Takemoto, Norio
2010-01-01
We analyze the attosecond electron dynamics in hydrogen molecular ion driven by an external intense laser field using ab-initio numerical simulations of the corresponding time-dependent Schr{\\"{o}}dinger equation and Bohmian trajectories. To this end, we employ a one-dimensional model of the molecular ion in which the motion of the protons is frozen. The results of the Bohmian trajectory calculations do agree well with those of the ab-initio simulations and clearly visualize the electron transfer between the two protons in the field. In particular, the Bohmian trajectory calculations confirm the recently predicted attosecond transient localization of the electron at one of the protons and the related multiple bunches of the ionization current within a half cycle of the laser field. Further analysis based on the quantum trajectories shows that the electron dynamics in the molecular ion can be understood via the phase difference accumulated between the Coulomb wells at the two protons. Modeling of the dynamics ...
Bohmian trajectories of Airy packets
Energy Technology Data Exchange (ETDEWEB)
Nassar, Antonio B., E-mail: anassar@hw.com [Science Department, Harvard-Westlake School, 3700 Coldwater Canyon, Studio City, 91604 (United States); Department of Sciences, University of California, Los Angeles, Extension Program, 10995 Le Conte Avenue, Los Angeles, CA 90024 (United States); Miret-Artés, Salvador [Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 123, 28006 Madrid (Spain)
2014-09-15
The discovery of Berry and Balazs in 1979 that the free-particle Schrödinger equation allows a non-dispersive and accelerating Airy-packet solution has taken the folklore of quantum mechanics by surprise. Over the years, this intriguing class of wave packets has sparked enormous theoretical and experimental activities in related areas of optics and atom physics. Within the Bohmian mechanics framework, we present new features of Airy wave packet solutions to Schrödinger equation with time-dependent quadratic potentials. In particular, we provide some insights to the problem by calculating the corresponding Bohmian trajectories. It is shown that by using general space–time transformations, these trajectories can display a unique variety of cases depending upon the initial position of the individual particle in the Airy wave packet. Further, we report here a myriad of nontrivial Bohmian trajectories associated to the Airy wave packet. These new features are worth introducing to the subject’s theoretical folklore in light of the fact that the evolution of a quantum mechanical Airy wave packet governed by the Schrödinger equation is analogous to the propagation of a finite energy Airy beam satisfying the paraxial equation. Numerous experimental configurations of optics and atom physics have shown that the dynamics of Airy beams depends significantly on initial parameters and configurations of the experimental set-up.
Bohmian trajectory from the "classical" Schrödinger equation.
Sengupta, Santanu; Khatua, Munmun; Chattaraj, Pratim Kumar
2014-12-01
The quantum-classical correspondence is studied for a periodically driven quartic oscillator exhibiting integrable and chaotic dynamics, by studying the Bohmian trajectory of the corresponding "classical" Schrödinger equation. Phase plots and the Kolmogorov-Sinai entropy are computed and compared with the classical trajectory as well as the Bohmian trajectory obtained from the time dependent Schrödinger equation. Bohmian mechanics at the classical limit appears to mimick the behavior of a dissipative dynamical system.
Bohmian Trajectories as the Foundation of Quantum Mechanics
Goldstein, Sheldon; Zanghi, Nino
2009-01-01
Bohmian trajectories have been used for various purposes, including the numerical simulation of the time-dependent Schroedinger equation and the visualization of time-dependent wave functions. We review the purpose they were invented for: to serve as the foundation of quantum mechanics, i.e., to explain quantum mechanics in terms of a theory that is free of paradoxes and allows an understanding that is as clear as that of classical mechanics. Indeed, they succeed in serving that purpose in the context of a theory known as Bohmian mechanics, to which this article is an introduction.
Bohmian Trajectories as the Foundation of Quantum Mechanics
Goldstein, Sheldon; Tumulka, Roderich; Zanghi, Nino
2009-01-01
Bohmian trajectories have been used for various purposes, including the numerical simulation of the time-dependent Schroedinger equation and the visualization of time-dependent wave functions. We review the purpose they were invented for: to serve as the foundation of quantum mechanics, i.e., to explain quantum mechanics in terms of a theory that is free of paradoxes and allows an understanding that is as clear as that of classical mechanics. Indeed, they succeed in serving that purpose in th...
Razavi, M.; Mollai, M.; Jami, S.; Ahanj, A.
2016-09-01
The Dirac equation has been applied to fermions scattering from the downward potential step. The results show that some particles do not fall off the edge of the step and reflect. Then, based on the de Broglie-Bohm interpretation of quantum mechanics (Bohmian mechanics) and Bohmian trajectories we have resolved the problem. Lastly, a phenomenological study of the Bohmian trajectory of the Klein paradox has been discussed.
Bohmian trajectories for an evaporating blackhole
Energy Technology Data Exchange (ETDEWEB)
Acacio de Barros, J. [Departamento de Fisica, Instituto de Ciencias Exatas, Universidade Federal de Juiz de Fora, CEP 36036-330, Juiz de Fora, Minas Gerais (Brazil)]. E-mail: acacio@fisica.ufjf.br; Oliveira-Neto, G. [Departamento de Fisica, Instituto de Ciencias Exatas, Universidade Federal de Juiz de Fora, CEP 36036-330, Juiz de Fora, Minas Gerais (Brazil)]. E-mail: gilneto@fisica.ufjf.br; Vale, T.B. [Departamento de Fisica, Instituto de Ciencias Exatas, Universidade Federal de Juiz de Fora, CEP 36036-330, Juiz de Fora, Minas Gerais (Brazil)]. E-mail: tiberio@fisica.ufjf.br
2005-03-14
In this work we apply Bohm's interpretation to the quantized spherically-symmetric blackhole coupled to a massless scalar field. We show that the quantum trajectories for linear combinations of eigenstates of the Wheeler-DeWitt equation form a large set of different curves that cannot be predicted by the standard interpretation of quantum mechanics. Some of them are consistent with the expected value of the time derivative of the mass, whereas other trajectories are not, because they represent blackholes that switch from absorbing to emitting regimes.
N-slit interference: Path integrals, Bohmian trajectories
Sbitnev, Valeriy I
2010-01-01
Path integrals give a possibility to compute in details routes of particles from particle sources through slit gratings and further to detectors. The path integral for a particle passing through the Gaussian slit results in the Gaussian wavepacket. The wavepackets prepared on N slits and superposed together give rise to interference pattern in the near-field zone. It transforms to diffraction in the far-field zone represented by divergent principal rays, at that all rays are partitioned from each other by (N-2) subsidiary rays. The Bohmian trajectories in the near-field zone of N-slit gratings show wavy behavior. And they become straight in the far-field zone. The trajectories show zigzag behavior on the interference Talbot carpet (ratio of particle wavelength to a distance between slits are much smaller than 1 and N >> 1). Namely, the trajectories prefer to pass through caustics and avoid lacunae, i.e., places with small probability densities. Monochromatic thermal neutrons (wavelength=0.5 nm) simulate radia...
Nassar, Antonio B; Miret-Artés, Salvador
2013-10-11
This Letter proposes an answer to a challenge posed by Bell on the lack of clarity in regards to the dividing line between the quantum and classical regimes in a measurement problem. To this end, a generalized logarithmic nonlinear Schrödinger equation is proposed to describe the time evolution of a quantum dissipative system under continuous measurement. Within the Bohmian mechanics framework, a solution to this equation reveals a novel result: it displays a time constant that should represent the dividing line between the quantum and classical trajectories. It is shown that continuous measurements and damping not only disturb the particle but compel the system to converge in time to a Newtonian regime. While the width of the wave packet may reach a stationary regime, its quantum trajectories converge exponentially in time to classical trajectories. In particular, it is shown that damping tends to suppress further quantum effects on a time scale shorter than the relaxation time of the system. If the initial wave packet width is taken to be equal to 2.8×10(-15) m (the approximate size of an electron), the Bohmian time constant is found to have an upper limit, i.e., τ(Bmax)=10(-26) s.
Chou, Chia-Chun
2014-03-14
The complex quantum Hamilton-Jacobi equation-Bohmian trajectories (CQHJE-BT) method is introduced as a synthetic trajectory method for integrating the complex quantum Hamilton-Jacobi equation for the complex action function by propagating an ensemble of real-valued correlated Bohmian trajectories. Substituting the wave function expressed in exponential form in terms of the complex action into the time-dependent Schrödinger equation yields the complex quantum Hamilton-Jacobi equation. We transform this equation into the arbitrary Lagrangian-Eulerian version with the grid velocity matching the flow velocity of the probability fluid. The resulting equation describing the rate of change in the complex action transported along Bohmian trajectories is simultaneously integrated with the guidance equation for Bohmian trajectories, and the time-dependent wave function is readily synthesized. The spatial derivatives of the complex action required for the integration scheme are obtained by solving one moving least squares matrix equation. In addition, the method is applied to the photodissociation of NOCl. The photodissociation dynamics of NOCl can be accurately described by propagating a small ensemble of trajectories. This study demonstrates that the CQHJE-BT method combines the considerable advantages of both the real and the complex quantum trajectory methods previously developed for wave packet dynamics.
Bohmian mechanics in the exact factorization of electron-nuclear wavefunction
Suzuki, Yasumitsu
2016-01-01
The exact factorization of an electron-nuclear wavefunction [A. Abedi, N. T. Maitra, and E. K. U. Gross, Phys. Rev. Lett. 105, 123002 (2010)] allows us to define the rigorous nuclear time-dependent Schr\\"{o}dinger equation (TDSE) with a time-dependent potential-energy surface (TDPES) that fully accounts for the coupling to the electronic motion and drives the nuclear wavepacket dynamics. Here, we study whether the propagation of multiple classical trajectories can reproduce the quantum nuclear motion in strong-field processes when their motions are governed by the quantum Hamilton-Jacobi equation derived by applying Bohmian mechanics to this exact nuclear TDSE. We demonstrate that multiple classical trajectories propagated by the force from the gradient of the exact TDPES plus the Bohmian quantum potential can reproduce the strong-field dissociation dynamics of a one-dimensional model of the H$_2^+$ molecule. Our results show that the force from the Bohmian quantum potential plays a non-negligible role in yie...
Bohmian mechanics in the exact factorization of electron-nuclear wave functions
Suzuki, Yasumitsu; Watanabe, Kazuyuki
2016-09-01
The exact factorization of an electron-nuclear wave function [A. Abedi, N. T. Maitra, and E. K. U. Gross, Phys. Rev. Lett. 105, 123002 (2010), 10.1103/PhysRevLett.105.123002] allows us to define the rigorous nuclear time-dependent Schrödinger equation (TDSE) with a time-dependent potential-energy surface (TDPES) that fully accounts for the coupling to the electronic motion and drives the nuclear wave-packet dynamics. Here, we study whether the propagation of multiple classical trajectories can reproduce the quantum nuclear motion in strong-field processes when their motions are governed by the quantum Hamilton-Jacobi equation derived by applying Bohmian mechanics to this exact nuclear TDSE. We demonstrate that multiple classical trajectories propagated by the force from the gradient of the exact TDPES plus the Bohmian quantum potential can reproduce the strong-field dissociation dynamics of a one-dimensional model of the H2 + molecule. Our results show that the force from the Bohmian quantum potential plays a non-negligible role in yielding quantum nuclear dynamics in the strong-field process studied here, where ionization and/or splitting of nuclear probability density occurs.
Zeno Paradox for Bohmian Trajectories: The Unfolding of the Metatron
de Gosson, Maurice
2010-01-01
We study an analogue of the quantum Zeno paradox for the Bohm trajectory of a sharply located particle (or a system of particles). We show that a continuously observed Bohm trajectory is the classical trajectory predicted by Hamiltonian mechanics.
Bohmian mechanics with complex action: a new trajectory-based formulation of quantum mechanics.
Goldfarb, Yair; Degani, Ilan; Tannor, David J
2006-12-21
In recent years there has been a resurgence of interest in Bohmian mechanics as a numerical tool because of its local dynamics, which suggest the possibility of significant computational advantages for the simulation of large quantum systems. However, closer inspection of the Bohmian formulation reveals that the nonlocality of quantum mechanics has not disappeared-it has simply been swept under the rug into the quantum force. In this paper we present a new formulation of Bohmian mechanics in which the quantum action, S, is taken to be complex. This leads to a single equation for complex S, and ultimately complex x and p but there is a reward for this complexification-a significantly higher degree of localization. The quantum force in the new approach vanishes for Gaussian wave packet dynamics, and its effect on barrier tunneling processes is orders of magnitude lower than that of the classical force. In fact, the current method is shown to be a rigorous extension of generalized Gaussian wave packet dynamics to give exact quantum mechanics. We demonstrate tunneling probabilities that are in virtually perfect agreement with the exact quantum mechanics down to 10(-7) calculated from strictly localized quantum trajectories that do not communicate with their neighbors. The new formulation may have significant implications for fundamental quantum mechanics, ranging from the interpretation of non-locality to measures of quantum complexity.
A trajectory description of quantum processes. II. Applications. A Bohmian perspective
Energy Technology Data Exchange (ETDEWEB)
Sanz, Angel S.; Miret-Artes, Salvador [CSIC, Madrid (Spain). Inst. de Fisica Fundamental (IFF-CSIC)
2014-07-01
Presents a thorough introduction to, and treatment of, trajectory-based quantum-mechanical calculations. Useful for a wide range of scattering problems. Presents the applications of the trajectory description of basic quantum processes. Trajectory-based formalisms are an intuitively appealing way of describing quantum processes because they allow the use of ''classical'' concepts. Beginning as an introductory level suitable for students, this two-volume monograph presents (1) the fundamentals and (2) the applications of the trajectory description of basic quantum processes. This second volume is focussed on simple and basic applications of quantum processes such as interference and diffraction of wave packets, tunneling, diffusion and bound-state and scattering problems. The corresponding analysis is carried out within the Bohmian framework. By stressing its interpretational aspects, the book leads the reader to an alternative and complementary way to better understand the underlying quantum dynamics.
Zeno Paradox for Bohmian Trajectories: The Unfolding of the Metatron
De Gosson, Maurice,; Hiley, Basil
2010-01-01
We analyse the track of an {\\alpha}-particle passing through a cloud chamber using the Bohm theory and show that the resulting classical track has its origins in the quantum Zeno effect. By assuming the ionised gas molecules reveal the positions of the {\\alpha}-particle on its trajectory and using these positions in a short time propagator technique developed by de Gosson, we show it is the failure of the quantum potential to develop quickly enough that leads to the appearance of the classica...
WKB Analysis of Bohmian Dynamics
Figalli, Alessio
2013-10-18
We consider a semiclassically scaled Schrödinger equation with WKB initial data. We prove that in the classical limit the corresponding Bohmian trajectories converge (locally in measure) to the classical trajectories before the appearance of the first caustic. In a second step we show that after caustic onset this convergence in general no longer holds. In addition, we provide numerical simulations of the Bohmian trajectories in the semiclassical regime that illustrate the above results. © 2014 Wiley Periodicals, Inc.
Directory of Open Access Journals (Sweden)
H Azizakram
2015-12-01
Full Text Available Although charged leptons, contrary to neutrinos, cannot oscillate, exploring whether a coherent superposition of charged lepton states can change to others during the propagation is an important problem in the neutrino oscillation theory. In this paper, we consider electrons and muons coming from the pions and W decays and study their propagation in relativistic Bohmian quantum mechanics. We find out that the Bohmian trajectories of them are separated after atomic distance propagations. In fact, the computed Bohmian trajectories of electrons and muons coming from W and pion decays show that Bohmin results are consistent with those of standard quantum mechanics.
Bohmian mechanics and quantum field theory.
Dürr, Detlef; Goldstein, Sheldon; Tumulka, Roderich; Zanghì, Nino
2004-08-27
We discuss a recently proposed extension of Bohmian mechanics to quantum field theory. For more or less any regularized quantum field theory there is a corresponding theory of particle motion, which, in particular, ascribes trajectories to the electrons or whatever sort of particles the quantum field theory is about. Corresponding to the nonconservation of the particle number operator in the quantum field theory, the theory describes explicit creation and annihilation events: the world lines for the particles can begin and end.
On the classical limit of Bohmian mechanics for Hagedorn wave packets
Dürr, Detlef
2010-01-01
We consider the classical limit of quantum mechanics in terms of Bohmian trajectories. For wave packets as defined by Hagedorn we show that the Bohmian trajectories converge to Newtonian trajectories in probability.
On the Dynamics of Bohmian Measures
Markowich, Peter A.
2012-05-08
The present work is devoted to the study of dynamical features of Bohmian measures, recently introduced by the authors. We rigorously prove that for sufficiently smooth wave functions the corresponding Bohmian measure furnishes a distributional solution of a nonlinear Vlasov-type equation. Moreover, we study the associated defect measures appearing in the classical limit. In one space dimension, this yields a new connection between mono-kinetic Wigner and Bohmian measures. In addition, we shall study the dynamics of Bohmian measures associated to so-called semi-classical wave packets. For these type of wave functions, we prove local in-measure convergence of a rescaled sequence of Bohmian trajectories towards the classical Hamiltonian flow on phase space. Finally, we construct an example of wave functions whose limiting Bohmian measure is not mono-kinetic but nevertheless equals the associated Wigner measure. © 2012 Springer-Verlag.
A dynamical systems approach to Bohmian trajectories in a 2D harmonic oscillator
Energy Technology Data Exchange (ETDEWEB)
Borondo, F [Departamento de Quimica, and Instituto Mixto de Ciencias Matematicas CSIC-UAM-UC3M-UCM, Universidad Autonoma de Madrid, Cantoblanco-28049 Madrid (Spain); Luque, A; Villanueva, J [Departament de Matematica Aplicada I, Universitat Politecnica de Catalunya, 08028 Barcelona (Spain); Wisniacki, D A [Departamento de Fisica ' J. J. Giambiagi' , FCEN, UBA, Pabellon 1, Ciudad Universitaria, 1428 Buenos Aires (Argentina)], E-mail: f.borondo@uam.es, E-mail: alejandro.luque@upc.edu, E-mail: jordi.villanueva@upc.edu, E-mail: wisniacki@df.uba.ar
2009-12-11
Vortices are known to play a key role in the dynamics of the quantum trajectories defined within the framework of the de Broglie-Bohm formalism of quantum mechanics. It has been rigourously proved that the motion of a vortex in the associated velocity field can induce chaos in these trajectories, and numerical studies have explored the rich variety of behaviors that due to their influence can be observed. In this paper, we go one step further and show how the theory of dynamical systems can be used to construct a general and systematic classification of such dynamical behaviors. This should contribute to establish some firm grounds on which the studies on the intrinsic stochasticity of Bohm's quantum trajectories can be based. An application to the two-dimensional isotropic harmonic oscillator is presented as an illustration.
Quantum-trajectory Monte Carlo method for study of electron-crystal interaction in STEM.
Ruan, Z; Zeng, R G; Ming, Y; Zhang, M; Da, B; Mao, S F; Ding, Z J
2015-07-21
In this paper, a novel quantum-trajectory Monte Carlo simulation method is developed to study electron beam interaction with a crystalline solid for application to electron microscopy and spectroscopy. The method combines the Bohmian quantum trajectory method, which treats electron elastic scattering and diffraction in a crystal, with a Monte Carlo sampling of electron inelastic scattering events along quantum trajectory paths. We study in this work the electron scattering and secondary electron generation process in crystals for a focused incident electron beam, leading to understanding of the imaging mechanism behind the atomic resolution secondary electron image that has been recently achieved in experiment with a scanning transmission electron microscope. According to this method, the Bohmian quantum trajectories have been calculated at first through a wave function obtained via a numerical solution of the time-dependent Schrödinger equation with a multislice method. The impact parameter-dependent inner-shell excitation cross section then enables the Monte Carlo sampling of ionization events produced by incident electron trajectories travelling along atom columns for excitation of high energy knock-on secondary electrons. Following cascade production, transportation and emission processes of true secondary electrons of very low energies are traced by a conventional Monte Carlo simulation method to present image signals. Comparison of the simulated image for a Si(110) crystal with the experimental image indicates that the dominant mechanism of atomic resolution of secondary electron image is the inner-shell ionization events generated by a high-energy electron beam.
Bohmian picture of Rydberg atoms
Indian Academy of Sciences (India)
Partha Ghose; Manoj K Samal; Animesh Datta
2002-08-01
Unlike the previous theoretical results based on standard quantum mechanics that established the nearly elliptical shapes for the centre-of-mass motion in Rydberg atoms using numerical simulations, we show analytically that the Bohmian trajectories in Rydberg atoms are nearly elliptical.
Massive Gravitons on Bohmian Congruences
Fathi, Mohsen
2016-01-01
Taking a quantum corrected form of Raychaudhuri equation in a geometric background described by a Lorentz-violating massive theory of gravity, we go through investigating a time-like congruence of massive gravitons affected by a Bohmian quantum potential. We find some definite conditions upon which these gravitons are confined to diverging Bohmian trajectories. The respective behaviour of those quantum potentials are also derived and discussed. Additionally, and through a relativistic quantum treatment of a typical wave function, we demonstrate schematic conditions on the associated frequency to the gravitons, in order to satisfy the necessity of divergence.
Energy Technology Data Exchange (ETDEWEB)
Sanz, A.S., E-mail: asanz@iff.csic.es [Instituto de Física Fundamental (IFF-CSIC), Serrano 123, 28006 Madrid (Spain); Martínez-Casado, R. [Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom); Peñate-Rodríguez, H.C.; Rojas-Lorenzo, G. [Instituto Superior de Tecnologías y Ciencias Aplicadas, Ave. Salvador Allende y Luaces, Quinta de Los Molinos, Plaza, La Habana 10600 (Cuba); Miret-Artés, S. [Instituto de Física Fundamental (IFF-CSIC), Serrano 123, 28006 Madrid (Spain)
2014-08-15
Classical viscid media are quite common in our everyday life. However, we are not used to find such media in quantum mechanics, and much less to analyze their effects on the dynamics of quantum systems. In this regard, the Caldirola–Kanai time-dependent Hamiltonian constitutes an appealing model, accounting for friction without including environmental fluctuations (as it happens, for example, with quantum Brownian motion). Here, a Bohmian analysis of the associated friction dynamics is provided in order to understand how a hypothetical, purely quantum viscid medium would act on a wave packet from a (quantum) hydrodynamic viewpoint. To this purpose, a series of paradigmatic contexts have been chosen, such as the free particle, the motion under the action of a linear potential, the harmonic oscillator, or the superposition of two coherent wave packets. Apart from their analyticity, these examples illustrate interesting emerging behaviors, such as localization by “quantum freezing” or a particular type of quantum–classical correspondence. The reliability of the results analytically determined has been checked by means of numerical simulations, which has served to investigate other problems lacking of such analyticity (e.g., the coherent superpositions). - Highlights: • A dissipative Bohmian approach is developed within the Caldirola–Kanai model. • Some simple yet physically insightful systems are then studied analytically. • Dissipation leads to spatial localization in free-force regimes. • Under the action of linear forces, dissipation leads to uniform motion. • In harmonic potentials, the system decays unavoidable to the well minimum.
Relativistic Bohmian mechanics without a preferred foliation
Galvan, Bruno
2015-01-01
In non-relativistic Bohmian mechanics the universe is represented by a probability space whose sample space is composed of the Bohmian trajectories. In relativistic Bohmian mechanics an entire class of empirically equivalent probability spaces can be defined, one for every foliation of spacetime. In the literature the hypothesis has been advanced that a single preferred foliation is allowed, and that this foliation derives from the universal wave function by means of a covariant law. In the present paper the opposite hypothesis is advanced, i.e., no law exists for the foliations and therefore all the foliations are allowed. The resulting model of the universe is basically the "union" of all the probability spaces associated with the foliations. This hypothesis is mainly motivated by the fact that any law defining a preferred foliation is empirically irrelevant. It is also argued that the absence of a preferred foliation may reduce the well known conflict between Bohmian mechanics and Relativity.
BITLLES: Electron Transport Simulation with Quantum Trajectories
Albareda, Guillermo; Benali, Abdelilah; Alarcón, Alfonso; Moises, Simeon; Oriols, Xavier
2016-01-01
After the seminal work of R. Landauer in 1957 relating the electrical resistance of a conductor to its scattering properties, much progress has been made in our ability to predict the performance of electron devices in the DC (stationary) regime. Computational tools to describe their dynamical behavior (including the AC, transient and noise performance), however, are far from being as trustworthy as would be desired by the electronic industry. While there is no fundamental limitation to correctly modeling the high-frequency quantum transport and its fluctuations, certainly more careful attention must be paid to delicate issues such as overall charge neutrality, total current conservation, or the back action of the measuring apparatus. In this review, we will show how the core ideas behind the Bohmian formulation of quantum mechanics can be exploited to design an efficient Monte Carlo algorithm that provides a quantitative description of electron transport in open quantum systems. By making the most of traject...
Bohmian mechanics, collapse models and the emergence of classicality
Toroš, Marko; Donadi, Sandro; Bassi, Angelo
2016-09-01
We discuss the emergence of classical trajectories in Bohmian mechanics, when a macroscopic object interacts with an external environment. We show that in such a case the conditional wave function of the system follows a dynamics which, under reasonable assumptions, corresponds to that of the Ghirardi-Rimini-Weber (GRW) collapse model. As a consequence, Bohmian trajectories evolve classically. Our analysis also shows how the GRW (istantaneous) collapse process can be derived by an underlying continuous interaction of a quantum system with an external agent, thus throwing a light on how collapses can emerge from a deeper level theory.
Bohmian mechanics, open quantum systems and continuous measurements
Nassar, Antonio B
2017-01-01
This book shows how Bohmian mechanics overcomes the need for a measurement postulate involving wave function collapse. The measuring process plays a very important role in quantum mechanics. It has been widely analyzed within the Copenhagen approach through the Born and von Neumann postulates, with later extension due to Lüders. In contrast, much less effort has been invested in the measurement theory within the Bohmian mechanics framework. The continuous measurement (sharp and fuzzy, or strong and weak) problem is considered here in this framework. The authors begin by generalizing the so-called Mensky approach, which is based on restricted path integral through quantum corridors. The measuring system is then considered to be an open quantum system following a stochastic Schrödinger equation. Quantum stochastic trajectories (in the Bohmian sense) and their role in basic quantum processes are discussed in detail. The decoherence process is thereby described in terms of classical trajectories issuing from th...
Book Review Bohmian Mechanics and Quantum Theory
Jäger, G
1999-01-01
A review of "Bohmian Mechanics and Quantum Theory: An Appraisal" (James Cushing, Arthur Fine and Sheldon Goldstein, Eds.), an extensive collection of articles on Bohmian mechanics. In addition to broad, critical overviews of Bohmian mechanics, the reviewed collection contains extensions and hybrid versions of the theory, as are several detailed applications to practical situtations.
Harder, T Mark
2016-01-01
It is shown how Fermionic material particles can emerge from a covariant formulation of the de Broglie-Bohm theory. Material particles are continuous fields, formed as the eigenvalue of the Schrodinger field operator, evaluated along a Bohmian trajectory. The motivation for this work is due to a theorem proved by Malament that states there cannot be a relativistic quantum mechanics of localizable particles.
Can Bohmian particle be a source of "continuous collapse" in GRW-type theories
Sverdlov, Roman
2011-01-01
The purpose of this paper is to unite Pilot Wave model with GRW ideas through a proposal that Bohmian particle serves as a source of continuous collapse. The continuous trajectory of a particle allows the particle-centered collapse mechanism to be continuous as well. This allows us to remove the "stochastic" element from typical GRW proposals.
Price-Dynamics of Shares and Bohmian Mechanics: Deterministic or Stochastic Model?
Choustova, Olga
2007-02-01
We apply the mathematical formalism of Bohmian mechanics to describe dynamics of shares. The main distinguishing feature of the financial Bohmian model is the possibility to take into account market psychology by describing expectations of traders by the pilot wave. We also discuss some objections (coming from conventional financial mathematics of stochastic processes) against the deterministic Bohmian model. In particular, the objection that such a model contradicts to the efficient market hypothesis which is the cornerstone of the modern market ideology. Another objection is of pure mathematical nature: it is related to the quadratic variation of price trajectories. One possibility to reply to this critique is to consider the stochastic Bohm-Vigier model, instead of the deterministic one. We do this in the present note.
Short Time Quantum Propagator and Bohmian Trajectories
De Gosson, Maurice,; Hiley, Basil
2013-01-01
We begin by giving correct expressions for the short-time action; following the work of one of us and Makri--Miller. We use these estimates to derive a correct expression modulo modulo delta(t)sqr for the quantum propagator and we show that the quantum potential is negligible modulo delta(t)sqr for a point source. We finally prove that this implies that the quantum motion is classical for very short times.
Can Bohmian Mechanics Be Made Background Independent?
Vassallo, Antonio
2015-01-01
The paper presents an inquiry into the question regarding the compatibility of Bohmian mechanics, intended as a non-local theory of moving point-like particles, with background independence. This issue is worth being investigated because, if the Bohmian framework has to be of some help in developing new physics, it has to be compatible with the most well-established traits of modern physics, background independence being one of such traits. The paper highlights the fact that the notion of background independence in the context of spacetime physics is slippery and interpretation-laden. It is then suggested that the best-matching framework developed by Julian Barbour might provide a robust enough meaning of background independence. The structure of Bohmian dynamics is evaluated against this framework, reaching some intermediate results that speak in favor of the fact that Bohmian mechanics can be made background independent.
What is Surrealistic about Bohm Trajectories?
Terra-Cunha, M O
1998-01-01
We discuss interferometers in Bohmian quantum mechanics. It is shown that, with the correct configuration space, Bohm trajectories in a which way interferometer are not surrealistic, but behaves exactly as common sense suggests. Some remarks about a way to generalize Bohmian mechanics to treat density matrix are also made. PACS: 03.65.Bz, 03.75.Dg Key words: Bohm Trajectories, Which Way Interferometers, ESSW
Diffraction in time of a confined particle and its Bohmian paths
Mousavi, S V
2011-01-01
Diffraction in time of a particle confined in a box which its walls are removed suddenly at $t=0$ is studied. The solution of the time-dependent Schr\\"{o}dinger equation is discussed analytically and numerically for various initial wavefunctions. In each case Bohmian trajectories of the particles are computed and also the mean arrival time at a given location is studied as a function of the initial state.
The Electron Trajectory in a Relativistic Femtosecond Laser Pulse
Institute of Scientific and Technical Information of China (English)
He Feng; Yu Wei; Lu Peixiang; Xu Han; Shen Baifei; Li Ruxin; Xu Zhizhan
2005-01-01
In this report, we start from Lagrange equation and analyze theoretically the electron dynamics in electromagnetic field. By solving the relativistic government equations of electron,the trajectories of an electron in plane laser pulse, focused laser pulse have been given for different initial conditions. The electron trajectory is determined by its initial momentum, the amplitude,spot size and polarization of the laser pulse. The optimum initial momentum of the electron for LSS (laser synchrotron source) is obtained. Linear polarized laser is more advantaged than circular polarized laser for generating harmonic radiation.
Can Bohmian mechanics be made relativistic?
Dürr, Detlef; Goldstein, Sheldon; Norsen, Travis; Struyve, Ward; Zanghì, Nino
2014-02-08
In relativistic space-time, Bohmian theories can be formulated by introducing a privileged foliation of space-time. The introduction of such a foliation-as extra absolute space-time structure-would seem to imply a clear violation of Lorentz invariance, and thus a conflict with fundamental relativity. Here, we consider the possibility that, instead of positing it as extra structure, the required foliation could be covariantly determined by the wave function. We argue that this allows for the formulation of Bohmian theories that seem to qualify as fundamentally Lorentz invariant. We conclude with some discussion of whether or not they might also qualify as fundamentally relativistic.
Bohmian measures and their classical limit
Markowich, Peter
2010-09-01
We consider a class of phase space measures, which naturally arise in the Bohmian interpretation of quantum mechanics. We study the classical limit of these so-called Bohmian measures, in dependence on the scale of oscillations and concentrations of the sequence of wave functions under consideration. The obtained results are consequently compared to those derived via semi-classical Wigner measures. To this end, we shall also give a connection to the theory of Young measures and prove several new results on Wigner measures themselves. Our analysis gives new insight on oscillation and concentration effects in the semi-classical regime. © 2010 Elsevier Inc.
Electron trajectories in free electron laser with realizable helical wiggler and ion channel guiding
Directory of Open Access Journals (Sweden)
S. Ebrahimi
2004-12-01
Full Text Available A detailed analysis of electron trajectories in a realizable helical wiggler free electron laser with ion channel guiding using electron (single particle dynamics is presented. Conditions for stability of electron orbit have been investigated, calculations are made to illustrate. Conclusion shows that there are differences stable (unstable condition(s electron trajectories between ideal helical wiggler(2D and realizable helical wiggler (3D.
On the Common Structure of Bohmian Mechanics and the Ghirardi-Rimini-Weber Theory
Allori, V; Tumulka, R; Zanghì, N; Allori, Valia; Goldstein, Sheldon; Tumulka, Roderich; Zanghi, Nino
2006-01-01
Bohmian mechanics and Ghirardi-Rimini-Weber theory provide opposite resolutions of the quantum measurement problem: the former postulates additional variables (the particle positions) besides the wave function, whereas the latter implements spontaneous collapses of the wave function by a nonlinear and stochastic modification of the Schr\\"odinger equation. Still, both theories, when understood appropriately, share the following structure: They are ultimately not about wave functions but about matter moving in space, represented by either particle trajectories, fields on space-time, or a discrete set of space-time points. The role of the wave function then is to guide the motion of the matter.
Weak measurement from the electron displacement current: new path for applications
Marian, D.; Colomés, E.; Zanghì, N.; Oriols, X.
2015-10-01
The interest on weak measurements is rapidly growing during the last years as a unique tool to better understand and predict new quantum phenomena. Up to now many theoretical and experimental weak-measurement techniques deal with (relativistic) photons or cold atoms, but there is much less investigation on (non-relativistic) electrons in up-to-date electronics technologies. We propose a way to perform weak measurements in nanoelectronic devices through the measurement of the total current (particle plus displacement component) in such devices. We study the interaction between an electron in the active region of a electron device with a metal surface working as a sensing electrode by means of the (Bohmian) conditional wave function. We perform numerical (Monte Carlo) simulations to reconstruct the Bohmian trajectories in the iconic double slit experiment. This work opens new paths for understanding the quantum properties of an electronic system as well as for exploring new quantum engineering applications in solid state physics.
Electron Trajectory Reconstruction for Advanced Compton Imaging of Gamma Rays
Plimley, Brian Christopher
Gamma-ray imaging is useful for detecting, characterizing, and localizing sources in a variety of fields, including nuclear physics, security, nuclear accident response, nuclear medicine, and astronomy. Compton imaging in particular provides sensitivity to weak sources and good angular resolution in a large field of view. However, the photon origin in a single event sequence is normally only limited to the surface of a cone. If the initial direction of the Compton-scattered electron can be measured, the cone can be reduced to a cone segment with width depending on the uncertainty in the direction measurement, providing a corresponding increase in imaging sensitivity. Measurement of the electron's initial direction in an efficient detection material requires very fine position resolution due to the electron's short range and tortuous path. A thick (650 mum), fully-depleted charge-coupled device (CCD) developed for infrared astronomy has 10.5-mum position resolution in two dimensions, enabling the initial trajectory measurement of electrons of energy as low as 100 keV. This is the first time the initial trajectories of electrons of such low energies have been measured in a solid material. In this work, the CCD's efficacy as a gamma-ray detector is demonstrated experimentally, using a reconstruction algorithm to measure the initial electron direction from the CCD track image. In addition, models of fast electron interaction physics, charge transport and readout were used to generate modeled tracks with known initial direction. These modeled tracks allowed the development and refinement of the reconstruction algorithm. The angular sensitivity of the reconstruction algorithm is evaluated extensively with models for tracks below 480 keV, showing a FWHM as low as 20° in the pixel plane, and 30° RMS sensitivity to the magnitude of the out-of-plane angle. The measurement of the trajectories of electrons with energies as low as 100 keV have the potential to make electron
Classical and Quantum Limits in Bohmian Quantum Cosmology
Shojai, F.; Shirinifard, A.
2005-01-01
In this paper we have investigated the classical limit in Bohmian quantum cosmology. It is observed that in the quantum regime where the quantum potential is greater than the classical one, one has an expansion in terms of negative powers of the Planck constant. But in the classical limit there are regions having positive powers of the Planck constant, and regions having negative powers and also regions having both. The conclusion is that the Bohmian classical limit cannot be obtained by lett...
Photodissociation of CCH: Classical trajectory calculations involving seven electronic states
Apaydın, Gökşin; Fink, William H.; Jackson, William M.
2004-11-01
The photodissociation dynamics of ethynyl radical, C2H, involving seven electronic states is studied by classical trajectory calculations. Initial values of the trajectories are selected based on relative absorption intensities calculated by Mebel et al. The energies and the derivatives are interpolated by three-dimensional cubic spline interpolator using an extended data pool. Mean square errors and standard deviations in interpolation of energies for 450 data points are found to be in the range 3.1×10-6-1.4×10-5 and 1.7×10-3-3.8×10-3 hartrees, respectively. The photofragments of C2 and H are produced mainly in the X 1Σg+, a 3Πu, b 3Σg-, c 3Σu+, A 1Πu, B 1Δg electronic states of C2 as product. The avoided crossings do not appear to be in the main dissociation pathways. The internal distributions are in good accord with the experimental results where comparison is possible, suggesting that the fragmentation mechanism of C2H2 into C2 and H is a two step process involving C2H radical as an intermediate with a life time long enough to allow complete collection of the phase space in the experiments.
Electron impact double ionization of helium from classical trajectory calculations
Geyer, T
2004-01-01
With a recently proposed quasiclassical ansatz [Geyer and Rost, J. Phys. B 35 (2002) 1479] it is possible to perform classical trajectory ionization calculations on many electron targets. The autoionization of the target is prevented by a M\\o{}ller type backward--forward propagation scheme and allows to consider all interactions between all particles without additional stabilization. The application of the quasiclassical ansatz for helium targets is explained and total and partially differential cross sections for electron impact double ionization are calculated. In the high energy regime the classical description fails to describe the dominant TS1 process, which leads to big deviations, whereas for low energies the total cross section is reproduced well. Differential cross sections calculated at 250 eV await their experimental confirmation.
Short-time quantum propagator and Bohmian trajectorie
de Gosson, M.; Hiley, Basil
2013-01-01
We begin by giving correct expressions for the short-time action following the work Makri–Miller. We use these estimates to derive an accurate expression modulo Δ t 2 for the quantum propagator and we show that the quantum potential is negligible modulo Δ t 2 for a point source, thus justifying an unfortunately largely ignored observation of Holland made twenty years ago. We finally prove that this implies that the quantum motion is classical for very short times.
Short-time quantum propagator and Bohmian trajectories
Energy Technology Data Exchange (ETDEWEB)
Gosson, Maurice de, E-mail: maurice.degosson@gmail.com [Universität Wien, Fakultät für Mathematik, NuHAG, Wien 1090 (Austria); Hiley, Basil [University of London, Birkbeck College, Theoretical Physics Unit, London WC1E 7HX (United Kingdom)
2013-12-06
We begin by giving correct expressions for the short-time action following the work Makri–Miller. We use these estimates to derive an accurate expression modulo Δt{sup 2} for the quantum propagator and we show that the quantum potential is negligible modulo Δt{sup 2} for a point source, thus justifying an unfortunately largely ignored observation of Holland made twenty years ago. We finally prove that this implies that the quantum motion is classical for very short times.
Valence atom with bohmian quantum potential: the golden ratio approach
Directory of Open Access Journals (Sweden)
Putz Mihai V
2012-11-01
Full Text Available Abstract Background The alternative quantum mechanical description of total energy given by Bohmian theory was merged with the concept of the golden ratio and its appearance as the Heisenberg imbalance to provide a new density-based description of the valence atomic state and reactivity charge with the aim of clarifying their features with respect to the so-called DFT ground state and critical charge, respectively. Results The results, based on the so-called double variational algorithm for chemical spaces of reactivity, are fundamental and, among other issues regarding chemical bonding, solve the existing paradox of using a cubic parabola to describe a quadratic charge dependency. Conclusions Overall, the paper provides a qualitative-quantitative explanation of chemical reactivity based on more than half of an electronic pair in bonding, and provide new, more realistic values for the so-called “universal” electronegativity and chemical hardness of atomic systems engaged in reactivity (analogous to the atoms-in-molecules framework.
How Does Quantum Uncertainty Emerge from Deterministic Bohmian Mechanics?
Solé, A.; Oriols, X.; Marian, D.; Zanghì, N.
2016-10-01
Bohmian mechanics is a theory that provides a consistent explanation of quantum phenomena in terms of point particles whose motion is guided by the wave function. In this theory, the state of a system of particles is defined by the actual positions of the particles and the wave function of the system; and the state of the system evolves deterministically. Thus, the Bohmian state can be compared with the state in classical mechanics, which is given by the positions and momenta of all the particles, and which also evolves deterministically. However, while in classical mechanics it is usually taken for granted and considered unproblematic that the state is, at least in principle, measurable, this is not the case in Bohmian mechanics. Due to the linearity of the quantum dynamical laws, one essential component of the Bohmian state, the wave function, is not directly measurable. Moreover, it turns out that the measurement of the other component of the state — the positions of the particles — must be mediated by the wave function; a fact that in turn implies that the positions of the particles, though measurable, are constrained by absolute uncertainty. This is the key to understanding how Bohmian mechanics, despite being deterministic, can account for all quantum predictions, including quantum randomness and uncertainty.
Hi-G electronic gated camera for precision trajectory analysis
Snyder, Donald R.; Payne, Scott; Keller, Ed; Longo, Salvatore; Caudle, Dennis E.; Walker, Dennis C.; Sartor, Mark A.; Keeler, Joe E.; Kerr, David A.; Fail, R. Wallace; Gannon, Jim; Carrol, Ernie; Jamison, Todd A.
1997-12-01
It is extremely difficult and expensive to determine the flight attitude and aimpoint of small maneuvering miniature air vehicles from ground based fixed or tracking photography. Telemetry alone cannot provide sufficient information bandwidth on 'what' the ground tracking is seeing and consequently 'why' it did or did not function properly. Additionally, it is anticipated that 'smart' and 'brilliant' guided vehicles now in development will require a high resolution imaging support system to determine which target and which part of a ground feature is being used for navigation or targeting. Other requirements include support of sub-component separation from developmental supersonic vehicles, where the clean separation from the container is not determinable from ground based film systems and film cameras do not survive vehicle breakup and impact. Hence, the requirement is to develop and demonstrate an imaging support system for development/testing that can provide the flight vehicle developer/analyst with imagery (combined with miniature telemetry sources) sufficient to recreate the trajectory, terminal navigation, and flight termination events. This project is a development and demonstration of a real-time, launch-rated, shuttered, electronic imager, transmitter, and analysis system. This effort demonstrated boresighted imagery from inside small flight vehicles for post flight analysis of trajectory, and capture of ground imagery during random triggered vehicle functions. The initial studies for this capability have been accomplished by the Experimental Dynamics Section of the Air Force Wright Laboratory, Armament Directorate, Eglin AFB, Florida, and the Telemetry Support Branch of the Army Material Research and Development Center at Picatinny Arsenal, New Jersey. It has been determined that at 1/10,000 of a second exposure time, new ultra-miniature CCD sensors have sufficient sensitivity to image key ground target features without blur, thereby providing data for
Bohmian mechanics. The physics and mathematics of quantum theory
Energy Technology Data Exchange (ETDEWEB)
Duerr, Detlef [Muenchen Univ. (Germany). Fakultaet Mathematik; Teufel, Stefan [Tuebingen Univ. (Germany). Mathematisches Inst.
2009-07-01
Bohmian Mechanics was formulated in 1952 by David Bohm as a complete theory of quantum phenomena based on a particle picture. It was promoted some decades later by John S. Bell, who, intrigued by the manifestly nonlocal structure of the theory, was led to his famous Bell's inequalities. Experimental tests of the inequalities verified that nature is indeed nonlocal. Bohmian mechanics has since then prospered as the straightforward completion of quantum mechanics. This book provides a systematic introduction to Bohmian mechanics and to the mathematical abstractions of quantum mechanics, which range from the self-adjointness of the Schroedinger operator to scattering theory. It explains how the quantum formalism emerges when Boltzmann's ideas about statistical mechanics are applied to Bohmian mechanics. The book is self-contained, mathematically rigorous and an ideal starting point for a fundamental approach to quantum mechanics. It will appeal to students and newcomers to the field, as well as to established scientists seeking a clear exposition of the theory. (orig.)
The time evolution of the Bohmian Pilot Wave
Kozlowski, Miroslaw; Marciak-Kozlowska, Janina
2004-01-01
In this paper the Newton-Schrodinger-Bohm equation is solved for particles with m>M_P. It is shown that the Bohmian pilot wave for particles with m>M_P oscillates with frequency omega=tau^{-1}_P, where tau_P is the Planck time. Key words: Macroscopic particles; Pilot wave.
Simulation of Electron Trajectories in the Multicusp Ion Source Using Geantn4 Monte Carlo Code
Khodadadi Azadboni, Fatemeh; Sedaghatizade, Mahmood
2010-04-01
To optimize the multicusp ion source, understanding of transport properties of electrons is indispensable. Since the transport of electrons in the multicusp ion source is a three-dimensional problem, we use the 3D computer code Geant4, to model the particle trajectories. The goal is to study the effect of electron injection into a cylindrical gas chamber and the electron trajectories. The role of the magnetic filter in contemporary negative ion sources is analyzed. The conditions in the magnetic filter adjacent to the plasma electrode optimum for the generation, formation, and extraction of an H- ion beam are found. The simulation results are in good agreement with the experimental data.
Particles, waves and trajectories: 210 years after Young's experiment
Sanz, A S
2014-01-01
Mermin's "shut up and calculate!" somehow summarizes the most widely accepted view on quantum mechanics. This conception has led to a rather constraining way to think and understand the quantum world. Nonetheless, a closer look at the principles and formal body of this theory shows that, beyond longstanding prejudices, there is still room enough for alternative tools. This is the case, for example, of Bohmian mechanics. As it is discussed here, there is nothing contradictory or wrong with this hydrodynamical representation, which enhances the dynamical role of the quantum phase to the detriment (to some extent) of the probability density. The possibility to describe the evolution of quantum systems in terms of trajectories or streamlines is just a direct consequence of the fact that Bohmian mechanics (quantum hydrodynamics) is just a way to recast quantum mechanics in the more general language of the theory of characteristics. Misconceptions concerning Bohmian mechanics typically come from the fact that many ...
DEFF Research Database (Denmark)
Power, Stephen; Thomsen, Morten Rishøj; Jauho, Antti-Pekka
2017-01-01
exceptional control of electron behavior, but it is hindered by the requirement to maintain ballistic transport over large length scales. Recent experiments have overcome this obstacle and observed distinct magnetoresistance commensurability peaks for perforated graphene sheets (antidot lattices...
Electron trajectories and growth rates of the plasma wave pumped free-electron laser
Jafari, S.; Jafarinia, F.; Nilkar, M.; Amiri, M.
2014-12-01
A theory for a plasma wave wiggler has been described which employs the plasma whistler wave for producing laser radiation in a free-electron laser (FEL). While electromagnetically pumped FELs have been proven to be an effective means generating short wavelengths, practical difficulties occur in the design of these wigglers. For this reason, it is found that a plasma wave wiggler can be employed in concept with an electromagnetic wave wiggler due to both higher tunability and holding the focus of pump wave and e-beam over a significant distance to achieve a suitable amplification. Plasma in the presence of static magnetic field supports a plasma whistler wave. The plasma wiggler period can be tuned by varying the plasma density and/or ambient magnetic field. Electron trajectories have been analyzed using single particle dynamics and regimes of orbital stability have been demonstrated. A polynomial dispersion relation for electromagnetic and space-charge waves has then been derived, analytically. Numerical studies of the dispersion relation reveal that the growth rates are sensitive functions of the cyclotron frequency. It has been shown that by increasing the axial magnetic field strength (or cyclotron frequency), the growth rate for groups I and III orbits increases, while a growth decrement has been obtained for groups II and IV orbits.
An alternative theory for the Bohmian mechanics
Directory of Open Access Journals (Sweden)
MJ Kazemi
2012-09-01
Full Text Available In this article, a causal model on the basis of trajectory is introduced for description of quantum systems. This theory is structurally very similar to Bohme mechanics, and like Bohme theory reproduces all statistical consequences of standard quantum mechanics. Particle trajectories in this model are different from anticipated ones by Bohme model. Quantum potential (force form, which is given, is different from Bohme theory. Actually, this model will convert to Bohme theory by annihilating the free parameter ( μ . Theoretical properties of this model are investigated in the same way as Galilean invariance. Also, a precise comparison between this theory and Bohme mechanics is made, and some suggestions are presented (through transit time distribution for experimental distinction between these two models. Finally, extension of this theory is investigated
Energy Technology Data Exchange (ETDEWEB)
Landry, Brian R.; Falk, Martin J.; Subotnik, Joseph E. [Department of Chemistry, University of Pennsylvania, 231 S. 34th Street, Philadelphia, Pennsylvania 19104 (United States)
2013-12-07
In a recent paper, we presented a road map for how Tully's fewest switches surface hopping (FSSH) algorithm can be derived, under certain circumstances, from the mixed quantum-classical Liouville equation. In this communication, we now demonstrate how this new interpretation of surface hopping can yield significantly enhanced results for electronic properties in nonadiabatic calculations. Specifically, we calculate diabatic populations for the spin-boson problem using FSSH trajectories. We show that, for some Hamiltonians, without changing the FSSH algorithm at all but rather simply reinterpreting the ensemble of surface hopping trajectories, we recover excellent results and remove any and all ambiguity about the initial condition problem.
Analysis of free text in electronic health records for identification of cancer patient trajectories
DEFF Research Database (Denmark)
Jensen, Kasper; Soguero-Ruiz, Cristina; Mikalsen, Karl Oyvind
2017-01-01
a methodology that allows disease trajectories of the cancer patients to be estimated from free text in electronic health records (EHRs). By using these disease trajectories, we predict 80% of patient events ahead in time. By control of confounders from 8326 quantified events, we identified 557 events......, there has never been a greater need to enforce evidence-led medical decision-making using available health care data. In the present work, we studied a cohort of 7,741 patients, of whom 4,080 were diagnosed with cancer, surgically treated at a University Hospital in the years 2004-2012. We have developed...
Jiang, Ke-Xia
2010-01-01
Based on the double-slit experiment of electrons, we suggest a proposal of thought experiment to distinguish between the Bohmian Interpretation (BI) and the Standard Quantum Mechanics (SQM). We mainly focus on the discussion of the meaning of the wave function (Schr\\"{o}dinger-$\\psi$). The key technique is require to insert some slow-electrons or weak electron current into the space between the double-slit and the detector plane. We find that the two theories finally give out two totally different results about the affections which the externally inserted electrons cause to the original pattern of the interference fringes. Under the BI, the externally inserted electrons also can be influenced by the Quantum Potential (QP) in a totally same way with the electrons which come from the slits, so the positions they arrived at are preferred to certain bright zones, and the interference pattern will become more clearer. While under the SQM, the Schr\\"{o}dinger-$\\psi$ does not represent an objectively real field, but...
Electron trajectory selection for high harmonic generation inside a short hollow fiber.
Igarashi, Hironori; Makida, Ayumu; Sekikawa, Taro
2013-09-09
The 19th harmonic beam divergences from a Ti:sapphire laser generated using a gas jet and 10-mm-long hollow fibers with bore diameters of 300 and 200 μm were investigated. The beam quality factor M(2) of the harmonic beam generated in a 300-μm hollow fiber was found to be better than the gas jet using the phase match including the atomic dipole phase induced by the short trajectory. On the other hand, a 200-μm hollow fiber was found to generate a more divergent beam with a larger M(2) because of the long trajectory. The electron trajectory contributing to high harmonic generation was selected using the phase-matching process inside a short hollow fiber.
A proposal for a Bohmian ontology of quantum gravity
Vassallo, Antonio
2013-01-01
The paper shows how the Bohmian approach to quantum physics can be applied to develop a clear and coherent ontology of non-perturbative quantum gravity. We suggest retaining discrete objects as the primitive ontology also when it comes to a quantum theory of space-time and therefore focus on loop quantum gravity. We conceive atoms of space, represented in terms of nodes linked by edges in a graph, as the primitive ontology of the theory and show how a non-local law in which a universal and stationary wave-function figures can provide an order of configurations of such atoms of space such that the classical space-time of general relativity is approximated. Although there is as yet no fully worked out physical theory of quantum gravity, we regard the Bohmian approach as setting up a standard that proposals for a serious ontology in this field should meet and as opening up a route for fruitful physical and mathematical investigations.
A Proposal for a Bohmian Ontology of Quantum Gravity
Vassallo, Antonio; Esfeld, Michael
2014-01-01
The paper shows how the Bohmian approach to quantum physics can be applied to develop a clear and coherent ontology of non-perturbative quantum gravity. We suggest retaining discrete objects as the primitive ontology also when it comes to a quantum theory of space-time and therefore focus on loop quantum gravity. We conceive atoms of space, represented in terms of nodes linked by edges in a graph, as the primitive ontology of the theory and show how a non-local law in which a universal and stationary wave-function figures can provide an order of configurations of such atoms of space such that the classical space-time of general relativity is approximated. Although there is as yet no fully worked out physical theory of quantum gravity, we regard the Bohmian approach as setting up a standard that proposals for a serious ontology in this field should meet and as opening up a route for fruitful physical and mathematical investigations.
On the Conceptual Issues Surrounding the Notion of Relational Bohmian Dynamics
Vassallo, Antonio
2016-01-01
The paper presents a program to construct a non-relativistic relational Bohmian theory, that is, a theory of $N$ moving point-like particles that dispenses with space and time as fundamental background structures. The relational program proposed is based on the best-matching framework originally developed by Julian Barbour. In particular, the paper focuses on the conceptual problems that arise when trying to implement such a program. It is argued that pursuing a relational strategy in the Bohmian context leads to a more parsimonious ontology than that of standard Bohmian mechanics without betraying the original motivations for adopting a primitive ontology approach to quantum physics. It is also shown how a relational Bohmian approach might clarify the issue of the timelessness of the dynamics resulting from the quantization of a classical relational system of particles.
On the Conceptual Issues Surrounding the Notion of Relational Bohmian Dynamics
Vassallo, Antonio; Ip, Pui Him
2016-08-01
The paper presents a program to construct a non-relativistic relational Bohmian theory, that is, a theory of N moving point-like particles that dispenses with space and time as fundamental background structures. The relational program proposed is based on the best-matching framework originally developed by Julian Barbour. In particular, the paper focuses on the conceptual problems that arise when trying to implement such a program. It is argued that pursuing a relational strategy in the Bohmian context leads to a more parsimonious ontology than that of standard Bohmian mechanics without betraying the original motivations for adopting a primitive ontology approach to quantum physics. It is also shown how a relational Bohmian approach might clarify the issue of the timelessness of the dynamics resulting from the quantization of a classical relational system of particles.
Garashchuk, Sophya; Jakowski, Jacek; Wang, Lei; Sumpter, Bobby G
2013-12-10
A massively parallel, direct quantum molecular dynamics method is described. The method combines a quantum trajectory (QT) representation of the nuclear wave function discretized into an ensemble of trajectories with an electronic structure (ES) description of electrons, namely using the density functional tight binding (DFTB) theory. Quantum nuclear effects are included into the dynamics of the nuclei via quantum corrections to the classical forces. To reduce computational cost and increase numerical accuracy, the quantum corrections to dynamics resulting from localization of the nuclear wave function are computed approximately and included into selected degrees of freedom representing light particles where the quantum effects are expected to be the most pronounced. A massively parallel implementation, based on the message passing interface allows for efficient simulations of ensembles of thousands of trajectories at once. The QTES-DFTB dynamics approach is employed to study the role of quantum nuclear effects on the interaction of hydrogen with a model graphene sheet, revealing that neglect of nuclear effects can lead to an overestimation of adsorption.
Xie, Weiwei; Domcke, Wolfgang; Farantos, Stavros C.; Grebenshchikov, Sergy Yu.
2016-03-01
A trajectory method of calculating tunneling probabilities from phase integrals along straight line tunneling paths, originally suggested by Makri and Miller [J. Chem. Phys. 91, 4026 (1989)] and recently implemented by Truhlar and co-workers [Chem. Sci. 5, 2091 (2014)], is tested for one- and two-dimensional ab initio based potentials describing hydrogen dissociation in the 1B1 excited electronic state of pyrrole. The primary observables are the tunneling rates in a progression of bending vibrational states lying below the dissociation barrier and their isotope dependences. Several initial ensembles of classical trajectories have been considered, corresponding to the quasiclassical and the quantum mechanical samplings of the initial conditions. It is found that the sampling based on the fixed energy Wigner density gives the best agreement with the quantum mechanical dissociation rates.
Discharge stratification in noble gases as convergence of electron phase trajectories to attractors
Golubovskii, Yu.; Valin, S.; Pelyukhova, E.; Nekuchaev, V.; Sigeneger, F.
2016-12-01
A new dynamic method to analyse resonance effects in glow discharges is proposed as a supplement to fluid and kinetic approaches for the investigation of discharge stratification. The method is applicable to striations, which are caused by the nonlocal electron behaviour at lower pressure and current. It is based on the analysis of the electron phase trajectories in spatially periodic fields. Being quite intuitive and easier than the solution of the Boltzmann equation, this method gives a quantitative description of the main effects arising from the kinetic analysis, for example, the appearance of attractors of the phase trajectories. The dynamic theory eliminates the main difficulty of the kinetic theory associated with the large relaxation length of the electron energy distribution function in periodic fields and describes the integer and rational resonances that correspond to S-, P- and R-striations. As a result, the stratification of the discharge can be interpreted as the excitation of one of the spatial resonator modes of the positive column.
Strategy for alignment of electron beam trajectory in LEReC cooling section
Energy Technology Data Exchange (ETDEWEB)
Seletskiy, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Blaskiewicz, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Fedotov, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Kayran, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Kewisch, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Michnoff, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Pinayev, I. [Brookhaven National Lab. (BNL), Upton, NY (United States)
2016-09-23
We considered the steps required to align the electron beam trajectory through the LEReC cooling section. We devised a detailed procedure for the beam-based alignment of the cooling section solenoids. We showed that it is critical to have an individual control of each CS solenoid current. Finally, we modeled the alignment procedure and showed that with two BPM fitting the solenoid shift can be measured with 40 um accuracy and the solenoid inclination can be measured with 30 urad accuracy. These accuracies are well within the tolerances of the cooling section solenoid alignment.
Calculation of electron trajectory and energy deposition in no screening region
Energy Technology Data Exchange (ETDEWEB)
Kia, Mohammad Reza, E-mail: m_r_kia@aut.ac.ir; Noshad, Houshyar, E-mail: hnoshad@aut.ac.ir
2016-01-01
The probability density function (PDF) of energy for inelastic collision is obtained by solving the integro-differential form of the quantity equation with the Bhabha differential cross section for particles with spin 1/2. Hence, the total PDF in no screening region is determined by folding theory with the following two assumptions: (1) the electron loses energy by collision and radiation and (2) the electron velocity does not change with a thin absorber. Therefore, a set of coupled stochastic differential equations based on the deviation and energy loss PDFs for electron is presented to obtain the electron trajectory inside the target. The energy PDFs for an electron beam with incident energy of 15.7 MeV inside aluminum and copper are calculated. Besides, the dose distributions for an electron beam with incident energies of 20, 10.2, 6, and 0.5 MeV in water are obtained. The results are in excellent agreement with the experimental data reported in the literature.
Institute of Scientific and Technical Information of China (English)
S. Saviz; E. Lashani; Farzin M. Aghamir
2012-01-01
A theory for the two-stream free-electron laser (TSFEL) with a helical wiggler and an axial guide magnetic field is developed.In the analysis,the effects of self-fields are taken into account.An analysis of the two-stream steady-state electron trajectories is given by solving the equation of motion.Numerical calculations show that there are seven groups of orbits in the presence of self-fields instead of two groups reported in the absence of self-fields.The stability of the trajectories is studied numerically.
Fang, Yigang; Liu, Jianbo
2009-10-22
Reaction of protonated tyrosine with the lowest electronically excited singlet state of molecular oxygen, (1)O(2) (a(1)Delta(g)), is reported over the center-of-mass collision energy (E(col)) range from 0.1 to 3.0 eV, using an electrospray-ionization, guided-ion-beam scattering instrument, in conjunction with ab initio electronic structure calculations and direct dynamics trajectory simulations. Only one product channel is observed, corresponding to generation of hydrogen peroxide via transfer of two hydrogen atoms from protonated tyrosine. Despite being exoergic, the reaction is in competition with physical quenching of (1)O(2) and is very inefficient. At low E(col), the reaction may be mediated by intermediate complexes and shows strong inhibition by collision energy. At high E(col), the reaction efficiency drops to approximately 1% and starts to have contribution from a direct mechanism. Quasi-classical trajectory simulations were performed to probe the mechanism at high collision energies. Analysis of trajectories shows that, at E(col) of 3.0 eV, a small fraction of hydrogen peroxide (25%) is produced via a direct, concerted mechanism where two hydrogen atoms are transferred simultaneously, but most hydrogen peroxide (75%) is formed by dissociation of hydroperoxide intermediates. According to ab initio calculations and trajectory simulations, collisions also lead to formation of various endoperoxides, and dissociation of endoperoxides may play a role in physical quenching of (1)O(2). The apparatus and experimental techniques are described in detail.
Directory of Open Access Journals (Sweden)
Алексей Андреевич Заславский
2010-09-01
Full Text Available In this paper the approach for the use of automated information system directly in the classroom to form a personal set of tasks for a particular student and build individual trajectory of its development.
Indian Academy of Sciences (India)
Rahmani Faramarz; Golshani Mehdi; Sarbishei Mohsen
2016-04-01
In this paper we shall argue that conformal transformations give some new aspects to a metric and changes the physics that arises from the classical metric. It is equivalent to adding a new potential to relativistic Hamilton–Jacobi equation. We start by using conformal transformations on a metric and obtain modified geodesics. Then, we try to show that extra terms in the modified geodesics are indications of a background force. We obtain this potential by using variational method. Then, we see that this background potential is the same as the Bohmian non-local quantum potential. This approach gives a method stronger than Bohm’s original method in deriving Bohmian quantumpotential. We do not use any quantum mechanical postulates in this approach.
A Bohmian approach to the perturbations of non-linear Klein--Gordon equation
Indian Academy of Sciences (India)
FARAMARZ RAHMANI; MEHDI GOLSHANI; MOHSEN SARBISHEI
2016-08-01
In the framework of Bohmian quantum mechanics, the Klein--Gordon equation can be seen as representing a particle with mass m which is guided by a guiding wave $\\phi(x)$ in a causal manner. Here a relevant question is whether Bohmian quantum mechanics is applicable to a non-linear Klein--Gordon equation? We examine this approach for $\\phi_{4}(x)$ and sine-Gordon potentials. It turns out that this method leads to equations for quantum states which are identical to those derived by field theoretical methods used for quantum solitons. Moreover, the quantum force exerted on the particle can be determined. This method can be used for other non-linear potentials as well.
María Ruth Vargas Leyva
2000-01-01
This is a study of the career trajectories of engineers in the company Sanyo Video Components. Three stages in the development of the professional career are recognized: initial career stage, mid-career and late stage career. Results indicate that the career’s trajectory is internally determined by the area of career development and job hierarchy. In external mobility, there are limitations of individual and family type; those of an individual type are age and area of career developmen...
Some Clarifications on the Relation Between Bohmian Quantum Potential and Mach's Principle
Rahmani, Faramarz; Golshani, Mehdi
2017-07-01
Mach's principle asserts that the inertial mass of a body is related to the distribution of other distant bodies. This means that in the absence of other bodies, a single body has no mass. In this case, talking about motion is not possible, because the detection of motion is possible only relative to other bodies. But in physics we are faced with situations that are not fully Machian. As in the case of general theory of relativity where geodesics exist in the absence of any matter, the motion has meaning. Another example which is the main topic of our discussion, refers to Bohmian quantum mechanics, where the inertial mass of a single particle does not vanish, but is modified. We can call such situations in which motion or mass of a single particle has meaning, pseudo-Machian situations. In this paper, we use the Machian or pseudo-Machian considerations to clarify under what circumstances and how a Machian effect leads us to Bohmian quantum mechanics. Then, we shall get the Bohmian quantum potential and its higher order terms for the Klein-Gordon particle through Machian considerations, without using any quantum mechanical postulate or operator formalism.
Some Clarifications on the Relation Between Bohmian Quantum Potential and Mach's Principle
Rahmani, Faramarz; Golshani, Mehdi
2017-10-01
Mach's principle asserts that the inertial mass of a body is related to the distribution of other distant bodies. This means that in the absence of other bodies, a single body has no mass. In this case, talking about motion is not possible, because the detection of motion is possible only relative to other bodies. But in physics we are faced with situations that are not fully Machian. As in the case of general theory of relativity where geodesics exist in the absence of any matter, the motion has meaning. Another example which is the main topic of our discussion, refers to Bohmian quantum mechanics, where the inertial mass of a single particle does not vanish, but is modified. We can call such situations in which motion or mass of a single particle has meaning, pseudo-Machian situations. In this paper, we use the Machian or pseudo-Machian considerations to clarify under what circumstances and how a Machian effect leads us to Bohmian quantum mechanics. Then, we shall get the Bohmian quantum potential and its higher order terms for the Klein-Gordon particle through Machian considerations, without using any quantum mechanical postulate or operator formalism.
Thomson, R; Kawrakow, I
2012-06-01
Widely-used classical trajectory Monte Carlo simulations of low energy electron transport neglect the quantum nature of electrons; however, at sub-1 keV energies quantum effects have the potential to become significant. This work compares quantum and classical simulations within a simplified model of electron transport in water. Electron transport is modeled in water droplets using quantum mechanical (QM) and classical trajectory Monte Carlo (MC) methods. Water droplets are modeled as collections of point scatterers representing water molecules from which electrons may be isotropically scattered. The role of inelastic scattering is investigated by introducing absorption. QM calculations involve numerically solving a system of coupled equations for the electron wavefield incident on each scatterer. A minimum distance between scatterers is introduced to approximate structured water. The average QM water droplet incoherent cross section is compared with the MC cross section; a relative error (RE) on the MC results is computed. RE varies with electron energy, average and minimum distances between scatterers, and scattering amplitude. The mean free path is generally the relevant length scale for estimating RE. The introduction of a minimum distance between scatterers increases RE substantially (factors of 5 to 10), suggesting that the structure of water must be modeled for accurate simulations. Inelastic scattering does not improve agreement between QM and MC simulations: for the same magnitude of elastic scattering, the introduction of inelastic scattering increases RE. Droplet cross sections are sensitive to droplet size and shape; considerable variations in RE are observed with changing droplet size and shape. At sub-1 keV energies, quantum effects may become non-negligible for electron transport in condensed media. Electron transport is strongly affected by the structure of the medium. Inelastic scatter does not improve agreement between QM and MC simulations of low
Energy Technology Data Exchange (ETDEWEB)
Yang, Mou, E-mail: yangmou1222@gmail.com [Laboratory of Quantum Information Technology, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China); Cui, Yan; Wang, Rui-Qiang; Zhao, Hong-Bo [Laboratory of Quantum Information Technology, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006 (China)
2012-03-05
We investigate the electronic structure of graphene ribbons under the competition between lateral electric and normal magnetic fields. The squeezing of quantum level spacings caused by either field is studied. Based on the knowledge of the dispersion under both fields, we analyze the electronic trajectories near the junctions of different electric and magnetic fields configurations. The junctions can split and join electron beams, and the conductance is quite robust against disorder near the junction interfaces. These junction devices can be used as bricks for building more complicated interference devices. -- Highlights: ► Unified physical picture of graphene ribbon under electric and magnetic fields is provided. ► Squeezing of level spacings caused by electric and magnetic fields is investigated. ► Graphene devices for electron beam split and joint are proposed.
Jiang, Wei; Wang, Langping; Zhou, Guangxue; Wang, Xiaofeng
2017-02-01
In order to study electron trajectories in an annular cathode high current pulsed electron beam (HCPEB) source based on carbon fiber bunches, the transmission process of electrons emitted from the annular cathode was simulated using a particle-in-cell model with Monte Carlo collisions (PIC-MCC). The simulation results show that the intense flow of the electrons emitted from the annular cathode are expanded during the transmission process, and the uniformity of the electron distribution is improved in the transportation process. The irradiation current decreases with the irradiation distance and the pressure, and increases with the negative voltage. In addition, when the irradiation distance and the cathode voltage are larger than 40 mm and -15 kV, respectively, a uniform irradiation current distribution along the circumference of the anode can be obtained. The simulation results show that good irradiation uniformity of circular components can be achieved by this annular cathode HCPEB source.
Directory of Open Access Journals (Sweden)
María Ruth Vargas Leyva
2000-11-01
Full Text Available This is a study of the career trajectories of engineers in the company Sanyo Video Components. Three stages in the development of the professional career are recognized: initial career stage, mid-career and late stage career. Results indicate that the career’s trajectory is internally determined by the area of career development and job hierarchy. In external mobility, there are limitations of individual and family type; those of an individual type are age and area of career development; those of a family type are civil state, spouse’s occupation and the presence and number of children. The results of other studies are confirmed in relation to the engineers’ practical training in the business, based on the initial career stage, the step from the technical dimension to the administrative, and the decrease in promotion potential which comes with age, as well as the professional conversion process of engineers who have various types of professional training.
Ermakov, A V; Ciftlikli, E Z; Syssoev, S E; Shuttleworth, I G; Hinch, B J
2010-10-01
We report on the application of a novel nondestructive in-vacuum technique for relative work function measurements, employing a grazing incidence electron deflection above a sample with a planar surface. Two deflected electron beam detectors are used as a position sensitive detector to control feedback to the sample potential as the sample work function changes. With feedback the sample potential exactly follows the surface sample-size averaged work function variation, so that the deflected beam trajectory remains stable. We also discuss methods to optimize the initial electron trajectories for this method, so as to minimize unwanted effects such as from uncontrolled external magnetic fields. As the electron beam does not impinge on the surface in this new technique electron induced desorption, ionization, dissociation, and/or decomposition is not induced at the interface. Importantly also the technique allows for free access to the surfaces enabling simultaneous deposition/evaporation and/or application of other surface characterization methods. We demonstrate its application in concurrent measurements of helium atom reflectivity and work function changes taking place during molecular oxygen exposure of a Cu(001) surface. A work function measurement sensitivity and stability is demonstrated at ∼10 mV at a sampling rate of 1 Hz and after application of an ∼7 s smoothing routine. In comparison to the helium atom reflectivity measurements, the work function measurements are more sensitive to the initial O uptake, and less so to the final coverage variations and possible surface reordering at higher O coverages.
A Bohmian approach to the non-Markovian non-linear Schrödinger–Langevin equation
Energy Technology Data Exchange (ETDEWEB)
Vargas, Andrés F.; Morales-Durán, Nicolás; Bargueño, Pedro, E-mail: p.bargueno@uniandes.edu.co
2015-05-15
In this work, a non-Markovian non-linear Schrödinger–Langevin equation is derived from the system-plus-bath approach. After analyzing in detail previous Markovian cases, Bohmian mechanics is shown to be a powerful tool for obtaining the desired generalized equation.
The Effect of Magnetic Field of Multicusp and Wall Material on Electron Trajectories
Khodadadi Azadboni, Fatemeh; Sedaghatizade, Mahmood
2010-04-01
In this paper, the effect of electron confinement with magnetic fields in the multicusp ion source has been investigated. That is, electron confinement with magnetic fields plays a very important role for the generation of negative ions at plasma. Three-dimensional spatial distributions of electrons production are obtained for a multicusp ion source. The electron confinement of magnetic fields from various surface materials (such as Al2O3, Al, Au, Cu, w and stainless-steel) have been compared in a multicusp plasma source. The electron confinement effect becomes stronger with increasing N (the number of rows of permanent magnets) and using Al for plasma chamber wall material. The results of investigations have demonstrated good correspondence with experimental data, and therefore the adequacy of the developed approach and the possibility to build more effective source on this basis.
Energy Technology Data Exchange (ETDEWEB)
Cotton, Stephen J.; Igumenshchev, Kirill; Miller, William H., E-mail: millerwh@berkeley.edu [Department of Chemistry and Kenneth S. Pitzer Center for Theoretical Chemistry, University of California, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
2014-08-28
It has recently been shown [S. J. Cotton and W. H. Miller, J. Chem. Phys. 139, 234112 (2013)] that a symmetrical windowing quasi-classical (SQC) approach [S. J. Cotton and W. H. Miller, J. Phys. Chem. A 117, 7190 (2013)] applied to the Meyer-Miller model [H.-D. Meyer and W. H. Miller, J. Chem. Phys. 70, 3214 (1979)] for the electronic degrees of freedom in electronically non-adiabatic dynamics is capable of quantitatively reproducing quantum mechanical results for a variety of test applications, including cases where “quantum” coherence effects are significant. Here we apply this same SQC methodology, within a flux-side correlation function framework, to calculate thermal rate constants corresponding to several proposed models of electron transfer processes [P. Huo, T. F. Miller III, and D. F. Coker, J. Chem. Phys. 139, 151103 (2013); A. R. Menzeleev, N. Ananth, and T. F. Miller III, J. Chem. Phys. 135, 074106 (2011)]. Good quantitative agreement with Marcus Theory is obtained over several orders of magnitude variation in non-adiabatic coupling. Moreover, the “inverted regime” in thermal rate constants (with increasing bias) known from Marcus Theory is also reproduced with good accuracy by this very simple classical approach. The SQC treatment is also applied to a recent model of photoinduced proton coupled electron transfer [C. Venkataraman, A. V. Soudackov, and S. Hammes-Schiffer, J. Chem. Phys. 131, 154502 (2009)] and population decay of the photoexcited donor state is found to be in reasonable agreement with results calculated via reduced density matrix theory.
Energy Technology Data Exchange (ETDEWEB)
Tran, H.N., E-mail: tranngochoang@tdt.edu.vn [Division of Nuclear Physics, Ton Duc Thang University, Tan Phong Ward, District 7, Ho Chi Minh City (Viet Nam); Faculty of Applied Sciences, Ton Duc Thang University, Tan Phong Ward, District 7, Ho Chi Minh City (Viet Nam); Dao, D.D. [Division of Nuclear Physics, Ton Duc Thang University, Tan Phong Ward, District 7, Ho Chi Minh City (Viet Nam); Faculty of Applied Sciences, Ton Duc Thang University, Tan Phong Ward, District 7, Ho Chi Minh City (Viet Nam); Incerti, S. [Division of Nuclear Physics, Ton Duc Thang University, Tan Phong Ward, District 7, Ho Chi Minh City (Viet Nam); Faculty of Applied Sciences, Ton Duc Thang University, Tan Phong Ward, District 7, Ho Chi Minh City (Viet Nam); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); Université de Bordeaux, CENBG, UMR 5797, F-33170 Gradignan (France); Bernal, M.A. [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, SP (Brazil); Karamitros, M. [CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); Université de Bordeaux, CENBG, UMR 5797, F-33170 Gradignan (France); Nhan Hao, T.V. [Center of Research and Development, Duy Tan University, K7/25 Quang Trung, Danang (Viet Nam); Center for Theoretical and Computational Physics, College of Education, Hue University, 34 Le Loi Street, Hue City (Viet Nam); Dang, T.M. [VNUHCM-University of Science (Viet Nam); Francis, Z. [Saint Joseph University, Beyrouth (Lebanon)
2016-01-01
In this work, we present a derivation of cross sections for single ionization and electron capture processes within the Classical Trajectory Monte Carlo (CTMC) approach. Specifically, we have used a potential stemming from an ab initio calculation in Green et al.’s framework to describe the dynamics of the water molecule system. Proposing a modified version of the Classical Over-Barrier (COB) potential, we have found that a cut-off of roughly 28 a.u. on the initial distance of the projectile produced a reasonable accuracy. A global agreement has been obtained in our calculations compared to experimental and other theoretical results for C{sup 6+} ion energies ranging from 10 keV/u to 10 MeV/u.
Electron density of states of Fe-based superconductors: Quantum trajectory Monte Carlo method
Kashurnikov, V. A.; Krasavin, A. V.; Zhumagulov, Ya. V.
2016-03-01
The spectral and total electron densities of states in two-dimensional FeAs clusters, which simulate iron-based superconductors, have been calculated using the generalized quantum Monte Carlo algorithm within the full two-orbital model. Spectra have been reconstructed by solving the integral equation relating the Matsubara Green's function and spectral density by the method combining the gradient descent and Monte Carlo algorithms. The calculations have been performed for clusters with dimensions up to 10 × 10 FeAs cells. The profiles of the Fermi surface for the entire Brillouin zone have been presented in the quasiparticle approximation. Data for the total density of states near the Fermi level have been obtained. The effect of the interaction parameter, size of the cluster, and temperature on the spectrum of excitations has been studied.
Institute of Scientific and Technical Information of China (English)
Zhao Di; Li Fu-Li
2013-01-01
We theoretically investigate high-order harmonic generation by employing strong-field approximation (SFA) and present a new approach to the extension of the high-order harmonic cutoff frequency via an exploration of the dependence of high-order harmonic generation on the waveform of laser fields.The dependence is investigated via detailed analysis of the classical trajectories of the ionized electron moving in the continuum in the velocity-position plane.The classical trajectory consists of three sections (Acceleration Away,Deceleration Away,and Acceleration Back),and their relationship with the electron recollision energy is investigated.The analysis of classical trajectories indicates that,besides the final (Acceleration Back) section,the electron recollision energy also relies on the previous two sections.We simultaneously optimize the waveform in all three sections to increase the electron recollision energy,and an extension of the cutoff frequency up to Ip + 20.26Up is presented with a theoretically synthesized waveform of the laser field.
Trajectory approach to the Schrödinger–Langevin equation with linear dissipation for ground states
Energy Technology Data Exchange (ETDEWEB)
Chou, Chia-Chun, E-mail: ccchou@mx.nthu.edu.tw
2015-11-15
The Schrödinger–Langevin equation with linear dissipation is integrated by propagating an ensemble of Bohmian trajectories for the ground state of quantum systems. Substituting the wave function expressed in terms of the complex action into the Schrödinger–Langevin equation yields the complex quantum Hamilton–Jacobi equation with linear dissipation. We transform this equation into the arbitrary Lagrangian–Eulerian version with the grid velocity matching the flow velocity of the probability fluid. The resulting equation is simultaneously integrated with the trajectory guidance equation. Then, the computational method is applied to the harmonic oscillator, the double well potential, and the ground vibrational state of methyl iodide. The excellent agreement between the computational and the exact results for the ground state energies and wave functions shows that this study provides a synthetic trajectory approach to the ground state of quantum systems.
Long-Time Asymptotics of a Bohmian Scalar Quantum Field in de Sitter Space-Time
Tumulka, Roderich
2015-01-01
We consider a model quantum field theory with a scalar quantum field in de Sitter space-time in a Bohmian version with a field ontology, i.e., an actual field configuration $\\varphi({\\bf x},t)$ guided by a wave function on the space of field configurations. We analyze the asymptotics at late times ($t\\to\\infty$) and provide reason to believe that for more or less any wave function and initial field configuration, every Fourier coefficient $\\varphi_{\\bf k}(t)$ of the field is asymptotically of the form $c_{\\bf k}\\sqrt{1+{\\bf k}^2 \\exp(-2Ht)/H^2}$, where the limiting coefficients $c_{\\bf k}=\\varphi_{\\bf k}(\\infty)$ are independent of $t$ and $H$ is the Hubble constant quantifying the expansion rate of de Sitter space-time. In particular, every field mode $\\varphi_{\\bf k}$ possesses a limit as $t\\to\\infty$ and thus "freezes." This result is relevant to the question whether Boltzmann brains form in the late universe according to this theory, and supports that they do not.
Hernandez-Zapata, Sergio; 10.1007/s10701-010-9413-7
2010-01-01
A completely Lorentz-invariant Bohmian model has been proposed recently for the case of a system of non-interacting spinless particles, obeying Klein-Gordon equations. It is based on a multi-temporal formalism and on the idea of treating the squared norm of the wave function as a space-time probability density. The particle's configurations evolve in space-time in terms of a parameter {\\sigma}, with dimensions of time. In this work this model is further analyzed and extended to the case of an interaction with an external electromagnetic field. The physical meaning of {\\sigma} is explored. Two special situations are studied in depth: (1) the classical limit, where the Einsteinian Mechanics of Special Relativity is recovered and the parameter {\\sigma} is shown to tend to the particle's proper time; and (2) the non-relativistic limit, where it is obtained a model very similar to the usual non-relativistic Bohmian Mechanics but with the time of the frame of reference replaced by {\\sigma} as the dynamical temporal...
Chattaraj, Pratim Kumar
2010-01-01
The application of quantum mechanics to many-particle systems has been an active area of research in recent years as researchers have looked for ways to tackle difficult problems in this area. The quantum trajectory method provides an efficient computational technique for solving both stationary and time-evolving states, encompassing a large area of quantum mechanics. Quantum Trajectories brings the expertise of an international panel of experts who focus on the epistemological significance of quantum mechanics through the quantum theory of motion.Emphasizing a classical interpretation of quan
Wang, Lei; Jakowski, Jacek; Garashchuk, Sophya; Sumpter, Bobby G
2016-09-13
The experimentally observed effect of selective deuterium substitution on the open circuit voltage for a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM; Nat. Commun. 2014, 5, 3180) is explored using a 221-atom model of a polymer-wrapped PCBM molecule. The protonic and deuteronic wave functions for the H/D isotopologues of the hexyl side chains are described within a quantum trajectory/electronic structure approach where the dynamics is performed with newly developed nonlinear corrections to the quantum forces, necessary to describe the nuclear wave functions; the classical forces are generated with a density functional tight binding method. The resulting protonic and deuteronic time-dependent wave functions are used to assess the effects of isotopic substitution (deuteration) on the energy gaps relevant to the charge transfer for the donor and acceptor electronic states. While the isotope effect on the electronic energy levels is found negligible, the quantum-induced fluctuations of the energy gap between the charge transfer and charge separated states due to nuclear wave functions may account for experimental trends by promoting charge transfer in P3HT:PCBM and increasing charge recombination on the donor in the deuterium substituted P3HT:PCBM.
Directory of Open Access Journals (Sweden)
Takahashi Hiromi
2015-01-01
Full Text Available The electron-cyclotron (EC -beam refraction due to the presence of plasma was investigated in the Large Helical Device. The transmitted-EC-beam measurement system was constructed and the beam pattern on the opposite side of the irradiated surface was measured using an IR camera. Clear dependence of the EC-beam refraction on the electron density was observed and the beam shift in the toroidal direction showed good agreement with the ray-trace calculation of TRAVIS. The influence of the peripheral density profile and the thermal effect on the beam refraction were discussed.
Energy Technology Data Exchange (ETDEWEB)
Sousa, A.A.; Hohmann-Marriott, M.F.; Zhang, G. [Laboratory of Bioengineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bldg. 13, Rm. 3N17, 13 South Drive, Bethesda, MD 20892-5766 (United States); Leapman, R.D. [Laboratory of Bioengineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bldg. 13, Rm. 3N17, 13 South Drive, Bethesda, MD 20892-5766 (United States)], E-mail: leapmanr@mail.nih.gov
2009-02-15
A Monte Carlo electron-trajectory calculation has been implemented to assess the optimal detector configuration for scanning transmission electron microscopy (STEM) tomography of thick biological sections. By modeling specimens containing 2 and 3 at% osmium in a carbon matrix, it was found that for 1-{mu}m-thick samples the bright-field (BF) and annular dark-field (ADF) signals give similar contrast and signal-to-noise ratio provided the ADF inner angle and BF outer angle are chosen optimally. Spatial resolution in STEM imaging of thick sections is compromised by multiple elastic scattering which results in a spread of scattering angles and thus a spread in lateral distances of the electrons leaving the bottom surface. However, the simulations reveal that a large fraction of these multiply scattered electrons are excluded from the BF detector, which results in higher spatial resolution in BF than in high-angle ADF images for objects situated towards the bottom of the sample. The calculations imply that STEM electron tomography of thick sections should be performed using a BF rather than an ADF detector. This advantage was verified by recording simultaneous BF and high-angle ADF STEM tomographic tilt series from a stained 600-nm-thick section of C. elegans. It was found that loss of spatial resolution occurred markedly at the bottom surface of the specimen in the ADF STEM but significantly less in the BF STEM tomographic reconstruction. Our results indicate that it might be feasible to use BF STEM tomography to determine the 3D structure of whole eukaryotic microorganisms prepared by freeze-substitution, embedding, and sectioning.
Complex dynamics in diatomic molecules. Part II: Quantum trajectories
Energy Technology Data Exchange (ETDEWEB)
Yang, C.-D. [Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 701, Taiwan (China)], E-mail: cdyang@mail.ncku.edu.tw; Weng, H.-J. [Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan 701, Taiwan (China)], E-mail: principlex@yahoo.com.tw
2008-10-15
The second part of this paper deals with quantum trajectories in diatomic molecules, which has not been considered before in the literature. Morse potential serves as a more accurate function than a simple harmonic oscillator for illustrating a realistic picture about the vibration of diatomic molecules. However, if we determine molecular dynamics by integrating the classical force equations derived from a Morse potential, we will find that the resulting trajectories do not consist with the probabilistic prediction of quantum mechanics. On the other hand, the quantum trajectory determined by Bohmian mechanics [Bohm D. A suggested interpretation of the quantum theory in terms of hidden variable. Phys. Rev. 1952;85:166-179] leads to the conclusion that a diatomic molecule is motionless in all its vibrational eigen-states, which also contradicts probabilistic prediction of quantum mechanics. In this paper, we point out that the quantum trajectory of a diatomic molecule completely consistent with quantum mechanics does exist and can be solved from the quantum Hamilton equations of motion derived in Part I, which is based on a complex-space formulation of fractal spacetime [El Naschie MS. A review of E-Infinity theory and the mass spectrum of high energy particle physics. Chaos, Solitons and Fractals 2004;19:209-36; El Naschie MS. E-Infinity theory - some recent results and new interpretations. Chaos, Solitons and Fractals 2006;29:845-853; El Naschie MS. The concepts of E-infinity. An elementary introduction to the cantorian-fractal theory of quantum physics. Chaos, Solitons and Fractals 2004;22:495-511; El Naschie MS. SU(5) grand unification in a transfinite form. Chaos, Solitons and Fractals 2007;32:370-374; Nottale L. Fractal space-time and microphysics: towards a theory of scale relativity. Singapore: World Scientific; 1993; Ord G. Fractal space time and the statistical mechanics of random works. Chaos, Soiltons and Fractals 1996;7:821-843] approach to quantum
Simulation of Electrons' Trajectories in the Lunar Electric and Magnetic Field%太阳风电子在月表电磁场中的运动
Institute of Scientific and Technical Information of China (English)
冯永勇; 赵华; 刘振兴
2011-01-01
月表磁异常区的分布是月球探测工程的重要内容.但是由于月表电磁环境错综复杂,通常认为月球表面在特殊的空间天气条件下会带有数千伏电压.以往的空间研究已经证实,表面的带电与放电容易造成卫星仪器的异常或失联.月表电场对电子反射法有重要影响,研究分析不同电磁条件下太阳风电子的运动轨迹,对月表环境(电磁环境,太阳风条件,等离子体参数等)的研究可以更加深入细致.通过模拟向月表运动的太阳风电子的运动轨迹,分析了月表电磁环境的改变对太阳风电子反射的影响,并着重研究了月表电场对电子反射法遥感探测月表磁异常的影响,为探测月表电磁环境提供了重要的信息.%The increasing interest in lunar exploration requires a better understanding of environment at the lunar surface. Like any object in plasma, the surface of the Moon charges to an electric potential that minimizes the total incident current. Surface charging is an universal process affecting all airless regolith-covered bodies. However, there are still many details that remain unclear and need to be discussed to understand those possible processes such as ion sputtering and electrically-driven dust transport. There are also many subjects that require further study, such as the temporal and spatial variation of lunar surface charging. Simulation and analysis of trajectories of the electrons under different conditions would help to predict surface potential, which in turn would benefit the understanding of the lunar environment. In this paper, the solar wind electrons which are moving toward the moon surface are traced to study the effect of surface potential on solar wind electrons reflected by the lunar crustal magnetic field. Statistic of number of electrons that reflected under different conditions is also analyzed. The calculations and simulations show that the variation of either magnetic field or potential
Collins, P.J.
2005-01-01
In this paper, we present a general framework for describing and studying hybrid systems. We represent the trajectories of the system as functions on a hybrid time domain, and the system itself by its trajectory space, which is the set of all possible trajectories. The trajectory space is given a na
Computing with spatial trajectories
2011-01-01
Covers the fundamentals and the state-of-the-art research inspired by the spatial trajectory data Readers are provided with tutorial-style chapters, case studies and references to other relevant research work This is the first book that presents the foundation dealing with spatial trajectories and state-of-the-art research and practices enabled by trajectories
Lunar and interplanetary trajectories
Biesbroek, Robin
2016-01-01
This book provides readers with a clear description of the types of lunar and interplanetary trajectories, and how they influence satellite-system design. The description follows an engineering rather than a mathematical approach and includes many examples of lunar trajectories, based on real missions. It helps readers gain an understanding of the driving subsystems of interplanetary and lunar satellites. The tables and graphs showing features of trajectories make the book easy to understand. .
Institute of Scientific and Technical Information of China (English)
Subbaiah Annadurai; Thiyagarajan Kalyani; Vincent Rajkumar Dare; Durairaj Gnanaraj Thomas
2008-01-01
Membrane computing is a branch of natural computing aiming to abstract computing ideas for the structure and the functioning of living cells as well as from the way the cells are organized in tissues or higher-order structures.Trajectories are used as a tool for modeling language operations and other related objects.A trajectory P system consists of a membrane structure in which the object in each membrane is a collection of words and the evolutionary rules are given in terms of trajectories.In this paper,we present some properties of trajectory P systems.
Geometric diffusion of quantum trajectories.
Yang, Fan; Liu, Ren-Bao
2015-07-16
A quantum object can acquire a geometric phase (such as Berry phases and Aharonov-Bohm phases) when evolving along a path in a parameter space with non-trivial gauge structures. Inherent to quantum evolutions of wavepackets, quantum diffusion occurs along quantum trajectories. Here we show that quantum diffusion can also be geometric as characterized by the imaginary part of a geometric phase. The geometric quantum diffusion results from interference between different instantaneous eigenstate pathways which have different geometric phases during the adiabatic evolution. As a specific example, we study the quantum trajectories of optically excited electron-hole pairs in time-reversal symmetric insulators, driven by an elliptically polarized terahertz field. The imaginary geometric phase manifests itself as elliptical polarization in the terahertz sideband generation. The geometric quantum diffusion adds a new dimension to geometric phases and may have applications in many fields of physics, e.g., transport in topological insulators and novel electro-optical effects.
Rodríguez-Cabello, Cristina; González-Pola, Cesar; Sánchez, Francisco
2016-09-01
A total of nine leafscale gulper sharks Centrophorus squamosus (Bonnaterre, 1788), were tagged with pop-up, satellite, archival, transmitting tags (PSAT) in the Marine Protected Area (MPA) of El Cachucho (Le Danois Bank) located in waters to the north of Spain, (NE Atlantic). Tags provided data on time, pressure and temperature that were used to examine movement patterns and diving behavior. Data collected from Argo floats in the study area have been used to devise a simple geolocation algorithm to infer the probable routes followed by this species. Tag release points revealed that C. squamosus moved both to the west (Galician waters) and to the north (Porcupine Bank) from the tagging area, suggesting well defined preferred pathways. The inferred trajectories indicated that sharks alternate periods constrained to specific geographical regions with quick and prompt movements covering large distances. Two sharks made conspicuous diurnal vertical migrations being at shallower depths around midnight and at maximum depths at midday, while other sharks did not make vertical migrations. Vertical movements were done smoothly and independently of the fish swimming long-distances or resting in the area. Overall results confirm that this species is highly migratory, supporting speeds of 20 nautical miles.day-1 and well capable to swim and make vertical migrations well above the abyssal plain.
14 CFR 417.207 - Trajectory analysis.
2010-01-01
... potential three-sigma trajectory dispersions about the nominal trajectory. (2) A fuel exhaustion trajectory...) Trajectory model. A final trajectory analysis must use a six-degree of freedom trajectory model to...
Energy Technology Data Exchange (ETDEWEB)
Rintoul, Mark Daniel [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Wilson, Andrew T. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Valicka, Christopher G. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Kegelmeyer, W. Philip [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Shead, Timothy M. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Newton, Benjamin D. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Czuchlewski, Kristina Rodriguez [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
2015-09-01
We want to organize a body of trajectories in order to identify, search for, classify and predict behavior among objects such as aircraft and ships. Existing compari- son functions such as the Fr'echet distance are computationally expensive and yield counterintuitive results in some cases. We propose an approach using feature vectors whose components represent succinctly the salient information in trajectories. These features incorporate basic information such as total distance traveled and distance be- tween start/stop points as well as geometric features related to the properties of the convex hull, trajectory curvature and general distance geometry. Additionally, these features can generally be mapped easily to behaviors of interest to humans that are searching large databases. Most of these geometric features are invariant under rigid transformation. We demonstrate the use of different subsets of these features to iden- tify trajectories similar to an exemplar, cluster a database of several hundred thousand trajectories, predict destination and apply unsupervised machine learning algorithms.
Ornithopter transition trajectories
Dietl, John M.; Garcia, Ephrahim
2010-04-01
The design of stable trim conditions for forward flight and for hover has been achieved. In forward flight, an ornithopter is configured like a conventional airplane or large bird. Its fuselage is essentially horizontal and the wings heave in a vertical plane. In hover, however, the body pitches vertically so that the wing stroke in the horizontal plane. Thrust directed downward, the vehicle remains aloft while the downdraft envelops the tail to provide enough flow for vehicle control and stabilization. To connect these trajectories dynamically is the goal. The naïve approach-to choose two stable trajectories and switch between them-has been accomplished. A new approach is to establish an open-loop trajectory through a trajectory optimization algorithm-optimized for shortest altitude drop, shortest stopping distance, or lowest energy consumption.
Automated Cooperative Trajectories
Hanson, Curt; Pahle, Joseph; Brown, Nelson
2015-01-01
This presentation is an overview of the Automated Cooperative Trajectories project. An introduction to the phenomena of wake vortices is given, along with a summary of past research into the possibility of extracting energy from the wake by flying close parallel trajectories. Challenges and barriers to adoption of civilian automatic wake surfing technology are identified. A hardware-in-the-loop simulation is described that will support future research. Finally, a roadmap for future research and technology transition is proposed.
Compressing spatio-temporal trajectories
DEFF Research Database (Denmark)
Gudmundsson, Joachim; Katajainen, Jyrki; Merrick, Damian
2009-01-01
A trajectory is a sequence of locations, each associated with a timestamp, describing the movement of a point. Trajectory data is becoming increasingly available and the size of recorded trajectories is getting larger. In this paper we study the problem of compressing planar trajectories such tha...
Moon Landing Trajectory Optimization
Directory of Open Access Journals (Sweden)
Ibrahim Mustafa MEHEDI
2016-03-01
Full Text Available Trajectory optimization is a crucial process during the planning phase of a spacecraft landing mission. Once a trajectory is determined, guidance algorithms are created to guide the vehicle along the given trajectory. Because fuel mass is a major driver of the total vehicle mass, and thus mission cost, the objective of most guidance algorithms is to minimize the required fuel consumption. Most of the existing algorithms are termed as “near-optimal” regarding fuel expenditure. The question arises as to how close to optimal are these guidance algorithms. To answer this question, numerical trajectory optimization techniques are often required. With the emergence of improved processing power and the application of new methods, more direct approaches may be employed to achieve high accuracy without the associated difficulties in computation or pre-existing knowledge of the solution. An example of such an approach is DIDO optimization. This technique is applied in the current research to find these minimum fuel optimal trajectories.
Weak Values from Displacement Currents in Multiterminal Electron Devices
Marian, D.; Zanghı, N.; Oriols, X.
2016-03-01
Weak values allow the measurement of observables associated with noncommuting operators. Up to now, position-momentum weak values have been mainly developed for (relativistic) photons. In this Letter, a proposal for the measurement of such weak values in typical electronic devices is presented. Inspired by the Ramo-Shockley-Pellegrini theorem that provides a relation between current and electron velocity, it is shown that the displacement current measured in multiterminal configurations can provide either a weak measurement of the momentum or strong measurement of position. This proposal opens new opportunities for fundamental and applied physics with state-of-the-art electronic technology. As an example, a setup for the measurement of the Bohmian velocity of (nonrelativistic) electrons is presented and tested with numerical experiments.
Trajectory Based Traffic Analysis
DEFF Research Database (Denmark)
Krogh, Benjamin Bjerre; Andersen, Ove; Lewis-Kelham, Edwin
2013-01-01
-and-click analysis, due to a novel and efficient indexing structure. With the web-site daisy.aau.dk/its/spqdemo/we will demonstrate several analyses, using a very large real-world data set consisting of 1.9 billion GPS records (1.5 million trajectories) recorded from more than 13000 vehicles, and touching most...
Directory of Open Access Journals (Sweden)
Maike Buchin
2015-03-01
Full Text Available The collective motion of a set of moving entities like people, birds, or other animals, is characterized by groups arising, merging, splitting, and ending. Given the trajectories of these entities, we define and model a structure that captures all of such changes using the Reeb graph, a concept from topology. The trajectory grouping structure has three natural parameters that allow more global views of the data in group size, group duration, and entity inter-distance. We prove complexity bounds on the maximum number of maximal groups that can be present, and give algorithms to compute the grouping structure efficiently. We also study how the trajectory grouping structure can be made robust, that is, how brief interruptions of groups can be disregarded in the global structure, adding a notion of persistence to the structure. Furthermore, we showcase the results of experiments using data generated by the NetLogo flocking model and from the Starkey project. The Starkey data describe the movement of elk, deer, and cattle. Although there is no ground truth for the grouping structure in this data, the experiments show that the trajectory grouping structure is plausible and has the desired effects when changing the essential parameters. Our research provides the first complete study of trajectory group evolvement, including combinatorial,algorithmic, and experimental results.
Sanz, A S; Gonzalez-Lezana, T
2011-01-01
In this work, we investigate the existence of transition state resonances on atom-diatom reactive collisions from a time-dependent perspective, stressing the role of quantum trajectories as a tool to analyze this phenomenon. As it is shown, when one focusses on the quantum probability current density, new dynamical information about the reactive process can be extracted. In order to detect the effects of the different rotational populations and their dynamics/coherences, we have considered a reduced two-dimensional dynamics obtained from the evolution of a full three-dimensional quantum time-dependent wave packet associated with a particular angle. This reduction procedure provides us with some information about the entanglement between the radial (r,R) degrees of freedom and the angular one (\\gamma), which here can be considered as a bath. The here proposed combined approach has been applied to study the F+HD reaction, for which the FH+D product channel exhibits a resonance-mediated dynamics.
Clustering vessel trajectories with alignment kernels under trajectory compression
de Vries, G.; van Someren, M.
2010-01-01
In this paper we apply a selection of alignment measures, such as dynamic time warping and edit distance, to the problem of clustering vessel trajectories. Vessel trajectories are an example of moving object trajectories, which have recently become an important research topic. The alignment measures
Analysis of Controlled Trajectory Optimization for Canard Trajectory Correction Fuze
Institute of Scientific and Technical Information of China (English)
郭泽荣; 李世义; 申强
2004-01-01
The optimization method of the canard trajectory correction fuze's controlled trajectory phase is researched by using the aerodynamics of aerocraft and the optimal control theory, the trajectory parameters of the controlled trajectory phase based on the least energy cost are determined. On the basis of determining the control starting point and the target point, the optimal trajectory and the variation rule of the normal overload with the least energy cost are provided, when there is no time restriction in the simulation process. The results provide a theoretical basis for the structure design of the canard mechanism.
Semantic enrichment of GPS trajectories
Graaff, de Victor; Keulen, van Maurice; By, de Rolf
2012-01-01
Semantic annotation of GPS trajectories helps us to recognize the interests of the creator of the GPS trajectories. Automating this trajectory annotation circumvents the requirement of additional user input. To annotate the GPS traces automatically, two types of automated input are required: 1) a co
Interference, Reduced Action, and Trajectories
Floyd, Edward R.
2007-09-01
Instead of investigating the interference between two stationary, rectilinear wave functions in a trajectory representation by examining the trajectories of the two rectilinear wave functions individually, we examine a dichromatic wave function that is synthesized from the two interfering wave functions. The physics of interference is contained in the reduced action for the dichromatic wave function. As this reduced action is a generator of the motion for the dichromatic wave function, it determines the dichromatic wave function’s trajectory. The quantum effective mass renders insight into the behavior of the trajectory. The trajectory in turn renders insight into quantum nonlocality.
Young adults' trajectories of Ecstasy use: a population based study.
Smirnov, Andrew; Najman, Jake M; Hayatbakhsh, Reza; Plotnikova, Maria; Wells, Helene; Legosz, Margot; Kemp, Robert
2013-11-01
Young adults' Ecstasy use trajectories have important implications for individual and population-level consequences of Ecstasy use, but little relevant research has been conducted. This study prospectively examines Ecstasy trajectories in a population-based sample. Data are from the Natural History Study of Drug Use, a retrospective/prospective cohort study conducted in Australia. Population screening identified a probability sample of Ecstasy users aged 19-23 years. Complete data for 30 months of follow-up, comprising 4 time intervals, were available for 297 participants (88.4% of sample). Trajectories were derived using cluster analysis based on recent Ecstasy use at each interval. Trajectory predictors were examined using a generalized ordered logit model and included Ecstasy dependence (World Mental Health Composite International Diagnostic Instrument), psychological distress (Hospital Anxiety Depression Scale), aggression (Young Adult Self Report) and contextual factors (e.g. attendance at electronic/dance music events). Three Ecstasy trajectories were identified (low, intermediate and high use). At its peak, the high-use trajectory involved 1-2 days Ecstasy use per week. Decreasing frequency of use was observed for intermediate and high-use trajectories from 12 months, independently of market factors. Intermediate and high-use trajectory membership was predicted by past Ecstasy consumption (>70 pills) and attendance at electronic/dance music events. High-use trajectory members were unlikely to have used Ecstasy for more than 3 years and tended to report consistently positive subjective effects at baseline. Given the social context and temporal course of Ecstasy use, Ecstasy trajectories might be better understood in terms of instrumental rather than addictive drug use patterns.
Trajectory Optimization: OTIS 4
Riehl, John P.; Sjauw, Waldy K.; Falck, Robert D.; Paris, Stephen W.
2010-01-01
The latest release of the Optimal Trajectories by Implicit Simulation (OTIS4) allows users to simulate and optimize aerospace vehicle trajectories. With OTIS4, one can seamlessly generate optimal trajectories and parametric vehicle designs simultaneously. New features also allow OTIS4 to solve non-aerospace continuous time optimal control problems. The inputs and outputs of OTIS4 have been updated extensively from previous versions. Inputs now make use of objectoriented constructs, including one called a metastring. Metastrings use a greatly improved calculator and common nomenclature to reduce the user s workload. They allow for more flexibility in specifying vehicle physical models, boundary conditions, and path constraints. The OTIS4 calculator supports common mathematical functions, Boolean operations, and conditional statements. This allows users to define their own variables for use as outputs, constraints, or objective functions. The user-defined outputs can directly interface with other programs, such as spreadsheets, plotting packages, and visualization programs. Internally, OTIS4 has more explicit and implicit integration procedures, including high-order collocation methods, the pseudo-spectral method, and several variations of multiple shooting. Users may switch easily between the various methods. Several unique numerical techniques such as automated variable scaling and implicit integration grid refinement, support the integration methods. OTIS4 is also significantly more user friendly than previous versions. The installation process is nearly identical on various platforms, including Microsoft Windows, Apple OS X, and Linux operating systems. Cross-platform scripts also help make the execution of OTIS and post-processing of data easier. OTIS4 is supplied free by NASA and is subject to ITAR (International Traffic in Arms Regulations) restrictions. Users must have a Fortran compiler, and a Python interpreter is highly recommended.
Going Ballistic: Bullet Trajectories
Directory of Open Access Journals (Sweden)
Amanda Wade
2011-01-01
Full Text Available This project seeks to answer at what angle does a gun marksman have to aim in order to hit the center of a target one meter off the ground and 1000 meters away? We begin by modeling the bullet's trajectory using Euler's method with the help of a Microsoft Excel spreadsheet solver, and then systematically search for the angle corresponding to the center of the target. It was found that a marksman shooting a target 1000 meters away and 1 meter off the ground has to aim the rifle 0.436° above horizontal to hit the center.
Trajectories in parallel optics.
Klapp, Iftach; Sochen, Nir; Mendlovic, David
2011-10-01
In our previous work we showed the ability to improve the optical system's matrix condition by optical design, thereby improving its robustness to noise. It was shown that by using singular value decomposition, a target point-spread function (PSF) matrix can be defined for an auxiliary optical system, which works parallel to the original system to achieve such an improvement. In this paper, after briefly introducing the all optics implementation of the auxiliary system, we show a method to decompose the target PSF matrix. This is done through a series of shifted responses of auxiliary optics (named trajectories), where a complicated hardware filter is replaced by postprocessing. This process manipulates the pixel confined PSF response of simple auxiliary optics, which in turn creates an auxiliary system with the required PSF matrix. This method is simulated on two space variant systems and reduces their system condition number from 18,598 to 197 and from 87,640 to 5.75, respectively. We perform a study of the latter result and show significant improvement in image restoration performance, in comparison to a system without auxiliary optics and to other previously suggested hybrid solutions. Image restoration results show that in a range of low signal-to-noise ratio values, the trajectories method gives a significant advantage over alternative approaches. A third space invariant study case is explored only briefly, and we present a significant improvement in the matrix condition number from 1.9160e+013 to 34,526.
Differentially Private Trajectory Data Publication
Chen, Rui; Desai, Bipin C
2011-01-01
With the increasing prevalence of location-aware devices, trajectory data has been generated and collected in various application domains. Trajectory data carries rich information that is useful for many data analysis tasks. Yet, improper publishing and use of trajectory data could jeopardize individual privacy. However, it has been shown that existing privacy-preserving trajectory data publishing methods derived from partition-based privacy models, for example k-anonymity, are unable to provide sufficient privacy protection. In this paper, motivated by the data publishing scenario at the Societe de transport de Montreal (STM), the public transit agency in Montreal area, we study the problem of publishing trajectory data under the rigorous differential privacy model. We propose an efficient data-dependent yet differentially private sanitization algorithm, which is applicable to different types of trajectory data. The efficiency of our approach comes from adaptively narrowing down the output domain by building...
Periodic billiard trajectories in polygons: generating mechanisms
Vorobets, Ya B.; Gal'perin, G. A.; Stepin, Anatolii M.
1992-06-01
CONTENTSIntroduction §1. Billiard trajectories in a plane domain §2. Fagnano's problem. Mechanical interpretations of periodic trajectories in triangles §3. An extremal property of billiard trajectories. Birkhoff's theorem. The non-existence of a unified construction of periodic trajectories in obtuse triangles §4. 'Perpendicular' trajectories in obtuse triangles of special shape §5. 'Perpendicular' trajectories in rational polygons and polyhedra §6. Stable trajectories §7. Stable perpendicular trajectories §8. Isolated trajectories §9. Isolated trajectories in acute and obtuse triangles. The bifurcation diagram of isolated trajectories (a 'hang-glider' configuration) §10. The density of F-triangles in a neighbourhood of (0, 0) §11. Generalization of the construction of isolated trajectories in obtuse triangles §12. Stable and unstable billiard trajectories in plane Weyl chambers §13. A criterion for the stability of periodic trajectories in a regular hexagonConclusionReferences
Interference, reduced action, and trajectories
Floyd, E R
2006-01-01
Instead of investigating the interference between two stationary, rectilinear wave functions in a trajectory representation by examining the two rectilinear wave functions individually, we examine a dichromatic wave function that is synthesized from the two interfering wave functions. The physics of interference is contained in the reduced action for the dichromatic wave function. As this reduced action is a generator of the motion for the dichromatic wave function, it determines the dichromatic wave function's trajectory. The quantum effective mass renders insight into the behavior of the trajectory. The trajectory in turn renders insight into quantum nonlocality.
Allen, Adriana; Hofmann, Pascale; Teh, Tse-Hui
2017-01-01
Water is an essential element in the future of cities. It shapes cities’ locations, form, ecology, prosperity and health. The changing nature of urbanisation, climate change, water scarcity, environmental values, globalisation and social justice mean that the models of provision of water services and infrastructure that have dominated for the past two centuries are increasingly infeasible. Conventional arrangements for understanding and managing water in cities are being subverted by a range of natural, technological, political, economic and social changes. The prognosis for water in cities remains unclear, and multiple visions and discourses are emerging to fill the space left by the certainty of nineteenth century urban water planning and engineering. This book documents a sample of those different trajectories, in terms of water transformations, option, services and politics. Water is a key element shaping urban form, economies and lifestyles, part of the ongoing transformation of cities. Cities are face...
Simulation of molecular transitions using classical trajectories
Energy Technology Data Exchange (ETDEWEB)
Donoso, A.; Martens, C. C. [University of California, California (United States)
2001-03-01
In the present work, we describe the implementation of a semiclassical method to study physical-chemical processes in molecular systems where electronic state transitions and quantum coherence play a dominant role. The method is based on classical trajectory propagation on the underlying coupled electronic surfaces and is derived from the semiclassical limit of the quantum Liouville equation. Unlike previous classical trajectory-based methods, quantum electronic coherence are treated naturally within this approach as complex weighted trajectory ensembles propagating on the average electronic surfaces. The method is tested on a model problem consisting of one-dimensional motion on two crossing electronic surfaces. Excellent agreement is obtained when compared to the exact results obtained by wave packet propagation. The method is applied to model quantum wave packet interferometry, where two wave packets, differing only in a relative phase, collide in the region where the two electronic surfaces cross. The dependence of the resulting population transfer on the initial relative phase of the wave packets is perfectly captured by our classical trajectory method. Comparison with an alternative method, surface hopping, shows that our approach is appropriate for modelling quantum interference phenomena. [Spanish] En este trabajo se describe la implementacion de un metodo semiclasico para estudiar procesos fisicos-quimicos en sistemas moleculares donde las transiciones entre estados electronicos y las coherencias cuanticas juegan un papel predominante. El metodo se basa en la propagacion de trayectorias clasicas sobre las correspondientes superficies electronicas acopladas y se deriva a partir del limite semiclasico de la ecuacion cuantica de Liouville. A diferencia de metodos previos basados en trayectoria clasica, dentro de este esquema, las coherencias electronicas cuanticas son tratadas de manera natural como ensamble de trayectorias con pesos complejos, moviendose en
Segmenting Trajectories by Movement States
Buchin, M.; Kruckenberg, H.; Kölzsch, A.; Timpf, S.; Laube, P.
2013-01-01
Dividing movement trajectories according to different movement states of animals has become a challenge in movement ecology, as well as in algorithm development. In this study, we revisit and extend a framework for trajectory segmentation based on spatio-temporal criteria for this purpose. We adapt
Geometric Algorithms for Trajectory Analysis
Staals, Frank
2015-01-01
Technology such as the Global Positing System (GPS) has made tracking moving entities easy and cheap. As a result there is a large amount of trajectory data available, and an increasing demand on tools and techniques to analyze such data. We consider several analysis tasks for trajectory data, and d
Aircraft Trajectory Optimization Using Parametric Optimization Theory
Valenzuela Romero, Alfonso
2012-01-01
In this thesis, a study of the optimization of aircraft trajectories using parametric optimization theory is presented. To that end, an approach based on the use of predefined trajectory patterns and parametric optimization is proposed. The trajectory pat
Trajectory Design to Benefit Trajectory-Based Surface Operations Project
National Aeronautics and Space Administration — Trajectory-based operations constitute a key mechanism considered by the Joint Planning and Development Office (JPDO) for managing traffic in high-density or...
Trajectory Design to Benefit Trajectory-Based Surface Operations Project
National Aeronautics and Space Administration — Trajectory-based operations constitute a key mechanism considered by the Joint Planning and Development Office (JPDO) for managing traffic in high-density or...
Fractional trajectories: Decorrelation versus friction
Svenkeson, A.; Beig, M. T.; Turalska, M.; West, B. J.; Grigolini, P.
2013-11-01
The fundamental connection between fractional calculus and subordination processes is explored and affords a physical interpretation of a fractional trajectory, that being an average over an ensemble of stochastic trajectories. Heretofore what has been interpreted as intrinsic friction, a form of non-Markovian dissipation that automatically arises from adopting the fractional calculus, is shown to be a manifestation of decorrelations between trajectories. We apply the general theory developed herein to the Lotka-Volterra ecological model, providing new insight into the final equilibrium state. The relaxation time to achieve this state is also considered.
Adaptive Trajectory Design (ATD) Project
National Aeronautics and Space Administration — Mission design within unstable/stable regions needs unification of individual trajectories from different dynamical regimes. NASA needs an automated process to blend...
Galileo's Trajectory with Mild Resistance
Groetsch, C. W.
2012-01-01
An aspect of Galileo's classical trajectory that persists in a simple resistance model is noted. The resistive model provides a case study for the classroom analysis of limiting behaviour of an implicitly defined function. (Contains 1 note.)
Trajectories in Operating a Handheld Tool
Heuer, Herbert; Sulzenbruck, Sandra
2009-01-01
The authors studied the trajectories of the hand and of the tip of a handheld sliding first-order lever in aiming movements. With this kind of tool, straight trajectories of the hand are generally associated with curved trajectories of the tip of the lever and vice versa. Trajectories of the tip of the lever exhibited smaller deviations from…
Trajectories in Operating a Handheld Tool
Heuer, Herbert; Sulzenbruck, Sandra
2009-01-01
The authors studied the trajectories of the hand and of the tip of a handheld sliding first-order lever in aiming movements. With this kind of tool, straight trajectories of the hand are generally associated with curved trajectories of the tip of the lever and vice versa. Trajectories of the tip of the lever exhibited smaller deviations from…
Designing Complex Interplanetary Trajectories for the Global Trajectory Optimization Competitions
Izzo, Dario; Simões, Luís F; Märtens, Marcus
2015-01-01
The design of interplanetary trajectories often involves a preliminary search for options that are later refined into one final selected trajectory. It is this broad search that, often being intractable, inspires the international event called Global Trajectory Optimization Competition. In the first part of this chapter, we introduce some fundamental problems of space flight mechanics, building blocks of any attempt to participate successfully in these competitions and we describe the use of the open source software PyKEP to assemble them into a final global solution strategy. In the second part, we formulate an instance of a multiple asteroid rendezvous problem, related to the 7th edition of the competition, and we show step by step how to build a possible solution strategy. We introduce two new techniques useful in the design of this particular mission type: the use of an asteroid phasing value and its surrogates and the efficient computation of asteroid clusters. We show how basic building blocks, sided to...
Complexity of trajectories in rectangular billiards
Baryshnikov, Yu
1994-01-01
To a trajectory of a billiard in a parallelogram we assign its symbolic trajectory --- the sequence of numbers of coordinate planes, to which the faces met by the trajectory are parallel. The complexity of the trajectory is the number of different words of length n occurring in it. We prove that for generic trajectories the complexity is well defined and calculate it, confirming the conjecture of Arnoux, Mauduit, Shiokawa and Tamura[AMST].
Complexity of trajectories in rectangular billiards
Baryshnikov, Yu.
1995-11-01
To a trajectory of the billiard in a cube we assign its symbolic trajectory-the sequence of numbers of coordinate planes, to which the faces met by the trajectory are parallel. The complexity of the trajectory is the number of different words of lengthn occurring in it. We prove that for generic trajectories the complexity is well defined and calculate it, confirming the conjecture of Arnoux, Mauduit, Shiokawa and Tamura [AMST].
Generic trajectory representation and trajectory following for wheeled robots
DEFF Research Database (Denmark)
Kjærgaard, Morten; Andersen, Nils Axel; Ravn, Ole
2014-01-01
This article presents the work towards a purely generic navigation solution for wheeled mobile robots motivated by the following goals: Generic: Works for different types of robots. Configurable: Parameters maps to geometric properties of the robot. Predictable: Well defined where the robot...... will drive. Safe: Avoid fatal collisions. Based on a survey of existing methods and algorithms the article presents a generic way to represent constraints for different types of robots, a generic way to represent trajectories using Bëzier curves, a method to convert the trajectory so it can be driven...
Trajectory generation of space telerobots
Lumia, R.; Wavering, A. J.
1989-01-01
The purpose is to review a variety of trajectory generation techniques which may be applied to space telerobots and to identify problems which need to be addressed in future telerobot motion control systems. As a starting point for the development of motion generation systems for space telerobots, the operation and limitations of traditional path-oriented trajectory generation approaches are discussed. This discussion leads to a description of more advanced techniques which have been demonstrated in research laboratories, and their potential applicability to space telerobots. Examples of this work include systems that incorporate sensory-interactive motion capability and optimal motion planning. Additional considerations which need to be addressed for motion control of a space telerobot are described, such as redundancy resolution and the description and generation of constrained and multi-armed cooperative motions. A task decomposition module for a hierarchical telerobot control system which will serve as a testbed for trajectory generation approaches which address these issues is also discussed briefly.
Trajectory Indexing Using Movement Constraints
DEFF Research Database (Denmark)
Pfoser, D.; Jensen, Christian Søndergaard
2005-01-01
With the proliferation of mobile computing, the ability to index efficiently the movements of mobile objects becomes important. Objects are typically seen as moving in two-dimensional (x,y) space, which means that their movements across time may be embedded in the three-dimensional (x,y,t) space...... is to reduce movements to occur in one spatial dimension. As a consequence, the movement occurs in two-dimensional (x,t) space. The advantages of considering such lower-dimensional trajectories are that the overall size of the data is reduced and that lower-dimensional data is to be indexed. Since off......-the-shelf database management systems typically do not offer higher-dimensional indexing, this reduction in dimensionality allows us to use existing DBMSes to store and index trajectories. Moreover, we argue that, given the right circumstances, indexing these dimensionality-reduced trajectories can be more efficient...
Dynamical Convergence Trajectory in Networks
Institute of Scientific and Technical Information of China (English)
TAN Ning; ZHANG Yun-Jun; OUYANG Qi; GENG Zhi
2005-01-01
@@ It is well known that topology and dynamics are two major aspects to determine the function of a network. We study one of the dynamic properties of a network: trajectory convergence, i.e. how a system converges to its steady state. Using numerical and analytical methods, we show that in a logical-like dynamical model, the occurrence of convergent trajectory in a network depends mainly on the type of the fixed point and the ratio between activation and inhibition links. We analytically proof that this property is induced by the competition between two types of state transition structures in phase space: tree-like transition structure and star-like transition structure. We show that the biological networks, such as the cell cycle network in budding yeast, prefers the tree-like transition structures and suggest that this type of convergence trajectories may be universal.
Fractional Trajectories: Decorrelation Versus Friction
2013-07-27
function, andmoving back to the time domain yields the fractional trajectory V(t) = Eα(Otα)V(0). (4) Note that the Mittag-Leffler function is defined...bxy) ∂ ∂x − (cy − δxy) ∂ ∂y , (35) with the vector V having the components x and y. The predictor– corrector integration method is adopted to solve...Using the predictor– corrector method with α = 1 we numerically integrate the system of differential equations to find the operational time trajectory
Classical trajectories and quantum tunneling
Ivlev, B I
2003-01-01
The problem of inter-band tunneling in a semiconductor (Zener breakdown) in a nonstationary and homogeneous electric field is solved exactly. Using the exact analytical solution, the approximation based on classical trajectories is studied. A new mechanism of enhanced tunneling through static non-one-dimensional barriers is proposed in addition to well known normal tunneling solely described by a trajectory in imaginary time. Under certain conditions on the barrier shape and the particle energy, the probability of enhanced tunneling is not exponentially small even for non-transparent barriers, in contrast to the case of normal tunneling.
Dynamic trajectory control of gliders
Dilão, Rui
2013-01-01
We propose a new dynamic control algorithm in order to direct the trajectory of a glider to a pre-assigned target point. The algorithms runs iteratively and the approach to the target point is self-correcting. The algorithm is applicable to any non-powered lift-enabled vehicle (glider) travelling in planetary atmospheres. As a proof of concept, we have applied the new algorithm to the command and control of the trajectory of the Space Shuttle during the Terminal Area Energy Management (TAEM) phase.
Diagnosis trajectories of prior multi-morbidity predict sepsis mortality
DEFF Research Database (Denmark)
Beck, Mette Kristina; Jensen, Anders Boeck; Nielsen, Annelaura Bach
2016-01-01
Sepsis affects millions of people every year, many of whom will die. In contrast to current survival prediction models for sepsis patients that primarily are based on data from within-admission clinical measurements (e.g. vital parameters and blood values), we aim for using the full disease history...... to predict sepsis mortality. We benefit from data in electronic medical records covering all hospital encounters in Denmark from 1996 to 2014. This data set included 6.6 million patients of whom almost 120,000 were diagnosed with the ICD-10 code: A41 'Other sepsis'. Interestingly, patients following...... recurrent trajectories of time-ordered co-morbidities had significantly increased sepsis mortality compared to those who did not follow a trajectory. We identified trajectories which significantly altered sepsis mortality, and found three major starting points in a combined temporal sepsis network: Alcohol...
Route Sanitizer: Connected Vehicle Trajectory De-Identification Tool
Energy Technology Data Exchange (ETDEWEB)
2017-03-01
Route Sanitizer is ORNL's connected vehicle moving object database de-identification tool and a graphical user interface to ORNL's connected vehicle de-identification algorithm. It uses the Google Chrome (soon to be Electron) platform so it will run on different computing platforms. The basic de-identification strategy is record redaction: portions of a vehicle trajectory (e.g. sequences of precise temporal spatial records) are removed. It does not alter retained records. The algorithm uses custom techniques to find areas within trajectories that may be considered private, then it suppresses those in addition to enough of the trajectory surrounding those locations to protect against "inference attacks" in a mathematically sound way. Map data is integrated into the process to make this possible.
Available Instruments for Analyzing Molecular Dynamics Trajectories.
Likhachev, I V; Balabaev, N K; Galzitskaya, O V
2016-01-01
Molecular dynamics trajectories are the result of molecular dynamics simulations. Trajectories are sequential snapshots of simulated molecular system which represents atomic coordinates at specific time periods. Based on the definition, in a text format trajectory files are characterized by their simplicity and uselessness. To obtain information from such files, special programs and information processing techniques are applied: from molecular dynamics animation to finding characteristics along the trajectory (versus time). In this review, we describe different programs for processing molecular dynamics trajectories. The performance of these programs, usefulness for analyses of molecular dynamics trajectories, strong and weak aspects are discussed.
Predicting Comorbid Conditions and Trajectories using Social Health Records.
Ji, Xiang; Ae Chun, Soon; Geller, James
2016-05-05
Many patients suffer from comorbidity conditions, for example, obese patients often develop type-2 diabetes and hypertension. In the US, 80% of Medicare spending is for managing patients with these multiple coexisting conditions. Predicting potential comorbidity conditions for an individual patient can promote preventive care and reduce costs. Predicting possible comorbidity progression paths can provide important insights into population heath and aid with decisions in public health policies. Discovering the comorbidity relationships is complex and difficult, due to limited access to Electronic Health Records by privacy laws. In this paper, we present a collaborative comorbidity prediction method to predict likely comorbid conditions for individual patients, and a trajectory prediction graph model to reveal progression paths of comorbid conditions. Our prediction approaches utilize patient generated health reports on online social media, called Social Health Records (SHR). The experimental results based on one SHR source show that our method is able to predict future comorbid conditions for a patient with coverage values of 48% and 75% for a top-20 and a top-100 ranked list, respectively. For risk trajectory prediction, our approach is able to reveal each potential progression trajectory between any two conditions and infer the confidence of the future trajectory, given any observed condition. The predicted trajectories are validated with existing comorbidity relations from the medical literature.
Classical Trajectories and Quantum Spectra
Mielnik, Bogdan; Reyes, Marco A.
1996-01-01
A classical model of the Schrodinger's wave packet is considered. The problem of finding the energy levels corresponds to a classical manipulation game. It leads to an approximate but non-perturbative method of finding the eigenvalues, exploring the bifurcations of classical trajectories. The role of squeezing turns out decisive in the generation of the discrete spectra.
Canonical Transformations of Kepler Trajectories
Mostowski, Jan
2010-01-01
In this paper, canonical transformations generated by constants of motion in the case of the Kepler problem are discussed. It is shown that canonical transformations generated by angular momentum are rotations of the trajectory. Particular attention is paid to canonical transformations generated by the Runge-Lenz vector. It is shown that these…
Privacy-Preserving Trajectory Collection
DEFF Research Database (Denmark)
Gidofalvi, Gyozo; Xuegang, Huang; Pedersen, Torben Bach
2008-01-01
. To remedy this situation, this paper first formally defines novel location privacy requirements. Then, it briefly presents a system for privacy--preserving trajectory collection that meets these requirements. The system is composed of an untrusted server and clients communicating in a P2P network. Location...
Trajectories of delinquency and parenting styles
Hoeve, M.; Blokland, A.; Dubas, J.S.; Loeber, R.; Gerris, J.R.M.; Laan, P.H. van der
2008-01-01
We investigated trajectories of adolescent delinquent development using data from the Pittsburgh Youth Study and examined the extent to which these different trajectories are differentially predicted by childhood parenting styles. Based on self-reported and official delinquency seriousness, covering
Trajectories of Delinquency and Parenting Styles
Hoeve, M.; Blokland, A.; Dubas, J.S.; Loeber, R.; Gerris, J.R.M.; Laan, P.H. van der
2008-01-01
We investigated trajectories of adolescent delinquent development using data from the Pittsburgh Youth Study and examined the extent to which these different trajectories are differentially predicted by childhood parenting styles. Based on self-reported and official delinquency seriousness, covering
Trajectories of Delinquency and Parenting Styles
Hoeve, M.; Blokland, A.; Dubas, J.S.; Loeber, R.; Gerris, J.R.M.; Laan, P.H. van der
2008-01-01
We investigated trajectories of adolescent delinquent development using data from the Pittsburgh Youth Study and examined the extent to which these different trajectories are differentially predicted by childhood parenting styles. Based on self-reported and official delinquency seriousness, covering
Trajectories of delinquency and parenting styles
M. Hoeve; A. van Blokland; J.S. Dubas; R Loeber; J.R.M. Gerris; P.H. van der Laan
2008-01-01
We investigated trajectories of adolescent delinquent development using data from the Pittsburgh Youth Study and examined the extent to which these different trajectories are differentially predicted by childhood parenting styles. Based on self-reported and official delinquency seriousness, covering
Trajectory Synthesis for Fisher Information Maximization
Wilson, Andrew D.; Schultz, Jarvis A.; Murphey, Todd D.
2015-01-01
Estimation of model parameters in a dynamic system can be significantly improved with the choice of experimental trajectory. For general nonlinear dynamic systems, finding globally “best” trajectories is typically not feasible; however, given an initial estimate of the model parameters and an initial trajectory, we present a continuous-time optimization method that produces a locally optimal trajectory for parameter estimation in the presence of measurement noise. The optimization algorithm is formulated to find system trajectories that improve a norm on the Fisher information matrix (FIM). A double-pendulum cart apparatus is used to numerically and experimentally validate this technique. In simulation, the optimized trajectory increases the minimum eigenvalue of the FIM by three orders of magnitude, compared with the initial trajectory. Experimental results show that this optimized trajectory translates to an order-of-magnitude improvement in the parameter estimate error in practice. PMID:25598763
The Trajectory Synthesizer Generalized Profile Interface
Lee, Alan G.; Bouyssounouse, Xavier; Murphy, James R.
2010-01-01
The Trajectory Synthesizer is a software program that generates aircraft predictions for Air Traffic Management decision support tools. The Trajectory Synthesizer being used by researchers at NASA Ames Research Center was restricted in the number of trajectory types that could be generated. This limitation was not sufficient to support the rapidly changing Air Traffic Management research requirements. The Generalized Profile Interface was developed to address this issue. It provides a flexible approach to describe the constraints applied to trajectory generation and may provide a method for interoperability between trajectory generators. It also supports the request and generation of new types of trajectory profiles not possible with the previous interface to the Trajectory Synthesizer. Other enhancements allow the Trajectory Synthesizer to meet the current and future needs of Air Traffic Management research.
Successful Aging: Multiple Trajectories and Population Heterogeneity
Fengyan Tang
2014-01-01
Following Rowe and Kahn¡¯s successful aging model, this study identified successful aging as a distinctive aging trajectory and examined gender differences in the aging process. Using the Health and Retirement Study data (2000-2008), this study applied group-based trajectory analysis to identify multiple aging trajectories in a sample of older Americans aged 65 and over (N=9,226). Six dimensions were analyzed in the multi-trajectory model: chronic disease, physical functional limitation, disa...
Minimal Exit Trajectories with Optimum Correctional Manoeuvres
Directory of Open Access Journals (Sweden)
T. N. Srivastava
1980-10-01
Full Text Available Minimal exit trajectories with optimum correctional manoeuvers to a rocket between two coplaner, noncoaxial elliptic orbits in an inverse square gravitational field have been investigated. Case of trajectories with no correctional manoeuvres has been analysed. In the end minimal exit trajectories through specified orbital terminals are discussed and problem of ref. (2 is derived as a particular case.
DEFF Research Database (Denmark)
Axén, Iben; Leboeuf-Yde, Charlotte
2013-01-01
Low back pain is not a self-limiting problem, but rather a recurrent and sometimes persistent disorder. To understand the course over time, detailed investigation, preferably using repeated measurements over extended periods of time, is needed. New knowledge concerning short-term trajectories...... indicates that the low back pain 'episode' is short lived, at least in the primary care setting, with most patients improving. Nevertheless, in the long term, low back pain often runs a persistent course with around two-thirds of patients estimated to be in pain after 12 months. Some individuals never have...... low back pain, but most have it on and off or persistently. Thus, the low back pain 'condition' is usually a lifelong experience. However, subgroups of patients with different back pain trajectories have been identified and linked to clinical parameters. Further investigation is warranted...
Trajectory Indexing Using Movement Constraints
DEFF Research Database (Denmark)
Pfoser, D.; Jensen, Christian Søndergaard
2005-01-01
With the proliferation of mobile computing, the ability to index efficiently the movements of mobile objects becomes important. Objects are typically seen as moving in two-dimensional (x,y) space, which means that their movements across time may be embedded in the three-dimensional (x,y,t) space....... Further, the movements are typically represented as trajectories, sequences of connected line segments. In certain cases, movement is restricted; specifically, in this paper, we aim at exploiting that movements occur in transportation networks to reduce the dimensionality of the data. Briefly, the idea...... is to reduce movements to occur in one spatial dimension. As a consequence, the movement occurs in two-dimensional (x,t) space. The advantages of considering such lower-dimensional trajectories are that the overall size of the data is reduced and that lower-dimensional data is to be indexed. Since off...
Ray trajectories for Alcubierre spacetime
Anderson, Tom H; Lakhtakia, Akhlesh
2011-01-01
The Alcubierre spacetime was simulated by means of a Tamm medium which is asymptotically identical to vacuum and has constitutive parameters which are ontinuous functions of the spatial coordinates. Accordingly, the Tamm medium is amenable to physical realization as a nanostructured metamaterial. A comprehensive characterization of ray trajectories in the Tamm medium was undertaken, within the geometric-optics regime. Propagation directions corresponding to evanescent waves were identified: these occur in the region of the Tamm medium which corresponds to the warp bubble of the Alcubierre spacetime, especially for directions perpendicular to the velocity of the warp bubble at high speeds of that bubble. Ray trajectories are acutely sensitive to the magnitude and direction of the warp bubble's velocity, but rather less sensitive to the thickness of the transition zone between the warp bubble and its background. In particular, for rays which travel in the same direction as the warp bubble, the latter acts as a ...
Quantum frictionless trajectories versus geodesics
Barbado, Luis C.; Barceló, Carlos; Garay, Luis J.
2015-10-01
Moving particles outside a star will generally experience quantum friction caused by the Unruh radiation reaction. There exist however radial trajectories that lack this effect (in the outgoing radiation sector, and ignoring backscattering). Along these trajectories, observers perceive just stellar emission, without further contribution from the Unruh effect. They turn out to have the property that the variations of the Doppler and the gravitational shifts compensate each other. They are not geodesics, and their proper acceleration obeys an inverse square law, which means that it could in principle be generated by outgoing stellar radiation. In the case of a black hole emitting Hawking radiation, this may lead to a buoyancy scenario. The ingoing radiation sector has little effect and seems to slow down the fall even further.
Interference, reduced action, and trajectories
2006-01-01
Instead of investigating the interference between two stationary, rectilinear wave functions in a trajectory representation by examining the two rectilinear wave functions individually, we examine a dichromatic wave function that is synthesized from the two interfering wave functions. The physics of interference is contained in the reduced action for the dichromatic wave function. As this reduced action is a generator of the motion for the dichromatic wave function, it determines the dichroma...
[Oxaliplatin -- A 10-Year Trajectory].
Kanaji, Shingo; Oki, Eiji; Saeki, Hiroshi; Kitao, Hiroyuki; Maehara, Yoshihiko; Kakeji, Yoshihiro
2016-06-01
Oxaliplatin(Elplat(®)iv infusion solution)is a third-generation 1,2-DACH-platinum derivative. A number of international clinical trials have investigated the effects of this drug for each of its four indications. Building on the results of these earlier studies, much research has also been carried out in Japan in terms of developing and accumulating evidence on oxaliplatin. This report reviews the trajectory of its use over the last 10-years and considers its future potential.
Periodic billiard trajectories in polyhedra
Bedaride, Nicolas
2011-01-01
We consider the billiard map inside a polyhedron. We give a condition for the stability of the periodic trajectories. We apply this result to the case of the tetrahedron. We deduce the existence of an open set of tetrahedra which have a periodic orbit of length four (generalization of Fagnano's orbit for triangles), moreover we can study completly the orbit of points along this coding.
Perching aerodynamics and trajectory optimization
Wickenheiser, Adam; Garcia, Ephrahim
2007-04-01
Advances in smart materials, actuators, and control architecture have enabled new flight capabilities for aircraft. Perching is one such capability, described as a vertical landing maneuver using in-flight shape reconfiguration in lieu of high thrust generation. A morphing, perching aircraft design is presented that is capable of post stall flight and very slow landing on a vertical platform. A comprehensive model of the aircraft's aerodynamics, with special regard to nonlinear affects such as flow separation and dynamic stall, is discussed. Trajectory optimization using nonlinear programming techniques is employed to show the effects that morphing and nonlinear aerodynamics have on the maneuver. These effects are shown to decrease the initial height and distance required to initiate the maneuver, reduce the bounds on the trajectory, and decrease the required thrust for the maneuver. Perching trajectories comparing morphing versus fixed-configuration and stalled versus un-stalled aircraft are presented. It is demonstrated that a vertical landing is possible in the absence of high thrust if post-stall flight capabilities and vehicle reconfiguration are utilized.
Mobile Information Collectors' Trajectory Data Warehouse Design
oueslati, wided
2010-01-01
To analyze complex phenomena which involve moving objects, Trajectory Data Warehouse (TDW) seems to be an answer for many recent decision problems related to various professions (physicians, commercial representatives, transporters, ecologists ...) concerned with mobility. This work aims to make trajectories as a first class concept in the trajectory data conceptual model and to design a TDW, in which data resulting from mobile information collectors' trajectory are gathered. These data will be analyzed, according to trajectory characteristics, for decision making purposes, such as new products commercialization, new commerce implementation, etc.
Path-based Queries on Trajectory Data
DEFF Research Database (Denmark)
Krogh, Benjamin Bjerre; Pelekis, Nikos; Theodoridis, Yannis
2014-01-01
a specific path by only retrieving data from the first and last edge in the path. To correctly answer strict path queries existing network-constrained trajectory indexes must retrieve data from all edges in the path. An extensive performance study of NETTRA using a very large real-world trajectory data set....... To efficiently support strict path queries, we present a novel NETwork-constrained TRAjectory index (NETTRA). This index enables very efficient retrieval of trajectories that follow a specific path, i.e., strict path queries. NETTRA uses a new path encoding scheme that can determine if a trajectory follows......, consisting of 1.7 million trajectories (941 million GPS records) and a road network with 1.3 million edges, shows a speed-up of two orders of magnitude compared to state-of-the-art trajectory indexes....
ARTISTIC VISUALIZATION OF TRAJECTORY DATA USING CLOUD MODEL
Directory of Open Access Journals (Sweden)
T. Wu
2017-09-01
Full Text Available Rapid advance of location acquisition technologies boosts the generation of trajectory data, which track the traces of moving objects. A trajectory is typically represented by a sequence of timestamped geographical locations. Data visualization is an efficient means to represent distributions and structures of datasets and reveal hidden patterns in the data. In this paper, we explore a cloud model-based method for the generation of stylized renderings of trajectory data. The artistic visualizations of the proposed method do not have the goal to allow for data mining tasks or others but instead show the aesthetic effect of the traces of moving objects in a distorted manner. The techniques used to create the images of traces of moving objects include the uncertain line using extended cloud model, stroke-based rendering of geolocation in varying styles, and stylistic shading with aesthetic effects for print or electronic displays, as well as various parameters to be further personalized. The influence of different parameters on the aesthetic qualities of various painted images is investigated, including step size, types of strokes, colour modes, and quantitative comparisons using four aesthetic measures are also involved into the experiment. The experimental results suggest that the proposed method is with advantages of uncertainty, simplicity and effectiveness, and it would inspire professional graphic designers and amateur users who may be interested in playful and creative exploration of artistic visualization of trajectory data.
Mobility, education and life trajectories
DEFF Research Database (Denmark)
Olwig, Karen Fog; Valentin, Karen
2015-01-01
the perspective that education includes a broad range of formative experiences, the articles explore different educational trajectories and the local, regional and transnational relations in which they are embedded. Three key issues emerge from the analyses: firstly, the central role of temporality in terms...... of both the overall historical conditions and the specific biographical circumstances shaping educational opportunities; secondly, the complex agendas informing individuals’ migration and the adjustment of these agendas in the light of the vagaries of migrant life; and thirdly, the importance of migrants...
Quantum Tunneling and Complex Trajectories
Meynig, Max; Haggard, Hal
2017-01-01
In general, the semiclassical approximation of quantum mechanical tunneling fails to treat tunneling through barriers if real initial conditions and trajectories are used. By analytically continuing classical dynamics to the complex plane the problems encountered in the approximation can be resolved. While, the complex methods discussed here have been previously explored, no one has exhibited an analytically solvable case. The essential features of the complex method will be discussed in the context of a novel, analytically solvable problem. These methods could be useful in quantum gravity, with applications to the tunneling of spacetime geometries.
Quantum frictionless trajectories versus geodesics
Barbado, Luis C; Garay, Luis J
2015-01-01
Moving particles outside a star will generally experience quantum friction caused by Unruh radiation reaction. There exist however radial trajectories that lack this effect (in the outgoing radiation sector, and ignoring back-scattering). They turn out to have the property that the variations of the Doppler and the gravitational shifts compensate each other. They are not geodesics, and their proper acceleration obeys an inverse square law, which means that could in principle be generated by outgoing stellar radiation. In the case of a black hole emitting Hawking radiation, this may lead to a buoyancy scenario. The ingoing radiation sector has little effect and seems to slow down the fall even further.
Privacy-Preserving Trajectory Collection
DEFF Research Database (Denmark)
Gidofalvi, Gyozo; Xuegang, Huang; Pedersen, Torben Bach
2008-01-01
In order to provide context--aware Location--Based Services, real location data of mobile users must be collected and analyzed by spatio--temporal data mining methods. However, the data mining methods need precise location data, while the mobile users want to protect their location privacy....... To remedy this situation, this paper first formally defines novel location privacy requirements. Then, it briefly presents a system for privacy--preserving trajectory collection that meets these requirements. The system is composed of an untrusted server and clients communicating in a P2P network. Location...
Spherical aberration from trajectories in real and hard-edge solenoid fields
Indian Academy of Sciences (India)
BISWAS B
2016-06-01
For analytical, real and hard-edge solenoidal axial magnetic fields, the low-energy electron trajectories are obtained using the third-order paraxial ray equation. Using the particle trajectories, it is shown that the spherical aberration in the hard-edge model is high and it increases monotonously with hard edginess, although the focal length converges, in agreement with a recentfield and spherical aberration model. The model paved the way for a hard-edge approximation that gives correct focal length and spherical aberration, which is verified here by the trajectory method. In essence, we show that exact hard-edge fields give infinite spherical aberrations.
Trajectory Codes for Flash Memory
Anxiao,; Langberg, Michael; Schwartz, Moshe; Bruck, Jehoshua
2010-01-01
Flash memory is well-known for its inherent asymmetry: the flash-cell charge levels are easy to increase but are hard to decrease. In a general rewriting model, the stored data changes its value with certain patterns. The patterns of data updates are determined by the data structure and the application, and are independent of the constraints imposed by the storage medium. Thus, an appropriate coding scheme is needed so that the data changes can be updated and stored efficiently under the storage-medium's constraints. In this paper, we define the general rewriting problem using a graph model. It extends many known rewriting models such as floating codes, WOM codes, buffer codes, etc. We present a new rewriting scheme for flash memories, called the trajectory code, for rewriting the stored data as many times as possible without block erasures. We prove that the trajectory code is asymptotically optimal in a wide range of scenarios. We also present randomized rewriting codes optimized for expected performance (g...
Debt trajectories and mental health.
Hojman, Daniel A; Miranda, Álvaro; Ruiz-Tagle, Jaime
2016-10-01
In the last few decades, there was a marked increase in consumer debt in the United States, Latin America and other emerging countries, spurring a debate about the real costs and benefits of household credit. Using a unique longitudinal dataset with detailed health and balance sheet information from a large sample of 10,900 Chilean households we study the relationship between debt trajectories in a three-year time window and mental health. We find that depressive symptoms are higher for those who have been persistently over-indebted, followed by those who transit from moderate to high debt levels. We also find that those who transition from over-indebtedness to moderate debt levels have no additional depressive symptoms compared to those with trajectories of moderate debt throughout (never over-indebted). This suggests that the debt-related contribution to depressive symptoms vanishes as debt levels fall. The association between debt and depressive symptoms seems to be driven by non-mortgage debt -primarily consumer credit- or late mortgage payments; secured debt (secured by collateral) per se is not associated with depressive symptoms. Policy interventions to reduce the negative association of over-indebtedness on mental health are discussed.
Winding light beams along elliptical helical trajectories
Wen, Yuanhui; Zhang, Yanfeng; Chen, Hui; Yu, Siyuan
2016-01-01
Conventional caustic methods in real or Fourier space produced accelerating optical beams only with convex trajectories. We develop a superposition caustic method capable of winding light beams along non-convex trajectories. We ascertain this method by constructing a one-dimensional (1D) accelerating beam moving along a sinusoidal trajectory, and subsequently extending to two-dimensional (2D) accelerating beams along arbitrarily elliptical helical trajectories. We experimentally implement the method with a compact and robust integrated optics approach by fabricating micro-optical structures on quartz glass plates to perform the spatial phase and amplitude modulation to the incident light, generating beam trajectories highly consistent with prediction. The theoretical and implementation methods can in principle be extended to the construction of accelerating beams with a wide variety of non-convex trajectories, thereby opening up a new route of manipulating light beams for fundamental research and practical ap...
Stochastic and fractal analysis of fracture trajectories
Bessendorf, Michael H.
1987-01-01
Analyses of fracture trajectories are used to investigate structures that fall between 'micro' and 'macro' scales. It was shown that fracture trajectories belong to the class of nonstationary processes. It was also found that correlation distance, which may be related to a characteristic size of a fracture process, increases with crack length. An assemblage of crack trajectory processes may be considered as a diffusive process. Chudnovsky (1981-1985) introduced a 'crack diffusion coefficient' d which reflects the ability of the material to deviate the crack trajectory from the most energetically efficient path and thus links the material toughness to its structure. For the set of fracture trajectories in AISI 304 steel, d was found to be equal to 1.04 microns. The fractal dimension D for the same set of trajectories was found to be 1.133.
Trajectory similarity join in spatial networks
Shang, Shuo
2017-09-07
The matching of similar pairs of objects, called similarity join, is fundamental functionality in data management. We consider the case of trajectory similarity join (TS-Join), where the objects are trajectories of vehicles moving in road networks. Thus, given two sets of trajectories and a threshold θ, the TS-Join returns all pairs of trajectories from the two sets with similarity above θ. This join targets applications such as trajectory near-duplicate detection, data cleaning, ridesharing recommendation, and traffic congestion prediction. With these applications in mind, we provide a purposeful definition of similarity. To enable efficient TS-Join processing on large sets of trajectories, we develop search space pruning techniques and take into account the parallel processing capabilities of modern processors. Specifically, we present a two-phase divide-and-conquer algorithm. For each trajectory, the algorithm first finds similar trajectories. Then it merges the results to achieve a final result. The algorithm exploits an upper bound on the spatiotemporal similarity and a heuristic scheduling strategy for search space pruning. The algorithm\\'s per-trajectory searches are independent of each other and can be performed in parallel, and the merging has constant cost. An empirical study with real data offers insight in the performance of the algorithm and demonstrates that is capable of outperforming a well-designed baseline algorithm by an order of magnitude.
Field structure and electron life times in the MEFISTO electron cyclotron resonance ion source
Energy Technology Data Exchange (ETDEWEB)
Bodendorfer, M. [EPFL - Ecole Polytechnique Federale de Lausanne (Switzerland); University of Berne, Institute of Physics, Space Research and Planetary Sciences, Siedlerstrasse 5, 3012 Berne (Switzerland)], E-mail: michael.bodendorfer@space.unibe.ch; Altwegg, K. [University of Berne, Institute of Physics, Space Research and Planetary Sciences, Siedlerstrasse 5, 3012 Berne (Switzerland); Shea, H. [EPFL - Ecole Polytechnique Federale de Lausanne (Switzerland); Wurz, P. [University of Berne, Institute of Physics, Space Research and Planetary Sciences, Siedlerstrasse 5, 3012 Berne (Switzerland)
2008-03-15
The complex magnetic field of the permanent magnet electron cyclotron resonance (ECR) ion source MEFISTO located at the University of Berne has been numerically simulated. For the first time the magnetized volume qualified for electron cyclotron resonance at 2.45 GHz and 87.5 mT has been analyzed in highly detailed 3D simulations with unprecedented resolution. New results were obtained from the numerical simulation of 25,211 electron trajectories. The evident characteristic ion sputtering trident of hexapole confined ECR ion sources has been identified with the field and electron trajectory distribution. Furthermore, unexpected long electron trajectory lifetimes were found.
Field structure and electron life times in the MEFISTO electron cyclotron resonance ion source
Bodendorfer, M.; Altwegg, K.; Shea, H.; Wurz, P.
2008-03-01
The complex magnetic field of the permanent magnet electron cyclotron resonance (ECR) ion source MEFISTO located at the University of Berne has been numerically simulated. For the first time the magnetized volume qualified for electron cyclotron resonance at 2.45 GHz and 87.5 mT has been analyzed in highly detailed 3D simulations with unprecedented resolution. New results were obtained from the numerical simulation of 25,211 electron trajectories. The evident characteristic ion sputtering trident of hexapole confined ECR ion sources has been identified with the field and electron trajectory distribution. Furthermore, unexpected long electron trajectory lifetimes were found.
Field structure and electron life times in the MEFISTO Electron Cyclotron Resonance Ion Source
Bodendorfer, Michael; Shea, Herbert; Wurz, Peter
2008-01-01
The complex magnetic field of the permanent-magnet electron cyclotron resonance (ECR) ion source MEFISTO located at the University of Bern have been numerically simulated. For the first time the magnetized volume qualified for electron cyclotron resonance at 2.45 GHz and 87.5 mT has been analyzed in highly detailed 3D simulations with unprecedented resolution. New results were obtained from the numerical simulation of 25211 electron trajectories. The evident characteristic ion sputtering trident of hexapole confined ECR sources has been identified with the field and electron trajectory distribution. Furthermore, unexpected long electron trajectory lifetimes were found.
Quantum Trajectory Approach to Molecular Dynamics Simulation with Surface Hopping
Feng, Wei; Li, Xin-Qi; Fang, Weihai
2012-01-01
The powerful molecular dynamics (MD) simulation is basically based on a picture that the atoms experience classical-like trajectories under the exertion of classical force field determined by the quantum mechanically solved electronic state. In this work we propose a quantum trajectory approach to the MD simulation with surface hopping, from an insight that an effective "observation" is actually implied in theMDsimulation through tracking the forces experienced, just like checking the meter's result in the quantum measurement process. This treatment can build the nonadiabatic surface hopping on a dynamical foundation, instead of the usual artificial and conceptually inconsistent hopping algorithms. The effects and advantages of the proposed scheme are preliminarily illustrated by a two-surface model system.
Directory of Open Access Journals (Sweden)
Normand Carpentier
2013-06-01
Full Text Available A broad range of services are developing in response to the needs of an aging population. Although most interventions are carried out in the patient’s living environment—at the heart of society—few studies on service utilization refer to social theory. This paper suggests that studies on older people with chronic health conditions would benefit from a stronger theoretical foundation. Drawing on 15 in-depth interviews, it highlights the relevance of individualization processes and the network society, 2 central theoretical concerns in sociology. The research provides a unique perspective on the entry into the care trajectory and expands our comprehension of the emergence of a social organization that can respond to the needs of elderly patients. Data of this nature may be useful in service planning and the development of a care-centered approach.
Low-thrust rocket trajectories
Energy Technology Data Exchange (ETDEWEB)
Keaton, P.W.
1986-01-01
The development of low-thrust propulsion systems to complement chemical propulsion systems will greatly enhance the evolution of future space programs. Two advantages of low-thrust rockets are stressed: first, in a strong gravitational field, such as occurs near the Earth, freighter missions with low-thrust engines require one-tenth as much propellant as do chemical engines. Second, in a weak gravitational field, such as occurs in the region between Venus and Mars, low-thrust rockets are faster than chemical rockets with comparable propellant mass. The purpose here is to address the physics of low-thrust trajectories and to interpret the results with two simple models. Analytic analyses are used where possible - otherwise, the results of numerical calculations are presented in graphs. The author has attempted to make this a self-contained report. 57 refs., 10 figs.
Low-thrust rocket trajectories
Energy Technology Data Exchange (ETDEWEB)
Keaton, P.W.
1987-03-01
The development of low-thrust propulsion systems to complement chemical propulsion systems will greatly enhance the evolution of future space programs. Two advantages of low-thrust rockets are stressed: first, in a strong gravitational field, such as occurs near the Earth, freighter missions with low-thrust engines require one-tenth as much propellant as do chemical engines. Second, in a weak gravitational field, such as occurs in the region between Venus and Mars, low-thrust rockets are faster than chemical rockets with comparable propellant mass. The purpose here is to address the physics of low-thrust trajectories and to interpret the results with two simple models. Analytic analyses are used where possible - otherwise, the results of numerical calculations are presented in graphs. The author has attempted to make this a self-contained report.
The LHC Orbit and Trajectory System
Bishop, D; Calvo-Giraldo, E; Cocq, D; Jensen, L; Jones, R; Savioz, J J; Waters, G
2003-01-01
This paper describes the definitive acquisition system selected for the measurement of the closed orbit and trajectory in the CERN-LHC and its transfer lines. The system is based on a Wide Band Time Normaliser (WBTN) followed by a 10-bit ADC and a Digital Acquisition Board (DAB), the latter developed by TRIUMF, Canada. The complete chain works at 40MHz, so allowing the position of each bunch to be measured individually. In order to avoid radiation problems with the electronics in the LHC tunnel, all the digital systems will be kept on the surface and linked to the analogue front-ends via a single mode fibre-optic connection. Slow control via a WorldFIP fieldbus will be used in the tunnel for setting the various operational modes of the system and will also be used to check power supply statuses. As well as describing the hardware involved, some results will be shown from a complete prototype system installed on four pick-ups in the CERN-SPS using the full LHC topology.
Towards Efficient Search for Activity Trajectories
DEFF Research Database (Denmark)
Zheng, Kai; Shang, Shuo; Yuan, Jing
2013-01-01
The advances in location positioning and wireless communication technologies have led to a myriad of spatial trajectories representing the mobility of a variety of moving objects. While processing trajectory data with the focus of spatio-temporal features has been widely studied in the last decad...
Trajectories of Intimate Partner Violence Victimization
Directory of Open Access Journals (Sweden)
Kevin M. Swartout
2012-08-01
Full Text Available Introduction: The purposes of this study were to assess the extent to which latent trajectories of female intimate partner violence (IPV victimization exist; and, if so, use negative childhood experiences to predict trajectory membership.Methods: We collected data from 1,575 women at 5 time-points regarding experiences during adolescence and their 4 years of college. We used latent class growth analysis to fit a series of personcentered, longitudinal models ranging from 1 to 5 trajectories. Once the best-fitting model was selected, we used negative childhood experience variables—sexual abuse, physical abuse, and witnessing domestic violence—to predict most-likely trajectory membership via multinomial logistic regression.Results: A 5-trajectory model best fit the data both statistically and in terms of interpretability. The trajectories across time were interpreted as low or no IPV, low to moderate IPV, moderate to low IPV, high to moderate IPV, and high and increasing IPV, respectively. Negative childhood experiences differentiated trajectory membership, somewhat, with childhood sexual abuse as a consistent predictor of membership in elevated IPV trajectories.Conclusion: Our analyses show how IPV risk changes over time and in different ways. These differential patterns of IPV suggest the need for prevention strategies tailored for women that consider victimization experiences in childhood and early adulthood. [West J Emerg Med. 2012;13(3:272–277.
Trajectories of CBCL Attention Problems in childhood
Robbers, S.C.C.; Oort, F.V.A. van; Polderman, T.J.C.; Bartels, M.; Boomsma, D.I.; Verhulst, F.C.; Huizink, A.C.
2011-01-01
The first aim of this study was to identify developmental trajectories of Attention Problems in twins followed from age 6 to 12 years. Second, we investigated whether singletons follow similar trajectories. Maternal longitudinal ratings on the Attention Problems (AP) subscale of the Child Behavior
Trajectories of Delinquency and Parenting Styles
Hoeve, Machteld; Blokland, Arjan; Dubas, Judith Semon; Loeber, Rolf; Gerris, Jan R. M.; van der Laan, Peter H.
2008-01-01
We investigated trajectories of adolescent delinquent development using data from the Pittsburgh Youth Study and examined the extent to which these different trajectories are differentially predicted by childhood parenting styles. Based on self-reported and official delinquency seriousness, covering ages 10-19, we identified five distinct…
Comment on "The envelope of projectile trajectories"
Butikov, E I
2003-01-01
Several simple alternative methods to obtain the equation of the envelope of the family of projectile trajectories corresponding to the same initial speed are suggested, including methods in which the boundary of the region occupied by the parabolic trajectories is found as an envelope of a set of circles. Two possible generalizations of the discussed problem are also suggested. (letters and comments)
Soccer Ball Lift Coefficients via Trajectory Analysis
Goff, John Eric; Carre, Matt J.
2010-01-01
We performed experiments in which a soccer ball was launched from a machine while two high-speed cameras recorded portions of the trajectory. Using the trajectory data and published drag coefficients, we extracted lift coefficients for a soccer ball. We determined lift coefficients for a wide range of spin parameters, including several spin…
Estimation of motility parameters from trajectory data
DEFF Research Database (Denmark)
Vestergaard, Christian L.; Pedersen, Jonas Nyvold; Mortensen, Kim I.;
2015-01-01
Given a theoretical model for a self-propelled particle or micro-organism, how does one optimally determine the parameters of the model from experimental data in the form of a time-lapse recorded trajectory? For very long trajectories, one has very good statistics, and optimality may matter little...... to which similar results may be obtained also for self-propelled particles....
Soccer Ball Lift Coefficients via Trajectory Analysis
Goff, John Eric; Carre, Matt J.
2010-01-01
We performed experiments in which a soccer ball was launched from a machine while two high-speed cameras recorded portions of the trajectory. Using the trajectory data and published drag coefficients, we extracted lift coefficients for a soccer ball. We determined lift coefficients for a wide range of spin parameters, including several spin…
A Framework for Context-aware Trajectory
Bogorny, V.; Wachowicz, M.
2009-01-01
The recent advances in technologies for mobile devices, like GPS and mobile phones, are generating large amounts of a new kind of data: trajectories of moving objects. These data are normally available as sample points, with very little or no semantics. Trajectory data can be used in a variety of ap
Efficient Spatial Keyword Search in Trajectory Databases
Cong, Gao; Ooi, Beng Chin; Zhang, Dongxiang; Zhang, Meihui
2012-01-01
An increasing amount of trajectory data is being annotated with text descriptions to better capture the semantics associated with locations. The fusion of spatial locations and text descriptions in trajectories engenders a new type of top-$k$ queries that take into account both aspects. Each trajectory in consideration consists of a sequence of geo-spatial locations associated with text descriptions. Given a user location $\\lambda$ and a keyword set $\\psi$, a top-$k$ query returns $k$ trajectories whose text descriptions cover the keywords $\\psi$ and that have the shortest match distance. To the best of our knowledge, previous research on querying trajectory databases has focused on trajectory data without any text description, and no existing work has studied such kind of top-$k$ queries on trajectories. This paper proposes one novel method for efficiently computing top-$k$ trajectories. The method is developed based on a new hybrid index, cell-keyword conscious B$^+$-tree, denoted by \\cellbtree, which enabl...
Simulation of Airplane and Rocket Trajectories
Wahbah, Magdy M.; Berning, Michael J.; Choy, Tony S.
1987-01-01
Simulation and Optimization of Rocket Trajectories program (SORT) contains comprehensive mathematical models for simulating aircraft dynamics, freely falling objects, and many types of ballistic trajectories. Provides high-fidelity, three-degrees-of-freedom simulation for atmospheric and exoatmospheric flight. It numerically models vehicle subsystems and vehicle environment. Used for wide range of simulations. Written in machine-independent FORTRAN 77.
Efficient Calculation of Earth Penetrating Projectile Trajectories
2006-09-01
CALCULATION OF EARTH PENETRATING PROJECTILE TRAJECTORIES by Daniel F . Youch September 2006 Thesis Advisor: Joshua Gordis... Daniel F . Youch 5. FUNDING NUMBERS 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval Postgraduate School Monterey, CA 93943-5000 8. PERFORMING...EFFICIENT CALCULATION OF EARTH PENETRATING PROJECTILE TRAJECTORIES Daniel F . Youch Lieutenant Commander, United States Navy B.S., Temple
Trajectories of CBCL Attention Problems in childhood
S.C.C. Robbers (Sylvana); F.V.A. van Oort (Floor); T.J.C. Polderman (Tinca); M. Bartels (Meike); D.I. Boomsma (Dorret); F.C. Verhulst (Frank); G.H. Lubke (Gitta); A.C. Huizink (Anja)
2011-01-01
textabstractThe first aim of this study was to identify developmental trajectories of Attention Problems in twins followed from age 6 to 12 years. Second, we investigated whether singletons follow similar trajectories. Maternal longitudinal ratings on the Attention Problems (AP) subscale of the Chil
Global 4-D trajectory optimization for spacecraft
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Global 4-D trajectory(x,y,z,t)is optimized for a spacecraft,which is launched from the Earth to fly around the Sun,just as star-drift of 1437 asteroids in the solar system.The spacecraft trajectory is controlled by low thrust.The performance index of optimal trajectory is to maximize the rendezvous times with the intermediate asteroids,and also maximize the final mass.This paper provides a combined algorithm of global 4-D trajectory optimization.The algorithm is composed of dynamic programming and two-point-boundary algorithm based on optimal control theory.The best 4-D trajectory is obtained:the spacecraft flies passing 55 asteroids,and rendezvous with(following or passing again)asteroids for 454 days,and finally rendezvous with the asteroid 2005SN25 on the day 60521(MJD),the final mass of the spacecraft is 836.53 kg.
Generation of electron Airy beams.
Voloch-Bloch, Noa; Lereah, Yossi; Lilach, Yigal; Gover, Avraham; Arie, Ady
2013-02-21
Within the framework of quantum mechanics, a unique particle wave packet exists in the form of the Airy function. Its counterintuitive properties are revealed as it propagates in time or space: the quantum probability wave packet preserves its shape despite dispersion or diffraction and propagates along a parabolic caustic trajectory, even though no force is applied. This does not contradict Newton's laws of motion, because the wave packet centroid propagates along a straight line. Nearly 30 years later, this wave packet, known as an accelerating Airy beam, was realized in the optical domain; later it was generalized to an orthogonal and complete family of beams that propagate along parabolic trajectories, as well as to beams that propagate along arbitrary convex trajectories. Here we report the experimental generation and observation of the Airy beams of free electrons. These electron Airy beams were generated by diffraction of electrons through a nanoscale hologram, which imprinted on the electrons' wavefunction a cubic phase modulation in the transverse plane. The highest-intensity lobes of the generated beams indeed followed parabolic trajectories. We directly observed a non-spreading electron wavefunction that self-heals, restoring its original shape after passing an obstacle. This holographic generation of electron Airy beams opens up new avenues for steering electronic wave packets like their photonic counterparts, because the wave packets can be imprinted with arbitrary shapes or trajectories.
Personalized trajectory matching in spatial networks
Shang, Shuo
2013-07-31
With the increasing availability of moving-object tracking data, trajectory search and matching is increasingly important. We propose and investigate a novel problem called personalized trajectory matching (PTM). In contrast to conventional trajectory similarity search by spatial distance only, PTM takes into account the significance of each sample point in a query trajectory. A PTM query takes a trajectory with user-specified weights for each sample point in the trajectory as its argument. It returns the trajectory in an argument data set with the highest similarity to the query trajectory. We believe that this type of query may bring significant benefits to users in many popular applications such as route planning, carpooling, friend recommendation, traffic analysis, urban computing, and location-based services in general. PTM query processing faces two challenges: how to prune the search space during the query processing and how to schedule multiple so-called expansion centers effectively. To address these challenges, a novel two-phase search algorithm is proposed that carefully selects a set of expansion centers from the query trajectory and exploits upper and lower bounds to prune the search space in the spatial and temporal domains. An efficiency study reveals that the algorithm explores the minimum search space in both domains. Second, a heuristic search strategy based on priority ranking is developed to schedule the multiple expansion centers, which can further prune the search space and enhance the query efficiency. The performance of the PTM query is studied in extensive experiments based on real and synthetic trajectory data sets. © 2013 Springer-Verlag Berlin Heidelberg.
Classical trajectory Monte Carlo investigation for Lorentz ionization of H (1s)
Institute of Scientific and Technical Information of China (English)
He Bin; Wang Jian-Guo; Liu Chun-Lei
2013-01-01
Lorentz ionization of H(1s) is investigated by classical trajectory Monte Carlo (CTMC) simulation.The effect of the transverse magnetic field on the considered process is analyzed in terms of the time evolution of interactions in the system,total electron energy,and electron trajectories.A classical mechanism for the ionization is found,where the variation of the kinetic energy of the nuclei is found to be important in the process.Compared with the results of tunneling ionization,the classical mechanism becomes more and more important with the increase of the velocity of the H-atom or the strength of the magnetic field.
Construction of a WMR for Trajectory Tracking Control: Experimental Results
Directory of Open Access Journals (Sweden)
R. Silva-Ortigoza
2013-01-01
Full Text Available This paper reports a solution for trajectory tracking control of a differential drive wheeled mobile robot (WMR based on a hierarchical approach. The general design and construction of the WMR are described. The hierarchical controller proposed has two components: a high-level control and a low-level control. The high-level control law is based on an input-output linearization scheme for the robot kinematic model, which provides the desired angular velocity profiles that the WMR has to track in order to achieve the desired position (x*,y* and orientation (φ*. Then, a low-level control law, based on a proportional integral (PI approach, is designed to control the velocity of the WMR wheels to ensure those tracking features. Regarding the trajectories, this paper provides the solution or the following cases: (1 time-varying parametric trajectories such as straight lines and parabolas and (2 smooth curves fitted by cubic splines which are generated by the desired data points x1*,y1*,…,xn*,yn*. A straightforward algorithm is developed for constructing the cubic splines. Finally, this paper includes an experimental validation of the proposed technique by employing a DS1104 dSPACE electronic board along with MATLAB/Simulink software.
Inferring Taxi Status Using GPS Trajectories
Zhu, Yin; Zhang, Liuhang; Santani, Darshan; Xie, Xing; Yang, Qiang
2012-01-01
In this paper, we infer the statuses of a taxi, consisting of occupied, non-occupied and parked, in terms of its GPS trajectory. The status information can enable urban computing for improving a city's transportation systems and land use planning. In our solution, we first identify and extract a set of effective features incorporating the knowledge of a single trajectory, historical trajectories and geographic data like road network. Second, a parking status detection algorithm is devised to find parking places (from a given trajectory), dividing a trajectory into segments (i.e., sub-trajectories). Third, we propose a two-phase inference model to learn the status (occupied or non-occupied) of each point from a taxi segment. This model first uses the identified features to train a local probabilistic classifier and then carries out a Hidden Semi-Markov Model (HSMM) for globally considering long term travel patterns. We evaluated our method with a large-scale real-world trajectory dataset generated by 600 taxis...
A heretical view on linear Regge trajectories
Diakonov, D; Diakonov, Dmitri; Petrov, Victor
2003-01-01
We discuss a possibility that linear Regge trajectories originate not from gluonic strings connecting quarks, as it is usually assumed, but from pion excitations of light hadrons. From this point of view, at large angular momenta both baryons and mesons lying on linear Regge trajectories are slowly rotating thick strings of pion field, giving rise to a universal slope computable from the pion decay constant. The finite resonance widths are mainly due to the semiclassical radiation of pion fields by the rotating elongated chiral solitons. Quantum fluctuations about the soliton determine a string theory which, being quantized, gives the quantum numbers for Regge trajectories.
An Examination of "The Martian" Trajectory
Burke, Laura
2015-01-01
This analysis was performed to support a request to examine the trajectory of the Hermes vehicle in the novel "The Martian" by Andy Weir. Weir developed his own tool to perform the analysis necessary to provide proper trajectory information for the novel. The Hermes vehicle is the interplanetary spacecraft that shuttles the crew to and from Mars. It is notionally a Nuclear powered vehicle utilizing VASIMR engines for propulsion. The intent of this analysis was the determine whether the trajectory as it was outlined in the novel is consistent with the rules of orbital mechanics.
Mars Ascent Propulsion Trades with Trajectory Analysis
Energy Technology Data Exchange (ETDEWEB)
Whitehead, J
2004-04-22
Optimized trajectories to a 500 km circular orbit are calculated for vehicles having a 100 kg Mars launch mass. Staging trades, thrust optimization, and the importance of vehicle shape for drag are all taken into consideration. The high acceleration of solid rockets requires a steep trajectory for drag avoidance, followed by a relatively large circularization burn, appropriate for a second stage. Liquid thrust reduces drag, resulting in less steep trajectories which have small circularization burns. Liquid propulsion requires less total {Delta}v, and offers options for multiple stages or just one. Graphs of payload mass versus stage propellant fractions are compared for liquid and solid propulsion.
Estimation of motility parameters from trajectory data
DEFF Research Database (Denmark)
Vestergaard, Christian L.; Pedersen, Jonas Nyvold; Mortensen, Kim I.;
2015-01-01
Given a theoretical model for a self-propelled particle or micro-organism, how does one optimally determine the parameters of the model from experimental data in the form of a time-lapse recorded trajectory? For very long trajectories, one has very good statistics, and optimality may matter little....... However, for biological micro-organisms, one may not control the duration of recordings, and then optimality can matter. This is especially the case if one is interested in individuality and hence cannot improve statistics by taking population averages over many trajectories. One can learn much about...
Helicopter trajectory planning using optimal control theory
Menon, P. K. A.; Cheng, V. H. L.; Kim, E.
1988-01-01
A methodology for optimal trajectory planning, useful in the nap-of-the-earth guidance of helicopters, is presented. This approach uses an adjoint-control transformation along with a one-dimensional search scheme for generating the optimal trajectories. In addition to being useful for helicopter nap-of-the-earth guidance, the trajectory planning solution is of interest in several other contexts, such as robotic vehicle guidance and terrain-following guidance for cruise missiles and aircraft. A distinguishing feature of the present research is that the terrain constraint and the threat envelopes are incorporated in the equations of motion. Second-order necessary conditions are examined.
Evaluating Trajectory Queries over Imprecise Location Data
DEFF Research Database (Denmark)
Xie, Scott, Xike; Cheng, Reynold; Yiu, Man Lung
2012-01-01
Trajectory queries, which retrieve nearby objects for every point of a given route, can be used to identify alerts of potential threats along a vessel route, or monitor the adjacent rescuers to a travel path. However, the locations of these objects (e.g., threats, succours) may not be precisely......, the query is quite time-consuming, since all the points on the trajectory are considered. In this paper, we study how to efficiently evaluate trajectory queries over imprecise location data, by proposing a new concept called the u-bisector. In general, the u-bisector is an extension of bisector to handle...
Soccer ball lift coefficients via trajectory analysis
Energy Technology Data Exchange (ETDEWEB)
Goff, John Eric [Department of Physics, Lynchburg College, Lynchburg, VA 24501 (United States); Carre, Matt J, E-mail: goff@lynchburg.ed [Department of Mechanical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom)
2010-07-15
We performed experiments in which a soccer ball was launched from a machine while two high-speed cameras recorded portions of the trajectory. Using the trajectory data and published drag coefficients, we extracted lift coefficients for a soccer ball. We determined lift coefficients for a wide range of spin parameters, including several spin parameters that have not been obtained by today's wind tunnels. Our trajectory analysis technique is not only a valuable tool for professional sports scientists, it is also accessible to students with a background in undergraduate-level classical mechanics.
Comparison study of sub-trajectory clustering in data mining
Yang, Guodong; Huang, Zhitao; Wang, Xiang
2017-06-01
Trajectory clustering is an important method to achieve moving object data mining, multi-sensor information fusion and trajectory knowledge discovery. Sub-trajectory clustering is an important method to extract useful information from a large number of trajectory data in trajectory analysis. In this paper, comparative experiments are made on the time consumption, similarity measure and clustering performance based on the existing sub-trajectory clustering methods. Based on the comparisons, the advantages and disadvantages of different methods are presented and an improved method is proposed for dealing with trajectories with low positioning accuracy and correlating tracklets from asynchronous sensors. Besides, a general framework of trajectory data mining is discussed.
Du, Ling-Ling; Li, Peng-Cheng; Zhou, Xiao-Xin
2017-08-01
We present the role of quantum trajectories on high-order harmonic generation (HHG) related to the various internuclear distances in hydrogen molecule ions in an intense laser field by solving two-dimensional time-dependent Schrödinger equation. We find that the contribution of the long trajectories in HHG is dominant at smaller internuclear distances, but the contribution of the short trajectories is dominant at larger internuclear distances, it implies that the role of quantum trajectories closes to those HHG of the atom. In addition, the HHG spectrum of hydrogen molecule ions exhibits an internuclear distance-dependent double plateau structure which is related to the electron migrating from one nucleus to another one. Combining with the Morlet transform of quantum time-frequency spectrum and an extended semiclassical analysis, the role of quantum trajectories on HHG with the various internuclear distance are clarified.
Boolean networks with robust and reliable trajectories
Energy Technology Data Exchange (ETDEWEB)
Schmal, Christoph; Peixoto, Tiago P; Drossel, Barbara, E-mail: schmal@physik.uni-bielefeld.d, E-mail: tiago@fkp.tu-darmstadt.d, E-mail: drossel@fkp.tu-darmstadt.d [Institut fuer Festkoerperphysik, TU Darmstadt, Hochschulstrasse 6, 64289 Darmstadt (Germany)
2010-11-15
We construct and investigate Boolean networks that follow a given reliable trajectory in state space, which is insensitive to fluctuations in the updating schedule and which is also robust against noise. Robustness is quantified as the probability that the dynamics return to the reliable trajectory after a perturbation of the state of a single node. In order to achieve high robustness, we navigate through the space of possible update functions by using an evolutionary algorithm. We constrain the networks to those having the minimum number of connections required to obtain the reliable trajectory. Surprisingly, we find that robustness always reaches values close to 100% during the evolutionary optimization process. The set of update functions can be evolved such that it differs only slightly from that of networks that were not optimized with respect to robustness. The state space of the optimized networks is dominated by the basin of attraction of the reliable trajectory.
Action Recognition Using Discriminative Structured Trajectory Groups
Atmosukarto, Indriyati
2015-01-06
In this paper, we develop a novel framework for action recognition in videos. The framework is based on automatically learning the discriminative trajectory groups that are relevant to an action. Different from previous approaches, our method does not require complex computation for graph matching or complex latent models to localize the parts. We model a video as a structured bag of trajectory groups with latent class variables. We model action recognition problem in a weakly supervised setting and learn discriminative trajectory groups by employing multiple instance learning (MIL) based Support Vector Machine (SVM) using pre-computed kernels. The kernels depend on the spatio-temporal relationship between the extracted trajectory groups and their associated features. We demonstrate both quantitatively and qualitatively that the classification performance of our proposed method is superior to baselines and several state-of-the-art approaches on three challenging standard benchmark datasets.
Affine trajectory correction for nonholonomic mobile robots
Pham, Quang-Cuong
2011-01-01
Planning trajectories for nonholonomic systems is difficult and computationally expensive. When facing unexpected events, it may therefore be preferable to deform in some way the initially planned trajectory rather than to re-plan entirely a new one. We suggest here a method based on affine transformations to make such deformations. This method is exact and fast: the deformations and the resulting trajectories can be computed algebraically, in one step, and without any trajectory re-integration. To demonstrate the possibilities offered by this new method, we use it to derive position correction, orientation correction, obstacle avoidance and feedback control algorithms for the general class of planar wheeled robots and for a tridimensional underwater vehicle.
OPTIMAL TRAJECTORY PLANNING OF MANIPULATORS: A REVIEW
Directory of Open Access Journals (Sweden)
ATEF A. ATA
2007-04-01
Full Text Available Optimal motion planning is very important to the operation of robot manipulators. Its main target is the generation of a trajectory from start to goal that satisfies objectives, such as minimizing path traveling distance or time interval, lowest energy consumption or obstacle avoidance and satisfying the robot’s kinematics and dynamics. Review, discussion and analysis of optimization techniques to find the optimal trajectory either in Cartesian space or joint space are presented and investigated. Optimal trajectory selection approaches such as kinematics and dynamics techniques with various constraints are presented and explained. Although the kinematics approach is simple and straight forward, it will experience some problems in implementation because of lack of Inertia and torque constraints. The application of Genetic Algorithms to find the optimal trajectory of manipulators especially in the obstacle avoidance is also highlighted. Combining the Genetic Algorithms with other classical optimization methods proves to have better performance as a hybrid optimization technique.
Trajectory Clustering with Applications to Airspace Monitoring
National Aeronautics and Space Administration — This paper presents a framework aimed at monitoring the behavior of aircraft in a given airspace. Trajectories that constitute typical operations are determined and...
Analytical Ballistic Trajectories with Approximately Linear Drag
Directory of Open Access Journals (Sweden)
Giliam J. P. de Carpentier
2014-01-01
Full Text Available This paper introduces a practical analytical approximation of projectile trajectories in 2D and 3D roughly based on a linear drag model and explores a variety of different planning algorithms for these trajectories. Although the trajectories are only approximate, they still capture many of the characteristics of a real projectile in free fall under the influence of an invariant wind, gravitational pull, and terminal velocity, while the required math for these trajectories and planners is still simple enough to efficiently run on almost all modern hardware devices. Together, these properties make the proposed approach particularly useful for real-time applications where accuracy and performance need to be carefully balanced, such as in computer games.
Trajectory Browser: An Online Tool for Interplanetary Trajectory Analysis and Visualization
Foster, Cyrus James
2013-01-01
The trajectory browser is a web-based tool developed at the NASA Ames Research Center for finding preliminary trajectories to planetary bodies and for providing relevant launch date, time-of-flight and (Delta)V requirements. The site hosts a database of transfer trajectories from Earth to planets and small-bodies for various types of missions such as rendezvous, sample return or flybys. A search engine allows the user to find trajectories meeting desired constraints on the launch window, mission duration and (Delta)V capability, while a trajectory viewer tool allows the visualization of the heliocentric trajectory and the detailed mission itinerary. The anticipated user base of this tool consists primarily of scientists and engineers designing interplanetary missions in the context of pre-phase A studies, particularly for performing accessibility surveys to large populations of small-bodies.
User Oriented Trajectory Search for Trip Recommendation
Ding, Ruogu
2012-09-08
Trajectory sharing and searching have received significant attention in recent years. In this thesis, we propose and investigate the methods to find and recommend the best trajectory to the traveler, and mainly focus on a novel technique named User Oriented Trajectory Search (UOTS) query processing. In contrast to conventional trajectory search by locations (spatial domain only), we consider both spatial and textual domains in the new UOTS query. Given a trajectory data set, the query input contains a set of intended places given by the traveler and a set of textual attributes describing the traveler’s preference. If a trajectory is connecting/close to the specified query locations, and the textual attributes of the trajectory are similar to the traveler’s preference, it will be recommended to the traveler. This type of queries can enable many popular applications such as trip planning and recommendation. There are two challenges in UOTS query processing, (i) how to constrain the searching range in two domains and (ii) how to schedule multiple query sources effectively. To overcome the challenges and answer the UOTS query efficiently, a novel collaborative searching approach is developed. Conceptually, the UOTS query processing is conducted in the spatial and textual domains alternately. A pair of upper and lower bounds are devised to constrain the searching range in two domains. In the meantime, a heuristic searching strategy based on priority ranking is adopted for scheduling the multiple query sources, which can further reduce the searching range and enhance the query efficiency notably. Furthermore, the devised collaborative searching approach can be extended to situations where the query locations are or- dered. Extensive experiments are conducted on both real and synthetic trajectory data in road networks. Our approach is verified to be effective in reducing both CPU time and disk I/O time.
Machine Learning for Biological Trajectory Classification Applications
Sbalzarini, Ivo F.; Theriot, Julie; Koumoutsakos, Petros
2002-01-01
Machine-learning techniques, including clustering algorithms, support vector machines and hidden Markov models, are applied to the task of classifying trajectories of moving keratocyte cells. The different algorithms axe compared to each other as well as to expert and non-expert test persons, using concepts from signal-detection theory. The algorithms performed very well as compared to humans, suggesting a robust tool for trajectory classification in biological applications.
Age trajectories of stroke case fatality
DEFF Research Database (Denmark)
Olsen, Tom Skyhøj; Andersen, Zorana Jovanovic; Andersen, Klaus Kaae
2011-01-01
Mortality rates level off at older ages. Age trajectories of stroke case-fatality rates were studied with the aim of investigating prevalence of this phenomenon, specifically in case-fatality rates at older ages.......Mortality rates level off at older ages. Age trajectories of stroke case-fatality rates were studied with the aim of investigating prevalence of this phenomenon, specifically in case-fatality rates at older ages....
Trajectory Control and Optimization for Responsive Spacecraft
2012-03-22
functions. The scalar function φ defines the cost associated with the terminal conditions, and is referred to as the Mayer cost. The scalar function L...defines the cost associated with the values of x and u throughout the trajectory, and is referred to as the Lagrange cost. When J contains both a Mayer ...optimal space trajectories and is a fundamental reference in a vast majority of the literature on this subject. [22] Building on Lawden’s work, Jean
User Oriented Trajectory Search for Trip Recommendation
Ding, Ruogu
2012-07-08
Trajectory sharing and searching have received significant attention in recent years. In this thesis, we propose and investigate the methods to find and recommend the best trajectory to the traveler, and mainly focus on a novel technique named User Oriented Trajectory Search (UOTS) query processing. In contrast to conventional trajectory search by locations (spatial domain only), we consider both spatial and textual domains in the new UOTS query. Given a trajectory data set, the query input contains a set of intended places given by the traveler and a set of textual attributes describing the traveler’s preference. If a trajectory is connecting/close to the specified query locations, and the textual attributes of the trajectory are similar to the traveler’s preference, it will be recommended to the traveler. This type of queries can enable many popular applications such as trip planning and recommendation. There are two challenges in UOTS query processing, (i) how to constrain the searching range in two domains and (ii) how to schedule multiple query sources effectively. To overcome the challenges and answer the UOTS query efficiently, a novel collaborative searching approach is developed. Conceptually, the UOTS query processing is conducted in the spatial and textual domains alternately. A pair of upper and lower bounds are devised to constrain the searching range in two domains. In the meantime, a heuristic searching strategy based on priority ranking is adopted for scheduling the multiple query sources, which can further reduce the searching range and enhance the query efficiency notably. Furthermore, the devised collaborative searching approach can be extended to situations where the query locations are ordered. Extensive experiments are conducted on both real and synthetic trajectory data in road networks. Our approach is verified to be effective in reducing both CPU time and disk I/O time.
Kinematic evaluation of virtual walking trajectories.
Cirio, Gabriel; Olivier, Anne-Hélène; Marchal, Maud; Pettré, Julien
2013-04-01
Virtual walking, a fundamental task in Virtual Reality (VR), is greatly influenced by the locomotion interface being used, by the specificities of input and output devices, and by the way the virtual environment is represented. No matter how virtual walking is controlled, the generation of realistic virtual trajectories is absolutely required for some applications, especially those dedicated to the study of walking behaviors in VR, navigation through virtual places for architecture, rehabilitation and training. Previous studies focused on evaluating the realism of locomotion trajectories have mostly considered the result of the locomotion task (efficiency, accuracy) and its subjective perception (presence, cybersickness). Few focused on the locomotion trajectory itself, but in situation of geometrically constrained task. In this paper, we study the realism of unconstrained trajectories produced during virtual walking by addressing the following question: did the user reach his destination by virtually walking along a trajectory he would have followed in similar real conditions? To this end, we propose a comprehensive evaluation framework consisting on a set of trajectographical criteria and a locomotion model to generate reference trajectories. We consider a simple locomotion task where users walk between two oriented points in space. The travel path is analyzed both geometrically and temporally in comparison to simulated reference trajectories. In addition, we demonstrate the framework over a user study which considered an initial set of common and frequent virtual walking conditions, namely different input devices, output display devices, control laws, and visualization modalities. The study provides insight into the relative contributions of each condition to the overall realism of the resulting virtual trajectories.
Trajectory generation for a remotely operated vehicle
2003-01-01
This paper addresses the problem of trajectory generation for a remotely operated vehicle (ROV). The ROV is a nonholonomic vehicle and has limited actuator capabilities. This means that the task of trajectory generation for the inspection of underwater structures is not a trivial one, and that it cannot be done without computer aided design tools. The approach is based on techniques developed for differential flat systems. The ROV model is presented and it is shown that it satisfies the diffe...
On Discovery of Gathering Patterns from Trajectories
DEFF Research Database (Denmark)
Zheng, Kai; Zheng, Yu; Yuan, Jing
2013-01-01
The increasing pervasiveness of location-acquisition technologies has enabled collection of huge amount of trajectories for almost any kind of moving objects. Discovering useful patterns from their movement behaviours can convey valuable knowledge to a variety of critical applications...... detection algorithms implemented with bit vectors, and incremental algorithms for handling new trajectory arrivals, collectively constitute an efficient solution for this challenging task. Finally, the effectiveness of the proposed concepts and the efficiency of the approaches are validated by extensive...
"Traditional knowledge" and local development trajectories
2005-01-01
The paper discusses the concept of "traditional knowledge": its definition, economic significance and role in shaping regional development trajectories. After outlining a conceptual framework for the analysis of traditional knowledge, the paper examines the changing position of traditional knowledge in two Italian regions that have followed quite different development trajectories since the 1950s: the "Sibillini Mountains Region", which has one of the most complex human landscapes in Europe, ...
Trajectory options for the DART mission
Atchison, Justin A.; Ozimek, Martin T.; Kantsiper, Brian L.; Cheng, Andrew F.
2016-06-01
This study presents interplanetary trajectory options for the Double Asteroid Redirection Test (DART) spacecraft to reach the near Earth object, Didymos binary system, during its 2022 Earth conjunction. DART represents a component of a joint NASA-ESA mission to study near Earth object kinetic impact deflection. The DART trajectory must satisfy mission objectives for arrival timing, geometry, and lighting while minimizing launch vehicle and spacecraft propellant requirements. Chemical propulsion trajectories are feasible from two candidate launch windows in late 2020 and 2021. The 2020 trajectories are highly perturbed by Earth's orbit, requiring post-launch deep space maneuvers to retarget the Didymos system. Within these windows, opportunities exist for flybys of additional near Earth objects: Orpheus in 2021 or 2007 YJ in 2022. A second impact attempt, in the event that the first impact is unsuccessful, can be added at the expense of a shorter launch window and increased (∼3x) spacecraft ΔV . However, the second impact arrival geometry has poor lighting, high Earth ranges, and would require additional degrees of freedom for solar panel and/or antenna gimbals. A low-thrust spacecraft configuration increases the trajectory flexibility. A solar electric propulsion spacecraft could be affordably launched as a secondary spacecraft in an Earth orbit and spiral out to target the requisite interplanetary departure condition. A sample solar electric trajectory was constructed from an Earth geostationary transfer using a representative 1.5 kW thruster. The trajectory requires 9 months to depart Earth's sphere of influence, after which its interplanetary trajectory includes a flyby of Orpheus and a second Didymos impact attempt. The solar electric spacecraft implementation would impose additional bus design constraints, including large solar arrays that could pose challenges for terminal guidance. On the basis of this study, there are many feasible options for DART to
Quantum trajectories based on the weak value
Mori, Takuya; Tsutsui, Izumi
2015-04-01
The notion of the trajectory of an individual particle is strictly inhibited in quantum mechanics because of the uncertainty principle. Nonetheless, the weak value, which has been proposed as a novel and measurable quantity definable to any quantum observable, can offer a possible description of trajectory on account of its statistical nature. In this paper, we explore the physical significance provided by this "weak trajectory" by considering various situations where interference takes place simultaneously with the observation of particles, that is, in prototypical quantum situations for which no classical treatment is available. These include the double slit experiment and Lloyd's mirror, where in the former case it is argued that the real part of the weak trajectory describes an average over the possible classical trajectories involved in the process, and that the imaginary part is related to the variation of interference. It is shown that this average interpretation of the weak trajectory holds universally under the complex probability defined from the given transition process. These features remain essentially unaltered in the case of Lloyd's mirror where interference occurs with a single slit.
A demonstration and evaluation of trajectory mapping
Energy Technology Data Exchange (ETDEWEB)
Morris, G.A. [Rice Univ., Houston, TX (United States). Dept. of Space Physics and Astronomy
1994-09-01
Problem of creating synoptic maps from asynoptically gathered data has prompted the development of a number schemes, the most notable being the Kalman filter, Salby-Fourier technique, and constituent reconstruction. This thesis presents a new technique, called trajectory mapping, which employs a simple model of air parcel motion to create synoptic maps from asynoptically gathered data. Four sources of trajectory mapping errors were analyzed; results showed that (1) the computational error is negligible; (2) measurement uncertainties can result in errors which grow with time scales of a week; (3) isentropic approximations lead to errors characterized by time scales of a week; and (4) wind field inaccuracies can cause significant errors in individual parcel trajectories in a matter of hours. All the studies, however, indicated that while individual trajectory errors can grow rapidly, constituent distributions, such as on trajectory maps, are much more robust, maintaining a high level of accuracy for periods on the order of several weeks. This technique was successfully applied to a variety of problems:(1) dynamical wave- breaking events; (2) satellite data validation for both instrument accuracy and precision; and (3) accuracy of meteorological wind fields. Such demonstrations imply that trajectory mapping will become an important tool in answering questions of global change, particularly the issue of ozone depletion.
Searching Trajectories by Regions of Interest
Shang, Shuo
2017-03-22
With the increasing availability of moving-object tracking data, trajectory search is increasingly important. We propose and investigate a novel query type named trajectory search by regions of interest (TSR query). Given an argument set of trajectories, a TSR query takes a set of regions of interest as a parameter and returns the trajectory in the argument set with the highest spatial-density correlation to the query regions. This type of query is useful in many popular applications such as trip planning and recommendation, and location based services in general. TSR query processing faces three challenges: how to model the spatial-density correlation between query regions and data trajectories, how to effectively prune the search space, and how to effectively schedule multiple so-called query sources. To tackle these challenges, a series of new metrics are defined to model spatial-density correlations. An efficient trajectory search algorithm is developed that exploits upper and lower bounds to prune the search space and that adopts a query-source selection strategy, as well as integrates a heuristic search strategy based on priority ranking to schedule multiple query sources. The performance of TSR query processing is studied in extensive experiments based on real and synthetic spatial data.
Directory of Open Access Journals (Sweden)
SUN Wenbin
2016-11-01
Full Text Available In order to improve the accuracy of low frequency (sampling interval greater than 1 minute trajectory data matching algorithm, this paper proposed a novel matching algorithm termed HMDP-Q (History Markov Decision Processes Q-learning. The new algorithm is based on reinforced learning on historic trajectory. First, we extract historic trajectory data according to incremental matching algorithm as historical reference, and filter the trajectory dataset through the historic reference, the shortest trajectory and the reachability. Then we model the map matching process as the Markov decision process, and build up reward function using deflected distance between trajectory points and historic trajectories. The largest reward value of the Markov decision process was calculated by using the reinforced learning algorithm, which is the optimal matching result of trajectory and road. Finally we calibrate the algorithm by utilizing city's floating cars data to experiment. The results show that this algorithm can improve the accuracy between trajectory data and road. The matching accuracy is 89.2% within 1 minute low-frequency sampling interval, and the matching accuracy is 61.4% when the sampling frequency is 16 minutes. Compared with IVVM (Interactive Voting-based Map Matching, HMDP-Q has a higher matching accuracy and computing efficiency. Especially, when the sampling frequency is 16 minutes, HMDP-Q improves the matching accuracy by 26%.
Larsen, E W; Lorek, E; Heyl, C M; Palecek, D; L'Huillier, A; Zigmantas, D; Mauritsson, J
2015-01-01
We experimentally investigate how the ellipticity of the driving laser pulses influences high-order harmonic generation from the first two sets of quantum trajectories. Using long pulses at a high repetition rate in a tight focusing configuration combined with a spectrometer that resolves the harmonic emission both spatially and spectrally, allows for a clear separation of the emission generated by the long and the short trajectories. We find that a model describing the long trajectories has to include a sub-cycle change in both ionization rate and initial electron velocity distribution as well as a change of the excursion time when the ellipticity is changed. Additionally, we find that the configuration interaction between two electrons influences the ellipticity dependence of both trajectories through the AC-Stark shift.
User oriented trajectory search for trip recommendation
Shang, Shuo
2012-01-01
Trajectory sharing and searching have received significant attentions in recent years. In this paper, we propose and investigate a novel problem called User Oriented Trajectory Search (UOTS) for trip recommendation. In contrast to conventional trajectory search by locations (spatial domain only), we consider both spatial and textual domains in the new UOTS query. Given a trajectory data set, the query input contains a set of intended places given by the traveler and a set of textual attributes describing the traveler\\'s preference. If a trajectory is connecting/close to the specified query locations, and the textual attributes of the trajectory are similar to the traveler\\'e preference, it will be recommended to the traveler for reference. This type of queries can bring significant benefits to travelers in many popular applications such as trip planning and recommendation. There are two challenges in the UOTS problem, (i) how to constrain the searching range in two domains and (ii) how to schedule multiple query sources effectively. To overcome the challenges and answer the UOTS query efficiently, a novel collaborative searching approach is developed. Conceptually, the UOTS query processing is conducted in the spatial and textual domains alternately. A pair of upper and lower bounds are devised to constrain the searching range in two domains. In the meantime, a heuristic searching strategy based on priority ranking is adopted for scheduling the multiple query sources, which can further reduce the searching range and enhance the query efficiency notably. Furthermore, the devised collaborative searching approach can be extended to situations where the query locations are ordered. The performance of the proposed UOTS query is verified by extensive experiments based on real and synthetic trajectory data in road networks. © 2012 ACM.
Trajectory attractors of equations of mathematical physics
Energy Technology Data Exchange (ETDEWEB)
Vishik, Marko I; Chepyzhov, Vladimir V [Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow (Russian Federation)
2011-08-31
In this survey the method of trajectory dynamical systems and trajectory attractors is described, and is applied in the study of the limiting asymptotic behaviour of solutions of non-linear evolution equations. This method is especially useful in the study of dissipative equations of mathematical physics for which the corresponding Cauchy initial-value problem has a global (weak) solution with respect to the time but the uniqueness of this solution either has not been established or does not hold. An important example of such an equation is the 3D Navier-Stokes system in a bounded domain. In such a situation one cannot use directly the classical scheme of construction of a dynamical system in the phase space of initial conditions of the Cauchy problem of a given equation and find a global attractor of this dynamical system. Nevertheless, for such equations it is possible to construct a trajectory dynamical system and investigate a trajectory attractor of the corresponding translation semigroup. This universal method is applied for various types of equations arising in mathematical physics: for general dissipative reaction-diffusion systems, for the 3D Navier-Stokes system, for dissipative wave equations, for non-linear elliptic equations in cylindrical domains, and for other equations and systems. Special attention is given to using the method of trajectory attractors in approximation and perturbation problems arising in complicated models of mathematical physics. Bibliography: 96 titles.
Thoracostomy tube function not trajectory dictates reintervention.
Kugler, Nathan W; Carver, Thomas W; Knechtges, Paul; Milia, David; Goodman, Lawrence; Paul, Jasmeet S
2016-12-01
Hemothorax and/or pneumothorax can be managed successfully managed with tube thoracostomy (TT) in the majority of cases. Improperly placed tubes are common with rates near 30%. This study aimed to determine whether TT trajectory affects the rate of secondary intervention. A retrospective review of all adult trauma patients undergoing TT placement over a 4-y period was performed. TT trajectory was classified as ideal, nonideal, or kinked-based on anterior-posterior chest x-ray. TTs with sentinel port outside the thoracic cavity were excluded. The primary outcome was any secondary intervention. Four-hundred eighty-six patients and a total of 547 hemithoraces underwent placement and met inclusion criteria. The majority of patients were male (76%), with a median age of 41 y, and majority suffered blunt trauma ideal trajectory was identified in 429 (78.4%). Kinked TTs were noted in 33 (6%) hemothoraces with a 45.5% replacement rate. Review with staff demonstrates inherent bias to replace kinked TTs. The overall secondary intervention rate was 27.8%. Kinked TTs were removed from final analysis due to treatment bias. Subsequent analysis demonstrated no significant difference between ideal and nonideal trajectories (25.1% versus 34.1%, P = 0.09). Intrathoracic trajectory of nonkinked TTs with the sentinel port within the thoracic cavity does not affect secondary intervention rates, including the rate of surgical intervention. Copyright Â© 2016 Elsevier Inc. All rights reserved.
EUROPA Multiple-Flyby Trajectory Design
Buffington, Brent; Campagnola, Stefano; Petropoulos, Anastassios
2012-01-01
As reinforced by the 2011 NRC Decadal Survey, Europa remains one of the most scientifically intriguing targets in planetary science due to its potential suitability for life. However, based on JEO cost estimates and current budgetary constraints, the Decadal Survey recommended-and later directed by NASA Headquarters-a more affordable pathway to Europa exploration be derived. In response, a flyby-only proof-of-concept trajectory has been developed to investigate Europa. The trajectory, enabled by employing a novel combination of new mission design techniques, successfully fulfills a set of Science Definition Team derived scientific objectives carried out by a notional payload including ice penetrating radar, topographic imaging, and short wavelength infrared observations, and ion neutral mass spectrometry in-situ measurements. The current baseline trajectory, referred to as 11-F5, consists of 34 Europa and 9 Ganymede flybys executed over the course of 2.4 years, reached a maximum inclination of 15 degrees, has a deterministic delta v of 157 m/s (post-PJR), and has a total ionizing dose of 2.06 Mrad (Si behind 100 mil Al, spherical shell). The 11-F5 trajectory and more generally speaking, flyby-only trajectories-exhibit a number of potential advantages over an Europa orbiter mission.
Bohmian mechanics and the quantum revolution
Goldstein, S
1995-01-01
This is a review-essay on ``Speakable and Unspeakable in Quantum Mechanics'' by John Bell and ``The Undivided Universe: An Ontological Interpretation of Quantum Mechanics'' by David Bohm and Basil Hiley. The views of these authors concerning the character of quantum theory and quantum reality---and, in particular, their approaches to the issues of nonlocality, the possibility of hidden variables, and the nature of and desiderata for a satisfactory scientific explanation of quantum phenomena---are contrasted, with each other and with the orthodox approach to these issues.
Bohmian Mechanics and the Quantum Revolution
Goldstein, Sheldon
1995-01-01
This is a review-essay on ``Speakable and Unspeakable in Quantum Mechanics'' by John Bell and ``The Undivided Universe: An Ontological Interpretation of Quantum Mechanics'' by David Bohm and Basil Hiley. The views of these authors concerning the character of quantum theory and quantum reality---and, in particular, their approaches to the issues of nonlocality, the possibility of hidden variables, and the nature of and desiderata for a satisfactory scientific explanation of quantum phenomena--...
Bohmian mechanics and quantum theory an appraisal
Goldstein, Sheldon; Cushing, James T
1996-01-01
We are often told that quantum phenomena demand radical revisions of our scientific world view and that no physical theory describing well defined objects, such as particles described by their positions, evolving in a well defined way, let alone deterministically, can account for such phenomena. The great majority of physicists continue to subscribe to this view, despite the fact that just such a deterministic theory, accounting for all of the phe nomena of nonrelativistic quantum mechanics, was proposed by David Bohm more than four decades ago and has arguably been around almost since the inception of quantum mechanics itself. Our purpose in asking colleagues to write the essays for this volume has not been to produce a Festschrift in honor of David Bohm (worthy an undertaking as that would have been) or to gather together a collection of papers simply stating uncritically Bohm's views on quantum mechanics. The central theme around which the essays in this volume are arranged is David Bohm's vers...
Compact electron beam focusing column
Energy Technology Data Exchange (ETDEWEB)
Persaud, Arun; Leung, Ka-Ngo; Reijonen, Jani
2001-07-13
A novel design for an electron beam focusing column has been developed at LBNL. The design is based on a low-energy spread multicusp plasma source which is used as a cathode for electron beam production. The focusing column is 10 mm in length. The electron beam is focused by means of electrostatic fields. The column is designed for a maximum voltage of 50 kV. Simulations of the electron trajectories have been performed by using the 2-D simulation code IGUN and EGUN. The electron temperature has also been incorporated into the simulations. The electron beam simulations, column design and fabrication will be discussed in this presentation.
3D Visualization of Cooperative Trajectories
Schaefer, John A.
2014-01-01
Aerodynamicists and biologists have long recognized the benefits of formation flight. When birds or aircraft fly in the upwash region of the vortex generated by leaders in a formation, induced drag is reduced for the trail bird or aircraft, and efficiency improves. The major consequence of this is that fuel consumption can be greatly reduced. When two aircraft are separated by a large enough longitudinal distance, the aircraft are said to be flying in a cooperative trajectory. A simulation has been developed to model autonomous cooperative trajectories of aircraft; however it does not provide any 3D representation of the multi-body system dynamics. The topic of this research is the development of an accurate visualization of the multi-body system observable in a 3D environment. This visualization includes two aircraft (lead and trail), a landscape for a static reference, and simplified models of the vortex dynamics and trajectories at several locations between the aircraft.
Robot Trajectories Comparison: A Statistical Approach
Directory of Open Access Journals (Sweden)
A. Ansuategui
2014-01-01
Full Text Available The task of planning a collision-free trajectory from a start to a goal position is fundamental for an autonomous mobile robot. Although path planning has been extensively investigated since the beginning of robotics, there is no agreement on how to measure the performance of a motion algorithm. This paper presents a new approach to perform robot trajectories comparison that could be applied to any kind of trajectories and in both simulated and real environments. Given an initial set of features, it automatically selects the most significant ones and performs a statistical comparison using them. Additionally, a graphical data visualization named polygraph which helps to better understand the obtained results is provided. The proposed method has been applied, as an example, to compare two different motion planners, FM2 and WaveFront, using different environments, robots, and local planners.
Robot Trajectories Comparison: A Statistical Approach
Ansuategui, A.; Arruti, A.; Susperregi, L.; Yurramendi, Y.; Jauregi, E.; Lazkano, E.; Sierra, B.
2014-01-01
The task of planning a collision-free trajectory from a start to a goal position is fundamental for an autonomous mobile robot. Although path planning has been extensively investigated since the beginning of robotics, there is no agreement on how to measure the performance of a motion algorithm. This paper presents a new approach to perform robot trajectories comparison that could be applied to any kind of trajectories and in both simulated and real environments. Given an initial set of features, it automatically selects the most significant ones and performs a statistical comparison using them. Additionally, a graphical data visualization named polygraph which helps to better understand the obtained results is provided. The proposed method has been applied, as an example, to compare two different motion planners, FM2 and WaveFront, using different environments, robots, and local planners. PMID:25525618
QCD Glueball Regge Trajectories and the Pomeron
Llanes-Estrada, F J; De Bicudo, P J A; Tavares-Ribeiro, J E F; Szczepaniak, A P; Llanes-Estrada, Felipe J.; Cotanch, Stephen R; Bicudo, Pedro J A; Szczepaniak, Adam P
2000-01-01
We report glueball Regge trajectories emerging from diagonalizing a confining Coulomb gauge Hamiltonian for constituent gluons. Using a BCS vacuum ansatz and gap equation, the dressed gluons acquire a mass, of order 800 MeV, providing the quasiparticle degrees of freedom for a TDA glueball formulation. The TDA eigenstates for two constituent gluons have orbital, L, excitations with a characteristic energy of 400 MeV and reveal clear Regge trajectories for each L and S combination giving J=L+S... |L-S|, where S is the total (sum) gluon spin. Significantly, all trajectories have the same 0.28 GeV-2 Regge slope, similar to the pomeron value of 0.25 GeV-2. Recent lattice data further supports this result and yields an intercept close to the pomeron.
Trajectory metaheuristic algorithms to optimize problems combinatorics
Directory of Open Access Journals (Sweden)
Natalia Alancay
2016-12-01
Full Text Available The application of metaheuristic algorithms to optimization problems has been very important during the last decades. The main advantage of these techniques is their flexibility and robustness, which allows them to be applied to a wide range of problems. In this work we concentrate on metaheuristics based on Simulated Annealing, Tabu Search and Variable Neighborhood Search trajectory whose main characteristic is that they start from a point and through the exploration of the neighborhood vary the current solution, forming a trajectory. By means of the instances of the selected combinatorial problems, a computational experimentation is carried out that illustrates the behavior of the algorithmic methods to solve them. The main objective of this work is to perform the study and comparison of the results obtained for the selected trajectories metaheuristics in its application for the resolution of a set of academic problems of combinatorial optimization.
Discovery of Convoys in Trajectory Databases
Jeung, Hoyoung; Zhou, Xiaofang; Jensen, Christian S; Shen, Heng Tao
2010-01-01
As mobile devices with positioning capabilities continue to proliferate, data management for so-called trajectory databases that capture the historical movements of populations of moving objects becomes important. This paper considers the querying of such databases for convoys, a convoy being a group of objects that have traveled together for some time. More specifically, this paper formalizes the concept of a convoy query using density-based notions, in order to capture groups of arbitrary extents and shapes. Convoy discovery is relevant for real-life applications in throughput planning of trucks and carpooling of vehicles. Although there has been extensive research on trajectories in the literature, none of this can be applied to retrieve correctly exact convoy result sets. Motivated by this, we develop three efficient algorithms for convoy discovery that adopt the well-known filter-refinement framework. In the filter step, we apply line-simplification techniques on the trajectories and establish distance b...
Centrifugally driven relativistic dynamics on curved trajectories
Rogava, A; Osmanov, Z; Rogava, Andria; Dalakishvili, George; Osmanov, Zaza
2003-01-01
Motion of test particles along rotating curved trajectories is considered. The problem is studied both in the laboratory and the rotating frames of reference. It is assumed that the system rotates with the constant angular velocity $\\omega = const$. The solutions are found and analyzed for the case when the form of the trajectory is given by an Archimedes spiral. It is found that particles can reach infinity while they move along these trajectories and the physical interpretation of their behaviour is given. The analogy of this idealized study with the motion of particles along the curved rotating magnetic field lines in the pulsar magnetosphere is pointed out. We discuss further physical development (the conserved total energy case, when $\\omega \
Romantic attraction and adolescent smoking trajectories.
Pollard, Michael S; Tucker, Joan S; Green, Harold D; Kennedy, David P; Go, Myong-Hyun
2011-12-01
Research on sexual orientation and substance use has established that lesbian, gay, and bisexual (LGB) individuals are more likely to smoke than heterosexuals. This analysis furthers the examination of smoking behaviors across sexual orientation groups by describing how same- and opposite-sex romantic attraction, and changes in romantic attraction, are associated with distinct six-year developmental trajectories of smoking. The National Longitudinal Study of Adolescent Health dataset is used to test our hypotheses. Multinomial logistic regressions predicting smoking trajectory membership as a function of romantic attraction were separately estimated for men and women. Romantic attraction effects were found only for women. The change from self-reported heterosexual attraction to lesbian or bisexual attraction was more predictive of higher smoking trajectories than was a consistent lesbian or bisexual attraction, with potentially important differences between the smoking patterns of these two groups.
Trajectory Optimization Design for Morphing Wing Missile
Institute of Scientific and Technical Information of China (English)
Ruisheng Sun; Chao Ming; Chuanjie Sun
2015-01-01
This paper presents a new particle swarm optimization ( PSO) algorithm to optimize the trajectory of morphing⁃wing missile so as to achieve the enlargement of the maximum range. Equations of motion for the two⁃dimensional dynamics are derived by treating the missile as an ideal controllable mass point. An investigation of aerodynamic characteristics of morphing⁃wing missile with varying geometries is performed. After deducing the optimizing trajectory model for maximizing range, a type of discrete method is put forward for taking optimization control problem into nonlinear dynamic programming problem. The optimal trajectory is solved by using PSO algorithm and penalty function method. The simulation results suggest that morphing⁃wing missile has the larger range than the fixed⁃shape missile when launched at supersonic speed, while morphing⁃wing missile has no obvious range increment than the fixed⁃shape missile at subsonic speed.
Trajectory surgical guide stent for implant placement.
Adrian, E D; Ivanhoe, J R; Krantz, W A
1992-05-01
This article describes a new implant placement surgical guide that gives both implant location and trajectory to the surgeon. Radiopaque markers are placed on diagnostic dentures and a lateral cephalometric radiograph is made that shows the osseous anatomy at the symphysis and the anterior tooth location. The ideal implant location and trajectory data are transferred to a surgical stent that programs the angle and location of the fixtures at time of surgery. The stent has the additional benefit of acting as an occlusion rim, a mouth prop, and tongue retractor. Use of this stent has resulted in consistently programming the placement of implant fixtures that are prosthodontically ideal.
Trajectories for Novel and Detailed Traffic Information
DEFF Research Database (Denmark)
Krogh, Benjamin Bjerre; Andersen, Ove; Torp, Kristian
2012-01-01
Trajectories based on GPS tracks have been studied for a number of years but only to a limited degree been used for analyzing and monitoring traffic. This paper shows how novel and important information about traffic can be computed from trajectories. Concretely the paper proposes to compute...... to analyzing individual intersections that enables traffic analysts to compute queue lengths and estimated time to pass an intersection. Finally, the paper uses associative rule mining for evaluating green waves on road stretches. Such information can be used to verify that signalized intersections......, extracting this information requires no expensive changes to the road-network infrastructure, which is a problem with the technologies currently used....
Trajectory Browser: An online tool for interplanetary trajectory analysis and visualization
Foster, C.
The Trajectory Browser is a web-based tool developed at the NASA Ames Research Center for finding preliminary trajectories to planetary bodies and for providing relevant launch date, time-of-flight and Δ V requirements. The site hosts a database of transfer trajectories from Earth to planets and small-bodies for various types of missions such as rendezvous, sample return or flybys. A search engine allows the user to find trajectories meeting desired constraints on the launch window, mission duration and Δ V capability, while a trajectory viewer tool allows the visualization of the heliocentric trajectory and the detailed mission itinerary. The anticipated user base of this tool consists primarily of scientists and engineers designing interplanetary missions in the context of pre-phase A studies, particularly for performing accessibility surveys to large populations of small-bodies. The educational potential of the website is also recognized for academia and the public with regards to trajectory design, a field that has generally been poorly understood by the public. The website is currently hosted on NASA-internal URL http://trajbrowser.arc.nasa.gov/ with plans for a public release in early 2013.
The Feynman trajectories: determining the path of a protein using fixed-endpoint assays.
Ketteler, Robin
2010-03-01
Richard Feynman postulated in 1948 that the path of an electron can be best described by the sum or functional integral of all possible trajectories rather than by the notion of a single, unique trajectory. As a consequence, the position of an electron does not harbor any information about the paths that contributed to this position. This observation constitutes a classical endpoint observation. The endpoint assay is the desired type of experiment for high-throughput screening applications, mainly because of limitations in data acquisition and handling. Quite contrary to electrons, it is possible to extract information about the path of a protein using endpoint assays, and these types of applications are reviewed in this article.
Frequent Trajectory Patterns Mining for Intelligent Visual Surveillance System
Institute of Scientific and Technical Information of China (English)
QU Lin; CHEN Yao-wu
2009-01-01
A frequent trajectory patterns mining algorithm is proposed to learn the object activities and classify the trajectories in intelligent visual surveillance system. The distribution patterns of the trajectories were generated by an Apriori based frequent patterns mining algorithm and the trajectories were classified by the frequent trajectory patterns generated. In addition, a fuzzy c-mcans (FCM) based learning algorithm and a mean shift based clustering procedure were used to construct the representation of trajectories. The algorithm can be further used to describe activities and identify anomalies. The experiments on two real scenes show that the algorithm is effective.
Towards managing nonlinear regional development trajectories
Hartman, Stefan; De Roo, Gert
2013-01-01
Regions can become 'locked' into a spatial-economic development trajectory, thereby losing their capacity to adapt to spatial dynamics. This is in contrast to those regions that seem to be able to reinvent themselves by adapting to processes that drive spatial change, deviating from past development
The emergence of an electric mobility trajectory
Dijk, M.; Orsato, R.J.; Kemp, R.P.M.
2013-01-01
In this paper, we analyse the emergence of a trajectory of electric mobility. We describe developments in electric vehicles before and after 2005. The central thesis of the paper is that electric mobility has crossed a critical threshold and is benefiting from various developments whose influence
Improved transition models for cepstral trajectories
CSIR Research Space (South Africa)
Badenhorst, J
2012-11-01
Full Text Available We improve on a piece-wise linear model of the trajectories of Mel Frequency Cepstral Coefficients, which are commonly used as features in Automatic Speech Recognition. For this purpose, we have created a very clean single-speaker corpus, which...
Filtering Drifter Trajectories Sampled at Submesoscale Resolution
2015-07-10
accelerations of the analyzed GLAD trajectories. In the region , the pdf is virtually indistinguishable from the Gaussian noise parabola with the rms...Pdf of the observed GLAD drifter accelerations (blue), the Gaussian model of the accelerations induced by the GPS noise (black parabola ), the pdf of
Graphical Method for Determining Projectile Trajectory
Moore, J. C.; Baker, J. C.; Franzel, L.; McMahon, D.; Songer, D.
2010-01-01
We present a nontrigonometric graphical method for predicting the trajectory of a projectile when the angle and initial velocity are known. Students enrolled in a general education conceptual physics course typically have weak backgrounds in trigonometry, making inaccessible the standard analytical calculation of projectile range. Furthermore,…
A STUDY OF SHUTTLECOCK'S TRAJECTORY IN BADMINTON
Directory of Open Access Journals (Sweden)
Yung-Jen Chen
2009-12-01
Full Text Available The main purpose of this study was to construct and validate a motion equation for the flight of the badminton and to find the relationship between the air resistance force and a shuttlecock's speed. This research method was based on motion laws of aerodynamics. It applied aerodynamic theories to construct motion equation of a shuttlecock's flying trajectory under the effects of gravitational force and air resistance force. The result showed that the motion equation of a shuttlecock's flight trajectory could be constructed by determining the terminal velocity. The predicted shuttlecock trajectory fitted the measured data fairly well. The results also revealed that the drag force was proportional to the square of a shuttlecock velocity. Furthermore, the angle and strength of a stroke could influence trajectory. Finally, this study suggested that we could use a scientific approach to measure a shuttlecock's velocity objectively when testing the quality of shuttlecocks. And could be used to replace the traditional subjective method of the Badminton World Federation based on players' striking shuttlecocks, as well as applying research findings to improve professional knowledge of badminton player training
Academic Trajectories of Newcomer Immigrant Youth
Suarez-Orozco, Carola; Gaytan, Francisco X.; Bang, Hee Jin; Pakes, Juliana; O'Connor, Erin; Rhodes, Jean
2010-01-01
Immigration to the United States presents both challenges and opportunities that affect students' academic achievement. Using a 5-year longitudinal, mixed-methods approach, we identified varying academic trajectories of newcomer immigrant students from Central America, China, the Dominican Republic, Haiti, and Mexico. Latent class growth curve…
Nonlinear Optimal Trajectories Using Successive Linearization
1977-06-28
integral sign represents a penalty for the local vertical and passing through the vehicle deviations of the perturbed trajectory from the at time equals... integral sign represents the penalty for control variations about the nominal, and needs z s - sin y (14) to be weighted to ensure that the control does
APT: Action localization Proposals from dense Trajectories
van Gemert, J.C.; Jain, M.; Gati, E.; Snoek, C.G.M.; Xie, X.; Jones, M.W.; Tam, G.K.L.
2015-01-01
This paper is on action localization in video with the aid of spatio-temporal proposals. To alleviate the computational expensive video segmentation step of existing proposals, we propose bypassing the segmentations completely by generating proposals directly from the dense trajectories used to repr
Test particle trajectories near cosmic strings
Indian Academy of Sciences (India)
Farook Rahaman; Subenoy Chakraborty; K Maity
2002-01-01
We present a detailed analysis of the motion of test particle in the gravitational ﬁeld of cosmic strings in different situations using the Hamilton–Jacobi (H–J) formalism. We have discussed the trajectories near static cosmic string, cosmic string in Brans–Dicke theory and cosmic string in dilaton gravity.
Towards managing nonlinear regional development trajectories
Hartman, Stefan; De Roo, Gert
2013-01-01
Regions can become 'locked' into a spatial-economic development trajectory, thereby losing their capacity to adapt to spatial dynamics. This is in contrast to those regions that seem to be able to reinvent themselves by adapting to processes that drive spatial change, deviating from past development
Quantum trajectory pictures of laser cooling
Nienhuis, G.; Kloe, J. de; Straten, P. van der
1997-01-01
We have applied the method of single atom trajectories to study the mechanism behind some cooling schemes in laser cooling. In several cases we recognize the cooling mechanism as being due to a "Sisyphus" process, where the atoms move in a spatially varying light shift potential and are optically pu
Effective Online Group Discovery in Trajectory Databases
DEFF Research Database (Denmark)
Li, Xiaohui; Ceikute, Vaida; Jensen, Christian S.;
2013-01-01
GPS-enabled devices are pervasive nowadays. Finding movement patterns in trajectory data stream is gaining in importance. We propose a group discovery framework that aims to efficiently support the online discovery of moving objects that travel together. The framework adopts a sampling...
Graphical Method for Determining Projectile Trajectory
Moore, J. C.; Baker, J. C.; Franzel, L.; McMahon, D.; Songer, D.
2010-01-01
We present a nontrigonometric graphical method for predicting the trajectory of a projectile when the angle and initial velocity are known. Students enrolled in a general education conceptual physics course typically have weak backgrounds in trigonometry, making inaccessible the standard analytical calculation of projectile range. Furthermore,…
Discovery of convoys in trajectory databases
DEFF Research Database (Denmark)
Jeung, Hoyoung; Yiu, Man Lung; Zhou, Xiaofang
2008-01-01
of trucks and carpooling of vehicles. Although there has been extensive research on trajectories in the literature, none of this can be applied to retrieve correctly exact convoy result sets. Motivated by this, we develop three efficient algorithms for convoy discovery that adopt the well-known filter...
Correlation Imaging with Arbitrary Sampling Trajectories
Li, Yu
2014-01-01
The presented work aims to develop a generalized linear approach to image reconstruction with arbitrary sampling trajectories for high-speed MRI. This approach is based on a previously developed image reconstruction framework, "correlation imaging" (1). In the presented work, correlation imaging with arbitrary sampling trajectories is implemented in a multi-dimensional hybrid space that is formed from the physical sampling space and a virtually defined space. By introducing an undersampling trajectory with both uniformity and randomness in the hybrid space, correlation imaging may take advantage of multiple image reconstruction mechanisms including coil sensitivity encoding, data sparsity and information sharing. This hybrid-space implementation is demonstrated in multi-slice 2D imaging, multi-scan imaging, and radial dynamic imaging. Since more information is used in image reconstruction, it is found that hybrid-space correlation imaging outperforms several conventional techniques. The presented approach will benefit clinical MRI by enabling correlation imaging to be used to accelerate multi-scan clinical protocols that need different sampling trajectories in different scans. PMID:24629517
Effective Online Group Discovery in Trajectory Databases
DEFF Research Database (Denmark)
Li, Xiaohui; Ceikute, Vaida; Jensen, Christian S.
2013-01-01
GPS-enabled devices are pervasive nowadays. Finding movement patterns in trajectory data stream is gaining in importance. We propose a group discovery framework that aims to efficiently support the online discovery of moving objects that travel together. The framework adopts a sampling-independen...
Generation of NEP heliocentric trajectory data
Horsewood, J. L.; Brice, K. B.
1972-01-01
A study, designed to generate representative nuclear electric propulsion data for rendezvous missions to the comet Encke using the variational calculus program HILTOP, is presented. Other purposes of the study include a comparison of the HILTOP data with equivalent data generated with QUICKTOP program and to propose approaches for storing and subsequently accessing the optimum trajectory and performance data in the QUICKLY program.
Academic Trajectories of Newcomer Immigrant Youth
Suarez-Orozco, Carola; Gaytan, Francisco X.; Bang, Hee Jin; Pakes, Juliana; O'Connor, Erin; Rhodes, Jean
2010-01-01
Immigration to the United States presents both challenges and opportunities that affect students' academic achievement. Using a 5-year longitudinal, mixed-methods approach, we identified varying academic trajectories of newcomer immigrant students from Central America, China, the Dominican Republic, Haiti, and Mexico. Latent class growth curve…
Developmental Trajectories of Early Communication Skills
Maatta, Sira; Laakso, Marja-Leena; Tolvanen, Asko; Ahonen, Timo; Aro, Tuija
2012-01-01
Purpose: This study focused on developmental trajectories of prelinguistic communication skills and their connections to later parent-reported language difficulties. Method: The participants represent a subset of a community-based sample of 508 children. Data include parent reports of prelinguistic communication skills at 12, 15, 18, and 21 months…
Developmental Trajectories of Early Communication Skills
Maatta, Sira; Laakso, Marja-Leena; Tolvanen, Asko; Ahonen, Timo; Aro, Tuija
2012-01-01
Purpose: This study focused on developmental trajectories of prelinguistic communication skills and their connections to later parent-reported language difficulties. Method: The participants represent a subset of a community-based sample of 508 children. Data include parent reports of prelinguistic communication skills at 12, 15, 18, and 21 months…
The emergence of an electric mobility trajectory
Dijk, M.; Orsato, R.J.; Kemp, R.P.M.
2013-01-01
In this paper, we analyse the emergence of a trajectory of electric mobility. We describe developments in electric vehicles before and after 2005. The central thesis of the paper is that electric mobility has crossed a critical threshold and is benefiting from various developments whose influence ca
Quantum trajectory pictures of laser cooling
Nienhuis, G.; Kloe, J. de; Straten, P. van der
1997-01-01
We have applied the method of single atom trajectories to study the mechanism behind some cooling schemes in laser cooling. In several cases we recognize the cooling mechanism as being due to a "Sisyphus" process, where the atoms move in a spatially varying light shift potential and are optically
Cullati, Stéphane
2014-07-01
Self-rated health (SRH) trajectories tend to decline over a lifetime. Moreover, the Cumulative Advantage and Disadvantage (CAD) model indicates that SRH trajectories are known to consistently diverge along socioeconomic positions (SEP) over the life course. However, studies of working adults to consider the influence of work and family conflict (WFC) on SRH trajectories are scarce. We test the CAD model and hypothesise that SRH trajectories diverge over time according to socioeconomic positions and WFC trajectories accentuate this divergence. Using longitudinal data from the Swiss Household Panel (N = 2327 working respondents surveyed from 2004 to 2010), we first examine trajectories of SRH and potential divergence over time across age, gender, SEP and family status using latent growth curve analysis. Second, we assess changes in SRH trajectories in relation to changes in WFC trajectories and divergence in SRH trajectories according to gender, SEP and family status using parallel latent growth curve analysis. Three measures of WFC are used: exhaustion after work, difficulty disconnecting from work, and work interference in private family obligations. The results show that SRH trajectories slowly decline over time and that the rate of change is not influenced by age, gender or SEP, a result which does not support the CAD model. SRH trajectories are significantly correlated with exhaustion after work trajectories but not the other two WFC measures. When exhaustion after work trajectories are taken into account, SRH trajectories of higher educated people decline slower compared to less educated people, supporting the CAD hypothesis. Copyright © 2014 Elsevier Ltd. All rights reserved.
Parental smoking exposure and adolescent smoking trajectories.
Mays, Darren; Gilman, Stephen E; Rende, Richard; Luta, George; Tercyak, Kenneth P; Niaura, Raymond S
2014-06-01
In a multigenerational study of smoking risk, the objective was to investigate the intergenerational transmission of smoking by examining if exposure to parental smoking and nicotine dependence predicts prospective smoking trajectories among adolescent offspring. Adolescents (n = 406) ages 12 to 17 and a parent completed baseline interviews (2001-2004), and adolescents completed up to 2 follow-up interviews 1 and 5 years later. Baseline interviews gathered detailed information on parental smoking history, including timing and duration, current smoking, and nicotine dependence. Adolescent smoking and nicotine dependence were assessed at each time point. Latent Class Growth Analysis identified prospective smoking trajectory classes from adolescence into young adulthood. Logistic regression was used to examine relationships between parental smoking and adolescent smoking trajectories. Four adolescent smoking trajectory classes were identified: early regular smokers (6%), early experimenters (23%), late experimenters (41%), and nonsmokers (30%). Adolescents with parents who were nicotine-dependent smokers at baseline were more likely to be early regular smokers (odds ratio 1.18, 95% confidence interval 1.05-1.33) and early experimenters (odds ratio 1.04, 95% confidence interval 1.04-1.25) with each additional year of previous exposure to parental smoking. Parents' current non-nicotine-dependent and former smoking were not associated with adolescent smoking trajectories. Exposure to parental nicotine dependence is a critical factor influencing intergenerational transmission of smoking. Adolescents with nicotine-dependent parents are susceptible to more intense smoking patterns and this risk increases with longer duration of exposure. Research is needed to optimize interventions to help nicotine-dependent parents quit smoking early in their children's lifetime to reduce these risks. Copyright © 2014 by the American Academy of Pediatrics.
Kamp Dush, Claire M; Taylor, Miles G
2012-03-01
Using typologies outlined by Gottman and Fitzpatrick as well as institutional and companionate models of marriage, the authors conducted a latent class analysis of marital conflict trajectories using 20 years of data from the Marital Instability Over the Life Course study. Respondents were in one of three groups: high, medium (around the mean), or low conflict. Several factors predicted conflict trajectory group membership; respondents who believed in lifelong marriage and shared decisions equally with their spouse were more likely to report low and less likely to report high conflict. The conflict trajectories were intersected with marital happiness trajectories to examine predictors of high and low quality marriages. A stronger belief in lifelong marriage, shared decision making, and husbands sharing a greater proportion of housework were associated with an increased likelihood of membership in a high happiness, low conflict marriage, and a decreased likelihood of a low marital happiness group.
MILP-Based 4D Trajectory Planning for Tactical Trajectory Management Project
National Aeronautics and Space Administration — Aurora Flight Sciences proposes to develop specialized algorithms and software decision-aiding tools for four-dimensional (4D) vehicle-centric, tactical trajectory...
Querying databases of trajectories of differential equations: Data structures for trajectories
Grossman, Robert
1989-01-01
One approach to qualitative reasoning about dynamical systems is to extract qualitative information by searching or making queries on databases containing very large numbers of trajectories. The efficiency of such queries depends crucially upon finding an appropriate data structure for trajectories of dynamical systems. Suppose that a large number of parameterized trajectories gamma of a dynamical system evolving in R sup N are stored in a database. Let Eta is contained in set R sup N denote a parameterized path in Euclidean Space, and let the Euclidean Norm denote a norm on the space of paths. A data structure is defined to represent trajectories of dynamical systems, and an algorithm is sketched which answers queries.
A Trajectory UML profile For Modeling Trajectory Data: A Mobile Hospital Use Case
Oueslati, Wided
2011-01-01
A large amount of data resulting from trajectories of moving objects activities are collected thanks to localization based services and some associated automated processes. Trajectories data can be used either for transactional and analysis purposes in various domains (heath care, commerce, environment, etc.). For this reason, modeling trajectory data at the conceptual level is an important stair leading to global vision and successful implementations. However, current modeling tools fail to fulfill specific moving objects activities requirements. In this paper, we propose a new profile based on UML in order to enhance the conceptual modeling of trajectory data related to mobile objects by new stereotypes and icons. As illustration, we present a mobile hospital use case.
Struyve, W; De Neve, J; De Weirdt, S
2004-01-01
We re-examine Peres' statement ``opposite momenta lead to opposite directions''. It will be shown that Peres' statement is only valid in the large distance or large time limit. In the short distance or short time limit an additional deviation from perfect alignment occurs due to the uncertainty of the location of the source. This error contribution plays a major role in Popper's orginal experimental proposal. Peres' statement applies rather to the phenomenon of optical imaging, which was regarded by him as a verification of his statement. This is because this experiment can in a certain sense be seen as occurring in the large distance limit. We will also reconsider both experiments from the viewpoint of Bohmian mechanics. In Bohmian mechanics particles with exactly opposite momenta will move in opposite directions. In addition it will prove particularly usefull to use Bohmian mechanics because the Bohmian trajectories coincide with the conceptual trajectories drawn by Pittman et al. In this way Bohmian mechan...
Excited state mass spectra and Regge trajectories of bottom baryons
Thakkar, Kaushal; Shah, Zalak; Rai, Ajay Kumar; C. Vinodkumar, P.
2017-09-01
We present the mass spectra of radial and orbital excited states of singly heavy bottom baryons; Σb+, Σb-, Ξb-, Ξb0, Λb0 and Ωb-. The QCD motivated hypercentral quark model is employed for the three body description of baryons and the form of confinement potential is hyper Coulomb plus linear. The first order correction to the confinement potential is also incorporated in this work. The semi-electronic decay of Ωb and Ξb are calculated using the spectroscopic parameters of the baryons. The computed results are compared with other theoretical predictions as well as with the available experimental observations. The Regge trajectories are plotted in (n ,M2) plane.
Getting Obstacle Avoidance Trajectory of Mobile Beacon for Localization
Directory of Open Access Journals (Sweden)
Huan-Qing CUI
2010-11-01
Full Text Available Localization is one of the most important technologies in wireless sensor network, and mobile beacon assisted localization is a promising localization method. The mobile beacon trajectory planning is a basic and important problem in these methods. There are many obstacles in the real world, which obstruct the moving of mobile beacon. This paper focuses on the obstacle avoidance trajectory planning scheme. After partitioning the deployment area with fixed cell decomposition, the beacon trajectory are divided into global and local trajectory. The approximate shortest global trajectory is obtained by depth-first search, greedy strategy method and ant colony algorithm, while local trajectory is any existing trajectories. Simulation results show that this method can avoid obstacles in the network deployment area, and the smaller cell size leads to longer beacon trajectory and more localizable sensor nodes.
Deepwater Horizon MC252 - Oil Spill: Oil Trajectories Maps
National Oceanic and Atmospheric Administration, Department of Commerce — Trajectory maps are produced using GNOME (General NOAA Operational Modeling Environment), which is an oil spill trajectory model developed by OR and academic...
Trajectories of personal control in cancer patients receiving psychological care
Zhu, Lei; Schroevers, Maya J.; van der Lee, Marije; Garssen, Bert; Stewart, Roy E.; Sanderman, Robbert; Ranchor, A.V.
2015-01-01
Objective This study aimed to (1) identify subgroups of cancer patients with distinct personal control trajectories during psychological care, (2) examine whether socio-demographic, clinical, and psychological care characteristics could distinguish trajectories, and (3) examine differential patterns
Optimal trajectory and insertion accuracy of sacral alar iliac screws
Directory of Open Access Journals (Sweden)
Katsutaka Yamada
2017-07-01
Conclusion: The optimal trajectories of SAISs in a Japanese patient population are more lateral in males and more caudal in females. This study examines the clinical safety and accuracy of SAIS insertion on these optimal trajectories.
Trajectories of personal control in cancer patients receiving psychological care
Zhu, Lei; Schroevers, Maya J.; van der Lee, Marije; Garssen, Bert; Stewart, Roy E.; Sanderman, Robbert; Ranchor, Adelita V.
2015-01-01
Objective: This study aimed to (1) identify subgroups of cancer patients with distinct personal control trajectories during psychological care, (2) examine whether socio-demographic, clinical, and psychological care characteristics could distinguish trajectories, and (3) examine differential pattern
Trajectories of personal control in cancer patients receiving psychological care
Zhu, Lei; Schroevers, Maya J.; Lee, van der Marije; Garssen, Bert; Stewart, Roy E.; Sanderman, R.; Ranchor, A.V.
2015-01-01
Objective This study aimed to (1) identify subgroups of cancer patients with distinct personal control trajectories during psychological care, (2) examine whether socio-demographic, clinical, and psychological care characteristics could distinguish trajectories, and (3) examine differential patterns
A trajectory observer for camera-based underwater motion measurements
DEFF Research Database (Denmark)
Berg, Tor; Jouffroy, Jerome; Johansen, Vegar
This work deals with the issue of estimating the trajectory of a vehicle or object moving underwater based on camera measurements. The proposed approach consists of a diffusion-based trajectory observer (Jouffroy and Opderbecke, 2004) processing whole segments of a trajectory at a time. Additiona...
Developmental Trajectories of Childhood Obesity and Risk Behaviors in Adolescence
Huang, David Y. C.; Lanza, H. Isabella; Wright-Volel, Kynna; Anglin, M. Douglas
2013-01-01
Using group-based trajectory modeling, this study examined 5156 adolescents from the child sample of the 1979 National Longitudinal Survey of Youth to identify developmental trajectories of obesity from ages 6-18 and evaluate associations of such trajectories with risk behaviors and psychosocial health in adolescence. Four distinctive obesity…
Developmental Trajectories of Childhood Obesity and Risk Behaviors in Adolescence
Huang, David Y. C.; Lanza, H. Isabella; Wright-Volel, Kynna; Anglin, M. Douglas
2013-01-01
Using group-based trajectory modeling, this study examined 5156 adolescents from the child sample of the 1979 National Longitudinal Survey of Youth to identify developmental trajectories of obesity from ages 6-18 and evaluate associations of such trajectories with risk behaviors and psychosocial health in adolescence. Four distinctive obesity…
Exploiting Multi-Step Sample Trajectories for Approximate Value Iteration
2013-09-01
succes - sive transitions through the problem space. More formally, an n-step trajectory is comprised of the following ordered set of samples: {(st0 , at0...trajectories can consist of trajectories of varied length and my not end with transitions to terminal states. The key insight behind TFQI is that the
Pregnancy anxiety and prenatal cortisol trajectories.
Kane, Heidi S; Dunkel Schetter, Christine; Glynn, Laura M; Hobel, Calvin J; Sandman, Curt A
2014-07-01
Pregnancy anxiety is a potent predictor of adverse birth and infant outcomes. The goal of the current study was to examine one potential mechanism whereby these effects may occur by testing associations between pregnancy anxiety and maternal salivary cortisol on 4 occasions during pregnancy in a sample of 448 women. Higher mean levels of pregnancy anxiety over the course of pregnancy predicted steeper increases in cortisol trajectories compared to lower pregnancy anxiety. Significant differences between cortisol trajectories emerged between 30 and 31 weeks of gestation. Results remained significant when adjusted for state anxiety and perceived stress. Neither changes in pregnancy anxiety over gestation, nor pregnancy anxiety specific to only a particular time in pregnancy predicted cortisol. These findings provide support for one way in which pregnancy anxiety may influence maternal physiology and contribute to a growing literature on the complex biological pathways linking pregnancy anxiety to birth and infant outcomes. Copyright © 2014 Elsevier B.V. All rights reserved.
Trajectory averaging for stochastic approximation MCMC algorithms
Liang, Faming
2010-01-01
The subject of stochastic approximation was founded by Robbins and Monro [Ann. Math. Statist. 22 (1951) 400--407]. After five decades of continual development, it has developed into an important area in systems control and optimization, and it has also served as a prototype for the development of adaptive algorithms for on-line estimation and control of stochastic systems. Recently, it has been used in statistics with Markov chain Monte Carlo for solving maximum likelihood estimation problems and for general simulation and optimizations. In this paper, we first show that the trajectory averaging estimator is asymptotically efficient for the stochastic approximation MCMC (SAMCMC) algorithm under mild conditions, and then apply this result to the stochastic approximation Monte Carlo algorithm [Liang, Liu and Carroll J. Amer. Statist. Assoc. 102 (2007) 305--320]. The application of the trajectory averaging estimator to other stochastic approximation MCMC algorithms, for example, a stochastic approximation MLE al...
Monotone viable trajectories for functional differential inclusions
Haddad, Georges
This paper is a study on functional differential inclusions with memory which represent the multivalued version of retarded functional differential equations. The main result gives a necessary and sufficient equations. The main result gives a necessary and sufficient condition ensuring the existence of viable trajectories; that means trajectories remaining in a given nonempty closed convex set defined by given constraints the system must satisfy to be viable. Some motivations for this paper can be found in control theory where F( t, φ) = { f( t, φ, u)} uɛU is the set of possible velocities of the system at time t, depending on the past history represented by the function φ and on a control u ranging over a set U of controls. Other motivations can be found in planning procedures in microeconomics and in biological evolutions where problems with memory do effectively appear in a multivalued version. All these models require viability constraints represented by a closed convex set.
QCD glueball Regge trajectory and the pomeron
Llanes-Estrada, F J; Ribeiro, J E F; Szczepaniak, Adam P
2002-01-01
Implementing many-body techniques successful in other fields, we report a glueball Regge trajectory emerging from diagonalizing a confining Coulomb gauge Hamiltonian for constituent gluons. Through a BCS vacuum ansatz and gap equation, the dressed gluons acquire a dynamic mass, of order 0.8 GeV, providing the quasiparticle degrees of freedom for a TDA glueball formulation. The TDA eigenstates for two constituent gluons have orbital, L, excitations with a characteristic energy of 0.4 GeV revealing a clear Regge trajectory. In particular, the J sup P sup C =2 sup + sup + glueball coincides with the pomeron given by alpha sub P (t)=1.08+(0.25 GeV sup - sup 2)t. We also ascertain that lattice data supports our result. Finally, we conjecture on the odderon puzzle.
Direct NOE simulation from long MD trajectories
Chalmers, G.; Glushka, J. N.; Foley, B. L.; Woods, R. J.; Prestegard, J. H.
2016-04-01
A software package, MD2NOE, is presented which calculates Nuclear Overhauser Effect (NOE) build-up curves directly from molecular dynamics (MD) trajectories. It differs from traditional approaches in that it calculates correlation functions directly from the trajectory instead of extracting inverse sixth power distance terms as an intermediate step in calculating NOEs. This is particularly important for molecules that sample conformational states on a timescale similar to molecular reorientation. The package is tested on sucrose and results are shown to differ in small but significant ways from those calculated using an inverse sixth power assumption. Results are also compared to experiment and found to be in reasonable agreement despite an expected underestimation of water viscosity by the water model selected.
Trajectories for Novel and Detailed Traffic Information
DEFF Research Database (Denmark)
Krogh, Benjamin Bjerre; Andersen, Ove; Torp, Kristian
2012-01-01
the central metric free-flow speed from trajectories, instead of using point-based measurements such as induction-loops. This free-flow speed is widely used to compute and monitor the congestion level. The paper argues that the actual travel-time is a more accurate metric. The paper suggests a novel approach...... are correctly coordinated, and navigational device manufacturers to advice drivers in real-time on expected behavior of signalized intersections. The main conclusion is that trajectories can provide novel insight into the actual traffic situation that is not possible using existing approaches. Further...... to analyzing individual intersections that enables traffic analysts to compute queue lengths and estimated time to pass an intersection. Finally, the paper uses associative rule mining for evaluating green waves on road stretches. Such information can be used to verify that signalized intersections...
Designing reduced beacon trajectory for sensor localization
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Localization is one of the substantial issues in wireless sensor networks. The key problem for the mobile beacon localization is how to choose the appropriate beacon trajectory. However, little research has been done on it. In this paper, firstly,we deduce the number of positions for a beacon to send a packet according to the acreage of ROI (region of interest); and next we present a novel method based on virtual force to arrange the positions in arbitrary ROI; then we apply TSP (travelling salesman problem) algorithm to the positions sequence to obtain the optimal touring path, i.e. the reduced beacon trajectory. When a mobile beacon moves along the touring path, sending RF signals at every position, the sensors in ROI can work out their position with trilateration. Experimental results demonstrate that the localization method, based on the beacon reduced path, is efficient and has flexible accuracy.
Variable length trajectory compressible hybrid Monte Carlo
Nishimura, Akihiko
2016-01-01
Hybrid Monte Carlo (HMC) generates samples from a prescribed probability distribution in a configuration space by simulating Hamiltonian dynamics, followed by the Metropolis (-Hastings) acceptance/rejection step. Compressible HMC (CHMC) generalizes HMC to a situation in which the dynamics is reversible but not necessarily Hamiltonian. This article presents a framework to further extend the algorithm. Within the existing framework, each trajectory of the dynamics must be integrated for the same amount of (random) time to generate a valid Metropolis proposal. Our generalized acceptance/rejection mechanism allows a more deliberate choice of the integration time for each trajectory. The proposed algorithm in particular enables an effective application of variable step size integrators to HMC-type sampling algorithms based on reversible dynamics. The potential of our framework is further demonstrated by another extension of HMC which reduces the wasted computations due to unstable numerical approximations and corr...
Robot trajectory planning via dynamic programming
Energy Technology Data Exchange (ETDEWEB)
Dohrmann, C.R.; Robinett, R.D.
1994-03-01
The method of dynamic programming is applied to three example problems dealing with robot trajectory planning. The first two examples involve end-effector tracking of a straight line with rest-to-rest motions of planar two-link and three-link rigid robots. These examples illustrate the usefulness of the method for producing smooth trajectories either in the presence or absence of joint redundancies. The last example demonstrates the use of the method for rest-to-rest maneuvers of a single-link manipulator with a flexible payload. Simulation results for this example display interesting symmetries that are characteristic of such maneuvers. Details concerning the implementation and computational aspects of the method are discussed.
Wen Xiaozhong; Kleinman Ken; Gillman Matthew W; Rifas-Shiman Sheryl L; Taveras Elsie M
2012-01-01
Abstract Background Modeling childhood body mass index (BMI) trajectories, versus estimating change in BMI between specific ages, may improve prediction of later body-size-related outcomes. Prior studies of BMI trajectories are limited by restricted age periods and insufficient use of trajectory information. Methods Among 3,289 children seen at 81,550 pediatric well-child visits from infancy to 18 years between 1980 and 2008, we fit individual BMI trajectories using mixed effect models with f...
Trajectories of Learning : Embodied Interaction in Change
Melander, Helen
2009-01-01
This dissertation is about learning as changing understanding in social and situated activities. It takes part in the development of a reconceptualization of learning initiated within participationist perspectives. Multiparty interaction in situated activities is a primordial site for the exploration of human action and cognition. Through the theoretical framework of Conversation Analysis (CA), a method for the analysis and description of trajectories of learning is proposed. Departing from a...
Hypersonic Flight Mechanics. [for atmospheric entry trajectories
Busemann, A.; Vinh, N. X.; Culp, R. D.
1976-01-01
The effects of aerodynamic forces on trajectories at orbital speeds are discussed in terms of atmospheric models. The assumptions for the model are spherical symmetry, nonrotating, and an exponential atmosphere. The equations of flight, and the performance in extra-atmospheric flight are discussed along with the return to the atmosphere, and the entry. Solutions of the exact equations using directly matched asymptotic expansions are presented.
The Envelope of Projectile Trajectories in Midair
Chudinov, P
2005-01-01
A classic problem of the motion of a point mass (projectile) thrown at an angle to the horizon is reviewed. The air drag force is taken into account with the drag factor assumed to be constant. Analytic approach is used for investigation. Simple analytical formulas are used for the constructing the envelope of the family of the point mass trajectories. The equation of envelope is applied for determination of maximum range of flight. The motion of a baseball is presented as an example.
Developmental Trajectories of Adolescent Substance Use
Yamada, Samantha; Pepler, Debra; Jiang, Depeng; Cappadocia, M. Catherine; Craig, Wendy; Connolly, Jennifer
2016-01-01
Longitudinal data from 746 adolescents in Toronto, Canada (54% females), was gathered in eight waves over seven years (1995 through 2001), beginning when the youths were 10 to 12 years old (mean age = 11.8, SD = 1.2 years). Five trajectories of substance use were identified: chronic-high, childhood onset-rapid high, childhood onset-moderate,…
Applying Deep Learning to Basketball Trajectories
Shah, Rajiv; Romijnders, Rob
2016-01-01
One of the emerging trends for sports analytics is the growing use of player and ball tracking data. A parallel development is deep learning predictive approaches that use vast quantities of data with less reliance on feature engineering. This paper applies recurrent neural networks in the form of sequence modeling to predict whether a three-point shot is successful. The models are capable of learning the trajectory of a basketball without any knowledge of physics. For comparison, a baseline ...
Spacecraft aerodynamics and trajectory simulation during aerobraking
Institute of Scientific and Technical Information of China (English)
Wen-pu ZHANG; Bo HAN; Cheng-yi ZHANG
2010-01-01
This paper uses a direct simulation Monte Carlo(DSMC)approach to simulate rarefied aerodynamic characteristics during the aerobraking process of the NASA Mars Global Surveyor(MGS)spacecraft.The research focuses on the flowfield and aerodynamic characteristics distribution under various free stream densities.The variation regularity of aerodynamic coefficients is analyzed.The paper also develops an aerodynamics-aeroheating-trajectory integrative simulation model to preliminarily calculate the aerobraking orbit transfer by combining the DSMC technique and the classical kinematics theory.The results show that the effect of the planetary atmospheric density,the spacecraft yaw,and the pitch attitudes on the spacecraft aerodynamics is significant.The numerical results are in good agreement with the existing results reported in the literature.The aerodynamics-aeroheating-trajectory integrative simulation model can simulate the orbit tran,sfer in the complete aerobraking mission.The current results of the spacecraft trajectory show that the aerobraking maneuvers have good performance of attitude control.
Academic trajectories of newcomer immigrant youth.
Suárez-Orozco, Carola; Gaytán, Francisco X; Bang, Hee Jin; Pakes, Juliana; O'Connor, Erin; Rhodes, Jean
2010-05-01
Immigration to the United States presents both challenges and opportunities that affect students' academic achievement. Using a 5-year longitudinal, mixed-methods approach, we identified varying academic trajectories of newcomer immigrant students from Central America, China, the Dominican Republic, Haiti, and Mexico. Latent class growth curve analysis revealed that although some newcomer students performed at high or improving levels over time, others showed diminishing performance. Multinomial logistic regressions identified significant group differences in academic trajectories, particularly between the high-achieving youth and the other groups. In keeping with ecological-developmental and stage-environment fit theories, School Characteristics (school segregation rate, school poverty rate, and student perceptions of school violence), Family Characteristics (maternal education, parental employment, and household structure), and Individual Characteristics (academic English proficiency, academic engagement, psychological symptoms, gender, and 2 age-related risk factors, number of school transitions and being overaged for grade placement) were associated with different trajectories of academic performance. A series of case studies triangulate many of the quantitative findings as well as illuminate patterns that were not detected in the quantitative data. Thus, the mixed-methods approach sheds light on the cumulative developmental challenges that immigrant students face as they adjust to their new educational settings.
Overall test evaluation based on trajectory tracking data
Institute of Scientific and Technical Information of China (English)
王正明; 段晓君
2001-01-01
According to the trajectory characteristics of ballistic missile, a reduced parameter model is constructed based on difference between telemetry trajectory and trajectory tracking data. By virtue of Bayesian theory and data fusion technique, a new test evaluation method is put forth, which can make full use of the trajectory tracking data, shooting range test data and relevant information. Since the impact point can be derived from trajectory difference and its kinetic characteristics, evaluation of the impact point is a special case of this method. The accurate evaluation and the accuracy of evaluation results can be provided by the new method.
Improved Propulsion Modeling for Low-Thrust Trajectory Optimization
Knittel, Jeremy M.; Englander, Jacob A.; Ozimek, Martin T.; Atchison, Justin A.; Gould, Julian J.
2017-01-01
Low-thrust trajectory design is tightly coupled with spacecraft systems design. In particular, the propulsion and power characteristics of a low-thrust spacecraft are major drivers in the design of the optimal trajectory. Accurate modeling of the power and propulsion behavior is essential for meaningful low-thrust trajectory optimization. In this work, we discuss new techniques to improve the accuracy of propulsion modeling in low-thrust trajectory optimization while maintaining the smooth derivatives that are necessary for a gradient-based optimizer. The resulting model is significantly more realistic than the industry standard and performs well inside an optimizer. A variety of deep-space trajectory examples are presented.
Reduced parameter model on trajectory tracking data with applications
Institute of Scientific and Technical Information of China (English)
王正明; 朱炬波
1999-01-01
The data fusion in tracking the same trajectory by multi-measurernent unit (MMU) is considered. Firstly, the reduced parameter model (RPM) of trajectory parameter (TP), system error and random error are presented,and then the RPM on trajectory tracking data (TTD) is obtained, a weighted method on measuring elements (ME) is studied and criteria on selection of ME based on residual and accuracy estimation are put forward. According to RPM,the problem about selection of ME and self-calibration of TTD is thoroughly investigated. The method improves data accuracy in trajectory tracking obviously and gives accuracy evaluation of trajectory tracking system simultaneously.
Progress in reentry trajectory planning for hypersonic vehicle
Institute of Scientific and Technical Information of China (English)
Jiang Zhao; Rui Zhou; Xuelian Jin
2014-01-01
The reentry trajectory planning for hypersonic vehicles is critical and chal enging in the presence of numerous nonlinear equations of motion and path constraints, as wel as guaranteed satisfaction of accuracy in meeting al the specified boundary con-ditions. In the last ten years, many researchers have investigated various strategies to generate a feasible or optimal constrained reentry trajectory for hypersonic vehicles. This paper briefly re-views the new research efforts to promote the capability of reentry trajectory planning. The progress of the onboard reentry trajectory planning, reentry trajectory optimization, and landing footprint is summarized. The main chal enges of reentry trajectory planning for hypersonic vehicles are analyzed, focusing on the rapid reentry trajectory optimization, complex geographic constraints, and coop-erative strategies.
Ares I-X Best Estimated Trajectory Analysis and Results
Karlgaard, Christopher D.; Beck, Roger E.; Starr, Brett R.; Derry, Stephen D.; Brandon, Jay; Olds, Aaron D.
2011-01-01
The Ares I-X trajectory reconstruction produced best estimated trajectories of the flight test vehicle ascent through stage separation, and of the first and upper stage entries after separation. The trajectory reconstruction process combines on-board, ground-based, and atmospheric measurements to produce the trajectory estimates. The Ares I-X vehicle had a number of on-board and ground based sensors that were available, including inertial measurement units, radar, air-data, and weather balloons. However, due to problems with calibrations and/or data, not all of the sensor data were used. The trajectory estimate was generated using an Iterative Extended Kalman Filter algorithm, which is an industry standard processing algorithm for filtering and estimation applications. This paper describes the methodology and results of the trajectory reconstruction process, including flight data preprocessing and input uncertainties, trajectory estimation algorithms, output transformations, and comparisons with preflight predictions.
Trajectory analysis and optimization system (TAOS) user`s manual
Energy Technology Data Exchange (ETDEWEB)
Salguero, D.E.
1995-12-01
The Trajectory Analysis and Optimization System (TAOS) is software that simulates point--mass trajectories for multiple vehicles. It expands upon the capabilities of the Trajectory Simulation and Analysis program (TAP) developed previously at Sandia National Laboratories. TAOS is designed to be a comprehensive analysis tool capable of analyzing nearly any type of three degree-of-freedom, point-mass trajectory. Trajectories are broken into segments, and within each segment, guidance rules provided by the user control how the trajectory is computed. Parametric optimization provides a powerful method for satisfying mission-planning constraints. Althrough TAOS is not interactive, its input and output files have been designed for ease of use. When compared to TAP, the capability to analyze trajectories for more than one vehicle is the primary enhancement, although numerous other small improvements have been made. This report documents the methods used in TAOS as well as the input and output file formats.
Trajectory analysis and optimization system (TAOS) user`s manual
Energy Technology Data Exchange (ETDEWEB)
Salguero, D.E.
1995-12-01
The Trajectory Analysis and Optimization System (TAOS) is software that simulates point--mass trajectories for multiple vehicles. It expands upon the capabilities of the Trajectory Simulation and Analysis program (TAP) developed previously at Sandia National Laboratories. TAOS is designed to be a comprehensive analysis tool capable of analyzing nearly any type of three degree-of-freedom, point-mass trajectory. Trajectories are broken into segments, and within each segment, guidance rules provided by the user control how the trajectory is computed. Parametric optimization provides a powerful method for satisfying mission-planning constraints. Althrough TAOS is not interactive, its input and output files have been designed for ease of use. When compared to TAP, the capability to analyze trajectories for more than one vehicle is the primary enhancement, although numerous other small improvements have been made. This report documents the methods used in TAOS as well as the input and output file formats.
On the Green's function and iterative solutions of Loop Quantum Cosmology
Shojai, F.; Shojai, A.
2006-01-01
Here we shall find the Green’s function of the difference equation of loop quantum cosmology. To illustrate how to use it, we shall obtain an iterative solution for closed model and evaluate its corresponding Bohmian trajectory.
The ESA's Space Trajectory Analysis software suite
Ortega, Guillermo
The European Space Agency (ESA) initiated in 2005 an internal activity to develop an open source software suite involving university science departments and research institutions all over the world. This project is called the "Space Trajectory Analysis" or STA. This article describes the birth of STA and its present configuration. One of the STA aims is to promote the exchange of technical ideas, and raise knowledge and competence in the areas of applied mathematics, space engineering, and informatics at University level. Conceived as a research and education tool to support the analysis phase of a space mission, STA is able to visualize a wide range of space trajectories. These include among others ascent, re-entry, descent and landing trajectories, orbits around planets and moons, interplanetary trajectories, rendezvous trajectories, etc. The article explains that STA project is an original idea of the Technical Directorate of ESA. It was born in August 2005 to provide a framework in astrodynamics research at University level. As research and education software applicable to Academia, a number of Universities support this development by joining ESA in leading the development. ESA and Universities partnership are expressed in the STA Steering Board. Together with ESA, each University has a chair in the board whose tasks are develop, control, promote, maintain, and expand the software suite. The article describes that STA provides calculations in the fields of spacecraft tracking, attitude analysis, coverage and visibility analysis, orbit determination, position and velocity of solar system bodies, etc. STA implements the concept of "space scenario" composed of Solar system bodies, spacecraft, ground stations, pads, etc. It is able to propagate the orbit of a spacecraft where orbital propagators are included. STA is able to compute communication links between objects of a scenario (coverage, line of sight), and to represent the trajectory computations and
Simulation Propulsion System and Trajectory Optimization
Hendricks, Eric S.; Falck, Robert D.; Gray, Justin S.
2017-01-01
A number of new aircraft concepts have recently been proposed which tightly couple the propulsion system design and operation with the overall vehicle design and performance characteristics. These concepts include propulsion technology such as boundary layer ingestion, hybrid electric propulsion systems, distributed propulsion systems and variable cycle engines. Initial studies examining these concepts have typically used a traditional decoupled approach to aircraft design where the aerodynamics and propulsion designs are done a-priori and tabular data is used to provide inexpensive look ups to the trajectory ana-ysis. However the cost of generating the tabular data begins to grow exponentially when newer aircraft concepts require consideration of additional operational parameters such as multiple throttle settings, angle-of-attack effects on the propulsion system, or propulsion throttle setting effects on aerodynamics. This paper proposes a new modeling approach that eliminated the need to generate tabular data, instead allowing an expensive propulsion or aerodynamic analysis to be directly integrated into the trajectory analysis model and the entire design problem optimized in a fully coupled manner. The new method is demonstrated by implementing a canonical optimal control problem, the F-4 minimum time-to-climb trajectory optimization using three relatively new analysis tools: Open M-DAO, PyCycle and Pointer. Pycycle and Pointer both provide analytic derivatives and Open MDAO enables the two tools to be combined into a coupled model that can be run in an efficient parallel manner that helps to cost the increased cost of the more expensive propulsion analysis. Results generated with this model serve as a validation of the tightly coupled design method and guide future studies to examine aircraft concepts with more complex operational dependencies for the aerodynamic and propulsion models.
Midcourse trajectory correction for solar sail starships
Matloff, Gregory L.
2016-10-01
Hyperthin solar sails deployed as close to the Sun as possible are the only currently feasible approach to extrasolar solar exploration and interstellar travel. This paper quantifies and investigates the effects of timing errors in the unfurlment (or inflation) of solar sails at the perihelion of parabolic solar orbits upon the spacecraft's trajectory direction. Methods of correcting such aim errors include on-board solar-, radioisotope-, or nuclear-electric thrusters, electromagnetic thrustless turning, application of electric or magnetic sails, and a new application of toroidal magnetic ion scoops.
Design of Quiet Rotorcraft Approach Trajectories
Padula, Sharon L.; Burley, Casey L.; Boyd, D. Douglas, Jr.; Marcolini, Michael A.
2009-01-01
A optimization procedure for identifying quiet rotorcraft approach trajectories is proposed and demonstrated. The procedure employs a multi-objective genetic algorithm in order to reduce noise and create approach paths that will be acceptable to pilots and passengers. The concept is demonstrated by application to two different helicopters. The optimized paths are compared with one another and to a standard 6-deg approach path. The two demonstration cases validate the optimization procedure but highlight the need for improved noise prediction techniques and for additional rotorcraft acoustic data sets.
Unparallel trajectory bistatic spotlight SAR imaging
Institute of Scientific and Technical Information of China (English)
ZHANG Lei; JING Wei; XING MengDao; BAO Zheng
2009-01-01
A new approach for unparallel trajectory bistatic spotlight SAR imaging is proposed. The approach utilizes the concept of instantaneous Doppler wavenumber and introduces two variants, the sum-range and subtraction-range, to develop the 2D frequency analytical formula. Based on the assumption of plane wavefront, the transmitting and receiving Doppler are separated and formulated via series reversion. And frequency scaling is applied to focus image. The algorithm is with high computational efficiency, and provides well focus for limited scene imaging. Simulation result confirms the validity of the approach.
Trajectory Design Considerations for Exploration Mission 1
Dawn, Timothy F.; Gutkowski, Jeffrey P.; Batcha, Amelia L.
2017-01-01
Exploration Mission 1 (EM-1) will be the first mission to send an uncrewed Orion vehicle to cislunar space in 2018, targeted to a Distant Retrograde Orbit (DRO). Analysis of EM-1 DRO mission opportunities in 2018 help characterize mission parameters that are of interest to other subsystems (e.g., power, thermal, communications, flight operations, etc). Subsystems request mission design trades which include: landing lighting, addition of an Orion main engine checkout burn, and use of auxiliary thruster only cases. This paper examines the evolving trade studies that incorporate subsystem feedback and demonstrate the feasibility of these constrained mission trajectory designs and contingencies.
Trajectories of Listeria-type motility in two dimensions
Wen, Fu-Lai; Leung, Kwan-tai; Chen, Hsuan-Yi
2012-12-01
Force generated by actin polymerization is essential in cell motility and the locomotion of organelles or bacteria such as Listeria monocytogenes. Both in vivo and in vitro experiments on actin-based motility have observed geometrical trajectories including straight lines, circles, S-shaped curves, and translating figure eights. This paper reports a phenomenological model of an actin-propelled disk in two dimensions that generates geometrical trajectories. Our model shows that when the evolutions of actin density and force per filament on the disk are strongly coupled to the disk self-rotation, it is possible for a straight trajectory to lose its stability. When the instability is due to a pitchfork bifurcation, the resulting trajectory is a circle; a straight trajectory can also lose stability through a Hopf bifurcation, and the resulting trajectory is an S-shaped curve. We also show that a half-coated disk, which mimics the distribution of functionalized proteins in Listeria, also undergoes similar symmetry-breaking bifurcations when the straight trajectory loses stability. For both a fully coated disk and a half-coated disk, when the trajectory is an S-shaped curve, the angular frequency of the disk self-rotation is different from that of the disk trajectory. However, for circular trajectories, these angular frequencies are different for a fully coated disk but the same for a half-coated disk.
Growth Trajectories of Health Behaviors from Adolescence through Young Adulthood
Directory of Open Access Journals (Sweden)
Nora Wiium
2015-10-01
Full Text Available Based on nine waves of data collected during a period of 17 years (1990–2007, the present study explored different developmental trajectories of the following unhealthy behaviors: regular smoking, lack of regular exercise, lack of daily fruit intake, and drunkenness. A baseline sample of 1195 13-year-old pupils was from 22 randomly selected schools in the Hordaland County in western Norway. Latent class growth analysis revealed three developmental trajectories. The first trajectory was a conventional trajectory, comprising 36.3% of participants, who showed changes in smoking, physical exercise, fruit intake, and drunkenness consistent with the prevailing age specific norms of these behaviors in the Norwegian society at the time. The second trajectory was a passive trajectory, comprising 25.5% of participants, who reported low levels of both healthy and unhealthy behaviors during the 17-year period. The third trajectory was an unhealthy trajectory, comprising 38.2% of participants, who had high levels of unhealthy behaviors over time. Several covariates were examined, but only sex and mother’s and father’s educational levels were found to be significantly associated with the identified trajectories. While these findings need to be replicated in future studies, the identification of the different trajectories suggests the need to tailor intervention according to specific needs.
Generating a Style-Adaptive Trajectory from Multiple Demonstrations
Directory of Open Access Journals (Sweden)
Yue Zhao
2014-07-01
Full Text Available Trajectory learning and generation from demonstration have been widely discussed in recent years, with promising progress made. Existing approaches, including the Gaussian Mixture Model (GMM, affine functions and Dynamic Movement Primitives (DMPs have proven their applicability to learning the features and styles of existing trajectories and generating similar trajectories that can adapt to different dynamic situations. However, in many applications, such as grasping an object, shooting a ball, etc., different goals require trajectories of different styles. An issue that must be resolved is how to reproduce a trajectory with a suitable style. In this paper, we propose a style-adaptive trajectory generation approach based on DMPs, by which the style of the reproduced trajectories can change smoothly as the new goal changes. The proposed approach first adopts a Point Distribution Model (PDM to get the principal trajectories for different styles, then learns the model of each principal trajectory independently using DMPs, and finally adapts the parameters of the trajectory model smoothly according to the new goal using an adaptive goal-to-style mechanism. This paper further discusses the application of the approach on small-sized robots for an adaptive shooting task and on a humanoid robot arm to generate motions for table tennis-playing with different styles.
Generating a Style-adaptive Trajectory from Multiple Demonstrations
Directory of Open Access Journals (Sweden)
Yue Zhao
2014-07-01
Full Text Available Trajectory learning and generation from demonstration have been widely discussed in recent years, with promising progress made. Existing approaches, including the Gaussian Mixture Model (GMM, affine functions and Dynamic Movement Primitives (DMPs have proven their applicability to learning the features and styles of existing trajectories and generating similar trajectories that can adapt to different dynamic situations. However, in many applications, such as grasping an object, shooting a ball, etc., different goals require trajectories of different styles. An issue that must be resolved is how to reproduce a trajectory with a suitable style. In this paper, we propose a style-adaptive trajectory generation approach based on DMPs, by which the style of the reproduced trajectories can change smoothly as the new goal changes. The proposed approach first adopts a Point Distribution Model (PDM to get the principal trajectories for different styles, then learns the model of each principal trajectory independently using DMPs, and finally adapts the parameters of the trajectory model smoothly according to the new goal using an adaptive goal-to-style mechanism. This paper further discusses the application of the approach on small-sized robots for an adaptive shooting task and on a humanoid robot arm to generate motions for table tennis-playing with different styles.
A Novel Semantic Matching Method for Indoor Trajectory Tracking
Directory of Open Access Journals (Sweden)
Sheng Guo
2017-07-01
Full Text Available The rapid development of smartphone sensors has provided rich indoor pedestrian trajectory data for indoor location-based applications. To improve the quality of these collected trajectory data, map matching methods are widely used to correct trajectories. However, these existing matching methods usually cannot achieve satisfactory accuracy and efficiency and have difficulty in exploiting the rich information contained in the obtained trajectory data. In this study, we proposed a novel semantic matching method for indoor pedestrian trajectory tracking. Similar to our previous work, pedestrian dead reckoning (PDR and human activity recognition (HAR are used to obtain the raw user trajectory data and the corresponding semantic information involved in the trajectory, respectively. To improve the accuracy and efficiency for user trajectory tracking, a semantic-rich indoor link-node model is then constructed based on the input floor plan, in which navigation-related semantics are extracted and formalized for the following trajectory matching. PDR and HAR are further utilized to segment the trajectory and infer the semantics (e.g., “Turn left”, “Turn right”, and “Go straight”. Finally, the inferred semantic information is matched with the semantic-rich indoor link-node model to derive the correct user trajectory. To accelerate the matching process, the semantics inferred from the trajectory are also assigned weights according to their relative importance. The experiments confirm that the proposed method achieves accurate trajectory tracking results while guaranteeing a high matching efficiency. In addition, the resulting semantic information has great application potential in further indoor location-based services.
Electronics and electronic systems
Olsen, George H
1987-01-01
Electronics and Electronic Systems explores the significant developments in the field of electronics and electronic devices. This book is organized into three parts encompassing 11 chapters that discuss the fundamental circuit theory and the principles of analog and digital electronics. This book deals first with the passive components of electronic systems, such as resistors, capacitors, and inductors. These topics are followed by a discussion on the analysis of electronic circuits, which involves three ways, namely, the actual circuit, graphical techniques, and rule of thumb. The remaining p
Kamp Dush, Claire M.; Taylor, Miles G.
2012-01-01
Using typologies outlined by Gottman and Fitzpatrick as well as institutional and companionate models of marriage, the authors conducted a latent class analysis of marital conflict trajectories using 20 years of data from the Marital Instability Over the Life Course study. Respondents were in one of three groups: high, medium (around the mean), or…
K. Dhana (Klodian); J.M. van Rosmalen (Joost); D. Vistisen (Dorte); M.A. Ikram (Arfan); A. Hofman (Albert); O.H. Franco (Oscar); M. Kavousi (Maryam)
2016-01-01
textabstractPatients with cardiovascular disease (CVD) are a heterogeneous group regarding their body mass index (BMI) levels at the time of diagnosis. To address the heterogeneity of CVD, we examined the trajectories of change in body mass index (BMI) and in other cardio-metabolic risk factors befo
Solvable Optimal Velocity Models and Asymptotic Trajectory
Nakanishi, K; Igarashi, Y; Bando, M
1996-01-01
In the Optimal Velocity Model proposed as a new version of Car Following Model, it has been found that a congested flow is generated spontaneously from a homogeneous flow for a certain range of the traffic density. A well-established congested flow obtained in a numerical simulation shows a remarkable repetitive property such that the velocity of a vehicle evolves exactly in the same way as that of its preceding one except a time delay $T$. This leads to a global pattern formation in time development of vehicles' motion, and gives rise to a closed trajectory on $\\Delta x$-$v$ (headway-velocity) plane connecting congested and free flow points. To obtain the closed trajectory analytically, we propose a new approach to the pattern formation, which makes it possible to reduce the coupled car following equations to a single difference-differential equation (Rondo equation). To demonstrate our approach, we employ a class of linear models which are exactly solvable. We also introduce the concept of ``asymptotic traj...
Trajectory averaging for stochastic approximation MCMC algorithms
Liang, Faming
2010-10-01
The subject of stochastic approximation was founded by Robbins and Monro [Ann. Math. Statist. 22 (1951) 400-407]. After five decades of continual development, it has developed into an important area in systems control and optimization, and it has also served as a prototype for the development of adaptive algorithms for on-line estimation and control of stochastic systems. Recently, it has been used in statistics with Markov chain Monte Carlo for solving maximum likelihood estimation problems and for general simulation and optimizations. In this paper, we first show that the trajectory averaging estimator is asymptotically efficient for the stochastic approximation MCMC (SAMCMC) algorithm under mild conditions, and then apply this result to the stochastic approximation Monte Carlo algorithm [Liang, Liu and Carroll J. Amer. Statist. Assoc. 102 (2007) 305-320]. The application of the trajectory averaging estimator to other stochastic approximationMCMC algorithms, for example, a stochastic approximation MLE algorithm for missing data problems, is also considered in the paper. © Institute of Mathematical Statistics, 2010.
Lumbar pedicle cortical bone trajectory screw
Institute of Scientific and Technical Information of China (English)
Song Tengfei; Wellington K Hsu; Ye Tianwen
2014-01-01
Objective The purpose of this study was to demonstrate the lumbar pedicle cortical bone trajectory (CBT) screw fixation technique,a new fixation technique for lumbar surgery.Data sources The data analyzed in this review are mainly from articles reported in PubMed published from 1994 to 2014.Study selection Original articles and critical reviews relevant to CBT technique and lumbar pedicle fixation were selected.Results CBT technique was firstly introduced as a new fixation method for lumbar pedicle surgery in 2009.The concepts,morphometric study,biomechanical characteristics and clinical applications of CBT technique were reviewed.The insertional point of CBT screw is located at the lateral point of the pars interarticularis,and its trajectory follows a caudocephalad path sagittally and a laterally directed path in the transverse plane.CBT technique can be used for posterior fixation during lumbar fusion procedures.This technique is a minimally invasive surgery,which affords better biomechanical stability,fixation strength and surgical safety.Therefore,CBT technique has the greatest benefit in lumbar pedicle surgery for patients with osteoporosis and obesity.Conclusion CBT technique is a better alternative option of lumbar pedicle fixation,especially for patients with osteoporosis and obesity.
Efficient compression of molecular dynamics trajectory files.
Marais, Patrick; Kenwood, Julian; Smith, Keegan Carruthers; Kuttel, Michelle M; Gain, James
2012-10-15
We investigate whether specific properties of molecular dynamics trajectory files can be exploited to achieve effective file compression. We explore two classes of lossy, quantized compression scheme: "interframe" predictors, which exploit temporal coherence between successive frames in a simulation, and more complex "intraframe" schemes, which compress each frame independently. Our interframe predictors are fast, memory-efficient and well suited to on-the-fly compression of massive simulation data sets, and significantly outperform the benchmark BZip2 application. Our schemes are configurable: atomic positional accuracy can be sacrificed to achieve greater compression. For high fidelity compression, our linear interframe predictor gives the best results at very little computational cost: at moderate levels of approximation (12-bit quantization, maximum error ≈ 10(-2) Å), we can compress a 1-2 fs trajectory file to 5-8% of its original size. For 200 fs time steps-typically used in fine grained water diffusion experiments-we can compress files to ~25% of their input size, still substantially better than BZip2. While compression performance degrades with high levels of quantization, the simulation error is typically much greater than the associated approximation error in such cases.
Maternal age and trajectories of cannabis use.
De Genna, Natacha M; Cornelius, Marie D; Goldschmidt, Lidush; Day, Nancy L
2015-11-01
Becoming a mother is a developmental transition that has been linked to desistance from substance use. However, timing of motherhood may be a key determinant of cannabis use in women, based on preliminary evidence from teenage mothers. The goal of this study was to identify trajectories of maternal cannabis use, and to determine if maternal age was associated with different trajectories of use. This prospective study examined 456 pregnant women recruited at a prenatal clinic, ranging in age from 13 to 42 years. The women were interviewed about their cannabis use 1 year prior to pregnancy and during each trimester of pregnancy, and at 6, 10, 14, and 16 years post-partum. A growth mixture model of cannabis use reported at each time point clearly delineated four groups: non/unlikely to use, decreasing likelihood of use, late desistance, and increasing likelihood/chronic use (Lo-Mendell-Rubin adjusted LRT test statistic=35.7, pcannabis across 17 years, including later desistance post-partum and increasing/chronic use. Other substance use and chronic depressive symptoms were also associated with more frequent use. These findings have implications for both prevention and treatment of cannabis use in mothers. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
MacDonald, R. Lee [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 4R2 (Canada); Thomas, Christopher G., E-mail: Chris.Thomas@cdha.nshealth.ca [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 4R2 (Canada); Department of Medical Physics, Nova Scotia Cancer Centre, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia B3H 1V7 (Canada); Department of Radiation Oncology, Dalhousie University, Halifax, Nova Scotia B3H 4R2 (Canada); Department of Radiology, Dalhousie University, Halifax, Nova Scotia B3H 4R2 (Canada)
2015-05-15
Purpose: To investigate potential improvement in external beam stereotactic radiation therapy plan quality for cranial cases using an optimized dynamic gantry and patient support couch motion trajectory, which could minimize exposure to sensitive healthy tissue. Methods: Anonymized patient anatomy and treatment plans of cranial cancer patients were used to quantify the geometric overlap between planning target volumes and organs-at-risk (OARs) based on their two-dimensional projection from source to a plane at isocenter as a function of gantry and couch angle. Published dose constraints were then used as weighting factors for the OARs to generate a map of couch-gantry coordinate space, indicating degree of overlap at each point in space. A couch-gantry collision space was generated by direct measurement on a linear accelerator and couch using an anthropomorphic solid-water phantom. A dynamic, fully customizable algorithm was written to generate a navigable ideal trajectory for the patient specific couch-gantry space. The advanced algorithm can be used to balance the implementation of absolute minimum values of overlap with the clinical practicality of large-scale couch motion and delivery time. Optimized cranial cancer treatment trajectories were compared to conventional treatment trajectories. Results: Comparison of optimized treatment trajectories with conventional treatment trajectories indicated an average decrease in mean dose to the OARs of 19% and an average decrease in maximum dose to the OARs of 12%. Degradation was seen for homogeneity index (6.14% ± 0.67%–5.48% ± 0.76%) and conformation number (0.82 ± 0.02–0.79 ± 0.02), but neither was statistically significant. Removal of OAR constraints from volumetric modulated arc therapy optimization reveals that reduction in dose to OARs is almost exclusively due to the optimized trajectory and not the OAR constraints. Conclusions: The authors’ study indicated that simultaneous couch and gantry motion
Broken-Plane Maneuver Applications for Earth to Mars Trajectories
Abilleira, Fernando
2007-01-01
Optimization techniques are critical when investigating Earth to Mars trajectories since they have the potential of reducing the total (delta)V of a mission. A deep space maneuver (DSM) executed during the cruise may improve a trajectory by reducing the total mission V. Nonetheless, DSMs not only may improve trajectory performance (from an energetic point of view) but also open up new families of trajectories that would satisfy very specific mission requirements not achievable with ballistic trajectories. In the following pages, various specific examples showing the potential advantages of the usage of broken plane maneuvers will be introduced. These examples correspond to possible scenarios for Earth to Mars trajectories during the next decade (2010-2020).
Solution space analysis of Double Lunar-Swingby periodic trajectory
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
The Double Lunar-Swingby(DLS)periodic trajectory is a type of large-scale trajectory in Restricted Three-Body Problem framework.First,the principium of the DLS periodic trajectory is studied,and a preliminary design of the DLS trajectory is developed by the Patched Conic method.Second,the solution space of the DLS periodic trajectory is discussed in detail and in combination with numerical simulation,a distribution about orbital parameter relationship in the solution space is given.Finally,the variations of the orbital elements with different rotation angular velocities of geocentric apsidal line are found,and two typical orbits are given according to three reference frames.It is shown that Patched Conic method is feasible for the DLS periodic trajectory solution space analysis,and the conclusions will be valuable to the deep-space exploration orbit design in future.
Self accelerating electron Airy beams
Voloch-Bloch, Noa; Lilach, Yigal; Gover, Avraham; Arie, Ady
2013-01-01
We report the first experimental generation and observation of Airy beams of free electrons. The electron Airy beams are generated by diffraction of electrons through a nanoscale hologram, that imprints a cubic phase modulation on the beams' transverse plane. We observed the spatial evolution dynamics of an arc-shaped, self accelerating and shape preserving electron Airy beams. We directly observed the ability of electrons to self-heal, restoring their original shape after passing an obstacle. This electromagnetic method opens up new avenues for steering electrons, like their photonic counterparts, since their wave packets can be imprinted with arbitrary shapes or trajectories. Furthermore, these beams can be easily manipulated using magnetic or electric potentials. It is also possible to efficiently self mix narrow beams having opposite signs of acceleration, hence obtaining a new type of electron interferometer.
A trajectory observer for camera-based underwater motion measurements
DEFF Research Database (Denmark)
Berg, Tor; Jouffroy, Jerome; Johansen, Vegar
This work deals with the issue of estimating the trajectory of a vehicle or object moving underwater based on camera measurements. The proposed approach consists of a diffusion-based trajectory observer (Jouffroy and Opderbecke, 2004) processing whole segments of a trajectory at a time....... Additionally, the observer contains a Tikhonov regularizer for smoothing the estimates. Then, a method for including the camera measurements in an appropriate manner is proposed....
Decoherence and the Branching of Chaos-less Classical Trajectory
Ishikawa, Takuji
2016-01-01
This study was started to know mysterious classicality of nuclei. This time, I found a new rule for decoherence. I used a model without chaos. As a result, it was shown that not only the intersection of classical trajectories but also branching of classical trajectories are needed for decoherence. In other words, it was shown that interactions between a main system and environments have to make enough branchings of classical trajectories of the main system for decoherence.
Trajectory tracking for robot manipulators using differential flatness
Directory of Open Access Journals (Sweden)
Elkin Veslin Diaz
2011-05-01
Full Text Available This paper proposes applying differential flatness to robot manipulator trajectory tracking. The trajectories for each generalised coordinate are proposed as a function and the corresponding input must be found to guarantee tracking. It is shown that the position in the generalised coordinates and their derivatives are flat inputs which, together with a PD controller, could determine (with some restrictions manipulator movement having minimal deviation throughout its trajectory in both plane movements and in space.
Design of MGA trajectories for main belt asteroid
Institute of Scientific and Technical Information of China (English)
崔祜涛; 乔栋; 崔平远; 栾恩杰
2003-01-01
Asteroid exploration is one of the most sophisticated missions currently being investigated. Gravityassist trajectories have proven valuable in interplanetary missions such as the Pioneer, Voyager and Galileo. In this paper, we design interplanetary trajectory for main belt asteroid exploration mission with the Mars gravityassist (MGA) using "pork chop" plots and patched-conic theory and give some initial valuable trajectory parameters on main belt asteroid exploration mission with MGA.
On the Discovery of Success Trajectories of Authors
Pradhan, Dinesh; Chakraborty, Tanmoy; Pandit, Saswata; Nandi, Subrata
2016-01-01
Understanding the qualitative patterns of research endeavor of scientific authors in terms of publication count and their impact (citation) is important in order to quantify success trajectories. Here, we examine the career profile of authors in computer science and physics domains and discover at least six different success trajectories in terms of normalized citation count in longitudinal scale. Initial observations of individual trajectories lead us to characterize the authors in each cate...
Dynamical Casimir effect in Circuit QED for Nonuniform Trajectories
Corona-Ugalde, Paulina; Wilson, C M; Mann, Robert B
2015-01-01
We propose a generalization of the superconducting circuit simulation of the dynamical Casimir effect where we consider relativistically moving boundary conditions following different trajectories. We study the feasibility of the setup used in the past to simulate the dynamical Casimir effect to reproduce richer relativistic trajectories differing from purely sinusoidal ones. We show how different relativistic oscillatory trajectories of the boundaries of the same period and similar shape produce a rather different spectrum of particles characteristic of their respective motions.
Trajectory optimization and applications using high performance solar sails
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
The high performance solar sail can enable fast missions to the outer solar system and produce exotic non-Keplerian orbits.As there is no fuel consumption,mission trajectories for solar sail spacecraft are typically optimized with respect to flight time.Several investigations focused on interstellar probe missions have been made,including optimal methods and new objective functions. Two modes of interstellar mission trajectories,namely "direct flyby" and "angular momentum reversal trajectory",are compare...
Versatile and Extensible, Continuous-Thrust Trajectory Optimization Tool Project
National Aeronautics and Space Administration — We propose to develop an innovative, versatile and extensible, continuous-thrust trajectory optimization tool for planetary mission design and optimization of...
Tracing developmental trajectories of oppositional defiant behaviors in preschool children.
Directory of Open Access Journals (Sweden)
Lourdes Ezpeleta
Full Text Available Previous studies on developmental trajectories have used ad hoc definitions of oppositional defiant behaviors (ODB, which makes it difficult to compare results. This article defines developmental trajectories of ODB from ages 3-5 based on five different standard measurements derived from three separate instruments.A sample of 622 three-year-old preschoolers, followed up at ages 4, 5, and 6, was assessed with the five measures of oppositionality answered by parents and teachers. Growth-Mixture-Modeling (GMM estimated separate developmental trajectories for each ODB measure for ages 3 to 5.The number of classes-trajectories obtained in each GMM depended on the ODB measure, but two clear patterns emerged: four trajectories (persistent low, decreasers, increasers/high increasers, persistent moderate/persistent high or three trajectories (persistent low, decreasers, increasers/high increasers. Persistent high trajectories accounted for 4.4%-9.5% of the children. The trajectories emerging from the different ODB measures at ages 3 to 5 discriminated disruptive disorders, comorbidity, use of services, and impairment at age 6, and globally showed a similar pattern, summarizing longitudinal information on oppositionality in preschool children in a similar way.Trajectories resulting from standard scales of the questionnaires have predictive validity for identifying relevant clinical outcomes, but are measure-specific. The results contribute to knowledge about the development of ODB in preschool children.
Locomotion trajectory with cooperative metrics in wireless sensor networks
Institute of Scientific and Technical Information of China (English)
QIN Ning-ning; ZHANG Lin; SHAN Xiu-ming; XU Bao-guo
2007-01-01
Detection coverage control is one of the most important topics in the intrusion detection problem of wireless sensor networks (WSN). However, its converse, i.e., to design an object locomotion trajectory in WSN, has not received enough attention. This article proposes a heuristic algorithm, namely, the security & speed (SS) algorithm, to depict such a trajectory that takes into consideration both security and speed. The merit of the SS algorithm is its topology independency. When compared with traditional algorithms, the SS algorithm approaches the optimal trajectory better, and enjoys considerably lower computational load, and a better and adjustable tradeoff between trajectory security and speed.
A Dropsonde Glider with Adaptive Trajectory Planning Project
National Aeronautics and Space Administration — Dropsondes are one of the primary atmospheric measurement tools available to researchers. Current dropsondes are deployed with a free fall parachute trajectory,...
Tracing developmental trajectories of oppositional defiant behaviors in preschool children.
Ezpeleta, Lourdes; Granero, Roser; de la Osa, Núria; Navarro, José Blas; Penelo, Eva; Domènech, Josep M
2014-01-01
Previous studies on developmental trajectories have used ad hoc definitions of oppositional defiant behaviors (ODB), which makes it difficult to compare results. This article defines developmental trajectories of ODB from ages 3-5 based on five different standard measurements derived from three separate instruments. A sample of 622 three-year-old preschoolers, followed up at ages 4, 5, and 6, was assessed with the five measures of oppositionality answered by parents and teachers. Growth-Mixture-Modeling (GMM) estimated separate developmental trajectories for each ODB measure for ages 3 to 5. The number of classes-trajectories obtained in each GMM depended on the ODB measure, but two clear patterns emerged: four trajectories (persistent low, decreasers, increasers/high increasers, persistent moderate/persistent high) or three trajectories (persistent low, decreasers, increasers/high increasers). Persistent high trajectories accounted for 4.4%-9.5% of the children. The trajectories emerging from the different ODB measures at ages 3 to 5 discriminated disruptive disorders, comorbidity, use of services, and impairment at age 6, and globally showed a similar pattern, summarizing longitudinal information on oppositionality in preschool children in a similar way. Trajectories resulting from standard scales of the questionnaires have predictive validity for identifying relevant clinical outcomes, but are measure-specific. The results contribute to knowledge about the development of ODB in preschool children.
Algorithms for computing efficient, electric-propulsion, spiralling trajectories Project
National Aeronautics and Space Administration — Develop techniques for rapidly designing many-revolution, electric-propulsion, spiralling trajectories, including the effects of shadowing, gravity harmonics, and...
Laser wakefield acceleration of polarized electron beams
Pugacheva, D. V.; Andreev, N. E.; Cros, B.
2016-11-01
The acceleration of highly polarized electron beams are widely used in state-of-the-art high-energy physics experiments. In this work, a model for investigation of polarization dynamics of electron beams in the laser-plasma accelerator depending on the initial energy of electrons was developed and tested. To obtain the evolution of the trajectory and momentum of the electron for modeling its acceleration the wakefield structure was determined. The spin precession of the beam electron was described by Thomas-Bargman-Michel-Telegdi equations. The evolution of the electron beam polarization was investigated for zero-emittance beams with zero-energy spread.
Adiponectin Trajectories Before Type 2 Diabetes Diagnosis
Tabák, Adam G.; Carstensen, Maren; Witte, Daniel R.; Brunner, Eric J.; Shipley, Martin J.; Jokela, Markus; Roden, Michael; Kivimäki, Mika; Herder, Christian
2012-01-01
OBJECTIVE The role of adiponectin in the natural history of diabetes is not well characterized. We set out to characterize prediagnosis trajectories of adiponectin in individuals who develop type 2 diabetes. RESEARCH DESIGN AND METHODS In a case-cohort study (335 incident diabetes case and 2,474 noncase subjects) nested in the Whitehall II study, serum adiponectin was measured up to three times per participant (1991–1993, 1997–1999, and 2003–2004). Multilevel models adjusted for age and ethnicity were fitted to assess 13-year trajectories of log-transformed adiponectin preceding diabetes diagnosis or a randomly selected time point during follow-up (year0) based on 755/5,095 (case/noncase) person-examinations. RESULTS Adiponectin levels were lower in diabetes case than in noncase subjects (median 7,141 [interquartile range 5,187–10,304] vs. 8,818 [6,535–12,369] ng/mL at baseline, P < 0.0001). Control subjects showed a modest decline in adiponectin throughout follow-up (0.3% per year, P < 0.0001) at higher levels in women than in men (difference at year0: 5,358 ng/mL, P < 0.0001). Female case and early-onset case (age at diagnosis <52 years) subjects had a steeper decline than control subjects (slope difference −1.1% per year, P = 0.001 in females, −1.6% per year in early-onset case subjects, P = 0.034). In men, adiponectin slopes for case and noncase subjects were parallel. The slope differences by diabetes onset were largely attenuated after adjustment for changes in obesity, whereas the sex-specific slope differences were independent of obesity. CONCLUSIONS Lower adiponectin levels were observed already a decade before the diagnosis of diabetes. The marked sex difference in trajectories suggests that sex-specific mechanisms affect the association between adiponectin levels and diabetes development. PMID:22933430
Hybrid Airy Plasmons with Dynamically Steerable Trajectories
Li, Rujiang; Lin, Xiao; Wang, Huaping; Xu, Zhiwei; Chen, Hongsheng
2016-01-01
With the intriguing properties of diffraction-free, self-accelerating, and self-healing, Airy plasmons are promising to be used in the trapping, transporting, and sorting of micro-objects, imaging, and chip scale signal processing. However, the high dissipative loss and the lack of dynamical steerability restrict the implementation of Airy plasmons in these applications. Here we reveal the hybrid Airy plasmons for the first time by taking a hybrid graphene-based plasmonic waveguide in the terahertz (THz) domain as an example. Due to the coupling between an optical mode and a plasmonic mode, the hybrid Airy plasmons can have large propagation lengths and effective transverse deflections, where the transverse waveguide confinements are governed by the hybrid modes with moderate quality factors. Meanwhile, the propagation trajectories of hybrid Airy plasmons are dynamically steerable by changing the chemical potential of graphene. These hybrid Airy plasmons may promote the further discovery of non-diffracting be...
Hybrid Airy plasmons with dynamically steerable trajectories.
Li, Rujiang; Imran, Muhammad; Lin, Xiao; Wang, Huaping; Xu, Zhiwei; Chen, Hongsheng
2017-01-26
With their intriguing diffraction-free, self-accelerating, and self-healing properties, Airy plasmons show promise for use in the trapping, transporting, and sorting of micro-objects, imaging, and chip scale signal processing. However, high dissipative loss and lack of dynamical steerability restrict the implementation of Airy plasmons in these applications. Here we reveal hybrid Airy plasmons for the first time by taking a hybrid graphene-based plasmonic waveguide in the terahertz (THz) domain as an example. Due to coupling between optical modes and plasmonic modes, the hybrid Airy plasmons can have large propagation lengths and effective transverse deflections, where the transverse waveguide confinements are governed by the hybrid modes with moderate quality factors. Meanwhile, the propagation trajectories of the hybrid Airy plasmons are dynamically steerable by changing the chemical potential of graphene. These hybrid Airy plasmons may promote the further discovery of non-diffracting beams along with the emerging developments of optical tweezers and tractor beams.
Trajectories and models of individual growth
Directory of Open Access Journals (Sweden)
Arseniy Karkach
2006-11-01
Full Text Available It has long been recognized that the patterns of growth play an important role in the evolution of age trajectories of fertility and mortality (Williams, 1957. Life history studies would benefit from a better understanding of strategies and mechanisms of growth, but still no comparative research on individual growth strategies has been conducted. Growth patterns and methods have been shaped by evolution and a great variety of them are observed. Two distinct patterns - determinate and indeterminate growth - are of a special interest for these studies since they present qualitatively different outcomes of evolution. We attempt to draw together studies covering growth in plant and animal species across a wide range of phyla focusing primarily on the noted qualitative features. We also review mathematical descriptions of growth, namely empirical growth curves and growth models, and discuss the directions of future research.
Stabilizing chaotic-scattering trajectories using control
Lai, Ying-Cheng; Tél, Tamás; Grebogi, Celso
1993-08-01
The method of stabilizing unstable periodic orbits in chaotic dynamical systems by Ott, Grebogi, and Yorke (OGY) is applied to control chaotic scattering in Hamiltonian systems. In particular, we consider the case of nonhyperbolic chaotic scattering, where there exist Kolmogorov-Arnold-Moser (KAM) surfaces in the scattering region. It is found that for short unstable periodic orbits not close to the KAM surfaces, both the probability that a particle can be controlled and the average time to achieve control are determined by the initial exponential decay rate of particles in the hyperbolic component. For periodic orbits near the KAM surfaces, due to the stickiness effect of the KAM surfaces on particle trajectories, the average time to achieve control can greatly exceed that determined by the hyperbolic component. The applicability of the OGY method to stabilize intermediate complexes of classical scattering systems is suggested.
Aging, life trajectories and female homosexuality
Directory of Open Access Journals (Sweden)
Andrea Moraes Alves
2010-01-01
Full Text Available The social science's literature about female homosexuality has recently grown in Brazil, showing the awakened interest in this issue. Since the 1990's, academic works have discussed female homosexuality: its meanings and its impact on gender issues, its relationships with social movements, specially the ones concerned with sexual rights in Brazil. Great part of these works focus on a young age rate, and some of them are dedicated to middle age women. However, there aren't works concerned with old age women and lesbianity. This article starts to fill this gap and takes into account old age lesbians and their perceptions about homosexuality and its place in their life trajectories.
SPATIAL TRAJECTORY PREDICTION OF VISUAL SERVOING
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
Target tracking is one typical application of visual servoing technology. It is still a difficult task to track high speed target with current visual servo system. The improvement of visual servoing scheme is strongly required. A position-based visual servo parallel system is presented for tracking target with high speed. A local Frenet frame is assigned to the sampling point of spatial trajectory. Position estimation is formed by the differential features of intrinsic geometry, and orientation estimation is formed by homogenous transformation. The time spent for searching and processing can be greatly reduced by shifting the window according to features location prediction. The simulation results have demonstrated the ability of the system to track spatial moving object.
Optimal growth trajectories with finite carrying capacity.
Caravelli, F; Sindoni, L; Caccioli, F; Ududec, C
2016-08-01
We consider the problem of finding optimal strategies that maximize the average growth rate of multiplicative stochastic processes. For a geometric Brownian motion, the problem is solved through the so-called Kelly criterion, according to which the optimal growth rate is achieved by investing a constant given fraction of resources at any step of the dynamics. We generalize these finding to the case of dynamical equations with finite carrying capacity, which can find applications in biology, mathematical ecology, and finance. We formulate the problem in terms of a stochastic process with multiplicative noise and a nonlinear drift term that is determined by the specific functional form of carrying capacity. We solve the stochastic equation for two classes of carrying capacity functions (power laws and logarithmic), and in both cases we compute the optimal trajectories of the control parameter. We further test the validity of our analytical results using numerical simulations.
Optimal growth trajectories with finite carrying capacity
Caravelli, F.; Sindoni, L.; Caccioli, F.; Ududec, C.
2016-08-01
We consider the problem of finding optimal strategies that maximize the average growth rate of multiplicative stochastic processes. For a geometric Brownian motion, the problem is solved through the so-called Kelly criterion, according to which the optimal growth rate is achieved by investing a constant given fraction of resources at any step of the dynamics. We generalize these finding to the case of dynamical equations with finite carrying capacity, which can find applications in biology, mathematical ecology, and finance. We formulate the problem in terms of a stochastic process with multiplicative noise and a nonlinear drift term that is determined by the specific functional form of carrying capacity. We solve the stochastic equation for two classes of carrying capacity functions (power laws and logarithmic), and in both cases we compute the optimal trajectories of the control parameter. We further test the validity of our analytical results using numerical simulations.
Dynamics of quantum trajectories in chaotic systems
Wisniacki, D A; Benito, R M
2003-01-01
Quantum trajectories defined in the de Broglie--Bohm theory provide a causal way to interpret physical phenomena. In this Letter, we use this formalism to analyze the short time dynamics induced by unstable periodic orbits in a classically chaotic system, a situation in which scars are known to play a very important role. We find that the topologies of the quantum orbits are much more complicated than that of the scarring and associated periodic orbits, since the former have quantum interference built in. Thus scar wave functions are necessary to analyze the corresponding dynamics. Moreover, these topologies imply different return routes to the vicinity of the initial positions, and this reflects in the existence of different contributions in each peak of the survival probability function.
Organized Sport Trajectories from Childhood to Adolescence and Health Associations.
Howie, Erin K; McVeigh, Joanne A; Smith, Anne J; Straker, Leon M
2016-07-01
The purpose of this study was to identify unique organized sport trajectories from early childhood to late adolescence in an Australian pregnancy cohort, the Raine Study. Participation in organized sport was assessed at ages 5, 8, 10, 14, and 17 yr. Physical activity, body composition, and self-rated physical and mental health were assessed at the age of 20 yr. Latent class analysis was used to identify patterns of sport participation. To assess the internal validity of the trajectory classes, differences in health characteristics between trajectories were analyzed using generalized linear models. For girls, three trajectory classes were identified: consistent sport participators (47.5%), sport dropouts (34.3%), and sport nonparticipators (18.1%). For boys, three trajectory classes were identified: consistent sport participators (55.2%), sport dropouts (36.9%), and sport joiners (8.1%). For girls, there were overall differences across trajectory classes in lean body mass (P = 0.003), lean mass index (P = 0.06), and physical health (P = 0.004). For boys, there were differences across classes in physical activity (P = 0.018), percent body fat (P = 0.002), lean body mass (P health (P = 0.06), and depression scores (P = 0.27). This study identified unique, sex-specific trajectories of organized sport participation. The differences in health outcomes between trajectory classes, such as participants with consistent sport participation having more preferable health outcomes at the age of 20 yr, support the internal validity of the trajectories. Strategies are needed to identify and encourage those in the dropout trajectory to maintain their participation and those in the nonparticipator or joiner trajectories to join sport earlier. Specifically, interventions to encourage early sport participation in girls and help nonparticipating boys to join sport during adolescence may help more children receive the benefits of sport participation.
Ferreting out correlations from trajectory data.
Cukier, Robert I
2011-12-14
Thermally driven materials characterized by complex energy landscapes, such as proteins, exhibit motions on a broad range of space and time scales. Principal component analysis (PCA) is often used to extract modes of motion from protein trajectory data that correspond to coherent, functional motions. In this work, two other methods, maximum covariance analysis (MCA) and canonical correlation analysis (CCA) are formulated in a way appropriate to analyze protein trajectory data. Both methods partition the coordinates used to describe the system into two sets (two measurement domains) and inquire as to the correlations that may exist between them. MCA and CCA provide rotations of the original coordinate system that successively maximize the covariance (MCA) or correlation (CCA) between modes of each measurement domain under suitable constraint conditions. We provide a common framework based on the singular value decomposition of appropriate matrices to derive MCA and CCA. The differences between and strengths and weaknesses of MCA and CCA are discussed and illustrated. The application presented here examines the correlation between the backbone and side chain of the peptide met-enkephalin as it fluctuates between open conformations, found in solution, to closed conformations appropriate to when it is bound to its receptor. Difficulties with PCA carried out in Cartesian coordinates are found and motivate a formulation in terms of dihedral angles for the backbone atoms and selected atom distances for the side chains. These internal coordinates are a more reliable basis for all the methods explored here. MCA uncovers a correlation between combinations of several backbone dihedral angles and selected side chain atom distances of met-enkephalin. It could be used to suggest residues and dihedral angles to focus on to favor specific side chain conformers. These methods could be applied to proteins with domains that, when they rearrange upon ligand binding, may have
Early growth trajectories affect sexual responsiveness.
Lee, Who-Seung; Metcalfe, Neil B; Réale, Denis; Peres-Neto, Pedro R
2014-02-22
The trajectory of an animal's growth in early development has been shown to have long-term effects on a range of life-history traits. Although it is known that individual differences in behaviour may also be related to certain life-history traits, the linkage between early growth or development and individual variation in behaviour has received little attention. We used brief temperature manipulations, independent of food availability, to stimulate compensatory growth in juvenile three-spined sticklebacks Gasterosteus aculeatus. Here, we examine how these manipulated growth trajectories affected the sexual responsiveness of the male fish at the time of sexual maturation, explore associations between reproductive behaviour and investment and lifespan and test whether the perceived time stress (until the onset of the breeding season) influenced such trade-offs. We found a negative impact of growth rate on sexual responsiveness: fish induced (by temperature manipulation) to grow slowest prior to the breeding season were consistently quickest to respond to the presence of a gravid female. This speed of sexual responsiveness was also positively correlated with the rate of development of sexual ornaments and time taken to build a nest. However, after controlling for effects of growth rate, those males that had the greatest sexual responsiveness to females had the shortest lifespan. Moreover, the time available to compensate in size before the onset of the breeding season (time stress) affected the magnitude of these effects. Our results demonstrate that developmental perturbations in early life can influence mating behaviour, with long-term effects on longevity.
Trajectory association across multiple airborne cameras.
Sheikh, Yaser Ajmal; Shah, Mubarak
2008-02-01
A camera mounted on an aerial vehicle provides an excellent means for monitoring large areas of a scene. Utilizing several such cameras on different aerial vehicles allows further flexibility, in terms of increased visual scope and in the pursuit of multiple targets. In this paper, we address the problem of associating objects across multiple airborne cameras. Since the cameras are moving and often widely separated, direct appearance-based or proximity-based constraints cannot be used. Instead, we exploit geometric constraints on the relationship between the motion of each object across cameras, to test multiple association hypotheses, without assuming any prior calibration information. Given our scene model, we propose a likelihood function for evaluating a hypothesized association between observations in multiple cameras that is geometrically motivated. Since multiple cameras exist, ensuring coherency in association is an essential requirement, e.g. that transitive closure is maintained between more than two cameras. To ensure such coherency we pose the problem of maximizing the likelihood function as a k-dimensional matching and use an approximation to find the optimal assignment of association. Using the proposed error function, canonical trajectories of each object and optimal estimates of inter-camera transformations (in a maximum likelihood sense) are computed. Finally, we show that as a result of associating objects across the cameras, a concurrent visualization of multiple aerial video streams is possible and that, under special conditions, trajectories interrupted due to occlusion or missing detections can be repaired. Results are shown on a number of real and controlled scenarios with multiple objects observed by multiple cameras, validating our qualitative models, and through simulation quantitative performance is also reported.
Stabilization of cat paw trajectory during locomotion.
Klishko, Alexander N; Farrell, Bradley J; Beloozerova, Irina N; Latash, Mark L; Prilutsky, Boris I
2014-09-15
We investigated which of cat limb kinematic variables during swing of regular walking and accurate stepping along a horizontal ladder are stabilized by coordinated changes of limb segment angles. Three hypotheses were tested: 1) animals stabilize the entire swing trajectory of specific kinematic variables (performance variables); and 2) the level of trajectory stabilization is similar between regular and ladder walking and 3) is higher for forelimbs compared with hindlimbs. We used the framework of the uncontrolled manifold (UCM) hypothesis to quantify the structure of variance of limb kinematics in the limb segment orientation space across steps. Two components of variance were quantified for each potential performance variable, one of which affected it ("bad variance," variance orthogonal to the UCM, VORT) while the other one did not ("good variance," variance within the UCM, VUCM). The analysis of five candidate performance variables revealed that cats during both locomotor behaviors stabilize 1) paw vertical position during the entire swing (VUCM > VORT, except in mid-hindpaw swing of ladder walking) and 2) horizontal paw position in initial and terminal swing (except for the entire forepaw swing of regular walking). We also found that the limb length was typically stabilized in midswing, whereas limb orientation was not (VUCM ≤ VORT) for both limbs and behaviors during entire swing. We conclude that stabilization of paw position in early and terminal swing enables accurate and stable locomotion, while stabilization of vertical paw position in midswing helps paw clearance. This study is the first to demonstrate the applicability of the UCM-based analysis to nonhuman movement.
Camera Trajectory fromWide Baseline Images
Havlena, M.; Torii, A.; Pajdla, T.
2008-09-01
Camera trajectory estimation, which is closely related to the structure from motion computation, is one of the fundamental tasks in computer vision. Reliable camera trajectory estimation plays an important role in 3D reconstruction, self localization, and object recognition. There are essential issues for a reliable camera trajectory estimation, for instance, choice of the camera and its geometric projection model, camera calibration, image feature detection and description, and robust 3D structure computation. Most of approaches rely on classical perspective cameras because of the simplicity of their projection models and ease of their calibration. However, classical perspective cameras offer only a limited field of view, and thus occlusions and sharp camera turns may cause that consecutive frames look completely different when the baseline becomes longer. This makes the image feature matching very difficult (or impossible) and the camera trajectory estimation fails under such conditions. These problems can be avoided if omnidirectional cameras, e.g. a fish-eye lens convertor, are used. The hardware which we are using in practice is a combination of Nikon FC-E9 mounted via a mechanical adaptor onto a Kyocera Finecam M410R digital camera. Nikon FC-E9 is a megapixel omnidirectional addon convertor with 180° view angle which provides images of photographic quality. Kyocera Finecam M410R delivers 2272×1704 images at 3 frames per second. The resulting combination yields a circular view of diameter 1600 pixels in the image. Since consecutive frames of the omnidirectional camera often share a common region in 3D space, the image feature matching is often feasible. On the other hand, the calibration of these cameras is non-trivial and is crucial for the accuracy of the resulting 3D reconstruction. We calibrate omnidirectional cameras off-line using the state-of-the-art technique and Mičušík's two-parameter model, that links the radius of the image point r to the
Collection of secondary electrons in scanning electron microscopes.
Müllerová, I; Konvalina, I
2009-12-01
Collection of the secondary electrons in the scanning electron microscope was simulated and the results have been experimentally verified for two types of the objective lens and three detection systems. The aberration coefficients of both objective lenses as well as maximum axial magnetic fields in the specimen region are presented. Compared are a standard side-attached secondary electron detector, in which only weak electrostatic and nearly no magnetic field influence the signal trajectories in the specimen vicinity, and the side-attached (lower) and upper detectors in an immersion system with weak electrostatic but strong magnetic field penetrating towards the specimen. The collection efficiency was calculated for all three detection systems and several working distances. The ability of detectors to attract secondary electron trajectories for various initial azimuthal and polar angles was calculated, too. According to expectations, the lower detector of an immersion system collects no secondary electrons I and II emitted from the specimen and only backscattered electrons and secondary electrons III form the final image. The upper detector of the immersion system exhibits nearly 100% collection efficiency decreasing, however, with the working distance, but the topographical contrast is regrettably suppressed in its image. The collection efficiency of the standard detector is low for short working distances but increases with the same, preserving strong topographical contrast.
A model of chemical etching of olivine in the vicinity of the trajectory of a swift heavy ion
Energy Technology Data Exchange (ETDEWEB)
Gorbunov, S.A., E-mail: s.a.gorbunov@mail.ru [Lebedev Physical Institute of the Russian Academy of Sciences, Leninskij pr. 53, 119991 Moscow (Russian Federation); Rymzhanov, R.A. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); Starkov, N.I. [Lebedev Physical Institute of the Russian Academy of Sciences, Leninskij pr. 53, 119991 Moscow (Russian Federation); Volkov, A.E. [Lebedev Physical Institute of the Russian Academy of Sciences, Leninskij pr. 53, 119991 Moscow (Russian Federation); Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); National Research Centre ‘Kurchatov Institute’, Kurchatov Sq. 1, 123182 Moscow (Russian Federation); Malakhov, A.I. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation)
2015-12-15
Searching of superheavy elements, the charge spectra of heavy nuclei in Galactic Cosmic Rays was investigated within the OLYMPIA experiment using the database of etched ion tracks in meteorite olivine. Etching results in the formation of hollow syringe-like channels with diameters of 1–10 μm along the trajectories of these swift heavy ions (SHI). According to the activated complex theory, the local chemical activity is determined by an increase of the specific Gibbs energy of the lattice stimulated by structure transformations, long-range elastic fields, and interatomic bonds breaking generated in the vicinity of the ion trajectory. To determine the dependencies of the Gibbs free energy increase in SHI tracks in olivine on the mass, energy and charge of a projectile, we apply a multiscale model of excitation and relaxation of materials in the vicinity of the SHI trajectory (SHI tracks). Effect of spreading of fast electrons from the ion trajectory causing neutralization of metallic atoms resulting in an increase of the chemical activity of olivine at long distances from the ion trajectory (up to 5 μm) is estimated and discussed.
A model of chemical etching of olivine in the vicinity of the trajectory of a swift heavy ion
Gorbunov, S. A.; Rymzhanov, R. A.; Starkov, N. I.; Volkov, A. E.; Malakhov, A. I.
2015-12-01
Searching of superheavy elements, the charge spectra of heavy nuclei in Galactic Cosmic Rays was investigated within the OLYMPIA experiment using the database of etched ion tracks in meteorite olivine. Etching results in the formation of hollow syringe-like channels with diameters of 1-10 μm along the trajectories of these swift heavy ions (SHI). According to the activated complex theory, the local chemical activity is determined by an increase of the specific Gibbs energy of the lattice stimulated by structure transformations, long-range elastic fields, and interatomic bonds breaking generated in the vicinity of the ion trajectory. To determine the dependencies of the Gibbs free energy increase in SHI tracks in olivine on the mass, energy and charge of a projectile, we apply a multiscale model of excitation and relaxation of materials in the vicinity of the SHI trajectory (SHI tracks). Effect of spreading of fast electrons from the ion trajectory causing neutralization of metallic atoms resulting in an increase of the chemical activity of olivine at long distances from the ion trajectory (up to 5 μm) is estimated and discussed.
Optimal Hankel Norm Model Reduction by Truncation of Trajectories
Roorda, B.; Weiland, S.
2000-01-01
We show how optimal Hankel-norm approximations of dynamical systems allow for a straightforward interpretation in terms of system trajectories. It is shown that for discrete time single-input systems optimal reductions are obtained by cutting 'balanced trajectories', i.e., by disconnecting the past
Automated Sensitivity Analysis of Interplanetary Trajectories for Optimal Mission Design
Knittel, Jeremy; Hughes, Kyle; Englander, Jacob; Sarli, Bruno
2017-01-01
This work describes a suite of Python tools known as the Python EMTG Automated Trade Study Application (PEATSA). PEATSA was written to automate the operation of trajectory optimization software, simplify the process of performing sensitivity analysis, and was ultimately found to out-perform a human trajectory designer in unexpected ways. These benefits will be discussed and demonstrated on sample mission designs.
BALCO 6/7-DoF trajectory model
Wey, P.; Corriveau, D.; Saitz, T.A.; Ruijter, W. de; Strömbäck, P.
2016-01-01
BALCO is a six- and seven-degree-of-freedom trajectory simulation program based on the mathematical model defined by the NATO Standardization Recommendation 4618. The primary goal of BALCO is to compute high-fidelity trajectories for both conventional and precision-guided projectiles. The 6-DoF mode
Teacher Performance Trajectories in High- and Lower-Poverty Schools
Xu, Zeyu; Özek, Umut; Hansen, Michael
2015-01-01
This study explores whether teacher performance trajectory over time differs by school-poverty settings. Focusing on elementary school mathematics teachers in North Carolina and Florida, we find no systematic relationship between school student poverty rates and teacher performance trajectories. In both high- (=60% free/reduced-price lunch [FRPL])…
Fluency, Accuracy, and Gender Predict Developmental Trajectories of Arithmetic Strategies
Carr, Martha; Alexeev, Natalia
2011-01-01
The purpose of this study was to determine whether there are different growth trajectories of arithmetic strategies and whether these trajectories result in different achievement outcomes. Longitudinal data were collected on 240 students who began the study as 2nd graders. In the 1st year of the study, the 2nd-grade students were assessed on…
Teacher Performance Trajectories in High- and Lower-Poverty Schools
Xu, Zeyu; Özek, Umut; Hansen, Michael
2015-01-01
This study explores whether teacher performance trajectory over time differs by school-poverty settings. Focusing on elementary school mathematics teachers in North Carolina and Florida, we find no systematic relationship between school student poverty rates and teacher performance trajectories. In both high- (=60% free/reduced-price lunch [FRPL])…
TRAJECTORY ATTRACTORS FOR NONCLASSICAL DIFFUSION EQUATIONS WITH FADING MEMORY
Institute of Scientific and Technical Information of China (English)
Yonghai WANG; Lingzhi WANG
2013-01-01
In this article,we consider the existence of trajectory and global attractors for nonclassical diffusion equations with linear fading memory.For this purpose,we will apply the method presented by Chepyzhov and Miranville [7,8],in which the authors provide some new ideas in describing the trajectory attractors for evolution equations with memory.
Complexity Science Applications to Dynamic Trajectory Management: Research Strategies
Sawhill, Bruce; Herriot, James; Holmes, Bruce J.; Alexandrov, Natalia
2009-01-01
The promise of the Next Generation Air Transportation System (NextGen) is strongly tied to the concept of trajectory-based operations in the national airspace system. Existing efforts to develop trajectory management concepts are largely focused on individual trajectories, optimized independently, then de-conflicted among each other, and individually re-optimized, as possible. The benefits in capacity, fuel, and time are valuable, though perhaps could be greater through alternative strategies. The concept of agent-based trajectories offers a strategy for automation of simultaneous multiple trajectory management. The anticipated result of the strategy would be dynamic management of multiple trajectories with interacting and interdependent outcomes that satisfy multiple, conflicting constraints. These constraints would include the business case for operators, the capacity case for the Air Navigation Service Provider (ANSP), and the environmental case for noise and emissions. The benefits in capacity, fuel, and time might be improved over those possible under individual trajectory management approaches. The proposed approach relies on computational agent-based modeling (ABM), combinatorial mathematics, as well as application of "traffic physics" concepts to the challenge, and modeling and simulation capabilities. The proposed strategy could support transforming air traffic control from managing individual aircraft behaviors to managing systemic behavior of air traffic in the NAS. A system built on the approach could provide the ability to know when regions of airspace approach being "full," that is, having non-viable local solution space for optimizing trajectories in advance.
Quantum hydrodynamic analysis of decoherence: quantum trajectories and stress tensor
Energy Technology Data Exchange (ETDEWEB)
Na, Kyungsun; Wyatt, Robert E
2002-12-30
Quantum trajectories, obtained by integrating equations of motion for elements of the probability fluid, are used to analyze decoherence in a model two-mode system. Analysis of trajectories, flux maps, and the stress tensor for two composite systems, in one of which the system is uncoupled from the environment, leads to a hydrodynamic interpretation of the decoherence process.
Trajectories of Depression Symptoms among Older Youths Exiting Foster Care
Munson, Michelle R.; McMillen, Curtis
2010-01-01
The purpose of this study was to determine the trajectories of depressive symptoms as older youths from the foster care system mature while also examining the correlates of these trajectories. Data came from a longitudinal study of 404 youths from the foster care system in Missouri, who were interviewed nine times between their 17th and 19th…
Exploring Categorical Body Mass Index Trajectories in Elementary School Children
Moreno-Black, Geraldine; Boles, Shawn; Johnson-Shelton, Deb; Evers, Cody
2016-01-01
Background: Studies of body mass index (BMI) change have focused on understanding growth trajectories from childhood to adolescence and adolescence to adulthood, but few have explored BMI trajectories solely in elementary (grades K-5) school children. This report complements these studies by exploring changes in obesity status using analytic…
Aircraft path planning with the use of smooth trajectories
Belokon', S. A.; Zolotukhin, Yu. N.; Nesterov, A. A.
2017-01-01
A simplified method of plane trajectory calculation is proposed for solving the problem of planning a path defined by a sequence of waypoints. The trajectory consists of oriented segments of straight lines joined by clothoids (Cornu spirals). The efficiency of the method is validated by means of numerical simulations in the MATLAB/Simulink environment.
Alcohol Use Growth Trajectories in Young Adolescence: Pathways and Predictors
Shamblen, Stephen R.; Ringwalt, Chris L.; Clark, Heddy K.; Hanley, Sean M.
2014-01-01
New analytical tools have facilitated the exploration of the trajectories of alcohol use; however, there are a limited number of studies that explore early adolescence. A sample of 5,903 youths followed from sixth through eighth grade was used to (1) examine the trajectories of alcohol use and (2) determine the degree to which common correlates…
Trajectories of Sexual Risk from Middle Adolescence to Early Adulthood
Moilanen, Kristin L.; Crockett, Lisa J.; Raffaelli, Marcela; Jones, Bobby L.
2010-01-01
Developmental trajectories of risky sexual behavior were identified in a multiethnic sample of 1,121 youth drawn from the Children of the National Longitudinal Survey of Youth data set (NLSY79). Group-based trajectory modeling of a composite index of sexual risk taking revealed four sexual risk groups from ages 16 to 22: low risk, decreasing risk,…
Obesity status trajectory groups among elementary school children
Little is known about patterns in the transition from healthy weight to overweight or obesity during the elementary school years. This study examined whether there were distinct body mass index (BMI) trajectory groups among elementary school children, and predictors of trajectory group membership. T...
Eye Movement Trajectories and What They Tell Us
Stigchel, van der S.
2007-01-01
The present thesis is concerned with how our eyes move trough space. Since the pioneering work of Yarbus it is known that the trajectories of the eyes can tell a great deal about the underlying cognitive processes. The current thesis is not just concerned with eye movement trajectories in general
Educational Trajectories of Graduate Students in Physics Education Research
Van Dusen, Ben; Barthelemy, Ramón S.; Henderson, Charles
2014-01-01
Physics education research (PER) is a rapidly growing area of PhD specialization. In this article we examine the trajectories that led respondents into a PER graduate program as well as their expected future trajectories. Data were collected in the form of an online survey sent to graduate students in PER. Our findings show a lack of visibility of…
BALCO 6/7-DoF trajectory model
Wey, P.; Corriveau, D.; Saitz, T.A.; Ruijter, W. de; Strömbäck, P.
2016-01-01
BALCO is a six- and seven-degree-of-freedom trajectory simulation program based on the mathematical model defined by the NATO Standardization Recommendation 4618. The primary goal of BALCO is to compute high-fidelity trajectories for both conventional and precision-guided projectiles. The 6-DoF mode
Predictors of Latent Trajectory Classes of Physical Dating Violence Victimization
Brooks-Russell, Ashley; Foshee, Vangie A.; Ennett, Susan T.
2013-01-01
This study identified classes of developmental trajectories of physical dating violence victimization from grades 8 to 12 and examined theoretically-based risk factors that distinguished among trajectory classes. Data were from a multi-wave longitudinal study spanning 8th through 12th grade (n = 2,566; 51.9 % female). Growth mixture models were…
Detecting Hotspots from Taxi Trajectory Data Using Spatial Cluster Analysis
Zhao, P. X.; Qin, K.; Zhou, Q.; Liu, C. K.; Chen, Y. X.
2015-07-01
A method of trajectory clustering based on decision graph and data field is proposed in this paper. The method utilizes data field to describe spatial distribution of trajectory points, and uses decision graph to discover cluster centres. It can automatically determine cluster parameters and is suitable to trajectory clustering. The method is applied to trajectory clustering on taxi trajectory data, which are on the holiday (May 1st, 2014), weekday (Wednesday, May 7th, 2014) and weekend (Saturday, May 10th, 2014) respectively, in Wuhan City, China. The hotspots in four hours (8:00-9:00, 12:00-13:00, 18:00-19:00 and 23:00-24:00) for three days are discovered and visualized in heat maps. In the future, we will further research the spatiotemporal distribution and laws of these hotspots, and use more data to carry out the experiments.
Trajectory Planning for Robots in Dynamic Human Environments
DEFF Research Database (Denmark)
Svenstrup, Mikael; Bak, Thomas; Andersen, Hans Jørgen
2010-01-01
This paper present a trajectory planning algorithm for a robot operating in dynamic human environments. Environments such as pedestrian streets, hospital corridors and train stations. We formulate the problem as planning a minimal cost trajectory through a potential field, defined from...... the perceived position and motion of persons in the environment. A Rapidly-exploring Random Tree (RRT) algorithm is proposed as a solution to the planning problem. A new method for selecting the best trajectory in the RRT, according to the cost of traversing a potential field, is presented. The RRT expansion...... vertex to the tree. Instead of executing a whole trajectory, when planned, the algorithm uses an Model Predictive Control (MPC) approach, where only a short segment of the trajectory is executed while a new iteration of the RRT is done. The planning algorithm is demonstrated in a simulated pedestrian...
Energy-efficient Trajectory Tracking for Mobile Devices
DEFF Research Database (Denmark)
Kjærgaard, Mikkel Baun; Bhattacharya, Sourav; Blunck, Henrik
2011-01-01
Emergent location-aware applications often require tracking trajectories of mobile devices over a long period of time. To be useful, the tracking has to be energy-efficient to avoid having a major impact on the battery life of the mobile de vice. Furthermore, when trajectory information needs...... to be sent to a remote server, on-device simplification of the trajectories is needed to reduce the amount of data transmission. While there has recently been a lot of work on energy-efficient position tracking, the energy-efficient tracking of trajectories has not been addressed in previous work....... In this paper we propose a novel on-device sensor management strategy and a set of trajectory updating protocols which intelligently determine when to sample different sensors (accelerometer, compass and GPS) and when data should be simplified and sent to a remote server. The system is configurable with regards...
Attitude and Trajectory Estimation Using Earth Magnetic Field Data
Deutschmann, Julie; Bar-Itzhack, Itzhack Y.
1996-01-01
The magnetometer has long been a reliable, inexpensive sensor used in spacecraft momentum management and attitude estimation. Recent studies show an increased accuracy potential for magnetometer-only attitude estimation systems. Since the Earth's magnetic field is a function of time and position, and since time is known quite precisely, the differences between the computer and measured magnetic field components, as measured by the magnetometers throughout the entire spacecraft orbit, are a function of both the spacecraft trajectory and attitude errors. Therefore, these errors can be used to estimate both trajectory and attitude. Traditionally, satellite attitude and trajectory have been estimated with completely separate system, using different measurement data. Recently, trajectory estimation for low earth orbit satellites was successfully demonstrated in ground software using only magnetometer data. This work proposes a single augmented extended Kalman Filter to simultaneously and autonomously estimate both spacecraft trajectory and attitude with data from a magnetometer and either dynamically determined rates or gyro-measured body rates.
Estimation of Cartesian Space Robot Trajectories Using Unit Quaternion Space
Directory of Open Access Journals (Sweden)
Aleš Ude
2014-08-01
Full Text Available The ability to estimate Cartesian space trajectories that include orientation is of great importance for many practical applications. While it is becoming easier to acquire trajectory data by computer vision methods, data measured by general-purpose vision or depth sensors are often rather noisy. Appropriate smoothing methods are thus needed in order to reconstruct smooth Cartesian space trajectories given noisy measurements. In this paper, we propose an optimality criterion for the problem of the smooth estimation of Cartesian space trajectories that include the end-effector orientation.Based on this criterion, we develop an optimization method for trajectory estimation which takes into account the special properties of the orientation space, which we represent by unit quaternions.The efficiency of the developed approach is discussed and experimental results are presented.
Simulation Study on Fuzzy Control of Rotary Steering Drilling Trajectory
Directory of Open Access Journals (Sweden)
Xue Qi-Long
2012-07-01
Full Text Available The purpose of this study is to establish a control method to make borehole trajectory smoother. Considering that the complexity of rotary steerable drilling trajectory control and uncertainty of underground work, analysis of the deficiencies for the traditional trajectory control and the rotary steerable drilling trajectory deviation vector control theory, introduced the concept of "trend Angle", combined with the deviation vector as joint control variables, using fuzzy control algorithm that established of rotary steerable drilling trajectory fuzzy control model. Designed the fuzzy controller using Matlab/Simulink toolbox and dynamic simulation analysis for the fuzzy control systems, simulation results show that the designed fuzzy controller can effectively track the well path design, has a strong adaptability and control results is better than traditional PID control method.
Trajectory Generation Method with Convolution Operation on Velocity Profile
Energy Technology Data Exchange (ETDEWEB)
Lee, Geon [Hanyang Univ., Seoul (Korea, Republic of); Kim, Doik [Korea Institute of Science and Technology, Daejeon (Korea, Republic of)
2014-03-15
The use of robots is no longer limited to the field of industrial robots and is now expanding into the fields of service and medical robots. In this light, a trajectory generation method that can respond instantaneously to the external environment is strongly required. Toward this end, this study proposes a method that enables a robot to change its trajectory in real-time using a convolution operation. The proposed method generates a trajectory in real time and satisfies the physical limits of the robot system such as acceleration and velocity limit. Moreover, a new way to improve the previous method, which generates inefficient trajectories in some cases owing to the characteristics of the trapezoidal shape of trajectories, is proposed by introducing a triangle shape. The validity and effectiveness of the proposed method is shown through a numerical simulation and a comparison with the previous convolution method.
Cell mechanics through analysis of cell trajectories in microfluidic channel
Bowie, Samuel; Alexeev, Alexander; Sulchek, Todd
The understanding of dynamic cell behavior can aid in research ranging from the mechanistic causes of diseases to the development of microfluidic devices for cancer detection. Through analysis of trajectories captured from video of the cells moving in a specially designed microfluidic device, insight into the dynamic viscoelastic nature of cells can be found. The microfluidic device distinguishes cells viscoelastic properties through the use of angled ridges causing a series of compressions, resulting in differences in trajectories based on cell stiffness. Trajectories of cell passing through the device are collected using image processing methods and data mining techniques are used to relate the trajectories to cell properties obtained from experiments. Furthermore, numerical simulation of the cell and microfluidic device are used to match the experimental results from the trajectory analysis. Combination of the modeling and experimental data help to uncover how changes in cellular structures result in changes in mechanical properties.
Efficient One-click Browsing of Large Trajectory Sets
DEFF Research Database (Denmark)
Krogh, Benjamin Bjerre; Andersen, Ove; Lewis-Kelham, Edwin
2014-01-01
Traffic researchers, planners, and analysts want a simple way to query the large quantities of GPS trajectories collected from vehicles. In addition, users expect the results to be presented immediately even when querying very large transportation networks with huge trajectory data sets. This paper...... presents a novel query type called sheaf, where users can browse trajectory data sets using a single mouse click. Sheaves are very versatile and can be used for location-based advertising, travel-time analysis, intersection analysis, and reachability analysis (isochrones). A novel in-memory trajectory...... index compresses the data by a factor of 12.4 and enables execution of sheaf queries in 40 ms. This is up to 2 orders of magnitude faster than existing work. We demonstrate the simplicity, versatility, and efficiency of sheaf queries using a real-world trajectory set consisting of 2.7 million...
Trajectory models and reference frames for crustal motion geodesy
Bevis, Michael; Brown, Abel
2014-03-01
We sketch the evolution of station trajectory models used in crustal motion geodesy over the last several decades, and describe some recent generalizations of these models that allow geodesists and geophysicists to parameterize accelerating patterns of displacement in general, and postseismic transient deformation in particular. Modern trajectory models are composed of three sub-models that represent secular trends, annual oscillations, and instantaneous jumps in coordinate time series. Traditionally the trend model invoked constant station velocity. This can be generalized by assuming that position is a polynomial function of time. The trajectory model can also be augmented as needed, by including one or more logarithmic transients in order to account for typical multi-year patterns of postseismic transient motion. Many geodetic and geophysical research groups are using general classes of trajectory model to characterize their crustal displacement time series, but few if any of them are using these trajectory models to define and realize the terrestrial reference frames (RFs) in which their time series are expressed. We describe a global GPS reanalysis program in which we use two general classes of trajectory model, tuned on a station by station basis. We define the network trajectory model as the set of station trajectory models encompassing every station in the network. We use the network trajectory model from the each global analysis to assign prior position estimates for the next round of GPS data processing. We allow our daily orbital solutions to relax so as to maintain their consistency with the network polyhedron. After several iterations we produce GPS time series expressed in a RF similar to, but not identical with ITRF2008. We find that each iteration produces an improvement in the daily repeatability of our global time series and in the predictive power of our trajectory models.
Brown, A C
2016-01-01
We propose a novel scheme for resolving the contribution of inner- and outer-valence electrons in XUV-initiated high-harmonic generation in neon. By probing the atom with a low energy (below the 2s ionisation threshold) ultrashort XUV pulse, the 2p electron is steered away from the core, while the 2s electron is enabled to describe recollision trajectories. By selectively suppressing the 2p recollision trajectories we can resolve the contribution of the 2s electron to the high-harmonic spectrum. We apply the classical trajectory model to account for the contribution of the 2s electron, which allows for an intuitive understanding of the process.
Trajectories of prediagnostic functioning in Parkinson's disease.
Darweesh, Sirwan K L; Verlinden, Vincentius J A; Stricker, Bruno H; Hofman, Albert; Koudstaal, Peter J; Ikram, M Arfan
2017-02-01
SEE BREEN AND LANG DOI101093/AWW321 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: At the time of clinical diagnosis, patients with Parkinson's disease already have a wide range of motor and non-motor features that affect their daily functioning. However, the temporal sequence of occurrence of these features remains largely unknown. We studied trajectories of daily functioning and motor and non-motor features in the 23 years preceding Parkinson's disease diagnosis by performing a nested case-control study within the prospective Rotterdam study. Between 1990 and 2013, we repeatedly performed standardized assessments of daily functioning (Stanford Health Assessment Questionnaire, Lawton Instrumental Activities of Daily Living Scale), potential prediagnostic motor (hypo- and bradykinesia, tremor, rigidity, postural imbalance, postural abnormalities) and non-motor features of Parkinson's disease, including cognition (Mini-Mental State Examination, Stroop Test, Letter-Digit-Substitution Test, Word Fluency Test), mood (Center for Epidemiological Studies-Depression Scale, Hamilton Anxiety and Depression Scale), and autonomic function (blood pressure, laxative use). In addition, the cohort was followed-up for the onset of clinical Parkinson's disease using several overlapping modalities, including repeated in-person examinations, as well as complete access to medical records and specialist letters of study participants. During follow-up, 109 individuals were diagnosed with Parkinson's disease, and each case was matched to 10 controls based on age and sex (total n = 1199). Subsequently, we compared prediagnostic trajectories of daily functioning and other features between Parkinson's disease cases and controls. From 7 years before diagnosis onwards, prediagnostic Parkinson's disease cases more commonly had problems in instrumental activities of daily functioning, and more frequently showed signs of movement poverty and slowness, tremor and subtle cognitive deficits. In the
US Decadal Survey Outer Solar System Missions: Trajectory Options
Spilker, T. R.; Atkinson, D. H.; Strange, N. J.; Landau, D.
2012-04-01
The report of the US Planetary Science Decadal Survey (PSDS), released in draft form March 7, 2011, identifies several mission concepts involving travel to high-priority outer solar system (OSS) destinations. These include missions to Europa and Jupiter, Saturn and two of its satellites, and Uranus. Because travel to the OSS involves much larger distances and larger excursions out of the sun's gravitational potential well than inner solar system (ISS) missions, transfer trajectories for OSS missions are stronger drivers of mission schedule and resource requirements than for ISS missions. Various characteristics of each planet system, such as obliquity, radiation belts, rings, deep gravity wells, etc., carry ramifications for approach trajectories or trajectories within the systems. The maturity of trajectory studies for each of these destinations varies significantly. Europa has been the focus of studies for well over a decade. Transfer trajectory options from Earth to Jupiter are well understood. Current studies focus on trajectories within the Jovian system that could reduce the total mission cost of a Europa orbiter mission. Three missions to the Saturn system received high priority ratings in the PSDS report: two flagship orbital missions, one to Titan and one to Enceladus, and a Saturn atmospheric entry probe mission for NASA's New Frontiers Program. The Titan Saturn System Mission (TSSM) studies of 2007-2009 advanced our understanding of trajectory options for transfers to Saturn, including solar electric propulsion (SEP) trajectories. But SEP trajectories depend more on details of spacecraft and propulsion system characteristics than chemical trajectories, and the maturity of SEP trajectory search tools has not yet caught up with chemical trajectory tools, so there is still more useful research to be done on Saturn transfers. The TSSM studies revealed much about Saturn-orbiting trajectories that yield efficient and timely delivery to Titan or Enceladus
Heating and Trapping of Electrons in ECRIS from Scratch to Afterglow
Heinen, A; Ortjohann, H W; Vitt, C; Andrae, H J
1999-01-01
Plasmas in Electron Cyclotron Resonance Ion Sources (ECRIS) are collisionless and can therefore be simulated by just following the motion of electrons in the confining static magnetic and oscillating microwave (MW) electric field of ECRIS. With a powerful algorithm the three-dimensional trajectories of 104 ECR-heated and confined electrons are calculated in a standard ECRIS with a deep minimum of |B| and a new ECRIS with a very flat minimum of |B|. The spatial electron (plasma) densities and electron energy densities deduced from these trajectories yield new and surprising insight in the performance of ECRIS. With computer animation we plan to present: The energy increase of certain electrons on extremely stable trajectories, the power dependence of the electron energy density up to the X-ray collapse, the time dependent build up of the electron density and energy density distributions, and the time evolution of these electron distributions under afterglow conditions.
Optimal guidance of extended trajectory shaping
Institute of Scientific and Technical Information of China (English)
Wang Hui; Lin Defu; Cheng Zhenxuan; Wang Jiang
2014-01-01
To control missile’s miss distance as well as terminal impact angle, by involving the time-to-go-nth power in the cost function, an extended optimal guidance law against a constant maneu-vering target or a stationary target is proposed using the linear quadratic optimal control theory. An extended trajectory shaping guidance (ETSG) law is then proposed under the assumption that the missile-target relative velocity is constant and the line of sight angle is small. For a lag-free ETSG system, closed-form solutions for the missile’s acceleration command are derived by the method of Schwartz inequality and linear simulations are performed to verify the closed-form results. Normalized adjoint systems for miss distance and terminal impact angle error are presented independently for stationary targets and constant maneuvering targets, respectively. Detailed discussions about the terminal misses and impact angle errors induced by terminal impact angle constraint, initial heading error, seeker zero position errors and target maneuvering, are performed.
Synchronized Trajectories in a Climate "Supermodel"
Duane, Gregory; Schevenhoven, Francine; Selten, Frank
2017-04-01
Differences in climate projections among state-of-the-art models can be resolved by connecting the models in run-time, either through inter-model nudging or by directly combining the tendencies for corresponding variables. Since it is clearly established that averaging model outputs typically results in improvement as compared to any individual model output, averaged re-initializations at typical analysis time intervals also seems appropriate. The resulting "supermodel" is more like a single model than it is like an ensemble, because the constituent models tend to synchronize even with limited inter-model coupling. Thus one can examine the properties of specific trajectories, rather than averaging the statistical properties of the separate models. We apply this strategy to a study of the index cycle in a supermodel constructed from several imperfect copies of the SPEEDO model (a global primitive-equation atmosphere-ocean-land climate model). As with blocking frequency, typical weather statistics of interest like probabilities of heat waves or extreme precipitation events, are improved as compared to the standard multi-model ensemble approach. In contrast to the standard approach, the supermodel approach provides detailed descriptions of typical actual events.
MAOA Influences the Trajectory of Attentional Development
Lundwall, Rebecca A.; Rasmussen, Claudia G.
2016-01-01
Attention is vital to success in all aspects of life (Meck and Benson, 2002; Erickson et al., 2015), hence it is important to identify biomarkers of later attentional problems early enough to intervene. Our objective was to determine if any of 11 genes (APOE, BDNF, HTR4, CHRNA4, COMT, DRD4, IGF2, MAOA, SLC5A7, SLC6A3, and SNAP25) predicted the trajectory of attentional development within the same group of children between infancy and childhood. We recruited follow up participants from children who participated as infants in visual attention studies and used a similar task at both time points. Using multilevel modeling, we associated changes in the participant’s position in the distribution of scores in infancy to his/her position in childhood with genetic markers on each of 11 genes. While all 11 genes predicted reaction time (RT) residual scores, only Monoamine oxidase A (MAOA) had a significant interaction including time point. We conclude that the MAOA single nucleotide polymorphism (SNP) rs1137070 is useful in predicting which girls are likely to develop slower RTs on an attention task between infancy and childhood. This early identification is likely to be helpful in early intervention. PMID:27610078
Quantum vortices and trajectories in particle diffraction
Delis, N; Contopoulos, G
2011-01-01
We investigate the phenomenon of the diffraction of charged particles by thin material targets using the method of the de Broglie-Bohm quantum trajectories. The particle wave function can be modeled as a sum of two terms $\\psi=\\psi_{ingoing}+\\psi_{outgoing}$. A thin separator exists between the domains of prevalence of the ingoing and outgoing wavefunction terms. The structure of the quantum-mechanical currents in the neighborhood of the separator implies the formation of an array of \\emph{quantum vortices}. The flow structure around each vortex displays a characteristic pattern called `nodal point - X point complex'. The X point gives rise to stable and unstable manifolds. We find the scaling laws characterizing a nodal point-X point complex by a local perturbation theory around the nodal point. We then analyze the dynamical role of vortices in the emergence of the diffraction pattern. In particular, we demonstrate the abrupt deflections, along the direction of the unstable manifold, of the quantum trajector...
Trajectories entropy in dynamical graphs with memory
Caravelli, Francesco
2015-01-01
In this paper we investigate the application of the graph entropy introduced in a previous work to study the evolving complexity in dynamical graphs. The measure is based upon the notion of Markov diffusion on a graph, and relies on the entropy applied to trajectories originating at a specific node. In particular, we study the model of reinforcement-decay graph dynamics, leading to scale free graphs, and introduced as a toy model to study memristive networks. We find that the node entropy characterizes the structure of the network in the two parameter phase-space describing the dynamical evolution of the weighted graph. We then apply an adapted version of the complexity measure to pure memristive networks. We show that meanwhile in the case of DC voltage using forward probability is enough to characterize the graph properties, in the case of AC voltage generators, one needs to consider both forward and backward based transition probabilities. We find that the entropy shows the self-organizing properties of me...
Pairwise Trajectory Management (PTM): Concept Overview
Jones, Kenneth M.; Graff, Thomas J.; Chartrand, Ryan C.; Carreno, Victor; Kibler, Jennifer L.
2017-01-01
Pairwise Trajectory Management (PTM) is an Interval Management (IM) concept that utilizes airborne and ground-based capabilities to enable the implementation of airborne pairwise spacing capabilities in oceanic regions. The goal of PTM is to use airborne surveillance and tools to manage an "at or greater than" inter-aircraft spacing. Due to the precision of Automatic Dependent Surveillance-Broadcast (ADS-B) information and the use of airborne spacing guidance, the PTM minimum spacing distance will be less than distances a controller can support with current automation systems that support oceanic operations. Ground tools assist the controller in evaluating the traffic picture and determining appropriate PTM clearances to be issued. Avionics systems provide guidance information that allows the flight crew to conform to the PTM clearance issued by the controller. The combination of a reduced minimum distance and airborne spacing management will increase the capacity and efficiency of aircraft operations at a given altitude or volume of airspace. This paper provides an overview of the proposed application, description of a few key scenarios, high level discussion of expected air and ground equipment and procedure changes, overview of a potential flight crew human-machine interface that would support PTM operations and some initial PTM benefits results.
The trajectory of the target probability effect.
Hon, Nicholas; Yap, Melvin J; Jabar, Syaheed B
2013-05-01
The effect of target probability on detection times is well-established: Even when detection accuracy is high, lower probability targets are detected more slowly than higher probability ones. Although this target probability effect on detection times has been well-studied, one aspect of it has remained largely unexamined: How the effect develops over the span of an experiment. Here, we investigated this issue with two detection experiments that assessed different target probability ratios. Conventional block segment analysis and linear mixed-effects modeling converged on two key findings. First, we found that the magnitude of the target probability effect increases as one progresses through a block of trials. Second, we found, by examining the trajectories of the low- and high-probability targets, that this increase in effect magnitude was driven by the low-probability targets. Specifically, we found that low-probability targets were detected more slowly as a block of trials progressed. Performance to high-probability targets, on the other hand, was largely invariant across the block. The latter finding is of particular interest because it cannot be reconciled with accounts that propose that the target probability effect is driven by the high-probability targets.
Reflections on a trajectory in Occupational Therapy
Directory of Open Access Journals (Sweden)
Selma Lancmam
2012-12-01
Full Text Available This text is part of the memorial presented as a requirement of the contest for full professor positionin Occupational Therapy at the School of Medicine from the University of Sao Paulo. The reflections presentedaim to trace the trajectory contextualized in different periods and institutions where the writer has worked, andhow they have blended with the academic development of Occupational Therapy itself. The text also seeks todiscuss the solidification process of the writer’s training as a researcher and the results arisen thereof. Thesecourses were built on research and culminated in the Mental Health and Work search line and its interfaces withOccupational Therapy. Across the text, the academic and scientific development in the field of occupationaltherapy is reflected and, finally, discussions are pointed out on the necessary consolidation of the area in researchand graduate studies and, therefore, in the dissemination of knowledge by publications indexed and relevant tothe field. The text is both a personal account and a true representation of the profession development in Brazilin the past thirty years.
High-density electroencephalography developmental neurophysiological trajectories.
Dan, Bernard; Pelc, Karine; Cebolla, Ana M; Cheron, Guy
2015-04-01
Efforts to document early changes in the developing brain have resulted in the construction of increasingly accurate structural images based on magnetic resonance imaging (MRI) in newborn infants. Tractography diagrams obtained through diffusion tensor imaging have focused on white matter microstructure, with particular emphasis on neuronal connectivity at the level of fibre tract systems. Electroencephalography (EEG) provides a complementary approach with more direct access to brain electrical activity. Its temporal resolution is excellent, and its spatial resolution can be enhanced to physiologically relevant levels, through the combination of high-density recordings (e.g. by using 64 channels in newborn infants) and mathematical models (e.g. inverse modelling computation), to identify generators of different oscillation bands and synchrony patterns. The integration of functional and structural topography of the neonatal brain provides insights into typical brain organization, and the deviations seen in particular contexts, for example the effect of hypoxic-ischaemic insult in terms of damage, eventual reorganization, and functional changes. Endophenotypes can then be used for pathophysiological reasoning, management planning, and outcome measurements, and allow a longitudinal approach to individual developmental trajectories. © The Authors. Journal compilation © 2015 Mac Keith Press.
An independent system for real-time dynamic multileaf collimation trajectory verification using EPID
Fuangrod, Todsaporn; Woodruff, Henry C.; Rowshanfarzad, Pejman; O'Connor, Daryl J.; Middleton, Richard H.; Greer, Peter B.
2014-01-01
A new tool has been developed to verify the trajectory of dynamic multileaf collimators (MLCs) used in advanced radiotherapy techniques using only the information provided by the electronic portal imaging devices (EPID) measured image frames. The prescribed leaf positions are resampled to a higher resolution in a pre-processing stage to improve the verification precision. Measured MLC positions are extracted from the EPID frames using a template matching method. A cosine similarity metric is then applied to synchronise measured and planned leaf positions for comparison. Three additional comparison functions were incorporated to ensure robust synchronisation. The MLC leaf trajectory error detection was simulated for both intensity modulated radiation therapy (IMRT) (prostate) and volumetric modulated arc therapy (VMAT) (head-and-neck) deliveries with anthropomorphic phantoms in the beam. The overall accuracy for MLC positions automatically extracted from EPID image frames was approximately 0.5 mm. The MLC leaf trajectory verification system can detect leaf position errors during IMRT and VMAT with a tolerance of 3.5 mm within 1 s.
Prosocial Behavior: Long-Term Trajectories and Psychosocial Outcomes.
Flynn, Elinor; Ehrenreich, Samuel E; Beron, Kurt J; Underwood, Marion K
2015-08-01
This study investigated developmental trajectories for prosocial behavior for a sample followed from age 10 - 18 and examined possible adjustment outcomes associated with membership in different trajectory groups. Participants were 136 boys and 148 girls, their teachers, and their parents (19.4% African American, 2.4% Asian, 51.9% Caucasian, 19.5% Hispanic, and 5.8% other). Teachers rated children's prosocial behavior yearly in grades 4 - 12. At the end of the 12(th) grade year, teachers, parents, and participants reported externalizing behaviors and participants reported internalizing symptoms, narcissism, and features of borderline personality disorder. Results suggested that prosocial behavior remained stable from middle childhood through late adolescence. Group-based mixture modeling revealed three prosocial trajectory groups: low (18.7%), medium (52.8%), and high (29.6%). Membership in the high prosocial trajectory group predicted lower levels of externalizing behavior as compared to the low prosocial trajectory group, and for girls, lower levels of internalizing symptoms. Membership in the medium prosocial trajectory group also predicted being lower on externalizing behaviors. Membership in the high prosocial trajectory group predicted lower levels of borderline personality features for girls only.
Effects of complex parameters on classical trajectories of Hamiltonian systems
Indian Academy of Sciences (India)
Asiri Nanayakkara; Thilagarajah Mathanaranjan
2014-06-01
Anderson et al have shown that for complex energies, the classical trajectories of real quartic potentials are closed and periodic only on a discrete set of eigencurves. Moreover, recently it was revealed that when time is complex $t(t = t_r e^{i_})$, certain real Hermitian systems possess close periodic trajectories only for a discrete set of values of . On the other hand, it is generally true that even for real energies, classical trajectories of non-PT symmetric Hamiltonians with complex parameters are mostly non-periodic and open. In this paper, we show that for given real energy, the classical trajectories of complex quartic Hamiltonians $H = p^2 + ax^4 + bx^k$ (where is real, is complex and = 1 or 2) are closed and periodic only for a discrete set of parameter curves in the complex -plane. It was further found that given complex parameter , the classical trajectories are periodic for a discrete set of real energies (i.e., classical energy gets discretized or quantized by imposing the condition that trajectories are periodic and closed). Moreover, we show that for real and positive energies (continuous), the classical trajectories of complex Hamiltonian $H = p^2 + x^4$, ($= _r$ e$^{i}$) are periodic when $ = 4 \\tan^{−1}$[($n/(2m + n)$)] for $\\forall n$ and $m \\mathbb{Z}$.
Foot trajectory approximation using the pendulum model of walking.
Fang, Juan; Vuckovic, Aleksandra; Galen, Sujay; Conway, Bernard A; Hunt, Kenneth J
2014-01-01
Generating a natural foot trajectory is an important objective in robotic systems for rehabilitation of walking. Human walking has pendular properties, so the pendulum model of walking has been used in bipedal robots which produce rhythmic gait patterns. Whether natural foot trajectories can be produced by the pendulum model needs to be addressed as a first step towards applying the pendulum concept in gait orthosis design. This study investigated circle approximation of the foot trajectories, with focus on the geometry of the pendulum model of walking. Three able-bodied subjects walked overground at various speeds, and foot trajectories relative to the hip were analysed. Four circle approximation approaches were developed, and best-fit circle algorithms were derived to fit the trajectories of the ankle, heel and toe. The study confirmed that the ankle and heel trajectories during stance and the toe trajectory in both the stance and the swing phases during walking at various speeds could be well modelled by a rigid pendulum. All the pendulum models were centred around the hip with pendular lengths approximately equal to the segment distances from the hip. This observation provides a new approach for using the pendulum model of walking in gait orthosis design.
Job satisfaction developmental trajectories and health: A life course perspective.
Dirlam, Jonathan; Zheng, Hui
2017-04-01
Understanding the health consequence of job dissatisfaction becomes increasingly important because job insecurity, stress and dissatisfaction have significantly increased in the United States in the last decade. Despite the extensive work in this area, prior studies nonetheless may underestimate the harmful effect of job dissatisfaction due to the cross-sectional nature of their data and sample selection bias. This study applies a life-course approach to more comprehensively examine the relationship between job satisfaction and health. Using data from the NLSY 1979 cohort, we estimate group based job satisfaction trajectories of respondents starting at age 25 and ending at age 39. Four job satisfaction trajectory groups are identified, a consistently high satisfaction group, a downward group, an upward group, and a lowest satisfaction group. We examine the effects of these trajectories on several physical and mental health outcomes of respondents in their early forties. We find membership in the lowest job satisfaction trajectory group to be negatively associated with all five mental health outcomes, supporting the accumulation of risks life course model. Those in the upward job satisfaction trajectory group have similar health outcomes to those in the high job satisfaction trajectory group, supporting the social mobility life course model. Overall, we find the relationship between job satisfaction trajectories and health to be stronger for mental health compared to physical health. Copyright © 2017 Elsevier Ltd. All rights reserved.
Trajectory Calculation as Forecasting Support Tool for Dust Storms
Directory of Open Access Journals (Sweden)
Sultan Al-Yahyai
2014-01-01
Full Text Available In arid and semiarid regions, dust storms are common during windy seasons. Strong wind can blow loose sand from the dry surface. The rising sand and dust is then transported to other places depending on the wind conditions (speed and direction at different levels of the atmosphere. Considering dust as a moving object in space and time, trajectory calculation then can be used to determine the path it will follow. Trajectory calculation is used as a forecast supporting tool for both operational and research activities. Predefined dust sources can be identified and the trajectories can be precalculated from the Numerical Weather Prediction (NWP forecast. In case of long distance transported dust, the tool should allow the operational forecaster to perform online trajectory calculation. This paper presents a case study for using trajectory calculation based on NWP models as a forecast supporting tool in Oman Meteorological Service during some dust storm events. Case study validation results showed a good agreement between the calculated trajectories and the real transport path of the dust storms and hence trajectory calculation can be used at operational centers for warning purposes.
Visual Uav Trajectory Plan System Based on Network Map
Li, X. L.; Lin, Z. J.; Su, G. Z.; Wu, B. Y.
2012-07-01
The base map of the current software UP-30 using in trajectory plan for Unmanned Aircraft Vehicle is vector diagram. UP-30 draws navigation points manually. But in the field of operation process, the efficiency and the quality of work is influenced because of insufficient information, screen reflection, calculate inconveniently and other factors. If we do this work in indoor, the effect of external factors on the results would be eliminated, the network earth users can browse the free world high definition satellite images through downloading a client software, and can export the high resolution image by standard file format. This brings unprecedented convenient of trajectory plan. But the images must be disposed by coordinate transformation, geometric correction. In addition, according to the requirement of mapping scale ,camera parameters and overlap degree we can calculate exposure hole interval and trajectory distance between the adjacent trajectory automatically . This will improve the degree of automation of data collection. Software will judge the position of next point according to the intersection of the trajectory and the survey area and ensure the position of point according to trajectory distance. We can undertake the points artificially. So the trajectory plan is automatic and flexible. Considering safety, the date can be used in flying after simulating flight. Finally we can export all of the date using a key
Flocking behavior with multiple leaders and global trajectory
Institute of Scientific and Technical Information of China (English)
李猛; 梁加红; 李石磊
2014-01-01
Aiming at the group of autonomous agents consisting of multiple leader agents and multiple follower ones, a flocking behavior method with multiple leaders and a global trajectory was proposed. In this flocking method, the group leaders can attain the information of the global trajectory, while each follower can communicate with its neighbors and corresponding leader but does not have global knowledge. Being to a distributed control method, the proposed method firstly sets a movable imaginary point on the global trajectory to ensure that the center and average velocity of the leader agents satisfy the constraints of the global trajectory. Secondly, a two-stage strategy was proposed to make the whole group satisfy the constraints of the global trajectory. Moreover, the distance between the center of the group and the desired trajectory was analyzed in detail according to the number ratio of the followers to the leaders. In this way, on one hand, the agents of the group emerge a basic flocking behavior; on the other hand, the center of the group satisfies the constraints of global trajectory. Simulation results demonstrate the effectiveness of the proposed method.
Reentry trajectory optimization for hypersonic vehicle satisfying complex constraints
Institute of Scientific and Technical Information of China (English)
Jiang Zhao; Rui Zhou
2013-01-01
The reentry trajectory optimization for hypersonic vehicle (HV) is a current problem of great interest. Some complex constraints, such as waypoints for reconnaissance and no-fly zones for threat avoidance, are inevitably involved in a global strike mission. Of the many direct methods, Gauss pseudospectral method (GPM) has been demonstrated as an effective tool to solve the tra-jectory optimization problem with typical constraints. However, a series of difficulties arises for complex constraints, such as the uncertainty of passage time for waypoints and the inaccuracy of approximate trajectory near no-fly zones. The research herein proposes a multi-phase technique based on the GPM to generate an optimal reentry trajectory for HV satisfying waypoint and no-fly zone constraints. Three kinds of specific breaks are introduced to divide the full trajectory into multiple phases. The continuity conditions are presented to ensure a smooth connection between each pair of phases. Numerical examples for reentry trajectory optimization in free-space flight and with complex constraints are used to demonstrate the proposed technique. Simulation results show the feasible application of multi-phase technique in reentry trajectory optimization with way-point and no-fly zone constraints.
Experimental observation of anomalous trajectories of single photons
Zhou, Zong-Quan; Liu, Xiao; Kedem, Yaron; Cui, Jin-Min; Li, Zong-Feng; Hua, Yi-Lin; Li, Chuan-Feng; Guo, Guang-Can
2017-04-01
A century after its conception, quantum mechanics still hold surprises that contradict many "common sense" notions. The contradiction is especially sharp in case one consider trajectories of truly quantum objects such as single photons. From a classical point of view, trajectories are well defined for particles, but not for waves. The wave-particle duality forces a breakdown of this dichotomy and quantum mechanics resolves this in a remarkable way: Trajectories can be well defined, but they are utterly different from classical trajectories. Here, we give an operational definition to the trajectory of a single photon by introducing a technique to mark its path using its spectral composition. The method demonstrates that the frequency degree of freedom can be used as a bona fide quantum measurement device (meter). The analysis of a number of setups, using our operational definition, leads to anomalous trajectories which are noncontinuous and in some cases do not even connect the source of the photon to where it is detected. We carried out an experimental demonstration of these anomalous trajectories using a nested interferometer. We show that the two-state vector formalism provides a simple explanation for the results.
Effect of flapping trajectories on the dragonfly aerodynamics
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The effects of translational, figure-eight and double-figure-eight flapping trajectories on the dragonfly aerodynamics were numerically studied by solving the Navier-Stokes equations. There is a common characteristic regarding the lift/drag force coefficients that the downstroke flapping provides the lift forces while the upstroke flapping creates the thrust forces for different flapping trajectories. The maximum lift force coefficient exceeds five for the translational trajectory. It is greater than six for the figure-eight and double-figure-eight flapping trajectories, which is sufficiently larger than unity under the steady state flight condition. The ellipse and double-figure-eight flapping trajectories yield the decrease of the lift force, while the figure-eight flapping trajectory yields higher lift force as well as the thrust force than the translational flapping one. During the insect flight, the wing flapping status should be changed instantaneously to satisfy various requirements. Study of the flapping trajectories on the insect aerodynamics is helpful for the design of the Micro-air-vehicles (MAVs).
Dissipative quantum trajectories in complex space: Damped harmonic oscillator
Chou, Chia-Chun
2016-10-01
Dissipative quantum trajectories in complex space are investigated in the framework of the logarithmic nonlinear Schrödinger equation. The logarithmic nonlinear Schrödinger equation provides a phenomenological description for dissipative quantum systems. Substituting the wave function expressed in terms of the complex action into the complex-extended logarithmic nonlinear Schrödinger equation, we derive the complex quantum Hamilton-Jacobi equation including the dissipative potential. It is shown that dissipative quantum trajectories satisfy a quantum Newtonian equation of motion in complex space with a friction force. Exact dissipative complex quantum trajectories are analyzed for the wave and solitonlike solutions to the logarithmic nonlinear Schrödinger equation for the damped harmonic oscillator. These trajectories converge to the equilibrium position as time evolves. It is indicated that dissipative complex quantum trajectories for the wave and solitonlike solutions are identical to dissipative complex classical trajectories for the damped harmonic oscillator. This study develops a theoretical framework for dissipative quantum trajectories in complex space.
Asthma trajectories in early childhood: identifying modifiable factors.
Directory of Open Access Journals (Sweden)
Lidia Panico
Full Text Available BACKGROUND: There are conflicting views as to whether childhood wheezing represents several discreet entities or a single but variable disease. Classification has centered on phenotypes often derived using subjective criteria, small samples, and/or with little data for young children. This is particularly problematic as asthmatic features appear to be entrenched by age 6/7. In this paper we aim to: identify longitudinal trajectories of wheeze and other atopic symptoms in early childhood; characterize the resulting trajectories by the socio-economic background of children; and identify potentially modifiable processes in infancy correlated with these trajectories. DATA AND METHODS: The Millennium Cohort Study is a large, representative birth cohort of British children born in 2000-2002. Our analytical sample includes 11,632 children with data on key variables (wheeze in the last year; ever hay-fever and/or eczema reported by the main carers at age 3, 5 and 7 using a validated tool, the International Study of Asthma and Allergies in Childhood module. We employ longitudinal Latent Class Analysis, a clustering methodology which identifies classes underlying the observed population heterogeneity. RESULTS: Our model distinguished four latent trajectories: a trajectory with both low levels of wheeze and other atopic symptoms (54% of the sample; a trajectory with low levels of wheeze but high prevalence of other atopic symptoms (29%; a trajectory with high prevalence of both wheeze and other atopic symptoms (9%; and a trajectory with high levels of wheeze but low levels of other atopic symptoms (8%. These groups differed in terms of socio-economic markers and potential intervenable factors, including household damp and breastfeeding initiation. CONCLUSION: Using data-driven techniques, we derived four trajectories of asthmatic symptoms in early childhood in a large, population based sample. These groups differ in terms of their socio-economic profiles
Temporal Parameter Optimization in Four-Dimensional Flash Trajectory Imaging
Institute of Scientific and Technical Information of China (English)
WANG Xin-Wei; ZHOU Yan; FAN Song-Tao; LIU Yu-Liang
2011-01-01
In four-dimensional fiash trajectory imaging, temporal parameters include time delay, laser pulse width, gate time, pulse pair repetition frequency and the frame rate of CCD, which directly impact on the acquisition of target trajectories over time. We propose a method of optimizing the temporal parameters of flash trajectory imaging. All the temporal parameters can be estimated by the spatial parameters of the volumes of interest, target scale and velocity, and target sample number. The formulae for optimizing temporal parameters are derived, and the method is demonstrated in an experiment with a ball oscillating as a pendulum.%In four-dimensional flash trajectory imaging,temporal parameters include time delay,laser pulse width,gate time,pulse pair repetition frequency and the frame rate of CCD,which directly impact on the acquisition of target trajectories over time.We propose a method of optimizing the temporal parameters of flash trajectory imaging.All the temporal parameters can be estimated by the spatial parameters of the volumes of interest,target scale and velocity,and target sample number.The formulae for optimizing temporal parameters are derived,and the method is demonstrated in an experiment with a ball oscillating as a pendulum.Four-dimensional flash trajectory imaging (FTI)based on time-delay-modulated range-gated viewing can directly image the trajectories of moving objects with backgrounds filtered and deduce target 3D positions over time,[1] which has potentials in astronomy,remote sensing and biomedical applications.[2 4] Temporal parameters are crucial for FTI.An unreasonable setting of temporal parameters will lead to failure in obtaining target trajectories.However,in the previous work,[1] the optimization of temporal parameters has not been discussed in detail.Therefore,in this Letter we give a method of estimating the temporal parameters of FTI.
Drug use trajectory patterns among older drug users
Directory of Open Access Journals (Sweden)
Tyndall B
2011-05-01
Full Text Available Miriam Boeri, Thor Whalen, Benjamin Tyndall, Ellen BallardKennesaw State University, Department of Sociology and Criminal Justice, Kennesaw GA, USAAbstract: To better understand patterns of drug use trajectories over time, it is essential to have standard measures of change. Our goal here is to introduce measures we developed to quantify change in drug use behaviors. A secondary goal is to provide effective visualizations of these trajectories for applied use. We analyzed data from a sample of 92 older drug users (ages 45 to 65 to identify transition patterns in drug use trajectories across the life course. Data were collected for every year since birth using a mixed methods design. The community-drawn sample of active and former users were 40% female, 50% African American, and 60% reporting some college or greater. Their life histories provided retrospective longitudinal data on the diversity of paths taken throughout the life course and changes in drug use patterns that occurred over time. Bayesian analysis was used to model drug trajectories displayed by innovative computer graphics. The mathematical techniques and visualizations presented here provide the foundation for future models using Bayesian analysis. In this paper we introduce the concepts of transition counts, transition rates and relapse/remission rates, and we describe how these measures can help us better understand drug use trajectories. Depicted through these visual tools, measurements of discontinuous patterns provide a succinct view of individual drug use trajectories. The measures we use on drug use data will be further developed to incorporate contextual influences on the drug trajectory and build predictive models that inform rehabilitation efforts for drug users. Although the measures developed here were conceived to better examine drug use trajectories, the applications of these measures can be used with other longitudinal datasets.Keywords: drug use, trajectory patterns
Association between trajectories of statin adherence and subsequent cardiovascular events.
Franklin, Jessica M; Krumme, Alexis A; Tong, Angela Y; Shrank, William H; Matlin, Olga S; Brennan, Troyen A; Choudhry, Niteesh K
2015-10-01
Trajectory models have been shown to (1) identify groups of patients with similar patterns of medication filling behavior and (2) summarize the trajectory, the average adherence in each group over time. However, the association between adherence trajectories and clinical outcomes remains unclear. This study investigated the association between 12-month statin trajectories and subsequent cardiovascular events. We identified patients with insurance coverage from a large national insurer who initiated a statin during January 1, 2007 to December 31, 2010. We assessed medication adherence during the 360 days following initiation and grouped patients based on the proportion of days covered (PDC) and trajectory models. We then measured cardiovascular events during the year after adherence assessment. Cox proportional hazards models were used to evaluate the association between adherence measures and cardiovascular outcomes; strength of association was quantified by the hazard ratio, the increase in model C-statistic, and the net reclassification index (NRI). Among 519 842 statin initiators, 8777 (1.7%) had a cardiovascular event during follow-up. More consistent medication use was associated with a lower likelihood of clinical events, whether adherence was measured through trajectory groups or PDC. When evaluating the prediction of future cardiovascular events by including a measure of adherence in the model, the best model reclassification was observed when adherence was measured using three or four trajectory groups (NRI = 0.189; 95% confidence interval: [0.171, 0.210]). Statin adherence trajectory predicted future cardiovascular events better than measures categorizing PDC. Thus, adherence trajectories may be useful for targeting adherence interventions. Copyright © 2015 John Wiley & Sons, Ltd.
Seven Steps Towards the Classical World
Allori, V; Goldstein, S; Zanghì, N; Allori, Valia; Goldstein, Shelly; Zangh\\'{\\i}, Nino
2001-01-01
Classical physics is about real objects, like apples falling from trees, whose motion is governed by Newtonian laws. In standard Quantum Mechanics only the wave function or the results of measurements exist, and to answer the question of how the classical world can be part of the quantum world is a rather formidable task. However, this is not the case for Bohmian mechanics, which, like classical mechanics, is a theory about real objects. In Bohmian terms, the problem of the classical limit becomes very simple: when do the Bohmian trajectories look Newtonian?
Trajectories for a Near Term Mission to the Interstellar Medium
Arora, Nitin; Strange, Nathan; Alkalai, Leon
2015-01-01
Trajectories for rapid access to the interstellar medium (ISM) with a Kuiper Belt Object (KBO) flyby, launching between 2022 and 2030, are described. An impulsive-patched-conic broad search algorithm combined with a local optimizer is used for the trajectory computations. Two classes of trajectories, (1) with a powered Jupiter flyby and (2) with a perihelion maneuver, are studied and compared. Planetary flybys combined with leveraging maneuvers reduce launch C3 requirements (by factor of 2 or more) and help satisfy mission-phasing constraints. Low launch C3 combined with leveraging and a perihelion maneuver is found to be enabling for a near-term potential mission to the ISM.
The analysis of control trajectories using symbolic and database computing
Grossman, Robert
1995-01-01
This final report comprises the formal semi-annual status reports for this grant for the periods June 30-December 31, 1993, January 1-June 30, 1994, and June 1-December 31, 1994. The research supported by this grant is broadly concerned with the symbolic computation, mixed numeric-symbolic computation, and database computation of trajectories of dynamical systems, especially control systems. A review of work during the report period covers: trajectories and approximating series, the Cayley algebra of trees, actions of differential operators, geometrically stable integration algorithms, hybrid systems, trajectory stores, PTool, and other activities. A list of publications written during the report period is attached.
Sensitivity in the trajectory of long-range -particle
Indian Academy of Sciences (India)
P V Kunhikrishnan; A Rajan Nambiar; K P Santhosh
2012-09-01
The factors influencing the trajectory of long-range -particle in the cold ternary fission of 252Cf are discussed. The trajectory of the -particle is studied by considering the influence of the force on the -particle due to Coulomb and proximity potentials and is found to have sensitive dependence on the initial position and initial energy of the -particle. The sensitivity to initial conditions signifies the presence of deterministic chaos which is characterized by Lyapunov exponent (LE). The LE is calculated using Wolf’s algorithm and found positive which implies that the objectives of trajectory calculations are restricted.
Optimal take-off trajectories in the presence of windshear
Miele, A.; Wang, T.; Melvin, W. W.
1986-01-01
The present consideration of takeoff trajectory optimization in eight different fundamental problems involving wind shears assumes that the power setting is held at the maximum value, and that the aircraft is controlled with respect to angle-of-attack. While the first three problems are least-squares ones of the Bolza type, the remaining five are minimax problems of the Chebyshev type which can be converted to Bolza type by means of suitable transformations. All problems are solved on the basis of the dual sequential gradient-restoration algorithm for optimal control problems. The trajectory solutions obtained are superior to constant angle-of-attack trajectories.
Key frame extraction based on spatiotemporal motion trajectory
Zhang, Yunzuo; Tao, Ran; Zhang, Feng
2015-05-01
Spatiotemporal motion trajectory can accurately reflect the changes of motion state. Motivated by this observation, this letter proposes a method for key frame extraction based on motion trajectory on the spatiotemporal slice. Different from the well-known motion related methods, the proposed method utilizes the inflexions of the motion trajectory on the spatiotemporal slice of all the moving objects. Experimental results show that although a similar performance is achieved in the single-objective screen, by comparing the proposed method to that achieved with the state-of-the-art methods based on motion energy or acceleration, the proposed method shows a better performance in a multiobjective video.
Investigation of Adaptive Controllers for Puma Trajectory Tracking
1991-06-01
Tarokh’s and Seraji’s Control Algorithms - Trajectory ] 4-14 vii 0 Imagen Laser Printer (im132) Owner dsims 00 Host wa7 //printer im132 Date Wed Apr...INVESTIGATION OF ADAPTIVE CONTROLLERS FOR PUMA TRAJECTORY TRACKING THESIS Daniel J. Sims Captain, USAF AFIT/GE/ENG/91J-05 Approved for public release...Adaptive Controllers for PUMA Trajectory Tracking. 6. AUTHOR(S) Daniel J. Sims, Capt, USAF 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8
Comparison of the secondary electrons produced by proton and electron beams in water
Energy Technology Data Exchange (ETDEWEB)
Kia, Mohammad Reza, E-mail: m-r-kia@aut.ac.ir; Noshad, Houshyar [Department of Energy Engineering and Physics, Amirkabir University of Technology (Tehran Polytechnic), P.O. Box 15875-4413, Hafez Avenue, Tehran (Iran, Islamic Republic of)
2016-05-15
The secondary electrons produced in water by electron and proton beams are compared with each other. The total ionization cross section (TICS) for an electron impact in water is obtained by using the binary-encounter-Bethe model. Hence, an empirical equation based on two adjustable fitting parameters is presented to determine the TICS for proton impact in media. In order to calculate the projectile trajectory, a set of stochastic differential equations based on the inelastic collision, elastic scattering, and bremsstrahlung emission are used. In accordance with the projectile trajectory, the depth dose deposition, electron energy loss distribution in a certain depth, and secondary electrons produced in water are calculated. The obtained results for the depth dose deposition and energy loss distribution in certain depth for electron and proton beams with various incident energies in media are in excellent agreement with the reported experimental data. The difference between the profiles for the depth dose deposition and production of secondary electrons for a proton beam can be ignored approximately. But, these profiles for an electron beam are completely different due to the effect of elastic scattering on electron trajectory.
Comparison of the secondary electrons produced by proton and electron beams in water
Kia, Mohammad Reza; Noshad, Houshyar
2016-05-01
The secondary electrons produced in water by electron and proton beams are compared with each other. The total ionization cross section (TICS) for an electron impact in water is obtained by using the binary-encounter-Bethe model. Hence, an empirical equation based on two adjustable fitting parameters is presented to determine the TICS for proton impact in media. In order to calculate the projectile trajectory, a set of stochastic differential equations based on the inelastic collision, elastic scattering, and bremsstrahlung emission are used. In accordance with the projectile trajectory, the depth dose deposition, electron energy loss distribution in a certain depth, and secondary electrons produced in water are calculated. The obtained results for the depth dose deposition and energy loss distribution in certain depth for electron and proton beams with various incident energies in media are in excellent agreement with the reported experimental data. The difference between the profiles for the depth dose deposition and production of secondary electrons for a proton beam can be ignored approximately. But, these profiles for an electron beam are completely different due to the effect of elastic scattering on electron trajectory.
Computational Appliance for Rapid Prediction of Aircraft Trajectories Project
National Aeronautics and Space Administration — Next generation air traffic management systems will be based to a greater degree on predicted trajectories of aircraft. Due to the iterative nature of future air...
Low Thrust Trajectory Design for GSFC Missions Project
National Aeronautics and Space Administration — The problem to be solved here is that of designing complex interplanetary trajectories to destinations which are difficult to reach via direct flights and chemical...
On-Line Trajectory Retargeting for Alternate Landing Sites Project
National Aeronautics and Space Administration — Barron Associates, Inc. proposes to develop a novel on-line trajectory optimization approach for Reusable Launch Vehicles (RLVs) under failure scenarios, targeting...
Computational Appliance for Rapid Prediction of Aircraft Trajectories Project
National Aeronautics and Space Administration — Next generation air traffic management systems will be based to a greater degree on predicted trajectories of aircraft. Due to the iterative nature of future air...
Instrument concept of a single channel dust trajectory detector
Li, Yanwei; Kempf, Sascha; Simolka, Jonas; Strack, Heiko; Grün, Eberhard; Srama, Ralf
2017-03-01
Charged dust particles in space can be detected by in situ sensors using charge induction. Such trajectory sensors are normally based on many grid or wire electrodes connected to individual charge sensitive amplifiers. In this article we describe a new approach to measure the trajectory of a charged dust particle by a single charge sensitive amplifier. The signal shape is used to calculate particle speed, mass and trajectory. The detector employs two half-circular grid electrodes, and the electrodes are connected to the differential input stage of an amplifier. Simulations using the Coulomb 9.0 software package were performed in order to determine the expected signal shapes depending on the particle parameters (entry location and incident angles). The simulated charge signals show, that the chosen measurement concept is an efficient method for low-power and low-mass dust trajectory sensors.
Trajectory Networks and Their Topological Changes Induced by Geographical Infiltration
Costa, Luciano da Fontoura
2008-01-01
In this article we investigate the topological changes undergone by trajectory networks as a consequence of progressive geographical infiltration. Trajectory networks, a type of knitted network, are obtained by establishing paths between geographically distributed nodes while following an associated vector field. For instance, the nodes could correspond to neurons along the cortical surface and the vector field could correspond to the gradient of neurotrophic factors, or the nodes could represent towns while the vector fields would be given by economical and/or geographical gradients. Therefore trajectory networks are natural models of a large number of geographical structures. The geographical infiltrations correspond to the addition of new local connections between nearby existing nodes. As such, these infiltrations could be related to several real-world processes such as contaminations, diseases, attacks, parasites, etc. The way in which progressive geographical infiltrations affect trajectory networks is ...
Curved trajectories of actin-based motility in two dimensions
Wen, Fu-Lai; Leung, Kwan-tai; Chen, Hsuan-Yi
2012-05-01
Recent experiments have reported fascinating geometrical trajectories for actin-based motility of bacteria Listeria monocytogenes and functionalized beads. To understand the physical mechanism for these trajectories, we constructed a phenomenological model to study the motion of an actin-propelled disk in two dimensions. In our model, the force and actin density on the surface of the disk are influenced by the translation and rotation of the disk, which in turn is induced by the asymmetric distributions of those densities. We show that this feedback can destabilize a straight trajectory, leading to circular, S-shape and other geometrical trajectories observed in the experiments through bifurcations in the distributions of the force and actin density. The relation between our model and the models for self-propelled deformable particles is emphasized and discussed.
Trajectory tracking of an underactuated fixed-wing UAV
Oland, Espen; Kristiansen, Raymond
2014-12-01
This paper presents a solution to the problem of trajectory tracking for a fixed-wing UAV. With its inherent actuator constraints, a fixed-wing UAV is not able to track an arbitrary trajectory, such that a guidance scheme is required in order to solve the trajectory tracking problem. In this paper, this is solved by first designing a virtual saturated control law that makes the position and velocity errors go to zero. Then the outputs from the virtual control law are mapped onto actuated variables that can be tracked using the available actuators. To that end, a model-based proportional speed controller and a quaternion-based sliding surface controller are presented, making all the errors go to zero. The solution is proved using Lyapunov theory and is validated through simulations where a fixed-wing UAV tracks a circular trajectory.
Frequency domain synthesis of trajectory learning controllers for robot manipulators
Directory of Open Access Journals (Sweden)
Tom Kavli
1993-07-01
Full Text Available Trajectory learning control is a method for generating near to optimal feedforward control for systems that are controlled along a reference trajectory in repeated cycles. Iterative refinements of a stored feedforward control sequence corresponding to one cycle of the control trajectory is computed based upon the recorded trajectory error from the previous cycle. Several learning operators have been proposed in earlier work, and convergence proofs are developed for certain classes of systems, but no satisfactory method for design and analysis of learning operators under the presence of uncertainties in the system model have been presented. This article presents frequency domain methods for analysing the convergence properties and performance of the learning controller when the amplitude and phase of the system transfer function is assumed to be within specified windows. Experimental results with an industrial robot manipulator confirm the theoretical results.
Parametric Approach to Trajectory Tracking Control of Robot Manipulators
Directory of Open Access Journals (Sweden)
Shijie Zhang
2013-01-01
Full Text Available The mathematic description of the trajectory of robot manipulators with the optimal trajectory tracking problem is formulated as an optimal control problem, and a parametric approach is proposed for the optimal trajectory tracking control problem. The optimal control problem is first solved as an open loop optimal control problem by using a time scaling transform and the control parameterization method. Then, by virtue of the relationship between the optimal open loop control and the optimal closed loop control along the optimal trajectory, a practical method is presented to calculate an approximate optimal feedback gain matrix, without having to solve an optimal control problem involving the complex Riccati-like matrix differential equation coupled with the original system dynamics. Simulation results of 2-link robot manipulator are presented to show the effectiveness of the proposed method.
Pneumatic motor speed control by trajectory tracking fuzzy logic controller
Indian Academy of Sciences (India)
Cengiz Safak; Vedat Topuz; A Fevzi Baba
2010-02-01
In this study, trajectory tracking fuzzy logic controller (TTFLC) is proposed for the speed control of a pneumatic motor (PM). A third order trajectory is deﬁned to determine the trajectory function that has to be tracked by the PM speed. Genetic algorithm (GA) is used to ﬁnd the TTFLC boundary values of membership functions (MF) and weights of control rules. In addition, artiﬁcial neural networks (ANN) modelled dynamic behaviour of PM is given. This ANN model is used to ﬁnd the optimal TTFLC parameters by ofﬂine GA approach. The experimental results show that designed TTFLC successfully enables the PM speed track the given trajectory under various working conditions. The proposed approach is superior to PID controller. It also provides simple and easy design procedure for the PM speed control problem.
Prediction of the discharge trajectories of bulk materials
Energy Technology Data Exchange (ETDEWEB)
Golka, K. (Pacific Power, Sydney, NSW (Australia))
1993-11-01
The theory of discharge trajectories of granular materials without cohesion and adhesion from material handling equipment is reviewed in terms of its application within the design process. Theoretical formulae of discharge trajectories are provided for underside and topside limits of the bulk material path. The fundamental force, velocity, and the continuity-flow relationships, are the main factors used in describing the material's trajectory functions. The analytical functions developed are for kinematic material stream conditions when discharging from: (a) head pulleys of belt conveyors; (b) chutes and cross belt samplers. To predict the trajectory path for real conditions, divergent coefficients have been introduced to the theoretical functions. Computer calculations and graphical representations indicate how the theoretical approach can be useful for practical design. 10 refs., 6 figs.
Trajectory Clustering and an Application to Airspace Monitoring
National Aeronautics and Space Administration — This paper presents a framework aimed at monitoring the behavior of aircraft in a given airspace. Trajectories that constitute typical operations are determined and...
Underwater navigation using diffusion-based trajectory observers
DEFF Research Database (Denmark)
Jouffroy, Jerome; Opderbecke, Jan
2007-01-01
This paper addresses the issue of estimating underwater vehicle trajectories using gyro-Doppler (body-fixed velocities) and acoustic positioning signals (earth-fixed positions). The approach consists of diffusion-based observers processing a whole trajectory segment at a time, allowing the consid......This paper addresses the issue of estimating underwater vehicle trajectories using gyro-Doppler (body-fixed velocities) and acoustic positioning signals (earth-fixed positions). The approach consists of diffusion-based observers processing a whole trajectory segment at a time, allowing...... the consideration of important practical problems such as different information update rates, outages, and outliers in a very simple framework. Results of contraction theory are used to prove that the observers are convergent, i.e., stable in the incremental sense. Simulation and experimental results are presented...
MGA trajectory planning with an ACO-inspired algorithm
Ceriotti, Matteo
2011-01-01
Given a set of celestial bodies, the problem of finding an optimal sequence of swing-bys, deep space manoeuvres (DSM) and transfer arcs connecting the elements of the set is combinatorial in nature. The number of possible paths grows exponentially with the number of celestial bodies. Therefore, the design of an optimal multiple gravity assist (MGA) trajectory is a NP-hard mixed combinatorial-continuous problem. Its automated solution would greatly improve the design of future space missions, allowing the assessment of a large number of alternative mission options in a short time. This work proposes to formulate the complete automated design of a multiple gravity assist trajectory as an autonomous planning and scheduling problem. The resulting scheduled plan will provide the optimal planetary sequence and a good estimation of the set of associated optimal trajectories. The trajectory model consists of a sequence of celestial bodies connected by twodimensional transfer arcs containing one DSM. For each transfer...
Quantifying ataxia: ideal trajectory analysis--a technical note
McPartland, M. D.; Krebs, D. E.; Wall, C. 3rd
2000-01-01
We describe a quantitative method to assess repeated stair stepping stability. In both the mediolateral (ML) and anterioposterior (AP) directions, the trajectory of the subject's center of mass (COM) was compared to an ideal sinusoid. The two identified sinusoids were unique in each direction but coupled. Two dimensionless numbers-the mediolateral instability index (IML) and AP instability index (IAP)-were calculated using the COM trajectory and ideal sinusoids for each subject with larger index values resulting from less stable performance. The COM trajectories of nine nonimpaired controls and six patients diagnosed with unilateral or bilateral vestibular labyrinth hypofunction were analyzed. The average IML and IAP values of labyrinth disorder patients were respectively 127% and 119% greater than those of controls (panalysis distinguishes persons with labyrinth disorder from those without. The COM trajectories also identify movement inefficiencies attributable to vestibulopathy.
The Best Estimated Trajectory Analysis for Pad Abort One
Kutty, Prasad; Noonan, Meghan; Karlgaard, Christopher; Beck, Roger
2011-01-01
I. Best Estimated Trajectory (BET) objective: a) Produce reconstructed trajectory of the PA-1 flight to understand vehicle dynamics and aid other post flight analyses. b) Leverage all measurement sources taken of vehicle during flight to produce the most accurate estimate of vehicle trajectory. c) Generate trajectory reconstructions of the Crew Module (CM), Launch Abort System (LAS), and Forward Bay Cover (FBC). II. BET analysis was started immediately following the PA-1 mission and was completed in September, 2010 a) Quick look version of BET released 5/25/2010: initial repackaging of SIGI data. b) Preliminary version of BET released 7/6/2010: first blended solution using available sources of external measurements. c) Final version of BET released 9/1/2010: final blended solution using all available sources of data.
Probabilistic Modeling of Aircraft Trajectories for Dynamic Separation Volumes
Lewis, Timothy A.
2016-01-01
With a proliferation of new and unconventional vehicles and operations expected in the future, the ab initio airspace design will require new approaches to trajectory prediction for separation assurance and other air traffic management functions. This paper presents an approach to probabilistic modeling of the trajectory of an aircraft when its intent is unknown. The approach uses a set of feature functions to constrain a maximum entropy probability distribution based on a set of observed aircraft trajectories. This model can be used to sample new aircraft trajectories to form an ensemble reflecting the variability in an aircraft's intent. The model learning process ensures that the variability in this ensemble reflects the behavior observed in the original data set. Computational examples are presented.
Visual traffic jam analysis based on trajectory data.
Wang, Zuchao; Lu, Min; Yuan, Xiaoru; Zhang, Junping; van de Wetering, Huub
2013-12-01
In this work, we present an interactive system for visual analysis of urban traffic congestion based on GPS trajectories. For these trajectories we develop strategies to extract and derive traffic jam information. After cleaning the trajectories, they are matched to a road network. Subsequently, traffic speed on each road segment is computed and traffic jam events are automatically detected. Spatially and temporally related events are concatenated in, so-called, traffic jam propagation graphs. These graphs form a high-level description of a traffic jam and its propagation in time and space. Our system provides multiple views for visually exploring and analyzing the traffic condition of a large city as a whole, on the level of propagation graphs, and on road segment level. Case studies with 24 days of taxi GPS trajectories collected in Beijing demonstrate the effectiveness of our system.
Some impulsive rendezvous trajectories and their possible optimality.
Peltier, J. P.
1972-01-01
Two- and three-impulse trajectories are investigated for fixed-time, fixed-angle rendezvous between vacant circular coplanar orbits, for trip angles less than, or equal to 2 pi in magnitude. For two-impulse trajectories, general features of the characteristic velocity function are outlined. Parameters of the intermediate orbit are reviewed. Attention is given to limiting cases. Computation of the adjoint system helps to define the domain of possible optimality foajectories: it is a closed domain in the trip time, trip angle plane. Waiting periods on terminal orbits are considered. The domain of possible optimality is defined using Lawden's primer vrtory. This domain extends to infinity if the radius ratio of terminal orbits is less than 15.6. Three-impulse trajectories are tried in cases where two-impulse trajectories, with or without cost, have been found nonoptimal. Improvements on the characteristic velocity are thus obtained.
Abnormal events detection in crowded scenes by trajectory cluster
Zhou, Shifu; Zhang, Zhijiang; Zeng, Dan; Shen, Wei
2015-02-01
Abnormal events detection in crowded scenes has been a challenge due to volatility of the definitions for both normality and abnormality, the small number of pixels on the target, appearance ambiguity resulting from the dense packing, and severe inter-object occlusions. A novel framework was proposed for the detection of unusual events in crowded scenes using trajectories produced by moving pedestrians based on an intuition that the motion patterns of usual behaviors are similar to these of group activity, whereas unusual behaviors are not. First, spectral clustering is used to group trajectories with similar spatial patterns. Different trajectory clusters represent different activities. Then, unusual trajectories can be detected using these patterns. Furthermore, behavior of a mobile pedestrian can be defined by comparing its direction with these patterns, such as moving in the opposite direction of the group or traversing the group. Experimental results indicated that the proposed algorithm could be used to reliably locate the abnormal events in crowded scenes.
Approximate aggregate nearest neighbor search on moving objects trajectories
Institute of Scientific and Technical Information of China (English)
Mohammad; Reza; Abbasifard; Hassan; Naderi; Zohreh; Fallahnejad; Omid; Isfahani; Alamdari
2015-01-01
Aggregate nearest neighbor(ANN) search retrieves for two spatial datasets T and Q, segment(s) of one or more trajectories from the set T having minimum aggregate distance to points in Q. When interacting with large amounts of trajectories, this process would be very time-consuming due to consecutive page loads. An approximate method for finding segments with minimum aggregate distance is proposed which can improve the response time. In order to index large volumes of trajectories, scalable and efficient trajectory index(SETI) structure is used. But some refinements are provided to temporal index of SETI to improve the performance of proposed method. The experiments were performed with different number of query points and percentages of dataset. It is shown that proposed method besides having an acceptable precision, can reduce the computation time significantly. It is also shown that the main fraction of search time among load time, ANN and computing convex and centroid, is related to ANN.
Spatial and temporal segmented dense trajectories for gesture recognition
Yamada, Kaho; Yoshida, Takeshi; Sumi, Kazuhiko; Habe, Hitoshi; Mitsugami, Ikuhisa
2017-03-01
Recently, dense trajectories [1] have been shown to be a successful video representation for action recognition, and have demonstrated state-of-the-art results with a variety of datasets. However, if we apply these trajectories to gesture recognition, recognizing similar and fine-grained motions is problematic. In this paper, we propose a new method in which dense trajectories are calculated in segmented regions around detected human body parts. Spatial segmentation is achieved by body part detection [2]. Temporal segmentation is performed for a fixed number of video frames. The proposed method removes background video noise and can recognize similar and fine-grained motions. Only a few video datasets are available for gesture classification; therefore, we have constructed a new gesture dataset and evaluated the proposed method using this dataset. The experimental results show that the proposed method outperforms the original dense trajectories.
Student Learning-Game Designs: Emerging Learning Trajectories
DEFF Research Database (Denmark)
Weitze, Charlotte Lærke
2016-01-01
in four learning games created by students, to investigate how these elements were em83 ployed, to determine what learning trajectories emerged in the two digital game tools and to offer reflections and suggestions regarding the learning processes students experienced when building the various learning...... trajectories for specific learning goals into the digital games. The article examines how specific features in the two digital game tools, Scratch and RGBMaker, afford creation of learning trajectories in various ways, enabling deep learning and gameplay processes for the players of the games. According...... to the study, the level of complexity of the built‐in learning trajectories in the games was mirrored in the cognitive complexity of the student game designers' learning processes. The article presents four student‐created games that demonstrate a progression in the depth of potential learning experiences...
A user's guide for a generalized interplanetary trajectory generation program
1972-01-01
The analysis, structure, and capability of a generalized precision interplanetary trajectory computation program are discussed, with emphasis being placed on the description of input and output. Sample cases showing input and output information are included.
Data fusion techniques for incomplete measurement of trajectory
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
This paper focuses on data processing for incomplete measurementof trajectory (IMT) in aerospace mea- surement and control. The IMT means that the principal equipment loses the measured data during some intervals so that trajectory parameters (position, velocity, etc.) cannot be determined independently. Based on a joint model for trajectory estimation with reduced parameter, a fusion way is put forth by making full use of measured data from auxiliary equipment with lower precision. In the superposition intervals of measurement between principal and auxiliary equipment, the technique of diagnosing and estimating system errors is applied to improving the estimate precision of trajectory parameters (TP) and determining the precision after data fusion. In practical test, this method operates so successfully that it can not only provide complete TP but improve their precision remarkably. Meanwhile, this way is also applicable to other problems of incomplete measurement.
School life and adolescents' self-esteem trajectories.
Morin, Alexandre J S; Maïano, Christophe; Marsh, Herbert W; Nagengast, Benjamin; Janosz, Michel
2013-01-01
This study investigates heterogeneity in adolescents' trajectories of global self-esteem (GSE) and the relations between these trajectories and facets of the interpersonal, organizational, and instructional components of students' school life. Methodologically, this study illustrates the use of growth mixture analyses, and how to obtain proper student-level effects when there are multiple schools, but not enough to support multilevel analyses. This study is based on a 4-year, six-measurement-point, follow-up of 1,008 adolescents (M(age) = 12.6 years, SD = 0.6 at Time 1.) The results show four latent classes presenting elevated, moderate, increasing, and low trajectories defined based on GSE levels and fluctuations. The results show that GSE becomes trait-like as it increases and that school life effects, moderated by gender, played an important role in predicting membership in these trajectories. © 2013 The Authors. Child Development © 2013 Society for Research in Child Development, Inc.
Tracking Trajectory Planning of Space Manipulator for Capturing Operation
Directory of Open Access Journals (Sweden)
Panfeng Huang
2008-11-01
Full Text Available On-orbit rescuing uncontrolled spinning satellite (USS using space robot is a great challenge for future space service. This paper mainly present a trajectory planning method of space manipulator that can track, approach and catch the USS in free-floating situation. According to the motion characteristics of USS, we plan a spiral ascending trajectory for space manipulator to approach towards USS in Cartesian space. However, it is difficult to map this trajectory into the joint space and realize feasible motion in joint space because of dynamics singularities and dynamics couple of space robot system. Therefore, we utilize interval algorithm to handle these difficulties. The simulation study verifies that the spiral ascending trajectory can been realized. Moreover, the motion of manipulator is smooth and stable, the disturbance to the base is so limited that the attitude control can compensate it.
Energy dependence of the rho-trajectory intercept
Energy Technology Data Exchange (ETDEWEB)
Garcia, A.; Canal, C.A.G.; Masperi, L.
1978-02-01
The forward ..pi..N charge-exchange differential cross section is studied in the framework of a recent model for the rho trajectory. Negative result shed doubts on the proposed nondiffractive renormalization mechanism for secondary Reggeons.
Sliding Mode Control for Trajectory Tracking of an Intelligent Wheelchair
Directory of Open Access Journals (Sweden)
Razvan SOLEA
2009-12-01
Full Text Available This paper deal with a robust sliding-mode trajectory tracking controller, fornonholonomic wheeled mobile robots and its experimental evaluation by theimplementation in an intelligent wheelchair (RobChair. The proposed control structureis based on two nonlinear sliding surfaces ensuring the tracking of the three outputvariables, with respect to the nonholonomic constraint. The performances of theproposed controller for the trajectory planning problem with comfort constraint areverified through the real time acceleration provided by an inertial measurement unit.
Genetic Algorithm Tuned Fuzzy Logic for Gliding Return Trajectories
Burchett, Bradley T.
2003-01-01
The problem of designing and flying a trajectory for successful recovery of a reusable launch vehicle is tackled using fuzzy logic control with genetic algorithm optimization. The plant is approximated by a simplified three degree of freedom non-linear model. A baseline trajectory design and guidance algorithm consisting of several Mamdani type fuzzy controllers is tuned using a simple genetic algorithm. Preliminary results show that the performance of the overall system is shown to improve with genetic algorithm tuning.
Earth-moon Trajectory Optimization Using Solar Electric Propulsion
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The optimization of the Earth-moon trajectory using solar electric propulsion is presented. A feasible method is proposed to optimize the transfer trajectory starting from a low Earth circular orbit (500 km altitude) to a low lunar circular orbit (200 km altitude). Due to the use of low-thrust solar electric propulsion, the entire transfer trajectory consists of hundreds or even thousands of orbital revolutions around the Earth and the moon. The Earth-orbit ascending (from low Earth orbit to high Earth orbit) and lunar descending (from high lunar orbit to low lunar orbit) trajectories in the presence of J2 perturbations and shadowing effect are computed by an analytic orbital averaging technique. A direct/indirect method is used to optimize the control steering for the trans-lunar trajectory segment, a segment fiom a high Earth orbit to a high lunar orbit, with a fixed thrust-coast-thrust engine sequence. For the trans-lunar trajectory segment, the equations of motion are expressed in the inertial coordinates about the Earth and the moon using a set of nonsingular equinoctial elements inclusive of the gravitational forces of the sun, the Earth, and the moon. By way of the analytic orbital averaging technique and the direct/indirect method, the Earth-moon transfer problem is converted to a parameter optimization problem, and the entire transfer trajectory is formulated and optimized in the form of a single nonlinear optimization problem with a small number of variables and constraints. Finally, an example of an Earth-moon transfer trajectory using solar electric propulsion is demonstrated.
Gender Differences in Anxiety Trajectories from Middle to Late Adolescence.
Ohannessian, Christine McCauley; Milan, Stephanie; Vannucci, Anna
2017-04-01
Although developmental trajectories of anxiety symptomatology have begun to be explored, most research has focused on total anxiety symptom scores during childhood and early adolescence, using racially/ethnically homogenous samples. Understanding the heterogeneous courses of anxiety disorder symptoms during middle to late adolescence has the potential to clarify developmental risk models of anxiety and to inform prevention programs. Therefore, this study specifically examined gender differences in developmental trajectories of anxiety disorder symptoms (generalized anxiety disorder, panic disorder, and social anxiety disorder) from middle to late adolescence in a diverse community sample (N = 1000; 57 % female; 65 % White), assessed annually over 2 years. Latent growth curve modeling revealed that girls exhibited a slight linear decrease in generalized anxiety disorder, panic disorder, and social anxiety disorder symptoms, whereas boys exhibited a stable course. These models suggested that one trajectory was appropriate for panic disorder symptoms in both girls and boys. Growth mixture models indicated the presence of four latent generalized anxiety disorder symptom trajectory classes: low increasing, moderate decreasing slightly, high decreasing, and very high decreasing rapidly. Growth mixture models also suggested the presence of five latent social anxiety disorder symptom trajectory classes: a low stable trajectory class and four classes that were qualitatively similar to the latent generalized anxiety disorder trajectories. For both generalized anxiety disorder and social anxiety disorder symptoms, girls were significantly more likely than boys to be in trajectory classes characterized by moderate or high initial symptoms that subsequently decreased over time. These findings provide novel information regarding the developmental course of anxiety disorder symptoms in adolescents.
Calculation of trajectory parameters of long pass in basketball.
Directory of Open Access Journals (Sweden)
Charikova K.M.
2011-08-01
Full Text Available Values of a ball's flight trajectory parameters depending on a distance of long pass, a corner of a ball's start and height of a throwing point are submitted in article. Coordinates of reference points installation for training to long pass with an optimum trajectory of a ball's flight are designed. Requirements to simulators design are determined. Corners of ball's long pass performance in various game situations are recommended.
Sociocultural approaches to trajectories of youth at risk
DEFF Research Database (Denmark)
Musaeus, Peter
2005-01-01
Sociocultural approaches to children and youth at risk are lacking. This paper presentation uses the notion of recognition and trajectory of participation in order to explain the participation of youth at risk while at residential care......Sociocultural approaches to children and youth at risk are lacking. This paper presentation uses the notion of recognition and trajectory of participation in order to explain the participation of youth at risk while at residential care...
Reversed graph embedding resolves complex single-cell trajectories.
Qiu, Xiaojie; Mao, Qi; Tang, Ying; Wang, Li; Chawla, Raghav; Pliner, Hannah A; Trapnell, Cole
2017-10-01
Single-cell trajectories can unveil how gene regulation governs cell fate decisions. However, learning the structure of complex trajectories with multiple branches remains a challenging computational problem. We present Monocle 2, an algorithm that uses reversed graph embedding to describe multiple fate decisions in a fully unsupervised manner. We applied Monocle 2 to two studies of blood development and found that mutations in the genes encoding key lineage transcription factors divert cells to alternative fates.
Lunar Landing Trajectory Design for Onboard Hazard Detection and Avoidance
Paschall, Steve; Brady, Tye; Sostaric, Ron
2009-01-01
The Autonomous Landing and Hazard Avoidance Technology (ALHAT) Project is developing the software and hardware technology needed to support a safe and precise landing for the next generation of lunar missions. ALHAT provides this capability through terrain-relative navigation measurements to enhance global-scale precision, an onboard hazard detection system to select safe landing locations, and an Autonomous Guidance, Navigation, and Control (AGNC) capability to process these measurements and safely direct the vehicle to a landing location. This paper focuses on the key trajectory design issues relevant to providing an onboard Hazard Detection and Avoidance (HDA) capability for the lander. Hazard detection can be accomplished by the crew visually scanning the terrain through a window, a sensor system imaging the terrain, or some combination of both. For ALHAT, this hazard detection activity is provided by a sensor system, which either augments the crew s perception or entirely replaces the crew in the case of a robotic landing. Detecting hazards influences the trajectory design by requiring the proper perspective, range to the landing site, and sufficient time to view the terrain. Following this, the trajectory design must provide additional time to process this information and make a decision about where to safely land. During the final part of the HDA process, the trajectory design must provide sufficient margin to enable a hazard avoidance maneuver. In order to demonstrate the effects of these constraints on the landing trajectory, a tradespace of trajectory designs was created for the initial ALHAT Design Analysis Cycle (ALDAC-1) and each case evaluated with these HDA constraints active. The ALHAT analysis process, described in this paper, narrows down this tradespace and subsequently better defines the trajectory design needed to support onboard HDA. Future ALDACs will enhance this trajectory design by balancing these issues and others in an overall system
Hybrid Models for Trajectory Error Modelling in Urban Environments
Angelatsa, E.; Parés, M. E.; Colomina, I.
2016-06-01
This paper tackles the first step of any strategy aiming to improve the trajectory of terrestrial mobile mapping systems in urban environments. We present an approach to model the error of terrestrial mobile mapping trajectories, combining deterministic and stochastic models. Due to urban specific environment, the deterministic component will be modelled with non-continuous functions composed by linear shifts, drifts or polynomial functions. In addition, we will introduce a stochastic error component for modelling residual noise of the trajectory error function. First step for error modelling requires to know the actual trajectory error values for several representative environments. In order to determine as accurately as possible the trajectories error, (almost) error less trajectories should be estimated using extracted nonsemantic features from a sequence of images collected with the terrestrial mobile mapping system and from a full set of ground control points. Once the references are estimated, they will be used to determine the actual errors in terrestrial mobile mapping trajectory. The rigorous analysis of these data sets will allow us to characterize the errors of a terrestrial mobile mapping system for a wide range of environments. This information will be of great use in future campaigns to improve the results of the 3D points cloud generation. The proposed approach has been evaluated using real data. The data originate from a mobile mapping campaign over an urban and controlled area of Dortmund (Germany), with harmful GNSS conditions. The mobile mapping system, that includes two laser scanner and two cameras, was mounted on a van and it was driven over a controlled area around three hours. The results show the suitability to decompose trajectory error with non-continuous deterministic and stochastic components.
Effect of polarization on the trajectory of dissipative solitons
Sadykov, N. R.
2009-01-01
We show that the optical Magnus effect for dissipative solitons is determined not only by the helicity but also by the topological index, i.e., by the magnetic quantum number or by the projection of the soliton orbital moment on its trajectory. In the case of inhomogeneous media, we find a relation between the optical Magnus effect and the nonholonomy of the field of unit vectors tangent to the trajectory.
Obesity status trajectory groups among elementary school children
Chen, Tzu-An; Baranowski, Tom; Jennette P. Moreno; O’Connor, Teresia M; Hughes, Sheryl O; Baranowski, Janice; Woehler, Deborah; Kimbro, Rachel T.; Johnston, Craig A.
2016-01-01
Background Little is known about patterns in the transition from healthy weight to overweight or obesity during the elementary school years. This study examined whether there were distinct body mass index (BMI) trajectory groups among elementary school children, and predictors of trajectory group membership. Methods This is a secondary analysis of 1651 elementary school children with complete biannual longitudinal data from kindergarten to the beginning of 5th grade. Heights and weights were ...
Hard electronics; Hard electronics
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-03-01
In the fields of power conversion devices and broadcasting/communication amplifiers, high power, high frequency and low losses are desirable. Further, for electronic elements in aerospace/aeronautical/geothermal surveys, etc., heat resistance to 500degC is required. Devices which respond to such hard specifications are called hard electronic devices. However, with Si which is at the core of the present electronics, the specifications cannot fully be fulfilled because of the restrictions arising from physical values. Accordingly, taking up new device materials/structures necessary to construct hard electronics, technologies to develop these to a level of IC were examined and studied. They are a technology to make devices/IC of new semiconductors such as SiC, diamond, etc. which can handle higher temperature, higher power and higher frequency than Si and also is possible of reducing losses, a technology to make devices of hard semiconducter materials such as a vacuum microelectronics technology using ultra-micro/high-luminance electronic emitter using negative electron affinity which diamond, etc. have, a technology to make devices of oxides which have various electric properties, etc. 321 refs., 194 figs., 8 tabs.
Momentum exchange in the electron double-slit experiment
Batelaan, Herman; Jones, Eric; Cheng-Wei Huang, Wayne; Bach, Roger
2016-03-01
We provide support for the claim that momentum is conserved for individual events in the electron double slit experiment. The natural consequence is that a physical mechanism is responsible for this momentum exchange, but that even if the fundamental mechanism is known for electron crystal diffraction and the Kapitza-Dirac effect, it is unknown for electron diffraction from nano-fabricated double slits. Work towards a proposed explanation in terms of particle trajectories affected by a vacuum field is discussed. The contentious use of trajectories is discussed within the context of oil droplet analogues of double slit diffraction.
A Measure of Similarity Between Trajectories of Vessels
Directory of Open Access Journals (Sweden)
Le QI
2016-03-01
Full Text Available The measurement of similarity between trajectories of vessels is one of the kernel problems that must be addressed to promote the development of maritime intelligent traffic system (ITS. In this study, a new model of trajectory similarity measurement was established to improve the data processing efficiency in dynamic application and to reflect actual sailing behaviors of vessels. In this model, a feature point detection algorithm was proposed to extract feature points, reduce data storage space and save computational resources. A new synthesized distance algorithm was also created to measure the similarity between trajectories by using the extracted feature points. An experiment was conducted to measure the similarity between the real trajectories of vessels. The growth of these trajectories required measurements to be conducted under different voyages. The results show that the similarity measurement between the vessel trajectories is efficient and correct. Comparison of the synthesized distance with the sailing behaviors of vessels proves that results are consistent with actual situations. The experiment results demonstrate the promising application of the proposed model in studying vessel traffic and in supplying reliable data for the development of maritime ITS.
Geometric calibration of the circle-plus-arc trajectory.
Hoppe, Stefan; Noo, Frédéric; Dennerlein, Frank; Lauritsch, Günter; Hornegger, Joachim
2007-12-07
In this paper, a novel geometric calibration method for C-arm cone-beam scanners is presented which allows the calibration of the circle-plus-arc trajectory. The main idea is the separation of the trajectory into two circular segments (circle segment and arc segment) which are calibrated independently. This separation makes it possible to reuse a calibration phantom which has been successfully applied in clinical environments to calibrate numerous routinely used C-arm systems. For each trajectory segment, the phantom is placed in an optimal position. The two calibration results are then combined by computing the transformation the phantom underwent between the independent calibration runs. This combination can be done in a post-processing step by using standard linear algebra. The method is not limited to circle-plus-arc trajectories and works for any calibration procedure in which the phantom has a preferred orientation with respect to a trajectory segment. Results are presented for both simulated as well as real data acquired with a C-arm system. We also present the first image reconstruction results for the circle-plus-arc trajectory using real C-arm data.
Target selection and transfer trajectories design for exploring asteroid mission
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Technique of target selection and profiles of transfer trajectory for Chinese asteroid exploring mission are studied systemically.A complete set of approaches to selecting mission targets and designing the transfer trajectory is proposed.First,when selecting a target for mission,some factors regarded as the scientific motivations are discussed.Then,when analyzing the accessibility of targets,instead of the classical strategy,the multiple gravity-assist strategy is provided.The suitable and possible targets,taking into account scientific value and technically feasible,are obtained via selection and estimation.When designing the transfer trajectory for exploring asteroid mission,an approach to selecting gravity-assist celestial body is proposed.Finally,according to the mission constraints,the trajectory profile with 2-years △V-EGA for exploring asteroid is presented.Through analyzing the trajectory profile,unexpected result that the trajectory would pass by two main-belts asteroids is found.So,the original proposal is extended to the multiple flybys mission.It adds the scientific return for asteroid mission.