit from additional observations of rotational motion. Keeping the overall number of traces constant, we compare observations from a surface seismic network with 44 three-component translational sensors (classic seismometers) with those obtained with 22 six-component sensors (with additional three-component rotational motions). Synthetic seismograms are calculated for known finite-source properties. The corresponding inverse problem is posed in a probabilistic way using the Shannon information content to measure how the observations constrain the seismic source properties. We minimize the influence of the source receiver geometry around the fault by statistically analyzing six-component inversions with a random distribution of receivers. Since our previous results are achieved with a regular spacing of the receivers, we try to answer the question of whether the results are dependent on the spatial distribution of the receivers. The results show that with the six-component subnetworks, kinematic source inversions for source properties (such as rupture velocity, rise time, and slip amplitudes) are not only equally successful (even that would be beneficial because of the substantially reduced logistics installing half the sensors) but also statistically inversions for some source properties are almost always improved. This can be attributed to the fact that the (in particular vertical) gradient information is contained in the additional motion components. We compare these effects for strike-slip and normal-faulting type sources and confirm that the increase in inversion quality for kinematic source parameters is even higher for the normal fault. This indicates that the inversion benefits from the additional information provided by the horizontal rotation rates, i.e., information about the vertical displacement gradient.

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Rout, P. K., S. N. Sahoo et G. C. Dash. « Effect of heat source and chemical reaction on MHD flow past a vertical plate with variable temperature ». Journal of Naval Architecture and Marine Engineering 13, n^o 1 (24 juin 2016) : 101–10. http://dx.doi.org/10.3329/jname.v13i1.23930.

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An analysis has been carried out to study the effect of heat source and chemical reaction on MHD flow past a vertical plate subject to a constant motion with variable temperature and concentration. The governing equations are solved by the Laplace transformation technique. The effects of various flow parameters on the flow dynamics are discussed. Findings of the present study reveal that the velocity of the fluid reduces due to the dominating effect of kinematic viscosity over molecular diffusivity in case of heavier species. Presence of heat source reduces the velocity of the flow. Presence of chemical reaction parameter decreases the concentration distribution.

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Bakulin, Andrey, Ilya Silvestrov et Maxim Protasov. « Evaluating strategies for estimation of local kinematic parameters in noisy land data : quality versus performance trade-offs ». Journal of Geophysics and Engineering 18, n^o 6 (décembre 2021) : 890–907. http://dx.doi.org/10.1093/jge/gxab060.

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Abstract Modern land seismic data are typically acquired using high spatial trace density with small source and receiver arrays or point sources and sensors. These datasets are challenging to process due to their massive size and relatively low signal-to-noise ratio caused by scattered near-surface noise. Therefore, prestack data enhancement becomes a critical step in the processing flow. Nonlinear beamforming had proved very powerful for 3D land data. However, it requires computationally intensive estimations of local coherency on dense spatial/temporal grids in 3D prestack data cubes. We present an analysis of various estimation methods focusing on a trade-off between computational efficiency and enhanced data quality. We demonstrate that the popular sequential «2 + 2 + 1» scheme is highly efficient but may lead to unreliable estimation and poor enhancement for data with a low signal-to-noise ratio. We propose an alternative algorithm called «dip + curvatures» that remains stable for such challenging data. We supplement the new strategy with an additional interpolation procedure in spatial and time dimensions to reduce the computational cost. We demonstrate that the «dip + curvatures» strategy coupled with an interpolation scheme approaches the «2 + 2 + 1» method's efficiency while it significantly outperforms it in enhanced data quality. We conclude that the new algorithm strikes a practical trade-off between the performance of the algorithm and the quality of the enhanced data. These conclusions are supported by synthetic and real 3D land seismic data from challenging desert environments with complex near surface.

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Sakai, Nobuyuki, Mareki Honma, Hiroyuki Nakanishi, Hirofumi Sakanoue et Tomoharu Kurayama. « The outer rotation curve project with VERA : Trigonometric parallax of IRAS 05168+3634 ». Proceedings of the International Astronomical Union 8, S289 (août 2012) : 95–98. http://dx.doi.org/10.1017/s1743921312021199.

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AbstractWe present a measurement of the trigonometric parallax of IRAS 05168+3634 with VERA. The parallax is 0.532 ± 0.053 milli-arcsec, corresponding to a distance of 1.88+0.21−0.17 kpc. This is significantly closer than the previous distance estimate of 6 kpc based on a kinematic distance measurement. This drastic change in the source distance implies the need for revised values of not only the physical parameters of IRAS 05168+3634, but it also impies a different location in the Galaxy, placing it in the Perseus arm rather than the Outer arm. We also measured the proper motion of the source. A combination of the distance and proper motion with the systemic velocity yields a rotation velocity Θ = 227+9−11 km s−1 at the source position, assuming Θ0 = 240 km s−1. Our result, combined with previous VLBI results for six sources in the Perseus arm, indicates that the sources rotate systematically more slowly than the Galactic rotation velocity at the local standard of rest. In fact, we derive peculiar motions in the disk averaged over the seven sources in the Perseus arm of (Umean, Vmean) = (11 ± 3, −17 ± 3) km s−1, which indicates that these seven sources are moving systematically toward the Galactic Center and lag behind the overall Galactic rotation.

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Maia, I. A., P. Jordan, A. V. G. Cavalieri et V. Jaunet. « Two-point wavepacket modelling of jet noise ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 475, n^o 2227 (juillet 2019) : 20190199. http://dx.doi.org/10.1098/rspa.2019.0199.

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This paper is focused on the study of a kinematic wavepacket model for jet noise based on two-point statistics. The model contains physical parameters that define its structure in terms of wavenumber, envelope shape and coherence decay. These parameters, which are necessary to estimate the sound pressure levels radiated by the source, were educed from a large-eddy simulation database of a Mach 0.4, fully turbulent jet. The sound pressure levels predicted by the model were compared with acoustic data and the results show that when the parameters are carefully educed from the data, the sound pressure levels generated are in good agreement with experimentally measured values for low Strouhal numbers and polar angles. Furthermore, here we show that a correct representation of both coherence decay and wavepacket envelope shape are key aspects to an accurate sound prediction. A Spectral Proper Orthogonal Decomposition (SPOD) of the model source was also performed motivated by the search for a low-rank model capable of capturing the acoustic efficiency of the full source. It is shown that only a few SPOD modes are necessary to recover acoustically important wavepacket traits.

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Buzzo, M. L., B. Ziegler, P. Amram, M. Verdugo, C. E. Barbosa, B. Ciocan, P. Papaderos, S. Torres-Flores et C. Mendes de Oliveira. « Physical and kinematic conditions of the local merging galaxy NGC 1487 ». Monthly Notices of the Royal Astronomical Society 503, n^o 1 (15 février 2021) : 106–23. http://dx.doi.org/10.1093/mnras/stab426.

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ABSTRACT We present optical VLT/MUSE integral field spectroscopy data of the merging galaxy NGC 1487. We use fitting techniques to study the ionized gas emission of this merger and its main morphological and kinematical properties. We measured flat and sometimes inverted oxygen abundance gradients in the subsystems composing NGC 1487, explained by metal mixing processes common in merging galaxies. We also measured widespread star-forming bursts, indicating that photoionization by stars is the primary ionization source of the galaxy. The kinematic map revealed a rotating pattern in the gas in the northern tail of the system, suggesting that the galaxy may be in the process of rebuilding a disc. The gas located in the central region has larger velocity dispersion (σ ≈ 50 km s−1) than the remaining regions, indicating kinematic heating, possibly owing to the ongoing interaction. Similar trends were, however, not observed in the stellar velocity dispersion map, indicating that the galaxy has not yet achieved equilibrium, and the nebular and stellar components are still kinematically decoupled. Based on all our measurements and findings, and specially on the mass estimates, metallicity gradients, and velocity fields of the system, we propose that NGC 1487 is the result of an ongoing merger event involving smallish dwarf galaxies within a group, in a pre-merger phase, resulting in a relic with mass and physical parameters similar to a dwarf galaxy. Thus, we may be witnessing the formation of a dwarf galaxy by merging of smaller clumps at z = 0.

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Cusin, Giulia, et Gianmassimo Tasinato. « Doppler boosting the stochastic gravitational wave background ». Journal of Cosmology and Astroparticle Physics 2022, n^o 08 (1 août 2022) : 036. http://dx.doi.org/10.1088/1475-7516/2022/08/036.

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Abstract One of the guaranteed features of the stochastic gravitational wave background (SGWB) is the presence of Doppler anisotropies induced by the motion of the detector with respect to the rest frame of the SGWB source. We point out that kinematic effects can be amplified if the SGWB is characterised by large tilts in its spectrum as a function of frequency, or by sizeable intrinsic anisotropies. Hence we examine the possibility to use Doppler effects as complementary probes of the SGWB frequency profile. For this purpose we work in multipole space, and we study the effect of kinematic modulation and aberration on the GW energy density parameter and on its angular power spectrum. We develop a Fisher forecast analysis and we discuss prospects for constraining parameters controlling kinematically induced anisotropies with future detector networks. As a case study, we apply our framework to a background component with constant slope in frequency, potentially detectable by a network of future ground-based interferometers. For this specific example, we show that a measurement of kinematic anisotropies with a network of Einstein Telescope and Cosmic Explorer will allow us to constrain the spectral shape with a precision of about 16%. We also show that, if a reconstruction of the spectral shape is done via other methods, e.g. frequency binning, a study of kinematic anisotropies can allow one to constrain our peculiar velocity with respect to the CMB frame with a precision of 30%. Finally, we identify cosmological and astrophysical scenarios where kinematic effects are enhanced in frequency ranges probed by current and future GW experiments.

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Wen, Jian, Jiankuan Xu et Xiaofei Chen. « The relations between the corner frequency, seismic moment and source dynamic parameters derived from the spontaneous rupture of a circular fault ». Geophysical Journal International 228, n^o 1 (27 août 2021) : 134–46. http://dx.doi.org/10.1093/gji/ggab346.

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SUMMARY The stress drop is an important dynamic source parameter for understanding the physics of source processes. The estimation of stress drops for moderate and small earthquakes is based on measurements of the corner frequency ${f_c}$, the seismic moment ${M_0}$ and a specific theoretical model of rupture behaviour. To date, several theoretical rupture models have been used. However, different models cause considerable differences in the estimated stress drop, even in an idealized scenario of circular earthquake rupture. Moreover, most of these models are either kinematic or quasi-dynamic models. Compared with previous models, we use the boundary integral equation method to simulate spontaneous dynamic rupture in a homogeneous elastic full space and then investigate the relations between the corner frequency, seismic moment and source dynamic parameters. Spontaneous ruptures include two states: runaway ruptures, in which the rupture does not stop without a barrier, and self-arresting ruptures, in which the rupture can stop itself after nucleation. The scaling relationships between ${f_c}$, ${M_0}$ and the dynamic parameters for runaway ruptures are different from those for self-arresting ruptures. There are obvious boundaries in those scaling relations that distinguish runaway ruptures from self-arresting ruptures. Because the stress drop varies during the rupture and the rupture shape is not circular, Eshelby's analytical solution may be inaccurate for spontaneous dynamic ruptures. For runaway ruptures, the relations between the corner frequency and dynamic parameters coincide with those in the previous kinematic or quasi-dynamic models. For self-arresting ruptures, the scaling relationships are opposite to those for runaway ruptures. Moreover, the relation between ${f_c}$ and ${M_0}$ for a spontaneous dynamic rupture depends on three factors: the dynamic rupture state, the background stress and the nucleation zone size. The scaling between ${f_c}$ and ${M_0}$ is ${f_c} \propto {M_0^{ - n}}$, where n is larger than 0. Earthquakes with the same dimensionless dynamic parameters but different nucleation zone sizes are self-similar and follow a ${f_c} \propto {M_0^{ - 1/3}}$ scaling law. However, if the nucleation zone size does not change, the relation between ${f_c}$ and ${M_0}$ shows a clear departure from self-similarity due to the rupture state or background stress.

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Ibarra-Pérez, Teodoro, José Manuel Ortiz-Rodríguez, Fernando Olivera-Domingo, Héctor A. Guerrero-Osuna, Hamurabi Gamboa-Rosales et Ma del Rosario Martínez-Blanco. « A Novel Inverse Kinematic Solution of a Six-DOF Robot Using Neural Networks Based on the Taguchi Optimization Technique ». Applied Sciences 12, n^o 19 (22 septembre 2022) : 9512. http://dx.doi.org/10.3390/app12199512.

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The choice of structural parameters in the design of artificial neural networks is generally based on trial-and-error procedures. They are regularly estimated based on the previous experience of the researcher, investing large amounts of time and processing resources during network training, which are usually limited and do not guarantee the optimal selection of parameters. This paper presents a procedure for the optimization of the training dataset and the optimization of the structural parameters of a neural network through the application of a robust neural network design methodology based on the design philosophy proposed by Genichi Taguchi, applied to the solution of inverse kinematics in an open source, six-degrees-of-freedom robotic manipulator. The results obtained during the optimization process of the structural parameters of the network show an improvement in the accuracy of the results, reaching a high prediction percentage and maintaining a margin of error of less than 5%.

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Katona, M., K. Trampert, C. Schwanengel, U. Krüger et C. Neumann. « Geometric system analysis of ILMD-based LID measurement systems using Monte-Carlo simulation ». Journal of Physics : Conference Series 2149, n^o 1 (1 janvier 2022) : 012015. http://dx.doi.org/10.1088/1742-6596/2149/1/012015.

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Abstract Imaging Luminance Measuring Device (ILMD) based luminous intensity distribution measurement systems are an established method for measuring the luminous intensity distribution (LID) of light sources in the far field. The advantage of this system is the high-resolution acquisition of a large angular range with one image. For the uncertainty budget, the mathematical description of the system can be divided into photometric and geometric contributions. In the following, we will present a Monte-Carlo approach to analyse the geometric contributions which are the uncertainty of measurement direction and measurement distance. Therefore, we set up a geometric system description based on kinematic transformations that describes the connection between detector and light source position. To consider all relevant input quantities we simulate the adjustment and measurement process. Finally, an analysis of the geometric input parameters is shown.

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Bagul, Samadhan Yuvraj, Randhir K. Bharti et Dolly Wattal Dhar. « Assessing biodiesel quality parameters for wastewater grown Chlorella sp. » Water Science and Technology 76, n^o 3 (18 avril 2017) : 719–27. http://dx.doi.org/10.2166/wst.2017.223.

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Microalgae are reported as the efficient source of renewable biodiesel which should be able to meet the global demand of transport fuels. Present study is focused on assessment of wastewater grown indigenous microalga Chlorella sp. for fuel quality parameters. This was successfully grown in secondary treated waste water diluted with tap water (25% dilution) in glass house. The microalga showed a dry weight of 0.849 g L−1 with lipid content of 27.1% on dry weight basis on 21st day of incubation. After transesterification, the yield of fatty acid methyl ester was 80.64% with major fatty acids as palmitic, linoleic, oleic and linolenic. The physical parameters predicted from empirical equations in the biodiesel showed cetane number as 56.5, iodine value of 75.5 g I2 100 g−1, high heating value 40.1 MJ kg−1, flash point 135 °C, kinematic viscosity 4.05 mm2 s−1 with density of 0.86 g cm3 and cold filter plugging point as 0.7 °C. Fourier transform infra-red (FTIR), 1H, 13C NMR spectrum confirmed the chemical nature of biodiesel. The results indicated that the quality of biodiesel was almost as per the criterion of ASTM standards; hence, wastewater grown Chlorella sp. can be used as a promising strain for biodiesel production.

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Qian, S. J., S. Britzen, T. P. Krichbaum et A. Witzel. « Possible evidence for a supermassive binary black hole in 3C454.3 ». Astronomy & ; Astrophysics 653 (31 août 2021) : A7. http://dx.doi.org/10.1051/0004-6361/202140583.

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Context. The kinematic behaviors of thirteen superluminal components observed at 43 GHz in blazar 3C454.3 are investigated and model-fitted in terms of the precessing jet-nozzle scenario previously proposed. Aims. In order to search for the possible precession of jet-nozzle and periodic ejection of superluminal components in 3C454.3, the thirteen components are divided into the following two groups: group-A and group-B. Group-A consists of six components (B4, B5, K2, K3, K09, and K14) and group-B consists of seven components (B1, B2, B3, B6, K1, K10, and K16). Methods. For each component of group-A and group-B, the observed kinematic features (trajectory, core separation, coordinates, and apparent velocity versus time) were model-fitted in terms of our precessing jet-nozzle scenario, and its kinematic parameters (bulk Lorentz factor, viewing angle, apparent velocity, and Doppler factor versus time) were derived and compared with the observations. Results. It is found that the superluminal components of group-A and group-B may be regarded to be produced by a double-jet system, consisting of jet-A and jet-B which ejects the components of group-A and group-B, respectively. Both jets are likely precessing with the same period of ∼10.5 yr (5.6 yr in the source frame) with modeled time coverages of ∼2 and ∼1.5 periods, respectively. The motion of these components in the inner-jet regions (core separation ≲0.3–0.5 mas) is explained to follow a precessing common trajectory respective for jet-A and jet-B. The recurrence of the curved trajectory for the pair of knots B6 and K10 exhibits a significant clue as to periodicity. Conclusions. The analysis and explanation of the entire kinematics of the thirteen superluminal components observed in 3C454.3 in terms of our precessing jet-nozzle scenario might possibly imply that blazar 3C454.3 hosts a supermassive binary black hole, which creates two precessing relativistic jets pointing closely toward us with small angles.

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Titov, Aleksei, Vladimir Kazei, Ali AlDawood, Ezzedeen Alfataierge, Andrey Bakulin et Konstantin Osypov. « Quantification of DAS VSP Quality : SNR vs. Log-Based Metrics ». Sensors 22, n^o 3 (28 janvier 2022) : 1027. http://dx.doi.org/10.3390/s22031027.

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The initial quantification of data quality is an important step in seismic data acquisition design, including the choice of sensing strategy. The signal-to-noise ratio (SNR) often drives the choice of distributed acoustic sensing (DAS) parameters in vertical seismic profiling (VSP). We compare this established approach for data quality assessment with metrics comparing DAS data products to available well logs. First, we create kinematic and dynamic data products derived from original seismic data, such as the interval velocity and amplitude of P-wave arrivals. Next, we quantify the quality of derived data products using well log data by calculating various statistical metrics. Using a large dataset of 220 different VSP experiments with a fixed source location and various DAS acquisition parameters, such as gauge length (GL), conveyance type, and lead-in length, we analyzed the statistical distribution of various metrics. The results indicate the decoupling between seismic-based and log-based metrics as well as between the quality of dynamic and kinematic data-products for the same record. Therefore, we propose using fit-for-purpose metrics to optimize the acquisition cost. In particular, for ray-based tomographic processing, it is sufficient to use traveltime-based metrics. On the other hand, for advanced dynamic analysis, amplitude-based metrics define the quality of final processing products. Hence, it is crucial to use fit-for-purpose metrics to optimize DAS VSP acquisition.

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Zhang, Yingkang, Tao An, Sándor Frey, Krisztina Éva Gabányi et Yulia Sotnikova. « Radio Jet Proper-motion Analysis of Nine Distant Quasars above Redshift 3.5 ». Astrophysical Journal 937, n^o 1 (1 septembre 2022) : 19. http://dx.doi.org/10.3847/1538-4357/ac87f8.

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Abstract Up to now, jet kinematic studies of radio quasars have barely reached beyond the redshift range z > 3.5. This significantly limits our knowledge of high-redshift jets, which can provide key information for understanding the jet nature and the growth of black holes in the early universe. In this paper, we selected nine radio-loud quasars at z > 3.5 which display milliarcsecond-scale jet morphology. We provided evidence of the source nature by presenting high-resolution very long baseline interferometry (VLBI) images of the sample at 8.4 GHz frequency and making spectral index maps. We also consider Gaia optical positions that are available for seven out of the nine quasars for better identification of the jet components within the radio structures. We find that six sources can be classified as core–jet blazars. The remaining three objects are more likely young jetted radio sources, compact symmetric objects. By including multiepoch archival VLBI data, we also obtained jet component proper motions of the sample and estimated the jet kinematic and geometric parameters (Doppler factor, Lorentz factor, and viewing angle). Our results show that at z > 3.5, the jet’s apparent transverse speeds do not exceed 20 times the speed of light (c). This is consistent with earlier high-redshift quasar measurements in the literature and the tendency derived from low-redshift blazars that fast jet speeds (>40c) only occur at low redshifts. The results from this paper contribute to the understanding of the cosmological evolution of radio active galactic nuclei.

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von Benzon, Malte, Fredrik Fogh Sørensen, Esben Uth, Jerome Jouffroy, Jesper Liniger et Simon Pedersen. « An Open-Source Benchmark Simulator : Control of a BlueROV2 Underwater Robot ». Journal of Marine Science and Engineering 10, n^o 12 (5 décembre 2022) : 1898. http://dx.doi.org/10.3390/jmse10121898.

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This paper presents a simulation model environment for the popular and low-cost remotely operated vehicle (ROV) BlueROV2 implemented in Simulink™ which has been designed and experimentally validated for benchmark control algorithms for underwater vehicles. The BlueROV2 model is based on Fossen’s equations and includes a kinematic model of the vehicle, the hydrodynamics of vehicle and water interaction, a dynamic model of the thrusters, and, lastly, the gravitational/buoyant forces. The hydrodynamic parameters and thruster model have been validated in a test facility. The benchmark model also includes the ocean current, modeled as constant velocity. The tether connecting the ROV to the top-site facility has been modeled using the lumped mass method and is implemented as a force input to the ROV model. At last, to show the usefulness of the benchmark model, a case study is presented where a BlueROV2 is deployed to inspect an offshore monopile structure. The case study uses a sliding mode controller designed for the BlueROV2. The controller fulfills the design criteria defined for the case study by following the provided trajectory with a low error. It is concluded that the simulator establishes a benchmark for future control schemes for position control and trajectory tracking under the influence of environmental disturbances.

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Shokravi, Hoofar, Hooman Shokravi, Norhisham Bakhary, Mahshid Heidarrezaei, Seyed Saeid Rahimian Koloor et Michal Petrů. « A Review on Vehicle Classification and Potential Use of Smart Vehicle-Assisted Techniques ». Sensors 20, n^o 11 (8 juin 2020) : 3274. http://dx.doi.org/10.3390/s20113274.

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Vehicle classification (VC) is an underlying approach in an intelligent transportation system and is widely used in various applications like the monitoring of traffic flow, automated parking systems, and security enforcement. The existing VC methods generally have a local nature and can classify the vehicles if the target vehicle passes through fixed sensors, passes through the short-range coverage monitoring area, or a hybrid of these methods. Using global positioning system (GPS) can provide reliable global information regarding kinematic characteristics; however, the methods lack information about the physical parameter of vehicles. Furthermore, in the available studies, smartphone or portable GPS apparatuses are used as the source of the extraction vehicle’s kinematic characteristics, which are not dependable for the tracking and classification of vehicles in real time. To deal with the limitation of the available VC methods, potential global methods to identify physical and kinematic characteristics in real time states are investigated. Vehicular Ad Hoc Networks (VANETs) are networks of intelligent interconnected vehicles that can provide traffic parameters such as type, velocity, direction, and position of each vehicle in a real time manner. In this study, VANETs are introduced for VC and their capabilities, which can be used for the above purpose, are presented from the available literature. To the best of the authors’ knowledge, this is the first study that introduces VANETs for VC purposes. Finally, a comparison is conducted that shows that VANETs outperform the conventional techniques.

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Bollen, D., D. Kamath, H. Van Winckel et O. De Marco. « A spatio-kinematic model for jets in post-AGB stars »,. Astronomy & ; Astrophysics 631 (18 octobre 2019) : A53. http://dx.doi.org/10.1051/0004-6361/201936073.

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Aims. We aim to determine the geometry, density gradient, and velocity structure of jets in post-asymptotic giant branch (post-AGB) binaries. Methods. Our high cadence time series of high-resolution optical spectra of jet-creating post-AGB binary systems provide us with a unique tomography of the jet. We determine the spatio-kinematic structure of the jets based on these data by fitting the synthetic spectral line profiles created by our model to the observed, orbital phase-resolved, Hα-line profiles of these systems. The fitting routine is provided with an initial spectrum and is allowed to test three configurations, derived from three specific jet launching models: a stellar jet launched by the star, an X-wind, and a disk wind configuration. We apply a Markov-chain Monte Carlo routine in order to fit our model to the observations. Our fitting code is tested on the post-AGB binary IRAS 19135+3937. Results. We find that a model using the stellar jet configuration gives a marginally better fit to our observations. The jet has a wide half-opening angle of about 76° and reaches velocities up to 870 km s−1. Conclusions. Our methodology is successful in determining some parameters for jets in post-AGB binaries. The model for IRAS 19135+3937 includes a transparent, low density inner region (for a half-opening angle < 40°). The source feeding the accretion disk around the companion is most likely the circumbinary disk. We will apply this jet fitting routine to other jet-creating post-AGB stars in order to provide a more complete description of these objects.

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Laban, Othman, Elsadig Mahdi et John-John Cabibihan. « Prediction of Neural Space Narrowing and Soft Tissue Injury of the Cervical Spine Concerning Head Restraint Arrangements in Traffic Collisions ». Applied Sciences 11, n^o 1 (25 décembre 2020) : 145. http://dx.doi.org/10.3390/app11010145.

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Common quantitative assessments of neck injury criteria do not predict anatomical neck injuries and lack direct relations to design parameters of whiplash-protection systems. This study aims to provide insights into potential soft tissue-level injury sites based on the interactions developed in-between different anatomical structures in case of a rear-end collision. A detailed finite element human model has exhibited an excellent biofidelity when validated against volunteer impacts. Three head restraint arrangements were simulated, predicting both the kinematic response and the anatomical pain source at each arrangement. Head restraint’s contribution has reduced neck shear and head kinematics by at least 70 percent, minimized pressure gradients acting on ganglia and nerve roots less than half. Posterior column ligaments were the most load-bearing components, followed by the lower intervertebral discs and upper capsular ligaments. Sprain of the interspinous ligamentum flavum at early stages has caused instability in the craniovertebral structure causing its discs and facet joints to be elevated compressive loads. Excessive hyperextension motion, which occurred in the absence of the head restraint, has promoted a stable avulsion teardrop fracture of the fourth vertebral body’s anteroinferior aspect and rupture the anterior longitudinal ligament. The observed neck injuries can be mathematically related to head–torso relative kinematics. These relations will lead to the development of a comprehensive neck injury criterion that can predict the injury level. This, in turn, will impose a significant impact on the design processes of vehicle anti-whiplash safety equipment.

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Gomer, Matthew R., et Liliya L. R. Williams. « Galaxy-lens determination of H0 : the effect of the ellipse + shear modelling assumption ». Monthly Notices of the Royal Astronomical Society 504, n^o 1 (5 avril 2021) : 1340–54. http://dx.doi.org/10.1093/mnras/stab930.

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ABSTRACT Galaxy lenses are frequently modelled as an elliptical mass distribution with external shear and isothermal spheres to account for secondary and line-of-sight galaxies. There is statistical evidence that some fraction of observed quads are inconsistent with these assumptions, and require a dipole-like contribution to the mass with respect to the light. Simplifying assumptions about the shape of mass distributions can lead to the incorrect recovery of parameters such as H0. We create several tests of synthetic quad populations with different deviations from an elliptical shape, then fit them with an ellipse + shear model, and measure the recovered values of H0. Kinematic constraints are not included. We perform two types of fittings – one with a single point source and one with an array of sources emulating an extended source. We carry out two model-free comparisons between our mock quads and the observed population. One result of these comparisons is a statistical inconsistency not yet mentioned in the literature: the image distance ratios with respect to the lens centre of observed quads appear to span a much wider range than those of synthetic or simulated quads. Bearing this discrepancy in mind, our mock populations can result in biases on H0$\sim 10{{\ \rm per\ cent}}$.

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