Artículos de revistas sobre el tema "Variables action-Angles"
Siga este enlace para ver otros tipos de publicaciones sobre el tema: Variables action-Angles.
Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros
Consulte los 35 mejores artículos de revistas para su investigación sobre el tema "Variables action-Angles".
Junto a cada fuente en la lista de referencias hay un botón "Agregar a la bibliografía". Pulsa este botón, y generaremos automáticamente la referencia bibliográfica para la obra elegida en el estilo de cita que necesites: APA, MLA, Harvard, Vancouver, Chicago, etc.
También puede descargar el texto completo de la publicación académica en formato pdf y leer en línea su resumen siempre que esté disponible en los metadatos.
Explore artículos de revistas sobre una amplia variedad de disciplinas y organice su bibliografía correctamente.
1
Monari, G., B. Famaey, J. B. Fouvry y J. Binney. "Distribution functions for resonantly trapped orbits in our Galaxy". Proceedings of the International Astronomical Union 13, S334 (julio de 2017): 341–42. http://dx.doi.org/10.1017/s1743921317006688.
Texto completoResumen
AbstractWe show how to capture the behaviour of the phase-space distribution function (DF) of a Galactic disc stellar population at a resonance. This is done by averaging the Hamiltonian over fast angle variables and re-expressing the DF in terms of a new set of canonical actions and angles variables valid in the resonant region. We then assign to the resonant DF the time average along the orbits of the axisymmetric DF expressed in the new set of actions and angles. This boils down to phase-mixing the DF in terms of the new angles, such that the DF for trapped orbits only depends on the new set of actions. This opens the way to quantitatively fitting the effects of the bar and spirals to Gaia data in terms of distribution functions in action space.
2
VIROVLYANSKY, A. L. "RAY CHAOS IN UNDERWATER ACOUSTIC WAVEGUIDES". International Journal of Bifurcation and Chaos 18, n.º 09 (septiembre de 2008): 2693–700. http://dx.doi.org/10.1142/s0218127408021907.
Texto completoResumen
The chaotic motion of a ray path in a deep water acoustic waveguide with internal-wave-induced fluctuations of the sound speed is investigated. A statistical approach for the description of chaotic rays is discussed. The behavior of ray trajectories is studied using Hamiltonian formalism expressed in terms of action-angle variables. It is shown that the range dependence of the action variable of chaotic ray can be approximated by a random Wiener process. On the basis of this result, analytical expressions for probability density functions of ray parameters are derived. Distributions of coordinates, momenta (grazing angles), and actions of sound rays are evaluated. Numerical simulation shows that statistical characteristics of ray parameters weakly depend on a particular realization of random perturbation giving rise to ray chaos.
3
Zhu, W. Q., Z. L. Huang y Y. Q. Yang. "Stochastic Averaging of Quasi-Integrable Hamiltonian Systems". Journal of Applied Mechanics 64, n.º 4 (1 de diciembre de 1997): 975–84. http://dx.doi.org/10.1115/1.2789009.
Texto completoResumen
A stochastic averaging method is proposed to predict approximately the response of quasi-integrable Hamiltonian systems, i.e., multi-degree-of-freedom integrable Hamiltonian systems subject to lightly linear and (or) nonlinear dampings and weakly external and (or) parametric excitations of Gaussian white noises. According to the present method an n-dimensional averaged Fokker-Planck-Kolmogrov (FPK) equation governing the transition probability density of n action variables or n independent integrals of motion can be constructed in nonresonant case. In a resonant case with α resonant relations, an (n + α)-dimensional averaged FPK equation governing the transition probability density of n action variables and α combinations of phase angles can be obtained. The procedures for obtaining the stationary solutions of the averaged FPK equations for both resonant and nonresonant cases are presented. It is pointed out that the Stratonovich stochastic averaging and the stochastic averaging of energy envelope are two special cases of the present stochastic averaging. Two examples are given to illustrate the application and validity of the proposed method.
4
Famaey, B., G. Monari, A. Siebert, J. B. Fouvry y J. Binney. "Distribution functions for Galactic disc stellar populations in the presence of non-axisymmetric perturbations". Proceedings of the International Astronomical Union 13, S334 (julio de 2017): 195–98. http://dx.doi.org/10.1017/s174392131700672x.
Texto completoResumen
AbstractThe present-day response of a Galactic disc stellar population to a non-axisymmetric perturbation of the potential, in the form of a bar or spiral arms, can be treated, away from the main resonances, through perturbation theory within the action-angle coordinates of the unperturbed axisymmetric system. The first order moments of such a perturbed distribution function (DF) in the presence of spiral arms give rise to non-zero radial and vertical mean stellar velocities, called breathing modes. Such an Eulerian linearized treatment however diverges at resonances. The Lagrangian approach to the impact of non-axisymmetries at resonances avoids this problem. It is based on the construction of new orbital tori in the resonant trapping region, which come complete with a new system of angle-action variables. These new tori can be populated by phase-averaging the unperturbed DF over the new tori. This boils down to phase-mixing the DF in terms of the new angles, such that the DF for trapped orbits only depends on the new set of actions. This opens the way to quantitatively fitting the effects of the bar and spirals to Gaia data with an action-based DF.
5
KOBE, DONALD H. "INVARIANCE OF THE GENERALIZED HANNAY ANGLE UNDER GAUGE TRANSFORMATIONS: APPLICATION TO THE TIME-DEPENDENT GENERALIZED HARMONIC OSCILLATOR". International Journal of Modern Physics B 07, n.º 11 (15 de mayo de 1993): 2147–62. http://dx.doi.org/10.1142/s021797929300281x.
Texto completoResumen
The Hannay angle of classical mechanics is generalized so that it is invariant under gauge transformations, which are a restricted class of canonical transformations. A distinction between the Hamiltonian and the energy is essential to make in time-dependent problems. A time-dependent generalized harmonic oscillator with a cross term in the Hamiltonian is taken as an example. The Hamiltonian of this system is not in general the energy. The energy, the time derivative of which is the power, is obtained from the equation of motion and related to the action variable. Hamilton’s equations give the time rate of change of the angle and action variables. The generalized Hannay angle is shown to be zero, and remains invariant under gauge transformations. On the other hand, if the original Hamiltonian is chosen as the energy, a nonzero generalized Hannay angle is obtained, but the power is given incorrectly. Nevertheless in the adiabatic limit, the total angle, which is the sum of the dynamical and Hannay angles, is equal to the one calculated from the correct energy.
6
McGibbon, Chris A. y David E. Krebs. "Discriminating age and disability effects in locomotion: neuromuscular adaptations in musculoskeletal pathology". Journal of Applied Physiology 96, n.º 1 (enero de 2004): 149–60. http://dx.doi.org/10.1152/japplphysiol.00422.2003.
Texto completoResumen
We identified biomechanical variables indicative of lower extremity dysfunction, distinct from age-related gait adaptations, and examined interrelationships among these variables to better understand the neuromuscular adaptations in gait. Sagittal plane ankle, knee, and hip peak angles, moments, and powers and spatiotemporal parameters were acquired during preferred-speed gait in 120 subjects: 45 healthy young, 37 healthy elders, and 38 elders with functional limitations due to lower extremity musculoskeletal pathology, primarily arthritis. Multiple analysis of covariance with discriminate analysis, adjusted for gait speed, was used to identify the variables discriminating groups. Correlation analysis was used to explore interrelationships among these variables within each group. Healthy elders were discriminated (sensitivity 76%, specificity 82%) from young adults via decreased late-stance ankle plantar flexion angle, increased late-stance knee power absorption, and early-stance hip extensor power generation. Disabled elders were discriminated (sensitivity 74%, specificity 73%) from healthy elders via decreased late-stance ankle plantar flexor moment and power generation, increased early-stance ankle dorsiflexor moment, and late-stance hip flexor moment and power absorption. Relationships among variables showed a higher degree of coupling for the disabled elders compared with the healthy groups, suggesting a reduced ability to alter motor strategies. Our data suggest that, beyond age-related changes, elders with lower extremity dysfunction rely excessively on passive action of hip flexors to provide propulsion in late stance and contralateral ankle dorsiflexors to enhance stability. These findings support a growing body of evidence that gait changes with age and disablement have a neuromuscular basis, which may be informative in a motor control framework for physical therapy interventions.
7
Zhu, W. Q. y Y. Q. Yang. "Exact Stationary Solutions of Stochastically Excited and Dissipated Integrable Hamiltonian Systems". Journal of Applied Mechanics 63, n.º 2 (1 de junio de 1996): 493–500. http://dx.doi.org/10.1115/1.2788895.
Texto completoResumen
It is shown that the structure and property of the exact stationary solution of a stochastically excited and dissipated n-degree-of-freedom Hamiltonian system depend upon the integrability and resonant property of the Hamiltonian system modified by the Wong-Zakai correct terms. For a stochastically excited and dissipated nonintegrable Hamiltonian system, the exact stationary solution is a functional of the Hamiltonian and has the property of equipartition of energy. For a stochastically excited and dissipated integrable Hamiltonian system, the exact stationary solution is a functional of n independent integrals of motion or n action variables of the modified Hamiltonian system in nonresonant case, or a functional of both n action variables and α combinations of phase angles in resonant case with α (1 ≤ α ⩽ n – 1) resonant relations, and has the property that the partition of the energy among n degrees-of-freedom can be adjusted by the magnitudes and distributions of dampings and stochastic excitations. All the exact stationary solutions obtained to date for nonlinear stochastic systems are those for stochastically excited and dissipated nonintegrable Hamiltonian systems, which are further generalized to account for the modification of the Hamiltonian by Wong-Zakai correct terms. Procedures to obtain the exact stationary solutions of stochastically excited and dissipated integrable Hamiltonian systems in both resonant and nonresonant cases are proposed and the conditions for such solutions to exist are deduced. The above procedures and results are further extended to a more general class of systems, which include the stochastically excited and dissipated Hamiltonian systems as special cases. Examples are given to illustrate the applications of the procedures.
8
Dmitriev, Vladimir G., Alexander N. Danilin, Anastasiya R. Popova y Natalia V. Pshenichnova. "Numerical Analysis of Deformation Characteristics of Elastic Inhomogeneous Rotational Shells at Arbitrary Displacements and Rotation Angles". Computation 10, n.º 10 (11 de octubre de 2022): 184. http://dx.doi.org/10.3390/computation10100184.
Texto completoResumen
Adequate mathematical models and computational algorithms are developed in this study to investigate specific features of the deformation processes of elastic rotational shells at large displacements and arbitrary rotation angles of the normal line. A finite difference method (FDM) is used to discretize the original continuum problem in spatial variables, replacing the differential operators with a second-order finite difference approximation. The computational algorithm for solving the nonlinear boundary value problem is based on a quasi-dynamic form of the ascertainment method with the construction of an explicit two-layer time-difference scheme of second-order accuracy. The influence of physical and mechanical characteristics of isotropic and composite materials on the deformation features of elastic spherical shells under the action of surface loading of “tracking” type is investigated. The results of the studies conducted have shown that the physical and mechanical characteristics of isotropic and composite materials significantly affect the nature of the deformation of the clamped spherical shell in both the subcritical and post-critical domains. The developed mathematical models and computational algorithms can be applied in the future to study shells of rotation made of hyperelastic (non-linearly elastic) materials and soft shells.
9
Fan, Zihao, Yang Xu, Yuhang Kang y Delin Luo. "Air Combat Maneuver Decision Method Based on A3C Deep Reinforcement Learning". Machines 10, n.º 11 (5 de noviembre de 2022): 1033. http://dx.doi.org/10.3390/machines10111033.
Texto completoResumen
To solve the maneuvering decision problem in air combat of unmanned combat aircraft vehicles (UCAVs), in this paper, an autonomous maneuver decision method is proposed for a UCAV based on deep reinforcement learning. Firstly, the UCAV flight maneuver model and maneuver library of both opposing sides are established. Then, considering the different state transition effects of various actions when the pitch angles of the UCAVs are different, the 10 state variables including the pitch angle, are taken as the state space. Combined with the air combat situation threat assessment index model, a two-layer reward mechanism combining internal reward and sparse reward is designed as the evaluation basis of reinforcement learning. Then, the neural network model of the full connection layer is built according to an Asynchronous Advantage Actor–Critic (A3C) algorithm. In the way of multi-threading, our UCAV keeps interactively learning with the environment to train the model and gradually learns the optimal air combat maneuver countermeasure strategy, and guides our UCAV to conduct action selection. The algorithm reduces the correlation between samples through multi-threading asynchronous learning. Finally, the effectiveness and feasibility of the method are verified in three different air combat scenarios.
10
Hu, Zhizheng, Haifeng Zeng, Yun Ge, Wendong Wang y Jiangkun Wang. "Simulation and Experiment of Gas-Solid Flow in a Safflower Sorting Device Based on the CFD-DEM Coupling Method". Processes 9, n.º 7 (17 de julio de 2021): 1239. http://dx.doi.org/10.3390/pr9071239.
Texto completoResumen
To study the movement characteristics and separation mechanism of safflower petals and their impurities under the action of airflow and lower the impurity rate in the cleaning operation process, integration of computational fluid dynamics (CFD) and discrete element method (DEM) codes was performed to study the motion and sorting behavior of impurity particles and safflower petals under different airflow inclination angles, dust removal angles and inlet airflow velocities by establishing a true particle model. In this model, the discrete particle phase was applied by the DEM software, and the continuum gas phase was described by the ANSYS Fluent software. The Box-Behnken experimental design with three factors and three levels was performed, and parameters such as inlet airflow velocity, airflow inclined angle, and dust remover angle were selected as independent variables that would influence the cleaning impurity rate and the cleaning loss rate. A mathematical model was established, and then the effects of various parameters and their interactions were analyzed. The test results show that the cleaning effect is best when the inlet airflow velocity is 7 m/s, the airflow inclined angle is 0°, and the dust remover angle is 25°. Confirmatory tests showed that the average cleaning impurity rate and cleaning loss rate were 0.69% and 2.75%, respectively, which dropped significantly compared with those from previous optimization. An experimental device was designed and set up; the experimental results were consistent with the simulation results, indicating that studying the physical behavior of safflower petals-impurity separation in the airflow field by using the DEM-CFD coupling method is reliable. This result provides a basis for follow-up studies of separation and cleaning devices for lightweight materials such as safflower petals.
11
Dos’Santos, Thomas, Christopher Thomas, Alistair McBurnie, Paul Comfort y Paul A. Jones. "Biomechanical Determinants of Performance and Injury Risk During Cutting: A Performance-Injury Conflict?" Sports Medicine 51, n.º 9 (3 de abril de 2021): 1983–98. http://dx.doi.org/10.1007/s40279-021-01448-3.
Texto completoResumen
Abstract Background Most cutting biomechanical studies investigate performance and knee joint load determinants independently. This is surprising because cutting is an important action linked to performance and non-contact anterior cruciate ligament (ACL) injuries. The aim of this study was to investigate the relationship between cutting biomechanics and cutting performance (completion time, ground contact time [GCT], exit velocity) and surrogates of non-contact ACL injury risk (knee abduction [KAM] and internal rotation [KIRM] moments) during 90° cutting. Design Mixed, cross-sectional study following an associative design. 61 males from multidirectional sports performed six 90° pre-planned cutting trials, whereby lower-limb and trunk kinetics and kinematics were evaluated using three-dimensional (3D) motion and ground reaction force analysis over the penultimate (PFC) and final foot contact (FFC). Pearson’s and Spearman’s correlations were used to explore the relationships between biomechanical variables and cutting performance and injury risk variables. Stepwise regression analysis was also performed. Results Faster cutting performance was associated (p ≤ 0.05) with greater centre of mass (COM) velocities at key instances of the cut (r or ρ = 0.533–0.752), greater peak and mean propulsive forces (r or ρ = 0.449–0.651), shorter FFC GCTs (r or ρ = 0.569–0.581), greater FFC and PFC braking forces (r = 0.430–0.551), smaller hip and knee flexion range of motion (r or ρ = 0.406–0.670), greater knee flexion moments (KFMs) (r = 0.482), and greater internal foot progression angles (r = − 0.411). Stepwise multiple regression analysis revealed that exit velocity, peak resultant propulsive force, PFC mean horizontal braking force, and initial foot progression angle together could explain 64% (r = 0.801, adjusted 61.6%, p = 0.048) of the variation in completion time. Greater peak KAMs were associated with greater COM velocities at key instances of the cut (r or ρ = − 0.491 to − 0.551), greater peak knee abduction angles (KAA) (r = − 0.468), and greater FFC braking forces (r = 0.434–0.497). Incidentally, faster completion times were associated with greater peak KAMs (r = − 0.412) and KIRMs (r = 0.539). Stepwise multiple regression analysis revealed that FFC mean vertical braking force and peak KAA together could explain 43% (r = 0.652, adjusted 40.6%, p < 0.001) of the variation peak KAM. Conclusion Techniques and mechanics associated with faster cutting (i.e. faster COM velocities, greater FFC braking forces in short GCTs, greater KFMs, smaller hip and knee flexion, and greater internal foot progression angles) are in direct conflict with safer cutting mechanics (i.e. reduced knee joint loading, thus ACL injury risk), and support the “performance-injury conflict” concept during cutting. Practitioners should be conscious of this conflict when instructing cutting techniques to optimise performance while minimising knee joint loading, and should, therefore, ensure that their athletes have the physical capacity (i.e. neuromuscular control, co-contraction, and rapid force production) to tolerate and support the knee joint loading during cutting.
12
Avramov, K. V., N. H. Sakhno y B. V. Uspensky. "Transient dynamic response of a nanocomposite conical shell with a ring stiff-ener under the action of an impact load". Technical mechanics 2020, n.º 3 (15 de octubre de 2020): 64–78. http://dx.doi.org/10.15407/itm2020.03.064.
Texto completoResumen
This work is devoted to the study of transient processes occurring in a nanocomposite shell with a ring stiffener under the action of an impact load. Nanocomposites are promising new materials for the aerospace industry. However, the analysis of dynamic processes in nanocomposite structures requires the development of new methods due to the anisotropic, functional-gradient nature of these materials. The problem is further complicated if a composed structure is to be analyzed. This paper proposes a model of deformation of a functionally graded composite conical shell reinforced with carbon nanotubes with an isotropic ring stiffener. The deformation of the functionally graded nanocomposite conical shell is described by Reddy’s high-order shear theory, and the deformation of the ring stiffener is described by the Euler–Bernoulli hypotheses. The Rayleigh–Ritz method is used to study the natural vibrations of the composite structure. The main variables are the displacements and angles of rotation of the conical shell. A mathematical model of the transient response of the structure under the action of an impact load is obtained in the form of a linear dynamic system in generalized coordinates. To obtain this system, the prescribed form method is used. Numerical studies of the free dynamics and transient response of a nanocomposite conical shell with an isotropic ring stiffener of rectangular section under the action of an impact load were carried out. The results of the numerical modeling of the transient process in the shell showed a close agreement with the results of finite element modeling in the ANSYS package. The effect of the ring stiffener on the amplitudes of the transient response of the nanocomposite shell is investigated. It is shown that the ring-stiffener significantly reduces the amplitude of the transient response of the composite conical shell when it is subjected to an impact load. The proposed method and the conclusions drawn may be used in the aerospace industry in the design of nanocomposite units for multistage launch vehicles.
13
Demareva, A. V. "ANALYSIS OF THE CONSERVATIVE SMOOTHING EFFECT ON THE ACCURACY OF DYNAMIC ELASTIC-PLASTIC SPHERICAL SHELLS BUCKLING NUMERICAL SIMULATION". Problems of strenght and plasticity 81, n.º 4 (2019): 474–87. http://dx.doi.org/10.32326/1814-9146-2019-81-4-474-487.
Texto completoResumen
Large changes of a lead spherical shell enclosed in an aluminum spacesuit under the action of an overload pulse are considered. The defining system of equations is formulated in Lagrange variables in a two-dimensional (axisymmetric) formulation. Strain and stress rates are determined in the local coordinate system. Kinematic relations are recorded in the metric of the current state. The relations of the flow theory with isotropic hardening are used as state equations. The contact interaction of the shell and the spacesuit is modeled by non-penetration conditions taking into account friction. The numerical solution of the problem under given boundary and initial conditions is based on the finite element method moment scheme and the explicit time integration “cross” type scheme. 4-node isoparametric finite elements with bilinear form functions are used to discretize the defining system of equations for spatial variables. To suppress the numerical solution high-frequency oscillations, the procedure of nodal displacements rates conservative smoothing is used. As shown by the results of numerical research spherical shell in the process of intensive dynamic loading undergoes large deformation and rotation angles as a rigid whole. The calculation results reliability is confirmed by a good correspondence to the experimental data. The influence of conservative smoothing procedure and moment components of deformations and stresses on the solution accuracy is analyzed. It is shown that without conservative smoothing procedure using, the shape of the spherical shell buckling obtained in the calculation does not correspond to the experimental data. Neglect of the moment components of strains and stresses leads to the development of instability of the “hourglass” type.
14
Demareva, A. V. "ANALYSIS OF THE CONSERVATIVE SMOOTHING EFFECT ON THE ACCURACY OF DYNAMIC ELASTIC-PLASTIC SPHERICAL SHELLS BUCKLING NUMERICAL SIMULATION". Problems of strenght and plasticity 81, n.º 4 (2019): 475–88. http://dx.doi.org/10.32326/1814-9146-2019-81-4-475-488.
Texto completoResumen
Large changes of a lead spherical shell enclosed in an aluminum spacesuit under the action of an overload pulse are considered. The defining system of equations is formulated in Lagrange variables in a two-dimensional (axisymmetric) formulation. Strain and stress rates are determined in the local coordinate system. Kinematic relations are recorded in the metric of the current state. The relations of the flow theory with isotropic hardening are used as state equations. The contact interaction of the shell and the spacesuit is modeled by non-penetration conditions taking into account friction. The numerical solution of the problem under given boundary and initial conditions is based on the finite element method moment scheme and the explicit time integration “cross” type scheme. 4-node isoparametric finite elements with bilinear form functions are used to discretize the defining system of equations for spatial variables. To suppress the numerical solution high-frequency oscillations, the procedure of nodal displacements rates conservative smoothing is used. As shown by the results of numerical research spherical shell in the process of intensive dynamic loading undergoes large deformation and rotation angles as a rigid whole. The calculation results reliability is confirmed by a good correspondence to the experimental data. The influence of conservative smoothing procedure and moment components of deformations and stresses on the solution accuracy is analyzed. It is shown that without conservative smoothing procedure using, the shape of the spherical shell buckling obtained in the calculation does not correspond to the experimental data. Neglect of the moment components of strains and stresses leads to the development of instability of the “hourglass” type.
15
Monari, G., B. Famaey, A. Siebert, C. Wegg y O. Gerhard. "Signatures of the resonances of a large Galactic bar in local velocity space". Astronomy & Astrophysics 626 (junio de 2019): A41. http://dx.doi.org/10.1051/0004-6361/201834820.
Texto completoResumen
The second data release of the Gaia mission has revealed a very rich structure in local velocity space. In terms of in-plane motions, this rich structure is also seen as multiple ridges in the actions of the axisymmetric background potential of the Galaxy. These ridges are probably related to a combination of effects from ongoing phase-mixing and resonances from the spiral arms and the bar. We have recently developed a method for capturing the behaviour of the stellar phase-space distribution function at a resonance by re-expressing it in terms of a new set of canonical actions and angles variables valid in the resonant region. Here, by properly treating the distribution function at resonances, and by using a realistic model for a slowly rotating large Galactic bar with pattern speed Ωb = 39 km s−1 kpc−1, we show that no fewer than six ridges in local action space can be related to resonances with the bar. Two of these ridges at low angular momentum correspond to the corotation resonance, and can be associated with the Hercules moving group in local velocity space. Another ridge at high angular momentum corresponds to the outer Lindblad resonance, and can tentatively be associated with the velocity structure seen as an arch at high azimuthal velocities in Gaia data. The other ridges are associated with the 3:1, 4:1, and 6:1 resonances. The last can be associated with the so-called “horn” of the local velocity distribution. While it is clear that effects from spiral arms and incomplete phase-mixing related to external perturbations also play a role in shaping the complex kinematics revealed by Gaia data, the present work demonstrates that, contrary to common misconceptions, the bar alone can create multiple prominent ridges in velocity and action space.
16
Kasper, S. "Depression". European Psychiatry 26, S2 (marzo de 2011): 2186. http://dx.doi.org/10.1016/s0924-9338(11)73889-5.
Texto completoResumen
Depression is one of the thoroughly evaluated diseases in psychiatry with regard to diagnosis as well as treatment variables. Like in other medical conditions, early treatment should be aimed and watchful waiting which is for instance also not done in the treatment of high blood pressure or diabetes, has not been proven to be a sophisticated approach based on neurobiological considerations. Like in other diseases, it is apparent that days of untreated depression may result in brain damage like reduced volume size of the hypocampus. The course of illness of depression shows that life events are less important in later stages of the illness than in earlier. The introduction of the group of selective serotonin reuptake inhibitors (SSRI) marked a revolution in the treatment of depression, since it was possible to treat patient for the first time effectively with a more minor side effect profile with this approach. Substantially more patients could be reached and the association with this phenomenon and the reduction of the suicide rates in different countries like Sweden, Austria and Hungary has been discussed. Dual reuptake inhibitors effecting both the serotonergic as well as the noradrenergic pathways and the dopaminergic noradrenergic medication bupropion have been introduced in the filed with specific angles of treatment goals like pain or somatic symptoms. With the introduction of agomelatine, a unique mechanism of action with the combination of melatonergic agonistic as well as serotonergic antagonistic activities has been achieved. With this approach a more potent influence on the circadian rhythm has been shown compared to other, previously used antidepressant properties. Deep brain stimulation and vagus nerve stimulation for treatment refractory depressed patients yield promising results. More thorough characterisation of the underlying pathophysiology of depression including brain imaging results as well as molecular biological variables will yield further inside of the understanding and treatment of depression.
17
Fan, Chao y Zhe Wang. "Spatiotemporal Characterization of Land Cover Impacts on Urban Warming: A Spatial Autocorrelation Approach". Remote Sensing 12, n.º 10 (20 de mayo de 2020): 1631. http://dx.doi.org/10.3390/rs12101631.
Texto completoResumen
There has been an increasing concern of rising temperatures as cities continue to expand and intensify. Urban warming is having significant impacts on the environment that are far beyond city limits. Understanding the development pattern of the urban heat island (UHI) effect is crucial for making action plans to mitigate urban warming. In this study, we combine multitemporal satellite imagery, spatial autocorrelation indices, and statistical analysis into a spatiotemporal study of the surface UHI effect in the Boise-Meridian metropolitan area. A continuous landscape modeling perspective was taken to quantitatively depict the abundance and spatial configuration of green vegetation and built-up areas at a landscape scale. We aim to (1) evaluate the variations in the land surface temperatures (LST) along the urban–rural gradients of Boise for multiple years, (2) identify the relationships of the LST variations with the land cover variables quantified using the spatial autocorrelation indices, and (3) analyze the changing climate in Boise in conjunction with its urbanization pattern over the last two decades. Results show that the region experienced a significant increase in the LST along with a great expansion of urban areas at the cost of agriculture. The warming effect of built-up areas was greater than the cooling effect of green vegetation, suggesting an urgent need for increasing greenspace in the city. Statistical analyses show that clustered vegetation and dispersed built-up features are beneficial for reducing the LST. Our study presents a spatiotemporal framework for analyzing the surface UHI effect from multiple angles. Scientific findings from this study can help make informed policies against urban warming via optimal planning of urban land cover.
18
Trick, Wilma H. "Identifying resonances of the Galactic bar in Gaia DR2: II. Clues from angle space". Monthly Notices of the Royal Astronomical Society 509, n.º 1 (7 de octubre de 2021): 844–65. http://dx.doi.org/10.1093/mnras/stab2866.
Texto completoResumen
ABSTRACT The Milky Way disc exhibits intricate orbit substructure of still debated dynamical origin. The angle variables (θϕ, θR) – which are conjugates to the actions (L$z$, JR), and describe a star’s location along its orbit – are a powerful diagnostic to identify l:m resonances via the orbit shape relation ΔθR/Δθϕ = −m/l. In the past, angle signatures have been hidden by survey selection effects (SEs). Using test particle simulations of a barred galaxy, we demonstrate that Gaia should allow us to identify the Galactic bar’s outer Lindblad resonance (OLR;l = +1, m = 2) in angle space. We investigate strategies to overcome SEs. In the angle data of the Gaia Data Release 2 (DR2) Radial Velocity Spectrometer (RVS) sample, we independently identify four candidates for the OLR and therefore for the pattern speed Ωbar. The strongest candidate, Ωbar ∼ 1.4Ω0, positions the OLR above the ‘Sirius’ moving group, agrees with measurements from the Galactic Centre, and might be supported by higher order resonances around the ‘Hercules/Horn’. But it misses the classic orbit orientation flip, as discussed in the companion study on actions. The candidate Ωbar ∼ 1.2Ω0 was also suggested by the action-based study, has the OLR at the ‘Hat’, is consistent with slow bar models, but still affected by SEs. Weaker candidates are Ωbar = 1.6Ω0 and 1.74Ω0. In addition, we show that the stellar angles do not support the ‘Hercules/Horn’ being created by the OLR of a fast bar. We conclude that – to resolve if ‘Sirius’ or ‘Hat’ is related to the bar’s OLR – more complex dynamical explanations and more extended data with well-behaved SEs are required.
19
CLARK, JEFFREY, PHIL CRANDALL y JESSICA SHABATURA. "Wearable Technology Effects on Training Outcomes of Restaurant Food Handlers". Journal of Food Protection 81, n.º 8 (2 de julio de 2018): 1220–26. http://dx.doi.org/10.4315/0362-028x.jfp-18-033.
Texto completoResumen
ABSTRACT Food safety training does not always result in behavior change, perhaps because of flaws inherent in traditional training designs. New technologies such as augmented reality headsets or head-mounted action cameras could transform the way food safety training is conducted in the food industry. Training conducted with wearable technology presents visual content in the first-person or actor's perspective, as opposed to the traditional third-person or observer perspective. This visual hands-on first-person perspective may provide an effective way of conveying information and encouraging behavior execution because it uses the mirror neuron system. There is little published literature about the impact of perspective on food safety training outcomes, such as motivation. The present study included a repeated-measures design to determine how first- and third-person camera angles affected hand washing training reactions among 108 currently employed restaurant food handlers. Participants were assessed on their posttraining compliance intentions, compliance self-efficacy, perceived utility of the training, overall satisfaction with the training, and video perspective preference. A significant proportion of food handlers (64%) preferred the first-person video perspective (z = 5.00, P < 0.001), and a significant correlation was found between compliance intentions and compliance self-efficacy (r(108) = 0.361, P < 0.001) for the first-person video. No significant differences in video preference were found for demographic variables, including age (χ2 (2, n = 104) = 1.69, P = 0.430), which suggests that the first-person training format appeals to a diverse workforce. These findings support the application of wearable technology to enhance hand washing training outcomes across a wide range of demographic groups. This research lays the framework for future studies to assess the impact of instructional design on compliance concerning hand washing and other food handling behaviors.
20
Mua, Kang Edwin y Kometa Sunday Shende. "The Response of Stream Competence to Topographic and Seasonal Variations in The Bamenda-Menchum Drainage Basin, North West Region, Cameroon". Journal of Geography and Geology 11, n.º 2 (30 de mayo de 2019): 21. http://dx.doi.org/10.5539/jgg.v11n2p21.
Texto completoResumen
The flow direction of streams remains an establishing mechanism in understanding drainage basin function and stream competence. The ability of streams to erode, transport and deposit loads in fluvial geomorphology exert a benchmark precursor for slope dynamics given the differential geological outcrop of the Bamenda-Menchum basin. Such competence in stream network generates slope instability as materials continuously move down slope from the volcanic escarpment face of Bamenda highlands to the sedimentary lowland area of Lower Bafut-Menchum basin. This paper investigate the influence of stream flow direction and stream competence on slope dynamics and how such dynamism affects the development prospects of the drainage basin. Slope range was obtained from AVL/EBI.JHO measurement. Stream length, density and flow direction were gotten from GIS Arc 21. Stream depth, channel width, flow rate and sedimentation levels were measured. Gully depth on slopes and landslide angles were measured using 30m tape and a graduated pole. Questionnaires were used to collect information on the vulnerability of households to slope dynamics orchestrated by stream competence. Findings revealed that stream competence varies from the two geological basements and that the escarpment face respond to high flow gravity and hydraulic action contributing to rapid erosion and transportation of loads. The results equally showed that the Bamenda escarpment face that is linked to the crystalline rocks produce differential erosion and landslide. 76.7% of slope instability is explained by geological structure and seasonality effect in the basin while 23.3% of slope dynamics is explained by other variables not specified in the study. The lower basin remains liable to deposition of materials on river channels and flood plain. The accumulation of sand, stones and alluvial deposits are extracted and exploited for the development prospects of the basin. The study recommends channel and slope management by integrating slope development control policy in drainage basin management and development.
21
Betkier, Igor, Szymon Mitkow y Magdalena Kijek. "Analysis of vehicle stability loss due to strong crosswind gusts using web services in the route planning process". Archives of Transport 52, n.º 4 (31 de diciembre de 2019): 47–56. http://dx.doi.org/10.5604/01.3001.0014.0207.
Texto completoResumen
Weather conditions play a significant role in road safety. One of its component is a wind influence, which may be affected the moving vehicle from different angles. The final result of such action can take typical kinds of behavior like overturn, slideslip and rotation. Accordingly, vehicles with high side profile are particularly vulnerable to such specific phenomena, what made the planning process more difficult and complex. The article analyses possibilities of a stability loss of a truck vehicle due to strong crosswind gusts. The authors synthesized the model proposed in the literature with available web technologies and the needs of a transport market. Moreover, a method which evaluate a danger of reaching the friction limit by all of the vehicle wheels (slideslip) was developed and is practicable to use. The proposed solution is based on the RESTful API of the weather and web mapping services which allows to collate a direction and a force of wind with a direction of movement and a side profile of the vehicle moving between two locations. What is more a weather forecast is allowed to adopt appropriate variables to compute the air density and evaluate friction coefficients. From the other hand the method uses actual parameters of a vehicle such as axle loads, distance between axles, center of mass location and kind of axle (driven or not). The assumption, which consist in sequencing routes for smaller parts, made it possible to achieve the high accuracy of results on tested areas. The proposed method is simple to implement in any programming language and it can be extended by new functionalities. The analyzed issue can also be a starting point for intelligent systems that can be used in autonomous vehicles.
22
Harara, Mitsuhiko, Hidekazu Suzuki, Tsuyoshi Takeo y Keiji Isoda. "Vehicle Dynamics Control with Variable Alignment Suspension". Journal of Robotics and Mechatronics 7, n.º 4 (20 de agosto de 1995): 301–6. http://dx.doi.org/10.20965/jrm.1995.p0301.
Texto completoResumen
This study discusses the effect of variable alignment control suspension on vehicle dynamics by altering the suspension arm's length. In this system, two of the four arms of the front multi-link suspension can extend or contract depending on each driving condition to control the camber and caster angles independently. a camber angle and a caster angle are altered by the action of upper and lower control actuators. The camber angle control contributes to the increase in a turning limit with the improvement of tire footprints condition, and the caster angle and caster trail control aid the wheel's ability to right itself with a suitable steering feeling for the driver. Vehicle tests are conducted using a prototype vehicle equipped with a variable alignment control system to clarify the above effects, and remarkable improvements in a vehicle dynamics are verified.
23
Lebedev, Alexander. "The Synthesis of Variable Structure System for the Control of Quadrotor Spatial Motion". Applied Mechanics and Materials 865 (junio de 2017): 486–91. http://dx.doi.org/10.4028/www.scientific.net/amm.865.486.
Texto completoResumen
The method of the synthesis of multi-channel decentralized variable structure system for the control of quadrotor spatial motion is developed in this paper. The control law based on the formation of the sliding mode in the separate subsystems of each coordinates control is formed. Each subsystem includes two loops for Cartesian coordinates and relevant Euler angles control. The conditions of the existence of stable sliding mode are obtained. These conditions take into account essential dynamic reciprocal effect between all control channels. The application of proposed control law provides high control quality and maximal fast-action at any variations of the quadrotor parameters within given ranges. This control law does not require the identification of changing object parameters. Efficiency of synthesized control system is confirmed by numerical simulation results. The control system can be realized in the real time by simple technical means.
24
Van Hees, Valérie, Ronny Bruffaerts y Maarten Vansteenkiste. "Student mental health: towards sustainable community of caring approach based on the public mental health perspective." International Journal of Integrated Care 23, S1 (28 de diciembre de 2023): 327. http://dx.doi.org/10.5334/ijic.icic23457.
Texto completoResumen
Attending university can be stressful and involve significant lifestyle changes: adjusting to the demands of a new learning environment, interacting with a diverse range of new people
and environments, and (coping with) being away from trusted support networks. Although sixty per cent of students navigate higher education without emotional problems, forty per cent experience mental health issues, and approximately one in five struggles with mental disorders.
Against this background, the Flemish Community (Belgium) has rolled out a sustainable student mental health strategy which takes a public mental health perspective as its starting point. Such an approach shifts the focus from high-risk students and mental disorders to the emotional health of the entire student population, and, accordingly, interventions that can improve the resilience of all students.
The new policy has several strengths. Monitoring is undertaken through the WHO World Mental Health International College Student initiative. A wide range of low-threshold e-health interventions free of charge to students is available on the MoodSpace internet platform. Going beyond these, the Flemish policy helps universities to adopt a more proactive, preventive approach. Students are actively involved in the development and evaluation of interventions and policy implementation.
Structure:
- Introduction: 15’ (Ronny Bruffaerts)
The introduction focuses on the key elements of the new mental health strategy policy
- Key element 1: Mental Health Monitor: 20’ (Ronny Bruffaerts - Maarten Vansteenkiste)
This contribution provides an overview of the Monitor which includes a set of process variables that are sensitive to monitoring student mental health, study motivation and detecting policy effects. The 2022 results and specific action points translated to the macro, meso and micro levels will be presented.
Q&A 10’
- Key element 2: MoodSpace: 20’ (Valérie Van Hees)
This contribution provides an overview of MoodSpace. This contribution will bring an overview of the results of students’ engagement with the e-interventions.
- Q&A 10’
- Key element 3: Community of Caring: 15’: (Valérie Van Hees, Ronny Bruffaerts)
This contribution provides a presentation of the gatekeeping training ‘We-care’. The training, designed for students and staff respectively, has been developed at Flemish level with the aim to detect emotional problems early and refer students to the help they need. Preliminary results are presented.
- Q&;A 10’
- Closing: Take home messages 15’ (Valérie Van Hees)
This contribution summarises the next steps and initiates a group discussion on the take home messages.
How to engage with the audience:
- Rooms will be organised in roundtables or a fish bowl setup
- Interactive tools will be used during presentations (eg., dynamic dashboard mental health monitor, video testimonials, demonstrations MoodSpace and We-care).
- Polling via mentimeter:
- Each speaker shares different angles of the new policy. After each contribution, a moderator will ask the audience questions through mentimeter about their
thoughts about each key element.
How to summarise the take home messages:
- The session will end with a last question asked by the moderator to the audience through the mentimeter app, on the take away that participants will bring home.
25
Moura, Michel dos Santos, Aldir Carpes Marques Filho, Carlos Roberto Souza Carmo, Liliane Catarina Pereira y Kléber Pereira Lanças. "INFLUÊNCIA DO ÂNGULO DE CORTE E DA VELOCIDADE DE COLHEITA NOS DANOS CAUSADOS PELAS FACAS DA COLHEDORA NA CULTURA DA CANA-DE-AÇÚCAR". ENERGIA NA AGRICULTURA 37, n.º 1 (30 de marzo de 2022): 52–63. http://dx.doi.org/10.17224/energagric.2022v37n1p52-63.
Texto completoResumen
INFLUÊNCIA DO ÂNGULO DE CORTE E DA VELOCIDADE DE COLHEITA NOS DANOS CAUSADOS PELAS FACAS DA COLHEDORA NA CULTURA DA CANA-DE-AÇÚCAR Michel dos Santos Moura1, Aldir Carpes Marques Filho2, Carlos Roberto Souza Carmo3, Liliane Catarina Pereira4, Kléber Pereira Lanças5 1 Departamento de Engenharia Rural, Faculdade de Ciências Agronômicas – UNESP, Avenida Universitária 3780, Altos do Paraiso, CEP 18610-034, Botucatu, São Paulo, Brasil, e-mail. michelsmoura@gmail.com 2 Departamento de Engenharia Agrícola, Universidade Federal de Lavras, Trevo Prof. Edmir Sá Santos s/n, Aquenta Sol, CEP 37200-900, Lavras, Minas Gerais, Brasil, e-mail. aldir@ufla.br 3 Faculdade de Ciências Contábeis da Univ. Federal de Uberlândia (FACIC-UFU), Av. João Naves de Ávila, 2121, Santa Mônica, CEP 38400-902, Uberlândia, Minas Gerais, Brasil, e-mail. carlosjj2004@hotmail.com 4 Departamento de Ciência Florestal, Faculdade de Ciências Agronômicas – UNESP, Avenida Universitária 3780, Altos do Paraiso, CEP 18610-034, Botucatu, São Paulo, Brasil, e-mail. liliane.pereira@unesp.br 5 Departamento de Engenharia Rural, , Faculdade de Ciências Agronômicas – UNESP, Avenida Universitária 3780, Altos do Paraiso, CEP 18610-034, Botucatu, São Paulo, Brasil, e-mail. Kp.lancas@unesp.br *Artigo extraído da dissertação do primeiro autor. RESUMO: Este estudo teve como objetivo avaliar os danos causados durante o corte basal da cana-de-açúcar, alterando as características operacionais, tais como a velocidade de deslocamento durante a operação e o ângulo de ataque do corte de base em laboratório, utilizando o DECCA (Dispositivo de Ensaio de Corte Basal da Cana-de-Açúcar), desenvolvido pela equipe do NEMPA (Núcleo de Ensaio de Máquinas e Pneus Agroflorestais) para utilização em laboratório, que reproduz a ação do cortador de base sobre os colmos da cultura. A amostra de pesquisa foi formada a partir de um total de 432 observações referentes à 9 combinações de três velocidades de deslocamento do dispositivo (3, 5 e 7 km h-1) e três ângulos de ataque do corte de base (12°, 15° e 18°), sendo que, para cada combinação foram coletadas e analisadas 48 unidades amostrais (3x3x48 = 432 observações) devidamente classificadas qualitativamente conforme metodologia proposta por Toledo, Silva e Furlani (2013). Os resultados obtidos nesta investigação, detectaram a influência dessas combinações sobre a ocorrência de danos extremos às soqueiras de cana-de-açúcar. Sendo que, a análise isolada de cada uma das variáveis sinalizou que, a velocidade de deslocamento do sistema de corte não é estatisticamente significativa para a expressão dos danos e, por outro lado, observou-se que a angulação utilizada para corte exerceu influência significativa sobre os danos extremos. Palavras-chave: dispositivo eletromecânico, perda invisível, corte basal. INFLUENCE OF CUTTING ANGLE AND HARVEST SPEED ON DAMAGE CAUSED BY HARVESTER KNIVES IN SUGARCANE CROP ABSTRACT: The objective of this study was to evaluate the damage caused during the basal cut of sugarcane, changing the operative characteristics, such as the displacement speed during the operation and the attack angle of the base cut in the laboratory, using DECCA (Sugarcane Basal Cut Test). Device, developed by the NEMPA equipment (Agroforestry Machines and Tires Testing Nucleus) for use in the laboratory, which maps the action of the base cutter on the tops of the crop. The research sample was formed from a total of 432 observations that refer to 9 combinations of three displacement speeds of the device (3, 5 and 7 km h-1) and three base cutting angles of attack (12°, 15 ° and 18 °), and for each combination, 48 units of study were collected and analyzed (3x3x48 = 432 observations) duly classified qualitatively based on the methodology proposed by Toledo, Silva e Furlani (2013). The results obtained in this investigation detected the influence of these combinations on the occurrence of extreme damage to sugarcane ratoons. The isolated analysis of each of the variables indicated that the displacement speed of the cutting system is not statistically significant for the expression of damage and, on the other hand, it was observed that the angle used for cutting exerted a significant influence on extreme damage. Keywords: electromechanically device, invisible loss, basal cut.
26
Pinheiro, Guilherme de Sousa, Xing Jin, Varley Teoldo Da Costa y Martin Lames. "Body Pose Estimation Integrated With Notational Analysis: A New Approach to Analyze Penalty Kicks Strategy in Elite Football". Frontiers in Sports and Active Living 4 (10 de marzo de 2022). http://dx.doi.org/10.3389/fspor.2022.818556.
Texto completoResumen
Body orientation of football players has proven to be an informative resource related to successful penalty kicks. OpenPose is one of the most popular open-source pose estimation technologies. This study aims: (i) to verify whether OpenPose can detect relevant body orientation angles from video data of penalty kicks in elite football and (ii) to investigate the relationship between these body angles and observable behaviors analyzed via an observational system for penalty kick analysis in football (OSPAF) with the penalty taker and goalkeeper strategy. A total of 34 penalty videos, with standardized viewing angle, from the main European leagues (2017–2020) were analyzed. Relevant body orientation variables were selected for penalty kicks analysis and were extracted from video data through OpenPose technique. The OSPAF, previously validated by experts, was used. The mean confidence score of OpenPose measures was 0.80 ± 0.14. OpenPose Retest reliability values was 0.976 ± 0.03. Logistic regressions were performed to investigate the relationship between OpenPose investigated variables (penalty taker: shoulder, hips, and nonkicking foot orientation; goalkeeper: right and left foot, anticipation), observable behaviors (OSPAF variables), and the strategy (penalty taker: goalkeeper dependent or independent; goalkeeper: shooter dependent or independent) in penalty kicks. The selected body orientation angle (goalkeeper anticipation) measured through OpenPose correlated significantly with the goalkeeper strategy. The prediction model of the goalkeeper's strategy had its accuracy increased to 97% when the variable goalkeeper anticipation was included [χ(35)2 = 49.648, p < 0.001]. Lower degrees of goalkeeper anticipation, the goalkeeper tactical action (awaiting), and run up speed (slow) were associated with a kicker-dependent strategy. Regarding the penalty taker, the selected body angles measured through OpenPose did not associate significantly with the shooter strategy. Body orientation analysis by using OpenPose has shown sufficient reliability and provides practical applications for analyzing the strategies adopted by goalkeepers in penalty kicks in elite football.
27
Lili, Lamprini, Katharina S Sunnerhagen, Tiina Rekand y Margit Alt Murphy. "Associations between upper extremity functioning and kinematics in people with spinal cord injury". Journal of NeuroEngineering and Rehabilitation 18, n.º 1 (26 de septiembre de 2021). http://dx.doi.org/10.1186/s12984-021-00938-9.
Texto completoResumen
Abstract Introduction More knowledge of the relationships between kinematic measures and clinical assessments is required to guide clinical decision making and future research. Objectives To determine which kinematic variables obtained during a drinking task were associated with clinical assessments of upper extremity functioning in people with spinal cord injury (SCI). Methods In total, 25 individuals with chronic cervical (n = 17) or thoracic (n = 8) complete (n = 14) or motor incomplete (n = 11) SCI (mean age 58.4, SD 13.8) were included. Kinematic data, including movement time, smoothness and joint angles was captured with a 5-camera optoelectronic system during a unimanual drinking task. Action Research Arm Test (ARAT), Sollerman Hand Function Test (SHFT) and basic hand classification of the Upper Extremity Data Set (ISCI-Hand) were used as clinical assessments. Multiple regression analysis was used to identify kinematic variables associated with clinical assessments after controlling for potential confounding factors, such as, age, severity of SCI, sensory function, and hand surgery. Results Movement time, smoothness and movement pattern kinematics including trunk displacement, elbow and wrist joint angles were correlated (p < 0.05) with all three clinical scales while the velocity-related kinematics and inter-joint coordination showed low correlations. Multiple regression analysis revealed that wrist angle combined with movement time or smoothness explained 82% and 77% of the total variance in ARAT and SHFT, respectively. Wrist angle alone explained 59% of the variance in ISCI-Hand. The proprioception of the hand increased the explanatory power in the models of ARAT and SHFT. Associations between kinematics and clinical assessments in the subgroup with cervical SCI were equivalent to the whole group analyses. The number of participants in the subgroup with thoracic SCI was small and only allowed limited analysis. Conclusions Wrist angle, movement time, movement smoothness are the most important kinematic variables associated with upper extremity clinical assessments in people with SCI. The results are most valid for individuals with cervical SCI. All three assessments are appropriate for SCI. Further research with larger representative sample of thoracic SCI needed.
28
Jia, Wantao, Weiqiu Zhu, Yong Xu y Weiyan Liu. "Stochastic Averaging of Quasi-Integrable and Resonant Hamiltonian Systems Under Combined Gaussian and Poisson White Noise Excitations". Journal of Applied Mechanics 81, n.º 4 (23 de septiembre de 2013). http://dx.doi.org/10.1115/1.4025141.
Texto completoResumen
A stochastic averaging method for quasi-integrable and resonant Hamiltonian systems subject to combined Gaussian and Poisson white noise excitations is proposed. The case of resonance with α resonant relations is considered. An (n + α)-dimensional averaged Generalized Fokker–Plank–Kolmogorov (GFPK) equation for the transition probability density of n action variables and α combinations of phase angles is derived from the stochastic integrodifferential equations (SIDEs) of original quasi-integrable and resonant Hamiltonian systems by using the jump-diffusion chain rule. The reduced GFPK equation is solved by using finite difference method and the successive over relaxation method to obtain the stationary probability density of the system. An example of two nonlinearly damped oscillators under combined Gaussian and Poisson white noise excitations is given to illustrate the proposed method. The good agreement between the analytical results and those from digital simulation shows the validity of the proposed method.
29
PAULA, GUSTAVO BRUNO DE, BRÉSCIA FRANÇA NONATO y CLÁUDIO MARQUES MARTINS NOGUEIRA. "AFFIRMATIVE ACTIONS AND HORIZONTAL STRATIFICATION: COMPARISON BETWEEN BONUS AND QUOTAS ACT AT THE UFMG". Educação em Revista 39 (2023). http://dx.doi.org/10.1590/0102-469837918t.
Texto completoResumen
ABSTRACT: In this article, we analyze the effects of two affirmative action policies adopted by the Federal University of Minas Gerais (UFMG): the bonus policy and the Quota Act. We compare the social inclusion produced by them by two angles: the access itself to UFMG and the distribution of the target groups among the institution’s programs, considering its internal horizontal hierarchy. We verify the changes in the student`s profile by focusing on three variables: race, school origin and family income. Based on descriptive statistics, it is concluded that the two policies had relevant effects on social inclusion. However, this occurred in different ways. The bonus policy was able to increase the access of students from public schools, blacks and with low-income, but mainly in the less selective programs. The Quota Act contributed more effectively to increasing the access of these students to the most selective programs of UFMG, reducing the horizontal inequalities. We observe, however, that remains expressive inequalities in the access to the universities programs still need to be addressed.
30
Danesi, Veronica, Ugo Locatelli y Marco Sansottera. "Existence proof of librational invariant tori in an averaged model of HD60532 planetary system". Celestial Mechanics and Dynamical Astronomy 135, n.º 3 (20 de abril de 2023). http://dx.doi.org/10.1007/s10569-023-10132-9.
Texto completoResumen
AbstractWe investigate the long-term dynamics of HD60532, an extrasolar system hosting two giant planets orbiting in a 3:1 mean motion resonance. We consider an average approximation at order one in the masses which results (after the reduction in the constants of motion) in a resonant Hamiltonian with two libration angles. In this framework, the usual algorithms constructing the Kolmogorov normal form approach do not easily apply and we need to perform some untrivial preliminary operations, in order to adapt the method to this kind of problems. First, we perform an average over the fast angle of libration which provides an integrable approximation of the Hamiltonian. Then, we introduce action-angle variables that are adapted to such an integrable approximation. This sequence of preliminary operations brings the Hamiltonian in a suitable form to successfully start the Kolmogorov normalization scheme. The convergence of the KAM algorithm is proved by applying a technique based on a computer-assisted proof. This allows us to reconstruct the quasi-periodic motion of the system, with initial conditions that are compatible with the observations.
31
Rubin, T., J. M. Rax y N. J. Fisch. "Guiding centre motion for particles in a ponderomotive magnetostatic end plug". Journal of Plasma Physics 89, n.º 6 (diciembre de 2023). http://dx.doi.org/10.1017/s0022377823001307.
Texto completoResumen
The Hamiltonian dynamics of a single particle in a rotating plasma column, interacting with an magnetic multipole is perturbatively solved for up to second order, using the method of Lie transformations. First, the exact Hamiltonian is expressed in terms of canonical action-angle variables, and then an approximate integrable Hamiltonian is introduced, using another set of actions and angles, which describe the centre of oscillation for the particle. The perturbation introduces an effective ponderomotive potential, which to leading order is positive. At the second order, the pseudopotential consists of a sum of terms of the Miller form, and can have either sign. Additionally, at second order, the ponderomotive interaction introduces a modification to the particle effective mass, when considering the motion along the column axis. It is found that particles can be axially confined by the ponderomotive potentials, but acquire radial excursions which scale as the confining potential. The radial excursions of the particle along its trajectory are investigated, and a condition for the minimal rotation frequency for which the particle remains radially confined is derived. Last, we comment on the changes to the aforementioned solution to the pseudopotentials and particle trajectory in the case of resonant motion, that is, a motion which has the same periodicity as the perturbation.
32
Riveros-Perez, Efrain, Lori Bolgla, Nianlan Yang, Bibiana Avella-Molano, Camila Albo y Alexander Rocuts. "Effect of table inclination angle on videolaryngoscopy and direct laryngoscopy: Operator’s muscle activation and laryngeal exposure analysis". BMC Anesthesiology 22, n.º 1 (3 de octubre de 2022). http://dx.doi.org/10.1186/s12871-022-01849-5.
Texto completoResumen
Abstract Background Optimal vocal cord visualization depends on the patient’s anatomical factors, characteristics of the laryngoscope, and the operator’s muscle action. This study evaluated the effect of table inclination and three different laryngoscopic methods on procedural variables. The primary aim of this study is to compare differences in laryngoscopic view among clinicians based on the instrument used and table orientation. The secondary aim is to determine differences in upper extremity muscle activity based on laryngoscope use and table inclination. Methods Fifty-five anesthesia providers with different experience levels performed intubations on a manikin using three angles of table inclination and three laryngoscopy methods. Time to intubation, use of optimization maneuvers, glottic view, operator’s comfort level, and upper extremity muscle activation measured by surface electromyography were evaluated. Results Table inclination of 15° and 30° significantly reduced intubation time and the need for optimization maneuvers. Fifteen degrees inclination gave the highest comfort level. Anterior deltoid muscle intensity was decreased when table inclination at 15° and 30° was compared to a flat position. Conclusion Table inclination of 15° reduces intubation time and the need to use optimization maneuvers and is associated with higher operator’s comfort levels than 0° and 30° inclination in a simulated scenario using a manikin. Different upper extremity muscle groups are activated during laryngoscopy, with the anterior deltoid muscle exhibiting significantly higher activation levels with direct laryngoscopy at zero-degree table inclination.
33
"The wing beat of Drosophila Melanogaster . III. Control". Philosophical Transactions of the Royal Society of London. B, Biological Sciences 327, n.º 1238 (28 de febrero de 1990): 45–64. http://dx.doi.org/10.1098/rstb.1990.0042.
Texto completoResumen
Two major problems have to be solved by a flying animal or machine, (i) On the time average, flight force has to be produced which is sufficient to keep the body airborne and to propel it through the air. (ii) To stabilize a given position or trajectory, the vector of the generated flight force has to be controlled in its magnitude, orientation and position relative to the body. In the present study, the response of wing-beat kinematics to wind and visual stimuli was investigated in tethered flying Drosophila melanogaster . When the fly is subjected to an air stream in a wind tunnel, or to striped patterns moving in its frontal field of view, the overall shape of the wing path is altered, including variations of the wing-beat amplitude and the angles of attack. The aerodynamic forces were calculated from the kinematic data according to the quasisteady aerodynamic theory, to investigate whether this approach is sufficient to describe the control mechanisms of the fly. The stimulus-induced changes of kinematic and aerodynamic variables were compared with control reactions expected in free flight or measured during tethered flight under similar stimulus conditions. In general, the calculated flight forces are too small to account for the measured lift, thrust and torque responses to the particular stimuli, or would even increase the input stimulus instead of being compensatory. This result supports the notion that unsteady aerodynamic mechanisms are likely to play the major role in flapping flight. Following this line of thought, some kinematic responses can be qualitatively understood in terms of unsteady aerofoil action.
34
Xu, X. D., G. G. Chen, S. Li y T. G. Lv. "Design and dry wind tunnel test of progressive flexible variable bending wing". Aeronautical Journal, 11 de julio de 2023, 1–26. http://dx.doi.org/10.1017/aer.2023.59.
Texto completoResumen
Abstract The deformable wing structure can change its aerodynamic shape according to the change of flight mission and flight environment, so as to obtain better lift-drag, stability and control characteristics, which is considered as one of the future research directions of aviation technology. Considering the current technology maturity and reliability, a gradient corrugated fin is designed to realise the bending deformation of the wing. The structure of the skin is optimised to keep the skin smooth during deformation. In addition, a progressive push and pull rod is proposed to drive the wing deformation, and the fluid-structure interaction simulation is carried out for the wing deformation. At the same time, the changes of wing aerodynamic characteristics under different angles of leading and trailing edges and different push rod action schemes are analysed. Finally, a dry wind tunnel simulation test of the designed progressive flexible variable bending wing is carried out. The results of fluid-structure interaction simulation and dry wind tunnel test show that the progressive flexible variable bending wing proposed in this paper has a simple and reliable structure and remarkable deformation effect. It has advantages in increasing lift and reducing drag, ensuring high lift-drag ratio and providing wing trim moment. The deformable wing dry wind tunnel test platform designed by this method is structurally reliable, easy to operate, and can accurately reflect the influence of wing deformation on its aerodynamic force, which provides a verification means for the development of the design method and the design of practical aircraft in the future.
35
Aslanov, Vladimir S. "Attitude Motion of Cylinder in Variable Electrostatic Field Near L1 Libration Point". Journal of Spacecraft and Rockets, 27 de febrero de 2023, 1–12. http://dx.doi.org/10.2514/1.a35635.
Texto completoResumen
This paper explores the spatial attitude motion of an electrostatic cylindrical container (E container) in a variable attracting electrostatic field. This field generated by the E container and the orbiting spacecraft (orbiter) located at the L1 libration point of the Mars–Phobos system is used to capture the E container by the orbiter in the Phobos Sample Return mission. Based on the Lagrange formalism and using the Euler angles, the equations of attitude motion of a cylindrical E container are constructed in the framework of the circular restricted three-body problem with the addition of the electrostatic force and torque acting on the E container. For modeling electrostatic force and torque acting on a cylindrical E container, the multisphere method is used, which was developed by Stevenson and Schaub (Multi-Sphere Method for Modeling Electrostatic Forces and Torques,” Advances in Space Research, Vol. 51, No. 1, 2013, pp. 10–20). The influence of gravitational, centrifugal, and electrostatic moments on angular motion for different initial conditions has been studied analytically by analyzing the equations of both attitude motion and numerical simulations. It is shown that the action of the aforementioned torques as the E container approaches the orbiter causes the excitation of high-frequency nutation oscillations with large amplitudes. On the other hand, there are no natural and artificial factors of physical nature that could lead to damping of oscillations of large amplitude, and this fact corresponds to the obtained equations of attitude motion. Also, the electrostatic torque is the greatest contributor to the oscillations with large amplitude. Hence, it is clear that the E container must have a spherical current-conducting shell: in which case, the electrostatic torque turns to zero.